| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical disk substrate and an optical disk that use a polymer having a &bgr;-phellandrene, which is a material obtainable from microorganisms, plants or the like such as carbon-neutral materials, as monomers.SOLUTION: In an optical disk substrate, (1) a &bgr;-phellandrene polymer with specific gravity equal to or more than 0.85 and less than 1.0 and transmittance equal to or more than 90% of light with a wavelength of 400 nm to 850 nm is included at 50 to 100 mass% relative to total mass of the optical disk substrate; (2) a number-average molecular weight Mn of the &bgr;-phellandrene polymer is equal to or more than 40,000; (3) at least a portion of olefinic carbon-carbon double bonds owned by the &bgr;-phellandrene polymer is hydrogenated; and (4) an optical disk includes the optical disk substrate, and a signal recording surface is formed in at least one surface of the optical disk substrate. |
