A Carbon Overcoated Thin Film Metal Alloy Magnetic Recording Disk With Laser-formed Optical Servo Tracks in the Carbon Overcoat
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Thin film metal alloy magnetic recording disks typically comprise a substrate, a cobalt-based magnetic layer and a protective overcoat of amorphous carbon deposited on the magnetic layer. A laser focused to a small spot is used to create optical servo tracks on the carbon overcoat. By controlling the laser power, the focused spot size and the rate at which the laser burns, a pattern of light and dark areas, the dark area being a film of intact carbon, can be formed on the carbon overcoat. The carbon is removed by the laser as carbon monoxide and carbon dioxide. The spacing of the optical servo tracks is the same order of magnitude as that available in optical recording disks. The same technology as is used in optical recording is used to write the servo tracks and read the pattern from the carbon overcoat.