JPH10115941A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic photoreceptor high in sensitivity to laser beams and enhanced in stability by incorporating a metal-free phthalocyanine as a charge generating material in a photosensitive layer, and a triphenylamine derivative as a charge transfer material and a hindered phenol derivative as an antioxidant. SOLUTION: The photosensitive layer 2 obtained by molecularly dispersing the charge generating material 21 into a binder on a conductive substrate 1 to form a material 22 and further obtained by dispersing the charge generating material 21. The conductive substrate 1 can be embodies by metallic material, such as, copper, aluminum, or a plastic coated with a metal, and the conductive substrate 1 may be formed into a cylindrical or plate and it is required for sufficient strength. This conductive substrate is coated with a solution obtained by dispersing and dissolving the metal-free phthalocyanien as the charge generating material, the triphenylamine derivative as the charge transfer material, the hindered phenol derivative as the antioxidant, the resin binder into an organic solvent, and dry it to form a monolayer photoreceptive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member as an image forming member used in an electrophotographic copying machine or a printer, and more particularly, to a photosensitive member having a single photosensitive layer made of an organic material. The present invention also relates to a positively charged electrophotographic photosensitive member that forms an image by positively charging its surface.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member as an image forming member used in an electrophotographic copying machine or a printer has a basic structure including a conductive base and a photosensitive layer provided thereon. The photosensitive layer includes a layer in which an inorganic photoconductive substance such as selenium is formed by vacuum evaporation, a layer in which an inorganic photoconductive substance such as zinc oxide and cadmium sulfide is dispersed in a resin binder, polyvinyl carbazole (PVK ), A layer in which an organic photoconductive substance such as a phthalocyanine compound or a bisazo compound is formed by vacuum evaporation, a layer in which a resin binder is dispersed, and the like. At present, a photosensitive layer in which an organic photoconductive material is dispersed in a resin binder is mainly used due to advantages such as diversity of materials, film forming property, low cost, and thermal stability.

The function of the electrophotographic photosensitive member is required to have a function of receiving light to generate electric charge and a function of receiving light and transporting the generated charge carrier. These functions are provided in the same layer. A single-layer photoreceptor having a single-layer photosensitive layer structure, a layer containing a charge generating substance having a function of receiving light to generate charge carriers by separating these functions,
The so-called charge generation layer, and a charge having the function of maintaining the surface potential of the photoreceptor in a dark place, transporting charge carriers generated and injected into the charge generation layer during photoreception, and neutralizing and eliminating the potential of the photoreceptor surface. There is a function-separated-type laminated photoreceptor having a structure including a photosensitive layer in which a layer containing a transport substance, that is, a charge transport layer is laminated. The function-separated type photoreceptor is formed by selecting excellent materials for each function and forming each functional layer, and combining them to form a photosensitive layer.
At the present time, it is possible to obtain a photosensitive member having high sensitivity and excellent characteristics.

In such a function-separated type photoreceptor, the charge generation layer is good for receiving light and generating charge carriers. The smaller the film thickness, the better the chargeability of the photoreceptor. , Micron order, preferably submicron order. On the other hand, the charge transport layer is usually formed to have a thickness of several tens of microns in order to maintain a charged potential. In order to protect such a thin charge generation layer and obtain the durability of the photoreceptor, generally, the photosensitive layer is generally laminated on a conductive substrate in the order of a charge generation layer and a charge transport layer. At present, the charge transporting substances practically used for the charge transporting layer are excellent in hole transporting ability. Therefore, such a photoreceptor
It is used in a negative charging type process in which the surface is negatively charged during image formation.

[0005]

However, as described above, since such a laminated type photoreceptor is used in a negative charge in an image forming process, the surface of the photoreceptor is charged by corona discharge which is usually performed. In this case, a negative corona discharge occurs, and a large amount of ozone (O ₃ ) and nitrogen oxide (NO _x ) is generated, and the photosensitive layer made of these organic materials is greatly deteriorated. There is a problem that it is not favorable to the environment. In the positive corona discharge, the amount of ozone (O ₃ ), nitrogen oxides (NO _x ), etc. generated is significantly smaller than in the negative corona discharge. Problems can be avoided. Furthermore, the negative charging has a problem that charging uniformity is poor.

If a charge transporting material having an excellent electron transporting ability is provided, a photosensitive member having a photosensitive layer laminated in the order of the above-described charge generating layer and charge transporting layer can be used in a positively charged image forming process. Therefore, research has been carried out diligently, but such a substance has not been found yet. By inverting the stacking order of the stack type photosensitive layer, a charge transport layer having a hole transport ability is formed, and a charge generation layer is formed thereon to obtain a photosensitive layer that can be used with positive charge. However, the charge generation layer of the thin film becomes the outer layer, and the printing durability of the photoreceptor deteriorates. Therefore, it is necessary to take measures such as providing a protective layer thereon.

Further, the laminated photoreceptor has a problem that the production process is complicated and the production yield is not good, and also a problem such as delamination between layers occurs. In order to solve the above-mentioned problems, a single-layer type photoreceptor having charge generation ability and charge transport ability in the same layer has recently been receiving attention. Examples of the single-layer photoreceptor include a photoreceptor using a charge transfer complex of polyvinyl carbazole and trinitrofluorenone, a photoreceptor using a eutectic complex composed of a thiapyrylium dye and polycarbonate, and a binder resin comprising a perylene pigment and a hydrazone compound. A photosensitive member having a photosensitive layer dispersed and dissolved therein is known. However, the first two photoreceptors have low sensitivity, and there is a practical problem in terms of characteristic fluctuation in repeated use, and the other one has low sensitivity and is not suitable for a high-speed image forming process. Absent. A single photosensitive layer is formed by simply mixing a charge generating substance and a charge transporting substance used in a laminated photoreceptor that has been put into practical use. The fact is that it cannot overcome the disadvantage that the characteristics fluctuate greatly during use.

In recent years, digital copiers and printers using a semiconductor laser diode as an exposure light source have been developed and spread, but a single-layer type photoconductor suitable for such an apparatus has not been put to practical use yet. The present invention has been made in view of the above points, and provides a positively charged single-layer type electrophotographic photoreceptor having high stability against ozone and nitrogen oxides and having high sensitivity to a semiconductor laser beam. The purpose is to:

[0009]

According to the present invention, there is provided an electronic device comprising a conductive substrate having a single photosensitive layer in which a charge generating substance and a charge transporting substance are dispersed in a resin binder. In a photographic photoreceptor, the photosensitive layer contains a metal-free phthalocyanine as a charge generating substance, contains a triphenylamine compound as a charge transporting substance, and further contains a hindered phenol compound as an antioxidant. It is solved by doing.

As the hindered phenol compound, a compound having the following formula (I) as a structural unit is preferable.

[0011]

Embedded image [In the formula (I), R ₁ and R ₂ each represent an alkyl group, and at least one of them represents a t-butyl group, and R ₃ represents any one of an alkyl group, an alkylene group, an aryl group, and an aralkyl group. Represents ]

[0012]

FIG. 1 is a schematic sectional view of one embodiment of a photosensitive member according to the present invention. In FIG. 1, reference numeral 1 denotes a conductive substrate, on which a photosensitive layer 2 composed of a layer in which a charge generation substance 21 is dispersed in a material 22 in which a charge transport substance is dispersed and contained in a resin binder is contained. Is formed.

As the conductive substrate, copper, aluminum,
Metal materials such as nickel, indium, and gold, and plastic sheets coated with these metals can be used. The shape of the substrate may be any of a cylindrical shape and a plate shape, but it is necessary to have sufficient strength for handling since it serves as a support for each layer. On such a conductive substrate,
Metal-free phthalocyanine as charge generation material (CGM), triphenylamine compound as charge transport material (CTM), hindered phenol compound as antioxidant, resin binder dispersed and dissolved in organic solvent, and applied And drying to form a single photosensitive layer.

Specific examples of the triphenylamine-based compound include the following compounds (CTM-1) to (CTM-5).

[0015]

Embedded image

[0016]

Embedded image Further, specific examples of the antioxidant include the following compound (AO
-1) to (AO-5) [An equivalent is a product of Ciba-Geigy (trade name "IRGANOX"). (A
O-1) = IRGANOX 1076, (AO-2) =
IRGANOX 245, (AO-3) = IRGANOX
259, (AO-4) = IRGANOX 1010,
(AO-5) = IRGANOX 1035FF].

[0017]

Embedded image As the resin binder, polycarbonate resin, polyester resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin,
Polyurethane resin, phenolic resin, alkyd resin,
Addition polymerization type resins such as silicone resin and melamine resin, polyaddition type resins, polycondensation type resins, and copolymer resins containing two or more of these repeating units, for example,
Examples thereof include vinyl chloride-vinyl acetate copolymer resin and vinyl chloride-vinyl acetate-maleic anhydride copolymer resin.

The charge generating substance is 0.1 to the entire photosensitive layer.
% To 20% by weight, preferably 1% to 10% by weight, and the charge transport material is 5% to 60% by weight based on the entire photosensitive layer.
% By weight, preferably 10% by weight to 50% by weight, and the antioxidant may be contained in the photosensitive layer in an amount of 0.1% by weight to 30% by weight, preferably 1% by weight to 20% by weight. The remainder is a resin binder. The thickness of the photosensitive layer is 5 μm.
１００100 μm is preferred. If the thickness is smaller than this, the charging ability is reduced, and if the thickness is larger, the sensitivity is reduced, which is not desirable.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. Examples 1 to 5 Metal-free phthalocyanine compounds as charge generating substances, and the above-mentioned (CTM-1) to (CTM-) as charge transporting substances
5) The above-mentioned (AO-1) to (AO-
5) Bisphenol Z polycarbonate as a resin binder (manufactured by Mitsubishi Gas Chemical Co., Ltd .; trade name "PCZ-
300)) as shown in Table 1 below, and mixed in a ratio of 5 parts by weight of a charge generating substance, 30 parts by weight of a charge transporting substance, 5 parts by weight of an antioxidant, and 60 parts by weight of a resin binder to obtain 300 parts by weight of tetrahydrofuran. And the mixture was kneaded for 4 hours, dissolved and dispersed, coated on a substrate made of an aluminum alloy, and dried to form a single photosensitive layer having a thickness of 20 μm. Example 1
Each photoconductor of Example 5 was produced.

[0020]

[Table 1] Comparative Example 1 A photoconductor was prepared by the same way as that of Example 1 except that the charge generation material was changed from metal-free phthalocyanine to zinc phthalocyanine. Comparative Example 2 In the same manner as in Example 1, except that the charge transporting substance was changed from the triphenylamine-based compound (CTM-1) to the following compound (CTM-6) which was an indole-based compound. A photoreceptor was produced.

[0021]

Embedded image Comparative Example 3 Example 1 was repeated except that the antioxidant was changed from the hindered phenol compound (AO-1) to 2,6-di-t-butyl-p-cresol (BHT). A photoreceptor was produced in the same manner as described above.

Comparative Example 4 A photoconductor was prepared in the same manner as in Example 1, except that the antioxidant was not used. Table 2 summarizes the compositions of the photosensitive layers of the respective photosensitive members of the above comparative examples.

[0023]

[Table 2] The electrophotographic characteristics of the photoreceptor thus obtained were compared with a paper analyzer EPA-8100 manufactured by Kawaguchi Electric Works.
Was evaluated. The surface of the photoreceptor is charged in a dark place by corona discharge at a discharge voltage of +6 kV, the corona discharge is stopped, and the surface potential V ₀ (V) after being left in a dark place for 5 seconds is measured. Then wavelength 7
The electricity is removed by irradiating 80 nm light. Exposure energy E _1/2 (μJ
/ Cm ² ). In addition, the residual potential _Vr after 5 seconds of irradiation
(V) is measured. The above-described charging / discharging process was repeated, and the characteristics at the first time and after 10,000 times were evaluated. Table 3 shows the results.

[0024]

[Table 3] As shown in Table 3, it is clear from the measurement results of the photoconductor of Comparative Example 1 that metal-free phthalocyanine is suitable as the charge generating substance. Also, from the measurement results of the photoconductor of Comparative Example 2, it is clear that a triphenylamine compound is suitable as the charge transporting substance. Comparative Example 3
From the measurement results of the photoreceptor of No. 4, the effect of using the hindered phenol compound having the specific structural unit represented by the formula (I) as the antioxidant is apparent.

[0025]

According to the present invention, there is provided an electrophotographic photoreceptor comprising a single photosensitive layer in which a charge generating substance and a charge transporting substance are dispersed in a resin binder on a conductive substrate.
The photosensitive layer contains a metal-free phthalocyanine as a charge generating substance, a triphenylamine compound as a charge transporting substance, and a hindered phenol compound as an antioxidant.

By providing a photoreceptor comprising such a photosensitive layer, it is possible to obtain a positively charged single-layer type electrophotographic photoreceptor having high stability against ozone and nitrogen oxides and high sensitivity to a semiconductor laser beam. Can be. As the antioxidant, a hindered phenol compound having the formula (I) as a structural unit is preferable.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a photoreceptor according to the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 conductive substrate 2 photosensitive layer 21 charge generating substance 22 material in which charge transport substance is dispersed and contained in a binder

Claims (2)

[Claims] 1. An electrophotographic photoreceptor comprising a single photosensitive layer in which a charge generating substance and a charge transporting substance are dispersed in a resin binder on a conductive substrate, wherein the photosensitive layer is a metal-free material as a charge generating substance. An electrophotographic photoreceptor comprising phthalocyanine, a triphenylamine compound as a charge transport substance, and a hindered phenol compound as an antioxidant. 2. The electrophotographic photoconductor according to claim 1, wherein the antioxidant is a hindered phenol compound having the following formula (I) as a structural unit. Embedded image [In the formula (I), R ₁ and R ₂ each represent an alkyl group, and at least one of them represents a t-butyl group, and R ₃ represents any one of an alkyl group, an alkylene group, an aryl group, and an aralkyl group. Represents ]