JPS5888753A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To obtain a photoreceptor having high sensitivity and high durability by forming an inhibiting layer for implantation of electric charge of amorphous silicon (a-Si) on the surface of a conductive substrate, a photosensitive layer of a-Si or a-Si doped with B, Ge and a surface protective layer of a-Si added with C successively. CONSTITUTION:An inhibiting layer 5 for implantation of electric charge is provided on the surface of a substrate 4 vapor deposited with Ni-Cr or a transparent conductor on an Al (alloy) or glass plate by forming an a-Si layer doped with several 10-several 100ppm B for positive charging and several 10-several 100ppm P for negative charging. A non-doped a-Si layer or an a-Si layer doped with several-several 10ppm b or an a-Si layer doped with Ge is formed as a photosensitive layer 6 on the layer 5. Further, the a-Si layer incorporated with C is formed as a surface protective layer 7 on the layer 6. Thus the photoreceptor having high sensitivity and high durability and suffiecient surface potential receiving power in both positive and negative charging is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor with high sensitivity and excellent durability.

The requirements for a certain material to be used as an electrophotographic photoreceptor are: 1) It must have excellent charge retention performance and surface potential acceptance ability in the dark. 2) It must have high photosensitivity and cover the entire emission spectrum of the light used. 3) Residual potential is low and does not increase even when used repeatedly 4) Less fatigue due to characteristics when used repeatedly 5) Mechanical strength, especially wear resistance It is excellent at and can be raised.

Amorphous silicon (a-St) Lg is expected to be used as an electrophotographic photoreceptor material because it has high photosensitivity over the entire visible light range and high mechanical strength. The dark resistivity of the 8i film is
The non-doped material had a resistance of ~109 Ω, which was as small as 10” Qcm even when doped with Ron, and the requirement 1) above was not satisfied.

FIG. 1 shows a conventional electrophotographic photoreceptor having a structure proposed to compensate for this drawback. In Figure 1, 1 is a −S
By doping several ppm to 10 ppm of poron Q3) into i, the dark resistivity can be increased from ~10''Ωm of non-doped
The photosensitive layer is increased to 11 Ωm, 2 is poron for positive charging, and phosphorus ω) is 100 to several 1 for negative charging.
A charge injection blocking layer made of a-8t doped with 100 pp. 3 is a support made of a conductive material, and Ni--Cr is deposited on an aluminum or glass plate.

In the electrophotographic photoreceptor having the above structure made for positive charging, the PN junction formed by the photosensitive layer 1 and the charge injection blocking layer 2 becomes a reverse bias state during charging, and prevents charge injection from the support 3. To prevent this.

Although the dark resistivity of the photosensitive layer 1 is as small as 10'1 Ωm, it has sufficient surface potential receiving ability.

On the other hand, the electrophotographic photoreceptor with the structure shown in Figure 1, which was made for negative charging, has a low surface potential acceptance ability despite having the same junction as that for positive charging, and does not meet the requirements for an electrophotographic photoreceptor. Not yet.

Furthermore, according to the findings of the present inventors, the electrophotographic photoreceptor having the structure shown in FIG. 1 exhibits significant deterioration in characteristics, particularly in surface potential receiving ability, when used repeatedly. For example, photosensitive layer 1 is ~4p
pmB dogu a dogu 1~5 μtn1 charge injection blocking layer 2 ~10100pp dogu a-8i ~0.1 μm1
Positive charging photoreceptor 'l + prepared with support 3 as M
When charging with a 7KV corona and then repeating photostatic charge removal for about 3 seconds, the initial surface potential decreased by about 15 degrees after cycling 50 times.

As mentioned above, in the electrophotographic photoreceptor having the structure shown in FIG.
For negative charging, the surface potential receiving ability is low, and for both positive and negative charging, the characteristics deteriorate significantly when used in reverse.

The present invention has been made to eliminate these drawbacks, and involves laminating a layer of amorphous silicon with carbon added to the surface of an electrophotographic photoreceptor having a support, a charge injection blocking layer, and a photosensitive layer. Its purpose is to have sufficient surface potential acceptance ability for both positive and negative charges, and <
To provide an electrophotographic photoreceptor with high sensitivity and excellent durability without deterioration of characteristics when used repeatedly.

Embodiments of the present invention will be described below with reference to the drawings. Second
The figure shows an embodiment of the present invention, and 4 is a support made of a conductive material, such as aluminum or aluminum alloy, or a glass plate with Ni-Cr or ITO deposited on it. A charge injection blocking layer 5 is formed on the surface of this support 4 . This charge injection blocking layer 5 is made of P-type amorphous silicon doped with zolon at a number of 0 to several 1.001) pm for positive charging, and doped with phosphorus at a number of 0 to several 100 ppm for negative charging. It is made of rlI type amorphous silicon. The surface of such a charge injection blocking layer 5 is doped with several to several tens of undoped or poron atoms.
A photosensitive layer 6 made of pprnppm-doped amorphous Φ silicon is formed on the surface of this photosensitive layer 60, a layer of carbon added to amorphous silicon (
A surface shielding layer 7 made of amorphous Φ silicon carbide is formed.

In the above example, the photosensitive layer 6 is made of non-doped amorphous silicon or amorphous silicon doped with zero haboron, but it may also be made of amorphous silicon doped with germanium or amorphous silicon doped with germanium.
It can also be amorphous silicon doped with germanium and boron. By doguing dalmanium, the photosensitive wavelength range can be extended to longer wavelengths.

FIG. 3 is a schematic diagram of an apparatus used for producing the electrophotographic photoreceptor having the above structure. In Figure 3, 8
is a vacuum pump, 9.15 is a stop valve, 10 is a reaction chamber, 11 is a high frequency power source, 12 is a cathode electrode, 13 is an anode electrode, 14 is a heating heater, 16, 17, 18
．． 19 is a gas flow controller, 20, 21, 22.2
3 is pressure reducing valve, 24 is 5IH4 gas? Empe, 25ke C, H
, gas cylinder, 26 is PHs (ioo PI)m)
10Ht gas) Zenpe, 27 is BzHa (100pp
m) 10 Ht gas cylinder, 28 is an aluminum substrate as the support 4 in FIG.

This device is used to electronically copy the structure shown in Figure 2 (the photoreceptor is
Let's talk about the case where nine works are made. However, in L7, the photosensitive layer is made of boron-doped amorphous silicon.

First, use the vacuum pump 8 to move the reaction chamber 1 () from 10-3 to 10-
After evacuation to 6 torr, if you want to make a positively charged photoreceptor, adjust SiH4 and BtHa with a gas flow controller so that the B2/81 ratio is several tens to several hundred ppm. Gas is introduced into the reaction chamber 10. Then, by applying high-frequency power between the electrodes 12 and 13 to generate a glow discharge, Garon (B) is placed on the substrate 28 which has been previously heated to 200 to 300°C by the heater 14. A doped charge injection blocking layer a-81 is formed. The film thickness is the required value (Equation 1
oooX), the glow discharge is temporarily stopped. Then, to form a photosensitive layer, B2 H6/S I H
After adjusting the flow rate so that the ratio of 4 to several tens of ppm, glow discharge is generated again to form a poron-doped a-Si photosensitive layer having a thickness of several to several tens of micrometers.

Next, 5IH4 and Ct H4 are adjusted to the flow rate ratio C2H4/Si
H4 is adjusted to 0.1 to 10, and consists of a layer of amorphous silicon with carbon added.
A surface protective layer of several μm is formed.

In this way, a photoreceptor for positive charging was created, however, the substrate was aluminum, and the charge injection blocking layer was made of B2H1l and SiH.
a-81-1 formed at ~150 ppm for 4
oooX, photosensitive layer contains BtHs ~4p for 5IH4
Formed as pm, 9a-81~5μm1 surface retention layer is S
A photoreceptor with a structure of ~1000A of amorphous silicon carbide formed as iL/Ct H4~1 was fabricated as a prototype, and when it was charged with a corona voltage of +7KV, the 1 surface capacity was ~40V7. □ and good reeds,
The dark decay half-life time was ~30 r, ec, and the half-life exposure tL in light decay was almost constant for light of 450 to 700 nm, showing a high sensitivity of ~0.4 μJ10/l.

In addition, in a repeating charge discharge test in which the cycle of charging → light removal w1 was set to 3 seconds, the surface potential receiving ability decreased only to the initial value of ~0.98 after 50 cycles, and the residual potential It showed good characteristics with no increase observed.

Next, a photoreceptor for negative IT was prepared, except that the substrate was aluminum and the IT charge injection blocking layer was formed with PH3 at ~65 ppm relative to SiH.
A, the photosensitive layer contains BtHa and Sin, ~4 pprr
a-St~5μm1 surface retention RM formed as I is 5
When a photoreceptor with a structure of amorphous silicon carbide ~100 DA formed with iHa/CtL = 1 was fabricated and charged with a corona voltage of -7 KV, the single surface capacity was good at ~40 V/μm. Yes, the half-life time for dark reduction is ~15 seconds, and the half-life exposure amount for light attenuation is constant for light in the range of 450 to 700 nm, and is ~0.
．． It showed a high sensitivity of 4 μJ/-.

In addition, in a repeated charge discharge test in which the cycle of charging → photostatic charge removal was set to 3 seconds, the surface potential receiving ability decreased only to the initial value of 0.95 after 50 repetitions, and the residual potential did not increase. I couldn't.

As is clear from the above description, in this invention.

By providing amorphous desilicon carbide, which is made by adding carbon to amorphous silicon, as a surface protective layer, it has a high surface potential receiving ability that could not be obtained with conventional methods, especially as a negative charging photoreceptor. It also has the advantage that the characteristics of both positively charged and negatively charged photoreceptors can be stabilized against repeated use.

In addition, amorphous silicon carbide has even higher hardness than a-St, and by providing it as a surface protective layer, an electrophotographic photoreceptor with higher wear resistance can be obtained. be. Therefore, the electrophotographic photoreceptor of the invention can be used in optical printers and electronic copying machines.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a conventional electrophotographic photoreceptor using amorphous silicon, FIG. 2 is a cross-sectional view showing an embodiment of the electrophotographic photoreceptor of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 2 is a schematic diagram of an apparatus used for the production. 4... Support, 5... Charge injection blocking layer, 6... Photosensitive layer. 7...Surface theory layer. Patent applicant Oki Electric Industry Co., Ltd.

Claims (1)

[Claims] a support; a charge injection blocking layer formed on the surface of the support and made of n-type or p-type amorphous silicon;
a photosensitive layer formed on the surface of the charge injection blocking layer; An electrophotographic photoreceptor comprising a layer made of amorphous Φ silicon with carbon added thereto, and a surface protective layer formed on the surface of the photosensitive layer.