Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2003-01-29
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
C430S108200
Reexamination Certificate
active
06780560
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 where a cationic charge control agent (CCA) is added as a coagulant during the aggregation process. The CCA coagulant type molecules can be large organic tetra-alkylated quaternary ammonium halide salts such as dimethyldioctadecyl-ammonium (DMDODA) bromide or chloride. More specifically, the present invention is directed to toner compositions and processes thereof, wherein the toner core and exterior are rendered more hydrophobic by the CCA coagulant quaternary ammonium salts thereby, for example, enhancing the surface charging performance of the toner particles enabling high triboelectric charge levels at 20 percent RH (Relative Humidity), and 80 percent RH of from about −30 to about −100 microcoulombs per gram, and about −20 to about −40 microcoulombs per gram, respectively; and a low relative humidity sensitivity, such as from about 1.1 to about 3.6. 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 more 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 further embodiments, the present invention is directed to a substantially free, or reduced surfactant process, and wherein the colorant dispersion contains a surfactant comprised of forming a latex of a polyester, such as a sodium sulfonated polyester resin in water, mixing the latex with a colorant, especially a pigment dispersion containing a coagulating organic complexing agent, such as a tetra-alkylated quaternary ammonium halide salt, and thereafter, heating the resulting mixture to primarily enable the generation of toner aggregates and coalesced toner particles. The polyester resin selected more specifically contains sulfonated groups thereby rendering them dissipatable, that is, the resin is formed from spontaneous emulsions in water without the use of organic solvents. The process of the present invention can be considered a substantially surfactant free chemical method wherein resins, such as sulfopolyester particles are aggregated and coalesced with organic complexing agents in the presence of a colorant dispersion by heating, 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 more specifically, 2 to about 10 microns. It is believed that during the heating the components of the sulfonated polyester latex and the colorant dispersion aggregate fuse together to form composite toner particles. Additionally, it is believed that the complex agents, such as tetra-alkylated quaternary ammonium halide salts, cause the sulfonated polyester latex and colorant to aggregate and coalesce into a toner composite. More specifically, it is believed, while not desired to be limited by theory, that the polyester colloidal particles are destabilized by adding a dilute solution of positively charged tetra-alkylated quaternary ammonium halide salts which are capable of adsorbing onto the negative sulfonated moieties protruding out of the colloidal particles, and therefore, nullifying the repulsive forces on the colloidal particle surfaces. Also, in embodiments thereof, the present invention is directed to an in situ process comprised of first dispersing a colorant like a pigment, such as a cyan, magenta, yellow, red, orange, yellow, 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, and which particles are more specifically, for example, of a size ranging from about 5 to about 500, and more specifically, 10 to about 250 nanometers in volume average diameter, as measured by the Brookhaven nanosizer. Thereafter, the resulting mixture is contacted with an organic complexing agent, and heated with stirring for a suitable time period of, for example, from about 1 to about 8 hours, and which heating is, for example, from about 40° C. to about 60° C., and more specifically, from about 45° C. to about 55° C., thereby resulting in the aggregation and simultaneous coalescence of the resin particles with the colorant, and permitting the formation of particles ranging in size of from about 0.5 micron to about 20 microns, and more 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 organic complexing agent selected and by the temperature of heating, and wherein the speed at which toner size particles are formed can also be controlled by the quantity of tetra-alkylated quaternary ammonium halide salt complexing agent used, and by the temperature. The particles obtained after heating can be subjected to washing with, for example, water to remove the residual organic complexing agent and then drying, whereby toner particles comprised of resin and colorant can be of various particle size diameters such as from 1 to about 25, and more 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.
FURTHER BACKGROUND AND REFERENCES
In reprographic technologies, such as xerographic and ionographic devices, toners with volume average diameter particle sizes of from about 9 microns to about 20 microns are effectively utilized. Moreover, in xerographic technologies, such as 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 more 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, more 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 desirable. Gloss matching is referred to as matching the gloss of the toner image to the gloss of the paper. For example, when a low gloss image of, more specifically, from about 1 to about 30 gloss is desi
Farrugia Valerie M.
Sacripante Guerino G.
Chapman Mark A.
Palazzo E. O.
Xerox Corporation
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