Patent ID: 7294303

Claim:
A manufacturing method for a broad band cholesteric liquid crystal film comprising: polymerizing a liquid crystal mixture that is free of an ultraviolet absorbent, containing a polymerizable mesogen compound (a), a polymerizable chiral agent (b) and a photopolymerization initiator (c) between two substrates, by irradiation of one side with ultraviolet light having an intensity of 1 to 20mW/cm 2 , wherein the two substrates are made of the same material, the broad band cholesteric liquid crystal film has a reflection bandwidth of 300 nm or more, a pitch length in the cholesteric liquid crystal film changes so as to narrow continuously from a side irradiated with ultraviolet light, and the pitch length is changed such that the difference in pitch length between the side of ultraviolet light irradiation and the opposite side is made at least 100 nm.