US3754965A - A method for making an electrophotographic plate - Google Patents

A method for making an electrophotographic plate Download PDF

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Publication number
US3754965A
US3754965A US00131021A US3754965DA US3754965A US 3754965 A US3754965 A US 3754965A US 00131021 A US00131021 A US 00131021A US 3754965D A US3754965D A US 3754965DA US 3754965 A US3754965 A US 3754965A
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Prior art keywords
photoconductive
layer
charge
photoconductive layer
image
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US00131021A
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English (en)
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J Mooney
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Varian Medical Systems Inc
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Varian Associates Inc
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    • 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
    • G03G5/085—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and being incorporated in an inorganic bonding material, e.g. glass-like layers

Definitions

  • ABSTRACT In an electrophotographic camera, a photon image to be recorded is focused through an optically transparent substrate and transparent electrode onto the back surface of a photoconductive layer.
  • the charge-retentive surface of an electrographic recording paper is disposed adjacent the photoconductive layer and the conductive backing of the paper is connected to an electrode for impressing a charge transfer potential across the photoconductor layer and the charge-retentive layer of the paper.
  • the potential is impressed across the photoconductor
  • electrons liberated in the photoconductor by the photon image to be recorded are transferred to the charge-retentive surface of the recording paper to form a charge image of the object to be recorded.
  • the charge image is subsequently developed by applying charged toner particles to the image for developing same.
  • the photoconductive layer comprises a substantially continuous layer of an interlocked matrix of crystals of active photoconductive material coated and bound together with a lead sealing glass interstitially disposed of the interlocking crystal matrix.
  • the resultant photoconductive layer has improved strength and resistance to abasion while producing acceptable photographic images.
  • the photoconductive layer is produced by heating a stratum including particles of lead sealing glass together with particles of preactivated photoconductive material in the presence of a molten solvent and proportions of one or more activators.
  • photoconductive layers have been produced by forming a stratum including particles of a material selected from the group consisting of sulphides, selenides and sulphoselenides of cadmium, recrystallizing said material in a molten solvent to a desired range of particle sizes, incorporating into said recrystallized material activator proportions of a halide and activator proportions of a metal selected from a group consisting of copper and silver, and evaporating the molten solvent.
  • the resultant layer is a substantially continuous layer of interlocked crystals of photoconductive material.
  • Such a sintered photoconductive material is described in U.S. Pat. No. 2,765,38
  • Such a photoconductive plate is described in an article titled Photoinduced Discharge Characteristics of Cadmium Sulphide Binder Layers in the Xerographic Mode appearing in the Journal of Applied Physics, Vol. 36, No. 11, of Nov. I965, pp 3475-3480.
  • the problem with using such a photoconductor as an electrographic camera plate is that it produces rather speckled images due to a lack of uniformity of the resultant layer, it has a relatively high dark background current, and is sensitive to the presence of moisture which tends to alter its photoconductive properties and to give rise to excessive dark conductivity.
  • this latter type of photoconductive plate suffers from memory effects, thereby precluding its use in a camera wherein the time interval between successive picture frames is desired to be as short as possible.
  • the principal object of the present invention is the provision of an improved photoconductive layer and method of making same.
  • One feature of the present invention is the provision of a sintered photoconductor comprising a layer of a substantially continuous polycrystalline matrix of interlocked photoconductive crystals of a substance selected from the group consisting of sulphides, selenides, tellurides and sulphoselenides of a member of the group consisting of zinc and cadmium, and containing activator proportions of a halide plus activator proportions of a metal selected from the group consisting of copper and silver and incorporating a glass binder interstitially disposed of said polycrystalline matrix, whereby a mechanically stable abrasion-resistant, highspeed photoconductive layer is formed having low memory and low dark current characteristics.
  • photoconductive crystals comprise crystals of cadmium sulphide containing activator proportions of chloride and copper and wherein the glass binder is a lead sealing glass.
  • the photoconductive layer is produced by a method including the steps of, forming a mixture including particles of solvent and activator mixed together with particles of a substance selected from the group consisting of sulphides, tellurides, selenides and sulphaselenides of a member of the group consisting of zinc and cadmium, activating said substance, mixing the activated substance with glass particles, forming a layer of said activated substance and glass mixture, recrystallizing at least portions of said substance in said layer and melting the glass particles which.are interstitially disposed of said activated photoconductive substance.
  • Another feature of the present invention is the same as the preceding feature wherein the glass particles have a softening temperature between 50 and 250C below the temperature at which the mixed particles are heated for melting the solvent.
  • FIG. 1 is a schematic line diagram, partly in section and partly in block diagram form, depicting an electrophotographic camera incorporating features of the DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • the camera 1 includes a lens 2 disposed at one end of a dark box 3 for focusing the light obtained from an object 4 onto the back side of a photoconductive layer 5 disposed at the image plane of the lens 2.
  • the photoconductive layer 5, as of 20 to I microns, is deposited over an optically transparent conductive electrode 6 which in turn is supported from an optically transparent substrate 7, as of borosilicate glass plate one-fourth thick.
  • a suitable transparent conductive electrode structure 6 comprises a tin oxide coating having a resistivity of 50 ohms per square and having a transparency, in the optical range, greater than 95 percent.
  • Other suitable conductive electrodes 6 include metal films of chromium and gold.
  • An electrographic recording paper 8 is disposed adjacent the photoconductive layer with the chargeretentive surface 9 of the paper 8 disposed adjacent the photoconductive layer 5.
  • the conductive layer 11 of the paper 8 is disposed facing a conductive electrode structure 12 for uniformly pressing the chargeretentive surface 9 of the paper 8 into nominal contact with the surface of the photoconductor 5.
  • a source of potential as of 500 to 900 volts, is connected across electrodes 6 and 12 via the intermediary of a timing switch 14.
  • An electrographic camera 1 of the type herein disclosed is described and claimed in copending U.S. application Ser. No. 599,069 filed Dec. 5, I966 and assigned to the same assignee as the present invention, now US. Pat. No. 3,502,408.
  • the image of the object 4 to be photographed is focused upon the photoconductive layer 5.
  • the timing switch 14 is closed for the appropriate ex posure time determined by the available light intensity and the speed of the photoconductive layer 5.
  • electrons liberated within the photoconductive layer 5 by the incident light image are caused to be transferred through the photoconductive layer 5 into the charge-retentive surface 9 of the electrographic paper 8.
  • a charge image of the object 4 is produced in the charge-retentive surface 9 of the paper.
  • the charge image is then developed by removing the paper 8 from the camera 1 and applying positively charged toner particles to the charge image for developing same.
  • the toner particles may be suspended in air or in a liquid dielectric vehicle. Alternatively, the polarity of the source 13 may be reversed to produce positive charge images on the charge retentive surface 9.
  • the photoconductor 5 is also sensitive to invisible radiation; i.e., photon of energy outside the visible range of wavelengths.
  • the photoconductor is useful for photographing X-ray, X-ray or neutron images.
  • the transparent electrode 6 and substrate 7 need only be transparent to the rays which are to form the image on the photoconductor 5.
  • the photoconductive layer 5 comprises a substantially continuous polycrystalline layer of a matrix of interlocked photoconductive crystals 15 of a photoconductive substance selected from the group consisting of sulphides, tellurides, selenides, and sulphoselenides of a member of the group consisting of zinc and cadmium and containing activator proportions of a halide plus activator proportions of a member of the group consisting copper and silver.
  • a lead sealing glass binder material 16 is interstitially disposed of the polycrystalline matrix 15, thereby binding the matrix together to make the matrix mechanically stable and resistant to abrasion.
  • Each of the photoconductive crystallites of the matrix 15 is fused to its neighboring photoconductive crystallites by means of a recrystallized bridge or junction therebetween, thereby producing low resistance electrical bridging connections between neighboring photoconductive crystallites of the matrix forming the photoconductive layer 5.
  • the surface of the photoconductive layer 5 which faces the charge-retentive surface 9 of the paper 8 is relatively smooth, having a surface ripple less than 5 microns.
  • the surface ripple is defined as the vertical distance between adjacent peaks and valleys in the surface of the photoconductor.
  • the glass binder 16 completely coats the surface of the photoconductive particles 15 at the exposed surface of the photoconductive layer 5, the thicknes of the glass is only on the order of a micron or less and does not interfere with proper operation of the photoconductive layer 5.
  • Photoconductive layers 5 produced in accordance with the teachings of the present invention are found to be resistant to abrasion, and to be mechanically strong for producing electrographic images of acceptable photographic quality; i.e., defects cannot be discerned by the unaided eye.
  • the method for producing the photoconductive layer 5 comprises the steps of: mixing together the powdered photoconductor and a suitable solvent or fusing agent and a suitable activator; firing the mixture at about 600C for about 25 minutes; mixing powdered glass into the fired mixture; dispersing the mixture into a suitable vehicle to form a paste; applying the mixture by a doctor blade or by spraying or by painting onto the transparent conductive electrode layer 6 as carried upon the glass substrate 7; firing the substrate containing the coating in an air furnace and sintering at 600C for approximately 15 minutes; cooling the resultant sintered photoconductive layer to room temperature.
  • a conductor is then painted onto the side edge of the substrate member to make contact with the optically transparent conductive electrode 6 and the photoconductive plate is then ready for use.
  • Suitable photoconductive materials include sulphides, tellurides, selenides and sulphoselenides of zinc or cadmium.
  • Suitable activator elements include a halide plus copper and/or silver.
  • Suitable solvents for the photoconductor include halides of cadmium or zinc.
  • Suitable vehicles for the powdered mixture include ethyl alcohol and xylene.
  • Suitable glasses include the lead sealing glasses having a softening temperature between 50 and 250C below the temperature at which the mixed particles are heated for melting the solvent. The glass particles preferably comprise between 10 percent and 45 percent by weight of the particulated photoconductive substance exclusive of the glass particles. In a preferred embodiment, the sealing glass has a softening point of approximately C below the temperature at which the particulated layer is fired in the furnace.
  • an intimate mixture is formed of 250 grams of cadmium sulphide, 0.25 grams of Cu CL 2 ZI-I O and 12.5 g of dry Cd cl- 2.5H2O.
  • a suitable cadmium sulphide powder is high purity powder obtained from Gallard Schlesingler Chemical Company of Carle Place, N.Y.. Batch No. B7649.
  • the cadmium chloride and copper chloride are predissolved in deionized water. and sufficient water is added to make a fluid paste (approximately 150 milliliters total).
  • the slurry is thoroughly blended (e.g.. by hand-mixing, ball-milling, etc.), then dried (e.g..
  • the dry material is pulverized, e.g., in a mortar and pestle until all of it passes through a -mesh sieve, blended and placed in a glassceramic dish. The mix is fired at 600C for minutes. then cooled and again crushed until all of it passes through a 50-mesh screen.
  • This is the preactivated photoconductor powder.
  • preactivated cadmium sulphide one adds another 12.5 grams of cadmium chloride and 50 grams of Coming No. 7570 glass powder with a particle size 325 mesh (coming Glass Works, Corning, N.Y.).
  • the mix is slurried up in a 16 oz. glass jar with about 200 milliliters of deionized water, cylindrical milling balls as X /2 inch) are added, and the slurry is milled for at least hours. If necessary, more water may be added to give a mix of the desired consistency.
  • the cadmium chloride melts, dissolving the copper salt and some of the cadmium sulphide.
  • ion exchange chemical reaction takes place.
  • copper activates the photoconductive cadmium sulphide material.
  • an ion exchange reaction occurs wherein chlorine ions enter the cadmium sulphide lattice to produce further activation of the photoconductive material.
  • the cadmium sulphide recrystallizes at the junctions between adjacent cadmium sulphide crystals and the unused cadmium chloride evaporates.
  • the recrystallized cadmium sulphide has incorporated therein activator proportions of copper and chlorine.
  • the additional cadmium chloride acts as a fusing agent for producing conductive bridging connections between the adjacent crystallite particles of the photoconductive material.
  • the cadmium sulphide crystals are interlocked with one another, forming a substantially continuous polycrystalline layer of interlocked photoconducting crystals on the glass plate. The resultant layer is extremely homogeneous and firmly adherent to the glass.
  • the lead sealing glass has a softening temperature of approximately 150 lower than the firing temperature of 600.
  • the sealing glass does not appear to react with the preactivated photoconducting crystals.
  • the glass upon melting, forms a coating around the photoconductor and provides a binder filling the interstitial spaces between the inerlocked crystallites of the photoconductive matrix.
  • the glass imparts mechanical strength and abrasion-resistant characteristics to the resultant photoconductive layer 5.
  • Cadmium sulphide and its equivalents will hereinafter be referred to as the host crystal.
  • cadmium chloride is introduced into the mixture to act as a solvent for the host crystal.
  • cadmium chloride in addition to cadmium chloride, other halides of cadmium or zinc may be used such as, for example, bromides or iodides of cadmium or zinc may be employed.
  • bromides or iodides of cadmium or zinc may be employed.
  • silver may he introduced into the host crystal as the activator.
  • the proportion of glas by weight of the host crystal preferably falls within the range of l0 percent to 45 percent with 20 percent being especially desirable.
  • a method for manufacturing an electrophotographic plate for transferring developable quantities of charge to an adjacent surface in response to photons incident upon the plate comprising the steps of:
  • the crystals selected from the group consisting of sulphides, tellurides, selenides, and sulphoselenides of a material selected from the group consisting of zinc and cadmium;
  • the glass particles comprise from about 9 percent to about 31 percent by weight of the weight of the fired mixture including the weight of the glass; providing a sustrate;
  • activator is a halide and of a metal selected from the group consisting of copper and silver, and the solvent is a halide of cadmium.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photoreceptors In Electrophotography (AREA)
US00131021A 1971-04-05 1971-04-05 A method for making an electrophotographic plate Expired - Lifetime US3754965A (en)

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AU (1) AU470738B2 (esLanguage)
BE (1) BE781652A (esLanguage)
CA (1) CA960522A (esLanguage)
FR (1) FR2136143A5 (esLanguage)
IT (1) IT953603B (esLanguage)
NL (1) NL7204491A (esLanguage)
SE (1) SE367876B (esLanguage)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4015984A (en) * 1973-05-17 1977-04-05 Kabushiki Kaisha Ricoh Inorganic photoconductor in glass binds with glass overcoat layer
US4162475A (en) * 1978-03-24 1979-07-24 Fisher Charles B Transducer utilizing sampling
US4221855A (en) * 1975-10-02 1980-09-09 Nippon Electric Co., Ltd. Electrophotographic plate produced by firing glass binder containing inorganic photoconductor and high melting point inorganic additive in non-reducing atmosphere
US4254200A (en) * 1976-09-30 1981-03-03 Siemens Aktiengesellschaft Electrophotographic element with bismuth oxide compound
EP0037193A3 (en) * 1980-03-31 1981-12-30 Xerox Corporation Xerographic reproduction method
US5072122A (en) * 1990-10-15 1991-12-10 Kansas State University Research Foundation Charge storage image device using persistent photoconductivity crystals
WO1996010194A1 (en) * 1994-09-29 1996-04-04 Yissum Research Development Company Of The Hebrew University Of Jerusalem A radiation detection system and processes for preparing the same
US5892227A (en) * 1994-09-29 1999-04-06 Yissum Research Development Company Of The Hebrew University Of Jerusalem Radiation detection system and processes for preparing the same
US20050214581A1 (en) * 2004-03-24 2005-09-29 Fuji Photo Film Co., Ltd. Photoconductive layer included in radiation imaging panel

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2698915A (en) * 1953-04-28 1955-01-04 Gen Electric Phosphor screen
US2765385A (en) * 1954-12-03 1956-10-02 Rca Corp Sintered photoconducting layers
US2857541A (en) * 1954-03-29 1958-10-21 Westinghouse Electric Corp Thin sheet of phosphor embedded glass and method of preparing
US2866117A (en) * 1955-04-15 1958-12-23 British Thomson Houston Co Ltd Electroluminescent panel
US2937353A (en) * 1959-02-27 1960-05-17 Sylvania Electric Prod Photoconductive devices
US3151982A (en) * 1962-04-02 1964-10-06 Xerox Corp Xerographic plate
US3248261A (en) * 1962-08-16 1966-04-26 Ibm Photoconducting layers

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2698915A (en) * 1953-04-28 1955-01-04 Gen Electric Phosphor screen
US2857541A (en) * 1954-03-29 1958-10-21 Westinghouse Electric Corp Thin sheet of phosphor embedded glass and method of preparing
US2765385A (en) * 1954-12-03 1956-10-02 Rca Corp Sintered photoconducting layers
US2866117A (en) * 1955-04-15 1958-12-23 British Thomson Houston Co Ltd Electroluminescent panel
US2937353A (en) * 1959-02-27 1960-05-17 Sylvania Electric Prod Photoconductive devices
US3151982A (en) * 1962-04-02 1964-10-06 Xerox Corp Xerographic plate
US3288603A (en) * 1962-04-02 1966-11-29 Xerox Corp Method of restoring xerographic properties to a glass binder plate
US3248261A (en) * 1962-08-16 1966-04-26 Ibm Photoconducting layers

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4015984A (en) * 1973-05-17 1977-04-05 Kabushiki Kaisha Ricoh Inorganic photoconductor in glass binds with glass overcoat layer
US4221855A (en) * 1975-10-02 1980-09-09 Nippon Electric Co., Ltd. Electrophotographic plate produced by firing glass binder containing inorganic photoconductor and high melting point inorganic additive in non-reducing atmosphere
US4254200A (en) * 1976-09-30 1981-03-03 Siemens Aktiengesellschaft Electrophotographic element with bismuth oxide compound
US4162475A (en) * 1978-03-24 1979-07-24 Fisher Charles B Transducer utilizing sampling
EP0037193A3 (en) * 1980-03-31 1981-12-30 Xerox Corporation Xerographic reproduction method
US5072122A (en) * 1990-10-15 1991-12-10 Kansas State University Research Foundation Charge storage image device using persistent photoconductivity crystals
WO1996010194A1 (en) * 1994-09-29 1996-04-04 Yissum Research Development Company Of The Hebrew University Of Jerusalem A radiation detection system and processes for preparing the same
AU699690B2 (en) * 1994-09-29 1998-12-10 T.T.I. (Target Technologies Israel) Ltd. A radiation detection system and processes for preparing the same
US5892227A (en) * 1994-09-29 1999-04-06 Yissum Research Development Company Of The Hebrew University Of Jerusalem Radiation detection system and processes for preparing the same
AU699690C (en) * 1994-09-29 2002-03-21 T.T.I. (Target Technologies Israel) Ltd. A radiation detection system and processes for preparing the same
US20050214581A1 (en) * 2004-03-24 2005-09-29 Fuji Photo Film Co., Ltd. Photoconductive layer included in radiation imaging panel

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Publication number Publication date
FR2136143A5 (esLanguage) 1972-12-22
IT953603B (it) 1973-08-10
NL7204491A (esLanguage) 1972-10-09
AU4069072A (en) 1973-10-11
AU470738B2 (en) 1973-10-11
CA960522A (en) 1975-01-07
SE367876B (esLanguage) 1974-06-10
BE781652A (fr) 1972-07-31

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