JPS61295560A - Photoconductive member - Google Patents

Abstract

PURPOSE:To obtain a photoconductive member having excellent electrostatic chargeability, low residual potential, high sensitivity over a wide wavelength region, good adhesiveness to a substrate and excellent environment resistance by using microcrystalline silicon in at least part of the photoconductive member. CONSTITUTION:This photoconductive member has a conductive base 21, a barrier layer 22 formed on the base 21 and a photoconductive layer 23 formed on the barrier layer 22. At least parts of the barrier layer 22 and the photoconductive layer 23 are formed of the microcrystalline silicon contg. the element belonging to the group III or V of the periodic table. The photoconductive member which has high resistance and excellent electrostatic charge characteristic, has the high photosensitive characteristic in visible light and near IR region, permits easy production and has high practicability is thus obtd.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is used for electrophotographic photoreceptors, etc., and has charging characteristics,
Photoconductive part with excellent photosensitivity and environmental resistance, etc. +4. Regarding.

[Technical background of the invention and its problems] Conventionally, as materials for forming the photoconductive layer of an electrophotographic photoreceptor, inorganic materials such as Cd55Zn0SSe, 5e-Te, or amorphous silicon, or poly-N-vinylcarbazole (PVCz) have been used. Or trinitrofluorene (
Organic materials such as TNF) are used. However, these conventional photoconductive materials have various problems in terms of photoconductive properties and manufacturing, and it is necessary to use these materials depending on the purpose of use, sacrificing some of the characteristics of the photoreceptor system. There is.

For example, Se and CdS are materials that are harmful to the human body, and special consideration must be given to safety measures when manufacturing them. Therefore, there are problems in that the manufacturing equipment becomes complicated and the manufacturing cost is high, and in particular, Se needs to be recovered, which adds to the recovery cost. Also,
In the Se or 5e-Te system, the crystallization temperature is 65°C
Since the photoconductivity is low, problems with photoconductive properties arise due to residual electricity during repeated copying, resulting in a short lifespan and low practicality.

Furthermore, ZnO is susceptible to oxidation-reduction and is significantly affected by the environmental atmosphere, resulting in a problem of low reliability in use.

Furthermore, organic photoconductive materials such as PVCz and TNF are suspected to be carcinogens and present human health concerns, and organic materials have low thermal stability and abrasion resistance. , has the disadvantage of short lifespan.

On the other hand, amorphous silicon (hereinafter abbreviated as a-Si)
has recently attracted attention as a photoconductive conversion material, and is being actively applied to solar cells, thin film transistors, and image sensors. As part of the application of a-3i, attempts have been made to use a-8L as a photoconductive material for electrophotographic photoreceptors, and photoreceptors using a-St are recycled because they are non-polluting materials. No processing required;
Compared to other materials, it has advantages such as high spectral sensitivity in the visible light region, high surface hardness, and excellent wear resistance and impact resistance.

This a-Si is being studied as a photoreceptor based on the Carlson method, but in this case, the photoreceptor characteristics require high resistance and high photosensitivity. Since it is difficult to satisfy the characteristics with a single-layer photoreceptor, a multilayer structure is used in which 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 doing so.

By the way, a-3t is usually formed by a glow discharge decomposition method using silane gas, but at this time, a-3t is
Hydrogen is incorporated into the 3i film, and the electrical and optical characteristics vary greatly due to the difference in the amount of hydrogen. That is, a-8ill
*If the amount of hydrogen that enters increases, the optical bandgap will increase and the resistance of a-3t will increase, but as a result, the photosensitivity to long wavelength light will decrease. Difficult to use with mounted laser beam printer. Also, a −Sf
If the hydrogen content in the simulated film is high, depending on the film forming conditions,
(S iH2). and S t H2, etc., 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. Conversely, when the amount of hydrogen penetrating into a-Si is reduced, the optical bandgap becomes smaller and its resistance decreases, but the photosensitivity to long wavelength light increases. However, when the hydrogen content is low, there is less hydrogen to combine with and reduce silicon dangling bonds. For this reason, the mobility of the generated carriers is reduced, the life span is shortened, and the photoconductive properties are deteriorated, making it difficult to use as an electrophotographic photoreceptor.

As a technique to increase the sensitivity to long wavelength light, there is a method of mixing silane-based gas and germane GeH4 and performing glow discharge decomposition to produce a film with a narrow optical bandgap. and G e
Since the optimum substrate temperature is different from H4, the produced film has many structural defects and cannot obtain good photoconductive properties. Moreover, since the waste gas of G e H4 becomes toxic gas when oxidized, the waste gas treatment is also complicated. Therefore, such technology is not practical.

[Objective of the Invention] The present invention has been made in view of the above circumstances, and has excellent charging ability, low residual potential, high sensitivity over a wide wavelength range, and good adhesion to a substrate. An object of the present invention is to provide a photoconductive member with excellent environmental resistance.

[Summary of the Invention] A photoconductive member according to the present invention includes an electrically conductive support, a barrier layer formed on the electrically conductive support, a photoconductive layer formed on the barrier layer, In the photoconductive member, at least a portion of the barrier layer and the photoconductive layer are formed of microcrystalline silicon containing an element belonging to Group I or V of the Periodic Table. do.

This invention was achieved through various experimental studies by the inventors of the present invention in order to overcome the drawbacks of the prior art described above and to develop a photoconductive member that has both excellent photoconductive properties (electrophotographic properties) and environmental resistance. As a result, microcrystalline silicon (hereinafter referred to as μC)
The present invention was completed based on the idea that objective 1 can be achieved by using a photoconductive material (abbreviated as -8i) for at least a portion of the photoconductive member.

[Embodiments of the Invention] The present invention will be specifically described below. A feature of this invention is that μC-3t is used instead of the conventional a-3t. That is, whether all or some regions of the photoconductive layer are formed of microcrystalline silicon (μC-8T) or a mixture of microcrystalline silicon and amorphous silicon (A-8T); Alternatively, it is formed of a laminate of microcrystalline silicon and amorphous silicon. In addition, in a function-separated type leading conductive member, μC is added to the charge generation layer.
-3i is used.

μC-5i is a-
3t and polycrystalline silicon (polycrystalline silicon)
clearly distinguished from That is, in X-ray diffraction measurement, a-3t is amorphous, so only a halo appears,
Although no diffraction pattern can be observed, μC-5t shows a crystal diffraction pattern in which the 2θ is around 27 to 28.5°. In addition, while polycrystalline silicon has a dark resistance of 108Ω, μC-8L has a dark resistance of 1ollΩ.
- Has a dark resistance of less than 2 cm. This μC-5i is formed by an aggregation of microcrystals having a grain size of approximately several tens of angstroms or more.

A mixture of μC-3t and a-3i is a mixture in which the crystalline region of μC-3i is mixed in a-8i, and μC-5i and a
-3t is present in the same volume ratio. Also,
The laminate of μC-5t and a-3t is mostly a-3
A layer consisting of i and a layer filled with μC-3i are laminated.

Similar to a-3i, a photoconductive layer containing μC-5i can be produced by depositing μC-3i on a conductive support using silane gas as a raw material using a high-frequency glow discharge decomposition method. can. In this case, if the temperature of the support is set higher than when forming a-8L and the high frequency power is also set higher than when forming a-Si, μ
It becomes easier to form C-3L. Furthermore, by increasing the support temperature and high frequency power, the flow rate of source gas such as silane gas can be increased, and as a result, the film formation rate can be increased. In addition, SiH of the raw material gas
By using a gas obtained by diluting high-order silane gas such as 4 and Si2H6 with hydrogen, μC-3t can be formed with higher efficiency.

FIG. 1 is a diagram showing an apparatus for manufacturing a photoconductive member according to the present invention. The gas cylinders 1, 2, and 3°4 contain source gases such as SiH, BH, H2°CH4, and the like, respectively. The gas in these gas cylinders 1, 2, 3.4 is supplied to a mixer 8 via a valve 6 and piping 7 for adjusting the flow ff1ffJ. Each cylinder is equipped with a pressure gauge 5, and by monitoring the pressure gauge 5 and adjusting the valve 6, the flow rate and mixing ratio of each raw material gas supplied to the mixer 8 can be adjusted. can. The gases mixed in the mixer 8 are supplied to a reaction vessel 9. A rotating shaft 10 is attached to the bottom 11 of the reaction vessel 9 so as to be rotatable around the vertical direction, and a disk-shaped support 12 is attached to the upper end of the rotating shaft 10 with its surface perpendicular to the rotating shaft 10. It has been fixed. Inside the reaction vessel 9, a cylindrical electrode 13 is installed on the bottom 11 with its axial center aligned with the axial center of the rotating shaft 10. The drum base 14 of the photoreceptor is placed on the support base 12 with its axial center aligned with the rotation axis 1.
A heater 15 for heating the drum base is disposed inside the drum base 14 . Between the electrode 13 and the drum base 14,
A high frequency power source 16 is connected, and a high frequency current is supplied between the electrode 13 and the drum base 14. The rotating shaft 10 is rotationally driven by a motor 18. The pressure inside the reaction vessel 9 is monitored by a pressure gauge 17, and the reaction vessel 9 is connected via a gate valve 18 to an appropriate evacuation means such as a vacuum pump.

When manufacturing a photoreceptor using an apparatus configured as described above, after installing the drum base 14 in the reaction vessel 9, the gate valve 19 is opened to increase the inside of the reaction vessel 9 to approximately 0.1 Torr. Evacuate to a pressure below r). Next, the required reaction gases from the cylinders 1, 2, 3.4 are mixed at a predetermined mixing ratio and introduced into the reaction vessel 9. In this case, the gas flow rate introduced into the reaction vessel 9 is such that the pressure inside the reaction vessel 9 is 0.
．． Set it so that it is 1 to 11°. Then,
The motor 18 is operated to rotate the drum base 14, the heater 15 heats the drum base 14 to a constant temperature, and the high frequency power supply 16 rotates the electrode 13 and the drum base 14.
A high frequency current is supplied between the two to form a glow discharge between the two. As a result, microcrystalline silicon (μC-3i) is deposited on the drum base 14. In addition,
N O, NH, NH, NO, N , C in the raw material gas
By using H4°CH, O gas, etc., these elements can be contained in μC-3L.

In this way, the photoconductive member according to the present invention is similar to the conventional a-
Similar to those using 5t, it can be manufactured using closed system manufacturing equipment, so it is safe for the human body. Further, since this photoconductive member has excellent heat resistance, moisture resistance, and abrasion resistance, it has the advantage of having a long service life with little deterioration even after repeated use over a long period of time. Furthermore, since a long wavelength sensitizing gas such as G e H4 is not required, there is no need to provide waste gas treatment equipment, and industrial productivity is extremely high.

It is preferable that μC-3t contains 0°1 to 30 atom % of hydrogen. As a result, the dark resistance and bright resistance become harmonious, and the photoconductive properties are improved. μC-
For example, when doping hydrogen into the 3T layer by a glow discharge decomposition method, a silane-based raw material gas such as SiH and Si2H6 and a carrier gas such as hydrogen are introduced into a reaction vessel and a glow discharge is performed. , SiF4 and Si
A mixed gas of a silicon halide such as C14 and hydrogen gas may be used, or a mixed gas of a silane gas and a silicon halide may be used. Furthermore, the μC-8i layer can be formed not only by the glow discharge decomposition method but also by a physical method such as sputtering.

Note that the photoconductive layer containing μC-8i has a photoconductive property of 1
It is preferable to have a film thickness of 8 θ μm to 8θ μm, and more preferably 5 to 50 μm.

Substantially the entire region of the photoconductive layer may be formed of μC-5t, or may be formed of a mixture or a laminate of a-8i and μC-3t. The charging ability is higher in the laminate, and the photosensitivity is higher in the long wavelength region of the infrared region, although it depends on the volume ratio, in the mixture, and in the visible light region, the two are almost the same.

Therefore, depending on the use of the photoreceptor, substantially all the regions may be made of μC-3i, or may be made of a mixture or a laminate.

It is preferable to dope μC-3i with at least one element selected from nitrogen, N, carbon, and oxygen. Thereby, the dark resistance of μC-8t can be increased and the photoconductive properties can be improved.

These elements precipitate at the grain boundaries of μC-3i and act as terminators for silicon dangling bonds,
It is thought that the density of states existing in the forbidden band between bands is reduced, thereby increasing the dark resistance.

In this invention, a barrier layer is provided between the conductive support and the photoconductive layer. This barrier layer comprises a conductive support and
By suppressing the flow of charge between the photoconductive layer and the photoconductive layer, the charge retention function on the surface of the photoconductive member is enhanced, and the charging ability of the photoconductive member is enhanced. In the Carlson method, when the surface of the photoreceptor is positively charged, the barrier layer is made p-type in order to prevent electrons from being injected from the support side to the photoconductive layer. On the other hand, when the surface of the photoreceptor is negatively charged, the barrier layer is made n-type in order to prevent holes from being injected from the support side to the photoconductive layer. It is also possible to form an insulating film on the second side of the support as a barrier layer. The barrier layer may be formed using μC-3i, or may be formed using a-8t.

In order to make μC-8i and a-8i p-type, it is preferable to dope them with elements belonging to Group 1 of the periodic table, such as boron B1 aluminum AI, gallium Ga, indium In, and thallium T1. ,μC-3L
In order to make the layer n-type, an element belonging to Group V of the periodic table, such as nitrogen N1 phosphorus P1 arsenic As, antimony S
It is preferable to dope b1 and bismuth Bi. ``This n-type impurity or doping with n-type impurities prevents charges from moving from the support side to the photoconductive layer.

Preferably, a surface layer is provided on top of the photoconductive layer.

Since μC-3i of the photoconductive layer has a relatively large refractive index of 3 to 4, light reflection easily occurs on the surface. When such light reflection occurs, the proportion of light absorbed by the photoconductive layer decreases, resulting in increased light loss. For this reason, it is preferable to provide a surface layer to prevent reflection. Also, by providing the surface layer, the photoconductive layer is protected from damage. Furthermore, by forming a surface layer, charging ability is improved,
The surface becomes more charged. Materials for forming the surface layer include St N , SiO, and SiC.

Al　O, a-8iN; H, a-5iO; H.

and a-3iC;H, and organic materials such as polyvinyl chloride and polyamide.

As described above, as a photoconductive member applied to an electrophotographic photoreceptor, a barrier layer is formed on a support, a photoconductive layer is formed on this barrier layer, and a surface layer is formed on this photoconductive layer. A charge transport layer (CTL) is formed on the support.
It is also possible to form a functionally separated structure in which a charge generation layer (CGL) is formed on the second side of the charge transport layer. In this case, a barrier layer may be provided between the charge transport layer and the support. The charge generation layer generates carriers upon irradiation with light. The charge generation layer is preferably made of microcrystalline silicon μC-8T in part or in its entirety, and has a thickness of 0.1 to 1.0 μm.

The charge transport layer is a layer that allows carriers generated in the charge generation layer to reach the support side with high efficiency. Therefore, it is necessary that the carriers have a long life, have large mobility, and have high transportability. . The charge transport layer may be formed of a-3t,
Alternatively, it may be formed of μC-5i. In order to increase dark resistance and improve chargeability, it is preferable to light-dope an element belonging to either Group 1 or Group V of the periodic table.

Furthermore, in order to further improve the charging ability and to have the functions of both a charge transport layer and a charge generation layer, one or more of the elements C, N, and 0 may be contained. If the charge transport layer is too thin or too thick, it will not perform its function satisfactorily.

Therefore, the thickness of the charge transport layer is preferably 3 to 80 um. By providing a barrier layer, even in a functionally separated photoconductive member having a charge transport layer and a charge generation layer, its charge retention function can be enhanced and charging ability can be improved. Note that whether the barrier layer is p-type or n-type is determined depending on its charging characteristics. This barrier layer may be formed of a-5i or μC-3t.

The feature of the invention according to this application is that the photoconductive layer and the barrier layer are
At least a portion thereof is formed of μC-3L, and the layer contains an element belonging to Group 1 or Group V of the periodic table. 2 and 3 are cross-sectional views of a photoconductive member embodying the present invention; in FIG. 2, a barrier layer 22 is formed on a conductive support 21; A photoconductive layer 23 is formed thereon. On the other hand, in FIG. 3, a surface layer 24 is further formed on the photoconductive layer 23. At least a portion of the photoconductive layer 23 and the barrier layer 22 are made of μC-3t and contain an element belonging to Group Ⅰ or Group V of the periodic table.

Since the leading conductive layer is mainly made of μC-S-i, the photoconductive member can be used with high sensitivity from the visible light region to the near-infrared region (for example, around 790 nm, which is the oscillation wavelength of a semiconductor laser). PP
This makes it possible to use this photoconductive member in both C (plain paper copiers) and laser printers. μC-5L itself is slightly n-type, but the leading conductive layer mainly made of μC-5i is light-doped (10 to 10-3 atomic %) with an element belonging to Group Ⅰ of the periodic table. By this,
The photoconductive layer 23 becomes an i-type (intrinsic) semiconductor, has a high dark resistance, and improves the S/N ratio and charging ability. Further, the photoconductive layer preferably has a thickness of 3 to 80 μm, more preferably 10 to 40 μm.

Further, the μC-8i constituting the barrier layer is also doped with an element belonging to Group Ⅰ or Group V of the periodic table.

The content is preferably 10-3 to 10 at%. By forming the barrier layer with μC-8t in this way, the resistance becomes low and the blocking ability is further improved. Furthermore, if the barrier layer 2'2 contains at least 18i or more elements among C, O, and N in the range of 0.1 to 20 atomic %, the charge blocking ability is further improved, which improves the electrophotographic properties. ,preferable. The crystallinity of the photoconductive layer 23 and the barrier layer 22 is preferably 10 to 30% by volume. This results in well-balanced and desirable electrophotographic characteristics.

As shown in FIG. 3, in a photoconductive member in which a surface layer 24 is formed on a photoconductive layer 23, this surface layer 24 is
It is formed of a-3i containing at least one element among C, 0, and N. This protects the surface of the photoconductive layer, improves environmental resistance, and improves charging ability. The content of C, 0, and N is preferably 10 to 50 atomic %. Further, the thickness of the surface layer 24 and the barrier layer 22 is preferably 0.01 to 10 μm, more preferably 0.1 to 2 μm.

Next, embodiments of the invention will be described.

Example I While heating an Al drum to 300°C, SiH4 gas was mixed with S t H,a from 0.01 to 3 with respect to the gas flow rate.
, 0% B2H6 gas, 1-300% N2 and CH
4 mixed gases, 1 to 1500% H2 and He mixed gases were mixed and supplied to the reaction vessel. The barrier layer 21 was formed by applying a high frequency power of 150 watts at a reaction pressure of 0.2 torr to cause glow discharge and forming a film for 30 minutes.

Next, the photoconductive layer is soaked in S i H4 gas, S t H4
0.01 to 1% of B 2 He and H
A mixed gas of 0.5 to 2000% of 2 and He was mixed and a film was formed for 5 hours under the conditions of a reaction pressure of 0.3 torr and a high frequency power of 300 watts. Furthermore, as a surface layer, SLH
The reaction pressure was 0.3 by flowing CH4 and N2 gas at a total flow rate from the same amount to several tens of times as much as the SiH4 gas flow rate.
The film was formed for 5 minutes under the conditions of torque and high frequency power of 150 watts. The pre-film thickness was 18 μm. When a voltage of +5 kV was applied to the photoreceptor thus formed, a potential of 250 V was obtained. Furthermore, when this photoreceptor was attached to a copying machine and an image was produced, an extremely good image could be obtained.

Example 2 Instead of BH0, PH was set to 0.0 for S I H4 flow rate.
The film was formed under the same conditions as in Example 1, except that the barrier layer was formed by mixing 0.01 to 2.0%, and the photoconductive layer was formed by mixing 1% or less. In this Example 2 as well, when this photosensitive drum was installed in a copying machine, good images could be obtained.

[Effects of the Invention] According to the present invention, a photoconductive material which has high resistance, excellent charging characteristics, high photosensitivity in the visible light and near-infrared light regions, is easy to manufacture, and has high practicality. A sexual member can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an apparatus for manufacturing a photoconductive member according to the present invention, and FIGS. 2 and 3 are sectional views showing a photoconductive member according to an embodiment of the present invention. 1.2, 3, 4; Cylinder, 5; Pressure gauge, 6; Valve, 7
;Piping, 8;Mixer, 9;Reaction container, 10-Rotating shaft, 1
3; Electrode, 14; Drum base, 15; Heater, 6; High frequency power source, 19; Gate valve, 21; Support, 22;
Barrier layer, 23; photoconductive layer, 24; surface layer. Applicant's agent Patent attorney Takehiko Suzue 1 (j Figure 1

Claims (5)

[Claims] (1) A photoconductive member comprising a conductive support, a barrier layer formed on the conductive support, and a photoconductive layer formed on the barrier layer, wherein the barrier layer and A photoconductive member, wherein at least a portion of the photoconductive layer is formed of microcrystalline silicon containing an element belonging to Group III or V of the periodic table. (2) A surface layer made of amorphous silicon containing at least one element selected from carbon, oxygen, and nitrogen is formed on the photoconductive layer. The photoconductive member described in . (3) The photoconductive member according to claim 1, wherein the photoconductive layer contains hydrogen. (4) The photoconductive layer according to any one of claims 1 to 3, wherein the photoconductive layer includes a region of microcrystalline silicon and a region of amorphous silicon. Conductive member. (5) The photoconductive layer according to any one of claims 1 to 3, wherein the photoconductive layer is a laminated layer of a microcrystalline silicon layer and an amorphous silicon layer. Element.