JPH0247666A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To decrease printing defects and to improve moisture resistance and adhesive property by providing a specific intermediate layer between the conductive base and charge generating layer of the separated function type laminated photosensitive body formed by laminating the charge generating layer and charge transfer layer on the conductive base. CONSTITUTION:The intermediate layer of the laminated type photosensitive body having at least the intermediate layer, the charge generating layer and the charge transfer layer on the conductive base is constituted of polyvinyl alcohol having 20-50mol% degree of saponification and 100-500 degree of polymn. The charge generating layer is then hardly soluble in a solvent such as tetrahydrofuran used at the time of formation of the layer by coating and particularly the good matching property with the photosensitive body formed with the charge generating layer consisting of a phthalocyanine compd. or the like is obtd. Generation of the degradation in characteristic is obviated and since the intermediate layer does not dissolve in water alone, the high moisture resistance is obtd.

Description

[Detailed Description of the Invention] [Summary] Regarding a functionally separated photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support, in an intermediate layer provided between the conductive support and the charge generation layer. , 'TIj, to provide a suitable intermediate layer that does not have problems such as being easily soluble in the solvent used for coating the charge generating layer, having poor compatibility with the charge generating layer, and having insufficient moisture resistance. The intermediate layer has a degree of saponification of 20 to 50 mol% and a degree of polymerization of 100 to 5.
00 polyvinyl alcohol.

[Industrial application field]

The present invention relates to an electrophotographic photoreceptor, and more particularly to a functionally separated layered photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support. Electrophotographic photoreceptors can be widely applied to copying machines, printers, etc. that apply electrophotography.

[Conventional technology]

As an example of electrophotography, it is common to obtain printed matter by repeating the steps of charging, exposing, developing, transferring, and fixing. Charging applies a uniform positive or negative electrostatic charge to the surface of a photoreceptor that is photoconductive. In the subsequent exposure process, an electrostatic latent image corresponding to the image information is formed on the photoreceptor by irradiating it with laser light or the like to erase the surface charge on a specific portion. Next, this latent image is electrostatically developed with powder ink called toner, thereby forming a visible image of the toner on the photoreceptor. Finally, this toner image is electrostatically transferred onto recording paper and fused using heat, light, pressure, etc. to obtain a printed matter.

Inorganic photoreceptors typified by selenium-based photoreceptors are widely used as photoreceptors having photoconductivity.

This inorganic photoreceptor is highly sensitive and resistant to mechanical abrasion, making it suitable for high-speed, large-scale machines. However, it must be manufactured using a vacuum evaporation method and must be collected because it is harmful to the human body. The problem is that the cost is high due to the fact that there is a problem, and it is difficult to apply it to maintenance-free, small, low-cost machines.

Organic photoreceptors were developed as an alternative to inorganic photoreceptors. This material can be manufactured by a coating method, which makes it easy to reduce costs through mass production, and because it has a wider range of materials to choose from than inorganic photoreceptors that use inorganic materials such as selenium, non-hazardous compounds can be selected. It has the advantage of being maintenance-free.

In particular, a functionally separated laminated photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support is attracting attention. Here, the charge generation layer has the function of absorbing incident light and generating electron-hole pairs (carrier pairs), and the charge transport layer retains a charge on its surface and carries carriers generated in the charge generation layer. It has the function of transporting one side of the photoreceptor to the surface of the photoreceptor to form an electrostatic latent image.

The charge generation layer is made by dispersing a charge generation substance that absorbs light and generates carrier pairs in a binder resin, applying this and drying it to have a film thickness of about 0.01 to 3ptn, particularly 1- or less. to form. Further, the charge transport layer is formed by dissolving a charge transport material having carrier transport ability in a binder resin, applying this and drying it to have a film thickness of 10 to 30. By separating the functions of the photoreceptor into two layers in this way, it is possible to select the optimal compound for each function almost independently, improving basic properties such as sensitivity, spectral characteristics, and mechanical abrasion resistance. can be done.

[Problem to be solved by the invention]

However, even in the function-separated layered photoreceptor as described above, it is difficult to obtain satisfactory performance from a practical standpoint simply by forming a photosensitive layer on a conductive support. That is, when charged by corona discharge or the like, there is a problem in that discharge breakdown often occurs and pinholes are produced, or printing defects are likely to occur due to the tendency to receive charge injection from the "LT4." support. Further, when forming a thin charge generating layer by coating, unevenness in film thickness and uneven coating are likely to occur due to extreme defects, dirt, etc. on the conductive support.

As a countermeasure against this problem, a method is known in which an intermediate layer made of a specific resin is provided between the conductive support and the charge generation layer. However, if a resin that is easily soluble in the solvent used to coat and form the charge generation layer is used for such an intermediate layer, there may be problems such as mixing of the intermediate layer and the charge generation layer, resulting in deterioration of characteristics or uneven coating. arise. Further, unless sufficient attention is paid to the properties of the resin and the compatibility between the intermediate layer and the charge generation layer, the characteristics of the photoreceptor may be significantly deteriorated. For example, epoxy, polyester, polyurethane, etc. are easily soluble in solvents, making it extremely difficult to select a solvent to be used for coating and forming the charge generation layer. In addition, casein, methylcellulose, ethylcellulose, etc. are not soluble in solvents, and are particularly compatible with photoreceptors using phthalocyanine compounds, but their moisture resistance is insufficient, resulting in decreased adhesion and sensitivity due to moisture absorption. There is a drawback that it does.

Therefore, the present invention aims to provide a practical functionally separated photoreceptor that eliminates the inconvenience of directly forming a photosensitive layer on a conductive support by providing an intermediate layer that does not have the above-mentioned problems. purpose.

[Means to solve the problem]

The above problems include a saponification degree of 20-50 mol% and a polymerization degree of 100-50 mol%.
A solution can be achieved by an intermediate layer consisting of 500% polyvinyl alcohol. That is, according to the present invention, on the conductive support,
An electrophotographic photosensitive material having at least an intermediate layer, a charge generation layer, and a charge transport layer, wherein the intermediate layer is made of polyvinyl alcohol having a degree of saponification of 20 to 50 mol% and a degree of polymerization of 100 to 500. The body is provided.

If the degree of saponification of the polyvinyl alcohol is too high, the moisture resistance will decrease, and if it is too low, it will be easily melted by heat, which is not preferable.

Furthermore, the higher the degree of polymerization, the better the film-forming properties and the less soluble it becomes in solvents, but if it is too high, coating formation becomes difficult. The preferred range is 200-400.

The preferred thickness of the intermediate layer is 0.1 to 3 mm, and the intermediate layer is formed by coating using an organic solvent that dissolves the polyvinyl alcohol, such as methanol, ethanol, acetone, dichloromethane, or dichloroethane, either alone or in combination. Can be done. Alternatively, a mixed solution of water and an organic solvent may be used.

Conductive supports include various metal cylinders, conductive resin cylinders, insulating cylinders with metal vapor-deposited or laminated on the surface, insulating cylinders coated with conductive organic thin films, and the above. A film or the like having a similar configuration can be used.

As the charge-generating substance contained in the charge-generating layer, phthalocyanine-based, azo-based, squarylium-based dyes and pigments can be used, and metal-free or metal phthalocyanine compounds are particularly preferred. As the binder resin for the charge generation layer, various resins such as polyester, epoxy, and silicone can be used, and the binder resin is selected in consideration of adhesion, dispersibility of the charge generation substance, and the like. The solvent used for forming the coating may be any solvent as long as it does not easily dissolve the polyvinyl alcohol, but it is selected depending on the binder resin of the charge generation layer. Various organic solvents such as tetrahydrofuran, methyl acetate, and methyl ethyl ketone can be used alone or in combination.

The charge transport layer may be anything that can transport the charges generated in the charge generation layer, and may be a hole-transporting charge transport substance such as hydrazone, triarylamine, or stilbene, or a charge transport material such as chloranil, bromanyl, or trinitrofluorenone. An electron-transporting charge-transporting substance dissolved in a binder resin can be used. Alternatively, a photoconductive polymer that itself has charge transport ability, such as polyvinylcarbazole, can also be used.

As the binder resin for the charge transport layer, known binder resins such as polyester, polycarbonate, and epoxy can be used. As the solvent, various organic solvents such as tetrahydrofuran, toluene, dichloromethane, and methyl cellosolve can be used alone or in combination, depending on the binder resin used.

[For production]

Although polyvinyl alcohol is soluble in a solvent such as tetrahydrofuran which is commonly used when forming a charge generating layer, it does not mix with the charge generating layer.

In addition, it has good compatibility with photoreceptors that use charge-generating substances such as phthalocyanine compounds, and does not cause any deterioration of properties. Unlike general polyvinyl alcohol, it is not soluble in water alone, so it has high moisture resistance. Therefore, it is suitable as an intermediate layer between the conductive support and the charge generation layer of a functionally separated laminated photoreceptor, and this intermediate layer prevents discharge destruction (pinholes) of the photosensitive layer and charge injection from the conductive support. Moreover, the base of the charge generation layer can be made uniform.

〔Example〕

Actual test: 1 part (by weight) of polyvinyl alcohol with a degree of saponification of 30 mol% and a degree of polymerization of 300 was dissolved in 10 parts of a mixed solvent of water/methanol (1:9), and this was applied on an aluminum support by dip coating. It was dried at 100° C. for 1 hour to form an intermediate layer having a thickness of about 1 inch.

Next, a mixture of 1 part (by weight) of copper phthalocyanine, 1 part of polyester, and 20 parts of tetrahydrofuran was dispersed and mixed for 24 hours using a hard glass pole and a hard glass pot, and the resultant mixture was dip-coated onto the intermediate layer and heated at 100°C for 1 hour. A charge generation layer having a thickness of about 0.5 mm was formed by drying for an hour.

Furthermore, one part of a hydrazone derivative represented by the following structural formula,
1 part of polycarbonate was dissolved in 10 parts of tetrahydrofuran, and the solution was applied onto the charge generation layer by dip coating, and dried at 70° C. for 2 hours to form a charge transport layer having a thickness of about 151M, thereby obtaining a photoreceptor of an example.

A photoreceptor of Comparative Example 1 was obtained in the same manner as in the Example except that the intermediate layer was not formed by coating.

, L Comparison'' In place of the intermediate layer in Example 1, 1 part of methylcellulose was dissolved in a mixed solution of 9 parts of pure water and 1 part of methanol, and the same procedure as in Example was used, except that the intermediate layer was formed using this solution. Comparative example 2
A photoreceptor was obtained.

When we carried out a printing test using the three types of photoreceptors mentioned above in our small prototype laser printer, we were able to obtain clear printing results with the photoreceptors of Example and Comparative Example 2, but the comparison example A large number of printing defects occurred in photoreceptor No. 1.

Furthermore, for the photoreceptors of Example and Comparative Example 2, 50°C, 1
After conducting an accelerated test with 00% RH humidity for 17 days, a cross-cut test (pitch 1.5 mm) was conducted at room temperature. The photoreceptor of the example maintained good adhesion, but the comparative example In photoreceptor No. 2, peeling occurred between the aluminum support and the photosensitive layer in 80% or more.

Further, as a result of the printing test, the photoreceptor of Example showed no change from before wetting, but the photoreceptor of Comparative Example 2 showed a decrease in density and image blurring.

〔Effect of the invention〕

According to the present invention, a specific method according to the present invention is provided between the conductive support and the charge generation layer of the functionally separated photoreceptor in which the charge generation layer and the charge transport layer are laminated on the conductive support. By providing the intermediate layer, it is possible to obtain a photoreceptor that is free from printing defects and has excellent moisture resistance and adhesion.

Claims (1)

[Claims] 1. A laminated photoreceptor having at least an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support, in which the intermediate layer is made of polyvinyl alcohol with a degree of saponification of 20 to 50 mol% and a degree of polymerization of 100 to 500. An electrophotographic photoreceptor characterized by: