JPS5820717A - Preparation of photo-conductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To prepare a photo-conductive CdS having extremely high crystallinity, and excellent image extinction because of the absence of the agglomerated particles, by mixing CdS having a bulk density of within a specific range with more than specific amount of a flux, and calcining the mixture at a temperature higher than the melting point of the flux by more than a specific level. CONSTITUTION:CdS having a bulk density of 1.5-2.5ml/g, especially 1.6- 2.1ml/g (JIS K-5101) is used as the starting material. The CdS having the above bulk density can be prepared by reacting CdSO4 with H2S keeping the normality of the acid in the reaction mixture to 2.5-3N and setting the precipitation temperature at 60-70 deg.C. The CdS is mixed with more than 20wt% flux such as CdCl2, ZnCl2, KCl, etc., and calcined at a temperature higher than the melting point of the flux by >=50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cadmium sulfide for electrophotography, and particularly to a method for producing cadmium sulfide for producing highly crystalline and uniform single particles. It is.

The most common method for producing photoconductive cadmium sulfide (OaS), which is typically used in electrophotographic materials, is to sulfide water-soluble salts of cadmium, such as cadmium sulfate and cadmium chloride, with hydrogen sulfide. A precipitate of cadmium particles is obtained, and then the cadmium sulfide particles are calcined at a high temperature in order to dope the activator.

That is, photoconductive cadmium sulfide is produced by mixing cadmium sulfide particles with a halide such as 0uOj, , 0uSO,f@ as an activator or 0601@@@Zn0jB as a fluxing agent and firing them.
7 etc. Q However, in such conventional methods, the OaS produced through the calcination process has a large number of defects near the surface of the aaS at the time of precipitate formation.

This surface defect becomes a trap unit for photocarriers, so it increases the optical memory of the aaS, that is, slows down the photoresponse speed. Electrostatic contrast between bright and dark areas becomes insufficient.

In addition, the particle shape of OaS manufactured by the method described above consists of secondary particles, which are strong aggregates formed by particles aggregating together, and these secondary particles aggregate three-dimensionally. They vary in shape, such as those shaped like nodules, or aggregated two-dimensionally to form a flat plate, but some of them are large.
There are some that range from a few microns to several tens of tons of talin.

A photoreceptor made using OaS containing a large number of such coarse particles has a poor surface condition, resulting in an image that is extremely gasy and has insufficient resolution. In addition, in the case of a photoreceptor further provided with an insulating layer, the insulating layer's zero
This causes penetration into the 4B layer, making it difficult to obtain a good photoreceptor.

The present invention solves these drawbacks of the conventional methods, and has the following features: (1) high contrast images can be formed from the initial stage of image formation, (2) high sensitivity, and (
3) To provide a method for producing photoconductive cadmium sulfide having good properties such as uniform particle shape, good resolution due to single particles, and excellent coating properties. The main purpose is to

The method for producing cadmium sulfide (aaS) according to the present invention has a bulk value (Japanese Industrial Standard 1c-5101) of L 5 w
It is characterized by mixing cadmium sulfide of 1/g N2L 51 d/g with a fluxing agent of 20 weight class or more and firing at a temperature 50° C. or more higher than the melting point of the fluxing agent.

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. Therefore, cadmium sulfide produced through a firing process has extremely few crystal defects near its surface that can become trap units for optical carriers, and is dispersed in an electrophotographic resin binder and coated on a support to form a photoconductive layer. By creating a photosensitive plate and applying it to a high-speed copying machine by forming an insulating layer on it as necessary,
It is recognized that high electrostatic contrast can be obtained. In addition, since the sulfurized cadmium powder obtained by the present invention has a uniform particle shape and uniform particle size, the coated surface of the photoconductive layer formed is dense and smooth, resulting in very high quality images. is obtained.

Further, cadmium sulfide used as a starting material for producing the photoconductive cadmium sulfide of the present invention has a bulk value of 1.
5 dl g-5L garlic/g is used. The cadmium sulfide particles used as the starting material are secondary or tertiary agglomerated, but particles that have become coarse have a small concentration value and are not completely converted into single particles during the firing process. Only 1 surface defect, etc. that existed in the calcined cadmium sulfide remains.
The result is an optical memory.

On the other hand, if the bulk value is large, it is considered that the powder has little secondary or tertiary agglomeration, but if such cadmium sulfide with an excessively small particle size is used, it will not be manufactured through the firing process according to the present invention. When OaS was applied to high-speed copying machines, it was observed that the sensitivity tended to decrease. From these experimental results, the bulk value of the Od8 powder used in the present invention is 15o~L5
0 @J/g, particularly preferably 160-2. , lO
m/g.

How to conceal the value of the power of sulfuric acid,
There are several methods, but the concentration of acid in the precipitation reaction solution, the temperature of the precipitation reaction solution, etc. are generally well known. The bulk value used in the present invention is 150 N250 m/g (18 is, for example, oaso).

degree, and the precipitation temperature is 60~? It can be easily obtained by setting the temperature to 0°C.

The flux used in the present invention is a flux generally used when diffusing the activator into OaS, and is 0d01. +
Zn0j1KOI, Ha, 01,' 0dLF3
It is a mixture of one or several types such as 04 in an appropriate ratio. A suitable example of a mixture is oaol;
Examples of alkali metal chlorides include mixtures of chloride and alkali metal chloride. Representative examples of the alkali metal chloride include NaOj and KO/. The content of the alkali metal chloride in the entire flux is preferably 90 mol or less and 10 mol % or more.

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

If it is less than 20%, the OdS particles produced will be sintered and become coarse particles, the surface shape will be uneven, and the potential retention will be insufficient.
In addition, the result is a bad ODA that lacks resolution. In addition, when firing is performed at a temperature lower than 50° higher than the melting point of the flux, the OaS particles produced have a large particle size, poor resolution and coating properties, and The electrostatic contrast of the initially formed image will be low. In the production method of the present invention, the firing temperature is preferably 600"0 or less. Also, the amount of flux added to OdS is preferably 65% or less from the viewpoint of yield.

In the present invention, in order to further improve crystallinity,
The obtained aaS is further processed for the purpose of annealing.
It is also effective to add a step of firing at 400 to 500°C.

'J-''ill,, :1゜oaso
, is 1 shoulder and 0u80n is l x 1.0-'mole
The bulk of OaS (raw powder) obtained by aerating H and S gas into a solution containing 2.9 N of a, SO, was measured and was found to be 1.10 d/g. .ko (7)
0 (100g of 1B raw flour and 20g of 0104.
After adding 30 g of 1, the mixture was mixed well, placed in a quartz crucible, and fired at 630° C. for 30 minutes. (From the phase diagram, the melting point of the mixed flux of 0(104, and MhOl is 0 dOJ,
The general direction of the OaS obtained in this way is 100 arcs, and according to an electron micrograph at 10,000x magnification, the particle surface is very smooth and has a characteristic hexagonal crystal shape. It was observed that each particle was a single particle with a diameter of 2 to 5 microns.

After dispersing this aaS 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 pasted on the resulting photosensitive plate to form a three-layered photoreceptor. When obtained, the surface was very smooth. When we applied a high-speed electrophotographic process to this photosensitive plate, which included charging, photoimage exposure, AO static removal, and then full-surface exposure, high-quality images with sufficient electrostatic contrast and sufficient sensitivity were obtained. Ta.

Furthermore, this photosensitive plate was heated at a high temperature of 35°0 and a humidity of 85°.
After being left in a 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 nor decrease in sensitivity was observed, and a good quality image was obtained. Further, when this photoreceptor was left in a copying machine for 12 hours, the dark potential was measured, and the dark potential was 5007V for the first sheet and 510V for the 50th sheet, the difference being IOV. Further, the change in potential contrast measured at 5°C and 50°0 was as small as XOV.

Comparative Example 1 Although the aaS treated in Example 1 at a firing temperature of 450'O had a relatively smooth particle surface, according to electron microscope observation, in Example 1, a single particle was formed on the para putty. It was observed that the particles had become secondary particles with a size of 10 μm or more and a complicated shape while remaining secondary agglomerated with each other. When a photoreceptor having a three-layer structure was prepared using this 0d13 in the same manner as in Example 1, the coated surface of the photoconductive layer was defective. Therefore, when an image was produced using a copying machine in the same manner as in Example 1, the resolution was 4.
The number of books/m was below.

Furthermore, after leaving this photoreceptor in a copying machine for 12 hours, aa
When I measured the rkm level, the potential of the first sheet was 5oov and the potential of the 150th sheet was 450V, and the difference was 1507V.
There was also.

Comparative Example 2 In Example 1, 4 g of 0 dOj, N
OaS was produced in the same manner by adding 6 g of a0j. As a result of electron microscopic observation, the obtained OaS primary particles were not single particles, but several to several tens of particles aggregated to form secondary particles of more than ten micron particles, and the primary particles were It was observed that some portions were coarsened due to sintering.

In addition, as a result of producing a photoreceptor in the same manner as in Example 1,
The surface smoothness is poor due to coarsening of the primary particles or secondary agglomeration, the resolution of the formed image is less than 5 lines/U, the image quality is rough, and the dark potential of the first image is approximately 300.
It was as low as v.

Comparative Example 3 In Example 1&c, 2 g of oa at was added as a fluxing agent.
As a result of manufacturing OaS in the same manner by adding 3 g of sMac/, the resulting Oas Fi was sintered and could not be disassembled sufficiently in the cleaning process. According to electron microscopic observation, coarsening of particles due to sintering was observed. It was possible to use it for electronic photography.

Example 2 0dS0.1 mole and 0u80, α5 x 10
-' The normality of the solution containing the mole is (1) 40
N, (2) KI M.

(3) 2.95, (4) &5 M and (5) λ2N
When we measured the bulk of Ode raw powder obtained by passing H, 8 gas into a solution prepared with H, So, we found that (1)
- (5) respectively (1) αfu, (2) L60
, (3) L Flo.

(4) E40. (5) It was 2L95.

Hereinafter, using these five types of OdS, a firing process was performed under the same conditions as in Example 1 to obtain five types of OaS.

A photoreceptor was prepared using each adB in the same manner as in Example 1. Next, 2,000 copies were made using each photoreceptor in an atmosphere of normal temperature and humidity. After leaving each of the nine bales in the dark for 12 hours in the copying machine, copies were made in the same manner as in Example 1. I measured the potential change of the dark potential in the 1st and 50th pictures. In addition, the half-attenuation exposure of each photoconductor was determined in the same manner as in Example 1 using OaS, which was manufactured using Example S and Example IK and was 90 dB. Regarding the photoreceptor formed by
When I left it in the dark and measured the dark potential, the first sheet was 5oov, and the s and o sheets were round (500V).Furthermore, after copying 10,000 sheets under the above conditions, 6a
When the rk potential was measured, it was found that the 1st sheet was 4707V and the 50th sheet was 500V, and the fluctuation range of the dark potential was very small (for Example IK, 100V
The dark potential after copying 0 sheets was 4407 for the 1st sheet and 500 V for the 50th sheet).

Applicant: Canon Co., Ltd. ζ1. ship steel

Claims (1)

[Claims] L bulk value (-5101 according to Japanese Industrial Standards) is 15d1g~
A method for producing photoconductive cadmium sulfide, which comprises mixing 5 iaJ/g of cadmium sulfide with a fluxing agent of 20 weight or more and firing at a temperature 50° C. or more higher than the melting point of the fluxing agent.