Optical disc substrate fabrication method, mold and optical disc

摘要

A disc substrate is injection-molded with a mold provided with a cavity and an angled surface portion. The cavity forms the disc substrate by an injected molten resin spreading to a circumference of and filling the cavity. The angled surface portion, which is formed at a predetermined region of an area of the cavity that molds an outer periphery portion of a recording surface of the disc substrate, gradually reduces a height dimension of the outer periphery portion from an inner side toward an outer side of the outer periphery portion. Of a disc substrate molded by this mold, an outer periphery portion has a smaller rate of contraction because molten resin charged into the cavity first solidifies quicker, and a center side has a larger rate of contraction because molten resin charged into the cavity later solidifies more slowly than at the outer periphery portion.