Importance

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Abstract

The present invention is directed to a method for the on-press development and printing of images. The method generally comprises the steps of providing a lithographic printing plate precursor element comprising a lithographic hydrophilic printing plate substrate, a photohardenable photoresist, and a layer of polymeric protective overcoat; imagewise exposing the precursor element to actinic radiation through said photoresist and overcoat layer sufficiently to photoharden the photoresist in exposed regions and provide a latent image in said photoresist layer; placing the precursor element onto a lithographic printing press; and running the press, whereby printing fluid effects removal of the overcoat and development of said latent image. In particular modes of practices, the method utilizes an overcoat having incorporated therein a water or fountain soluble or dispersible crystalline compound. The overcoat can be used as an oxygen barrier and/or to provide a non-tacky surface on the printing plate. By the incorporation of the crystalline compound, on-press removability of the overcoat is facilitated.

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First Claim