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Abstract

The invention relates to a positive-working, radiation-sensitive mixture which contains an organic polymeric binder which is insoluble in water but soluble or at least swellable in aqueous alkaline solution and at least one IR-absorbing cyanine dye having a betaine structure or having a betaine structure and containing an anion and having the formula (I) ##STR1## in which R.sup.1 to R.sup.8 independently of one another, are a hydrogen or halogen atom, a sulfonate, carboxylate, phosphonate, hydroxyl, (C.sub.1 -C.sub.4)alkoxy, nitro, amino, (C.sub.1 -C.sub.4)alkylamino, di(C.sub.1 -C.sub.4)alkylamino group or a (C.sub.6 -C.sub.10)aryl group which in turn may be substituted by one or more halogen atoms and/or one or more sulfonate, carboxylate, phosphonate, hydroxyl, (C.sub.1 -C.sub.4)alkoxy, nitro, amino, (C.sub.1 -C.sub.4)alkylamino and/or di(C.sub.1 -C.sub.4)alkylamnino groups, R.sup.9 and R.sup.10 independently of one another, are a straight-chain or branched (C.sub.1 -C.sub.6)alkyl, a (C.sub.7 -C.sub.6)aralkyl or a (C.sub.6 -C.sub.10)aryl group, each of which in turn may be substituted by one or more halogen atoms and/or one or more sulfonate, carboxylate, phosphonate, hydroxyl, (C.sub.1 -C.sub.4)alkoxy, nitro, amino, (C.sub.1 -C.sub.4)alkylamino and/or di(C.sub.1 -C.sub.4)alkylamino groups, R.sup.11 and R.sup.12 independently of one another, are (C.sub.1 -C.sub.4)alkyl or (C.sub.6 -C.sub.10)aryl groups which in turn may be substituted, Z.sup.1 and Z.sup.2 independently of one another, are a sulfur atom, a di(C.sub.1 -C.sub.4)alkylmethylene group or an ethene-1,2-diyl group and A is a carbon atom or a chain having conjugated double bonds which results in the formation of a delocalized II-electron system between the quaternary nitrogen atom of the 3H-indolium, quinolinium or benzothiazolium radical and the enolate oxygen atom of the pyrimidine-2,4,6-trione radical. After imagewise exposure to a laser, the recording material prepared using this mixture can be readily developed with an aqueous alkaline solution without additional processing steps (such as post-bake or postexposure). The invention also relates to a process for the production of printing plates for offset printing from a recording material according to the invention.

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First Claim