Cationic 1,3,4-thiadiazole dyestuffs

A cationic thiadiazolyldiphenylamine dyestuff of the formula (I) ##STR35## in which R.sup.1 and R.sup.2, independently of one another, denote hydrogen, alkyl, alkenyl, cycloalkyl, aralkyl or a heterocycle, or R.sup.1 and R.sup.2 together with the nitrogen atom to which they are bound form a heterocycle,

• R.sup.3 denotes alkyl, alkenyl, cycloalkyl or aralkyl,
• R.sup.4 and R.sup.5, independently of one another, denote hydrogen, alkyl, alkoxy or halogen,
• R.sup.6 denotes hydrogen, alkyl, alkoxy, aryloxy, arylamino, halogen, cyano, alkoxycarbonyl or nitro, or
• R.sup.5 and R.sup.6 together form a --CH.dbd.CH--CH.dbd.CH-- bridge,
• R.sup.7 denotes hydrogen, alkyl, cycloalkyl, alkenyl, aralkyl or aryl,
• R.sup.8 and R.sup.9, independently of one another, denote hydrogen, alkyl, alkoxy, aryloxy, halogen, cyano, alkoxycarbonyl, nitro or C.sub.1 -C.sub.4 -acylamino, or
• R.sup.4 and R.sup.7 form a 2- or 3-membered carbon bridge which is unsubstituted or substituted by 1 to 3 alkyl groups, or
• R.sup.4 and R.sup.9 form a direct bond or an oxygen bridge, and
• X.sup..crclbar. denotes an anion,
• said heterocycle being defined as a thienyl, furyl or pyridyl radical, said alkyl, alkenyl, cycloalkyl, aralkyl, aryl, alkoxy and heterocyclic radicals being unsubstituted or substituted by cyano, hydroxyl, fluorine, chlorine, bromine, nitro, alkyl, monoalkylamino, dialkylamino, alkoxy, phenyl, acyloxy, acylamino, alkoxycarbonyl, alkoxycarbonyloxy, carboxyl groups, ammonium groups or pyridinium groups.