Photosensitive member for use in electrophotography

The photosensitive member is constituted by a supporting member made of pure aluminum coated with a porous amorphous aluminum oxide anhydride layer, a photoconductive layer formed on the supporting member and comprises a hydrogenated amorphous silicon layer, an intermediate layer laminated on the photoconductive layer and consists of amorphous silicon nitride or amorphous silicon carbide and a surface layer laminated on the intermediate layerand consists of hydrogen containing amorphous boron nitride.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a photoconductive member for use in 
electrophotography, and more particularly to a novel construction of the 
photoconductive member for use in electrophotography capable of preventing 
flow and blur of images. 
2. Description of the Prior Art 
In recent years, as a substitute for inorganic photoconductive materials 
(hereinafter photoconductive material is often called photoconductor) such 
as Se, Cds and ZnO, or organic photoconductive material such as 
poli-n-vynil carbozol and trinitrofluorenone, amorphous silicon 
photosensitive member using hydrogenated amorphous silicon layer as a 
photoconductor have become noted for use in electrophotography because of 
their excellent heat resistance property, wear resistant property, 
harmless property and high photosensitivity. 
As the amorphous silicon type photoconductor for use in electrophotography, 
a photoconductor comprising an aluminum supporting member and an amorphous 
silicon layer formed thereon to act as a photoconductive layer has been 
widely used. However, since the adhesive force of the amorphous silicon to 
aluminum is not sufficiently large, we have succeeded to improve the 
adhesive property by subjecting the surface of an aluminum layer 11 to an 
almite treatment (oxidation treatment) to form a porous layer 12B formed 
of an anhydrous amorphous aluminum layer whose surface containing numerous 
fine pores and then applying a hydrogenated amorphous layer 13 to the 
porous layer 12b without sealing the fine pores as shown in FIG. 6. 
Then an amorphous boron layer 14 (a-BN) is applied to the upper surface of 
the hydrogenated amorphous silicon layer. The amorphous boron nitride 
layer 14 has properties of an excellent insulating strength and a small 
light absorption, and can prevent light reflection and is not influenced 
by environment condition variation. 
In the art of electrophotography, the recording of images is made in the 
following manner. More particularly, after applying uniform electric 
charge onto the surface of a photoconductor by using corona discharge, a 
light image is projected. Due to the absorption of the projected light, 
electron-hole pairs are formed in the photoconductive layer and the 
electrons and holes thus formed are caused to migrate due to the surface 
charge so as to cause to remain the surface charge only at regions not 
irradiated or exposed to light (formation of a latent image). When an 
oppositely charged toner is sprinkled onto the latent image thus formed, 
the remaining surface charge attracts the toner through the photoconductor 
layer and the insulative amorphous boron nitride layer, thus developing or 
visualizing the latent image. Then the developed toner image is transfer 
printed onto a copying paper. At this time, there is a tendency of flow or 
blur of the image, thus failing to obtain a clear copy. 
Although it is considered that this is caused by the decrease of the 
electrostatic attractive force due to the presence of the photoconductive 
layer and the surface layer, this cause has been considered impossible to 
eliminate. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to obtain a novel 
photosensitive member for use in electrophotography capable of obtaining 
clear copy or record free from flow or blur of the image. 
According to this invention, there is provided a photosensitive member for 
use in electrophotography of the type wherein the surface of a supporting 
member is coated with a porous amorphous aluminum oxide anhydride, a 
hydrogenated amorphous silicon layer acting as a photoconductive layer, 
and a hydrogen containing amorphous boron nitride layer acting as a 
surface layer, characterized by an intermediate layer interposed between 
the photoconductive layer and the surface layer, the intermediate layer 
consisting of amorphous silicon nitride (a-SiN) or amorphous silicon 
carbide (a-SiC).

DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in FIG. 1, the photosensitive member of this invention for use in 
electrophotography comprises a lamination of a cylindrical or sheet shaped 
aluminum 1 having a purity of higher than 99.5% and is formed on its 
surface with an almite layer not containing any chemically combined water, 
a hydrolized amorphous silicon layer 3 (a-Si :H) having a thickness of 20 
microns, containing hydrogen in 9.3 atm % and formed on the surface of the 
almite layer to act as a photoconductive layer, and an amorphous silicon 
nitride layer (a-SiN).sub.4 having a thickness of 100 .ANG. and acting as 
an intermediate layer and a hydrogen containing amorphous boron nitride 
layer 5 (a-BN) acting as a surface layer. 
The almite layer is of the double layer construction consisting of a dense 
barrier layer made of aluminum oxide of a thickness of 100A and a porous 
layer having a thickness of 1 micron and made of anhydride amorphous 
aluminum oxide containing numerous micropores. 
A method of manufacturing the photosensitive member will now be described. 
At first, an electrolytic treatment is performed using as an anode pure 
aluminum formed into a cylinder, a sheet or other suitable configuration 
and electrolyte such as sulfuric acid and oxalic acid so as to form an 
almite layer 2 consisting of a barrier layer 2a having a thickness of 100 
.ANG. and a porous layer 2b having a thickness of 1 micron. The 
electrolysis voltage was 10-20 V, the electrolysis time of 2-30 minutes, 
the temperature of the electrolyte was 10.degree.-25.degree. C., the 
concentration was 10-20% and the current density was 1-2 A/dm.sup.2. 
Then as shown in FIG. 2b, without sealing the micropores of the almite 
layer 2, a boron doped hydrogenated amorphous silicon layer 3 having a 
thickness of 20 micron and containing hydrogen in an amount of 9.3 atm % 
is coated on the surface of the porous layer 2 by plasma CVD method, 
thereby forming a photoconductive layer. The layer forming conditions were 
as follows: substrate (supporting member) temperature: 325.degree. C.; 
reaction gas: a mixture of silan (SiH.sub.4) and diboran (B.sub.2 
H.sub.6); gas pressure 1.0 Torr; quantity of gas flow: SiH.sub.4 100 SCCM, 
B.sub.2 H.sub.6 50 SCCM; applied frequency: 13.56 MHz; and power: 100 W. 
The hydrogen content of a layer thus formed varies depending upon the 
substrate temperature. the relation between the substrate temperature and 
the hydrogen content is shown in FIG. 3. 
In the same manner, an amorphous silicon nitride layer 4 having a thickness 
of 100 .ANG. and acting as an intermediate layer 4 is coated on the layer 
3 by plasma CVD method. The layer forming conditions were: substrate 
temperature: 325.degree. C.; reaction gas: a mixture of silane (SiH.sub.4) 
and ammonium (NH.sub.3); gas pressure 1.0 Torr; quantity of gas flow: 
SiH.sub.4 50 SCCM, NH.sub.3 50 SCCM; applied frequency: 13.56 MHz; and 
power: 100 W (FIG. 2c). 
Further, a hydrogen containing amorphous boron nitride layer having a 
thickness of 1500 .ANG. and acting as a surface layer was coated with (CVD 
method). The layer forming conditions were: substrate temperature: 
325.degree. C., reaction gas: a mixture of diborane (B.sub.2 H.sub.6) and 
ammonium (NH.sub.3); gas pressure: 1.0 Torr; quantity of gas flow B.sub.2 
H.sub.6 100 SCCM, NH.sub.3 50 SCCM; applied frequency: 13.56 MH.sub.3, and 
power: 100 W. 
The hydrogenated amorphous silicon layer 3, the amorphous silicon nitride 
layer 4, and the amorphous boron nitride layer 5 can be consecutively 
formed by switching the reaction gases. 
When forming a layer, the supporting member is set in the reaction chamber 
of a plasma CVD apparatus and then the reaction chamber is evacuated to a 
vacuum of about 10.sup.-6 Torr. 
After stabilizing the temperature of the support to 325.degree. C., the gas 
mixture is admitted into the reaction chamber while adjusting the flow 
quantity with a mass flow controller and then the pressure in the reaction 
chamber is set to 1.0 Torr with a gas pressure controller. 
Under these conditions, the supporting member is grounded and a layer is 
formed by applying a high frequency power while matching the impedance 
with an impedance box. 
When a desired layer thickness is reached, application of the high 
frequency power and the admission of the reaction gas are stopped. 
By repeating the above described operation, the three layers are 
sequentially formed. 
Finally, after evacuating the reaction chamber, the heating of the 
supporting member is stopped, and after breaking the vacuum, the 
supporting member is taken out from the reaction chamber. 
In the photosensitive member described above, as the thickness alone of the 
amorphous silicon nitride layer acting as the intermediate layer is 
varied. The relation between the layer thickness and the picture image 
characteristics is shown in the following Table I in which symbol " 
.circleincircle." designates very excellent, " .circle." good, ".DELTA." 
normal and "x" bad. This table shows that the thickness of the amorphous 
silicon nitride layer should be less than 2000 .ANG.. 
TABLE I 
______________________________________ 
Layer 
thickness (.ANG.) 
0 25 50 100 200 500 1000 2000 5000 
______________________________________ 
Picture .DELTA. 
.DELTA. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circle. 
.DELTA. 
X 
image 
character- 
istic 
______________________________________ 
Where the amorphous boron nitride layer and the amorphous silicon nitride 
layer are respectively used as the surface layer and the intermediate 
layer the surface, the comparison data of the potential, photosensitivity, 
and the picture image characteristics are shown in FIG. 5 where only the 
amorphous silicon nitride layer is used as the surface layer and where 
only the amorphous boron nitride layer is used as the surface layer. 
As can be clearly noted from FIG. 5, the surface potential, 
photosensitivity and picture image characteristics are excellent where 
amorphous silicon nitride is used as the intermediate layer, and amorphous 
boron nitride is used as the intermediate layer. 
In contrast, where only the amorphous silicon nitride layer is used, the 
surface potential and the photosensitivity are not sufficiently high, 
whereas where only the amorphous boron nitride is used, the picture image 
tends to blur. 
The picture image characteristic in case the nitrogen content of the 
amorphous silicon nitride is varied is shown in the following Table II. 
TABLE II 
______________________________________ 
Quantity 
of N 
(at %) 0 1 5 10 20 30 40 50 
______________________________________ 
Picture .DELTA. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circle. 
.DELTA. 
X 
image 
character- 
istic 
______________________________________ 
From this table, it can be clearly noted that it is advantageous that the 
quantity of nitrogen content should be less than 40 atm %. 
The photosensitive member prepared in the manner described above can 
prevent flow and blur of the image by the use of an intermediate layer, 
thereby providing a clear copy. 
Moreover, the photoconductive layer and the supporting member can be 
strongly bonded together, and the photoelectric property is excellent. 
Although the thickness of the barrier layer 2a and the porous layer 2b of 
the almite layer can be varied by varying the reaction conditions at the 
anode oxidation step, the relation between the adhesive power and the 
photoelectric characteristic of the thickness .alpha. of the barrier layer 
2a, and the thickness .beta. of the porous layer 2b (photoconductive 
layer) is shown in Table III, in which symbol " .circle." means excellent, 
"x" inferior and ".DELTA." practically employable although not so 
excellent. 
TABLE III 
______________________________________ 
Barrier 
layer .alpha. 
(A) 
Porous 
layer .beta.(.mu.m) 
10 100 200 500 1000 
______________________________________ 
0 X X X X X Adhesive force 
.circle. 
.circle. 
.circle. 
.DELTA. 
X Photoelectric 
characteristic 
3 .circle. 
.circle. 
.circle. 
.circle. 
.circle. 
Adhesive force 
.circle. 
.circle. 
.circle. 
.DELTA. 
X Photoelectric 
characteristic 
5 .circle. 
.circle. 
.circle. 
.circle. 
.circle. 
Adhesive force 
.DELTA. 
.DELTA. 
.DELTA. 
X X Photoelectric 
characteristic 
7 .circle. 
.circle. 
.circle. 
.circle. 
.circle. 
Adhesive force 
X X X X X Photoelectric 
characteristic 
______________________________________ 
This table shows that the adhesive force is increased as the thickness of 
the porous layer increases and that it is advantageous to limit the 
thickness of the porous layer to at most 5 microns when one considered the 
photoelectric characteristic. Although a thin barrier layer is preferred, 
the photoelectric characteristic will not be affected so long as the 
thickness lies in a range of 10 .ANG.-500 .ANG.. 
At the time of forming the photoconductive layer, a photosensitive member 
was prepared by varying the quantity of hydrogen (atm %) in the 
hydrogenated amorphous silicon layer by changing the composition of the 
reaction gas, and the relation between the quantity of hydrogen and the 
charging performance (V/.mu.) was measured. The result of measurement is 
shown in FIG. 4 in which the ordinate shows the charging characteristic 
and the abscissa shows the hydrogen quantity. FIG. 4 clearly shows that 
especially excellent results can be obtained when the hydrogen content is 
maintained to be less than 20 atm %, especially in a range of 5-13 atm %. 
As above described, a photosensitive member comprising a pure aluminum 
cylinder or sheet formed on its surface with an almite layer not 
comprising crystalline water, a hydrolized amorphous silicon layer acting 
as a photoconductive layer, an amorphous silicon nitride layer acting as 
an intermediate layer and an amorphous boron nitride layer acting as a 
surface layer, which are laminated sequentially, is free from flow of the 
image and has excellent properties in the adhesive force and the 
photoelectric characteristics. 
Although in this embodiment, an amorphous silicon nitride layer was used as 
the intermediate layer, this layer can be substituted by an amorphous 
silicon carbide layer. 
Further, the thickness .alpha. of the barrier layer of the almite layer on 
the surface of the supporting member was made to be 100 .ANG., and the 
thickness .beta. of the porous layer was made to be 6 micron. The barrier 
layer may be omitted. When it is made as thinner as possible, the 
photoelectric electric characteristic can be improved. However, the 
barrier layer is inevitably formed at the time of the almite forming 
treatment so that it is preferable to select the treatment conditions so 
as to determine .alpha. and in the ranges of 10 
.ANG..ltoreq..alpha..ltoreq.500 .ANG. and 0.ltoreq..beta..ltoreq.5 .mu.m. 
The hydrogen content C.sub.H of the photoconductive layer is selected to be 
C.sub.H .ltoreq.20 atm %, more preferably 5 atm % C.sub.H 13 atm %, still 
more preferably 7 atm %.ltoreq.C.sub.H .ltoreq.10 atm %. 
The thickness of the photoconductive layer is selected in a range of 
5.mu..ltoreq.t.ltoreq.80.mu.. With less than 5 microns a desired surface 
level could not be obtained whereas with higher than 80 microns the 
photoelectric characteristic would decrease. The quantity of boron doped 
in the photoconductive layer is selected in a range of 10.sup.-7 atm 
%-10.sup.-5 atm %. Because with higher than 10.sup.-5 atm % of boron, a 
desired surface potential can not be obtained and since the amorphous 
silicon is a n type semiconductor in a not doped state, with less than 
10.sup.-7 atm %, the resistance becomes low, thus failing to obtain a 
desired surface potential. 
It is advantageous to make 1:1, the composition ratio of boron and nitrogen 
in the amorphous boron nitride comprising the surface layer. More 
particularly when setting B.sub.x and N.sub.1-x, x is selected to be in a 
range of 0.2.ltoreq.x.ltoreq.0.8. With regard to the layer thickness d, it 
is desirable to select it in a range of 0.01.mu..ltoreq.d 10.mu., 
preferably 0.05.mu..ltoreq.d.ltoreq.5.mu.. If the surface layer were too 
thin, blocking affect could not be expected whereas if it were too thick 
the photoelectric effect would degrade.