JP2001343770A - Photoreceptor and device for image formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both residual potential and pressure resistance. SOLUTION: In an electrophotographic photoreceptor 1, an electric insulating layer 5a consisting of silicon (Si), electrically non-insulating a-Si layer 4, electric insulating layer 5b consisting of silicon (Si), charge injection preventing layer 6 consisting of a-Si:H and photoconductive layer 7 consisting of a-SiH are successively deposited by CVD, such as a glow discharge decomposition method on a conductive substrate 3, and then a surface protective layer 8 is deposited on the photoconductive layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoreceptor having a hydrogenated amorphous silicon photoconductive layer.
Further, the present invention relates to an image forming apparatus equipped with the photoconductor.

[0002]

2. Description of the Related Art A photoreceptor using amorphous silicon (hereinafter, amorphous silicon is abbreviated as a-Si) as a photoconductive layer has already been commercialized, but the a-Si photoreceptor is formed on a conductive substrate. A charge injection blocking layer made of hydrogenated amorphous silicon (hereinafter abbreviated as a-Si: H) and an a-Si: H photoconductive layer are sequentially laminated by glow discharge decomposition to further protect the surface. This is a layer configuration in which the layers are covered. The a-Si: H charge injection blocking layer is doped with, for example, a Group IIIa element of the periodic table to form a potential barrier for electrons, thereby preventing injection of electrons from the conductive substrate and positively charging. Electrophotographic photoreceptor is obtained.

Further, a technique has been proposed in which the charge injection blocking layer has a laminated structure. That is, the charge injection blocking layer has a three-layer structure in which a p-layer, an i-layer, and an n-layer are sequentially stacked, a three-layer structure in which an n-layer, an i-layer, and a p-layer are sequentially stacked, or a p-layer and an n-layer. , A two-layer structure in which n layers and p
An electrophotographic photoreceptor has been proposed which has a two-layer structure in which layers are sequentially laminated to significantly improve the withstand voltage of the layer itself, thereby increasing the surface potential, and stably obtaining a good image. No. 59-200244).

Further, it has been studied to specify a material constituting the charge injection blocking layer. For example, JP
In Japanese Patent Application No. 9-45445, a charge injection blocking layer is composed of a mixture of an oxide and a nitride of amorphous hydrogenated silicon.

In these prior arts, the charge injection blocking layer itself is improved. In addition, silicon atoms are used as a base material between the conductive substrate and the charge injection blocking layer.
An electrophotographic photoreceptor in which an auxiliary layer of an amorphous material containing up to 43 atomic% of nitrogen atoms as constituent atoms is interposed to improve the adhesion to a conductive substrate has also been proposed (Japanese Patent Application Laid-Open No. 58-145961 and Japanese Patent Application Laid-Open No. Sho 58-145961). 58-145962
No.).

[0006]

However, in the electrophotographic photoreceptor having an auxiliary layer of an amorphous material as described above, there is a technique for improving the durability of the photoreceptor with almost no residual potential. This auxiliary layer is formed as a single layer, and furthermore, the residual potential is reduced by defining the film thickness to be thin, and furthermore there is no auxiliary potential. However, on the other hand, there is a problem that it is difficult to increase the breakdown voltage.

In view of the above circumstances, the present inventor has made intensive studies and as a result, has found that an electrically insulating layer made of silicon and an electrically non-insulating a layer are provided between the conductive substrate and the charge injection blocking layer. It has been found that the residual potential is reduced as much as possible and the withstand voltage is improved by interposing a stack of an -Si layer and an electrical insulating layer made of silicon.

Accordingly, the present invention has been accomplished based on the above findings, and an object of the present invention is to provide a laminate of an electrically insulating layer made of silicon, an electrically non-insulating a-Si layer, and an electrically insulating layer made of silicon. Accordingly, it is an object of the present invention to provide a high-performance and high-quality electrophotographic photosensitive member having improved residual potential and withstand voltage.

Another object of the present invention is to provide an electrophotographic photosensitive member suitable for a high-speed printing image apparatus by improving both the residual potential and the withstand voltage.

A further object of the present invention is to provide a high-performance image forming apparatus equipped with such an excellent electrophotographic photosensitive member.

[0011]

The electrophotographic photoreceptor (photoreceptor) of the present invention comprises an electrically insulating layer made of silicon, an electrically non-insulating a-Si layer, and a silicon substrate. An electrically insulating layer, a charge injection blocking layer made of a-Si, a photoconductive layer made of a-Si, and a surface protection layer are sequentially laminated.

The image forming apparatus of the present invention comprises the photoreceptor of the present invention, charging means for applying a charge to the surface of the photoreceptor, and exposing means for irradiating the charged area of the photoreceptor with light,
The charging unit and the exposure unit form an electrostatic latent image on the surface of the photoconductor, and a developing unit that forms a toner image corresponding to the electrostatic latent image on the surface of the photoconductor. A transfer means for transferring, a cleaning means for removing residual toner on the surface of the photoreceptor after the transfer, and a charge removing means for removing a residual electrostatic latent image after the transfer are provided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Configuration of Electrophotographic Photoreceptor FIG. 1 shows a layer configuration of an electrophotographic photoreceptor 1 according to the present invention. By the CVD, an electrically insulating layer 5a made of silicon (Si), an a-Si layer 4 having conductivity, that is, electrically non-insulating, an electrically insulating layer 5b made of silicon (Si), and a-Si : H charge injection blocking layer 6
And a photoconductive layer 7 made of a-Si: H are sequentially laminated, and a surface protective layer 8 is laminated on the photoconductive layer 7.

The conductive substrate 3 is made of copper, brass, SUS, A
Metallic conductors such as 1 and Ni, or insulators such as glass and ceramic, each of which has a surface coated with a conductive thin film. The conductive substrate 3 may be a sheet-shaped, belt-shaped or web-shaped flexible conductive sheet. Such a sheet may be a metal sheet of SUS, Al, Ni, or the like, or a polymer resin film of polyester, nylon, polyimide, or the like. A metal such as Al or Ni, or a transparent conductive material such as indium tin oxide (ITO) or an organic conductive material is coated thereon by vapor deposition or the like, and is subjected to a conductive treatment.

As for the charge injection blocking layer 6, a-Si:
Periodic Table IIIa as a valence electron controlling impurity for H
A group element (hereinafter abbreviated as a group IIIa element) and / or a group Va element of the periodic table (hereinafter abbreviated as a group Va element) may be doped, so that carrier movement can be controlled.

Oxygen or nitrogen may be contained in the charge injection blocking layer 6 to increase the forbidden band width, thereby increasing the barrier in terms of the function of blocking charge injection.

For the photoconductive layer 7 made of a-Si: H, a group IIIa element or V
A group a element may be added, and when light enters this layer, photoconductive carriers are generated. A surface charge is formed by exposing the electrophotographic photoreceptor 1 to corona discharge, and the photoconductive carrier cancels the surface charge,
An electrostatic latent image is formed on the photoreceptor surface. Such photoresponsiveness can be controlled by the above-mentioned impurity addition amount. Furthermore, the density distribution of the acceptor level and the donor level can be adjusted by controlling unpaired bonds in the film or improving the film quality. Here, the film quality means that the bonding of the film is made dense, furthermore, the bonding defects such as unpaired bonding are minimized and extra trap levels are reduced.

In the present invention, an electrically insulating layer 5a, an electrically non-insulating a-Si layer 4 and an electrically insulating layer 5b are laminated between the conductive substrate 3 and the charge injection blocking layer 6. By interposing the photoconductor, the thickness of the entire photoreceptor is increased, thereby significantly increasing the breakdown voltage and reducing or eliminating the residual potential.

Even if the residual potential does not become zero at all, it is adjusted by the image forming apparatus, that is, by increasing the difference between the post-exposure potential and the developing bias (the post-exposure potential becomes large). By increasing the developing bias, the black solid density can be increased to an appropriate level even if the potential after static elimination is large, and as a result, the residual potential is reduced to the same level as when the potential is zero. Excellent results are obtained.

The a-Si layer 4 and the electrically insulating layers 5a,
5b facilitates adjusting the withstand voltage to a required value.

The surface protective layer 8 includes a-Si,
Glow discharge decomposition, vacuum deposition, active reactive deposition, ion plating, RF sputtering, DC sputtering, RF magnetron sputtering, DC, amorphous silicon carbide, amorphous silicon nitride, amorphous silicon oxide, Magnetron sputtering method, thermal CV
A film is formed by the method D or the like. When an organic material is used, a film is formed by coating or the like.

Hydrogen is contained in the charge injection blocking layer 6, the photoconductive layer 7, and the surface protective layer 8 to compensate for dangling bonds. However, by including halogen such as fluorine in addition to hydrogen, dangling is prevented. Ring bonds may be compensated.

In the present invention, the electrophotographic photosensitive member 1 having such a laminated structure is further provided with an electrically insulating layer 5a made of silicon (Si) and an electrically non-insulating a-Si layer 4 in the present invention.
And an electrically insulating layer 5b made of silicon (Si).

The a-Si layer 4 is a layer for improving the breakdown voltage in particular, and it is preferable that the film quality is as good as the photoconductive layer 7 made of a-Si: H. However, this a-Si
In many cases, the layer 4 has photosensitivity. Therefore, the film quality and thickness of the charge injection blocking layer 6, the photoconductive layer 7, and the surface protective layer 8 are controlled so that photoconductive carriers are not generated.
An exposure wavelength such as a long wavelength penetrates deep into the film, and it is better to consider this point.

Such an a-Si layer 4 exhibits some n-type semiconductor characteristics when no valence electron controlling impurity is added, but further has an i-type conductivity by adding a group IIIa element. It is desirable to make this electrically neutral and to minimize the number of carriers.

The thickness of the a-Si layer 4 should be 20 μm or less, preferably 1 to 10 μm, and most preferably 5 to 10 μm, so that the residual potential and the amount of generated carriers are reduced.

The electric insulating layers 5a and 5b are also provided to increase the withstand voltage, but further have a large energy barrier to prevent the residual potential from being generated or to increase. Made of excellent silicon material. For example, silicon nitride (S
iN), an amorphous material made of silicon carbide (SiC), silicon oxide (SiO), or the like, an amorphous material having some crystallinity, or a polycrystalline material.

By using such a silicon material, the amount of photocarriers generated is reduced, and the ability to block carriers from the conductive substrate 3 is increased. Even if the film thickness is increased to further increase the breakdown voltage, the residual potential increase rate decreases.

The thickness of the electrically insulating layer 5 (5a, 5b) is
It is good to be 5 μm or less, preferably 0.5 to 1 μm, so that the residual potential and the amount of generated carriers are reduced. Further, the resistance of this layer 5 is preferably 10 ¹² Ωcm or more.

Thus, in the electrophotographic photoreceptor 1 of the present invention, the electrically insulating layer 5a, the electrically non-insulating a-Si layer 4 and the electrically non-insulating a-Si layer 4 are provided between the conductive substrate 3 and the charge injection blocking layer 6. By interposing the lamination with the insulating layer 5b, the thickness of the entire photoreceptor is increased, so that the withstand voltage is significantly increased, and the residual potential is reduced or eliminated.

Even if the residual potential does not become zero at all, it is possible to increase the potential after static elimination by adjusting the image forming apparatus, that is, by increasing the difference between the post-exposure potential and the developing bias. Also, the solid black density can be increased to an appropriate density, and as a result, excellent results up to the same level as when the residual potential becomes zero can be obtained.

Moreover, the a-Si layer 4 and the electrically insulating layer 5
The lamination with a and 5b makes it easy to adjust the breakdown voltage to a required value. That is, fine adjustment is performed by roughly improving the withstand voltage by the electric insulating layers 5a and 5b, and further by adjusting the film thickness of the a-Si layer 4 in which the withstand voltage improvement ratio is small and the residual potential is hardly generated.

Configuration of Image Forming Apparatus FIG. 2 shows an image forming apparatus 9 having a printer configuration equipped with the photoreceptor of the present invention. Reference numeral 10 denotes a photoreceptor.
0, a corona charger 11, an exposure unit 12 (LED head) for irradiating light after charging, and a photoconductor 1
Developing device 1 provided with toner 13 for forming on the surface of
4 and a transfer device 1 for transferring the toner image to the transfer material 15
6, a cleaning means 17 for removing the residual toner on the surface of the photoreceptor after the transfer, and a charge removing means 18 for removing the residual electrostatic latent image after the transfer. Also,
Reference numeral 19 denotes a fixing device for fixing the toner image transferred to the transfer material 15 by heat or pressure.

In the Carlson method, the following processes (1) to (6) are repeated. (1) The peripheral surface of the photoconductor 8 is charged by the corona charger 9. (2) An image is exposed by the exposure device 10 to form an electrostatic latent image as a potential contrast on the surface of the photoconductor 8. (3) The electrostatic latent image is developed by the developing machine 12. By this development, the black toner adheres to the surface of the photoreceptor by electrostatic attraction with the electrostatic latent image and is visualized. (4) The toner image on the photoreceptor surface is electrostatically transferred from the back surface of the transfer material 13 such as paper by applying an electric field having a polarity opposite to that of the toner,
Thus, an image is obtained on the transfer material 13. (5) Cleaning means 15 for removing residual toner on the photoreceptor surface
To remove mechanically. (6) Exposing the entire surface of the photoreceptor with strong light,
Removes the remaining electrostatic latent image.

The image forming apparatus 9 has a printer configuration. However, if an optical system such as a lens or a mirror that transmits light reflected from a document is used in place of the exposure unit 12, the image forming apparatus 9 has a configuration similar to that of a copier. Become.

The image forming apparatus 9 employs ordinary dry development, but is also applicable to liquid developers used for wet development.

[0037]

The embodiments will be described below.

[0038] Glow discharge decomposition was carried out on a cylindrical substrate made of Al having a purity of 99.9% under the film forming conditions shown in Table 1 (the conditions are values in one chamber). Insulating layer 5a, a-Si layer 4, and electrically insulating layer 5
b, the charge injection blocking layer 6, the photoconductive layer 7, and the surface protection layer 8 are laminated.

[0039]

[Table 1]

Example 1 Reference Example In this example, under the film forming conditions shown in Table 1, the a-Si layer 4 was not formed,
A single electrically insulating layer 5 was formed. In this film formation, the flow rate ratio of NH ₃ gas to SiH ₄ gas (NH ₃ / Si
H ₄ ) and introduced in various ways as shown in Table 2, and the film thickness was changed in three ways of 1 μm, 5 μm, and 10 μm. No. 1 to No. 1 1
8 was prepared.

The residual potential, image evaluation, and withstand voltage of these electrophotographic photosensitive members were measured, and the results shown in Table 2 were obtained.

The measuring method and measuring conditions are as follows. Residual potential: The average value of the values measured in one round of charging, exposure, and static elimination using a self-made general-purpose inspection machine. The measurement conditions are
Drum surface temperature: 42 ° C., drum speed: linear velocity about 1140
mm / sec, and the amount of neutralization light: 600 μW. Evaluation evaluation of image: A commercially available high-speed printer was used. Pressure resistance: Measured by a contact needle pressure resistance method (tip diameter of electrode needle shape: φ1.4 mm). The surface of the photosensitive drum is brought into contact with the needle tip, but glycerin is used as a medium in order not to be affected by air.

[0043]

[Table 2]

Regarding the evaluation judgment of the image,
The mark was divided into three types of X, the mark ○ indicates that a normal and good image was obtained, the mark Δ indicates a case where fogging was slightly observed, and the mark X indicates that fogging was remarkably observed. This is the case when it becomes inappropriate.

As is clear from the results shown in Table 2, Sample No. 1 having a film thickness of 1 μm was used. 1, sample no. 4, sample no.
7, sample no. 10, sample no. 13, sample no. 16
In, as the flow rate ratio (NH ₃ / SiH ₄ ) increases, the breakdown voltage increases both positive and negative. However, the sample No. In the case of No. 16, the residual potential also becomes large, which is not suitable.

The sample No. having a thickness of 5 μm was used. 2, Sample No. 5, sample no. 8, sample no. 11, sample no.
In 14, also, as the flow ratio (NH ₃ / SiH ₄ ) increases, the withstand voltage increases both positive and negative.

Sample No. In No. 8, although a downward tendency was recognized in part of the image determination, it was confirmed that it was sufficiently practical. Incidentally, it was confirmed that the sharpness and the density of the image were remarkably reduced when the residual potential was around 150 V.

However, the sample No. 11 and sample no. 14
In this case, the residual potential becomes large, which is not suitable.

Further, Sample No. having a film thickness of 10 μm was used.
3, sample no. 6, sample no. 9, sample no. In 12, also, as the flow ratio (NH ₃ / SiH ₄ ) increases, the breakdown voltage increases both positive and negative. However, the sample No. 9 and sample no. In the case of No. 12, the residual potential also becomes large, which is not suitable.

Example 2 Next, in this example, an a-Si layer 4 was formed as shown in Table 1 (the film thickness was set to 5 μm).
Further, an electric insulating layer 5a (setting the film thickness to 1 μm) and an electric insulating layer 5b (setting the film thickness to 1 μm) with different flow rate ratios (NH ₃ / SiH ₄ ) are formed. An electrophotographic photoreceptor having the other film forming configurations as shown in Table 1 was produced, and the residual potential, image evaluation judgment, and breakdown voltage were measured in the same manner. The results shown in Table 3 were obtained. In Table 3, "substrate side" corresponds to the electrically insulating layer 5a, and "blocking layer side" corresponds to the electrically insulating layer 5b.

[0051]

[Table 3]

As is clear from this table, a-S
It can be seen that even when the i-layer 4 is formed, the breakdown voltage is increased without increasing the residual potential.

(Example 3) Next, for both the electric insulating layer 5a and the electric insulating layer 5b, the film thickness is set to 1 μm, the flow rate ratio (NH ₃ / SiH ₄ ) is set to 1.0, and An electrophotographic photoreceptor was manufactured by changing the thickness of the a-Si layer 4 in various ways, and the residual potential, image evaluation judgment, and breakdown voltage were measured in the same manner. The results shown in Table 4 were obtained.

[0054]

[Table 4]

As is clear from the table, the breakdown voltage increases as the thickness of the a-Si layer 4 increases, and it can be seen that the breakdown voltage can be obtained as required by adjusting the thickness. In addition, it was found that the film thickness of the a-Si layer 4 hardly affected the image and the residual potential.

(Example 4) In this example, as shown in Table 5, the electric insulation layer 5a (the film thickness is set to 1 μm) and the electric insulation layer 5a in which the flow rate ratio (CH ₄ / SiH ₄ ) was changed in various ways were used. Layer 5b
(Set the film thickness to 1 μm), and a film thickness of 5 μm.
An m-type a-Si layer 4 was formed, and an electrophotographic photoreceptor having the same other film forming configuration as in Example 1 was manufactured. Similarly, the residual potential, image evaluation judgment, and breakdown voltage were measured. The result as shown in FIG. 5 was obtained.

[0057]

[Table 5]

As is clear from the results shown in this table, the breakdown voltage increases both positive and negative as the flow rate ratio (CH ₄ / SiH ₄ ) increases.

[0059]

As described above, according to the electrophotographic photoreceptor of the present invention, an electrically insulating layer made of Si, an electrically non-insulating a-Si layer, and an electrically By sequentially laminating the insulating layer, the a-Si charge injection blocking layer, the a-Si photoconductive layer, and the surface protection layer, both the residual potential and the withstand voltage are improved, thereby providing high performance and high quality. As a result, a high-speed printing image device could be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a layer configuration of a photoreceptor according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an image forming apparatus of the present invention.

[Description of Signs] 1 electrophotographic photoreceptor 3 conductive substrate 4 electrically non-insulating a-Si layer 5a, 5b electrically insulating layer 6 charge injection blocking layer 7 photoconductive layer 8 surface protective layer 9 image forming apparatus 11 corona Charger 12 Exposure device 13 Toner 14 Developing device 15 Transfer receiving material 16 Transfer device 17 Cleaning means 18 Static elimination means

Claims (2)

[Claims] An electric insulating layer made of silicon, an amorphous silicon layer, an electric insulating layer made of silicon, a charge injection blocking layer made of amorphous silicon, and a photoconductive layer made of amorphous silicon on a conductive substrate. And a surface protective layer sequentially laminated. 2. The photoconductor of claim 1, comprising: a charging unit for applying a charge to the surface of the photoconductor; and an exposure unit for irradiating the charged area of the photoconductor with light. Forms an electrostatic latent image on the surface of the photoconductor,
Developing means for forming a toner image corresponding to the electrostatic latent image on the surface of a photoreceptor, transfer means for transferring the toner image to a transfer material, and cleaning means for removing residual toner on the photoreceptor surface after the transfer An image forming apparatus, comprising: a charge removing unit that removes a residual electrostatic latent image after the transfer.