JPH11110748A - Magnetic disc, its manufacture and magnetic recording/ reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a levitation height constant regardless of a position and obtain excellent electromagnetic conversion characteristics without applying a specific process to a magnetic head by a method wherein the cross-sectional areas in the radial direction of guard band grooves which are formed continuously or continually on a disc-type nonmagnetic substrate concentrically are gradually increased from the inner circumference side toward the outer circumference side. SOLUTION: A plurality of guard band grooves 13 are formed on a substrate with constant intervals in a radial direction and, further, recording tracks 14 are formed continually between the respective guard band grooves 13 adjacent to each other in the radial direction. Preferably, the guard band grooves 13 are so formed on a nonmagnetic substrate made of plastic as to have their depths H or radial direction widths W gradually increased from the inner circumference side toward the outer circumference side and, further, a stamper having transfer patterns corresponding to the guard band grooves 13 and recording tracks 14 is placed in a mold for injection molding or compression molding and the transfer patterns are transferred onto the nonmagnetic substrate simultaneously when the nonmagnetic substrate is formed by molding to obtain a magnetic disc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk used as a recording medium for storing data and the like in a computer, a method of manufacturing the same, and a magnetic recording / reproducing apparatus.

[0002]

2. Description of the Related Art In general, a magnetic disk includes a disc-shaped non-magnetic substrate and a magnetic layer formed on a magnetic head-facing side surface of the substrate.
The substrate is provided with a plurality of concentric and circumferentially continuous or intermittent guard band grooves at substantially equal intervals in the radial direction, and a recording track is provided between each of the radially adjacent guard band grooves. Is formed.

Conventionally, for example, Japanese Patent Laid-Open No. 63-25581
As disclosed in Japanese Unexamined Patent Publication No. 6 (1994), a method is known in which the same plastic as an optical disk substrate is used as a substrate material, and the substrate is formed by injection molding. A pattern corresponding to a guard band groove or a recording track is previously formed on the inner surface of the injection molding die, and the pattern is transferred to the substrate at the same time when the substrate is molded by the injection molding. Thus, the guard band groove and the recording track are formed.

When forming a physical format of a magnetic disk, a magnetic head is used to form a physical layer over the entire area of the magnetic layer.
Much time is spent recording the matte signal.
As a new form of magnetic disk for avoiding this, as disclosed in Japanese Unexamined Patent Publication No. 3-86912, a servo signal is uniformly determined in advance in the uneven state of a substrate, and the same signal is formed by injection molding or the like. Mass production of substrates having irregularities on the substrate, uniformly forming a magnetic layer on the irregularities side of each substrate, forcibly magnetizing the magnetic layer in one direction, and detecting a leakage magnetic field generated by the irregularities with a magnetic head. Some attempt to read the servo signal. this is,
It is promising as a means for providing a large amount of magnetic disks on which a physical format is formed at low cost.

[0005] Such a magnetic disk is widely used as a recording medium for storing data in a computer, for example. A magnetic recording / reproducing apparatus using this magnetic disk is referred to as a so-called winch-esta type as a method for floating a magnetic head with respect to the magnetic disk. In other words, in this magnetic recording / reproducing apparatus, the magnetic head is floated from the surface of the magnetic disk by an air flow generated by relative movement with the magnetic disk so as to keep a small interval of 50 nm or less, and the magnetic head and the magnetic head By transmitting and receiving a magnetic field between disks,
Recording or reproduction of data or the like.

[0006]

However, the relative speed between the magnetic head and the magnetic disk is higher when the magnetic head is located on the outer peripheral side of the magnetic disk when accessing the magnetic head than when it is located on the inner peripheral side. The flying height of the magnetic head tends to increase as the magnetic head is located on the outer peripheral side. For this reason, there is a problem that the electromagnetic conversion characteristics deteriorate as the magnetic head is located on the outer peripheral side of the magnetic disk.

Therefore, conventionally, various attempts have been made on the slider surface of the magnetic head to suppress abnormal floating of the magnetic head. However, processing of the slider surface of the magnetic head becomes complicated. At present, the cost of magnetic heads has increased significantly and has not been a practical solution.

In view of such circumstances, the present invention provides a good electromagnetic conversion by maintaining the flying height of the magnetic head at any position on the inner and outer circumferences of the magnetic disk without processing the magnetic head. It is intended to provide a magnetic disk capable of obtaining characteristics. Also, the present invention
It is an object of the present invention to provide a method of manufacturing a magnetic disk capable of obtaining the magnetic disk in large quantities at low cost, and a magnetic recording / reproducing apparatus which further includes the magnetic disk and can appropriately transmit and receive data.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the guard band grooves provided on the disc-shaped non-magnetic substrate have been shifted from the inner peripheral side to the outer peripheral side. If the magnetic head has the same cross-sectional area, the levitation pressure increases as the magnetic head is located on the outer peripheral side, but when the cross-sectional area of the guard band groove is larger on the outer peripheral side than on the inner peripheral side,
The inventors have found that the increase in the floating pressure is suppressed, and have completed the present invention.

That is, the present invention comprises a disk-shaped non-magnetic substrate and a magnetic layer formed on the magnetic head-facing side surface of the substrate, and the magnetic head-facing side surface of the substrate is concentric with the substrate. And a plurality of guard band grooves continuous or intermittent in the circumferential direction are provided at substantially equal intervals in the radial direction, and a recording track is formed between each of the radially adjacent guard band grooves. A magnetic disk according to claim 1, wherein said guard band groove is set such that a cross-sectional area along a radial direction becomes larger as the guard band groove is located closer to the outer peripheral side than to the circumferential side of said substrate. Claims 1 to 3).

Further, according to the present invention, there is provided a method of manufacturing a magnetic disk having a disk-shaped non-magnetic substrate formed of plastic, wherein a stamper having a guard band groove and a transfer pattern corresponding to a recording track is injected. It is arranged in a mold for injection molding or injection compression molding, and the plastic is injection molded or injection compression molded to form a disc-shaped non-magnetic substrate, and at the same time, the transfer pattern is transferred to the substrate. Method of manufacturing magnetic disk (claim 4)
It is related to. Further, the present invention relates to a magnetic recording / reproducing apparatus provided with the above-mentioned magnetic disk (claim 5).

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an example of the magnetic disk of the present invention, and FIG. 2 is an enlarged sectional view showing a part of FIG. In this example, a pre-embossed magnetic disk M is shown in which a concave / convex mark (prepit) is physically provided on the side (one surface) of the disk-shaped non-magnetic substrate facing the magnetic head.

1 and 2, reference numeral 1 denotes a disc-shaped non-magnetic substrate, which is made of, for example, a plastic as a non-magnetic material. And at least the magnetic layer 2 is formed thereon. Reference numeral 3 denotes a driven central hole formed in the substrate 1. A magnetic layer may be formed on the other surface of the substrate 1.

FIG. 3 is a perspective view showing the surface structure of the substrate 1 of the magnetic disk M. In FIG. 3, reference numeral 12 denotes a magnetic disk M corresponding to one surface of the disc-shaped non-magnetic substrate 1.
The magnetic head disposed above the magnetic head 12.
Performs a recording or reproducing operation by relatively moving along a locus of the magnetic disk M in the circumferential direction (the direction of arrow a).

On one surface of the disc-shaped non-magnetic substrate 1, the magnetic head 12 is concentric with the substrate 1, that is, parallel to the circumferential locus of the magnetic head 12 and continuous or intermittent in the circumferential direction. A plurality of guard band grooves 13 are provided at substantially equal intervals in the radial direction (the direction of arrow b), and a recording track 14 is circumferentially provided between each of the radially adjacent guard band grooves 13. It is provided intermittently in the direction.

A plurality of recording tracks 14 in the radial direction form a data recording area 18, and a servo area 19 is provided between each adjacent data recording area 18 in the circumferential direction. In the servo area 19, a row of servo pits 15, a row of phase pits 16, and a row of clock pits 17 are formed. The rows of servo pits 15 are arranged circumferentially and radially offset with respect to the recording track center 14a, and the magnetic output from the radially adjacent servo pits 15 detected by the magnetic head 12 is provided. The position of the magnetic head 12 is controlled so that is equal. Thus, the magnetic head 12 always keeps the track center 14a.
Is positioned.

FIG. 4 shows an example of the track format of the magnetic disk M. In FIG. 4A, the recording track 14 is composed of a plurality of sectors (1 to M), and the sector is divided into a plurality of segments (1 to N), and a servo track is provided at the front end of each segment. -SM (SM) is formed. The service mark (SM) is an access code.
And a black mark and a fine pattern. Headers are sector mark, track N
o, sector number, redundancy check (CRC), and automatic gain control (AGC).

FIG. 4B shows the plan shape of the above-mentioned servo mark. The access code is used to check the moving speed of the magnetic head 12 at the time of access, and the clock mark is used to determine the timing of the synchronous clock and the servo mark position when performing recording and reproduction using the magnetic head 12. Used to get. That is, the clock mark is set to appear continuously for every N clocks, and is processed by the servo circuit. The fly pattern is a pattern for indicating a relative position (phase) from the track center 14a, and a tracking operation is performed by obtaining position information from the magnetic head 12.

In this magnetic disk M, the guard band groove 13 is set such that the one located closer to the outer periphery than the inner periphery of the substrate 1 has a larger sectional area along the radial direction. More specifically, as shown in FIG. 5, the depth H of the guard band groove
Is set to be large.

Next, a method of manufacturing the magnetic disk M will be described with reference to FIG. The steps up to manufacturing the substrate 1 are the same as the well-known optical disk substrate manufacturing steps. That is, first, as shown in FIG. 7A, a photoresist layer 22 is applied to the surface of a circular glass master 21 and formed by a light beam L having a short wavelength (λ = 351 nm). By cutting and developing the photoresist layer 22, a desired uneven pattern 22a is formed as shown in FIG. 7B.

As shown in FIG. 7C, the surface of the master 21 is nickel-plated to produce a stamper 23. At this time, the transfer pattern 2 corresponding to the guard band groove 13 and the recording track 14 is formed by the uneven pattern 22a.
The transfer pattern 23 is formed such that the guard band groove 13 is deeper as the guard band groove 13 is located on the outer peripheral side.
a. This may be controlled by the thickness of the photoresist layer 22.

Next, the stamper 23 is moved to the position shown in FIG.
As shown in the figure, a mold 2 for injection molding or injection compression molding.
4 (24A, 24B). In this mold 24, plastic as a base material is injection-molded or injection-compressed to produce a disc-shaped non-magnetic substrate 1. The transfer pattern 23a on the stamper 23 side is transferred to the substrate 1 to form a desired guard band groove 13 and the like.

The plastics used as the material of the substrate 1 include polyetherimide, polyethersulfone, polyphenylene sulfide, polyacrylate, polyetherketone, polymethylpentene, and polymethylmethacrylate.
Resins having excellent heat resistance and transferability, such as resin, polycarbonate and norbornene resin. In order to avoid contamination (contamination by harmful substances) contained in the plastic material, polycarbonate or a norbornene resin is particularly preferable.

After the above-mentioned molding, the substrate 1 is taken out from the mold 24, and as shown in FIG. 7E, the magnetic layer 2 and the protective layer (not shown) are formed on one surface of the substrate 1 by a sputtering method. ) Are sequentially formed. The constituent material of the magnetic layer 2 includes a cobalt-platinum alloy, a cobalt-chromium-platinum alloy, a cobalt-palladium alloy, and the like. The constituent material of the protective layer includes carbon and silicon oxide.

The magnetic layer 2 is preferably provided with an underlayer such as chromium or molybdenum so that a high coercive force can be obtained even at a low temperature. Further, for the purpose of preventing cracks in the magnetic layer 2 due to a difference in the coefficient of thermal expansion between the substrate 1 and the magnetic layer 2 and improving magnetic properties, aluminum, titanium, Alternatively, an amorphous material such as aluminum / titanium alloy, silicon, silicon nitride, or silicon oxide, or a ceramic material may be formed on the substrate 1.

After the formation of the magnetic layer 2, a burnishing process is performed using a brush 25 as shown in FIG. 7F to remove fine projections on the surface of the protective layer. Finally, in order to improve the running property of the magnetic head 12, a lubricant 26 is applied by a spin coating method as shown in FIG.
As the above lubricant, for example, “FomblinZ-
DOL "(product name) or the like.

Next, a method of magnetizing the magnetic disk M will be described with reference to FIG. First, as shown in FIG. 8A, the magnetic layer 2 formed on the substrate 1 is moved in one direction (black arrow direction) by a strong magnetic field 32A by a magnetizing magnetic head 31.
To the saturation magnetization. Thereafter, as shown in FIG.
By the magnetic head 31, a weak magnetic field 32B is applied to the magnetic layer 2 in the opposite direction, and only the portion of the magnetic layer 2 corresponding to the protrusion 33 on one surface of the substrate 1 is magnetized. As a result, as shown in FIG. 8C, a leakage magnetic flux 35 is generated from the concave portion 34 side of the substrate 1. Accordingly, by detecting the leakage magnetic flux 35 with the magnetic head 12, a signal corresponding to the pit can be detected as shown in the lower part of FIG. 8C.

As described above, since the substrate 1 is formed by injection molding or injection compression molding of the plastic, the substrate 1 can be manufactured in large quantities at low cost, and the guard band 13 and the recording track 14 can be formed. Since the stamper 23 having the corresponding transfer pattern 23a is arranged and molded in the molding die 24, the guard band groove 13 having a desired shape can be formed on the substrate without increasing the die cost. It can be easily formed simultaneously with molding. Further, by employing the above-described magnetizing method, it is possible to greatly reduce the physical format time of the magnetic disk M.

The disc-shaped non-magnetic substrate 1 is not limited to a plastic substrate, but may be a metal material such as aluminum or a glass material. In that case, the guard band groove 13 and the like can be processed by a method such as chemical etching or ion milling.

Next, FIGS. 9 and 10 show an example of a magnetic recording / reproducing apparatus N provided with the magnetic disk M. FIG. In both figures, the base 41 and this base 41
A spindle motor 44 is installed in a case 43 including a cover 42 fitted to the motor.
One or a plurality of magnetic disks M can be mounted so as to be substantially coaxial with the center of rotation of the motor 44.

Numeral 45 denotes an actuator for moving the magnetic head arranged in the case 43, and is composed of, for example, a voice coil motor. This actuator 45
Are designed to position the magnetic head 12 radially with respect to the magnetic disk M via the support spring 46. Spindle motor 44 and actuator 4
5 and the recording / reproducing operation of the magnetic head 12 are controlled by a controller (not shown) provided in the case 43.

The magnetic head 12 is, as shown in FIG.
The support spring 46 is supported on the distal end side via the slider 51. The magnetic head 12 and the slider 51
Are the viscosity of the air flow generated by the relative movement with respect to the magnetic disk M, the buoyancy generated by the shape of the slider 51, the weight of the magnetic head 12 and the slider 51, and the supporting force of the support spring 46. Is set so as to float at a minute interval of 20 to 200 nm, preferably 50 nm or less with respect to the magnetic disk M.

The relative speed between the magnetic head 12 and the magnetic disk M becomes larger when the magnetic head 12 accesses the outer peripheral side than when it accesses the inner peripheral side of the magnetic disk M. The levitation force is about to increase. However, the guard band groove 13 of the magnetic disk M
Since the depth H is set to be greater on the outer peripheral side than on the inner peripheral side, the pressure of the air for floating the magnetic head is increased as the magnetic head 12 is located on the outer peripheral side.
This is reduced by the band groove 13. Therefore, as the relative speed between the magnetic head 12 and the magnetic disk M increases, the flying height of the magnetic head 12 is suppressed from increasing, and as a result, the magnetic disk M becomes uniform from the inner circumference to the outer circumference. Electromagnetic conversion characteristics can be obtained.

In the above-described embodiment, the depth H of the guard band groove 13 is set to be larger as it is located closer to the outer peripheral side of the substrate 1, but as shown in FIG. Even if the radial width W of the band groove 13 is set to be larger on the outer peripheral side of the substrate 1, the same effect as described above can be obtained.

[0035]

EXAMPLES Examples of the present invention will be described below in more detail.

Embodiment 1 In the magnetic disk M shown in FIGS. 1 to 4, the guard band groove 13 is formed with a radius of 20 mm on the inner peripheral side as shown in FIG.
, The width W is 0.6 μm and the depth H is 0.1 μm. On the outer peripheral side, the width W is 0.6 μm at a radius of 43 mm.
m, the depth H was 0.2 μm, and the depth H from the inner peripheral side to the outer peripheral side was linearly changed. The pitch of the recording track 14 was 4.7 μm.

Embodiment 2 In the magnetic disk shown in FIGS. 1 to 4, the guard band groove 13 is provided with a width W of 0.6 μm and a depth of 20 mm on the inner peripheral side at the inner peripheral side as shown in FIG. H is 0.2 μm,
On the outer peripheral side, at a position with a radius of 43 mm, the width W is 1.0 μm,
The depth H was 0.2 μm, and the width W from the inner peripheral side to the outer peripheral side was changed linearly. In addition, recording track 1
The pitch of No. 4 was 4.7 μm.

COMPARATIVE EXAMPLE In the magnetic disk shown in FIGS. 1 to 4, the guard band groove 13 has the same depth H from the inner peripheral side to the outer peripheral side.
15 μm). The pitch of the recording track 14 was 4.7 μm.

The electromagnetic conversion characteristics of the magnetic disks of Examples 1 and 2 and Comparative Example were measured. For the measurement, the recording track width was 4.6 μm and the gap width was 0.4 μm.
m, reproduction track width: 3.4 μm, gap length: 0.35 μm
m MR / inductive composite head was used. Further, a recording / reproducing test was performed by rotating the magnetic disk at 5,400 rpm. Resolution is 135kfci and 33.7
The reproduction amplitude ratio is 5 kfci, and the S / N ratio is 135 kf
ci is the value recorded and reproduced.

As shown in FIG. 12, the above measurement results showed that the resolution was constant from the inner circumference to the outer circumference of the substrate 1 in both the first and second embodiments. On the other hand, in the comparative example, the resolution decreased toward the outer peripheral side. As for the S / N ratio, as shown in FIG. 13, in Example 1, good results were shown from the inner peripheral side to the outer peripheral side. In the second embodiment, since the recording area becomes narrower as the width W of the guard band groove 13 located on the outer peripheral side increases, the outer peripheral side deteriorates more than the inner peripheral side. As shown in the figure, the S / N ratio did not significantly degrade toward the outer peripheral side, and the S / N ratio could be surely improved. In the first embodiment, it is necessary to control the thickness of the photoresist layer 22 from the inner peripheral side to the outer peripheral side, so that the manufacturing conditions are somewhat complicated, but the electromagnetic conversion characteristics are the best.

[0041]

As described above, according to the present invention, the cross-sectional area along the radial direction of a plurality of guard band grooves formed concentrically on a disc-shaped non-magnetic substrate is set closer to the outer periphery than to the inner periphery. The height of the magnetic head is kept almost constant from the inner circumference to the outer circumference without having to perform complicated processing on the magnetic head, etc. It is possible to obtain a magnetic disk having excellent characteristics.

In manufacturing the magnetic disk, a stamper having a transfer pattern corresponding to a guard band groove or a recording track is arranged in a mold for injection molding or injection compression molding to form a plastic. Since the transfer pattern is transferred to a disk-shaped non-magnetic substrate at the same time as the substrate is formed, the substrate having guard band grooves and recording tracks can be manufactured in large quantities and at low cost. Further, by using the above-mentioned magnetic disk, it is possible to obtain a magnetic recording / reproducing apparatus capable of performing recording / reproducing properly in a state where the flying height of the magnetic head is small.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a magnetic disk according to the present invention.

FIG. 2 is an enlarged sectional view showing a portion A in FIG. 1;

FIG. 3 is a perspective view showing a surface structure of the magnetic disk.

FIG. 4 is an explanatory diagram of a track format of the magnetic disk.

FIG. 5 is a cross-sectional view showing a substrate in which the depth of the guard band groove is increased toward the outer peripheral side.

FIG. 6 is a cross-sectional view showing a substrate in which the width of the guard band groove in the radial direction is increased toward the outer peripheral side.

FIG. 7 is a cross-sectional view showing a method for manufacturing the magnetic disk in the order of steps.

FIG. 8 is an explanatory diagram of a method of magnetizing a magnetic layer.

FIG. 9 is a plan view showing a magnetic recording / reproducing apparatus provided with a magnetic disk with a cover removed.

FIG. 10 is a sectional view of the magnetic recording / reproducing apparatus.

FIG. 11 is an explanatory diagram of a floating state of a magnetic head.

FIG. 12 is a characteristic diagram showing measurement results of the resolution with respect to the radial position of the magnetic disks of Examples 1 and 2 and Comparative Example.

FIG. 13 is a characteristic diagram showing measurement results of the S / N ratio with respect to the position in the radial direction of the magnetic disks of Examples 1 and 2 and Comparative Example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc-shaped non-magnetic substrate 2 Magnetic layer 13 Guard band groove 14 Recording track 23 Stamper 23a Transfer pattern 24 Mold a Circumferential direction b Radial direction H depth W Radial direction width

Claims (5)

[Claims] 1. A non-magnetic substrate having a disk shape and a magnetic layer formed on a magnetic head-facing side surface of the substrate, wherein the magnetic head-facing side surface of the substrate is concentric and circumferentially concentric with the substrate. A plurality of guard band grooves continuous or intermittent in the direction are provided at substantially equal intervals in the radial direction, and a recording track is formed between each of the radially adjacent guard band grooves. A magnetic disk, wherein the guard band groove is set such that a cross-sectional area along a radial direction is larger as the guard band groove is located on an outer peripheral side than on an inner peripheral side of the substrate. 2. The guard band groove is set such that the depth or the radial width increases as the guard band groove is located closer to the outer periphery than the inner periphery of the disc-shaped non-magnetic substrate. 2. The magnetic disk according to 1. 3. The magnetic disk according to claim 1, wherein the disk-shaped non-magnetic substrate is formed of plastic. 4. A method for producing a magnetic disk according to claim 3, wherein a stamper having a guard band groove and a transfer pattern corresponding to a recording track is arranged in a mold for injection molding or injection compression molding. A method for manufacturing a magnetic disk, comprising forming a disk-shaped non-magnetic substrate by injection molding or injection compression molding of plastic, and transferring the transfer pattern to the substrate. 5. A magnetic recording / reproducing apparatus comprising the magnetic disk according to claim 1.