To provide a manufacturing method of a substrate for a lithographic plate which reduces a severe ink stain or the like and can be manufactured at a low cost even when a raw material wherein components of very small amounts are segregated and aluminum crystal grains are exposed is used.
The substrate for the lithographic plate is manufactured from an aluminum alloy sheet W. When the aluminum exposed on the surface of the aluminum alloy sheet W has a prescribed size and an electrochemical surface roughening treatment is applied to the aluminum alloy sheet W, the existence rate of Cu exposed on the surface of the aluminum alloy sheet becomes 5 (mm2/m2) or above. In the present manufacturing method of the substrate for the lithographic plate, the treatment comprising at least the following processes (1) and (2) is applied sequentially to this aluminum alloy sheet W. (1) A hydrochloric acid electrolytic treatment process wherein the electrochemical surface roughening treatment is conducted in a hydrochloric acid solution by using an alternating current in an electrical quantity of 1-300 C/dm2. (2) A sulfuric acid electrolytic treatment process wherein the electrochemical surface roughening treatment is conducted in a sulfuric acid solution by using the alternating current.
MASUDA YOSHITAKA
SAWADA HIROKAZU
UESUGI AKIO
