| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a positive-working planographic printing original plate which enables direct platemaking by scanning exposure to IR laser light or the like based on digital signals and which has excellent plate wear and chemical resistance. <P>SOLUTION: An image recording layer containing (A) a novolac resin and (B) a photothermal conversion agent and increasing its solubility with an alkaline aqueous solution by IR laser exposure is formed on a hydrophilic support body. The novolac resin (A) has ≥500 and ≤3,000 weight average molecular weight (Mw) in terms of polystyrene obtained by gel permeation chromatography (GPC) using monodispersion polystyrene as the reference and ≤1.7 dispersion degree (Mw/Mn), or ≥3,000 and ≤4,500 Mw and ≤2.0 Mw/Mn, or ≥4,500 and ≤10,000 Mw and (Mw/Mn)≤[(4 Mw-1,500)/5500]. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
