JPS63187256A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the traveling property of a carrier in a surface layer by alternately laminating thin fine-crystalline Si films contg. N and thin semiconductor films essentially consisting of B and N, thereby forming the surface layer. CONSTITUTION:A photoconductive layer 3 and the surface layer 4 are formed on a conductive base 1. The layer 4 is formed into the superlattice structure alternately laminated with the thin fine-crystalline Si (muc-SiN:H) films contg. N and the thin semiconductor (a-BN) films essentially consisting of B and N respectively to 30-500Angstrom film thicknesses. >=1 Kinds of elements belonging to group III or V of periodic table are preferably incorporated into this layer 4. The layer 3 is preferably formed of a-Si:H or 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.

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.

[Conventional technique #1] Amorphous silicon containing hydrogen (H) (hereinafter referred to as a)
-8t: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, ZnOSe, or 5e-Te, or organic materials such as poly-N-vinylcarbazole (PVCZ) or trinitrofluorenone (TNF) have been used as materials constituting the photoconductive layer of an electrophotographic photoreceptor. It was used.

However, compared to these inorganic or organic materials, a-8i: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-8i:H
is attracting attention as a photoreceptor material for electrophotographic processes.

This a-3i: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.

[Problems to be Solved by the Invention] Conventionally, the surface layer is a-8i(:, 1a-
An insulating single layer consisting of 3i N, a-8i O, etc. is used, but such a surface layer has many structural defects such as dangling bonds and voids, so it is not suitable for photoreceptor characteristics. It has no impact. 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 surface of the photoreceptor and neutralize the surface charge, resulting in a decrease in charging ability.

Conversely, if the surface layer is thin, the surface potential of the photoreceptor decreases, creating a burden on the process design of copying machines, printers, and 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.

[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 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 includes a microcrystalline silicon thin film containing nitrogen and a semiconductor mainly composed of boron and nitrogen. It is characterized in that it is constructed by alternately laminating thin films, and each thin film has a thickness of 30 to 500 layers.

The nitrogen concentration in the nitrogen-containing microcrystalline silicon (μc-s+N) thin film is preferably 0.1 to 10 atomic %, more preferably 0.5 to 5 atomic %.

μc-8i 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 near 5' and is clearly distinguished from amorphous a-8t in which only a halo appears. Second, the dark resistance of .mu.c-8t can be adjusted to more than 10.OMEGA..alpha., and it is clearly distinguished from polycrystalline silicon, which has a dark resistance of 105 .OMEGA..alpha..

(Function) In the electrophotographic photoreceptor of the present invention, the surface layer has a superlattice structure, and the carrier life in the thin film constituting the superlattice structure is 5 to 10 times longer than that in the bulk layer due to the child effect. In addition, since each sII film is thin, carriers can easily pass through sm due to the tunnel effect, so the effective ν mobility of carriers is equal to the mobility in the bulk layer, that is, the mobility of carriers is Are better.

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-3i (microcrystalline silicon) or a-8i:
)l, or a-BN:H (amorphous boron to which nitrogen and hydrogen are added) may be used. Furthermore, an insulating film may be used. For example, μc
A high-resistance insulating barrier layer can be formed by incorporating one or more elements selected from carbon C1 nitrogen N and oxygen 0 into -8l:H or a-8i:H. The thickness of the barrier layer 2 is preferably 100 μm 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. In other words, when the surface of the photoreceptor is positively charged and the surface is negatively charged, the distance is 1 m! 2 is N type,
This prevents holes from being injected into the photoconductive layer which neutralizes the surface charge. 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. In addition, μc-8i:H or a
In order to make -81:H P-type, it is preferable to dope it with an element belonging to Group Ⅰ of the periodic table, such as boron B1 aluminum AL1 gallium Ga, indium In1, and thallium Tf. Also, μC-8i:H and a-
8i: To make H type N-type, elements belonging to Group V of the periodic table, such as nitrogen, phosphorus P, arsenic AS1 antimony Sb
It is preferable to dope with 1, bismuth 81, or the like.

The photoconductive layer 3 formed on the barrier layer 2 is a-8i:H
Alternatively, it can be composed of μc-8t: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 μC-8IN:H1 and a-BN thin films. Photoconductive layer 3
a-8t:H, etc., which constitute the a-8t:H, etc., have a refractive index of 3 to 3.
Since it is relatively large at 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, a surface layer 4 is provided to prevent reflection. Also, by providing the surface layer 4, the photoconductive layer 3 is protected from damage. Furthermore, by forming a surface layer,
The charging ability is improved, and the charge is better placed on the surface.

Barrier layer 2, photoconductive layer 3 and surface! i! a constituting 4
-3l:H, uC-8i:H and μc-8iN:
The content of hydrogen in H 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-3i: To form 8 layers by glow discharge decomposition method, silane gases such as SiHs and 5i2Hs are introduced into the reaction as raw materials, and H is added into the thin layer by glow discharge with high frequency. be able to. If necessary, hydrogen or helium gas can be used as a carrier gas for silanes. On the other hand, silicon halides such as S I F4 gas and S I CJL+ gas can be used as the raw material 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 layers can be formed not by the glow discharge decomposition method but also by a physical method such as sputtering.

Similarly to a-8::@, the μc-Si layer can also be formed by high-frequency glow discharge decomposition using silane gas as a raw material. In this case, the temperature of the support is set to a-8i
:) If it is set higher than when forming l, and the high frequency power is also set higher than when forming a-3+:H, μC-8
l: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. Further, by using a gas obtained by diluting the raw material gas SiHs and a high-order silane gas such as 5I2H6 with hydrogen, μC-8i:H can be formed with higher efficiency.

μC-8iN:H, one of the thin films constituting the surface layer 4
In order to form N in the raw material gas in the above method,
201NH3, NO2, N2, etc. may be added.

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) is incident, carriers of electrons and holes are generated in the photoconductor 113. Electrons in the conduction band are accelerated toward the surface [14] 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 described above, the superlattice structure in which thin layers are laminated makes it possible to obtain high photoconductivity and to obtain images that are clearer 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, 82Hs, H2
, CH4, and other raw material gases are contained therein. 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 determined by the WA clause. 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 rotate vertically. 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 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 2Q 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 vessel 29, and then the gate valve 39 is opened to exhaust the inside of the reaction vessel 29 to a pressure of about 0.1 Torr or less. Next, cylinder 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 gas flow rates introduced into the two reaction vessels are set so that the pressure within the reaction vessel 29 is 0.1 to 1.0 Torr. 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, μc-8i:H
and a-3): H is deposited. In addition, N20 is added to the raw material gas.
．． By using NH3, NO2, N2, CH4, C2H4,02 gas, etc., nitrogen, carbon, and oxygen can be
It can be contained in 8i:H or 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 If necessary, to prevent interference, an aluminum drum base with a diameter of 80 mg and a width of 350 mm, which has been subjected to acid treatment, alkali treatment, and sandblasting, is installed in the reaction vessel. It was evacuated to a vacuum level of Torr.

The drum base was heated to 250°C, and while rotating at 10 p-, Si H4 gas was heated at 500 SCCM, B2 H6
Gas was introduced into the reactor at a flow rate ratio of 10"3 to SiH + gas, the pressure inside the reactor was adjusted to 1 Torr, and 13.56 MHz high frequency power was applied to generate plasma. A barrier layer made of P-type a-3i:H was formed.

Next, 5008CCM of SiH4 gas and 2CCM of +2 gas.
00SCCM, B2 H6 gas was introduced into the reaction chamber at a flow rate ratio of 10-6 to SiH+ gas, and 500 W of high frequency power was applied to form a photoconductive layer consisting of 30 layers of type 1 a-8i:H.

Next, add 50 SCCM% of SiH+ gas to 500 SCCM% of H2 gas.
SCCM and 58 CCM of N2 gas were introduced, and 800 W of high frequency power was applied to form 50 μC-8iN:8m films. Next, the S i H4 gas was changed to O, 3008 CCM of 5% B2 Hs gas diluted with N2 and 2008 CCM of +2 gas were introduced, and 600 W of high frequency power was applied to form 50 a-BNN films. Repeat these operations to create 15i1 a-8i: He1l and 15
A surface layer of 1500 layers consisting of a-BN thin film was formed.

When the surface of the photoreceptor thus formed is positively charged at about 500 V 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.

Note that the types of thin layers are not limited to two types as in the above test example, but three or more types of thin layers may be repeatedly laminated. In short, it is sufficient if the boundary between the μc-8i1 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, and FIG. f 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. Applicant's agent Patent attorney Takehiko Suzue'A 1. Figure 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 microcrystalline silicon thin films containing nitrogen and semiconductor thin films mainly composed of boron and nitrogen. 1. An electrophotographic photoreceptor comprising: each thin film having 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.