Optical bodies including rough strippable boundary layers

Abstract

Optical bodies are disclosed that include a first optical film, a second optical film and at least one rough strippable boundary layer disposed between the first and second optical films. Also disclosed are optical bodies including a strippable boundary layer disposed between the first and second optical films and including a first polymer and a second polymer that is substantially immiscible in the first polymer. The present disclosure also provides methods of processing optical bodies that include stretching the optical bodies.

What is claimed is: 
     
         1 . A method of processing an optical body, comprising the steps of:
 providing an optical body comprising at least one rough strippable boundary layer between a first optical film and a second optical film; and   stretching the optical body.   
     
     
         2 . The method of  claim 1 , wherein the optical body further comprises at least one smooth strippable boundary layer. 
     
     
         3 . The method of  claim 1 , wherein the optical body is stretched biaxially. 
     
     
         4 . The method of  claim 1 , wherein the optical body is stretched substantially uniaxially. 
     
     
         5 . A method of processing an optical body, comprising the steps of:
 providing an optical body comprising at least one strippable boundary layer between a first optical film and a second optical film, the strippable boundary layer comprising a first polymer and a second polymer substantially immiscible in the first polymer; and   stretching the optical body.   
     
     
         6 . The method of  claim 5 , wherein the optical body further comprises at least one smooth strippable boundary layer. 
     
     
         7 . The method of  claim 5 , wherein the optical body is stretched biaxially. 
     
     
         8 . The method of  claim 5 , wherein the optical body is stretched substantially uniaxially. 
     
     
         9 . A method for processing an optical body, comprising:
 providing an optical body comprising a first optical film, a second optical film and at least one rough strippable boundary layer disposed between the first and second optical films;   conveying the optical body into a stretching region;   stretching the optical body to increase a transverse dimension of the optical body while conveying the opposing edges of the optical body along generally diverging paths in a machine direction, wherein the generally diverging paths are configured and arranged to provide a machine direction draw ratio (MDDR), a normal direction draw ratio (NDDR) and a transverse direction draw ratio (TDDR) that approach the following relationship:
   MDDR=NDDR=(TDDR) −1/2    
   
       during the stretching. 
     
     
         10 . The method of  claim 9 , wherein the diverging paths are substantially parabolic. 
     
     
         11 . The method of  claim 9 , wherein the diverging paths are linear approximations of substantially parabolic paths. 
     
     
         12 . The method of  claim 9 , wherein the diverging paths are coplanar. 
     
     
         13 . The method of  claim 9 , wherein in the stretched optical body at least one of the first and second optical films comprises a reflective polarizer. 
     
     
         14 . The method of  claim 9 , wherein stretching the film comprises stretching the optical body to a draw ratio in excess of four. 
     
     
         15 . The method of  claim 9 , wherein the step of stretching comprises moving the opposing edge portions along diverging paths that are substantially symmetrical about a center axis of the optical body. 
     
     
         16 . The method of  claim 9 , further comprising providing the optical body to the stretcher in a continuous manner from a roll of film. 
     
     
         17 . The method of  claim 9 , further comprising coextruding the optical body in-line with stretching. 
     
     
         18 . The method of  claim 17 , wherein coextruding the optical body comprises multiplication and the at least one boundary layer is added prior to multiplication. 
     
     
         19 . The method of  claim 9 , wherein the stretched film comprises at least one material with indices of refraction in a length direction corresponding to the machine direction and a thickness direction that are substantially the same but substantially different from an index of refraction in a width direction. 
     
     
         20 . The method of  claim 9 , wherein the minimum value of the extent of uniaxial character, U, is at least 0.7, wherein U is defined as
 U=(1/MDDR −1)/(TDDR 1/2 −-1).   
     
     
         21 . The method of  claim 9 , wherein the optical body is stretched to a draw ratio in excess of four within the stretcher by moving the opposing edge portions along diverging non-linear paths, wherein, during the stretching, the minimum value of the extent of uniaxial character, U, is at least 0.7 over a final portion of the stretching after achieving a TDDR of 2.5 and U is less than 1 at the end of the stretching, wherein U is defined as
 U=(1/MDDR−1)/(TDDR 1/2 −1)   
       wherein MDDR is the machine direction draw ratio and TDDR is the transverse direction draw ratio as measured between the diverging paths. 
     
     
         22 . A method of processing an optical body, the method comprising:
 providing an optical body comprising a first optical film, a second optical film and at least one rough strippable boundary layer disposed between the first and second optical films;   conveying the optical body within a stretcher along a machine direction while holding opposing edge portions of the optical body; and   stretching the optical body within the stretcher by moving the opposing edge portions along diverging non-linear paths, wherein, during the stretching of the optical body, the speed of the film along the machine direction decreases by a factor of approximately λ 1/2  where λ is the transverse direction draw ratio.