JPS60257452A - Manufacture of zinc oxide particles for electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enable manufacure of zinc oxide particles capable of forming a photosensitive body prevented from abrasion of an insulating resin and decomposition and dropout of zinc oxide agglomerates and superior in surface hardness by compressing zinc oxide powder with a prescribed pressure and crushing the compressed bodies to form particles having prescribed bulk density and particle diameter. CONSTITUTION:The zinc oxide particles used here are prepared by compressing the zinc oxide powder to be used for forming the photoconductive layer of the electrophotographic sensitive body by using a pressure of 20-150kg/cm<2> with an arbitrary compressor, crushing the bodies obtained by compression, classifying them through sieves to obtain particles having <=2mm., and generally having a bulk density of 0.6-1.5g/cm<3>. When the particle diameter is >2.0mm., it takes unfavorably too long time to disperse them, and the lower limit of the particle diameter is not strictly regulated, and it is desirable to have a hardness of 2.0- 10.0g measured by the prescribed method. The surface hardness of the photosensitive body prepared by using these zinc oxide particles is good enough to improve abrasion resistance and durability.

Description

[Detailed description of the invention] The present invention relates to a method for producing zinc oxide particles.

Traditionally, titanium oxide (lead photoreceptor) is a photoreceptor with a thickness of approximately 10 μm that is mainly composed of zinc oxide powder and adhesive resin, and is placed on a support such as conductive treated paper or plastic film. It is made by applying a conductive layer.

The zinc acetate powder conventionally used to form the above-mentioned photoconductive layer is usually less than 1μ. It is a powder with a particle size of 2 to 0.5 microns, and silicone resin, acrylic resin, alkyd resin, etc. are used as the insulating resin.

When forming the photoconductive layer, the weight ratio of zinc oxide powder to insulating resin is approximately 4 in an organic solvent solution of insulating resin.
It is produced by dispersing zinc oxide powder at a ratio of ~7:1 and coating the dispersion on a support.

When printing using a zinc oxide photoreceptor as a base plate for offset printing or transfer, the number of prints is small. at least 3
However, the conventional zinc oxide photoreceptor coated with a photoconductive layer as described above is required to have a durability that allows printing of 000 sheets, preferably 5000 sheets or more, because the surface hardness of the photoconductive layer is not sufficient. It is easily worn out and causes stains on the background and blurred images during printing.

There are various possible causes for this, one of which is that the photoconductive layer that has formed a latent or developed image on the zinc oxide photoreceptor is worn away by the insulating resin 11, which serves as a binder, during repeated printing or transfer, resulting in detachment or separation. When it is peeled off, the zinc oxide powder itself falls off, making the image unclear, or the zinc oxide is exposed, and the developer or toner is deposited there, staining both sides of the print.

For this reason, if a hard resin, for example a polyester resin, is used as an insulating resin as a means of adjusting the surface hardness of the photoconductive layer, the light sensitivity of the layer may decrease, or the photoconductive layer may be damaged. : r? This is not preferable because the flexibility of the light guide layer 111 becomes poor, and the light guide 111 layer is likely to crack and cause unevenness.

In making a lead powder-insulating resin dispersion, when lead powder is dispersed in an insulating resin solution, the zinc oxide powder becomes a single powder particle. The behavior is that they agglomerate to form aggregates, which remain in that form even when the dispersion is applied to a support and dried. This aggregate has only a relatively weak cohesive force with fine cavities in it, and therefore, when the photoreceptor is used for printing, the photoconductive layer is damaged due to the wear of the insulating resin and the zinc oxide aggregates due to frictional force. They break off and fall off or cave in, resulting in the drawbacks mentioned above.

The present invention provides a method for producing zinc oxide particles that can overcome the drawbacks of the conventional photoreceptor having a photoconductive layer using zinc oxide powder and an insulating resin and can produce an IC photoreceptor with excellent surface hardness. It is in.

The present invention compresses zinc oxide powder at a pressure of 20 to 150 Kp/cn and crushes the compressed body to reduce the bulk density to at least 0.6! The present invention provides a method for producing zinc oxide particles for electrophotographic photoreceptors, which comprises forming particles with an i'/cn particle size of 20M or less.

The zinc oxide powder used in the present invention is the zinc oxide powder conventionally used for forming photoconductive layers of electrophotographic photoreceptors.

Any compressor, such as a hydraulic press for forming mosaic tile substrates, can be used to compress the zinc oxide powder to produce a compressed body. 20 Kq/c when compressing zinc oxide powder
tl~150 Kq/an, preferably +#: 40
A pressure of K/d to 100/d is used. 9 to 20
If the pressure is lower than /cA, the bonding force of the particles obtained by subsequently crushing the compressed body will not be sufficient, and the particles may be further crushed when dispersed in an insulating resin solution. This is undesirable because the surface hardness of the photoconductive layer becomes insufficient. Moreover, if the pressure is higher than 150 Kv/ad, the photosensitivity of the photoconductive layer may be lowered, which is unwise. Furthermore, if the gap is too large, it will take time and effort to crush the compressed body, and it is not practical to crush the compressed body unnecessarily due to the performance of the compressor.

According to the present invention, the compressed zinc oxide body obtained by compression as described above is crushed by II%. The crushing can be achieved by passing the compressed body through a sieving process, and a rotating sieve or a flat sieve is used, or a vibrating sieve is preferable. Alternatively, the zinc oxide particles can be compressed and crushed at the same time by introducing the zinc oxide powder into the nip of two rolls adjusted to apply the above pressure and applying one pressure.

If necessary, the zinc oxide particles obtained by crushing are sieved to a particle size of 2. Omyyr or less preferably 0.3 rrm~1
．． It is assumed to be a particle of 0 tone. These particles are generally 06-1.
5P/c-/preferably 0.7-1.2 P/ca
It has a bulk density of

The above particle size is 2. If it is larger than Oran, it will take a long time to disperse when producing a dispersion of zinc oxide particles, which is not preferable. There is no strict regulation on the lower limit of particle size. In addition, the manufactured zinc oxide particles were measured by the following method and had a weight of 2.0 to 10.0 g/Special K 3. O~6.0
Preferably, the hardness is 1. It has been found that within this range, the surface hardness of the photoreceptor made using the zinc oxide particles according to the present invention is good and the durability can be improved. The hardness was measured as follows. i.e. diameter 0.8
4+Ln (20 meshes) ~],, 7 ran (
Take 10 mesh particles and measure the weight (reading limit) of 0.
A 5V spring-type weighing machine was mounted to compress the particles, and the amount of electricity displayed when the particles became dull was used as an indication of hardness.

When using the zinc oxide particles having the above particle size produced in the present invention,
Unlike the case of using the conventional zinc oxide powder described above, it is possible to form a photoconductive layer with excellent surface hardness.

The zinc oxide powder produced by the method of the present invention can be electrophotographed by dispersing it in an organic solvent solution of an insulating resin, applying it to a known support, and drying it by a conventionally known method.
/(Can be used as a light body.

This invention will be explained below with reference to examples and reference examples.

Example 1 Zinc oxide powder with a particle size of 02 to 05μ for ordinary electrophotography was used in a hydraulic press for mosaic tiles.
40 Kp/"l""141" shape 550 particles were then crushed and sieved using a vibrating sieve to obtain 50y of zinc oxide particles having a particle size of 1 mm or less.

Examples 2 and 3 Same as Example 1, respectively at a pressure of 80 7/cl.
and 100 Kg/cn to obtain 551 zinc oxide particles with a particle size of 1 m or less, respectively. Using each of the zinc oxide particles prepared in Examples 1, 2, and 3 above, quantified zinc dispersion with the following formulation. I made a liquid.

A dispersion liquid was prepared by dispersing the above-mentioned components of 350 y of zinc oxide particles and 80 y of toluene in a ball mill for 4 hours. The back side is coated with a polymeric conductive agent (vcR manufactured by Dow Chemical Company).
The above dispersion was applied to the surface of the paper which had been subjected to conductivity treatment in -77) and dried at 100°C for 5 minutes to produce a zinc oxide photosensitive paper. The coating rate was 22 F/G (solid content).

As a comparative example, a zinc oxide photosensitive paper was similarly prepared using ordinary photoconductive zinc oxide powder 3501 instead of the zinc oxide particles used in the above dispersion. Application test is the same < 22
! / nt' (solid +)).

The characteristics of these photosensitive papers were as follows.

○ in the table indicates no scratches. △ means scratches are observed; × means scratches occur on the entire surface.

1-.As is clear from the data in Table J, the photosensitive paper made using the zinc oxide particles made by the method of the present invention has no significant difference in charging characteristics and photosensitivity compared to the conventional comparative example. ,
Moreover, the hardness of the photosensitive layer is improved. For this reason, these are used as electrophotographic photoreceptors such as offset printing original plates and transfer original plates.

Patent applicant: Hakusui Chemical Industry Co., Ltd. ’hi 1is”X

Claims (1)

[Scope of Claims] 1. A clove photographic sensitizer characterized by compressing zinc oxide powder at a pressure of 20 to 50 Kp/cJ and crushing the compressed body to obtain particles with a particle size of 20 or less. Method for producing zinc oxide particles. 2. A manufacturing method according to claim 1, in which the zinc oxide powder has a bulk density of at least 0.6 f//cd. 3. A patent in which the zinc oxide particles have a hardness that can be crushed under a load of 20 to 100 y. The manufacturing method according to claim 1 or 2.