GB2355013A - Water soluble dyes & cationic species each containing a solubility varying group which changes when deposited on a substrate and causes dye &c to precipitate - Google Patents

Abstract

A water-soluble dye for a printing composition (especially ink-jet inks), the dye comprising a chromophore and at least one solubility-varying group which undergoes a change when the composition is deposited on a substrate to cause the dye to precipitate. In one variant, no free water-solubilising group is directly substituted onto any aromatic ring or aromatic ring system of the chromophore. In another variant the solubility-varying group is selected from one or more of:- <SL> <LI>(a) groups which oxidise upon drying of the composition; <LI>(b) zwitterionic groups; <LI>(c) anionic surfactant groups; and <LI>(d) pH-dependent tautomers. </SL> Compounds of formula (VIII) are claimed per se:<BR> <BR> A<SP>1</SP> G L<SP>2</SP> G Q<SP>+</SP> G B (VIII)<BR> <BR> [wherein L<SP>2</SP> is absent or is a suitable linking group,<BR> A<SP>1</SP> is a solubility-varying group which undergoes a change when a composition containing the dye is precipitated on a substrate, Q<SP>+</SP> is a charged heteroatom containing moiety and B is a hydrophobic group (such as a C<SB>4</SB>-C<SB>30</SB> (preferably C<SB>8</SB>-C<SB>20</SB>) alkyl group) or an aralkyl group (such as benzyl) the valency of Q<SP>+</SP> being completed (as appropriate) by one or more small substituents such as hydrogen or C<SB>1</SB>-<SB>4</SB> alkyl] and may be used to block water-solubilising groups in the dyes referred to above by ion-pairing.

Description

2355013 DYES

Technical Field

The present invention relates to dyes, particularly, although not exclusively, dyes intended for use in water-based compositions such as inks for ink-jet printing on any suitable substrate, for example paper and other water based compositions for printing 10 on a textile such as cotton.

Background of the Invention

The need to be water-fast after printing is one of the most important properties for any ink. In the case of ink-jet printing, prints produced by most common ink-jet printers are not adequately water-fast. This is believed to be due to the nature of the dye. The need for development of a water-based ink which is water-fast after printing has attracted considerable attention over recent years.

For example, a range of dyes specifically intended for ink-jet printing based on 2-[7-(2sulpho-phenyl-azo)-g-hydroxy-3,6-disulpho-naphthyl-amino]triazine units are described in GB-A-2 308,376, '377, '378, '379 and '380.

Recently, relatively water-fast dyes have been proposed, wherein a disulphonated-, tertiary amino-copper phthalocyanine chromophore is substituted with an alkylated piperiazinyl group via an alkylene suphonamido linkage (P. Gregory et al, Proc. Conf. Colourchem, Manchester, 1997). The heterocyclic group is believed to change the solubility of the molecule upon deposition on the substrate. 30 2 Further, Gregory, P., in Proc. Col. Sci- (1998), Harrogate, describes ink Jet colourants, in which a chromophore having a number of pendant sulphonyl water-solubilising groups is further substituted by an amino group and a carboxyl anion. The latter two are also proposed as groups which vary the solubility of the molecule during the 5 printing process.

However, no existing dye for water based ink-jet inks is %vater-fast to an adequate degree.

New structures of dyes have now been discovered which gives a significantly improved degree of resistance to running and/or smearing when the printed substrate is wetted.

Definition of the Invention The dyes according to the present invention can differ structurally from those of the closest state of the prior art in two distinct ways. Each of these differences constitutes a separate aspect of the invention. Thus, materials according to the invention may possess one other, or both of these differences. 20 The first difference is that unlike the materials proposed by Gregory, there is no pendant free sulphonyl or other water- solub i 11 sing group directly substituted on any aromatic moiety of the chromophore. This gives better control of solubility/precipitation during the process of deposition onto the substrate. 25 The second difference is constituted by new forms of solubility-varying groups which offer one or more advantages over those proposed in the two Gregory references.

As mentioned above, the first point of difference is the lack of sulphonyl or other water30 solubilising groups on any aromatic moiety of the chromophore.

3 Thus, according to a first aspect of the present invention, there is provided a watersoluble dye for a printing composition, the dye comprising a chromophore and at least one solubility-varying group which undergoes a change when the composition is deposited on a substrate to cause the dye to precipitate, wherein no free water- solubilising group is directly substituted onto any aromatic ring or aromatic ring system of the chromophore.

Turning now, to the second point of difference, it should be noted that in principle, solubility-varying group(s) may function to vary the solubility of the dye upon deposition on the substrate by one or more different mechanisms. Two different mechanisms utilised by dyes according to the present invention are first, a change in the group driven by the pH of the environment in which the dye is situated and second, oxidation of the group when the coating composition containing the composition, dries. The former mechanism is that utilised by the colourants described in the Gregory references above.

The applicants have, however, discovered three classes improved variants of the pHdependent solubility variation mechanism which are new. One of these variants comprises use of one or more zwitterionic, groups. The second kind of variant uses one or more solubility varying groups which are anionic surfactants. The third kind of variant comprises use of one or more pH-dependent tautomeric groups. Solubilityvarying groups embodying different variants can, in principle, be combined in a single dye molecule.

The use of groups which oxidise upon drying is in itself a completely novel mechanism of solubility variation for inkjet dyes.

Thus, a second aspect of the present invention provides a water-soluble dye for a printing composition, the dye comprising a chromophore and at least one solubility- varying group which undergoes a change when the composition is deposited on a 4 substrate, to cause the dye to precipitate, wherein at least one of the solubility-varying group(s) is/are selected from one or more of the following- (a) groups which oxidise upon drying of the composition; (b) zwitterionic groups-, (c) anionic surfactant groups, and (d) pH-dependent tautomers.

Detailed Description of the Invention in either the first or second aspect of the present invention, the dye may therefore be represented by formula (I):- Aln RIP -- D Ll M 2 A s t wherein D represents a chromophore, each R independently represents an (optionally blocked) water-solubilising group, each L I is an optional linking group linking respective A' groups and A2 groups to the chromophore D via one or more bonds, each group A' is a solubility-varying group which undergoes a change when a composition containing the dye is precipitated on a substrate and each group A 2 is a group other than a solubility-varying group, p being 0 or the total number of R I groups, each n is independently 0 or the total number of Al groups for each value of t, each s is independently 0 or the total number of A 2 groups for each value of t, each rn is independently 0 or the total number of L' groups and t is 0 or the total number of groups [L'. (A 1 n) A 2 j with the proviso that if there are no A I groups then p is I or greater and at least one R' group is blocked with a group or molecule which comprises a solubility-varying group. In the first aspect of the present invention, no group R1 is a free water-solubilising group unless substituted onto a non-aromatic moiety of the chromophore. In the second aspect to the present invention, at least one (most preferably, all) of the A' groups is independently selected from groups which oxidise upon drying of a composition containing the dye, zwitterionic groups and pH-dependent tautomers.

In the formula (1), if other than zero, p is preferably from I to 10, more preferably from I to 8, still more preferably from I to 4. If t is other than zero, then preferably it is from I to 3, more preferably from I to 2. If any n is other than zero, then independently from any other n, it is preferably from I to 4, more preferably from I to 2. If any s is other than zero, then independently from any other s, it is preferably from 1 to 4, more preferably from I to 2. Preferably, rn. = t.

Chromophores (D) Suitable chromophore groups (D) may for example be selected from any of the classes or specific materials disclosed in Colour Chemistry (2nd Edition), H. Zollinger, VCH Verlagsgesellschaft mbH, Weinheim 1991. These classes include polyene and polymethine dyes, di- and tri- arylmethine dyes and their aza analogues, aza[ I 8]annul enes, nitro and nitroso dyes, azo dyes, carbonyl dyes and sulphur dyes.

Subclasses of typical chromophore groups D include azo, anthroquinone, phthalocyanine, formazan, dichloro-diphenyl-dioxazine, or triphendioxazine chromophores which are readily available as commercially available dyes or their precursors are available as commercially available dyes. Often, such chromophores in the commercially available form will have the group L (or a derivative thereof) already attached.

One preferred subclass of these chromophores is the monoazo dyes, e.g. those having the formula (II):- 6 2 R _N=N-R-N(R)- wherein R 2 represents a phenyl or naphthyl group, optionally substituted by one or more blocked water-solubilisin groups, R 3 represents a phenylene or naphthylene linkage, 9 optionally substituted by one or more blocked water-solubilising groups and R 4 represents hydrogen oT a C14 alkyl group.

Solubility-VaTying Groups A') Dyes according to either the first or the second aspect of the present invention contain at least one solubility-varying group A' and/or at least one blocking group or molecule of the water-solubilising group R I must be blocked with a group or molecule which comprises a solubility- varying group. In principle, for the first aspect of the present invention, each solubility-varying group can be any which changes the water-solubility of the dye when the ink-jet composition is printed upon the substrate. Thus, it may for example be any of the groups proposed for this purpose in the Gregory references. However, preferred for the first aspect and essential for the second aspect of the invention, are solubility -varying groups chosen from the following classes-.- (a) groups which oxidise upon drying of the composition; (b) zwitterionic groups-, (c) anionic surfactant groups; and (d) pH-dependent tautomers.

(a) oxidative cbying groups Preferred groups which oxidise upon drying of the ink-jet composition when printed are groups which oxidise to form disulphide-linked oligomers or polymers of the dye.

Typical such groups have the formula -S-SR5 where R 5 is a group which is eliminated 7 in the reaction to form the disulphide linkage. R' may for example selected from groups of formula -S03 H, -CH2CO2H and -(CH2)n-SO3H where n is from I to 6.

(b) zwitterionic groups Preferred zwitterionic groups are either amino acids or synthetic amino acid residues, for example of formula (III):-Xl-(CH2)k-y' where k is from 0 to 5 (preferably from I to 4), X I is selected from groups of formula -S-, -0-, -NH-, -NH-CO-CH(R 6)_CH2- (where R6 is hydrogen, halo or a C1-4 alkyl group), -CH(R 6)-CH2- (where R is as heTeinbefore defined), -CONH- and - NHCO-, and Y' is selected from groups of formulae:15 N-H 0 -CH-COO NH3 coo + 0 -NIH3 0 --C H-COO NH3 coo + Preferred groups of formula (III) include serine, lysine, cysteine and histidine substituents, that is to say where Y' is -CH(NH3+)COO and, respectively: where X1 is -0- and k is 1; where X1 is -NH- and k is 4; where X1 is -S- and m is 1; and where X 1 is 4,5-imidazolyl and k is 1. 25 8 Compounds containing groups of formulae (111) are amphoteric. They may be deprotonated under alkaline conditions and they may be protonated under acidic conditions. In both the latter forms the dyes become water soluble but as the point of equal charge (the iso-ionic point) is approached, the dyes become totally water- insoluble. This concept is best illustrated by way of example only using the model dye based on cysteine:- NH3 + I D-X'---CH2-CH I - coo (water insoluble form) Off HZ NH2 NH3+ I I D-X1 CH2_CH D-X (J42-CH coo COOH (water soluble form) (water soluble form) Surprisingly, when dissolved in water at the appropriate pH (8-11 or 1-5) dyes containing groups of formula (111) can be made into water based printing inks which produce printed images on paper of extraordinary high water resistance; equally there is no problem in selecting hues of high brilliance or tertiary muted hues, either by mixing two, three or more dyes together or using self shades.

In the case of alkali-based printing inks (more likely to be useful since acid-based inks will corrode printer components), the source of the above high degree of water resistance is thought to be mainly due to the formation of the zwitterionic form of the dye when imaged, due to the ability of the substrate to buffer the pH downwards.

9 Especially prefer-red are the groups of formula (III) derived from cysteine:

-S-CH,-CH-NH,' I COO or lysine:

-NH-(CH2)4-CH-NH3+ I coo In the case of printing ink dyes derived from ion-paired reactive dyes based on reactive halogenated heterocycles both lysine and cysteine are of equal value; however in the case of printing ink dyes derived from vinylsulphone dyes cysteine gives the most preferred product.

This is believed to be due to the fact that the lysine reaction product can be easily double protonated - changing the amphoteric character of the system, e.g. for the lysine derivative:

+ /NH3 D-S02-CH2CH2-NH2-(CH2)4-CH \ coo G Q+ -B) q (wherein (G - Q ±B) is a water-solubilising group G blocked with an ion- pairing blocking group Q ±B, wherein each Q + is a charged heteroatom. and each is a hydrophobic group such are as defined hereinbelow, each Q + and B respectively being the same or different, and q is from I to 10.

or for the cysteine derivative:

4- NHI D-S02 ---CH2CH2-S-CH2-CH \ C00- By contrast, the lysine f:-.-amino group attached to nitrogen heterocycles has arnide character and is thus not easily protonated. 5 (c) anionic surfactant groups Suitable anionic surfactant groups comprise a hydrophobic moiety typically a saturated or, unsaturated hydrophobic chain (optionally (poly) alkoxylated to introduce a region of hydrophilic character) and a terminal hydrophilic moiety such as a sulphonate, aryl sulphonate, sulphosuccinate, carboxylate or dicarboxylate group. The hydrophobic moiety will be attached to the chromophore directly, or via a linking group.

These groups may for example be any of those derived from commercially available anionic surfactants such as primary and secondary alkyl sulphates, alkyl ether sulphates, olefin sulphonates, alkyl benzene sulphonates, dialkyl sulphosuccinates, fatty acid ester sulphonates, alkyl carboxylates or dicarboxylates. and olefin carboxylates or dicarboxylates, in any of which, the hydrophobic moiety contains from I to 22, 20 preferably from 8 to 20, for example from 12 to 15 carbon atoms.

in the final dye molecule, these anionic surfactant groups will normally be present in the form of an alkali metal salt (e.g. sodium salt) thereof.

Some preferred anionic surfactant groups of the mono- or dicarboxylate kinds are of the following general formulae (IV) or (V).

I I -Xl-(CH2)g-COOH (IV) or -Xl-(CH2)g-CH-COOH I CUU11 (V) wherein X1 is as hereinbefore defined and g is from I to 22, preferably from 8 to 20, for example from 12 to 15. 5 (d) pH-dependent tautomers The pH-dependent tautomeric groups are those which exist in one tautomeric form in the aqueous solution of the dye which is the ink and a second tautomeric form when the ink is deposited on the substrate, such that the solubility of the dye is reduced in the second (printed form).

One class of tautomeric groups suitable for this purpose comprises aromatic heterocyclic moieties in which one or more (e.g. two) carbonyl or thiol groups are incorporated in the ring, and having for example, a total of from five to seven carbon atoms and heteroatoms, and optionally substituted by one or more electron withdrawing group, such as halo, nitro or hydroxyl. In these groups, the carbonyl or thiol groups adopt one or other of the tautomeric forms X-M + X "'K where X is oxygen or sulphur and M+ is a counter-ion (e.g. an alkali metal such as sodium), The left-hand ionic form causes the dye to be soluble in the ink and the righthand form induces precipitation onto the substrate. 25 12 Typical of these groups are those of formula (VI) H R8 Y R7 Y NE X wherein X is as hereinbefore defined, R 7 is nitrogen or c,arbon and R 8 is hydrogen or an electron withdrawing group.

Non- Solub ility-VaEy ing Groups ( 2) Optionally, the dye of formula (1) may have one or more non-solubilising groups attached to the chromophore, preferably via a linking group L'. These may for example be selected from halo, sulpho, thiosulphato, thiocyanato and Cyanato groups or groups of formula (Vll):

-X1-R9 VII wherein X I is as hereiribefore defined and R 9 is selected from C1-6 alkyl, aryl (e.g. phenyl) and aryl-CI-6 alkyl (e.g. benzyl), Linking Groups Ll) -L Typical linking groups L' include nitrogen-containing heterocycles, typically having a substituent -NHgroup by which the group is attached to the chromophore group D.

Especially preferred such heterocycles include mono- or bicyclic moieties containing at least one or two nitrogen atoms optionally substituted by a group of formula 13 -NE-Ph-S02-R - (where Ph is phenylene and R'0 is C14 alkylene) to which a (or one of the) solubility-varying groups is attached. Other suitable linking groups include C14 alkysulphonyl and (optionally halogenated) C14alkylamido groups. A further suitable linking group is a sulphone ethylene linkage (-S02-CH2CH2-). The latter 5 group is found in the reactive dyes in the class of vinyl sulphones.

Water-Solubilising Groups (R) Dyes according to the first aspect of the present invention cannot contain any free water-solubilising group directly bonded to an aromatic moiety of the chromophore although optionally such free group(s) may be present, bonded to another part of the molecule. In the first aspect of the present invention, the dyes may also have one or more blocked water- solubilising groups directly bonded to an aromatic part of the chromophore or on any other part of the molecule. Dyes according to the second aspect of the invention may or may not comprise one or more free water-solubilising groups (or indeed, blocked solubilising groups) on any part of the molecule.

In formula (I), typical water-solubilising groups R1 (as found in many commercially available materials) are usually sulphonyl, or occasionally, carboxyl groups. However, in theory, others are possible, such as phosphonyl, phosphoryl, hydroxy C1.4 alkyl, halo (e.g. chloro), hydroxy and amino groups. Of course, where there is more than one, they may be the same or different and each is independently blocked or not blocked.

Acidic or basic water-solubilising groups are preferably present in the neutralised, i.e. salt form, especially as an alkali metal (e.g. sodium) salt, if anionic or as the acid (e.g. halide) salt if the solubilising group is a cation.

As well as, or instead of optionally blocked water-solubilising groups, dyes according to the invention may optionally have one or more substituents. which are semi- 14 solubilising groups (i.e. groups which increase the water-solubility of the dye to a limited extent) for example one or more _S02NU2 and./or _S02CH3 groups, Optional Blocking - General If any dye according to the first aspect of the present invention has a water-solub il i sing group on an aromatic moiety of the chromophore, this must be blocked but apart from this restriction, any other water-solub 111 sing groups in dyes according to either the first or the second aspect of the invention may or may not be blocked.

Basically, there are two ways of blocking such groups. First, they may be reacted with a molecule which results in a group of lower solubility. For example, if the solubilising group is a sulphonic, carboxylic, phosphonyl or phosphoryl acid group, it may be reacted to form a corresponding ester group or it may be reacted with an amine to forrn a sulphonamide, amide etc. Similarly, if the solubilising group is a halo, hydroxyl, hydroxyl-containing or amino group, it may also be reacted-out to form a corresponding ether, ester, amide, etc.

The second way of blocking is possible in cases where the watersolubilising group is charged, or can be converted to charged form - In that case, the blocking can conveniently be effected by ion-pairing with a molecule of opposite charge. Especially preferred is when the water-solubilising group is an acid (or salt thereof), especially a sulphonic or carboxylic acid group and ion pairing is effected with a molecule containing a charged hereoatom, e.g. an "onium" ion such as a quaternary ammonium, oxonium, sulphoniurn or phosphonium ion, quaternary ammonium being especially preferred. Alternatively, the charged heteroatom may be in a charged heterocyclic compound such as the quaternary nitrogen atom in a pyridinium ion.

Thus, a typical blocking group of this kind will have the formula Q ±B where Q + is a charged heteroatom containing moiety such as described in the preceding paragraph and B is a hydrophobic group such as a C4-C30 (preferably C8-C20) alkyl group or an aralkyl group such as benzyl, the valency of Q+ being completed (as appropriate) by one or more small substituents such as hydrogen or C14 alkyl.

It is preferable to select an ion-pairing agent Q+ - B which gives rapid precipitation of water soluble dyes from aqueous solution and furthermore gives coloured precipitates which are easily filterable. Of particular value are cationic surfactants such as lauryl trim ethylammonium bromide:

C12H25--N±(CH3)3Br Another useful commercially available ion pairing agent is that sold under the trade name Tinegal MRTm, ex Ciba, which has a C12-C14 alkyl chain.

(i i) Optional Blocking with Solubility- Varying Groups Formula (1) contains the proviso that if there are no A' groups at all in the dye molecule, then p is I or greater and at least one R1 group is blocked with a group or molecule which comprises a solubility-varying group. This means that if no solubilityvarying group A' is present then the solubility-varying function is still present by way of at least one blocking group which has a structure adapted for that purpose. Of course, it is also possible to have solubility-varying groups which are both comprised in one or more blocking groups and also attached to the main molecule. In any event, when there is a plurality of solubility-varying groups, these may be the same or different.

When a blocking group comprises a solubility-varying group, the blocking group is preferably of the ion-pairing type. These will have the formula (VIII):- Al -L2 -Q+ -B VIII 16 wherein A', B and Q + are as hereinbefore defined and 1,2 is absent or is a suitable linking group, for example as hereinbefore defined for the group L', or a hydroxylated C1-6 alkylene linkage. Compounds of formula (VIII) Constitute another aspect of the present invention. 5 Preferred Structures Two preferred subclasses of compounds of formula (1) are those of fon- nulae (IX):- / R" D-NE-Z R 12 OX) q wherein D, G-, Q', B and q are as hereiribefore defined-, Z is a nitrogen containing heterocycle such as s-triazine, 1,3-pyrimidine, quinoxaline, 15 plithalazine or pyridazone, q is an integer from I to 10, R 11 is selected from groups of formula (111), (IV) and (\') as hereiribefore defined; and R 12 is independently selected from any of the groups defined for R", groups of formulae (VII) as hereiribefore defined and any of the other groups specified hereinbefore as possible non-solubility varying groups (A 2).

Another preferred subclass of compounds of formulae (1) are those derived from sulphonated reactive dyes originally containing viny1sulphone or substituted ethylsulphone residues, e.g. having the general formula (X):

I I D-S02-CH2CH2-R ( X) (G-Q+ -B)q wherein, D, R1 1, G_,Q +, B and q have the meanings as hereiribefore defined.

Yet another preferred subclass of compounds of formula (I) are those derived from sulphonated reactive dyes originally containing ahaloacrylamido residues, e.g. having the general formulae (XI) and (XII).

0 11 D-N.H-C-C1-1-CH2-R1 I I 1 11 X -R M) (G Q + -B) q 0 11 11 D-IN11-C-CH-C112-R I Hal x1i (G Q + -B) q where D, X', R", G Q +, B and q have the meanings described above and Hal is a halogen atom, preferably bromine. In formula (XI) the R" groups may be the same or different.

A further variation of compounds of formulae (1) can include ion-paired printing ink dyes derived from reactive dyes containing both heterocyclic and vinylsulphone reactive groups e.g., those of formula QU11):

R11 D-NH--Z\ NE 12 __\'S02_CH2 CH2_X R (G Q -B), where D, Z, R1 1, X I, R12, G-, Q B and q are all as hereinbefore defined.

As mentioned above, it is convenient to prepare amphoteric, ion-paired printing ink dyes from commercially available sulphonate reactive dyes, but it is feasible, especially to those skilled in the art, to prepare dyes from amphoteric intermediates; these dyes may optionally be non-sulphonated and in this case ion-pairing is unnecessary. Typical structures for those of formulae (XIV) and (XV).

D-R) ( XIV (G Q -B) q D-RII XV wherein D, R", G', Q -, B and q are as hereinbefore defined.

Synthetic Routes Dyes according to the present invention may, for example, be prepared by taking a commercially available dye having group(s) L' attached, the L' group(s) having at least one group capable of reacting with a corresponding group of a precursor in which the corresponding group is linked to one or more A' and/or A 2 groups, if desired, blocking any water-solubilising group(s) on the chromophore, and reacting the optionally blocked product with the precursor.

19 Alternatively, the precursor(s) may contain a respective linking group L 2, having a moiety capable of reacting with a group of the chromophore to effect bonding of the A' and/or A 2 group(s) to the chromophore via the linking group. In some cases, there may 5 be no linking group, mutually reactive groups being substituted directly on the chromophore and the A I and/or A 2 group(s) respectively. If any of these starting materials is not commercially available, it may easily be fabricated by those skilled in the art of synthetic organic chemistry. Optional blocking of any watersolubilising groups may be effected before, during or after reaction between the chromophore and precursor starting materials, dependent on the particular species involved.

in the case of dyes in which one or more solubility-varying groups are present as part of blocking groups, these may simply be prepared by reacting one or more compounds of formula (VIII) with a commercial dye having one or more sulphonyl and/or other water solubilising groups.

The compounds of formula (VIII) may be prepared by reacting a compound of formula (XVI): - R13 -Q+ B XVI with a compound of formula (XVII):- Al -R14 XVII wherein Q+, A I and B are as hereinbefore defined and R 13 and R 14 are mutually reactive groups which are either eliminated to bond Q+ and A' or form the linking group L' in the compound of formula (VIII).

For example, the mutually reactive groups R 13 and R 14 (or indeed, the mutually reactive groups of the chromophore and precursor groups used to form the dye or formula (1)) may be selected from any of the following mutually reactive pairs:- 1 (a) a thiol, amine or hydroxy group, and (b) an epoxy, carboxylic acid, carboxylic acid anhydride, carboxylic acid halide, acrylate, isocyanate, or halide group.

2. (a) an acrylate or methacrylate group, and (b) a thiol or amine group.

3. (a) an epoxy or isocyanate group; and (b) a carboxylic acid, carboxylic acid anhydride or carboxylic acid halide group.

One preferred example of such a reaction (wherein Q+, B and R" are hereinbefore defined and Y/Y- is halide) is'.

Y Q -CH2-CH-CH2 Y I i B 6H NaOH Y Q -CH2-CH-CH2 4 N aY 0 HS-RII Y Q + -CH2-CH-S-RI I I I B UH 21 Ink Formulations Dyes according to the present invention are suitable for use in inks, especially waterbased inks and most preferably, water-based inks for use in ink-jet printing.

In water-based compositions, the dye will usually be dissolved in an amount of from 0. 1 % to 20%, preferably from I % to 10% and most preferably from I % to 4% by weight of the total composition. As well as water and the dye, water based inks using dyes according to the present invention may optionally contain one or more other ingredients such as one or more of the following10 from 1% to 15% of a humectant such as one or more of diethyleneglycol, dipropyleneglycol and other polyols such as 1,2 propanediol, 1,3 propanediol and glycerin-, from 1% to 15% of a co-solvent such as one or more of 2-pyrollidinone,Cl- C4 alcohols, N-methyl-2-pyrollidinone and 1-(2-hydroxy) ethyl-2- pyrrolidinone; up to 0.5% of a biocide such as that sold under the trade name Bactrachern TM orProxel GXL TM; and 20 up to 0.5% of a buffering agent such as one or more of sodium carbonate, triethanolamine and borax; all percentages being expressed as percent by weight of the total composition. 25 The viscosity of such an ink if intended for ink-jet printing is preferably from I to 20 cps, more preferably from I to 12 cps, these viscosities being as measured at a shear rate of 20 s-1.

The present invention will now be explained in more detail by the following nonlimiting examples.

22 Examples (a) Preparation of ion-paired Intermediates Dye Purification-General The following intermediates are prepared from commermally available dyes. In all cases, the starting material (dye) was purified as follows.

The dye (7.5 g/0.01 16 mmol) was dissolved in 150-200ml distilled water and stirred at room temperature until in solution, and was then salted out with the addition of 10- 15% potassium thiocyanate (KSCN). The dye was left stirring for around 15 minutes and then filtered to give the purified dye. The dye was then stirred in acetone to remove the excess KSCN. The purified dye being insoluble in acetone was the collected by 15 filtration.

Example A Blocked, dichloro-s-triazinyl dye Five grams of Procion Red NIX 5B dye (ex BASF) was dissolved in 150-200ml of distilled water and Stirred at room temperature until into solution. Once the dye was in solution a quaternary alkyl ammonium salt (Tinegal MR, ex Ciba) was slowly dripped into the solution; the dye precipitated out since the quaternary ammonium salt blocked or "ion-paired" the sulphonic acid groups of the dye, eliminating the dye's solubility in 25 water.

The water insoluble "Ion-paired" dichloro-s-triazinyl reactive dye was then recovered by filtration and washed thoroughly with distilled water to remove any excess Tinegal MR. After several washes the "ion-paired" dye was then dried in an oven to a constant 30 weight.

23 Example B Ion-12aired monchloro-s-triazinyl dye Five grams of Procion Orange P-R dye (ex BASF) was dissolved in 150-200ml of distilled water and stirred at room temperature until into solution. Once the dye was in solution a quaternary alkyl ammonium salt (Tinegal MR, ex Ciba) was slowly dripped into the solution; the dye precipitated out since the quaternary ammonium salt blocked or "ion-paired" the sulphonic acid groups of the dye, eliminating the dye's solubility in the water.

The water insoluble "ion paired "dichloro-s-triazinyl reactive dye was then recovered by filtration and washed thoroughly with distilled water to remove any excess Tinegal MR. After several washes the ion-paired dye was then dried in an oven to a constant weight.

Example C Blocked fluro-chloropyrimi dine dy Five grams of Drimarene Red K4BL was dissolved in 150-200ml of distilled water and stirred at room temperature until into solution. Once the dye was in solution a quaternary alkyl ammonium salt (Tinegal NIP, ex Ciba) was slowly dripped into the solution; the dye precipitated out since the quaternary ammonium salt blocked or -ionpaired" the sulphonic acid group of the dye, eliminating the dye's solubility in water.

The water insoluble "ion paired" fluro-chloropyrimi dine dye was the recovered by filtration and washed thoroughly with distilled water to remove any excess Tinegal NIR. After several washes the ion-paired dye was then dried in an oven to a constant weight.

24 Example D Blocked vinyl sulphone dy Five grams of Remazol Brilliant Blue R was dissolved in 150-200ml of distilled water and activated at pH 8.5 for 2 hours at 70-75 'C for 2 hours, to convert the dye into the vinyl sulphone form, Once the dye was activated into the vinyl sulphone form, a quaternary alkyl ammonium salt (Tinegal NK ex Ciba) was slowly dripped into the solution-, the dye precipitated out since the quaternary ammonium salt blocked or "ion10 paired" the sulphonic acid group of the dye, eliminating the dye's solubility in water. The water insoluble "Ion paired" fluro- chloropyrimidine dye was then recovered by filtration and washed thoroughly with distilled water to remove any excess Tinegal MR. After several washes the ion-paired dye was then dried in an oven to a constant weight. 15 Example E.- The preparation of an "ion-paired" blocked commercially available dy Five grams of Levafix'Yellow E-G was dissolved in 150-200m] of distilled water and 20 stirred at room temperature until into solution. Once the dye was in solution a quaternary alkyl ammonium salt (Tinegal MR, ex Ciba) was slowly dripped into the solution; the dye precipitated out since the quaternary ammonium salt blocked or "ionpaired" the sulphonic acid group of the dye, eliminating the dye's solubility in water. 25 The water insoluble "ion paired" dye was then recovered by filtration and washed thoroughly with distilled water to remove any excess Tinegal NIR_ After several washes the ion-paired dye was then dried in an oven to a constant weight. 30 Example F Blocked -dichloro-s-triazinyl dy Quab 342 (ex Degusa) (2.79g, 0.003 mol) was stirred at room temperature to which purified Procion MX-513 (1g, 0.0015 mol) in solution (-I 00ml distilled water) was added slowly. The dye precipitated out since the quaternary ammonium salt blocked or "ion-paired" the sulphonic acid groups of the dye, eliminating the dye's solubility in water.

The ion-paired dye was then recovered by filtration and washed thoroughly with distilled water to remove any excess Quab 342. After several washes the "ion-paired" dye was then dried to a constant weight.

(b) Examples of the Invention Example I Bis-cysteinate derivative of a blocked dichloro-s-triazinyl dye.

The material of Example A (2g) was dissolved in a mixture of acetone (200ml) and distilled water (100ml) and reacted with around an excess of cysteine (3g) at pH 8-9. The pH was maintained by the addition of Na2CO3 when required. The solution was left stirring at room temperature for one hour until reaction was complete as judged by no further drop in pH and High Performance Liquid Chromatography. The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum.

Example 2 Mono-cysteine derivative of a blocked mono-chloro dy The material of Example B (2g) was reacted with an excess of Cysteine (3g) at around pH 9-10. The pH was maintained by the addition of Na2CO3 when required. The solution was left stirring at room temperature for one hour until reaction was complete as judged by no further drop in pH and High Performance Liquid Chromatography.

The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum.

26 Example 3 Bis-lysine derivative of a blocked dichlor.o.-:5-triazinyl dve The material of Example A (2g) was dissolved in a mixture of acetone (200ml) and distilled water (100ml) and reacted with an excess of lysine (3g) at around pH 9. The pH was maintained by the addition of Na2CO3 when required. The solution was stirred initially at 30'C and then at the boil for around one hour until reaction was complete as judged by no further drop in pH and was confirmed using High Performance Liquid Chromatography. The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum.

Example 4 Mono- lysi ne-s-tri azine derivative of a blocked mono-chloro dy The material of Example B (2g) was dissolved in a mixture of acetone (200ml) and distilled water (I 00m]) and reacted with a slight excess of lysine at around pH 9-10. The pH was maintained by the addition of Na2CO3 when required. The solution was stirred initially at between 30'C and 40'C for around one hour reaction was complete as judged by no further drop in pH and was confirmed using High Performance Liquid Chromatography. The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum.

Example 5 Bis-cysteinate derivative of a blocked chloro-pyrimidin The material of Example C (2g) was dissolved in a mixture of acetone (200ml) and distilled water (I 00ml) and reacted with a two fold excess of cysteine (-4g) at pH-9. The pH was maintained by the addition of Na2CO3 when required. The solution was left stirring at room temperature for one hour until reaction was complete as judged by no further drop in pH and confinned by High Performance Liquid Chromatography.

27 The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum.

Example 6 Bis-cysteinate derivative of a blocked vinyl sulphone dy The material of Example D (2g) was dissolved in a mixture of acetone (200m]) and distilled water (100ml) and reacted with a two fold excess of cysteine (-4g) at pH-9, The pH was maintained by the addition of Na2CO3 when required. The solution was left stirring at room temperature for one hour until reaction was complete as judged by no further drop in pH and confirmed by High Performance Liquid Chromatography. The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum.

Example 7 Bis-lysine derivative of a blocked commercially available dye The material of Example E (2g) (previous side) was dissolved in a mixture of acetone (200ml) and distilled water (100mi) and reacted with a two fold excess of lysine (-4g) at pH-9. The pH was maintained by the addition of Na2CO3 when required. The solution was left stirring at initially 30'C and then the boil for around 2 hours until reaction was complete as judged by no further drop in pH and confirmed by High Performance Liquid Chromatography. The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum.

Example 8 Di-hydroxy derivative of a blocked di-chloro, dy The material of Example A (2g) was dissolved in a mixture of acetone (200ml) and distilled water (100ml) and reacted with around two-fold excess of cysteine (-4g) at pH 8-9. The pH was maintained by the addition of Na2CO3 when required. The solution 28 was left stirring at room temperature for one hour until the reaction was complete as judged by no further drop in pH and High Performance Liquid Chromatography, The dye was then precipitated out on addition of acid and then isolated by filtration under vacuum. 5 Example 9 Di-hyd -ox I derivative of a blocked di-chloro dye The material of Example A (2g) was refluxed at the boll with NaOH using ethanol as a co-solvent due to solubility problems. The solution was stirred for around 6 hours until reaction was complete as judged by TLC and High Performance Liquid Chromatography.

Example 10 Di-thiourea derivative of a blocked di-chlorod e I I --Y The material of Example A (2g) was dissolved in a mixture of acetone and water and reacted with an excess of thiourea to produce the diiso- thiouranium dye. The dye was then boiled under reflux with NaOH at pH 10 to produce the final dithiourea modified dye.

Example I I Bis-cyt nnate derivative of a blocked-dichloro dy The material of Example F(Ig) was dissolved in acetone (200ml) and distilled water (100ml) and reacted with an excess of cysteine (3g) at around pH 9. The pH was maintained by the addition of Na2CO3 when required. The solution was left stirring at room temperature for one hour until the reaction was complete as judged by no further drop in pH and Higher Performance Liquid Chromatography (HPLC). The dye was then precipitated out with careful addition of acid and then isolated by filtration under vacuum.

29 Example 12 Bis-lysine derivative of a blocked dichloro reactive dy The material of Example F (1g) was dissolved in a mixture of acetone (200ml) and distilled water (I 00ml) and reacted with an excess of lysine (3g) at around pH 9. The pH was maintained by the addition of Na2CO3 when require. The solution was stirred initially at 30'C and then at the boil for around one hour until reaction was complete as judged by no further drop in pH and as confirmed using HPLC. The dye was then precipitated on careful addition of acid and then isolated by filtration under vacuum.

(c) Performance Evaluation Inks formulations were made using some dyes synthesised in the previous examples. These are formulation Examples 13 and 14, respectively.

As controls, commercially availabel inks (drained from Hewlett Packard cartridges) were used. These are respectively referred to as "Commercial Ink I" and "Commercial Ink 2". As a further control, an ink analogous to those using dyes according to the invention but using Procion Red MX5B dye was also formulated. This is referred to as "Control 3".

The ink samples were either drawn down onto the paper substrate using a 4 micron K bar or they were printed. The ink samples were printed using a Hewlett Packard DeskJet 500 printer. Black print cartridges (HP 51626A) for this printer were emptied and flushed out using distilled water before the new ink formulation was put into the cartridge.

The printed or drawn down samples were then tested in two ways.

1. Dip Test A set area of print was cut from the sample prints (or draw-downs), and placed in de ionised water for 5 minutes. Once the paper was dry the results were judged on how much colour had been retained by the print / drawn down. This was measured by recording the optical density of the print / draw down both before and after the test, and working out the % colour retention after the test. Results are shown in Table 1.

2. Rub Test The prints or draw-downs were rubbed with a finger wetted with de-ionised water, five times. The optical density was recorded both before and after the test had taken place.

This enabled the calculation of the % colour retention, The results indicate that relative to the untreated dye and -the commercial ink formulations, the dye examples in this patent had a greater degree of water resistance.

Results are shown in Table 2.

31 Table 1. Results obtained for the dip test water resistance tests.

Ink Formulation Formulation Optical Density Optical Density % Colour before Dip Test after Dip Test Retention Commercial Ink 1 Unknown 1.67 0.90 54 Commercial Ink 2 Unknown 1.17 0.76 65 Example 13 2% Dye of Example 1 1.30 0.94 72 8% Diethylene glycol 0,04% Sodium Hydrogen Carbonate 0.05% Triethanol Amine 89.91% De-ionised water Example 14 2% Dye of Example 3 1.66 1.20 75 8% Diethylene glycol 0.04% Sodium Hydrogen Carbonate 0.05% Triethanol Arnine 2.5% Formic Acid 87.41% De-ionised water Control 3 2% Dye Procion Red MX 5B 1.58 0.67 42 8% Diethylene glycol 0.04% Sodium Hydrogen Carbonate 0.05% Triethanol Amine 5% Ethanol 84.91 % De-ionised Water 32 Table 2. Results obtained for the rub test water resistance tests Ink Formulation Formulation Optical Density Optical Density % Colour before Rub Test after Rub Test Retention Commercial Ink I Unknown 1.67 1.02 61 Commercial Ink 2 Unknown 1.17 0.80 68 Example 2% Dy, -IF Example 1 1.82 1.65 90 8% Diethylene glycol 0.04% Sodium Hydrogen Carbonate 0,05% Triethanol Amine 89.91% De-ionised Water Control 3 2% Dye Original Procion Red MX 5B 1.64 1.04 63 8% Diethylene glycol 0.04% Sodium Hydrogen Carbonate 0.05% Triethanol Amine 5% Ethanol 84.9 1 % De-lonised Water 33

Claims (28)

CLAIMS:

1. A water-soluble dye for a printing composition, the dye comprising a chromophore and at least one solubility-varying group which undergoes a change when the composition is deposited on a substrate to cause the dye to precipitate, wherein no free water-solubilising group is directly substituted onto any aromatic ring or aromatic ring system of the chromophore.

2. A dye according to claim 1, wherein the solubility-varying group(s) is/are independently selected from either or both of groups which oxidise upon drying of the composition and groups which undergo a change dependent upon pH.

3. A dye according to claim.2, wherein the group(s) which undergo a change dependent upon pH is/are selected from one or more of zwitterionic groups, anionic surfactant groups and pH-dependent tautomers.

4. A water-soluble dye for a printing composition, the dye comprising a chromophore and at least one solubility-varying group which undergoes a change when the composition is deposited on a substrate, to cause the dye to precipitate, wherein the solubility-varying group(s) is/are selected from one or more of-(a) groups which oxidise upon drying of the composition; (b) zwitterionic groups; (c) anionic surfactant groups; and (d) pH-dependent tautomers.

5. A dye according to any preceding claim, having general formula (I):Aln Rlp - D Llm \ A2S I t 34 wherein D represents a chromophore, each R I independently represents an (optionally blocked) water-solubilising group, each L I is an optional linking group linking respective A' groups and A' groups to the chromophore D via one or more bonds, each group A' is a solubility- varying group which undergoes a change when a composition containing the dye is precipitated on a substrate and each group A 2 is a group other than a solubility-varying group, p being 0 or the total number of R1 groups, each n is independently 0 or the total number of A' groups for each value of t, each s is independently 0 or the total number of A 2 groups for each value of t, each m is independently 0 or the total number of L' groups and t is 0 or the total number of groups [L',, (Aln) A 2'] with the proviso that if there are no A' groups then p is I or greater and at least one R'group is blocked with a group or molecule which comprises a solubility-varying group.

6. A dye according to any preceding claim, wherein one or more of the solubilityvarying group(s) are zwItterionic group(s) independently selected from amino acid groups and synthetic amino acid analogues.

7- A dye according to claim 6, wherein the zwitterionic group(s) is/are selected from those of formula (III)-- ---X'-(CH2)k-y' where k is from 0 to 5 (preferably from I to 4), X I is selected from groups of formula -S-, -0-, -NH-, -NB-CO-CH(R 6 KH2- (where R 6 is hydrogen, halo or a C14 alkyl group), -CH(R 6)_CH2- (where R 6 is as hereiribefore defined), -CONH- and -NHCO-, and Y' is selected from groups of formulae,-- /--N -H 0 -C H-COO NH3 00- + -C41 C 0NI-13 + -CO)-C I H-COO NH3 coo +

8. A dye according to any preceding claim, wherein one or more of the solubilityvarying group(s) are anionic surfactant group(s) independently selected from primary and secondary alkyl sulphates, alkyl ether sulphates, olefin sulphonates, alkyl benzene sulphonates, dialkyl sulphosuccinates, fatty acid ester sulphonates, alkyl carboxylates or dicarboxylates and olefin carboxylates or dicarboxylates, in any of which, the hydrophobic moiety contains from I to 22, preferably from 8 to 20, for example from 12 to 15 carbon atoms.

9. A dye according to claim 8, wherein the anionic surfactant group(s) is/are independently selected from those of formulae (IV) or (V):-Xl-(CH2)g-COOH I V or -Xl-(CH2)g-CH-COOH I UUU11 V wherein X1 is as defined in claim 7 and g is from I to 22, preferably from 8 to 20, for example from 12 to 15.

36

10. A dye according to any preceding claim, wherein one or more of the solubilityvarying group(s) are pli-dependent tautomers selected from aromatic heterocyclic moieties in which one or more (e.g. two) carbonyl or thiol groups are incorporated in the ring, and having for example, a total of from five to seven carbon atoms and heteroatoms, and optionally substituted by one or more electron withdrawing group, such as halo, nitro or hYdroxyl.

11. A dye according to claim 10, wherein the pH-dependent tautomer(s) is/are independently selected from those of formula (Vl)-- R8 R7 Mi VI X wherein X is oxygen or sulphur, R 7 is nitrogen or carbon and R 8 is hydrogen or an electron withdrawing group.

12. A dye according to any preceding claim, wherein one or more of the solubilityvarying group(s) are groups which oxidise upon drying of the composition, independently selected from groups which oxidise to form disulphide-linked oligomers or polymers of the dye.

13. A dye according to claim 12, wherein the groups) which oxidise upon drying of the composition are selected from groups of formula -S--SR 5 where R' is a group which is eliminated in the reaction to form a disulphide linkage.

14, A dye according to claim 13, wherein R 5 is selected from groups of formula -S03H, -CH2CO2H, -(CH2)n-SO3H, where n is from I to 6.

37

15. A dye according to any preceding claim, wherein an aromatic ring or aromatic ring system of the chromophore is substituted by one or more blocked watersolubillsing groups.

16. A dye according to claim 15, wherein one or more of the water-solubi I i sing group(s) are blocked by ion-pairing.

17. A dye according to claim 16, wherein the blocking of one or more of the ionpaired blocking groups is a compound having the formula Q ±B where Q + is a charged heteroatom containing moiety and B is a hydrophobic group such as a C4-C30 (preferably C8-C20) alkyl group or an aralkyl group such as benzyl, the valency of Q+ being completed (as appropriate) by one or more small substituents such as hydrogen or CI-4 alkyl.

18. A dye according to claim 15 or claim 16, wherein one or more of the ion-paired blocking, group(s) has a solubility-varying substituent (A I).

19. A dye according to claim 18, wherein at least one of the ion-paired blocking groups has the formula (VIII):- Al -L -Q+ -B VIE wherein A' is as defined in claim 5, B and Q + are defined in claim 17, and L 2 is absent or is a suitable linking group.

20. A dye according to any preceding claim, comprising one or more optionally blocked water-solubilising group(s) independently selected from sulphonyl, carboxyl, phosphonyl, phosphoryl, hydroxy CI-4 alkyl, halo (e.g. chloro), hydroxy and amino groups.

38

21. A dye according to any preceding claim, further comprising one or more semisolubilising groups.

22. A dye according to claim 21, wherein the semi-solubilising group(s) is/are selected from groups of formula _S02NH2 and/or _S02CH3 -

23. A dye according to any preceding claim, comprising at least one linking group (L) between the chromophore and a solubility-varying group, the linking groups being independently selected from CI-4 alkysulphonyl groups, (optionally halogenated) CI-4 alkylamido groups, sulphone ethylene (_S02-CH2C"2_) groups, nitrogencontaining heterocycles, typically having a substituent -NH- group by which the linking group is attached to the chromophore, preferably heterocycles which include mono- or bicyclic moieties containing at least one or two nitrogen atoms optionally substituted by a group of formula -NTi-Ph-SO2-R - (where Ph is phenylene and R10 is CI-4 alkylene) to which the respective solubility-varying group is attached.

24. A dye according to any preceding claim, wherein the chromophore is selected from polyene and polyrnethine dyes, di- and tri- arylmethine dyes and their aza analogues, aza[ I 8]annulenes, nitro and nitroso dyes, azo dyes, carbonyl dyes and sulphur dyes.

25. A dye according to claim 24, wherein the chromophore is selected from include :1 azo, anthroquinone, phthalocyanine, formazan, dichloro-ciiphenyl- dioxazine, or triphendioxazine chrornophores.

26. A dye accordIng to claim 24 or claim 25, wherein the chromphore has the I I general formula (11).

2 3 R _N=N-R _N(R')- (11) 39 wherein R 2 represents a phenyl or naphthyl group, optionally substituted by one or more blocked water-solubilising groups, R 3 represents a phenylene or naphthylene linkage, optionally substituted by one or more blocked water-solubilising groups and R 4 represents hydrogen or a CI-4 alkyl group.

27. A compound of formula (VIIl):

Al -U -Q+ -B VIII wherein A' is as defined in claim 5, B and Q + are as defined in claim 17, and L 2 is absent or is a suitable linking group.

28. An ink for ink-j et printing comprising from 0. 1% to 20%, preferably from I% to 10%, more preferably from I% by weight of the total composition of a dye according to any of claims 1-26 and optionally one or more other ingredients, the balance being water.