JP2009238890A - Charge transport film, and organic electroluminescence element - Google Patents

Abstract

Provided is a charge transport film having high mechanical properties and hardness, further suppressing crystallization of a charge transport material, and having good film uniformity and transparency.
A charge transport film comprising a charge transport material and a polymer of a compound having a polymerizable functional group, wherein the compound having the polymerizable functional group has an aromatic ring density of 0.37 or more. It is a charge transport film characterized.
[Selection figure] None

Description

  The present invention relates to a charge transport film, and more particularly to an organic charge transport film having excellent charge transport properties, film uniformity, durability, and mechanical properties. The present invention also relates to an organic electroluminescence device using the same.

In recent years, charge transport materials have been widely used for electrophotographic photoreceptors, organic electroluminescence elements, organic semiconductors, and the like.
An electrophotographic organic photoreceptor can be obtained by sequentially laminating a charge generation layer and a charge transport layer on a conductive support. The charge transport layer is usually composed of a charge transport material alone or a charge transport material and a binder resin (binder).
Electrophotography is a system that performs modeling by repeating charging, exposure, development, transfer, cleaning, and static elimination on a photoconductor. In an electrophotographic organic photoconductor, friction between the blade and the photoconductor during cleaning is performed. However, it is known that the photoconductor may be scraped or scratched to shorten the life of the photoconductor.
In order to improve it, a photoreceptor having a crosslinked structure and a surface having high hardness has been proposed (for example, Patent Document 1). As a method for introducing a crosslinked structure, a method in which a polyfunctional monomer having a plurality of polymerizable groups is added and polymerized by light, heat, or electron beam is often used.

Similarly, the charge transport layer of the organic electroluminescence element is composed of a charge transport material alone or a charge transport material and a binder resin. In an organic electroluminescence element, mixing of components occurs between the charge transport layer and the light emitting layer due to long-term use, and a decrease in light emission efficiency may be a problem. In order to improve it, it is disclosed that the lifetime of the device is extended by improving the hardness of the charge transport layer and suppressing the mixing of the components of the layers (for example, Patent Document 2).
In addition, when an organic electroluminescence element is subjected to a heat resistance test, there is a problem that a short circuit or a pixel defect occurs due to crystallization of the charge transport material in the charge transport layer. In order to solve this, an organic EL element material having excellent heat resistance and long life has been proposed (for example, Patent Document 3). In addition, it has been proposed to improve heat resistance by using an organic binder having crosslinkability (for example, Patent Document 4).
JP-A-8-26279 JP 2005-332633 A International Publication No. 2005/089027 Japanese Patent No. 2921382

  In many cases, the charge transport layer is produced by dissolving a charge transport material and a binder in a solvent, applying the solution onto a substrate, and drying the solution. Triarylamines including N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1 ′] biphenyl-4,4′-diamine (TPD) as charge transport materials Shows good electrical characteristics and is widely used, but triarylamines have high crystallinity, and their precipitation often becomes a problem during coating and drying. In any of the charge transport layers having the crosslinked structure, the dried product is dried by heating after exposure curing, and has a residual solvent at the time of curing. If sufficient drying is performed prior to curing, crystallization of the charge transport material occurs. In the method of exposing in a state having a residual solvent, the amount of the residual agent may be different in actual production, which causes variations in charge transport ability and hardness for each product.

  An object of the present invention is to provide a charge transport film having high mechanical properties and hardness, further suppressing crystallization of the charge transport material, and having good film uniformity and transparency, and an organic electroluminescence device using the same. Is to provide.

Means for solving the above-mentioned problems are as follows.
<1> A charge transport film comprising a charge transport material and a polymer of a compound having a polymerizable functional group, wherein the aromatic ring density of the compound having the polymerizable functional group is 0.37 or more. A charge transport membrane.
<2> The charge transport film according to <1>, wherein the compound having a polymerizable functional group is a compound composed of a carbon atom, a hydrogen atom, and an oxygen atom.
<3> The charge transport film according to <1> or <2>, further comprising a polymer binder.
<4> The charge transport film according to any one of <1> to <3>, wherein the charge transport material is any of an arylamine derivative and a benzidine derivative or a mixture thereof.
<5> An organic electroluminescence device having the charge transport film according to any one of <1> to <4>.

  According to the present invention, a charge transport film having high mechanical properties and hardness, further suppressing crystallization of the charge transport material, and having good film uniformity and transparency, and an organic electroluminescence device using the same Can be provided.

Hereinafter, the present invention will be described in detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
The present invention relates to a charge transport film containing a charge transport material and a polymer of a compound having a polymerizable functional group. In the charge transport film of the present invention, the aromatic ring density of the compound having a polymerizable functional group is 0.37 or more. Hereinafter, each component will be described in detail.

<Compound having a polymerizable functional group>
The compound having a polymerizable group that can be used in the present invention has an aromatic ring density of 0.37 or more. “Aromatic ring density” refers to the value of B / A where A is the total molecular weight of a compound having a polymerizable functional group, and B is the molecular weight of the aromatic ring portion of the compound having a polymerizable functional group. Here, the molecular weight B of the aromatic ring portion is a molecular weight of a constituent atom of the aromatic ring and a hydrogen atom directly bonded thereto. When there is a group having 1 or more atoms (other than a hydrogen atom) directly bonded to a ring-constituting atom, the molecular weight B of the aromatic ring moiety is calculated excluding the group. In a compound having a plurality of aromatic rings in one molecule, the molecular weight B of the aromatic ring portion is the sum of the molecular weights of the plurality of aromatic ring sites. For example, in the compound (1) described later, the molecular weight A is 336.38, the molecular weight B of the aromatic ring portion is 152.19, and the aromatic ring density is calculated as 152.19 / 336.38 = 0.552. .

  When the aromatic ring density of the compound having a polymerizable functional group is 0.37 or more, crystallization of the charge transport material can be suppressed, and a charge transport film excellent in uniformity and transparency can be produced. The aromatic ring density is preferably 0.37 to 0.85, more preferably 0.40 to 0.80, and still more preferably 0.43 to 0.75.

  Examples of the aromatic ring in the compound having a polymerizable group include any of an aromatic hydrocarbon ring and an aromatic heterocyclic ring having a hetero atom such as a nitrogen atom, a sulfur atom, or an oxygen atom. From the viewpoint of electrical characteristics, an aromatic hydrocarbon ring is preferable, and more specifically, a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a triphenylene ring, and the like are preferable.

The polymerizable functional group is a radical polymerizable, cationic polymerizable, anionic polymerizable, or coordination polymerizable functional group, and is preferably a radical polymerizable or cationic polymerizable functional group for ease of polymerization. A radical polymerizable functional group is more preferable. Specific examples include carbon-carbon double bonds such as acryloyl group, methacryloyl group, and styryl group.
Moreover, it is preferable that there are two or more polymerizable functional groups in the molecule. When there are two or more, the heat resistance test and the effect of suppressing the crystallization of the charge transport material over a long period of time are enhanced, and a charge transport film having a high hardness and a high elastic modulus can also be obtained. An example of a compound having two or more polymerizable functional groups in the molecule includes a single or a plurality of aromatic rings in the molecule, and at least one atom (for example, carbon atom) constituting each aromatic ring is A compound bonded to a polymerizable functional group directly or through a linking group.

The polymerizable functional group is a functional group bonded to an atom (for example, a carbon atom) constituting the aromatic ring directly or via a linking group. Examples of the linking group include an alkylene group having 1 to 30 carbon atoms, an NR ¹ group (R ¹ is a hydrogen atom or an alkyl group having 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, A divalent linking group comprising a sulfonyl group or a combination thereof is preferred. However, it is not limited to these.

  The compound having a polymerizable functional group is preferably composed only of carbon atoms, hydrogen atoms, and oxygen atoms from the viewpoint of electrical characteristics (high charge mobility).

Preferred specific examples of the compound having a polymerizable functional group in the present invention will be given below (numbers are aromatic ring densities).

These compounds having a polymerizable functional group may be used alone or in combination of two or more.
The content of the compound having a polymerizable functional group in the charge transport film is preferably 5 to 80% by mass, more preferably 10 to 60% by mass, and still more preferably 15 to 50% by mass. When the content is within the above range, good film strength and film uniformity can be obtained.

<Charge transport material>
There is no particular limitation on the charge transport material that can be used in the present invention. Examples include (a) triazole derivatives described in U.S. Pat. No. 3,112,197 and (b) oxadi described in U.S. Pat. No. 3,189,447. Azole derivatives, (c) imidazole derivatives described in JP-B-37-16096, (d) US Pat. Nos. 3,615,402, 3,820,989, 3,542,544 Polyarylalkanes described in JP-B-45-555, JP-A-51-10983, JP-A-51-93224, JP-A-55-108667, JP-A-55-156953, JP-A-56-36656, and the like. Derivatives (e) U.S. Pat. Nos. 3,180,729, 4,278,746, JP-A-55-88064, 55-88065, 49-105537, Pyrazoline derivatives and pyrazolone derivatives described in JP-A-5-51086, JP-A-56-80051, JP-A-56-88141, JP-A-57-45545, JP-A-54-112737, JP-A-55-74546, (F) U.S. Pat. No. 3,615,404, Japanese Patent Publication Nos. 51-10105, 46-3712, 47-28336, Japanese Patent Laid-Open Nos. 54-83435, 54-1110836, 54-1119925 (G) U.S. Pat. Nos. 3,567,450, 3,180,703, 3,240,597, 3,658,520 No. 4,232,103, No. 4,175,961, No. 4,012,376, West German Patent (DAS) No. 1,110,518, Shoko No. 9-35702, 39-27577, JP-A-55-144250, 56-119132, 56-22437, and the like, (h) US Patent No. Amino-substituted chalcone derivatives described in US Pat. No. 3,526,501, (i) N, N-bicarbazyl derivatives described in US Pat. No. 3,542,546, etc., (j) US Pat. No. 3,257, Oxazole derivatives described in No. 203 specification, (k) styrylanthracene derivatives described in JP-A-56-46234, etc., (l) fluorenone derivatives described in JP-A No. 54-110837, etc. (M) U.S. Pat. No. 3,717,462, JP-A-54-59143 (corresponding to U.S. Pat. No. 4,150,987), 55-52063 Hydrazone derivatives described in Japanese Patent No. 55-52064, 55-46760, 55-85495, 57-11350, 57-14849, 57-104144, and the like, (N) U.S. Pat. Nos. 4,047,948, 4,047,949, 4,265,990, 4,273,846, 4,299,897, 4,306, Benzidine derivatives described in the specification of No. 008, etc., (o) described in JP-A Nos. 58-190953, 59-95540, 59-97148, 59-195658, 62-36674, etc. Stilbene derivatives and the like. From the viewpoint of charge transportability, (f) a phenylenediamine derivative, (g) an arylamine derivative, (n) a benzidine derivative, and (o) a stilbene derivative are preferable, and (n) a benzidine derivative is most preferable.

  The content of the charge transport material in the charge transport film is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and still more preferably 25 to 60% by mass. When the content is within the above range, a favorable charge transport property can be obtained.

<Charge transport membrane>
The charge transport film of the present invention can be produced by various methods. An example is as follows.
First, a coating solution of a composition containing a charge transport material and a compound having a polymerizable functional group is prepared. There is no restriction | limiting in particular about the solvent used for preparation of a coating liquid. The solvent used is generally an organic solvent having a boiling point of 30 to 200 ° C., preferably 30 to 150, more preferably 30 to 130 ° C. under atmospheric pressure. More specifically, 2-butanone, 2,4-dimethyl-3-pentanone, ethyl acetate, 1-butanol, fluorobenzene, 1,2-dimethoxyethane, acetone, methylene chloride, tetrahydrofuran, toluene and the like can be mentioned.

A polymerization initiator is preferably added to the composition. There is no restriction | limiting in particular about a polymerization initiator. Either a photopolymerization initiator or a thermal polymerization initiator may be used, and can be selected according to the polymerizable functional group of the compound.
The photopolymerization initiator is not particularly limited as long as radicals generated by light and other active species react with the polymerizable double bond in the monomer. Examples of usable photopolymerization initiators include acetophenone derivatives, benzophenone derivatives, benzyl derivatives, benzoin derivatives, benzoin ether derivatives, benzyl dialkyl ketal derivatives, thioxanthone derivatives, acylphosphine oxide derivatives, metal complexes, p-dialkylaminobenzoates. Acids, azo compounds, peroxide compounds and the like are included. Acetophenone derivatives, benzyl derivatives, benzoin ether derivatives, benzyl dialkyl ketal derivatives, thioxanthone derivatives, and acyl phosphine oxide derivatives are preferable, and acetophenone derivatives, benzoin ether derivatives, benzyl dialkyl ketal derivatives, and acyl phosphine oxide derivatives are particularly preferable.

Specific examples of the photopolymerization initiator include acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, benzophenone, p, p′-dichlorobenzophenone, p, p′-bis. Diethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin isopropyl ether, benzoin-n-propyl ether, benzoin isobutyl ether, benzyldimethyl ketal, 1-hydroxy-cyclohexyl phenyl ketone, tetramethylthiuram monosulfide, thioxanthone, 2- Chlorothioxanthone, 2,4-dimethylthioxanthone, 2,2-dimethylpropioyl diphenylphosphine oxide, 2-methyl-2-ethyl Xanoyl diphenylphosphine oxide, 2,6-dimethylbenzoyl diphenylphosphine oxide, 2,6-dimethoxybenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 2,3,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,3,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6- Trimethoxybenzoyl-diphenylphosphine oxide, 2,4,6-trichlorobenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl naphthyl phosphonate, Scan (eta ^{5-2,4-cyclopentadiene-1-yl)} - bis (2,6-difluoro-3-(1H-pyrrol-1-yl) - Finiru) titanium, p- dimethylaminobenzoic acid, p- Diethylaminobenzoic acid, azobisisobutyronitrile, 1,1′-azobis (1-acetoxy-1-phenylethane), benzoin peroxide, di-tert-butyl peroxide and the like are included.
Further, as examples of photopolymerization initiators, mention may be made of photopolymerization initiators described on pages 65 to 148 of “Ultraviolet curing system” written by Kayo Kiyosaku (General Technology Center Co., Ltd .: 1989). Can do. These photopolymerization initiators can be used alone or in combination of two or more, and may be used in combination with a sensitizer.

  The content of the photopolymerization initiator in the charge transport film is preferably 0.1 to 15% by mass, and more preferably 0.2 to 10% by mass.

When using thermal polymerization as a polymerization reaction of the compound having a polymerizable functional group, it is preferable to add a thermal polymerization initiator to the composition. The thermal polymerization initiator is not particularly limited as long as radicals generated by heat and other active species react with the polymerizable functional group.
Examples of the thermal polymerization initiator that can be used include azobis compounds, peroxides, hydroperoxides, redox catalysts, and the like. More specifically, inorganic peroxides such as potassium persulfate and ammonium persulfate; t-butyl peroctoate, benzoyl peroxide, isopropyl percarbonate, 2,4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroper Organic peroxides such as oxide and dicumyl peroxide; 2,2′-azobisisobutyrate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile) ), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2,4,4-trimethylpentane), 2,2′-azobiscyanovaleric acid, 2,2′-azobis ( 2-Amidinopropane) hydrochloride, 2,2′-azobis [2- (5-methyl-2-imi Ethylbenzthiazoline-2-yl) propane] hydrochloride, 2,2'-azobis {2-methyl -N- [1,1'-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, and the like; includes. These initiators are preferably oil-soluble and particularly preferably azobis compounds. Accordingly, examples of particularly preferred thermal polymerization initiators include 2,2′-azobisisobutyrate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile). ), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (2,4,4-trimethylpentane) and the like.

  The content of the thermal polymerization initiator in the charge transport film is preferably 0.1 to 10% by mass, and more preferably 0.2 to 8% by mass.

Next, a coating solution of the composition is applied to the surface. There is no restriction | limiting in particular in the method of application | coating. It can apply | coat on surfaces, such as a support body, by the apply | coating methods, such as a spin coat, a dip coat, and an extrusion coat.
In addition, a layer containing a polymerizable compound can be formed on the surface of a support or the like by using a vapor deposition method or the like.
There are no particular restrictions on the material of the support. For example, both glass and polymer can be used. Examples of the polymer include norbornene resins (for example, “ARTON” (Nippon Synthetic Rubber), cycloolefin polymers (“ZEONEX” (Nippon Zeon)), cellulose acylate (“Fujitac” (Fuji Film)), polyester Polycarbonate, polyacrylate, polysulfone, polyethersulfone, etc. The support may be transparent or opaque, and is selected according to the application. A metal such as aluminum, gold, or platinum may be deposited, or a layer of a conductive compound such as iridium-tin-oxide (ITO) may be formed. You may form the thin film of this invention on the support body which has these.

Next, polymerization is advanced to cure the coating layer to form a thin film. The polymerization can be initiated by irradiating with radiation and / or by heating.
In the case of using radiation, α rays, γ rays, X rays, ultraviolet rays, visible rays, electron beams and the like can be used. Of these, ultraviolet rays and visible rays are preferably used from the viewpoint of cost and safety, and ultraviolet rays are more preferably used. When ultraviolet rays or visible rays are used as radiation, the above photopolymerization initiator is used in combination in order to initiate polymerization. As the polymerization light beam, an electron beam, an ultraviolet ray, a visible ray, and an infrared ray (heat ray) can be used as necessary. Generally, an ultraviolet ray is used. Low-pressure mercury lamps (sterilization lamps, fluorescent chemical lamps, black lights), high-pressure discharge lamps (high-pressure mercury lamps, metal halide lamps), short arc discharge lamps (super-high pressure mercury lamps, xenon lamps, mercury xenon lamps) Can be mentioned.
Irradiation can be performed before, during or after drying of the coating solvent, but generally is preferably performed after drying because the operation is simple.
When performing thermal polymerization, the heat at the time of drying of a coating solvent can also be utilized.
The polymerization is preferably performed in an inert gas (for example, argon, helium, nitrogen) from the viewpoint of polymerization rate.

  There is no restriction | limiting in particular about the thickness of the charge transport film | membrane of this invention. It can be determined according to the application. Generally, it is about 0.1-30 micrometers, and 20 micrometers or less are preferable.

Moreover, the charge transport film of the present invention may further contain a polymer binder. Examples of polymer binders include polycarbonate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer Polymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, Polymer charge transport materials such as polysilane and polyester polymer charge transport materials can be used, and polycarbonate resins and polyester resins are preferably used. These polymer binders may be used alone or in combination of two or more. The molecular weight of these polymer binders is appropriately selected depending on the thickness of the charge transport film and the type of solvent used in the coating solution, but the weight average molecular weight is preferably 3000 to 300,000, and preferably 20,000 to More preferably, it is 200,000.
The charge transport film containing the polymer binder can be prepared by preparing a coating solution containing the polymer binder together with the charge transport material and the compound having a polymerizable functional group, and by the same method as described above. it can.

  The charge transport film of the present invention can be used for various uses as it is, for example, for production of a photoconductive material. If desired, another functional layer can be disposed on or below the charge transport film of the present invention. Examples of other functional layers include a charge generation layer, an electron transport layer, a light absorption layer, and an electrode layer.

  The charge generation layer can be disposed on an upper layer or a lower layer of the charge transport film of the present invention. In general, the charge generation layer can be produced by applying a coating solution prepared by dissolving a dye in an appropriate solvent by a method such as spin coating, dip coating, or extrusion coating. Moreover, it can produce by vapor-depositing the same material. Moreover, it can produce by apply | coating the composition by which the pigment pigment was solid-dispersed in suitable polymers (Polyester, polyethylene, polymethacrylate, polyacrylate, etc.). For solid dispersion, a paint shaker, a sand grinder mill, or the like is used.

  In general, phthalocyanine-based, perylene-based, polycyclic quinone-based, azo-based compounds, and the like can be used as the dye and pigment that absorb visible light. Moreover, as a pigment | dye and pigment which absorb infrared light, a phthalocyanine series, azulenium series compound, etc. can be used. As the charge generation layer, compounds known in the field of electrophotography (for example, compounds described in Electrophotographic Society, edited by Electrophotographic Technology Fundamentals and Applications, pages 440-442 (Corona, 1988)) can be used. A containing layer may be utilized.

  Further, a protective film may be formed on the charge transport film of the present invention. Examples of protective film materials include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, and chlorosulfonated. Polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate and other high-molecular substances and silane coupling agents, etc. The organic substance can be mentioned. A cumulative film formed by Langmuir-Blodgett method (LB method) such as ω-tricosanoic acid, dioctadecyldimethylammonium chloride, and methyl stearate can also be used.

The charge transport film of the present invention can be used for various applications. For example, the charge transport film of the present invention can be used as a member of an organic EL display device. In general, an organic EL display device has an organic compound layer laminated in the order of a hole transport layer, a light emitting layer, and an electron transport layer from the anode side. Furthermore, a charge blocking layer or the like may be provided between the hole transport layer and the light-emitting layer, or between the light-emitting layer and the electron transport layer. A hole injection layer may be provided between the anode and the hole transport layer, and an electron injection layer may be provided between the cathode and the electron transport layer. Further, the light emitting layer may be a single layer, or the light emitting layer may be divided into a first light emitting layer, a second light emitting layer, a third light emitting layer, and the like. Furthermore, each layer may be divided into a plurality of secondary layers.
The charge transport film of the present invention can be used as a hole transport layer of the organic EL display device of the above aspect.

Hereinafter, functions of each layer, examples of materials used for manufacturing the layers, and the like will be described.
(anode)
The anode usually has a function as an electrode for supplying holes to the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element. , Can be appropriately selected from known electrode materials. As described above, the anode is usually provided as a transparent anode. The transparent anode is described in detail in Yutaka Sawada's “New Development of Transparent Electrode Film” published by CMC (1999). When using a plastic substrate with low heat resistance as the substrate, ITO or IZO is used, and a transparent anode formed at a low temperature of 150 ° C. or lower is preferable.

(cathode)
The cathode usually has a function as an electrode for injecting electrons into the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element, It can select suitably from well-known electrode materials.
Examples of the material constituting the cathode include metals, alloys, metal oxides, electrically conductive compounds, and mixtures thereof. Specific examples include Group 2 metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, lithium-aluminum alloys, magnesium-silver alloys, rare earth metals such as indium, ytterbium, and the like. These may be used alone, but two or more can be suitably used in combination from the viewpoint of achieving both stability and electron injection.

  Among these, as a material constituting the cathode, a material mainly composed of aluminum is preferable. The material mainly composed of aluminum refers to aluminum alone or an alloy of aluminum and 0.01 to 10% by mass of an alkali metal or a Group 2 metal (for example, lithium-aluminum alloy, magnesium-aluminum alloy). The cathode material is described in detail in JP-A-2-15595 and JP-A-5-121172. Moreover, you may insert the dielectric material layer by the thickness of 0.1-5 nm between the cathode and the said organic compound layer with the fluoride, oxide, etc. of an alkali metal or 2 group metals. This dielectric layer can also be regarded as a kind of electron injection layer.

The thickness of the cathode can be appropriately selected depending on the material constituting the cathode and cannot be generally defined, but is usually about 10 nm to 5 μm, and preferably 50 nm to 1 μm.
Further, the cathode may be transparent or opaque. The transparent cathode can be formed by depositing a thin cathode material to a thickness of 1 to 10 nm and further laminating a transparent conductive material such as ITO or IZO.

(Light emitting layer)
The light emitting layer receives holes from an anode, a hole injection layer, or a hole transport layer when an electric field is applied, receives electrons from a cathode, an electron injection layer, or an electron transport layer, and recombines holes and electrons. It is a layer having a function of providing light and emitting light. The light emitting layer may be composed of only the light emitting material, or may be a mixed layer of the host material and the light emitting material. The light emitting material may be a fluorescent light emitting material or a phosphorescent light emitting material, and the dopant may be one type or two or more types. The host material is preferably a charge transport material. The host material may be one kind or two or more kinds, and examples thereof include a configuration in which an electron transporting host material and a hole transporting host material are mixed. Furthermore, the light emitting layer may include a material that does not have charge transporting properties and does not emit light. Further, the light emitting layer may be a single layer or two or more layers, and each layer may emit light in different emission colors.

  Examples of the fluorescent light-emitting material include, for example, benzoxazole derivatives, benzimidazole derivatives, benzothiazole derivatives, styrylbenzene derivatives, polyphenyl derivatives, diphenylbutadiene derivatives, tetraphenylbutadiene derivatives, naphthalimide derivatives, coumarin derivatives, condensed aromatics. Compound, perinone derivative, oxadiazole derivative, oxazine derivative, aldazine derivative, pyralidine derivative, cyclopentadiene derivative, bisstyrylanthracene derivative, quinacridone derivative, pyrrolopyridine derivative, thiadiazolopyridine derivative, cyclopentadiene derivative, styrylamine derivative, di Typical examples include ketopyrrolopyrrole derivatives, aromatic dimethylidin compounds, metal complexes of 8-quinolinol derivatives and metal complexes of pyromethene derivatives. Various metal complexes are, polythiophene, polyphenylene, polyphenylene vinylene polymer compounds include compounds such as organic silane derivatives.

Examples of the phosphorescent material include a complex containing a transition metal atom or a lanthanoid atom. Although it does not specifically limit as said transition metal atom, Preferably, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, and platinum are mentioned, More preferably, they are rhenium, iridium, and platinum.
Examples of the lanthanoid atom include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these lanthanoid atoms, neodymium, europium, and gadolinium are preferable.

  Examples of the ligand of the complex include G. Wilkinson et al., Comprehensive Coordination Chemistry, Pergamon Press, 1987, H. Yersin, “Photochemistry and Photophysics of Coordination Compounds,” Springer-Verlag, 1987, Akio Yamamoto. Examples of the ligands described in the book “Organic Metal Chemistry-Fundamentals and Applications-” published in 1982 by Hankabosha.

  Examples of the host material contained in the light emitting layer include those having a carbazole skeleton, those having a diarylamine skeleton, those having a pyridine skeleton, those having a pyrazine skeleton, those having a triazine skeleton, and those having an arylsilane skeleton. And materials exemplified in the sections of a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer described later.

(Hole injection layer and hole transport layer)
The hole injection layer and the hole transport layer are layers having a function of receiving holes from the anode or the anode side and transporting them to the cathode side. The charge transport film of the present invention can be used as a hole transport layer. The hole injection layer is composed of carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styryl. Contains charge transport materials such as anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidin compounds, porphyrin compounds, organosilane derivatives, carbon, etc. It is preferable that the layer be

(Electron injection layer and electron transport layer)
The electron injection layer and the electron transport layer are layers having a function of receiving electrons from the cathode or the cathode side and transporting them to the anode side. Specifically, the electron injection layer and the electron transport layer are triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, Carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, aromatic tetracarboxylic anhydrides such as naphthalene and perylene, phthalocyanine derivatives, metal complexes of 8-quinolinol derivatives, metal phthalocyanines, benzoxazoles and benzothiazoles as ligands It is preferably a layer containing various metal complexes typified by metal complexes, organosilane derivatives, and the like.

(Hole blocking layer)
The hole blocking layer is a layer having a function of preventing holes transported from the anode side to the light emitting layer from passing through to the cathode side. As the organic compound layer adjacent to the light emitting layer on the cathode side, a hole blocking layer can be provided. In addition, the electron transport layer / electron injection layer may also function as a hole blocking layer.
Examples of the organic compound constituting the hole blocking layer include aluminum complexes such as BAlq, triazole derivatives, phenanthroline derivatives such as BCP, and the like.
In addition, a layer having a function of preventing electrons transported from the cathode side to the light emitting layer from passing through to the anode side can be provided at a position adjacent to the light emitting layer on the anode side. The hole transport layer / hole injection layer may also serve this function.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the following, unless otherwise specified, “part” represents “part by mass” and “molecular weight” represents “weight average molecular weight”.

Example 1
(Transparency, hardness evaluation)
<Coating liquid 1>
N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1 ′] biphenyl-4,4′-diamine (TPD) 4 parts by mass bisphenol Z polycarbonate resin (viscosity average molecular weight: 4 10,000) Compound having 4 parts by mass of polymerizable functional group (compound (2)) Compound having 0.6 parts by mass of polymerizable functional group (compound (3)) 1.2 parts by mass of 2,2-dimethoxy-2-phenyl Acetophenone 0.2 parts by mass Tetrahydrofuran 40 parts by mass

The coating solution 1 was coated on a 1 mm glass substrate using a coating bar, and then dried with a blow dryer at 120 ° C. for 1 hour. Next, while heating to 120 ° C., light curing was performed under the conditions of a halogen lamp: irradiation intensity: 67 mW / cm ² and irradiation time: 30 seconds to obtain a cured film having a thickness of 25 μm.

When the transparency of the obtained cured film was visually evaluated, no crystallization of TPD was observed, and the film was transparent and uniform.
Next, when the strength of the obtained cured film was evaluated by a pencil hardness test according to JIS-K5400, the hardness was 4H.
Moreover, when the storage elastic modulus at 150 degreeC of this obtained cured film was measured with the dynamic viscoelasticity measuring device "Vibron: DVA-225" (made by IT measurement control Co., Ltd.), it was 9.4x10. ⁵ Pa.

(Characteristic evaluation of electrophotographic photoreceptor)
As a charge generation material, a mixture composed of 15 parts by mass of titanyl phthalocyanine, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar) as a binder resin, and 300 parts by mass of n-butyl alcohol was used. This mixture was dispersed with a ball mill for 12 hours, and then the dispersion was dispersed on a conductive support (75 μm polyethylene terephthalate support using a wire round rod. Trade name Metal Me 75TS, Toray Industries, Inc. ) Manufactured) and dried to obtain a charge generation layer having a thickness of about 0.5 μm.
Next, the coating liquid 1 having the above composition was applied onto the charge generation layer using an application bar, and then dried at 120 ° C. for 1 hour using a blower dryer. Next, while heating to 120 ° C., light irradiation is performed under the conditions of a halogen lamp: irradiation intensity: 67 mW / cm ² and irradiation time: 30 seconds to form a charge transport layer having a thickness of 25 μm. And an electrophotographic photosensitive member having a photosensitive layer composed of two layers of a charge transport layer.

The produced photoreceptor was evaluated for electrophotographic characteristics as follows (measured by a static method) using an electrostatic copying paper testing apparatus (SP-428 type, manufactured by Kawaguchi Electric Manufacturing Co., Ltd.). First, the photoreceptor was charged by -6 KV corona discharge, and the surface potential V ₀ when left in a dark place for 30 seconds was measured. Next, the light from the tungsten lamp was exposed so that the illuminance on the surface of the photosensitive member was 3 lux, and the exposure amount E ₅₀ required for the surface potential to attenuate to half of the initial surface potential V ₀ was measured. The same measurement was repeated 3000 times. The results are shown in Table 1.

(Characteristic evaluation of organic electroluminescence device)
150 parts by mass of tetrahydrofuran was further added to the coating liquid 1 having the above composition to prepare a coating liquid for an organic hole transport film.
Next, the coating solution was applied by spin coating on a glass substrate of 25 mm × 25 mm × 0.7 mm having an anode made of ITO having a thickness of 150 nm, and dried to obtain a coating film. Next, while heating at 120 ° C., the film was cured by irradiation with light under the conditions of a halogen lamp: irradiation intensity: 67 mW / cm ² and irradiation time: 30 seconds, to prepare a cured film having a film thickness of 40 nm.

Next, a tris (8-quinolinolato) aluminum (III) complex is formed as an electron transporting material on the cured film by a vacuum deposition method, and a 0.05 μm electron transporting layer is laminated thereon. In addition, magnesium and silver are co-evaporated at a molar ratio of 10: 1 to form an electrode layer having a thickness of 0.2 μm, and the charge transport layer, the electron transport layer, and the electrode layer are formed on the ITO coated glass substrate in this order. A laminated organic electroluminescence device was obtained.
Using the ITO film of the organic electroluminescence element as an anode and the Mg / Ag electrode layer as a cathode, a direct current electric field was applied between the electrodes at room temperature and in the atmosphere to emit light, and the luminance was measured with a luminance meter ( BM-8 (manufactured by Topcon Corp.), green light emission with a luminance of 55000 cd / m ² was observed.

(Example 2)
A coating solution is prepared by changing 0.6 parts by mass of compound (2) and 1.2 parts by mass of compound (3) in coating solution 1 to 1.8 parts by mass of compound (2). A charge transport film, an electrophotographic photosensitive member, and an organic electroluminescence element were produced in the same manner as in Example 1 except that they were used in Example 1. Evaluation was performed in the same manner as in Example 1. Each evaluation result is shown in Table 1.

(Example 3)
A coating solution was prepared by changing 0.6 parts by mass of the compound (2) and 1.2 parts by mass of the compound (3) in the coating solution 1 to 1.8 parts by mass of the compound (6). A charge transport film, an electrophotographic photosensitive member, and an organic electroluminescence element were produced in the same manner as in Example 1 except that they were used in Example 1. Evaluation was performed in the same manner as in Example 1. Each evaluation result is shown in Table 1.

Example 4
A coating solution is prepared by changing 0.6 parts by mass of compound (2) and 1.2 parts by mass of compound (3) in coating solution 1 to 1.8 parts by mass of compound (7). A charge transport film, an electrophotographic photosensitive member, and an organic electroluminescence element were produced in the same manner as in Example 1 except that they were used in Example 1. Evaluation was performed in the same manner as in Example 1. Each evaluation result is shown in Table 1.

(Example 5)
A coating solution is prepared by changing 0.6 parts by mass of compound (2) and 1.2 parts by mass of compound (3) in coating solution 1 to 1.8 parts by mass of compound (11). A charge transport film, an electrophotographic photosensitive member, and an organic electroluminescence element were produced in the same manner as in Example 1 except that they were used in Example 1. Evaluation was performed in the same manner as in Example 1. Each evaluation result is shown in Table 1.

(Comparative Example 1)
0.6 parts by mass of the compound (2) and 1.2 parts by mass of the compound (3) in the coating liquid 1 are changed to 1.8 parts by mass of dipentaerythritol hexaacrylate (aromatic ring density: 0). A charge transport film, an electrophotographic photosensitive member, and an organic electroluminescence element were produced in the same manner as in Example 1 except that it was prepared and used instead of the coating liquid 1. However, crystals of TPD precipitated during the drying of the coating solution, and a uniform charge transport film could not be obtained.

(Comparative Example 2)
0.6 parts by mass of the compound (2) and 1.2 parts by mass of the compound (3) in the coating liquid 1 are changed to 1.8 parts by mass of the following compound A (aromatic ring density: 0.359) to change the coating liquid. A charge transport film, an electrophotographic photosensitive member, and an organic electroluminescence element were produced in the same manner as in Example 1 except that it was prepared and used instead of the coating liquid 1. However, crystals of TPD precipitated during the drying of the coating solution, and a uniform charge transport film could not be obtained.

(Comparative Example 3)
4 parts by mass of bisphenol Z polycarbonate resin, 0.6 parts by mass of compound (2) and 1.2 parts by mass of compound (3) in coating liquid 1 were changed to 5.8 parts by mass of bisphenol Z polycarbonate resin, A charge transport film, an electrophotographic photosensitive member, and an organic electroluminescence device were prepared and prepared in the same manner as in Example 1 by using instead of the coating liquid 1. Evaluation was performed in the same manner as in Example 1. Each evaluation result is shown in Table 1.

  From the results shown in the above table, it can be understood that the charge transport films of the examples of the present invention have high film strength, are not opaque due to crystal precipitation, and have high transparency. In addition, it can be understood that the electrophotographic photosensitive member and the organic EL element using the charge transport film of the present invention exhibit excellent characteristics equivalent to those of the conventional art.

Claims (5)

A charge transport film comprising a charge transport material and a polymer of a compound having a polymerizable functional group, wherein the compound having the polymerizable functional group has an aromatic ring density of 0.37 or more. Transport membrane. The charge transport film according to claim 1, wherein the compound having a polymerizable functional group is a compound composed of a carbon atom, a hydrogen atom, and an oxygen atom. The charge transport film according to claim 1, further comprising a polymer binder. The charge transport film according to any one of claims 1 to 3, wherein the charge transport material is any of an arylamine derivative and a benzidine derivative or a mixture thereof. The organic electroluminescent element which has a charge transport film of any one of Claims 1-4.