JPS5820718A - Photo-conductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To prepare a photo-conductive CdS having low Cl content and rich in Cu, by mixing CdS with more than specific amount of a flux, subjecting the mixture to the primary calcination at a temperature higher than the melting point of the flux by more than a specific temperature, and then to the secondary calcination at a temperature lower than the first calcination temperature. CONSTITUTION:CdS is mixed with >=15wt% (especially 30-50%) flux, e.g. CdCl2, ZnCl2, KCl, etc. The mixture is subjected to the primary calcination at a temperature higher than the melting point of the flux by >=50 deg.C, preferably at <=600 deg.C, and then to the secondary calcination at a temperature lower than the primary calcination temperature for the annealing of the product. The photo- conductive CdS obtained by this process contains <=100ppm of Cl and 29+ or -16ppm of Cu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to cadmium sulfide for electrophotography, and particularly to cadmium sulfide that is highly crystalline and in a uniform single particle state.

- The most common method for making photoconductive cadmium sulfide (OaS) scissors, which is typically used as a photosensitive material, is as follows:
Hydrogen sulfide is applied to a water-soluble salt of cadmium such as sulfuric acid, cadmium chloride, etc. (to obtain a precipitate of cadmium sulfide particles, and then high-temperature calcination is performed to dope the cadmium sulfide particles with an activator. It's something you can get by doing.

On the other hand, photoconductive cadmium sulfide is produced by mixing cadmium sulfide particles with halides such as OuOtz, Cu80a, etc. as activators and halides such as 0dC1z, +ZrrO12, etc. as fluxing agents, and firing them.
However, in such conventional methods, the Cd8 produced through the calcination process becomes Cd8 when the precipitate is formed.
has many defects near its surface.

These surface defects become trap levels for photocarriers, thus increasing the optical memory of Cd8, i.e., slowing down the photoresponse arrest and further arresting the single-photon body created using such Cd8. When applied to a copying machine, the difference between bright and dark areas is t! Ipm contrast becomes insufficient.

In addition, the particle shape of Cd8 produced by the above method consists of secondary particles, which are soaked aggregates formed by aggregation of particles, and these secondary particles are three-dimensionally aggregated. They may be lump-like, or they may be two-dimensionally aggregated and plate-like.

There are various sizes, and some of them are as large as 10-odd microns to several tens of microns.

A photoreceptor made using Cd8 containing a large number of such coarse particles has a poor surface condition, and its unleaded image is extremely rough and has insufficient resolution. Furthermore, in the case of a photoconductor further provided with an insulating layer, the insulating layer may seep into the Cd8 layer, making it difficult to obtain a good photoconductor. Therefore, the present invention solves these conventional drawbacks, and includes (1) In! An image with island contrast can be formed from the early stage of image formation (2)
The particle shape of cadmium sulfide is uniform, and since it is a single particle, it has good resolution and also works on coating properties.
To provide a photoconductive cadmium sulfide which is not sensitive to temperature fluctuations and has good properties such as high electric retention rate and sensitivity.
) is mixed with cadmium sulfide and 15% or more of a flux, and heated at a temperature of 50°C or more above the melting point of the flux.
After the next firing, it is obtained by performing a second firing at a lower temperature than the first firing. Ot to 1 (10pp or less, Ou to 29±16pp
It is characterized by containing m.

The cadmium sulfide according to the present invention has high crystallinity, and shape observation using a scanning electron microscope shows that the particles are single particles that do not aggregate with each other and have a smooth surface.
). Therefore, cadmium sulfide produced through a firing process has extremely few crystal defects that become trap levels for optical carriers near the surface, and is dispersed in an electrophotographic & fat binder and coated on a support. Create a storm layer,
Furthermore, it is suggested that a high electrostatic contrast can be obtained by forming a photosensitive plate by forming an insulating layer thereon as required and applying it to a high-speed copying machine. In addition, since the cadmium sulfide powder obtained according to the present invention has a uniform particle shape and a uniform particle size, the surface of the light guiding layer produced is dense and smooth, resulting in very high quality images. That's what you get.

The flux used in the present invention is a flux commonly used when diffusing an activator into OdS, and includes CdC4z, CdC4z,
Zn0t2, KOL, Na0t,' N
A mixture of one or several types of H4Cd, '0d804, etc. in an appropriate ratio is also σ. Preferred examples of the alkali metal chloride used in combination include a mixture of caclg and an alkali metal chloride;
Na0j and MCI are representative. The content of the alkali metal chloride in the entire flux is 90 mol% or more, preferably 10 mol% or more.

According to j) of the present invention, the flux is preferably 20% or more, preferably 30 to 50%. If it is more than 20%, the Cd8 particles produced will be sintered and become coarse particles, the surface shape will be uneven, the potential retention will not be sufficient, and the resolution will be poor (+tiS [7fru- In addition, if the firing is performed at a temperature that is less than 50°C higher than the melting point of the flux, the Cd8 particles produced will have a large particle size and have poor resolution and coatability. The electrostatic contrast of the resulting image will be low.The primary firing temperature is 600℃.
C or lower is suitable. Further, from the viewpoint of yield, the amount of addition of the flux to Cd8 is preferably 65% or less.

In order to further improve the crystallinity, the secondary firing temperature for the purpose of annealing the obtained Cd8 is lower than the primary firing temperature.The hexagonal degree of Cd8 according to the present invention is 90% or more, sometimes 95%.
% or more is suitable. Further, since the crystallinity of Cd8 according to the present invention becomes extremely high due to the firing treatment, the hexity of the raw material CaS itself may be 50% or more.

In addition, in conventional Cd8 with low crystallinity, even without adding C) or In, which acts as a donor impurity, there are 1° or more due to lattice defects, etc., and if left as is, light attenuation is slow and dark resistance is low. It was in a low state and not suitable for electrophotography.

Therefore, a measure has been taken to electrically compensate for this by adding Ou or Ag as an acceptor impurity in multiple bolts.

Since the present invention (jd8) has high crystallinity as mentioned above, there are extremely few donors due to defects, etc., and the content of Cu as an acceptor impurity is 29 ± 16 pp+n, which is about - orders of magnitude lower than that of the conventional system. Particularly preferably, it is 16 to 35 ppm. If the content is less than 1, the durability of the photoreceptor for repeated use and tφ will decrease due to the reason that the above-mentioned damage repair is thought to be insufficient. If the temperature exceeds 541, the infection rate rapidly decreases and the 8i degree characteristic also decreases by 1d].The cause of this is probably the segregation of copper sulfide, which is a p-type semiconductor, on the powder surface.Also, impurities in the donor tights It is also important to control certain Ct starvation.In this case, at is not actively added as an activator, but is a contamination during the production of the raw material Od8 or a flux during calcination. In the present invention, the amount of chloride is 1 (1) during the second firing.
loppm or less is particularly preferably 50 pl·m or less, and if the value is greater than that, the light attenuation rate is slow <iL, which is not preferable.

Example 1 0d804 sulfur m r'tr solution with divine concentration 0u
804 was added to precipitate OdS containing Ou at various concentrations through Hz & gas. 0dO4 for this Cd8! 2
0g and 311g of NaCt were added, mixed well, placed in a quartz crucible, and fired at 530°C for 30 minutes.

(In addition, the melting point number j of the mixed flux of 0dC7-2 and Na01
1 From the phase diagram, the melting point of 0dOt2 ・2NaC/- is 4
The temperature of the Cd8 thus obtained is 95 to 100%, and according to an electron micrograph at 10,000x magnification, the particle surface is very smooth and has the characteristic of hexagonal M1 shape. It was observed that each particle was a single particle with a diameter of 2 to 5 microns. The CZ content was 30 ppm or more, and the Cu content was 5 to 11 Oppm.

The fired CdS was thoroughly washed with water, thoroughly stirred together with the cationic and anionic exchange resins, and dried in a deionized oven at 70"O for 12 hours.

(A quartz crucible was filled with highly calcined CdS, annealed at 450°C for 1 hour, then washed with water and deionized at 70°C.
Dry for hr.

This Cd84i was dispersed in a cyclized hynyl/vinyl acetate copolymer, then coated on an aluminum substrate to a thickness of 40μ and dried.A 15μ thick υ) polyester film was attached to the resulting photosensitive plate to form a three-layered photosensitive plate. When the body was obtained, the surface was very smooth. As a result of measuring the exposure capacity, durable potential retention rate, and moisture absorption potential retention rate of this photoconductor, the durable potential retention rate was reduced to 0, which differs depending on the Cu content, as shown in the first example. Applying a primary charge to the plate, then optical image blood light AC static neutralization, and then applying a high-speed electronic transfer process of whole blood light to the dark level of the first light when taking 2001) sheets of cohes. The 2000th copy of J, the ratio of dark potential of - is 'a' + C.
g & wet potential retention rate is when the photoreceptor is heated at 30°C and the density is 90°C.
% high temperature and high humidity for 24 hours, and as a result of exposing the flesh image in a copying machine, the first copy's dar
This is the ratio of the 1000th dark [place] to the kII 1st place.

Example 2 Cd8 with Cu content of 10 (0 dct24 in Ig)
1grN@O7-9gr was thoroughly mixed and packed in a quartz crucible, and the same experiment as in Example 1 was conducted. The result was as shown in Figure 2.

Comparative Example Among the conditions of Example 2, the primary firing temperature was changed from 530°C to 450°C.
Cd8 with 190 ppm of ct miya'44'k was prepared (Ou is 22 ppu+). ) approximately 1.5 times as large.

The potential of the photocopying machine was lowered by 20%.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing changes in the durable potential retention rate, g&wet potential retention weight, and half-attenuation light application amount of the photoreceptor with respect to the Cu content in CdS, respectively.

Claims (1)

[Claims] 1. A product obtained by mixing cadmium sulfide with a flux of 15% by weight or more and firing at a temperature of 50°C or more higher than the melting point of the flux, followed by secondary firing at a temperature lower than the primary firing. A photoconductive cadmium sulfide characterized by containing 100 PPm or less of aZ and 29±16 PPm of Ou.