Stock material or miscellaneous articles – Composite – Of fluorinated addition polymer from unsaturated monomers
Reexamination Certificate
1999-11-29
2004-11-23
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Composite
Of fluorinated addition polymer from unsaturated monomers
C428S329000, C428S422000, C526S242000, C526S250000, C526S253000, C526S255000, C524S430000, C524S431000, C524S432000
Reexamination Certificate
active
06821626
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fuser members useful for heat-fixing a heat-softenable toner material to a substrate. More particularly, the invention relates to materials usable as a toner release layer in a fuser member.
BACKGROUND OF THE INVENTION
Heat-softenable toners are widely used in imaging methods such as electrostatography, wherein electrically charged toner is deposited imagewise on a dielectric or photoconductive element bearing an electrostatic latent image. Most often in such methods, the toner is then transferred to a surface of another substrate, such as, e.g., a receiver sheet comprising paper or a transparent film, where it is then fixed in place to yield the final desired toner image.
When heat-softenable toners, comprising, e.g., thermoplastic polymeric binders, are employed, the usual method of fixing the toner in place involves applying heat to the toner once it is on the receiver sheet surface to soften it and then allowing or causing the toner to cool.
One such well-known fusing method comprises passing the toner-bearing receiver sheet through the nip formed by a pair of opposing rolls, at least one of which (usually referred to as a fuser roll) is heated and contacts the toner-bearing surface of the receiver sheet in order to heat and soften the toner. The other roll (usually referred to as a pressure roll) serves to press the receiver sheet into contact with the fuser roll. In some other fusing methods, the configuration is varied and the “fuser roll” or “pressure roll” takes the form of a flat plate or belt. The description herein, while generally directed to a generally cylindrical fuser roll in combination with a generally cylindrical pressure roll, is not limited to fusing systems having members with those configurations. For that reason, the term “fuser member” is generally used herein in place of “fuser roll” and the term “pressure member” in place of “pressure roll”.
The fuser member usually comprises a rigid core covered with a resilient material, which will be referred to herein as a “base cushion layer.” The resilient base cushion layer and the amount of pressure exerted by the pressure member serve to establish the area of contact of the fuser member with the toner-bearing surface of the receiver sheet as it passes through the nip of the fuser member and pressure members. The size of this area of contact helps to establish the length of time that any given portion of the toner image will be in contact with and heated by the fuser member. The degree of hardness (often referred to as “storage modulus”) and stability thereof, of the base cushion layer are important factors in establishing and maintaining the desired area of contact.
In some previous fusing systems, it has been advantageous to vary the pressure exerted by the pressure member against the receiver sheet and fuser member. This variation in pressure can be provided, for example in a fusing system having a pressure roll and a fuser roll, by slightly modifying the shape of the pressure roll. The variance of pressure, in the form of a gradient of pressure that changes along the direction through the nip that is parallel to the axes of the rolls, can be established, for example, by continuously varying the overall diameter of the pressure roll along the direction of its axis such that the diameter is smallest at the midpoint of the axis and largest at the ends of the axis, in order to give the pressure roll a sort of “bow tie” or “hourglass” shape. This will cause the pair of rolls to exert more pressure on the receiver sheet in the nip in the areas near the ends of the rolls than in the area about the midpoint of the rolls. This gradient of pressure helps to prevent wrinkles and cockle in the receiver sheet as it passes through the nip. Over time, however, the fuser roll begins to permanently deform to conform to the shape of the pressure roll and the gradient of pressure is reduced or lost, along with its attendant benefits. It has been found that permanent deformation (alternatively referred to as “creep”) of the base cushion layer of the fuser member is the greatest contributor to this problem.
Particulate inorganic fillers have been added to base cushion layers to improve mechanical strength and thermal conductivity. High thermal conductivity is advantageous when the fuser member is heated by an internal heater, so that the heat can be efficiently and quickly transmitted toward the outer surface of the fuser member and toward the toner on the receiver sheet it is intended to contact and fuse. High thermal conductivity is not so important when the roll is intended to be heated by an external heat source.
Optimal metal-particle filled elastomer fuser members have long been sought. At one time, it was predicted that:
“The metal of the metal-containing filler dispersed in the elastomer may be easily selected by one skilled in the art without undue experimentation by testing the metal-containing filler, such as a metal, metal alloy, metal oxide, metal salt or other metal compound, in an elastomer. The general classes of metals which are applicable to the present invention include those metals of Groups 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6b, 7b, 8 and the rare earth elements of the Periodic Table.” (U.S. Pat. No. 4,264,181 to Lentz et al, column 10, lines 42-53; also U.S. Pat. No. 4,272,179 to Seanor, column 10, lines 45-54.)
This prediction of easy selection of the metal for a metal-containing filler has proven false in the face of later efforts in the art. A metal-containing filler which provides good results in one elastomer may provide very poor results in another elastomer, even if the elastomers are very similar.
U.S. Pat. No. 4,515,884 to Field et al, discloses a fuser member which utilizes metal oxide filled polydimethylsiloxane. The metal oxides are iron oxide and tabular alumina. Calcined alumina is described as being unsuitable per se. (column 9. line 50-column 10 line 47)
In U.S. Pat. No. 4,264,181 to Lentz et al, good results were obtained when lead oxide was used as a filler in various fluorocarbon elastomers (Viton E430™, Viton E60C™, Viton GH™; Examples X, XI, XII). U.S. Pat. No. 5,017,432 to Eddy et al, on the other hand, teaches against the use of lead oxide in similar fluorocarbon elastomers (for example, Viton GF™) on the basis that it would produce an unacceptable fuser member. In these fluoroelastomers, cupric oxide is preferred.
U.S. Pat. No. 4,272,179 to Seanor and U.S. Pat. Nos. 4,264,181 and 4,257,699 to Lentz teach the use, as a release oil, of a polydimethylsiloxane that incorporates mercapto functional groups. These patents indicate that lead oxide filler in the outer elastomer layer interacts with the mercapto functionalized PDMS fluid to yield a release film on the surface of the fuser member.
Preparation of metal containing elastomers remains problematic. U.S. Pat. No. 4,515,884 to Field et al, and U.S. Pat. No. 5,017,432 to Eddy et al, cite large numbers of critical features or important aspects of their metal containing elastomers: choice of material (Field, column 9, lines 50-65 and column 10, lines 24-25), interaction of filler surface and elastomer (Field, column 9, lines 32-65), particle size (Field, column 10, lines 1-8 and lines 25-30; Eddy, column 9, line 65-column 10, line 3), concentration of metal-filler (Field, column 10, lines 9-23 and lines 31-47), capability of interacting with functional groups of release agent (Eddy, column 9, lines 26-30), reactivity of the metal filler with the elastomer (Eddy, column 9, lines 33-43), and acid-base characteristics of the metal filler (Eddy, column 9, lines 43-56). The lists of critical features and important aspects in Field and Eddy do not fully correlate. It is unknown whether this difference represents real differences in material characteristics or only differences in techniques and analysis.
In electrophotographic fuser systems, fuser members are commonly made with an overcoat layer of polysiloxane elastomer, polyfluorocarbon resin, or polyfluorocarbon elastomer.
Polysiloxane e
Boulatnikov Nataly
Davis Stephen V.
Pickering Jerry A.
Chen Vivian
NexPress Solutions LLC
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