JPS6261265B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor using a specific azo pigment. Conventional photoreceptors containing organic pigments on a conductive layer include (i) a layer in which pigments are dispersed in an insulating binder on a conductive layer as disclosed in Japanese Patent Publication No. 52-1667 (electrophotographic plate); (ii) A charge transporting substance or such substance and an insulating binder as disclosed in JP-A-47-30328 (electrophotographic plate) and JP-A-47-18545 (electrophotographic imaging method); (iii) Disclosed in JP-A-49-105537 (electrophotographic plate), in which a layer in which a pigment is dispersed in a charge transport medium consisting of a binder (the binder itself may be a charge transport material) is provided on a conductive layer. (iv) an organic pigment in a charge transfer complex as disclosed in JP-A-49-91648 (photoconductive member); (v) Others. Many pigments have been proposed for use in such photoreceptors, such as phthalocyanine pigments, polycyclic quinone pigments, azo pigments, and quinacritone pigments, but so far very few have been put into practical use. . The reason is that organic photoconductive pigments are different from inorganic Se.
This is because it is inferior to CdS.ZnO etc. in terms of sensitivity and durability. On the other hand, inorganic photoreceptors also have problems; Se-based photoreceptors easily crystallize due to factors such as temperature, humidity, dust, and finger squeezing, especially when the ambient temperature of the photoreceptor is 40°C.
If it exceeds this range, crystallization becomes noticeable, resulting in drawbacks such as a decrease in chargeability and the appearance of white spots on images. Although the lifespan of Se-based photoreceptors is said to be around 30,000 to 50,000 copies, because environmental conditions vary widely depending on the region and location where the copying machine is installed, many photoreceptors do not reach the above-mentioned lifespan. The current situation is that In the case of a CdS photoconductor coated with an insulating layer, the lifetime is also
However, it is extremely difficult to overcome the poor moisture resistance caused by CdS, and the current situation is that supplementary measures such as heaters are required to prevent the photoreceptor from absorbing moisture. It is. In the case of ZnO photoreceptors, they are sensitized with dyes such as rose bengal, so there are problems such as deterioration due to energization due to corona charging and photofading of the dye, and the current lifespan of the photoreceptor is approximately 1000 copies. has been done. The sensitivity of conventional photoreceptors is half-attenuation exposure (E1/2)
When expressed in
sec, and for CdS photoreceptors, the sensitized Se
It has a sensitivity similar to that of ZnO-based photoreceptor, and
It is about 12Iux・sec. The E1/2 value is PPC for the sensitivity of a practical photoreceptor.
For copying machines, 20 lux/sec or less is desirable, and for PPC copying machines with high copying speeds, 15 lux/sec or less is more desirable. However, depending on the application, it may be possible to use it even if the sensitivity is less than the above-mentioned sensitivity. The present inventors have conducted intensive research to overcome the drawbacks of conventional inorganic photoreceptors and to improve the drawbacks of organic electrophotographic photoreceptors that have been proposed so far, and have discovered a coupler represented by the following general formula in the molecule. At least one type, preferably two or three types of azo groups bonded to the residue
Photoreceptors containing azo pigments have high sensitivity and durability that can be put to practical use, and they also have improved heat resistance (Se crystallization), moisture resistance, and The present invention was achieved by discovering that the electrophotographic photoreceptor can be an excellent electrophotographic photoreceptor that solves problems such as photobleaching. general formula In the formula, R ₁ represents an aryl group (eg, phenyl group, α-naphthyl group, β-naphthyl group, etc.). As a substituent or atom in R ₁ ,
Alkyl groups (e.g., methyl, ethyl, propyl, iso-propyl, butyl, t-butyl, etc.), alkoxy groups (e.g., methoxy, ethoxy, propoxy, butoxy, etc.), dialkylamino groups (e.g., dimethylamino group, diethylamino group, dipropylamino group, dibutylamino group, dibenzylamino group, etc.), diarylamino group (diphenylamino group, ditolylamino group, dixylylamino group, etc.), halogen atom (e.g., chlorine atom) , bromine atom, iodine atom, etc.), a nitro group, or a cyano group. R is an optionally substituted alkyl group (e.g., methyl group, ethyl group, propyl group, iso-propyl group, butyl group, t-butyl group, benzyl group, phenethyl group, chlorobenzyl group, dichlorobenzyl group, methylbenzyl group) basis,
Ethylbenzyl group, methoxybenzyl group, 2-methoxyethyl group, 3-methoxypropyl group, 2-
chloroethyl group, 3-chloropropyl group, 2-hydroxyethyl group, etc.) or aryl group (e.g., phenyl group, tolyl group, xylyl group, biphenyl group, chlorophenyl group, dichlorophenyl group, trichlorophenyl group, nitrophenyl group,
cyanophenyl group, methoxyphenyl group, dimethoxyphenyl group, dichloromethoxyphenyl group,
α-naphthyl group, β-naphthyl group, etc.). Among the azo pigments used in the present invention, preferred are bisazo pigments or trisazo pigments represented by the following general formula (1). General formula (1) In the formula, p represents 2 or 3, R ₁ and R have the same meanings as above, and R ₁ represents an optionally substituted aryl group. R represents an optionally substituted alkyl group or aryl group. A is (a) a hydrocarbon group having at least one benzene ring, (b) at least two
A nitrogen-containing hydrocarbon group having two benzene rings or
(c) Indicates a hydrocarbon group having at least two benzene rings and at least one heterocycle. mentioned above
The benzene ring in (a) and (b) may be fused with one or more other benzene rings to form a fused ring,
Furthermore, the benzene ring in (c) may be fused with one or more other benzene rings or heterocycles to form a fused ring. The hydrocarbon group (a), the nitrogen-containing hydrocarbon group (b), and the hydrocarbon group (c) are suitable atoms,
For example, oxygen atoms, halogen atoms (chlorine atoms, bromine atoms, iodine atoms) or organic residues, such as alkyl groups (methyl group, ethyl group, propyl group, iso-
propyl group, butyl group, t-butyl group, etc.), alkoxy group (methoxy group, ethoxy group, propoxy group, butoxy group, etc.), dialkylamino group (dimethylamino group, diethylamino group, dipropylamino group, dibutylamino group, dibenzylamino group, etc.), diarylamino group (diphenylamino group, ditolylamino group, dixylylamino group, etc.), acylamino group (acetylamino group,
(propionylamino group, butyrylamino group, benzoylamino group, trioylamino group, etc.), nitro group, or hydroxy group. To explain more specifically, the above (a), (b) and
Specific examples of (c) are as follows. As an example of (a), etc. can be mentioned. In the formula, R ₂ represents a hydrogen atom or a cyano group.
R ₃ represents a hydrogen atom or an alkoxy group (methoxy group, ethoxy group, propoxy group, butoxy group, etc.). R ₄ and R ₅ are hydrogen atoms, halogen atoms (chlorine atoms, bromine atoms, iodine atoms), alkyl groups (methyl group, ethyl group, propyl group, iso
-propyl group, butyl group, t-butyl group, etc.),
Indicates an alkoxy group (methoxy, ethoxy, propoxy, butoxy, etc.) or nitro group. Further, R ₄ and R ₅ may be the same group at mutually symmetrical positions, or may be different groups except when both are hydrogen atoms. As an example of (b), etc. can be mentioned. As an example of (c), Further, the -S- group in the formula was substituted with an oxygen atom.

[Formula] or etc. can be mentioned. R ₆ and R ₇ are hydrogen atoms, lower alkyl groups (e.g. methyl group, ethyl group, propyl group, iso
-propyl group, butyl group, t-butyl group, etc.) or a halogen atom (for example, chlorine atom, bromine atom, iodine atom, etc.). Z represents an oxygen atom, a sulfur atom or _〓NR15 . _R15 is a hydrogen atom or a lower alkyl group (e.g. methyl group, ethyl group, propyl group, iso-
propyl group, butyl group, t-butyl group, etc.). R ₈ is a hydrogen atom, a halogen atom (e.g.
_R9 represents a hydrogen atom, a halogen atoms (e.g. chlorine atom, bromine atom, iodine atom, etc.), lower alkyl groups (e.g. methyl group, ethyl group, propyl group, iso-propyl group, butyl group,
t-butyl group, etc.), alkoxy groups (e.g., methoxy group, ethoxy group, propoxy group, butoxy group, etc.), hydroxy group, nitro group, dialkylamino group (e.g., dimethylamino group, diethylamino group, dipropylamino group, etc.) ) or an acylamino group (eg, acetylamino group, propionylamino group, butyrylamino group, benzoylamino group, trioylamino group, etc.). Further, n is 0 or 1, and m is an integer of 1 to 4. R ₁₀ is a single bond, each may be substituted

[Formula] or -CH=CH- group. Examples of substituents or atoms include halogen atoms (e.g., chlorine atom, bromine atom, iodine atom, etc.),
Alkyl groups (e.g. methyl, ethyl, propyl, iso-propyl, butyl, t-butyl, etc.), alkoxy groups (e.g. methoxy, ethoxy, propoxy, butoxy), cyano Examples include groups. R ₁₁ and R ₁₂ are a hydrogen atom, a halogen atom (chlorine atom, bromine atom, iodine atom, etc.), a lower alkyl group (methyl group, ethyl group, propyl group, iso-
propyl group, butyl group, t-butyl group, etc.). R ₁₃ and R ₁₄ are hydrogen atoms, halogen atoms (chlorine atoms, bromine atoms, iodine atoms, etc.), lower alkyl groups, (methyl groups, ethyl groups, propyl groups, iso-
propyl group, butyl group, t-butyl group, etc.), alkoxy group (methoxy group, ethoxy group, propoxy group, butoxy group, etc.), nitro group or acylamino group (acetylamino group, propionylamino group, butyrylamino group, benzoylamino group) ,
(trioylamino group, etc.). The azo pigment represented by the general formula (1) is produced by tetrazotizing a starting material compound, an amine represented by the general formula A-(NH ₂ ) _o (in the formula, n and A have the same meanings as before), by a conventional method. Or hexazotized and then a coupler represented by the general formula below (wherein R and R ₁ are the same as in general formula (1)) in the presence of an alkali, or the tetrazonium salt or hexazonium salt of the above amine is once isolated in the form of a borofluoride salt or a zinc chloride salt. It can be easily produced by coupling it with the above coupler in the presence of an alkali in a suitable solvent such as N.N-dimethylformamide or dimethyl sulfoxide after separation. The electrophotographic photoreceptor of the present invention is characterized by having a photosensitive layer containing an azo pigment represented by the general formula (1), and is any of the types of electrophotographic photoreceptors described in (i) to (v) above. However, in order to increase the transport efficiency of charge carriers generated by light absorption of the azo pigment represented by general formula (1), it is necessary to use photoreceptors of types (ii), (iii), and (iv). It is desirable to use it as Furthermore, we separated the charge carrier generation and transport functions.
The (iii) type photoreceptor is the most desirable in terms of taking advantage of the characteristics of the pigment. Therefore, this type of electrophotographic photoreceptor will be described in detail. As for the layer structure, a conductive layer, a charge generation layer, and a charge transport layer are essential, and the charge generation layer may be either above or below the charge transport layer, but in an electrophotographic photoreceptor of the type that is used repeatedly. It is preferable to laminate a conductive layer, a charge generation layer, and a charge transport layer in this order mainly from the viewpoint of physical strength and in some cases from the viewpoint of chargeability. An adhesive layer may be provided as necessary for the purpose of improving the adhesiveness between the conductive layer and the charge generation layer. As the conductive layer, a metal plate or foil made of aluminum or the like, a plastic film coated with a metal such as aluminum or aluminum foil glued to paper, or paper treated with conductivity is used. Effective materials for the adhesive layer include resins such as casein, polyvinyl alcohol, water-soluble polyethylene, and nitrocellulose. The thickness of the adhesive layer is
A suitable value is 0.1 to 5μ, preferably 0.5 to 3μ. After forming the azo pigment represented by the general formula (1) into particles on the conductive layer or the adhesive layer applied to the conductive layer, it is dispersed without a binder or in an appropriate binder solution if necessary, and then applied and dried. and set it up. When dispersing the azo pigment, known methods such as ball mills and attritors can be used, and the pigment particles are preferably 5 μm or less, preferably 2 μm or less.
It is desirable to set it to 0.5μ or less. The azo pigment can also be applied by dissolving it in an amine solvent such as ethylenediamine. Conventional methods such as plaid, Mayer bar, and spray dipping are used for dispensing. The thickness of the charge generation layer is 5μ or less, preferably 0.01~
1μ is desirable. When using a binder in the charge generation layer, a large amount of binder will affect sensitivity, so the ratio of binder in the charge generation layer should be 80%.
% or less, preferably 40% or less. Binders used include polyvinyl butyral, previnyl acetate, polyester, polycarbonate, phenoxy resin, acrylic resin,
Polyacrylamide, polyamide, polyvinylpyridine resin, cellulose resin, urethane resin,
Various resins such as epoxy resin, casein, and polyvinyl alcohol are used. A charge transport layer is provided on the charge generation layer provided in this manner. If the charge transport material does not have film-forming ability, a solution prepared by dissolving a binder in a suitable organic solvent is coated and dried in a conventional manner to form a charge transport layer. Charge transport materials include electron transport materials and hole transport materials. Examples of electron transporting substances include chloranil, brumoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitrofluorenone, 2,4,7 - Electron-withdrawing substances such as trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone, and 2,4,8-trinitrothioxanthone, and polymerized versions of these electron-withdrawing substances, etc. . Suitable hole-transporting substances include, for example, hydrazones. Pyrazolines (1) 1-phenyl-3-(4-N・N-diethylaminostyryl)-5-(4-N・N-diethylaminophenyl)pyrazoline (2) 1-phenyl-3-(4-N・N-dipropylstyryl)-5-(4-N・N-diethylaminophenyl)pyrazoline (3) 1-phenyl-3-(4-N・N-dibenzylstyryl)-5-4-(N・N -dibenzylaminophenyl)pyrazoline (4) 1-[pyridyl-(2)]-3-(4-N・N-diethylaminostyryl)-5-(4-N・N-diethylaminophenyl)pyrazoline (5 ) 1-[quinolyl-(2)]-3-(4-N・N-diethylaminostyryl)-5-(4-N・N-diethylaminophenyl)pyrazoline(6) 1-[quinolyl-(4)] -3-(4-N・N-diethylaminostyryl)-5-(4-N・N-diethylaminophenyl)pyrazoline (7) 1-[3-methoxy-pyridyl (2)]-3-(4
-N・N-diethylaminostyryl)-5-(4
-N・N-diethylaminophenyl)pyrazoline (8) 1-[lepidyl-(2)]-3-(4-N・N-diethylaminostyryl)-5-(4-N・N-diethylaminophenyl)pyrazoline (9) 1-phenyl-3-(4-N・N-diethylaminostyryl)-4-methyl-5-(4-N・
N-diethylaminophenyl)pyrazoline (10) 1-phenyl-3-(α-methyl-4-N.
N-diethylaminostyryl)-5-(4-N・
N-diethylaminophenyl)pyrazoline (11) 1-[pyridyl-(3)]-3-(4-N・N-diethylaminostyryl)-5-(4-N・N-diethylaminophenyl)pyrazoline (12) 1-phenyl-3-(α-benzyl-4-
N・N-diethylaminostyryl)-5-(4-
N・N-diethylaminophenyl) pyrazoline diaryl alkanes (1) 1,1-bis(4-N・N-dimethylaminophenyl)propane (2) 1,1-bis(4-N・N-diethylamino phenyl)propane(3) 1,1-bis(4-N·N-diethylamino-2-methylphenyl)propane(4) 1,1-bis(4-N·N-diethylamino-2-methoxyphenyl)propane (5) 1,1-bis(4-N・N-dibenzylamino-2-methoxyphenyl)-2-methylpropane(6) 1,1-bis(4-N・N-diethylamino-2-methylphenyl )-2-phenylpropane (7) 1,1-bis(4-N・N-diethylamino-2-methylphenyl)heptane (8) 1,1-bis(4-N・N-dibenzylamino-2- methylphenyl)-1-synchrohexylmethane (9) 1,1-bis(4-N·N-dimethylaminophenyl)heptane (10) 1,1-bis(4-N·N-dibenzylaminophenyl) Normal butane triaryl alkanes (1) 1,1-bis(4-N·N-dimethylaminophenyl)-1-phenylmethane (2) 1,1-bis(4-N·N-diethylaminophenyl)- 1-Phenylmethane (3) 1,1-bis(4-N・N-diethylamino-2-methylphenyl)-1-phenylmethane(4) 1,1-bis(4-N・N-diethylamino-2-ethylphenyl)- 2-phenylethane (5) 1,1-bis(4-N·N-diethylamino-2-methylphenyl)-3-phenylpropane(6) 1,1-bis(4-N·N-diethylamino-2,5 -dimethoxyphenyl)-3-phenylpropane oxadiazole (1) 2,5-bis(4-N·N-dimethylaminophenyl)-1,3,4-oxadiazole (2) 2. 5-bis(4-N・N-diethylaminophenyl-1,3,4-oxadiazole(4)) 2,5-bis(4-N・N-dipropylaminophenyl)-1,3,4 -Oxadiazole (5) 2,5-bis(4-N·N-dibenzylaminophenyl)-1,3,4-oxadiazole(6) 2-methyl-5-(3-carbazolyl)- 1・
3,4-oxadiazole(7) 2-ethyl-5-(3-carbazolyl)-1.
3,4-oxadiazole (8) 2-ethyl-5-(9-ethyl-3-carbazolyl)-1,3,4-oxadiazole (9) 2-N・N-diethylamino-5-(9 -ethyl-3-carbazolyl)-1,3,4-oxadiazole(10) 2-styryl-5-(3-carbazolyl)-
1,3,4-Oxadiazoleanthracenes (1) 9-styrylanthracene (2) 9-(4-N·N-dimethylaminostyryl)anthracene (3) 9-(4-N·N-diethylaminostyryl) Anthracene(4) 9-(4-N・N-dibenzylaminostyryl)anthracene(5) 4-bromo-9-(4-N・N-diethylaminostyryl)anthracene(6) α-(9-anthryl)- β-(3-carbazolyl)ethylene(7) α-(9-anthryl)-β-(9-ethyl-
3-Carbazolyl) ethylene oxazole (1) 2-(4-N・N-diethylaminophenyl)-4-(4-N・N-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole (2) 2-(4-N・N-diethylaminophenyl)-5-phenyloxazole (3) 4-(4-N・N-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole (4) 2- (4-N・N-dimethylaminophenyl)-4・5-diphenyloxazole (5) 2-(4-N・N-dimethylaminophenyl)-4-(4-N・N-diethylaminophenyl )-5-(2-chlorophenyl)oxazole(6) 2,5-di-(2-chlorophenyl)-4-
(4-N.N-diethylaminophenyl)oxazole and the like can be mentioned. Others: pyrene, N
-Ethylcarbazole, triphenylamine, poly-N-vinylcarbazole, halogenated poly-
N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine,
Poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, etc. can also be used.
The charge transport substance is not limited to those described here, and when used, one type or a mixture of two or more types of charge transport substances can be used. However, when an electron-transporting substance and a hole-transporting substance are mixed, charge transfer absorption occurs in the visible region, and even when exposed, light may not reach the charge generation layer located below the charge transport layer. The thickness of the charge transport layer is 5
-30μ, preferably 8-20μ. As the binder, acrylic resin, polystyrene, polyester, polycarbonate, etc. can be used. As the binder for the low-molecular hole-transporting substance, a hole-transporting polymer such as the aforementioned poly-N-vinylcarbazole can be used as the binder. On the other hand, as a binder for a low molecular weight electron transporting substance, a polymer of an electron transporting monomer as described in US Pat. No. 4,122,113 can be used. 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, it is necessary to positively charge the surface of the charge transport layer, and when exposed to light after charging, 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 charges, resulting in attenuation of the surface potential and an electrostatic contrast between the exposed area and 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 or plastic film 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 one or any known method and are not limited to a specific one. On the other hand, when the charge transport material is made of a hole transport material, the surface of the charge transport layer must be negatively charged.
When imagewise exposed after charging, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, neutralizing the negative charges that have reached the surface, causing a decrease in the surface potential and a gap between the exposed area and the unexposed area. Electrostatic contrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where a charge transport material is used. The (i) type photoreceptor is produced by adding an azo pigment represented by the general formula (1) to an insulating binder solution such as that used for the charge transport layer of the (iii) type photoreceptor, and after dispersing it, a conductive support is formed. It is obtained by applying it to the body and drying it. The (ii) type photoreceptor is prepared by dissolving the charge transport material of the (iii) type photoreceptor and an insulating binder such as that used in the charge transport layer in a suitable solvent, and then adding an azo pigment represented by the general formula (1). After adding and dispersing, it is obtained by coating and drying on a conductive support. Type (iv) photoreceptors form a charge transfer complex when the electron transport material and hole transport material described in type (iii) photoreceptor are combined. ) is added, dispersed, and then applied and dried on a conductive support. The azo pigment used in any of the photoreceptors contains at least one type of pigment selected from the azo pigments represented by the general formula (1), and if necessary, pigments with different light absorptions are used in combination to increase the sensitivity of the photoreceptor. Azo pigments represented by general formula (1) are used in combination with two or more types of azo pigments, or they are used in combination with a charge-generating material selected from known dyes and pigments, for the purpose of increasing the photoreceptor and obtaining a panchromatic photoreceptor. It is also possible to do so. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers and CRTs.
It can also be widely used in electrophotographic applications such as printers. Next, the azo pigment used in the present invention will be specifically explained using synthesis examples. Synthesis example: Pigment below 2,5-di(ar-aminophenyl)-1,3.
4-Oxadiazole, 4.52g (0.0179mol) water
After cooling a dispersion consisting of 55 ml and 10.0 ml of concentrated hydrochloric acid to 4°C, a solution of 3.60 g (0.0376 mol) of nitrous acid leader dissolved in 9 ml of water was added dropwise over 15 minutes, and then the temperature of the solution was raised to 3 to 6°C. Stirring was continued for 30 minutes, and activated carbon was added and filtered to obtain a tetrazonium aqueous solution. Next, add 17.8g of sodium hydroxide to 3.80ml of water, 8
-(ethylbenzoyl-amino)-naphthol(2)
Dissolve 11.5g (0.0395mol) and add this solution to 6-8
The tetrazonium aqueous solution synthesized earlier was added dropwise over 30 minutes while maintaining the temperature at °C, and after stirring for an additional 2 hours, it was left at room temperature overnight. The reaction solution was filtered, and the resulting pigment was washed with water, acetone, and dried to obtain 13.5 g of a crude pigment. Next, after sequentially washing with DMF and THF,
After drying, 10.8 g of purified pigment was obtained.

[Table] The method for synthesizing pigment No. 1 has been described above, but other azo pigments represented by general formula (1) are also synthesized in the same manner. Next, examples of the present invention will be shown. Example 1 A polyvinyl alcohol aqueous solution was applied onto an aluminum plate having a thickness of 100 μm and dried to form an adhesive layer with a coating weight of 0.8 g/m ² . Next, 5 g of the above No. 1 pigment and 10 g of polyester (Adhesive 49000 manufactured by DuPont, solid content 20%),
After dispersing 80 ml of THF, it was applied onto the adhesive layer, and the coating amount after drying was 0.20 g/m ² . Next, 5 g of 4-N・N-diethylaminobenzaldehyde-N・N-diphenylhydrazone, polymethyl methacrylate resin (number average molecular weight 10
5 g/m2 was dissolved in 70 ml of THF and applied to the charge generation layer, and the coating amount after drying was 10 g/ ^m2 . The electrophotographic photoreceptor thus prepared was corona-charged at 5Kv using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., and after being held in a dark place for 10 seconds, the illuminance was 5lux. The charging characteristics were investigated by exposing to light. The initial potential is Vo (V), the potential retention rate for 10 seconds in the dark is Vk (%), and the half-decay exposure is E1/2 (lux・
sec) shows the charging characteristics of this photoreceptor. Vo: 520, Vk: 91%, E1/2: 7.8lux・sec Examples 2 to 22 In the azo pigment represented by the general formula (1), P, A,
5 g of azo pigment in which R and R ₁ are as shown in Table 1 and 2 g of butyral resin (degree of butyralization 65 mol%)
The mixture was dispersed in a ball mill with a solution dissolved in 95 ml of ethanol, and then coated on the adhesive layer with a Mayer bar to form a charge generation layer having a coating weight of 0.2 g/m ² after drying. Next, the same charge transport layer solution used in Example 1 was applied using a Baker applicator to give a film thickness of 10 g/m ² after drying. The charge measurement of the photoreceptor was carried out in the same manner as in Example 1. Table 1 shows the structure of the pigment used, and Table 2 shows the charging characteristics.

【table】

【table】

【table】

【table】

[Table] Example 23 2.4.
5g of 7-trinitrofluorenone and poly-4.
Dissolve 6 g of 4'-dioxydiphenyl-2,2-carbonate (viscosity average molecular weight 30,000) in 10 ml of tetrahydrofuran, and make a coating amount of 12 g/m ² after coating and drying.
And so. Charge measurement was carried out in the same manner as in Example 1,
Its characteristic values were as follows. However, the charging characteristics are the same. Vo: 520V Vk: 88% E1/2: 18.7lux·sec Example 24 An ammonia aqueous solution of casein was applied and dried on a 100μ thick aluminum plate to form an adhesive layer with a coating weight of 1.0g/m ² . Next, 2-(4-N·N-diethylaminophenyl)-4-(4-N·N-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole 5
1.0 g of the No. 5 pigment used in Example 5 was added to a solution of 5 g of poly-N-vinylcarbazole (number average molecular weight: 300,000) dissolved in 70 ml of tetrahydrofuran, dispersed, and then applied and dried on the adhesive layer. Coating amount 12
g/ ^m2 . The photoreceptor thus prepared was subjected to charge measurement in the same manner as in Example 1, and the measured values were as follows. However, the charging polarity was determined. Vo: 500V Vk: 90% E1/2: 20.4lux・sec Example 25 1-phenyl-3(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline 5g and poly-2,2-propane bis (4-phenylisophthalic acid/terephthalic acid ester)
(Isophthalic acid terephthalic acid molar ratio 1:1) 5 g
was dissolved in 70 ml of tetrahydrofuran, 1.0 g of No. 1 pigment used in Example 1 was added, and after dispersion, it was applied and dried on the adhesive layer used in Example 9 to give a coating weight of 12
g/ ^m2 . The photoreceptor thus prepared was subjected to charge measurement in the same manner as in Example 1, and the measured values were as follows. However, the charging polarity was determined. Vo: 525V Vk: 91% E1/2: 17.8lux・sec Examples 26-30 5 g of pigment No. 11 used in Example 11 and 2 g of butyral resin (degree of butyralization 63 mol%) were dissolved in 95 ml of ethanol. After being dispersed with the liquid, it was applied to the aluminum surface of an aluminum vapor-deposited mylar film, and the coating amount after drying was 0.2 g/ ^m2 . A solution prepared by dissolving 5 g of PKHH) in 70 ml of THF was applied to the above charge generation layer and dried, resulting in a coating amount of 11
A charge transport layer of g/m ² was formed. The photoreceptor thus prepared was subjected to charge measurement in the same manner as in Example 1, and its characteristics are shown in Table 4.

【table】

【table】

【table】

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor having a photosensitive layer, the photosensitive layer contains an azo pigment having at least one azo group bonded to a coupler residue represented by the following general formula in the molecule. Characteristic electrophotographic photoreceptor. general formula (In the formula, R represents an optionally substituted alkyl group or aryl group. R ₁ represents an optionally substituted aryl group.)