JPH0743543B2 - Photoconductive member - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a photoconductive member sensitive to light (which means an electromagnetic wave in a range from ultraviolet to visible, infrared, X-ray, γ-ray, etc.).

[Technical background of the invention and its problems]

The photoconductive material that constitutes the photoconductive layer in solid-state imaging devices, electrophotographic photoconductors, etc., has a high specific resistance in the dark (usually 10 ¹³ Ωcm or more) for the purpose of its use, and the specific resistance due to light irradiation. Must have the property of becoming small.

Here, taking electrophotography as an example, the principle thereof and the conditions required as a photoconductor will be briefly described. In electrophotography, the surface of a photoconductor is charged by corona discharge. Then, when the photoconductor is irradiated with light, a pair of electron and hole is formed, and one of these pairs neutralizes the charge on the surface. For example, when positively charged, the latent image of positive charge is formed on the surface of the photoconductor by being neutralized by electrons in the pair formed by light irradiation. Visualization is performed by attracting black powder called toner, which is charged with a different sign from the charge on the surface of the photoconductor, to the surface of the photoconductor by Coulomb force. At this time, even if there is no electric charge on the surface of the photoconductor, in order to avoid being attracted to the photoconductor by the charge of the toner, the electric potential of the developing device is adjusted so that an electric field due to the electric charge is generated between the photoconductor and the developing device. Is being processed. This is called developing bias. The above is the principle. Next, the conditions necessary for the photoconductor will be described. First, the charge charged by the first corona discharge is retained until light irradiation, and second, the charge of electrons and holes generated by light irradiation is retained. One is that the pair neutralizes the surface charge and the other reaches the support of the photosensitive layer in a short time without the pair being recombined.

Conventionally, there is an amorphous chalcogenide material as a material used for forming a photoconductive layer in a photoconductive member. Amorphous chalcogenide-based materials are excellent photoconductive materials that can easily achieve a large area, but since the edge of the light absorption region is from the visible region to a position near the ultraviolet region, it is practically in the visible region. Since it has low photosensitivity and low hardness, it has some problems such as a short life when applied to an electrophotographic photoreceptor.

Amorphous silicon is one of the photoconductive materials that has recently received attention based on such problems (hereinafter referred to as a-Si). a-Si has a wide absorption wavelength range and is fully chromatic (Panchromatic)
The light sensitivity is also high. In addition, a-Si has high hardness, and when applied to an electrophotographic photoreceptor, it is expected to have a life of 10 times or more that of a conventional one. In addition, a-Si is harmless to the human body and has many advantages over single-crystal silicon, such as being inexpensive and easily increasing the area.

However, since the specific resistance of a-Si in the dark (hereinafter referred to as dark resistance) is usually as low as about 10 ⁸ Ωcm to ^{10 10} Ωcm, it is common in electrophotographic photoreceptors that form an electrostatic latent image. Cannot retain the charge that is charged on its surface. However, in the electrophotographic photoreceptor, it has been attempted to prevent carrier injection from the support by interposing silicon nitride, silicon carbide, silicon oxide, or the like between the amorphous silicon photosensitive layer and the support. .

However, if the thickness of the layer made of the above material interposed between the amorphous silicon photosensitive layer and the support is increased by this attempt, the passage of carriers flowing from the a-Si layer thereabove to the support is blocked. As a result, there arises a problem that the residual potential becomes high. Further, if the thickness of the layer made of the above material interposed between the amorphous silicon photosensitive layer and the support is reduced, it becomes impossible to provide a sufficient potential holding ability, and dielectric breakdown due to the development bias may occur. It has the drawback of occurring.

On the other hand, there is also a method in which a semiconductor film having P-type or n-type conductivity is provided between the conductive substrate and the photoconductive layer. Usually, P-type or n-type amorphous silicon which is heavily doped with boron (B) or phosphorus (P) is used. Such a layer is called a charge injection prevention layer. The charge injection preventing ability in this layer is improved by doping a large amount of B or P.
Such a film has a problem that the strain inside the film is large and the film peels off when a film having a different strain is laminated on the film. In addition, light absorption of amorphous silicon occurs over a wide wavelength range, and the absorption gradually decreases even near the light absorption edge. That is, in the wavelength range of 700 nm to 800 nm, the absorption decreases but does not become zero, and it slightly absorbs. When the photoconductive layer is made of such a material, if the photoconductive layer is thick like an electrophotographic photoreceptor, long-wavelength light is absorbed even near the substrate of the photoconductive layer. Since the mobility of amorphous silicon along with electrons and holes is not so high, carriers generated by exposure far from the surface of the photoconductor are likely to remain. In an electrophotographic apparatus, there is a process called charge removal that removes electric charges remaining on the surface of a photoconductor after forming one image, but when this is performed by light irradiation, carriers remaining in the film are removed due to the above reason. The surface charge due to the charging of the surface of the photoconductor to obtain the next image is neutralized. Therefore, there is a problem in that the charging ability immediately after exposure is significantly lower than the charging ability after being left in the dark.

[Object of the Invention]

The present invention has been made based on the above circumstances, is excellent in charging ability without causing residual potential, has a high photosensitivity in a wide wavelength range from ultraviolet to near infrared, and withstands long-term use. It is intended to provide a photoconductive member to be obtained.

[Outline of Invention]

In a photoconductive member comprising a conductive support, and a charge injection prevention layer, a photoconductive layer and a surface coating layer, which are sequentially laminated, the charge injection prevention layer is a P-type or n-type amorphous material containing boron or phosphorus. The surface coating layer is made of amorphous silicon containing a predetermined amount of carbon, nitrogen, or oxygen, and the photoconductive layer has a thickness of 0.1 μm to 5.0 μm. A first photoconductive layer made of amorphous silicon having boron and a boron-containing surface coating layer provided between the first photoconductive layer and the surface coating layer. Containing a smaller amount of nitrogen than any of carbon, nitrogen, or oxygen contained in, and having a specific resistance higher than that of the first photoconductive layer and higher than that of the first photoconductive layer. Optical bandgage smaller than the surface coating layer And a second photoconductive layer made of non-crystalline silicon nitride having a cap.

Example of Invention

Hereinafter, the present invention will be described based on an embodiment shown in the drawings. In the figure, ( 1 ) is a photoconductive member used as an electrophotographic photoreceptor, for example. This photoconductive member ( 1 ) comprises a charge injection prevention layer (3) made of amorphous silicon carbide laminated on a flat plate-shaped or drum-shaped conductive support (2) and a charge injection prevention layer (3). 0.1-5.0 μm thick a-Si on top
A first photoconductive layer (4) having laminated layers, and a second photoconductive layer (5) made of amorphous silicon nitride laminated on the first photoconductive layer (4). More preferably, the surface coating layer (6) is formed by laminating amorphous silicon carbide, silicon nitride or silicon oxide having a film thickness of 500Å to 5 μm on the second photoconductive layer (5).

Next, each layer will be described. First, the reason for laminating P-type or n-type amorphous silicon carbide doped with boron (B) or phosphorus (P) as the charge injection prevention layer (3) is that a-Si is boron (B) or phosphorus. By doping a large amount of (P), the strain in the film becomes large and the film becomes easy to peel off, whereas amorphous silicon carbide does not have such a problem and a large amount of boron (B) or phosphorus (P) is contained. Doping becomes possible, and a film excellent as the charge injection preventing layer (3) can be obtained. Also, the role of the first photoconductive layer (4) is to make up for the drawbacks of using amorphous silicon nitride for the second photoconductive layer (5) laminated on top. That is, amorphous silicon nitride has a wider optical bandgap and a narrower photosensitive wavelength range than a-Si. Therefore, the a-Si layer should be 0.1% depending on the light source used for exposure.
A film thickness of about 5.0 μm is enough.

Further, the second photoconductive layer (5) may be a-Si, but a-
Si has a low specific resistance, and its charging ability and potential holding ability are not satisfactory. On the other hand, since amorphous silicon nitride has a high specific resistance, the charging ability and the potential holding ability were improved by about 20 to 30% as compared with a-Si.

Further, by doping a small amount of boron (B) into these photoconductive layers (4) and (5), the specific resistance is further increased, and the mobility of holes, that is, the ease of movement is also higher than that in the case where it is not doped. Higher results are obtained with good results.

Next, the film forming method of the photoconductive member of the present invention based on the above configuration will be described. First, the conductive support (2) is attached to a vacuum reaction chamber (not shown), and the reaction chamber is set to 10 ^-3 to 10 by a mechanical booster pump and an oil rotary pump (not shown).
^-4 Torr vacuum state. At this time, the support (2)
Is kept at a temperature of 100 ° C to 400 ° C.

Next, a gas containing Si atoms in the reaction chamber, such as SiH ₄ or Si ₂
A gas such as H ₆ or SiF ₄ is introduced, the exhaust speed is adjusted so that the pressure is about 0.1 to 1 Torr, and the process waits until a steady state is reached.

Next, a film can be formed by applying 13.56 MHz high frequency power between the electrodes in the reaction chamber.

Further, a-Si can control valence electrons by doping with a Group IIIa element or a Va group element of the periodic table, and can also control specific resistance. Furthermore, the specific resistance can be increased by adding nitrogen, carbon, or oxygen. In addition, the method of adding impurities enables film formation by mixing a gas containing Si atoms and a gas containing an element to be added into the reaction chamber during film formation.

Therefore, an example will be described in which an electrophotographic photosensitive member is obtained by laminating the film on the cylindrical support made of, for example, Al by using the above film forming method. First, 1 × 10 ⁻³ or more of boron (B) was formed on the conductive support (2).
Amorphous silicon carbide containing 1.0 atomic% is laminated to form a charge injection prevention layer (3). The film forming conditions at this time are as follows: CH ₄ gas is mixed with SiH ₄ gas in an amount of 20% to 100% and B ₂ H ₆ (concentration 20,000 ppm) gas diluted with He gas is 1 to 10 with respect to SiH ₄ gas. % Mixed.

Next, a first photoconductive layer (4) made of a-Si was formed to a film thickness of 0.
It is desirable to dope a small amount of boron (B) for stacking 1 to 5 μm. At that time, B ₂ H ₆ (concentration 20 ppm) gas diluted with He gas is mixed with SiH ₄ gas to form 1 to 10%. To film.

Next, the second photoconductive layer (5) made of amorphous silicon nitride contains 5% to 40% of N ₂ or NH ₃ gas with respect to SiH ₄ gas.
It is the same as the first photoconductive layer (4) made of a-Si except that it is mixed to some extent. At this time, the optical band gap of the obtained film is 1.7 eV or 1.9 eV, which is a great advantage as compared with a-Si.

Further, the surface coating layer (6) is deposited by mixing the same amount or more _{CH 4, C 2 H 6,} C 2 H 2, O 2, N 2, NH 3 gas to SiH _4, The film thickness is preferably about 500 Å to 5.0 μm, and a large optical band gap of 2.0 eV or more can be obtained.

As a result of using the Al cylindrical support (2) layered in this way as an electrophotographic photosensitive member, it has a charging ability and a charge holding ability that can be sufficiently used for positive charging. It has been proved that the copy has no image distortion and can be used for a long period of time.

On the other hand, when the charge injection prevention layer (3) is doped with phosphorus (P) instead of boron (B), it becomes for negative charging, and the same electrophotographic photoreceptor as described above can be obtained.

〔The invention's effect〕

As described above, according to the present invention, since there is no residual potential on the surface of the photoconductive member and the charging ability and the charge holding ability are excellent, a special effect that the life can be extended for a long time is exhibited. Is.

[Brief description of drawings]

The drawing is a schematic configuration diagram of a photoconductive member showing an embodiment of the present invention. 1 ... Photoconductive member, 2 ... Conductive support 3 ... Charge injection preventing layer, 4 ... First photoconductive layer 5 ... Second photoconductive layer, 6 ... Surface coating layer

Claims (1)

[Claims] 1. A photoconductive member comprising a conductive support, on which a charge injection prevention layer, a photoconductive layer and a surface coating layer are sequentially laminated, wherein the charge injection prevention layer is a P-type or boron-containing phosphorous type. It is composed of n-type amorphous silicon carbide, and the surface coating layer is composed of amorphous silicon containing a predetermined amount of carbon, nitrogen, or oxygen.
The photoconductive layer has a thickness of 0.1 μm to 5.0 μm and is made of amorphous silicon containing boron, the first photoconductive layer, and the surface coating layer. Between the first photoconductive layer and the first photoconductive layer, which contains boron and contains a smaller amount of nitrogen than the amount of carbon, nitrogen or oxygen contained in the surface coating layer. A second photoconductive layer made of amorphous silicon nitride having a specific resistance and an optical bandgap larger than that of the first photoconductive layer and smaller than that of the surface coating layer. Photoconductive member.