A negative image-recording material which can be imagewise exposed to IR
radiation from IR lasers and ensures direct image formation from digital
data of a computer or the like. The material, when used in a lithographic
printing plate, ensures good hardenability in an image area and exhibits
good printing durability, even if not heated for image formation, and
ensures a large number of good prints from the printing plate. The
recording material contains (A) an IR absorber, (B) a radical generator
having an onium salt structure, (C) a radical-polymerizing compound, and
(D) a reducing additive, and this is imagewise exposed to IR radiation for
image formation. Preferably, the reducing additive (D) is highly reactive
with radicals and a reaction product with a radical has high reductivity.
Preferred examples of the reducing additive are ether-type hydrogen
donors, alcohol-type hydrogen donors, vinyl ethers and phosphine-type
compounds.
