Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2002-02-04
2003-04-01
Goodrow, John (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
06541175
ABSTRACT:
BACKGROUND OF THE INVENTION
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, the present invention is directed to the economical chemical in situ preparation of toners without the utilization of the known pulverization and/or classification methods, and wherein in embodiments toner compositions with a volume average diameter of from about 1 to about 25, and specifically from 1 to about 10 microns and narrow GSD of, for example, from about 1.14 to about 1.25 as measured on the Coulter Counter can be obtained. The resulting toners can be selected for known electrophotographic imaging, digital, printing processes, including color processes, and lithography.
In embodiments, the present invention is directed to a substantial free surfactant process comprised of forming a latex of a polyester, such as a sodium sulfonated polyester resin, in water, mixing the latex with a colorant, especially pigment dispersion containing coagulating metal ions resulting from water insoluble metal salt or oxides in the presence of an inorganic or an organic acid, and thereafter, heating the resulting mixture to primarily enable the generation of toner aggregates and coalesced toner particles. The polyester resin selected specifically contains sulfonated groups thereby rendering them dissipatable, that is, they form spontaneous emulsions in water without the use of organic solvents, above the glass transition temperature, Tg, of the polyester resin. The process of the present invention can be considered a surfactant free chemical method wherein sulfopolyester particles in the presence of a colorant dispersion are aggregated and coalesced with water and insoluble metal salts or oxides in the presence of an inorganic or an organic acids which salts and acids slowly react to release metal ion flocculents. The reaction between the water insoluble metal salts or oxides in the presence of an acid permits the controlled release of flocculent, since the metal salts or oxides being substantially insoluble in water are well dispersed in the aqueous phase of the sulfonated polyester emulsion and react with the acid slowly to give rise to metal ions, and wherein during the heating no surfactants are utilized. Heating the mixture at temperatures of from about 45° C. to about 55° C. generates toner size particles with, for example, an average particle volume diameter of from about 1 to about 25, and specifically about 2 to about 10 microns. It is believed that during the heating the components of the sulfonated polyester latex and the colorant dispersion aggregate and fuse together to form composite toner particles.
In specific embodiments, the present invention is directed to an in situ process comprised of first dispersing a colorant like a pigment, such as HELIOGEN BLUE™ or HOSTAPERM PINK™, reference the Color Index, in an aqueous mixture utilizing a high shearing device, such as a Brinkmann Polytron, microfluidizer or sonicator, thereafter shearing this mixture with a latex of suspended polyester resin particles, andi which particles are specifically, for example, of a size of from about 5 to about 500, and specifically, about 10 to about 250 nanometers in volume average diameter as measured by a Brookhaven nanosizer. Thereafter, the aforesaid mixture is contacted with a metal ion complexing agent, resulting from the reaction between a metal salt or metal oxide with an inorganic or organic acid and heated with stirring for a suitable time period of, for example, at a temperature of from about 1 to about 8 hours, and which heating is, for example, at a temperature of from about 40° C. to about 60° C., and specifically from about 45° C. to about 55° C., thereby resulting in the simultaneous aggregation and coalescence of the resin particles with the colorant, and permitting the formation of particles in a size of from about 0.5 micron to about 20 microns, and specifically from about 2 to about 10 microns in average diameter size as measured by the Coulter Counter (Microsizer II). The size of the coalesced particles and their distribution can be controlled by, for example, the amount of the metal ions resulting from the addition of water insoluble metal salts or oxides in presence of an acid and by the heating temperature, and wherein the speed at which toner size particles are formed can be controlled by the quantity of coagulant complexing agent used and by the temperature. The metal salts or oxides are insoluble or substantially insoluble in water, but are readily dispersible in water, the reaction between the acid and the metal salt or metal oxide allows a controlled flocculent release of metal ions in the latex emulsion colorant mixture. The particles obtained after heating can be subjected to washing with, for example, water to remove residual salts or ions and drying whereby toner particles comprised of resin and colorant, and which toner can be of various particle size diameters, such as from 1 to about 20, and specifically about 12 microns in volume average particle diameter. The aforementioned toners are especially useful for the development of colored images with excellent line and solid resolution, and wherein substantially no background deposits are present.
In reprographic technologies, such as xerographic and ionographic devices, toners with volume average diamreter particle sizes of from about 9 microns to about 20 microns are effectively utilized. Moreover, in xerographic technologies, such as in the high volume Xerox Corporation 5090 copier-duplicator, high resolution characteristics and low image noise are highly desired, and can be attained utilizing the small sized toners of the present invention with, for example, a volume average particle diameter of from about 2 to about 11 microns and specifically less than about 7 microns, and with a narrow geometric size distribution (GSD) of from about 1.16 to about 1.3. Additionally, in xerographic systems wherein process color is utilized, such as pictorial color applications, small particle size colored toners, specifically of from about 3 to about 9. microns, are desired to avoid paper curling. Also, it is preferable to select small toner particle sizes, such as from about 1 to about 7 microns, and with higher colorant loading, such as from about 5 to about 12 percent by weight of toner, such that the mass of toner layers deposited onto paper is reduced to obtain the same quality of image and resulting in a thinner plastic toner layer on paper after fusing, thereby minimizing or avoiding paper curling. Toners prepared in accordance with the present invention enable in embodiments the use of lower image fusing temperatures, such as from about 120° C. to about 150° C., thereby avoiding or minimizing paper curl. Lower fusing temperatures minimize the loss of moisture from paper, thereby reducing or eliminating paper curl. Furthermore, in process color applications, and especially in pictorial color applications, toner to paper gloss matching is highly desirable. Gloss matching refers to matching the gloss of the toner image to the gloss of the paper. For example, when a low gloss image of from about 1 to about 30 gloss is desired, low gloss paper is utilized, such as from about 1 to about 30 gloss units as measured by the Gardner Gloss metering unit, and which after image formation with small particle size toners, specifically of from about 3 to about 5 microns and fixing thereafter, results in a low gloss toner image of from about 1 to about 30 gloss units as measured by the Gardner Gloss metering unit. Alternatively, when higher image gloss is desired, such as from about 30 to about 60 gloss units as measured by the Gardner Gloss metering unit, higher gloss paper is utilized, such as from about 30 to about 60 gloss units, and which after image formation with small particle size toners of the present invention of, for example, from about 3 to about 5 microns, and fixing thereafter results in a higher gloss toner im
Hopper Michael A.
Jiang Lu
Mychajlowskij Walter
Patel Raj D.
Sacripante Guerino G.
Goodrow John
Palazzo E. O.
Xerox Corporation
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