Abstract: Sulfonic acid esters are used as (a) compounds for forming a strong acid on irradiation in radiation-sensitive, positive or negative working mixtures also comprising (b) either a compound with at least one acid-decomposable C--O--C or C--O--Si bond (for positive working mixtures) or a compound with at least acid-cross-linkable groups (for negative working mixtures) and c) a binder which is insoluble in water but soluble or at least swellable in aqueous alkaline solutions, wherein said sulfonic acid esters are formula?R.sup.1 --CR.sup.2 (CF.sub.3)--O--SO.sub.2 --!.sub.n R.sup.3(I)orR.sup.1 ?--CR.sup.2 (CF.sub.3)--O--SO.sub.2 --R.sup.3 !m (II)wherein R.sup.1, R.sup.2, R.sup.3, n and n are defined with the body of the disclosure. These mixtures are particularly suitable for exposure to deep UV radiation in the formation of recording materials suitable for the production of photoresists, electronic components, and printing plates.

Abstract: Crude 4,4'-diamino-l,l'-dianthraquinonyl-3,3'-disulfonic acids or salts thereof are purified by subjecting an aqueous solution containing the crude products to salting-out using inorganic salts, the aqueous solution being adjusted within a range of from acid to neutral region, whereby a product usable as such for the production of 4,4'-diamino-1,1'-dianthraquinonyl red pigments having excellent pigmentary properties is obtained in high yields with industrial advantages.