The invention provides an infrared-sensitive positive-working image forming material which provides excellent development latitude, image formability and image region strength, and in which decrease in development property is prevented even when a certain time has passed after pattern exposure until development treatment; an infrared-sensitive positive-working planographic printing plate precursor which is formed from the image forming material and has excellent image formability and image region printing durability; and a method for manufacturing a planographic printing plate using the planographic printing plate precursor. The image forming material includes; on a support, a lower layer containing a polymer having carboxylic acid groups at side chains thereof, at least a part of the carboxylic acid groups forming a salt structure with a monovalent basic compound, and an infrared absorbing agent; and an upper layer whose solubility to aqueous alkaline solution is increased by heat, in this order.
本发明提供了一种红外敏感的正向成像材料,其具有出色的开发宽容度、图像成形性和图像区域强度,在图案曝光后到开发处理之间即使经过一定时间,也能防止开发性能的降低;一种红外敏感的正向平版印刷版前体,其由该成像材料形成,具有出色的图像成形性和图像区域印刷耐久性;以及使用该平版印刷版前体制造平版印刷版的方法。该成像材料包括:在支撑体上,一个下层,其含有具有
羧酸基侧链的聚合物,其中至少部分
羧酸基与单价碱性化合物形成盐结构,以及一个红外吸收剂;和一个上层,其在热作用下对
水性碱性溶液的溶解度增加,依此顺序。