JPS59192254A - Manufacture of electrophotographic cadmium sulfide - Google Patents

Abstract

PURPOSE:To obtain CdS particles high in crystallinity, and uniform in size and composed of single particles by introducing H2S into an aq.soln. of CdSO4 and H2SO4 to precipitate CdS, adding water, again introducing H2S, then adding H2SO4, filtering CdS, adding fluxes, and calcining it. CONSTITUTION:CdS is pptd. by introducing H2S for 5min into 900cc of an aq. soln. contg. 1mol of CdSO4 and 5 N H2SO4. CdS is again pptd. by adding pure water to make about 2 liters, and again introducing H2S. H2SO4 is again added to this soln. to make 5 N, and it is allowed to stand for a night while agitation is continued. Water washing is repeated till the conductivity of its supernatant soln. reaches a prescribed value or lower, and then it is dried at 200 deg.C. CuCl2 is added to this CdS in a CuCl2/CdS molar ratio of 1X10<-4>, and fluxes of CdCl2 and NaC are added and the mixture is calcined at 530 deg.C for 60min. The CdS thus obtained has 2-4mum average particle diameter and composed of single particles and suitable for forming an electrophotographic sensitive body high in sensitivity and superior in durability and image forming performance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cadmium sulfide for electrophotography, and particularly to a method for producing cadmium sulfide particles that are extremely crystalline and uniform.

The most common method for producing photoconductive cadmium sulfide (Cd5), which is used as an electrophotographic photosensitive material, is to cause precipitation of cadmium sulfide particles by reacting hydrogen sulfide with a water-soluble salt of cadmium such as cadmium sulfate or cadmium chloride. Gain,
The cadmium sulfide particles are then fired at a high temperature in order to dope them with an activator. That is, the photoconductive cadmium sulfide is prepared by adding CuC12, CuSO4, etc. as an activator to cadmium sulfide particles, and GdCf1 as a fluxing agent.
z.

It is generally manufactured by doping Cu, I, Q, etc. into cadmium sulfide by mixing a halide such as ZnG12 and firing.

However, Cd produced by such conventional methods
The particle shape of S consists of secondary particles, which are strong aggregates formed by particles aggregating with each other, and these secondary particles may aggregate three-dimensionally to form a nodule, or two-dimensionally. They can be aggregated on a flat plate, and some of them are large, ranging in size from 10-odd microns to several tens of microns.

A photoreceptor made using CdS containing a large number of such coarse particles has a poor surface condition, and as a result, the image written is extremely rough and has 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 present invention solves the drawbacks of such conventional methods, and provides a cadmium sulfide for electrophotography that has good image resolution and excellent coating properties by uniformly and unifying cadmium sulfide particles. The main purpose is to provide a manufacturing method for.

The method for producing cadmium sulfide for electrophotography according to the present invention is to precipitate cadmium sulfide by passing hydrogen sulfide into an aqueous solution containing cadmium sulfate and sulfuric acid, and then adding water to reduce the concentration of ions and acids in the aqueous solution. The method is characterized by comprising the steps of adding sulfuric acid to the aqueous solution, and adding a flux to the cadmium sulfide separated from the aqueous solution and calcining it.

That is, in the present invention, in an aqueous solution system containing cadmium sulfate and sulfuric acid, cadmium sulfate and sulfuric acid are reacted with hydrogen sulfide in a fairly temporary state to form crystal nuclei, and then
By adding pure water or the like to reduce the concentration to an appropriate level and reacting with hydrogen sulfide, several particles with a particle size of several jL are aggregated.

After adding an appropriate amount of sulfuric acid, the mixture is agglomerated and broken into single particles by continuing stirring. Since the single particles have a smooth surface, the particle size targeted by the present invention can be obtained by firing them together with a small amount of flux.

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.

- Dissolve the distributed particles in an electrophotographic resin/inter, apply it to a support to create a photoconductive layer, and then form an insulating layer on top of it to create a photosensitive plate for high-speed copying. It is recognized that high electrostatic core trust can be obtained by applying it to a machine. In addition, since the cadmium sulfide powder obtained by the present invention has a uniform particle shape and uniform particle size, the coated surface of the photoconductive layer created is dense and smooth, resulting in very high quality images. It is something that can be done.

In order to obtain single particles in the present invention, aggregates of particles with an average particle diameter of several p are created by precipitation, and then stirred and left in an aqueous sulfuric acid solution to cause a redissolution and reprecipitation reaction to form single particles. It is something to do.

The precipitation method for obtaining aggregates consisting of several particles is Mi M
Hydrogen sulfide is applied for a short period of time in a fairly highly concentrated solution of cadmium and sulfuric acid to generate crystal nuclei. The formation of crystal nuclei is suppressed by the reaction at high concentrations. Therefore, although the particle size grows due to the subsequent reaction, the contact between the particles decreases, and the final result is an agglomeration of several particles.

The reaction time for crystal nucleation is 3 to 15 minutes, especially 5 minutes.
~10 minutes is sufficient. The temperature is preferably equal to or higher than the reaction temperature after adding water.

At the end of the crystal nucleation period, the reaction is stopped and water is added to reduce the concentration of the solution.

As a result, the degree of aggregation of the generated crystal nuclei decreases because the concentration of the generated crystal nuclei is lowered, and there are fewer opportunities for particles to come into contact with each other during subsequent reactions.

It is preferable that the amount of water added is 0.8 to 1.5 times the initial solution amount, that is, the concentration is 0.56 to 0.4. The temperature of the second reaction is preferably in the range from a temperature equal to the temperature of the initial reaction to a temperature 10' lower, but it may be specifically selected in consideration of the desired particle size, workability, etc.

When the desired temperature is reached, the reaction is restarted and continued until the cadmium sulfate is completely dissolved. at this point
When the sample was taken out and its surface shape examined using an electron microscope, it was found to be an agglomeration of several particles.

After the reaction is complete, sulfuric acid is added to the solution and left to stand while stirring. This operation converts the aggregated particles into single particles. The sulfuric acid concentration depends on the stirring time and desired particle size, but is between 4 and 6.
The range of N is good. If the stirring time is increased as the sulfuric acid concentration is increased, the formation of single particles becomes complete, but the particle size becomes smaller and the yield decreases. As the concentration decreases, the effect of forming single particles decreases, and as a result, the stirring time becomes significantly longer. The relationship between the standing time, particle size, and sulfuric acid concentration is determined as appropriate, but for example, by stirring and leaving for about 10 to 12 hours, monoparticulate particles having an average particle size of about 2 to 4 liters are obtained. For this purpose, it is preferable that the sulfuric acid concentration is in the range of 4 to 6N.

The cadmium sulfide produced at this stage has been successfully made into single particles, but its surface smoothness is somewhat inferior.

Therefore, the particles must be fired for the purpose of smoothing the surface, but since their shape is almost complete, they can be fired with a small amount of flux and at a temperature range of 0 to 50°C higher than the melting point of the flux. However, if the amount of flux is increased or firing is performed at a temperature higher than the above temperature, new particles will be formed due to the process of remelting and reprecipitation during firing.
It is inferior in terms of sensitivity, response speed, etc., which can maintain the properties at the time of precipitation.

The amount of flux is 1.~1 per 100 parts by weight of cadmium sulfide.
0, particularly 2 to 5 parts by weight, is preferred; at low temperatures, the amount of fluxing agent is small, and as the temperature rises, increasing the amount of fluxing agent generally results in better surface smoothness.

The fluxing agent used in the present invention is a fluxing agent that is generally used when diffusing an activator into CdS.
It is a mixture of one or several types of C12, KCI, NH4C:l, CdSO4, etc. in an appropriate ratio. A preferred example of a mixture used in combination is a mixture of CdCfL2 and an alkali metal chloride. Representative alkali metal chlorides include Na11 and KO2. The content of the alkali metal chloride in the entire flux is preferably 90 mol% or less and 10 mol% or more.

In the present invention, in order to compensate for surface defects generated in the firing process (to compensate for traps and to further improve crystallinity), the obtained CdS is further re-fired for 40 to 40 minutes for annealing purposes. It is effective to add a step of firing at 500°C.

Further, copper is usually doped to control the durability and image quality when used as a photoreceptor. Copper is co-precipitated during precipitation or added during re-firing. The addition amount is suitably between 5 x 10 2 moles and 2 x 10 ' moles or less per 1 mole of cadmium sulfide = 5 moles. As the copper compound added to CdS, copper chloride, sulfide, sulfate, etc. are used, and copper chloride and copper sulfate are particularly preferred. The method of adding a copper compound to CdS can be by adding the copper compound as a solid, or
If the copper compound is water-soluble, it is once made into a tree and treated with CdS.
Both wet methods, in which the water is evaporated after addition, give good results, but the wet method is better in terms of uniformity.

Example Me 9 containing 1 mole of cadmium and sulfur q65N
00 cc aqueous solution was kept at 75°C and hydrogen sulfide was heated at 300°C.
It was run for 5 minutes at a flow rate of C/min. Then 1100cc of pure water
When the reaction temperature reaches 67°C, restart the reaction.
The reaction was completed by passing hydrogen sulfide at a flow rate of 300 cc/min for 90 minutes. Sulfuric acid was added to this solution to make sulfuric acid 5N, and the solution was left overnight with stirring. Thereafter, water washing was repeated until the electrical type conductivity of the supernatant liquid became 200 ps/c+n or less, and then heat-dried at a temperature of 200°C.

After adding CuC father 2 to CdS to the precipitated cadmium sulfide I00gr at a molar ratio of lXl0-4mm,
Add 1 g of Cdl and 1.5 g of NaCl, and mix well
After 7 hours of mixing, the mixture was filled into a quartz crucible and fired at 530'0 for 60 minutes. After the firing, the powder was added to pure water and washed repeatedly with water by tecantation until the electrical conductivity of the supernatant liquid reached 30 ls/cm. After that, 20 cc each of cation exchange resin (manufactured by Mitsubishi Kasei: 5K-IB) and anion exchange resin (manufactured by Mitsubishi Kasei, SA-1OA) were added.
By stirring for 0 minutes, fifiM impurities deposited near the particle surface were removed. Thereafter, the cadmium sulfide and the resin were separated, passed through the mouth, and then dried at a temperature of 60'C.

This cadmium sulfide was filled into a quartz crucible, and
Calcining was carried out in air at a temperature of 60 minutes. After firing,
Using the above cleaning method, the sulfiding power of 1”mium was cleaned at 60°.
The mixture was further dried overnight at a temperature of 30°C to complete a cadmium sulfide for electrophotography.

The hexagonal degree of the cadmium sulfide obtained in this way is 10
According to an electron micrograph at 10,000 times magnification, the particle surface is extremely smooth and has a unique hexagonal crystal shape, and each particle is a single particle with a diameter of 2 to 5 pL. Admitted.

This cadmium sulfide was dispersed in a vinyl chloride/vinyl acetate copolymer, and then coated on an aluminum substrate to a thickness of 40 μm and dried. A polyester film with a rolling pressure of 15 mm was attached to the resulting photosensitive plate to form a three-layer photosensitive plate. When the body was obtained, the surface was very smooth. When this photosensitive plate was subjected to a high-speed electrophotographic process of primary charging, then photoimage exposure, AC static elimination, and then full-surface exposure, a high-quality image based on sufficient electrostatic contrast and good sensitivity was obtained. In particular, the resolution
There were 6 wood/■ or more, and a sharp image was obtained.

In addition, as an incidental effect, when we measured the dark potential after leaving this photoreceptor in a copying machine for 12 hours, we found that the first sheet
0V, the 50th sheet was 510V, and the difference was 1OV. Further, the change in potential contrast measured at 5° C. and 50° C. was as small as 10 μ.

Applicant: Canon Co., Ltd.

Claims (1)

[Claims] (1) Tj & aqueous solution containing acid cadmium and sulfuric acid i
A step of precipitating cadmium sulfide through hydrogen sulfide, adding water to reduce the ion and acid concentration in the aqueous solution, and further precipitating cadmium sulfide through hydrogen sulfide; adding sulfuric acid to the aqueous solution; and a process for producing cadmium sulfide for electrophotography, comprising the steps of adding a flux to cadmium sulfide separated from the aqueous solution and firing the mixture.