JPS63135950A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To lessen residual voltage of the titled body, and to prevent generation of fogging in an image by specifying an atomic composition ratio of C and Si in a carrier injection retarding layer, and that of C and Si in a carrier transfer layer and that of Si and Ge, and Si and C in a carrier generating layer, respectively. CONSTITUTION:The laminated type photosensitive body is formed by laminating a carrier injection retarding layer 5, a carrier transfer layer 6, a carrier generating layer 7 and a surface protective layer 8 on a conductive substrate 1 in this order. The carrier transfer layer 6 is specified the atomic composition ratio of C and Si elements to a range of (1:100)-(1:9), preferably, a range of (1:50)-(1:9), in case of forming the carrier transfer layer 6 by a-SiC layer. Thus, the mobility of carrier of the carrier transfer layer 6 is improved, and the carrier generating layer 7 is composed of a-SiGeC layer, and the atomic composition ratio thereof is specified within a specific range, thereby improving optical sensitivity against a long wavelength ray. And, the carrier injection retarding layer 5 is formed by a-SiC layer, thereby enlarging remarkably charge of the titled body and reducing dark attenuation thereof.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor that has a low residual potential to prevent image fogging and is capable of high-speed copying suitable for semiconductor laser beam printers. It is.

[Prior art and its problems]

In recent years, progress in electrophotographic photoreceptors has been remarkable, and the development of ultra-high-speed copying machines and laser beam printers is actively underway.The photoreceptors used in these devices are used at high speeds for long periods of time, so their operation is slow. Stability and durability are required. In response to this demand, hydrogenated amorphous silicon is attracting attention because it has excellent heat resistance, wear resistance, non-pollution properties, and photosensitivity characteristics.

In addition, with the development of laser beam printers capable of high-speed printing, compact and highly reliable semiconductor lasers have come to be used as laser light sources. ) When a photoreceptor is mounted, there is a problem in that the oscillation wavelength of this laser light is in the vicinity of near infrared rays, so that the photosensitivity characteristics of the a-5i light on the light receiving side are inferior. In order to solve this problem, it has been proposed to dope the a-Si photoconductive layer of the photoreceptor with an appropriate amount of germanium (Ge) to shift the photosensitivity region of this layer to the longer wavelength side. The problem has been that the surface potential becomes smaller as a result.

In order to solve this problem, a functionally separated type photoreceptor as shown in FIG. 2 has been proposed in Japanese Patent Laid-Open No. 192044/1983.

That is, according to FIG. 2, a carrier M feeder 71 (made of amorphous silicon carbide) is placed on a conductive substrate (1).
2) , amorphous silicon germanium (hereinafter a)
A laminate has been proposed in which a carrier generation layer (3) and a surface protective layer (4) made of (abbreviated as -SiGe) are sequentially formed, and this carrier transport layer (2) has a high dark resistivity and carrier mobility. It is made of amorphous silicon carbide (hereinafter abbreviated as a-SiC), which can be a material with a large amount of heat, and is intended to have excellent surface potential and photosensitivity, and to have a small residual potential.

However, in forming the carrier transport layer made of amorphous silicon carbide (hereinafter abbreviated as a-5iC) disclosed in this publication, silicon element (Si)
The atomic composition ratio of carbon element (C) and carbon element (C) is l:9 to 9:1.
If it is set within the range of As a result, fog is likely to occur in the image.

Furthermore, in semiconductor laser beam printers, since the light source is coherent light, there is a problem in that interference fringes are likely to occur in images. The cause of this interference fringe pattern is that coherent light reaches the substrate, and the reflected light on the substrate interferes with the incident light. To solve this problem, the substrate surface is processed to create the desired surface. It has been proposed to set the roughness so that the light reaching the substrate is diffusely reflected. However, this surface roughening treatment inevitably increases manufacturing costs, and a solution that eliminates the need for this treatment is desired.

[Purpose of the invention]

Therefore, the present invention was completed in view of the above circumstances, and its purpose is to further improve the carrier mobility of the a-5iC carrier transport layer, thereby reducing the residual potential and preventing fogging on images. An object of the present invention is to provide an electrophotographic photoreceptor that has the following properties.

Another object of the present invention is to provide an electrophotographic photoreceptor for semiconductor laser beam printers capable of high-speed copying and high-speed printing.

Still another object of the present invention is to provide an electrophotographic photoreceptor which is free from interference fringe patterns in images and which achieves cost reduction.

[Means for solving problems]

According to the present invention, in the electrophotographic photoreceptor in which at least a carrier injection blocking layer, a carrier transporting layer, and a carrier generating layer are formed on a substrate, the carrier injection blocking layer is a-S
The carrier transport layer is made of iC, and the atomic composition ratio of C and Si is set within the range of 1:9 to 9:1, and the carrier transport layer is a-5.
Consists of iC and has an atomic composition ratio of C and Si of 1:100.
The ratio is set within the range of 1:9 to 1:9, and the carrier generation layer is a
-SiGeC, and the atomic composition ratio of Si and Ge is set within the range of 2:1 to 100:1, and the atomic composition ratio of Si and C is set within the range of 1:1 to 100:1. An electrophotographic photoreceptor is provided.

The present invention will be explained in detail below.

FIG. 1 shows a typical layer structure of the electrophotographic photoreceptor of the present invention. According to this figure, a carrier injection blocking layer (5), a carrier transporting layer (6) are formed on a conductive substrate (1). , shows a laminated photoreceptor in which a carrier generation layer (7) and a surface protection layer (8) are sequentially formed, and a carrier transport layer (6) and a carrier generation layer (7) are applied to this photoreceptor. A laminated photoreceptor with a different lamination order may also be used.

According to the present invention, the carrier transport 1! (6) as a-
When forming by 3iC, the atomic composition ratio of C element and St element is set within the range of 1:100 to 1:9, preferably within the range of 1:50 to 1:9, thereby improving this carrier transport. The carrier mobility of the layer (6) is improved, and the carrier generation layer (7) is made of a-SiGe.
The carrier injection blocking layer (5) is formed of a-5iC, and its atomic composition ratio is set within a predetermined range, thereby increasing the photosensitivity to long wavelength light. It is characterized by increasing the dark decay and decreasing the dark decay.

First, the reason why the carrier transport layer (6) was determined to have the above atomic composition ratio is that the atomic composition ratio of C element and Si element is 1:
If the atomic composition ratio deviates from 100, the effect of increasing the dark resistivity of the carrier transport layer to raise the surface potential becomes less noticeable, and if the atomic composition ratio deviates from 1:9, the dark resistivity of the carrier transport layer increases. This is because the surface potential increases as the surface potential increases, but on the other hand, the carrier mobility tends to decrease, which increases the residual potential and tends to cause fogging on the image.

The thickness of the carrier transport layer (6) is 1 to 50 μm.

It is preferably set within the range of 5 to 30 μm,
If it is less than 1 μm, the charge retention ability will be poor and the ghost phenomenon will become noticeable, and if it exceeds 50 μm, the image resolution will deteriorate and the residual potential will become thick.

This carrier transport IJ (6) contains an element of group Va of the periodic table (hereinafter abbreviated as group Va element) or an element of group Ma of the periodic table (hereinafter abbreviated as group IIIa element) within the required range. It's okay.

That is, when containing Va group elements, the content is O to 10.000 ppm, preferably 0.1 to 1100 ppm.
When the content is within the range of 0 pp, the photoreceptor becomes advantageous for negative charging, and the Va group elements include p, N, As, Sb, etc., and P is particularly desirable.

In addition, when containing a group IIIa element, the content should be 0.1 to 10. When OOOppm is contained, preferably within the range of 0.5 to 11000 ppm, the photoreceptor becomes advantageous for positive charging, and the ma group elements include B, AI, G
a.

Among them, B is preferable.

When doping impurity elements as described above to charge the material as required, it is advantageous to add a Ma group element for the purpose of further increasing the dark resistivity and increasing the surface potential. .

The carrier generation layer (7) is made of an a-SiGeC layer, and when the spectral sensitivity characteristics of this layer were measured, it was found that the spectral sensitivity was particularly 650.
The photosensitivity can be increased in the wavelength range of 850 nm to 850 nm, making it suitable for photoreceptors for semiconductor laser beam printers.

Moreover, this a-SiGeC carrier generation layer (7) and a-
When SiC carrier transport layers (6) are combined in the stacking order shown in Figure 1, carrier transport N (6) is carrier generation N.
It has the function of transporting the carriers generated in step (7) and holding the potential, and can also have the function of preventing carriers from being injected from the substrate (1).

When the carrier transport layer (6) is interposed between the carrier generation layer and the substrate in this way, the mobility of the carriers in this layer is relatively high, so that the carriers are trapped inside this layer. As a result, high photosensitivity and reduced residual potential can be achieved.

According to the present invention, when the carrier transport layer (6) is formed as described above, it is difficult to sufficiently increase the charging ability due to the relatively small amount of carbon, but this drawback can be overcome by a-S
It is supplemented by iGeC carrier generation N(7).

That is, since the carrier transport layer (6) has a small carbon content, it is not possible to set the dark resistivity to a sufficiently large value, but instead, the a-5iGeC carrier generation layer (
7) contains carbon, which makes it possible to sufficiently increase the charging ability of the photoreceptor.

Furthermore, according to the present invention, photocarriers are substantially generated in the a-SiGeC carrier generation layer (7) by the lamination order shown in FIG. 1, so that the incident light does not reach the substrate (1). , As a result, the problem of interference fringes in the image is resolved.

For this carrier generation layer (7), Si element and Ge
The content ratio of the elements may be set within the range of 2:1 to 100:1, preferably within the range of 3:1 to 30:1,
Within this range, the light absorption rate for long wavelength light becomes high, thereby increasing photosensitivity and preventing the generation of interference fringes due to laser light.

In addition, the content ratio of St element and C element is 1:1 to 100.
:1, preferably within the range of 3:1 to 100:1. Within this range, the dark conductivity can be sufficiently reduced and the charging ability can be improved.

Furthermore, the thickness of the carrier generation layer (7) is determined as appropriate so that this layer can substantially serve as a photocarrier generation layer.
As a result of experiments conducted by the present inventors with various thicknesses, it was found that the thickness was adjusted so that the transmittance of the carrier generation layer (7) to incident light was 30% or less, preferably 20% or less. If set, no light will reach the substrate (1) at all. The transmittance of this layer (7) can be reduced as its thickness is increased, but on the other hand, the residual potential of this photoreceptor tends to increase. Therefore, the thickness of the carrier generation layer (7) is determined by its transmittance and residual potential, and according to experiments repeatedly conducted by the present inventors, the thickness is 1 to 100 μm, preferably 1 to 30 μm.
It has been found that the optimum thickness may be set within the range of 1 to 5 μm.

The carrier injection blocking layer (5) is a carrier transporting layer (6).
It is formed of a-5iC in order to prevent carrier injection into the a-5iC, and the atomic composition ratio of the C element and the St element is within the range of 1:9 to 9:1, preferably 2:8 to 8:2. It is recommended to set it to .

When this atomic composition ratio deviates from 1:9, the effect of blocking carrier injection from the substrate side is insufficient, resulting in a decrease in surface potential and an increase in dark decay. The effect of inhibiting the injection of excited carriers into the substrate side becomes significant, and the residual potential increases.

In forming this carrier injection blocking I'1 (5), the conductivity type is controlled to P type when the photoreceptor is charged to positive polarity, and to N type when charged to negative polarity. This further improves the carrier injection blocking effect.For example, the P-type semiconductor material contains a Ma group element such as B, and the N-type semiconductor material contains a Va group element such as P at a concentration of 50 to 10. The content is within the range of 000 ppm.

Further, the thickness of the carrier injection blocking layer (5) is 0.2 to 5.
．． It is preferable to set the thickness to 0 μm, preferably within the range of 0.5 to 3.0 am, and if the thickness is within this range, the ability to stop carriers from the substrate will be sufficient and the residual potential will be small. It is desirable in that sense.

In addition, a-SiC carrier injection blocking layer (5) and a-5
When both layers of the tC carrier transport layer (6) contain a Va group element or a Ma group element, the carrier injection blocking layer (5)
) is preferably contained in a larger amount than that in the carrier transport layer (6), and this has an advantageous effect of inhibiting carrier injection.

Carrier injection prevention 1 mentioned above! (5), carrier transport layer (6) and carrier generation layer (7) are a-SiC or a-
Although it is substantially composed of SiGeC, it is necessary to contain hydrogen elements (H) and halogen elements in order to terminate the dangling bonds in the amorphous state, and the content of these elements is preferably 5 to 50 at%. 5 to 4
0 atom%, optimally 10 to 30 atom%, usually
H element is used. Since this H element is easily incorporated into the terminal portion, it reduces the local level density in the band gap, thereby providing excellent semiconductor properties.

In addition, a part of this H element may be replaced with a halogen element. The substitution ratio is preferably 0.01 to 50 atom%, preferably 1 to 30 atom% of the total elements for dangling bond termination.The halogen elements include F, CI, Br+I+^, etc., among others, The use of F is desirable because its large electronegativity increases the bonding between atoms, resulting in excellent thermal stability.

Various materials can be used for the surface protection layer (8) as long as they themselves have high insulation properties, high corrosion resistance, and high hardness properties. For example, organic materials such as polyimide resin, 5i01. SiO, Altos, SiC, Si3N
It is formed using an inorganic material such as 4+a-5t or a-5iC, thereby increasing the durability and environmental resistance of the photoreceptor.

Next, a method for manufacturing the electrophotographic photoreceptor of the present invention will be described.

a-5iC carrier injection stop layer (5), a-5IC carrier transport layer (6) and a-SiGeC carrier generation j
W (7) can be formed by a thin film forming method such as a glow discharge decomposition method, an ion blating method, a reactive sputtering method, a vacuum evaporation method, or a thermal CVD method.

Moreover, the raw material used for this may be solid, liquid, or gas.

For example, gaseous raw materials used in the glow discharge decomposition method include SiH4+5izHb, 5iJs, SiF4, etc. (7)
Si-based gas, CH4, C2114,, C2H2, C
211&, C-based gas such as C, H, GeIT a +
A Ge-based gas such as G e 2 Hb may be used;
Further, H2+ He + N e + Ar or the like is used as a carrier gas.

In addition, when forming the surface protection layer 8IJW (8), it is preferable to form the layer using a-5j or a-5iC in that the same thin film forming means can be used, and furthermore, the same thin film forming method can be used. When the apparatus is used, there is an advantage that the thin film can be continuously laminated using a common thin film forming means.

Next, when the electrophotographic photoreceptor described in the embodiments of the present invention is formed from a-5iC or a-5iGeC using a glow discharge decomposition method, the manufacturing method is performed using a capacitively coupled glow discharge decomposition apparatus shown in FIG. explain.

In the figure, tanks (9) (10) (11) (12)
(13) (14) respectively 5iHn+CzHz,
GeH4, BzHh (contains 20 ppm when diluted with Ih gas)
,)1. , No gas is sealed, and 112 is also used as a carrier gas. These gases are controlled by the corresponding regulating valves (15) (16) (17) (1B) (19
) (20), and its flow rate is controlled by the mass flow controllers (21) (22) (2
3) Controlled by (24) (25) (26),
Tank (9) (10) (11) (12) (13
) is sent to the main pipe (27), and No gas from the tank (14) is sent to the main pipe (28). Furthermore, (29) (
30) is a stop valve.

The gas flowing through the main pipes (27) and (28) flows through the reaction pipes (
31), but a capacitively coupled discharge electrode (32) is installed inside this reaction tube (31).
Appropriately, the high frequency power applied thereto is from 50 to 3,000 MHz, and the frequency is from IMHz to 50 MIIZ. Inside the reaction tube (31), a cylindrical film-forming substrate (33) made of aluminum is placed on a sample holder (34), and this holder (34) is moved by a motor (35). It is designed to be rotationally driven, and the substrate (33
) is uniformly heated to a temperature of about 200 to 400 degrees Celsius, preferably about 200 to 350 degrees Celsius, by suitable heating means.

Furthermore, the interior of the reaction tube (31) is kept in a high vacuum state (gas pressure during discharge of 0.1 to 2.0 Torr) during the formation of the a-SiC film.
r ) is connected to a rotary pump (36) and a diffusion pump (37).

In the glow discharge decomposition device configured as above,
For example, when forming an a-5iGeC film on the substrate (34), the adjustment valves (15) (16) (17) (19)
and SiH4, CzHz+GeHa, f(
Release z gas. The release amount is determined by a mass flow controller (
21) (22) (23) (25), and these mixed gases are sent to the reaction tube (3) via the main pipe (27).
1). The inside of the reaction tube (31) is 0.1 to 2. A vacuum state of approximately QTorr, a substrate temperature of 200 to 400°C, and a capacitively coupled discharge electrode (32
) has a high frequency power of 50 to 3, and a frequency of 1 to 5.
Coupled with the fact that the frequency is set to 0 MHz, glow discharge occurs, the gas is decomposed, and an a-SiGeC film is formed on the substrate at high speed. Although H2 gas is used in the above-described example of forming the a-3iGeC carrier-generated N (7), this gas is not essential, and it can be formed without using the lh gas.

C Example] Next, examples of the present invention will be described.

(Example 1) In this example, a-S of a single composition is used throughout the layer thickness direction.
i A GeC film was formed and its spectral sensitivity characteristics were measured.

That is, a 3 x 3 cm square aluminum flat plate was prepared, a part of the peripheral surface of the aluminum cylindrical substrate (33) shown in Fig. 3 was cut out, and this flat plate was installed in the cutout. 9), GeH gas from the tank (11), C2Hz gas from the tank (10), and H2 gas from the tank (13) at the gas flow rates shown in Table 1, and the manufacturing conditions were also specified. A-Si with a thickness of 5 μm was deposited on the above flat plate using the glow discharge decomposition method.
A C film or an a-SiGeC film was formed.

(Left below) Sample A (a-3iC film) and sample B (a-3iC film) thus obtained.
The results of measuring the spectral sensitivity characteristics of the a-SiGeC films were as shown in FIG. ○ mark in the diagram, O
The marks and marks are plots of the spectral sensitivities of samples A, B, and C, respectively, and Ly+2 is the respective spectral sensitivity curve. Note that this measured value of spectral sensitivity indicates the photoconductivity when uniform energy light is irradiated at each wavelength using the comb electrode method.

As is clear from this result, as the Ge content increases, the spectral sensitivity peak shifts to the longer wavelength side, making the electrophotographic photoreceptor suitable for semiconductor laser beam printers.

(Example 2) Using the glow discharge decomposition apparatus shown in FIG. 3 and the manufacturing conditions shown in Table 2, a carrier injection blocking layer (5), a carrier transport layer (6), a carrier generation layer ( 7
) and a surface protective layer (8) were sequentially formed to produce an electrophotographic photosensitive drum. Note that the carrier injection blocking layer (6) is doped with oxygen and nitrogen using NO gas to improve its adhesion to the substrate.

When the photoreceptor thus obtained was corona charged at +5.6 KV, the surface potential became approximately 900 ■. ), the photosensitivity was 0.
20cm"erg-', and the residual potential was significantly reduced to about 20V2.Then, this photoreceptor drum was transferred to a semiconductor laser beam printer (copying speed 40 sheets/min).
When the camera was attached to the camera and an image was produced, there were no interference fringes in the image, and a high-density, highly clear image was obtained with no fog.

A part of the film forming substrate (33) is cut out, a 3x3 cm rectangular aluminum flat plate is attached to the cutout, and the carrier transport layer is placed on the flat plate under the conditions shown in Table 1. The content ratio of C and Si in the film was analyzed by Auger electron spectroscopy and found to be 1:30.

(Example 3) In this example, the carrier injection blocking layer (5
) and carrier transport layer (6), Si t
l Change the flow rate ratio of 4 gases and C, H, gases, and
In forming the carrier generation layer (7), SiH, gas,
By changing the flow rate ratio of C2H2 gas and GeH4 gas, a carrier injection blocking layer (5), a carrier transport N (6), and a carrier generation layer (7) each having various atomic composition ratios are formed, and the surface The protective layer (8) is (Example 1)
), and ten types of photoreceptors were manufactured.

These photoreceptors are installed in a semiconductor laser beam printer (copying speed 40 sheets/min) equipped with the harsh conditions where fogging is most likely to occur, and images are produced, and the density of these images or if fogging occurs. When the capri density of the sample was measured using an image densitometer, the results shown in Table 3 were obtained.

In addition, the image quality evaluation in the table is divided into the standard ◎ mark, ○ mark, and Δ mark. ■ mark indicates that the image density is high and no fogging occurs, O mark indicates that the image density is high and fogging does not occur. The mark Δ represents a case where almost no color is observed and there is virtually no problem, and the mark Δ represents a case where the image density is slightly low or some fog is observed.

As is clear from Table 3, excellent image quality was obtained for photoreceptors E, F, and G, which are within the scope of the present invention, and in particular, photoreceptor F did not cause fogging at all. However, photoreceptor A,
In B, C, H, 1 and J, the atomic composition ratio of the carrier transport layer or carrier generation layer was outside the range of the present invention, so the image density was slightly low and some fogging was observed.

〔Effect of the invention〕

As mentioned above, according to the electrophotographic photoreceptor of the present invention, a-3
When manufacturing a functionally separated photoreceptor comprising an iC carrier transport layer, by setting the atomic composition ratio of C and Si within a predetermined range, the residual potential is reduced and no fogging occurs in the image. According to this photoreceptor, the effect is remarkable when it is installed in a high-speed copying machine where fogging is most likely to occur.Therefore, the electrophotographic photoreceptor of the present invention can be provided as a photoreceptor suitable for high-speed copying machines. can.

Furthermore, according to the electrophotographic photoreceptor of the present invention, by forming an a-5iC carrier injection blocking layer having a predetermined atomic composition ratio, the surface potential can be further increased1, thereby increasing image density and preventing capri. As a result, it can be provided as a photoreceptor suitable for the above-mentioned high-speed copying machine.

Further, according to the electrophotographic photoreceptor of the present invention, a-SiGe
The C layer could be used as a carrier generation layer for long wavelength light, and as a result, the photoreceptor could be made suitable for semiconductor laser beam printers. Furthermore, according to this photoreceptor, since the incident light does not reach the substrate, interference fringes do not occur in the image, and there is no need to roughen the surface of the substrate to increase its surface roughness. A low-cost electrophotographic photoreceptor is provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the layer structure of an electrophotographic photoreceptor shown in an embodiment of the present invention, FIG. 2 is a cross-sectional view of the layer structure illustrating a conventional functionally separated photoreceptor, and FIG. 3 is a capacitive coupling FIG. 4 is a schematic diagram of a type glow discharge decomposition device; FIG. 4 is a diagram showing a spectral sensitivity curve of amorphous silicon germanium carbide layer. 1... Conductive substrate 5... Carrier injection blocking layer 2.7
...Carrier transport layer 3,8 ...Carrier generation layer 4,9 ...Surface protection layer Patent applicant (663) Kyocera Corporation Representative: Kin Judo Anjo Contaminant: Takao Yoroto (8898) Patent attorney: Katsuhiko Tahara゛Figure 15 - Figure

Claims (1)

[Claims] In an electrophotographic photoreceptor in which at least a carrier injection blocking layer, a carrier transporting layer, and a carrier generation layer are formed on a substrate, the carrier injection blocking layer is made of amorphous silicon carbide, and the atomic composition ratio of carbon and silicon is 1:9 to 9. :1, the carrier transport layer is made of amorphous silicon carbide, and the atomic composition ratio of carbon and silicon is 1:100 to 1.
:9, the carrier generation layer is made of amorphous silicon germanium carbide, and the atomic composition ratio of silicon and germanium is 2:1 to 100.
1. An electrophotographic photoreceptor characterized in that the atomic composition ratio of silicon and carbon is set within the range of 1:1 and 1:1 to 100:1.