Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1999-10-28
2001-12-11
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C156S137000, C156S304600, C156S308400
Reexamination Certificate
active
06328922
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to a seam surface treatment system and, more specifically, to a post ultrasonically welded seam treatment system for flexible imaging member 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 image 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 include the mentioned types, for simplicity reasons, the discussion hereinafter will be focus 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 may possibly happen in ionographic imaging member belts as well.
The flexible electrostatographic imaging member belts are fabricated from a sheet cut from an imaging member 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 imaging member sheet with vacuum against a flat anvil surface and guiding the flat end of an ultrasonic vibrating horn transversely across the width of the sheet, over and along the length of the overlapped ends, to form a welded seam.
When ultrasonically welded into a belt, the seam of multilayered electrophotographic imaging flexible member belts may occasionally contain undesirable high protrusions such as peaks, ridges, spikes, 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 efficiency and service life. Moreover, the protrusion high spots 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 imaging member. Another frequently observed mechanical failure in the imaging belts during image cycling is that the ultrasonically welded seam of an electrophotographic imaging member belt can also cause initiation of cracks in the seam which then propagate and lead to delamination after being subjected to extended 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 against stationary web edge guides of a belt support module during cycling. Seam cracking and delamination has also been found to be further aggravated when the belt is employed in electrophotographic imaging systems utilizing blade cleaning devices and some operational imaging subsystems. 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 impact the overall physical, electrical, mechanical, and other properties of the belt such as well as coating layer uniformity, 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 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 116 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 s
Domm Edward A.
Grabowski Edward F.
Horgan Anthony M.
Hsieh Bing R.
Mishra Satchidanand
Tentoni Leo B.
Xerox Corporation
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