| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical polyester resin, having low photoelastic coefficient, excellent in heat resistance, suppressing side effect during molding, wherein birefringence obtainable upon orientation is suitably controlled for a retardation film application. Ž<P>SOLUTION: A fluorene polyester resin has a glass transition temperature of ≥125°C, photoelastic coefficient of ≥-25×10<SP>-12</SP>/Pa and ≤25×10<SP>-12</SP>/Pa, controls birefringence obtainable upon stretch orientation by means of copolymer composition, and does not contain multiple bonds other than fluorene, ester groups. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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