Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2001-01-26
2003-03-04
Hess, Bruce H. (Department: 1774)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C428S195100
Reexamination Certificate
active
06527387
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ink jet printing method for improving the light stability and waterfastness of a printed image containing an ink jet ink containing a water-soluble anionic dye and a cationic receiver.
BACKGROUND OF THE INVENTION
Inkjet 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 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.
An inkjet recording element typically comprises a support having on at least one surface thereof an ink-receiving or image-forming layer. The ink-receiving layer may be a polymer layer which swells to absorb the ink or a porous layer which imbibes the ink via capillary action.
Ink jet prints, prepared by printing onto ink jet recording elements, are subject to environmental degradation. They are especially vulnerable to water smearing, dye bleeding, coalescence and light fade. For example, since inkjet dyes are water-soluble, they can migrate from their location in the image layer when water comes in contact with the receiver after imaging. Highly swellable hydrophilic layers can take an undesirably long time to dry, slowing printing speed, and will dissolve when left in contact with water, destroying printed images. Porous layers speed the absorption of the ink vehicle, but often suffer from insufficient gloss and severe light fade.
EP Publication 1 002 660 A1 discloses an ink jet recording sheet containing an image-receiving layer containing a cationic polymer derived from a vinylbenzyltrialkylammonium salt. The specific examples of alkyl moieties in these salts include only methyl, benzyl and hydroxyethyl. However, there is a problem with these salts which contain alkyl moieties having methyl or benzyl groups in that the image formed in the image-receiving layer has poor light stability, as will be shown hereafter.
U.S. Pat. No. 4,575,465 relates to an inkjet recording sheet having an image-receiving layer containing a vinyl pyridine/vinylbenzyl quaternary salt copolymer. The example of the alkyl moiety in this salt disclosed is methyl.
U.S. Pat. No. 5,856,023 relates to an ink jet recording sheet having an image-receiving layer containing a vinylbenzyl quaternary ammonium salt terpolymer. At least one of the vinylbenzyl quaternary ammonium salt moieties contains three alkyl groups of 1 to 4 carbon atoms. There is a problem with these salts which contain alkyl moieties having 1 to 4 carbon atoms in that the image formed in the image-receiving layer has poor light stability, as will be shown hereafter.
It is an object of this invention to provide an inkjet printing method using anionic dyes that will provide images with improved light stability over the prior art using a receiving element having a particular mordant.
SUMMARY OF THE INVENTION
This and other objects are achieved in accordance with this invention which relates to an inkjet 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 cationic polymer containing at least one ethylenically unsaturated monomer containing a trialkylammonium salt, each trialkylammonium salt containing at least one alkyl group having greater than 8 carbon atoms;
C) loading the printer with an ink jet ink composition comprising water, a humectant, and a water-soluble anionic 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 light stability.
DETAILED DESCRIPTION OF THE INVENTION
Any anionic, water-soluble dye may be used in composition employed in the method of the invention such as a dye having an anionic group, e.g., a sulfo group or a carboxylic group. The anionic, water-soluble dye may be any acid dye, direct dye or reactive dye listed in the COLOR INDEX but is not limited thereto. Metallized and non-metallized azo dyes may also be used as disclosed in U.S. Pat. No. 5,482,545, the disclosure of which is incorporated herein by reference. Other dyes which may be used are found in EP 802246-A1 and JP 09/202043, the disclosures of which are incorporated herein by reference. In a preferred embodiment, the anionic, water-soluble dye which may be used in the composition employed in the method of the invention is a metallized azo dye, a non-metallized azo dye, a xanthene dye, a metallophthalocyanine dye or a sulfur dye. Mixtures of these dyes may also be used. An example of an anionic dye which may be used in the invention is as follows:
The dye 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.
Any cationic polymer can be employed in the invention provided it contains at least one at least one ethylenically unsaturated monomer containing a trialkylammonium salt, each trialkylammonium salt containing at least one alkyl group has greater than 8 carbon atoms, as described above. In a preferred embodiment of the invention, the cationic polymer has the formula
wherein:
R represents H or an alkyl group of from 1 to about 4 carbon atoms;
R
1
and R
2
each independently represents an alkyl group of from 1 to about 8 carbon atoms;
R
3
represents an alkyl group of greater than 8 to about 20 carbon atoms;
Z represents at least one ethylenically unsaturated, nonionic monomer;
m represents a mole % of from about 5 to about 100;
n represents a mole % of from 0 to about 95; and
X represents an anion.
As noted above, Z in the formula represents at least one ethylenically unsaturated, nonionic monomer. Examples of these include styrene, alpha alkylstyrene where the alkyl group has 1 to 4 carbon atoms and the aromatic group may be substituted or part of a larger ring system. Other examples of Z include acrylate esters derived from aliphatic alcohols or phenols; methacrylate esters; acrylamides; methacrylamides; N-vinylpyrrolidone or suitably substituted vinylpyrrolidones; vinyl esters derived from straight chain and branched acids, e.g., vinyl acetate; vinyl ethers, e.g., vinyl methyl ether; vinyl nitrites; vinyl k
Chen Tien-Teh
Lawrence Kristine B.
Wang Yongcai
Cole Harold E.
Eastman Kodak Company
Grendzynski Michael E.
Hess Bruce H.
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