Water soluble dyes amp; cationic species each containing a solubility varying group which changes when deposited on a substrate and causes dye amp;c to precipitate

摘要

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 ASP1/SP G LSP2/SP G QSP+/SP G B (VIII)BR BR [wherein LSP2/SP is absent or is a suitable linking group,BR ASP1/SP is a solubility-varying group which undergoes a change when a composition containing the dye is precipitated on a substrate, QSP+/SP is a charged heteroatom containing moiety and B is a hydrophobic group (such as a CSB4/SB-CSB30/SB (preferably CSB8/SB-CSB20/SB) alkyl group) or an aralkyl group (such as benzyl) the valency of QSP+/SP being completed (as appropriate) by one or more small substituents such as hydrogen or CSB1/SB-SB4/SB alkyl] and may be used to block water-solubilising groups in the dyes referred to above by ion-pairing.