JPS603176B2 - Method for producing photoconductive powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a photoconductive powder used in a photoconductive layer for electrophotography, and more specifically, a process for producing agglomerates of photoconductive cadmium compound powder produced during a sintering process. It concerns an efficient method for dissolving individual particles.

Photoreceptors for electrophotography include zinc sulfide, zinc telluride, zinc selenide, cadmium sulfide, cadmium selenide, cadmium telluride, lead sulfide, lead selenide, selenium telluride,
A photoconductive crystalline powder selected from among these solid ports is dispersed in a binder, and this is coated on the electrode plate to a thickness of several tens of microns, and then a transparent highly insulating layer is applied on top of it. It is manufactured by laminating bodies. The photoconductive substance powder used in this process is an activator that gives high photosensitivity to the highly refined raw material powder, and provides electrical compensation when the activator is diffused into the crystal lattice. It is usually produced by adding a new and old skin-melting agent and firing at a high temperature in an inert gas or specific active gas atmosphere. By the way, the photoconductive material obtained by firing in this way phosphorsizes and becomes lump-like due to the presence of the brooding agent, so before it is transferred to the subsequent classification and water washing process, it is subjected to a decomposition treatment to separate individual particles. However, photoconductive substance powder is unstable and easily distorted by external mechanical forces, so photoconductive powder that has been subjected to severe vibrations and shocks cannot be used for electrophotography. When applied to a photoreceptor, the electrostatic contrast is significantly lowered than when using a photoreceptor that is not subjected to severe external mechanical forces. Therefore, in order to disintegrate the photoconductive material nodules into individual particles, the photoconductive powder nodules are mixed with an appropriate amount of water, placed in a processing container made of stainless steel or porcelain, and then gently vibrated. However, this method has the drawback that disintegration progresses slowly and requires a long treatment time, usually 2 to 4 hours. If the vibration is increased, the processing time will be shortened, but this will be accompanied by a decrease in properties and a decrease in yield. The object of the present invention is to eliminate the drawbacks of such conventional methods and to provide a method for dissolving agglomerates of photoconductive material into individual particles in a short time and without impairing electrophotographic properties. shall be.

The method of the present invention includes the steps of adding a fluxing agent and an activator to photoconductive cadmium compound particles and firing them to form a crystallized cadmium compound nodule, and immersing the nodule in an acid solution to form a solid cadmium compound nodule. This process includes a process of corroding and dissolving the grain boundaries and decomposing each particle, and a process of classifying the thus decomposed particles, which makes it possible to separate each particle without damaging its properties in any way. can.

The photoconductive powder that can be treated by the method of the present invention is a photoconductive cadmium compound whose grain boundaries can be corroded and dissolved by an acid solution when agglomerated. Examples of such powder include cadmium sulfide, selenium Examples include cadmium oxide and cadmium telluride. Acid solutions used in the method of the present invention include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, cyanide, tartaric acid, picric acid, oxalic acid,
Examples include aqueous solutions of organic acids such as maleic acid, succinic acid, citric acid, malonic acid, and salicylic acid.

These acids may be used alone or in combination of two or more. The concentration of these acid solutions is 0.05~
5 normal range is preferred. Concentrations higher than this are undesirable because they result in a decrease in fractionation and adversely affect electrophotographic properties, while concentrations lower than this are undesirable because corrosion takes time. The treatment time in the method of the present invention depends on the type of photoconductive substance, the firing conditions, the type of acid used, its concentration, etc., but a range of several minutes to several tens of minutes is sufficient.

The treatment temperature is not particularly limited and any temperature between 0°C and 100°C can be used, but the treatment is usually carried out at room temperature. In this way, immersion in the acid solution preferentially corrodes the grain boundaries, which are the areas where lattice defects are concentrated in the nodules, and by applying gentle vibration, each particle is easily decomposed and the particles are uniform. A suspension is formed.

After removing coarse particles from this suspension by a classification operation,
After removing the residual acid by washing with water and drying, the desired photoconductive material powder can be obtained in high yield. The method of the present invention has the advantage that agglomerates of scale particles can be disintegrated to obtain a high-quality powder in a very short time without the need for special equipment and without damaging the properties of the photoconducting turtle substance. There is.

Next, the present invention will be explained in more detail with reference to Examples. Example 1 4 parts by weight of potassium chloride to 10 parts by weight of cadmium sulfide,
0.0 parts by weight of chloride steel, 0.02 parts by weight of sulfur powder and 10 parts by weight of water were added, dried under reduced pressure at 80°C for 4 hours, and then fired at 70°C and 0°C for 4 hours in a nitrogen gas atmosphere. A striped cadmium sulfide was prepared.

The pseudo-cadmium sulfide 200 particles thus obtained were 0.
After adding 500 g of an aqueous solution of indicative nitric acid and stirring for 10 minutes at 70 ml, the mixture was passed through a 350 mesh sieve to remove extremely large particles. The portion that passed through this sieve was thoroughly washed with deionized water to remove residual acid and halogen compounds, and then dried. In this way, photoconductive cadmium sulfide powder could be obtained with a yield of 93.5%. Next, 8 parts by weight of vinyl acetate resin was added as a binder to 100 parts by weight of the photoconductive cadmium sulfide powder obtained, and this was dispersed in 10 parts by weight of an isotropic mixture of methyl ethyl ketone and acetone.

This mixture was coated on an aluminum substrate to a thickness of approximately 60 mm, and a polyethylene terephthalate film having a thickness of approximately 16 mm was laminated thereon to produce a three-layer electrophotographic photoreceptor. Here, as a comparative example, 100 parts by weight of pure water was added to 10 parts by weight of the scale-stripe cadmium sulfide obtained by firing in the above example, and the mixture was placed in a Shiji container. A gentle vibration was applied during the insect time.

Photoconductive cadmium sulfide powder was thus obtained with a yield of 86%. More than 10% of the loss at this time was due to the amount remaining on the sieve. Next, an electrophotographic photoreceptor having a three-layer structure was prepared in the same manner as in the above example, and this was used as a comparative product. The two types of electrophotographic photoreceptors obtained in this way were first heated at 16,000 V in the first step.
Then, as a secondary step, a -6000V corona discharge is applied at the same time as exposure, and as a tertiary step, after performing backlight to uniformly irradiate the entire surface, the surface potential of the photoreceptor is was measured.

Next, the photoreceptor was subjected to 16,000y as a first step.
Then, as a secondary step, corona discharge of -6000V is performed without exposure, and as a tertiary step, post-exposure is performed to uniformly irradiate the entire surface, followed by photo-sensitization. The surface potential of the body was measured. The difference in surface potential determined by the above method is defined as the electrostatic contrast, and FIG. 1 shows the relationship between the electrostatic contrast and the exposure amount obtained by varying the exposure amount in the secondary step. In the figure, the horizontal axis represents the amount of light irradiation Lx applied to the surface of the photosensitive plate in the secondary process. sec, and the vertical axis is electrostatic contrast. Further, curve A shows the relationship between the exposure amount and electrostatic contrast for the photoreceptor obtained in Example 1, and curve B shows the results for the photoreceptor obtained in Comparative Example. As is clear from the figure, the photoreceptor obtained in this example showed a significant increase in electrostatic contrast compared to that in the comparative example. Example 2 A pure water aqueous solution containing 200 g of precipitated cadmium sulfide and 9 g of oxalic acid obtained under the firing conditions of Example 1 was heated to 500 g.
and stirred for 15 minutes at room temperature.

Thereafter, by processing in the same manner as in Example 1, photoconductive cadmium sulfide powder could be obtained with a yield of 92.5%. Next, an electrophotographic photoreceptor having a three-layer structure was prepared in the same manner as in Example 1, and the electrostatic contrast was measured. 1200V for sec
, ILx. At a low illuminance of 350 V, an extremely excellent electrostatic contrast could be obtained. Example 3 10 parts by weight of cadmium sulfide, 1 part by weight of cadmium chloride, 0.01 part by weight of steel chloride, 0.01 part by weight of sulfur, and 1 part by weight of water.
0 parts by weight were added and the mixture was vacuum dried at 80 qo and then calcined for 28 minutes at 570 qo.

To 200 μl of the condensed cadmium sulfide thus obtained were added 500 μl of pure water containing 16 μl of tartaric acid, and the mixture was stirred at room temperature for 20 minutes. Thereafter, by processing in the same manner as in Example 1, photoconductive cadmium sulfide powder could be obtained with a yield of 93%. Next, an electrophotographic photoreceptor having a three-layer structure was prepared in exactly the same manner as in Example 1, and the surface potential of the photoreceptor was measured.

As a result, exposure Toyoyama x. 125 in sec
It shows an electrostatic contrast of 0V and ILx. At an exposure dose of sec, an electrostatic contrast of 30 sec was obtained. Example 4 The cadmium sulfide obtained under the firing conditions of Example 3 was heated to 200 ml and 0.00 ml. Added 500ml of hydrochloric acid solution and stirred at room temperature for 15 minutes.

Thereafter, an electrophotographic photoreceptor having a three-layer structure was prepared in the same manner as in Example 1, and the surface potential of the photoreceptor was measured to determine the electrostatic contrast. As a result, the exposure amount in the secondary process was x. sec shows 1300V, ILx. An electrostatic contrast of 280 V was obtained with an exposure amount of sec.

As described above, according to the present invention, in order to disintegrate the photoconductive powder that has become agglomerated by firing into a uniform powder, the processing time is reduced to 1/2 compared to the conventional method. When the photoconductive powder obtained by the present invention is applied to electrophotography, the photoconductive powder obtained by the present invention can be shortened to 1 Bok, and it is possible to stably obtain a high yield. Therefore, a static latent image with extremely excellent electrostatic contrast can be formed.

The present invention can also be applied to photoconductive substance powders of cadmium selenide, cadmium telluride, and solid solutions thereof, which are examples of photoconductive substances other than cadmium sulfide, and can achieve the same effects as in each of the above embodiments. It is something to play.

Brief Description of the Drawings The drawings show an electrophotographic photoreceptor formed using photoconductive cadmium sulfide powder obtained by the method of the present invention and a photoconductor formed using photoconductive cadmium sulfide powder obtained by the conventional method. 2 is a graph showing the electrophotographic characteristics of the electrophotographic photoreceptor.

Claims (1)

[Claims] 1. A step of adding a flux and an activator to photoconductive cadmium compound particles and firing them to form a sintered cadmium compound nodule, and immersing the nodule in an acid solution to form cadmium compound particles. 1. A method for producing a photoconductive powder, comprising a step of corroding and dissolving intergranular boundaries to disintegrate each particle, and a step of classifying the thus disaggregated particles. 2. The method according to claim 1, wherein the acid solution has a concentration of 0.05 to 5 normal. 3. The method according to claim 2, wherein the acid solution is an inorganic acid aqueous solution. 4. The method according to claim 2, wherein the acid solution is an organic acid aqueous solution.