JPS63285553A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent image fogging by a residual potential by providing an intermediate layer between a photoconductive layer and surface layer and setting the inter-gap level density of the intermediate layer larger than the inter-gap level density of the photoconductive layer. CONSTITUTION:An electrophotographic sensitive body is constituted by laminating a lower layer 2, the photoconductive layer 3, the intermediate layer 4 and the surface layer 5 on a conductive base body 1. The photoconductive layer 3 consists essentially of amorphous silicon contg. H and B, P are incorporated therein. The intermediate layer 4 is formed of an amorphous semiconductor contg. Si, C, H, P, and B and is set larger in the inter-gap level density than the photoconductive layer 3. Si and C are incorporated into the surface layer 5 to increase the optical band gap thereof larger than the optical band gap of the photoconductive layer 3. The photosensitive body constituted in such a manner is mounted on a copying machine for negative electrostatic charge and the good image is formed thereon. Since the inter-gap level density of the intermediate layer is formed under the specific conditions, the electrophotographic sensitive body which can be charged to both positive and negative electrostatic charges is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an electrophotographic photoreceptor, and more particularly to a photoreceptor in which a photoconductive layer is mainly made of amorphous silicon a-Si.

<Prior art> A photoreceptor that can be used in the electrophotographic process currently in practical use is basically required to have both high resistance and high photosensitivity. resin-dispersed type, in which cadmium sulfide powder is dispersed in organic resin, and amorphous selenium (a-Se).
or amorphous (1!vn arsenic (a -Asz Se
Two types have been most widely used: those based on amorphous materials such as s).

However, it is desired to develop alternative materials for all of these materials due to pollution and other reasons, and in recent years, amorphous silicon has been attracting attention as an alternative to the above-mentioned photoreceptor materials.

In addition to being non-polluting, amorphous silicon has high photosensitivity and is extremely hard, and is expected to be an excellent photoreceptor material. However, amorphous silicon alone does not have a sufficient resistance value to exhibit charge retention characteristics throughout the electrophotographic process, and in order to use amorphous silicon as an electrophotographic photoreceptor, it is necessary to use amorphous silicon while maintaining high photosensitivity. It was necessary to devise a way to maintain a high charging potential.

As one such measure, it has been proposed to increase the resistance of the amorphous silicon layer itself that serves as the photoreceptor. large drift mobility,
In order to effectively utilize long-wavelength sensitivity, etc., it is necessary to provide a blocking layer with a large energy bandgap on the surface (and substrate) for charging, rather than increasing the resistance of the photoconductive layer itself to obtain high charging ability as described above. It is preferable to measure the retention of

In addition, this type of surface layer with a large energy bandgap not only maintains charge, but also protects the photoreceptor from harsh corona ion bombardment in the electrophotographic process, and also protects the photoreceptor from changes in the environment (temperature, humidity, etc.). It is considered to be essential for surface stabilization as a surface protective film that reduces fluctuations in the surface area. Naturally, it is preferable for this surface layer to have a large energy band gap as a surface protective film.

Providing a surface layer with a large energy bandgap as described above is preferable not only from the viewpoint of charge retention but also from the viewpoint of surface protection. However, if a layer with a large energy band gap is formed immediately after the surface of the amorphous silicon that is the photoconductive layer, characteristics undesirable for an electrophotographic photoreceptor will appear.

One of them is mechanical instability.

When a large surface layer of an amorphous silicon optical stam IIC energy keycap is formed, stable adhesion between the surface layer and the photoconductive layer cannot be obtained due to the difference in thermal expansion coefficient between the two, resulting in peeling.

Furthermore, if a surface layer with a large energy band gap is directly formed on the photoconductive layer, undesirable electrical characteristics will appear. In other words, during the electrophotographic process, when a photoreceptor whose surface area has been charged in advance is irradiated with light, the light generates charges on the photoconductive layer that have the opposite polarity to the surface charges of the surface layer. This charge moves through the photoconductive layer and acts to electrostatically cancel out the surface charge. However, when the energy bandgap of the surface layer is large as mentioned above, the gap at the boundary between the two becomes extremely large, preventing smooth charge transfer.
It accumulates near the interface between the surface layer and the photoconductive layer, and appears as a residual potential. This residual potential is not desirable, and when the residual potential increases, it causes deterioration of the characteristics of the photoreceptor.

Furthermore, the residual potential often induces lateral movement of accumulated carriers, causing the problem of blurring of image quality.

As mentioned above, a surface layer with a large energy band gap is indispensable in terms of charge retention and surface protection, but it also causes mechanical and electrical problems, making it difficult for electrophotography. However, it has not yet been possible to obtain an amorphous silicon photoreceptor that satisfies the process requirements.

Further, in electrophotographic photoreceptors that have a photoconductive layer containing amorphous silicon as a main component, the use thereof is limited to either positive charging or negative charging. Therefore, in the carrier migration ability of the photoconductive layer, only holes are large in the photoconductive layer for positive charging, and on the contrary, only electrons are large in the photoconductive layer for negative charging, and both are large. However, there was no electrophotographic photoreceptor with sufficiently large running ability. However, none of the existing electrophotographic photoreceptors has good sensitivity when charged either positively or negatively.

<Object of the Invention> The object of the present invention is to provide an electrophotographic photoreceptor having a photoconductive layer containing amorphous silicon a-Sit as a main component and a surface layer having a larger optical band gap than the photoconductive layer. In this case, the problem is to prevent the existence of a problematic high residual potential, and the image capriulation and cross-flow caused by the residual potential.

Another object of the present invention is to provide an electrophotographic photoreceptor that can be charged in both positive and negative polarities.

Further, another object of the present invention is to obtain not only the initial image but also the initial image.
It is an object of the present invention to provide an electrophotographic photoreceptor capable of obtaining an image as good as an initial image even after copying a large number of copies, such as 500,000 copies.

<Example> Hereinafter, the configuration of the present invention will be explained with reference to the drawings.

The figure is a diagram showing the structure of an electrophotographic photoreceptor according to an embodiment of the present invention. layer (surface blocking layer). Note that the lower layer 2 is not an essential requirement of the present invention.

In the wooden embodiment, the lower layer 2 is amorphous silicon containing nitrogen N, and the front E surface layer 4
is carbon Cf: amorphous silicon containing a-B
It consists of

The film forming conditions for each layer are shown in Tables 1 to 4 below.

Table 1 Table 2 Table 3 When the photoreceptor manufactured under the above conditions was installed in a positively charging copying machine, a good initial image with no image capri or cross-flow was obtained, and 500,000 copies were printed. Even after printing, no deterioration was observed not only in photoreceptor characteristics but also in copy image quality.

Furthermore, when the photoreceptor was installed in a negatively charged copying machine, the same results as those obtained when positively charged were obtained.

Note that the inter-gap (band) quasi-position degree of the intermediate layer 4 is greater than the inter-gap (band) level density of the photoconductive layer 3.

The present invention is not limited to the above-described embodiments, and various modifications can be made, which can be conceived by those skilled in the art.

Effect> As described above, according to the electrophotographic photoreceptor according to the present invention, certain conditions (such as regulating the size of the inter-gap level density) are satisfied between the surface layer and the photoconductive layer. By providing the intermediate layer, an electrophotographic photoreceptor that can be charged both positively and negatively can be obtained, and can be used in a wide range of applications.

BRIEF DESCRIPTION OF THE DRAWINGS The figure is a structural diagram of an electrophotographic photoreceptor according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive substrate, 2... Lower layer, 3... Photoconductive layer, 4... Intermediate layer, 5... Surface layer.

Claims (1)

[Claims] 1. A photoconductive layer mainly composed of amorphous silicon containing H and a surface layer having a larger optical band gap than the photoconductive layer on a conductive substrate. An electrophotographic photoreceptor, characterized in that an intermediate layer is provided between the photoconductive layer and the surface layer. 2. The electrophotographic photoreceptor according to claim 1, wherein the surface layer contains at least Si and C. 3. The electrophotographic photoreceptor according to claim 2, wherein the intermediate layer is made of an amorphous semiconductor containing at least Si, C, H, P, and B. 4. The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer contains B and P. 5. The electrophotographic photoreceptor according to claim 1, wherein the inter-gap level density of the intermediate layer is higher than the inter-gap level density of the photoconductive layer.