To provide an optical material comprising a hydrogenated polystyrene-based resin, particularly an optical material to satisfy prescribed properties for a substrate of an optical disk having a high recording density.
The optical material comprises a hydrogenated product of a styrene/ conjugated diene block copolymer. The styrene/conjugated diene block copolymer has a star type branched structure consisting of a core and branched chains linearly extending therefrom, the branched chain comprising a styrene component and a conjugated diene component. The styrene component and the conjugated diene component account for 70-99 wt.% and 30-1 wt.%, respectively, based on the total weight of the both components, and the hydrogenated product is obtained by hydrogenating at least 90 mole % of all double bonds in the both components. Further, the core is derived from an alkoysilane or an aromatic hydrocarbon bearing at least two substituents bearing a vinyl group. This optical material is excellent in transparency and heat resistance and superior in melt flowability enough to exhibit excellent moldability without deteriorating dynamic characteristics compared with those obtained from a hydrogenated product having a linear structure.
YAMAURA MICHIO
TAKEUCHI MASAKI
HASHIZUME KIYOSHIGE
KONO KAZUTERU
IWATA KAORU
KIDO NOBUAKI
MATSUMURA SHUNICHI
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