Coating processes – Nonuniform coating – Paper or textile base
Reexamination Certificate
2000-11-06
2001-10-09
Henderson, Christopher (Department: 1713)
Coating processes
Nonuniform coating
Paper or textile base
Reexamination Certificate
active
06299941
ABSTRACT:
BACKGROUND OF THE INVENTION
The use of resin emulsion particles in pigmented inks is illustrated in copending application U.S. Ser. No. 08/869,962, the disclosure of which is wholly incorporated herein by reference, which discloses, for example, a resin emulsion comprised of from about 40 to 60 weight percent of benzyl methacrylate, from about 5 to about 20 weight percent of methacrylic acid, and from about 20 to about 40 percent by weight of polyethyleneglycol methacrylate, or more generally, a low molecular weight polyethylene glycol capped with a methacrylate or acrylate group.
The present invention is generally directed to ink compositions. More specifically, the present invention is directed to aqueous ink compositions particularly suitable for use in ink jet printing processes, and especially thermal ink jet processes, wherein the inks enable images with excellent smear resistant characteristics, and which inks contain unsaturated dye molecules incorporated into the resin emulsion particle by emulsion polymerization. Moreover, with the inks of the present invention the optical density of the developed images is excellent, 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, colorant, especially dye, or 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 and improved optical density, excellent waterfastness, minimum or very low showthrough, and excellent MFLEN.
PRIOR ART
Ink jet printing can be considered a non-impact method that generates droplets of ink that are deposited on a substrate, such as paper or transparent film, in response to an electronic digital signal.
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 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 toward 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 the small openings.
Another important measured property for an ink jet ink is high optical density and 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 run 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 characteristic for ink jet inks, especially for pigment, such as carbon black, based inks, is for the pigment dispersion to remain stable throughout the life of the ink jet cartridge. Dye 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, with in some instances high optical density with high waterfastness, excellent smear resistance and acceptable lightfastness. Therefore, pigments are a preferred alternative to dyes provided the pigment dispersions can be stabilized to prevent flocculation and/or aggregation and settling. Some cosolvents that are suitable as clogging inhibitors cause destabilization of pigment dispersions and, therefore, cannot readily 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 inks that provide high latency and also remain stable throughout the life of the ink jet cartridge. There is also a need for inks with colorants, such as dyes or pigments, 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 aqueous ink jet ink compositions comprising water, colorant, especially pigment particles, and certain colored resin emulsion particles. More specifically, the present invention relates to inks containing a resin emulsion derived from olefinic monomers, and wherein one of the olefinic monomers contains a colorant, especially a dye. In embodiments, the olefinic dye molecules can be prepared from the condensation reaction of a functional colorant, especially a dye with an olefinic containing reactive material such as metacryloyl chloride, acryloyl chloride or 4-isocyanate-styrene as illustrated by the formula
that is wherein an unsaturated isopropenyl group is chemically bonded, or linked to the R group, and wherein Dye represents the colorant, especially dye chromophore, and R is a carbonyl, oxygen, arylene with, for example, from 7 to about 25 carbon atoms, such as phenylene, and the like, and R′ is a hydrogen or alkyl group of from about 1 to about 6 carbon atoms. Thereafter, the colored resin emuls
Cheng Chieh-Min
Fu Min-Hong
Marsh Daniel G.
Nichols Garland J.
Sacripante Guerino G.
Henderson Christopher
Palazzo E. O.
Xerox Corporation
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