Patent ID: 7037635

Claim:
A presensitized plate, comprising: a support of a lithographic printing plate including concave pits having an average opening diameter of 20–300 nm and an average ratio of a depth of the concave pit to an opening diameter of the concave pit (pit depth/pit diameter) ranging from 0.15 to 1.0 formed by electrochemical roughening treatment in an aqueous solution of nitric acid and/or electrochemical roughening treatment in an aqueous solution of hydrochloric acid on the surface of an aluminum plate containing 0.15–0.5 wt % of Fe; 0.03–0.15 wt % of Si; 0.003–0.050 wt % of Ti, 0.002–0.015 wt % of Cu and 0.001–0.1 wt % of Mg and having an aluminum purity of not less than 99 wt %; and a photosensitive layer formed on the surface of said aluminum plate, wherein a fatigue fracture strength of the presensitized plate after a heat treatment at 300° C. for 7 minutes is not less than 75% of the fatigue fracture strength thereof before the heat treatment.