JP2596403B2 - Photoconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoreceptor having a photoconductive layer containing at least amorphous silicon.

[0002]

2. Description of the Related Art In recent years, amorphous silicon (amorp) produced by a glow discharge decomposition method or a sputtering method has been used.
Application of hous silicon (hereinafter abbreviated as a-Si) to a photoreceptor has attracted attention. Similarly, application of amorphous silicon-germanium (hereinafter, a-Si: Ge), which improves sensitivity in a long wavelength region and enables image formation by a semiconductor laser, has been receiving attention. This is a-Si, a-Si: G
This is because e is more excellent in environmental pollution resistance, heat resistance, abrasion resistance, photosensitivity characteristics and the like as compared with conventional selenium and CdS photoconductors.

However, a-Si, a-Si: Ge
Has a disadvantage that the dark resistance is insufficiently low and cannot be used as it is as a photoconductive layer also serving as a charge holding layer. For this reason, it has been proposed to increase the dark resistance by containing oxygen or nitrogen, but on the contrary, there is a disadvantage that photosensitivity is reduced, and the content is also limited. As a result, for example, as shown in JP-A-57-115551, a-Si containing a large amount of carbon is formed on the a-Si photoconductive layer.
It is conceivable to improve the charge retention by forming an insulating layer.

[0004]

However, the electrophotographic characteristics of such a photoreceptor vary considerably depending on the carbon content. For example, when the carbon content in the a-Si insulating layer is relatively small, not only high resistance cannot be attained, but also image fatigue occurs due to high light fatigue and high humidity. On the other hand, when the carbon content is increased, the charge retention rate is improved, and the translucency is improved to some extent, but there is a disadvantage that the surface hardness is reduced. Further, under high humidity conditions, white spots due to film defects appear on the image.

On the other hand, when the a-Si photoconductive layer is formed directly on a conductive substrate, pinholes and white spots are generated on an image. This is due to leakage of charge carriers due to a film defect, and is caused by a surface condition of the conductive substrate, contamination, and the like. Further, there is a problem that dark decay is accelerated due to charge injection from the substrate side, and the charge retention ability is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned facts, and has as its object the object of the present invention is to provide excellent photosensitivity, charge retention, and excellent electrophotographic properties including surface hardness without light fatigue, and to improve substrate properties Prevents charge injection from the side and increases the residual potential and eliminates image degradation due to substrate noise.
It is an object of the present invention to provide a photoreceptor capable of obtaining a good image over a long period of time even under high humidity conditions or in repeated copying.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a photoreceptor having a barrier layer, a photoconductive layer and an overcoat layer sequentially laminated on a conductive support, wherein the barrier layer comprises at least amorphous silicon; A group IIIA impurity of the periodic table of 200 ppm or less based on silicon atoms in the barrier layer;
And 5 to 60 atomic for silicon atoms in barrier layer
% Oxygen, the photoconductive layer is a photoconductive layer containing at least amorphous silicon, and the overcoat layer is at least amorphous silicon, and 5 to 60 atomic% carbon based on silicon atoms in the overcoat layer. And an overcoat layer containing 10 atomic% or less of oxygen based on silicon atoms in the overcoat layer.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

FIG. 1 shows the structure of a photoreceptor according to the present invention, in which (1) is a conductive substrate on which at least a-S
i, oxygen and impurities of group IIIA of the periodic table or a-S
a barrier layer (2) containing i, carbon and oxygen; a photoconductive layer (3) containing at least a-Si;
A light-transmitting overcoat layer (4) containing -Si, carbon and oxygen is sequentially laminated.

The barrier layer (2) is formed, for example, by a glow discharge decomposition method at about 30 ° to 2 microns, preferably 50 to 5 microns.
000 mm, optimally between 100 and 2000 mm thick. As described above, the barrier layer (2) contains at least a-Si, oxygen and an impurity of Group IIIA of the periodic table as one embodiment thereof, and includes a-SixO1-x or a- (SixO1 containing hydrogen). -x) It is obtained by adding a Group IIIA impurity to yH1-y. Oxygen content is about 5-6
When the content is 0 atomic%, the dark resistance of the barrier layer is remarkably improved, and charge injection from the substrate (1) is effectively prevented. Further, it is effective for the covering property with the substrate (1) and the leveling effect, and also prevents the adverse effect due to the substrate noise. However, in the present invention, in addition to oxygen, a Group IIIA impurity of the periodic table, preferably boron, is added at 200 p.
Contains less than pm. The boron content allows the charge carrier generated in the photoconductive layer (3) to move to the substrate (1) side and prevents the residual potential from rising. Oxygen content about 5-6
The reason for setting the atomic ratio to 0 atomic% is that if the atomic ratio is 5 atomic% or less, the resistance of the barrier layer cannot be increased, and if the atomic ratio is 60 atomic% or more, image fogging occurs irrespective of the boron content and the residual potential also increases. The reason why the boron content is less than 200 ppm is that if the boron content is more than 200 ppm, the charging ability of the photoreceptor rapidly decreases. Note that a-Si may be a-Si: Ge.

[0011]

The photoconductive layer (3) containing a-Si formed on the barrier layer (2) also has a thickness of 5 to 100 μm, preferably 10 to 60 μm, for example, by a glow discharge decomposition method.
μm. As an example, an a-Si photoconductive layer containing hydrogen formed on a substrate by generating a glow discharge under application of high-frequency power and feeding a SiH6, Si2H6 gas or the like into a decompressible reaction chamber using H2 or Ar as a carrier gas. Or an a-Si: Ge photoconductive layer formed by injecting GeH4 gas in parallel. However, the photoconductive layer obtained in this way has an insufficiently low dark resistance.
Group A impurities (preferably boron), trace amounts of oxygen, carbon, nitrogen and the like may be contained.

The overcoat layer (4) formed on the photoconductive layer (3) is similarly formed to a thickness of 0.01 to 3 μm by, for example, a glow discharge decomposition method. The overcoat layer (4) has a higher resistance than the photoconductive layer (3), and its resistance is substantially constant throughout the entire layer, or is sequentially higher in the thickness direction than the interface with the photoconductive layer (3). It is formed so that it becomes. Specifically, as described above, the overcoat layer (4) is made of a-Si or a-Si: Ge containing carbon and oxygen, thereby improving not only resistance but also surface hardness and light sensitivity characteristics. And the environmental resistance is remarkably improved. That is, the overcoat layer containing only carbon in a-Si has a disadvantage that the surface hardness gradually decreases as the carbon content increases, and is not suitable for long-term repeated use. Further, if only carbon is contained, a sufficiently high resistance cannot be attained, and a white spot pattern is generated on an image under high humidity conditions to cause image bleeding.

[0014] The overcoat layer (4) of the present invention solves the above-mentioned problems by causing oxygen in addition to carbon. The oxygen content markedly improved the translucency of the overcoat layer (4).
The photosensitivity of the Si overcoat layer containing only about 40 atomic% of carbon and the photoreceptor containing about 5 atomic% of oxygen in addition to 40 atomic% of carbon is about 1.8 times higher in the latter. Is also expensive. Also, the surface hardness does not decrease,
Rather, it has improved. Further, even under repeated high-humidity conditions, even in repeated copying, a good image can be formed for a long period without image deletion or white spots. The amounts of carbon and oxygen contained in the overcoat layer (4) differ depending on whether they are contained substantially uniformly throughout the entire layer or when they are contained with a gradient in the thickness direction, but are contained uniformly. Sometimes about 5 to 60 atomic% carbon and about 10 atomic% to a-Si.
It is preferable that the oxygen is oxygen. If the carbon content is at least 5 atomic% and the amount of oxygen is very small (about 0.1 atomic% or more), the resistance of the overcoat layer cannot be increased, the light fatigue is large, and the light transmittance is insufficient. The reason why the maximum is about 60 atomic% of carbon and 10 atomic% of oxygen is that image flow occurs at a higher value. On the other hand, when the content is contained with a gradient in the thickness direction, the content is made to gradually increase in the thickness direction of the overcoat layer, and about 1 to 6
It can contain 0 atomic% carbon and from trace amounts up to about 25 atomic% oxygen. Note that the oxygen content may be gradually increased while the carbon content is kept constant, or vice versa. However, in the latter case, the oxygen content must be at most 10 atomic%.

In the above, the source gas for forming each layer is effectively used when a-Si is contained.
SiH4, Si2H6, Si3H containing H and H as constituent atoms
8, silicon hydride gas such as silanes such as Si 4 H 10, etc.
And a saturated hydrocarbon having 5 carbon atoms, an ethylene hydrocarbon having 1 to 5 carbon atoms, and an acetylene hydrocarbon having 2 to 4 carbon atoms. Specifically, methane (CH4) as a saturated hydrocarbon,
Ethane (C2H6), propane (C3H8), n-butane (nC4H10), and ethylene hydrocarbons include ethylene (C2H4), propylene (C3H6), butene (C4
H8), acetylene (C2
H2), methylacetylene (C3H4), butyne (C4H
6) and the like. Further, as an oxygen-based source gas,
Oxygen (O2), ozone (O3), carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen monoxide (N2O), nitrogen trioxide (N
2O3), nitrogen tetroxide (N2O4), nitrogen pentoxide (N2
O5), nitric oxide (NO3) and the like.
Note that germanium may be contained in each layer in addition to the hydrogen silicon gas, as described above. In this case, GeH4,
Ge2H6 gas or the like may be used in combination.

Next, a capacitively coupled glow discharge decomposition apparatus for manufacturing a photoreceptor according to the present invention will be described. FIG.
In the first, second, third, fourth, and fifth tanks (5), (6), (7), (8), and (9), H
2, SiH4, B2H6, C2H4 and O2 gas are sealed. Here, the H2 gas in the first tank (5) is a carrier gas of SiH4 gas. However, instead of H2 gas, Ar, He
May be used. The carrier of the B2H6 gas is also hydrogen. When each layer contains germanium, GeH4
Prepare a gas tank. These gases in the first to fifth tanks are first, second, third, fourth and fifth regulating valves (10),
(11), (12), (13), and (14) are released by opening and the flow rate is regulated by the mass flow controllers (15), (16), (17), (18), and (19), First to fourth tanks (5), (6),
The gas from (7) and (8) goes to the first main pipe (20), and the oxygen gas from the fifth tank (9) goes to the second main pipe (21).
Sent to. (22), (23), (24),
(25), (26), (27) and (28) are stop valves.

The gas flowing through the first and second main pipes (20) and (21) is supplied to the third main pipe (3) in the reaction chamber (29).
Merge at 0). In the reaction chamber (29), a-
A turntable (3) on which a conductive substrate (31) such as aluminum, stainless steel or NESA glass on which a Si photoconductive layer (2) is formed can be rotated by a motor (32).
3) The substrate (31) itself is electrically grounded, and is uniformly heated to a temperature of about 100 to 400 ° C., preferably 150 to 300 ° C. by a suitable heating means. . Numeral (34) is a cylindrical electrode plate provided so as to surround the conductive substrate (31) and is grounded to the high-frequency power source (35). The main pipes (30) and (36) are connected. Further, a gas discharge hole (not shown) is formed on the inner wall surface of the electrode plate (34), and a generated gas introduced from the third main pipe (30) is jetted to the surface of the conductive substrate (31). While the gas released from the ejection hole is decomposed, the gas is also sucked from the gas suction hole formed on the inner wall surface and the fourth main pipe (36).
Is to be discharged through. The high frequency power supply (35) applies about 0.05 to 1.5 k to the electrode plate (34).
W high frequency power is applied, and the frequency is suitably 1 to 50 MHz. Further, the reaction chamber (2
The inside of 9) requires a high vacuum state (discharge voltage: 0.5 to 2.0 Torr) when forming the barrier layer, photoconductive layer and overcoat layer, so that the rotary pump (37) and the diffusion pump (38) It is connected to.

In the capacitively coupled glow discharge decomposition apparatus having the above-described structure, first, when the barrier layer (2) containing a-Si, oxygen and boron is formed on the conductive substrate (31), the first and second barrier layers are formed. , The third and fifth regulating valves (10), (11),
(12) and (14) are opened and H2 and SiH4 gases are supplied from the first and second tanks (5) and (6) at an appropriate flow ratio, B2H6 gas and a fifth tank ( 9) The 02 gas is released. When carbon is further contained, C2H4 gas is released from the fourth tank (8). The release amount was determined by mass flow controllers (15), (16), (1
7), (18), (19), SiH4 gas, B2H6 gas or C2H4 gas using H2 as a carrier gas
The mixed gas is sent through the first main pipe (20), and the oxygen gas having a constant molar ratio to SiH4 is sent through the second main pipe (21) together with the first main pipe (20). The three are merged by the main pipe (30) and sent into the electrode plate (34).
In addition to the uniform release of gas from the gas discharge holes, the inside of the reaction chamber (25) is in a vacuum state of about 0.5 to 2.00 Torr, the substrate temperature is 100 to 400 ° C., and the electrode plate is
The high frequency power to (34) is set to 0.05 to 1.5 kW, and the frequency is set to 1 to 50 MHz, and glow discharge occurs, and the gas is decomposed and at least a-Si, A barrier layer (2) containing boron, oxygen or carbon is formed at a rate of about 0.5 to 5 microns / 60 minutes.

When the barrier layer (2) having a desired thickness is formed,
After the glow discharge is interrupted continuously or once, the photoconductive layer (3) is formed. This is the first to third tanks (5),
(6), (7) and hydrogenation which is carried out by releasing gas from the fifth tank (9) and contains boron and a trace amount of oxygen.
-Si photoconductive layer (3) is formed.

Subsequently, an overcoat layer (4) is formed on the photoconductive layer (3) containing a-Si. This is done by releasing gas from the first to fifth tanks (5), (6), (7), (8), (9), but the fourth, fifth tanks (8), (9) ) Indicates that the content of C2
Releases H4 and O2 gas. At this time, when the overcoat layer has a uniform resistance in its thickness direction, that is, when the contents are made equal, the release amount of the C2H4 and O2 gases may be kept constant. When the resistance is formed so as to increase sequentially in the thickness direction, the release amount of C2H4 and / or O2 gas is gradually increased.

[0021]

【Example】

EXPERIMENTAL EXAMPLE 1 In the glow discharge decomposition apparatus shown in FIG. 2, a rotary pump (37) and then a diffusion pump (38) were operated to make the inside of the reaction chamber (29) a high vacuum of about 10-6 Torr. , First to third and fifth regulating valves (10), (11),
(12) and (14) are opened, H2 gas from the first tank (5), SiH4 gas diluted to 30% with H2 from the second tank (6), and 200 ppm in H2 from the third tank (7).
The B2H6 gas diluted to a pH of 5 and the O2 gas from the fifth tank (9) were allowed to flow into the mass flow controllers (15), (16), (17) and (19) under an output pressure gauge of 1 kg / cm2. Then, the scale of each mass flow controller was adjusted to adjust the flow rate of H2 to 383 sccm and SiH4 to 150 sccc.
m, B2H6 and O2 were set to 22.5 sccm and 45 sccm, respectively, and flowed into the reaction chamber (29). After the respective flow rates became stable, the internal pressure of the reaction chamber (29) was adjusted to be 1.0 Torr. On the other hand, as the conductive substrate (31), an aluminum drum having a diameter of 120 mm was used, and was previously heated to 200 ° C., and a high-frequency power supply (35) was turned on while the flow rates of the respective gases were stable and the internal pressure was stable. 34) was applied with a power of 300 W (frequency 13.56 MHz) to generate glow discharge. This glow discharge is continued for 3 minutes,
On a conductive substrate (29), a film containing hydrogen a-Si, 200 ppm of boron and about 25 atomic% of oxygen having a thickness of 0.1
A micron barrier layer (2) was formed. Thereafter, the application of power from the high-frequency power supply (35) is temporarily stopped, and the flow rate of each mass flow controller is set to 0 to set the reaction chamber (2).
9) was sufficiently degassed. Next, the first to third and fifth control valves (10), (11), (12), and (14) are opened, and H2, SiH4, B2H6, and O2 gas are supplied from the respective tanks to the mass flow controllers (15), ( 16), (1
7) and (19). Then, adjust the scale of each mass flow controller to adjust the flow rate of H2 to 274 seconds.
Ccm, SiH4 were set to 300 sccm, B2H6 was set to 25 sccm, and O2 was set to 1 sccm. The electrode plate (34) was also applied with a high-frequency power of 300 W to generate glow discharge. This glow discharge was continued for about 7 hours to form an a-Si photoconductive layer (3) having a thickness of 20 microns containing hydrogen, boron and a small amount of oxygen on the barrier layer (2).

Subsequently, 3 H 2 gas was supplied from the first tank (5).
90 sccm, 150 sccm of SiH4 gas diluted to 30% with H2 from the second tank (6), 90 sccm of C2H4 gas from the fourth tank (8), and 10 sccm of O2 gas from the fifth tank (9) into the reaction chamber. Inlet, internal pressure is 1.0 Torr
Then, a high frequency power supply (35) was turned on and 300 W of power was applied. The discharge was continued for 3 minutes to form an overcoat layer (4) of about 0.1 micron. The carbon content at this time is about 40 atomic%, and oxygen is about 5 atomic%.

The photoreceptor thus obtained was set in a powder image transfer type copying machine EP-520 manufactured by Minolta Camera Co., Ltd. and copied. As a result, a clear, high-density image with excellent resolution and good tone reproducibility was obtained. . Even after continuous copying of 200,000 sheets, no deterioration in image characteristics was observed, and a good copy was obtained to the end. Further, the electrophotographic characteristics and the image characteristics did not change at all at room temperature under the high temperature and high humidity conditions of 30 ° C. and 80%.

The above photoreceptor is further charged to a white light of 2.0 luxs.
The residual potential was measured by exposing under ec.
v, several tens of volts after copying 200,000 sheets.

[0025]

[0026]

EXPERIMENTAL EXAMPLE 2 Under the same conditions as in Experimental Example 1, except that a B2H6 gas was further supplied from the third tank (7) at a flow rate of 45 s during the formation of the barrier layer.
40cm atomic carbon to a-Si
%, About 5 atomic% of oxygen, and 200 ppm of boron, a barrier layer was formed thereon, and the same photoconductive layer and overcoat layer were formed thereon. When this photoreceptor was set on EP-520 and continuous copying of 200,000 sheets was performed, an excellent image without image fog was obtained to the end. Also, the residual potential hardly increased.

[0028]

[0029]

Comparative Example 1 The same photoreceptor as that produced in Experimental Example 1, except that no boron was contained in the barrier layer, was prepared and set in EP-520 for continuous copying. Image fog was observed, and became remarkable by repeated copying.
Incidentally, the initial residual potential was 50 V.

Comparative Example 2 The same photoreceptor as that prepared in Experimental Example 2, except that the barrier layer contained about 25 atomic% of oxygen, was prepared.
When set on P-520 and continuously copied, several hundred
Image fog occurred from the 0th sheet.

Comparative Example 3 The same photoreceptor as that prepared in Experimental Example 3, except that the overcoat layer had an oxygen content of about 30 atomic%, was prepared and continuously copied. Was done.

[0033]

According to the photoreceptor of the present invention, a barrier layer containing at least amorphous silicon, oxygen and an impurity of Group A of the periodic table, and a photoconductive layer containing at least amorphous silicon are provided on a conductive support. And a light-transmitting insulating overcoat layer containing at least amorphous silicon, carbon, and oxygen. Excellent in electrophotographic properties including surface hardness, preventing charge injection from the substrate side, no increase in residual potential and no image deterioration due to substrate noise,
A photoreceptor capable of obtaining a good image over a long period of time even under high humidity conditions or in repeated copying was provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a photoconductor according to the present invention.

FIG. 2 is a diagram showing a schematic configuration of a glow discharge decomposition apparatus for manufacturing a photoreceptor according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 barrier layer 3 photoconductive layer 4 overcoat layer 5 first tank 6 second tank 7 third tank 8 fourth tank 9 fifth tank 29 reaction chamber 31 conductive substrate 35 high-frequency power supply

Claims (1)

(57) [Claims] 1. A photoconductor comprising a barrier layer, a photoconductive layer and an overcoat layer sequentially laminated on a conductive support,
The barrier layer is a barrier layer containing at least amorphous silicon, 200 ppm or less Group IIIA impurity of the periodic table with respect to silicon atoms in the barrier layer, and 5 to 60 atomic% of oxygen with respect to silicon atoms in the barrier layer.
The photoconductive layer is a photoconductive layer containing at least amorphous silicon, and the overcoat layer is at least amorphous silicon, 5 to 60 atomic% of carbon with respect to silicon atoms in the overcoat layer, and 10 atomic with respect to silicon atoms in the overcoat layer. % Of oxygen containing overcoat layer.