JPS63292145A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body not deteriorated in the mobility of carriers and life by increasing film thickness and good in electric chargeability to both polarities by alternately laminating 2 kinds of thin films different in optical band gap from each other to form a barrier layer of superlattice structure. CONSTITUTION:The photosensitive body is obtained by laminating on a conductive supporting body 1 the barrier layer 2 and on this layer a photoconductive layer 3, and further on this a surface layer 4, and the barrier layer 2 is composed of a superlattice structure 5 of 2 kinds of thin semiconductor films one of both containing conductivity governing element, such as an element of III or V of the periodic table, and an overlaid superlattice structure 6 of 2 kinds of thin semiconductor films, thus permitting the obtained electrophotographic sensitive body to be low in residual potential, high in sensitivity in a wide wavelength region up to the near infrared region, and good in adhesion between the barrier layer 2 and the conductive substrate, and chargeability to both polarities.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides an electrophotographic method that has excellent charging characteristics, dark decay characteristics, photosensitivity characteristics, environmental resistance, etc., and is capable of being charged both positively and negatively. Regarding photoreceptors.

(Prior art) Amorphous silicon (hereinafter referred to as a) containing hydrogen (H)
-3i:H) has recently attracted attention as a photoelectric conversion material, and has been applied to photoreceptors in electrophotographic processes as well as solar cells, thin film transistors, image sensors, and the like.

Conventionally, CdS, znO9Se, or S has been used as a material constituting the photoconductive layer of an electrophotographic photoreceptor.

-Inorganic materials such as To or poly-N-vinylcarbazole (PVCz or trinitrofluorenone (TN)
Organic materials such as F) were used.

However, compared to these inorganic or organic materials, a-Sl:H is a non-polluting substance, so there is no need for recovery treatment, and it has high spectral sensitivity in the visible light region.
It also has advantages such as high surface hardness and excellent wear resistance and impact resistance. Therefore, a-3i:H
is attracting attention as a photoreceptor for electrophotographic processes.

This a-Sl:H is being studied as a photoreceptor material based on the Carlson method, but in this case, the photoreceptor is required to have high resistance and photosensitivity. However, since it is difficult to satisfy both of these characteristics with a single photoreceptor, the light guide 'r! These requirements are satisfied by providing a layered structure in which a barrier layer is provided between the first layer and the conductive support, and a surface charge retention layer is provided on the photoconductive layer.

(Problems to be Solved by the Invention) Conventionally, a high-resistance insulating single layer has been used as a barrier layer, but when such a barrier layer is thick, it separates from the photoconductive layer to the support. Carriers flowing to the barrier layer cannot pass through the barrier layer, and as a result, the residual potential becomes high. On the other hand, if the film is thin, dielectric breakdown will occur due to the development bias. In addition, when a p-type or n-type semiconductor is used as a barrier layer, if the film is thick, carriers will be trapped in structural defects such as dangling bonds, resulting in a high residual potential, whereas if the film is thin, the residual potential will be high. In this case, it is not possible to block the carrier from the support, and the charging ability decreases.

On the other hand, for purposes such as two-color copying and dual use as a printer and a copy, a photoreceptor that can be charged both positively and negatively is desired. When such a photoreceptor is formed of amorphous silicon, it is conceivable to add oxygen to the amorphous silicon or to provide an insulating layer between the photoconductive layer and the support. However, in the former case, the addition of oxygen increases film defects and deteriorates sensitivity, residual potential, etc. In the latter case, if the insulating layer is thick, carriers will be trapped and the residual potential will increase, whereas if it is thin, dielectric breakdown will occur during image development, which is not preferable.

The present invention has been made in view of such circumstances, and
Excellent charging ability, low residual potential, high photosensitivity over a wide wavelength range up to the near-infrared region, good adhesion to the substrate, excellent environmental resistance, and good charging performance in both positive and negative charging. The purpose of the present invention is to provide an electrophotographic photoreceptor having the following functions.

[Structure of the Invention] (Means for Solving the Problems) As a result of various studies, the present inventors have found that the above object can be achieved by using a superlattice structure as a barrier layer of an electrophotographic photoreceptor. This discovery led to the completion of the present invention.

That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor comprising an electrically conductive support, a photoconductive layer, and a barrier layer, wherein the barrier layer is a semiconductor thin film containing atoms that control the conductivity type. A laminate formed by alternately laminating intrinsic semiconductor thin films, and a laminate formed by alternately laminating semiconductor thin films and intrinsic semiconductor thin films formed on this laminate and containing atoms of a conductivity type different from that of the semiconductor thin film. The present invention provides an electrophotographic photoreceptor that can be charged both positively and negatively.

In the electrophotographic photoreceptor of the present invention, the element controlling the conductivity type contained in the semiconductor film constituting the barrier layer is, for example, an element belonging to Group I or Group V of the periodic table. The content of these elements is preferably 10-3 to 1 atomic %, more preferably 10'2 to 10-1 atomic %.

The semiconductor thin film in the present invention can be made of a-81 or microcrystalline silicon (μc-8i).

Microcrystalline silicon (μc-3i) is thought to be formed from a mixed phase of microcrystalline silicon and amorphous silicon with a grain size of approximately several tens of angstroms, and has the following physical properties. are doing.

First, X-ray diffraction measurements show a crystal diffraction pattern with 2θ in the vicinity of 28 to 28.5°, which is clearly distinguishable from amorphous a-3t in which only a halo appears. Second, μc-
The dark resistance of Si can be adjusted to 1010 Ω or more, and it can be clearly distinguished from polycrystalline silicon, which has a dark resistance of 10 5 Ω.

The optical node gap (Eg'') of the μc-81 used in the present invention is preferably set to, for example, 1.55eV.However, it can be set arbitrarily within a certain range.A desired Eg can be obtained. Therefore, it is preferable to add a predetermined amount of hydrogen to each of them and use them as μc-Si:H.This compensates for the dangling bonds of silicon,
Dark resistance and bright resistance are balanced, and photoconductive properties are improved.

(Function) In the electrophotographic photoreceptor of the present invention, since the barrier layer is provided with the superlattice structure, carriers generated in this region have a long lifetime and a high mobility. Although the theory has not yet been fully established, there is no doubt that this is a quantum effect due to the periodic well potential characteristic of the superlattice structure, and this is particularly referred to as the superlattice effect.

In this way, the mobility of carriers in the barrier layer increases and the lifetime of the carriers increases, resulting in a marked improvement in the sensitivity of the electrophotographic photoreceptor.

(Example) FIG. 1 is a diagram showing a cross-sectional structure of an electrophotographic photoreceptor according to an example of the present invention. In the figure, conductive support 1
A barrier layer 2 is formed on top of the barrier layer 2, and a light guiding layer 3 is formed thereon. Further, a surface layer 4 is formed on the photoconductive layer 3.

Hereinafter, the structure of the electrophotographic photoreceptor shown in FIG. 1 will be explained in more detail.

The conductive support 1 usually consists of a drum made of aluminum.

The barrier layer 2 is composed of a superlattice structure 5 of two types of semiconductor thin films and a superlattice structure 6 of two other types of semiconductor thin films formed thereon. One of the two types of semiconductor thin films constituting one of the superlattice structures 5 contains atoms that govern the conductivity type, for example, atoms belonging to Group I or Group V of the periodic table. Examples of elements belonging to Group Ⅰ of the periodic table include boron B, aluminum Ai, gallium Ga, indium Ins, and thallium TI. Furthermore, examples of elements belonging to Group V of the periodic table include nitrogen, phosphorus P1 arsenic Ass antimony Sb1, and bismuth B1. One of the two types of semiconductor thin films constituting the other superlattice structure 6 contains atoms of a conductivity type different from that of the semiconductor thin film. The semiconductor thin film constituting the barrier layer can be made of .mu.c-3l or a-Sl, and hydrogen can be added thereto (.mu.c-Sl:H, a-Si:H). The thickness of the barrier layer 2 is preferably 100 to 10 μm.

The barrier layer 2 is formed in order to suppress the flow of charges between the conductive support 1 and the photoconductive layer 3, thereby increasing the charge retention function of the photoreceptor surface and increasing the charging ability of the photoreceptor. It is something. Therefore, when forming a Carlson type photoreceptor using a semiconductor layer as a barrier layer, the barrier layer 2 must be made of
type or N type. That is, when the surface of the photoreceptor is positively charged, the barrier layer 2 is made of P type to prevent electrons that neutralize the surface charge from being injected into the photoconductive layer. Conversely, when the surface is negatively charged, the barrier layer 2 is made of N type to prevent holes that neutralize the surface charge from being injected into the photoconductive layer. Since the carriers injected from the barrier layer 2 become noise with respect to the carriers generated in the photoconductive layer 3 upon incidence of light, preventing carrier injection as described above improves the sensitivity.

The photoconductive layer 3 generates carriers when light is incident thereon. Among these carriers, carriers of one polarity neutralize the charges on the surface of the photoreceptor, and carriers of the other polarity travel within the photoconductive layer 3 and become conductive. The sexual support 1 is reached.

The photoconductive layer 3 is pc-5i:H%a-81:H
It can be configured by Further, the photoconductive layer 3 may contain atoms belonging to Group Ⅰ or Group V of the periodic table. Furthermore, the photoconductive layer 3 may contain at least one selected from carbon, oxygen, and nitrogen.

The hydrogen content in a-81:H and μc-Sl:H constituting the barrier layer 2 and the photoconductive layer 3 is 0, O1~
30 atom % is preferable, and 1 to 25 atom % is more preferable. Such hydrogen content compensates for the dangling bonds of silicon, brings the dark resistance and bright resistance into balance, and improves the photoconductive properties.

a-51: To form the H layer by the glow discharge decomposition method, silane gases such as SiH4 and 512H6 are introduced into the reaction chamber as raw materials, and H is added into the thin film by glow discharge using high frequency. Can be done. If necessary, hydrogen or helium gas can be used as a carrier gas for silanes. On the other hand, SiF4 gas and Sl
Silicon halide such as ci4 gas can be used as the source gas. Furthermore, a-8i:H containing H can be similarly formed by reacting with a mixed gas of silane gas and silicon halide gas. Note that these thin films can be formed not only by the glow discharge decomposition method but also by a physical method such as sputtering.

Similarly to a-5t:H, the μc-81 layer can also be formed using silane gas as a raw material by the high-frequency glow discharge decomposition method. In this case, the temperature of the support is a-8t;
The high frequency power is set higher than when forming H, and the high frequency power is also a-
If it is set higher than the case of Sl:H, μc-Sl:H
becomes easier to form. Furthermore, by increasing the support temperature and high frequency power, the flow rate of source gas such as silane gas can be increased, and as a result, the film formation rate can be increased. In addition, SiH4 and Si of the raw material gas
By using a gas obtained by diluting a high-order silane gas such as 2H6 with hydrogen, μC-5i:H can be formed with higher efficiency.

In order to make the μc-8i:H and a-8i:HIp types, elements belonging to Group 1 of the periodic table, such as boron B1
Aluminum AI, Gallium Gas Indium In
, thallium TI, etc., and in order to make μc-8l:H and a-8i:H n-type, an element belonging to Group V of the periodic table, such as nitrogen N1
Phosphorus P1 Arsenic Ass Antimony Sb1 and Bismuth B1
It is preferable to dope. 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, μc-8
1:H and a-3i:H, carbon C1 nitrogen N and oxygen O
By containing at least one element selected from the following, high resistance can be achieved and the surface charge retention ability can be increased.

A surface layer 4 is provided on the photoconductive layer 3.

Since μc-St:H and the like constituting the photoconductive layer 3 have a relatively large refractive index of 3 to 3.4, light reflection easily occurs on the surface. When such light reflection occurs, the ratio of the amount of light absorbed by the photoconductive layer decreases, resulting in increased light loss.For this reason, it is preferable to provide the surface layer 4 to prevent reflection. By providing the surface layer 4, the photoconductive layer is protected from damage.Furthermore, by forming the surface layer, the charging ability is improved and the charge is better placed on the surface.Formation of the surface layer The material to be used is a-8IN:
These include inorganic compounds such as H, a-3I O:H, and a-3IC:H, and organic materials such as polyvinyl chloride and polyamide.

When the surface of the electrophotographic photoreceptor constructed in this manner is charged with a positive voltage of about 500 V by corona discharge, a potential barrier is formed. When light (hv) is incident on this photoreceptor, carriers of electrons and holes are generated in the photoconductive layer 3. Electrons in the conduction band are accelerated toward the surface layer 4 side, and holes are accelerated toward the conductive support 1 side by the electric field in the photoreceptor. In this case, if a conventional barrier layer consisting of a single high-resistance insulating layer is used, as mentioned above, if the film is thick, carriers flowing from the photoconductive layer to the support cannot pass through the barrier layer. , the residual potential becomes high. On the other hand, if the film is thin, dielectric breakdown will occur due to the development bias. In addition, when a p-type or n-type semiconductor is used as a barrier layer, if the film is thick, carriers will be trapped in structural defects such as dangling bonds, resulting in a high residual potential, whereas if the film is thin, the residual potential will be high. In this case, the carriers in the support cannot be blocked, resulting in a decrease in charging ability. On the other hand, when the barrier layer has a superlattice structure as in the photoreceptor of the present invention, in the potential well layer, due to quantum effects, compared to the case of a single layer without a superlattice structure,
Carrier life is 5 to 10 times longer. Furthermore, in a superlattice structure, a periodic barrier layer is formed due to bandgap discontinuity, but carriers easily pass through the bias layer due to the tunnel effect, so the effective carrier mobility is equal to the bulk mobility. The carrier has excellent running performance.

As described above, the superlattice structure in which thin films with different optical band gaps are laminated can provide high photoconductivity and provide clearer images than conventional photoreceptors.

Referring to FIG. 2, an apparatus and a manufacturing method for manufacturing the electrophotographic photoreceptor of the above embodiment by a glow discharge method will be described below. In the figure, gas cylinders 21, 22, 23.
24, for example, SI H4, B2 Is, H2
A raw material gas such as 1CH4 is contained. The gas in these gas cylinders is controlled by a valve 26 and piping 27 for adjusting the flow rate.
The water is supplied to the mixer 28 via the mixer 28. A pressure gauge 25 is installed in each cylinder, and the pressure gauge 25
mixer 2 by adjusting valve 26 while monitoring
The flow rate and mixing ratio of each raw material gas supplied to 8 can be adjusted. The gases mixed in the mixer 28 are supplied to a reaction vessel 29. A rotating shaft 30 is attached to the bottom 31 of the reaction vessel 29 so as to be rotatable around the vertical direction. At the upper end of the rotating shaft 30, a disk-shaped support base 32 has its surface aligned with the rotating shaft 3.
It is fixed perpendicular to 0. Inside the reaction vessel 29,
A cylindrical electrode 33 is installed on the bottom 31 with its axial center aligned with the axial center of the rotating shaft 30.

A drum base 34 of a photoreceptor is placed on a support base 32 with its axial center aligned with the axial center of the rotating shaft 30, and a heater 3 for heating the drum base is installed inside the drum base 34.
5 are arranged. A high frequency power source 36 is connected between the electrode 33 and the drum base 34, so that a high frequency current is supplied between the electrode 33 and the drum base 34. The rotating shaft 30 is rotationally driven by a motor 38. The pressure inside the reaction vessel 29 is monitored by a pressure gauge 37,
The reaction vessel 29 is connected via a gate valve 38 to a suitable exhaust means such as a vacuum pump.

When manufacturing a photoreceptor using the above-mentioned manufacturing apparatus, the drum base 34 is placed in the reaction container 29, and then the gate valve 39 is opened to exhaust the inside of the reaction container 29 to a pressure of about 0.1 orr or less. Next, cylinders 21, 22, 23.
24, the required reaction gases are mixed at a predetermined mixing ratio and introduced into the reaction vessel 29.

In this case, the flow rate of the gas introduced into the reaction container 29 is such that the pressure inside the reaction container 29 ranges from 0.1 to 1.0. Set it so that it is Oorr. Next, the motor 38 is operated to rotate the drum base 34, the heater 35 heats the drum base 34 to a constant temperature, and the high frequency power supply 36 supplies high frequency current between the electrode 33 and the drum base 34.
A glow discharge is formed between the two. As a result, a-8l, :H is deposited on the drum base 34. Note that N20. NH3, NO2, N2, CHa *C2
By using Ha, 02 gas, etc., these elements can be contained in a-Sl:H.

As described above, since the electrophotographic photoreceptor according to the present invention can be manufactured using a closed system manufacturing apparatus,
Safe for humans.

Next, the results of testing the electrophotographic properties of an electrophotographic photoreceptor according to the present invention formed into a film will be described.

Test Example 1 A diameter of 8C1+m, which was subjected to acid treatment, alkali treatment and sandblasting treatment to prevent interference as necessary.
A 350 am wide aluminum drum substrate was mounted within the reaction vessel and the reaction vessel was evacuated to a vacuum of approximately 10-5 Torr. The drum base was heated to 250°C, and while rotating at 10 rpm, 5 iHz gas was applied at 500 SCCM.SH2 gas was applied at 500 SCCM.

PH, gas was introduced into the reaction vessel at a flow rate ratio of 104 to 5IH4 gas, and the pressure inside the reaction vessel was set to 0.
It was adjusted to 8 Torr. And 13.5Ei M H
Plasma was generated by applying high frequency power of z to form a 50 n-type a-Sl thin film on the drum substrate. next,
The flow rate of PH3 gas was set to 0, and 50 i-type a-Si thin films were formed. By repeating these operations, a superlattice structure of 1,500 people was formed. Then add %B2H6 gas to 5IH
Introduced at a flow rate ratio of 5xlO' to 4 gas flow rates,
Fifty p-type a-Si thin films were formed. Next, B2H,
50 i type a-s with 0 gas! A thin film was formed.

By repeating this thin film forming operation, a superlattice structure of 1,500 people was formed. As a result, a barrier layer was formed.

Next, B2H6 gas is 1 x for 5IH4 gas flow rate
It was introduced at a flow rate of 10' to form a photoconductive layer of 30 μm.

Finally, a 0.5 μm surface layer consisting of a-3tC:H was formed.

When the surface of the photoreceptor thus formed is positively charged at about 500 μm and exposed to white light, this light is absorbed by the photoconductive layer and carriers of electron-hole pairs are generated. In this test example, a large number of carriers were generated, the carriers had a long life, and high running performance was obtained. This resulted in clear, high-quality images. In addition, when the photoreceptor manufactured in this test example was repeatedly charged, the reproducibility and stability of the transferred image were extremely good, and the durability such as corona resistance, moisture resistance, and abrasion resistance was also improved. It has been proven that the properties are excellent.

Test Example 2 n-type a-8iH constituting the initial superlattice structure of the barrier layer
A p-type a-9L film is formed instead of the film, and an n-type a-9I film is formed instead of the p-type a-8IH film that constitutes the second superlattice structure.
An electrophotographic photoreceptor was formed in the same manner as in Example 1 except that -81 film was formed.

When an image was formed using this photoreceptor in the same manner as in Test Example 1, a clear and high quality image was obtained.

Test Example 3 μc-S instead of i-type a-Si thin film constituting the barrier layer
An electrophotographic photoreceptor was produced in the same manner as in Test Example 1, except that a thin film was formed. μc-81 thin film is SiH
The flow rates of 4 gas and H2 gas are each 30SCCM,
600 SCCM, the pressure inside the reaction vessel was 1 Torr, and 1 kW of high frequency power was applied.

When an image was formed using this photoreceptor in the same manner as in Test Example 1, a clear and high quality image was obtained.

Test Example 4 P-type μc instead of p-type a-Si thin film constituting the barrier layer
An electrophotographic photoreceptor was produced in the same manner as in Test Example 1, except that -Sl thin film was formed and an n-type μC-9T thin film was formed instead of the n-type a-Si thin film. p-type μc-8t
For the thin film, the flow rate of 5IH4 gas is 30SCCM, the flow rate of H2 gas is 900SCCM, and the flow rate of B2o3 gas is SiH.
The flow rate ratio to the flow rates of the four gases was set to 10'2, and 1 kW of high frequency power was applied. Further, the n-type μc-81 thin film was formed by setting the flow rate of PH3 gas to the flow rate of 5IH4 gas at a flow rate ratio of 104 and applying 700 W of high frequency power.

When an image was formed using this photoreceptor in the same manner as in Test Example 1, a clear and high quality image was obtained.

Test Example 5 As shown in Test Example 4, p-type a-S+ constituting the barrier layer
forming a p-type μC-31 thin film instead of the thin film, and forming an n-type μC-8F thin film instead of the n-type A-8L thin film,
Further, as shown in Test Example 3, an electrophotographic photoreceptor was manufactured by forming a μc-Si thin film instead of the i-type a-Si thin film.

When an image was formed using this photoreceptor in the same manner as in Test Example 1, a clear and high quality image was obtained.

Above, we have explained the test example in which the superlattice structure of the barrier layer is composed of two types of thin films, but the invention is not limited to this, and three or more types of thin films may be laminated. Just form a boundary.

[Effects of the Invention] According to the present invention, a superlattice structure formed by stacking thin films with different optical band gaps is used for the barrier layer, so carrier mobility is high and the film thickness can be reduced. It is possible to obtain a photoreceptor having good charging ability in both positive and negative charging without deteriorating carrier mobility or life even if the thickness is increased.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an electrophotographic photoreceptor according to an embodiment of the present invention, and FIG. 2 is a diagram showing an apparatus for manufacturing an electrophotographic photoreceptor according to an embodiment of the invention. 1: Conductive support, 2: Barrier layer, 3: Photoconductive layer, 4: Surface layer.

Claims (1)

[Scope of Claims] (1) In an electrophotographic photoreceptor comprising a conductive support, a photoconductive layer, and a barrier layer, the barrier layer includes a semiconductor thin film containing atoms governing conductivity type and an intrinsic semiconductor thin film. A laminate formed by alternately laminating semiconductor thin films and intrinsic semiconductor thin films formed on this laminate and containing atoms of a conductivity type different from that of the semiconductor thin film. An electrophotographic photoreceptor that can be charged both positively and negatively. (2) The electrophotographic photoreceptor according to claim 1, wherein the barrier layer is made of amorphous silicon and/or at least a partially microcrystalline semiconductor. (3) The electrophotographic photoreceptor according to claim 1 or 2, wherein the thin film has a thickness of 30 to 500 Å. (4) Any one of claims 1 to 3, wherein the barrier layer contains at least one element selected from elements belonging to Group III or Group V of the periodic table.
The electrophotographic photoreceptor described in . (5) The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer is made of an amorphous material and/or a semiconductor material that is at least partially microcrystalline. (6) The electrophotographic photoreceptor according to claim 1 or 5, wherein the photoconductive layer contains at least one element selected from elements belonging to Group III or V of the periodic table. . (7) The photoconductive layer according to any one of claims 1 to 6, wherein the photoconductive layer contains at least one element selected from the group consisting of carbon, oxygen, and nitrogen. Electrophotographic photoreceptor. (8) The electrophotographic photoreceptor according to claim 1, further comprising a surface layer on the photoconductive layer.