JPS63187250A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance the traveling property of a carrier by alternately laminating thin amorphous Si films contg. >=1 kinds among C, O and N, thin amorphous Si films and thin amorphous Si films contg. Ge, thereby constituting a barrier layer. CONSTITUTION:The barrier layer 2, a photoconductive layer 3 and a surface layer 4 are successively laminated on a conductive base 1. The layer 2 is formed by alternately laminating the thin amorphous Si films contg. >=1 kinds among C, O, N, the thin amorphous Si films and the thin amorphous Si films contg. Ge. The thicknesses of the respective above-mentioned thin films are preferably 30-500Angstrom . The layer 2 is preferably made into a p- or n-type by implanting a group III element (e.g.: B) or group V element (e.g.: P) of periodic table into the layer 2 according to the kind of the electric charge to be charged on the surface of the photosensitive body. Degradation in the mobility and life of the carrier is obviated according to this constitution, even if the film thicknesses are increased. The photosensitive body having good electric chargeability in both positive and negative charges is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor that has excellent charging characteristics, dark decay characteristics, photosensitivity characteristics, environmental resistance, etc., and can be charged both positively and negatively.

[Prior art] Amorphous silicon (hereinafter referred to as
a-Si: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, inorganic materials such as CdS, ZnO, Ss, or 5e-To, or poly-N-vinylcarbazole (PVC) have been used as materials constituting the photoconductive layer of electrophotographic photoreceptors.
z) or organic materials such as trinitronefluorenone (TNF). However, m-81:H
Compared to these inorganic or organic materials, it is a non-polluting substance, so there is no need for recovery treatment, it has high spectral sensitivity in the visible light range, and it has a high surface hardness and has high abrasion and impact resistance. It has advantages such as superior performance. This ninth a-8t:H is attracting attention as a photoreceptor material for electrophotographic processes.

A-81:H is being studied as a material for a photoreceptor based on the Carlson system, but in this case, the photoreceptor is required to have high resistance and photosensitivity. However, it is difficult to satisfy both of these characteristics with a single photoreceptor, so a barrier layer is provided between the photoconductive layer and the conductive support, and a surface charge retention layer is provided on the photoconductive layer. These requirements can be met by creating a laminated structure.

[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. While flowing to the barrier layer, Yaria 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 by structural defects such as dangling holes, resulting in a high residual potential, whereas if the film is thin, the residual potential will be high. 1 carrier from the support
0, 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 defects in the film, deteriorating 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
It has excellent charging ability, low residual potential, high sensitivity over a wide wavelength range up to the near infrared region, good adhesion to the substrate, excellent environmental resistance, and good both positive and negative charging properties. An object of the present invention is to provide an electro-electrophotographic photoreceptor having charging ability.

[Structure of the Invention] (Means for Solving the Problems) As a result of various studies, the present inventors have achieved the above object by using a superlattice structure as a barrier layer of an electrophotographic photoreceptor. We have found that it is possible to obtain the desired results, and have completed the present invention.

That is, the present invention provides an electrophotographic photoreceptor having a conductive support, a barrier layer, and a photoconductive layer, wherein the barrier layer is an amorphous silicon thin film containing at least one selected from carbon, oxygen, and nitrogen. The present invention provides an electrophotographic photoreceptor capable of being charged both ways, characterized in that it is constructed by alternately laminating amorphous silicon thin films and germanium-containing amorphous silicon thin films.

The concentration of at least one selected from carbon, oxygen and nitrogen in the amorphous silicon (a-81) thin film is preferably 1 to 30 atoms, more preferably 5 to 15 atoms.

Further, the concentration of germanium in the amorphous silicon (a-81) is preferably 5 to 40 atoms, more preferably 10
~20 atoms.

(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 layer 2 is formed on the 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.

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 includes an a-8t thin film containing at least lai selected from carbon, oxygen, and nitrogen, an a-81 thin film, and r
It has a superlattice structure in which a-8i thin films containing rumanium are alternately stacked. These a-8i thin films can be hydrogen-doped (a-8i:H).

The barrier layer 2 is formed to enhance the charge retention function of the photoreceptor surface by suppressing the flow of charges between the conductive support 1 and the charge generation layer 4, 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 2t
It can be p5J1 or n-type. That is, when the surface of the photoreceptor is positively charged, the barrier layer 2 is made p-type to prevent electrons that neutralize the surface charge from being injected into the charge generation layer. Conversely, when the surface is negatively charged, the barrier layer 2 is made n-type to prevent holes that neutralize the surface charge from being injected into the charge generation layer. Since carriers injected from the barrier layer 2 become noise with respect to carriers generated in the charge generation layer O upon incidence of light, preventing carrier injection as described above improves sensitivity. In addition, in order to make a-81 a p-type, elements belonging to group Ⅰ of the periodic table,
For example, boron B, aluminum AL, gallium Ga.

It is preferable to dope with indium In, thallium Tt, or the like. Further, in order to make a-St n-type, it is preferable to dope it with an element belonging to Group 1 of the periodic table, such as nitrogen, phosphorus P1 arsenic As, antimony Sb1, and bismuth Bi.

The thickness of the barrier layer 2 is preferably 1OOX to 10 μm.

The photoconductive layer 3 formed on the barrier layer 2 is a-8t:H
Alternatively, it can be made of microcrystalline silicon (μc-8l:T()).

Microcrystalline silicon (μe-81) is thought to be formed from a mixed layer of microcrystalline silicon and amorphous silicon with a grain size of about several tens of Angstroms, and has the following physical properties. It has the above 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-8i in which only a halo appears. Second, μc-
The dark resistance of 81 can be adjusted to 10 Ω·2 or more, and it is clearly distinguished from polycrystalline silicon, which has a dark resistance of 10 Ω·2.

When light enters the photoconductive layer 3, carriers are generated. Among these carriers, carriers of one polarity neutralize the charges on the surface of the photoreceptor, and carriers of the other polarity travel on the photoconductive layer 3 and become conductive. Reach the sexual support.

A barrier layer 2 and a photoconductive layer 3 are constituted. The hydrogen content in a-81:H and μc-8t:H is 0.01
~30 atoms are preferred, and 1 to 25 atoms are even more preferred. Such a hydrogen content compensates for silicon dangling, brings the dark resistance and bright resistance into balance, and improves the photoconductive properties.

a-8l: To form the H layer using the glow discharge decomposition method, SiH and a silane gas such as s1□H6 are introduced into the reaction chamber as raw materials, and a thin layer is formed by glow discharge using high frequency. H can be added therein.

If necessary, hydrogen or helium gas can be used as a carrier gas for the silanes.

On the other hand, SiF, gas and 5ICt, f! Silicon halides such as gas can be used as the raw material gas. Furthermore, a-8t:H containing H can be similarly formed by reacting with a mixed gas of silane gas and silicon halide gas. In addition, regardless of the glow discharge decomposition method,
For example, these thin layers can also be formed by physical methods such as sputtering.

Similarly to a-81:H, the μc-8i 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-81:
Hf: When forming, set it high and set the high frequency power to a
-8l: When set higher than in the case of H, μc-81:
It becomes easier to form H. By increasing the primary support temperature and high-frequency power, the flow rate of source gas such as 7-run gas can be increased, and as a result, the film formation rate can be increased. In addition, the raw material gas SiH and S
By using a gas obtained by diluting a high-order silane gas such as 1□H6 with hydrogen, μc-81:H can be formed with higher efficiency.

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

Since a-8i: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 proportion of the amount of light absorbed by the photoconductive layer decreases, increasing optical loss.

For this reason, it is preferable to provide the surface layer 4 to prevent reflection. Furthermore, by providing the surface layer 4, the conductive layer 3
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.

As a material forming the surface area, a-SiN:H
These include inorganic compounds such as 5a-8iO:Hl and a-8iC:H, and organic materials such as polyvinyl chloride and polyamide.

The surface of the electrophotographic photoreceptor constructed in this manner is charged with a positive voltage of approximately 500 V by corona discharge, and then 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 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, and as a result, Residual potential becomes high. On the other hand, if the film is thin, dielectric breakdown may occur due to the development bias. Also, as a barrier layer, p-type or n-type
If a type semiconductor is used, will it cause dangling if the film is thick? Carriers are trapped in structural defects such as bonds, resulting in a high residual potential.On the other hand, if the film is thin, carriers cannot be removed from the support, resulting in a decrease in charging ability. On the other hand, if the barrier layer has a superlattice structure as in the photoreceptor of the present invention, what happens when the barrier layer has a superlattice structure? Due to the quantum effect, the lifetime of the intermediate well layer is 5 to 10 times longer than that of a single layer without a superlattice structure. In addition, in a superlattice structure, a periodic barrier layer is formed due to the discontinuity of the bandgap, but the carriers can easily pass through the bias layer due to the tunnel effect, so the effective mobility of carriers in the bulk is (equivalent to the carrier mobility), and the carrier has excellent runnability. 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.

In addition, a photoreceptor having a barrier layer with such a surface superlattice structure has good charging ability for both positive and negative charging without decreasing carrier mobility or lifetime even if the thickness of the barrier layer is increased. are doing.

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 dampers 21, 22, 23.
24, for example, SIH□B2H6, H2, CH,
It contains raw material gases such as:

These gases in the gas container are fed by a pulp 26 for flow rate adjustment.
and is supplied to a mixer 28 via a pipe 27. each? A pressure gauge 25 is installed in the pump.
By adjusting the pulp 26 while monitoring the pressure gauge 25, the flow rate and mixing ratio 1c of each raw material gas supplied to the mixer 28 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 3I of the reaction container 29 so as to be rotatable around the vertical direction. The rotating shaft 3
At the upper end of 0, a disk-shaped support 32 has its surface aligned with the rotation axis 30.
It is fixed vertically. 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. A high frequency power source 36 is connected between the electrode 33 and the drum base 34.
A high frequency current is supplied between them. The rotating shaft 30 is rotationally driven by a motor 38. Reaction container 29
The pressure inside is monitored by a pressure gauge 37, and the reaction vessel 29 is connected to an appropriate evacuation means such as a vacuum pump via a Kate pulp 38. When manufacturing a photoreceptor using the above manufacturing apparatus, , after installing the drum base 34 in the reaction vessel 29, f-) the pulp 39 is opened and the inside of the reaction vessel 29 is set at about 0, I Torr.
Evacuate to below pressure. Next, Dembe 21.22,2
From 3.24 onwards, 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. Set it to OTorr. Next, the motor 38 is operated to rotate the drum base 34, and the heater 35 rotates the drum base 34.
4 is heated to a constant temperature, and a high frequency current is supplied between the stain electrode 33 and the drum base 34 by a high frequency power source 36 to form a glow discharge between them. As a result, μe-81:H+a-8i:H is deposited on the drum base 34. In addition, N20 + NH5mN in the raw material gas
O2m N2 * CH4 * C2H4 * By using O□ gas, nitrogen, carbon, and oxygen can be reduced to μc-3i.
:H or a-81: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 If necessary, to prevent interference, an aluminum drum base with a diameter of 89 m and a width of 350111, which has been subjected to acid treatment, alkali treatment, and Sandgelast treatment, is installed in the reaction vessel, and the reaction vessel is approximately 10 The vacuum was evacuated to -5 torr. The drum base was heated to 250°C and rotated at 10 rpm, while SiH and gas were heated at 25 SCCM and CH4.
500,800M of gas was introduced, and the pressure inside the reaction vessel was reduced to 0.
8 Torr and applying 100 W of high frequency power to 5
A 0X a-8iC thin film was formed.

Next, 300,800 M of 5in4 gas was introduced, the pressure inside the reaction vessel was set to 0.6 Torr, and a high frequency power of 200 W was applied to form a 50X a-81 thin film. Next G
eH4 gas was introduced at lOO800M, and a high frequency power of 40 () W was applied to form a 50X a-8 IGeH film.

These operations were repeated to form a barrier layer having a 7500X superlattice structure.

Next, 500 SCCM of 5tH4 gas, B2H6
Gas was introduced into the reaction vessel at a flow rate such that the flow rate ratio of SiH4 to gas was 10, and the inside of the reaction vessel was set to 1 Torr.
1 type A-3 of 15 μm by applying high frequency power of 300 W
A t:H photoconductive layer was formed.

Finally, a surface layer of 6-810:H with a thickness of 0.5 μm was formed.

When a voltage of +6.5 kV was applied to the photoreceptor thus formed, a surface potential of 500 V was obtained, and the retention rate after 5 seconds was 70 cm. Next, when a voltage of -6.5V was applied, a surface potential of -400V was obtained, and the retention rate after 5 seconds was 50%.

Furthermore, when this photoreceptor was installed in a copying machine and images were formed, clear and good images were obtained in both positive and negative charging cases.

Test Example 2 An electrophotographic photoreceptor was produced in the same manner as in Test Example 1, except that a 1-8IN thin layer was formed in place of the a-8i C thin layer, which is one of the forming layers of the barrier layer. .

Note that the a-8IN thin layer has a SiH4 concentration of 20 SCC.
M.

N2 gas was set at 6008 CCM, and the pressure inside the reaction chamber was
1. Obtained by applying 200 W of high frequency power as OTorr.

When this photoreceptor was attached to a copying machine and an image was formed in the same manner as in Test Example 1, clear and good images were obtained in both positive and negative charging cases.

The types of thin layers are not limited to three types as in the above test example, but four types.
More than one type of thin layer may be laminated, in short, a predetermined three
A-81 lamina combinations of different types may be included.

[Effects of the invention] According to the present invention, since a superlattice structure of three types of thin films is used for the barrier layer, carrier mobility is high, and even if the film thickness is increased, the carrier mobility and lifespan decrease. A photoreceptor can be obtained that has good charging ability in both positive and negative charging without causing problems.

[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: Obstruction layer, 3: Photoconductive layer, 4: Surface layer. Applicant's agent Patent attorney Takehiko Suzue No. 1 Cause No. 2ryJ

Claims (6)

[Claims] (1) In an electrophotographic photoreceptor having a conductive support, a barrier layer, and a photoconductive layer, the barrier layer includes an amorphous silicon thin film containing at least one selected from carbon, oxygen, and nitrogen; 1. An electrophotographic photoreceptor capable of being bi-charged, characterized in that it is constructed by alternately laminating a crystalline silicon thin film and an amorphous silicon thin film containing germanium. (2) The thickness of each thin film constituting the barrier layer is 30 to 50
The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor has a thickness of 0 Å. (3) The electrophotographic photoreceptor according to claim 1, wherein the barrier layer contains at least one element selected from elements belonging to Group III or V of the periodic table. (4) The electrophotographic photoreceptor according to claim 1, wherein the photoconductive region of the barrier layer contains at least one of carbon, oxygen, and nitrogen. (5) The electrophotographic photoreceptor according to claim 1, wherein at least a portion of the photoconductive layer is microcrystalline. (6) The electrophotographic photoreceptor according to claim 1, wherein a surface layer is formed on the photoconductive layer.