ANIONIC INFRARED ABSORBENT, PHOTOSENSITIVE COMPOSITION AND LITHOGRAPHIC ORIGINAL PLATE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To obtain a new anionic infrared absorbent having absorption in long wavelength capable of preferably using for an image forming material and capable of providing a photosensitive composition for infrared laser for direct plate making having good development latitude in high sensitivity. SOLUTION: This anionic infrared absorbent is represented by formula I [L is a methine chain having >=7 conjugated carbon atom number; X+ is a cation; and Y1 to Y6 and Z1 to Z6 are each H or a substituent group], e.g. a compound of formula II. The compound of formula II is obtained by adding triethylamine to a beaker in which a compound of formula III, a compound of formula IV and methanol are charged, reacting these compounds under stirring and carrying out salt exchange of the resultant compound. Another objective photosensitive composition is obtained by including an anionic infrared light absorbent of formula V [M is >=7C conjugated chain; Ga is an anionic substituent group; Gb is a neutral substituent group; Xm+ is 1 to m-valent cation including proton; and (m) is 1-6] and a polymer compound insoluble in water and soluble in an alkaline aqueous solution. The photosensitive composition becomes soluble in the alkaline aqueous solution by irradiation of infrared laser.