Process for manufacturing polymeric optical film

Abstract

A process for making an optical film includes stretching a polyolefin film in a first direction and stretching the polyolefin film in a second direction different than the first direction forming a biaxially stretched polyolefin film. At least a portion of the stretching of the polyolefin film in the second direction occurs simultaneous with the stretching of the polyolefin film in the first direction. The biaxially stretched polyolefin film has a length and a width and substantially non-absorbing and non-scattering for at least one polarization state of visible light. The biaxially stretched polyolefin film has x, y, and z orthogonal indices of refraction where at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an out-of-plane retardance being 50 nm or greater.

1 . A process for making an optical film comprising: 
 a) providing an extruded polymeric film;    a) stretching the polymeric film in a first direction; and    b) stretching the polymeric film in a second direction different than the first direction forming a biaxially stretched polymeric film, wherein the stretching of the polymeric film in the second direction occurs sequentially with the stretching of the polymeric film in the first direction;    wherein the biaxially stretched polymeric film has a length and a width and is substantially non-absorbing and non-scattering for at least one polarization state of visible light; the biaxially stretched polymeric film having x, y, and z orthogonal indices of refraction wherein at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an out-of-plane retardance being 50 nm or greater.    
   
   
       2 . The process according to  claim 1 , further comprising cooling the entire width of the biaxially stretched polymeric film.  
   
   
       3 . The process according to  claim 1 , wherein the in-plane retardance changes less than 4 nm/cm along the width and length of the layer of biaxially stretched polymeric film.  
   
   
       4 . The process according to  claim 1 , wherein the stretching in the first direction is not equal to the stretching in the second direction.  
   
   
       5 . The process according to  claim 1 , wherein the stretching in one direction is up to 50% greater than the stretching in the other direction.  
   
   
       6 . The process according to  claim 1 , further comprising the step of surface treating the biaxially stretched polymeric film.  
   
   
       7 . The process according to  claim 6 , wherein the step of surface treating the biaxially stretched polymeric film comprises at least one of corona, flame, plasma, adhesion enhancing coating, chemical etching and hydrolysis treatments.  
   
   
       8 . The process according to  claim 1 , further comprising adhering the biaxially stretched polymeric film to another optical film.  
   
   
       9 . A process for making an optical film comprising: 
 a) providing providing an extruded polymeric film;    b) stretching the polymeric film in a first direction; and    c) stretching the polymeric film in a second direction different than the first direction forming a biaxially stretched polymeric film, wherein the stretching of the polymeric film in the second direction occurs sequentially with the stretching of the polymeric film in the first direction;    wherein the biaxially stretched polymeric film is substantially non-absorbing and non-scattering for at least one polarization state of visible light; the biaxially stretched polymeric film having x, y, and z orthogonal indices of refraction wherein at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an out-of-plane retardance being 50 nm or greater and a length and width of at least 0.65 meter and the in-plane and out-of-plane retardance are substantially uniform across the length and width.    
   
   
       10 . The process according to  claim 9 , wherein the in-plane retardance changes less than 4 nm/cm along the length and width of the layer of biaxially stretched polymeric film.  
   
   
       10 . The process according to  claim 9 , wherein the stretching in the first direction is not equal to the stretching in the second direction.  
   
   
       11 . The process according to  claim 9 , wherein the stretching in one direction is up to 50% greater than the stretching in the other direction.  
   
   
       13 . The process according to  claim 9 , further comprising the step of surface treating the biaxially stretched polymeric film.  
   
   
       14 . The process according to  claim 13 , wherein the step of surface treating the biaxially stretched polymeric film comprises at least one of corona, flame, plasma, adhesion enhancing coating, chemical etching and hydrolysis treatments.  
   
   
       15 . The process according to  claim 9 , further comprising adhering the biaxially stretched polymeric film to another optical film.  
   
   
       16 . A process for making an optical film comprising: 
 a) providing an extruded polymeric film;    b) stretching the polymeric film in a first direction; and    c) stretching the polymeric film in a second direction different than the first direction forming a biaxially stretched polymeric film, wherein the stretching of the polymeric film in the second direction occurs sequentially with the stretching of the polymeric film in the first direction;    wherein the biaxially stretched polymeric film has a length and a width and is substantially non-absorbing and non-scattering for at least one polarization state of visible light; the biaxially stretched polymeric film having x, y, and z orthogonal indices of refraction wherein at least two of the orthogonal indices of refraction are not equal, an in-plane retardance being 100 nm or less and an out-of-plane retardance being 50 nm or greater and a thickness of 5 microns to 200 microns.    
   
   
       17 . The process according to  claim 16 , further comprising cooling the entire width of the biaxially stretched polymeric film.  
   
   
       18 . The process according for  claim 16 , wherein the biaxially stretched polymeric film has a thickness of 10 micrometers to 50 micrometers and an out-of-plane retardance being 75 nm or greater.  
   
   
       19 . The process according for  claim 16 , wherein the biaxially stretched polymeric film has a thickness of 10 micrometers to 50 micrometers and an out-of-plane retardance being 75 nm or greater.  
   
   
       20 . The process according for  claim 19 , wherein the biaxially stretched polymeric film has a thickness of 10 micrometers to 50 micrometers and an out-of-plane retardance being 75 nm or greater.