| abstract |
Lithographic printing plates of aluminum or aluminum alloys are provided with an anodized surface layer, to which a photosensitive layer may be directly applied, which displays excellent adhesion and durability in use. For this purpose, anodization is carried out with an aqueous solution containing a polybasic mineral acid such as sulfuric and a higher concentration of a polybasic aromatic sulfonic acid containing at least one additional nuclear acidic substituent, preferably two, selected from the group consisting of a carboxylic acid group and a phenolic hydroxyl group. |