| 摘要 |
PURPOSE:To obtain an offset printing plate capable of giving positive image on its plate by using a system in which thermal printing is made on a lithographic printing plate formed by providing a layer containing a colorless basic dye, a developer, a heat-meltable substance, and a specific hydrophilic binder on a water-resistant supporter. CONSTITUTION:A paint liquid, obtained by dispersing a heat-sensitive element composed of a colorless basic dye (e.g., crystal violet lactone) and a developer (e.g., 4,4-isopropylidene diphenol), a heat-meltable substance (e.g., paraffin wax) of a grain size of 0.1-10mum and a melting point of 60-180 deg.C, and acetoacetylated polyvinyl alcohol as a hydrophilic binder, together with a pigment (e.g., clay) as needed, in an aqueous medium, is coated on a supporter and dried to obtain a lithographic printing plate. Thermal printing is made on the lithographic printing plate by using a thermal printer, e.g. thermal facsimile, etc., to obtain an offset printing plate having a positive image formed by color forming reaction of the colorless basic dye and the developer on the printing plate. |
