Methods of Making Light Diffusing Films and Articles Using the Same

Abstract

Disclosed herein are light diffusing films, methods of making the same and articles using the same. In one embodiment, a method for producing a film, comprising: combining, to form a combination, a polycarbonate having a yellowness index of about 0.8 to about 1.5 as measured in accordance with ASTM E313-73 (D1925), a phosphite stabilizer, an epoxy stabilizer, and light diffusing; forming the combination into the film; wherein the film comprises a hiding power of 0 to about 0.5.

1 . A method for producing a film, comprising:
 combining, to form a combination,
 a polycarbonate having a yellowness index of about 0.8 to about 1.5 as measured in accordance with ASTM E313-73 (D1925), 
 a phosphite stabilizer, 
 an epoxy stabilizer, and 
 light diffusing; 
   forming the combination into the film;   wherein the film comprises a hiding power of 0 to about 0.5 that is mathematically described by the following equation:   
       
         
           
             
               
                 Hiding 
                  
                 
                     
                 
                  
                 
                   power 
                    
                   
                     ( 
                     % 
                     ) 
                   
                 
               
               = 
               
                 
                    
                   
                     1 
                     - 
                     
                       
                         
                           ∑ 
                           
                             i 
                             = 
                             1 
                           
                           
                             n 
                             - 
                             1 
                           
                         
                          
                         
                             
                         
                          
                         
                           
                             L 
                             i 
                           
                            
                           
                             ( 
                             on 
                             ) 
                           
                         
                       
                       
                         
                           ∑ 
                           
                             j 
                             = 
                             1 
                           
                           
                             n 
                             - 
                             1 
                           
                         
                          
                         
                             
                         
                          
                         
                           
                             L 
                             j 
                           
                            
                           
                             ( 
                             off 
                             ) 
                           
                         
                       
                     
                   
                    
                 
                 × 
                 100 
               
             
           
         
       
       wherein: L i (on) is luminance above i th  cold cathode fluorescent lamp, L j (off) is luminance at a midpoint between cold cathode fluorescent lamp j and cold cathode fluorescent lamp j+1, and n equals number of CCFL lamps; and
 wherein the light diffusing film has a 13 points average luminance that is greater than a 13 points average luminance of a polycarbonate film, as determined by a 13 points test using a Topcon BM-7 instrument, wherein the polycarbonate film comprises about 3.5 wt % acrylate particles based on a total weight of the polycarbonate film, and the polycarbonate film has a thickness of 2 millimeters and a transmission of 50.4% as determined in accordance with ASTM D1003-00 and as measured with instrument Macbeth 7000A, D65 light source illuminant, 10° observer. 
 
     
     
         2 . The method of  claim 1 , wherein the light diffusing particles have a refractive index of about 1.3 to about 1.7 as measured at the Sodium D line with a wavelength of 589 nanometers (nm). 
     
     
         3 . The method of  claim 2 , wherein the refractive index is about 1.50 to about 1.53. 
     
     
         4 . The method of  claim 1 , further comprising combining a hindered phenol stabilizer with the polycarbonate, the phosphite stabilizer, the epoxy stabilizer, and the light diffusing particles to form the combination. 
     
     
         5 . The method of  claim 1 , wherein forming the combination into the film further comprises extruding the combination from an extruder onto calendaring rolls. 
     
     
         6 . The method of  claim 5 , wherein the extruder has an extruder speed of about 65 rpm to about 85 rpm, an average barrel temperature of about 200° C. to about 235° C., and a ratio of flow rate (kg/hr) to the extruder speed (rpm) is about 3.5 to about 6.0. 
     
     
         7 . The method of  claim 6 , wherein the extruder speed is about 70 rpm to about 80 rpm, and the average barrel temperature is about 204° C. to about 228° C., and the ratio is about 3.7 to about 5.8. 
     
     
         8 . The method of  claim 1 , wherein the combining comprises combining about 0.015 wt % to about 0.04 wt % epoxy stabilizer, about 0.04 wt % to about 0.09 wt % phosphite stabilizer, and about 0.001 wt % to about 7 wt % light diffusing particles, wherein the weight percent is based upon a total weight of the combination. 
     
     
         9 . The method of  claim 1 , wherein the combining comprises combining about 0.015 wt % to about 0.03 wt % epoxy stabilizer, about 0.01 wt % to about 0.03 wt % hindered phenol stabilizer, and about 0.04 wt % to about 0.09 wt % phosphite stabilizer, wherein the weight percent is based upon a total weight of the combination. 
     
     
         10 . The method of  claim 1 , wherein the light diffusing particles comprise polyorgano silsesquioxane. 
     
     
         11 . The method of  claim 1 , wherein the light diffusing particles comprise a material are selected from the group consisting of poly(styrene), poly(acrylic acid), poly(methyl methacrylate), poly(acrylic acid-styrene) copolymers, poly(C 1-8  alkylacrylate-C 1-8  alkylmethacrylate) copolymers, and combinations comprising at least one of the foregoing. 
     
     
         12 . A film formed in accordance with the method of  claim 1 . 
     
     
         13 . A method for producing a film, comprising:
 combining, to form a combination,
 about 90 wt % to about 99.9 wt % virgin polycarbonate powder which has not been heat processed, and which has a yellowness index of about 0.8 to about 1.5 as measured in accordance with ASTM E313-73 (D1925); 
 about 0.04 wt % to about 0.09 wt % phosphite stabilizer, 
 about 0.015 wt % to about 0.03 wt % epoxy stabilizer, 
 about 0.01 wt % to about 0.03 wt % hindered phenol stabilizer, and 
 about 0.001 wt % to about 10 wt % light diffusing particles having a refractive index of about 1.3 to about 1.7, 
 wherein the weight percentages are based upon a total weight of ingredients combined prior to any reaction; 
   forming the combination into the film;   wherein the film comprises a hiding power of 0 to about 0.5 that is mathematically described by the following equation:   
       
         
           
             
               
                 Hiding 
                  
                 
                     
                 
                  
                 
                   power 
                    
                   
                     ( 
                     % 
                     ) 
                   
                 
               
               = 
               
                 
                    
                   
                     1 
                     - 
                     
                       
                         
                           ∑ 
                           
                             i 
                             = 
                             1 
                           
                           
                             n 
                             - 
                             1 
                           
                         
                          
                         
                             
                         
                          
                         
                           
                             L 
                             i 
                           
                            
                           
                             ( 
                             on 
                             ) 
                           
                         
                       
                       
                         
                           ∑ 
                           
                             j 
                             = 
                             1 
                           
                           
                             n 
                             - 
                             1 
                           
                         
                          
                         
                             
                         
                          
                         
                           
                             L 
                             j 
                           
                            
                           
                             ( 
                             off 
                             ) 
                           
                         
                       
                     
                   
                    
                 
                 × 
                 100 
               
             
           
         
       
       wherein: L i (on) is luminance above i th  cold cathode fluorescent lamp, L j (off) is luminance at a midpoint between cold cathode fluorescent lamp j and cold cathode fluorescent lamp j+1, and n equals number of CCFL lamps. 
     
     
         14 . The method of  claim 13 , wherein the light diffusing film has a 13 points average luminance that is greater than a 13 points average luminance of a polycarbonate film, as determined by a 13 points test using a Topcon BM-7 instrument, wherein the polycarbonate film comprises about 3.5 wt % acrylate particles based on a total weight of the polycarbonate film, and the polycarbonate film has a thickness of 2 millimeters and a transmission of 50.4% as determined in accordance with ASTM D1003-00 and as measured with instrument Macbeth 7000A, D65 light source illuminant, 10° observer.