A negative-working infrared radiation-sensitive lithographic printing plate precursor can be imaged and developed on-press to provide a lithographic printing plate. Such precursor has an initiator composition that contains compound A of Structure (I) and one or more compounds collectively as compound B of Structure (II) or Structure (III):

##STR00001##

wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are independently alkyl groups each having 3 to 6 carbon atoms; at least one of R.sub.3 and R.sub.4 is different from R.sub.1 or R.sub.2; the difference of total number of carbon atoms in R.sub.1 and R.sub.2 and the total number of carbon atoms in R.sub.3 and R.sub.4 is 0, 1, or 2; the difference of total number of carbon atoms in R.sub.1 and R.sub.2 and the total number of carbon atoms in R.sub.5 and R.sub.6 is 0, 1, or 2; and X.sub.1, X.sub.2 and X.sub.3 are the same or different anions.

Provided is a method of producing a planographic printing plate, including: subjecting a planographic printing plate precursor, which has a support and a positive-working image recording layer, to image-wise exposure; and developing it using an alkaline aqueous solution which contains a specific compound and has a pH of from 8.5 to 10.8, in this order. The recording layer has: a lower layer containing a water-insoluble and alkali-soluble resin and an infrared ray absorbing agent; and an upper layer containing a water-insoluble and alkali-soluble polyurethane resin and a polyorganosiloxane. The specific compound is a nonionic or anionic surfactant, or at least one compound represented by Formula (1) or (2), wherein R.sup.11, R.sup.12, and R.sup.13 each represent an alkyl group; R.sup.14 represents an alkylene group; and R.sup.15 represents a single bond or a divalent linking group containing a hetero atom; and R.sup.21, R.sup.22, and R.sup.23 each represent an alkyl group. ##STR00001##

Provided is a method of producing a planographic printing plate, including: subjecting a planographic printing plate precursor, which has a support and a positive-working image recording layer, to image-wise exposure; and developing it using an alkaline aqueous solution which contains a specific compound and has a pH of from 8.5 to 10.8, in this order. The recording layer has: a lower layer containing a water-insoluble and alkali-soluble resin and an infrared ray absorbing agent; and an upper layer containing a water-insoluble and alkali-soluble polyurethane resin and a polyorganosiloxane. The specific compound is a nonionic or anionic surfactant, or at least one compound represented by Formula (1) or (2), wherein R.sup.11, R.sup.12, and R.sup.13 each represent an alkyl group; R.sup.14 represents an alkylene group; and R.sup.15 represents a single bond or a divalent linking group containing a hetero atom; and R.sup.21, R.sup.22, and R.sup.23 each represent an alkyl group. ##STR00001##

An on-press development type lithographic printing plate precursor includes 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 at least one compound selected from the group consisting of a compound represented by Formula (1) and a compound represented by Formula (2) (in Formulae (1) and (2), Ra.sub.1 and Ra.sub.2 represent an alkyl group, Rb.sub.1 and Rb.sub.3 represent an alkyl group, Rb.sub.2 and Rb.sub.4 represent an alkyl group, and EWG's each independently represent a hydrogen atom or an electron-withdrawing group, provided that at least one of the four EWG's in Formula (1) represents an electron-withdrawing group).

A lithographic printing plate precursor has a support and an image-recording layer on the support. The image-recording layer contains an infrared absorber, a polymer A that has a weight-average molecular weight of more than 15,000 and 150,000 or less, and a polymerizable compound B that has a weight-average molecular weight of 1,000 or more and 15,000 or less, and the polymer A is a polymer represented by Formula (I):
A.sup.P-(B.sup.P).sub.nPFormula (I) In Formula (I), A.sup.P represents an nP-valent organic group having a hydrogen bonding group, B.sup.P represents a group having 2 or more Polymerizable groups, nP represents an integer of 2 or more, and weight-average molecular weight of A.sup.P/(molecular weight of B.sup.PnP) is 1 or less.

Flexographic printing members are prepared from a flexographic printing plate precursor consisting essentially of: backing film, water- or water-dispersible photosensitive layer, and cover sheet in contact with the photosensitive layer. The cover sheet is removed and a mask element is laminated directly in contact with the photosensitive layer. Exposure through the mask element provides exposed regions and non-exposed regions. The non-exposed regions are removed with an aqueous developer having: a) a C.sub.12-20 saturated or unsaturated fatty acid (or alkali metal salt) at 0.25-2.0 weight %, and at least 85 weight % of a C.sub.18 mono- or poly-unsaturated fatty acid (or alkali metal salt); b) an aminopolycarboxylic acid (or alkali metal salt) at 0.05-0.30 weight %; c) a buffer at 05-0.60 weight %; and d) water. The photosensitive layer has a controlled release of 5-500 g/cm using ASTM D-3330 Method D, between its front imaging surface and the mask element.

An on-press development type lithographic printing plate precursor, including an image-recording layer on a support, in which the image-recording layer contains an infrared absorber A, a borate compound B, an iodonium compound C, and a color forming substance precursor D, and a surface free energy of an outermost layer on an image-recording layer side is 115 mJ/m.sup.2 or less, and a method of preparing a lithographic printing plate, a lithographic printing method, and a laminate using the on-press development type lithographic printing plate precursor.

An actinic ray-sensitive or radiation-sensitive resin composition includes a resin (A) containing a repeating unit represented by General Formula (4) and a crosslinking agent (C) containing a polar group, in which the crosslinking agent (C) is a compound represented by General Formula (1) or a compound in which two to five structures represented by General Formula (1) are connected via a linking group or a single bond represented by L.sub.1 in General Formula (3). ##STR00001##

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.

An on-press development type lithographic printing plate precursor has a support, an image-recording layer, and an outermost layer in this order. The image-recording layer contains an infrared absorber, an electron-accepting polymerization initiator, and a polymerizable compound. LUMO of the electron-accepting polymerization initiator-LUMO of the infrared absorber is 0.45 eV or more, and the outermost layer contains a discoloring compound. A method of preparing a lithographic printing plate and a lithographic printing method employ the on-press development type lithographic printing plate precursor.