JP2000241997A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure stable electrical characteristics even in repetitive use and to reduce potential difference between the 1st and subsequent revolutions of a photoreceptor by using a terpolymer obtained by graft-polymerizing vinyl chloride on an ethylene-vinyl acetate copolymer as a resin binder in an electric charge generating layer. SOLUTION: A photosensitive layer 3 is disposed on an electrically conductive substrate 1 by way of an undercoat layer 2 by successively laminating an electrical charge generating layer 4 and an electric charge transferring layer 5 to obtain the objective negative electrification type function-separated laminate type photoreceptor. The electric charge generating layer 4 consists of an organic electric charge generating material such as titanyl phthalocyanine, metal-free phthalocyanine, tin phthalocyanine or copper phthalocyanine and a terpolymer obtained by graft-polymerizing vinyl chloride on an ethylene-vinyl acetate copolymer as a resin binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoreceptor for electrophotography (hereinafter, also simply referred to as "photoreceptor"), and more particularly, to an electrophotographic system in which a photosensitive layer containing an organic material is provided on a conductive substrate. And a photoreceptor for electrophotography used in printers, digital copiers and the like.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member has a basic structure in which a photosensitive layer having a photoconductive function is laminated on a conductive substrate. In recent years, research and development of organic electrophotographic photoreceptors that use organic compounds as functional components responsible for charge generation and transport have been actively promoted due to the diversity of materials, high productivity, safety, and other factors. Applications to printers and printers are being promoted.

A photoreceptor is required to have a function of retaining a surface charge in a dark place, a function of receiving light to generate a charge, and a function of transporting the generated charge. A so-called single-layer type photoreceptor with a photosensitive layer, a charge generation layer mainly responsible for charge generation at the time of photoreception, and a function of holding surface charge in a dark place and a charge generation layer at the time of photoreception. A charge generation layer having a function of transporting the generated charge and a photosensitive layer in which a layer having a function separation is laminated.
There is a so-called function-separated laminated photoconductor.

Recently, an organic pigment is used as a charge generating material and dissolved in an organic solvent together with a resin binder.
A layer formed by applying the dispersed coating liquid to form a charge generation layer,
Function separation and lamination of a layer in which a low-molecular organic compound is used as a charge transport material, and a coating solution formed by dissolving and dispersing this in an organic solvent together with a resin binder into a film is formed as a charge transport layer, and these are laminated to form a photosensitive layer Electrophotographic photoconductors have become mainstream.

[0005]

However, at present, the organic photoreceptor cannot always be said to satisfy the required characteristics required for the photoreceptor. This is one of the required characteristics for which improvement is strongly desired. Specifically, when the photoreceptor is used continuously and repeatedly in an actual machine, the potential (especially, the residual potential) fluctuates, and the print quality and copy image quality are reduced. Factors of such potential fluctuations include the generation of light, heat, and ozone due to continuous use in the actual machine, and the fatigue and deterioration of organic materials due to changes in the temperature and humidity conditions of the use environment. Can be

[0006] Also, in the recent trend of advanced information technology,
There is an increasing market need for digital copiers that combine the technology of conventional analog copiers with the technology of laser printers and LED printers that can digitize images. In the field of digital copiers, one rotation of the photoconductor, which was not used in the process of the conventional laser printer or LED printer, was demanded to increase the speed of the first copy or shorten the recovery time from the power saving mode. Many processes are designed from the eyes for use in image formation. In this case, the conventional photoreceptor has a new problem that the image that has undergone the first rotation process has a ground fogging defect, and the image corresponding to the second and subsequent rotations recovers to a level that is not a problem. In addition, the ground fog defect of the first rotation is about 10
After electrical fatigue due to continuous use of 10,000 sheets, 30
When the copying operation was performed again after being left for a predetermined time of about one minute to one hour, the result was worse than the initial failure. Subsequent studies have revealed that the ground fogging failure in the first rotation is largely due to poor charging of the photoconductor, and it is currently required to minimize the potential difference between the first rotation and the second and subsequent rotations of the photoconductor. .

The causes of the above-mentioned phenomena include accumulation of charges generated in processes such as exposure of a photoreceptor and charge removal in an organic film, and fatigue and deterioration of an organic material. Is believed to be caused by trapping of charges in the charge generation layer and the charge transport layer or at the interface between them, and improvements have been made mainly on charge generation materials and charge transport materials. However, it is a fact that means and materials that can be sufficiently solved have not been found yet.

In view of the above-described problems, the present invention has stable electrical characteristics even when repeatedly used or when the use environment changes, and performs the first and second rotation of the photosensitive member. It is an object of the present invention to provide an organic electrophotographic photoreceptor having a reduced potential difference.

[0009]

In order to solve the above-mentioned problems, an electrophotographic photoreceptor of the present invention includes a photosensitive layer formed by sequentially laminating a charge generation layer and a charge transport layer on a conductive substrate. Wherein the charge generation layer is formed of a terpolymer obtained by graft-polymerizing vinyl chloride on an ethylene-vinyl acetate copolymer as the resin binder. It is.

Further, another electrophotographic photoreceptor of the present invention comprises:
The terpolymer has an ethylene-vinyl acetate copolymer content of 30% by weight or less.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific configuration of a preferred example of the photoconductor of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing one configuration example of the photoreceptor of the present invention. A charge generation layer 4 and a charge transport layer 5 are sequentially formed on a conductive substrate 1 via an undercoat layer 2. This is a negatively-charged function-separated multi-layered photoconductor having a configuration in which the stacked photoconductive layers 3 are provided.

The conductive substrate 1 serves as one electrode of the photoreceptor and serves as a support for each layer constituting the photoreceptor, and may have any shape such as a cylindrical shape, a plate shape, and a film shape. May be made of a metal such as aluminum, stainless steel, nickel, or the like, or a material obtained by performing a conductive treatment on a surface of glass, resin, or the like.

The undercoat layer 2 is made of a layer mainly composed of a resin or a metal oxide film such as alumite. The undercoat layer 2 controls the injectability of electric charge from the conductive substrate to the photosensitive layer or covers defects on the surface of the substrate. It is provided as necessary for the purpose of improving the adhesiveness between the photosensitive layer and the base. As a resin material used for the undercoat layer, casein, polyvinyl alcohol,
Examples thereof include insulating polymers such as polyamide, melamine, and cellulose, and conductive polymers such as polythiophene, polypyrrole, and polyaniline. These resins can be used alone or in appropriate combination and mixed.
In addition, these resins may contain a metal oxide such as titanium dioxide and zinc oxide.

The charge generation layer 4 is composed of an organic charge generation material and a resin binder. As a charge generation material,
Titanyl phthalocyanine, metal-free phthalocyanine, tin phthalocyanine, copper phthalocyanine, and the like can be used. In particular, as the titanyl phthalocyanine, α-type titanyl phthalocyanine, β-type titanyl phthalocyanine, Y-type titanyl phthalocyanine, and the like are preferable. Among them, CuKα: X described in JP-A-8-209523 is preferable.
Bragg angle 2θ is 27.3 ° in X-ray diffraction spectrum
Or those having a maximum peak at 9.6 ° are preferred.
As for the metal-free phthalocyanine, X-type metal-free phthalocyanine, τ-type metal-free phthalocyanine, amorphous metal-free phthalocyanine and the like can be used. Further, a pigment system other than the phthalocyanine compound may be used, and is not limited to the above range. The amount of the charge generation material to be used is 5 to 500 parts by weight, preferably 10 to 100 parts by weight, based on 10 parts by weight of the resin binder.

In the present invention, a terpolymer obtained by graft-polymerizing an ethylene-vinyl acetate copolymer with vinyl chloride is used as a resin binder for the charge generation layer. As such a terpolymer, those having an ethylene-vinyl acetate copolymer content of 30% by weight or less are preferable, and those having a content of 5% by weight to 30% by weight are more preferably used. If the content is less than 5% by weight, the improvement of the electrical properties becomes insufficient, and if it exceeds 30% by weight, the electrical properties may be rather deteriorated. The terpolymer is not necessarily required to be used at 100% in the resin binder, and another resin binder, for example, vinyl chloride may be used by mixing up to 30%. Since the charge transport layer 5 is laminated on the charge generation layer 4, its thickness is determined by the light absorption coefficient of the charge generation substance, and is generally 5 μm or less, preferably 1 μm or less.

The charge transport layer 5 is composed of a charge transport material and a resin binder. As the charge transporting material, a hydrazone compound, a butadiene compound, a diamine compound, an indole compound, an indoline compound, a stilbene compound, a distilbene compound, or the like is used alone or in combination as appropriate. As the resin binder, a polycarbonate resin such as a bisphenol A type, a bisphenol Z type, a bisphenol A type-biphenyl copolymer, a polystyrene resin, a polyphenylene resin, or the like is used alone or in combination as appropriate. The amount of the charge transporting material to be used is 2 to 50 parts by weight, preferably 3 to 30 parts by weight, based on 100 parts by weight of the resin binder. In addition, the thickness of the charge transport layer is 3 to 50 in order to maintain a practically effective surface potential.
It is preferably in the range of μm, more preferably 15 to 40 μm.

The undercoating layer and the charge transporting layer may optionally contain an electron accepting material for the purpose of improving sensitivity, reducing residual potential, or improving environmental resistance and stability against harmful light. , An antioxidant, a light stabilizer and the like. Compounds used for such purposes include chromal derivatives such as tocopherol and etherified compounds, esterified compounds, polyarylalkane compounds, hydroquinone derivatives, dietherified compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds, phenylenediamines Derivatives,
Examples include, but are not limited to, phosphonate esters, phosphite esters, phenol compounds, hindered phenol compounds, linear amine compounds, cyclic amine compounds, hindered amine compounds, and the like.

Further, the photosensitive layer may contain a leveling agent such as silicone oil or fluorine-based oil for the purpose of improving the leveling property of the formed film and imparting further lubricity.

Further, on the surface of the photosensitive layer, a surface protective layer may be further provided as necessary for the purpose of further improving environmental resistance and mechanical strength. The surface protective layer is made of a material with excellent durability against mechanical stress and environmental resistance,
It is desirable that the charge generation layer has a performance of transmitting sensitive light with as low a loss as possible.

[0020]

Embodiments of the present invention will be described below. Example 1 An alcohol-soluble nylon (“CM8000” manufactured by Toray Industries, Inc.) (5 parts by weight) and titanium oxide fine particles (5 parts by weight) treated with aminosilane were mixed with methanol 90 as an undercoat layer on the outer periphery of an aluminum cylinder as a conductive substrate. A coating solution prepared by dissolving and dispersing in parts by weight was dip-coated, and the temperature was 1
After drying at 00 ° C. for 30 minutes, an undercoat layer having a thickness of about 2 μm was formed.

On the undercoat layer, 1 part by weight of a τ-type metal-free phthalocyanine as a charge generating material and an ethylene-vinyl acetate copolymer as a resin binder have a content of 8% by weight (ethylene-vinyl acetate). Copolymerization) -vinyl chloride graft terpolymer resin (“ZE” manufactured by Shin-Daiichi PVC Co., Ltd.)
STGRE ") and 1.5 parts by weight of tetrahydrofuran 6
The coating solution prepared by dissolving and dispersing in 0 parts by weight was dip-coated and dried at a temperature of 120 ° C. for 30 minutes to obtain a film thickness of about 0.3 μm.
m of the charge generation layer was formed.

On this charge generation layer, the following structural formula (I) as a charge transport material: A hydrazone compound represented by “(CTC manufactured by Annan Co., Ltd.)
191 ") and 100 parts by weight of a polycarbonate resin as a resin binder (" Tuffet B "manufactured by Idemitsu Kosan Co., Ltd.)
-500 ") in 100 parts by weight of dichloromethane in 900 parts by weight of dichloromethane to form a film.
Drying for about 25 minutes to form a charge transport layer having a thickness of about 25 μm,
A photoreceptor for organic electrophotography was prepared.

Example 2 The charge transport material used in Example 1 was replaced by the following structural formula (II): A photoreceptor for organic electrophotography was prepared in the same manner as in Example 1 except that the compound represented by the following formula was used.

Example 3 The charge transporting material used in Example 1 was replaced by the following structural formula (III): A photoreceptor for organic electrophotography was prepared in the same manner as in Example 1 except that the compound represented by the following formula was used.

Example 4 The charge transporting material used in Example 1 was replaced by the following structural formula (IV): A photoreceptor for organic electrophotography was prepared in the same manner as in Example 1 except that the compound represented by the following formula was used.

Example 5 The resin binder in the charge generation layer used in Example 1 was prepared by using an ethylene-vinyl acetate copolymer having a content of 45% by weight.
(Ethylene-vinyl acetate copolymer) -vinyl chloride graft terpolymer resin ("ZEST" manufactured by Shin-Daiichi PVC Co., Ltd.)
A photoreceptor for organic electrophotography was produced in the same manner as in Example 1, except that GR5L ") was used instead.

Comparative Example 1 The procedure of Example 1 was repeated except that the resin binder in the charge generation layer used in Example 1 was changed to a special vinyl chloride copolymer (“MR-110” manufactured by Zeon Corporation). A photoreceptor for organic electrophotography was produced in the same manner.

Comparative Example 2 Example 1 was repeated except that the resin binder in the charge generation layer used in Example 1 was changed to a vinyl formal copolymer (“S-LEC KS-1” manufactured by Sekisui Chemical Co., Ltd.).
A photoconductor for organic electrophotography was prepared in the same manner as in the above.

The photosensitive members produced in the above Examples and Comparative Examples were mounted on a digital copying machine modified to measure the surface potential of the photosensitive members, and the stability of the potential at the initial stage and after copying 100,000 sheets, and The difference between the charged positions after the first rotation and after the second rotation was evaluated. Further, the stability of the potential when the use environment of the copying machine was changed was also evaluated. These results are shown in Table 1 below.
To 3 respectively.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3] * 1: Temperature 5 ° C, humidity 10%, * 2: Temperature 25 ° C, humidity 60%, * 3: Temperature 35 ° C, humidity 90%

As is apparent from the above results, the photoreceptors of Examples 1 to 5 using (ethylene-vinyl acetate copolymer) -vinyl chloride graft terpolymer resin as the resin binder of the charge generation layer are the same as those of Examples 1 to 5. Compared to the comparative example using the resin binder of the above, various characteristics such as the residual potential stability after continuous use, the charge position difference between the first rotation and the second rotation, and the potential stability in the use environment of the photoreceptor. It has been found that there is a great improvement effect.

When Examples 1 to 4 and 5 are compared, the photosensitive member of Example 5 has a high absolute value of the residual potential at the initial stage and after continuous use, and therefore the content of the ethylene-vinyl acetate copolymer is high. Is less than 30% by weight (ethylene-vinyl acetate copolymer)-It is considered that the photoconductors of Examples 1 to 4 using the vinyl chloride graft terpolymer have more excellent properties. .

[0035]

According to the present invention, it is possible to provide an organic electrophotographic photoreceptor having a small difference in residual potential at the initial stage or even after actual printing fatigue, and to obtain a good image, and to increase the first copy speed. Or, it is possible to respond to market demands such as shortening the return time from the power saving mode.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a negatively-charged-function-separated multi-layer electrophotographic photosensitive member according to an example of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 undercoat layer 3 photosensitive layer 4 charge generation layer 5 charge transport layer

Claims (2)

[Claims] 1. A function-separated laminated electrophotographic photoconductor comprising a photosensitive layer formed by sequentially laminating a charge generation layer and a charge transport layer on a conductive substrate, wherein the charge generation layer has a resin binder as a resin binder. Ethylene-
An electrophotographic photoreceptor comprising a terpolymer obtained by graft-polymerizing vinyl chloride onto a vinyl acetate copolymer. 2. The content of an ethylene-vinyl acetate copolymer in the terpolymer is 30% by weight or less.
The photoconductor for electrophotography according to the above.