JPH07109516B2 - Photoconductive member - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention is used for electrophotographic photoreceptors and the like,
The present invention relates to a photoconductive member having excellent photosensitivity characteristics and environment resistance.

[Technical background of the invention and its problems] Conventionally, as a material for forming a photoconductive layer of an electrophotographic photoreceptor, an inorganic material such as CdS, ZnO, Se, Se-Te, or amorphous silicon, or poly-N-vinylcarbazole. (PV
Organic materials such as Cz) or trinitrofluorene (TNF) are used. However, in these conventional photoconductive materials, there are various problems in terms of photoconductive characteristics or manufacturing, and these materials are selectively used according to the purpose of use while sacrificing the characteristics of the photoreceptor system to some extent. There is.

For example, Se and CdS are materials that are harmful to the human body, and require special consideration in safety measures when manufacturing them. Therefore, there is a problem in that the manufacturing apparatus becomes complicated and thus the manufacturing cost is high, and in particular, Se is required to be recovered, which causes an additional recovery cost. Further, in the Se or Se-Te system, since the crystallization temperature is as low as 65 ° C,
While the copying is repeated, a problem in photoconductivity occurs due to residual electricity and the like, so that the life is short and the practicality is low.

Further, ZnO has a problem that its reliability is low in use because it is easily oxidized and reduced and is significantly affected by the environmental atmosphere.

Furthermore, organic photoconductive materials such as PVCz and TNF are suspected to be carcinogens, which poses a problem for human health, and in addition, organic materials have low thermal stability and abrasion resistance. However, it has a short life.

On the other hand, amorphous silicon (hereinafter abbreviated as a-Si)
Recently, has attracted attention as a photoconductive conversion material, and its application to solar cells, thin film transistors, and image sensors has been actively made. As part of the application of this a-Si,
Attempts have been made to use a-Si as a photoconductive material for electrophotographic photoconductors. Since a photoconductor using a-Si is a non-polluting material, there is no need for recovery treatment, and other materials. Compared with the above, it has advantages such as high spectral sensitivity in the visible light region, high surface hardness and excellent abrasion resistance and impact resistance.

This a-Si is being studied as a photoconductor based on the Carlson system, but in this case, it is required that the photoconductor has high resistance and high photosensitivity. Since it is difficult to satisfy the photoconductor, a barrier layer is provided between the photoconductive layer and the conductive support, and a surface charge holding layer is provided on the photoconductive layer to form a laminated structure. These requirements are satisfied.

By the way, a-Si is usually formed by a glow discharge decomposition method using a silane-based gas. At this time, hydrogen is taken into the a-Si film, and the electrical and optical characteristics are different due to the difference in the amount of hydrogen. Fluctuates greatly. That is, when the amount of hydrogen penetrating into the a-Si film increases, the optical bandgap increases and the resistance of a-Si increases, but the photosensitivity to long-wavelength light decreases accordingly. For example,
It is difficult to use in a laser beam printer equipped with a semiconductor laser. Further, when the hydrogen content in the a-Si film is high, (SiH ₂ ) _n and SiH ₂ may be changed depending on the film forming conditions.
In some cases, those having a bonding structure such as occupy most of the region in the film. Then, voids increase and silicon dangling bonds increase, so that the photoconductive property deteriorates and it becomes unusable as an electrophotographic photoreceptor. Conversely, a-
When the amount of hydrogen penetrating into Si decreases, the optical bandgap decreases and the resistance decreases, but the photosensitivity to long-wavelength light increases. However, when the hydrogen content is low, less hydrogen is required to combine with the silicon dangling bond to reduce it. Therefore, the mobility of the generated carriers is reduced, the life is shortened, and the photoconductive properties are deteriorated, which makes it difficult to use as an electrophotographic photoreceptor.

As a technique for increasing the sensitivity to long-wavelength light, there is a technique in which a silane-based gas and germane GeH ₄ are mixed and decomposed by glow discharge to produce a film having a narrow optical band gap. With gas and GeH ₄ ,
Since the optimum substrate temperature is different, the produced film has many structural defects, and good photoconductive characteristics cannot be obtained. Also, Ge
Waste gas treatment is complicated because H ₄ waste gas becomes toxic gas when oxidized. Therefore, such a technique is not practical.

[Object 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. It is an object of the present invention to provide a photoconductive member having excellent environment resistance.

[Outline of the Invention] A photoconductive member according to the present invention is provided on a conductive support and the conductive support, contains hydrogen, and
10 ⁻³ to 10 atom% of Group III or V element of the periodic table,
A barrier layer made of microcrystalline silicon containing at least one of carbon, nitrogen, and oxygen at a concentration of 0.1 to 20 atomic% and having a thickness of 0.01 to 10 μm; A photoconductive layer made of microcrystalline silicon containing 30 atomic% and having a thickness of 3 to 80 μm, and provided on the photoconductive layer, 10 to 50 atomic% of at least one of carbon, nitrogen and oxygen. Consisting of amorphous silicon contained at a concentration of 0.1 to 0.1
A surface layer having a thickness of 2 μm, and the crystallinity of each of the barrier layer and the photoconductive layer is 10 to 30% by volume.

[Examples of the Invention] The present invention will be specifically described below. A feature of the present invention is that μC-Si is used in place of conventional a-Si. That is, all or part of the photoconductive layer is formed of microcrystalline silicon (μC-Si). Further, in the function-separated photoconductive member,
ΜC-Si is used for the charge generation layer.

μC-Si is a-Si due to the following physical properties.
And polycrystalline silicon (polycrystalline silicon). That is, in X-ray diffraction measurement,
Since -Si is amorphous, only a halo appears and a diffraction pattern cannot be recognized, but in the case of μC-Si, 2θ is
The crystal diffraction pattern at around 27 to 28.5 ° is shown. Polycrystalline silicon has a dark resistance of 10 ⁶ Ω · cm, whereas μC-Si has a dark resistance of 10 ¹¹ Ω · cm or more. This μC-Si is formed by aggregating fine crystals having a grain size of about several tens of angstroms or more.

Such a photoconductive layer having μC-Si can be manufactured by depositing μC-Si on a conductive support using silane gas as a raw material by a high frequency glow discharge decomposition method, similarly to a-Si. it can. In this case, if the temperature of the support is set higher than in the case of forming a-Si and the high frequency power is set higher than in the case of forming a-Si, μC-Si is easily formed. Further, by increasing the temperature of the support and the high frequency power, the flow rate of the raw material gas such as silane gas can be increased, and as a result, the film formation rate can be increased. Further, by using a gas obtained by diluting a high-order silane gas such as SiH ₄ and Si ₂ H _{6 as} a raw material gas with hydrogen, μC-Si can be formed with higher efficiency.

FIG. 1 is a diagram showing an apparatus for producing a photoconductive member according to the present invention. Source gases such as SiH ₄ , B ₂ H ₆ , H ₂ , and CH ₄ are contained in the gas cylinders 1, 2, 3, and ₄ , respectively.
The gas in these gas cylinders 1, 2, 3, 4 is supplied to the mixer 8 via a valve 6 and a pipe 7 for adjusting the flow rate. A pressure gauge 5 is installed in each cylinder, and the flow rate and mixing ratio of each raw material gas supplied to the mixer 8 can be adjusted by monitoring the pressure gauge 5 and adjusting the valve 6. it can. The gas mixed in the mixer 8 is supplied to the reaction container 9. A rotary shaft 10 is attached to the bottom 11 of the reaction vessel 9 so as to be rotatable in the vertical direction, and a disc-shaped support 12 is attached to the upper end of the rotary shaft 10 so that its surface is perpendicular to the rotary shaft 10. It has been fixed. In the reaction container 9, a cylindrical electrode 13 is installed on the bottom 11 with its axis center coinciding with the axis center of the rotary shaft 10. A drum base 14 of a photoconductor is mounted on a support base 12 with its axis center coinciding with the axis of the rotary shaft 10.
A heater 15 for heating the drum substrate is disposed inside the. A high frequency power supply 16 is provided between the electrode 13 and the drum base 14.
Are connected so that a high-frequency current is supplied between the electrode 13 and the drum base 14. Rotating shaft 10 is a motor
It is rotationally driven by 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 exhaust means such as a vacuum pump.

When a photoconductor is manufactured by the apparatus configured as described above, after the drum substrate 14 is installed in the reaction container 9, the gate valve 19 is opened and the inside of the reaction container 9 is set to about 0.1 Torr.
Exhaust below the pressure of r). Then, the required reaction gases are mixed from the cylinders 1, 2, 3, 4 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 set so that the pressure in the reaction vessel 9 is 0.1 to 1 torr. Next, the motor 18 is operated to rotate the drum substrate 14, the heater 15 heats the drum substrate 14 to a constant temperature, and the high frequency power supply 16 supplies a high frequency current between the electrode 13 and the drum substrate 14, A glow discharge is formed between them. As a result, microcrystalline silicon (μC-Si) is deposited on the drum substrate 14. Incidentally, by using the _{N 2 O, NH 3, NH} 3, NO 2, N 2, CH 4, C 2 H 4, O 2 gas or the like in the raw material gas, containing these elements in [mu] C-Si Can be made.

As described above, the photoconductive member according to the present invention has the conventional a-
Similar to the one using Si, it can be manufactured with a closed system manufacturing device, so it is safe for the human body. Further, since this photoconductive member is excellent in heat resistance, moisture resistance and abrasion resistance, there is an advantage that even if it is repeatedly used for a long period of time, it is less deteriorated and has a long life. Furthermore, since long-wavelength sensitizing gas such as GeH ₄ is unnecessary, it is not necessary to install a waste gas treatment facility, and industrial productivity is extremely high.

It is preferable that 0.1 to 30 atomic% of hydrogen be contained in μC-Si. As a result, the dark resistance and the light resistance are balanced, and the photoconductive characteristics are improved. When the μC-Si layer is doped with hydrogen, for example, in the case of a glow discharge decomposition method, a silane-based source gas such as SiH ₄ and Si ₂ H ₆ is used.
A carrier gas such as hydrogen is introduced into the reaction vessel for glow discharge, or a silicon halide such as SiF ₄ and SiCl ₄ , and a mixed gas of hydrogen gas may be used, or
You may react with the mixed gas of a silane type gas and a silicon halide. Furthermore, the μC-Si layer can be formed by a physical method such as sputtering instead of the glow discharge decomposition method.

It is preferable that the μC-Si is doped with at least one element selected from nitrogen N, carbon C and oxygen O. As a result, the dark resistance of μC-Si can be increased and the photoconductive characteristics can be improved. It is considered that these elements are precipitated at the grain boundaries of μC-Si, and act as terminators of silicon dangling bonds to reduce the density of states existing in the forbidden band between bands, which increases the dark resistance. To be

In the present invention, a barrier layer made of μC-Si is provided between the conductive support and the photoconductive layer. This barrier layer suppresses the flow of charges between the conductive support and the photoconductive layer, thereby enhancing the function of retaining charges on the surface of the photoconductive member and enhancing the chargeability of the photoconductive member. . In the Carlson method, when the surface of the photoreceptor is positively charged, the barrier layer is of p-type in order to prevent electrons from being injected into the photoconductive layer from the support side. 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 into the photoconductive layer from the support side.

In order to make μC-Si p-type, it is preferable to dope with an element belonging to Group III of the periodic table, such as boron B, aluminum Al, gallium Ga, indium In, and thallium Tl. In order to make the Si layer n-type, an element belonging to Group V of the periodic table, for example, nitrogen N,
It is preferable to dope with phosphorus P, arsenic As, antimony Sb, bismuth Bi and the like. This p-type impurity or n-type impurity doping prevents charges from moving from the support side to the photoconductive layer.

It is preferable to provide a surface layer on the photoconductive layer. Since μC-Si of the photoconductive layer has a relatively large refractive index of 3 to 4, light reflection on the surface is likely to occur. When such light reflection occurs, the ratio of the amount of light absorbed by the photoconductive layer decreases, and the light loss increases. Therefore, it is preferable to provide a surface layer to prevent reflection. Also, the provision of the surface layer protects the photoconductive layer from damage. Further, by forming the surface layer, the charging ability is improved and the electric charges are well distributed on the surface. Materials for forming the surface layer include inorganic compounds such as a-SiN; H, a-SiO; H, and a-SiC; H.

As the photoconductive member applied to the electrophotographic photoreceptor, as described above, the barrier layer is formed on the support, the photoconductive layer is formed on the barrier layer, and the surface layer is formed on the photoconductive layer. In addition to the above, the charge transport layer (CTL) may be formed on the support and the charge generation layer (CGL) may be formed on the charge transport layer to form a function separation type. In this case, a barrier layer may be provided between the charge transport layer and the support. The charge generation layer generates carriers by irradiation with light. This charge generation layer is made of microcrystalline silicon μC-Si partially or wholly and has a thickness of
It is preferably 0.1 to 10 μm. The charge transport layer is a layer that allows the carriers generated in the charge generation layer to reach the support side with high efficiency. Therefore, it is necessary that the carrier has a long life, high mobility, and high transportability. The charge transport layer may be formed of μC-Si. In order to increase dark resistance and improve charging ability, it is preferable to perform light doping with an element belonging to either Group III or Group V of the periodic table. Further, in order to further improve the charging ability and to have both functions of the charge transport layer and the charge generation layer, any one or more of C, N and O elements may be contained. The charge transport layer does not exhibit its function sufficiently when the film thickness is too thin or too thick. Therefore, the thickness of the charge transport layer is preferably 3 to 80 μm. By providing the barrier layer, even in the function-separated type photoconductive member having the charge transport layer and the charge generation layer, the charge retention function can be enhanced and the chargeability can be improved. Whether the barrier layer is p-type or n-type is determined according to its charging characteristics. This barrier layer may be formed of μC-Si.

The feature of the invention according to this application is that the photoconductive layer and the barrier layer are
At least a part of it is formed of μC-Si. 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, and a barrier layer 22 is formed on the barrier layer 22. A photoconductive layer 23 is formed on. On the other hand, in FIG. 3, a surface layer 24 is further formed on the photoconductive layer 23.

Since the photoconductive layer is mainly formed of μC-Si, the photoconductive member can be moved from the visible light region to the near infrared region (for example, near the oscillation wavelength of a semiconductor laser of 790 nm).
The sensitivity can be increased, which makes it possible to use this photoconductive member in both a PPC (plain paper copier) and a laser printer. μC-Si itself is slightly n
The photoconductive layer mainly composed of μC-Si is lightly doped with an element belonging to Group III of the periodic table (10 ⁻⁷
To 10 ⁻³ atom%), the photoconductive layer 23 becomes an i-type (intrinsic) semiconductor, the dark resistance is increased, and the SN ratio and the chargeability are improved. The photoconductive layer preferably has a film thickness of 3 to 80 μm, more preferably 10 to 40 μm.
m.

In addition, in the μC-Si forming the barrier layer, the periodic table II
An element belonging to Group I or Group V is doped.
The content is preferably 10 ^{−3 to} 10 atom%. By thus forming the barrier layer of μC-Si, the resistance becomes low and the blocking ability is further improved. Furthermore, when at least one element of C, O and N is contained in the barrier layer 22 in the range of 0.1 to 20 atom%, the charge blocking ability is further improved, which is preferable in terms of electrophotographic characteristics. The crystallinity of the photoconductive layer 23 and the barrier layer 22 is 10 to
It is preferably 30% by volume. This makes the electrophotographic characteristics harmonious and preferable.

Also, by setting the crystallinity of the barrier layer and the photoconductive layer to 10 to 30% by volume, the chargeability of the photoconductive layer is increased and the reflection of light at the interface between the barrier layer and the photoconductive layer is increased. It is possible to prevent the light from being absorbed by the photoconductive layer and absorb the light not absorbed by the photoconductive layer by the barrier layer. Therefore, the charging ability of the entire photoconductor can be increased, and light interference can be effectively prevented.

As shown in FIG. 3, in the photoconductive member in which the surface layer 24 is formed on the photoconductive layer 23, the surface layer 24 is C, O, N.
Of these, it is formed of a-Si containing at least one element. This protects the surface of the photoconductive layer, improves the environment resistance, and improves the charging ability. The content of C, O, N is preferably 10 to 50 atom%. Further, the thickness of the surface layer 24 and the barrier layer 22 is 0.01 to
The thickness is preferably 10 μm, more preferably 0.1 to 2 μm.

Next, an embodiment of the present invention will be described.

Example 1 While heating an Al drum to 300 ° C., 30 SCCM of SiH ₄ gas was added to the SiH ₄ gas flow of 0.1% B ₂ H ₆ gas, 30%.
% N ₂ and CH ₄ mixed gas (N ₂ : CH ₄ = 1: 1), 200% H ₂
And He mixed gas (H2: He = 1: 1) were mixed and supplied to the reaction vessel. The reaction pressure was 0.2 torr, high-frequency power of 150 watts was applied to cause glow discharge, and the barrier layer 21 was formed by forming a film for 30 minutes. As a result, a 0.8 μm barrier layer made of microcrystalline silicon was formed. The barrier layer contained 0.06 atomic% of boron, 7 atomic% of nitrogen and 10 atomic% of carbon. Next, the photoconductive layer is replaced with 100SCC.
For SiH ₄ gas of M, B ₂ H ₆ is 0.02 for SiH ₄ gas flow rate.
%, A mixed gas of H2 and He (H2: He = 1: 1) was mixed at 200% to form a film for 5 hours under the conditions of a reaction pressure of 0.3 torr and a high frequency power of 300 watts. This formed a 17 μm photoconductive layer of microcrystalline silicon. This photoconductive layer contained 13 atom% of hydrogen. Further, as the surface layer, 30 SCCM of SiH ₄ gas and CH ₄ and N ₂ gas at a flow rate which is twice the total flow rate of SiH ₄ gas are made to flow, and reaction pressure is set.
A film was formed for 5 minutes under the conditions of 0.3 torr and high frequency power of 150 watts. As a result, it consists of amorphous silicon.
A 2 μm surface layer was formed. 20 carbon in the surface layer
It contained 12 atomic% of atomic% and 12 atomic% of nitrogen. The crystallinity of the barrier layer is 10% by volume, and the crystallinity of the photoconductive layer is 13% by volume.
Met. The total film thickness was 18 μm. When a voltage of +5 kV was applied to the photoconductor thus formed,
A potential of 50 V was obtained. When this photoconductor was mounted on a copying machine and an image was produced, a very good image could be obtained.

Example 2 Instead of B ₂ H ₆ , PH ₃ was mixed 0.07% with SiH ₄ flow rate to form a barrier layer, and PH ₃ was mixed 0.01% with SiH ₄ flow rate to form a photoconductive layer. A film was formed under the same conditions as in Example 1 except for the points. As a result, in this embodiment, the photosensitive layer was the same as that in the first embodiment except that it contained no boron and contained 0.05% phosphorus (P) in the barrier layer and 0.007% phosphorus (P) in the photoconductive layer. A body drum was formed. Also in Example 2, when this photoconductor drum was mounted in a copying machine, a good image could be obtained.

[Effects of the Invention] As described above, in the present invention, the crystallinity of the photoconductive layer is set to 10 to 30% by volume, thereby increasing the dark resistance of the photoconductive layer and improving the chargeability of the barrier layer. I am trying to assist the function to make. At the same time, by setting the crystallinity of the barrier layer to 10 to 30% by volume, the change in the crystal structure at the interface between the photoconductive layer and the barrier layer is reduced, and the reflection of light at the interface is prevented to prevent the photoconductive layer. The light that is not absorbed in is incident on the barrier layer so that the light is absorbed in the barrier layer. In this way, by making the barrier layer also have the light absorption ability that the photoconductive layer originally should have, the light reflected by the conductive support is reduced,
Light reflected on the surface of the microcrystal silicon layer,
It is possible to prevent interference with the light reflected by the conductive support or the like. Therefore, according to the present invention, by stacking these layers, the photoconductive member as a whole has high long-wavelength sensitivity and chargeability, and it is possible to prevent light interference from occurring. Further, since the crystallinity of the photoconductive layer and the barrier layer are in substantially the same range,
Film peeling between layers does not occur. Furthermore, in the present invention, carbon, nitrogen, an amorphous silicon layer containing at least one kind of oxygen of 10 to 50 atomic% is provided on the surface of the photoconductive layer to reduce the amount of light reflected on the surface of the photoconductive layer. Therefore, the above-mentioned light interference can be prevented more effectively. Further, since the thickness of the surface layer is set to 0.1 to 2 μm, the electric charge retained in the surface layer does not remain during the exposure. Further, in such a laminated structure, the photoconductive layer contains 0.1 to 30% hydrogen.
Since it contains atomic% and has a thickness of 3 to 80 μm, the dark resistance and the light resistance are harmonized, and carriers can be sufficiently generated. The barrier layer contains a group III or V element of the periodic table at a concentration of 10 ⁻³ to 10 atom%, and at least one of carbon, nitrogen and oxygen at a concentration of 0.1 to 20 atom%,
Since it has a thickness of 0.01 to 10 μm, the blocking ability as a barrier layer can be improved, and the residual potential does not increase due to the provision of the barrier layer, and the charging ability of the photoconductive member can be improved. Can be further improved.

[Brief description of drawings]

FIG. 1 is a view showing a photoconductive member manufacturing apparatus 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 vessel, 10; rotating shaft, 13; electrode, 14; drum substrate, 15; heater , 16; high frequency power supply, 19; gate valve, 21;
Support, 22; Barrier layer, 23; Photoconductive layer, 24; Surface layer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Yoshizawa 70 Yanagimachi, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Yanagimachi factory (72) Inventor Miki Miki 70 Yanagimachi, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Corporation Inside the Yanagimachi Plant (72) Wataru Mitani 70 Yanagicho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Yanagimachi Plant, Toshiba Corporation (72) Inventor Mariko Yamamoto 70 Yanagicho, Sachi-ku, Kawasaki City, Kanagawa Prefecture Yanagicho Plant, Toshiba Corporation (56) References JP-A-59-121050 (JP, A)

Claims (1)

[Claims] 1. A conductive support, which is provided on the conductive support, contains hydrogen, and contains an element of Group III or V of the Periodic Table from 10 ⁻³ to 10 atomic%, carbon, 0.1-20 at least one of nitrogen and oxygen
A barrier layer made of microcrystalline silicon containing at a concentration of atomic% and having a thickness of 0.01 to 10 μm; microcrystalline silicon provided on the barrier layer and containing 0.1 to 30 atomic% of hydrogen; 80 μm
And a photoconductive layer having a thickness of 0.1 to 2 μm, which is made of amorphous silicon provided on the photoconductive layer and containing at least one kind of carbon, nitrogen and oxygen at a concentration of 10 to 50 atomic%. And a surface layer having a thickness, the crystallinity of the barrier layer and the photoconductive layer are both 10 ~
30% by volume of photoconductive member.