JPS6258268A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain the titled body having an excellent electrostatic charge capacity, a low residual potential, a high sensitivity at a broad wavelength range of an up to a near infra-red ray, a good sticking property to a substrate, and an excellent resisting property to an environment by specifying forming materials of an electrostatic charge generating layer and an electrostatic charge transfer layer and a thickness of a laminated body. CONSTITUTION:The electrostatic charge generating layer 31 is composed of a laminated body of the 1st layer 24 made of an a-Si and having 0.1-5mum a thickness and the 2nd layer 23 made of an n-type muc-Si and having 1-10mum a thickness. The electrostatic transfer layer 22 has 30-80mum a thickness, and is composed of an amorphous silicon carbide (a-Si:C), an amorphous silicon nitride (a-Si:N) or an amorphous silicon oxide (a-Si:O). Thus, the titled body having the high resistance and the excellent electrostatic charge property and a high optical sensitivity at the range of a visible and a near infra-red rays and also capable of easily producing is obtd.

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, as materials for forming the photoconductive layer of electrophotographic photoreceptors, inorganic materials such as CdS, ZnO1SeSSe-Te, or amorphous silicon, or poly-N-vinylcarbazole (PVCz) have been used. or trinitrofluorene (TNF)
However, these conventional photoconductive materials have various problems in their photoconductive properties or in manufacturing, and some of the properties of the photoreceptor system have to be sacrificed. These materials are used differently depending on the purpose of use.

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, the 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 arise due to residual 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 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-8i)
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 this application of a-81, attempts have been made to use a-S+ as a photoconductive material for electrophotographic photoreceptors, and photoreceptors using a-3i 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-8i 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, a layered structure is created 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. It satisfies these demands.

By the way, a-8i is usually formed by a glow discharge decomposition method using silane gas, but at this time, a-8i is
Hydrogen is incorporated into the 8i film, and the electrical and optical characteristics vary greatly due to the difference in the amount of hydrogen. That is, as the amount of hydrogen that enters the a-3i film increases, the optical bandgap increases and the resistance of a-8i 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. In addition, if the hydrogen content in the a-8+ film is high, depending on the film formation conditions, (S
iH2) and those having a bonding structure such as SiH2 may occupy most of the area in the film. Then,
Due to the increase in voids and silicon dangling bonds, the photoconductive properties deteriorate, making it unusable as an electrophotographic photoreceptor. Conversely, reducing the amount of hydrogen penetrating into a-8i reduces the optical band gap and its resistance, but increases photosensitivity to long wavelength light. 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.

In addition, as a technique to increase the sensitivity to long wavelength light, there is a method of mixing silane-based gas and germane GeH+ and generating a film with a narrow optical band gap by glow discharge decomposition, but in general, silane-based gas and GeH+
Since the optimum substrate temperature is different between the two methods, the produced film has many structural defects and cannot obtain good photoconductive properties.

Furthermore, waste gas treatment is complicated because GeH+ waste gas becomes toxic gas when oxidized. Therefore, such technology 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 up to the near infrared region, and It is an object of the present invention to provide an electrophotographic photoreceptor that has good adhesion to the substrate and excellent environmental resistance.

[Summary of the Invention] An electrophotographic photoreceptor according to the present invention includes a conductive support, a charge transport layer formed on the conductive support, and a charge generating layer formed on the charge transport layer. In the electrophotographic photoreceptor, the charge generation layer has a first layer formed of amorphous silicon with a layer thickness of 0.1 to 5 μm, and an n-type microcrystalline layer with a layer thickness of 1 to 10 μm. It is a laminate with a second layer made of silicon, and the charge transport layer has a layer thickness of 3 to 80 μm.
It is characterized by being formed of amorphous silicon carbide, amorphous silicon nitride, or amorphous silicon oxide of m.

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 a photoreceptor (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. That is, whether all or some regions of the photoconductive layer are formed of microcrystalline silicon (μc-3i) 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 functionally separated electrophotographic photoreceptor, μ is added to the charge generation layer.
I am using c-8i.

μc-8i is a-
8l and polycrystalline silicon (polycrystalline silicon)
clearly distinguished from That is, in X-ray diffraction measurement, since a-8l is amorphous, only a halo appears;
Although no diffraction pattern can be observed, μc-3i shows a crystal diffraction pattern in which 2θ is around 27 to 28.5°. In addition, while polycrystalline silicon has a dark resistance of 108Ω・1, μc-3i has a dark resistance of 1011Ω.
- Has a dark resistance of 1 or more. This μc-8i is formed by aggregation of microcrystals having a grain size of about several tens of angstroms or more.

A mixture of μC-8i and a-8i means that the crystal region of μc-8I is mixed in a-8i, and μc-3i and a
-8i exists in a similar volume ratio. Also,
The laminate of μc-8i and a-8i is mostly a-8
A layer consisting of i and a layer filled with μc-8t are laminated.

Similar to a-3i, a photoconductive layer having μC-5t can be produced by depositing μC-31 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 concentration of the support is set higher than when forming a-8i and the high frequency power is also set higher than when forming a-3i, μC
-S+ 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.

In addition, by using gas obtained by diluting the raw material gas SiH+ and high-order silane gas such as 3i2Hs with hydrogen,
μc-8i can be formed with higher efficiency.

FIG. 1 is a diagram showing an apparatus for manufacturing an electrophotographic photoreceptor according to the present invention. For example, the gas cylinders 1.2° and 3.4 contain SiH+ and B2Hs, respectively.

Source gases such as H2 and CH4 are contained. The gas in these gas cylinders 1.2.3.4 is supplied to a mixer 8 via a valve 6 and piping 7 for flow rate adjustment. A pressure gauge 5 is installed in each cylinder, and by adjusting the pulp 6 while monitoring the pressure gauge 5, 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.

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, and a heater 15 for heating the drum base is arranged inside the drum base 14. It is set up. A high frequency power source 16 is connected between the electrode 13 and the drum base 14, so that 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 the apparatus configured as described above, after installing the drum base 14 in the reaction vessel 9, the gate valve 19 is opened to control the inside of the reaction vessel 9 at approximately 0.1 Torr. Evacuate to below pressure. Next, cylinder 1
．． From 2.3.4, the required reaction gases are mixed at a predetermined mixing ratio and introduced into the reaction vessel 9. In this case, reaction vessel 9
The gas flow rate introduced into the reaction vessel 9 is such that the pressure inside the reaction vessel 9 is 0.1.
Set it so that it is between 1 Torr and 1 Torr. Next, the motor 18
is activated 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 supplies a high frequency current between the electrode 13 and the drum base 14 to create a glow between them. form a discharge.

As a result, microcrystalline silicon (μc-3i) 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 electrophotographic photoreceptor according to the present invention has a conventional a
Similar to those using -3i, it can be manufactured using closed system manufacturing equipment, so it is safe for the human body. Furthermore, this electrophotographic photoreceptor has excellent heat resistance, moisture resistance, and abrasion resistance, so it has the advantage of having a long lifespan with little 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-3i contain 0.1 to 30 at % of hydrogen H. As a result, the dark resistance and bright resistance become harmonious, and the photoconductive properties are improved. μc
The optical energy gap Ea of -3i is the optical energy gap Ea of a-8I (1,65 to 1.708
V) is small compared to V). In other words, the optical energy gap of μc-3i changes depending on the crystal grain size and crystallinity of the μc-8i microcrystal, and as the crystal grain size and crystallinity increase, the optical energy gap decreases. The optical energy gap approaches the 1.1ev of crystalline silicon. By the way, the μc-8i layer and the a-8i layer absorb light with a larger energy than this optical energy gap, and transmit light with a smaller energy. Therefore, a-3i absorbs only visible light energy, but μc-3i, which has a smaller optical energy gap than a-3i, can also absorb near-infrared light, which has a longer wavelength and lower energy than visible light. I can do it. Therefore, μc-8i has high photosensitivity over a wide wavelength range.

μc-8t having such characteristics is suitable as a photoreceptor material for a laser printer using a semiconductor laser as a light source. When this a-8i is used as a photoreceptor for a laser printer, the light wavelength of the semiconductor laser is 790 nm and a-
Since 8t is longer than the wavelength region in which the sensitivity is high, the sensitivity of the photoreceptor becomes insufficient, and therefore it is necessary to apply a laser intensity to the photoreceptor that exceeds the capability of the semiconductor laser, which poses a practical problem. On the other hand, when the photoreceptor is formed using μc-8i, its high sensitivity region extends to the near-infrared region, so that it is possible to obtain a photoreceptor for semiconductor laser printers with extremely excellent photosensitivity characteristics.

In order to further improve the photoconductive properties of μc-8i, which has such excellent photosensitivity characteristics, μc
-3i preferably contains hydrogen.

Doping hydrogen into the μc-8i layer is performed, for example, by glow discharge decomposition method, by introducing a silane-based source gas such as SiH+ and 5i2Hs and a carrier gas such as hydrogen into a reaction vessel and causing glow discharge. Alternatively, a mixed gas of a silicon halide such as S i F4 and 5ICl+ 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 glow discharge decomposition but also by physical methods such as sputtering. Note that the photoconductive layer containing μc-8i preferably has a thickness of 1 to 80 μm, and more preferably 5 to 50 μm, in view of photoconductive properties.

Substantially all regions of the photoconductive layer may be formed of μc-3i, or may be formed of a mixture or a laminate of a-8i and μc-3i. 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 the entire area may be made of .mu.c-8i, or may be made of a mixture or a layered material.

Preferably, μc-3i is doped with at least one element selected from nitrogen, nitrogen, 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-8i and act as terminators for silicon dangling bonds,
It is believed that the density of states existing in the forbidden cloth between the bands is reduced, thereby increasing the dark resistance.

Preferably, a barrier layer is provided between the conductive support and the photoconductive layer. This barrier layer suppresses the flow of charge between the conductive support and the photoconductive layer, thereby increasing the charge retention function on the surface of the photoconductive member and increasing the charging ability of the photoconductive member. .

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 photoreceptor surface is negatively charged, a barrier layer is formed to prevent holes from being injected from the support side to the photoconductive layer.
Make it into a mold. It is also possible to form an insulating film on the support as a barrier layer. The barrier layer may be formed using μc-8i, or it may be formed using a-3i.

In order to make μc-8l and a-8i p-type, it is preferable to dope them with elements belonging to Group Ⅰ of the periodic table, such as boron B1 aluminum A11 gallium Ga, indium In1, and thallium T1. -8i
To make the layer n-type, an element belonging to group V of the periodic table, such as nitrogen N1 phosphorus P1 arsenic As1 antimony S
It is preferable to dope b1 and (smas3i).

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. The material forming the surface layer is Sis N4.8102 and SiC.

A I 20 a , a S i N ; H-a
SIO: There are inorganic compounds such as H1 and a-8iC:H and organic materials such as polyvinyl chloride and polyamide.

As described above, the electrophotographic photoreceptor is not limited to one in which 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. It is also possible to form a functionally separated structure in which a charge transfer layer (CTL) is formed on a support and a charge generation layer (CGL) is formed on the charge transfer layer. In this case, a barrier layer may be provided between the charge transfer layer and the support. The charge generation layer is
Carriers are generated by light irradiation. Part or all of this charge generation layer is made of microcrystalline aluminum μc-3i, and its thickness is 1 to 10 μm.
It is preferable to The charge transfer layer is a layer that allows carriers generated in the charge generation layer to reach the support side with high efficiency, and therefore, the carriers need to have a long life, high mobility, and high transportability. The charge transfer layer can be formed of a-3i. 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 transfer 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 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 type photoreceptor having a charge transfer layer and a charge generation layer, its charge retention function and charging ability can be improved. In addition,
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-8+ or μc-8i.

The feature of the invention according to this application is that the charge generation layer has a layer thickness of 0.
．． It is a laminate of a first layer formed of a-8i with a thickness of 1 to 5 μm and a second layer formed of n-type μC-3i with a layer thickness of 1 to 10 μm, and the charge transport layer has a layer thickness of 3 to 80μ
m, amorphous silicon carbide (a Si:
c>, it is formed of amorphous silicon nitride (a-8i:N) or amorphous silicon oxide (a-8i;O). FIG. 2 is a cross-sectional view of an electrophotographic photoreceptor embodying the present invention, in which a charge transport layer 22 is formed on a conductive support 21, and a charge generation layer 31 is formed on the charge transport layer 22. It is formed. This charge generation layer 31 includes a second layer 23 formed of n-type μc-8i on the charge transport layer 22, and a first layer 24 formed of a-3i on this second layer. have

Since the charge generation layer 31 is a laminate of the first layer 24 made of A-3i and the second layer 23 made of μC-8i, the photoreceptor can be heated from the visible light region to the near-infrared region (e.g. High sensitivity can be achieved up to 790 nm, which is the oscillation wavelength of a semiconductor laser. In other words, since the optical energy gap Ea of μC-8i is smaller than the optical energy gap of 1.65 to 1.70 eV of a-8i,
It has the ability to absorb long wavelength light with low energy, such as near-infrared light, and generate electric charges. For this reason, μc-8i
The second layer 23 formed of the above has high spectral sensitivity to long wavelength light such as semiconductor laser light having an oscillation wavelength of 790 nm. On the other hand, a-8i has high spectral sensitivity to visible light. Therefore, by using μc-8i and a-3i in the charge generation layer, this photoreceptor can be used in both PPC (plain paper copying machines) and laser printers using semiconductor lasers. μc-8i itself is
Although it is slightly n-type, this μc-8i is made to contain an element belonging to Group V of the periodic table, such as P, to actively make μc-8i n-type. Thereby, the sensitivity of the dc-s+ second layer to long wavelength light can be further increased. This Chapter V
The doping amount of group elements is 10-” to 10°3 atomic%.
, preferably 10-11 to 104 at.%. If the amount of doping is too large, μC-Si will become a strong n-type, and the specific resistance in the dark (dark specific resistance) will become too low, and if the amount of doping is too small, the sensitivity to long wavelength light will be insufficient. be.

Although the specific resistance of μC-8+ is relatively low, it is a-S t
The first layer 24 made of That is, a-Si has a relatively high resistivity, and by disposing a-8l, the charging ability can be increased.

The first layer 24 formed of this a-3i has the first layer of the periodic table.
Light doping (10-7 to 10
-3 at.

Further, by incorporating at least one element among C, O, and N into the charge generation layer 31 (the first layer 24 and the second layer 23) to an extent that the photoconductivity does not decrease, the dark specific resistance is increased. Charging ability (charge retention function) can be further enhanced. The content of C, O, and N is preferably 0.1 to 10 atomic percent.

The layer thicknesses of the 11124 and second layer 23 are 0.1 to 5 μm and 1 to 10 μm, respectively. If the charge generation layer is too thick, it will take a long time to form the film and the layer will easily peel off. On the other hand, if the charge generation layer is too thin,
This is because the carrier generation efficiency becomes low. In addition, the first
The layer 24 is located above the second layer 23 (on the light incident side) (
FIG. 2) is preferred over the opposite case. This is μC
-8i also absorbs visible light, so if the μc-8i second layer is above, the visible light will be absorbed by the μc-8i second layer before reaching the lower a-8i first layer. This is because the charge generation efficiency is low.

The charge transport layer 22 is a layer provided to transport carriers generated in the charge generation layer 31 to the support 21 with high efficiency, and contains at least one element selected from C, O, and N. a-8i (a-8i ; C, a-8i ; Q
, or a-31;N). By configuring the charge transport layer 22 in this way, the charge transport layer 22 can be made to have high resistance. Further, it is ideal that the charge transport layer does not have traps (density of states) that trap carriers. In this case, silicon dangling bonds that act as traps can be removed by containing a trace amount of C, O, and N in the charge transport layer 22. Considering the running properties of the carrier, the amounts of C, O, and N are as follows:
It is preferably 20 atomic % or less. By lightly doping this charge transport layer 22 with an element belonging to Group 1 of the periodic table, its dark resistance can be increased and the charge retention function can be indirectly improved. The layer thickness of the charge transport layer is 3 to 8
It is 0 μm. In order to maintain a high chargeability of the charge transport layer, it is necessary to increase the layer thickness, but if the charge transport layer is too thick, it becomes difficult for carriers to travel and it is difficult for the carriers to reach the support. This is because it becomes difficult.

The electrophotographic photoreceptor constructed in this way has a charge transport layer with excellent charge transport ability and high resistance, and a charge generation layer with a relatively high resistance and a small refractive index on the surface, so that the electrophotographic photoreceptor has excellent charge transport ability. and extremely excellent photosensitivity.

[Effects of the Invention] According to the present invention, electrophotography 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 photoreceptor can be obtained.

[Brief explanation of the drawing]

The first factor is a diagram showing an apparatus for manufacturing an electrophotographic photoreceptor according to the present invention, and FIG. 2 is a sectional view showing an electrophotographic photoreceptor according to an embodiment of the 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 Nidram base, 15; Heater, 16: High frequency power supply, 19; Gate valve, 21: Support, 22;
Charge transport layer, 23; second layer, 24; first layer, 31; charge generation layer.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor having a conductive support, a charge transport layer formed on the conductive support, and a charge generation layer formed on the charge transport layer, the charge The generation layer is a laminate of a first layer formed of amorphous silicon with a layer thickness of 0.1 to 5 μm and a second layer formed of n-type microcrystalline silicon with a layer thickness of 1 to 10 μm, The charge transport layer has a layer thickness of 3 to 8
An electrophotographic photoreceptor characterized in that it is formed of 0 μm amorphous silicon carbide, amorphous silicon nitride, or amorphous silicon oxide. (2) the second layer is formed on the charge transport layer, and the second layer is formed on the charge transport layer;
The layer is formed on a second layer, the second layer contains an element belonging to Group V of the Periodic Table, and the first layer contains an element belonging to Group III of the Periodic Table. An electrophotographic photoreceptor according to claim 1, characterized in that: