JPS62123470A - Electrophotographic sensitive body having improved surface hardness - Google Patents

Abstract

PURPOSE:To obtain the titled body having the improved surface hardness by forming a photoconductive layer composed of zinc oxide contg. fine particles of zinc oxide having a bulk density and a particle size of a prescribed range as a main component, and an insulating resin on a substrate. CONSTITUTION:The photosensitive body is formed by providing with the photoconductive layer composed of zinc oxide and the insulating resin on the substrate. Said zinc oxide contains a calcined zinc oxide particle having at least 0.6g/cm<3> bulk density and <=2.0mm particle size as the main component. The calcined zinc oxide particle has the hardness which is crushed with loads of 3-10g. More than 10wt% the zinc oxide particles contd. in the photoconductive layer are formed by a compression molding, followed by calcining it. Thus, the titled body having the improved surface hardness is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a photoconductive layer with excellent surface hardness.

Photoreceptors have traditionally been used in electrophotography.

A photoconductive layer having a thickness of about 10 μm and containing zinc oxide powder and an insulating resin as main components is provided on a support such as electrically conductive treated paper or plastic film.

The zinc oxide powder forming the photoconductive layer has a particle size of less than Ig, usually 0.2 to 0.5, and a maximum density of 0.3 to 0.
．． It is a powder of 45 g/c+s3, and silicone resin, acrylic resin, alkyd resin, etc. are used as the insulating resin.

To form a photoconductive layer, zinc oxide powder is dispersed in an organic solvent solution of an insulating resin so that the weight ratio of zinc oxide powder to insulating resin is about 4 to 7:1, and this dispersion is It is manufactured by coating a support with:

When a zinc oxide photoconductive layer is used for offset printing, it is required to have the durability to print at least 3,000 sheets, preferably 5,000 sheets or more. The photoreceptor is coated with a zinc oxide photoconductive layer.

Since the surface hardness of the photoconductive layer is not sufficient, it is easily abraded, causing stains on the background and blurred images during plate making and printing. There are various possible causes for this, but one of them is that the insulating resin, which is the binder in the light guide layer that formed the image on the photoreceptor, is worn away during repeated printing, detached or peeled off, and the zinc oxide powder itself may fall off and make the image unclear,
Alternatively, the zinc oxide is exposed and the developer or toner adheres thereto, staining the printed screen.

Leading for this? One way to improve the surface hardness of [ is to use a hard resin such as polyester resin as the insulating resin, but this method
This is not preferable because the photosensitivity of the layer decreases, or the flexibility of the photoconductive layer becomes poor, and the photoconductive layer tends to crack and cause unevenness.

Moreover, when zinc oxide powder is dispersed in an insulating resin solution when making a conventional zinc oxide powder-insulating resin dispersion for making a photoconductive layer, the zinc oxide powder behaves as I'tj-powder particles. First, they aggregate to form aggregates, and these aggregates remain as they are even when the dispersion is applied to a support and dried. Since these aggregates have minute cavities within them, they have a relatively weak cohesive force. Therefore, when the photoreceptor is used for printing, the photoconductive layer is ftl. They may break due to frictional force, fall off, or cave in, resulting in the above-mentioned drawbacks.

The present invention aims to overcome the drawbacks of the conventional photoreceptor having a photoconductive layer using zinc oxide powder and an insulating resin, and to provide an electrophotographic photoreceptor with excellent surface hardness.

The present invention provides an electrophotographic photoreceptor in which a photoconductive layer made of zinc oxide and an insulating resin is provided on a support, wherein the zinc oxide has a maximum density of at least 7 cm3 and a particle size of 2.0 am or less. A photoreceptor for offset printing using fired zinc oxide having the following characteristics.

The calcined zinc oxide used in the present invention is at least 0.8 glc layer 3 as described above, typically 0.6 to 1.5 g/c
The particles have a bulk density of 3, preferably 0.7 to 1.2 g/c, and a particle size of 2 to 1, preferably 0.3 to 1.0 g/c.

Such zinc oxide particles can be produced as follows. I! D. Zinc oxide powder, which has traditionally been used to form the photoconductive layer of electrophotographic photoreceptors.

It can be made by compressing at a pressure of at least 20 Kg/cm2, crushing the compressed body, and then firing at 200 to 600°C.

Any compressor, such as a hydraulic press for molding mosaic tile substrates, can be used for compression. When compressing the zinc oxide powder, the compression ratio is at least 20 Kg/C112, preferably 150 Kg/C layer 2 or less, and more preferably 40 Kg/C112.
A pressure of cm' to 100 Kg/cm2 is adopted. If the pressure is lower than 2CIKg/c layer 2, 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. The surface hardness of the photoconductive layer formed by
If the g/c ratio is greater than 2, the photosensitivity of the photoconductive layer may be lowered, which is not preferable. Also, if the size is too large, it will take time to crush the compressed body, and it is not practical to make it unnecessarily large from the viewpoint of the performance of the compressor.

Next, the compacted body obtained as described above is crushed. The crushing can be achieved by passing the compressed body through a sieving process, and a rotating sieve or a flat sieve may be used, but a vibrating sieve is more preferable. Alternatively, zinc oxide powder may be introduced into the knee 7 of two rolls adjusted to apply the above pressure and compressed, thereby compressing and crushing the zinc oxide particles. can.

Next, the zinc oxide particles obtained by crushing are sieved, if necessary, to obtain particles with a particle size of 2 mm or less, preferably 0.3 to 1.0 mm. These particles are fired at a temperature of 200 to 600°C, preferably 200 to 400°C. Even at 200°C, an improvement in sensitivity is observed compared to unfired particles, but the hardness of the photoreceptor is not sufficient, and temperatures above 600°C In this case, time is spent dispersing the zinc oxide particles and the insulating resin, and a low f value occurs at the center of the band, resulting in a dim image density. Further, the firing can be carried out in a commonly used firing furnace such as a rotary kiln, a tunnel kiln, or a Matsufuru furnace. These particles generally contain at least 0.6 g/crl", usually 0.7
It has a maximum density of ~1.2 g/c 3.

If the particle size is larger than 2.0 am, it will take a long time to disperse when producing a dispersion of zinc oxide particles, which is undesirable.There is no strict regulation on the lower limit of the zero particle size. In addition, the manufactured zinc oxide particles have a hardness of 2.0 to 10.0 [particularly preferably 3.0 to 6.0 g, as measured by the following method, within this range] It was found that the surface hardness of the photoreceptor made using the zinc oxide particles according to the present invention was good, and the durability could be improved. The hardness was measured as follows. That is, in diameter 0.84mm
(20 meshes) ~ 1.7mm (10 meshes) particles are taken, and a spring-type scale F1 machine with the (reading limit) set to 0.5g is placed on the machine to compress the particles, and the display shows when the particles collapse. Heavy elm was used as an indication of hardness.

By using the fired zinc oxide particles of the present invention as described above, it is possible to form a photoconductive layer with excellent surface hardness, unlike when using the conventional zinc oxide powder as described above.

The baked zinc oxide particles produced by the method of the present invention can be used for electrophotography by dispersing them in a solution of an insulating resin in an insulating solvent, applying them to a known support, and drying them using a conventionally known method. It can be a photoreceptor.

The present invention will be explained below with reference to reference examples and examples.

Reference Example: Using a hydraulic press for mosaic tiles, zinc oxide powder with a particle size of 0.2 to 0.5 g for ordinary electrophotography was
The resulting compressed body was then crushed and sieved using a vibrating sieve to obtain 500 g of zinc oxide particles having a particle size of 1 square or less.

Example 1 A zinc oxide dispersion having the following formulation was prepared using each of the zinc oxide particles prepared in the above reference examples.

Zinc oxide particles 35.0g Acrylic resin LR-637 (manufactured by Mitsubishi Rayon Co., Ltd., trade name) 17.5g Bromophenol blue 1% methanol solution 0.5cc Toluene 80cc L Each component was dispersed in a ball mill for 4 hours to produce a dispersion liquid. did. The back side is coated with a polymeric conductive agent (ECR-77 manufactured by Dow Chemical Company).
) The above dispersion was applied to the surface of the paper that had been conductively treated in step 1.
Zinc oxide photosensitive paper was prepared by drying at 00°C for 5 minutes. The coating tank was set at 22 g/.2 (solid content).

As a comparative example, a zinc oxide photosensitive paper was similarly prepared using 35.0 g of ordinary photoconductive zinc oxide powder instead of the zinc oxide particles used in the above dispersion. The amount applied is the same <22g/
112 (solid content).

The properties of these photosensitive papers are shown in Table 1.

(Left below) Example 2 Zinc oxide photosensitive paper was produced by using the zinc oxide particles of the reference example above, which were fired at 300°C for 1 hour, together with ordinary photoconductive zinc oxide powder in the formulation shown in Table 2. Had made. Coating ti is 22g
/m2 (solid content).

The properties of these photosensitive papers are also shown in Table 2.

As is clear from the data in Table 51 and Table 2, the photosensitive paper made using the calcined Jlj lead oxide particles of the present invention has the following characteristics: Not only the sensitivity and hardness of the photosensitive layer are improved compared to those using ordinary photoconductive powder and unfired particles, but also the use of fired particles mixed with ordinary photoconductive powder improves the sensitivity and hardness of the photosensitive layer. The sensitivity and hardness of the photosensitive layer can be further improved. For this reason, these are excellent as photoreceptors for electrophotography such as original plates for offset printing and original plates for transfer.

Patent Applicant: Hakusui Chemical Industry Co., Ltd. Claims Procedure Amendment (Voluntary) 1. Indication of the Case 1985 Patent Application No. 151654 2. Name of the Invention Electrophotographic photoreceptor with improved surface hardness (corrected today) )3
, Person making the amendment 4, Column 5 of "Title of the invention", "Claims" and "Detailed description of the invention" in the specification of the application to be amended, Contents of the amendment (1) "Description of the invention" in the application "Name" has been corrected to "electrophotographic photoreceptor with improved surface hardness."

(2) The "Scope of Claims" in the specification will be corrected as shown in the attached sheet.

(3) In the “Table” on pages 10 and 11 of the specification tube, the line “Zinc oxide properties, highest density (g/cm2) J”, “Comparative example,
Conventional photoconductivity (1) In an electrophotographic photoreceptor comprising a photoconductive layer made of zinc oxide and an insulating resin on a support, the zinc oxide has a maximum density of at least 0.6 g/am3 and 2. A photoreceptor for electrophotography, characterized in that it is mainly composed of fired zinc oxide particles having a particle size of 0 mm or less.

(2) The electrophotographic photoreceptor according to claim 1, wherein the fired zinc oxide particles have a hardness that can be crushed under a load of 3 to 10 g.

(3) 10% by weight of zinc oxide particles contained in the photoconductive layer
The electrophotographic photoreceptor according to claim 1, wherein the above is compression molded and then fired.

Claims (3)

[Claims] (1) In an electrophotographic photoreceptor in which a photoconductive layer made of zinc oxide and an insulating resin is provided on a support, the zinc oxide has a maximum density of at least 0.6 g/cm^3 and a
．． 1. A photoreceptor for electrophotography, characterized in that it is mainly composed of fired zinc oxide particles having a particle size of 0 mm or less. (2) The electrophotographic photoreceptor according to claim 1, wherein the fired zinc oxide particles have a hardness that can be crushed under a load of 3 to 10 g. (3) The electrophotographic photoreceptor according to claim 1, wherein 10% by weight or more of the zinc particles contained in the photoconductive layer are obtained by compression molding and then firing.