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US 4,729,940 AGranted
Method of manufacturing master for optical information carrier
AssigneeCBS Inc.
InventorsHanphire H. Nee, Vasil D. Tasi
Life of this patent
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Abstract
For manufacturing a master for the replication of optical discs a plate of fine-grained copper is coated with a photoresist and exposed by a laser beam which is turned on and off in accordance with information to be recorded on the disc. After developing the photoresist, the exposed portions of the copper layer is etched to a predetermined depth and the photoresist stripped from the etched copper surface.
Claims14
Method of manufacturing a disc-shaped information carrier provided with a substantially spiral track of information pits of predetermined depth, comprising the steps of:
- coating a metallic disc-shaped substrate with a layer of fine-grained copper to a thickness at least as great as the predetermined depth of the information pits,
- coating the surface of the copper layer with a photoresist,
- exposing the photoresist to radiation in a sequence of spaced areas which correspond to the information arranged in a spiral track,
- developing the photoresist,
- electrolytically etching the exposed portions of the copper layer to said predetermined depth in an electrolyte comprising a water solution of compounds selected from the group consisting of tetra-potassium pyrophosphate and tetra-sodium pyrophosphate in which the concentration of the pyrophosphate is in the range from about 1.0% to about 7.0% and the pH of the solution is in the range from about 7 to about 10, and
- stripping the photoresist from the etched copper surface.
3 more elements
Dependencies are inferred from the claim text.