Aromatic disazo compounds having strong infra-red absorption

An azo compound of the formula:

• A--N.dbd.N--B--N.dbd.N--D (P)
• wherein:
• A is selected from:
• (i) a substituted phenyl group of the formula:
• ##STR13## wherein:
• two of R, R.sup.1 and R.sup.2 are independently selected from NO.sub.2, CN, CNS, 2,2-dicyanovinyl, 1,2,2-tricyanovinyl, SO.sub.2 CF.sub.3, COCOT, COT, SO.sub.2 T, CONT.sub.2 and SO.sub.2 NT.sub.2, and the third is chosen from H, OH, C.sub.1-4 -alkyl, O--C.sub.1-4 -alkyl, NT.sub.2, Cl, Br, CN, NO.sub.2, CF.sub.3, COT, SO.sub.2 T, CONT.sub.2 and SO.sub.2 NT.sub.2
• (ii) an aromatic heterocycle of the formula:
• ##STR14## wherein:
• Z is S, X is N, .sup.+ N--T or C--T.sup.2 and W is N, .sup.+ N--T or C--T.sup.3
• Z is N or .sup.+ N--T, X is S and W is N or .sup.+ N--T;
• or Z is N--T.sup.4, X is N, .sup.+ N--T or C--T.sup.2 and W is N, .sup.+ N--T or C--T.sup.3 ;
• T.sup.1, T.sup.2 and T.sup.3 are each independently selected from H, CN, SCN, NO.sub.2, F, Cl,
• Br, C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, C.sub.1-4 -alkoxy-C.sub.1-4 -alkyl, CF.sub.3 CHO, CN--C.sub.1-4 -alkyl, SO.sub.2 CF.sub.3, COCOT, COT, SO.sub.2 T, COOT, SO.sub.2 OT, CONT.sub.2, SO.sub.2 NT.sub.2, OCOT, OSO.sub.2 T, OCOOT, COCl, COF, COBr, SO.sub.2 Cl, SO.sub.2 F, SO.sub.2 Br;
• or when X is C--T.sup.2 or W is C--T.sup.3,
• T.sup.1 and T.sup.2 or T.sup.3 together with the adjacent carbon atoms to which they are attached form a benzene or pyridine ring, fused to said aromatic heterocycle;
• and T.sup.4 is selected from H, C.sub.1-4 -alkyl, phenyl and benzyl;
• (iii) pyrid-2-yl;
• (iv) isothiazol-3-yl
• (v) 2,1-benzoisothiazol-3-yl;
• (vi) a group of the formula:
• ##STR15## wherein R.sup.5 is selected from H, C.sub.1-4 -alkyl, O--C.sub.1-4 -alkyl and NHCOT;
• R.sup.6 is selected from H, C.sub.1-4 -alkyl and O--C.sub.1-4 -alkyl;
• and
• R.sup.7 and R.sup.8 are independently selected from H, C.sub.1-4 -alkyl, aryl, C.sub.4-8 -cycloalkyl and C.sub.1-4 -alkyl, substituted by a group selected from OH, aryl, O--C.sub.1-4 -alkylene-O--C.sub.1-4 -alkyl, halogen, and O--C.sub.1-4 -alkyl;
• (vii) a substituted naphthylamine of the formula:
• ##STR16## wherein R.sup.9 is phenyl or naphthyl either unsubstituted or substituted by a group selected from NO.sub.2, CN, CNS, SO.sub.2 CF.sub.3, COCOT, COT, SO.sub.2 T, CONT.sub.2 and SO.sub.2 NT.sub.2, and the third is chosen from H, OH, C.sub.1-4 -alkyl, O--C.sub.1-4 -alkyl, NT.sub.2, Cl, Br, CN, NO.sub.2, CF.sub.3, COT, SO.sub.2 T, CONT.sub.2 and SO.sub.2 NT.sub.2 ;
• (viii) a group of the formula:
• ##STR17## wherein R.sup.10 is selected from SO.sub.3 T, COOT, CONT.sub.2 and SO.sub.2 NT.sub.2 ;
• (ix) a group of the formula:
• ##STR18## and (x) a group of the formula:
• CH.sub.3 --CO--CH.sub.2 --CO--NH--R.sup.9 X
• wherein
• R.sup.9 is phenyl or naphthyl either unsubstituted or substituted by a group selected from NO.sub.2, CN, CNS, SO.sub.2 CF.sub.3, COCOT, COT, SO.sub.2 T, CONT.sub.2 and SO.sub.2 NT.sub.2, OH, C.sub.1-4 -alkyl, O--C.sub.1-4 -alkyl, NT.sub.2, Cl, Br and CF.sub.3 each T is independently selected from H, C.sub.1-4 -alkyl, phenyl and benzyl;
• B is 3-cyanothiophen-2,5-ylene;
• D is selected from the groups defined as vi to x in the definition of A.