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.

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