Fremgangsmåde til fremstilling af en positiv lysfølsom litografisk trykplade

摘要

A positive photosensitive composition showing a difference in solubility in an alkali developer as between an exposed portion and a non-exposed portion, which comprises, as components inducing the difference in solubility, (a) a light-absorbing dye having an absorption band covering a part or whole of a wavelength region of from 650 to 1300 nm as a photo-thermal conversion material. (b) a high molecular compound, of which the solubility in an alkali developer is changeable mainly by a change other than a chemical change, and (c) a solubility-suppressing agent capable of lowering the dissolution rate, in the alkali developer, of a blend comprising a light-absorbing dye of component (a) and a high molecular compound of component (b).