Optical polarizer

Abstract

A reflective polarizer and a dichroic polarizer are combined to provide an improved optical polarizer. The dichroic and reflective polarizers are typically in close proximity to each other, and are preferably bonded together to eliminate the air gap between the polarizers. The combination of the two polarizers provides a high reflectivity of one polarization and high transmission for the perpendicular polarization from the reflective polarizer side of the combined polarizer, and high absorption and transmission for light of orthogonal polarization from the dichroic polarizer side. The combination also reduces iridescence as seen in transmission and when viewed in reflection from the dichroic polarizer side. The increased extinction ratio and low reflectivity of the optical polarizer allows use of a lower extinction ratio dichroic polarizer in applications requiring a given extinction ratio and high transmission.

1 . A display, comprising: 
 a liquid crystal display module;    a backlight;    a broadband reflective polarizer having anisotropic refractive indices such that light having a first polarization state is reflected and light having a second polarization state is transmitted, the reflective polarizer having a viewing side facing the liquid crystal display module and an opposing side facing the backlight; and    an absorbing polarizer disposed between the reflective polarizer and the liquid crystal display module and being aligned to absorb light of the first polarization and to transmit light of the second polarization such that light of the first polarization reflected by the opposing side of the reflective polarizer is used to increase brightness of the display while providing antireflection to the viewing side of the reflective polarizer by absorbing light of the first polarization.    
     
     
         2 . An optical display as recited in  claim 1 , wherein absorbing polarizer is boned to the viewing side of the reflective polarizer.  
     
     
         3 . A display as recited in claims  1 , wherein the reflective polarizer comprises an polymeric material.  
     
     
         4 . A display as recited in  claim 1 , wherein the reflective polarizer comprises a multilayer stack of two different materials.  
     
     
         5 . A display as recited in  claim 1 , wherein the reflective polarizer exploits constructive interference to reflect light of the first polarization.  
     
     
         6 . A display as recited in  claim 4 , wherein the reflective polarizer wherein the multilayer stack comprises alternating layers of crystalline naphthalene dicarboxilic acid and a copolyester of naphthalene dicarboxilic acid and tetephthalic acid.