Patent ID: 8081272

Claim:
A preparation method comprising: disposing a chiral or cholesteric liquid crystal, a photoreactive monomer, and a photoinitiator in a liquid crystal cell; and illuminating a principal surface of the liquid crystal cell with ultraviolet light selected to have a non-uniform ultraviolet light intensity profile in the liquid crystal cell, the illuminating cooperating with the photoinitiator to polymerize at least a portion of the photoreactive monomer near the principal surface to generate a surface polymer network component having a density corresponding to the non-uniform ultraviolet light intensity profile, the polymer network biasing the liquid crystal toward a selected helical alignment direction; and uniformly illuminating a principal surface of the liquid crystal cell with ultraviolet light selected to have a substantially uniform ultraviolet light intensity profile in the liquid crystal cell, the uniform illuminating cooperating with the photoinitiator to polymerize at least a portion of the photoreactive monomer to generate a volume polymer network component having a density that is substantially uniform in the liquid crystal cell.