A source of actinic radiation for curing printing plates. The source includes a base with a heat sink and has a length greater than its width. One or more circuit boards, mounted on a planar mounting surface of the base disposed parallel to the target illumination plane, collectively provide a plurality of light emitting diodes (LEDs) having an ultraviolet center emission wavelength distributed over the length of the mounting surface. A transparent or translucent cover together with the base defines an enclosure for the plurality of LEDs. The heat sink has a heat transfer surface area defined by a plurality of projections with indentations therebetween. The source may be configured to replace a fluorescent bulb.

A lithographic printing plate precursor has a support and an image-recording layer on the support, in which the image-recording layer contains an infrared absorber, a polymerization initiator, and a polymer A. The weight-average molecular weight of the polymer A is more than 15,000 and 150,000 or less, and the ethylenically unsaturated bond valence of the polymer A is 3.0 mmol/g or more.

A lithographic printing plate precursor including on a substrate which has a hydrophilic surface or which is provided with a hydrophilic layer, a coating comprising a photopolymerisable layer including a polymerisable compound, a photoinitiator and adhesion promoting compound containing at least one thiol group and at least one group capable of adhering to the substrate.