JPH035746B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention belongs to the technical field of amorphous silicon photoreceptors, particularly amorphous silicon photoreceptors that can be used in image forming apparatuses. [Technical background of the invention and its problems] In recent years, conventional selenium, zinc oxide, and resin dispersion sulfide have been used as materials necessary for forming a photosensitive layer in an electrophotographic photoreceptor used in an image forming device, such as an electrophotographic device. Amorphous silicon (hereinafter abbreviated as a-Si), which has high photosensitivity, mechanical strength, and heat resistance and is harmless to the human body, is being developed in place of cadmium and the like. a-Si has a lower specific resistance at room temperature than conventional photoreceptor materials. Therefore, simply by forming a single layer of a-Si on the surface of a conductive substrate, it is not possible to exhibit the charging function as an electrophotographic photoreceptor. Therefore, a
A photosensitive layer consisting of a plurality of layers has been proposed in which a blocking layer is formed on the conductive substrate side and a surface side is formed on the opposite side of the conductive substrate, sandwiching the -Si layer. However, when multiple photosensitive layers are formed,
Due to the difference in internal stress of each layer, a large strain occurs in the photosensitive layer itself, and each layer peels off at the interface thereof. Also,
Since a large amount of polysilane produced as a by-product during the formation of the photosensitive layer adheres to the interface between each layer, the photosensitive properties are significantly deteriorated. In addition, the formation of multiple layers requires stopping the discharge, exhausting the gas required for the formed layer, stabilizing the gas flow rate for forming the next layer, etc. for each layer, so the overall It takes a long time to form a photosensitive layer. [Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and is an amorphous silicon photosensitive material which has good photosensitive characteristics, has small layer distortion, and has a single photosensitive layer that can be layered quickly. The purpose is to provide the body. [Summary of the invention] The outline of this invention for achieving the above object is as follows:
In the amorphous silicon photosensitive layer having at least amorphous silicon formed on the surface of the conductive substrate, at least the group A or group A photosensitive layer of the amorphous silicon photosensitive layer is capable of controlling valence electrons.
and a second element consisting of C, O, or N that changes at least the optical forbidden band width or dielectric constant of the amorphous silicon photosensitive layer, and the first element is The concentration gradient is such that the content decreases as the distance from the interface with the conductive substrate increases, and the second element is on the surface of the amorphous silicon photosensitive layer opposite to the interface with the conductive substrate. It is characterized by having a concentration gradient such that the concentration is high in the vicinity. [Embodiments of the Invention] An amorphous silicon photoreceptor according to the present invention has a single-layer amorphous silicon photosensitive layer containing at least a-Si on a conductive substrate, and in the amorphous silicon photosensitive layer, In the amorphous silicon photosensitive layer, at least a first element capable of controlling valence electrons and a second element capable of varying at least the optical forbidden band width or dielectric constant of the amorphous silicon photosensitive layer are combined into an amorphous silicon photosensitive layer. It has a structure in which the concentration is distributed with a concentration gradient in the thickness direction of the layer. Examples of the conductive substrate include a flat conductive substrate made of aluminum, a drum-shaped conductive substrate, and the like. The first element and second element contained in the amorphous silicon photosensitive layer are elements excluding Si, H, and halogen. The first element is an element doped to enable control of valence electrons in the amorphous silicon photosensitive layer, and includes group A elements such as B and Ga, and group A elements such as P, As, and Sb. Examples include elements. The first element has a concentration gradient such that its content is high near the interface between the amorphous silicon photosensitive layer and the conductive substrate, and the content decreases as it moves away from the conductive substrate. Preferably, it is contained in the silicon photosensitive layer.
When the first element is included in the amorphous silicon photosensitive layer with such a concentration gradient, the amorphous silicon photosensitive layer is given rectifying properties, and the surface of the amorphous silicon photosensitive layer can be charged either positively or negatively. In addition, the movement of charge carriers generated when an amorphous silicon photoreceptor is exposed to light is not hindered. For example, an amorphous silicon photoreceptor that uses a Group A element such as B or Ga as the first element becomes a positively charging photoreceptor, and a Group A element such as P, Sb, or As as the second element.
An amorphous silicon photoreceptor using a group element becomes a negatively charged photoreceptor. Further, an amorphous silicon photosensitive layer containing a-Si and H or a halogen element has slightly n-type properties, and its dark resistance is as low as 10 ⁹ to 10 ¹¹ Ωcm. However, in the amorphous silicon photosensitive layer containing a-Si and H or a halogen element,
When group elements are added to about 10 ¹⁶ to ^{10 17} atm/cm ² ,
The amorphous silicon photosensitive layer can eliminate n-type properties and increase the dark resistance to 10 ¹⁰ to ^{10 12} Ωcm, and as a result, the charge retention ability of the amorphous silicon photoreceptor can be increased. Also, a
- When a trace amount of B is further added to the amorphous silicon photosensitive layer containing Si and H or a halogen element, the amorphous silicon photosensitive layer loses its n-type properties and has a dark resistance of 10 ¹⁰ to 10 ¹² Ω
cm, and also increases the transport capacity of the optical carrier, resulting in the formation of clear images. Therefore, the concentration gradient of Group A elements in the thickness direction of the amorphous silicon photosensitive layer is, for example, 10 ¹⁹ to 10 ²⁰ atm/cm ² near the interface with the conductive substrate; Preferably, the concentration is between 10 ¹⁶ and 10 ¹⁷ atm/cm ² . Furthermore, the concentration gradient of the Group A element may be such that, for example, the concentration is high near the interface with the conductive substrate, but the concentration is 0 in other regions. Further, in the amorphous silicon photosensitive layer, the Group A element may be contained in a high concentration near the interface with the conductive substrate, and the Group A element may be contained in a low concentration in other regions. The second element is doped in order to vary the optical bandgap or dielectric constant of the amorphous silicon photosensitive layer, further reduce the strain of the amorphous silicon photosensitive layer, and improve the chemical stability against the external atmosphere. For example, C,
Examples include N and O. When the second element is contained in the amorphous silicon photosensitive layer, the optical forbidden band width of the amorphous silicon photosensitive layer is increased,
Dielectric constant and reflectance can be lowered.
In particular, when C, N, and O are incorporated into an amorphous silicon photosensitive layer containing B, the strain of the amorphous silicon photosensitive layer can be significantly reduced. Furthermore, by increasing the content of the second element, the chemical stability of the amorphous silicon photosensitive layer can be significantly improved. Therefore,
As the concentration gradient of the second element in the amorphous silicon photosensitive layer, the content of the second element is increased near the free surface of the amorphous silicon photosensitive layer (that is, the surface on the opposite side from the interface with the conductive substrate). Preferably, it is concentrated. By doing so, the vicinity of the free surface of the amorphous silicon photosensitive layer can be made extremely chemically stable against the outside world, and light reflection on the free surface can be reduced to enable efficient light absorption. It is possible to enable light absorption in a wide range deep into the amorphous silicon photosensitive layer, which can reduce the probability of recombination of photogenerated charge carriers, and as a result, the amorphous silicon photosensitive layer can be Sensitivity can be adjusted. Further, in the amorphous silicon photosensitive layer, the content of the second element may be increased to a high concentration near the interface of the conductive substrate. By doing so, it is possible to reduce the strain of the amorphous silicon photosensitive layer with respect to the conductive substrate, and to improve the ability to prevent charge carriers from being injected from the conductive substrate into the amorphous silicon photosensitive layer during charging. . The first element and the second element with a constant concentration gradient.
The amorphous silicon photosensitive layer having the elements of
Molecules containing silicon atoms such as SiH ₄ , Si ₂ H ₆ ,
A source gas containing Si ₃ H ₈ , SiF ₄ , etc., a gas containing the first element, a gas containing the second element, and
It can be formed by a glow discharge decomposition method using a carrier gas such as H ₂ , Ar, or He, or a reactive sputtering method. Next, the amorphous silicon photoreceptor and its production according to the present invention will be explained in more detail. Experimental Example 1 An amorphous silicon photoreceptor was manufactured using the amorphous silicon photoreceptor manufacturing apparatus shown in FIG. The amorphous silicon photoreceptor manufacturing apparatus shown in FIG. 1 includes a reaction vessel 2, a gas supply section 4, and an exhaust device (not shown). Inside the reaction vessel 2, a conductive substrate 6, for example, a mirror-polished aluminum plate of 150 mm x 200 mm, can be mounted, and a heater 8 is provided for heating the conductive substrate 6 to a predetermined temperature, for example, 100 to 300°C. A substrate support 10 is provided, and an electrode 14 is provided above and opposite to the substrate support 10 and has a large number of gas blowing holes 12 . The electrode 14 and the conductive substrate 10 are connected to a high frequency power source 18 (for example, 13.56 MHz, rated
500W) is electrically connected. Further, the electrode 14 as a whole also serves as a gas blowing device, and the gas supplied from the gas supply section 4 is supplied to the electrode 14.
and the conductive substrate 6.
Therefore, by applying a high frequency electric field between the electrode 14 and the conductive substrate 6 while blowing out gas from the electrode 14, plasma gas excited by glow discharge can be generated. Note that the electrode 14 is connected to the reaction container 2 and the gas supply section 4.
They are electrically insulated by insulators 20 and 22. Further, the reaction container 2 is connected to an exhaust device (not shown) via a flow rate adjustment device 24 that adjusts the flow rate of gas exhausted from the inside of the reaction container 2. The gas supply unit 4 is, for example, SiH ₄ gas, CH ₄ gas, N ₂ gas,
B ₂ H ₆ diluted with H ₂ to 20 ppm (B ₂ H ₆ /
H ₂ 20ppm gas), B ₂ H ₆ diluted with H ₂ to 200 ppm (B ₂ H ₆ /H ₂ 200 ppm gas), and B ₂ H ₆
Gas diluted with _H2 to 2000ppm ( _{B2H6 /}
It has six gas cylinders 26 each filled with _H2 2000ppm gas, a valve 28, a flow rate controller 30, and a pressure reducing valve 32, so that various gases can be arbitrarily supplied into the reaction vessel 2. configured. An amorphous silicon photoreceptor according to the present invention was manufactured using the amorphous silicon photoreceptor manufacturing apparatus having the above configuration and under the following manufacturing conditions. Heating temperature of conductive substrate...240℃ Discharge power...75W Reaction chamber pressure during discharge...0.35Torr Gas flow rate...As shown in Table 1

[Table] The thickness of the photosensitive layer of the amorphous silicon photoreceptor obtained by discharging for 240 minutes was 21.5 μm.
The concentration changes of B and C in the thickness direction in the amorphous silicon photosensitive layer are as follows:
This corresponded to changes in the flow rate of the supplied gas over time.
To the obtained amorphous silicon photoreceptor, ++
When corona discharge was performed at a voltage of 5KV, the photosensitive characteristics were that the surface potential was +520V, the dark resistance decay rate was 28% after 15 seconds after corona discharge, and the amount of exposure from a halogen lamp to halve the surface potential was
It was 0.8lux・sec. Furthermore, after subjecting the obtained amorphous silicon photoreceptor to +5KV corona charging, image exposure was performed at a light intensity of 3lux sec.
When developed by a two-component dry magnetic brush method, a toner image of good quality was obtained. Experimental Example 2 Using the same amorphous silicon photoconductor manufacturing equipment used in Experimental Example 1, B ₂ H ₆ was added to each concentration of H ₂
An amorphous silicon photoreceptor was manufactured under the same manufacturing conditions as in Experimental Example 1, except that the flow rates of the diluted gas and CH ₄ gas were changed over time as shown in Table 2.

【table】

〔Effect of the invention〕

According to this invention, since the first element and the second element are contained with a concentration gradient in the thickness direction, an amorphous silicon photoreceptor with excellent photosensitivity can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an amorphous silicon photoreceptor manufacturing apparatus which is an example of manufacturing an amorphous silicon photoreceptor according to the present invention, and
FIG. 2 is a characteristic diagram showing changes over time in the flow rate of supplied gas. 6... Conductive substrate.

Claims (1)

[Claims] 1. In an amorphous silicon photosensitive layer having at least amorphous silicon formed on the surface of a conductive substrate, at least a group A or a first member belonging to group A capable of controlling valence electrons of the amorphous silicon photosensitive layer is formed on the surface of a conductive substrate. and a second element consisting of C, O, or N that changes at least the optical forbidden band width or dielectric constant of the amorphous silicon photosensitive layer, and the first element is at the interface with the conductive substrate. The concentration gradient is such that the content of the second element decreases as the distance increases from An amorphous silicon photoreceptor characterized by having a concentration gradient as shown in FIG.