| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a digital video disk substrate which hardly causes cracks in the forming process and has small birefringence and excellent transfer performance. <P>SOLUTION: The digital video disk substrate is composed of a polycarbonate which has a viscosity average mol.wt. from 10,000 to 17,000, has a main chain of a structure expressed by formula I and has a terminal group expressed by formula II (wherein R<SP>3</SP>is a halogen atom, 1-20C alkyl or 6-20C aryl; and r is an integer of 0-5) and at least 25 mol% of the terminal group is expressed by formula III. <P>COPYRIGHT: (C)2003,JPO |
