JPS58211158A - Electrophotographic receptor - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic receptor good in repetition fatigue characteristics, by vapor-depositing a selenium material having width of peak temps. of exothermic reaction measured by differential thermal analysis in a specified range on a substrate to form a photosensitive layer. CONSTITUTION:The selenium material, such as selenium or its alloy, such as selenium and tellurium alloy is analyzed by the differential thermal analysis, and the material is selected having temp. width measured of the peaks (temp. difference between the initial peak temp. and the end peak temp.) of exothermic reaction within the range of 8-30 deg.C. The selected material is vapor-deposited onto the substrate of aluminum or the like to obtain the intended electrophotographic receptor low in fatigue. The differential thermal analysis is conducted in the following conditions: alpha-Al2O3 as the standard sample, chromel-alumel as the thermocouple are used, and + or -250muV differential heat, and 10 deg.C/min temp. rising speed are adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor having a photosensitive layer made of selenium material.

Such electrophotographic photoreceptors used in electrostatic copying machines, printers, etc. are manufactured by placing a container containing granular selenium in a vacuum chamber, dissolving and evaporating the granular selenium, and then molding it into an aluminum tube, for example. This type of photoreceptor is manufactured by forming a photosensitive layer by vapor deposition on a conductive substrate. However, this type of photoreceptor suffers from a decrease in charging and an increase in residual potential, even if the photosensitive layer is deposited under the same deposition conditions. The phenomenon of repeated fatigue, especially an increase in the residual potential, occurs, and when actually used in a copying machine, the white background turns black and the black-white contrast decreases.In order to obtain a photoreceptor with good repeated fatigue characteristics, selenium is used. Other elements or oxides are added.According to Japanese Patent Application Laid-open No. 139737/1984, exothermic reaction measured by differential thermal analysis is used as a criterion for selecting photosensitive layer materials for the repeated fatigue characteristics of photoreceptors. It is said that a selenium material whose peak temperature is in a temperature range of 150° C. or higher is desirable.

Another object of the present invention is to provide a photoreceptor with good repeated fatigue characteristics using another selection criterion.

This object is achieved by forming the photosensitive layer by depositing a material whose exothermic reaction peak temperature range, as measured by differential thermal analysis, is in the range of 8 DEG to 30 DEG C.

The effects of the present invention could be understood from the test examples described below. Multiple lots of alloys containing approximately 5.5% tellurium were prepared as raw material selenium alloys, and differential thermal analysis was performed on samples taken from each lot. Differential thermal analysis uses α as a standard sample.
- AI, 0. , using chromel alumel as a thermocouple,
The test was carried out under the conditions of differential heat ±250 μV1 and temperature increase rate of 10° C./min. The measuring device is Rigaku Denki DTA-M800.
5 was used. As a result, it was found that although the compositions were almost the same, the width of the exothermic peak (the temperature difference between the initial temperature and the final temperature of the peak) differed depending on the lot. Next, these raw materials were deposited on an aluminum substrate kept at a temperature of 55 to 65°C at a deposition rate of 1 μm/min for about 60 min.
It was deposited to a thickness of μm. For these samples, the charging potential, sensitivity, and residual potential after 300 repetitions were measured.

The results are shown in Table 1.

Table 1 As is clear from Table 1, the peak width of the exothermic reaction was 8°C.
Below 30℃, the residual potential due to repeated fatigue is large.
Above this, the charging potential decreases. Therefore, the peak width is 8 to 30
It is desirable to deposit with an alloy in the range of .degree.

It was confirmed that the width of the exothermic peak of the Se/Te alloy in the photosensitive layer produced in that case was in the range of 8 to 30°C. Note that when the peak width exceeds 30°C, the darkening table also increases.

The photosensitive layer consists of a carrier generation layer (OGL) and a carrier movement layer (
In a functionally separated laminated photosensitive layer consisting of OTL, the charging potential and residual potential are affected by OTL.
According to the present invention, it is effective to use a selenium alloy having an exothermic peak width in the range of 8 to 30° C. for OTL vapor deposition. A 55 μm deposited film was formed on a cylindrical aluminum substrate using <5.5% Te/Se alloy according to the present invention as OTL, and 22.5% Te/S was deposited on top of it as OGL.
A selenium alloy photoreceptor on which an e-alloy vapor deposited layer is formed has good repeated fatigue characteristics, and other xerographic characteristics are comparable to conventional ones, making it suitable for a large number of copies and prints.

When using selenium or a selenium alloy that has a wide exothermic peak width in the range of 8 to 30°C in differential thermal analysis, why does it have good repeated fatigue characteristics as a photoreceptor for electrophotography? I don't know the details about that. As a physical phenomenon, the exothermic peak is a crystallization process. A possible reason for the widening of the crystallization temperature range is that the amount of impurities or the types of impurities are large. Further, it is thought that there are many types of molecular structures such as Se8 link, Se6 link, long chain, short chain, etc. However, the relationship between these and photoreceptor characteristics is not clear. .

As described above, the present invention provides a low-fatigue electrophotographic photoreceptor by depositing selenium or selenium material whose exothermic peak width in differential thermal analysis is in the range of 8 to 30°C on a substrate such as aluminum. The effect obtained as an excellent evaluation method for photosensitive layer materials is extremely large.

Claims (1)

[Claims] 1) An electrophotographic photoreceptor characterized in that the photosensitive layer is formed by vapor-depositing a selenium material whose peak temperature range of exothermic reaction measured by differential thermal analysis is in the range of 8 to 30°C.