JPS58208137A - Manufacture of photoconductive cadmium sulfide - Google Patents

Abstract

PURPOSE:To obtain CdS having more favorable properties as fine particles and more favorable photoconductive characteristics, by heating a mixture of CdS with a flux to a specified temp. below the m.p. of the flux before calcination. CONSTITUTION:When a mixture of CdS with >=20wt% flux basing on the amount of the CdS is put in a calcining vessel such as a quartz crucible and calcined, the mixture is held at a certain uniform temp. above 100 deg.C for a while before the flux is melted. All of water contained in the CdS and flux is evaporated, and the internal temp. of the crucible is made uniform. The mixture is then calcined by uniform heating to a temp. >=50 deg.C above the m.p. of the flux. Since uniform calcination is carried out at any place in the crucible, reproducibility in the shape and electric characteristics of particles can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing photoconductive cadmium sulfide, and in particular to a method for producing cadmium sulfide sulfide for producing highly crystalline and uniform single particles. It's a good thing.

The most common method for producing light-guiding cadmium sulfide (CdS), which is typically used as an electrophotographic photosensitive material, is as follows:
It is obtained by reacting hydrogen sulfide with an aqueous cadmium salt such as cadmium sulfate or cadmium chloride to precipitate cadmium sulfide particles, and then firing at a high temperature to dope the cadmium sulfide particles with an activator.

That is, photoconductive cadmium sulfide contains cadmium sulfide, CuCl2. By mixing CuSO4, etc., or a halogenide such as CdC6z J ZnCJz as a flux and firing, Cu, Cj! Generally, cadmium sulfide is doped with cadmium sulfide.

However, in such conventional methods, the CdS produced through the firing process has a large number of defects near the surface of the CdS at the time of precipitate formation. This surface defect interferes with the trap level of photocarriers, so CdS
If the photoreceptor made using such CdS is applied to a high-speed copying machine, the electrostatic contrast between bright and dark areas will be insufficient.

The particle shape of CdS produced by the method described above consists of secondary particles, which are strong aggregates formed by aggregation of particles together, and these secondary particles are three-dimensional. There are various types of particles, such as aggregates in a nodule shape or two-dimensional aggregates in a flat plate shape, and some of them are large, ranging in size from 10 micrometers to 20 micrometers.

A photoreceptor made using CdS' containing a large number of such coarse particles has a poor surface condition, and as a result, the resulting image is extremely rough and has insufficient resolution. 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.

By solving these drawbacks of conventional methods, (1) high-contrast images can be formed from the initial 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 is also easy to coat. (8)
As a method for producing photoconductive cadmium sulfide, which has good properties such as being less susceptible to humidity and temperature effects, the melt M'! There is a method of mixing and firing at a temperature of 50℃ or more higher than the point.Cadmium sulfide produced by this method has a high dregs quality, so the cadmium sulfide near the surface is There are extremely few crystal defects that can become trap levels for light carry, and the surface of the particles is smooth and does not aggregate with each other, making them single particles, so the mold surface of the photoconductive layer produced is dense and smooth. However, the main purpose of the present invention is to improve this method and provide a method for producing cadmium sulfide particles with even better fineness and photoconductive properties. purpose.

In the method for producing photoconductive cadmium sulfide according to the present invention, a mixture of cadmium sulfide and a flux of 20,000 or more weight to cadmium sulfide is placed in a firing container, and the entire mixture in the firing container is io.

After heating to a certain temperature selected in the range of °C or higher and lower than the melting point of the flux, 50 °C below the melting point.
A general method for firing cadmium sulfide is to fill a firing container, such as a quartz crucible, with a mixture of cadmium sulfide and a flux, and then In order to raise the temperature to the set temperature in the crucible, the area near the crucible wall inevitably heats up faster than the area near the center, resulting in uneven temperature, and the time it takes to reach the melting point of the flux varies depending on the location. As a result, differences in particle growth occur, and the particle sizes tend to be uneven, which may have a negative effect on image quality.

Moisture absorption of cadmium sulfide and the flux is considered to be a contributing factor to the uneven temperature history inside the crucible. The first
As you can see from the figure, during the temperature rise in the temperature pattern, the temperature may stop rising for a period of time. This appears at around 100℃, and may or may not appear depending on the temperature measurement position in the crucible. . From this, it is thought that the shoulder of the temperature pattern near 100°C is due to temperature stagnation due to vaporization of moisture. Also, since the water content i differs depending on the location in the crucible, it may appear or not appear -D. No matter how dry cadmium sulfide and flux are used, they will inevitably absorb moisture during processes such as weighing, mixing, and rubbing with light. It is also interesting that the l&humidity stable is uniform within the crucible. In other words, depending on the location in the crucible, the shoulder around 100°C due to moisture vaporization may be large or small, so even if firing is performed for the same amount of time from a roughly saturated temperature, the amount of moisture absorbed 0 will have a completely different temperature history depending on
In order to reduce these temperature irregularities, it is possible to reduce the size of the crucible, but when considering the overall productivity, it is necessary to use a crucible of a certain size or more, and the above-mentioned problems will occur. It will happen. Therefore, in the present invention, in the process of mixing and firing the flux, the temperature is gradually raised to a certain temperature of 100°C or higher before the flux melts.
By keeping it in place, all of the water contained in the cadmium sulfide and flux is vaporized, and at the same time the temperature inside the crucible becomes warm.
After that - let the temperature rise to the heavens and warm the anus inside Luciho? It is called "Niteru".

With this 2'L, 1
Since a short firing process is required, the reproducibility of the particle shape 1 and the electrical properties are improved.

The flux used in the 2E investigation is a flux commonly used when diffusing activators into CdS, and CdCA2+
ZnC& + KCIJ, IJaCA + NH+CI
It is a mixture of one or several types such as r Cd50+ in a whitening ratio. A suitable example of a mixture of CdCjllt and an alkali metal chloride is a mixture of CdCjllt and an alkali metal chloride.As an alkali metal chloride, NaCA
And KCI is a typical example. The content of the alkali metal chloride in the entire flux is preferably 90 moles or more, preferably 10 moles or more.

In the present invention, the flux t is 20% or more (i.e.,
CdS]003iitl: 20 parts by weight or more) Particularly preferably 30% or more.

1-J for less than 20 inches, the CdS particles that are cooked tend to sinter and become coarse particles, and the surface shape of the edges is uneven, '+f
L: Powerful with sufficient retention, and poor C with poor resolution.
dS K gal.

In addition, according to the manufacturing method of the present invention (2), the firing temperature is 600
°C or less is suitable. Further, from the viewpoint of yield, the amount added to the 11th fusion CdS is preferably 65% or less, particularly 50Lfb or less.

Example 1) After adding CuCJ2 at a molar ratio of 1x1o' to CdS to 1000 g of precipitated CdS powder with little addition of impurities,
Furthermore, 412.5g of CdCA and 87.5g of NaCA
After adding g and mixing well, it was filled into a quartz crucible with an inner diameter of 140 rrm and a volume of 2000 cc, and the thermoelectric material for temperature measurement was placed at the center of the crucible (1), between the center and the wall (2), and near the wall (3). The temperature inside the furnace is 200℃.
(The melting point of the mixed flux used here is approximately 397°C) and the rate of temperature rise at each point was measured. (2
) and (1) each reached 200°CK. He kept the furnace at 200℃ for another 20 minutes, and the furnace temperature ke b L) O'
I set it to C and after reaching 7b, Tanoka reached 530'OK.
(2) and tl) were both heated to 530°C within 5 minutes. I held it for another 30 minutes and finished firing. The temperature rise curves marked Ll), (2) and () for this process are shown in Figure 2.
The air temperature around the crucible increased by 811M.

In addition, when the same experience as n was repeated four more times, a temperature rise curve almost similar to that shown in Figure 2 was obtained all four times. Smooth, 3-4μ diameter particles were obtained by dispersing these CdS'i['' in vinyl chloride/vinyl acetate copolymer and then coating them to a thickness of 40μ on an aluminum substrate and letting them dry. When a three-layered photoreceptor was obtained by gluing a 15 μm thick polyester film onto the outer photoreceptor plate, the surface was extremely flat.
7 = When a high-speed electrophotographic process of optical AC static elimination followed by full exposure was applied, a good quality image based on sufficient electrostatic contrast and sufficient sensitivity was obtained. In particular, the resolution was 10'GQm or more, and an image of 7 degrees or more was obtained.

Further, the impression voltage applied to the -order charging and AC static elimination was approximately the same value for all five times. Furthermore, after leaving these photosensitive sheets for 24 hours in a high temperature and high humidity environment with a temperature of 35 degrees Celsius and a humidity of 85 degrees Celsius, images were produced again using a copying machine. As a result, a decrease in contrast between bright and dark areas and a decrease in sensitivity were observed. The photoreceptor was left in a copying machine for 12 hours, and then the dark potential was measured.
The first sheet was 500V, and the 50th sheet was 510V, and there was a difference in IOV.Also, the change in potential contrast measured at 5℃ and 50℃ was as small as 10V.On the other hand, in comparison As an example, from the beginning, the temperature rise curves (1) to (4) in the crucible, which were set at 130°C (furnace temperature) and raised, were close to the melting point of about 400°C, as shown in Figure 1. The temperature unevenness in (1) to (3) was not resolved even after the temperature was exceeded.

I had the same funny experience as this one (after repeating C 4 times,
Each emfi had a different temperature rise curve, and some reports were near 100°C and others were not. When looking at these particles under an electron microscope with a magnification of 10,000 times, the surfaces of the particles were smooth, but the size of the particles varied from about 3 to 4 microns to about 2 to 5 microns.

Using each of the cadmium sulfides obtained in this way, a photosensitive plate similar to that of the example according to the present invention was prepared and similarly evaluated using an actual machine. Variations were observed in the applied voltage values.

Example 2) To 1000 g of CdS powder to which 5XlO' mole of Cu was added, 4200 g of CdC, NaC/!
300 g of the mixture was added, thoroughly mixed, and then filled into the same large quartz crucible as in Example 1. After keeping the temperature at 200°C for 60 minutes while measuring the temperature at the center of the lump, the temperature was raised to 530°C and baked for 30 minutes. When a similar experiment was conducted using a small crucible with a total internal diameter of 8 f) ma and a volume of 300 m1, a temperature increase curve similar to that of the large crucible described above was obtained. When the same evaluation as in Example 1 was carried out using a diameter (both VC of about 3 to 4 μm), good quality images and good characteristics were similarly obtained.

As a comparative example, a large crucible was used to raise the temperature to 530℃ at once.
When the temperature at the center of the crucible reached 530° C. and then firing for 30 minutes, the particle size was 2 to 7 μm, which was clearly different from the above two examples.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing temperature increase curves within the crucible. 1...Temperature rise curve at the center of the crucible, 2...Temperature rise curve between the center and wall inside the crucible, 3...Temperature rise curve near the wall inside the crucible, 4...Temperature rise curve around the crucible Temperature rise curve of the atmosphere. Applicant Canon Co., Ltd. Agent Maru E Gi Go'- □-□91＾

Claims (1)

[Claims] (1 ton for cadmium sulfide and 2 for cadmium sulfide
A mixture with 0% by weight or more of a flux was placed in a firing container, and the entire mixture in the firing container was heated to a certain temperature selected in the range of 100°C or higher and lower than the melting point of the flux. A method for producing photoconductive cadmium sulfide, which is then fired at a temperature 50° C. or more higher than the melting point.