Patent ID: 7232645

Claim:
A support for a lithographic printing plate obtained by performing graining treatment including electrochemical graining treatment on an aluminum plate, wherein said aluminum plate is an aluminum plate which is manufactured by a method including molten metal treatment, and contains Fe of 0.20 to 0.29 wt %, Si of 0.03 to 0.15 wt %, Cu of 0.032 to 0.040 wt % and Ti of 0.050 wt % or less and whose remaining portion is composed of Al and unavoidable impurities, and wherein surface area ratio and steepness obtained from three-dimensional data by measuring 512×512 points in 5 μm×5 μm on the surface with an atomic force microscope each satisfies the following conditions (i) to (vi): (i) surface area ratio ΔS 5 is 30 to 70%; (ii) surface area ratio ΔS 5(0.2-5) is 10 to 30%; (iii) surface area ratio ΔS 5(0.02-0.2) is 30 to 70%; (iv) steepness a45 5 is 20 to 50%; (v) steepness a45 5(0.2-5) is 5 to 20%; and (vi) steepness a45 5(0.02-0.2) is 20 to 60%, wherein ΔS 5 which is found by the following equation from actual area S x 5 found by an approximation three-point method from said three-dimensional data and geometrically measured area S 0 5 is surface area ratio expressed by ΔS 5 =[(S x 5 −S 0 5 )/S 0 5 ]×100(%); ΔS 5(0.2-5) which is found by the following equation from actual area S x 5(0.2-5) obtained by extracting a component with wavelength of 0.2 μm or longer and 5 μm or shorter from said three-dimensional data and geometrically measured area S 0 5 is surface area ratio expressed by ΔS 5(0.2-5) =[(S x 5(0.2-5) −S 0 5 )/S 0 5 ]×100(%); ΔS 5(0.02-0.2) which is found by the following equation from actual area S x 5(0.02-0.2) obtained by extracting a component with wavelength of 0.02 μm or longer and 0.2 μm or shorter from said three-dimensional data and geometrically measured area S 0 5 is surface area ratio expressed by ΔS 5(0.02-0.2) =[(S x 5(0.02-0.2) −S 0 5 )/S 0 5 ]×100(%); steepness a45 5 is an area rate of a portion (area) having a slant with size of angle of 45° or bigger (gradient of 45° or bigger) to actual area S x 5 found by approximation three-point method from said three-dimensional data; steepness a45 5(0.2-5) is an area rate of a portion (area) having a slant with size of angle of 45° or bigger (gradient of 45° or bigger) to actual area S x 5(0.2-5) found by extracting a component with wavelength of 0.2 μm or longer and 5 μm or shorter from said three-dimensional data; and steepness a45 5(0.02-0.2) is an area rate of a portion (area) having a slant with size of angle of 45° or bigger (gradient of 45° or bigger) to actual area S x 5(0.02-0.2) found by extracting a component with wavelength of 0.02 μm or longer and 0.2 μm or shorter from said three-dimensional data.