JPH0233145B2 - DENSHISHASHIN KANKOTAI - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor. Conventionally, as electrophotographic photoreceptors, Se or Se
Photoreceptor doped with As, Te, Sb, etc., ZnO and CdS
Photoreceptors, etc., in which the compound is dispersed in a resin binder are known. However, these photoreceptors have problems in terms of environmental pollution, thermal stability, and mechanical strength. On the other hand, electrophotographic photoreceptors using amorphous silicon (hereinafter referred to as a-Si) as a matrix have been proposed in recent years. a-Si is Si-Si
It has a so-called dangling bond in which the supply chain is broken, and many localized levels exist within the energy gap due to this defect. For this reason, hopping conduction of thermally excited carriers occurs, resulting in a small dark resistance, and photoexcited carriers are trapped in localized levels, resulting in poor photoconductivity. Therefore, the dangling bonds are filled by compensating for the defects with hydrogen atoms (H) and bonding H to Si. The resistivity of such amorphous hydrogenated silicon (hereinafter referred to as a-Si:H) in the dark is
It is 10 ⁸ to 10 ⁹ Ω-cm, which is about 1/10,000 times lower than that of amorphous Se. Therefore, a-Si:H
A photoreceptor consisting of a single layer has problems in that the dark decay rate of the surface potential is high and the initial charging potential is low. However, on the other hand, when irradiated with light in the visible and infrared regions, the resistivity is greatly reduced, so it has extremely excellent properties as a photosensitive layer of a photoreceptor. In addition, photoreceptors with a-Si:H surfaces are susceptible to the effects of long-term exposure to the atmosphere and moisture.
Up to now, sufficient studies have not been made regarding the chemical stability of the surface, such as the influence of chemical species generated by corona discharge. For example, it has been found that when left for more than one month, the acceptance potential decreases significantly due to the influence of moisture. On the other hand, regarding amorphous silicon carbide (hereinafter referred to as a-SiC:H),
Its manufacturing method and existence are described in "Phil.Mag.Vol.35" (1978), etc., and its characteristics include high heat resistance and surface hardness, and high dark resistance compared to a-Si:H. (10 ¹² to 10 ¹³ Ω-cm), and the optical energy gap is 1.6 to 1.6 depending on the carbon content.
It is known that it varies over a range of 2.8 eV. An electrophotographic photoreceptor combining such a-SiC:H and a-Si:H has been proposed, for example, in Japanese Patent Laid-Open No. 17952/1983. According to this, a-Si:H
The layer is a photosensitive (photoconductive) layer, and a first layer is formed on the light-receiving surface.
An a-SiC:H layer is formed, and a second a-SiC:H layer is formed on the back surface (support electrode side) to obtain a photoreceptor with a three-layer structure. The inventor of the present invention particularly investigated photoreceptors using a-SiC:H and found that conventional photoreceptors had the following drawbacks. That is, the optical energy gap of, for example, an a-SiC:H layer as a charge transport layer is the same as that of a photoconductive layer (for example, an a-SiC:H layer).
layer), there is a fairly large band gap between the two layers, and as a result, carriers generated within the photoconductive layer during light irradiation cannot sufficiently overcome the band gap, resulting in a decrease in photosensitivity. becomes insufficient. In particular, it was found that when the band gap was 0.3 eV or more, the photosensitivity decreased considerably. As a result of intensive study on this problem, the inventors of the present invention have found that by interposing a third layer between the charge transport layer and the photoconductive layer, the movement of charges is smoothed, and the electrostatic charge such as photosensitivity is improved. The present invention was achieved by discovering a structure that can improve characteristics. That is, the present invention provides an electrophotographic photoreceptor comprising a laminate in which at least a charge transport layer and a charge generation layer are sequentially laminated on a substrate, in which an optical band gap between the charge transport layer and the charge generation layer is at least , 0.3 eV, and one or two transition layers having a uniform composition are provided between the charge transport layer and the charge generation layer, so that the charge transport layer and the charge generation layer are The optical band gap between each layer is set to be 0.3 eV or less, and the charge transport layer has a carbon atom content of 15 to 15.
70 atomic%, and the hydrogen atom content is 1~
40 atomic% and a thickness of 2 to 80 μm of amorphous hydrogenated and/or fluorinated silicon carbide, the transition layer having a carbon atom content of 5 to 65 atomic%.
%, the hydrogen atom content is 1 to 40 atomic %, and the charge generation layer is made of amorphous hydrogenated and/or fluorinated silicon carbide having a thickness of 50 Å to 2 μm, and the charge generation layer has a hydrogen atom content of 1 to 40 atomic %.
The present invention relates to an electrophotographic photoreceptor characterized in that it is made of amorphous hydrogenated and/or fluorinated silicon with a thickness of 40 atomic % and a thickness of 2500 Å to 10 μm. With this configuration, the rather large optical bandgap between the charge transport layer and the photoconductive layer is alleviated (in other words, reduced) by the transition layer, and the bandgap between each layer is reduced. In addition, electrons or holes generated during light irradiation can easily move from the photoconductive layer to the charge transport layer,
Photoelectric conversion rate or photosensitivity can be improved. Furthermore, the above-mentioned a-SiC:H/a-Si:H/
Even compared to the three-layer structure of a-SiC:H, etc., it has sufficient charging characteristics, provides a practical charging potential with small dark decay, and has a small residual potential. The invention will now be illustrated in detail with reference to the drawings. As shown in FIG. 1, the recording medium according to the present invention, for example, a photoreceptor, is provided with a charge transport layer formed on a conductive support substrate 1, which has a high resistance, if necessary, by doping with a group A element of the periodic table. a-SiC:H layer 2
and, if necessary, a-SiC:H layer 3 as a transition layer with similarly high resistance, and a photoconductive layer (photosensitive layer).
It consists of a laminate in which a-Si:H layers 4 are sequentially stacked. In the column of FIG. 2, the substrate 1
and a-SiC:H layer 2, an N ⁺ type or P type (even P ⁺ type) a-SiC:H as a blocking layer doped with a group A or group A element of the periodic table.
A layer 5 is provided. Although the same may be applied to the example of FIG. 1, in the example of FIG. 2, the photoconductive layer 4
A surface modification layer (for example, an Al ₂ O ₃ layer) 6 is provided thereon. What should be noted here is that the optical band gap between the a-SiC:H layer 2 and the photoconductive layer 4 is
0.3eV or more, an a-SiC:H layer 3 is provided as a transition layer between these two layers to alleviate the band gap, and due to the existence of this transition layer, the a-SiC:H layer 2 and the photoconductive layer The optical band gap between each layer between the two layers is suppressed to 0.3 eV or less. Figure 3 shows how the optical energy gap changes depending on the carbon atom content of a-SiC:H. By controlling the amount of carbon during growth, the energy gap between layers 2 and 3 can be formed with good controllability. Furthermore, by reducing the carbon content of the transition layer by at least 5 atomic% or more than the carbon content of the charge transport layer, the band gap between the photoconductive layer 4, the transition layer 3, and the charge transport layer 2 can be effectively reduced to 0.3 eV or less. It can be done. The carbon content of each layer is also important for increasing the resistance and maintaining the surface charge potential, and from this point of view, the carbon content of layer 2 is 15~
A good value is 70 atomic%. The carbon content of layer 3 is preferably between 5 and 65 atomic percent. The effect of providing the transition layer 3 in this way is explained in the fourth section.
5 and 5 will be described in detail. FIG. 4 shows an example in which the blocking layer 5 is N ⁺ type and the photoreceptor is negatively charged.
Band gap (conduction band)
CB difference) ΔE exists. A transition layer 3 exhibiting an intermediate energy level exists between these two layers, and this transition layer 3 and both layers 2,
The band gap with respect to 4 is gradually smaller (for example, about 1/2) than the above ΔE. Therefore, when the surface is negatively charged and then irradiated with light, among the carriers generated within the photoconductive layer 4, electrons are transferred to the charge transport layer 4.
It easily moves to the transition layer 3 whose energy level is lower than that of the charge transport layer 2, and further moves to the next charge transport layer 2. At this time, since the band gap between each layer 4-3 and 3-2 is smaller than 0.3 eV, electrons can easily move smoothly from the photoconductive layer 4 to the charge transport layer 2 and then to the substrate 1 side. ing. On the other hand, the generated holes can easily move to the surface, so that the photoreceptor has sufficient photosensitivity and the phenomenon of residual electricity is reduced. On the other hand, if the transition layer is not provided, electrons cannot easily move to the charge transport layer 2 due to the band gap ΔE, resulting in a decrease in carrier transport ability and a deterioration in photosensitivity. Note that holes are about to be injected from the substrate 1, but the band gap (difference in valence band VB) between the substrate 1 and the blocking layer 5 is such that the blocking layer is N ⁺ type and the valence band shifts downward. Since it is large, hole injection is substantially blocked, and the retention of surface potential is not affected. FIG. 5 shows an example in which the blocking layer 5 is made into a P ⁺ type and is used for normal voltage. In this case also, the charge transport layer 2 and the photoconductive layer 4 are
Since the transition layer 3 is present between the two layers, the band gap between each layer is considerably small. Therefore, the holes generated in the photoconductive layer 4 during light irradiation move to the transition layer 3 and further to the charge transport layer 2, and the efficiency of movement towards the substrate 1 side increases, resulting in good photosensitivity and eliminating the remaining holes. There will also be less electricity. Furthermore, during charging, electrons try to be injected from the substrate 1, but since the blocking layer 2 is P ⁺ type and a sufficient energy barrier is formed between it and the substrate 1, the injection of electrons is substantially prevented. The surface potential can still be maintained high. In addition, if the resistivity of the above layer 2 (or even 3) is increased to the point where it becomes intrinsic by impurity doping (for example, 10 ¹³ Ω-cm or more), it is possible to improve the surface resistance while retaining the charge transport function. The potential can also be kept high, thereby reducing dark decay and improving the charging potential.This also means that the photoconductive layer 4 can also be doped with impurities to make it highly resistive (or made intrinsic: the dark resistivity is 10 ¹⁰ Ω-cm or more), further improvement can be achieved. An additional effect of providing the transition layer 3 is that when the charge transport layer 2 with a high carbon content is in direct contact with the photoconductive layer 4, it is difficult to bond therebetween, resulting in insufficient bonding properties. However, by interposing the transition layer 3 having a relatively low carbon content, the bonding between a-SiC:H and a-Si:H becomes good. The photoreceptor shown in FIGS. 1 and 2 according to this embodiment can be produced by glow discharge decomposition method, in particular, the a-SiC:H layer 5 is prepared using diborane or phosphine gas and silicon compound gas (e.g. (monosilane) must be selected appropriately. Figure 6 shows a-SiC:H layer 5 (carbon content is
20atomic%) upon the formation of PH ₃ (phosphine) and
The change in dark resistivity (ρ _D ) of the same layer is shown when the flow rate ratio (scale is logarithmic scale) with SiH ₄ (monosilane) is changed. As a result of phosphorus doping with PH ₃ ,
ρ _D decreases, especially below 10 ⁶ Ω-cm (heavy dope)
It has been found that a blocking layer can be obtained which can sufficiently prevent the injection of carriers from the substrate as described above. It is desirable to further increase the amount of phosphorus doping and lower ρ _D to 10 ⁴ to ^{10 5} Ω-cm. From the above, the flow rate ratio of PH ₃ /SiH ₄ is preferably set to 100 to 10,000 ppm. FIG. 7 shows a-SiC:H layer 5 (carbon content is
The figure shows the change in dark resistivity (ρ _D ) depending on the flow rate ratio of diborane and monosilane (scale is logarithmic scale) when doping with impurities (group A) to 20 atomic %). In general, undoped a-SiC:H exhibits a conductivity type that is somewhat N-type, but when doped with boron, the impurities are compensated and the state becomes essentially intrinsic, and the amount of boron doped is If you increase , it will be converted to P type. According to the results shown in FIG. 7, if the flow rate ratio (B ₂ H ₆ /SiH ₄ ) is appropriately selected to achieve the purpose of the present invention, a-SiC:H
By heavily doping layer 5, it becomes P type (even P ⁺ type)
To do this, B ₂ H ₆ /SiH ₄ must be
100000ppm. Next, an apparatus (glow discharge apparatus) that can be used to manufacture a photoreceptor according to the present invention will be described with reference to FIG. In the vacuum chamber 12 of this apparatus 11, the substrate 1 is fixed on a substrate holder 14, and the substrate 1 can be heated to a predetermined temperature by a heater 15. A high frequency electrode 17 is arranged opposite to the substrate 1, and a glow discharge is generated between the high frequency electrode 17 and the substrate 1. In addition, 20, 21, 22, 23, 24, 27, 28,
29, 30, 35, 36, 38 are each valve, 31
is a source of SiH ₄ or a gaseous silicon compound, 3
2 is a source of CH ₄ or gaseous carbon compounds, 33 is a source of CH 4 or gaseous carbon compounds;
Carrier gas source such as Ar or _H2 , 34 is 1%
Argon diluted diborane gas or phosphine source. In this glow discharge device, first, the surface of a support, for example, an Al substrate 1, is cleaned and then placed in a vacuum chamber 12, and the valve 36 is adjusted so that the gas pressure in the vacuum chamber 12 is 10 ^-6 Torr. Then, the substrate 1 is heated and maintained at a predetermined temperature, for example, 200°C. Then SiH ₄ or gaseous silicon compound, phosphine gas or diborane gas, and high purity inert gas as carrier gas,
A mixed gas obtained by diluting an appropriate amount of CH ₄ or a gaseous carbon compound is introduced into the vacuum chamber 12, and high frequency power is applied by the high frequency power source 16 under a reaction pressure of 0.01 to 10 Torr. As a result, each of the above reaction gases is decomposed by glow discharge, and a-SiC:H containing hydrogen is deposited on the substrate 1 as the above layer 5. a-SiC: H layer 2, 3
Diborane gas may also be supplied during formation. By appropriately adjusting the flow rate ratio of silicon compound and carbon compound and substrate temperature, a-Si ₁ -xCx having a desired composition ratio and optical energy gap:
It is possible to precipitate H (for example, up to x of about 0.9), and to deposit a-SiC:H at 1000 Å/
It is possible to deposit a-SiC:H at a rate of min or more. Furthermore, in order to deposit a-Si:H (photosensitive layer 4 above), the silicon compound may be decomposed by glow discharge, together with diborane if necessary, without supplying the carbon compound. In this case 10 ¹⁰
A photoconductive layer with a high resistance and a dark resistivity of Ω-cm or more can be obtained. It is necessary that each of the above a-SiC:H layers contain hydrogen, but if they do not contain hydrogen, the charge retention characteristics of the photoreceptor will not be practical. Therefore, the hydrogen content is 1~
It is desirable to set it to 40 atomic% (even 10 to 30 atomic%). The hydrogen content in the photoconductive layer 3 is essential to compensate for dangling bonds and improve photoconductivity and charge retention properties, and is usually 1 to 40 atomic%, and 3.5 to 20 atomic%. It is more desirable to have one. FIG. 9 shows a vapor deposition apparatus used for producing a photoreceptor according to the present invention by a vapor deposition method. The bell jar 41 is connected to a vacuum pump (not shown) via an exhaust pipe 43 having a butterfly valve 42.
The inside of the bell gear 41 is thereby brought into a high vacuum state of, for example, 10 ^-3 to 10 ^-7 Torr, and the substrate 1 is placed inside the bell gear 41 and heated to a temperature of 150 to 500° C., preferably, by a heater 45. is 250
While heating to ~450°C, the DC power supply 46 applies 0 to -10KV, preferably -1 to -6KV to the substrate 1.
While applying a negative direct current voltage of , and introducing active hydrogen and hydrogen ions into the bell gear 41 from a hydrogen gas discharge tube 47 whose outlet is connected to the bell gear 41 so that its outlet faces the substrate 1, the substrate 1 is heated. The silicon evaporation source 48 and the aluminum or antimony evaporation source 49, which are provided to face each other, are heated, and the shutters S above each are opened to evaporate silicon and aluminum or antimony at an evaporation rate such that the evaporation rate ratio is, for example, 1:0.01 to 0.2. methane gas activated by a discharge tube 50 is introduced into the bell gear 41, thereby forming an a-SiC:H layer 5 containing a predetermined amount of aluminum or antimony (see FIGS. 1 and 2). ) to form. When forming the a-SiC:H layers 2 and 3, B ₂ H ₆ is supplied as necessary. When forming the a-Si:H layer 4, the supply of methane gas may be stopped. For example, the structure of the discharge tubes 47 and 50 described above is shown for the discharge tube 47. As shown in FIG. , discharge space 6
3, a discharge space member 64 made of, for example, cylindrical glass
and another ring-shaped electrode member 66 having an outlet 65 provided at the other end of this discharge space member 64, and a DC or AC voltage is applied between the one electrode member 62 and the other electrode member 66. For example, hydrogen gas supplied through the gas inlet 61 causes a glow discharge in the discharge space 63, whereby active hydrogen consisting of hydrogen atoms or molecules activated by electron energy and ionized hydrogen are generated. Ions are discharged from the outlet 65. The discharge space member 64 in this illustrated example has a double pipe structure and is configured to allow cooling water to flow therethrough, and 67 and 68 indicate a cooling water inlet and an outlet. 6
9 is a cooling fin for one electrode member 62. The distance between the electrodes in the hydrogen gas discharge tube 47 is 10 to 15 cm, and the applied voltage is 600V in the discharge space 6.
The pressure in No. 3 is said to be about 10 ^-2 Torr. Note that when forming each layer using this vapor deposition apparatus, the amount of evaporation of aluminum is 100 to 100% that of silicon even when forming the a-SiC:H layer 5.
The amount of evaporation of antimony is preferably 100 to 10,000 ppm relative to silicon. Next, each layer of the photoreceptor according to the present invention will be explained in more detail. Charge Transport Layer This a-SiC:H layer 2 has the functions of both potential retention and charge transport, has a dark resistivity of 10 ¹³ Ω-cm or more, has high electric field resistance, and has a thickness per unit film thickness. Since the potential held by the photosensitive layer 4 is high and the electrons or holes injected from the photosensitive layer 4 exhibit large mobility and lifetime, the charge carriers are efficiently transported to the support 1 side.
Further, since the size of the energy gap can be adjusted by changing the composition of carbon, charge carriers generated in response to light irradiation in the photosensitive layer 4 can be injected efficiently without creating a barrier. Moreover, a-SiC:H also has the property of good adhesion and film formation with the support 1, for example, an Al electrode.
This a-SiC:H layer 2 maintains a high surface potential at a practical level and efficiently and quickly transports the charge carriers generated in the a-SiC:H layer 4, resulting in a photoreceptor with high sensitivity and no residual potential. There is work. In order to achieve these functions, a-SiC:H layer 2
The film thickness is, for example, 2 μm to 80 μm (or even 5 μm) in order to apply the Carlson dry phenomenon method.
~20 μm) is desirable. This film thickness is 2μ
If it is less than 80 μm, the surface potential necessary for development will not be obtained because it is too thin, and if it exceeds 80 μm, the surface potential will become high and the peelability of the attached toner will be poor, and the carrier of the two-component developer will also adhere. Resulting in. However, even if the film thickness of this a-SiC:H layer is made thinner (for example, 10-odd μm) than that of the Se photoreceptor, a surface potential at a practical level can be obtained. Transition Layer As mentioned above, this a-SiC:H layer 3 acts as a transition layer for smooth carrier movement, and has the effect of reducing the band gap between the layers through which the carrier moves.
It facilitates bonding between SiC:H and a-Si:H and improves the bonding characteristics. The thickness of the a-SiC:H layer 3 is 50 Å to 2 μm (and
500 Å to 1 μm), but if it is less than 50 Å, it will be difficult to separate the a-SiC:H layer 2 and the a-Si:H layer 4 with the profile described above, and
If it exceeds 2 μm, it is not practical. In addition,
This transition layer may be formed of a stack of a plurality of a-SiC:H layers as required, and the energy level described above may be changed in multiple steps. Blocking layer This layer 5 forms an energy gap with the substrate that can sufficiently block the injection of carriers (holes) from the substrate 1, so it eliminates the charge neutralization phenomenon caused by carrier injection and It functions to maintain the electric potential and, in turn, maintain good charging characteristics. For this reason, it is important that the a-SiC:H layer 5 is doped with impurities to become N ⁺ type or P type as described above. In addition, the film thickness is 50Å to 1μ.
m (more preferably 400 Å to 5000 Å).
If it is less than 50 Å, there is no effect, and if it exceeds 1 μm, the potential retention property tends to deteriorate. Also, the carbon content of this blocking layer may be the same as that of the a-SiC:H layer 2. a-Si:H layer (photoconductive layer or photosensitive layer) This a-Si:H layer 4 has high photoconductivity for visible light and infrared light.
ρ _D /ρ _L (dark resistivity/
The resistivity (when irradiated with light) reaches a maximum of ~ ¹⁰⁴ . This a
By using -Si:H as a photosensitive layer, it is possible to create a photoreceptor that is highly sensitive to light in the entire visible region and in the infrared region. In order to absorb visible light and infrared light without waste and generate charge carriers, the thickness of the a-Si:H layer 4 is desirably 2500 Å to 10 μm (more preferably 5000 Å to 5 μm). If the film thickness is less than 2500 Å, all of the irradiated light will not be absorbed and some of it will be absorbed by the underlying a
-SiC: Since it reaches the H layer 2, the photosensitivity decreases significantly. Further, the a-Si:H layer 4 does not need to be thicker than the thickness necessary for light absorption as a photosensitive layer.
A thickness of 10 μm is sufficient. Surface Modification Layer This surface modification layer 6 (see FIG. 2) is preferably provided in order to modify the surface of the photoreceptor and make the a-Si photoreceptor practically excellent. That is,
This enables the basic operations of an electrophotographic photoreceptor: charge retention on the surface and attenuation of the surface potential due to light irradiation. Therefore, the repetitive characteristics of charging and optical attenuation are very stable, and good potential characteristics can be reproduced even if left for a long period of time (for example, one month or more). On the other hand, in the case of a photoreceptor having an a-Si:H surface, it is easily affected by humidity, air, ozone atmosphere, etc., and the potential characteristics change significantly over time. In addition, the surface-modified layer made of inorganic material such as a-SiC:H has high surface hardness, so it is resistant to abrasion during processes such as development, transfer, and cleaning. A process that applies heat can be applied.
As the above surface modified layer, SiO, SiO ₂ , Al ₂ O ₃ ,
_Ta2O5 , _CeO2 , _ZrO2 , _TiO2 , _MgO , ZnO,
PbO, SnO ₂ MgF ₂ , ZnS, amorphous silicon carbide, and amorphous silicon nitride (however, it is preferable that these amorphous silicon compounds contain the above-mentioned hydrogen or fluorine, but they do not necessarily need to contain them. It is possible to use at least one selected from the group consisting of: It has been found that when this surface modified layer is formed of a-SiC:H, it is also important to select the carbon composition. If the composition ratio is expressed as a-Si ₁ -xCx:H, x should be 0.4 or more, especially 0.4≦x≦0.9 (carbon atom content is between 40 atomic% and 90 atomic%).
%) is desirable. That is, if 0.4≦x, the optical energy gap is approximately 2.3 eV or more, and it is substantially photoconductive to visible and infrared light (where ρ _D is the resistivity in the dark, ρ _L is the resistivity at the time of light irradiation, and the smaller ρ _D /ρ _L is, the lower the photoconductivity. (charge generation layer)
It will reach 4. Conversely, if x<0.4,
A portion of the light is absorbed by the surface layer 6, and the photosensitivity of the photoreceptor tends to decrease. Furthermore, if x exceeds 0.9, most of the layer becomes carbon, and not only the semiconductor properties are lost, but also the deposition rate when forming the a-SiC:H film by the glow discharge method decreases, so x≦0.9 It is better to The thickness of this surface modified layer 6 is 50 Å.
~1 μm (preferably 400 Å to 5000 Å) is sufficient; if it is less than 50 Å, it will be difficult for the surface to be charged by the tunnel effect, causing dark decay and a decrease in photosensitivity; if it exceeds 1 μm, the residual potential will increase. becomes high, and the photosensitivity tends to decrease. In the example explained above, in order to compensate for dangling bonds, fluorine is introduced into a-Si instead of H or in combination with H, and a-Si:F, a-Si:H:F, a-SiC:
F, a-SiC:H:F can also be used. In this case, the amount of fluorine is preferably 0.01 to 20 atomic%, and 0.5
~10 atomic% is more desirable. The above-mentioned manufacturing method is based on a glow discharge decomposition method or a vapor deposition method, but the photoreceptor can also be manufactured by a sputtering method, an ion plating method, or the like. In addition to SiH ₄ , the reaction gas used can be Si ₂ H ₆ , SiHF ₃ or its derivative gas, and lower hydrocarbon gases other than CH ₄ such as C ₂ H ₆ and C ₃ H ₈ . Further, as impurities to be doped, other than the above-mentioned boron and aluminum, other Group A elements of the periodic table such as gallium and indium, and Group VA elements such as arsenic in addition to phosphorus and antimony can be used. Next, an example in which the present invention is applied to an electrophotographic photoreceptor will be specifically described. Example 1 An electrophotographic photoreceptor having the structure shown in FIG. 1 or 2 was prepared on an Al support by a glow discharge decomposition method.
First, a clean Al support with a smooth surface was placed in a reaction (vacuum) chamber of a glow discharge device. After evacuating the reaction tank to a high vacuum level of 10 ^-6 Torr and heating the support to 200°C, high-purity Ar gas was introduced.
A high-frequency power with a frequency of 13.56 MHz and a power density of 0.04 W/cm ² was applied under a back pressure of 0.5 Torr, and a preliminary discharge was performed for 15 minutes. Next, a reaction gas consisting of SiH ₄ and CH ₄ is introduced, and a mixed gas (Ar + SiH ₄ + CH ₄ ) with a flow rate ratio of 3:1:0.2 to 4 and PH ₃ or B ₂ H ₆
By glow discharge decomposition of gas, a-SiC:H layer that prevents carrier injection, as well as a-SiC:H layer and transition layer that play potential holding and charge transport functions, are formed at a deposition rate of 350 Å/min. did. After the reaction tank is once evacuated, CH ₄ is not supplied and SiH ₄ and, if necessary, B ₂ H ₆ are discharge decomposed using Ar as a carrier gas, and boron-doped a-
After forming the Si:H photosensitive layer, a surface modification layer was further provided to complete the electrophotographic photoreceptor. The photoconductor produced in this way is coated with each polarity.
When a 6KV corona discharge was performed, the surface was charged to a negative or positive potential. After 6 seconds of dark decay,
The surface potential attenuated almost linearly with 1 lux light irradiation. At this time, the half-decreased exposure amount was small, there was almost no residual potential, and the charging/exposure repetition characteristics were also very good. Comparative Example 1 In Example 1, samples without a transition layer were prepared. All of these samples had large dark decay, increased half-exposure, low maximum image density, and insufficient sensitivity during image formation. Performance tests were conducted on the photoreceptor according to the present invention and the comparative photoreceptor (both manufactured using the glow discharge method) using an electrometer manufactured by Kawaguchi Electric Co., Ltd. and a modified U-BixV-2 machine, and the results are shown in the table below.

【table】

[Table] In this table, the image quality evaluation is as follows. ◎ High density and very good image quality. 〇 High density and good image quality. △ Density is slightly low and image quality is slightly poor. × Low density and very poor image quality. In the above table, V in the electrostatic characteristics is the initial charging potential, and ΔV/V is the dark decay rate of the charge 6 seconds after the end of charging. From these results, the photoreceptor according to the present invention has high sensitivity, sufficient charging potential, low dark decay rate and residual potential, and good copy image quality.
It was found that clear, high-density images could be obtained. On the other hand, it can be seen that the comparative example has poor photosensitivity, potential, and dark decay, and is also significantly inferior in copy image quality.

[Brief explanation of drawings]

The drawings illustrate the present invention, and FIGS. 1 and 2 are partial cross-sectional views of two examples of electrophotographic photoreceptors, and FIG. 3 is a cross-sectional view of a-SiC:H according to carbon content.
Figures 4 and 5 are energy band diagrams of the photoreceptor, Figures 6 and 7 are graphs showing changes in dark resistivity depending on the flow rate ratio of the reactant gas, and Figure 8 is a graph showing the energy gap of the photoreceptor. FIG. 9 is a schematic cross-sectional view of the vapor deposition apparatus, and FIG. 10 is a cross-sectional view of the discharge section. In addition, in the symbols shown in the drawings, 1...
... Support (substrate), 2 ... Charge transport layer, 3 ... Transition layer, 4 ... Photosensitive layer (photoconductive layer), 5 ... Blocking layer, 6 ... Surface modification layer, 11 ... Glow discharge Apparatus, 17... High frequency electrode, 31... Gaseous silicon compound supply source, 32... Gaseous carbon compound supply source, 33... Carrier gas supply source, 34...
B ₂ H ₆ or PH ₃ supply source, 41... vapor deposition tank, 47,
50...discharge part, 48...silicon evaporation source, 49
...It is an aluminum or antimony evaporation source.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a laminate in which at least a charge transport layer and a charge generation layer are sequentially laminated on a substrate, wherein an optical band gap between the charge transport layer and the charge generation layer is provided. at least
0.3 eV, and one or two transition layers having a uniform composition are provided between the charge transport layer and the charge generation layer, thereby providing a transition layer between the charge transport layer and the charge generation layer. The optical band gap between each layer is set to be 0.3 eV or less, and the charge transport layer has a carbon atom content of 15 to 15.
70 atomic%, and the hydrogen atom content is 1~
40 atomic% and a thickness of 2 to 80 μm of amorphous hydrogenated and/or fluorinated silicon carbide, the transition layer having a carbon atom content of 5 to 65 atomic%.
%, the hydrogen atom content is 1 to 40 atomic %, and the charge generation layer is made of amorphous hydrogenated and/or fluorinated silicon carbide having a thickness of 50 Å to 2 μm, and the charge generation layer has a hydrogen atom content of 1 to 40 atomic %.
40 atomic% and a thickness of 2500 Å to 10 μm, an electrophotographic photoreceptor comprising amorphous hydrogenated and/or fluorinated silicon.