Ink-jet printing is a non-impact printing technique in which droplets of ink are ejected through a fine nozzle onto a substrate without bringing the nozzle into contact with the substrate.

There are many demanding performance requirements for dyes and inks used in ink-jet printing. For example they desirably provide sharp, non-feathered images having good water, light and ozone fastness and optical density. The inks are often required to dry quickly when applied to a substrate to prevent smudging, but they should not form a crust over the tip of an ink-jet nozzle because this will stop the printer from working. The inks should also be stable to storage over time without decomposing or forming a precipitate that could block the fine nozzle.

Colour ink-jet printers typically use four inks of differing hues: magenta, yellow, cyan, and black. Colours other than these may be obtained using differing combinations of these inks. Thus, for optimum print quality, the colourants used must be able to form ink with a specific precise hue. This can be achieved by mixing colourants but is advantageously achieved by used a single colourant with the exact hue required.

Therefore new colourants with differing hues and the physical/chemical properties which allow them to be used in ink-jet printing inks are always required.

According to the present invention there is provided a metal complex of Formula (1) or salt thereof : Formula (1) wherein : each R'independently is a substituent; R2 is H or optionally substituted alkyl ;

each R3 independently is carboxy, phosphato, sulfo, nitro or cyano; each G independently is a substituent; M is a metal ; m is 1 to 4 ; p is 1 to 3; z is 0 to 5 ; q is 0 to 4 ; and x is 1 to 4.

Each R'is independently selected from: optionally substituted alkyl (preferably Cri-4- alkyl), optionally substituted alkenyl (preferably C1 4-alkenyl), optionally substituted alkynyl (preferably C1 4-alkynyl), optionally substituted alkoxy (preferably C1 4-alkoxy), optionally substituted aryl (preferably phenyl), optionally substituted aryloxy (preferably phenoxy), optionally substituted heterocyclic, polyalkylene oxide (preferably polyethylene oxide or polypropylene oxide), carboxy, phosphato, sulfo, nitro, cyano, halo, ureido,-S02F, hydroxy, ester,-NR4R5,-COR4,-CONR4R5,-NHCOR4, carboxyester, sulfone, and- S02NR4R5 wherein R4 and R5 are each independently H or optionally substituted alkyl (especially C1 4-alkyl). Optional substituents for any of the substituents described for R' may be selected from the same list of substituents.

Preferably at least one R'is optionally substituted alkyl more preferably at least one R'is optionally substituted C1 4-alkyl.

It is especially preferred that at least one R'is methyl.

Preferably R2 is H or optionally substituted C1 4-alkyl, more preferably R2 is H or methyl.

When R2 is optionally substituted alkyl then the optional substituents are preferably selected from: optionally substituted alkenyl (preferably C1 4-alkenyl), optionally substituted alkynyl (preferably C1 4-alkynyl), optionally substituted alkoxy (preferably C1 4-alkoxy), optionally substituted aryl (preferably phenyl), optionally substituted aryloxy (preferably phenoxy), optionally substituted heterocyclic, polyalkylene oxide (preferably polyethylene <BR> <BR> oxide or polypropylene oxide), carboxy, phosphato, sulfo, nitro, cyano, halo, ureido, - SO2F, hydroxy, ester,-NR4R5,-COR4,-CONR4R5,-NHCOR4, carboxyester, sulfone, and- S02NR4R5 wherein R4 and R5 are each independently H or optionally substituted alkyl (especially C1 4-alkyl). Optional substituents for any of the substituents described for R2 may be selected from the same list of substituents.

R3 is preferably carboxy.

Preferably m is 1.

Preferably p is 1.

Preferably z is 0.

Preferably q is 0.

Each G is independently selected from the same list of substituents as is given above for R'.

M may be any metal suitable for use in an ink-jet printing process. The major factor in the suitability of a metal for an ink-jet printing process is the tendency of some metals to form precipitates on long term storage and block the nozzles in an ink-jet printing head.

M is preferably a transition metal. More preferably M is selected from nickel, cobalt, copper, zinc and chromium. It is especially preferred that M is nickel, particularly Ni2+.

Preferably x is 2.

A preferred metal complex of Formula (1) is of Formula (2): Formula (2) wherein: R'is optionally substituted C14alkyl ; R2 is H or optionally substituted C14alkyl ; and R3 is carboxy, phosphato, sulfo, nitro or cyano.

R'and R2 and optional substituents thereon are as described and preferred above.

R3 is preferably carboxy.

In compounds of Formula (2) and compounds of Formula (1) when x is greater than 1 the metal ligands in the metal complex may be the same or different but preferably they are the same.

The metal complexes of Formula (1) and Formula (2) may also comprise 1 or more additional ligands. These ligands may be coloured or colourless and when there is more than 1 they may be the same or different.

Acid or basic groups on the metal complex's of Formula (1) and Formula (2), particularly acid groups, are preferably in the form of a salt. Thus, the Formulae shown herein include compounds as free acids and salts.

Preferred salts are alkali metal salts, especially lithium, sodium and potassium, ammonium and substituted ammonium salts (including quaternary amines such as

((CH3) 4N+) and mixtures thereof. Especially preferred are salts with sodium, lithium, ammonia and volatile amines, more especially sodium salts. The metal complex may be converted into a salt using known techniques.

The metal complexes of Formula (1) and Formula (2) may exist in tautomeric forms other than those shown in this specification. These tautomers are included within the scope of the present invention.

The metal complexes of Formula (1) and Formula (2) have attractive, strong magenta shades and are valuable colorants for use in the preparation of ink-jet printing inks.

They benefit from a good balance of solubility, storage stability and fastness to water and light. In particular they display excellent light and ozone fastness.

The metal complexes of Formula (1) and Formula (2) may be prepared by firstly forming a substituted pyridin-2-yl-hydrazine, for example, by reacting a substituted 2- bromopyridine with hydrazine monhydrate under reflux. This hydrazine is reacted with a 1, 2-naphthoquinone-4-sulfonic acid under acidic conditions. The product of this reaction is converted into a sulfonamide by first forming the corresponding chlorosulfonic acid by reaction with a chlorinating agent such as POCI3. This chlorsulphonic acid group is then reacted with a substituted amino benzene to give a ligand as shown in Formula (1) and Formula (2) which may then be converted into a metal complex of Formula (1) and Formula (2) by mixing with a suitable salt of the desired metal.

According to a second aspect of the present invention there is provided a composition comprising a metal complex of Formula (1), preferably Formula (2), according to the first aspect of the invention and a liquid medium.

Preferably the composition comprises: (a) from 0.01 to 30 parts of a metal complex of Formula (1), preferably Formula (2), as hereinbefore defined; and (b) from 70 to 99.99 parts of a liquid medium; wherein all parts are by weight and the number of parts of (a) + (b) =100.

The number of parts of component (a) is preferably from 0.1 to 20, more preferably from 0.5 to 15, especially from 1 to 5 parts. The number of parts of component (b) is preferably from 99.9 to 80, more preferably from 99.5 to 85, especially from 99 to 95 parts.

The composition may of course contain further ingredients in addition to (a) and (b).

Preferably component (a) is completely dissolved in component (b). Preferably component (a) has a solubility in component (b) at 20°C of at least 10%. This reduces the chance of component (a) precipitating if evaporation of the liquid medium occurs during storage.

Preferred liquid media include water, a mixture of water and organic solvent and organic solvent free from water.

When the liquid medium comprises a mixture of water and organic solvent, the weight ratio of water to organic solvent is preferably from 99: 1 to 1: 99, more preferably from 99: 1 to 50: 50 and especially from 95: 5 to 80: 20.

It is preferred that the organic solvent present in the mixture of water and organic solvent is a water-miscible organic solvent or a mixture of such solvents. Preferred water- miscible organic solvents include C1 6-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol and cyclohexanol ; linear amides, preferably dimethylformamide or dimethylacetamide ; ketones and ketone-alcohols, preferably acetone, methyl ether ketone, cyclohexanone and diacetone alcohol ; water-miscible ethers, preferably tetrahydrofuran and dioxane; diols, preferably diols having from 2 to 12 carbon atoms, for example ethylene glycol, propylene glycol, butylen glycol, pentylen glycol, hexylen glycol and thiodiglycol and oligo-and poly-alkyleneglycols, preferably pentane-1, 5-diol, diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol ; triols, preferably glycerol and 1,2, 6-hexanetriol ; mono-C14-alkyl ethers of diols, preferably mono-C14-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxyethanol, 2- (2-methoxyethoxy) ethanol, 2- (2-ethoxyethoxy)-ethanol, 2- [2- (2-methoxyethoxy) ethoxy] ethanol, 2- [2- (2-ethoxyethoxy)- ethoxy]-ethanol and ethyleneglycol monoallylether ; cyclic amides, preferably 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, caprolactam and 1, 3-dimethylimidazolidone ; cyclic esters, preferably caprolactone ; sulfoxides, preferably dimethyl sulfoxide and sulfolan. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-soluble organic solvents.

Especially preferred water-soluble organic solvents are cyclic amides, especially 2- pyrrolidone, N-methyl-pyrrolidone and N-ethyl-pyrrolidone ; diols, especially pentane-1, 5-diol, ethyleneglycol, thiodiglycol, diethyleneglycol and triethyleneglycol ; and mono-C14-alkyl and Cl-4-alkyl ethers of diols, more preferably mono-C14-alkyl ethers of diols having 2 to 12 carbon atoms, especially 2-methoxy-2-ethoxy-2-ethoxyethanol.

Although not usually necessary, further colorants may be added to the composition medium to modify the shade and performance properties of the composition. Examples of such colorants include C. I. Direct Yellow 86,132, 142 and 173; C. I. Direct Blue 199, and 307; C. I. Food Black 2; C. I. Direct Black 168 and 195; C. I. Acid Yellow 23; and any of the dyes used in ink-jet printers sold by Seiko Epson Corporation, Hewlett Packard Company, Canon Inc. & Lexmark International.

Examples of further suitable liquid media comprising a mixture of water and one or more organic solvents are described in US 4,963, 189, US 4,703, 113, US 4,626, 284 and EP 4,251, 50A.

When the liquid medium comprises organic solvent free from water, (i. e. less than 1% water by weight) the solvent preferably has a boiling point of from 30° to 200°C, more preferably of from 40° to 150°C, especially from 50 to 125°C. The organic solvent may be water-immiscible, water-miscible or a mixture of such solvents. Preferred water-miscible organic solvents are any of the hereinbefore described water-miscible organic solvents and mixtures thereof. Preferred water-immiscible solvents include, for example, aliphatic hydrocarbons; esters, preferably ethyl acetate; chlorinated hydrocarbons, preferably

CH2CI2 ; and ethers, preferably diethyl ether; and mixtures thereof.

When the liquid medium comprises water-immiscible organic solvent, preferably a polar solvent is included because this enhances solubility of the dye in the liquid medium.

Examples of polar solvents include C14-alcohols. In view of the foregoing preferences it is especially preferred that where the liquid medium is organic solvent free from water it comprises a ketone (especially methyl ethyl ketone) and/or an alcohol (especially a Cul-4- alkanol, more especially ethanol or propanol).

The organic solvent free from water may be a single organic solvent or a mixture of two or more organic solvents. It is preferred that when the medium is organic solvent free from water it is a mixture of 2 to 5 different organic solvents. This allows a medium to be selected which gives good control over the drying characteristics and storage stability of the composition.

Liquid media comprising organic solvent free from water are particularly useful where fast drying times are required and particularly when printing onto hydrophobic and non-absorbent substrates, for example plastics, metal and glass.

Preferably the composition according to the second aspect of the invention is an ink-jet printing ink or a liquid dye concentrate. Concentrates are useful as a means for transporting colorant and so minimising costs associated with drying the dye and transporting excess liquid.

Compositions are preferably prepared using high purity ingredients and/or by purifying the composition after it has been prepared. Suitable purification techniques are well known, e. g. ultrafiltration, reverse osmosis, ion exchange and combinations thereof (either before or after they are incorporated in a composition according to the present invention). This purification results in the removal of substantially all of the inorganic salts and by-products resulting from its synthesis. Such purification assists in the preparation of a low viscosity aqueous solution suitable for use in an ink-jet printer.

Preferably the composition has a viscosity of less than 20 cP, more preferably less than 10 cP, especially less than 5 cP, at 25°C. These low viscosity compositions are particularly well suited for application to substrates by means of ink-jet printers.

Preferably the composition contains less than 500ppm, more preferably less than 250ppm, especially less than 100pm, more especially less than 10ppm in total of divalent and trivalent metal ions (other than any divalent and trivalent metal ions bound to a component of the composition). Higher levels of these free metals can precipitate and so block the fine nozzles found in many ink-jet printers.

Preferably the composition has been filtered through a filter having a mean pore size below 10, m, more preferably below 311m, especially below 211m, more especially below 1, um. This filtration removes particulate matter that could otherwise block the fine nozzles found in many ink-jet printers.

Preferably the composition contains less than 500ppm, more preferably less than 250ppm, especially less than 100pm, more especially less than 10ppm in total of halide

ions. Higher levels of halide ions may lead to corrosion of the print heads and can also co-precipitate with some components used in ink-jet printing inks.

The liquid medium may also of course contain further additives which are conventionally used in ink-jet printing inks, for example viscosity and surface tension modifiers, corrosion inhibitors, biocides, kogation reducing additives and surfactants which may be ionic or non-ionic.

A third aspect of the invention provides a process for forming an image on a substrate comprising applying a composition according to the second aspect of the invention thereto by means of an ink-jet printer.

The ink-jet printer preferably applies the composition to the substrate in the form of droplets which are ejected through a small orifice onto the substrate. Preferred ink-jet printers are piezoelectric ink-jet printers and thermal ink-jet printers. In thermal ink-jet printers, programmed pulses of heat are applied to the composition in a reservoir by means of a resistor adjacent to the orifice, thereby causing the composition to be ejected in the form of small droplets directed towards the paper during relative movement between the substrate and the orifice. In piezoelectric ink-jet printers the oscillation of a small crystal causes ejection of the composition from the orifice. Alternately the ink can be ejected by an electromechanical actuator connected to a moveable paddle or plunger, for example as described in WO 00/48938 and WO 00/55089.

The substrate is preferably paper, plastic, a textile, metal or glass more preferably paper, an overhead projector slide or a textile material, especially paper.

Preferred papers are plain, coated or treated papers which may have an acid, alkaline or neutral character.

A fourth aspect of the present invention provides a substrate, especially paper, an overhead projector slide, a textile material, a plastic, glass or metal, printed with a metal complex according to the first aspect of the invention or a composition according to the second aspect of the invention or by a process according to the third aspect of the invention. Preferably the substrate is a paper.

Preferred papers are plain, coated or treated papers which may have an acid, alkaline or neutral character.

A fifth aspect of the present invention provides an ink-jet printer cartridge comprising a chamber and an composition wherein the composition is in the chamber and the composition is as defined in the second aspect of the present invention.

The invention is further illustrated by the following Examples in which all parts and percentages are by weight unless otherwise stated. Example 1 Preparation ofi

Stage 1 Preparation of (5-methyl-pyridin-2-yl)-hydrazine A mixture of 2-bromo-5-methylpyridine (25g, 0. 15mol) and hydrazine monohydrate (100mol) was stirred at reflux for 24 hours, the reaction mixture was allowed to cool to room temperature and then added to water (100mol). The product was precipitated by the addition of sodium chloride and the resultant solid was filtered off and dried in a vacuum desiccator to give 23.9g (69% pure) of white crystals.

Stage 2 Preparation of 4-hydroxy-3- (5-methyl-pyridin-2-ylazo)-naphthalene-1-sulfonic acid A 0.05M aqueous solution of (5-methyl-pyridin-2-yl)-hydrazine from stage 1 (500ml) was added to a suspension of 1, 2-naphthoquinone-4-sulfonic acid (26g) in concentrated hydrochloric acid (200ml). The reaction mixture was stirred for 2 hours at room temperature and the solid was collected by filtration. The crude product was then dissolved in water (600ml) and adjusted to pH9 with a 2M sodium hydroxide solution. The product was re-precipitated by lowering the pH to 4 via the addition of 2M hydrochloric acid and adding sodium chloride to 10% w/v. The purified solid was collected by filtration and dried to give 32. 1g (88% yield) of a red solid.

Stage 3 Preparation of 4- [4-hydroxy-3 (5-methyl-pyridin-2-ylazo)-naphthalene-1-sulfonylamino]- benzoic acid Phosphorus oxychloride (25ml) was added dropwise to a suspension of the product from stage 2 (10g) in tetramethylene sulfone (100ml). The reaction mixture was stirred at 55-65°C for 10 hours, added to a mixture of ice and water (500mi) and the resultant precipitate was collected by filtration. The solid was dissolved in chloroform (500ml) and dried over magnesium sulfate before the solvent was evaporated under reduced pressure. A mixture of the residue and 4-aminobenzoic acid (3.43g in N, N-

dimethylacetamide (200ml) was stirred for 24 hours at room temperature and then added to water (1000ml). The product was collected by filtration, washed with water (200moi) and dried in a vacuum desiccator to give 5.6g (40% yield) of a red powder.

Stage 4 Preparation of the title dye: A solution of nickel acetate tetrahydrate (0.63g) in water (10ml) was added dropwise to a suspension of the product from stage 3 (2. 31g) in N, N-dimethylformamide (50ml). The reaction mixture was stirred at 70°C for 3 hours, added to water (500ml) and the product collected by filtration. The solid was stirred in acetonitrile (50ml) at reflux for 10 min and then cooled. The product was then filtered off and pulled dry under vacuum to give 2.2g (90% yield) of a purple solid.

Example 2 Preparation of: The metal complex of Example 2 was prepared using an analogous process to that described in Example 1 except that in stage 1 in place of 2-bromo-5-methylpyridine there was used 2-bromo-4-methylpyridine.

Example 3 Preparation of Inks 1 and 2 Inks 1 and 2 were prepared by dissolving the corresponding metal complex of Examples 1 to 2 (2 g) in 98 ml of a liquid medium consisting of 8 parts 2-pyrrolidone ; 8 parts diethylene glycol ; 8 parts pentan-1, 5-diol ; 1 part/Surfyno) 465 and 73 parts water.

Example 4 ink-jet Printing Inks 1 and 2 were ink-jet printed onto a variety of papers using a Hewlett Packard 970. The hue of each print was measured using a Xrite 98T" Spectrodensitometer with

0°/45° measuring geometry with a spectral range of 400-700nm at 20nm spectral intervals, using illuminant C with a 2° (CIE 1931) observer angle and a density operation of status T. No less than 2 measurements were taken diagonally across a solid colour block on the print with a size greater than 10mm x 10mm. The properties of the resultant prints are shown in Table 1.

Table 1 Ink Jet Print Properties Ink Xerox 4024 Epson Premium HP Premium Canon Plus HR101 Ink 1 338 335 335 332 Ink 2 338 336 337 334 Further Inks The inks described in Tables A and B may be prepared wherein the Dye described in the first column is the metal complex made in the above Example of the same number.

Numbers quoted in the second column onwards refer to the number of parts of the relevant ingredient and all parts are by weight. The inks may be applied to paper by ink- jet printing.

The following abbreviations are used in Tables A and B: PG = propylene glycol DEG = diethylene glycol NMP = N-methyl pyrollidone DMK = dimethylketone IPA = isopropanol MEOH = methanol 2P = 2-pyrrolidone MIBK = methylisobutyl ketone P12 = propane-1, 2-diol BDL = butane-2, 3-diol CET= cetyl ammonium bromide PHO Na2HP04 and TBT = tertiary butanol TDG = thiodiglycol TABLE A Dye Dye Water PG DEG NMP DMK NaOH Na IPA MEOH 2P MIBK Content Stearate 1 2.0 80 5 6 4 5 2 3.0 90 5 5 0.2 2 10.0 85 3 3 3 5 1 2 2.1 91 8 1 1 3.1 86 5 0.2 4 5 1 1.1 81 9 0.5 0.5 9 2 2.5 60 4 15 3 3 6 10 5 4 2 5 65 20 10 2 2.4 75 5 4 5 6 5 1 4.1 80 3 5 2 10 0.3 1 3.2 65 5 4 6 5 4 6 5 2 5.1 96 4 1 10.8 90 5 5 2 10.0 80 2 6 2 5 1 4 2 1.8 80 5 15 2 2.6 84 11 5 1 3.3 80 2 10 2 6 1 12.0 90 7 0.3 3 1 5.4 69 2 20 2 1 3 3 1 6. 0 91 4 5 TABLE B Dye Dye Water PG DEG NMP CET TBT TDG BDL PHO 2P P12 Content 1 3.0 80 15 0.2 5 2 9.0 90 5 1.2 5 2 1.5 85 5 5 0.15 5.0 0.2 2 2.5 90 6 4 0.12 1 3.1 82 4 8 0.3 6 1 0.9 85 10 5 0.2 2 8.0 90 5 5 0.3 2 4.0 70 10 4 1 4 11 2 2.2 75 4 10 3 2 6 1 10.0 91 6 3 1 9.0 76 9 7 3.0 0.95 5 1 5.0 78 5 11 6 2 5.4 86 7 7 2 2.1 70 5 5 5 0.1 0. 2 0. 1 5 0. 1 5 2 2.0 90 10 1 2 88 10 1 5 78 5 12 5 1 8 70 2 8 15 5 1 10 80 8 12 1 10 80 10