Brightness enhancement film, and methods of making and using the same

Abstract

A brightness enhancement film comprises a base film, wherein a stress retardation gradient of the base film is calculated to be less than or equal to 50 nanometers per inch, wherein a first surface of the base film is textured, and wherein a light-redirecting structure is disposed on a first surface of the base film.

1 . A brightness enhancement film comprising: 
 a base film, wherein a stress retardation gradient of the base film is calculated to be less than or equal to 50 nanometers per inch, wherein a first surface of the base film is textured, and wherein a light-redirecting structure is disposed on the first surface of the base film.    
   
   
       2 . The brightness enhancement film of  claim 1 , wherein the stress retardation gradient is calculated to be less than or equal to 30 nanometers per inch.  
   
   
       3 . The brightness enhancement film of  claim 2 , wherein the stress retardation gradient is calculated to be less than or equal to 15 nanometers per inch.  
   
   
       4 . The brightness enhancement film of  claim 1 , wherein the first surface comprises a surface roughness (Ra) of 0.3 micrometers to 2.2 micrometers.  
   
   
       5 . The brightness enhancement film of  claim 1 , wherein the second surface is a polished surface comprising a surface roughness (Ra) of less 0.3 micrometers.  
   
   
       6 . The brightness enhancement film of  claim 1 , wherein the second surface is a textured surface comprising a surface roughness (Ra) greater than 0.3 micrometers.  
   
   
       7 . The brightness enhancement film of  claim 1 , wherein the base film comprises a haze value of about 20% to about 80% as measured according to ASTM D1003, and a transmission of greater than or equal to about 85%.  
   
   
       8 . The brightness enhancement film of  claim 1 , wherein the base film comprises a haze value of less than or equal to about 50% as measured according to ASTM D1003, and a transmission of greater than or equal to about 89%.  
   
   
       9 . The brightness enhancement film of  claim 1 , further comprising a curable coating disposed on the first surface of the base film, wherein the curable coating comprises an index of refraction of greater than or equal to about 1.5  
   
   
       10 . The brightness enhancement film of  claim 9 , wherein the curable coating comprises a polymerizable compound comprising a functional group selected from the group consisting of acrylate, methacrylate, vinyl, and epoxide.  
   
   
       11 . The brightness enhancement film of  claim 9 , wherein the curable coating further comprises metal oxide nanoparticles.  
   
   
       12 . The brightness enhancement film of  claim 1 , wherein the base film comprises polycarbonate and phosphonium sulfonate.  
   
   
       13 . The brightness enhancement film of  claim 12 , wherein the phosphonium sulfonate is fluorinated phosphonium sulfonate.  
   
   
       14 . The brightness enhancement film of  claim 1 , wherein the light-redirecting structure is a random prismatic structure, and wherein the random prismatic structure comprises a plurality of prisms each comprising a peak comprising a radius of curvature of about 0.1% to about 30% of a pitch of the prismatic structure.  
   
   
       15 . A brightness enhancement film comprising: 
 a thermoplastic base film comprising greater than or equal to about 80 wt. % polycarbonate, wherein weight percents are based on a total weight of the thermoplastic base film, wherein a stress retardation gradient of the thermoplastic base film is calculated to be less than or equal to 15 nanometers per inch, and wherein a light-redirecting structure is disposed on a first surface of the thermoplastic base film.    
   
   
       16 . A brightness enhancement film comprising: 
 a thermoplastic base film comprising about 93 wt. % to about 99.6 wt. % polycarbonate; and about 0.4 wt. % to about 7 wt. % fluorinated phosphonium sulfonate, wherein weight percents are based on a total weight of the thermoplastic base film, and wherein a stress retardation gradient of the base film is calculated to be less than or equal to 50 nanometers per inch, and wherein a light-redirecting structure is disposed on a first surface of the base film.    
   
   
       17 . The brightness enhancement film of  claim 16 , wherein the first surface of the base film is textured.  
   
   
       18 . The brightness enhancement film of  claim 17 , wherein a second surface is textured.  
   
   
       19 . A method of making a brightness enhancement film comprising: 
 disposing a light-redirecting structure onto a first surface of a base film, wherein a stress retardation gradient of the thermoplastic base film is calculated to be less than or equal to 50 nanometers per inch, wherein the first surface of the thermoplastic base film is textured.    
   
   
       20 . The method of  claim 19 , further comprising forming the base by melting a thermoplastic resin at a temperature greater than or equal to a glass transition temperature of the thermoplastic resin; 
 extruding the thermoplastic resin into a gap between a first calendering roll and a second calendering roll, wherein the first calendering roll comprises a textured surface and an elastomeric material; and    cooling the thermoplastic resin to a temperature below the glass transition temperature of the thermoplastic resin to produce the thermoplastic base film.    
   
   
       21 . The method of  claim 19 , further comprising coating the first surface of the base film with a curable coating material.  
   
   
       22 . A method of making a brightness enhancement film comprising: 
 disposing a light-redirecting structure onto a surface of a base film, wherein a stress retardation gradient of the base film is calculated to be less than or equal to 15 nanometers per inch.    
   
   
       23 . A method of making a brightness enhancement film comprising: 
 disposing a light-redirecting structure onto a surface of a thermoplastic base film comprising about 93 wt. % to about 99.6 wt. % polycarbonate; and about 0.4 wt. % to about 7 wt. % fluorinated phosphonium sulfonate, wherein weight percents are based on a total weight of the thermoplastic base film, and wherein a stress retardation gradient of the thermoplastic base film is calculated to be less than or equal to 50 nanometers per inch.    
   
   
       24 . A display device comprising: 
 an optical source;    a light guide in optical and physical communication with the light source; and    a brightness enhancement film comprising a base film, wherein a stress retardation gradient of the base film is calculated to be less than or equal to 50 nanometers per inch, wherein a first surface of the base film is textured, and wherein a light-redirecting structure is disposed on the first surface of the base film.