Photosensitive lithographic printing plate

#The present invention relates to a photosensitive lithographic printing plate which is suitable for laser drawing and excellent in the development properties and stain resistance in a non-image part and the printing tolerance in an image part.

#It has been a practice to obtain a lithographic printing plate by forming a photosensitive resin layer on a substrate having hydrophilic surface, subjecting the thus obtained photosensitive lithographic printing plate to plane exposure (mask exposure) via a lith film and then removing non-image parts by using a developing solution. Owing to the recent digitalization techniques, however, there have been developed computer to plate (CTP) systems whereby a printing plate is directly exposed, without resort to a lith film, by scanning highly directional light such as laser beams on the printing plate in accordance with digitalized image data. Also, there have been developed photosensitive lithographic printing plates appropriate for these systems.

#As an example of such photosensitive lithographic printing plates appropriate for laser exposure, a photosensitive lithographic printing plate with the use of a photopolymerizable photosensitive layer can be cited. This is because the sensitivity of a photopolymerizable photosensitive layer can be easily elevated by selecting an appropriate initiator or an appropriate initiation system, compared with other existing photosensitive layers. In such a photopolymerizable photosensitive layer, however, high printing tolerance due to the adhesiveness to the substrate mainly in an image part and favorable printing properties and stain resistance in a non-image part can be hardly achieved at the same time. Thus, various attempts have been made to solve this problem.

#The mode of an embodiment of the invention will be illustrated.

#In the photosensitive lithographic printing plate according to the invention, an intermediate layer which contains a low-molecular weight compound having a quaternary ammonium group and an acid anion group in a single molecule is formed on a substrate having hydrophilic surface and a photopolymerizable photosensitive layer is further formed thereon.

#(Intermediate Layer)