Abstract: A method for forming a planographic printing member is disclosed. A hydrophilic layer is formed on a support by contacting the support with a silicate solution that contains a silicate and a particulate material. An image layer is provided over the hydrophilic layer. The hydrophilic layer is treated to ensure that the image layer is able to change color on exposure. The hydrophilic layer may be treated with an acid, with a buffer formulation, with a colloidal suspension, or with a salt. Preferably the hydrophilic layer is treated with aluminum sulphate.

Abstract: A planographic printing member comprising a substrate, an oleophilic layer, an infra-red sensitive/ablatable layer, and a hydrophilic layer. The hydrophilic layer is derived from a silicate solution, optionally containing particulate materials such as alumina and/or titania. The printing member may be exposed to radiation from a laser which ablates the infra-red sensitive/ablatable layer to reveal areas of the oleophilic layer. An exposed printing member may be used in wet lithographic printing.

Abstract: A positive image can be obtained from a positive-working element that is sensitive to infrared radiation. The element comprises an imaging layer containing an alkali-soluble reactive resin (such as a phenolic resin), an infrared radiation absorbing compound, a thermochemical acid generating compound, and a dissolution inhibitor that has acid-cleavable C--O--C groups. Upon laser exposure, a Bronsted acid is generated which then breaks the bonds of the C--O--C groups, allowing the exposed regions of the reactive resin to be solubilized in an alkaline developer solution.