| 摘要 |
PROBLEM TO BE SOLVED: To obtain an original plate for a negative direct lithographic printing plate having good image reproducibility by sequentially providing a heat sensitive layer containing a compound made of an at least polymethine pigment and capable of being decomposed by irradiating with a laser and a thermosetting compound, and an ink repellant layer on a base plate. SOLUTION: A compound capable of being decomposed by irradiating with a laser is made of at least a polymethine pigment near infrared absorption pigment to efficiently absorb a near infrared laser beam and to convert it into a heat, and as the compound, a carbon black is preferably used from views of its photothermal conversion rate, economy and handleability. As a thermosetting compound, a phenol resin or the like is used, the compound decomposed by a laser beam, and curing of the compound is proceeded in a heat sensitive layer. As an ink repellant layer, a hydrophilic layer made of a vinyl alcohol or the like or a silicone rubber layer or the like can be used. A negative waterless lithographic printing plate in which only the repellant layer of the part irradiated with the laser beam is removed is obtained. |
