| 摘要 |
PURPOSE: To obtain an optical device having low double refraction and such a sufficiently high glass transition temp. as to impart dimensional stability by using a specified optically anisotropic polyester as a polymer material. CONSTITUTION: Practically optically anisotropic polyester consisting of repeating diol units derived from 9,9-bis(4-hydroxyphenyl)-fluorene, at least about 40wt.% repeating diacid units derived. from aliphatic or alicyclic dicarboxylic acid and the balance repeating diacid units derived from arom. dicarboxylic acid is used as a polymer material. The pref. glass transition temp. of the polyester is about >=125 deg.C, especially >=150 deg.C. Since the polymer has a sufficiently high glass transition temp. and very low double refraction, the objective optical device with a coating having a low index of double refraction is obtd. This device has satisfactory dimensional stability because of the high glass transition temp. of the coating. |
