JPH0370218B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor in which a photosensitive layer contains a specific azo pigment. [Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known. On the other hand, since it was discovered that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene, carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones,
Organic pigments and dyes such as low-molecular organic photoconductors such as polyarylalkanes, phthalocyanine pigments, azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes, or methine squaritate dyes are used. Are known. In particular, organic pigments and dyes with photoconductivity are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has expanded. Photoconductive organic pigments and dyes have been proposed. For example, US Patent No. 4123270, US Patent No. 4247614, US Patent No.
No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747,
As disclosed in No. 4,293,628, electrophotographic photoreceptors are known in which a disazo pigment exhibiting photoconductivity is used as a charge-generating substance in a photosensitive layer that is functionally separated into a charge-generating layer and a charge-transporting layer. Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, so they can be produced with extremely high productivity and at low cost. Although this photoreceptor has the advantage of being able to freely control the sensitive wavelength range by selecting the photoreceptor, it has poor sensitivity and durability, and so far only a few have been put into practical use. [Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photoreceptor. Another object of the present invention is to provide an electrophotographic photoreceptor having practically excellent sensitivity and durability. [Means for solving the problem] According to the present invention, the following general formula 1 (In the formula, R ₁ and R ₂ represent alkyl, aralkyl, aryl, or acyl which may have a substituent, and Ar ₁ , Ar ₂ and Ar ₃ each represent an arylene or a heterocyclic ring which may have a substituent. There is provided an electrophotographic photoreceptor characterized in that the photosensitive layer contains an azo pigment represented by the following formula (A represents a coupler residue having a phenolic OH group). In the above general formula (1), R ₁ and R ₂ are defined as alkyl groups such as methyl, ethyl, propyl,
Examples of the aralkyl group include benzyl, phenethyl, and naphthylmethyl; examples of the aryl group include phenyl, diphenyl, and naphthyl; and examples of the acyl group include acetyl, propionyl, butyryl, and benzoyl. Also,
Examples of substituents that R ₁ and R ₂ may be substituted include hydroxy group, halogen (chloro, bromo, iodo, etc.), alkyl (methyl, ethyl, propyl, butyl, etc.), alkoxy (methoxy, ethoxy, propoxy, butoxy) ), aryloxy groups (phenyloxy, etc.), substituted amino (dimethylamino, diethylamino, dibenzylamino, pyrrolidino, piperidino, morpholino, etc.),
Examples include nitro, cyano, and acyl (acetyl, benzoyl, etc.). Furthermore, as definitions of _Ar1 to _Ar3 , arylene is, for example, phenylene, biphenylene, naphthylene, anthrylene, etc., and the heterocyclic group is, for example, a divalent group such as benzoxazole, benzothiazole, pyridine, quinoline, thiophene, carbazole, etc. These may be further substituted with the above-mentioned substituents. Furthermore, the phenolic nature of A in general formula (1)
Examples of coupler residues having an OH group include 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 ₃ and R ₄ are hydrogen,
Alkyl, aralkyl, aryl or heterocyclic groups which may have substituents or together form a cyclic amino group with a nitrogen atom; R ₅ and R ₆
represents alkyl, aralkyl, or aryl, each of which may have a substituent; Y is an aromatic hydrocarbon divalent group or forms a heterocyclic divalent group together with a nitrogen atom; R ₇ , R ₈ represents an aryl or heterocyclic group which may have a substituent; R ₉
and R ₁₀ each represent an alkyl, aralkyl, aryl or heterocyclic group which may have a hydrogen substituent). Examples of the polycyclic aromatic ring of X include naphthalene, anthracene, carbazole, benzcarbazole, dibenzofuran, benzonaphthofuran,
Examples include diphenylene sulfide. These may be substituted with the substituents described above. Note that the fused ring of X is preferably naphthalene, anthracene, or benzcarbazole. In addition, in the case of R ₃ and R ₄ , alkyl is, for example, methyl,
Ethyl, propyl, butyl, etc. are shown, aralkyl is, for example, benzyl, phenethyl, naphthylmethyl, etc., and aryl is, for example, phenyl, diphenyl, naphthyl, anthryl, etc. In particular, R ₃ is hydrogen and R ₄ is halogen at the 0-position,
Compounds having a structure of a phenyl group having an electron-withdrawing group such as nitro, cyano, or trifluoromethyl are preferred in terms of electrophotographic properties. These may have substituents. Examples of the heterocycle include carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. Specific examples of R ₅ and R ₆ are the same as those exemplified above for R ₃ and R ₄ . These may be substituted with the substituents described above. Furthermore, R ₃ to _{R 6} are other substituents such as alkoxy groups such as methoxy, ethoxy, propoxy, chlorol, chloro, bromo,
It may be substituted with a halogen such as iodine, a nitro group, a cyano group, a substituted amino group such as dimethylamino, diethylamino, dibenzylamino, diphenylamino, etc. In the definition of Y, examples of divalent aromatic hydrocarbon groups include monocyclic aromatic hydrocarbon groups such as 0-phenylene, 0-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 with a nitrogen atom include 3,4-pyrazolediyl group, 2,3-pyridinediyl group, 4,5-pyrimidinediyl group, and 6,7-indazolediyl group. basis,
5,6-benzimidazolediyl group, 6,7-
Examples include 5- to 6-membered heterocyclic divalent groups such as quinolinediyl group. Examples of the aryl group or heterocyclic group for R ₇ and R ₈ include phenyl, naphthyl, anthryl, pyrenyl, etc.; pyridyl, thienyl, furyl, carbazolyl, etc. These may be substituted with the substituents described above. Substituents for the aryl group and heterocyclic group represented by R ₇ and R ₈ include halogens such as fluorine, chlorine, bromine, and iodine, alkyl groups such as methyl, ethyl, propyl, and butyl, methoxy, ethoxy, propoxy, butoxy, etc. alkoxy group, nitro group, cyano group,
Examples include substituted amino groups such as dimethylamino, diethylamino, dipropylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino. Furthermore, R ₇ and R ₈ represent residues that form a 5- to 6-membered ring together with the central carbon;
The ~6-membered ring may have a fused aromatic ring. Examples of such groups include cyclopentylidene, cyclohexylidene, 9-fluorenylidene, 9-xanthenylidene, and the like. R ₉ and R ₁₀ in formula (8) may have a hydrogen atom substituent, an alkyl group such as methyl, ethyl, propyl, butyl, an aralkyl group such as benzyl, phenethyl, naphthylmethyl, phenyl, naphthyl, It represents an aryl group such as anthryl and diphenyl, or a heterocyclic group such as carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole, and pyridine. Substituents for the alkyl group, aralkyl group, aryl group, and heterocyclic group represented by R ₉ and R ₁₀ include halogens such as fluorine, chlorine, bromine, and iodine, methyl,
Alkyl groups such as ethyl, propyl, butyl, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, nitro group, cyano group, substituted amino groups such as dimethylamino, dipropylamino, dibenzylamino, diphenylamino, morpholino, piperidino, pyrrolidino, etc. Examples include groups. Although the present invention is not bound by theory, an alkyl, aralkyl, aryl, or acyl group is introduced as a substituent R ₁ or R ₂ to the nitrogen atom of the diarylamine that forms the skeleton of the disazo pigment of general formula (1). This changes the polarity of the pigment and improves carrier generation efficiency and/or carrier transportability, improving the sensitivity of the photoreceptor and ensuring potential stability during long-term use. . In this way, high sensitivity is achieved, making it possible to apply it to high-speed copying machines, laser beam printers, LED printers, liquid crystal printers, etc. Also, since a stable potential is ensured regardless of the previous history of the photoreceptor, stable and beautiful images can be produced. An image is obtained. 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 ₂ , Ar ₁ , and Ar ₂ in the formula have the same meanings as the symbols in general formula (1)) are tetrazotized by a conventional method, and then the corresponding coupler is converted into Alternatively, the tetrazonium salt of the diamine described above is isolated in the form of a borofluoride salt or zinc chloride double salt, and then in a suitable solvent such as N,N-dimethylformamide or dimethyl sulfoxide. It can be easily produced by coupling with a coupler in the presence of an alkali. Next, a typical synthesis example of the disazo pigment used in the present invention is shown below. Synthesis example (synthesis of disazo pigment No. 1 illustrated above): In a 500ml beaker, add 80ml of water, 16.6ml (0.19 mol) of concentrated hydrochloric acid, and 9.22 g (0.029 mol) was added thereto, and the mixture was stirred while being cooled in an ice-water bath to bring the liquid temperature to 3°C. Next, 4.2g of sodium nitrite
(0.061 mol) dissolved in 7 ml of water and the temperature of the solution
The mixture was added dropwise over 10 minutes while controlling the temperature within the range of 10°C, and after the addition was completed, the mixture was stirred for an additional 30 minutes at the same temperature. After the reaction, carbon was added and filtered to obtain a tetrazotized solution. Next, put 700 ml of water in 2 beakers and dissolve 21 g (0.53 mol) of caustic soda, then naphthol AS (3
-Hydroxy-2-naphthoic acid anilide) 16.1g
(0.061 mol) was added and dissolved. Cool this coupler solution to 6℃ and reduce the liquid temperature to 6-10℃.
Add the above-mentioned tetrazotization solution while controlling the temperature at
The mixture was added dropwise over 30 minutes with stirring, and then stirred at room temperature for 2 hours and further left overnight. The reaction solution was filtered and then washed with water to obtain a water paste containing 23.2 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. Next, after repeating stirring twice each time with 400 ml of methyl ethyl ketone, the purified pigment was dried under reduced pressure at room temperature.
Obtained 21.9g. The yield was 88%. Melting point > 250℃ Elemental analysis: Calculated value (%) Experimental value (%) C: 74.89 74.85 H: 4.90 4.87 N: 12.94 12.90 The synthesis method of typical pigments has been described above, but there are other methods as shown in general formula (1). Disazo pigments are synthesized in the same manner. However, when performing a coupling reaction using a coupler that is easily hydrolyzed, such as a coupler in an alkaline aqueous solution, the coupler should be mixed with DMF,
It is preferable to dissolve it in a solvent such as DMAc and react it with a tetrazonium salt using an organic base such as sodium acetate, pyridine, trimethylamine, or triethylamine, while being careful not to hydrolyze the coupler or the reaction solvent. In a preferred embodiment of the present invention, a disazo pigment represented by the general formula (1) can be used as a charge generating substance in an electrophotographic photoreceptor in which a photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. The charge generation layer contains as much of the disazo pigment as possible in order to obtain sufficient absorbance, and a thin film layer, e.g. It is preferable to form a thin film layer with a thickness of 5 microns or less, preferably 0.01 micron to 1 micron. 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 must be injected into the charge transport layer without being deactivated by recombination or trapping. This is due to the fact that The charge generating layer can be formed by dispersing the above-mentioned disazo pigment in a suitable binder and coating it on a substrate, or it can be obtained by forming a vapor deposited film using a vacuum vapor deposition apparatus. Binders that can be used to form the charge generating layer by coating can be selected from a wide range of insulating resins, and 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 (bisphenol A, Z type, etc.)
Examples include insulating resins such as polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, urethane resin, epoxy 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.
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 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 a draft for a time 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 reason is to prevent the charge transport layer from having a filter effect and reducing sensitivity. The term "electromagnetic source" 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. Charge-transporting substances include charge-transporting substances and hole-transporting substances, and electron-transporting substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, and 2,4,7-trinitro-9-fluorenone. , 2, 4, 5, 7-
Tetranitro-9-fluorenone, 2,4,7-
trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
Examples include electron-withdrawing substances such as 2,4,8-trinitrothioxanthone, and polymerized versions of these electron-withdrawing substances. As the hole transport substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N
-Methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3
-methyldene-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 Hydrazones such as -3-methylbenzthiazolinone-2-hydrazone, 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole, 1-phenyl-3-(P-diethylaminostyryl) )-5
-(P-diethylaminophenyl)pyrazoline,
1-[quinolyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(P-diethylaminostyryl)-5-( P-diethylaminophenyl)pyrazoline, 1-[6-methoxy-pyridyl(2)]-3-(P-diethylaminostyryl)-
5-(P-diethylaminophenyl)pyrazoline,
1-[Pyridyl(3)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl, pyrazoline, 1-[L-pyridyl(4-N,N-dimethyl-amino-2-methylphenyl)ethane Polyarylalkanes such as triphenylamine, stilbene derivatives, aromatic polycyclic compounds having a styryl group, heterocyclic compounds, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenyl, etc. Enylanthracene, pyrene formaldehyde resin, ethyl carbazole formaldehyde resin, etc. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium amorphous silicon, and cadmium sulfide can also be used. The charge transport substance is 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 polyarylate, polyester, polycarbonate (bisphenol A, Z type) polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide,
Examples include insulating resins such as 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. Typically it is between 5 microns and 30 microns, with a preferred range between 8 microns and 20 microns. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. As the substrate having the conductive layer, materials that are conductive themselves such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, isodium, gold, and platinum can be used. In addition, plastics have a layer formed by vacuum deposition of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene, terephthalate). , acrylic resin, polyethylene fluoride, etc.), conductive particles (e.g. carbon black, silver particles, etc.) coated on plastic with a suitable binder, substrates made of plastic or paper impregnated with conductive particles, and conductive materials. Plastics with polymers, 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 0.1 micron to 5 micron.
Preferably, 0.5 micron to 3 micron 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 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 the surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transport material is used. Another specific example of the present invention is an electrophotographic photoreceptor containing the above-mentioned disazo pigment and a charge transport material in the same layer. On this occasion,
In addition to the charge transport materials mentioned above, 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 forming a film using the resulting coating liquid. In any of the photoreceptors, the pigment used contains at least one type of pigment selected from disazo pigments represented by general formula (1), and its crystal form may be amorphous or crystalline. . Furthermore, if necessary, two or more types of disazo 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 40 Ammonia aqueous solution of casein (casein 11.2 28% ammonia water 1g, water 222ml)
was applied with a Mayer bar so that the film thickness after drying was 1.0 microns, 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 mol%) was added to the dissolved liquid and dispersed for 2 hours using a sand mill. This dispersion was applied onto the previously formed casein layer using a Mayer bar so that the film thickness after drying would be 0.5 microns, 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
A photoreceptor 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 microns, and drying to form a charge transport layer. Photoreceptors of Examples 2 to 40 were prepared in the same manner using the azo pigments shown in Table 1 instead of Azo 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 the illuminance was 2lux. The charging characteristics were measured by exposing the sample to light. As for charging characteristics, the surface potential (Vo) and the exposure amount E1/2 (lux·sec) required to attenuate the potential to 1/2 when dark decayed for 1 second were measured. Results first
Shown in the table.

【table】

[Table] As is clear from the results in Table 1, it was confirmed that all the photoreceptors of the present invention had extremely excellent electrophotographic sensitivity. Examples 41 to 45 Using the photoreceptors used in Examples 1, 3, 4, 17, and 19, variations in light and dark potential and dark area potential during repeated use were measured. The method is -5.6kV corona charger,
The prepared photoreceptor was 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. This copying machine is configured to produce an image on transfer paper as a cylinder is driven. Using this copier, the initial light/dark potential (V _L ) and dark potential (V _D ) were set to around -100 V and 600 V, respectively, and the light/dark potential (V _L ) and dark potential (V _D ) after being used 5000 times. was measured. The results are shown in Table 2.

〔Effect of the invention〕

In the present invention, by using a specific azo pigment in a photosensitive layer, either one or both of carrier generation efficiency and carrier transport efficiency within the photosensitive layer containing the azo pigment is improved, and sensitivity and durability during use are improved. A photoreceptor with excellent potential stability can be obtained.

Claims (1)

[Claims] 1 The following general formula 1 (In the formula, R ₁ and R ₂ represent alkyl, aralkyl, aryl, or acyl which may have a substituent, and Ar ₁ , Ar ₂ and Ar ₃ each represent an arylene or a heterocyclic ring which may have a substituent. 1. An electrophotographic photoreceptor characterized in that a photosensitive layer contains an azo pigment represented by the following formula (A represents a coupler residue having a phenolic OH group). 2. An electrophotographic photoreceptor according to claim 1, wherein A in the above general formula is represented by the following general formulas 2 to 8: (In _the formula _, or taken together with the nitrogen atom to form a cyclic amino group; R ₅
and R ₆ represent alkyl, aralkyl, or aryl, each of which may have a substituent; Y is a divalent aromatic hydrocarbon group or forms a divalent heterocyclic group together with a nitrogen atom. ; R ₇ and R ₈ each represent an aryl group or a heterocyclic group which may have a substituent, or a residue forming a 5- to 6-membered ring together with the central carbon, and this 5- to 6-membered ring is a fused It may have an aromatic ring; R ₉ and R ₁₀ represent hydrogen, an alkyl group that may have a substituent, an aralkyl group, an aryl group, or a heterocyclic group). 3. Claims 1 and 2, wherein 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 contains an azo pigment represented by the above general formula (1). Electrophotographic photoreceptor. 4 R ₃ in the above general formula (2) is hydrogen, and R ₄
is the general formula 3. The electrophotographic photoreceptor according to claim 2, wherein R ₁₁ is a substituted phenyl represented by a substituent selected from halogen, nitro, cyano, and trifluoromethyl.