Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-10-28
2003-11-25
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272200, C156S272800, C156S275100, C156S304600, C156S308400, C264S345000
Reexamination Certificate
active
06652691
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to a seam treatment process and, more specifically, to a stress release and protrusions elimination process for seams of flexible belts.
Flexible electrostatographic belt imaging members are well known in the art. Typical electrostatographic flexible belt imaging members include, for example, photoreceptors for electrophotographic imaging systems, electroreceptors such as ionographic imaging members for electrographic imaging systems, and intermediate transfer belts for transferring toner images in electrophotographic and electrographic imaging systems. These belts are usually formed by cutting a rectangular sheet from a web containing at least one layer of thermoplastic polymeric material, overlapping opposite ends of the sheet, and joining the overlapped ends together to form a welded seam. The seam extends from one edge of the belt to the opposite edge. Generally, these belts comprise at least a supporting substrate layer and at least one imaging layer comprising thermoplastic polymeric matrix material. The “imaging layer” as employed herein is defined as the dielectric imaging layer of an electroreceptor belt, the transfer layer of an intermediate transfer belt and, the charge transport layer of an electrophotographic belt. Thus, the thermoplastic polymeric matrix material in the imaging layer is located in the upper portion of a cross section of an electrostatographic imaging member belt, the substrate layer being in the lower portion of the cross section of the electrostatographic imaging member belt. Although the flexible belts of interest consist of these mentioned types, nonetheless for simplicity reason, the discussion hereinafter will be focused only on the electrophotographic imaging member belts.
Flexible electrophotographic imaging member belts are usually multilayered photoreceptors that comprise a substrate, an electrically conductive layer, an optional hole blocking layer, an adhesive layer, a charge generating layer, and a charge transport layer and, in some embodiments, an anti-curl backing layer. One type of multilayered photoreceptor comprises a layer of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. A typical layered photoreceptor having separate charge generating (photogenerating) and charge transport layers is described in U.S. Pat. No. 4,265,990, the entire disclosure thereof being incorporated herein by reference. The charge generating layer is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer.
Although excellent toner images may be obtained with multilayered belt photoreceptors, it has been found that as more advanced, higher speed electrophotographic copiers, duplicators and printers were developed, fatigue induced cracking of the charge transport layer at the welded seam area is frequently encountered during photoreceptor belt cycling. Moreover, the onset of seam cracking has also been found to rapidly lead to seam delamination due to fatigue thereby shortening belt service life. Dynamic fatigue seam cracking and delamination also occurs in ionographic imaging member belts and may possibly happen in intermediate transfer belts as well.
The flexible electrophotographic imaging member belts are fabricated from sheets cut from a web. The sheets are generally rectangular in shape. All edges may be of the same length or one pair of parallel edges may be longer than the other pair of parallel edges. The sheets are formed into a belt by joining overlapping opposite marginal end regions of the sheet. A seam is typically produced in the overlapping marginal end regions at the point of joining. Joining may be effected by any suitable means. Typical joining techniques include welding (including ultrasonic), gluing, taping, pressure heat fusing, and the like. Ultrasonic welding is generally the preferred method of joining because is rapid, clean (no solvents) and produces a thin and narrow seam. In addition, ultrasonic welding is preferred because the mechanical pounding of the welding horn causes generation of heat at the contiguous overlapping end marginal regions of the sheet to maximize melting of one or more layers therein. A typical ultrasonic welding process is carried out by holding down the overlapped ends of a flexible sheet with vacuum over a flat anvil and guiding the flat end of an ultrasonic vibrating horn transversely across the width of the sheet and along the length of the overlapped ends to form a welded seam.
When ultrasonically welded into a belt, the seam of multilayered imaging flexible members may occasionally contain undesirable high protrusions such as peaks, ridges and mounds. These seam protrusions present problems during image cycling of the belt machine because they interact with cleaning blades to cause blade wear and tear which ultimately affect cleaning blade life and efficiency. Moreover, the high protrusions in the seam may also interfere with the operation of subsystems of copiers, printers and duplicators by damaging electrode wires used in development subsystems that position the wires parallel to and closely spaced from the outer imaging surface of belt photoreceptors. These closely spaced wires are employed to facilitate the formation of a toner powder cloud at a development zone adjacent to a toner donor roll and the imaging surface of the belt photoreceptor. Another frequently observed mechanical failure in imaging belts during image cycling is that the ultrasonically welded seam of an electrophotographic imaging member belt can also develop cracks which then propagate into delamination after being subjected to extended fatigue bending and flexing cycles over small diameter belt support rollers of an imaging machine or when due to lateral forces caused by mechanical rubbing contact with stationary web edge guides of a belt support module during cycling. Seam cracking/delamination has also been found to be further aggravated when the belt is employed in electrophotographic imaging systems utilizing blade cleaning devices. Alteration of materials in the various photoreceptor belt layers such as the conductive layer, hole blocking layer, adhesive layer, charge generating layer, and/or charge transport layer to suppress cracking and delamination problems is not easily accomplished. The alteration of the materials may adversely affect the overall electrical, mechanical and other properties of the belt such as well as residual voltage, background, dark decay, flexibility, and the like.
For example, when a flexible imaging member belt used in an electrophotographic machine is a photoreceptor belt fabricated by ultrasonic welding of overlapped opposite ends of a sheet, the ultrasonic energy transmitted to the overlapped ends melts the thermoplastic sheet components in the overlap region to form a seam. The ultrasonic welded seam of a multilayered photoreceptor belt is relatively brittle and low in strength and toughness. The joining techniques, particularly the welding process, can result in the formation of a splashing that projects out from either side of the seam in the overlap region of the belt. The overlap region and the spashings on each side of the overlap region comprise a strip from one edge of the belt to the other that is referred herein as the “seam region”. Because of the splashing, a typical flexible imaging member belt is about 1.6 times thicker in the seam region than that of the remainder of the belt (e.g., in a typical example, 188 micrometers versus 1.6 micrometers).
The photoreceptor belt in an electrophotographic imaging apparatus undergoes bending strain as the belt is cycled over a plurality of support and drive rollers. The excessive thickness of the photoreceptor belt in the seam region due to the presence of the splashing results in a large induced bending strain as the seam travels over each roller. Generally, small diameter support rollers are highly desirable for simple, reliable copy paper stripping syst
Avery Stephen T.
Domm Edward A.
Grabowski Edward F.
Griffin Scott J.
Horgan Anthony M.
Thompson Robert
Xerox Corporation
Yao Sam Chuan
LandOfFree
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