JPH0417423B2 - - 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 disazo 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 shown in U.S. Pat. No. 3,397,086, U.S. Pat. No. 3,816,118, etc. ing. In addition, as organic semiconductors used in electrophotographic photoreceptors, for example, US Pat.
4315983, U.S. Patent No. 4327169 and "Reseach Disclosure" 20517 (May 1981), pyrylium dyes, U.S. Patent No. 38247099, methine squaritate dyes, U.S. Patent No. 3898084 Publication, 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 a durable electrophotographic photoreceptor that can be used in all existing electrophotographic processes and has excellent sensitivity in practice and stable potential characteristics during repeated use. It is in. [Means for Solving the Problems] That is, the present invention provides an electrophotographic photoreceptor having a photoconductive layer on a conductive substrate, in which the photoconductive layer has the general formula
(1) {In the formula, R ₁ , R ₁ ′, R ₂ , and R ₂ ′ represent hydrogen, halogen, nitro group, cyano group, or an alkyl group, aralkyl group, alkoxy group, and aryl group that may have a substituent. , A is the following general formula (2) to (4) (In the formula, Y represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group having a nitrogen atom.) (In the formula, Y represents the same as the above general formula (2).) (In the formula, Z is fused with a benzene ring to represent a polycyclic aromatic ring or a heterocyclic ring, and R ₃ and R ₄ are hydrogen, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group which may have a substituent. This is an electrophotographic photoreceptor characterized by containing a disazo pigment represented by the following. In general formula (1), the alkyl groups in R ₁ , R ₁ ', R ₂ and R ₂ ' are, for example, groups such as methylethyl and propyl, and the aralkyl groups are, for example, benzyl,
Groups such as phenethyl and naphthylmethyl, aryl groups include phenyl, diphenyl, and naphthyl, and alkoxy groups include, for example, methoxy,
Groups such as ethoxy, halogens, fluorine, chlorine, bromine, and iodine. Examples of substituents that R may be substituted with include alkyl groups such as methyl, ethyl, propyl, and butyl, alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy, halogen atoms such as chlorine, bromine, and iodine, and cyano groups. , nitro group, etc. In general formulas (2) and (3), the divalent group of aromatic hydrocarbon in Y includes, for example, a divalent group of monocyclic aromatic hydrogen such as o-phenylene, o-naphthylene, perinaphthylene, 1,2-antrylene, 9,10-
Divalent groups of condensed polycyclic aromatic hydrocarbons such as phenanthrylene are mentioned, and examples of multi-ring divalent groups having a nitrogen atom include 3,4-pyrazolediyl, 2,3-pyridinediyl, 4 , 5-pyrimidinediyl, 6,7-indazolediyl,
Examples include 5- to 6-membered heterocyclic divalent groups such as 5,6-benzimidazolediyl and 6,7-quinolinediyl. In formula (4), examples of the alkyl group for R ₃ and R ₄ include methyl, ethyl, propyl, butyl, etc., examples of the aralkyl group include benzyl, phenethyl, naphthylmethyl, etc., and examples of the aryl group include phenyl. , naphthyl, anthryl, diphenyl, and the like, and examples of the heterocyclic group include carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. Substituents that R ₃ and R ₄ may have include halogens such as fluorine, chlorine, bromine, and iodine, alkyl groups such as methyl, ethyl, propyl, and butyl, and alkyl groups such as methoxy, ethoxy, propoxy, and butoxy. group, nitro group,
Cyano group, dimethylamino, dipropylamino,
Examples include substituted amino groups such as dibenzylamino, diphenylamino, morpholino, pyridino, and pyrrolidino. Examples of polycyclic aromatic rings formed by condensation of Z in formula (4) include naphthalene and anthracene; examples of heterocycles include carbazole, benzcarbazole, dibenzofuran, benzonaphthofuran,
Examples include diphenylene sulfite. The disazo pigment according to the present invention can further improve sensitivity by bonding hydrogen to the N atom of diarylamine and incorporating a specific coupler residue. By using the electrophotographic photoreceptor using the disazo pigment of the present invention, high sensitivity is achieved,
high-speed copying materials and laser beam printers,
It has become possible to apply it to LED printers, liquid crystal printers, etc., and it has also become possible to obtain stable and beautiful images because it ensures a stable electric field regardless of the previous history of the photoreceptor. As described above, the object of the present invention can be achieved by using the disazo pigment represented by the general formula (1) in the photosensitive layer. Representative examples of the disazo pigments used in the present invention are listed below. These disazo pigments can be used alone or in combination of two or more. Additionally, these pigments may have, for example, the general formula (However, R ₁ , R ₁ ′, R ₂ , and R ₂ ′ in the formula have the same meanings as the symbols in general formula (1).) A diamine having a secondary amine represented by the formula is tetrazotized by a conventional method, and then Either by aqueous coupling of the corresponding coupler in the presence of an alkali, or once the tetrazonium salt of the diamine has been isolated in the form of a borofluoride salt or zinc chloride double salt, etc., a suitable solvent such as N,N-dimethylformamide is added. can be easily produced by coupling with a coupler in the presence of an alkali in a solvent such as dimethyl sulfoxide. The coating containing the above-mentioned disazo pigment 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 disazo pigment on a conductive support 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 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 it can be obtained by forming a deposited film by vacuum deposition. . The binder that can be used when forming the charge generating layer by coating can be selected from a wide range of insulating resins, as well as organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylacetracene, and polyvinylpyrene. can. 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 resin, epoxy Examples include insulating resins such as resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone.
The resin contained in the charge generation layer is 80% by weight or less,
Preferably, 40% by weight or less is suitable. 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, and resin group 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 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 a charge transport layer is formed on a charge generation layer, the substance 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 non-sensitive. 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 substances, and electron-transporting substances include chloranil, bromoanil, tetracyanoethylene,
Tetracyanoquine dimethane, 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 positive 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-diethylbezaldehyde-3-methylbenzthiazolinone-2- Hydrazones such as hydrazone, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, 1-
Phenyl-3-(p-diethylaminostyryl)-
5-(p-diethylaminophenyl)pyrazoline,
1-[quinolyl(2)]-3-(p-diethylaminostyl)-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
Oxazole compounds such as -diethylaminophenyl)-4-(p-diethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2-(p-diethylaminophenyl)-5-(2-chlorophenyl)oxazole,
thiazole compounds such as -diethylaminostyl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane,
1,1-bis(4-N,N-diethylamino-2
-methylphenyl)heptane, 1,1,2,2-
Tetrakis (4-N,N-dimethylamino-2-
Polyarylalkanes such as methylphenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylacetrane, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, etc. There is. 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, acrylic resin, polyacrylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone,
Examples include insulating resins such as polyacrylamide, polyamide, and chlorinated rubber, and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and 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, any suitable 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 a conductive layer, it is possible to use a substrate which itself is conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold or platinum. In addition, plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, (acrylic resin, polyethylene fluoride, etc.), 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 film layer of the undercoat layer has a thickness of 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 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. 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 known methods, and are not limited to specific ones. On the other hand, when the charge transport material is made of a hole transport material, it is necessary to charge the charge transport surface negatively, 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. After that, it reaches the surface and neutralizes the negative charge, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area.
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 formed in this way 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 disazo 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 disazo pigment together with a binder. Another specific example of the present invention is an electrophotographic photoreceptor containing the above-mentioned compound together with a charge transport material 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 disazo 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 disazo pigments shown in (1), and its crystal form may be amorphous or crystalline. If necessary, a disazo pigment represented by the general formula (1) may be used in combination to increase the sensitivity of the photoreceptor or to obtain a panchromatic photoreceptor.
It is also possible to use a combination of more than one kind, or a 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. [Examples] The present invention will be explained below using examples. Examples 1 to 9 An ammonia aqueous solution of casein (11.2% casein, 1 g of aqueous ammonia, 222 ml of water) was applied onto 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 disazo pigment No. 1 was added to 95 ml of ethanol with butyral resin (butyralization degree 63).
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 100,000) were added to 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 thickness after drying would be 12μ, and drying to form a charge transport layer. Photoreceptors corresponding to Examples 2 to 9 were prepared in exactly the same manner using other exemplary pigments shown in Table 1 in place of disazo 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 21ux. It was exposed to light and its charging characteristics were investigated. As for the charging characteristics, the surface potential (Vo) and the exposure amount (E1/2) required to attenuate the potential to 1/2 when dark decayed for 1 second were measured. The results are shown in Table 1.

[Table] Comparative Examples 1 to 5 In place of the exemplified disazo pigment (1), the coupler structure of the pigment was Azo pigment described in published patent publication No. 58-80643
Let No. 1 be the comparative pigment (1). Next, the central skeleton of the pigment is These comparative pigments are referred to as comparative pigments (2) to (5), respectively. Using Comparative Examples 1 to 5, photoreceptors were prepared in place of the pigment in Example 1 in exactly the same manner as in Example 1, and charging measurements were performed. The results are shown in Table 2.

[Table] As is clear from the results in Table 2, the photoreceptor of the present invention is better than a pigment in which >NH in the central skeleton of the pigment is replaced with H, or a pigment in which the coupler structure is of the 3-hydroxynaphthalenecarboxylic acid anilide type. In both cases, it was confirmed that the electrophotographic sensitivity was significantly improved. Examples 10 to 13 and Comparative Examples 6 to 10 Changes in bright area potential and dark area potential during repeated use of the photoreceptors used in Examples 1, 2, 3, and 8 and the photoreceptors used in Comparative Examples 1 to 5 was measured. The method includes a -5.6kV corona charger, exposure optical system, developer,
The photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with 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 dark area potential (V _D ) were set to around -100V and -600V, respectively, and the bright area potential and dark area potential were measured after using it 5000 times. The results are shown in Table 3.

[Table] The photoreceptor of the present invention had extremely good stability in V _D and V _L even during repeated use. [Effects of the Invention] The present invention provides that, by using a specific azo pigment in a photosensitive layer, either one or both of the carrier generation efficiency and the carrier transport efficiency within the photosensitive layer containing the azo pigment is improved. A photoreceptor with excellent sensitivity and potential stability during long-term use can be obtained.

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor having a photoconductive layer on a conductive substrate, the photoconductive layer has the general formula (1). {In the formula, R ₁ , R ₁ ′, R ₂ , and R ₂ ′ represent hydrogen, halogen, nitro group, cyano group, or an alkyl group, aralkyl group, alkoxy group, and aryl group that may have a substituent. , A is the following general formula (2) to (4) (In the formula, Y represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group having a nitrogen atom.) (In the formula, Y represents the same as the above general formula (2).) (In the formula, Z is fused with a benzene ring to represent a polycyclic aromatic ring or a heterocyclic ring, and R ₃ and R ₄ are hydrogen, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic group which may have a substituent. An electrophotographic photoreceptor characterized by containing a disazo pigment represented by the following. 2. The electronic device according to claim 1, wherein the photoconductive layer is of a functionally separated type having a charge generation layer and a charge transport layer, and the charge generation layer contains an azo pigment represented by the above general formula (1). Photographic photoreceptor.