JP2789700B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor. More specifically, the present invention relates to an electrophotographic photosensitive member having extremely excellent durability.

[Prior Art] In recent years, electrophotographic technology has been widely used and applied not only in the field of reproduction machines but also in the field of various printers because of its immediacy and high-quality images.
Photoconductors, which are the core of electrophotographic technology, have recently been formed from inorganic photoconductors such as selenium, arsenic-selenium alloy, cadmium sulfide, and zinc oxide as photoconductive materials. A photoreceptor using an organic photoconductive material having advantages such as easy and easy production has been developed.

Among organic photoconductors, a so-called stacked photoconductor in which a charge generation layer and a charge transfer layer are stacked has been devised, and has been the mainstream of research.

Laminated photoreceptors are highly efficient charge generating substances,
In addition, a highly sensitive photoreceptor can be obtained by combining the charge transfer material, a photoreceptor with a wide selection of materials and high safety can be obtained, and coating productivity is high and the cost is relatively advantageous. Therefore, there is a high possibility that the photoconductor will become the mainstream of the photoconductor, and it is being eagerly developed.

[Problems to be Solved by the Invention] However, the laminated photoreceptor conventionally put into practical use has a decrease in charging potential, accumulation of residual potential, fluctuation of sensitivity, and the like when used repeatedly, and is not necessarily required. Life is not enough. In particular, the accumulation of the residual potential often causes a problem in the organic photoreceptor, and is a major factor that hinders high printing durability of the organic photoreceptor. There are several possible causes of the accumulation of the residual potential, but the most influential one is attributed to impurities in the charge transfer layer. Such impurities are those originally present in the composition, those generated by corona discharge, image exposure, repeated exposure to light from a neutralization lamp, etc., and deterioration due to exposure to external light during maintenance, etc. What is generated is conceivable.

That is, it is considered that such impurities serve as traps to capture carriers and form immovable space charges, resulting in a residual potential.

As one of means for suppressing the residual potential considered to be caused by such traps in the charge transfer layer, attempts have been made to add an electron-withdrawing substance to the charge transfer layer.

Generally, when an electron-withdrawing substance is added to an electron-donating compound, a charge-transfer complex is formed and its new absorption appears on the longer wavelength side. When light corresponding to the absorption band of the electrotransfer complex is irradiated, a small amount of movable carriers (hole-electrons) are generated in the charge transfer layer, and the carriers neutralize space charges that cannot move. It is considered that the residual potential is suppressed. However, at present, many electron-withdrawing substances known so far have problems such as insufficient suppression of residual potential, increase in dark decay, decrease in surface potential due to repeated use, and decrease in sensitivity. is there.

Means for Solving the Problems The present inventors have conducted intensive studies on an electron-withdrawing compound that has a sufficient effect of suppressing the residual potential and has little effect on other electric characteristics. The present inventors have found that an amphoteric compound exhibits extremely excellent performance, and reached the present invention.

That is, the gist of the present invention is to provide an electrophotographic photosensitive member having at least a charge generation layer and a charge transfer layer on a conductive substrate, wherein the charge transfer layer contains an electron withdrawing compound represented by the following general formula (1). An electrophotographic photoreceptor characterized in that:

(Wherein, R ¹ and R ² each independently represent a halogen atom, R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom,
Or a halogen atom, and X represents a cyano group, an alkoxycarbonyl group, an optionally substituted aryloxycarbonyl group, or an optionally substituted aryl group. Hereinafter, the present invention will be described in detail.

The photoreceptor of the present invention is provided on a conductive support. As the conductive support, aluminum, stainless steel, copper,
A metal material such as nickel; an insulating support such as a polyester film or paper provided on the surface with a conductive layer such as aluminum, copper, palladium, tin oxide, or indium oxide is used.

A well-known barrier layer may be provided between the conductive support and the charge generation layer.

As the barrier layer, for example, an anodized aluminum film, an inorganic layer such as aluminum oxide and aluminum hydroxide, an organic layer such as polyvinyl alcohol, casein, polyvinyl pyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, etc. Layers are used.

Examples of the charge generation material used in the charge generation layer include selenium and its alloys, arsenic-selenium, cadmium sulfide, zinc oxide, other inorganic photoconductive materials, phthalocyanine, azo dyes, quinacridone, polycyclic quinone, pyrylium salts, and thiapyrylium salts. And various organic pigments and dyes such as isodigo, thioindigo, anthantrone, pyranthrone and cyanine.

Among them, metals such as metal-free phthalocyanine, copper indium chloride, gallium chloride, tin, oxytitanium, zinc, vanadium and the like, or oxides thereof, phthalocyanines coordinated with chloride, monoazo, bisazo, trisazo, and azo such as polyazos Pigments are preferred. The charge generation layer may be formed of any of these substances, for example, polyester resin, polyvinyl acetate, polyacrylate, polymethacrylate, polyester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin, epoxy resin, urethane resin, cellulose ester. It is used in a form bound with various binder resins such as cellulose ether and cellulose ether. In this case, the ratio of the charge generating substance used is 100 in the binder resin.
Used from 30 to 500 parts by weight for parts by weight,
The film thickness is usually 0.1 μm to 2 μm, preferably 0.15 μm
m to 0.8 μm is preferred.

Further, the charge generation layer may contain various additives such as a leveling agent, an antioxidant, and a sensitizer for improving coating properties, if necessary.

The charge transfer layer is basically composed of an electron withdrawing compound represented by the following general formula (1) together with a charge transfer material and a binder resin.

However, R ¹ and R ² each independently represent a halogen atom such as chlorine, bromine and iodine. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom; or a halogen atom such as chlorine, bromine or iodine.

X is a cyano group; an alkoxycarbonyl group such as a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, or a butoxycarbonyl group; an aryloxycarbonyl group such as an optionally substituted phenoxycarbonyl group or a naphthoxycarbonyl group; Represents an aryl group such as a phenyl group and a naphthyl group,
Examples of the substituent of the aryloxycarbonyl group and the aryl group include a cyano group; a nitro group; an alkyl group such as a methyl group and an ethyl group; and a halogen atom such as chlorine, bromine and iodine.

The electron-withdrawing compound represented by the general formula (1) can be easily synthesized, for example, by condensing a benzaldehyde represented by the general formula (2) with a nitrile compound represented by the general formula (3). .

Here, in the general formulas (2) and (3), R ^{1 to} R ⁵ and X represent the same substituents as described above.

Next, main specific examples of the compound represented by the general formula (1) will be shown.

Examples of the charge transfer material include heterocyclic compounds such as carbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, and thiadiazole, aniline derivatives, hydrazone compounds, aromatic amine derivatives, stilbene derivatives, and groups comprising these compounds. And an electron-donating substance such as a polymer having in a main chain or a side chain. Examples of the binder resin used in the charge transfer layer include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, polycarbonate, polyester, polyester carbonate, polysulfone, polyimide, phenoxy, epoxy, and silicone resins. And the like, and partially crosslinked cured products thereof can also be used.

The ratio of the electron-withdrawing compound represented by the general formula (1) to the binder resin is 0.0 to 100 parts by weight of the binder resin.
It is used in the range of 1 to 30 parts by weight, preferably 0.1 to 10 parts by weight.

The ratio between the charge transfer material and the binder resin is 30 to 200 parts by weight, preferably 40 to 200 parts by weight, based on 100 parts by weight of the binder resin.
Used in the range of 120 parts by weight.

The charge transfer layer may contain various additives such as an antioxidant and a sensitizer as needed. The thickness of the charge transfer layer is preferably 10 to 60 μm, and more preferably 10 to 45 μm.

[Effect of the Invention] The electrophotographic photoreceptor in which the specific electron-attracting compound is contained in the charge transfer layer according to the present invention hardly accumulates a residual potential even when it is repeatedly used, and furthermore, the chargeability and the sensitivity fluctuate very much. And the stability is extremely good.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but it should not be construed that the invention is limited thereto.

Production Example [Exemplified Compound (5)] After dissolving 1.1 g of 2,3,6-trichlorobenzaldehyde and 0.4 g of malononitrile in 5 ml of tetrahydrofuran, 1 drop of piperidine was added and reacted at 65 ° C. for 1 hour. After cooling to room temperature, the precipitated crystals were collected by filtration and recrystallized from isopropanol to obtain 1.1 g of pale yellow crystals. The melting point was 75-77 ° C.

Example 1 10 parts by weight of a bisazo compound having the following structure was added to 150 parts by weight of 4-methoxy-4-methylpentanone-2,
Pulverization and dispersion treatment was performed with a sand grind mill. The pigment dispersion obtained here was added to a 5% 1,2-dimethoxyethane solution of polyvinyl butyral (trade name # 6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.), and finally, the solid content concentration was 4.0%.
Was prepared.

The thus obtained dispersion was applied to an aluminum-evaporated surface of a 75 μm-thick polyester film on which aluminum had been evaporated so that the dry film thickness was 0.7 g / mm ^2, and a charge generation layer was provided.

Next, a hydrazone compound 95 shown below is formed on the charge generation layer.
Parts by weight 1.5 parts by weight of Exemplified Compound (5) and 100 parts by weight of a polycarbonate resin having the following structure After applying a solution dissolved in a mixed solvent of 1,4-dioxane and tetrahydrofuran, the solution was dried at room temperature for 30 minutes and at 125 ° C. for 30 minutes, and a charge transfer layer was provided so that the film thickness after drying was 20 μm. . The photoreceptor thus prepared was mounted on a photoreceptor characteristic measuring machine, and the cycle of charging at a peripheral speed of 260 mm / sec (set to −700 V with a scorotron at an initial stage), exposure, and charge removal was repeated 300,000 times. The fluctuation of the dark potential and the residual potential at that time were measured.

Table 1 shows the results. From this result, it can be seen that the dark potential does not change and the accumulation of the residual potential is small even after 300,000 repetitions.

Examples 2 to 7 Instead of the electron-withdrawing compound used in Example 1, exemplified compounds (1), (2) of the general formula (1),
A photoconductor was prepared in the same manner as in Example 1 except that (6), (7), (9) and (10) were used, and the characteristics were evaluated. Table 1 shows the results.

It can be seen that all of these photoconductors have little residual potential accumulation.

Comparative Example A photoconductor was prepared in the same manner as in Example 1 except that the electron-withdrawing compound was not added, and its characteristics were evaluated. Table 1 shows the results. As is clear from the results in Table 1, the accumulation of the residual potential is large.

As is clear from the above results, the photoreceptor of the present invention has very excellent performance.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-7643 (JP, A) JP-A-1-287570 (JP, A) JP-A-50-137543 (JP, A) JP-A-59-76 7956 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 5/05 104 B G03G 5/06 313

Claims (1)

(57) [Claims] An electrophotographic photosensitive member having at least a charge generation layer and a charge transfer layer on a conductive substrate, wherein the charge transfer layer contains an electron withdrawing compound represented by the following general formula (1). An electrophotographic photosensitive member characterized by the following. (Wherein, R ¹ and R ² each independently represent a halogen atom, R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom,
Or a halogen atom, and X represents a cyano group, an alkoxycarbonyl group, an optionally substituted aryloxycarbonyl group, or an optionally substituted aryl group. )