Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2002-08-07
2004-08-24
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
C523S335000
Reexamination Certificate
active
06780559
ABSTRACT:
BACKGROUND
The present invention is generally directed to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner compositions. In embodiments there is disclosed the economical in situ chemical preparation of toners without the utilization of the known pulverization and/or classification methods, and wherein in embodiments positively charging pigments are coated with hydrophobic silica particles rendering the pigment particles negatively charging, thereby preventing the toner particles from becoming positively charging in for example, a xerographic development process, and which toners possess in embodiments substantially similar, or the same triboelectrical charging characteristics without the aid of external additives. The toners prepared also possess, for example, an average volume diameter of from about 1 to about 25, and preferably from 2 to about 10 microns, and a narrow GSD (geometric standard deviation) of, for example, from about 1.16 to about 1.26 both as measured on the Coulter Counter. The resulting toners can be selected for known electrophotographic imaging processes, printing processes, including color processes, and lithography.
In embodiments there is illustrated herein toners wherein triboelectric charge sign reversal is substantially prevented, wherein toner surface additives can be avoided or minimized, and wherein there is selected a hydrophobic silica within which the toner colorant, such as pigment and dye for each toner is dispersed and which colorant is water repelling and negative charging, such as silicas like those illustrated herein that have been treated with a hydrophobic agent, including hexamethyldisilazane treated silica, R812S™ available from Degussa, and other similar silicas treated with other hydrophobic agents, including silane and polymer coated silicas. The hydrophobic silica selected for the colorant dispersion in embodiments repels water, therefore it is not water dispersable without the use of a surfactant, and thus cannot be easily removed by washing with water, in contrast to the positive charging pigment itself, which may contain a dye component that is water soluble, and which dye thus can disappear in the washing process in the absence of the hydrophobic silica. Furthermore, the hydrophobic silica selected also enables stable, for example no or little colorant settling, colorant dispersions wherein the colorant diameter size is for example, from about 60 to about 100 manometers as measured on a disc centrifuge, thereby enabling the pigment/dye to be easily dispersed in latex particles. Moreover, in embodiments of the present invention the toners obtained can be comprised of resin and pigment, such as toners each with different pigments, especially those pigments which exhibit positive charging characteristics, such as Rhodamine Pigment Red 81.3, Pigment Violet 3, Pigment Violet 23, Pigment Blue 61 and pigment Green 4, such that the natural positive pigment charge behavior is substantially prevented even though different pigments are selected for each toner, and different concentrations of pigments and dyes contained therein may be present. Moreover, there can be substantially prevented the conversion of the pigment charge to a positive value in a xerographic development system that requires negatively charging toner, and which characteristics can be of value with respect to the generation of full process color copies, such as the generation of developed colored images in the Xerox Corporation 5750®, 5790®, DC2045®, DC2060®, DC12®, and iGEN-3®.
REFERENCES
A number of processes are known for the preparation of toners, such as, for example, conventional processes wherein a resin is melt kneaded or extruded with a pigment, micronized and pulverized to provide toner particles with an average volume particle diameter of from about 9 microns to about 20 microns, and with a broad geometric size distribution of from about 1.3 to about 1.7. In these processes, it is usually necessary to subject the aforementioned toners to a classification procedure such that the geometric size distribution of from about 1.3 to about 1.4 is attained. To obtain a further improved geometric toner size distribution, the toners may need to be further classified, which can result in unsatisfactory toner yields. Generally, during the preparation of toners with average particle size diameters of from about 11 microns to about 15 microns, toner yields range from about 70 percent to about 85 percent after classification. Additionally, during the preparation of smaller sized toners with particle sizes of from about 7 microns to about 11 microns, lower toner yields can be obtained after classification such as from about 50 percent to about 70 percent. In addition, the preparation of toners with conventional processes, where the pigment is positively charging, can evidence reversal of the toner charge from for example, negative to positive in a xerographic development system. With the processes of the present invention in embodiments, for example those containing pigments that are positively charging, such as Pigment Red 81.3, small average particle sizes of, for example, from about 3 microns to about 9 microns, and more specifically about 5 microns, are attained without resorting to classification processes, and wherein narrow geometric size distributions are attained, such as from about 1.16 to about 1.30, and preferably from about 1.16 to about 1.25, high toner yields are also attained, such as from about 90 percent to about 96 percent.
There are illustrated in U.S. Pat. Nos. 5,364,729 and 5,403,693 methods of preparing toner particles by blending together latexes with pigment particles. Also mentioned are U.S. Pat. Nos. 4,996,127; 4,797,339 and 4,983,488. The disclosures of each of these patents are totally incorporated herein by reference.
Emulsion/aggregation/coalescence processes for the preparation of toners are illustrated in a number of Xerox Corporation patents, the disclosures of each of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654; U.S. Pat. No. 5,278,020; U.S. Pat. No. 5,308,734; U.S. Pat. No. 5,370,963; U.S. Pat. No. 5,344,738; U.S. Pat. No. 5,403,693; U.S. Pat. No. 5,418,108; U.S. Pat. No. 5,364,729; and U.S. Pat. No. 5,346,797; and also of interest may be U.S. Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658; 5,585,215; 5,650,255; 5,650,256; 5,501,935; 5,723,253; 5,744,520; 5,763,133; 5,766,818; 5,747,215; 5,827,633; 5,853,944; 5,804,349; 5,840,462; 5,869,215; 5,863,698; 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488; 5,858,601; and 5,977,210. The appropriate components and processes of the above Xerox Corporation patents can be selected for the processes of the present invention in embodiments thereof.
SUMMARY
It is a feature of the present invention to provide toner processes with many of the advantages illustrated herein.
In another feature of the present invention there are provided simple and economical processes for the direct preparation of a set of black and colored toner compositions, including toners with positive charging pigments with for example, excellent pigment dispersions, stable triboelectric charging values, and which toners possess substantially no charging sign reversal on aging.
It is another feature of the present invention to provide a process for obtaining a full set of xerographic color toners having properties such as (a) an excellent color gamut, (b) an acceptable projection efficiency (over about 75 percent and from about 80 to about 95 percent in embodiments), and (c) stable excellent triboelectrical properties. With the toners obtained in accordance with embodiments of the present invention there is enabled the combination of wide color gamut, excellent projection efficiencies, and desired triboelectric toner charge, which charge can remain negative without showing any sign reversal to positive charging on aging. Projection efficiency is essentially a measure of the amount of light transmitted and a measur
McDougall Maria N. V.
Patel Raj D.
Veregin Richard P. N.
Chapman Mark A.
Palazzo E. O.
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