JPS62105152A - Photoconductor - Google Patents

Abstract

PURPOSE:To obtain a photoconductor having an excellent electrostatic characteristic and high spectral sensitivity characteristic over a wide wavelength region by laminating the 1st layer consisting of muC-Si, the 2nd layer consisting of N-type muC-Si and the 3rd layer consisting of a-Si to form a photoconductive layer to be laminated via an electric charge injection preventive layer. CONSTITUTION:A drum-shaped base body 12 is set to a supporting bar 16 and thereafter a prescribed gaseous pressure is maintained and the base body is heated to a prescribed temp. in the case of forming a photosensitive body 24 with a glow discharger 10. While the specified gaseous pressure is maintained, the necessary electric power is impressed between the base body 12 and a cylindrical electrode 18 by a high-frequency power source 17 for the prescribed time to form the film of the charge injection preventive layer 24a. The 1st layer muC-Si 25a which is the photoconductive layer 25, the 2nd layer of the N-type muC-Si 25b and the 3rd layer of a-Si 25c are formed on the layer 24a in succession thereto while the film forming conditions such as the temp. of the base body 12, the gas to be introduced, electric energy, and the time for impression of the electric power are successively reset to prescribed values in the same reaction vessel 11. The various film forming conditions are further reset to prescribed conditions within the same reaction vessel 11 and a surface layer 24b is formed on the layer 25, by which the formation of the body 24 is completed.

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a photoconductor for forming an electrostatic latent image in an image forming apparatus such as a semiconductor laser device. [Technical background of the invention and its problems] In recent years, with the diversification of functions and models of image forming devices such as electrophotographic devices, cadmium sulfide [CdS] and zinc oxide (ZnO) are being used as photoreceptor materials. , selenium (S
e), selenite alloy [5e-Te3. Various materials such as inorganic materials such as poly-N-vinylcarbazole (hereinafter referred to as PVCz) and organic materials such as trinitrofluorene (hereinafter referred to as TNF) have been developed. However, among the photoreceptor materials mentioned above, selenium (Sa), cadmium sulfide (CdS), etc. are inherently harmful to the human body, so the manufacturing equipment becomes complicated due to safety measures and manufacturing costs are high. is raised, while
It must be recovered after use, which not only increases costs but also increases the crystallization temperature of selenium (Se) and selenium-tellurium alloy (Ss-Te), which is approximately 65%
('C), it has low characteristics, so it is easy to crystallize, and during repeated copying, residual charges are generated in the crystallized part, which tends to cause problems such as staining the image, which ultimately leads to a longer life. The disadvantage is that it is not possible to and zinc oxide (
ZnO), due to its physical properties, l! It is easily reduced by light and is significantly affected by the environmental atmosphere such as temperature and humidity.
The drawback is that the image quality is unstable and reliability is poor. In addition, organic materials such as (PVCz) and (TNF) have poor thermal stability and wear resistance, making it difficult to extend their service life, and recently they have been suspected of being carcinogenic. . Therefore, in recent years, in order to eliminate the above-mentioned drawbacks, it is non-polluting, does not require recovery treatment, has a high surface hardness, has excellent abrasion resistance and impact resistance, and has a higher spectral sensitivity than before. Application of amorphous silicon (hereinafter referred to as (a-5i)) to photoreceptor materials is being considered. Specifically, since the photoreceptor is required to have high resistance and high spectral sensitivity as its characteristics, in order to satisfy both of these characteristics, a A laminated type (a-5i) photoreceptor has been developed in which the photoreceptor has an excellent charge retention ability and is provided with a charge injection prevention layer that has excellent effects on optical fatigue characteristics, cycling characteristics, and the like. However, when (a-5i) is formed by a glow discharge decomposition method using a gas containing silane (Si), (a-3
i) There is a problem in that the electrical properties and optical properties vary greatly depending on the amount of hydrogen atoms [Hl] incorporated into the film. That is, (a-5i) As the amount of hydrogen atoms (Hl) incorporated into the film increases, the optical band gap becomes larger and the resistance becomes higher. When used in a laser beam printer using a semiconductor laser, fogging, crushed type, afterimages, uneven density due to interference fringes, etc. may occur, making the printer unusable. Si+!-) n] bond and (S
It has a bond structure like iL) bond, and (a-5
i) It becomes dominant in the film, and as a result, [SiH] bonds are broken, structural defects such as dangling bonds and voids increase, and photoconductivity deteriorates. on the other hand(
a-5i) When the amount of hydrogen atoms (H) incorporated into the film decreases, the spectral sensitivity to long wavelength light increases, but on the other hand,
The optical bandgap becomes smaller and the resistance becomes lower, and since the hydrogen atoms (Hl) no longer compensate for the dangling bonds, the mobility and lifetime of the generated carriers decrease, and the photoconductivity also deteriorates. Therefore, as a method to increase the spectral sensitivity to long wavelength light, a gas containing silane (Si) and a germane gas (Ge14) are mixed to produce a glow. A method of forming a film with a narrow optical bandgap using the discharge decomposition method has been implemented, but in general, the optimal support temperature during glow discharge is silane (
40 for Si) containing gas and germane gas (GeH4)
Since the difference is ~50 degrees, structural defects are likely to occur in the formed film, resulting in a decrease in photoconductivity, and furthermore, if the germane gas (CGeH) is oxidized, it may become toxic. However, the disadvantage is that the waste gas treatment becomes complicated. [Purpose of the Invention] This invention was made based on the above circumstances, and although it has excellent charging characteristics due to its ability to maintain high resistance, it also has high spectral sensitivity characteristics over a wide wavelength range, and is useful for laser printers, etc. It is an object of the present invention to provide a photoconductor that can obtain clear and high-quality images even in the case of a photoconductor, and can be manufactured easily and at reduced cost. [Summary of the Invention] In order to achieve the above object, the present invention uses microcrystalline silicon (hereinafter referred to as (μC-5i)) to form a photoconductive layer layered on a conductive support via a charge injection prevention layer. ), a second layer of n-type (μC-5i), and a third layer of (a-3i), which have excellent charging characteristics and a wide range of A photoconductor having high spectral sensitivity characteristics over a wavelength range is obtained. [Embodiments of the Invention] In explaining the present invention in detail, the optical bandgap is smaller than that of (a-5i), which is approximately 1.7 [θV], and the optical bandgap is small, near the near-infrared region. The characteristics of (μC-5L), which is sensitive to long wavelength light, has few structural defects, and has high mobility, will be described. In other words, this (μC-3i) belongs to non-single-crystal silicon, but when X-ray diffraction measurements are performed, a halo appears because (a-3i) is amorphous, as shown by the dotted line in Figure 3. (μ
C-3i), [2θ] is 27 ~ as shown by the solid line in Figure 3.
It shows a crystal diffraction pattern around 28.5 [degrees]. On the other hand, polycrystalline silicon has a dark resistance of 10
@[Ω・l] or less, whereas (μC-5i) is 1
It has a high resistance of 0"1 [Ω・13 or more. Due to the above-mentioned characteristics, (μC-3L) is distinguished from other non-single crystal silicon (a-3i) and polycrystalline silicon, Its structure is thought to be formed by an aggregation of microcrystals with a particle size of about several tens of microns or more.
μC-5i) can be manufactured using sputtering, glow discharge decomposition method, etc. as in (a-5i), but (a-3i
) Formation becomes easier if the temperature of the conductive support on which the film is formed is set higher or the high frequency power is increased compared to the time of manufacture. That is, by raising the temperature of the support and increasing the high-frequency power, the flow rate of the raw material silane (SL)-containing gas can be increased, and as a result, the film formation rate is increased (μC-3L).
This is because it becomes easier to form. Furthermore, if a gas diluted with hydrogen [H], including silane (Sin) and disilane (including higher-order silane gas such as Si28G3), is used as a raw material,
(μC-3i) is more likely to be formed effectively. In addition, in the (μC-3i) layer to be formed, hydrogen [l
When the content of In order to obtain excellent photoconductivity with a good balance between light resistance and light resistance, it is desirable that the (μC-3i) layer contains 0.1 to 30 [atomic %] of hydrogen (CH). This (μC-5i) layer is doped with hydrogen using silane (Sil14) or disilane C5xz as a raw material.
A silane-containing gas such as He 3 and hydrogen gas (+1.) as a carrier gas are introduced into the reaction vessel to perform glow discharge, or halogens such as silicon tetrafluoride [SiF] or trichlorosilane [5iCQ4] are introduced into the reaction vessel. The reaction may be carried out using a mixed gas of silicon oxide and hydrogen gas [H2] as a raw material, or furthermore, a mixed gas of a silane (Si)-containing gas and a silicon halide may be used as a raw material. Furthermore, in the (μC-5i) layer, hydrogen atoms (H) and other elements may be added, for example, to prevent charge injection into the photoconductive layer, to enhance photosensitivity characteristics, to increase resistance, etc. Doping impurities such as boron (CB), aluminum (
With the increase in the doping amount of elements of group ma of the periodic table, such as i), the characteristics of the (μC-3i) layer shift from i-type to n-type, while periodic table V
When doped with group a elements, the (μC-5i) layer becomes n
The characteristics become more pronounced as the amount of doping increases. In this n-type (μC-5i), for example, phosphine (PH
As the doping amount of 3) increases, the conductivity in the dark [σdark] and the conductivity when irradiated with a wavelength of 790 [nm], which is the oscillation wavelength of a semiconductor laser (a photo (at 790 nm) ):l are both increased together, and disilane [
If the doping ratio (PH3/512US) of phosaine [PH, ] to 51211G) is 10-6 or more, compared to the non-doped case, a dark),
[:crphoto(at 790(r+m)))] is increased by at least one order of magnitude or more. On the other hand, 10-≦PHI/5ill, ≦10
-5 range, (a photo) and (a da
The S/N ratio, which is the ratio of rk), can maintain approximately 3 digits. Therefore, by using n-type (μC-3i) having such characteristics in the photoconductive layer of the photoreceptor, it is possible to increase the spectral sensitivity in the long wavelength region around 790 (nm). In addition, when the optical band gap and activation energy of this n-type (μC-5i) were measured, it was found that (PH3/
The results showed that the optical bandgap was kept constant even when Si, He) was increased, but the activation energy was decreased. This shows that the high sensitivity of n-type (μC-5i) in the long wavelength region is due to the shift of the Fermi level toward the conductor side as the doping ratio increases. Furthermore, in addition to the above impurities, nitrogen [N],
Carbon [C] and oxygen

It is desirable to dope at least one type of [0]. If you do it like this. This is because these elements precipitate at the grain boundaries of (μC-5j,), act as terminators of the gungling bonds of silicon (SL), and reduce the density of states existing in the forbidden bodies between bands. . Next, an embodiment of the present invention using (μC-5i) and n-type (μC-3i) having the above-mentioned characteristics will be described with reference to FIGS. 1 and 2. Glow discharge device [(
The reaction vessel (11) of 10) has a built-in heater (13) and is rotated by a motor (14) in order to support the drum-shaped base (12), which is a conductive support and is made of aluminum. A support rod (16) is provided. or,
The support (16) is surrounded by a cylindrical electric Fi (18) connected to a high frequency power source (17) of 13.56 [MHz], and above the support (16), silane gas [5IH4 ) A gas supply system having a large number of gas cylinders (19a)...(19n) and a gas mixer (20a) so that diborane gas [13, H6], hydrogen gas (H2), etc. can be supplied as necessary ( 20) is provided with a gas introduction pipe (21) connected to the gas introduction valve (21a). (18a) - (18n) are each gas cylinder (19a)
- Valve (19n), (9a)...(9n) are pressure regulators. Furthermore, (22) is an exhaust valve connected to an exhaust device (not shown) that exhausts air into the reaction vessel (11), and (23) is a vacuum gauge that measures the atmospheric pressure inside the reaction vessel (11). . Further, (24) is a photoreceptor of an electrophotographic device which is a photoconductor, and a charge injection prevention layer (24) is sequentially formed on a drum-shaped substrate (12).
4a) and the first layer (25a) consisting of (p C-3i)
, a second layer (25b) consisting of n-type (a C-3L)
A photoconductive layer (25) having a third layer (25c) consisting of (a-5i) and a surface layer (24b) are laminated. When forming a photoreceptor (24) using a glow discharge device (lO), after setting a drum-shaped substrate (12) on a support (16), the inside of one reaction vessel (11) is brought to a predetermined atmospheric pressure. The exhaust valve (22) is opened, and the exhaust gas is treated by the exhaust device (not shown), and the drum-shaped substrate (12) is heated to a predetermined temperature by the heater (13). Then, while maintaining the gas pressure in one reaction vessel (11) constant through the gas introduction pipe (21), the high frequency power source (17) is used to generate the necessary air pressure between the drum-shaped substrate (12) and the cylindrical electrode (18). The charge injection prevention layer (2
4a) film formation is performed. Next, in the same reaction vessel (11), the temperature of the drum-shaped substrate (12) and the introduced gas, as well as the film forming conditions such as the amount of electric power and the time of applying electric power, are sequentially reset to predetermined values, and then charge injection is performed. The first Jtl (25a) to the third layer (25c) of the light guide ffl M (25) are formed on the prevention layer (24a). Furthermore, the same reaction vessel (1
In step 1), each film forming condition is reset to the specified one, a surface layer (24b) is formed on the photoconductive M (25), and a surface layer (24b) is formed on the photoconductor (25).
24) is completed. Next, the action of the photoreceptor (24) for positively charging will be described. First, the drum-shaped base (12) is set on the support (16), the exhaust valve (22) is opened, and the exhaust device (not shown) is installed.
The inside of the reaction vessel (11) is reduced to 0. ], CTorr)
The drum-shaped substrate (12) is heated to 400['C] by the heater (13). Next, from the gas supply system (2o), silane gas (Si11.) was supplied at 200 (SCCM) through the gas introduction pipe (21).
:/gas (CH,) is 10100 (SCC, carbon gas [8, 11,) wo (B2HJSiH,) is IX
10-' into the reaction vessel (11), and while maintaining the pressure inside the reaction vessel (11) at 1 (Torr) using an exhaust device (not shown), the drum-shaped substrate is heated by the motor (15). (12) while rotating the high frequency power source (12).
7), a power of 300 [W] is applied to the drum-shaped base (12).
and a circular electrode (18) for 15 minutes to form a charge injection prevention layer (24a) made of amorphous silicon carbide (a-si; C) with a thickness of 2 [μm]. The supply of electricity and various gases will be cut off. Next, charge injection prevention JW (
In order to form a photoconductive layer (25) on 24a), silane gas (SiHn
] to 500 (SCCM), hydrogen gas [H2] to 10
100 (SCC, diborane gas (B, Il,)
0-'' (at. 17), a power of 600 [W] was applied between the drum-shaped substrate (12) and the cylindrical electrode (18) for 2 hours,
The first layer of film thickness 10 [μm] made of i-type (μC-3i)
The layer (25a) was formed, and then 500 (SCCM) of silane gas (SiH4) and 10100 (SCC) of hydrogen gas [H2], phosphine (PH,
) was introduced into the reaction vessel (1
1) The pressure inside is 2 (Torr) and 600 (W)
power was applied for 1 hour to form a second layer of n-type (μC-3i) with a thickness of 5 [μm], and then the reaction vessel (11
500 cscc of silane gas [SiH, ] in ),
Diborane gas (B, HG) as txto-' (atomic%)
the pressure inside the reaction vessel (11) is 1 (Torr).
Then, a power of 300 [W] was applied for 20 minutes, and (a-
3i) After forming the third layer with a thickness of 3 [μm], the supply of electric power and various gases was stopped. Next, the reaction vessel (11)
Silane gas (Sil(, (50 ESCCM),
Nitrogen gas [N2] (600 ESCCM) was introduced, the pressure inside the reaction vessel (11) was set to 1 (Torr), and the pressure was increased to 400 (Torr).
Applying power of Wl for 5 minutes, amorphous silicon nitride (Q-
5i; 0.5 (μm) thick surface layer consisting of N) (
24b), and finally stop the power and gas supply.
The production of the photoreceptor (24) is completed. It should be noted that the second layer (
When the optical bandgap of 25b) was measured, it was approximately 1
．． It was 5 (eV). Furthermore, when the photoreceptor (24) was actually attached to a laser printer equipped with a semiconductor laser with an oscillation wavelength of 790 (nm) and an image was formed, a clear and high-quality image was obtained without density unevenness due to interference fringes. Obtained. With this structure, two types of i-type and n-type (μC-5i) are layered in the photoconductive layer (25), and the i-type (μC-5i) is layered in the photoconductive layer (25).
The first layer (25a) made of n-type (μC-3
The second layer (25b) made of i) also achieves higher sensitivity in the longer wavelength light region, and the third layer (25b) made of (a-3L), which has a higher resistivity than the other (μC-5i), 25c), it is possible to increase the sensitivity in the visible light region and prevent a decrease in charging ability due to a decrease in specific resistance.
Sufficient sensitivity can be obtained even for semiconductor laser light having a nearby oscillation wavelength, and application to laser printers and the like is possible without causing image density unevenness due to interference fringes. Furthermore, if this photoreceptor (24) is used, since the material is harmless to the human body, there is no need to take special safety measures during manufacturing, and there is no need to treat waste gas.
24) is not necessary to be recovered, and as a result, costs can be reduced. On the other hand, in addition to boron (B), the charge injection prevention layer (24a) is doped with carbon [C] to fill in the unevenness that would occur on the surface of the film if only boron CB) was used. Adhesion with the drum-shaped substrate (12) is improved, making it difficult to peel off, and carbon [C]
Due to its own insulating properties, the insulating properties of the charge injection prevention layer (24a) are also improved. Furthermore, as in this example, a surface layer (
By providing 24b), it is possible to prevent a decrease in light absorption efficiency and also protect the third layer (25c). In other words, (μC-5L) and (a-5i) have a refractive index of 3 due to their characteristics.
Although it is relatively large at ~4 and easily causes light reflection on its surface,
By providing amorphous silicon nitride (a-sx; N) whose refractive index is reduced by doping with nitrogen (N), this reflected light is reduced and the amount of light absorbed by the third Fm (25c) is reduced. Increased. Note that this invention is not limited to the above-mentioned embodiments, and various design changes are possible.1 For example, the layer structure of the photoconductor is arbitrary, and the surface layer may not be provided as long as it can compensate for wear resistance and light reflection. However, the lamination order and film thickness of each layer of the photoconductive layer are arbitrary, but in order to achieve higher sensitivity, (a-5i)
It is preferable to provide the third layer made of (μC-3i) on the top of the photoconductive layer, and when applied to a device that uses near-infrared light as a light source such as a laser printer device, the first layer made of (μC-3i) is preferably provided on the top of the photoconductive layer. is 3 to 50 [μm], the second layer made of n-type (μC-5i) is 1 to 10 [μm], and the third layer made of (a-Si) is about 0.1 to 5 [μm]. It is preferable to have a thickness within a range. Further, although the type of (μC-5i) in the first layer is arbitrary, if it is i-type, the resistance value becomes maximum, so that the charging ability can be further improved. Furthermore, the type of the charge injection prevention layer is also arbitrary, and when positively charging the photoconductor surface, doping with an element of Group Ma of the periodic table is used to prevent injection of electrons from the support. On the other hand, when the photoconductor surface is to be negatively charged, it may be made into an n-type by doping with an element of Group Va of the periodic table to prevent injection of holes from the support. However, the structure may be either (a-SL) or (μC-5i), but when it is formed from (μC-3i), it has better light absorption such as laser light and can be easily removed from the support. This eliminates the occurrence of reflected light, and furthermore, it is possible to more reliably prevent density unevenness due to interference fringes caused by reflected light on the surface, and it is possible to obtain a clearer image. In addition, the material to be doped into the charge injection prevention layer to improve adhesion to the support or insulation is not limited to carbon [C], but nitrogen (N) or oxygen [○] can be doped to form an amorphous material. Silicon carbide (a-
3i; C) or amorphous silicon oxide (a-S
i; 0) may be used as a charge injection prevention layer. And its thickness is also arbitrary. Preferably, the thickness is between 100 [μm] and 10 [μm]. Furthermore, the manufacturing method for each layer may also be a photo-CVD method, a sputtering method, or the like. In addition, when providing a surface layer, its material is nitrogen silicon [8
13N4], alumina Ugzoi), amorphous silicon oxide (a-S 1 : O; H),
Organic materials such as polyvinyl chloride and polyamide are optional. [Effects of the Invention] As explained above, according to the present invention, the photoconductive layer (
μC-5L), n-type (pC-3i), (a-5
Since it is composed of the three layers i), it is possible to obtain high spectral sensitivity in the visible light region, near-infrared light region, and even longer wavelength light region while maintaining the necessary charging ability, making it suitable for light sources. Application to laser printers etc. using long wavelength semiconductor laser light is fully possible, and high quality images can be obtained. In addition, its production can be carried out safely using a closed system production equipment using a reaction vessel, and since the material is harmless to the human body, there is no need to install special waste gas treatment equipment as in the past. In addition, there is no need to collect the photoreceptor after use, and it is possible to reduce costs. Incidentally, if a surface layer is provided as in the embodiment. In addition to prolonging the life of the photoconductor, if the surface layer is made of an inorganic compound with a low refractive index, the amount of light reflected from one surface will be reduced, which will improve the light absorption efficiency and further improve the image quality. is planned.

[Brief explanation of drawings]

FIGS. 1 and 2 show an embodiment of the present invention. Fig. 1 is a schematic explanatory diagram showing the film forming apparatus, Fig. 2 is a partial sectional view showing the photoreceptor, and Fig. 3 is (μC-3i) and (μC-3i).
It is a graph showing X-ray diffraction of a-Si). 10... Glow discharge device [11... Reaction vessel 12...
- Drum-shaped base 13... Heater 16... Support 17... High frequency power source 18... Cylindrical electrode 20... Gas supply system 24... Photoreceptor
24a... Charge injection prevention layer 24b... Surface layer 25... Photoconductive layer 25a... First
Layer 25b...Second layer 25c...Third layer

Claims (1)

[Claims] 1. A charge injection prevention layer and a photoconductive layer are provided on a conductive support, wherein the photoconductive layer is a first layer made of microcrystalline silicon and a first layer made of n-type microcrystalline silicon. A photoconductor comprising a second layer made of amorphous silicon and a third layer made of amorphous silicon. 2. The first layer is a film layer 3 [μm] to 50 [μm], the second layer
The photoconductor according to claim 1, wherein the layer has a thickness of 1 [μm] to 10 [μm], and the third layer has a film thickness of 0.1 [μm] to 5 [μm]. .