Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2003-02-20
2004-11-30
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
C430S108300
Reexamination Certificate
active
06824944
ABSTRACT:
The present invention is generally directed to toner compositions and processes thereof, and more specifically, to the surface modification of compositions and components, such as toners, including chemical toners, such as in situ, encapsulated or emulsion aggregated toners, and toner compositions directly generated by conventional melt kneading, pulverization and classification process. In embodiments, the present invention is generally directed to a toner process, and more specifically, the present invention relates to a toner process wherein the toner surface is chemically modified by a reduction process to provide, for example, positively charging toners converted from toners that have tendencies to charge negatively. Typically, for example, toners containing polyester resins with sulfonic acid or carboxylic acid groups tend to charge negatively, and with the present invention in embodiments can be initially rendered as positively charging toners. More specifically, the present invention is directed to a toner process wherein the surface layer of the toner is chemically modified by a reducing agent, the gain of electrons, for example, with an aqueous solution of reducing agent, such as sodium borohydride and a metal halide catalyst, such cobalt (II) chloride thereby, for example, enhancing the surface charging performance of the toner particles and enabling positive triboelectric charge values of, for example, from about 10 to about 90 microcoulombs per gram, and preferably from about 20 to about 40 microcoulombs per gram, respectively.
In embodiments, the present invention is directed to the economical in situ, chemical or direct preparation of toners comprised of a resin, a colorant, optionally a wax, and wherein the toner surface layer is chemically modified by a reduction process with an aqueous solution of a reducing agent, such as sodium borohydride, and a metal halide catalyst, such cobalt (II) chloride, thereby, for example, enhancing the surface charging characteristics of the toner particles and enabling high positive triboelectric charge levels; and sulfopolyester based toner obtained by an emulsion coalescence process, and which process is comprised of (i) subjecting a colloidal aqueous solution comprised of, for example, about 10 to about 20 percent solids of, for example, sodio-sulfonated polyester resin particles, and coalescing the resin with a coalescence agent comprised of, for example, zinc acetate as disclosed in U.S. Pat. No. 5,593,807, the disclosure of which is totally incorporated herein by reference; and (ii) treatment of the toner by a reduction process with an aqueous solution of reducing agent, such as sodium borohydride and metal halide catalyst, such cobalt (II) chloride, and thereby, for example, enhancing the surface charging characteristics of the toner particles and providing positively triboelectric charge levels of from about 10 to about 90 microcoulombs per gram, and preferably from about 20 to about 40 microcoulombs per gram, respectively. The resulting surface treated toner particles display in embodiments enhanced triboelectric charging levels, especially in the higher 80 percent relative humidity zone, and lower RH sensitivity of charging performance between the 20 percent relative humidity zone and the 80 percent relative humidity zone without compromising the low melt toner fusing properties, and wherein the toner minimum fusing temperature is, for example, from about 125° C. to about 140° C. as determined at a crease area of about 60 units, and which toner also possesses in embodiments high gloss characteristics with peak gloss levels of, for example, from about 40 to about 70 gloss units as measured with a Gardner gloss meter.
The toner composites or compositions of the present invention display in embodiments thereof an average volume diameter of, for example, from about 1 to about 25, and preferably from 1 to about 10 microns, and a narrow GSD of, for example, from about 1.16 to about 1.26 or about 1.18 to about 1.28, both as measured on the Coulter Counter; a particle morphology which is nearly spherical in shape; and low or no vinyl offset of from about 0.03 to about 0.11 percent, measured as the percentage of toner mass transferred from a fused image transferred onto a MYLAR® sheet over a period of 48 hours at 50° C. The process of the present invention in embodiments enables the utilization of polymers obtained by polycondensation reactions, such polymers including, for example, polyesters, and more specifically, the sulfonated polyesters as illustrated in U.S. Pat. Nos. 5,348,832; 5,658,704, 5,604,076, and 5,593,807, the disclosures of each of which are totally incorporated herein by reference, and which polyesters may be selected for low melting toners.
The toners of the present invention can be selected for known electrophotographic imaging methods, printing processes, including color processes, digital methods, and lithography.
REFERENCES
Patents which may disclose the surface modification of certain toners are known. More specifically, illustrated in U.S. Pat. No. 5,213,938, the disclosure of which is totally incorporated herein by reference, is a process for the preparation of toner compositions, which comprises the oxidation and metal chelation of the toner surface, and subsequently coalescing by absorption of a fluoro containing polymer to provide negative charging toners.
U.S. Pat. No. 6,143,457, the disclosure of which is totally incorporated herein by reference, discloses a toner comprised of a polyester resin, colorant and thereover a quaternary organic component ionically bound to the toner surface, thereby enhancing negative charging toner and reducing the relative humidity sensitivity. Moreover, in U.S. Pat. No. 6,203,963, the disclosure of which is totally incorporated herein by reference, there is disclosed a toner particulate surface treatment comprised of treating an aqueous dispersion of toner particles with a first solution of a water soluble alkyl carboxylate metal salt and a second solution of water soluble metal salt resulting in toner particles uniformly coated with colloidal particles.
U.S. Pat. No. 4,626,490, the disclosure of which is totally incorporated herein by reference, discloses an encapsulated toner comprised of a core material comprised of a long chain organic compound and a higher carboxylic acid encapsulated with a thin shell, and an external additive comprised of a powdery silica. There is also disclosed in U.S. Pat. No. 4,797,339, the disclosure of which is totally incorporated herein by reference, an in situ toner comprising an inner layer comprised of a resin ion complex having a coloring agent and an outer layer containing a flowability imparting agent; see column 5, lines 3 to 13, wherein the flowability imparting agents in addition to the perfluoroalcohol acrylate agent includes a benzo derivative formaldehyde resin and hydrophobic silica. Similarly, U.S. Pat. Nos. 4,789,617; 4,601,968; 4,592,990; 4,904,562; 4,465,756; 4,468,446; 4,533,616; 4,565,763 and 4,592,990, the disclosures of which are totally incorporated herein by reference, disclose the use of external toner surface additives.
Polyester based chemical toners substantially free of encapsulation are also known, reference U.S. Pat. No. 5,593,807, the disclosure of which is totally incorporated herein by reference, wherein there is illustrated a process for the preparation of a toner comprised of a sodio sulfonated polyester resin and pigment, and wherein the aggregation and coalescence of resin particles is mediated with an alkali halide. Other U.S. Patents that may be of interest, the disclosures of which are totally incorporated herein by reference, are U.S. Pat. Nos. 5,853,944; 5,843,614; 5,840,462; 5,604,076; 5,648,193; 5,658,704 and 5,660,965.
SUMMARY
It is a feature of the present invention to provide dry toner compositions with positive triboelectric charging, such as from about 50 to about 90 microcoulombs per gram, and preferably from about 10 to about 40 microcoulombs per gram, respectively.
In another featur
Farrugia Valerie M.
Hawkins Michael S.
Sacripante Guerino G.
Chapman Mark A.
Palazzo E. O.
Xerox Corporation
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