Patent ID: 8027014

Claim:
A method of evaluating a birefringence functional layer, comprising: measuring an amount of residual double bonds of a birefringence functional layer in an optical element, comprising a light-transmitting substrate, a birefringence functional layer made of a polymerizable liquid crystal material provided above the light-transmitting substrate, a coloring layer provided between the light-transmitting substrate and the birefringence functional layer, directly or indirectly on a surface of the birefringence functional layer, and an alignment film for aligning a driving liquid crystal material provided directly or indirectly on a surface of the birefringence functional layer, whereby the birefringence functional layer is formed by aligning a polymerizable liquid crystal monomer having a polymerizable group at least at one terminal followed by fixation, and a degree of reduction of residual double bond in the birefringence functional layer before and after heat treatment at 250° C. for 1 hr is less than 0.25; applying heat treatment at 250° C. for 1 hr, followed by leaving until the optical element comes to room temperature; measuring an amount of residual double bonds of the heat-treated birefringence functional layer; and calculating a difference between the amounts of the residual double bonds before and after the heat treatment to obtain another degree of reduction of residual double bonds.