Planographic printing plate

摘要

A planographic printing plate precursor comprising:an aluminum substrate which has been subjected to a roughening treatment and an anodizing treatment; and a photosensitive layer which provided on a surface of said substrate, and which contains an infrared absorbing agent and a water-insoluble and alkali aqueous solution-soluble polymer compound, and whose solubility in an alkali developing solution varies by infrared laser exposure, wherein said substrate is obtained by electrochemically roughening an aluminum alloy plate which contains a trace amount of certain elements to an aluminum alloy of high purity.