JPH0212262A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance photosensitivity and to reduce residual potential by forming a specified amorphous carbon (a-C) layer for the electrophotographic photosensitive body. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive substrate 1 an a-SiC photoconductive layer 2 for generating electric charge and an organic photoconductive layer 3 for transferring charge, and the amorphous carbon (a-C) layer 4 is formed between the layers 2 and 3, and it has a thickness of 10-2,000Angstrom and an optical band of >=2.0eV, thus permitting photosensitivity to be enhanced and residual potential to be reduced.

Description

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

[Prior art and its problems]

Photoconductive materials for electrophotographic photoreceptors include Se, 5e-Te+
There are inorganic materials such as A-mouth Saz+ZnO+cdss amorphous silicon and various organic materials. Among them, Se was the first to be put into practical use, and then ZnO, Cd
S, amorphous silicon has also been put into practical use. On the other hand, among organic materials, PVK-TNP was first put into practical use, and then
A functionally separated photoreceptor has been proposed in which the functions of charge generation and charge transport are shared by separate organic materials, and this functionally separated photoreceptor has led to dramatic advances in the development of organic materials.

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

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

Therefore, Japanese Unexamined Patent Application Publication No. 14241/1988 proposes a laminated photoreceptor consisting of an amorphous silicon carbide photoconductive layer and an organic photoconductor layer. The properties of pollution resistance and high light sensitivity were obtained.

However, when the present inventors manufactured such an electrophotographic photoreceptor and measured its photosensitivity and residual potential, it was found that both characteristics were still unsatisfactory, and further improvements were needed. There was found.

Therefore, the present invention has been completed in view of the above,
The purpose is to provide an electrophotographic photoreceptor that has high photosensitivity and reduced residual potential.

[Means for solving problems]

According to the present invention, in an electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer (hereinafter amorphous silicon carbide is abbreviated as a-SiC) and an organic photoconductive layer are sequentially laminated on a conductive substrate, the a-SiC Provided is an electrophotographic photoreceptor, characterized in that an amorphous carbon layer having a thickness within the range of 10 to 2000 carbon atoms and an optical band gap of 2.0 eV or more is formed between the conductive layer and the organic optical semiconductor layer. be done.

The present invention will be explained in detail below.

FIG. 1 shows the layer structure of the electrophotographic photoreceptor of the present invention.
According to the figure, an a-SiC photoconductive layer (2) and an organic photo-semiconductor layer (3) are sequentially laminated on a conductive substrate (1). The a-5iC photoconductive layer (2) has a function of charge generation, and the other organic photoconductive layer (3) has a function of charge transport.

The present invention relates to the a-StC photoconductive F! Amorphous carbon between 1 (2) and the organic optical semiconductor layer (3)! (4)
(Hereinafter, amorphous carbon is abbreviated as a-C) is formed, thereby improving both the characteristics of photosensitivity and residual potential.

The dark conductivity of a-SiC photoconductive N(2) is about 10-” ~
1013(Ω・cm)−', and the dark conductivity of the other organic optical semiconductor 1i(3) is approximately 10−” to 1O−IS(Ω
・cm)-', and therefore the a-3iC photoconductive layer (
The carriers generated in step 2) do not flow smoothly to the organic optical semiconductor layer (3) due to the large difference in dark conductivity. Therefore, the present inventors have found that it is possible to form a-CIW (4) with low dark conductivity, thereby reducing the difference in dark conductivity at the interface between both layers (2) and (3).

Such a-C layer (4) is expressed by the optical bandgap and thickness as shown below.

The optical bandgap is 2.0eV or more, preferably 2.0eV or more.
It is best to set it to 3 eV or higher, which will cause the layer (4
) can be set between the respective dark conductivities of the a-SiC photoconductive layer (2) and the organic photoconductive layer (3), so that the a-SiC photoconductive N(2) The carriers generated flow smoothly into the organic optical semiconductor layer (3).

This bandgap can be controlled by changing the hydrogen content of the a-C layer (4).

The thickness of a-Clti (4) is 10 to 2000
If the number of people is less than 10, the characteristics of photosensitivity and residual potential cannot be improved, and if the number of people is more than 2,000, the residual potential becomes large. There is a tendency to

The a-3iC photoconductive FW (2) is essentially a photocarrier generation layer, and its element ratio is preferably set within the following range.

This layer (2) consists of amorphous Si element and C element, and furthermore, hydrogen (H) element and halogen element (hereinafter, this terminating element is referred to as H element) to terminate the dangling bonds of both elements. ), and the compositional formula of these elements is (Si.

CX) +-y When expressed as Ay, the y value is 0
°05 < x < 0.5, preferably 0.1 < x
< 0.4, y value is 0.1 < y < 0
．． 5, preferably within the range of 0.2 < y < 0.5, optimally within the range of 0.25 < y < 0.45. When the y value or y value is set within the above range, excellent photoconductive properties and high photosensitivity properties can be obtained.

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

The C element content of the a-SiC photoconductive layer (2) may be varied in the layer thickness direction. For example, there are examples shown in FIGS. 6 to 11, in which the horizontal axis is the layer thickness direction, a is the interface between the a-3iC photoconductive iJ (2) and the substrate (1), and b is the interface between the a-3iC photoconductive iJ (2) and the substrate (1). -SiC photoconductive layer (2) and a-CM (4)
The vertical axis represents the C element content.

Note that when the C element content is changed in the layer thickness direction inside the a-SiC photoconductive layer (2), the C element content ratio (X
value) corresponds to the average content ratio of C element per whole Iti(2).

The substrate (1) includes a metal conductor such as copper, brass, SUS, or AI, or an insulator such as glass or ceramics coated with a conductor thin film on the surface.
AI is advantageous in terms of cost and adhesion to the a-SiC layer.

Further, the electrophotographic photoreceptor of the present invention is an organic photoconductor N(3).
It can be set to a negatively charged type or a positively charged type by selecting the material. That is, in the case of a negatively charged electrophotographic photoreceptor, an electron-donating compound is selected as the organic photosemiconductor N(3);
In the case of a positively charged electrophotographic photoreceptor, an organic optical semiconductor layer (3
) is selected as an electron-withdrawing compound.

As an electron donating compound, poly-N is used as a high molecular weight compound.
- Vinylcarbazole, polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensation polymer, etc., and low molecular weight ones include oxadiazole, oxazole, pyrazoline, triphenylmethane, hydrazone, triarylamine, N-phenylcarbazole, Examples include stilbene, and this low-molecular substance is used after being dispersed in a binder such as polycarbonate, polyester, methacrylic resin, polyamide, acrylic epoxy, polyethylene, phenol, polyurethane, butyral resin, polyvinyl acetate, or urea resin.

Electron-withdrawing compounds include 2,4,7-trinitrofluorene.

(According to the electrophotographic photoreceptor of the present invention, a-CT4
By forming this, it was possible to increase photosensitivity and reduce residual potential.

Further, in the electrophotographic photoreceptor of the present invention, a-SiC
The photoconductive N(2) is an element of Group Ma of the periodic table (hereinafter referred to as NLA).
1 to sooppm of the ma group element (s), preferably 2 to 20
It is preferable to contain 0 ppm.

This Ma group element content is expressed by the average value per a-SiC counterfeit body, and the average content is 1
At ppn+ or below, the dark conductivity tends to increase, and a decrease in photosensitivity is observed.
If it is more than m, the dark conductivity becomes significantly large, and the ratio of photoconductivity to dark conductivity becomes small, making it difficult to obtain the desired photosensitivity.

When incorporating Ma group elements into the a-SiC photoconductive layer (2), the doping distribution is uniform over the layer thickness direction.
Or it may be non-uniform. In the case of non-uniform doping, there may be a layer region in which the Ma group element is not contained in a part of this FJ (2), and in that case, there may be a layer region containing the Ma group element and the a-5iCN consisting of both a-3iC [6J (range) which does not contain
The average content of Ma group elements in the whole is 1 to 500 ppn
Must be +.

This ma group element includes B+ALGa+ In, etc.
B is desirable because it has excellent covalent bonding properties and can sensitively change semiconductor properties, and also because it provides excellent charging ability and photosensitivity.

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

To form a-SiCN or a-CJii, there are thin film forming methods such as a glow discharge decomposition method, an ion blating method, a reactive sputtering method, a vacuum evaporation method, and a CVO method.

When forming an a-SiC layer using a glow discharge decomposition method, a Si element-containing gas and a c-element containing gas are combined, and this mixed gas is plasma decomposed to form a film.

This Si element-containing gas contains 5i114,5tzll*,
Si:+IIa, SiF4+5ic14,5tllcl
i, etc., and C element-containing gases include CH4, CJ, etc.
CJz, CJz, CJs, etc., and C2H2 is particularly desirable because it can provide high-speed film formation.

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

In the figure, the first tank (4), second tank (5), third tank (6), and fourth tank (7) each have S! Ht+C
zn□, Bzllb, (BdI& is diluted with hydrogen at a concentration of 40 ppm) and H2 are sealed, and these gases are passed through the corresponding first regulating valve (8) and second regulating valve (9), respectively.
, by opening the third regulating valve (10) and the fourth regulating valve (11).

The flow rates of the released gases are controlled by mass flow controllers (12), (13), (14), and (15), and each gas is mixed and sent to the main pipe (16). Note that (17) and (1B) are stop valves.

The gas flowing through the main pipe (16) flows into the reaction tube (19), and a capacitively coupled discharge electrode (20) is installed inside this reaction tube (19), and a cylindrical film-forming substrate is installed inside the reaction tube (19). (2) is placed on the substrate support (22), the substrate support (22) is rotationally driven by the motor (23), and the substrate (21) is rotated accordingly. Then, the electrode (2
0) Power 5011~3 Kw, Frequency 1~50MHz
high-frequency power is applied, and the substrate (21) is heated to about 200-400°C, preferably about 20°C by suitable heating means.
Heated to a temperature of 0-350°C. In addition, a reaction tube (19
) is connected to a rotary pump (24) and a diffusion pump (25), which maintains the necessary vacuum state (gas pressure during discharge of 0.1 to 2.0 Torr) during film formation by glow discharge.
r) can be set.

The substrate (2
When forming an a-SiC layer on 1), the first regulating valve (
8), open the second regulating valve (9), the third ill regulating valve (10), and the fourth regulating valve (11) and SiL+C*L+B! I(
Each gas of i+IIg is released, and the amount of release is controlled by a mass flow controller (12) (13) (14) (1
5), each gas is mixed and sent to the main pipe (16
) into the reaction tube (19). Then, by setting the vacuum inside the reaction tube, the substrate temperature, and the high-frequency power applied to the electrodes to predetermined conditions, a glow discharge occurs, and as the gas decomposes, the a-5iC film containing B element is rapidly spread onto the substrate. to form.

After forming the a-SiC layer by the thin film forming method described above, an organic optical semiconductor layer is then formed.

The organic optical semiconductor layer is formed by a dip coating method or a coating method. In the former method, the photosensitive material is immersed in a coating solution in which it is dispersed in a solvent, then pulled up at a constant speed, and then
This method involves natural drying and heat aging (approximately 150°C, approximately 1 hour), and the latter coating method involves applying a photosensitive material dispersed in a solvent using a coater. , followed by hot air drying.

〔Example〕

Next, examples of the present invention will be described.

(Example 1) Using the glow discharge decomposition device shown in Fig. 2, SiL gas is
H2 gas at 270 sccm at a flow rate of 00sccII+
Then, the flow rate of CzHt 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 approximately 1 μm) 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. Si+XCX
The vertical axis represents the conductivity, the ○ mark is a plot of photoconductivity for light with an emission wavelength of 550 nm (light intensity 50 μW/cm"), and the mark is a plot of dark conductivity. , and a and b are their 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 Si+-x CxOX value, and the vertical axis is the hydrogen content, i.e. (Si1-C,l)ty H
This is the y value of y, the ◯ mark is a plot of the amount of hydrogen bonded to the Si atom, the * mark is the plot of the amount of hydrogen bonded to the C atom, and c and d are the respective characteristic curves.

As is clear from FIG. 4, it can be seen that the a-SiC films of this example all have y values within the range of 0.3 to 0.4.

Furthermore, as is clear from Fig. 3, if the carbon content ratio X is within the range of 0.05 < It turns out that is obtained.

(Example 2) Next, in this example, SiH4 gas is fed at a flow rate of 200 seconds, C, t+t gas is fed at a flow rate of 20 seconds, and OX
Gas was introduced at a flow rate of θ~1000scc+++, and the high frequency power was 50~300W and the gas pressure was 0.3~1.
．． The a-5iC film (film thickness: about 1 μm) was formed by glow discharge at a pressure of 2 Torr.

In this way, various a-SiC films were formed with the carbon content ratio x set to 0.3 and the hydrogen content changed.
When the photoconductivity and dark conductivity of each film were measured, the results shown in FIG. 5 were obtained.

In Fig. 5, the horizontal axis represents the hydrogen content, that is, (Sl+-x C8
] is the y value of +-yHy °, the vertical axis represents the conductivity,
○ indicates emission wavelength of 550nm (light intensity 50μ-/cab)
) is a plot of photoconductivity against light, * marks are plots of dark conductivity, and elf are respective characteristic curves.

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

(Example 3) An a-3iC photoconductive layer (2) and an a-C layer (4) were sequentially formed on a mirror-finished substrate (21) under the conditions shown in Table 1.

The optical band gap of the a-C layer (4) was measured and found to be 2.5 eV.

On the thus formed laminated layer, an organic photoconductor layer (film thickness of about 15 μm) made of polycarbonate in which a hydrazone compound was diffused was formed to obtain an electrophotographic photoreceptor.

When the properties of the thus obtained electrophotographic photoreceptor were measured using an electrophotographic property measuring device, it was found that excellent photosensitivity and low residual potential were obtained.

(Example 4) In manufacturing the electrophotographic photoreceptor of (Example 3) above,
An electrophotographic photoreceptor was manufactured in which only the a-5iC light guide xi was formed without forming the a-Ci, and the same organic optical semiconductor layer was formed.

When the photosensitivity of this electrophotographic photoreceptor was measured, (Example 3
), the residual potential was about 12χ lower than that of the electrophotographic photoreceptor, and the residual potential was about 8χ higher.

(Example 5) The present inventors have developed a-Cf related to the electrophotographic photoreceptor of (Example 3).
In forming fj, C211□ gas and 11□
By changing the flow rate of each gas, and also changing the film forming time, gas pressure, and high frequency power, a-C
The optical band gaps and film thicknesses of the layers were varied as shown in Table 2, and the other manufacturing conditions were set the same as in (Example 3), thus eight types of electrophotographic photoreceptors (photoreceptors A to H) were prepared. was produced.

Furthermore, when the photosensitivity and residual potential of these electrophotographic photoreceptors were measured, the results shown in Table 2 were obtained.

In the same table, photosensitivity is classified into three levels based on relative evaluation: ◎, ○, and Δ. ◎ indicates the best photosensitivity, and O indicates somewhat better photosensitivity. is obtained, and the mark Δ is a case where the photosensitivity is slightly inferior to the others.

In addition, the residual potential is also evaluated relative to three levels.
The ■ mark indicates a case where the residual potential became small, the ○ mark indicates a case where a slight decrease in the residual potential was observed, and the Δ mark indicates a case where a reduction in the residual potential was not observed compared to the others.

No. table Photoreceptors marked with * are outside the scope of the present invention.

As is clear from Table 2, photoconductor B and photoconductor D-G
Excellent photosensitivity was obtained, and a reduction in residual potential was also observed.

However, for photoreceptors ^ and H, the thickness of the a-C layer is that of photoreceptor C.
The optical band gaps of the a-C layers were different from those of the present invention, and therefore no improvement in photosensitivity or residual potential was observed.

〔Effect of the invention〕

As described above, according to the electrophotographic photoreceptor of the present invention, a-C
By forming the layer, excellent photosensitivity could be obtained, and the residual potential could be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the layer structure of the electrophotographic photoreceptor of the present invention, FIG. 2 is a schematic diagram of a glow discharge decomposition device used in Examples, and FIG. 3 is a line showing the relationship between carbon content and electrical conductivity. 4 is a diagram showing the relationship between carbon content and hydrogen content, FIG. 5 is a diagram showing the relationship between hydrogen content and electrical conductivity, and FIGS. Figure 8, Figure 9, 1O
The figure and FIG. 11 are diagrams showing the carbon content in the layer thickness direction of the amorphous silicon carbide photoconductive layer. Conductive substrate Amorphous silicon carbide Photoconductive layer Organic optical semiconductor layer Amorphous carbon layer Patent applicant (663) Kyocera Corporation Representative Kinjudo Anjo Takao Kawamura

Claims (1)

[Claims] In an electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer and an organic photosemiconductor layer are sequentially laminated on a conductive substrate, the thickness is within the range of 10 to 2000 Å between the amorphous silicon carbide photoconductive layer and the organic photosemiconductor layer. An electrophotographic photoreceptor comprising an amorphous carbon layer having an optical band gap of 2.0 eV or more.