Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
1999-08-26
2001-02-27
Chapman, Mark (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
Reexamination Certificate
active
06194117
ABSTRACT:
REFERENCE TO ISSUED PATENTS
Attention is directed to commonly owned and assigned U.S. Pat. No. 5,674,656, issued Oct. 7, 1997, entitled “Processes for Stabilizing Developer Chargability and Imaging Processes Thereof”, which patent discloses a process for controlling At transience comprising: providing in a developer housing, a two component developer composition comprising toner particles comprised of a resin, a pigment, a mixture of at least two charge additives, and unpreconditioned coated carrier core particles, wherein the developer is prepared by combining and thereafter blending a mixture of from 1 to about 10 parts by weight of toner particles with from about 100 parts by weight of carrier particles for about 10 minutes to about 30 minutes until an At value of from about 60 to about 100 is attained; and forming and thereafter developing electrostatographic latent images on a photoconductive member in a two component development electrostatographic imaging apparatus with the developer composition; wherein the developer composition has an At transient of less than about 20 relative units; U.S. Pat. No. 4,614,165, issued Sep. 30,1986, entitled “Extended Life Development System”, wherein there is disclosed an apparatus which develops an electrostatic latent image recorded on a photoconductive member employed in an electrophotographic printing machine having a finite, usable life, which apparatus employs a developer material which ages during the life of the electrophotographic printing machine, and thus a continuous supply of carrier granules is furnished to the developer material; U.S. Pat. No. 4,948,686, issued Aug. 14,1990, entitled “Process For Forming Two Color Images”, discloses a development process using a specific coated carrier with a coating weight of about 0.05 weight percent of the carrier core; U.S. Pat. No. 4,678,734, issued Jul. 7, 1987, to Laing et al., entitled “Process For Developer Composition”, discloses a process for making a developer composition comprising: 1) providing carrier particles having a core with a coating thereover; 2) introducing the carrier particles into a blending apparatus; 3) adding to the blending apparatus fine toner particles with a diameter of from about 2 to about 10 microns, these particles being comprised of toner resin particles, pigment particles, and a charge enhancing additive; 4) effecting blending for a period of time sufficient to enable the classified toner particles to alter the tribogenerating ability of the surface of the carrier particles and become embedded therein; 5) subsequently adding to the resulting blended mixture toner particles of a diameter of from about 2 to about 18 microns, and which particles are comprised of toner resin, pigment particles, and a charge enhancing additive; and 6) blending for a period of from about 1 minute to about 5 minutes; U.S. Pat. No. 5,927,510, entitled “Carrier Composition And Processes Thereof”, wherein there is disclosed a process comprising: blending resin coated carrier particles; separating the resulting blended carrier particles from fine particles formed while blending; and blending the blended carrier particles with toner particles to form a two component developer; and U.S. Pat. No. 5,882,834, entitled “Method of Making Developer with Stable Triboelectric Charging Properties”, wherein there is disclosed a method of preparing a developer composition comprising: 1) blending carrier particles with finely divided toner particles, wherein blending is carried out for a period of time sufficient to enable the toner particles to alter the tribocharging ability of the carrier particles and become embedded therein; 2) dividing the blend of toner particles and carrier particles into coarse particles and fine particles; and 3) blending the coarse particles with toner particles.
The disclosures of each the above mentioned patents are incorporated herein by reference in their entirety. The appropriate components and processes of these patents may be selected for the toners, developers and processes of the present invention in embodiments thereof.
BACKGROUND OF THE INVENTION
The present invention is generally directed to developer compositions and processes for the preparation thereof, and more specifically, the present invention is directed to developer compositions with high conductivities, for example, from about 10
−12
(ohm-cm)
−1
to about 10
−7
(ohm-cm)
−1
. More specifically the present invention relates to carrier and developer preparative processes, comprising, for example, blending resin coated or uncoated carrier particles in a fluidized bed jet mill and continuously separating fine particles formed therein from the resulting blended carrier particles, to provide high conductivity developers which possess highly desirable developer, development, and image properties, for example, bulk density, mass flow, conductivity, and conductivity stability with respect to developer lifetime in a xerographic development environment, excellent triboelectric charge and charge stability with respect to developer lifetime in a xerographic development environment and as a function of ambient environment, particularly temperature and relative humidity.
A problem encountered with two component electrostatic developers is the phenomena known as “charge through”, which is observed when fresh or replenishing toner is added to an developer contained in a developer housing after extended operation and limited toner throughput. Although not desired to be limited by theory, it is believed that charge through causes the fresh toner to acquire a very high level of charge of the same sign as the toner in the housing prior to addition of the fresh toner. At the same time, the toner that is already present in the developer, referred to as the incumbent toner, looses much of its existing charge, and in extreme cases some or even the majority of the incumbent toner acquires a charge opposite to that of its original charge. In a xerographic developer, this will cause the incumbent toner to be developed out in background areas of a xerographic print, which undesired background area development is an unacceptable and often considered a catastrophic image quality defect. Further, it is believed that charge through may be caused by low levels of fine particle contamination contained in the developer and which contamination is believed to arise from material which is stripped or abraded from the carrier particle surface, such as metallic asperities or resin coating. The contaminants are scavenged by toner particles already present in the developer and thereby adversely alters the charging properties of both incumbent toner and fresh toner.
The above mentioned problem and related problems are overcome in embodiments of the present invention.
PRIOR ART
In U.S. Pat. No. 5,569,572, issued Oct. 29, 1996, to Laing, et al., there is disclosed a process for the preparation of developer compositions comprising providing a first developer comprised of carrier and first toner comprised of resin, pigment, polyolefin, compatibilizer, charge control agent, and surface additive, and adding thereto a second replenisher comprised of carrier, and second toner comprised of resin, pigment, polyolefin, compatibilizer, charge control agent, and surface additive, and wherein the surface additive of the second toner is present in a lesser amount than the surface additive of the first toner.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner resin, are also known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with certain finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer compos
Henderson K. Derek
Hollenbaugh, Jr. William H.
Lafica Susan J.
Silence Scott M.
Smith Lewis S.
Chapman Mark
Haack John L.
Xerox Corporation
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