JPS59166962A - Manufacture of photoconductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To give good sensitivity to long wavelength light, to reduce light memory, and to raise resistance by burning a mixture of CdS contg. In and a specified amt. of flux, then, washing it to remove the flux, reburning it, and heat- treating the obtained CdS in sulfuric acid. CONSTITUTION:>=20wt% flux is mixed with CdS contg. In in an amt. of (5- 30)X10<-4>mol In per mole of Cd, and the mixture is burned at a temp. >=50 deg.C higher than the m.p. of the flux. After the flux is removed in the washing process, CdS is again burned and the obtained CdS is heat-treated with 0.1-0.3 N sulfuric acid. The CdS thus obtained is uniform in particle shapes and their diameters and the coated face of a photoconductive layer is not coarse and rough, but fine and smooth. Therefore, an image of excellent quality is obtained, and said layer is improved in sensitivity to long wavelength light and enhanced in dark resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing photoconductive cadmium sulfide, particularly 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 (cdS), which is typically used in electrophotographic materials, is to react hydrogen sulfide with a water-soluble salt 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 CuCl2. to cadmium sulfide particles as an activator. CuSO4 etc. and CdCl2. as a fluxing agent. It is generally manufactured by doping Cu, Cl, etc. into cadmium sulfide by mixing a halide such as ZnC1!2 and firing. However, in such conventional methods, the CdS produced through the calcination process has a large number of defects near the surface of the CdS when the precipitate is formed.

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 method described above is derived from secondary particles, which are strong aggregates formed by aggregation of particles, and these secondary particles are three-dimensional. There are various types of soot, such as the soot that aggregates in a nodule shape, or the soot that aggregates two-dimensionally and has a tabular shape, and some of them are large, ranging 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.

Regarding the above-mentioned drawbacks, Japanese Patent Application Laid-Open No. 1983-1999, which is an invention of the present applicant,
This problem has been overcome by the method described in Japanese Patent No. 129825.

However, recently, interest in intelligent copying machines has increased9, and in particular, as the demand for copying machines using laser light sources has begun to appear, photoreceptor particles with long wavelengths, especially 750 to 800 Hrn or more due to laser light There is a need for something with sensitivity at . 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 inventors have discovered that 'IiR cadmium for electrophotography is
It has already been confirmed that the presence of n can extend the sensitivity to longer wavelengths. However, in order to dope the necessary amount of In to extend the sensitivity to long wavelengths and to have the necessary dark resistance for electrophotography, K should be adjusted according to the amount of In.
U must be added as an acceptor, but when this is applied to the above method, as the amount of Cu increases,
Electrophotographic photoreceptors made using the resulting cadmium sulfide tend to have poor carrier injection properties from the substrate, especially in types with a three-layer structure in which an insulating layer is provided on the photoconductive layer. , there is a tendency for the dark area potential to decrease and the sensitivity to decrease.

If only the amount of Cu is reduced and the amount of In is not reduced, the sensitivity extends to longer wavelengths, but the optical memory increases, resulting in a very low-resistance IMt cadmium oxide with a low dark potential.

+m L It is an object of the present invention to provide a method for producing CdS that is an improvement on the above method.

That is, it is an object of the present invention 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 spot.

In the method of the present invention, cadmium chloride containing indium is mixed with 20% more flux by weight, fired at a temperature 50°C or more higher than the melting point of the flux, and the flux is removed through a washing process. After removal, the sulfiding power obtained by re-firing is 0.
．． 4N~3. It is characterized by heat treatment in ON sulfuric acid.

The cadmium sulfide produced by 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 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 longer wavelengths, particularly 800 to 850 Hm.

In the present invention, the concentration of sulfuric acid used for surface treatment of cadmium sulfide after firing is O.IN~3. ON is effective. 0. I
If the concentration is less than N, even if the treatment is carried out for a long time, the effect will be small and manufacturing efficiency will be poor. Furthermore, treatment at a concentration of 3N or more is unsuitable because the sensitivity tends to decrease due to heating.

Furthermore, in the present invention, by performing the sulfuric acid treatment under heating, the treatment time can be shortened, and sulfuric acid with a low intensity can be used to obtain the same treatment effect. The heating concentration is 7
The temperature is preferably 0°C or higher, particularly 80°C or higher. Long wavelength side -
The minimum amount of indium required to provide sensitivity is 5 x 10-' mol per 1 mol of cadmium sulfide produced, and the maximum amount is 30 x 10-4 mol to satisfy the dark resistance for electrophotography. It is.

Indium can be added to the reaction solution and included in the cadmium sulfide by coprecipitation, or it can be effectively included 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 before firing, by mixing with cadmium sulfide and then firing. CdS
As the copper compound to be added, copper chlorides, sulfides, sulfates, etc. are used, and copper chloride and sulfuric acid steel are particularly preferred.

The copper compound can be added before firing by adding and mixing the complex 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 to be added differs depending on the amount of indium, but it is 1'ic per mole of cadmium sulfide, 1 x 10-4 to 15 x 10-4 mol, especially 3 x 10-4 to i
ox i O-4 moles are required.

The fluxing agent used in the present invention is a fluxing agent commonly used when diffusing into the activator'i CdS, and CdC7z
, ZnCl2. KCl, NaC/? , NfL
It is a mixture of one or several types of CJ, Cd5Q4, etc. 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
1 and KCf are representative ones. The content of alkali metal chlorides in the total flux (d, 1 at 90 mol.
In the present invention, the fluxing agent amount is preferably 0 molar ratio or more, and is preferably 20% or more, particularly preferably 30 to 50 molar ratio.

If it is less than 20%, the produced CdS particles will be sintered and become coarse particles, the surface shape of the grooves will be uneven, the potential retention will be insufficient, and the CdS will be coarse and poor in resolution. If the firing is carried out at a temperature lower than t = 50° C. higher than the melting point of the agent, 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 less is suitable. Further, the amount of flux added to CdS is preferably 65% 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. Preferably, the re-firing is carried out at a temperature below 500''C, particularly between 400 and 450C.

Example 1 Cadmium sulfate 1 mole, copper sulfate 8'X 10
-'mode indium sulfate 20 X 10-' mo
The temperature of the 3N sulfuric acid acidic aqueous solution 21 containing lle was set to 60''.
The temperature of the reactor was maintained at 30° C., and hydrogen sulfide was heated 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 excess impurities present on the particle surface, and then dried overnight at a temperature of 100'O. For 100g of this cadmium sulfide, add 201 CrtC4 and 3O NaCl.
Add f′, mix well, and fill in a quartz crucible.
Calcined at 530°O for 30 minutes (note that CdC12 and Na
The melting point of the mixed flux C1 can be determined from the phase diagram cdCI! 2・2
NaCI! (corresponds to the melting point of 426°C). The CdS thus obtained was washed with water, residual ions were removed using an ion exchange resin, and then dried. This cadmium sulfide is 450
Refired for 1 hour at 'C. After re-baking, this was placed in a 2.5N sulfuric acid aqueous solution and heated while stirring. Liquid temperature is 90°C
After heating was continued for another 40 minutes, the supernatant was washed with pure water and the electrical conductivity of the supernatant was reduced to 10 μS/cm.
After the ion exchange resin was added and stirred for 60 minutes, it was confirmed that the electrical conductivity was 1.0 μS/cm or less, and the resin was separated, filtered, and heated to a temperature of 60°C. It was dried.

After dispersing this CdS in a vinyl chloride/vinyl acetate copolymer, it was coated on an aluminum substrate to a thickness of 40μ and dried.A 15μ thick polyester film was attached to the resulting photoreceptor to obtain a three-layered photoreceptor. The surface was very smooth. When this photoreceptor was subjected to a high-speed electrophotographic process of primary charging, photoimage exposure, AC static elimination, and then full-surface exposure, a good quality image was obtained based on sufficient electrostatic contrast and sufficient sensitivity.

lF! The resolution was 6 lines/cylinder or more, and a sharp image was obtained. Furthermore, this photoconductor was left in a high temperature and high humidity environment of 35°C and humidity of 85% for 24 hours, and then the image was produced again in a copying machine.As a result, no decrease in contrast between bright and dark areas was observed, and the image was of good quality. was gotten.

Example 2 From a 3N sulfuric acid water bath solution containing 1 mole of cadmium sulfate,
Cadmium sulfide was precipitated by the same method as in Example 1. The cadmium sulfide 1007 contained 3 x 10' of copper and indium, respectively, per mole of cadmium sulfide.
, 6 x 10-' moles were added in the form of sulfuric acid, copper, and indium sulfate, and after homogeneous mixing by a wet method, it was dried at a temperature of 100'0. CdCl2.40
Mixed molten Mll consisting of gr, NaCl, 10gr
After thorough mixing, the mixture was baked at 500°C for 30 minutes. The cadmium sulfide prepared in this way was added to a 0.3N sulfuric acid aqueous solution and heated.

While stirring, heating was continued for 120 minutes after reaching 90°C. After water washing, filtration, and drying, 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 Exactly the same as in Example 1 except for the sulfuric acid treatment. A photoreceptor was produced in the same manner as in Example 1 using the cadmium sulfide particles produced by the method described above.

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. The characteristics of the photoreceptors manufactured in the above Examples and Comparative Examples 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. The measurement was performed by closing the relay switch 5 for 0.2 seconds and applying a high voltage (Va).
After leaving it for 2 seconds (open), it was irradiated with light at 0.degree. for 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. Similarly, Vp is the voltage applied to the photoconductive layer.

Further, as a pre-exposure, 0.25(9) of white light from the halogen lamp 1 was irradiated by the shutter 2, and
1, then Va was applied, and after being left for 0.2 seconds, light was irradiated for 0.2 seconds and the voltage change (p') at that time was measured. Vp and Vp' when Va -2000V
The VpO value is measured when Va is set to +2000V, and the size of the optical memory can be determined from Vp-Vp' when Va: -12000V is applied.

Next, the tr'g degree 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 IF current power source 6 via a relay switch 5. In the measurement, white light from halogen lamp 1 is used as pre-exposure with shutter 2 at 0,
After irradiating for 2 seconds and leaving it for 0.2 seconds, close the relay switch 5 for 0.2 seconds and apply high voltage (Va) to the light body, and after leaving it for 0.2 seconds, apply a sufficiently strong light. After irradiating for 02 seconds, the pressure (
Va') was measured using a metal plate 7 at the same voltage as the photoreceptor and a surface potentiometer 8. The voltage (Vp) applied to the photoconductive layer when applying a high voltage can be calculated from Va - Va', so Vp
Va becomes 600V (hereinafter referred to as Va -600)
was determined and the sensitivity was measured using the following method.

That is, the photoreceptor is irradiated with measurement light (800 nm)' while applying Va -600. After leaving it for 02 seconds after irradiation with light, irradiate the photoreceptor for 02 seconds with sufficient intensity as above and measure the voltage (Va'') on the surface of the photoconductor in the same manner as above. Va-600 application and simultaneous measurement When irradiated with light Since the voltage (Vp'') applied to the photoconductive layer in can be calculated as Va-600-Va'', the exposure amount (■) of the measurement light required to make Vp'' 300V is the half-reduced exposure amount (Ei/2). , p2 H7 of the photoreceptor can be displayed.

The characteristics are shown in the table below.

From the table, for the photoreceptor treated with sulfuric acid, Vp -V
The difference in p' is smaller than that of 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.

Compared to the comparative example, the Vp′ is larger.
7, it is a high resistance type and changes in the direction that the potential can be taken. Both optical memory and sensitivity are improved compared to the comparative example.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an apparatus for measuring the sensitivity of a photoreceptor. 4...°transparent'i Takumi Kiwami 5...Relay switch 6
... [￥, 5 pressure 1 negative current (Ryo 7 Fri)],
・An 8° angle electrometer 9...1□113 original body developer Yayanon Co., Ltd.

Claims (1)

[Claims] (1) 5 to 30 x 10- of indium per mole
Cadmium sulfide containing 4 moles is mixed with a flux of 20% or more by weight, fired at a temperature of 5°C or more higher than the melting point of the flux, and after the flux is removed through a washing process, it is further fired. The cadmium sulfide obtained by
1. A method for producing photoconductive cadmium sulfide, comprising heat treatment in sulfuric acid.