JPS63187254A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve a traveling property of a carrier in a surface layer by alternately laminating thin amorphous Si films contg. N and thin semiconductor films essentially consisting of B and N, thereby forming the surface layer. CONSTITUTION:The surface layer 4 of a photosensitive body formed with a photoconductive layer 3 and the surface layer 4 on a conductive base 1 is constituted by alternately laminating the thin amorphous Si (a-SiN:H) films contg. N and the thin semiconductor (a-BN) films essentially consisting or B and L. The film thicknesses of the a-SiN:H films and the a-BN films are respectively specified to 30-500Angstrom . At least part of the layer 3 consists preferably of a-Si:H or finely crystallized semiconductor (muc-Si:H). A barrier layer 2 consisting of a-Si:H, muc-Si or a-BN:H is preferably provided between the base 1 and the layer 3. The photosensitive body having the good traveling property of the carrier in the layer 4, the long life thereof and excellent electric charge characteristic is obtd. according to this constitution.

Description

DETAILED DESCRIPTION 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, and the like.

[Prior art] Amorphous silicon (hereinafter referred to as a) containing hydrogen (H)
-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, and image sensors.

Conventionally, inorganic materials such as CciS, Zn0%Se, or 5e-Te, or poly-N-vinylcarbazole (PVCZ) have been used as materials constituting the photoconductive layer of electrophotographic photoreceptors.
Alternatively, organic materials such as trinitrofluorenone (TNF) have been used.

However, compared to these inorganic or organic materials, a-81: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 excellent abrasion resistance and impact resistance due to its surface hardness. Therefore, a-8i:H
is attracting attention as a photoreceptor material for electrophotographic processes.

This a-8t:H 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, it is difficult to satisfy both of these characteristics with a single photoreceptor layer, so a barrier layer is provided between the photoconductive layer and the conductive support, and the surface protection, antireflection, and surface potential are improved. For these purposes, such requirements are satisfied by forming a laminated structure in which a surface layer is provided on the photoconductive layer.

[Problem to be solved by the invention] By the way, a-3iC has conventionally been used as the surface layer.

An insulating single layer made of a-8i N, a-8i O, etc. is used, but such a surface layer has many structural defects such as dangling bonds and voids, which may affect the photoreceptor characteristics. is having an unfavorable impact on 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, electrons tunnel through the surface layer and neutralize the charge on the surface of the photoreceptor. Therefore, if the surface layer is thick, carriers cannot pass through the surface layer, resulting in poor sensitivity and image memory. Furthermore, as described above, since the surface layer contains many defects, carriers are trapped in the defects, resulting in an increase in residual potential. Furthermore, when light irradiation is performed in the next cycle, some of the carriers trapped in the surface layer travel toward the photoreceptor surface.
Since the surface charge is neutralized, the charging ability decreases.

On the other hand, if the surface layer is thin, the surface potential of the photoreceptor decreases, creating a burden on the design of a copying machine, printer, or the like.

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

[Configuration of the Invention (Means for Solving 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. This discovery led to the completion of 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 is composed of an amorphous silicon thin film containing nitrogen and mainly boron and nitrogen. It is characterized in that it is constructed by alternately laminating semiconductor thin films, and each thin film has a thickness of 30 to 500 layers.

The nitrogen concentration in the nitrogen-containing amorphous silicon (a-8iN) film is preferably 1 to 301 N atoms, more preferably 5 to 15 at. %.

(Function) In the electrophotographic photoreceptor of the present invention, the surface layer has a superlattice structure, and the lifetime of carriers in the thin film constituting the superlattice structure is 5 to 10 times longer than that in the bulk layer due to quantum effects. In addition, since each thin film is thin, carriers can easily pass through III due to the tunnel effect, so the effective mobility of carriers is equal to the mobility in the bulk layer, that is, carriers have excellent mobility. ing.

As described above, since the life of the carrier in the surface layer is long and the carrier has excellent running properties, the sensitivity of the electrophotographic photoreceptor is significantly improved.

(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 more detail.

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

The barrier layer 2 is made of μc-8i (microcrystalline silicon) or a-3i:
It may be formed using a-BN:H (amorphous boron to which nitrogen and hydrogen are added). Furthermore, an insulating film may be used. For example, μ
A high-resistance insulating barrier layer can be formed by containing one or more elements selected from carbon, C, nitrogen, N, and oxygen in c-8i:H or a-8I:H.

The thickness of the barrier layer 2 is preferably 100 μm to 10 μm.

μc-8t is considered to be formed of a mixed layer of microcrystalline silicon and amorphous silicon with a grain size of about several tens of angstroms, and has the following physical characteristics. First, in X-ray diffraction measurement, 2θ is 28 to 28
．． It shows a crystal diffraction pattern around 5° and is clearly distinguished from amorphous a-3i, in which only a halo appears. Second, the dark resistance of μc-8i can be adjusted to more than 10”Ω·α, and it is clearly distinguished from polycrystalline silicon, which has a dark resistance of 10 6 Ω·1.

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 charged negatively rather than positively 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 carriers injected from the barrier 112 become noise with respect to carriers generated in the photoconductive layer 3 upon incidence of light, preventing carrier injection as described above improves sensitivity. In addition, μc-8t:H or a
In order to make -8i:H P-type, it is preferable to dope it with an element belonging to Group Ⅰ of the periodic table, such as boron B, aluminum AJL1 gallium Qa, indium In, and thallium 74. Also, μC-8i:H and a
-8i: To make H type N-type, use an element belonging to Group V of the periodic table, such as nitrogen or phosphorus P.

It is preferable to dope with arsenic AS1 antimony sb, bismuth 81, or the like.

The photoconductor 113 formed on the barrier layer 2 is a-8i:
H or μc-8i:H.

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 surface layer 4 is formed on the photoconductive layer. The surface layer 4 has a superlattice structure formed by alternately laminating a-s+N:H thin films and a-BN thin films.

Since a-3i: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 3 decreases, increasing optical loss. For this reason, surface 1! f4 is provided to prevent reflection. Also, by providing the surface layer 4, the photoconductive 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.

a-8i:H, a-8iN:H and μc-8i:H constituting the barrier layer 2, the light guiding layer 3 and the surface layer 4
The content of water and element in is preferably 0.01 to 30 at%, more preferably 1 to 25 at%. This hydrogen content compensates for the dangling bonds of silicon, and balances the dark and bright resistances.
Photoconductive properties are improved.

a-8i: To form the H layer by glow discharge decomposition, S (H4 and silane gases such as 3i2Hs) are introduced into the reaction chamber as raw materials, and H is produced in the thin layer by glow discharge using high frequency. If necessary, hydrogen or helium gas can be used as a carrier gas for silanes.On the other hand, silicon halides such as SiF4 gas and SiCf4 gas can be used as a raw material gas. Furthermore, a-3i:)-1 containing H can be similarly formed by reacting with a mixed gas of a silane gas and a silicon halide 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.

In order to form a-8iN:H which is one of the four layers constituting the surface layer 4, in the above-mentioned method, 1 cN in the raw material gas is added.
2o, Nf-1s, NO2, N2, etc. may be added.

Similarly to a-3i:H, the μc-3+ 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 set to a-8t
:H is set higher than in the case of forming a-8i:H, and the high frequency power is also set higher than in the case of a-8i:H.
:) (). Also, by increasing the support concentration and high frequency power, the flow rate of raw material gas such as silane gas can be increased, and as a result, the film formation rate can be increased. Further, by using a gas obtained by diluting SiHs as a raw material gas and a high-order silane gas such as 5)2H6 with hydrogen, μC-8i:)-1 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 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 surface 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 surface cannot pass through the surface layer, resulting in sensitivity In addition, 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 thin, the surface potential of the photoreceptor decreases, creating a burden on process design for copying machines, printing, etc. On the other hand, when the surface layer has a superlattice structure as in the photoreceptor of the present invention, the lifetime of carriers in the potential well layer becomes 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 easily pass through the bias layer due to the tunnel effect, so the effective mobility of carriers is determined by the mobility in the bulk. The carrier has excellent runnability. As mentioned above, according to the superlattice structure made of laminated thin layers,
It is possible to obtain high photoconductivity properties, and it is possible to obtain clearer images than 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, S i H4, B2 Hs 1H, respectively.
2. Contains raw material gas such as CH4. The gas in these gas cylinders is controlled by a valve 26 for flow rate adjustment and piping 2.
7 to a mixer 28.

A pressure gauge 25 is installed in each cylinder, and the pressure gauge 25 is installed in each cylinder.
By adjusting the pulp 26 while monitoring 5, the flow rate and mixing ratio 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 31 of the reaction vessel 29 so as to be rotatable around the vertical direction. A disk-shaped support 32 is fixed to the upper end of the rotating shaft 30 with its surface perpendicular to the rotating shaft 30. 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 to a suitable evacuation means such as a vacuum pump via a gate pulp 38.

When manufacturing a photoreceptor using the above manufacturing apparatus, the drum base 34 is placed in the reaction vessel 29, and then the gate valve 39 is opened to evacuate the inside of the reaction vessel 29 to a pressure of about 0.1 Torr 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. .

Set it so that it becomes Torr. Next, the motor 38
is activated to rotate the drum base 34, and the heater 35 heats the drum base 34 to a constant temperature, and the high frequency power supply 36 supplies a high frequency I current between the electrode 33 and the drum base 34 to create a current between them. Forms a glow discharge. As a result, μC-8i:H and a
-3i: ) (is deposited. Note that N201 in the source gas
NH3, N 02 s N2 , CH4, C2H4,0
Nitrogen, carbon, and oxygen can be
C-8i:H can be contained in a-8i: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 80mm and a width of 350H, which has been subjected to acid treatment, alkali treatment, and sandblasting, is installed in the reaction vessel. The vacuum was evacuated to 104 torr. While heating the drum base to 250°C and rotating it at 10 rpm, 500 SCCM of S I H4 gas, B2 H6
Gas was introduced into the reactor at a flow rate ratio of 10°1 to SiH4 gas, the pressure inside the reactor was adjusted to 1 Torr, and a high frequency power of 13.56 MHz was applied to generate plasma. A barrier layer made of P-type a-3i:H was formed.

Next, 500 SCCM of SiH+ gas and 2
00SCCM, B2 H6 gas was introduced into the reactor at a flow rate ratio of 10-6 to SiH+ gas, and a high frequency power of 500 W was applied to form a photoconductive layer consisting of 30 μ- i type a-8i:H.

Next, 8 i Introduced 1508 CCM of H4 gas, 150 SCCM of H2 gas, and 300 SCCM of N2 gas, and
50 people a-8I N by applying 00W high frequency power
: A Hiil film (nitrogen concentration: 3 at.%) was formed. Then the 5I84 gas was zeroed and the 5%82 diluted with N2
8a Gas! 250sccM, H2 gas e300scc
M, N2 gas @ 150 SCCM was introduced, and 400 W of high frequency power was applied to form 50 A-8NW111. Repeat this operation to create 10 layers of a-8iN:)
A surface layer of 1,000 layers was formed consisting of -11 film and 10 layers of BN thin film.

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. Proven to be excellent.

Test Example 2 An electrophotographic photoreceptor was manufactured in the same manner as in Test Example 1, except that the surface layer was composed of a superlattice structure of three types of thin films. The three types of thin films were two types of 5) 1m in Test Example 1.
Same as a-8iN:H (nitrogen concentration 3@%) and a-BN
The third thin film was made of a-8iN:H (nitrogen concentration 8 at%).This thin film was made of SiH+ gas at 150SCCM%H2Ga2f300sccM1N2
This was obtained by introducing 3008 CCM of gas and applying 400 W of high frequency power. The thickness of the third layer 1111 was 50 layers, and the thickness of the entire surface layer was 2500 layers.

The photoreceptor manufactured in this manner has high sensitivity even to long wavelength light of 780 to 790 nm, 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 ergd.

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.

Note that the types of thin layers are not limited to two and three types as in the above test example, and more types of thin layers may be repeatedly laminated. In short, it is sufficient if the boundary between the a-8iN thin layer and the BN thin layer is formed.

[Effects of the Invention] According to the present invention, since a superlattice structure is used in the surface layer, carrier mobility in the surface layer is good, the carrier has a long life, and an electrophotographic photosensitive material with excellent charging characteristics can be obtained. You can get a body.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an electrophotographic photoreceptor according to an embodiment of the present invention. The figure shows an apparatus for manufacturing an electrophotographic photoreceptor according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive support body, 2... Barrier layer, 3... Photoconductive layer, 4... Surface layer. Applicant's agent Patent attorney Takehiko Suzue No. 1 No. 2

Claims (8)

[Claims] (1) In an electrophotographic photoreceptor having a conductive support, a photoconductive layer, and a surface layer, the surface layer is formed by alternately laminating an amorphous silicon thin film containing nitrogen and a semiconductor thin film mainly composed of boron and nitrogen. 1. An electrophotographic photoreceptor characterized in that each thin film has a thickness of 30 to 500 Å. (2) The electrophotographic photoreceptor according to claim 1, wherein the surface layer contains at least one element selected from elements belonging to Group III or V of the periodic table. (3) The electrophotographic photoreceptor according to claim 1, wherein the photoconductive 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 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 made of an amorphous semiconductor or at least a portion of a microcrystalline semiconductor. (6) 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. (7) 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. (8) The electrophotographic photoreceptor according to claim 1, wherein the barrier layer contains at least one of carbon, oxygen, and nitrogen.