Ink jet printing method

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Reference is made to commonly assigned, co-pending U.S. patent applications:

[0002] Ser. No. ______ by Lawrence et al., (Docket 82382) filed of even date herewith entitled “Ink Jet Recording Element”;

[0003] Ser. No. ______ by Lawrence et al., (Docket 82383) filed of even date herewith entitled “Ink Jet Printing Method”;

[0004] Ser. No. ______ by Lawrence et al., (Docket 82384) filed of even date herewith entitled “Ink Jet Recording Element”.

FIELD OF TH INVENTION

[0005] This invention relates to an ink jet printing process for improving the light stability of an inkjet printed image containing a water-soluble dye.

BACKGROUND OF THE INVENTION

[0006] 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 that 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 inkjet, 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.

[0007] The inks used in the various inkjet printers can be classified as either dye-based or pigment-based. A dye is a colorant that 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.

[0008] 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 that swells to absorb the ink or a porous layer that imbibes the ink via capillary action.

[0009] 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 or fade induced by atmospheric ozone.

[0010] WO 99/26935 relates generally to the use of amido or carbamate substituted trisaryl-1,3,5-triazines to protect against degradation. However, there is no disclosure in this patent for use of these materials in an ink jet recording system.

[0011] U.S. Pat. No. 6,045,917 relates to the use of cationic mordants in an ink jet image-recording layer. However, there is a problem with this element in that images formed in the image-receiving layer have poor light stability, as will be shown hereafter.

[0012] It is an object of this invention to provide an inkjet printing method using dyes suitable for use in aqueous inks for inkjet printing that will provide images with better Dmax density and light stability.

SUMMARY OF THE INVENTION

[0013] This and other objects are achieved in accordance with this invention which relates to an inkjet printing method, comprising the steps of:

[0014] A) providing an ink jet printer that is responsive to digital data signals;

[0015] B) loading the printer with an ink jet recording element comprising a support having thereon the following layers in order:

[0016] i) a base layer comprising a polymeric binder and a polymeric mordant; and

[0017] ii) an overcoat layer comprising a trisaryl-1,3,5-triazine ultraviolet light absorbing material;

[0018] C) loading the printer with an inkjet ink composition comprising water, a humectant, and a water-soluble dye; and

[0019] D) printing on the overcoat layer using the ink jet ink in response to the digital data signals.

[0020] It has been found that use of the above dyes and image-receiving layer provides excellent Dmax density and light stability.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Any water-soluble dye may be used in the 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 that may be used in the invention is as follows:

[0022] 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 inkjet ink composition, preferably from about 0.3 to about 3% by weight. Dye mixtures may also be used.

[0023] In a preferred embodiment of the invention, the trisaryl-1,3,5-triazine ultraviolet light absorbing material has the formula:

[0024] wherein:

[0025] each R independently represents hydrogen; hydrocarbyl group, such as alkyl, cycloalkyl, aryl, aralkyl, alkaryl, alkenyl, cycloalkenyl or alkynyl groups having up to 24 carbon atoms; or a hydrocarbyl group substituted with hydroxyl, amino, carboxyl, thio, amido, carbamoyl, activated methylene, isocyanato, cyano, epoxy, allyl, methallyl, acryloyl, methacryloyl, maleate, or maleimido; and

[0026] R1 represents R, OR, —SR, halogen, —SO2R, —SO3R, —COOR, —COR, —OCOR, —NRR or cyano.

[0027] Specific examples of trisaryl-1,3,5-triazine ultraviolet light absorbing materials useful in the invention include the following:

[0028] The trisaryl-1,3,5-triazine ultraviolet light absorbing materials employed in the invention can be used in an amount of from 0.05 to about 4.0 g/m2, preferably from about 0.20 to about 1.5 g/m2.

[0029] Any polymeric mordant can be used in the invention. In a preferred embodiment, the mordant can be a cationic protonated amine-containing polymer or a polymer that contains a quaternary ammonium group. Examples of these mordants include poly(1-vinylimidazole), poly(4-vinylpyridine), poly(styrene-co-N-benzyl-N,N-dimethyl-N-vinylbenzyl-ammonium chloride-co-divinylbenzene) (49:49:2 mole ratio), poly(N,N,N-tributyl-N-vinylbenzyl-ammonium chloride), poly(N,N-dimethyl-N-benzyl-N-vinylbenzyl-ammonium chloride), poly(styrene-co-N,N,N-trimethyl-N-vinylbenzyl-ammonium chloride) (1:1 mole ratio), poly(N,N,N-trimethyl-N-vinylbenzyl-ammonium chloride-co-divinylbenzene) (87:13 mole ratio), poly(N,N-dimethyl-N-octadecyl-N-vinylbenzyl-ammonium chloride), poly(styrene-co-1-vinylimidazole-co-3-hydroxyethyl-1-vinylimidazolium chloride) (5:4:1 mole ratio), poly(styrene-co-1-vinylimidazole-co-3-benzyl-1-vinylimidazolium chloride) (5:4:1 mole ratio), poly(styrene-co-1-vinylimidazole-co-3-hydroxyethyl-1-vinylimidazolium chloride) (2:2:1 mole ratio), poly(styrene-co-4-vinylpyridine-co-1-hydroxyethyl-4-vinylpyridinium chloride) (5:4:1 mole ratio), poly(diallydimethylammonium chloride) and chitosan.

[0030] The polymeric mordant employed in the invention can be used in an amount of from 0.2 to about 16 g/m2, preferably from about 0.4 to about 8 g/m2.

[0031] The binder employed in the base layer is preferably a hydrophilic polymer. Examples of hydrophilic polymers useful in the invention include polyvinyl alcohol, polyvinyl pyrrolidone, poly(ethyl oxazoline), poly-N-vinylacetamide, non-deionized or deionized Type IV bone gelatin, acid processed ossein gelatin, pig skin gelatin, acetylated gelatin, phthalated gelatin, oxidized gelatin, chitosan, poly(alkylene oxide), sulfonated polyester, partially hydrolyzed poly(vinyl acetate/vinyl alcohol), poly(acrylic acid), poly(1-vinyl pyrrolidone), poly( sodium styrene sulfonate), poly(2-acrylamido-2-methane sulfonic acid), polyacrylamide or mixtures thereof. In a preferred embodiment of the invention, the binder is gelatin or poly(vinyl alcohol).

[0032] The hydrophilic polymer may be present in an amount of from about 0.1 to about 30 g/m2, preferably from about 0.2 to about 16 g/m2 of the base layer.

[0033] The weight ratio of polymeric mordant to binder is from about 1:99 to about 8:2, preferably from about 1:9 to about 4:6.

[0034] Latex polymer particles and/or inorganic oxide particles may also be used in the binder in the base layer to increase the porosity of the layer and improve the dry time. Preferably, the latex polymer particles and /or inorganic oxide particles are cationic or neutral. Preferably, the latex polymer particles are porous. Examples of inorganic oxide particles include barium sulfate, calcium carbonate, clay, silica or alumina, or mixtures thereof In that case, the weight % of particulates in the image receiving layer is from about 70 to about 98%, preferably from about 80 to about 95%.

[0035] The pH of the aqueous ink compositions employed in the invention may be adjusted by the addition of organic or inorganic acids or bases. Useful inks may have a preferred pH of from about 2 to 10, depending upon the type of dye being used. Typical inorganic acids include hydrochloric, phosphoric and sulfuric acids. Typical organic acids include methanesulfonic, acetic and lactic acids. Typical inorganic bases include alkali metal hydroxides and carbonates. Typical organic bases include ammonia, triethanolamine and tetramethylethylenediamine.

[0036] A humectant is employed in the ink jet composition employed in the invention to help prevent the ink from drying out or crusting in the orifices of the printhead. Examples of humectants which can be used include polyhydric alcohols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, tetraethylene glycol, polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol and thioglycol; lower alkyl mono- or di-ethers derived from alkylene glycols, such as ethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol mono-methyl or mono-ethyl ether, propylene glycol mono-methyl or mono-ethyl ether, triethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, and diethylene glycol monobutylether; nitrogen-containing cyclic compounds, such as pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone; and sulfur-containing compounds such as dimethyl sulfoxide and tetramethylene sulfone. A preferred humectant for the composition employed in the invention is diethylene glycol, glycerol, or diethylene glycol monobutylether.

[0037] Water-miscible organic solvents may also be added to the aqueous ink employed in the invention to help the ink penetrate the receiving substrate, especially when the substrate is a highly sized paper. Examples of such solvents include alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol; ketones or ketoalcohols such as acetone, methyl ethyl ketone and diacetone alcohol; ethers, such as tetrahydrofuran and dioxane; and esters, such as, ethyl lactate, ethylene carbonate and propylene carbonate.

[0038] Surfactants may be added to adjust the surface tension of the ink to an appropriate level. The surfactants may be anionic, cationic, amphoteric or nonionic.

[0039] A biocide may be added to the composition employed in the invention to suppress the growth of microorganisms such as molds, fungi, etc. in aqueous inks. A preferred biocide for the ink composition employed in the present invention is Proxel® GXL (Zeneca Specialties Co.) at a final concentration of 0.0001-0.5 wt. %.

[0040] A typical ink composition employed in the invention may comprise, for example, the following substituents by weight: colorant (0.05-5%), water (20-95%), a humectant (5-70%), water miscible co-solvents (2-20%), surfactant (0.1-10%), biocide (0.05-5%) and pH control agents (0.1-10%).

[0041] Additional additives, which may optionally be present in the inkjet ink composition employed in the invention, include thickeners, conductivity enhancing agents, anti-kogation agents, drying agents, and defoamers.

[0042] The inkjet inks employed in this invention may be employed in ink jet printing wherein liquid ink drops are applied in a controlled fashion to an ink receptive layer substrate, by ejecting ink droplets from a plurality of nozzles or orifices of the print head of an inkjet printer.

[0043] The image-recording layer used in the process of the present invention can also contain various known additives, including matting agents such as titanium dioxide, zinc oxide, silica and polymeric beads such as crosslinked poly(methyl methacrylate) or polystyrene beads for the purposes of contributing to the non-blocking characteristics and to control the smudge resistance thereof; surfactants such as non-ionic, hydrocarbon or fluorocarbon surfactants or cationic surfactants, such as quaternary ammonium salts; fluorescent dyes; pH controllers; anti-foaming agents; lubricants; preservatives; viscosity modifiers; dye-fixing agents; waterproofing agents; dispersing agents; UV-absorbing agents; mildew-proofing agents; mordants; antistatic agents, anti-oxidants, optical brighteners, and the like. A hardener may also be added to the ink-receiving layer if desired.

[0044] The support for the inkjet recording element used in the invention can be any of those usually used for ink jet receivers, such as paper, resin-coated paper, polyesters, or microporous materials such as polyethylene polymer-containing material sold by PPG Industries, Inc., Pittsburgh, Pa. under the trade name of Teslin®, Tyvek® synthetic paper (Dupont Corp.), and OPPalyte® films (Mobil Chemical Co.) and other composite films listed in U.S. Pat. No. 5,244,861. Opaque supports include plain paper, coated paper, synthetic paper, photographic paper support, melt-extrusion-coated paper, and laminated paper, such as biaxally oriented support laminates. Biaxally oriented support laminates are described in U.S. Pat. Nos. 5,853,965; 5,866,282; 5,874,205; 5,888,643; 5,888,681; 5,888,683; and 5,888,714, the disclosures of which are hereby incorporated by reference. These biaxally oriented supports include a paper base and a biaxially oriented polyolefin sheet, typically polypropylene, laminated to one or both sides of the paper base. Transparent supports include glass, cellulose derivatives, e.g., a cellulose ester, cellulose triacetate, cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate; polyesters, such as poly(ethylene terephthalate), poly(ethylene naphthalate), poly(1,4-cyclohexanedimethylene terephthalate), poly(butylene terephthalate), and copolymers thereof; polyimides; polyamides; polycarbonates; polystyrene; polyolefins, such as polyethylene or polypropylene; polysulfones; polyacrylates; polyetherimides; and mixtures thereof. The papers listed above include a broad range of papers, from high end papers, such as photographic paper to low end papers, such as newsprint.

[0045] The support used in the invention may have a thickness of from about 50 to about 500 μm, preferably from about 75 to 300 μm. Antioxidants, antistatic agents, plasticizers and other known additives may be incorporated into the support, if desired. In a preferred embodiment, paper is employed.

[0046] In order to improve the adhesion of the image-recording layer to the support, the surface of the support may be subjected to a corona-discharge-treatment prior to applying the image-recording layer.

[0047] In addition, a subbing layer, such as a layer formed from a halogenated phenol or a partially hydrolyzed vinyl chloride-vinyl acetate copolymer can be applied to the surface of the support to increase adhesion of the image recording layer. If a subbing layer is used, it should have a thickness (i.e., a dry coat thickness) of less than about 2 μm.

[0048] The image-recording layer may be present in any amount that is effective for the intended purpose. In general, good results are obtained when it is present in an amount of from about 2 to about 60 g/m2, preferably from about 6 to about 40 g/m2, which corresponds to a dry thickness of about 2 to about 50 μm, preferably about 6 to about 40 μm.

[0049] The overcoat layer may be present in any amount that is effective for the intended purpose. In general, good results are obtained when it is present in an amount of from about 1.1 to about 10.7 g/m2, preferably from about 1.6 to about 5.4 g/m2, which corresponds to a dry thickness of about 1.0 to about 10 μm, preferably about 1.5 to about 5 μm.

[0050] The following examples illustrates the utility of the present invention.

EXAMPLES

[0051] The following mordants were used as controls in the image-recording layer:

[0052] MP-1: poly(N-vinylbenzyl-N,N,N-trimethylammonium chloride-co-divinylbenzene) (about 90/10 mol %) (U.S. Pat. No. 6,045,917)

[0053] MP-2: poly(styrene-co-N-vinylbenzyl-N,N,N-trimethylammonium chloride-co-divinylbenzene) (about 49/49/2 mol %) (U.S. Pat. No. 6,045,917)

[0054] MP-3: poly(styrene-co-N-vinylimidazole-co-3-hydroxyethyl-1-vinylimidazolium chloride) (about 50/40/10 mol %)

Example 1

Preparation of UVD-1 Dispersion

[0055] 600.0 g of triazine UV absorber compound UV-1 was added to 360.0 g of tris-2-ethylhexyl phosphate and heated to 100° C. with stirring to form an organic composition. An aqueous composition was prepared by combining 480.0 g of a deionized bone gelatin with 4131.4 g of deionized water, 8.6 g of a 0.7 weight percent solution of Kathon LX® biocide and 420.0 g of a 10.0 weight percent solution of Alkanol XC® (DuPont Corp.) surfactant. The aqueous composition was heated to 80° C.

[0056] The organic composition was added to the aqueous composition while shearing with a Brinkman rotor-stator mixer and the resulting premix was passed one time through a high energy multiple orifice homogenizer to form a dispersion.

Example 2

Preparation of UVD-2 Dispersion

[0057] 225.0 g of triazine UV absorber compound UV-1 and 75.0 g of triazine UV absorber compound UV-2 was added to 180.0 g of tris-2-ethylhexyl phosphate and heated to 100° C. with stirring to form an organic composition. An aqueous composition was prepared by combining 240.0 g of a deionized bone gelatin with 2065.7 g of deionized water, 4.3 g of a 0.7 weight percent solution of Kathon LX® biocide and 210.0 g of a 10.0 weight percent solution of Alkanol XC® (DuPont Corp.) surfactant. The aqueous composition was heated to 80° C.

[0058] The organic composition was added to the aqueous composition while shearing with a Brinkman rotor-stator mixer and the resulting premix was passed one time through a high energy multiple orifice homogenizer to form a dispersion.

Example 3

Light Stability in Gelatin Based Coatings

[0059] Preparation of a Water Soluble, anionic Dye Ink Composition, I-1

[0060] Ink I-1 containing Dye 1 identified above was prepared by mixing the dye concentrate (3.1%) with de-ionized water containing humectants of diethylene glycol (Aldrich Chemical Co.) and glycerol (Acros Co.), each at 6%, a biocide, Proxel GXL® biocide (Zeneca Specialties) at 0.003 wt %, and a surfactant, Surfynol 465® (Air Products Co.) at 0.05 wt. %.

[0061] The dye concentration was based on solution absorption spectra and chosen such that the final ink when diluted 1:1000, would yield a transmission optical density of approximately 1.0.

[0062] Preparation of a Water Soluble, Anionic Dye Ink Composition, I-2

[0063] Ink I-2 containing Dye 2 identified above (Reactive Red 31, CAS-12237-00-2) was composed of Novajet Magenta Ink (Lyson Inc.) prepared by mixing 100 g of the commercial ink with 0.5 g of Surfynol 465® surfactant (Air Products Inc.).

[0064] Preparation of Control Ink Recording Elements C-1 through C-3

[0065] The composite side of a polyethylene resin-coated photographic grade paper based support was corona discharge treated prior to coating. Control Ink Recording Elements were composed of a mixture of 0.86 g/m2 of control polymers MP-1 through MP-3, 7.75 g/m2 of gelatin and 0.09 g/m2 of S-100 12 μm polystyrene beads (ACE Chemical Co.), and coated from distilled water on the above mentioned paper support. In the preparation of C-3, a 60:40 mixture of distilled water to methanol was used in place of distilled water to dissolve MP-3.

[0066] Preparation of Invention Ink Recording Elements E-1 through E-3

[0067] Recording elements E-1 through E-3 of the invention were prepared by overcoating C-1 through C-3 prepared above with a mixture of 20 g of UVD-1 dispersion prepared in Example 1 above, 86 g of a 11.6% solution of gelatin, 2 g of a 10% solution of Olin 10G® surfactant and 298 g of distilled water yielding a dry layer thickness after coating of 1.51 g/m2.

[0068] Preparation of Invention Ink Recording Elements E-4 through E-6

[0069] Recording elements E-4 through E-6 of the invention were prepared analogous to E-1 through E-3 above except UVD-2 dispersion from Example 2 was used in place of UVD-1.

[0070] Printing

[0071] Elements E-1 through E-6 and control elements C-1 through C-3 were printed using an Epson 200® printer and inks I-1 and I-2 described above. After printing, all images were allowed to dry at room temperature overnight, and the densities were measured at all steps using an X-Rite 820® densitometer. The Dmax densities at step 11 were recorded for I-1 and I-2 in Table 1 below.

[0072] The images were then subjected to a high intensity daylight fading test for 2 weeks, 50Klux, 5400° K., approximately 25% RH. The Status A blue or green reflection density nearest to 1.0 was compared before and after fade and a percent density retained was calculated for the yellow and magenta dyes with each receiver element. The results can be found in Table 1 below.

1TABLE 1Record-ingDmax% RetainedDmax Density,% RetainedElementDensity, I-1After Fade, I-1I-2After Fade, I-2E-11.70762.0177E-21.48901.8386E-31.49911.8789E-41.57812.0272E-51.47851.8480E-61.56911.8790C-11.50701.8261C-21.40631.8360C-31.59672.1968

[0073] The above results show that the recording elements E-1 through E-6 of the invention, as compared to the control recording elements C-1 through C-3 gave higher Dmax densities and % retained densities after high intensity daylight fading with both inks.

[0074] The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Ink jet printing method

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