Electrophotography – Image formation – Transfer
Reexamination Certificate
2000-12-04
2002-10-08
Tran, Hoan (Department: 2852)
Electrophotography
Image formation
Transfer
C399S308000
Reexamination Certificate
active
06463248
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electrostatographic printing machines, and more particularly to an electrostatographic printing machine wherein toner images deposited on an intermediate belt are transferred with a high percentage of efficiency to a transfuse belt used for simultaneously transferring and fusing toner images to various substrate media such as plain paper.
BACKGROUND OF THE INVENTION
Electrostatographic printers are known in which a single color toner image is electrostatically formed on a charge retentive member such as a photoreceptor drum or belt. The toner image is directly transferred to a receiving substrate, typically paper or other suitable print receiving material. The toner image is subsequently fused or affixed to the substrate, usually by the simultaneous application of heat and pressure.
In other electrostatographic color printers, a plurality of toner imaging systems each including a charge retentive member are used to create multiple color toner images on a single image receiving member. The color toner images are electrostatically transferred from the charge retentive members to an intermediate transfer member to form a composite toner image on the intermediate transfer member. The intermediate transfer member could be an Intermediate Transfer Belt (ITB) or an intermediate transfer drum. The composite toner image is electrostatically transferred to the final substrate. Such systems that use electrostatic transfer to transfer the composite toner image from the intermediate belt to the final substrate and then subsequently fix the image on the substrate in a fusing system have transfer limitations. For example, there are limitations due to stresses introduced with rougher paper stock, foils, paper moisture content variations, etc. Also, the need to electrostatically transfer a fully layered color composite toner image to the substrate creates additional high stresses for electrostatic transfer. Stressful system conditions can include, for example, systems that use papers at wide ranges of relative humidity, and systems that create images on a large range of paper size and thickness. Such stresses can adversely affect transfer due to their effect on the electrostatic transfer fields, and they can also have significant effect on paper transport.
In addition with direct transfer to paper from an imaging module, is fibers, talc and other particulate debris or chemical contaminants can readily transfer from the paper to the imaging modules during direct contact in the electrostatic transfer zones. This tends to contaminate the imaging medium, development systems, cleaner systems, etc., and can lead to early failure of the such systems. This is especially true for certain stress inherent paper types including, for example, certain types of recycled papers. Due to all these and other problems, systems that use direct transfer to the final media generally have narrow media latitude for obtaining and/or for maintaining high print quality.
Alternatively, in another prior art printer, a toner image is formed on a photoreceptor. The toner image is transferred to a single intermediate transfer member usually referred to as a transfuse member. The transfuse member generally simultaneously transfers and fuses the toner image to a substrate. The use of a single transfer member in a transfuse system can result in high transfer efficiency of background toner on the photoreceptor to the substrate due to high adhesion between the toner and typical materials used for the transfuse member, such as silicone materials. In addition, oil oligomer is generally present or else added onto silicone or other materials used for transfuse members to assist toner release to paper under the high temperature conditions used for eventual transfer and fix of the image from the transfuse member to the final receiver substrate. The photoreceptor can be contaminated by heat and oil on the transfuse member via the transfer nip.
To overcome some of the deficiencies of these single transfer and double-transfer arrangements, prior systems have employed two transfer belts. Toner images are formed on photoreceptors and transferred to a first or intermediate transfer belt. The toner images are subsequently transferred to a second transfer member such as a transfuse belt.
Transfer of toner images has been addressed in many different ways as depicted in the patents noted below and incorporated herein by reference. In addition to possibly having some relevance to the question of patentability of the present invention, these references, together with the detailed description to follow, may provide a better understanding and appreciation of the present invention.
U.S. Pat. No. 6,088,565 granted to Jia et al on Jul. 11, 2000, discloses an electrostatographic printing machine that has multiple toner image producing stations, each forming a developed toner image of a component color. The developed toner images are electrostatically transferred at the first transfer nip to an intermediate transfer member to form a composite toner image thereon. Rheological assisted electrostatic transfer transfers the composite toner image at a second transfer nip to a transfuse member. The transfuse member preferably has improved conformability and other properties for improved transfusion of the composite toner image to a substrate. The transfuse member is maintained above the glass transition temperature of the composite toner image at the second transfer nip. The composite toner image and the substrate are brought together in a third transfer nip to simultaneously transfer the composite toner image and fuse the composite toner image to the substrate to form a final document.
U.S. Pat. No. 5,119,140 granted to Berkes et al on Jun. 2, 1992 discloses a method and apparatus wherein very efficient transfer of low toner masses from an intermediate image receiving member without degradation of high toner mass transfer is achieved using DC pretransfer corotron treatment of the toner on the intermediate followed by biased roll transfer to plain paper. U.S. Pat. No. 4,341,455 (Fedder), discloses an apparatus for transferring magnetic and conducting toner from a dielectric surface to plain paper by interposing a dielectric belt mechanism between the dielectric surface of an imaging drum and a plain paper substrate such that the toner is first transferred to the dielectric belt and subsequently transferred to a plain paper in a fusing station. The dielectric belt is preferably a material such as Teflon or polyethylene to which toner particles will not stick as they are fused in the heat-fuser station.
U.S. Pat. No. 5,612,773 granted to Berkes et al Mar. 18, 1997 discloses a transfusing member having a compression layer comprised of a highly conformable, low durometer material with a low surface free energy. The transfusing member forms a first transfer nip characterized by a first pressure with a photoreceptive surface and a second transfer nip characterized by a second pressure, which is of the same order of magnitude as the first pressure, with a backup roller.
U.S. Pat. No. 5,805,967 granted to DeBock et al on Sep. 8, 1998 discloses single-pass, multi-color electrostatographic printer has a transfer member that is driven along a continuous path. Toner images of different colors are simultaneously electrostatically deposited in powder form in registration with each other on the transfer member to form a multiple-layered toner image. The substrate is fed into contact with the transfer member for transfer of the multiple-layered toner image to at least one face of the substrate. The printer includes a heater for the multiple-layered toner image on the transfer member in advance of the transfer of the image to the substrate, and cooling capability for the transfer member following the transfer of the multiple toner image to the substrate, to a temperature below the glass transition temperature, T
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of the toner, prior to deposition of further toner images on the transfer member. The second transfer member is coo
Fletcher Gerald M.
Jia Nancy Y.
Palazzo E. O.
Tran Hoan
Xerox Corporation
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