Patent ID: 7763413

Claim:
A method of providing an imaged and developed lithographic printing plate comprising: A) using a laser providing infrared radiation having a λ max of from about 750 to about 1200 nm, imagewise exposing a negative-working imagable lithographic printing place comprising an aluminum-containing hydrophilic substrate having directly thereon an outermost negative-working imagable layer to provide exposed and non-exposed regions, said outermost negative-working imagable layer comprising: a free radically polymerizable component that is an ethylenically unsaturated free-radical polymerizable monomer, oligomer, or crosslinkable polymer, an initiator composition capable of generating free radicals sufficient to initiate polymerization of free radically polymerizable groups upon exposure to imaging radiation, said initiator composition comprising a diaryliodonium borate that is represented by the following Structure (IB): wherein X and Y are independently halo, alkyl, alkoxy, aryl, or cycloalkyl groups, or two or more adjacent X or Y groups can be combined to form a fused carbocyclic or heterocyclic ring with the respective phenyl groups, p and q are independently 0 or integers of 1 to 5 as long as either p or q is at least 1 and the sum of the carbon atoms in the X and Y substituents or fused ring(s) is at least 6, and Z ⊖ is an organic anion represented by the following Structure (IB Z ): wherein R 1 , R 2 , R 3 and R 4 are independently alkyl, aryl, alkenyl, alkynyl, cycloalkyl, or heterocyclyl groups, or two or more of R 1 , R 2 , R 3 and R 4 can be joined together to form a heterocyclic ring with the boron atom, an infrared radiation absorbing compound that is an infrared radiation sensitive dye having a tetraaryl pentadiene chromophore, and a primary polymeric binder that is represented by the following Structure (IA): -(A) w -(B) x -(C) y -(D) z - (IA) wherein said A recurring units are derived from at least an allyl (meth)acrylate or styryl (meth)acrylate, said B recurring units are derived from one or more of (meth)acrylonitrile, said C recurring units are derived from one or more of (meth)acrylic acid, 4-carboxyphenyl (meth)acrylate, and 4-carboxystyrene, said D recurring units are derived from one or more of vinyl carbazole, methyl (meth)acrylate, poly(ethylene glycol) methyl ether (meth)acrylate, and a styrene monomer, w is from about 5 to about 50 mol %, x is from about 30 to about 70 mol %, y is from about 5 to about 20 mol %, and z is from 10 to about 40 mol %, B) with or without a post-exposure baking step, developing said imagewise exposed lithographic printing plate with a gum, off-press to remove only said non-exposed regions to provide an imaged and developed lithographic printing plate, said gum having a pH greater than 7 and up to about 11 and comprising at least 1 weight % of one or more anionic surfactants.