Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1997-06-05
2001-12-11
Morris, Terrel (Department: 1771)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C260SDIG031, C524S458000, C524S460000, C106S031250, C106S031280
Reexamination Certificate
active
06329446
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally directed to aqueous ink compositions. More specifically, the present invention is directed to colored, especially pigmented, aqueous ink compositions particularly suitable for use in ink jet printing processes, and especially thermal ink jet processes, and wherein the inks enable images with excellent smear resistant characteristics. Moreover, with the inks of the present invention paper curl is minimized and image smearing is minimal, or avoided. In embodiments, the present invention relates to imaging processes with ink jet inks comprised of water, pigment, and resin emulsion particles. Further, images developed with the inks of the present invention in embodiments enable ink jet prints of excellent resolution, acceptable density, excellent waterfastness, minimum or very low showthrough, and excellent MFLEN.
PRIOR ART
Ink jet printing can be considered a non-impact method that produces droplets of ink that are deposited on a substrate, such as paper or transparent film, in response to an electronic digital signal. Thermal or bubble jet drop-on-demand ink jet printers have found broad application as output for personal computers in the office and the home In existing thermal ink jet printing, the printhead typically comprises one or more ink jet ejectors, such as disclosed in U.S. Pat. No. 4,463,359, the disclosure of which is totally incorporated herein by reference, each ejector including a channel communicating with an ink supply chamber, or manifold, at one end and having an opening at the opposite end, referred to as a nozzle. A thermal energy generator, usually a resistor, is located in each of the channels, a predetermined distance from the nozzles. The resistors are individually addressed with a current pulse to momentarily vaporize the ink and form a bubble which expels an ink droplet. As the bubble grows, the ink rapidly bulges from the nozzle and is momentarily contained by the surface tension of the ink as a meniscus. This is a very temporary phenomenon, and the ink is quickly propelled toward a print sheet. As the bubble begins to collapse, the ink still in the channel between the nozzle and bubble starts to move toward the collapsing bubble, causing a volumetric contraction of the ink at the nozzle, and resulting in the separation from the nozzle of the bulging ink as a droplet. The feed of additional ink provides the momentum and velocity for propelling the droplet towards a print sheet, such as a piece of paper. Since the droplet of ink is emitted only when the resistor is actuated, this type of thermal ink jet printing is known as “drop-on-demand” printing. Other types of ink jet printing, such as continuous-stream or acoustic, are also known.
In a single-color ink jet printing apparatus, the printhead typically comprises a linear array of ejectors, and the printhead is moved relative to the surface of the print sheet, either by moving the print sheet relative to a stationary printhead, or vice-versa, or both. In some types of apparatus, a relatively small printhead moves across a print sheet numerous times in swathes, much like a typewriter. Alternatively, a printhead, which consists of an array of ejectors and extends the full width of the print sheet, may be passed once down the print sheet to give full-page images in what is known as a “full-width array” (FWA) printer. When the printhead and the print sheet are moved relative to each other, imagewise digital data is used to selectively activate the thermal energy generators in the printhead over time so that the desired image will be created on the print sheet.
With the demand for higher resolution printers, the nozzles in ink jet printers are decreasing in size. Nozzle openings are typically about 50 to 80 micrometers in width or diameter for 300 spi printers. With the advent of 600 spi printers, these nozzle openings are typically about 10 to about 40 micrometers in width or diameter. These small dimensions require inks that do not plug or minimize plugging of the small openings.
Therefore, an important requirement for an ink jet ink is the ability of the ink to be stable with minimal or no settling, the ability of the ink to remain in a fluid condition in a printhead opening an exposure to air, and moreover, wherein when the inks are selected for ink jet printing there is minimized paper curl, or wherein paper curl can be controlled.
Another important measured property for an ink jet ink is the latency or decap time, which is the length of time over which an ink remains fluid in a printhead opening or nozzle when exposed to air and, therefore, capable of firing a drop of ink at its intended target. Latency is the maximum idling times allowed for ink to be jetted by a printer with a speed equal to or greater than 5 m/s (equivalent to an ink traveling a distance of 0.5 millimeter in less than 100 &mgr;s) without a failure. This test is operated with the printhead or nozzles uncovered or decapped, and generally at a relative humidity of 15 percent. The time interval is the longest length of time that the printhead, uncovered, will still fire a specified drop without drop displacement or loss of density. The longer the latency time rating, the more desirable the ink. The inks of the present invention possess many of these characteristics in embodiments thereof.
Moreover, an important requirement for ink jet inks, especially for pigment, such as carbon black, based inks, is for the pigment dispersion to remain substantially stable throughout the life of the ink jet cartridge. Dye-based ink jet inks can suffer from deficiencies in waterfastness, smear resistance and lightfastness after being printed on various substrates. Pigments provide an image, on a wide variety of substrates, having high optical density with high waterfastness, smear resistance and lightfastness. Therefore, pigments are a preferred alternative to dyes, provided the pigment dispersions can be made stable to prevent flocculation and/or aggregation and settling. Some cosolvents that function as clogging inhibitors cause destabilization of pigment dispersions and, therefore, cannot be used in pigmented inks.
There is thus a need for aqueous ink compositions that can be utilized in high resolution ink jet printers. Additionally, there is a need for pigmented inks that provide high latency and also remain stable throughout the life of the ink jet cartridge. There is also a need for pigmented inks that provide high optical density in a single application or pass. More importantly, there is a need for ink jet inks wherein paper curl, and/or image smearing can be eliminated or minimized when such inks are selected for ink jet printing processes.
SUMMARY OF THE INVENTION
The present invention relates to an aqueous ink jet ink composition comprising water, colored, especially pigment, particles, and an ink smear reducing additive comprised of a certain latex, that is resin emulsion. More specifically, the present invention relates to ink additives comprised of a resin emulsion comprised of first resin particles, and solubilized resin derived from the polymerization in water of an olefinic acid, such as acrylic acid or methacrylic acid, and an olefinic (meth)acrylate, such as methyl methacrylate, benzyl methacrylate and polyethyleneglycol methacrylate, and wherein the resin possesses, for example, a number average molecular weight of from about 1,000 grams per mole to about 15,000 grams per mole, and the weight average molecular weight thereof is from about 1,500 grams per mole to about 40,000 grams per mole. The resin emulsion is preferably comprised of from about 60 to about 99 weight percent of resin particles, of average diameter of from about 30 nanometers to about 300 nanometers, and from about 2 to about 40 weight percent of solubilized resin. Both the resin particles and solubilized resin can be generated from a free radical type process in water, and wherein one of the monomers is water soluble, such as an acrylic acid or methacrylic acid, and the other monomer(s), or second m
Cheng Chieh-Min
Kneisel Elizabeth A.
Nichols Garland J.
Sacripante Guerino G.
Morris Terrel
Palazzo E. O.
Xerox Corporation
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