The present invention relates to azo dyes of formula (1), wherein D is a radical of formula (2) or (3), R1 and R2 independently denote hydrogen; C6-C10 aryl which is unsubstituted or substituted by cyano, carboxy, hydroxy, halogen, C1-C6alkyl, or C1-C6alkoxy; C1-C12alkyl which may be interrupted one or more times by —O—, —S—, —NR4—, —CO—, —COO— or —OOC—, and is unsubstituted or substituted by cyano, carboxy, hydroxy, C6-C10 aryl, or C6-C10 aryloxy, which C6-C10 aryl or C6-C10 aryloxy is unsubstituted or substituted by cyano, carboxy, hydroxy, halogen, C1-C6alkyl, or C1-C6alkoxy; R3 and R4 are each independently of the other hydrogen, halogen, nitro, cyano, trifluoromethyl, carboxy, C1-C6alkyl, C1-C6alkoxy, C1-C6alkylcarbonyl, C6-C10 arylcarbonyl, C1-C6alkoxycarbonyl, C1-C6alkylsulfonyl, C1-C6alkylsulfonylamino or C1-C4 alkanoylamino; and R5 is halogen, nitro, cyano, trifluoromethyl, carboxy, C1-C6alkyl, C1-C6alkoxy, C1-C6alkylcarbonyl, C6-C10 arylcarbonyl, C1-C6alkoxycarbonyl, C1-C6alkylsulfonyl, C1-C6alkylsulfonylamino or C1-C4 alkanoylamino; and R6, R7, R8 and R9 independently of each other are hydrogen, hydroxy, halogen, cyano, nitro or C1-C4 alkanoylamino, and the radicals X independently denote N or C—H, with the proviso that at least one radical X denotes C—H, which are distinguished by their good lightfastness properties.