Method and apparatus for development of lithographic printing plate precursor
To provide a development system for lithographic printing plate precursors using a neutral developer, capable of preventing the non-image area of the resulting printing plates from being stained. In developing a lithographic printing plate precursor with a neutral developer having a pH of from 5.8 to 8.6, ultrasonic waves and/or an electric current are imparted to the neutral developer.
1. A method for developing a lithographic printing plate precursor that comprises an image-forming layer comprising an unsaturated double-bond containing substance, a graft polymer that has a poly(alkyleneoxide) unit in the side branch thereof, and a photothermal conversion substance, said method comprising:
developing said precursor with a neutral developer having a pH of from 5.8 to 8.6 in combination with a means for removing non-imaged parts of said lithographic printing plate precursor, while said neutral developer is subjected to ultrasonic waves at a frequency of from 10 to 100 kHz and an output of from 10 to 400 W,
wherein the removing means is a brush roller, morton roller, or developer-jetting nozzle.
2. The method of claim 1 , further comprising:
treating said lithographic printing plate precursor in a pretreatment step before developing with a neutral pretreatment liquid having a pH of from 5.8 to 8.6, wherein said neutral pretreatment liquid is subjected to ultrasonic waves, an electric current, or to both.
3. The method of claim 2 wherein both said developer and neutral pretreatment liquid are subjected to ultrasonic waves or to both ultrasonic waves and an electric current.
4. The method of claim 1 wherein image formation in said precursor is accomplished by thermal crosslinking reaction of the unsaturated double bond-containing substance.
5. The method of claim 1 wherein said developer has a pH of from 6 to 8.
6. The method of claim 1 wherein said developer contains an organic solvent in an amount of from 0.1 to 5% based on the total weight of said developer.
7. The method of claim 1 wherein said developer contains a surfactant in an amount of from 0.001 to 5% based on total weight of the developer.
8. The method of claim 2 such that when said neutral pretreatment liquid is subjected to an electric current, an electrolyte is added to said neutral pretreatment liquid in an amount of from 0.01 to 5% based on the mass of the neutral pretreatment liquid, and the electric current is direct current at a voltage of from 1 to 100V and current of from 0.1 to 10 A.
9. The method of claim 1 wherein said lithographic printing plate precursor comprises an overcoat layer over said image-forming layer.
10. The method of claim 1 wherein said developing is carried out on a printer.
11. An apparatus for developing the lithographic printing plate precursor of claim 1 , which comprises:
a development tank containing a neutral developer having a pH of from 5.8 to 8.6 for application to a lithographic printing plate precursor,
a development-promoting means for imparting ultrasonic waves to said neutral developer at a frequency of from 10 to 100 kHz and an output of from 10 to 400 W, and
a removing means for removing non-imaged parts of said lithographic printing plate precursor that is a brush roller, a morton roller, or a developer-jetting nozzle.
12. The apparatus of claim 11 further comprising a pretreatment tank for applying a neutral pretreatment liquid having a pH of from 5.8 to 8.6 to the lithographic printing plate precursor before development, and
wherein said development-promoting unit is designed for imparting ultrasonic waves or an electric current to said neutral pretreatment liquid.
13. The method of claim 1 wherein said removing means is a brush roller or a morton roller.