IR-sensitive lithographic printing plate precursors provide a stable print-out image using a unique IR-sensitive image-recording layer. The IR radiation-sensitive layer includes: (1) a free radical initiator composition with an electron-donating agent and one or more iodonium cations; (2) a free radically polymerizable composition; and (3) a color-changing compound of Structure (I) having an indene ring in the conjugated chain between the aromatic terminal groups. The IR radiation-sensitive composition and layer also contains one or more borate ions such that the molar ratio of one or more borate ions to the one or more iodonium ions is at least 0.5:1. After IR imaging, these precursors exhibit desirable printout images both fresh and after dark storage. The precursors can be developed on-press.

A radiation-sensitive resin composition includes: an onium salt compound represented by formula (1), a resin including a structural unit having an acid-dissociable group, and an alcohol-based solvent having a boiling point of 90 C. or higher. R.sup.1 is a substituted or unsubstituted monovalent hydrocarbon group or a group including a divalent hetero atom-containing group between two adjacent carbon atoms of the hydrocarbon group; R.sup.2 and R.sup.3 are each independently a hydrogen atom or a monovalent hydrocarbon group, one of R.sup.f11 and R.sup.f12 is a fluorine atom, and the other is a fluorine atom or a monovalent fluorinated hydrocarbon group, m1 is an integer of 1 to 3; m2 is an integer of 0 to 8; and Z.sub.1.sup.+ represents a monovalent radiation-sensitive onium cation.

##STR00001##

A radiation-sensitive resin composition includes: a first onium salt compound represented by formula (1); a second onium salt compound represented by formula (2); a resin including an acid-dissociable group; and a solvent. R.sup.1 is a substituted or unsubstituted monovalent hydrocarbon group or the like; R.sup.2 and R.sup.3 are each independently a hydrogen atom, a fluorine atom, or the like; and Z.sup.+ represents a monovalent radiation-sensitive onium cation. R.sup.4 is a monovalent organic group; one of R.sup.f21 and R.sup.f22 is a fluorine atom, and the other is a fluorine atom or a monovalent fluorinated hydrocarbon group; Ar is a monovalent organic group including an aromatic ring; R.sup.5, R.sup.6, R.sup.7, and R.sup.8 each independently represent a hydrogen atom, a hydroxy group, a halogen atom, or a monovalent organic group; and X is a single bond or a divalent hetero atom-containing group.

##STR00001##

A radiation-sensitive resin composition includes: a first onium salt compound represented by formula (1); a second onium salt compound represented by formula (2); a resin including a structural unit having an acid-dissociable group; and a solvent. R.sup.1 is a substituted or unsubstituted monovalent hydrocarbon group or the like; R.sup.2 and R.sup.3 are each independently a hydrogen atom or a monovalent hydrocarbon group; one of R.sup.f11 and R.sup.f12 is a fluorine atom, and the other is a fluorine atom or a monovalent fluorinated hydrocarbon group; and Z.sub.1.sup.+ represents a monovalent radiation-sensitive onium cation. R.sup.4 is a monovalent organic group including a cyclic structure; R.sup.f21 and R.sup.f22 each independently represent a fluorine atom or a monovalent fluorinated hydrocarbon group; and Z.sub.2.sup.+ represents a monovalent radiation-sensitive onium cation.

##STR00001##

A photocurable composition is curable by exposure to visible light, and comprises a free-radical polymerizable compound and a photoinitiating system, the photoinitiating system comprising a) a dye which is excitable by visible light and has a triplet energy form 150 kJ/mol to 250 kJ/mol, such as Eosin Yellow and Fluorescein, and b) an -halogen carbonyl compound. Preferably, the composition comprises a compound with a CH-acidic hydrogen atom adjacent to at least one carbonyl group. The composition is cured by visible light in an oxygen-containing atmosphere and results in tack-free, colorless coatings.

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 a compound represented by Formula (1), a method of preparing a lithographic printing plate using the on-press development type lithographic printing plate precursor, a lithographic printing method, and a novel compound. In the formula, R.sup.1 represents a group represented by Formula (2) or Formula (3), R.sup.10 represents a monovalent organic group having an aryl group, R.sup.11 to R.sup.14 and R.sup.17 to R.sup.20 each independently represent a hydrogen atom, an alkyl group, or an aryl group, R.sup.15 and R.sup.16 each independently represent a hydrogen atom, an alkyl group, or an aryl group, and at least two of R.sup.11 to R.sup.20 may be bonded to each other to form a ring structure.

##STR00001##

A resist pattern is formed by (i) applying a resist composition comprising a hypervalent iodine compound, a carboxylic acid, and a solvent onto a substrate or an underlying film to form a resist film, (ii) exposing the resist film to high-energy radiation, (iii) baking the exposed resist film, and (iv) dry etching the baked resist film for development.

A betaine type iodonium salt containing a C6-C18 alkyl or C4-C18 fluorinated alkyl group and having a iodonium cation and a carboxylate anion within a common molecule is a useful quencher. A chemically amplified positive resist composition comprising the iodonium salt exhibits improved lithography properties such as resolution, LER and pattern profile when processed by photolithography.