| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyimide copolymer having high glass transition temperature and excellent thermal discoloration resistance and colorless transparency and useful as a peripheral material for optical parts or optical elements and provide a polyamic acid for the polyimide copolymer. SOLUTION: The polyimide copolymer has an average total repeating unit number (number-average value) of 10-1,000 and contains 10-90 mol% repeating unit expressed by formula (1) (Ar is a bivalent organic group such as a polycyclic aromatic group and a siloxane-containing group; and (m) is an integer of 1-100) and 10-90 mol% repeating unit expressed by formula (2) (X is none or O, S, SO2 , CO or C(CF3 )2 ; and (n) is an integer of 1-100).
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