CA1153238A - Electrophotographic member with an amorphous silicon layer containing hidrogen - Google Patents
Electrophotographic member with an amorphous silicon layer containing hidrogenInfo
- Publication number
- CA1153238A CA1153238A CA000375665A CA375665A CA1153238A CA 1153238 A CA1153238 A CA 1153238A CA 000375665 A CA000375665 A CA 000375665A CA 375665 A CA375665 A CA 375665A CA 1153238 A CA1153238 A CA 1153238A
- Authority
- CA
- Canada
- Prior art keywords
- amorphous silicon
- layer
- electrophotographic member
- region
- silicon layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/02—Charge-receiving layers
- G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
- G03G5/08—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic
- G03G5/082—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and not being incorporated in a bonding material, e.g. vacuum deposited
- G03G5/08214—Silicon-based
- G03G5/08235—Silicon-based comprising three or four silicon-based layers
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/02—Charge-receiving layers
- G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
- G03G5/08—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic
- G03G5/082—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and not being incorporated in a bonding material, e.g. vacuum deposited
- G03G5/08214—Silicon-based
- G03G5/08221—Silicon-based comprising one or two silicon based layers
Abstract
Abstract:
An electrophotographic member employs an amorphous silicon photoconductive layer. A part that is at least 10 nm thick inwardly of the amorphous silicon layer from the surface (or interface) of the amorphous silicon layer is made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 1010.OMEGA..cm. The electrophotographic member exhibits a satis-factory resolution and good dark-decay characteristics.
Further, a region which has an optical forbidden band gap narrower than that of the amorphous silicon forming the surface (or interface) region is disposed within the amor-phous silicon layer to a thickness of at least 10 nm, whereby the sensitivity of the electrophotographic member to longer wavelengths of light is enhanced.
An electrophotographic member employs an amorphous silicon photoconductive layer. A part that is at least 10 nm thick inwardly of the amorphous silicon layer from the surface (or interface) of the amorphous silicon layer is made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 1010.OMEGA..cm. The electrophotographic member exhibits a satis-factory resolution and good dark-decay characteristics.
Further, a region which has an optical forbidden band gap narrower than that of the amorphous silicon forming the surface (or interface) region is disposed within the amor-phous silicon layer to a thickness of at least 10 nm, whereby the sensitivity of the electrophotographic member to longer wavelengths of light is enhanced.
Description
Electrophotographic member This invention relates to the structure of a photo-conductive member for use in an electrophotographic sensitive plate. More particularly, it relates to an electrophotographic member that employs amorphous silicon for a photoconductive layer.
Photoconductive materials previously used for electro-photographic members include inorganic substances such as Se, CdS and ZnO and organic substances such as polyvinyl carbazole IP~K) and trinitrofluorenone (TNF). They exhibit high photo-conductivities. However, when forming photoconductive layerswith these materials as they are or by dispersing them in powder form in organic binders, there has been the disadvantage that the layers exhibit insufficient hardnesses, so that their surfaces can become flawed or worn during operation.
In addition, many of these materials are harmful to the human body. It is therefore undesirable that the layers should wear away with the risk of adhering to copying paper even in small amounts. To mlnlmise these dlsadvantages, it has been proposed to employ amorphous sillcon for the photoconductive ~; ~ 20 layer Irefer, for example, to Japanese Laid-open Patent Application No. 54-78135). An amorphous silicon layer is higher in hardness than the previously mentioned conventional photoconductive layers and is scarcely toxic. However, an amorphous silicon layer exhibits a dark resistivity which is too low for an electrophotographic member. An amorphous silicon layer having a comparatively high resistivity of the order of 101Q.cm exhibits too low a pho~oelectric gain and .. ~. . . . . .
,., : ~ .
.. ..
- : .
is unsatisfactory as an electrophotographic member. To overcome this disadvantage, there has been proposed a layered structure wherein at least two sorts of amorphous silicon layers having different conductivity types, such as n-type, n+-type, p-type, p+-type and i-type, are formed into a junction and wherein photo-carriers are generated in a depletion layer formed at the junction (refer, for example, to Japanese Laid-open Patent Application No. 54-121743). ~owever, when a depletion layer is generated by forming two or more layers of different conductivity types into a junction in this way, it is difficult to generate the depletion layer in the surface of the photoconductive layer. The important surface of the photoconductive layer which must hold a charge pattern thus exhibits a low resistivity giving rise to a lateral flow of the charge pattern with consequent risk of degrading of resoltuion.
SummarY of the invention The main object of the present invention is to peovide an electrophotographic member that eliminates such risk of degradation of resolution in an electrophotographic member employing amorphous silicon and which has good dark decay characteristics.
A further object of an embodiment of this invention is to provide an electrophotographic member with improved sensitivity to longer wavelength light.
To this end the invention consists of providing in an electrophotographic member comprising at least a predetermined supporter having a conductive surface and an amorphous silicon layer which is electrically in contact with said conductive surface and which contains hydrogen and silicon as indispensable constituent elements thereof, the improvement comprising an amorphous silicon layer in which the silicon amounts to at least 50 atomic % and the ~' .,~
.: -~1532~8 hydrogen amounts to at least 1 atomic % and, at most, 50 atomic %; said amorphous layer comprising a first region and a second region, said first region being at least lOnm thick, extending inwardly from an outer surface of said amorphous silicon layer and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV
and a resistivity of at least 101Q.cm, and said second region being located at least lOnm from said surface of said amorphous layer, having a thickness of at least lOnm, and being made of amorphous silicon which has an optical forbidden band gap that is smaller than that of said first region at the surface of the amorphous silicon and that is at least 1.1 eV.
Embodiments of the invention are illustrated by way of example in the drawings.
Figure 1 is a graph showing the relationship between the pressure of hydrogen during sputtering and the optical forbidden band gap of an amorphous silicon layer;
Figure 2 is a diagram showing the energy band model of an amorphous-silicon photoconductive layer according to an embodiment of this invention;
Figures 3, 5 and 6 are sectional views each showing the structure of an electrophotographic member according to the embodiments of this invention;
Figure 4 is a view for explaining reactive-sputtering equipment, and Figure 7 is a graph showing the spectral sensitivity characteristics of an electrophotographic member according to embodiments of this invention.
Detailed Description of the Embodiments An amorphous silicon layer made only of pure silicon exhibits localized high density areas, and has almost no photoconductivity. However, the amorphous silicon layer can have the localized density reduced sharply and be - 3a -endowed with a photoconductivity by doping it with hydrogen, or it can be given p-type or n-type conductivity by doping it with imnpurities. Elements effective to thus reduce the localized density in the amorphous silicon are those of the halogen group, such as fluorine, chlorine, bromine and iodine, in addition to hydrogen. Although the halogen group has the effect of reducing the localized density in the amorphous silicon, it cannot greatly vary the optical forbidden band gap of the amorphous silicon.
In contrast, hydrogen doping can sharply increase the optical forbidden band gap of the amorphous silicon or can increase the resistivity thereof.
., ~i~3Z;~8 It is therefore especially useful for obtaining a high-resistivity photoconductive layer.
Well-known methods for forming the amorphous silicon containing hydrogen (usually, expressed as a-Si:H) are (1) the glow discharge process which is based on low-temperature decomposition of monosilane SiH4, (2) the reactive sputtering process in which the sputter-evaporation of silicon is per-formed in an atmosphere containing hydrogen, (3) the ion-plating process. Usually, amorphous silicon layers prepared by these methods contain from several atomic-% to several tens of atomic-% of hydrogen and have optical forbidden band gaps that are considerably greater than 1.1 eV of the pure silicon.
The localized density in pure amorphous silicon containing no hydrogen is presumed to be the order of 102 /cm3.
Supposing that hydrogen atoms extinguish the localized density at 1 : 1 when the amorphous silicon is doped with hydrogen, all the localized density areas ought to be extinguished with a hydrogen-doping quantity of approximately 0.1 atomic-%.
However, it is only when the hydrogen content exceeds approx-imately 1 atomic-~ that the amorphous silicon becomes useful as a photoconductor due to the appearance then of photo-conductivity and the occurence of the variation of the optical forbidden band gap. Hydrogen can be contained up to approx-imately 50 atomic-~, but a content of at most 30 atomic-% is practical. A material in which part of the silicon is replaced by germanium, carbon or the like can also be used for the electrophotographic member. Useful as the quantity of the substitution by germanium or carbon is within 30 atomic-%.
In order to vary the hydrogen content of the amorphous silicon layer, one may control the substrate temperature, the concentration of hydrogen in the atmosphere, the input power, etc. Among the layer forming methods mentioned abovel one that is excellent in relation to process controllability and which can readily produce a photoconductive amorphous silicon layer of high reslstivity and good quality is the reactive sputtering process.
The present inventors can produce an a-Si:H layer having a resistivity of at least 101~.cm permitting its use as an ., , .
~lS32~8 electrophotographic member, by the reactive sputtering of silicon in a mixed atmosphere consisting of argon and hydro-gen. The layer is the so-called intrinsic semiconductor which exhibits the high resistivity and simultaneously a high photoconductivity and whose Fermi level lies near the middle of the forbidden band thereof. In a semiconductor of fixed forbidden band gap, the highest resistivity i5 usually pre-sented in the intrinsic (i-type) state, and the resistivity lowers when the conductivity type is changed into n-type or p-type by doping the semiconductor with an impurity. Accord-- ingly, if a layer is obtained having in the intrinsic state a resistivity high enough to permit its use as an electro-photographic member, it becomes unnecessary to intentionally utilize a depletion layer, and hence, it becomes unnecessary to form the electrophotographic member by stacking two or more amorphous silicon layers of different conductivity types. The present construction provides improvement in the spectral sensitivity and in the dark decay characteristics by employing an a-Si:H layer which has the high resistivity necessary for the electrophotographic member even as a single layer.
Now, in a light receiving device of the storage type, such as an electrophotographic member, the resistivity of the photoconductive layer must satisfy the following two require-ments:
(1) The resistivity of the photoconductive layer must be above approximately 101Q.cm to avoid the risk of charges stuck on the surface of the layer by corona discharge or the like being discharged in the thickness direction of the layer before exposure.
Photoconductive materials previously used for electro-photographic members include inorganic substances such as Se, CdS and ZnO and organic substances such as polyvinyl carbazole IP~K) and trinitrofluorenone (TNF). They exhibit high photo-conductivities. However, when forming photoconductive layerswith these materials as they are or by dispersing them in powder form in organic binders, there has been the disadvantage that the layers exhibit insufficient hardnesses, so that their surfaces can become flawed or worn during operation.
In addition, many of these materials are harmful to the human body. It is therefore undesirable that the layers should wear away with the risk of adhering to copying paper even in small amounts. To mlnlmise these dlsadvantages, it has been proposed to employ amorphous sillcon for the photoconductive ~; ~ 20 layer Irefer, for example, to Japanese Laid-open Patent Application No. 54-78135). An amorphous silicon layer is higher in hardness than the previously mentioned conventional photoconductive layers and is scarcely toxic. However, an amorphous silicon layer exhibits a dark resistivity which is too low for an electrophotographic member. An amorphous silicon layer having a comparatively high resistivity of the order of 101Q.cm exhibits too low a pho~oelectric gain and .. ~. . . . . .
,., : ~ .
.. ..
- : .
is unsatisfactory as an electrophotographic member. To overcome this disadvantage, there has been proposed a layered structure wherein at least two sorts of amorphous silicon layers having different conductivity types, such as n-type, n+-type, p-type, p+-type and i-type, are formed into a junction and wherein photo-carriers are generated in a depletion layer formed at the junction (refer, for example, to Japanese Laid-open Patent Application No. 54-121743). ~owever, when a depletion layer is generated by forming two or more layers of different conductivity types into a junction in this way, it is difficult to generate the depletion layer in the surface of the photoconductive layer. The important surface of the photoconductive layer which must hold a charge pattern thus exhibits a low resistivity giving rise to a lateral flow of the charge pattern with consequent risk of degrading of resoltuion.
SummarY of the invention The main object of the present invention is to peovide an electrophotographic member that eliminates such risk of degradation of resolution in an electrophotographic member employing amorphous silicon and which has good dark decay characteristics.
A further object of an embodiment of this invention is to provide an electrophotographic member with improved sensitivity to longer wavelength light.
To this end the invention consists of providing in an electrophotographic member comprising at least a predetermined supporter having a conductive surface and an amorphous silicon layer which is electrically in contact with said conductive surface and which contains hydrogen and silicon as indispensable constituent elements thereof, the improvement comprising an amorphous silicon layer in which the silicon amounts to at least 50 atomic % and the ~' .,~
.: -~1532~8 hydrogen amounts to at least 1 atomic % and, at most, 50 atomic %; said amorphous layer comprising a first region and a second region, said first region being at least lOnm thick, extending inwardly from an outer surface of said amorphous silicon layer and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV
and a resistivity of at least 101Q.cm, and said second region being located at least lOnm from said surface of said amorphous layer, having a thickness of at least lOnm, and being made of amorphous silicon which has an optical forbidden band gap that is smaller than that of said first region at the surface of the amorphous silicon and that is at least 1.1 eV.
Embodiments of the invention are illustrated by way of example in the drawings.
Figure 1 is a graph showing the relationship between the pressure of hydrogen during sputtering and the optical forbidden band gap of an amorphous silicon layer;
Figure 2 is a diagram showing the energy band model of an amorphous-silicon photoconductive layer according to an embodiment of this invention;
Figures 3, 5 and 6 are sectional views each showing the structure of an electrophotographic member according to the embodiments of this invention;
Figure 4 is a view for explaining reactive-sputtering equipment, and Figure 7 is a graph showing the spectral sensitivity characteristics of an electrophotographic member according to embodiments of this invention.
Detailed Description of the Embodiments An amorphous silicon layer made only of pure silicon exhibits localized high density areas, and has almost no photoconductivity. However, the amorphous silicon layer can have the localized density reduced sharply and be - 3a -endowed with a photoconductivity by doping it with hydrogen, or it can be given p-type or n-type conductivity by doping it with imnpurities. Elements effective to thus reduce the localized density in the amorphous silicon are those of the halogen group, such as fluorine, chlorine, bromine and iodine, in addition to hydrogen. Although the halogen group has the effect of reducing the localized density in the amorphous silicon, it cannot greatly vary the optical forbidden band gap of the amorphous silicon.
In contrast, hydrogen doping can sharply increase the optical forbidden band gap of the amorphous silicon or can increase the resistivity thereof.
., ~i~3Z;~8 It is therefore especially useful for obtaining a high-resistivity photoconductive layer.
Well-known methods for forming the amorphous silicon containing hydrogen (usually, expressed as a-Si:H) are (1) the glow discharge process which is based on low-temperature decomposition of monosilane SiH4, (2) the reactive sputtering process in which the sputter-evaporation of silicon is per-formed in an atmosphere containing hydrogen, (3) the ion-plating process. Usually, amorphous silicon layers prepared by these methods contain from several atomic-% to several tens of atomic-% of hydrogen and have optical forbidden band gaps that are considerably greater than 1.1 eV of the pure silicon.
The localized density in pure amorphous silicon containing no hydrogen is presumed to be the order of 102 /cm3.
Supposing that hydrogen atoms extinguish the localized density at 1 : 1 when the amorphous silicon is doped with hydrogen, all the localized density areas ought to be extinguished with a hydrogen-doping quantity of approximately 0.1 atomic-%.
However, it is only when the hydrogen content exceeds approx-imately 1 atomic-~ that the amorphous silicon becomes useful as a photoconductor due to the appearance then of photo-conductivity and the occurence of the variation of the optical forbidden band gap. Hydrogen can be contained up to approx-imately 50 atomic-~, but a content of at most 30 atomic-% is practical. A material in which part of the silicon is replaced by germanium, carbon or the like can also be used for the electrophotographic member. Useful as the quantity of the substitution by germanium or carbon is within 30 atomic-%.
In order to vary the hydrogen content of the amorphous silicon layer, one may control the substrate temperature, the concentration of hydrogen in the atmosphere, the input power, etc. Among the layer forming methods mentioned abovel one that is excellent in relation to process controllability and which can readily produce a photoconductive amorphous silicon layer of high reslstivity and good quality is the reactive sputtering process.
The present inventors can produce an a-Si:H layer having a resistivity of at least 101~.cm permitting its use as an ., , .
~lS32~8 electrophotographic member, by the reactive sputtering of silicon in a mixed atmosphere consisting of argon and hydro-gen. The layer is the so-called intrinsic semiconductor which exhibits the high resistivity and simultaneously a high photoconductivity and whose Fermi level lies near the middle of the forbidden band thereof. In a semiconductor of fixed forbidden band gap, the highest resistivity i5 usually pre-sented in the intrinsic (i-type) state, and the resistivity lowers when the conductivity type is changed into n-type or p-type by doping the semiconductor with an impurity. Accord-- ingly, if a layer is obtained having in the intrinsic state a resistivity high enough to permit its use as an electro-photographic member, it becomes unnecessary to intentionally utilize a depletion layer, and hence, it becomes unnecessary to form the electrophotographic member by stacking two or more amorphous silicon layers of different conductivity types. The present construction provides improvement in the spectral sensitivity and in the dark decay characteristics by employing an a-Si:H layer which has the high resistivity necessary for the electrophotographic member even as a single layer.
Now, in a light receiving device of the storage type, such as an electrophotographic member, the resistivity of the photoconductive layer must satisfy the following two require-ments:
(1) The resistivity of the photoconductive layer must be above approximately 101Q.cm to avoid the risk of charges stuck on the surface of the layer by corona discharge or the like being discharged in the thickness direction of the layer before exposure.
(2) The sheet resistance of the photoconductive layer must be sufficiently high to avoid the risk of a charge patt-ern formed on the surface of the photoconductive layer upon exposure disappearing before developing as a result of lateral ~low of the charges. In terms of the resistivity, this amounts to above approximately 101Q.cm as in the preceding item.
Both of the above items concern the migrations of the charges in the dark before and after exposure. The former ~ill be referred to the "dark decay in the thickness dlrection ' ~ .
~1~3Z;~
of the layer" and the latter the "dark decay in the surface direction of the layer".
In order to meet the conditions of these two items, the resistivity at and near the surface of the photconductive layer to hold the charges must be above approximately 101Q.cm, but a resistivity of at least 101Q.cm need not be possessed uniformly in the thickness direction of the layer. Letting Il denote the time constant of the dark decay in the thickness direction of the layer, Cl denote the capacitance per unit area of the layer and Rl denote the resistance in the thickness direction per unit area of the layer, the following relation holds:
~1 = Rl C 1 .................................. (1) Since ll may be sufficiently long as compared with the period of time from charging to developing, RL may be sufficiently great with the thickness direction of the layer viewed macro-scopically.
The present inventors have discovered that, as a factor that determines the macroscopic resistance in the thickness direction of the layer in a high-resistivity thin-film device such as an electrophotographic member, charges injected from an interface with an electrode play an important role besides the resistivity of the layer itself. It has been found that, in order to prevent the injection of charges from such an interface on the side opposite the charged surface or the side of a substrate holding the photoconductive layer in the electrophotographic member employing amorphous silicon, a satisfactory effect is obtained by making the resistivity of the amorphous silicon layer in the vicinity of the interface with the substrate a high value of at least 101Q.cm. Ordi-narlly, such high-resistivity region is the intrinslc semi-conductor (i-type). This region functions as a layer that blocks the injection of charges from the electrode into the photoconductive layer, and it needs to be at least 10 nm thick, lest the charges should pass through the region due to the ~unnel effect. Further, in order to effectively block the injection of charges from the electrode, it is also effective to interpose a thin layer (usually, termed "blocking layer") . .
~1~323~
2 2~ 2 3~ Sb2Se3~ As2S3~ As2Se3 or the like bet ween the electrode and the amorphous silicon layer.
It will have become apparent from the above description that, in order to suppress the dark decay in the thickness direction of the photoconductive layer and the dark decay in the surface direction, the resistivity in the vicinity of the surface (or interface) of the amorphous silicon layer must be as high as at least 101Q.cm. In this regard, the required thickness of the high-resistivity portion is not alway fixed, because it is dependent upon the resistivity of the low-resistivity portion adjoining the high-resistivity portion.
However, as explained above, the high~resistivity portion needs to be at least 10 nm thick. When considering the close proximity to the surface of the amorphous silicon layer, for example, a region of several atomic layers, it is possible that the adsorption of an atmospheric gas modifies the con-ductivity to produce a low resistivity. However, it should be taken as a requisite of the present construction that a sufficiently high resistance is observed when the surface resistance is measured by an ordinary method.
The resistivity in the vicinity of the surface (or interface) of the amorphous silicon layer must be sufficiently high, but the resistivity of the interior of the layer need not always be high. On the basis of the principle of electro-photography, the macroscopic resistance Rl of the photo-conductive layer may meet Expression (1) above. This is convenient for another feature of the present construction, improvements ¦in the spectral sensitivity characteristics.
Usually, the a-Si:H layer havlng a high resistivity of at least 101Q.cm has an optical forbldden band gap of approximately 1.7 eV and is insensitive to light of wa~elengths longer than the long wavelength region of visible radiation. This fact is inconvenient when using an a-Si:H layer as a photoconductive layer for laser beam printer equipment that employs as its light source a semiconductor laser having a wavelength near 800 nm. On the other hand, it is difficult to make an a-Si:H
layer highly sensitive to the longer wavelength light with a high resistivity of at least 101Q.cm.
.~
llS32;~8 To aid solving this problem, it has been found by the present inventors that the spectral sensitivity character-istics of an electrophotographic sensitive plate can be shifted towards the longer wavelength by forming a region exhibiting a longer wavelength light-sensitivity within the a-Si:H layer while keeping the macroscopic resistance of the whole layer sufficiently high. Figure 1 illustrates the relationship between the pressure of hydrogen in the atmo-sphere in the reactive sputtering process and the optical forbidden band gap of an a-Si:H layer. As appears from this graph, a region of small optical forbidden band gap can be formed within a photoconductive layer if the hydrogen pressure is high during the initial stage of the formation of the layer, is thereafter temporarily lowered and raised again for the final stage of the layer formation. The minimum value of optical forbidden band gap realizable with this method is 1.1 eV which is the optical forbidden band gap of pure silicon.
When a region of narrow forbidden band gap has been formed within the photoconductive layer in this manner, the longer wavelength light is absorbed in this region to generate electron-hole pairs. The situation is illustrated as an energy band model in Figure 2. Since, in both the region of wide forbidden band gap and the region of narrow forbidden band gap, the resistances of the portions themselves are desired to be as high as possible, the photoconductive layer shouId preferably be fully intrinsic (i-type). The energy band model then has a shape vertically symmetric with respect to the Fermi level. Photo-carriers generated in the con-striction or the region of narrow forbidden band gap are cap-tured in this region by a built-in field existing therein. In order to draw the photo-carriers out of this region by an external electric field and to utilize them as effective photo-carriers, such external field must be greater than the built-in field of this region. Stated conversely, when form-ing the region of narrow forbidden band gap, the built-in field to arise therein must be made smaller than the external electric field. The built-in field of this region depends upon the depth IPotential difference) D and the width W of `:
g ~th~region in the energy band model. An abrupt change of the band gap generates a larger built-in field, whereas a gentle change of the band gap generates a smaller built-in field.
When the shape of the region approximates that of an isos-celes triangle, the condition for drawing out the photo-carriers is:
Ea> 2 D/W ...................................... (2) where Ea denotes the external electric field.
It is desirable from the viewpoint of utilization of incident light tha~, within the amorphous-silicon photo-conductive layer, the portion in which the region of narrow forbidden hand gap exists should lie as close to the incident piane of light as possible. However, in a case where the incident light is monochromatic as in, for example, the laser beam printer equipment, and where the coefficient of absorp-tion in the portion other than the region of narrow forbidden band gap is small, there is no significant difference in effect wherever the region lies in the thickness direction within the layer. To generate effective photo-carriers in the region of narrow forbidden band gap, the width W of this region needs to be, in effect, at least 10 nm. The maximum limit of this width is, of course, the entire thickness of the amorphous silicon layer, but the width W is desirably no more than half of the whole thickness of the layer in order to keep the total resistance Rl in the thickness direction suffi-ciently hiyh.
The whole thickness of the amorphous-silicon photocon-ductive layer ls determined by the surface potential, which in turn varies depending upon the kind of toner used and the service conditlons of the photoconductive layer~ However, the withstand voltage of the amorphous silicon layer is considered to be 10 V - S0 V per ~m. Acccordingly, when the surface potential is S00 V, the entire layer thickness becomes lO~m -50~m. Values for the entire layer thickness exceeding lOO~m are not practicable.
There will now be described specific examples of an electrophotographic member having an amorphous-silicon photo-conductive layer.
~iS3~3~3 Figure 3 is a sectional view showing a typical such example, wherein numeral 1 designates a substrate, and num-eral 2 a photoconductive layer including an amorphous silicon layer. The substrate 1 may be any metal plate, such as alum-inum, stainless steel or nichrome, or maybe an organic materialsuch as polyimide, glass, ceramics etc. When the substrate is an electrical insulator, an electrode 11 needs to be deposited on its surface. When the substrate is a conductor, it can also serve as the electrode. Used as the electrode is a thin film of a metal material such as aluminum and chromium, or a transparent electrode of an oxide such as SnO2 and In-Sn-O. The photoconductive layer 2 is disposed on the electrode. If the substrate 1 is light-transmissive and the electrode 11 is transparent, light to enter the photoconduct-ive layer 2 is sometimes projected through the substrate 1.
In this example, the layer 2 has a three-layered struc-true. The first layer 21 adjacent the substrate 1 is for suppressing injection of excess carriers from the substrate side. For this purpose, a layer of a high-resistivity oxide, sulfide or selenide such as SiO, SiO2, A12O3, CeO2, V2O3, Ta2O, As2Se3 and As2S3 is used, or a layer of an organic substance such as polyvinyl carbazole is sometimes used. The last layer 25 is for suppressing the injection of charges from the outer side. For this there are similarly used SiO, SiO2, A12O3, CeO2, V2O3, Ta2O, As2Se3, As2S3, polyvinyl carbazole, etc.
These layers 21 and 25 serve to improve the electrophotographic characteristics of the photoconductive layer. However~ they are not always necessary, since essentially the presence of layers 22, 23 and 24 satisfies the basic requirements.
All the layers 22, 23 and 24 are layers whose principal constiuents are amorphous silicon. Each of the layers 22 and 24 exhibits an optical forbidden band gap of at least 1.6 eV
and a resistivity of at least 101Q.cm and has a thickness of at least 10 nm. The layer 23 has an optical forbidden band gap of at least 1.1 eV but not exceeding that of the layer 22 or 24 and has a thickness of at least 10 nm. Naturally, the resistivity of the layer 23 can be less than 101Q.cm.
Even in that event no bad influence is exerted on the dark ~ .
~; :
. .
~lS32;~
decay characteristics owing to the presence of the layers 22 and 24. Sometimes the amorphous silicon layer is doped with carbon or a very small amount of boron to increase the resistivity and the optical forbidden band gap of each of the layers 22 and 24, or the amorphous silicon layer is doped with germanium to reduce the optical forbidden band gap of the layer 23. However, it is necessary for ensuring photocon-ductive characteristics that at least 50 atomic-~ of silicon is contained on the average within the layer. As long as this requirement is fulfilled, such layers fall within the scope of this invention whatever other elements they may contain.
As already mentioned, known methods for forming the amorphous silicon layer containing hydrogen include the decomposition of SiH4 by a glow discharge, the reactive sputtering process, the ion-plating process etc. With any of these methods, a layer having the best photoelectric con-version characteristics is obtained when the substrate temp-erature during the formation of the layer is 150 - 250C.
In the glow discharge process, the hydrogen content of the formed layer is intensely dependent upon the substrate temp-erature during the formation of the layer. It is therefore difficult to determine the photoelectric conversion character-istics and the hydrogen content of the layer independently of each other. A layer of good photoelectric conversion char-acteristics has a resistivity as low as 106 - 107Q.cm and is unsuitable for electrophotography. Therefore, such a con-sideration as doping the layer with a slight amount of boron to raise its resistivity is also necessary. In contrast, the reactive sputtering process and the ion-platlng process can independently determine the substrate temperature during the formation of the layer and the hydrogen content of the layer, so that they are especially effective in cases where the layers of different optical forbidden band gaps need to be stacked in the thickness direction as in the present construction.
Further, the reactive sputtering process can form a uniform layer of large area by employing a sputtering target of sufficiently large area. It is therefore particularly useful for forming a photoconductive layer for electrophotography.
1153;~38 The reactive sputtering process is usually performed by equipment as shown in Figure 4 where numeral 31 designates a bell ~ar, numeral 32 an evacuating system, numeral 33 a radio-frequency power source, numeral 34 a sputtering target, numeral 35 a substrate holder, numeral 36 a substrate, and nuMerals 37 and 38 gas cylinders containing gases to be introduced. Sputtering equipment includes, not only structure that serves to perform a sputter-evaporation on a flat sub-strate as shown in the figure, but also a structure that can perform a sputter-evaporation on a cylindrical or drum-shaped substrate. Suchvariations ~can be adopted in accordance with the intended use.
The reactive sputtering process is carried out by evac-uating the bell jar 31, introducing hydrogen and such an inert gas as argon thereinto, and supplying a radio-frequency voltage from the radio-frequency power source 33 to cause a discharge. The frequency is usually 13.56 MHz. The input power is 0.1 W/cm2 - 100 W/cm2. The amount of hydrogen in a layer formed in this way is determined principally by the pressure of the hydrogen during the discharge. An amorphous silicon layer containing hydrogen suited for use in the pre-sent construction is produced when the hydrogen pressure during sputtering lies in the range of from 1 x 10 5 Torr to 5 x 10 Torr. The deposition rate of the layer is 1 A/sec-30 A~sec. The total gas pressure is generally set within arange of 1 x 10 4 Torr - 0.1 Torr. The substrate temperature during the deposition is selected from within a range of 50C
_ 400C. I
Example 1 .
Figure 5 is a sectional view of an electrophotographic member.
An aluminum cylinder whose surface 41 was mirror-polished was heated at 300C in an oxygen atmosphere for 2 hours to form an A12o3 film 42 on the surface 41. The cylinder was installed in rotary magnetron type sputterng equipment, the interior of which was evacuated up to 1 x 10 6 Torr. Thereafter, while holding the cylinder at 200C, an amorphous silicon film 43 was deposited thereon to a thickness of 30~m at a deposition .:
'' ~
:.
3Z;~8 rate of 2 A/sec using a radio-frequency output of 13.56 MHz and 350 W in a mixed atmosphere consisting of 2 x 10 5 Torr of hydrogen and 3 x 10 3 Torr of argon. The film 43 had an optical forbidden band gap of 1.5 eV and a resistivity of 108Q.cm. It had a hydrogen content of 4 atomic-%. Subse-quently, while the substrate temperature was held at 200C, an amorphous silicon film 44 was found to a thickness of l~m using the radio-frequency output of 13.56 MHz and 350 W
in a mixed atmosphere consisting of 2 x 10 3 Torr of hydrogen and 3 x 10 3 Torr of argon. This film 44 had an optical forbidden band gap of 1.95 eV and a resistivity of lOll~.cm.
Thereafter, the resulting cylinder was taken out of the sputtering equipment and installed in vacuum evaporation equipment. While holding the substrate temperature at 80C
under a pressure of 2 x 10 6 Torr, an As2Se3 film 45 was evaporated to a thickness of 1,000 A.
Since the electrophotographic member thus formed has as a surface layer the amorphous silicon layer 44 whose optical forbidden band gap is at least 1.6 eV and whose resistivity is at least 101Q.cm, it can establish an especially high surface potential. Table 1 lists the changes of surface potential when the amorphous silicon layer 44 has not been fully dis-posed and is having its thickness varied. The listed results were obtained by measuring the surface potential 1 sec. after the electrophotographic member had been charged by a corona discharge at 6.5 kV. A high surface potential signifies that charges are retained well. It will be understood from the results of Table 1 that the present construction provides a remarkable effect.
..
~lS3Z;~
Table 1 Thickness of Surface potential layer 44 (relative value) .
No layer 0.02 5 (nm) 0.1 10 (nm) 0.6 20 (nm) 0.8 1 l~m) 1.0 .. _ .. _._ The decay of the surface potential after 1 sec. was below 10 %, and the dark decay characteristics were satis-factory.
Example 2:
This example will be explained with reference to Figure 6.
On a hard glass cylinder 1, a transparent electrode 11 of SnO2 was formed by the thermodecomposition of SnC14 at 450C. The resulting cylinder was installed in rotary sputt-ering equipment, the interior of which was evacuated to 2 x 10 6 Torr. Subsequently, while holding the cylinder at 250C, an amorphous silicon film 22 (hYdrogen content: 17.5 atomic-%) having an optical forbidden band gap of 1.95 eV and a resist-ivity of 1011Q.cm was deposited to a thickness of 500 A at a deposition rate of 1 A/sec by a radio-frequency power of 300 W (at a frequency of 13.56 MH2) in a mlxed atmosphere consist-ing of 2 x 10 3 Torr of hydrogen and 2 x 10 3 Torr of argon.Thereafter, while holding the pressure of argon constant, the pressure of hydrogen was gradually lowed to 3 x 10 5 Torr over a period of 20 minutes. The amorphous silicon film 23 formed at the minimum hydrogen pressure (hydrogen content:
9 atomic-~) had an optical forbidden band gap of 1.6 eV and a resistivity of 103Q.cm. Further, while holding the argon pressure constant, the hydrogen pressure was gradually raised .
-, - ~
.
. : .' ' - - ' . ' ' ~ . - , '. ' ~ ' ' ' ' ;32~8 again to 2 x 10 3 Torr again over 20 minutes. The sputtering was continued to form an amorphous silicon film 24 until the whole thickness of the amorphous silicon layer became 25 ~m.
The region whose optical forbidden band gap was below 1.95 eV
was approximately 2,400 A thick.
A film of As2Se3 or the like may be inserted on the transparent electrode 11 as a blocking layer. As stated be-fore, a blocking layer may also be disposed on the photo-conductive layer 24.
Figure 7 illustrates the spectral sensitivity of a photo-conductive layer formed in this way. The dotted line 51 in-dicates the spectral sensitivity in a case in which the hydrogen pressure was not lowered, and the solid line 52 in the case where it was. As seen from the result, the sensiti-vity to longer wavelength light is improved by the hydrogen pressure reduction.
Example 3:
In this example, amorphous silicon containing carbon is employed for the surface and the interface of a conductive layer. The fundamental structure is as shown in Figure 6.
On a polyimide film 1 a chrome film 11 was vacuum-evaporated to a thickness of 400 A, to prepare a substrate.
The resuItant was installed in sputtering equipment, the interior of which was evacuated to 5 x 10 7 Torr. Thereafter, while holding the substrate at 150C and employing a target of polycrystalline silicon containing 10% of carbon, a film 22 of amorphous silicon - carbon having an optical forbidden band gap of 2.0 eV and a resistivity of 1013Q.cm was formed to a thickness of 5 ~m at a deposition rate of 3 A/sec under radio-frequency power of 350 W in a gaseous mlxture consisting of 1 x 10 3 Torr of hydrogen and 4 x 10 3 Torr of argon. The hydrogen content of this film was approximately 14 atomic-~.
Thereafter, sputtering was performed using a target made of silicon only in a gaseous mixture consisting of 2 x 10 3 Torr of argon and 3 x 10 3 Torr of hydrogen, to form a film 23 of amorphous silicon having a thickness of 60 nm and exhibiting an optical forbidden band gap of 1.95 eV as well as a resist-ivity of 1012Q.cm. Further, on the film 23, a film 24 of the ~lS32;~
first amorphous silicon - carbon was formed to 5 ~m.
An electrophotographic member having a satisfactory resolution and good dark-decay characteristics was realized.
Example 4:
Reference is again had to Figure 6.
On a hard glass cylinder 1, an SnO2 transparent electrode 11 was formed by the thermodecomposition of SnC14 at 450C.
The resultant cylinder was installed in rotary sputtering equipment, the interior of which was evacuated to approximately 2 x 10 6 Torr. Subsequently, while holding the cylinder at 250C, an amorphous silicon film 22 thydrogen content: 17.5 atomic-~) was deposited to 500 A by radio-frequency power of 13.56 MHz and 300 W in a mixed atmosphere consisting of 2 x 10 3 Torr of hydrogen and 2 x 10 3 Torr of argon. The optical forbidden band gap of this film was 1.95 eV, and the resist-ivity was 1011Q.cm. Thereafter, using a sputtering target in which silicon and germanium were juxtaposed, a germanium-containing amorphous silicon film 23 was deposited to a thick-ness of 0.1 ~m. The sputtering was a gaseous mixture con-sisting of 1 x 10 3 Torr of hydrogen and 2 x 10 3 Torr ofargon. The content of germanium was 30 atomic-%, and that of hydrogen was 10 atomic-%. In addition, the optical forbidden band gap was approximately 1.40 eV, and the resistivity was approximately 109Q.cm. Subsequently, an amorphous silicon film 24 was formed under the same conditions as those of the first amorphous silicon film. The thickness of the whole layer was made 25 ~m. The optical forbidden band gap of the film 24 was 1.95 eV, and the resistivity was 1011n.cm. When the germanium-containing amorphous silicon was used in this manner, an electrophotographic member having a satisfactory resolution and good dark-decay characteristics was realized.
- , . . : .
- ' .~ , :
:
Both of the above items concern the migrations of the charges in the dark before and after exposure. The former ~ill be referred to the "dark decay in the thickness dlrection ' ~ .
~1~3Z;~
of the layer" and the latter the "dark decay in the surface direction of the layer".
In order to meet the conditions of these two items, the resistivity at and near the surface of the photconductive layer to hold the charges must be above approximately 101Q.cm, but a resistivity of at least 101Q.cm need not be possessed uniformly in the thickness direction of the layer. Letting Il denote the time constant of the dark decay in the thickness direction of the layer, Cl denote the capacitance per unit area of the layer and Rl denote the resistance in the thickness direction per unit area of the layer, the following relation holds:
~1 = Rl C 1 .................................. (1) Since ll may be sufficiently long as compared with the period of time from charging to developing, RL may be sufficiently great with the thickness direction of the layer viewed macro-scopically.
The present inventors have discovered that, as a factor that determines the macroscopic resistance in the thickness direction of the layer in a high-resistivity thin-film device such as an electrophotographic member, charges injected from an interface with an electrode play an important role besides the resistivity of the layer itself. It has been found that, in order to prevent the injection of charges from such an interface on the side opposite the charged surface or the side of a substrate holding the photoconductive layer in the electrophotographic member employing amorphous silicon, a satisfactory effect is obtained by making the resistivity of the amorphous silicon layer in the vicinity of the interface with the substrate a high value of at least 101Q.cm. Ordi-narlly, such high-resistivity region is the intrinslc semi-conductor (i-type). This region functions as a layer that blocks the injection of charges from the electrode into the photoconductive layer, and it needs to be at least 10 nm thick, lest the charges should pass through the region due to the ~unnel effect. Further, in order to effectively block the injection of charges from the electrode, it is also effective to interpose a thin layer (usually, termed "blocking layer") . .
~1~323~
2 2~ 2 3~ Sb2Se3~ As2S3~ As2Se3 or the like bet ween the electrode and the amorphous silicon layer.
It will have become apparent from the above description that, in order to suppress the dark decay in the thickness direction of the photoconductive layer and the dark decay in the surface direction, the resistivity in the vicinity of the surface (or interface) of the amorphous silicon layer must be as high as at least 101Q.cm. In this regard, the required thickness of the high-resistivity portion is not alway fixed, because it is dependent upon the resistivity of the low-resistivity portion adjoining the high-resistivity portion.
However, as explained above, the high~resistivity portion needs to be at least 10 nm thick. When considering the close proximity to the surface of the amorphous silicon layer, for example, a region of several atomic layers, it is possible that the adsorption of an atmospheric gas modifies the con-ductivity to produce a low resistivity. However, it should be taken as a requisite of the present construction that a sufficiently high resistance is observed when the surface resistance is measured by an ordinary method.
The resistivity in the vicinity of the surface (or interface) of the amorphous silicon layer must be sufficiently high, but the resistivity of the interior of the layer need not always be high. On the basis of the principle of electro-photography, the macroscopic resistance Rl of the photo-conductive layer may meet Expression (1) above. This is convenient for another feature of the present construction, improvements ¦in the spectral sensitivity characteristics.
Usually, the a-Si:H layer havlng a high resistivity of at least 101Q.cm has an optical forbldden band gap of approximately 1.7 eV and is insensitive to light of wa~elengths longer than the long wavelength region of visible radiation. This fact is inconvenient when using an a-Si:H layer as a photoconductive layer for laser beam printer equipment that employs as its light source a semiconductor laser having a wavelength near 800 nm. On the other hand, it is difficult to make an a-Si:H
layer highly sensitive to the longer wavelength light with a high resistivity of at least 101Q.cm.
.~
llS32;~8 To aid solving this problem, it has been found by the present inventors that the spectral sensitivity character-istics of an electrophotographic sensitive plate can be shifted towards the longer wavelength by forming a region exhibiting a longer wavelength light-sensitivity within the a-Si:H layer while keeping the macroscopic resistance of the whole layer sufficiently high. Figure 1 illustrates the relationship between the pressure of hydrogen in the atmo-sphere in the reactive sputtering process and the optical forbidden band gap of an a-Si:H layer. As appears from this graph, a region of small optical forbidden band gap can be formed within a photoconductive layer if the hydrogen pressure is high during the initial stage of the formation of the layer, is thereafter temporarily lowered and raised again for the final stage of the layer formation. The minimum value of optical forbidden band gap realizable with this method is 1.1 eV which is the optical forbidden band gap of pure silicon.
When a region of narrow forbidden band gap has been formed within the photoconductive layer in this manner, the longer wavelength light is absorbed in this region to generate electron-hole pairs. The situation is illustrated as an energy band model in Figure 2. Since, in both the region of wide forbidden band gap and the region of narrow forbidden band gap, the resistances of the portions themselves are desired to be as high as possible, the photoconductive layer shouId preferably be fully intrinsic (i-type). The energy band model then has a shape vertically symmetric with respect to the Fermi level. Photo-carriers generated in the con-striction or the region of narrow forbidden band gap are cap-tured in this region by a built-in field existing therein. In order to draw the photo-carriers out of this region by an external electric field and to utilize them as effective photo-carriers, such external field must be greater than the built-in field of this region. Stated conversely, when form-ing the region of narrow forbidden band gap, the built-in field to arise therein must be made smaller than the external electric field. The built-in field of this region depends upon the depth IPotential difference) D and the width W of `:
g ~th~region in the energy band model. An abrupt change of the band gap generates a larger built-in field, whereas a gentle change of the band gap generates a smaller built-in field.
When the shape of the region approximates that of an isos-celes triangle, the condition for drawing out the photo-carriers is:
Ea> 2 D/W ...................................... (2) where Ea denotes the external electric field.
It is desirable from the viewpoint of utilization of incident light tha~, within the amorphous-silicon photo-conductive layer, the portion in which the region of narrow forbidden hand gap exists should lie as close to the incident piane of light as possible. However, in a case where the incident light is monochromatic as in, for example, the laser beam printer equipment, and where the coefficient of absorp-tion in the portion other than the region of narrow forbidden band gap is small, there is no significant difference in effect wherever the region lies in the thickness direction within the layer. To generate effective photo-carriers in the region of narrow forbidden band gap, the width W of this region needs to be, in effect, at least 10 nm. The maximum limit of this width is, of course, the entire thickness of the amorphous silicon layer, but the width W is desirably no more than half of the whole thickness of the layer in order to keep the total resistance Rl in the thickness direction suffi-ciently hiyh.
The whole thickness of the amorphous-silicon photocon-ductive layer ls determined by the surface potential, which in turn varies depending upon the kind of toner used and the service conditlons of the photoconductive layer~ However, the withstand voltage of the amorphous silicon layer is considered to be 10 V - S0 V per ~m. Acccordingly, when the surface potential is S00 V, the entire layer thickness becomes lO~m -50~m. Values for the entire layer thickness exceeding lOO~m are not practicable.
There will now be described specific examples of an electrophotographic member having an amorphous-silicon photo-conductive layer.
~iS3~3~3 Figure 3 is a sectional view showing a typical such example, wherein numeral 1 designates a substrate, and num-eral 2 a photoconductive layer including an amorphous silicon layer. The substrate 1 may be any metal plate, such as alum-inum, stainless steel or nichrome, or maybe an organic materialsuch as polyimide, glass, ceramics etc. When the substrate is an electrical insulator, an electrode 11 needs to be deposited on its surface. When the substrate is a conductor, it can also serve as the electrode. Used as the electrode is a thin film of a metal material such as aluminum and chromium, or a transparent electrode of an oxide such as SnO2 and In-Sn-O. The photoconductive layer 2 is disposed on the electrode. If the substrate 1 is light-transmissive and the electrode 11 is transparent, light to enter the photoconduct-ive layer 2 is sometimes projected through the substrate 1.
In this example, the layer 2 has a three-layered struc-true. The first layer 21 adjacent the substrate 1 is for suppressing injection of excess carriers from the substrate side. For this purpose, a layer of a high-resistivity oxide, sulfide or selenide such as SiO, SiO2, A12O3, CeO2, V2O3, Ta2O, As2Se3 and As2S3 is used, or a layer of an organic substance such as polyvinyl carbazole is sometimes used. The last layer 25 is for suppressing the injection of charges from the outer side. For this there are similarly used SiO, SiO2, A12O3, CeO2, V2O3, Ta2O, As2Se3, As2S3, polyvinyl carbazole, etc.
These layers 21 and 25 serve to improve the electrophotographic characteristics of the photoconductive layer. However~ they are not always necessary, since essentially the presence of layers 22, 23 and 24 satisfies the basic requirements.
All the layers 22, 23 and 24 are layers whose principal constiuents are amorphous silicon. Each of the layers 22 and 24 exhibits an optical forbidden band gap of at least 1.6 eV
and a resistivity of at least 101Q.cm and has a thickness of at least 10 nm. The layer 23 has an optical forbidden band gap of at least 1.1 eV but not exceeding that of the layer 22 or 24 and has a thickness of at least 10 nm. Naturally, the resistivity of the layer 23 can be less than 101Q.cm.
Even in that event no bad influence is exerted on the dark ~ .
~; :
. .
~lS32;~
decay characteristics owing to the presence of the layers 22 and 24. Sometimes the amorphous silicon layer is doped with carbon or a very small amount of boron to increase the resistivity and the optical forbidden band gap of each of the layers 22 and 24, or the amorphous silicon layer is doped with germanium to reduce the optical forbidden band gap of the layer 23. However, it is necessary for ensuring photocon-ductive characteristics that at least 50 atomic-~ of silicon is contained on the average within the layer. As long as this requirement is fulfilled, such layers fall within the scope of this invention whatever other elements they may contain.
As already mentioned, known methods for forming the amorphous silicon layer containing hydrogen include the decomposition of SiH4 by a glow discharge, the reactive sputtering process, the ion-plating process etc. With any of these methods, a layer having the best photoelectric con-version characteristics is obtained when the substrate temp-erature during the formation of the layer is 150 - 250C.
In the glow discharge process, the hydrogen content of the formed layer is intensely dependent upon the substrate temp-erature during the formation of the layer. It is therefore difficult to determine the photoelectric conversion character-istics and the hydrogen content of the layer independently of each other. A layer of good photoelectric conversion char-acteristics has a resistivity as low as 106 - 107Q.cm and is unsuitable for electrophotography. Therefore, such a con-sideration as doping the layer with a slight amount of boron to raise its resistivity is also necessary. In contrast, the reactive sputtering process and the ion-platlng process can independently determine the substrate temperature during the formation of the layer and the hydrogen content of the layer, so that they are especially effective in cases where the layers of different optical forbidden band gaps need to be stacked in the thickness direction as in the present construction.
Further, the reactive sputtering process can form a uniform layer of large area by employing a sputtering target of sufficiently large area. It is therefore particularly useful for forming a photoconductive layer for electrophotography.
1153;~38 The reactive sputtering process is usually performed by equipment as shown in Figure 4 where numeral 31 designates a bell ~ar, numeral 32 an evacuating system, numeral 33 a radio-frequency power source, numeral 34 a sputtering target, numeral 35 a substrate holder, numeral 36 a substrate, and nuMerals 37 and 38 gas cylinders containing gases to be introduced. Sputtering equipment includes, not only structure that serves to perform a sputter-evaporation on a flat sub-strate as shown in the figure, but also a structure that can perform a sputter-evaporation on a cylindrical or drum-shaped substrate. Suchvariations ~can be adopted in accordance with the intended use.
The reactive sputtering process is carried out by evac-uating the bell jar 31, introducing hydrogen and such an inert gas as argon thereinto, and supplying a radio-frequency voltage from the radio-frequency power source 33 to cause a discharge. The frequency is usually 13.56 MHz. The input power is 0.1 W/cm2 - 100 W/cm2. The amount of hydrogen in a layer formed in this way is determined principally by the pressure of the hydrogen during the discharge. An amorphous silicon layer containing hydrogen suited for use in the pre-sent construction is produced when the hydrogen pressure during sputtering lies in the range of from 1 x 10 5 Torr to 5 x 10 Torr. The deposition rate of the layer is 1 A/sec-30 A~sec. The total gas pressure is generally set within arange of 1 x 10 4 Torr - 0.1 Torr. The substrate temperature during the deposition is selected from within a range of 50C
_ 400C. I
Example 1 .
Figure 5 is a sectional view of an electrophotographic member.
An aluminum cylinder whose surface 41 was mirror-polished was heated at 300C in an oxygen atmosphere for 2 hours to form an A12o3 film 42 on the surface 41. The cylinder was installed in rotary magnetron type sputterng equipment, the interior of which was evacuated up to 1 x 10 6 Torr. Thereafter, while holding the cylinder at 200C, an amorphous silicon film 43 was deposited thereon to a thickness of 30~m at a deposition .:
'' ~
:.
3Z;~8 rate of 2 A/sec using a radio-frequency output of 13.56 MHz and 350 W in a mixed atmosphere consisting of 2 x 10 5 Torr of hydrogen and 3 x 10 3 Torr of argon. The film 43 had an optical forbidden band gap of 1.5 eV and a resistivity of 108Q.cm. It had a hydrogen content of 4 atomic-%. Subse-quently, while the substrate temperature was held at 200C, an amorphous silicon film 44 was found to a thickness of l~m using the radio-frequency output of 13.56 MHz and 350 W
in a mixed atmosphere consisting of 2 x 10 3 Torr of hydrogen and 3 x 10 3 Torr of argon. This film 44 had an optical forbidden band gap of 1.95 eV and a resistivity of lOll~.cm.
Thereafter, the resulting cylinder was taken out of the sputtering equipment and installed in vacuum evaporation equipment. While holding the substrate temperature at 80C
under a pressure of 2 x 10 6 Torr, an As2Se3 film 45 was evaporated to a thickness of 1,000 A.
Since the electrophotographic member thus formed has as a surface layer the amorphous silicon layer 44 whose optical forbidden band gap is at least 1.6 eV and whose resistivity is at least 101Q.cm, it can establish an especially high surface potential. Table 1 lists the changes of surface potential when the amorphous silicon layer 44 has not been fully dis-posed and is having its thickness varied. The listed results were obtained by measuring the surface potential 1 sec. after the electrophotographic member had been charged by a corona discharge at 6.5 kV. A high surface potential signifies that charges are retained well. It will be understood from the results of Table 1 that the present construction provides a remarkable effect.
..
~lS3Z;~
Table 1 Thickness of Surface potential layer 44 (relative value) .
No layer 0.02 5 (nm) 0.1 10 (nm) 0.6 20 (nm) 0.8 1 l~m) 1.0 .. _ .. _._ The decay of the surface potential after 1 sec. was below 10 %, and the dark decay characteristics were satis-factory.
Example 2:
This example will be explained with reference to Figure 6.
On a hard glass cylinder 1, a transparent electrode 11 of SnO2 was formed by the thermodecomposition of SnC14 at 450C. The resulting cylinder was installed in rotary sputt-ering equipment, the interior of which was evacuated to 2 x 10 6 Torr. Subsequently, while holding the cylinder at 250C, an amorphous silicon film 22 (hYdrogen content: 17.5 atomic-%) having an optical forbidden band gap of 1.95 eV and a resist-ivity of 1011Q.cm was deposited to a thickness of 500 A at a deposition rate of 1 A/sec by a radio-frequency power of 300 W (at a frequency of 13.56 MH2) in a mlxed atmosphere consist-ing of 2 x 10 3 Torr of hydrogen and 2 x 10 3 Torr of argon.Thereafter, while holding the pressure of argon constant, the pressure of hydrogen was gradually lowed to 3 x 10 5 Torr over a period of 20 minutes. The amorphous silicon film 23 formed at the minimum hydrogen pressure (hydrogen content:
9 atomic-~) had an optical forbidden band gap of 1.6 eV and a resistivity of 103Q.cm. Further, while holding the argon pressure constant, the hydrogen pressure was gradually raised .
-, - ~
.
. : .' ' - - ' . ' ' ~ . - , '. ' ~ ' ' ' ' ;32~8 again to 2 x 10 3 Torr again over 20 minutes. The sputtering was continued to form an amorphous silicon film 24 until the whole thickness of the amorphous silicon layer became 25 ~m.
The region whose optical forbidden band gap was below 1.95 eV
was approximately 2,400 A thick.
A film of As2Se3 or the like may be inserted on the transparent electrode 11 as a blocking layer. As stated be-fore, a blocking layer may also be disposed on the photo-conductive layer 24.
Figure 7 illustrates the spectral sensitivity of a photo-conductive layer formed in this way. The dotted line 51 in-dicates the spectral sensitivity in a case in which the hydrogen pressure was not lowered, and the solid line 52 in the case where it was. As seen from the result, the sensiti-vity to longer wavelength light is improved by the hydrogen pressure reduction.
Example 3:
In this example, amorphous silicon containing carbon is employed for the surface and the interface of a conductive layer. The fundamental structure is as shown in Figure 6.
On a polyimide film 1 a chrome film 11 was vacuum-evaporated to a thickness of 400 A, to prepare a substrate.
The resuItant was installed in sputtering equipment, the interior of which was evacuated to 5 x 10 7 Torr. Thereafter, while holding the substrate at 150C and employing a target of polycrystalline silicon containing 10% of carbon, a film 22 of amorphous silicon - carbon having an optical forbidden band gap of 2.0 eV and a resistivity of 1013Q.cm was formed to a thickness of 5 ~m at a deposition rate of 3 A/sec under radio-frequency power of 350 W in a gaseous mlxture consisting of 1 x 10 3 Torr of hydrogen and 4 x 10 3 Torr of argon. The hydrogen content of this film was approximately 14 atomic-~.
Thereafter, sputtering was performed using a target made of silicon only in a gaseous mixture consisting of 2 x 10 3 Torr of argon and 3 x 10 3 Torr of hydrogen, to form a film 23 of amorphous silicon having a thickness of 60 nm and exhibiting an optical forbidden band gap of 1.95 eV as well as a resist-ivity of 1012Q.cm. Further, on the film 23, a film 24 of the ~lS32;~
first amorphous silicon - carbon was formed to 5 ~m.
An electrophotographic member having a satisfactory resolution and good dark-decay characteristics was realized.
Example 4:
Reference is again had to Figure 6.
On a hard glass cylinder 1, an SnO2 transparent electrode 11 was formed by the thermodecomposition of SnC14 at 450C.
The resultant cylinder was installed in rotary sputtering equipment, the interior of which was evacuated to approximately 2 x 10 6 Torr. Subsequently, while holding the cylinder at 250C, an amorphous silicon film 22 thydrogen content: 17.5 atomic-~) was deposited to 500 A by radio-frequency power of 13.56 MHz and 300 W in a mixed atmosphere consisting of 2 x 10 3 Torr of hydrogen and 2 x 10 3 Torr of argon. The optical forbidden band gap of this film was 1.95 eV, and the resist-ivity was 1011Q.cm. Thereafter, using a sputtering target in which silicon and germanium were juxtaposed, a germanium-containing amorphous silicon film 23 was deposited to a thick-ness of 0.1 ~m. The sputtering was a gaseous mixture con-sisting of 1 x 10 3 Torr of hydrogen and 2 x 10 3 Torr ofargon. The content of germanium was 30 atomic-%, and that of hydrogen was 10 atomic-%. In addition, the optical forbidden band gap was approximately 1.40 eV, and the resistivity was approximately 109Q.cm. Subsequently, an amorphous silicon film 24 was formed under the same conditions as those of the first amorphous silicon film. The thickness of the whole layer was made 25 ~m. The optical forbidden band gap of the film 24 was 1.95 eV, and the resistivity was 1011n.cm. When the germanium-containing amorphous silicon was used in this manner, an electrophotographic member having a satisfactory resolution and good dark-decay characteristics was realized.
- , . . : .
- ' .~ , :
:
Claims (10)
1. In an electrophotographic member comprising at least a predetermined supporter having a conductive surface and an amorphous silicon layer which is electri-cally in contact with said conductive surface and which contains hydrogen and silicon as indispensable constituent elements thereof, the improvement comprising an amorphous silicon layer in which the silicon amounts to at least 50 atomic % and the hydrogen amounts to at least 1 atomic %
and, at most, 50 atomic %; said amorphous layer comprising a first region and a second region, said first region being at least 10nm thick, extending inwardly from an outer surface of said amorphous silicon layer and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 1010 .OMEGA.cm, and said second region being located at least 10nm from said surface of said amorphous layer, having a thickness of at least 10nm, and being made of amorphous silicon which has an optical forbidden band gap that is smaller than that of said first region at the surface of the amorphous silicon and that is at least 1.1 eV.
and, at most, 50 atomic %; said amorphous layer comprising a first region and a second region, said first region being at least 10nm thick, extending inwardly from an outer surface of said amorphous silicon layer and being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV and a resistivity of at least 1010 .OMEGA.cm, and said second region being located at least 10nm from said surface of said amorphous layer, having a thickness of at least 10nm, and being made of amorphous silicon which has an optical forbidden band gap that is smaller than that of said first region at the surface of the amorphous silicon and that is at least 1.1 eV.
2. An electrophotographic member according to claim 1, wherein said amorphous silicon layer is formed by a reactive sputtering process in an atmosphere containing hydrogen.
3. An electrophotographic member according to claim 1, wherein said amorphous silicon layer has a third region on a side opposite to said surface side formed by said first region, said third region being made of amorphous silicon which has an optical forbidden band gap of at least 1.6 eV
and a resistivity of at least 1010.OMEGA..cm.
and a resistivity of at least 1010.OMEGA..cm.
4. An electrophotographic member according to claim 1, wherein said amorphous silicon layer further contains at least one element selected from the group consisting of germanium and carbon which is substituted for silicon in an amount up to 30 atomic %.
5. An electrophotographic member according to claim 1, wherein said member further comprises a conducter in contact with said amorphous silicon layer.
6. An electrophotographic member according to claim 1, wherein said supporter includes a substrate which is a conductive material and which is in contact with said amorphous silicon layer.
7. An electrophotographic member according to claim 1, wherein said supporter comprises an insulating substrate and a conductive electrode formed on said substrate and in contact with said amorphous silicon layer.
8. An electrophotographic member according to claim 1, further comprising a layer on the side of the supporter in electrical contact with the amorphous silicon for suppressing the injection of excess carriers from the supporter side.
9. An electrophotographic member according to claim 1, further comprising a layer for suppressing the injection of charges from the surface side of said amorphous silicon layer.
10. An electrophotographic member according to claim 8 or claim 9, wherein said suppressing layer comprises a material which is SiO, SiO2, A12O3, CeO2, V2O3, Ta2O, As2Se3, As2S3, or polyvinyl carbazole.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4923680A JPS56146142A (en) | 1980-04-16 | 1980-04-16 | Electrophotographic sensitive film |
| JP49236/1980 | 1980-04-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1153238A true CA1153238A (en) | 1983-09-06 |
Family
ID=12825247
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000375665A Expired CA1153238A (en) | 1980-04-16 | 1981-04-16 | Electrophotographic member with an amorphous silicon layer containing hidrogen |
Country Status (5)
| Country | Link |
|---|---|
| US (2) | US4378417A (en) |
| EP (1) | EP0038221B1 (en) |
| JP (1) | JPS56146142A (en) |
| CA (1) | CA1153238A (en) |
| DE (1) | DE3172873D1 (en) |
Families Citing this family (66)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4484809B1 (en) * | 1977-12-05 | 1995-04-18 | Plasma Physics Corp | Glow discharge method and apparatus and photoreceptor devices made therewith |
| JPS56150752A (en) * | 1980-04-25 | 1981-11-21 | Hitachi Ltd | Electrophotographic sensitive film |
| JPS5717952A (en) * | 1980-07-09 | 1982-01-29 | Oki Electric Ind Co Ltd | Electrophotographic receptor |
| JPS5723544U (en) * | 1980-07-09 | 1982-02-06 | ||
| JPS5727263A (en) * | 1980-07-28 | 1982-02-13 | Hitachi Ltd | Electrophotographic photosensitive film |
| JPS5744154A (en) * | 1980-08-29 | 1982-03-12 | Canon Inc | Electrophotographic image formation member |
| JPH0629977B2 (en) * | 1981-06-08 | 1994-04-20 | 株式会社半導体エネルギー研究所 | Electrophotographic photoconductor |
| US4569719A (en) * | 1981-07-17 | 1986-02-11 | Plasma Physics Corporation | Glow discharge method and apparatus and photoreceptor devices made therewith |
| JPS5821257A (en) * | 1981-07-30 | 1983-02-08 | Seiko Epson Corp | Electrophotographic receptor |
| JPS5888753A (en) * | 1981-11-24 | 1983-05-26 | Oki Electric Ind Co Ltd | Electrophotographic photoreceptor |
| US4483911A (en) * | 1981-12-28 | 1984-11-20 | Canon Kabushiki Kaisha | Photoconductive member with amorphous silicon-carbon surface layer |
| US4522905A (en) * | 1982-02-04 | 1985-06-11 | Canon Kk | Amorphous silicon photoconductive member with interface and rectifying layers |
| US4452874A (en) * | 1982-02-08 | 1984-06-05 | Canon Kabushiki Kaisha | Photoconductive member with multiple amorphous Si layers |
| US4452875A (en) * | 1982-02-15 | 1984-06-05 | Canon Kabushiki Kaisha | Amorphous photoconductive member with α-Si interlayers |
| US4490450A (en) * | 1982-03-31 | 1984-12-25 | Canon Kabushiki Kaisha | Photoconductive member |
| US4517269A (en) * | 1982-04-27 | 1985-05-14 | Canon Kabushiki Kaisha | Photoconductive member |
| JPS5934675A (en) * | 1982-08-23 | 1984-02-25 | Hitachi Ltd | Photo detector |
| NL8204056A (en) * | 1982-10-21 | 1984-05-16 | Oce Nederland Bv | PHOTOGRAPHIC ELEMENT FOR APPLICATION IN ELECTROPHOTOGRAPHIC COPYING PROCESSES. |
| JPS59149371A (en) * | 1983-02-16 | 1984-08-27 | Hitachi Ltd | Photodetecting surface |
| JPS59231879A (en) * | 1983-06-13 | 1984-12-26 | Matsushita Electric Ind Co Ltd | Photoconductor and manufacture thereof |
| JPS6011849A (en) * | 1983-06-21 | 1985-01-22 | Sanyo Electric Co Ltd | Electrostatic latent image bearing material |
| DE3429899A1 (en) * | 1983-08-16 | 1985-03-07 | Canon K.K., Tokio/Tokyo | METHOD FOR FORMING A DEPOSITION FILM |
| US4513073A (en) * | 1983-08-18 | 1985-04-23 | Minnesota Mining And Manufacturing Company | Layered photoconductive element |
| JPS6045258A (en) * | 1983-08-23 | 1985-03-11 | Sharp Corp | Electrophotographic sensitive body |
| JPS6083957A (en) * | 1983-10-13 | 1985-05-13 | Sharp Corp | Electrophotographic sensitive body |
| US4544617A (en) * | 1983-11-02 | 1985-10-01 | Xerox Corporation | Electrophotographic devices containing overcoated amorphous silicon compositions |
| JPH067270B2 (en) * | 1983-12-16 | 1994-01-26 | 株式会社日立製作所 | Electrophotographic photoconductor |
| DE3447671A1 (en) * | 1983-12-29 | 1985-07-11 | Canon K.K., Tokio/Tokyo | PHOTO-CONDUCTIVE RECORDING MATERIAL |
| JPS60174864A (en) * | 1984-02-15 | 1985-09-09 | Showa Alum Corp | Surface treatment of aluminum substrate for forming thin film |
| DE3506657A1 (en) * | 1984-02-28 | 1985-09-05 | Sharp K.K., Osaka | PHOTO-CONDUCTIVE DEVICE |
| JPH0656498B2 (en) * | 1984-09-26 | 1994-07-27 | コニカ株式会社 | Photoreceptor and image forming method |
| US4664999A (en) * | 1984-10-16 | 1987-05-12 | Oki Electric Industry Co., Ltd. | Method of making electrophotographic member with a-Si photoconductive layer |
| US4613556A (en) * | 1984-10-18 | 1986-09-23 | Xerox Corporation | Heterogeneous electrophotographic imaging members of amorphous silicon and silicon oxide |
| DE3616608A1 (en) * | 1985-05-17 | 1986-11-20 | Ricoh Co., Ltd., Tokio/Tokyo | Light-sensitive (photosensitive) material for electrophotography |
| US4701395A (en) * | 1985-05-20 | 1987-10-20 | Exxon Research And Engineering Company | Amorphous photoreceptor with high sensitivity to long wavelengths |
| US5753542A (en) | 1985-08-02 | 1998-05-19 | Semiconductor Energy Laboratory Co., Ltd. | Method for crystallizing semiconductor material without exposing it to air |
| US5962869A (en) * | 1988-09-28 | 1999-10-05 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor material and method for forming the same and thin film transistor |
| US4721663A (en) * | 1985-08-26 | 1988-01-26 | Energy Conversion Devices, Inc. | Enhancement layer for negatively charged electrophotographic devices |
| US4713309A (en) * | 1985-08-26 | 1987-12-15 | Energy Conversion Devices, Inc. | Enhancement layer for positively charged electrophotographic devices and method for decreasing charge fatigue through the use of said layer |
| JPS62148966A (en) * | 1986-12-02 | 1987-07-02 | Oki Electric Ind Co Ltd | Electrophotographic sensitive body |
| DE3717727A1 (en) * | 1987-05-26 | 1988-12-08 | Licentia Gmbh | ELECTROPHOTOGRAPHIC RECORDING MATERIAL AND METHOD FOR THE PRODUCTION THEREOF |
| JP2629223B2 (en) * | 1988-01-07 | 1997-07-09 | 富士ゼロックス株式会社 | Manufacturing method of electrophotographic photoreceptor |
| US4885220A (en) * | 1988-05-25 | 1989-12-05 | Xerox Corporation | Amorphous silicon carbide electroreceptors |
| US4992348A (en) * | 1988-06-28 | 1991-02-12 | Sharp Kabushiki Kaisha | Electrophotographic photosensitive member comprising amorphous silicon |
| US5239397A (en) * | 1989-10-12 | 1993-08-24 | Sharp Kabushiki | Liquid crystal light valve with amorphous silicon photoconductor of amorphous silicon and hydrogen or a halogen |
| US5210050A (en) * | 1990-10-15 | 1993-05-11 | Semiconductor Energy Laboratory Co., Ltd. | Method for manufacturing a semiconductor device comprising a semiconductor film |
| US5849601A (en) | 1990-12-25 | 1998-12-15 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device and method for manufacturing the same |
| US7115902B1 (en) | 1990-11-20 | 2006-10-03 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device and method for manufacturing the same |
| KR950013784B1 (en) | 1990-11-20 | 1995-11-16 | 가부시키가이샤 한도오따이 에네루기 겐큐쇼 | Field effect trasistor and its making method and tft |
| US7154147B1 (en) | 1990-11-26 | 2006-12-26 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device and driving method for the same |
| KR950001360B1 (en) * | 1990-11-26 | 1995-02-17 | 가부시키가이샤 한도오따이 에네루기 겐큐쇼 | Electric optical device and driving method thereof |
| US8106867B2 (en) | 1990-11-26 | 2012-01-31 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device and driving method for the same |
| US7576360B2 (en) * | 1990-12-25 | 2009-08-18 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device which comprises thin film transistors and method for manufacturing the same |
| US7098479B1 (en) | 1990-12-25 | 2006-08-29 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device and method for manufacturing the same |
| EP0499979A3 (en) | 1991-02-16 | 1993-06-09 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device |
| JP2794499B2 (en) | 1991-03-26 | 1998-09-03 | 株式会社半導体エネルギー研究所 | Method for manufacturing semiconductor device |
| JP2845303B2 (en) * | 1991-08-23 | 1999-01-13 | 株式会社 半導体エネルギー研究所 | Semiconductor device and manufacturing method thereof |
| US6693681B1 (en) | 1992-04-28 | 2004-02-17 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device and method of driving the same |
| JP2814161B2 (en) | 1992-04-28 | 1998-10-22 | 株式会社半導体エネルギー研究所 | Active matrix display device and driving method thereof |
| JPH07120953A (en) * | 1993-10-25 | 1995-05-12 | Fuji Xerox Co Ltd | Electrophotographic photoreceptor and image forming method using the same |
| US7081938B1 (en) * | 1993-12-03 | 2006-07-25 | Semiconductor Energy Laboratory Co., Ltd. | Electro-optical device and method for manufacturing the same |
| JP2900229B2 (en) | 1994-12-27 | 1999-06-02 | 株式会社半導体エネルギー研究所 | Semiconductor device, manufacturing method thereof, and electro-optical device |
| US5834327A (en) | 1995-03-18 | 1998-11-10 | Semiconductor Energy Laboratory Co., Ltd. | Method for producing display device |
| US20040135209A1 (en) * | 2002-02-05 | 2004-07-15 | Tzu-Chiang Hsieh | Camera with MOS or CMOS sensor array |
| US20130341623A1 (en) * | 2012-06-20 | 2013-12-26 | International Business Machines Corporation | Photoreceptor with improved blocking layer |
| WO2021133622A1 (en) | 2019-12-23 | 2021-07-01 | Dow Silicones Corporation | Sealant composition |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2746967C2 (en) * | 1977-10-19 | 1981-09-24 | Siemens AG, 1000 Berlin und 8000 München | Electrophotographic recording drum |
| AU530905B2 (en) * | 1977-12-22 | 1983-08-04 | Canon Kabushiki Kaisha | Electrophotographic photosensitive member |
| DE2954552C2 (en) * | 1978-03-03 | 1989-02-09 | Canon K.K., Tokio/Tokyo, Jp | |
| US4217374A (en) * | 1978-03-08 | 1980-08-12 | Energy Conversion Devices, Inc. | Amorphous semiconductors equivalent to crystalline semiconductors |
| JPS554040A (en) * | 1978-06-26 | 1980-01-12 | Hitachi Ltd | Photoconductive material |
| JPS55127561A (en) * | 1979-03-26 | 1980-10-02 | Canon Inc | Image forming member for electrophotography |
| JPS58189643A (en) * | 1982-03-31 | 1983-11-05 | Minolta Camera Co Ltd | Photoreceptor |
-
1980
- 1980-04-16 JP JP4923680A patent/JPS56146142A/en active Granted
-
1981
- 1981-04-15 US US06/254,294 patent/US4378417A/en not_active Ceased
- 1981-04-15 EP EP81301671A patent/EP0038221B1/en not_active Expired
- 1981-04-15 DE DE8181301671T patent/DE3172873D1/en not_active Expired
- 1981-04-16 CA CA000375665A patent/CA1153238A/en not_active Expired
-
1986
- 1986-09-11 US US07/162,312 patent/USRE33094E/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0038221A3 (en) | 1982-02-03 |
| US4378417A (en) | 1983-03-29 |
| JPH0115866B2 (en) | 1989-03-20 |
| EP0038221B1 (en) | 1985-11-13 |
| EP0038221A2 (en) | 1981-10-21 |
| USRE33094E (en) | 1989-10-17 |
| DE3172873D1 (en) | 1985-12-19 |
| JPS56146142A (en) | 1981-11-13 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |