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Abstract

The present invention provides a support for a lithographic printing plate prepared by cold rolling a sheet while intermediate annealing is omitted to save energy and the number of the cold rolling steps are decreased to simplify the sheet production steps and to give a desired strength of the sheet, and by inhibiting precipitation of Si particles in the substrate to give extremely excellent resistance to ink staining in the nonimage areas during printing, and a process for producing a substrate therefore. The production process comprises homogenization heat-treating an aluminum alloy slab comprising 0.10 to 0.40 wt % of Fe, 0.03 to 0.15 wt % of Si, 0.004 to 0.03 wt % of Cu, and the balance of Al and unavoidable impurities, hot rolling the heat-treated slab, and cold-rolling the hot-rolled strip without intermediate annealing, the cold rolling including a final pass after which the sheet temperature becomes at least the recovery temperature of the sheet and the following rapid cooling, whereby an aluminum alloy substrate for a lithographic printing plate having a content of precipitated Si of up to 30 ppm and a tensile strength of from 145 to 180 MPa is produced. When the aluminum alloy is electrolytically grained and anodically oxidized, the resultant anodic oxide film can contain up to 200/mm.sup.2 of precipitated Si particles having an average particle size of at least 0.5 .mu.m.

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First Claim