| 摘要 |
PURPOSE:To reduce the warpage of the titled disk by forming a substrate with a specified copolymer. CONSTITUTION:The substrate is formed with a copolymer consisting essentially of 60-97.5wt% methyl methacrylate unit and 2.5-40wt% N-substituted maleimide or a copolymer consisting essentially of 40-97.5wt% methyl methacrylate unit, 2.5-40wt% N-substituted maleimide unit and <=20wt% styrene unit and wherein the weight ratio of the styrene unit to the N-substituted maleimide unit is controlled to <=1. The purity of the N-substituted maleimide must be adjusted to >=95% and the content of the monomer remaining in the disk is preferably regulated to <=0.8wt% or more preferably to <=0.4wt%. Consequently, the warpage due to creep, etc., can be reduced when the substrate is molded. |
