To obtain a compsn. which has excellent printing durability and maintains good visible image property after development and which enables formation of an image by exposure to IR rays such as inexpensive compact semiconductor laser without using UV rays as an exposing means, by incorporating an acid-decomposable compd. which changes into alkali-soluble in the presence of acid. an alkali-soluble resin, an acid producing agent, an IR-absorbing dye and a pigment.

This compsn. contains an acid-decomposable compd. which changes into alkali-soluble in the presence of acid, an alkali-soluble resin, an acid producing agent, an IR-absorbing dye and a pigment. The acid- decomposable compd. is expressed by formula. In the formula, R1 to R4 are hydrogen atoms, alkyl groups, etc., and two of R1 to R4 may be bonded to form a ring. The compsn. contains a crosslinking agent which can crosslink with an alkali-soluble compd. in the presence of acid, and this crosslinking agent preferably has methylol groups or acetylated methylol groups. As for the pigment, a pigment selected from phthalocyanine and carbon black is preferable in order to improve the printing durability and to obtain the visibility of an image after development.