Claims
- 1. 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.
- 2. The optical data storage medium according to claim 1, wherein said storage medium is an optical disk.
- 3. The optical disk according to claim 2, wherein the copolycarbonate has acceptable pit/groove replication.
- 4. The optical disk according to claim 3, wherein R.sup.2 is methyl and p is 0.
- 5. The optical disk according to claim 4, wherein each of A.sup.1 and A.sup.2 is a p-phenylene and Y is isopropylidene.
- 6. The optical disk according to claim 4, wherein the copolycarbonate is thixotropic at shear rates from 10-100 sec.sup.-1 at 250.degree. C.
- 7. The optical disk according to claim 5, wherein R.sup.1 is m-phenyleneoxy.
- 8. The optical disk according to claim 5, wherein R.sup.1 has formula III.
- 9. The optical disk according to claim 8, wherein n is from 6-18.
- 10. The optical disk according to claim 9 wherein n is 8 to 10.
- 11. The optical disk according to claim 5, wherein the units of the formula (1) have the formula: ##STR10##
- 12. The optical disk according to claim 3, wherein the copolycarbonate is prepared using a synthesis technique selected from the group consisting of interfacial polymerization, transesterification, redistribution and solid state polymerization.
- 13. A method of making an optical data storage medium which comprises molding a copolycarbonate comprising: (A) less than 40 mole percent of structural units of the formula ##STR11## 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 ##STR12## wherein R.sup.1 is m-phenyleneoxy, an alkylene hydroxy acid or ##STR13## and n is in the range of about 4-25; and (C) a balance comprising structural units of the formula ##STR14## 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.
- 14. The method according to claim 13, wherein the optical storage medium is an optical disk.
- 15. The method according to claim 14, wherein the optical disk has an acceptable pit/groove replication.
- 16. A copolycarbonate comprising:
- (A) less than 40 mole percent of structural units of the formula ##STR15## 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 ##STR16## wherein R.sup.1 is m-phenyleneoxy and (C) a balance comprising structural units of the formula ##STR17## 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.
- 17. An optical data storage medium comprising the copolycarbonate according to claim 16.
Parent Case Info
This application claims priority from Provisional Application No. 60/070,473, filed Jan. 5, 1998.
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