Patent ID: 7011913

Claim:
A method of making a reflective film, the method comprising: (a) preparing a cholesteric mixture that includes a cholesteric liquid crystal material and at least one type of polymerizable compound; (b) forming a cholesteric mixture layer in which the cholesteric liquid crystal material forms a helical structure, having continuously changing helical pitches, approximately along a normal to the layer; (c) exposing the cholesteric mixture layer to an actinic ray at a temperature, at which the cholesteric mixture exhibits a cholesteric phase, thereby polymerizing the at least one type of polymerizable compound, wherein a Tni point of the cholesteric mixture increases by performing the step (c); wherein the step (a) includes the step of preparing the cholesteric mixture that includes a non-polymerizable nematic liquid crystal material and a polymerizable chiral agent, and the step (c) includes the step of causing a variation ΔTni of about 5 degrees C. to about 30 degrees C. in the Tni point of the cholesteric mixture.