JPS61165763A - Amorphous silicon electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain high acceptance potential by forming an electrostatic charge blocking layer made of amorphous silicon higher in the energy gap than an amorphous silicon photosensitive layer. CONSTITUTION:The charge blocking layer 41 formed on a substrate drum 12, in a thickness of 8-30mum, evacuating the inside of a vessel 13 to a vacuum of 10<-6>torr, heating the drum 12 to 200-300 deg.C, opening valves 19, 20, 23, 27, 28 to introduce a gas mixture of diborane, disilane, and silane gases from each cylinder 22, 26, 30 into the vessel 13, and applying high frequency voltage between an electrode 16 and the drum 12 to cause glow discharge. Then, the amorphous silicon photosensitive layer 42 is formed in a thickness of 8-30mum on this layer 41 from silane, thus permitting the charge blocking layer 41 enhanced in the energy band by using the silane type gas mixture contg. disilane to be formed on the conductive substrate 12, and hence to effectively prevent injection of charge from the conductive substrate 12.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor comprising an amorphous silicon layer formed on a conductive support, in which the conductive support and the amorphous silicon layer are interposed, The present invention relates to a charge blocking layer that prevents charge migration from a conductive support.

The photoconductive layer of a recording drum having a photoconductive layer formed around it is uniformly charged, and the photoconductive layer is selectively irradiated with laser light based on printed information to change the charged potential of the photoconductive layer. Electrophotographic devices such as laser printers are well known, which selectively lower the latent image to form a latent image, develop the latent image by attaching charged toner to the area where the latent image is formed, and transfer and record the developed printed image onto recording paper. be.

[Conventional technology]

Conventionally, selenium (Se) has been used as such a photoconductive layer.
Se-based materials were used, but this Se is toxic;
There is a risk of pollution problems when discarded after long-term use, and the mechanical strength is low, causing scratches on the surface of the photoconductive layer, leading to problems such as deterioration of printing quality when used for a long time. many.

Therefore, recently, a recording drum has been developed in which an amorphous silicon photoreceptor layer, which is harmless to the human body and has high mechanical strength, is formed around a rotating drum made of aluminum (Al; l) as a photoconductive layer instead of Se. .

By the way, as a characteristic of such an electrophotographic photoreceptor, in order to accumulate the necessary charge on the surface of the photoreceptor, the resistance when no light is irradiated, that is, the dark resistance, must be 10 to 110 Ω-1 or more. . However, in the case of amorphous silicon, a small amount of wide atoms such as boron (B)
Even if you try to increase the resistance by doping 10
Only the resistance of Ω-1 can be obtained, which is necessary for the photoreceptor.
o.3~10'1Ω-10 value cannot be obtained. Therefore, in order to use amorphous silicon as a photoreceptor, it is necessary to provide a charge blocking layer 2 for blocking charge injection from the conductive support 1, as shown in FIG. This charge blocking layer 2 must suppress charge injection from the conductive support 1 and must allow photocarriers generated within the photoreceptor layer 3 to pass through.

As a charge blocking layer that satisfies such requirements, ■
An amorphous silicon layer doped with a wide atom such as phosphorus (P) at a high concentration to make it N-type, or an amorphous silicon layer doped with a wide atom such as boron (B) at a high concentration to make it a P-type is used. ing. (2) When doped with broad atoms, it can act as a negatively charged charge blocking layer; (2) When doped with broad atoms, it can be positively charged.

Further, between the conductive support 1 and the photoreceptor layer 3, a silicon carbide compound made of a compound of Si and carbon (C), or a silicon nitride made of a compound of Si and nitrogen (N), which has a large energy band gap, is used. It is also possible to form the charge blocking layer 2 by forming a system compound.

[Problem that the invention seeks to solve]

When producing amorphous silicon by the glow discharge CVD method, silane (SiH4) is used as the raw material gas.
, disilane (Si2Hs), etc. are used. Since these raw material gases are expensive, when amorphous silicon is used as a photoreceptor, it is desired to reduce the thickness of the photosensitive layer.

When a P-type or N-type amorphous silicon film is used as a charge blocking layer, a certain amount of charge is injected from the conductive support, so the charging potential of the amorphous silicon photosensitive layer above the charge blocking layer is 40 μ/
It saturates at a value of about μ−. Therefore, there is a limit to reducing the thickness of the photosensitive layer.

Further, when a silicon carbide compound or a silicon nitride compound is used as a charge blocking layer, a charging potential of 50 to 60 μm/μm can be obtained. However, since these films have high insulating properties, charges accumulate in the film or at the interface with the photosensitive layer.

Since this charge causes problems such as residual potential, these films are not preferred as charge blocking layers.

[Means for solving problems]

The above problem is that the charge blocking layer of an amorphous silicon electrophotographic photoreceptor in which an amorphous silicon photosensitive layer is provided on a conductive support via a charge blocking layer is formed by glow discharge CVD of a silane gas containing disilane gas.
This problem is solved by the amorphous silicon electrophotographic photoreceptor of the present invention, which is formed using amorphous silicon and has a larger energy gap than an amorphous silicon photosensitive layer.

[Effect]

That is, in the amorphous silicon electrophotographic photoreceptor of the present invention, the energy band gap value of amorphous silicon made from disilane (Si2Hs) gas or a mixed gas of Si2H6 gas and monosilane (Si)fa) gas is 2. OeV, and the fact that it is possible to obtain a film with a larger energy band gap than that of amorphous silicon, which is 1.6 to 1.7 eV when formed from SiH4 gas alone, is used.

By using amorphous silicon formed using a silane-based gas containing Si2H6 gas as a charge bronking layer, a charge blocking layer that is highly effective in blocking charge injection from the support and generates little residual charge can be achieved. A layer is formed to obtain an electrophotographic photoreceptor with a high charging potential.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an apparatus for manufacturing the amorphous silicon electrophotographic photoreceptor of the present invention.

As shown in the figure, a cylindrical drum 12 with a heater 11 provided therein and serving as a conductive support is placed in an airtightly sealed container 13 and rotated by a motor 14 . A cylindrical electrode 15 having a hollow center and a double structure on the sides is provided around the drum 12. Inside the double structure electrode 15, an amorphous silicon photoreceptor is placed. A forming gas is introduced.

A large number of gas exhaust ports 16 are provided on the surface of this electrode 15 facing the drum 12, and the lead-out end connected to the electrode 15 is lead out to the outside of the container 13. A power source 17 is connected.

Further, this outlet end is a gas introduction pipe 18, and diborane (B
2H6) Connected to the gas cylinder 22, further valve 23,
24, is connected to a disilane (5i2H6) gas cylinder 26 via a flowmeter 25, and further connected to a silane (SiHa) gas cylinder 30 via a valve 27, 38 and a flowmeter 29.

Further, a mechanical booster pump 33 and a rotary pump 34 are connected to the exhaust port 31 of the container 13 via a vacuum valve 32, and a diffusion pump 36 is connected via a vacuum valve 35.
A rotary pump 38 is connected via.

The case where the amorphous silicon electrophotographic photoreceptor of the present invention is formed using such an apparatus will be described.

First, the supporting body 12 which becomes the rotating body of the photosensitive drum is installed in the container 13, the vacuum valves 35 and 37 are opened, and the inside of the container 13 is brought to a vacuum level of 10-6 torr using the diffusion pump 36 and the rotary pump 38. Evacuate until the Next, using the heater 11, the drum 12 is
Heat until the temperature reaches 0-300°C. Furthermore, valve 1
9, 20.23.24.27.28 open and B2H
A mixed gas of 6 gas, Si2 H6 gas, and SiH4 gas is introduced into the container 13, and a high frequency voltage is applied between the electrode 16 and the drum 12 using the high frequency power supply 17 with a frequency of 13.56 MHz to generate a glow discharge. let The gas introduced by this discharge is turned into a plasma state, and the decomposed components of the gas are deposited on the drum 12, and as shown in FIG. Form layer 41.

Then valves 19, 20, 23, 24 are closed and container 13
SiH4 gas is introduced into the chamber, and an amorphous silicon photoreceptor layer 42 made of SiH4 gas is formed to a thickness of 8 to 30 .mu.m on the charge blocking layer 41 shown in FIG.

In this way, Si2 H6 is formed on the conductive support 12.
Since a charge blocking layer with a large energy bandgap is formed by the silane-based gas containing the gas, a charge pro-noking layer 41 that more effectively prevents charge injection from the conductive support 12 is obtained.

Using the energy distribution diagram in FIG. 3, we will discuss the reason why the charge blocking layer is suppressed from moving from the conductive support when a charge blocking layer is formed using a material with an energy band gap of 1.

In the figure, reference numeral 51 indicates the interface between the conductive support 52 made of sardine and the bronking layer 53. This charge pro-nokink layer 5
Consider the case where an amorphous silicon photosensitive layer is formed on No. 3 and its surface is positively charged.

During charging, electrons 54 are injected from the conductive support 52 into the charge protection layer 53. The electron 54 has a charge
In order to be injected into the knocking layer 53, an interface 511 is formed between the conductive support 52 and the charge pro-noking layer 53.
This cannot be achieved unless the energy is greater than the barrier (qφB) between the two. This barrier is the energy difference between the conduction band energy Ec of the charge blocking layer 53 and the Fermi energy Ep.

In order to reduce the number of electrons 54 from the conductive support 52 that pass through the blocking layer 53 and are injected into the amorphous silicon photosensitive layer, the barrier may be made larger.

Further, the electrons injected into the charge blocking layer 53 move within the charge blocking layer 53 during the electron lifetime τ. Further, the moving distance l is expressed as l=μτE when the electric field applied to the charge blocking layer 53 is E and the electron mobility is μ. If the moving distance l is reduced, the number of injected charges decreases, and therefore the charging potential increases. For this purpose, boron (B) may be added to amorphous silicon.

In another example, phosphorus (
P) may be added to make it N-type. However, this is the time when the photoreceptor is negatively charged. Alternatively, undoped amorphous silicon may be used as a charge blocking layer using a mixed gas of Si2 H6 gas and SiH4 gas without adding impurity atoms.

Furthermore, in the above embodiments, non-doped amorphous silicon is formed using Si2H6 gas alone,
Also, using this Si2H6 gas, dope with P or B to form impurity-doped amorphous silicon,
This may also be used as a charge blocking layer.

〔Effect of the invention〕

According to the amorphous silicon electrophotographic photoreceptor of the present invention as described above, charges injected from the conductive support are effectively blocked by the charge blocking layer. Therefore, the amorphous silicon photosensitive layer formed on the charge blocking layer can have a high charging potential.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus for forming an amorphous silicon electrophotographic photoreceptor of the present invention, FIG. 2 is a sectional view showing the structure of the amorphous silicon electrophotographic photoreceptor of the present invention, and FIG. 3 is an electrophotographic photoreceptor of the present invention. Energy Diagram in Photoreceptor FIG. 4 is a sectional view showing the structure of a general amorphous silicon electrophotographic photoreceptor. In the figure, 11 is a heater, 12.52 is a conductive support,
13 is a container, 14 is a motor, 15 is an electrode, 16 is a discharge hole, 17 is a high frequency power source, 18 is a gas introduction pipe, 19.20.
23.24° 27, 28 are valves, 21, 25.29 are flow meters, 22 is a diborane gas cylinder, 26 is a disilane gas cylinder, 30 is a silane gas cylinder, 31 is an exhaust port, 3
2.35.37 is a vacuum/N/lube, 33 is a mechanical booster pump, 34.38 is a rotary pump, 36 is a diffuser pump, 41.53 is a charge blocking layer, 42 is an amorphous silicon photoreceptor layer, 51 indicates the interface between the conductive support and the charge blocking layer, and 54 indicates electrons. Figure 1 No. 31! 1 No. 41! I

Claims (3)

[Claims] (1) The charge blocking layer of an amorphous silicon electrophotographic photoreceptor in which an amorphous silicon photosensitive layer is provided on a conductive support via a charge blocking layer is formed of amorphous silicon having a larger energy gap than the amorphous silicon photosensitive layer. An amorphous silicon electrophotographic photoreceptor characterized by: (2) Claim (1) characterized in that the charge blocking layer is formed by decomposing a silane gas containing disilane gas by a glow discharge CVD method.
The amorphous silicon electrophotographic photoreceptor described in . (3) The amorphous silicon forming the charge blocking layer is a non-doped type made of Si atoms alone, or an impurity atom-doped type added with impurity atoms that impart P-type or N-type conductivity. An amorphous silicon electrophotographic photoreceptor according to claim (1) or (2), characterized in that: