| abstract |
A birefringence adjusting agent capable of reducing birefringence of a resin in a negative direction is provided. A birefringence regulator is composed of a polyester resin having a dicarboxylic acid component (A) containing a fluorene-based dicarboxylic acid component (A1) and a diol component (B) as polymerization components. The dicarboxylic acid component (A) may contain 50 mol% or more of the fluorene-based dicarboxylic acid component (A1), and may contain another dicarboxylic acid component (A2) composed of an aromatic dicarboxylic acid component. . The diol component (B) may be at least one selected from an aliphatic diol, an alicyclic diol, and an araliphatic diol. [Selection figure] None |