Patent ID: 6022942
Filing Date: 2000-02-08
Classification: C08G,G11B

Abstract:
An optical data storage medium having a substrate with a vertical birefringence less than 3.0.times.10.sup.-4, said substrate comprising a copolycarbonate having a glass transition temperature less than 150.degree. C. and an MVI of at least 40 cc/10 min, said copolycarbonate comprising:(A) less than 40 mole percent of structural units of the formula ##STR6## wherein R.sup.2 is C.sub.1-3 alkyl or phenyl, R.sup.3 is C.sub.1-3 alkyl and p is 1 or 2;(B) about 50-85 mole percent of structural units of the formula ##STR7## wherein R.sup.1 is m-phenyleneoxy, an alkylene hydroxy acid or ##STR8## and n is in the range of about 4-25; and (C) a balance comprising structural units of the formula ##STR9## wherein each of A.sup.1 and A.sup.2 is independently unsubstituted or substituted m- or p-phenylene, Y is a linking group wherein 1 or 2 atoms separate A.sup.1 from A.sup.2 and n is 0 or 1.