Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-12-13
2004-06-15
Thomas, Alexander S. (Department: 1772)
Electrophotography
Image formation
Transfer
C428S058000, C474S253000, C474S254000
Reexamination Certificate
active
06751435
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to transfer members useful in electrostatographic, including digital apparatuses. In specific embodiments, the present invention is directed to seamed or seamless members. In embodiments, the present invention relates to xerographic component imageable seamed or seamless members comprising a charge transport layer. In embodiments, the charge transport layer may be a substrate, or may be a layer positioned on a substrate. In an embodiment, the charge transport layer comprises a charge transport molecule, an oxidized charge transport molecule, or mixtures thereof. The member, in embodiments wherein a seam is present, allows for image transfer at the seam, which cannot be accomplished with known seemed belts. Image transfer is accomplished partly because the present layer possesses the desired conductivity and release properties required for sufficient transfer. More specifically, in embodiments, the layer overcomes the narrow conductivity latitude problem, because the layer material provides controlled conductivity at changes in relative humidity, temperature and electrical cycling. In embodiments, the member is easily fabricated into a belt configuration due to the unique properties of the layer, which can be welded to form a seamed belt by ultrasonic means or by using solvent bonding or by heat fusion techniques. The charge transport layers can be manufactured with ease at high yields, also because the conductivity can be achieved reproducibly. In addition, the layers have many advantages over known layers such as the fact that they are stable over a wide range of changes, are frequency independent, are tunable, have homogeneous conductivity, have excellent wear resistance, exhibit low creep compliance under constant applied belt tension, and high dielectric strength.
In a typical electrostatographic reproducing apparatus such as an electrophotographic imaging system using a photosensitive member, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of a developer mixture. One type of developer used in such printing machines is a liquid developer comprising a liquid carrier having toner particles dispersed therein. Generally, the toner is made up of resin and a suitable colorant such as a dye or pigment. Conventional charge director compounds may also be present. The developer material is brought into contact with the electrostatic latent Image and the colored toner particles are deposited thereon in image configuration. In dry xerographic processes, the developer consists of polymer coated magnetic carrier beads and particles of thermoplastic toner materials with opposite tribo polarity relative to the carrier beads.
The developed toner image recorded on the imaging member surface is transferred to an image receiving substrate such as paper via an intermediate transfer member. The toner particles may be transferred by heat and/or pressure to an intermediate transfer member, or more commonly, the toner image particles may be electrostatically transferred to the intermediate transfer member by means of an electrical potential between the imaging member and the intermediate transfer member. After the toner has been transferred to the immediate transfer member, it is then transferred to the image receiving substrate, for example by contacting the substrate with the toner image on the intermediate transfer member under heat and/or pressure.
Employing intermediate transfer members enable high throughput at modest process speeds. In four-color photocopier or printer systems, the intermediate transfer member also improves registration of the final color toner image. In such systems, the four component colors of cyan, yellow, magenta and black may be synchronously developed onto one or more imaging members and transferred in registration onto an intermediate transfer member at a transfer station.
In electrostatographic printing and photocopy machines in which the toner image is transferred from the intermediate transfer member to the image receiving substrate, it is desired that the intermediate transfer of the toner particles from the transfer member to the image receiving substrate be substantially 100 percent. Less than complete transfer to the image receiving substrate results in image degradation and low resolution. Complete transfer is particularly desirable when the imaging process involves generating full color images since undesirable color deterioration in the final colors can occur when the color images are not completely transferred from the intermediate transfer member.
Thus, it is desirable that the intermediate transfer member surface have excellent release characteristics with respect to the toner particles. Conventional materials known in the art for use as transfer members often possess the strength, conformability and electrical conductivity necessary for use as intermediate transfer members, but can suffer from poor toner release characteristics, especially with respect to higher gloss image receiving substrates.
Polyimide substrate intermediate transfer members in seamless belt form are suitable for high performance applications because of their outstanding mechanical strength and thermal stability, in addition to their good resistance to a wide range of chemicals. However, from manufacturing feasibility and cost considerations, seamless polyimide intermediate belt fabrication is limited only to the size of a 3-pitch belt. Therefore, in order to overcome the high cost of manufacturing unseamed polyimide belts has led to the introduction of a seamed belt.
In the electrostatic transfer applications, use of a seamed intermediate transfer polyimide intermediate transfer member belt results in insufficient transfer in that the developed image occurring on the seam is not adequately transferred. This incomplete transfer is partially the result of the difference in seam height to the rest of the belt. A “bump” is formed at the seam, thereby hindering transfer and mechanical performance. Also, incomplete image transfer at the seam area is largely the result of the composition and property discontinuity at the seam joint. Specifically, an adhesive material different from the polyimide substrate is normally necessary for bonding the two opposite mated ends of a polyimide sheet into a seamed intermediate transfer belt. The reason a different adhesive material is needed is because polyimide is itself a thermoset plastic, and therefore, cannot be welded into a seam joint by conventional ultrasonic welding processes. Polyimides can also not be welded into a seam by heat fusion techniques, by solvent bonding, or the like bonding means. The development of puzzle cut seams has increased the quality of image transfer somewhat, by decreasing the seam height, thereby allowing smooth cycling. However, even with the improvements made with puzzle cut seams, quality imaging in the seamed area is not obtainable at present due, in part, to contrast in transfer caused by differences in electrical and release properties between known seaming adhesives and substrates, because perfect matching of properties is difficult to achieve. Further, known polyimide substrates and puzzle cut seams have many problems, including weak seam rupture strength, the presence of non-imageable seam areas, narrow conductivity latitude, and electrical property easily affected by environmental conditions. In addition, polyimide is not easily fabricated into intermediate transfer member substrates, because it involves very complex material compounded processes.
U.S. Pat. No. 5,549,193 relates to an endless flexible seamed belt comprising puzzle cut members, wherein at least one receptacle has a substantial depth in a portion of the belt material at the belt ends.
U.S. Pat. No. 5,721,032 discloses a puzzle cut seamed belt having a strength-enhancing strip.
U.S. Pat. No. 5,487,707 discloses a puzzle cut seamed b
Foley Geoffrey M. T.
Freeman T. Edwin
Horgan Anthony M.
Hsieh Bing R.
Mishra Satchidanand
Bade Annette L.
Thomas Alexander S.
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