Lithographic printing plate support, method of manufacturing the same, and presensitized plate

Abstract

A lithographic printing plate support in which surface unevenness due to surface treatment has been suppressed and a presensitized plate of excellent sensitivity are produced from an aluminum alloy plate containing iron, silicon, titanium and boron by specifying the state in which TiB 2 particles are present in the surface layer and the width of the crystal grains, and by having specific indicators relating to the respective concentrations of iron and silicon in the surface layer following graining treatment fall within specific ranges. In a method of manufacturing the lithographic printing plate support, an aluminum alloy melt having specified alloying ingredients is subjected to a specified casting process to have the amount of the alloying ingredients in solid solution following cold rolling fall within specified ranges.

1 . A lithographic printing plate support obtainable by carrying out a graining treatment comprising at least alkali etching and subsequent electrochemical graining on a surface of an aluminum alloy plate which is produced from an aluminum alloy melt containing iron, silicon, titanium and boron, which has a surface layer of up to 20 μm from the surface that is free of TiB 2  particles or contains TiB 2  particles at least 95% of which have a width of less than 100 μm, and in which crystal grains present in the surface layer have an average width of 20 to 200 μm and a maximum width of at most 2,000 μm; 
 wherein the surface layer of up to 20 μm from the surface of the plate following the graining treatment has an iron concentration and a silicon concentration such that, for each, a ratio of a difference between a concentration in high-concentration areas and a concentration in low-concentration areas to the concentration in the low-concentration areas is at most 20%.    
     
     
         2 . The lithographic printing plate support according to  claim 1 , wherein the aluminum alloy plate is obtainable by carrying out: 
 a continuous casting step in which the aluminum alloy melt is fed through a melt feed nozzle between a pair of cooling rollers where the aluminum alloy melt is rolled as it is solidified to thereby form the aluminum alloy plate;    a cold rolling step in which the aluminum alloy plate obtained in the continuous casting step is cold rolled to reduce a thickness of the aluminum alloy plate;    an intermediate annealing step in which the cold-rolled aluminum alloy plate is heat treated; and    a finish cold rolling step in which the aluminum alloy plate after the intermediate annealing step is rolled to further reduce the thickness of the aluminum alloy plate.    
     
     
         3 . The lithographic printing plate support according to  claim 2 , wherein the aluminum alloy plate is obtainable by carrying out, prior to the continuous casting step: 
 a filtering step in which the aluminum alloy melt is filtered using a filtration tank, and    a melt feeding step in which the filtered aluminum alloy melt is fed from the filtration tank to the melt feed nozzle through a flow channel;    wherein, in the melt feeding step, agitating means provided in a recess formed in a base of the flow channel agitates the aluminum alloy melt near the recess.    
     
     
         4 . The lithographic printing plate support according to  claim 2 , wherein an inner wall of the melt feed nozzle that comes into contact with the aluminum alloy melt is coated beforehand with a parting agent containing filler particles having a particle size distribution with a median diameter of 5 to 20 μm and a modal diameter of 4 to 12 μm.  
     
     
         5 . The lithographic printing plate support according to  claim 2 , wherein, in the continuous casting step, a carbon graphite-containing parting agent is applied to surfaces of the pair of cooling rollers, then the applied parting agent is made uniform in thickness, and the melt feed nozzle has an opening with an outer edge which does not contact the cooling rollers or which contacts the cooling rollers only at a tip thereof.  
     
     
         6 . The lithographic printing plate support according to  claim 2 , wherein Equation:  
           V≧ 5×10 −5 ×( D/t   2 )  
       (where V is a circumferential velocity (m/min) of the cooling rollers, t is a thickness (m) of the aluminum alloy plate and D is a diameter (m) of the cooling rollers in the continuous casting step) is satisfied.  
     
     
         7 . The lithographic printing plate support according to  claim 1 , wherein the graining treatment includes, in order, at least a first alkali etching treatment, a first electrochemical graining treatment using an alternating current in a nitric acid-containing electrolyte, a second alkali etching treatment, and a second electrochemical graining treatment using an alternating current in a hydrochloric acid-containing electrolyte.  
     
     
         8 . A presensitized plate which is obtainable by forming an image recording layer on the lithographic printing plate support of  claim 1 .  
     
     
         9 . A presensitized plate which is obtainable by forming an image recording layer on the lithographic printing plate support of  claim 2 .  
     
     
         10 . The presensitized plate according to  claim 8 , wherein the image recording layer is a laser-imageable image recording layer.  
     
     
         11 . The presensitized plate according to  claim 10 , wherein the laser-imageable image recording layer is of a photopolymer type or a thermal positive type.  
     
     
         12 . A method of manufacturing a lithographic printing plate support which comprises: 
 a filtering step in which an aluminum alloy melt is filtered using a filtration tank;    a melt feeding step in which the filtered aluminum alloy melt is fed from the filtration tank to a melt feed nozzle through a flow channel;    a continuous casting step in which the aluminum alloy melt is fed through the melt feed nozzle between a pair of cooling rollers where the aluminum alloy melt is rolled as it is solidified to thereby form an aluminum alloy plate;    a cold rolling step in which the aluminum alloy plate obtained in the continuous casting step is cold rolled to reduce a thickness of the aluminum alloy plate;    an intermediate annealing step in which the cold-rolled aluminum alloy plate is heat treated;    a finish cold rolling step in which the aluminum alloy plate after the intermediate annealing step is rolled to further reduce the thickness of the aluminum alloy plate, and    a graining treatment step in which a graining treatment comprising at least alkali etching and subsequent electrochemical graining is carried out on a surface of the aluminum alloy plate after the finish cold rolling step;    wherein, in the melt feeding step, agitating means provided in a recess formed in a base of the flow channel agitates the aluminum alloy melt near the recess;    the aluminum alloy melt contains at least 95 wt % of aluminum, 30 to 5,000 ppm of iron, 300 to 2,000 ppm of silicon, and 1 to 500 ppm of copper; and    the aluminum alloy plate after the finish cold rolling step contains in solid solution at least 20 ppm of iron, at least 20 ppm of silicon, and at least 70 wt % of copper in relation to the total amount of copper in the plate.    
     
     
         13 . A method of manufacturing a lithographic printing plate support which comprises: 
 a continuous casting step in which an aluminum alloy melt is fed through a melt feed nozzle between a pair of cooling rollers where the aluminum alloy melt is rolled as it is solidified to thereby form an aluminum alloy plate;    a cold rolling step in which the aluminum alloy plate obtained in the continuous casting step is cold rolled to reduce a thickness of the aluminum alloy plate;    an intermediate annealing step in which the cold-rolled aluminum alloy plate is heat treated;    a finish cold rolling step in which the aluminum alloy plate after the intermediate annealing step is rolled to further reduce the thickness of the aluminum alloy plate, and    a graining treatment step in which a graining treatment comprising at least alkali etching and subsequent electrochemical graining is carried out on a surface of the aluminum alloy plate after the finish cold rolling step;    wherein (a) the melt feed nozzle has, at a tip thereof, a bottom outside face which is acutely angled with respect to the direction in which the aluminum alloy melt is discharged from the nozzle, and/or (b) the melt feed nozzle includes a top plate member which contacts the aluminum alloy melt from above and a bottom plate member which contacts the aluminum alloy melt from below, each of the members being vertically movable, and the top plate member and bottom plate member being each subjected to pressure by the aluminum alloy melt and thereby pushed against an adjoining cooling roller surface;    the aluminum alloy melt contains at least 95 wt % of aluminum, 30 to 5,000 ppm of iron, 300 to 2,000 ppm of silicon, and 1 to 500 ppm of copper; and    the aluminum alloy plate after the finish cold rolling step contains in solid solution at least 20 ppm of iron, at least 20 ppm of silicon, and at least 70 wt % of cupper in relation to the total amount of copper in the plate.    
     
     
         14 . A method of manufacturing a lithographic printing plate support which comprises: 
 a continuous casting step in which an aluminum alloy melt is fed through a melt feed nozzle between a pair of cooling rollers where the aluminum alloy melt is rolled as it is solidified to thereby form an aluminum alloy plate;    a cold rolling step in which the aluminum alloy plate obtained in the continuous casting step is cold rolled to reduce a thickness of the aluminum alloy plate;    an intermediate annealing step in which the cold-rolled aluminum alloy plate is heat treated;    a finish cold rolling step in which the aluminum alloy plate after the intermediate annealing step is rolled to further reduce the thickness of the aluminum alloy plate, and    a graining treatment step in which a graining treatment comprising at least alkali etching and subsequent electrochemical graining is carried out on a surface of the aluminum alloy plate after the finish cold rolling step;    wherein an inner wall of the melt feed nozzle that comes into contact with the aluminum alloy melt is coated beforehand with a parting agent containing filler particles having a particle size distribution with a median diameter of 5 to 20 μm and a modal diameter of 4 to 12 μm;    the aluminum alloy melt contains at least 95 wt % of aluminum, 30 to 5,000 ppm of iron, 300 to 2,000 ppm of silicon, and 1 to 500 ppm of copper; and    the aluminum alloy plate after the finish cold rolling step contains in solid solution at least 20 ppm of iron, at least 20 ppm of silicon, and at least 70 wt % of cupper in relation to the total amount of copper in the plate.    
     
     
         15 . A method of manufacturing a lithographic printing plate support which comprises: 
 a continuous casting step in which an aluminum alloy melt is fed through a melt feed nozzle between a pair of cooling rollers where the aluminum alloy melt is rolled as it is solidified to thereby form an aluminum alloy plate;    a cold rolling step in which the aluminum alloy plate obtained in the continuous casting step is cold rolled to reduce a thickness of the aluminum alloy plate;    an intermediate annealing step in which the cold-rolled aluminum alloy plate is heat treated;    a finish cold rolling step in which the aluminum alloy plate after the intermediate annealing step is rolled to further reduce the thickness of the aluminum alloy plate, and    a graining treatment step in which a graining treatment comprising at least alkali etching and subsequent electrochemical graining is carried out on a surface of the aluminum alloy plate after the finish cold rolling step;    wherein, in the continuous casting step, a carbon graphite-containing parting agent is applied to surfaces of the pair of cooling rollers, then the applied parting agent is made uniform in thickness, and the melt feed nozzle has an opening with an outer edge which does not contact the cooling rollers or which contacts the rollers only at a tip thereof;    the aluminum alloy melt contains at least 95 wt % of aluminum, 30 to 5,000 ppm of iron, 300 to 2,000 ppm of silicon, and 1 to 500 ppm of copper; and    the aluminum alloy plate after the finish cold rolling step contains in solid solution at least 20 ppm of iron, at least 20 ppm of silicon, and at least 70 wt % of cupper in relation to the total amount of copper in the plate.