4-Hydroxy-3-arylamino-1,8-naphthalimides and 3-(and 4-)Hydroxy-2-(and 5-)arylamino-7H-benzimidazo-(2,1-a)-benz(d,e)-isoquinolin-7-ones. Red Dyes for Synthetic-polymer Fibres

4-Hydroxy-1,8-naphthalimides and the isomer mixtures of 3- and 4-hydroxy-7H-benzimidazo-(2,1-a)-benz(d,e)-isoquinolin-7-ones were coupled with diazotised arylamines to yield orange-red to bluish-red dyes having good coloration properties and excellent fastness to light on polyester fibres. Structure-property relationships in the dyes are discussed with respect to the nature of the substituents in the imide, imidazole and arylazo moieties