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
  • G03G5/08207—Selenium-based
• • 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
  • G03G5/005—Materials for treating the recording members, e.g. for cleaning, reactivating, polishing

Definitions

• ABSTRACT A method for separating a coating, such as of selenium, from the smooth surface of a base material such as a metal electrophotographic plate comprising rapidly reducing the temperature of the coated base metal to far below freezing temperature of water, wetting the coated surface of the refrigerated base metal with a liquid such as water which forms a frozen layer such as ice on the coated side of the base metal, and then applying heat to effect separation of the frozen layer from the base metal with the coating adhered to the separated frozen layer, and wherein the coating material is separated as a solid from the liquid phase of the removed frozen layer,
• a suitable plate or cylinder having a photoconductive surface formed of a thin coating of a photoconductive material such as selenium
• a metal substrate having an exceptionally smooth surface which is relatively free of defects. If it were otherwise, the thin coating of the photoconductive material would reveal the surface defects as defects in the image that is formed and in the copy that is produced thereof.
• the need for such fine surface finish on the substrate demands that high grade substrate material be used and that extreme care be taken in the preparation of the surface for the photoconductive coating. These add up to a relatively expensive base material for photoconductive plates and cylinders.
• the selenium or other material, making up the photoconductive coating is rather expensive material and it would be most desirable, from the standpoint of economics and supply, to be able to remove the coating from the substrate in a manner which enables substantially complete recovery in a form which enables re-use in the production of fresh photoconductive coatings on suitable substrates.
• a complete and clean removal or stripping of the selenium coating from the surface of a metal plate can be achieved by a sequence of steps which comprises:
• the selenium stripped from the surface of the plate is not altered by the sequence of freezing for ice formation and heating for ice layer separation and thus can be recovered simply by separating the solid selenium from the water after the ice has been allowed to re-melt.
• the selenium remains in its original state for recovery and re-use, even without reformulation in the event that it is to be re-used in forming photoconductive coatings on a suitable base metal.
• the thermal shock to which the selenium coated plate is exposed during the initial refrigeration step operates to effect separation of the selenium layer from the underlying smooth surface of the base plate, and that the subsequent formation of an ice layer and removal provides the medium by which the separated selenium layer is removed from the plate surface in a medium from which it can be easily recovered.
• the preferential adhesion of the selenium layer for the ice layer coupled with the weakened bond between the selenium layer and the smooth surface of the base metal, as a result of thermal shock or differences in contraction upon cooling and expansion upon heating, operates to enable the clean removal of the selenium layer with the ice layer formed on the selenium surface.
• the metal base operates as a heat sink which retains the extremely cold temperature after the ice layer has been formed on the surface thereof to supercool the ice layer to the point of embrittlement.
• separation of the ice layer with the adhered selenium can be effected in response to application of heat to the side having the ice layer, or to the opposite side or both.
• the heating means such as water at ambient temperature or above
• the ice layer breaks up into multiple pieces. If the heat is applied to the surface opposite the ice layer, then the ice layer tends to separate more as a continuous sheet. In actual practice, it is preferred to make use of a water spray onto the ice layer since the applied stream of water will operate to wash the separated pieces from the surface of the base metal.
• Use is made of an aluminum drum having a diameter of 233 mm and a length of 348 mm, a wall thickness of 6 /2 mm with a thin selenium coating on the outer surface of the drum in which the surface has a smoothness of 8 micro inches.
• the drum is immersed, at atmospheric pressure, in a bath of liquid nitrogen having a temperature of about l96C.
• the drum is immersed until boiling substantially ceases, indicating that the drum has been cooled to approximately the temperature of the liquid nitrogen.
• the drum was immersed in the liquid nitrogen for 2 minutes.
• the refrigerated drum Upon removal from the bath of liquid nitrogen, the refrigerated drum is quickly immersed in a bath of cold water for a period of time sufficient to form an ice layer on the surface of the drum but insufficient to effect material elevation in the temperature of the metal portion of the drum. In the illustrated example, the refrigerated drum was immersed in the ice water for about 30 seconds.
• the aluminum drum is still far below freezing temperature and the cold is transmitted from the metal drum to the ice layer to cause supercooling of the ice layer with corresponding embrittlement. It is desirable to hold a drum for a period of time, such as 30 seconds to about minutes, preferably 1 to 2 minutes, to enable the desired super-cooling effect to be achieved.
• the water can be applied, as by spraying, onto the surface of the ice layer. Under these conditions, the ice layer breaks up into pieces which are washed by the water spray from the surface with the selenium adhered thereto.
• the ice with the selenium can be allowed to melt, leaving the selenium material as a solid which can be easily separated from the water by filtration, decantation, centrifugation, or the like liquid-solid separating means.
• the concepts described can be applied to strip other coatings from base materials wherein the coating and the base material are characterized by a marked difference in their thermal coefficients of expansion and contraction whereby, in response to exposure to cold shock and/or heat shock, the coating tends to separate from the base material at their interface.
• the coating exhibits a preferential adhesion to the layer of ice or other frozen liquid by comparison to the smooth surface of the base material between which it is sandwiched, the separated coating can be cleanly removed from the base material.
• the process is enhanced when the base material is characterized by a rapid heat transfer rate.
• the method as claimed in claim 9 which includes the step of holding the ice coated metal base for a period of time sufficient to enable cold to transfer from the cold metal base to the ice layer to super-cool the ice layer.
• the method as claimed in claim 1 in which the temperature is raised by wetting the side of the element 13.
• the method as claimed in claim 1 which includes the step of allowing the separated ice layer to melt to the liquid phase having the separated selenium present as a solid therein, and then separating the solid seleopposite the selenium coating with water above freez- 5 nium from the water.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Photoreceptors In Electrophotography (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Printing Plates And Materials Therefor (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23357722

Family Applications (1)

Country Status (7)

Cited By (6)

Citations (7)

• 1973
  • 1973-03-29 US US00346051A patent/US3837815A/en not_active Expired - Lifetime
• 1974
  • 1974-03-19 CA CA195,325A patent/CA1015551A/en not_active Expired
  • 1974-03-26 NL NL7404047A patent/NL7404047A/xx unknown
  • 1974-03-26 GB GB1340874A patent/GB1429598A/en not_active Expired
  • 1974-03-27 BR BR742429A patent/BR7402429D0/pt unknown
  • 1974-03-28 JP JP49034056A patent/JPS49128831A/ja active Pending
  • 1974-03-28 FR FR7410772A patent/FR2223085B1/fr not_active Expired

Patent Citations (7)

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