JPH04240655A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent drop of surface resistivity due to attachment of dust, such as paper dust, at the time of repeating use of the electrophotographic sensitive body and to prevent trailing of an image. CONSTITUTION:The electrophotographic sensitive body is formed by laminating on a conductive substrate an electric charge transfer layer and a charge generating layer and a protective layer in this order, and the protective layer comprises a thermosetting silicone resin, a fluororesin, hydrophobic silica, a higher fatty acid, and a fluorinated graft polymer or a silicone type graft polymer, thus permitting the obtained electrophotographic sensitive body to be sensitive in the case of positive charging, stable against change of temperature and humidity, especially, freed of image trailing due to drop of surface resistivity under high temperature and high humidity caused by paper dust and the like attached to the surface after repeated uses, and high in hardness film strength, and superior in abrasion resistance and durability.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor containing an organic photoconductive substance, and more particularly to a laminated electrophotographic photoreceptor used for positive charging.

0002

[Prior Art] In the past, photoreceptors made of inorganic photoconductive materials such as selenium, selenium-tellurium alloy, cadmium sulfide, and zinc oxide have been widely used as electrophotographic photoreceptors. Research is progressing on organic photoconductive materials, which have characteristics such as the ability to select compounds that exhibit photoconductivity in an appropriate wavelength range.

Electrophotographic photoreceptors using organic photoconductive substances in their photosensitive layers have advantages such as easy film formation, high flexibility and a large degree of freedom in design, low cost, and non-polluting properties. However, the sensitivity and photoreceptor life were inferior compared to inorganic photoconductive materials. In order to improve these problems, a laminated electrophotographic photoreceptor in which a photosensitive layer is formed by separating the functions of a charge generation layer and a charge transport layer has been proposed and put into practical use. Since the charge transport agent generally used in this laminated electrophotographic photoreceptor is an electron-donating substance such as pyrazoline, hydrazone, or oxazole, the charge transport layer is a hole transport type, and therefore the charge transport layer is placed on the charge generation layer. When laminated, it is used with negative charge.

On the other hand, these electrophotographic photoreceptors are usually repeatedly subjected to the processes of charging, exposure, development, transfer, cleaning, and static elimination, but in this series of processes, positive charging is faster than negative charging. Corona discharge is stable, and the amount of ozone generated is small, so there is little property deterioration due to ozone oxidation. In addition, conventionally used inorganic photoreceptors such as selenium and selenium-tellurium alloys are used with a positive charge, so there is a strong demand for an organic photoreceptor that can be used with a positive charge because these electrophotographic processes can be shared.

[0005] In order to obtain a positive charge with a structure in which a charge transport layer is stacked on a normal charge generation layer, an electron-accepting substance such as trinitrofluorenone may be used as a charge transport agent. Receptive substances are not generally used because they are rarely available with high mobility, are chemically unstable, and have harmful effects such as carcinogenicity. Therefore, in order to enable positive charging using an electron donating substance, a structure has been proposed in which a charge transport layer and a charge generation layer are laminated in this order on a conductive support. They have drawbacks such as large carrier injection into the charge transport layer, which reduces chargeability, and generally because the charge generation layer is a thin layer, mechanical strength is low and durability is poor.

Therefore, we have proposed a three-layer structure in which a protective layer of a thin resin film is further provided on the charge transport layer and charge generation layer, or a four-layer structure consisting of a charge transport layer, a charge generation layer, a charge injection blocking layer, and a surface protection layer. Proposal of the structure, as well as the charge transport layer and charge generation layer.
In the layer structure, increase the resin ratio of the charge generation layer to 5μm.
Proposals have been made to improve mechanical strength by increasing the thickness of the charge generation layer, and to maintain sensitivity by adding a charge transport agent to the charge generation layer. (For example, The Third International Congress on Advance Inn
Non-impact printing technology:
The 3rd International Con
Grace on Advances in Non-
Impact Printing Technology
ies Proceedings p115, Proceedings of the 59th Research Conference of the Electrophotographic Society p184, etc.) In general, resin thin films are made of polyester resin, polyvinyl butyral resin, phenol resin, cellulose acetate, styrene maleic anhydride copolymer, etc. as a protective layer for photoreceptors. combination, polyamide resin, polyimide resin, melamine resin, etc. (for example,
8-15446, Japanese Patent Publication No. 51-15748, Japanese Patent Publication No. 52-24414, Japanese Patent Publication No. 56-348
Publication No. 60, Special Publication No. 56-53756, Special Publication No. 6
0-55357, Japanese Patent Publication No. 61-22345, etc.), but they are not sufficient in terms of durability such as scratch resistance and abrasion resistance due to repeated use, environmental stability, etc. Due to surface deposits such as paper dust after repeated use,
There is a problem of image blurring or image blurring due to a decrease in surface resistance under high temperature and high humidity conditions.

[0007] In addition, these protective layers made of thin resin films do not have sufficient durability when they are thin, and on the other hand, when the film thickness is increased, the residual potential increases and the repeatability characteristics deteriorate.

[0008] Therefore, a method of using a protective layer in which a metal oxide is dispersed in a binder resin (for example,
Special Publication No. 57-39846, Special Publication No. 58-1210
44, Japanese Patent Publication No. 59-223445, etc.), however, metal oxides in the binder resin are insoluble in the binder resin and solvent, and their shape is lumpy, so they may not be present in the protective layer. Even if the content is constant, the resistance value will fluctuate depending on the dispersion state, making the characteristics unstable. Also, unless the blending ratio, particle size, etc. are carefully controlled, environmental fluctuations in chargeability and residual potential, It has the disadvantage of causing repeated fluctuations.

[0009]

[Problem to be solved by the invention] Therefore, in any case, there have not been many satisfactory characteristics in terms of sensitivity, durability, etc., and only high durability against scratches and abrasion during repeated use has been obtained. In addition, it has less surface resistance reduction due to surface deposits such as paper dust, is stable in use environments such as temperature and humidity, can be used with positive charge, and satisfies the characteristics required as an electrophotographic photoreceptor. It is desired to develop an electrophotographic photoreceptor with a long life.

0010

[Means for Solving the Problems] In view of the above-mentioned problems, the present invention provides a structure in which a charge transport layer, a charge generation layer, and a protective layer are laminated in this order on a conductive support, and the protective layer is thermosetting. The present invention provides a laminated electrophotographic photoreceptor formed of an electrophotographic photoreceptor containing a silicone resin, a fluororesin, hydrophobic silica, a higher fatty acid, and a fluorine-based graft polymer or a silicone-based graft polymer.

[0011]

[Function] The electrophotographic photoreceptor of the present invention is positively charged and sensitive by laminating a charge transport layer, a charge generation layer and a protective layer in this order on a conductive support.

Further, in the electrophotographic photoreceptor of the present invention, by using a thermosetting silicone resin as a protective layer, a coating film with high hardness and excellent light transmittance and weather resistance can be obtained. At the same time, by containing fluororesin, it improves abrasion resistance, prevents the inherent moisture permeability of silicone resin, stabilizes the resistance of the protective layer under high temperature and high humidity, and improves image fading. be.

Furthermore, by containing a fluororesin, it is possible to prevent cracks caused by curing shrinkage of the silicone resin during film formation and to improve adhesion to the lower layer.

[0014] The electrophotographic photoreceptor of the present invention includes the following in the protective layer:
In addition to thermosetting silicone resin and fluororesin, hydrophobic silica is also included to improve the hardness of the photoreceptor surface and reduce the surface friction coefficient, increasing the durability and toner filming resistance of the photoreceptor, and making it more practical. This makes it possible to significantly improve the service life.

[0015] The silica contained at the same time must be hydrophobic, and by being hydrophobically treated, it prevents the adsorption of ions such as moisture and ozone products, and improves image blurring under high temperature and high humidity conditions. It is something that can be done.

Furthermore, the electrophotographic photoreceptor of the present invention further contains a higher fatty acid, particularly stearic acid, in the protective layer, thereby reducing the coefficient of friction on the surface of the photoreceptor and preventing cleaning equipment such as blades from depositing on the surface. This improves the performance, prevents image fading due to a decrease in surface resistance due to deposits such as paper dust during repeated use, and significantly extends the actual service life.

Furthermore, the electrophotographic photoreceptor of the present invention further includes a fluorine-based graft polymer or a silicone-based graft polymer in the protective layer, thereby improving the water repellency of the surface of the photoreceptor and reducing the coefficient of friction on the surface. This reduces the adhesion of surface deposits to the protective layer, prevents image blur due to a decrease in surface resistance due to deposits such as paper dust during repeated use, and significantly improves the actual usage life. be.

[0018]

EXAMPLES The electrophotographic photoreceptor of the present invention will be explained in detail below.

The thermosetting silicone resin used in the protective layer of the electrophotographic photoreceptor of the present invention is a thermosetting silicone resin of an alkoxysilane hydrolyzate, and the hydrolyzate is trifunctional or tetrafunctional. Any type of alkyl group may be used as long as it has a functional silanol group, and examples of the alkyl group include a methyl group.

These thermosetting silicone resins are preferably those that are soluble in alcoholic solvents as a hydrolyzate of alkoxysilane, can be applied without corroding the lower layer, and can be condensed by heat treatment after forming the coating. It hardens to produce a highly hard and durable film.

[0021] Similarly, the fluororesin contained in the protective layer is preferably one that is soluble in alcoholic solvents because it does not corrode the underlying layer.

[0022] Alcohol-based solvent-soluble fluororesins include copolymers of fluoroolefins and ethylenically unsaturated monomers such as vinyl ethers or vinyl esters, such as Lumiflon LF-300 and LF-916 (both manufactured by Asahi Glass Co., Ltd.). (manufactured by) etc. can be used.

[0023] At the same time, the hydrophobic silica contained in the protective layer is high-purity silica with an average primary particle size of 5 to 50 nm, which is treated with an organosilicon compound such as organosilane or silicone oil. relative humidity of at least 80
% water absorption is preferably 1% or less. Examples include those in which silica is reacted with dimethyldichlorosilane and the silanol groups on the silica surface are replaced with dimethylsilyl groups, and those in which trimethylsilyl groups are substituted.

[0024] At the same time, the fluorine-based graft polymer contained in the protective layer contains fluorocarbon in the side chain of an anchor polymer such as acrylic having an average molecular weight of several hundred to several hundred thousand, and has a total solid content of at least 100% by weight of the protective layer. It is preferable that water repellency can be imparted such that the contact angle of the protective layer with respect to pure water is 90° or more when added in an amount of 10 parts by weight or less.

[0025] At the same time, the silicone-based graft polymer contained in the protective layer has a silicone functional group in the side chain of an anchor polymer such as acrylic having an average molecular weight of several hundred to several hundred thousand, and has at least a total solid content of the protective layer. It is preferable that the protective layer be able to provide water repellency such that the contact angle with respect to pure water is 90° or more when added in an amount of 10 parts by weight or less per 100 parts by weight.

The protective layer of the electrophotographic photoreceptor of the present invention is prepared by dissolving a hydrolyzate of these alkoxysilanes and a fluororesin in a solvent that dissolves both, and dispersing hydrophobic silica.
Further, a coating liquid in which a silicone-based graft polymer is dissolved is applied onto the photosensitive layer by a conventional coating method, dried, and then hardened by heat treatment to form the photosensitive layer. The heat treatment temperature is 80°C to 200°C, and preferably about 80°C to 140°C in consideration of the heat resistance of the photosensitive layer. The thickness of the protective layer is 0.1 to 5 .mu.m, and preferably 0.2 to 2 .mu.m in consideration of electrophotographic properties, adhesion, and abrasion resistance.

Furthermore, the ratio of the thermosetting silicone resin to the fluororesin in the protective layer is 2:2 in solid weight ratio after drying.
8 to 8:2 is preferable; if the ratio of silicone resin is small, the surface hardness will be poor, and if the ratio of silicone resin is too high, cracks may occur due to curing shrinkage of the silicone resin during film formation, and the lower layer may deteriorate. Adhesion becomes poor.

Furthermore, the hydrophobic silica dispersed in the protective layer has the following properties in terms of coating liquid stability, coating film strength, film formability, etc.
The amount added is in the range of 1 to 100 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the total solid content of the protective layer.

Furthermore, the amount of the silicone graft polymer dissolved in the protective layer is 0.1 to 20 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the total solid content of the protective layer. This is within the scope of the department.

Examples of the electron-donating substance used in the charge transport layer of the electrophotographic photoreceptor of the present invention include compounds having an electron-donating group such as an alkyl group, an alkoxy group, an amino group, and an imide group, anthracene, pyrene, and phenanthrene. Polycyclic aromatic compounds or derivatives containing them, heterocyclic compounds such as indole, oxazole, oxadiazole, carbazole, thiazole, pyrazoline, imidazole, triazole, etc. or derivatives containing them. These electron-donating substances and binder resin are dissolved in a suitable solvent, coated and dried using a normal coating method to form a charge transport layer. However, when the electron-donating substance is a polymer compound, a binder resin is mixed. Alternatively, the charge transport layer may be formed alone. The thickness of the charge transport layer is from several μm to several tens of μm, preferably from 5 to 25 μm.

[0031] Further, as the charge generating substance used in the charge generating layer of the electrophotographic photoreceptor of the present invention, phthalocyanine type,
Azo series, squarerium series, cyanine series, quinone series,
Examples include various pigments or dyes such as perylene-based pigments. The charge generation layer is formed by adding and dispersing these pigments or dyes and a suitable binder resin, applying a coating solution prepared by a conventional coating method, and heating and drying to form a film with a thickness of several μm, but preferably. It is preferable to form the film to a thickness of 0.2 to 2 μm.

[0032] The binder resin used in the charge generation layer and the charge transport layer is used as necessary for the purpose of improving adhesion with other layers, improving uniformity of the coating film, adjusting fluidity during coating, etc. , specifically polyester, polyvinyl chloride,
Polyvinyl butyral, polyvinyl acetate, polycarbonate, fluororesin, methacrylic resin, silicone resin,
Alternatively, copolymers of these resins may be mentioned. The solvent may be one that dissolves the charge generating agent, the charge transporting agent, or the binder resin, and specifically includes halogenated hydrocarbons, halogenated aromatics, aromatics,
Ketones, esters, ethers, etc. can be used.

The conductive support used in the electrophotographic photoreceptor of the present invention may be any conventionally known conductive support, including metal plates and drums made of aluminum, aluminum alloy, tin oxide, Plates made of metal oxides such as indium oxide, or those metals and metal oxides, etc., are vacuum evaporated, sputtered, laminated,
These include various plastic films, papers, etc. that have been applied by coating and treated to be conductive.

Furthermore, the electrophotographic photoreceptor of the present invention has an adhesive layer or adhesive layer of casein, polyvinyl alcohol, polyvinyl butyral, polyamide, etc. between the conductive support and the charge transport layer, as in the case of ordinary electrophotographic photoreceptors. A barrier layer can be provided.

The electrophotographic photoreceptor of the present invention is thus formed by laminating a photosensitive layer consisting of a charge transport layer and a charge generation layer and a protective layer on a conductive support. A charge transport layer, a charge generation layer, and a protective layer are laminated in this order, and are positively charged and sensitive.

Examples of the present invention will be described in detail below, but the present invention is not limited to the combinations shown in the following examples.

An electrophotographic photoreceptor according to an embodiment of the present invention will be described below. 1,1-bis(P-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene
1 part by weight and 1 part by weight of polycarbonate (manufactured by Bayer AG, trade name: Macrohole N) were dissolved in 9 parts by weight of methylene chloride, and this coating liquid was dip coated on an aluminum drum with an outer diameter of 25 mm, and 1 part by weight was heated at 80°C. After drying for a while, a charge transport layer having a thickness of 20 μm was formed.

Next, 5 parts by weight of τ-type metal-free phthalocyanine (manufactured by Toyo Ink Mfg. Co., Ltd.) and a thermosetting acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Dianal HR) were added.
664) 4 parts by weight and melamine resin (manufactured by Dainippon Ink Co., Ltd., trade name Super Beckamine L145-60
) was dispersed in 115 parts by weight of s-butyl alcohol. This coating liquid was dip coated onto the charge transport layer, and 1
It was dried at 30° C. for 1 hour to form a charge generation layer with a thickness of 0.2 μm.

In addition, 70 parts by weight of thermosetting silicone resin (manufactured by Toshiba Silicone Corporation) and fluororesin (manufactured by Asahi Glass Co., Ltd.) were also added.
Co., Ltd. (trade name: Lumiflon LF-916) dissolved in 1000 parts by weight of n-butyl alcohol.
0 parts by weight was added, dispersed by ultrasonic dispersion, further 5 parts by weight of stearic acid was added as a higher fatty acid, and a fluorine-based graft polymer (manufactured by Toagosei Kagaku Co., Ltd.) was added.
A coating liquid was prepared by adding 5 parts by weight of GF-300). This coating liquid was dip-coated onto the charge generation layer, heat-treated at 110° C. for 1 hour, and cured to form a protective layer with a thickness of 1 μm.

The electrophotographic photoreceptor obtained in this manner was installed in a self-made image testing machine and exposed to high temperature and high humidity (35°C, 85R).
H%) 1000 sheets, 2000 sheets, 3000 sheets, 400 sheets
0 pieces, 5000 pieces, 6000 pieces, 7000 pieces, 8000 pieces
The state of image bleeding when printed was evaluated. FIG. 1 is a block diagram of an image testing machine for an electrophotographic photoreceptor in an embodiment of the present invention.

In FIG. 1, 1 is a main charging section, 2 is a laser exposure section for writing an electrostatic latent image, 3 is a non-magnetic one-component DC flying developing section, 4 is a paper and paper transport section, 5 is a transfer section, and 6 is a transfer section. The fixing section 7 is a toner cleaning section using a urethane blade.

The evaluation results are shown in (Table 1).

[0043]

[Table 1]

As described above, according to this embodiment, an electrophotographic photoreceptor is formed by laminating a charge transport layer, a charge generation layer, and a protective layer in this order on a conductive support, and a thermosetting layer is used as the protective layer. By containing silicone resin, fluororesin, hydrophobic silica, stearic acid, and fluorine-based graft polymer, it is positively charged and sensitive, and is stable against temperature and humidity, especially for paper powder after repeated use. An electrophotographic photoreceptor that does not suffer from image blurring due to a decrease in surface resistance due to surface deposits under high temperature and high humidity conditions, has high hardness and film strength even with a thin protective layer, and has excellent abrasion resistance and durability. It provides:

A second embodiment of the present invention will be described below. In the protective layer of the first example, a fluorine-based graft polymer (GF-300 manufactured by Toagosei Chemical Co., Ltd.)
Instead of 5 parts by weight, silicone-based graft polymer (
A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in the first example except that 5 parts by weight of GS-30 (manufactured by Toagosei Kagaku Co., Ltd.) was added to prepare the coating liquid. Image evaluation was performed in the same manner as in Example 2.

The evaluation results are shown in (Table 1). A third embodiment of the present invention will be described below.

In the protective layer of the first example, the coating liquid was prepared by adding 5 parts by weight of palmitic acid instead of 5 parts by weight of stearic acid as the higher fatty acid.
A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in the first example, and image evaluation was performed in the same manner as in the first example.

[0048] The evaluation results are shown in (Table 1). A fourth embodiment of the present invention will be described below.

[0049] The same procedure as in Example 1 was performed, except that in the protective layer of Example 1, 5 parts by weight of oleic acid was added instead of 5 parts by weight of stearic acid as the higher fatty acid. A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner, and image evaluation was performed in the same manner as in the first example.

The evaluation results are shown in (Table 1). A fifth embodiment of the present invention will be described below.

In the protective layer of the first example, 70 parts by weight of a thermosetting silicone resin (manufactured by Toshiba Silicone Corporation) and 30 parts by weight of a fluororesin (manufactured by Asahi Glass Co., Ltd., trade name Lumiflon LF-916) were substituted. A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in the first example except that 50 parts by weight of the thermosetting silicone resin and 50 parts by weight of the fluororesin were used. Image evaluation was performed in the same manner.

The evaluation results are shown in (Table 1). Further, as a comparative example of the present invention, a sample was prepared with a protective layer consisting only of a thermosetting silicone resin, a fluororesin, and hydrophobic silica.

In the first example, a charge transport layer, a charge generation layer, and a protective layer were prepared in the same manner as in the first example, except that the protective layer was made of only a thermosetting silicone resin, a fluororesin, and a hydrophobic silica. was formed, and image evaluation was performed in the same manner as in the first example.

[0054] The evaluation results are shown in (Table 1).

[0055]

As described above, in the present invention, an electrophotographic photoreceptor is formed by laminating a charge transport layer, a charge generation layer, and a protective layer in this order on a conductive support, and the protective layer is thermosetting. By containing silicone resin, fluororesin, hydrophobic silica, higher fatty acid, and fluorine-based graft polymer or silicone-based graft polymer, it has positive charge sensitivity, is stable against temperature and humidity, and is particularly useful for repeated use. There is no image blurring due to a decrease in surface resistance under high temperature and high humidity conditions due to surface deposits such as paper dust, and even with a thin protective layer, the film has high hardness and film strength, and has excellent abrasion resistance and durability. It can be used as an electrophotographic photoreceptor.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an image testing machine for an electrophotographic photoreceptor in a first embodiment of the present invention.

[Explanation of symbols]

1 Main charging section 2 Laser exposure section for electrostatic latent image writing 3 Non-magnetic one-component DC flying development section 4 Paper and paper transport section 5 Transfer section 6 Fixing section

Claims (6)

[Claims] 1. An electrophotographic photoreceptor formed by laminating a photosensitive layer and a protective layer for the photosensitive layer on a conductive support, wherein the protective layer comprises a thermosetting silicone resin, a fluororesin, and a hydrophobic silica. An electrophotographic photoreceptor characterized by containing a higher fatty acid and further a fluorine-based graft polymer. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is formed by laminating a charge transport layer and a charge generation layer in this order on a conductive support. 3. The electrophotographic photoreceptor according to claim 1, wherein the higher fatty acid is selected from stearic acid, palmitic acid, and oleic acid. 4. An electrophotographic photoreceptor formed by laminating a photosensitive layer and a protective layer for the photosensitive layer on a conductive support, wherein the protective layer comprises a thermosetting silicone resin, a fluororesin, and a hydrophobic silica. An electrophotographic photoreceptor characterized by containing a higher fatty acid and further a silicone graft polymer. 5. The electrophotographic photoreceptor according to claim 4, wherein the photosensitive layer is formed by laminating a charge transport layer and a charge generation layer in this order on a conductive support. 6. The electrophotographic photoreceptor according to claim 4, wherein the higher fatty acid is selected from stearic acid, palmitic acid, and oleic acid.