Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
1997-10-29
2002-11-05
Rodee, Christopher (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
06475691
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally directed to toner processes, and more specifically, to processes which utilize aggregation and coalescence or fusion of the latex, colorant, such as pigment, dye, or mixtures thereof, and optional additive particles. In embodiments, the present invention is directed to processes which provide toner compositions with a volume average diameter of from about 1 micron to about 20 microns, and preferably from about 2 microns to about 12 microns and a narrow particle size distribution of, for example, from about 1.10 to about 1.45 as measured by the Coulter Counter method, without the need to resort to conventional pulverization and classification methods. The resulting toners can be selected for known electrophotographic imaging and printing processes, including digital color processes. In embodiments, the present invention is directed to a process comprised of blending an aqueous colorant, especially pigment dispersion containing an ionic surfactant with a latex emulsion comprised of polymer, or resin particles, preferably submicron in size, of from, for example, about 0.05 micron to about 1 micron in volume average diameter, a nonionic surfactant and an ionic surfactant of opposite charge polarity to that of the ionic surfactant in the colorant dispersion, and water miscible chain transfer agents, or wherein there is selected a nonionic surfactant with chain transfer characteristics which covalently bond to the surface of the latex selected and thereby, for example, enabling improvements in the latex stability; thereafter, heating the resulting flocculent mixture at, for example, below about or about equal to the resin glass transition temperature, and more specifically, from about 35° C. to about 60° C. (Centigrade) to form toner sized aggregates of from about 2 microns to about 20 microns in volume average diameter, and which toner is comprised of polymer, colorant, especially pigment and optionally additive particles, followed by heating the aggregate suspension above about or about equal to the resin glass transition temperature, and more specifically at, for example, from about 70° C. to about 100° C. to effect coalescence or fusion of the components of the aggregates and to form mechanically stable integral toner particles. The water soluble, or miscible chain transfer agent can regulate the molecular weight of the resin, control the product surface characteristics, avoids the use of costly and hazardous odor producing components, such as carbon tetrabromide, alkyl thiols, such as butanethiol, octanethiol, and the like, reference U.S. Pat. No. 5,561,025 which also discloses emulsion/aggregation/coalescence processes with water phase termination agents and which agents are not water miscible. With the selection of the nonionic surfactant with chain transfer characteristics chain transfer agents like carbon tetrabromide can be avoided, and moreover, the process of the present invention is sediment free, or substantially sediment free. Additionally, in embodiments there can be provided toner particles with spherical shape at lower coalescence temperatures and/or shorter coalescence times. Toners with a smoother surface, and in particular with a spherical shape, transfer efficiently from the photoreceptor surface to the substrate, thereby effectively preserving image integrity during the transfer step, affording higher image signal-to-noise ratios, and thus higher image quality. High toner transfer efficiency also reduces or eliminates toner waste and enables a substantially “cleaner-less” machine design in that the developed images are completely or virtually completely transferred to the substrate, leaving essentially no residual toners on the imaging member, such as the photoreceptor, and thus substantially no waste toner. A cleaner-less machine design also significantly prolongs the photoreceptor life since the mechanical abrasion wear of the photoreceptor as a result of cleaning is eliminated, thus enabling reduced machine maintenance service requirement and lowered hardware cost.
The particle size of the toner compositions provided by the processes of the present invention in embodiments can be preferably controlled by the temperature at which the aggregation of latex, colorant, and optional additives is conducted. In general, the lower the aggregation temperature, the smaller the aggregate size, and thus the final toner size. For a latex polymer with a glass transition temperature (Tg) of about 55° C. and a reaction mixture with a solids content of about 12 percent by weight, an aggregate size of about 7 microns in volume average diameter is obtained at an aggregation temperature of about 53° C.; the same latex will provide an aggregate size of about 5 microns at a temperature of about 48° C. under similar conditions. In embodiments of the present invention, an aggregate size stabilizer can be optionally added during the coalescence to prevent the aggregates from growing in size with increasing temperature, and which stabilizer is generally an ionic surfactant with a charge polarity opposite to that of the ionic surfactant in the colorant, especially pigment dispersion.
In embodiments thereof, the present invention relates to a direct toner preparative process comprised of blending an aqueous colorant dispersion containing, for example, a colorant, such as HELIOGEN BLUE™ or HOSTAPERM PINK™, and a cationic surfactant, such as benzalkonium chloride (SANIZOL B-50™), and a latex emulsion containing an anionic surfactant, such as sodium dodecylbenzene sulfonate (for example NEOGEN R™ or BIOSOFT D40™), and a water miscible chain transfer agent like acids, alcohols, ethers, amines, carbonyl compounds, and the like, and wherein the latex polymer is derived from emulsion polymerization of monomers selected, for example, from the group consisting of styrene, acrylates, methacrylates, acrylonitrile, butadiene, acrylic acid, methacrylic acid, and the like, thereby resulting in the flocculation of the polymer particles with the colorant particles and optional additives; and which flocculent mixture, on further stirring at a temperature of from about 35° C. to about 60° C., results in the formation of toner sized aggregates having an aggregate size of, for example, from about 2 microns to about 10 microns in volume average diameter as measured by the Coulter Counter (Microsizer II) and a particle size distribution of about 1.15 to about 1.35; thereafter, heating the aggregate suspension at from about 70° C. to about 95° C. to form toner particles; followed by filtration, washing, and drying in an oven, or the like. The aforementioned toners are especially useful for imaging processes, especially xerographic processes, which usually require high toner transfer efficiency, such as those having a compact machine design without a cleaner or those that are designed to provide high quality colored images with excellent image resolution and signal-to-noise ratio as well as image uniformity.
PRIOR ART
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. In U.S. Pat. No. 4,983,488, there is disclosed a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters su
Cheng Chieh-Min
Kmiecik-Lawrynowicz Grazyna E.
Palazzo E. O.
Rodee Christopher
Xerox Corporation
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