Abstract:
Presensitized planographic printing plate for use in dry planography. A positive acting plate having a flexible base and a relatively thick (0.02 to 2.00 mil) silicone rubber layer, overlying a photo-polymerizable and photoadhesive-layer. Upon exposure to light through a positive transparency, the photoadhesive layer in the exposed non-image area polymerizes and adheres firmly to the thick silicone rubber overlayer, but the photoadhesive layer in the unexposed image area remains nonadhesive to the silicone overlayer. Following the exposure, the surface of the plate is treated with developing liquid capable of swelling silicone rubber. The thick silicone rubber layer in the unexposed image area is easily removed, exposing a sharp image of oleophilic photoadhesive layer underlying the removed silicone layer, while the silicone rubber layer in the exposed background area remains bound to the photoadhesive underlayer. The exposed surface of the photoadhesive layer accepts ink from inking rollers, while the silicone rubber background area does not remove ink from the rollers, and thus remains ink-free.