JPS6221167A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photoconductive member having excellent electrostatic charging property by forming a photoconductive layer in such a manner that the region of microcrystalline silicon and the region of amorphous silicon mixedly exist therein and determining the volumetric ratio of the microcrystalline silicon region at 50-90%. CONSTITUTION:A barrier layer 22 is formed on a substrate 21 and the photoconductive layer 23 is formed on the barrier layer. A surface layer 25 is formed on the photoconductive layer. The region of the microcrystalline silicon and the region of the amorphous silicon mixedly exist in the photoconductive layer. The volumetric ratio at which the microcrystalline silicon occupies in the photoconductive layer is determined at 50-90%. The volume ratio of muC-Si is required to be made <=90% in order to thoroughly assure the electrostatic charging property and the volume ratio of muC-Si is required to be >=50% in order to improve photosensitivity in a wide wavelength region by muC-Si.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electrophotographic photoreceptor having excellent charging characteristics, photosensitivity characteristics, environmental resistance, etc.

[Technical background of the invention and its problems] Conventionally, materials for forming the photoconductive layer of electrophotographic photoreceptors include CdS, ZnO, Se, 5e-Te or amorphous silicon, or poly- N-vinylcarbazole (PVCz) or trinitrofluorene (T
Organic materials such as NF) are used. however,
These conventional photoconductive materials have various problems in terms of photoconductive properties or manufacturing, and these materials are used depending on the purpose of use, sacrificing the properties of the photoreceptor system to some extent.

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
Therefore, during repeated copying, problems with the photoconductive properties may occur due to remaining snow, etc., and therefore, the service life is short and practicality is low.

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 carcinogens and present human health concerns, and organic materials have poor thermal stability and abrasion resistance. , has the disadvantage of short lifespan.

On the other hand, amorphous silicon (hereinafter abbreviated as a-3i)
has recently attracted attention as a photoconductive conversion material, and is being actively applied to solar cells, 1lllll transistors, and image sensors. As part of this application of a-8i, attempts have been made to use a-5i as a photoconductive material for electrophotographic photoreceptors, and photoreceptors using a-8i are recycled as they are non-polluting materials. It has advantages such as no need for treatment, higher spectral sensitivity in the visible light region than other materials, high surface hardness, and excellent wear resistance and impact resistance.

This a-3i is being studied as a photoreceptor based on the Carlson method, but in this case, the photoreceptor characteristics are required to be high resistance and photosensitivity. Since it is difficult to satisfy the requirements with a photoreceptor, we created an f11 layer structure 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. , satisfies these requirements.

By the way, a-3i is usually formed by a glow discharge decomposition method using silane gas, but at this time, a-3i is
Hydrogen is incorporated into the 8illi, and the electrical and optical properties vary greatly due to the difference in the amount of hydrogen. That is, a-8:
As m of hydrogen that enters the film increases, the optical bandgap increases and the resistance of a-8i increases, but as a result, the photosensitivity to long wavelength light decreases. Difficult to use with mounted laser beam printer. In addition, if the hydrogen content in the a-3i film is high, depending on the film formation conditions, (
Those having bonding structures such as SiH2)rL and S i H2 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, reducing the amount of hydrogen penetrating into a-8i reduces the optical bandgap and reduces its resistance, but increases its photosensitivity to long wavelength light. However, when the hydrogen content is low, there is less hydrogen to combine with and reduce silicon dangling bonds. As a result, the mobility of the generated carriers decreases, the life span becomes short, and the photoconductive properties deteriorate, 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 GeH+
Since the optimum substrate temperature is different between the two, the resulting film has many structural defects and cannot exhibit good photoconductive properties.In addition, the waste gas of GeH4 becomes a toxic gas when oxidized, so Gas processing is also complex, so such technology is impractical.

[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] An electrophotographic photoreceptor according to the present invention includes an electrically conductive support, a barrier layer formed on the electrically conductive support, and a photoconductive layer formed on the barrier layer. In the electrophotographic photoreceptor, the photoconductive layer has a microcrystalline silicon region and an amorphous silicon region mixed together, and the volume ratio of the microcrystalline silicon region to the photoconductive layer is 50 to 90. %.

The present invention was achieved by the inventors of the present invention, who have conducted various experimental studies in order to overcome the drawbacks of the prior art described above and to develop an electrophotographic photoreceptor that has both excellent photoconductive properties (electrophotographic properties) and environmental resistance. As a result, microcrystalline silicon (hereinafter referred to as μ
The present invention was completed based on the idea that this object could be achieved by using C-8i (abbreviated as C-8i) for at least a portion of an electrophotographic photoreceptor.

[Embodiments of the Invention] The present invention will be specifically described below. The feature of this invention is that μC-3i is used instead of the conventional a-8i. In other words, all or part of the photoconductive layer is made of microcrystalline silicon (μC-3i).
It is formed of a mixture of microcrystalline silicon and amorphous silicon (A-8i''), or it is formed of a laminate of microcrystalline silicon and amorphous silicon.Functionally separated type In this photoconductive member, μC-8i is used for the charge generation layer.

μC-8i is a-
8i and polycrystalline silicon (polycrystalline silicon)
clearly distinguished from That is, in X-ray diffraction measurement, since a-8i is amorphous, only a halo appears;
Although no diffraction pattern can be observed, μC-8i shows a crystal diffraction pattern with a 2θ of around 27 to 28.5°. In addition, while polycrystalline silicon has a dark resistance of 10"Ω・cra, μC-8i has a dark resistance of 10"
It has a dark resistance of 1Ω·cIn or more. This μC-8i is formed by agglomeration of microcrystals having a grain size of approximately several tens of angstroms or more.

A mixture of μC-8i and a-3i means that the crystal #4 region of μC-8i is mixed in a-8i, and μC-S + and a-3i exist in a similar volume ratio. say something In addition, the laminate of μC-8i and a-8i is mostly a
-8i and a layer filled with μC-8i are laminated together.

Similar to a-8i, a photoconductive layer having μC-8i 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-3i and the high frequency power is also set higher than when forming a-8i, μ
It becomes easier to form C-8i. 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, the raw material gas SiH4
By using a gas obtained by diluting a high-order silane gas such as 5i2Hs with hydrogen, μC-8i can be formed with even higher efficiency.

FIG. 1 is a diagram showing an apparatus for manufacturing a photoconductive member according to the present invention. Gas cylinders 1, 2, and 3°4 contain, for example, SiH+, B2 Hs, and H2, respectively.

A raw material gas such as CH4 is contained. The gas in these gas cylinders 1, 2, 3, 4 is controlled by a valve 6 for adjusting the flow rate.
and is supplied to a mixer 8 via a pipe 7. 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 electric Ti 13 is installed on the bottom 11 with its axial center aligned with the axial center of the rotating shaft 10. A drum base 14 of a photoreceptor is placed on a support base 12 with its axial center aligned with the axial center of the rotating shaft 10,
A heater 15 for heating the drum base is disposed inside the drum base 14. Electrode 13 and drum base 14
A high frequency electric current [16 is connected between the electrode 1
A high frequency current is supplied between the drum base member 14 and the drum base member 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 the Vt device configured as described above, after installing the drum base 14 in the reaction vessel 9,
The gate valve 19 is opened to evacuate the inside of the reaction vessel 9 to a pressure of about 0.1 Torr or less. 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 1 Torr. Next, motor 1
8 to rotate the drum base 14, and
The drum base 14 is heated to a constant temperature, and a high frequency current is supplied between the N pole 13 and the drum base 14 by the high frequency electric current 1ti16 to form a glow discharge between them. As a result, microcrystalline silicon (μC-8t) is deposited on the drum base 14. Note that N20. NH3, NO2, N2, CH4.

These elements can be contained in μC-8i by using C2H4,02 gas or the like.

In this way, the photoconductive member according to the present invention is similar to the conventional a-
Similar to those using 3i, it can be manufactured using closed system manufacturing equipment, so it is safe for the human body. Additionally, this photoconductive member has excellent heat resistance, moisture resistance, and abrasion resistance.

Therefore, it has the advantage of having a long life and less deterioration even after repeated use over a long period of time. Furthermore, since a long wavelength sensitizing gas such as GeH+ is not required, there is no need to provide waste gas treatment equipment, and industrial productivity is extremely high.

It is preferable that μC-8i contains 0.1 to 30 at % 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 8i layer by a glow discharge decomposition method, a silane-based raw material gas such as SiH+ and 5i2Hs and a carrier gas such as hydrogen are introduced into a reaction vessel and a glow discharge is performed. A mixed gas of a silicon halide such as , S i F4, and SiC+4 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 photoconductive properties,
It is preferable to have a film thickness of 1 to 80 μm, and furthermore, I
It is desirable that the ll thickness be 5 to 50 μm.

Preferably, μC-8i is doped with at least one element selected from nitrogen (N), carbon (C), and oxygen (0). Thereby, the dark resistance of μC-8i can be increased and the photoconductive properties can be improved.

These elements precipitate at the grain boundaries of μC-8i and act as terminators for silicon dangling bonds,
It is thought that the density of states existing in the forbidden charge 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 layer on the support as a barrier layer. The barrier layer may be formed using μC-8i, or may be formed using a-8i.

In order to make μC-8i and a-3i p-type, it is preferable to dope them with elements belonging to Group Ⅰ of the periodic table, such as boron B1 aluminum A1, gallium Ga, indium In, and thallium T1. , μC-8i
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 with b1 and bismuth 3i.

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 the amount of light absorbed by the photoconductive layer decreases, increasing optical 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 forming the surface layer include 5i9N4, SiO2, 5iC1AI2
03, a-8iN;H, a-8iO:H.

and a-8iC:H, and organic materials such as polyvinyl chloride and polyamide.

As described above, a photoconductive member applied to an electrophotographic photoreceptor is formed by forming a barrier layer on a support, a photoconductive layer on this barrier layer, and a surface layer on this photoconductive layer. charge transport 11 (CTL) on the support.
), and a charge generation layer (CGL) is formed on the charge transport layer to form a functionally separated structure. 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. This charge generation layer is made of microcrystalline silicon μC-SI in part or in whole,
The thickness thereof is preferably 0.1 to 10 μm. The charge transport layer is a layer that allows carriers generated in the charge generation layer to reach the support side with island efficiency, and therefore, the carriers must have a long life, high mobility, and high transportability. The charge transport layer may be formed of a-8i or μC-8i. In order to increase dark resistance and improve chargeability, it is preferable to light-dope with an element belonging to either Group Ⅰ 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 O 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 μm. 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 layer I1 may be formed of a-3i or μC-8i.

A feature of the invention according to this application is that in the photoconductive layer, a region of microcrystalline silicon and a region of amorphous silicon coexist, and the volume ratio of the region of microcrystalline silicon to the photoconductive layer is 50 to 9.
The reason is that it is 0%. The volume fraction of μC-8i corresponds to the crystallinity of the photoconductive layer. Therefore, as the volume ratio of μC-81 increases, the degree of crystallinity increases and approaches μC-8i alone. However, the dark resistance of μC-8 alone is slightly lower than that of a-Si, and therefore the charging ability is lower than that of a-8i. In order to sufficiently ensure this charging ability, the volume ratio of μC-8i needs to be 90% or less. On the other hand, a-8i has high photosensitivity to visible light, but since a-3i has a large optical energy gap, it has low photosensitivity to near-infrared light, which has a longer wavelength and lower energy than visible light.

However, since μC-S + has a small optical energy gap, it has sufficient sensitivity even in the near-infrared region. Therefore, in order for the photoreceptor to have high photosensitivity over a wide wavelength range, it is better for the volume ratio of μC-8i to be high.

In this way, in order to increase the photosensitivity in a wider wavelength range by μC-8i, the volume ratio of μC-8i needs to be 50% or more.

Next, embodiments of the invention will be described.

After washing and drying the aluminum drum serving as the conductive substrate on the support 11, the reaction vessel was heated to 400° C. while evacuating the inside of the reaction vessel to about 0.1 torr or less using a diffusion pump. Then, SiH+ gas at a flow rate of 200 SCCM, 82 Hs gas at a flow rate ratio of lX10' to this Si H4 gas flow rate, and 1100 SCCM.
5 CC of CH4 gas was mixed and supplied to the reaction vessel. While rotating the AI todrum by the motor 18, 13.5
A glow discharge was caused by applying a high frequency power of 300 watts at 6MH2. The pressure inside the reaction vessel is 1 torr and 15
As a result of continuing film formation for several minutes, as shown in FIG.
A barrier layer 21 of 2.1 μm was formed on top of 1. Thereafter, the flow rate of S i H4 was set to 5008 CCM, the flow rate of hydrogen gas was set to 15008 CCM, the reaction pressure was 0.8 Torr, and the high frequency power was IKW to form a film for 4 hours. This formed a photoconductor 1124 with a thickness of 10 μm. Then, 300 SCCM of SiH+ gas and 1
50 SCCM of CH4 gas was introduced and the pressure was set at 1 Torr. In this state, a high frequency power of 200 watts was applied to form a film for 15 minutes to form a surface layer 25 of 1 μm. The crystallinity and crystal grain size of the photoconductive layer 24 of the photoreceptor according to Example 1 were measured by XJ1 diffraction method. As a result, the crystallinity was 50% and the crystal grain size was about 60%.

11L In Example 2, as shown in FIG.
This example differs from Example 1 in that a second photoconductive layer 23 is formed between the photoconductive layer 24 made of μC-8i and the photoconductive layer 24 made of μC-8i. This second photoconductive film 23 is made of a-8i, and the film forming conditions are as follows:
The flow rate of H+ gas is 3008 CCM, and the reaction pressure is 1
．． 2 Torr, high frequency power is 250 Watts. Other film forming conditions are the same as in Example 1. Further, the crystallinity of the photoconductive layer was 50%, and the crystal grain size was about 60%.

1m The film-forming conditions for the photoconductive layer 24 made of μC-3i in Example 2 were changed, and the film-forming conditions for the other layers were the same as in Example 2.
A photoreceptor was formed in which the crystallinity and crystal grain size of the photoconductive layer were as shown below. Note that Examples 4 and 5 below are also similar to Example 3.

Crystallinity: 65% Grain size: Approx. 62 Crystallinity: 85% Grain size: 62 Crystallinity: 95% Grain size: Approx. 65% For comparison with Examples 1 to 5, μC-8 of Example 1
A photoreceptor was manufactured in which the photoconductive layer 24 was made of a-8'+ instead of the photoconductive layer 24 made of i. The film forming conditions for the photoconductive layer made of this a-3i are as follows: S i H4 gas flow rate is 300
8CCM, reaction pressure 0.9 Torr, high frequency power 200
That's Watsuto.

FIG. 4 shows the spectral sensitivities of the photoreceptors of Examples 1 to 5 and Comparative Example. As is clear from this Figure 4, a-3
In the case of the comparative example having a photoconductive layer consisting of i, the sensitivity on the long wavelength side is low, but Examples 1 to 5 have excellent photosensitivity even at a long wavelength of 700 nm because they contain μc-8i. Therefore, in Examples 1 to 5, the oscillation wavelength is 79
It is effective as a photoreceptor for a laser printer using a 0 nm semiconductor laser. As is clear from Figure 4, the spectral sensitivity on the long wavelength side increases as the degree of crystallinity increases, and in order to have extremely high spectral sensitivity at the oscillation wavelength of a semiconductor laser, the degree of crystallinity must be 60%. It is preferable that it is above.

Next, an evaluation test was conducted on the electrophotographic characteristics of the photoreceptors of Examples 1 to 5 and Comparative Example manufactured in this manner. The results are shown in Table 1.

Table 1 However, the surface potential is when +6 kV is applied.

As is clear from Table 1, Examples 1 to 5 in which μC-8i was used as the photoconductive layer had higher photosensitivity than the comparative example having the photoconductive layer made of a-81. However, as the degree of crystallinity in the photoconductive layer increases, the charging ability decreases, and when the degree of crystallinity exceeds 90%, the degree of crystallinity decreases significantly and becomes unusable. Therefore, the crystallinity or the volume ratio of μC-8i is 90% or less, preferably 80% or less.
% or less.

The photoreceptors of each example and comparative example were mounted on a laser printer, and a test was conducted to determine the quality of the images. The results are shown in Table 2.

Note that the unit of the number of copies is the square, and in the table, ◎ indicates that the image condition is extremely good, O indicates that the image condition is good, and △.
indicates that the product is slightly defective, and × indicates that it is defective. As is clear from Table 2, in the case of the photoreceptor according to the example of the present invention, the image is good even when the number of copies exceeds 120,000, and the lifespan is extremely longer than that of the photoreceptor of the comparative example. This has been proven.

[Effects of the Invention] According to the present invention, the photoconductive material has high resistance, excellent charging characteristics, high photosensitivity characteristics in visible light and near-infrared light of 1 tU, 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, FIGS. 2 and 3 are cross-sectional views showing a photoconductive member according to an embodiment of the present invention, and FIG. 4 is a diagram showing a photoconductive member manufacturing apparatus according to an embodiment of the present invention. It is a graph diagram showing the effect. 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, 16; High frequency power supply, 19; Gate valve, 21; Support, 22;
Barrier layer, 23; photoconductive layer, 24; surface layer. Applicant's agent Patent attorney Takehiko Suzue

Claims (6)

[Claims] (1) In an electrophotographic photoreceptor having a conductive support, a barrier layer formed on the conductive support, and a photoconductive layer formed on the barrier layer, the photoconductive layer teeth,
The microcrystalline silicon region and the amorphous silicon region coexist, and the volume ratio of the microcrystalline silicon region to the photoconductive layer is 50%.
An electrophotographic photoreceptor characterized in that the electrophotographic photoreceptor is 90% to 90%. (2) The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer contains hydrogen. (3) The photoconductive layer contains at least one element selected from elements belonging to Group III or Group V of the periodic table.
The electrophotographic photoreceptor described in . (4) Claims 1 to 3, characterized in that the barrier layer is formed of microcrystalline silicon or amorphous silicon containing at least one element selected from carbon, oxygen, and nitrogen. The electrophotographic photoreceptor according to any one of the above items. (5) A patent characterized in that the barrier layer is formed of microcrystalline silicon or amorphous silicon containing at least one element selected from elements belonging to Group III or Group V of the periodic table. An electrophotographic photoreceptor according to any one of claims 1 to 4. (6) The photoconductive layer contains at least one element selected from halogen, carbon, oxygen, and nitrogen, according to any one of claims 1 to 5. electrophotographic photoreceptor.