JPH0431575B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) 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 an electrophotographic photoreceptor that uses a photoconductive substance as a photosensitive material, inorganic photoconductive substances such as selenium, zinc oxide, titanium oxide, and cadmium oxide have been conventionally used as the photoconductive substance. It has been mainly used. However, many of these are generally highly toxic and there are problems with 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 generating device has been considered (Japanese Patent Application Laid-Open No. 57-90639, JP-A No. 58-86556,
JP-A-60-202449, JP-A-60-108860). (Problems to be Solved by the Invention) When considering the undercoat layer, it should be noted that there should be no image defects, there should be no deterioration in chargeability, there should be no deterioration in electrophotographic properties, and the method for forming it should be simple. , especially when formed by 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 charge generation layer coating liquid 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-accepting 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, the number of bound formaldehydes per melamine nucleus being 2 to 4, and the number of methylol groups being 1 to 2, and (b) an electron-donating carboxylic acid compound and/or an electron. The present invention relates to an electrophotographic photoreceptor containing a cured film containing a donating polycarboxylic acid 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, γ, γ′, η
and η'-type metal-free phthalocyanine have high sensitivity even to long wavelengths, and are also effective as electrophotographic photoreceptors for printers equipped with diode lasers.
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 suppressor, and the like, which are commonly used in electrophotographic photoreceptors, can be used in the charge generation layer as 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 is electrically insulating 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, the 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-accepting charge transport material used in the charge transport layer has a function of transporting negative charge carriers (electrons), and specifically, 2,7-dinitro-
9-fluorenone, 2,4,7-trinitro-9
-fluorenone, 4H-indeno(1,2,6)
Thiophen-4-one, 3,7-dinitro-dibenzothiophene-5-oxide, tetrachlorophthalic anhydride, 2,5-dichloro-1,4-benzoquinone, 2,6-dichloro-1,4-benzoquinone , 2,3,5,6-tetrachlor-1,4-
Benzoquinone, anthraquinone, 2-chloroanthraquinone, 1,8-dichloroanthraquinone,
1,5-dichloroanthraquinone, 1,2,5,
8-tetrahydroxyanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 2,
3-dichloro-1,4-naphthoquinone, 2,3,
5-trichloro-1,4-naphthoquinone, 2,3
-dichloro-5-prom-1,4-naphthoquinone, 2-nitro-3-methyl-1,4-naphthoquinone, 2,3-dibrom-5-methyl-1,4-
naphthoquinone, 2,3-dibromo-5-ethyl-
1,4-naphthoquinone, tetracyanoethylene,
Electron-accepting compounds such as trinitrobenzene, tetracyanoquinodimethane, 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 amount of the binder is preferably 400% by weight or less based on the charge transport material so as not to deteriorate the electrophotographic properties, and the amount of the binder is preferably 50% by weight or more for the low molecular weight charge transport material in view of film properties. The amount of other additives is preferably 5% by weight or less based on the charge transport material. Next, the subbing layer will be explained. The undercoat layer of the present invention is mainly formed of a cured film of a specific butyl etherified melamine/formaldehyde resin and an electron-donating carboxylic acid compound and/or an electron-donating polycarboxylic acid anhydride. can be obtained by curing a coating film containing these 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-donating carboxylic acid compound and/or an electron-donating polycarboxylic acid anhydride. (1) Since the electron-donating carboxylic acid compound and/or the electron-donating 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 drying process is also simplified. (2) The effectiveness reaction is accelerated and the undercoat layer becomes extremely tough, making it difficult to damage the undercoat layer 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 donating, this property is introduced into the undercoat layer. As a result, holes are efficiently injected from the charge generation layer to the undercoat layer, and a decrease in sensitivity due to the provision of the undercoat layer and an increase in residual potential after light irradiation can be extremely minimized. Therefore, the thickness of the undercoat layer can be increased, and the effect of the undercoat layer can be further exhibited. The above-mentioned electron-donating carboxylic acid compound includes an electron-donating group such as an amino group, a hydroxyl group, a halogen group,
There are compounds that have one or more aromatic rings substituted with one or more alkoxyl groups, alkyl groups, etc. and a carboxyl group, and compounds that have an electron-donating skeleton and a carboxyl group.
aminobenzoic acid, 4-dimethylaminobenzoic acid,
3,4-bis(dimethylamino)benzoic acid, 3,
4,5-tris(dimethylamino)phthalic acid, salicylic acid, 4-chloro-salicylic acid, 3,4-dibromobenzoic acid, 3,4-dimethoxybenzoic acid,
3,4,5-trimethoxybenzoic acid, 2,4,5
-trimethoxybenzoic acid, 3,4,5-trimethoxyphenylacetic acid, diphenylamine-2-carboxylic acid, 2,5-pyridinecarboxylic acid, 3,4,
5-trimethoxyphthalic acid, 3-ethyl-4,5
-dimethoxybenzoic acid, 3,4-dimethoxy-5
-Chlorphenylpropionic acid, 4-t-butyl-5-methoxybenzoic acid, 1-carboxy-2,
3-dimethylaminonaphthalene, 1,8-dicarboxy-2,3,4-trimethoxynaphthalene,
These include 2-carboxy-3,6,7-trimethoxyanthracene, 2-carboxy-3,6-bis(dimethylamino)anthracene, and the latter include oxazole, oxydiazole, pyrazoline, stilbenehydrazone, pyrrole, and imidazole. , carbazole, indole, etc., and their derivatives, with one or more carboxyl groups substituted; specifically, 2-
(2-carboxy-4diethylamino)phenyl-1,3-oxazole, 1-(4-carboxy)
Phenyl-3-(4-diethylaminostyryl)-
5-(4-diethylamino)phenylpyrazoline,
Examples include α-phenyl-4'-N,N'-dicarboxyphenylaminostilbene, N-methyl-N-carboxyphenylhydrazono-3-methylidene-9-ethylcarbazole, and pyrrole-2-carboxylic acid. The electron-donating polycarboxylic acid anhydride is an acid anhydride of one of the electron-donating carboxylic acid compounds having two or more carboxyl groups,
Specifically, 3,4,5-tris(dimethylamino)phthalic anhydride, 3,4,5-trimethoxyphthalic anhydride, 1,8-dicarboxy-2,
Examples include acid anhydride of 3,4-trimethoxynaphthalene. One or more of the electron-donating carboxylic acid compounds and electron-donating polycarboxylic anhydrides are used, and the amount used is determined based on the butyl etherified melamine/formaldehyde resin.
0.1 to 80% by weight is preferred, particularly 1 to 50% by weight. 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 subbing layer in the present invention further includes a fluidity imparting agent that may be used in the charge generation layer and the charge transport layer.
Additives such as pinhole suppressants may also be included. 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 10 μm, particularly preferably 0.5 to 5 μm. If the undercoat layer is less than 0.1 μm, the effect of providing the undercoat layer is small, and if it exceeds 10 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 voltage 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 other additives as necessary are mixed with acetone, methyl ethyl ketone, or tetrahydrofuran. It can be formed by uniformly dissolving it in an organic solvent such as , isopropyl alcohol, isobutyl alcohol, etc., then coating it on the conductive layer and curing it by heating. The heating temperature at this time is 90 to 140
°C is preferred. The charge generation layer can be formed by vacuum evaporation if only an organic pigment is used, but the organic pigment and optionally a binder and additives can be formed using acetone, methyl ethyl ketone, tetrahydrofuran, toluene, xylene, or chloride. It can also be formed by uniformly dissolving or dispersing it in a solvent such as methylene or trichloroethane, then coating and drying. When forming a charge transport layer, a charge transport substance,
It can be formed by uniformly dissolving the binder and optionally additives in the same solvent as in the case of the charge generation layer, and then 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 positively 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. (Example) Next, the present invention will be explained in detail based on an example.
The present invention is not limited to this. Each material used in the following examples is illustrated 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 according to Gardner (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 sodium sulfite method. 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-donating carboxylic acid compound or electron-donating polycarboxylic acid anhydride Γ 3,4,5-trimethoxyphenylacetic acid Γ 3,4-bis(dimethylamino)phthalic anhydride (2) Charge Organic pigment that generates γ-type metal-free phthalocyanine (γ-H ₂ Pc) (3) Charge transport substance 2,3,5-trichloro-1,4-naphthoquinone (4) Binder (A) Binder for charge generation layer Silicone varnish: KR−255
[Product name of Shin-Etsu Chemical Co., Ltd.] (B) Binder for charge transport layer Polyester resin: Vylon 200
[Product name of Toyobo Co., Ltd.] Comparative example 1 γ-H ₂ Pc 2.0g, silicone varnish (KR-
255) 4.0g and 94g of tetrahydrofuran were mixed into
Kneaded for hours. The resulting 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 form a charge generation layer with a thickness of about 1.0 μm. Next, 4 g of 2,3,5-trichloro-1,4-naphthoquinone, 8 g of Vylon 200, and 88 g of a mixed solvent of dichloromethane/dichloroethane = 1/1 were completely dissolved. The obtained solution was applied onto the charge generation layer using an applicator and heated at 90°C for 1 hour.
A charge transport layer of 15 μm was formed by drying for hours. 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 undercoat 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 sample was heated at 110° C. for 1 hour (Comparative Example 4), a uniform charge generation layer could not be formed and it could not be used as an electrophotographic photoreceptor. 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. Examples 1 to 5 A solution of the undercoat layer material having the composition ratio shown in Table 2 (using a mixed solvent of tetrahydrofuran and isobutyl alcohol (1:1 weight ratio), solid content 10% by weight),
The same surface as in Comparative Example 1 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 5 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 forming subbing layer after immersion)
- (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) x 100 (%) Also, Comparative Example 1, Comparative Example 5, and Example 1 The electrophotographic properties of the electrophotographic photoreceptor obtained in steps 5 to 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 positive 5KV corona is discharged for 10 seconds in dynamic measurement, and the dark decay V _K indicates the charge potential when a positive 5KV corona is discharged for 10 seconds in dynamic measurement.
Indicates the potential retention rate when left for 30 seconds, E ₅₀ is
It shows the amount of light (lx・s) required for the potential to decrease by 50% when irradiated with 10 lux of white light. The residual potential V _R is
Shows the surface potential after irradiation with 10 lux white light for 30 seconds. The repetition characteristic indicates the rate of decrease in the initial potential when the process of charging for 10 seconds and exposing for 5 seconds is repeated 300 times. Furthermore, Comparative Example 1, Comparative Example 5, and Examples 1 to 5
The adhesion of the electrophotographic photoreceptor obtained 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, the image quality of the electrophotographic photoreceptors of Comparative Example 1, Comparative Example 5, and Examples 1 to 5 was evaluated using an image evaluation machine. Table 3 for the results of adhesion and image quality evaluation
Shown below.

【table】

【table】

[Table] The photoreceptor of Comparative Example 1 had good initial electrophotographic characteristics and good image quality, but after repeated charging and exposure, the initial potential decreased by as much as 47% (Table 2), and the adhesion was slightly inferior. There are problems in that (Table 3) and many image defects occur (Table 3). On the other hand, if a butyl etherified melamine/formaldehyde resin outside the scope of the present invention is used as the material for the undercoat layer, the solvent resistance will be low, and the undercoat layer will be attacked by the coating liquid for the charge generation layer during the formation of the charge generation layer, resulting in a uniform coating. A charge generation layer could not be formed (Comparative Examples 2 and 3). When a butyl etherified melamine/formaldehyde resin within the scope of the present invention was used alone as the material for the undercoat layer (Comparative Examples 4 to 5), compared to Comparative Examples 2 to 3,
That is, compared to the case where butyl etherified melamine/formaldehyde resin, which is outside the scope of the present invention, is used as the material for the undercoat layer, it has higher thermosetting properties and can be heated at 140°C.
When the curing condition was 2 hours (Comparative Example 5), the solvent resistance of the undercoat layer was improved and the charge generation layer could be formed almost uniformly. However, the electrophotographic properties deteriorate, i.e. E ₅₀
There is also a problem that the VR and V _R increase, and the background of the image is significantly smudged. However, as in Examples 1 to 5, the undercoat layer using a specific melamine resin and an electron-donating carboxylic acid compound or an acid anhydride has further improved thermosetting properties and solvent resistance, and can be used at low temperatures and for short periods of time. Even if the undercoat layer is formed under curing conditions, a uniform charge generation layer can be formed without being attacked by the charge generation layer coating liquid when forming the charge generation layer thereon. In addition, the effects of providing an undercoat layer are (1) improved charging performance (initial potential increased by 130 V or more compared to Comparative Example 1), (2) suppressed decrease in initial potential during repeated use (Comparative Example 1 increased by 47 (17% or less in all examples), (3) improved adhesion, and (4) reduced number of image defects based on surface defects on the aluminum plate (compared to 13 in Comparative Example 1). Examples 1-5
(all of them are 5 or less). Moreover, no deterioration in electrophotographic properties or deterioration in image quality due to the provision of the subbing layer as seen in Comparative Example 5 was observed. As described above, the electrophotographic photoreceptors obtained in Examples 1 to 5 maintain good electrophotographic properties that function under normal charges, have improved chargeability and adhesion, and are free from surface defects in the conductive layer. It was confirmed that this is an electrophotographic photoreceptor that provides good images without being reflected in the image. (Effects of the invention) A cured film containing a specific butyl etherified melamine/formaldehyde resin and an electron-donating carboxylic acid compound and/or an electron-donating polycarboxylic acid anhydride between the conductive layer and the charge generation layer according to the present invention. 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)

[Scope of Claims] 1. An electrophotographic photoreceptor in which a subbing layer, a charge generation layer, and a charge transport layer containing an electron-accepting charge transport material are sequentially laminated on a conductive layer, wherein the subbing layer is (a ) Butyl etherified melamine/formaldehyde resin having a number average molecular weight of 1500 or less, the number of bound formaldehydes per melamine nucleus being 2 to 4 and the number of methylol groups being 1 to 2, and (b) an electron-donating carboxylic acid compound; An electrophotographic photoreceptor comprising a cured film containing/or an electron-donating polycarboxylic anhydride as a component.