Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-10-29
2001-04-10
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031850, C106S472000, C106S473000, C106S476000, C106S478000, C106S499000, C106S505000
Reexamination Certificate
active
06214100
ABSTRACT:
TECHNICAL FIELD
The present invention relates to ink-jet compositions for inkjet printers, including thermal inkjet, piezoelectric inkjet, drop on demand, and continuous printing applications for home, office, large format printers, and textile printers. The inks herein comprise pigments that have been chemically modified to be water dispersible by addition of functional groups to the surface of the pigment, resulting in water dispersible macromolecular chromophore particles. The performance of these macromolecular chromophores is improved by the addition of specific ester functional groups that provide improved black to color bleed control and high waterfastness.
BACKGROUND ART
Ink-jet printing is a non-impact printing process in which droplets of ink are deposited on print media, such as paper, transparency film, or textiles. Low cost and high quality of the output, combined with relatively noise-free operation, have made ink-jet printers a popular alternative to other types of printers used with computers. Essentially, ink-jet printing involves the ejection of fine droplets of ink onto print media in response to electrical signals generated by a microprocessor.
There are two basic means currently available for achieving ink droplet ejection in ink-jet printing: thermally and piezoelectrically. In thermal ink-jet printing, the energy for drop ejection is generated by electrically-heated resistor elements, which heat up rapidly in response to electrical signals from a microprocessor to create a vapor bubble, resulting in the expulsion of ink through nozzles associated with the resistor elements. In piezoelectric ink-jet printing, the ink droplets are ejected due to the vibrations of piezoelectric crystals, again, in response to electrical signals generated by the microprocessor. The ejection of ink droplets in a particular order forms alphanumeric characters, area fills, and other patterns on the print medium.
Inks useful in ink-jet printing are typically composed of either pigments or dyes. Pigments are very small insoluble solid colorant particles wherein the molecules are strongly associated with one another through intermolecular forces such as Van der Waals attraction, pi-pi interactions or hydrogen bonding. These forces of attraction prevent solvation of the molecules by common solvents such that they cannot form solutions like their dye counterparts. Conventionally, pigments are used in printing inks by suspending them in a liquid medium using a high-energy dispersion process with the aid of dispersing agents. One disadvantage of using pigments is that their dispersions are inherently thermodynamically unstable and eventually the pigment particles agglomerate to larger particles that tend to settle. Moreover, pigments lead to the inks taking a relatively long time to dry on the media, which in turn leads to increased opportunity for the ink to run or smear when subjected to moisture or water; the degree of water resistance is called “waterfastness”. Further, the tendency of one color of ink to run into the adjacent color is know at “bleed”. This is most apparent with black ink bleeding into color inks. Several methods have been employed by ink formulators to achieve bleed control to varying degrees of success. Many pigmented inks possess one or more of the foregoing properties. However, few ink compositions possess all of those properties, since an improvement in one property often results in the degradation of another. Thus, inks used commercially represent a compromise in an attempt to achieve a pigmented ink evidencing at least an adequate dispersibility and performance in each of the aforementioned properties.
Accordingly, investigations continue into developing ink formulations that have both good dispersibility and improved properties such as improved bleed control and good waterfastness all without sacrificing performance in other necessary properties.
DISCLOSURE OF INVENTION
In accordance with the invention, inks used in ink-jet printing are provided wherein the black to color bleed and water resistance of the inks are improved through the use of an ink which contains at least one colorant where the colorant comprises pigment particles (preferably carbon black), wherein the surface has been treated with a combination of dispersing groups and specific ester functional groups. This modified pigment particle is also known as a “macromolecular chromophore” or (MMC). This treatment results in water-dispersibility and improved print properties of the pigmented-based ink.
Additionally, methods of ink-jet printing that use the disclosed inks and exploits the ink's properties are provided.
In the practice of the present invention, specific functional groups are applied to a colorant particle with a useful mean diameter ranging from 0.005 to 10 &mgr;m. If the colorant particles are larger than this, they do not remain in solution well enough to be useful in the practice of this invention. Likewise, if the colorant particles are too small, they lack the appropriate properties to be useful in this invention. Colorants of this type result from chemical reactions where the colorant particles are derivatized with solubilizing groups that render the colorant dispersible in water. This resulting functionalized pigment, or MMC, is water-dispersible, with stability being similar to that of well known and commercially used water-soluble acidic and basic dyes.
Examples of water-dispersible black chromophores (or pigments) suitable for use herein are made from commercially available pigments obtained from colorant vendors such as Cabot Corp. Although many base pigments are useful in the practice of this invention, the following pigments comprise a partial list of useful base colorants in this invention; however, this listing is not intended to limit the invention. Base Cabot pigments would include Monarch® 1400, Monarch® 1300, Monarch® 1100, Monarch® 1000, Monarch® 900, Monarch® 880, Monarch® 800, and Monarch® 700, Cab-O-Jet® 200 and Cab-O-Jet® 300. The following pigments are available from Columbian: Raven 7000, Raven 5750, Raven 5250, Raven 5000, and Raven 3500. The following pigments are available from Degussa: Color Black FW 200, Color Black FW 2, Color Black FW 2V, Color Black FW 1, Color Black FW 18, Color Black S160, Color Black FW S 170, Special Black 6, Special Black 5, Special Black 4A, Special Black 4, Printex U, Printex 140U, Printex V, and Printex 140V. Tipure® R-101 is available from DuPont.
Ester Functional Groups
The ester structure that imparts bleed control and waterfastness benefits is:
R can be from about 2 to about 4 carbons. R can be branched or unbranched. Preferred R groups include ethyl, n-propyl, isopropyl, n-butyl, isobutyl and t-butyl.
Functional Groups Imparting Water-dispersibility
For modification, one preferred method is treatment of the carbon black pigment with aryl diazonium salts prepared from aromatic compounds containing the carboxylate functional groups. Examples of aryl diazonium salts include those prepared from aminoisophthalic acid.
The base pigments are modified by the addition of one or more organic compounds of the structure:
wherein M
+
can be Na
+
, Li
+
, K
+
, NH
4
+
, tetramethylammonium ((CH
3
)
4
N+), and trimethylammonium ((CH
3
)
3
NH
+
) cations, although any suitable counterion may be used herein.
Synthesis
Although any method known to those skilled in the art can be used to attach these functional groups, one method herein begins with a ratio of water-dispersible group reactants to ester group reactants at treatment levels of from about 0.3/0.5 to about 0.5/0.3 mmol/g macromolecular chromophore (MMC). One preferred ratio of water-dispersible reactants to ester-based, bleed control reactants is a ratio of 0.5:0.5 mmol/g MMC. Another preferred ratio is 0.3:0.3 mmol/g MMC. In general, see U.S. Pat. Nos. 5,707,432; 5,630,868; 5,571,311; and 5,554,739 for a discussion of modified carbon black pigments and methods of attaching functionalized groups. The final ratio of functional groups on
Amici Robert M
Gambale Ronald J
Parazak Dennis P
Hewlett--Packard Company
Jones Michael D.
Klemanski Helene
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