Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-03-29
2001-06-26
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S111350
Reexamination Certificate
active
06251554
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 with amine, such as a number of the amines of the above copending applications and patents, and a second polymer containing a carboxylic acid functionality, or a sulfonic acid functionality.
In embodiments of the present invention, the carrier particles are comprised of a core with a coating thereover of a polymer or polymers generated from a mixture, or blend of an amine, such as dimethylaminoethyl methacrylate, substituted alkyl aminoethyl methacrylate, butylaminoethyl methacrylate, and the like, and a second polymer containing a carboxylic acid functionality, or a sulfonic acid functionality. The carrier may include the polymer coating thereover in admixture with other suitable polymers, and more specifically, with a polymer, such as a fluoropolymer, polymethylmethacrylate, poly(urethane), especially a crosslinked polyurethane, such as a poly(urethane) polyester and the like, and moreover, the copolymer coating may contain a conductive component, such as carbon black, 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 important advantage associated with the carriers of the present invention with a second polymer containing a carboxylic acid functionality, or a sulfonic acid functionality polymer thereover include the enablement of a crosslinked polymer, which crosslinking permits, for example, 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) 30 to about 100 microcoulombs per gram, and preferably from about a positive 40 to about a positive 70 microcoulombs per gram, and most preferably from about a positive 35 to about a positive 60 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, digital systems, such as the Xerox Corporation Document Center 240/265, 5090, DocuTech Production Publisher, Model 135, 5775, 5100, a combination of xerographic and digital systems, and wherein 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 dispersant component applied to the carrier core, and optionally the type and amount of the conductive component selected.
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 unstable triboelectrical values.
There are 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 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, carrier containing a mixture of polymers, such as two polymers, not in close proximity in the triboelectric series. Moreover, in U.S. Pat. No. 4,810,611, the disclosure of which is totally incorporated herein by reference, there is disclosed the addition to carrier coatings of colorless conductive metal halides in an amount of from about 25 to about 75 weight percent, such halides including copper iodide, copper fluoride, and mixtures thereof. The appropriate components and processes of the '166 and '326 patents may be selected for the present invention in embodiments thereof. The present invention advantage in embodiments over this prior art is, for example, achieving high stable positive triboelectric charge on the carrier particles, that is high, up to about a 100 negative triboelectric charge is imparted to the toner particles developed onto a photoreceptor in, for example, a xerographic development environment. Further, the full range of electrical properties of the carrier particles can be achieved at high triboelectric charging values, from carrier conductivities of 10
−17
mho/cm to 10
−6
mho/cm, t
Bayley Robert D.
Fox Carol A.
Henderson K. Derek
Hoffend Thomas R.
Silence Scott M.
Goodrow John
Palazzo E. O.
Xerox Corporation
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