JPS59160148A - Manufacture of photoconductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To enhance crystallinity of cadmium sulfide and uiforty of the particles by burning a mixture of cadmium sulfide and a flux at a specified temp. and treating the surface of the obtanined cadmium sulfide with sulfuric acid specified in concn. CONSTITUTION:A mixture of CdS and >=20wt% flux is burned at temp. >=50 deg.C higher than the m.p. of the flux, such as 500 deg.C. After the burning, its surface is treated with 0.5-5.0 N sulfuric acid. The CdS thus obtained is high in crystallinity, it is found to consist of nonagglomerated single particles to each other and to have smooth surfaces by shape observation with a scanning type electron microscope. Since the particles are uniform in shape and size, the face of the coated photoconductive layer is dense and smooth, and an image good in quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing photoconductive cadmium sulfide, particularly for producing highly crystalline and uniform 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 adding an activator to cadmium sulfide particles to form CuCl2. Also CdC/2 as a fluxing agent such as CuSO4.

It is generally manufactured by doping Cu, C11, etc. into cadmium sulfide by mixing a halide such as ZnCl2 and firing. However, in such conventional methods, Cd8 produced through the firing process
has a large number of defects near the surface of Cd8 during precipitate formation.

Since this surface defect becomes a trap level for photocarriers, it increases the original memory of Cd8, that is, the electrostatic contrast between the bright and dark areas in P becomes insufficient.

In addition, the particle shape of Cd8 produced by the method described above consists of secondary particles, which are strong aggregates formed by particles aggregating together, and these secondary particles aggregate six-dimensionally. They vary in size, such as in the form of nodules, or in the form of two-dimensional plates, and some of them are large, ranging in size from more than 10 microns to several tens of microns.

A photoreceptor made using CdS containing a large number of such coarse particles has a poor surface condition, resulting in images that are extremely rough and have insufficient resolution. Furthermore, in the case of a photoreceptor further provided with an insulating layer, the insulating layer may seep into the CdS layer, making it difficult to obtain a good photoreceptor.

The above-mentioned drawbacks have been overcome by the method described in Japanese Patent Application Laid-Open No. 57-129825.

Therefore, an object of the present invention is to provide a method for producing CdS that is an improvement on the above-mentioned method. In other words, it is possible to manufacture high-resistance CdS with a small optical memory and a sufficient dark potential, and the bulk of the manufactured CdS (md/g
: JIS K-5101) increases, so the porosity can be increased when used as a photoconductive layer, and as a result, the capacitance of the photoconductive layer decreases and the charged potential can be high.
It is an object of the present invention to provide a manufacturing method capable of manufacturing CdS, which can produce CdS No. 8, and furthermore, can shorten the cleaning process time during the CdS cleaning process due to the high sedimentation rate of CdS particles.

The method of the present invention involves mixing 20 wt% or more of a flux with CdS, firing at a temperature 50°C or more higher than the melting point of the flux, and then surface-treating the mixture in 0.5 to 5.0% sulfuric acid. It is characterized by:

CdS produced by the present invention has high crystallinity, and
Observation of the shape using a scanning electron microscope shows that the particles are single particles that do not aggregate with each other, and the surface is smooth.

Since the CdS particles obtained by the present invention have a uniform particle shape and a uniform particle size, the coated surface of the photoconductive layer created is dense and smooth, resulting in a very high quality image. reactor.

In the present invention, the concentration of sulfuric acid used for surface treatment of CdS after firing is 0.5 to 5. ON is effective, and this effect is correlated with processing time. That is, at low concentrations, long-term treatment is required, whereas at high concentrations, effects can be achieved in a relatively short time. However, if the pressure is less than 0.5N, even if the treatment is carried out for a long time, the effect will be small and manufacturing efficiency will be poor. Further, processing at a concentration of 5N or more is inappropriate because it tends to reduce sensitivity.

In addition, copper can be added in advance to a cadmium salt aqueous solution and co-precipitated to be included in CdS, or before firing,
It can also be included in CdS by mixing it with CdS and then firing it. As the copper compound added to CdS, copper chloride, sulfide, sulfide, etc. are used, and copper chloride and copper sulfate are particularly preferred.

The copper compound can be added before firing by adding and mixing the copper compound as a solid, or if the copper compound is water-soluble, it can be made into an aqueous solution and added to CdS, and then the water can be evaporated. Although good results can also be obtained using the wet method, the wet method is better in terms of uniformity.

The fluxing agent used in the present invention is a fluxing agent that is generally used when diffusing an activator into CdS.
nCl2 + KCl+ NaCl+ NH4C1)
+ caso4 etc. or V types are mixed in an appropriate ratio. A suitable example of a mixture of CdCl2 and an alkali metal chloride is a mixture of CdCl2 and an alkali metal chloride.As an alkali metal chloride, NaC
6 and KCI are representative ones. The content of alkali metal chloride in the entire flux is 90 molti or less and 10
More than molty is suitable.

In the present invention, the amount of the flux is preferably 20% or more, particularly preferably 30 to 50%. Below 20 inches,
The produced Cd8 particles are sintered to become coarse particles, and have a non-uniform surface shape, resulting in poor Cd8 with insufficient potential retention and poor resolution. In addition, when calcination is performed at a temperature 50°C higher than the melting point of the flux, the particle size of the produced Cd8$Q particles is large;
Poor resolution and coating properties.

In addition, in the manufacturing method of the present invention, the firing temperature is 600
°C or less is suitable. Further, the amount of fluxing agent added to CdS is preferably 65% or less from the viewpoint of yield.

(Example 1) The temperature of a monosulfuric acid aqueous solution 21 containing 1 mol of cadmium sulfate and 3×10 mol of copper sulfate was maintained at 60° C., and hydrogen sulfide was passed through the solution at a flow rate of 300 cc/r11in for 95 minutes.

The cadmium sulfide produced in this reaction was washed with pure water to remove excessive impurities present on the particle surface, and then dried overnight at a temperature of 100'C. For 100g of this cadmium sulfide, add 20g of CdCd2 and 3g of NaC1.
Add 0g, mix well, and fill in a quartz crucible.
Calcined at 500℃ for 30 minutes (note that CdCl2 and NaC
From the phase diagram, the melting point of the mixed flux No. 1 is CdCl2 ・2N
aC1 melting point of 426°C).

The CdS thus obtained was placed in a 4N sulfuric acid aqueous solution and left to stand for 3 hours while stirring. Thereafter, the particles were washed with pure water to remove the sulfuric acid, but the sedimentation rate of the particles was extremely fast and the washing was completed in a short time. This is 70℃
It was dried.

This Cd8 was dispersed in a vinyl chloride/vinyl acetate copolymer, and then coated on an aluminum substrate to a thickness of 4 μm and dried. A 15 μm thick polyester film was attached to the resulting photosensitive plate to obtain a three-layered photoreceptor. The surface was very smooth. When this photosensitive plate was subjected to a high-speed electrophotographic process of primary charging, photoimage exposure, AC static elimination, and then full-surface exposure, a high-quality image with an electrostatic contrast of 650 V and sufficient sensitivity was obtained. Especially the resolution is 6
i or more, and a sharp image was obtained. Furthermore, this photosensitive plate was heated at a high temperature of 35°C and a humidity of 85% for 24 hours.
After leaving it for a while, the image was produced again using a copying machine. As a result, no decrease in contrast between bright and dark areas was observed, and a good quality image was obtained.

(Example 2) Cadmium sulfide was precipitated from a 6N sulfuric acid aqueous solution containing 1 moe of cadmium sulfate in the same manner as in Example 1. Copper was added to 100 g of this cadmium sulfide in the form of 4×10 mol copper sulfate per 1 mol of cadmium sulfide,
After uniform mixing using a wet method, the mixture was dried at 100°C. CdC7
A mixed flux consisting of 1.240 g of NaC and 110 g of NaC was mixed, and after thorough mixing, it was fired at 530° C. for 60 minutes.

The cadmium sulfide thus prepared was added to a 1N sulfuric acid aqueous solution and left to stand for 8 hours while stirring.

After washing with water, passing through two mouths, and drying, the obtained CdS was made into a photoreceptor and evaluated in the same manner as in Example 1, and the same good results as in Example 1 were obtained.

Comparative Example 1 A photoreceptor was produced in the same manner as in Example 1 using cadmium sulfide particles produced in exactly the same manner as in Example 1 except for the sulfuric acid treatment.

Comparative Example 2 A photoreceptor was manufactured in the same manner as in Example 2 using cadmium sulfide particles manufactured in exactly the same manner as in Example 2 except for the sulfuric acid treatment.

Regarding the photoreceptors manufactured in the above Examples and Comparative Examples, the first
The characteristics of the photoreceptor were measured using the measuring device shown in the figure.

That is, a glass plate 6 having a transparent electrode 4 was pressed against the insulating layer surface of the photoreceptor 9. The transparent electrode 4 is connected to a high voltage DC power supply B via a relay switch 5.

The measurement beam meter 5 is closed for 0.2 seconds and the high voltage (V
a) was applied, left for 0.2 seconds (open), and then light was irradiated for 0.2 seconds, and the voltage change (Vp) at that time was measured using the metal plate 7 and the surface electrometer 8, which were at the same voltage as the photoreceptor. still,
Vp is the voltage applied to the photoconductive layer.

Further, as a pre-exposure, white light from the halogen lamp 1 is irradiated for 0.2 seconds by the shutter 2, and after being left for 0.2 seconds, ■a is applied, and after being left for 0.2 SeC, the light is irradiated again for 0.2 seconds.
Irradiated for 2 seconds and measured the voltage change ■p' when va mini-2000V vp and ■p'
Further, the value of Vp is measured when Va is set to +2000 V, and the size of the original memory can be determined from ■p−■p' when Va mini-2000 is applied.

Next, the sensitivity of the photoreceptor was measured.

That is, the glass plate 6 having the transparent electrode 4 was pressed against the insulating layer surface of the photoreceptor 9. The transparent electrode 4 is connected to a high voltage DC power source 6 via a relay switch 5.

The measurement was performed by irradiating white light from a halogen lamp 1 for 3.2 seconds with the shutter 2 as a pre-exposure, leaving it for 0.2 seconds, then closing the relay switch 5 for 0.2 seconds and applying a high voltage (
Va) is applied to the photoconductor, left for 0.2 seconds, and then irradiated with sufficiently strong light for 0.2 seconds, the voltage (Va') on the photoconductor surface (i.e., the surface of the insulating layer) is set to the same voltage as the photoconductor. It was measured using a certain metal plate 7 and a surface potential meter 8. The voltage (Vp) applied to the photoconductive layer when applying a high voltage can be calculated by Va - Va', so Va (hereinafter Va
-600) and measured the sensitivity using the following method. That is, after irradiating measurement light (520 nm) with Va-600 applied to the photoreceptor and leaving it for 0.2 seconds after light irradiation,
Irradiate a sufficiently strong source for 0.2 seconds in the same manner as above and measure the voltage (Va'') on the surface of the photoreceptor in the same manner as above.
The voltage applied to the conductive layer (Vp") is Va-600-Va"
Since it can be calculated as follows, the amount of exposure (0) of the measurement light necessary for f to be 6oo'y is the half-reduction source i amount (El/2), and the confusing sensitivity of the t-body can be displayed.

Their characteristics are listed in the table below.

In the above table, the difference in vp Vp' is smaller in the example than in the comparative example. This shows that the influence of pre-exposure is smaller, in other words, the speed of light attenuation is faster in the photosensitive plate of the example.

Therefore, for those treated with sulfuric acid, ■p' becomes larger, and the original memory becomes even smaller.
Compared to the comparative example, the resistance is higher and the potential is higher. On the other hand, the sensitivity was the same as that of the comparative example, and there was no decrease in sensitivity despite the increased resistance.

In addition, the cadmium sulfide particles manufactured in the comparative example were
In this case, the sedimentation rate of particles in the water washing step after firing was slow and not efficient.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an apparatus for measuring the sensitivity of a photoreceptor.

Claims (1)

[Claims] 1. Mix cadmium sulfide with 20% by weight or more of a fluxing agent and sinter at a temperature 50°C or more higher than the melting point of the fluxing agent, then surface treat the resulting cadmium sulfide with 0.5-5N sulfuric acid. A method for producing photoconductive cadmium sulfide.