Dynamic magnetic information storage or retrieval – General recording or reproducing – Thermomagnetic recording or transducers
Reexamination Certificate
2001-02-02
2004-05-04
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Thermomagnetic recording or transducers
C369S013250
Reexamination Certificate
active
06731446
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This applications claims the priority of Japanese Patent Nos. 2000-025854, 2000-048721, 2000-075226, 2000-110418, 2000-134611, 2000-234227, 2000-255876, the contents of all of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a magnetic pattern in a is magnetic recording medium used for a magnetic recording device, a magnetic recording medium, or a magnetic recording device. In particular, the present invention relates to a method for forming a magnetic pattern in a magnetic recording medium, a magnetic recording medium, or a magnetic recording device wherein the magnetic recording medium has a magnetic layer, a protective layer, and a lubricant layer, where a flying/contact magnetic head used for recording or reproducing.
2. Background of the Invention
Magnetic recording devices such as a magnetic disk device (a hard disk drive) have widely been used as external memory devices for information processing devices such as computers, and have recently been used as recording devices for devices for recording dynamic images or set-top boxes.
A typical magnetic disk device includes a shaft for holding a single or plurality of magnetic disks while penetrating the center of the magnetic disk or disks, a motor for rotating the magnetic disk or disks that is or are connected to the shaft by interposing a bearing or bearings, a magnetic head for recording/reproduction information, an arm for supporting the magnetic head, and an actuator for moving the magnetic head via the arm to a desired position on the magnetic recording medium. As the recording/reproduction head, a flying magnetic head capable of moving above the magnetic recording medium at a constant flight height is generally used.
In addition to a flying magnetic head, a contact magnetic head is proposed in order to reduce the distance from the magnetic head to the medium. The magnetic recording medium to be placed in the magnetic disk device is prepared, in general, by forming a NiP layer on the surface of a substrate that includes an aluminum alloy, applying a smoothening treatment, a texturing treatment, or the like thereon, and then forming a metallic underlayer, a magnetic layer (an information recording layer), a protective layer, a lubricant layer, and the like in this order thereon. Or, the magnetic recording medium is prepared by forming a metallic underlayer, a magnetic layer (an information recording layer), a protective layer, a lubricant layer, and the like on the surface of a substrate made of glass or the like. The magnetic recording medium includes a longitudinal magnetic recording medium and a perpendicular magnetic recording medium. In the longitudinal magnetic recording medium, longitudinal recording is generally conducted.
The rate of increase in the density of magnetic recording media is increased year by year, and various techniques for increasing density have been proposed. For example, there are attempts to make the flying height of the magnetic head smaller, to employ a GMR head as the magnetic head, to improve a magnetic material used for the recording layer of the magnetic disk so as to have a strong coercive force, and to reduce the space between tracks for recording information in the magnetic disk. For example, a density of track of 100 ktpi or more is needed in order to realize 100 Gbit/inch
2
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In each track, a magnetic pattern for controlling the magnetic head is formed. For example, it produces signals used for controlling the position of the magnetic head or signals used for synchronous control. When the space between adjacent information recording tracks is narrowed to increase the number of tracks, it is necessary to increase the density of the signals for controlling the position of a data-recording/reproduction head (hereinbelow, referred to as “a servo signal”) in the radial direction of the disk. In other words, in response to the increased number of tracks, an increased number of signals for controlling the position of a data-recording/reproduction head much is required so that precision control can be performed.
Further, there is an increased demand for increases in the width of the data recording area. This would allow an increase in the data recording capacity by reducing the surface area not used for recording data, namely, the servo areas used for recording servo signals and the gap portions between the servo areas and the data recording areas. Thus, it is necessary to increase the data content of the servo signals or to increase the accuracy of synchronizing signals.
In a conventional method that is used widely in manufacturing, an opening is formed in the vicinity of the head actuator of the drive (magnetic recording device) and a pin with an encoder is inserted into the opening to engage the actuator with the pin. Servo signals are then recorded by moving the head to a correct position. However, methods based upon this approach encountered difficulty in correctly recording the servo signals because the position of the center of gravity of the actuator was different from the position of the center of gravity of a positioning mechanism, so that highly accurate track position control could not be obtained.
On the other hand, it has been proposed that laser beams be irradiated onto a magnetic disk to locally deform the surface of the disk. Minute projections and recesses can thus be physically formed and servo signals recorded by the minute projections and recesses. In this technique, however, there are problems such as the fact that: the projections and recesses make the flying magnetic head unstable and adversely influence the recording and/or reproduction of information; costly high power lasers are necessary for forming the projections and recesses; and relatively large amounts of time were required to successively form the individual projections and recesses.
In view of the above, several servo signal forming methods have been proposed.
For example, in one method a servo pattern is formed in a master disk having a magnetic layer with a high coercive force. The master disk is brought into close contact with a magnetic recording medium and then an external auxiliary magnetic field is applied to the magnetic recording medium, thus printing a magnetic pattern, as described in U.S. Pat. No. 5,991,104.
In another exemplary method, a medium that has previously been magnetized along a certain direction is formed. First, a ferromagnetic layer that includes a soft magnetic layer is formed by patterning on a master disk, and the master disk is brought into close contact with the medium. Then, an external magnetic field is applied. The soft magnetic layer functions as a shield, and a magnetic pattern is printed to an unshielded area, as described in Japanese Patent JP-A-50-60212, U.S. Pat. No. 3,869,711, Japanese Patent JP-A-10-40544, EP915456, and the article “Readback Properties of Novel Magnetic Contact Duplication Signals with High Recording Density FD” authored by R. Sugita et al., and published by IEEE in the Digest of InterMag 2000, GP-06 on Apr. 9, 2000.
With respect to forming a shield or using a magnetic recording source, the above-mentioned techniques use a master disk, and a magnetic pattern is formed in the medium by applying a strong magnetic field.
The intensity of a magnetic field generally is a function of distance. When a magnetic pattern is recorded by applying a magnetic field, the transitions in the magnetic pattern are apt to be blurred due to a leakage of the magnetic field. Accordingly, it is necessary to bring the master disk into intimate contact with the medium in order to minimize the influence of the leakage of the magnetic field. As the magnetic pattern becomes finer, it is necessary to intimately contact the master disk to the medium without any gap. Usually, both members are press-contacted using vacuum suction.
Further, the higher that the coercive force of the medium is, the larger the magnetic field required for tran
Arita Youji
Ikeda Hiroyuki
Kawashima Masahiro
Kuriwada Takeshi
Seo Yuzo
Davidson Dan I.
Sniezek Andrew L.
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