Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2003-02-18
2004-10-12
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
C524S392000
Reexamination Certificate
active
06803166
ABSTRACT:
BACKGROUND
The present invention is directed to a toner process, and more specifically, to chemical toner processes which involve the aggregation and fusion of latex, colorant like pigment or dye, and optional toner additive particles.
In embodiments, the present invention is directed to toner compositions and processes thereof, and wherein a polymer present in the latex possesses a number of molecular weight characteristics, such as M
z
, M
n
, and M
w
to, for example, thereby control the polymer stringiness, which stringiness can be adversely affected by the viscosity and polymer molecular weight and to permit excellent developed image surface gloss and avoid/minimize undesirable toner offset. More specifically, stringiness refers, for example, to one of the toner properties characteristics with high molecular compounds. As stringiness increases, stripping during oil-less fixing worsens. Stringiness is affected by the polymer molecular weight. When the resin has a high, for example, equal to or in excess of about 35,000 molecular weight, stringiness can be easily controlled within a practical a fixing temperature of, for example, about 130° C. to about 190° C., fixing temperature range, however, the resulting fixed image cannot usually be provided with a desirable, for example, from about 25 to about 65 gloss units surface gloss, especially when an amorphous binder resin is selected. Further, when the binder resin has a low M
w
of, for example, equal to or lower than about 20,000 the appearance of stringiness can be suppressed, occasionally providing image gloss, however, toner and image offset can result at high temperatures of, for example, about 170° C. As stringiness increases, stripping during oil-less fixing decreases, and thus the stripping force that may be required for stripping of a fused toner image from a fuser roll can be increased. Stringiness can be characterized by the measurement of the stripping force. Stripping force is measured by using a remodeled version of a Color 645 Stripping Force Fixture of fused toner on Fuji Xerox S paper with a controlled toner mass per unit area of 1.35 milligram/cm
2
with the fixing rate being predetermined to 200 mm/sec, the carried amount of toner being predetermined to 4.5 g/m
2
, 9 g/m
2
and 13.5 g/m
2
, and the fixing temperature being predetermined to 160° C., 180° C. and 200° C. The fused toners, fused at, for example, about 160° C., 180° C. and 200° C., respectively, can be peeled from a fuser roll without any substantial resistance regardless of the carried amount of the toner. In general, it is desirable to have a low stripping force, such as for example a stripping force below 25 gram-force, and more specifically, gram-cm/sec
2
and preferably below 20 gram-force, to for example, achieve a fixed image with a high surface gloss and no high temperature offset occurring.
The toners generated with the processes of the present invention can be selected for copying and printing processes, including color processes, and for imaging processes, and which toners can provide, for example, high quality colored images with excellent image resolution, acceptable signal-to-noise ratio, substantial insensitivity to relative humidity, certain selected gloss characteristics, minimum toner offsetting from fuser rolls, and image uniformity. Also, the toners obtained with the processes illustrated herein can be selected for digital imaging systems and processes, such as the Xerox Corporation DocuCenter Color 500/550 and similar Xerox Corporation DocuColor products.
REFERENCES
In xerographic systems, especially color systems, small sized toners of, for example, from about 2 to about 8 microns can be important to the achievement of high image quality for process color applications. It is also important to have a low image pile height to eliminate, or minimize image feel and avoid paper curling after fusing. Paper curling can be particularly pronounced 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 may be useful to select certain toner particle sizes, such as from about 2 to about 10 microns, 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 necessary for attaining the required optical density and color gamut can be significantly reduced to eliminate or minimize paper curl. Lower toner mass also ensures the achievement of image uniformity. However, higher pigment loadings often adversely affect the charging behavior of toners. For example, the charge levels may be too low for proper toner development or the charge distributions may be too wide and toners of wrong charge polarity may be present. Furthermore, higher pigment loadings may also result in the sensitivity of charging behavior to charges in environmental conditions, such as temperature and humidity. Toners prepared in accordance with the processes of the present invention minimize, or avoid these disadvantages.
There is illustrated in U.S. Pat. No. 4,996,127, the disclosure of which is totally incorporated herein by reference, 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, the disclosure of which is totally incorporated herein by reference, 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 suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70 microns, are obtained. In U.S. Pat. No. 4,797,339, the disclosure of which is totally incorporated herein by reference, there is disclosed a process for the preparation of toners by resin emulsion polymerization wherein similar to the '127 patent certain polar resins are selected; and in U.S. Pat. No. 4,558,108, the disclosure of which is totally incorporated herein by reference, there is disclosed a process for the preparation of a copolymer of styrene and butadiene by specific suspension polymerization.
Polyester based chemical toners substantially free of encapsulation are also known, reference U.S. Pat. No. 5,593,807, the disclosure of which is totally incorporated herein by reference, wherein there is disclosed a process for the preparation of a toner comprised of a sodio sulfonated polyester resin and pigment, and wherein the aggregation and coalescence of resin particles is mediated with an alkali halide. Other U.S. Patents that may be of interest,
Albright Amy A.
Cheng Chieh-Min
Moore Emily L.
Ng Tie Hwee
Chapman Mark A.
Palazzo E. D.
Xerox Corporation
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