JPS63241550A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body good in carrier transferability in a surface layer, long in carrier life, and superior in electric chargeability characteristics by using superlattice structure for the surface layer. CONSTITUTION:The electrophotographic sensitive body is composed of a conductive supporting body 1, a photoconductive layer 3, and the surface layer 4, and the surface layer 4 is formed by alternately laminating a first thin film of amorphous silicon and a thin film of microcrystalline silicon, and a second thin film of amorphous silicon containing at least one of C, O, and N, thus permitting the surface layer 4 to have superlattice structure, and accordingly, carrier life in the surface layer to be extended, carrier transferability to be enhanced, and sensitivity of the electrophotographic sensitive body to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electrophotographic photoreceptor having excellent charging characteristics, dark decay characteristics, photosensitivity characteristics, environmental resistance, etc.

[Conventional technology]

Amorphous silicon containing hydrogen (H) (hereinafter referred to as a)
-8i: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, materials constituting the photoconductive layer of electrophotographic photoreceptors include inorganic materials such as CdS, ZnO, Se, or 5e-Te, or polyvinylcarboxylate (PVC).
Organic materials such as linitrofluorenone (TNF) were used.

However, compared to these inorganic or organic materials, a-8i:H does not require recovery treatment because it is a non-polluting substance, has high spectral sensitivity in the visible light region, and has a high surface hardness. It has advantages such as excellent wear resistance and impact resistance. Therefore, a-8i:
H is attracting attention as a photoreceptor material for electrophotographic processes.

This a-8i2H is being studied as a material for a photoreceptor 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 layer, a barrier layer is provided between the photoconductive layer and the conductive support, and surface protection, antireflection, and surface protection are required. For the purpose of improving the performance, etc., such demands are satisfied by creating a laminated structure in which a surface layer is provided on the leading ttJ-.

[Problem that the invention seeks to solve]

By the way, conventionally, a-8iC1a-8i was used as the surface layer.
An insulating single layer made of N, a-8io, etc. is used, but this surface layer has many structural defects such as dangling bonds and voids, which may have an unfavorable effect on the photoreceptor characteristics. is giving. For example, when a photoreceptor is charged and irradiated with light, photocarriers are generated in the photoconductive layer. Among the photocarriers, holes travel toward the conductive support, and electrons travel toward the surface layer. In this case, 1
The 1IL electrons pass through the surface layer by tunneling effect and neutralize the charge on the surface of the photoreceptor. Therefore, if the surface layer O film thickness is thick, carriers cannot pass through the surface layer, resulting in poor sensitivity.
In addition, since the surface layer contains many defects as described above, carriers are dragged to the defects, resulting in an increase in residual potential. Furthermore, when light irradiation is performed in the first cycle, some of the carriers trapped in the surface layer travel toward the surface of the photoreceptor and neutralize the surface charge, resulting in a decrease in charging ability.

On the other hand, if the surface layer is thin (1), the surface potential of the photoreceptor decreases, creating a burden on the gross design of copying machines, printers, and the like.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an electrophotographic photoreceptor that has excellent charging ability, low residual potential, and high sensitivity.

[Structure of the invention]

(Means for Solving the Problems) As a result of various studies, the present inventors have discovered that the above object can be achieved by using a superlattice structure as the surface layer of an electrophotographic photoreceptor. , we have completed the present invention.

That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a conductive support, a photoconductive layer, and a surface layer, wherein the surface layer includes a first amorphous silicon thin film and a microcrystalline silicon thin film. It is characterized by being constructed by alternately stacking a thin film and a second amorphous silicon thin film containing at least one element selected from carbon, oxygen, and nitrogen.

Carbon and oxygen contained in the second amorphous silicon thin film,
The concentration of nitrogen is preferably from 0.1 to 4 o atoms, more preferably from 0.5 to 3 o atoms.

Microcrystalline silicon (μc-8i) used in the present invention
) is thought to be formed by a mixed phase of microcrystalline silicon and amorphous silicon each having a grain size of about several tens of angstroms, and has the following physical characteristics. 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-81 in which only a halo appears. Second, μc
The dark resistance of -8i can be adjusted to more than 1010 Ω, and it can be clearly distinguished from the polycrystalline silicon foil with a dark resistance of 10' Ω.

(Function) In the electrophotographic photoreceptor of the present invention, the surface layer has a superlattice structure, and the a-81 and μc
The lifetime of carriers in the -8i thin film is 5 to 10 times longer than that in the bulk layer due to quantum effects.Furthermore, due to the thin film thickness of the respective a-8i and μc-81 thin films, carriers are easily transported by tunneling effects. Since the carrier can pass through the a-8i and μc-8i thin films, the effective mobility of the carrier is equal to that in the bulk layer, that is, the carrier has excellent mobility.

As described above, the life of the carrier in the surface layer is long and the carrier has excellent running properties.

When the sensitivity of an electrophotographic photoreceptor is significantly improved, it becomes K.

(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, 1 is a conductive support. A barrier m2 is formed on the cough conductive support, and a photoconductive layer 3 is formed thereon. Furthermore, 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 detail.

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

Barrier layer 2 is p c −S i +a −S i :H
Alternatively, a-BN:H (amorphous boron to which nitrogen and hydrogen are added) may be used. Furthermore, an insulating film may be used. For example, pc-8
i:H or a-8i:HK By containing one or more elements selected from carbon C1 nitrogen N and oxygen O,
A high resistance insulating barrier layer can be formed. The thickness of the barrier layer 2 is preferably 100 A to 10 μm.

The barrier layer 2 is formed to suppress the flow of charges between the conductive support 1 and the photoconductive layer 3, and to enhance the charge retention function of the surface of the photoreceptor, thereby increasing the charging ability of the photoreceptor. It is something that will be done. 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 ffj2 is made 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. Nao, pc-8l :H+a-8l
:In order to make H type P, group ■Kll of the periodic table must be used!
Elements 1 such as boron B, aluminum 8! , gallium Ga, indium In, thallium TI, etc. are preferably doped. Also, μC-8i: H and a
-8i: To make H into N-type, K is an element belonging to Group V of the periodic table, such as nitrogen, phosphorus P, arsenic AS, antimony S
It is preferable to dope with B, bismuth B, or the like.

The photoconductive layer 3 formed on the barrier layer 2 has a -8i
:H or μc-8i:H).

Light guiding i! When light enters layer 1 3, carriers are generated, carriers of one polarity neutralize the charges on the surface of the photoreceptor, and carriers of the other polarity conduct photoconductivity N! I3 to reach the conductive support.

Light guide? A surface layer 4 is formed on the layer. surface layer 4
has a superlattice structure in which two types of a-8i:H thin films and μC-81:H thin films are alternately laminated. Since the a-8i:)1 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 proportion of the amount of light absorbed by the photoconductive layer 3 decreases, and light loss increases significantly. For this reason.

A surface f@4 is provided to prevent reflection.

Also, by providing the surface layer 4, the photoconductive layer 3 is protected from damage. Furthermore, when a surface layer is formed, the charging ability is improved, and the charge can be easily deposited on the surface.

a-8 constituting the barrier layer 2, photoconductive layer 3 and surface layer 4
The hydrogen content in i:Hl and pc-81:HK is preferably 0.01 to 30 atoms, more preferably 1 to 25 atoms. 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-8i: H layer is formed by glow discharge decomposition method. K is formed by introducing SiH and silane gases such as 8i, H, etc. into the reaction chamber as raw materials, and performing jiglow discharge using high frequency. H can be added to the thin layer. If necessary, hydrogen or helium gas can be used as a carrier gas for silanes. On the other hand, 8iF4 gas and 5t
Silicon halide such as C74 gas can be used as the source gas. Furthermore, a-8i:H containing KH can be similarly formed by reacting with a mixed gas of silane gas and 710 silicon oxide gas. Note that these thin layers can be formed not by the glow discharge decomposition method but also by a physical method such as sputtering.

Similarly to a-8i:H, the PC-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-8i:
When forming an H, the height is set high and the high frequency power is also
In the case of 3i:H, if the value is set high, μc-8i;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, the raw material gas 8iH4 and St
By using a high-order silane gas such as , H, etc. diluted with hydrogen, μC-8i:H can be formed with higher efficiency.

The surface of the electrophotographic photoreceptor constructed in this manner is charged with a positive voltage of approximately 500 V by corona discharge, and exposed to light (
hv), electron and hole carriers are generated in the photoconductive layer 3. Electrons in the conduction band are accelerated toward the surface layer 4 side by the electric field within the photoreceptor, and holes are accelerated toward the conductive support 1 side. In this case, if a conventional surface layer consisting of a single high-resistance insulating layer is used, as mentioned above, if the film is thick, the light guide M and the carriers flowing from the layer to the surface cannot pass through the surface layer. Sensitivity is poor,
Furthermore, carriers are trapped in defects such as dangling bonds, leading to an increase in residual potential. On the other hand, if the film thickness is too thin, the surface potential of the photoreceptor decreases (1), creating a burden on the process design of copying machines, grids, etc. On the other hand, when one surface layer has a superlattice structure as in the photoreceptor of the present invention, the lifetime of carriers in the potential well layer is shorter than that of a single layer without a superlattice structure due to quantum effects. It is 5 to 10 times longer. In addition, in a superlattice structure, a periodic barrier layer is formed due to discontinuity in the band gap, but carriers can easily pass through the bias layer due to the tunnel effect, so the effective mobility of carriers is The mobility is equivalent to that in bulk, and carrier mobility is excellent. As described above, the superlattice structure in which thin layers are laminated makes it possible to obtain high photoconductivity and to obtain clearer images than with conventional photoreceptors.

Referring to FIG. 3, 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, 5i) I, , B, I(,, H,
, CH4, and other raw material gases are contained therein. The gas in the gas cylinder is supplied through 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
By adjusting the pulp 26 while monitoring the mixer 2
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 the reaction chamber 429. A rotating shaft 30 is attached to the bottom 3) 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.
A heater 35 for heating the drum base is disposed inside the drum 4. There is a high frequency i between the electrode 33 and the drum base 34.
source 36 is connected, electrode 33 and drum base 3
A high frequency current is supplied between the two. The rotating shaft 3θ is rotationally driven by a motor 38. Reaction container 2
The pressure inside the reaction vessel 29 is monitored by a pressure gauge 37.
is connected to a suitable exhaust means such as a vacuum pumper via a gate pulp 38.

When manufacturing a photoreceptor using the above-mentioned manufacturing apparatus, after the drum base 34 is installed in the reaction container 29.

When the gate pulp 39 is opened, the inside of the reaction vessel 29 is approximately 0.1
The cylinder 21 is then evacuated to a pressure below TOrr.
Required reaction gases from 22, 23, and 24 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 vessel 29 is set so that the pressure within the reaction vessel z9 is 0.1 to 1.0 Torr.

Next, the motor j8 is operated to rotate the drum base 34, the heater 35 heats the υ drum base 34 to a constant temperature, and the high frequency power supply 36 applies a high frequency current between the stain pole 33 and the drum base 34. A glow discharge is formed between the two. From this point on, p is placed on the drum base 34.
c-8i: H+a-8i: H is deposited. Note that N, O, NH, , No, , N, , C are present in the raw material gas.
Nitrogen, carbon, and oxygen can be contained in μc-84:H by using H, , C, H, , O, gases, and the like.

In this way, the electrophotographic photoreceptor according to Jin's invention can be manufactured using a closed system manufacturing apparatus, so
Safe for humans.

Next, the results of forming a film on the electrophotographic photoreceptor according to the present invention and testing its electrophotographic properties will be explained.

Test Example 1 If necessary, to prevent interference, an aluminum drum base with a diameter of 89 u and a width of 350 tll, which has been subjected to acid treatment, alkali treatment, and sandblasting treatment, is installed in the reaction vessel, and the reaction vessel is approximately 10 The vacuum was evacuated to -1 Torr. While heating the drum base to 250°C and rotating it at 10 rpm, SiH, gas, 500 SCCM, B, H
, gas is introduced into the reaction vessel at a flow rate ratio of 10 to SiH gas, and the pressure inside the reaction vessel is set to l To
rr, apply high frequency power of 13.56MTIz to generate plasma, and place P type a-8i on the drum base.
A barrier layer made of HH was formed.

Next, SiH4 gas was introduced into the reaction chamber at 5 Q Q SCCM, H gas at 500 SCCM, B, H gas and SiH gas at a flow rate ratio of 101, and 300 W of high frequency power was applied to form a 20 μm i-type a. A photoconductive layer made of -8i:H was formed.

Next, 81H gas was introduced (3Q SCCM, CH gas was introduced at 3608CCM, H gas was introduced at 3Q -8fC:H thin film was formed. Next, CH and gas were changed to O, and H and gas were changed to 60f.
080CM, the pressure inside the reaction vessel is 1'l'or
r, and a high frequency power of 800 W was applied to form a 100 A μc-8iHH thin film. Next, the SiH gas was set to 2008CCM, and the pressure inside the reaction vessel was set to O18'po.
rr, and a high frequency power of 300 W was applied to form a 50 A a-8i:H thin film. By repeating this table operation, a surface layer with a superlattice structure of 2,000 people was formed.

When the surface of the photoreceptor thus formed is positively charged at approximately 500 μm and exposed to n beams of 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. has been proven to be superior.

Test Example 2 A-8 in place of the a-8iC:H thin film constituting the surface layer
An electrophotographic photoreceptor was manufactured in the same manner as in Test Example 1 except that an iN:H thin film was formed.

Note that the a-S i N :H thin film was obtained by introducing 45QSCCM N gas instead of CH4 gas.

The photoreceptor manufactured in this manner has high sensitivity even to long wavelength light of 780 to 79 Qnm, which is the oscillation wavelength of a semiconductor laser. When this photoreceptor was installed in a semiconductor laser printer and an image was formed by the Carlson process, a clear, high-resolution image could be obtained even when the exposure amount on the photoreceptor surface was 25 ergc+d.

When this photoreceptor was repeatedly charged, the transferred image had high reproducibility and stability, and had excellent durability such as corona resistance, moisture resistance, and abrasion resistance.

〔Effect of the invention〕

According to the present invention, since a superlattice structure is used in the surface layer, it is possible to obtain an electrophotographic photoreceptor that has good carrier mobility in the surface layer, has a long carrier life, and has excellent charging characteristics. can.

[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. DESCRIPTION OF SYMBOLS 1... Conductive support body, 2... Barrier layer, 3... Photoconductive layer, 4... Surface layer.

Claims (7)

[Claims] (1) In an electrophotographic photoreceptor having a conductive support, a photoconductive layer, and a surface layer, the surface layer is selected from a first amorphous silicon thin film, a microcrystalline silicon thin film, carbon, oxygen, and nitrogen. 1. An electrophotographic photoreceptor comprising a second amorphous silicon thin film containing at least one of the following elements: (2) The electrophotographic photoreceptor according to claim 1, wherein the thin film has a thickness of 30 to 500 Å. (3) The first amorphous silicon thin film and the microcrystalline silicon thin film contain at least one element selected from carbon, oxygen, and nitrogen. electrophotographic photoreceptor. (4) Any one of claims 1 to 3, wherein the surface layer contains at least one element selected from elements belonging to Group III or V of the periodic table. The electrophotographic photoreceptor according to item 1. (5) A barrier layer made of an amorphous semiconductor or at least a partially microcrystalline semiconductor is provided between the conductive support and the photoconductive layer. electrophotographic photoreceptor. (6) The electrophotographic photoreceptor according to claim 5, wherein the barrier layer contains at least one element selected from elements belonging to Group III or Group V of the periodic table. (7) The electrophotographic photoreceptor according to claim 5, wherein the barrier layer contains at least one of carbon, oxygen, and nitrogen.