AU741552B2 - Alkaline ink and coated substrate suitable for use with ink jet printers - Google Patents

Description

PCrAu 7 0 0 7 28 P:\OPER\MJC\BLAZER.PCT. 2/9/98 RECEIVED 2 1 SEP 1998 -1- METHOD OF PRINTING AN IMAGE This invention relates to a method of printing an image onto a coated substrate. More particularly, the invention relates to printing an alkaline ink onto a substrate coated with a polymeric resin composition, the method advantageously being particularly useful for ink jet printing.

Ink jet printing is a quick and efficient method for printing digital images on ink receivers.

However conventional inks and receivers used with ink jet printers suffer from a number of disadvantages.

One problem with the use of ink jet printers is the small size (generally between 10 and microns) of the ink jet nozzles through which the ink must pass. For this reason most current ink jet printers use dye based inks in which the dye is completely dissolved in a aqueous medium. Such inks have a low viscosity and cause minimal blockage of the ink jets.

These dye based inks, however, result in printed image which are not water resistant or light fast. Accordingly these images tend to wash or rub off the substrate, or fade in a short period of time. Also the dyes tend to wick in the fibres of paper substrate causing feathering of the images.

Advantageously, the present invention overcomes or at least alleviates one or more of the abovementioned disadvantages of the prior art.

According to the present invention, there is provided a method of printing an image onto a substrate comprising the steps of: providing a substrate coated with a coating composition comprising a polymeric resin which is insoluble in neutral water but soluble in alkaline water, and a solvent for said resin; printing the image onto said coated substrate with an alkaline ink such that said ink V1tsjeast partially softens said coating of said substrate; and ]i AMEND D SHEET IeiU/au PcAu 9 7 1 0 0 7 2 8 P:\OPER\IC\BLAZER.PCT 21/9/98 RECEIVED 2 1 SEP 1998 -2evaporating off, or allowing to evaporate alkaline components of said ink such that said coating substantially rehardens with said image applied thereto.

There is also provided a substrate having an image printed thereon, the image being applied to the substrate by the method described in the immediately preceding paragraph.

The method of printing according to the present invention advantageously allows the printing of images which exhibit high gloss, good water and rub resistance, fast drying, good light fastness, controlled dot gain and reduced feathering.

Preferably, the alkaline ink comprises a pigment, a polymeric resin insoluble in neutral water, but soluble in alkaline water, a water miscible organic solvent, and water.

The phrase "insoluble in neutral water, but soluble in alkaline water" as used herein means that at a pH of 7 the polymeric resin is substantially insoluble in water, but that at some pH above 7 the p-lymeric resin becomes soluble. This pH is preferably above 7.5 and more preferably above 8.

As used herein the term "pigment" refers to a finely divided insoluble colourant. The pigment may be any known organic or inorganic pigment, or combination of pigments and may be natural or artificial. The pigment may be black, white or coloured. For ink jet printing applications the pigment particles must be sufficiently small to pass through the ejecting nozzles of the ink jet printer. The pigment particles may have a particle size less than 30%, more preferably less than 10%, of the diameter of the ink jet nozzles. For most ink jet printers this will mean a particle size of 0.005 to 15 microns, more preferably 0.005 to 5 microns and even more preferably 0.005 to 1 micron. Most preferably the mean particle size is less than 0.5 micron, with 80% of the particles having a particle size of less than 0.2 micron being particularly preferred. The fine particle size also enables improved gloss, greater translucency, and improved colour strength in the applied ink.

1 AMENCED .HEET !r-&A PC'AU 9 7 0 0 7 2 8 P:\OPER\MJC\BLAZER. PCT 219/98 RECEIVED 2 1 SEP 1998 RECEIVED 2 1 SEP 1998 -3- Examples of suitable pigments include Permanent Yellow DHG, Permanent Yellow GR, Permanent Yellow G, Permanent Yellow NCG-71, Permanent Yellow GG, Hansa Yellow RA, Hansa Brilliant Yellow 5GX-02, Hansa Yellow X, Novoperm® Yellow HR, Novoperm® Yellow FGL, Hansa Brilliant Yellow 10X, Permanent Yellow G3R-01, Hostaperm® Yellow H4G, Hostaperm® Yellow H3G, Hostaperm® Orange GR, Hostaperm® Scarlet GO and Permanent Rubine F6B by Hoechst, Chromophtal® Yellow 3G, Chromophtal® Yellow GR, Chromophtal® Yellow 8G, Irgazin® Yellow 5GT, Irgalite® Rubine 4BL, Monastral® Magenta, Monastral® Scarlet, Monastral® Violet R and Monastral® Violet Maroon B by Ciba Geigy, Dalamar® Yellow YT-858-D and Heucophthal® Blue G, XBT-583D by Heubach, Paliogen® Orange, Heliogen® Blue L 6901F, Heliogen® Blue NBD 7010, Heliogen® Blue K 7090, Heliogen® Blue L 7101F, Paliogen® Blue L 6470, Heliogen® Green K 8683 and Heliogen® Green L 9140 by BASF, Quindo® Magenta, Indofast® Brilliant Scarlet, Quindo® Red R6700, Quindo® Red R6713 and Indofast® Violet by Mobay Chemicals, and Special Black 4A by Degussa.

To reduce flocculation in the ink it is preferred that the pigment is provided in predispersed form, either in aqueous form or in the form of a wet presscake. Examples of commercially available predispersed pigments include representative commercial pigments that can be used in the form of a water wet presscake or other aqueous dispersion include: Heucophthal® Blue, Toluidine Red Y, Quindo® Magenta and Magenta RV-6831 presscake by Mobay Chemicals, Sunfast® Magenta 122, Indo® Brilliant Scarlet, Toluidine Red B, Watchung® Red B, Permanent Rubine F6B13-1731, Hansa® Yellow, Sunbrite® Yellow 17 by Sun Chemical Corp, Hostafine Yellow GR, Hostafine Yellow HR, Hostafine Red HF35, Hostafine Red FR1l, Hostafine Rubine F6B, Hostafme Blue B29, Hostafine Green GN and Hostafine Black T/Ts by Hoechst and Microlith pigments from Bayer.

Other pigments include metal or metal oxides such as oxides of silicon, aluminium, titanium and the like and fine particles of copper, iron, steel, aluminium and the like. If the pigment particles need to be milled to size this can be done in accordance with methods known in the rt. In this regard microshearing processes are particularly suitable.

AMEN 'D HET ipA.AU PC/AU 9g 7 0 0 Z U P:\OPER\M2C\BLAZER.PCT- 21/9/98 RECEIVED 2 1 SEP 1998 -4- The polymeric resin of the coating composition and the alkaline ink may be any suitable alkaline soluble resin which is insoluble in neutral water. Examples of suitable polymeric resins include shellac and acrylic resins. Preferably the polymeric resin is an acrylic resin.

The acrylic resin may be homopolymer or copolymer of an acrylic monomer. Examples of suitable acrylic monomers include acrylic acid, methacrylic acid, itaconic acid, tertbutylaminoethyl methacrylate, dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxy ethyl acrylate, N-hydroxymethyl acrylamide, N-hydroxymethyl methacrylamide, glycidyl methacrylate, 1,4-butylene dimethacrylate, crotonic acid, isocrotonic acid, methyl methacrylate, butyl acrylate, butyl methacrylate, 2ethylhhexylacrylate, isobutyl methacrylate, acrylonitrile, acrylamide, methacrylamide, N,Ndimethylacrylamide, N,N-dimethylmethacrylamide, N,N-dibutylacrylamide, N,Ndibutylmethacrylamide, N,N-dioctylacrylamide, N,N-dioctylmethacrylamide, Nmonobutylacrylamide, N-monobutylmethacrylamide, N-monooctylacrylamide, Nmonooctylmethacrylamide, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2hydroxypropyl methacrylate, 2,4-dihydroxy-4'- v inylbenzophenone, N-(2hydroxyethyl)acrylamide, N-(2-hydroxyethyl)methacrylamide, octyl methacrylate, lauryl methacrylate (LMA), stearyl methacrylate, phenyl methacrylate, 2-ethoxyethyl methacrylate, methacrylonitrile, 2-trimethylsiloxythyl methacrylate, p-tolyl methacrylate, sorbyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, phenyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate acrylonitrile, 2-trimethyl-siloxyethyl acrylate, glycidyl acrylate, p-tolyl acrylate, and sorbyl acrylate.

The acrylic resin may be a homopolymer or copolymer of acrylic monomers, or may be a copolymer of acrylic monomers with other suitable monomers. Other suitable monomers include butadiene, styrene, vinyl chloride, vinylidene chloride and vinyl acetate.

Acrylic copolymers may be in the form of random, block or graft copolymers.

Y e acrylic homopolymers and copolymers may be formed by any of the techniques known 4 MEM":-J' D CrT/AU 9 7 00 2 P:OPER1MJC\BLAZER.PCT -21/9/98 RECEIVED 2 1 SEP 1998 to the art including solution, emulsion and suspension polymerisation techniques. Preferred acrylic copolymers are emulsion copolymers such as those provided under the trademarks Carboset" by B F Goodrich, Acrysol T ASE from Rohm and Haas. Most preferably the acrylic copolymer is Carboset 525 from B F Goodrich. The resin may be obtained in solid or dissolved form.

The water miscible organic solvent may be selected from alcohols, such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol and the like; ketones, such as acetone, methyl ethyl ketone, diacetone alcohol and the like; esters, such as, ethyl acetate, ethylene carbonate, ethyl lactate and the like; ethers, such as tetrahydrofuran, dioxane, ethylene glycol mono-methyl ether, diethylene glycol mono-ethyl ether and the like; heterocyclic solvents such as pyrrolidone, N-methyl-2-pyrrolidinone (NMP) 1,3-dimethyl-2-imidazolidinone and the like; and sulfur containing solvents, such as dimethylsulfoxide (DMSO), tetramethylene sulfone and the like.

In order to make the ink alkaline, the ink may include an alkaline component. The alkaline component may be any suitable basic material capable of adjusting the pH of the ink to 7, including mixtures of such materials. The alkaline component may be selected from inorganic bases such as ammonia, alkali metal or alkaline earth metal hydroxides or carbonates, alkaline earth metal hydrogen carbonates and the like, or organic bases such as pyridine, morpholine, triethylamine and the like, or mixtures thereof. Preferred alkaline components are ammonia and morpholine, with the combination of ammonia and morpholine being particularly preferred.

The pH of the ink is preferably greater than about 7.5, and more preferably greater than about 8.

The relative proportions of the pigment, resin, organic solvent water and alkaline component are preferably chosen to provide an alkaline ink of low viscosity suitable for use in an ink jet 4 rinter. For most applications a pigment content of 0.1 to 30% by weight of the ink will be AMEN!' HE,,i PCr/AU 97 /0 0 7 2 8 P:\OPER\MJC\BLAZER.PCT -2119198 -6sufficient. More preferably the pigment content will be in the range of 6 to 7% by weight.

The amount of resin will generally be in the range of 0.1 to 5 more preferably in the range of 0.5 to 1%.

The ink may contain various other additives known to the art, or known to related arts such as the textiles, paints and crafts industries.

In this regard the ink may include stabilisers such as tinuvin 123 by Ciba Geigy, viscosity modifiers such as Carboset 515 by B F Goodrich, UV inhibitors, such as tinuvin 384 and 1170 by Ciba Geigy, defoaming agents, such as N.S. Defoamer by Additives of Australia and Albagal FFAby Ciba Geigy, dispersing agents such as Emulsifier A by Stelco Chemicals, biocides, such as Proxyl by ICI, surfactants such as Coco DEA and G.C. 2002 by G G Distributors, and the like. Preferred surfactants are those of the anionic variety, such as alkyl sulphates, alkylarene sulphates, and phosphates, and non-ionic surfactants, such as alkyl and aryl polyoxyethylenes, or mixtures thereof. Anionic surfactants are more preferred. Coco DEA is particularly preferred.

In a preferred embodiment the ink composition includes a humectant. Examples of suitable humectants include glycerine, mono, di and tri ethylene glycol and Bookbinder" humectant by Stelco.

It has been found that a particularly effective ink can be prepared by including lubricant, such as a lubricating oil, in the ink composition to help keep the ink jet nozzles lubricated, minimise flocculation and improve water resistance.

Examples of suitable lubricating oils include fixed (fatty oils), such as marine and vegetable oils, mineral oils, such as petroleum oils and synthetic oils, such as polyalkylene glycols and polyethylenes of appropriate molecular weight. Examples of suitable vegetable oils include those containing oleic and linoleic acid such as canola oil, rapeseed oil, palm oil, corn oil, tall oil, peanut oil, caibra oil, sunflower oil, cottonseed oil, and the like. In view of <VMEN.I,- y.-'i S~Fc)4.AU PC/AU 9 7 /0 0 7 2 8 P:\OPER\MJC\BLAZER.PCT 21/9198 RECEIVED 2 1 SEP 1998 -7saponification which can occur in the alkaline conditions it is preferable to use a synthetic oil, such as a polyethylene glycol (PEG) (for example PEG 100 or PEG 900), a polypropylene glycol (PPG) or a polyhexylene glycol.

The pigmented ink may be prepared using any of the methods known to the art, however a particularly preferred method involves initial preparation of base medium followed by addition of a predispersed pigment.

Accordingly the alkaline ink is preferably prepared by a method which comprises: dissolving the polymeric resin of the alkaline ink in an aqueous alkaline medium including at least a portion of an alkaline component, by stirring, to form an alkaline resin solution; adding the water miscible organic solvent and remainder, if any, of the alkaline component to the alkaline resin solution prepared in step to produce a base medium; adding predispersed pigment to the base medium of step and stirring until homogeneous; and filtering the homogeneous mixture of step through a filter having a mesh size less than 15 microns.

In preferred embodiments the solution of step and step are stirred until homogeneous and/or filtered through a filter having a mesh size less than 15 microns.

Preferably the filter of step and optional filter of steps and has a mesh size less than 5 microns, more preferably less than 1 micron.

tBi*PA^ PCTAU 7 O O 2 8 POPER\MJC\LAZERPCT- 2119/98 RECEIVED 2 1 SEP 1998 -8- Other components of the ink composition may be added in any of steps and although preferably they are added during step The base medium prepared in step may be stored in a sealed container prior to addition of the predispersed ink.

The solvent of the coating composition may be any solvent or solvent system capable of dissolving the polymeric resin. The solvent may be an organic solvent, such as a water miscible organic solvent as described above, an aqueous solvent or a mixture of an aqueous solvent and a water miscible organic solvent. Preferably the solvent is an alkaline aqueous solvent comprising water and an alkaline component or a mixture of such an alkaline aqueous solvent with a water miscible organic solvent. Most preferably the solvent comprises a mixture of water, a water miscible organic solvent and an alkaline component.

The coating composition preferably contains a water absorbing component, such as Carbapol EZ2", microsponges or superabsorbers. This water absorbing component is preferably added in an amount of 0.1 to 0.5 more preferably about 0.15 to 0.3% and most preferably about 0.2% by weight of the coating composition. The addition of such a component increases the receptiveness of the coated substrate to the alkaline ink. Preferably the coating composition also contains a UV inhibitor.

Examples of suitable substrates to be coated in accordance with the invention include paper, cardboard, polypropylene, vinyl and other polymeric substrates, textiles, metals, foils, mesh, ink transfer mediums, wood, composite boards, laminex and the like. The term includes substrates which are not capable of receiving an ink image unless coated with the coating composition.

The alkaline ink may be an alkaline pigmented ink as described above or any other alkaline ink, which may include a dye. The alkaline ink may or may not include a polymeric resin omponent as previously described. Examples of suitable dyes include acid dyes, such as

AMEND"'-)

A IP PCT/AU 97 /0 0 7 2 8 P:\OPER\MJC\BLAZER.PCT 219/98 RECEIVED 2 1 SEP 1998 -9acid yellow 23, acid red 51, acid blue 9, acid black 194, basic dyes, such as basic dye yellow 11, basic dye red 22, basic dye blue 3, astrazon black WRL and direct dyes, such as yellow 28, blue 1, red 81, black 22 and violet 51.

The printing of the alkaline ink onto the substrate is preferably performed with an ink jet printer.

The coating composition may contain various other additives known to the art, or known to related arts such as the textiles, paints and craft industries, including those previously described in relation to the alkaline ink.

In order to improve the hardness, and the water, rub, chemical and fade resistance, the coating composition may further include a suitable cross-linking agent. Examples of crosslinking agents suitable for use with acrylic resins include melamine, and other crosslinking agents known to the art.

The coating composition may also include a suitable initiator system. Examples of free radical-providing initiator systems are benzoyl peroxide, t-butylhydroperoxide, lauroyl peroxide, cumene hydroperoxide, tetralin peroxide, acetyl peroxide, caproyl peroxide, tbutylperbenzoate, t-butyldiperphthalate, methylethylketone peroxide, hydrogen peroxide- Fe2+-ascorbic acid, riboflavin-light, methylene blue-light, and various persulfate salts in conjunction with N,N,N',N'-tetramethylethylenediamine (TEMED), diethylmethylaminediamine (DEMED), 3-dimethylaminopropionitrile (DMAPN) or similar reagents and ammonium persulfate-metabisulfite. Another class of free radical generating initiators are azocompounds such as azodiiosobutyronitrile, azodiisobutyramide, azobis (dimethylvaleronitrile), azobis (methylbutyronitrile), dimethyl, diethyl, or dibutylazobismethylvalerate. These and similar reagents contain a N,N triple bond attached to aliphatic carbon atoms, at least one of which is tertiary. The amount and type of initiator is generally indicated by the nature and concentrations of the monomer and crosslinking agent used. Other initiator systems known to the art such as sulphonic acid initiator/amine blocker AME". FD .HE'E-7T iP:EA['AU PCT/AU 9 7 U o RECEIVED 2 1 SEP 1998 P\OPER\MJC\BLAZER.PCT- 21/998 systems may also be used. The optimum amount of initiator is also affected by the presence of any accompanying impurities. Generally speaking, however, the initiator can be employed in the amount of approximately 0.3 to 5 wt. based on the total amount of the monomer and crosslinking agent. The preferred initiator system is a sulphonic acid/amine blocker system.

The application of the coating to the substrate can be performed using methods known to the art. Examples of suitable coating techniques include scraper blade technique, a reverse roll coater and mayer rod application. Other techniques would be apparent to those skilled in the art.

The coating is preferably applied to the substrate in a precise controlled manner so that the coating is smooth, even and of a uniform weight. The film weight can be varied to suit specific requirements but would generally fall within the range of 12 to 35 g/m 2 more preferably within the range of 15 to 30g/m 2 and most preferably within the range of 20 to 25g/m 2 The rate of drying of the coating can also be important as the film or coating should be fully dried before re-rolling, to prevent blocking. However the drying temperature should not be so high as to damage the substrate and thereby reduce the receptive properties of the coating.

Ideally the coating is applied slowly and passed through an oven with a combination of heat and extraction. Preferably the dryer or oven temperature does not exceed 70 0

C.

When the coating composition contains a crosslinking agent curing of the composition may be achieved by any of the methods known to the art including thermal curing and radiation curing, such as UV, infrared, microwave or electron beam curing. The particular method used will depend on the type of resin, and the nature of the crosslinking agent and any initiator system present. The crosslinking can be performed at any suitable time in the process, before or after printing of the ink on the substrate.

.By using an alkaline ink in combination with the coated substrate according to the method i\ AMENLDD -3HiEiT iPEWAAU PC/AU9 7 0 0 7 2 8 P:\OPER\MJC\BLAZER.PCT 21i9/98 RECEIVED 2 1 SEP 1998 of the present invention it is possible to produce a print which exhibits high gloss, good water resistance, good rub resistance, fast drying, good light fastness and controlled dot gain.

Additionally the final prints, when compared to conventionally produced prints may exhibit improved colour saturation, better shadow and highlights detail, improved colour gamut, improved skin tones and larger tonal range.

The coating composition is preferably a clear composition, producing a clear coating. The clarity of the composition is advantageously made possible through the use of an acrylic resin.

An image applied to a clear coated substrate by an ink jet printer will generally have improved colour brilliance, clarity and depth when compared to images printed on substrates having coatings which are not clear.

The coated substrate used in accordance with the present invention also allows images to be printed with more clarity and depth than images printed onto substrates having coatings containing a large quantity of microsponges or superabsorbers. The presence of large quantities of microsponges or superabsorbers in a coating results in muting of the ink dots and poorer image definition compared to the images produced in accordance with the present invention.

When improved hardness is required through crosslinking, such as with truck signs, flag and textile printing, vehicle bodies and the like, the inks and coatings can be modified to include crosslinking agents and initiators as described previously. The crosslinking of the ink and/or the substrate coating may be achieved after the image is printed on to the coated substrate by any of the curing methods known to the art. The type of curing method will depend on the types of resins, crosslinking agents and initiators contained in the ink or coating composition.

The ink and coating may contain different resins, crosslinking agents and initiators so that curing can be achieved separately, or more preferably, may contain the same or similar 'WY14 ins, crosslinking agents and initiators so that curing of the ink and the coating can be ,OFO AMEN DED SHEET PCT/AU 9 7 0 7 2 8 P:\OPER\JC\BLAZER.PCT- 21/9/98 RECEIVED 2 1 SEP 1998 -12achieved in one step. Depending on the type of resins, crosslinking agents and initiator systems present in the inks and coating composition, crosslinking may be achieved by thermal curing or radiation curing.

In a preferred embodiment the coating composition and/or the ink includes an acrylic resin, melamine crosslinking agent and an initiator system comprising a sulphonic acid and an amine blocker. Crosslinking of such inks and coating compositions may be achieved thermally with temperatures in the range of 70°C to 130°C.

Curing may be achieved by feeding the finished print through a conveyor oven set at the required temperature, or exposing the print to infrared (IR) flash curing or by subjecting the finished print to other radiation curing. The curing system may be integrated with the printer, such that after printing the print is fed directly to a curing oven, or is passed directly through an IR flash unit or other radiation curing unit.

In a preferred embodiment the finished print is exposed to IR flash curing. IR flash units generally contain either ceramic or quartz IR elements that expose the print to a controlled short burst of intense heat that enables the surface to reach the required temperature, but minimises heat penetration through the substrate.

Preferably the cure temperature of the coating composition and the ink is above room temperature, e.g. above 25°C, so that crosslinking can be achieved in a controlled manner after printing of the ink. More preferably the cure temperature will be greater than 40°C and most preferably greater than In order to increase the weather resistance of the printed image it is preferably laminated in accordance with standard techniques, such as spray coating. With conventional laminated prints it is important for the laminating layer to cover the edges of the print, otherwise exposure to weather will tend to cause delamination. With the printed images according to 4Q the present invention it is not necessary for the laminating layer to cover the edges to protect AMENDED SHEET 2)F~4 PCT/AU 9 7 0 07 2 P:\OPER\MJC\BLAZER.PCT 21/9/98 -13against delamination from exposure to weather, and it is accordingly possible to cut the laminated printed images of the present invention on the edges without substantially increasing the risk of delamination.

In order to facilitate an understanding of the invention reference will be made to the following example which illustrates a preferred embodiment of the invention. However it is to be understood the following descriptions does not supersede the generality of the preceding description of the invention.

EXAMPLES

Example 1 A coating composition was prepared by admixing the following components: Carboset 525 M Water 74% Ammonia 25 solution 3% Morpholine 2% Defoam 1% This composition was stirred for 2 hours and after settling, the viscosity was adjusted to 400 C.P. by adding ethanol For individual requirements this particular coating can be adjusted with additives such as Tinuvan 384", Carboset 531"*, melamine resin, such as Cymal 481T and Cymal 303T by Cytec, and sulphonic acid.

This composition was applied to a paper substrate in a controlled manner using mayer rod application to provide a smooth even coating of uniform film weight. The coated substrate was passed through an oven with a combination of heat and extraction. The temperature in i AMENDD 8HE£T >y i AbdU PCT/AU 9 7 0 0 7 2 B P:'OPER\MJC\BLAZER.PCT /9/98 RECEIVED 2 1 SEP 1998 -14the oven was 65-70 0

C.

An alkaline ink was prepared having the following composition: deionized water 28.0% GC 2002 28.0% NMP solvent 10.0% Ammonia 25 solution Morpholine Glycerine Canola oil De foam Carboset 525* (10% solution) 10.0% Pigment dispersion B F Goodrich Ciba Geigy G C Distribution A base medium without pigment is first prepared as follows: The Carboset 525 solution is first prepared- Hot Water 88% Morpholine 2% Carboset 525 10% added slowly while stirring This was then stirred for 1 hour until all the resin was dissolved.

The ingredients without the pigment dispersion were then combined and stirred with a homogeniser mixer for 15 minutes. After settling, the medium was pumped through a one nicron, nominal filter and stored in a sealed container to prevent contamination.

t y A/.A PCT/AU 7/ 0 0 7 2 8 P:\OPER\MJC\BLAZER.PCT 21/9/98 RECEIVt.. L 1 5 tP 1998 The pigment was added to the base medium in an amount of 6-7% by weight and the mixture was homogenised for 15 minutes. The ink was then pumped through a 1 micron nominal filter and packaged for later use.

The ink was then printed onto the coated substrate using a Encad T ink jet printer and the image assessed.

Example 2 A coating composition was prepared by admixing the following components: Carboset 525 M 99.8% (in the form of 25 solution in an alkaline alcohol/water solvent) Carbopol EZ2 M 0.2% For individual requirements this particular coating can also be adjusted with additives such as Tinuvan 384TM.., Carboset 531TM,, melamine resin, such as Cymal 481TM and Cymal 303TM by Cytec, and sulphonic acid.

This composition was applied to a paper substrate in a controlled manner using mayer rod application to provide a smooth even coating of uniform film weight. The coated substrate was passed through an oven with a combination of heat and extraction. The temperature in the oven was 65-70'C.

An alkaline ink was prepared having the following composition: Deionized water 60.8% Methanol 10.0% Ammonia 25% solution AMP 95 TEA S Coco DEA NP/ AMENEc SmEET 'PEAiAO PCAU 97 0 0 7 2 8 S P:,OPER\MJC\BLAZER.PCT 21/9/98 CI 2 1 SEP 1998 RECEIVED 2 1 SEP 1998 -16- Albegel FF* 0.2% PEG 400 10.0% PPG Pigment Dispersion 5.9% Ciba Geigy The ingredients without the pigment dispersion were then combined and stirred with a homogeniser mixer for 15 minutes. After settling, the medium was pumped through a one micron, nominal filter and stored in a sealed container to prevent contamination.

The pigment dispersion was added to the base medium in an amount of 4-9% by weight and the mixture was homogenised for 15 minutes. The ink was then pumped through a 1 micron nominal filter and packaged for later use.

The ink was then printed onto the coated substrate using a EncadTM ink jet printer and the image assessed.

The images produced in Examples 1 and 2 were found to exhibit high gloss, good water and rub resistance, fast drying, good light fastness, no observable feathering, and good dot gain.

In addition the final prints exhibit, when compared to dye prints and other pigment inks, improved colour saturation, better shadow and highlight detail, improved colour gamut and a larger tonal range.

The inks performed well in the ink jet printer with minimum pigment settling, long noncrusting time, no corrosion of parts of the ink jet printer in contact with ink and minimum jet/nozzle blockage. The ink also had good storage stability.

Some saponification was found to occur with the product of Example 1 after some months.

The image of Example 2, however, was particularly stable over time.

-7 AMEl^D SHEET Q) i3VAU T/AU 9 7 0 0 28 S P:\OPER\MJC\BLAZER.PCT 21/9/98 RECEIVED 2 1 SEP 1998 -17- Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions and substrates referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.

SAMENIDED SH&-T

-'FEA/AU

Claims (2)

18- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A method of printing an image onto a substrate comprising the steps of: providing a substrate coated with a coating composition comprising a polymeric resin which is insoluble in neutral water but soluble in alkaline water, and a solvent for said resin; printing the image onto said coated substrate with an alkaline ink such that said ink at least partially softens said coating of said substrate; and evaporating off, or allowing to evaporate alkaline components of said ink such that said coating substantially rehardens with said image applied thereto. 2. A method according to claim 1, wherein the polymeric resin is an acrylic resin. 3. A method according to claim 1, wherein the solvent comprises water and an alkaline component. 4. A method according to claim 3 wherein the solvent further comprises a water miscible organic solvent. A method according to claim 1, wherein said coating composition further comprises a water absorbing component in an amount of 0.1 to 0.5% by weight of said coating composition. 6. A method according to claim 1, wherein said coating composition further includes a cross-linking agent. 7. A method according to claim 6, wherein said coating composition further includes an initiation system. 8. A method according to claim 1, wherein greater than 90% of the coated surface area 'y e coated substrate has a film weight of 20 to 35 g/m 2 AME^OS .jHEET A M E HIM PCT/AU 9 7 00 7 2 8 RECEIVED 2 1 SEP 1998 11 P:\OPERMJCBLAZER.PCT -21/9/98

19- 9. A method according to claim 8, wherein 98 to 100% of the coated surface area of the coated substrate has a film weight of about 30 g/m 2 A method according to claim 1, wherein the coating on the coated substrate is clear. 11. A method according to claim 1, wherein the alkaline ink comprises a pigment, a polymeric resin insoluble in neutral water but soluble in alkaline water, a water miscible organic solvent, and water. 12. A method according to claim 11, wherein the pigment has a mean particle size of 0.005 to 15 microns. 13. A method according to claim 11, wherein the pigment has a particle size of 0.005 to 1 micron. 14. A method according to claim 11, wherein the polymeric resin of the alkaline ink is an acrylic resin. A method according to claim 11, wherein the water miscible organic solvent is an alcohol. 16. A method according to claim 11, wherein the alkaline ink further includes a lubricating oil. 17. A method according to claim 16, wherein the lubricating oil is a polyalkylene glycol. 18. A method according to claim 11, wherein the alkaline ink is prepared by a method comprising: dissolving the polymeric resin of the alkaline ink in an aqueous alkaline 4 medium including at least a portion of an alkaline component, by stirring, to form an AMEiTf H5, T SIPA/AU PCT/AU 9 7 0 0 7 2 8 RECEIVED 2 1 SEP 1998. d P:\OPER\MJC\BLAZER.PCT 21/9/98 alkaline resin solution; adding the water miscible organic solvent and remainder, if any, of the alkaline component to the alkaline resin solution prepared in step to produce a base medium; adding predispersed pigment to the base medium of step and stirring until homogeneous; and filtering the homogeneous mixture of step through a filter having a mesh size less than 15 microns. 19. A method according to claim 1, wherein said alkaline ink is applied to the coated substrate using an ink jet printer charged with said alkaline ink. A substrate having an image printed thereon, said image being applied to said substrate by a method according to any one of the preceding claims. AME>~E~ S3H2ET