Master information carrier for magnetic transfer
View Patent ↗A master information carrier has on its surface a signal area where an embossed pattern formed by protruding portions and recessed portions and representing a signal pattern to be transferred has been formed. The shortest bit length of the embossed patter is 300 nm or shorter, and the embossed pattern is formed so that the total of the areas of the upper surfaces of the protruding portions of the embossed pattern is smaller than the total of the areas of inter-protruding-portions in the signal area.
1. A master information carrier having on its surface a signal area where an embossed pattern formed by protruding portions and recessed portions and representing a signal pattern to be transferred has been formed, wherein the improvement comprises that
the shortest bit length of the embossed pattern is 300 nm or shorter, and
the embossed pattern is formed so that a total of areas of upper surfaces of the protruding portions of the embossed pattern is smaller than a total of areas of inter-protruding-portions in the signal area,
wherein the signal area in which the embossed pattern has been formed and a non-signal area in which there is no embossed pattern are present on the surface of the master information carrier,
an average height of the upper surfaces of the protruding portions of the embossed pattern is not smaller than 50 nm, and
dispersion 3σ of heights of the upper surfaces of the protruding portions is not larger than 10 nm.
2. The master information carrier as defined in claim 1 , wherein the upper surfaces of the protruding portions are higher than a surface of a non-signal area by a height in a range from 500 nm to 800 nm.
3. A method for producing a magnetic disk which carries information represented by a signal pattern, comprising the steps of:initial-magnetizing a magnetic recording layer by applying a magnetic field in a predetermined direction to a disk-shaped slave medium having the magnetic recording layer at least on a surface of a non-magnetic substrate; and
magnetically transferring information by applying a magnetic field in an approximately opposite direction to the direction in initial-magnetizing while the magnetic recording layer on the slave medium, which has been initial-magnetized and a surface of a disk-shaped master information carrier which carries the signal patter to be transferred are placed in close contact with each other, wherein the disk-shaped master information carrier has a signal area in which an embossed pattern representing the signal pattern to be transferred has been formed on the surface of the disk-shaped master information carrier, wherein a shortest bit length of the embossed pattern in a direction of track is 300 nm or less, wherein a total of areas of upper surfaces of protruding portions of the embossed pattern is less than 50% of a total of the signal area,
wherein the signal area in which the embossed pattern has been formed and a non-signal area in which there is no embossed pattern are present on the surface of the master information carrier,
an average height of the upper surfaces of the protruding portions of the embossed pattern is not smaller than 50 nm, and
dispersion 3 σ of heights of the upper surfaces of the protruding portions is not larger than 10 nm.
4. The method for producing a magnetic disk, as defined in claim 3 , wherein the signal pattern to be transferred is a servo signal.