G - Physics – 11 – B
Patent
G - Physics
11
B
352/31.3
G11B 5/596 (2006.01) G11B 5/58 (2006.01) G11B 5/74 (2006.01) G11B 5/82 (2006.01) G11B 7/09 (2006.01) G11B 7/24 (2006.01) G11B 21/10 (2006.01) G11B 23/30 (2006.01)
Patent
CA 1241741
ABSTRACT A structure provides variable electromagnetic property (variable, resistance, capacitive, or other variable impedance or other variable electromagnetic property) contrast on the surface marking servo tracks on data storage media, Such media include magnetic or optical storage disks and tapes. The media can be conductive metallic or nonmetallic and can be composed for example of poorly conductive media, dielectric media, or semiconductive media. The variable electromagnetic impedance can vary in the optical, electrical or other portions of the electromagnetic spectrum. A very small variation of the thickness of the protective layer above the magnetic recording medium is employed to mark the servo track information of the medium. Information to be detected by means of a capacitive sensor can be recorded in the protective layer above or below the magnetic recording or optical storage medium. For example, a thin film metallic protective layer 0.07 micrometers thick can be patterned with about 0.02 micrometers of the protective layer. For a plated disk, the top 0.02 micrometers of the protective layer can be patterned. A pattern for providing a variable impedance for representing data can be formed subtractively by sputter etching, or additively formed by a lift-off process or by deposition through a mask, or by the oxidation of or nitriding of materials such as Al, Si or valve metals. This system provides capacitive or other variable impedance contrast for position signals on conductive metallic media for magnetic disks and tapes by means of a very small amount of modulation of the thickness of the protective layer above the magnetic recording medium. Optionally, the protective layer may be planarized by subsequent oxidation, or the use of an additional layer.
477749
Best John S.
Romankiw Lubomyr T.
Scranton Robert A.
Thompson David A.
International Business Machines Corporation
Saunders Raymond H.
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