公开(公告)号：US5250393A

公开(公告)日：1993-10-05

申请号：US808607

申请日：1991-12-17

申请人： Masanori Imai, deceased ,  Keiji Akiyama ,  Tadao Toyama ,  Akinobu Koike

发明人： Masanori Imai, deceased ,  Keiji Akiyama ,  Tadao Toyama ,  Akinobu Koike

IPC分类号： G03F7/32 ,  G03F7/30 ,  G03F7/021

CPC分类号： G03F7/322

摘要： A method for preparinq a lithographic printing plate comprising the steps of imagewise exposing, to light, a negative-working presensitized plate for use in making a lithographic printing plate which comprises a substrate provided thereon with a light-sensitive layer comprising an aromatic diazonium compound having at least one member selected from the group consisting of carboxyl groups, phenolic hydroxyl groups, sulfonic acid residues, sulfinic acid residues and phosphorus atom-containing oxyacid residues and developing the imagewise exposed presensitized plate with a developer which comprises an aqueous solution of an alkali metal or ammonium silicate having a ratio: [SiO.sub.2 ]/[M], wherein [SiO.sub.2 ] and [M] represent the molar concentrations of SiO.sub.2 and the alkali metal or ammonia in the developer respectively, ranging from 0.15 to 0.75 and an SiO.sub.2 content ranging from 1.0 to 4.0% by weight on the basis of the total weight of the developer to remove the unexposed portion of the light-sensitive layer.The method for preparing lithographic printing plate makes it possible to treat both negative- and positive-working presensitized plates with a single developer and a single automatic developing machine and can provide a lithographic printing plate having excellent printing durability and free of background contamination. Moreover, the replenisher for developer of the present invention permits repeated development process over a long time period without deteriorating the developability thereof and makes it possible to perform developing process without accompanying any formation of deposits due to the light-sensitive resin components at the bottom of a developing bath.