JPH09148072A - Electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroluminescent element excellent in luminous efficiency, luminous brightness and stability, having small power consumption, and capable of being easily manufactured, by providing a layer containing an organic positive hole transporting material composed of the specified compound between transparent electrodes. SOLUTION: A layer containing an organic positive hole transporting material is provided between a pair of electrodes in which at least one electrode is transparent or semi-transparent, and an organic electroluminescent element is provided. As the organic positive hole transporting material, at least one ore more compound indicated by the expressions I, II, III (R<1> to R<4> , R<6> to R<9> , R<11> to R<16> are a hydrogen atom, a halogen atom, an alkyl group, an alkoxyl group, an aryl group, R<5> and R<10> and a hydrogen atom, a halogen atom, a siano group, a nitro group, an alkyl group, an alkoxyl group, an aryl group, (a) to (d), (f) to (p) are 1 to 5, and (e) is 1 to 6) is used. It is preferable that the layer has a single layer structure from a view of facilitation of manufacture, and the layer is formed by a vapor phase epitaxy method such as a solution applying method or a vacuum depositing method.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an organic electroluminescence device.

[0002]

2. Description of the Related Art Light emission from an organic electroluminescence device is based on the fact that holes and electrons injected from an electrode are recombined in a light emitting layer to excite fluorescent molecules contained in the light emitting layer. It is considered. Aromatic tertiary amines such as triphenylamine, phthalocyanines, polysilanes and the like have been conventionally used as hole transporting substances for electroluminescent elements. Further, oxadiazoles and the like have been conventionally used as the electron transport material.

[0003]

However, organic electroluminescent elements containing these charge-transporting substances are capable of emitting light with high brightness at a lower voltage than conventional electroluminescent elements, and can easily be made large in area. However, it has advantages such as multicolor emission, but it is difficult to maintain emission intensity and electron injection efficiency is low, so stability and emission efficiency are improved. Is a big issue. As one of the causes of the decrease in light emission intensity, deterioration and crystallization of the hole transport substance due to heat generation during light emission of the electroluminescence element are considered. On the other hand, the cause of the low electron injection efficiency is considered to be the size of the energy barrier between the cathode and the electron transport material. The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide an organic electroluminescence device which is excellent in light emission efficiency, light emission luminance and stability, consumes less power, and is easy to manufacture.

[0004]

Means for Solving the Problems The present inventors have conducted extensive studies to solve the above problems, and as a result, general formulas (1), (2), and (3) which have not been conventionally studied as organic electroluminescence element materials. It has been found that the compound represented by can be used as a hole transporting material and has excellent thermal stability. At the same time, they found that the energy levels of the compounds represented by the general formulas (4), (5), and (6) were closer to the cathode than that of the fluorescent substance, and found that they can be used as an electron transporting substance. Of.

Therefore, the electroluminescent device of the present invention has the general formulas (1), (2),
It is characterized by containing the compound represented by (3). Further, another organic electroluminescence device of the present invention is characterized by containing the compounds represented by the general formulas (4), (5) and (6) as an organic electron transporting substance.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The organic electroluminescence device of the present invention is a compound represented by the general formula (1), (2) or (3) or a compound represented by the general formula (4), (5) or (6). The layer structure is not particularly limited as long as it contains the compound described above, but a single layer structure is particularly preferable in terms of easiness of production and the like. Further, the layer contains other components that do not inhibit the function of the compound represented by the general formula (1), (2), (3) or the general formula (4), (5), (6). May be. The film thickness of each layer in the organic electroluminescence element of the present invention is not particularly limited, and may be set in an optimum range according to the structure and the like. Each layer is formed by a conventionally known method. For example, it can be formed by a so-called solution coating method in which a coating solution in which a material forming a layer is dissolved in a suitable solvent is coated on a substrate or another layer and dried. It can also be formed by a vapor phase growth method such as a vacuum vapor deposition method.

As specific examples of the hole transporting material represented by the general formula (1), compounds represented by the following formulas (1-1) to (1-9) are preferably used. Especially those of formula (1-1) are preferred.

[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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[0013]

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[0014]

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[0015]

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[0016]

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As specific examples of the hole transporting material represented by the general formula (2), compounds represented by the following formulas (2-1) to (2-3) are preferably used. Especially those of formula (2-1) are preferred.

[0018]

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[0019]

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[0020]

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As specific examples of the hole transport material represented by the general formula (3), compounds represented by the following formulas (3-1) to (3-6) are preferably used. Especially those of formula (3-1) are preferred.

[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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As specific examples of the electron transporting substance represented by the general formula (4), compounds represented by the following formulas (4-1) to (4-3) are preferably used. Particularly preferred are those of formula (4-1).

[0029]

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[0030]

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[0031]

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As a specific example of the electron transporting material represented by the general formula (5), a compound represented by the following formula (5-1) is preferably used.

[0033]

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As specific examples of the electron transporting material represented by the general formula (6), compounds represented by the following formulas (6-1) and (6-2) are preferably used. Especially those of formula (6-1) are preferred.

[0035]

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[0036]

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The conductive material used as the anode of the organic electroluminescence device of the present invention preferably has a work function of more than 4 eV, such as carbon, aluminum, vanadium, iron, cobalt, nickel, copper, zinc,
Tungsten, silver, tin, gold and the like and alloys thereof, tin oxide and indium oxide are used. On the other hand, the conductive material used as the cathode preferably has a work function smaller than 4 eV, and magnesium, calcium, titanium, yttrium, lithium, gadolinium, ytterbium, ruthenium, manganese and alloys thereof are used. .

At least one of the electrodes needs to be transparent or semi-transparent. At this time, if a transparent electrode is used for the cathode, the transparency is likely to be impaired, so the anode is preferably transparent or semitransparent. When the transparent electrode is formed, the conductive material may be formed on the transparent substrate by a method such as vapor deposition or sputtering so that the desired translucency can be ensured. The transparent substrate is not particularly limited as long as it has a proper strength and is transparent and is not easily affected by heat due to vapor deposition or the like when an electroluminescence element is formed. For example, a glass substrate or a transparent resin such as polyethylene, polypropylene, polyether sulfone or polyether ether ketone can be preferably used. ITO with a transparent electrode formed on a glass substrate,
NESA and the like are commercially available.

Fluorescent substances that can be used in the present invention include:
A conventionally known one can be used. For example, epidrizine,
2,5-bis [5,7-JI-t-pentyl-2-benzoxazolyl] thiophene, 2,2 '-(1,4-phenylenedivinylene) bisbenzothiazole, 2,2'-
(4,4′-biphenylene) bisbenzothiazole, 5
-Methyl-2- {2- [4- (5-methyl-2-benzoxazolyl) phenyl] benzoxazole, 2,5-
Bis (5-methyl-2-benzoxazolyl) thiophene, anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, perinone, 1,4-diphenylbutadiene, tetraphenylbutadiene, coumarin,
Macridine stilbene, 2- (4-biphenyl) -6-
Phenylbenzoxazole, aluminum trisoxine, magnesium bisoxine, bis (benzo-8-
Quinolinol) zinc, bis (2-methyl-8quinolinoleate) aluminum oxide, indium trisoxine, aluminum tris (5-methyloxine),
Tris (8-quinolinol) aluminum, lithium oxine, gallium trioxine, calcium bis (5-
Chlorooxin), polyzinc-bis (8-hydroxy-
5-quinolinonyl) methane) dilithium epindridione, zinc bisoxine, 1,2-phthaloperinone, 1,
2-naphthaloperinone etc. are mentioned. Further, general fluorescent dyes such as fluorescent coumarin dye, fluorescent perylene dye, fluorescent pyran dye, fluorescent thiopyran dye, fluorescent polymethine dye, fluorescent merocyanine dye, fluorescent imidazole dye and the like can also be used. Among these, tris (8-quinolinol) aluminum is particularly preferable.

The binder resin which can be used in the present invention includes saturated polyester, polyamide resin, acrylic resin, ethylene-vinyl acetate resin, ionic cross-linked olefin copolymer (ionomer), styrene-butadiene block copolymer, polycarbonate and chloride. Thermoplastic resin such as vinyl-vinyl acetate copolymer, cellulose ester, polyimide, styrene resin; thermosetting of epoxy resin, urethane resin, silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin, thermosetting acrylic resin, etc. Resins; photocurable resins; photoconductive resins such as polyvinylcarbazole, polyvinylpyrene, polyvinylanthracene, and polyvinylpyrrole. These can be used alone or in combination. Of these, polymethyl methacrylate is particularly preferably used. These electrically insulating resins are individually measured 1 x 1
It preferably has a volume resistance of 0 ¹² Ωcm or more.

[0041]

Next, the present invention will be described in more detail with reference to examples. Example 1 An ITO film is formed on a glass substrate by spattering to form a hole injection electrode. After washing the substrate with a neutral detergent, ultrasonic cleaning is performed in acetone for 15 minutes and in ethanol for 15 minutes. Next, the substrate is placed in boiling ethanol for 10 minutes, and then immediately blown dry. A compound represented by the formula (1-1) is used as a hole transporting substance, tris (8-quinolinol) aluminum is used as a fluorescent substance, and polymethylmethacrylate is used as a binder resin in 1,2-dichloroethane solvent. Hang it on the board,
A uniform film is formed by spin coating. After the film is sufficiently dried, a Mg-Ag alloy (Mg: Ag is 10: 1 by weight) is evaporated to a thickness of 150 nm on the film by an evaporation method.
An electroluminescent device of the present invention was created.

Using the ITO film of the electroluminescence device prepared as described above as an anode and the Mg-Ag electrode layer as a cathode, a direct current electric field is applied between both electrodes in a vacuum at room temperature to cause the light emitting layer to emit light, and the light emission thereof. The luminance was measured with a luminance meter (“LS-100” manufactured by Minolta Co., Ltd.). As a result, blue-violet emission with a brightness of 180 cd / m ² was observed at a driving voltage of 18V. In addition, no change in appearance was observed even when this device was continuously illuminated for 40 hours under vacuum at room temperature, and the emission brightness was at the same level as at the beginning. Example 2 An electroluminescent device was prepared in the same manner as in Example 1 except that the compound represented by formula (2-1) was used as the hole transporting material, and the luminance was measured. A blue-violet emission of 240 cd / m ² was observed at a driving voltage of 18V. Also,
Even when the device was continuously made to emit light under vacuum at room temperature for 40 hours, no change in appearance was observed and the emission brightness was at the same level as at the beginning. Example 3 An electroluminescence device was prepared in the same manner as in Example 1 except that the compound represented by the formula (3-1) was used as the hole transport material, and the luminance was measured. A violet emission of 284 cd / m ² was observed at a driving voltage of 18V. In addition, no change in appearance was observed even when this device was continuously illuminated for 40 hours under vacuum at room temperature, and the emission brightness was at the same level as at the beginning. Example 4 An ITO substrate is prepared in the same manner as in Example 1. A compound represented by the formula (4-1) as an electron transporting material, and N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'- as a hole transporting material. Diamine, tris (8-quinolinol) aluminum as a fluorescent substance, and polymethylmethacrylate as a binder resin are dissolved in a 1,2-dichloroethane solvent, and the solution is dropped on the above substrate to form a uniform film by spin coating. After the film is sufficiently dried, M is deposited on the film by a vapor deposition method.
g-Ag alloy (weight ratio Mg: Ag is 10: 1) 15
The electroluminescence element of the present invention was prepared by vapor deposition to 0 nm.

Using the ITO film of the electroluminescence device prepared as described above as an anode and the Mg-Ag electrode layer as a cathode, a direct current electric field is applied between the two electrodes in a vacuum at room temperature to cause the light emitting layer to emit light, and the light emission thereof. The luminance was measured with a luminance meter (“LS-100” manufactured by Minolta Co., Ltd.). As a result, green light emission with a luminance of 310 cd / m ² was observed at a drive voltage of 18V. In addition, no change in appearance was observed even when this device was continuously illuminated for 40 hours under vacuum at room temperature, and the emission brightness was at the same level as at the beginning. Example 5 An electroluminescence device was prepared in the same manner as in Example 4 except that the compound represented by the formula (5-1) was used as the electron transport substance, and the luminance was measured. Green light emission of 290 cd / m ² was observed at a driving voltage of 18V. In addition, no change in appearance was observed even when this device was continuously illuminated for 40 hours under vacuum at room temperature, and the emission brightness was at the same level as at the beginning. Example 6 An electroluminescence device was prepared in the same manner as in Example 4 except that the compound represented by the formula (6-1) was used as the electron transport substance, and the luminance was measured. Green light emission of 298 cd / m ² was observed at a driving voltage of 18V. Also,
Even when the device was continuously made to emit light under vacuum at room temperature for 40 hours, no change in appearance was observed and the emission brightness was at the same level as at the beginning. Comparative Example 1 An electroluminescence device was prepared in the same manner as in Example 1 except that polyvinylcarbazole was used as the hole transport material, and the brightness was measured. A yellow emission of 120 cd / m ² was observed at a driving voltage of 66V. In addition, the emission luminance of this device was reduced under vacuum at room temperature for 1 hour of continuous light emission. Comparative Example 2 An electroluminescent device was prepared and luminance was measured in the same manner as in Example 4 except that oxadiazole was used as the electron transport material. 170 at a driving voltage of 30V
Green light emission of cd / m ² was observed.

[0044]

As described above, the organic electroluminescent device of the present invention has the general formula (1), (2), (3) as a hole transport material.
Since the compound represented by is used, deterioration of the substance or crystallization due to heat generation at the time of light emission of the device does not occur and a decrease in emission intensity is prevented. Further, the other organic electroluminescent element of the present invention, as an electron transport material, the general formula (4), the energy order is closer to that of the cathode than the fluorescent material,
Since the compounds represented by (5) and (6) are used, electrons can be easily injected from the cathode to enable high-luminance emission at low potential. Further, the electroluminescent element of the present invention,
Since it is made of an organic material, a flexible large-area light emitting element can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a laminated organic electroluminescence element.

FIG. 2 is a schematic sectional view showing an example of a single-layer organic electroluminescence element.

[Explanation of symbols]

 1 Cathode 2 Electron Transport Layer 3 Light Emitting Layer 4 Anode 5 (Electron Transport Material + Fluorescent Material) Layer

Claims (4)

[Claims] 1. An electroluminescent device having a layer containing an organic hole transporting material between a pair of electrodes, at least one of which is transparent or semitransparent, wherein the organic hole transporting material is represented by the following general formula: ] [Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different,
Represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, or an aryl group which may have a substituent, and R ⁵ represents a hydrogen atom, halogen An atom, a cyano group, a nitro group, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, or an aryl group which may have a substituent.
a, b, c and d are the same or different and each represents an integer of 1 to 5, and e represents an integer of 1 to 6. [Chemical formula 2] [Wherein R ⁶ , R ⁷ , R ⁸ and R ⁹ are the same or different,
Represents a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, or an aryl group which may have a substituent, and R ¹⁰ represents a hydrogen atom, a halogen atom An atom, a cyano group, a nitro group, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, or an aryl group which may have a substituent.
f, g, h and i are the same or different and each represents an integer of 1 to 5, and j represents an integer of 1 to 4. ] [Chemical 3] [Wherein R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group,
It represents an alkoxy group or an aryl group, and the alkyl group, the alkoxy group and the aryl group may have a substituent. j, k, l, m, n, and p are the same or different and each represents an integer of 1 to 5. ] The at least 1 or more compound represented by this is used, The electroluminescent element characterized by the above-mentioned. 2. The electroluminescent device according to claim 1, which has a single-layer structure. 3. An electroluminescent device having a layer containing an organic electron charge transporting material between a pair of electrodes, at least one of which is transparent or semi-transparent, wherein the organic electron transporting material has the following general formula: [Wherein R ¹⁷ , R ¹⁸ , R ¹⁹ , R ²⁰ and R ²¹ are the same or different and each is a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent] ,
The aryl group which may have a substituent, the aralkyl group which may have a substituent, or the phenoxy group which may have a substituent is shown. [Chemical formula 5] [In the formula, R ²² and R ²³ are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyloxycarbonyl group, a hydrogen group, a nitro group or a cyano group. X represents a group: O, N-CN or C (CN) ₂ . ] [Chemical 6] [In the formula, R ^{24 to} R ²⁷ are the same or different and each represents a hydrogen atom, an alkyl group, an aryl group, an alkoxy group or a halogen atom. ] The at least 1 or more compound represented by this is used, The electroluminescent element characterized by the above-mentioned. 4. The electroluminescent device according to claim 3, which has a single-layer structure.