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
  • G03G15/2017—Structural details of the fixing unit in general, e.g. cooling means, heat shielding means
  • G03G15/2025—Structural details of the fixing unit in general, e.g. cooling means, heat shielding means with special means for lubricating and/or cleaning the fixing unit, e.g. applying offset preventing fluid
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G2215/00—Apparatus for electrophotographic processes
  • G03G2215/20—Details of the fixing device or porcess
  • G03G2215/2093—Release agent handling devices
  • G03G2215/2096—Release agent handling devices using porous fluoropolymers for wicking the release agent

Definitions

• the present invention relates to the use of a porous polytetrafluoroethylene structure as an oil transfer component for oiling and/or wiping a fuser roll in a copying machine, which term includes plain paper copying and fax machines and laser printers.
• toner images applied to the surface of paper or other recording medium are fixated by application of heat and pressure.
• fixation is accomplished by passing the image-bearing recording medium between a hot thermal fixation roll and a pressure roll.
• the toner material is directly contacted by a roll surface, and a portion of the toner usually becomes adhered to the roll surface.
• the adhered toner material may be redeposited on the recording medium resulting in undesirable offset images, stains, or smears; or in severe cases the recording medium may stick to the adhered toner material on the roll and become wrapped around the roll.
• materials having good release properties such as silicone rubber or polytetrafluoroethylene are often used for the roll surfaces. Although improving performance of the thermal fixation devices, use of silicone rubber or polytetrafluoroethylene roll surfaces alone does not eliminate the problem.
• Another approach is to include release agents with the toner materials, which prevent the toner materials from adhering to the roll surface. These oil-less toners improve the performance of the thermal-fixation devices but again, particularly in the case of high-speed type copying machines, do not completely eliminate the problems associated with toner pick-up and transfer.
• Toner pick-up by the rolls can be controlled by coating the surface of at least one of the rolls with a liquid release agent, such as a silicone oil. It is important that the release liquid be applied uniformly and in precise quantities to the surface of the roll. .Too little liquid or non-uniform surface coverage, will not prevent the toner from being picked up and redeposited on the roll. On the other hand, excessive quantities of the release liquid may cause silicone rubber roll surfaces to swell and wrinkle, thus producing copies of unacceptable quality.
• a liquid release agent such as a silicone oil
• Devices to uniformly meter and coat a release liquid onto copy machine roll surfaces are described in Japanese laid-open patent No. 62-178992. These devices consist of an oil permeation control layer adhered to a thick porous material which serves as a wick or reservoir for supplying oil to the permeation control layer.
• the permeation control layer is typically a porous polytetrafluoroethylene film which has been impregnated with a mixture of silicone oil and silicone rubber followed by a heat treatment to cross-link the silicone rubber.
• the thick porous material to which the permeation control layer is adhered is typically a porous thermosetting resin foam or a felt of No ex (Trademark) fibres, glass fibres, carbon fibres, polytetrafluoroethylene fibres, or any other high temperature fibre.
• Conventional plain paper copiers which use silicone oil as the liquid release agent generally comprise a means for coating the silicone oil onto the fuser roll and also a means for wiping the roll to remove undesirable adhered toner, paper dust and other undesirable material. .
• the coating and wiping functions are performed by a single device.
• a reservoir wick which is generally formed of a Nomex felt, with a cover wick placed over the top of it for metering the flow of oil from the reservoir wick to the fuser roll and also for providing improved wear and distribution characteristics.
• the cover wick is typically a Nomex fabric. It is found, however, that the cover wick has only a limited lifetime, typically lasting for around 60,000 copies before requiring replacement. It would be desirable to have a cover wick which lasts as long as the life of the fuser rollers.
• the oil coating and wiping function is provided by a length of felt, typically formed of Nomex or polytetrafluoroethylene fibres.
• the roll is typically 435 millimetres wide by 1.4 metres long. Whilst the machine is copying, the roll, which is laden with silicone oil, travels past the fuser roll at a speed of about 2cm per hour. This oiling roll applies silicone oil. Also excess toner cleaned from the fuser roll is picked up and carried away on the oiling roll.
• the felt of the oiling roll has a weight of 700 grammes per square metre and a thickness of 1.3 milimetres.
• British published patent application 2242431 (9106768.6) discloses a porous polytetrafluoroethylene structure for use as a filter in industrial filtration.
• the porous polytetrafluoroethylene material is produced by fusing particles of polytetrafluoroethylene such as to form a porous integral network of interconnected particles.
• the disclosure of this patent specification is incorporated herein. The specification is particularly concerned with the filtration of aqueous slurries.
• the present invention envisages the use of a porous polytetrafluoroethylene material such as disclosed in GB 2242431 for use as an oil transfer component for coating or wiping a fuser roll in a copying machine.
• the material is able to withstand the high temperatures (around 200°C) encountered and has excellent mechanical properties and durability in this application.
• one aspect of the invention provides an oil transfer component for coating or wiping a fuser roll in a copying machine which comprises a porous polytetrafluoroethylene structure formed from particles of granular-type polytetrafluoroethylene fused together such as to form a porous integral network of interconnected particles.
• the porous polytetrafluoroethylene (PTFE) structure will generally include a support means for supporting the structure within the copying machine.
• the support means may be in the form of a frame or pair of parallel rods extending along either side of the cover wick strip.
• the porous polytetrafluoroethylene structure may be laminated to a reservoir material acting as a support structure.
• the porous polytetrafluoroethylene structure may also be provided in the form of a roll or may be applied onto a roller formed of an oil reservoir material (such as a foam as disclosed in Japanese 62-178992 or a porous ceramic) which is optionally covered by a felt cover.
• the porous polytetrafluoroethylene structure is in the form of a sheet material, typically of a thickness in the range 50 microns to 750 microns, particularly 100 to 400 microns, and especially 200 to 500 microns.
• the porous polytetrafluoroethylene structure is hydrophobic but has a high affinity for liquid release agents such as silicone oil.
• oil transfer component is to be used for coating the fuser roll, it will generally be supplied pre-loaded with release oil.
• the oil will constitute 20 to 80% by weight of the total weight of the oil transfer component, particularly 40 to 60% by weight.
• the porous polytetrafluoroethylene structure usually has a specific gravity of 0.8 to 1.8, typically 0.9 to 1.2.
• pure non-porous PTFE typically has a specific gravity of 2.16.
• the porous polytetrafluoroethylene structure does not include any filler materials, since these are generally of mineral origin and tend to be of an abrasive nature which would damage the fuser rolls.
• the porous polytetrafluoroethylene structure have a slightly uneven surface texture.
• This surface texture can be obtained by spraying onto a smooth substrate in order to produce the porous PTFE structure. After spraying and heat treating, the porous PTFE may be peeled from the substrate to yield a sheet material which is smooth on the side which was adjacent the substrate and textured on the other side as a result of the spray technique. In use the textured surface is placed adjacent the photocopier roll.
• the surface texture could also be provided by spraying onto a substrate carrying an embossed pattern of ridges, valleys, indentations, protrusions etc. such that the textured surface is provided on the side of the sheet facing the substrate.
• a surface texture on the porous PTFE structure such as by pulsing the laydown of the material, e.g. by using a vibrating doctor-blade.
• the surface of the PTFE could be mechanically embossed e.g. by passage through the nip of embossing rollers.
• the texture is provided by applying a fabric of suitable material (e.g. a Nomex fabric) over the PTFE surface.
• a fabric of suitable material e.g. a Nomex fabric
• the surface texture acts to scrape unused material off the surface of the copier roll and to carry it away in the depressions in the textured surface pattern.
• the porous polytetrafluoroethylene structure of the present invention provides excellent wear characteristics in comparison to conventional materials and does not shed fibres. In the case of an oiling roll, the porous polytetrafluoroethylene structure can be provided much thinner than conventional felts, which allows much longer lengths to be used, whilst maintaining the same oiling and wiping characteristics. There is also reduced frictional drag on the rollers.
• the porous polytetrafluoroethylene structure may be produced as described in patent specification GB 2242431. It is particularly preferred to form the structure from a mixture of particles of different grades of granular-type polytetrafluoroethylene.
• PTFE is produced in two distinct types so-called “granular PTFE” and so-called “fine powder PTFE”. These materials have quite different properties and the present invention is concerned with the former.
• a particularly useful product for use in the present invention comprises 40 to 60% of Teflon (Trademark) resin grade 7A; and 40 to 60% of Teflon resin grade 9B. Teflon resin grades 7A and 9B are available from Du Pont Speciality Polymers Division, Wilmington, U.S.A.
• the porous polytetrafluoroethylene structure is usually prepared by spraying onto a substrate, such as a ceramic tile or sheet of metal.
• Figure 1 shows a conventional PTFE-covered fuser roll 2 and a silicone rubber covered roll 4, which are oiled and wiped by an oil-containing oiling roll or web 6 of porous PTFE wound on a spool 8, which passes around pressure rollers 10, 12 onto take-up spool 14.
• Figure 2 shows a similar arrangement, except that oil is applied to the porous PTFE oiling roll or web by means of an oil supply mechanism 16.
• Figure 3 shows a conventional PTFE covered fuser roll 2 and silicone rubber covered roll 4 to which silicone oil is applied by oil supply mechanism 16, reservoir wick 26, and cover wick 20.
• the cover wick is formed of porous PTFE and is supported on a pair of rods 22, 24.
• Figure 4 shows use of a roller 30 to deliver oil onto the conventional PTFE-covered fuser roller 2. Alternatively, it may contact the silicone rubber covered roller 4.
• the roller has a porous PTFE covering.
• the roller may be pre-oiled, or oil may be supplied into the centre of the roller by an oil supply mechanism.
• FIG. 5 shows a laser printer arrangement.
• An oil-containing felt 40 in channel 42 applies oil to a conventional PTFE-covered fuser roll 2.
• the felt has a porous PTFE covering laminated thereto. Specific Examples of the invention will now be described.
• An oiling assembly for the fuser rolls in a conventional Kodak Ektoprint 850 photocopier comprises a reservoir formed of 1600 gms per square metre Nomex felt of thickness approximately 16mm, and a cover wick comprising a Nomex felt of 400 gms per square metre fitted with side bars for locating the cover wick against the fuser roll (i.e. in the manner of Figure 3).
• a conventional Siemens ND2 photocopying machine comprises an oil-containing oiling roll which oils the fuser roll with silicone oil and also wipes it clean (in the manner of Figure 1) .
• the conventional roll is formed of 700 gms per square metre PTFE felt, of thickness 1.3 mm, 435 mm wide and 1.4 metres long.
• the felt is wound on bakelite spools and the roll has an overall diameter of approximately 63 mm., which represents the maximum allowed according to the photocopying machine construction.
• the oiling roll is advanced at a rate of 2 cm per hour of copying operation, which delivers 1.06 grams/hour to the fuser roll. Typically, the roll requires to be changed three times a month.
• the conventional roll was replaced by a roll of porous polytetrafluoroethylene material (of composition given in Example 1) having the same width.
• the porous polytetrafluoroethylene material had a thickness of 375 microns, a weight of 375 gram/m 2 , and a length of 4.2 metres for the same 63 mm diameter roll. This is three times as long as the conventional roll.
• the oiling roll was advanced at 2 cm per hour of copying operation.
• the roll contained 0.8 grams/cc of silicone oil and provided 1.6 grams/hour to the fuser roller.
• the porous polytetrafluoroethylene material transferred oil well and wiped well and produced prints of consistently high quality. There was no apparent wear nor shedding of material. It is therefore possible to obtain at least three times the lifetime from an oil retention roll of the present invention (up to 30 days of operation) as opposed to the conventional material.
• Certain Cannon, Xerox, Minolta and Konica photocopiers use a thin web of Nomex and polyester having a weight of 25-35 grams/m 2 and a thickness of 0.060 - 0.080 mm (in the manner of Figure 1) .
• a length of 10 - 13 m of the web is wound onto a metal core (roll diameter 31.5mm) and impregnated with an average of 31 grams/m 2 of silicone oil.
• the web is advanced at about 2mm per minute of copier operation, delivering 0.018 grams/min of oil to the fuser roll.
• the standard web may be replaced by a shorter length of porous polytetrafluoroethylene film of the composition of.
• Example 1 The film has a weight of 125 grams/m 2 and a thickness of 0.125 mm. The final diameter of the roll (31.5mm) allows 7.2m of film to be wound onto the core.
• the film holds twice as much oil as the conventional web, and is therefore advanced at half the speed i.e. lmm/min. This provides an increased lifetime for the film of 120 hours, compared to a lifetime of 96 hours for the conventional web.
• the film also has better oil retention properties, eliminating any oil drops; and gives good toner and paper dust adsoirption. Higher fusing temperatures may be used, and there is reduced frictional drag.
• a conventional web of layers of polyester and Nomex in a Siemens ND2 photocopying machine was replaced by a sheet of PTFE as in Example 1 having a layer of woven Nomex fabric bonded to the front face thereof (i.e. the face in contact with the fuser roll) .
• the material performed well and had a lifetime at least three times as long as the conventional web.
• Nomex felt Conventional laser printers use as the oil supply and wiping mechanism a square section length of Nomex felt, typically 2 cm 2 cm x 40 cm (see Figure 5) .
• Nomex felts conventionally suffer from fibre shed and may run dry through lack of oil towards the end of their working life.
• An oil transfer component according to the present invention was produced by laminating a surface sheet of porous polytetrafluoroethylene as used in Example 1 over the surface of the Nomex felt.
• the life of the component was 250,000 copies in comparison to 80,000 with the conventional component.
• This material may also be impregnated with oil for use as a coating/wiping component on a laser printer, or may be used dry as a wiper.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Fixing For Electrophotography (AREA)
• Fats And Perfumes (AREA)
• Coating Apparatus (AREA)
• Laminated Bodies (AREA)
• Lubricants (AREA)
• Cleaning In Electrography (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=10703575

Family Applications (1)

Country Status (11)

Cited By (8)

Families Citing this family (2)

Citations (7)

Family Cites Families (1)

• 1991
  • 1991-10-26 GB GB919122750A patent/GB9122750D0/en active Pending
• 1992
  • 1992-10-26 CA CA002121128A patent/CA2121128A1/en not_active Abandoned
  • 1992-10-26 AU AU28096/92A patent/AU661060B2/en not_active Ceased
  • 1992-10-26 GB GB9222444A patent/GB2261400B/en not_active Expired - Fee Related
  • 1992-10-26 JP JP5507582A patent/JPH07500927A/ja active Pending
  • 1992-10-26 DK DK92921850.1T patent/DK0609318T3/da active
  • 1992-10-26 EP EP92921850A patent/EP0609318B1/en not_active Expired - Lifetime
  • 1992-10-26 WO PCT/GB1992/001958 patent/WO1993008512A1/en active IP Right Grant
  • 1992-10-26 DE DE69213953T patent/DE69213953T2/de not_active Expired - Fee Related
  • 1992-10-26 ES ES92921850T patent/ES2092701T3/es not_active Expired - Lifetime
  • 1992-10-26 AT AT92921850T patent/ATE143152T1/de not_active IP Right Cessation
• 1996
  • 1996-12-11 GR GR960403378T patent/GR3021956T3/el unknown

Patent Citations (7)

Non-Patent Citations (2)

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