JPH0222375B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to a laminated electrophotographic photoreceptor having a layer containing a charge-generating substance (charge-generating layer) and a layer containing a charge-transporting substance (charge-transporting layer). Conventionally, electrophotographic photoreceptors using inorganic photoconductive materials such as selenium, selenium alloys, zinc oxide, cadmium sulfide-resin dispersion layers, and polyvinylcarbazole-based photoconductive polymers, polyvinylcarbazole/2.4 .7-trinitro-9-
Those using organic photoconductive substances, such as charge transfer complexes such as fluorene-based ones, and fine particulate eutectic complexes of pyrylium dyes and alkylidene diarylenes, are known. In addition, in recent years, the ability to absorb visible light and generate free carriers (charge generation ability) and the function to transport the generated free carriers (charge transport ability) have been assigned to multiple members, thereby improving charge retention characteristics and photoresponse. sex,
Many photoreceptors have been proposed that have improved electrophotographic characteristics such as spectral sensitivity characteristics, mechanical strength, and repeat durability. These photoreceptors usually have a structure in which a layer responsible for charge generation (charge generation layer) and a layer responsible for charge transport (charge transport layer) are laminated on a conductive support. The most important properties of such a laminated photoreceptor are photoresponsiveness and stability of potential characteristics during repeated use. In order to satisfy these characteristics, the following conditions are necessary. (1) Carrier pairs of free electrons and free holes are efficiently generated in charge-generating materials by absorption of active light. (2) Of the photogenerated free carrier pairs, the majority carriers for the charge transport material are efficiently injected into the charge transport material. (3) The injected majority carriers efficiently travel within the charge transport layer via the charge transport material. (4) Minority carriers for the charge transport substance remaining in the charge generation layer efficiently travel within the charge generation layer via the charge generation substance. To date, many technologies for photoreceptors with laminated structures consisting of a combination of a charge generation layer and a charge transport layer have been proposed, but no combination that satisfies all of the above conditions is known. That is, a laminated photoreceptor can exhibit excellent properties for a short period of time in repeated electrophotographic processes, but when used repeatedly, the charging potential increases, the photoresponsiveness decreases, Phenomena such as an increase in residual potential appear, degrading the characteristics of the photoreceptor. This phenomenon is often caused by the fact that the above-mentioned condition (4) is not satisfied. The thickness of the charge generation layer is LG, and the mobility of minority carriers within the charge generation layer with respect to the charge transport substance is μG.
If the lifetime is τG and the electric field applied to the charge generation layer is EG, then condition (4) is equivalent to equation (5) below. μGτG≧LG/EG (5) In most cases, the multilayer photoreceptors that have been proposed so far are made of charge-generating substances that have many carriers of holes, such as phthalocyanine pigments, bisazo pigments, and trisazo pigments, and pyrazoline compounds, hydrazone compounds, It is composed of a combination with a hole-transporting charge-transporting substance such as a triphenylmethane compound. In such a configuration, holes among the free carrier pairs photogenerated in the charge generation layer are injected into the charge transport layer and can efficiently travel within the charge transport layer. However, since the electrons remaining in the charge generation layer are minority carriers for the charge generation substance, the product μGτG of mobility μG and lifetime τG is small, making it difficult to satisfy condition (4) or equation (5). As a result, electrons remain in the charge generation layer and generate space charges. When a photoreceptor is used repeatedly, this space charge accumulates, resulting in significant deterioration of repeated stability, such as fluctuations in potential, decrease in photosensitivity, and increase in residual potential. In order to satisfy condition (4) or equation (5), it is necessary to significantly reduce the thickness LG of the charge generation layer to about 0.1 μm, for example. However, even with such technology, it has been difficult to completely solve the above problems. Now, zinc oxide is a photoconductive material in which electrons are majority carriers. Therefore, the above problems should be solved by designing a photoreceptor with a laminated structure based on a combination of zinc oxide in the charge generation layer and a charge transport layer containing a hole transporting substance. In fact, a few proposals have been made regarding the laminated photoreceptor having such a structure (for example, Japanese Patent Application Laid-Open No. 50-67659, Nguyen Chiang K.
Isamu Shimizu, Eiichi Inoue: Photographic Science and Engineering Vol. 25, p. 254, 1981). However, all of the photoreceptors proposed above had slow photoresponsiveness and did not have practical electrophotographic properties. The present applicant had previously proposed a laminated electrophotographic photoreceptor with a new structure containing dye-sensitized zinc oxide in the charge generation layer (Japanese Patent Application No. 58-032837;
No. 69093) proposed a technique that significantly improves the above problems. However, even in the above proposal by the present applicant, there were still problems in the photoresponsiveness and repetition characteristics that should be improved. In view of the above circumstances, the applicant of the present application has conducted intensive studies to solve the problems of laminated electrophotographic photoreceptors, and as a result, has arrived at the present invention. That is, an object of the present invention is to provide a laminated electrophotographic photoreceptor having a novel layer structure. Another object of the present invention is to provide a laminated electrophotographic photoreceptor with excellent photoresponsiveness and repeatability. The object of the present invention described above is to sequentially stack an intermediate layer containing a viologen compound represented by the general formula (), a charge generation layer containing zinc oxide, and a charge transport layer containing a hole transport substance on a conductive support. This was achieved using an electrophotographic photoreceptor characterized by the following. The present invention will be explained in detail below. The applicant provided an intermediate layer containing various compounds between a conductive support and a charge generation layer containing zinc oxide, and developed an electronic process of free electrons and free holes generated in the charge generation layer by light irradiation. Observed in detail.
As a result, we discovered that when the intermediate layer contains a viologen compound, photogenerated free electrons migrate from the charge generation layer to the intermediate layer at an extremely angular velocity and are captured by the viologen compound. As a result, the present inventors have discovered that the photoresponsiveness and repetition characteristics of the photoreceptor are improved without the formation of space charges due to electrons in the charge generation layer, and have thus arrived at the present invention. It is believed that the above-mentioned phenomenon of capture of free terminals by the viologen compound is due to a unique electronic interaction between zinc oxide and the viologen compound. In the present invention, the viologen compound contained in the intermediate layer is represented by the following general formula (). However, R represents an alkyl group, an alkenyl group, an aryl group, or an aralkyl group, and X represents a halogen atom. Among the viologen compounds, specific examples suitable for the present invention are listed below. 1 1,1'-dimethyl-4,4'-dipyridinium dichloride 2 1,1'-dimethyl-4,4'-dipyridinium dibromide 3 1,1'-dimethyl-4,4'-dipyridinium diio Died 4 1,1'-diethyl-4,4'-dipyridinium dichloride 5 1,1'-diethyl-4,4'-dipyridinium dibromide 6 1,1'-diethyl-4,4'-dipyridinium dibromide Iodide 7 1,1'-di-n-propyl-4,4'-dipyridinium dichloride 8 1,1'-di-n-propyl-4,4'-dipyridinium dibromide 9 1,1'-dipyridinium dibromide -n-propyl-4,4'-dipyridinium diiodide 10 1,1'-diphenyl-4,4'-dipyridinium dichloride 11 1,1'-diphenyl-4,4'-dipyridinium dibromide 12 1 ,1'-diphenyl-4,4'-dipyridinium diiodide 13 1,1'-dibenzyl-4,4'-dipyridinium dichloride 14 1,1'-dibenzyl-4,4'-dipyridinium dibromide 15 1,1'-dibenzyl-4,4'-dipyridinium diiodide 16 1,1'-diallyl-4,4'-dipyridinium dichloride 17 1,1'-diallyl-4,4'-dipyridinium dibromide 18 1,1'-diallyl-4,4'-dipyridinium diaiodide The intermediate layer used in the present invention is prepared by coating a solution containing a viologen compound and a binder on a conductive support,
Preferably, it is formed by drying. The binder used here is preferably a resin that is compatible with the viologen compound, such as casein, gelatin, starch, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, hydroxypropyl cellulose, water-soluble polyvinyl butyral, polyacrylic acid, and polymethacrylate. Hydrophilic resins such as acid, polyethyleneimine, polyethylene glycol, water-soluble polyester, water-soluble epoxy resin, water-soluble acrylic resin, and water-soluble alkyd resin can be mentioned. The blending ratio of the binder and the viologen compound is preferably 0.1 to 50 parts by weight per 100 parts by weight of the binder. The thickness of this intermediate layer is
A range of 0.5 to 10 μm is suitable. As the coating method used when forming the intermediate layer, use a conventional method such as blade coating, rod coating, spray coating, roll coating, dip coating, bead coating, air knife coating, or curtaining coating. Can be done. As the charge generation layer used in the present invention, any layer containing zinc oxide is effective, such as a layer in which zinc oxide powder is dispersed in a binder, or a crystalline zinc oxide thin film deposited by a sputtering method. When the charge generation layer is a layer in which zinc oxide powder is dispersed in a binder, the zinc oxide powder used can be a conventionally known zinc oxide for electrophotography manufactured by the French method. Furthermore, zinc oxide, which has traditionally not been used in electrophotographic photoreceptors due to its low photoconductivity, such as zinc oxide with a specific surface area of approximately 8 m ² /g or more, acicular zinc oxide, or manufactured using the American method. Zinc oxide is also effective in the present invention. In particular, zinc oxide or acicular zinc oxide having a specific surface area value of about 8 m ² /g or more is preferred for the present invention. It is extremely preferable to dye the zinc oxide powder with a dye sensitizer from the viewpoint of improving photoresponsiveness and controlling spectral sensitivity characteristics. Dye sensitizers suitable for the present invention include fluorescein, dichlorofluorescein, dibromofluorescein, diiodofluorescein, tetrachlorfluorescein, tetrabromofluorescein, tetraiodofluorescein, tetrachlortetrabromofluorescein, tetrachlortetraiodofluorescein, Xanthene dyes such as tetrabromotetraiodofluorescein, phenolsulfophthalein dyes such as bromophenol blue, tetrabromophenol blue, tetraiodophenol blue, bromothymol blue, bromcresol purple, and bromcresol green, and thiazine dyes such as methylene blue. Dyes conventionally used in zinc oxide photoreceptors can be used as they are, such as triphenylmethane dyes such as crystal violet and malachite green, and acridine dyes such as acridine yellow and acridine orange. Although the amount of these dye sensitizers added varies depending on the specific surface area of zinc oxide, it is generally appropriate to use them in an amount in the range of 0.5 parts by weight to 10 parts by weight per 100 parts by weight of zinc oxide. Conventionally known techniques can be used to dye zinc oxide with a dye sensitizer. For example, a method in which a dye sensitizer solution and zinc oxide are mixed, the dye sensitizer is adsorbed onto the surface of the zinc oxide, and then the solution containing the unadsorbed dye sensitizer is removed. After mixing the dye sensitizer and zinc oxide and adsorbing the dye sensitizer on the surface of the zinc oxide, a binder solution is added without removing the solution containing the unadsorbed dye sensitizer. A method for preparing a charge generation layer coating solution. A method of simultaneously adding a dye sensitizer solution, zinc oxide and a binder solution and mixing and dispersing them is also effective. The dye sensitizer is dissolved in a suitable solvent, and a coating solution in which zinc oxide is added to this dye solution is sufficiently mixed and dispersed in a ball mill etc. to adsorb the dye sensitizer on the surface of the zinc oxide. drying the dyed zinc oxide cake by removing the solution containing the dye sensitizer;
A dye sensitization method suitable for the present invention is a method of preparing zinc oxide powder that has been previously dyed with a dye sensitizer (hereinafter abbreviated as dyed zinc oxide powder). As a method for removing the solution containing the unadsorbed dye sensitizer, filtration, heat drying, freeze drying, spray drying, or the technique disclosed in Japanese Patent Publication No. 39819/1986 are all effective. When the charge generation layer is a layer in which zinc oxide powder is dispersed in a binder, a mixture consisting of yarn-dyed zinc oxide powder, binder, and dispersion solvent is processed using a ball mill, attritor, sand mill, Keday mill, three-roll mill, etc. The coating liquid can be uniformly mixed and dispersed using a dispersing machine, and then formed using coating methods such as blade coating, reverse coating, rod coating, gravure coating, knife coating, and spray coating. can. Examples of the binder include film-forming polymers that are hydrophobic, have a high dielectric constant, and are electrically insulating. Examples include, but are not limited to, the following: Polycarbonate, polyarylate, polysulfone, polyethersulfone, phenoxy resin,
Poly(2,6-dimethyl-1,4-phenylene ether), polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, poly-N-vinylcarbazole, styrene-acrylonitrile copolymer, vinyl chloride-vinyl acetate Copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, vinylidene chloride-acrylonitrile copolymers, silicone resins, alkyd resins, polyester resins, polyvinyl formal, polyvinyl butyral, polyvinyl acetate, etc. These resins can be used alone or as a mixture of two or more. Dispersion solvents used in the charge generation layer coating solution include aromatic hydrocarbons such as benzene, toluene and xylene, methylene chloride, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,
Examples include halogenated hydrocarbons such as 2-trichloroethane, 1,1,2,2-tetrachloroethane, and chlorobenzene, and cyclic ethers such as tetrahydrofuran and 1,4-dioxane. The blending ratio of yarn-dyed zinc oxide and binder in the charge generation layer is 100 parts by weight of yarn-dyed zinc oxide.
It is preferable that the amount of the binder is 200 parts by weight or less. The charge transport layer in the present invention is formed by applying a coating liquid in which a charge transport substance and a resin binder are dissolved in a suitable solvent and drying the coating liquid. As the charge transport material, conventionally known compounds can be used. Among these, compounds represented by the following general formula () or general formula (), or poly-N-vinylcarbazoles are suitable charge transport materials for the present invention. (However, in the formula, R ₁ , R ₂ , R ₃ , and R ₄ are hydrogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, or aralkyl groups, and R ₅ and R ₆ are hydrogen atoms. , a substituted or unsubstituted alkyl group, cycloalkyl group, alkenyl group, cycloalkenyl group, or aryl group,
R ₇ , R ₈ , R ₉ , R ₁₀ are hydrogen atoms, hydroxyl groups,
Substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, alkoxy groups,
or represents an amino group, and further R ₅ and R ₆
may be cyclized with each other to form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms. ) (However, in the formula, A represents a substituted or unsubstituted heterocyclic group, R ₁ and R ₂ may be the same or different, and include hydrogen, an alkyl group having 1 to 4 carbon atoms, and a halogen-substituted alkyl group. , represents a hydroxyalkyl group, an alkoxy-substituted alkyl group, a cyanoalkyl group, or an aralkyl group, and R ₁ and R ₂ may be bonded to each other to form a nitrogen-containing heterocycle. Also, R ₃ is hydrogen , represents an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a halogen.) Specific examples of the compound represented by the general formula () are listed below. CA-1 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)-1-phenylmethane CA-2 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)-1-(methoxyphenyl) enyl)methane CA-3 1.1-bis(4-N,N-dimethylamino-2-methoxyphenyl)-1-phenylmethane CA-4 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)- 1-(2.4-dimethoxyphenyl)methane CA-5 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)-1-(2-chlorophenyl)methane CA-6 1.1-bis(4-N, N-diethylaminophenyl)-1-phenylmethane CA-7 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-phenylmethane CA-8 1.1-bis(4-N,N-diethylamino-2- methoxyphenyl)-1-phenylmethane CA-9 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(1-methoxyphenyl)methane CA-10 1.1-bis(4-N,N -diethylamino-2.5-dimethoxyphenyl)-1-phenylmethane CA-11 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(2.5dimethoxyphenyl)methane CA-12 1.1-bis(4 -N,N-diethylamino-2-methylphenyl)-1-(3.4methylenedioxyphenyl)methane CA-13 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(4-N, N-
dimethylaminophenyl)methane CA-14 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(4-N,N-
diethylaminophenyl)methane CA-15 1.1.1-tris(4-N,N-dimethylaminophenyl)methane CA-16 1.1.1-tris(4-N,N-dimethylamino-2-methylphenyl)methane CA -17 1.1.1-Tris(4-N,N-diethylaminophenyl)methane CA-18 1.1.1-Tris(4-N,N-diethylamino-2-methylphenyl)methane CA-19 1.1-bis(4- N,N-diethylamino-2-methylphenyl)-1-(4-N,N-
dimethylamino-2-methylphenyl)methane CA-20 1.1-bis(4-N,N-dibenzylaminophenyl)-1-phenylmethane CA-21 1.1-bis(4-N,N-dibenzylamino-2- methylphenyl)-1-phenylmethane CA-22 1.1-bis[4-N,N-di(p-tolyl)aminophenyl]-1-phenylmethane CA-23 1.1-bis[4-N,N-di(p-tolyl) Amino-2-methylphenyl]-1-phenylmethane CA-24 1.1-bis(4-N,N-dibenzylamino-2-methylphenyl)-3-phenylpropane CA-25 1.1-bis(4-N,N- dibenzylamino-2-methylphenyl)pentane CA-26 1.1-bis(4-N,N-dibenzylamino-2-methylphenyl)cyclohexane CA-27 1.1-bis(4-N,N-dibenzylamino-2.5- dimethylphenyl)heptane CA-28 1.1-bis(4-N,N dibenzylamino-2-methylphenyl)-1-(4-N,N-
diethylaminophenyl)methane CA-29 1.1-bis(4-N,N-dibenzylamino-2-methylphenyl)-1-(4-N,N
-diethylamino-2-methylphenyl)methane CA-30 1.1.1-tris(4-N,N-dibenzylamino-2-methylphenyl)methane CA-31 1.1-bis(4-N,N-dibenzylamino-2 -methoxyphenyl)-1-phenylmethane CA-32 1.1-bis(4-N,N-dibenzylamino-2.5-dimethoxyphenyl)-1-phenylmethane CA-33 1.1-bis(4-N,N-dibenzylamino-2.5-dimethoxyphenyl)-1-phenylmethane CA-33 Benzylamino-2-methylphenyl)-1-(2.4-methylenedioxyphenyl)methane CA-34 1.1-bis(4-N,N-dibenzylamino-2-methoxyphenyl)-1-(2.4-methylene dioxyphenyl)methane CA-35 2.2-bis(4-N,N-diethylamino-2-methylphenyl)propane CA-36 2.2-bis(4-N,N-diethylamino-2-methoxyphenyl)propane CA- 37 2.2-bis(4-N,N-dibenzylamino-2-methylphenyl)propane CA-38 2.2-bis(4-N,N-dibenzylamino-2-methoxyphenyl)propane Represented by general formula () Specific examples of such compounds are listed below. CB-1 1.1-bis(4-N,N-diethylaminophenyl)-2-pyridylmethane CB-2 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-2-pyridylmethane CB-3 1.1 -bis(4-N,N-diethylaminophenyl)-3-pyridylmethane CB-4 1.1-bis(4-N,N-diethylaminophenyl)-4-pyridylmethane CB-5 1.1-bis(4-N , N-diethylaminophenyl)-2-furylmethane CB-6 1.1-bis(4-N,N-diethylaminophenyl)-2-thienylmethane CB-7 1.1-bis(4-N,N-diethylaminophenyl) )-3-indolylmethane CB-8 1.1-bis(4-N,N-diethylaminophenyl)-2-pyrrolylmethane CB-9 1.1-bis(4-N,N-diethylaminophenyl)-4-quinolylmethane CB -10 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-4-pyridylmethane CB-11 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-2-furylmethane CB-12 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-2-thienylmethane CB-13 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-3-pyridylmethane CB-14 1.1- Bis(4-N,N-diethylamino-3-methylphenyl)-2-furylmethane CB-15 1.1-bis(4-N,N-diethylamino-3-ethylphenyl)-2-pyridylmethane CB-16 1.1-bis( 4-N,N-diethylamino-3-ethylphenyl)-6-indolylmethane CB-17 1.1-bis(4-N,N-di-n-butylaminophenyl)-3-pyridylmethane CB-18 1.1- Bis(4-N,N-di-n-butylaminophenyl)-4-quinolylmethane CB-19 1.1-Bis(4-N-chloroethyl-N
-ethylaminophenyl)-2-furylmethane CB-20 1.1-bis(4-N-chloroethyl-N
-ethylaminophenyl)-2-pyrrolylmethane CB-21 1.1-bis(4-N-hydroxyethyl-N-ethylaminophenyl)-2-pyridylmethane CB-22 1.1-bis(4-N-ethyl-N -hydroxyethylaminophenyl)-2-furylmethane CB-23 1.1-bis(4-N-methyl-N-benzylaminophenyl)-2-thienylmethane CB-24 1.1-bis(4-N-methyl- N-benzylaminophenyl)-2-pyridylmethane CB-25 1.1-bis(4-morpholinophenyl)
-4-quinolylmethane CB-26 1.1-bis(4-morpholinophenyl)
-2-furylmethane CB-27 1.1-bis(4-N,N-dimethylamino-2-methoxyphenyl)-4-pyridylmethane CB-28 1.1-bis(4-N,N-dimethylamino-2- methoxyphenyl)-3-indolylmethane CB-29 1.1-bis(4-N,N-dimethylamino-2-methoxyphenyl)-2-pyrylmethane CB-30 1.1-bis(4-N,N-dimethyl amino-2-chlorophenyl)-2-pyridylmethane CB-31 1.1-bis(4-N,N-dimethylamino-3-chlorophenyl)-2-thienylmethane CB-32 1.1-bis(4-N,N-dimethyl Amino-2-methylphenyl)-3-(1-ethyl-
2-phenyl)indolylmethane CB-33 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)-2-(9-ethylcarbazole)methane Specific examples of poly(N-vinylcarbazole) are shown below. Listed below. CC-1 Poly(N-vinylcarbazole) CC-2 Poly(3-chloro-N-vinylcarbazole) CC-3 Poly(3-bromo-N-vinylcarbazole) CC-4 Poly(3-iodo-N-vinyl Carbazole) CC-5 Poly(3.6-dichloro-N-vinylcarbazole) CC-6 Poly(3.6-dibrome-N-vinylcarbazole) CC-7 Poly(3.6-diiodo-N-vinylcarbazole) CC-8 Poly(3 -Nitro-N-vinylcarbazole) CC-9 Poly(3-amino-N-vinylcarbazole) CC-10 Poly(3-dimethylamino-N-vinylcarbazole) CC-11 Poly-N-allylcarbazole Charge transport layer As the binder used for the formation, a film-forming polymer that is hydrophobic, has a high dielectric constant, and is electrically insulating can be used, such as polycarbonate, polyarylate, polysulfone, polyethersulfone, phenoxy resin, polycarbonate, etc. (2.6
-dimethyl-1,4-phenylene ether), polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, styrene-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer Examples include polymers, vinylidene chloride-acrylonitrile copolymers, silicone resins, alkyd resins, polyester resins, polyethylene, polypropylene, polyurethane, and copolymer resins containing two or more repeating units of these resins. Solvents used in the charge transport layer coating solution include aromatic hydrocarbons such as benzene, toluene, and xylene;
Examples include halogenated hydrocarbons such as methylene chloride, chloroform, 1.1-dichloroethane, 1.2-dichloroethane, 1.1.2-trichloroethane, 1.1.2.2-tetrachloroethane, and chlorobenzene, and cyclic ethers such as tetrahydrofuran and 1.4-dioxane. Can be done. The appropriate blending ratio of the charge transport material and the binder in the charge transport layer is 20 to 1000 parts by weight of the binder to 100 parts by weight of the charge transport material.
The thickness of this charge transport layer is preferably 2 to 100 μm, more preferably 5 to 30 μm. Conductive supports include metal plates such as aluminum, nickel, and chromium; metals such as aluminum, nickel, and palladium deposited or sputtered on paper or plastic film; and metal foil such as aluminum and paper or plastic film. A carbon-containing paper, a low-resistance paper treated with an organic or inorganic conductive treatment agent, a glass plate or a plastic film provided with a transparent film of tin oxide and/or indium oxide, etc. can be used. The shape of the conductive support is sheet, long roll,
Ended belts, endless belts, drums, etc. can be selected and used. The electrophotographic photoreceptor of the present invention can have the configuration shown in FIG. In FIG. 1, an intermediate layer 2 containing a viologen compound is provided on a conductive support 1, a charge generation layer 3 containing zinc oxide is provided thereon, and a charge transport layer containing a charge transport substance is provided on top in this order. The electrophotographic photoreceptor of the present invention has the above-mentioned structure, and as is clear from the examples described later, it has remarkable photoresponsiveness and stability in repeated use compared to conventional laminated electrophotographic photoreceptors. Are better. EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the embodiments of the present invention are not limited thereto. Example 1 Preparation of yarn-dyed zinc oxide 1.0 part by weight of tetrachlorotetraiodofluorescein is added to 100 parts by weight of tetrahydrofuran and completely dissolved. Next, 100 parts by weight of zinc oxide (fine zinc white, manufactured by Sakai Chemical Industry Co., Ltd.) having a specific surface area of 9.5 m ² /g was added to this dye sensitizer solution, and the mixture was placed in a porcelain ball mill for 3 hours. Mix and disperse. Transfer the resulting coating liquid to a beaker and completely evaporate the tetrahydrofuran while stirring at 80°C. In this way, zinc oxide dyed with tetrachloroiodofluorescein was prepared. Preparation of photoreceptor and evaluation of electrophotographic properties 1.3 parts by weight of 1'-dimethyl-4.4'-dipyridium dichloride was added to 100 parts by weight of a 10% by weight aqueous solution of water-soluble polyvinyl butyral (Eslec W201, manufactured by Sekisui Chemical Co., Ltd.). This solution was coated on a conductive support made of a polyester film on which aluminum was vapor-deposited, and dried at 110° C. for 10 minutes to form an intermediate layer with a thickness of 2 μm. Next, polycarbonate (Panlite L-1225,
50 parts by weight of the previously prepared yarn-dyed zinc oxide was added to a solution of 5 parts by weight (manufactured by Teijin Kasei Ltd.) dissolved in 195 parts by weight of 1,2-dichloroethane, and the mixture was dispersed in a porcelain ball mill for 24 hours. The resulting coating liquid was applied onto the previously formed intermediate layer by a blade coating method and dried at 110°C for 2 minutes to form a charge generation layer with a thickness of 2 μm. Next, 10 parts by weight of a charge transport material designated as CA-21 and 10 parts by weight of polycarbonate (Panlite L-1225) were added.
A charge transport layer coating solution prepared by dissolving 90 parts by weight of 1,2-dichloroethane was applied onto the formed charge generation layer by a blade coating method, and dried at 140°C for 2 minutes to form a charge transport layer with a thickness of 13 μm. An electrophotographic photoreceptor of this example was prepared. The electrophotographic properties of the thus produced electrophotographic photoreceptor were measured according to the following procedure.
The photoreceptor was attached to an electrostatic recording paper tester SP-428 (manufactured by Kawaguchi Electric Seisakusho Co., Ltd.), and the corona discharge voltage -
Under the conditions of 6 KV and a scanning speed of 250 mm/sec, the potential V ₀ [V] immediately after charging and the potential V ₅ [V] after dark decay for 5 seconds are measured. Next, tungsten light with a color temperature of 2854 [°K] and an illuminance of 2 lux was used to increase the surface potential.
Exposure required to attenuate to V ₅ /2 [V] (half-reduced exposure) E _1/2 [lux・sec] and 20 [lux・sec]
The surface potential (residual potential) after exposure with an exposure amount of V _R
[V] was determined for each. Similar measurements were also made for 1000
I went there repeatedly. The results are shown in Table 1.

[Table] Comparative Example 1 Except that the intermediate layer was prepared without adding 1.1'-dimethyl-4.4'-dipyridinium dichloride,
An electrophotographic photoreceptor of this comparative example was produced in the same manner as in Example 1, and its electrophotographic properties were measured. Display the results -
Shown in 2.

[Table] Example 2 Electrophotographic exposure of this example was carried out in the same manner as in Example 1 except that 1.1'-dibenzyl-4.4'-dipyridinium dichloride was used instead of 1.1'-dimethyl-4.4'-dipyridinium dichloride. A body was prepared and the photoreceptor characteristics were evaluated. The results are shown in Table-3.

[Table] Example 3 Literature [Asahi Glass Technology Promotion Association Research Report Volume 39, No. 285
(1981)], argon (flow rate:
300ml/min), and nitrogen as diluent gas (flow rate 1500ml/min).
ml/min) with a specific surface area of 14.6
Acicular zinc oxide of m ² /g was synthesized. Yarn-dyed zinc oxide was prepared in the same manner as in Example 1 except that this acicular zinc oxide was used and the dye sensitizer was added in an amount of 1.5 parts by weight. was created. The electrophotographic properties of this photoreceptor were evaluated and the results shown in Table 4 were obtained.

[Table] Comparative Example 2 After preparing the intermediate layer without adding 1.1'-dimethyl-4.4'-dipyridinium dichloride, an electrophotographic photoreceptor of this comparative example was prepared in the same manner as in Example 3, and the photoreceptor Characteristics were evaluated. The results are shown in Table-5.

[Table] Example 5 A crystalline zinc oxide thin film having a thickness of 1.2 μm was deposited on the intermediate layer prepared according to the procedure of Example 1 using a commercially available high frequency sputtering device under the following setting conditions. Target: Pressure molded sintered zinc target Distance between substrate (intermediate layer) and target: 35m/m Introduced gas: Ultra-high purity oxygen gas Introduced gas pressure: 1.3×10 ^-2 Pascal Gas pressure during sputtering: 2.7 ×10 ^-1 Pascal Substrate temperature: 50 to 55°C High frequency power density: 1.5 W/cm ² -wire sputtering time: 60 minutes The crystalline zinc oxide thin film thus prepared was coated with a 0.8% by weight solution of tetrachlorotetraiodofluorescein in tetrahydrofuran. Soak for 10 minutes in
After taking it out, it was dried at 90°C for 1 minute and dyed to form the charge generation layer of this example. Next, a charge transport layer was formed in the same manner as in Example 1 to obtain the electrophotographic photoreceptor of this example. The electrophotographic properties of this photoreceptor were evaluated and the results shown in Table 6 were obtained.

[Table] Comparative Example 3 A crystalline zinc oxide thin film was formed in the same manner as in Example 4 on the intermediate layer formed according to the procedure in Comparative Example 1 without adding 1.1'-dimethyl-4.4'-dipyridinium dichloride. A charge generation layer and a charge transport layer were prepared by depositing and dyeing the electrophotographic photoreceptor of this comparative example. Table 7 shows the evaluation results of the electrophotographic properties of this photoreceptor.

[Table] As is clear from the above Examples and Comparative Examples, the electrophotographic photoreceptor of the present invention has significantly improved photoresponsiveness than the electrophotographic photoreceptor of the comparative example, and furthermore, the electrophotographic photoreceptor of the present invention has significantly improved photoresponsiveness, as well as potential, sensitivity, and residual potential due to repeated cycles. It can be seen that there is little change in , indicating excellent stability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the structure of the electrophotographic photoreceptor of the present invention. 1... Conductive support, 2... Intermediate layer, 3... Charge generation layer, 4... Charge transport layer.

Claims (1)

[Claims] 1. An intermediate layer containing a viologen compound represented by the following general formula (), a charge generation layer containing zinc oxide, and a charge transport layer containing a hole transport substance are sequentially laminated on a conductive support. An electrophotographic photoreceptor characterized by comprising: However, R represents an alkyl group, an alkenyl group, an aryl group, or an aralkyl group, and X represents a halogen atom.