Provided is a lithographic printing plate precursor having an aluminum support and an image-recording layer on the aluminum support, in which the image-recording layer contains an infrared absorber, a polymerization initiator, a polymerizable compound, and an addition polymerization-type resin having a dispersible group, and in a case where a capacitance Cp of the lithographic printing plate precursor is set to satisfy Cp (t)/Cp (20 seconds)=0.95, t satisfies t<12 seconds or the capacitance Cp of the lithographic printing plate precursor satisfies Cp (0 seconds)>400 nF. Also provided are a method for preparing lithographic printing plate or a lithographic printing method using the lithographic printing plate precursor. The capacitance Cp of the lithographic printing plate precursor is measured by bringing at least a measurement portion of the image-recording layer into contact with a 2% by mass aqueous sodium chloride solution at 25° C.

Provided is an on-press development type lithographic printing plate precursor having an aluminum support and an image-recording layer on the aluminum support, in which the image-recording layer contains an infrared-absorbing polymethine colorant having HOMO of −5.2 eV or less, a polymerization initiator, and a polymerizable compound having 7 or more functional groups and contains or does not contain a polymer having a molecular weight 10,000 or more, and in a case where the image-recording layer contains the polymer having a molecular weight of 10,000 or more, a ratio Wp/Wm of a content Wp of the polymer having a molecular weight of 10,000 or more to a content Wm of the polymerizable compound having 7 or more functional groups is 1.00 or less. Also provided are a method for preparing a lithographic printing plate and a lithographic printing method using the lithographic printing plate precursor.

Provided is an on-machine development type planographic printing plate precursor having a support and an image-recording layer on the support, in which the image-recording layer contains an initiator, an infrared absorber capable of donating electrons to the initiator, and a color-developing substance precursor, the image-recording layer can form an image by exposure to infrared laser, and in a case where the image-recording layer is exposed to an infrared laser with a wavelength of 830 nm at an energy density of 110 mJ/cm.sup.2, a brightness change ΔL of the image-recording layer before and after the exposure is 3.0 or more. Also provided are a method for preparing a planographic printing plate or a planographic printing method in which the on-machine development type planographic printing plate precursor is used.

A lithographic printing plate precursor has an infrared radiation-sensitive image-recording layer containing an IR absorber, and an ozone-blocking material of 1500 or less molecular weight and has structure (I), (II), or (III):

##STR00001##

wherein R is a hydrocarbon having 14-30 carbon atoms; m is 1 or 2; n is 1-6; the sum of m and n is >2 and <8; and A is a multivalent organic moiety free of R and OH groups and has a valence m+n;

##STR00002##

wherein R.sub.1 and R.sub.2 are alkyl groups of 14-22 carbon atoms, and o is 1-3;

R.sub.3C(═O)NR.sub.4R.sub.5   (III)

wherein R.sub.3 is an alkenyl with a C═C bond within a carbon-carbon chain of 16-30 carbons, and R.sub.4 and R.sub.5 are hydrogen or unsubstituted alkyls of 1-4 carbon atoms. Such ozone-blocking materials can be used to protect infrared radiation-sensitive dyes that may be degraded by ozone and thus improve imaging sensitivity.

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound and an optionally substituted trihaloalkyl sulfone photoinitiator, and (ii) a toplayer provided above the photopolymerisable layer; characterized in that the toplayer includes an infrared absorbing dye capable of forming a print-out image upon exposure to heat and/or IR radiation.

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound, a borate compound and/or a photoinitiator and (ii) a toplayer provided above the photopolymerisable layer; characterized in that the toplayer has a thickness comprised between 0.1 g/m2 and 1.75 g/m2 and includes an 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.

IR-sensitive lithographic printing plate precursors provide a stable print-out image using a unique IR radiation-sensitive composition. This IR radiation-sensitive composition includes: a) free radically polymerizable component; an b) IR radiation absorber; c) an initiator composition; a d) borate compound; and a e) compound capable of forming a colored boronic complex during or after exposure of the infrared radiation-sensitive image-recording layer to infrared radiation. The resulting print-out image exhibits an excellent color contrast between the exposed and non-exposed regions. After IR imaging, these precursors can be developed off-press or on-press.

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound and a photoinitiator, and a toplayer provided above the photopolymerisable layer; characterized in that the toplayer has a thickness comprised between 0.1 g/m.sup.2 and 1.75 g/m.sup.2 and includes an infrared absorbing compound which includes a thermocleavable group which transforms into a group which is a stronger electrondonor upon exposure to heat and/or IR radiation, and is capable of forming a printout image upon exposure to heat and/or IR radiation.

Provided are a planographic printing plate precursor including a support, and an image recording layer in this order, in which the image recording layer contains polymer particles containing an addition polymerization type resin, and the addition polymerization type resin contains a polymerizable group and a hydrophilic structure; a method of producing a planographic printing plate using the planographic printing plate precursor; a planographic printing method using the planographic printing plate precursor; and a curable composition containing the polymer particles.

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound and an optionally substituted trihaloalkyl sulfone photoinitiator, and (ii) a toplayer provided above the photopolymerisable layer; characterized in that the toplayer includes an infrared absorbing dye capable of forming a print-out image upon exposure to heat and/or IR radiation.