Planographic printing plate

A planographic printing plate precursor comprising:

• an aluminum substrate which has been subjected to a roughening treatment and an anodizing treatment;
• and
• a photosensitive layer which is provided on a surface of said substrate, and which contains an infrared absorbing agent and a water-insoluble and alkali aqueous solution-soluble polymer compound, and whose solubility in an alkali developing solution varies by infrared laser exposure,
• wherein said substrate is obtained by electrochemically roughening an aluminum alloy plate which contains 0.05 to 0.5% by weight of Fe, 0.03 to 0.15% by weight of Si, 60 to 300 ppm of Cu, 100 to 400 ppm of Ti and 10 to 200 ppm of Mg, contains 1 to 100 ppm of at least one element selected from the group of elements consisting of Li, Na, K, Rb, Cs, Ca, Sr, Ba, Sc, Y, Nb, Ta, Mo, W, Tc, Re, Ru, Os, Co, Rh, Ir, Pd, Pt, Ag, Au, C, Ge, P, As, S, Se, Te and Po, and has an aluminum purity of 99.0% by weight or more wherein a reverse surface of said substrate has different average surface roughnesses Ra along a longitudinal direction and a transverse direction, and given that the average surface roughness Ra along a direction of larger average surface roughness is represented by Ral and the average surface roughness Ra along a direction of smaller average surface roughness is represented by Ras, Ral and Ras satisfy the following relational formula:
• 1.1≦Ral/Ras ≦5.0.

A planographic printing plate precursor comprising:

• an aluminum substrate which has been subjected to a roughening treatment and an anodizing treatment;
• and
• a photosensitive layer which is provided on a surface of said substrate, and which contains an infrared absorbing agent, a water-insoluble and alkali aqueous solution-soluble polymer compound, and whose solubility in an alkali developing solution varies by infrared laser exposure,
• wherein said substrate is obtained by electrochemically roughening an aluminum alloy plate which contains 0.05 to 0.5% by weight of Fe, 0.03 to 0.15% by weight of Si, 60 to 300 ppm of Cu, 100 to 400 ppm of Ti and 10 to 200 ppm of Mg, contains 1 to 100 ppm of at least one element selected from the group of elements consisting of K, Rb, Cs, Ca, Sr, Ba, Sc, Y, Nb, Ta, Mo, W, Tc, Re, Ru, Os, Co, Rh, Ir, Pd, Pt, Ag, Au, C, Ge, P, As, S, Se, Te and Po, and has an aluminum purity of 99.0% by weight or more,
• wherein micropores present in an anodized film on said substrate have a pore diameter of 1 to 5 nm and a pore density of 8×1015 to 2×1016/m2.