Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-09-20
2003-04-29
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S450000, C528S031000, C524S588000, C399S333000, C492S056000, C492S059000
Reexamination Certificate
active
06555237
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electrostatographic printing and/or reproduction devices, and more particularly to fuser apparatus comprising a donor roller having a polymeric surface layer thereon which is release agent swellable and resistant to toner contamination. The fuser apparatus is particularly useful for fusing toners prepared with relatively low-melting polymeric binder resins, such as polyester resins, employed in process color applications and/or high-speed printing or reproduction processes.
BACKGROUND OF THE INVENTION
In the process of electrophotography, a light image of an original document to be printed or copied is typically recorded by either digital or analog means in the form of an electrostatic latent image upon a photosensitive member with subsequent rendering to make the latent image visible by application of electrostatically charged marking particles, commonly referred to as toner. The residual toner image can be either fixed directly upon the photosensitive member, or transferred from the photosensitive member to another support or receiver member, such as a sheet of plain paper, with subsequent affixing of the toner image thereto.
In order to fix or otherwise fuse the toner material onto a support member permanently, it is generally necessary to apply heat so as to elevate the toner material to a temperature at which constituents of the toner material coalesce and become tacky. This action causes the toner to flow to some extent into the fibers or pores of the support member or to otherwise adhere to the surface thereof. Thereafter, as the toner material cools, solidification occurs causing the toner material to be bound firmly to the receiver.
One method for thermal fusing of toner images onto a supporting substrate has been to pass the receiver with an unfused toner image thereon between a toning nip formed by a pair of opposed roller members that are in contact with each other, wherein at least one of the roller members is heated. During operation of a fusing system of this type, the receiver to which the toner image is electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the fuser roller thereby to affect heating of the toner image within the nip. Typical of such fusing devices are two roller systems wherein a fuser roller is coated with an abhesive material, such as a silicone rubber; other low surface energy elastomers, such as a Viton® fluoroelastomers available from E. I. DuPont De Nemours of Wilmington, Del.; or other low surface energy material, such as tetrafluoroethylene polymer resins like, for example, Teflon® resins also sold by DuPont. Silicone elastomers generally used to form a surface layer of the fuser member can be classified into three groups according to the vulcanization method and temperature employed to form such layer, i.e., room temperature vulcanization type silicone rubbers referred to as RTV silicone rubber; liquid silicone rubber referred to as LSR silicone rubber; and high temperature vulcanization type silicone rubber referred to as HTV rubber. These types of silicone elastomers are commercially available.
In the foregoing fusing systems, however, since the toner image is tackified by heat it frequently happens that a part of the image carried on the receiver will be retained by the heated fuser roller and not penetrate into the receiver surface. This tackified material can stick to the surface of the fusing roller and come in contact with a subsequent receiver sheet bearing another toner image to be fused. Thus, a tackified image which has been partially removed from a first sheet, may thereafter transfer to a subsequent second sheet in non-image portions of the second sheet. In addition, a portion of the tackified image of the second sheet may also adhere to the heated fuser roller. In this way and with the fusing of subsequent sheets bearing toner images, the fuser roller can eventually become thoroughly contaminated and unusable, thereby requiring replacement of the fuser roller itself. In addition, since the fuser roller continues to rotate when there is no substrate bearing a toner image to be fused, toner that may be adhered to the fuser roller can be transferred from the fuser roller to the pressure roller, and also to other rollers and components associated with the fuser system, thereby contaminating the overall fuser system. The foregoing conditions are referred to generally in the printing/copying art as “offset”. Attempts have been made to control heat transfer to the toner and thereby control offset. However, even with abhesive surfaces provided by the silicone elastomers and the other materials mentioned hereinabove, this has not been entirely successful.
It has also been proposed to provide toner release agents such as silicone oil, and in particular poly(organosiloxane) oils like poly(dimethylsiloxane), that are applied to the surface of the fuser roller to act as a polymeric release agent and thereby reduce offset. The use of such release agents is reported, for example, in U.S. Pat. Nos. 3,964,431 and 4,056,706, the teachings of which are incorporated herein by reference. These release agents possess a relatively low surface energy and have been found generally suitable for use in a heated fuser roller environment. In practice, a thin layer of poly(organosiloxane) oil (also referenced as silicone oil hereinafter) release agent is applied to the surface of the heated fuser roller to form an interface between the fuser roller surface and the toner image carried on the support material. Thus, a low surface energy, easily parted layer is presented to the toners that pass through the fuser toning nip and thereby reduces the amount of toner which offsets to the fuser roller surface.
Some more recent developments in fuser rollers, polymeric release agents, and fusing systems are described in U.S. Pat. Nos. 4,264,181; 4,257,699; and 4,272,179, the teachings of which are also incorporated herein by reference. These patents describe fuser rollers and methods of fusing thermoplastic resin toner images to a substrate, wherein a poly(organosiloxane) type release agent having functional groups is applied to the surface of the fuser roller. The fuser roller employed generally consists of a base member having an elastomeric surface with a metal-containing filler material incorporated therein, wherein the elastomeric surface has been cured with a curing agent. Exemplary of such fuser rollers is an aluminum base member with a poly(vinylidenefluoride-hexafluoropropylene) copolymer (such as a Viton® type fluoroelastomer available from DuPont) cured with bisphenol curing agent and having lead oxide filler particles dispersed therein, and the fusing system generally utilizes a functionalized polyorganosiloxane oil as a polymeric release agent. In the disclosed fusing processes, the polymeric release agents have functional groups (also designated as chemically reactive functional groups) which are said to “interact” with the metal-containing filler dispersed in the elastomer material of the fuser roller surface to form a thermally stable film. The film is said to release thermoplastic resin toner or otherwise hinder the thermoplastic resin toner from contacting the elastomer material of the fuser roller surface so as to reduce toner offset thereon. A metal oxide, metal salt, metal alloy or other suitable metal compound filler dispersed in the elastomer or resin on the fuser roller surface is said to interact with the functional groups of the polymeric release agent to create this condition. Preferably, the metal-containing filler materials do not cause degradation of or have any adverse effect upon the polymeric release agent having functional groups. Because of the interaction between the elastomer having a metal containing filler and the polymeric release agent having functional groups, excellent release and the production of high quality copies are said to be obtained.
In the foregoing patents, the interaction of the functional
Aslam Muhammed
Chen Jiann Hsing
Pavlisko Joseph A.
Wu Fangsheng
Moore Margaret G.
NexPress Solutions LLC
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