Optical film, polarizing plate and display device utilizing the film, and production method of optical film

Abstract

An optical film obtained by a process comprising the steps of: (a) casting a dope comprising a cellulose ester and a non-chlorinated solvent on a metal support, the cellulose ester having a total acyl substitution degree of 2.6 to 2.85 and having a ratio of a weight-average molecular weight to a number-average molecular weight of 1:1 to 3:1; (b) drying the cast dope on the metal support so as to obtain a cellulose ester film; (c) pealing the cellulose ester film from the metal support; (d) further drying the cellulose ester film while providing a longitudinal stretch or a lateral stretch to the cellulose ester film; and (e) providing a metal oxide layer on the cellulose ester film.

What is claimed is:  
     
         1 . An optical film obtained by a process comprising the steps of: 
 (a) casting a dope comprising a cellulose ester and a non-chlorinated solvent on a metal support, the cellulose ester having a total acyl substitution degree of 2.6 to 2.85 and having a ratio of a weight-average molecular weight to a number-average molecular weight of 1:1 to 3:1;    (b) drying the cast dope on the metal support so as to obtain a cellulose ester film;    (c) pealing the cellulose ester film from the metal support;    (d) further drying the cellulose ester film while providing a longitudinal stretch or a lateral stretch to the cellulose ester film; and    (e) providing a metal oxide layer on the cellulose ester film.    
     
     
         2 . The optical film of  claim 1 , wherein the process further comprises the step of: 
 (f) providing an interlayer between the cellulose film and the metal oxide layer.    
     
     
         3 . The optical film of  claim 1 , wherein the dope is prepared with a cold dissolving method.  
     
     
         4 . The optical film of  claim 1 , wherein the dope further comprises an additive in an amount of 0.5 to 30 weight % based on the total weight of the dope, the additive being a compound having at least three substituents selected from the group consisting of a phenyl group, a cycloalkyl group and a cycloalkenyl group.  
     
     
         5 . The optical film of  claim 1 , wherein the metal oxide layer is provided using a plasma CVD method.  
     
     
         6 . The optical film of  claim 1 , wherein the metal oxide layer comprises metal oxide particles.  
     
     
         7 . A polarization plate comprising the optical film of  claim 1 .  
     
     
         8 . A display apparatus comprising the optical film of  claim 1 .  
     
     
         9 . A process for producing an optical film comprising the steps of: 
 (a) casting a dope comprising a cellulose ester and a non-chlorinated solvent on a metal support, the cellulose ester having a total acyl substitution degree of 2.6 to 2.85 and having a ratio of a weight-average molecular weight to a number-average molecular weight of 1:1 to 3:1;    (b) drying the cast dope on the metal support so as to obtain a cellulose ester film;    (c) pealing the cellulose ester film from the metal support;    (d) further drying the cellulose ester film while providing a longitudinal stretch or a lateral stretch to the cellulose ester film; and    (e) providing a metal oxide layer on the cellulose ester film.    
     
     
         10 . The process of  claim 9 , further comprising the step of: 
 (f) providing an interlayer between the cellulose film and the metal oxide layer.    
     
     
         11 . The process of  claim 9 , wherein the step of pealing the cellulose ester film from the metal support is finished within 60 seconds after drying the cast dope on the metal support.  
     
     
         12 . The process of  claim 9 , wherein the step of pealing the cellulose ester film from the metal support is finished with 60 second after drying the cast dope on the metal support, and the process further comprising the step of: 
 (f) providing an interlayer between the cellulose film and the metal oxide layer.