Method for postbaking a lithographic printing plate
A method for making a lithographic printing plate is disclosed wherein the method comprises the steps of: (i) providing a lithographic printing plate precursor comprising a photosensitive coating on a substrate having a hydrophilic surface, (ii) image-wise exposing said photosensitive coating, (iii) developing said exposed coating to form an image on said substrate and optionally gumming the plate and (iv) baking the image on the plate, wherein said baking step is carried out within a dwell-time of less than 1 minute and wherein the chemical resistance of the coating against printing liquids and press chemicals is improved. This baking step is preferably carried out by exposing the printing plate to an infrared radiation source, preferably in a dynamic configuration.
1 . Method for making a lithographic printing plate comprising the steps of
providing a lithographic printing plate precursor comprising a photosensitive coating on a substrate having a hydrophilic surface,
image-wise exposing said photosensitive coating,
developing said exposed coating to form an image on said substrate and optionally gumming the plate,
baking the image on the plate,
characterised in that said baking step is carried out within a dwell-time of less than 1 minute.
2 . Method according to claim 1 wherein said baking step is carried out by exposing the printing plate to an infra-red radiation source.
3 . Method according to claim 2 wherein said infra-red radiation source is a near infra-red lamp or a middle infra-red lamp.
4 . Method according to claim 2 wherein said baking step is carried out by the following steps:
radiating by an infra-red source, and
transporting said printing plate relatively to said radiation source.
5 . Method according to claim 1 wherein said photosensitive coating comprises an infra-red absorbing compound.
6 . Method according to claim 5 wherein said infra-red absorbing compound has an absorption maximum between 750 nm and 3000 nm.
7 . Method according to claim 1 wherein said photosensitive coating is an infra-red sensitive coating.
8 . Method according to claim 1 wherein said printing plate is isolated to prevent heat conduction to the environment.
9 . Method according to claim 2 wherein said baking step is carried out by exposing the printing plate to an infra-red radiation source combined with an ultraviolet radiation source.
10 . Method according to claim 1 wherein said substrate, having a hydrophilic surface, is an anodised aluminum plate.
11 . Apparatus for baking an image obtained after developing an image-wise exposed photosensitive coating on a substrate having a hydrophilic surface, said apparatus comprising an infra-red radiation source, characterised in that said infra-red radiation source is a near infra-red lamp or a middle infra-red lamp.
12 . Processor for developing a lithographic printing plate comprising the apparatus according to claim 11.