JPH03135576A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve photosensitive characteristics and mechanical strength by forming a surface protecting layer with a soln. contg. thermosetting silicone resin, methyl-etherified and/or methyl and butyl-etherified melamine- formaldehyde resin and thermoplastic resin but not contg. an electrical conductivity rendering agent. CONSTITUTION:A photosensitive layer is coated with a coating soln. contg. thermosetting silicone resin, 25-100 pts. wt. methyl-etherified and/or methyl and butyl mixed etherified melamine-formaldehyde resin basing on 100 pts. wt. nonvolatile solid matter in the silicone resin and 10-20 wt.% thermoplastic resin basing on the total amt. of the nonvolatile solid matter in the silicon resin and the etherified melamine-formaldehyde resin but not contg. an electrical conductivity rendering agent and the coating soln. is hardened to form a surface protecting layer. No harmful influence is exerted on photosensitive characteristics and the formed surface protecting layer has high surface hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a surface protective layer.

<Prior Art> In an image forming apparatus such as a copying machine that utilizes the so-called Carlson process, an electrophotographic photoreceptor in which a photosensitive layer is formed on a conductive base material is used.

Electrophotographic photoreceptors are repeatedly subjected to electrical, optical, and mechanical shocks during the image forming process, so in order to improve their durability against these shocks, a surface made of a binder resin is added on top of the photosensitive layer. Lamination of protective layers is practiced.

As the binder resin, a thermosetting silicone resin is mainly used in order to improve the hardness of the surface protective layer. However, using the thermosetting silicone resin alone has problems such as being brittle against sliding friction and being easily damaged.

Therefore, electrophotographic photoreceptors that use a combination of thermosetting silicone resin and thermoplastic resin such as polyvinyl acetate as a binder resin for the surface protective layer (see Japanese Patent Application Laid-open No. 18354/1983), and thermosetting silicone An electrophotographic photoreceptor using a resin and a butyl etherified melamine/formaldehyde resin has been proposed (see Japanese Patent Laid-Open No. 63-2071).

<Problem to be solved by the invention> However, in the former combination system, the sensitivity of the photoreceptor is not sufficient, and the surface hardness is lower than in the case of using thermosetting silicone resin alone, making it more susceptible to damage. In addition to problems with the physical properties of the surface protective layer, especially in systems that use polyvinyl acetate in combination with thermosetting silicone resin, the coating solution used to form the surface protective layer lacks stability, resulting in a short pot life. There was also a problem that whitening of the film would occur if too much was used.

On the other hand, in the latter combined system, the resins that make up the system are all thermosetting resins that form a three-dimensional structure with high hardness when cured, so the formed surface protective layer has a high surface hardness. However, because the compatibility between the silicone site and the melamine site in the layer is not sufficient, there are many voids between the two sites that act as structural traps, resulting in poor charging characteristics and repeated exposure. There was a risk that the photosensitive characteristics of the electrophotographic photoreceptor would be adversely affected, such as a decrease in potential stability.

According to the studies of the present inventors, instead of the butyl etherified melamine/formaldehyde resin, methyl etherified melamine/formaldehyde resin or methyl-butyl mixed etherified melamine/formaldehyde resin (hereinafter, the above two are collectively referred to as "specific In the combination system using etherified melamine◆formaldehyde resin J),
The specific etherified melamine/formaldehyde resin has higher crosslinking properties than conventional butyl etherified melamine/formaldehyde resins, and does not covalently bond with the SL -OH group of the thermosetting silicone resin during curing. It was found that because a sufficiently large molecular interaction occurs with the group, the compatibility between the silicone site and the melamine site in the layer is improved, and a dense film with fewer structural traps can be formed. In addition, in the above combination system, it is assumed that the conductivity of the layer is improved by the aromatic π electrons of melamine, so it is possible to incorporate a large amount of melamine/formaldehyde resin. When blending exceeds 15 parts by weight in the case of methyl etherified melamine/formaldehyde resin and 30 parts by weight in the case of methyl-butyl mixed etherified melamine/formaldehyde resin, based on 100 parts by weight of volatile solids. had a problem in that the interaction with the thermosetting silicone resin was too strong, causing internal stress in the surface protective layer and causing cracks and the like.

Therefore, after further consideration, we found the above crack,
Structural traps, clouding of the layer, damage caused by sliding friction, etc. that occur between the silicone site and the melamine site are dispersed in the surface protective layer in order to facilitate charge injection into the underlying layer during the image forming process. It has been found that this is facilitated by conductive metal oxide particles as a conductivity imparting agent. This means that the conductive metal oxide particles are
The main cause is considered to be that the continuity of the layer is inhibited because the physical properties such as expansion and contraction rate are significantly different from those of the resin constituting the layer.

The present invention was made in view of the above circumstances, and does not adversely affect the photosensitive characteristics, physical properties, etc. of an electrophotographic photoreceptor, and is less brittle against sliding friction than a thermosetting silicone resin alone. It is an object of the present invention to provide an electrophotographic photoreceptor having a surface protective layer with improved conductivity.

Means for Solving the Problems> In order to solve the above problems, the electrophotographic photoreceptor of the present invention includes a thermosetting silicone resin and a thermosetting silicone resin containing 100 parts by weight of non-volatile solids of the thermosetting silicone resin. te25~1
00 parts by weight of methyl etherified melamine/formaldehyde resin and/or methyl-butyl mixed etherified melamine/formaldehyde resin, based on the total amount of the non-volatile solid content of the thermosetting silicone resin and etherified melamine/formaldehyde resin. It is characterized by having a surface protective layer formed by applying a coating liquid containing 10 to 20% by weight of a thermoplastic resin and not containing a conductivity imparting agent onto the photosensitive layer and curing the coating liquid.

In the electrophotographic photoreceptor of the present invention having the above configuration, the specific etherified melamine/formaldehyde resin contained in the coating liquid has higher crosslinking properties than the conventional butyl etherified melamine/formaldehyde resin, and upon curing, Although it does not covalently bond with the St -OH group of the thermosetting silicone resin, it creates a sufficiently large molecular interaction with the 5LOH group, improving the compatibility between the silicone site and the melamine site in the layer. However, a dense film with few structural traps is formed. In addition, the coating solution does not contain conductivity imparting agents (conductive metal oxide particles) that inhibit layer continuity, and the thermoplastic resin contained in the coating solution In the protective layer, it acts as a buffer to reduce internal stress, so
Even if a larger amount of the specified etherified melamine formaldehyde resin is blended into the layer, there is no risk of cracks occurring, and the conductivity of the layer is improved by the large amount of aromatic π electrons based on the specified etherified melamine formaldehyde resin. It is estimated that further improvements can be made. Therefore, the electrophotographic photoreceptor of the present invention has excellent photosensitivity. In addition, as mentioned above, the main components of the layer are a thermosetting silicone resin that forms a three-dimensional structure when cured, and a specific etherified melamine/formaldehyde resin, so the surface protective layer after curing has a low surface hardness. It gets expensive. Moreover, as mentioned above, both resins are highly compatible;
After curing, the three-dimensional structure becomes complex,
Together with the provision of elasticity by the thermoplastic resin and the improvement of layer continuity by not containing a conductivity imparting agent,
Compared to the case of using thermosetting silicone resin alone, the brittleness against sliding friction is improved.

In addition, the content of the specific etherified melamine/formaldehyde resin is 25 to 100 parts by weight based on 100 parts by weight of the non-volatile solid content of the thermosetting silicone resin in the coating solution.
Within the range of parts by weight, the content ratio of the thermoplastic resin is limited to within the range of 10 to 20% by weight of the total amount of the non-volatile solid content of the silicone resin and the specific etherified melamine/formaldehyde resin. is due to the following reasons.

In other words, if the content of the specific etherified melamine/formaldehyde resin is less than 25 parts by weight, problems such as brittleness against sliding friction will occur in the surface protective layer after curing, regardless of the content ratio of the thermoplastic resin, and the layer will also deteriorate. The photosensitive characteristics deteriorate due to a lack of aromatic π electrons.

On the other hand, if the formaldehyde resin content in the specified etherified melamine exceeds 100 parts by weight, the interaction with the thermosetting silicone resin will be too strong, causing internal stress in the surface protective layer regardless of the blending ratio of the thermoplastic resin. This causes cracks and the like, making it impossible to obtain a clean surface protective layer.

Moreover, if the content ratio of the thermoplastic resin is less than 10% by weight,
The higher the content of the specific etherified melamine/formaldehyde resin, the more internal stress will be generated in the surface protective layer, and cracks will occur, making it impossible to obtain a clean surface protective layer.

If the content of the thermoplastic resin exceeds 20% by weight, the surface protective layer will become softened, and the lower the content of the specific etherified melamine/formaldehyde resin, the more clouding and deterioration of photosensitivity will occur.

The thermosetting silicone resin contained in the coating solution includes tetraalkoxysilane, trialkoxyalkylsilane,
Silane-based compounds such as organosilanes such as dialkoxydialkylsilanes, organo/Xlogensilanes such as trichloroalkylsilanes and dichlorodialkylsilanes,
A hydrolyzate (so-called organopolysiloxane) of a single substance or a mixture of two or more thereof, or an initial condensation reaction product thereof, is dissolved or dispersed in a solvent as a non-volatile solid content, and is a non-volatile solid content of a hydrolyzate (so-called organopolysiloxane) or a mixture of two or more thereof, dissolved or dispersed in a solvent. Examples of groups include methoxy group, ethoxy group, impropoxy group, t
-Butoxy group, glycidoxy group, methyl, ethyl, etc.
Examples include lower groups having about 1 to 4 carbon atoms.

Among the specific etherified melamine/formaldehyde resins used in combination with the above thermosetting silicone resin, methyl etherified melamine/formaldehyde resin is a mono- or hexa-methylol melamine that is a reaction product of melamine and formaldehyde. It is preferably used that is partially or entirely methyl etherified or its initial condensation reaction product, and is supplied in a liquid or syrup state.

The number average molecular weight of the methyl etherified melamine/formaldehyde resin is not particularly limited in this invention;
If it exceeds 500, the reactivity decreases, so the number average molecular weight is preferably 1,500 or less. Moreover, the number of bound formaldehydes per melamine nucleus in the resin is 3 to 6, and it is preferable that 3 to 6 of them are methyl etherified. If the number of bound formaldehydes per melamine nucleus is less than 3, there is a risk that the surface protective layer will have poor mechanical strength. Furthermore, if the number of methyl etherified formaldehydes is less than three, the coating solution for the surface protective layer may lack stability.

On the other hand, the methyl-butyl mixed etherified melamine/formaldehyde resin is one in which at least one of the methylol groups in the mono- or hexa-methylol melamine is methyl etherified and at least one of the remaining methylol groups is butyl etherified, or an initial condensation thereof. It is a reactant, and those supplied in a liquid or syrupy state are preferably used.

The number average molecular weight of the secondary methyl-butyl mixed etherified melamine/formaldehyde resin is not particularly limited in the present invention, or if it exceeds 1,500, the reactivity decreases, so the number average molecular weight is preferably 1,500 or less. In addition, the above resin has 3 to 6 formaldehyde bonds per melamine nucleus, of which 2 to 5
It is preferable that 1 or 2 are methyl etherified and 1 or 2 are butyl etherified. If the number of bound formaldehydes per melamine nucleus is less than 3, the surface protective layer may have poor mechanical strength. Furthermore, if the number of methyl etherified formaldehydes is less than 2, the surface potential will decrease significantly due to repeated exposure, and if it exceeds 5, cracks may easily occur.

Furthermore, if the number of butyl etherified particles is less than one, cracks are likely to occur, and if it exceeds three, there is a risk that the surface potential will decrease significantly due to repeated exposure.

Note that each of the above-mentioned curable resins can be cured by simply heating without using a catalyst depending on the conditions.
Usually, a catalyst is often used to complete the curing reaction smoothly and uniformly.

As the curing catalyst, various catalysts can be used, such as inorganic acids, organic acids, and alkalis such as amines.

Further, if necessary, a conventionally known curing aid or the like can be used in combination.

The thermoplastic resins contained in the surface protective layer together with the thermosetting silicone resin and the specific etherified melamine/formaldehyde resin include styrene polymers; acrylic polymers; styrene-acrylic copolymers; polyethylene, ethylene- Olefin polymers such as vinyl acetate copolymers, chlorinated polyethylene, polypropylene, and ionomers; polyvinyl chloride; vinyl chloride-vinyl acetate copolymers; polyvinyl acetate; saturated polyesters; polyamides; thermoplastic polyurethane resins; polycarbonates; Various synthetic resin materials can be used, such as arylate, polysulfone, ketone resin, polyvinyl butyral resin, and polyether resin, but polyvinyl acetate and acrylic polymers are particularly preferably used.

In systems using polyvinyl acetate as the thermoplastic resin, the flexibility of polyvinyl acetate improves the brittleness of the surface protective layer, improves mechanical strength, and makes it possible to extend the lifespan.

On the other hand, polymethyl methacrylate (
In a system using an acrylic polymer such as PMMA), further photosensitivity can be achieved based on the high optical properties of the acrylic polymer.

In addition, the above polyvinyl acetate and acrylic polymer are
Each can be used alone or both can be used in combination, and it is also possible to mix other thermoplastic resins.

Examples of solvents for dissolving or dispersing the above components to form a coating solution for the surface protective layer include isopropyl alcohol; aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane; benzene, toluene, and xylene; Aromatic hydrocarbons; halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether; acetone, methyl ethyl ketone, cyclohexanone, etc. Ketones; esters such as ethyl acetate and methyl acetate; dimethylformamide; dimethyl sulfoxide; these may be used alone or in combination of two or more.

As the binder resin constituting the surface protective layer, thermosetting resins other than those mentioned above can be used in combination as long as the properties of the film are not impaired. Other thermosetting resins other than those mentioned above include curable acrylic resins; alkyd resins; unsaturated polyester resins; diallyl phthalate resins; phenol resins; urea resins; benzoguanamine resins; melamine resins other than specific etherification type and butyl etherification type. is exemplified.

The surface protective layer contains conventionally known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene;
Fluorene compounds such as N-diphenylhydrazino)fluorene and 9-rubazolyliminofluorene; Conductivity imparting agents; Deterioration inhibitors such as amine-based and phenol-based antioxidants, and benzophenone-based ultraviolet absorbers. ; Various additives such as plasticizers can be contained.

The thickness of the surface protective layer is 0.1 to 10 μm, particularly 2 to 10 μm.
It is preferably within the range of 5μ.

The photoreceptor of the present invention can be constructed using the same materials as the conventional photoreceptor except for the surface protective layer.

First, the conductive base material will be described.

The conductive base material is formed into an appropriate shape, such as a sheet shape or a drum shape, depending on the mechanism and structure of the image forming apparatus in which the electrophotographic photoreceptor is installed.

Further, the conductive base material may be entirely composed of a conductive material such as metal, or the base material itself may be formed of a structural material that does not have conductivity, and its surface may be imparted with conductivity. .

In addition, the conductive materials used in the conductive base material having the former structure include those whose surfaces are alumite-treated,
Alternatively, metal materials such as untreated aluminum, copper, tin, platinum, gold, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass are preferred.

On the other hand, in the latter structure, a thin film made of a conductive material such as the above-mentioned metal, aluminum iodide, tin oxide, or indium oxide is deposited on the surface of a synthetic resin base material or a glass base material using a vacuum evaporation method or A structure in which a film of the above-mentioned metal material is laminated on the surface of the above-mentioned synthetic resin molded product or glass base material, a structure in which a film of the above-mentioned metal material, etc. is laminated on the surface of the above-mentioned synthetic resin molded product or glass base material, etc. An example is a structure in which a substance imparting conductivity is injected into the surface.

Note that the conductive base material may be surface-treated with a surface treatment agent such as a silane coupling agent or a titanium coupling agent to improve adhesion to the photosensitive layer, if necessary.

Next, the photosensitive layer formed on the conductive substrate will be described.

The photosensitive layer can be made of a semiconductor material, an organic material, or a composite material thereof and has the following structure.

■ Single-layer photosensitive layer made of semiconductor material.

■ A single-layer organic photosensitive layer containing a charge-generating material and a charge-transporting material in a binder resin.

■ A laminated organic photosensitive layer consisting of a charge generation layer containing a charge generation material in a binder resin and a charge transport layer containing a charge transport material in a binder resin.

(2) A composite photosensitive layer in which a charge generation layer made of a semiconductor material and the organic charge transport layer described above are laminated.

Semiconductor materials that can be used as a charge generation layer in a composite photosensitive layer and can also form a photosensitive layer by themselves include:
For example, amorphous chalcogenides such as a-As2Sei, a-5eAsTe, amorphous selenium (
a-Se) and amorphous silicon (a-3t). The photosensitive layer or charge generation layer made of the above semiconductor material can be formed by a known thin film forming method such as a vacuum deposition method or a glow discharge decomposition method.

Organic or inorganic charge-generating materials used in the charge-generating layer in single-layer or laminated organic photosensitive layers include:
For example, powders of semiconductor materials as exemplified above: n-vt group fines such as ZnO1cdS; biryllium salts; azo compounds; bisazo compounds; phthalocyanine compounds: anthanthrone compounds; perylene compounds; indigo compounds;
Examples include triphenylmethane compounds; thren compounds; toluidine compounds; pyrazoline compounds; quinacridone compounds; and pyrrolovirol compounds. and,
Among the above-exemplified compounds, aluminum phthalocyanine, copper phthalocyanine, metal-free phthalocyanine, oxotitanyl phthalocyanine, etc., which belong to phthalocyanine compounds and have various crystal forms such as α-type, β-type, and γ-type, are preferably used, and in particular, the above-mentioned Metal-free phthalocyanine and/or oxotitanyl phthalocyanine are more preferably used. Note that the charge generating materials described above may be used alone or in combination.

Further, as the charge transport material contained in the charge transport layer in the single layer type or multilayer type organic photosensitive layer or the composite type photosensitive layer, for example, tetracyanoethylene; 2,4.7-
Fluorenone compounds such as 1-linitro-9-fluorenone; nitrated compounds such as dinitroanthracene; succinic anhydride; maleic anhydride; dibromomaleic anhydride; triphenylmethane compounds; 2,5-di(4-dimethylaminophenyl) )-Oxadiazole compounds such as 13,4-oxadiazole, styryl compounds such as 9-(4-diethylaminostyryl)anthracene; poly-N
- Carbazole compounds such as vinyl carbazole; 1-
Pyrazoline compounds such as phenyl-3-(p-dimethylaminophenyl)pyrazoline; amine derivatives such as 4',4'-tris(N,N-diphenylamino)triphenylamine; 1,1-bis( Conjugated unsaturated compounds such as 4-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene; hydrazone compounds such as 4-(N,N-diethylamino)benzaldehyde-N,N-diphenylhydrazone; indole compounds , oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, pyrazoline compounds,
Nitrogen-containing cyclic compounds such as triazole compounds; fused polycyclic compounds are exemplified. The above charge transport materials can also be used alone or in combination. Incidentally, among the above-mentioned charge transport materials, a polymeric material having photoconductivity such as the above-mentioned poly-N-vinylcarbazole can also be used as a binder resin for the photosensitive layer.

In addition, in layers such as the single layer type or laminated type organic photosensitive layer and the charge transport layer in the composite type photosensitive layer, deterioration inhibitors such as the sensitizer, fluorene compound, antioxidant, and ultraviolet absorber, Additives such as plasticizers can be included.

In the single-layer type organic photosensitive layer, the content ratio of the charge generating material to 100 parts by weight of the binder resin is preferably within the range of 2 to 20 parts by weight, particularly within the range of 3 to 15 parts by weight; The content ratio of the charge transport material to 100 parts by weight of the binder resin is within the range of 40 to 200 parts by weight, particularly 50 parts by weight.
It is preferably within the range of 100 parts by weight. This is because if the charge generation material is less than 2 parts by weight or the charge transport material is less than 40 parts by weight, the sensitivity of the photoreceptor becomes insufficient or the residual potential increases.
This is because if the amount exceeds 0 parts by weight or if the amount of the charge transport material exceeds 200 parts by weight, sufficient abrasion resistance of the photoreceptor cannot be obtained.

The single-layer type photosensitive layer can be formed to have an appropriate thickness, but it is usually preferably formed within a range of 10 to 50 μm, particularly 15 to 25 μm.

On the other hand, among the layers constituting the laminated organic photosensitive layer, the content ratio of the charge generating material in the charge generating layer to 100 parts by weight of the binder resin is within the range of 5 to 500 parts by weight, particularly 1
It is preferably within the range of 0 to 250 parts by weight. If the charge generation material is less than 5 parts by weight, the charge generation ability is too small;
This is because if the amount exceeds 0.00 parts by weight, the adhesion with other adjacent layers or the base material will decrease.

The thickness of the charge generation layer is 0.01 to 3 μm5, especially 0.01 μm to 3 μm5.
It is preferably within the range of 1 to 2 μm.

Further, among the layers constituting the laminated organic photosensitive layer and the composite photosensitive layer, the content ratio of the charge transport material to 100 parts by weight of the binder resin in the charge transport layer is within the range of 10 to 500 parts by weight, particularly It is preferably within the range of 25 to 200 parts by weight. This is because if the amount of the charge transport material is less than 10 parts by weight, the charge transport ability will not be sufficient, and if it exceeds 500 parts by weight, the mechanical strength of the charge transport layer will decrease.

The thickness of the charge transport layer is 2 to 100 μm, especially 5 to 3 μm.
It is preferably within the range of 0 μm.

The organic layers described above, such as the single-layer type or laminated type organic photosensitive layer, the charge transport layer of the composite type photosensitive layer, and the surface protective layer, are coated with each layer containing the above-mentioned components. Lamination can be formed by preparing a liquid, applying these coating liquids to the conductive substrate layer by layer in order so as to form the above-mentioned layer structure, and drying or curing the coating liquid.

In addition, when preparing the above-mentioned coating liquid, various solvents can be used depending on the type of binder resin and the like used. The above-mentioned solvents include aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane; aromatic hydrocarbons such as benzene, xylene, and toluene; halogenated hydrocarbons such as dichloromethane, carbon tetrachloride, chlorobenzene, and methylene chloride; and methyl alcohol. , ethyl alcohol, isopropyl alcohol, allyl alcohol, cyclopentanol, benzyl alcohol, furfuryl alcohol, diacetone alcohol, and other alcohols; dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, and other ethers Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; Esters such as ethyl acetate and methyl acetate; Dimethyl formamide; Dimethyl sulfoxide; used.

Further, when preparing the above coating liquid, a surfactant, a leveling agent, etc. may be used in combination to improve dispersibility, coatability, etc.

In addition, the above coating liquid can be prepared by a conventional method such as a mixer.
It can be prepared using a ball mill, paint shaker sand mill, attritor, ultrasonic dispersion machine, etc.

<Examples> The present invention will be described in more detail below based on Examples.

Examples 1 to 6, Comparative Examples 1 to 16 100 parts by weight of Boria Relay 1 (manufactured by Unitika, trade name U-100) as a binder resin, 4-(N,N-diethylamino)benzaldehyde as a charge transport material N
, 100 parts by weight of N-diphenylhydrazone and 900 parts by weight of methylene chloride (CH2Cl2) as a solvent.
■ After coating on an aluminum tube with a length of 340 m + w, it was heated and dried at 90°C for 30 minutes to form a film with a thickness of 20 μm.
A charge transport layer was formed.

Next, on the charge transport layer, 2□ as a charge generating material is applied.
80 parts by weight of 7-dibromoanthanthrone (manufactured by IC1) and metal-free phthalocyanine (manufactured by BASF)
20 parts by weight of polyvinyl acetate (manufactured by Nippon Gosei Kagaku Co., Ltd., trade name: Y5-N) as a binder resin, and 2000 parts by weight of diacetone alcohol as a solvent. It was dried by heating at 110° C. for 30 minutes to form a charge generation layer having a thickness of 0.5 μm.

Next, 57.4 parts by weight of 0.02N hydrochloric acid and 36 parts by weight of isopropyl alcohol were mixed, and the liquid temperature of the above mixture was lowered to 2.
While stirring and maintaining the temperature at 0 to 25°C, 80 parts by weight of methyltrimethoxysilane and 20 parts by weight of glycidoxypropyltrimethoxysilane were gradually added dropwise.
A silane hydrolyzate solution was obtained by standing for a period of time. Then, in this silane hydrolyzate solution, a specific etherified melamine/formaldehyde resin in the amount shown in Table 1 and the non-volatile solid content of the thermosetting silicone resin are added to the non-volatile solid content in the solution. Polyvinyl butyral (manufactured by Denki Kagaku Co., Ltd.,
A coating solution for a surface protective layer was prepared by blending the product with Denka Butyral 5000A (trade name).

Then, the coating liquid is applied onto the charge generation layer, and 11
The material was cured by heating at 0° C. for 1 hour to form a surface protective layer having a thickness of 2.5 μm, thereby producing a drum-shaped electrophotographic photoreceptor having a laminated photosensitive layer.

Examples 7 to 16, Comparative Examples 17 to 32 Instead of polyvinyl butyral, polyvinyl acetate (manufactured by Nippon Gosei Kagaku Co., Ltd., trade name Y5-N) with the blending ratio shown in Table 2 was used.
Electrophotographic photoreceptors were produced in the same manner as in Examples 1 to 6 above, except that .

Examples 17 to 28, Comparative Examples 33 to 48 Instead of polyvinyl butyral, an acrylic polymer (manufactured by Mitsubishi Rayon Co., Ltd., trade name BR-1) with a blending ratio shown in Table 3 was used.
Electrophotographic photoreceptors were produced in the same manner as in Examples 1 to 6 above, except that 05) was used.

The following tests were conducted on the electrophotographic photoreceptors produced in the above Examples and Comparative Examples.

Measurement of surface potential Each of the electrophotographic photoreceptors described above was loaded into an electrostatic copying tester (manufactured by Zientic Co., Ltd., Model 9730M machine), and its surface was positively charged to determine the surface potential V+S, p, (
■) was measured.

Each electrophotographic photoreceptor in the above-mentioned charged state was exposed to light using a No. 10 Gen lamp, which is the exposure light source of the above-mentioned electrostatic copying tester, at an exposure intensity of 0, 92 mW/c4, and an exposure time of 60 msec. Surface potential V1s, p.

Find the time required for the value to become 1/2, and calculate the half-reduction exposure ff1
E 1/2 (Iux-8ee) was calculated.

Further, the surface potential 0.4 seconds after the start of the exposure was measured as the residual potential Vr,p (V).

Abrasion resistance test Each electrophotographic photoreceptor was subjected to a drum polishing tester (manufactured by Sanda Kogyo Co., Ltd.)
At the same time, an abrasive test paper (manufactured by Sumira 3M Co., Ltd., trade name Imperial Wrapping Film, particle size 12 μm aluminum oxide powder attached to the surface) was loaded,
Apply this abrasive test paper to the surface of the photoreceptor at a linear pressure of 10 g/mm.
The amount of wear (μm) when the photoreceptor was rotated 100 times while being pressed was measured.

exterior The appearance of the surface protective layer was visually observed.

The above results are shown in Tables 1 to 3. Note that *1 to *5 in Tables 1 to 3 and Table 4 described later are as follows.

*I BEMH : Methyl-butyl mixed etherification method Lamin formaldehyde resin Methyl etherified melamine form aldehyde resin Butyl etherified melamine foam aldehyde resin MEM! (: BEMH: *2 PVB: Polyvinyl butyral PVAc: Polyvinyl acetate AC Niacrylic polymer *3 Unable to measure due to cracks.

*4 Unable to measure due to cloudiness.

(Left below) From the results in Tables 1 to 3 above, it is clear that in any of the three combination systems using polyvinyl butyral, polyvinyl acetate, and acrylic polymer as the thermoplastic resin, the non-volatile solid state of the thermosetting silicone resin The content of the specified etherified melamine/formaldehyde resin is within the range of 25 to 100 parts by weight, and the content ratio of the thermoplastic resin is equal to the non-volatile solid content of the silicone resin and the specified etherified resin. Only when the amount is within the range of 10 to 20% by weight of the total amount of melamine/formaldehyde resin, it has excellent photosensitivity, physical properties, etc., has improved brittleness against sliding friction, and has better conductivity. It has been found that an electrophotographic photoreceptor having an excellent surface protective layer can be produced.

Also, when comparing each prefecture, systems using polyvinyl acetate as thermoplastic resin have superior wear resistance compared to other systems.
It has been found that the system using an acrylic polymer has excellent photosensitive characteristics such as a half-decreased exposure amount and a small residual potential compared to other systems.

Example 29, Comparative Example 49 The silane hydrolyzate solution prepared in Examples 1 to 6 was added with 50 parts by weight of etherified melamine/formaldehyde resin based on the non-volatile solid content in the solution, and the above thermosetting resin. 9.09% by weight of acrylic polymer (manufactured by Mitsubishi Rayon Co., Ltd., product name: BR
-105) to prepare a coating solution for a surface protective layer, and then electrophotographic photoreceptors were produced in the same manner as in Examples 1 to 6 above.

The electrophotographic photoreceptors of the above examples and comparative examples were subjected to the above-described surface potential measurement, half-decrease exposure measurement, and appearance observation tests, as well as the following surface potential change after repeated exposure.

Measurement of surface potential change after repeated exposure Each of the above electrophotographic photoreceptors was used in a copying machine (manufactured by Sanda Kogyo Co., Ltd.).

After loading oc-t t into a molding machine and copying 500 sheets, the surface potential was determined to be the surface potential after repeated exposure V,
It was measured as s, p, (V).

Further, from the surface potential measurement values V, S, p, and the surface potential measurement value V2SJ after repeated exposure, the following formula (1
), the surface potential change value -ΔV<V) was calculated.

- ΔV (V) − V2 s, p, (V) V+ 5−p−(V)...
(1) The above results are shown in Table 4. (Hereinafter, blank space) From the results of Cloth 4 above, it was found that in systems using butyl etherified melamine/formaldehyde resins, which are not included in the specified etherified melamine/formaldehyde resins, the photosensitivity characteristics deteriorate significantly with repeated exposure.

<Effects of the Invention> Since the electrophotographic photoreceptor of the present invention is constructed as described above, it does not adversely affect the photosensitivity characteristics, physical properties, etc. of the electrophotographic photoreceptor, and when the thermosetting silicone resin is used alone, Compared to this, the brittleness against sliding friction has been improved,
Moreover, it has a surface protective layer with even better conductivity.

In addition, when polyvinyl acetate is used as the thermoplastic resin, the flexibility of polyvinyl acetate improves the brittleness of the surface protective layer, improves mechanical strength, and extends the service life. .

On the other hand, polymethyl methacrylate (
When an acrylic polymer such as PMMA) is used, even higher sensitivity can be achieved based on the high optical properties of the acrylic polymer.

Claims (1)

[Claims] 1. Thermosetting silicone resin and 25 to 1 part by weight per 100 parts by weight of non-volatile solid content of the thermosetting silicone resin.
00 parts by weight of methyl etherified melamine/formaldehyde resin and/or methyl-butyl mixed etherified melamine/formaldehyde resin, based on the total amount of the non-volatile solid content of the thermosetting silicone resin and etherified melamine/formaldehyde resin. an electrophotographic photosensitive layer comprising: a surface protective layer formed by applying a coating liquid containing 10 to 20% by weight of a thermoplastic resin and not containing a conductivity imparting agent onto the photosensitive layer and curing the coating liquid; body. 2. The electrophotographic photoreceptor according to claim 1, wherein the thermoplastic resin is polyvinyl acetate. 3. Thermosetting silicone resin and 25 to 1 part by weight per 100 parts by weight of non-volatile solid content of this thermosetting silicone resin.
00 parts by weight of methyl etherified melamine/formaldehyde resin and/or methyl-butyl mixed etherified melamine/formaldehyde resin, based on the total amount of the non-volatile solid content of the thermosetting silicone resin and etherified melamine/formaldehyde resin. Electrophotography, characterized in that it has a surface protective layer formed by applying a coating liquid containing 10 to 20% by weight of an acrylic polymer and not containing a conductivity imparting agent onto a photosensitive layer and curing the coating liquid. Photoreceptor.