Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse... – Magnetic field and light beam
Reexamination Certificate
2001-12-21
2004-12-07
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Magnetic field and light beam
Reexamination Certificate
active
06829201
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information recording medium and a method for recording and reproducing the same, and particularly to an information recording medium on which tracking servo information is magnetically preformat-recorded, and a method for recording and reproducing for an information recording medium in which at least one of recording and reproduction of information is carried out while reading servo information using the information recording medium and performing tracking. The present invention also relates to an information recording method in which information is recorded on the image recording medium by a magneto-optic system utilizing near field light. Further, the present invention relates to a manufacturing method of an information recording medium, and particularly to a manufacturing method of an information recording medium on which tracking servo information is magnetically preformat-recorded.
2. Description of the Related Art
With a rapid increase in the amount of information to be handled by a personal computer, large-capacity and low-cost information recording media which permit reduction of access time have been developed one after another. Examples of such large capacity information recording media include a built-in magnetic recording medium such as a hard disk, and a removable magnetic recording medium such as a Zip disk developed by Iomega Corp.(in U.S.). The hard disk or Zip disk realizes large capacity recording by reducing the width of each track to increase a track density. In order that a narrow track be accurately scanned by a magnetic head and a recording signal be reproduced at a favorable signal to noise ratio (S/N), tracking servo technique in which the position of a magnetic head is corrected by detecting relative displacement of the magnetic head and the track, performs an important function.
In the hard disk or Zip disk, a tracking servo signal, an address information signal, a reproduction clock signal and the like are in advance recorded (preformat-recorded) with high positional accuracy at the time of manufacturing magnetic recording media. A region in which these signals are recorded, that is, a servo region is disposed discretely to the surface of a disk, and a magnetic head accurately scans a track while confirming and correcting the position of the head by reproducing these signals.
As a next-generation high density recording system, a recording system utilizing near field light (a near-field light recording system) is considered to be effective. In this recording system, it is expected that high density recording of 100 gigabits/inch
2
or more becomes possible.
Near field light is non-propagation light which is generated when light scatters and diffracts in a micro-aperture having a diameter which is the wavelength or less, and is localized in the vicinity of the micro-aperture (that is, in a region from a light emission end of the micro-aperture to the wavelength of the light). Further, near field light can also be generated by condensing light in a solid immersion lens (SIL). Due to light recording using the near field light, a recording mark smaller than a recording mark obtained by normal light recording can be formed, thereby resulting in a remarked increase in the surface recording density of information.
The near field light exists only in a region from a light emission end of the micro-aperture or SIL, which is a recording head, to the wavelength of light. Therefore, recording and reproducing needs to be carried out in such a manner that means for generating near field light and a detector (head) of the light are disposed extremely in the vicinity of the recording medium (specifically, in a region apart from the recording medium by a distance of several tens nm or less).
However, accompanied with a further increase in the recording density, the track width is becoming narrower. In a conventional servo system, there exists a problem in that accurate scanning of tracks by a magnetic head (servo following) is not permitted. There is a high possibility that a problem may arise in servo following, particularly in the recording density of 100 gigabits/inch
2
or more. Further, if a trial to reliably perform servo following is made by increasing the ratio of a servo region to the area of a disk, a recording region is reduced and a large recording capacity is difficult to maintain.
Further, in an optical disk, a servo system is employed wherein tracking is performed by using a tracking guide having a land/groove structure in which tracks are provided concentrically or spirally in the disk. However, this system has a problem in that large unevenness exists on the disk surface. Accordingly, in the next-generation high density recording system in which a detector needs to be disposed extremely in the vicinity of a recording medium, it is difficult to realize a stable running or flying state of the head.
Moreover, exact positioning accuracy is required by preformat-recording. Therefore, conventionally, a magnetic recording medium is built in a drive, and thereafter, recording is carried out by a magnetic head which is exactly position-controlled by using a servo recording device dedicated thereto.
However, the amount of signals to be preformat-recorded increases accompanied with the increase in magnetic recording density. Therefore, there exists a problem in that a lot of time is required for preformat-recording, which leads to deterioration of production efficiency.
Further, there has also been proposed a method in which a magnetic-transfer master carrier with a predetermined magnetization pattern being formed thereon by a magnetic layer, is used and the predetermined magnetization pattern is transferred to a slave medium to allow preformat-recording. However, in the conventional transfer method, it was necessary to use a magnetic-transfer master carrier having coercive force (HC) which is at least three times the coercive force of the slave medium such that the magnetization pattern of the magnetic-transfer master carrier should not be demagnetized even if it is excited by an external magnetic field. When a flat magnetic body is partially magnetized, the antimagnetic force of a magnetic body used in a magnetic recording medium for high density recording is a high value, that is, 2000 Oe or thereabouts, and the coercive force of the magnetic-transfer master carrier is 6000 Oe or more. Accordingly, a certain magnetic material can only be used for the magnetic-transfer master carrier, and it was virtually difficult to form a minute magnetic pattern.
SUMMARY OF THE INVENTION
The present invention has been achieved in view of the problems of the above-described prior art, and an object thereof is to provide an information recording medium which permits accurate tracking servo, particularly, an information recording medium which allows stable running of the head even when a detector is disposed extremely in the vicinity of the recording medium. Another object of the present invention is to provide a method for recording and reproducing for an information recording medium, in which recording (high density recording) and reproducing of signals can be carried out at a favorable S/N by carrying out at least one of recording and reproducing of information while accurately performing tracking servo.
Further, still another object of the present invention is to provide a manufacturing method of an information recording medium, in which an information recording medium which permits accurate tracking servo can be manufactured precisely in a short time.
In order to achieve the above-described objects of the present invention, there are provided a 1st to a 39th aspects.
A 1st aspect of the present invention is an information recording medium comprising a substrate disposed thereon a magnetic recording layer for magnetically recording information,
wherein the magnetic recording layer is in advance magnetized concentrically or spirally around a center of a disk for tracking and is disp
Nagao Makoto
Nishikawa Masakazu
Usami Yoshihisa
Usuki Kazuyuki
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