JPH0535425B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a photoconductive member sensitive to light (electromagnetic waves such as ultraviolet to visible, infrared, X-rays, and gamma rays). [Technical background of the invention and its problems] Photoconductive materials constituting photoconductive layers of solid-state image sensors, electrophotographic photoreceptors, etc. have a high specific resistance in the dark (usually low 10 ¹³ Ωcm or more),
In addition, it is necessary that the material has a property that its specific resistance decreases when irradiated with light. To explain the principle using electrophotography as an example, first, an electric charge is applied to the surface of a photoreceptor by corona discharge. Next, when the photoreceptor is irradiated with light, pairs of electrons and holes are created, and one of them neutralizes the charge on the surface. For example, if the photoreceptor is positively charged, it is neutralized by electrons among the pairs generated by light irradiation, and a positively charged latent image is formed on the surface of the photoreceptor. Next, visualization is achieved by attracting toner charged to the opposite polarity to the surface of the photoreceptor by Coulomb force. At this time, in order to avoid toner being attracted to the photoconductor due to the toner charge even if there is no charge, the potential of the developer is set high so that an electric field in the opposite direction to the electric field due to the charge is generated between the photoconductor and the developer. A so-called developing bias process is performed. In the electrophotography described above, the photoreceptor is required to satisfy the following conditions.
In other words, firstly, the charge generated by corona discharge is retained until light irradiation, and secondly, the electron-hole pair generated by light irradiation does not recombine, and one neutralizes the surface charge. Furthermore, it is required that the other side instantly reach the support of the photoreceptor. By the way, amorphous chalcogenide-based materials have conventionally been used as photoconductive materials. Amorphous chalcogenide has characteristics such as being easily formed into a large area and having excellent photoconductivity. However, such amorphous chalcogenide has a light absorption band close to the visible to ultraviolet range, and in practical terms, it has low sensitivity to light in the visible range, low hardness, and short lifespan when applied to electrophotography. Various problems arose. For this reason, amorphous silicon (hereinafter referred to as a-Si) has recently been used as a photoconductive material.
The use of is attracting attention. a-Si has a wide absorption wavelength range, is panchromatic, and has high sensitivity. It also has high hardness, and when applied to electrophotographic photoreceptors, it is expected to have a lifespan more than 10 times longer than conventional ones. Furthermore, it is harmless to the human body, and has many advantages when compared to single crystal silicon, such as being inexpensive and easily obtainable over a large area. However, a-Si has a low specific resistance in the dark (hereinafter referred to as dark resistance), usually between 10 ⁸ Ωcm and ^{10 10} Ω.
cm, and a device that forms an electrostatic latent image, such as an electrophotographic photoreceptor, is unable to retain charges on its surface. Therefore, in an example where a-Si is applied to electrophotography,
A high resistivity a-Si layer containing N, C, O, etc. added between the photosensitive layer and the support, or a p-type, n-type a-
Attempts have been made to provide a Si layer to prevent carrier injection from the support. However, the latter a-Si
When using layers, a p-type a-Si layer that blocks electrons and allows holes to pass is used in the case of a positive charge, and an n-type a-Si layer is used in the case of a negative charge. A photoreceptor having such a structure can have a high charging ability. However, in the former structure, if the a-Si layer doped with N, C, and O is thickened, it also blocks the passage of carriers flowing from the photosensitive layer to the support, resulting in a problem that the residual potential becomes high. On the other hand, when the a-Si layer is made thinner, dielectric breakdown occurs due to development bias. In the latter structure p
The former problem does not occur even if the thickness of the a-Si layer is increased. However, the a-Si layer
The addition of group elements makes the layer p-type, and the addition of group A elements makes it n-type, but the addition of these impurities causes strain in the layer. When such an a-Si layer is used as a blocking layer and a photoconductive layer is laminated thereon, the strain of each layer is different, resulting in inconveniences such as delamination. Also,
Similar problems arise with surface coating layers that are laminated to the photoconductive layer. Furthermore, a photoconductive member having a structure combining both of the above-mentioned a-Si layers has also been proposed (Japanese Unexamined Patent Application Publication No. 1983-1999).
No. 177156). That is, this photoconductive member was made by sequentially laminating a p-type or n-type a-Si layer and an a-Si layer doped with N, C, O, etc. on a support, and further laminating a photosensitive layer thereon. It is something. However, in the case of such a photoconductive member, if the a-Si layer added with N, C, O, etc. is thickened, the residual potential will naturally increase. If the layer is made thinner, dielectric breakdown may occur. [Objective of the Invention] The present invention was made in view of the above circumstances, and aims to provide a long-life photoconductive member that can improve chargeability and retention ability to the same level or higher than conventional ones, and prevents peeling between layers. It is something to do. [Summary of the Invention] The present invention provides a photoconductive member in which a blocking layer, a photoconductive layer, and a surface layer are sequentially laminated on a support. , C, group A or group A, and H or a halogen. Between these layers, near the interface between the blocking layer and the photoconductive layer, the C
The concentration of Group A or Group A decreases continuously from the blocking layer toward the photoconductive layer, and the concentration of Group A or Group A decreases in the vicinity of the interface between the photoconductive layer and the surface layer. is characterized in that it increases continuously from the photoconductive layer toward the surface layer. The blocking layer may be a single layer, but it is more preferably two layers. in this case,
The concentration of Group A or Group A elements in the first blocking layer (on the support side) and the second blocking layer can be adjusted to make the optical bandgap of the second blocking layer a little wider than that of the first blocking layer. It is preferable to set the first blocking layer to be higher than the second blocking layer because it is advantageous in terms of improving the retention ability. Next, one method of manufacturing the photoconductive member of the present invention will be explained. First, a conductive support is placed in a vacuum reaction vessel,
A vacuum of 10 ^-3 to 10 ^-4 torr is created in the reaction vessel using a mechanical booster pump and an oil diffusion pump. At this time, the support is maintained at a temperature of 100 to 400°C. Next, a gas containing Si atoms, e.g.
SiH ₄ , Si ₂ H ₆ , SiF ₄ etc. and group A elements or group A
Doping gas containing group elements, and if necessary
A gas containing C atoms such as CH ₄ is introduced at the desired mixing ratio, the exhaust speed of the exhaust system is adjusted so that the pressure is approximately 0.1 to 1 torr, and the system waits until a steady state is reached. Then, between the electrodes in the reaction vessel
A blocking layer, a photoconductive layer, and a surface coating layer are sequentially formed on the support by applying high frequency power of 13.56 MHz. At this time, by sequentially adjusting the ratio of the doping gas or the ratio of the gas containing C atoms as necessary, it is possible to continuously change the ratio of the constituent elements near the interface of each layer. Note that by exciting the doping gas in advance with electromagnetic waves such as microwaves, it is possible to improve doping efficiency and film formation rate. Accordingly, the photoconductive member according to the present invention has a blocking layer containing at least Si and a common constituent element of Group A, a photoconductive layer, and a surface coating layer laminated in sequence on a support, and Since the structure has a portion where the ratio of the constituent elements continuously changes near the interface of each layer, it is possible to reduce the strain difference between each layer, prevent delamination, and achieve a long life.
In addition, by changing the layer structure from the support side to a blocking layer, a photoconductive layer, and a surface coating layer that at least commonly contain Si, group A, and group A, charging ability and retention ability equivalent to conventional ones can be achieved. A photoconductive member can be obtained having the following. Note that the blocking layer is divided into two layers, and the second
By adjusting the content of conductive impurities in the blocking layer so that the optical bandgap is smaller than that of the first blocking layer, and by making the first and second blocking layers of amorphous silicon carbide containing C, It is possible to obtain a photoconductive member that has significantly higher chargeability and retention ability than conventional ones. Furthermore, by forming the photoconductive layer of p-type or n-type amorphous silicon carbide containing group A or group A and C, the specific resistance can be reduced to 10 _{11 to 10 11} .
It has a high mobility of 10 ¹³ Ωcm, and has excellent characteristics comparable to that of ordinary amorphous silicon. In other words, when amorphous silicon carbide is made into an undoped intrinsic semiconductor, the specific resistance is often low, and even if a blocking layer is provided, the carriers generated by exposure are not limited to the thickness direction.
It also tends to run horizontally, causing blurred images. Note that amorphous silicon carbide is a material in which the bond between Si and C is extremely small compared to the bond between Si and Si or Si and H. [Embodiments of the Invention] Next, embodiments of the present invention will be described with reference to the drawings. First, the conductive support 1 made of Al was placed in a vacuum reaction vessel, and the inside of the reaction vessel was evacuated to 10 ⁻³ to 10 ⁻⁴ torr using a mechanical booster pump and an oil rotary pump. At this time, the support 1 was maintained at a temperature of 100 to 400°C. Next, SiH 4 , B ₂ H 6 and CH ₄ were introduced into the reaction vessel so that the flow rate of B ₂ H ₆ /SiH _{4 was} 1×10 ^-3 and the flow rate of CH ₄ /SiH ₄ was 8% _. A mixed gas was introduced, and the exhaust speed of the exhaust system was adjusted so that the reaction pressure was 0.5 torr. Continuing, when the reaction pressure reaches a steady state, between the electrodes of the reaction vessel
After applying 200 W of 13.56 MHz high frequency power and maintaining this state for 5 minutes, the mixed gas was adjusted sequentially so that the flow rate ratio of B ₂ H ₆ /SiH ₄ decreased to 5 × 10 ^-7 in 5 minutes. Introduced into support 1 with a thickness of 7 μm, B/
The maximum layer value of B+Si is 5×10 ^-2 atom%, C/C+
A first blocking layer 2 made of amorphous silicon carbide containing 1.0 atom % of Si was formed. Next, under the same high frequency power and the same reaction pressure,
After holding the flow rate of B ₂ H ₆ /SiH ₄ and CH ₄ /SiH ₄ for 5 minutes without changing it, CH ₄ /SiH ₄ was reduced to about 0.01% in 5 minutes.
A mixed gas of SiH ₄ , B ₂ H ₆ and CH ₄ was successively adjusted and introduced so as to reduce the amount of the blocking layer to 1%, and the layer thickness was 2 μm and the maximum value of B/B+Si was 1.
×10 ^-4 atom%, maximum value of C/C+Si layer is 1.0 atom
% of amorphous silicon was continuously formed. Next, under the same high-frequency power and the same reaction pressure, SiH 4 and B 2 were injected without changing the flow rate ratios of B ₂ H ₆ /SiH ₄ and CH ₄ /SiH ₄ to 5×10 ^-7 and approximately 0.01 _% , _{respectively.} H _6
A mixed gas of
A photoconductive film 4 made of amorphous silicon carbide of 10 ^-4 atom% and C/C+Si=0.01 atom% was continuously formed. Then, stop applying high frequency power and leave it for 10 minutes.
The flow rate ratio of B ₂ H ₆ /SiH ₄ is 1×10 ^-7 , CH ₄ /SiH ₄
The flow rate ratio decreases and increases to approximately 300%, respectively.
SiH ₄ , B ₂ H ₆ and CH ₄ were sequentially adjusted and introduced, and a high frequency power of 200 W was applied for the last minute to form a layer with a thickness of 0.1 μm and a maximum value of B/B+Si on the photoconductive layer 4. 5×10 ^-4 atom%, the maximum layer value of C/C+Si is
A photoreceptor was manufactured by continuously forming a 20 atom % surface coating layer 5 (as shown in FIG. 1). Incidentally, an energy model in the thickness direction of such a photoreceptor is shown in FIG. 2. In addition, when forming each layer,
Figure 3 shows flow models for SiH ₄ , B ₂ H ₆ and CH ₄ . In addition, 〓〓〓 in Fig. 3 is SiH ₄ and 〓〓〓 is
B ₂ H ₅ (2000ppm), 〓〓〓 is B ₂ H ₆ (20ppm), 〓〓
〓 is CH ₄ , and the flow rates of these gases are set as shown in the table below.

〔Effect of the invention〕

As detailed above, according to the present invention, the photoconductive material is effective as an electrophotographic photoreceptor, etc., in which charging ability and holding ability are improved to the same level or higher than conventional ones, and delamination is prevented and the service life is improved. It can provide sex members.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a photoconductor manufactured in an example of the present invention, FIG. 2 is a diagram showing an energy model in the thickness direction of the photoconductor in FIG. 1, and FIG. 3 is a diagram showing the structure of each layer in the example. FIG. 3 is a diagram showing a flow rate model of SiH ₄ , B ₂ H ₆ , and CH ₄ during membrane formation. 1...Support, 2...First blocking layer, 3
...Second blocking layer, 4...Photoconductive layer, 5
...Surface coating layer.

Claims (1)

[Claims] 1 A blocking layer, a photoconductive layer on a support,
In the photoconductive member in which the blocking layer, the photoconductive layer and the surface layer are sequentially laminated, all of the blocking layer, the photoconductive layer and the surface layer are made of amorphous amorphous atom added with C, group A or group A, and H or halogen. The concentration of the C and Group A or Group A continuously decreases from the blocking layer toward the photoconductive layer in the vicinity of the interface between the blocking layer and the photoconductive layer between these layers. A photoconductive member, characterized in that near the interface between the photoconductive layer and the surface layer, the concentration of the C and group A or group A continuously increases from the photoconductive layer toward the surface layer.