Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2001-10-15
2003-06-10
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
Reexamination Certificate
active
06576389
ABSTRACT:
BACKGROUND
The present invention is generally directed to toner processes, and more specifically, to chemical processes which involve the aggregation and fusion of latex resin, colorant like pigment, or dye, and additive particles into toner particles, and wherein aggregation can be primarily controlled by utilizing a two cationic coagulants comprised of (i) a polyaluminum halide, and (ii) a silica, such as a colloidal silica with an alumina coating, that is for example, a colloidal dispersion of discrete spherical silica particles of pure, about 100 percent, amorphous silicon dioxide and wherein the surface is modified to attain cationic properties with a coating of Al
2
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3
on the silica core thereby providing a functionalized colloidal silica, and wherein there is selected a latex comprised, for example, of submicron resin particles in the size range of, for example, about 0.1 to about 0.3 micron in volume average diameter, suspended in an aqueous phase comprised of a mixture of water, an anionic surfactant and a colorant dispersion comprising submicron pigment particles in the size range of, for example, about 0.08 to about 0.3 micron in volume average diameter as measured by a disc centrifuge suspended in an aqueous phase of water and an anionic surfactant, and optionally a nonionic surfactant or mixtures thereof, which are blended together in the presence of a dual coagulant, and wherein the resultant blend is stirred and heated to a temperature below the resin Tg, resulting in aggregates to which optionally is added a second latex to provide a coating on the formed toner aggregates, followed by adjusting the pH of the mixture with a base, and heating the mixture to a temperature above the resin Tg, followed by adjusting the pH of the mixture with an acid to fuse the aggregates. More specifically, the present invention is generally directed to the aggregation and coalescence or fusion of latex, colorant like pigment, dye, and additives like a wax in the presence of a dual coagulant systems, such as polyaluminum chloride (PAC) and aluminum coated silica, wherein when the PAC concentration is about 0.14 to 0.02 percent by weight of toner and the aluminum coated silica concentration about 0.5 to 2 percent by weight of toner provides a toner which exhibits a high gloss and a lower minimum fixing temperature (MFT) wherein the MFT is reduced by a minimum of 10° C., and when the define PAC concentration is about 0.3 to 0.15 percent by weight of toner and the aluminum coated silica concentration is in the range of 1 and 3 percent by weight of toner, and wherein the toner prepared exhibits low gloss or matte wherein low gloss is, for example, from about 8 GGU to about 35 GGU and an increase of about 10° C. to about 30° C. in the hot offset temperature is obtained, compared to a toner prepared just by PAC alone and wherein the dual coagulants are particulates, for example, in the diameter size range of about 0.005 about 0.2 micron, and wherein there are generated toner compositions with, for example, a volume average diameter of from about 1 micron to about 25 microns, and more specifically, from about 2 microns to about 10 microns, and with a narrow particle size distribution of, for example, from about 1.10 to about 1.33, and more specifically, a size distribution in the range of about 1.11 to about 1.26, the size and size distribution being measured by a Coulter Counter without the need to resort to conventional pulverization and classification methods. The resulting toners after washing exhibits provides a suitable toner triboelectrical charge in the range of about −35 to about −15 &mgr;C/g at 20 percent RH. The toners generated can be selected for known electrophotographic imaging and printing processes, including digital color processes such as in the Xerox Corporation 5090 or the Xerox Corporation Docutech 265.
Toners prepared by the process of the present invention possess a number of advantages as compared to a number of toners generated by known emulsion aggregation processes, which advantages include, for example, the ability to control the finish of the fused developed toner image, for example a glossy or a matte image by controlling the amount of the colloidal aluminized silica and the amount of PAC used as the coagulants, wherein when the PAC concentration is between 0.14 to 0.02 percent by weight of toner and the aluminum coated silica, or referred as aluminized silica concentration is between 0.5 to 2.0 percent by weight of toner provides a toner which exhibits a high gloss and a lower minimum fixing temperature (MFT) wherein the MFT is reduced by a minimum of 10° C., and when the PAC concentration is between 0.3 to 0.15 percent by weight of toner and the aluminum coated silica concentration is in the range of 1 and 3 percent by weight of toner, the toner prepared exhibits low gloss or matte wherein low gloss is defined as 35 GGU or less and an increase in hot offset.
Another advantage of the present invention in embodiments resides in using a colloidal aluminized silica as an additional coagulant which permits about 100 percent, incorporation of the silica into the toner particles as compared to using colloidal silica in the toner formulation, which is then aggregated with other known coagulants, such as polyaluminum chloride (PAC) or polyaluminum sulfosilicate (PASS) wherein the silica retention is, for example, less than about 20 percent. Furthermore, another advantage of the present invention in embodiments resides in an increase of reactor productivity by about 10 to 30 percent as compared to a number of known emulsion aggregation processes where the coagulants utilized are PAC and PASS. Furthermore, when the toners generated are roll milled and aged over a period of, for example, about 2 to about 3 hours there results stable and negative toner charging with, for example, no or minimal wrong sign positively charged toner.
The toners generated with the processes of the present invention are especially useful for imaging processes, especially xerographic processes, which usually require toner transfer efficiency in excess of greater than about 90 percent, such as those with a compact machine design without a cleaner or those that are designed to provide high quality colored images with excellent image resolution, acceptable signal-to-noise ratio, and image uniformity.
REFERENCES
In xerographic systems, especially color systems, small sized toners of preferably from about 2 to about 8 microns volume average diameter are of value to the achievement of high image quality for process color applications. Also, of value is to achieve a low image pile height to eliminate, or minimize image feel and avoid paper curling after fusing. Paper curling can be present in xerographic color processes primarily because of the presence of relatively high toner coverage as a result of the application of three to four color toners. During fusing, moisture escapes from the paper due to high fusing temperatures of from about 120° C. to about 200° C. In the situation wherein only one layer of toner is selected, such as in one-color black or highlight color xerographic applications, the amount of moisture driven off during fusing can be reabsorbed by the paper and the resulting print remains relatively flat with minimal paper curl. In process color where toner coverage is high, the relatively thick toner plastic covering on the paper can inhibit the paper from reabsorbing the moisture, and cause substantial paper curling. These and other imaging shortfalls and problems are avoided or minimized with the toners and processes of the present invention.
Also, it is desired in some instances to select certain toner particle sizes, such as from about 2 to about 15 microns, and with a high colorant, especially pigment loading such as from about 4 to about 15 percent by weight of toner, so that the mass of toner for attaining a certain optical density and color gamut can be reduced to eliminate or minimize paper curl. Lower toner mass also ensures the achievement of image uniformit
Boils Danielle C.
Halfyard Kurt I.
Hopper Michael A.
Patel Raj D.
Sanders David J.
Chapman Mark A.
Palazoo Eugene O.
Xerox Corporation
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