Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-02-17
2001-01-23
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S555000, C524S815000, C526S287000, C526S311000, C526S312000
Reexamination Certificate
active
06177485
ABSTRACT:
TECHNICAL FIELD
The present relates generally to ink-jet inks, and, more particularly, to additives, specifically, polymeric additives, for improving bleed control, water-fastness, and smear-fastness of ink-jet inks.
BACKGROUND ART
Thermal ink-jet printers offer a low cost, high quality, and comparatively noise-free option to other types of printers commonly used with computers. Such printers employ a resistor element in a chamber provided with an egress for ink to enter from a plenum. The plenum connects to a reservoir for storing the ink. A plurality of such resistor elements forms a pattern in a printhead. This pattern is called a primitive. Each of the resistor elements line up with a nozzle in a nozzle plate, through which ink is expelled toward a print medium. The entire assembly of printhead and reservoir comprises an ink-jet pen.
In operation, each resistor element connects through a conductive trace to a microprocessor, where current-carrying signals cause one or more selected elements to heat. The heating creates a bubble of ink in the chamber, which is expelled through the nozzle toward the print medium. Firing a plurality of such resistor elements, in a particular order, in a given primitive, forms alphanumeric characters, performs area-fills, and provides other print capabilities on the medium.
Ink-jet inks used in thermal ink-jet printing typically comprise a colorant and a vehicle, with the vehicle often containing water and other relatively low surface tension liquids. The colorant may comprise a water-miscible dye or a water-insoluble pigment that is dispersed in the ink with a dispersing agent.
The tight tolerances of the nozzles (typically 50 mm diameter) require that the ink not clog the nozzles. Furthermore, repeated firings of the resistor elements, which must withstand about 10 million firings over the life of the ink cartridge, can result in fouling of the resistor element. Kogation is the term used for this type of fouling. The ink composition must be capable of interacting with the print medium, especially paper, to penetrate it without undue spreading. The ink composition should be smear- and water-resistant on the paper. Finally, bleed between colors must be controlled, so that any invasion of a color by another color is reduced or even eliminated.
Many inks possess one or more of the foregoing properties. However, few ink compositions posses all of those properties, since an improvement in one property often results in the degradation of another property. Thus, inks used commercially represent a compromise in an attempt to achieve an ink evidencing at least an adequate performance in each of the aforementioned properties.
Accordingly, investigations continue into developing ink formulations that have improved properties such as reduced kogation and reduced crusting (i.e. improved decap). Further properties sought to be improved include high edge acuity, high optical density, fast drying times, good water-fastness, and good smear-fastness, all without sacrificing performance in other necessary properties.
Recent advances in ink-jet inks have incorporated pigments in place of the earlier water-miscible dyes. However, pigments by definition are not water-miscible, and require the presence of a dispersing agent. Further investigations into the use of pigments have determined that surface treatment of the pigment, to form either anionic or cationic functional groups on the surface, provides a macromolecular chromophore (MMC) that is water-soluble, thus eliminating the requirement for a dispersing agent.
Investigation continues into the use of pigments that have been treated to be water-miscible, but which possess most, if not all, of the foregoing desired properties. Further, there continues to be a need for inks that employ water-miscible dyes where it is desired to also improve the foregoing properties.
DISCLOSURE OF INVENTION
In accordance with the invention, the properties of ink-jet inks containing a colorant (pigment, macromolecular chromophore, or dye) are improved by adding thereto an additive, specifically, one or more polymers derived from unsaturated surfactants. The unsaturated surfactant(s) has at least one carbon-carbon double bond (C═C). The polymer may be simply an polymer of the unsaturated surfactant. Alternatively, the polymer may be co-polymerized with one or more vinyl monomers or one or more polymers based on the vinyl monomers may be mixed with the unsaturated surfactant polymer. As used herein, the term “copolymer” is used to include polymers derived from co-polymerizing two or more monomers as well as mixtures of polymers. The vinyl monomer(s) or polymer(s) is used to adjust or “tweak” the properties of the resultant polymer. For example, the more hydrophobic the polymer or the higher its molecular weight, then the greater the water-fastness afforded the ink-jet ink.
The additive of the invention improves bleed control, water-fastness, and smear-fastness of ink-jet inks, particularly thermal ink-jet inks.
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Moffatt John R
Tsang Joseph W
Hewlett--Packard Company
Jagannathan Vasu
Shosho Callie E.
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