| 摘要 |
PROBLEM TO BE SOLVED: To suppress the damage of an irradiated part in a developing step as well as to remove an unirradiated part by exposing an original plate with a photosensitive layer containing a negative type photosensitive composition with IR laser and carrying out development with an alkali developer containing a nonreducing sugar and a base. SOLUTION: A planographic printing original plate with a photosensitive layer formed by applying a negative type photosensitive composition for IR laser on a hydrophilic substrate is imagewise exposed with IR laser. In a developing step, the unexposed part is dissolved in an alkali developer and removed, and the exposed part remains. The alkali developer contains at least on nonreducing sugar and at least one base. By using the alkali developer the photosensitive composition in the unexposed part is thoroughly removed, the cured negative type photosensitive composition in the exposed part remains without deterioration and the adhesion of the photosensitive layer is kept in a good state. |
