JPS60115941A - Electrophotographic sensitive material - Google Patents

Abstract

PURPOSE:To improve the dark resistance and to improve simultaneously the photosensitivity, and the mechanical property by laminating successively a P type a-Si film doped with boron, an a-Si film doped with C, and an undoped a-Si film on an electroconductive substrate. CONSTITUTION:An electrophotographic sensitive body is formed by laminating successively a P type a-Si film 2 doped with boron, an a-SiC film doped with C, and an undoped a-Si film 4 on an electroconductive substrate 1. An a-SiC film 3 doped with C may be further added to the above-described uppermost a-Si film 4. By this constitution, the resistivity of the film is improved and the half level period of the dark surface potential is prolonged, and high photosensitivity is maintained by the effect of the a-Si film. The film thichness of the photoconductive layer is thus reduced and advantageous result is realized in the production cost. If the a-SiC layer 3 is further added to above the uppermost layer 4, higher surface potential in the dark state can be maintained, and the mechanical strength is improved and the life is prolonged.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an electrophotographic photoreceptor.

BACKGROUND OF THE INVENTION It is well known that electrophotographic photoreceptors are made by depositing a thin film of photoconductive material on a conductive substrate, typically by vacuum deposition or by coating a dispersion of the photoconductor. Such a photoconductive layer, by its nature, must be a good insulator in the dark and must be able to retain charge on its surface; on the other hand, upon irradiation with light, its electrical resistance decreases and the surface charge is retained. It must be able to dissipate quickly.

Currently, photoreceptor materials (photoconductive materials) for electrophotography include:
Inorganic photoconductive materials such as Se, CdS, and ZnO are commonly used, but they have problems in terms of mechanical strength, heat resistance, and photosensitivity, and they have to be replaced after tens of thousands of copies, resulting in a long service life. There are also problems with this, and further problems such as pollution remain due to the materials used.

Recently, as a new electrophotographic photoreceptor material, mechanical strength,
Amorphous silicon (hereinafter abbreviated as a-5i) is attracting attention because it is significantly harder in terms of heat resistance and photosensitivity than the above-mentioned existing photoreceptor materials, and is also non-polluting. This α-
The Vickers strength of 5i is approximately 1500 to 2ookyA-
and the strength of conventional photoreceptor materials, e.g. a -5t
3Qkg/mm”.

a-5t-Ta 60k17mm", a-A
s, Sg I 50kl/mm" considerably higher than L. However, while α-5i has the above advantages, α-5i itself has a dark resistivity of 109 to 1
Relatively low rR of 0.011Ωcm and clear as an electrophotograph
In order to maintain a surface potential of several hundred r necessary for image formation, a film thickness of several tens of microns is required, which poses a problem from a manufacturing standpoint. That is, the above-mentioned required film thickness of α-5i is too thick and takes a long time to manufacture considering the current lamination technology of about 10 microns per hour, which is a problem in terms of productivity and cost.

BACKGROUND OF THE INVENTION The present inventors have discovered that while having the above-mentioned excellent physical properties,
It has been found that another drawback of α-, which is low resistivity in the dark, can be improved by doping with impurities (carbon and boron).

This is done by doping α-5i with impurities (C,'B) w to increase the resistance of the α-5i photoconductive film and to widen the film thickness within a range that satisfies the functionality of the electrophotographic photoreceptor. However, new problems have arisen, such as the shortening of the spectral sensitivity due to the increase in the band gap due to carbon doping, and the capture of photogenerated carriers by impurity levels, which deteriorates the photosensitivity. It became a point.

Purpose of the Invention Therefore, the purpose of the present invention is to improve the drawback of α-5i, which has the above-mentioned excellent physical properties but has a low resistivity in the dark of 1/1, and which has high resistance and photosensitivity. It is an object of the present invention to provide an electrophotographic photoreceptor which is excellent in terms of performance and which satisfies electrophotographic functions with a photoconductive material layer having a small thickness.

Structure of the Invention The electrophotographic photoreceptor according to the present invention is formed by sequentially stacking a boron-doped P-type a-5i film, a carbon-doped α-5iC film, and a pure α-5i film on a conductive substrate. It is characterized by the fact that P-type σ-5i film and α-5
Due to the lamination with iC film, it has high resistance and a surface area of 1μ in the dark.
A photoconductive layer with a long half-attenuation time of about 100 nm can be obtained, and the film thickness can be greatly reduced.
By further laminating an α-5i film, which is not doped with impurities and has excellent photosensitivity, on the layered structure of the film, the photosensitivity, which is easily deteriorated by the impurity doping, is compensated for.

Another electrophotographic photoreceptor according to the present invention has 7) type α-separate film, α-5iC film and pure α
It is characterized by laminating an α-5iC film on top of a laminated α-5i film, and maintains the characteristics of the electrophotographic photoreceptor having the laminated structure as described above, and
By placing an a-SiC film in the outermost layer, which has superior mechanical strength and significantly higher dark resistivity than a pure α-5i film, we aim to further increase the resistance and improve the mechanical strength of the surface. It is something to improve.

Aspects and Functions of the Invention The layer structure of the electrophotographic photoreceptor according to the present invention is shown in FIGS. 1 and 2. In FIG. 1, 1 is a conductive substrate;
Usually an aluminum substrate is used. 2 is a boron-doped P-type α-5i film, 3 is a carbon-doped α-5tC film, and 4 is a pure α-5i film. In FIG. 2, on top of the laminated structure shown in FIG.
5iC films 3 are laminated.

Next, an example of a method for manufacturing an electrophotographic photoreceptor according to the present invention will be described. First, a so-called P-type a-5i film with a doping concentration of boron CB>, usually about a few M to several tens of thousands of PPM, is formed on an aluminum substrate. Approximately 0.01~
Layers of several microns, preferably 0.5 microns,
Thereon, an a-5iC film having a carbon (C) doping concentration of about 20 to 80 degrees is formed in a thickness of about several microns to more than ten microns by the same glow discharge decomposition method. Finally, pure a-5
The I film is similarly stirred by the glow discharge decomposition method.

A pure α-5i film plays the role of generating photocarriers, and from its absorption coefficient, a film thickness of 1 to 2 μm is sufficient. The method for manufacturing other electrophotographic photoreceptors of the present invention is basically the same as above, and as described above, P-type α-5
After laminating the α-5i film, α-5iC film, and pure α-5i film, α-5i film was further stacked using the glow discharge decomposition method as above.
A C film is formed.

According to the research conducted by the present inventors, the resistivity of α-5i film can be increased from 1012 to 101Ωam by doping with carbon.
was found to change. This is attributable to the fact that the band gap of the α-5i film is widened by carbon doping. This is shown in FIG. Figure 3 shows α-5
The influence of changes in the doping concentration of carbon in the i-film on the dark conductivity and bandgap is shown. The lower the dark conductivity, the higher the resistance, but from Figure 3, the larger the bandgap, the lower the dark conductivity, which means the higher the resistance, and the higher the carbon doping concentration, the higher the bandgap. It can be seen that it spreads and therefore the resistance increases.

Furthermore, in the present invention, by stacking an α-5iC film on a P-type α-5i film, an effect similar to a PN junction can be obtained, and the half-decay time of the surface potential in the dark becomes longer. As is well known, the density contrast when an electrostatic latent image is developed is determined by the contrast in surface charge density after exposure.

However, when a charged photoconductive pongee green film is exposed to light to attenuate its surface potential, in addition to attenuation due to light, charge attenuation due to the dark conductivity of the film is also included. Therefore, the smaller the dark decay after corona discharge stops, that is, the longer the half-decay time of the surface potential in the dark, the clearer the image will be formed.

In the present invention, an effect similar to a semiconductor PM junction can be obtained by stacking a P-type α-5i film and an α-5iC film, and the half-decay time of the surface potential in the dark can be lengthened. However, while these effects can be obtained, as mentioned above, there are also problems such as deterioration of photosensitivity, such as shortening of wavelength of spectral sensitivity due to increase in band gap due to carbon doping, and capture of photogenerated Yaria due to impurity levels. The phenomenon becomes a problem. In the present invention, a pure α-5i film with excellent photosensitivity is entirely laminated on the P-type α-5i film and α-5iC film to compensate for photosensitivity.

Here, the relationship between the type of laminated structure and photosensitivity is shown in Table 1 below.

Table-1 pop a -Si/a -SiC+number~l1shiLwx
azgtyP type a-5i/a -SiC/a -Si
Number Ltbx*ztc From Table 1 above, the effect of stacking the α-5i films is clear.

Further, in another electrophotographic photoreceptor of the present invention, an α-5iC film is present in the outermost layer. As is clear from FIG. 3, this α-5iC film has a high resistivity in the dark and also has a higher Vickers strength than the α-5i film. Therefore, α-5
The presence of the iC film in the outermost layer makes it possible to increase the resistance of the surface of the electrophotographic photoreceptor, and further improves the mechanical strength.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 P5 was deposited on an aluminum substrate by glow discharge decomposition method.
p a -5ie o, s /I, a-5iC film 6μ,
A-5i films of 1μ are sequentially laminated to form an electrophotographic photoreceptor A? Manufactured.

Example 2 P-type a was formed on an aluminum substrate by glow discharge decomposition method.
-5i film 0.5μ, a-5iC film 6μ, a-5i film 1μ
and a-SiC film of 0.5 μm were sequentially laminated to produce an electrophotographic photoreceptor B.

The characteristics of photoreceptors A and B obtained in Examples 1 and 2 above were measured. The results are shown in Table 2. In addition, P-type a-5i films of 0.5μ and α-5i were deposited on the aluminum substrate.
The results for the photoreceptor C' obtained by sequentially laminating 6μ of C films are also shown for reference.

Table 2 RokuT Co., Ltd. 1) Surface potential: This is the sample surface potential when charged by corona discharge (6.3Ky), and the higher the potential for a photoreceptor material, the more desirable it is.

2) Dark half-life 2 This is the time it takes for the above surface potential to expire.

C3) Half exposure dose: This is the exposure dose until the surface potential is halved.

As for the characteristics of the photoreceptor material, it is desirable that the surface potential is high (meaning that the film has a high resistance), the dark half-life is long, and the half-life is small, but the results are not shown in Table 2 above. As is clear, photoreceptors A and B are superior to photoreceptor C in all characteristics. Furthermore, it can be seen that in the case of photoreceptor A, there is a particularly sharp increase in the half-life exposure, and in the case of photoreceptor B, the entrance potential and dark half-life are particularly high.

Effects of the Invention As described above, the electrophotographic photoreceptor according to the present invention has a P-type α-5i film doped with boron, an a-5i film doped with carbon, a SiC film, and a pure α-5i film on a conductive substrate. -5
i films are sequentially stacked, and the P-type α-5i film and α-5
The stacking with the iC film increases the resistivity of the film (increasing the surface potential) and increases the half-decay time of the surface potential in the dark.The stacking of the α-5i film increases the resistance to light. Sensitivity remains high. Therefore, the film thickness of the photoconductive layer can be significantly reduced, providing special advantages in terms of productivity and cost. Furthermore, in another electrophotographic photoreceptor of the present invention,
Since an α-5iC film is further laminated as the outermost layer on the above laminated structure, the surface potential in the dark can be maintained even higher, and the α-5iC film can be used with a pure α-5i film or an existing photoreceptor. Due to their high mechanical strength compared to other materials, they have the particular advantage of extremely long service life.

[Brief explanation of drawings]

1 and 2 are partial vertical cross-sectional views showing the laminated structure of an electrophotographic photoreceptor according to the present invention, and FIG. 3 shows changes in the doping concentration of carbon to the α-5i film on dark conductivity and band gap. It is a graph showing the influence. 1 is a conductive substrate, 2 is a P-type α-5i film, and 3 is α-5iC
Membrane 4 is α-5i membrane. Applicant: Komatsu Ltd. Representative Patent Attorney Masaaki Hara Patent Attorney Tadashi Serimoto (8g)

Claims (1)

[Claims] 1 P-type α-5 doped with boron on a conductive substrate
i film, carbon-doped a-5iC film and pure α
An electrophotographic photoreceptor characterized in that it is formed by sequentially laminating -5i films. 2 P-type α-5 doped with boron on a conductive substrate
i film, carbon-doped a-5iC film, pure α-
1. An electrophotographic photoreceptor comprising a 5i film and a carbon-doped α-5iC film stacked one after another.