g high sensitivity and high printing durability.
The inventors of the present invention have conducted various studies to solve the aforementioned problem and, as a result, found that the drop of the heat of a recording layer is prevented and a hydrophilic/hydrophobic region is formed without decreasing adhesion between a support and a recording layer, for example, by using a material having low thermal conductivity and by providing a layer having the ability to make the surface thereof hydrophilic by using an alkali developing solution or by using a support which itself has such an ability. The present invention was thus completed.
Accordingly, the planographic printing plate of the present invention comprises forming a first layer which is made of an heat-insulating material having a low thermal conductivity and is made hydrophilic by treating using an alkali or a silicate in an alkali developing solution after being exposed and a second layer which is an infrared ray-sensitive recording layer to be changed in alkali developing ability without being abraded by irradiation with infrared rays in this order on a support.
Also, in one embodiment, the planographic printing plate of the present invention uses, as the support, a material made of a low heat-conductive insulating material and having the ability to make the surface thereof hydrophilic by treating using an alkali or a silicate in an alkali developing solution after being exposed and an infrared-sensitive layer which is changed in alkali developing ability by irradiation with infrared rays is disposed on the support.
Here, the thermal conductivity of the above heat-insulating material is 3.0 (Wxc2x7mxe2x88x921xc2x7Kxe2x88x921) or less and preferably 1.0 (Wxc2x7mxe2x88x921xc2x7Kxe2x88x921) or less.
Also, the layer made of a heat-insulating material and provided with a surface to be made hydrophilic preferably has an average thickness ranging from 0.2 to 50 xcexcm. When such a heat-insulating material is used as the support itself, the average thickness of t