US3630743A - A method of improving the photosensitivity of metal oxide semiconductors - Google Patents

A method of improving the photosensitivity of metal oxide semiconductors Download PDF

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US3630743A
US3630743A US706186A US3630743DA US3630743A US 3630743 A US3630743 A US 3630743A US 706186 A US706186 A US 706186A US 3630743D A US3630743D A US 3630743DA US 3630743 A US3630743 A US 3630743A
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photoconductor
titanium dioxide
oxygen
stoichiometry
atmosphere
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US706186A
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Martin L Harvill
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Northrop Grumman Guidance and Electronics Co Inc
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Itek Corp
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide
    • C01G23/08—Drying; Calcining ; After treatment of titanium oxide
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/705—Compositions containing chalcogenides, metals or alloys thereof, as photosensitive substances, e.g. photodope systems
    • 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

Definitions

  • the reversible latent image pattern exists for a finite time during which said pattern can be converted to an irreversible form and read out visually by contacting said pattern with a suitable image-forming material, such as a chemical redox system.
  • a suitable image-forming material such as a chemical redox system.
  • the radiation-sensitive material is combined with at least one component of an imageforming material prior to exposure to activating means.
  • US. Pat. No. 3,152,904 describes photosensitive copy media comprising a photosensitive material such as titanium dioxide in combination with a reducible metal ion such as silver nitrate. This copy media is exposed to activating means and then contacted with a reducing agent to produce a visible image.
  • 3,152,903 discloses a system wherein the photosensitive material is used in combination with both oxidizing agent such as silver nitrate and a reducing agent such as hydroquinone. Upon exposure to suitable activating means, a visible image is formed.
  • oxidizing agent such as silver nitrate
  • reducing agent such as hydroquinone.
  • suitable activating means Upon exposure to suitable activating means, a visible image is formed.
  • One of the limitations of the above-mentioned data or image storage systems is that they lack the photographic speed of systems such as silver halide. Therefore, in order to expand the possible uses of these photographic systems described in the abovementioned patents and application, it is highly desirable to increase the photographic speed of these systems. Much research effort has been spent in trying to find ways of increasing the speed of these systems. However, up to the time of the present invention, these efforts have met with little or no success.
  • photographic response of metal-containing semiconductors may be substantially improved by heating the semiconductor, i.e. photoconductor, at elevated temperature and rapidly quenching the heated photoconductor.
  • the photoconductor is heated in an atmosphere which reversibly alters the stoichiometry of the photoconductor and then the heated photoconductor is rapidly quenched in the same atmosphere.
  • the atmosphere is preferably a reducing atmosphere which contains oxygen and, during the heating step the photoconductor is reduced, i.e. the stoichiometry of the photoconductor is altered.
  • the surface of the photoconductor chemisorbs oxygen on exposure to the atmosphere while the mass of the photoconductor remains substantially unchanged from the heat-induced nonstoichiometry.
  • the chemisorption of the atmospheric oxygen is quite rapid at or near room temperature and equilibrium is rapidly attained, i.e. no further chemisorption of oxygen by the surface occurs and the surface of the photoconductor is equilibrated with oxygen.
  • oxygen is provided in the form of a mixture with other gases, such as carbon dioxide, or formed in situ as in mixtures of carbon monoxide and carbon dioxide, preferably at a fugacity of oxygen of less than one.
  • gases such as carbon dioxide
  • the photoconductors, or photocatalysts, preferred in this invention are metal-containing photoconductors.
  • a preferred group of such photosensitive materials are the inorganic materials such as compounds of a metal and nonmetallic element of group VIA of the Periodic Table* (*Periodic Table from Langes HANDBOOK OF CHEMISTRY, 9th Edition pp. 56-57, 1966) such as oxides, e.g. zinc oxide, titanium dioxide, zirconium dioxide, germanium dioxide, indium trioxide; metal sulfides, e.g.
  • Titanium dioxide is a preferred metal oxide because of its unexpectedly good properties. Titanium dioxide having an average particle size of about 250 millimicrons or less and especially, that titanium dioxide produced by high-temperature pyrolysis of titanium halide.
  • titanium dioxide is made nonstoichiometric by some means, it cannot readily become stoichiometric in its crystallite bulk at room temperature. For example, oxygen diffusion through the crystal lattice of titanium dioxide will not occur to a degree below the Tammann temperature which is about half the melting temperature in degrees Kelvin (780 C. for titanium dioxide).
  • the overall equilibrium composition should be very nearly TiO m so that there is a tendency to become stoichiometric even though the equilibrium composition cannot be established throughout the bulk of the crystal. Therefore, the surface of the photoconductor can be returned to or near any desired, stoichiometry while the mass of the photoconductor remains substantially unchanged, i.e. the nonstoichiometry of the mass of the photoconductor created by heating is frozenin.
  • This nonstoichiometry yields electrons in or very near the conduction band so that they are relatively mobile, especially compared to oxygen ions. Therefore, oxygen from the atmosphere could possibly remove electrons from the conduction band and become chemisorbed to the surface yielding an overall composition which is nearly the equilibrium composition even through the oxygen could still not reach the interior of the crystal. This process would build up a potential difference between the interior and the exterior of each particle, and the potential difference would increase as nonstoichiometry of the bulk increased until essentially no further oxygen can be chemisorbed on the surface, at which the point the difference would become constant.
  • Activating radiation i.e., bandgap energy light will create hole-electron pairs which, because of the potential difference between the bulk and the surface of the crystal, would become separated with the holes possibly combining with chemisorbed oxygen and thereby releasing the oxygen and leaving an electron trapped in the conduction band.
  • the electron could either slowly recombine with atmospheric oxygen or, if placed in a reducible metal ion-containing solution, e.g. silver ion, could combine to form the elemental metal.
  • a reducible metal ion-containing solution e.g. silver ion
  • the efficiency of the photographic properties of the photoconductor increases as the potential difference between the bulk and the surface increases until the nonstoichiometry becomes so great that substantially no further chemisorption is possible, and then electrons begin to pile up in the conduction band. These excess electrons decrease the efficiency due to the increased probability of combination of the holes with electrons before the holes could reach the chemisorbed oxygen for removal. As the excess electrons also reduce silver ion, the photographic response (speed) begins to decrease at about the point where fog would begin to develop.
  • the return of oxygen to the surface after a light-effected change would be slower for materials with more oxygen already on the surface than for those with less of the surface covered, i.e. the image decay time increases with increasing bulk nonstoichiometry.
  • the photographic response would be expected to increase, go through a maximum, and then decrease as the nonstoichiometry increases.
  • the image decay time increases as the nonstoichiometry increases.
  • the photoconductor is heated in any suitable manner, e.g. as described in commonly assigned copending applications Ser. No. 463,037 filed June 10, 1965 now abandoned. in its broadest aspects, the practice of this invention involves heating the photoconductor at the selected elevated temperature and selected time period and rapidly quenching the heated photoconductor, i.e. cooling to a temperature below about 50 C. and preferably to or just below room temperature. For best results, the heated sample is quenched as rapidly as possible. Usually, a time period of up to about 2-3 minutes is practicable and gives acceptable results. After quench, the photoconductor is exposed to the ambient atmosphere to permit equilibration of the surface with oxygen which, as previously indicated, is quite rapid.
  • the equilibration of the surface with atmospheric oxygen is preferred for obvious reasons, e.g. ease of handling, no requirement for special equipment, etc.
  • the equilibration can be accomplished using any oxygen-containing atmosphere from which the surface of the photoconductor can absorb oxygen.
  • Such an atmosphere can be introduced into the quench zone of the furnace apparatus described herein or, alternatively, the sample may be inserted into a suitable apparatus in which the desired oxygen atmosphere is maintained.
  • the present process is carried out in a system which permits maintenance of the required atmosphere during the heating step.
  • a furnace system as shown in FIG. 1 may be used.
  • the system is composed of a furnace zone (22) and a quench zone (23) with gas inlet (24) and outlet means (25).
  • a receptacle (26) for the photoconductor sample e.g., a platinum boat, is heated in the furnace zone (22) and, after heating, quenched in the quenching zone (23) by manipulation of means (27) for moving the receptacle (26).
  • the receptacle (26) is removed and exposed to atmospheric oxygen, or alternatively, the entire furnace is opened to the atmosphere and the sample thus exposed.
  • the oxygen fugacity of the atmosphere in the sample chamber is controlled by using known mixtures of gases which will provide the desired partial pressure of oxygen. Especially suitable are mixtures of oxygen/ carbon dioxide and carbon monoxide/ carbon dioxide which provide fugacities over a wide range.
  • the gas inlet and outlet means are both within the hot zone of the furnace which is preferably maintained at constant temperature (112 C.) over the entire sample to minimize variation.
  • the constant temperature also allows to thermal separation of the gases which may occur were there a gradient between the inlet and outlet.
  • carbon dioxide When carbon dioxide is used it is first purged of 0 before it is mixed with other gases, e.g. by passing it over copper tumings at elevated temperature. Pure carbon dioxide at 750 C. will yield an oxygen fugacity of l.8 l0"' atmospheres. When mixed with carbon monoxide, the oxygen fugacity can be lowered to l.7 l0 Mixing carbon dioxide with oxygen permits variation of the oxygen fugacity from 1X10 atmospheres.
  • the powdered photoconductor is placed in the receptacle and heated in the desired atmosphere until the desired extent of change in the stoichiometry occurs, after which the sample is quenched as described.
  • the samples are heated for a period of 24 hours although maximum stoichiometric change generally is achieved in shorter time.
  • heating titanium dioxide at 750 C. usually requires a time of about 16 hours, but heating for longer periods has no adverse effect on the samples.
  • heating in the reducing atmosphere has a beneficial effect on the photoconductor regardless of whether maximum change in stoichiometry is achieved, but, optimum results being most desirable, maximum alteration is almost invariably sought.
  • the heating of the photoconductor is conducted at a temperature of at least 500 C. with preferred temperatures in the range from about 700 C. to about 800 C. Temperatures higher than 800 C. are usually avoided since sintering of the photoconductor can occur at extreme temperatures and little advantage is gained.
  • the receptacle containing the treated sample is drawn into a quench zone and brought to or near room temperature, and preferably slightly below room temperature.
  • the quench zone may be, for example, watercooled and, desirably, the sample is cooled within a period of 2-3 minutes. The fast quenching of the sample minimizes or prevents the return of the mass to the original stoichiometry, e.g. reoxidation of the titanium dioxide bulk.
  • the starting material of the present invention is any form of the photoconductor which is suitable for use in image formation as described in the aforesaid copending applications.
  • samples of titanium dioxide were preheated to 650 C. for 3 hours to remove chloride and other volatile impurities.
  • the photoconductor is then used to make photosensitive media on which photographic evaluations are made, for example, handsheets of the sample materials by coating a film or paper with a dispersion of the photoconductor.
  • the dispersions are prepared using an ultrasonic probe for blending the dispersions.
  • dispersing agents there may be employed sodium hexametaphosphate, potassium tripolyphosphate, and other dispersing agents known to the art.
  • the preferred coating method employs a roll coater in which the coating is applied by pulling the paper rather than the rod.
  • the inert carrier on which the photoconductor is deposited comprises any suitable backing of sufficient strength and durability to satisfactorily serve the intended purpose.
  • Reproduction carrier sheets can be in any form, such as, for example,
  • This sheet may be made of any suitable material such as wood, rag content paper, pulp paper, plastics such as, for example, polyethylene terephthalate and cellulose acetate, cloth, metallic sheets, such as an aluminum sheet, and glass.
  • the preferred form of the carrier sheet is a thin sheet which is flexible and durable.
  • binder agent to bind the photoconductor to the carrier sheet.
  • these binders are translucent or transparent so as not to interfere with transmission of light therethrough.
  • Preferred binder materials are organic materials such as resins. Examples of suitable resins are butadiene-styrene copolymers, poly(alkyl-acrylates) such as poly(methylmethacrylate), polyamides, poly-vinyl acetate, polyvinyl alcohol and polyvinylpyrrole.
  • the photoconductor may also be in the form of finely divided particles dispersed in a support, such as paper.
  • the photoconductor may also be in the form of a continuous film, alone or in combination with a separate support.
  • the photoconductor Before photoexposure, the photoconductor is conditioned in the dark, generally for from 1 to 24 hours. After conditioning, the photoconductor is not exposed to light prior to its exposure to activating radiations for recording an image pattern.
  • the period of exposure will depend upon the intensity of the light source, the particular imaging material, the particular photoconductor, and like factors known to the art. in general, however, the exposure may vary from about seconds to several minutes.
  • Image-forming materials which are useful in this invention are those such as described in US. Pat. No. 3,152,903 and in copending application Ser. No. 199,21 1, now abandoned. These image-forming materials include preferably an oxidizing agent and a reducing agent. Such image-forming materials are often referred to in the art as physical developers.
  • the oxidizing agent is generally the image-forming component of the image-forming material. However, this is not necessarily always the case. Either organic or inorganic oxidizing agents may be employed as the oxidizing component of the imageforming material.
  • Preferred oxidizing agents comprise the reducible metal ions having at least the oxidizing power of cupric ion and include such metal ions as Ag Hg, Pb, Au, Pt, Ni, Sn, Pb, Cu, and Cu.
  • Other suitable oxidizing agents useful in this invention as components of an image-forming material are permanganate (MnOf) ion, various leuco dye materials such as disclosed in copending application Ser. No. 623,534 filed in the name of L. Case, and the like.
  • Organic oxidizing agents include tetrazolium salts, such as tetrazolium blue and red, and diphenyl carbazone, and genarcyl red 6B (methine dye).
  • the reducing agent components of the image-forming materials of this invention include organic compounds such as the oxalates, formates, substituted and unsubstituted hydroxylamine, and substituted and unsubstituted hydrazine, ascor' bic acid, aminophenols, and the dihydric phenols. Also, polyvinylpyrrolidone, alkali and alkaline earth metal oxalates and formates are useful as reducing agents. Suitable reducing compounds include hydroquinone or derivatives thereof, 0-
  • the image-forming materials or physical developers may contain organic acids which can react with metal ions to form complex metal anions. Further, the developers may contain other complexing agents and the like to improve image formation and other properties found to be desirable in this art.
  • electrical toners may be used as image-forming materials in this invention.
  • Additional stabilizing and fixing steps such as known to the art may also be added to the processes of this invention in order to increase the life and permanence of the final print.
  • EXAMPLE 1 The determination of optimum conditions for obtaining optimum results is accomplished by routine experimentation utilizing a furnace unit as shown in FIG. 1. A sample of photoconductor is heated in the receptacle (26) at various fugacities of oxygen and then quenched to room temperature, and equilibrated with atmospheric oxygen, after which the photoresponse of the photoconductor is determined. A plot of the fugacity of oxygen versus the photographic speed will indicate the optimum fugacity for optimum photographic speed.
  • samples of titanium dioxide were preheated at 650 C. for 3 hours and then were heated at 750 C. for 24 hours at different fugacities of oxygen, provided in the form of mixtures with gas(es). Samples heated beyond 16 hours show no change of photographic response.
  • the inlet and outlet gases were both within the hot zone of the furnace which is maintained 12 C. over the entire sample chamber. After heating, the platinum receptacle boat was drawn into the quench zone (which was water cooled) and brought to room temperature, or slightly below, within 2-3 minutes, after which the samples were exposed to atmospheric oxygen for about 5-10 minutes.
  • Handsheets of the sample materials were then made and the photographic evaluations were made on a sensitometer using a 10" second exposure and a neutral density filter which is 1 .54 in the region of sensitivity of titanium dioxide.
  • a Wratten 2A Cutoff filter is placed along one edge of the stepwedge used. (This filter cuts off at 405420 millimicrons). No response is detectable through this filter.
  • samples were processed in freshly made solutions.
  • the decay time of the latent image formed on the samples subsequent to photoexposure was determined for samples l, 111 and Vll by processing at time intervals after exposure.
  • EXAMPLE 2 Titanium dioxide different from that employed in example 1 was subjected to the same procedure as in example 1.
  • EXAMPLE 3 EXAMPLE 4 The procedure of example 3 is repeated using the titanium dioxide sample of example 2 equilibrated at a fugacity of oxygen of 1Xl0'". The resulting coated sheet is suitable for photographic use.
  • EXAMPLE 5 The titanium dioxide sample used in example 3 is dispersed in gelatin and the dispersion is coated on a cellulose triacetate sheet. The resulting sheet is suitable for photographic use.
  • polyethylene terephthalate sheets are coated with the same gelatin dispersion to obtain useful photographic material.
  • the gelatin dispersion is prepared by forming a slurry of the photoconductor in water to which is added an aqueous gelatin solution.
  • the plastic sheet is then coated with the gelatin dispersion by means of a wire wound rod.
  • L.E.S. (abbreviation for light exposure speed) refers to a speed-rating system developed at the Wright Air Development Division of the Air Research and Development Command (U.S.A.F. and is defined as the reciprocal of the exposure in meter candle seconds which is required to produce a double diffuse reflection density of 0.2 density units above the sum of the base plus fog densitiesv As in the more conventional ASA system used to rate silver halide films. the higher the L.E.S. number the faster the photographic exposure speed of the film
  • the latent image is convened to a visible image by contact with a saturated solution of silver nitrate in methanol and then a solution of 5 g. of phenidone, 40 g. of citric acid monohydrate and l liter of methanol.
  • the visible image-bearing print is fixed with methanolic potassium cyanate stop bath, then fixed in aqueous sodium thiosulfate solution and finally washed in water.
  • the spectral response of the products of the present invention may be altered bydoping with foreign metal ions such as chromium ions or by use of dyes, especially those which extend the spectral response into the visible region of the spectrum.
  • dyes are described in commonly assigned eopending application Ser. Nos. 633,689 filed Apr. 26, I967 and 623,534 filed March I9, 1967 What we claim is:
  • a process of improving the photographic properties of metal oxide photoconductors from the group consisting of titanium dioxide, zinc oxide and indium oxide having an average particle size of 250 millimicrons or less which comprises the steps of:
  • Process of improving the photographic properties of titanium dioxide which comprises heating particulate titanium dioxide in a reducing atmosphere at a temperature of between about 500 and about 900 C. at an oxygen fugacity of less than one for a period of time sufficient to change the stoichiometry of the titanium dioxide in the bulk, rapidly quenching the heated titanium dioxide in said atmosphere to a temperature below about 50 C. and equilibrating the quenched titanium dioxide with oxygen.
  • titanium dioxide is of an average particle size of about 250 millimicrons or less.
  • a metal oxide photoconductor from the group consisting of titanium dioxide, zinc oxide and indium oxide the stoichiometry of the mass of which differs from the stoichiometry of the surface thereof to create a significant potential difference between said surface and said mass, and wherein said photoconductor has been treated according to the process of claim l5.
  • An image reproduction system having improved photographic speed comprising a partially reduced metal oxide photoconductor from the group consisting of titanium dioxide, zinc oxide and indium oxide having an average particle size of 250 millimicrons or less and having an anion deficient or cation excessive stoichiometry in the bulk, the surface of which photoconductor is equilibrated with oxygen until substantially no further chemisorption can occur and wherein the anion deficiency or cation excess of the stoichiometry is not so great as to cause excessive background-fogging when the image reproduction system is exposed and contacted with a developer comprising silver nitrate, and wherein the photoconductor has been treated according to the process of claim 27.
  • An image reproduction system having improved photographic speed comprising titanium dioxide having improved photographic speed comprising titanium dioxide having an average particle size of about 250 millimicrons or less and having an oxygen deficient stoichiometry in the bulk, the surface of which titanium dioxide is equilibrated with oxygen until substantially no further chemisorption can occur, wherein the oxygen deficiency of the stoichiometry is not so great as to cause excessive background fogging when the image reproduction system is exposed and contacted with a developer comprising silver nitrate, and wherein the titanium dioxide has been treated according to the process of claim 17.

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US706186A 1968-02-16 1968-02-16 A method of improving the photosensitivity of metal oxide semiconductors Expired - Lifetime US3630743A (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3864127A (en) * 1971-08-12 1975-02-04 Fuji Photo Film Co Ltd Method for preparing ZnO-TiO{HD 2 {B bichargeable electrophotographic material
US4264914A (en) * 1978-12-27 1981-04-28 The United States Of America As Represented By The United States Department Of Energy Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same
EP2385425A1 (en) 2010-05-07 2011-11-09 Fujifilm Corporation Silver halide photographic light-sensitive material for movie
US20200064749A1 (en) * 2018-08-24 2020-02-27 Canon Kabushiki Kaisha Electrophotographic photosensitive member, process cartridge and electrophotographic apparatus
US20200064750A1 (en) * 2018-08-24 2020-02-27 Canon Kabushiki Kaisha Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1408425A (en) * 1972-05-05 1975-10-01 Zochem Ltd Production of photoconductive zinc oxide

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2408475A (en) * 1941-07-18 1946-10-01 Gen Electric Fluorescent zinc oxide
US3170886A (en) * 1961-04-26 1965-02-23 Gen Telephone & Elect Method for treating photoconductive cadmium sulfide cell
US3409429A (en) * 1964-04-15 1968-11-05 Itek Corp Transparency and method of making and using a thin transparent radiation sensitive film consisting essentially of titanium dioxide
US3453141A (en) * 1963-08-06 1969-07-01 Gen Electric Method for making a high-speed reusable x-ray plate using orthorhombic lead oxide and resulting article

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2408475A (en) * 1941-07-18 1946-10-01 Gen Electric Fluorescent zinc oxide
US3170886A (en) * 1961-04-26 1965-02-23 Gen Telephone & Elect Method for treating photoconductive cadmium sulfide cell
US3453141A (en) * 1963-08-06 1969-07-01 Gen Electric Method for making a high-speed reusable x-ray plate using orthorhombic lead oxide and resulting article
US3409429A (en) * 1964-04-15 1968-11-05 Itek Corp Transparency and method of making and using a thin transparent radiation sensitive film consisting essentially of titanium dioxide

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3864127A (en) * 1971-08-12 1975-02-04 Fuji Photo Film Co Ltd Method for preparing ZnO-TiO{HD 2 {B bichargeable electrophotographic material
US4264914A (en) * 1978-12-27 1981-04-28 The United States Of America As Represented By The United States Department Of Energy Wide-band-gap, alkaline-earth-oxide semiconductor and devices utilizing same
EP2385425A1 (en) 2010-05-07 2011-11-09 Fujifilm Corporation Silver halide photographic light-sensitive material for movie
US20200064749A1 (en) * 2018-08-24 2020-02-27 Canon Kabushiki Kaisha Electrophotographic photosensitive member, process cartridge and electrophotographic apparatus
US20200064750A1 (en) * 2018-08-24 2020-02-27 Canon Kabushiki Kaisha Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus
US10754267B2 (en) * 2018-08-24 2020-08-25 Canon Kabushiki Kaisha Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus
US10948838B2 (en) * 2018-08-24 2021-03-16 Canon Kabushiki Kaisha Electrophotographic photosensitive member, process cartridge and electrophotographic apparatus

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