JPH0513504B2 - - 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 containing an azo pigment having a coupler component with a specific structure. [Prior Art] Conventionally, as electrophotographic photoreceptors using inorganic photoconductive substances, those using selenium, cadmium sulfide, zinc oxide, etc. are widely known. On the other hand, electrophotographic photoreceptors using organic photoconductive substances include photoconductive polymers typified by poly-N-vinylcarbazole and 2,5-bis(p-
Products using low-molecular organic photoconductive substances such as (diethylaminophenyl)-1,3,4-oxadiazole, and combinations of such organic photoconductive substances with various dyes and pigments are known. It is being An electrophotographic photoreceptor using an organic photoconductive substance has good film-forming properties, can be produced by coating, has extremely high productivity, and has the advantage of being able to provide an inexpensive photoreceptor. In addition, it has the advantage that color sensitivity can be freely controlled by selecting the sensitizers used, such as dyes and pigments, and has been extensively studied. Particularly recently, with the development of a functionally separated photoreceptor, which has an organic photoconductive pigment as a charge generation layer and a charge transport layer made of the aforementioned photoconductive polymer or low-molecular organic conductive substance, Significant improvements have been made in the sensitivity and durability, which were considered to be drawbacks of electrophotographic photoreceptors. Many pigments have been proposed for use in this type of photoreceptor, but azo pigments in particular have been extensively studied because pigments with various properties can be easily synthesized by combining amine components and coupler components. However, there are problems with sensitivity and potential stability during repeated use, and only a few materials are in practical use. Coupler components used in such azo pigments include naphthol AS couplers described in JP-A No. 47-37543, benzcarbazole couplers described in JP-A-58-122967, etc. Naphthalimide couplers described in JP-A No. 54-79632 and perinone couplers described in JP-A-57-176055 are already known. As a result of repeated research to solve the above problems, the present inventors discovered that an electrophotographic photoreceptor containing an azo pigment using a specific coupler described below has practical sensitivity and stable potential characteristics. Ta. [Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photoreceptor, and to provide an electrophotographic photoreceptor that has practical high sensitivity characteristics and stable potential characteristics during repeated use. That's true. [Means for Solving the Problems, Effects] The present invention provides an electrophotographic photoreceptor having a photosensitive layer containing an azo pigment represented by the following general formula (1) on a conductive support. at least one of
The electrophotographic photoreceptor is composed of an electrophotographic photoreceptor characterized in that is a coupler residue represented by the general formula (2). Ar-(N=N-Cp) _o (1) In the formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group which may be bonded via a bonding group, and Cp is Indicates a coupler residue having a phenolic hydroxyl group, n is 1, 2,
Indicates an integer of 3 or 4. In the formula, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and A represents a divalent aromatic hydrocarbon group that may have a substituent or a nitrogen atom in the ring. represents a divalent heterocyclic group contained in Indicates a bare ring group. Specifically, Ar includes aromatic hydrocarbon groups such as benzene, naphthalene, fluorene, phenanthrene, anthracene, and pyrene, furan, thiophene, pyridine, indole, benzothiazole, carbazole, acridone, dibenzothiophene, benzoxazole, and benzene. Aromatic heterocyclic groups such as triazole, oxadiazole, thiazole, etc., and those in which the above aromatic rings are bonded directly or with an aromatic group or a non-aromatic group, such as triphenylamine, diphenylamine, N-
Methyl diphenylamine, biphenyl, terphenyl, binaphthyl, fluorenone, phenanthrenequinone, anthraquinone, benzanthrone,
Examples include diphenyloxadiazole, phenylbenzoxazole, diphenylmethane, diphenylsulfone, diphenyl ether, benzophenone, stilbene, distyrylbenzene, tetraphenyl-p-phenylenediamine, and tetraphenylbenzidine. The optional substituents of the aromatic hydrocarbon group or aromatic heterocyclic group that may be bonded via the above-mentioned bonding group include alkyl groups such as methyl, ethyl, propyl, and butyl, and alkyl groups such as methoxy and ethoxy. groups, dialkylamino groups such as dimethylamino and diethylamino, fluorine atoms, chlorine atoms,
Examples include halogen atoms such as bromine atoms, hydroxy groups, nitro groups, cyano groups, and halomethyl groups. In R ₁ , examples of the alkyl group include methyl, ethyl, propyl, etc., examples of the alkoxy group include methoxy, ethoxy, etc., and examples of the halogen atom include groups such as fluorine atom, chlorine atom, and bromine atom. Regarding A, specifically, o-phenylene,
o-Naphthylene, perinaphthylene, 1,2-antrylene, 3,4-pyrazoldiyl, 2,3-
pyridinediyl, 4,4-pyridinediyl, 6,
Examples include groups such as 7-indazolediyl and 6,7-quinolinediyl. Examples of substituents that these divalent aromatic hydrocarbon groups or divalent heterocyclic groups containing a nitrogen atom in the ring may include alkyl groups such as methyl, ethyl, and propyl, methoxy, ethoxy, Examples include alkoxy groups such as propoxy, halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms, halomethyl groups such as trifluoromethyl, cyano groups, and nitro groups. In addition, in Cp in general formula (1), preferred examples of coupler residues that may coexist other than the coupler residue shown in general formula (2) include the following general formula
Examples include coupler residues having the structures shown in (4) to (8). X in the above general formulas (4), (5), and (6) includes a naphthalene ring, an anthracene ring, a carbazole ring, a benzcarbazole ring, a dibenzofuran ring, etc., which may be fused with a benzene ring and have a substituent. Residues required for formation are shown. R ² and R ³ represent a hydrogen atom, an alkyl group that may have a substituent, an aryl group, an aralkyl group, a heterocyclic group, or a cyclic amino group containing a nitrogen atom to which R ² and R ³ are bonded, and R ⁴ represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group, or a heterocyclic group which may have a substituent. R ⁵ represents an alkyl group, an aryl group, an aralkyl group, or a heterocyclic group which may have a substituent. Z represents an oxygen atom or a sulfur atom, and l represents 0 or 1. Y represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group containing a nitrogen atom in the ring. Specifically o-phenylene, 0-naphthylene,
perinaphthylene, 1,2-antrylene, 3,4
-Pyrazolediyl, 2,3-pyridinediyl,
Examples include groups such as 4,5-pyridinediyl, 6,7-indazolediyl, and 6,7-quinolinediyl. Examples of the alkyl group in the above expression include groups such as methyl, ethyl, propyl, and butyl; examples of the aralkyl group include groups such as benzyl, phenethyl, and naphthylmethyl; and examples of the heterocyclic group include pyridyl, thienyl, furyl, Examples include groups such as thiazolyl, carbazolyl, dibenzofuryl, benzimidazolyl, and benzothiazolyl. Examples of cyclic amino groups containing a nitrogen atom in the ring include pyrrole, pyrroline, pyrrolidine, pyrrolidone, indole, indoline, isoindole, carbazole, benzindole, and imidazole. , pyrazole, pyrazoline, oxazine, phenoxazine,
Examples include cyclic amino groups derived from benzocarbazole and the like. Examples of substituents include alkyl groups such as methyl, ethyl, and propyl; alkoxy groups such as methoxy and ethoxy; substituted amino groups such as diethylamino and dimethylamino; halogen atoms such as fluorine, chlorine, and bromine; Examples thereof include a carbamoyl group, a nitro group, a cyano group, and a halomethyl group such as trifluoromethyl. Representative examples of azo pigments used in the present invention are listed below. Note that the azo pigment of the present invention is not limited to these exemplified pigments. The specific azo pigment of the present invention can be produced by diazotizing the corresponding amine by a conventional method and coupling it with the coupler represented by the general formula (2) in an aqueous system in the presence of an alkali, or by converting the diazonium salt into a borofluoride salt or a zinc chloride double salt. It can be easily synthesized by coupling with a coupler in an organic solvent such as N,N-dimethylformamide or dimethyl sulfoxide in the presence of a base such as sodium acetate, triethylamine or triethanolamine. In addition, when synthesizing a disazo pigment in which a coupler other than the coupler represented by general formula (2) coexists in the molecule, the corresponding diamine is tetrazotized by a conventional method, isolated as the above-mentioned soluble salt, and then the general formula
Either 1 mol of the coupler shown in (2) is coupled and then 1 mol of a different type of coupler is combined to synthesize the diamine, or one amino group of the diamine is protected with an acetyl group, etc., and this is diazotized to form the general formula
After coupling the coupler shown in (2), the protective group is hydrolyzed with hydrochloric acid or the like, this is again diazotized, and the compound can be synthesized by coupling with a different type of coupler. Trisazo pigments and tetrakisazo pigments in which a coupler other than the coupler represented by general formula (2) coexists in the molecule are also synthesized in a similar manner. Synthesis Example (Synthesis of Exemplary Pigment (2-9)) In a 300ml beaker, 150ml of water, 20ml of concentrated hydrochloric acid (0.23 mol) and 2,5-bis(p-aminophenyl)-1,
Add 8.0 g (0.032 mol) of 3,4-oxadiazole, cool to 0°C, and add sodium nitrite to it.
A solution prepared by dissolving 4.6 g (0.067 mol) in 10 ml of water was added dropwise over 10 minutes while controlling the liquid temperature to 5°C or less. After stirring for 15 minutes, carbon filtration was performed to obtain a tetrazotized liquid. 10.5g of borofluorinated soda in this liquid
(0.096 mol) dissolved in 90 ml of water was added dropwise, and the precipitated borofluoride salt was collected by filtration, washed with cold water, washed with acetonitrile, and dried under reduced pressure at room temperature. Yield 11.8g, yield 82.0% Next, add 500ml of DMF to one beaker. After dissolving 11.4g (0.042mol) and cooling the liquid temperature to 5℃, 9.0g of the borofluoride salt obtained earlier
(0.020 mol) and then triethylamine
5.1 g (0.050 mol) was added dropwise over 5 minutes. After stirring for 2 hours, the precipitated pigment was collected by filtration and diluted with DMF for 4 hours.
After washing twice and three times with water, it was freeze-dried. Yield: 14.2g Yield: 87.0% Melting point: 300°C or above (decomposition) Elemental analysis Calculated value (%) Actual value (%) C 73.69 73.75 H 3.22 3.38 N 17.19 17.02 The film containing the azo pigment described above exhibits photoconductivity, Therefore, it can 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 can be prepared by dispersing the azo pigment in a suitable binder and forming a film on a conductive support. In a preferred embodiment of the present invention, as a charge generating substance in an electrophotographic photoreceptor in which the photosensitive layer of the electrophotographic photoreceptor is functionally separated into a charge generation layer and a charge transport layer,
Photoconductive coatings containing the specific azo pigments mentioned above can be applied. The charge generation layer contains as much of the above-mentioned specific azo pigment exhibiting photoconductivity as possible in order to obtain sufficient absorbance, and the generated charge carriers are at the interface with the charge transport layer or at the conductive support. A thin film layer, e.g. 5μ, is required for efficient transport to the interface of
It is desirable to form a thin film layer having a thickness of 0.01 to 1 μm, preferably 0.01 to 1 μm. 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. 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, polyvinyl benzal,
Polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, casein, polyvinyl alcohol, Examples include insulating resins such as polyvinylpyrrolidone. The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less. Solvents that dissolve these resins vary depending on the type of resin, and are 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 isopropyl alcohol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N,N-dimethylformamide and N,N-dimethylacetamide, and dimethyl sulfoxide. Sulfoxides, ethers such as tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate,
Aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, etc., or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. . Coating methods include dip coating method, spray coating method, spinner coating method, bead coating method, Meyer bar coating method, blade coating method, roller coating method,
This can be done using a coating method such as a curtain 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 to 200° C. for 5 minutes to 2 hours, either stationary or with 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. Charge-transporting substances include electron-transporting substances and hole-transporting substances, and electron-transporting substances include chloranyl, tetracyanoethylene, tetracyanoquinodimethane, and 2,4,5,7-tetranitro-9.
- Electron-withdrawing substances such as fluorenone, 2,4,5,7-tetranitroxanthone, and 2,4,8-trinitrothioxanthone, and polymerized products of these electron-withdrawing substances are included. Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole,
N,N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, p-diethylaminobenzaldehyde-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-[pyridyl(2)]-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl(3)]- 3-(p
-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridine(2)]-3-(p-diethylaminostyryl)-4
-Methyl-5-(p-diethylaminophenyl)
Pyrazolines such as pyrazoline, 1-phenyl-3-(p-diethylaminostyryl)-4-methyl-5-(p-diethylaminophenyl)pyrazoline, spiropyrazoline, α-phenyl-4-N,
N-diphenylaminostilbene, N-ethyl-
3-(α-phenylstyryl)carbazole, 9
-Dibenzylaminobenzylidene-9H-fluorenone, 5-p-ditolylaminobenzylidene-
Styryl compounds such as 5H-dibenzo[a,d]cycloheptene, 2-(p-diethylaminostyryl)-6-diethylaminobenzoxazole, 2-(p-diethylaminophenyl)-4-
Oxazole compounds such as (p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2-(p-diethylaminostyryl)-6
-thiazole compounds such as diethylaminobenzothiazole, bis(4-diethylamino-2-
Triarylmethane compounds such as methylphenyl)-phenylmethane, 1,1-bis(4-N,
N-diethylamino-2-methylphenyl)heptane, 1,1,2,2tetrakis(4-N,N-
Polyarylalkanes such as diethylamino-2-methylphenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin etc. In addition to these organic charge transport materials, organic 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-vinyl carbazole. , polyvinylanthracene, polyvinylpyrene, and other organic photoconductive polymers. 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 to 30 μm, but the preferred range is 8 to 20 μm. 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 conductive support. Examples of the conductive support include aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, etc., which have conductivity themselves.
Gold, platinum, etc. can be used, and in addition,
Plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyethylene terephthalate, polyvinyl chloride, polyethylene terephthalate, acrylic resin, (e.g., ethylene chloride), a support made of conductive particles (e.g. carbon black, silver particles, etc.) coated on plastic together with a suitable binder, a support made of plastic or paper impregnated with conductive particles, or a support made of conductive particles impregnated with plastic or paper. For example, plastics containing polymers having a high molecular weight can be used. A subbing layer having barrier and adhesive functions may also be provided between the conductive support and the photosensitive layer. The undercoat 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. Can be formed. The thickness of the undercoat layer is 0.1 to 5 μm, preferably 0.5 to 5 μm.
3 μm is appropriate. When using an electrophotographic photoreceptor in which a conductive support, a charge generation layer, and a charge transport layer are laminated in this order, when the charge transport material is an electron transport material,
It is necessary to positively charge the surface of the charge transport layer, and when exposed to light after charging, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface and neutralize the positive charge, causing the surface Attenuation of the potential occurs and electrostatic contrast occurs between the exposed area and the unexposed area. A visible image is 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 or plastic film, 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 transport layer must be negatively charged.
When exposed to light after being charged, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface to neutralize the negative charge, resulting in attenuation of the surface potential and an electrostatic contrast between the exposed area and the unexposed area. occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used. When using an electrophotographic photoreceptor in which a conductive support, a charge transport layer, and a charge generation layer are laminated in this order, when the charge transport material is an electron transport material,
It is necessary to charge the surface of the charge generation layer negatively, and when exposed to light after charging, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the conductive support. On the other hand, holes generated in the charge generation layer reach the surface, causing attenuation of the surface potential and creating an electrostatic contrast with the unexposed area. A visible image is obtained by developing the electrostatic latent image thus formed with a positively charged toner. This can be directly fixed, or the toner image can be transferred to paper or plastic film, 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 layer is made of a hole transporting substance, 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 conductive support. On the other hand, electrons generated in the charge generation layer reach the surface, the surface potential is attenuated, and an electrostatic contrast is generated between the charge generation layer and 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. Further, as the electrophotographic photoreceptor of the present invention, an electrophotographic photoreceptor containing the above-mentioned specific azo pigment and a charge transport substance in the same layer can be mentioned. At this time, a charge transfer complex compound consisting of poly-N-vinylcarbazole and trinitrofluorenone can be used in addition to the charge transport substance. The electrophotographic photoreceptor of this example can be prepared by dispersing the specific azo pigment and charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran, and then forming a film thereon. The pigment used in any electrophotographic photoreceptor contains at least one type of pigment selected from azo pigments represented by general formulas (1) and (2), and its crystal form may be either amorphous or crystalline. . In addition, if necessary, pigments represented by the above general formulas (1) and (2) 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 two or more types of azo pigments, 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 in electrophotographic copying machines, but also in a wide range of electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making. [Example] Examples 1 to 12 A solution of 5 g of methoxymethylated nylon (average molecular weight 32,000) and 10 g of alcohol-soluble copolymerized nylon (average molecular weight 29,000) dissolved in 95 g of methanol was placed on an aluminum substrate using a Mayer tube. Apply with a bar,
A subbing layer having a thickness of 1 μm after drying was provided. Next, add 5 g of the exemplified pigment (1-1) to 95 ml of cyclohexanone and add butyral resin (butyralization degree) to 95 ml of cyclohexanone.
63 mol%) was added to the dissolved liquid and dispersed for 20 hours using a sand mill. This dispersion was applied onto the previously formed undercoat layer using a Mayer bar so that the film thickness after drying was 0.2 μm, and dried to form a charge generation layer. Next, the structural formula 5 g of hydrazone compound and 5 g of polymethyl methacrylate (number average molecular weight 100,000) were dissolved in 40 ml of toluene, and this solution was applied onto the charge generation layer using a Mayer bar so that the dry film thickness was 20 μm and dried. A charge transport layer was formed, and an electrophotographic photoreceptor of Example 1 was prepared. Electrophotographic photoreceptors corresponding to Examples 2 to 12 were prepared in the same manner as in Example 1, except that the following exemplified pigment was used in place of exemplified pigment (1-1) for the azo pigment. The electrophotographic photoreceptor thus prepared was tested using an electrostatic copying paper tester (Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.).
The sample was statically charged with a corona at -5KV using a 1000V, held in a dark place for 1 second, and then exposed to light at an illuminance of 10 lux to examine its charging characteristics. 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 decaying for 1 second were measured. Show the results.

【table】

[Table] Comparative Examples 1 and 2 A photoreceptor was prepared in the same manner as in Example 1, except that the azo pigment used in Example 1 was replaced with an azo pigment having the structural formula below, and the charging characteristics were evaluated in the same manner. . Show the results. Vo: −650V E1/2: 4.4lux, sec (Comparative example 2) Vo: -550V E1/2: 3.8lux, sec From the results of Example 2 and Comparative Examples 1 and 2 above, it can be seen that the electrophotographic photoreceptor of the present invention has sufficient charging ability and excellent sensitivity. . Examples 13 to 17 Using the electrophotographic photoreceptors prepared in Examples 2, 3, 5, 7, and 9, fluctuations in bright area potential and dark area potential during repeated use were measured. The measurement method was to attach a photoreceptor to the cylinder of an electrophotographic copying machine equipped with a -5.6KV corona charger, exposure optical system, developer, transfer charger, static elimination exposure optical system, and cleaner. The structure is such that an image is obtained on the transfer paper as the cylinder is driven. Using this copier, the initial dark potential (V _D ) and light potential (V _L ) were set to -700V and -200V, respectively, and the amount of variation in dark potential (△
V _D ) and the amount of variation in light area potential (ΔV _L ) were measured. Show the results. Note that a negative sign in the amount of change in potential represents a decrease in potential, and a positive sign represents an increase in potential.

[Table] Comparative Examples 3 and 4 The electrophotographic photoreceptors prepared in Comparative Examples 1 and 2 were measured for potential fluctuations during repeated use in the same manner as in Example 13. Show the results.

[Table] From the above results, the electrophotographic photoreceptor of the present invention has
It can be seen that there is little potential fluctuation during repeated use. Example 18 A polyvinyl alcohol film having a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. Next, the dispersion of the disazo pigment used in Example 7 was applied onto the previously formed polyvinyl alcohol layer using a Mayer bar so that the film thickness after drying was 0.2 μm, and dried to form a charge generation layer. did. Then, A solution prepared by dissolving 5 g of styryl compound and 5 g of polyarylate (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) in 40 ml of tetrahydrofuran was applied onto the charge generation layer so that the film thickness after drying was 20 μm. , and dried to form a charge transport layer. The charging characteristics and durability characteristics of the electrophotographic photoreceptor thus prepared were measured in the same manner as in Examples 1 and 13. Show the results. Vo: -700V, E1/2: 0.9lux, sec △V _D : +5V △V _L : +5V Example 19 The charge generation layer and charge transport layer of the electrophotographic photoreceptor prepared in Example 7 were applied in the reverse order. An electrophotographic photoreceptor was prepared, and its charging characteristics were evaluated in the same manner as in Example 1. However, the charging polarity was set to +. Vo: +700V E1/2: 1.6lux, sec Example 20 On the charge generation layer formed in Example 7, 2,
5 g of 4,7-trinitro-9-fluorenone,
A film obtained by dissolving 5 g of poly-4,4'-dioxydiphenyl-2,2-propane carbonate (molecular weight 300,000) in 70 ml of chlorobenzene has a film thickness of 15 μm after drying.
It was applied so that it became m and dried. The charging characteristics of the electrophotographic photoreceptor thus prepared were evaluated in the same manner as in Example 1. However, the charging polarity was set to +. Vo: +650V E1/2: 3.3lux, sec Example 21 2,4,7 trinitro-9-fluorenone 5g
and poly-N-vinylcarbazole (number average molecular weight
A charge transfer complex compound was prepared by dissolving 5 g of 300,000) in 70 ml of tetrahydrofuran. 1 g of this charge transfer complex compound and the exemplary pigment (2-9) were mixed with polyester (trade name: Vylon, Toyobo Co., Ltd.)
Co., Ltd.) was dissolved in 70 ml of tetrahydrofuran and dispersed. This dispersion was applied onto the undercoat layer formed in Example 1 and dried to form a photosensitive layer with a thickness of 16 μm. The charging characteristics of the electrophotographic photoreceptor thus prepared were evaluated in the same manner as in Example 1. However, the charging polarity was set to +. Vo: +680V E1/2: 3.6lux, sec [Effect of the invention] By using a specific azo pigment in the photosensitive layer, the electrophotographic photoreceptor of the present invention has a high carrier generation efficiency inside the photosensitive layer containing the azo pigment. The electrophotographic photoreceptor is improved in either or both carrier transport efficiency and has excellent sensitivity and potential stability during long-term use.

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor having a photosensitive layer containing an azo pigment represented by the following general formula (1) on a conductive support, at least one of Cp in the general formula (1) is represented by the general formula An electrophotographic photoreceptor characterized by having a coupler residue shown in (2). Ar-(N=N-Cp) _o (1) In the formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group which may be bonded via a bonding group, and Cp is Indicates a coupler residue having a phenolic hydroxyl group, n is 1, 2,
Indicates an integer of 3 or 4. In the formula, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and A represents a divalent aromatic hydrocarbon group that may have a substituent or a nitrogen atom in the ring. represents a divalent heterocyclic group contained in 2. The electrophotographic photoreceptor according to claim 1, wherein at least two layers, a charge generation layer and a charge transport layer containing an azo pigment represented by formulas (1) and (2), are provided on a conductive support. 3. An electrophotographic photoreceptor comprising a photosensitive layer containing an azo pigment represented by the following general formula (3) on a conductive support. In the formula, Ar represents a substituted or unsubstituted aromatic hydrocarbon group or aromatic heterocyclic group which may be bonded via a bonding group, and R ₁ is a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, It represents a cyano group or a nitro group, and A represents a divalent aromatic hydrocarbon group which may have a substituent or a divalent heterocyclic group containing a nitrogen atom in the ring. 4. The electrophotographic photoreceptor according to claim 3, wherein at least two layers, a charge generation layer and a charge transport layer containing an azo pigment represented by formula (3), are provided on a conductive support.