Lithographic printing plate discarded plate precursor, a lithographic printing plate discarded plate precursor aggregate, and a method for making a plate discarded for a lithographic printing plate

摘要

PROBLEM TO BE SOLVED: To provide a key original plate for planographic printing plates, which is superior in retainability of a matting agent, flaw resistance, properties of preventing adhesion between the key original plates for planographic printing plates, and setter conveyability, and which has color sensor suitability and which hardly leaves behind colors after developed, and to provide a cumulative body of the key original plates and a plate-making method of a key plate by using the key original plate.;SOLUTION: The key original plate for planographic printing plates has a non-photosensitive layer and a hydrophilic layer in this order on an aluminum support, contains a colorant having the absorption maximum within 350-550 nm in the non-photosensitive layer and/or the hydrophilic layer, and contains the matting agent in the hydrophilic layer. The cumulative body of the key original plates is obtained by layering a plurality of the key original plates on one another directly without using inserting paper. The plate-making method of the key plate for planographic printing plates comprises a key original plate preparation step of preparing the key original plate and a development step of developing the key original plate by an alkaline developer to obtain the key plate.;COPYRIGHT: (C)2012,JPO&INPIT