the formula str2 and the rings a and b may be further substituted or fused to a benzene ring and r 1 and r 2 are each hydrogen or unsubstituted or substituted alkyl aralkyl or cycloalkyl or together with the nitrogen atom form piperidino pyrrolidino or morpholino and r 3 is hydrogen alkyl or cycloalkyl are particularly useful as dyes in liquid crystalline media application_number US 77646185 A description examples of suitable substituents for the ring a are chlorine bromine methyl ethyl methoxy ethoxy acetylamino propionylamino or a fused benzene ring the ring b may carry as substituents for example chlorine bromine methyl ethyl methoxy ethoxy acetylamino propionylamino or a fused benzene ring in addition to being hydrogen r 1 and r 2 are each for example methyl ethyl propyl butyl hexyl dodecyl cyclohexyl 2 phenylethyl 2 cyanoethyl 2 hydroxyethyl 2 acetoxyethyl 2 butyryloxyethyl allyl phenylmethyl or 4 butylphenylmethyl in addition to being hydrogen r 3 is for example methyl ethyl butyl or cyclohexyl r is hydrogen or for example phenyl phenylmethyl phenylethyl phenoxy phenoxymethyl phenoxyethyl phenylmethylthio or phenylethylthio the stated radicals being unsubstituted or substituted by c 1 c 24 alkyl u03b5 1 c 24 alkoxy c 1 c 24 alkoxycarbonyl c 1 c 24 acyloxy c 5 c 7 cycloalkyl 4 c 1 c 12 alkylcyclohexyl phenyl chlorine or bromine or r is c 5 c 7 cycloalkyl or is c 1 c 24 alkylthio or c 1 c 24 alkyl which is unsubstituted or substituted by hydroxyl c 1 c 24 alkoxy c 1 c 24 alkoxycarbonyl c 1 c 24 alkyl or dialkylcarbamyl or c 1 c 24 acyloxy.