| abstract |
Objects of the present invention are to provide a positive working presensitized plate of a thermal type, which has damage resistance, and which is handled easily in conventional operation, high in sensitivity and excellent in press life when used as a lithographic printing plate, and to provide a support for a lithographic printing plate, which is suitably used for the same. The objects have been achieved by a support for a lithographic printing plate obtained by performing graining treatment, alkali etching treatment and anodizing treatment on an aluminum plate, wherein a ratio of a real area of a surface thereof to an apparent area of the surface set larger by 1.3 to 1.8 times, comprising a pit having an average diameter of 0.3 to 1.0 mum and a micro grained structure inside on the surface, wherein a ratio of an apparent area of the pits to the apparent area of the surface is 90% or more; and a presensitized plate comprising the support for a lithographic printing plate and a photosensitive layer that can become alkali-soluble by heating provided on the support. |