A recording medium comprises an oleophilic substrate and, thereover, a topmost oleophobic layer comprising a cured polymeric silicone matrix that consists essentially of the addition-cure reaction product of a vinyl-functional polydialkylsiloxane and a silane cross-linking agent. The vinyl-functional polydialkylsiloxane has a molecular weight ranging from 30,000 to 75,000 or 110,000 to 130,000. If the molecular weight of the vinyl-functional polydialkylsiloxane is within the range of 30,000 to 75,000, the molar ratio of silane groups to vinyl groups is within the range of about 11:1 to about 25:1; and if the molecular weight of the vinyl-functional polydialkylsiloxane is within the range of 110,000 to 130,000, the molar ratio of silane groups to vinyl groups is from about 5:1 to about 27:1. The recording medium may be used as a lithographic printing plate.

An imaging member includes a surface layer comprising a fluoroelastomer-perfluoropolyether composite formed from a reaction mixture comprising a fluoroelastomer and a perfluoropolyether compound. Methods of manufacturing the imaging member and processes for variable lithographic printing using the imaging member are also disclosed.

An on-machine development type planographic printing plate precursor has a support and an image-recording layer on the support. 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 L of the image-recording layer before and after the exposure is 3.0 or more. A method for preparing a planographic printing plate and a planographic printing method employ the on-machine development type planographic printing plate precursor.

A negative-working lithographic printing plate precursor includes a support and a coating containing a photopolymerizable layer including a polymerizable compound including: a free radical polymerizable group, and at least one moiety having a structure according to Formula (I): ##STR00001## wherein n represents an integer equal to 0 or 1; L.sup.1 represents a divalent linking group; and * denotes the linking positions to the rest of the structure, with the proviso that the carbonyl groups in Formula (I) are bonded to a carbon atom.

Negative-working, IR-sensitive printing plates utilize a radiation-sensitive composition having a component polymerizable by a free-radical mechanism, at least part of which comprises or consists essentially of a non-particulate, aliphatic urethane acrylic oligomer that is infinitely water-dilutable but not water-soluble.

By a lithographic printing plate precursor including a support having provided thereon an image-recording layer capable of forming an image by supplying at least any of printing ink and dampening water on a printing machine after image exposure to remove an unexposed area thereof, wherein the image-recording layer contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound and a polysaccharide having a sulfonic acid group or a group made by a salt thereof and a plate making method of a lithographic printing plate using the same, a lithographic printing plate precursor which exhibits good development property while maintaining printing durability of a lithographic printing plate after development and a plate making method of a lithographic printing plate using the same can be provided.

By a lithographic printing plate precursor including a support having provided thereon an image-recording layer capable of forming an image by supplying at least any of printing ink and dampening water on a printing machine after image exposure to remove an unexposed area thereof, wherein the image-recording layer contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound and a polysaccharide having a sulfonic acid group or a group made by a salt thereof and a plate making method of a lithographic printing plate using the same, a lithographic printing plate precursor which exhibits good development property while maintaining printing durability of a lithographic printing plate after development and a plate making method of a lithographic printing plate using the same can be provided.

A lithographic printing plate precursor is disclosed which includes a support and a coating comprising a photopolymerisable layer including a polymerisable compound, an initiator and a pH sensitive colorant precursor and a protective overcoat layer provided above the photopolymerisable layer including a heat sensitive color-forming IR dye, which upon exposure to heat and/or light forms a print-out image which remains stable or increases during storage of the precursor in light or dark environment.

An object of the present invention is to provide an on-press development-type planographic printing plate precursor which suppresses color-forming defect after a lapse of time and has excellent visibility. Another object of the present invention is to provide a manufacturing method of a planographic printing plate and a printing method. The planographic printing plate precursor of the present invention is an on-press development-type planographic printing plate precursor including a support and an image-recording layer, in which the support has an aluminum alloy plate and an anodic oxide film disposed on the aluminum alloy plate, a density of intermetallic compounds having a major axis of 2.0 m or more on a surface of the support on a side opposite to the image-recording layer is 1,000 pieces/mm.sup.2 or less, the image-recording layer contains an infrared absorber and an acid color-forming agent, and a color-forming factor of the acid color-forming agent, which is determined by a predetermined measuring method, is 20,000 or more.

Provided are an on-press development type lithographic printing plate precursor including: a support; and an image-recording layer on the support, in which the image-recording layer contains an electron-accepting polymerization initiator, an electron-donating polymerization initiator, an infrared absorber, and a salt compound A, and an HOMO value of an anion constituting a salt in the salt compound A is 6.2 eV or more and 4.4 eV or less, and a method of preparing a lithographic printing plate or a lithographic printing method using the on-press development type lithographic printing plate precursor.