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 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.   
     
     
         2 . 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.   
     
     
         3 . 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.   
     
     
         4 . 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.   
     
     
         5 . A lithographic printing plate support which is obtainable by the method according to claim  12 . 
     
     
         6 . A presensitized plate which is obtainable by forming an image recording layer on the lithographic printing plate support of  claim 5 . 
     
     
         7 . A presensitized plate of  claim 6 , wherein the image recording layer is a laser-imagable image recording layer. 
     
     
         8 . The presensitized plate of  claim 7 , wherein the laser-imagable image recording layer is of a photopolymer type or a thermal positive type.