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Abstract

The present invention refers to lithographic printing and, in particular, to highly solvent-resistant thermally imaging elements and to methods for using the same as well as to corresponding lithographic printing plates comprising said thermally imageable elements. It also refers to processes for making plates and assemblies for use in lithography. The heat imaging positive array of the present invention comprises: A--a hydrophilic substrate; B--a thermally-sensitive imaging element having a composite structure comprising: (1) a first layer on the substrate and a second layer on the first layer, a) the first layer comprising:--a polymeric material which is insoluble or substantially insoluble in aqueous alkaline developing solutions, modified by a first compound which renders the composition comprising the polymeric material more soluble in alkaline developing solutions; b) a second layer on the first layer, said second layer comprising:--a polymeric material modified by a second compound which renders more soluble or dispersible in aqueous alkaline developing solutions, during the developing process, after heating or through absorbance of electromagnetic radiation; the heated or exposed areas of the assembly becoming significantly more soluble or dispersible in aqueous alkaline developing solutions than the non-imaged or un-imaged areas. Or (2) a pre-mix previously prepared from the components of said first and second layers, wherein said pre-mix is subsequently applied on the substrate as a single layer

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