Teijin Limited

Keisuke Shinohara

Katsushi Sasaki

Wataru Funakoshi

Masanori Abe

A polycarbonate copolymer which consists essentially of 5 to 95 mol % of recurring units containing a specific spiroglycol unit and 95 to 5 mol % of recurring units containing a specific biphenol unit, and has a reduced viscosity (.eta..sub.sp /c), measured at 20.degree. C. in a solution containing methylene chloride as a solvent and having a concentration of 0.5 g/dl, of at least 0.3 dl/g, a photoelasticity coefficient of 70.times.10.sup.-13 cm.sup.2 /dyne or less, and a glass transition temperature of at least 95.degree. C.; and a process for the production thereof. This polycarbonate copolymer is useful as a material for an information transmission medium or an information recording medium.

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Iwakuni, Japan

Keisuke Shinohara