JPS63241560A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a photosensitive body superior in electric chargeability characteristics, low in residual potential, and high in sensitivity in a wide wavelength region up to a near infrared region by using a barrier layer having superlattice structure. CONSTITUTION:The electrophotographic sensitive body is composed of a conductive supporting body 1, the barrier layer 2 having superlattice structure formed by alternately laminating 2 kinds of amorphous silicon thin films, at least one of both kinds containing conductivity governing atom, and each of both films having a film thickness of 30-500Angstrom , and a photoconductive layer 3, thus permitting the obtained photosensitive body to have high carrier transferability, high resistivity, superior chargeability characteristics, and optimum photoconductive characteristics to optional wavelength regions.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an electrophotographic photoreceptor having excellent charging characteristics, dark decay characteristics, photosensitivity characteristics, environmental resistance, etc. Technology] Amorphous silicon containing hydrogen (hereinafter a=8
i:H) has recently attracted attention as a photoelectric conversion material, and has been applied to photoreceptors in electrophotographic processes as well as solar cells, thin film transistors, image sensors, etc.

Conventionally, inorganic materials such as CdS, ZnO, 8e, or 5e-Te, or poly-N-vinylcarbazole (PVCZ) have been used as materials constituting the photoconductive layer of electrophotographic photoreceptors.
Alternatively, organic materials such as trinitrone fluorenone (TNF) have been used. However, a-8i:H
Compared to these inorganic or organic materials, it is a non-polluting substance, so there is no need for recovery treatment, it has high spectral sensitivity in the visible light region, and it has a high surface hardness and is resistant to abrasion and impact. For this reason, 1-8i:H has attracted attention as a photoreceptor material for electrophotographic processes.

This a-8i:H is being studied as a material for a photoreceptor based on the Carlson method, but in this case, the photoreceptor is required to have high resistance and photosensitivity. However, since it is difficult to satisfy both of these characteristics with a single photoreceptor layer, 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. The laminated structure of the present invention satisfies these requirements.

[Problem that the invention seeks to solve]

By the way, conventionally, a high-resistance insulating single layer is used as a barrier layer, but when such a barrier layer is thick, the core rear flowing from the photoconductive layer to the support passes through the barrier layer. As a result, the residual potential becomes high. On the other hand, if the film thickness is thin, υ dielectric breakdown will occur due to the development bias. In addition, when a p-type or n-type semiconductor is used as a barrier layer, if the film is thick, the intermediate layer will be dragged by structural defects such as dangling bonds, increasing the residual potential; In such cases, carriers from the support cannot be blocked, resulting in a decrease in charging ability.

The present invention has been made in view of such circumstances, and
Provides electrophotographic photoreceptors with excellent charging ability, low residual potential, high sensitivity over a wide wavelength range up to the near-infrared region, good bonding with substrates, and excellent environmental resistance. The purpose is to

[Structure of the invention]

(Means for solving the problem) As a result of various studies, the present inventors discovered that the above object can be achieved by using a superlattice structure as a barrier layer of an electrophotographic photoreceptor. , we have completed the present invention.

That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor comprising a conductive support, a barrier layer, and a photoconductive layer.
The barrier layer is constituted by alternately laminating two types of amorphous silicon thin films, at least one of which contains atoms dominating the conductivity type, and each thin film has a thickness of 30 to 500X.
It is characterized by

In the electrophotographic photoreceptor of the present invention, the element controlling the conductivity type contained in at least one amorphous silicon thin layer of the superlattice structure constituting the barrier layer is, for example, a group 1 or group V element of the periodic table. It is an element belonging to The content of these elements is preferably 10-s to IIg, %, more preferably 1
0-1 to 10-1 atomic % (Example) FIG. 1 is a diagram showing a cross-sectional structure of an electrophotographic photoreceptor according to an example of the present invention. In four times, 1 is a conductive support. A barrier 1ij2 is formed on the conductive support, and a photoconductive layer 3 is formed thereon. Furthermore,
A surface layer 4 is formed on the photoconductive layer 3.

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

The barrier layer 2 has a superlattice structure of an a-8i thin film.
These thin films can be hydrogen-doped (a-si:a).

The barrier layer 2 is formed to enhance the charge retention function of the photoreceptor surface (by suppressing the flow of charges between the conductive support 1 and the photoconductive layer 3) and to increase the charging ability of the photoreceptor. It is something that will be done. Therefore, when forming a Carlson type photoreceptor using a semiconductor layer as a barrier layer, the amorphous silicone thin film forming the barrier s2 should be changed to p-type so as not to reduce the ability to retain charges on the surface. or n-type. That is, when the surface of the photoreceptor is positively charged, the barrier layer 2 is made p-type to prevent electrons that neutralize the surface charge from being injected into the charge generation layer. Conversely, when the surface is negatively charged, the barrier layer 2 is set to nfi to prevent holes that neutralize the surface charge from being injected into the charge generation layer. Since the carriers injected from the barrier layer 2 cause noise to the carriers generated in the layer 3 when light is incident, preventing the injection of carriers as described above will improve the sensitivity. , a-5f to be p-type, it is preferable to dope them with elements belonging to Group 1 of the periodic table, such as boron B, aluminum gallium Ga, indium In, and thallium T1. Further, in order to make a-8i n-type, it is preferable to dope it with an element belonging to Group V of the periodic table, such as nitrogen, phosphorus P1 arsenic As, antimony Sb1, and bismuth Bi.

Furthermore, by incorporating one or more elements selected from carbon, nitrogen, and oxygen into a-81 constituting the barrier layer 2, the barrier layer can be made to have high resistance.

The thickness of the barrier layer 2 is preferably 100X to 10 μm. The photoconductive layer 3 formed on the barrier layer 2 is a-8i:H
Alternatively, it can be made of microcrystalline silicon.

Microcrystalline silicon (μc-8i) is thought to be formed by a mixed phase of microcrystalline silicon and amorphous silicon with a grain size of about several tens of Angstroms, and has the following properties: It has physical characteristics.

First, X-ray diffraction measurements show a crystal diffraction pattern with 2θ in the vicinity of 28 to 28.5°, which is clearly distinguishable from amorphous a-83 in which only a halo appears.

Second, the dark resistance of μc-87 can be adjusted to 1016 Ω·α or more, and it can be clearly distinguished from polycrystalline silicon, which has a dark resistance of 1 fΩ·α.

When light enters the photoconductive layer 3, carriers are generated. Among these carriers, carriers of one polarity neutralize the charges on the surface of the photoreceptor, and carriers of the other polarity travel on the photoconductive layer 3 and become conductive. Reach the sexual support.

The hydrogen content in a-81:H and μc-8i:H constituting the barrier layer 2 and the photoconductive layer 3 is 0.01
-30 atom% is preferable, and 1-25 atom% is more preferable. Such hydrogen content compensates for the dangling bonds of silicon, balances dark resistance and bright resistance, and improves photoconductive properties.

To form a-8t-H into a film by glow discharge decomposition method,
H can be added into the thin layer by introducing SiH4 and a silane gas such as Si, H, etc. into the reaction chamber as raw materials and generating a jiglow discharge using high frequency waves. as needed,
Hydrogen or helium can be used as a carrier gas for the silanes. On the other hand, SiF4 gas and 5i
(2) Logonized silicon such as C14 gas can be used as the raw material gas. Further, even if a mixed gas of a silane gas and a silicon halide gas is reacted, a film of 1-8i:H containing H can be similarly formed. Note that this thin layer can also be formed by a physical method such as sputtering, instead of using the glow discharge decomposition method.

Similarly to a-8i:H, the μc-81 layer can also be formed using a high-frequency glow discharge decomposition method using silane gas as a raw material. In this case, the temperature of the support is a-81:
When forming H) is also set high, and the high frequency power is also
- If set higher than in the case of S i a H, μc
-S i *H becomes easier to form. Furthermore, by increasing the support temperature and high frequency power, the flow rate of raw material gas such as silane gas can be increased, and as a result, the film formation rate can be increased. In addition, by using a raw material gas of 8iH4 and a gas obtained by diluting high-order silane gas such as Si, H・, etc. with hydrogen, μc-84:H
can be formed with even higher efficiency.

A surface layer 4 is provided on top of the light guiding layer 3.

Since a-8t:H and the like constituting the photoconductive layer 3 have a relatively large refractive index of 3 to 3.4, light reflection easily occurs on the surface. When such light reflection occurs, the proportion of the amount of light absorbed by the photoconductive layer 3 decreases, increasing optical loss. For this reason, it is preferable to provide the surface layer 4 to prevent reflection. Also, by providing the surface layer 4, the photoconductive layer 3 is protected from damage. Furthermore, as a material for forming the surface layer, a-84:H
, a-8i:H, and a-8iC:H, and organic materials such as polyvinyl chloride and polyamide.

The surface of the electrophotographic photoreceptor constructed in this manner is charged with a positive voltage of approximately 500 V by corona discharge, and then exposed to light (
hv), electron and hole carriers are generated in the photoconductive layer 3. Electrons in the conduction band are accelerated toward the surface layer 4 side by the electric field within the photoreceptor, and holes are accelerated toward the conductive support 1 side. In this case, if a conventional barrier layer consisting of a single high-resistance insulating layer is used, as mentioned above, if the film is thick, carriers flowing from the photoconductive layer to the support cannot pass through the barrier layer. , the residual potential becomes high. On the other hand, if the film is thin, dielectric breakdown may occur due to the development bias. Furthermore, when a p-type or n-type semiconductor is used as a barrier layer, if the film is thick, carriers will be trapped in structural defects such as dangling bonds, increasing the residual potential. If it is thin, carriers from the support cannot be blocked, resulting in a decrease in charging ability. On the other hand, when the barrier layer has a superlattice structure as in the photoreceptor of the present invention, the carrier lifespan in the potential well layer is longer than in the case of a single layer without a superlattice structure due to quantum effects. has increased by 5 to 10 times. In addition, in the superlattice structure, due to bandgap discontinuity,
Although a periodic barrier layer is formed, carriers easily pass through the bias layer due to the tunnel effect, so the effective mobility of carriers is equivalent to that in the bulk, and carrier mobility is excellent. . As described above, the superlattice structure made of laminated thin layers can provide high photoconductivity and provide clear images even with conventional photoreceptors. See Figure 2 below. An apparatus and a manufacturing method for manufacturing the electrophotographic photoreceptor of the above embodiment by a glow discharge method will be described. In the figure, gas cylinders 21, 22, 23,
For example, 8 i H4 @ JH6 @ CH
4th class raw material gas is accommodated. The gas in these gas cylinders is supplied to a mixer 28 via a pulp 26 and piping 27 for flow rate adjustment. Each cylinder is equipped with a pressure gauge 25, and by adjusting the pulp 26 while monitoring the pressure gauge 25, the flow rate and mixing ratio of each raw material gas supplied to the mixed white 28 can be adjusted. The gases mixed in the mixer 28 are supplied to a reaction vessel 29. At the bottom 31 of the reaction vessel 29, a rotating shaft 30 is rotatably attached to a vertical turn. At the upper end of the rotating shaft 30, a disc-shaped support 32 is attached with its surface facing the rotating shaft 30. The metal is fixed vertically. , ff Inside the prison container 29, a cylindrical ti 33 is installed on the bottom 31 with its axial center aligned with the axial center of the rotating shaft 30. A drum base 34 of a photoreceptor is placed on a support base 32 with its axial center aligned with the axial center of the rotating shaft 30.
A heater 35 for heating the drum base is disposed inside the drum. A high frequency power source 36 is installed between the electrode 33 and the drum base 34.
A high frequency current is supplied between the two. The rotating shaft 30 is rotationally driven by a motor 38. Reaction container 2
The pressure inside the reaction vessel 29 is monitored by a pressure gauge 37.
is connected to a suitable evacuation means such as a vacuum pump via a gate pulp 38.

When manufacturing a photoreceptor using the above manufacturing apparatus, after installing the drum base 34 in the reaction vessel 29, the dirt pulp 39 is opened and the inside of the reaction vessel 29 is evacuated to a pressure of about 0.0 Torr or less. . Next, cylinders 21, 22, 23.
24, the required reaction gases are mixed at a predetermined mixing ratio and introduced into the reaction vessel 29.

In this case, the flow rate of the gas introduced into the reaction vessel 29 is set so that the pressure within the reaction vessel 29 is 0.1 to 1.0 Torr. Next, the motor 38 is operated to rotate the drum base 34, the heater s5I/c heats the citrus base 34 to a constant humidity, and the high frequency power supply 36 applies a high frequency current between the stain electrode 33 and the drum base 34. A glow discharge is formed between the two. In addition, the PC-8i is placed on the drum base 34: H! a-8i: H is deposited. Note that the raw material gas contains N, O, NH,, No,
,N, ,CH,.

By using C, H4, O□ gas, etc., C,0
, Nt-μc-8i:H or a-8i:H.

As described above, since the electrophotographic photoreceptor according to the present invention can be manufactured using a closed system manufacturing apparatus,
Safe for humans.

Next, the results of testing the electrophotographic properties of an electrophotographic photoreceptor according to the present invention formed into a film will be described.

Test Example 1 If necessary, to prevent interference, an aluminum drum base with a diameter of 8 on and a width of 35011 nm, which has been subjected to acid treatment, alkali treatment, and sandblasting, is installed in the reaction vessel, and the reaction vessel is heated to approximately 10 mm. The vacuum was evacuated to 1 torr. The drum base was heated to 250"CK, and while rotating at 10 rpm, 8iH, gas was heated to 5008 CCM% B, H.
, the gas is 8iH, the flow rate ratio to the gas is 10-'', H,
Gas was introduced into the reaction vessel at a flow rate of 3008 ccM, and the pressure inside the reaction vessel was adjusted to 1 Torr. And 35
A high frequency power of 0 W was applied to generate plasma to form 50 p-plastic a-8i:H films on the drum base.

Next, the flow rate ratio of B, H, and gases to 3i H4 gas was set to 10-4, and 5oXop type a-8i:H
A thin film was formed. These operations were repeated to form barrier layers each having a 2000^ superlattice structure consisting of 50 p-type a-8i:H thin films.

Next KSiH,, f 500 S CCMs B2H6
The scum was introduced into the reaction vessel at a flow rate such that the flow rate ratio to the SIH gas was 10-6, the inside of the reaction vessel was set to 1 Torr, and a high frequency power of 300 W was applied to form a 30-layer I-type a.
-8i:H photoconductive layer was formed.

Finally, a surface layer of a-8iC:H with a thickness of 0.1 μm was formed.

When the surface of the photoreceptor thus formed is positively charged at about 500 V and exposed to white light, this light is absorbed by the light guide [ffi] and carriers of electron-hole pairs are generated. In this test example, a large number of carriers were generated, the carriers had a long life, and high running performance was obtained. As a result, clear and high quality images were obtained. In addition, when the photoreceptor manufactured in this test example was repeatedly charged, the reproducibility and stability of the transferred image were extremely good. It has been proven that it has excellent durability.

Test Example 2 An electrophotographic photoreceptor was manufactured in the same manner as in Test Example 1, except that the barrier layer had a superlattice structure of an N-type a-8i:H thin film. That is, instead of the B, H, and gases in test row 1, PH, and ys were introduced at a flow rate ratio of 5 x 10-'' to the SiH4 gas, the pressure in the reaction chamber was set to I Torr, and a high-frequency power of 350 W was applied. was applied to form a 50^N heat-8i:H@ film.
PH, the flow rate ratio of gas to SiH4 gas is 1 (f'-
Similarly, 50X N type a-8i:
A H thin film was formed. Repeat this operation until 2000
A barrier layer having a superlattice structure of X was formed.

When this photoreceptor was repeatedly charged, the transferred image had high reproducibility and stability, and had excellent durability such as corona resistance, moisture resistance, and abrasion resistance.

In addition, the types of thin layers are not limited to two types as in the above test example, but three or more types of thin layers may be stacked.In short, the optical band cap forms a boundary between different thin layers. Good.

〔Effect of the invention〕

According to the present invention, since a superlattice structure is used for the barrier layer, it is possible to obtain an electrophotographic photoreceptor that has high carrier mobility and has high resistance and excellent charging characteristics. In particular, the present invention has the advantage that by appropriately combining the materials forming the thin layer, it is possible to obtain a photoreceptor having optimal photoconductive properties for light in any wavelength band.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an electrophotographic photoreceptor according to an embodiment of the present invention, and FIG. 2 is a diagram showing an apparatus for manufacturing an electrophotographic photoreceptor according to an embodiment of the invention. 1... Conductive support, 2... Barrier layer, 3... Photoconductive layer, 4... Surface layer 〇 Applicant's representative Patent attorney Takehiko Suzue N. 1st cause 2nd prisoner

Claims (7)

[Claims] (1) In an electrophotographic photoreceptor comprising a conductive support, a barrier layer, and a photoconductive layer, the barrier layer consists of alternating layers of two types of amorphous silicon thin films, at least one of which contains atoms dominating the conductivity type. An electrophotographic photoreceptor characterized in that the electrophotographic photoreceptor is constructed by laminating two thin films, each having a thickness of 30 to 500 Å. (2) The electrophotography according to claim 1, wherein the element that dominates the conductivity type is at least one element selected from elements belonging to Group III and Group V of the periodic table. Photoreceptor. (3) The electrophotographic photoreceptor according to claim 1 or 2, wherein the barrier layer contains at least one of carbon, oxygen, and nitrogen. (4) Any one of claims 1 to 3, wherein the photoconductive layer is made of an amorphous material and/or a semiconductor material that is at least partially microcrystalline.
The electrophotographic photoreceptor described in . (5) Any one of claims 1 to 4, wherein the photoconductive layer contains at least one element selected from elements belonging to Group III or V of the Periodic Table. The electrophotographic photoreceptor according to item 1. (6) The electrophotographic photoreceptor according to any one of claims 1 to 5, wherein the photoconductive layer contains at least one of carbon, oxygen, and nitrogen. (7) The electrophotographic photoreceptor according to any one of claims 1 to 6, further comprising a surface layer on the photoconductive layer.