Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
  • G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
  • G03G15/2014—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat
  • G03G15/2053—Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating
  • G03G15/2057—Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating relating to the chemical composition of the heat element and layers thereof

Definitions

• ABSTRACT Tetrafluoroethylene resin-coated fuser rolls in which the resin is applied in a single-fusion process, for use in xerographic reproducing apparatus.
• the singlefusion process involves successive application of tetrafluoroethylene coats 0.6 to 0.9 mil thick until a coating of about 6 mils is attained. Between each application, the rolls are heated to about 180 F. in order to flash off water and volatile materials. The coating is fused by a single baking step at the end of the process.
• the invention relates to an improved heated-roll fusing device.
• the invention is considered to have general application, it is particularly useful in the field of xerography and has an important application in the fusing of resinous powder images produced by electrophotography or xerography onto sheets of paper and the like to which the powder images have been transferred after they have been formed by deposition of powder on an electrostatic latent image. Therefore, for convenience of illustration, theinvention is described with reference to its use as a heat fuser for xerographic powder images. However, it is to be understood that it may be employed with equal facility in other fields.
• a xerographic plate comprising a layer of photoconductive insulating material on a conductive backing, is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques.
• This exposure discharges the plate areas inaccordance with the radiation intensity that reaches them, and thereby creates an electrostatic latent image on or in the photoconductive layer.
• Development of the latent image is effected with an electrostatically charged, finely divided developing material or toner which is brought into surface contact with the photoconductive layer and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image.
• the developed xerographic powder image is usually transferred to a support surface, such as paper, to which it may be fixed by any suitable means.
• Such developing materials are compounded to permit them to be fixed to the surface of a transfer material either by heat fixing or vapor fixing techniques, in accordance with the particular application in which they are employed, that is, the individual particles of resin (toner) soften and coalesce when heated or plasticized by solvent, so that they become sticky or tackified and readily adhere to the surface of the transfer material.
• tackified and the several variant forms thereof used throughout this specification are employed to define the condition of the powder particles of the xerographic powder image when heated or plasticized by a solvent in a manner such that the individual particles soften and coalesce and in which state they become sticky and readily adhere to other surfaces.
• this condition necessarily requires a flowing together of the particles to effect a thorough fusion thereof, it is to be understood that the extent of such 1 flowing is not sufficient to extend beyond the boundary phy comprises its use in automatic copying machines for general office use wherein the powder images formed on a xerographic plate are transferred to paper and then fixed thereon by heat fusing.
• toner onto the heating surface led to the development of improved methods and apparatus for fusing the toner image, notably the process and apparatus described in Van Dorn U.S. Pat. No. 3,268,351, issued Aug. 23, 19.66.
• the toner images were fused by forwarding the sheet or web of paper bearing said image between two heated rolls, the roll contacting the image being provided with a thin coating of tetrafluoroethylene resin and a silicone oil film to prevent toner offset.
• the tetrafluoroethylene resin is sold under the trademark Teflon by E. l. DuPont De Nemours & Co.
• Both the tetrafluoroethylene resin and the silicone oil have physical characteristics such that they are substantially abhesive to dry or tackified xerographic developing materials.
• Abhesive is a relatively new term coined by the Dow Corning Corporation, primarily in connection with their silicone to define a surface that has release characteristics such that it is highly repellent to sticky or tacky substances.
• Another object of this invention is to provide a tetrafluoroethylene resin-coated roll which will have greater durability.
• Still another object of this invention is to provide the method of manufacturing the resin-coated rolls so as to achieve improved efficiency and economy.
• the process of this invention is a multiple step process involving: (1) application of a tetrafluoroethylene primer; (2) heating the primer-coated roll at a temperature sufflciently high to cause baking of the primer substance; (3) applying a thin coating of tetrafluoroethylene enamel liquid; (4) passing the enamel-coated roll through a temperature zone no higher than 180 F. in order to flash off water and solvent, repetition of steps (3) and (4) until one attains the desired thickness of tetrafluoroethylene enamel on the roll, and (5) heating the coated roll to a high temperature in order to fuse the coating.
• the surface of the roll Prior to applying the tetrafluoroethylene primer, it is essential that the surface of the roll be properly prepared.
• the surface should be clean and free of all greasy substances.
• adhesion of the primer is improved if the surface has been slightly roughened in a uniform manner.
• Methods of properly preparing the surfaces such as solvent cleaning, grit blasting, chemical etching, wheel sanding, etc. are well known to a person skilled in the art.
• the tetrafluoroethylene primer is applied.
• a number of primer substances are available; DuPonts Teflon 850-204 is especially suitable for application in xerographic reproducing machine fuser rolls.
• One coat of primer is applied and its thickness should be about 0.3 mil and no higher than 0.7 mi].
• the primer film which is a liquid, may be conveniently applied by air atomization, either manually or, preferably, automatically.
• the liquid primer film typically contains 30 to 50 percent water and other volatile materials.
• a drying step is necessary prior to curing the film. This must be done at a temperature of 180 F. or below, and is preferably done by air drying. The drying step can also be performed at room temperature, by allowing the coated rolls to stand for 10 to 15 minutes under a low humidity conditions. After the drying step has been completed, the rolls are ordinarily subjected to a baking temperature of from about 725 to 800 F. in order to fuse the tetrafluoroethylene primer. It is essential to use these high temperatures when one uses a multifusing process in the application of the tetrafluoroethylene enamel.
• the baking of the tetrafluoroethylene primer can be accomplished at a significantly lower temperature, namely at about 400 F. for 20 minutes or at from 450 to 500 F. for a period of 10 minutes.
• the use of these significantly lower temperatures is one of the principal advantages derived from this invention.
• each coat should have a dry film thickness of from about 0.6 to about 0.9 mil.
• a roll After the application of each tetrafluoroethylene enamel coat, a roll is subjected to a temperature no higher than 180 F., preferably from to F., in order to flash off the major portion of the water and other volatile materials contained in the film. This is conveniently done by passing the coated roll into a drying zone having the requisite temperature. After the drying is completed, the coated roll should be allowed to return to close to room temperature before application of the next enamel coating. With a drying temperature of 180 F., about 7 to 10 minutes will elapse between successive coatings.
• the optimum thickness of tetrafluoroethylene resin coating on rollers used in xerographic reproducing apparatus is between about 1.5 to 6 mils.
• the coated roll is then subjected to a fusion temperature of from about 700 to 900 F., preferably from about 730 to 750 F.
• the fusion time is about 10 to 20 minutes.
• Fuser rolls for xerographic reproducing apparatus which have been coated with Teflon 850-204 primer and baked at a temperature of 475 F. are mounted on a moving conveyor. They are then carried through a spray booth past a spray gun apparatus from which they receive one coat of Teflon 851-224 enamel, with a dry film thickness of 0.9 mil. After about 1 /2 minutes, the rolls pass through a flash-off zone where they are subjected to warm dry air at the temperature of 180 F. The volatile solvents and approximately 70 percent of the water in the enamel film are removed by this treatment. The conveyor speed is adjusted so that the parts sprayed with the Teflon 851-224 enamel are again presented to the spray guns in about 10 minutes.
• the cycle of spraying and drying is continued for four more passes until a film of about 5.4 mils is attained.
• the rolls are then removed, placed in baskets and air dried in a baking oven at a temperature of about 170 F. After this final drying process is completed, the coated rolls are removed immediately to a fusing oven where the temperature is maintained at about 720 F. The rolls are subjected to this temperature for minutes. They are observed to have a durable non-laminar coatmg.
• a method for manufacturing a tetrafluoroethylene polymer-coated roll for use in a xerographic reproducing apparatus for fixing a resin-based powder image onto a support surface to which the powder is loosely adhering comprising the steps of:
• a method for manufacturing a tetrafluoroethylene polymer coated roll for use in a xerographic reproducing apparatus for fixing a resin-based powder image onto a support surface to which the powder is loosely adhering comprising the steps of:
• tetrafluoroethylene primer in a thickness of from about 0.3 to about 0.7 mil;
• a method for manufacturing a tetrafluoroethylene polymer-coated roll for use in a xerographic reproducing apparatus for fixing a resin-based powder image onto paper to which the powder is loosely adhering comprising the steps of:
• tetrafluoroethylene polymer primer in a thickness of about 0.5 mils

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Fixing For Electrophotography (AREA)
• Rollers For Roller Conveyors For Transfer (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22688033

Family Applications (1)

Country Status (10)

Cited By (12)

Families Citing this family (1)

Family Cites Families (2)

• 0
  • BE BE789728D patent/BE789728A/xx not_active IP Right Cessation
• 1971
  • 1971-10-06 US US00187208A patent/US3776760A/en not_active Expired - Lifetime
• 1972
  • 1972-09-29 DE DE2247821A patent/DE2247821C3/de not_active Expired
  • 1972-09-29 CA CA152,899A patent/CA990149A/en not_active Expired
  • 1972-10-03 GB GB4547572A patent/GB1410025A/en not_active Expired
  • 1972-10-04 CH CH1443872A patent/CH597633A5/xx not_active IP Right Cessation
  • 1972-10-05 AT AT855072A patent/AT335842B/de not_active IP Right Cessation
  • 1972-10-05 AU AU47469/72A patent/AU465141B2/en not_active Expired
  • 1972-10-05 ZA ZA727133A patent/ZA727133B/xx unknown
  • 1972-10-06 JP JP10058672A patent/JPS5317062B2/ja not_active Expired

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