Water-less lithographic plates

Abstract

There is described a method of preparing a positive working water-less lithographic plate which comprises a support having an oleophilic surface, there being coated on the support a mixture which comprises as one component an ink-repellant and water-repellant polymer or a mixture of such polymers or polymer precursors, and as the other essential component of the mixture an infra-red or heat sensitive composition selected from (a) an organic solvent soluble diazo compound and an infra-red absorbing compound, (b) a photopolymer and an infra-red absorbing dye, or (c) a mixture of a free-radically polymerisable ethylenically unsaturated compound or compounds together with either a photoinitiator which is infra-red sensitive or an initiator which is heat sensitive together with an infra-red absorbing compound, the ratio of ink-repellant polymer to infra-red or heat sensitive composition (a), (b) or (c) in the mixture being from 20-80 ink repellant polymer to 80-20 infra-red or heat sensitive composition by weight, imagewise acting on the coated mixture, developing the acted on mixture with the appropriate developing solution depending on the composition (a), (b) or (c) used, to remove the composition and the water-repellant polymer in the unacted on areas to reveal the oleophilic surface of the support in the unacted on areas of the plate and leaving the coated mixture in the acted on areas of the plate.

Dependencies are inferred from the claim text.