JPH0448388B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor using a new electrophotographic photosensitive material, and more specifically to an electrophotographic photoreceptor containing a tetrakisazo pigment having a specific molecular structure in a photoconductive layer. This relates to photoreceptors. [Prior Art] Pigments and dyes exhibiting photoconductivity have been published in numerous publications. For example, “RCA Review” Vol.23.P.413-P.419
(1962.9) published on the photoconductivity of phthalocyanine pigments, and an electrophotographic photoreceptor using this phthalocyanine pigment was patented in the United States.
This is disclosed in Publication No. 3397086, US Patent No. 3816118, and the like. In addition, examples of organic semiconductors used in electrophotographic photoreceptors include US Pat. No. 4,315,983
No. 4,327,169 and “Reseach
Diaclosure” 20517 (May 1981), methine squaritate dye shown in U.S. Patent No. 3824099, U.S. Patent No. 3898084, U.S. Patent No. 4251613, etc. Examples include disazo pigments.Such organic semiconductors are easier to synthesize than inorganic semiconductors, and can be synthesized as compounds that have photoconductivity for light in the required wavelength range. Electrophotographic photoreceptors in which a conductive support is coated with a film of an organic semiconductor have the advantage of improved color sensitivity, but only a few of them can be put to practical use in terms of sensitivity and durability. [Problems to be Solved by the Invention] An object of the invention is to provide a novel photoconductive material. Another object of the invention is to provide a novel photoconductive material that can be used in all existing electrophotographic processes. An object of the present invention is to provide an electrophotographic photoreceptor having practical high sensitivity characteristics and stable potential characteristics during repeated use. In an electrophotographic photoreceptor provided with
(1) (In the formula, A is a coupler residue having a phenolic OH group; Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , Ar ₅ and Ar ₆ are each an arylene group which may have a substituent, a divalent fused polyamide an organic group containing a ring aromatic group or a divalent heterocyclic group; X is NR, O, S, SO ₂ or C=O;
R represents a hydrogen atom, an alkyl group, an aryl group, an acyl group, a heterocyclic group, or a nitroso group. In the above general formula (1), the coupler residue having a phenolic OH group of A is represented by the following general formulas (2) to (8), for example: (In the formula, Z is a residue that is fused with a benzene ring to form a polycyclic aromatic ring or a heterocyclic ring; R ₁ and R ₂ are hydrogen atoms, alkyl, aralkyl, aryl, or heterocyclic groups that may have substituents) or residues which together with the nitrogen atom form a cyclic amino group;
R ₃ and R ₄ each represent alkyl or aralkylaryl which may have a substituent; Y is a divalent group of aromatic hydrocarbon or together with a nitrogen atom forms a divalent heterocyclic group Residues; R ₅ and R ₆
are each a hydrogen atom, an alkyl, aralkyl, aryl, heterocyclic group which may have a substituent, or a residue whose bonded carbon atoms together form a 5- to 6-membered ring; R ₇ and R ₈ are each hydrogen atom, alkyl, aralkyl, aryl, or heterocyclic group which may have a substituent). Examples of the polycyclic aromatic and heterocyclic rings of Z include naphthalene, anthracene, carbazole,
Examples include benzcarbazole, dibenzofuran, benzonaphtran, and diphenylene sulfite. In the case of R ₁ and R ₂ , examples of alkyl include methyl, ethyl, propyl, butyl, etc., examples of aralkyl include benzyl, phenethyl, naphthylmethyl, etc., and examples of aryl include phenyl, diphenyl, naphthyl,
Examples include Anthril. In particular, R ₁ is hydrogen, and R ₂ is halogen, nitro, cyano,
Preferably, the compound has a structure of a phenyl group having an electron-withdrawing group such as trifluoromethyl and an alkyl group such as ethyl, methyl, butyl. Examples of the heterocycle include carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. Specific examples of R ₃ and R ₄ are the same as those exemplified above for R ₁ and R ₂ . In addition, the alkyl groups of R ₁ , R ₂ , R ₃ and R ₄ above,
Aralkyl groups, aryl groups, and heterocyclic groups may be further substitued with other substituents, such as the aforementioned alkyl groups, alkoxy groups such as methoxy, ethoxy, and propoxy, halogen atoms, nitro groups, cyano groups, or dimethylamino, diethylamino, and dibenzylamino groups. , diphenylamino, morpholino, piperidine, pyrrodilino, and the like. In the definition of Y, the divalent aromatic hydrocarbon group includes, for example, a monocyclic aromatic hydrocarbon group such as o-phenylene, 0-naphthylene, perinaphthylene, 1,2-antrylene, 9,10-phenanthrylene, etc. Examples include fused polycyclic aromatic hydrocarbon groups. Further, as examples of forming a divalent heterocycle with nitrogen, 3,4-pyrazolediyl group,
2,3-pyridinediyl group, 4,5-pyrimidinediyl group, 6,7-indazolediyl group, 5,
Examples include 5- to 6-membered heterocyclic divalent groups such as 6-benzimidazolediyl group and 6,7-quinolinediyl group. Examples of alkyl, aralkyl and aryl for R ₅ and R ₆ include the same ones as exemplified for R ₁ to R ₄ . In addition, examples of the heterocyclic group for R ₅ and R ₆ include pyridyl,
Examples include thienyl, furyl, carbazoyl, and the like. These groups may be substituted with the substituents described above. Furthermore, R ₅ and R ₆ represent residues that together form a 5- to 6-membered ring. This 5- to 6-membered ring may have a fused aromatic ring. Examples of such groups include cyclopentylidene, cyclohexylidene, 9-fluorenidene, 9-xanthenylidene, and the like. Specific examples of alkyl, aryl, and aralkyl for R ₇ and R ₈ include the same ones as mentioned above. Heterocycles include carbazole, dibenzofuran, benzimidazolone, benzthiazole,
Examples include thiazole and pyridine. These may be substituted with the substituents described above. Z in formulas (7) and (8) has the same specific example as Z in formula (2) above. In particular, the ring to which Z is bonded is preferably an anthracene ring, a benzcarbal ring, or a carbazole ring. In particular, the benzcarbazole ring has a great effect of expanding the spectral sensitivity range to a long wavelength range, and is suitable for producing a photoreceptor having high sensitivity in the semiconductor laser range. In the above general formula (1), Ar ₁ , Ar ₂ , Ar ₃ ,
Specifically, Ar ₄ , Ar ₅ and Ar ₆ are, for example, arylene groups such as phenylene, naphthalene, biphenylene, anthrylene, indene, acenaphthene, fluorene, perylene, fluorenone, anthrone,
Divalent fused polycyclic aromatic ring groups such as anthraquinone and benzanthrone, or pyridine, quinoline, benzoxazole, benzothiazole, benzimidazole, benzotriazole, phenylbenzoxazole, phenylbenzothiazole, phenylbenzimidazole, dibenzofuran, Examples include divalent organic groups containing a heterocycle such as carbazole, xanthene, acridine, phenothiazone, and diphenyloxadiazole. These groups may be substituted with the above-mentioned substituents, other acyl groups such as acetyl and benzoyl, trifluoromethyl groups, and the like. Further, in the definition of X in the above general formula (1), specific examples of R include the same as those exemplified above. These groups may be substituted with the above-mentioned substituents. According to the present invention, without being bound by theory,
By having the group represented by as the center of the molecular skeleton, having four azo coupler components symmetrically via N, and having a structure containing a long π-electron conjugated system,
It is thought that the photoconductivity of the pigment is improved and either or both of carrier generation efficiency and transportability are improved, thereby ensuring sensitivity and potential stability during long-term use. In addition, high sensitivity and long wavelengths in the spectral sensitivity range are achieved, making it possible to apply to advanced copying machines, laser beam printers, LED printers, liquid crystal printers, etc. Furthermore, stable potential can be achieved regardless of the previous history of the photoreceptor. A stable and beautiful image can be obtained. Representative examples of the tetrakisazo pigments used in the present invention are listed below. These tetrakisazo pigments may be one or two types.
More than one species can be used in combination. Additionally, these pigments may have, for example, the general formula (However, Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , Ar ₅ ,
(Ar ₆ represents the same meaning as the symbol in general formula (1)) A tetraamine represented by the formula (1) is octazotized by a conventional method, and then the corresponding coupler is hydrogen-coupled in the presence of an alkali, or a tetrazonium salt of the diamine is Once isolated in the form of a borofluoride salt or zinc chloride double salt, etc., it is easily coupled with a coupler in the presence of an alkali in a suitable solvent such as N,N-dimethylformamide or dimethyl sulfoxide. can be manufactured. The detailed conditions for producing the above-mentioned tetrakisazo pigment will become clearer from the reference examples described below. The coating containing the tetrakisazo pigment described above exhibits photoconductivity and can therefore be used in the photosensitive layer of the electrophotographic photoreceptor described below. That is, in a specific example of the present invention, an electrophotographic photoreceptor is formed by forming a film of the above-mentioned tetrakisazo pigment on a conductive support by vacuum evaporation, or by dispersing it in a suitable binder and forming a film. It can be prepared. In a preferred embodiment of the present invention, the photoconductive coating described above can be applied as a charge generation layer in an electrophotographic photoreceptor in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. The charge generation layer contains as much of the above-mentioned photoconductive compound as possible in order to obtain sufficient absorbance, and is a thin film layer, for example, 5μ or less, in order to shorten the range of the generated charge carriers. Preferably
A thin film layer having a thickness of 0.01 to 1 μm is preferable. This means that most of the incident light is absorbed by the charge generation layer and generates a large number of charge carriers, and that the generated charge carriers are not deactivated by recombination or trapping, and the charge transport layer This is due to the need to inject. The charge generation layer can be formed by dispersing the above-mentioned compound in a suitable binder and coating it on the substrate, or can be obtained by forming a vapor deposition layer using a vacuum vapor deposition apparatus. . Binders that can be used to form the charge generating layer by coating can be selected from a wide range of insulating resins and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. You can choose. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, urethane. Examples include insulating resins such as resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer or undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and dichlorohexanone, N,N-dimethylformamide,
Amides such as N,N-dimethylacetamide,
Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogens such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene. Hydrocarbons or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. Coating can be carried out using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at a temperature of 30℃ to 200℃ for 5 minutes to 2
It can be carried out stationary or under blown air for a period of time within a range of hours. The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing. At this time, this charge transport layer may be laminated on or under the charge generation layer. When the charge transport layer is formed on the charge generation layer, the material that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport material) is substantially in the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. Preferably, it is insensitive to. The term "electromagnetic waves" used herein includes a broad definition of "light rays" that includes gamma rays, X-rays, ultraviolet rays, visible light, near infrared rays, infrared rays, far infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both layers capture each other, resulting in a decrease in sensitivity. Charge-transporting substances include electron-transporting substances and hole-transporting positive substances, and electron-transporting substances include chloranil, pcomoanil, tetracyanoethylene, tetracyanoquinodimethane, and 2,4,7-trinitro-9-fluorenone. , 2, 4, 5, 7-
Tetranitro-9-fluorenone, 2,4,7-
trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
Examples include electron-withdrawing substances such as 2,4,8-trinitrothioxanthone, and polymerization of these electron-withdrawing substances. Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-isopropylcarbazole,
N-Methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-
3-methylidene-10-ethylphenothiazine,
N,N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, P-diethylaminobenzaldehyde-N,N-diphenylhydrazone, P-diethylaminobenzaldehyde-N
-α-Naphthyl-N-phenylhydrazone, P-
Pyrrolidinobenzaldehyde-N,N-diphenylhydrazone, 1,3,3-trimethylsyndorenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone hydrazones such as 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole, 1
-Phenyl-3-(P-diethylaminostyryl)
-5-(P-diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]- 3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[6-methoxy-pyridyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1- [Pyridyl(3)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[Lepidyl(2)]-3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-
3-(P-diethylaminostyryl)-4-methyl-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(α-methyl-P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-phenyl-3'-
(P-diethylaminostyryl)-4-methyl-5
-(P-diethylaminophenyl)pyrazoline,
1-Phenyl-3-(α-benzyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, spiropyrazoline and other pyrazolines, 2-(P-diethylaminostyryl)
-6-diethylaminobenzoxazole, 2-
(P-diethylaminophenol)-4-(P-dimethylaminophenyl)5-(2-chlorophenyl)
Oxazole compounds such as oxazole, 2-
Thiazole compounds such as (P-diethylaminostyryl)-6-diethylaminobenzothiazole,
Triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1,1-bis(4-N,N-diethylamino-2-methylphenol)heptane, 1,1,
Polyarylalkanes such as 2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, poly-N-
Examples include vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium amorphous silicon, and cadmium sulfide can also be used. Moreover, these charge transport substances may be one or two types.
More than one species can be used in combination. When the charge transport material does not have film-forming properties,
A film can be formed by selecting an appropriate binder. Resins that can be used as binders are:
For example, insulating resins such as acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolomer, acrylonitrile-butadiene copolomer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, or poly- Mention may be made of organic photoconductive polymers such as N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5-30μ, but the preferred range is 8-20μ. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. As the substrate having the conductive layer, materials that are conductive themselves such as aluminum, aluminum alloy, copper, zinc, stainless steel, panadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum can be used. In addition, plastics (such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic, conductive particles (e.g. aluminum powder, tin oxide, zinc oxide, titanium oxide, carbon black,
a substrate in which silver particles, etc.) are coated on plastic or the above-mentioned conductive substrate together with a suitable binder;
A substrate made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used. A subbing layer having a Bayer function and an adhesive function can also be provided between the conductive layer and the photosensitive layer. The subbing layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon
610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the undercoat layer is 0.1 to 5μ, preferably 0.5 to 3μ.
is appropriate. When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material is an electron transport material, the surface of the charge transport layer must be positively charged, and when exposed to light after charging, In the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the positive charges, resulting in attenuation of the surface potential and an electrostatic contrast between the layer and the unexposed area. A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. Either fix this directly, or transfer the toner image to paper or plastic film, etc.
It can be developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones. On the other hand, when the charge transporting material consists of a hole transporting material, the charge transporting surface needs to be negatively charged.
After charging, when exposed to light, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the negative charge, causing a decrease in the surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used. When using a photoreceptor in which a conductive layer, a charge transport layer, and a charge generation layer are laminated in this order, if the charge transport material is an electron transport material, the surface of the charge generation layer must be negatively charged, and exposure after charging is required. Then,
In the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer and then reach the substrate. On the other hand, holes generated in the charge generation layer reach the surface and the surface potential is attenuated, creating an electrostatic contrast with the unexposed area. A visible image can be obtained by developing the electrostatic latent image thus formed with a positively charged toner. This can be directly fixed, or the toner image can be transferred to paper, plastic film, etc. and then developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or methods, and are not limited to specific ones. On the other hand, when the charge generation layer is made of a hole transporting substance, the surface of the charge generation layer must be positively charged.
When exposed to light after charging, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer and then reach the substrate. On the other hand, electrons generated in the charge generation layer reach the surface and the surface potential is attenuated, creating an electrostatic contrast with the unexposed area. During development, it is necessary to use a negatively charged toner, contrary to the case where an electron transporting substance is used. In another specific example of the present invention, organic photoconductive materials such as the aforementioned hydrazones, pyrazolines, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamines, poly-N-vinylcarbazoles, etc. The photosensitive film may contain the above-mentioned tetrakisazo pigment as a sensitizer for photoconductive substances and inorganic photoconductive substances such as zinc oxide, cadmium sulfide, and selenium. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned tetrakisazo pigment together with a binder. Another specific example of the present invention is an electrophotographic photoreceptor containing the aforementioned tetrakisazo pigment and a charge transporting substance in the same layer. In this case, in addition to the above-mentioned charge transport materials, a charge transfer complex compound consisting of poly-N-vinylcarbazole and trinitrofluorenone can be used. The electrophotographic photoreceptor of this example can be prepared by dispersing the aforementioned tetrakisazo pigment and charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran, and then forming a film thereon. The pigment used in both photoreceptors has the general formula
It contains at least one type of pigment selected from the tetrakisazo pigments shown in (1), and its crystal form may be amorphous or crystalline. In addition, if necessary, two or more types of tetrakisazo pigments represented by the general formula (1) may be used in combination for the purpose of increasing the sensitivity of the photoreceptor or obtaining a bank chromatic photoreceptor by using a combination of pigments with different light absorption. Combine or
Alternatively, it can be used in combination with a charge generating substance selected from known dyes and pigments. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers and CRTs.
Printers, LED printers, LCD printers,
It can also be widely used in electrophotographic applications such as laser engraving. The present invention will be explained below with reference to Examples. Reference Example Synthesis of Tetrakisazo Pigment No. 1 Add 80 ml of water and 33.2 ml (0.38 mol) of concentrated hydrochloric acid to a 500 ml beaker, and while cooling in an ice water bath, add an amine with the following structure (the amine was synthesized by the method described in French Patent No. 1398240) 16.35 g (0.029 mol) was added and stirred while cooling in an ice water bath to bring the liquid temperature to 3°C. Next, a solution prepared by dissolving 8.2 g (0.122 mol) of sodium nitrite in 7 ml of water was added dropwise over 10 minutes while controlling the temperature within the range of 3 to 10°C, and after the addition was completed, the mixture was stirred for an additional 30 minutes at the same temperature. Carbon was added to the reaction solution to obtain a tetrazotized solution. Next, add dimethylformamide to 2 beakers.
Add 700ml and 53.6g (0.53mol) of triethylamine
and 3-hydroxy-2-naphthoic acid anilide.
32.12g (0.122mol) was added and dissolved. Cool this coupler solution to 6℃ and reduce the liquid temperature to 6-10℃.
Add the above-mentioned tetrazotization solution while controlling the temperature at
The mixture was added dropwise over 30 minutes with stirring, and then stirred at room temperature for 2 hours and further left overnight. The reaction solution was filtered and washed with water to obtain a water paste containing 41.72 g of crude pigment in terms of solid content. Next, using 400 ml of N,N-dimethylformamide, the mixture was stirred and filtered four times at room temperature. after that
After repeating stirring twice with 400 ml of methyl ethyl ketone, dry under reduced pressure at room temperature to obtain purified pigment.
39.5g was obtained. The yield was 82%. Melting point > 250° Elemental analysis Calculated value (%) Actual value (%) C 75.21 75.30 H 4.43 4.49 N 12.65 12.61 Although the synthesis method of typical pigments has been described above, other tetrakisazo pigments represented by general formula (1) are synthesized in the same way. Examples 1 to 60 An ammonia aqueous solution of casein (11.2% casein, 1 g of aqueous ammonia, 222 ml of water) was coated on an aluminum plate using a Mayer bar so that the film thickness after drying was 1.0 μm and dried. Next, 5 g of the above-mentioned tetrakisazo pigment No. 1
was added to a solution prepared by dissolving 2 g of butyral resin (degree of butyralization: 6.3 mol %) in 9.5 ml of ethanol, and the mixture was dispersed in a sand mill for 2 hours. This dispersion was applied onto the previously formed casein layer using a Mayer bar so that the film thickness after drying was 0.5 μm, and dried to form a charge generation layer. Then the structural formula 5 g of hydrazone compound and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) were added to benzene.
The photoreceptor of Example 1 was prepared by dissolving the solution in 70 ml and applying it onto the charge generation layer using a Mayer bar so that the dry film thickness was 12 μm, and drying to form a charge transport layer. Examples 2 to 60 using other tetrakisazo pigments shown in Table 1 in place of tetrakisazo pigment No. 1
A corresponding photoreceptor was prepared in exactly the same manner. The electrophotographic photoreceptor thus prepared was statically charged with corona at -5kV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., kept in a dark place for 1 second, and then exposed at an illuminance of 21ux. The charging characteristics were investigated. As for the charging characteristics, the surface potential (Vo) and the exposure amount (E1/2) required to attenuate the potential by 1/2 when dark decaying for 1 second were measured, and the results are shown in Table 1.

【table】

【table】

[Table] Examples 61 to 65 Using the photoreceptors used in Examples 1, 8, 33, 38, and 69, fluctuations in bright area potential and dark area potential during repeated use were measured. The method is -5.6kV corona charger,
This copying machine has a photoreceptor attached to the cylinder of an electrophotographic copying machine equipped with an exposure optical system, a developing device, a transfer charger, a static elimination exposure optical system, and a cleaner.
The structure is such that an image is obtained on the transfer paper as the cylinder is driven. Using this copying machine, the initial bright area potential V _I and dark area potential V _D are −
The bright area potential V _L and the dark area potential V _D were measured after being set at around 100 V and -600 V and used 5000 times. The results are shown in Table 2.

[Table] From the data of Examples 1 to 65, the photoreceptor of the present invention has extremely good electrophotographic sensitivity, and even after repeated use, V _D ,
The stability of _VL was extremely good. Example 66 On the charge generation layer prepared in Example 1, 2,
After drying a coating solution prepared by dissolving 5 g of 4,7-trinitro-9-fluorenone and 5 g of poly-4,4'-dioxydiphenyl-2,2'-propane carbonate (molecular weight 300,000) in 70 ml of tetrahydrofuran. It was applied so that the coating amount was 10 g/m ² and dried. The electrostatic charge of the electrophotographic photoreceptor thus prepared was measured in the same manner as in Example 1. At this time, the charging polarity was set. The results were as follows: Vo: 540 volts E1/2: 4.2 lux·sec Example 67 A polyvinyl alcohol film with a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. Next, the dispersion of the tetrakisazo pigment used in Example 1 was applied onto the previously formed polyvinyl alcohol layer using a Mayer bar so that the film thickness after drying was 0.5μ, and dried to form a charge generating layer. was formed. Then, the structural formula A solution prepared by dissolving 5 g of pyrazoline compound and 5 g of polyarylate resin (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) in 70 ml of tetrahydrofuran was placed on the charge generation layer to determine the film thickness after drying.
It was applied to a thickness of 10μ and dried to form a charge transport layer. The charging characteristics and durability characteristics of the photoreceptor thus prepared were measured in the same manner as in Examples 1 and 61. The results are shown in Table 3.

[Table] From the results in Table 3, the above photoreceptor has good sensitivity and good potential stability during long-term use. Example 68 An ammonia aqueous solution of casein was coated on an aluminum plate with a thickness of 100 microns and dried to form a subbing layer with a thickness of 0.5 microns. Next, 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-N-vinylcarbazole (number average molecular weight 300,000) were dissolved in 70 ml of tetrahydrofuran to form a charge transfer complex. This charge transfer complex compound and the above-mentioned tetrakisazo pigment No. 74
1g of polyester resin (manufactured by Byron Toyobo)
5 g was added to a solution of 70 ml of tetrahydrofuran and dispersed. This dispersion was applied onto the undercoat layer so that the film thickness after drying was 12 microns, and dried. The charging characteristics and durability characteristics of the photoreceptor thus prepared were measured in the same manner as in Example 1. However, the charging polarity was determined. The results were as follows: Vo: 550V E1/2: 4.0 lux・sec Example 69 The charge transport layer of Example 1 was placed on the casein layer of the aluminum substrate coated with the casein layer used in Example 1. A photoreceptor was formed in the same manner as in Example 1 except that the charge generation layers were sequentially laminated and the layer structure was different, and the charge was measured in the same manner as in Example 1. However, the charging polarity was determined. The results were as follows: Vo: 550V E1/2: 4.2 lux・sec Example 70 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 22.2 ml of water) was dipped and coated on an aluminum cylinder. It was coated by the method and dried to form a subbing layer with a coating weight of 1.0 g/m ² . Next, 1 part by weight of the aforementioned tetrakisazo pigment No. 46, 1 part by weight of butyral resin (Eslec BM-2, manufactured by Sekisui Chemical Co., Ltd.) and 30 parts by weight of isopropyl alcohol.
Parts by weight were dispersed for 4 hours using a ball mill disperser. This dispersion was applied onto the previously formed subbing layer by a dip coating method and dried to form a charge generation layer. The film thickness at this time was 0.3 microns. Next, 1 part by weight of the hydrazone compound used in Example 1, 1 part by weight of polysulfone resin (P1700: manufactured by Union Carbide), and 6 parts by weight of monochlorobenzene.
Parts by weight were mixed and dissolved by stirring with a stirrer. This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer. The film thickness at this time was 12 microns. The photoreceptor thus prepared was corona charged at -5 kV. The surface potential at this time was measured. (Initial potential Vo). Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay Vκ).
Sensitivity is the amount of exposure required to attenuate the potential Vκ by half after dark decay (E1/2 microjoules/cm ² )
It was evaluated by measuring. At this time, the light source was a potassium/aluminum/arsenic ternary semiconductor laser (output: 5 mW; oscillation wavelength 778 nm).
was used. These results were as follows. Vo: -520 volts Vκ: 94% E1/ ² : microjoules/cm Second, the above is applied to a laser beam printer (LBP-CX manufactured by Canon), which is a reversal development type electrophotographic printer equipped with the same semiconductor laser. The photoreceptor was replaced with an LBP-CX photoreceptor, and an actual image forming test was performed. The conditions are as follows. Surface potential after primary charging: -700V, surface potential after image exposure: -150V (exposure amount: 2 μJ/cm ² ), transfer potential:
+700V, developer polarity: negative polarity, process speed: 50mm/sec, development conditions (development bias): -
450V, image exposure scan method; image scan,
Primary pre-charging exposure: 50 lux·sec red full-surface exposure Image formation was performed by line scanning a laser beam in accordance with character and image signals, and good prints were obtained for both characters and images. [Effects of the Invention] According to the present invention, by incorporating a specific tetrakisazo pigment into the photosensitive layer, either or both of the carrier generation efficiency and the carrier transport efficiency within the photosensitive layer are significantly improved. As a result, an electrophotographic photoreceptor with excellent sensitivity and potential stability during long-term use can be obtained.

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor in which a photosensitive layer is provided on a conductive substrate, the photosensitive layer has the following general formula (1). (In the formula, A is a coupler residue having a phenolic OH group; Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , Ar ₅ and Ar ₆ are each an arylene group which may have a substituent, a divalent fused polyamide an organic group containing a ring aromatic group or a divalent heterocyclic group; X is NR, O, S, SO ₂ or C=O;
R represents a hydrogen atom, an alkyl group, an aryl group, an acyl group, a heterocyclic group, or a nitroso group. 2 A in the above general formula (1) is the following general formula (2) to (8)
An electrophotographic photoreceptor according to claim 1, which is represented by: (In the formula, Z is a residue that is fused with a benzene ring to form a polycyclic aromatic ring or a heterocycle; R ₁ and R ₂ are a hydrogen atom, an alkyl, aralkyl, aryl, or a heterocycle that may have a substituent) group or residues that together form a cyclic amino group with a nitrogen atom; R ₃ and R ₄ each represent alkyl, aralkyl, or aryl which may have a substituent; Y is a divalent aromatic hydrocarbon; or a residue that forms a divalent heterocyclic group together with a nitrogen atom; R ₅
and R ₆ are each a hydrogen atom, an alkyl, aralkyl, aryl, a heterocyclic group which may have a substituent, or together have 5 to 6 carbon atoms bonded together.
Residues forming a membered ring; R ₇ and R ₈ each represent a hydrogen atom, an alkyl, aralkyl, aryl, or a heterocyclic group which may have a substituent). 3. The photosensitive layer is of a functionally separated type consisting of a charge generation layer and a charge transport layer, and the charge generation layer has the above general formula.
An electrophotographic photoreceptor according to claim 1, which contains a tetrakisazo pigment represented by (1). 4 R ₁ in the above general formula 2 is a hydrogen atom,
R ₂ is the general formula 3. The electrophotographic photoreceptor according to claim 2, which is a substituted phenyl represented by the formula (wherein R ₉ represents a substituent selected from halogen, nitro, cyano, trifluoromethyl, and acyl). 5 In the above general formula (2), R ₁ is a hydrogen atom,
R ₂ is a phenyl group which may have a substituent,
Z together with the benzene ring forms the following group: An electrophotographic photoreceptor according to claim 2, which forms an electrophotographic photoreceptor.