JPH03135573A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve photosensitive characteristics and surface hardness by coating a photosensitive layer with a coating soln. contg. thermosetting silicone resin and methyl and butyl mixed etherified melamine-formaldehyde resin and by hardening the coating soln.to form a surface protecting layer. CONSTITUTION:A photosensitive layer is coated with a coating soln. contg. thermosetting silicon resin and 0.1-30 pts. wt. methyl and butyl mixed etherified melamine-formaldehyde resin basing on 100 pts. wt. nonvolatile solid matter in the silicone resin and the coating soln. is hardened to form a surface protecting layer. It is preferable that electrically conductive metal oxide particles as an electrical conductivity rendering agent are uniformly dispersed in the surface protecting layer by mixing the coating soln. with a colloidal soln. of the metal oxide particles. No harmful influence is exerted on photosensitive characteristics and physical properties 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 φ 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, many voids that become structural traps are created between the two sites, resulting in deterioration of 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, in a combination system using a methyl etherified melamine/formaldehyde resin instead of the butyl etherified melamine/formaldehyde resin, the methyl etherified melamine/formaldehyde resin is・It has higher crosslinking properties than formaldehyde resins, and does not form a covalent bond with the SL -OH group of the thermosetting silicone resin during curing, but it does generate a sufficiently large molecular interaction with the 5 LOH group, so It was found that the compatibility between silicone sites and melamine sites in the layer was improved, and a dense film with fewer structural traps could be formed. However, in the above combination system, in order to improve the conductivity of the layer by the aromatic π electrons of melamine, the methyl etherified melamine/formaldehyde resin is added to 100 parts by weight of the non-volatile solid content of the thermosetting silicone resin. However, if the amount exceeds 15 parts by weight, the interaction between the two resins is too strong, causing internal stress in the surface protective layer and causing cracks and the like.

As mentioned above, the butyl etherified melamine/formaldehyde resin does not interact strongly with the thermosetting silicone resin, as does the methyl etherified melamine/formaldehyde resin, so the aromatic π electrons of melamine improve the conductivity of the layer. It was also considered to use this butyl etherified melamine/formaldehyde resin together with the methyl etherified melamine/formaldehyde resin as a curing component, but since the curing temperatures of both melamine/formaldehyde resins are different, it was difficult to form an even film. However, there was a problem in that cracks and the like were generated.

The present invention has been made in view of the above circumstances, and has no adverse effect on the photosensitive characteristics, physical properties, etc. of an electrophotographic photoreceptor, and is less susceptible to IN dynamic 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 and improved conductivity.

<Means and effects for solving the problems> In order to solve the above problems, the electrophotographic photoreceptor of the present invention comprises a thermosetting silicone resin and 100 parts by weight of non-volatile solid content of the thermosetting silicone resin. A coating solution containing 0.1 to 30 parts by weight of methyl-butyl mixed etherified melamine/formaldehyde resin is coated on the photosensitive layer and cured to form a surface protective layer.

Further, it is preferable that the conductive metal oxide particles are uniformly dispersed in the surface protective layer by mixing a colloidal solution of conductive metal oxide particles as a conductivity imparting agent into the coating liquid. .

In the electrophotographic photoreceptor of the present invention having the above structure, the melamine/formaldehyde resin used in combination with the thermosetting silicone resin is a methyl-butyl mixed etherified melamine/formaldehyde resin alone, so that cracks etc. do not occur. A uniform film can be formed.

And the above methyl-butyl mixed etherified melamine.
Formaldehyde resin has higher crosslinking properties than conventional butyl etherified melamine/formaldehyde resin (during curing, it does not form a covalent bond with the SL OR group of the thermosetting silicone resin, but it has sufficient bonding with the 5LOH group mentioned above). Because large molecular interactions occur in the layer, the compatibility between silicone sites and melamine sites in the layer improves, forming a dense film with few structural traps.In addition, the methyl-butyl mixed etherified melamine/formaldehyde Since the methyl etherified melamine/formaldehyde resin does not have strong cross-linking properties, there is no risk of cracks occurring even if a larger amount than the methyl etherified melamine/formaldehyde resin is blended into the layer. It is presumed that the electroconductivity of the layer can be further improved due to the large amount of aromatic π electrons.Therefore, the electrophotographic photoreceptor of the present invention has excellent photosensitive characteristics. Furthermore, since both resins constituting the layer are thermosetting resins that form a three-dimensional structure upon curing, the surface protective layer has a high surface hardness after curing.

Moreover, as mentioned above, both resins are highly compatible, resulting in a complex three-dimensional structure after curing, which improves the brittleness against sliding friction compared to the case of thermosetting silicone resin alone. It becomes something.

In addition, the content of the methyl-butyl mixed etherified melamine/formaldehyde resin is limited to 0.1 to 30 parts by weight based on 100 parts by weight of the non-volatile solid content of the thermosetting silicone resin in the coating solution. , due to the following reasons. That is, if the content of the methyl-butyl mixed etherified melamine/formaldehyde resin is less than 0.1 part by weight, the effect of its addition will not be sufficiently obtained, and the surface protective layer after curing will have problems such as brittleness against sliding friction. In addition to this, the photosensitive characteristics deteriorate due to a lack of aromatic π electrons in the layer. On the other hand, if the content of the methyl-butyl mixed etherified melamine/formaldehyde resin exceeds 30 parts by weight, the interaction between the two resins will be too strong, causing internal stress in the surface protective layer.
Cracks and the like will occur, making it impossible to obtain a clean surface protective layer.

The thermosetting silicone resin contained in the coating solution includes tetraalkoxysilane, trialkoxyalkylsilane,
Hydrolysates of silane compounds, such as organosilanes such as dialkoxydialkylsilanes, organohalogensilanes such as trichloroalkylsilanes and dichlorodialkylsilanes, singly or in combination of two or more (so-called organoborinoxanes), or their The initial condensation reaction product is dissolved or dispersed in a solvent as a non-volatile solid content, and the alkoxy group and alkyl group of the silane compound include methoxy group, ethkyne group, isopropoxy group, t-
Examples include lower groups having about 1 to 4 carbon atoms, such as a butoxy group, a glycidoquine group, methyl, and ethyl.

The methyl-butyl mixed etherified melamine/formaldehyde resin used in combination with the above thermosetting silicone resin is
Various mono- to hexa-methylol melamine, which is a reaction product of melamine and formaldehyde.At least one of the methylol groups in melamine is methyl etherified and at least one of the remaining methylol groups is converted to butyl ether, or it is an initial condensation reaction product thereof, and is a liquid. Those supplied in the form of syrup or syrup are preferably used.

The number average molecular weight of the methyl-butyl mixed etherified melamine/formaldehyde resin is not particularly limited in this invention, but if it exceeds 1500, the reactivity decreases, so
The number average molecular weight is preferably 1,500 or less. Further, it is preferable that the number of bound formaldehyde per melamine nucleus in the resin is 3 to 6 g, of which 2 to 5 are methyl etherified and 1 to 2 are butyl 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 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.

Examples of solvents for dissolving or dispersing the thermosetting silicone resin and methyl-butyl mixed etherified melamine/formaldehyde resin to form a coating solution for the surface protective layer include isopropyl alcohol/n-hexane,
Aliphatic hydrocarbons such as octane and cyclohexane; Aromatic hydrocarbons such as benzene, toluene, and xylene; Halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene; Dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, Ethers such as ethylene glycol diethyl ether and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethyl formamide; dimethyl sulfoxide, etc. These may be used alone or in combination. A mixture of the above is used.

The coating liquid for the surface protective layer containing the above-mentioned thermosetting silicone resin and methyl-butyl mixed etherified melamine/formaldehyde resin can be cured simply by 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.

It is preferable that a conductivity-imparting agent is dispersed in the surface protective layer made of the above-mentioned resins for the purpose of facilitating the injection of charge into the lower layer in the image forming process.

Examples of the conductivity imparting agent include elemental metal oxides such as tin oxide, titanium oxide, indium oxide, and antimony oxide;
Examples include conductive metal oxides such as solid solutions of tin oxide and antimony oxide. The above-mentioned conductive metal oxide generally includes:
In the form of fine particles, they are stirred and mixed into the coating solution before curing, and are dispersed into the surface protective layer as the coating film hardens.However, in the form of fine particles, they tend to aggregate, and it takes a long time to uniformly disperse them in the coating solution. As mentioned above, since time stirring is required,
It is preferable to mix it into the coating liquid in the form of a colloidal solution. In the above colloidal solution, the fine particles of conductive metal oxide repel each other due to their respective surface charges and prevent agglomeration in the coating solution. can be dispersed into

The method for producing a colloidal solution of conductive metal oxide particles varies depending on the type of conductive metal oxide. For example, a colloidal solution of antimony pentoxide (Sb20s) is produced by mixing anhydrous antimony trioxide and nitric acid, heating and then , α-hydroxycarboxylic acid, and N.

A method in which an organic solvent such as N-dimethylformamide (DMF) is added in this order and water as a byproduct is removed by distillation (see JP-A-47-11382),
A state in which antimony trioxide is dispersed in a hydrogen halide such as hydrogen chloride, a monohydric or dihydric or higher alcohol such as ethylene glycol, a hydrophilic organic solvent such as DMF, and α-hydroxycarboxylic acid. A method of oxidizing with hydrogen peroxide solution (Japanese Patent Application Laid-Open No. 52-384
95, JP-A-52-38496), etc.

As a dispersion medium for preparing the above-mentioned antimony pentoxide colloidal solution, so as not to attack the underlying photosensitive layer,
Organic small methyl alcohol, ethyl alcohol,
It is preferable to use alcohols such as n-propyl alcohol, isopropyl alcohol, butyl alcohol.

In addition, in the case of a colloidal solution of a solid solution of tin oxide (SnO2, SnO, etc.) and antimony oxide (Sb205.5b203, etc.), for example, as shown in FIG. Silicon oxide particles of degree 2
It can be prepared by a method of adsorbing .... In the structure shown in FIG. 1, the silicon oxide particles 2 adsorbed on the surface of the solid solution particles 1 generate OH groups and become negatively charged by contact with a polar solvent as a dispersion medium. The surface of the solid solution particles 1 is made to have an electric charge.

The above-mentioned solid solution particles of tin oxide and antimony oxide are usually formed by doping fine particles of tin oxide with antimony, and are not particularly limited, but the content ratio of antimony in the solid solution particles is 0.001 to 30% by weight. %, more preferably 5 to 20% by weight. The content of antimony in the solid solution particles is 0
．． If the amount is less than 0.001% by weight or exceeds 30% by weight, there is a risk that sufficient conductivity may not be obtained.

In addition, the particle size of the solid solution particles is not particularly limited, but 1
It is preferably 0 to 20 na+. When the particle size of the solid solution particles is less than 10n11, the electrical resistance of the surface protective layer increases, and when it exceeds 20 nm, the light transmittance of the surface protective layer tends to decrease.

The proportion of silicon oxide added to the solid solution particles is also not particularly limited, but is preferably 10 parts by weight or less per 100 parts by weight of the solid solution particles. If the ratio of silicon oxide to 100 parts by weight of the solid solution particles exceeds 10 parts by weight, there is a risk that sufficient electrical conductivity may not be obtained.

As the dispersion medium constituting the colloidal solution together with the solid solution particles, as described above, a polar solvent is used to negatively charge silicon oxide. Alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, butyl alcohol, etc., which do not have the risk of damaging the photosensitive layer as a geological layer, are preferably used.

The binder resin constituting the surface protective layer may contain thermosetting resins or thermoplastic resins other than those mentioned above, as long as the properties of the film are not impaired.

Other binder resins other than those mentioned above include curable acrylic resins, alkyd resins, unsaturated polyester resins, diallyl phthalate resins, phenol resins, urea resins, benzoguanamine resins, methyl-butyl mixed etherification systems, and butyl etherification systems. Melamine resins, styrene polymers; acrylic polymers: styrene-acrylic copolymers; olefin polymers such as polyethylene, ethylene-vinyl acetate copolymers, chlorinated polyethylene, polybutylene, and ionomers; polyvinyl chloride Vinyl chloride-vinyl acetate copolymer; polyvinyl acetate: saturated polyester: polyamide; thermoplastic polyurethane resin; polycarbonate; polyarylate polysulfone; ketone resin; polyvinyl butyral resin; polyether resin.

The surface protective layer contains conventionally known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene;
Fluorene compounds such as N-diphenylhydrazino)fluorene and 9-carbazolyliminofluorene; 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 included.

The film thickness of the above-mentioned surface preservation aI layer is 0.1 to 10 μm1, especially 2
It is preferably within the range of 5 to 5.

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 aAS2 Scz, a5eAsTe, and amorphous selenium (
a-So) and amorphous silicon (a-5L). 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, powder of the semiconductor material mentioned above; zTIO, CdS
Etc. IT Y Sensitive M products; H'J 'J '7 Mu salts; azo compounds; bisazo compounds; phthalocyanine compounds; anthanthrone compounds; perylene compounds; indigo compounds; triphenylmethane compounds; Examples include toluidine-based compounds; pyrazoline-based compounds; quinacridone-based compounds; and pyrrolovirol-based compounds. 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. , the above-mentioned metal-free phthalocyanine and/or oxotitanylphthalonanine are more preferably used. Note that the above charge generating materials can be used alone, or
Multiple types may be used together.

In addition, examples of the charge transporting material contained in the charge transporting layer in the single-layer type or laminated type organic photosensitive layer or the composite type photosensitive layer include tetracyanoethylene, 2,4.7-
Fluorenone compounds such as dolinitro-9-fluorenone; nitrated compounds such as dinitroanthracene; succinic anhydride; maleic anhydride; dibromomaleic anhydride; triphenylmethane compounds; 2,5-di(4-dimethylaminophenyl)- Oxadiazole compounds such as 1,3,4-oxadiazole; Styryl compounds such as 9-(4-diethylaminostyryl)anthracene: Poly-
Carbazole compounds such as N-vinylcarbazole; 1
- Pyrazoline compounds such as phenyl-3-(p-dimethylaminophenyl)pyrazoline, 4.4', 4'-
Amine derivatives such as 1-lis(N, N-diphenylamino)triphenylamine; Conjugated unsaturated compounds such as 1,1-bis(4-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene; 4 - Hydrazone compounds such as (N,N-diethylamino)benzaldehyde-N,N-diphenylhydrazone; indole compounds, oxazole compounds, isoxazole compounds,
Nitrogen-containing cyclic compounds such as thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, pyrazoline compounds, and 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 to have a thickness in the range of 10 to 50 μm, particularly 15 to 25 μI.

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 preferably in the range of 0.01 to 3 #Il, particularly 0.1 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, particularly 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 Alcohols such as alcohol, ethyl alcohol, isopropyl alcohol, allyl alcohol, cyclopentanol, benzyl alcohol, furfuryl alcohol, diacetone alcohol; dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol diethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, etc. ethers; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone;
Various solvents are exemplified, such as esters such as ethyl acetate and methyl acetate; dimethylformamide; and dimethyl sulfoxide, and these may be used alone or in combination of two or more. 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 4, Comparative Examples 4 and 5 100 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
A charge transport coating solution was prepared consisting of 100 parts by weight of N,N-diphenylhydrazone and 90,000 parts by weight of methylene chloride (CH2(Jz)) as a solvent, and this coating solution was applied onto an aluminum tube with an outer diameter of 78 mm and a length of 340 cm. After coating, heat dry at 90℃ for 30 minutes to obtain a film thickness of 20℃.
A charge transport layer of .mu.m was formed.

Next, on the charge transport layer, 2,
80 parts by weight of 7-dibromoanthanthrone (manufactured by IC1) and metal-free phthalonanine (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 0.511 m.

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 glycidoxyprobyltrimethoxysilane were gradually added dropwise, and then the mixture was heated to room temperature for 1 hour.
Obtain a silane hydrolyzate solution by standing for a period of time,
To 100 parts by weight of the non-volatile solid content of this silane hydrolyzate solution, methyl-butyl mixed etherified melamine formaldehyde resin (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumimaru M65 B) was blended in the amount shown in the following table. A coating solution for a surface protective layer was prepared.

Next, 60 parts by weight of antimony-doped tin oxide fine powder (manufactured by Sumitomo Cement Co., Ltd., solid solution particles of tin oxide and antimony oxide, containing 10% by weight of antimony) was added to 100 parts by weight of the resin solid content in the coating solution. ff was added and stirred and mixed in a ball mill for 150 hours. And -F
A mixture of the above coating solution and antimony-doped tin oxide fine powder was applied onto the charge generation layer and cured by heating at 110° C. for 1 hour to form a surface protective layer with a film thickness of 2.5 μm. A drum-shaped electrophotographic photoreceptor having layers was produced.

Examples 5 to 8 Instead of the antimony-doped tin oxide fine powder, a colloidal solution in which fine particles of antimony pentoxide were dispersed in isopropyl alcohol (manufactured by Sansan Kagaku Co., Ltd., trade name Sancolloid,
This colloidal solution was prepared so that the resin solid content (P) in the coating liquid and the solid content (M) in the colloidal solution were P + M = 100: 60 (weight ratio ), except that it was blended into the silicone resin coating solution and stirred and mixed in a ball mill for 1 hour.
Electrophotographic photoreceptors were produced in the same manner as in Examples 1 to 4 above.

Examples 9 to 12 Instead of the antimony-doped tin oxide fine powder, solid solution particles of tin oxide and antimony oxide (containing 10% by weight of antimony, particle size 10 to 20 nm) were used as the solid solution particles 1.
A colloidal solution (manufactured by 8 Sankagaku Co., Ltd.) which is negatively charged with 9 parts by weight of silicon oxide particles per 00 parts by weight and dispersed in isopropyl alcohol as a dispersion medium is used. , the resin solid content (P) in the coating liquid and the solid content (M) in the colloidal solution are PGM
- 100:60 (weight ratio) in the above silicone resin coating solution, stirred in a ball mill for 1 hour,
Except for mixing, in the same manner as in Examples 1 to 4 above,
An electrophotographic photoreceptor was produced.

Comparative Example 1 Examples 1 to 1 above except that 10 parts of butyl etherified melamine/formaldehyde resin (manufactured by Mitsui Cyinamide Co., Ltd., trade name: Niepan 128) was blended in place of the methyl-butyl mixed etherified melamine/formaldehyde resin. An electrophotographic photoreceptor was produced in the same manner as in Example 4.

Comparative Example 2 Except that 10 parts by weight of polyvinyl acetate (manufactured by Nippon Gosei Kagaku Co., Ltd., trade name Y5-N) was blended instead of the methyl-butyl mixed etherified melamine/formaldehyde resin.
Electrophotographic photoreceptors were produced in the same manner as in Examples 1 to 4 above.

Comparative Example 3 Example 1 to above except that methyl-butyl mixed etherified melamine/formaldehyde resin was not blended.
In the same manner as in 4 (7), an electrophotographic photoreceptor was produced.

Comparative Example 6 Instead of the methyl-butyl mixed etherified melamine/formaldehyde resin, 1.0 parts by weight of butyl etherified melamine/formaldehyde resin (manufactured by Mitsui Cyinamide Co., Ltd., trade name: Niepan 128) and methyl etherified melamine/formaldehyde resin (Mitsui Cyinamide Co., Ltd., trade name Niepan 128) were used. Electrophotographic photoreceptors were produced in the same manner as in Examples 1 to 4 above, except that 10 parts by weight of Cymel 370 (trade name, manufactured by Co., Ltd.) was blended.

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 30M), and its surface was positively charged to determine the surface potential V1s, p, (
V) was measured.

Measurement of half-decreased exposure amount and residual potential Each electrophotographic photoreceptor in the above charged state was subjected to an exposure intensity of 0.92 mW/-1 exposure time of 60 msec using a halogen lamp which is the exposure light source of the electrostatic copying tester. The time required for the surface potentials V, s, and p to become 1/2 after exposure is determined, and the half-reduction exposure ff1E I/2 (Iux-3
ee) was calculated.

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

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.).

DC-111 model) and after 500 copies were processed, the surface potential was changed to the surface potential after repeated exposure V2 s
, p, (V).

Furthermore, from the surface potential measurement value V, s, p, and the surface potential measurement value V2S, ri, after repeated exposure, the following formula [
11, Table 1Iili potential change value -ΔV (V) was calculated.

ΔV (V) ~ V25-p-(V) V + s, p, (V) -[
1] Abrasion resistance test Each electrophotographic photoreceptor was tested using a drum polishing tester (manufactured by Sanda Kogyo Co., Ltd.)
At the same time, an abrasive test paper (manufactured by Sumitomo 3M, trade name Imperial Wrapping Film, particle size 12 μm aluminum oxide powder adhered to the surface),
Apply this abrasive test paper to the surface of the photoconductor with a linear pressure of 10 z/mm.
The amount of wear (μm) when the photoreceptor was rotated 100 times while being pressed with was measured.

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

The above results are shown in the table below. (Margins below) From the results in the above table, it can be seen that the electrophotographic photoreceptors of Examples 1 to 12 had a greater amount of change in surface potential after repeated exposure than Comparative Example 1, which contained butyl etherified melamine/formaldehyde resin. It is extremely small, and from this reason, the above Examples 1 to 1
It was predicted that the surface protective layer in No. 2 had good compatibility between the silicone sites and the melamine sites in the layer, resulting in a dense film with few structural traps. In addition, it was found that even if up to 30 parts by weight of the methyl-butyl mixed etherified melamine/formaldehyde resin was blended in the formulations of the examples, cracks did not occur and a uniform film could be formed.

In addition, in Examples 1 to 2 above, the amount of change in surface potential after repeated exposure, residual potential, and half-reduced exposure amount were the same as in Comparative Example 3 in which melamine/formaldehyde resin was not blended.
Therefore, by blending methyl-butyl mixed etherified melamine/formaldehyde resin,
It was found that the photosensitivity characteristics were improved.

From the results of the abrasion resistance test, the surface protective layers in Examples 1 to 12 had better abrasion resistance than Comparative Example 3, in which no melamine/formaldehyde resin was blended, and Comparative Example 2, in which polyvinyl acetate was blended. There was found.

Furthermore, from the results of Examples 1 to 12 and Comparative Examples 4 and 5, it was found that the amount of methyl-butyl mixed etherified melamine/formaldehyde resin per 100 parts by weight of non-volatile solids of the nicole resin.

It was found that a clean film could not be formed if the amount was outside the range of 0.1 to 30 parts by weight.

Additionally, from the results of Comparative Example 6, cracks occurred when methyl etherified melamine formaldehyde resin and butyl etherified melamine formaldehyde resin were used together, and from this, it was found that simply blending the two did not form a uniform film. It turned out that it couldn't be done.

And each Al of Examples 1 to 4 and Examples 5 to 12
From the l+ constant results, when a colloidal solution of a conductive metal oxide is used as a conductivity imparting agent, stirring for 1 hour will improve the conductivity imparting agent for 150 hours compared to when a conductive metal oxide is used in the form of a fine powder. It has been found that better dispersibility than stirring and mixing can be obtained.

<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, conductive metal oxide particles as a conductivity imparting agent,
If it is mixed into the coating solution in the form of a colloidal solution,
It becomes easy to uniformly disperse the conductive metal oxide particles in the surface protective layer.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a state in which the solid solution particles of tin oxide and antimony oxide are charged by adsorbing silicon oxide particles onto the surface of the solid solution particles. ]...Solid solution particles, 2...Silicon oxide particles.

Claims (1)

[Claims] 1. Thermosetting silicone resin and 0.1 to 100 parts by weight of non-volatile solid content of the thermosetting silicone resin.
30 parts by weight of methyl-butyl mixed etherified melamine.
1. An electrophotographic photoreceptor comprising a surface protective layer formed by coating a photosensitive layer with a coating liquid containing a formaldehyde resin and curing the coating liquid. 2. Thermosetting silicone resin and 0.1 to 100 parts by weight of non-volatile solid content of this thermosetting silicone resin.
30 parts by weight of methyl-butyl mixed etherified melamine.
A coating solution containing a formaldehyde resin and a colloidal solution of conductive metal oxide particles is applied onto the photosensitive layer and cured, so that the conductive metal oxide particles are uniformly applied as a conductivity imparting agent. An electrophotographic photoreceptor characterized by having a surface protective layer dispersed in.