Cyanine dyes

Claim 1

A compound of the general formula: in which: m + p = 2, n is 0 or 1, s is 0 or 1, Z i and Z 2 independently represent the non-metallic atoms necessary to complete a 5 or 6 membered heterocyclic nucleus which may possess substituents, R' and R 2 independently represent an alkyl, substituted alkyl, alkenyl, substituted alkenyl or aralkyl group of up to 20 carbon atoms, R 3 and R 4 independently represent a hydrogen atom or an alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkoxy or substituted alkoxy group of up to 10 carbon atoms, R 5 , R 6 , R 7 and R 8 , which together may not contain more than 12 carbon atoms, independently represent a hydrogen atom, an alkyl, substituted alkyl, alkenyl, substituted alkenyl, aryl or alkaryl group, and Y represents in which: X represents =O or =S, and R 9 and R , Q independently represent a hydrogen atom, and alkyl group which may be substituted, alkenyl, substituted alkenyl, an aryl group which may be substituted or an aralkyl group, any of which groups may contain up to 25 carbon atoms, with the proviso that Y contains (i) at least one aliphatic group having at least 8 carbon atoms, (ii) at least one predominantly aliphatic group which is a group having at least 8 carbon atoms in which at least half of the carbon atoms present are in the form of aliphatic carbon atoms, or (iii) two groups which are aliphatic groups or predominantly aliphatic groups which together have at leat 8 carbon atoms.