JPS6130269B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is an additional invention of Patent No. 1287245 (Japanese Patent Publication No. 60-9260), and can not only be used for the same purpose as conventional xerographic members and electrofax members. The present invention relates to an electrophotographic film member that can be used in the same way as a silver halide emulsion photographic film.

The original photographic film consists of a thin stable substrate, preferably a flexible plastic sheet, bonded to a thin layer of an ohmic resistive material such as indium oxide, and cadmium sulfide deposited by radio frequency sputtering. and a thin film coating of a photoconductive, electrically anisotropic inorganic material such as. The thickness of its photoconductive coating is about 3000
Angstrom, ohm resistance layer thickness is approximately 500
angstrom, the substrate thickness is a fraction of a millimeter. This electrophotographic film has a hard, abrasion-resistant surface, is highly transparent, and is flexible even though its conductive coating is microcrystalline. Furthermore, this electrophotographic film has high photoelectric gain and sensitivity, so it can be used in high-speed photography. The electrophotographic film itself can be rapidly charged, and its charge can be selectively maintained after exposure to allow toning in a nearly infinite number of tones.

Nevertheless, it is desirable to further improve such an electrophotographic film, and the present invention provides a further improvement to such an electrophotographic film.

The invention comprises a substrate and a pure inorganic photoconductive material radio frequency sputtered onto the substrate;
extremely dense, microcrystalline, substantially transparent, having a dark resistivity of at least 10 ¹² Ω-cm and a dark-to-light resistivity ratio of at least 10 ⁴ , capable of accepting high velocity loads, and an electrically anisotropic thin film coating having the property of retaining the charge and performing toning, and an ohm interposed between the coating and the substrate to promote charging of the coating before exposure. an electrophotographic film member of the type comprising a thin film layer of a resistive material, characterized in that an adhesion enhancing member consisting of a transparent, extremely thin layer of a pure inorganic material is provided between the ohmic resistive layer and the substrate. do.

BRIEF DESCRIPTION OF THE DRAWINGS Before describing the present invention in detail with reference to the drawings, some expressions used to define phenomena observed in this specification and in the art will be explained.

In this specification, the expression "thin film" is used.
Generally, in the scientific literature, a thin film is defined by examining the properties of a thin film material and noting that these properties differ from those of the bulk of the same material. Here, the latter characteristic will be referred to as "bulk characteristic." Simply put, certain materials behave differently when forming a ``film'' than when forming a ``body.'' For a review of the differences between thin film and bulk properties of similar materials, reference may be made, for example, to "Thin Films" by Lieber and Chapman, Wickham Publishing Co., London, 1971. In this document, the thickness of the "thin film" is "usually 1 micron or less". This general definition is due to the broad subject matter of this document.

When considering the objectives and requirements of a structure in which a certain type of material is to be used, the boundaries between thin film and bulk properties must take these objectives and requirements into account. Characteristics that are not important to solving the problem do not need to be considered important and therefore do not set physical criteria. For example, if a certain material is used in a container that utilizes its sound-reflecting properties and its thickness is reduced to 2 microns or less, a sudden change in the sound-reflecting properties of this material occurs due to the film effect. exhibits a thin film effect. On the other hand, if the same material is used in applications where its resistivity is important, its thickness may be reduced to 0.5
The material is still a bulk material at thicknesses greater than about 0.5 microns if its resistivity changes rapidly when reduced to microns or less.

The materials used in the present invention are associated with a number of properties that are advantageous to the present invention, and the meaning of "thin film" as used in the present invention relates only to these properties and other purposes of thickness that may be called a thin film. is independent of the properties of the material. As used herein, the expression "thin film" refers to the thickness at which the desired properties of the material cease to act as bulk properties and begin to act as a coating or thin film. Its thickness in all known embodiments is approximately 1 micron (10,000 angstroms)
Below, very few of the test coatings or layers were larger than 5000 angstroms. Therefore, a "thin film" can be considered to be one with a thickness of approximately 1 micron or less.

As used herein, "photoelectric gain" has a meaning that requires explanation. The speed and efficiency of electrophotographic film members is directly related to the "hole-electron pairs" generated when exposed to light. Conventional coatings used in xerography or electrofaxing require a large number of photons (very bright light) to generate one hole-electron pair. The number of photons is usually about 1000. If an electrophotographic film can generate one hole-electron pair upon the incidence of one photon or two photons, its "photoelectric gain" will be extremely large. Therefore, "high photoelectric gain" expressing the gain of this type of electrophotographic film member shall mean a state in which at most several photons are required to generate one hole-electron pair. . "High photovoltaic gain" also applies to the ability of electrophotographic film members to allow hole-electron pairs to recombine and produce an electrical discharge over time.

As used herein, "electrophotographic film" or "photographic film" shall mean an entire article having several layers or thin films used in some photographic processing. Although the substrate or substrate member used in the present invention can be regarded as a film in the usual sense, the term "film" will not be used for the substrate or substrate member in this specification. It will be appreciated that the substrate is preferably a thin, flexible, transparent member of plastic sheeting, commonly known as plastic film.

The improved electrophotographic film of the present invention comprises applying a thin film coating of a pure inorganic, crystalline, radio frequency sputtered photoconductive material to a substrate with an extremely thin layer of radio frequency sputtered photoconductive material of the same type as said coating. Coating onto a thin film layer of ohmic or conductive material adhered to the coating. The substrate is preferably a highly stable, thin, flexible insulating plastic sheet such as polyethylene terephthalate (sold under the trade name "Mylar").

Photoconductive coating or layer 12 is an important component of the present invention and the elements that make up the electrophotographic film of the original invention. This is because the photoconductive layer exhibits functional and physical properties that make the present invention and original invention advantageous over the prior art.

The material forming this photoconductive coating or layer is described in detail below and is one of several known photoconductive compounds.
Although these compounds have been used in the past, to the present knowledge there are no examples of their being successfully combined in electrophotographic members of the type to which the present invention relates to obtain the advanced properties of the present invention. . for example,
A preferred compound discussed in detail below is cadmium sulfide. This compound can be pulverized and embedded in an organic matrix and introduced into a thick photoconductive coating;
Although sputtering has been attempted to form completely inorganic coatings, conventional methods have not been able to achieve the advantageous results of the present invention and the original invention.

In the present invention, the best results were obtained when cadmium sulfide (CdS) was used as in the electrophotographic film member of the original invention. Other compounds include indium zinc sulfide (ZnIn ₂ S ₄ ), arsenic trisulfide (As ₂ S ₃ ), zinc selenide (ZnSe), zinc sulfide (ZnS), zinc telluride (ZnTe), cadmium selenide ( Preferred examples include cadmium telluride (CdSe), gallium arsenide (GaAs), and antimony trisulfide (Sb ₂ S ₃ ).

The characteristics of the electrophotographic film members of the present invention and the original invention are as follows. The photoconductive coating is a pure inorganic microcrystalline, several thousand angstroms thick. Previously effective cadmium sulfide coatings are mixtures with organic binders and matrix materials, and therefore are significantly thicker than those of the present invention.
Very low flexibility and transparency. The photoconductive coating of the present invention is intentionally crystalline and thin, i.e.
Since it is formed as thin as 3500 Å to 5000 Å, it is extremely flexible and transparent. By making the coating thin and crystalline in this manner, conduction of electrons and holes through the coating is facilitated. The crystals are expected to be oriented vertically, i.e. at right angles to the surface on which the layer is deposited;
This crystalline structure can be obtained by a sputtering process using radio frequency sputtering techniques to generate a second dark zone between the plasma and the anode in addition to the conventional cathode dark zone.

The "edge effect" characteristic of conventional xerography is
For example, it has been confirmed that most of the particles are removed when the surface of the photoconductive layer 12 of the present invention is toned. This "edge effect" occurs when a reconstructed image with uniformly colored areas is brighter in the center and darker at the edges. The larger the uniformly colored area, the more
The "edge effect" becomes noticeable, so the center of a large area that needs to be black will not be reflected. Photographs cannot be reproduced at even a fraction of their original quality without the use of a screen that moves relative to the original. Negative originals, ie documents written with thin white lines on a black background, cannot be reproduced using current xerography or electrofaxing methods because of this "edge effect."

The electrophotographic film of the original invention and the present invention can faithfully reproduce documents and photographs without the use of intermediate screens or toner bias. That is,
Negative areas are clearly transmitted to this film without any "edge effects". In practice, toner bias can remove traces of "edge effects" and achieve very high quality photographic reproduction. The reproduction quality obtained with photoconductive coating 12 is higher than that obtained with today's most common photographs. This is because although the latter film has fine particles, the factors that limit the texture of the reproduced image on the coating 12 are the size of the toner particles and the size of the crystals forming the coating. Both of these typically have small dimensions of a fraction of a micron.

This advantage is believed to be achieved because each crystal is oriented perpendicular to the substrate surface and creates an individual electric field in its vicinity when stimulated with electrons. Therefore, the toner particles are attracted by these countless electric fields and are not attracted to the part where the gradient between the charged part and the non-charged part is the greatest. The attraction of toner particles to this slope is the reason for the commonly experienced "edge effect."

An example of the flexibility achieved when the photoconductive and ohmic resistive layers are deposited on a 0.127 mm (0.005 inch) thick flexible polyester sheet, the resulting xerographic film is 6.35 mm (0.25 inch) in diameter. Because the photoconductive layer is crystalline, it can still be rolled onto inch cylinders without cracking or cracking. The ability to wrap it onto a cylinder having a diameter of a fraction of an inch means that the electrophotographic film can be transferred to processing and display equipment without any problems.

Other properties associated with the fact that photoconductive layer 12 is made of an inorganic material and is thin and crystalline are that it is extremely dense and hard. As mentioned above, the surface of the photoconductive layer is hard like glass. Abrasion resistance is important when handling films. The reason for this is that by increasing the wear resistance, it is possible to prevent scratches, cuts, etc. that cause loss of details and data, especially when the subject matter is minute. In this way, when manufacturing an electrophotographic film, no problem arises even if it is necessary to move the film in a frictionally engaged state by engaging the surface of the film with a friction roller or the like.

It is believed that the abrasion resistance of photoconductive coating 12 is related to the density of the compound resulting from the method in which it is deposited. This also allows the electrical properties to be significantly improved over known coatings.

Photoconductive materials are electrically anisotropic, especially because of their thinness, semiconducting properties, and other reasons. This means that the material has a non-uniform charge pattern of electrons and holes supplied to or generated within the material, as required for use as electrophotographic films and photoconductors as mentioned above. This means that it can be maintained for at least a considerable period of time. Furthermore, it means that a fine resolution pattern can be accurately and faithfully formed in a latent image.

Coating 12 has the high photoconductive gain properties defined above. This coating therefore requires a large number of photons to generate one hole-electron pair, whereas in conventional photoconductors,
Only one or two photons are required to drive the charge carriers to the trap or recombination center, creating a coating of significantly higher xerographic efficiency. This mechanism is referred to herein as "gain." The "gain" of the doped film of the present invention is many times greater than the "gain" of the undoped film.

It is important to have high gain characteristics. This is because the high gain characteristics increase the sensitivity of this type of electrophotographic film to the point where it balances that of high speed photographic films, without the loss of detail due to coarse grains. There are no particles in the material of the present invention, and its crystal structure is extremely fine.

The increase in gain of the photoconductive materials of the present invention is believed to be the result of freeing free electrons from the bandgap energy level of the photoconductor and is exponentially related to the thinness of the photoconductor. In other words, the thinner the layer, the more electrons will be emitted and the more sensitive the electrophotographic film will be.

Since absorption of photons of light is necessary to discharge the photoconductive coating, it is clear that the photoconductive coating must absorb some visible light or electromagnetic radiation. On the other hand, the thinner the coating, the higher the gain.

The thickness of the photoconductive coating 12 should be such that there is enough material to provide the desired light absorption and anti-abrasion properties and thin enough to provide the desired gain. it is obvious.
Layers can be deposited to a thickness that achieves the maximum gain at the minimum practical thickness. Such a thickness can be determined by measuring the optical absorption with appropriate equipment, as well as measuring the abrasion resistance and strength, for any desired material, to find a practical balance between the above properties and the desired photoconductive gain. This can be easily determined experimentally by continuing to deposit material until a compromise point is found.

Light absorption requirements must be met in all cases.

Photoconductive coatings have high dark resistivity which facilitates charge acceptance and retention. Cadmium sulfide coatings suitable as photoconductive coatings are of n-conducting type in nature and in their pure state, as when deposited in accordance with the present invention.
It has a dark resistivity of 10 ¹² to ^{10 14} Ω-cm. Its optical resistivity is approximately 10 ⁸ Ω-cm, and its energy gap is approximately 2.45 eV. Measurements of these resistivities are static and can be made by the known method of gluing electrodes to the surface of the photoconductive coating, applying a direct voltage, and measuring and calculating the current. Measurements of dark resistivity are performed in the dark. However, this measurement is performed with no charge on the photoconductive layer. The photoconductive layer of the present invention is so thin that when a charge is applied to its surface, this electrode penetrates the surface and drives the free charge towards the ohmic resistance layer. The effect appears to be considerable throughout the photoconductive layer. In the absence of such charge, discharge is inhibited during the post-charging period and the dark resistivity increases. Dynamic measurements of dark resistivity define the dark decay characteristics of capacitors as
This can be done by assuming that it is an RC discharge and comparing its characteristics with those calculated and graphed for various specific resistances. Using such a technique, the dark resistivity of the charged cadmium sulfide layer of the present invention can be increased by at least several times at the starting point of the characteristic.
After that, it was confirmed that it increased by about 1000 times. It is clear that the dynamic ratio of dark to light resistivity also increases.

In the following it is assumed that the resistivity is static. As mentioned above, the dark resistivity is 10 ¹² to 10 ¹⁴ Ω
−cm or more. As far as is currently known, the resistivities of electrophotographic members of the present invention and different types of conventional relatively thick electrophotographic members are approximately the same statically and dynamically.

A high resistivity coating 12 represents a good insulating material, and a high dark-to-light resistivity ratio on the order of 10 ⁵ represents an abrupt change in resistance. An example of this coating would be approximately 3500 Å thick and have a light transmission of 70-85%. The increase in conductivity upon irradiation is related to the sensitivity of the coating.

Another effective photoconductive compound, indium zinc sulfide, has a dark resistivity similar to that of cadmium sulfide, but a somewhat higher light resistivity, so the dark-to-light resistivity ratio is higher than that of cadmium sulfide. It's not that big. The energy gap of indium zinc sulfide is approximately 2.3 eV. Indium zinc sulfide does not perform as well as cadmium sulfide as a photoconductive coating, at least when electrophotographic films using it as the photoconductive layer have been tested.

Although not necessary, the cadmium sulfide can be doped with known impurities such as small amounts of copper, iodine, etc. to provide additional carriers for electrons. This addition of impurities makes the coating more n-conducting than pure cadmium sulfide and allows for even greater gain.

The proportions of each element forming the photoconductive layer must be stoichiometrically accurate, and this can be achieved by controlling the deposition conditions. When using an added impurity, it is necessary to control the proportion of this impurity, but since the entire layer is an inorganic substance, this can be controlled relatively easily by conventional control methods.

Photoconductive coatings of the type described above, consisting of cadmium sulphide, are panchromatic in nature.

The photoconductive coatings of the present invention and of the original invention can be easily seeded by special methods, thereby obtaining their unique properties. This method allows uniform deposition to be produced at high speed in a controlled manner.

The photoconductive coating 12 is deposited in each case by radio frequency RF sputtering in a vacuum chamber. All materials making up the coating are introduced into the vacuum chamber, with or without added impurities. These materials are introduced as consumable targets or as gases or sublimated compounds into the vessel atmosphere after the start of the process.
The stoichiometrically precise proportions are easily controlled by known techniques to obtain a nearly complete and uniform product.

Sputtering of the photoconductive coating 12 is a critical part of the present invention and, to the best of our knowledge, the formation of a second dark region can significantly improve properties over the prior art. This can be done by connecting the radio frequency circuit of the sputtering device to a bias circuit. In some cases, the second
The dark side can be self-induced.

The characteristics mentioned above are not exclusive, but are considered to be essential. As a result of the properties mentioned above and below, many other advantages are obtained at the same time.

Ohmic resistive layer 14 is a conductive layer deposited on substrate member 16 prior to deposition of photoconductive layer 12. The first purpose of providing the conductive layer is to promote charging of the surface of the photoconductive layer. Furthermore, this conductive layer also serves to assist in adhering the photoconductive layer to the substrate member. If a P-type coating or layer 12 is used, the ohmic resistive layer 14 facilitates discharge. When coating 12 is used in the manufacture of electrophotographic film, layer 14 is transparent.

This ohmic resistance layer 14 is much thinner than the photoconductive layer 12, preferably about 500 Å. This thickness does not interfere with the clarity and flexibility of the final electrophotographic film product. Ohmic resistance layer 14 includes photoconductive layer 12 and substrate member 16.
and acts as one element of a capacitive circuit during charging of the surface of the photoconductor.

A suitable material for the ohmic resistance layer 14 is high purity semiconductor indium oxide or a material to which a small amount (approximately 10%) of tin oxide is added. This semiconductor material can be easily adhered to aluminum edges or conductor strips. This semiconductor material can also be easily and conveniently deposited by sputtering techniques in the same equipment used to deposit the photoconductive layer. This method is used in embodiments of the invention. Vacuum or vapor deposition may be used, but it is often not possible to obtain a dense, smooth layer that is well adhered to the substrate.

The substrate member 16 includes a photoconductive layer 12 and an ohmic resistance layer 1.
4 and the support for the adhesion-enhancing layer 18, ie, the mechanical support. The mechanical properties necessary for the substrate include flexibility, strength, transparency, adhesion to the deposited layer and, crucially, stability. Stability here also means dimensional stability, stability in thickness retention, and stability against any changes that may occur under the influence of electrical phenomena and temperature changes that occur in the pressure chamber during the deposition process. do. Abrasion resistance is also a desirable property to consider in selecting a substrate material.

As mentioned above, an example of a satisfactory substrate is the thickness.
There is 0.127 mm (0.005 inch) of polyethylene terephthalate. This material is an organic polymer. For example, such a material manufactured by EI DuPont, sold under the trade name "Mylar", has excellent properties. This material must have its internal stresses removed before use, and this removal process is referred to as normalization. This treatment can be carried out by exposing the film to a temperature of about 190°C for about 30 minutes. Such processing is known.

The substrate material must be free of occluded gas, which can be removed by degassing in a suitable chamber. Similarly, the seats must be thoroughly cleaned.

The above is the electrophotographic film 10 to which the present invention relates.
Details about the main components of.

The main improvements of the invention are, in particular, that the ohmic resistance layer 1
An object of the present invention is to provide an electrophotographic film having an extremely thin, i.e., 50 to 300 angstrom, adhesive layer 18 deposited directly on the substrate between the substrate 16 and the substrate 16. This improves the upper ohmic resistance and the adhesive affinity of the substrate to the photoconductive coatings 14 and 12. The so-called adhesion layer 18 is formed of cadmium sulfide which is radio frequency sputtered directly onto the substrate under the conditions used for depositing the photoconductive layer 12. The thickness of this adhesive layer is of an order of magnitude that cannot be easily measured even by interferometric techniques and is approximated by comparison with the measurable thickness of the photoconductive coating. Preferably, an ohmic resistive layer 14 on the order of 300 Angstroms is radio frequency sputtered onto the adhesive layer 18, and a photoconductive layer 12 of cadmium sulfide is radio frequency sputtered onto the ohmic resistive layer 14. The cadmium sulfide adhesive layer 18 effectively becomes part of the substrate, but because of its thinness it does not appreciably affect the overall transparency of the film member.

As shown, in use, the photoconductive layer does not extend over the entire ohmic resistor, but a portion may be exposed to provide a contact 19 to this portion of the ohmic resistive layer. In the figure, 20 indicates a high-voltage power supply, 21 indicates a corona generator, and the circuit symbolically indicates a charging circuit that supplies a surface charge to the photoconductive thin film layer.

The cathode or target of the sputtering device is
The layer is formed by the material to be formed or the several elements to be used. Other elements can be added by introducing them into the sputtering chamber. In one example conducted for testing purposes, the cathode was a semiconductor indium oxide. This material is the material for depositing the ohmic resistance layer 14. The spacing between the cathode and anode is determined according to the physical characteristics of the particular sputtering chamber and takes into account the geometry and the voltage to be used. In this example, the sputtering chamber is approximately 10 ^-7
It was evacuated to a pressure range of Torr. This state is almost a vacuum. Extremely pure argon, i.e. H ₂ O and
Argon with a N ₂ content of less than 10 ppm was introduced, and the pressure in the chamber was approximately 50 mTorr.

At an appropriate point in time, a radio frequency electric field is applied to ionize the argon to form electrons that impinge on the target, the cathode, knocking out indium oxide particles from the target, thus creating a plasma between the cathode and the anode. A vapor is formed and these indium oxide particles are transported towards the anode and deposited on the adhesion enhancing layer previously deposited on the substrate member.

This sputtering is carried out at a rate determined by room conditions, typically using a target of about 1 to 2 square inches and about 15 to 40 square inches for industrial applications.
It is carried out at a speed of Å/sec. The thickness is monitored using optical equipment well known in the art to approximate the final thickness.
Make it 500Å.

The substrate member is then removed from the sputtering chamber and transferred or placed in another processing chamber. The same chamber can be used when processing in the laboratory or in small-scale production, but the cathode, or target, must be replaced. Similarly rigorous processing is required to remove all residual material and prevent contamination. Careful sealing of the target and plasma can minimize indoor contamination.

In any case, the substrate member 16 comprising the ohmic resistance layer 14, in this example a first coating layer consisting of indium oxide alone or indium oxide combined with tin oxide, and the pre-applied lower adhesive coating 18 is again applied to the anode support. or transferred to a rotating anode, etc.

In the case of a cadmium sulfide photoconductive layer, the cathode or target is made of cadmium sulfide or cadmium alone. The pressure is first reduced to 10 ^-8 Torr and then adjusted to 20 mTorr by introducing argon gas and hydrogen sulfide. The hydrogen sulfide precisely defines the amount of sulfur in the plasma vapor and deposits stoichiometrically accurate proportions of cadmium and sulfur on top of the ohmic resistive layer. In effect, hydrogen sulfide acts as a background gas that balances the vapor pressure of sulfur. This prevents decomposition of cadmium sulfide and controls stoichiometry. During any deposition process, the backside surface of substrate member 16 is blocked or masked to prevent deposits from adhering to the backside during normal processing. A first dark area created by the shield around the target prevents side and backside deposition. When using a cadmium sulfide cathode, the amount of hydrogen sulfide introduced is approximately 500 to 15,000 ppm of argon. This percentage is increased if a cadmium cathode is used. The final pressure of deposition ranged from 7 to 15 mTorr.

A small amount of copper in the form of sublimated copper chloride can be introduced into the sputtering chamber, and this can be done by keeping the copper salt in an evacuated vessel that communicates with the sputtering chamber through a control valve. .
Copper in this case is an added impurity that increases the trap level of cadmium sulfide, which is originally n-type. Alternatively, hydrogen iodide can be used to provide an iodine impurity to add trap levels for deposited cadmium sulfide.

Other impurity addition methods include ion implantation and diffusion transfer.

The application of radio frequency high pressure generates the necessary plasma, which deposits cadmium sulfide onto the ohmic resistance layer to form the photoconductive layer 12. In experiments, the deposition rate was approximately 6-15 Å/sec. This speed can be increased in industrial equipment. Add 5×10 ^-4 of copper or hydrogen iodide to the cadmium sulfide on the ohmic resistance layer with a well-controlled small amount as needed.
Add only % by weight. Most of the examples are quite pure. Sputtering is continued until the photoconductive layer 12 has a thickness of 3000 Å to 3500 Å.

As mentioned above, one of the most important points of the present invention is
One is to use a special sputtering method. This method is used to deposit the adhesion-enhancing layer 18, the ohmic-resistive layer 14, and the photoconductive coating 12, but specifically sputters the photoconductive material to form the adhesion-enhancing layer 18 and the photoconductive coating 12.
It is also important to apply it to form.

In conventional sputtering methods, the cathode or target is connected to the "high voltage" side of the output of the radio frequency oscillator, usually through a matching network, and the anode or substrate support is connected to ground. The radio frequency energy ionizes the argon gas introduced into the chamber, thus forming a plasma between the target and the anode, forming a relatively small dark area immediately adjacent to the surface of the target. Literally knocks out target atoms with argon gas ions,
The plasma is moved across the interstitial space and impinges on any object located on the anode. This object serves as a substrate member, and the particles themselves are deposited on the substrate either directly or after reacting with other reactive elements that can be introduced into the chamber.

It has been determined that by biasing the radio frequency circuit in the manner described above, the atoms of the deposited material can be deposited very densely, thus providing the unique electrical properties described above. With this bias arrangement, a second dark area is generated directly above the anode.

It was also confirmed that the second dark region can sometimes be generated by adjusting the geometrical arrangement of the indoor target, shield, anode, etc. This second
Once the dark area is generated, the desired amount of deposition is achieved without changing the circuit configuration, so the presence of the second dark area is a more pressing requirement than the circuit.

Finally, the embodiments of the present invention are summarized as follows.

1. The ultra-thin layer 18 is mainly composed of radio frequency sputtered cadmium sulfide.

2. The ohmic resistance layer 14 is mainly composed of indium oxide.

3. The ohmic resistance layer 14 is mainly composed of indium oxide containing tin oxide at a concentration of about 10%.

Additional Relationships The present invention is an additional invention of Patent No. 1287245 (Japanese Patent Publication No. 60-9260), which includes an electrophotographic film member as a substrate, an ohmic resistance thin film layer adhered to the substrate, and the ohmic resistance thin film layer bonded to the substrate. a thin film coating of an inorganic, electrically anisotropic, photoconductive material adhered to the layer; This invention achieves the same object as the original invention, and improves the adhesion between the ohmic resistance layer and the substrate of the electrophotographic film member of the original invention.

[Brief explanation of the drawing]

The drawing is a sectional view of an example of the electrophotographic film of the present invention. 12... Photoconductive thin film coating, 14...
Ohmic resistance thin film layer, 18... Adhesion-enhancing ultra-thin coating, 16... Substrate, 19... Contact, 20...
Voltage source, 21...corona generator.

Claims (1)

[Claims] 1 a substrate 16 and a pure inorganic photoconductive material radio frequency sputtered onto the substrate, which is extremely dense, microcrystalline, substantially transparent, and has at least a
It has a dark resistivity of 10 ¹² Ω-cm and a dark-to-light resistivity ratio of at least 10 ⁴ , has the property of being able to accept high-speed charges and retain this charge for toning, and a thin film coating 12 that is symmetrically anisotropic;
an adhesive layer between the ohmic resistive layer 14 and the substrate 16; An extremely thin layer 18 of the same photoconductive material as said photoconductive coating 12 is radio frequency sputtered onto the substrate as a layer, the thickness of the adhesive layer being a fraction of the thickness of the ohmic resistive layer. An electrophotographic film member characterized in that it is slanted.