JPH0477900B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a laminated electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor in which at least a charge transport layer and a charge generation layer are sequentially laminated on a conductive support. BACKGROUND 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 Pat.
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. In particular, with regard to azo pigments, there are many variations in materials, and research has been active in recent years, and several have been put into practical use. When using it, it has a structure in which a charge generation layer and a charge transport layer are laminated in this order on a conductive support, and a material with strong electron donating properties is used as the charge transport material used in the charge transport layer to improve hole transportability. , it was common to charge the photoreceptor. Reasons for this include the fact that there are almost no electron-transporting materials with excellent properties, and that they are carcinogenic and cannot be used due to pollution concerns. When negative corona discharge is performed, a large amount of ozone is generated, and an ozone filter must be attached to the camera body, which increases costs. Furthermore, as the ozone filter gradually deteriorates over the years, periodic maintenance such as filter replacement is required. Furthermore, negative corona discharge tends to cause uneven discharge due to dirt on the discharge wire, etc., causing image unevenness. Furthermore, the generated ozone has a negative effect on the durability life of the OPC. During charging, a large amount of ozone is generated, causing problems such as material deterioration on the surface of the photoreceptor and adhesion of ionic substances generated by corona charging to the photoreceptor. This causes local or total image blurring or image defects in the subject image formed by electrophotography. On the other hand, positive corona discharge generates 1/5 to 1/1 the amount of ozone compared to negative corona discharge.
It is about 0, and uneven discharge due to dirt on the discharge wire is unlikely to occur. It is also very advantageous for the life of the photoreceptor. As described above, charging has many disadvantages, and there is an urgent need to develop a charged photoreceptor. One method for producing a charged laminated photoreceptor is to sequentially laminate a hole-transporting charge transport layer and a charge generation layer on a conductive support. However, when the thickness of the charge generation layer is increased, carriers generated by light become more likely to be trapped within the charge generation layer, resulting in larger optical memory and increased bright area potential during repeated use. Therefore, it is customary to have an extremely thin film thickness of about 0.1 to 0.5 μm. However, when the charge generation layer is on the surface layer of the photoreceptor, it is difficult to charge, imagewise expose, develop, transfer the toner image to a transfer member such as paper or plastic film, separate the transfer member from the photoreceptor, clean, and perform cleaning before and after cleaning. When such a photoreceptor is used in copying methods such as static elimination, the surface layer of the photoreceptor will be scratched during processes such as development, transfer, and cleaning where parts come into contact with the photoreceptor, resulting in decreased sensitivity of the photoreceptor during long-term use. The current problem is that the change becomes extremely large, and in extreme cases, the charge generation layer is scratched away and no longer exhibits sensitivity. Problems to be Solved by the Invention The first object of the present invention is to provide a highly sensitive electrophotographic photoreceptor for charging, in which at least a charge transport layer and a charge generation layer are sequentially laminated on a conductive support. . A second object of the present invention is to provide an electrophotographic photoreceptor for charging, which has improved electrophotographic properties and has at least a charge transport layer and a charge generation layer sequentially laminated on a conductive support. A third object of the present invention is to provide an electrophotographic photoreceptor for charging, which has improved durability and has at least a charge transport layer and a charge generation layer laminated in sequence on a conductive support. Means for Solving the Problems, Actions, and Effects of the Invention An object of the present invention is to sequentially stack at least a hole-transporting charge transport layer and a charge generation layer on a conductive support. This is accomplished by incorporating a photoconductive azo pigment and a specific hole-transporting charge transport material. It is believed that the reason why a particular charge transport material must be selected is that there is selectivity in the injection of carrier from the photoconductive azo pigment, which is the carrier injection material, to the charge transport material in the charge generation layer. If an attempt is made to increase the physical strength of the photoconductor surface by increasing the amount of binder resin in the charge generation layer, the transportability of the carrier in the charge generation layer will be significantly reduced, resulting in decreased sensitivity, deterioration of optical memory, and brightness during long-term use. This usually resulted in an increase in the potential of the parts. However, by including a specific hole-transporting charge transporting material in the charge generation layer, it has become possible to ensure sufficient carrier transportability in the charge generation layer even when the amount of binder is increased. As a result, a photoreceptor with strong physical strength on the surface of the photoreceptor and excellent sensitivity and optical memory can be obtained. Furthermore, abrasion of the photosensitive layer during long-term use is significantly reduced, and a photoreceptor with less change in sensitivity during long-term use can be achieved, thereby achieving the object of the present invention. As the azo photoconductive pigment used in the present invention, an azo pigment having a phenolic OH group is used, and more specifically, an azo pigment represented by the general formula A(-N=N-B) ₁ () is particularly effective. In the formula, 1 represents 2 or 3. In the formula, A is a divalent organic group or a divalent organic group in which the carbon atoms to which the azo group is bonded form a conjugated double bond system.

It is characterized by being represented by the following formula. A specific example of a divalent organic group is etc. can be mentioned. R ₁ to _{R 28} are hydrogen, halogens such as chlorine, bromine, and iodine, alkyl groups such as methyl, ethyl, and propyl, alkoxy groups such as methoxy, ethoxy, and propoxy, aralkyl groups such as benzyl and phenethyl, nitro groups, and cyano groups. etc. x is -O-,
-S-,,

[Formula] is shown. R ₂₉ represents hydrogen, the above alkyl or aralkyl group, or an aryl group such as phenyl or naphthyl. Specific examples of divalent organic groups include the general formulas (1) to
Also included is a group represented by (8) in which a phenylazo group, which may have a substituent, is attached to both ends. m and n represent 0 or 1, and may be the same or different. In the general formula (), B represents a coupler having a phenolic OH group, and more specifically, etc. are particularly effective. In the general formula (10), Y represents a residue necessary to form a polycyclic aromatic ring or a heterocycle such as a naphthalene ring, anthracene ring, carbazole ring, benzcarbazole ring, dibenzofuran ring, etc. by condensation with a benzene ring. In the general formulas (13) and (14), Z represents a divalent aromatic hydrocarbon group or a heterocyclic divalent group containing an N atom in the ring. R ₃₀ to _{R 32} represent an alkyl group, an aralkyl group, or an aryl group represented by R ₁ to _{R 29} . The aryl group in the aryl group and the aralkyl group further includes R ₁
~ _R29 may be substituted with an alkyl group, an alkoxy group, a nitro group, a cyano group, a halogen, an aralkyl group, an aryl group, or a substituted amino group such as dimethylamino, diethylamino, and dibenzylamino. Specific examples of preferable azo pigments used in the present invention are shown below. As the specific hole transport material used in the charge transport layer of the present invention, a di- or triarylmethane charge transport material is used, and a particularly preferable material among the di- or triarylmethane charge transport materials has the following general formula: It is represented by In the general formula (), R ₁ , R ₂ , R ₃ and R ₄ are alkyl groups such as methyl, ethyl, propyl, butyl,
These groups include aralkyl groups such as benzyl and phenethyl, and aryl groups such as phenyl and naphthyl. It may be substituted with an alkoxy group such as. Also R ₁ , R ₂ and R ₃ , R ₄
may be a residue that forms a 5- to 6-membered heterocycle, such as pyrrolidino, piperidino, and morpholino, together with the nitrogen atom. R ₅ and R ₆ are hydrogen atoms, respectively substituted and unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups,
Indicates a cycloalkenyl group, an aryl group, or a heterocyclic group. R ₅ and R ₆ may be cyclized with each other to form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms. Examples of the alkyl group in R ₅ and R ₆ include methyl, ethyl, propyl, butyl, pentyl, hexyl, etc., and cycloalkyl groups include cyclopentyl, cyclohexyl, etc. Alkenyl has 6 carbon atoms, cycloalkenyl has 5 to 6 carbon atoms
Member ring groups, aryl groups such as phenyl, naphthyl, etc., heterocyclic groups such as pyridine, furan,
Examples include thiophene, carbazole, and phenothiazine. Examples of the hydrocarbon ring obtained by cyclization of R ₅ and R ₆ include a cyclohexane ring, a cyclopentane ring, a cyclohexaene ring, and a cyclohexadiene ring. Specific examples of preferred di- or triarylmethane compounds used in the present invention are shown below. Di- or triarylmethane type The azo photoconductive pigment used in the charge generation layer is dispersed in a solution system of a suitable binder resin and a di- or triarylmethane charge transport material, and then coated on the charge transport layer prepared in advance. As a result, a charge generation layer can be formed. Binders that can be used to form the charge generating layer by coating can be selected from a wide variety of insulating resins, as well as organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. can. Preferably, in addition to the photoconductive polymer, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, Examples include insulating resins such as urethane resin and epoxy resin. The resin contained in the charge generation layer is preferably 10 to
80% by weight, more preferably from the viewpoint of physical strength of the photoreceptor surface and carrier transportability within the charge generation layer.
The content is preferably 30 to 60% by weight. The proportion of the charge transporting material contained in the charge generation layer is preferably 10 to 70% by weight, and more preferably 20 to 60% by weight for the same reason as the amount of resin. The proportion of charge generation material contained in the charge generation layer is
The content is preferably 0.3 to 80% by weight. The solvent used in the paint for the charge generation layer is selected based on the resin used, the solubility of the charge transport material, and the dispersion stability of the charge generation material. It is also necessary to choose. Specific organic solvents include alcohols such as methanol, ethanol and isopropanol, amides such as acetone, MEK, cyclohexanone, N,N-dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethylsulfoxide, tetrahydrofuran, Ethers such as 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, trichlorethylene, benzene, toluene, Aromatics such as xylene, ligroin, motochlorobenzene, 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 can be carried out at a temperature of 30 to 200° C. for a period of time ranging from 5 minutes to 2 hours, either stationary or under ventilation. The charge transport layer is electrically connected to the charge generation layer described above, receives charge carriers injected from the charge generation layer in the presence of an electric field, and transfers these charge carriers to the surface of the conductive support or the conductive layer. It has the function of being able to transport to the surface of the undercoat layer interposed between the charge transport layer and the charge transport layer. For the charge transport layer, a hole transporting charge transport material is used. Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-isopropylcarbazole,
N-Methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole-N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-
3-methylidene-10-ethylphenothiazine,
N,N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, P-diethylaminobenzaldehyde-N,N-diphenylhydrazone, P-diethylaminobenzaldehyde-N
-α-Naphthyl-N-phenylhydrazone, P-
Pyrrolidine benzaldehyde-N,N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, etc. hydrazones 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)]-(P-diethylaminostyryl)-5-
(P-diethylaminophenyl)pyrazoline, 1
-[Pyridyl(3)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[Lepidyl(2)]-3-(P-diethylaminostyryl)-5-(P -diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(P
-diethylaminostyryl)-4-methyl-5-
(P-diethylaminophenyl)pyrazoline, 1
-[Pyridyl(2)]-3-(α-methyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-phenyl-3-(P-
diethylaminostyryl)-4-methyl-5-(P
-diethylaminophenyl)pyrazoline, 1-phenyl-3-(α-benzyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, spiropyrazoline and other pyrazolines, 2-(P-diethylaminostyryl)- 6
-(diethylaminobenzoxazole, 2-(P
Oxazole compounds such as -diethylaminophenyl)-4-(P-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2-(P-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole,
-diethylaminostyryl) -thiazole compounds such as 6-diethylaminobenzothiazole, bis(4-diethylamino-2-methylphenyl)
-Triarylmethane compounds such as phenylmethane, 1,1-bis(4-N,N-diethylamino-2-methylphenyl)heptane, 1,1,2,
2-tetrakis(4-N,N-dimethylamino-
Polyarylalkanes such as 2-methylphenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9
-Vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole 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. 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- Mention may be made of organic photoconductive polymers such as vinylcarbazole, polyvinylanthracene, polyvinylpyrene. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5-30μ, but the preferred range is 8-20μ. When forming the charge transport layer by coating, 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, the substrate itself can be conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel indium, gold, platinum, etc. In addition, plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyethylene fluoride, etc.), conductive particles (e.g. carbon black,
A substrate made of plastic coated with silver particles (silver particles, etc.) together with a suitable binder, a substrate made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used. A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the charge transport layer. The undercoat layer may be 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. It can be formed by The thickness of the undercoat layer is 0.1 to 5μ, preferably 0.5 to 3μ.
is appropriate. The electrophotographic photoreceptor used in the present invention is contaminated by oil deteriorated by ultraviolet rays, ozone, etc., damaged by metal chips, etc., and the photoreceptor is scratched or scraped by photoreceptor contact members such as developing members, transfer members, cleaning members, etc. A protective layer may be further provided on the charge generation layer for the purpose of preventing this. In order to form an electrostatic latent image on this protective layer, it is desirable that the surface resistivity is 10 ¹¹ Ω or more. The protective layer used in the present invention is made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide,
It can be formed by dissolving a resin such as polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer, etc. in a suitable organic solvent and coating the photosensitive layer on the photosensitive layer and drying it. Additionally, additives such as ultraviolet absorbers can be added to the resin liquid. At this time, the thickness of the protective layer is generally 0.05~
20μ, particularly preferably in the range of 0.2 to 5μ. The layer structure of the electrophotographic photoreceptor of the present invention is as shown in the drawings. When using a photoreceptor in which a conductive layer, a charge transport layer, and a charge generation layer are laminated in this order, the charge transport material consists of a hole transport material, so the surface of the charge generation layer must be positively charged, and exposure after charging is required. Then, in the exposed area, holes generated in the charge generation layer are injected into the charge transport layer. On the other hand, electrons generated by exposure reach the surface and neutralize the positive charges, causing attenuation of the 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. 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. The present invention will be explained below based on examples. Examples 1 to 14 Ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 ml of water) on an aluminum plate
was applied with a Mayer bar so that the film thickness after drying was 1.0μ, and dried. Next, 5 g of the above-exemplified triarylmethane compound B-1 and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) were added to 70 ml of benzene.
This was applied onto the undercoat layer using a Mayer bar so that the film thickness after drying was 12 μm, and dried to form a charge transport layer. Next, add triarylmethane compound B-1 to 45
g, and 45 g of polymethyl methacrylate resin (number average molecular weight 100,000) dissolved in 800 M of chlorobenzene, add the following formula. Add 10g of the disazo pigment shown in and use a sand mill.
Dispersed for 10 hours. This dispersion was applied onto the previously formed charge transport layer by a dipping method and dried to form a charge generation layer having a thickness of 5 μm, thereby producing the photoreceptor of Example 1. Examples 2 to 14 were prepared in exactly the same manner as in Example 1, except that, apart from the photoreceptor of Example 1, the compounds used in the charge generation layer were replaced with di- or triarylmethane compounds B-2 to B-14. A photoreceptor was created. The electrophotographic photoreceptor thus prepared was statically charged with corona at +5 KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.
After keeping it in the dark for 1 second, it was exposed to light at an illuminance of 5 lux to examine the charging characteristics. As for the charging characteristics, the surface potential (V ₀ ) and the exposure amount (E1/2) required to attenuate the potential by 1/2 when dark decaying for 1 second were measured. The results are shown in Table 1.

[Table] As shown in the table, the photoreceptor of the present invention exhibited good charging properties and sensitivity during charging. Comparative Example 1 Example 1 except that no di- or triarylmethane compound was used in the charge generation layer of Example 1.
A photoreceptor was prepared in exactly the same manner as described above, and its characteristics were investigated. Surface potential +570V E1/2 21lux.sec. Compared to the photoreceptor of the present invention, the sensitivity is extremely low and it is completely impractical. Examples 15 to 25 A polyvinyl alcohol film having a thickness of 1.1 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film by dip coating. Next, photoreceptors of Examples 15 to 25 were prepared in exactly the same manner as in Example 1, using the materials shown in Table 2 instead of the charge transport layer, the charge generation material used in the charge generation layer, and the charge transport material in Example 1. The potential was measured. Table 3 shows the results.
Shown below. Optical memory has been added as a potential measurement item. By exposing a photoreceptor to light before charging, the charging potential of a photoreceptor with a strong optical memory decreases significantly, causing an extreme decrease in image density or a whiteout phenomenon in the pre-exposed area. As a method for evaluating optical memory, a pre-exposure of 600 lux3 minutes is given, and the difference in surface potential (△V ₀ ) is expressed as a decrease in surface potential compared to when no pre-exposure was performed.

【table】

【table】

【table】

[Table] Comparative Examples 2 to 5 Examples 15 and 20 except that the charge transport material shown in Table 4 was used in place of the di- or triarylmethane compound in the charge generation layer of Examples 15, 20, 23, and 24. ,
Comparative photoreceptors 2 to 5 were prepared in exactly the same manner as in Examples 23 and 24. The results of potential measurement are shown in Table 5.

【table】

【table】

[Table] When the di- or triarylmethane compound in the charge generation layer is replaced with another charge transport material,
The results were significantly worse in terms of sensitivity and optical memory than in the case of di- or triarylmethane compounds.
The charge generation layer of the present invention contains an azo photoconductive pigment and a
It has been proven that a system using a combination of triarylmethane or triarylmethane compounds is extremely effective. Example 26 Each layer was sequentially laminated on an aluminum cylinder with a diameter of 60 mm by the dipping method using the same coating solution except that the binder resin used for the charge generation layer in Example 1 was replaced with polycarbonate resin (number average molecular weight 75,000). An electrophotographic photoreceptor was prepared. Using a charging PPC copying machine (prototype) manufactured by Canon Inc., the initial dark area potential was set to 700V, and the initial dark area potential was set to 100V, and 10,000 images were printed using a charging toner, and the durability was achieved. , the potential was measured after leaving it for one night. The drum of the test prototype is equipped with a charging corona charger, an exposure section, a developing section, a transfer corona charger, a blade cleaner, and a pre-exposure lamp. The results of the potential measurement are: Initial durability potential After 10,000 sheets of durability (+V) (+V) Dark potential 700 730 Light potential 100 135 Sensitivity fluctuations due to image exposure durability are small, and the image is free from blurring and image defects due to ozone deterioration. No discharge unevenness due to corona wire contamination was observed1
Beautiful images were obtained even after 10,000 prints. Example 27 A methanol solution of polyvinyl butyral resin (saponification degree 100%, butyralization degree, 75% by weight average molecular weight 30,000) was applied by dipping onto a photoconductor prepared in exactly the same manner as in Example 26, and after drying. The film thickness of
A protective layer of 3μ was formed. Using this photoconductor and using the same equipment as in Example 26, a durability test of 20,000 images was carried out in exactly the same manner as in Example 26, and the images obtained were extremely beautiful, making it a highly durable photoconductor. One thing has been proven.

[Brief explanation of the drawing]

1 to 4 show the layer structure of the electrophotographic photoreceptor of the present invention. 1 is an azo photoconductive pigment, 2 is a binder resin + G, triallylmethane charge transport material, 3 is a charge generation layer, 4 is a charge transport layer, 5 is a conductive support, 6 is an undercoat layer, 7 indicates a protective layer or an insulating layer.

Claims (1)

[Scope of Claims] 1. At least a hole-transporting charge transport layer and a charge generation layer are sequentially laminated on a conductive support, and the charge generation layer contains an azo photoconductive pigment and a di- or triarylmethane-based pigment. A laminated electrophotographic photoreceptor characterized by containing a charge transport material. 2. The aso-based photoconductive pigment used in the charge generation layer is represented by the general formula A(-N=N-B) ₁ (), and the di- or triarylmethane compound used in the charge generation layer is represented by the general formula A(-N=N-B) 1 (). However, in the general formula (), A represents a divalent organic group or [Formula] in which the carbon atoms to which the azo group is bonded form a conjugated double bond system, and B represents a phenolic OH group. 1 represents 2 or 3, and in the general formula ()
R ₁ , R ₂ , R ₃ and R ₄ represent an optionally substituted alkyl group, aralkyl group, or aryl group, or R ₁ , R ₂ and R ₃ , R ₄ together with a nitrogen atom Indicates a residue forming a 5- to 6-membered heterocycle,
R ₅ , R ₆ represent hydrogen, an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group or a heterocyclic group which may have a substituent, or R ₅ and R ₆ are cyclized with each other. may form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms, R ₇ , R ₈ , R ₉ and R ₁₀ are hydrogen,
The laminated electrophotographic photoreceptor according to claim 1, which is a material exhibiting a halogen atom, an alkyl group, or an alkoxy group. 3. The laminated electrophotographic photoreceptor according to claim 1 or 2, wherein a protective layer or an insulating layer having a surface resistivity of 10 ¹¹ Ω or more is provided in the charge generation layer.