JPS59148063A - Photoconductive cadmium sulfide particles - Google Patents

Abstract

PURPOSE:To obtain a photosensitivie body prevented from remarkable deterioration of sensitivity and stable in characteristics by using photoconductive CdS particles specified in the max. to min. particle diameter ratio,, the distribution of particle diameter, and the contents of copper and indium. CONSTITUTION:The photoconductive CdS particles to be used has a max. to min. diameter ratio in one particle is <=3, (a) in the distribution of particle diameter the most number group is 1.5-2.5mum, and its number is <=50% of the total number, and (b) on the basis of the number of said group as 100%, the distribution is as follow: a group of <=1mum is <=15%, that of 1.0-1.5mum is 10-40%, that of 2.5-3mum is 10-50%, that of 3-3.5mum is 5-30%, that of 3.5- 4.0 and 4.0-4.5mum are each <=20%, and that of >=4.5mum is <=15%. A content of copper is 0.5-2.5X 10<-4> mole per mole of CdS, and a content of indium is 0.1- 2.5X10<-4> mole, and thier content ratio is 0.2 < indium/copper <1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermophotographic material for electrophotography, particularly a main constituent material of a photosensitive layer of a three-layer electrophotographic photosensitive material whose basic composition is an insulating photosensitive layer and an electrode layer. AZ relates to photoconductive cadmium sulfide particles.

Cadmium sulfide particles, which have traditionally been considered problematic, have a number of problems, and the main causes are the shape and diameter distribution of the particles. That is, conventional cadmium sulfide particles have an anisotropic and extremely complex shape, so they have a random particle size distribution and a large specific surface area. Therefore, it was easily influenced by the environment, etc., and its properties were unstable when used as a photoreceptor.

Although there are conventional examples of using particles to reduce the influence of the environment on the particle surface, when these particles are used, the sensitivity of the photoreceptor is significant. The present invention provides cadmium sulfide particles for electrophotography. The present invention can provide an electrophotographic photoreceptor that exhibits extremely stable characteristics when used as a photoreceptor without causing a significant decrease in sensitivity.

As a result of various studies, the present inventor has determined that the following is necessary in order to resolve the above-mentioned drawbacks.

That is, many of the causes of unstable photoreceptor characteristics, such as a decrease in charge retention due to high humidity, are related to defects on the surface of particles and/or in the vicinity of the surface. Therefore, in order to prevent this, it is effective to reduce the surface area of the particles and to protect the surface by coating it with an appropriate material. However, in the latter case, it is desirable to minimize the thickness or amount of the layer so as not to reduce sensitivity.

In order to achieve the above conditions, the cadmium sulfide particle shape and its particle size distribution may be as follows.

(1) In order to reduce the surface area and uniformly adhere to the substrate, the shape of the particles is preferably isotropic, that is, close to a sphere. However, many particles become isotropic particles (
Excluded are cases where secondary particles are created. In the present invention, the standard of isotropy is expressed as the ratio of the maximum and minimum diameters of one particle, and in this case, for most particles, this ratio is 3.
It is 0 or less, preferably 2.0 or less, particularly preferably 1.5 or less.

(2) The basic method for forming CdS particles on the photosensitive layer in the photoreceptor is to mix them with the substrate and/or the binder before coating, but in this case, the movement of charges within the photosensitive layer is Smoothness leads to stable characteristics. To this end, it is desirable that the particles be uniformly and evenly distributed within the photosensitive layer. To achieve this, it is not sufficient that the particle size is isotropic, but that the particle size has a regular distribution and a narrow width.

(3) The particles are mainly small in size compared to the float of the photosensitive layer and do not cause a significant decrease in sensitivity, and larger particles are also included for sensitization.

According to the study of the present inventor, particles whose particle size distribution basically follows a normal distribution or a lognormal distribution are suitable, and in that case, the arithmetic mean particle size is 1.5 to 3.0 microns, preferably It was preferable that the diameter was between 1.5 and 2.5 microns, with a standard deviation of 2 microns, particularly preferably 1.5 microns or less. To be more specific, 1.5 to 2.5
The maximum number of particles is in the micron range, and the number is 50% or less of the total number, preferably 40% or less.

In addition, the particle size distribution is 1.0 to 1.5 microns, preferably 15% or less, preferably 10% or less, and 1.0 to 1.5 microns to 10 to 10%, based on the number of 1.5 to 2.5 micron particles. 40% preferably 10
~30% Less than 2.5-3 microns ~10-50% Preferably 25-35 microns Preferably 10-20% Less than 3.5-4 microns and 4-4.5 microns 20% or less Preferably 5-35% 204 4.5 microns or less - 1-15% or less, preferably 10% or less.

Cadmium sulfide, which satisfies the above conditions, has a significantly smaller specific surface area than conventional cadmium sulfides, which reduces the number of donor-type defects present near the surface, leaving a problem of decreased sensitivity.

Therefore, in the present invention, indium is added as an impurity to serve as a donor. However, as a photosensitive material for electrophotography, there is a limit to expanding the spectral sensitivity to long wavelengths, so the amount of indium added is preferably 0.2 to 3.0 x 10' moles per mole of cadmium sulfide. , especially 0.5
~2.5 x 10' mole is suitable. At this time, there are suitable values for the amount of copper to be added as an acceptor and the content ratio of indium and copper for the donor type according to surface defects and indium, l/(1). The amount of is 0
,2 to 3.0 x 10-4 mol is desirable, especially 0.5 to 3.0
2.5×10 −4 mol is preferred, and the ratio is preferably 0.2 (<1).

By using the cadmium sulfide of the present invention, a highly stable electrophotographic photoreceptor can be obtained without causing a significant decrease in sensitivity.

In the present invention, as a method for producing cadmium sulfide, cadmium sulfide obtained by a normal wet reaction method is added to
0wt'X flux, for example Nl], CI, CdCl2 powder, is fired in air at a temperature above the melting point of the flux, for example 500°C or above, and then further heated with air to further reduce surface defects. Methods such as performing heat treatment inside are being discussed.

In order to use this as a photoreceptor, the CdS particles must be found υ,
According to the example wet reaction method, a suitable resin gold is applied to CdS raw powder to which Ctt and In have been added as impurities, and cdC122 is applied at a hit ratio.
0i, 30% NaCl was mixed as a flux, and after thorough mixing, it was fired at 530°C for 30 minutes, and then reheated at 450°C for 60 minutes.
Bake for a minute. When the obtained CdS particles were observed using a scanning electron microscope, it was found that the individual particles were isotropic and the ratio of the maximum diameter to the minimum diameter was approximately 2.5. When measured on a photocopy, the particle size distribution shown in the attached figure was obtained.

This distribution follows a log-normal distribution, and the average particle size is 2.
0 micron, and the product moment deviation was 0.80 micron. An NP photosensitive drum (three-layer structure) was produced using this CdS. The photosensitive layer thickness was 40 microns. NP the drum
A secondary test was conducted using a copying machine (NP200J) equivalent to 10,000 copies, and the retention rate of the voltage potential was over 90π, indicating that the sensation was
Schiff) It:r: showed good characteristics of within 10%.

In addition, the porosity of the photosensitive layer was measured to be 35 to 40 koto, which was 60 to 80% lower than that of conventional CdS, indicating that the light filling of the 668 particles in the photosensitive layer was improved. .

At this time, the added Cu and In were 1 mol of CdS and 2.0 mol of CdS. Although the value was UXlo-'molar, sufficient sensitivity for use in an actual machine was obtained without impairing the reproducibility of red originals.

[Brief explanation of the drawing]

Claims (1)

[Claims] (1) In photoconductive cadmium sulfide powder, which is the main constituent material of the photosensitive layer in an electrophotographic photoreceptor, (a)
The particle shape is such that the ratio of the maximum diameter to the minimum diameter within one particle is 3 or less, and (b) the particle size in the particle size distribution is (a) the maximum number is between 1.5 and 2.5 microns. (b) When the number of particles of 1.5 to 2.5 microns is 100X, the number of particles of 1 micron or less is 15% or less, 1
．． 0-1.5 microns 10-40%, 2.5-3 microns 10-50%, 3-3.5 microns 5-30%
, 3.5-4 and 4.0-4.5 microns are respectively 2
0% or less, 4.5μ or more has a distribution of 15% or less, (
C) The amount of copper contained is 1 mole of cadmium sulfide, 0.5 to 2.5 x 10 mole, and 0.5 x 10 mole of indium.
Photoconductive cadmium sulfide particles having a molecular weight of 1 to 2.5 x 10' moles, and characterized in that: