| 摘要 |
PURPOSE:To obtain a highly reliable disk comprising a transparent substrate having high heat resistance and small water absorption and causing no birefringence by using crosslinked polymer of 1,2-polybutadiene for the transparent substrate. CONSTITUTION:Since a transparent substrate consisting of crosslinked polymer of 1,2-polybutadiene has high heat resistance, it is hardly deformed in the stage for forming a memory functioning film. There is no fear for deteriorating a memory functioning film nor generating warp in the substrate itself due to its small water absorption. Moreover, since no benzene ring, etc., is contained in the crosslinked polymer the degree of orientation of the molecule and the birefringence are practically negligible. Suitable 1,2-polybutadiene to be used for the material of the transparent substrate is pellets of syndiotactic 1,2- polybutadiene, or liquid polybutadiene, etc. Suitable initiator for crosslinking for hardening the 1,2-polybutadiene is pref. radial generator causing hardly coloration at the hardening stage, such as peroxide, etc. |
