JPH09241629A - Organic electroluminescence device - Google Patents

Abstract

(57) An object of the present invention is to provide an organic electroluminescence device (organic EL device) which has a long life such that a change in emission color is small even if it is driven for a long time and has high efficiency. An organic compound layer having at least a recombination region in which holes and electrons are recombined and a light emitting region emitting light in response to the recombination, and a pair of electrodes sandwiching the organic compound layer are provided. In the organic electroluminescence device, a condensed polycyclic hydrocarbon of a mother skeleton is composed of four or more aromatic rings as a fluorescent dopant in the recombination region and / or the light emitting region, and each has 1 to 1 carbon atoms.
At least one selected from a specific compound group such as a compound having only 1 to 4 substituents which are 10 alkyl groups or cycloalkyl groups is contained at a ratio of 0.1 to 8% by weight. It is an organic electroluminescent element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (hereinafter abbreviated as EL) element, and more specifically, it has a long life such as a small change in emission color even when it is driven for a long time, and has a high life. The present invention relates to an efficient organic EL device.

[0002]

2. Description of the Related Art An EL element utilizing electroluminescence has high visibility because it is self-luminous and is a completely solid-state element.
Due to its characteristics such as excellent impact resistance, attention has been paid to its use as a light emitting element in various display devices. This EL element includes an inorganic EL element that uses an inorganic compound as a light emitting material and an organic EL element that uses an organic compound. Among them, the organic EL element is capable of significantly lowering the applied voltage. As a next-generation display device, research for its practical use is being actively conducted.

By the way, in this organic EL device,
In order to develop a blue light emitting device with long life and high efficiency, much effort has been focused on researches on blue light emitting materials, and various blue light emitting materials such as high brightness and high efficiency distyrylarylene-based blue light emitting materials (special (Kaihei 2-247278), high-brightness chelate-based blue light-emitting material (JP-A-5-1)
No. 98378), high-luminance diamine-based blue light-emitting material (JP-A-6-220437), and the like are disclosed. However, these blue light-emitting materials were usually used in the structure of anode / hole injecting / transporting layer / light-emitting layer / electron injecting / transporting layer / cathode and exhibited their performance, but they are not necessarily satisfactory in terms of life. Instead, for example, (1) the color changes to green and the luminescent color changes as the driving time elapses, and (2) the half life at an initial luminance of 100 cd / m ² is as short as about 1000 hours (practically several times). 1000 hours or more are required), etc.

On the other hand, there has been proposed an element in which a compound having a perylene structure having different substituents similar to the fluorescent dopant in the present invention is used as a material for a light emitting layer (Japanese Patent Laid-Open No. HEI 3).
No. 791, JP-A-3-162485), there is no mention of the function of the fluorescent dopant added in a small amount. Further, Japanese Patent Laid-Open No. 6-9953 and International Patent Publication No. 94-6157 disclose a distyrylarylene-based material which is a charge injection auxiliary agent to be added to a light emitting layer. This material also works as a fluorescent dopant, but the half-life of the device using this material is 1
Short as about 000 hours (initial brightness 100 cd / m ² ),
Improvement was required. Furthermore, JP-A-5-21433
In JP-A-2, a condensed polycyclic hydrocarbon compound is referred to as (R ^5-
Q) A technique of incorporating it into an aluminum chelate represented by ₂ Al-OL is disclosed, and in Japanese Patent Laid-Open No. 5-198777, a similar condensed polycyclic hydrocarbon compound (R ⁵ -Q) is disclosed.
_{2 Al-O-Al (Q} -R 5) technology to be contained in the aluminum chelate represented by ₂ is disclosed. They emit blue light by doping with an unsubstituted condensed polycyclic hydrocarbon. Even with the best combination of these, the half life is 2000 hours or less, and the efficiency is about 1 lm / W. Because it was low, improvement was required.

[0005]

DISCLOSURE OF THE INVENTION The present invention has improved the drawbacks of the conventional organic EL device described above and has a long life such as a small change in the luminescent color even when it is driven for a long time and a high life. It is intended to provide an efficient organic EL device.

[0006]

As a result of intensive studies to develop an organic EL device having a long life and high efficiency, the present inventors have found that at least the hole-electron coupling region or the light-emitting region of the device can be obtained. It has been found that the purpose can be achieved by adding a specific compound as a fluorescent dopant at a predetermined ratio to either of them. The present invention has been completed based on such findings. That is, the present invention includes an organic compound layer having at least a recombination region where holes and electrons are recombined and a light emitting region which emits light in response to the recombination, and a pair of electrodes sandwiching the organic compound layer. In the provided organic electroluminescence device, in the recombination region and / or the light emitting region, condensed polycyclic hydrocarbon of a mother skeleton is composed of four or more aromatic rings, and each is an alkyl group having 1 to 10 carbon atoms. Alternatively, 0.1 to 8% by weight as a fluorescent dopant is at least one selected from compounds having only 1 to 4 substituents which are cycloalkyl groups.
The present invention provides an organic electroluminescence device characterized by being contained at a ratio of. Further, in the present invention, the condensed polycyclic hydrocarbon of the mother skeleton is composed of three or more aromatic rings and a five-membered ring consisting of carbon, and each is an alkyl group or a cycloalkyl group having 1 to 10 carbon atoms. Also provided is an organic electroluminescence device characterized by containing at least one selected from compounds having only 1 to 4 substituents as a fluorescent dopant in a proportion of 0.1 to 8% by weight. is there. Hereinafter, the present invention will be described in more detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the fluorescent dopant of the present invention, the mother skeleton has the following general formulas (1) to (30).

[0008]

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[0009]

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[0010]

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[0011]

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[0012]

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Is represented by any one of the following: one or more substituents R
It is preferable to contain at least one kind selected from the compounds having a structure substituted only by 0.1 to 8% by weight. In the compounds having a mother skeleton structure represented by the above general formulas (1) to (30), each substituent R has 1 carbon atom.
To 10 alkyl groups or cycloalkyl groups. Here, specific examples of the alkyl group having 1 to 10 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, Examples thereof include an isooctyl group.
Further, specific examples of the cycloalkyl group include, for example, a cyclohexyl group, a cyclopentyl group and the like. Specific examples of the compound having the mother skeleton structure of the general formulas (1) to (30) include compounds having the structures shown below.

[0014]

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[0015]

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[0016]

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[0017]

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[0018]

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In the above compound, the number n of the substituents is 1 to
It is preferably an integer of 6, and the positions of these substituents are not particularly limited. Therefore, the structural isomer or n is 1 to
It may be a mixture of 6.

In the present invention, one of these compounds may be used as the fluorescent dopant, or two or more thereof may be used in combination. The fluorescent dopant in the present invention is a compound that emits light in response to recombination of holes and electrons in a recombination region or a light emitting region of an organic EL device. It is contained in a small amount in the substance to be formed (host material). Here, the recombination region is a place in the device where holes and electrons meet and combine to form an excited state. Further, the light emitting region is a place where the excited state formed in the recombination region moves and diffuses depending on the case, and specifies the diffusion range.

In the present invention, the above-mentioned fluorescent dopant is contained in at least one of the recombination region and the light emitting region, that is, only in the recombination region, only in the light emitting region, or in both regions, 0.1 to 8% by weight. It is necessary to contain it in the ratio of. If this content is less than 0.1% by weight, the effect of the fluorescent dopant is not sufficiently exhibited, and the object of the present invention cannot be achieved. On the other hand, if it exceeds 8% by weight, the disappearance phenomenon may occur due to the association between the fluorescent dopants, and the effect may not be sufficiently exhibited. From the viewpoint of long life and high efficiency of the element,
The preferable content of the fluorescent dopant is in the range of 0.3 to 4% by weight, and particularly preferably in the range of 0.8 to 3% by weight.
The method of incorporating the fluorescent dopant into the recombination region or the light emitting region is not particularly limited, but for example, it is preferable to adopt a co-evaporation method with a material (host material) forming the recombination region or the light emitting region. . In this method, a host material and a fluorescent dopant are vacuum-deposited from separate boats in which each is contained to form recombination and emission regions. In the organic EL device of the present invention, an organic compound layer having at least a recombination region and a light emitting region is used. Since the recombination region and the light emitting region are usually present in the light emitting layer, in the present invention,
As the organic compound layer, only the light emitting layer may be used, but if necessary, other than the light emitting layer, for example, a hole injection layer, an electron injection layer, an organic semiconductor layer, an electron barrier layer, an adhesion improving layer, etc. can also be used. .

Next, a typical constitutional example of the organic EL element of the present invention will be shown. Of course, it is not limited to this. Anode / hole injection layer / light emitting layer / cathode Anode / hole injection layer / light emitting layer / electron injection layer / cathode Anode / light emitting layer / electron injection layer / cathode Anode / organic semiconductor layer / light emitting layer / cathode Anode / organic semiconductor Layer / electron barrier layer / light-emitting layer / cathode Anode / hole injection layer / light-emitting layer / adhesion improving layer / cathode Of these, the usual constitution is preferably used.

The recombination region and the light emitting region in the device of the present invention are usually present in the light emitting layer as described above. Therefore, the fluorescent dopant is usually contained in the light emitting layer.
However, in some cases, other layers, such as hole injection layers,
The electron injection layer, the organic semiconductor layer, the electron barrier layer, the adhesion improving layer, etc. may also participate in recombination and light emission. in this case,
It is preferable to include it also in these layers.

The organic EL device of the present invention has a structure in which the organic compound layer is sandwiched between a pair of electrodes, that is, an anode and a cathode, and the anode is a metal having a large work function (4 eV or more). , Alloys, electrically conductive compounds and mixtures thereof are used as electrode materials. Specific examples of such an electrode material include a metal such as Au and a dielectric transparent material such as CuI, ITO, SnO ₂ and ZnO. The anode can be prepared by forming a thin film of these electrode substances by a method such as vapor deposition or sputtering. When light is extracted from this electrode, the transmittance is desirably higher than 10%, and the sheet resistance of the electrode is preferably several hundred Ω / □ or less. Furthermore, the film thickness depends on the material,
Usually, the range of 10 nm to 1 μm, particularly 10 to 200 nm is preferable.

On the other hand, as the cathode, a material having an electrode substance of a metal, an alloy, an electrically conductive compound or a mixture thereof having a low work function (4 eV or less) is used. Specific examples of such an electrode material include sodium, sodium-potassium alloy, magnesium, lithium, magnesium-silver alloy, Al / AlO ₂ , aluminum-lithium alloy, indium and rare earth metal. The cathode can be manufactured by forming a thin film of these electrode substances by a method such as evaporation or sputtering. The sheet resistance of the electrode is several hundred Ω /
□ or less is preferable, and the film thickness is usually 10 nm to 1 μm, particularly preferably 50 to 200 nm. In the device of the present invention, although not particularly specified, it is preferable that either the anode or the cathode is transparent or semi-transparent because light emission is transmitted and extraction efficiency is good.

In the light emitting layer of the device of the present invention,
As the light emitting material (host material), the general formula (I) is used.

[0027]

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A distyrylarylene compound represented by the following is preferably used. This compound is disclosed in JP-A 2-24
It is disclosed in Japanese Patent No. 7278.

In the above general formula (I), Y¹~ Y^FourHaso
Hydrogen atom, C1-6 alkyl group, and C1
~ 6 alkoxy group, C7-8 aralkyl group,
A substituted or unsubstituted aryl group having 6 to 18 carbon atoms, substituted
Or unsubstituted cyclohexyl group, substituted or non-substituted
Substituted C6-18 aryloxy group, C1-6
Represents an alkoxy group. Here, the substituent has 1 to 6 carbon atoms.
Alkyl group, C1-C6 alkoxy group, C7
~ 8 aralkyl groups, C6-18 aryloxy
Group, acyl group having 1 to 6 carbon atoms, acyl group having 1 to 6 carbon atoms
Xy group, carboxyl group, styryl group, carbon number 6-20
Arylcarbonyl group having 6 to 20 carbon atoms
Xycarbonyl group, alkoxycarbonyl having 1 to 6 carbon atoms
Group, vinyl group, anilinocarbonyl group, carbamoyl
Groups, phenyl groups, nitro groups, hydroxyl groups or halogens
Show. These substituents may be single or plural. Also,
Y ¹~ Y^FourCan be the same or different from each other
Ku, Y¹And Y^TwoAnd Y^ThreeAnd Y ^FourAre groups that are substituting for each other
Substituted or unsubstituted saturated five-membered ring or substituted with
Alternatively, an unsubstituted saturated 6-membered ring may be formed. Ar is
A substituted or unsubstituted arylene group having 6 to 20 carbon atoms
Represents a single substitution or multiple substitutions
The binding site may be ortho, para, or meta.
Yes. However, when Ar is an unsubstituted phenylene group, Y¹~ Y
^FourAre alkoxy groups having 1 to 6 carbon atoms and 7 to 7 carbon atoms, respectively.
8 aralkyl groups, substituted or unsubstituted naphthyl groups,
Biphenyl group, cyclohexyl group, aryloxy group
It was chosen. Such a styryl allie
Examples of the ren-based compound include:

[0030]

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[0031]

Embedded image And the like.

As another preferable light emitting material (host material), a metal complex of 8-hydroxyquinoline or a derivative thereof can be mentioned. Specifically, it is a metal chelate oxinoid compound containing a chelate of oxine (generally 8-quinolinol or 8-hydroxyquinoline). Such compounds exhibit a high level of performance and are easily formed into thin film form. An example of this oxinoid compound satisfies the following structural formula.

[0033]

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(In the formula, Mt represents a metal, n is an integer of 1 to 3, Z is independent in each position, and
It indicates the atoms necessary to complete at least two or more fused aromatic rings. ) Here, the metal represented by Mt can be a monovalent, divalent or trivalent metal, such as lithium,
It is an alkali metal such as sodium or potassium, an alkaline earth metal such as magnesium or calcium, or an earth metal such as boron or aluminum. Generally, any monovalent, divalent or trivalent metal known to be a useful chelating compound can be used.

Z represents an atom that forms a heterocycle in which one of at least two fused aromatic rings is azole or azine. Here, if necessary, another different ring can be added to the condensed aromatic ring. Also, in order to avoid adding bulky molecules without functional improvement, the number of atoms represented by Z is 18
It is preferable to keep below. Furthermore, specifically exemplifying the chelated oxinoid compound, tris (8-
Quinolinol) aluminum, bis (8-quinolinol) magnesium, bis (benzo-8-quinolinol)
Zinc, bis (2-methyl-8-quinolinate) aluminum oxide, tris (8-quinolinol) indium, tris (5-methyl-8-quinolinol) aluminum, 8-quinolinol lithium, tris (5-chloro-8-quinolinol) Gallium, bis (5-chloro-8)
-Quinolinol) calcium, 5,7-dichloro-8-
Examples include quinolinol aluminum and tris (5,7-dibromo-8-hydroxyquinolinol) aluminum.

Further, the metal complex of phenolate-substituted 8-hydroxyquinoline described in JP-A-5-198378 is preferable as a blue light emitting material. Specific examples of the metal complex of phenolate-substituted 8-hydroxyquinoline include bis (2-methyl-8-quinolinolato) (phenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (o-cresolate) aluminum. (III), bis (2-methyl-8-quinolinolato) (m-cresolate) aluminum (II
I), bis (2-methyl-8-quinolinolato) (p-cresolate) aluminum (III), bis (2-methyl-)
8-quinolinolato) (o-phenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (m-phenylphenolato) aluminum (II
I), bis (2-methyl-8-quinolinolato) (p-phenylphenolato) aluminum (III), bis (2-
Methyl-8-quinolinolato) (2,3-dimethylphenolate) aluminum (III), bis (2-methyl-8)
-Quinolinolate) (2,6-dimethylphenolate)
Aluminum (III), bis (2-methyl-8-quinolinolate) (3,4-dimethylphenolate) Aluminum (III), bis (2-methyl-8-quinolinolate)
(3,5-Dimethylphenolate) Aluminum (II
I), bis (2-methyl-8-quinolinolato) (3,5
-Di-t-butylphenolate) aluminum (III),
Bis (2-methyl-8-quinolinolato) (2,6-diphenylphenolato) aluminum (III), bis (2)
-Methyl-8-quinolinolate) (2,4,6-triphenylphenolate) aluminum (III) and the like. These light emitting materials may be used alone or in combination of two or more.

Examples of the method of forming the light emitting layer in the device of the present invention include vapor deposition, spin coating, casting,
It can be formed by thinning it by a known method such as the LB method, but a molecular deposition film is particularly preferable. Here, the molecular deposition film is a thin film formed by depositing the compound in a vapor phase state, or a film formed by solidifying a molten state or a liquid phase state of the compound.
Normally, this molecular deposited film can be distinguished from a thin film (molecule accumulation film) formed by the LB method by a difference in a cohesive structure and a higher-order structure and a functional difference resulting therefrom. Further, this light emitting layer can be formed by dissolving it in a solvent together with a binder such as a resin to form a solution, and then thinning it by a spin coating method or the like. The thickness of the light emitting layer thus formed is not particularly limited and may be appropriately selected depending on the circumstances, but is preferably 1 nm to 10 μm.
m, particularly preferably 5 nm to 5 μm.

Next, the hole injection layer is not necessarily required for the element of the present invention, but it is preferable to use it for improving the light emitting performance. This hole injecting layer is a layer that assists in injecting holes into the light emitting layer, has a high hole mobility, and generally has an ionization energy as small as 5.5 eV or less. As such a hole injection layer, a material that transports holes to the light emitting layer at a lower electric field is preferable, and further, the mobility of holes is at least 10 when an electric field of 10 ⁴ to 10 ⁶ V / cm is applied. ^More preferably, it is ⁻⁶ cm ² / V · sec. There is no particular limitation on such a hole injecting material as long as it has the above preferable properties.
In the light-transmitting material, any material can be selected and used from materials commonly used as hole charge transport materials and known materials used in hole injection layers of EL devices.

Examples of the hole injection material include triazole derivatives (see US Pat. No. 3,112,197, etc.),
Oxadiazole derivatives (see U.S. Pat. No. 3,189,447, etc.) and imidazole derivatives (JP-B-37-160)
No. 96, etc.), polyarylalkane derivatives (US Pat. Nos. 3,615,402 and 3,820,989,
3,542,544, JP-B-45-555, JP-A-51-10983, JP-A-51-93224, JP-A-55-17105, JP-A-56-4148, and JP-A-55-108667. , Ibid. 55-15695
Nos. 3 and 56-36656), pyrazoline derivatives and pyrazolone derivatives (US Pat. No. 3,180,72).
No. 9, No. 4,278,746, JP-A-55-88
Nos. 064 and 55-88065 and 49-1
JP-A-055537, JP-A-55-51086 and JP-A-56-51086
-80051, 56-88141, 5
JP-A-7-45545 and JP-A-54-112637,
And phenylenediamine derivatives (U.S. Pat. No. 3,615,404, JP-B-51).
Nos. -10105 and 46-3712, 47
JP-A-25-336, JP-A-54-53435,
JP-A-54-110536, JP-A-54-119925, etc.), arylamine derivatives (U.S. Pat.
7,450,3,180,703,3,240,597
No. 3,658,520, No. 4,232,103, No. 4,175,961, No. 4,012,376, JP-B-49-35702, JP-A-39-27577, and JP-A-55-144250. Gazette, 56-119
No. 132, 56-22437, West German Patent No.
1,110,518, etc.), amino-substituted chalcone derivatives (see U.S. Pat. No. 3,526,501, etc.), oxazole derivatives (described in U.S. Pat.
No. 46234), fluorenone derivatives (see Japanese Patent Application Laid-Open No. 54-110837, etc.), and hydrazone derivatives (US Pat. No. 3,717,462, Japanese Patent Application Laid-Open No. 54-59).
Nos. 143 and 55-52063 and 55-5
Nos. 2064 and 55-46760 and 55-
No. 85495, No. 57-11350, No. 57.
And stilbene derivatives (JP-A-61-210363 and 61-228451).
Gazette, JP-A-61-14642, JP-A-61-7225
No. 5, JP-A-62-47646, JP-A-62-366.
No. 74, No. 62-10652, No. 62-30.
No. 255, No. 60-93445, No. 60-9
No. 4462, No. 60-174749, No. 60
1755052). Furthermore, silazane derivatives (U.S. Pat. No. 4,950,950), polysilane-based (JP-A-2-204996), aniline-based copolymers (JP-A-2-28263), conductive polymer oligomers (JP-A-1). -2113
No. 99), especially thiophene-containing oligomers.

In the present invention, these compounds can be used as the hole injecting material, and the following porphyrin compounds (described in JP-A-63-295965 and the like) and aromatic tertiary Amine compounds and styrylamine compounds (US Pat. No. 4,127,412,
JP-A-53-27033, JP-A-54-58445, JP-A-54-149634, and JP-A-54-6429.
No. 9, No. 55-79450, No. 55-144
Nos. 250, 56-119132 and 61-
295558, 61-98353, 6
3-295695, etc.), and it is particularly preferable to use the aromatic tertiary amine compound.

As a typical example of the porphyrin compound,
Porphine, 1,10,15,20-tetraphenyl-
21H, 23H-porphine copper (II); 1,10,1
5,20-Tetraphenyl 21H, 23H-porphine zinc (II); 5,10,15,20-Tetrakis (pentafluorophenyl) -21H, 23H-porphine;
Silicon phthalocyanine oxide; aluminum phthalocyanine chloride; phthalocyanine (metal-free); dilithium phthalocyanine; copper tetramethyl phthalocyanine;
Copper phthalocyanine; chromium phthalocyanine; zinc phthalocyanine; lead phthalocyanine; titanium phthalocyanine oxide; magnesium phthalocyanine; copper octamethylphthalocyanine and the like.

Typical examples of the aromatic tertiary amine compound and the styrylamine compound include N, N, N ',
N'-tetraphenyl-4,4'-diaminophenyl,
N, N'-diphenyl-N, N'-di (3-methylphenyl) -4,4'-diaminobiphenyl, 2,2-bis (4-di-p-tolylaminophenyl) propane,
1-bis (4-di-p-tolylaminophenyl) cyclohexane, N, N, N ', N'-tetra-p-tolyl-
4,4'-diaminobiphenyl, 1,1-bis (4-di-p-tolylaminophenyl) -4-phenylcyclohexane, bis (4-dimethylamino-2-methylphenyl) phenylmethane, bis (4-di -P-tolylaminophenyl) phenylmethane, N, N'-diphenyl-
N, N'-di (4-methoxyphenyl) -4,4'-diaminobiphenyl, N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether, 4,4'
-Bis (diphenylamino) quadriphenyl, N,
N, N-tri (P-tolyl) amine, 4- (di-p-tolylamino) -4 '-[4 (di-p-tolylamino) styryl] stilbene, 4-N, N-diphenylamino-
(2-diphenylvinyl) benzene, 3-methoxy-
4'-N, N-diphenylaminostilbenzene, N-
Examples include phenylcarbazole and aromatic dimethylidin compounds.

The hole injection layer in the EL device of the present invention can be formed by forming the above compound into a film by a known thin film method such as a vacuum vapor deposition method, a spin coating method and an LB method. The thickness of the hole injection layer is not particularly limited, but is usually 5 nm to 5 μm. This hole injection layer may be composed of a single layer made of one or more of the above hole injection materials, or a hole injection layer made of a compound different from the hole injection layer is laminated. It may be one. The organic semiconductor layer is a layer for assisting hole injection or electron injection into the light emitting layer, and is 10 ⁻¹⁰ S / cm.
Those having the above-mentioned conductivity are suitable. Examples of the material for such an organic semiconductor layer include conductive oligomers such as thiophene-containing oligomers and arylamine-containing oligomers,
A conductive dendrimer such as an arylamine-containing dendrimer can be used.

On the other hand, the electron injection layer is a layer for assisting the injection of electrons into the light emitting layer and has a high electron mobility, and the adhesion improving layer has a particular adhesion to the cathode among the electron injection layers. It is a layer made of a good material. Preferable examples of the material used for the electron injection layer include a metal complex of 8-hydroxyquinoline or a derivative thereof, or an oxadiazole derivative. Further, as a material used for the adhesion improving layer, a metal complex of 8-hydroxyquinoline or its derivative is particularly suitable. Specific examples of the metal complex of 8-hydroxyquinoline or a derivative thereof include metal chelate oxinoid compounds containing a chelate of oxine (generally 8-quinolinol or 8-hydroxyquinoline). On the other hand, as the oxadiazole derivative, general formulas (II), (III) and (IV)

[0045]

[Chemical 21]

(In the formula, Ar ^{10 to} Ar ¹³ each represent a substituted or unsubstituted aryl group, and Ar ¹⁰ , Ar ¹¹ and Ar ¹²
And Ar ¹³ may be the same or different in each case, and Ar ¹⁴ represents a substituted or unsubstituted arylene group. ) And an electron transfer compound represented by. Here, examples of the aryl group include a phenyl group, biphenyl group, anthranyl group, perylenyl group, and pyrenyl group, and examples of the arylene group include a phenylene group, a naphthylene group, a biphenylene group, an anthracenylene group, a perylenylene group, and a pyrenylene group. To be Moreover, as a substituent, a C1-C10 alkyl group, a C1-C1
10 alkoxy groups or cyano groups can be mentioned. The electron transfer compound is preferably a thin film-forming compound. Specific examples of the electron transfer compound include:

[0047]

Embedded image And the like.

In the method for producing the dopant used in the present invention, pyrene, perylene, benzoperylene,
Pentacene, fluoranthene, etc. are selected for the condensed polycyclic hydrocarbon ring, and a bulky alkyl group such as isopropyl group, t-butyl group or cyclohexyl group is introduced. By introducing a bulky alkyl group, interaction with the host is avoided and excimer emission does not occur. In addition, the introduction of an alkyl group has an advantage that the sublimation temperature rises and the doping rate can be easily controlled during device fabrication. Friedel-Crafts (Friedel-
The Crafts) alkylation reaction is a reaction in which a carbonium cation is produced as an intermediate, and therefore an alkyl group that may be transferred such as a primary halide cannot be introduced. To introduce a primary alkyl group, Grignard (Gr
ignard) coupling reaction must be used. The Friedel-Crafts alkylation reaction is generally difficult to control and polyalkylation occurs. Further, the olefin generated from the carbonium cation intermediate is polymerized,
Since a large amount of polyolefin is produced as a by-product, the stoichiometric reaction is generally difficult, and the halide must be used in a large excess as a solvent.

Further, the position of the substituent is often different depending on the size of the introduced alkyl group. For example, in the following formula, a perylene-based compound has the highest reactivity at the 3-position, and when an acyl group or the like is introduced, a substituent is introduced at the 3-position, but the t-butyl group is bulky, so the position is at the 2-position. However, there is a tendency of selectivity such that only a substituent is introduced.

[0050]

Embedded image The pyrene-based compound has the highest reactivity at the 1-position in the following formula, and when a isopropyl group or the like is introduced, a substituent is introduced at the 1-position, but since the t-butyl group is bulky, only the 2-position is substituted. There is a tendency for selectivity such as not containing a group.

[0051]

Embedded image The Friedel-Crafts alkylation reaction catalyst is not particularly limited, but a solid acid such as aluminum chloride can be used.

[0052]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, in Production Examples, alkylation using a compound having a typical skeleton of the present invention as a raw material,
Although an example of synthesis using a phenylation reaction is given, other compounds can be synthesized by the same method.

Production Example 1 [Synthesis of 2,5,8-tri-t-butylfluoranthene (IK-2)] 3.0 g (15 mmol) of fluoranthene was dissolved in 100 ml of t-butyl chloride and ground chloride. 1.0 g (7.5 mmol) of aluminum was added to the mixture at room temperature for 10
The mixture was stirred for 1 minute and refluxed for 2 hours. 100 ml of water was added to the reaction mixture, the organic layer was separated, washed with 60 ml of a saturated aqueous sodium hydrogen carbonate solution, dried over magnesium sulfate, and the solvent was distilled off to obtain a yellow liquid. This is distilled under reduced pressure to give a colorless liquid (boiling point 38-74 ° C / 5 Torr
r) was removed and the residue was purified twice by column chromatography (silica gel / hexane) to obtain 2.8 g of the desired pale yellow amorphous solid (yield of (IK-2): 50%). The physical properties of the obtained solid were as follows. ¹ H-NMR (CDCl ₃ , TMS) 1.45 (9H, s) 1.49 (9H, s) 1.50 (9H, s) 7.39 (1H, dd) 7.8 to 8.0 ( 1H, dd) Further, the outline of the reaction of Production Example 1 is shown in the following reaction formula.

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Production Example 2 [Synthesis of Hexabutyldecacyclene (IK-11)] 1.0 g (2.2 mmol) of decacyclene was suspended in 100 ml of t-butyl chloride, and 0.3 g (2. (2 mmol) and refluxed for 2 hours. The insoluble matter was filtered off, and the filtrate was washed with 60 ml of water and 60 ml of a saturated aqueous sodium hydrogen carbonate solution,
It was dried over magnesium sulfate and the solvent was distilled off to obtain a yellow liquid. This is distilled under reduced pressure to give a colorless liquid (boiling point 38-70).
C./5 Torr), and the residue was purified twice by column chromatography (silica gel / hexane + 30% dichloromethane, silica gel / hexane + 5% dichloromethane) to give 20 mg of yellow plate crystals ((IK-11) yield: 1
%) Was obtained. The physical properties of the obtained plate crystals were as follows. Melting point: 215 to 219 ° C. ¹ H-NMR (CDCl ₃ , TMS) 1.66 (54H, s) 7.92 (6H, s) 8.96 (6H, s) In addition, the outline of the reaction of Production Example 2 is described. The reaction formula is shown below.

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Production Example 3 [Synthesis of diphenylbenzofluoranthene (IK-17)] 1.5 g (5.5 mmol) of diphenylisobenzofuran,
0.8 g (5.3 mmol) of acenaphthylene was added to 15 xylene.
It was dissolved in milliliter and refluxed for 7 hours. The solvent was distilled off from the reaction mixture to obtain a brown oil. Crystallization occurred by rubbing the wall of the flask, which was filtered off and washed with hexane to obtain 1.8 g of a pale yellow solid (yield of intermediate: 80%). The obtained solid was suspended in 8 ml of acetic acid,
% Hydrobromic acid (1 ml) was added and the mixture was refluxed for 2 hours. The solid was filtered off and recrystallized from 60 ml of acetic acid to obtain 1.1 g of light brown needle crystals (yield of (IK-17): 83%). The physical properties of the obtained needle crystals were as follows. Melting point: 270 to 271 ° C. ¹ H-NMR (CDCl ₃ , TMS) 6.61 (2H, d) 7.92 to 7.7 (18H, m) In addition, the reaction of Production Example 3 is outlined below. Shown in.

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Production Example 4 [Synthesis of tributyldiphenylbenzofluoranthene (IK-12)] 1.1 g (2.7 mmol) of diphenylbenzofluoranthene was suspended in 100 ml of t-butyl chloride and ground aluminum chloride. 0.4 g (3.0 mmol)
Was added and the mixture was refluxed for 2 hours. The reaction mixture was washed with 60 ml of water and 60 ml of a saturated aqueous sodium hydrogen carbonate solution, dried over magnesium sulfate, and the solvent was distilled off to obtain a light brown liquid. A solid was formed when it was left standing overnight, and this was filtered off and recrystallized from hexane containing a small amount of dichloromethane to give a white solid 0.4 g ((IK-12) yield: 2
6%) was obtained. The physical properties of the obtained solid were as follows. Melting point: 300 ° C. or higher ¹ H-NMR (CDCl ₃ , TMS) 1.19 (18H, s) 1.30 (9H, s) 6.64 (2H, d) 7.4 to 7.7 (15H, m) ) Further, the outline of the reaction of Production Example 4 is shown in the following reaction formula.

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Examples 1 to 6 and Comparative Examples 1 and 2 On a glass substrate of 25 mm × 75 mm × 1.1 mm, IT
A transparent support substrate was prepared by forming a film of O to a thickness of 100 nm by a vapor deposition method (manufactured by Geomatic). This substrate was ultrasonically cleaned in isopropyl alcohol for 5 minutes, then sprayed with nitrogen and dried, and then UV ozone cleaning (UV3
00, manufactured by Samco International Co., Ltd.) for 30 minutes. This transparent support substrate was fixed to a substrate holder of a commercially available vapor deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.), MTDATA 200 mg was put in a molybdenum resistance heating boat, and DPVBi20 was put in another molybdenum resistance heating boat.
0 mg, another molybdenum resistance heating boat was charged with 200 mg of NPD, which is a hole transport material, and another molybdenum resistance heating boat was charged with 200 mg of the fluorescent dopant [compound (A)] of the type shown in Table 1. The vacuum chamber was evacuated to 1 × 10 ⁻⁴ Pa. After that, the boat containing MTDATA was heated to 215 to 220 ° C. and vapor-deposited at a vapor deposition rate of 0.1 to 0.3 nm / sec on a transparent support substrate to form a hole injection layer having a thickness of 60 nm. .

Next, without taking out the substrate from the vacuum chamber, the boat containing NPD was heated to form a hole transport layer having a film thickness of 20 nm on the hole injection layer. At this time, the temperature of the substrate was room temperature. Without removing this from the vacuum chamber, DPVBi was used as a host material on the NPD layer.
nm stacked. At this time, the boat of the compound (A) was simultaneously heated to mix the compound (A) with the light emitting layer. The deposition rate at this time is the deposition rate of the compound (A) (C) with respect to the deposition rate of DPVBi ((B) shown in Table 1).
(Shown in Table 1). Therefore, the mixing ratio [ratio of compound (A) to host material] was (D) (shown in Table 1). Then, the vacuum chamber was returned to atmospheric pressure, and a new molybdenum resistance heating boat was charged with 8-hydroxyquinoline aluminum complex, which is the material for the electron injection layer,
Further, 1 g of magnesium ribbon was put in a resistance heating boat made of molybdenum, 500 mg of silver wire was put in a basket made of tungsten, and the vacuum chamber was depressurized to 1 × 10 ⁻⁴ Pa. Next, the deposition rate is 0.01 to 0.03 nm / sec.
A hydroxyquinoline / aluminum complex was deposited to form an electron injection layer of 20 nm. Furthermore, silver deposition rate is 0.1n
m / sec and magnesium were co-deposited at a vapor deposition rate of 1.4 nm / sec to use a silver: magnesium mixed electrode as a cathode. The film thickness was 150 nm. A voltage of 8 V was applied to the obtained device, the amount of current and the device brightness were measured, and the luminous efficiency was calculated. Table 2 shows the obtained results. In addition, MTDAT
The structures of A, DPVBi and NPD are as follows.

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[Table 1]

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[Table 2]

As a result of the above, the device of the present invention has a luminous efficiency higher than that of Comparative Example 1 and Comparative Example 2 in which perylene (fluorescent dopant described in JP-A-5-198378) was used as the fluorescent dopant. It turns out that is excellent. Next, each element was driven in an atmosphere of dry nitrogen at an initial luminance of 300 cd / m ² , and the half-life (time at which the initial luminance becomes half) was determined. The results are shown in Table 3. Initial brightness 1
As a result of the test at 00 cd / m ² , the life is about 3.5 times that of Table 3. Therefore, the device of the present invention can be used for 2500 hours to 110 hours under the condition of the initial luminance of 100 cd / m ^2.
A life of 0 hours can be obtained.

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[Table 3]

As can be seen from Table 3, the device of the present invention has a significantly improved life as compared with those of Comparative Examples 1 and 2.

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The organic EL device of the present invention has a fluorescent dopant having a specific structure in at least one of a recombination region where holes and electrons recombine or a light emitting region which emits light in response to the recombination. It has a long life, such as a small change in emission color even when it is driven for a long time, and has high emission efficiency, and is suitably used for, for example, a display of information industrial equipment.

Claims (7)

[Claims] 1. An organic compound layer having at least a recombination region in which holes and electrons are recombined and a light emitting region emitting light in response to the recombination, and a pair of electrodes sandwiching the organic compound layer. In the organic electroluminescence device, the condensed polycyclic hydrocarbon of the mother skeleton is composed of four or more aromatic rings in the recombination region and / or the light emitting region,
And, at least one selected from compounds having only 1 to 4 substituents, each of which is an alkyl group having 1 to 10 carbon atoms or a cycloalkyl group, is used as a fluorescent dopant in a proportion of 0.1 to 8% by weight. An organic electroluminescence device characterized by being contained. 2. An organic compound layer having at least a recombination region in which holes and electrons are recombined and a light emitting region emitting light in response to the recombination, and a pair of electrodes sandwiching the organic compound layer. In the organic electroluminescent device described above, the condensed polycyclic hydrocarbon of the mother skeleton is composed of three or more aromatic rings and a five-membered ring composed of carbon in the recombination region and / or the light emitting region, and each has a carbon number. 1-1
At least one selected from compounds having only 1 to 4 substituents which are 0 alkyl groups or cycloalkyl groups is contained as a fluorescent dopant in a proportion of 0.1 to 8% by weight. Organic electroluminescent device. 3. A condensed polycyclic hydrocarbon having a mother skeleton of a compound contained as a fluorescent dopant has the following structural formula: Embedded image Embedded image Embedded image Embedded image The organic electroluminescence device according to claim 1 or 2, wherein the organic electroluminescence device is represented by any one of the following. 4. The substituent of the compound contained as the fluorescent dopant has 3 to 10 carbon atoms and is a secondary or tertiary hydrocarbon, and any one of claims 1 to 3 is characterized in that The organic electroluminescence device described in 1. 5. The following formula: The organic electroluminescence device according to claim 1 or 2, wherein diphenylbenzofluoranthene represented by the formula (1) is contained as a fluorescent dopant in a proportion of 0.1 to 8% by weight. 6. The organic electroluminescence device according to claim 1, wherein the light emitting layer contains a fluorescent dopant. 7. The device constitution is anode / hole injection layer / light emitting layer / electron injection layer / cathode or anode / hole injection layer / hole transport layer / light emitting layer / electron injection layer / cathode. Item 7. The organic electroluminescence device according to any one of items 1 to 6.