| abstract |
(57) [Problem] To provide a plate making method of a positive photosensitive lithographic printing plate having a large developing latitude and excellent processing stability. SOLUTION: In an image forming material having a positive photosensitive composition layer containing (A) a photothermal conversion substance and (B) an alkali-soluble resin on a support, the alkali-soluble resin is a novolak resin and / or a phenol resin. Containing A positive-working image-forming material, wherein an alkali-soluble resin component having a weight average molecular weight of 2,000 or less accounts for 55% by weight or less of the whole alkali-soluble resin. |