JPS63243956A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To improve the sensitivity of a sensitive body in a wide region to the near infrared region and the traveling property of carriers by forming a region consisting of laminated amorphous thin films contg. Ge, thin films of amorphous Si and thin films of amorphous Si contg. a prescribed element in the photoconductive layer. CONSTITUTION:A region consisting of laminated amorphous thin films contg. Ge, e.g., thin a-SiGe films, thin films of amorphous Si and thin film of amorphous Si contg. one or more element among C, O and N, e.g., a-SiC is formed in a photoconductive layer. For example, the photoconductive layer is composed of an electric charge transferring layer 5 and an electric charge generating layer 6 and the layer 6 is formed by successively laminating thin a-SiC films thin a-SiGe films and thin a-Si films. By this structure, a sensitive body having high sensitivity over the region from visible light to near infrared rays, high resistance and superior electrostatic charge characteristics is obtd. and the traveling property of generated carriers is improved.

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.

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

Conventionally, inorganic materials such as CdS, ZnO, Se, or Kuha5e-Te, or poly-N-vinylcarbazole (PVC) have been used as materials constituting the photoconductive layer of electrophotographic photoreceptors.
Organic materials such as Z) or trinitrofluorenone (TNF) have been used.

However, compared to these inorganic or organic materials, a-3i: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 lrJ impact resistance. For this reason, a-8i
:@ is attracting attention as a photoreceptor material for electrophotographic processes.

This a-8i:H is being studied as a photoreceptor material based on the Carlson method, but in this case, high resistance and photosensitivity are required as photoreceptor characteristics. 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 are met by creating a multilayer structure.

(Problems to be Solved by the Invention) By the way, a-8i:H is usually formed by a glow discharge decomposition method using a silane gas, but at this time,
a-8i: @Hydrogen is incorporated into the film, and the electrical and optical properties vary greatly due to the difference in the amount of hydrogen. That is,
As more hydrogen enters the a-8i:H film, the optical bandgap increases and the resistance of a-8iH increases, but as a result, the photosensitivity to long wavelength light decreases. For example, it is difficult to use it in a laser beam printer equipped with a semiconductor laser. Furthermore, when the hydrogen content in the a-3i@ film increases, depending on the film forming conditions, those having bonding structures such as (SiH2)n and 5iHz may occupy most of the area in the film. In this case, voids increase and silicon dangling bonds increase, resulting in deterioration of photoconductive properties and rendering the material unusable as an electrophotographic photoreceptor. On the contrary, a-3i:@
As the amount of hydrogen incorporated therein decreases, the optical bandgap decreases and its resistance decreases, but the photosensitivity to long wavelength light increases. However, if the hydrogen content is low, there is less hydrogen to bond with and reduce the dangling bonds of silicon. For this reason, the mobility of the generated carriers decreases, the lifespan is shortened, and
The photoconductive properties deteriorate, making it difficult to use as an electrophotographic photoreceptor.

In this way, the photoconductive layer of the electrophotographic photoreceptor can be formed into a single a-8
If it is configured only with i:HIi, a-3i:HI
There is a problem that the characteristics change greatly depending on the manufacturing conditions of i, making it impossible to obtain desired characteristics.

The present invention was made in consideration of such circumstances, and
To provide an electrophotographic photoreceptor that has excellent charging ability, low residual potential, high photosensitivity over a wide wavelength range up to the near infrared region, good adhesion to a substrate, and excellent environmental resistance. With the goal.

[Structure of the Invention] (Means for Solving the Problems) As a result of various studies, the present inventors have discovered that the photoreceptor layer of an electrophotographic photoreceptor has a stack of multiple semiconductor films, that is, a superlattice structure. The inventors have discovered that the above object can be achieved by forming regions, and have completed the present invention.

That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor comprising an electrically conductive support and a photoconductive layer, the photoconductive layer comprising an amorphous T'l film containing Ge and a non-crystalline T'l film. crystalline silicon 3
1111 and an amorphous silicon thin film containing at least one element selected from carbon, oxygen, and nitrogen.

The degree m of carbon, oxygen, and nitrogen contained in the amorphous silicon thin film is preferably 0.1 to 40 atomic %, more preferably 0.5 to 30 atomic %.

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

In this way, the mobility of carriers in the photoconductive @ layer increases,
Furthermore, the sensitivity of the electrophotographic photoreceptor is significantly improved due to the longer life of the carrier.

Furthermore, in the present invention, since the a-5i thin film contains at least one of carbon, oxygen, and nitrogen, it is possible to not only adjust the band gap as described above but also increase the resistance of the photoconductive layer. The charge retention ability of the surface can be increased.

(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, 7 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 H4 is formed on the photoconductive layer 3.

FIG. 2 is a diagram showing the cross-sectional structure of an electrophotographic photoreceptor according to another embodiment of the present invention. In this embodiment, a functionally separated photoconductive layer consisting of a charge generation layer and a charge transport layer is provided. . That is, a charge transport layer 5 is formed on the conductive support 1 and the 'IJW layer 2, and a charge generation layer 11 is formed on the charge transport layer.
6 is formed.

Furthermore, a surface layer 4 is formed on the charge generation layer 6.

Details of each part in the embodiment shown in FIGS. 1 and 2 are as described below.

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

Barrier layer 2 is made of microcrystalline silicon μc-8i or a-8i:
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, μc-
8i: H and a-8i: H with carbon C1 nitrogen N
By containing one or more elements selected from oxygen and oxygen, a high-resistance insulating barrier layer can be formed. The thickness of the barrier layer 2 is preferably 100 to 10 μm.

Microcrystalline silicon (μc-8i) is thought to be formed from a mixed phase of microcrystalline silicon with a grain size of about several tens of angstroms and amorphous silicon, and has the following physical characteristics: have. 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-3i in which only a halo appears. Second, the dark resistance of μc-8i is 101
Can be adjusted to more than 0Ω・α, dark resistance is 105Ω
・It is also clearly distinguished from polycrystalline silicon in No. 1.

The optical bandgap (Eg'') of the μc-8t used in the present invention is preferably set to, for example, 1.55cV. However, it can be set arbitrarily within a certain range. It is preferable to add a predetermined amount of hydrogen to and use it as μc-8i:H.This compensates for the dangling bonds of silicon,
Dark resistance and bright resistance are balanced, and photoconductive properties are improved.

The barrier layer 2 increases the charge retention function of the photoreceptor surface by suppressing the flow of charges between the conductive support 1 and the photoconductive N layer 3 (or the charge generation layer 5), and improves the charging performance of the photoreceptor. It is formed to increase the Therefore, when a Carlson type photoreceptor is constructed using a semiconductor layer as a barrier layer, the barrier layer 2 is made to be P type or N type in order not to reduce the ability to retain charges charged on the surface. That is, when the surface of the photoreceptor is positively charged, the barrier Ji2 is set to P type to prevent electrons that neutralize the surface charge from being injected into the light>jJii layer. On the other hand, when the surface is negatively charged, the barrier layer 2 is made of N type, and the holes that neutralize the surface charge become light guide 'R'.
Prevent injection into the layer. Since the carriers injected from the barrier layer 2 become noise to the carriers generated in the photoconductive layer 3.6 upon the incidence of light, preventing carrier injection as described above improves the sensitivity. . In addition, in order to make μc-8i:H or a-8i:@ p-type, elements belonging to Group Ⅰ of the periodic table, such as boron B1 aluminum A℃, gallium Qa, indium In, and thallium Tρ, etc. It is preferable to dope. In addition, in order to make μc-8i:H or a-8i:H N-type, elements belonging to Group V of the periodic table, such as nitrogen, phosphorus P,
It is preferable to dope with arsenic AS, antimony Sb1, bismuth Bi, or the like.

In the embodiment shown in FIG. 1, the photoconductive layer 3 generates carriers upon incidence of light, and one polarity of these carriers neutralizes the electrical charge on the surface of the photoreceptor, and the other carrier generates photoconductivity. 113 to conductive support 1. In addition, in a functionally separated type photoreceptor (Fig. 2), carriers are generated in the charge generation layer 6 due to the incidence of light, and one of these carriers runs on the charge transport layer 5 and moves to the conductive support 1. reach up to.

The photoconductive layer 3 shown in FIG. 1 and the charge generation layer 6 shown in FIG. 2 are composed of three types of thin layers alternating with fa layers. These thin layers have different optical bandgaps and each range in thickness from 30 to 500 nm.

As explained above, by stacking thin films with different optical bandgaps, the optical bandgap becomes larger than the film with a small optical bandgap, regardless of the size of the optical bandgap itself. A superlattice structure having periodic potential barriers is formed in which the film serves as a barrier. In this superlattice structure, since the barrier '; mm is extremely thin, carriers pass through the barrier and travel in the superlattice structure due to the carrier tunneling effect in WlplA. Furthermore, in such a superlattice structure, a large number of carriers are generated by incident light. Therefore, it has high photosensitivity. Note that by changing the bandgap and film thickness of one film of the superlattice structure, the apparent bandgap of the layer having the heterojunction superlattice structure can be freely adjusted.

In the electrophotographic photoreceptor of the present invention, the hydrogen content in a-3i:H1μc-8i:H, etc. constituting the photoconductive layer is preferably 0.01 to 30 atomic %, and 1 to 25 atomic %.
Atomic % is more preferred. 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: To form the H layer by the glow discharge decomposition method, SiH+ and silane gases such as 3i 2 Hs are introduced into the reaction chamber as raw materials, and H is produced in the thin layer by glow discharge using high frequency. Can be added. If necessary, hydrogen or helium gas can be used as a carrier gas for silanes. On the other hand, silicon halides such as SiF+ gas and 5iCff4 gas can be used as the source gas. Furthermore, a-8i:H containing H can be similarly formed by reacting with a mixed gas of silane gas and silicon halide gas.

Note that these thin films can be formed not only by the glow discharge decomposition method but also by a physical method such as sputtering.

Similarly to a-8i:H, uc-811i3 can also be formed into a film 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-3
If it is set higher than when forming i:H and the high frequency power is also set higher than when forming a-81:H, μc-3i
: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 S i H4 and a high-order silane gas such as 5i21-1s with hydrogen, μC-8t:H can be formed with higher efficiency.

In order to make μc-8i:H and a-8t:H p-type, an element belonging to Group Ⅰ of the periodic table, such as boron B1
Aluminum 82, gallium Qa.

It is preferable to dope with indium In, thallium 2, etc., μc-8i:H and a-8i:
In order to make H the n-type, elements belonging to Group V of the periodic table, such as nitrogen N, phosphorus P1 arsenic AS, antimony S
It is preferable to dope with b1, bismuth 81, or the like. This n-type impurity or doping with n-type impurities prevents charges from moving from the support side to the photoconductive layer. On the other hand, for uc-8i:H and a-8i:H,
At least one selected from carbon C1 nitrogen N and oxygen O
By containing a seed element, resistance can be achieved and the surface charge retention ability can be increased.

A surface layer 4 is provided on the photoconductive layer 3 or charge generation layer 6 . a-8i of the light guide r1 layer 3 or charge generation layer 6
:H etc. have a relatively large refractive index of 3 to 3.4, so light reflection easily occurs on the surface.

When such light reflection occurs, the proportion of the amount of light absorbed by the optical six layer or the charge generation layer decreases, resulting in an increase in optical loss. For this reason, it is preferable to provide the surface layer 4 to prevent reflection. In addition, by providing the surface I4, photoconductive! 3 or charge generation m6 is protected from damage. In general, by forming a surface layer, the charging ability is improved, and the charge is more easily deposited on the surface. Materials forming the surface layer include inorganic compounds such as a-8i N :H, a-8i O:H, and a-8iC:H, and organic materials such as polyvinyl chloride and polyamide.

When the surface of the electrophotographic photoreceptor constructed in this way is charged with a positive voltage of approximately 500 V by corona discharge, for example, in the case of the functionally separated electrophotographic photoreceptor shown in FIG. 2, charge generation 116 occurs. A potential barrier is formed.

When light (hν) is incident on this photoreceptor, charge is generated 116
Electron and hole carriers are generated in the foot lattice structure. Electrons in the conduction band are accelerated toward the surface layer 4 side, and holes are accelerated toward the conductive support 1 side by the electric field in the photoreceptor. In this case, the number of carriers generated at the boundary between thin films with different optical bandgaps is significantly greater than the number of carriers generated in the bulk.

Therefore, this superlattice structure has high photosensitivity.

Furthermore, in the potential well layer, due to quantum effects, the lifetime of carriers is 5 to 10 times longer than in the case of a single layer without a superlattice structure. Furthermore, in a superlattice structure, a periodic barrier layer is formed due to bandgap discontinuity, but carriers easily pass through the bias layer due to the tunnel effect, so the effective carrier mobility is equal to the bulk mobility. The carrier has excellent runnability. As described above, according to the superlattice structure in which I films having different optical band gaps are stacked, it is possible to obtain photoconductive layer characteristics and to obtain a clearer image 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, Si H4, 82Hs, H
2. A raw material gas of Cl-14@ is contained. The gas in these gas cylinders is supplied to a mixer 28 via an outflow regulating valve 26 and piping 27. Each cylinder is equipped with a pressure gauge 25, and by adjusting the valve 26 while monitoring the pressure gauge 25, the flow rate and mixing ratio of each raw material gas supplied to the mixer 28 can be adjusted. The gas mixed in the mixer 28 is transferred to the reaction container 29.
supplied to A rotating shaft 30 is attached to the bottom 8II31 of the reaction container 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. Reaction container 2
9, a cylindrical electrode 33 has its axial center aligned with the rotating shaft 30.
It is installed on the bottom part 31 so as to be aligned with the axial center of the.

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, and 1! A high frequency Wi current is supplied to the pole 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, and the reaction vessel 29 is connected via a gate valve 38 to an appropriate exhaust means such as a vacuum pump.

After installing the drum base 34 in the reaction vessel 29, the gate valve 39 is opened and the inside of the reaction vessel 29 is heated to approximately 0.1 T.
Evacuate to below orr pressure. Next, cylinder 21,2
, 2.23.24, 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 vessel 29 is 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, a-
8i: H is deposited. Note that N20. N.H.
3. NO2, N2.

By using CH4, C2H4,02 gas, etc.
These elements can be contained in a-5i:@, etc.

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 the electrophotographic photoreceptor according to the present invention will be described.

Test Example 1 If necessary, to prevent interference, an aluminum drum base with an M diameter of 80a1 and a width of 350sI, which has been subjected to acid treatment, alkali treatment, and sandblasting treatment, is installed in the reaction vessel, and the reaction vessel is approximately The vacuum was evacuated to 10-5 torr. While heating the drum base to 250°C and rotating it at 10 rpm, SiH4 gas was heated to 5003 CCM and 82 H.
6 gas was introduced into the reaction vessel at a flow rate ratio of 10 −3 to 5iHs gas, and the pressure inside the reaction vessel was adjusted to 1 Torr. Then, a high frequency power of 13.56 MHz was applied to generate plasma, and a barrier layer made of p-type a-3iC:H was formed on the drum base.

Next, H2 gas was introduced into the reaction vessel at a flow rate of 300 SCCM and 82 H6 gas at a flow rate ratio of 10-6 to SiH+ gas, and high frequency power was applied to form a charge consisting of a-8i:@ with a thickness of 20 μm. A transport layer was formed.

Next, the flow rate of Cl-14 gas is set to 30SCCM, and 40
By applying 0W high frequency power, 50 people a-8iCi
ll! l was formed. Fifty a-8iC thin films were then formed under the same conditions as in the charge transport layer format. Next, 300 SCCM of S+H4 gas, 1008 CCM of Ge H4 gas, and 500 SCCM of H2 gas were introduced, and a high frequency power of 200 W was applied to form 100 a-8iGe:Hat films. These operations were repeated to form a charge generation layer having a superlattice structure of 5 μm.

Finally, a surface layer of 0.5 μm of a-8iC:H 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 charge generation layer and carriers of electron-hole pairs are generated. In this test example, a large number of carriers were generated, the carriers had a long life, and high running performance was obtained. This resulted in clear, high-quality images. In addition, when the photoreceptor manufactured in this test example was repeatedly charged, the reproducibility and stability of the transferred image were extremely good, and the durability such as corona resistance, moisture resistance, and abrasion resistance was also improved. It has been proven that the properties are excellent.

The photoreceptor manufactured in this manner has high sensitivity even to long wavelength light of 780 to 790 n1M, which is the emission 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.

Test Example 2 a-8i C'; flWA, a-S i Ge '4
An electrophotographic photoreceptor was manufactured in the same manner as in Test Example 1, except that the charge generation layer was formed by forming m and a-8iN films in this order.

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

Test Example 3 An electrophotographic photoreceptor was manufactured in the same manner as in Test Example 1, except that an a-8iN thin film was formed instead of the a-8i C thin film. Note that the a-8iN thin film was made using 500 SCCM of Si H4 gas, 3008 CCM of H2 gas, and 3008 CCM of N2 gas.
Obtained by introducing 1208 CCM of gas.

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

Test Example 4 a-3i NillEl, a-8t Ge till, a
An electrophotographic photoreceptor was manufactured in the same manner as in Test Example 3, except that the charge generation layer was formed by forming -3i thin films in this order.

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

[Effects of the Invention] According to the present invention, since a superlattice structure is used in part or all of the photoconductive layer, island sensitivity is achieved over a wide wavelength range from visible light to near-infrared light, It is possible to obtain an electrophotographic photoreceptor that has high carrier mobility, high resistance, and excellent charging characteristics.

In particular, the present invention has the advantage that by appropriately combining materials forming the thin film, it is possible to obtain a photoreceptor having optimal photoconductive properties for light in any wavelength band.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an electrophotographic photoreceptor according to an embodiment of the present invention, FIG. 2 is a sectional view showing an electrophotographic photoreceptor according to another embodiment, and FIG. 3 is an embodiment of the invention. 1 is a diagram showing a manufacturing apparatus for an electrophotographic photoreceptor according to the present invention. 1: conductive support, 2: barrier layer, 3: photoconductive layer, 4: surface layer, 5:1! Charge transport layer, 6: charge generation layer.

Claims (7)

[Claims] (1) In an electrophotographic photoreceptor having a conductive support and a photoconductive layer, the photoconductive layer is selected from an amorphous thin film containing Ge, an amorphous silicon thin film, carbon, oxygen, and nitrogen. What is claimed is: 1. An electrophotographic photoreceptor comprising a region formed by laminating a thin amorphous silicon film containing at least one of the above elements. (2) The electrophotographic photoreceptor according to claim 1, wherein the thin film has a thickness of 30 to 500 Å. (3) The electrophotographic photoreceptor according to claim 1 or 2, wherein the photoconductive layer contains at least one element selected from elements belonging to Group III and Group V of the periodic table. . (4) A patent claim characterized in that a barrier layer made of an amorphous material or a semiconductor material in which at least a portion thereof is microcrystalline is formed between the conductive support and the photoconductive layer. The electrophotographic photoreceptor according to item 1. (5) The electrophotographic photoreceptor according to claim 4, wherein the barrier layer contains at least one element selected from elements belonging to Group III and Group V of the periodic table. (6) The electrophotographic photoreceptor according to claim 4 or 5, wherein the barrier layer contains at least one element selected from carbon, oxygen, and nitrogen. (7) The electrophotographic photoreceptor according to claim 1, wherein a surface layer is formed on the photoconductive layer.