JPS62138326A - Production of zinc oxide powder for electrophotography - Google Patents

Abstract

PURPOSE:To obtain ZnO powder showing excellent performance as a constitutive material of electrophotographic sensitive body by compression-treating ZnO powder so that bulk density is regulated to the specified range or furthermore performing calcination treatment for it in the range of specified temp. CONSTITUTION:ZnO powder for forming a photoconductive layer for electrophotography used heretofore is compressed by using a compressor e.g. a closed type screw compressor. In case of using this screw compressor, the above- mentioned compressor having 5-10cm pitch width is used and ZnO powder for electrophotography having >=0.3g/cm<3>-<0.6g/cm<3> bulk density required is obtained by performing the compression in 2-3 times. Also sensitivity as a constitutive material for a photosensitive body is furthermore increased and also hardness can be increased by calcining the compressed ZnO powder at 200-600 deg.C especially at 200-500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved method for producing zinc oxide powder for use in electrophotographic photoreceptors.

[Prior Art] A zinc oxide photoreceptor conventionally used in electrophotography is a photoreceptor with a thickness of about 10 mm containing zinc oxide powder and an insulating resin as main components, on a support such as paper or plastic film that has been subjected to conductive treatment. It is made by applying a photoconductive layer on the body.

Above light guide 1! The zinc oxide powder traditionally used to form the layer is less than 1g, more typically 0.2-0.
It is a powder with a particle size of 5 ml, 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:

[Problems to be Solved by the Invention] When printing using a zinc oxide photoreceptor for offset printing or as a transfer plate, the number of printed sheets is at least 300.
However, the conventional zinc oxide photoreceptor coated with a photoconductive layer as described above does not have sufficient surface hardness. Easy to wear, dirt on the background during printing,
This causes the image to become unclear. There are various possible causes for this, but one is that the insulating resin, which is the binder for the photoconductive layer that forms the latent or visible image on the zinc oxide photoreceptor, is worn away during repeated printing or transfer, causing it to separate. Otherwise, the zinc oxide powder itself may fall off, making the image unclear, or the zinc oxide may be exposed, and the developer or toner may adhere thereto, staining the printed screen.

For this reason, one possible method for improving the surface hardness of the photoconductive layer is to use a hard resin, such as polyester resin, as the insulating resin, but this method may result in a decrease in the photosensitivity of the photoconductive layer. Otherwise, the flexibility of the photoconductive layer becomes poor, and the photoconductive layer is likely to crack and cause unevenness, which is undesirable.

When making a conventional zinc oxide powder-insulating resin dispersion for making a photoconductive layer, when zinc oxide powder is dispersed in an insulating resin solution, the zinc oxide powder does not behave as a single powder particle but aggregates. The dispersion liquid forms aggregates, and these aggregates remain as they are even when the dispersion is applied to a support and dried. These aggregates have a relatively weak cohesive force and have minute cavities within them, so when the photoreceptor is used for printing, the zinc oxide aggregates are also broken by frictional force and fall off when the insulating resin is worn away. Or it may cave in, causing the above-mentioned drawbacks.

The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to eliminate the drawbacks of the conventional photoreceptor having a photoconductive layer using zinc oxide powder and an insulating resin, and to provide a photoreceptor with excellent surface hardness. An object of the present invention is to provide a method for producing zinc oxide powder that can provide zinc oxide powder.

[Means for solving the problems] The present invention compresses zinc oxide powder to have a bulk density of 0.3 g/c.
113 or more and less than 0.6 g/Cm3, or a method for producing zinc oxide powder for electrophotography, which comprises firing the compressed zinc oxide powder at 200 to 600°C.

[Function] As the zinc oxide powder used in the present invention, the zinc oxide powder conventionally used for forming photoconductive layers for electrophotography can be used.

Any compressor, such as a closed screw compressor, can be used to compress the zinc oxide powder to produce a compressed powder. When compressing zinc oxide powder, the pitch width is 3 cm to 1
It is better to use a 0c+* screw compressor (,3c
A pitch width smaller than +s requires a large amount of power and the bulk density becomes 0.8 g/cm3 or more, which may reduce the photosensitivity of the photoconductive layer, which is undesirable. , bulk density is 0.25g
/ Cm3 or less, which is undesirable because the surface hardness of the photoconductive layer is insufficient like that of ordinary photoconductive powders, and when using a hermetic screw compressor, the pitch width is 5 to 5.
1OC11, and by carrying out this process 2 to 3 times to achieve the required bulk density of 0.3 g/cm3 or more and less than 0.8 g/cm3, the objective can be achieved.

Alternatively, a similar objective can be achieved by using a continuous deaerator to provide the bulk density described above.

In the present invention, this compressed zinc oxide powder is
By firing at 200 to 500°C, preferably more than 0°C, the sensitivity as a photoreceptor constituent material can be further increased.
Hardness can be increased. Even below 200"C, a slight improvement in sensitivity is observed compared to unfired powder, but the hardness of the photoreceptor is not sufficient, and when the temperature exceeds 600"C, the charge level of the photoconductive layer decreases, resulting in a tingling of image density. In addition, for firing, a commonly used firing furnace such as a rotary kiln, tunnel kiln, Matsufuru furnace, etc. can be used.

By using the fired or unfired zinc oxide powder having the above-mentioned bulk density produced in accordance with the present invention, a photoconductive layer with excellent surface hardness can be formed, unlike the case where the conventional zinc oxide powder described above is used.

The zinc oxide powder produced by the method of the present invention is dispersed in an organic solvent solution of an insulating resin by a conventionally known method, applied to a known support, and dried to obtain an electrophotographic photoreceptor. be able to.

[Example] Example d Zinc oxide powder with a particle size of 0.2 to 0.5 for regular electrophotography was compressed once using a closed screw compressor (3 pitches with a pitch width of 10 cm, 5 pitches with 5CII+). , twice, three times, and four times to obtain zinc oxide powders with different bulk densities.

Among these, zinc oxide powder having a bulk density of 0.34 g/cm3 was added at 200℃, 300℃, 1400℃, 500℃, 60℃.
Each sample was fired at 0°C for 1 hour to obtain fired zinc oxide powder.

Reference Example Using the compressed zinc oxide powder (fired and unfired) prepared in the above example, a zinc oxide dispersion having the following formulation was prepared.

Compressed zinc fertilized powder 35.0g Acrylic resin LR-637 (manufactured by Mitsubishi Rayon Co., Ltd., trade name) 17.5g Bromophenol blue 1% methanol solution - 5cc Toluene 80cc The above components were dispersed in a ball mill for 4 hours to form a dispersion liquid. was manufactured. The back side is coated with a polymer conductive agent (ECR-7 manufactured by Dow Chemical Company).
Applying the above dispersion to the surface of the paper treated with conductivity in 7),
It was dried at 100'C for 5 minutes to produce zinc oxide photosensitive paper.

The coating amount was 22 g/112 (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 compressed zinc oxide powder used in the above dispersion. The amount of application is the same <2
It was set as 2g/+s2 (solid content).

The properties of these photosensitive papers were as shown in Tables 1 and 2.

(Margin below) As is clear from the data in the table above, the photosensitive paper made using the zinc oxide powder made by the method of the present invention is different from that of ordinary photoconductive powder, as shown in the comparative example, which is a conventional example. The sensitivity and hardness of the photosensitive layer are improved. For this reason, these are excellent as photoreceptors for electrophotography such as original plates for offset printing and original plates for transfer.

[Effects of the Invention] The present invention is configured as described above, and an electrophotographic photoreceptor can be produced by compressing it so that the bulk density falls within a specific range, or by subsequently performing a baking process at a specific temperature. It has now become possible to provide zinc oxide powder that exhibits excellent performance as a constituent material.

Claims (2)

[Claims] (1) Compress zinc oxide powder to a bulk density of 0.3 g/cm
A method for producing zinc oxide powder for electrophotography, characterized in that the zinc oxide powder is ^3 or more and less than 0.6 g/cm^3. (2) Compress zinc oxide powder to a bulk density of 0.3 g/cm
^3 or more 0.6g/cm^3 less than 200-60
A method for producing zinc oxide powder for electrophotography, characterized by firing at 0°C.