Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1998-02-27
2001-03-27
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S405000, C428S421000, C428S447000, C428S448000, C428S451000, C399S333000, C492S056000
Reexamination Certificate
active
06207243
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to heat fusing members and methods of making same. More particularly, it relates to an improved fuser roller surface that decreases toner offset and abrasion and increases toner release and thermal conductivity.
BACKGROUND OF THE INVENTION
In electrophotographic fuser systems, fuser roller overcoats are made with layers of polydimethylsiloxane (PDMS) elastomers, fluorocarbon resins and fluorocarbon elastomers. PDMS elastomers have low surface energy and relatively low mechanical strength, but is adequately flexible and elastic and can produce high quality fused images. After a period of use, however, the self-release property of the roller degrades and offset begins to occur. Application of a PDMS oil during use enhances the release property of the fuser roller surface but shortens roller life due to oil swelling. Fluorocarbon resins like polytetrafluoro-ethylene (PTFE) have good release property but less flexibility and elasticity than PDMS elastomers. Fluorocarbon elastomers, such as Viton™ and Fluorel™, are tough, flexible, resistant to high temperatures, durable and do not swell, but they have relatively high surface energy and poor thermal conductivity.
Particulate inorganic fillers have been added to fluorocarbon elastomers and silicone elastomers to increase mechanical strength and thermal conductivity. High thermal conductivity is an advantage because heat needs to be efficiently and quickly transmitted from an internally heated core to the outer surface of the fuser roller to fuse the toners and yield the desired toner images. However, incorporation of inorganic fillers to improve thermal conductivity has a major drawback: it increases the surface energy of fuser roller surface and also increases the interaction of the filler with the toner and receiver. After a period of use, the toner release properties of the roller degrade and toner offset begins to occur due to roller wear and weak interaction between the filler and the polymer matrix. It would be desirable to provide a fuser member having a fluorocarbon elastomer overcoat layer containing thermally conductive inorganic fillers, but which still has a moderately low surface energy and good toner release property. In addition, it should be compatible with the functionalized polymeric release agent employed during fixing process.
Fuser members of fluorocarbon elastomer containing inorganic filler are disclosed, for example, in U.S. Pat. No. 5,464,698 to Chen et al. which describes fuser rollers having a surface layer comprising fluorocarbon elastomer and tin oxide fillers. The fillers provide active sites for reacting the mercapto-functional polydimethylsiloxane. However, the inorganic fillers are untreated and remain highly reactive with the toner and charge control agent, and this is undesirable.
U.S. Pat. No. 5,595,823 to Chen et al. describes fuser rollers having a surface layer comprising fluorocarbon elastomer and aluminum oxide fillers which also are untreated and are prone to high reactivity with toner and charge control agent which, again, is undesirable.
U.S. Pat. No. 5,017,432 to Eddy et al. describes a fluorocarbon elastomer fuser member which contains cupric oxide to interact with the polymeric release agent and provide an interfacial barrier layer.
Fuser members of condensation-crosslinked PDMS elastomers filled with metal oxides are disclosed, for example, in U.S. Pat. No. 5,401,570 to Heeks et al. This patent describes a silicone rubber fuser member containing aluminum oxide fillers which react with a silicone hydride release oil.
U.S. Pat. No. 5,480,724 to Fitzgerald et al. discloses tin oxide fillers which decrease fatigue and creep (or compression) of the PDMS rubber during continuous high temperature and high stress (i.e. pressure) conditions.
Some metal oxide filled condensation-cured PDMS elastomers are also disclosed in U.S. Pat. No. 5,269,740 (cupric oxide filler), U.S. Pat. No. 5,292,606 (zinc oxide filler), U.S. Pat. No. 5,292,562 (chromium oxide filler), and U.S. Pat. No. 5,336,596 (nickel oxide filler). All provide good results.
Unfortunately, as fuser rollers wear, the metal oxide fillers become exposed and react not only with the functionalized polymeric release agent, but also with the toner, paper substrate and charge control agent. Such reactions build up debris on the surface of the fuser roller, impairing toner release and reducing the life of the fuser roller. There is therefore a need in the industry for fuser rollers with metal oxide fillers that interact more with the roller material (e.g. fluoroelastomer) so that they are less prone to exposure as the rollers wear. Such fillers must also be compatible with polymeric release agents.
In U.S. patent applications U.S. Ser. Nos. 08/962,129; 08/961,838; and 08/962,108, incorporated herein in their entirety, Tan et al. taught that metal oxide particles that are treated with a coupling agent having amino functional groups can decrease abrasion of the fuser member overcoat and also enhance fuser/toner release. It is believed that the amino functional groups on the coupling agent interact with the fluorocarbon polymers and bond with them.
There is the need, however, to have different coupling reactive chemistry other than the amino-functionalized coupling reagents taught by Tan et al.
SUMMARY OF THE INVENTION
The present invention provides an alternative to amino functionalized coupling reagents by providing: a fuser member comprising a support and coated thereon, a fluoroelastomer layer comprising a metal oxide filler selected from aluminum oxide, cupric oxide, and mixtures thereof, said filler being associated with a mercapto-functionalized silane coupling agent.
The present invention also provides a method of making a fuser member comprising the steps of: providing a cylindrical core; compounding a fluoroelastomer with a metal oxide filler selected from aluminum oxide, cupric oxide, and mixtures thereof, the filler being associated with a mercapto-functionalized silane coupling agent; coating the fluoroelastomer on the cylindrical core; and curing the fuser member.
Metal oxide fillers which have been thus modified can interact with fluorocarbon polymers and bond with them. Such fillers also help to wet the surface and thereby facilitate compounding. The fuser member of the invention greatly improves fuser/toner release, toner offset on the roller surface and decreases abrasion of the fuser member overcoat. The invention provides an effective, durable fuser roller and high quality copies at high speed.
The toner/fuser release can be further improved by applying to the outermost layer of the fuser member an effective amount of a polymethyldisiloxane (PDMS) release agent that, optionally, includes at least one functional group reactive with the fluoroelastomer, followed by incubation at an elevated temperature. While not wishing to be bound by the proposed theory, it is believed that the functional groups on the releasing agent bring about an interaction between filler and release fluid, thereby forming a protective layer between toner and filler.
An additional advantage is that this invention allows for a high percentage of metal oxide fillers in the fluoroelastomer and therefore high thermal conductivity can be achieved. At the same time, critical fuser properties such as release and wear are not sacrificed.
DETAILED DESCRIPTION OF THE INVENTION
The fluorocarbon elastomers used in the invention were prepared according to the method described in commonly owned U.S. Ser. No. 08/805,479 of Chen et al., filed Feb. 25, 1997, titled Toner Fuser Member Having A Metal Oxide Filled Fluoroelastomer Outer Layer With Improved Toner Release and incorporated herein by reference.
In the fuser member of the present invention, the outermost layer comprises a cured fluoroelastomer, preferably a terpolymer of vinylidene fluoride (VF), tetrafluoroethylene (TFE), and hexafluoropropylene (HFP), that includes at least about 21 mole percent HFP and, preferably, at least about 50 mole percent VF. Among
Binga Tonya D.
Chen Jiann-Hsing
Ferrar Wayne T.
Tan Biao
Eastman Kodak Company
Thibodeau Paul
Wells Doreen M.
Zacharia Ramsey
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