JPH03211562A - Laminated electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To eliminate picture blurring especially under high temp. and humidity conditions and to improve the wear resistance and durability of the sensitive body by successively laminating a charge transfer layer, a charge generating layer and a protective layer on a conductive substrate and incorporating a thermosetting silicone resin, a urethane elastomer and further phthalic anhydride into the protective layer. CONSTITUTION:The charge transfer layer, charge generating layer and protective layer are successively laminated on the conductive substrate, and the thermosetting silicone resin, urethane elastomer and phthalic anhydride are incorporated into the protective layer to obtain a high-hardness coating film excellent in light transmission and weatherability which improves the wear resistance of the sensitive body. Besides, the moisture permeability characteristic of the silicone resin is prevented, the resistance of the protective layer is stabilized under high temp. and humidity conditions, and picture flowing is improved. Consequently, a laminated electrophotographic sensitive body having sensitivity when positively charged, stable to environmental temp. and humidity, without picture blurring under high temp. and humidity conditions and excellent in wear resistance and durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrophotographic photoreceptor containing an organic photoconductive substance, and particularly relates to a laminated electrophotographic photoreceptor used for positive charging. Conventional technology Photoreceptors made of inorganic photoconductive materials such as selenium, selenium, selenium, selenium, selenium, sulfurization, zinc oxide, etc. have been widely used as electrophotographic photoreceptors. Research is progressing on organic photoconductive materials that have characteristics such as the ability to select compounds that exhibit conductivity.

An electrophotographic photoreceptor using an organic photoconductive material in the photosensitive layer.It has the advantages of being easy to form a film, being highly flexible, offering a high degree of freedom in design, and being inexpensive and non-polluting. Sensitivity and photoreceptor life were inferior compared to inorganic photoconductive materials. Therefore, in order to improve these, the functions of a charge generation layer and a charge transport layer are separated to form a photosensitive layer. A type electrophotographic photoreceptor was proposed and put into practical use.The charge transport agent generally used in this laminated type electrophotographic photoreceptor is an electron-donating substance such as pyrazoline, hydrazone, or oxazole.The charge transport layer is a hole-transfer layer. It is a mobile type, so if a charge transport layer is laminated on a charge generation layer, it can be used with a negative charge.
Strength that is repeatedly used in the processes of development, transfer, cleaning, and static elimination In this series of processes, positive charging is more stable in corona discharge than negative charging, and the amount of ozone generated is small, resulting in less ozone oxidation. There is little deterioration in characteristics ~ Also, inorganic photoreceptors such as selenium and selenium-tellurium alloys that have been used in the past can be used with positive charging because these electrophotographic processes can be shared. There is a strong demand for organic photoreceptors (~ here, in order to achieve positive charging with a structure in which a charge transport layer is laminated on a normal charge generation layer), it is possible to use an electron-accepting substance such as trinitrofluorenone as a charge transport agent. Good power (These electron-accepting substances are not commonly used because they are rarely available with high mobility, are chemically unstable, and have harmful effects such as carcinogenicity.) t 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 low conductivity support (in this case, a charge transport layer and a charge generation layer are stacked in this order). If the carrier injection into the charge transport layer is large and the chargeability decreases, the charge generation layer is generally thin and has low mechanical strength (it has disadvantages such as poor durability).・Proposal for a three-layer structure in which a protective layer of a thin resin film is further provided on the charge generation layer, or a proposal for a four-layer structure consisting of a charge transport layer, a charge generation layer, a charge injection blocking layer, and a surface protection layer, or a charge transport layer and a charge injection layer. In the two-layer structure of the charge generation layer, there are proposals to increase the resin ratio of the charge generation layer to make the film thicker to about 5 μm to improve mechanical strength, and to maintain sensitivity by adding a charge transport agent to the charge generation layer. For example, The 3rd International Combination of Advanced Non-Impact Printing Technology (The 3rd International
ational Congress on Advance
ces in Non-Impa Member Printing
Tect+nologies) Proceedings p115, Proceedings of the 59th Research Conference of the Society of Electrophotography p184, etc.Also, in the case of thin resin films, polyester resin, polyvinyl butyral resin, phenol resin, cellulose acetate, styrene maleic anhydride copolymer, etc. Not yet
Polyamide resin, polyimide resin, melamine resin, etc. (eg.
-15748 Publication Special Publication No. 52-24414
Special Publication No. 56-34860 Publication No. 56-5375
Publication No. 6 Special Publication No. 60-55357 Publication No. 61 of Special Publication
-22345, etc.) are not sufficient in terms of durability such as low abrasion resistance and environmental stability due to repeated use. Thin films are not durable enough, -;a
Although increasing the film thickness has drawbacks such as an increase in the residual potential and deterioration of the repeatability, there is a method using a protective layer in which a metal oxide is dispersed in a binder resin as a protective layer (for example, (L Special Public Service 1977-
39846, Japanese Patent Publication No. 58-121044, Japanese Patent Publication No. 59-223445, etc.) have also been proposed. Even if the content in the layer is constant, depending on the state of dispersion, the resistance value may fluctuate and the characteristics may become unstable.
In addition, unless the compounding ratio, particle size, etc. are precisely controlled, environmental or repeated fluctuations in chargeability and residual potential will occur, which is the problem that the invention aims to solve. However, there are not many products with satisfactory characteristics, which are stable in the usage environment such as temperature and humidity, can be used with positive charging, and have a longer lifespan that satisfies the characteristics required as an electrophotographic photoreceptor. The development of a laminated electrophotographic photoreceptor is desired.

In view of the above-mentioned problems, the present invention has been developed to have sensitivity with positive charging, little increase in residual potential due to repetition, stable against temperature and humidity, no image fading especially under high temperature and high humidity, and excellent abrasion resistance.
The present invention aims to provide a laminated electrophotographic photoreceptor with excellent durability. The laminated electrophotographic photoreceptor of the present invention is a laminated electrophotographic photoreceptor in which the protective layer contains a thermosetting silicone resin, a urethane elastomer, and phthalic anhydride. The laminated electrophotographic photoreceptor of the present invention can be positively charged and sensitive by laminating a charge transport layer, a charge generation layer, and a protective layer in this order. , a coating film with high hardness and excellent light transmission and weather resistance is obtained.Furthermore, by containing a urethane elastomer at the same time as a thermosetting silicone resin, it improves abrasion resistance and prevents the inherent moisture permeability of silicone resin. It stabilizes the resistance of the protective layer under high temperature and high humidity conditions and improves image blurring.It also contains urethane elastomer to prevent cracks caused by curing shrinkage of the silicone resin during film formation and to prevent adhesion to the underlying layer. The laminated electrophotographic photoreceptor of the present invention (with thermosetting silicone resin and urethane elastomer in the protective layer)
Furthermore, by containing phthalic anhydride, it is possible to reduce the increase in residual potential due to repetition and extend the actual service life of the photoreceptor. In the following, the laminated electrophotographic photoreceptor of the present invention will be described in detail. Protection of the laminated electrophotographic photoreceptor of the present invention The thermosetting silicone resin used in the layer may be one in which the monomer is a hydrolyzate of alkoxysilane and has a bifunctional or trifunctional silanol group, and the alkyl group may be a methyl group or a phenyl group. These thermosetting silicone resins are preferably monomers that are soluble in alcoholic solvents, so they can be applied without corroding the underlying layer, and after forming the coating, they condense and harden through heat treatment. Similarly, the urethane elastomer contained in the protective layer does not corrode the underlying layer. After polymerizing an excess of the polyol in a low boiling point solvent such as acetone, n-hexane, or ethyl acetate, 1-propano-/
2-Flobanol/L, 1-butanol 2-butanol 2-methylpropano-/k 1-pentano-/k 2-pentanol is replaced with an alcoholic solvent containing at least one selected from diacetone alcohol and the like. The protective layer of the laminated electrophotographic photoreceptor of the present invention can also be obtained by dissolving the thermosetting silicone resin, urethane elastomer, and further phthalic anhydride in a solvent (L/%) on the photosensitive layer. It is formed by coating and drying using a normal coating method and then hardening by heat treatment.

The heat treatment temperature is 80°C to 200°C (preferably 80°C to 120°C considering the heat resistance of the photosensitive layer).
℃ In addition, the thickness of the protective layer is preferably 0.1 to 5 μm.Electrophotographic Poetry Adhesion Method Considering abrasion resistance, a thickness of 0.2 to 2 μm is particularly preferable. The ratio of silicone resin to urethane elastomer is preferably 2:8 to 8:2 in terms of solid content weight ratio after drying. If it is too thick (if it is too thick, the environmental stability will be poor and image blurring will occur at high temperatures). Hydrogen is substituted with at least one halogen or nitro group, specifically phthalic anhydride,
3-chlorophthalic anhydride, 4-chlorophthalic anhydride,
Examples include 3-nitrophthalic anhydride, 3,6-dichlorophthalic anhydride, 4,5-dichlorophthalic anhydride, and tetrachlorophthalic anhydride.
As the content of nitrated benzoic acid (1 g solid content of mixed resin of thermosetting silicone resin and urethane elastomer)
preferably 1 x 10-liol to 5 x 10-'n
The laminated electronic device of the present invention has a good content of +ol, and if the content is less than this, the residual potential will be large, and if the content is large, the charging property will be poor and the contrast potential of the electrostatic latent image will be small. As an electron-donating substance used in the charge transport layer of a photographic photoreceptor (alkyl group alkoxy group)
Amino group Compounds having electron-donating groups such as imide groups Polycyclic aromatic compounds such as anthracene, pyrene, and phenanthrene, or derivatives containing them Indole, Oxasheetk Oxadiazol-)k Carbacy/l
< Chia sheets k pyrazoline, imidazo-/l,,
These electron-donating substances and binder resins are dissolved in a suitable solvent, and the force (electron When the donating substance is a polymer compound, the charge transport layer may be formed alone without mixing with a binder resin.The thickness of the charge transport layer is from several μm to several tens of μm, preferably 5 μm. Charge generation method for the laminated electrophotographic photoreceptor of the present invention A coating solution prepared by adding and dispersing a phthalocyanine pigment with a suitable binder resin is mixed into a coating solution with a thickness of ~25 μm. Apply by coating method Heat dry L Force to form a film with a thickness of several μm (preferably, form a film with a thickness of 0.2 to 2 μm) , other metal phthalocyanis, metal-free phthalocyanine, etc. can be used. By using phthalocyanine pigments in the charge generation layer, high sensitivity can be achieved in combination with a protective layer containing phthalic anhydride, especially in the near-infrared region. The reason for this has not been elucidated in detail. It can be inferred that the potential barrier is small in the bonding between the charge generation layer and the protective layer. It is used as needed for the purpose of improving the adhesion with the uniformity of the coating film and adjusting the fluidity during coating. Examples include polycarbonate, acrylic resin, methacrylic resin, silicone resin, and copolymers of these resins.
The solvent may be any solvent as long as it dissolves the charge generating agent L, charge transporting agent, or binder resin.
Ketones, esters, ethers, alcohols, etc. may be used as the conductive support used in the laminated electrophotographic photoreceptor of the present invention. A metal plate such as an aluminum alloy, a slope made of a metal oxide such as tin oxide or indium oxide, or a conductive treatment by adhering such metals and metal oxides by vacuum evaporation, sputter link lamination, coating, etc. The laminated electrophotographic photoreceptor of the present invention is similar to ordinary electrophotographic photoreceptors, with casein, polyvinyl alcohol/k, between the conductive support and the charge transport layer. An adhesive layer or barrier layer such as polyvinyl butylar/k polyamide can be provided. In this way, a photosensitive layer consisting of a charge transport layer, a charge generation layer and a protective layer are laminated on a conductive support. The laminated electrophotographic photoreceptor of the present invention (which has a charge transport layer, a charge generation layer, and a protective layer laminated in this order on a conductive support and is positively charged and sensitive) will now be described in detail. (Example 1) 1, 1-bis(P-diethylaminophenyl) 4.4
- 1 part by weight of diphenyl-1,3-butadiene and 1 part by weight of polycarbonate (manufactured by Mitsubishi Chemical Industries, Ltd., trade name: TUVALEX 7030A) were dissolved in 9 parts by weight of methylene chloride, and this coating solution was applied to an aluminum plate by seed coating LA 80. ℃ for 1 hour to form a charge transport layer with a thickness of 25 μm. HR664) and 1 part by weight of melamine resin (trade name: Super Beckamine L145-60, manufactured by Dainippon Ink Co., Ltd.) were dispersed in 115 parts by weight of S-butyl alcohol. Seed coating and drying at 100°C for 1 hour to form a charge generation layer with a film thickness of 0.2 μm. 7 parts by weight of thermosetting silicone resin (trade name Tosgard 520, manufactured by Toshiba Silicone Corporation) and urethane elastomer (manufactured by Mitsui). Manufactured by Toatsu Chemical Co., Ltd. Product name: Orester NL22
In a solution of 3 parts by weight of 49E) dissolved in 115 parts by weight of n-butyl alcohol, 0.37 parts by weight of phthalic anhydride was added.
Part by weight of the coating liquid is applied onto the charge generation layer by seed coating L.
Heat treated at 120℃ for 1 hour and cured to a film thickness of 1μ
The thus obtained laminated electrophotographic photoreceptor was charged and exposed 500 times using an electrostatic copying paper tester (EPA-8100, manufactured by Kawaguchi Electric Seisakusho). At the initial stage and at the 500th time, charging potential VO (V), then surface potential when left in the dark for 1 second Vl (V), 4 μW/C
When exposed to mQ 800 nm light, the surface potential is 1 /
Exposure amount required to attenuate to 2 Vl E 1/
2 (μJ/cm") and the residual potential VR (V) after 3 seconds of exposure were measured, respectively. The evaluation results are shown in Table 1.

(Example 2) A charge transport layer, a charge generation layer, and a protective layer were formed in the same manner as in Example 1 except that tetrachlorophthalic anhydride was used instead of phthalic anhydride in the protective layer of Example 1. The characteristics were measured using the following methods and the results are shown in Table 1.

(Comparative Example) As a comparative example, a charge transport layer and a charge generation layer were prepared in the same manner as in Example 1, in which a sample was prepared with a structure in which the protective layer did not contain phthalic anhydride, except that it did not contain phthalic anhydride. A protective layer was formed with the same composition as in Example 1, and its properties were measured.The results are shown in Table 1.

Effects of the Invention A detailed explanation of the laminated electrophotographic photoreceptor of the present invention (a laminated electrophotographic photoreceptor of the present invention (i.e., a charge transport layer, a charge generation layer, and a protective layer are formed on a conductive support in this order) Formed in a laminated manner, and the protective layer contains thermosetting silicone resin, urethane elastomer, and phthalic anhydride, it is positively charged and sensitive, and there is little increase in residual potential due to repetition, making it suitable for environments with high temperature and humidity. Natsu9 is a laminated electrophotographic photoreceptor that is stable under various conditions, does not cause image fading, especially under high temperature and high humidity conditions, and has excellent abrasion resistance and durability.

[Brief explanation of drawings]

The figure is a characteristic comparison diagram between the performance of the embodiment of the present invention and the performance of the conventional example.

Claims (4)

[Claims] (1) In a laminated electrophotographic photoreceptor formed by laminating a photosensitive layer and a protective layer for the photosensitive layer on a conductive support,
A laminated electrophotographic photoreceptor, wherein the protective layer contains a thermosetting silicone resin, a urethane elastomer, and further phthalic anhydride. (2) The phthalic anhydride is phthalic anhydride itself;
Alternatively, the laminated electrophotographic photoreceptor according to claim 1, wherein hydrogen in the benzene ring of phthalic anhydride is substituted with at least one halogen or nitro group. (3) The laminated 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. . (4) The laminated electrophotographic photoreceptor according to claim (1), wherein the charge generation layer of the photosensitive layer contains a phthalocyanine pigment.