JPH0422966A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a good image free from moire by specifying the relation between the maximum surface roughness and the film thickness of an undercoat layer. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive substrate the undercoat layer containing an inorganic pigment, an electric charge generating layer, and a charge transfer layer, and the relation between the maximum surface roughness (Rmax) of the conductive substrate and the film thickness (t) of the undercoat layer is expressed by t <=5x Rmax. As the conductive substrate material, metals, such as Al, Ni, Cu, and stainless steel, and plastics containing conductive powder, such as carbon, Al, and Cu, and the like can be used. It is preferred that the undercoat layer contains the inorganic pigment, thus permitting occurrence of moire to be prevented and a good image to be obtained by specifying the relation between the maximum roughness of the conductive substrate and the film thickness of the undercoat layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor used in a printer or the like to which an electrophotographic process is applied.

[Prior art and problems to be solved by the invention] Conventionally, Se and Se alloys have been used as photoreceptors for electrophotographic printers that use coherent light (laser light) as a light source.

Cadmium sulfide/resin dispersion systems, charge transfer complexes of polyvinyl carbazole and trinitrofluorenone, etc. have been used, and gas lasers such as helium-cadmium, argon, and helium-neon have been used, but recently small and low-cost lasers have been used. Semiconductor lasers, which can be directly modulated, have come to be used due to their cost. However, many semiconductor lasers have an oscillation wavelength of 750 nm or more, and the photoreceptor described above has low sensitivity in that wavelength range, making it difficult to use. Therefore, laminated organic photoreceptors that can relatively freely select the photosensitive wavelength range are attracting attention as photoreceptors for semiconductor lasers.

The laminated organic photoreceptor has a structure in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support, and an undercoat layer may be provided below the charge generation layer.

The charge generation layer has the role of absorbing light and generating free charges, and its thickness is usually as thin as 0.1 to 5 - to shorten the range of the generated photocarriers.

The charge transport layer has the role of transporting free charges, and a material that hardly absorbs image forming light is used. Its thickness is usually 5~
It is 50-.

The two-layer structure described above also functions as a photoreceptor.

Improving the adhesion between the substrate and the photosensitive layer, improving the coating properties of the photosensitive layer,
It is preferable to provide an undercoat layer for the purpose of improving the chargeability of the photoreceptor. Further, it is desirable that the undercoat layer contains an inorganic pigment. As this inorganic pigment, a white pigment having a relatively high refractive index of 1.9 or more in visible light and near-infrared light is particularly desirable.

When we use such a photoreceptor to create an image by scanning a line with a laser beam, there is no problem with line images such as characters, but with halftone images, moiré (striped density unevenness) occurs.
may occur. The reason for this is that, as mentioned above, the charge generation layer is formed as a thin layer, which limits the amount of light absorbed by the charge generation layer, and as a result, the light that has passed through the charge generation layer is reflected on the surface of the undercoat layer. This is thought to be due to interference between the reflected light and the reflected light on the surface of the photosensitive layer.

As a means to prevent such moiré, light is scattered by roughening the bare surface of the conductive support.

There is a method to prevent moire (Japanese Patent Application Laid-Open No. 60-25615
Publication No. 3).

However, a photoreceptor including an undercoat layer using an inorganic pigment has a problem in that moire generation due to reflection of incident light on the surface of the undercoat layer cannot be ignored.

It is an object of the present invention to solve the problems of the prior art and to provide an electrophotographic photoreceptor capable of obtaining good images free of moiré.

[Means to solve the problem]

In order to solve the above problems, the present inventors conducted extensive studies. In order to prevent moire caused by reflection of incident light on the surface of an undercoat layer using an inorganic pigment, it is necessary to scatter light on the surface of the undercoat layer.

However, it is thought that the optimum surface roughness of the undercoat layer is not only due to the material, but is also deeply related to the surface roughness of the conductive support and the thickness of the undercoat layer. Therefore, we conducted experiments by varying the thickness of the undercoat layer and the surface roughness of the conductive support, and found that there is an optimal relationship between these thicknesses and surface roughness for moire prevention. The present invention has now been completed.

That is, according to the present invention, in an electrophotographic photoreceptor in which an undercoat layer containing an inorganic pigment, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support, the largest surface of the conductive support There is provided an electrophotographic photoreceptor characterized in that the relationship between roughness (RIIlax) and the thickness (1) of the undercoat layer is t≦5Rmax.

The configuration of the present invention will be explained in detail below.

The electrophotographic photoreceptor of the present invention has a structure in which an undercoat layer, a charge generation layer, and a charge transport layer are laminated in this order on a conductive support.

As the conductive support, in addition to metals such as AQ, Ni, Cd, and stainless steel, conductive powders (carbon, AQ,
Plastics containing Cu, etc.) can also be used.

It is desirable that the undercoat layer contains an inorganic pigment. Examples of such inorganic pigments include titanium dioxide, zinc oxide, zinc white, lead white, lithopone, calcium oxide, barium, white carbon, etc., and preferably have a refractive index of 1.9 or more in visible light or near infrared light. A material with a high refractive index is desirable.

The binder for the undercoat layer must meet the following conditions: (1) it has good adhesion to the surface of the conductive support, and (2) it is not attacked by the photosensitive layer forming liquid applied on the undercoat layer. You can use anything. For example, urethane resin, epoxy resin, alkyd resin, melamine resin, polyester resin,
Thermosetting resins such as acrylic-melamine resin, polyester resin, acrylic-melamine resin, and alkyd melamine resin.

Water or alcohol soluble polyvinyl alcohol.

Examples include sodium polyacrylate, CMC, casein, nylon, and copolymerized nylon.

The ratio of the binder to the pigment is 1 part of the binder and 10 parts or less of the inorganic pigment, preferably 0.05 to 10.
About 100% is appropriate.

To form an undercoat layer using these materials.

A solvent, an inorganic pigment, and a binder are added, dispersed well using a ball mill, etc., and coated on a conductive substrate and dried. The appropriate thickness of the undercoat is 0.3 to 20 pn.

The charge-generating layer is made of polyester, charge-generating substances such as azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, square pigments, selenium powder, selenium alloy powder, amorphous silicon powder, zinc oxide powder, and cadmium sulfide powder. It is formed by dispersing in a solution of a binder resin such as polycarbonate, polyvinyl butyral, or acrylic resin, and coating this on the undercoat layer.

The appropriate thickness of the charge generation layer is about 0.000000000000000000000000000000000000000000000000000

The charge transport layer is an α-phenylstilbene compound (Japanese Patent Application Laid-open No.
8-198043), hydrazone compounds (
A charge transporting substance such as those described in JP-A No. 55-46760 is dissolved in a film-forming resin such as polyester, polysulfone, polycarbonate, polymethacrylic acid ester, polystyrene, etc., and this is applied onto the charge generation layer. It may be applied to a thickness of about 10 to 30 tones. The film-forming resin is used here because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself.

With a laminated electrophotographic photoreceptor that simply laminates each layer as described above, when line-scanning a laser beam (coherent light) and producing a halftone image with a printer, moiré may occur as described above. . This is considered to be due to insufficient roughness of the surface of the undercoat layer, and therefore, in the present invention, the maximum surface roughness (Rmax) of the conductive support and the film thickness of the undercoat layer (1
) is defined so as to satisfy the relationship t≦5Rmax, thereby making it possible to prevent the occurrence of moiré.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited only to these Examples.

Example 1 Preparation of coating liquid-1 (coating liquid for undercoat layer) Titanium oxide tie bake A-100 (manufactured by 6 Hara Sangyo Co., Ltd.) 6QOg methyl ethyl ketone 300 g or more was placed in a ball mill and dispersed for 24 hours, followed by methyl ethyl ketone. 200 g was added and dispersed in a ball mill for an additional 5 minutes, and the resulting liquid was filtered to obtain Coating Liquid-1 for undercoating.

Preparation of conductive support (AΩ drum) After the surface of the AR drum was processed by cutting with a cutting tool, the surface roughness was measured using a Tokyo Seimitsu Surfcom (E-ST-5o-3A), and the maximum surface roughness was Rmax = 0.5 JR. Met.

Coating liquid-1 on the conductive support consisting of the above AQ drum.
After coating by dip coating, dry at 120℃ for 10 minutes to a film thickness of 1
．． 5. A subbing layer of n was formed.

Preparation of Coating Solution-2 (Coating Solution for Charge Generation Layer) 10 g of butyral resin (S-LEC BL-5; manufactured by Sekisui Chemical Co., Ltd.) was dissolved in 300 g of cyclohexanone, and a trisazo pigment represented by the following structural formula was added to the solution. 20 g was added and dispersed in a ball mill for 48 hours. Next, 420 g of cyclohexanone was added to this material and dispersed for 3 hours, then taken out into a container and diluted with cyclohexanone while stirring so that the solid content was 1.5% by weight. It was designated as coating liquid-2.

Preparation of coating liquid-3 (coating liquid for charge transport layer) Polycarbonate resin (1300 for Panlite; Teijin Chemicals Ltd. ll) 2
40g was dissolved in 1800g of tetrahydrofuran, and the following structural formula CH was dissolved therein.

140 g of the charge transporting substance represented by was dissolved to prepare coating liquid 3 for charge transport.

Coating solution 2 was applied onto the undercoat layer by dip coating, and then dried at 120° C. for 10 minutes to form a charge generation layer with a thickness of 0.3 mm.
Further, coating liquid-3 was applied thereon by dip coating.

This was dried at 120° C. for 13 minutes to form a charge transport layer having a thickness of 22 mm, thereby producing an electrophotographic photoreceptor.

Examples 2 to 6 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the maximum surface roughness Rmax of the AQ drum as a conductive support and the film thickness t of the undercoat layer were changed as shown in Table 1. It was created.

Comparative Examples 1 to 2 An electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that the maximum surface roughness Rmax of the AQ drum as a conductive support and the film thickness t of the undercoat layer were changed as shown in Table 1. It was created.

Table-1 Surface roughness (pm) Undercoat layer thickness ([)Rmax Example 1 0.53 1.5JT 2
051 2.511310
3.0 ff41.0 5.0 #520 5.0 #620 10.0 Comparative example 1 0.52 3.01'210
7.0 Each of the electrophotographic photoreceptors prepared as described above was mounted on an Imageo copying machine manufactured by Ricoh Co., Ltd. to produce an image, and the occurrence of moiré was examined. The results are shown in Table-2.

Table-2 Moiré Example 10! 1 × n2 × indicates that the occurrence of moiré significantly exceeded the allowable range.

〔Effect of the invention〕

According to the present invention, in an electrophotographic photoreceptor using an undercoat layer containing an inorganic pigment, by specifying the relationship between the maximum surface roughness of the conductive support and the thickness of the undercoat layer, moire can be reduced. This can be prevented and good images can be obtained.

Patent applicant Rico Co., Ltd.

Claims (1)

[Claims] (1) an undercoat layer containing an inorganic pigment on a conductive support;
In an electrophotographic photoreceptor formed by sequentially laminating a charge generation layer and a charge transport layer, the maximum surface roughness (R
max) and the film thickness (t) of the undercoat layer, t≦5Rmax.