Method for treating photosensitive lithographic printing plate
View Patent ↗A method for treating a photosensitive lithographic printing plate, which comprises exposing the photosensitive lithographic printing plate to laser light, developing with a developer containing an alkali metal silicate and then carrying out post-exposure treatment, said photosensitive lithographic printing plate being prepared by forming a photopolymerizable photosensitive layer having a film thickness of from 1.2 to 4 g/m 2 and further forming a protective layer having a film thickness of from 2 to 8 g/m 2 on a support having a centerline average height (Ra) of at least 0.35 μm.
1. A method for treating a photosensitive lithographic printing plate, which comprises exposing the photosensitive lithographic printing late to laser light, developing and then carrying out post-exposure treatment at a light intensity of from 20 to 700 mW/cm 2 on a surface to be exposed at the time of the post-exposure treatment, said photosensitive lithographic printing plate being prepared by forming a photosensitive layer comprising a photopolymerizable composition containing ethylenic compound, a photopolymerization initiator and a high molecular binder on the surface of a support.
2. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the light intensity on the surface to be exposed at the time of post-exposure is at least 50 mW/cm 2 .
3. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the temperature on the surface to be exposed at the time of post-exposure is from 40 to 300° C.
4. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein a mercury lamp is used as a light source for post-exposure.
5. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the photopolymerization initiator contains titanocenes as a radical-generating agent.
6. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the photopolymerization initiator contains a photosensitizes having an absorption in a visible light zone.
7. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the high molecular binder contains a polymer having an ethylenic unsaturated bond on a side chain.
8. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the photosensitive lithographic printing plate further has a protective layer formed on the photosensitive layer comprising the photopolymerizable composition.
9. The method for treating a photosensitive lithographic printing plate according to claim 8 , wherein the support has a centerline average height (Ra) of at least 0.35 μm, and the photosensitive layer has a film thickness of from 1.2 to 4 g/m 2 , and the protective layer has a film thickness of from 2 to 8 g/m 2 .
10. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the developing treatment is carried out by using a developer containing an alkali metal silicate.
11. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein the developing treatment is carried out by using a developer having a pH value of at most 12.
12. The method for treating a photosensitive lithographic printing plate according to claim 1 , wherein said light intensity is from 20 to 500 mW/cm 2 .
13. The method for treating a photosensitive lithographic printing plate according to claim 12 , wherein said light intensity is from 20 to 300 mW/cm 2 .