JPS60127230A - Preparation of photo-conductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To prepare uniform particles of photo-conductive CdS having improved durability, by blending CdS containing a proper amount of Cu with a suitable amount of flux, calcining it at a temperature higher than the melting point of the flux, heat-treating it again at a temperature corresponding to the amount of Cu added. CONSTITUTION:CdS mixed with Cu during formation of CdS precipitate is blended with >=20wt% flux, and calcined at a temperature >=50 deg.C higher than the melting point of the flux. A mixture of CdCl2 and NaCl having 10-90mol% NaCl is preferably used as the flux used. The flux is removed from the prepared calcined material by washing, the material is heat-treated again at a temperature range satisfying an inequality shown by the formula -250/8A+ 250<T<-200/3A+600 wherein reheating temperature is T, and an amount of Cu added is AX10<-4>mol based on 1mol CdS (with the proviso that A>=4X 10<-4>mol, and T>=50 deg.C), to give photoconductive CdS consisting of uniform and simple particles having high crystallizability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing photoconductive cadmium sulfide, and particularly to a method for producing highly durable, highly crystalline, uniform, and single particles.

The most common method for producing photoconductive cadmium sulfide (CdS), which is typically used in electrophotographic materials, is to react hydrogen sulfide with water-soluble salts of cadmium, such as cadmium sulfate or cadmium chloride, to produce cadmium sulfide. The cadmium sulfide particles are precipitated and then calcined at a high temperature to dope the cadmium sulfide particles with an activator. That is, photoconductive cadmium sulfide is produced by mixing cadmium sulfide particles with a small amount of a halide such as CuC42, CuSO4, etc. as an activator, and a small amount of a halide such as ZnC12 as a fluxing agent, and then firing the mixture. It is generally manufactured by doping cadmium.

However, the photoconductive cadmium sulfide particles obtained by such conventional methods are composed of secondary particles that are strong aggregates formed by aggregating each other, and these secondary particles are three-dimensional. They may gather together in a lump-like shape, or 2
There are various types of particles that are dimensionally aggregated and shaped like a flat plate, and some of them are large in size, ranging from 10-odd microns to 100 microns.

A photoreceptor made using CdS containing a large number of such coarse particles has a poor surface condition1, resulting in images that are extremely rough and have insufficient resolution.

Furthermore, in the case of a photoconductor further provided with an insulating layer, the insulating layer may seep into the CdS layer, making it difficult to obtain a good photoconductor.

The above drawbacks have been overcome by a method as described in Japanese Patent Laid-Open No. 57-129825.

However, when greater durability is required than ever before, such as when used in high-speed copying machines, cadmium sulfide with a small amount of copper cannot meet that requirement.

The present invention has particularly improved durability in order to meet such requirements, and since the obtained CdS particles are almost uniformly formed into single particles, the following additional effects also appear.

1. Excellent coating properties during photoreceptor production and high quality images can be obtained.

2. Not easily affected by humidity and temperature.

3. It has very high crystallinity and has few surface defects that become trap levels for photocarriers.

In general, CdS for electrophotography is doped with donor and acceptor impurities, and its properties are controlled by the balance between them. However, there are defect-based donors on the CdS particle surface. CdS produced by the sintering method used in the present invention utilizes its surface defects, and there is no need to add donor impurities. In this system, the amount of copper added and the reheating treatment compensate for the amount of surface defects present on the surface and maintain an acceptor/donor balance. A simple way to improve durability is to increase the amount of copper added, but this does not simultaneously increase the accessor concentration, and in order to obtain the properties used for electrophotography, it is necessary to increase the particle surface. Donor amount must be increased. In general, the amount of compensation for surface defects that act as donors varies depending on the reheating temperature.
In order to balance the acceptors, it is necessary to lower the reheat temperature.

As a result of numerous experiments, the present inventor has found that the shaded area in FIG. 1 has an appropriate combination of reheating temperature and amount of copper added. That is, in a method for manufacturing photoconductive CdS that includes a step of mixing 20% or more flux with CdS, firing at a temperature 50°C higher than the melting point of the flux, and then heat-treating again, the reheating temperature is set to T1. The amount of copper added is A per 1 mole of CdS
When it is 10-' mole, -'p A + 600
It was confirmed that the region defined by the inequality (where A≧4×10″−′, T≧50° C.) is an appropriate region.

A is 4 X to achieve the purpose of improving durability.
10-' mole or more is required; if it is more than 10XIO-' mole, the acceptor on the surface becomes excessive and an appropriate area cannot be obtained by reheating treatment or the like.

On the other hand, the reheating temperature is determined by the amount of copper added, but if it is too low, the heating effect will not appear.
A temperature of 0°C or higher is required.

As a specific method of the present invention, a firing step is required before the reheating treatment (5). In this step, a flux of 20% by weight or more is added to CdS and mixed uniformly, and then fired at a temperature 50° C. or more higher than the melting point of the flux. The flux used is a flux commonly used when diffusing an activator into CdS, and CdC62°ZnCA2. KCl,
It is a mixture of one or more of NaCl, NH2Cl, CdSO4, etc. in an appropriate ratio.

A preferred example of a mixture of CdC22 and an alkali metal chloride is a mixture of CdC22 and an alkali metal chloride. Typical alkali metal chlorides are NaCt and KCl. The content of the alkali metal chloride in the entire flux is preferably 90 molti or less and 10 molti or more.

The appropriate range of the above-mentioned reheating treatment in the present invention is defined as a range in which the objective of the invention can be achieved as a result of numerous implementations, assuming the above-mentioned CdS production conditions.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 When CdS precipitate is formed, the molar ratio of copper is already 6.0 x 1
Cdct
2 to 20? and NaC1f 30 y- were added, mixed well, and then mixed with quartz rutz? (The melting point of the mixed flux of CdC62 and NaC1 corresponds to the melting point of CdC42.2NaC4 at 426°C from the phase diagram).

This was washed for the purpose of mainly removing the flux, and then heated again at 150° C. for 60 minutes.

The CdS obtained in this way has a major orientation of 1 oon, and according to an electron micrograph at a magnification of 10,000 times, the particle surface is extremely smooth and has a unique hexagonal crystal shape, with each particle having a
A single particle with a diameter of 5μ was observed.

This CdS i was dispersed in vinyl chloride/vinyl acetate copolymer, then coated on an aluminum substrate to a thickness of 40 μm and dried. A 15 μm thick polyester film was attached to the resulting photosensitive plate to obtain a three-layered photoreceptor. When obtained, the surface was extremely smooth. When this photosensitive plate was subjected to a high-speed electrophotographic process of primary charging, image exposure, AC static elimination, and then full-surface exposure, high-quality images with sufficient electrostatic contrast and sufficient sensitivity were obtained. Especially the resolution is 6/
-S or more, sharp and sharp images were obtained. Furthermore, this photosensitive plate was placed in a high temperature and high humidity environment of 35°C and 85°C for 2 hours.
After leaving it for 4 hours, the image was produced again using a copying machine. As a result, no decrease in contrast between bright and dark areas nor decrease in sensitivity was observed, and a good quality image was obtained. Furthermore, when this photoreceptor was left in a copying machine for 12 hours, the dark potential was measured.
The first piece is 500v150th piece is 510■ and the difference is IO
It was V. Further, the change in potential contrast measured at 5°C and 50°C was as small as 10V. As a result, it was confirmed that the photoreceptor of this example had excellent electrophotographic properties.

Table 1 Copper Reheating Temperature Example 2 4.0 (Kari O-4 Mol Breast 5-ax) 250
℃Example 3 8.0 60℃Examples 2 and 3 When the same manufacturing method as Example 1 was used, only the amount of added steel and the reheating temperature were changed as shown in Table 1, the particle shape was the same as in Example 1, As for coating properties and electrophotographic properties, good properties comparable to those of Example 1 were obtained.

Next, if these photosensitive plates are subjected to the basic process of positive charging, AC static neutralization simultaneous exposure, and full-surface exposure, each photosensitive plate will cost 20,000 yen with a copying machine.
When we conducted a 0-time durability test and measured the potential retention rate after durability, we obtained the results shown in the table.
The retention rate was higher than that of the comparative example in which the molar reheating temperature was 450°C, demonstrating the effect of the present invention.

All of the samples whose electrophotographic spectral sensitivities were measured in the above Examples were made into photosensitive plates in the same manner as in Example 1.

(9) Measurements were carried out as follows using the measuring device shown in FIG. That is, the transparent electrode 2 was pressed against the insulating layer surface of the photoreceptor 1.

Transparent electrode 2 is connected to high voltage power supply 9 via relay switch 81. The measurement was performed by irradiating white light from the light source 41 for 0.2 seconds with the shutter 51 as pre-exposure.
After leaving it for a while, the relay switch 81 was closed by 0.2 saa, a high voltage was applied so that the voltage V applied to the photoconductive layer was 600 V, and after 0.2 gee oven, the light was turned off by 0.2 saa.
AEC was irradiated, and the voltage change V at that time was measured using a metal plate 10 at the same voltage as the photoreceptor and a surface electrometer 11. Sensitivity is determined by applying light from the light source 42 to the shutter 52 through the filter 62 at the same time as voltage application, changing the exposure amount, measuring the change in Vp, drawing an EV curve, and calculating the half-reduced exposure amount from this curve. I got it. Furthermore, by changing the filter 62, the half-reduced exposure amount at each wavelength was determined, and the spectral sensitivity was measured.

FIG. 3 summarizes the measurement results of Examples 1 to 3.

As described above, the spectrum of the sandals obtained with each combination varies and can be extended to the longer wavelength side by increasing the reed and copper content and reheating under the conditions of the present invention.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the range of reheating temperature and copper content in the present invention, and FIG. 2 is a schematic diagram of the overall configuration of a measuring device used to measure the spectrum of cadmium sulfide obtained according to an example of the present invention. FIG. 3 is a graph showing the spectrum measurement results of the example. 1...Photoconductor 2...Transparent electrode 3...Earth plate 41.42...Light source for exposure 51.52...Shutter 61.62...Filter 7...Reflector 9. ...High voltage power supply 10...Metal plate for potential detection 11...Surface electrometer (
11) Figure 1

Claims (1)

[Scope of Claims] 1. Photoconductive sulfide comprising the step of mixing 20 wt% or more of a flux with respect to cadmium sulfide, firing at a temperature 50°C or more higher than the melting point of the flux, and then heat-treating again. In the cadmium manufacturing method, when the reheating treatment temperature is T1 and the amount of copper added is 9AX10 moles per mole of cadmium sulfide, (A≧4×10 moles, T≧50°C) Ippei A+250<T< 1. A method for producing photoconductive cadmium sulfide, comprising reheating in a temperature range that satisfies the inequality -1,000A+600.