GB2400855A

GB2400855A - Magenta ink-jet printing inks

Info

Publication number: GB2400855A
Application number: GB0405684A
Authority: GB
Inventors: Gavin Wright; Mark Kenworthy
Original assignee: Avecia Ltd
Current assignee: Avecia Ltd
Priority date: 2003-04-08
Filing date: 2004-03-15
Publication date: 2004-10-27
Anticipated expiration: 2024-03-15
Also published as: GB0308061D0; GB2400855B; GB0405684D0

Abstract

An ink comprising a liquid medium, a dispersant and colorant of Formula (1): <EMI ID=1.1 HE=40 WI=40 LX=884 LY=684 TI=CF> <PC>wherein: <DL TSIZE=8> <DT>W and X<DD>are each independently C(O)R<1> or optionally substituted aryl; R<1> is selected from H, optionally substituted alkyl, optionally substituted aryl and optionally substituted aralkyl; and </DL> rings A and B are each independently unsubstituted or carry one or more substituents. Also ink-jet printing processes, printed images and ink-jet printer cartridges.

Description

MAGENTA INK-JET PRINTING INKS

This invention relates to inks and to their use in ink jet printing ("IJP").

IJP 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 IJP. For example, they desirably provide sharp, non-feathered images having good water-fastness, light-fastness, 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 which could block the fine nozzle.

Magenta colorants such as C.l. Acid Red 52 and their use in IJP are known. Many magenta colorants have poor ozone and/or light fastness. Others have an undesirable shade or low chrome. Our own recent studies have shown the deleterious effect ozone can have on prints, causing accelerated fading even in the dark. With ever increasing manufacturer and customer requirements for long term print fastness there is a need for magenta colorants suitable for ink jet with good shade, light fastness and ozone fastness According to the first aspect of the present invention there is provided an ink comprising a liquid medium, a dispersant and a colorant of Formula (1): Formula (1) wherein: W and X are each independently C(0)R' or optionally substituted aryl; R' is selected from H. optionally substituted alkyl, optionally substituted aryl and optionally substituted aralkyl; and rings A and B are each independently unsubstituted or carry one or more substituents.

Preferably any optional substituents on rings A and B are independently selected from -OH, -Br, -Cl, -F. -CN, -NO2, optionally substituted phosphoramide, optionally substituted alkyl, optionally substituted aryl, optionally substituted aralkyl, - SR2, -SO2R2, SO2NR2R3, -oR2, -NR2R3, C(0)R2, -C(0)0R2 and -NHC(0)R2, wherein R2 and R3 are each independently selected from H. optionally substituted alkyl, optionally substituted aryl, optionally substituted aralkyl, or R2 and R3 together with the nitrogen atom to which they are attached form an optionally substituted 5or 6- membered ring. Rings A and B are each preferably unsubstituted or carry 1 to 4 substituents.

When W and/or X are optionally substituted aryl the preferred substituents are selected from -OH, -Br, -Cl, -F. -CF3, -NO2, -ON, optionally substituted phosphoramide, optionally substituted alky, optionally substituted aralkyl, optionally substituted aryl, -SR2, SO2R2, -SO2NR2R3, -oR2, -NR2R3, -C(0)R2, -C(0)OR2 and -NHC(0)R2, wherein R2 and R3 are preferably each independently selected from H. optionally substituted alkyl, optionally substituted aryl, optionally substituted aralkyl, or R2 and R3 together with the nitrogen atom to which they are attached form an optionally substituted 5- or 6- membered ring.

Rings A and B are each preferably unsubstituted or carry 1 to 4 substituents.

Preferred colorants of Formula (1) are those wherein X and W are identical. Also preferred are colorants of Formula (1) wherein rings A and B are identical. Especially preferred are colorants of Formula (1) wherein X and W are identical to each other and rings A and B are identical to each other, such that the colorant molecule has rotational 1 5 symmetry.

The colorant of Formula (1) is preferably of Formula (2): Formula (2).

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

The colorants of Formula (1) may be prepared by the reaction of an optionally substituted indigo of Formula (3) with an acid chloride of Formula (4), and acid chloride of Formula (5) and then benzoyl chloride: 3 WCH2 CCI XCH2CC

O H

Formula (3) Formula (4) Formula (5) wherein: 7^ rings A and B and substitutents W and X are as hereinbefore defined.

The optionally substituted indigo may be reacted with the acid chlorides of Formula (4) and Formula (5) sequentially or simultaneously. If the optionally substituted indigo of Formula (3) is reacted with the acid chlorides of Formulae (4) and (5) simultaneously and W and X are not identical then a mixture of colorants of Formula (1) results which may be used in the ink as a mixture or said mixture may be purified to give a single colorant of Formula (1).

The reaction is preferably performed in a high boiling inert solvent, for example 1,2-dichlorobenzene, at a temperature preferably from 70 C to 200 C. The duration of the reaction depends on the reaction temperature and on the reactivities of the reactants but is typically 20 to 40 hours.

Optionally substituted indigos of Formula (3) can be prepared from correspondingly optionally substituted indoles using techniques known in the art, for example by the hydroperoxide synthesis described in EP 0339887. In the hydroperoxide synthesis an optionally substituted indole is mixed with a carboxyl-containing compound (e.g. benzoic acid), an organic hydroperoxide (e.g. cumene hydroperoxide), a catalyst (e.g. a boric acid ester and/or a metal catalyst e.g. molybdenum hexacarbonyl) and a solvent (e.g. toluene). The mixture is heated typically in air, to a reaction temperature typically approximately 80 C for approximately 10 hours. The optionally substituted indigo formed typically precipitates from the mixture and is typically filtered-off after cooling. The optionally substituted indigo may be washed with small amounts of cumene and methanol and dried at 50 C. The hydroperoxide synthesis is particularly suited for preparing indigos of Formula (3) having substitutents on rings A and/or B such as alky, alkoxy, aryl, hydroxy, halogen, nitro, aryl, hydroxy, halogen, nitro, acyl, carboxylic acid ester, dialkyl amino or sulfo.

Brominated or chlorinated indigos of Formula (3) can be prepared by the reaction of indigo with the corresponding halogen in nitrobenzene typically under a nitrogen gas atmosphere. The reaction is typically performed between 30 C and 105 C for a duration of 2 to 10 hours. By varying the conditions (temperature, duration, amount of halogen) the degree of halogenation can be controlled. Bromine substituents in the colorant of Formula (1) can be readily converted to cyano groups by conventional substitution reactions.

Many sulphonated indigos of Formula (3) are commercially available.

Alkyl or alkoxy substituted indigos of Formula (3) can also be prepared by reacting a corresponding alkyl or alkoxy substituted nitronate intermediate of Formula (4) with potassium hydroxide and sodium hydrosulfite typically at a temperature of 0 to 10 C typically for a period of 1 to 2 hours. NO2

OH

Formula (4) wherein T is alkyl or alkoxy.

The alkyl or alkoxy substituted nitronate intermediate of Formula (4) can be prepared by reaction of the corresponding alkyl or alkoxy 3substituted-2-nitro benzaldehyde of Formula (5) with nitromethane and sodium methoxide in methanol, at 0 to 20 C for 1 to 2 hours. <NO2

Formula (5) wherein T is alkyl or alkoxy.

Preferably the liquid medium comprises water. More preferably the liquid medium comprises water and a water-miscible organic solvent. Preferred water-miscible organic solvents include C,-alkanols, preferably methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, npentanol, 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; dials, preferably dials having from 2 to 12 carbon atoms, for example pentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol and thiodiglycol and oligo- and poly alkyleneglycols, preferably diethylene glycol, triethylene glycol, polyethylene glycol and polypropylene glycol; triols, preferably glycerol and 1,2,6-hexanetriol; mono-C' .-alkyl ethers of diols, preferably mono-C, <-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; sulphoxides, preferably dimethyl sulphoxide and sulpholane. Preferably the liquid medium comprises water and 2 or more, especially from 2 to 8, water-soluble organic solvents.

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

When the medium comprises a mixture of water and a water-miscible organic solvent, the weight ratio of water to water miscible organic solvent is preferably from 99:1 to 1:99, more preferably from 99:1 to 50:50 and especially from 95:5 to 70:30.

Dispersants aid dispersion of colorants. They further stabilize the dispersion against flocculation.

Dispersants can be natural but are preferably synthetic.

Natural dispersants include, for example, proteins such as gelatin, casein and albumen; polysaccarides such as gum arable, xanthan gum; lignins; glucosides such as saponin; alginic acid; cellulose and fatty acids.

Synthetic dispersants include, for example, of vinyl, polyurethane, polyester and polyethylene oxide containing polymers and oligomers. Preferred vinyl polymers and oligomers include poly (meth)acrylates, styrenics, poly acrylonitriles, poly vinyl alcohol, poly vinyl pyrrolidone. Synthetic dispersants can be homopolymers but are preferably copolymers.

Synthetic copolymer dispersants preferably comprise both hydrophobic monomers and hydrophilic monomers. Hydrophobic monomers normally comprise residues from aryl ring compounds preferably benzene and naphthalene and/or fatty alkyl chains, rings or branches with three of more carbon atoms. Hydrophilic monomers can comprise non-ionic groups (e.g. hydroxy groups and ethylene oxide residues), cationic groups (e.g. protonated substituted amines and quaternary ammonium salts) but preferably comprise anionic groups. Preferred anionic monomers comprise carboxy, sulpho and phosphato groups. These can be in the acid form or in the salt form.

Copolymer dispersants can be random copolymers but are preferably block copolymers.

Dispersants can be non-ionic but are preferably ionic. Ionic dispersants can be cationic, amphoteric but are preferably anionic. Preferred anionic dispersants incorporate a sulpho, carboxy or phosphato functional group. These can be in the acid form or in the salt form.

Preferred dispersants are polymeric or oligomeric. Preferably the dispersants have a number averaged molecular weight of at least 1000. Especially preferred are anionic polymeric and oligomeric dispersants. A preferred anionic polymeric or oligomeric dispersant is Disperbyk_-190.

The amount of dispersant required will vary depending upon the nature of the colorant. Preferably the amount of dispersant is from 0.01 parts to 10 parts, more preferably 0.1 parts to 8 parts and especially 1 part to 6 parts by weight based on the total weight of the ink.

A preferred ink of the invention comprises: (a) from 0.01 to 40 parts of the colorant of Formula (1); (b) from 10 to 99.97 parts of water; (c) from 0.01 to 40 parts of a water-miscible organic solvent; and (d) from 0.01 to 10 parts of a dispersant; wherein all parts are by weight and the number of parts (a) + (b) +(c) + (d) = 100.

Inks of the present invention preferably also comprise a surfactant.

A preferred ink of the present invention comprises: (a) from 0.01 to 35 parts of the colorant of Formula (1); (b) from 10 to 99.96 parts of water; (c) from 0.01 to 35 parts of water-miscible organic solvent; (d) from 0.01 to 10 parts of dispersant; and (e) from 0.01 to 10 parts of surfactant; wherein all parts are by weight and the number of parts (a) + (b) + (c) + (d) + (e) = 100.

Surfactants reduce the surface tension of ink jet compositions and aid droplet firing.

Surfactants used herein include, for example, anionic surfactants, (e.g. fatty acid salts and alkylsulfuric acid ester salts), non-ionic surfactants (e.g. polyoxyethylene alkyl ethers and polyoxyethylene phenyl ether), cationic surfactants and amphoteric surfactants.

More preferred surfactants are non-ionic surfactants, such as polyoxyethylene alkyl ethers and polyoxyethylene phenyl ethers. These surfactants are advantageous over the ionic surfactants in that foaming of the ink can be reduced. Specific examples on such anionic surfactants include Nissan Nonion_ K-211, K-220, P-213, E-215, E-220, S 215, S-220, HS-220, NS-212, and NS-220 (tradenames; manufactured by Nippon Oils & Fats Co. Ltd.). Especially preferred surfactants include acetylene glycol surfactants among the non-ionic surfactants. Examples of acetylene glycol surfactants include Surtynol_ 61, 82, 104, 440, 465 and 485 (tradenames; manufactured by Air Products and Chemicals, Inc.). Acetylene glycol surfactants, when added to ink and composition, can substantially prevent foaming, and have excellent properties in relation to dynamic surface tension at high shear rates which facilitates better droplet firing.

The colorant of Formula (1) is soluble or preferably insoluble in water. Where the colorant is insoluble in water the ink can be made by first milling the colorant of Formula (1), optionally in the presence of a dispersant and/or liquid medium, then mixing the resultant ground colorant with any remaining ingredients required to produce a composition according to the invention. Typically grinding is performed using a grinding aid such as glass or zirconia beads for several hours. Millbases (i.e. milled colorants) tend to be relatively rich in colorant and are later "let down" or diluted with further liquid medium to produce the desired ink. Preferably the water- insoluble colorant is milled down to a give a colorant of Formula (1) which has an average particle size of less than 5 microns, more preferably less than 1 micron.

Preferably the ink 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 ink).

Preferably the ink has been filtered through a filter having a mean pore size below 10'um, more preferably below 3pm, especially below 2pm, more especially below 1 m.

This filtration removes particulate matter that could otherwise block the fine nozzles found in many inkjet printers. In the present invention selection of the mean pore size of the filter used will be governed by the average particle size of the colorant in the ink.

Preferably the ink contains less than 500ppm, more preferably less than 250ppm, especially less than 100ppm, more especially less than 1 Oppm in total of halide ions.

The viscosity of the ink is preferably less than 20 mPa.s, more preferably less than mPa.s, especially less than 5 mPa.s at 25 C.

The surface tension of the ink is preferably in the range 20-65 dynes/cm, more preferably in the range 30-60 dynes /cm at 25 C.

Thus a particularly preferred ink of the present invention has a viscosity of less than 20cP at 25 C; a surface tension in the range 20-65 dynes/cm at 25 C, contains less than 500ppm in total of divalent and trivalent metal ions (other than any divalent and trivalent metal ions bound to a component of the ink); contains less than 500ppm halide ions; and has been filtered through a filter having a mean pore size below Mum.

The ink may, of course, also contain additional components conventionally used in ink jet printing inks, for example viscosity modifiers, pH buffers (e.g. 1:9 citric acid/sodium citrate) corrosion inhibitors, biocides and kogation reducing additives.

According to a second aspect of the present invention there is provided a process for printing an image on a substrate comprising applying an ink according to the first aspect of the present invention to the substrate by means of an ink jet printer.

The ink jet printer preferably applies the ink 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 ink in a reservoir by means of a resistor adjacent to the orifice, thereby causing the ink to be ejected in the form of small droplets directed towards the substrate during relative movement between the substrate and the orifice. In piezoelectric ink jet printers the oscillation of a small crystal causes ejection of the ink 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 International Patent Application W000/48938 and International Patent Application W000/55089.

The substrate is preferably paper, plastic, a textile, metal or glass, more preferably paper, an overhead projector slide or a textile material, especially paper. Glossy papers are especially preferred. More especially photographic quality paper is preferred - 7^ According to a third aspect of the present invention there is provided a paper, an overhead projector slide or a textile material printed with an ink according to the first aspect of the present invention by means of a process according the second aspect of the present invention. Preferred papers are plain or treated papers which may have an acid, alkaline or neutral character. Glossy papers are especially preferred. More especially photographic quality paper is preferred Examples of commercially available papers include, HP Premium Coated Paper, HP Photopaper (all available from Hewlett Packard Inc), Stylus Pro 720 dpi Coated Paper, Epson Photo Quality Glossy Film, Epson Photo Quality Glossy Paper (available from Seiko Epson Corp.), Canon HR 101 High Resolution Paper, Canon GP 201 Glossy Paper, Canon HO 101 High Gloss Film (all available from Canon Inc.) , Wiggins Conqueror paper (available from Wiggins Teape Ltd), Xerox Acid Paper and Xerox Alkaline paper (available from Xerox).

It is especially preferred that the third aspect of the invention is a photographic quality print.

Preferred plastic films are transparent polymeric films, especially those suitable for use as overhead projector slides, for example polyesters (especially polyethylene terephthalate), polycarbonates, polyimides, polystyrenes, polyether sulphones, cellulose diacetate and cellulose triacetate films.

According to a fourth aspect of the present invention there is provided an ink jet printer cartridge comprising a chamber and an ink wherein the ink is present in the chamber and the ink is according to the first 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 of: Compound (1) Thionyl chloride (112.2 parts, 0.944mol) was added dropwise to a suspension of phenylacetic acid (73.4 parts, 0.538mol) in 1,2-dichlorobenzene (350ml). The reaction mixture was slowly heated to 115 C and then stirred at this temperature for 1 hr. Indigo (65 parts, 0.248mol) was added in portions to the cooled phenylacetyl chloride solution, the reaction mixture was then stirred at 100 C for 18hrs. Benzoyl chloride (70.4 parts, 0.50mol) was added dropwise to the reaction mixture which was then stirred at 170 C for 4hrs, cooled to room temperature and the precipitated product collected by filtration. The crude product was washed with 1,2-dichlorobenzene (4 x 50ml) and then ethanol (4 x 40ml) and dried to give 30.4 parts (27%) of a purple solid.

Example 2

Preparation of an ink containing compound (1): A mixture of 12 parts Compound (1), 6 parts BYK Chemie Disperbyk-190_ and 82 parts water was milled in a sand mill, using Zirconia beads for 13hrs to give a millbase.

An ink was prepared containing the following ingredients: Millbase 25 parts 2-pyrrolidone 10 parts glycerol 5 parts 1,5-pentanediol 4 parts Surfyinol_ 465 1.4parts Water 54.6 parts The above ink was then printed using a Hewlet Packard 2250 ink jet printer onto HP Printing paper_, HP Premium plus_, Canon HG201_, PR101_ and SEC Premium photo Tests The following colour measurements were performed on the resultant prints: (a) Initial Print Measurements The optical density (OD) and CIE colour coordinates of each initial print (a, b, L, Chroma "C" and hue "H") were measured using a X-Rite 983 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 status of T. No less than 2 measurements were taken diagonally across a solid colour block on the print with a size greater than 1 Omm x 1 Omm.

(b) Light-fastness (LF) 4 years One set of the initial prints was tested for light fastness (LF) in a 4 years equivalent test. Here prints were exposed to light provided by a No. 11 Atlas fluorescent lamp for 64 hrs in an Atlas HPUV Weatherometer.

(c) Ozone-fastness (OF) 1 ppm 24 hr A second set of the initial prints was tested for ozone fastness (OF) in a 1ppm ozone test performed without light. Here prints were exposed to 1 ppm of ozone for 24 hrs at 40 C and 50% relative humidity in a Hampden Ozone Test Cabinet model N 903.

After the exposure tests, the OD and CIE colour co-ordinates were remeasured.

The degree of fade AE is defined as the overall change in CIE colour coordinates L, a, b of the print and is expressed by the equation: 15AE = (AL2 + Aa2 + Ab2)0 5 The %OD loss is expressed by (OD INITIAL - OD Exposed) x 100

OD INITIAL

20As a result of the definitions low AE and low %OD loss values indicate better fade resistance.

- - - - - - -

a) en

- - - - - - - - -

I en of us u) ED us Cal on N 1 N (1 1 1 (NI C1 (1 (1 Cod Cl U) CNI O O O (O CO C,) CO Be) m go_ 1- 1 1 m c,) (, of a, O (A O 0' 0) N oO N (NI v) A) C,) C,) 1 me) C\1 C1 7 Cal ;t O t oo) (O (0 (O C{) (0 CO (0 CC) CC) (0 0 0 oo a) o, o, a) a, oo co co oO (D CO t 1 CO N U.) oO (0 cO CC) O CO (0 a) 6 O O O O CD 1 _ _ _ _ _ _ _

I Z

g g g g g g g g g O g g O g g C] J:1

I I I

Z Z Z N N N O O O 5 5 m _ c: a: D: lr rr a: tL I I () O ()

_ _ _ _ _ _ __

Table (1) shows the substrate/paper type (column 1), the test method (column 2), the depth percentage of print (column 3), the optical density (column 4), the colour space characteristics of the print ( L, a, b, C, H) (columns 5 to 9) and the degree of fade (column 10) AK.

Each substrate has three rows of results in Table (1). Starting from top to bottom the first row of each substrate result shows the initial or unexposed results. The second row of each substrate result shows the light fastness after the equivalent of 4 years irradiation (via the accelerated test). The third row in each substrate result shows the ozone fastness after exposure to 1 ppm ozone for 24 hours. With AE values typically around 2 - 3 the results show excellent ozone and light fastness.

Thus the inkjet prints of the above example show excellent initial colour, OD, light fastness and ozone fastness.

Further Inks The inks described in Tables A and B may be prepared wherein the Dye described in the first column is the compound 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 Table A and B: PG = propylene glycol DEG = diethylene glycol NMP = N-methyl pyrrolidone DMK = dimethylketone IPA = isopropanol MEOH = methanol 2P = 2-pyrollidone MIBK = methylisobutyl ketone P12 = propane-1,2- diol BDL = butane-2,3-diol CET= cetyl ammonium bromide PHO = Na2HPO4 and TBT = tertiary butanol TDG = 1,3-bis(2-hydroxyethyl) urea DBYK = Disperbyk_-190 S465 = Surfynol_ 465 OIVew v - . _ 10 U1 10 10 N N N N N t0 17 11 117 10 N N N N N m u, u, u, N N N N N N N N N N U, U) CO N U. a) CD IS) U) ) llD O 10 =D t N CD O U' U) () <1 Z a) N O O

J I

N. . O ( O (0 U) O I, Z (C1 1D v) N N N a N 0 <D L0 N t, 10 > 10 C0 N N N 1- N C' ) 1 (D (O N 1- 1- 1 O (D U = Cv Cvv= == 03 Q) O 0 0 U) N 0 O. OD CO O. t O O O N N CV7 N N cv U O O N, _y _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ tO _ _ _ _ _ N N N N N L) U. U. In N N N N N m u u7 u N N N N N U) U) U) N N N N N N 1D (D lo (0 U) 1D tn N I O No O C! N U) m N O O O N oo m O O N. U,== U1OD oo U' (0 O Ll) O O a., u, 0 C) U) IS) U) N = N a) CO (D 1 e h" (O (O CO X=- == = = 0 0 0 U.) tr) CD 0 0 N o O O d. O N ID CO O O 88 mm N O oD N a) u) U) N N 8 9-- --- - --= - - - -- -evl

Claims

1. An ink comprising a liquid medium, a dispersant and colorant of Formula (1): 0 Formula (1) wherein: W and X are each independently C(0)R' or optionally substituted aryl; R'is selected from H. optionally substituted alkyl, optionally substituted aryl and optionally substituted aralkyl; and rings A and B are each independently unsubstituted or carry one or more substituents.

2. An ink according to claim 1 wherein the colorant of Formula (1) is of Formula (2): Formula (2).

3. An ink according to any one of the preceding claims wherein the colorant is insoluble in water.

4. An ink according to claim 3 wherein the colorant has an average particle size of less than 5 microns.

5. An ink according to any one of the preceding claims wherein the liquid medium comprises water.

6. An ink according to any one of the preceding claims wherein the liquid medium comprises water and a water-miscible organic solvent.

7. An ink according to claim 1 comprising: (a) from 0.01 to 40 parts of a colorant of Formula (1); (b) from 10 to 99.97 parts of water; (c) from 0.01 to 40 parts of a water-miscible organic solvent; (d) from 0.01 to 10 parts of a dispersant; wherein all parts are by weight and the number of parts (a) + (b) +(c) + (d) = 100.

8. An ink according to any of the preceding claims wherein the dispersant is an anionic polymeric or oligomeric dispersant.

9. An ink according to any of the preceding claims wherein the ink has been filtered through a filter have a mean pore size of less than 10 microns.

10. An ink according to any of the preceding claims having a viscosity less than 20mPa.s at 25 C.

11. A process for printing an image on a substrate comprising applying an ink according to any one of the preceding claims to the substrate by means of an ink jet printer.

12. A paper, an overhead projector slide or a textile material printed with an ink according to any one of claims 1 to 10 by means of a process according to claim 11.

13. An ink jet printer cartridge comprising a chamber and an ink wherein the ink is present in the chamber and the ink is according to any one of claims 1 to 10.