JPH0715591B2 - Multilayer electrophotographic photoconductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated electrophotographic photoreceptor containing an organic photoconductive substance.

2. Description of the Related Art Conventionally, as an electrophotographic photosensitive member, a photosensitive member made of an inorganic photoconductive substance such as selenium, selenium-tellurium alloy, cadmium sulfide and zinc oxide has been widely used. In recent years, research on organic photoconductive substances having characteristics such as easy synthesis and selection of a compound exhibiting photoconductivity in an appropriate wavelength range has been advanced.

An electrophotographic photoreceptor using an organic photoconductive substance as a photosensitive layer is
The electrophotographic process has advantages such as easy film formation, high flexibility and high degree of freedom in design, inexpensiveness and no pollution, etc., which is not possible with a photoconductor made of an inorganic photoconductive substance. (For example, a belt-shaped photoconductor is used). Among them, in order to improve the sensitivity and the life of the photoconductor, a laminated electrophotographic photoconductor in which a charge generation layer and a charge transport layer are separated in function to form a photoconductive layer, is proposed,
Furthermore, active research is being conducted on the improvement of sensitizers and the development of sensitizing methods. (For example, Proceedings of the 16th Workshop of the Electrophotographic Society) Problems to be Solved by the Invention However, the above-mentioned organic photoconductor also sufficiently satisfies the requirements as various electrophotographic photoconductors such as sensitivity and repeatability. The current situation is that it has not yet been achieved. Therefore,
It is desired to develop a high-sensitivity electrophotographic photosensitive member that fully satisfies the characteristics required for the electrophotographic photosensitive member by taking advantage of the organic photoconductive substance.

Means for Solving the Problems In view of the above problems, the present invention contains a charge generation layer containing a benzopyrylium salt having a trimethine structure represented by the following structural formula, and at least poly-N-vinylcarbazole. Brominated poly-N- with the charge transport layer
By providing an intermediate layer containing vinylcarbazole and sequentially laminating it on a conductive support, an electrophotographic photosensitive member having high sensitivity and good repeated stability is provided.

(In the formula, R1 is hydrogen or a phenyl group, R2 is hydrogen, P-
Methoxyphenyl group, 4'-methoxynaphthyl 1'group or 2'-methoxynaphthyl 1'group, R3 is hydrogen, methoxy group, nitro group or phenyl group, R4 is hydrogen or methoxy group, and X is oxygen or sulfur atom. ing. ) Action The laminated electrophotographic photoreceptor of the present invention has an intermediate layer provided between the charge generation layer and the charge transport layer, and thus an intermediate layer containing brominated-poly-N-vinylcarbazole. Although the sensitivity is improved and the residual potential is decreased by providing, the theoretical elucidation of this effect has not been made yet. However, in the laminated type photoreceptor, the interface between the charge generation layer and the charge transport layer has a great influence on the electrophotographic characteristics, and when the charge generation layer elutes in the charge transport layer, the characteristics are impaired.
Further, if the interfacial barrier between both layers is too large, sufficient characteristics cannot be obtained. Therefore, it is considered that the provision of the intermediate layer improves the injection efficiency at the interface between both layers, and such an effect can be obtained.

Examples Hereinafter, the laminated electrophotographic photoreceptor of the present invention will be described in detail.

The charge generating layer of the laminated electrophotographic photoreceptor of the present invention is obtained by dispersing or dissolving a benzopyrylium salt having a trimethine structure by adding a suitable binder resin, and coating the benzopyrylium salt on a conductive support. To be

As the benzopyrylium salt having a trimethine structure,
Specifically, 2- [3′-3 ″ -phenyl-6 ″ -methoxy-2 ″ -benzopyranylidene) propenyl] -3-
Phenyl-6-methoxybenzopyrylium perchlorate, 2- [3'-3 ", 6" -diphenyl-4 "-p-methoxyphenyl-2" -benzopyranylidene) propenyl] -3,6-diphenyl- 4-p-methoxybenzopyrylium perchlorate, 2- [3 ′-(3 ″ -phenyl-2 ″ -benzopyranylidene) propenyl] -3-phenylbenzopyrylium perchlorate and the like can be mentioned.

The brominated poly-N-vinylcarbazole used for the intermediate layer is one in which 0.5 to 2 bromine atoms are substituted for one vinylcarbazole ring, and poly-N-vinylcarbazole is mixed with chlorobenzene-benzene. It can be easily synthesized by treating with a small amount of N-bromosuccinimide in the presence of a small amount of benzoyl peroxide in a solvent, heating and pouring into methanol.

Although brominated poly-N-vinylcarbazole alone has a film-forming property, it may be used as necessary for the purpose of improving the adhesiveness with other layers, improving the uniformity of the coating film, and adjusting the fluidity during coating. A binder resin can be used. In particular,
Examples thereof include polyvinyl butyral, polyvinyl acetate, polycarbonate, acrylic resin, methacrylic resin, and copolymers of these resins. Further, the solvent for dissolving the brominated poly-N-vinylcarbazole and the binder resin is limited by the brominated poly-N-vinylcarbazole, but specifically, it is halogenated carbonized such as chloroform, methylene chloride, and ethylene chloride. Hydrogen and halogenated aromatics such as chlorobenzene can be used.

The coating solution thus dispersed and prepared is applied by a normal coating solution, dried by heating, and a charge generation layer and an intermediate layer are sequentially formed with a film thickness of several μm, preferably 0.2 to 2 μm.
It is preferable to form the film with a thickness of.

The charge transport layer is obtained by applying a coating liquid in which poly-N-vinylcarbazole is dissolved as a charge transport agent on the intermediate layer. Aromatic hydrocarbons such as toluene and xylene can be used as a solvent for dissolving the coating liquid. The coating solution prepared in this manner is applied by a usual coating method and heated and dried to form a charge transport layer having a film thickness of several μm to several tens of μm, preferably 5 μm.
It is preferable to form the film with a thickness of up to 25 μm.

The conductive support used in the laminated electrophotographic photosensitive member of the present invention may be any one having a conventionally known conductivity, and may be a metal plate such as aluminum or aluminum alloy and a metal drum, tin oxide, or oxide. It is a plate made of a metal oxide such as indium, or various plastic films, paper and the like to which a metal and a metal oxide thereof are attached by vacuum vapor deposition, sputtering, laminating, coating or the like to have been electroconductively treated.

Furthermore, in order to improve the flexibility, uniformity, mechanical strength, etc. of the coating film, the intermediate layer and charge transport layer constituting the laminated electrophotographic photosensitive member of the present invention include o-terphenyl and an epoxy compound. Plasticizers such as phthalates, maleates and chlorinated paraffins may be added.
Further, as in the case of an ordinary electrophotographic photoreceptor, an adhesive layer or a barrier layer of casein, polyvinyl alcohol, polyvinyl butyral or the like can be provided between the conductive layer and the charge generation layer.

Thus, the electrophotographic photosensitive member of the present invention formed by laminating the charge generation layer, the intermediate layer and the charge transport layer on the conductive support has a charge generation layer, an intermediate layer, and an intermediate layer on the conductive support. The charge transport layer may be sequentially laminated, or may be laminated on the conductive support in the order of the charge transport layer, the intermediate layer and the charge generation layer. The former case has negatively charged sensitivity and the latter case has positively charged sensitivity, but the former is preferable from the viewpoint of surface film strength and durability.

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

Example 1 2- [3 ′-(3 ″, 6 ″ -diphenyl-4 ″ -methoxyphenyl-2 ″ benzopyranylidene) propenyl] -3,
1 part by weight of 6-diphenyl-4-methoxyphenylbenzopyrylium perchlorate and 1 part by weight of vinyl chloride-vinyl acetate copolymer (trade name VMCH manufactured by Union Carbide Co.) were dissolved in 100 parts by weight of methylene dichloride. This coating solution was spin-coated on an aluminum plate at 300 rpm and dried at 80 ° C. for 1 hour to form a charge generation layer having a thickness of 0.3 μm. next,
1 part by weight of brominated poly-N-vinylcarbazole and O-
0.2 parts by weight of terphenyl was dissolved in 50 parts by weight of dioxane, and this coating liquid was spin-coated at 200 rpm on the charge generation layer,
It was dried at 80 ° C. for 1 hour to form an intermediate layer having a film thickness of 0.5 μm. Furthermore, 1 part by weight of poly-N-vinylcarbazole (trade name Tubicor # 210, manufactured by Anan Fragrance Co., Ltd.) and O-
0.3 parts by weight of terphenyl was dissolved in 10 parts by weight of toluene. This solution is blade-coated on the intermediate layer,
After drying for an hour, a charge transport layer having a film thickness of 15 μm was formed.

Using the electrostatic copying paper tester (EPA-8100 manufactured by Kawaguchi Denki Seisakusho Co., Ltd.), the laminated electrophotographic photoreceptor thus obtained was charged at −6 kV to obtain a surface potential V ₀ (V), After that, the surface potential V ₁ (V) when left in a dark place for 1 second, and the exposure amount E1 / 2 (lux ・ lux) required for the surface potential to decay to 1/2 V ₁ (V) when exposed to 5 lux white light sec) and the surface potential VR ₆ (V) after 6 seconds of exposure were measured. Table 1 shows the measurement results.

(Example 2) 2- [3 '-(3 ", 6" -diphenyl-4 "-methoxyphenyl-2" -benzopyranylidene) propenyl]-
2- [3 ′-(3 ″ -phenyl-2 ″ -benzopyranylidene) propenyl] -3-instead of 3,6-diphenyl-4-methoxyphenylbenzopyrylium perchlorate
A photoreceptor was prepared and its characteristics were measured in the same manner as in Example 1 except that phenylbenzopyrylium perchlorate was used. The results are shown in Table 1.

(Comparative Example 1) As a comparative example, a sample having only the charge generation layer and the charge transport layer was prepared without providing the intermediate layer.

2- [3 '-] 3 ", 6" -diphenyl-4 "-methoxyphenyl-2" -benzopyranylidene) propenyl]-
Dissolve 1 part by weight of 3,6-diphenyl-4-methoxyphenylbenzopyrylium perchlorate and 1 part by weight of vinyl chloride-vinyl acetate copolymer (trade name VMCH manufactured by Union Carbide Co.) in 100 parts by weight of methylene dichloride. did. Using this coating liquid, a charge generation layer was prepared in the same manner as in Example 1. Further, the charge transport layer was also prepared in the same manner as in Example 1,
The characteristics were measured. The results are shown in the table.

(Comparative Example 2) 2- [3 '-] 3 ", 6" -diphenyl-4 "-methoxyphenyl-2" -benzopyranylidene) propenyl]-
2- [3 ′-(3 ″ -phenyl-2 ″ -benzopyranylidene) propenyl] -3-instead of 3,6-diphenyl-4-methoxyphenylbenzopyrylium perchlorate
A photoreceptor was prepared and its characteristics were measured in the same manner as in Comparative Example 1 except that phenylbenzopyrylium perchlorate was used. The results are shown in the table.

EFFECTS OF THE INVENTION As described above, the laminated electrophotographic photoreceptor of the present invention has been described in detail. The laminated electrophotographic photoreceptor of the present invention includes a charge generation layer containing a benzopyrylium salt having a trimethine structure and at least poly-. An intermediate layer containing brominated poly-N-vinylcarbazole is provided between the charge transporting layer containing N-vinylcarbazole and the layers are sequentially laminated on a conductive support to form a highly sensitive layer. Became.

Claims (2)

[Claims] 1. A charge generation layer containing a benzopyrylium salt having a trimethine structure represented by the following structural formula:
An intermediate layer containing brominated poly-N-vinylcarbazole is provided between the charge transporting layer containing at least poly-N-vinylcarbazole, and is sequentially laminated on a conductive support. Multilayer electrophotographic photoreceptor. (In the formula, R ₁ is hydrogen or a phenyl group, R ₂ is hydrogen, p-
Methoxyphenyl group, 4'-methoxynaphthyl 1'group or 2'-methoxynaphthyl 1'group, R ₃ is hydrogen, methoxy group, nitro group or phenyl group, R ₄ is hydrogen or methoxy group, X is oxygen or sulfur atom Is represented. ) 2. The laminated type according to claim 1, wherein the brominated poly-N-vinylcarbazole is substituted with 0.5 to 2 bromine atoms per one carbazole ring. Electrophotographic photoreceptor.