POSITIVE PHOTOSENSITIVE COMPOSITION AND LITHOGRAPHIC PRINTING PLATE FORMED BY USING SAME

摘要

PROBLEM TO BE SOLVED: To obtain the positive photosensitive composition for the lithographic printing plate high in sensitivity and superior in contrast between image parts and nonimage parts and retained enough in film endurance and superior in scratch resistance and high enough in printing durability by using a photothermoconverting material in response to light in the near infrared region and a compound having a specified vinyloxy group. SOLUTION: This positive photosensitive composition comprises (A) an alkali- soluble organic polymer having phenolic hydroxyl groups and (B) a photothermoconverting material absorbing light from an exposure light source of an image and converting it into heat, and (C) a compound having >=2 vinyloxy group in the molecule. A preferable compound for the (C) component is a compound represented by formula I or II in which R is a polyalcohol or the like; R is a polyvalent carboxylic group; R is an optionally substituted alkylene group; each of R -R is an alkyl group; (m) is an integer of 0-10; and (n) is an integer of 0-10.