Positive-type light-sensitive lithographic printing plate

摘要

A positive-type light-sensitive lithographic printing plate comprising a grained and anodized aluminum plate having formed on the surface thereof a layer of a light-sensitive composition containing a) an o-naphthoquinonediazide compound, b) an alkaline water-soluble and water-insoluble resin, c) a compound which generates an acid by light, d) a blue dye the tone of which is changed with an acid, and e) a yellow dye having a specific structure and the absorbance of which at 417 nm is at least 70% of the absorbance at 436 nm. The light-sensitive lithographic printing plate has a high sensitivity and, wherein unnecessary images of the edge portions of film are difficult to form on the plate at the reproduction of dots, the image-visibility after exposure and the suitability for plate inspection after development are good, and register marks are easy to see.