Optical film, method for producing the same and polarizing plate using the same

Abstract

A method for producing an optical film comprising the steps of: (i) melt casting a cellulose ester resin or a cycloolefin resin by extruding melt of the cellulose ester resin or the cycloolefin resin from a die onto a roll-shaped cooling drum; (ii) cooling and solidifying the extruded melt to form a film; (iii) stretching the film in a lateral direction of the film; and (iv) winding the film in a roll, wherein the cooling drum has plural regions divided predeterminedly in an axis direction of the cooling drum, a temperature of each region being independently controlled.

1 . A method for producing an optical film comprising the steps of: 
 (i) melt casting a cellulose ester resin or a cycloolefin resin by extruding melt of the cellulose ester resin or the cycloolefin resin from a die onto a roll-shaped cooling drum;    (ii) cooling and solidifying the extruded melt to form a film;    (iii) stretching the film in a lateral direction of the film; and    (iv) winding the film in a roll, 
 wherein the cooling drum has plural regions divided predeterminedly in an axis direction of the cooling drum, a temperature of each region being independently controlled.  
   
   
   
       2 . The method of  claim 1 , wherein a width of the roll film is 1000 to 4000 mm.  
   
   
       3 . The method of  claim 1 , wherein the cellulose ester resin comprises at least one compound selected from the group consisting of: cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate and cellulose phthalate.  
   
   
       4 . The method of  claim 1 , wherein the cooling drum is divided into 2 to 10 regions.  
   
   
       5 . The method of  claim 1 , wherein 
 (a) a width of the cooling drum is 1100 to 4400 mm; and    (b) a diameter of the cooling drum is 300 to 3500 mm.    
   
   
       6 . The method of  claim 1 , wherein 
 (c) a temperature difference between any adjacent regions is 5 to 30° C.; and    (d) a temperature difference between a maximum temperature and a minimum temperature in a temperature profile of all over the cooling drum is 5 to 50° C.    
   
   
       7 . The method of  claim 1 , wherein a thickness of the optical film is 40 to 120 μm.