JP2678449B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an electrophotographic photoreceptor suitable for plain paper copiers by increasing the light sensitivity on both the short wavelength side and the long wavelength side. (Prior art and its problems) In recent years, development of ultra-high-speed copying machines, laser beam printers, etc. has been actively promoted, and along with this, stable operation characteristics of the electrophotographic photosensitive drum mounted in this equipment. In addition, durability is required. In response to this demand, amorphous silicon has been attracting attention because it is excellent in wear resistance, heat resistance, pollution resistance, and photosensitivity. As an electrophotographic photosensitive member made of amorphous silicon (hereinafter abbreviated as a-Si), a laminated photosensitive member as shown in FIG. 3 has been proposed. That is, according to FIG. 3, a carrier injection blocking layer (2), an a-Si photoconductive layer (3) and a surface protective layer (4) are sequentially laminated on a conductive substrate (1) such as aluminum. Cage,
The carrier injection blocking layer (2) is formed to prevent carrier injection from the substrate (1) and reduce the residual potential, and the surface protection layer (4) is made of a high hardness material. It is used to increase the durability of the photoconductor. However, in such an a-Si photoreceptor,
When the photoreceptor is mounted on a plain paper copier (hereinafter abbreviated as PPC) using white light as a light source, such as a halogen lamp, the photosensitivity on the long wavelength side is high. Is poor in reproducibility. In order to solve such a problem, a filter is used to cut red wavelength light. However, the intensity of light incident on the photosensitive layer is reduced, and as a result, the photosensitivity of the photoconductor itself is apparently reduced. Lower. (Object of the Invention) Accordingly, an object of the present invention is to provide an electrophotographic photoreceptor capable of increasing the light sensitivity on the short wavelength side and the long wavelength side. Another object of the present invention is to provide an electrophotographic photosensitive member suitable for PPC. (Means for Solving Problems) According to the present invention, at least a photoconductive a-Si layer and a photoconductive amorphous silicon carbide layer (hereinafter referred to as amorphous silicon carbide a-
An electrophotographic photosensitive member formed by sequentially forming SiC)
Silicon (Si) element and carbon (C) in the a-SiC layer
The atomic ratio of the elements is in the range of 0.01 ≦ x ≦ 0.5 in the x value of Si _(1-x) C _x and the thickness thereof is set in the range of 0.05 to 5 μm, and the a-SiC layer has a thickness of 0.5 to 5 μm. Periodic Table III of 100ppm
Provided is an electrophotographic photosensitive member containing an a-group element. Hereinafter, the present invention will be described in detail. The basic layer constitution of the electrophotographic photoreceptor of the present invention is as shown in FIG. 1, and a photoconductive a-Si layer (6) and a photoconductive a-SiC layer (7) are formed on a conductive substrate (5). ) Are sequentially stacked. According to experiments by the present inventors, the above-mentioned a-SiC layer (7)
It was found that the photosensitivity on the short wavelength side was significantly enhanced when a predetermined amount of Group IIIa element (hereinafter abbreviated as Group IIIa element) was contained in Based on this, the present invention has been completed. That is, according to the layer structure shown in FIG. 1, when the thickness of the layer (7) is set within a predetermined range, the shorter wavelength side of the incident light is absorbed by the a-SiC layer (7), and a-S
Light transmitted through the iC layer (7), that is, light on the long wavelength side is a-Si
It is characterized in that it is absorbed by the layer (6), thereby increasing the light sensitivity on both the short wavelength side and the long wavelength side. First, according to the a-SiC layer (7), the amorphous Si element and the C element are formed as indispensable constituent elements, and the hydrogen (H) element and the halogen element are added in a required range to terminate the dangling bond. Photoconductivity arises by being contained within. When the present inventors have conducted experiments to ascertain the photoconductive also changed to several kinds of content of carbon, Si elements and C elements of atomic ratio, i.e., Si _(1-x) C _x of x
When the value is set in the range of 0.01 ≦ x ≦ 0.5, preferably 0.05 ≦ x ≦ 0.3, the dark conductivity decreases, and the light sensitivity on the short wavelength side can be increased. Further, the content of the element A for terminating dangling bonds such as an H element and a halogen element is preferably such that the y value represented by [Si _{(1-x) Cx} ] _1-y [A] _y is 0.05 ≦ y ≦ 0.5, Has 0.05 ≦ y ≦ 0.4,
Optimally, it is preferable to set so as to be in the range of 0.1 ≦ y ≦ 0.3. Such an element A is usually used because the element H is easily incorporated into the end portion of the dangling bond and the localized level density in the band gap is reduced. The thickness of such a-SiC layer (7) is 0.05 to 5 μm,
Preferably, the thickness is set in the range of 0.1 to 3 μm, and when the thickness is less than 0.05 μm, absorption of short-wavelength light is insufficient to increase the light sensitivity, and when the thickness exceeds 5 μm, The residual potential increases. The a-SiC layer (7) may have either an atomic ratio of Si element to C element, that is, a case where the x value is uniform in the layer thickness direction or a case where the x value changes. . When the x value changes in the layer thickness direction, the x value is represented by the average value of the entire layer (7), and the average x value is within the range of 0.01 ≦ x ≦ 0.5. Must be set. The carbon doping distribution in the case where the x value changes in the layer thickness direction as described above is, for example, as shown in FIGS. 4 to 9. In each figure, the horizontal axis represents the layer thickness direction of the a-SiC layer (7), a is the interface with the a-Si layer (6), b is the opposite interface, and the vertical axis is Indicates the carbon content. Further, in the a-SiC layer (7), a Group IIIa element is uniformly distributed in the layer thickness direction at 0.5 to 100 ppm, preferably 1 to 50 ppm.
It is good to contain it within the range of, and if this content is less than 0.5 ppm, a sufficiently high photosensitivity cannot be obtained, while 100 p
If it exceeds pm, the charging ability will decrease. The IIIa group elements include B, Al, Ga, In, etc.
B is desirable in that it has an excellent covalent bond property and can sensitively change the semiconductor characteristics, and in addition, excellent charging ability and photosensitivity can be obtained. As described above, when the Group IIIa element is contained in the a-SiC layer (7), its doping distribution may be made nonuniform over the layer thickness direction. For example, as shown in FIGS. is there. In each figure, the horizontal axis indicates the layer thickness direction of the a-SiC layer (7), a is the interface with the a-Si layer (6), b is the interface on the opposite side, and the vertical direction. The axis represents the group IIIa element content. When the group IIIa element content is changed in the layer thickness direction in this manner, the content is an average value per a-SiC layer (7). The a-Si layer (6) is composed of an amorphous Si element and an H element or a halogen element for terminating the dangling bond, and absorbs light of a longer wavelength side of incident light. The thickness of the a-Si layer (6) is 5 to 100 μm, preferably 1 to 100 μm.
It is desirable to set it in the range of 0 to 50 μm, and if it is in this range, it is advantageous in that a high charging ability can be obtained and long-wavelength light can be effectively absorbed. Further, the a-Si layer (6) is a layer containing substantially no carbon element, but may contain a very small amount of carbon. In that case, this carbon is 1000ppm or less, preferably 5
Within the range of 00 ppm or less, the photosensitivity of long-wavelength light is not significantly reduced. Furthermore, the a-Si layer (6) contains 0.01 to 10 pp of Group IIIa element.
It may be contained in m, preferably in the range of 0.1 to 5 ppm. Within this range, it is advantageous in that a high chargeability can be obtained and the residual potential can be reduced. This II
The doping distribution of the group Ia element may be uniform or non-uniform in the layer thickness direction, and the content in the case of non-uniform doping is the average value for the entire layer (6). Then, as described above, III is contained in the a-Si layer (6).
Group a elements include B, Al, Ga and In. Thus, when the electrophotographic photoreceptor of the present invention is mounted on a PPC using white light such as a halogen lamp as a light source, light on the short wavelength side is mainly absorbed by the a-SiC layer, and Is mainly absorbed by the a-Si layer, whereby a filter for cutting off infrared wavelength light is not required, and the photosensitivity of the photoreceptor itself is significantly increased. The two-layer structure as described above is indispensable for the electrophotographic photoreceptor of the present invention. In addition, a carrier injection blocking layer and a surface protective layer may be formed. For example, FIG. 2 shows a typical layer structure in which a carrier injection blocking layer (8) is provided between the substrate (5) and the a-Si layer (6), and on the a-SiC layer (7). A surface protective layer (9) is formed on the surface. The carrier injection blocking layer (8) prevents carrier injection from the substrate (5), and the surface protection layer (9) protects the a-SiC layer (7) to improve moisture resistance and the like. In addition, both layers (8) and (9) can reduce the dark conductivity of the photoreceptor and increase the charging ability. Various materials can be used for the surface protective layer (9) as long as the material itself has high insulation properties, high corrosion resistance and high hardness. For example, an organic material such as polyimide resin or an inorganic material such as SiC, SiO, Al ₂ O ₃ , or SiN can be used. Also, the same material as the above-mentioned material for the surface protective layer can be used for the carrier injection blocking layer (8). Next, a method for producing the electrophotographic photosensitive member according to the present invention will be described. To form the a-Si layer or the a-SiC layer, there are thin film forming methods such as glow discharge decomposition method, ion plating method, reactive sputtering method, vacuum deposition method, and CVD method. When the glow discharge decomposition method is used, glow discharge decomposition is performed by using a Si element-containing gas or a combination of the gas with a C element-containing gas. This Si element-containing gas includes SiH ₄ , Si ₂ H ₆ , Si ₃
There are H ₈ , SiF ₄ , SiCl ₄ , SiHCl ₃ and the like, and the C element-containing gas includes CH ₄ , C ₂ H ₄ , C ₂ H ₂ , C ₃ H ₈ and the like.
₂ H ₂ is desirable in that high-speed film forming properties can be obtained. The capacity engaging type glow discharge decomposition apparatus used in the embodiment of the present invention will be described with reference to FIG. In the figure, the first, second, third, fourth, fifth, and sixth tanks (10) (11) (12) (13) (14) (15)
SiH ₄ , C ₂ H ₂ , B ₂ H ₆ (0.2% content by dilution with H ₂ gas), B ₂ H ₆ (H
_{It is} diluted with ₂ gases and contains 38 ppm), H ₂ and NO gas are sealed, and H ₂ is also used as a carrier gas. These gases correspond to the corresponding first, second, third, fourth, fifth,
The sixth control valve (16) (17) (18) (19) (20) (21) is released by opening and the flow rate is controlled by the mass flow controllers (22) (23) (24) (25) (26) A first, second, third, fourth, fifth tank (10) controlled by (27)
(11) (12) (13) (14) The gas from the first main pipe (28)
The NO gas from the sixth tank (15) is sent to the second main pipe (29). Incidentally, (30) and (31) are stop valves. Gas flowing through the first main pipe (28) and the second main pipe (29) is sent to the reaction tube (32), and a capacitively coupled discharge electrode (33) is installed inside the reaction tube (32). The high frequency power applied to it is 50W to 3kW, and the frequency is 1
~ 50 MHz is appropriate. Inside the reaction tube (32), a cylindrical film-forming substrate (34) made of aluminum is placed on the sample holder (3).
5), the holding table (35) is driven to rotate by a motor (36), and the substrate (34) is heated to about 200 to 400 ° C. by a suitable heating means. ,
Preferably, it is uniformly heated to a temperature of about 200-350 ° C. Further, the inside of the reaction tube (32) is connected to the rotary pump (37) and the diffusion pump (38) by requiring a high vacuum condition (discharge voltage 0.1 to 2.0 Torr) when forming the a-SiC film. In the glow discharge decomposition apparatus configured as described above, for example, when an a-SiC film is formed on the substrate (34), the first, second, and fifth regulating valves (16), (17), and (20) are opened. SiH ₄ , C ₂ H ₂ , and H ₂ gas are released from each, and the release amount is controlled by mass flow controllers (22), (23), and (26). The mixed gas of SiH ₄ , C ₂ H ₂ , and H ₂ is It is poured into the reaction tube (32) via the first main pipe (28). And the reaction tube (32)
The inside of the vacuum state is about 0.1 to 2.0 Torr, the substrate temperature is 200
At ~ 400 ° C, the high frequency power applied to the capacitively coupled discharge electrode (33) is set to 50W to 3kW and the frequency is set to 1 to 50MHz, which causes glow discharge and gas decomposition. A-SiC film is formed on the substrate at high speed. (Example) Next, an example of the present invention will be described. Example 1 A photoconductive layer was formed on an aluminum substrate using the glow discharge decomposition apparatus shown in FIG. 16 under the film forming conditions shown in Table 1.
A -Si layer (6) and a photoconductive a-SiC layer (7) were sequentially laminated to produce a photosensitive drum as shown in FIG. The photosensitive drum thus obtained was irradiated with a unit light of 0.3 μW / cm ² which was dispersed by a visible light spectroscope, and the spectral sensitivity was measured by obtaining the half time of the surface potential, and as shown in FIG. The result was obtained. In the figure, the horizontal axis is wavelength, the vertical axis is photosensitivity, and ○ is a plot of measurement results, and a is its characteristic curve. FIG. 17 shows the photoconductive a-Si
A photoconductor drum from which the C layer was removed is shown as a comparative example. When its spectral sensitivity was measured, a plot of the measurement results indicated by a black circle was obtained, and b is its characteristic curve. As is clear from the results, it is found that the photoreceptor drum of the present invention has significantly increased light sensitivity on the short wavelength side. When the carbon content of the photoconductive a-SiC layer was determined by ESCA analysis, the x value of Si _1-x C _x was 0.12, and its B content was determined by a secondary ion mass spectrometer. When found, it was 25 ppm. Example 2 In this example, a carrier injection blocking layer (8), a photoconductive a-Si layer (6), and a photoconductive a-SiC were formed on an aluminum substrate under the film forming conditions shown in Table 2. The layer (7) and the surface protective layer (9) were sequentially laminated to produce a photosensitive drum as shown in FIG. The photoconductor drum thus obtained is mounted on a PPC, and since a red cut filter is not used, a halogen lamp is used as a light source, and a voltage of +5.6 kV is applied by a corona charger to positively charge the surface. When the lines were measured for potential, photosensitivity and potential, the following results were obtained. Surface potential --- + 390V Photosensitivity (recording exposure amount) ... 0.54lux.sec Residual potential (value 5 seconds after the start of exposure ... 20V Also, this photosensitive drum is mounted on a high-speed PPC, 50 sheets /
When an image output test was performed at a speed of 1 minute, faithful reproducibility was obtained for the black portion and the red portion, and a clear image with high density and no fog was obtained. (Example 3) Next, in this example, with respect to the photoconductor drums obtained in (Example 2), the thickness of the photoconductive a-SiC layer was changed in any number of ways, and the photoconductor drums A to The surface potential of G, the photosensitivity (recording exposure amount) and the remaining potential (value 5 seconds after the start of exposure) were measured, and the results as shown in Table 3 were obtained. As is apparent from Table 3, the photosensitive drums B to
It can be seen that F has a high surface potential, a small residual potential and excellent light sensitivity. However, the photosensitive drum A is inferior in light sensitivity, and the photosensitive drum G has a large residual potential. (Example 4) In this example, the carbon content B and the content of the photoconductive a-SiC layer in the photoconductor drum obtained in (Example 2) were changed in any number of ways, and thus obtained. Surface potential of photoconductor drums HO, photosensitivity (recording exposure amount)
When the residual potential (the value 5 seconds after the start of exposure) was measured, the results shown in Table 4 were obtained. As is clear from Table 4, the photosensitive drums J to
It can be seen that M has a high surface potential, a low residual potential, and excellent light sensitivity. However, the photoconductor drums H and I are inferior in photosensitivity, and the photoconductor drums N and O are both low in surface potential, large in residual potential, and inferior in photosensitivity. Further, the present inventors have proposed that the photosensitive drums B to F and J to
When M was mounted on each high-speed PPC and an image output test was performed at a speed of 50 sheets / minute, faithful reproducibility for the black and red areas was obtained, and the density was high and clear without fog. It was confirmed that an image could be obtained. (Effect of the Invention) As described above, according to the electrophotographic photoreceptor of the present invention, a photoconductive a-Si layer and a photoconductive a-SiC layer are laminated, and the a-S
By setting the atomic ratio and thickness of the iC layer and the group IIIa element content within the respective predetermined ranges, it is possible to enhance the photosensitivity on both the long wavelength side and the short wavelength side. Provided is an electrophotographic photosensitive member for PPC which can obtain excellent photosensitivity without using a wavelength light cut filter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a basic layer structure of an electrophotographic photoreceptor of the present invention, and FIG. 2 is a sectional view showing a typical layer structure of an electrophotographic photoreceptor of the present invention. The drawings are cross-sectional views showing the layer structure of a conventional electrophotographic photosensitive member, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG.
FIG. 9 and FIG. 9 are diagrams showing the distribution of carbon doping, and FIG.
Figures 10, 11, 12, 13, 14, and 15 are diagrams showing doping distributions of Group IIIa elements of the Periodic Table,
FIG. 17 is a schematic diagram of a glow discharge decomposition apparatus, and FIG. 17 is a diagram showing spectral sensitivity. 1,5 …… Conductive substrate 2,8 …… Carrier injection blocking layer 4,9 …… Surface protection layer 6 …… Photoconductive amorphous silicon layer 7 …… Photoconductive amorphous silicon carbide layer

Continuation of front page    (72) Inventor Hiroshi Ito               At 1166 Haseno, Jamizocho, Yokaichi, Shiga Prefecture               6 Kyocera Corporation Shiga Yokaichi Factory (72) Inventor Hitoshi Takemura               At 1166 Haseno, Jamizocho, Yokaichi, Shiga Prefecture               6 Kyocera Corporation Shiga Yokaichi Factory (72) Inventor Kokichi Ishikura               At 1166 Haseno, Jamizocho, Yokaichi, Shiga Prefecture               6 Kyocera Corporation Shiga Yokaichi Factory                (56) References JP-A-61-94054 (JP, A)                 JP-A-61-189558 (JP, A)                 JP-A-61-238065 (JP, A)                 JP 61-256354 (JP, A)                 JP-A-61-267057 (JP, A)                 JP-A-61-272748 (JP, A)

Claims (1)

(57) [Claims] An electrophotographic photoreceptor used for PPC using a halogen lamp for corona charging, in which a photoconductive amorphous silicon layer and a photoconductive amorphous silicon carbide layer are sequentially formed on a conductive substrate, and a silicon element and a carbon element. The atomic ratio of is 0.01 ≤ x value of Si _(1-x) C _x
When x ≦ 0.5, the amorphous silicon carbide layer having a thickness of 0.05 to 5 μm was added with a Group IIIa element of the periodic table of 0.5
An electrophotographic photoreceptor characterized by containing up to 100 ppm.