JPH04277750A - Processing method for electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the sensitivity, stabilization and printing resistance of the electrophotographic sensitive body to be used for printers and copying machines. CONSTITUTION:The org. photosensitive body of a single layer type or multilayered type of a separated function type is irradiated with X-rays or electron beams, by which the sensitivity, stability and printing resistance are improved. The irradiation effect is further improved by incorporating metals or metal oxides into this body in the case of irradiation with X-rays.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing an electrophotographic photoreceptor, which makes it possible to improve the photosensitivity of the electrophotographic photoreceptor, which involves processes such as charging, exposure, development, and neutralization.

0002

[Prior Art] Compared to inorganic photoreceptors, organic photoreceptors (hereinafter abbreviated as OPC) have the advantage of being able to synthesize materials with high sensitivity to various wavelengths through molecular design, being non-polluting, and being superior in productivity and economy. It has characteristics such as being inexpensive and is currently being actively researched and developed. Significant improvements have also been made in terms of durability and sensitivity, which were conventionally regarded as problems with OPC, and some of these improvements have been put into practical use, and are now becoming the mainstay of photoreceptors for electrophotography.

[0003] OPC is usually used with a double layer structure consisting of a charge generation layer (abbreviated as CGL) that absorbs light and generates carriers and a charge transfer layer (abbreviated as CTL) that moves the generated carriers, and its high sensitivity The goal is to

Materials used in CGL (abbreviated as CGM)
Various organic materials such as various perylene compounds, various phthalocyanine compounds, thiapyrylium compounds, anthanthrone compounds, squarylium compounds, bisazo compounds, trisazo pigments, and azulenium dyes have been investigated.

On the other hand, various hydrazone compounds, oxazole compounds, triphenylmethane compounds, arylamine compounds, and the like have been developed as materials for use in CTL (abbreviated as CTM).

Furthermore, in recent years, there has been an increasing demand for the use of these OPCs in the near-infrared region, which corresponds to semiconductor laser light (780-830 nm), as photoreceptors for digital recording in laser printers and the like. The development of OPC with high sensitivity characteristics is active.

Organic photoreceptors are advantageous in terms of sensitivity than inorganic photoreceptors in such areas. These materials are formed on a substrate such as a drum or belt by a relatively simple coating method together with a binder polymer. Binder polymers used for this purpose include polyester resins, polycarbonate resins, acrylic resins, acrylic-styrene resins, and the like.

Generally, in a double-layer structure, the CGL layer is coated to a thickness of about 1 micron to increase sensitivity;
The TL layer is applied at a thickness of 10-20 microns. At this time, for reasons such as strength and printing durability, the CGL layer is usually formed on the substrate side and the CTL layer is formed on the surface side. In such a structure, since only a CTM in which the CTM operates by the movement of holes has been put into practical use, the double layer photoreceptor is of a negatively charged type.

However, in such a negative charging method,
There were problems in that (1) oxygen in the air turned into ozone due to the negative charge used for charging, (2) charging was unstable, and (3) it was easily affected by the drum surface. Ozone is not only harmful to the human body, but also often reacts with photoreceptors, shortening the life of the photoreceptor. In addition, the instability of charging often leads to a decline in image quality, and the fact that the drum surface is greatly affected requires the drum to be given a mirror finish or an undercoat, leading to an increase in manufacturing costs. Furthermore, such a two-layer system has problems such as (4) the manufacturing process becomes complicated and the yield is poor, and (5) stability becomes a problem due to peeling between layers.

[0010] Photoreceptors, especially single-layer organic photoreceptors (OP
C) has poor photosensitivity at the initial stage, but tends to gradually improve when used continuously and repeatedly. In the early stages of poor photosensitivity, there were problems in that normal development resulted in fogging in white background areas, and reversal development resulted in white spots in solid black areas. As a countermeasure to this problem, a method of improving the photoconductor has been adopted to improve the photosensitivity by irradiating the photoconductor with light with a wavelength of 300 to 800 nm or by performing a preliminary operation of charging and photo-neutralizing the photoconductor several times before starting copying. has been done. Furthermore, recently there has been a demand for organic photoreceptors that have a long life and high sensitivity similar to inorganic photoreceptors.

[0011]

[Problems to be Solved by the Invention] As countermeasures to these problems, development of raw materials or processing of materials can be considered. Examples of material processing include irradiation with ultraviolet or visible light, as described above. However, in this case, even if the photosensitivity improves once, after a certain period of time, the photosensitivity returns to its original level to some extent, so there is a problem in that a preliminary operation must be performed each time copying is performed.

The present invention solves the above problems, and by irradiating the photoreceptor with high-energy ionizing radiation, the photosensitivity can be improved and maintained for a long time, and the light before copying can be improved. The object of the present invention is to provide a method for processing an electrophotographic photoreceptor that does not require preliminary operation to improve sensitivity.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the present invention irradiates an organic photoreceptor with X-rays or electron beams, which are ionizing radiation with higher energy than light with a wavelength of 300 to 800 nm. .

In the case of light irradiation, there is no change in the structure of the material itself unless it has a special functional group. Since X-rays or electron beams have high energy, when irradiated with more than a certain amount, organic materials undergo crosslinking reactions and decomposition reactions. By irreversibly causing such a reaction, it was possible to improve the sensitivity and stability of the organic photoreceptor.

In the case of X-rays, the absorption rate of organic matter is low, so the reaction efficiency is also low. Therefore, X-ray irradiation is effective if a metal element with high X-ray absorption is mixed in the form of metal powder or metal compound into the photoreceptor. Phthalocyanine, which is known as a charge generating agent, is well known as a metal complex, but in this case there is no need to further add metal powder. A similar effect can be obtained by using an organic complex such as metal phthalocyanine in place of the metal powder. The metal powder or metal compound may be one that has good compatibility with the binder resin or compound constituting the photoreceptor and does not particularly deteriorate the photosensitivity. For example, Al, In, S
In addition to n, Cu, Pb, etc., these oxides, La, Co
, Si, W, and other oxides are also used. Since X-rays have good transparency, if the composition of the layers constituting the photoreceptor is uniform, the entire layer can be uniformly irradiated with X-rays. When the photoreceptor is of a functionally separated type and has a multilayer structure, by using a component with high X-ray absorption only in a certain layer, it is possible to selectively bring about the X-ray irradiation effect only in that layer. For single-layer photoreceptors, the entire layer can provide an X-ray effect.

On the other hand, in the case of an electron beam, since the absorption coefficient is high, the irradiation effect can be obtained only on the surface. Therefore, in this case, unlike in the case of X-ray irradiation, there is no effect of metal contamination. However, even when the functionally separated type had a charge generation layer or a charge transport layer on the surface, improvements in sensitivity, stability, and printing durability were observed by electron beam irradiation. Similarly, when a single-layer type photoreceptor, for example, a photoreceptor made only of a binder resin and a phthalocyanine system, was irradiated with an electron beam, improvements in sensitivity, stability, and printing durability were also observed.

[0017]

[Action] As mentioned above, by irradiating the organic photoreceptor with X-rays or electron beams, the sensitivity is improved, its characteristics are stabilized,
Printing durability can be improved.

[0018]

[Examples] Examples of the present invention will be explained in detail below while comparing them with comparative examples.

(Example 1) An experiment was conducted on a functionally separated type organic photoreceptor having a two-layer structure. As the charge generating agent, τ-type Cu phthalocyanine and X-type metal-free phthalocyanine were used, and as the binder resin, polybutyral was used. The weight ratio of the mixture was 1:1. The film thickness was approximately 0.3μ. The charge transfer agent is CTC- which is a type of hydrazone compound.
236 (manufactured by Anan Kogyo Co., Ltd.) was used. Polyester was used as the binder resin, and the mixing ratio was 4:5 by weight. As photoreceptors, both a negative charging type in which the charge transfer layer is located below the Al substrate and a positive charging type in which the charge transfer layer is located above the Al substrate were prepared. Irradiation was performed using Cu white X-rays as the X-rays and an SEM as the electron beam. The photosensitive characteristics were measured using an EPA-8100 paper analyzer manufactured by Kawaguchi Electric Co., Ltd. Table 1 shows the results of the irradiation amount and sensitivity characteristics of the negatively charged photoreceptor. Sensitivity is expressed as E1/2. The measurement wavelength is 7
It is 80 nm.

[0020]

[Table 1]

[0021] As can be seen from this (Table 1), it can be seen that the sensitivity is improved by about twice as much by X-ray irradiation. Furthermore, it can be seen that this sensitivity is maintained even if left alone. Even when irradiated with ultraviolet light, the sensitivity may improve by about 1.5 times after irradiation, but if left untreated, the sensitivity returns to the same level as before irradiation.

[0022] Cu of phthalocyanine as an X-ray irradiation effect
When compared with the case of no metal, the case of Cu was more effective. (Table 2) shows the results when electron beam irradiation was performed in the case of the positive charging method. In this case as well, an improvement in sensitivity can be seen.

[0023]

[Table 2]

(Example 2) A negative charging type photoreceptor was prepared by mixing Al2O3 powder in an amount of 5% based on the weight of the phthalocyanine in the charge generation layer using the metal-free phthalocyanine shown in Example 1. When X-ray irradiation was performed in the same manner as in Example 1, the properties were improved to the same extent as Cu phthalocyanine.

(Example 3) Surface abrasion occurs on an organic photoreceptor when printing is performed using an actual machine. Although some abrasion is considered effective in maintaining a fresh surface, it is generally desired to improve the abrasion resistance of the surface. Therefore, we used a copying machine to actually print out the images and investigated the effects of irradiation on printing durability.

As the photoreceptor, a positively charged single layer type photoreceptor consisting of only metal-free phthalocyanine and a binder resin was used. Coating was performed so that the initial film thickness was 20 μm. Initial sensitivity is 3
．． It was 8 μJ/cm2, but when X-ray irradiation was performed, 1
．． It became 8 μJ/cm2. When a picture printing test was conducted on an actual machine before X-ray irradiation, the film thickness decreased by about 3 μm after printing 5,000 sheets. Similarly, when a test was conducted on a sample after X-ray irradiation, the film thickness decreased by about 1.2 μm, confirming that the wear resistance was improved by X-ray irradiation.

[0027]

As described above, the present invention provides an excellent electrophotographic photosensitive material that improves sensitivity, stability, and printing durability by irradiating an organic photoreceptor with X-rays or electron beams. It has the advantage of being able to provide the body.

Claims (3)

[Claims] 1. A method for processing an electrophotographic photoreceptor, which comprises irradiating the organic photoreceptor with X-rays or electron beams. 2. A method for processing an electrophotographic photoreceptor, wherein the organic photoreceptor according to claim 1 is of a single layer type. 3. A method for processing an electrophotographic photoreceptor according to claim 1 or 2, wherein the organic photoreceptor contains a metal element having a large mass absorption coefficient for X-rays.