JPH0332062B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to an electrophotographic photoreceptor used in electrostatic copying machines, computer printers, and the like. BACKGROUND ART This type of photoreceptor is generally coated on a conductive support made of aluminum (the term "aluminum" is used in this specification to include its alloys) to improve adhesion. A photoconductive layer made of a photoconductive insulating material is formed through the interface layer. Various materials mainly composed of amorphous selenium have been widely used as photoconductive materials, but recently, materials with even better properties in terms of photosensitivity, spectral characteristics, acceptance potential, charge retention, etc. have been widely used. Amorphous silicon (hereinafter referred to as a-
The promising use of Si (abbreviated as Si) has attracted attention, and efforts are being made to put it into practical use. However, even when conventional selenium-based photoconductive materials are used, especially when forming a photoconductive layer with a-Si, the adhesion of the photoconductive layer to the conductive support and the charging and Problems often arise in terms of residual potential characteristics after exposure. Conventionally, when using a conductive support made of aluminum, in order to improve the adhesion of the photoconductive layer, the support is previously subjected to anodization treatment using a sulfuric acid method as a base treatment, and a base layer is applied to the surface of the support. It is known to form an anodic oxide film as a treatment interface layer (for example, Japanese Patent Publication No. 104938/1983). Problems to be Solved by the Invention It is true that the anodic oxide film formed by such base treatment, especially the sulfuric acid film, has a highly adsorbent surface and relatively good adhesion to the photoconductive layer when not sealed. It is possible to realize sexuality. However, in the image forming process of electrophotography, the residual potential after light irradiation, that is, the residual potential after light attenuation, is relatively high, which has a disadvantage in that it has a particularly harmful effect on continuous tone image formation. . For example, the most common anodizing conditions are 15% sulfuric acid concentration and 20% temperature.
When an aluminum electrode support is anodized at a current density of 1.3 A/dm ² using an electrolyte at ℃, the anodizing voltage will vary slightly depending on the material used, but will be about 15 to 20 V. The thickness of the barrier layer (insulating layer under the surface porous layer) of the resulting anodic oxide film is said to be approximately 150 to 200 Å. When such a film is used as an interface layer between a support and a photoconductive layer, relatively good adhesion can be obtained due to the presence of a porous layer with high adsorption properties on the surface. However, there was a problem in that the residual potential after exposure was high and it was not always possible to obtain a photoreceptor of high quality in terms of electrical properties. As a result of intensive research aimed at overcoming the above-mentioned problems, the present inventors have found that the cause of the deterioration of electrical characteristics is mainly a barrier layer that is inevitably formed in the lower layer of the anodic oxide film. The present invention was completed based on this knowledge. Therefore, the intended purpose of the present invention is to maintain relatively good adhesion to the photoconductive layer while controlling the thickness of the barrier layer to be extremely thin, 100 Å or less, to reduce the residual potential after exposure. The object of the present invention is to provide a method for forming an interfacial anodic oxide film that can reduce the amount of damage caused by anodic oxidation, that is, a method for anodizing a conductive support layer. Means for Solving the Problems Therefore, the present invention forms an anodic oxide film on the surface of a conductive support made of aluminum as a surface treatment interface layer for closely covering a photoconductive layer. In this case, the anodizing treatment for forming the film is carried out by a stepwise or continuous stepwise substantially multi-stage electrolytic treatment in which a relatively lower anodizing voltage is applied to the later stages. With,
The first stage of electrolysis is performed by applying a voltage of 10V or more, and the final nth stage is performed by applying a voltage of 10V or less, which is relatively lower than the first stage electrolysis voltage. The gist of the present invention is a method for surface treatment of an electrophotographic photoreceptor, which is characterized by controlling the thickness of the barrier layer under the surface porous layer in the anodic oxide film to 100 Å or less. It is advantageous to perform the above anodic oxidation treatment in about three stages, preferably by lowering the anodization voltage sequentially, and for the final n-th stage electrolysis, apply a voltage of 5V or less. It is preferable that the Specific Description of Means The type of electrolytic treatment bath for forming the anodic oxide film is not particularly limited in this invention, but in general, solutions such as sulfuric acid, phosphoric acid, and oxalic acid are preferably used. It will be done. However, when a conductive support is anodized using such an electrolytic solution, an anodized film having the low residual potential effect desired by the present invention cannot be formed under normal electrolytic treatment conditions. Therefore, in order to produce the anodic oxide film 2 that can exhibit the above-mentioned effects, the present invention improves the porous layer 2 on the surface of the anodic oxide film 2.
The present invention proposes specific anodizing treatment conditions that make it possible to control the thickness _t1 of the barrier layer 2a, which is located below b and acts particularly as an insulating layer, to an extremely thin value of 100 Å or less. Therefore, the processing conditions according to the method of the present invention are basically such that the anodizing treatment is carried out in substantially two or more stages, and as the latter stage is reached, the relative strength is increased from the earlier stage. This is a so-called multi-stage anodic oxidation treatment method in which a low anodizing voltage is applied to the anodizing process. More specifically, the method of the present invention performs the initial first stage anodizing electrolytic treatment under normal conditions, for example, preferably by applying a voltage of 15 to 20 V and performing electrolysis at a constant voltage or constant current. After forming an anodic oxide film having a surface porous layer of a predetermined thickness that can achieve sufficient adhesion for photoconductivity, a voltage lower than the initial voltage is applied in stages or successively. By performing electrolytic treatment in the second stage and further in the latter stage of the third stage, the barrier layer 2a is mainly
The thickness t ₁ is gradually decreased. The thickness of the barrier layer 2a of the obtained film is mainly determined by the thickness of the final nth layer.
It is determined by the electrolytic voltage of the stage. Therefore,
In order to control the barrier layer to a thickness of 100 Å or less as stipulated in this invention, it is necessary to set the final step formation voltage to generally 2 to 10 V or less, preferably 3 to 8 V. It is desirable to set the voltage within a certain range, especially 5V or less. Also,
When performing the next stage of electrolysis by rapidly lowering the voltage from the first stage of electrolysis to the low voltage region mentioned above,
During effective voltage electrolysis, the required current does not recover easily, and the process requires a lot of time. For this reason, it is advantageous that the electrolytic treatment is preferably carried out in about three stages, and the voltage is relatively lowered by about 5 to 10 V as the latter stages progress. The electrolysis at each stage may be carried out as completely separate steps, or may be carried out in series in the same bath by gradually lowering the formation voltage. Other electrolytic treatment conditions may follow general treatment conditions. Therefore, for example, in the case of the sulfuric acid method,
Concentration is 10-70%, particularly preferably 10-20%, temperature
The temperature can be changed arbitrarily within the range of about 15 to 30°C. Moreover, the electrolysis time can be changed within a range of about 10 to 60 minutes. When using a phosphoric acid solution, a porous layer with a particularly large pore size can be obtained;
This is advantageous in that it can be expected to further improve adhesion. In the case of phosphoric acid method, the concentration is 5 to 20
% is suitable, temperature is about 10 to 30℃, time 3
The time can be changed as appropriate within the range of ~30 minutes. Furthermore, when using the oxalic acid method, the concentration is 1 to 5%,
The temperature is about 10 to 30°C, and the treatment time is about 5 to 30 minutes. In this invention, the type of aluminum material used as a constituent material of the conductive support is not particularly limited, and can be selected from various commercially available aluminum materials in consideration of machinability, strength, hardness, etc. You can use whatever you choose. Generally, wrought aluminum materials such as pure aluminum and A3000 series are preferably used. Effects of the Invention In this invention, the anodic oxide film to be interposed as an interface layer between the conductive support and the photoconductive layer formed thereon has a thickness that is smaller than the normal thickness of the barrier layer. It can be formed to a thickness of 100 Å or less, which cannot be achieved by anodizing. Therefore, even though the interface layer is an anodic oxide film, it has low insulation properties, does not hinder the rapid light attenuation of the photoconductive layer during charging and exposure, and even after exposure. The residual potential of can be made sufficiently low. Therefore, it is possible to provide a photoreceptor with good electrical characteristics and excellent resolution of continuous tone images. Since the interfacial layer is originally formed as an anodic oxide film on the surface of the aluminum conductive support, it has a porous layer on the surface that exhibits good adhesion to the photoconductive layer. Not only when a-Si type photoconductive materials are used, but also when using a-Si type photoconductive materials, separation, blistering, and cracking of the photoconductive layer may occur during the cooling process after the formation of the photoconductive layer. This can contribute to the production of stable photoreceptors that do not cause such phenomena. Examples Example 1 An aluminum cylindrical body made of A1070-H14 with an outer diameter of 80 mm, an inner diameter of 74 mm, and a length of 340 mm was used as a conductive support, the surface was polished to a mirror finish, and the surface was degreased with a weak alkaline degreaser. , the anodic oxidation electrolytic treatment was carried out in three stages under the following treatment conditions. 1st stage electrolysis: Electrolyte 15% sulfuric acid Temperature 20℃ Current density 1.3A/dm ² (Formation voltage 16-18V) Time 3 minute electrolysis method Constant current electrolysis 2nd stage electrolysis: Electrolyte Same as 1st stage Temperature Same voltage as 1st stage 8V Time 3 minute electrolysis method Constant voltage electrolysis 3rd stage electrolysis: Electrolyte Same temperature as 1st stage Same voltage as 1st stage 3V Time 5 minutes electrolysis method Constant voltage electrolysis Then, After thoroughly washing the support having the anodic oxide film and drying it naturally, on the support,
Approximately 20μm thick made of a-Si by glow discharge method
A photoconductive layer was formed thereon, and the sample was naturally cooled to room temperature to obtain sample No. 1 of the electrophotographic photoreceptor of the present invention. Example 2 Inventive sample No. 2 of a photoreceptor having an a-Si photoconductive layer on the surface was obtained in the same manner as in Example 1, except that the electrolytic treatment conditions at each stage were as follows. 1st stage electrolysis: Electrolyte 10% phosphoric acid Temperature 30℃ Voltage 20V constant voltage electrolysis time 3 minutes 2nd stage electrolysis: Electrolyte Same temperature as 1st stage Same voltage as 1st stage 10V constant voltage electrolysis time 7 minutes 3rd stage electrolysis: Electrolyte Same temperature as the 1st stage Same voltage as the 1st stage 5V constant voltage electrolysis time 5 minutes Example 3 The electrolytic treatment conditions for each stage were as follows. Sample No. 3 of the present invention, a photoreceptor having an a-Si photoconductive layer on the surface, was obtained in the same manner as in Example 1. 1st stage electrolysis: Electrolyte 2% oxalic acid Temperature 35℃ Voltage 20V constant voltage electrolysis time 7 minutes 2nd stage electrolysis: Electrolyte Same temperature as the 1st stage Same voltage as the 1st stage 15V constant voltage electrolysis time 3 minutes 3rd stage electrolysis: Electrolyte Same temperature as the 1st stage Same voltage as the 1st stage 10V constant voltage electrolysis time 5 minutes Comparative Examples 1-2 Aluminum cylindrical conductive similar to Examples 1-3 After pretreating the support, 15
% sulfuric acid electrolyte at a temperature of 20° C. and a current density of 1.3 A/dm ² for 3 minutes. Then, an unsealed anodic oxide film (Comparative Sample No. 1) and another that had been subjected to a sealing treatment using a conventional method (Comparative Sample No. 2) were made.
Thereafter, in the same manner as in Examples 1 to 3, comparative samples of photoreceptors having an a-Si photoconductive layer on the surface were prepared.
Nos. 1 and 2 were obtained. For each of the present invention samples No. 1 to 3 and comparative example samples No. 1 to 2 of the above examples, the thickness of the barrier layer and porous layer of the anodic oxide film was measured, and the adhesion of the photoconductive layer was measured. was evaluated. Furthermore, these photoreceptor samples were subjected to corona voltage in the dark.
Charge with 5.5KV, then 10 minutes with a halogen lamp.
The residual potential after χ·s exposure was measured. These results are shown in the table below.

[Table] From the results shown in the above table, the photoreceptor manufactured using the surface treatment method according to the present invention has a particularly good effect of reducing the residual potential after exposure while maintaining good adhesion of the photoconductive layer. It was something to gain.

[Brief explanation of drawings]

The drawing is a schematic diagram showing the structure of the interface between the support and the photoconductive layer of a photoreceptor produced by subjecting it to the surface treatment of the present invention. 1... Conductive support, 2... Anodic oxide film, 2a...
Barrier layer, 2b... Porous layer, 3... Photoconductive layer.

Claims (1)

[Claims] 1. When forming an anodic oxide film as a surface treatment interface layer for closely covering a photoconductive layer on the surface of a conductive support made of aluminum, anodizing treatment for forming the film is sequentially performed at a later stage. The electrolytic treatment is carried out in substantially multiple stages in a stepwise or continuous manner by applying a relatively low anodizing voltage as the process progresses, and the first stage of electrolysis is performed at a voltage of 10 V or higher. and the last nth
The thickness of the barrier layer under the surface porous layer in the anodic oxide film is controlled to be 100 Å or less, assuming that the stage electrolysis is performed by applying a voltage of 10 V or less, which is relatively lower than the first stage electrolysis voltage. A method for treating a surface of a photoreceptor for electrophotography, characterized in that: