JP2004288640A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element of which driving voltage is reduced compared with a conventional one, or the organic electroluminescent element of which emission lifetime is improved. <P>SOLUTION: This electroluminescent element at least contains a 4,4'-biphenylenediamine derivative expressed as a general formula [III] [in the formula, R<SP>10</SP>to R<SP>17</SP>show respectively a hydrogen atom, an alkyl group of the carbon number 1 to 6, or an alkoxy group or a phenyl group which may be mutually the same or different, and R<SP>10</SP>and R<SP>11</SP>, R<SP>11</SP>and R<SP>13</SP>, R<SP>12</SP>and R<SP>13</SP>, R<SP>14</SP>and R<SP>15</SP>, R<SP>15</SP>and R<SP>17</SP>and R<SP>16</SP>and R<SP>17</SP>may form a ring by being bonded together] as a positive hole transport layer material in a positive hole transport layer of a plurally-layered structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescence device (organic EL device). More specifically, the present invention relates to an organic EL device in which an arylenediamine derivative is used as a component of an organic EL device, in particular, as a hole transporting material having a multilayer structure, whereby the emission lifetime is remarkably improved.

Conventionally, various configurations of organic EL devices have been known. However, as materials for the hole transport layer in the device configuration of ITO (Indium Tin Oxide) / hole transport layer / light emitting layer / cathode, aromatic It is disclosed that a tertiary amine is used (Patent Document 1). With this device configuration, high luminance of several hundred cd / m ² can be achieved with an applied voltage of 20 V or more.
Furthermore, by using TPD [N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine] as an aromatic tertiary amine, It is disclosed that a luminance of 100 cd / m ² can be obtained with an applied voltage of 8 V even with blue light emission (Patent Document 2). However, the diamine derivative disclosed herein has a drawback that the two amino groups are separated from each other, so that the contribution of the resonance structure is weak and the ionization potential is high. The voltage cannot be sufficiently reduced, and the half-life of the device is several tens of hours, which is insufficient for practical use.
Further, a compound using m-phenylenediamine as a diamine is disclosed (Patent Document 3). Since this compound has only a phenylene group between two amino groups, it is expected to have a sufficient electron-donating property. However, since the m-phenylenediamine skeleton in the compound does not take a resonance structure, it is even more than the above-described diamine derivative. It has a drawback that the ionization potential is high, the drive voltage of the EL element cannot be sufficiently reduced, and the light emission life is short.
By the way, when the application of the EL element to a flat panel display or the like is considered, it is necessary to improve the light emission lifetime. Patent Document 4 discloses that a triamine compound can be used as a charge transporting material for an EL device, but does not sufficiently satisfy the above demand.
JP-A-63-295695 JP-A-3-231970 JP-A-5-105647 JP-A-5-107785

  An object of the present invention is to provide an organic EL element with a reduced driving voltage or an organic EL element with significantly improved light-emitting life under such circumstances.

Therefore, the present inventors have conducted intensive studies to develop an organic EL device having the above-mentioned preferable properties. As a result, an arylenediamine derivative having a specific structure was used as a component of the organic EL device, particularly as a hole transport material. It has been found that by using such an organic EL device, an organic EL device having a long emission life can be obtained.
In addition, the present inventors use a 4,4′-biphenylenediamine derivative having a certain structure and a specific structure among the above arylenediamine derivatives as a component of an organic EL device, particularly as a hole transport material. As a result, the present inventors have also found that an organic EL device having significantly improved luminescence life can be obtained. The present invention has been completed based on such findings.
That is, the present invention
General formula (III)

[In the formula, R ^{10 to} R ¹⁷ each represent a hydrogen atom, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or a phenyl group, which may be the same or different. ¹⁰ and R ¹¹ , R ¹¹ and R ¹³ , R ¹² and R ¹³ , R ¹⁴ and R ¹⁵ , R ¹⁵ and R ^17, and R ¹⁶ and R ¹⁷ may be bonded to each other to form a ring. ]
The present invention provides an organic electroluminescence device containing at least a 4,4′-biphenylenediamine derivative represented by the following formula (1) as a hole transport layer material in a hole transport layer having a multilayer structure.

  The organic EL device of the present invention contains a 4,4′-biphenylenediamine derivative as a hole transporting material in a hole transporting layer having a multilayer structure, and significantly improves the emission life and durability of the organic EL device. be able to.

で表される５つのビフェニル基を有する４，４’−ビフェニレンジアミン誘導体であり、特に、複層構造の正孔輸送層に用いた場合に、有機ＥＬ素子の耐久性を著しく向上させる。 The arylenediamine derivative used in the present invention has a general formula (III)

Is a 4,4′-biphenylenediamine derivative having five biphenyl groups, and particularly when used in a hole transport layer having a multilayer structure, significantly improves the durability of the organic EL device.

In the above general formula (III), R ^{10 to} R ¹⁷ each represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a cyclopropyl group, an n- Butyl group, isobutyl group, sec-butyl group, tert-butyl group, cyclobutyl group, n-pentyl group, cyclopentyl group, n-hexyl group, cyclohexyl group and the like, and alkoxy group having 1 to 6 carbon atoms such as methoxy group , Ethoxy, n-propoxy, isopropoxy, cyclopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclobutoxy, n-pentoxy, cyclopentoxy, n -Represents a hexoxy group, a cyclohexoxy group or the like, or a phenyl group.
In the formula (III), R ^{10 to} R ¹⁷ may be the same or different, and R ¹⁰ and R ¹¹ , R ¹¹ and R ¹³ , R ¹² and R ¹³ , R ¹⁴ and R ^{14 15} , R ¹⁵ and R ^17, and R ¹⁶ and R ¹⁷ may be bonded to each other to form a ring.
By using the 4,4′-biphenylenediamine derivative represented by the general formula (III) as a component of an organic EL device, particularly, a hole transporting layer material having a multilayer structure, the emission life of the EL device is significantly improved. can do.

〔式中、Ｇ及びＧ’は、同一又は異なる保護基、例えば、アセチル基，ベンジル基，トリフルオロアセチル基，ｔ−ブトキシカルボニル基など、好ましくはアセチル基を示す。〕
で表される保護されたジアミン誘導体と、一般式(XI)

〔式中、Ｘハロゲン原子（フッ素，塩素，臭素，ヨウ素），Ｒ¹⁰及びＲ¹¹は、前記と同じである。〕
で表されるハロゲン化アリール化合物とを縮合させたのち、保護基Ｇ，Ｇ’を外し、さらに同様の縮合を行う方法、 Next, a method for producing the 4,4′-biphenylenediamine derivative represented by the general formula (III) will be described.
The 4,4′-biphenylenediamine derivative represented by the general formula (III) is, for example,
(1) General formula (X)

[In the formula, G and G ′ represent the same or different protecting groups, for example, acetyl, benzyl, trifluoroacetyl, t-butoxycarbonyl, and preferably acetyl. ]
And a protected diamine derivative represented by the general formula (XI)

[In the formula, X halogen atom (fluorine, chlorine, bromine, iodine), R ¹⁰ and R ¹¹ are the same as described above. ]
After condensation with the aryl halide compound represented by the formula, the protective groups G and G ′ are removed, and the same condensation is performed.

〔式中、Ｒ¹⁰〜Ｒ¹³は、前記と同じである。〕
で表されるアミンと、一般式(XIII)

〔式中、Ｘは前記と同じであり、２つのＸはたがいに同じであっても異なっていてもよい。〕
で表されるジハロゲン化アリール化合物とを縮合させる方法、
(3) 上記一般式(XII) で表されるアミンと、一般式(XIV)

〔式中、Ｘは前記と同じであり、また、アミノ基は保護基で保護されていてもよい。〕
表されるハロゲン化アリール化合物とを縮合させる方法、
などによって製造することができる。 (2) General formula (XII)

Wherein R ^{10 to} R ¹³ are the same as described above. ]
With an amine represented by the general formula (XIII)

[Wherein, X is the same as above, and two Xs may be the same or different. ]
A method of condensing with a dihalogenated aryl compound represented by
(3) an amine represented by the general formula (XII) and a general formula (XIV)

[Wherein, X is the same as described above, and the amino group may be protected with a protecting group. ]
A method of condensing with the represented aryl halide compound,
It can be manufactured by such as.

などが、一般式(XI)で表されるハロゲン化アリール化合物の具体例としては、 Specific examples of the protected diamine derivative represented by the general formula (X) include:

And the like, as specific examples of the aryl halide compound represented by the general formula (XI),

などが、一般式(XII) で表されるアミンの具体例としては、

Are specific examples of the amine represented by the general formula (XII):

などが、一般式(XIII)で表されるジハロゲン化アリール化合物の具体例としては、

And the like, as specific examples of the dihalogenated aryl compound represented by the general formula (XIII),

などが、一般式(XIV) で表されるハロゲン化アミノアリール化合物の具体例としては、

And the like, as specific examples of the halogenated aminoaryl compound represented by the general formula (XIV),

などが挙げられる。

And the like.

In the above method (1), it is also possible to produce an asymmetric diamine derivative by removing the protecting groups G and G 'stepwise.
In the method of (3), the amino group of the halogenated aminoaryl compound represented by the general formula (XIV) is protected with a protecting group, and the protecting group is eliminated in a stepwise manner. It is also possible to produce asymmetric diamine derivatives. Examples of the protective group include the same as those exemplified in the description of G and G ′.
In the condensation reaction in the above methods (1) to (3), a base is used. As the base, for example, alkali metal or alkaline earth metal carbonates, hydroxides, hydrides, amines, alkyllithiums and the like are used, and potassium carbonate is particularly preferable. In this condensation reaction, a catalyst can be used if desired. Examples of the catalyst include copper or a salt thereof, nickel, and palladium. The shape of the catalyst is preferably powder, and the particle size is preferably in the range of 10 nm to 1 mm, and particularly preferably in the range of 100 to 500 nm.
The condensation reaction may be performed in a solid phase without using a solvent or in a solvent, but is preferably performed in a solvent. In this case, the solvent is preferably one having a high boiling point, for example, nitrobenzene, dimethylsulfoxide, dimethylformamide, sulfolane and the like are used. Of these, dimethyl sulfoxide is particularly preferred.
The condensation reaction temperature is usually selected in the range of 100 to 400 ° C, preferably 150 to 250 ° C. The pressure for the condensation reaction is usually normal pressure, but the reaction may be performed under pressure if necessary. The condensation time depends on the type of raw material and catalyst, the temperature, and the like, and cannot be unconditionally determined, but is generally about 3 to 36 hours.
Specific examples of the 4,4′-biphenylenediamine derivative represented by the general formula (III) include:

And the like.
The organic EL device of the present invention uses the 4,4'-biphenylenediamine derivative represented by the general formula (III) as a hole transport layer material in a hole transport layer having a multilayer structure. At this time, the diamine derivative may be contained alone or in combination of two or more.

  It is preferable that all the organic EL elements of the present invention are supported by a substrate. The substrate is not particularly limited, and a substrate commonly used in conventional organic EL elements, for example, a substrate made of glass, transparent plastic, quartz, or the like can be used.

The layer containing the 4,4′-biphenylenediamine derivative is a hole transporting layer having a multilayer structure.
The hole transporting layer containing the 4,4′-biphenylenediamine derivative is a multilayer of a 4,4′-biphenylenediamine derivative and a layer of a substance conventionally used as a hole transporting layer material of an organic EL device. It may be a structure. Further, it may have a multilayer structure including a layer made of a mixture of the 4,4′-biphenylenediamine derivative and a substance conventionally used as a hole transport layer material of an organic EL device.

  The hole transporting layer containing the 4,4′-biphenylenediamine derivative is formed using a 4,4′-biphenylenediamine derivative and, if necessary, another material for the hole transporting layer, using a vacuum deposition method, a casting method, or the like. It can be formed by a coating method, a spin coating method, or the like. Furthermore, a casting method, a coating method, a spin coating method, or the like using a solution in which the 4,4′-biphenylenediamine derivative is dispersed in a transparent polymer such as polycarbonate, polyurethane, polystyrene, polyarylate, or polyester, or a transparent polymer Can also be formed by co-evaporation.

Except for the layer containing the 4,4′-biphenylenediamine derivative, it can be formed using the same material as the conventional organic EL device.
For example, as a material of the anode, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (4 eV or more) is preferably used. Specific examples include metals such as Au and dielectric transparent materials such as CuI, ITO, SnO ₂ , and ZnO. The anode can be manufactured by forming a thin film of the above-described material by a method such as an evaporation method or a sputtering method. When light emitted from the organic light emitting layer is extracted from the anode, the transmittance of the anode is desirably greater than 10%. The sheet resistance of the anode is preferably several hundred Ω / □ or less. The thickness of the anode depends on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

On the other hand, as a material for the cathode, a metal, an alloy, an electrically conductive compound or a mixture thereof having a small work function (4 eV or less) is preferably used. Specific examples of the cathode material include sodium, lithium, a magnesium / copper mixture, Al / Al ₂ O ₃ , and indium. This cathode can be manufactured by forming a thin film of the above-mentioned material by a method such as an evaporation method or a sputtering method. When light emitted from the organic light emitting layer is taken out from the cathode, it is desirable that the transmittance of the cathode is greater than 10%. The sheet resistance of the cathode is preferably several hundred Ω / □ or less. The thickness of the cathode depends on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 50 to 200 nm.
From the viewpoint of efficiently extracting light emitted from the organic light emitting layer, it is preferable that at least one of the anode and the cathode is formed of a transparent or translucent substance.

Examples of the organic light-emitting layer material in the organic EL device of the present invention include polycyclic fused aromatic compounds, benzoxazole-based, benzothiazole-based, benzimidazole-based fluorescent whitening agents, metal-chelated oxanoid compounds, and the like. A compound having a good thin-film forming property such as a distyrylbenzene-based compound can be used.
Here, specific examples of the polycyclic fused aromatic compound include a condensed ring light-emitting substance containing an anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene skeleton and the like, and 8 to 20, preferably 8 condensed rings. And other condensed ring luminescent materials.

  Examples of the above-described benzoxazole-based, benzothiazole-based, benzimidazole-based fluorescent whitening agents include those disclosed in JP-A-59-194393. Typical examples thereof include 2,5-bis (5,7-di-t-pentyl-2-benzooxazolyl) -1,3,4-thiadiazole; 4,4′-bis (5,7-t -Pentyl-2-benzoxazolyl) stilbene; 4,4'-bis (5,7-di- (2-methyl-2-butyl) -2-benzoxazolyl) stilbene; 2,5-bis ( 5,7-di-t-pentyl-2-benzoxazolyl) thiophene; 2,5-bis (5- (α, α-dimethylbenzyl) -2-benzoxazolyl) thiophene; 2,5-bis (5,7-di- (2-methyl-2-butyl) -2-benzoxazolyl) -3,4-diphenylthiophene; 2,5-bis (5-methyl-2-benzooxazolyl) thiophene 4,4'-bis (2-benzoxazolyl) biphenyl; 5- Methyl-2- (2- (4- (5-methyl-2-benzoxazolyl) phenyl) vinyl) benzoxazole; 2- (2- (4-chlorophenyl) vinyl) naphtho (1,2-d) oxazole Benzothiazoles such as 2,2 ′-(p-phenylenedivinylene) -bisbenzothiazole and benzoimidazoles such as 2- (2- (4-carboxyphenyl) vinyl) benzimidazole. Fluorescent whitening agents are exemplified.

  As the metal chelated oxanoid compound, for example, those disclosed in JP-A-63-295695 can be used. Typical examples thereof include tris (8-quinolinol) aluminum, bis (8-quinolinol) magnesium, bis [benzo (f) -8-quinolinol] zinc, bis (2-methyl-8-quinolinolate) aluminum oxide, tris ( 8-quinolinol) indium, tris (5-methyl-8-quinolinol) aluminum, 8-quinolinollithium, tris (5-chloro-8-quinolinol) gallium, bis (5-chloro-8-quinolinol) calcium, poly (zinc) Examples thereof include 8-hydroxyquinoline-based metal complexes such as (II) -bis (8-hydroxy-5-quinolinonyl) methane and dilithium epindridione.

Further, as the distyrylbenzene-based compound, for example, those disclosed in European Patent No. 03753582 can be used. As typical examples, 1,4-bis (2-methylstyryl) benzene; 1,4-bis (3-methylstyryl) benzene; 1,4-bis (4-methylstyryl) benzene; distyrylbenzene; 1,4-bis (2-ethylstyryl) benzene; 1,4-bis (3-ethylstyryl) benzene; 1,4-bis (2-methylstyryl) -2-methylbenzene; 1,4-bis (2- Methylstyryl) -2-ethylbenzene and the like.
Also, a distyrylpyrazine derivative disclosed in JP-A-2-252793 can be used as a material for the organic light emitting layer. Typical examples thereof are 2,5-bis (4-methylstyryl) pyrazine; 2,5-bis (4-ethylstyryl) pyrazine; 2,5-bis [2- (1-naphthyl) vinyl] pyrazine; , 5-bis (4-methoxystyryl) pyrazine; 2,5-bis [2- (4-biphenyl) vinyl] pyrazine; and 2,5-bis [2- (1-pyrenyl) vinyl] pyrazine.

In addition, dimethylidin derivatives disclosed in European Patent No. 0388768 and JP-A-3-231970 can be used as a material for the organic light emitting layer. Typical examples thereof include 1,4-phenylenedimethylidin; 4,4′-biphenylenedimethylidin; 2,5-xylylenedimethylidylidine; 2,6-naphthylenedimethylidin; 1,4-biphenylene Dimethylidin; 1,4-p-terephenylenedimethylidin; 9,10-anthracenediyl dimethylidin; 4,4 ′-(2,2-di-t-butylphenylvinyl) biphenyl; 4,4 ′ -(2,2-diphenylvinyl) biphenyl and the like, and derivatives thereof.
Further, coumarin derivatives disclosed in JP-A-2-191694, perylene derivatives disclosed in JP-A-2-196885, naphthalene derivatives disclosed in JP-A-2-255789, The phthaloperinone derivatives disclosed in JP-A-289676 and JP-A-2-88689 and the styrylamine derivative disclosed in JP-A-2-250292 can also be used as the material for the organic light emitting layer.

  These organic light emitting layer materials are appropriately selected according to a desired light emission color, performance, and the like. The organic light emitting layer in the organic EL device may be formed by adding a fluorescent substance as disclosed in US Pat. No. 4,769,292. When the organic light emitting layer is formed by adding a fluorescent substance, the amount of the fluorescent substance added is preferably several mol% or less. Since the fluorescent substance emits light in response to recombination of electrons and holes, it plays a part in the light emitting function.

  Further, as the organic light emitting layer material, a compound having no thin film forming property can be used. Specific examples include 1,4-diphenyl-1,3-butadiene; 1,1,4,4-tetraphenyl-1,3-butadiene; and tetraphenylcyclopentadiene. However, an organic EL device using these materials which do not have a thin film forming property has a drawback that the lifetime of the device is short.

  As a hole transport layer of the organic EL device of the present invention, a multilayer structure of a layer of the 4,4′-biphenylenediamine derivative and a layer of a substance conventionally used as a hole transport layer material of the organic EL device; Alternatively, any of a multilayer structure including a layer made of a mixture of a 4,4′-biphenylenediamine derivative and a substance conventionally used as a hole transport layer material of an organic EL device may be used. The preferred layer structure in this case is a layer structure of the 4,4′-biphenylenediamine derivative layer and a layer of a porphyrin compound (as disclosed in JP-A-63-295695) or a layer of an organic semiconductor oligomer. It has a multilayer structure.

Representative examples of the above porphyrin compounds include polyfin, 5,10,15,20-tetraphenyl-21H-, 23H-porphine copper (II); 5,10,15,20-tetraphenyl-21H-, 23H-porphine. Zinc (II); 5,10,15,20-tetrakis (perfluorophenyl) -21H-, 23H-porphine; silicon phthalocyanine oxide; aluminum phthalocyanine chloride; phthalocyanine (metal-free); dilithium phthalocyanine; copper tetramethyl phthalocyanine; Phthalocyanine; chromium phthalocyanine; zinc phthalocyanine; lead phthalocyanine; titanium phthalocyanine oxide; magnesium phthalocyanine; copper octamethylphthalocyanine.
In addition, the organic semiconductor oligomer is particularly preferably represented by the general formula (XV)

〔式中、Ｒ¹⁸，Ｒ¹⁹及びＲ²⁰は、それぞれ炭素数１〜１０のアルキル基，炭素数１〜１０のアルコキシ基又はシクロヘキシル基を示し、それらはたがいに同一でも異なっていてもよく、ｋ，ｍ及びｎは、それぞれ１〜３の整数であって、それらの合計量は５以下である。〕で表される化合物が好適である。

[Wherein, R ¹⁸ , R ¹⁹ and R ²⁰ each represent an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a cyclohexyl group, which may be the same or different, k, m and n are each an integer of 1 to 3, and their total amount is 5 or less. Are preferred.

  In an organic EL element, an electron injection layer (electron injection transport layer) provided as needed only needs to have a function of transmitting electrons injected from a cathode to an organic light emitting layer. Any of known electron transfer compounds can be selected and used.

で表される化合物が挙げられる。 Preferred examples of the electron transfer compound include, for example,

The compound represented by is mentioned.

The electron injecting layer is a layer having any of an electron injecting property, a transporting property, and an obstacle property. In addition to the compounds of (98) to (102), a crystal of Si type, SiC type, CdS type or the like is used. A crystalline or non-crystalline material can also be used.
The organic EL element may have a layer for improving the adhesion between the layers, in addition to the anode, the cathode, the organic light emitting layer, the hole transport layer and the electron injection layer provided as needed. Specific examples of the material of such a layer, for example, a layer for improving the adhesion between the organic light emitting layer and the cathode include quinolinol metal complexes such as tris (8-quinolinol) aluminum and tris (8-quinolinol) indium. Systemic compounds can be mentioned.

The organic EL device described above can be manufactured, for example, as follows, depending on the configuration.
(A) Manufacture of an organic EL device having a structure of an anode / a hole transport layer having a multilayer structure (including a 4,4′-biphenylenediamine derivative layer) / an organic light emitting layer / a cathode. An electrode material, for example, a thin film made of an anode material is formed by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably in the range of 10 to 200 nm, to produce an anode. Next, a hole transport layer having a multilayer structure is provided by forming a thin film of the 4,4′-biphenylenediamine derivative and another material of the hole transport layer on the anode. The thinning of the 4,4′-biphenylenediamine derivative can be performed by a method such as a vacuum evaporation method, a spin coating method, and a casting method. However, a uniform film is easily obtained and a pinhole is hardly generated. From the viewpoint, the vacuum deposition method is preferable.

When a vacuum deposition method is applied to make the 4,4′-biphenylenediamine derivative into a thin film, the deposition conditions include the type of the 4,4′-biphenylenediamine derivative used, the crystal structure of the intended organic light emitting layer, and the like. Generally, the boat heating temperature is 50 to 400 ° C., the degree of vacuum is 10 ^-6 to 10 ^-3 Pa, the deposition rate is 0.01 to 50 nm / sec, the substrate temperature is -50 to + 300 ° C., and the film thickness is 5 nm to 5 μm, although it depends on the association structure. It is preferable to select appropriately within the range.
Next, an organic light emitting layer is provided on the hole transport layer having a multilayer structure using a desired organic light emitting layer material. The organic light emitting layer can be formed by thinning the organic light emitting layer material by a method such as a vacuum evaporation method, a spin coating method, a casting method, etc. However, a uniform film is easily obtained and pinholes are generated. A vacuum deposition method is preferable because it is difficult. Thereafter, a thin film made of a cathode material is formed by a method such as evaporation or sputtering so as to have a thickness of 1 μm or less, preferably 10 to 200 nm, to produce a cathode. Thereby, a desired organic EL element is obtained. In the production of this organic EL device, it is possible to reverse the production order and produce a cathode, an organic light emitting layer, a hole transport layer having a multilayer structure, and an anode on a substrate in this order.

(B) Manufacture of an organic EL device having a structure of an anode / a hole transport layer having a multilayer structure (including a 4,4′-biphenylenediamine derivative layer) / an organic light emitting layer / an electron injection layer / a cathode. An anode, a hole transporting layer having a multilayer structure (including a 4,4′-biphenylenediamine derivative layer) and an organic light emitting layer are formed thereon in the same manner as in the above (a).
After forming the organic light emitting layer, a thin film made of an electron transfer compound is formed on the organic light emitting layer by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably in the range of 5 to 100 nm. An electron injection layer is formed. Thereafter, a thin film made of a cathode material is formed on the electron injection layer in the same manner as in the above (a) to form a cathode. Thereby, a desired organic EL element is obtained. In the production of this organic EL device, the production order can be reversed, and a cathode / electron injection layer / organic light-emitting layer / hole transport layer / anode can be formed on the base electrode in this order.

The organic EL element that can be manufactured in this manner emits light by applying a DC voltage of 5 to 40 V with the anode having a positive polarity and the cathode having a negative polarity. Even if a voltage is applied with the opposite polarity, no current flows and no light emission occurs. When an AC voltage is applied, light emission occurs only when the anode has a positive polarity and the cathode has a negative polarity. When an AC voltage is applied, the waveform of the AC may be arbitrary.
The organic EL device of the present invention contains a 4,4′-biphenylenediamine derivative having five biphenyl groups as a hole transporting material in a hole transporting layer having a multilayer structure, and has an improved light emission lifetime and improved durability. Very good nature.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Production Example 1
N, N'-diacetyl-4,4'-benzidine (manufactured by Tokyo Chemical Industry Co., Ltd.) 5.03 g (18.8 mmol), 4-iododiphenyl 12.3 g (43.8 mmol), anhydrous potassium carbonate 11 g ( 80 mmol) and 1 g (16 mmol) of copper powder were placed in a 300 ml eggplant flask, suspended in 200 ml of DMSO, reacted at 180 ° C. for 5 hours, inorganic substances were filtered, and the filtration was extracted with methylene chloride. After drying over anhydrous sodium sulfate, the solvent was distilled off using an evaporator.
Next, this was dissolved in 500 ml of tetrahydrofuran (THF), 50 ml of an aqueous solution in which 20 g of potassium hydroxide was dissolved and 300 ml of ethanol were added, and the mixture was heated and stirred in a 1 liter flask for 5 hours to hydrolyze. This was extracted with ethyl acidate and dried over anhydrous sodium sulfate. The obtained compound was purified using a column supporting Wakogel C-200 [manufactured by Hiroshima Wako Co., Ltd.] using methylene chloride as a developing solvent, to obtain 9.3 g of an intermediate ocher powder.
1.02 g (2.09 mmol) of this intermediate, 1.54 g (5.50 mmol) of 4-iododiphenyl, 1.99 g (14.4 mmol) of anhydrous potassium carbonate and 1 g (16 mmol) of copper powder were obtained. The mixture was placed in a 300 ml three-necked flask, suspended in 200 ml of DMSO, and reacted at 180 ° C. for 5 hours. Next, the inorganic substance was filtered, the mother liquor was extracted with methylene chloride, dried over anhydrous sodium sulfate, and then the solvent was distilled off using an evaporator. The resulting compound was purified using a column supporting Wakogel C-200 [manufactured by Hiroshima Wako Co., Ltd.] using toluene as a developing solvent to obtain 0.50 g of a pale yellow powder.
As a result of an IR measurement, absorption was observed at 3490, 3050, 1610, 1500, 1430, 1300, 850, 770 and 710 cm ^-1 . Further, when the FD-MS was measured, a peak of m / z = 792 was obtained for C ₆₀ H ₄₄ N ₂ = 792. ¹ H-NMR was measured (solvent: chloroform-d, reference substance: tetramethylsilane (TMS)). The spectrum diagram is shown in FIG.
From these results, the pale yellow powder was identified as N, N, N ', N'-tetrakis (4-biphenyl) -4,4'-benzidine [compound (61)]. The yield was 20% and the melting point was 265 ° C.

Production Example 2
1.03 g (2.12 mmol) of the intermediate prepared in Production Example 1, 2.02 g (6.87 mmol) of 4'-methyl-4-iododiphenyl, 2.00 g (14.6 mmol) of anhydrous potassium carbonate, 1 g (16 mmol) of copper powder was reacted in the same manner as in Production Example 1 to obtain 0.47 g of a pale yellow powder.
As a result of an IR measurement, absorption was observed at 3490, 3060, 1600, 1500, 1420, 1290, 850, 770, and 710 cm ^-1 . Furthermore, measurement of the FD-MS, with respect to _{C 62 H 48 N 2 = 820} , a peak of m / z = 820 was obtained. Further, ¹ H-NMR was measured (solvent: deuterated chloroform, reference substance: tetramethylsilane (TMS)). The spectrum diagram is shown in FIG.
From these results, the pale yellow powder was found to be N, N'-bis (4-biphenyl) -N, N'-bis (4'-methyl-4-biphenyl) -4,4'-benzidine [compound (62) )]. The yield was 27% and the melting point was 257 ° C.

Example 1
A transparent support substrate was formed by forming an ITO electrode with a thickness of 100 nm on a glass substrate of 25 mm x 75 mm x 1.1 mm. This was ultrasonically cleaned with isopropyl alcohol.
This transparent support substrate was fixed to a substrate holder of a vacuum evaporation apparatus (manufactured by Japan Vacuum Engineering Co., Ltd.), and 200 mg of tris (3-methylphenylphenylamino) triphenylamine (MTDATA) was placed in a molybdenum resistance heating boat. 200 mg of the compound (61) obtained in Production Example 1 was put into another molybdenum resistance heating boat, and 4,4'-bis (2,2-diphenylvinyl) biphenyl was put into another molybdenum resistance heating boat. (DPVBi) 200 mg was added.
After the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa, the boat containing MTDATA was heated to form a film of 60 nm MTDATA on the ITO electrode at a rate of 0.1 to 0.3 nm / sec. Thereafter, the boat containing the compound (61) was heated, and the compound (61) was deposited at a deposition rate of 0.1 to 0.3 nm / sec to form a hole transport layer having a thickness of 20 nm. Subsequently, on the hole transport layer, DPVBi was deposited in a thickness of 40 nm from another boat as a light emitting layer. The deposition rate was 0.1-0.2 nm.
Next, the inside of the vacuum chamber was returned to the atmospheric pressure, and a molybdenum boat containing 100 mg of tris (8-quinolinol) aluminum (Alq) was attached to the vapor deposition apparatus, and the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa. did. 20 nm of Alq (electron injection layer) was deposited from this boat at 0.1 to 0.2 nm / sec.
Finally, it was taken out of the vacuum chamber, a stainless steel mask was placed on the injection layer, and fixed again to the substrate holder. Also, after 0.5 g of silver wire was put in a tungsten basket and 1 g of magnesium ribbon was put in a molybdenum boat, the pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa, and magnesium was changed to 1.8 nm / sec. Was deposited at a deposition rate of 0.1 nm / sec to produce a cathode.

Example 2
A device was prepared in the same manner as in Example 1 except that the compound (62) obtained in Production Example 2 was used instead of the compound (61) obtained in Production Example 1 as a hole transporting material. Was prepared.

Comparative Example 1
In Example 1, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′- instead of the compound (61) obtained in Production Example 1 as a hole transport material. A device was produced in the same manner as in Example 1, except that biphenyl-4,4'-diamine (TPD) was used.
Comparative Example 2
Example 1 was repeated except that N, N, N ', N'-tetraphenyl-p-phenylenediamine was used as the hole transport material in place of the compound (61) obtained in Production Example 1. An element was produced in the same manner as in Example 1.
Comparative Example 3
In Example 1, N, N, N ', N'-tetrakis- (4-biphenyl) -m-phenylenediamine was used as the hole transport material instead of the compound (61) obtained in Production Example 1. Except for the above, an element was fabricated in the same manner as in Example 1.
Comparative Example 4
In Example 1, instead of the compound (61) obtained in Production Example 1 as a hole transporting material, N, N, N ', N'-tetrakis- (4-biphenyl) -3,3'-dimethyl- A device was produced in the same manner as in Example 1, except that 4,4′-benzidine was used.

Table 1 shows the emission lifetimes of the devices of Examples 1 and 2 and Comparative Examples 1 to 4.
Emission lifetime constant current driving each of the elements is the time from the initial brightness 100 cd / m ² until the luminance is halved to 50 cd / m ² for the first time.
The devices of Examples 1 and 2 have remarkably improved light emission lifetimes as compared with TPD (Comparative Example 1) which is a hole transporting material having the longest light emission lifetime among known techniques.
N, N, N ', N'-tetraphenyl-p-phenylenediamine of Comparative Example 2 is a known hole transporting material, which has high crystallinity because there are only five benzene rings in the molecule. Dielectric breakdown occurred during the life measurement. On the other hand, since the compounds of Examples 1 and 2 all have six or more benzene rings in the molecule, they do not crystallize and can maintain a uniform thin film for a long time.
The N, N, N ′, N′-tetrakis- (4-biphenyl) -m-phenylenediamine of Comparative Example 3 also has six or more benzene rings in the molecule, and thus has no problem in thin film properties, but has an emission lifetime. It was remarkably short.
N, N, N ', N'-tetrakis- (4-biphenyl) -3,3'-dimethyl-4,4'-benzidine of Comparative Example 4 also has six or more benzene rings in the molecule, and thus has a thin film property. Although there was no problem, the emission life was extremely short.

FIG. 1 is a ¹ H-NMR spectrum of the compound obtained in Production Example 1. FIG. 2 is a ¹ H-NMR spectrum of the compound obtained in Production Example 2.

Claims (1)

General formula (III)

[In the formula, R ^{10 to} R ¹⁷ each represent a hydrogen atom, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or a phenyl group, which may be the same or different. ¹⁰ and R ¹¹ , R ¹¹ and R ¹³ , R ¹² and R ¹³ , R ¹⁴ and R ¹⁵ , R ¹⁵ and R ^17, and R ¹⁶ and R ¹⁷ may be bonded to each other to form a ring. ]
An organic electroluminescence device comprising at least a 4,4′-biphenylenediamine derivative represented by the formula (1) as a hole transport layer material in a hole transport layer having a multilayer structure.

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