JPH06220437A - Electroluminescent element - Google Patents

Abstract

(57) [Summary] [Structure] An electroluminescent device characterized in that at least one of the organic compound layers is a layer containing an organic compound represented by the following general formula 1 as a constituent component. [Chemical 1] [Effects] The electroluminescent device of the present invention can provide high-luminance light emission for a long period of time even with a low driving voltage and can exhibit various color tones, and the device can be easily manufactured by a vacuum deposition method or the like. Since it can be performed, it has an advantage that an inexpensive and large-area element can be efficiently produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a light emitting layer made of a light emitting material, and can directly convert electric energy into light energy by applying an electric field, which is different from conventional incandescent lamps, fluorescent lamps or light emitting diodes. Differently, the present invention relates to an electroluminescence device that enables realization of a large-area planar light-emitting body.

[0002]

2. Description of the Related Art An electroluminescence device has an intrinsic electroluminescence device which emits light only in an alternating electric field by (1) exciting a light emitter by local movement of electrons and holes in a light emitting layer due to a difference in emission excitation mechanism. The element is divided into (2) a carrier injection type electroluminescent element that operates by a DC electric field by injecting electrons and holes from an electrode and recombining the electrons and holes in the light emitting layer to excite a luminescent body. The intrinsic electroluminescence type light emitting device of (1) is generally ZnS.
An inorganic compound to which Mn, Cu, etc. are added is used as a light emitter, but it requires a high AC electric field of 200 V or more for driving, high manufacturing cost, insufficient brightness and durability, etc. Has many problems.

In the carrier injection type electroluminescent device (2), a thin film organic compound has been used as a light emitting layer, and a high brightness device has been obtained. For example, JP-A-59-194393, U.S. Pat. No. 4,539,507,
Japanese Patent Laid-Open No. 63-2956695, US Pat. No. 4,720,4
32 and Japanese Patent Laid-Open No. 63-264692 disclose an electroluminescent device comprising an anode, an organic hole injecting and transporting zone, an organic electron injecting luminescent material and a cathode. Examples of materials used for these are organic materials. Aromatic tertiary amines are representative examples of hole injecting and transporting materials, and aluminum trisoxine and the like are representative examples of organic electron injecting light emitting materials.

In addition, Jpn. Journal of A
applied Physicd, vol. 27, p71
3-715 reports an electroluminescent device comprising an anode, an organic hole transport layer, a light emitting layer, an organic electron transport layer and a cathode. Materials used for these are N, N as organic hole transport materials. '-Diphenyl-N,
N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, and as an organic electron transport material, 3,4,9,10-perylenetetracarboxylic acid bisbenzimidazole In addition, phthaloperinone is exemplified as the light emitting material.

In these examples, in order to use an organic compound as a hole transport material, a light emitting material, and an electron transport material, various characteristics of these organic compounds are sought, and these characteristics are effectively combined to form an electroluminescent device. It means that the research and development of a wide range of organic compounds is necessary.

Further, the carrier injection type electroluminescent device using an organic compound as a light emitting body, including the above examples, has a short history of research, and it can be said that research into its materials and devices is still sufficient. However, in reality, there are many problems such as further improvement of brightness, control of emission wavelength, and improvement of durability.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to provide an electroluminescent device having excellent durability in which light emitting performance is maintained for a long time. Especially.

[0008]

Means for Solving the Problems The inventors of the present invention have diligently studied the constituent elements of a light emitting layer for solving the above problems, and as a result, have made a positive electrode and a negative electrode and one or a plurality of layers sandwiched between them. In an electroluminescent device including an organic compound layer, at least one of the organic compound layers is a layer containing an organic compound represented by the following general formula 1 as a constituent component. The present invention has been found to be effective for the above problems, and the present invention has been completed.

[Chemical 1]

In the present invention, the organic compound represented by the general formula (I) (Formula 1) contained in the electroluminescent device is
A novel compound, which is generally synthesized by a combination of N-alkyl substitution reaction or N-aryl substitution reaction and N-pyrenyl substitution reaction of the corresponding amino compound. Corresponding halides are generally used in the alkylation, arylation and pyrenylation reactions, and the arylation reaction is generally carried out by the Ullmann reaction.

When carrying out the Ullmann reaction, N, N-dimethylformamide, nitrobenzene, dimethyl sulfoxide, dichlorobenzene or the like is used as a solvent. As the basic compound as a deoxidizer, potassium carbonate, sodium carbonate, sodium hydrogen carbonate, sodium hydride and the like are used. The reaction temperature is usually 160 to 25
The temperature is 0 ° C., and the reaction is carried out in the presence or absence of a solvent. Further, when the reactivity is poor, a higher temperature reaction may be carried out using an autoclave or the like. In some cases, it is usually more advantageous to carry out the reaction by adding copper powder or a catalyst such as copper oxide or copper halide.

In the general formula (I), when R ¹ is an aryl group, specific examples include a phenyl group, a biphenylyl group,
Examples include non-condensed hydrocarbon groups such as terphenylyl groups and condensed polycyclic hydrocarbon groups.

The condensed polycyclic hydrocarbon group preferably has 18 or less carbon atoms forming a ring, for example, pentalenyl group, indenyl group, naphthyl group, azulenyl group,
Heptalenyl group, biphenylenyl group, as-indacenyl group, fluorenyl group, s-indacenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrylenyl group, Examples thereof include an aceanthrylenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, and a naphthacenyl group. Also,
Specific examples of R ¹ being a heterocyclic group include a pyridyl group, a furanyl group, a thiofuranyl group, a quinolyl group, an indolyl group and a carbazolyl group.

Further, the following formula 2 in the general formula is

[Chemical 2] When it is an arylene group, specific examples thereof include a divalent group of a monocyclic hydrocarbon compound such as benzene, diphenyl ether, diphenyl thioether, and diphenyl sulfone, or biphenyl, polyphenyl, diphenylalkane,
Specific examples of divalent radicals or R ¹ of non-condensed polycyclic hydrocarbon compounds such as diphenylalkene, diphenylalkyne, triphenylmethane, distyrylbenzene, 1,1-diphenylcycloalkane, polyphenylalkane and polyphenylalkene The divalent group of the condensed polycyclic hydrocarbon compound mentioned above or the divalent group of the ring assembly hydrocarbon compound such as 9,9-diphenylfluorene can be mentioned. When it is a heterocyclic group, specific examples include divalent groups such as carbazole, dibenzofuran, dibenzothiophene, oxadiazole and thiadiazole.

When R ¹ is an aryl group or a heterocyclic group, and

[Chemical 2] When represents a divalent group such as an arylene group or a heterocyclic group, it can have the following substituents.

(1) Halogen atom, cyano group, nitro group (2) Alkyl group, preferably C _{1 to} C _12, especially C ₁
To C ₈ and more preferably C _{1 to} C ₄ linear or branched alkyl groups, and these alkyl groups further include a fluorine atom, a hydroxyl group, a cyano group, a C _{1 to} C ₄ alkoxy group,
A phenyl group substituted with a phenyl group or a halogen atom, a C _{1 to} C ₄ alkyl group or a C _{1 to} C ₄ alkoxy group may be contained. Specifically, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a t-butyl group,
s-butyl group, n-butyl group, i-butyl group, trifluoromethyl group, 2-hydroxyethyl group, 2-cyanoethyl group, 2-ethoxyethyl group, 2-methoxyethyl group, benzyl group, 4-chlorobenzyl group Group, 4-methylbenzyl group, 4-methoxybenzyl group, 4-phenylbenzyl group and the like.

(3) Alkoxy group (-OR ₁ ); R ₁ represents the alkyl group defined in (2). Specifically, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, t-butoxy group, n-butoxy group, s-butoxy group, i-butoxy group, 2-hydroxyethoxy group, 2
-Cyanoethoxy group, benzyloxy group, 4-methylbenzyloxy group, trifluoromethoxy group and the like can be mentioned.

(4) Aryloxy group: Examples of the aryl group include a phenyl group and a naphthyl group. This is C ₁
Alkoxy group -C _4, alkyl group, or a halogen atom C ₁ -C ₄ may contain a substituent group. Specifically, phenoxy group, 1-naphthyloxy group, 2-naphthyloxy group, 4-methylphenoxy group, 4-methoxyphenoquino group, 4-chlorophenoxy group, 6-methyl-2.
-A naphthyloxy group etc. are mentioned.

(5) Alkyl mercapto group (--S
R ₁ ); R ₁ represents an alkyl group defined in (2). Specific examples include a methylthio group, an ethylthio group, a phenylthio group, a p-methylphenylthio group and the like.

[0019] Represents an alkyl group or an aryl group, and
Are, for example, phenyl group, biphenylyl group or naphthyl group.
Group, which is C₁~ C_FourAlkoxy group of C
₁~ C_FourAlkyl group or halogen atom as a substituent
May be included. R₂And R₃May jointly form a ring
Yes. Also, forming a ring in cooperation with the carbon atom on the aryl group
Good. ) Specifically, an amino group, a diethylamino group,
N-methyl-N-phenylamino group, N, N-dipheny
Ruamino group, N, N-di (p-tolyl) amino group, diamino
Benzylamino group, piperidino group, morpholino group, Juro
Examples thereof include a lysyl group. (7) such as methylenedioxy group or methylenedithio group
Examples include alkylenedioxy groups and alkylenedithio groups.
You can

Typical examples of the organic compound represented by the general formula (I) are shown below.

[Table 1- (1)]

[Table 1- (2)]

[Table 1- (3)]

[Table 1- (4)]

[Table 1- (5)]

[Table 1- (6)]

[Table 1- (7)]

In the electroluminescent device of the present invention, the organic compound described above is formed to a thickness of less than 2 μm, more preferably 0.05 μm to 0.5 μm, by the vacuum evaporation method, solution coating or the like. It is constituted by forming an organic compound layer by thinning it and holding it by an anode and a cathode.

The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a typical example of the electroluminescent device of the present invention, which has a structure in which an anode, a light emitting layer and a cathode are sequentially provided on a substrate. The electroluminescent device according to FIG. 1 is particularly useful when a single compound has a hole transporting property, an electron transporting property and a light emitting property, or when a compound having each property is mixed and used.

FIG. 2 shows a light emitting layer formed by combining a hole transporting compound and an electron transporting compound. This structure is a combination of preferable characteristics of organic compounds. By combining compounds having excellent hole transporting properties or electron transporting properties, it is possible to smoothly inject holes or electrons from electrodes and obtain an element having excellent light emitting properties. It is what In addition, in the case of this type of electroluminescent element, since the light emitting substance varies depending on the organic compound to be combined, it is not possible to unambiguously determine which compound emits light.

FIG. 3 shows that the light emitting layer is formed by a combination of a hole transporting compound, a light emitting compound and an electron transporting compound, which is considered to be a type which further advances the above idea of functional separation. You can

Since this type of electroluminescent device can be obtained by appropriately combining compounds having hole transporting properties, electron transporting properties and light emitting properties,
Since the target range of the compound becomes extremely wide, not only the selection thereof becomes easy, but also various compounds having different emission wavelengths can be used, so that there are many advantages that the emission hue of the device is diversified.

The compounds of the present invention are all compounds having excellent light emission characteristics, and can have the constitutions shown in FIGS. 1, 2 and 3 if necessary.

Further, in the present invention, both the compound having an excellent hole transporting property and the compound having an excellent electron transporting property are provided by appropriately selecting the kinds of X, R ¹ and R ² in the general formula 1. It is possible.

Therefore, in the case of the structures shown in FIGS. 2 and 3, two or more compounds represented by the general formula 1 may be used as the light emitting layer forming component.

In the present invention, the compound represented by the above general formula 1 is used as a light emitting layer forming component. If necessary, an aromatic tertiary amine or N, N 'is used as a hole transporting compound. -Diphenyl-N, N'-
Bis (3-methylphenyl) -1,1'-biphenyl-
4,4′-diamine and the like, and aluminum trisoxine, perylene tetracarboxylic acid derivative and the like as the electron transporting compound can be used.

The electroluminescent device of the present invention electrically biases the light emitting layer to emit light. However, since it may cause a short circuit due to a slight pinhole and the device may not function as a light emitting layer. It is desirable to use a compound having excellent film-forming property in combination. Further, such a compound having an excellent film forming property may be combined with, for example, a polymer binder to form a light emitting layer. Examples of the polymer binder that can be used in this case include polystyrene, polyvinyltoluene, poly-N-vinylcarbazole, polymethylmethacrylate, polymethylacrylate, polyester, polycarbonate and polyamide. Further, in order to improve the efficiency of charge injection from the electrode, a charge injection / transport layer can be separately provided between the electrode and the electrode.

Examples of the anode material include nickel, gold, platinum, palladium and alloys thereof, or metals having a large work function such as tin oxide (SnO ₂ ), indium tin oxide (ITO) and copper iodide, alloys and compounds thereof, Further, conductive polymers such as poly (3-methylthiophene) and polypyrrole can be used.

On the other hand, as the cathode material, silver, tin, lead, magnesium, manganese, aluminum, or an alloy thereof having a small work function is used. At least one of the materials used as the anode and the cathode is preferably sufficiently transparent in the emission wavelength region of the device. Specifically, it is desirable to have a light transmittance of 80% or more.

In the present invention, it is preferable that the transparent anode is formed on the transparent substrate to have the structure as shown in FIGS. 1 to 3, but the reverse structure may be adopted depending on the case. Further, as the transparent substrate, glass, plastic film or the like can be used.

Further, in the present invention, in order to improve the stability of the electroluminescent device thus obtained, particularly to protect it against atmospheric moisture, a separate protective layer may be provided or the entire device may be placed in a cell. It may be filled with silicone oil or the like.

[0035]

EXAMPLES The present invention will be described in more detail based on the following examples.

[Compound No. Synthesis Example of 3] Production Example (Synthesis Example of Compound No. 3) N, N′-bis (o-tolyl) -m-phenylenediamine 6.0 g (0.021 mol), 1-iodopyrene 1
5.1 g (0.046 mol), anhydrous potassium carbonate 10.
200 to 21 by mixing 8 g (0.078 mol), Cu powder 1.3 g (0.02 mol) and nitrobenzene 20 ml.
The reaction was carried out at 0 ° C for 24 hours. After completion of the reaction, toluene 20
0 ml was added and dissolved, insoluble matter was filtered off, washed with water and concentrated to dryness. The obtained crystals were purified by column (carrier; silica gel, eluent: toluene / hexane = 1/2) to give N, N '.
-Bis (1-pyrenyl) -N, N'-bis (o-tolyl) -m-phenylenediamine 7.9 g (yield; 54.
6%). The melting point was 263.5-264.5 ° C. The elemental analysis values were as follows as C ₅₂ H ₃₆ N ₂ . C (%) H (%) N (%) Calculated value 90.67 5.27 4.07 Measured value 90.60 5.48 4.11 The infrared absorption spectrum (KBr mirror agent method) of this compound is shown in FIG. Show. Other organic compounds were synthesized in the same manner as above.

Example 1 Compound No. 1 was placed on a glass substrate having an ITO anode having a surface resistance of 20 Ω / □. The compound of 5 is vacuum-deposited to a thickness of 1000
The light emitting layer of Å was formed. Then, a cathode made of aluminum was vacuum-deposited on 1500 Å to manufacture an electroluminescence device as shown in FIG. When the device thus obtained was bonded to a power source and driven, it showed a luminance of ²⁰ cd / m ² at a driving current of 50 mA / cm ^{2, and} a maximum emission wavelength of 4
It was 78 nm. Incidentally, this element was an element having excellent stability, with almost no aggregation crystallization of the film observed over a long period of time.

Examples 2 to 5 Electroluminescent devices were produced in the same manner as in Example 1 except that the compounds constituting the light emitting layer were replaced with the compounds shown in Table 2 below. When the device thus obtained was driven by bonding a power source, the device characteristics shown in Table 2 were exhibited. Incidentally, in all of these devices, the aggregation and crystallization of the film were hardly observed over a long period of time, and the devices were excellent in stability.

[Table 2]

Example 6 A compound No. 3 was vacuum-deposited on a glass substrate having an ITO anode having a surface resistance of 20Ω / □ to form a hole transport layer having a thickness of 500Å. Then, aluminum trisoxine represented by the following chemical formula 3 is vacuum-deposited to a thickness of 500 Å
The electron transport layer of was formed. Finally, a cathode made of aluminum was vacuum-deposited on 1500 L to prepare an electroluminescence device as shown in FIG. When the device thus obtained was driven by bonding a power source to the device, yellow-green light emission showing a luminance of 1090 cd / m ² was observed at a driving current of 50 mA / cm ² . Incidentally, this element was an element having excellent stability with almost no film aggregation or crystallization observed over a long period of time.

[Chemical 3]

Examples 7 to 9 Electroluminescent devices were prepared in the same manner as in Example 6 except that the compounds forming the hole transport layer were replaced with the compounds shown in Table 3 below. When the device thus obtained was driven by connecting a power source, the device characteristics shown in Table 3 were exhibited.
All of these devices were excellent in stability, with almost no film aggregation or crystallization observed over a long period of time.

[Table 3]

Example 10 On a glass substrate having an ITO anode having a surface resistance of 20 Ω / □, the compound 4 shown below was used as a hole transport layer, and the compound No. 4 was used as a light emitting layer. 3 was 150 Å, and the following compound 5 was evaporated as an electron transport layer to 400 Å to prepare an electroluminescent device as shown in FIG. When a DC voltage was applied to the device thus obtained to drive it, a drive voltage of 6.
640 cd / at 4 V and current density of 30 mA / cm ² .
The emission luminance was m ² , and the emission peak wavelength was 475 nm.

[Chemical 4]

[Chemical 5]

Examples 11 to 21 Electroluminescent devices were produced in the same manner as in Example 10 except that the compounds constituting the light emitting layer were replaced by the compounds shown in Table 4 below. When the device thus produced was driven by applying a DC voltage, the device characteristics shown in Table 4 were exhibited.

[Table 4]

[0043]

Since the electroluminescent device of the present invention uses the compound represented by the general formula 1 as a constituent material of the organic compound layer, it is possible to obtain high-luminance light emission for a long period of time even at a low driving voltage. With it, it becomes possible to exhibit various color tones. Further, since the element can be easily produced by a vacuum vapor deposition method or the like, there is an advantage that an element having a large area can be efficiently produced at a low cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an electroluminescent device according to the present invention.

FIG. 2 is a schematic cross-sectional view of another electroluminescent device according to the present invention.

FIG. 3 is a schematic cross-sectional view of still another electroluminescent device according to the present invention.

FIG. 4 is an infrared absorption spectrum of compound No3 used in the organic compound layer in the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Chihaya Adachi 1-3-3 Nakamagome, Ota-ku, Tokyo Within Ricoh Company (72) Teruyuki Onuma, Inventor Teruyuki Onuma 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Company, Ltd. (72) Mitsutoshi Anzai 45 Miyukigaoka, Tsukuba, Ibaraki Hodogaya Chemical Co., Ltd. In-house (72) Inventor Masaki Okubo 45 Miyukigaoka, Tsukuba City, Ibaraki Prefecture Hodogaya Chemical Co., Ltd.

Claims (2)

[Claims] 1. An electroluminescent device comprising an anode and a cathode and one or a plurality of organic compound layers sandwiched therebetween, wherein at least one of the organic compound layers has the following general formula 1. An electroluminescent device, which is a layer containing the represented organic compound as a constituent component. [Chemical 1] 2. The electroluminescent device according to claim 1, wherein in the general formula 1, R ¹ is a substituted or unsubstituted aryl group.