JPH02140754A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body preventing the blurring of a latent electric charge image and having high reliability over a long period of time as well as to increase the surface hardness of the sensitive body by laminating an amorphous silicon carbide layer having specified ratios among the elements on an org. photosemiconductor layer. CONSTITUTION:A photoconductive amorphous silicon carbide (a-SiC) layer 2, an org. photosemiconductor layer 3 and an a-SiC surface layer 4 are successively laminated on an electrically conductive substrate 1. The a-SiC of the photoconductive layer 2 has a compsn. represented by a formula (Si1-xCx)1-aAa (where A is H or halogen, 0.01<x<0.5 and 0.1<a<0.5) and the a-SiC of the surface layer 4 has a compsn. represented by a formula (Si1-yCy)1-bBb (where B is H or halogen, 0.5<y<0.95 and 0.05<b<0.5). The photosensitivity and surface potential of the resulting sensitive body can be increased and the residual potential can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor comprising a laminated layer of an amorphous silicon carbide layer and an organic optical semiconductor layer.

[Prior art and its problems]

Photoconductive materials for electrophotographic photoreceptors include Se, 5e-Te,
There are inorganic materials such as AszSe3, ZnO, CdS, and amorphous silicon, as well as various organic materials, of which Se was first put into practical use, followed by ZnO and CdS.
, amorphous silicon has also been put into practical use. On the other hand, among organic materials, PVK was first put into practical use, and thereafter, functionally separated photoreceptors were provided in which the functions of charge generation and charge transport were shared by different materials.

On the other hand, an electrophotographic photoreceptor in which an organic photoconductive layer is laminated on an inorganic photoconductive layer has also been proposed.

For example, there is a laminated photoreceptor made of SeN and an organic optical semiconductor layer.
Although this photoreceptor has already been put into practical use, it has the disadvantage that Se itself is harmful and that the sensitivity is poor on the long wavelength side.

Therefore, a laminated photoreceptor consisting of an amorphous silicon carbide photoconductive layer and an organic photoconductor layer was proposed (see Japanese Patent Laid-Open No. 14241/1983), which solved the above problems and achieved non-pollution and high photosensitivity. Characteristics were obtained.

However, in the photoreceptor proposed above, the organic photoconductor layer is exposed on the surface, and the hardness of this layer is relatively low, which causes the problem that wear of the photoreceptor surface progresses over a long period of time. There is a point.

In addition, when the above-mentioned photoreceptor is used for a long period of time, the organic photoconductor layer is repeatedly exposed to corona discharge, which causes the surface of the layer to change in quality, resulting in a decrease in surface potential or a decrease in moisture resistance. As a result, moisture may be adsorbed onto the surface of the photoreceptor, causing blurring of the charge latent image, resulting in a problem of lowering the reliability of the photoreceptor.

Furthermore, in the field of electrophotographic photoreceptors, various efforts have been made to improve photosensitivity and surface potential, as well as to reduce residual potential, and improvements in these properties are desired.

[Purpose of the invention]

Therefore, the present invention was completed in view of the ridges, and its purpose is to increase the hardness of the photoreceptor surface and prevent blurring of the latent charge image, thereby achieving long-term reliability. An object of the present invention is to provide an electrophotographic photoreceptor.

Another object of the present invention is to provide a high-performance electrophotographic photoreceptor with increased photosensitivity and surface potential and reduced residual potential.

[Means for solving problems]

According to the present invention, a photoconductive first layer is provided on a conductive substrate.
An electrophotographic photoreceptor in which an amorphous silicon carbide layer, an organic optical semiconductor layer, and a second amorphous silicon carbide layer are sequentially laminated, wherein the element ratio of the first amorphous silicon carbide layer is expressed by the composition formula 5ll-X
Set the value within the range of 0.01 < x < 0.5,
Furthermore, the element ratio of the second amorphous silicon carbide layer is set to 0.5 < V by the y value of the composition formula Si1-, C2.
Provided is an electrophotographic photoreceptor characterized in that it is set within a range of <0.95.

The present invention will be explained in detail below.

FIG. 1 shows the layer structure of the electrophotographic photoreceptor of the present invention.
An amorphous silicon carbide (hereinafter abbreviated as a-3iC) photoconductive layer (2), an organic optical semiconductor Ji (3), and an a-SiC surface layer (4) are sequentially laminated on a conductive substrate (1). . The a-5iC photoconductive layer (2) has a function of generating charges, and the organic photoconductive layer (3)
has a function called charge transport.

The present invention is characterized by increasing the hardness of the photoreceptor surface through the above-described layer structure, improving electrophotographic properties such as photosensitivity, surface potential, and residual potential, and achieving long-term stability. .

First, the a-SiC photoconductive layer (2) consists of an amorphous St element and C element, as well as a hydrogen (H) element or a halogen element introduced at the end of a dangling bond between these elements, and its composition formula is as follows. It is recommended to set it as follows.

(St+-xCX) l-J m (A is H element or halogen element) 0.01 < x < 0.5 Preferably 0.05 < x < 0.5 Optimally Q, l
< x < 0.4 0.1 < a < 0.5 Preferably 0.2 < a < 0.5 Optimally 0.25 < a < 0.45X value is 0.0
Excellent photoconductivity is obtained within the range of 1 < x < 0.5, and 0.05 < x < 0.5.
When it is set within this range, the photosensitivity on the short wavelength side is increased, and the photoconductivity is also significantly increased, so that the excitation function of photocarriers is increased.

In addition, when the a value is 0.1 or less, the film quality deteriorates, thereby significantly reducing the photoconductivity, and 0.2 <
When it is set within the range of a < 0.5, the dark conductivity decreases and the photoconductivity increases, resulting in excellent photoconductivity and excellent adhesion to the substrate.

This a-SiC photoconductive layer (2) contains a hydrogen (H) element and a halogen element for terminating dangling bonds, but of these elements, element II is easily incorporated into the terminating portion, and optical This is desirable in that the localized level density in the target bandgap is reduced.

Moreover, the thickness of the a-SiC photoconductive layer (2) is 0.05 to 5
It may be set within the range of μm, preferably 0.1 to 3 μm, and within this range high photosensitivity can be obtained and the residual potential will be low.

7. The a-SiC surface layer (4) also consists of amorphous Si element and C element, as well as hydrogen ()I) element or halogen element introduced at the end of the dangling bond of these elements, and its composition formula is as follows: It is recommended to set it as follows.

(5in-yCy) t-bB b (where B is H element or halogen element) 0.5 < y < 0.95 Preferably
0.6 < V < 0.9 optimally 0.65 < y
< 0.85 0.05 < b < 0.5 Preferably 0.05 < b < 0.3 Optimally 0.0
5 < b < 0.2y If 4K is less than 0.5, high surface hardness cannot be obtained, poor wear resistance, and
The small optical bandgap increases the absorption of short wavelength light, which reduces photosensitivity.

When the y value is 0.95 or more, the defect density in the film becomes high, carriers are trapped, and the residual potential becomes high.

Furthermore, when the b value is 0.05 or less, the residual potential increases due to an increase in the defect density in the film.

When the b value is 0.5 or more, the moisture resistance decreases and the charge latent image becomes blurred.

This a-SiC surface 1! The thickness of (4) is 0.05 to 5
p.m.

The thickness may preferably be set within the range of 0.1 to 3 μm, and within this range, high photosensitivity and low residual potential can be obtained.

The organic optical semiconductor N (3) includes an electron-donating compound or an electron-withdrawing compound, and the former includes high molecular weight compounds such as poly-N-vinylcarbazole, polyvinylpyrene,
Examples include polyvinylanthracene, pyrene-formaldehyde condensation polymer, and low molecular weight ones such as oxadiazole, oxazole, pyrazoline, triphenylmethane, and hydrazone. These include triarylamine, N-phenylcarbazole, and stilbene, and these low-molecular substances are useful for polycarbonate, polyester, methacrylic resin, polyamide, acrylic epoxy, polyethylene, phenol, polyurethane, butyral resin, polyvinyl acetate, urea resin, etc. It is used dispersed in a binder.

Furthermore, examples of electron-withdrawing compounds include 2.4.7-)linitrofluorene.

If an electron-donating compound is selected, the electrophotographic photoreceptor will be negatively charged, and if an electron-withdrawing compound is selected, the photoreceptor will be positively charged.

In addition, the thickness of the organic optical semiconductor N(3) is 10 to 50 μm,
It is preferable to set it within the range of 10 to 30 μm (within this range, a high surface potential can be obtained and the residual potential will be low).

According to the electrophotographic photoreceptor having the above layer structure, the surface layer (4) contains a larger amount of carbon element than the photoconductive N (2), which provides high hardness characteristics and increases resistance. It was possible to increase the surface potential.

Moreover, the incident light passes through the surface layer (4) and is substantially received by the photoconductive layer (2), and the generated carriers pass through the organic optical semiconductor N (3) and are transferred to the surface of the surface layer (4). to be charged.

Thus, by forming these two types of SiC layers, it was possible to increase the surface potential and photosensitivity, and to reduce the residual potential.

Moreover, since the organic photosemiconductor layer (3) is not exposed on the surface, there is no deterioration of the surface of the photoreceptor, which makes it possible to maintain a high surface potential, and also improves moisture resistance and charges latent images. No blurring occurs.

Further, in the electrophotographic photoreceptor of the present invention, the photoconductive layer (
2) contains 1 to 500 ppm of Ma group elements, preferably 2 to 2
It is preferable to contain 00 ppm.

This ma group element content is expressed by the average value for the entire a-3iC layer, and the average content is lp
If it is below pm, the dark conductivity tends to increase,
Moreover, a decrease in photosensitivity was observed, while at 500 ppm
In the above case, the dark conductivity becomes extremely large, and the ratio of photoconductivity to dark conductivity becomes small, making it impossible to obtain the desired photosensitivity.

When the photoconductive layer (2) contains the Ma group element, the doping distribution may be either uniform or non-uniform over the layer thickness direction.If the photoconductive layer (2) is doped non-uniformly, this J! ! IE in which a part of (2) does not contain ma group elements
There may be an ipl region, in which case the average content of ma group elements in the entire a-SiC layer consisting of both the a-SiC 11m1 region containing group IIIa elements and the a-SiC layer region not containing group II elements. The amount is 1~500ppm
Must be.

The MA group elements include B, AI, Ga, In, etc., and the B element has excellent covalent bonding properties and can sensitively change semiconductor properties.In addition, it provides excellent charging ability and photosensitivity. It is desirable in that sense.

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

To form the a-SiC layer, there are thin film forming methods such as glow discharge decomposition method, ion blating method, reactive sputtering method, vacuum evaporation method, and CVD method.

When using the glow discharge decomposition method, Si element-containing gas and C
A film is formed by combining element-containing gases and plasma decomposing the mixed gas. This Si element-containing gas contains SiH
* + S 1 t Hh + S 1 a Hs +
S I F a + S i C1a + S i
HCl x, etc., and C element-containing gases include CH
a, CzH4, CzH! +CJl1 etc., among others,
CzHt is desirable in that it can provide high-speed film formation.

The glow discharge decomposition device used in this example will be explained with reference to FIG.

In the figure, 5iHa, CzHz, and H2 are sealed in the first tank (5), second tank (6), and third tank (7), respectively, and these gases are supplied to the corresponding first regulating valve (8).
, is released by opening the second regulating valve (9) and the third regulating valve (10). The flow rate of the released gas is determined by the mass flow controller (11) (12) (13).
controlled by the main pipe (14), each gas is mixed
sent to. Note that (15) and (16) are stop valves.

The gas flowing through the main pipe (14) flows into the reaction tube (17), and a capacitively coupled discharge electrode (18) is installed inside this reaction tube (17), and a cylindrical film-forming electrode (18) is installed inside the reaction tube (17). The substrate (19) is placed on the substrate support (20) i! l! The substrate support (20) is rotated by the motor (21), and the substrate (]9) is rotated accordingly. Then, power to the electrode (18) is 50W ~ 3Kw % frequency 1 ~
A high frequency power of 50 Mflz was applied, and the substrate (
19) is heated by suitable heating means to a temperature of about 200-400°C, preferably about 200-350°C. Also,
The reaction tube (17) is equipped with a rotary pump (22) and a diffusion pump (2).
3), which enables the required reduced pressure state (gas pressure during discharge from 0.1 to
2.0 Torr) is maintained.

A substrate (1
When forming an a-SiC layer on top of 9), the first regulating valve (
8), the second regulating valve (9), and the third regulating valve (10) are opened to release each gas of SiH4 and CJz+Ht, and the released amount is controlled by the mass flow controller (11) (12) (
13), each gas is mixed, and the main pipe (1
4) into the reaction tube (17). Then, when the reduced pressure inside the reaction tube, the substrate temperature, and the high-frequency power applied to the electrodes are set to predetermined conditions, glow discharge occurs, and an a-SiC layer is rapidly formed on the substrate as the gas decomposes. .

As described above, after forming the a-SiCN (i.e., a-SiC photoconductive layer), the organic photoconductor N (3) is then formed on the a-3iC layer (2).

The organic photosemiconductor layer is formed by a dip coating method or a coating method. According to the latter coating method, a photosensitive material dispersed in a solvent is applied using a coater, and then dried with hot air. conduct.

After that, a-5iC layer is again formed on the organic optical semiconductor layer,
That is, the a-SiC surface J! (4) is formed. This a-
The method for forming the SiC layer (4) is basically the same as the method for forming the a-3iC photoconductive layer (2) described above, but the film forming conditions (for example, the film forming temperature ) is preferably set within a predetermined range.

When setting the film-forming temperature, it should be noted that the upper limit thereof is more strictly limited than the film-forming temperature at the time of forming the a-SiC photoconductive layer.

〔Example〕

Next, examples of the present invention will be described.

(Example 1) Using the glow discharge decomposition device shown in Fig. 2, the flow rate of Sin gas is 200 sccra, and the flow rate of H2 gas is 210 sccr.
m, and the flow rate of CJz gas was changed, and the gas pressure was 0.6 Torr and the high frequency power was 150 W.
, the substrate temperature was set at 250°C, and a
- A SiC film (film thickness of about 1μ111) was formed.

In this way, the carbon content ratio of the a-SiC film was changed, and the amount of carbon in the film was measured by the XMA method.
Further, when the photoconductivity and dark conductivity were measured, the results shown in FIG. 3 were obtained.

In Figure 3, the horizontal axis is the carbon content ratio, i.e. 5i4-xC
It is the X value of , c, and d are respective characteristic curves.

Furthermore, when the hydrogen content of each of the above a-SiC films was determined by infrared absorption measurement, the results shown in FIG. 4 were obtained.

In Fig. 4, the horizontal axis is the X value of 5L-xc +c, and the vertical axis is the hydrogen content, that is, (Si1□G, ) l-a H
, the symbol ◯ is a plot of the amount of hydrogen bonded to the Si atom, the symbol • is the plot of the amount of hydrogen bonded to the C atom, and e+f is the respective characteristic curve.

As is clear from FIGS. 3 and 4, it can be seen that the a-values of the aSiC films of this example are all within the range of 0.3 to 0.4. In addition, the carbon content ratio X is 0.2<X<
It can be seen that within the range of 0.5, the ratio of photoconductivity to dark conductivity becomes significantly thicker, and an excellent light intensity can be obtained.

(Example 2) Next, in this example, H
2 gases were introduced at a flow rate of 0 to 101,000 sc, and the high frequency power was 50 to 300 W and the gas pressure was 0.3 to 1.
The a-SiC film (
A film thickness of about 1 μm) was formed.

In this way, various a-3tC films were formed with the carbon content ratio X set to 0.3 and the hydrogen content ita varied, and the photoconductivity and dark conductivity of each film were measured. The results shown in Figure 5 were obtained.

In Figure 5, the horizontal axis is the hydrogen content, i.e. (Sio, y CG
, ff ) +-a HjOa value, the vertical axis represents the conductivity, and the circle mark indicates the emission wavelength of 550 nm (light intensity 50 u
is a plot of photoconductivity versus W/cm”),
The marks are plots of dark conductivity, and g and h are respective characteristic curves.

As is clear from Figure 5, when the a value exceeds 0.2,
It can be seen that high photoconductivity as well as low dark conductivity are obtained.

(Example 3) In this example, an a-SiC photoconductive layer (2) is formed on an aluminum substrate (1) under the film forming conditions shown in Table 1, and then a polycarbonate layer is formed on this N (2). An organic optical semiconductor layer (3) (thickness: 30 μm) containing a hydrazone compound dispersed therein was formed by coating, followed by a ζaSiC surface layer (
4) was formed.

Margin below c] Regarding the electrophotographic photoreceptor obtained by the above manufacturing method, a-
When the amount of carbon in the 3iC layer was measured by the XMA method, it was found that the a-3iC photoconductive layer (2) and the a-3iC surface layer (4
) of each carbon I (x value, y value) is X・0.2
0, y = 0.70.

When the properties of the electrophotographic photoreceptor thus obtained were measured using an electrophotographic property measuring device, it showed excellent photosensitivity and high surface potential, and moreover, the residual potential was significantly reduced.

Furthermore, when the electrophotographic photoreceptor of this example was repeatedly charged 10,000 times and its photosensitivity and residual potential were measured, no change was observed in these characteristics, and no blurring occurred in the charge latent image. Ta.

(Example 4) In producing the electrophotographic photoreceptor of (Example 3), the film forming conditions for each a-SiCM were changed as shown in Table 2, and electrophotographic photoreceptors were produced in the same manner.

In addition, the a-5iC photoconductive layer (2) and the a-SiC photoconductive layer of this example
The carbon I (x value, y value) of each surface layer (4) was X·0.25, y = 0.80.

When the photosensitivity, surface potential and residual potential of the electrophotographic photoreceptor thus obtained were measured, good characteristics were obtained in all of them. Further, even after repeated charging tests were performed 10,000 times, no blurring occurred in the charge latent image.

(Example 5) An electrophotographic photoreceptor was manufactured in the same manner as in (Example 4) under the film forming conditions shown in Table 3.

In addition, the x value and y value of the carbon amount are each 0.20.0.
．． It was 70.

[Margin below]

The electrophotographic photoreceptor thus obtained also had good photosensitivity, surface potential, and residual potential, and no blurring of the charge latent image occurred even after repeated charging tests were performed 10,000 times.

(Example 6) In this example, from the electrophotographic photoreceptor of (Example 3), a-3
An electrophotographic photoreceptor from which the iC surface layer was removed was manufactured.

When this electrophotographic photoreceptor was subjected to a repeated charging test 10,000 times, it was observed that the photosensitivity decreased by approximately 10χ, the residual potential increased by approximately 8χ, and blurring occurred in the latent image. It was done.

In addition, the photosensitivity and residual potential of the electrophotographic photoreceptors obtained by removing the a-5iC surface layer from the electrophotographic photoreceptors of (Example 4) and (Example 5), respectively, were degraded in the same manner as in this example, and , blurring was observed in the latent image.

〔Effect of the invention〕

As described above, according to the electrophotographic photoreceptor of the present invention, an a-3iC surface layer is formed on the organic optical semiconductor compared to conventional ones, thereby increasing the hardness of the photoreceptor surface, and It was possible to provide an electrophotographic photoreceptor with high performance and long-term reliability, which does not cause blurring of latent charge images, has increased photosensitivity and surface potential, and has reduced residual potential.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the layer structure of the electrophotographic photoreceptor of the present invention;
Figure 2 is an explanatory diagram of the glow discharge decomposition device, Figure 3 is a diagram showing conductivity characteristics, Figure 4 is a diagram showing hydrogen content, and Figure 5 is a diagram showing the hydrogen content.
The figure is a diagram showing electrical conductivity. (1) Conductive substrate (2) Semiconductor layer amorphous silicon carbide surface layer with amorphous silicon carbide photoconductive layer Patent applicant (6
63) Kyocera Corporation Representative Kinjudo Anjo Takao Kawamura

Claims (4)

[Claims] (1) An electrophotographic photoreceptor in which a first amorphous silicon carbide layer having photoconductivity, an organic optical semiconductor layer, and a second amorphous silicon carbide layer are sequentially laminated on a conductive substrate, the first amorphous silicon carbide layer having The element ratio is set within the range of 0.01<x<0.5 with the x value of the composition formula Si_1_-_xC_x, and the element ratio of the second amorphous silicon carbide layer is set according to the composition formula Si
An electrophotographic photoreceptor characterized in that the y value of _1__yC_y is set within the range of 0.5<y<0.95. (2) The electrophotographic photoreceptor according to claim 1, wherein the first amorphous silicon carbide layer has a thickness in the range of 0.05 to 5 μm. (3) The electrophotographic photoreceptor according to claim 1, wherein the second amorphous silicon carbide layer has a thickness in the range of 0.05 to 5 μm. (4) The electrophotographic photoreceptor according to claim 1, wherein the thickness of the organic optical semiconductor layer is within the range of 10 to 50 μm.