JPH0431576B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor having a subbing layer on the surface of a conductive layer and a photosensitive layer laminated thereon. [Prior Art] In electrophotographic photoreceptors that use photoconductive substances as photosensitive materials, inorganic photoconductive substances such as selenium, zinc oxide, titanium oxide, and cadmium sulfide have conventionally been used as the main photoconductive substances. It has been used in However, many of these are generally highly toxic and there are problems in how to dispose of them. On the other hand, photosensitive materials using organic photoconductive compounds are generally less toxic than those using inorganic photoconductive substances, and also have higher transparency, flexibility, and
Recently, it has been widely studied because it is advantageous in terms of lightness, surface smoothness, cost, etc. Among them, a composite photoreceptor that separates the functions of charge generation and transport, that is, a photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive layer, is a photoreceptor that uses an organic photoconductive compound. Rapid progress has been made in recent years because it can greatly improve sensitivity, which was a major drawback of conventional methods. However, by providing a charge generation layer directly on the conductive layer, surface defects such as scratches and corrosion on the conductive layer are reflected directly in the image, resulting in image defects such as black spots and white spots. be. In addition, various problems tend to occur, such as a decrease in surface charge due to charge injection from the conductive layer, that is, a decrease in chargeability, or poor adhesion between the conductive layer and the charge generation layer. Therefore, as a measure to improve these problems, a method of providing an undercoat layer between the conductive layer and the charge generation layer has been considered (Japanese Patent Application Laid-Open No. 57-90639, JP-A No. 58-86556, Publication No. 60-202449, Japanese Patent Publication No. 60-108860). [Problems to be solved by the invention] When considering the undercoat layer, it should be noted that there are no image defects, that the charging property does not deteriorate, that the electrophotographic characteristics do not deteriorate, that the method for forming it is simple, Particularly when forming using a coating method, it has good coating properties and can be formed under low temperature and short heating conditions.
When the charge generation layer is laminated on the undercoat layer, the necessary conditions include not being attacked by the coating liquid for the charge generation layer and having excellent adhesion. However, conventional studies have not found a subbing layer that satisfies all of these requirements. An object of the present invention is to provide an electrophotographic photoreceptor provided with an undercoat layer that satisfies the above requirements. [Means for Solving the Problems] The present invention solves the above problems by providing a specific subbing layer. That is, the present invention provides an electrophotographic photoreceptor in which an undercoat layer, a charge generation layer, and a charge transport layer containing an electron-donating charge transport substance are sequentially laminated on a conductive layer, in which the undercoat layer comprises (a) Butyl etherified melamine/formaldehyde resin having a number average molecular weight of 1500 or less and having 2 to 4 bound formaldehydes and 1 to 2 methylol groups per melamine nucleus; (b) electron-accepting carboxylic acid compound and/or electron The present invention relates to an electrophotographic photoreceptor comprising (c) an organic charge generating material contained in a cured film containing a receptive polycarboxylic anhydride as a component. The materials used in the electrophotographic photoreceptor of the present invention will be described in detail below. First, in the present invention, the conductive layer is a conductive material such as paper or plastic film subjected to conductivity treatment, a plastic film laminated with metal foil such as aluminum, a metal plate, a metal drum, or the like. Organic pigments that generate charges and are included in the charge generation layer include azoxybenzene, disazo, trisazo, benzimidazole, polycyclic quinoline, indigoid, quinacridone, phthalocyanine, perylene, and methine. It is possible to use pigments known to generate electric charge upon irradiation with light such as . These pigments, for example,
No. 47-37543, JP-A-47-37544, JP-A-47-
No. 18543, JP-A-47-18544, JP-A-48-43942
No., JP-A-48-70538, JP-A-49-1231, JP-A-49-105536, JP-A-50-75214, JP-A-Sho
It is disclosed in Publication No. 50-92738 and the like. In particular, the γ, γ′η, and η′ type metal-free phthalocyanines described in JP-A-58-182640 and European Patent Application Publication No. 92255 have high sensitivity to long wavelengths and are equipped with diode lasers. It is also effective as an electrophotographic photoreceptor for printers. In addition to these, any organic pigment that generates charge carriers upon irradiation with light can be used. Further, additives such as a binder, a plasticizer, a fluidity imparting agent, a pinhole inhibitor, and the like, which are commonly used in electrophotographic photoreceptors, can be used in the charge generation layer, if necessary. Examples of the binder include silicone resin, polyamide resin, polyurethane resin, polyester resin, epoxy resin, polyketone resin, polycarbonate resin, polystyrene resin, polymethyl methacrylate resin, and polyacrylamide resin. Heat and/or photocurable resins can also be used. In any case, there is no particular restriction as long as the resin has electrical insulation properties and can form a film under normal conditions. In the charge generation layer, the binder is used in an amount of 500% by weight or less based on the organic pigment. If it exceeds 500% by weight, electrophotographic properties will deteriorate. Examples of the plasticizer include halogenated paraffin, dimethylnaphthalene, and dibutyl phthalate. Examples of fluidity imparting agents include Modaflow (manufactured by Monsanto Chemical Company) and Acronal 4F (manufactured by Basf Company), and examples of pinhole inhibitors include:
Examples include benzoin and dimethyl phthalate. Each of these is preferably used in an amount of 5% by weight or less based on the organic pigment. The electron-donating charge transport substance used in the charge transport layer has a function of transporting positive charge carriers (holes), and specifically includes carbazole, 3-
Phenylcarbazole, 2-phenylindole, 2-phenylnaphthalene, oxadiazole, oxatriazole, 1-phenyl-3-
Low molecular weight compounds such as (4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, 2-phenyl-4-(4-diethylaminophenyl)-5-phenyloxazole, triphenylamine, imidazole, poly -N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylindoquinoxaline, polyvinylbenzothiophene, polyvinylanthracene, polyvinylacridine, polyvinylpyrazoline, and other polymeric compounds, and derivatives thereof. The same binder, plasticizer, fluidity imparting agent, pinhole inhibitor, etc. as in the charge generation layer can be used in the charge transport layer as necessary. Among these, the binder is preferably 400% by weight or less based on the charge transport material so as not to deteriorate the electrophotographic properties, and when using a low-molecular compound, this should be avoided due to the film properties.
It is preferably 50% by weight or more. Other additives are
Each content is preferably 5% by weight or less based on the charge transporting substance. Next, the subbing layer will be explained. The subbing layer of the present invention contains (a) a specific butyl etherified melamine formaldehyde resin, (b) an electron-accepting carboxylic acid compound and/or an electron-accepting polycarboxylic acid anhydride, and (c) an organic charge-generating material. It can be obtained by curing a coating film by heating. The number average molecular weight of the butyl etherified melamine/formaldehyde resin used in the present invention is
1500 or less, and if the number average molecular weight exceeds 1500, the reactivity decreases. The resin also has 2 to 4 bound formaldehydes per melamine core. 4
When the number exceeds 2, the reactivity decreases, and when the number is less than 2, the storage stability of the resin deteriorates and the cured coating film becomes brittle. Furthermore, the resin has 1 to 2 methylol groups per melamine nucleus. If the number of methylol groups exceeds 2, the storage stability of the resin will be poor and the cured coating will become brittle. Moreover, if it is less than one, the reactivity is poor. Such butyl etherified melamine/formaldehyde resin can be produced by dissolving melamine in butanol and dropping formaldehyde thereto to perform an addition reaction and butyl etherification reaction, or by dissolving melamine and formaldehyde in butanol and adding this solution. It can be produced by a method of heating and performing an addition reaction and a butyl etherification reaction. In these methods, the reaction is preferably carried out under acidic conditions, preferably at pH 3 to 6, by adding an acidic catalyst such as nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, p-toluenesulfonic acid, etc., and the reaction temperature is the reflux temperature of butanol, preferably is preferably about 90-100°C. In the present invention, 4 to 5 moles of butanol and 3 to 5 moles of formaldehyde are used per mole of melamine.
Preferably, 7 mol is used to carry out the reaction. The butyl etherified melamine/formaldehyde resin used in the undercoat layer of the present invention can be cured at a lower temperature than conventional melamine resins, so that deformation of the conductive layer can be prevented during formation of the undercoat layer. The present invention further adds the following features by using an electron-accepting carboxylic acid compound and/or an electron-accepting polycarboxylic acid anhydride. (1) Since the electron-accepting carboxylic acid compound and/or the electron-accepting polycarboxylic acid anhydride accelerate the curing reaction, the curing reaction can be completed at a lower temperature and in a shorter time. As a result, the effect of preventing deformation of the conductive layer is further improved, and the working process is also simplified. (2) The curing reaction is accelerated and the undercoat layer becomes extremely tough, making it less likely to be scratched and making it easier to handle in subsequent steps. Also,
Since the solvent resistance of the undercoat layer is improved, a uniform charge generation layer can be formed without damaging the undercoat layer. (3) Since carboxylic acids and acid anhydrides are electron-accepting, this property is introduced into the undercoat layer. As a result, electrons are efficiently injected from the charge generation layer to the undercoat layer, and a decrease in sensitivity and an increase in residual potential after light irradiation due to the provision of the undercoat layer can be suppressed. The electron-accepting carboxylic acid compound is a compound having one or more carboxyl groups and exhibiting electron-accepting properties, and has an electron-withdrawing group such as a nitro group, a nitrile group, or a carbonyl group in the compound. You can leave it there. Specifically, butyric acid, valeric acid,
Heptanoic acid, acrylic acid, methacrylic acid, tiglic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, undecanniic acid, maleic acid, glutaconic acid, propane-1,2,3-tricarboxylic acid,
Butane-1,1,4-tricarboxylic acid, pentane-1,3,3,5-tetracarboxylic acid, quinobic acid, phenylpropionic acid, phenyl acetic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid,
trimellitic acid, hemimellitic acid, trimesic acid, merofanic acid, pyromellitic acid, cinnamic acid,
Cinnamylidenic acid, benzyl acrylic acid, α-phenylcrotonic acid, benzalpropionic acid, biphenyl-2-carboxylic acid, diphenic acid, α-naphthoic acid, β-naphthoic acid, naphthalene-1,2-
dicarboxylic acid, naphthalic acid, naphthalene-1,
4,5-tricarboxylic acid, naphthalene-1,4,
5,8-tetracarboxylic acid, anthracene-1-
Carboxylic acid, anthracene-1,9-dicarboxylic acid, anthracene-2,3-dicarboxylic acid, phenanthrene-1-carboxylic acid, phenanthrene-
9-carboxylic acid, dibenzothiophene-1-carboxylic acid, thianaphthene-2,3-dicarboxylic acid,
perylene-3,4,9,10-tetracarboxylic acid,
3-nitroheptanoic acid, 2-nitroadipic acid,
4-nitrobenzoic acid, 2,3-dinitrobenzoic acid, 2,4,6-trinitrobenzoic acid, 3-nitrophthalic acid, 4,6-dinitroisophthalic acid,
2,6-dinitroterephthalic acid, 4-cyanobenzoic acid, 4,6-dicyanoisophthalic acid, benzophenone-2,2'-dicarboxylic acid, benzophenone-2,4,2',4'-tetracarboxylic acid, 4- Nitro-2-naphthoic acid, 8-nitro-1-naphthoic acid, anthrone-9-carboxylic acid, 2-nitro-
Anthracene-1-carboxylic acid, 2-carboxy-1,4-benzoquinone, p-benzoquinoylacetic acid, 5-carboxy-1,4-naphthoquinone, 2
Examples include -nitro-5-carboxy-1,4-naphthoquinone, 1-carboxy-anthraquinone, and 2-carboxy-4,7-dinitrofluorenone. The electron-accepting polycarboxylic acid anhydride is an acid anhydride of one of the electron-accepting galboxylic acid compounds having two or more carboxyl groups,
Specifically, succinic anhydride, glutaric anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, naphthalic anhydride, naphthalene-1,4,5-tricarboxylic acid anhydride, naphthalene-1,4,5,8-tetracarboxylic anhydride, anthracene-2,3-
Examples include dicarboxylic anhydride and 3-nitrophthalic anhydride. One or more of the electron-accepting carboxylic acid compounds and electron-accepting polycarboxylic anhydrides are used, and the amount used is 0.1 to 400 parts by weight per 100 parts by weight of the butyl etherified melamine/formaldehyde resin. is preferable, especially 1 to 100
Parts by weight are preferred. If the amount used is too small, it will be difficult to exhibit the above-mentioned characteristics, and if it is too large, the moisture resistance of the undercoat layer will tend to decrease. The undercoat layer of the present invention further contains an organic charge generating material as a third component in an amount of 0.01 to 10% by weight. When the organic charge generating material is contained within this range, an increase in residual potential can be suppressed even if the thickness of the undercoat layer is increased. If the content is less than 0.01% by weight, the effect of suppressing residual potential will be small, and 10
If it exceeds % by weight, the charging property tends to decrease.
As the organic charge generating material used in the undercoat layer, the organic pigments used in the charge generating layer described above can be used. The undercoat layer in the present invention may further contain additives such as a fluidity imparting agent and a pinhole inhibitor that may be used in the charge generation layer and the charge transport layer. The electrophotographic photoreceptor according to the present invention has a structure in which an undercoat layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive layer. In this electrophotographic photoreceptor, the thickness of the subbing layer is
The thickness is preferably 0.1 to 15 μm, particularly preferably 0.5 to 10 μm. If the undercoat layer is less than 0.1 μm, the effect of providing the undercoat layer is small, and if it exceeds 15 μm, the residual potential tends to increase. The thickness of the charge generation layer is preferably 0.001 to 10 μm,
Particularly preferred is 0.2 to 5 μm. Charge generation layer is 0.001μm
If it is less than 10 μm, electrophotographic properties (especially sensitivity) tend to be poor, and if it exceeds 10 μm, chargeability tends to decrease. The thickness of the charge transport layer is preferably 5 to 50 μm, particularly preferably 8 to 20 μm. If it is less than 5 μm, the initial potential tends to be low, and if it exceeds 50 μm, the sensitivity tends to decrease. As a method for forming the undercoat layer, the above-mentioned butyl etherified melamine/formaldehyde resin, electron-accepting carboxylic acid compound and/or electron-accepting polycarboxylic acid anhydride, and organic charge-generating material, as well as other additives as necessary, are used. It can be formed by dispersing or dissolving it in an organic solvent such as acetone, methyl ethyl ketone, tetrahydrofuran, isopropyl alcohol, isobutyl alcohol, etc., and then applying the solution onto the conductive layer and curing it by heating. The heating temperature at this time is preferably 90 to 140°C. When only an organic pigment is used as a method for forming the charge generation layer, vacuum deposition can be used. ,
It can also be formed by uniformly dissolving or dispersing in a solvent such as trichloroethane, then coating and drying. When forming a charge transport layer, a charge transporting substance, a binder, and optionally an additive may be uniformly dissolved in the same solvent as in the case of the charge generation layer, and then it can be formed by coating and drying. . The electrophotographic photoreceptor of the present invention may further have a protective layer immediately above the charge transport layer. When copying or printing using the electrophotographic photoreceptor of the present invention, the surface is negatively charged and exposed in the same manner as before, and then developed to transfer an image onto a transfer material such as plain paper. All you have to do is transfer it and fix it. [Examples] Next, the present invention will be described in detail based on Examples.
The present invention is not limited to this. Each material used in the examples below is listed below. Abbreviations are shown in parentheses. (1) Materials for subbing layer (A) Butyl etherified melamine formaldehyde resin (BMF) (Synthesis of BMF-1) In a flask equipped with a stirrer, reflux condenser, and thermometer, 126 g of melamine, 444 g of n-butanol, and
After adding 0.2g of 61% nitric acid aqueous solution and raising the temperature to 100℃,
169 g of paraformaldehyde was added at equal intervals in 6 portions over 30 minutes, and the mixture was then reacted at reflux temperature for 30 minutes to remove water and desolvent so that the heating residue was 50%. The resulting resin solution had a viscosity of B as a cardner (25°C). (Synthesis of BMF-2) Using the same equipment as in the synthesis of BMF-1, 126 g of melamine, 444 g of n-butanol, and a 61% aqueous nitric acid solution were prepared.
0.2 g and 169 g of paraformaldehyde were mixed and charged, the temperature was raised to 100°C, and the mixture was reacted for 30 minutes. Thereafter, reflux dehydration was performed for 30 minutes to remove water and the solvent was removed so that the heating residue was 50%. The viscosity of the resulting resin solution was Gardner (25
It was C at ℃). (Synthesis of BMF-3) Using the same apparatus as in the synthesis of BMF-1, 217.5 g of paraformaldehyde, 444 g of n-butanol, and 126 g of melamine were weighed out, and an addition reaction was performed at 90 to 100°C for 30 minutes. Thereafter, the mixture was cooled to 40 to 45°C, 0.1 g of phthalic acid was added, and reflux dehydration and dissolution were performed under acidic conditions. After this, the heating residue was adjusted to 50%. The viscosity at this time is (Gardner/25℃) B
It was hot. The number of formaldehyde bound, the number of butyl ether groups, the number of methylol groups, and the number average molecular weight per melamine nucleus of BMF-1, BMF-2, and BMF-3 are shown in Table 1 below. However, the number of bound formaldehyde is determined by measuring the amount of unreacted formaldehyde using the charged amount and the sodium sulfite method, and the number of butyl ether groups is determined by measuring the amount of butanol charged and unreacted butanol by gas chromatography using sec-butyl alcohol as an internal standard solution. The methylol group was determined from the above number of butyl ether groups and the NMR spectrum. Further, the number average molecular weight was determined by gel permeation chromatography using a standard polystyrene calibration curve.

[Table] (B) Electron-accepting carboxylic acid compound or electron-accepting polycarboxylic acid anhydride, pyromellitic anhydride, 3-nitrophthalic acid (C) Organic pigment that generates charge γ-type metal-free phthalocyanine (γ-H ₂ PC) (2) Organic pigment used in the charge generation layer γ-type metal-free phthalocyanine (γ-H ₂ PC) (3) Charge transport substance 2-(p-dimethylamino)phenyl-4-(p
-Dimethylaminophenyl-5-(O-chlorophenyl)-1,3-oxazole (OXZ) (4) Binder (A) Binder for charge generation layer Silicone varnish: KR-255 [Shin-Etsu Chemical Co., Ltd.]
Product name] (B) Binder for charge transport layer Polyester resin: Vylon 200 [Product name of Toyobo Co., Ltd.] Comparative example 1 2.0 g of γ-H ₂ PC, 4.0 g of silicone varnish, and 94 g of tetrahydrofuran were mixed in a ball mill (Nippon Kagaku Co., Ltd.) The mixture was kneaded for 8 hours using a 3-inch pot mill (manufactured by Yamaha Motor Co., Ltd.).
The obtained pigment dispersion was applied to an unpolished aluminum plate (thickness: 0.1 mm) using an applicator, and dried at 100°C for 15 minutes to a thickness of approximately 1.0 μm.
A charge generation layer was formed. Next, 5 g of OXZ and 15 g of Byron 200 were mixed with 140 g of tetrahydrofuran and completely dissolved. The obtained solution was applied onto the charge generation layer using an applicator and dried at 90° C. for 20 minutes to form a charge transport layer with a thickness of 15 μm. Comparative Examples 2-3 BMF-3 20g (solid content 10g) was mixed with tetrahydrofuran and isobutyl alcohol (weight ratio 1:1)
was dissolved in 80g of mixed solvent. Comparative Example 1
A similar surface was applied to an unpolished aluminum plate using an applicator to form a 1 μm thick subbing layer. The curing conditions are shown in Table 2. Next, when the charge generation layer coating liquid used in Comparative Example 1 was applied onto this undercoat layer using an applicator, the undercoat layer was attacked and a uniform charge generation layer could not be formed. Comparative Examples 4-5 20g of BMF-1 (solid content 10g) was mixed with tetrahydrofuran and isobutyl alcohol (1:1 weight ratio).
was dissolved in 80g of mixed solvent. Comparative Example 1
A similar surface was applied to an unpolished aluminum plate using an applicator to form a 1 μm thick subbing layer. The curing conditions are shown in Table 2. Next, when the charge generation layer coating liquid used in Comparative Example 1 was applied onto this undercoat layer using an applicator, it was found that when the undercoat layer was cured at 140°C for 2 hours (Comparative Example 5), The charge generation layer was applied almost uniformly, but the curing conditions were
When the temperature was 110° C. for 1 hour (Comparative Example 4), a uniform charge generation layer could not be formed. In Comparative Example 5, a charge transport layer was further formed on the charge generation layer in the same manner as in Comparative Example 1. Comparative Examples 6 to 7 18 g of BMF-1 (9 g of solid content) and 1 g of pyromellitic anhydride were dissolved in 81 g of isobutyl alcohol.
This solution was applied using an applicator onto an unpolished aluminum plate similar to Comparative Example 1, and cured at 105°C for 1 hour. The film thickness is shown in Table 2. Approximately
A 1 μm charge generation layer and a 15 μm charge transport layer were sequentially laminated. In this case, the charge generation layer could be formed uniformly. Examples 1 to 5 Undercoat layer materials having the composition ratios shown in Table 2 were kneaded in a ball mill for 8 hours using a mixed solvent of tetrahydrofuran and isobutyl alcohol at a weight ratio of 1:1 so that the solid content was 10% by weight. As in Comparative Example 1, this dispersion was applied onto an unpolished aluminum plate using an applicator. Table 2 shows the film thickness and curing conditions. Next, a charge generation layer of about 1 .mu.m and a charge transport layer of 15 .mu.m were sequentially laminated on this undercoat layer in the same manner as in Comparative Example 1. In this case, the charge generation layer could be formed uniformly. The solvent resistance of the undercoat layers obtained in Comparative Examples 2 to 7 and Examples 1 to 5 was evaluated. The evaluation method was to immerse the undercoat layer, which was formed on an aluminum plate according to the method, film thickness, and curing conditions described above in each Comparative Example and each Example, for 5 minutes in tetrahydrofuran, which is the solvent for the coating liquid for the charge generation layer, together with the aluminum plate. From the weight change before and after immersion, the weight ratio eluted into tetrahydrofuran was measured using the following formula. The results are shown in Table 2. Weight ratio of eluted =
(Weight of aluminum plate with subbing layer formed after dipping) -
(Weight of the aluminum plate alone)/(Weight of the aluminum plate on which the subbing layer was formed before dipping) - (Weight of the aluminum plate alone) × 100 (%) Also, Comparative Example 1, Comparative Examples 5 to 7, and Examples 1~
The electrophotographic properties of the electrophotographic photoreceptor obtained in step 5 were measured using an electrostatic recording paper tester (SP-428 manufactured by Kawaguchi Electric). The results are shown in Table 2. In addition, the initial potential V _O (V) in the table indicates the charging potential when a negative 5 kV corona is discharged for 10 seconds in dynamic measurement, and the dark decay V _k indicates the charge potential after discharging a negative 5 kV corona for 10 seconds.
Indicates the potential retention rate when left for 30 seconds, E ₅₀ is
The amount of light (l _xs ) required to reduce the potential by 50% when irradiated with 10 l _ux of white light is shown. Residual potential V _R is 10l _ux
This shows the surface potential after irradiation with white light for 30 seconds.
The repeatability is based on the process of 10 seconds of charging and 5 seconds of exposure.
It shows the rate of decrease in initial potential when repeated 300 times. Furthermore, Comparative Example 1, Comparative Examples 5 to 7, and Example 1
The adhesion of the electrophotographic photoreceptor obtained in steps 5 to 5 was tested. Adhesion was determined by making a mesh-like scratch on the surface with a knife and then performing a peel test using cellophane tape. Furthermore, Comparative Example 1, Comparative Examples 5 to 7, and Examples 1 to 5
The image quality of the electrophotographic photoreceptor was evaluated using an image evaluation machine. Table 3 shows the results of adhesion and image quality evaluation.

【table】

〔Effect of the invention〕

A cured film containing a specific butyl etherified melamine/formaldehyde resin, an electron-accepting carboxylic acid compound, and/or an electron-accepting polycarboxylic acid anhydride between the conductive layer and the charge-generating layer according to the present invention, and an organic charge-generating material An electrophotographic photoreceptor provided with a subbing layer containing the above provides excellent electrophotographic properties and good images, and exhibits little deterioration in properties upon repeated use.

Claims (1)

[Claims] 1. In an electrophotographic photoreceptor in which a subbing layer, a charge generation layer, and a charge transport layer containing an electron-donating charge transport substance are sequentially laminated on a conductive layer, the subbing layer ( a) Butyl etherified melamine/formaldehyde resin having a number average molecular weight of 1500 or less and having 2 to 4 formaldehydes and 1 to 2 methylol groups bound per melamine nucleus; (b) Electron-accepting carboxylic acid compound and/or an electrophotographic photoreceptor comprising a cured film containing an electron-accepting polycarboxylic anhydride as a component and (c) an organic charge-generating material. 2. The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer contains 0.01 to 20% by weight of the organic charge generating material used in the undercoat layer.