Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-08-17
2002-03-19
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S137130
Reexamination Certificate
active
06358659
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is generally directed to developer compositions, and more specifically, the present invention relates to developer compositions with coated carrier components, or coated carrier particles that can be prepared by, for example, solution and preferably by dry powder processes. More specifically, the present invention relates to compositions, especially carrier compositions comprised of a core, and thereover a polymer or polymers, and dispersed therein a conductive component, such as an inorganic polymer like a polyphosphazene, a polysiloxane, a polymetallic nitrile, and the like. Accordingly, in aspects of the present invention there are provided carriers comprised of a core, a polymer, or mixture of polymers thereover, and an inorganic conductive polymer, and which polymer is preferably colorless, and wherein there is enabled carrier particles having excellent conductivity characteristics, that is conductivities that can be preselected and conductivities that are relatively stable over extended time periods. The carrier may also include the polymer coating thereover in admixture with other suitable polymers, and more specifically, a polymer, such as a fluoropolymer, polymethylmethacrylate, poly(urethane), especially a crosslinked polyurethane, such as a poly(urethane)polyester and the like, and wherein the polymer coating contains the inorganic polymer conductive component, and which conductive component is preferably dispersed in the polymer coating. With the conductive component, there can be enabled carriers with increased developer triboelectric response at relative humidities of from about 20 to about 90 percent, improved image quality performance, excellent high conductivity ranges of from about 10
−10
to about 10
−7
(ohm-cm)
−1
, and the like. An advantage associated with the carriers of the present invention include robust, extended life carriers with lifetimes, for example, of 1,000,000 imaging cycles, a high triboelectrical charge, for example a carrier tribo range of from about a plus (positive charge) 25 to about 100, and more specifically, from about a positive 25 to about a positive 55 microcoulombs per gram, and yet more specifically, from about a positive 30 to about a positive 50 microcoulombs per gram.
The carrier particles of the present invention can be selected for a number of different imaging systems and devices, such as xerographic copiers and printers, inclusive of high speed color xerographic systems, printers associated with computers, digital processes, such as the Xerox Corporation 1090 Marathon, Document Centre 265, the DocuTech series, DocuColor 40, and the like, and wherein monochrome or colored images with excellent and substantially no background deposits are achievable. Developer compositions comprised of the carrier particles illustrated herein and prepared, for example, by a dry coating process are generally useful in electrostatographic or electrophotographic imaging systems, especially xerographic imaging and printing processes, and digital processes. Additionally, the invention developer compositions comprised of substantially conductive carrier particles are useful in imaging methods wherein relatively constant conductivity parameters are desired. Furthermore, in the aforementioned imaging processes the triboelectric charge on the carrier particles can be preselected, which charge is dependent, for example, on the polymer composition and the conductive dispersant component applied to the carrier core, and optionally the type and amount of the conductive component selected.
Examples of specific advantages for the carriers of the present invention include in embodiments high robust carrier tribo charge of a positive value, high toner tribo charge of a negative value, excellent admix, for example, from about 1 to about 30 seconds as determined in the known charge spectrograph, increased resistance of the carrier to mechanical aging in a xerographic environment and a decreased sensitivity of the carrier triboelectric value to the relative humidity of the environment, and the like. More specifically, the toner tribo can be, for example, from about a minus 25 to about a minus 100, from about −50 to about −80, or from about −60 to about −70, with corresponding positive tribo charges for the carrier. The tribo can be determined by a number of known methods, such as the use of a Faraday Cage. With respect to high toner tribo charge of a negative value, this property is important to xerographic imaging, especially color applications, primarily because there is enabled development of toner particles into regions of the imaging member, such as a photoreceptor where strong fringe electrical fields exist, that is, at the borders of solids areas and lines. Developing toner particles through these fringe fields minimizes or eliminates the untoned part of the image which appears between two adjacent colors in an image.
PRIOR ART
The electrostatographic process, and particularly the xerographic process, is well known. This process involves the formation of an electrostatic latent image on a photoreceptor, followed by development, and subsequent transfer of the image to a suitable substrate. Numerous different types of xerographic imaging processes are known wherein, for example, insulative developer particles or conductive toner compositions are selected depending on the development systems used. Moreover, of importance with respect to the aforementioned developer compositions is the appropriate triboelectric charging values associated therewith, especially at a variety of relative humidities.
Carrier particles for use in the development of electrostatic latent images are described in many patents including, for example, U.S. Pat. No. 3,590,000, the disclosure of which is totally incorporated herein by reference. These carrier particles can contain various cores, including steel, with a coating thereover of fluoropolymers, and terpolymers of styrene, methacrylate, and silane compounds. A number of these coatings can deteriorate rapidly, especially when selected for a continuous xerographic process where a portion of, or the entire coating may separate from the carrier core in the form of, for example, chips or flakes, and which resulting carrier can fail upon impact, or abrasive contact with machine parts and other carrier particles. These flakes or chips, which cannot generally be reclaimed from the developer mixture, usually adversely effect the triboelectric charging characteristics of the carrier particles thereby providing images with lower resolution in comparison to those compositions wherein the carrier coatings are retained on the surface of the core substrate. Further, another problem encountered with some prior art carrier coatings resides in fluctuating triboelectric charging characteristics, particularly with changes in relative humidity, and relatively low triboelectrical values.
There is illustrated in U.S. Pat. No. 4,233,387, the disclosure of which is totally incorporated herein by reference, coated carrier components comprised of finely divided toner particles clinging to the surface of the carrier particles. Specifically, there is disclosed in this patent coated carrier particles obtained by mixing carrier core particles of an average diameter of from between about 30 microns to about 1,000 microns with from about 0.05 percent to about 3.0 percent by weight, based on the weight of the coated carrier particles, of thermoplastic or thermosetting resin particles. The resulting mixture is then dry blended until the resin particles adhere to the carrier core by mechanical impaction, and/or electrostatic attraction. Thereafter, the mixture is heated to a temperature of from about 320° F. to about 650° F. for a period of 20 minutes to about 120 minutes, enabling the resin particles to melt and fuse on the carrier core.
There is illustrated in U.S. Pat. Nos. 4,937,166 and 4,935,326, the disclosures of which are totally incorporated herein by reference, carrie
Drappel Stephan V.
Foucher Daniel A.
MacLeod Paula J.
Palazzo E. D.
Rodee Christopher
Xerox Corporation
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