JPH01178971A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain sensitivity in positive charging, to reduce rise of residual potential, and to enhance abrasion resistance and durability by laminating on a conductive supporting body an electric charge transfer layer, a charge generating layer, and a protective layer containing a thermosetting acrylic resin and picric acid. CONSTITUTION:The protective film high in hardness and superior in light transmittance and weather resistance is obtained by using the thermosetting acrylic resin, and rise of residual potential due to repeated uses is reduced and durability and practical use life of a photosensitive body are enhanced by adding picric acid. The sensitivity at the time of positive charging is obtained by laminating on the conductive supporting body the charge transfer layer, the charge generating layer, and the protective layer, and sensitivity can be enhanced by combining addition of a phthalocyanine pigment to the charge generating layer with the addition of picric acid to the protective layer, thus permitting sensitivity in positive charging to be obtained, rise of residual potential to be reduced, and abrasion resistance and durability to be enhanced.

Description

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

2. Description of the Related Art Conventionally, 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 certain wavelength ranges.

An electrophotographic photoreceptor using an organic photoconductive substance in the photosensitive layer is
It has advantages such as easy film formation, high flexibility and flexibility in design, low cost and non-polluting properties, but compared to inorganic photoconductive materials, it has lower sensitivity and photoreceptor life. It was inferior. 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. The charge transport agent generally used in this laminated electrophotographic photoreceptor is an electron-donating substance such as pyrazoline, hydrazone, or oxazole, so the charge transport layer is a hole transport type, and therefore a charge transport layer is formed on the charge generation layer. When MJ layer is used, it is negatively charged.

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, corona discharge is more likely to occur when positively charged than when negatively charged. It is stable, and the amount of ozone generated is small, so there is little property deterioration due to ozone oxidation. In addition, since inorganic photoreceptors such as selenium and selenium-tellurium alloys that have been used in the past are used with a positive charge,
Because these electrophotographic processes can be shared, there is a strong demand for organic photoreceptors that can be used with positive charging.

Here, in order to achieve positive charging with a structure in which a charge transport layer is laminated on a normal charge generation layer, a charge transport agent and an electron-accepting substance such as cytetrinitrofluorenone may be used.
These electron-accepting substances are not generally used because they have not been found to have high mobility, are chemically unstable, and have carcinogenic and other harmful effects.
Therefore, in order to enable sexual 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 had 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 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. In addition, in the 2N configuration of the charge transport layer and charge generation layer, the resin ratio of the charge generation layer was increased to make the film thicker to about 5 μm to improve mechanical strength, and a charge transport agent was added to the charge generation layer to improve sensitivity. Proposals have been made to maintain this.

Problems to be Solved by the Invention However, in the above-mentioned proposal, the durability of the photoreceptor having a three-layer protective layer is not sufficient if the protective layer is thin, and on the other hand, increasing the thickness increases the residual potential. It has drawbacks such as poor repeatability. A photoreceptor with a four-layer structure has a complicated structure, and requires many manufacturing steps due to the formation of a charge injection blocking layer.

In addition, photoreceptors with thicker charge generation layers have drawbacks such as not very high sensitivity and large ozone deterioration.

In any case, it has not been possible to obtain a material with satisfactory characteristics in terms of sensitivity, durability, etc., and it can be used with positive charging without sacrificing its advantages as an organic photoreceptor, and is required as an electrophotographic photoreceptor. It is desired to develop an electrophotographic photoreceptor with a longer life span that satisfies the characteristics described above.

Means for Solving the Problems In view of the above 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 made of thermosetting acrylic. By using an electrophotographic photoreceptor containing a resin and picric acid, an electrophotographic photoreceptor is provided which is positively charged and sensitive, has little increase in residual potential, and has excellent abrasion resistance and durability.

Function: By using a thermosetting acrylic resin as a protective layer, the electrophotographic photoreceptor of the present invention can obtain a coating film with high hardness and excellent light transmittance and weather resistance, and furthermore, by containing picric acid, it can be easily resisted by repeated use. Reduces the increase in residual potential,
The durability and actual service life of the photoreceptor can be improved.

In addition, the electrophotographic photoreceptor of the present invention has sensitivity with positive charging by laminating a charge transport layer, a charge generation layer, and a 1 ff retention layer on a conductive support in this order, and furthermore, the charge generation layer contains a phthalocyanine-based By containing a pigment, sensitivity can be improved in combination with a protective layer containing picric acid.

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

Examples of the thermosetting acrylic resin used in the protective layer of the electrophotographic photoreceptor of the present invention include modified acrylic resins such as melamine-modified and epoxy-modified acrylic resins, and acrylic resins having functional groups such as epoxy groups and vinyl groups. .

These thermosetting acrylic resins are cured by condensation or addition reaction of functional groups by heat treatment, and as curing agents, nitrogen-containing compounds such as isocyanates, saturated or unsaturated polyhydric carboxylic acids or their acid anhydrides, etc. May contain.

Further, the picric acid contained in the T-keeping J layer is preferably 1 x 10°' m per 1 g of thermosetting acrylic resin.
ol/g to 5 x 10' mol/g is good; if the content is small, the residual potential will be large, and if the content is large, the charging property will be poor and the contrast of the electrostatic latent image will be small. .

The protective layer of the electrophotographic photoreceptor of the present invention is prepared by dissolving these thermosetting acrylic resins and picric acid in a solvent that dissolves both, coating the photosensitive layer by a conventional coating method, drying it, and then subjecting it to heat treatment. harden and form. The heat treatment temperature is 80°C to 200°C, but preferably about 80°C to 120°C in consideration of the heat resistance of the photosensitive layer. In addition, the thickness of the protective layer is 0.1 to 5 μm, but the electrophotographic properties
Considering adhesiveness and abrasion resistance, the thickness is preferably 0.2 to 2 μm.

Examples of the electron-donating substance used in the charge transport layer of the electrophotographic photoreceptor of the present invention include compounds having electron-donating groups such as alkyl groups, alkoxy groups, amino groups, and imide groups, and polycyclic compounds such as anthracene, pyrene, and phenanthrene. Examples include aromatic compounds or BM 8 compounds containing them, heterocyclic compounds such as indole, oxazole, oxadiazole, carbazole, thiazole, birapurine, imidazole, triazole, and 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.

Further, the charge generation layer of the electrophotographic photoreceptor of the present invention contains a phthalocyanine pigment, and a coating solution prepared by adding and dispersing this pigment with an appropriate binder resin is applied by a normal coating method and heated. It is dried and formed to a thickness of several μm, preferably 0.2 to 2 μm. As the phthalocyanine pigment, ε-type, α-type, β-type copper phthalocyanine, other metal phthalocyanines, and metal-free phthalocyanines can be used. By containing a phthalocyanine pigment in the charge generation layer, high sensitivity can be achieved in combination with a protective layer containing picric acid, particularly in the near-infrared region. Although the reason for this has not been elucidated in detail, it is presumed that the potential barrier is small at the junction between the charge generation layer and the protective layer.

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

The conductive support used in the electrophotographic photoreceptor of the present invention is
Any material that has conventionally known conductivity may be used, such as metal plates and metal drums made of aluminum or aluminum alloys, plates made of metal oxides such as tin oxide or indium oxide, or metals and metal oxides thereof. These include various plastic films, papers, etc. that have been treated to be conductive by attaching them by vacuum evaporation, sputtering, laminating, coating, etc.

Further, in the electrophotographic photoreceptor of the present invention, casein, polyvinyl alcohol, polyvinyl butyral,
An adhesive or barrier layer, such as polyamide, can be provided.

In this way, the electrophotographic photoreceptor of the present invention is formed by laminating a photosensitive layer comprising a charge transport layer and a charge generation layer and a protective layer on a conductive support.・
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 specifically described below, but the present invention is not limited to the combinations shown in the following examples.

(Example 1) 1-phenyl-1,2,3,4-tetrahydroquinoline-6-carpoxyaldehyde 1,1-diphenylhydrazone 1 part by weight and polycarbonate (manufactured by Mitsubishi Chemical Industries, Ltd., trade name Tubarex 7030A) 1 part by weight was dissolved in 9 parts by weight of methylene chloride, and this coating liquid was mixed with butyral resin (manufactured by Sekisui Chemical Co., Ltd., trade name: Sledge BL).
The adhesive layer of -1) was applied by dip coating onto an aluminum plate having a thickness of 0.3 μm and dried at 80° C. for 1 hour to form a charge transport layer with a thickness of 25 μm.

Next, 4 parts by weight of τ-type metal-free phthalocyanine (manufactured by Toyo Ink Manufacturing Co., Ltd.), 3 parts by weight of acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name DIANAL HR664) and melamine resin (trade name Super, made by Dainippon Ink Co., Ltd.) were added. 1 part by weight of V-Kamine L145-60) was dispersed in 100 parts by weight of an S-butyl alcohol/xylene mixed solvent.

This coating liquid was dip coated onto the charge transport layer and dried at 100° C. for 30 minutes to form a charge generation layer with a thickness of 0.3 μm.

In addition, 7 parts by weight of acrylic resin (trade name DIANAL HR664, manufactured by Mitsubishi Rayon Co., Ltd.) and melamine resin (trade name Superbenkamin Shi 14, manufactured by Dainippon Ink Co., Ltd.)
A coating solution containing 0.57 parts by weight of picric acid added to a solution of 3 parts by weight of n-butyl alcohol/xylene mixed solvent was applied on the charge generating layer by dip coating. Heat treated at ℃ for 1 hour and cured to a film thickness lI! A protective layer of m was formed.

The thus obtained electrophotographic photoreceptor was charged and exposed 500 times using an electrostatic copying paper tester (■ EPA-8100 manufactured by Kawaguchi Electric Manufacturing Co., Ltd.), and at the initial and 500th times, the charging potential vO (■ ), and then left in the dark for 1 second, the surface potential V 1 (V), 4 pW/d, 8
When exposed to 00 nm light, the surface potential becomes 1/2 VI (
The exposure amount required to attenuate to V) is EI/2 (μJ/
The residual potential VR3 (V) after 3 seconds of exposure was measured.

The measurement results are shown in Table 1.

(Comparative Example) As a comparative example, a sample was created in which the protective layer did not contain picric acid.

A charge transport layer and a charge generation layer were prepared in the same manner as in Example 1, and an i-retaining layer was formed with the same composition as in Example 1 except that it did not contain picric acid, and its properties were measured. The results are shown in Table 1.

(Margins below) Table 1 Effects of the Invention As described above, the electrophotographic photoreceptor of the present invention is formed by laminating a charge transport layer, a charge generation layer, and a protective layer in this order on a conductive support. By containing a thermosetting acrylic resin and picric acid, an electrophotographic photoreceptor was obtained that was positively charged, sensitive, and had a small increase in residual potential (and excellent abrasion resistance and durability).

Claims (3)

[Claims] (1) An electrophotographic photoreceptor characterized in that it is formed by laminating a photosensitive layer and a protective layer for the photosensitive layer on a conductive support, and the protective layer contains a thermosetting acrylic resin and picric acid. . (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 charge generation layer of the photosensitive layer contains a phthalocyanine pigment.