JPS5849618A - Preparation of photoconductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To prepare photoconductive cadmium sulfide having high crystallinity, uniform particle shape, sharp particle size distribution, and high sensitivity to long wavelength light, by mixing a flux to cadmium sulfide containing indium, calcining the mixture, and recalcining together with a chloride. CONSTITUTION:Cadmium sulfide containing 5-30/10<4>mol of indium based on 1mol of the cadmium sulfide, is mixed with >=20wt% flux, calcined at a temperature higher than the melting point of the flux by >=50 deg.C, and recalcined in the presence of a chloride. The chloride to be added in the recalcination process is preferably cadmium chloride or ammonium chloride which does not leave impurity cations in the cadmium sulfide after calcination. Addition of 1/10<3>- 1/10<2>mol of the chloride to 1mol of the cadmium sulfide is sufficient to attain the aimed effect. Although the chloride may be added in the form of solid, however, it is preferable for the uniform distribution of the chloride in the cadmium sulfide to use a wet-process comprising the addition of an aqueous solution of the chloride to cadmium sulfide followed by the evaporation of water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cadmium sulfide for electrophotography, and in particular a method for producing cadmium sulfide particles that are extremely crystalline, uniform, single, and sensitive to long wavelengths at tV. It's about.

The most common method for producing photoconductive cadmium sulfide (CdS), which is used as an example of an electrophotographic photosensitive material, is to react sulfur or hydrogen chloride with a water-soluble salt of cadmium such as cadmium sulfate or cadmium chloride. The precipitate of cadmium sulfide particles is then obtained by high-temperature firing in order to dope the cadmium sulfide particles with an activator.

That is, photoconductive cadmium sulfide is produced by mixing cadmium sulfide particles with CaCl2, CuSO4, etc. as an activator, and halide such as CdC42, znC62, etc. as a fluxing agent, and firing the mixture to sulfide Cu, CL, etc. It is generally manufactured by doping cadmium.

However, in such conventional methods, the CdS produced through the calcination process has a large number of defects near the bottom surface of the CdS at the time of precipitate formation.

These surface defects become trap levels for photocarriers, increasing the optical memory of CdS, that is, slowing down the optical response speed, and making photoreceptors made using such CdS' difficult to use in high-speed copying machines. If applied to the initial copy, the electrostatic contrast between bright and dark areas will be insufficient.

In addition, the particle shape of CdS produced by the above method consists of secondary particles, which are strong aggregates formed by aggregation of particles, and these secondary particles are three-dimensional. There are various types of particles, such as those that are aggregated in the shape of a nodule, or those that are two-dimensionally aggregated and are tabular, and some of them are large, ranging in size from 10-odd microns to several tens of microns.

A photoreceptor made using CdS'e containing a large number of such coarse particles has a poor six-fold condition, and as a result, the resulting image is extremely rough and has insufficient resolution. Furthermore, in the case of a photoconductor further provided with an insulation N, the insulating layer may seep into the CdS layer, making it difficult to obtain a good photoconductor.

Regarding the above-mentioned drawbacks, the applicant's patent application 1982-
This problem has been overcome by methods such as those described in US Pat. No. 10,966.

However, as interest in intelligent copiers has recently increased, and in particular there has been a demand for copiers that use laser light sources, photoreceptor particles with long wavelengths, especially 750 to 800 nm or more due to laser light, have become increasingly popular. There is a need for something with a sensitivity of The particles according to the invention have no sensitivity on the long wavelength side, and are insufficiently sensitive to light in the infrared region, so they cannot be used for the above purpose.

The present invention relates to a method for producing cadmium sulfide particles having the features of the above invention and having sensitivity to longer wavelengths.

The present inventors have confirmed that the sensitivity of cadmium sulfide for electrophotography can be extended to longer wavelengths due to the presence of salts and innoum, as described in JP-A No. 52-58542. However, since chlorine ions have the necessary dark resistance for electrophotography as conventionally used,
．． When applied to Manso Patent Application No. 10966/1983, which is based on the present applicant's invention, and uses all the raw material cadmium sulfide precipitated in an aqueous solution of cadmium containing hydrochloric acid of low N or less, a flux is added at the firing stage. Because the entire firing process was carried out at a temperature 50°C or more higher than the melting point of the particles, there was almost no chlorine content in the fired particles, which resulted in insufficient sensitivity to long wavelengths.

In order to overcome this drawback, the present inventors added a small amount of chloride in the ladle-firing process and added a small amount of chloride to the cadmium sulfide particles that are generated. I discovered that the feeling is carried out.

The method of the present invention involves mixing 20% by weight or more of a flux with cadmium sulfide containing indium, and
It is characterized by being fired at a temperature higher than 0°C and then re-fired with the addition of chloride.

Cadmium sulfide produced according to the present invention has high crystallinity, and when observed using a scanning electron microscope, it is found to be a single particle with no agglomeration of particles, and its optical surface is smooth.

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 was found that the sensitivity was extended to long wavelengths, particularly 800 to 850 nm.

In the present invention, the chloride added at the time of recalcination is appropriately selected from cadmium chloride, zinc chloride, potassium chloride, sodium chloride, ammonium chloride, etc., but in particular, impurity cations are not left in the generated cadmium sulfide. Cadmium chloride and ammonium chloride (5) are preferred. Moreover, the effect can be seen when the amount of addition is sufficient at a molar ratio of 10 to 10 to cadmium sulfide. As for the addition method, the above chloride may be added and mixed in its solid state, or a wet method in which the chloride is made into an aqueous solution, added to cadmium sulfide, stirred uniformly, and then evaporated water has yielded good results. However, in order to uniformly diffuse the chloride into the cadmium sulfide, the wet method is by far the most appropriate method.

In order to extend the sensitivity to the long wavelength side, chlorine and indium must work together, but the amount of indium is determined by the balance with the amount of chlorine. The minimum amount to have sensitivity on the long wavelength side is 5 x 1 per mole of cadmium sulfide produced.
o−' moles are required, and the maximum amount is 30×IO moles, which satisfies the dark resistance for electrophotography.

Also, if the amount of indium is large and the amount of chlorine is small, the amount of chlorine must be reduced, and vice versa. It is necessary to increase L'.

Indium can also be added to cadmium sulfide by co-precipitation (6) by adding it to the solution, or
Even if it is mixed with cadmium sulfide before firing, it can also be effectively embedded.

The fluxing agent used in the present invention is a fluxing agent that is generally used when diffusing into the activator i CdS.
It is a mixture of one or more of nC4, KCl, NaC2, NHC1, CdSO4, etc. in an appropriate ratio.

A preferred example of a mixture of CaCl2 and an alkali metal chloride is a mixture of CaCl2 and an alkali metal chloride. NaCt and KCl are substitutes for the alkali metal chloride. The content of the alkali metal chloride in the entire flux is preferably 90 moles or less and 10 moles or more.

In the present invention, the amount of flux is preferably 20% or more, particularly preferably 30 to 50%. If the thickness is less than 20 inches, the CdS particles produced will be sintered into coarse particles, and the shape of the narrow surface will be non-uniform, resulting in poor CdS with insufficient potential retention and poor resolution. Furthermore, if the firing is carried out at a temperature lower than the melting point of the flux, which is 50° C., the CdS particles produced will have a large particle size and poor resolution and coating properties.

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

The thus fired cadmium sulfide is further fired again. This re-baking process further stabilizes the electrostatic contrast of the image formed when used on a photoreceptor. Cell firing is below 500℃, especially 400-450℃
It is preferable to carry out the process at a temperature of . In particular, at a firing temperature of 500° C. or higher, residual charges tend to remain in the photoreceptor.

The present invention further uses Nabeondogu as an acceptor. Copper can be precipitated in advance in a cadmium salt aqueous solution (can be included in cadmium iiiitide, or can be incorporated into cadmium before firing or re-firing). It can also be incorporated into cadmium sulfide by mixing it with cadmium sulfide and then firing or re-calcining it.As the copper compound added to CdS, copper chloride, sulfide, sulfide, etc. are used. Copper chloride and copper sulfate are particularly preferred.

To add all the copper compound before firing or re-firing, you can add and mix the copper compound as a solid, or if the copper compound is water-soluble, make it into an aqueous solution and add it to CdS, then evaporate the water. Although any of the wet methods can give good results, the wet method is better in terms of uniformity.

The optimum amount of copper added differs depending on the amount of chlorine and indium, but it is 1 x ] O for 1 mole of cadmium sulfide.
-' to 15 X 10-' moles, especially 3 X 10-'
'~10 x 10'''' moles are required.

This will be explained below using examples.

Example 1 Cadmium sulfide 1001 K CuC62 containing 12X10-4 mol based on indium total cadmium sulfide
After adding 5×10 molar ratio to S, CaCl
2e 20.9 and 30 g of NaC1"it were added, mixed well, packed in a quartz mold, and heated at 530°C for 30 g.
(The melting point of the mixed flux of CdC42 and NaCL corresponds to 426° C., which is the melting point of CdCt2.2Na C1 from the phase diagram). The temperature of 60,000 degrees for the CdS obtained in this way is 100%, and according to an electron micrograph at a magnification of 10,000 times, the particle surface is very clear and has a unique hexagonal shape, and each particle is Single particles with a diameter of 2 to 5 μm were observed.

Next, wet-method cadmium chloride was added to the CdS thus obtained at a molar ratio of 4 X I F3, and the mixture was thoroughly mixed and then recalcined at 450° C. for 1 hour. After re-baking, it was washed with water, residual ions were removed using an ion exchange resin, and dried. This CdS" was dispersed in a vinyl chloride/vinyl acetate copolymer, then coated on an aluminum substrate in a 40μ floating type and dried. A 15μ thick polyester film was attached to the resulting photosensitive plate to form a three-layer structure. When a photoreceptor was obtained, the surface was extremely smooth.

Next, I measured the 9% accuracy of this photosensitive plate and found that it was 75.
0.851 uxaec at 0 nm, 141 at 800 nm
A value of 3.71 uxgec was obtained at uxaecs 850 nm.

- 10,000 \ Particles created by the same method as in (10) except that they do not contain indium or chlorine are made into a photosensitive plate in the same manner,
When the sensitivity was measured, it was 571uxse at 750 nm.
cs at 800 nm was 10.31 ux·sec, which clearly showed that the sensitivity was increased when the particles of the present invention were used.

Example 2 The molar ratio of indium and copper was 30XIO""'
.

Cadmium sulfide containing 10 x 10''-'CdCl
A mixed flux of 230I and KCl 20.9 was mixed, and after thorough mixing, it was fired at 480°C for 30 minutes.

Thereafter, re-firing was performed in the same manner as in Example 1, and the obtained Cd
When S was made into a photoreceptor and evaluated, good results similar to those in Example 1 were obtained. Note that, from the phase diagram, the melting point of the mixed flux of CdCl2 and KCl corresponds to the melting point of KCdC15, 390°C.

Example 3 Precipitated CdS raw powder 1001/without added impurities
K CuCZ2 indium was converted to Cd by wet method.
8, molar ratio 3 X 10-', 5 X 10-'
After addition, CdCl2 f 41 f/ -NaC
tf 91/ was added, mixed well, and filled into a quartz crucible, followed by firing at 500° C. for 30 minutes. Thereafter, recalcination treatment was performed in the same manner as in Example 1, using ammonium chloride instead of chloride. The 60,000 degrees of CdS obtained in this way is 1
According to the electron micrograph, the particle bottom surface is very smooth, and each particle has a hexagonal crystal shape.
It was observed that the particles were uniform single particles with a diameter of ~5μ. When the obtained Cd5t sensitizer was made into a sensitizer and evaluated, good results similar to those of Example 1 were obtained.

Claims (1)

[Claims] After mixing 20% by weight or more of a flux with cadmium sulfide containing 5 to 30 x 10" moles of sindium per mole, and firing at a temperature 50°C or more higher than the melting point of the flux,
A method for producing photoconductive cadmium sulfide, which comprises recalcining with chloride.