Abstract: A presensitized plate in which an image recording layer is formed on a support for a lithographic printing plate obtainable by performing a treatment with an aqueous solution containing one or more divalent or multivalent cations at a concentration ranging from 0.0001 mol/L to less than 0.020 mol/L is excellent in both scum resistance and press life when processed into a lithographic printing plate.

Abstract: The present invention relates to a planographic printing plate precursor, in which an intermediate layer comprising a polymer having a lactone group and a recording layer are successively provided on or over a support. The polymer preferably has not only the lactone group but also an acidic group.

Abstract: The present invention provides a planographic printing plate precursor having an intermediate layer containing a polymer having a structure represented by the formula (I) at its side chain and an infrared laser photosensitive positive recording layer, disposed on a support in this order. In the formula (I), Y represents a connecting group connected with a main chain of the polymer, R1 represents a hydrogen atom or a hydrocarbon group and R2 represents a divalent hydrocarbon group.

Abstract: The present invention relates to a planographic printing plate precursor, in which an intermediate layer comprising a polymer having a lactone group and a recording layer are successively provided on or over a support. The polymer preferably has not only the lactone group but also an acidic group.

Abstract: A presensitized plate in which an image recording layer is formed on a support for a lithographic printing plate obtainable by performing a treatment with an aqueous solution containing one or more divalent or multivalent cations at a concentration ranging from 0.0001 mol/L to less than 0.020 mol/L is excellent in both scum resistance and press life when processed into a lithographic printing plate.

Abstract: Decrease in sensitivity can be avoided to obtain a stable and highly sensitized photosensitive layer in a process for preparing a photopolymerizing lithographic plate including a coating step and using rubber rollers before and after the coating site. This is achieved by excluding an antioxidant and/or aging retardant from at least the surface of rubber rollers placed before and after the coating site. The photopolymerizing lithographic plate excellent in its sensitivity as compared with the conventional one can be obtained.

Abstract: Decrease in sensitivity can be avoided to obtain a stable and highly sensitized photosensitive layer in a process for preparing a photopolymerizing lithographic plate including a coating step and using rubber rollers before and after the coating site. This is achieved by excluding an antioxidant and/or aging retardant from at least the surface of rubber rollers placed before and after the coating site. The photopolymerizing lithographic plate excellent in its sensitivity as compared with the conventional one can be obtained.

Abstract: Decrease in sensitivity can be avoided to obtain a stable and highly sensitized photosensitive layer in a process for preparing a photopolymerizing lithographic plate including a coating step and using rubber rollers before and after the coating site. This is achieved by excluding an antioxidant and/or aging retardant from at least the surface of rubber rollers placed before and after the coating site. The photopolymerizing lithographic plate excellent in its sensitivity as compared with the conventional one can be obtained.

Abstract: A support for a lithographic printing plate having a corrugated surface processed by roughening, wherein the corrugation on the support surface comprises big corrugation having an average pitch of from not less than 5 .mu.m to not more than 30 .mu.m, and middle corrugation superimposed on the big corrugation, the middle corrugation comprising honeycomb pits having an average diameter of from not less than 0.5 to not more than 3.0 .mu.m, and the support surface has a surface inclination distribution which comprises an inclination of not less than 30 degrees in a proportion of from not less than 5% to not more than 20% as determined by an atomic force microscope. A process for the preparation of the support and an electrolytic treatment apparatus for the process are also described.