JPS61204641A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor in which at least an undercoat layer and a photosensitive layer are formed on a substrate.

[Prior art]

Electrophotographic photoreceptors have various configurations in order to obtain predetermined characteristics or depending on the type of electrophotographic process to which they are applied. By the way, organic photoconductive materials have advantages over inorganic photoconductive materials, such as lighter weight and higher productivity, but their low sensitivity has made it difficult to put them into practical use. Therefore, several sensitization methods have been proposed, and an effective method is known to be the use of a laminated photoreceptor in which the photosensitive @tl charge generation layer and the charge transport layer are separated in function.

Since the charge generation layer in such a photoreceptor is very thin, it is easily affected by the substrate surface when forming a coating pattern, and therefore the charge generation layer is susceptible to coating unevenness caused by the roughness of the substrate surface. This causes unevenness in film thickness.

Since the occurrence of such unevenness causes image defects and density unevenness, it is necessary to avoid it as much as possible. Therefore, conventionally, in order to reduce the roughness of the substrate surface, processes such as cutting and mirror polishing have been added to the surface. However, such a process reduces the cost of electrophotographic photoreceptors.

It was the cause of de. In order to improve the above-mentioned problems, it has been attempted to coat the substrate with a paint to improve its surface smoothness without subjecting the substrate to surface treatment. Such paints should (1) have surface smoothness, C2) have low electrical resistance and do not accumulate residual charge due to their characteristics, and (3)
) the electrophotographic properties are not adversely affected; (4) the adhesion to the base is sufficient; and (5) the solvent resistance to the paint applied thereon is sufficient. .

Conventionally, as an undercoat layer, I-rivinyl alcohol, polyvinyl methyl ether, poly-N-vinyl iotasol,
Ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, casein, gelatin, polyamide, etc. are known.

By the way, the first characteristic required of the undercoat layer is electrical characteristics. Since it is used in an electrophotographic photoreceptor, it is important that the electrophotographic properties are not adversely affected, and for this purpose, it is necessary that the electrical resistance be stable. If the electrical resistance is high, a charged potential is applied to the undercoat layer, causing fogging on the image as a so-called residual potential.

Furthermore, it is necessary that the electrical resistance is unaffected by changes in the external environment, in particular by changes in atmospheric humidity. For example, when the electrical resistance increases due to low humidity, fogging may occur.

It is also necessary to control the dielectric constant. If the dielectric constant is large, it becomes easier to maintain the contrast of the image, but it also becomes easier to fog. If it is too small, the contrast of the image will not be adequate.

It is also necessary to control the thickness of the undercoat layer.

When the thickness of the undercoat layer is large, the electrical resistance becomes high and a charged potential is applied to the undercoat layer, causing fogging on the image as a so-called residual potential. Furthermore, if the film thickness is too small, the hiding power of the substrate surface roughness is insufficient, and the performance as an undercoat layer is not exhibited.

[Problem that the invention seeks to solve]

The purpose of the present invention is to reduce the residual potential by regulating the volume resistivity and dielectric constant of the undercoat layer within a certain range, and to stabilize the potential retention and barrier properties during repeated use. It is an object of the present invention to provide an electrophotographic photoreceptor that can always obtain good image quality without being affected by changes.

[Means for solving problems]

According to the present invention, there is provided an electrophotographic photoreceptor in which at least an undercoat layer and a photosensitive layer are formed on a substrate, wherein the mosquito undercoat layer contains a dielectric constant control agent and has a volume electrical resistivity of 1010 to 1.
Provided is an electrophotographic photoreceptor having a dielectric constant of 0.013 Ω·d and a dielectric constant of 8 to 200.

Examples of resins used in the undercoat layer of the present invention include EVA, polyvinyl alcohol, polyvinyl methyl ether, poly-N-vinylimidazole, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, casein, gelatin, polyamide, phenolic resin, butyral resin. , polyurethane, ? Liacrylonitrile etc. are mentioned, and I! l! fK polyamide, phenol resin, and phenol resin with butyral resin have particularly stable volume resistance.

Examples of the dielectric constant control agent added to the above resin include conductive zinc oxide, conductive titanium oxide, and succinonitrile. Titanium oxide, succinonitrile, etc. are preferred.

The undercoat layer is formed by dissolving or dispersing the resin in an organic solvent as required, dispersing a dielectric constant control agent therein, applying the resulting coating liquid onto a substrate, and drying it.

If the substrate is in the form of a sheet, the application method is spray)'
If the substrate is cylindrical, dip coating is suitable.

The thickness of the coating film varies depending on the surface roughness of the substrate, and a thickness that provides smoothness is selected, but it is preferably at least twice the maximum roughness of the substrate surface. The thickness of the undercoat layer of the present invention is 0.5 to 5.0 μm%, particularly 1.0 to 5.0 μm%.
A range of 3.0 μm is preferred.

Furthermore, in order to stabilize the image quality, a conductive layer in which conductive powder is dispersed in a binder resin is provided between the substrate and the undercoat layer, so that roughness on the surface of the substrate can be sufficiently hidden.

Further, the photosensitive layer may be a single layer, or a laminated photosensitive layer having functionally separated charge generation layer and charge transport layer may be used.

The charge generation layer is made of azo pigments such as Sudan Red, Diane Blue, and Jenas Green B, Algol Yellow,
Quinone pigments such as pyrenequinone, indanthre/brilliant violet RRP, quinocyanine pigments, perylene pigments, indigo pigments such as indigo 9, thioindigo,
Bisbenzimidazole pigments such as India Fast Orange Toner, phthalocyanine pigments such as copper phthalocyanine, charge-generating substances such as quinacridone pigments, etc.? It is formed by dispersing in a binder resin such as polyester, polystyrene, polyvinyl butyral, Ilipinylpyro IJ), methylcellulose, polyacrylic acid esters, and cellulose ester. Its thickness is about 0.01 to 1 micron, preferably about 0.05 to 0.5 part.

In addition, the charge transport layer may contain polycyclic aromatic compounds such as anothracene, bire/, phenanthrene, coronene, etc., or indole, carbazole, oxazole, inoxazole, thiazole, imidazole, pyrazole, etc. in the main chain or side chain.
It is formed by dissolving a hole-transporting substance such as a compound having a nitrogen-containing formal structure such as oxadiazole, pyrazoline, thiadiazole, or triazole, or a hydrazone compound in a resin that has film-forming properties. This is because when the charge transporting substance has a low molecular weight, it has poor film-forming properties by itself. Such resins include Bori carfnate, polymethacrylic acid esters, polyarylate, polystyrene, polyester, etc. Examples include resulfone, styrene-acrylonitrile copolymer, styrene-methyl methacrylate copolymer, and the like. The thickness of the charge transport layer is 5 to 20 microns.

Further, the substrate can be selected from a wide variety of conductive materials. Specifically, aluminum, brass,
Metals such as stainless steel and nickel are pressed into cylinder or plate shapes, or aluminum, indium oxide, and tin oxide are made of plastic.

Examples include those deposited or laminated on paper or paper.

Hereinafter, the present invention will be explained according to examples.

Example 1 Conductive titanium oxide [high purity ultrafine titanium oxide average primary particle diameter 300 Name: Titanium Oxide P-25 Japan 7
After 0 parts, the mixture was dispersed in a stainless steel gall mill for 48 hours. This paint was applied as a base onto an aluminum cylinder of 60 φ x 260 m by dipping method and dried at 80° C. for 10 minutes to obtain an undercoat layer with a width of 2.0 μm. The volume electrical resistance and dielectric constant of this undercoat layer were measured under different environments. The measurement results are shown in the table below.

On this undercoat layer, 10% of a disazo pigment having the following structural formula is applied.
(same below for important parts), 6 parts of cellulose acetate butyrate resin (trade name: caB-381: manufactured by Eastman Chemical Co., Ltd.) and 60 parts of cyclohexanone were mixed in a sand mill apparatus with a diameter of 1φ of 2 using a Raspize.
It was dispersed for 00 hours. Add 10% of methyl ethyl ketone to this dispersion.
0 parts of the undercoat layer was added, and the undercoat layer was applied by dip coating, followed by heating and drying at 100° C. for 10 minutes to form a charge generating layer with a coating weight of 0.117 m 2 .

Next, 1 part of a hydrazone compound having the following structural formula and 15 parts of a styrene-methyl methacrylate copolymer resin (trade name: MS200, manufactured by Tetsuto Kagaku Co., Ltd.) were dissolved in 80 parts of toluene. This liquid was applied onto the charge generation layer and dried with hot air at 100° C. for 1 hour to form a charge transport layer with a thickness of 16 μm.

Example 2 An aluminum cylinder of 60φ x 260m was prepared as a base. However, the surface of this aluminum cylinder was rough, and the maximum roughness of the surface was measured to be 6μ. To compensate for the surface roughness of this aluminum cylinder, titanium oxide powder (product name: 5R-1, manufactured by Sakai Kagaku-yo Co., Ltd.) and conductive titanium oxide powder (product name: ICT-62, manufactured by Titanium Industry Co., Ltd.) were each used at 209K, and phenol was used as a binder. 20 parts of resin (Pryophen J-325, manufactured by Dainippon Ink) and 20 parts each of methanol and methyl cellosolve were added to de-
Dispersion was carried out for 8 hours using Lumil. This paint was applied onto the cylinder by dipping and dried at 140° C. for 20 minutes to form a layer with a thickness of 20 μm. This layer is called a conductive layer because it imparts electrical conductivity.

By providing this conductive layer, the surface roughness of the cylinder was improved to 0.8 μm. On this conductive layer, 20 parts of phenol resin (Pryophen J-325, manufactured by Dainippon Ink), 5 parts of butyral resin (Sure, Ri B, 8H-3 manufactured by Sekisui Chemical) were added, 80 parts of methanol and 40 parts of butanol.
After adding 15 parts of conductive titanium oxide (the same high-purity ultrafine particle titanium oxide as in Example 1) to the solution dissolved in 1 part, the paint was dispersed for 48 hours in a stainless steel Gale mill and then applied by dipping at 150°C for 20 minutes. was dried to obtain an undercoat layer with a thickness of 3 μm. The volume electrical resistance and dielectric constant of this undercoat layer were measured under different environments. A charge generation layer and a charge transport layer similar to those in the example were formed on the undercoat layer.

Comparative Example 1 Methyl cellulose resin (trade name: Metrose 5M-15) was used as an undercoat layer, and the film thickness was 2.0 μm. The volume electrical resistance and dielectric constant of this undercoat layer were measured under the same environment as in Examples 1 and 2. The results are shown in the table below.

The electrophotographic photoreceptors prepared in Example 1, Example 2, and Comparative Example were charged at -5.5 kV, exposed to image, developed with dry toner, transferred to plain paper, and then coated with a 9-layer urethane coated sheet with a thickness of 1 gourd and a hardness of 700. Surface leveling was carried out under the above-mentioned environment using a copying machine that cleans the blade by pressing at an angle of 300 and a pressure of 411 w/cm. As a result, good quality images were obtained in all environments with the photoreceptors of Examples 1 and 2, but with the photoreceptor of the comparative example, fogging occurred under low temperature and low humidity conditions, and fogging occurred under high temperature and high humidity conditions. White spots appeared on the petablack image.

Claims (3)

[Claims] (1) An electrophotographic photoreceptor having at least an undercoat layer and a photosensitive layer formed on a substrate, the undercoat layer containing a dielectric constant control agent and having a volume electrical resistance of 10^1^0 to 10^ 1
An electrophotographic photoreceptor characterized by having a dielectric constant of ^3Ω·cm and a dielectric constant of 8 to 200. (2) Claim 1, wherein the dielectric constant control agent is conductive zinc oxide, conductive titanium oxide, or succinonitrile.
The electrophotographic photoreceptor described in . (3) The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer has a thickness in the range of 0.5 to 5.0 μm.