| 摘要 |
A positive-working lithographic printing starting plate for an infrared laser is provided that includes a support having a hydrophilic surface and a heat-sensitive layer provided above the support. The heat-sensitive layer includes a water-insoluble and alkali-soluble resin, an infrared-absorbing dye, and a sulfonium salt represented by Formula below. The heat-sensitive layer increases its solubility in aqueous alkaline solution upon exposure to an infrared laser. (In the formula, R1 and R2 independently denote an optionally substituted alkyl group having 1 to 12 carbons, an optionally substituted cycloalkyl group having 3 to 8 carbons, an optionally substituted aralkyl group having 7 to 12 carbons, or an optionally substituted aryl group having 6 to 15 carbons, R1 and R2 may bond to each other to form a cyclic structure; Ar denotes an optionally substituted aromatic hydrocarbon group having 6 to 15 carbons and having at least one OH group at the ortho- and/or para-position; and X<-> denotes an anion of an organic acid.)
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