JPS61143768A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent uneven density due to interference effect by using an electrophotographic sensitive body having 3 surface layers made of silicon contg. carbon as a constituent element. CONSTITUTION:The electrophotographic sensitive body is formed by depositing a photoconductive layer 21 made of a amorphous Si as a base on a conductive substrate of cylindrical aluminum by plasma discharge decomposition of gases of SiH4, Si2H6, or the like and laminating on this layer 21 the first, second, and third surface layers 22, 23, 24 in this order each formed by the plasma discharge decomposition method using a gas mixture of SiH4, Si2H6, and an C-contg. gas, such as CH4 or C2H6, so as to change each value of an optical band gap somewhat from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor that can be applied to a laser solinter.

[Technical background of the invention and its problems]

In recent years, amorphous silicon (hereinafter referred to as a) has been used as a photoreceptor for electrophotography.
-Si) is attracting attention. Conventionally, selenium, selenium/arsenic, selenium/tellurium, cadmium sulfide resin dispersion, organic photoconductive materials, etc. have been used as electrophotographic photoreceptors, but a-Si electrophotographic photoreceptors are harmless. Demand for commercialization has rapidly increased due to the fact that it does not cause pollution, can withstand high operating temperatures, has a high surface hardness, is easy to handle, and has high spectral sensitivity in the visible region. Enter.

On the other hand, in recent years, electrophotographic printers using photoreceptors in terminals such as facsimiles, word processors, and computers have been developed. This printer uses various types of light sources, but among them, electrophotographic laser printers use a laser as the light source, and gas lasers such as He-No lasers are used as the laser light source. Recently, semiconductor lasers have been mainly used because of their ability to make printers smaller, lower costs, and easier to perform modulation.

By the way, when trying to use a-St for the photoconductor of an electrophotographic laser printer that uses a semiconductor laser as the light source, the emission wavelength of the semiconductor laser is currently about 780 nm, and the &-81 photosensitive The body's photosensitivity is rather low in the emission wavelength range of this semiconductor laser, so clear images may not be obtained. Therefore, in order to have sufficient photosensitivity even at the emission wavelength of a semiconductor laser, it is common practice to introduce Gs (r-rumanium) into the a-81 photoreceptor to reduce the optical band gap. Still, lowering the hydrogen content of the photoconductive layer in A-81 photoreceptors lowers the optical bandgap and increases long wavelength sensitivity.

However, when an image is formed by line-scanning the laser beam with a laser printer using a semiconductor laser as the light source using the a-Si photoconductor described above, the image overlaps with the character image, resulting in density unevenness in the form of interference fringes. may appear. Further, this density unevenness can be eliminated by increasing the amount of laser exposure, but even in that case, the character image will still show white streaks in places, making it impossible to obtain a good image. Furthermore, even if it does not appear in a character image, when halftones are taken, density unevenness due to interference fringes may appear in this No.-7 tone. The cause of this is the laser beam reflected on the surface of the A-81 photoreceptor, the laser beam that passes through the inside of the A-8L photoreceptor, is reflected on the conductive substrate, specifically the surface of the At tube, and the reflection that comes out from the surface again. This is because interference occurs with the laser beam.

In the case of a-8i photosensitive light, the photoconductive layer formed on the At blank tube has some thickness unevenness, and this may result in a difference in optical path length on the drum that causes interference. It will be done.

Then, the interference effect between the reflected light from the surface of the A-81 photoreceptor and the reflected light that is reflected from the At tube surface and comes out again from the surface actually enters the inside of the A-81 photoreceptor, This effectively limits the amount of carriers generated, and as described above, density unevenness appears in response to film thickness unevenness. Therefore, as a countermeasure, it is sufficient to reduce the intensity of either of the reflected lights, and generally, the surface of the At element tube is appropriately roughened or an antireflection film is applied to the surface.

By the way, when trying to use a-8t in an electrophotographic photoreceptor, since the dark resistance of a-8i itself is about 10100 Nishiki, it is generally necessary to use a conductive substrate on a conductive substrate to increase the surface charge retention ability. A so-called laminated structure is used in which a blocking layer is provided to prevent charge injection from the photoconductive layer, and a surface layer for charge retention is provided on top of the photoconductive layer.

Therefore, when the surface of the At base tube is roughened as a countermeasure against the interference fringes described above for the a-3i photosensitive photo of such a laminated structure, the narrowly spaced interference fringes corresponding to the uneven thickness of the photoconductive layer disappear, but Widely spaced interference fringes may appear in halftone images. This is due to the interference effect corresponding to the thickness unevenness of the surface layer.

Therefore, in order to eliminate these widely spaced interference fringes, it is first necessary to form a uniform surface layer with a thickness that satisfies the anti-reflection conditions. However, if the surface layer is so thin that uniform film formation is impossible, the interference effect can be prevented by attaching an antireflection film on top of the surface layer.

As mentioned above, the interference fringes that appear in radar printers can be solved by various methods, but when considering the simplification, labor saving, and productivity of the manufacturing process of the A-81 photoreceptor, it is possible to solve them as much as possible. It is better to finally manufacture the A-81 photoreceptor using only the membrane device and avoid increasing other manufacturing costs. Therefore, it is disadvantageous to form an antireflection film using a material having a refractive index compatible with a-8i.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and an object thereof is to provide an electrophotographic photoreceptor that can prevent the occurrence of image density unevenness due to interference effects without increasing the manufacturing process. be.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides an electrophotographic photoreceptor in which a photoconductive layer containing silicon atoms as a matrix and made of an amorphous material is provided on a conductive substrate. Gap is 1.60~2. OOe
V, and the first surface layer is made of an amorphous material containing carbon as a constituent element, and has an optical band gap of 1.
80 to 2.50 eV, and a second surface layer made of an amorphous material containing carbon as a constituent element; By laminating a third surface layer made of an amorphous material containing as a constituent element on top of this layer, it is possible to prevent unevenness in image density due to the interference effect of laser light, and to provide high sensitivity and good electron It is designed to have both photographic properties and environmental resistance.

[Embodiments of the invention]

Hereinafter, the present invention will be explained with reference to an illustrated embodiment.

FIG. 3 is a schematic diagram of a film forming apparatus for an electrophotographic photoreceptor according to the present invention. Inside the reaction vessel 1, there is an electrode 2 for applying high-frequency power, a supporting stand 3 that is grounded opposite to this, and a conductive substrate 4 for film formation on the upper part of the supporting stand 3, and a heater for heating on the lower part. 5 is provided. The high-frequency power application electrode 2 is insulated from the reaction vessel 1 with an insulator such as Teflon 6, and is connected to the plasma discharge decomposition via a matching circuit made of an LC circuit for matching high-frequency power outside the reaction vessel 1. It is connected to a high frequency power source 8 for supplying power having a frequency for performing the following.

Reference numeral 9 denotes a gas introduction pipe through which raw material gas, for example 5I
H4,5t2H6 introduces etc. 1θ is a first exhaust system that is evacuated by a diffusion pump, 11 is a second exhaust system that is evacuated by a mechanical booster pump during film formation, and 12, 13° and 14 are valves.

Next, an electrophotographic photoreceptor according to the present invention manufactured using the film forming apparatus described above is shown in FIGS. 1 and 2.

In the electrophotographic photoreceptor shown in FIG. 1, a photoconductive layer 21 made of an amorphous material containing silicon atoms as a matrix is provided on top of a cylindrical conductive substrate 2o made of At. The photoconductive layer 21 is formed by plasma discharge decomposition using a gas such as SiH4, 512H6, etc. At the time of film formation, in addition to the silicon-containing gas, in order to increase the specific resistance of the film, a gas containing gas such as SiH4, 512H6, etc. It is also common to form a film by mixing gases containing elements of the above group.

Note that the optical band gap of this photoconductive layer 21 is 1.
62 to 1.70 eV, and the film thickness is 10 to 70 eV.
Good electrophotographic properties can be obtained when the thickness is 15 to 40 μm.

Further, on the top of the photoconductive layer 21, a first surface layer 22, a second surface layer 23, and a third surface layer 24 are laminated in this order. It is formed by a plasma discharge decomposition method by mixing a gas containing silicon atoms, such as SiH4, Si2H6, etc., and a gas containing carbon, such as CH4, C2H4, etc., and has an optical band gap of 1.60 to 2. It is in the range of .00 eV. Further, the second surface layer 23
It is formed by the same method as the surface layer 22 of , and has an optical band gap in the range of 1.80 to 2.50 ev. Further, the third surface layer 24 is formed by the same method as the first surface layer 2 and the second surface layer 22, and has an optical band gap of 2.20 to 3.00 e.
It is within the range of V.

Further, the first surface layer 22 has a film thickness of 100X to 5μ.
m1 is more preferably 200X to 3 μm.

Still, the second surface layer 23 has a film thickness of 100X to 10μ.
m, more preferably 500X to 5 μm.

Furthermore, the third surface layer 24 has a thickness of 100X to 5 μm.
1, more preferably 200X to 3 μm.

According to the above configuration, by providing the first surface layer 22, the second surface layer 23, and the third surface layer 24 on the top of the photoconductive layer 21, laser light incident on the surface of the electrophotographic When entering the interior after being partially reflected by the third surface layer 24,
By setting the optical bandgap and film thickness of the third surface layer 24 to the values described above, reflection of laser light on the third surface layer 24 can be reduced.

Furthermore, the radar light incident on the inside of the third surface layer 24 reaches the second surface layer 23, but here as well, as described above,
By setting the optical bandgap and film thickness of the second surface layer 23, reflection of laser light on the second surface layer 23 can be reduced. Furthermore, the laser beam incident on the inside of the second surface layer 23 reaches the first surface layer 22, but here as well, the optical bandgap and film thickness of the first surface layer 22 are set as described above. By doing so, reflection of laser light on the first surface layer 22 can be reduced.

Next, the laser beam transmitted through the second surface layer 23 is transmitted to the photoconductive layer 2.
However, if the optical bandgap of the photoconductive layer 21 is set so that the optical bandgap of the photoconductive layer 21 and the optical bandgap 0 of the first surface layer 22 do not change significantly. , reflection on the surface of the photoconductive layer 21 can also be reduced.

That is, the third surface layer 24
In addition, the interface between the third surface layer 24 and the second surface layer 23, the second surface layer 23 and the first surface layer
The purpose of this is to suppress the reflection of laser light at the interface with the surface layer 22 and the interface between the first surface layer 22 and the photoconductive layer 21 to prevent interference effects between reflected laser lights.

In addition, by laminating the first surface layer 22, the second surface layer 23, and the third surface layer 24, electrophotographic images with excellent charging ability and excellent corona ion resistance, ozone resistance, and environment resistance can be obtained. A photoreceptor can be provided.

However, in the electrophotographic photoreceptor of the present invention shown in FIG. 2, the photoconductive layer 21, first surface layer 22, second surface layer 23, and third surface layer 24 are the same as those in the electrophotographic photoreceptor shown in FIG. However, for the purpose of improving electrophotographic properties including charging ability, a blocking layer 2 is provided between the conductive substrate 2Q and the photoconductive layer 21.
5.

〔Concrete example〕

The At base tube that has been thoroughly cleaned and dried is placed in a vacuum container 1, and the inside of the vacuum container 1 is evacuated using a mechanical booster pump. At the same time, the power of the heater 5 for heating the At blank tube is turned on, and the set temperature is set to 300° C. to perform heating. The temperature of the At blank tube was stabilized at 300°C for about 1 hour. Also, the degree of vacuum inside the vacuum container 1 is 1.2 X i O
'It was Torr. Next, the first layer blocking layer 2
In order to form a film in step 5, the flow rate of SiH4 was set to 300
The flow rate ratio of scc++t+B2H6 to 5iH4 was 5 x 10', the flow rate ratio of CH4 to SiH4 was 20cm, argon gas was adjusted to 2001000M, and the mixture was introduced into the vacuum vessel 1 for approximately Hold the position for 10 minutes. Approximately 10
After confirming that the flow rate of the fractional removal gas was stable, the high frequency power source with a frequency of 13.56 h was turned on, high frequency power of 200 W was applied, and glow discharge was performed. Note that the reaction pressure at this time was 0.8 Torr. Further, the film forming time in this case was 10 minutes, and the film thickness of a separately formed film was measured to be 1.5 μm.

After forming the first blocking layer 25, all gases were stopped and the gas in the vacuum container 1 was diluted for 15 minutes. After that, the SiH4 flow rate was 6008 CCM, and the argon gas flow rate was 500 scwrB2H6.
The flow rate ratio was adjusted to 1×10 2 using a mass flow controller and maintained at that state for about 10 minutes.

After confirming that the flow rate of the removed gas was stable for about 10 minutes, the high frequency power was set to 400 W and glow discharge was performed.

Note that the reaction pressure in this case was 1.4 Torr.

As a result, a second photoconductive layer 21 was formed with a thickness of 35 μm by film formation for 2 hours. The optical bandgap of this product was 1.63 eV. After forming the photoconductive layer 21 described above, all gases were turned off and the gas inside the vacuum container 1 was nosed for 15 minutes. Thereafter, in order to form the first surface layer 22, the flow rate of 5IH4 was increased to 100 sc.
After adjusting the flow rate of cw r CH4 to 3001000M,
It was kept in that state for about 10 minutes. After the flow rate of each gas was stabilized, the high frequency power was set to 150 W and glow discharge was performed. Note that the reaction pressure in this case is Q, 5 Torr
Met. The film formation time was 15 minutes, and the film thickness was 0.8 μm.
Met. Also, the optical bandgap is 1.77eV
Met.

After forming the first surface layer 22, the flow rate of CH4 was increased to 500.
After increasing the temperature to gcc+a and maintaining that state for about 10 minutes to stabilize the flow rate, the high frequency power was set to 200 W and the second surface layer 23 was formed. The reaction pressure in this case is 0.
It was 8 Torr. The film forming time was 15 minutes, and the film thickness was about 1.8 μm. Moreover, the optical band gap was 1.9 eV.

After forming the 8th layer 23 on the second surface, the flow rate of CH4 was increased to 450.
The temperature was lowered to 8 CCM, maintained in that state for about 10 minutes, and after the flow rate became stable, the high frequency power was set to 150 W and the third surface layer was formed. The reaction pressure in this case is 0.68 To
It was rr. Film formation time is 3 minutes, film thickness is approximately 650X
Met. Also, the optical bandgap is 2.10 eV
Met.

After forming the third surface layer 24, the heating heater 5 is turned off, all gases are stopped, the gas is subjected to A'-di for 20 minutes, and then nitrogen gas is introduced into the vacuum container 1.
The drum on which the film has been formed is cooled, and when the temperature drops to below 100°C, the nitrogen gas and the apparatus are turned off and the drum is taken out.

When the electrophotographic photoreceptor thus obtained was evaluated using an evaluation device, the surface potential was 535V.

Retention rate 72% after 15 seconds, half-reduction exposure 0.5 tux・
@ec, a residual potential of 12 V and good electrophotographic properties were obtained.

Furthermore, when we took sample images with a laser printer equipped with a semiconductor laser with an oscillation wavelength of 790 nm, we were able to obtain good images with no density unevenness due to interference effects in both character images and noftones. did it.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a good image without striped density unevenness caused by interference effects.

[Brief explanation of the drawing]

1 and 2 are schematic configuration diagrams showing an electrophotographic photoreceptor according to the present invention, and FIG. 3 is a schematic configuration diagram showing a film forming apparatus for forming a film on the electrophotographic photoreceptor according to the present invention. It is a diagram. 20... Conductive substrate, 21... Photoconductive layer, 22...
- First surface layer, 23... Second surface layer, 24...
Third surface layer, 25...blocking layer.

Claims (5)

[Claims] (1) In an electrophotographic photoreceptor in which a photoconductive layer and a surface layer made of an amorphous material containing silicon atoms as a matrix are provided on a conductive substrate, the surface layer contains carbon as a constituent element and has three layers. An electrophotographic photoreceptor comprising: (2) Of the three surface layers made of an amorphous material containing carbon as a constituent element laminated on the photoconductive layer, the first layer on the substrate side
Let Eg^1 be the optical bandgap of the surface layer, Eg^2 be the optical bandgap of the second surface layer laminated on this first surface layer, and let Eg^2 be the optical bandgap of the second surface layer laminated on this first surface layer. The optical band gap of the third surface layer is Eg^3
The electrophotographic photoreceptor according to claim 1, wherein the following relationship exists between these optical band gaps: Eg^1≦Eg^2≦Eg^3. (3) Of the three surface layers made of an amorphous material containing carbon as a constituent element laminated on the photoconductive layer, the optical band gap Eg^1 of the first surface layer on the substrate side is 1.60 to 2. ．．
The electrophotographic photoreceptor according to claim 1 or 2, characterized in that the electrophotographic photoreceptor has a voltage in the range of 00 eV. (4) Optical bandgap Eg of the second surface layer laminated on the first surface layer among the three surface layers made of an amorphous material containing carbon as a constituent element laminated on the photoconductive layer The electrophotographic photoreceptor according to claim 1 or 2, wherein ^2 is in the range of 1.80 to 2.50 eV. (5) Optical bandgap Eg of the third surface layer layered on the second surface layer among the three surface layers made of an amorphous material containing carbon as a constituent element layered on the photoconductive layer. 3. The electrophotographic photoreceptor according to claim 1 or 2, wherein ^3 is in the range of 2.20 to 3.00 eV.