JPH0212264A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance photosensitivity and to reduce residual potential by forming an amorphous silicon carbide photoconductive layer having a specified layer region rich in carbon content in contact with an organic semiconductor layer. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive substrate 1 the a-SiC photoconductive layer 2 and the organic semiconductor layer 3, and the layer 2 is composed of the first layer region 2a in contact with the layer 3 containing carbon in high concentration, and a second layer region 2b containing carbon in comparatively low concentration. The region 2a has a thickness of 10-2,000Angstrom , and its atomic composition is expressed by Si1-xCx, where x is set to 0.2<x<0.5, and the region 2a contains at least one of 0 and N in an amount of 0.01-30 atomic %, thus permitting high sensitivity to be obtained and residual potential to be reduced.

Description

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

[Prior art and its problems]

Photoconductive materials for electrophotographic photoreceptors include Se and 5e-Te.

^szS *s+There are inorganic materials such as ZnO, CdS, and amorphous silicon, and various organic materials. Among them, Se was the first to be put into practical use, and then ZnO,
CdS and amorphous silicon have also been put into practical use. On the other hand,
Among organic materials, PVK-TNF was first put into practical use, and later, a functionally separated photoreceptor was proposed in which the functions of charge generation and charge transport were shared between separate organic materials. The development of materials is progressing rapidly.

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 with a Se layer 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, JP-A-56-14241 proposes a laminated photoreceptor consisting of an amorphous silicon carbide photoconductive layer and an organic photoconductor layer. According to this photoreceptor, the above-mentioned problems can be solved. The properties of pollution-free property 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 up to the point described 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-StC) and an organic photoconductive layer are sequentially laminated on a conductive substrate, the a-SiC A layer region containing a large amount of C element is formed inside the conductive layer in contact with the interface between both layers, and the thickness of this layer region is within the range of 10 to 2000, and the Si element and C element in the layer region are The atomic composition ratio is 5it-*c.

When expressed as , the x value is set within the range of 0.2 <
Provided is an electrophotographic photoreceptor characterized by containing 0.01 to 30 atom % of one type of element. 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-3iC photoconductive layer (2) and an organic photo-semiconductor layer (3) are sequentially laminated on a conductive substrate (1). The a-SiC photoconductive layer (2) has a function of charge generation, and the other organic optical semiconductor layer (3) has a function of charge transport.

The present invention provides both layers (
2) A layer region containing a large amount of C element is formed so as to be in contact with the interface in (3), and this layer region also contains oxygen and/or nitrogen elements, thereby improving both photosensitivity and residual potential. It is characterized by improved characteristics.

According to FIG. 1, the a-SiC photoconductive layer (2) is formed from a first N region (2a) with a high content of C element and a second layer region (2b) with a relatively low content of C element. When such a layer region is formed, the a-SiC photoconductive layer (2)
The difference in dark conductivity between the Fi (2) (3) and the organic optical semiconductor layer (3) becomes significantly smaller, and thereby carriers are no longer trapped at the interface of both Fi (2) (3).

That is, the dark conductivity of the a-SiC light guide 11(2) is approximately 101
~10-''(Ω・cIll)-', and the dark conductivity of the other organic optical semiconductor layer (3) is approximately 10-''~10-''(
Ω·clI)−1, and therefore carriers generated in the a-3iC photoconductor N(2) do not flow smoothly to the organic photoconductor layer (3) due to the large difference in dark conductivity. Therefore, the present inventors have developed a first N N region (2
a), thereby reducing the dark conductivity of the layer region (2a) and reducing the difference in dark conductivity at the interface between both layers (2) and (3).

In addition, the present inventors have found that when the first N region (2a) contains at least one element of oxygen and nitrogen (hereinafter abbreviated as oxygen/nitrogen element), the surface potential can be further increased. I also found out.

In this way, the first MSM region (2a) is represented by the C element content ratio and thickness, as well as the oxygen and nitrogen element contents.

The C element content ratio is 0.2 < x in the x value of Si and □Cx.
<0.5, preferably within the range of 0.3 < y < 0.5. If the x value is 0.2 or less, both I
If the difference in dark conductivity between W(2) and (3) cannot be reduced as required, and as a result, the respective characteristics of photosensitivity and residual potential cannot be improved, and the x value is 0.5 or more. In this case, carriers are likely to be trapped in the a=sic photoconductive layer, resulting in a decrease in photosensitivity.

In addition, the thickness is 10 to 2000, preferably 500 to 2000.
o.

It is best to set it within the range of 20 people; if the number of people is less than 10, the characteristics of optical ambiguity and residual potential cannot be improved.
When the number of people exceeds 00, the residual potential tends to increase.

The content of oxygen and nitrogen elements is preferably set within the range of 0.01 to 30 at%, preferably 0.1 to 10 at%, and if the content is 0.01 at%, the surface potential and light If the sensitivity or residual potential cannot be further increased and the residual potential exceeds 30 at%, the residual rg! The potential increases significantly.

The other second layer region (2b) is substantially a photocarrier generation layer, and the element ratio thereof is preferably set within the following range.

The second layer region (2b) is made of amorphous Si element and C element, and hydrogen (I element and halogen element) for terminating the dangling bonds of both elements (this terminating element is hereinafter referred to as The compositional formula of these elements is (Si+--Cx) +
-y^, the X value is 0.05 < x
< 0.5, preferably 0.1 < x < 0.4, the y value is in the range 0.1 < y < 0.5, preferably 0.2 is 0.25 < y
It is preferable to set it within the range of <0.45. When the X value or the y value is set within the above range, excellent photoconductive properties and high photosensitivity properties can be obtained.

The thickness of the second layer region (2b) may be set within the range of 0.05 to 5 μm, preferably 0.1 to 3 μm; within this range, high photosensitivity can be obtained and residual potential can be reduced. It gets lower.

Such a first layer region (2a) and a 20th layer region (
The C element content and the oxygen/nitrogen element content in 2b) may be varied in the layer thickness direction. When the C element content is varied, for example, as shown in FIGS. 6 to 11. In addition, there are examples shown in Figures 12 to 16 when the oxygen and nitrogen element contents are changed. In these figures, the horizontal axis is the layer thickness direction, and a is the thickness direction. 2 layer area (
2b) and the interface between substrate (1), b is the first layer region (2a)
and the interface of the second N region (2b), and C is the interface of the first N region (2b).
It represents the interface between the region (2a) and the organic optical semiconductor layer (3), and the vertical axis represents the C element content or the oxygen/nitrogen content.

In addition, when the C element content or the oxygen/nitrogen element content is changed in the layer thickness direction inside the first layer region (2a) or the second layer region (2b), the content ratio of each element is N
wI range (2a) (2b) Corresponds to the overall average content ratio.

The substrate (1) includes a metal conductor such as copper, brass, SO5, At, or an insulator such as glass or ceramics coated with a conductor thin film on the surface.
is advantageous in terms of cost and adhesion to a-SiCFi.

Further, the electrophotographic photoreceptor of the present invention has an organic photoconductor layer (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 for the organic optical semiconductor layer (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.

Examples of electron-withdrawing compounds include 2,4,7-dolinitrofluorene.

Thus, according to the electrophotographic photoreceptor of the present invention, by forming the C element high content layer region containing oxygen and nitrogen elements, the photosensitivity can be increased and the residual potential can be reduced.

In addition, in the electrophotographic photoreceptor of the present invention, a-9i
The C photoconductive layer (2) contains an element of group NLA of the periodic table (hereinafter referred to as n
1 to 500 ppm, preferably 2
It is preferable to contain up to 200 ppm.

This ma group element content is expressed by the average value for the entire a-5iC layer, and the average content is lp
When the temperature is below pm, the dark conductivity tends to be thicker.
Moreover, a decrease in photosensitivity was observed, while 500ppn+
In these cases, 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 the Ma group element into the a-SiC photoconductive layer (2), the doping distribution may be either uniform or non-uniform over the layer thickness direction. In the case of non-uniform doping, there may be a part of this layer (2) in which there is an N region in which no Ma group element is contained. a that does not contain
-3iC1JsIf region, the average content of Ma group elements in the entire a-SiCN consisting of both regions must be 1 to 500 ppm.

This MA group element includes B, AI + Ga + In, etc., but B is desirable because it has excellent covalent bonding properties and can sensitively change semiconductor properties, and also because it can provide excellent charging ability and photosensitivity. .

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 SiH4+
hJi+513H11+SxF*4iC1*+5tHC
1s, etc., and the C element-containing gas has CHa=C
There are tHa, CtH2+C3HI1, etc., especially cz
oz is desirable in that high-speed film formation can be achieved.

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

In the figure, 5iH41C, II, BZI16. (B,
II6 is 40ppm? Hydrogen is diluted by agriculture),
11□ and NO are sealed, and these gases are supplied to the corresponding first regulating valve (9), second regulating valve (10), third regulating valve (11), fourth regulating valve (12) and fifth regulating valve, respectively. Valve (13
) is released by opening. The flow rate of the released gas is determined by the mass flow controller (14) (15) (16), respectively.
) (17) and (18), each gas is mixed and sent to the main pipes (19) and (20). still,(
21) (22) are stop valves.

Gas flowing through the main pipe (19) flows into the reaction tube (23), and a capacitively coupled discharge electrode (24) is installed inside this reaction tube (23), and a cylindrical film-forming substrate is installed inside the reaction tube (23). (25) is placed on a substrate support (26), the substrate support (26) is rotationally driven by a motor (27), and the substrate (25) rotates accordingly. Then, the electrode (2
4) Power 50W ~ 3 Kw, frequency 1 ~ 50MHz
high-frequency power is applied, and the substrate (25) 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 (23
) is connected to a rotary pump (28) and a diffusion pump (29), which provide the necessary vacuum state B (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 a-5iCq on 5), the 111th regulating valve (9), the second regulating valve (10), the third regulating valve (11),
Open the fourth regulating valve (12) and the fifth regulating valve (13) and
xl14. Each of the gases CJ2, B□H&, It□, and NO is released, and the release amount is controlled by a mass flow controller (14) (15) (16) (17) (18), and each gas is mixed. Main manager (19) (2
0) into the reaction tube (23). Then, when the vacuum state inside the reaction tube, the substrate temperature, and the high-frequency power applied to the electrodes are set to predetermined conditions, a glow discharge occurs.
With the decomposition of gas, a-5i containing each element of B, N, and 0
A C film is formed on the substrate at high speed.

After forming the a-3iC layer by the thin film forming method as 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, S i II
, gas at a flow rate of 200 sec, +12 gas at 270 sec
The flow rate of c Z i Z gas was changed, the gas pressure was set to Q, 5 Torr, the high frequency power was set to 150 W, and the substrate temperature was set to 250° C., and a-3iCIl! was generated by glow discharge. (film thickness approximately 1 μm) was formed.

In this way, the carbon content ratio of the a-3iC 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 FIG. 3, the horizontal axis represents the carbon content ratio, that is, Si.

It is the X value of XCX, the vertical axis represents the conductivity, the ○ mark is a plot of photoconductivity for light with an emission wavelength of 550r+n+ (light intensity 50 μw/cm2), the mark is a plot of dark conductivity, and , a, b are respective characteristic curves.

Furthermore, when the hydrogen content of each of the above a-3iC 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 5il-XCX, the vertical axis is the hydrogen content, that is, the y value of (Sil□CX)+-yHy, and the O symbol indicates the amount of hydrogen bonded to the Si atom. It is a plot, and the mark is a plot of the amount of hydrogen bonded to the C atom,
Moreover, c and d are respective characteristic curves.

As is clear from FIG. 4, it can be seen that the a-3iC 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, 5il14 gas is
C, lh gas at a flow rate of 20 sec, I+
2 gases at a flow rate of 0 to 101,000 sc by 4 people, high frequency power of 50 to 300 W, and gas pressure of 0.3 to 1.
The a-3iC film (
A film thickness of about 1 μm) was formed.

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

In Fig. 5, the horizontal axis represents the hydrogen content, that is, (Si+-x C+
i) + - y) It is the y value of Iy, the vertical axis represents the conductivity, and the O mark indicates the emission wavelength of 550 ns (light intensity 50 μ-/cm)
) is a plot of photoconductivity against light, the * mark is a plot of dark conductivity, and e and f 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) A-5iC photoconductive 1 (2) was formed using the film forming conditions shown in Table 1.
was formed.

And the first one! When the content of oxygen and nitrogen elements in the region was measured, it was approximately 2 at.%.

[Margin below]

On the thus formed a-SiC photoconductive layer, an organic photoconductor layer (about 15 μm in thickness) consisting of polycarbonate and a hydrazone compound dispersed therein 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) The present inventors have discovered that the first N related to the electrophotographic photoreceptor of (Example 3)
In forming the Su region, the flow rate of NO gas is changed and the film formation time is also changed.
Nine types of electrophotographic photoreceptors (photoreceptor A-1) were manufactured by changing the oxygen and nitrogen element contents and film thicknesses of the layer regions as shown in Table 2.

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

Surface potential is evaluated relative to three levels: ◎ mark, ○ mark, and Δ mark. ■ mark indicates that the best surface potential was obtained, and O mark indicates that somewhat better surface potential was obtained. The Δ mark indicates a case where the surface potential is somewhat inferior compared to the others.

Photosensitivity was also classified into three levels based on relative evaluation: ◎, ○, and Δ. ■: The best photosensitivity was obtained, and ○: slightly better photosensitivity. The Δ mark indicates 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 residual potential was observed, and the mark Δ indicates a case where a reduction in residual potential was not observed compared to the others.

[Margin below]

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, the surface potential was high, and a reduction in residual potential was observed.

However, the thickness of the first layer region of photoreceptors A and H and the content of oxygen and nitrogen elements in the first layer region of photoreceptors C and I are respectively different from those of the present invention. No improvement in sensitivity or residual potential was observed.

〔Effect of the invention〕

As described above, according to the electrophotographic photoreceptor of the present invention, a-S
High C element content 1' containing oxygen and nitrogen elements inside the iC photoconductive layer! ! By forming the %J1 region, excellent photosensitivity was obtained, a high surface potential was obtained, and the residual potential was able to 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, Figure 10
11 and 11 are diagrams showing the carbon content in the layer thickness direction of the amorphous silicon carbide photoconductive layer, and FIGS. FIG. 2 is a diagram showing the content of oxygen and nitrogen elements in the thickness direction of a conductive layer. l ・ 2a ・ 2b ・ 3 ・ Conductive substrate amorphous silicon carbide photoconductive layer Layer region of tube 1 Second layer region Organic optical semiconductor layer Patent applicant (663) Kyocera Corporation Representative Kinju Anjo Takao Kawamura

Claims (1)

[Claims] In an electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer and an organic photoconductive layer are successively laminated on a conductive substrate, a layer containing a large amount of carbon element is provided inside the amorphous silicon carbide photoconductive layer and in contact with an interface between both layers. The thickness of this layer region is 10 to 2000 Å.
and the atomic composition ratio of silicon element and carbon element in the layer region is expressed as Si_1_−_xC_x, the x value is set within the range of 0.2<x<0.5, and the above layer is further An electrophotographic photoreceptor characterized in that a region contains 0.01 to 30 at % of at least one element of oxygen and nitrogen.