| 摘要 |
A positive-working printing plate precursor for wet lithographic printing comprises a support and a coating comprising a first layer containing oleophilic phenolic resin soluble in aqueous alkaline developer, and second layer containing amphyphilic polymer. The second layer is capable of preventing the aqueous alkaline developer from penetrating into the first layer. A positive-working printing plate precursor for wet lithographic printing comprises a support having a hydrophilic surface and a coating comprising a first layer closest to the support and containing oleophilic phenolic resin soluble in aqueous alkaline developer, and second layer containing amphyphilic polymer. The second layer is capable of preventing the aqueous alkaline developer from penetrating into the first layer to an extent that no dissolution of unexposed coating occurs upon immersion in the aqueous alkaline developer during a time t2. The capability of the second layer to prevent the aqueous alkaline developer from penetrating into the first layer is reduced upon exposure to heat or light to an extent that complete dissolution of exposed coating occurs upon immersion in the aqueous alkaline developer during a time t1, where t2 is greater than t1 and t2-t1 is at least 10 seconds. The amphyphilic polymer is a block- or graft-polymer comprising poly(alkylene oxide) block and a block comprising siloxane and/or perfluorohydrocarbon units. An independent claim is also included for a method of making a lithographic printing plate comprising image-wise exposure of a lithographic printing plate precursor and subsequent processing by immersing the precursor in the aqueous alkaline developer during a time between t1 and t2. |
