Ink jet printing method

Details Ink jet printing method Ink jet printing method

2000-11-21

2003-02-25

Hess, Bruce H. (Department: 1774)

Incremental printing of symbolic information

Ink jet

Medium and processing means

C428S195100

Reexamination Certificate

active

06523950

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an ink jet ink printing method using an ink jet ink composition containing a quaternized nitrogen heterocyclic azo dye and a particular receiving layer.
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 element 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 dissolved in the carrier medium. A pigment is a colorant that is insoluble in the carrier medium, but is dispersed or suspended in the form of small particles, often stabilized against flocculation and settling by the use of dispersing agents. The carrier medium can be a liquid or a solid at room temperature in both cases. Commonly used carrier media include water, mixtures of water and organic co-solvents and high boiling organic solvents, such as hydrocarbons, esters, ketones, etc.
The choice of a colorant in ink jet systems is critical to image quality. For colors such as cyan, magenta, yellow, green, orange, etc., the peak wavelength (&lgr;-max), the width of the absorption curve and the absence of secondary absorptions are important. The colorant should also have a high degree of light fastness after printing onto the ink-receiving element. For aqueous dye-based inks, the dye needs to be sufficiently soluble in water to prepare a solution that is capable of producing adequate density on the receiving element and stable for extended periods of storage without precipitation. High quality ink jet printing with dye-based inks requires dyes which will provide both bright hue and good light stability. It is difficult to find dyes which meet all of these requirements.
Another group of dyes is basic or cationic dyes which were developed mainly for the dyeing of synthetic textile fibers such as acrylics and acid-modified polyesters. These dyes are positively charged, due to either the incorporation of pendant, positively-charged substituent groups, such as tetraalkylammonium, or by virtue of the basic chromophore comprising a delocalized cationic system such as a cyanine, azacyanine or azo (diazacyanine).
U.S. Pat. No. 6,143,061 relates to the use of cationic azo dyes derived from the quaternization of pyrazoleazoaminothiazole dyes. As will be shown hereafter, these dyes have poor light stability and unwanted hue shifts in receiver elements containing various anionic polymers.
It is an object of this invention to provide an ink jet printing method using cationic dyes suitable for use in aqueous inks for ink jet printing that will provide more light stable images using certain receiver elements.
SUMMARY OF THE INVENTION
This and other objects are achieved in accordance with this invention which relates to an ink jet printing method, comprising the steps of:
A) providing an ink jet printer that is responsive to digital data signals;
B) loading the printer with ink-receptive elements comprising a support having thereon an image-receiving layer comprising a mixture of an anionic polymer and a hydrophilic polymer;
C) loading the printer with an ink jet ink composition comprising water, a humectant, and a delocalized cationic azo dye derived from the quaternization of a nitrogen heterocyclic azo dye; and
D) printing on the image receiving layer using the ink jet ink in response to the digital data signals
It has been found that use of the above dyes and image-receiving layer provides excellent hue characteristics and light stability.
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment of the invention, the cationic dye has the following formula:
wherein:
Z represents the atoms necessary to complete a nitrogen-containing heterocyclic ring containing 2 or 3 nitrogen atoms and the balance carbon atoms;
R
1
and R
2
each independently represents hydrogen or a substituted or unsubstituted alkyl group of 1 to about 6 carbon atoms;
R
4
, R
5
and R
6
each independently represents the same substituents as R
1
and R
2
, halogen, cyano, substituted or unsubstituted alkoxy, acyl, benzoyl or alkoxycarbonyl; with the proviso that at least one of R
4
, R
5
and R
6
represents a substituted or unsubstituted alkyl group of 1 to about 6 carbon atoms attached to a nitrogen atom;
R
3
represents the same groups as R
4
, R
5
and R
6
; hydroxy; a polyoxyalkylene group of 2-20 alkylene oxide residues; carboxy or sulfo or phospho ester; carbamoyl; substituted or unsubstituted alkyl-, aryl- aralkyl-, diaryl- or dialkyl-carbamoyl of 1 to about 20 carbon atoms; sulfamoyl; substituted or unsubstituted alkyl-, aryl-, aralkyl-, diaryl- or dialkyl-sulfamoyl of 1 to about 20 carbon atoms; acylamino; sulfonyl- amino; amino; a substituted or unsubstituted alkyl-, aryl-, aralkyl-, diaryl- or dialkylamino-of 1 to about 20 carbon atoms; or a quaternary ammonium or phosphonium group; or may be combined with R
2
to form a carbocyclic or heterocyclic 5 or 6 membered ring;
m is 1 to 4;
n is 1 except when Z represents the atoms necessary to complete a nitrogen-containing heterocyclic ring containing 3 nitrogen atoms, in which case n is 0; and
X represents a counterion, such as citrate, gluconate or lactate; with the proviso that when Z represents the atoms necessary to complete a nitrogen-containing heterocyclic ring of 3 nitrogen atoms, then R
3
is combined with R
2
to form a carbocyclic or heterocyclic 5 or 6 membered ring.
Quaternized nitrogen heterocyclic-azo dyes are not new. They have been used for dyeing fabrics, particularly polyacrylonitrile fabrics. Typical examples are quaternized pyrazole-azo, imidazole-azo, triazole-azo dyes. Their use has been described for this purpose in “Chemistry and Application of Dyes” ed. D. R. Waring and G. Hallas, (Plenum Press), p184. A typical preparation of dyes of this type is also described in the above reference (p197).
Examples of dyes which can be used in the invention are as follows:

&lgr;-
max
Dye
R
1
R
7
R
3
R
4
R
5
Y
(nm)
1
n-C
4
H
9
CH
3
CH
3
CH
3
CH
3
CHCH
3
547
2
H
CH
3
CH
3
CH
3
CH
3
CHCH
3
534
3
n-C
4
H
9
CH
3
CH
3
C
2
H
5
C
2
H
5
CHCH
3
549
4
C
2
H
5
H
H
CH
3
CH
3
O
546
5
C
2
H
4
OH
CH
3
H
CH
3
CH
3
CHCH
3
544

Dye
R
1
R
3
R
6
&lgr; max
6
n-C
4
H
9
CH
3
CON (C
2
H
4
OH)
2
551
7
C
2
H
4
Cl
CH
3
CO
2
CH
3
530
8
C
2
H
5
H
CONHC
4
H
9
550
9
n-C
4
H
9
CH
3
CO
2
CH
3
546

Dye
R
1
R
2
R
3
R
6
&lgr; max
10
C
2
H
5
C
2
H
5
H
CN
550
11
n-C
3
H
7
n-C
3
H
7
3-NHCOCH
3
CO
2
CH
3
544
12
C
2
H
5
C
2
H
5
3-CH
3
CN
554
In a preferred embodiment of the invention, R
1
in the above formula represents hydrogen. In another preferred embodiment, R
1
represents n-C
4
H
9
. In still another preferred embodiment, R
2
and R
3
are taken together and represent a tetrahydroquinoline ring. In yet another preferred embodiment, R
4
represents CN or CON(C
2
H
4
OH)
2
. In still another preferred embodiment, R
4
and R
5
each represents CH
3
. In another preferred embodiment, Z represents a triazole or pyrazole ring.
In general, the above dyes comprise from about 0.2 to about 5%, preferably from about 0.5 to 3%, by weight of the ink jet composition.
The water solubility of cationic dyes is signi

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