JPS60102641A - Vapor deposited selenium film improved in electrophotographic characteristics and its manufacture - Google Patents

Abstract

PURPOSE:To enhance dark resistance characteristics of a photosensitive body made of Se by lowering the content of C in the Se source so as to reduce said content in the deposited film to a specified value or less in the vapor deposition process. CONSTITUTION:The Cl content in a Se deposited film can be lowered by using the source of Se reduced in said content in the vapor deposition process. As the method for reducing the Cl content in the Se source, the vacuum evaporation of Se under high vacuum, reduced pressure distillation of Se in an atm. of high- purity H2, sufficient washing of Se with pure water after production of Se reduced with SO2, etc. are used. As a result, deterioration of dark resistance characteristics of the Se photosensitive body can be prevented by lowering the Cl content of the Se vapor deposited film to <=3ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a selenium vapor-deposited film for electrophotographic photoreceptors and a method for producing the same, and in particular is characterized in that the chlorine content in the pure selenium vapor-deposited film is reduced to 3 ppm or less. It is something.

Electrophotography is a photographic method that utilizes the photoconductivity of substances and electrostatic phenomena, and several methods have been established.Among them, one method uses a selenium vapor-deposited film as an electrophotographic photoreceptor and obtains an electrophotograph by transfer. is called the Xerox method.

The Xerox method consists of the following steps: (Al charging: The surface of a photosensitive plate on which amorphous selenium with high dark resistance is deposited on a metal substrate is charged.

(BL exposure (printing): When exposed with a light image, the electrical resistance of selenium in the irradiated area decreases, the surface charge escapes to the metal substrate, and the residual charge density on the photosensitive plate changes depending on the amount of exposure. A difference occurs, and an electrostatic latent image with the same shape as the original image is formed on the selenium surface.

(C) Development: By sprinkling the surface of the photosensitive plate with a mixed powder of a toner made of fine carbon powder coated with a resin and a carrier consisting of glass beads, the toner adheres to the latent image area, and the latent image becomes a visible image.

fdl transfer: When a sheet of paper is evenly placed on the surface of the photosensitive plate after development and a corona discharge is caused from the back side, the toner on the photosensitive plate is attracted to the paper and the toner powder image is transferred to the paper.

tel fixing: After the transfer is completed, the paper is peeled off and heated with an infrared heater to fuse the toner resin to the paper.

By carrying out each of the above steps, a copied image (electrophotography) of the original image is obtained, but the sharpness of the copied image or the reproducibility with respect to the original image largely depends on the performance of the selenium photoreceptor. To judge the performance of a photoreceptor, (a) corona charging characteristics that represent the amount of charge given by corona discharge with a constant output, and (b) the amount of charge lost while the photoreceptor charged by corona discharge is kept in a dark place. Dark decay characteristic related to charge amount, P→
The charge voltage exposure attenuation characteristic, which shows the speed at which the amount of charge held in the dark disappears due to exposure to light, and the residual potential, which shows the potential that remains without disappearing to zero after exposing the photoreceptor to light, are taken into consideration. However, if the dark decay of the potential is large, it becomes impossible to use it as a photoreceptor, so it is one of the characteristics that needs to be improved.

When selenium is used as a photoreceptor for copying machines, even the presence of a very small amount of certain impurities can significantly affect its properties. - For example, if the Fe content exceeds 2 ppm,
F
It has been reported that the e content should be 2m)pm or less (Japanese Patent Application Laid-open No. 5F-67752).

By the way, it is well-established that adding halogens (chlorine, bromine, iodine) is effective as a measure to improve the electrophotographic properties of selenium, and several documents and patent publications state that addition of halogens to selenium-based alloys is effective. - It has been reported that adding rogens is effective in improving properties. (
For example, JP 57-53753.55-124569
．． 56-149046 and many others).

However, these studies did not investigate the effects of trace amounts of chlorine on pure selenium, and as a result of the inventors' investigation into the effects of chlorine on pure selenium, they found that it contains chlorine, contrary to the conventional wisdom. It was found that selenium significantly deteriorates the properties, especially the dark decay properties. This was completely unexpected, contrary to the general concept in the field that the addition of halogen was believed to be effective in improving the electrophotographic properties of selenium.

The present invention is based on this unexpected discovery, and aims to improve the electrophotographic properties of selenium by reducing the chlorine content in selenium as much as possible. As a result of detailed experimental studies by the inventors, the chlorine content in selenium was 5 ppm.
I found out what to do below. The dark decay characteristic of the selenium deposited film increases as the amount of chlorine added increases, and when the amount exceeds 3 ppm, the surface potential decays by more than 20 min.

Thus, the present invention provides a selenium deposited film for electrophotographic photoreceptors having a chlorine content of 3 ppm or less. Furthermore, when producing a selenium vapor deposited film for an electrophotographic photoreceptor, the chlorine content in the raw material selenium is reduced to 3 ppm or less, and the raw material selenium is vacuum vapor deposited. The present invention also provides a method for producing a selenium vapor deposited film for an electrophotographic photoreceptor, which has unique characteristics.

The present invention will be specifically explained below.

As mentioned above, it is generally believed that the residual potential can be reduced by adding chlorine and the characteristics can be improved. Experimental results in which chlorine was added using sulfur (0,21)I)m, chlorine (0,04 ppm, bromine <o, oo6 ppm, and iodine (0,02 ppm) below the lower limit showed that the characteristics deteriorated as described above. It turned out to be happening.

The attached graph shows the relationship between the amount of chlorine added and the surface potential after 2 seconds, using the experimental process shown later in the experimental example. As is clear from the graph, considering the dark decay characteristics of the surface potential after 2 seconds, (1) the chlorine content is 0. lpp
(2) If the chlorine content is 0.1 to 3 ppm, the potential will attenuate by about 20% or less, and (3) If the chlorine content exceeds 3 ppm, the potential will decrease. It can be seen that the dark decay of is significant. If the dark decay of the potential is large, it becomes impossible to use a photoconductor for a normal copying machine, so chlorine-containing go
It is very important for selenium photoreceptors to reduce the content to ppm or less.

Reduction of the chlorine content in the selenium vapor-deposited film is achieved by performing vacuum evaporation using raw material selenium with reduced selenium content. Vacuum distillation of selenium under (2)
Methods such as distillation under reduced pressure in a volume of high-purity water and (3) thorough washing of selenium with pure water after producing SO2-reduced selenium are effective. The conditions for vacuum-depositing the vapor-deposited selenium film are not particularly limited, and commonly used conditions are sufficient.

For example, a metal such as aluminum or steel, or a material such as metallized paper or plastic is used as the substrate that supports the selenium-deposited film.

In addition, the evaporation source temperature is 250°C to 350°C, the substrate temperature is 55°C to 70°C, and the degree of vacuum is IG-”Torr to 1O-6.
Torr, vapor deposition time is from 60 minutes to 130 minutes, and the experiment is carried out by selecting appropriate conditions.Experimental ExampleIn order to clarify the influence of chlorine on the electrophotographic properties of selenium, purified selenium as shown in the table below was used. SeCla for high purity selenium
A certain amount of was added and vacuum sealed in an ampoule for doping, and the characteristics were evaluated.

The above mixture was deposited onto a 55a x 55mm mirror finished aluminum substrate by resistance heating.

The deposition conditions are as follows.

The thickness of the selenium vapor deposited film formed on the aluminum substrate under the following conditions: evaporation source temperature: 270° C., substrate temperature: 60° C., vacuum degree: 2×10′[”orr, evaporation time: 60 minutes or more] was 50 μm.

The photoelectric properties (surface potential) of the selenium vapor-deposited film thus obtained were examined using an electrostatic tester under the following conditions.

The attached graph shows the measurement results of a corona discharge voltage of 5 KV, a dark decay time of 2 seconds, a static elimination illuminance of 20,000 lux, and a repetition rate of 5θ times or more for 2 seconds.

As mentioned above, it can be seen that when the amount of chlorine added exceeds 3 ppm, the surface potential decreases by more than 20X after 2 seconds.

As explained above, according to the present invention, contrary to the conventional wisdom, the dark decay characteristics are particularly improved by reducing the chlorine content in the selenium-deposited film. Reducing the chlorine content is also advantageous in that it leads to stabilization of the general properties of selenium as a photoreceptor, since if chlorine is added, traps are formed in the selenium and the properties tend to deteriorate. It is.

[Brief explanation of drawings]

The figure is a graph showing the influence of the amount of chlorine added on dark decay characteristics.

Claims (1)

[Claims] 1) A selenium vapor-deposited film for an electrophotographic photoreceptor having a chlorine content of 3 ppm or less. 2) When producing a selenium vapor-deposited film for an electrophotographic photoreceptor, the chlorine content in the raw material selenium is reduced to 3 ppm or less, and the raw material selenium is vacuum-deposited. A method for producing a selenium vapor deposited film for an electrophotographic photoreceptor. 3) The reduction of the chlorine content in the raw material selenium can be achieved by (a) vacuum distillation of selenium under high vacuum, (b) vacuum distillation in high purity hydrogen, or (/-1so2 selenium pure water after producing the original selenium). The method according to claim 2, which is carried out by thorough washing with.