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Protective Coating for a Magnetic Disc

IP.com Disclosure Number: IPCOM000081543D
Original Publication Date: 1974-Jun-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 19K

Publishing Venue

IBM

Related People

Bassous, E: AUTHOR [+2]

Abstract

A procedure is provided for applying a protective layer between a magnetic film and its supporting substrate, so as to avoid the growth of hillocks, etc., through the magnetic film.

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Protective Coating for a Magnetic Disc

A procedure is provided for applying a protective layer between a magnetic film and its supporting substrate, so as to avoid the growth of hillocks, etc., through the magnetic film.

Prior to applying the protective coating, a substrate 2, made of AlMg or other alloy suitable for a disc substrate is cleaned after which a thin film 4 of aluminum is evaporated onto the substrate. Immediately after such evaporation, the aluminum 4 is anodized in a solution to form a barrier-type oxide layer over the aluminum layer 4. A suitable solution is a 17% solution of ammonium pentaborate in ethylene glycol at room temperature. Only a very thin layer of the evaporated aluminum film is anodized. The substrate and its anodized layer is baked out at a temperature of ~300 degrees C to eliminate traces of the anodizing solution, followed by annealing to produce a stable aluminum oxide layer. A magnetic layer 6 that serves as the storage film and a suitable passivating layer 8 complete the disc.

Since much of corrosion consists in the growth of dendrites protruding from the substrate 2 through the uppermost layer 8 of a storage disc, a protective coating prepared as described above should greatly diminish the growth of such dendrites.

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