JP4622433B2 - Compound, electron transport material and organic electroluminescence device - Google Patents

Description

  The present invention relates to a novel organic compound, and more particularly to an organic compound that is stable even when it is repeatedly subjected to electrical oxidation and reduction, and a high-efficiency and long-life organic EL device using the same.

Conventionally, as a thin film type electroluminescent (EL) element, there are ZnS, CaS, SrS, etc. which are inorganic material II-VI compound semiconductors, Mn which is an emission center, rare earth elements (Eu, Ce, Tb, Sm, etc.) ) Is generally used, but an EL element made from the above inorganic material is
1) AC drive is required (50-1000Hz),
2) High drive voltage (~ 200V),
3) Full color is difficult (especially blue),
4) The cost of the peripheral drive circuit is high.
Has the problem.

  However, in recent years, EL devices using organic thin films have been developed to improve the above problems. In particular, in order to improve luminous efficiency, the type of electrode is optimized for the purpose of improving the efficiency of carrier injection from the electrode, and a hole transporting layer made of aromatic diamine and a light emitting layer made of 8-hydroxyquinoline aluminum complex, As a result of the development of an organic electroluminescent device provided with (see Non-Patent Document 1), the luminous efficiency is greatly improved as compared with a conventional EL device using a single crystal such as anthracene. In addition, for example, by using 8-hydroxyquinoline aluminum complex as a host material and doping with a fluorescent dye for laser such as coumarin (see Non-Patent Document 2), the emission efficiency is improved and the emission wavelength is converted. It is approaching practical characteristics.

  In addition to the electroluminescent device using the low molecular weight material as described above, as a material of the light emitting layer, poly (p-phenylene vinylene), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4 Development of electroluminescent devices using polymer materials such as -phenylenevinylene] and poly (3-alkylthiophene), and devices that combine low molecular light emitting materials and electron transfer materials with polymers such as polyvinylcarbazole. Has been done.

  As an attempt to increase the luminous efficiency of the device, the use of phosphorescence instead of fluorescence has been studied. If phosphorescence is used, that is, light emission from a triplet excited state is used, an efficiency improvement of about three times is expected as compared with a conventional device using fluorescence (singlet). For this purpose, it has been studied to use a coumarin derivative or a benzophenone derivative as a light emitting layer (see Non-Patent Document 3), but only a very low luminance was obtained. Thereafter, the use of a europium complex has been studied as an attempt to utilize the triplet state, but this also did not lead to highly efficient light emission.

  Recently, it has been reported that highly efficient red light emission is possible by using the platinum complex (T-1) shown below (see Non-Patent Document 4). Thereafter, by doping the light emitting layer with the following iridium complex (T-2), the efficiency is further greatly improved by green light emission (see Non-Patent Document 5).

In order to apply the organic electroluminescence device to a display device such as a flat panel display, it is necessary to improve the light emission efficiency of the device and at the same time to ensure sufficient stability during driving.
However, the organic electroluminescence device using the phosphorescent molecule (T-2) described in the above-mentioned document has high efficiency light emission but has insufficient driving stability for practical use (Non-Patent Document 6). It is difficult to realize an efficient display element.

  Many of the organic electroluminescence devices using phosphorescent molecules developed so far are characterized by using a material containing a carbazolyl group as a host of the light emitting layer. For example, the biphenyl derivative shown below is used as the host material in the above document (Non-patent Document 5).

  However, in a device using a triarylamine compound for the hole injection / transport layer and an aluminum complex for the electron injection / transport layer, the hole mobility tends to exceed the electron mobility. In an electroluminescent device, if a normal triarylamine compound and / or carbazole compound is used as the host material of the light emitting layer, the recombination position of charges tends to be biased toward the cathode side, making it difficult to balance.

  As new material systems, Patent Documents 1 and 2 propose pyridine-based compounds represented by the following compounds for use in fluorescent light-emitting devices or hole transport materials and / or light-emitting layer materials for electrophotographic photoreceptors. .

However, since these have a structure in which the nitrogen atom on the pyridine ring and the nitrogen atom on the arylamino group (including the carbazole group) can be conjugated, the redox potential difference is relatively small, It is considered that the performance is insufficient for application to a phosphorescent light emitting device.
Patent Document 3 proposes a fluorescent material represented by the following general formula.

However, the above compounds are only proposed as fluorescent dyes that mainly emit blue light, and there is no disclosure of other specific application methods.
On the other hand, in blue light-emitting elements and phosphorescent elements, the recombination region, which tends to be biased toward the cathode side, is concentrated in the light-emitting layer, thereby improving the exciton generation efficiency in the light-emitting layer and improving the light emission efficiency and light emission color. In order to achieve a high purity, it has been studied to provide a hole blocking layer between the light emitting layer and the electron transport layer.

As a hole blocking layer provided between the light emitting layer and the cathode, tris (5,7-dichloro-8-hydroxyquinolino) aluminum (Patent Document 4) is used as a material having an ionization potential larger than that of the light emitting layer. And silacyclopentadiene (see Patent Document 5) have been proposed, but the driving stability of organic electroluminescence devices using these has not been sufficient.

Causes of this drive deterioration include thermal deterioration due to the low glass transition temperature (Tg) of the hole blocking material, and electrochemistry in which the hole blocking material is reduced and oxidized due to injection of electrons and holes. Some factors have been pointed out.
High-efficiency phosphorescent devices such as iridium complexes include Balq (aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate) and SAlq (aluminum (III) bis (2-methyl-8-quinolinato) triphenylsilanolate). ) And other aluminum complex-based hole blocking materials have been actively used to achieve a certain long life (see Non-Patent Document 7). However, since these devices do not have sufficient hole blocking ability, the device luminous efficiency is insufficient, or some of the holes pass through the hole blocking material and escape to the electron transporting layer. There was a problem that oxidation deterioration occurred.
JP 2000-186066 A JP 2000-169448 A CS-262585 Japanese Patent Laid-Open No. 2-195683 JP-A-9-87616 Appl. Phys. Lett., 51, 913, 1987 J. Appl. Phys., 65, 3610, 1989 The 51st Japan Society of Applied Physics, 28a-PB-7, 1990 Nature, 395, 151, 1998 Appl. Phys. Lett., 75, 4 pages, 1999 Jpn. J.Appl. Phys., 38, L1502, 1999 Appl. Phys. Lett., 81, 162, 2002

For the reasons described above, rapid charge recombination in the light emitting layer and high emission efficiency of the dopant, or prevention of holes passing through the light emitting layer from escaping to the electron transport layer, and hole blocking material It is necessary for itself to have electrical oxidation-reduction durability, and further improvement studies have been desired for materials and device structures for producing devices with high luminous efficiency and stability.
In view of the above circumstances, the present inventor has provided an electron electrotransport property that is excellent in electron transport properties, has excellent electrical redox durability and a wide redox potential difference, and further has high efficiency and high driving stability. As a result of intensive studies aimed at providing an element, it was found that the above-mentioned problems can be solved by using a specific compound, and the present invention has been completed.

  That is, the present invention is an electron transport material represented by the following general formula (I):

(In the formula, ring A is a pyridine ring, and R ¹ and R ⁴ are optional substituents. R ² and R ³ each independently represent a hydrogen atom or an optional substituent.
N representing the number of rings A is an integer of 1 to 10, and Z represents a direct bond or an n-valent linking group. However, when n = 1, Z corresponds to any substituent bonded to ring A. When n ≧ 2, the plurality of R ^{1 to} R ⁴ contained in one molecule may be the same or different.

R ¹ to R ⁴ and Z do not include a diarylamine skeleton. )
And an organic electroluminescent device using the same. Further, the present invention resides in a compound represented by the following general formula (II), which does not have a planar structure when the compound has a most stabilized structure.

(In the formula, ring B is a pyridine ring.
R ⁵ and R ⁸ are an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.
R ⁶ and R ⁷ each independently represents a hydrogen atom or an arbitrary substituent.
m is an integer of 2 to 10 representing the number of rings B.
Z ₁ represents a direct bond, an m-valent aromatic hydrocarbon group or an aromatic heterocyclic group that bonds a plurality of rings B in one molecule.
A plurality of rings B contained in one molecule are conjugated via Z ₁ .
A plurality of R ^{5 to} R ⁸ contained in one molecule may be the same or different.
R ^{5 to} R ⁸ and Z ₁ do not contain a diarylamine skeleton. )
Since the compound represented by the general formula (II) is a structure that cannot substantially take a single planar structure as a molecular structure, π-π stacking interaction between molecules is suppressed, and the amorphous structure , Excellent in solubility and sublimation.

  In addition, when the film is an aggregate of molecules, it is possible to suppress the phenomenon that the absorption maximum wavelength and the fluorescence emission maximum wavelength increase compared to a solution state (a state in which molecules are scattered), Because it can suppress the phenomenon that the triplet excitation level is lowered and the phenomenon that the electric redox potential difference is lowered, it can store large energy (light, electricity, heat, etc.) and efficiently The stored energy can be released (as light, electricity, heat, etc.).

  Moreover, this invention exists in the compound represented by the following general formula (III).

^{(.Ar 11 ~Ar 13 .Ar 11 ~Ar} 13 is representative of the aromatic group wherein ring D is representative of the pyridine ring, each may be the same or different. Ring D, Ar ¹¹ ~ Ar ^{11 to} Ar ¹³ may have an aromatic hydrocarbon group as a substituent, in addition to Ar ^{13. The} aromatic hydrocarbon group has a substituent. (However, there is no pyridine ring other than ring D in the molecule.)
The compound represented by the general formula (III) has only one pyridine ring in the molecule, and
Since the 2,4,6-position is substituted with an aromatic group, it has a stable electron transport property and also has an excellent hole blocking property, without impairing the electron transport property. Excellent heat resistance and high triplet excitation standard can be realized.

  Since the charge transport material of the present invention has both high electron transport properties and hole blocking properties, it is effective for various applications. Further, by using such a compound in a layer provided in contact with the cathode side interface of the light emitting layer in the organic electroluminescent device, it is possible to obtain a device having high luminous efficiency and a long driving life.

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and the contents are not specified.
The electron transport material of the present invention is an electron transport material represented by the following general formula (I).

(In the formula, ring A is a pyridine ring, and R ¹ and R ⁴ are optional substituents. R ² and R ³ each independently represent a hydrogen atom or an optional substituent.
N representing the number of rings A is an integer of 1 to 10, and Z represents a direct bond or an n-valent linking group. However, when n = 1, Z corresponds to any substituent bonded to ring A. When n ≧ 2, the plurality of R ^{1 to} R ⁴ contained in one molecule may be the same or different. R ^{1 to} R ⁴ and Z do not include a diarylamine skeleton. )
The ring A in the general formula (I) is a pyridine ring having an arbitrary substituent (not having a diarylamine skeleton) at the 2,4,6-position. By using a pyridine ring having a substituent at the 2,4,6-position, it becomes an electron transport material having excellent electrical redox durability.

However, a hydrogen atom or an arbitrary substituent (not including a diarylamine skeleton) is applicable to the 3,5-position.
The hole blocking property, which is an important characteristic of the electron transport material of the present invention, is remarkably impaired when it has a diarylamine skeleton. Therefore, it is preferable that the skeleton does not contain the skeleton. Furthermore, although not as much as the diarylamine skeleton, it is more preferable that it does not contain an aryloxide skeleton or an arylsulfide skeleton because it has a strong hole transport property and lowers the hole blocking property. .

  The diarylamine skeleton in the present invention refers to an amine skeleton in which at least two arbitrary aromatic rings are substituted as substituents on the N atom, and examples thereof include a diphenylamine skeleton, a phenylnaphthyl skeleton, and a triphenylamine skeleton. Also included are those in which substituents are bonded to form a ring, and examples thereof include a carbazole skeleton, an N-phenylcarbazole skeleton, an N-phenylindole skeleton, etc. Excluding the skeleton to which is bound (eg acridine, phenazine, etc.). Each of them is one of skeletons having extremely strong hole transport properties.

  The aryloxide skeleton in the present invention refers to an oxide skeleton in which at least one aromatic ring is substituted as a substituent on the O atom, and examples thereof include a phenyloxide skeleton and a diphenyloxide skeleton. Also included are those in which substituents are bonded to form a ring, and examples thereof include a benzofuran skeleton, a dibenzofuran skeleton, and a dibenzo [1,4] dioxin skeleton. Each of them is one of skeletons having strong hole transport properties.

The aryl sulfide skeleton in the present invention refers to a sulfide skeleton in which at least one aromatic ring is substituted as a substituent on the S atom, and examples thereof include a phenyl sulfide skeleton and a diphenyl sulfide skeleton. Also included are those in which substituents are bonded to form a ring, and examples thereof include a benzothiophene skeleton, a dibenzothiophene skeleton, and a thianthrene skeleton. Any of them is one of skeletons having a strong hole transporting property.
(R ¹ ~R ⁴⁾
Any group (not having a diarylamine skeleton) can be applied to R ^{1 to} R ^{4 according to the} present invention as a substituent on ring A and Z (when n representing the number of ring A is 1) Z And each may be the same or different, and may be bonded to each other to form a ring.
For example,
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom),
An alkyl group which may have a substituent (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, 2-propyl, n-butyl, isobutyl, tert -Butyl group, etc.)
An alkenyl group which may have a substituent (for example, an alkenyl group having 1 to 8 carbon atoms, such as vinyl, allyl, 1-butenyl group, etc.),
An alkynyl group which may have a substituent (for example, an alkynyl group having 1 to 8 carbon atoms, such as ethynyl, propargyl group, etc.),
An aralkyl group which may have a substituent (for example, an aralkyl group having 1 to 8 carbon atoms, such as a benzyl group);
An acyl group which may have a substituent (preferably an acyl group having 1 to 8 carbon atoms which may have a substituent, for example, formyl, acetyl, benzoyl group, etc.),
An alkoxycarbonyl group which may have a substituent (preferably an alkoxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, methoxycarbonyl, ethoxycarbonyl group, etc.),
An aryloxycarbonyl group which may have a substituent (preferably an aryloxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, an acetoxy group),
Carboxyl group,

(R ^a is an arbitrary substituent, preferably an alkyl group having 1 to 8 carbon atoms, an aralkyl group, or an aryl group which may have a substituent. R ^b is a hydrogen atom or an arbitrary group. A substituent, preferably an alkyl group having 1 to 8 carbon atoms, an aralkyl group, or an aryl group, which may have a substituent.

(R ^c and R ^d are a hydrogen atom or an arbitrary substituent, and preferably represent any one of an optionally substituted alkyl group having 1 to 8 carbon atoms, an aralkyl group, and an aryl group),
A cyano group,
A silyl group which may have a substituent (for example, a trimethylsilyl group, a triphenylsilyl group, etc.),
An optionally substituted boryl group (for example, a dimesitylboryl group),
A phosphino group which may have a substituent (for example, a diphenylphosphino group and the like are included),
A C6-C20 aromatic hydrocarbon ring group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring) , Triphenylene ring, fluoranthene ring, etc.)
Or an aromatic heterocyclic group consisting of a 5- or 6-membered monocyclic ring or a 2-3 condensed ring which may have a substituent (eg, furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxalate ring, Diazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, and azulene ring))
Etc.

R ¹ , R ⁴ and Z (when n representing the number of rings A is 1) are preferably aromatic rings from the viewpoint of improving electrical redox durability and improving heat resistance, An example is shown below.

Above all,
R-1 to 9, 12, 18, 19, 21, 26, 28, 30, 31, 34, 35, 39, 43 are preferred,
R-1 to 6, 12, 43 are more preferable,
R-1 to 6 are more preferable,
R-1,4 is most preferred.

R ² and R ³ in the general formula (I) are preferably a hydrogen atom or a hydrocarbon group from the viewpoint of restricting molecular vibration and not impairing luminous efficiency when the compound is applied to a light emitting device. More preferably, they are a hydrogen atom, an alkyl group or an aryl group, and more preferably a hydrogen atom.
(Z)
When n representing the number of rings A is 2 or more, the linking group Z according to the present invention is applicable to a direct bond that connects the rings A to each other or any linking group (having no diarylamine skeleton). .

Preferably,
Direct bond,
An alkene group (a divalent group derived from an alkene) which may have a substituent,
Alkyne group (divalent group derived from alkyne) which may have a substituent,
An aromatic hydrocarbon group which may have a substituent (for example, derived from benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene, etc. n-valent group is included)
Or an aromatic heterocyclic group which may have a substituent (eg, furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine Ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc.)
Or a group formed by connecting two or more of these,
Etc.

  From the viewpoint of electrical redox durability, a compound in which two or more rings A contained in one molecule are conjugated with each other through a linking group Z is preferable. In order to obtain such a compound, a direct bond between ring A,

Or the case where it connects with the partial structure which combines these is preferable. (G ¹ to G ³ each independently represent a hydrogen atom or an arbitrary substituent, or constitute a part of the aromatic hydrocarbon ring or aromatic heterocyclic ring described above as an example of Z. G ¹ to G ³ contained in the Z group may be the same or different.)
Among these, between ring A is

Is more preferable, and it is particularly preferable that G ¹ and G ² constitute a part of the aromatic hydrocarbon group in the Z group.
Preferred examples of the linking group Z are shown below.

Above all, from the viewpoint of sufficiently widening the redox potential difference and the repeated redox durability,
Z-1 (direct bond), Z-2 to 69, 79, 82, 84, 89, 96, 103, 105, 108, 109, 111 to 114, 117, 118, 121, 124, 167, 170 are preferred,
Z-2, 8, 11-13, 15, 17, 19, 20, 22, 23-25, 27-30, 34, 37, 44, 47-61, 63-69, 89, 105, 109, 114, 124, 167, 170 are more preferable,
Z-2, 8, 12, 13, 15, 17, 19, 20, 22, 23, 25, 27-30, 34, 37, 44, 47-50, 63, 64, 66, 67, 89, 109, 114, 124, 167 are more preferred,
Z-2, 8, 12, 13, 15, 17, 19, 20, 23, 28 to 30, 34, 66 are most preferable.

The linking group Z in the above specific example may have an arbitrary substituent (having no diarylamine skeleton, aryloxide skeleton and arylsulfide skeleton),
For example,
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom),
An alkyl group which may have a substituent (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, 2-propyl, n-butyl, isobutyl, tert -Butyl group, etc.)
An alkenyl group which may have a substituent (for example, an alkenyl group having 1 to 8 carbon atoms, such as vinyl, allyl, 1-butenyl group, etc.),
An alkynyl group which may have a substituent (for example, an alkynyl group having 1 to 8 carbon atoms, such as ethynyl, propargyl group, etc.),
An aralkyl group which may have a substituent (for example, an aralkyl group having 1 to 8 carbon atoms, such as a benzyl group);
An acyl group which may have a substituent (preferably an acyl group having 1 to 8 carbon atoms which may have a substituent, for example, formyl, acetyl, benzoyl group, etc.),
An alkoxycarbonyl group which may have a substituent (preferably an alkoxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, methoxycarbonyl, ethoxycarbonyl group, etc.),
An aryloxycarbonyl group which may have a substituent (preferably an aryloxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, an acetoxy group),
Carboxyl group,

Group (R ^a is an arbitrary substituent, preferably an alkyl group having 1 to 8 carbon atoms, an aralkyl group or an aryl group which may have a substituent. R ^b is a hydrogen atom or an arbitrary group Which is preferably an alkyl group having 1 to 8 carbon atoms, an aralkyl group or an aryl group which may have a substituent.

Group ( ^Rc , ^Rd is a hydrogen atom or an arbitrary substituent, and preferably represents an alkyl group having 1 to 8 carbon atoms, an aralkyl group or an aryl group, which may have a substituent),
A cyano group,
A silyl group which may have a substituent (for example, a trimethylsilyl group, a triphenylsilyl group, etc.),
An optionally substituted boryl group (for example, a dimesitylboryl group),
A phosphino group which may have a substituent (for example, a diphenylphosphino group and the like are included),
An aromatic hydrocarbon ring group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. Included)
Or an aromatic heterocyclic group which may have a substituent (eg, furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine Ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring and the like))
From the viewpoint of limiting molecular vibration, a hydrogen atom, a methyl group, a phenanthyl group, or a phenyl group is more preferable, and a hydrogen atom is most preferable.

From the viewpoint of electrical repeated reduction durability, the linking group Z in the general formula (I) is preferably an arbitrary linking group capable of substantially conjugating the rings A to each other in the molecule. Any group can be used as long as it is a linking group capable of binding to the ring A.
The electron transport material of the present invention can exhibit the most excellent reduction durability when it has two or more pyridine rings that can be substantially conjugated to each other in the molecule, thereby providing excellent electron transport properties. To express. From such a viewpoint, n representing the number of the ring A is preferably an integer of 1 or more, more preferably 2 or more. On the other hand, when there are too many rings A, the tolerance with respect to oxidation will fall, or basicity will become high too much, stability in the air may fall, and the ease of refinement | purification operation may fall. From such a viewpoint, n representing the number of rings A is preferably 10 or less, more preferably 5 or less, still more preferably 3 or less, and most preferably 2 or less. On the other hand, when a plurality of rings A are conjugated in the molecule, hole acceptability appears, and the probability of oxidative degradation cannot be ignored in practice. When used for blocking applications, n representing the number of rings A is 1, or when n is 2 or more, it is particularly preferred that the rings A are non-conjugated.

The electron transport material according to the present invention can satisfy a wide range of redox potential difference, resistance to oxidation, resistance to reduction, and electron transport properties at a high level, except when the ring A is a hydrocarbon group other than the pyridine ring. This is particularly preferable because it can be performed.
From this point of view, R ¹ and R ⁴ are each independently particularly preferably a hydrocarbon group, and most preferably an aromatic hydrocarbon group. R ² and R ³ are particularly preferably a hydrogen atom or a hydrocarbon group, and most preferably an aromatic hydrocarbon group. Z is particularly preferably a direct bond or a hydrocarbon group, and most preferably an aromatic hydrocarbon group.

The molecular weight of the electron transport material of the present invention is usually 4000 or less, preferably 3000 or less, more preferably 2000 or less, and usually 200 or more, preferably 300 or more, more preferably 400 or more. If the molecular weight exceeds the upper limit value, the ease of purification may be reduced, or the sublimation property may be significantly reduced, which may hinder the use of vapor deposition when producing electroluminescent devices. If the value is lower than the lower limit, the glass transition temperature, melting point, vaporization temperature, etc. may decrease, or the crystallinity may become too high, so that the durability may be insufficient.

  Next, although the preferable specific example of the electron transport material of this invention is shown below, this invention is not limited to these.

The electron transport material of the present invention can be synthesized by selecting a raw material according to the structure of the target product and using a known method. For example,
A) When Z- (CHO) _n is used as a raw material,
1) Angew. Chem. Int. Ed. Engl. (1962) 1 , 626 and Synthesis (1976), 1-24 and J. Heterocyclic Chem. (1977) 14 , 147 and Collect. Czech.Chem.Commun. 57 ( 1992) 2, 385-392 and CS-262585, etc., 1 equivalent of aldehyde and 0.5 to 2 equivalents of acetylide in acetic acid (or alcohol) solvent in the presence of a strong acid such as sulfuric acid. The mixture is stirred for 1 to 10 hours at room temperature, or in the presence of a strong base such as sodium hydroxide in an alcohol and / or water solvent under heating conditions for 1 to 10 hours to obtain an intermediate (-CH = C
R-CO-), which is synthesized by reacting an acylpyridinium salt and ammonium acetate in an acetic acid solvent under heating conditions,

2) Boron trifluoride and the like disclosed in Liebigs Ann. Chem. (1974), 1415-1422, J. Org. Chem. 38 , (2002) 6, 830-832, and Japanese Patent Application Laid-Open No. 2000-186066. A method in which an aldehyde and acetylide are reacted in a toluene solvent under heating conditions in the presence of an oxidizing agent such as perchloric acid to form a pyrylium salt, which is reacted with ammonia in water or an alcohol solvent;

3) J. Am. Chem. Soc. (1952) 74 , 200, etc. discloses a one-step synthesis method from ammonium acetate, aldehyde, and acetylide under heating conditions in an acetic acid (or alcohol) solvent,

4) Chem. Commun. (Cambridge) (2000) 22 , 2199-2200, etc. In the presence of a strong base such as sodium hydroxide, aldehyde and 2 equivalents of acetylide are used in a mortar in the absence of solvent at room temperature. A method in which an intermediate (diketone) is produced by rubbing and then synthesized by reacting ammonium acetate in an acetic acid (or alcohol) solvent under heating conditions,

5) A method of synthesizing in one step from aldehyde and ethylidene vinylamine, disclosed in J. Org. Chem. (1988), 53, 5960, etc.

Etc. are applicable.
B) When a pyridine ring in which a halogen atom such as chlorine, bromine or iodine is substituted in at least one of the 2,4,6-positions is used as a raw material, the halogen element can be converted into an arbitrary substituent.
For example, there is a method disclosed in Org. Lett. 3 (2001) 26, 4263-4265 and the like, by synthesizing zinc bromide or boronic acid under heating conditions in the presence of a palladium catalyst.

C) In addition, in the introduction of various substituents and the formation of the linking group Z, known methods can be arbitrarily applied as necessary.
For example, when Z is a direct bond,
1) Paraformaldehyde is used as an aldehyde, and an aromatic acyl compound is used as an acetylide, and an aromatic ring group at the 2,6-position (in the present invention, an aromatic hydrocarbon group and an aromatic heterocyclic group are collectively referred to as “aromatic ring group”). Pyridine), and halogenating the 4-position of the pyridine ring using a halogenating agent such as N-bromosuccinimide to obtain a halogen compound, and the halogen atom is converted to -B ( OH) ₂ group, -ZnCl group or -MgBr group and the halogen compound and a method of synthesizing it by a coupling reaction,
2) The above halogen compound is lithiated with n-butyllithium or the like and then treated with N, N-dimethylformamide to have an aromatic ring group at the 2,6-position and a -CHO group at the 4-position. A method of synthesizing a pyridine ring having a second pyridine ring by reacting with acetylide,
3) By heating and stirring 2,6-dichloro-4-iodopyridine mentioned as the starting material of B) at 150 to 250 ° C. using a copper catalyst such as copper powder in the presence of a base, 2,6 , 2 ′, 6′-tetrachloro- [4,4 ′] bipyridyl, and a method of synthesizing it by treating in the same manner as in B above.

In addition, although the aldehyde (Ra-CHO) used at the time of a synthesis | combination can use a normally available reagent suitably, if needed,
1) For example, a halide (Ra-X) or a hydrocarbon compound having an active hydrogen atom (Ra-
H) is reacted with an alkyl lithium such as butyl lithium, a strong base such as sodium hydride, triethylamine, tert-butoxy potassium or sodium hydroxide (preferably an alkyl lithium such as butyl lithium), and then N, N-dimethylformamide (Organic & Biomolecular Chemistry (2003) 1, 7, 1157-1170; Tetrahedron Lett. 42 (2001) 37, 6589-6592),
2) -CO ₂ R group (R is hydrogen atom, chlorine atom, alkyl group, aromatic ring group, amino group) is reduced with lithium aluminum hydride, sodium borohydride, etc., and after alcoholation, pyridinium chlorochromate, dioxide Oxidation with manganese, iodoxybenzoic acid, peroxodisulfate, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, etc. to form -CHO (J. Med. Chem. ( 1990) 33, 2408-2412; Angew. Chem., Int. Ed. 40 (2001) 23,
4395-4397; J. Am. Chem. Soc. (2002) 124, 10, 2245-58; J. Am. Chem. Soc. (1993) 115,
9, 3 752-3759; J. Chem. Res., Synop. (2001) 7, 274-276; Synthesis (2001) 15,
2273-2276; Bull. Korean Chem. Soc. 20 (1999) 11, 1373-1374; Arzneim.-Forsch. 47
(1997) 1, 13-18; J. Org. Chem. 63 (1998) 16, 5658-5661; J. Chem. Soc. Sec. C; Organic (1968) 6, 630-632),
3) Reduce the -CO ₂ R group (where R is a hydrogen atom, chlorine atom, alkyl group, aromatic ring group, amino group) with lithium tris (dialkylamino) aluminum hydride, sodium tris (dialkylamino) aluminum hydride, etc. -CHO method in stages (Bull. Korean Chem. Soc., 13 (1992) 6, 670-676; Bull. Korean Chem. Soc., 12 (1991) 1, 7-8; Org.
Prep. Proced. Int. 24 (1992) 3,335-337),
4) A method in which —CO ₂ R group (where R is a hydrogen atom, chlorine atom, alkyl group, aromatic ring group, amino group) is made into —CHO in the presence of hydrogen and a palladium catalyst (Chem. Ber. (1959 ) 92, 2532-2542; WO 00/12457; Bull. Chem. Soc. Jpn. (2001) 74,1803-1815),
5) -CN group with lithium tris (dialkylamino) aluminum hydride, etc.
A method of reducing and converting to -CHO (Bull. Korean Chem. Soc., 13 (1992) 6,670-676;
6) Ar-CH ₃ group (Ar is an aromatic ring group) by reacting o-Iodylbenzoic acid, Dess-Martinperiodinane, Acetoxyiodosylbenzoic acid, etc., directly into Ar-CHO (J. Am. Chem. Soc.
(2002) 124, 10, 2245-58),
7) Ar-CH ₃ group (Ar is an aromatic ring group) converted to Ar-CH ₂ OH via Ar-CH ₂ Br and Ar-CH ₂ OAcO, then pyridinium chlorochromate, manganese dioxide, iodoxiben Oxidation with zoic acid or the like to form -CHO (J. Org. Chem. (1993) 58,3582-3585),
8) Method of synthesizing aryl carboxaldehyde by reacting 1-ethyl-1-arylallyl alcohol with Vilsmeier reagent (Indian Journal of Chemistry (1988) 27B, 213-216
),
9) A method of synthesizing aryl carboxaldehyde by reacting 1,4-Cyclohexadiene with Vilsmeier reagent (Synthesis (1987), 197-199; Synthesis (1985), 779-781)
10) After bromination of Ar-CH ₃ group (Ar is an aromatic ring group) using bromine, N-bromosuccinimide, etc. to make Ar-CH ₂ Br, 2-Nitropropanecarboanion reagent, Hexamethylenetetramine, etc. are allowed to act on Ar-CHO method (Collect.Czech. Chem. Commun. (1996) 61, 1464-1472; Chem. Eur. J. (1996) 2, 12,1585-1595; J. Chem. Research (S), (1999) 210-211),
11) A method for obtaining an aryl aldehyde (such as 1,3,5-triformylbenzene) from a polymethium salt (such as heptamethinium salt) (Collect. Czech. Chem. Commun. (1965) 30, 53-60),
12) A method of obtaining 1,3,5-triformylbenzene by self-condensation of triformylmethane (Collect.Czech. Chem. Commun. (1962) 27, 2464-2467),
13) Ar-CHO using Ar-CHBr ₂ groups (Ar is an aromatic ring group) using dialkylamine (Bulletinde La Societe Chmique De France (1966) 9, 2966-2971)
Etc. can be easily synthesized.

As the ketone (Rt—CO—CH ₂ —Rs) used in the synthesis of the compound of the present invention, a commonly available reagent can be appropriately used.
1) By treating Rt-CO ₂ R group (R is hydrogen atom, chlorine atom, alkyl group, aromatic ring group, amino group) with various alkylating agents (alkyl lithium, dimethyl sulfate, dimethyl sulfoxide, etc.), Rt -CO-CH ₂ Rs (J. Am. Chem. Soc. (1959), 81, 935-939; J. Am. Chem. Soc. (1961) 83, 4668-; Tetrahedron Lett. (1967) 1073-; J. Chem. Soc. (1960) 360-; J. Chem. Soc., Perkin Trans. 1 (1977) 680; JP5-5062039),
2) Synthesis by reacting an acylating agent such as acid chloride in the presence of a Lewis acid catalyst such as aluminum chloride (very common Friedel-Crafts reaction)
Etc. can be easily synthesized.

In addition, the target product is separated from the reaction product by filtration, extraction or concentration from the reaction product according to a conventional method, and the product of the present invention is purified by a method such as recrystallization or column chromatography as appropriate. Obtainable.
When applying the electron transport material of the present invention to an electroluminescent device,
1) When applied to an electron transport layer, the electron transport material of the present invention can be used alone, and if necessary, a trace amount of a hole transport material may be further mixed as long as the performance of the present invention is not impaired. It is also possible to use it.
2) When applied as a host material for the light-emitting layer, if the dopant has sufficient hole transportability, the electron transport material of the present invention can be used alone, but it is optional as long as the performance of the present invention is not impaired. It is preferable to use a hole transporting material in combination.

  When the electron transport material of the present invention is applied to an organic electroluminescent device, particularly excellent luminous efficiency and driving life are obtained when an organometallic complex that is a phosphorescent dye is used as a dopant in the light emitting layer. Among them, the effect is remarkable when the organometallic complex is one in which a ligand having a 2-arylpyridine skeleton and a metal element are linked by a carbon-metal sigma bond and a nitrogen-metal coordination bond. It is.

As the central metal, it is preferable that the light emission mechanism of the complex to be generated contains at least a charge transfer from the ligand orbital to the metal atom orbital.
The electron transport material of the present invention includes a ligand having a 2-arylaminopyridine skeleton, a dopant having a ligand having a 2-arylaminopyridine skeleton, the same layer (light emitting layer) and / or the dopant. When applied to a layer adjacent to the layer (a hole blocking layer and / or an electron transport layer), the electron transport material has a physicochemical similarity and an electrochemical similarity with a ligand containing a 2-arylpyridine skeleton. , The similarity of triplet excitation levels, etc. exerts an effect, improving the recombination efficiency of charges on the dopant, improving the energy transfer efficiency from the host molecule to the dopant, excitation between the light emitting layer and the hole blocking layer This is preferable because it reduces the probability of child inactivation.

Since the electron transport material in the present invention has high electron transport properties and hole blocking properties, it is suitable as an electron transport material for an electrophotographic photosensitive member, an organic electroluminescent device, a photoelectric conversion device, an organic solar cell, an organic rectifying device, and the like. Can be used.
Further, by using the electron transporting material, an organic electroluminescent element that has excellent heat resistance and can be stably driven (emitted) for a long period of time can be obtained. Therefore, it is suitable as an organic electroluminescent element material.

Next, the organic electroluminescent element of the present invention will be described.
The organic electroluminescent element of the present invention is characterized in that an anode, a light emitting layer, and a cathode are sequentially laminated, and has a layer containing the electron transport material of the present invention represented by the general formula (I).
In particular, in order to take advantage of the excellent electron transport property of the electron transport material of the present invention, the layer containing the electron transport material is a light emitting layer or an electron transporting layer provided between the light emitting layer and the cathode. Is preferred. In order to make use of the excellent hole blocking property of the electron transport material of the present invention, the layer containing the electron transport material may be a hole blocking layer provided in contact with the cathode side interface of the light emitting layer. preferable.

  In the organic electroluminescent element of the present invention, two or more kinds of the electron transport material of the present invention may be contained in the same layer, and when the present invention electron transport material is contained in two or more layers, The electron transport materials contained in these layers may be the same or different. The electron transport material of the present invention can be used as a host or hole blocking material of the light emitting layer in the device, but is more preferably used for both the host and hole blocking layer of the light emitting layer from the viewpoint of driving life. In this case, the electron transport materials used for the host and hole blocking layer of the light emitting layer may be the same or different. A plurality of them may be mixed.

In the organic electroluminescence device of the present invention, a layer provided between the cathode and the light emitting layer is referred to as an “electron transport layer”, and in the case of two or more layers, a layer in contact with the cathode is referred to as an “electron injection layer”, and other layers. The layers are collectively referred to as “electron transport layers”. Of the layers provided between the cathode and the light emitting layer, the layer in contact with the light emitting layer may be particularly referred to as a “hole blocking layer”.
Embodiments of the organic electroluminescent device of the present invention will be described below in detail with reference to the accompanying drawings, taking as an example the case where the electron transport material of the present invention is contained in a hole blocking layer.

FIG. 1 is a cross-sectional view schematically showing a structural example of a general organic electroluminescence device used in the present invention. 1 is a substrate, 2 is an anode, 4 is a hole transport layer, 5 is a light emitting layer, and 6 is a light emitting layer. A hole blocking layer, 8 represents a cathode.
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate, a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone, or a film is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

  An anode 2 is provided on the substrate 1, and the anode 2 plays a role of hole injection into the hole transport layer 4. The anode 2 is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, metal oxide such as oxide of indium and / or tin, metal halide such as copper iodide, carbon black, or poly It is composed of conductive polymers such as (3-methylthiophene), polypyrrole, and polyaniline. In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. Further, when the anode 2 is formed of metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, It can also be formed by dispersing and coating on the substrate 1. Further, when the anode 2 is formed of a conductive polymer, a polymerized thin film can be directly formed on the substrate 1 by electrolytic polymerization, or a conductive polymer can be applied to the substrate 1 (Appl). Phys. Lett., 60, 2711, 1992).

The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.
The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and if desired, it may be formed of metal to serve as the substrate 1.

  In the element having the configuration shown in FIG. 1, a hole transport layer 4 is provided on the anode 2. As conditions required for the material of the hole transport layer, it is necessary that the material has a high hole injection efficiency from the anode and can efficiently transport the injected holes. For this purpose, the ionization potential is small, the transparency to visible light is high, the hole mobility is high, the stability is high, and impurities that become traps are less likely to be generated during manufacturing and use. Required. Further, in order to contact the light emitting layer 5, it is required not to quench the light emitted from the light emitting layer or to form an exciplex with the light emitting layer to reduce the efficiency. In addition to the above general requirements, when the application for in-vehicle display is considered, the element is further required to have heat resistance. Therefore, a material having a Tg value of 85 ° C. or higher is desirable.

Examples of such a hole transport material include two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, and two or more Aromatics having a starburst structure such as aromatic diamines in which a condensed aromatic ring is substituted with a nitrogen atom (Japanese Patent Laid-Open No. 5-234681), 4,4 ', 4 "-tris (1-naphthylphenylamino) triphenylamine Group amine compounds (J. Lumin., 72-74, 985, 1997), aromatic amine compounds consisting of tetramers of triphenylamine (Chem. Commun., 2175, 1996), 2, 2 Spiro compounds such as', 7,7 "-tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth.
Metals, 91, 209, 1997). These compounds may be used alone or in combination as necessary.

In addition to the above compounds, polyarylene ether sulfone (Polym. Adv. Tech.) Containing polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953), and tetraphenylbenzidine as the material of the hole transport layer 4 is used. , 7, p. 33, 1996).
The hole transport layer 4 may be formed by a normal coating method such as a spray method, a printing method, a spin coating method, a dip coating method, or a die coating method, a wet film forming method such as various printing methods such as an ink jet method or a screen printing method, or a vacuum. It can be formed by a dry film formation method such as a vapor deposition method.

  In the case of the coating method, one or more hole transport materials are added, and if necessary, additives such as binder resins and coating property improving agents that do not trap holes are added and dissolved in a suitable solvent. A solution is prepared, applied onto the anode 2 by a method such as spin coating, and dried to form the hole transport layer 4. Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the binder resin is added in a large amount, the hole mobility is lowered.

In the case of the vacuum evaporation method, the hole transport material is put in a crucible installed in a vacuum vessel, the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then the crucible is heated, The hole transport material is evaporated and a hole transport layer 4 is formed on the substrate 1 on which the anode 2 is formed, which is placed facing the crucible.
The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and is usually 300 nm or less, preferably 100 nm or less. In order to uniformly form such a thin film, a vacuum deposition method is generally used.

In the element shown in FIG. 1, a light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is excited by recombination of holes injected from the anode and moving through the hole transport layer and electrons injected from the cathode and moved through the hole blocking layer 6 between the electrodes to which an electric field is applied. And formed from a luminescent compound that exhibits strong luminescence.
The light-emitting compound used for the light-emitting layer 5 has a stable thin film shape, exhibits high emission (fluorescence or phosphorescence) quantum yield in the solid state, and can efficiently transport holes and / or electrons. It must be a compound. Further, it is required to be a compound that is electrochemically and chemically stable and does not easily generate impurities as traps during production or use.

  As a material that satisfies such conditions and forms a light emitting layer that emits fluorescence, a metal complex such as an aluminum complex of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), 10-hydroxybenzo [h] quinoline Metal complexes (JP-A-6-322362), bisstyrylbenzene derivatives (JP-A-1-245087, JP-A-2-222484), bisstyrylarylene derivatives (JP-A-2-247278), (2- Hydroxyphenyl) benzothiazole metal complexes (Japanese Patent Laid-Open No. 8-315983), silole derivatives, and the like. These light emitting layer materials are usually laminated on the hole transport layer by a vacuum deposition method. Of the hole transport layer materials described above, an aromatic amine compound having a light emitting property can also be used as the light emitting layer material.

  The electron transport material of the present invention can also be used as the light emitting layer material. In that case, the general formula of the present invention is selected from other electron transporting materials and hole blocking materials represented by the known materials described above as materials that can be used for the hole blocking layer 6 or the electron transport layer 7. It is preferable to select and use a material having an ionization potential greater by 0.1 eV or more than the electron transport material represented by (I).

  Furthermore, in the organic electroluminescent device of the present invention, as described above, the electron transport material represented by the general formula (I) is provided on both the light emitting layer and the layer (for example, hole blocking layer) in contact with the cathode side interface of the light emitting layer. May be used, and is particularly preferable from the viewpoint of driving life. When the light emitting layer does not contain a dopant, an electron transport material having a difference in ionization potential of 0.1 eV or more is selected from the group consisting of the electron transport materials represented by the general formula (I), and What is necessary is just to use for a hole prevention layer, respectively. When the light emitting layer contains a dopant, an electron transport material larger than the ionization potential of the dopant by 0.1 eV or more is selected from the electron transport material group represented by the general formula (I), and the light emitting layer and the hole blocking layer are respectively Use it.

For the purpose of improving the light emission efficiency of the device and changing the emission color, for example, doping a fluorescent dye for laser such as coumarin with an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Phys., Volume 65). , 3610, 1989). This doping technique can also be applied to the light emitting layer 5, and various fluorescent dyes can be used as a doping material in addition to coumarin.
Examples of fluorescent dyes that emit blue light include perylene, pyrene, anthracene, coumarin, and derivatives thereof. Examples of the green fluorescent dye include quinacridone derivatives and coumarin derivatives. Examples of yellow fluorescent dyes include rubrene and perimidone derivatives. Examples of red fluorescent dyes include DCM compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene and the like.

Other than the above-mentioned fluorescent dyes for doping, depending on the host material, listed in Laser Research, 8, 694, 803, 958 (1980); 9, 9, 85 (1981). Fluorescent dyes and the like that can be used as a doping material for the light emitting layer.
The amount by which the fluorescent dye is doped with respect to the host material is preferably 10 ⁻³ wt% or more, more preferably 0.1 wt% or more. Moreover, 10 weight% or less is preferable and 3 weight% or less is more preferable. If the lower limit is not reached, it may not be possible to contribute to improving the luminous efficiency of the device. If the upper limit is exceeded, concentration quenching may occur, leading to a reduction in luminous efficiency.

On the other hand, a light-emitting layer that emits phosphorescence is usually formed including a phosphorescent dopant and a host material. Examples of the phosphorescent dopant include organometallic complexes containing a metal selected from Groups 7 to 11 of the periodic table, and charge transporting organic compounds having a T1 higher than the T1 (lowest excited triplet level) of the metal complex. It is preferable to use it as a host material.
Preferred examples of the metal in the phosphorescent organometallic complex containing a metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Preferred examples of these organometallic complexes include compounds represented by the following general formula (X) or general formula (VI).

(In the formula, M represents a metal, k represents a valence of the metal, L and L ′ represent a bidentate ligand, and j represents 0, 1 or 2.)

(In the formula, M ⁷ represents a metal, T represents carbon or nitrogen. When T is nitrogen, there is no R ¹⁴ or R ¹⁵ , and when T is carbon, R ¹⁴ or R ¹⁵ represents a hydrogen atom, a halogen atom, or an alkyl. Group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group, hydroxyl group, aryloxy group, substituent Represents an aromatic hydrocarbon group or an aromatic heterocyclic group.

R ¹² and R ¹³ are hydrogen atom, halogen atom, alkyl group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group , A hydroxyl group, an aryloxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and may be linked to each other to form a ring. )
In the general formula (X), the bidentate ligands L and L ′ each represent a ligand having the following partial structure.

(Ring A1 and Ring A1 ′ each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group, which may have a substituent. Ring A2 and Ring A2 ′ are nitrogen-containing aromatic heterocyclic groups. R ′, R ″, and R ′ ″ each represent a halogen atom; an alkyl group; an alkenyl group; an alkoxycarbonyl group; a methoxy group; an alkoxy group; an aryloxy group; (Amino group; diarylamino group; carbazolyl group; acyl group; haloalkyl group or cyano group)
More preferable examples of the compound represented by the general formula (X) include compounds represented by the following general formulas (Va), (Vb), and (Vc).

(Wherein M ⁴ represents a metal, k represents a valence of the metal, ring A 1 represents an aromatic hydrocarbon group which may have a substituent, and ring A 2 may have a substituent. Represents a good nitrogen-containing aromatic heterocyclic group.)

(In the formula, M ⁵ represents a metal, k represents a valence of the metal, ring A 1 represents an aromatic hydrocarbon group or aromatic heterocyclic group which may have a substituent, and ring A 2 represents a substituent. Represents a nitrogen-containing aromatic heterocyclic group which may have

(In the formula, M ⁶ represents a metal, k represents a valence of the metal, and j represents 0, 1 or 2. Ring A1 and ring A1 ′ each independently represents an aromatic group which may have a substituent. An aromatic hydrocarbon group or an aromatic heterocyclic group, and ring A2 and ring A2 ′ each independently represent a nitrogen-containing aromatic heterocyclic group which may have a substituent.)
As the ring A1 and ring A1 ′ of the compounds represented by the general formulas (Va), (Vb), (Vc), preferably a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, a thienyl group, a furyl group, a benzothienyl Group, benzofuryl group, pyridyl group, quinolyl group, isoquinolyl group, or carbazolyl group.

Ring A2 and ring A2 ′ are preferably a pyridyl group, pyrimidyl group, pyrazyl group, triazyl group, benzothiazole group, benzoxazole group, benzimidazole group, quinolyl group, isoquinolyl group, quinoxalyl group, or phenanthridyl group. Can be mentioned.
Examples of the substituent that the compounds represented by the general formulas (Va), (Vb) and (Vc) may have include a halogen atom such as a fluorine atom; a C 1-6 carbon atom such as a methyl group and an ethyl group An alkyl group; an alkenyl group having 2 to 6 carbon atoms such as a vinyl group; an alkoxycarbonyl group having 2 to 6 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; an alkoxy group having 1 to 6 carbon atoms such as a methoxy group and an ethoxy group; An aryloxy group such as a phenoxy group and a benzyloxy group; a dialkylamino group such as a dimethylamino group and a diethylamino group; a diarylamino group such as a diphenylamino group; a carbazolyl group; an acyl group such as an acetyl group; A haloalkyl group; a cyano group, and the like, which may be linked to each other to form a ring.

In addition, the substituent which ring A1 and the substituent which ring A2 has may combine, or the substituent which ring A1 'and the substituent which ring A2' may combine may form one condensed ring, Examples of such a condensed ring include a 7,8-benzoquinoline group.
As the substituent for ring A1, ring A1 ′, ring A2 and ring A2 ′, an alkyl group, an alkoxy group, an aromatic hydrocarbon group, a cyano group, a halogen atom, a haloalkyl group, a diarylamino group, or a carbazolyl group is more preferable. Can be mentioned.

M4 to M5 in the formulas (Va) and (Vb) are preferably ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold. M ⁷ in the formula (VI) is preferably ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold, and particularly preferably a divalent metal such as platinum or palladium.

  Specific examples of the organometallic complexes represented by the general formulas (X), (Va), (Vb) and (Vc) are shown below, but are not limited to the following compounds.

  Specific examples of the organometallic complex represented by the general formula (VI) are shown below, but are not limited to the following compounds.

  In addition, as mentioned above, from the point of the effect resulting from the affinity with the electron transport material of the present invention, ring A1 may have a substituent as the organometallic complex contained in the light emitting layer. Ligand L which is an aromatic hydrocarbon ring and ring A2 is an optionally substituted pyridine ring (that is, has a 2-arylpyridine skeleton), and / or ring A1 ′ has a substituent An aromatic hydrocarbon ring optionally having a ligand L ′ in which ring A2 ′ is a pyridine ring optionally having a substituent (that is, having a 2-arylpyridine skeleton) An organometallic complex represented by the formula (X) is preferable.

In particular,
i) Ring A1 is an optionally substituted aromatic hydrocarbon ring, and ring A2 is an optionally substituted pyridine ring (ie, having a 2-arylpyridine skeleton). A compound represented by the formula (Va):
ii) Ring A1 is an optionally substituted aromatic hydrocarbon ring, and Ring A2 is an optionally substituted pyridine ring (ie, having a 2-arylpyridine skeleton), A compound represented by the formula (Vb):
iii) Ring A1 is an optionally substituted aromatic hydrocarbon ring, and Ring A2 is an optionally substituted pyridine ring (ie, having a 2-arylpyridine skeleton), and / Or ring A1 ′ is an optionally substituted aromatic hydrocarbon ring, and ring A2 ′ is an optionally substituted pyridine ring (that is, having a 2-arylpyridine skeleton) ) And any of the compounds represented by formula (Vc) are particularly preferred.

The ring A2 and / or the ring A2 ′ is a pyridine ring which may have a substituent, and the ring A1 and / or the ring A1 ′ is R ¹ and / or R ⁴ in the general formula (I). Most preferred is the same ring structure.
The host material used for the light emitting layer exhibiting phosphorescence emission includes the materials described above as the host material used for the light emission layer exhibiting fluorescence emission (including the electron transport material of the present invention represented by the general formula (I)). In addition, carbazole derivatives such as 4,4′-N, N′-dicarbazole biphenyl (WO 00/70655), tris (8-hydroxyquinoline) aluminum (USP 6,303,238), 2 , 2 ′, 2 ″-(1,3,5-benzenetolyl) tris [1-phenyl-1H-benzimidazole] (Appl. Phys. Lett., 78
Volume, 1622, 2001), polyvinylcarbazole (Japanese Patent Laid-Open No. 2001-257076), and the like.

Furthermore, the light emitting layer in the organic electroluminescent element of the present invention may contain the above-described fluorescent dye together with the host material and the phosphorescent dopant.
The amount of the organometallic complex contained as a dopant in the light emitting layer is preferably 0.1% by weight or more, and more preferably 30% by weight or less. If the lower limit is not reached, it may not be possible to contribute to improving the luminous efficiency of the device. If the upper limit is exceeded, concentration quenching may occur due to the formation of a dimer between organometallic complexes, etc. There is.

  The amount of the phosphorescent dopant in the light emitting layer exhibiting phosphorescence tends to be preferably slightly larger than the amount of the fluorescent dye (dopant) contained in the light emitting layer in a conventional device using fluorescence (singlet). There is. When the fluorescent dye is contained in the light emitting layer together with the phosphorescent dopant, the amount of the fluorescent dye is preferably 0.05% by weight or more, and more preferably 0.1% by weight or more. Moreover, 10 weight% or less is preferable and 3 weight% or less is more preferable.

The thickness of the light emitting layer 5 is usually 3 nm or more, preferably 5 nm or more, and is usually 200 nm or less, preferably 100 nm or less.
The light emitting layer can also be formed by the same method as the hole transport layer. A method for doping the above-described fluorescent dye and / or phosphorescent dye (phosphorescent dopant) into the host material of the light emitting layer will be described below.

  In the case of coating, the above light emitting layer host material, a doping dye, and if necessary, additives such as a binder resin that does not serve as an electron trap or a light quenching quencher, and a coating property improving agent such as a leveling agent are added and dissolved. The applied coating solution is prepared, applied onto the hole transport layer 4 by a method such as spin coating, and dried to form the light emitting layer 5. Examples of the binder resin include polycarbonate, polyarylate, and polyester. If the amount of the binder resin added is large, the hole / electron mobility is lowered.

In the case of the vacuum deposition method, the host material is put in a crucible installed in a vacuum vessel, the dye to be doped is put in another crucible, and the inside of the vacuum vessel is 1.0 × 10 ⁻⁴ Torr with an appropriate vacuum pump. After evacuating to a degree, each crucible is heated and evaporated simultaneously to form a layer on the substrate placed opposite the crucible. As another method, a mixture of the above materials in a predetermined ratio may be evaporated using the same crucible.

When each said dopant is doped in a light emitting layer, although doped uniformly in the film thickness direction of a light emitting layer, there may exist concentration distribution in a film thickness direction. For example, it may be doped only in the vicinity of the interface with the hole transport layer, or conversely, it may be doped in the vicinity of the interface of the hole blocking layer.
The light emitting layer can also be formed by the same method as the hole transport layer, but usually a vacuum deposition method is used.

In addition, the light emitting layer 5 may contain components other than the above in the range which does not impair the performance of this invention.
In the element shown in FIG. 1, the hole blocking layer 6 is laminated on the light emitting layer 5 so as to be in contact with the cathode side interface of the light emitting layer 5.
The hole blocking layer has a role of blocking the holes moving from the hole transport layer from reaching the cathode, and a compound that can efficiently transport the electrons injected from the cathode toward the light emitting layer. Preferably it is formed. The physical properties required for the material constituting the hole blocking layer are required to have high electron mobility and low hole mobility. The hole blocking layer 6 has a function of confining holes and electrons in the light emitting layer and improving luminous efficiency.

In the element of the present invention, it is preferable to use the electron transport material of the present invention represented by the general formula (I) for the hole blocking layer. The electron transport material of the present invention may be used alone or in combination of two or more in the hole blocking layer. Furthermore, you may use together the compound which has a well-known hole-blocking function in the range which does not impair the performance of the electron transport material of this invention.
The ionization potential of the hole blocking layer used in the present invention is preferably at least 0.1 eV greater than the ionization potential of the light emitting layer (or the ionization potential of the dopant when the light emitting layer contains a host material and a dopant). (It is more preferable that the ionization potential is 0.1 eV or more larger than the ionization potential of the host material.) The ionization potential is defined by the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of the substance to the vacuum level. Is done. The ionization potential can be defined directly by photoelectron spectroscopy or can be determined by correcting the electrochemically measured oxidation potential relative to the reference electrode. In the case of the latter method, for example, when a saturated sweet potato electrode (SCE) is used as a reference electrode,
Ionization potential = oxidation potential (vs. SCE) + 4.3 eV
Defined by ("Molecular Semiconductors", Springer-Verlag, 1985, page 98).

  Furthermore, the electron affinity (EA) of the hole blocking layer used in the present invention is equivalent to the electron affinity of the light emitting layer (when the light emitting layer contains a host material and a dopant, the electron affinity of the host material). The above is preferable. Similarly to the ionization potential, the electron affinity is defined by the energy at which the electrons in the vacuum level fall to the LUMO (lowest unoccupied molecular orbital) level of the material and stabilize, with the vacuum level as a reference. The electron affinity can be obtained by subtracting the optical band gap from the above-mentioned ionization potential, or similarly obtained from the electrochemical reduction potential by the following formula.

Electron affinity = reduction potential (vs. SCE) +4.3 eV
Therefore, the hole blocking layer used in the present invention uses an oxidation potential and a reduction potential,
(Oxidation potential of hole blocking material) − (oxidation potential of light emitting material) ≧ 0.1V
(Reduction potential of hole blocking material) ≧ (Reduction potential of light emitting material)
It can also be expressed.

Further, in the case of an element having an electron transport layer described later, the electron affinity of the hole blocking layer is preferably equal to or less than that of the electron transport layer.
(Reduction potential of electron transport material) ≧ (Reduction potential of hole blocking material) ≧ (Reduction potential of light emitting material)
The thickness of the hole blocking layer 6 is usually 0.3 nm or more, preferably 0.5 nm or more, and is usually 100 nm or less, preferably 50 nm or less. The hole blocking layer can also be formed by the same method as the hole transporting layer, but usually a vacuum deposition method is used.

The cathode 8 serves to inject electrons into the light emitting layer 5 through the hole blocking layer 6. The material used for the cathode 8 can be the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection, such as tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy. Furthermore, inserting an ultra-thin insulating film (0.1-5 nm) such as LiF, MgF ₂ , Li ₂ O at the interface between the cathode and the light emitting layer or the electron transport layer is also an effective method for improving the efficiency of the device. (Appl. Phys. Lett., 70, 152, 1997; JP-A-10-74586; IEEE Trans. Electron. Devices, 44, 1245, 1997). The film thickness of the cathode 8 is usually the same as that of the anode 2. For the purpose of protecting the cathode made of a low work function metal, further laminating a metal layer having a high work function and stable to the atmosphere on the cathode increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used.

For the purpose of further improving the luminous efficiency of the device, an electron transport layer 7 may be provided between the hole blocking layer 6 and the cathode 8 as shown in FIGS. The electron transport layer 7 is formed of a compound that can efficiently transport electrons injected from the cathode between the electrodes to which an electric field is applied in the direction of the hole blocking layer 6.
Materials satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives, Styryl biphenyl derivative, silole derivative, 3- or 5-hydroxyflavone metal complex, benzoxazole metal complex, benzothiazole metal complex, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound No. 207169), phenanthroline derivatives (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide, n-type sulfide Examples include zinc and n-type zinc selenide.

Further, the electron transport material is doped with an alkali metal (described in Japanese Patent Application Laid-Open No. 10-270171, Japanese Patent Application No. 2000-285656, Japanese Patent Application No. 2000-285657, etc.), thereby improving the electron transport property. Therefore, it is preferable.
The electron transport layer 7 is formed by laminating on the hole blocking layer 6 by a coating method or a vacuum deposition method in the same manner as the hole transport layer 4. Usually, a vacuum deposition method is used.

The electron transport material of the present invention may be used for this electron transport layer 7. In that case, the electron transport layer 7 may be formed using only the electron transport material of the present invention, or may be used in combination with the various known materials described above.
When the electron transport material of the present invention is used for the electron transport layer 7, the electron transport material of the present invention may be used for the light emitting layer 5 and the hole blocking layer 6 described above, or only for the electron transport layer 7. The electron transport material of the present invention may be used, and other known hole blocking materials may be used for the hole blocking layer 6.

The thickness of the electron transport layer 6 is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.
The electron transport layer 7 is formed by laminating on the hole blocking layer 6 by a coating method or a vacuum deposition method in the same manner as the hole transport layer 4. Usually, a vacuum deposition method is used.
An anode buffer layer 3 is also inserted between the hole transport layer 4 and the anode 2 for the purpose of further improving the efficiency of hole injection and improving the adhesion of the entire organic layer to the anode. ing(
(See FIG. 3). By inserting the anode buffer layer 3, the driving voltage of the initial element is lowered, and at the same time, an increase in voltage when the element is continuously driven with a constant current is suppressed. As conditions required for the material used for the anode buffer layer, it is possible to form a uniform thin film with good contact with the anode and thermally stable, that is, the melting point and the glass transition temperature are high, and the melting point is 300 ° C. or higher. The glass transition temperature is preferably 100 ° C. or higher. Furthermore, the ionization potential is low, hole injection from the anode is easy, and the hole mobility is high.

For this purpose, porphyrin derivatives, phthalocyanine compounds (JP-A 63-295695), hydrazone compounds, alkoxy-substituted aromatic diamine derivatives, p- (9-anthryl) have been used as materials for the anode buffer layer 3 so far. ) -N, N'-di-p-tolylaniline, polythienylene vinylene, poly-p-phenylene vinylene, polyaniline (Appl. Phys. Lett., 64, 1245, 1994), polythiophene (OpticalMaterials, 9 Vol. 125, 1998), organic compounds such as starbust aromatic triamine (JP-A-4-308688), sputtered carbon film (Synth. Met. 91, 73, 1997) , Vanadium oxide, ruthenium oxide,
Metal oxides such as molybdenum oxide (J. Phys. D, 29, 2750, 1996) have been reported.

  In addition, a layer containing a hole injection / transporting low molecular organic compound and an electron accepting compound (described in JP-A-11-251067, JP-A-2000-159221, etc.), an aromatic amino group, etc. A layer obtained by doping the contained non-conjugated polymer compound with an electron-accepting compound as necessary (Japanese Patent Laid-Open Nos. 11-135262, 11-283750, 2000-36390, Examples include JP 2000-150168, JP-A 2001-223084, and WO 97/33193), or layers containing a conductive polymer such as polythiophene (JP-A 10-92584). It is not limited to.

As the anode buffer layer material, either a low molecular compound or a high molecular compound can be used.
Of the low molecular weight compounds, those often used include porphine compounds and phthalocyanine compounds. These compounds may have a central metal or may be metal-free. Preferred examples of these compounds include the following compounds:
Porphin
5,10,15,20-Tetraphenyl-21H, 23H-porphine
5,10,15,20-Tetraphenyl-21H, 23H-porphine cobalt (II)
5,10,15,20-Tetraphenyl-21H, 23H-porphine copper (II)
5,10,15,20-Tetraphenyl-21H, 23H-porphine zinc (II)
5,10,15,20-Tetraphenyl-21H, 23H-porphine vanadium (IV) oxide
5,10,15,20-Tetra (4-pyridyl) -21H, 23H-porphine
29H, 31H-phthalocyanine copper (II) phthalocyanine zinc (II) phthalocyanine titanium phthalocyanine oxide magnesium phthalocyanine lead phthalocyanine copper (II) 4,4'4 '', 4 '''-tetraaza-29H, 31H-phthalocyanine anode buffer layer In this case, a thin film can be formed in the same manner as the hole transport layer, but in the case of an inorganic material, a sputtering method, an electron beam evaporation method, or a plasma CVD method is further used.

When the anode buffer layer 3 formed as described above is formed using a low molecular weight compound, the lower limit is usually 3 nm, preferably about 10 nm, and the upper limit is usually 100 nm, preferably about 50 nm. is there.
When using a polymer compound, for example, the polymer compound or the electron-accepting compound, and if necessary, additives such as a binder resin and a coating agent such as a leveling agent that do not trap holes are added and dissolved. A coating solution is prepared, applied to the anode 2 by a normal coating method such as a spray method, a printing method, a spin coating method, a dip coating method, a die coating method, an ink jet method or the like, and dried to form the anode buffer layer 3. A thin film can be formed. Examples of the binder resin include polycarbonate, polyarylate, and polyester. Since the binder resin may reduce hole mobility when the content of the binder resin is large, it is desirable that the content of the binder resin in the anode buffer layer 3 is 50% by weight or less.

Alternatively, a thin film may be formed in advance on a medium such as a film, a support substrate, or a roll by the above-described thin film forming method, and the thin film on the medium is thermally or pressure transferred onto the anode 2. it can.
As described above, the lower limit of the film thickness of the anode buffer layer 3 formed using the polymer compound is usually 5 nm, preferably about 10 nm, and the upper limit is usually about 1000 nm, preferably about 500 nm.

  The organic electroluminescence device of the present invention has a structure opposite to that shown in FIG. 1, that is, a cathode 8, a hole blocking layer 6, a light emitting layer 5, a hole transport layer 4 and an anode 2 can be laminated on a substrate in this order. As described above, it is also possible to provide the organic electroluminescence device of the present invention between two substrates, at least one of which is highly transparent. Similarly, the layers can be stacked in the reverse order of the layer configuration shown in FIG. 2 or FIG. Moreover, in any layer structure of FIGS. 1-3, in the range which does not deviate from the meaning of this invention, it may have arbitrary layers other than the above-mentioned, and the layer which has the function of several said layers together By providing, it is possible to appropriately modify the layer structure, for example.

Alternatively, a top emission structure, a transmissive type using a transparent electrode for both the cathode and the anode, and a structure in which the layer configuration shown in FIG. 1 is stacked in multiple layers (a structure in which a plurality of light emitting units are stacked) are used. It is also possible. In this case, instead of the interfacial layer (between the light emitting units) (when the anode is ITO and the cathode is Al, the two layers) V2O5 or the like is used as the charge generation layer (CGL) as a barrier between the steps. From the viewpoint of luminous efficiency and driving voltage.

The present invention can be applied to any of an organic electroluminescent element having a single element, an element having a structure arranged in an array, and a structure having an anode and a cathode arranged in an XY matrix.
According to the organic electroluminescent element of the present invention, by including an electron transport material having a specific skeleton, an element having good color purity and greatly improved driving stability can be obtained. In particular, in a blue (fluorescent) light-emitting element or phosphorescent light-emitting element in which formation of a hole blocking layer has been difficult due to difficulty in material selection, an element excellent in luminous efficiency, emission color purity, and driving stability can be obtained. Therefore, it can exhibit excellent performance in application to full-color or multi-color panels.

  Among the electron transport materials of the present invention, a compound represented by the following general formula (II), which does not have a planar structure when the compound has the most stabilized structure, is the electron of the present invention. Although it is an example of the compound used for a transport material, it is a novel compound as well as an electron transport material.

In the formula, ring B is a pyridine ring.
R ⁵ and R ⁸ are an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.
R ⁶ and R ⁷ each independently represents a hydrogen atom or an arbitrary substituent.
m is an integer of 2 to 10 representing the number of rings B.
Z ₁ represents a direct bond, an m-valent aromatic hydrocarbon group or an aromatic heterocyclic group that bonds a plurality of rings B in one molecule.
A plurality of rings B contained in one molecule are conjugated via Z ₁ .
A plurality of R ^{5 to} R ⁸ contained in one molecule may be the same or different.
R ^{5 to} R ⁸ and Z ₁ do not contain a diarylamine skeleton.

That is, since the compound represented by the general formula (II) is a structure that does not substantially take a single planar structure as a molecular structure, π-π stacking interaction between molecules is suppressed,
Excellent in amorphousness, solubility and sublimation.
In addition, when the film is an aggregate of molecules, it is possible to suppress the phenomenon that the absorption maximum wavelength and the fluorescence emission maximum wavelength increase compared to a solution state (a state in which molecules are scattered), Because it can suppress the phenomenon that the triplet excitation level is lowered and the phenomenon that the electric redox potential difference is lowered, it can store large energy (light, electricity, heat, etc.) and efficiently The stored energy can be released (as light, electricity, heat, etc.).

The molecular weight of the compound represented by the general formula (II) is usually 4000 or less, preferably 3000 or less, more preferably 2000 or less, and usually 200 or more, preferably 300 or more, more preferably 400 or more.
If the molecular weight exceeds the upper limit, the sublimation property is significantly reduced, which may cause problems when using an evaporation method when producing an organic electroluminescent device, or the solubility in an organic solvent may be reduced, or the synthesis process. With the increase in impurity components generated in the process, it may be difficult to increase the purity of the material (that is, to remove the deterioration-causing substance). On the other hand, if the molecular weight is lower than the lower limit, the glass transition temperature, melting point, vaporization temperature and the like are lowered, so that the heat resistance may be significantly impaired.

The melting point of the compound represented by the general formula (II) is usually 100 ° C. or higher, preferably 120 ° C. or higher, usually 600 ° C. or lower, preferably 500 ° C. or lower. Exceeding the upper limit is not preferable because it may cause a decrease in sublimation and solubility, and if it is less than the lower limit, the heat resistance of the device may be decreased.
The glass transition point of the compound represented by the general formula (II) is usually 50 ° C. or higher, preferably 60 ° C. or higher. Below the lower limit, the heat resistance of the device may be lowered, which is not preferable.

The oxidation potential of the compound represented by the general formula (II) is usually +1.3 V or more, preferably +1.5 or more, usually +2.5 V or less, preferably +2.0 V or less. If the upper limit is exceeded, the drive voltage of the device may be increased, which is not preferable. If the lower limit is not reached, the hole blocking property is decreased, and the light emission efficiency may be decreased.
The reversibility in the electrode oxidation reaction is not particularly required and may be irreversible or reversible. However, when applied to a purpose of transporting positive charges, it is desirable that the reversibility criteria described in the present invention are cleared. .

The reduction potential of the compound represented by the general formula (II) is usually −1.6 to −2.6 V, preferably −1.8 to −2.4 V. Exceeding the upper limit is not preferable because the electron transport property is lowered, and if it is less than the lower limit, there is a possibility that the delivery of electrons to the light emitting material (phosphorescent dye) may be hindered.
The reversibility in the electrode reduction reaction is an important factor, and it is important that the reversibility criteria described in the present invention are cleared.

Here, the most stabilized structure of the compound referred to in the present invention is an ordinary MM2 calculation method (for example, co-authored by MJ Dudek, JW Ponder, “J. Compute. Chem.” (16, 791). -816 (1995))))) refers to the structure obtained by deriving the most stable structure of the organic compound of the present invention.
When the most stable structure is taken, not taking a planar structure means substantially not taking a single planar structure. For example, when two adjacent aromatic rings constituting a molecule have a planarity equivalent to that of biphenyl (FIG. C), it is said that they have a planar structure. More specifically, in the most stabilized structure, the face angle formed by any two adjacent aromatic rings constituting the molecule is strictly 30 degrees or less, more strictly 20 degrees or less, and more strictly 15 degrees. It is as follows.

(R ^5, R ⁸⁾
In the general formula (II), R ⁵ and R ⁸ represent any aromatic hydrocarbon group or aromatic heterocyclic group. The aromatic hydrocarbon group or the aromatic heterocyclic group may have a substituent.
As the aromatic hydrocarbon group or the aromatic heterocyclic group, an aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, A monovalent group derived from a 5- or 6-membered monocyclic ring or a 2-5 condensed ring, such as a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, or a fluoranthene ring)
Or an aromatic heterocyclic group which may have a substituent (for example, furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring , Pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, etc. Group included)
Etc.

R ⁵ and R ⁸ are preferably aromatic hydrocarbon groups.
The molecular weights of R ⁵ and R ⁸ including the substituents are each preferably 400 or less, more preferably 250 or less.
The substituent that these may have is not particularly limited as long as the performance of the compound of the present invention is not impaired, but preferably represents an alkyl group, an aromatic hydrocarbon group, or an alkyl-substituted aromatic hydrocarbon group. Specific examples thereof include alkyl groups having about 1 to 6 carbon atoms such as methyl, ethyl, isopropyl and tert-butyl groups; about 6 to 18 carbon atoms such as phenyl, naphthyl and fluorenyl groups. An alkyl-substituted aromatic hydrocarbon group having a total carbon number of about 7 to 30 such as a tolyl group, a mesityl group, and a 2,6-dimethylphenyl group.

Specific examples of R ₅ and R ₈ include R- ^{1 to} R-43 described in the above (R ^{1 to} R ⁴ ).
Among them, since groups that improve electrical redox durability and heat resistance are preferable, R-1 to 9, 12, 18, 19, 21, 26, 28, 30, 31, 34, 35, 39, 43 are Preferably
R-1 to 6, 12, 43 are more preferable,
R-1 to 6 are more preferable,
R-1 is most preferred.
(R ^6, R ⁷⁾
R ⁶ and R ⁷ each independently represents a hydrogen atom or an arbitrary substituent.
Examples thereof are the same as those described in (R ^{1 to} R ⁴ ) above.

The molecular weights of R ⁶ and R ⁷ including the substituents are each preferably 400 or less, more preferably 250 or less.
R ⁶ and R ⁷ are preferably a hydrogen atom, an alkyl group, or an aryl group from the viewpoint of restricting molecular vibrations and not impairing luminous efficiency when the compound is applied to a light-emitting device. The case where it is a C1-C4 alkyl group is more preferable.

R ^{5 to} R ⁸ may be connected to each other to form a ring.
(Z ₁ )
Z ₁ represents a direct bond, or a linking group which is an m-valent aromatic hydrocarbon group or aromatic heterocyclic group, which bonds a plurality of rings B in one molecule. Further, the rings B in one molecule are conjugated with each other through Z ₁ .

Examples when Z ₁ is an m-valent aromatic hydrocarbon group or aromatic heterocyclic group are as follows.
An aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. Of m-valent groups)
An aromatic heterocyclic group which may have a substituent (for example, furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring) , A quinoline ring, an isoquinoline ring, a sinoline ring, a quinoxaline ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, an azulene ring, etc.).
Alternatively, a group formed by linking two or more of these may be used.

Z ₁ is preferably an aromatic hydrocarbon group.
The substituent that the aromatic hydrocarbon group and the aromatic heterocyclic group may have is not particularly limited as long as the performance of the compound of the present invention is not impaired, but preferably an alkyl group, an aromatic hydrocarbon group, Or represents an alkyl-substituted aromatic hydrocarbon group. Specific examples thereof include alkyl groups having about 1 to 6 carbon atoms such as methyl, ethyl, isopropyl and tert-butyl groups; about 6 to 18 carbon atoms such as phenyl, naphthyl and fluorenyl groups. An alkyl-substituted aromatic hydrocarbon group having a total carbon number of about 7 to 30 such as a tolyl group, a mesityl group, and a 2,6-dimethylphenyl group.

As preferable specific examples of Z _1, of Z- ₁ to Z-173 exemplified in the above (Z),
A direct bond, an aromatic hydrocarbon group or an aromatic heterocyclic group. Among them, preferred examples are also the same as the above (Z) (except that they are not a direct bond, an aromatic hydrocarbon group or an aromatic heterocyclic group).
The molecular weight of Z ₁ including the substituent is preferably 400 or less, more preferably 250 or less.

Here, a preferable molecular structure of the compound represented by the general formula (II) will be described. Preferred example 1)
The compound represented by the general formula (II) has at least two rings B and a linking group Z ₁ that are on the same plane when the compound has the most stabilized structure. From the viewpoint of not impairing the properties and excellent charge transportability. In this case, when there are only two rings B in one molecule, at least one of the substituents of the ring B and / or Z ₁ may not be on the same plane.

  Examples of such ring B include the following.

In this case, Z ₁ is not particularly limited as long as it is an aromatic hydrocarbon group or an aromatic heterocyclic group. Specifically, Z-1 (direct bond) exemplified in the above (Z), Z-2, 3, 6, 19, 22, 34, 35, 36, 39, 44, 47, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 74, 79, 85, 86, 90, 91, 92, 94, 97, 98, 104, 105, 106, 107, 109, 112, 113, 114, 133, 134, 149, 150, 152, 153, 166 are preferred,
Z-1 (direct bond), Z-2, 3, 6, 19, 22, 34, 35, 36 are more preferred,
Z-2, 19, 22, and 34 are more preferable,
Z-2 is most preferred.

Z ₁ , R ⁵ and R ⁸ have the same meaning as in the general formula (II). Z ₁ , R ⁵ and R ⁸ are each preferably an aromatic hydrocarbon group.
Specific examples of the compound represented by the general formula (II) include

Etc.
Preferred example 2)
The compound represented by the general formula (II) has a wide electric redox potential difference that when the compound has the most stabilized structure, the arbitrary ring B is not substantially on the same plane as the linking group Z _1. In view of the above, it is desirable from the viewpoint of a high triplet excitation level.

  As ring B,

Z < ₁ > and R < ⁵ > -R < ⁸ > are synonymous with the said general formula (II).
In this case, as Z ₁ , Z-1 (direct bond) exemplified in the above (Z), Z-2 to 48, 63 to 69, 79, 82, 84, 89, 96, 103, 105, 108, 109 , 111-114, 117, 118, 121, 124, 167, 170 are preferred,
Z-1 (direct bond), Z-2, 4-13, 15, 17, 19, 20, 22, 23-25, 27-31, 34, 37, 38, 40, 44, 47, 48, 89, 105 is more preferable,
Z-2, 4, 5, 7 to 11, 34, 38, 40 are more preferable,
Z-2 is most preferred.

  Specific examples of the compound represented by the general formula (II) include

Etc.
It should be noted that when the compound has the most stabilized structure, the arbitrary ring B is not on the same plane as the linking group Z _{1. The} above example when the compound has a planar structure can be considered in reverse. .
Specifically, when two adjacent aromatic rings constituting a molecule have non-planarity comparable to that of 2-methylbiphenyl (FIG. D), they are not on the same plane.

More specifically, in the most stabilized structure, the face angle formed by any two adjacent aromatic rings constituting the molecule is strictly 15 degrees or more, more strictly 20 degrees or more, more strictly 30 degrees. That's all.
Furthermore, any other aromatic ring (referred to as Ar2) bonded to at least one aromatic ring (referred to as Ar1) in the molecule and an optional substituent (referred to as Rr) in Ar1 are adjacent to each other. It is desirable to be substituted. However, Rr may be bonded to Ar1 or another substituent to form a ring.

Examples of such include the following.

  The molecular weight of the compound represented by the general formula (II) is usually 4000 or less, preferably 3000 or less, more preferably 2000 or less, and usually 200 or more, preferably 300 or more, more preferably 400 or more. If the molecular weight exceeds the upper limit, the sublimation property is significantly reduced, which may cause problems when using an evaporation method when producing an electroluminescent device, or the solubility in an organic solvent may be reduced, or in the synthesis process. As the amount of impurity components increases, it may be difficult to increase the purity of the material (that is, to remove the deterioration-causing substances). When the molecular weight is below the lower limit, the glass transition temperature, melting point, vaporization temperature, etc. Since it falls, there exists a possibility that heat resistance may be impaired remarkably.

The melting point of the compound represented by the general formula (II) is usually 100 ° C. or higher, preferably 120 ° C. or higher, usually 500 ° C. or lower, preferably 600 ° C. or lower.
The glass transition point of the compound represented by the general formula (II) is usually 50 ° C. or higher, preferably 60 ° C. or higher.
The oxidation potential of the compound represented by the general formula (II) is usually +1.3 V or more, preferably +1.5 V or more, usually +2.2 V or less, preferably +2.0 V or less.

The reversibility in the electrode oxidation reaction is not particularly required and may be irreversible or reversible. However, when applied to a purpose of transporting positive charges, it is desirable that the reversibility criteria described in the present invention are cleared. .
The reduction potential of the compound represented by the general formula (II) is usually −1.6 to −2.6 V, preferably −1.8 to −2.4 V.

  The compound of the present invention is represented by the following general formula (III).

^{(.Ar 11 ~Ar 13 .Ar 11 ~Ar} 13 is representative of the aromatic group wherein ring D is representative of the pyridine ring, each may be the same or different. Ring D, Ar ¹¹ ~ Ar ^{11 to} Ar ¹³ may have an aromatic hydrocarbon group as a substituent, in addition to Ar ^{13. The} aromatic hydrocarbon group has a substituent. (However, there is no pyridine ring other than ring D in the molecule.)
Since the compound represented by the general formula (III) has only one pyridine ring in the molecule, and its 2,4,6-position is substituted with an aromatic hydrocarbon group, In addition to having excellent transportability, it has excellent hole blocking properties, and has a condensed aromatic hydrocarbon group in the molecule, so it has excellent heat resistance without impairing electron transport properties. High triplet excitation levels can also be realized.

The molecular weight of the compound represented by the general formula (III) is preferably 200 or more, more preferably 300 or more, particularly preferably 400 or more, preferably 4000 or less, more preferably 3000 or less, particularly preferably 2000 or less. .
The compound represented by the general formula (III) preferably has no arylamino group in the molecule so as not to lower the hole blocking property.

Ar ^{11 to} Ar ¹³ represent an aromatic group. Ar ^{11 to} Ar ¹³ may be the same as or different from each other. Preferably, Ar ^{11 to} Ar ¹³ are each a phenyl group for high triplet excitation levels and excellent electrochemical resistance.
The molecular weight of each of Ar ^{11 to} Ar ¹³ is preferably 10 or more, more preferably 50 or more, preferably 400 or less, more preferably 250 or less. The aromatic group includes an aromatic hydrocarbon group and an aromatic complex. Although a cyclic group is mentioned, an aromatic hydrocarbon group is preferable because of its high triplet excited level and excellent electrochemical durability.

Examples of the aromatic hydrocarbon group include groups derived from a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring and the like. Of these, a phenyl group is preferred because of its high triplet excited level and excellent electrochemical durability.
Aromatic heterocyclic groups include furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, cinnoline ring, quinoxaline And a group derived from a ring, a perimidine ring, a quinazoline ring, a quinazolinone ring, an azulene ring, and the like.

Ar ^{11 to} Ar ¹³ may have an aromatic hydrocarbon group as a substituent. Each substituent of Ar ^{11 to} Ar ¹³ may be the same or different.
Aromatic hydrocarbon group as the substituent of Ar ¹¹ to Ar ¹³ are the same as those described above Ar ¹¹ to Ar ¹³ are mentioned as examples of the case where the aromatic hydrocarbon group.

The aromatic hydrocarbon group as a substituent for Ar ^{11 to} Ar ¹³ may further have a substituent. Preferably, it is a substituent having a molecular weight of about 300 or less, and examples thereof include a phenyl group, a naphthyl group, a biphenyl group, a phenanthyl group, a triphenylenyl group, and a terphenylyl group.
Ring D may have a substituent other than Ar ^{11 to} Ar ¹³ . Examples of the substituent include an alkyl group and a phenyl group. Ring D preferably has no substituent other than Ar ^{11 to} Ar ¹³ .

Among the compounds represented by the general formula (III), the compound represented by the general formula (III-1) is particularly electrically oxidized because the rings D and E ^{1 to} E ³ can be substantially on the same plane. This is preferable because it is excellent in durability against reduction and heat resistance.

^{(Wherein, .Ar 21 ~Ar 29 Ar 21 ~Ar} 29 is representing a hydrogen atom or an aromatic hydrocarbon group,
Each may be the same or different. Ar ^{21 to} Ar ²⁹ may be bonded to each other to form a condensed aromatic hydrocarbon group. Ring D may have a substituent other than rings E ^{1 to} E ³ . Rings E ^{1 to} E ³ may have a substituent other than Ar ^{21 to} Ar ²⁹ . )
Ar ^{21 to} Ar ²⁹ represent a hydrogen atom or an aromatic hydrocarbon group. Ar ^{21 to} Ar ²⁹ may be the same or different from each other. Preferably, Ar ²² , Ar ²⁵ and Ar ²⁸ are hydrogen atoms, and at least one of Ar ²¹ , Ar ²³ , Ar ²⁴ , Ar ²⁶ , Ar ²⁷ and Ar ²⁹ is an aromatic hydrocarbon group. More preferably, at least two or more of Ar ²¹ , Ar ²³ , Ar ²⁴ , Ar ²⁶ , Ar ²⁷ and Ar ²⁹ are aromatic hydrocarbon groups.

The molecular weight of each of Ar ^{21 to} Ar ²⁹ is preferably 50 or more, more preferably 70 or more, preferably 500 or less, more preferably 300 or less. Examples of the aromatic hydrocarbon group include benzene ring, naphthalene ring, and anthracene. And groups derived from a ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, a fluoranthene ring, and the like. Among them, a phenyl group and a phenanthyl group are preferable because of improved heat resistance, high triplet excited level, and excellent electrochemical durability.

Ar ^{21 to} Ar ²⁹ may be bonded to each other to form a condensed aromatic hydrocarbon group with the rings E ^{1 to} E ³ . Examples of the condensed aromatic hydrocarbon group include a naphthyl group, a phenethyl group, a triphenylenyl group, and an anthryl group. Among them, a phenanthyl group and a triphenylenyl group are preferable because of a high triplet excitation level.

Ar ^{21 to} Ar ²⁹ may further have a substituent. Preferably, it is a substituent having a molecular weight of about 300 or less, and examples thereof include an alkyl group, a phenyl group, a naphthyl group, and a phenanthyl group.
Each of the rings E ^{1 to} E ³ may have a substituent other than Ar ^{21 to} Ar ²⁹ . Examples of the substituent include an alkyl group, a phenyl group, a naphthyl group, and a phenanthyl group. Ring D preferably has no substituent other than rings E ^{1 to} E ³ , and rings E ^{1 to} E ³ preferably have no substituent other than Ar ^{21 to} Ar ²⁹ . The reason for this is that when the ring D and the rings E ^{1 to} E ³ all have substantially the same plane, the most excellent electrical redox stability is exhibited.

The compounds represented by the general formulas (II) and (III) can be synthesized by the method described as the method for synthesizing the electron transport material of the present invention.
The compound of the present invention is suitable as an electron transport material for an organic electroluminescent device because it has an essentially excellent redox stability, but is not limited to an organic electroluminescent device, but can be used for an electrophotographic photoreceptor. Is also useful.

  Furthermore, the compound of the present invention is excellent in amorphousness, solubility, heat resistance and durability in addition to the high performance of the electron transport material of the present invention. Therefore, not only for electron transport materials, but also for luminescent materials, solar cell materials, battery materials (electrolytes, electrodes, separation membranes, stabilizers, etc.), medical, coating materials, coating materials, organic semiconductors It is also useful for materials, toiletries, antistatic materials, thermoelectric element materials, and the like.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.
Example 1

Terephthalaldehyde (2.0 g), acetophenone (7.2 g), ammonium acetate (30 g), and acetic acid (75 ml) were stirred for 80 minutes under heating reflux. The obtained solution was extracted with methylene chloride and purified by silica gel column chromatography to obtain the target product 1 (0.4 g). It was confirmed to be the target product 1 by DEI-MS (m / z 536 (M +)) and ¹ H-NMR.

¹ H-NMR (270 MHz, CDCl3), 8.26-8.21 (m, 8H), 7.96 (s, 4H), 7.92 (s, 4H), 7.58-7.44 (m,
12H)
As a result of TG-DTA measurement, the melting point of this compound was 290 ° C., the vaporization temperature was 458 ° C., and the glass transition temperature was 100 ° C.
(Example 2)

  While stirring terephthalaldehyde (3.9 g), acetophenone (10.6 g), concentrated sulfuric acid (9.4 ml) and acetic acid (84 ml) in the atmosphere at room temperature for 5.5 hours, with stirring Water (100 ml) and methanol (30 ml) were added, and the deposited precipitate was filtered and washed with water and methanol. Further, the suspension was washed in methanol (150 ml) and dried under reduced pressure to obtain the intended product 2 (9.9 g).

  The desired product 2 (6.9 g), 1-phenacylpyridinium bromide (17.1 g), ammonium acetate (78.6 g), acetic acid (230 ml), N, N-dimethylformamide (230 ml) were heated under reflux. Water (80 ml) and methanol (20 ml) were added to the resulting solution with stirring for a period of time, and the deposited precipitate was filtered, washed with methanol (3 × 50 ml), and then reconstituted from chloroform-toluene-ethanol. Purification by crystals gave the target product 1 (6.8 g).

As a result of DEI-MS measurement, it was confirmed that the obtained product was the target product 1 as in Example 1.
(Example 3)

  Concentrated sulfuric acid (8.0 ml) was added to a mixture of isophthalaldehyde (2.7 g), acetophenone (9.6 g) and acetic acid (57 ml) in the atmosphere at room temperature, and the mixture was stirred at room temperature for 6 hours. Methanol (50 ml) was added to the resulting solution and stirred, and then the precipitate was filtered and washed with methanol to obtain the desired product 3 (2.6 g).

In a nitrogen stream, the target compound 3 (2.6 g), 1-phenacylpyridinium bromide (6.3 g), ammonium acetate (29 g), acetic acid (130 ml), N, N-dimethylformamide (130 ml) were heated under reflux. The mixture was stirred for 8.5 hours, and water (80 ml) and methanol (80 ml) were added to the resulting solution and stirred. The deposited precipitate was filtered, washed with methanol, and then purified by recrystallization from toluene-ethanol to obtain the desired product 4 (1.7 g). It was confirmed to be the target product 4 from EI-MS (m / z = 536 (M +)) and ¹ H-NMR.

¹ H-NMR (270 MHz, CDCl3), 8.25-8.21 (m, 8H), 8.06 (t, 1H), 7.96 (s, 4H), 7.87-7.83 (dd,
2H), 7.73-7.68 (dd, 1H), 7.56-7.43 (m, 12H)
The melting point of this compound was 205 ° C., the vaporization temperature was 414 ° C., and the glass transition temperature was 79 ° C.
Example 4

9-anthracenecarboxaldehyde (4.1 g), acetophenone (4.8 g), ammonium acetate (20 g), and acetic acid (50 ml) were stirred for 5.2 hours while heating under reflux. The obtained solution was extracted with toluene, washed with water, and purified by silica gel column chromatography to obtain the intended product 5 (0.40 g). From DEI-MS (m / z 407 (M +)) and ¹ H-NMR, it was confirmed to be the target product 5.

¹ H-NMR (270 MHz, CDCl3), 8.58 (s, 1H), 8.27-8.22 (m, 4H), 8.11-8.08 (d, 2H), 7.84 (s,
2H), 7.76-7.73 (d, 2H), 7.56-7.36 (m, 10H)
As a result of TG-DTA measurement, this product had a melting point of 220 ° C. and a vaporization temperature of 382 ° C. (Example 5)

  To a mixture of isophthalaldehyde (2.7 g), α-tetralone (8.8 g) and acetic acid (57 ml) was added concentrated sulfuric acid (6.4 ml) at room temperature in the atmosphere, and the mixture was stirred at room temperature for 6.5 hours. Water (100 ml) and ethanol (100 ml) were added to the resulting solution and stirred, and then the precipitate was filtered and washed with ethanol to obtain the desired product 6 (6.5 g).

In a nitrogen stream, target product 6 (6.5 g), 1-phenacylpyridinium bromide (14 g), ammonium acetate (65 g), acetic acid (240 ml), N, N-dimethylformamide (240 ml) were heated under reflux for 18 hours. The resulting solution was allowed to cool and the deposited precipitate was filtered, washed with ethanol, washed with suspension in ethanol under heating, and further purified by recrystallization from toluene-pyridine-ethanol, The target product 7 (2.0 g) was obtained. It was confirmed to be the target product 7 from EI-MS (m / z = 588 (M +)) and ¹ H-NMR.

¹ H-NMR (270 MHz, CDCl3), 8.60-8.57 (dd, 2H), 8.21-8.18 (td, 4H), 7.66 (s, 2H), 7.64-7.61 (d, H), 7.53-7.32 (m, 13H), 7.27-7.16 (m, 2H), 3.05-2.89 (m, 8H)
(Example 6)

Terephthalaldehyde (4.0 g), α-tetralone (13 g), concentrated sulfuric acid (9.6 ml)
), Acetic acid (86 ml) in the atmosphere at room temperature for 5.3 hours, water (50 ml) and methanol (100 ml) were added with stirring, and the deposited precipitate was filtered and washed with methanol did. Further, the suspension was washed in methanol (120 ml) and dried under reduced pressure to obtain the desired product 8 (11 g).

The desired product 8 (3.9 g), 1-phenacylpyridinium bromide (8.3 g), ammonium acetate (39 g), acetic acid (140 ml), N, N-dimethylformamide (140 ml) were heated to 9.3 under reflux. Water (150 ml) and methanol (100 ml) were added with stirring to the resulting solution, and the deposited precipitate was filtered, washed with methanol (3 × 50 ml), and then heated under reflux in chloroform-methanol. The suspension was washed, and further purified by reprecipitation from toluene-pyridine-ethanol to obtain the intended product 9 (1.1 g). It was confirmed to be the target product 9 by EI-MS (m / z = 588 (M +)) and ¹ H-NMR.

¹ H-NMR (270 MHz, CDCl3), 8.62-8.57 (d, 4H), 8.23-8.20 (d, 4H), 7.68 (s, 2H), 7.56-7.16 (m, 14H), 3.07-2.90 (m, 8H)
(Example 7)

  To a solution obtained by stirring terephthalaldehyde (1.3 g), 2-acetylnaphthone (3.4 g), concentrated sulfuric acid (3.2 ml), and acetic acid (29 ml) at room temperature in the atmosphere for 7 hours, stirring While adding water (30 ml) and ethanol (100 ml), the deposited precipitate was filtered and washed with methanol. Further, under heating, suspended and washed in an ethanol solvent and a chloroform-toluene solvent, and dried under reduced pressure, the target product 10 (2.7 g) was obtained.

The target product 10 (2.7 g), 1-phenacylpyridinium bromide (5.2 g), ammonium acetate (24 g), acetic acid (100 ml), N, N-dimethylformamide (100 ml) were stirred with heating under reflux for 8 hours. Water (30 ml) and ethanol (120 ml) were added to the resulting solution with stirring, and the deposited precipitate was filtered, washed with ethanol, purified by recrystallization from toluene-pyridine, and the target compound 11 ( 2.0 g) was obtained. It was confirmed to be the target compound 11 from DEI-MS (m / z = 636 (M +)) and ¹ H-NMR.

¹ H-NMR (270 MHz, CDCl3), 8.71 (br s, 2H), 8.43-8.40 (dd, 2H), 8.30-8.27 (td, 4H), 8.13-8.12 (d, 2H), 8.03-7.99 (m , 10H), 7.94-7.90 (m, 2H), 7.60-7.47 (m, 10H)
(Example 8)

  While stirring, a solution obtained by stirring isophthalaldehyde (4.0 g), 1-acetonaphthone (15.3 g), concentrated sulfuric acid (9.6 ml) and acetic acid (86 ml) in the atmosphere at room temperature for 6 hours was stirred. Water (100 ml) and methanol (50 ml) were added, and the precipitated oil was dissolved by adding toluene. After extraction, the toluene layer was washed with an aqueous sodium hydrogen carbonate solution, an aqueous sodium chloride solution and water. The toluene layer was concentrated and purified by silica gel column chromatography to obtain the oily target product 12 (13 g).

  The desired product 12 (5.0 g), 1-phenacylpyridinium bromide (9.5 g), ammonium acetate (43.9 g), acetic acid (110 ml), N, N-dimethylformamide (110 ml) were heated under reflux. The solution obtained by stirring for a period of time was poured into water (250 ml), and the deposited precipitate was filtered, washed with methanol (300 ml), and then purified by silica gel column chromatography to obtain the desired product 13 (1.75 g). Obtained.

From DEI-MS (m / z = 636 (M +)), it was confirmed to be the target product 13.
The vaporization temperature of this product was 486 ° C. and Tg was 106 ° C.
Example 9

  Benzaldehyde (1.1 g), α-tetralone (2.9 g), ammonium acetate (10 g), and acetic acid (25 ml) were stirred for 1.8 hours under heating reflux. Water (30 ml) and methanol (30 ml) were added to the resulting solution, and the precipitated solid was separated by filtration, washed with methanol, and purified by silica gel column chromatography to obtain the desired product 14 (0.74 g). From DEI-MS (m / z 359 (M +)), it was confirmed to be the target product 14.

  As a result of TG-DTA measurement, this product had a melting point of 180 ° C. and a vaporization temperature of 345 ° C. (Example 10)

Terephthalaldehyde (3.35 g), 2′-bromoacetophenone (14.9 g),
Concentrated sulfuric acid (12 ml) was added to a mixture of acetic acid (71 ml) and nitrobenzene (20 ml) in air at room temperature, and the mixture was stirred at 30 ° C. for 7 hours. Water (50 ml) and methanol (150 ml) were added to the obtained solution and stirred, and then the precipitate was filtered, purified by ethanol washing and suspension washing in methanol (300 ml), and the target product 15 (7.95 g). Got.

  In a nitrogen stream, the target compound 15 (7.95 g), 1-phenacylpyridinium bromide (13.4 g), ammonium acetate (61.8 g), acetic acid (180 ml), N, N-dimethylformamide (150 ml), nitrobenzene ( 70 ml) was stirred for 7 hours under reflux with heating, and water (100 ml) and ethanol (100 ml) were added to the resulting solution and stirred. The deposited precipitate was filtered and washed with ethanol, and then purified by suspension washing in ethanol (400 ml) to obtain the desired product 16 (7.69 g).

In a nitrogen stream, the target product 16 (7.69 g), phenylboronic acid (4.05 g), tetrakis (triphenylphosphine) palladium (1.02 g), tripotassium phosphate (9.4 g), toluene (300 ml), A mixture of ion-exchanged water (22 ml) was stirred with heating under reflux for 7 hours, washed with water (150 ml), dried over anhydrous magnesium sulfate, and filtered. The filtrate was concentrated and purified by reprecipitation from acetone (20 ml) -methanol (100 ml) and silica gel column chromatography to obtain the target product 17 (2.88 g). D
From EI-MS (m / z = 688 (M +)), it was confirmed to be the target compound 17. This had a melting point of 232 ° C., a vaporization temperature of 483 ° C., and a glass transition temperature of 106 ° C.
(Example 11)

  Concentrated sulfuric acid (1.6 ml) was added with stirring to 3,5-dibromobenzaldehyde (2.64 g), acetophenone (1.44 g) and acetic acid (22 ml) in air, and then stirred at 30 ° C. for 8 hours. . Water (30 ml) and methanol (30 ml) were added to the resulting solution, and the precipitated solid was separated by filtration, washed with a methanol-water mixed solvent, purified by suspension in methanol, and purified by the target product 18 (1.66 g). )

  The target product 18 (1.66 g), 1-phenacylpyridinium bromide (1.51 g), ammonium acetate (8.72 g), acetic acid (78 ml), N, N-dimethylformamide (78 ml) were heated and refluxed in the air. The mixture was stirred for 5 hours, and water (80 ml) and ethanol (60 ml) were added to the resulting solution and stirred. The deposited precipitate was filtered, washed with ethanol and purified to obtain the intended product 19 (1.36 g).

In a nitrogen stream, the target product 19 (0.75 g), 9-phenanthreneboronic acid (1.44 g), tetrakis (triphenylphosphine) palladium (0.15 g), tripotassium phosphate (2.06 g), toluene ( 100 ml), water (4.9 ml) and ethanol (3 ml) were stirred with heating under reflux for 9.2 hours, and then the toluene layer was separated and concentrated, and purified by GPC to obtain the target product 20 (0.71 g). ) From DEI-MS (m / z = 659 (M ⁺ )), it was confirmed to be the target product 20. This had a glass transition temperature of 141 ° C. and a boiling point of 571 ° C.
(Example 12)
Thin films (thickness 50 nm) of the objects 1 and 17 were formed on a glass substrate by vacuum deposition. The obtained thin film was a transparent amorphous film. The fluorescence emission spectrum when excited at the maximum absorption wavelength of the obtained thin film is shown in FIG. From this result, it is clear that the intermolecular interaction in the thin film state is suppressed in the compound of the present invention represented by the general formula (II). (Example 13)
An organic electroluminescent element having the structure shown in FIG. 3 was produced by the following method.

An indium tin oxide (ITO) transparent conductive film 2 deposited on a glass substrate 1 with a thickness of 150 nm (sputtered film; sheet resistance: 15Ω) is formed into a 2 mm wide stripe using ordinary photolithography and hydrochloric acid etching. An anode was formed by patterning. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  As a material for the anode buffer layer 3, a non-conjugated polymer compound (PB-1) having an aromatic amino group having the structural formula shown below

Weight average molecular weight: 29400
Number average molecular weight: 12600
An electron-accepting compound (A-1)

In addition, spin coating was performed under the following conditions.
Solvent Ethyl benzoate Coating solution concentration 2 [wt%]
PB-1: A-1 10: 1
Spinner speed 1500 [rpm]
Spinner rotation time 30 [seconds]
Drying conditions 100 ° C. for 1 hour A uniform thin film having a thickness of 30 nm was formed by the above spin coating.
Next, the substrate on which the anode buffer layer was formed was placed in a vacuum evaporation apparatus. After roughly exhausting the apparatus with an oil rotary pump, the apparatus was exhausted with an oil diffusion pump until the degree of vacuum in the apparatus was 1.1 × 10 ⁻⁶ Torr (about 1.5 × 10 ⁻⁴ Pa) or less. Arylamine compound (H-1) shown below, placed in a ceramic crucible placed in the above apparatus

Vapor deposition was performed by heating with a tantalum wire heater around the crucible. The temperature of the crucible at this time was controlled in the range of 318 to 334 ° C. The degree of vacuum during deposition was 1.1 × 10 ⁻⁶ Torr (about 1.4 × 10 ⁻⁴ Pa), the deposition rate was 0.15 nm / sec, and a hole transport layer 4 having a thickness of 60 nm was obtained.
Subsequently, a carbazole derivative (E-1) shown below as a main component (host material) of the light-emitting layer 5 and an organic iridium complex (D-1) as a subcomponent (dopant) were placed in separate ceramic crucibles, and binary Film formation was performed by the co-evaporation method.

The crucible temperature of the compound (E-1) is 184 to 196 ° C., the deposition rate is 0.11 nm / second, and the compound (D
The crucible temperature of -1) was controlled to 245 to 246 ° C., and the light emitting layer 5 containing 30% of the film thickness and containing 6% by weight of the compound (D-1) was laminated on the hole transport layer 4. The degree of vacuum during vapor deposition was 1.0 × 10 ⁻⁶ Torr (about 1.3 × 10 ⁻⁴ Pa).
Furthermore, the object 4 (HB-1) synthesized in Example 3 as the hole blocking layer 6

The crucible temperature was 190 to 196 ° C., and the film was laminated with a film thickness of 10 nm at a deposition rate of 0.13 nm / second. The degree of vacuum during the deposition was 0.7 × 10 ⁻⁶ Torr (about 0.9 × 10 ⁻⁴ Pa).
An aluminum 8-hydroxyquinoline complex (ET-1) shown below as an electron transport layer 7 on the hole blocking layer 6

Was deposited in the same manner. At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex is controlled in the range of 250 to 262 ° C., the vacuum during deposition is 0.7 × 10 ⁻⁶ Torr (about 0.9 × 10 ⁻⁴ Pa), and the deposition rate is 0.21 nm / The film thickness was 35 nm in seconds.
The substrate temperature when vacuum-depositing the hole transport layer, the light emitting layer, and the electron transport layer was maintained at room temperature.

Here, the element on which the electron transport layer 6 has been deposited is once taken out from the vacuum deposition apparatus into the atmosphere, and a 2 mm wide striped shadow mask is used as the cathode deposition mask.
In close contact with the ITO stripe, the device is placed in a separate vacuum deposition apparatus, and the degree of vacuum in the apparatus is 2.7x10 ^-6 Torr (about 2.0x10 ^-4 Pa) in the same manner as the organic layer. Exhaust until below. As the cathode 8, first, lithium fluoride (LiF) is deposited at a deposition rate of 0.01 nm / second, a degree of vacuum of 3.0 × 10 ⁻⁶ Torr (about 4.0 × 10 ⁻⁴ Pa) and a thickness of 0.5 nm using a molybdenum boat. A film was formed on the transport layer 7. Next, aluminum is similarly heated by a molybdenum boat to form an aluminum layer having a film thickness of 80 nm at a deposition rate of 0.48 nm / second and a degree of vacuum of 8.5 × 10 ⁻⁶ Torr (about 1.1 × 10 ⁻³ Pa). Completed. The substrate temperature at the time of vapor deposition of the above two-layer cathode 8 was kept at room temperature.

As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The light emission characteristics of this element are shown in Table-1. In Table 1, the maximum light emission luminance is a value at a current density of 0.25 A / cm ² , and the light emission efficiency, luminance / current, and voltage are values at a luminance of 100 cd / m ² , respectively. The maximum wavelength of the emission spectrum of the device was 510 nm, which was identified as that from the organic iridium complex (D-1). The chromaticity was CIE (x, y) = (0.29,0.62).

(Example 14)
A device was fabricated in the same manner as in Example 13 except that the target 1 (HB-2) synthesized in Example 2 was used instead of the target 4 (HB-1) in the hole blocking layer. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 512 nm, and the chromaticity was CIE (x, y) = (0.28,0.63), which was identified as that from the organic iridium complex (D-2).

(Example 15)
A device was fabricated in the same manner as in Example 13 except that the target 17 synthesized in Example 10 was used instead of the target 4 (HB-1) in the hole blocking layer. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 510 nm, and the chromaticity was CIE (x, y) = (0.28,0.61), which was identified as that from the organic iridium complex (D-2).
(Example 16)
A device was fabricated in the same manner as in Example 13 except that the target 20 (HB-4) synthesized in Example 11 was used instead of the target 4 (HB-1) in the hole blocking layer. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 512 nm, and the chromaticity was CIE (x, y) = (0.29, 0.61), which was identified as that from the organic iridium complex (D-1).

(Comparative Example 1)
A device was fabricated in the same manner as in Example 13 except that the mixed ligand complex (HB-3) shown below was used instead of the target 4 (HB-1) of the hole blocking layer. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 510 nm, and the chromaticity was CIE (x, y) = (0.29,0.62), which was identified as that from the organic iridium complex (D-2). Luminous efficiency was low compared with Examples 13-16.

Example 17 Drive Life Test A drive life test was performed on the devices manufactured in Example 13 and Example 16 under the following conditions.
Temperature room temperature
Initial brightness 1000cd / m2
Drive system DC drive (DC drive)
Table 2 shows the drive characteristics of the element. L / L0 is the luminance / initial luminance after 2850 hours, and ΔV is a voltage increase value (= voltage−initial driving voltage).

It is the schematic cross section which showed an example of the organic electroluminescent element. It is the schematic cross section which showed another example of the organic electroluminescent element. It is the schematic cross section which showed another example of the organic electroluminescent element. It is a fluorescence emission spectrum when it excites with the maximum absorption wavelength of the thin film of the target object 1 and the target object 17 (Example 12).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Anode buffer layer 4 Hole transport layer 5 Light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Cathode

Claims (13)

An electron transport material represented by the following general formula (I):

(In the above general formula (I) , ring A is a pyridine ring,
R ¹ and R ⁴ are optional substituents. R ² and R ³ each independently represent a hydrogen atom or an arbitrary substituent.
N representing the number of rings A is an integer of 2 to 10, and Z represents a direct bond or an n-valent linking group . A plurality of R ^{1 to} R ⁴ contained in one molecule may be the same or different.
However, R ^{1 to} R ⁴ and Z do not include a diarylamine skeleton.
Also, compounds having a bipyridyl structure are excluded. ) 2. The electron transport material according to claim 1, wherein R ¹ and R ⁴ in the general formula (I) are each independently an aromatic hydrocarbon group which may have a substituent. The electron transport material according to claim 1 or 2, wherein R ² and R ³ in the general formula (I) are each independently a hydrocarbon group which may have a substituent. On a substrate, comprising an anode, a cathode, and an organic light emitting layer provided between the two electrodes, characterized in that it includes a layer containing an electron transporting material according to any one of claims 1 to 3 organic Electroluminescent device. The organic electroluminescent element according to claim 4, wherein the layer containing the electron transport material according to any one of claims 1 to 3 is an organic light emitting layer. 5. The organic electroluminescent device according to claim 4, further comprising a layer containing the electron transport material according to any one of claims 1 to 3 between the organic light emitting layer and the cathode. Claim a layer containing an electron transporting material according to any one of claims 1 to 3 having between the organic light-emitting layer and the cathode, characterized in that it is a layer in contact with the cathode side interface of the organic light-emitting layer 6. The organic electroluminescent element according to 6. Further, the organic light-emitting layer, the organic electroluminescent device according to claim 6 or 7, characterized in that it comprises an electron transport material according to any one of claims 1 to 3. The organic light-emitting layer, Ir, Pt, organic electroluminescent device according to any one of claims 4 to 8, characterized in that it contains an organic metal complex, of which central metal is Au or Pd. The organic electroluminescent element according to claim 9, wherein the organometallic complex has a ligand having a 2-arylpyridine skeleton which may have a substituent. A compound represented by the following formula (II), the compound in which the compound when taking the most stable structures, characterized in that not a planar structure.

(In the above general formula (II) , ring B is a pyridine ring.
R ⁵ and R ⁸ are an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.
R ⁶ and R ⁷ each independently represents a hydrogen atom or an arbitrary substituent.
m is an integer of 2 to 10 representing the number of rings B.
Z ₁ represents a direct bond, an m-valent aromatic hydrocarbon group or an aromatic heterocyclic group that bonds a plurality of rings B in one molecule.
A plurality of rings B contained in one molecule are conjugated via Z ₁ .
A plurality of R ^{5 to} R ⁸ contained in one molecule may be the same or different.
However, R ^{5 to} R ⁸ and Z ₁ do not include a diarylamine skeleton.
Also, compounds having a bipyridyl structure are excluded. ) The compound according to claim 11, wherein in the general formula (II), R ⁵ , R ⁸ and Z ₁ are each independently an aromatic hydrocarbon group which may have a substituent. Compound represented by the general formula (II) is, when taking the most stable structures A compound according to claim 11 or 12, characterized in that at least two rings B and Z ₁ are coplanar.

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