| 摘要 |
PURPOSE:To obviate the generation of a tracking error even after continuous use by maintaining the internal residual strain of a film within 0.02% and the intra-surface anisotropy of the coefft. of thermal expansion of a disk within 6X10<-6>/ deg.C. CONSTITUTION:The internal residual strain of the film is maintained within 0.02% and the intra-surface anisotropy of the coefft. of thermal expansion of the disk within 6X10<-6>/ deg.C. The maintenance of the internal residual strain within 0.02% signifies that the change rate (shrinkage and elongation percentage) of the film held in an unloaded state for 72hr in an atmosphere of 60 deg.C and 80% RH is within 0.02% in any direction. The polyester for such film is mainly a PE terephthalate and PE-2,6-naphthalate. The PE terephthalate is the polyester in which >=80mol% of the dibasic acid component is a terephthalic acid and >=90mol% of the glycol component is ethylene glycol. |
