| 摘要 |
PROBLEM TO BE SOLVED: To obtain a negative direct writing-type waterless lithographic printing plate excellent in plate durability and image reproducibility with an ink mileage kept good by anode-oxidizing the surface of an aluminum substrate in an original plate of a direct writing-type lithographic printing plate in which a thermosensible layer and an ink repelling layer are formed on the aluminum substrate. SOLUTION: In the original plate of a direct writing-type lithographic printing plate in which at least a thermosensible layer and an ink repelling layer are formed in this order on an aluminum substrate, the surface of the substrate is anode-oxidized. In order to abode-oxidize the surface of the substrate, a high voltage is applied to an original plate in an electrolyte solution. A compound which is decomposed by being irradiated with laser beams or a thermosetting compound is preferably added into the thermosensible layer. A silicone rubber layer is preferable as the ink repelling layer. As the silicon rubber layer, either an addition polymerization type or a condensation polymerization type can be used. In this way, a negative direct writing-type lithographic printing plate excellent in plate durability and image reproducibility is obtained.
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