| http://www.w3.org/ns/prov#value | - Transparent resins such as poly(methyl methacrylate), polystyrene and polycarbonate are mainly used at present as the plastic material for these optical devices, but these materials have problems in that the thermoplastic resins not only have low heat resistance, as typified by a thermal deformation temperature, but also have low solvent resistance and a low elastic modulus.
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