Photosensitive composition

#1. Field of the Invention

#The present invention relates to a photopolymerizable composition hardenable by exposure to infrared light, and more particularly to an infrared sensitive composition adapted for use in a recording layer of a negative printing plate precursor.

#2. Description of the Related Art

#In the following, the present invention will be clarified in more details by examples thereof, but the scope of the invention is not limited by such examples.

#Preparation of Aluminum Support

#A molten metal of a JIS A1050 alloy, containing 99.5% or higher of aluminum, 0.30% of Fe, 0.10% of Si, 0.02% of Ti and 0.013% of Cu, was subjected to a purifying process and cast. The purifying process was conducted by a degassing in order to eliminate unnecessary gas such as hydrogen in the molten metal, and by a ceramic tuber filtration. The casting was conducted by a DC casting. A solidified ingot of a thickness of 500 mm was surfacially scraped off by 10 mm from the surface, and was subjected to a homogenization process for 10 hours at 550° C. in order to avoid rough growth of intermetallic compounds. It was then subjected to a hot rolling at 400° C., an intermediate annealing for 60 seconds at 500° C. in a continuous annealing furnace, and a cold rolling to obtain a rolled aluminum plate of a thickness of 0.3 mm. A roughness of rolling rollers was so controlled as to obtain a center line average height Ra of 0.2 μm after the cold rolling. Thereafter, a process by a tension leveler was executed in order to improve the flatness.