Process for making optical disk substrates
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorKazuo Inoue
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Abstract
A process for producing high-density thin type optical disk substrates having good replicability and birefringence sufficient for practical use. In filling the resin into the cavity, the stress on the resin is reduced by controlling the relation of the cavity width and the injection compression force to reduce birefringence. Further, the mirror surface of the mold is maintained at a certain temperature to facilitate the resin flow and a good replicability and reduction of birefringence is achieved by terminating the resin filling and starting the compression process at the time at which the pressure of the resin filling is at a minimum.
Claims4
A process for producing an optical disk substrate comprising the steps of injecting molten resin into a cavity formed between a pair of molds and narrowing the width of the cavity by compressing the molds, wherein the minimum cavity width is narrower than the desired optical disk substrate thickness by more than 0 mm and less than 0.1 mm, the maximum cavity width is wider than the minimum cavity width by more than 0.15 mm and less than 0.3 mm, and at least one initial force selected from the group consisting of the initial mold clamping force and the initial injection compression force is applied in filling the resin into the cavity and the force is more than 0 ton and less than 10 tons.
Dependencies are inferred from the claim text.