JPS6163852A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To stabilize the surface of a photosensitive body and to improve the reliability thereof by providing a surface layer of a-SiNx added with fluorine on an a-Si photoconductive layer. CONSTITUTION:The photosensitive body is constituted of the photoconductive layer 3 consisting essentially of a-Si and the surface layer 4 which consists of the a-SiNx added fluorine, has a large optical energy band gap and is formed on said layer. The optical energy band gap of the a-SiNx of the layer 4 is made 2.0eV and the film thickness thereof is made in a 0.01-0.1mum range or 0.1-0.3mum. The a-SiNx used for such layer 4 is thermally stable dielectric break down electric field is high and has water repellency, thus having the effect of preventing the deterioration in the characteristics owing to adsorption of water, etc. A blocking layer 2 is preferably provided on the substrate 1 prior to the formation of the layer 3 to block carrier implantataion and to maintain electrostatic charge. The surface of the photosensitive body is thus stabilized by providing the a-SiNx surface layer 4, by which the reliability thereof is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an improvement in a T-photographic photoreceptor using amorphous silicon.

<Technical background of the invention and its problems> A photoreceptor that can be used in the electrophotographic process currently in practical use is basically required to have both a high resistance value and high photosensitivity. . Until now, materials with such characteristics can be roughly divided into selenium-based materials such as amorphous selenium (a-5e), amorphous selenium tilt element (aA S 2 S ea ),
Resin-dispersed materials, organic materials, etc., in which cadmium sulfide powder is dispersed in organic resins, have been used. However, for all of these materials, there is a desire to develop alternative materials for reasons such as pollution, and in recent years, amorphous silicon (a-5i) has been attracting attention in place of the above-mentioned photoreceptor material.

Unlike conventional electrophotographic photoreceptor materials, a5i is non-polluting, has high photosensitivity, and has a Vickers strength of 15
It is believed to be an ideal photoreceptor material because it has many excellent properties such as being extremely hard with a weight of 00 to 2000 kg*ari+. However, a-5i alone does not have sufficient resistance to maintain the charge required for electrophotography.
In order to use a-5i as an electrophotographic photoreceptor, it is necessary to maintain this high photosensitivity while maintaining a high charging potential. For this purpose, it is possible to add additives to a-5i to increase its resistance and obtain high charging ability, but this method is not preferred because it sacrifices the photosensitivity of a-5i. a-3i's excellent photoconductive properties (strong optical absorption,
In order to effectively utilize the relatively large drift mobility of electrons and holes, long wavelength sensitivity, etc., it is necessary to provide an electrical blocking layer on the surface (and substrate) rather than increasing the resistance of the photoconductive layer itself. It is preferable to measure the retention of charge. In addition, the surface layer with a large energy band gap not only maintains charge, but also protects the photoreceptor from the harsh impact of corona ions in the electrophotographic process, and further reduces fluctuations in characteristics due to changes in the environment such as humidity. Necessary as a protective film.

As this surface layer, amorphous silicon nitride IF5'
! (a 5iNx) has a large energy hunt capacitance and is structurally stable, and the film is dense, so N
It is considered to be excellent as a surface protective film because it is difficult for ions such as a'- to pass through. By providing a-5iNx as a surface layer, it is possible to obtain good basic characteristics as an electrophotographic photoreceptor.

However, there are still some deficiencies in final reliability. One of them is the problem of dielectric breakdown. Since the photoconductive layer a-5i is usually formed at a substrate temperature of 200 to 300°C, in order not to change the properties of the photoconductive layer,
The surface layer also needs to be formed at the same temperature. Generally a
The SiNx film is formed by glow discharge decomposition of a mixed gas of S + H4 and NH or N2, but if it is formed at a substrate temperature of 200 to 300°C, it becomes a film containing hydrogen. This hydrogen moves into the film, exhibits unstable behavior, and is thought to cause local dielectric breakdown. the result,
After long-term repeated use, minute white spots appear on copies. Other than electrophotographic photoreceptors, a SiN
It is known that when x is used as a protective film of a MOS-LSI, hydrogen diffuses to form traps and deteriorate the characteristics.

As mentioned above, in an electrophotographic photoreceptor using a-5i, a surface layer with a large energy band gap is essential in terms of charge retention and surface protection. Although it is particularly excellent, it has not yet achieved satisfactory characteristics in terms of reliability during repeated use.

<Object of the Invention> The present invention has been made in view of the above points, and an object of the present invention is to provide a novel electrophotographic photoreceptor with a stabilized surface layer and improved reliability of the photoreceptor. In order to achieve this object, the electrophotographic photoreceptor of the present invention includes a photoconductive layer mainly composed of amorphous silicon, and an optical photoreceptor made of fluorine-doped amorphous silicon nitride formed on the photoconductive layer. and a surface layer with a large energy bandgap.

<Embodiments of the Invention><Embodiments of the Invention> An electrophotographic photoreceptor according to the present invention includes a photoconductive layer containing a-5i as a main component deposited on a conductive substrate, and a photoconductive layer made of fluorine-doped silicon nitride. It has been reported that fluorine-doped a-5iNx is thermally stable and has a high dielectric breakdown field of lOMv/a11. Further, a-5iNx to which fluorine is added has water repellency and has the effect of preventing deterioration of properties due to adsorption of moisture and the like.

By applying such fluorine-doped a-SiNx to the surface layer of an electrophotographic photoreceptor, the stability of the surface is improved, which is expected to improve the reliability of the photoreceptor.

Next, the present invention will be specifically described with reference to Examples.

A-5i, the main component forming the photoconductive layer, is obtained by glow discharge decomposition (plasma CVD) of monosilane gas S i H4.
method). The manufacturing apparatus uses an inductively coupled type, and the photoconductor drum for depositing the photoconductive layer is grounded, and a high frequency power of 13.56 MHz is applied to the coil through an impedance matching circuit. The reactive gas is introduced into the reaction chamber through a mass flow controller while controlling its flow rate.

The temperature of the photosensitive drum installed in the reaction chamber is 250 to 300°C.
is maintained.

The figure is a sectional view showing the structure of an electrophotographic photoreceptor according to the present invention.

As shown in this figure, a substrate-side blocking layer 2 is provided on a drum (substrate) 1 before the photoconductive layer is formed. This is to prevent injection of carriers from the substrate (drum) l and to maintain electrical charge. The blocking layer 2 on the substrate side is a 1-3 μm thick a-3i with boron or phosphorus added.
and a-5i layer with large bandgap.
There is a method using Nx. a When using SiNx as the substrate-side blocking layer 2, the thickness is 0.01 to 0.1 μm.

The photoconductive layer 3 mainly composed of a-5i contains diborane gas B2.
A film is formed by appropriately adding boron by decomposing H6. The film thickness is 15 to 30 μm.

The conditions for forming the photoconductive layer 3 are shown below.

Under these conditions, after the photoconductive layer 3 is formed, the surface layer 4 is formed.

Fluorine-doped a-5i which is the surface layer 4 according to the present invention
Nx is 5i) I4, 5iF4. It is produced by glow discharge decomposition of a mixed gas of NH3. The energy band gap of the surface layer 4 produced under these film-forming conditions is 2. Oe
It was more than V.

The characteristics of the photoreceptor produced in this manner are summarized as follows.

When this photoconductor was installed in a copying machine and an aging test was conducted, it was found that even after approximately 300,000 sheets had been passed through, the charge potential remained stable at less than 10%, and there was almost no change in the image quality of the copies. It showed good characteristics. Further, no change in characteristics was observed even after being left for about 10 months.

Further, in order to compare the characteristics with the above-mentioned Examples, a surface layer (based on the conventional technique) was formed under the following conditions. Note that this comparative example was produced under the same conditions as the above example except for the surface area.

(ll a-5iNx film It was produced by decomposing SiH4 and NH3.

The initial characteristics of the photoreceptor produced in this manner were almost the same as those of the above examples. However, as a result of an aging test with the device attached to a copying machine, after approximately 300,000 sheets had been passed through, the variation in charging potential remained stable at less than 10%, but minute white spots were observed on the copies. There was something. No changes in characteristics were observed depending on the device.

(11) No surface layer A photoreceptor without a surface layer had a rather low initial charging potential and showed deterioration due to standing. When a photoreceptor without a surface layer was left for several months, white spots and blur appeared on the copies.

This seems to be due to surface deterioration due to neglect. In addition, when installed in a copying machine and subjected to an aging test, after passing approximately 10,000 sheets,
The charging potential decreased by 30% to 40%, and the number of white spots on copies also increased significantly. Furthermore, in high humidity (RH85-90%, 35
℃), the copy was significantly blurred.

From these results, it was found that the a-5i photoreceptor without a surface layer showed large fluctuations in the image quality and potential of copies due to standing and aging, and no material exhibiting stable characteristics as an electrophotographic photoreceptor was obtained.

In addition, when a-5iNx was provided as the surface layer, the initial characteristics were good and stable characteristics were obtained with little fluctuation in potential due to storage and aging, but after aging, some copies showed white spots. , which was not a satisfactory characteristic.

Other Examples of the Present Invention> tll The surface layer 4 of the a-5iNx film doped with fluorine was formed to a film thickness of 0.1 to 0 under the same conditions as the above film formation conditions.
．． One with a thickness of 3 μm was produced.

A photoreceptor having such a surface layer has both initial characteristics and aging characteristics with a film thickness of 0.01 to 0.01 as described in the above examples.
It showed good results, equivalent to those of 0.1 tL m.

However, a residual potential of 30V to 50V occurred. Although this level of residual potential does not pose a major problem when used as a photoreceptor, it is preferable that the residual potential is lower. In addition, the film thickness is 0.3μmLJ,
If it is set upward, the residual potential will increase, which is not desirable.

f21 SiF4. N2. Fluorine-containing a 5INx+ made from a mixed gas of N2.

With a-5iNx containing fluorine as the surface layer, Si
It was made from a mixed gas of F4, N2, and N2.

When the energy bandgap of the fabricated solution was 2.0eV or more, it exhibited good characteristics similar to those of the example.

<Effects of the Invention> As described above, according to the present invention, by forming a surface layer made of fluorine-doped amorphous silicon nitride on a photoconductive layer, the surface can be stabilized, and as a result, As a result, the reliability of the amorphous silicon photoreceptor can be improved.

[Brief explanation of drawings]

The figure is a sectional view showing the structure of an electrophotographic photoreceptor according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate (drum), 2... Substrate side pro-7 king layer, 3... Amorphous silicon (a-8i) leading i layer, 4... Surface layer made of fluorine-doped silicon nitride.

Claims (1)

[Claims] 1. A photoconductive layer containing amorphous silicon as a main component, and a surface layer with a large optical energy bandgap formed on the photoconductive layer and made of fluorine-doped amorphous silicon nitride. An electrophotographic photoreceptor characterized by comprising: 2. The optical energy bandgap of the fluorine-doped amorphous silicon nitride of the surface layer is 2.0 eV.
An electrophotographic photoreceptor according to claim 1, characterized in that the electrophotographic photoreceptor has the above characteristics. 3. The electrophotographic photoreceptor according to claim 1 or 2, wherein the surface layer has a thickness of 0.01 to 0.1 μm. 4. The electrophotographic photoreceptor according to claim 1 or 2, wherein the surface layer has a thickness of 0.1 to 0.3 μm.