JPH04184346A - Organic electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To attain the omission of a processing of smoothness for the base surface and to obtain an excellent image superior in the electric characteristics by making a film thickness of an undercoating layer 5 times of more as thick as a center line average roughness Ra of the conductive body surface and incorporating a lower resistant material. CONSTITUTION:By making the film thickness of the undercoating layer 5 times or more as thick as Ra, the occurrence of image defects caused to the surface shape of the base body is prevented. For the formation of the undercoating layer a resin binder is used such as polyvinyl alcohol, methyl cellulose. Also it is efficient to incorporate the lower resistant material in the undercoating layer and conductive fine particles, e.g. ZnO, SiO2, etc., are used and the size of the conductive fine powders are preferably <=0.5mum. In this case the adhesiveness to the base, the dispersibility of the conductive fine powders and the solvent resistance, etc., are necessary to be excellent and as the binder used epoxy resin, alkyl resin, etc., are suited. As a result even without carrying out the smoothing processing of the base surface, the electric characteristics are superior and the excellent image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an organic electrophotographic photoreceptor comprising an undercoat layer between a conductive substrate and a photosensitive layer containing an organic photosensitive material.

[Conventional technology]

Organic electrophotographic photoreceptors are usually produced by coating a conductive substrate with a coating solution in which an organic photosensitive material, a resin binder, etc. are dispersed and dissolved in a solvent to form a photosensitive layer. An undercoat layer is provided between the substrate and the photosensitive layer for the purpose of improving the coating properties of the photosensitive layer, which is a film, preventing defects on the substrate from adversely affecting the photosensitive layer, and improving the electrical characteristics of the photosensitive layer. It is being said.

In order to obtain a good image, the surface of the conductive substrate is smoothed by surface polishing 1, surface cutting, etc., and the surface roughness is usually 0.5 μm or less in terms of center line average roughness. It will be finished.

[Problem to be solved by the invention]

A sophisticated technique is required to uniformly perform the smoothing process as described above. Therefore, when manufacturing an organic electrophotographic photoreceptor, the cost of smoothing the substrate occupies a large proportion of the manufacturing cost, and has become a factor in high costs.

The present invention solves the above-mentioned problems and provides an organic electrophotographic photoreceptor that can omit smoothing of the substrate surface, has excellent electrical properties, and can obtain good images. make it a problem to be solved.

[Means for Solving the Problems 2] According to the present invention, the above problems are achieved in an organic electrophotographic photoreceptor comprising an undercoat layer between a conductive substrate and a photosensitive layer comprising an organic photosensitive material. This can be solved by making the thickness of the undercoat layer five times or more the center line average roughness Ra of the surface of the conductive substrate.

When an undercoat layer having the thickness described above is provided, accumulation of residual charges may become a problem, but this problem can be solved by containing a low-resistance substance in the undercoat layer.

Further, depending on the type of low-resistance substance, some substances have the property of injecting free carriers into the photosensitive layer when included in the undercoat layer, which deteriorates the charge retention rate. In order to prevent such injection of free carriers, it is effective to further provide a resin layer between the undercoat layer and the photosensitive layer.

2Ra indicates the average roughness from the center line of the unevenness on the surface of the conductive substrate. On the other hand, the thickness of the undercoat layer is usually measured using an eddy current film meter, and its reference plane (the plane showing the seven points)
almost coincides with the center of gravity line mentioned above. Focusing on this point, R
After intensive study on the relationship between Ra and the thickness of the underneat layer from the viewpoint of preventing image defects, we found that by making the thickness of the undercoat layer five times or more than Ra, image defects caused by the surface shape of the substrate can be prevented. It was found that the occurrence of 5) can be prevented. By providing an undercoat layer with such a thickness, the surface Ra of the conductive substrate can be set to 0.
It becomes unnecessary to perform smoothing processing such as making the thickness 5 μm.

When forming the undercoat layer according to the present invention, a resin binder is used. For example, polyvinyl alcohol, methylcellulose, ceratin, polyamide, etc., which are soluble in water or alcohol, are effective.

In addition, the undercoat layer has a very high electrical resistance and no residual charge accumulates, especially at low temperatures.

It is desired that residual charge does not accumulate even in a low-humidity environment, and it is effective to include a low-resistance substance in the undercoat layer in order to satisfy such a demand. Examples of such low resistance materials include ZnO, 5n02. T+
[]2. Conductive fine powder such as In, 03, etc. can be used. In order to obtain the desired resistance, it is necessary to appropriately select the type of conductive fine powder and the mixing ratio with the resin binder. The size of the conductive fine powder is particularly preferably 0.5 μm or less. In the case of an undercoat layer containing dispersed conductive fine powder as in 2, it is essential that it has good adhesion to the substrate, good dispersibility of the conductive fine powder, and solvent resistance. Examples of resin binders include Epoquine resin, alkyd resin, and polyurethane resin.

Thermosetting resins such as silicone resins and phenolic resins are suitable.

Furthermore, depending on the type of conductive fine powder, some have the property of injecting free carriers into the photosensitive layer when included in the undercoat layer, and in such cases, the charge retention rate of the photosensitive member deteriorates. In order to prevent this phenomenon, it is effective to further form a thin second resin-only layer between the undercoat layer and the photosensitive layer to form a protective layer that prevents carrier injection. The second resin layer can be formed using polyvinyl alcohol, methylcellulose, ceratin, polyamide, Epoquin, polyurethane, or the like.

〔Example〕

As a conductive substrate, the outer diameter is 60 m, the inner diameter is 58 m, and the length is 2.
A 46 mm aluminum ED tube is used. The center line average roughness Ra of the outer surface of this substrate was 06 μm.

2nO (particle size: 0.1 μm) 10-weight part as conductive fine powder.

Polyamide resin as a resin binder (product name: CM
8000. (manufactured by Toshi) was well dispersed in 80 parts by weight of methanol using a sand mill. This dispersion was applied to the outer surface of the substrate by a dip method, and treated at a temperature of 120° C. for 30 minutes to form an undercoat layer with a thickness of 5 μm.

Next, a 10% methanol solution of polyamide resin (trade name: CM8000, manufactured by Toshi) was applied onto this undercoat layer to form a resin layer having a thickness of 0.5 μm.

This is a resin layer that does not contain conductive fine powder.

A charge generation layer and a charge transport layer were sequentially laminated on this resin layer to form a photosensitive layer, thereby preparing a photoreceptor. The charge generation layer was prepared by applying a dispersion of 1 part by weight of X-type metal-free phthalonanine, 1 part by weight of polyester resin (trade name: Vylon 200, manufactured by Toyobo) and 98 parts by weight of dichloromethane in a paint shaker for 3 hours using a dip method. A layer having a thickness of 02 μm was formed by drying and smoking at a temperature of 80° C. for 30 minutes. The charge transport layer was prepared by dipping a coating solution in which 10 parts by weight of a charge transport substance having the following structural formula and 10 parts by weight of polycarbonate resin (product name: PCZ-300, manufactured by Mitsubishi Gas Chemical) were dissolved in 80 parts by weight of dichloromethane. The film was coated by a method and dried by heating at a temperature of 80° C. for 2 hours to form a layer with a thickness of 20 μm.

Comparative Example 1 Same as Example 1 except that the thickness of the undercoat layer containing 2nO fine powder was changed to 2 μm (less than 5 times the Ra of the outer surface of the substrate). A photoreceptor was prepared.

The photoreceptor thus obtained was printed on an electrophotographic printer (N
When the images were evaluated by attaching them to EC's P CP R601), good images were obtained with the photoconductor of Example 1, but poor images were obtained with the photoconductor of Comparative Example 1 with noticeable black spots. The image quality was good.

Example 2 TlO2 (particle size: 005 μm) as conductive fine powder and polyamide resin (trade name: CM8000, manufactured by Toshi) were mixed at a ratio of 1:1, methanol was appropriately added to this, and the mixture was well dispersed using a sand mill. Several kinds of dispersions with different solid ratios (i.e., viscosities) were prepared and applied to the outer surface of the substrate similar to that used in Example 1 by the dip method to obtain a film thickness of 1 μm.
m, 2μm, 4μm.

Five types of substrates were prepared with five different undercoat layers of 6 μm and 10 μm. A polyamide resin layer, a charge generation layer, and a charge transport layer each having a thickness of 05 μm were sequentially formed on these substrates in the same manner as in Example 1, thereby producing five types of photoreceptors that differed only in the thickness of the undercoat layer. .

Image evaluation was performed on the photoreceptors of Example 2 in the same manner as in Example 1. The results are shown in Table 1.

Table 1 As shown in Table 1, there is a clear difference in image quality (especially black dots) when the thickness of the undercoat layer reaches 3 μm, which is 5 times the Ra of the substrate surface.

[Effect of the invention 2- According to the invention, in the organic electrophotographic photoreceptor, the thickness of the undercoat layer provided between the conductive substrate and the photosensitive layer is 5 times or more the center line average roughness Ra of the substrate. By doing so, the roughness of the substrate surface can be covered, so a photoreceptor with excellent electrical properties and good images can be produced without the need for smoothing the substrate surface, and manufacturing costs can be reduced. I can do it.

In addition, when an undercoat layer with the thickness described above is provided, accumulation of residual electric charge may become a problem, but if the undercoat layer contains a low-resistance substance, such accumulation of residual electric potential can be prevented. It is possible to prevent this.

In addition, when the undercoat layer contains a low-resistance substance, injection of free carriers into the photosensitive layer may become a problem, but by providing a resin layer between the undercoat layer and the photosensitive layer, free carriers can be can be prevented from being injected, and a decrease in charge retention rate can be prevented.

Claims (1)

[Scope of Claims] 1) An organic electrophotographic photoreceptor comprising an undercoat layer between a conductive substrate and a photosensitive layer containing an organic photosensitive material, wherein the undercoat layer covers the surface of the conductive substrate. An organic electrophotographic photoreceptor characterized in that the film thickness is five times or more the center line average roughness Ra. 2) The organic electrophotographic photoreceptor according to claim 1, wherein the undercoat layer contains a low resistance substance. 3) The organic electrophotographic photoreceptor according to claim 2, characterized in that a resin layer is provided between the undercoat layer and the photosensitive layer.