Lithographic printing original plate

Abstract

A presensitized plate having a long press life and excellent resistance to scum and corrosive micro-stains and capable of on-press development is provided. The presensitized plate includes a photosensitive layer containing (A) a sensitizing dye, (B) a polymerization initiator, (C) a polymerizable compound, and (D) a binder polymer; and a protective layer which are formed on a support in this order. The support is prepared from an aluminum alloy plate containing intermetallic compound particles with a circle equivalent diameter of 0.2 μm or more at a surface density of 35,000 pcs/mm 2 or more and aluminum carbide particles with a maximum length of 1 μm or more in an amount of up to 30,000 pcs/g.

1 . A presensitized plate comprising: an image recording layer containing (K) an infrared absorber and (L) an alkali-soluble resin and formed on a support, exposed portions of the image recording layer having an increased alkali solubility after exposure to infrared radiation,
 wherein the support is formed from an aluminum alloy plate containing intermetallic compound particles with a circle equivalent diameter of 0.2 μm or more at a surface density of more than 35,000 pcs/mm 2 .   
     
     
         2 . The presensitized plate according to  claim 1 , wherein the alkali-soluble resin (L) is a phenol resin. 
     
     
         3 . The presensitized plate according to  claim 2 , wherein the phenol resin is a novolac resin. 
     
     
         4 . The presensitized plate according to  claim 1 , wherein the aluminum alloy plate contains intermetallic compound particles with a circle equivalent diameter of 1.0 μm or more at a density of up to 2,500 pcs/mm 2 . 
     
     
         5 . The presensitized plate according to  claim 1 , wherein the aluminum alloy plate is manufactured by a continuous casting process. 
     
     
         6 . The presensitized plate according to  claim 5 , wherein the aluminum alloy plate is obtained by the continuous casting process which includes feeding an aluminum alloy melt through a melt feed nozzle between a pair of cooling rollers and rolling the aluminum alloy melt while solidifying with the pair of cooling rollers. 
     
     
         7 . The presensitized plate according to  claim 1 , wherein the support is one obtained by subjecting a surface of the aluminum alloy plate to surface roughening treatment 
     
     
         8 . The presensitized plate according to  claim 7 , wherein the surface roughening treatment is one including anodizing treatment following the electrochemical graining treatment. 
     
     
         9 . The presensitized plate according to  claim 8 , wherein the anodizing treatment is one using an electrolytic solution containing sulfuric acid or phosphoric acid. 
     
     
         10 . A method of manufacturing a lithographic printing plate comprising:
 an image recording step for recording an image on the presensitized plate according to  claim 1  by imagewise exposure; and   a development step for developing the presensitized plate having the image recorded thereon with a developer at a pH of 9 or more to obtain the lithographic printing plate.