Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2002-06-27
2003-08-19
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C399S045000, C399S302000, C430S042100
Reexamination Certificate
active
06608641
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to electrostatography and more particularly to an electrophotographic printing apparatus and method for using receiver members having a variety of surfaces including smooth, textured, and rough surfaces.
BACKGROUND OF THE INVENTION
An exemplary modular color printer, such as an electrographic or ink jet copier or printer, includes a number of tandemly arranged imaging-forming modules (see for example, Tombs, U.S. Pat. No. 6,184,911). Such a printer includes two or more single-color image forming stations or modules arranged in tandem and an insulating transport web for moving receiver members such as paper sheets through the image forming stations, wherein a single-color toner image is transferred from an image carrier, i.e., a photoconductor (PC) or an intermediate transfer member (ITM), to a receiver held electrostatically or mechanically to the transport web, and the single-color toner images from each of the two or more single-color image forming stations are successively laid down one upon the other to produce a plural or multicolor toner image on the receiver.
As is well known, a toner image may be formed on a PC by the sequential steps of uniformly charging the PC surface in a charging station using a corona charger, exposing the charged PC to a pattern of light in an exposure station to form a latent electrostatic image, and toning the latent electrostatic image in a development station to form a toner image on the PC surface. The toner image may then be transferred in a transfer station directly to a receiver, e.g., a paper sheet, or it may first be transferred to an ITM and subsequently transferred to the receiver. The toned receiver is then moved to a fusing station where the toner image is fused to the receiver by heat and/or pressure.
In a digital electrophotographic copier or printer, a uniformly charged PC surface may be exposed pixel by pixel using an electro-optical exposure device comprising light emitting diodes, such as for example described by Y. S. Ng et al., Imaging Science and Technology, 47th Annual Conference Proceedings (1994), pp. 622-625.
A widely practiced method of improving toner transfer is by use of so-called surface treated toners. As is well known, surface treated toner particles have adhered to their surfaces sub-micron particles, e.g., of silica, alumina, titania, and the like (so-called surface additives or surface additive particles). Surface treated toners generally have weaker adhesion to a smooth surface than untreated toners, and therefore surface treated toners can be electrostatically transferred more efficiently from a PC or an ITM to another member.
As disclosed in the Rimai et al. patent (U.S. Pat. No. 5,084,735) and in the Zaretsky and Gomes patent (U.S. Pat. No. 5,370,961), use of a compliant ITM roller coated by a thick compliant layer and a relatively thin hard overcoat improves the quality of electrostatic toner transfer from an imaging member to a receiver, as compared to a non-compliant intermediate roller.
A receiver carrying an unfused toner image may be fused in a fusing station in which a receiver carrying a toner image is passed through a nip formed by a heated compliant fuser roller in pressure contact with a hard pressure roller. Compliant fuser rollers are well known in the art. For example, the Chen et al. patent (U.S. Pat. No. 5,464,698) discloses a toner fuser member having a silicone rubber cushion layer disposed on a metallic core member, and overlying the cushion layer, a layer of a cured fluorocarbon polymer in which is dispersed a particulate filler. Also, in the Chen et al. patent application (U.S. Patent application Ser. No. 08/879,896) is disclosed an improved compliant fuser roller including three concentric layers, each of which layers includes a particulate filler.
An electrophotographic process for non-electrostatic transfer of a toned image from a photoconductive imaging member using an intermediate transfer roller with applied heat and pressure is disclosed in the Y. S. Ng et al. patent (U.S. Pat. No. 5,110,702). This process may be used for producing high-quality toner images on rough paper (paper roughness not defined in the Ng et al. patent), and full color images may be made by successive registered transfers of color separation toner images to form a composite toner color image on a receiver. The process suffers from a disadvantage in that prolonged exposure to heat by contact with the intermediate transfer roller can have a deleterious effect upon the life of the photoconductive imaging member.
According to the Dalal et al. patent (U.S. Pat. No. 5,999,201), an electrostatographic imaging method suitable for making high quality toner images on a rough recording sheet such as a rough paper employs electrostatic transfer of a sub-monolayer toner image from an imaging member to a compliant intermediate transfer member, followed by heating the toner image at a filming station, and subsequently transfusing the filmed toner image from the intermediate transfer member to a recording sheet (paper roughness not characterized quantitatively). Color images may be made by forming a composite film on the ITM from successive registered transfers of color separation toner images to the ITM, using the filming station after each transfer, with the composite film being subsequently transfused to a receiver. This method of making a full color image is more cumbersome than conventional methods employing intermediate transfer, i.e., in which a filming station is not used.
In common parlance or usage, paper roughness is an ill-defined quantity and has a subjective meaning related to the context. Thus, in ordinary speech one can speak of a “rough uncoated paper” in comparison to a “rough coated paper”, with the latter being generally perceived as being quite smooth. Similarly, a “smooth uncoated paper” might be described or perceived as quite rough. For objective comparisons of roughness or smoothness, it is necessary to have resort to various techniques which have been developed for measuring surface contour parameters, e.g., of papers.
A printing medium having predetermined physical characteristics suitable for color xerographic printing, including paper smoothness, is disclosed in the Foley et al. patent (U.S. Pat. No. 5,935,689). This patent relates to usage of a base paper having a smoothness of less than or equal to about 110 Hagerty units. In common parlance or usage, a smoothness of less than about 120 Hagerty units would generally represent a quite smooth paper. Certain papers, according to U.S. Pat. No. 5,935,689, are not intended for electrophotographical printing. These excluded classes are known in the art as “Kraft”, “Tissue”, “Multiboard”, “Corrugated Medium” and “Roofing” papers. Smoothness of paper or other receiver can be related to a surface roughness parameter and may be measured by a variety of techniques, including the Sheffield method, the Bekk method, surface photomicrography, the Gardner gravure method, the Brush surface analyzer, and the Chapman method, all of which are briefly described in, for example, Mead Paper Knowledge (Mead Corporation, Chillicothe, Ohio, first edition, 1990, pp. 164-166). See also TAPPI Test Methods, 1994-1995, published by TAPPI Press, Atlanta, Ga. The Sheffield method in particular is widely used, and is described in TAPPI publication T 538 om-88. Commercial instruments are available, such as Model 538 Paper Smoothness Tester from Hagerty Technologies, Inc., of Queensbury, N.Y., as well as the Sheffield Paper Gage, available from Testing machines Inc., of Amityville, N.Y. The Sheffield surface roughness parameter and unit of roughness is described in, for example, G. A. Hagerty et al., TAPPI Journal, January 1998, pp. 101-106. According to U.S. Pat. No. 5,935,689, Sheffield units and Hagerty units are interchangeable terms. Sheffield units are usually referred to in the literature and are used henceforth herein.
The Kawabata et al. patent (U.S. Pat. No. 5,905,925) discloses apparatus for forming electrophotographicall
Alexandrovich Peter Steven
Allen Richard George
Aslam Muhammed
Chen Jiann-Hsing
Herrick Diane M.
Kessler Lawrence P.
Nexpress Solutions LLC
Pendegrass Joan
LandOfFree
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