A planographic printing plate precursor includes: a support; and an image recording layer which includes a radical initiator, a radical polymerizable component, and a radiation absorption compound, and in which the image recording layer shows two or more peaks of a radical generation amount in a radical generation amount-versus-time curve after exposure to image forming radiation, in which the radical initiator includes an electron-donating radical initiator and an electron-accepting radical initiator, and the radiation absorption compound comprises a compound represented by the following Formula 1. ##STR00001##

Provided is a lithographic printing plate precursor having an aluminum support and an image-recording layer formed on the aluminum support, in which the image-recording layer contains resin particles A that have an ethylenically unsaturated group and a compound B that has an ethylenically unsaturated group other than the resin particles A and has an ethylenically unsaturated bond valence of 1.5 mmol/g or more. Also provided are a method for preparing lithographic printing plate or a lithographic printing method using the lithographic printing plate precursor.

A lithographic printing plate precursor is disclosed including on a support a coating comprising (i) a photopolymerisable layer including a polymerisable compound, a first infrared absorbing dye including at least one electron withdrawing substituent and a photoinitiator; and (ii) a top layer provided above the photopolymerisable layer which includes a second infrared absorbing compound which includes a thermocleavable group which transforms into a group which is a stronger electron-donor upon exposure to heat and/or IR radiation, and is capable of forming a print-out image upon exposure to heat and/or IR radiation.

A curable composition includes a salt compound having a) an organic anion in which, in Hansen solubility parameter, δd is 16 or more, δp is 16 or more and 32 or less, and δH is 60% or less of δp and b) a counter cation. A lithographic printing plate precursor having an image-recording layer containing the curable composition, a method for producing a lithographic printing plate using the lithographic printing plate precursor, and a compound that is used in the image-recording layer in the lithographic printing plate precursor are also set out.

Provided are a lithographic printing plate precursor having an image-recording layer on an aluminum support, in which the image-recording layer contains a polymerization initiator, an infrared absorber, a polymer particle, and a polymerizable compound, and the polymerizable compound has a) a molecular weight of 1,500 to 3,000, b) a double bond equivalent of 200 or less, and c) a CLog P of 9 or less and a method for producing a lithographic printing plate in which the lithographic printing plate precursor is used.

A system for preparing a photopolymer printing plate includes an imager, a plate unloader configured to automatically unload the plate from the imager and deliver the plate to an exposure unit comprising a plurality of UV LEDs, and a controller configured to operate the imager, the plate unloader, and the exposure unit. The imager has a rotatable drum configured to rotate while laser beams ablate portions of an ablatable layer of the printing plate in accordance with imaging data. The UV LEDs include a back array and a front array configured to expose the front of the UV-curable plate, at least one of which is configured to emit UV radiation toward the plate during relative motion between the plate and the array.

Disclosed is a infrared radiation sensitive positive-working imageable element. The imageable element comprises: (a) a substrate, (b) an inner coating covering the substrate, and (c) an outer coating covering the inner coating. The inner coating comprises a repeating unit derived from a maleimide monomer and a (meth)acrylamide monomer, and a polymer hinder P that is soluble in an alkaline developing solution; and the outer coating comprises an infrared radiation absorbing compound and a polymer binder Q which is different from that in the inner coating. The imageable element is designed such that same is not only sensitive to radiation with a maximum wavelength of 700-1200 nm, but also has a good resistance to chemical solvents when used as a lithographic printing plate precursor, and same is not easily corroded and dissolved by printing chemicals during use, thus facilitating the prolonging of the service life of a lithographic printing plate.

Provided is an on-press development type lithographic printing plate precursor having a support and an image-recording layer on the support, in which the image-recording layer contains a compound A that has a partial structure satisfying Δd≥15.5 wherein δd is a value of a dispersion element in the Hansen solubility parameters, and a content of the partial structure satisfying Δd≥15.5 in the compound A is 50% by mass or more with respect to a total mass of the compound. Also provided is a method of preparing lithographic printing plate or a lithographic printing method using the lithographic printing plate precursor.

Provided is an on-press development type lithographic printing plate precursor having a support and an image-recording layer on the support, in which the image-recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and a color-developing substance precursor, and in a case where the image-recording layer is exposed to an infrared laser having a wavelength of 830 nm at an energy density of 110 mJ/cm.sup.2, a loss of ethylenically unsaturated bonds in an exposed area in the image-recording layer is 10% to 40% of ethylenically unsaturated bonds in a non-exposed area in the image-recording layer. Also provided is a method for preparing a lithographic printing plate or a lithographic printing method using the on-press development type lithographic printing plate precursor.

Lithographic printing plate precursors are prepared with a unique aluminum-containing substrate prepared using two separate anodizing processes to provide an inner aluminum oxide layer of average dry thickness (T.sub.i) of 300-3,000 nm and a multiplicity of inner micropores of average inner micropore diameter (D.sub.i) of ≤100 nm. An outer aluminum oxide layer is also provided to have a multiplicity of outer micropores of average outer micropore diameter (D.sub.o) of 15-30 nm and a dry thickness (T.sub.o) of 30-650 nm. A hydrophilic layer disposed on the outer aluminum oxide layer at 0.0002-0.1 g/m.sup.2 has at least a hydrophilic copolymer composed of (a) recurring units having an amide group and (b) recurring units comprising an —OM group directly connected to a phosphorus atom, wherein M represents a hydrogen, sodium, potassium, or aluminum atom.