JPH02110470A - electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To improve moisture resistance and plate wear resistance by using carbon contg. a slight amount of gallium to form the free surface side of a surface layer consisting of amorphous carbon. CONSTITUTION:This photosensitive body has a photoconductive layer 3 consisting of an amorphous silicon material on a conductive base body 1 and the photoconductive layer 3 is coated with a surface layer 5 consisting of an amorphous material essentially composed of carbon via a buffer layer 4. The surface layer 5 has the two-layered structures consisting of the 1st layer 5a in contact with a buffer layer 4 and a 2nd layer 5b which is lower in electric resistance than the 1st layer 5a and exists on the free surface side. The 2nd layer 5b consists of hydrogenated amorphous carbon contg. gallium atoms. Consequently, the buffer layer side 5a of the surface layer 5 usually plays the role of holding the electrostatic charge accumulated in the surface of the free surface side. The formation of the thick free surface of the surface layer 5, i.e. the surface of the photosensitive body is possible in this way and the plate wear resistance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor using an amorphous silicon-based material as a photoconductive layer.

[Conventional technology]

In recent years, amorphous hydrogenated silicon (a-Si(H))
Because it has excellent photosensitivity and heat resistance, has high hardness, can be formed into large-area thin films relatively easily, and is not particularly concerned about environmental pollution, it has attracted attention and development as a photoconductive material for electrophotographic photoreceptors. It is progressing.

a-3i (H) is - gas containing silicon for boat fishing,
For example, it is produced by plasma CVD using Sl 14> gas as a raw material gas. a-3i(H) produced by this method has few localized levels in the forbidden band and has high photoconductivity, and it is also possible to use gases such as ciborane (BJ6) and phosphine (PHi) as the raw material gas. When mixed with the raw material gas, conductivity control and monovalent electron control are possible and high resistance can be achieved.Furthermore, by mixing an appropriate gas into the raw material gas, carbon (C), nitrogen (N), oxygen (0), etc. -S
i (H) can also be introduced into the photoreceptor, and has the required charging performance and photosensitivity as a photoreceptor.

A photoreceptor having a photosensitive layer made of a-3i(tl) has extremely excellent performance because it can provide properties that satisfy temperature characteristics 1, mechanical strength, and the like.

[Problem to be solved by the invention]

However, although a photoreceptor with such a-Si(H) as a surface layer can initially produce good images,
It has been found that when images are copied after being stored in the atmosphere or in high humidity for a long period of time, image defects often occur. It has also been found that images become increasingly blurred as the copying process is repeated many times. It has been confirmed that such deteriorated photoreceptors are likely to cause screen blur, especially in high humidity environments, and that as the number of copies increases, the critical humidity at which image blur begins to occur tends to gradually decrease.

As mentioned above, a photoreceptor with a-3i(H) as a surface layer is exposed to the atmosphere or moisture for a long period of time, or is exposed to chemical species (ozone, nitrogen oxides, etc.) generated by corona discharge during the copying process.

It is thought that the outermost surface of the photoreceptor is easily affected by nascent oxygen (e.g., nascent oxygen) and some kind of chemical alteration causes image defects, but the mechanism of this deterioration has not yet been fully elucidated.

In order to prevent the occurrence of such image defects and improve printing durability and moisture resistance, attempts have been made to provide chemical stabilization by providing a protective layer on the surface of the photoreceptor.

For example, hydrogenated amorphous silicon carbide (a-3+++C+-x(H)+0<X4) as the second surface protective layer,
Or hydrogenated amorphous silicon nitride (a-3+
There is a known method for preventing deterioration of the surface layer of a photoreceptor due to the copying process or environmental atmosphere by providing xN1-x()I)Q<x<l (Japanese Patent Laid-Open No. 57-1155).
Publication No. 59).

However, if the carbon concentration or nitrogen concentration in the surface protective layer is selected to an optimal value, printing durability can be considerably improved, but it is difficult to maintain moisture resistance in a high humidity atmosphere (relative humidity of 80% or more). However, after copying tens of thousands of sheets, image blur occurs at relative humidity levels of 60%, and even with these surface protective layers, rigidity and moisture resistance cannot be significantly improved. It is in.

Furthermore, it has been known that amorphous carbon (a-C) is very effective as a material for such a surface protective layer, but the chemical stability and moisture resistance of the photoreceptor can be improved by using a-C. Although this is a significant improvement, the residual potential, which affects image characteristics, increases, making it impossible to apply a thick surface layer.

It is an object of the present invention to eliminate the above-mentioned drawbacks, to prevent characteristic deterioration phenomena during long-term storage and repeated use, to hardly cause any deterioration in characteristics such as defective output images even in a high humidity atmosphere, and furthermore, to It is an object of the present invention to provide a photoreceptor whose surface is not easily abraded or damaged by output image forming processes such as cleaning, and which has excellent moisture resistance and printing durability.

Furthermore, the purpose is to prevent an increase in residual potential due to thickening of the surface layer.

[Means to solve the problem]

In order to achieve the above object, according to the present invention, a photoconductive layer made of an amorphous silicon-based material is provided on a conductive substrate, and the photoconductive layer is made of amorphous carbon (a-C) through a buffer layer. In the photoreceptor coated with a surface layer consisting of carbon, the surface layer is made of carbon containing a trace amount of gallium.

[Effect]

In a photoreceptor having such a configuration, charges are accumulated not on the free surface but at the interface between the first layer (high resistance layer) and the second layer (low resistance layer). Therefore, the residual potential is determined by the first layer, and there is no effect even if the second layer is added to 7 (7). In other words, printing durability can be increased by increasing the thickness of the second layer.

In addition, as a means of lowering the resistance of the second layer, the present researchers have conducted extensive research and have found that adding impurities is effective.

Fluorine addition has the effect of widening the optical energy gap. On the other hand, if we consider the energy gap to be constant (2.4 eV or more is required for the a-3i photoreceptor considering the window effect of the surface layer), this is synonymous with a decrease in electrical resistance.

It is also possible to increase the number of donor atoms by adding 6a. In addition, this effect is approximately 100 to 110,000pp
We also found that it was significant in the range of

〔Example〕

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

FIG. 1 is a schematic cross-sectional view showing the layer structure of an embodiment of the photoreceptor according to the present invention.

The conductive substrate 1 may be cylindrical, plate-like, or sheet-like, and may be made of metal such as aluminum, stainless steel, etc.
Alternatively, it may be made of glass or resin that has been subjected to conductive treatment.

The blocking layer 2 is provided to prevent charge injection from the conductive substrate l. 8j in terms of materials! ,0. ,
A j'N, Si0.5in2. Hydrogenated fluorinated amorphous silicon carbide (a-3i l -xCx
(F, H)), hydrogenated amorphous nitride silicon<a-3iN-(H)), hydrogenated amorphous carbon (a-C(+1)), fluorinated amorphous carbon (a-C(F)), periodic law a-C(H), a-C(F), a-3i(
H) etc. can be used. The thinner the film thickness is, 1 μm or less, the better.

The photoconductive layer 3 is preferably made of a material that has excellent absorption ability for target light and high photoconductivity, such as a-8i (H).

a-3i(F, 11>, a-3il-x[:1L(
H)(0<x<0.3), a-5iNx(H)(0<
X<0.2), a-SiDx(11) (0<x<0.
1), a-3i, -xGex (If), etc., and materials in which these are doped with elements of Group M and Group II of the periodic table are preferable. The film thickness is practically preferably 3 μm or more and 60 μm or less.

The purpose of the buffer layer 4 is to alleviate material heterogeneity between the layer 1 closer to the substrate, such as the photoconductive layer 3, and the surface layer 5.

In terms of materials, a-C(H), a-C(H,F).

a-3i+-x[x(H) (0<x<1), a-S
i+-xCx(F,)I)(0<x<1>a-S+Nx
(H) (0<x<4/3), a-8+0x()I)(
0<x<2), a 5IOK(F, H) (0< to <2), etc. can be used. The thickness of the buffer layer 4 is determined by the spectral sensitivity 1 residual potential, electrical consistency on adjacent layers, etc., and is preferably 1 μm or less.

The surface layer 5 is made of amorphous carbon containing hydrogen (a-C(H)
), and is basically a film whose diffraction pattern by X-rays or electron beams is not clear, and even if it contains some crystal parts, the proportion thereof is low. a-C(
H) Hydrogen contained in the surface layer binds to the dangling bonds of carbon and contributes to its stabilization.

Surface @5 is formed by decomposing hydrocarbon gas containing C and hydrogen, for example, by glow discharge decomposition method to form an a-C(H) film. (H
) The properties of the membrane will differ. Generally speaking, for the same raw material, if the flow rate of raw rice gas is increased and the gas pressure is increased, the E
g, electrical resistance is high and hardness is low.

According to the findings of the present inventors, the bonding form between hydrogen atoms and carbon atoms contained in the layer consisting of a-C(H) reflects the soft bonding between carbon atoms, and the formed a −[(
It has been found that the +1) layer is one of the major factors that determines whether or not the layer can be applied as a surface layer of an electrophotographic photoreceptor and is important. Bonding states between carbon atoms include diamond bonds (tetracoordinated) and graphite bonds (tricoordinated).

It is known that a-C(H) films, which are mainly composed of graphite bonds and polymeric bonds (-C)+2-)n made of carbon and hydrogen, have poor chemical resistance and mechanical strength. On the other hand, a-C(I
f) The membrane is known to have excellent chemical resistance and mechanical strength.

In view of this, the present inventors have conducted intensive studies on the infrared absorption spectrum of the a-C(H) film, its chemical resistance, and mechanical strength, and the results show that the a-C(H) film formed by
In order for the -C(H) surface layer to function sufficiently as a surface protective layer of the electrophotographic photoreceptor, the absorption coefficient α at 2920 cm-' of the infrared absorption spectrum of the a-C(H) surface layer,
and the absorption coefficient α2 at 2960 cm', the ratio α2/
The value of α is preferably 0.8 or more.

As a means for stabilizing carbon dangling bonds, not only hydrogen but also fluorine, oxygen and nitrogen can be used.

To manufacture a photoreceptor having the structure shown in FIG. 1, an amorphous film producing apparatus such as the one shown in FIG. 2 is used, for example. The electrode 13 is arranged, and the holding part 12. Electrode 13
are each equipped with a heater 14,15. An aluminum alloy cylindrical base 1 that has been degreased and cleaned with trichlorethylene is fixed to the holding part 12, and the pressure inside the vacuum chamber 11 is set to 1.
The exhaust pump 16 exhausts the air through the exhaust valve 17 so that the pressure becomes 0-' Torr. Heater 14 and heater 1 are used to maintain the temperature of base 1 and electrode 13 to a predetermined temperature.
Heat according to step 5.

The holding part 12 and the base body 1 are rotated to obtain uniformity of the film in the circumferential direction. Next, from among the source gas pressure vessels 21 to 25, a pressure vessel 1 for gas necessary for film formation, for example, a valve 1B of 21
Open the valve, pass the flow controller Ig, and connect the stop/stop valve 20.
is opened and gas is supplied into the vacuum chamber 11. Other gases are also supplied in the same manner as necessary. Next, the pressure inside the tank is set to a predetermined pressure 1, for example, 0,001 to 5 Torr.
After adjusting to a predetermined pressure within the range of , the radio frequency (RF) power source 31
High frequency <13.56 MHz> power from insulation material 3
2 to the electrode 13, and a glow discharge is generated between it and the substrate 1 to form a film.

Specific examples will be described below.

Example 1 An aluminum alloy cylindrical substrate 220 that had been degreased and cleaned with trichlorethylene was attached to the holding part 12 in the vacuum chamber 11 of the manufacturing apparatus shown in FIG. 2, and a blocking layer 2 with a thickness of 0.2 μm was formed under the following conditions. .

SiH4 (100%) flow 1 250cc/
minB2H6 (5000ppm, 82 base) flow rate
20cc 7 minutes gas pressure Q 5
7 orr RF power substrate temperature film formation time Further on top of this, a film was formed to a thickness of 25 μm.

5t) 14 (100%) Flow rate 82116 (20 ppm, Hz Hose) Flow 1 Gas pressure RF main power element temperature Film forming time Further, a film was formed with a variation of 0.1 μm under the following conditions.

SIH, (100%) flow rate C) 14 (100%) flow rate BJ @ (2000 pHm, ) 12 base) flow rate Gas pressure RF main power body temperature Filming time 0W 200°C 10 minutes The photoconductive layer 3 is thickened under the following conditions. 200cc 7 minutes 1Qcc 7 minutes 1.2 Torr 00W 200℃ 3 o'clock closing layer 4 with a thickness of 100cc 7 minutes 80cc 7 minutes 15cc 7 minutes l QTorr 00W 200℃ 2 minutes Furthermore, on top of this, the 8771 layer side under the following conditions Layer 5a (0
, 1 μm thick), followed by a layer 5b (2 μm thick) on the free surface side.
thickness) was formed to form the surface layer 5.

CJs (99,99%) flow m 20cc/min
10cc 7 minutes Gas pressure 0.05Torr
O,01TorrRF power 20
0 W 300 w Substrate temperature
100℃ 100℃ film formation time 5
The energy gap (Eg) of the photoconductive layer 3 of the photoconductor produced in the manner of 30 minutes or more was 1.8 eV.
, the composition of the buffer layer 4 is a-3+o, co, s
(11) and its Eg is 2.1 eV. In addition, among the surface layers 5, the layer 5a on the buffer layer side has an E g of 2.4 eV.
, hardness 400 kg/n+m', specific resistance 1
014ΩcI111 layer 5b on the free surface side is Eg2.4e
ν.

Hardness 1200 kg/ll1111', specific resistance 5
It was XIO”001m.

The hardness is measured using an ultra-micro hardness meter DUH-50 manufactured by Shimabara Seisakusho.
This is a value measured using a load of 0.05 g.

The photoreceptor of this example was installed in a Carlson-type plain paper copying machine and 50,000 copies were made, but no deterioration in the characteristics of the photoreceptor was observed and images with very good quality were obtained. Further, there was no image deterioration even when copying in an atmosphere at a temperature of 35° C. and a relative humidity of 85%.

The residual potential at this time was IOV.

Comparative Example A sample prepared under the same conditions as in Example up to buffer layer 4, with only layer 5a on the buffer layer side provided as a 5 μm surface layer, had almost no photosensitivity and produced a pitch black image.

This is because the residual potential is too high.

Example 2 A sample was prepared under the same conditions as in Example 1 except that the conditions for the surface layer 50 were changed as shown below.

C, H, (+00%) flow IJt 20cc/min
10cc 7 minutes Gas pressure Q, Q7Torr 0.05Torr RF power 150 W 200
W base temperature 100℃ 100℃
Film forming time 5 minutes 60 minutes Also, among the surface layer 5, the layer 5a on the buffer layer side is E g2.3e
V, hardness 700 kg/u', specific resistance 5X
10”ΩC11l, layer 5b on the free surface side is E g 2.
5eV, hardness 1000kg/mm2. Specific resistance l
XlO12Ωcffl. B concentration in the film is 200p
It is pm. The hardness is a value measured using an ultra-micro hardness meter DU H-50 manufactured by Shimabara Seisakusho under a load of 0.05 g.

The photoreceptor of this example was installed in a Carlson type plain paper copying machine and 50,000 copies were made, but no deterioration in the characteristics of the photoreceptor or wear on the surface was observed, and extremely clear images were obtained. It was done. Also, the temperature is 35℃.

Good images were obtained at 85% RH.

(C2L) When examining the dependence of vGaGa flow rate on Gaa degree, it was found that below 1100 pp, the electrical resistance increased and the residual potential increased. 1000 again
At 0 pI]m or more, the energy gap decreases, which is thought to be due to the graphite-like structure becoming the main structure, and the window effect is not achieved.

〔Effect of the invention〕

According to the present invention, a photoconductive layer made of an a-5i material is provided on a conductive substrate, and the photoconductive layer is covered with a surface layer made of a-C(H) via a buffer layer. In a photoreceptor, the electrical resistance of the surface layer on the side in contact with the buffer layer is increased, and the electrical resistance on the free surface side is made smaller.

By making the surface layer have such a layer structure, the buffer layer side of the surface layer plays the role of retaining the electrical charge that is normally stored on the surface of the free surface side, and the free surface of the surface layer, that is, the photoreceptor. It enables thickening of the surface and dramatically improves printing durability. As a result, the surface of the photoreceptor is less likely to be worn out by output image forming processes such as development and cleaning, has excellent rigidity resistance and moisture resistance, and does not suffer from characteristic deterioration during long-term storage or repeated use, and does not exhibit defective output images even in high-humidity environments. This results in an electrophotographic photoreceptor in which almost no particles are generated.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the layer structure of the photoreceptor of the present invention;
FIG. 2 is a conceptual system diagram of an example of an apparatus capable of manufacturing the photoreceptor of the present invention. 1 conductive substrate, 2 blocking layer, 3 photoconductive layer,
4 buffer layer, 5 surface layer, 5a layer on buffer 1 side, 5b layer on free surface side. Figure 1 Figure 2

Claims (1)

[Claims] 1) An electrophotographic photoreceptor having a photoconductive layer made of an amorphous silicon-based material on a conductive substrate, and the photoconductive layer covered with a surface layer made of an amorphous substance mainly composed of carbon via a buffer layer. The surface layer has a two-layer structure consisting of a first layer in contact with the buffer layer and a second layer that has lower electrical resistance than the first layer and is located on the free surface side, and the second layer is made of gallium atoms. An electrophotographic photoreceptor comprising hydrogenated amorphous carbon containing 100 to 10,000 ppm of