Ink jet printing process

Details Ink jet printing process Ink jet printing process

1999-07-30

2001-08-28

Barlow, John (Department: 2853)

Incremental printing of symbolic information

Ink jet

Fluid or fluid source handling means

C347S101000, C347S105000

Reexamination Certificate

active

06280026

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an ink jet printing process for improving the dye density and fixability of an ink jet image ink containing a water-soluble cationic or basic dye.
BACKGROUND OF THE INVENTION
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets in a pixel-by-pixel manner to an image-recording element in response to digital signals. There are various methods which may be utilized to control the deposition of ink droplets on the image-recording clement to yield the desired image. In one process, known as continuous ink jet, a continuous stream of droplets is charged and deflected in an imagewise manner onto the surface of the image-recording element, while unimaged droplets are caught and returned to an ink sump. In another process, known as drop-on-demand ink jet, individual ink droplets are projected as needed onto the image-recording element to form the desired image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation. Ink jet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging.
The inks used in the various ink jet printers can be classified as either dye-based or pigment-based. A dye is a colorant which is molecularly dispersed or solvated by a carrier medium. The carrier medium can be a liquid or a solid at room temperature. A commonly used carrier medium is water or a mixture of water and organic co-solvents. Each individual dye molecule is surrounded by molecules of the carrier medium. In dye-based inks, no particles are observable under the microscope. Although there have been many recent advances in the art of dye-based ink jet inks, such inks still suffer from deficiencies such as low optical densities on plain paper and poor light-fastness. When water is used as the carrier medium, such inks also generally suffer from poor water-fastness.
The ink jet receiving elements that can be used with the above mentioned inks must meet several requirements including producing high density images that will not smear, bleed or wander when exposed to water for short periods of time.
U.S. Pat. No. 5,560,996 relates to the use of a printing paper containing an intercalated compound that can chemically fix water soluble, cationic or anionic dyes to the paper by an electrostatic attraction between the dye and the intercalated compound. Although this type of an ink receiving layer does provide an image with good fixability, there is a problem with this material in that the overall density of the images generated is too low, as will be shown hereafter.
It is an object of this invention to provide an ink jet printing process for improving the fixability of an ink jet image so that it does not smear or wander when subjected to water for a period of time. It is another object of this invention to provide an ink jet printing process wherein the ink jet image is of high density.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with the present invention which comprises an ink jet printing process for improving the dye density and fixability of an ink jet image comprising:
a) providing an ink jet recording element comprising a support having thereon an image-recording layer comprising a mixture of an anionic, water dispersible polyester ionomer and a hydrophilic polymer; and
b) applying droplets of a liquid ink on the image-recording layer in an image-wise manner, the ink comprising water, humectant and a water-soluble cationic or basic dye.
It was found that the fixability of the printed ink jet image is of high density and does not smear or wander when subjected to water for a period of time.
DETAILED DESCRIPTION OF THE INVENTION
A variety of basic or cationic dyes may be used in the invention as disclosed in U.S. Pat. No. 5,560,996, the disclosure of which is hereby incorporated by reference. In a preferred embodiment of the invention, the dye is an azo dye, a triphenylmethane dye, an azine dye, an oxazine dye, a thiazine dye, each having an amine salt residue or a quaternary ammonium group. Such inks may be prepared directly from the basic or cationic dyes or by redissolving the leuco or deprotonated, electrically neutral forms (precursor) of these dyes in dilute aqueous acids, as described in U.S. Pat. Nos. 4,880,769; 3,992,140; and 5,559,076 and U.S. Ser. Nos. 09/299,480 and 09/299,412, both filed Apr. 26, 1999, the disclosures of which are hereby incorporated by reference. Examples of such electrically neutral forms of cationic dyes include the following:
The dyes described above may be employed in any amount effective for the intended purpose. In general, good results have been obtained when the dye is present in an amount of from about 0.2 to about 5% by weight of the ink jet ink composition, preferably from about 0.3 to about 3% by weight. Dye mixtures may also be used.
In a preferred embodiment of the invention, the anionic, water-dispersible polyester ionomer polymers have the following general formula:
wherein:
A is the residue of one or more diol components which together comprise 100 mole % of recurring units and is represented by the following structure:
—O—(CHR
2
CHR
3
O)
m
—R
1
—(OCHR
2
CHR
3
)
n
—O—
 wherein:
m and n independently represent an integer from 0-4;
R
1
represents S, an alkylene group of 1 to about 16 carbon atoms; a cycloalkylene group of 5 to about 20 carbon atoms; a cyclobisalkylene group of about 8 to about 20 carbon atoms, a bi- or tri-cycloalkylene group of about 7 to about 16 carbon atoms, a bi- or tri-cyclobisalkylene group of about 9 to about 18 carbon atoms, an arenebisalkylene group of from 8 to about 20 carbon atoms or an arylene group of 6 to about 12 carbon atoms, a carbinol-terminated polydimethylsiloxane segment; and
R
2
and R
3
each independently represents H, a substituted or unsubstituted alkyl group of about 1 to about 6 carbon atoms or a substituted or unsubstituted aryl group of about 6 to about 12 carbon atoms;
B is the residue of a diacid component which comprises 8 to 50 mole % of recurring units and is represented by one or more of the following structures:
 wherein:
M
+
represents alkali metals, such as Li, Na and K; ammonium groups such as ammonium, methylammonium, triethylammonium, tetralkylammonium, aryltrialkylammonium, etc.; phosphonium groups such as triphenylphosphonium; tetrabutylphosphonium; heteroaromatic ammonium groups such as pyridinium, imidazolium and N-methylammonium; sulfonium groups; guanidinium groups; amidinium groups, etc.; and
D is the residue of a diacid component which comprises 50 to 92 mole % of recurring units and is represented by one or more of the following structures:
 wherein p represents an integer from 2 to 12.
Some typical diols which A represents include ethylene glycol, diethylene glycol, triethylene glycol, thiodiethanol, cyclohexanedimethanol, bisphenol A, trans-1,4-cyclohexanediol, dodecanediol, cis-exo-2,3-norbornanediol, 5-norbomene-2,2-dimethanol, hydroquinone bis(2-hydroxyethylether), carbinol terminated polydimethylslioxane, MW=1000 (DMS-C15), (Gelest Inc.), etc.
The polyester employed in the invention preferably has a Tg between about −50° C. and 100° C. A plasticizer may also be added if desired. In a preferred embodiment of the invention, the polyesters have a number average molecular weight of from about 10,000 to about 250,000 more preferably from 20,000 to 100,000. Except where noted water dispersible polyester ionomers of invention were prepared analogous to what was described in U.S. Pat. No. 5,317,001.
Examples of anionic, water-dispersible polyesters used in the invention include the following:
P-1: AQ55D® (Eastman Chemical Co.), poly[isophthalic acid-co-5-sodiosulfoisophthalic acid (82:18 molar ratio)-diethylene glycol-co-1,4-cyclohexanedimethanol (57:43 molar ratio)], Tg=55° C.
P-2: AQ38D® (Eastman Chemical Co.), poly[isoph

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