Positive type photosensitive composition

Abstract

Abstract PURPOSE:To obtain a positive type photosensitive composition for a lithographic plate with high sensitivity and giving a visible image easy to discriminate by mixing a specified sulfophthalein pH indicator and a basic substance soluble in org. solvent into an o-quinone diazide photosensitizer. CONSTITUTION:A photosensitive soln. is prepared by mixing a sulfophthalein pH indicator represented by the formula (where each of A1-A4 is denoted by H or halogen and each of R1-R4 and R1'-R4' is H, halogen or lower alkyl) and a basic substance soluble in org. solvent into an o-quinone diazide photosensitizer such as o-naphthoquinone diazidosulfonate. The soln. is applied to an Al plate for a lithographic plate, dried, and contact exposed through a positive film. The color of exposed part turns into light-yellow and is clearly discriminated from the unexposed part in color with yellow safe light. Accordingly, locating can be made easily in superposition printing of many-sided printing in a printing or plate making process.

Inventors

• 👤 Takateru Asano

Bibliographic Details