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 50 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.

It is an object of the present invention to overcome or at least alleviate one or more of the abovementioned disadvantages of the prior art.

Accordingly in a first aspect the present invention provides an alkaline pigmented ink comprising: a pigment, a polymeric resin insoluble in neutral water, but soluble in alkaline water,

a water miscible organic solvent, and water.

The alkaline pigmented ink according to the present invention 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.

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 polymeric 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 most preferably 0.005 to 1 micron. The fine particle size also enables improved gloss, greater translucency, and improved colour strength in the applied ink.

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, NovopermX Yellow HR, NovopermX Yellow FGL, Hansa Brilliant Yellow 10X, Permanent Yellow G3R-01, HostapermX Yellow H4G, HostapermX Yellow H3G, HostapermX Orange GR, Hostaperms Scarlet GO and Permanent Rubine F6B by Hoechst, ChromophtalX Yellow 3G, ChromophtalX Yellow GR, ChromophtalX Yellow 8G, IrgazinX Yellow 5GT, IrgaliteX Rubine 4BL, MonastralX Magenta, MonastralX Scarlet, Monastrals Violet R and MonastralX Violet Maroon B by Ciba Geigy,

DalamarX Yellow YT-858-D and HeucophthalX Blue G, XBT-583D by Heubach, PaliogenX Orange, Heliogens Blue L 6901 F, HeliogenX Blue NBD 7010, HeliogenX Blue K 7090, HeliogenX Blue L 7101F, PaliogenX Blue L 6470, HeliogenX Green K 8683 and HeliogenX Green L 9140 by BASF, QuindoX Magenta, IndofastX Brilliant Scarlet, QuindoX Red R6700, QuindoX Red R6713 and IndofastX 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: HeucophthalX Blue, Toluidine Red Y, QuindoX Magenta and Magenta RV-6831 presscake by Mobay Chemicals, SunfastX Magenta 122, IndoX Brilliant Scarlet, Toluidine Red B, WatchungX Red B, Permanent Rubine F6B13-1731, HansaX Yellow, SunbriteX Yellow 17 by Sun Chemical Corp, Hostafine Yellow GR, Hostafine Yellow HR, Hostafine Red HF35, Hostafine Red Full, Hostafine Rubine F6B, Hostafine 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 art. In this regard microshearing processes are particularly suitable.

The polymeric resin 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, tert-butylaminoethyl 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, 2-ethyffihexylacrylate, isobutyl methacrylate, acrylonitrile, acrylamide, methacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N- dibutylacrylamide, N, N-dibutylmethacrylamide, N,N-dioctylacrylamide, N,N- dioctylmethacrylamide, N-monobutylacrylamide, N-monobutylmethacrylamide, N- monooctylacrylamide, N-monooctylmethacrylamide, 2-hydroxyethyl acrylate, 2- hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2,4-dihydroxy4 '-vinylbenzophenone, N-(2-hydroxyethyl)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.

The acrylic homopolymers and copolymers may be formed by any of the techniques known to the art including solution, emulsion and suspension polymerisation techniques. Preferred acrylic copolymers are emulsion copolymers such as those provided under the trademarks Carbosetm by B F Goodrich, Acrysolm 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 printer. For most applications a pigment content of 0.1 to 30% by weight of the ink will be sufficient. 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 æ, more preferably in the range of 0.5 to 1%.

The ink according to the invention 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 Bookbinderm 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, canbra oil, sunflower oil, cottonseed oil, and the like. In view of saponification 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 in a second aspect the invention provides a method for preparing a pigmented ink according to the first aspect which comprises: (A) dissolving the polymeric resin in an aqueous alkaline medium including at least a portion of an alkaline component, by stirring, (B) adding the water miscible organic solvent and remainder, if any, of the alkaline component to the alkaline resin solution prepared in step (A) to produce a base medium, (C) adding predispersed pigment to the base medium of step (B) and stirring until homogeneous, (D) filtering homogeneous mixture of step (C) through a filter having a mesh size less than 15 microns.

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

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

Other components of the ink composition may be added in any of steps (A), (B) and (C), although preferably they are added during step (B).

The base medium prepared in step (B) may be stored in a sealed container prior to addition of the predispersed ink. This base medium represents a third aspect of the present invention.

The ink according to the present invention may be applied to any suitable substrate capable of receiving an alkaline ink. Polymeric, or polymeric coated substrates are preferred.

Suitable coatings include acrylic, polyvinyl alcohol, polyvinyl acetate, starch based coatings and the like.

In order to maximise the properties of the alkaline ink according to the present invention it is preferred that the ink is applied to a substrate coated with or comprising a particular polymeric resin coating.

Accordingly in a fourth aspect of the present invention there is provided an alkaline coating composition for an ink receiving substrate which includes: a polymeric resin insoluble in neutral water, but soluble in alkaline water, a solvent for said resin.

Preferably the composition also contains a 1w inhibitor.

The polymeric resins and alkaline components suitable for preparing the coating composition are those described previously in relation to the alkaline pigmented ink.

The solvent 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.

As used herein the term "ink receiving substrate" refers to any substrate upon which an ink image is to be printed. Examples of suitable substrates 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 an ink receiving coating.

According to a fifth aspect of the invention there is provided a coated substrate for receiving an alkaline ink which includes an ink receiving substrate coated with a coating composition according to the fourth aspect of the invention. The alkaline ink may be an alkaline pigmented ink according to the first aspect of the invention or any other alkaline ink, which may include a dye. The alkaline ink may or may not include a polymeric resin component 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 cross- linking 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, t- butylperbenzoate, 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 cross linking agent used. Other initiator systems known to the art such as sulphonic acid initiator/amine blocker 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 gum~2, more preferably within the range of 15 to 30gum~2 and most preferably within the range of 20 to 25gm-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 70or.

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.

An image may be printed onto the coated substrate according to the fifth aspect of the invention with any alkaline ink, including the pigment ink according to the first aspect of the invention. Accordingly in a sixth aspect the invention provides a method of printing an image onto a substrate comprising providing a substrate coated with a coating composition, said coating composition comprising polymeric resin insoluble in neutral water but soluble in alkaline water, and a solvent for said polymeric resin, and printing image onto said coated substrate with a printing device charged with an alkaline ink.

In one embodiment the alkaline ink is an alkaline pigmented ink according to the first aspect of the invention.

Another alkaline ink which may be used in combination with the coated substrate is an ink according to the first aspect of the invention which does not include the polymeric resin component.

In another embodiment the alkaline ink comprises a dye, a water soluble organic solvent and water, optionally together with a polymeric resin insoluble in neutral water, but soluble in alkaline water. The alkaline dye inks which include a polymeric resin are novel and represent a seventh aspect of the present invention. Examples of suitable dyes include acid dyes, such

as acid 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.

By using an alkaline ink in combination with the coated substrate 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 conventional dye prints and prints produced by other pigment dyes may exhibit improved colour saturation, better shadow and highlights detail, improved colour gamut, improved skin tones and larger tonal range.

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

An image applied to a clear coated substrate according to the present invention 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 of 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 resins, crosslinking agents and initiators so that curing of the ink and the coating can be achieved 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 1300C.

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 25do, 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 50"C.

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 the present invention it is not necessary for the laminating layer to cover the edges to protect against 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 525to 20% 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 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 28.0% GC 2002TM*** 28.0% NMP solvent 10.0% Ammonia 25 % solution 5.0% Morpholine 2.0% Glycerine 8.0% Canola oil 1.5% Dye foam 0.5% Carboset 525>+ (10% solution) 10.0% Pigment dispersion 7.0% BF 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 micron, nominal filter and stored in a sealed container to prevent contamination.

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 Encadm ink jet printer and the image assessed.

Example 2 A coating composition was prepared by admixing the following components: Carboset 525to 99.8% (in the form of 25 % solution in an alkaline alcohol/water solvent) Carbopol EZ2 0.2% For individual requirements this particular coating can also be adjusted with additives such as Tinuvan 384w**, Carboset 531TM*, melamine resin, such as Cymal 481TM and Cymal 303tom 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 1.0% AMP 95 2.5% TEA 2.5% Coco DEA 3.0% Albegel FF* 0.2% PEG 400 10.0% PPG 5.0% 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 Encadz 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 non- crusting 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.

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.