| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lens having a low specific gravity and capable of retaining good optical and mechanical characteristics by using a copolymer of a radical polymerizable unsaturated compound having a specified skeleton and a specified component and providing a specified specific gravity. SOLUTION: The lens is made of a copolymer of a radical polymerizable unsaturated compound (A) havingα,ω-polybutadiene glycol of formula I or hydrogenatedα,ω-polybutadiene glycol of formula II (B) as a skeleton and a monomer (C) copolymerizable with the component (A) and has a specific gravity of <1. The number (n) of the repeating units of the component B is 10-60 and the number average molecular weight is about 800-3,500. The component A is preferably a (meth)acrylate obtained by subjecting 50-100 wt.% of the hydroxyl groups of the component B to urethane modification or ester modification. The amounts of the components A and C are preferably 5-70 wt.% and 95-30 wt.%, respectively, when the component A is a urethane modified (meth)acrylate.
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