ELECTROFORMING METHOD FOR MASTER DISK OF STAMPER FOR PRODUCTION OF OPTICAL RECORDING MEDIUM AND SPECIFIC GRAVITY MEASURING MACHINE AND ELECTROFORMING DEVICE USED IN THE METHOD

摘要

PURPOSE: To electroform the master disk for a stamper which decreases the variations in the film thickness value and film thickness distribution of an electroforming film by continuously measuring the sp. gr. of an electroforming liquid, replenishing the electroforming liquid with necessary components and maintaining the sp. gr. of the electroforming liquid within a prescribed range. ;CONSTITUTION: The electroforming liquid is supplied through a filter 10 and a discharge port 11 by a pump 9 for liquid circulation from an electroforming standby vessel 6 into an electroforming main vessel 5 and is again returned from an overflow vessel 14 into the standby vessel 6. Electroforming is executed by applying a DC voltage between an anode 8 and cathode 7 in the electroforming main vessel 5. A floating type sp. gr. measuring machine 1, a pH measuring instrument 17 and a liquid component replenishing device 16 are installed in the standy vessel 6. The sp. gr. of the electroforming liquid is measured by the sp. gr. measuring machine 1. The electroforming liquid is replenished with the necessary components from the replenishing device 16 in accordance with the measured value thereof, to control the sp.gr. of the electroforming liquid within ±0.001 and to maintain the ion concn. of the electroforming liquid to maintain constant. As a result, the electroformed stamper having the decreased variations in the film thickness and film thickness distribution of the electroforming film is obtd.;COPYRIGHT: (C)1995,JPO