The azo dyes relate to thiophene azo dyes of the general formula: where R1 is Cyano or C1-C5 alkoxy carbonyl; R2 is hydrogen, halogene, C1-C2 alkyl, phenyl, or substituted phenyl; and R3 is C1-C5 alkoxy carbonyl, C1-C4 alkanoyl, benzoyl, phenyl, alkyl substituted phenyl, or alkoxy phenyl; or R2 and R3 are fused cycloalkane with C3-C5.