JP2789701B2 - 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 copying machines but also in the field of various printers in recent years because of its immediacy; high-quality images can be obtained.
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 become 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, and various studies have been made.

[Problems to be Solved by the Invention] However, the laminated photoreceptor that has been put to practical use in the past, when used repeatedly, has a decrease in charging potential, accumulation of residual potential, fluctuation in sensitivity, and the like due to electrical characteristics, and it is not always useful. Is not enough. In particular, accumulation of residual potential often becomes a problem in organic photoconductors, which is one of the major factors that hinder high printing durability of organic photoconductors. There are several possible causes for the accumulation of residual potential,
The most influential factor is due to impurities present in the charge transfer layer. That is, it is considered that such impurities serve as traps to capture carriers and form immovable space charges, resulting in a residual potential.
Increasing the thickness of the charge transfer layer is advantageous in several respects, such as reducing the effect of film reduction due to abrasion such as blade cleaning on electrical characteristics and improving the sensitivity. The amount of impurities in the layer increases, and the accumulation of residual potential in repeated use becomes extremely large. 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 compound to the charge transfer layer.

In general, when an electron-withdrawing compound is added to an electron-donating compound, a charge-transfer complex is formed and its new absorption appears on the longer wavelength side. Therefore, when light corresponding to the absorption band of the charge transfer 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 compounds 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 a cyanovinyl compound exhibits extremely excellent performance, and reached the present invention.

That is, the gist of the present invention is characterized in that, in an electrophotographic photosensitive member having at least a charge generation layer and a charge transfer layer on a conductive substrate, the charge transfer layer contains a cyanovinyl compound represented by the following general formula [I]. In the electrophotographic photoreceptor.

(Wherein, R ¹ and R ² each represent a hydrogen atom or a halogen atom, X represents an optionally substituted aryl group or an optionally substituted aryloxy group, Y represents a cyano group, an alkoxycarbonyl Represents an aryloxycarbonyl group which may be substituted or an aryl group which may be substituted.) 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 with a conductive layer such as aluminum, copper, palladium, tin oxide, or indium oxide on the surface;

A well-known barrier layer which is usually used 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.

As the charge generating material used in the charge generating layer, selenium and its alloys, arsenic-selenium, cadmium sulfide and zinc oxide and other inorganic photoconductive materials, phthalocyanine, azo dye, quinacridone, polycyclic quinone, pyrylium salt, thiapyrylium salt, Various organic pigments and dyes such as isodigo, thioindigo, anthantrone, pyranthrone and cyanine can be used. Among them, metal-free phthalocyanine and copper indium chloride, gallium chloride, tin, oxytitanium,
Metals such as zinc and vanadium or oxides thereof, phthalocyanines coordinated with chloride, and azo pigments such as monoazo, bisazo, trisazo and polyazo are preferred.

The charge generating layer converts these substances into, for example, polyester resin, polyvinyl acetate, polyacrylate,
It is used by being bound with various binder resins such as polymethacrylic acid ester, polyester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin, epoxy resin, urethane resin, cellulose ester and cellulose ether. In this case, the charge generating substance is used in an amount of 30 to 500 parts by weight with respect to 100 parts by weight of the binder resin, and the film thickness is usually 0.1 μm to 2 parts.
μm, preferably 0.15 μm to 0.8 μm is suitable.
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 a cyanovinyl compound represented by the following general formula [I] together with a charge transfer material and a binder resin.

Here, R ¹ and R ² represent a hydrogen atom; or a halogen atom such as chlorine, bromine or iodine.

X represents an optionally substituted aryl group such as a phenyl group or a naphthyl group, or an aryloxy group such as a phenoxy group or a naphthoxy group, and the substituent is usually a halogen atom such as chlorine, bromine or iodine; A nitro group; a methyl group, an alkyl group such as an ethyl group; a methoxy group;
An alkoxy group such as an ethoxy group or the following formula The group represented by is used.

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

The compound represented by the general formula [I] can be easily synthesized, for example, by condensing an aldehyde represented by the general formula [II] and a nitrile compound represented by the general formula [III].

(In the formula, R ¹ , R ² , X and Y have the same meanings as described above.) Next, main specific examples of the cyanovinyl compound represented by the general formula [I] will be shown.

Illustrative compounds 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 cyanovinyl compound represented by the general formula [I] and the binder resin is based on 100 parts by weight of the binder resin.
It is used in the range of 0.01 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 cyanovinyl compound is contained in the charge transfer layer according to the present invention hardly accumulates a residual potential even when used repeatedly, and furthermore, the chargeability and sensitivity change are very small. Very good stability.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the invention is not particularly limited thereto.

Production Example [Exemplified Compound (21)] The following formula [IV] Was dissolved in 20 ml of isopropanol and 1.00 g of malononitrile was added thereto.
The reaction was performed at 80 ° C. for 1 hour. After cooling, the precipitated crystals were collected and recrystallized from a mixed solvent of toluene and ethyl acetate to obtain 0.5 g of pale yellow crystals of p-nitrophenyl-4- (β, β-dicyanovinyl) benzoate. Melting point was 202 ° C.

The compound [IV] was synthesized by condensing p-formylbenzoyl chloride and p-nitrophenol.

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 dispersion obtained in this manner, the surface of mirror-finish has an outer diameter 80 mm, length 340 mm, so that the dry film thickness aluminum cylinder was dip-coated in the thickness 1.0mm is 0.7 g / mm ² A charge generation layer was provided.

Next, this aluminum cylinder was mixed with 95 parts by weight of a hydrazone compound shown below. Compound having the following structure [p-nitrophenyl-4-
(Β, β-dicyanovinyl) benzoate] 1.5 parts by weight And 100 parts by weight of a polycarbonate resin having the following structure After dip coating in a solution dissolved in a mixed solvent of 1,4-dioxane and tetrahydrofuran, 30 minutes at room temperature and 30 minutes at 125 ° C.
The charge transfer layer was provided so that the film thickness after drying was 40 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 even after 300,000 repetitions, and the accumulation of the residual potential is extremely small.

Examples 2 to 10 Instead of the cyanovinyl compound used in Example 1, exemplified compounds (1), (4),
(7), (11), (19), (20), (23), (24),
A photoconductor was prepared in the same manner as in Example 1, except that (36) was used, and the characteristics were evaluated. Table 1 shows the results.

It can be seen that all of these photoconductors exhibit very stable characteristics.

Comparative Example A photoconductor was prepared in the same manner as in Example 1 except that the cyanovinyl compound was not added, and its characteristics were evaluated. Table 1 shows the results. As is clear from the results in Table 1, it is found that the residual potential is extremely accumulated.

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] 1. An electrophotographic photoreceptor having at least a charge generation layer and a charge transfer layer on a conductive substrate, wherein the charge transfer layer has the following general formula [I]: (Wherein, R ¹ and R ² each represent a hydrogen atom or a halogen atom, X represents an optionally substituted aryl group or an optionally substituted aryloxy group, and Y represents a cyano group or an alkoxycarbonyl group. And an optionally substituted aryloxycarbonyl group or an optionally substituted aryl group.).