| 摘要 |
PROBLEM TO BE SOLVED: To provide a platemaking method of a lithographic printing machine in which solution resistance of a non-exposure part (image part) and solubility of an exposure part (non-image part) are made compatible by using alkali aqueous solution with pH suppressed as low for development processing.SOLUTION: A platemaking method of a lithographic printing machine includes: an exposure process of performing image exposure of a positive type lithographic printing original plate having a positive type recording layer which contains polymer containing a structural unit derived from (meta) acrylonitrile and a structural unit derived from styrene, water-insoluble and alkali-soluble resin, and an infrared adsorbent, and whose solubility to alkali aqueous solution is improved by infrared exposure by infrared rays; and a development process of developing the lithographic printing original plate after exposure by using the alkali aqueous solution containing ammonium salts and a betaine ampholytic surface active agent to be expressed by the following general formula (I), and with pH of 8.5-10.8 in this order on a support. In the general formula (I), R-Rindependently express alkyl groups, etc., respectively, and the total of the number of carbons which R-Rhave does not exceed 20. Xrepresents against anion. |
