Optical film

Abstract

The present invention provides an optical film with functions of light collimating, light polarization for brightness enhancement and limiting viewing angle and a method for preparing the same. The optical film includes a plurality of layers of a cholesteric liquid crystal film bound together via an optical adhesive and a quarter-wavelength retardation plate bound with the cholesteric liquid crystal film via the optical adhesive. Therein, at least one layer of the cholesteric liquid crystal film has a polarized separated wavelength range covering the wavelength range of visible light of three primary colors of red, green and blue.

1 . A method for preparing an optical film, comprising:
 (a) providing a first cholesteric liquid crystal layer and a second cholesteric liquid crystal layer;   (b) binding the second cholesteric liquid crystal layer with the first cholesteric liquid crystal layer by optical adhesive, and thereby obtaining a laminated cholesteric liquid crystal film having a first surface and an opposed second surface; and   (c) binding a quarter-wavelength retardation plate to the first surface of the cholesteric liquid crystal film via the optical adhesive,   wherein at least one layer of the cholesteric liquid crystal film has selective reflection wavelength range covering the wavelength range of visible light of three primary colors of red, green and blue.   
     
     
         2 . The method according to  claim 1 , further comprising:
 after step (b), providing a third cholesteric liquid crystal layer and bonding the third cholesteric liquid crystal layer with the second cholesteric liquid crystal layer by the optical adhesive, and thereby obtaining the laminated cholesteric liquid crystal film having a first surface and a third surface opposed to the first surface.   
     
     
         3 . The method according to  claim 1 , further comprising:
 providing a substrate before step (a) such that one of the first and second cholesteric liquid crystal layers is formed on a surface of the substrate.   
     
     
         4 . The method according to  claim 2 , further comprising:
 providing a substrate before step (a) such that one of the first and second cholesteric liquid crystal layers is formed on a surface of the substrate.   
     
     
         5 . The method according to  claim 1 , wherein the cholesteric liquid crystal film separates circularly polarized light having the wavelength ranging from 450 nm to 700 nm. 
     
     
         6 . The optical film according to  claim 1 , wherein the optical adhesive has a refractive index of 1.3 to 1.65 
     
     
         7 . The method according to  claim 1 , wherein the optical adhesive is made of one selected from the group consisting of acrylic resin, unsaturated polyester, polyurethane, epoxy resin, and a mixture thereof. 
     
     
         8 . The method according to  claim 5 , wherein the cholesteric liquid crystal film is made of a same liquid crystal material or different liquid crystal materials. 
     
     
         9 . The method according to  claim 1 , further comprising step (d) of removing the substrate if necessary. 
     
     
         10 . The method according to  claim 4 , wherein the cholesteric liquid crystal film is made of nematic liquid crystals and chiral dopant. 
     
     
         11 . The method according to  claim 10 , wherein the nematic liquid crystals have undergone aligning treatment and helical pitches thereof have been adjusted.