JPH01295263A - Photoconductive member - Google Patents

Abstract

PURPOSE:To obtain excellent electrification characteristics and to form a sharp good-quality image even with a laser beam printer and the like by forming a barrier layer or a well layer composed of a microcrystalline type thin layers having superlattice structure continuously changed in crystallization degree in each layer. CONSTITUTION:The electric charge genearating layer 50 of a part of a photoconductive layer is made of the microcrystalline silicon muc-Si:H of superlattice structure formed by alternately laminating first thin layers 50a and second thin layers 50b continuously changed in the band gap in each layer, accordingly, the layer 50 generates many carriers by irradiation with light as compared with a single charge generating layer, it has high spectral sensitivity, high carrier mobility, long life, and superior photoconductive characteristics. The barrier layer 50a maintains the optical bang gap in or above a prescribed value, and it does not invite lowering of resistance, thus permitting high spectral sensitivity to be obtained in a wide wavelength region from the visible wavelength region to the near infrared wavelength region, applicable to the laser beam printer, and a sharp and good-quality image to be obtained.

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a photoconductive member that forms an electrostatic latent image in an image forming apparatus such as a copying machine or a laser beam printer. (Prior art) In recent years, with the diversification of functions and models of image forming devices such as electrophotographic devices, photoreceptor materials such as cadmium sulfide [CdS], zinc oxide (ZnO), and selenium (Se) have been used.
, inorganic materials such as selenite alloy ('5e-Te),
Various organic materials such as poly-N-vinylcarbazole (hereinafter referred to as PVCz) and 1-helinitrofluorene (hereinafter referred to as TNF) have been developed. However, among the photoreceptor materials, selenium (Se),
Cadmium sulfide [CdS] is a material that is inherently harmful to the human body, so the manufacturing equipment becomes complicated for safety reasons, which increases manufacturing costs.
It must be recovered after use, which not only causes a rebound in cost but also increases the crystallization temperature of selenium (Se) and selenium-tellurium alloy [5e-Te], which is approximately 65%
Because it has a low temperature [°C], it is easily crystallized, and during repeated copying, residual charges are generated in the crystallized portion, which tends to cause problems such as staining the image. There is a drawback that there is no and zinc oxide [Zn
Due to its physical properties, O] is susceptible to oxidation-reduction and is significantly affected by environmental conditions such as temperature and humidity, resulting in unstable image quality and poor reliability. Furthermore, 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 also been suspected of being carcinogenic. Therefore, in recent years, as a solution to 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 higher spectral sensitivity than before. amorphous silicon (hereinafter referred to as a-3i)
: Called H. ) are being considered for application to photoreceptor materials. Specifically, since the photoreceptor is required to have high resistance and high spectral sensitivity, in order to satisfy both of these characteristics, a conductive support and (a-3i: H) are used.
A laminated type (a-5i: t
l) A photoreceptor has been developed. However, (a-3i: H) is silane (Si)
When forming a film using a glow discharge decomposition method using a gas containing (a-5i: H), hydrogen atoms [
11], the electrical characteristics and optical characteristics vary greatly depending on the amount. That is, (a-
3: H) As the amount of hydrogen atoms (H) incorporated into the film increases, the optical bread gap becomes larger and the resistance becomes higher. Spectral sensitivity decreases, and when used in a laser beam printer using a semiconductor laser, fogging, crushed type, afterimages, density unevenness due to interference fringes, etc. may occur, making the printer unusable. ((
Bond structures such as SiH7)n] bond and l:5iH2) bond become dominant in the (a-3i:11) film, and as a result, the (SjH) bond is severed, creating dangling bonds and voids. There is a problem that structural defects such as the like increase and the photoconductivity deteriorates. On the other hand (a-3i:
t+) When the amount of hydrogen atoms [)1] incorporated into the film decreases, the spectral sensitivity to long wavelength light increases, but on the other hand, the optical bandgap becomes smaller, resulting in lower resistance and hydrogen atoms [)] ] is dunk ring bong 1~
As a result, the mobility and lifetime of the generated carriers are reduced, resulting in a decrease in photoconductivity and the problem that it becomes impossible to use the photoreceptor. (Problems to be Solved by the Invention) Conventionally, the spectral sensitivity characteristics or resistance values of (a-3i: H) were made to conflict with each other depending on the change in the hydrogen content in the (a-5i: H) film. It has excellent optical and electrical properties (a-3i:
H) It is not possible to obtain a photoreceptor, resulting in a problem of deterioration of image quality. Therefore, the present invention solves the above problems by using a non-polluting semiconductor with high surface hardness, while maintaining high resistance.
In addition to obtaining excellent charging characteristics, it also has high spectral sensitivity characteristics over a wide wavelength range, and can even be used with laser-on-11 printers to obtain clear, high-quality images.
A further object of the present invention is to provide a photoconductive member that has good adhesion to a substrate and excellent environmental resistance. [Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides at least a portion of the photoconductive layer with a thin layer of microcrystalline of 30 to 200 layers. A large number of barrier P layers and well layers consisting of are laminated, and either the barrier layer or the well layer,
Alternatively, a superlattice structure is employed in which the degree of crystallinity in both layers varies continuously for each layer. (Function) The present invention improves photoconductive properties over a wide wavelength range and prevents deterioration of spectral sensitivity characteristics and charging characteristics against long wavelength light by the above-mentioned means, thereby making it suitable for laser beam printers and the like. This makes it possible to apply it. (Example) In explaining the present invention in detail, the characteristics of microcrystalline silico (hereinafter referred to as μC-3j: 11) and the superlattice structure which is the principle of the present invention will be described. First, (μC-5j: t() is (a-3i: H)
Compared to the above, it has a smaller optical bandgap, is sensitive to long wavelength regions near the near-infrared region, and has fewer structural defects. In other words, this (μC-3i: t()) belongs to non-single-crystal silicon, but when X-ray diffraction measurements are performed, it is found to be (a-3i: H) or amorphous, as shown by the dotted line in Figure 4. Therefore, only a halo appears and no diffraction pattern is observed, whereas (μC-3i: tl) shows a crystal diffraction pattern in the vicinity of [20] of 28 to 28.5 degrees, as shown by the solid line in Figure 4. On the other hand, polycrystalline silicon has a dark resistance of 106 [Ω・am] or less, whereas (μC-3]: 11) has a dark resistance of 10” (Ω・cm).
It can be adjusted to have a high dark resistance. Due to the above-mentioned characteristics, (μC-3i: H) is distinguished from other non-single-crystal silicon (a-3j: H) and polycrystalline silicon, and its structure has a grain size of about several tens of nanometers or more. It is thought that it is formed by aggregation of microcrystals. To produce such (μC-3i: tl), sputtering, glow discharge decomposition method, etc. are used in the same way as (a-5i: H), but (a-5i: tl)
l) It becomes easier to form 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 raw material silane (Si
) The flow rate of the containing gas can be increased, resulting in an increase in the film formation rate (μC-3i: t()). Hydrogen [including secondary silane gas]
11], using a gas diluted with (μC-5i:
H) becomes more likely to be formed effectively. Further, the (μC-5i: II) formed into a film has a characteristic that as the hydrogen content increases, the degree of crystallinity increases and the band gap decreases. Furthermore, in order to improve the photosensitivity characteristics and increase the resistance, (
In addition to hydrogen atoms [+1], impurities are doped into the μC-5i: H) layer, and as with (a-5i: H), which will be described later, in order to make it P-type, the periodic law Elements in group Ⅰ of the table are suitable, while elements in group Ⅰ of the periodic table are suitable for making the material n-type. Also (μC-
3i: In order to increase the dark resistance of H) and improve the photoconductive properties, nitrogen (N'l, carbon [C], and oxygen

It is desirable that at least one type of [0] be 1-pinned. In this way, these elements become (μC-3i: H
) is precipitated at grain boundaries and acts as a terminator for dangling bonds of silicon [Sil], reducing the density of states existing in the forbidden cloth between bands. Due to such characteristics, by using (μc-si:H) in the photoconductive layer of a photoreceptor, it becomes possible to increase the spectral sensitivity in the long wavelength region near the near-infrared region. Next, we will discuss the superlattice structure. That is, it may be either crystalline or amorphous, but it is extremely thin with a thickness of about 30 [people] to 200 [people],
In a semiconductor layer consisting of a stack of multiple thin layers with different band gaps, the optical band gap is relatively large, regardless of the absolute size of the optical band gap itself. A superlattice structure having a periodic potential barrier is formed in which the smaller layer is used as a well layer and the layer with a relatively larger optical bandgap is used as a barrier layer. In this superlattice structure, since the barrier layer is extremely thin, carriers easily pass through the barrier layer due to the carrier tunneling effect in the thin layer, and are accelerated by the electric field in the superlattice structure, compared to the case of a single layer. and travels through the superlattice structure with high mobility. Furthermore, in this superlattice structure, a significantly larger number of carriers are generated compared to the number of carriers generated in a single layer upon incidence of light, resulting in high spectral sensitivity. Furthermore, in the potential well layer, the superlattice structure has excellent photoconductive properties, as the lifetime of carriers is 5 to 10 times longer than in the case of a single layer due to quantum effects. Specifically, the electrically conductive member is formed as shown in FIGS. 5 to 10, and in the example 1 shown in FIG. A charge injection prevention layer (11) is formed, and a photoconductive layer (12) and a surface layer (13) are formed on the charge injection prevention layer (11). In addition, in (Specific Example 2) shown in FIG. 6, the photoconductive layer (12) in (Specific Example 1) is
It is functionally separated into a charge generation layer and a charge transport layer,
A charge transport layer (16) is formed on the conductive support (10) and the charge injection prevention layer (11). A charge generation layer (17) is formed on the charge transport layer (6), and a surface layer (13) is formed on the charge generation layer (17). In (Specific Example)), the photoconductive layer (12) generates carriers upon incidence of light, and one polarity of these carriers neutralizes the charges on the photoreceptor surface, and the other polarity neutralizes the charges on the surface of the photoreceptor. Things are photoconductive! (12) to the conductive support (10). Further, in (Specific Example 2), carriers are generated in the charge generation M (17) due to the incidence of light, and one of these carriers travels through the charge transport layer (16) and transfers to the conductive support ( 10). When the photoconductive layer (12) or charge generation layer (17) in these (specific examples) is enlarged, it becomes as shown in FIG. 7, and the optical band gap is different, and the thickness of each is 30 mm
The first (a-5i: H) layer (
18) and the second (a-3i:H) layer (20) are alternately laminated to have a superlattice structure. For example, the first (a-3]: H) JFJ (18) has a hydrogen content of 30 [%], and the second (a-3j, : H) layer (
20) has a hydrogen content of 12% and is continuously varied in the photoconductive layer (12) or the charge generation layer (7) as shown in FIG. -5i
: 11) The optical bandgap of the layer (18) is 1. ．．
8 (eV: l, and the optical band gap of the second (a-5i: t() layer (20)) is], 68 [eV]
Therefore, the energy band diagram in the thickness direction in the superlattice structure is the first (a-3i: H
) layer (18) serves as a potential barrier, while the second (a-3j, :t() layer (20) serves as a potential well, and a potential barrier layer and a well layer are formed periodically. Furthermore, each layer (1, 8), (
By changing the optical bandgap or layer thickness of 20), the apparent bandgap of the layer having a Peter junction superlattice structure can be freely adjusted. In addition, the material forming such a superlattice structure has a hydrogen content of 30 [atomic %] and a band gap of 1. ．．
(a-3j, : H) such as 8 (eV), hydrogen content of 12 [atomic %] and band gap], 68 [eV], etc.
Alternatively, nitrogen [N], carbon [C], and oxygen can be added to increase the optical band gap to 1.9 [eV].

[0] Amorphous silicon nitride (hereinafter referred to as a-5iN:
It is called H. ), amorphous silicon carbide (hereinafter a-5
jC: Referred to as H. ), amorphous silicon oxide (hereinafter referred to as a-3jO: H), etc. (a-3j: t(
) system, or the optical band gear mentioned above is 1.5 (
eV] or higher (μC-5i: H) or microcrystalline silicon carbide (hereinafter μC-3iN: H)
It is called. ), microcrystalline silicon carbide (hereinafter referred to as μC-5]C: II), microblister phosphoric silicon oxide (hereinafter referred to as μC-3iO: H), etc. (μC-5j: l() system, and this etc. generally exhibit weak n-type in the case of non-doped materials, and by increasing the doping of elements in group Ⅰ of the periodic table such as boron (CB) and aluminum (1), they shift from type 1 to p-type. On the other hand, by increasing the doping of elements of group I of the periodic table, such as phosphorus (P) and nitrogen (N1, etc.), n-type characteristics become noticeable. Furthermore, by doping with an element of Group 1 or Group 2 of the periodic table, the mobility of carriers is further improved. Other materials have an optical Hunt gap of 1.5 (eV).
) is amorphous germanium silicon (hereinafter referred to as a-
3iGe: Referred to as H. ) Amorphous germanium nitride (hereinafter referred to as a-GeN:11), amorphous germanium carbide (hereinafter referred to as a-GeC:t).
, amorphous germanium oxide (hereinafter a-GeO:
It is called t+. ) etc. In addition to the fluctuation of the optical bandgap, in each of these materials, it is necessary to compensate for the dangling bonds of silicon, balance dark resistance and bright resistance, and improve photoconductivity. In order to achieve this, it is desirable that hydrogen (H) contains 0.01 to 30 [atomic %] gold. And for example (a-3i: H),
Alternatively, when forming a thin layer of (μC-3i:H) by glow discharge decomposition method, silane (SiH4
:l and a silane gas such as disilane (Si, 1(6)) are introduced into the reaction chamber, and H can be added into the thin layer by glow discharge using high frequency.
iN: H) or (μC-3j, N: It)
In order to form this, a required amount of nitrogen gas [N7] or ammonia gas (NH3) or the like may be added to the raw material gas. Furthermore, (a-3iGe: H) is usually silane [S]
The film is formed by glow discharging a mixed gas of H4] and germane [GeH4]. Further, if necessary, hydrogen gas [N2] or helium gas [He] can be used as a carrier gas for silanes. On the other hand, silicon tetrafluoride [5IF4] gas and 1-lichlorosilane [:5
Silicon halide such as iC14] dregs can also be used as the raw material dregs. Furthermore, even if the mixture of silane gas and silicon halide gas is reacted, (a-5iN: H) and (a-3i:
1-1), and furthermore, (μC-3iN:H) can be formed. Note that these thin layers can be formed not by the glow discharge decomposition method but also by a physical method such as sputtering. Note that the charge injection prevention layer (1]) in (Specific Example 1) and (Specific Example 2) consists of a conductive support (10) and a photoconductive layer (
12) Alternatively, by suppressing the flow of charge between the photoreceptor and the charge generation layer (17), the charge retention function on the surface of the photoreceptor is enhanced, and the bandgap performance of the photoreceptor is improved. In the Carlson method, when positively charging the photoreceptor surface,
In order to prevent electrons from being injected from the support side to the photoconductive layer, the charge injection prevention layer is made of a p-type semiconductor. on the other hand,
When the surface of the photoreceptor is negatively charged, the charge injection prevention layer is made of an n-type semiconductor in order to prevent holes from being injected from the support side to the photoconductive layer. It is also possible to form an insulating film on the support as a charge injection prevention layer. As a semiconductor charge injection prevention layer, (μC-3i
: H), (μC-5iN: H), (a-3j: H), (a-3iN: 11), etc. And (μC-3i: H)
In order to make (a-3i: H) etc. p-type, an element belonging to Group Ⅰ of the periodic table, such as boron CB),
It is preferable to dope aluminum [A1], gallium (Ga), indium [In], thallium (Tl'1, etc.), and (μC-3i: H) and (a-5
In order to make i: 11) n-type, we need to
Elements belonging to the group, such as nitrogen (CN), phosphorus [P], arsenic (As:l), antimony (sb), and bismuth [B
1] etc. is preferably doped. This doping with p-type impurities or n-type impurities prevents charges from moving from the support side to the photoconductive layer. On the other hand, (μ
C-3i: H) and (a-3j: H), etc., carbon [C], nitrogen [N] and oxygen

By containing at least one element selected from [0], a high-resistance insulating charge injection prevention layer can be formed. The thickness of the charge injection prevention layer is between 00 [μ] and 10 [μ].
m] is preferred. Furthermore, in (Specific Example 1) and (Specific Example 2), the photoconductive layer (12) or charge generation J# (+7
) J- is provided with a surface M (13) for the following reason. i.e. photoconductive layer (12) or charge generation layer (17)
(a-5i: It) etc. have a refractive index of 3 to 3.
．． Since it is relatively large at 4, light reflection easily occurs on the surface. When such light reflection occurs, the ratio of the amount of light absorbed by the photoconductive layer or the charge generation layer decreases, resulting in an increase in optical loss. For this reason, it is preferable to provide a surface layer (13) to prevent reflection. Moreover, by providing the surface layer (13), photoconductive! (12) or the charge generating layer (17) is protected from damage. Furthermore, by forming the surface layer, the charging ability is improved, and the charge can be easily deposited on the surface. The material forming the surface layer is (a-3iN:
H), (a-5iO: H), and (a-3iC: I
I), (p C-5iN: tl), (p C-5i
These include inorganic compounds such as C: H), (μC-5lO: II), and organic materials such as polyvinyl chloride and polyamide. When the surface of the photoconductive member constructed in this way is charged with a positive voltage of about 500 [V] by corona discharge, =
16- For example, in the functionally separated type shown in FIG. 6 (Specific Example 2), a potential barrier as shown in FIG. 10 is formed. When light (hν) is incident on this photoconductive member, electrons (21) are generated in the superlattice structure of charge generation N (17).
and hole (22) carriers are generated. Electrons (21) in the conduction band are accelerated toward the surface layer (13) by the electric field in the photoconductive member, and holes (22)
is accelerated toward the conductive support (10) side. In this case, the number of carriers generated at the boundary between thin layers with different optical band gaps is much larger than the number of carriers generated in the bulk. Therefore, charge generation in this superlattice structure! (1, 7), the spectral sensitivity becomes high. Also,
In the potential well layer, due to quantum effects,
The carrier lifetime is 5 to 10 times longer than that of a single layer without a superlattice structure. Furthermore, in a superlattice structure, a periodic barrier layer is formed due to the discontinuity of the bread gap, but carriers easily pass through the bias layer due to the tunnel effect, so the effective mobility of carriers in the bulk is The mobility is the same, and the carrier has excellent runnability. As described below, with a photoconductive member having a superlattice structure in which thin layers with different optical huffs and gaps are laminated, high photoconductive properties can be obtained and images are clearer than conventional photoreceptors. can be obtained. Based on the above principle, one embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Glow discharge device (2
6) Inside the reaction vessel (27) is a conductive support,
In order to support the drum-shaped base (28) made of aluminum, a support rod (32) has a built-in heater (30) and is rotated by a motor (31) via a shaft (31a).
A support stand (33) is provided to support the support rod (32). Moreover, the surrounding area of the support body (32) is 13, 56
(It is surrounded by a cylindrical electrode (36) connected to a high frequency power source (34) of MHz and supported on the bottom (27a), and above the support rod (32), silane gas [5IH4], diborane gas [5xzHc ], hydrogen gas [H2], methane gas CCH4) and other raw material gases can be supplied as needed.
A gas introduction pipe (40) is provided which is connected to a gas supply system (38) having a gas supply system (37n) and a gas mixer (38a) via a gas introduction valve (40a). Furthermore (4),
a)...(41n) is each gas cylinder (37a)...(3
Valve 7n), (42a)...(42n) are pressure gauges. Furthermore, (43) is an exhaust valve connected to an exhaust device (not shown) that exhausts the inside of the reaction container (27), and (44) is a vacuum gauge that measures the atmospheric pressure inside the reaction container (27). . Further, (46) is a photoreceptor such as a laser printer, which is a photoconductive member, and has a drum-shaped base (28) J-, a charge injection prevention layer (47) and a charge transport layer (48), and a band with low crystallinity. Large gap (μC-3i:
A betero junction superlattice in which a barrier layer (50a) consisting of H) and a well M (sob) consisting of a high crystallinity and a small band gap (μC-5i: II) are alternately and repeatedly stacked at an arbitrary thickness. A charge generation layer (50) and a surface layer (51) of the structure are laminated. However, in the charge generation layer (50), the crystallinity of the barrier layer (50a) and/or the well layer (50b) is continuously changed for each layer. Note that (52) is a charge transport layer (48) and a charge generation layer (50).
) is a photoconductive layer consisting of When forming the photoreceptor (46) in the glow discharge device (26), after setting the drum-shaped substrate (28) on the support (32), the inside of the reaction vessel (27) is heated to 0.1 torr or less. The exhaust valve (43) is opened so that the atmospheric pressure is at a certain level, and the exhaust gas is treated by an exhaust device (not shown), and the crumb substrates (28) are heated to a predetermined temperature by the heater (30). Then, a required predetermined gas is supplied to the reaction vessel (2) from the gas supply system (38) via the gas introduction pipe (40).
7), and the drum-shaped substrate (28) and the cylindrical A necessary power is applied between the electrodes (36) for a predetermined period of time to form a charge injection prevention layer (47) on the drum-shaped substrate (28). Next, the charge transport layer (
48), a charge generation layer (50) and a surface layer (51) are formed to complete the formation of the photoreceptor (46). Next, a test example in which film formation was actually performed based on this example will be described. [Test Example 1] A sample with a diameter of 80 mm was subjected to acid treatment, alkali treatment, and Sand Plus 1 ~ treatment to prevent interference, if necessary.
An aluminum drum-shaped base with a width of 350 mm (28
) was installed in the reaction vessel (27), and the reaction vessel (27) was evacuated to a degree of vacuum of about 1.0" (1-L). Then,
The drum-shaped substrate (28) is heated by the heater (30) at 250°C.
[''C] and heated to 1.0 (r,
p, m, ), from the gas supply system (38),
Via the gas introduction pipe (40), silane gas (SiH4) was introduced at a flow rate of 500 ESCCM), diborane gas [:B, H5) at a flow rate ratio of 10-6 to silane gas [SjH,], and methane gas l:c14.1 at a flow rate of 1.001: SCCM) was introduced into the reaction vessel (27) at a flow rate of 5001:1 by the high frequency power supply (34) while maintaining the pressure in the reaction vessel (27) at 1 [torr] using an exhaust device (not shown).
tl] is applied between the drum-shaped substrate (28) and the cylindrical electrode (36), and p-type (a-3jC: H)
A charge injection prevention layer with a film thickness of 0.31 μml (47
). Next, diborane gas (B21 (6)
] with a flow rate of 10-7 and methane gas [:CH4
) and further increased the high frequency power between the l-ram-shaped substrate (28) and the cylindrical electrode (36) to 1 [kW],
■Charge transport layer (48
) was formed on the charge injection prevention J# (47)l until the film thickness was 20 [μm]. After this, without changing other film forming conditions, high frequency power was first applied (μc-sj: H
) is formed, and then the high frequency power is lowered to 1200 (W) to form a well N (50b) of the charge generation layer (50).
(μC-3i: 11) with a crystallinity of 1
5 [%], the optical band gap is about 1. ．． 63 [eV
) of the charge generation layer (50), and further increase the high frequency power to 1252 (ltl) to form the well WJ.
(50b) was deposited for 50 [people], and high frequency power was applied to 120 [people].
Return to 0 [11, l, barrier layer (50a) to 50 [people]
Form a film. In this way, the high frequency power is increased to 1500 (ltl
50 [persons] are deposited in increments of 1 [W] until they reach ).
a well layer (50b) consisting of (μC-3]:H);
50 [people] deposited with high frequency power 1200 (1t1)
Barrier layer (50a) consisting of (μC-3i: H)
A charge generation layer (50) having a heterojunction superlattice structure and having a thickness of 2.5 [μm] is formed by alternately forming a film of 250M each. Regarding the well layer (SOB), as the special high frequency power for film formation is raised to 1251 (11), its crystallinity gradually increases by 1 to 60%, and as shown in the third figure, the optical The target bandgap is gradually reduced to 1.53 CeV). Finally, add silane gas (SiH4) to the reaction vessel (27) at a rate of 250 (SCCM) and methane gas [
CH4] was introduced at a flow rate of 2000 (SCC old), and while maintaining the pressure in the reaction vessel (27) at 1 [Torr],
[: kW) high frequency power is applied, (a-5j, C:
A surface layer (51) having a thickness of 0.5 [μm] made of H) is formed, and the production of the photoreceptor (46) is completed. The photoreceptor (46) thus obtained was heated to about 500 (V
) was positively charged and exposed to white light, a large number of electrons/
Hole pair carriers are generated, the carrier has a long life, and high running properties are obtained.When the photoreceptor (46) was actually installed in a copying machine and image formation was performed, a clear and high quality image was obtained. In addition, it has good image reproducibility and stability due to repeated charging, and also has good adhesion and excellent durability such as corona discharge resistance, moisture resistance, and abrasion resistance. It turned out that there was. -Force photoreceptor (46)
It has high spectral sensitivity even to long wavelength light of around 780 to 790 (nm), and when it was actually attached to a semiconductor laser beam printer and image formation was performed, it showed fogging and
We were able to obtain clear, high-resolution images with no crushed print. With this configuration, the charge generation layer (50), which is a part of the photoconductive layer, has a first thin layer (50a) and a second thin layer (50a) whose band gaps are continuously varied for each layer. 50b)
Because it is formed from (μC-8i:H) with a superlattice structure in which layers are alternately stacked, the number of carriers generated by light irradiation is larger than that in a case where the charge generation layer is formed from a single layer. It has high spectral sensitivity, excellent carrier mobility, long life, and excellent photoconductive properties, and the optical bandgap is maintained at a constant level by the barrier layer (50a). Since it does not cause low resistance, high spectral sensitivity can be obtained over a wide wavelength range from visible light to near-infrared light, and it can be applied to laser beam printers, and it has the same charging ability as conventional devices. There is no reduction in image quality, blurring of images, or fogging.
Clear, high-quality images can be obtained. It should be noted that the present invention is not limited to the embodiment described in 1, but can be modified in various ways. For example, the photoconductive layer is not separated into a charge generation layer and a charge transport layer; It may have a similar structure, or it may constitute a superlattice structure (μC-3
i: H) band gap size, film thickness and number of layers,
Further, the thickness of the charge generation layer is not limited, and by adjusting the thickness, it is possible to obtain a photoreceptor having optimal photoconductive characteristics for light of any wavelength. In addition, the variation of the bandgap for each layer of the barrier layer and the well layer is also arbitrary.
During film formation, the high frequency power may be changed in steps of 2 [W], and the form of bandgap variation may be as long as it forms a boundary between thin layers with different optical bandgaps, as shown in Figure 1. In the first modification, as in the first modification to the fifth modification shown in (a) to e), the well layer (60
b) is kept constant and the punt cap of the barrier layer (60a) is gradually reduced; in the second variant, the barrier layer (6], a) is kept constant and the hunt cap of the well layer (61b) is may be gradually increased, or furthermore, as in the third and fourth modifications, the barrier layer (62a),
(63a) and a well layer (62b). (63b), or as in the fifth modification, the bandgap of the barrier layer (64a) is decreased and then increased, while the well layer The bandgap of (64b) may be increased by one step and then decreased. Furthermore, the material of the thin film can also be adjusted for optical bandgap adjustment.
carbon [C], oxygen

[0], nitrogen [N], or an element from group Ⅰ or group of the periodic table for the ``2'' orientation of carriers. Note that the change in crystallinity in the superlattice structure, that is, the change in band gap, does not have to be linearly continuous. For example, in [Test Example 1], when forming the charge generation layer (50), high frequency power was applied. , barrier layer (50a
) and during the well layer (50b) formation, the high frequency power was continuously changed from 1.251[:W] to 1.
By returning the power to 200 [W] and then increasing it continuously to 1.252 (IJ), the band cap in the superlattice structure is changed to the barrier layer (66a) as in the sixth modification shown in FIG. The well layer (66b) may be changed in a curved manner. [Effects of the Invention] As explained above, according to the present invention, the material has excellent durability and a long service life, is non-polluting, and does not require collection after use (μC-5i : II) system material is used for the photoconductive layer, and it has high spectral sensitivity over a wide wavelength range from visible light to near-infrared light, and has excellent photoconductivity especially for long wavelength light. A photoconductive material that exhibits characteristics, does not have low resistance like conventional products, has excellent charging characteristics, can obtain clear and high resolution images, and can be applied to laser beam printers, etc. can be obtained.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, FIG. 1 is a schematic explanatory diagram showing a film forming apparatus, FIG. 2 is a partial cross-sectional view showing a photoreceptor, and FIG. Graphs showing a part of the energy band of the charge generation layer of Test Example 1], Figures 4 to 10 illustrate the principle of the present invention, and Figure 4 shows its (μc-
A graph showing X-ray diffraction of 3i:H) and (a-5i:H), FIG. 5 is a partial cross-sectional view showing the photoreceptor of (Specific Example 1), and FIG. 6 is a graph showing the photoreceptor of (Specific Example 2). FIG. 7 is an enlarged cross-sectional view of a part of FIGS. 5 and 6, and FIG. ), FIG. 9 is a graph showing part of the energy band of the photoconductive layer or charge generation layer, and FIG. FIGS. 11(a) to 11(e) are schematic diagrams showing the energy gaps of FIGS. FIG. 12 is a graph showing part of the energy band of the charge generation layer of the sixth modification. 26 glow discharge device, 27 reaction vessel, 2
8. Drum-shaped base, 32 Support rod, 34.
High frequency power supply, 36・Cylindrical electrode, 37a,・
・37n,...Gas cylinder, 38...Gas supply system, 4
6... Photoreceptor, 47 Charge injection prevention layer, 48... Charge transport layer, 50 Charge generation layer, 51... Surface layer, 52... Photoconductive layer. Agent: Patent Attorney Norio Ogo Figure 5. i-1-go i213 ra] Figure 8 Figure 6/2. /7 / Fig. 7 (ev'J 0 700 200 .300 Nakai film thickness tA) Fig. 9

Claims (1)

[Claims] In a device having a charge injection prevention layer and a photoconductive layer on a conductive support, at least a part of the photoconductive layer has a superlattice structure in which a large number of barrier layers and well layers made of microcrystalline thin layers are laminated. A photoconductive member characterized in that the degree of crystallinity of the barrier layer and/or the well layer changes continuously from layer to layer.