Patent ID: 8338073

Claim:
A method of preparing a lithographic printing plate support comprising the steps of: filtering an aluminum alloy melt containing iron, silicon, titanium and boron, downstream from the position where the titanium and boron are added in the form of TiB 2 to an aluminum melt; producing an aluminum alloy plate from the aluminum melt, wherein the aluminum alloy has a surface layer of up to 20 μm from the surface that is free of TiB 2 particles or contains TiB 2 particles at least 95% of which have a width of less than 100 μm, and has crystal grains present in the surface layer having an average width of 20 to 200 μm and a maximum width of at most 2,000 μm; and carrying out a graining treatment comprising at least alkali etching and subsequent electrochemical graining on the surface of the aluminum alloy plate so that after the graining treatment, the iron concentration and a silicon concentration in the surface layer up to 20 μm from the surface of the plate each show a fluctuation of not more than 20%, wherein a difference of the concentration in high-concentration and low-concentration areas to the concentration in the low-concentration areas determined by EPMA as follows: Fluctuation(%)=100×[( PC s )−( PC BA )]/( PC BA ) wherein (PC s )=(peak count for streaks) and (PC BA )=(peak count for blank areas).