Method for fabricating broadband cholesteric liquid crystal film

Abstract

The invention provides a broadband cholesteric liquid crystal film, a method for fabricating the same, a polarization device employing the same, and high light efficiency liquid crystal display employing the same. The cholesteric liquid crystal film is a single-layer liquid crystal material structure, and has a top surface and a bottom surface. Further, the cholesteric liquid crystal film includes a first region, a second region, and a third region, and the first region is adjacent to the top surface of the cholesteric liquid crystal film, the third region is adjacent to the bottom surface of the cholesteric liquid crystal film, and the second region is located between the first and third regions, and the average helical pitch P1 of the first region and the average helical pitch P3 of the third region are both larger than the average helical pitch P2 of the second region.

What is claimed is: 
     
         1 . A method for fabricating a broadband cholesteric liquid crystal film, comprising the steps of (A)-(D):
 (A) dissolving a cholesteric liquid crystal composition and a photoinitiator in a solvent to prepare a solution;   (B) coating the solution to a substrate, obtaining a cholesteric liquid crystal coating layer;   (C) heating the cholesteric liquid crystal coating layer in a first atmosphere containing a first pre-fixed oxygen concentration, wherein the first pre-fixed oxygen concentration is a fixed value of between 10-30 vol %; and   (D) curing the cholesteric liquid crystal coating layer in a second atmosphere containing a second pre-fixed oxygen concentration, obtaining the aforementioned broadband cholesteric liquid crystal film, wherein the second pre-fixed oxygen concentration is a fixed value of between 0.01-10 vol %.   
     
     
         2 . The method as claimed in  claim 1 , wherein the cholesteric liquid crystal coating layer is cured by irradiation by UV radiation or heat. 
     
     
         3 . The method as claimed in  claim 1 , wherein the first pre-fixed oxygen concentration of the first atmosphere is a fixed value of between 15-25 vol %.