Squarylium dyes, and processes and intermediates for the preparation thereof

Abstract

Squarylium compounds of the formula: ##STR1## (in which Q.sup.1 and Q.sup.2 are each a chromophoric group having an aromatic unsaturated system conjugated with the squarylium ring and such that in the compounds of formulae Q.sup.1 CH.sub.2 R.sup.1 and Q.sup.2 CH.sub.2 R.sup.2 the methylene hydrogens are active hydrogens, R.sup.1 and R.sup.2 are each independently a hydrogen atom or an aliphatic or cycloaliphatic group, and R.sup.3 and R.sup.4 are each independently a hydrogen atom, or an acyl, aliphatic, cycloaliphatic, aromatic or heterocyclic group, subject to the proviso that one of R.sup.3 and R.sup.4 may be an amino or substituted amino group, or one of R.sup.3 and R.sup.4 is a hydrogen atom and the other is an organosulfonyl group, or R.sup.3 and R.sup.4 together with the intervening nitrogen atom form a nitrogenous heterocyclic ring) are useful as near infra-red absorbers. The presence of the amino group on the squarylium ring enables minor changes in absorption wavelength to be achieved by modifications of this group, and also allows functional groups to be incorporated into the dye without changing the chromophoric groups.

Dependencies are inferred from the claim text.