Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
2001-01-26
2002-07-23
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C347S105000
Reexamination Certificate
active
06423398
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ink jet printing process for improving the light stability, waterfastness, gloss and density of a printed image containing an ink jet ink containing a water-soluble anionic dye and a cationic receiver.
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 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 ink jet 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 ink jet 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. There is a need to provide an ink jet recording element which overcomes the above deficiencies.
EP Publication 1 002 660 A1 discloses an ink jet recording sheet containing an image-receiving layer containing a water soluble 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 polymers derived from these salts in that they are water soluble and images formed in the image-receiving layer has poor light stability, as will be shown hereafter.
U.S. Pat. No. 6,045,917 relates to the use of poly(N-vinyl benzyl-N,N,N-trimethyl ammonium chloride-co-ethyleneglycol dimethacrylate) particles in an ink jet image-recording layer. However, there is a problem with these particles in that images formed in the image-receiving layer have poor light stability, as will be shown hereafter.
It is an object of this invention to provide an ink jet printing method using anionic dyes suitable for use in aqueous inks for ink jet printing that will provide images with better light stability, waterfastness, gloss and density 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 binder and cationic polymer particles containing at least one ethylenically unsaturated monomer containing a trialkylammonium salt, each the trialkylammonium salt containing at least one alkyl group greater than 4 carbon atoms in length;
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, waterfastness, gloss and density.
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 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 cationic polymer particles comprise a polymer having 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 4 carbon atoms;
R
3
represents an alkyl group greater than 4 to about 20;
Z represents at least one ethylenically unsaturated, nonionic monomer;
Y represents an ethylenically unsaturated monomer which is capable of forming a water-insoluble homopolymer;
m represents a mole % of from about 5 to about 80;
n+p represents a mole % of from 20 to about 95; and
X represents an anion.
As noted above, Z in the formula represents at least one ethylenically unsaturated, nonionic monomer. Preferably Z represents a water soluble monomer including, for example, acrylamides; methacrylamides, isobutoxymethyl acrylamide, poly(ethylene glycol) (meth)acrylate, N-vinylpyrrolidone or suitably substituted vinylpyrrolidones.
Y in the above formula represents an ethylenically unsaturated monomer which is capable of forming a water-insoluble homopolymer. Examples of Y include styrene, divinyl benzene, alpha alkylstyrene where the alkyl group has 1 to 4 carbon atoms and the aromatic group in the alkylstyrene monomer may be substituted. Other examples of Y include acrylate and methacrylate esters derived from aliphatic alcohols or phenols; vinyl esters derived from straight chain and branched acids, e.g., vinyl acetate; vinyl ethers, e.g., vinyl methyl ether; vinyl nitriles; vinyl ketones; halogen-con
Chen Tien-Teh
Lawrence Kristine B.
Wang Yongcai
Cole Harold E.
Eastman Kodak Company
Hess Bruce H.
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