ALUMINUM PLATE MATERIAL FOR LITHOGRAPHIC PRINTING PLATE

摘要

PROBLEM TO BE SOLVED: To provide an aluminum plate material for a lithographic printing plate in which blister caused by aluminum carbide mixed in the aluminum material is not produced when it is used as an original plate for the lithographic printing plate.

SOLUTION: The aluminum plate material for the lithographic printing plate is characterized in that the existing number of the aluminum carbide with a circle equivalent diameter of≥3μm measured by the PoDFA (porous disc filtration apparatus) method is≤4. The measurement of the existing number of the aluminum carbide with the circle equivalent diameter of≥3μm by the PoDFA method is performed by: dissolving 3,000 g of the aluminum plate material for the lithographic printing plate in a crucible in an electric furnace; filtrating 2,000 g of the obtained molten aluminum with an exclusive filter; solidifying 1,000 g of the molten aluminum while it is left on the exclusive filter; and observing the aluminum carbide in the inclusions in the molten aluminum accumulated on the filter top face by a microscope with respect to the central part (14 mm×10 mm) of a diameter longitudinal section of the coagulated molten aluminum by the height of 10 mm on the filter as an observation face.

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