JPH02167556A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance photosensitivity and surface potential and to reduce residual potential by forming layer regions containing specified amounts of element of group IIIa and Va, respectively, in the inside of an a-SiC photoconductive layer. CONSTITUTION:The amorphous silicon carbide (a-SiC) photoconductive layer 2 has a layer structure formed by successively laminating a first layer region 2a containing an element of group IIIa of the periodic table in an amount of 0 - 10,000ppm, a second layer region 2b containing an element of group IIIa of the periodic table in an amount of 0 - 200ppm, and a third layer region containing an element of group Va of the periodic table in an amount of 1 - 300ppm, and each thickness of the layer regions 2a, 2b, 2c is set in the range of 0.01 - 3mum, thus permitting the obtained electrophotographic sensitive body to be enhanced in photosensitivity and surface potential and reduced in residual potential.

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, 5e-Te,
AS2S a:++ There are inorganic materials such as ZnO and Cd51 amorphous silicon, and various organic materials. Among them, Se was the first to be put into practical use, followed by ZnO.
, CdS, and amorphous silicon have also been put into practical use. On the other hand, among organic materials, PVK-TNP was first put into practical use, and later, a functionally separated photoreceptor was proposed in which the functions of charge generation and charge transport are shared between separate materials.
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 an 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 the sensitivity is poor on the long wavelength side.

Therefore, Japanese Patent Application Laid-Open No. 56-14241 proposes a laminated photoconductor consisting of an amorphous silicon carbide photoconductive layer and an organic photoconductor layer, and this photoconductor solves the above problems and is non-polluting. Characteristics of high light sensitivity and light sensitivity were obtained.

However, when the present inventors manufactured such an electrophotographic photoreceptor and measured its photosensitivity, surface potential, and residual potential, satisfactory characteristics were still not obtained, and further improvements were needed. It has been found.

Therefore, the present invention was completed in view of the ridges, and its object is to provide an electrophotographic photoreceptor that can obtain high photosensitivity and surface potential, and furthermore, has a 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-5iC) and an organic photoconductive layer are sequentially laminated on a conductive substrate, the a-3iC The photoconductive layer has a layer structure in which a first layer region, a second layer region, and a third layer region are formed in sequence, and the first layer region contains 1 to 110,000 pp of Group IIIa elements of the periodic table. 0 to 200 p of Group Ia elements of the periodic table in the second layer region.
pm, the third layer region contains 1 to 30 (lppm) of Group Va elements of the periodic table, and the thickness of the first layer region is within the range of 0.0 to 3 μm, and the second layer The thickness of the third layer region is within the range of 0.01 to 3 μm, and the thickness of the third layer region is o.
, oi to 3 μm is provided.

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 aSiC photoconductive layer (2) and an organic photo-semiconductor layer (3) are sequentially laminated on a conductive substrate (1). The a-3iC 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 provides a first layer region (2a), a second layer region (2b) and a third layer region (
2C) in order to make the first layer region (2a) contain an element of group Ma of the periodic table (hereinafter abbreviated as group IIIa element) within a predetermined range, and furthermore, the third layer region (2a) contains 2c) contains Group Va elements of the periodic table (hereinafter abbreviated as Group Va elements) within a predetermined range, and the thickness of each layer region is set within a predetermined range, thereby increasing photosensitivity. It is characterized by improved surface potential and residual potential.

Another feature is that by forming such a layer region, it becomes a positively charging electrophotographic photoreceptor.

First, the a-5iC photoconductive layer (2) consists of an amorphous Si 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.

(5it-x to C)+-yAy (A is H element or halogen element) 0<x<0.5 Preferably 0.01<x<0.4 Optimally
0.05 < x < 0.20.1 < V <
0.5 preferably 0.2 <y <0.5 optimally 0.
25 < y < 0.45 If the X value is within the range of O < x < 0.5, high photoconductivity is obtained;
When set within the range of x < 0.4, the photosensitivity on the short wavelength side is increased, and the photoconductivity is significantly increased, so that the excitation function of photocarriers is increased.

Furthermore, when the y value is less than 0.1, the film quality deteriorates, which significantly reduces the photoconductivity, and furthermore, 0.2 < V
When it is set within the range of <0.5, the dark conductivity is small and the photoconductivity is large, resulting in excellent photoconductivity and excellent adhesion to the substrate.

This a-3iC photoconductive layer (2) contains hydrogen (H) element and halogen element for dangling bond termination, but among these elements, H element is easily incorporated into the termination part, and this This is desirable in that the local unit density in the band gap is reduced by this.

Moreover, the thickness of the a-5iC photoconductive layer (2) is 0.15 to 5
It may be set within the range of μm, preferably 0.2 to 3 μm, and within this range high photosensitivity can be obtained and the residual potential will be low.

Next, for the first layer region (2a), the l1la group element is contained in an amount of 1 to 110,000 pp, preferably 300 to 3,000 pp.
ppm, thereby forming a P-type semiconductor, a-
Photocarriers generated in the 5iC photoconductive layer (2), especially positive charges, can flow smoothly to the substrate side, and carriers on the substrate side can be prevented from flowing into the a-5iC photoconductive layer (2). be able to. That is, the first layer region (2a) can be said to be in non-ohmic contact with the substrate (1) in that it has rectifying properties.

Therefore, this non-ohmic contact increases the surface potential and reduces the residual potential.

Such a first N region (2a) is expressed by the content of the Ma group element, but when the content is non-uniform over the layer thickness direction, it is expressed by the average content.

If the Group IIIa element is less than 1 ppm, it has no effect of blocking carrier injection from the substrate side and improving charging ability, and if it exceeds 110,000 ppm, internal defects in this layer region increase, the film quality deteriorates, and the surface potential decreases. This causes a decrease in the residual potential and an increase in the residual potential.

Further, the first layer region (2a) is set more specifically by its thickness as well as the IIIa group element content.

That is, the thickness of the first layer region (2a) is 0.01 to 3 μm.
, preferably within the range of 0.1 to 0.5 μm, and within this range, the residual potential can be reduced and the withstand voltage of the photoreceptor can be increased.

Further, it is desirable that the first layer region (2a) is set according to the SiC group type ratio, as well as the Group IIIa element content and thickness.

That is, when expressed by the composition formula Sj, -,,CX, 0.1
It is preferable to set it within the range of < x < 0.5, and within this range, the surface potential can be increased and the adhesion to the substrate can be improved.

In addition, in setting the C element ratio as described above,
It is preferable to make the ratio larger than that of the second layer region (2b), which is advantageous in that the surface potential can be increased and the adhesion with the substrate can be improved.

The above-mentioned NLA group elements include B+AI+Ga+In, and B is preferable because it has excellent covalent bonding properties and can sensitively change semiconductor properties, and also provides excellent charging ability and photosensitivity.

For the third layer region (2c), 1 to 3 Va group elements are added.
00 ppm, preferably 3 to 1100 ppm, thereby forming an n-type semiconductor layer on the organic optical semiconductor layer (3) side inside the a-5iC photoconductive layer (2), and causing The photocarriers, especially the negative charges, are transferred to the organic photoconductor layer (3).
As a result, the surface potential increases and the residual potential decreases.

In this way, the third layer region (2c) is represented by the content of the Va group element, but if the content is non-uniform over the layer thickness direction, it is represented by the average content.

If the amount of the Va group element is less than 1 ppm, the charging ability cannot be improved, and if it exceeds 300 ppm, the ability to generate photoexcited carriers is poor and the photosensitivity is reduced.

Further, the third layer region (2c) is set more specifically by its thickness as well as the Va group element content.

That is, the thickness of the third layer region (2c) is 0.01 to 3 μm.
, is preferably set within the range of 0.1 to 0.5 μm, and within this range high photosensitivity can be obtained and the residual potential will be low.

The Va group elements mentioned above include N, P, As+Sb, Bi, etc., but P has excellent covalent bonding properties and can sensitively change semiconductor properties, and it is said that it can also provide excellent charging ability and photosensitivity. desirable in that respect.

The second layer region (2b) does not contain Va group elements or contains L1la group elements in a range of less than 200 ppm, thereby forming an i-type semiconductor layer. And aSiC
This is the main carrier generation layer of the photoconductive layer (2).

The thickness of the second layer region (2b) may be set within the range of 0.01 to 3 μm, preferably 0.1 to 2 μm, and within this range, high photosensitivity can be obtained and the residual potential becomes lower.

As mentioned above, the a-3iC photoconductive layer (2) has p-1-n
A junction is formed, so that among the carriers generated in this N(2), electrons go toward the organic optical semiconductor layer (3), while holes go toward the substrate (1). Therefore, it becomes a positively charged electrophotographic photoreceptor.

In such a positively charged electrophotographic photoreceptor, an electron-withdrawing compound is selected for the organic optical semiconductor layer (3), and examples of this compound include 2,4,7-1-linitrofluorenone.

Further, the substrate (1) is made of copper, brass, SUS, AI.
There are metal conductors such as, or insulators such as glass and ceramics coated with a thin conductive film.
Among these, AI is advantageous in terms of cost and adhesion to the a-5iC layer.

Thus, according to the present invention, the a-5iC photoconductive layer contains III
By forming a layer region containing a group A element and a group Va element within a predetermined range, surface potential and residual potential are improved, and photosensitivity is increased.

Further, according to the present invention, the C element content of each of the first layer region (2a), the second layer region (2b), and the third layer region (2c) is varied in the layer thickness direction. Good too. For example, there are examples shown in FIGS. 6 to 10, in which the horizontal axis is the layer thickness direction, and a is the first layer region (2a
) and the substrate, b is the interface between the first layer region (2a) and the second layer region (2b), and C is the interface between the second layer region (2b) and the third layer region (2b).
The interface between the layer region (2c) and d represents the interface between the third layer region (2c) and the organic optical semiconductor layer (3), and the vertical axis represents C.
Represents elemental content.

In addition, when the C element content is changed in the layer thickness direction inside the first layer region (2a), the second layer region (2b), or the third layer region (2c), the C element content The ratio (X value) corresponds to the average content ratio of C element in the entire layer regions (2a), (2b), and (2c), respectively.

Furthermore, in the electrophotographic photoreceptor of the present invention, the I of each of the first layer region (2a) and the third layer region (2c) is
The IIa group element content and the Va group element content may be varied in the layer thickness direction. Examples are shown in FIGS. 11 to 16. In particular, it is desirable to include the Va group element in the third layer region (2c) so that it gradually increases toward the organic optical semiconductor layer (3) in terms of reducing the residual potential.

In these figures, the horizontal axis is the layer thickness direction, a is the interface between the substrate (1) and the first layer region (2a), and b is the interface between the first layer region (2a) and the second layer region (2b). ), C represents the interface between the second layer region (2b) and the third layer region (2c), d represents the interface between the third layer region (2c) and the organic optical semiconductor layer (3), and , the vertical axis represents the respective content of Ma group elements or Va group elements.

In this way, the first layer region (2a) or the third layer region (2a)
When the content of each Ma group element or Va group element is changed in the layer thickness direction in c), the element content corresponds to the average content in each layer region (2a) (2c) as a whole. do.

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

To form the a-5iC layer, there are thin film forming methods such as a glow discharge decomposition method, an ion blating method, a reactive sputtering method, a vacuum deposition method, and a CVD method.

When using the glow discharge decomposition method, Si element-containing gas and C
Element-containing gases are combined and the mixed gas is plasma decomposed to form a film. This St element containing gas is 5it14
, 5izl16+ 5tl118. SiF4,5iC
I4.5illCI3, etc., and C element-containing gases are CI+4. , C211,,czu21C3H
Among them, C, ll□ is preferable because it allows high-speed film formation.

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

In the figure, the first tank (4), second tank (5), third tank (6), fourth tank (7), and fifth tank (8) each contain 5iHt+ C2H2+ PH3+ 82116
(PHi gas and B2H6 gas are both diluted with hydrogen gas) and H2 are sealed, and these gases are supplied to the corresponding first regulating valve (9) and second regulating valve (10), respectively.
, the third regulating valve (11), the fourth regulating valve (12) and the fifth regulating valve (13) are opened. The flow rate of the released gas is controlled by a mass flow controller (14).
(15) (16) (17) (18), each gas is mixed and sent to the main pipe (19). Note that (20) and (21) are stop valves.

The gas flowing through the main pipe (19) flows into the reaction tube (22), and a capacitively coupled discharge electrode (23) is installed inside this reaction tube (22). A substrate (24) is placed on a substrate support (25), and the substrate support (25) is rotationally driven by a motor (26), thereby rotating the substrate (24). Then, the electrode (2
3) Power 50~3 KW, frequency 1~50Ml1z
high frequency power is applied, and the substrate (24) is heated to about 200 to 400° C., preferably about 20° C., by suitable heating means.
Heat to a temperature of 0-350°C. In addition, a reaction tube (22
) is connected to a rotary pump (27) and a diffusion pump (28), which maintains the vacuum state required during film formation by glow discharge (gas pressure during discharge of 0.01 to 2.0 To
rr) is maintained.

The substrate (2
4) When forming the a-3iC layer on the second layer, open the first regulating valve (9), the second regulating valve (10), the third regulating valve (11) and the fifth regulating valve (]3). S+114. Cdl□,P
II3. Each gas of llz is released and the released amount is controlled by a mass flow controller (14) (15) (16)
(18), each gas is slipped into the main pipe (
19) into the reaction tube (22). 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-3iC film containing P element is rapidly spread onto the substrate. to form.

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. The former was sprayed into a coating solution dispersed in a photosensitive medium, then pulled at a constant speed, and then air-dried and heat aged (about 150°C for about 1 hour). According to the latter coating method, a photosensitive material dispersed in a solvent is applied using a coater (air machine), and then hot air drying is performed.

〔Example〕

Next, examples of the present invention will be described.

(Example 1) Using the glow discharge decomposition device shown in Fig. 2, S i If
A gas at a flow rate of 200 seconds, H2 gas at a flow rate of 270 seconds
ecm, the flow rate of C2H2 gas was changed, the gas pressure was Q, 5 Torr, and the high frequency power was 1
The 5OL substrate temperature was set at 250° C., and an a-5iC film (film thickness of approximately 1 μm) was formed by glow discharge.

In this way a-3iCIt! When the carbon content ratio of the film was changed, the amount of carbon in the film was measured by the XMA method, and the photoconductivity and dark conductivity were also 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 circle 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, Moreover, a and 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 Figure 4, the horizontal axis is the 5h-XC X value, and the vertical axis is the hydrogen content, that is (S++-x Cx ]I-y Hy
The O 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 in all the a-5iC films of this example, y (i) is 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 0.2 < It can be seen that excellent photosensitivity can be obtained.

(Example 2) Next, in this example, SiH4 gas is fed at a flow rate of 200 seconds, C2112 gas is fed at a flow rate of 20 seconds, and 11
□ Gas is introduced at a flow rate of 0 to 101,000 sc, and the high frequency power is 50 to 300 W and the gas pressure is 0.3 to 1.
The a-3iC film (
A film thickness of about 1 μm) was formed.

In this way, various a-5iC 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 FIG. 5 were obtained.

In Figure 5, the horizontal axis is the hydrogen content (C3i+-XC-)
It is the y value of I-y fly, the vertical axis represents the conductivity, and the circle mark indicates the emission wavelength of 550 nm (light intensity of 50 μW/cm
It is a plot of the photoconductivity against light of J, 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 were obtained.

(Example 3) An aluminum substrate (25 mm x 50 mm) was installed inside the reaction tube of a glow discharge decomposition device, and the first layer region (2a) and the second layer region (2a) were sequentially coated according to the film forming conditions shown in Table 1. 2b) and a third layer region (2C) are formed.

Next, an organic optical semiconductor layer (film thickness approximately 15 μm) containing 2.4.7-dolinitrofluorenone as a main component was formed,
This was a positively charged electrophotographic photoreceptor.

and B of each of the first layer region and the second layer region.
When the P element content in the third layer region was measured using a secondary ion mass spectrometer, it was found that 11
000pp, 40ppm, and 40ppm.

In addition, when the carbon content (y value) of the first layer region was measured by the XMA method, x = 0.23, and the hydrogen content (y value) was determined by infrared absorption measurement method. y
=0.35. Similarly, the y value and y value of the second layer region were found to be 0.3 and 0.17, respectively, and the y value and y value of the third layer region were 0.3 and 0.40, respectively. there were.

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

[Margin below]

(Example 4) In manufacturing the electrophotographic photoreceptor of (Example 3), the present inventors changed the PH, l gas flow rate and Btl16 gas flow rate, thereby achieving the first 14 types of electrophotographic photoreceptors with different B element content in the layer region and P element content in the third layer region (photoreceptors A - N)
was produced.

When the photosensitivity, surface potential 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 ○ indicates somewhat better photosensitivity. is obtained, and the mark Δ is a case where the photosensitivity is slightly inferior to the others.

Characteristic evaluation of surface potential is also divided into three stages: ◎ mark, ○ mark, and Δ mark. ◎ mark is the case where the highest surface potential is obtained;
The ○ mark indicates a case where a somewhat high surface potential was obtained, and the △ mark indicates a case where a higher surface potential was not observed compared to the others.

In addition, the residual potential is also evaluated relative to three levels.
The ◎ mark indicates the case where the residual potential is the smallest, the ○ mark indicates the case where a slight decrease in the residual potential is observed, and the ∆ mark indicates the case where the residual potential is not reduced compared to the others. It is.

[Margin below]

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

As is clear from Table 2, photoreceptors A-J and N had excellent photosensitivity, high surface potential, and reduced residual potential.

However, it can be seen that the photosensitivity and residual potential of the photoreceptor are inferior, and that the characteristics of the photosensitivity, surface potential, and residual potential of the photoreceptor K and the photoreceptor are not improved.

(Example 5) In this example, when manufacturing the electrophotographic photoreceptor in (Example 3), the content of the Ma group element in the second layer region (2b) was changed as shown in Table 3, and thereby, Six types of electrophotographic photoreceptors (photoreceptors 0 to T) were manufactured.

[Margin below]

As is clear from Table 3, the photoreceptor O-S had excellent photosensitivity, had a high surface potential, and was found to have a reduced residual potential.

(Example 6) In manufacturing the electrophotographic photoreceptor of (Example 3), the present inventors continuously and gradually added the Va group element in the third layer region (2c) from 600 to 1200 sccm as the bottom film was formed. increased.

When the residual potential of the electrophotographic photoreceptor thus obtained was measured, it was found to have decreased by about 20x.

〔Effect of the invention〕

As mentioned above, according to the electrophotographic photoreceptor of the present invention, a-3
By forming each layer region containing TIIa group elements and Va group elements within a predetermined range inside the iC photoconductive layer, excellent photosensitivity is obtained, the surface potential is increased, and the residual potential is reduced. I was able to do that.

Further, according to this electrophotographic photoreceptor, the a-5iC photoconductive layer is in non-oak contact with the substrate, which improves the rectifying function and enables positive charging with high surface potential and low residual potential. We were able to provide an electrophotographic photoreceptor.

[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 ratio and electrical conductivity. 4 is a diagram showing the relationship between carbon content ratio and hydrogen content, FIG. 5 is a diagram showing the relationship between hydrogen content and electrical conductivity, and FIGS. 8, 9 and 10 are diagrams showing the carbon content in the thickness direction of the amorphous silicon carbide photoconductive layer. 11, 12, 13, 14, 1
5 and 16 show the l1la group element content and Va in the layer thickness direction of the amorphous silicon carbide photoconductive layer.
It is a diagram showing group element content. 1 Conductive substrate 2 Amorphous silicon carbide photoconductive layer First layer region Second layer region Third layer region Organic optical semiconductor layer 2a, 2b, 2c, 3 Patent applicant (663) Kyocera Corporation Representative Takao Kawamura, Anjo Nokata

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer and an organic photoconductive layer are sequentially laminated on a conductive substrate, the amorphous silicon carbide photoconductive layer is arranged in a first layer region, a second layer region and The third layer region has a layer structure formed in sequence, and the first layer region contains 1 to 10,000 ppm of Group IIIa elements of the periodic table,
0 to 200p of Group IIIa elements of the periodic table in the second layer region
pm, the third layer region contains 1 to 300 ppm of Group Va elements of the periodic table, and the thickness of the first layer region is within the range of 0.01 to 3 μm, and the thickness of the second layer region is within the range of 0.01 to 3 μm. 0.
The thickness of the third layer region is within the range of 0.01 to 3 μm.
An electrophotographic photoreceptor characterized in that the thickness is set within a range of 1 to 3 μm. (2) A claim (
1) The electrophotographic photoreceptor described above.