JP2003016735A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which allows excellent track control and easy production thereof. SOLUTION: A magnetic pattern which is made by alternately forming two phase patterns 10A, 10B is recorded to the magnetic recording medium by means of magnetic transfer. The respective patterns 10A, 10B comprise a plurality of elements 10a, 10b intersecting obliquely in the track direction X of data track t and, therein, the value αof inclination with respect to the direction R vertical to the track direction X of the elements 10a, 10b (the radial direction) is made to be within ±45 deg., preferably within ±30 deg..

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium having a magnetic pattern corresponding to a signal for tracking servo. 2. Description of the Related Art In general, in a magnetic recording medium, as the amount of information increases, a large capacity for recording a large amount of information, a low cost, and preferably a required portion can be read out in a short time. A medium capable of high-speed access is desired. As an example of this, a high-density magnetic recording medium such as ZIP (Iomega Corporation) composed of a hard disk and a flexible disk is known. In these high-density magnetic recording media, the information recording area is composed of narrow tracks, and the narrow track width is accurately scanned by a magnetic head, resulting in a high S /
In order to reproduce a signal with N, a so-called tracking servo technique plays a major role. In order to perform tracking servo, a sector servo system has been widely employed. In the sector servo system, servo signals for track positioning, servo information such as track address information signals, playback clock signals, etc. are recorded in servo fields regularly arranged at a fixed angle on the data surface of the disk. The magnetic head scans the servo field, reads servo information, and confirms and corrects its own position. As a servo signal for track positioning, a method using reproduction amplitude information of a servo signal is widely known, but a method using reproduction phase information is also known to be suitable for higher accuracy track positioning. Yes. Generally, a phase servo pattern is formed across a plurality of magnetization inversion regions (herein referred to as elements) which are formed across a plurality of tracks and which are obliquely crossed with respect to the track direction and arranged at intervals in the track direction. ), And by alternately arranging elements having different inclination directions with respect to an axis perpendicular to the track direction,
It is formed so that the phase of the reproduction servo signal changes. These servo signals need to be recorded on the magnetic recording medium in advance as a preformat when the magnetic recording medium is manufactured, and are currently preformatted using a dedicated servo recording device (servo track writer). Yes. Currently used servo recording devices write a pattern while moving a magnetic head having a predetermined width in the track width direction little by little in the radial direction. They are connected together, and this constitutes a macroscopically continuous element. In order to improve accuracy in servo signal detection by the magnetic head during data recording / reproduction, it is preferable to eliminate such a microscopic step and to have a linear edge that is microscopically continuous. By reducing the moving pitch of the magnetic head, the level difference can be reduced. However, if the moving pitch is reduced, the time required for preformatting becomes longer and the productivity is lowered. Further, it is difficult to form a line having no step. As a method of manufacturing a magnetic recording medium having ideal elements without steps, Japanese Patent Laid-Open No. 10-83640 discloses a resist pattern corresponding to a servo pattern on the surface of a support. A method has been proposed in which a groove is formed in a pattern using, a hard magnetic layer is embedded in the groove of a support, and a magnetic layer is uniformly formed thereon. The hard magnetic layer embedded in the groove and the magnetic layer thereon are magnetized to form a portion corresponding to the above-described element.
Since the resist pattern is formed using an exposure mask for forming the groove, there is no step if the portion corresponding to each element of the exposure mask is formed by a shape surrounded by a continuous line such as a straight line or a curve. An ideal element can be obtained. However, the layer structure of this magnetic recording medium is complicated, and its manufacturing process is very complicated, so it is not practical. On the other hand, as a method for performing preformatting accurately and efficiently, a method of transferring a pattern carrying servo information formed on a master carrier onto a magnetic recording medium by magnetic transfer is disclosed in Japanese Patent Application Laid-Open No. 63-183623. ,
Japanese Patent Laid-Open Nos. 10-40544 and 10-2695
No. 66 is proposed. For this magnetic transfer, a master carrier having a concavo-convex pattern having a magnetic layer on the convex surface corresponding to information to be transferred to a magnetic recording medium (slave medium) such as a magnetic disk medium is prepared. A magnetic pattern corresponding to information (for example, servo signals) carried by the concave / convex pattern of the master carrier is magnetically transferred to the slave medium by applying a transfer magnetic field with the carrier and the slave medium in close contact with each other. Advantages of being able to record statically without changing the relative positions of the master carrier and slave medium, enabling accurate preformat recording, and extremely short recording time have. In view of the above circumstances, an object of the present invention is to provide a magnetic recording medium having a phase pattern capable of good track control even with a narrow track width. The magnetic recording medium of the present invention is a magnetic recording medium provided with a servo signal pattern magnetically, and the pattern crosses obliquely with respect to the track direction. And a phase pattern composed of a plurality of elements arranged at intervals in the track direction, wherein the pattern is formed by magnetic transfer. Here, each element of “a plurality of elements extending obliquely with respect to the track direction...” Is preferably in a shape having microscopically continuous linear edges. Each element is preferably formed across a plurality of tracks. Here, the element is a region where the magnetization is reversed with respect to the peripheral portion of the element.
A phase pattern composed of a plurality of elements is formed by forming a plurality of elements (regions having magnetizations opposite to the one direction) on a magnetic layer magnetized in one direction. The inclination of each element with respect to the direction perpendicular to the track direction is preferably within ± 45 degrees, and more preferably within ± 30 degrees. When the magnetic recording medium is a magnetic disk, the track direction means the circumferential direction, and the direction perpendicular to the track direction means the disk radial direction. The magnetic recording medium of the present invention comprises a phase pattern including a plurality of elements extending at an interval in the track direction and extending obliquely in the track direction of the data track. Since this phase pattern is formed by magnetic transfer, it can be provided with a highly accurate magnetization pattern very easily. By using magnetic transfer, each element constituting the phase pattern can be formed into a shape having microscopically continuous linear edges. Since the magnetic head provided in the conventional servo recording apparatus has a predetermined width extending in the direction perpendicular to the normal track direction, the length of each element constituting the magnetic pattern is the magnetic head. It was very difficult to form long elements with microscopically continuous edges, limited by the shape of the head. On the other hand, in magnetic transfer, since a master carrier having patterns corresponding to elements of various shapes can be easily formed, elements having shapes having microscopic continuous linear edges are formed. Is also easy. Further, it is not necessary to consider variations such as the head width for each magnetic head of the servo recording apparatus. If each element has a shape having a linear edge that is microscopically continuous, position control can be performed with higher accuracy than a phase pattern made of a conventional element having a stepped edge. Further, a large number of magnetic recording media can be preformatted using one master carrier.
Since the transfer time per sheet is also short, the production efficiency of the preformatted magnetic recording medium can be improved. In general, a magnetic pattern is transferred onto the entire surface of a disk-shaped magnetic recording medium by generating a magnetic field in a part of the track direction (circumferential direction) and bringing the master carrier and the magnetic recording medium into close contact with the magnetic field. Rotate in the state where The present applicants experimentally confirmed the in-plane angle margin for obtaining good transfer performance by such a magnetic transfer method, and the inclination of each element with respect to the direction perpendicular to the track direction (disk radial direction) is ± 45. Within 3 degrees, more preferably ± 3
It has been found that within 0 degree is suitable. When the angle is more than this, even if an attempt is made to optimize a parameter such as a transfer magnetic field, the transfer signal quality, for example, the reproduction signal CNR is clearly deteriorated. That is, if the inclination of each element with respect to the direction perpendicular to the track direction (the radial direction of the disk) is within ± 45 degrees, a magnetized pattern with good transfer quality can be transferred, and even within ± 30 degrees. Better transfer quality can be obtained. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment of the magnetic recording medium of the present invention. FIG. 1 is a partially enlarged view of a recording / reproducing layer of a magnetic recording medium, and shows a part of a servo signal pattern.
The magnetic recording medium is a disk-shaped magnetic recording medium such as a high-density flexible disk or a hard disk, and has a configuration in which a recording / reproducing layer made of a magnetic layer is provided on a support. In particular, in order to achieve high density, a thin layer coated magnetic layer or a metal thin film magnetic layer is preferably used as a recording / reproducing layer. The support may be flexible or hard. A plurality of tracks are formed on the recording / reproducing layer of the magnetic recording medium, and a magnetic pattern carrying a servo signal is recorded on the magnetic recording medium of this embodiment by magnetic transfer described later. This magnetic pattern 10 includes phase patterns 10A and 10B, and can be visualized and confirmed by means such as magnetic development as necessary. The magnetic pattern 10 carrying the servo signal shown in FIG. 1 is formed by alternately forming two phase patterns 10A and 10B having different inclinations with respect to the track direction. , A plurality of elements crossing diagonally in the track direction X of the data track t
10a and 10b. In this embodiment, the elements 10a and 10b extend over four tracks tn to tn + 3 and have an inclination of α with respect to a direction R (radial direction) perpendicular to the track direction X. The magnitude α of the inclination is within ± 45 °, preferably within ± 30 °. In FIG. 1, the inclination angles of the patterns 10A and 10B are set to the same α for simplicity, but may be different from each other.
As typically shown in the track tn + 1 in FIG. 1, the element is a region in which the magnetization is reversed with respect to another region,
The edge 11 of this element is formed in a microscopically continuous line. Although the phase pattern is formed with 4 tracks as a unit here, the number of tracks as a unit is not limited to this. The track positioning is performed by detecting the position information based on the phase difference between the reproduction servo signals of the pattern 10A and the pattern 10B. The edge 11 of each element is formed in a line that is microscopically continuous, so the sensitivity of pattern detection by the head is higher and the accuracy is higher than in the case of a conventional pattern with microscopic steps on the edge. Good track positioning is possible. As the magnetic pattern carrying the servo signal, only the single pattern 10A shown in FIG. 1 is recorded in addition to the magnetic pattern combining the two phase patterns having different inclinations shown in FIG. May be. Even with such a single phase pattern 10A alone, it is possible to detect head position information using phase detection. FIG. 2 shows a magnetic pattern in the magnetic recording medium of the second embodiment. The magnetic pattern 20 of the second embodiment includes a pattern 20A in which a plurality of elements 20a crossing obliquely in the track direction of a data track are arranged in a fan shape with the track tn side closed, and an element 20b is a track t
Patterns 20B arranged in a fan shape with the n + 3 side closed are arranged alternately. Fan-shaped magnetic pattern 20 as shown in FIG.
That is, if the patterns 20A and 20B have different elements 20a at different positions in the track width direction, the head position information is detected by utilizing the reproduction frequency and phase of the reproduction servo signal depending on the head position. Thus, positioning can be performed. Next, a method for forming a magnetic pattern carrying a servo signal on the magnetic recording medium of the present invention will be described. The magnetic pattern is formed by magnetic transfer in which information is magnetically transferred to a magnetic recording medium, which is a slave medium, using a master carrier. The basic process will be described with reference to FIGS. FIG. 3 is a perspective view showing the slave medium 2 and the master carriers 3 and 4. As described above, the slave medium 2 is a magnetic recording medium having data surfaces (recording / reproducing surfaces) 2d and 2e in which magnetic layers are formed on both surfaces of a flexible or hard disk-shaped support 2c. The master carriers 3 and 4 are formed into an annular disk by a rigid body, and the magnetic recording medium 2 is formed on one side thereof.
The recording / reproducing surfaces 2d and 2e have a transfer information carrying surface formed with a concavo-convex pattern corresponding to a servo signal. The master carriers 3 and 4 are respectively provided with concave and convex patterns for the lower recording / reproducing surface 2d and the upper recording / reproducing surface 2e of the magnetic recording medium 2. The concavo-convex pattern includes a phase pattern carrying a servo signal. For example, when a magnetic pattern as shown in FIG. 1 is formed on a magnetic recording medium, according to each element constituting the magnetic pattern, The convex part which inclines in a disk radial direction should just be formed. The master carriers 3 and 4 shown in FIG.
The substrate 3a, 4a on which the concavo-convex pattern is formed and the soft magnetic layers 3b, 4b formed on the concavo-convex pattern, but only the substrate when the substrate 3a, 4a is a ferromagnetic material such as Ni. The magnetic transfer is possible, and the soft magnetic layers 3b and 4b are not necessarily covered. However, better magnetic transfer can be performed by providing a magnetic layer with good transfer characteristics. When the substrate is a nonmagnetic material, it is necessary to provide a magnetic layer. Furthermore, if a protective film such as diamond-like carbon (DLC) is coated on the uppermost layer, this protective film improves the contact durability and enables multiple times of magnetic transfer. Further, a Si film may be formed under the DLC protective film by sputtering or the like. FIG. 3 shows a state in which the magnetic recording medium 2 and the master carriers 3 and 4 are separated from each other. Actual magnetic transfer is performed by using the recording / reproducing surfaces 2d and 2e of the magnetic recording medium 2 and the master carrier 3 as shown in FIG. The four soft magnetic layers 3b and 4b are in close contact with each other. FIG. 4 is a diagram for explaining the basic steps of this magnetic transfer. FIG. 4 (a) is a step in which a magnetic field is applied in one direction and the magnetic recording medium is initially DC magnetized. (C) is a view showing a state after magnetic transfer, in which a master carrier and a magnetic recording medium are in close contact with each other and a magnetic field in the opposite direction is applied. In FIG. 4, only the lower surface recording / reproducing surface 2d of the magnetic recording medium 2 is shown. As shown in FIG. 4A, an initial DC magnetization is applied to the magnetic recording medium 2 in advance by applying an initial magnetic field Hin in one direction in the track direction. After that, as shown in FIG. 4B, the recording / reproducing surface 2d of the magnetic recording medium 2 and the information carrying surface formed by coating the magnetic layer 3b on the concave / convex pattern of the substrate 3a of the master carrier 3 are brought into close contact with each other. The magnetic field for transfer H in the direction opposite to the initial magnetic field Hin in the track direction of the recording medium 2
Magnetic transfer is performed by applying du. As a result, as shown in FIG. 4C, information (here, a servo signal) corresponding to the uneven pattern of the information carrier surface of the master carrier 3 is magnetically transferred to the recording / reproducing surface 2d of the magnetic recording medium 2. To be recorded. Here, the lower recording surface 2d and the lower master carrier 3 of the magnetic recording medium 2 have been described, but the upper recording / reproducing surface 2e of the magnetic recording medium 2 is also brought into close contact with the upper master carrier 4 to similarly perform magnetic transfer. Do. Note that the magnetic transfer to the upper and lower recording / reproducing surfaces 2d and 2e of the magnetic recording medium 2 may be performed simultaneously or sequentially one by one. It should be noted that the initial magnetic field and the magnetic field for transfer need to adopt values determined in consideration of the coercive force of the magnetic layer of the magnetic recording medium and the relative magnetic permeability of the magnetic layer of the master carrier and the magnetic recording medium. . Elements 10 that are not orthogonal to the track direction (head movement direction), such as the magnetic pattern 10 in FIG.
Although it is difficult to provide a with high accuracy by the conventional servo write method, it can be easily formed by using magnetic transfer as in this embodiment. FIG. 5 is a perspective view showing a main part of a magnetic transfer apparatus 1 for performing magnetic transfer. This magnetic transfer device
A magnetic field in the circumferential direction is generated in a part of the track longitudinal direction (circumferential direction) over the length of the disk radius and the holder 8 that holds the magnetic recording medium 2 and the master carriers 3 and 4 in close contact with each other. An electromagnet device 5 as a magnetic field generating means and a holder 8
Is provided with a moving means (not shown) that makes one rotation relative to the magnetic field generated by the electromagnet device 5. As described above, the magnetization of the magnetic layer of the magnetic recording medium 2 is previously magnetized in one direction of the track, and thereafter, the magnetic recording medium 2 and the master carrier 3 are brought into close contact with each other and accommodated in the holder 8 to be magnetized. Set in the transfer device 1. The electromagnet device 5 applies a transfer magnetic field Hdu opposite to the initial magnetization direction to a part of the track direction over the radial direction of the disk. In this state, the magnetic pattern is transferred to the magnetic recording medium 2 by rotating the holder 8 once. At this time, since the inclination of the elements constituting the magnetic pattern formed on the magnetic recording medium with respect to the radial direction of the disk is within ± 45 °, preferably within ± 30 °, good magnetic pattern transfer is possible. It can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially enlarged view of a magnetic recording medium according to a first embodiment of the present invention. FIG. 2 is a partially enlarged view of a magnetic recording medium according to a second embodiment of the present invention. FIG. 4 is a perspective view showing a master carrier and a magnetic recording medium. FIG. 4 is a diagram showing basic steps of a magnetic transfer method. FIG. 5 is a diagram showing a main part of a magnetic transfer apparatus. 3, 4 Master carrier 5 Electromagnet device 10, 20 Magnetic pattern 10a, 10b Magnetic pattern element

─────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme code (reference) G11B 21/10 G11B 21/10 B F term in Fuji Photo Film Co., Ltd. (reference) 5D006 DA02 5D044 BC01 CC04 DE02 DE46 EF05 5D096 AA02 GG01 GG10

Claims (1)

What is claimed is: 1. A magnetic recording medium in which servo signal patterns are magnetically provided, wherein the patterns extend obliquely with respect to the track direction and have an interval in the track direction. A magnetic recording medium comprising a phase pattern composed of a plurality of elements arranged in a magnetic field, wherein the pattern is formed by magnetic transfer.