Heat setting optical films

Abstract

A method of making an optical film includes providing a film, substantially uniaxially orienting the film, and heat setting the oriented film. The film includes a polymeric material capable of developing birefringence.

1 . A method of processing a film, the method comprising:
 conveying a film along a machine direction while holding opposing edge portions of the film;   stretching the film by moving the opposing edge portions along diverging, curvilinear paths to form a stretched film; and   heat setting the stretched film.   
   
   
       2 . The method of  claim 1 , wherein the diverging paths are substantially parabolic. 
   
   
       3 . The method of  claim 1 , wherein the step of heat setting comprises heating the film to a temperature above a Tg of at least one polymeric component thereof. 
   
   
       4 . The method of  claim 1 , wherein the step of heat setting comprises heating the film to a temperature above a Tg of all polymeric components thereof. 
   
   
       5 . The method of  claim 1 , wherein the step of heat setting comprises heating the film to a temperature between a Tg and a melting point of the film. 
   
   
       6 . The method of  claim 1 , wherein stretching the film comprises stretching the film to a draw ratio in excess of four. 
   
   
       7 . A film made by the process of  claim 1 .