VARIABLE IMPEDANCE CONTRAST IN DATA STORAGE MEDIA

摘要

ABSTRACTA structure provides variable electromagnetic property(variable, resistance, capacitive, or other variableimpedance or other variable electromagnetic property)contrast on the surface marking servo tracks on data storagemedia, Such media include magnetic or optical storage disksand tapes. The media can be conductive metallic ornonmetallic and can be composed for example of poorlyconductive media, dielectric media, or semiconductivemedia. The variable electromagnetic impedance can vary inthe optical, electrical or other portions of theelectromagnetic spectrum. A very small variation of thethickness of the protective layer above the magneticrecording medium is employed to mark the servo trackinformation of the medium. Information to be detected bymeans of a capacitive sensor can be recorded in theprotective layer above or below the magnetic recording oroptical storage medium. For example, a thin film metallicprotective layer 0.07 micrometers thick can be patternedwith about 0.02 micrometers of the protective layer. For aplated disk, the top 0.02 micrometers of the protectivelayer can be patterned. A pattern for providing a variableimpedance for representing data can be formed subtractivelyby sputter etching, or additively formed by a lift-offprocess or by deposition through a mask, or by the oxidationof or nitriding of materials such as Al, Si or valve metals.This system provides capacitive or other variable impedancecontrast for position signals on conductive metallic mediafor magnetic disks and tapes by means of a very small amountof modulation of the thickness of the protective layer abovethe magnetic recording medium. Optionally, the protectivelayer may be planarized by subsequent oxidation, or the useof an additional layer.