JPH07306539A - Photoconductive member - Google Patents

Abstract

PURPOSE:To prevent flawing of an image by continuously increasing contents of nitrogen, carbon, oxygen, etc., to be incorporated into the amorphous silicon (a-Si) of a surface layer from the part in contact with a photoconductive layer to the extreme surface layer. CONSTITUTION:An a-Si photoreceptor consists of a base, a charge implantation blocking layer, the photoconductive layer and a functionally gradient material type surface layer. The surface layer is composed of the a-Si contg. at least one among the nitrogen, carbon and oxygen. The surface layer is composed of the contents of the nitrogen, carbon and oxygen at the ratios continuously increasing from the part in contact with the photoconductive layer to the extreme surface layer. The thickness of the surface layer is made thicker than the depth of flawing caused at an ordinary treatment. As a result, the appearance of the flaws on the image does not arise even if the photoreceptor has the flaws. Even more, charges do not accumulate at the boundary between the surface layer and the photoconductive layer and, therefore, generation of residual potential is prevented and there is no possibility of generating pinholes in the image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductive member which is an amorphous silicon (a-Si) photoconductor, which has recently attracted attention among photoconductors used in copying machines and printers.

[0002]

2. Description of the Related Art Since an a-Si photoconductor has very attractive characteristics such as long life, long wavelength sensitivity, and no pollution,
Research is being done vigorously. As shown in FIG. 8, many conventional a-Si photoconductors are basically composed of a support, a charge injection blocking layer, a photoconductive layer, and a surface layer. High sensitivity and high resolution have been achieved. However, there is a problem that the image is easily scratched.

[0003]

It is considered that the scratches on the image as described above are caused by the loss of the surface layer due to the scratches on the photoreceptor. The resistance of the a-Si photoconductive layer is about 10 ¹² Ωcm at most, and the chargeability is insufficient as a single layer film.
It cannot be used as a photoconductor. This relatively low resistance a-Si
In order to have sufficient chargeability and to function as a photoconductor, the conventional a-Si photoconductor is provided with a charge injection blocking layer and a surface layer. In general, when the photoconductor is scratched, the surface layer disappears, the chargeability there is lost, and the image is scratched. It is considered that the loss of the surface layer due to scratches entering the photoconductor causes damage to the image.Therefore, if the thickness of the surface layer is made thicker than the depth of scratches that would occur during normal handling, damage to the image will not occur. Although it can be prevented, it becomes difficult for the charges generated by exposure to combine with the charged charges on the surface, and the residual potential increases. If the residual potential becomes excessive, breakdown of the surface layer occurs, so the residual potential tends to saturate, but this breakdown may cause pinholes in the surface layer, which may cause pinholes in the image. is there. The present invention thickens the surface layer and at the same time a-Si of the surface layer.
An object of the present invention is to provide a photoconductive member capable of solving the problem of scratches by continuously increasing the content of N, C, O, etc. mixed in the film from the portion in contact with the photoconductive layer to the outermost surface layer. Is. In addition, generally, the content of C, O, and N in the surface layer is about 60 at%, which is a uniform distribution.

[0004]

Therefore, according to the present invention, in a photoconductive member having amorphous silicon as a base material, the surface layer formed on the photoconductive layer is at least one of nitrogen, carbon and oxygen. It is composed of amorphous silicon containing one, and has a composition in which the contents of nitrogen, carbon, and oxygen continuously increase from the portion in contact with the photoconductive layer to the outermost surface layer. It is a means to

[0005]

According to the present invention, since the surface layer is thicker than the depth of the scratches that would otherwise occur during normal handling, scratches will not appear on the image even if the photoreceptor is scratched. Moreover, since no electric charge is accumulated at the interface between the surface layer and the photoconductive layer, the generation of residual potential can be suppressed and there is no risk of pinholes.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments of the drawings. First, in order to explain the present invention in an easy-to-understand manner, a conventional type photoconductor, a surface layer simple thick film type photoconductor, and a surface layer functionally graded material type photoconductor of the present invention are shown in FIGS. 3, 4 and 5. A band diagram before and during charging (positive charging) / exposure will be described. As shown in FIG. 3, in the conventional photoconductor, since the surface layer is thin (0.2 to 0.3 μm), the electrons generated by the exposure tunnel through the surface layer and are combined with the surface charge to disappear. On the other hand, in the photoconductor having a simple thick surface layer, the surface layer is thick as shown in FIG. 4, and therefore electrons generated by exposure cannot easily tunnel the surface layer, and the electrons of the surface layer and the photoconductive layer are not easily tunneled. Electrons are accumulated at the interface to generate a residual potential. In the present invention, since the band profile shown in FIG. 5 is obtained at the time of charging and exposure, no barrier for electrons is generated in the surface layer, and therefore no residual potential is generated. That is, according to the present invention, to prevent damage to the image,
It is possible to achieve both suppression of residual potential.

FIG. 1 shows the structure of an a-Si photosensitive member according to an embodiment of the present invention. For film formation, a parallel plate type R as shown in FIG.
An F plasma CVD apparatus was used. Then, for the purpose of verifying the principle, a film is formed on a 50 mm × 50 mm Al substrate by the apparatus of FIG.
The characteristics were evaluated. First, the film forming method is 50 mm x 50 mm x
After setting the 2mmAl substrate on the substrate holder, the chamber is evacuated by the rotary pump and the oil diffusion pump,
Raise the substrate temperature with a heater. When the substrate temperature reaches a predetermined temperature and the degree of vacuum reaches 10 ^-6 Torr, the vacuum suction system is switched to the system of mechanical booster pump and rotary pump, and the source gas is introduced. The raw material gases are adjusted to a predetermined flow rate by a mass flow controller and then merged, and then injected toward the center through a hole (φ1 mm) provided on the center side of the ring-shaped gas pipe (φ120 mm). After adjusting the gas pressure to a predetermined pressure, a predetermined RF power is applied to the RF electrode from the RF power source to cause discharge and generate plasma of the raw material gas. After forming the film for a predetermined time, the film forming conditions are changed to form the next layer. In this way, the charge injection blocking layer, the photoconductive layer and the surface layer are sequentially formed. After forming each layer, in order to remove impurities and change the substrate temperature, supply of RF power and raw material gas is stopped for about 30 minutes, and vacuuming is continued.

Next, the film forming conditions for each layer will be described below. (1) Charge injection blocking layer Substrate temperature: 250 ° C. Source gas flow rate: SiH ₄ (100%): 40 SCCM, 0.5
% B ₂ H ₆ (H ₂ base): 16 SCCM Gas pressure: 150 mTorr RF power: 10 W Film formation time: 12 minutes Film thickness: 0.2 μm (2) Photoconductive layer Substrate temperature: 250 ° C. Source gas flow rate: SiH ₄ ( 100%): 60SCCM, 50pp
m B ₂ H ₆ (H ₂ base): 10 SCCM Gas pressure: 150 mTorr RF power: 50 W Film formation time: 6.5 hours Film thickness: 22 μm

(3) Surface layer Substrate temperature: 350 ° C. Source gas flow rate: SiH ₄ (100%), NH ₃ (100
%) And N ₂ (100%) are used, and the band profile of the surface layer is as shown in FIG. 5 (a), that is, 0.2 μm of the outermost layer has a constant band gap of 3.8 eV and the remaining 1.3
The film forming conditions for each film thickness of 0.1 μm were set as follows so that μm decreases almost linearly from 3.8 eV to 1.8 eV of the photoconductive layer. Here, the reason why the composition of the outermost surface layer of 0.2 μm is made constant is to prevent the occurrence of image blurring due to abrasion and the like to reduce the content of N and the like on the outermost surface.

[Table 1]

[Table 2] Gas pressure: 1 Torr RF power: 100 W Film thickness: 1.5 μm

[0010] film forming condition photosensitive member was fabricated with a functional gradient without material reduction, simple thick surface layer of a thickness of 1.5μm at a uniform nitrogen concentration for comparison, the raw material gas flow rate SiH _4: 35
_{SCCM, NH 3: 200SCCM, N} 2:. 1000SCCM, deposition cyan outside a 39'45 "was the same as the conditions in this manner the two types of charging exposure characteristics of the photosensitive member was fabricated by electrostatically charged Evaluated with a test device (MODEL EPA-8200, Kawaguchi Electric Co., Ltd.) Wavelengths of 660 mm and 780
Fig. 6 shows the charging exposure characteristics when the exposure amount is mm and the exposure amount is 1 mW / cm ² .
Shown in. In the case of the simple thick film surface layer, there is a residual potential of about 40 V even after 5 seconds, whereas in the case of the functionally gradient material type surface layer, the residual potential becomes almost 0 V in about 3 seconds. Also, the sensitivity has been slightly improved by using a functionally graded material. That is, it can be seen that the use of the functionally graded material for the surface layer can prevent the generation of residual potential even if the film is thick.

On the other hand, the problem of scratches is that if the surface layer is thickened,
It has been separately confirmed that there are no scratches in the image.
Previously A-Si photosensitive drum manufactured by Company A (surface layer thickness 0.3 μm)
However, there is a problem that the image is very likely to be scratched. Therefore, a printing test was conducted using a photosensitive drum having a surface layer thickly formed to 1.0 μm, and it was confirmed that the image was not scratched at all even after long-term use. Moreover, the pinholes gradually increased in the image during long-term use. It is considered that this is because the breakdown of the surface layer was caused by the high electric field applied to the surface layer due to the accumulated charges at the interface between the surface layer and the photoconductive layer which caused the residual potential, and the breakdown was gradually increased. In the photoconductor having the functionally gradient material type surface layer in which the residual potential does not occur as described above, there is no fear of such pinholes.

Since it has been confirmed that damage to the image can be prevented by increasing the thickness of the surface layer, a scratch test was conducted to prove that the image of the present invention is not damaged. For the scratch test, a continuous weight type surface texture measuring machine (Tri-gear TYPE: 22 Shinto Kagaku Co., Ltd.) was used. First, when the photosensitive drum manufactured by Company A, which had been used for a long period of time, was closely examined, the deepest scratch depth was 0.7 μm. Then, a part of the photosensitive drum manufactured by Company A was cut out, and the load at which a 0.7 μm scratch was generated was examined by the scratch tester, and it was 9.1 g. Next, when a scratch test was conducted on the photoconductor having the functionally gradient material type surface layer formed under the above conditions, a scratch having a depth of 0.65 μm was formed under a load of 9.1 g. This is well below the surface layer thickness of 1.5 μm. Further, the nitrogen concentration at this depth is sufficiently high and the band gap is 3 eV or more, so that it sufficiently functions as a surface layer. Therefore, it is necessary to prepare a photosensitive drum and perform a print test, and
It can be seen that the -Si photoconductor can prevent damage to the image. The content and slope of C, O or N in the surface layer are as shown in FIG.

[0013]

As described in detail above, in the photoconductive layer as the a-Si photoconductor having the functionally gradient material type surface layer of the present invention, the surface layer is thicker than the depth of the scratches that would be introduced during normal handling. Even if the body is slightly scratched, the image will not be scratched. Moreover, since the hand profile is as shown in FIG. 5 at the time of charging / exposure, electric charges are not accumulated at the interface between the surface layer and the photoconductive layer, and the generation of residual potential can be suppressed. Therefore, there is no risk of pinholes. That is, the method of the present invention can prevent damage to an image and prevent the occurrence of residual potential and pinholes at the same time.

[Brief description of drawings]

FIG. 1 is a structural diagram of an a-Si photoconductor according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an a-Si photoconductor film forming apparatus according to an embodiment of the present invention.

FIG. 3 is a band diagram of a conventional a-Si photoconductor.

FIG. 4 is a band diagram of a surface-layer simple thick film a-Si photoconductor.

FIG. 5 is a surface layer functionally gradient material a according to an embodiment of the present invention.
FIG. 3 is a band diagram of a —Si photoconductor.

FIG. 6 is an explanatory diagram showing charging exposure characteristics of an a-Si photoconductor when the surface layer is made thick and when it is made a functionally gradient material.

FIG. 7 is an explanatory diagram showing the contents and slopes of C, O and N in the surface layer.

FIG. 8 is a configuration diagram of a conventional a-Si photoconductor.

Claims (1)

[Claims] 1. A photoconductive member comprising amorphous silicon as a base material, wherein a surface layer formed on the photoconductive layer comprises:
It is composed of amorphous silicon containing at least one of nitrogen, carbon and oxygen, and has a composition in which the contents of the nitrogen, carbon and oxygen continuously increase from the portion in contact with the photoconductive layer to the outermost surface layer. A photoconductive member comprising: