JP2814235B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor having a water-soluble polyvinyl acetal-based intermediate layer. 2. Description of the Related Art Conventionally, a general electrophotographic photoreceptor having a photosensitive layer provided on a conductive substrate, particularly a laminated electrophotographic photoreceptor in which the photosensitive layer is composed of a charge generation layer and a charge transfer layer, has high chargeability and high chargeability. Various attempts have been made to provide sensitivity and low residual potential. As one of them, it has been proposed to provide an intermediate layer for preventing a charge having a polarity opposite to that of a charged charge from being injected from a conductive substrate side into a highly sensitive charge generation layer during charging. For example, JP-A-47-6341, 48-3544 and 48-1203
No. 4 has a cellulose nitrate-based resin intermediate layer as disclosed in JP-A-48-473.
44, 52-25638, 58-30757, 58-63945, 58-95351, 58
Nos. 98739 and 60-66258 have a polyamide resin interlayer, JP-A-48-26141 has a vinyl acetate resin interlayer, and JP-A-49-69332 and 52-10138 have a maleic acid resin. An interlayer is disclosed, and JP-A-58-106549 discloses a water-soluble polyvinyl butyral resin interlayer. Among them, a water-soluble polyvinyl acetal-based material such as polyvinyl butyral has an electric resistance of about 10 ¹⁰ Ωcm, which is suitable as an intermediate layer, and is not easily attacked by an organic solvent. This is the most preferable intermediate layer because it can easily contribute to the improvement of the coating characteristics of the photosensitive layer because it is easy to form a good uniform coating. However, the photoconductor provided with a polyvinyl acetal intermediate layer is particularly suitable for high temperature and high humidity. When used repeatedly, the chargeability is good, but the sensitivity is reduced, and the residual potential accumulates after image exposure, and the background potential rises, resulting in the generation of background stains, especially in solid white areas. Was. Purpose The object of the present invention is to maintain a high sensitivity even when repeatedly used under a low temperature and a low humidity, as well as a high temperature and a high humidity, and to have a durability that does not cause ground fouling, despite having a water-soluble polyvinyl acetal intermediate layer. To provide a reliable electrophotographic photoreceptor. The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which an intermediate layer and a photosensitive layer are sequentially provided on a conductive substrate, wherein the intermediate layer contains water-soluble polyvinyl acetal as a main component, and the polyvinyl acetal is contained in the intermediate layer. Wherein the amount of acetic acid, inorganic acid and / or an alkali metal salt thereof contained as an impurity is set to 0.5% by weight or less of the intermediate layer. Here, the water-soluble polyvinyl acetal has a degree of acetalization of 40 mol% or less and a vinyl alcohol component of 50 mol% or more. The present inventors have made various studies in order to eliminate the drawbacks of the conventional photoreceptor having a water-soluble polyvinyl acetal intermediate layer. As a result, it has been found that the conventional disadvantage is caused by impurities contained in the water-soluble polyvinyl acetal. In general, water-soluble polyvinyl acetal is obtained by saponifying polyvinyl acetate in the presence of an alkali such as caustic soda to obtain polyvinyl alcohol. It is manufactured as a sum. For example, as shown in the following formula, acetic acid and its alkali metal salt (usually sodium salt) or inorganic acid (usually hydrochloric acid or sulfuric acid) and its alkali metal salt (usually sodium salt) are contained in the obtained water-soluble polyvinyl alcohol. Is mixed in a considerable amount. In this case, a solvent mainly composed of alcohol is generally used as the reaction solvent.Solubility of the mixed sodium acetate, sodium chloride, etc. in the alcohol is lower than that of the water-soluble polyvinyl acetal. Can be removed, but still
About 5wt is inevitable. Examples of aldehydes for acetalization and examples of acetalization reactions are also shown below. The alkali metal ions as described above move (ion conduction) in the intermediate layer by repeated charging and exposure under high temperature and high humidity to reach the photosensitive layer in contact with the intermediate layer, and as a result, decrease the light attenuation sensitivity or , It is assumed that the residual potential is increased. On the other hand, it is presumed that the acid ions reduce the chargeability by coming into contact with the photosensitive layer regardless of the repetition of charge and exposure. On the other hand, the water-soluble polyvinyl acetal-based intermediate layer of the present invention has reduced the amount of salts such as acetates and acids such as acetic acid, which causes these defects, to 0.5 wt% or less, so that the amount of ions in the intermediate layer, Therefore, the amount of alkali ions in contact with the photosensitive layer, that is, the amount of alkali ions and acid ions in contact with the photosensitive layer is reduced, and even when repeatedly used under high temperature and high humidity, there is almost no decrease in light attenuation sensitivity or increase in residual potential. . However, when the content exceeds 0.5 wt%, the sensitivity (light attenuation sensitivity) decreases, and background contamination due to an increase in residual potential becomes severe, as in the conventional case. Therefore, in the water-soluble polyvinyl acetal used for the intermediate layer of the present invention, it is necessary to remove a predetermined amount of salts such as sodium acetate and acids such as acetic acid from the conventionally used water-soluble polyvinyl acetal. Salts and acids such as those contained as impurities in the water-soluble polyvinyl acetal are difficult to remove by generally used chemical industrial means such as distillation, extraction, liquid separation, and filtration. It can be removed by a method of separating ions such as a dialysis method or an electrodialysis method or a method of separating ions based on a difference in molecular size.
In each case, commercially available polyvinyl acetal is dissolved in pure water or a mixed solvent of pure water and methanol and purified in a solution state. The ion exchange method uses an anion exchange resin and a cation exchange resin, or an anion exchange membrane and a cation exchange membrane, or an anion exchange agent such as an acetate ion or a chloride ion using an anion exchange fiber and a cation exchange fiber. ) To hydroxyl ion,
Further, salts such as sodium acetate and acids such as acetic acid are removed in such a manner that cations (bases) such as sodium ions are replaced with hydrogen ions. Since an anion exchange resin is generally commercially available in a state in which chloride ions are bonded, the chlorine ions are replaced with, for example, hydroxyl ions with a 1N aqueous solution of sodium hydroxide, and are sufficiently washed with pure water before use. Cation exchange resins are generally commercially available with sodium or hydrogen ions bound thereto. For example, sodium ions are replaced with hydrogen ions in a 3N aqueous solution of hydrogen chloride and sufficiently washed with pure water before use. In the case of an ion-exchange resin to which hydrogen ions are bonded, the resin is similarly treated with a hydrogen chloride solution and used. The ion exchange resin may be used by filling an anion exchange resin and a cation exchange resin in separate columns, or may be used by mixing and filling one column. The degree of saponification of the water-soluble polyvinyl acetal varies depending on the degree of acetalization, the degree of polymerization, and the alkyl group of the aldehyde which is an acetalizing agent, but about 3 to 15% by weight of an aqueous solution or a mixed solution of methanol and water is about 0.5 to 10 cc / min. A pure water-soluble polyvinyl acetal solution having a concentration of an acid group and a base of 100 ppm or less can be obtained by treating at a column development speed of. The dialysis method is performed using a dialysis membrane such as a cellophane membrane, a collodion membrane, a sulfuric acid paper, an acetylcellulose membrane, a protein membrane, and a synthetic resin membrane. Since it has dissolved, wash it thoroughly with pure water to remove glycerin, etc. to make holes of several tens of kilometres, treat with zinc chloride or sodium hydroxide aqueous solution to adjust the pore size (expand), and wash again thoroughly Used. The solution of the water-soluble polyvinyl acetal is wrapped in the cellophane tube or sheet treated as described above, tied with a nylon thread or the like, and suspended in a 50 to 100 times stirring stirred pure water tank. A pure water-soluble polyvinyl acetal solution can be obtained by replacing the pure water with fresh water 4 to 5 times every 5 to 20 hours. In the electrodialysis method, an electrode made of a material having a low ionization tendency, such as platinum, is placed between the polyvinyl acetal solution side and the pure water side of the above dialysis method, and a current is made to flow by using the polyvinyl acetal side as the electrode and the pure water side as the electrode. Remove the ion (base), then replace the pure water tank with a new one, remove the anion (acid group) by passing current with the polyvinyl acetal side as the electrode and the pure water side as the electrode, and remove the pure polyvinyl acetal. It is a method of obtaining a solution. In any case, in both methods using the dialysis membrane, since water enters by osmotic pressure, it is necessary to adjust the solid concentration of the polyvinyl acetal after the treatment. The basic structure of the photoreceptor of the present invention is such that a water-soluble polyvinyl acetal intermediate layer 2 is formed on a conductive substrate 1 as shown in FIG.
And a monolayer type photosensitive layer 3 and, as shown in FIG. 2, a laminated type photosensitive layer comprising a conductive substrate 1, a water-soluble polyvinyl acetal intermediate layer 2, a charge generation layer 4 and a charge transfer layer 5. This is provided with a layer 3 '. In the present invention, in order to prevent light interference required for a photoreceptor for a printer using a laser light source, as shown in FIGS. A light-scattering or light-sucking undercoat layer 6 can be inserted between the substrate and the intermediate layer 2. Next, each constituent material used in the present invention will be described. The conductive substrate is a layer intended to supply a charge having the opposite polarity to the charge to the substrate side, and has an electric resistance of 10 ⁸ Ωcm.
The following materials are used that can withstand the film forming conditions of each intermediate layer and photosensitive layer. Examples of these materials include Al, N
i, Cr, Zn, stainless steel and other electrically conductive metals and alloys, as well as inorganic insulating materials such as glass and ceramics, and organic insulating materials such as polyester, polyimide, phenolic resin, nylon resin, and paper. Examples thereof include those which are coated with a conductive material such as Al, Ni, Cr, Zn, stainless steel, carbon, SnO ₂ , In ₂ O _{3 and the} like and subjected to a conductive treatment by a method such as sputtering or spray coating. The water-soluble polyvinyl acetal-based intermediate layer prevents charge injection from the conductive substrate to the photosensitive layer during charging of the photoconductor,
It has the function of maintaining the chargeability and moving one of the charge pairs generated in the photosensitive layer during exposure to the photoreceptor, that is, the charge of the opposite polarity to the charge blocked on the conductive substrate side, to the conductive substrate side. In particular, when the photosensitive layer has a high sensitivity, the chargeability of the photosensitive layer is deteriorated, which is necessary. This intermediate layer is formed by applying a solution of high-purity polyvinyl acetal obtained as described above on a substrate. An appropriate thickness is 0.2 to 2 μm. The single-layer type photosensitive layer is a layer for forming a latent image charge by image exposure. This type of photosensitive layer includes photoconductive powders such as dye-sensitized zinc oxide, titanium oxide and zinc sulfide, selenium powder, amorphous silicon powder, polyvinyl carbazole, phthalocyanine pigment, oxadiazole pigment, azo A pigment or the like is applied and formed on the intermediate layer together with a binder resin and / or an electron-donating compound described below, if necessary. Further, a single-layer type photosensitive layer can be formed by using a composition in which an electron-donating compound is added to a eutectic complex formed from a pyrylium-based dye and a bisphenol A-based polycarbonate. As the binder resin, the same resin as that of the laminated photosensitive layer described later is used. An appropriate thickness is 5 to 30 μm. On the other hand, in the case of a laminated photosensitive layer, the charge generation layer is a layer for the purpose of generating and separating a latent image charge by image exposure. The charge generation layer is formed by applying an organic facial cleanser, crystalline selenium, arsenic selenide, or the like as a charge generation material on the intermediate layer together with a binder resin. As organic pigments, phthalocyanine pigments, disazo pigments, trisazo pigments,
There are perylene pigments, squaric salt dyes, azulenium salt dyes, quinone condensed polycyclic compounds, and the like. Among them, disazo pigments and trisazo pigments are preferable, and specific examples thereof include the following. Examples of the binder resin used in combination with these organic pigments include condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polycarbonate, and polyether, and polystyrene, polyacrylate, polymethacrylate, poly-N-vinylcarbazole, and polyvinyl. Butyral, styrene-butadiene copolymer, styrene-
Adhesive and insulating resins such as polymers and copolymers such as acrylonitrile copolymers are included. The content of the organic dye / pigment is preferably from 60 to 100% by weight. When an organic dye or pigment is used, the thickness of the charge generation layer is suitably 0.05 to 0.5 μm. When crystalline selenium or arsenic selenide alloy particles are used, they are used in combination with an electron donating binder and / or an electron donating organic compound. Examples of such an electron donating substance include polyvinyl carbazole and derivatives thereof (for example, those having a carbazole skeleton having a halogen such as chlorine or bromine, a substituent such as a methyl group or an amino group), polyvinyl pyrene, oxadiazole, pyrazoline, and hydrazone. ,
There are nitrogen-containing compounds such as diarylmethane, α-phenylstilbene, and triphenylamine compounds, and diarylmethane compounds, and polyvinyl carbazole and its derivatives are particularly preferable. Further, these substances may be used as a mixture. Also in the case of mixing and using, it is preferable to add another electron donating organic compound to polyvinyl carbazole and its derivative. The content of such an inorganic charge generating substance is suitably from 30 to 90% by weight of the whole layer. When an inorganic charge generation material is used, the thickness of the charge generation layer is suitably 0.2 to 5 μm. The charge transfer layer provided on the charge generation layer is a layer for holding the charge on the surface thereof, and transferring and separating the charge generated and separated in the charge generation layer by exposure to the held charge. It is. High electrical resistance is required to achieve the purpose of retaining the charged electric charge, and in order to achieve the purpose of obtaining a high surface potential with the retained charged electric charge, a low dielectric constant and good charge mobility are required. Required. To satisfy these requirements, an organic charge transfer layer containing an organic charge transfer material as an active ingredient is used. Examples of the organic charge transfer material include poly-N-vinylcarbazole compounds, pyrazoline compounds, α-phenylstilbene compounds, hydrazone compounds, diarylmethane compounds, triphenylamine compounds, divinylbenzene compounds, and fluorene. Conventionally known compounds such as a compound based on anthracene, an anthracene based compound, an oxadiazole based compound and a diaminocarbazole based compound can be used. These organic charge transfer materials other than polymers such as polyvinyl carbazole are used together with a resin similar to the binder resin for the charge generation layer such as polycarbonate and silicone oil as a binder. In addition, a plasticizer is added to these as needed. Examples of such a plasticizer include polymers and copolymers of halogenated paraffin, dimethylnaphthalene, dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, and the like, and polyester. The charge transfer layer is formed by applying a solution in which the above components are dissolved on the charge generation layer.
The thickness of the charge transfer layer is suitably from 5 to 30 μm. The weight ratio of the charge transfer material to the binder is suitably 2/8 to 8/2. The amount of silicone oil used is suitably from 0.001 to 1% by weight of the binder. The light-scattering undercoat layer and the light-absorbing undercoat layer are layers for preventing light interference in the photoreceptor for a printer as described above, and the light-scattering undercoat layer is made of a conductive material such as tin oxide and antimony oxide. A powder and a white pigment such as titanium oxide, zinc oxide, zinc sulfide and the like are dispersed in a thermosetting resin as described below. The light-absorbing undercoat layer is made of, for example, a conductive light such as carbon or various metals. It is constituted by dispersing an absorbing pigment and / or a light absorbing organic pigment in a similar thermosetting resin. The thermosetting resin used here is, for example, active hydrogen (—OH group, —NH ₂
And a compound containing a plurality of isocyanate groups and / or a compound containing a plurality of epoxy groups. Examples of the compound containing a plurality of active hydrogen include, for example, polyvinyl butyral, phenoxy resin, phenol resin, polyamide, acrylic resin containing active hydrogen such as hydroxyethyl methacrylate group, and the like.
Examples of the compound containing a plurality of isocyanate groups include tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, and prepolymers thereof, and the compound containing a plurality of epoxy groups is bisphenol A type epoxy resin. Is raised. In any case, the light-scattering or light-absorbing undercoat layer is formed by applying a solution in which the above components are dissolved or dispersed on a substrate and thermally polymerizing the solution at 50 to 200 ° C. The thickness of the undercoat layer is suitably from 1 to 10 μm. The weight ratio of the conductive powder, the white pigment and the thermosetting resin is suitably from 2 to 6/1 to 5/2 to 6, and the conductive light-absorbing pigment and / or the light-absorbing organic pigment are suitable. The weight ratio of the thermosetting resin to the thermosetting resin is suitably from 4 to 9/1 to 6. Hereinafter, the present invention will be described with reference to examples. Example 1 A 10% by weight aqueous solution of a commercially available water-soluble polyvinyl acetal (Eslec W201, manufactured by Sekisui Chemical Co., Ltd.) was ion-exchanged as shown in FIG. 5 (where 7 is a high-purity water-soluble polyvinyl acetal aqueous solution, and 8 is a drop-adjustment). A valve, 9 an anion exchange resin, 10 a cation exchange resin, 11 an aqueous solution of a commercially available water-soluble polyvinyl acetal, 12 a pressure regulating valve, 13
Was processed by passing through N ₂ gas for pressurization to produce a high-purity water-soluble polyvinyl acetal aqueous solution of about 10% by weight. As an anion exchange resin, Dowex MS Dowex MS
About 80 cc of A-1 and about 80 cc of Dowex 50W as the cation exchange resin.
/ Min. Analysis result (content per solid: unit = ppm): It is therefore expected that untreated commercial water-soluble polyvinyl acetal will contain about 2.4% by weight of sodium acetate and about 1.1% by weight of sodium chloride. In comparison, the high-purity water-soluble polyvinyl acetal after treatment contains sodium acetate and sodium chloride in a total amount of 0.001.
1% by weight or less, and acetic acid and hydrochloric acid in a total amount of 0.05% by weight
The following will be included. As a result of estimating the acetyl group content from the results of analysis by gas chromatography, it was found that the degree of saponification did not change before and after the treatment. Next, the following intermediate layer coating liquid was prepared using the high-purity water-soluble polyvinyl acetal aqueous solution. Also, a mixed solution of 100 parts by weight of a 10% by weight aqueous solution of the untreated commercially available polyvinyl alcohol and 67 parts by weight of methanol was prepared as a comparative coating liquid-7. Next, the coating liquids 1 to 7 are each dip-coated on a 0.3 mm-thick Al plate which has been washed with perclene vapor, and dried at 130 ° C. for 10 minutes to form a 1 μm-thick water-soluble polyvinyl acetal intermediate layer. did. The composition of this intermediate layer is as follows. On the other hand, in a 15 cm φ glass pot, 1 cm
φ stainless steel ball, 400g cyclohexanone and 25g
The above azo pigment 1 was charged and milled for 48 hours. After further adding 408 g of cyclohexanone and milling for an additional 24 hours, 800 g of tetrahydrofuran was added dropwise with stirring to 800 g of the dispersion solution taken out to obtain a coating liquid-8 for charge generation layer. Next, this coating liquid-8 was applied onto the intermediate layer by dip coating.
After drying at 0 ° C. for 10 minutes, a charge generating layer having a thickness of about 0.1 μm was formed. Subsequently, a coating liquid 9 for a charge transfer layer having the following formulation was dip-coated on the charge generation layer, dried at 130 ° C. for 1 hour, and dried to a thickness of 21 μm.
A thick charge transfer layer was formed. Each photoreceptor prepared as described above was subjected to low temperature and low humidity (10
C, 15%) and high-temperature, high-humidity (30 ° C, 90%) measurement environment.
After charging with a −6 KV corona discharge for 20 seconds using a mold), the surface potential Vm of the photoreceptor was measured, and after leaving it in a dark place for 20 seconds, the surface potential Vpo was measured. Next, a tank stainless lamp light is applied so that the illuminance on the photoreceptor surface becomes 4.5 lux, and the exposure amount E1 / 2 until Vpo becomes 1/2.
And the residual surface potential Vr after irradiation for 30 seconds. In order to know the repetitive fatigue characteristics, charging at -7.5 KV and exposure at 30 lux were repeated for 1 hour with the above equipment, and the surface electric area Vm ', surface potential Vpo', exposure amount E1 / 2 'and residual amount after fatigue were repeated. The surface potential Vr 'was measured. Table-Results under low temperature and low humidity
Table 1 shows the results under high temperature and high humidity. Example 2 In a 15 cmφ glass pot, 400 g of the following resin solution of 1 cmφ agate ball and 1/2 g of the volume, and 25 g of the azo pigment No. 47
And milled for 48 hours. After additionally charging 580 g of the resin solution and milling for an additional 24 hours, 950 g of methyl ethyl ketone was stirred while stirring 950 g of the dispersion solution taken out.
Was dropped to obtain a coating liquid for charge generation layer-10. Resin solution Polyvinyl butyral (trade name, manufactured by XYHL Union Carbide) 10 parts by weight Cyclohexanone 970 parts by weight Next, this coating liquid-10 was used in place of the coating liquid-8 for the charge generation layer in the same manner as in Example 1. Thus, a photoreceptor was prepared, and the electrical characteristics under high temperature and high humidity were similarly measured. Table 3 shows the results. Example 3 A 100 μm thick aluminum terephthalate film on which aluminum was vacuum-deposited was coated with a coating liquid-1 with a wet gap of 50 μm on an Al-deposited surface, dried at 120 ° C. for 10 minutes, and dried to a thickness of about 1.5 μm. A μm intermediate layer was formed. Next, a coating liquid-8 was coated on this intermediate layer with a wet gap of 50 [mu] m and dried at 120 [deg.] C. for 10 minutes to form a charge generating layer having a thickness of about 0.1 [mu] m. Further, a coating liquid-9 was coated on the charge generation layer with a wet gap of 200 μm by using a blade.
For 20 minutes to form a charge transfer layer having a thickness of about 20 μm, thereby forming a photoreceptor. This photoreceptor is affixed to an 80 mmφ Al drum and the FT4060
It was set in a copying machine manufactured by Ricoh Co., Ltd., and copying was carried out. As a result, a beautiful black image without background stains was obtained, in which the background, particularly the white solid image, was uniformly white. here
The FT4060 used a charging and electrophotographic charger and a developing bias power supply modified to a negative polarity, and used a two-component developer containing a positively charged toner. Next, after removing the developer from the copier and repeating the operation equivalent to 10,000 copies, except for the development and transfer processes, the developer was attached again and the image was copied.When the image was copied, the same clean copy as the initial one was obtained. Was. Comparative Example 1 A photoconductor was prepared in the same manner as in Example 3 except that the coating liquid-7 was used for coating the intermediate layer, and image copying, electrostatic repetition and post-repetition were performed in the same manner as in Example 3. When the image was copied, the background portion, especially the solid white image portion, was beautifully copied as in Example-3. However, the copy image after repeated copying for 10,000 copies was particularly soiled with the solid white portion. Was observed. Example 4 In a 9 cmφ glass pot, a sintered alumina ball of 1 cmφ of 1/2 volume, 8 g of tin oxide fine powder containing 10 wt% of antimony oxide, 5 g of titanium oxide powder, and a butyral resin having a solid concentration of 12 wt% (Sekisui 65 g of a methyl ethyl ketone solution of BL-1) was milled for 72 hours, and then 47 g of methyl ethyl ketone was added and milled for 45 hours. Next, 8 parts by weight of a 20 wt% solution of triene diisocyanate in methyl ethyl ketone was added to 80 parts by weight of the removed pigment dispersion, followed by stirring to obtain a light-scattering undercoat layer coating liquid. The coating solution was applied on the same Al substrate as in Example 1 by dip coating, and was heated and cured at 130 ° C. for 1 hour to form a light-scattering undercoat layer having a thickness of about 3 μm. Next, an intermediate layer, a charge generation layer and a charge transfer layer were formed on the undercoating layer in the same manner as in Example 2 to prepare a photoreceptor. Thereafter, the electrical characteristics of this photoreceptor were measured in the same manner as in Example 1 under high temperature and high humidity.
Table 4 shows the results. Result Since the intermediate layer of the photoreceptor of the present invention is composed of the high-purity water-soluble polyvinyl acetal as described above, it has high chargeability, high light extinction sensitivity, and low residue even at high temperature and high humidity as well as at low temperature and low humidity. It has an advantage that it shows a potential and there is little change in electrical characteristics due to the environment.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 are structural views of an example of the photoreceptor of the present invention, and FIG. 5 is a sectional view of an ion exchange column used in Example 1. 1 conductive substrate 2 water-soluble polyvinyl acetal intermediate layer 3 single-layer photosensitive layer 3 ′ laminated photosensitive layer 6 composed of charge generation layer 4 and charge transfer layer 5 light scattering or Light-absorbing undercoat layer 7: high-purity water-soluble polyvinyl acetal aqueous solution 9: anion exchange resin, 10: cation exchange resin 11: commercially available water-soluble polyvinyl acetal aqueous solution

Claims (1)

(57) [Claims] In an electrophotographic photoreceptor in which an intermediate layer and a photosensitive layer are sequentially provided on a conductive substrate, the intermediate layer contains water-soluble polyvinyl acetal as a main component, and acetic acid contained as an impurity of the polyvinyl acetal in the intermediate layer. An electrophotographic photoreceptor, wherein the amount of the acid and / or the alkali metal salt thereof is set to 0.5% by weight or less of the intermediate layer. 2. The light-scattering or light-absorbing undercoat layer comprising a white pigment or a light-absorbing pigment and a thermosetting resin as main components between the substrate and the intermediate layer. Photoconductor. 3. 3. The photoreceptor according to claim 1, wherein the intermediate layer mainly comprises a water-soluble polyvinyl acetal containing 0.5% by weight or less of sodium acetate and sodium chloride.