GB2102028A

GB2102028A - Electrophotographic photosensitive member and process for production thereof

Info

Publication number: GB2102028A
Application number: GB08218177A
Authority: GB
Inventors: Toshiyuki Komatsu; Katsumi Nakagawa; Yutaka Hirai; Tadaji Fukuda; Teruo Misumi
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1977-12-22
Filing date: 1978-12-22
Publication date: 1983-01-26
Also published as: GB2102028B

Abstract

An electrophotographic photosensitive member comprising a substrate and, overlying the substrate, a photoconductive layer of a form of amorphous silicon having suitable for electrophotography and at least one additional layer which may be a layer of specified refractive index, a non-conductive layer or a barrier layer.

Description

SPECIFICATION Electrophotographic photosensitive member and process for production thereof This invention relates to an electrophotographic photosensitive member used for forming images by using electromagnetic waves, for example, ultraviolet rays, visible rays, infrared rays, Xrays, gamma rays, and the like, and a process for preparing the photosensitive member.

Heretofore, there have been used inorganic photoconductive materials such as Se, CdS and ZnO and organic photoconductive materials such as poly - N N -vinyl - carbazole, and trinitrofluorenone as a photoconductive material for photoconductive layers of electrophotographic photosensitive members.

However, these suffer from various drawbacks.

For example, Se has only a narrow spectral sensitivity range, and when the spectral sensitivity is widened by incorporating Te or As, light fatigue increases. Se, As and Te are harmful to man. When Se photoconductive layers are subjected to a continuous and repeating corona discharge, the electric properties deteriorate, and Se photoconductive layers are of poor solvent resistance. Even if the surface of an Se photoconductive layer is covered with a surface protective coating layer, the problems are not sufficiently solved.

Se photoconductive layers may be formed in an amorphous state so as to have a high dark resistance, but crystallization of Se occurs at a temperature as low as about 65 C so that the amorphous Se photoconductive layers easily crystallize during handling, for example, under the ambient temperature or friction heat generated by rubbing with other members during image forming steps, and the dark resistance is lowered.

ZnO and CdS are usually mixed with and dispersed in an appropriate resinous binder. The resulting binder type photoconductive layer is so porous that it is adversely affected by humidity and its electric properties are lowered and developers can enter the layer resulting in lowering the release properties and cleaning properties. In particular, when a liquid developer is used, the liquid developer penetrates the layer to give the above disadvantages. CdS is poisonous to man. ZnO binder type photoconductive layers have low photosensitivity, a narrow spectral sensitivity range in the visible light region, high light fatigue and slow photoresponse.

Electrophotographic photosensitive members comprising organic photoconductive mateials are of low humidity resistance, low corona ion resistance, have poor cleaning properties, low photosensitivity, a narrow range of spectral sensitivity in the visible light region and the spectral sensitivity range is in a shorter wave length region. Some of the organic photoconductive materials cause cancer.

In order to solve the above mentioned problems, the present inventors have researched amorphous silicon (hereinafter called "a-Si") and succeeded in obtaining an electrophotographic photosensitive member free from these drawbacks.

Since the electric and optical properties of a-Si film vary depending upon the manufacturing processes and manufacturing conditions and the reproducibility is very poor (Journal of Electrochemical Society, Vol.116, No. 1, pp7781,January 1969). For example, a-Si film produced by vacuum evaporation or sputtering contains a lot of defects such as voids so that the electrical and optical properties are adversely affected to a great extent. Therefore, a-Si had not been studied for a long time. However, in 1976 success in producing a p-n junction in a-Si was reported (Applied Phisics Letter, Vol. 28, No. 2, pp.

105-7, 15Jan. 1976). Since then, a-Si drew the attention of scientists. In addition, luminescence which can be only weakly observed in crystalline silicon (c-Si) can be observed at a high efficiency in a-Si and therefore, a-Si has been researched for solar cells (for example, U.S. Patent No.4064521.

However, a-Si as developed for solar cells cannot be directly used to form the photoconductive layers of practical electrophotographic photosensitive members.

Solar cells take out solar energy in the form of electric current and therefore, the a-Si film should have a low dark resistance for the purpose of obtaining efficiently the electric current at a good SN ratio [ photo-current (Ip)/dark current (Id9, but if the resistance is so low, the photosensitivity is lowered and the SN ratio is degraded. Therefore, the dark volume resistivity should be 195 108 ohm cm.

However, this is so low for photoconductive layers of electrophotographic photosensitive members that such an a-Si film cannot be used for the photoconductive layers.

Photoconductive materials for electrophotographic apparatuses should have gamma value at a low light exposure region of nearly 1 since the incident light is a reflection light from the surface of materials to be copied and the power of the light source built in electrophotographic aparatus is usually limited.

Known a-Si cannot satisfy the conditions necessary for electrophotographic processes.

Another report concerning a-Si discloses that when the dark resistance is increased, the photosensitivity is lowered. For example, an a-Si film having a dark volume resistivity of about 1010 ohm~cm shows a lowered photoconductive gain (photocurrent per incident photon). Therefore, known a-Si film cannot be used for electrophotography even from this point of view.

Other various properties and conditions required for photoconductive layers of electrophotographic photosensitive member such as electrostatic characteristics, corona ion resistance, solvent resistance, light fatigue resistance, humidity resistance, heat resistance, abrasion resistance, cleaning properties and the like have not been known as for a-Si films at all.

The present inventors have succeeded in producing a-Si film suitable for electrophotography by a particular procedure as detailed below.

According to one aspect of the invention there is provided an electrophotographic photosensitive member comprising a substrate and, overlying the substrate, a photoconductive layer of a form of amorphous silicon having characteristics suitable for electrophotography and overlying the photoconductive layer, a layer having a refractive index between the refractive index of the photoconductive layer and that of air.

According to another aspect of the invention there is provided an electrophotographic photosensitive member comprising a substrate and overlying the substrate, a photoconductive layer of a form of amorphous silicon having characteristics suitable for electrophotography and, overlying the photoconductive layer, a covering layer of a non-conductive material.

According to another aspect of the invention there is provided an electrophotographic photosensitive member comprising a substrate and, overlying the substrate, a photoconductive layer of a form of amorphous silicon having characteristics suitable for electrophotography and, in contact with the photoconductive layer, a barrier layer capable of preventing injection of electric charge carriers into the photoconductive layer during charging of the photosensitive member.

In the drawings: FIG. 1 and FIG. 2 are schematic cross sectional views of embodiments of electrophotographic photosensitive members according to the present invention; and FIG.3, FIG. 4 and FIG. 5 are schematic diagrams of apparatuses suitable for conducting the process for preparing an electrophotographic photosensitive member according to the present invention.

Referring to FIG. 1, an electrophotographic photosensitive member 1 is composed of substrate 2, suitable for electrophotography and photoconductive layer 3 mainly composed of amorphous silicon (a-Si), and the photoconductive layer 3 has free surface 4 which becomes an image bearing surface.

Substrate 2 may be electroconductive or electrically insulating. As a conductive substrate, there may be mentioned metals such as stainless steel, Al, Cr, Mo, Au, Ir, Nb, Ta, V, Ti, Pt, Pd and alloys thereof.

As an electrically insulating substrate, there may be used films or sheets of synthetic resins such as polyesters, polyethylenes, polycarbonates, cellulose triacetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, or polyamides or materials such as glass, ceramics and paper. At least one surface of an electrically insulating substrate is preferably conductivized.

For example, in the case of glass, its surface may be conductivized e.g. with In203, SnO2. In the case of a synthetic resin film such as polyester film, its surface may be conductivized with e.g. Al, Ag, Pb, Zn, Ni, Au, Cr, Mo, Ir, Nb, Ta, V, Ti, or Pt e.g. by vapor deposition, electron beam vapor deposition, or sputtering, or by laminating the surface with such metal.

The substrate can be in the form of a drum (i.e.

cylindrical), belt, plate or other optional shape. In the case of continuous high speed copying, an endless belt or drum shape is preferable.

The thickness of the substrate is optional. When a flexible electrophotographic photosensitive member is desired, a thickness as thin as possible is preferable, but it is usually not less than 10 microns from the manufacturing, handling and mechanical strength points of view.

An a-Si photoconductive layer 3 is prepared on substrate 2 with silicon and/or silane or other silicon compound e.g. by glow discharge, sputtering, ion plating or ion implantation. These manufacturing methods may be optionally selected depending upon manufacturing conditions, capital investment, manufacture scales, electrophotographic properties and the like. Glow discharge is preferably used because its control to obtain desirable electrophotographic properties is relatively easy and impurities e.g. of Group Ill or Group V of the Periodic Table can be introduced into the a-Si layer in a substitutional manner for the purpose of controlling the characteristics.

Further, according to the present invention, glow discharge and sputtering in combination can be conducted in the same system for form an a-Si layer and this is a very efficient and effective method.

The a-Si photoconductive layer 3 is controlled by providing a source of hydrogen so that as a result, H is contained in the a-Si layer in order to obtain a desirable dark volume resistivity and photoconductive gain suitable for a photoconductive layer of an electrophotographic photosensitive member.

In the present invention, "H is contained in the a-Si layer" means one of or a combination of possible states, i.e. "H is bonded to Si", and "ionized H is weakly bonded to Si in the layer", and "H is present in the layer in the form of H2"- The source of hydrogen may comprise a silicon compound such as a silane, for example, SiH4 or Si2H6, or H2 (hydrogen gas) may be introduced into the system producing the photoconductive layer 3, and then heat-decomposed or subjected to glow discharge to decompose the compound or H2 and incorporate H in the a-Si layer as the layer grows, or H may be incorporated in the a-Si layer by ion implantation.

According to the present inventor's opinion, the content of H in an a-Si photoconductive layer 3 is a very important factor affecting whether the a-Si photoconductive layer is suitable for electrography.

In the photoconductive layer for the electrophotographic photosensitive member, the content of H in the a-Si layer is preferably 1040 atomic %, more preferably, 1530 atomic %.

No theoretical reason why the content of H in the a-Si layer is preferably within the above-mentioned range is yet clear, but when the content of H is outside of the above range, a photoconductive layer made of such a-Si in an electrophotographic photosensitive member has a low dark resistivity which is not normally suitable forthe photoconductive layer and the photosensitivity can be very low, i.e. further increase in carriers upon light irradiation is very little.

For the purpose of incorporating H in the a-Si layer (i.e. so that H is contained in the a-Si layer), when a glow discharge is employed, a silicon hydride gas such as SiH4 or 5i2H6 may be used as the starting material for forming the a-Si layer, and therefore, H is automatically incorporated in the a-Si layer upon formation of the a-Si layer by decomposition of such silicon hydride. In order to carry out this incorporation of H more efficiently, H2 gas may be introduced into the system where glow discharge is carried out to form a-Si layer.

Where sputtering is employed, in a rare gas such as Ar or a gas mixture atmosphere containing a rare gas, sputtering is carried out with Si as a target while introducing H2 gas into the system or introducing silicon hydride gas such as SiH4 or 5i2H6 or introducing B2H6, PH, or like gas which can also serve to dope the a-Si with impurities.

Controlling the amount of H to be contained in the a-Si layer can be effected by controlling the substrate temperature and/or an amount introduced into the system of a source material used for incorporating H.

The a-Si layer can be made intrinsic by appropriately doping with impurities when prepared and the type of conductivity can be controlled. Therefore, the polarity of charging upon forming electrostatic images on an electrophotographic photosensitive member so prepared can be optionally selected, that is, positive or negative polarity can be optionally selected.

In the case of a conventional Se photoconductive layer, only a p-type or at most an intrinsic type (i-type) of photoconductive layer can be obtained by controlling the substrate temperature, type of impurities, amount of dopant and other preparation conditions, and moreover, even when the p-type is prepared, the substrate temperature should be strictly controlled. In view of the foregoing, the a-Si layer is much better and more convenient that conventional Se photoconductive layers.

As an impurity used for doping the a-Si layer to make it p-type there may be mentioned elements of Group Ill A of the Periodic Table such as B, Al, Ga, In and Tl, and as an impurity for doping the a-Si layer to make it n-type, there may be mentioned elements of Group V A of the Periodic Table such as N, P, As, Sb and Bi.

These impurities are contained in the a-Si layer in an order of ppm. so that problem of pollution is not so serious as that for a main component of a photoconductive layer. However, it is naturally preferable to pay attention to such problem of pollution. From this viewpoint, B, As, P and Sb are the most appropriatetaking into consideration electrical and optical characteristics of a-Si photoconductive layers to be produced.

The content of impurity to which the a-Si layers may be doped, may be appropriately selected depending upon the desired electrical and optical characteristics of the a-Si photoconductive layer. In the case of impurities of Group Ill A of the Periodic Table, the amount is usually 10-6 - 10 3 atomic %, preferably,10 - 10-4 atomic %, and in the case of impurities of Group V A of the Periodic Table, the amount is usually 10-8 - 10 5 atomic %, preferably 10 8~10 7 10-7atomic%.

The a-Si layers may be doped with these impurities by various methods depending upon the type of method for preparing the a-Si layer. These will be mentioned later in detail.

Referring to FIG. 1, electrophotographic photosensitive member 1 contains an a-Si photoconductive layer 3 which has a free surface 4. In the case of an electrophotographic photosensitive member to the surface of which charging is applied forthe purpose of forming electrostatic images, it is preferable to dispose between the a-Si photoconductive layer 3 and substrate 2 a barrier layer capable of suppressing injection of carriers from the side of the substrate 2 upon charging for producing electrostatic images.

As a material for such barrier layer, there may be selected insulating inorganic oxides such as Awl203, SiO, and SiO2, insulating organic compounds such as polyethylene, polycarbonate, polyurethane and polyparaxylylene and metals such as Au, Ir, Pt, Rh, Pd and Mo.

The thickness of the a-Si photoconductive layer is selected taking into consideration its desired electrostatic characteristic, and depending, for example, whether flexibility is required. It is usually 5-80 microns, preferably, 10-70 microns, and more preferably, 10-50 microns.

As shown in FIG. the a-Si photoconductive layer surface is directly exposed and since the refractive index (n) of the a-Si layer is as high as about 3.3-3.9, light reflection at the surface is apt to occur upon exposure, as compared with conventional photoconductive layers; the amount of light absorbed in the photoconductive layer is lowered resulting in some loss of light. In orderto reduce the loss of light, it is helfpul to dispose an antireflection layer on an a-Si photoconductive layer.

Materials for the antireflection layer are appropriately selected taking the following conditions into consideration. They should have: i) No adverse effect on the a-Si photoconductive layer; ii) High antireflecting property; and iii) Appropriate electrophotographic characteristics; e.g. the electric resistivity should be higher than a certain value; they should be transparent to the lightto be absorbed by the photoconductive layer; they should have good solvent resistance when used for a liquid developing process; they should not cause deterioration of the already prepared a-Si photoconductive layer during their own preparation.

Further, for the purpose of facilitating antireflection, it is desirable to select a refractive index for the material which is between that of the a-Si layer and that of air. This will be clearfrom a simple calculation of optics.

The thickness of the antireflection layer is preferably A/4swhere n is the refractive index of the a-Si layer and A is the wavelength of exposure light, or (2k + 1) times A/4swhere k is an integer such as 0, 1, 2,3 most preferably A/4+ taking into consideration the light absorption of the antireflection layer itself.

Taking these optical conditions into account, the thickness of the antireflection layer is preferably 50-100 m,a assuming that the wavelength of the exposure light is roughly in the wavelength region of visible light.

Representative materials for an antireflection layer are inorganic fluorides and oxides such as MgF2, Awl203, ZrO2, TiO2, ZnS, CeO2, CeF2, SiO2, SiO, Ta2O and AIFa'3NaF, and organic compounds such as polyvinyl chloride, polyamide resins, polyimide resins, polyvinylidene fluoride, melamine resins, epoxy resins, phenolic resins and cellulose acetate.

The surface of the a-Si photoconductive layer 3 may be provided with a surface coating layer which may be a protective layer, or an electrically insulating layer as in known electrophotographic photosensitive members. FIG. 2 shows such an electrophotographic photosensitive member having a covering layer.

Now referring to FIG. 2, the electrophotographic photosensitive member 5 has a covering layer 8 on the a-Si photoconductive layer 7, but the remaining structure is the same as that of FIG. 1.

The characteristics required of the covering layer 8 vary depending upon each electrophotographic process. For example, when an electrophotographic process such as that of U.S. Patent Nos. 3,666,363 and 3,734,609 is used, it is required that the covering layer 8 is electrically insulating and has a sufficient electostatic charge retaining property when sub jected to charging and a thickness thicker than a certain minimum thickness. However, when a Carlson type electrophotographic process is used, a very thin covering layer8 is required since potentials at the light portions of electrostatic images are preferably very low.Covering layer 8 is prepared so as to satisfy the desired electrical characteristics and furthermore, the following are taken into consideration: not adversely affecting the a-Si photoconductive layers chemically and physically, electrical contact and adhesivity with the a-Si photoconductive layer, moisture resistance, abrasion resistance and clean ing properties.

Representative materials for a covering layer are synthetic resins such as polyethyiene terephthalate, polycarbonate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polystyrene, polyamides, polyethylene tetrafluoride, polyethylene trifluoride chloride, polyvinyl fluoride, polyvinylidene fluoride, copolymers of propylene hexafluoride and ethylene tetrafluoride, copolymers of ethylene trifluoride and vinylidene fluoride, polybutene, polyvinyl butyral and polyurethane, and cellulose derivatives such as the diacetate and triacetate.

These synthetic resins and cellulose derivative in the form of film may be adhered to the surface of the a-Si photoconductive layer, or a coating liquid of these materials may be coated on an a-Si photoconductive layer 5. The thickness of the covering layer may be appropriately selected depending upon the required characteristics and type of material, but it is preferably 0.5-70 microns.When the covering layer is used as a protective layer, the thickness is appropriately, for example, not more than 10 microns and when it is used as an electrically insulating layer, the thickness is appropriately, for example, not less than 10 microns although this value, 10 microns is not critical, but only an example, because such value varies depending upon type of the material, the electrophotographic process and structure of the elec trophotographic photosensitive member.

The covering layer 8 may also serve as an antireflection layer and its function effectively widened.

The preparation of an electrophotographic photosensitive member of the present invention is exemp lifted by a glow discharge process and a sputtering process described below.

Referring to FIG. 3, there is illustrated a diagrammatic glow discharge process of the capacitance type for producing an electrophotographic photosensitive member.

A glow discharge deposition chamber 10 contains a substrate 11 fixed to a fixing member 12 and an a-Si photoconductive layer is formed on the substrate 11. Under the substrate 11 is disposed a heater 13 for heating the substrate 11. At an upper part of the deposition chamber 10 are wound capacitance type electrodes 15 and 15' connected to a high frequency power source 14. When the power source 14 is turned on, a high frequency voltage is applied to electrodes 15 and 15' to cause a glow discharge in deposition chamber 10.

To the top portion of the deposition chamber 10 is connected a gas introducing conduit to introduce gases from gas pressure vessels 16, 17 and 18 into the deposition chamber 10 when required.

Flow meters 19,20 and 21, flow rate controlling valves 22, 23 and 24, valves 25, 26 and 27 and auxiliary valve 28 are provided.

The lower portion of the deposition chamber 10 is connected to an exhausting device (not shown) through main valve 29. Valve 30 serves to break the vacuum in the deposition chamber 10.

A cleaned substrate 11 is fixed to fixing member 12 with the cleaned surface kept upward.

The surface of substrate 11 may be cleaned as shown below. It can be cleaned with an alkali or acid, (a kind of chemical treatment), or by disposing a substrate cleaned to some extent in deposition chamber 11 at a fixed portion and then applying a glow discharge. In the latter case, the cleaning of the substrate 11 and the formation of an a-Si photoconductive layer can be carried out in the same system without breaking the vacuum thereby avoiding dirt contamination of the cleaned surface by impurities.

After fixing substrate 11 to fixing member 12,the main valve 29 is fully opened to evacuate the deposition chamber 10 to bring the pressure down to about 10 5 Torr. Then heater 13 starts to heat the substrate 11 up to a predetermined temperature, and the temperature is maintained while auxiliary valve 28 is fully opened; then valve 25 of gas pressure vessel 16 and valve 26 of gas pressure vessel 17 are fully opened. Gas pressure vessel 16 contains, for example, a diluting gas such as Ar and gas pressure vessel 17 contains a gas forming a-Si, for example, silicon hydride gas such as SiH4, Si2H6, Si4H,o or their mixture. Pressure vessel 18 may be used, if desired, for storing a gas capable of incorporating impurities in an a-Si photoconductive layer, for example, PH3, P2H4, B2H6 and the like. Flow rate controlling valves 22 and 23 are gradually opened while observing flow meters 19 and 20 to introduce a diluent gas, e.g., Ar, and a gas for forming a-Si, e.g., SiH4 into deposition chamber 10. The diluting gas is not always neces sary, but SiH4 alone may be introduced into the system. When Ar gas is mixed with a gas for forming a-Si, e.g. SiH4, and then introduced, the ratio may be determined depending upon each particular situation. Appropriately the gas for forming a-Si is more than 10 vol.% based on the diluting gas. As the diluting gas, an inert gas such as He or Ar may be used.

When gases are introduced from pressure vessels 16 and 17 into deposition chamber 10, main valve 29 is adjusted to keep a particular vacuum degree; appropriately, an a-Si layer forming gas pressure is 10 t2 - 3 Torr. Then, to electrodes 15 and 15' is applied a high frequency voltage, for example, 0.2 30 MHz, from high frequency power source 14 to cause a glow discharge in deposition chamber 10, and SiH4 is decomposed to deposit Si on substrate 11 to form an a-Si layer.

impurities may be introduced into an a-Si photoconductive layer to be formed by introducing a gas from pressure vessel 18 into deposition chamber 10 upon forming an a-Si photoconductive layer. By controlling valve 24, and amount of gas introduced into deposition chamber 10 from pressure vessel 18 can be controlled. Therefore, an amount of impurities incorporated in an a-Si photoconductive layer can be optionally controlled and in addition, the amount may be varied in the direction of thickness of the a-Si photoconductive layer.

In FIG. 3, the glow discharge deposition system uses a glow discharge process of RF (radio frequency) capacitance type, but in place of this there may be used a glow discharge process of RF inductance type or DC diode type. Electrodes for glow discharge may be disposed in or outside of deposition chamber 10.

In order to efficiently carry out glow discharge in a glow discharge apparatus of capacitance type as shown in FIG. 3, the current density is appropriately 0.1-10 mA/cm2, preferably 0.1-5 mA/cm2, more preferably, 1-5 mA/cm2, of AC or DC, and further the voltage is appropriately 100-5000 V, preferably 300-5000 V, so as to obtain sufficient power.

The characteristics of an a-Si photoconductive layer depend on the temperature of the substrate to a great extent and therefore, it is preferable to control the temperature strictly. The temperature of substrate according to the present invention is usually 50-350 C, preferably 100-200 C so as to obtain an a-Si photoconductive layer for electrophotography having desirable characteristics. In addition, the substrate temperature may be changed continuously or batchwise to produce desirable characteristics. The growing speed of the a-Si layer also affects the physical properties of the resulting a-Si layer to a great extent, and according to the present invention, it is appropriately 0.5-100 A/sec., preferably 1-50 ksec.

FIG. 4 shows a diagrammatic system for producing electrophotographic photosensitive members by sputtering.

Deposition chamber 31 contains a substrate 32 fixed to a fixing member 33 which is conductive and is electrically insulated from deposition chamber 31.

A heater 34 is disposed under the substrate 32, which is to be heated by heater 34. Over substrate 32 and facing substrate 32, there is disposed a polycrystal line or single crystal silicon target 35. A high frequency voltage is applied between fixing member 33 and silicon target 35 from a high frequency power source 36.

To deposition chamber 31 are connected gas pressure vessels 37 and 38 through valves 39 and 40, flow meters 41 and 42, flow rate controlling valves 43 and 44, and auxiliary valve 45. Gases may be introduced into deposition chamber 30 when wanted.

An a-Si photoconductive layer can be formed on substrate 32 by the apparatus of FIG. 4 as shown below. Deposition chamber 31 is evacuated to the direction of arrow B to obtain an appropriate degree of vacuum. Then substrate 32 is heated to a particulartemperature by heater 34.

When sputtering is employed, the temperature of the substrate 32 is appropriately 50-350 C, prefer ably, 100-200"C. This substrate temperature affects the growing speed of the a-Si layer, the structure of the layer, void formation and the physical properties of the resulting a-Si layer, and therefore, strict control is necessary.

The substrate temperature may be kept constant during the formation of an a-Si layer, or may be raised or lowered or both raised and lowered in sequence as the a-Si layer grows. For example, at the beginning of formation of an a-Si layer a substrate temperature is kept at a relatively low temperature T1 and when the a-Si layer grows to some extent, the substrate temperature is raised up to T2 (T2 > T1) during formation of the a-Si layer, and then at the end of the a-Si layer formation the substrate temperature is lowered down to a temperature T3 lower than T2. In this way, the electrical and optical properties of the a-Si photoconductive layer can be constantly or continuously changed in the direction of thickness of the layer.

Since the layer growing speed of a-Si is slower than, for example, Se, there is a fear that the a-Si formed at the beginning (a-Si near the substrate) may change its original characteristics before the layer formation is completed where the layer is thick.

Therefore, it is preferable to form the layer by raising the substrate temperature from the beginning to the end so as to obtain an a-Si layer having uniform characteristics in the direction of thickness.

The substrate temperature controlling method may also be employed when a glow discharge process is carried out.

After detecting that the temperature of the substrate 32 is heated to a predetermined temperature, auxiliary valve 45, valves 39 and 40 are fully opened and then while main valve 46 and flow rate controlling 44 are controlled, silicon hydride gas such as SiH4 and/or hydrogen gas are introduced from pressure vessel 38 into deposition chamber 31 resulting in a decrease in the degree of vacuum and then the resulting degree of vacuum is kept.

Then, flow rate controlling valve 43 is opened and an atmosphere gas such as Ar gas is introduced from pressure vessel 37 into deposition chamber 31 until the degree of vacuum decreases. The flow rates of silicon hydride gas, hydrogen gas, and the atmos phere gas such as Ar are appropriately determined so as to obtain desired physical properties of the a-Si photoconductive layer. For example, the pressure of a mixture of an atmosphere gas and hydrogen gas in deposition chamber is usually 10-3.101 Torr., preferably 5 x 10-3-3 x 102. In place of Ar gas, there may be used other inert gases such as He gas.

After an atmosphere gas such as Ar and the like, and H2 gas or silicon hydride gas are introduced into deposition chamber 31, a high frequency voltage is applied between substrate 32 (via fixing member 33) and silicon target 35 from a high frequency power source 36 at a predetermined frequency and voltage to discharge and ions of the resulting atmosphere gas, such as Ar ions, serve to sputter silicon from the silicon target to form an a-Si layer on substrate 32.

FIG. 4 is explained concerning sputtering by a high frequency discharge, but there may be used sputtering by DC discharge. In the case of sputtering by high frequency discharge, the frequency is appropriately 0.2-30 MHz, preferably 5-20 MHz, and the current density of discharge is appropriately 0.1-10 mA/cm2, preferably 0.1-5 mA/cm2, more preferably 1-5 mA/cm2. In addition, forthe purpose of obtaining sufficient power, the voltage is appropriately controlled to 100-5000 V, preferably 300-5000 V.

The growing speed of an a-Si layer by sputtering is mainly determined by the substrate temperature and discharging conditions, and affects the physical properties of the resulting a-Si layer to a great extent. A growing speed of an a-Si layer for attaining the purpose of the present invention is appropriately 0.5-100 Alsec., preferably 1-50 lsec. In a sputtering method as well as a glow discharge method, it is possible to control the resulting a-Si photoconductive layer to n-type or p-type by doping with impurities. Introduction of impurities in a sputtering method is similartothat in a glow discharge method.For example, a material such as PH3, P2H4, B2H6 and the like is introduced into the deposition chamber in a gaseous form upon producing an a-Si layer and the a-Si layer is doped with P or B as an inpurity. Further, impurities can be introduced into an already produced a-Si layer by an ion implantation method and it is possible to control the very thin surface layer of the a-Si layer to a particular conductive type.

FIG. 5 illustrates diagrammatically a glow discharge deposition system for producing an electrophotographic photosensitive member by inductance type glow discharge.

Glow discharge deposition chamber 47 contains a substrate 48 on which an a-Si photoconductive layer is formed. Substrate 48 is fixed to a fixing member 49. Under substrate 48 is disposed a heater 50 to heat substrate 48. An inductance type electrode 52 connected to a high frequency power source 51 is wound around the upper portion of deposition chamber 47. When the power source is on, high frequency waves are applied to the electrode 52 to cause a glow discharge in deposition chamber 47. To the top of deposition chamber 47 is connected a gas introducing pipe capable of introducing gases from gas pressure vessels 53, 54 and 55 when required.

The gas introducing pipe is equipped with flow meters 56, 57 and 58, flow rate controlling valves 59, 60 and 61, valves 62, 63 and 64 and auxiliary valve 65.

The bottom portion of deposition chamber 47 is connected to an exhausting device (not shown) through main valve 66. Valve 67 is used for breaking the vacuum in deposition chamber 47. Gases from pressure vessels 53, 54 and 55 are not directly introduced into deposition chamber 47, but are mixed in advance in a mixing tank 68 and then the resulting mixture gas is introduced into deposition chamber 47. In this way when the gases are once introduced into mixing tank 68 and mixed at a predetermined ratio and then the resulting mixture is introduced into deposition chamber 47 from mixing tank 68, it is possible to introduce always a gas mixture of a constant mixing ratio into deposition chamber47 at any time. This is very advantageous.

An a-Si photoconductive layer having a desired characteristics is formed on substrate 48 as shown below.

Cleaned substrate 48 is fixed to fixing member 49 with the cleaned surface upward. Cleaning the surface of substrate 48 is conducted as in FIG. 3.

Deposition chamber 47 and mixing tank 68 are evacuated while main valve 66 and auxiliary valve 65 are kept fully open. The pressure in the system is brought down to about 1010 Torr., and then substrate 48 is heated to a predetermined temperature by heater 50 and the temperature is maintained.

Then auxiliary valve is closed and valves 62 and 63 are fully opened. Gas pressure vessel 53 contains a diluting gas such as Ar gas; gas pressure vessel 54 contains a gas for forming a-Si such as a silicon hydride gas, for example, SiH4, Si2H6, Si4H,o or mixture thereof, and gas pressure vessel 55 contains a gas for forming impurities to be introduced into the a-Si photoconductive layer, if desired, such as PHB. P2H4, B2H6 and the like.

Flow rate controlling valves 59 and 60 are gradually opened while watching flow meters 56 and 57 and thus gases in pressure vessels 53 and 54 are fed to mixing tank 68 at a desired ratio in a desired amount to form a gas mixture, for example, a mixture of Ar and SiH4. Then flow rate controlling valves 59 and 60 are closed and auxiliary valve 65 is gradually opened to introduce the gas mixture into the deposition chamber 47 from mixing tank 68. In this case, a diluting gas such as Ar is not always necessary and it is permissible to introduce only a gas for forming a-Si such as SiH4 and the like.

The ratio of a diluting gas to a gas for forming a-Si introduced into mixing tank 68 may be optionally selected as wanted. The ratio is appropriately more than 10 vol.% of a gas forforming a-Si based on a diluting gas. As the diluting gas, He gas may be used in place of Ar gas. Deposition chamber 47 is maintained at a desired pressure for example 10 2 3 Torr.

by controlling main valve 66. Then, to the electrode of induction type 52 wound around deposition chamber 47 is applied a predetermined high frequency voltage, for example, 0.2-30 MHz, from high frequency power source 51 to cause a glow discharge in deposition chamber47 and decompose the SiH4 gas to deposit Si on substrate 48 to form an a-Si layer.

If it is desired to introduce impurities into an a-Si photoconductive layer, the gas in pressure vessel 55 is introduced into mixing tank 68 together with the other gases. The amount of impurity-introducing gas can be controlled by flow rate controlling valve 61 so that the amount of impurities introduced into the a-Si photoconductive layer can be optionally controlled.

In a glow discharge apparatus of inductance type as in FIG. 5, the high frequency power for producing an a-Si layer having desired characteristics may be determined accordingly, but it is appropriately 0.1300 W, preferably 0.1-150 W, more preferably 5-50 W. The characteristics of the resulting a-Si photoconductive layer are affected by the substrate temperature upon growing the a-Si layer and the growing speed of the layer to a great extent. Therefore, these factors should be strictly controlled. The desirable conditions of substrate temperature and growing speed of an a-Si layer in a glow discharge apparatus of inductance type are similar to those mentioned concerning FIG. 3.

The invention will be understood more readily by reference to the following examples.

EXAMPLE 1 In accordance with the procedure described below, an electrophotographic photosensitive member of the present invention was prepared by using an apparatus as shown in Fig. 3, and an image forming treatment was applied to the photosensitive member.

An aluminum substrate was cleaned in such a manner that the surface of the substrate was treated with a 1% solution of NaOH and sufficiently washed with water and then dried. This substrate, which was 1 mm in thickness and 1 Ocm x 5cm in size, was firmly disposed at a fixed position in a fixing member 12 placed at a predetermined position in a deposition chamber 10 for glow discharge so that the substrate was kept apart from a heater 13, equipped to the fixing member 12, by about 1.0cm.

The air in the deposition chamber 10 was evacuated by opening fully the main valve 29 to bring the chamber to a vacuum degree of about 5 x 10-5 Torr.

The heater 13 was then energised to heat uniformly the aluminum substrate to 150 C, and the substrate was kept at this temperature while a subsidiary valve 28 was fully opened, and subsequently a valve 25 of a bomb 16 to which Ar was charged and a valve 26 of a bomb 17 which was filled with SiH4 were also opened fully, and thereafter, flow controlling valves 22, 23 were gradually opened so that Ar gas and SiH4 gas were introduced into the deposition chamber 10 from the bombs 16, 17. At that time, the vacuum degree in the deposition chamber 10 was brought to and kept at about 0.075 Torr. by regulating the main valve 29.

A high frequency power source 14 was switched on to apply a high frequency voltage of 13.56 MHz between electrodes 15 and 15' so that a glow discharge was caused, thereby depositing and forming an a-Si type photoconductive layer on the aluminum substrate. At that time, the glow discharge was initiated with an electric current density of about 0.5 mA/cm2 and a voltage of 500 V. Further, the growth rate ofthe a-Si layer was about 4 angstroms per second and the deposition was effected for 15 hours.

The so formed a-Si layer had a thickness of 20 microns.

After completion of the deposition, while the main valve 29, valves 25 and 26, flow controlling valves 22 and 23, and subsiduary valve 28 were closed, a valve 30 was opened to break the vacuum in the deposition chamber 10. The prepared photosensitive member was taken out from the apparatus.

To the a-Si type photoconductive layer surface of the photosensitive member was applied a negative corona discharge with a power source voltage of 5500 V in a dark place. Image exposure of 15 Iux#sec.

was carried out to form an electrostatic image, which was then developed with a positively charged toner in accordance with the cascade method. The developed image was transferred to a transfer paper and then fixed so that an extremely sharp image with a high resolution was obtained.

The image forming process as mentioned above was repeatedly carried out in order to test the durability of the photosensitive member. As a result, the image on a transfer paper obtained when such process was repeated ten thousand (10,000) times was extremely good in quality. Although such image was compared with the first image on a transfer paper obtained at the time of the initial operation of the image forming process, no difference was observed therebetween. Therefore, it was found that the photosensitive member was excellent in corona discharging resistance, abrasion resistance, cleaning property and the like and showed extremely good durability. The photosensitive member was cleaned after the transferring step, using a blade formed of urethane rubber.

The foregoing image forming process was repeated under the same conditions except that a positive corona discharge was applied with a voltage of 6,000 V to the photosensitive member and a negatively charged toner was used for the developing.

The resulting image formed on a transfer paper had an image density lower than that of the image obtained in the foregoing image forming process using negative corona discharge. As a result, it was recognized that the photosensitive member prepared in this example depends upon the polarity.

EXAMPLE2 In accordance with the procedure and condition used in Example 1, an a-Si type layer of 20 microns in thickness was formed on the aluminum substrate.

The structure was taken out from the deposition chamber 10, and polycarbonate resin was then coated onto the a-Si type layer to form an electrically insulating layer having a thickness of 15 microns after drying.

To the insulating layer surface of the electrophotographic photosensitive member obtained in the above-mentioned manner was applied a positive corona discharge with a power source voltage of 6,000 V, as the primary charging, for 0.2 sec. so that such surface was charged to a voltage of + 2,000 V.

Next, negative corona discharging with a voltage of 5,500 V was carried out as the secondary charging simultaneously with image exposure in an exposure quantity of 15 lux#sec., and the whole surface of the photosensitive member was then exposed uniformly to form an electrostatic image. This image was developed with a negatively charged toner by the cascade method, and the developed image was transferred to a transfer paper and fixed so that an image of extremely good quality was obtained.

EXAMPLE 3 In the following manner similar to that in Example 1, an electrophotographic photosensitive member was prepared using the apparatus illustrated in Fig. 3 and an image forming treatment was applied to the photosensitive member.

An aluminum substrate having a thickness of 1 mm and a size of 10cm x 10cm was first treated with a 1% solution of NaOH and sufficiently washed with water and dried to clean the surface of the substrate.

The substrate was firmly disposed at a fixed position in a fixing member 12 placed at a predetermined position in a deposition chamber 10 for glow discharge so that it might be kept apart from a heater 13 positioned in the fixing member 12 by about 1.0cm.

The main valve 29 was fully opened to evacuate the air in the deposition chamber 10 so that the vacuum degree in the chamber was adjusted to about 5 x 15-5 Torr. The heater 13 was then energised to heat uniformly the aluminum substrate to 1 500C, the substrate being kept at that temperature. Then, a subsidiary valve 28 was first opened fully, and successively a valve 25 of a bomb 16 containing Ar and a valve 26 of a bomb 17 containing SiH4 were fully opened. Thereafter, the flow controlling valves 22 and 23 were gradually opened so that Ar gas and SiH4 gas were introduced into the deposition chamber 10 from the bombs 16 and 17, respectively.

At this time, the vacuum degree in the deposition chamber 10 was kept at about 0.075 Torr. by regulat ing the main valve 29, and while flow meters 19 and 20 were carefully observed, the flow controlling valves 22 and 23 were regulated to control the flow of the gases so that the flow of the SiH4 gas was kept to 10% by volume based on that of the Ar gas.

A valve 27 of a bomb 18 containing B2H6 was fully opened and a flow controlling valve 24 was slowly opened to introduce B2H6 gas into the deposition chamber 10 while the flow of the gas was controlled to 5 x 10 by volume based on the flow amount of the SiH4 gas. In this case, the main valve 29 was regulated to retain the vacuum degree in the deposition chamber 10 to 0.075 Torr.

Subsequently, a high frequency power source 14 was switched on in order to apply a high frequency voltage of 13.56 MHz between electrodes 15 and 15' to give rise to the glow discharge so that an a-Si type photoconductive layer was formed on the aluminum substrate by deposition. At the time of the glow discharge, the current density was about 3 mA/cm2 and the voltage 500 V. The growth rate of the a-Si type layer was about 4 angstroms/sec., the period of time forthe deposition 15 hours, and the thickness of the a-Si type layer 20 microns. After completion of the deposition, the main valve 29, subsidiary valve 28, flow controlling valves 22, 23, 24, and valves 25, 26, 27 were closed, but the valve 30 was opened to break the vacuum in the deposition chamber 10.Then, the electrophotographic photosensitive member obtained in the above mentioned manner was taken out from the apparatus.

To the a-Si type photoconductive layer surface of the photosensitive member was applied a negative corona discharge with a voltage of 5,500 V in a dark place. Image exposure was of 20 Iux#sec. was carried out to form an electrostatic image, which was then developed with a positively charged toner in accordance with the cascade method. The developed image was transferred to a transfer paper and then fixed so that an excellent sharp image was obtained.

The image forming process as mentioned above was repatedly carried out in order to test the durability of the photosensitive member. As a result, the image on a transfer paper obtained when such process was repeated ten thousand (10,000) times was extremely good in quality. When such image was compared with the first image on transfer paper obtained at the time of the initial operation of the image forming process, no difference was observed therebetween. Therefore, it was found that the photosensitive member was excellent in durability.

The photosensitive member was cleaned after the transferring step using a blade formed of urethane rubber.

Further, a positive corona discharge with a power source voltage of 6,000 V was applied to the photosensitive member in a dark place and image exposure of 20 Iuxsec. was carried out to form an electrostatic image. This electrostatic image was developed with a negatively charged toner by the cascade method. The developed image was then transferred to a transfer paper and fixed so that an image with extreme sharpness was obtained.

It was found from this result and the beforementioned result that the photosensitive member obtained in this example did not have dependance upon the charged polarity, but possessed properties of a photosensitive member which produces good images when either polarity is used.

EXAMPLE 4 The same procedure as in Example 3 was repeated except that the flow of the B2H6 gas was adjusted to 5 x x 10 by volume based on the flow of the SiH4 gas, to prepare an electrophotographic photosensitive member having an a-Si type photoconductive layer of 20 microns in thickness on the aluminum substrate.

In accordance with the same conditions and manner as in Example 3, the image forming process was carried out using the obtained photosensitive member to form an image on a transfer paper. The image formed by the process using positive corona discharge was excellent in quality and very sharp as compared with that obtained by the process em ploy- ing negative corona discharge.

It was recognized from the result that the photosensitive member of this example depends upon the polarity. In addition, this polarity dependance is contrary to that of the photosensitive member obtained in Example 1.

EXAMPLES In accordance with the procedure and conditions used in Example 4, an a-Si type layer of 20 microns in thickness was formed on the aluminum substrate.

The structure was then taken out from the deposition chamber 10, and polycarbonate resin was then coated onto the a-Si type layertoform an electrically insulating layer having a thickness of 15 microns after drying.

To the insulating layer surface of the electrophotographic photosensitive member obtained in the above-mentioned manner was applied a negative corona discharge with a power source voltage of 6,000 V, as the primary charging, for 0.2 sec. so that such surface was charged to a voltage of - 2,000 V.

Positive corona discharging with a voltage of 5,500 V was carried out as the secondary charging simultaneously with image exposure of 15 lux#sec., and the whole surface of the photosensitive member was then exposed uniformly to form an electrostatic image. This image was developed with a positively charged toner by the cascade method, and the thus developed image was transferred to a transfer paper and fixed so that an image of extremely good quality was obtained.

EXAMPLE 6 Photosensitive members were prepared by repeating the same procedure under the same conditions as in Example 1 except that the temperature of the substrate was varied as shown in Table 1 below. The prepared photosensitive members are indicated by Sample Nos. 1-8 in Table 1.

Using the photosensitive members, image formation was carried out under the same conditions as in Example 3 to form images on transfer paper. The results are as shown in Table 1.

As understood from the results, it is necessary to form the a-Si layer at a temperature of the substrate ranging from 50 C to 350"C to achieve good performance.

Table 1

Sample No. 1 2 3 4 )5 )6 7 8 Substrate temp., C 50 100 150 200 250 300 350 400 Image I Charged t X A A A X X X X quality | polarity # 9 Do 0ODo 9 D A X mage quality is that of transferred image.

q Very good; i) Good; A Acceptable for practical use; X Poor EXAMPLE 7 Photosensitive members were prepared by repeating the same procedure and conditions as in Example 3 except that the temperature of the substrate was varied as shown in Table 2 below. The prepared photosensitive members are indicated by Sample Nos. 9-16 in Table 2.

Using the photosensitive members, image formation was carried out using the same procedure and conditions as in Example 3 to form images on transfer paper. The results are as shown in Table 2.

As understood from the results, it is necessary to form the a-Si layer at a temperature of the substrate ranging from 500C to 3500C to achieve good performance.

Table 2

Sample No. 9 10 11 112 13 14 15 16 Substrate temp., T 50 100 150 200 250 300 350 400 Image | Charged # , Qo Qo Qo 0 0 A X quality | polarity 1 A Qo Qo~~'#) Qo n D A X Image quality is that of transferred image.

9i Very good; D Good; A Acceptable for practical use; X Poor EXAMPLE8 Photosensitive members were prepared by repeating the same procedure and conditions as in Exampie 4 except that the temperature of the substrate was varied as shown in Table 3 below. The prepared photosensitive members are indicated by Sample Nos. 17-24 in Table 3.

Using the photosensitive members, image formation was carried out employing the same procedure and conditions as in Example 4to form images on transfer paper. The results are as shown in Table 3.

As understood from the results, it is necessary to form the a-Si type layer at a temperature of the subs trate ranging from 50into 350into achieve good performance.

Table 3

Sample No. 17 18 19 20 21 22 23 24 Substrate temp 50 100 150 200 250 300 350 400 Image | Charged t A , oD D Q A X quality | polarity | X A A A X X X X Image quality is that of transferred image.

EVery good; Q Good; A Acceptable for practical use; X Poor EXAMPLE 9 A cylinder made of aluminum having a thickness of 2mm and a size of 150 mm diameter x 300mm was disposed in a deposition apparatus for glow discharge as shown in Fig. 3 so that it might rotate freely, and a heater was mounted so as to heatthe cylinder from the inside of the cylinder.

The air in deposition chamber 10 was evacuated by opening fullythe main valve 29to bring the chamber to a vacuum degree of about 5 x 10-5 Torr.

The heater 13 was energised to heat uniformly the cylinder to 1 500C simultaneously with the cylinder being rotated at a speed of three revolutions per minute, and the cylinder was kept at that temperature. A subsidiary valve 28 was fully opened, and subsequently a valve 25 of a bomb 16 containing Ar and a valve 26 of a bomb 17 which was filled with SiH4 were also opened fully, and thereafter, flow controlling valves 22,23 were gradually opened so that Ar gas and SiH4 gas were introduced into the deposition chamber 10 from the bombs 16,17. At that time, the vacuum degree in the deposition chamber 10 was brought to and kept at about 0.075 Torr. by regulating the main valve 29. Further, the flow of the SiH4 gas was adjusted to 10% by volume based on that of the Ar gas.

After fully opening a valve 27 of a bomb 18, containing B2He, a flow controlling valve 24 was gradually opened while a flow meter 21 was carefully observed, to adjust the flow amount of B2H6 gas to 10 5% by volume based on that of the SiH4 gas, thereby introducing the B2H6 gas into the deposition chamber 10. Also atthat time, the main valve 29 was regulated to bring the vacuum degree in the deposition chamber 10 to about 0.075 Torr.

A high frequency power source 14 was switched on to apply a high frequency voltage of 13.56 MHz between electrodes 15 and 15' so that a glow discharge was caused, thereby depositing and forming an a-Si type photoconductive layer on the cylinder substrate. At that time, the glow discharge was initiated with an electric current density of about 3 mA/cm2 and a voltage of 1,500 V. Further, the growth rate of the a-Si type layer was about 2.5 angstroms per second and the deposition was effected for 23 hours and further the so formed a-Si type layer had a thickness of 20 microns.

After completion of the deposition, while the main valve 29, subsidiary valve 28, flow controlling valves 22 and 23, valves 25 and 26 were closed, a valve 30 was opened to break the vacuum in the deposition chamber 10. The prepared electrophotographic photosensitive member was taken out from the deposition apparatus.

To the a-Si type photoconductive layer surface of the photosensitive member was applied negative corona discharge with a power source voltage of 5,500 V in a dark place. Image exposure of 20 lux~sec was carried out to form an electrostatic image, which was then developed with a positively charged toner in accordance with the cascade method. The developed image was transferred to a transfer paper and then fixed so that an extremely sharp image was obtained.

The image forming process mentioned above was repeatedly carried out in order to test the durability of the photosensitive member. As a result, the image on the transfer paper obtained when such process was repeated ten thousand (10,000) times was extremely good in quality. Although such image was compared with the first image on transfer paper obtained at the time of the initial operation of the image forming process, no difference was observed therebetween. Therefore, it was found that the photosensitive member was extremely good in durability. The photosensitive member was cleaned after the transferring step using a blade formed of urethane rubber.

The foregoing image forming process was repeated under the same conditions except that a positive corona discharge was applied with a power source voltage of 6,000 V to the photosensitive member and a negatively charged toner was used for the development. The obtained image formed on the transfer paper had an image density lower than that of the image obtained in the foregoing image forming process using negative corona discharge.

As a result, it was recognized that the photosensitive member prepared in this example depended upon the polarity.

EXAMPLE 10 Electrophotographic photosensitive members, which are indicated by Sample Nos. 25-29 in Table 4 given below, were prepared by conducting the same procedure under the same conditions as in Example 3 except that the flow of the B2H6 gas based on that of the SiH4 gas was varied in order to control the amount of the boron (B) doped into the a-Si type layer to various values as shown in Table 4.

The image formation was effected employing the photosensitive members under the same conditions as in Example 3 to obtain images on transfer paper.

The results are shown in Table 4. It is clear from the results that it is desirable to dope the a-Si type layer, using boron (B), in an amount of 10-6-10-3 atomic percent. Table 4

Sample No. 25 26 27 28 29 Doping amount 106 10 6 1 0 5 10 1 of B, atomic % Image quality Q Qo Qo LL x Image quality is that of transferred image.

0. Very good; Good; X Poor EXAMPLE 11 In accordance with the procedure described below, an electrophotographic photosensitive member was prepared using an apparatus as shown in Fig. 4, and an image forming treatment was applied to the photosensitive member.

An aluminum substrate of 1 mm in thickness and 10cm x 10cm in size was cleaned in such a manner that the surface of the substrate was treated with a 1% solution of NaOH and sufficiently washed with water and dried, and then Mo was deposited to this substrate to about 1,000 angstroms in thickness.

This substrate was firmly fixed at a predetermined position in a fixing member 33 placed in a deposition chamber 31 so that the substrate was kept apart from a heater 34 by about 1.0cm. Also, the substrate was spaced from a target 35 of polycrystalline silicon having a purity of 99.999% by about 8.5cm.

The air in the deposition chamber 31 was evacuated to bring the chamber to a vacuum degree of about 1 x 10-6 Torr. The heater 34 was energised to heat uniformly the substrate to 1 50"C, and the substrate was kept at this temperature. A valve 45 was fully opened, and subsequently a valve 40 of a bomb 38 was also opened fully, and thereafter, a flow controlling valve 44 was gradually opened so that H2 gas was introduced into the deposition chamber 31 from the bomb 38. At that time, the vacuum degree in the deposition chamber 31 was brought to and kept at about 5.5 x 10-4 Torr. by regulating the main valve 46.

Subsequently, after fully opening valve 39, a flow controlling valve 43 was gradually opened while a flow meter 41 was carefully observed, to introduce Ar gas into the deposition chamber 31 in which the vacuum degree was adjusted to 5 x 10-3 Torr.

A high frequency power source 36 was switched on to apply a high frequency voltage of 13.56 MHz, 1 KV between the aluminum substrate and polycrystalline silicon target so that a discharge was caused, thereby starting formation of an a-Si layer on the aluminum substrate. This operation was conducted continuously with a growth rate of the a-Si layer being controlled to about two angstroms per second for 30 hours. The formed a-Si layer was 20 microns in thickness.

To the so prepared electrophotographic photosensitive member was applied a negative corona discharge with a power source voltage of 5,500 V in a dark place. Image exposure of 15 Iux#sec. was carried out to form an electrostatic image, which was then developed with a positively charged toner in accordance with the cascade method. The developed image was transferred to a transfer paper and then fixed so that an extremely sharp image was obtained.

EXAMPLE 12 Electrophotographic photosensitive members, which are indicated by Sample Nos. 3036 in Table 5 given below, were prepared by conducting the same procedure under the same conditions as in Example 11 except that the flow amount of the H2 gas based on that of the Ar gas was varied in order to control the amount of the hydrogen (H) doped into the a-Si type layer to various values as shown in Table 5.

The image formation was effected by employing the photosensitive members under the same conditions as in Example 11 to obtain images on transfer papers. The results are shown in Table 5. It is clear from the results that it is desirable to dope the a-Si type layer with H in an amount of 1040 atomic percent.

Table S

Sample No. 30 31 32 33 34 35 36 Doping amount 5 10 15 25 30 40 50 of H, atomic % Image quality X ~ %) Qo- Qo QoJ X Image quality is that of transferred image.

CoO Very good; Q Good; X Poor EXAMPLE 13 The electrophotographic photosensitive members prepared in Examples 1,3 and 4 were each allowed to stand in an atmosphere of high temperature and humidity, i.e., at a temperature of 40"C and relative humidity of 90 RH%. After the lapse of 96 hours, the photosensitive members were taken out into an atmosphere at a temperature of 23"C and relative humidity of 50 RH%. Immediately thereafter, the same image forming processes as in Examples 1,3 and 4 were conducted under the same conditions using the photosensitive members to obtain images of sharpness and good quality on transfer paper.

This result showed that the photosensitive member of the present invention is very excellent also in moisture resistance.

EXAMPLE 14 An electrophotographic photosensitive member was prepared in the same manner as that in Example 1. To the member was applied a negative corona discharge at a voltage of 6,000 V in a dark place and image exposure was then conducted in an exposure quantity of 20 iux-sec. to form an electrostatic image, which was then developed with a liquid developer containing a chargeable toner dispersed in an isoparaffinic hydrocarbon solvent. The developed image was transferred to a transfer paper followed by fixing. The fixed image was extremely high in resolution and of good image quality and sharpness.

The above described image forming process was repeated in order to test the solvent resistance, in other words, liquid developer resistance of the photosensitive member. The above-mentioned image on the transfer paper was compared with an image on a transfer paper obtained when the image forming process was repeated ten thousand (10,000) times. No difference was found therebetween, which showed that the photosensitive member of the present invention is excellent in solvent resistance.

Blade cleaning was used, the blade being formed of urethane rubber.

EXAMPLE 15 In accordance with the procedure described below, an electrophotographic photoser.sitive member was prepared using a depositing apparatus for glow discharge as illustrated in Fig. 5 and an image forming process was carried out by employed ing the photosensitive member.

An aluminum substrate 48 having a size of 10cm x 1 Ocm x 1 mum already cleaned by the same surface treatment as in Example 1 was firmly disposed at a fixed position in a fixing member 49 placed in a deposition chamber 47 so that the substrate might be kept apart from a heater 50 by 1.0cm or so.

A main valve 66 and subsidiary valve 65 were fully opened to evacuate the air in the deposition chamber 47 and mixing tank 68, to bring them to the vacuum degree of about 5 x 10 5 Torr. The heater 50 was then energised to heat uniformly the aluminum substrate to 1 50"C, the substrate being kept at that temperature.

The subsidiary valve 65 was then closed, while a valve 62 of a bomb 53 which was filled up with Ar and valve 63 of a bomb 54 containing SiH4 were fully opened. Flow controlling valves 59,60 for the gas bombs 53, 54 were regulated while flow meters 56, 57 were observed so that Ar gas and SiH4 gas were fed to the mixing tank 68 at a ratio by volume of Ar:SiH4 = 10:1. While the flow controlling valves 59, 60 were then closed, the subsidiary valve 65 was gradually opened to introduce a gas mixture of Ar and SiH4 into the deposition chamber47.Atthat time, the main valve 66 was regulated to retain the vacuum degree in the deposition chamber 47 at about 0.075 Torr.

Subsequently, a high frequency power source 51 was switched on to apply a high frequency voltage of 13.56 MHzto inductance type coil 52. A glow discharge took place, forming an a-Si type photoconductive layer on the aluminum substrate by deposition. Atthattime, the high frequency powerwas about 50 W and the growth rate of the layer about three angstroms per second. The period of time for the deposition was 20 hours and the formed a-Si type layer had a thickness of about 20 microns.

To the a-Si type photoconductive layer surface of the prepared photosensitive member was applied a negative corona discharge with a source voltage of 5,500 V in a dark place. Image exposure of 15 Iux#sec.

was carried out to form an electrostatic image, which was then developed with a positively charged toner by the cascade method. The developed image was transferred to a transfer paper and fixed. As a result, an image of high resolution and sharpness was obtained.

EXAMPLE 16 In accordance with the procedure described below, an electrophotographic photosensitive member was prepared using an apparatus as illustrated in Fig. 5 and the image forming process was carried out employing the photosensitive member.

An aluminum substrate having a thickness of 1 mm and size of 10cm x 10cm was cleaned in such a manner that the surface was treated with a 1% solution of NaOH, sufficiently washed with water and dried. This substrate was firmly disposed at a pre determined position in a fixing member 49 placed in a deposition chamber 47 so that the substrate was spaced from a heater 50 by 1.0cm or so.

A main valve 66 and subsidiary valve 65 were fully opened to evacuate the air in the deposition chamber 47 and mixing tank 68, to bring them to a vacuum degree of about 5 x 10-5 Torr. The heater 50 was then energised to heat uniformly the aluminum substrate to 1 50"C, the substrate being kept at that temperature.

The subsidiary valve 65 was then closed, while a valve 62 of a bomb 53 and valve 63 of bomb 54 were fully opened. Flow controlling valves 59, 60 were gradually opened while flow meters 56, 57 were observed so that Ar gas and SiH4 gas were introduced from the bombs 53, 54, respectively, to the mixing tank 68 at a ratio by volume of Ar:SiH4 = 10:1. After a predetermined amountofthe Ar and SiH4 gases were fed to the tank 68, the flow controlling valves 59, 60 were then closed.

Next, a valve 64 of a bomb 55 was fully opened, and thereafter a flow controlling valve 61 was gradually opened to introduce B2H6 gas into the mixing tank 68 from the bomb 55 while the flow of the B2H6 gas was controlled to a ratio by volume of SiH4:B2H6= 1:3 x 10 5. After a predetermined amount of the B2H6 gas was fed to the tank 68, the valve 61 was closed. Then, the subsidiary valve 65 was gradually opened to introduce a gas mixture of Ar, SiH4 and B2H6 gases from the tank 68 into the deposition chamber 47. At this time, the main valve 66 was regulated to bring the vacuum degree in the deposition chamber 47 to 0.075 Torr.

Subsequently, a high frequency power source 51 was switched on to apply a high frequency voltage of 13.56 MHz to inductance type coil 52. A glow discharge took place, forming an a-Si type photoconductive layer on the aluminum substrate by deposition. At that time, the high frequency power was about 50 W and the growth rate of the layer about4 angstroms per second. The period of time for the deposition was 15 hours and the formed a-Si type layer had a thickness of about 20 microns.

After completion of the deposition, the main valve 66 and subsidiary valve 65 were closed, but the valve 67 was opened to break the vacuum in the deposition chamber 47. The prepared photosensitive member was taken out from the apparatus.

To the a-Si type photoconductive layer surface of the thus prepared photosensitive member was applied negative corona discharge with a source voltage of 5,500 V in a dark place. Image exposure of 20 Iux#sec. was carried out to form an electrostatic image, which was then developed with a positively charged toner by the cascade method. The developed image was transferred to a transfer paper and fixed. As a result, an image with very sharpness was obtained.

The image forming process as mentioned above was repeatedly carried out in order to test the durability of the photosensitive member. As a result, the image on the transfer paper obtained when such process was repeated ten thousand (10,000) times was extremely good in the quality. When such image was compared with the first image on a transfer paper obtained at the time of the initial operation of the image forming process, no difference was observed therebetween. Therefore, it was found that the photosensitive member was excellent in durability. The photosensitive member was cleaned after the transferring step using a blade formed of urethane rubber.

EXAMPLE 17 An electrophotographic photosensitive member was prepared using the same procedure and conditions as in Example 11 except that in place of the H2, SiH4 was charged to the bomb 38 and SiH4 gas was introduced into the deposition chamber 31.

Image formation was effected using the photosensitive member in the same manner as in Example 11 under equivalent conditions. The obtained result was similartothat in Example 11.

EXAMPLE 18 In accordance with the procedure described below, an electrophotographic photosensitive member was prepared using an apparatus as shown in Fig. 3, and an image forming treatment was applied to the photosensitive member.

An aluminum substrate of 1 mm in thickness and 10cm x 5cm in size was cleaned in such a manner that the surface of the substrate was treated with a 1% solution of NaOH and sufficiently washed with water and then dried. This substrate was firmly fixed at a predetermined position in a fixing member 12 placed in a deposition chamber 10 for glow discharge so that the substrate was spaced from a heater 13, fitted to the fixing member 12, by about 1.0cm.

The air in the deposition chamber 10 was evacuated by opening fully a main valve 29 to bring the chamberto a vacuum degree of about 5 x 10-5 Torr.

A subsidiary valve 28 was fully opened, and subsequently a valve 25 of a bomb 16 was also opened fully, and thereafter, a flow controlling valve 22 was gradually opened so that Ar gas was introduced into the deposition chamber 10 from the bomb 16. At that time, the inside pressure in the deposition chamber 10 was brought to and kept at about 0.075 Torr.

A high frequency power source 14 was switched on to apply a high frequency voltage of 13.56 MHz between electrodes 15 and 15' so that a glow discharge was caused, thereby cleaning the surface of the aluminum substrate. At that time, the glow discharge was initiated with a current density of about 0.5 mA/cm2 and a voltage of 500 V. After completion of the cleaning treatment, the subsidiary valve 28, valve 25 and flow controlling valve 22 were closed.

Subsequently, in accordance with the procedure and conditions used in Example 1, an a-Si layer of about 20 microns in thickness was formed on the aluminum substrate to obtain an electrophotographic photosensitive member.

The photosensitive member was used in an image forming process in the same manner and under the same conditions as in Example 1 to obtain an image transferred to paper. A similar result to that in Example 1 was obtained. Further, as to the durability of the photosensitive member, the same result was obtained.

EXAMPLE 19 An electrophotographic photosensitive member having an a-Si layer was prepared by employing the same procedure and conditions as in Example 1.

Deposition of Ta2O5 to the surface of the photocon ductive layer was effected by electron beam deposi tion to form an anti-reflection layer of 70 millimic rons in thickness.

The image forming process described in Example 1 1 was repeated using the prepared photosensitive member. As a result, it was found that the photosen sitive member required an exposure of only about 12 Iux#sec. to attain a transferred image density similar to that obtained in Example 1.

EXAMPLE 20 In accordance with the procedure described below, an electrophotographic photosensitive member was prepared using apparatus as shown in Fig. 3, and an image forming treatment was applied to the photosensitive member.

An aluminum substrate of 1 mm in thickness and 10cm x 10cm in size was cleaned in such a manner that the surface of the substrate was treated with a 1% solution of NaOH and sufficiently washed with water and then dried. This substrate was firmly fixed at a predetermined position in a fixing member 12 placed in a deposition chamber 10 for glow dis charge so that the substrate was spaced from a hea ter 13 by about 1.0cm.

The air in the deposition chamber 10 was evacu ated by opening fully a main valve 29 to bring the chamber to a vacuum degree of about 5 x 10 5 Torr.

The heater 13 was energised to heat uniformly the aluminum substrate to 1 50"C, and the substrate was kept at this temperature. A subsidiary valve 28 was fully opened, and subsequently a valve 25 of a bomb 16 and a valve 26 of a bomb 17 were also opened fully, and thereafter, flow controlling valves 22, 23 were gradually opened so that Ar gas and SiH4 gas F were introduced into the deposition chamber 10 from the bombs 16 and 17, respectively. At that time, the vacuum degree in the deposition chamber 10 was brought to and kept at about 0.075 Torr by reg ulating the main valve 29.

A A high frequency power source 14 was switched on to apply a high frequency voltage of 13.56 MHz between electrodes 15 and 15' so that a glow dis charge was caused, thereby depositing and forming an a-Si type photoconductive layer on the aluminum substrate. At that time, the glow discharge was initi ated with an electric current density of about 5 mA/cm2 and a voltage of 2,000 V. The growth rate of the a-Si type layer was about 4 angstroms per sec ond and the deposition was effected for 15 hours.

The so formed a-Si type layer had a thickness of 20 microns.

After completion of the deposition, while the main valve 29, valves 25 and 26, flow controlling valves 22 and 23, and subsidiary valve 28 were closed, a valve 30 was opened to break the vacuum in the deposi tion chamber 10. The prepared photosensitive member was then taken out from the deposition chamber.

To the a-Si type photoconductive layer surface of the photosensitive member was applied a negative corona discharge with a source voltage of 5,500 V in a dark place. Image exposure of 15 lux#sec. was carried out to form an electrostatic image, which was then developed with a positively charged toner in accordance with the cascade method. The developed image was transferred to a transfer paper and then fixed so that a sharp image of high resolution was obtained.

The image forming process as mentioned above was repeatedly carried out in order to test the durability of the photosensitive member. As a result, the image on the transfer paper obtained when such process was repeated ten thousand (10,000) times was of extremely good quality. When such image was compared with the first image on transfer paper obtained at the time of the initial operation of the image forming process, no difference was observed therebetween. Therefore, it was found that the photosensitivie member was excellent in corona discharging resistance, abrasion resistance, cleaning property and the like and showed extremely good durability. The photosensitive member was cleaned after the transferring step using a blade formed of urethane rubber.

The foregoing image forming process was repeated under the same conditions except that a positive corona discharge was applied with a voltage of 6,000 V to the photosensitive member and negatively charged toner was used for the development.

The obtained image formed on the transfer paper had an image density lower than that of the image obtained in the foregoing image forming process using negative corona discharge.

EXAMPLE2 1 In accordance with the procedure and condition used in Example 20, an a-Si type layer of 20 microns in thickness was formed on an aluminum substrate.

The structure was taken out from the deposition chamber 10 to the outside, and polycarbonate resin was then coated onto the a-Si type layer to form an electrically insulating layer having a thickness of 15 microns after drying.

To the insulating layer surface of the electrophotographic photosensitive member obtained in the above-mentioned manner was applied a positive corona discharge with a power source voltage of 6,000 V, as the primary charging, for 0.2 sec. so that such surface was charged to a voltage of +2,000 V.

Negative corona discharging with a voltage of 5,500 V was carried out as the secondary charging simultaneously with image exposure of 15 Iux#sec., and the whole surface of the photosensitive member was then exposed uniformly to form an electrostatic image. This image was developed with a negatively charged toner by the cascade method, and the developed image was transferred to a transfer paper and fixed and an image of excellent quality was obtained.

EXAMPLE 22 In the following manner similar to that in Example 20, an electrophotographic photosensitive member was prepared using the apparatus illustrated in Fig. 3 and an image forming treatment was applied to the photosensitive member.

This substrate was firmly disposed at a fixed position in a fixing member 12 placed in a deposition chamber 10 for glow discharge so that it was spaced from a heater 13 positioned in the fixing member 12 by about 1.0cm.

A main valve 29 was fully opened to evacuate the air in the deposition chamber 10 so that the vacuum degree in the chamber was adjusted to about 5 x 10 5 Torr. The heater 13 was energised to heat uniformly the aluminum substrate to 1 50"C, the substrate being kept atthattemperature. Then, a subsidiary valve 28 was first opened fully, and successively a valve 25 of a bomb 16 containing Ar and a valve 26 of a bomb 17 containing SiH4 were fully opened. Thereafter, the flow controlling valves 22 and 23 were gradually opened so that Ar gas and SiH4 gas were introduced into the deposition chamber 10 from the bombs 16 and 17, respectively.

Atthis time, the vacuum degree in the deposition chamber 10 was kept at about 0.075 Torr. by regulating the main valve 29, and while flow meters 19 and 20 were carefully observed, the flow amount controlling valves 22 and 23 were regulated to control the flow of the gases so that the flow of the SiH4 gas was 10% by volume based on that of the Ar gas.

A valve 27 of a bomb 18 containing B2H6was fully opened and then a flow controlling valve 24 was slowly opened to introduce B2H6 gas into the deposition chamber 10 while the flow of the gas was controlled to 5 x 10-3% by volume based on the flow of SiH4 gas. In this case, the main valve 29 was regulated to retain the vacuum degree in the deposition chamber 10 to 0.075 Torr.

Subsequently, a high frequency power source 14 was switched on in order to apply a high frequency voltage of 13.56 MHz between electrodes 15 and 15' to give rise to a glow discharge so that an a-Si type photoconductive layer is formed on the aluminum substrate by deposition. At the time of the glow discharge, the current density was about 3 mA/cm2 and the voltage 1,500 V. Further, the growth rate of the a-Si type layer was about 4 angstroms/sec., the period of time for the deposition 15 hours, and the thickness of the a-Si type layer 20 microns. After completion of the deposition, the main valve 29, subsidiary valve 28, flow controlling valves 22,23, 24, and valves 25,26, 27 were closed, but the valve 30 was opened to break the vacuum in the deposition chamber 10.Then, the electrophotographic photosensitive member obtained in the above mentioned manner was taken out from the apparatus.

To the a-Si type photoconductive layer surface of the photosensitive member was applied a negative corona discharge with a voltage of 5,500 V in a dark place. Image exposure of 20 lux sec. was carried out to form an electrostatic image, which was then developed with a positively charged toner in accordance with the cascade method. The developed image was transferred to a transfer paper and then fixed so that an extremely sharp image was obtained.

The image forming process mentioned above was repeatedly carried out in order to test the durability of the photosensitive member. As a result, the image on the transfer paper obtained when such process was repeated ten thousand (10,000) times was extremely good in quality. When such image was compared with the first image on a transfer paper obtained atthetimeofthe initial operation of the image forming process, no difference was observed therebetween. Therefore, it was found that the photosensitive member was excellent in durability.

Further, a positive corona discharge with a power source voltage of 6,000 V was applied to the photosensitive member in a dark place and image exposure of 20 Iux#sec. carried out to form an electrostatic image. This electrostatic image was developed with a negatively charged toner by the cascade method.

The developed image was then transferred to a transfer paper and fixed so that an image with extreme sharpness was obtained.

It was found from this result and the previous result that the photosensitive member obtained in this example does not depend upon the charging polarity, but possesses properties of a photosensitive member which can be advantageously used with both polarities.

EXAMPLE23 The same procedure as in Example 22 was repeated except that the flow of B2H6 gas was adjusted to 5 x 10-4% by volume based on the flow of the SiH4 gas, to prepare an electrophotographic photosensitive member having an a-Si type photoconductive layer of 20 microns in thickness on the aluminim substrate.

In accordance with Example 3, an image forming process was carried out using the obtained photosensitive member to form an image on a transfer paper. The image formed by the process using positive corona discharge was excellent in quality and very sharp as compared with that obtained by the process employing negative corona discharge.

It was recognized from the result that the photosensitive member of this example depended upon the polarity of charging. In addition, this polarity dependability was contrarytothat of the photosensitive member obtained in Example 1.

EXAMPLE 24 In accordance with the procedure and conditions used in Example 23, an a-Si type layer of 20 microns in thickness was formed on an aluminum substrate.

Positive corona discharging with a voltage of 5,500 V was carried out as the secondary charging simultaneously with image exposure of 151wosec., and the whole surface of the photosensitive member was then exposed uniformly to form an electrostatic image. This image was developed with a positively charged toner by the cascade method, and the developed image was transferred to a transfer paper and fixed and an image of excellent quality was obtained.

EXAMPLE 25 Photosensitive members were prepared by repeating the same procedure and conditions as in Example 20 except that the temperature of the substrate was varied as shown in Table 6 given below. The prepared photosensitive members are indicated by Sample Nos. 3744 in Table 6.

Using the photosensitive members, image formation was carried out employing the same manner and conditions as in Example 22 to form images on transfer paper. The obtained results are as shown in Table 6.

As understood from the results, it is necessary to form the a-Si type layer at a temperature of the subs trate ranging from 50"Cto 350"C forthe purpose of achieving good performance.

Table 6

I 1 I Sample No. 37 38 39 40 41 42 43 44 Substrate temp. "C 50 100 150 200 250 300 350 400 Image | Charged 1 X A A A X X X X quality | polarity | Q A DC l o# Q Q A X Image quality is that of transferred image.

') Very good; D ) Good; A Acceptable for practical use; X Poor EXAMPLE26 Photosensitive members were prepared by repeating the same procedure and conditions as in Example 22 except that the temperature of the substrate was varied as shown in Table 7 below. The prepared photosensitive members are indicated by Sample Nos. 45-52 in Table 7.

Using the photosensitive members, image formation was carried out under the same conditions as in Example 22 to form images on transfer paper. The obtained results are as shown in Table 7.

As understood from the results, it is necessary to form the a-Si type layer at a temperature of the subs trate ranging from 50"Cto 350"Cforthe purpose of achieving good performance.

Table 7

Sample No. 45 46 2 47 48 49 50 [ 51 152 Substratetemp."C 50 100 150 200 250 300 350 400 Image | Charged O) t 8 Qq 3 ~ 3 3 A X quality polarity e A Qo ii O 3 A X Image quality is that of transferred image.

Very good; ) Good; A Acceptable for practical use; X Poor 45 50 EXAMPLE 27 Photosensitive members were prepared by repeating the same procedure and conditions as in Example 23 except that the temperature of the substrate was varied as shown in Table 8 given below. The prepared photosensitive members are indicated by Sample Nos. 53-60 in Table 8.

By using the photosensitive members, the image formation was carried out under the same conditions as in Example 23 to form images on transfer paper. The obtained results are as shown in Table 8.

As understood from the results, it is necessary to form the a-Si type layer at a temperature ofthe subs trate ranging from 50"C to 350 C forthe purpose of achieving good performance.

Table 8

Sample No. 53 54 55 56 57 58 59 60 Substrate temp., "C 50 100 150 200 250 300 350 400 Image | Charged On A Do Qo Do 3 n A X quality | polarity | Q X A A A X X X X Image quality is that of transferred image.

CD Very good; Q Good; A Acceptable for practical use; X Poor EXAMPLE 28 Electrophotographic photosensitive members, which are indicated by Sample Nos. 61-65 in Table 9 given below, were prepared by conducting the same procedure under the same conditions as in Example 22 except that the flow of the B2H,gas based on that of SiH4 gas was varied in order to control the amount of the boron (B) doped into the a-Si type layerto various values as shown in Table 9.

Image formation was effected employing the photosensitive members under the same conditions as in Example 22 to obtain images on transfer paper.

The results are shown in Table 9. As is clear from the results it is desirable to dope the a-Si type layer, using boron (B), in an amount of 10 6-10-3 atomic percent.

Table 9

T Sample No. 67 62 63 64 65 Doping amount 10~6 10-5 10 4 10-3 of B, atomic % Image quality D Qo Q f3 x image quality is that of transferred image.

'CD Very good; Q Good; X Poor EXAMPLE 29 The photosensitive members prepared in Examples 20,22 and 23 were each allowed to stand in an atmosphere of high temperature and humidity, i.e., at a temperature of 40"C and relative humidity of 90 RH%. After a lapse of 96 hours, the photosensitive members were taken out into an atmosphere at a temperature of 230C and relative humidity of 50 RH%. Immediately thereafter, the same image forming processes as in Examples 20,22 and 23 were conducted under the same conditions using the photosensitive members to obtain images of sharpness and good quality. This result showed that the photosensitive member of the present invention is excellent also in moisture resistance.

EXAMPLE 30 An electrophotographic photosensitive member was prepared in the same manner as in Example 20.

To the member was applied a negative corona discharge with a power source voltage of 6,000 V in a dark place and image exposure of 20 Iux#sec. was carried out to form an electrostatic image, which was then developed with a liquid developer containing a chargeable toner dispersed in an isoparaffinic hydrocarbon solvent. The developed image was transferred to a transfer paper followed by fixing. The fixed image was extremely high in resolution and of good image quality and sharpness.

The above described image forming process was repeated in order to test the solvent resistance, in other words, liquid developer resistance, of the photosensitive member. The foregoing image on the transfer paper was compared with an image on a transfer paper obtained when the image forming process was repeated ten thousand (10,000) times.

No difference was found therebetween, which showed that the photosensitive member of the present invention is excellent in solvent resistance.

Blade cleaning was used, the blade being formed of urethane rubber.

EXAMPLE3 1 An electrophotographic photosensitive member was prepared using the same procedure and conditions as in Example 1 except that the temperature of the aluminum substrate was continuously raised from 1 000C to 3000C for the duration between the start of the a-Si layer formation and the completion thereof.

The same image forming process as in Example 1 was applied to the thus prepared photosensitive member. It was found that the photosensitive member was excellent in light fatigue resistance as compared with that of Example 1. As to the other properties, similar results were obtained.

EXAMPLE 32 An electrophotographic photosensitive member was prepared by repeating the same manner and conditions as in Example 1 exceptthatthetemperature of the aluminum substrate was controlled as mentioned below. The substrate temperature was adjusted to 1 000C at the time of starting the formation of the a-Si layer, and then continuously raised as the layer grew so that the temperature was adjusted to 3000C immediately before expiration of the layer forming period and subsequently decreased to 2800C until the layer formation was completed.

The same image forming treatment as in Example 1 was conducted using the photosensitive member so prepared. As a result, the photosensitive member was excellent in light fatigue resistance as compared with that obtained in Example 1, and as to other properties, similar results were obtained.

This application is divided from Application No.

49872/78.

Claims

1. An electrophotographic photosensitive member comprising a substrate and, overlying the substrate, a photoconductive layer of a form of amorphous silicon having characteristics suitable for electrophotography and overlying the photoconductive layer, a layer having a refractive index between the refractive index of the photoconductive layer and that of air.

2. An electrophotographic photosensitive member comprising a substrate and overlying the substrate, a photoconductive layer of a form of amorphous silicon having characteristics suitable for electrophotography and, overlying the photoconductive layer, a covering layer of a non-conductive material.

3. An electrophotographic photosensitive member comprising a substrate and, overlying the substrate, a photoconductive layer having a thickness of at least 5 microns of a form of amorphous silicon suitable for electrophotography and, in contact with the photoconductive layer, a barrier layer capable of preventing injection of electric charge carriers into the photoconductive layer during charging of the photosensitive member.

3. An electrophotographic photosensitive member comprising a substrate and, overlying the substrate, a photoconductive layer of a form of amorphous silicon having characteristics suitable for electrophotography and, in contact with the photoconductive layer, a barrier layer capable of preventing injection of electric charge carriers into the photoconductive layer during charging of the photosensitive member.

4. An electrophotographic photosensitive member according to claim 3 in which the barrier layer is interposed between the photoconductive layer and the substrate.

5. An electrophotographic photosensitive member according to claim 1 or 2 including interposed between the substrate and the photoconductive layer, a barrier layer capable of preventing injection of electric charge carriers from said substrate during charging of the photosensitive member.

6. An electrophotographic photosensitive member according to any of claims 1 to 5 wherein the photoconductive layer is from 5 to 80 microns in thickness.

7. An electrophotographic photosensitive member according to any preceding claim wherein the substrate is in the shape of a cylinder.

8. An electrophotographic photosensitive member according to claim 1 in which the layer having the said refractive index is composed of an inorganic fluoride selected from MgF2, CeF2, AIF3 and NaF.

9. An electrophotographic photosensitive member according to claim 1 in which the layer having the said refractive index is composed of an inorganic oxide selected from AI2O3, ZrO2, TiO2, CeO2, SiO2, SiO and Ta2O5.

10. An electrophotographic photosensitive member according to claim 3 or any of claims 4 to 9 as dependent thereon in which said barrier layer is composed of an insulating inorganic oxide.

11. An electrophotographic photosensitive member according to claim 10 in which said insulating inorganic oxide is selected from Al2O3, SiO and SiO2.

12. An electrophotographic photosensitive member according to claim 3 or any of claims 4 to 9 as dependent thereon in which said barrier layer is composed of an insulating organic compound selected from polyethylene, polycarbonate, polyurethane and polyparaxylene.

13. An electrophotographic photosensitive member according to claim 3 or any of claims to 4to 9 as dependent thereon in which said barrier layer is of a metal selected from Au, Ir, Pt, Rh, Pd and Mo.

New claims or amendments to claims filed on 20 July 1982.

Superseded claims 1 to 3.

New or amended claims:- 1 to 3.

1. An electrophotographic photosensitive member comprising a substrate and, overlying the substrate, a photoconductive layer having a thickness of at least 5 microns of a form of amorphous silicon suitable for electrophotography and overlying the photoconductive layer, a layer having a refractive index between the refractive index of the photoconductive layer and that of air.

2. An electrophotographic photosensitive member comprising a substrate and overlying the substrate, a photoconductive layer having a thickness of at least 5 microns of a form of amorphous silicon suitable for electrophotography and, overlying the photoconductive layer, a covering layer of a non-conductive material.