Ink jet printing process

Abstract: An ink jet printing process for improving the water-fastness of an ink jet image comprising: a) providing an ink jet recording element comprising a support having thereon an image-recording layer comprising a cross-linkable polymer of acetoacetylated poly(vinyl alcohol) and a mordant, b) applying liquid ink droplets of an anionic, water-soluble dye on the image-recording layer in an image-wise manner, and c) submerging the element in an aqueous solution of a hardener to cross-link the binder.

Description: This invention relates to an ink jet printing process for improving the water-fastness of an ink jet image formed from an aqueous ink containing an anionic dye. 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. JP 10-219157 relates to an ink jet ink comprising an aqueous medium, a colorant and a very small amount of glutaraldehyde as a biocide. There is a problem with using this ink, however, in that when it is printed on an image-recording element, the resultant image has poor water-fastness. It is an object of this invention to provide an ink jet printing process for improving the water-fastness of an ink jet image formed from an aqueous ink containing an anionic dye. It is another object of this invention to provide an ink jet printing process wherein a hardener is applied to improve the water-fastness of the ink jet image. It is another object of the invention to provide an ink jet printing process where the hardener can be applied non-imagewise to the entire element. In accordance with the present invention, there is provided an ink jet printing process for improving the water-fastness of an ink jet image comprising: a) providing an ink jet recording element comprising a support having thereon an image-recording layer comprising a cross-linkable polymer of acetoacetylated poly(vinyl alcohol) and a mordant, b) applying liquid ink droplets of an anionic, water-soluble dye on the image-recording layer in an image-wise manner, and c) submerging the element in an aqueous solution of a hardener to cross-link the polymer. It was found that the water-fastness of the image is improved with this treatment with a hardener solution. This process offers an advantage over incorporating a hardener in an ink since the hardener can be applied in both imaged and non-imaged areas. Any hardener can be used in the invention provided it cross-links the cross-linkable binder employed. Hardeners may be used at concentrations ranging from 0.10 to 5.0 weight percent of active ingredient in the aqueous solution, preferably 0.25 to 2.0 weight percent. The aqueous hardener solution may also contain, if desired, co-solvents, humectants, surfactants, and other ingredients commonly added to ink jet inks. Examples of hardeners that can be employed in the invention fall into several different classes such as the following (including mixtures thereof): a) formaldehyde and compounds that contain two or more aldehyde functional groups such as the homologous series of dialdehydes ranging from glyoxal to adipaldehyde including succinaldehyde and glutaraldehyde; diglycolaldehyde; aromatic dialdehydes, etc.; b) blocked hardeners (substances usually derived from the active hardener that release the active compound under appropriate conditions) such as substances that contain blocked aldehyde functional groups, such as tetrahydro-4-hydroxy-5-methyl-2(1H)-pyrimidinone polymers, polymers of the type having a glyoxal polyol reaction product consisting of 1 anhydroglucose unit: 2 glyoxal units, dimethoxylethanal-melamine non-formaldehyde resins, 2,3-dihydroxy-1,4-dioxane, blocked dialdehydes and N-methylol compounds obtained from the condensation of formaldehyde with various aliphatic or cyclic amides, ureas, and nitrogen heterocycles; c) active olefinic compounds having two or more olefinic bonds, especially unsubstituted vinyl groups, activated by adjacent electron withdrawing groups, such as divinyl ketone; resorcinol bis(vinylsulfonate); 4,6-bis(vinylsulfonyl)-m-xylene; bis(vinylsulfonylalkyl) ethers and amines; 1,3,5-tris(vinylsulfonyl) hexahydro-s-triazine; diacrylamide; 1,3-bis(acryloyl)urea; N,N'-bismaleimides; bisisomaleimides; bis(2-acetoxyethyl) ketone; 1,3,5-triacryloylhexahydro-s-triazine; and blocked active olefins of the type bis(2-acetoxyethyl) ketone and 3,8-dioxodecane-1,10-bis(pyridinium perchlorate) bis(vinyl sulfonylmethane), bis(vinyl sulfonylmethyl ether), and the like; d) compounds that contain two or more amino groups such as ethylene diamine; and e) inorganic salts such as aluminum sulfate; potassium and ammonium alums of aluminum; ammonium zirconium carbonate; chromium salts such as chromium sulfate and chromium alum; and salts of titanium dioxide, zirconium dioxide, etc. Specific examples of hardeners useful in the invention include the following: Hardener 1: aluminum sulfate Hardener 2: bis(vinyl sulfonylmethane) (Eastman Kodak Company) Hardener 3: 2,3-dihydroxy-1,4-dioxane (Aldrich Chemical Co.) Hardener 4: ethylene diamine Hardener 5: glyoxal Hardener 6: bis(vinyl sulfonylmethyl ether) (Eastman Kodak Company) Hardener 7: glutaraldehyde Hardener 8: a glyoxal polyol reaction product consisting of 1 anhydroglucose unit:2 glyoxal units, SEQUAREZ ® 755 (Sequa Chemicals, Inc.) Hardener 9: a cyclic urea glyoxal condensate consisting of 1 cyclic urea unit: 1 glyoxal unit, SUNREZ ® 700M (Sequa Chemicals, Inc.) Hardener 10: dimethoxylethanal-melamine non-formaldehyde resin, Sequa CPD3086-100 (Sequa Chemicals, Inc) In a preferred embodiment, the image-recording layer employed in the process of the invention may also contain a hardener such as those listed above for use in an aqueous solution. The hardener in this embodiment may be employed in an amount of from 0.008 to 0.2 g/m 2 , preferably 0.02 to 0.09 g/m 2 . Any anionic, water-soluble dye may be used in the invention such as a dye having an anionic group, e.g., a sulfo group or a carboxylic group. The anionic 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 US-A-5,482,545. Other dyes which may be used are found in EP 802246-A1 and JP 09/202043. In a preferred embodiment, the anionic, water-soluble dye which may be used in 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. The dye may be present in an amount of from 0.1 to 10 % by weight, preferably from 0.25 to 3 % by weight. Any mordant can be used in the invention provided it produces the desired result of fixing the anionic dye. For example, there may be used a cationic polymer, e.g., a polymeric quartenary ammonium compound, or a basic polymer, such as poly(dimethylaminoethyl)methacrylate, polyalkylenepolyamines, and products of the condensation thereof with dicyanodiamide, amine-epichlorohydrin polycondensates; divalent Group II metal ions; lecithin and phospholipid compounds. In a preferred embodiment of the invention, the following mordants are employed: Mordant 1 vinylbenzyl trimethyl ammonium chloride/ethylene glycol dimethacrylate (Eastman Kodak Company) Mordant 2 poly(vinylbenzyl trimethylammonium chloride) SP2 707 (SP2 Company) Mordant 3 poly(2-N,N,N-trimethylammonium)ethyl methacrylate methosulfate (Eastman Kodak Company) Mordant 4 poly(3-N,N,N-trimethylammonium)propyl methacrylate chloride, Polycare ® 133 (Rhone-Poulenc Co.) Mordant 5 poly(diallyldimethyl ammonium chloride) (Aldrich Chemical Co.) Mordant 6 cationic polyethylene polyamine resin, Niccajet ®117 (Nicca-USA) Mordant 7 amine and glycidyl polymer, Niccajet ® 450, (Nicca-USA) Mordant 8 hydroxyethylcellulose derivitized with (3-N,N,N-trimethylammonium)propyl chloride, Celquat ® SC-240C (National Starch Co.) Mordant 9 alumina coated colloidal silica, Ludox ® CL (DuPont) Mordant 10 copolymer of vinylbenzyltrimethylammonium chloride, butyl acrylate, and bis-vinylbenzene in a 50:30:20 ratio (Eastman Kodak Company) The mordant used in the invention may be employed in any amount effective for the intended purpose. In general, good results are obtained when the mordant is present in an amount of from 0.5 to 5 g/m 2 of element. The acetoacetylated poly(vinyl alcohol) useful in the invention is described, for example, in US-A-4,350, 788. These materials are available commercially as Gohsefimer ® from Nippon Gohsei. 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. Ink jet inks used in the process of the present invention are well-known in the art. The ink compositions used in ink jet printing typically are liquid compositions comprising a solvent or carrier liquid, dyes, humectants, organic solvents, detergents, thickeners, preservatives, conductivity enhancing agents, anti-kogation agents, drying agents, defoamers, etc. The solvent or carrier liquid can be solely water or can be water mixed with other water-miscible solvents such as polyhydric alcohols. Inks in which organic materials such as polyhydric alcohols are the predominant carrier or solvent liquid may also be used. Particularly useful are mixed solvents of water and polyhydric alcohols. A carrier can be present in the ink jet ink and can vary widely, depending on the nature of the ink jet printer for which the inks are intended. For printers which use aqueous inks, water, or a mixture of water with miscible organic co-solvents, is the preferred carrier medium. Co-solvents (0-20 wt. % of the ink) are added to help prevent the ink from drying out or crusting in the orifices of the printhead or to help the ink penetrate the receiving substrate. Preferred co-solvents for the inks employed in the present invention include glycerol, ethylene glycol, propylene glycol, 2-methyl-2,4-pentanediol, and diethylene glycol, and mixtures thereof, at overall concentrations ranging from 5 to 20 wt. % of the ink. The support for the ink jet recording element used in the invention can be any of those usually used for ink jet receivers, such as paper, resin-coated paper, poly(ethylene terephthalate), poly(ethylene naphthalate) and microporous materials such as poly polyethylene polymer-containing material sold by PPG Industries, Inc., Pittsburgh, Pennsylvania under the trade name of Teslin ®, Tyvek ® synthetic paper (DuPont Corp.), and OPPalyte® films (Mobil Chemical Co.) and other composite films listed in US-A-5,244,861. The support used in the invention may have a thickness of from 50 to 500 µm, preferably from 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. 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. 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 2 µm. The image-recording layer may be present in any amount which is effective for the intended purpose. In general, good results are obtained when it is present in an amount of from 5 to 30 g/m 2 , preferably from 8 to 15 g/m 2 , which corresponds to a dry thickness of 5 to 30 µm, preferably 8 to 15 µm. The following example is provided to illustrate the invention. A photographic grade, polyethylene resin-coated paper was given a corona discharge treatment and then coated with an imaging layer of 7.7 g/m 2 of acetoacetylated poly(vinyl alcohol), Gohsefimer ® Z-200, (Nippon Gohsei) and 0.9 g/m 2 of Mordant 1. Some of the coatings also contained Hardener 5 in the amounts as listed in Table 1. The coatings were applied using a extrusion hopper and air dried. A Hewlett-Packard ink cartridge (HP 51649A) containing cyan anionic dyes was obtained. The cyan ink contained a mixture of Direct Blue 199 and Acid Blue 9 (6:1 by weight). This ink is described in US-A-5,536,306. A cyan patch was then printed on the receivers at 100% laydown using a Hewlett-Packard Printer (HP690C) and the above cartridge. All the receiving elements, except for the controls, were submerged in a bath containing a hardener solution containing a 1% solution of a Hardener, as identified in Table 1, unless otherwise stated, and allowed to air dry overnight. The elements were then immersed in distilled water for 1 hour and then allowed to air dry overnight. The optical density was measured before and after immersion in water with an X-Rite ® densitometer. Water-fastness is measured as the per cent retained optical density after immersion in water. Values closest to 100% are preferred. Values over 100% indicate an undesirable "dot spread". The following results were obtained: Hardener 5 in Coating (wt. %) Hardener in Bath % Retained Optical Density After Water Test None None (Control) 8 (0.25) None (Control) 172 (0.50) None (Control) 161 (0.75) None (Control) 163 None 1 73 (0.25) 1 93 (0.50) 1 97 (0.75) 1 101 None 2 80 (0.25) 2 107 (0.50) 2 91 (0.75) 2 97 None 3 97 (0.25) 3 93 (0.50) 3 107 (0.75) 3 98 None 4 92 (0.25) 4 96 (0.50) 4 97 (0.75) 4 97 None 5 101 (0.25) 5 97 (0.50) 5 95 (0.75) 5 98 None None (Control) 179 (0.25) 5 (0.25) 99 (0.25) 5 (0.50) 96 (0.25) 5 (1) 109 (0.25) 5 (2) 110 (0.25) 5 (5) 101 The above data show that an ink jet image obtained in accordance with the invention has superior water-fastness (numbers closest to 100%) as compared to control elements not submerged in a hardener solution. While also including a hardener in the coating improved the results in some cases, it did not provide any improvement if there were no hardener in the bath.

Claims: An ink jet printing process for improving the water-fastness of an ink jet image comprising: a) providing an ink jet recording element comprising a support having thereon an image-recording layer comprising a cross-linkable polymer of acetoacetylated poly(vinyl alcohol) and a mordant, b) applying liquid ink droplets of an anionic, water-soluble dye on said image-recording layer in an image-wise manner, and c) submerging said element in an aqueous solution of a hardener to cross-link said polymer. The process of Claim 1 wherein said element also contains a hardener. The process of Claim 1 wherein said cross-linkable polymer is present in an amount of from 5 to 30 g/m 2 . The process of Claim 1 wherein said mordant is a cationic mordant or a basic polymer. The process of Claim 1 wherein said mordant is present in an amount of from 0.5 to 5 g/m 2 . The process of Claim 1 wherein said anionic dye is a metallized or non-metallized azo dye, a xanthene dye, a metallophthalocyanine dye or a sulfur dye. The process of Claim 1 wherein said liquid ink has a water carrier. The process of Claim 1 wherein said support is paper. The process of Claim 1 wherein said element also contains a hardener in the amount of from 0.008 to 0.2 g/m 2 .

Inventors: GALLO ELIZABETH ANN, ROMANO CHARLES EUGENE JR, GALLO, ELIZABETH ANN, ROMANO, CHARLES EUGENE, JR.
Applicants: EASTMAN KODAK CO, EASTMAN KODAK COMPANY
Application year: 1999
Main classification: B41M5
IPC codes: B41J2, B41M7, B41M5, C09D11