POLYCARBONATE.

摘要

A polycarbonate polymer containing repeating units represented by the following general formula wherein: X is selected from single bond, -O-, -S-, -SO2-, wherein: R<1> and R<2> are each independently selected from hydrogen atom: alkyl radical of 1 to 6 carbon atoms; cycloalkyl radical of 5 to 6 carbon atoms; wherein p is an integer having a value of from 0 to 3, phenyl radicals substituted at para position by a substituent seleced from alkoxy radicals of 1 to 5 carbon atoms, phenoxy radicals, or halogen radicals; or p-biphenylyl radical, -(CH2)-q wherein q is an integer having a value of from 2 to 10; or wherein r is an integer having a value of from 4 to 8, and having a reduced viscosity [ eta sp/c] of at least 0.2 dl/g as measured in methylene chloride at a concentration of 0.5 g/dl at 20 DEG C. Such polycarbonates exhibit excellent optical properties such as high birefringence, and are useful as materials for optical devices. Also, a process for preparing the polycarbonates and novel dihydric phenols which can be used as materials for the polycarbonates are disclosed.