JPS59164633A - Manufacture of photoconductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To manufacture photoconductive CdS having sensitivity of light of longer wavelengths by calcining CdS contg. a small amount of In together with a proper amount of a flux, removing the flux by washing, carrying out calcination again, and treating the surface of the resulting CdS with sulfuric acid. CONSTITUTION:CdS contg. In by 5-30X10<-4> mole per 1 mole CdS or further contg. Cu by about 1-15X10<-4> mole is mixed with >=20wt%, preferably about 30-50% flux such as CdCl2-NaCl mixture, and the prepd. mixture is calcined at a temp. >=50 deg.C above the m.p. of the flux, preferably <= about 600 deg.C. The calcined CdS is washed with water or the like to remove the flux, and the CdS is calcined again at <= about 500 deg.C, preferably about 400-450 deg.C. The surface of the resulting CdS is then treated with 0.5-5N sulfuric acid to obtain high resistance CdS having a uniform and simple grain shape. The CdS has sufficient sensitivity to light of longer wavelengths and small optical memory, and it ensures sufficient dark potential.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing photoconductive cadmium sulfide, and in particular a method for producing cadmium sulfide particles that are highly crystalline, uniform, single, and sensitive to long wavelengths. It is related to.

The most common method for producing photoconductive cadmium sulfide (Cd8), 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 CuC/2. Cu80. etc. Also, by mixing a halide such as CdC/, '1nclt, etc. as a flux and performing firing, Cu, CI! It is generally manufactured by doping cadmium sulfide. However, in such conventional methods, the CdS produced through the calcination process has a large number of defects near the 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, making photoreceptors made using such CdS suitable for high-speed copying machines. If applied, the electrostatic contrast between bright and dark areas in the initial copy 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 particles aggregating together, and these secondary particles are three-dimensionally aggregated. There are various types of particles, such as those that are shaped like nodules, or those that are two-dimensionally aggregated and are tabular, and some of them are large, ranging in size from several microns to several tens of microns. A photoreceptor made using a large amount of CdS 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 drawbacks have been overcome by a method as described in Japanese Patent Laid-Open No. 57-129825.

However, recently, interest in intelligent copying machines has increased, and in particular, demand has begun to appear for copying machines using laser light sources.As a result, photoreceptor particles need to be sensitive to longer wavelengths, especially 750 to 800 nm or more due to laser light. You will need what you have. The particles used in the above method are sensitive to long wavelengths, but are not sufficiently sensitive to light in the infrared region and cannot be used for the above purpose. It has already been confirmed that the sensitivity of cadmium sulfide can be extended to longer wavelengths due to the presence of In. However, in order to dope the amount of In necessary to extend the sensitivity to long wavelengths, and still have the necessary dark resistance for electrophotography, it is necessary to add Cu as an acceptor in accordance with the amount of In. However, when this method is applied to the method described in the above-mentioned publication, as the Cu i increases, an electrophotographic photoreceptor made using the resulting cadmium sulfide is reduced in the amount of carrier from the substrate. Injection properties tend to deteriorate, and in particular, in a type such as a three-layer structure in which an insulating layer is provided on a photoconductive layer, the dark potential tends to decrease and the sensitivity tends to decrease.

If only the amount of Cu is reduced and the amount of In is not reduced, the sensitivity will extend to longer wavelengths, but the optical memory will increase, resulting in cadmium with a very low resistance and a low dark potential.

Therefore, an object of the present invention is to provide a method for producing CdS that is an improvement on the above-mentioned method.

That is, the object is to provide a manufacturing method capable of manufacturing high-resistance CdS that has sufficient sensitivity to long wavelengths, has a small optical memory, and has a more sufficient dark potential.

The method of the present invention involves mixing 20% by weight or more of a flux with cadmium sulfide containing indium, and
After firing at a temperature higher than 0°C, the cadmium sulfide was re-fired through a cleaning process and heated to a temperature of 0.5 N to 5. It is characterized by surface treatment in ON sulfuric acid and then re-firing.

Cadmium sulfide produced according to the present invention has good crystallinity, and when observed using a scanning electron microscope, it is found to be a single particle with no agglomeration of particles, and its 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 also found that the sensitivity was extended to long wavelengths, particularly 800 to 850 nm.

In the present invention, the concentration of sulfuric acid used for surface treatment of cadmium sulfide after re-firing is 0.5 N to 5. ON is effective,
This effect is correlated with processing time. That is, at low concentrations, long-term treatment is required, while at high concentrations, effects can be obtained in a short time. However, if the concentration is 0.5N or less, the processing effect is small and the processing time needs to be lengthened, resulting in poor manufacturing efficiency.Additionally, if the concentration is 5N or more, the sensitivity tends to decrease. Therefore, it is inappropriate. The minimum amount of indium required to provide sensitivity on the long wavelength side is 5×10 mol per mol of cadmium sulfide produced, and the maximum amount is 30×10 mol, which satisfies the dark resistance for electrophotography.

Indium can be added to the reaction solution and incorporated into the cadmium sulfide by coprecipitation, or it can be effectively incorporated by mixing it with the cadmium sulfide before firing.

In addition, copper can be added in advance to a cadmium salt aqueous solution and co-precipitated to be included in cadmium sulfide.
It can also be included in cadmium sulfide by mixing it with cadmium sulfide before firing and then firing it. Cd8
As the copper compound to be added, copper chloride, sulfide, sulfate, etc. can be 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 optimum amount of copper added varies depending on the amount of indium, but it is from 1x10 to 15x per mole of cadmium sulfide.
10 mol, in particular 3×10 5 to 10×10 8 mol, is required.

The flux used in the present invention is a flux generally used when diffusing an activator into CdS, and includes CdC/2,
ZnC/2. KC1! , NaCl, NH4C/
! , CdSO4, etc., or a mixture of them in an appropriate ratio. A preferred example of a mixture of CdC and an alkali metal chloride is a mixture of CdC and an alkali metal chloride. As an alkali metal chloride, NaC
1 and KCt are representative. The content of alkali metal chloride in the entire flux is 90 mol% or less and 10
A mole % or more is preferable.

In the present invention, the amount of flux is preferably 20% or more, particularly preferably 30 to 50%.

If it is less than 20%, the CdS particles produced will be sintered and become coarse particles, and the surface shape will be non-uniform, resulting in poor CdS that does not have sufficient potential retention and lacks resolution. Furthermore, if the firing is performed at a temperature lower than 50° C. higher than the melting point of the flux, the CdS particles produced will have a large particle size and poor resolution and coating properties.

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

The cadmium sulfide thus calcined is recalcined before being treated with sulfuric acid according to the present invention. Through this re-firing process,
When used on a photoreceptor, the electrostatic contrast of the image formed becomes more stable. Re-firing is preferably carried out at a temperature of 500°C or lower, particularly 400-450°C.

Example 1 Cadmilla sulfate A 1 mog, copper sulfate 10 X 10
The temperature of the 3N sulfuric acid acidic aqueous solution 21 containing 30×10 moles of model 1 indium sulfate A was kept at 60° C., and hydrogen sulfide was passed through the solution at a flow rate of 300 cc/min 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 filtered through the mouth and dried overnight at 100°C.

For this cadmium sulfide 100fK, CdCl! t to 20
1 and NaCl were added, mixed well, and then filled in a quartz crucible and fired at 530°C for 30 minutes (note that c
From the phase diagram, the melting point of the mixed flux of ctcz and NaCl is CdC1! , corresponds to the melting point of -2NaCl of 426°C). The CdS thus obtained was washed with water, residual ions were removed using an ion exchange resin, and then dried and left for 4 hours with stirring. This CdS was washed with water, residual ions were removed using an ion exchange resin, and dried. This CdS can be converted into vinyl chloride/
The resulting photoreceptor was dispersed in vinyl acetate copolymer, coated on an aluminum substrate to a thickness of 40μ, and dried.
When a thick polyester film was attached to obtain a three-layered photoreceptor, the surface was extremely smooth. When this photoreceptor was subjected to a multi-speed electrophotographic process consisting of primary charging, photoimage exposure, AC static elimination, and then full-surface exposure, a high-quality image with sufficient electrostatic contrast and sufficient sensitivity was obtained. In particular, the resolution was more than 6 lines per shot, and sharp images were obtained. Furthermore, this photoreceptor was heated at a temperature of 35°C and a humidity of 85°C.
After being left in a high temperature and high humidity environment for 24 hours, 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 3N sulfuric acid aqueous solution containing 1 mode of cadmium sulfide in the same manner as in Example 1. Copper and indium were added to the cadmium sulfide 1009 at a concentration of 4X 10, respectively, per mole of cadmium sulfide. '
Sulfuric acid steel and indium sulfate were added so as to contain 12×10 −4 moles, and after homogeneous mixing by a wet method, the mixture was dried at a temperature of 100° C. cctcz, 40
f s NaCl 10 ? A mixture of molten β consisting of 100% molten carbonate was added, and after thorough mixing, it was fired at 500°C for 30 minutes.

The cadmium sulfide thus prepared was added to a 0.5N sulfuric acid water bath and left to stand for 20 hours with stirring. Washed with water, filtered through 9 mouths, dried, and then refired in the same manner as in Example 1.
When dS was made into a photoreceptor and evaluated, good results similar to those of 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 except for the following.

The characteristics of the photoreceptors manufactured in the above Examples and Comparative Examples were measured using the measuring apparatus shown in FIG.

The photosensitive characteristics of the photoreceptor were measured using the measuring apparatus shown in FIG.

That is, the glass plate 3 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. For measurement, close the relay switch 5 for 0.2 seconds and apply a high voltage (Va) to 0.2 seconds.
After being left open for a second, light was irradiated for 0.2 seconds and the voltage change (Vp) at that time was measured using a metal plate 7 at the same voltage as the photoreceptor and a surface potentiometer 8. This is the voltage being applied.

Furthermore, as a pre-exposure, white light from a halogen lamp 1 was irradiated for 90.2 seconds through the shutter 2, and after being left for 0.2 (8), va was applied, and after being left for 0.2 seconds, light was applied again for 0.2 seconds.
The voltage change (p') at that time was measured.

Measure the Vp and Vp' when Va is set to -2000V and the VpO value when Va is set to +2000V.
: The size of the optical memory can be determined from Vp-Vp' when -2QOOV is applied.

Next, the sensitivity of the photoreceptor was measured using the same measuring device.

That is, the glass plate 3 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 using white light of 10 gen lamp 1 as pre-exposure with shutter 2 of 0.2
1iet1! After irradiating and leaving it for 0.2 (8), the relay switch 5 is turned on for 0.2 seconds and the voltage (Va') on the surface (i.e., the surface of the insulating layer) is set to the metal plate 7 at the same voltage as the photoreceptor.
was measured using a surface electrometer 8. The voltage (Vp) applied to the photoconductive layer when applying a high voltage can be calculated as Va-Va', so Va (hereinafter Va-,
66) was determined and the sensitivity was measured using the following method. That is, the measurement light (
800℃m). After leaving it for 0.2 seconds after light irradiation,
Irradiate sufficiently strong light 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. Photoconductive layer during Va-0°0 application and simultaneous measurement light irradiation. The applied voltage (Vp″) to “−aoo −Va
Since it can be calculated by ``, the exposure amount (E) of the measurement light required to obtain v, j/ f 300 sq. is the half-reduced exposure amount (E%), and the sensitivity of the photoreceptor can be displayed.

The characteristics are shown in the table below.

From the table, for photoreceptors treated with sulfuric acid, vp-vp
' difference is smaller than that of the comparative example. This shows that. In addition, since vp' is larger, it is a higher resistance type than the comparative example, and the potential is changed in the direction that it can be obtained. Furthermore, the sensitivity is within a usable range, and the optical memory is improved compared to the comparative example.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of an apparatus for measuring the sensitivity of a photoreceptor. 4...Transparent electrode, 5...Relay switch, 6...
High-voltage DC power supply, 7... Gold plate, 8... Surface electrometer,
9...Photoreceptor. Applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) Cadmium sulfide containing 5 to 30 x 10' moles of indium per mole is mixed with 20% by weight or more of a flux and fired at a temperature 50°C or more higher than the melting point of the flux,
A method for producing photoconductive cadmium sulfide, which comprises surface-treating the cadmium sulfide obtained by removing the flux through a washing step and then re-firing with 0.5N to 5N sulfuric acid.