Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2002-10-31
2004-08-03
Goodrow, John L. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S058150, C430S058250, C430S058500, C430S058800, C430S064000
Reexamination Certificate
active
06770410
ABSTRACT:
BACKGROUND
The present invention is generally directed to imaging members, imaging apparatus, and processes thereof. More specifically, the present invention relates to multilayered electrophotographic imaging members having a novel charge transport layer composition comprising a charge transport compound dissolved in a polymer, and wherein the low molecular weight fraction of the polymers has been selectively removed from the polymer prior to charge transport layer preparation. The present invention also relates to processes for forming images on the member.
Typical imaging members include, for example: (1) photosensitive members or photoreceptors, which are commonly utilized in electrophotographic imaging systems, such as, xerographic machines, and (2) electroreceptors, like ionographic imaging members, which are used for electrographic imaging systems. Imaging members are usually available in two forms, the rigid drum configuration and the flexible belt. The flexible imaging member belts may either be seamless or seamed belts. Typical electrophotographic imaging member belts comprise an imaging layer of a charge transport layer and a charge generating layer coated over one side of a flexible supporting substrate and an anti-curl back coating applied to the opposite side of the substrate to provide imaging member flatness. Electrographic imaging member belts are somewhat simpler in structure; they typically comprise a dielectric imaging layer on one side of a flexible supporting substrate and may also have an anti-curl back coating on the opposite side of the substrate. A typical flexible imaging member belt has a ground strip coated near one edge of the belt and adjacent to the imaging layer.
Photosensitive members having at least two electrically operative layers provide electrostatic latent images when charged with a uniform negative electrostatic charge, exposed to a light image and then developed with finely divided electroscopic marking particles. The resulting toner image is usually transferred to a suitable receiving member such as paper.
As more advanced, higher speed electrophotographic imaging copiers, duplicators and printers were developed, in some instances, degradation of image quality was encountered during extended cycling. Moreover, complex, highly sophisticated duplicating and printing systems operating at very high speeds have placed stringent requirements including narrow operating limits on photoreceptors. For electrophotographic imaging members having flexible belt configuration, the numerous layers selected from photoconductive imaging members should be highly flexible, adhere well to adjacent layers, and exhibit predictable electrical characteristics within narrow operating limits to provide excellent toner images over many thousands of cycles. One type of multi-layered photoreceptor that has been employed as a belt in electrophotographic imaging systems comprises a flexible support substrate, a conductive layer, a blocking layer, an adhesive layer, a charge generating layer, a charge transport layer, and a conductive ground strip layer adjacent to one edge of the imaging layers. This photoreceptor belt usually comprises an additional layer such as an anti-curl back coating on the back side of the support substrate in order to provide the desired belt flatness.
Flexible photoreceptor belts are fabricated from sheets cut from an electrophotographic imaging member web stock. The cut sheets are generally rectangular in shape and 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 sheet is fabricated into a belt by joining the overlapping opposite marginal end regions of the sheet. A seam is typically produced in the overlapping opposite marginal end regions at the point of joining. Joining may be effected in any suitable manner, such as welding including for example ultrasonic processes, gluing, taping, pressure/heat fusing, and the like methods. However, ultrasonic seam welding is generally utilized in embodiments as the method of joining because it is rapid, clean, generally free of solvent application, and produces a thin and narrow strong seam. The fabricated flexible photoreceptor belt mounted around a multi-roller belt support module and selected in an electrophotographic imaging machine may undergo bending and flexing as the belt is dynamically cycled over the plurality of support and drive rollers of the belt support module.
In a machine service environment, a flexible imaging member belt, mounted on a belt supporting module, is generally exposed to repetitive electrophotographic image mechanical cycling which subjects the outer exposed anti-curl back coating to abrasion due to mechanical fatigue and interaction with the belt drives and other support rollers as well as sliding contact with backer bars. This repetitive cycling can lead to a gradual deterioration in the physical/mechanical integrity of the exposed anti-curl backing layer. When the anti-curl back coating is worn the thickness thereof is reduced and the anti-curl back coating experiences a loss of ability to counteract the tendency of imaging members upward curling which leads to the exhibition of belt curl-up at both edges. Moreover, uneven wear of the anti-curl back coating has been found to cause early development of belt ripples which are ultimately manifested as copy printout defects. Thus, the anti-curl back coating wear that results from mechanical contact interaction during dynamic imaging operations is a significant problem that shortens the service life of the belt and adversely affects image quality. Let it be pointed out here that anti-curl back coating wear is an unique problem only to the imaging member belt configuration, since rigid imaging member drums do not require this coating.
Also, numerous other imaging members for electrostatographic imaging systems are known including selenium, selenium alloys, such as arsenic selenium alloys; layered inorganic imaging members, and layered organic members. Examples of layered organic imaging members include those containing a charge transporting layer and a charge generating layer. Thus, for example, an illustrative layered organic imaging member can be comprised of a conductive substrate, overcoated with a charge generator layer, which in turn is overcoated with a charge transport layer. Examples of generator layers that can be employed in these members include, for example, charge generator materials such as; selenium, cadmium sulfide, vanadyl phthalocyanine, x-metal free phthalocyanine, benzimidazole perylent (BZP), hydroxygallium phthalocyanine (HOGaPc), chlorogallium phthalocyanine, and trigonal selenium dispersed in binder resin, while examples of transport layers include dispersions of various diamines, reference, for example, U.S. Pat. No. 4,265,990, the disclosure of which is incorporated herein by reference in its entirety.
A further mechanical problem associated with a photoreceptor belt, comprising a charge generating layer and the charge transport layer, is that the thickness of the outermost charge transport layer tends to become thinner during image cycling as a result of wear. This decrease in thickness may cause changes in the electrical performance of the photoreceptor. Thus, to maintain image quality, complex and sophisticated electronic equipment is of value in the imaging machine to compensate for the electrical changes. This increases the complexity of the machine, cost of the machine, size of the footprint occupied by the machine, and the like. Without proper compensation of the changing electrical properties of the photoreceptor during cycling, the quality of the images formed can degrade due to spreading of the charge pattern on the surface of the imaging member and result in a decline in image resolution. High quality images are of value for digital copiers, duplicators, printers, and facsimile machines, particularly laser exposure machines that demand high resolution images.
There continues to be a need for improved imaging mem
Carmichael Kathleen M.
Fuller Timothy J.
Yu Robert C. U.
Goodrow John L.
Oliff & Berridg,e PLC
Palazzo Eugene O.
Xerox Corporation
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