JPH0435752B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor using a novel electrophotographic photosensitive material, and more specifically, an electrophotographic photoreceptor containing a pentakisazo pigment having a specific molecular structure in a photoconductive layer. It's about the body. [Prior Art] Pigments and dyes exhibiting photoconductivity have been published in numerous publications. For example, “RCA Review” Vol.23, P.413~
P.419 (September 1962), there was a presentation on the photoconductivity of phthalocyanine pigments, and electrophotographic photoreceptors using this phthalocyanine pigment were disclosed in U.S. Patent No. 3397086 and U.S. Patent No. 381611. has been done. In addition, as organic semiconductors used in electrophotographic photoreceptors, for example, US Pat.
4315983, U.S. Patent No. 4327169 and "Reseach Disclosure"2'0517 (May 1981), pyrylium dyes, U.S. Patent No. 3824099, methine squaritate dyes, U.S. Patent No. Publication No. 3898084, U.S. Patent No.
Examples include disazo pigments disclosed in Publication No. 4251613 and the like. 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. An electrophotographic photoreceptor formed on a conductive support has the advantage of improved color sensitivity, but only a few of them are practical in terms of sensitivity and durability. [Problems to be Solved by the Invention] An object of the present invention is to provide a novel photoconductive material. Another object of the present invention is to provide an electrophotographic photoreceptor that can be used in all existing electrophotographic processes and has practical high sensitivity characteristics and stable potential characteristics during repeated use. [Means for Solving the Problems] In the electrophotographic photoreceptor in which a photosensitive layer is provided on a conductive substrate according to the present invention, the photosensitive layer has the following general formula:
(1) (In the formula, 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 condensed polycyclic aromatic group, or a divalent group containing a heterocyclic group) (A represents a coupler residue having a phenolic OH group) An electrophotographic photoreceptor containing a pentakisazo pigment represented by the following formula is provided. In the formula, Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , Ar ₅ , Ar ₆ are arylene groups such as phenylene, naphthylene, he-phenylene, anthrylene, indene, acenaphthine, fluorene, perylene, fluorenone, anthrone, anthraquinone, benzo Divalent fused polycyclic aromatic ring groups such as anthrone, or pyridine, quinoline, benzoxazole, benzothiazole, benzimidazole, benzotriazole, phenylbenzoxazole, phenylbenzothiazole, phenylbenzimidazole, dibenzofuran, carbazole, xanthene , axozine, phenothiazine, diphenyloxadiazole, etc., and represents a divalent organic group containing a heterocycle. These arylene groups, divalent condensed polycyclic aromatic ring groups, and divalent heterocycle-containing organic groups include alkyl groups such as methyl, ethyl, propyl, butyl, alkoxy groups such as methoxy, ethoxy, and propoxy, benzyl, phenethyl,
Aralkyl groups such as naphthylmethyl, aryl groups such as phenyl, diphenyl, and naphthyl, halogen atoms such as chlorine, bromine, and iodine, acyl groups such as acetyl and benzoyl, nitro groups, trifluoromethyl groups, or cyano groups as substituents. It doesn't matter if you do. In addition, the phenolic OH of A in general formula (1)
Examples of the coupler residue having a group include those represented by the following general formulas (2) to (8): (In the formula, X 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 hydrogen,
Alkyl, aralkyl, aryl, or heterocyclic group which may have a substituent, or a residue bonded to each other to form a cyclic amino group with a nitrogen atom; R ₃
and R ₄ are alkyl, aralkyl, and aryl groups each of which may have a substituent; Y is a residue forming a divalent aromatic hydrocarbon group or a divalent heterocyclic group having a nitrogen atom; R ₅ and R ₆ are hydrogen atoms,
Indicates an alkyl, aralkyl, aryl, or heterocyclic group which may have a substituent, or a residue bonded to each other to form a 5- to 6-membered ring; R ₇ and R ₈
each represents a hydrogen atom, an alkyl, aralkyl, aryl, or a heterocyclic group which may have a substituent). Examples of the polycyclic aromatic ring and heterocyclic ring-forming residues of X include naphthalene, anthracene, carbazole, benzcarbazole, dibenzofuran, benzonaphthofuran, and diphenylene sulfide. In addition, in the case of R ₁ and R ₂ , alkyl is, for example, methyl,
Ethyl, propyl, butyne, etc. are shown, aralkyl is, for example, benzyl, phenethyl, naphthylmethyl, etc., and aryl is, for example, phenyl, diphenyl, naphthyl, anthryl, etc. In particular, compounds having a structure in which R ₁ is hydrogen and R ₂ is a phenyl group having an electron-withdrawing group such as halogen, nitro, cyano, or trifluoromethyl and an alkyl group such as methyl, ethyl, or butyl at the o-position are preferable. 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,
The aralkyl group, aryl group, and heterocyclic group may further include other substituents, such as the aforementioned alkyl group, askoxy group, halogen atom, nitro group, cyano group, or dimethylamino, diethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, It may be substituted with a substituted amino group such as pyrrolidino. In the definition, Y is a divalent aromatic hydrocarbon group such as a monocyclic aromatic hydrocarbon group such as O-phenylene, O-naphthylene, perinaphthylene,
Examples include fused polycyclic aromatic hydrocarbon groups such as 1,2-antrylene and 9,10-phenanthrylene. Further, examples of forming a divalent heterocycle having a nitrogen atom include 3,4-pyrazolediyl group, 2,
2-pyridinediyl group, 4,5-pyrimidinediyl group, 6,7-indazolediyl group, 5,6-
Examples include 5- to 6-membered heterocyclic divalent groups such as benzimidazolediyl group and 6,7-quinolinediyl group. Examples of the aryl group, aralkyl group, or heterocyclic group for R ₅ and R ₆ include phenyl, naphthyl, anthryl,
Pyrenyl, etc.: benzyl, phenethyl, naphthylmethyl, etc. Aralkyl: pyridyl, thienyl,
Examples include heterocyclic groups such as furyl and carbazolyl. These may be substituted with the substituents described above. Furthermore, R ₅ and R ₆ represent residues that combine with each other to 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-fluorenylidene, 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. The specific example of X in formulas (7) and (8) is the same as that of X in formula (2) above. In particular, the ring to which X is attached is an anthracene ring, a benzcarbazole ring,
A carbazole ring is preferred. 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 photoreceptor according to the present invention, a pentakisazo pigment characterized by a structure in which four azo coupler components are bonded symmetrically around an azo group having divalent organic groups on both sides and via N is used as a photoconductive material. As can be easily inferred from its structure, the π-electron conjugated system is long and smooth, and either or both of carrier generation efficiency and carrier transport efficiency are significantly improved. Therefore, the photoreceptor of the present invention has high sensitivity, has a spectral sensitivity range extending over long wavelengths, and has good potential stability during long-term use. Therefore, high-speed copying machines and laser beam printers,
It can be applied to LED printers, liquid crystal printers, etc., and stable images can be obtained because a stable potential is ensured regardless of the previous history of the photoreceptor. Representative examples of the pentakisazo pigment used in the present invention are listed below. These pentakisazo pigments are one or two types.
More than one species can be used in combination. Additionally, these pigments may have, for example, the general formula (Ar ₁ , Ar ₂ , Ar ₃ , Ar ₄ , Ar ₅ , Ar ₆ in the formula have the same meanings as the symbols in general formula (1)) The tetraamine represented by is octazotized by a conventional method, and then the corresponding Once the coupler is aqueous coupled in the presence of an alkali, or the tetrazonium salt of the diamine is isolated in the form of a borofluoride salt or zinc chloride double salt, a suitable solvent such as N,N-dimethylformamide, dimethyl It can be easily produced by coupling with a coupler in a solvent such as sulfoxide in the presence of an alkali. Next, a typical synthesis example of the pentakisazo pigment used in the present invention is shown below. Synthesis Example 1 (Pentakisazo Pigment No. 1 as exemplified above)
synthesis): In a 500ml beaker, 80ml of water, 33.2ml of concentrated hydrochloric acid (0.38ml)
16.72 g (0.029 mol) of the amine having the following structure (the amine was synthesized by the method described in French Patent No. 1398240) while cooling in an ice-water bath. was added and stirred while cooling in an ice water bath to bring the liquid temperature to 3°C. Next, add 8.2 g (0.122 mol) of sodium nitrite to 7 ml of water.
ml of the solution was added dropwise over 10 minutes while controlling the temperature within the range of 3 to 10°C, and after the dropwise addition was completed, the solution was further stirred at the same temperature for 30 minutes. Carbon was added to the reaction solution to obtain an octazotized solution. Next, add dimethylformamide to 2 beakers.
Add 700ml and 53.6g (0.53mol) of triethylamine
was added, and 32.12 g (0.122 mol) of 3-hydroxy-2-naphthoic acid anilide was added and dissolved. This coupler solution is cooled to 6℃ and the liquid temperature is 6~
The above-mentioned octazotized solution was added dropwise while stirring over 30 minutes while controlling the temperature at 10°C, and then the mixture was stirred at room temperature for 2 hours and further left overnight. The reaction solution was filtered and then washed with water to obtain a water paste containing 40.7 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.
Obtained 38.83g. The yield was 80.0%. Melting point＞
250° Elemental analysis Calculated value (%) Experimental value (%) C 74.63 74.49 H 4.34 4.40 N 13.39 13.50 The synthesis method of typical pigments has been described above, but other pentakisazo pigments represented by general formula (1) can also be synthesized in the same way. are synthesized. The coating containing the pentakisazo 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 prepared by forming a film of the above-mentioned pentakisazo pigment on a conductive substrate by vacuum evaporation, or by dispersing it in a suitable binder and forming a film. be able to. 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, generating many charge carriers, and that the generated charge carriers are not deactivated by recombination or trapping, but are transferred to the charge transport layer. This is due to the need for injection. The charge generation layer can be formed by dispersing the above-mentioned compound in a suitable binder and coating it on the substrate, or it can be obtained by forming a vapor deposited film using a vacuum vapor deposition apparatus. . The binder that can be used when forming the charge generation layer by coating can be selected from a wide range of insulating resins.
It can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably, polyvinylbutyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.) polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, Examples include insulating resins such as urethane 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 cyclohexanone, amides such as N,N-dimethylformamide and N,N-dimethylacetamide, and dimethyl sulfoxide. sulfoxides such as, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate,
Aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, etc., or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. . Coating methods include dip coating method, spray coating method, spinner coating method, bead coating method, Meyer bar coating method, blade coating method, roller coating method,
This can be carried out using a coating method such as a Curtin coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying can be carried out at a temperature of 30° C. to 200° C. for a period of time ranging from 5 minutes to 2 hours, either stationary or under ventilation. 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 trap each other, resulting in a decrease in sensitivity. Charge-transporting substances include electron-transporting substances and hole-transporting substances, and electron-transporting substances include chloranil, promoanil, tetracyanoethylene,
Tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone,
2,4,5,7-tetranitroxanthone, 2,
These include electron-withdrawing substances such as 4,8-trinitrothioxanthone, and polymerized versions 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-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone hydrazones such as 2,5-bis(P-diethylaminophenyl)-1,3,4-axadiazole, 1
-Phenyl-3-(P-diethylaminostyryl)
-5-(P-diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(P-diethylaminostyl)-5-(P-diethylaminophenyl)
Pyrazoline, 1-[pyridine(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[6-methoxy-pyridyl(2)]-3-(P-diethylaminostyryl) Styril)
-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridine(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-[pyridine(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-
Oxazole compounds such as (P-diethylaminophenyl)-4-(P-dimethylaminophenyl)-5-(2-chlorophenyl)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-methylphenyl)heptane, 1,
Polyarylalkanes such as 1,2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, poly-N-vinylcarpazole, polyvinylpyrene,
Examples include 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 copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, etc. 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, the substrate itself can be conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, platinum, etc. In addition, plastics (e.g., 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 laminated with a conductive layer, a charge generation layer, and a charge transport layer, and the charge transport material is an electron transport material, the surface of the charge transport layer must be positively 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 surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic contrast with 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 an electrostatic latent image is transferred onto an insulating layer of transfer paper on a photoreceptor, and 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 transport material consists of a hole transport material, the surface of the charge transport layer 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 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 substance is an electron transport substance, 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 area and then reach the substrate. On the other hand, holes generated in the charge generation layer reach the surface and the surface potential attenuates, 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 transport material is a hole transport material, it is necessary to positively charge the surface of the charge generation layer, and when exposed to light after charging, the holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. Then reach the base. 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 aforementioned pentakisazo pigment as a sensitizer for photoconductive substances and inorganic photoconductive substances such as zinc oxide, cadmium oxide, and selenium. This photosensitive film is formed by coating these photoconductive substances and the aforementioned pentakisazo pigment together with a binder. Another specific example of the present invention is an electrophotographic photoreceptor containing the aforementioned pentakisazo pigment and a charge transport material in the same layer. At this time, 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 pentakisazo pigment and charge transfer complex compound in a polyester solution 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 pentakisazo pigments shown in (1), and its crystal form may be amorphous or crystalline. In addition, if necessary, two or more types of pentakisazo 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 panchromatic photoreceptor by using a combination of pigments with different light absorption. 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. Examples 1 to 60 An ammonia aqueous solution of casein (11.2% casein in aqueous ammonia, 1 g, 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, 1.5 g of the above-exemplified pentakisazo pigment No. 1 was added to a solution prepared by dissolving 2 g of butyral resin (degree of butyralization: 63 mol %) in 9.5 ml of ethanol, and 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 100000) in benzene
The photoreceptor of Example 1 was prepared by dissolving the solution in 70 ml and coating it on the charge generation layer using a Mayer bar so that the dry film thickness was 12μ, and drying to form a charge transport layer. Photoreceptors corresponding to Examples 2 to 60 were prepared in exactly the same manner using other exemplary pigments shown in Table 1 in place of pentakisazo pigment No. 1. 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., and held in a dark place for 1 second, then at an illuminance of 2ux. It was exposed to light and its charging characteristics were investigated. The charging characteristic is the surface potential (V _p )
Table 1 shows the results of measuring the amount of exposure (E _1/2 ) required to attenuate the potential by 1/2 when dark decaying for 1 second.

【table】

【table】

[Table] Examples 61 to 65 The photoreceptors used in Examples 1, 8, 29, 40, and 83 were repeatedly used, and the fluctuations in bright area potential and dark area potential were measured. The measurement method is as follows. The photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with a −5.6 kV corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copier, the initial bright area potential (V _L )
and the dark potential (V _D ) are −100V and −600V, respectively.
Bright area potential (V _L ) after 5000 times of use with a setting near
The dark potential (V _D ) was measured. The results are shown in Table 3.

[Table] From the data of Examples 1 to 65, the photoreceptor of the present invention has extremely good electrophotographic sensitivity, and even when used repeatedly, 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 was applied. It was applied so that the working 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 to ○+. The results are shown in Table 4. Table 4 V _p : +550V E _1/2 : 4.3ux·sec Example 67 A polypynyl 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 pentakisazo 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 generation layer. did. 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 is 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 Example 1.
The results are shown in Table 5. Table 5 V _p :-585V E _1/2 :3.2lux・sec Initial After 5000 cycles V _D V _L V _{D V L} −600V −100V −625V −130V From the results in Table 5, the sensitivity of the present invention is The potential stability during long-term use is also good. Example 68 An ammonia aqueous solution of casein was applied onto 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 added to 70 ml of tetrahydrofuran.
to form a charge transfer complex. This charge transfer complex compound and the above-mentioned pentakisazo pigment
No. 74.1 g was added to a solution in which 5 g of polyester resin (Vylon, manufactured by Toyobo) was dissolved in 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. The results are shown in Table 6. However, the charging polarity was set to ○+. Table 6 V _p :○+560V E _1/2 :4.2us・sec Example 69 The charge transport layer and charge generation layer of Example 1 were placed on the casein layer of the casein layer-coated aluminum substrate used in Example 1. A photoreceptor was prepared in exactly the same manner as in Example 1 except that the layers were sequentially laminated and the order of the layer structure was different, and the charging was measured in the same manner as in Example 1. However, the charging polarity was set to ○+. Table 7 shows the power outage characteristics. Table 7 V _p ○＋560V E _1/2 4.1ux・sec Example 70 Casein ammonia aqueous solution (casein 11.2g, 28% ammonia water
1g, 22.2ml of water) was applied using the dip coating method.
It was dried to form a subbing layer with a coating weight of 1.0 g/m ² . Next, 1 part by weight of the aforementioned pentakisazo pigment No. 46, 1 part by weight of Petitral 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 were mixed and dissolved by stirring with a stirrer. This liquid is applied onto the charge generation layer using a dip coating method,
It was dried to form a charge transport layer. The film thickness at this time was 12 microns. A -5 kV corona discharge was applied to the photoreceptor thus prepared. The surface potential at this time was measured (initial potential V _p ). Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay V _k ). Sensitivity was evaluated by measuring the exposure amount (E _1/2 microjoule/cm ² ) required to attenuate the potential V _k by 1/2 after dark decay. At this time, a gallium/aluminum/arsenic ternary semiconductor laser (output: 5 mW, oscillation wavelength 778 nm) was used as a light source. These results were as follows. V _p : -520 volts V _k : 92% E _1/2 : 1.4 microjoules/cm ^Second , a laser beam printer (Canon's LBP- An actual image forming test was carried out by replacing the above photoreceptor with an LBP-CX photoreceptor. The conditions are as follows. Surface potential after primary charging: -700V, surface potential after image exposure: -150V (exposure amount 2μJ/cm ² ), transfer potential;
+700V, developer polarity: negative polarity, process speed: 50mm/sec, development conditions (development bias): -
450V, current exposure scan method; image scan,
Exposure before primary charging: 50us・sec full red exposure. Image formation was performed by line scanning a laser beam in accordance with character signals and image signals, and good prints were obtained for both characters and images.

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, 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 condensed polycyclic aromatic group, or a divalent group containing a heterocyclic group) (A represents a coupler residue having a phenolic OH group) An electrophotographic photoreceptor comprising a pentakisazo pigment represented by the following. 2 A in the above general formula (1) is the following general formula (2) to (8)
An electrophotographic photoreceptor according to claim 1 represented by: (In _the formula _,
Aralkyl, aryl, or heterocyclic group, or residues that combine with each other to form a cyclic amino group with a nitrogen atom; R ₃ and R ₄ are alkyl, aralkyl, or aryl groups that each may have a substituent; Y is aromatic Residues forming divalent groups of hydrocarbons or divalent groups of heterocycles having a nitrogen atom; R ₅ and
R ₆ is each a hydrogen atom, an alkyl, aralkyl, aryl, a heterocyclic group which may have a substituent, or a residue bonded to each other to form a 5- to 6-membered ring;
R ₇ and R ₈ each represent a hydrogen atom, an optionally substituted alkyl, aralkyl, aryl, or a heterocyclic group). 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 pentakisazo pigment represented by (1). 4 R ₁ in the above general formula (2) is a hydrogen atom,
R ₂ is the general formula (In the formula, R ₉ is a halogen atom, nitro, cyano,
The electrophotographic photoreceptor according to claim 2, which is a substituted phenyl group represented by the following (indicating a substituent selected from trifluoromethyl and an acyl group). 5 The above general formula (2) is the following formula (R ₂ is the same as above) The electrophotographic photoreceptor according to claim 2.