Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2001-04-30
2003-06-03
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S101000, C347S095000, C347S096000, C106S031600
Reexamination Certificate
active
06572226
ABSTRACT:
TECHNICAL FIELD
The present invention relates to anisotropic colorants and ink-jet ink compositions that comprise the anisotropic colorants. These anisotropic colorants are highly stable and can be designed to provide enhanced chroma, gloss, gloss uniformity, smearfastness, print quality, drytime, and improved resistance to water when applied to a media. Moreover, inks formulated with these new colorants are useful in ink-jet printing, including thermal ink jet printing, piezoelectric ink jet printing, and continuous ink jet printing.
BACKGROUND ART
Most colorants used commercially are either discreet dyes or dispersed pigments. In the case of the latter, the pigment particle is typically either dispersed with polymers (through non-covalent interactions), or modified covalently with solubilizing moieties (forming “self-dispersed” pigments). In neither instance is the resulting spatial homogeneity (or inhomogeneity) of the discreet particle a consideration.
This necessarily dictates that no order or structuring of the colorants on the printed substrate can subsequently be imposed. This is an important point, because it places hard limits on certain performance attributes of the pigments, in particular chroma and gloss (and gloss uniformity). Pigments are well known in the industry to be inferior to dyes with respect to chroma and gloss on non-specialized media. Part of this lack of performance can be attributed directly to the amorphous nature of the pigment itself and the consequent amorphous nature of the pigment ensemble on the substrate.
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 is connected to a reservoir for storing the ink. A plurality of such resistor elements are arranged in a particular pattern, called a primitive, in a printhead. Each resistor element is associated with a nozzle in a nozzle plate, through which ink is expelled toward a print medium. The entire assembly of printhead and reservoir comprise an ink-jet pen.
On operation, each resistor element is connected via a conductive trace to a microprocessor, where current-carrying signals cause one or more selected elements to heat up. The heating creates a bubble of ink in the chamber, which is expelled through the nozzle toward the print medium. In this way, firing of a plurality of such resistor elements in a particular order in a given primitive forms alphanumeric characters, performs area-fill, 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.
As noted above, there are two general classifications of colorants: dye-based and pigment-based. Dyes have the advantage of being water-soluble. However, problems with dyes include poor waterfastness, poor smearfastness, poor bleed control between colors, and poor lightfastness. Pigments are generally water-insoluble and require a dispersant or other means to make it soluble in water. For the non-covalently dispersed pigments, the nature of the dispersant and the mass ratio of pigment to dispersant are the factors that are controlled. For the self-dispersed pigments, the nature of the covalently-attached solubilizing groups and their density on the pigment surface are the factors that are controlled. From the colorant's frame of reference, these modifications are spatially random by their nature. The resulting pigments are thus a statistical ensemble of the dispersion processes.
Although the relevant art contains many examples of ink-jet ink formulations using these colorants, a need exists for ink compositions comprising stable, water soluble colorants which provide improved chroma, gloss, gloss uniformity, smearfastness, print quality, drytime, and improved resistance to water when applied to a media.
DISCLOSURE OF INVENTION
In accordance with the invention, an ink-jet ink composition is provided which comprises a colorant that is both water-soluble and contains discreet, specifically attached substituents on the colorant particle. These attachments may be homogeneously or inhomogeneously arranged on the particle; however the attachments are not randomly attached like typical pigments used heretofore.
In this embodiment, colorants are synthesized, dispersed, or modified in such a fashion that the resulting discreet particles are anisotropic with respect to their dispersants, polymers, or other attached additives. In other words, on a microscopic or molecular level, one or more “sides” or “faces” of the particle are purposefully chemically/physically distinct from another face or faces. Restating this, the dispersion process is now meant to impart anisotropy, distinct morphology, and/or chirality to the pigment. This is done with the purpose to impart 2- and 3-dimensional structure to the resulting printed substrate.
By creating anisotropic colorants, and thereby influencing the resulting orientation of the particles on the substrate, it is possible to change the surface energy of the printed substrate to a substantial degree. This results in improvements to properties such as improved waterfastness, smearfastness, chroma, and gloss.
One can design specific sites or faces on the colorant to interact preferentially with the substrate, the environment, or both. Surfactant-like molecules may be attached to one side of the colorants to “anchor” it to the substrate, while hydrophobic or non-wetting moieties (fluoropolymers, siloxanes, etc.) can be designed to be present on the surface.
There are several ways that the colorants of this invention may be dispersed anisotropically. While these methods are known in art of molecule design and synthesis, examples include:
the presence of steric bulk on a dispersant, such that the region around the attachment site is no longer available for subsequent reactions. This may also be envisioned as a partial encapsulation.
the use of biphasic or heterogeneous reactions, in which only part of the pigment surface is exposed toward the reactants.
modification of the entire surface of a larger particle with subsequent break up, thereby exposing unreacted surfaces.
Inks comprising these anisotropic colorants are very effective in reducing smear and have increased waterfastness, gloss, gloss uniformity, and improved print quality. The ink may contain further components to aid in providing improved print quality and performance in an ink-jet printer.
Additionally, a method of ink-jet printing which uses the disclosed inks and exploits the inks' properties is provided.
All concentrations herein are in weight percent, unless otherwise indicated. The purity of all components is that employed in normal commercial practice for ink-jet inks. All references are hereby incorporated by reference.
BEST MODES FOR CARRYING OUT THE INVENTION
One example of anisotropic colorants useful herein include modified black pigments obtained from colorant vendors such as Cabot Corp. and Orient Chemical. Many pigments are useful in the practice of this invention. The following pigments comprise a partial list of useful colorants in this invention.
Paliogen® Orange, Heliogen® Blue L 6901F, Heliogen® Blue NBD 7010, Heliogen® Blue K 7090, Heliogen® Blue L 7101F, Paliogen® Blue L 6470, Heliogen® Green K 8683, and Heliogen® Green L 9140, are all available from BASF Corp.
The following pigments are available from Cabot: Monarch® 1400, Monarch® 1300, Monarch® 1100, Monarch® 1000, Monarch® 900, Monarch® 880, Monarch® 800, and Monarch® 700.
The following pigments are available from Ciba: Chromophtal® Yellow 3G, Chromophtal® Yellow GR, Chromophtal® Yellow 8G, Igrazin®D Yellow 5GT, Igralite® Rubine 4BL, Monastral® Magenta, Monastral® Scarlet, Monastral® Violet R, Monastral® Red B, and Monastral® Violet Maroon B.
The following pigments are available from Columbian: Raven 7
Gordon Raquel Yvette
Hewlett -Packard Development Company, L.P.
Jones Michael D.
Shah Manish
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