JP2000019759A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having superior printing resistance force to maintain suprior image quality for a long period, while having a surface layer thickness of 0.6 μm or more. SOLUTION: In an electrophotographic photoreceptor composed of amorphous Si material films layered on a conductive base material, the amorphous Si material film containing C and/or N, and having 2.2-2.6 ev of optical band gap energy and 0.7-5.0 μm of film thickness is provided as a surface layer via a gradient composition layer, in this photoreceptor. Since the optical band gap energy of the surface layer containing C and/or N is 2.0-2.6 ev, photocharges are effectively generated inside a photoconductive layer without absorbing incident light while restraining deffects in the film to a low level, electric resistance of the film is maintain at a high value, and the photocharges reaches thereby effectively to a surface even when the thickness of the surface layer is increased upto 0.7-5.0 μm, so as to provide an excellent image free from an after-image and an image void.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member having excellent printing durability.

[0002]

2. Description of the Related Art As an electrophotographic photoreceptor, an organic photoreceptor (OPC) is generally and widely used at present. However, there is a problem that the photoreceptor is easily damaged due to its softness and lacks printing durability.
For this reason, amorphous Si with high hardness and excellent sensitivity
Attempts have been made to apply (hereinafter a-Si) to electrophotographic photoreceptors.

However, even if a-Si is undoped, the dark resistivity is as small as 10 ^-11 Ωcm, so that the dark decay during charging is large and the charge holding function is small, so that this point needs to be improved. As an effective method for increasing the charge holding ability while maintaining high sensitivity, as shown in FIG.
A charge injection blocking layer 2 for preventing charge injection from the conductive substrate 1 between the Si photoconductive layer 3 and a surface layer on the a-Si photoconductive layer 3 for preventing charge leakage from the surface. 4 is known. As a specific example, between the conductive substrate 1 made of an Al substrate and the a-Si photoconductive layer 3, B
And a P-doped a-Si layer, an a-SiC _x layer, etc., sandwiching the charge injection blocking layer 2, and a-Si
By forming the surface layer 4 electrical resistance such as C _x is a high material,
A sufficient charge holding function can be obtained. In addition, since the surface layer wears with printing, it is desirable to make the surface layer as thick as possible in order to increase printing durability.

However, a-S used as a surface layer
iC _x etc. although high abrasion resistance, there are many defects called localized rank in the film, the light charges the photosensitive generated in the photoconductive layer when the thickness of the surface layer to earn printing durability of the photosensitive member There is a problem in that the residual potential rises and the residual image rises and a white spot in the image occurs, because the residual potential cannot be removed to the body surface. Therefore, in order to maintain good image quality, the thickness of the surface layer is 0.5 to 0.6 μm.
Is the limit.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides an electrophotographic photosensitive member which has a surface layer having a thickness of 0.6 μm or more and which has excellent printing durability and can maintain good image quality for a long period of time. The purpose is to do.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that an electrophotographic photosensitive member comprising an amorphous Si-based material film laminated on a conductive base material. In the body, C having an optical band gap energy of 2.0 to 2.6 ev and a film thickness of 0.7 to 5.0 μm
By providing a surface layer made of an amorphous Si-based material film containing N and / or N via a gradient composition layer, the surface layer can be made thicker without deteriorating the image quality, and the printing durability is excellent. It has been found that an electrophotographic photosensitive member can be obtained.

In the present invention, the surface band containing C and / or N has an optical band gap energy of 2.0 to 2.0.
By setting it to 2.6 ev, it is possible to efficiently generate photocharges in the photoconductive layer without absorbing incident light while keeping defects in the film low, and it is possible to maintain a high electric resistance of the film. . Therefore, the surface layer has a thickness of 0.7 to 5.0 μm.
Even if the film thickness is increased to m, the photocharge efficiently reaches the surface, so that a good image free from afterimages and white spots in the image can be obtained.

In order to control the optical band gap energy of the surface layer to 2.0 to 2.6 ev, the composition ratio of Si to C and / or N contained in the surface layer may be adjusted.

When the proportion of C and / or N in the surface layer decreases, the number of defects in the film decreases, so that photocharges generated in the photoconductive layer efficiently reach the surface. However, if the proportion of C and / or N is excessively reduced, the optical band gap energy is reduced, and the incident light is absorbed, so that the efficiency of photocharge generation in the photoconductive layer is reduced and the photosensitivity of the photoconductor is reduced. Would. Further, if the proportion of C and / or N contained in the surface layer is too low, the electric resistance is lowered, the charged potential is lowered, and the image becomes liable to be stained or blurred.
Therefore, the optical band gap energy is 2.0 e
The ratio of C and / or N is decreased so as to be not less than v. As the proportion of C and / or N contained in the surface layer increases, the optical bandgap energy increases, the absorption of incident light decreases, and photocharges can be generated efficiently in the photoconductive layer. However, if the ratio of C and / or N contained in the surface layer is excessively increased and the optical bandgap energy exceeds 2.6 ev, the defect density in the film increases, which hinders the transfer of photocharge to the surface. In addition, afterimages and image white spots due to residual charges are likely to occur. In the present invention, the reason for setting the optical band gap energy of the surface layer to 2.0 to 2.6 ev is as described above.

Further, in the present invention, by providing the gradient composition layer between the photoconductive layer and the surface layer, the band energy caused by the difference in composition between the photoconductive layer and the surface layer is eliminated, and the photo charge is reduced. Can reach the surface more efficiently and a good image can be obtained. The gradient composition layer is an a-Si-based material film layer in which the composition of C and / or N changes in the thickness direction. The interface between the photoconductive layer and the gradient composition layer does not contain C and / or N, and the surface layer It is desirable to form the interface between the surface layer and the gradient composition layer so as to contain the same amount of C and / or N as the surface layer. That is, from the interface between the photoconductive layer and the gradient composition layer to the interface between the surface layer and the gradient composition layer, C and / or N
Can be said to be a layer in which the amount of is increased. The increase in the amount of C and / or N is not limited to the case where the amount is continuously increased, and even if there is a portion that does not partially increase, the effect is not substantially affected.

When the surface layer is composed of an a-SiC _x layer, the gradient composition layer is composed of a-SiC _x , and the C composition extends from the interface between the photoconductive layer and the gradient composition layer to the interface between the gradient composition layer and the surface layer. What is necessary is just to make it the layer whose quantity increases continuously. Also,
If the surface layer is composed of a-SiN _x layer, gradient composition layer is made of a-SiN _x, toward the interface of the photoconductive layer and the graded composition layer from the interface of the graded composition layer and the surface layer, N amount is continuously What is necessary is just to make it the layer which increases gradually.

In the present invention, the thickness of the surface layer is set to 0.7 μm or more in order to secure printing durability. However, if the thickness exceeds 5 μm, the moving distance of the photocharge becomes long, and defects contained in the surface layer are reduced. Since the amount of charges trapped and remaining in the surface layer increases, afterimages and white spots in images tend to occur. Therefore, the thickness of the surface layer is set to 0.7 to 5.0 μm.

In the electrophotographic photoreceptor according to the present invention, an a-Si-based material film comprising a charge injection blocking layer, a photoconductive layer, a gradient composition layer, and a surface layer is laminated on a conductive substrate. Can be obtained by A conventionally known technique may be applied to the conductive substrate and the charge injection blocking layer. For example,
An a-Si based material film such as an a-Si layer or an a-SiC _x layer doped with B or P can be used as the conductive substrate, and an Al drum as the charge injection blocking layer.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a first embodiment and a second embodiment.
A description will be given based on an embodiment. (First Embodiment) An a-Si-based material film is formed on a conductive substrate by a plasma CVD method using ordinary high-frequency glow discharge.
The electrophotographic photosensitive member having the structure shown in FIG. 1 was produced by laminating the layers. In FIG. 1, reference numeral 1 denotes a conductive substrate composed of a degreased and cleaned Al drum, on which a charge injection blocking layer 2 composed of a B-doped a-SiCx film under the conditions shown in Tables 1 and 2. , An a-Si photoconductive layer 3, a-
A gradient composition layer 5 composed of a SiCx film and a surface layer 4 composed of an a-SiCx film were sequentially formed.

Here, the flow rate of C ₂ H ₄ of the gradient composition layer 5 is set to zero at the start of film formation (the interface with the photoconductive layer 3), and thereafter, at the end of film formation (the interface with the surface layer 4). ) In SiH ₄
And it was deposited by flow rate ratio of C ₂ H ₄ increases the flow rate of C ₂ H ₄ to be the same as the conditions for forming the surface layer 4 at a constant rate. When the gradient composition layer 5 of the produced electrophotographic photoreceptor was analyzed by Auger electron spectroscopy (hereinafter, AES), C was not contained at the interface with the photoconductive layer 3.
It was confirmed that C continuously increased toward the interface with the surface layer 4 and that the interface with the surface layer 4 had a gradient composition distribution including C equivalent to that of the surface layer.

Table 1 shows film forming conditions for changing the optical band gap energy of the surface layer. Samples obtained by these conditions are referred to as Examples 1 to 3 of the present invention and Comparative Examples 1 and 2. In order to change the optical band gap energy of the surface layer, the flow rates of the source gases SiH ₄ and C ₂ H ₄ were adjusted to control the composition ratio of Si and C. Table 2 shows the film forming conditions for changing the thickness of the surface layer, and the samples obtained thereby are referred to as Examples 4 to 6 of the present invention and Comparative Example 3.

In Tables 1 and 2, the composition ratio of Si and C contained in the surface layer 4 was measured by the AES method. FIG. 3 shows a measurement chart of Example 1 of the present invention as an example of the measurement data. As can be seen from the figure, from the surface to the depth of 0.7 μm, the area where the value of the composition ratio C / Si of C and Si is constant at 0.8 and corresponds to the gradient composition layer having a depth of 0.7 μm to 1.0 μm. In the above, the value of the composition ratio C / Si of C and Si is 0.1.
It changes continuously from 8 to almost 0, and in a region corresponding to the photoconductive layer deeper than 1.0 μm in depth, it can be observed that it is almost Si. In addition, the optical band gap of the surface layer 4 was evaluated by a transmission spectroscopy of a single film prepared in advance under the same conditions as the surface layer.

The obtained samples of Examples 1 to 6 and Comparative Examples 1 to 3 were mounted on an electrophotographic printing test apparatus and subjected to a continuous printing test under the conditions shown in Table 3. 5
The printed matter after printing 100,000 sheets was visually evaluated for the presence of afterimages and white spots in the images. The results are shown in Table 4.
As shown in Table 4, the samples of Examples 1 to 6 of the present invention did not show any afterimages or white spots in the images. On the other hand, in Comparative Example 1, background smearing of an image, which is considered to be caused by a decrease in the electric resistance of the surface layer, was observed from the start of printing. Comparative Example 2
In Comparative Example 3, afterimages and white spots in images, which are considered to be caused by residual charges in the film, were observed from the start of printing.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

[0022]

[Table 4]

(Second Embodiment) The electrophotographic photosensitive member shown in FIG. 1 was subjected to the conditions shown in Tables 5 and 6 in the same manner as in the first embodiment except that the gradient composition layer 5 and the surface layer 4 were a-SiNx films. Prepared.

Here, the flow rate of NH ₃ of the gradient composition layer 5 is set to zero at the start of film formation (interface with the photoconductive layer 3), and thereafter, at the end of film formation (interface with the surface layer 4). SiH ₄
And a flow rate ratio of NH ₃ was formed by increasing the flow rate of NH ₃ to be the same as the conditions for forming the surface layer 4 at a constant rate. When the gradient composition layer 5 of the produced electrophotographic photoreceptor was analyzed by Auger electron spectroscopy (AES), the gradient composition layer 5 did not contain N at the interface with the photoconductive layer 3, but the surface layer did not contain N. N continuously increased toward the interface with the surface layer 4, and it was confirmed that the interface with the surface layer 4 had a gradient composition distribution including C equivalent to that of the surface layer.

Table 5 shows the film forming conditions for changing the optical band gap energy of the surface layer. Samples obtained thereby are referred to as Examples 7 to 9 of the present invention. In order to change the optical band gap energy of the surface layer, the raw material gas Si
The composition ratio of Si and N was controlled by adjusting the flow rates of H ₄ and NH ₃ . Table 6 shows the film forming conditions for changing the thickness of the surface layer.
Let it be 2.

In Tables 5 and 6, the composition ratio of Si and N contained in the surface layer 4 was measured by the AES method.
The optical band gap of the surface layer 4 was evaluated by the same method as in the first embodiment.

The same evaluation as in the first embodiment was performed on the obtained samples of Examples 7 to 12 of the present invention, and the results are shown in Table 7. As shown in Table 7, in the samples of Invention Examples 7 to 12,
No afterimages or white spots on the images were observed.

For comparison, an electrophotographic photoreceptor was prepared under the same conditions as in Example 8 of the present invention except that a gradient composition layer was not prepared, and was evaluated in the same manner. Due to the resulting band energy jump, an afterimage, which is considered to be caused by the residual charge at the layer interface, was observed from the start of printing.

[0029]

[Table 5]

[0030]

[Table 6]

[0031]

[Table 7]

[0032]

According to the present invention, C and / or N
The optical band gap energy of the surface layer containing
By setting the value to ~ 2.6 ev, it is possible to efficiently generate photocharges in the photoconductive layer without absorbing incident light while keeping defects in the film low, and to maintain a high electric resistance of the film. Therefore, even if the thickness of the surface layer is increased to 0.7 to 5.0 [mu] m, the photocharge efficiently reaches the surface, and a good image with no afterimages or white spots on the image can be obtained. Further, in the present invention, the provision of the gradient composition layer between the photoconductive layer and the surface layer eliminates the band energy jump caused by the difference in the composition between the photoconductive layer and the surface layer, so that the photocharge is more increased. The surface can be more efficiently reached and a good image can be obtained.
Therefore, according to the present invention, a thickness of 0.7 to 5.0 μm
An electrophotographic photoreceptor having excellent printing durability and capable of maintaining good image quality for a long period of time while having a surface layer of (1) is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of an embodiment of an electrophotographic photosensitive member according to the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of a conventional electrophotographic photosensitive member.

FIG. 3 is a chart showing the composition distribution of the cross section of the electrophotographic photosensitive member according to the present invention measured by AES.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 charge injection blocking layer (a-Si based material film) 3 photoconductive layer (a-Si based material film) 4 surface layer (a-Si based material film) 5 gradient composition layer (a-Si based film) Material film)

Continued on the front page (72) Inventor Toshiro Kobayashi 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Inside Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Masaki Kono 4-6-kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 22 Mitsubishi Heavy Industries, Ltd. Hiroshima Laboratory (72) Katsuho Hananaka 4-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Laboratory F-term (reference) 2H068 DA05 DA07 DA15 DA17 DA20 DA23 FA03

Claims (1)

[Claims] 1. An electrophotographic photoreceptor comprising a photoconductive layer comprising an amorphous Si-based material film laminated on a conductive substrate, wherein the optical band gap energy is 2.0 to 2.6 ev.
An electrophotographic photoreceptor characterized in that a surface layer made of an amorphous Si-based material film containing C and / or N having a thickness of 0.7 to 5.0 μm is provided via a gradient composition layer.