JPH0435751B2 - - 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, “RCAReview” 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 shown in U.S. Patent No. 3397086 and U.S. Patent No. 3816118, etc. ing. In addition, as organic semiconductors used in electrophotographic photoreceptors, for example, US Pat.
4315983 Publication Pyrylium dyes disclosed in U.S. Patent No. 4327169 and "Reseach Disclosure" 20517 (1981.5), methine squarate dyes disclosed in U.S. Patent No. 3824099, U.S. Patent 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 problem] 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, A is a coupler residue having a phenolic OH group; Ar ₁ is a divalent organic group containing a heterocyclic group which may have a substituent; Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ are each An electrophotographic image containing a tetrakisazo pigment represented by (representing a divalent organic group containing an arylene group, a divalent condensed polycyclic aromatic ring group, or a heterocyclic group which may have a substituent) A photoreceptor is provided. 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: ( _{wherein ,} or residues that combine with each other to form a cyclic amino group together with a nitrogen atom; R ₅ and R ₄ are alkyl, aralkyl, or aryl groups each of which may have a substituent; Y is a divalent aromatic hydrocarbon group; or a residue forming a divalent group of a heterocyclic group having a nitrogen atom; R ₅ and R ₆
are each a hydrogen atom, an alkyl, aralkyl, aryl, heterocyclic group which may have a substituent, or a residue bonded to each other to form a 5- to 6-membered ring with a bonded carbon atom; R ₇ and R ₈ are each hydrogen atom,
(Indicates an alkyl, aralkyl, aryl, or heterocyclic group that may have a substituent). Examples of the polycyclic aromatic ring and heterocycle of X include naphthalene, anthracene, carbazole, benzcarbazole, dibenzofuran, benzonaphthofuran, 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. , Unthrill, 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 ethyl, methyl, or butyl at the 0-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,
Aralkyl groups, aryl groups, and heterocyclic groups may indeed be substituted 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, piperidino, pyrrolidino, and other substituted amino groups. In the definition of Y, examples of divalent aromatic hydrocarbon groups include monocyclic aromatic hydrocarbon groups such as o-phenylene, o-naphthylene, perinaphthylene, 1,2-antrylene, and 9,10-phenanthrylene. Examples include fused polycyclic aromatic hydrocarbon groups. In addition, examples of forming a divalent heterocycle having nitrogen include 3,4-pyrazolediyl group, 2,3
- 5- to 6-membered heterocyclic divalent groups such as pyridinediyl group, 4,5-pyrimidinediyl group, 6,7-indazolediyl group, 5,6-benzimidazolediyl group, 6,7-quinolinediyl group, etc. Can be mentioned. 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 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-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. Examples of X in formulas (7) and (8) are the same as those for X in formula (2) above. In particular, the ring to which X is bonded is preferably an anthracene ring, a benzcarbazole 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 is specifically, for example, pyridine, quinoline, benzoxozole, benzothiazole, benzimidazole, benzotriazole, phenylbenzoxazole, phenylbenzothiazole, phenylbenzimidazole, dibenzofuran, Examples include divalent organic groups containing heterocyclic groups such as carbazole, xanthene, phenothiazine, and diphenyloxadiazole. Further, these groups may be substituted with the above-mentioned substituents. Furthermore, Ar ₂ , Ar ₃ , Ar ₄ and
Ar ₅ is a divalent heterocyclic group such as pyridine, quinoline, oxadiazole, benzoxazole, benzimidazole, benzothiazole, benzotriazole, dibenzofuran, carbazole, xanthene; arylene group; divalent fused polycyclic aromatic ring Examples include groups. These groups may be substituted with the substituents described above. According to the present invention, although not bound by theory, the tetrakisazo pigment of general formula (1) has a divalent organic group containing a heterocycle as the center of its molecular skeleton, and four azo couplers are symmetrically connected via N. component and long π
By having a structure containing an electronic conjugated system, the photoconductivity of the pigment is improved, and carrier generation efficiency and/or transportability are improved, thereby ensuring sensitivity and potential stability during long-term use. it is conceivable that. In addition, high sensitivity and long wavelengths in the spectral sensitivity range are achieved, making it possible to apply it to high-speed copying machines, laser beam printers, LED printers, liquid crystal printers, etc., and in fact, stable potential can be maintained 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 in the formula
represents the same meaning as the symbol in general formula (1)) is octazotized by a conventional method, and then the corresponding coupler is coupled in an aqueous system in the presence of an alkali, or the tetrazonium salt of the diamine is octazotized by a conventional method. It is easily produced by once isolating it in the form of zinc chloride salt or zinc chloride double salt, and then coupling it with a coupler in the presence of an alkali in a suitable solvent such as N,N-dimethylformamide or dimethyl sulfoxide. be able to. 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 prepared by forming a film of the above-mentioned tetrakisazo pigment on a conductive substrate by vacuum evaporation, or by dispersing it in a suitable binder and forming a film. can do. 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, 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 cyclohexanone, 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" as used herein includes a broad definition of "light rays" including r-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. The charge transport layer includes an electron transporting substance and a hole transporting substance, and the 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,
Examples include electron-withdrawing substances such as 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-trimethylindolenine-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-[pyridine(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-
Oxazole compounds such as (P-diethylaminophenyl)-4-(P-diethylaminophenyl)-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-diethylamino-2-methylphenyl)ethane, triphenylamine, poly-
N-vinylgalbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacrysine,
Examples include poly-9-vinylphenylanthracene, pyrene-formahidehyde 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, or poly-N - Organic photoconductive polymers such as vinylcarbazole, polyvinylanthracene, polyvinylpyrene, etc. may be mentioned. 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 themselves conductive can be used, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum. 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 barrier and adhesive functions 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 suitably 0.1 to 5 microns, preferably 0.5 to 3 microns. 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 a charge 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 between the exposed area and the exposed area. . A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be defined directly, or the toner image can be transferred to paper, plastic film, etc., 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 and then developed. The type of developer, development method, and definition method may be any known one or any known method, 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 must 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 exposed area. Electrocontrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where a charge 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 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 between the layer and the exposed area. A visible image can be obtained by developing the electrostatic latent image thus formed with a positively charged toner. This can be defined directly, 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 consists of a hole transport material, the surface of the charge generation layer must be positively charged, and when exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. and then reaches 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 between the layer and the exposed 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, triphenylamine, and poly-N-vinylcarbazoles may be used. The photosensitive film may contain the aforementioned tetrakisazo pigment as a sensitizer for inorganic photoconductive substances such as photoconductive substances, 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 the crystal form thereof may be amorphous. In addition, if necessary, two or more types of tetrakisazo pigments represented by the general formula (1) may be used in combination to increase the sensitivity of the photoreceptor or to obtain a panchromatic photoreceptor by combining pigments with different light absorption. Combine or
Alternatively, it can also 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 with ice water, add an amine with the following structure (the amine was synthesized according to the method described in French Patent No. 1398240). ) 23.14g (0.029mol) and stir while cooling in an ice water bath until the liquid temperature reaches 3℃.
And so. Next, a solution prepared by dissolving 8.2 g (0.122 mol) of sodium zincate 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 dropwise addition was completed, the mixture was stirred for an additional 30 minutes at the same temperature. Carbon was added to the reaction solution and filtered through a furnace to obtain an octazoization solution. Next, add dimethylformamide to the 2 peaker.
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 through a furnace and then through a water washing furnace to obtain a water paste containing 43.9 g of crude pigment in terms of solid content. Next, filtration in a stirred oven was repeated four times at room temperature using 400 ml of N,N-dimethylformamide. after that
After repeating filtration with 400 ml of methyl ethyl ketone twice in a stirring oven, the purified pigment was dried under reduced pressure at room temperature.
Obtained 41.1g. The yield was 84%. Melting point > 250° Elemental analysis Calculated value (%) Actual value (%) C 74.77 74.88 H 4.24 4.16 N 12.45 12.33 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 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, add 1.5 g of the above tetrakisazo pigment to 9.5 ml of ethanol and add butyral resin (butyralization degree 63) to 9.5 ml of ethanol.
Add 2g (mol%) to the dissolved liquid and add 2g with a sand mill.
Spread out time. 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 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 photoreceptor corresponding to the above was prepared in exactly the same manner. The electrophotographic photoreceptor thus prepared was statically charged with corona at -5 kV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., held in a dark place for 1 second, and then exposed at an illuminance of 2 lux. The charging characteristics were investigated. As for the charging characteristics, the surface potential (V _p ) and the exposure amount (E1/2) required to attenuate the potential to 1/2 when dark decaying for 1 second were measured. The results are shown in Table 1.

【table】

【table】

[Table] Examples 61 to 65 Using the photoreceptors used in Examples 1, 7, 51, 62, and 80, 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 _L and dark area potential V _D are set to 100 V and −
Bright area potential after setting around 600V and using 5000 times
V _L and light area potential V _D were measured. 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 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 were as follows: V _p : ○ + 550 volts E1/2: 5.5 lux.sec. Example 67 A polyvinyl alcohol film with a thickness of 0.5μ 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 it was dried to generate a charge. formed a layer. 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 Examples 1 and 61. The results are shown in Table 3.

〔Effect of the invention〕

According to the present invention, by incorporating a specific tetrakisazo pigment into the photosensitive layer, carrier generation efficiency and/or carrier transport efficiency within the photosensitive layer are significantly improved, resulting in improved sensitivity and durability. An electrophotographic photoreceptor with excellent potential stability 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 is a divalent organic group containing a heterocyclic group which may have a substituent; Ar ₂ , Ar ₃ , Ar ₄ and Ar ₅ are each An electrophotographic image containing a tetrakisazo pigment represented by (representing a divalent organic group containing an arylene group, a divalent condensed polycyclic aromatic ring group, or a heterocyclic group which may have a substituent) Photoreceptor. 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 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 with a bonded carbon atom; R ₇ and R ₈ are each represents a hydrogen atom, an alkyl, aralkyl, aryl, or a heterocyclic group that 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 (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.