Radiation-sensitive mixture and recording material made thereof for offset printing plates

摘要

Positive-or negative-working radiation-sensitive mixture contains a carbon black pigment (I) with a primary particle size < 80 nm as infra-red (IR)-absorbing component. This is pre-dispersed in a polymer (II) containing acid units with a pKa value < 13. Also claimed are: (i) recording material with a substrate and a radiation-sensitive layer of this mixture; and (ii) a method of making a printing plate. Preferably (I) has a BET surface area NOTLESS 30 m<2>/g and a pH < 7 in aqueous dispersion. The average primary particle size is < 60, especially < 30 nm. PREFERRED POLYMER - In (II), the acid units have an acid proton linked to a hetero-atom and especially have amino (-NH2), imino (-NH-), phenolic hydroxyl (-OH) or carboxyl (-COOH) groups. (II) contains NOTLESS 1, especially NOTLESS 1.5 mmole acid groups/g