JPS59164632A - Manufacture of photoconductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To manufacture photoconductive CdS having high crystallizability and sensitivity to light of longer wavelengths by mixing CdS contg. a small amount of In with a proper amount of a flux, calcining the mixture at a temp. above the m.p. of the flux, treating the calcined CdS with sulfuric acid, and calcining it again. 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 surface of the calcined CdS is treated with 0.5-5.0N sulfuric acid, and the treated CdS is washed, dried, and calcined again at <= about 500 deg.C, preferably about 400-450 deg.C to obtain high resistance CdS powder having a uniform grain shape and a single grain size. The CdS powder has very high crystallizability, 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 (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 added to cadmium sulfide particles as an activator by CuC1! , , Cu5O, etc. Also,
Generally, cadmium sulfide is manufactured by doping p, Cu, C/2, etc. by mixing a halide such as cacz, ZnC/2, etc. as a flux and firing. However, in such conventional methods, the CdS produced through the calcination process becomes Cd8 during precipitate formation.
0 has many defects near the surface.

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 use in 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, such as those that are shaped like a nodule or two-dimensionally aggregated and shaped like a plate, but some of the larger ones are i.

Photoreceptors made using CdS containing large numbers of such coarse particles have a surface condition that is poor, resulting in images that are extremely rough and have poor resolution. will also be insufficient. 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 demand for copying machines that use laser light sources has begun to appear.As photoreceptor particles have long wavelengths, especially laser light, wavelengths of 750 to 800 nm or more have become necessary. Something with sensitivity is needed. The particles in the method are:
It has no sensitivity on the long wavelength side and has insufficient sensitivity to light in the infrared region, so it cannot be used for the above purpose.

The present inventors have already confirmed that the sensitivity of cadmium sulfide can be extended to long wavelengths due to the presence of 'n.

However, in order to dope as much In as necessary to extend the sensitivity to long wavelengths and to have the necessary dark resistance for photographic work gloves, it is necessary to add Cu as an acceptor in accordance with the amount of In. This is the aforementioned Japanese Patent Application Publication No. 5
When a method such as that described in Publication No. 7-129825 is applied, as the amount of Cu increases, the electrophotographic photoreceptor produced using the resulting cadmium sulfide has a poor carrier injection property from the substrate. It tends to deteriorate, especially in the type with a three-layer structure in which an insulating layer is placed on the photoconductive layer.
There is a tendency for the dark potential to decrease and the sensitivity to decrease.

If only %cuit is decreased and the In amount is not decreased, the sensitivity will extend to longer wavelengths, but the optical memory will increase, resulting in cadmium sulfide having a low dark potential and a very low resistance.

Therefore, an object of the present invention is to provide a method for producing Cd8 which is an improvement on the above-mentioned method.

That is, the purpose of the present invention 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 sufficient dark potential. 20% by weight or more of a flux is mixed with the melting agent, and the melting point is 5%
After firing at a temperature higher than 0°C, 0.5 N to 5. It is characterized by surface treatment in ON sulfuric acid and then re-firing.

The cadmium sulfide produced according to the present invention has high crystallinity, and when its shape is observed using an erotaxis type electronic facial 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, especially from 800 to 35 Qnrri.

In the present invention, the concentration of sulfuric acid used for surface treatment of valorized cadmium after firing is 0.5N to 5.0N. 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 are achieved in a relatively short time. However, if the concentration is 0.5N or less, even if the treatment is carried out for a long time, the effect will be small and the manufacturing efficiency will be poor.However, treatment with a concentration of 5N or more is not suitable because the sensitivity tends to decrease. The minimum amount of indium required to have sensitivity on the long wavelength side is 5XlO mol per 1 mol of cadmium sulfide produced, and the maximum amount is 30xl to satisfy the dark resistance for electrophotography.
It is O mole.

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. CdS
As the copper compound to be added, copper chloride, sulfide, sulfide, etc. are used, and copper chloride and abrasive steel 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 1 x 10" to 15 x 1 per mole of cadmium sulfide.
0' mole, especially 3×10” to 10×IO mole is required.

The flux used in the present invention is a flux commonly used when diffusing an activator into CdS, and includes CdCt,
ZnClt, KCI, NaCl, N1(4
CI! , Cd50. It is a mixture of one or several of these in an appropriate ratio. A preferred example of a mixture of cac72 and an alkali metal chloride is a mixture of cac72 and an alkali metal chloride. As an alkali metal chloride, Na
C7! and KCJ are representative examples. The content of the alkali metal chloride in the entire flux is preferably 90 mol % or less and io mol % or more.

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. However, if the firing is performed at a temperature less 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 flux added to CdS is preferably 65% or less from the viewpoint of yield.

The cadmium sulfide thus calcined is treated with sulfuric acid according to the present invention and then further calcined. This re-baking process further stabilizes the electrostatic contrast of the formed image when used on a photoreceptor. Re-firing is preferably carried out at a temperature of 500°C or lower, particularly 400-450°C.

Example 1 Cadmilla sulfate A 1 mole, copper sulfate 6 X 10
mole.

The temperature of the 3N sulfuric acid acidic water bath G21 containing indium sulfate A 10 X I Q-'mo/e was maintained at 60° C., and hydrogen sulfide was passed through the bath at a flow rate of 300 cc/excitation for 95 minutes. After washing the cadmium sulfide produced in this reaction with pure water to remove excess impurities present on the particle surface,
It was dried overnight at a temperature of 0°C.

edch for this cadmium sulfide 1oor, 201
30f of N, aCl were added, mixed well, and then filled in a quartz crucible and fired at 530°C for 30 minutes (note that C
dC1! From the phase diagram, the melting point of the mixed flux of CdCl2-2NaCl corresponds to 426°C, which is the melting point of CdCl2-2NaCl. ). The CdS thus obtained was placed in a 4N sulfuric acid aqueous solution and left for 5 hours with stirring. After washing with pure water and removing sulfuric acid, it was dried at a temperature of 60°C.

The cadmium sulfide thus obtained was heated to 1
Refired for an hour. After re-baking, it was washed with water, residual ions were removed using an ion exchange resin, and dried. After dispersing this Cd8 in a vinyl chloride/vinyl acetate copolymer, it was coated on an aluminum base to a thickness of 40 μm and dried. A 15 μm thick polyester film was pasted onto the photoreceptor, resulting in a three-layered photoreceptor. When obtained, the surface was extremely smooth. When this photoreceptor was subjected to a related electrophotographic process of primary charging, then photoimage exposure AC static elimination, and then full exposure, a good quality image based on sufficient electrostatic contrast and sufficient sensitivity was obtained. In particular, the resolution was more than 6 lines per frame, and sharp images were obtained. Furthermore, after leaving this photoreceptor in a high temperature and humid environment with a temperature of 35°C and a humidity of 8556' for 24 hours, image generation 7 was performed again in a copying machine. As a result, no decrease in contrast between bright and dark areas was observed, and a good quality image was obtained. was gotten.

Example 2 Cadmium sulfate 1 mol! Elytic cadmium was precipitated from a 3N sulfuric acid water bath solution containing E by the same method as in Example 1. Copper and indium per 1 mole of cadmium sulfide are each 4 X I per 100 mol of cadmium sulfide.
Copper monosulfate and indium sulfate were added so as to contain O-4+ 10 X I O'moJe, and after homogeneous mixing by a wet method, the mixture was dried at a temperature of 100°C. Next, CdC/
140? A mixed flux consisting of 1 (l) of NaCe was mixed in and thoroughly mixed, followed by firing at 500°C for 30 minutes.

The cadmium sulfide thus prepared was added to an aqueous IN sulfuric acid solution and left overnight (14 hours) with stirring. After washing with water and passing through 9 mouths and drying, the CdS was re-fired in the same manner as in Example 1, and when the obtained CdS was made into a photoreceptor and evaluated, the same good results as in Example 1 were obtained.

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

That is, a glass plate 3 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 source 6 via a relay switch 5. For measurement, close the relay switch 5 for 0.2 seconds and apply the desired voltage (Va) to 0.
After being left in an oven for 2 seconds, the sample was irradiated with light for 02 seconds, and the voltage change (Vp) at that time was measured with the metal plate 7 at the same voltage as the photoreceptor and a surface potential of 1.8. Note that vp is the voltage applied to the photoconductive layer.

4. As a pre-exposure, white light from the halogen lamp 1 was irradiated in 02 directions using the shutter 2, and after leaving it for 02111oc,
After applying va and leaving it at 0.2SeC, light was applied again for 0.2 seconds.
The voltage change vp' at that time was measured.

Va -2000V To LJ'c Case No Vp Oyo U
Measure the value of Vp when Vp' i fcVa is +2000 V, and calculate vp-V when applying va mini-2000.
The size of the optical memory can be determined from p'.

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 direct current source 6 via a relay switch 5. The measurement was performed using white light from a halogen lamp 1 as a pre-exposure using shutter 2 at 0.2
After irradiating the See and leaving the 02 type, relay switch 5
A high voltage (Va) is applied to the photoreceptor for 0.2 seconds,
After leaving it for 0.2 seconds and irradiating it with sufficiently strong light for 0.2 seconds, the 'voltage (va') on the photoreceptor surface (i.e., the insulating layer surface)
) was measured using a metal plate 7 at the same voltage as the photoreceptor and a surface potentiometer 8. Applied voltage to the photoconductive layer when applying high voltage (
Vp) can be calculated by Va-Va' Renault-r, Vl)
Ka600 VK Null Va (hereinafter referred to as Va-60°)
Sensitivity was measured using the following method.

That is, the measurement light (
8000 m). After leaving it for 0.2 seconds after irradiation with light, irradiate it with 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.■a, □1o applied. Since the voltage (Vp') applied to the photoconductive layer during simultaneous measurement light irradiation can be calculated from Va,...-■3'', the necessary measurement light exposure t(E) to make vp' 300■ is This is half exposure jt (By2), and the sensitivity of the photoreceptor can be displayed.

From the table, for the photoreceptor treated with sulfuric acid, Vp-Vp
' difference 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. Also, vp
′ is larger, which indicates that the resistance type is higher than that of the comparative example, and the potential is changed in the direction that can be obtained. Both optical memory and sensitivity are improved compared to the comparative example.

[Brief explanation of the drawing]

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 direct current "source of evil," 7. Metal plate, 8. Surface electrometer,
9...Photoreceptor. Applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) Cadmium sulfide containing 5 to 30 XIO moles of indium per mole is mixed with 20% by weight or more of a flux, and the resulting sulfide is fired at a temperature 50 or more higher than the melting point of the flux. Cadmium from 0.5N to 5. A method for producing photoconductive cadmium sulfide, which comprises surface treatment with ON sulfuric acid and further firing.