| 摘要 |
A positive photosensitive lithographic printing plate which is capable of being operated under white light containing ultraviolet light, said printing plate comprising on a support a positive photosensitive composition which shows, upon scanning exposure to light in the wavelength range from 650 to 1100 nm, a difference in solubility in an alkali developer between an exposed portion and a non-exposed portion, characterized in that said composition comprises (i) a dye which absorbs said light, (ii) an alkali-soluble resin which is a novolak resin, a resol resin, a poly-vinylphenol resin or a copolymer of an acrylic acid derivative, and (iii) a solubility-suppressing agent which is capable of lowering the dissolution in an alkaline developer of a blend comprising the dye and the alkali-soluble resin,
with the proviso that the composition does not comprise an onium salt and that the solubility-suppressing agent is not selected from the group consisting of a quinolinium compound, a benzothiazolium compound, a pyridinium compound and an imidazoline compound.
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