JP2806347B2 - Magnetic disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording or reproducing technique for recording and reproducing information magnetically while controlling tracking of a magnetic head.

[0002]

2. Description of the Related Art In a conventional magnetic recording medium for recording digital information with a magnetic head, the eccentricity of the magnetic recording medium is made sufficiently small, the track width is made sufficiently large, and the accuracy of the magnetic recording device mechanism is increased. Since a method of reducing the relative position error between the magnetic recording medium and the magnetic head was employed, it was not necessary to perform precise tracking control.
In the case of a magnetic recording medium for recording digital information, a magnetic film is sputtered on a disk substrate, for example, an aluminum substrate, and after initial magnetization, the magnetic disks are initialized one by one by a magnetic head using a servo writer or a magnetic recording device. ing.

[0003]

The prior art does not take the following points into consideration. In other words, in order to further reduce the recording track width of the current magnetic recording medium and increase the density of the disk, it is necessary to further increase the processing accuracy of the magnetic recording medium and the mechanism of the magnetic recording device. The productivity of the disk is reduced, and furthermore, ultra-precision is required for the mechanism of the magnetic recording device, and the magnetic recording device becomes very large in terms of stability, cost, and the like.

Further, in order to increase the density of a magnetic recording medium, it is necessary to make the recording track width narrower and perform servo writing. Therefore, the processing accuracy of the magnetic recording medium and the mechanical section of the magnetic recording apparatus is increased. This has the disadvantage that the productivity of the disk is reduced, and the mechanism of the magnetic recording device is required to be ultra-precise, resulting in a very large magnetic recording device in terms of stability and specification. is there.

[0005] Conventionally, there have been the following attempts to record a certain signal on a magnetic disk by using uneven pits.

Japanese Patent Application Laid-Open No. 53-001507 describes a concept of detecting a signal from a recording film adhered on an uneven pattern. However, in this case, the magnetic flux was continuous in the recording film on the uneven pattern. For this reason, when trying to detect a signal with a ring-shaped magnetic head, there has been a problem that the amount of magnetic flux leaking from the recording film is small and the output of a reproduced signal is small.

Japanese Patent Application Laid-Open No. 63-191316 describes a concept of detecting a signal from a recording film adhered on an uneven pattern. However, this method uses a perpendicular recording film, detects magnetic flux from the recording film with a magnetoresistive head, and changes the reproduction signal according to the change in the distance between the recording film and the head caused by the uneven structure. It is to detect. This technique also has a problem that the output of the reproduced signal is small.

US Pat. No. 4,746,580 describes a method in which a recording film on a substrate is locally removed to form concavities and convexities, thereby obtaining a signal. However, the process of removing the recording film by etching or the like is complicated. Therefore, it must be said that there is a problem in mass productivity of the magnetic disk.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium and a magnetic recording apparatus which enable high-accuracy tracking electronic control of a magnetic head and enable highly reliable high-density recording, and manufacture of a magnetic disk. Another object of the present invention is to provide a magnetic recording / reproducing technique using a magnetic disk which is excellent in mass productivity by eliminating complicated steps.

[0010]

According to the present invention, a magnetic recording medium is provided with meandering uneven pits which can be read magnetically, and a magnetic head is provided with a magnetic flux distribution formed by magnetic poles generated at the ends of the uneven pits. , A tracking signal is detected magnetically, and the recording position of the magnetic head is servo-controlled to record information magnetically.

The recording medium used in the present invention has magnetically readable meandering pits on a magnetic recording medium.

More specifically, in a magnetic disk drive for recording or reproducing a magnetic disk for magnetically recording and reproducing information along a track, a wobbling is performed on a substrate of the magnetic disk along a track in a direction perpendicular to the track direction. Pits are formed on the surface of the substrate, and a magnetic recording film is formed on the surface of the substrate in the shape of the pits.The magnetic disk drive uses the magnetic flux leaking from the magnetic recording film attached to the side surfaces of the pits. It has a magnetic head that detects and obtains an electric signal, a tracking circuit that obtains a tracking signal based on the electric signal, and a servo circuit that performs recording or reproduction while controlling the position of the magnetic head based on the tracking signal. Alternatively, a magnetic head that obtains an electric signal by detecting a magnetic flux leaking from a magnetic pole formed at an end of the concave and convex pit, a tracking circuit that obtains a tracking signal based on the electric signal, and a magnetic head based on the tracking signal And a servo circuit that performs recording or reproduction while controlling the position of.

[0013]

According to the present invention, meandering uneven pits are used as marks for detecting tracking signals, and a tracking signal is generated by a magnetic head floating on a magnetic recording medium from a local magnetic field formed in the uneven pits. Since it uses the principle of detection, it is small and can detect a tracking signal with high S / N. Further, since the tracking information is formed on the magnetic recording medium by irregularities, it is possible to easily produce a large number of disks in the same manner as an optical disk.

[0014]

FIG. 1 shows a magnetic recording medium according to an embodiment of the present invention, and shows tracking pits provided on recording tracks formed on the magnetic recording medium.

In FIG. 1A, a magnetic recording medium substrate 1
Is made of glass, resin, or aluminum.
As shown in (b), the uneven tracking pits 3, 3 ', 4, 4' provided on the tracks 2, 2 'are formed by etching or injection shaping. The tracking pit can be shared between adjacent tracks 2 and 2 'as shown in FIG. FIG.
As shown in (d), the tracking pits may be formed wide so as to partially overlap when viewed in the circumferential direction. A magnetic recording thin film medium 5 is sputtered on the medium base 1. After sputtering, this magnetic recording medium is initially magnetized uniformly by a magnet while being rotated. The magnetization direction 6 coincides with the circumferential direction of the disk, that is, the data recording direction.

FIG. 2 shows the uneven pits 3 and 3 'of the present invention.
4 and 4 'are sectional views taken along the disk circumferential direction, that is, along the data recording direction.

FIG. 2A shows an embodiment of the present invention. The magnetic thin film medium 5 is magnetized in one direction 6 by the initial magnetization, and there is no leakage magnetic field at a position apart from the concave and convex pits. However, in the uneven pit portions 3, 3 ', 4, 4', plus and minus magnetic poles 7, 8 are formed on both walls of the pit,
As a result, magnetic fields 9 and 11 are generated in the pit portion. The strength of this magnetic field decreases as the pit center is the largest and symmetrical and deviates from the center.

In FIG. 2A, the magnetic recording thin film medium 5 is formed on the entire surface of the medium substrate 1 on which uneven tracking pits are formed.
Was provided.

Here, as in the comparative example shown in FIGS. 2B to 2D, the magnetic thin film in the pit portion may be removed, but there is a problem that the mass productivity is poor. That is, FIG.
In (b) to (d), the magnetic recording medium substrate 1 is made of glass, resin or aluminum, and has pits 3, 3 ', 4, 4' provided on tracks 2, 2 '. A magnetic recording thin film medium 5 is formed on the medium base 1, but no magnetic thin film exists in the pits 3, 3 ', 4, 4', and the initial magnetization direction 6 is the disk circumferential direction, that is, the data recording direction. Suitable for all.

FIGS. 2B, 2C and 2D are comparative examples, except that the process is complicated, and the principle of detection is shown in FIG.
(A) It is almost the same. FIG. 3 is a cross-sectional view of the pits 3, 3 ', 4, 4' along the disk circumferential direction, that is, along the data recording direction. FIG. 2B shows pit portions 3, 3 ', 4,
This is an example in which the 4 'pit portion is flat and there is no magnetic film in that portion. As a result, N and S magnetic poles 7 and 8 are formed on both end walls of the pit, and as a result, a magnetic field is generated in the pit portion. FIG. 2C shows a case where the pits 3, 3 'and 4, 4' are convex, and the magnetic film 5 is not provided in the convex pit portion. FIG. 2D shows a case where the pits 3, 3 'and 4, 4' are concave. Similarly, the magnetic film 5 does not exist in the concave pit portion. The pit depth is desirably about the same as the pit width in the data recording direction. For example, when the thickness of the magnetic film 5 is 0.1 μm, the pit depth is 0.1 to 0.5.
Micron, the pit width in the data recording direction may be about 0.5 micron, and the pit width in the disk radial direction may be about 1 to 20 microns.

2A, 2B, 2C, and 2D, N and S magnets 7, 8 are formed on both end walls of the pits 3, 3 ', 4, 4'. As a result, a magnetic field 9 is generated in the pit portion. By detecting the magnetic flux 9 formed by the pit portions 3, 3 ', 4, 4' with the magnetic head 10, a tracking signal can be obtained. However,
As shown in FIG. 2A, by forming a recording film uniformly on the substrate surface having uneven pits and magnetizing the protrusions in one direction, a strong magnetic reproduction signal can be obtained in a simple process. In order to initially magnetize only the convex portion in one direction, the difference in the distance between the magnetic head for initial magnetization and the magnetic film 5 is used to magnetize the convex portion, but generate a magnetic flux from the magnetic head such that the concave portion cannot be magnetized. What is necessary is just to apply.

FIG. 3 shows the magnetic flux 11 passing through the magnetic coil 12 when the magnetic head 10 travels in the uneven pit portion in a direction perpendicular to the data recording direction. A desirable output signal is obtained when the magnetic flux 11 has a dimension in the direction perpendicular to the data recording direction of the magnetic head 10 substantially equal to the width of the concave / convex pits in the direction perpendicular to the data recording direction. In FIG. 3, the magnetic flux 11 is symmetric with respect to the center of the pit. From this, the magnitude of the track shift can be known, but the direction of the track shift cannot be detected.

FIG. 4 shows a concave / convex pit meandering with respect to the center of a track on a magnetic recording medium for detecting the magnitude and direction of a track deviation according to an embodiment of the present invention. FIG.
A case where both the recording and reproduction of data and the detection of a tracking signal can be performed by one magnetic head 10 will be described. The truck is
It is separated into a servo area for detecting a tracking signal and a data area for recording data, and detects a signal in a time-division manner with one magnetic head.

The operation of detecting a tracking signal from the meandering pits 3 and 4 shown in FIG. 4 will be described with reference to FIGS. In FIG. 5, the center of the magnetic head 10 is A, B,
Consider the case of passing along each of C. When the magnetic head passes along A, the pit 3 passes near the center of the magnetic head, so that the pit 3 detected by the magnetic head
Is large, while the signal of pit 4 is small.
Therefore, the detection signal shown in FIG. 6A is obtained. FIG.
B indicates that when the magnetic head 10 passes along B in FIG.
FIG. 6C shows a detected waveform when the magnetic head passes along C in FIG. To control the position of the magnetic head 10 to be at the center of the track, the position of the magnetic head 10 may be moved to + X for the waveform A and to -X for the waveform C so that the detected waveform B is always obtained. .

FIG. 7 shows another embodiment of the present invention. The pit train 12 has a frequency f ₁ at a position slightly displaced in the −X direction from the center of the ratchet and a frequency f ₂ at a position displaced in the + X direction. , 13 are formed.

The outline of the tracking circuit used in the embodiment of FIG. 7 will be described with reference to FIG. The detection signal is divided into frequency f ₁ and f ₂ components by a frequency discriminator. Each component is amplified by a differential amplifier and used for position correction of the magnetic head.

FIG. 9 shows a method of producing a magnetic medium having no magnetic thin film in the pit portion shown in FIG. 2 which is a comparative example of the present invention.

In FIG. 9, for example, the meandering pit pattern shown in FIG. 1 is recorded on a chromium photomask with an ultraviolet laser beam, developed, and then the resist in the exposed portion is dissolved, and then the metal film is etched. A chrome mask 21 having the shape as shown in FIG. 1 is obtained. In FIG. 9A, a negative resist 22 is applied on an aluminum or glass disk substrate 1, and a metal mask 21 is adhered to the photoresist-coated disk substrate 1 and exposed. In FIG. 9B, after the exposure of the negative resist 22, the resist other than the pits is dissolved by development, but the resist 23 is left only in the pits.
Remains. Another embodiment of the present invention for leaving the resist 23 only in the pit portion can be realized by reversal development of a positive resist instead of the negative resist of FIG. In FIG. 9C, the magnetic film 5 is applied to the entire surface of the display substrate 1 where the resist 23 remains, for example, by a spinner, and then heated to harden the magnetic film 5. In FIG. 9D, the magnetic film 5 'applied to the pit portion by being raised is removed. For example, when the surface of the disk is polished thinly, the magnetic film in the pit portion which has been raised and applied is removed. As described above, a magnetic recording medium having no magnetic film only in the pit portion shown in FIG. 2B can be easily produced by the method for producing a magnetic medium shown in FIG. In the method of FIG. 9, an arbitrary pattern other than pits can be formed on the mask 21. For example, if a linear groove is formed, a direct groove without a magnetic thin film can be formed on a magnetic recording medium. is there.

FIG. 10 shows an embodiment of an optical system according to the present invention for forming rectangular pits 3, 3 ', 4, 4' on a photomask by laser. In order to form a pit having a rectangular shape having a width of, for example, 0.5 μm and a length of 10 μm, a rectangular laser spot having a width of 0.5 μm and a length of 10 μm is formed on a photomask by a laser beam using an optical system. It is necessary to form with. In FIG. 10A,
The objective lens L2 has a high numerical aperture (NA), for example, NA = 0.
936, a rotationally symmetric diffraction limited lens. Laser wavelength w = 0.45 microns, laser beam diameter D = 5m
Assuming that m is m and the focal length is f = 2.67 mm, a circular spot having a diameter d = 2Wf / D = 0.48 microns is obtained as a spot formed by the objective lens L2 using the laser light. In FIG. 10 (b), a rectangular spot by placing the cylindrical L ₁ on the laser incident side of the objective lens L ₂ is obtained. X direction of the cylindrical lenses L _1, each f _x the focal length in the y-direction, when f _y, is f _x infinity, f _y is a finite, for example, 1 m.

Now, if f ₁ = f _y is written, FIG.
The amount of defocus in the y-axis direction between the optical systems in FIG. 10B is z = (f ₁ ) ² / (f ₂ + f ₂ −a) (1). The defocus amount X in the x-axis direction between the systems does not change, and X = 0. Where a is the distance of the lens L ₁ and L _2. From the optical system of FIG. 10B, a relational expression of y / z = D / f ₂ ... (2) is established, and from the above two expressions, f ₁ −a = D ₁ f ₂ / y. can get. a is the distance between the lenses L ₁ and L ₂ .
Equation (3) shows that the laser beam east diameter D = 5 mm and the focal length is f ₂ =
Substituting 2.67 mm, y = 10 microns, f ₁ −a =
1335 mm is obtained. Since (f ₁ -a) is 1.3 m and the focal length of the lens L ₁ is very large, the influence of aberration caused by the cylindrical lens L ₁ is small, the spot size in the x direction is small at 0.48 μm, and the spot size in the y direction is small. Only the spot size is 10 microns. By thus installing a cylindrical lens L ₁ having a focal distance of 10m from 50cm in front of the objective lens L _2, forming a laser spot and the width 0.5 microns, a rectangular shape of length 5-10 microns It is possible to do.

[0031]

According to the present invention, by tracking the magnetic head with high accuracy, not only high-density recording can be achieved, but also a large number of disks can be produced at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a magnetic recording medium of the present invention.

FIG. 2 is a cross-sectional view of a medium illustrating the principle of the present invention.

FIG. 3 is a waveform chart showing the principle of the present invention.

FIG. 4 is a plan view illustrating a configuration of a tracking signal detection unit used in the present invention and an operation principle thereof.

FIG. 5 is a plan view illustrating a configuration of a tracking signal detection unit used in the present invention and an operation principle thereof.

FIG. 6 is a waveform chart for explaining the configuration of a tracking signal detection unit used in the present invention and the operation principle thereof.

FIG. 7 is a plan view for explaining another embodiment of the present invention.

FIG. 8 is a circuit diagram for explaining another embodiment of the present invention.

FIG. 9 is a sectional view showing an example of a method for producing a magnetic recording medium according to the present invention.

FIG. 10 is a conceptual diagram showing an embodiment of an optical system for recording a pattern on a photomask with a laser beam according to the present invention.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Sho Ito 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-62-232720 (JP, A) JP-A-63 -234465 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G11B 5/596

Claims (2)

(57) [Claims] 1. A magnetic disk drive for recording or reproducing a magnetic disk for magnetically recording and reproducing information along a track, comprising: an uneven surface wobbled along a track in a direction perpendicular to the track direction on a substrate of the magnetic disk. Pits are formed, and a magnetic recording film is formed on the surface of the substrate in the form of uneven pits. The magnetic disk device leaks from the magnetic recording film adhered to the side surfaces of the uneven pits. It has a magnetic head that obtains an electric signal by detecting a magnetic flux, a tracking circuit that obtains a tracking signal based on the electric signal, and a servo circuit that performs recording or reproduction while controlling the position of the magnetic head based on the tracking signal. Magnetic disk drive. 2. A magnetic disk device for recording or reproducing a magnetic disk for recording and reproducing information magnetically along a track, wherein the unevenness wobbled along the track in a direction perpendicular to the track direction on the substrate of the magnetic disk. Pits are formed, a magnetic recording film is formed on the surface of the substrate in the form of uneven pits, and the magnetic disk device controls a magnetic flux leaking from a magnetic pole formed at an end of the uneven pit. A magnetic disk having a magnetic head that detects and obtains an electric signal, a tracking circuit that obtains a tracking signal based on the electric signal, and a servo circuit that performs recording or reproduction while controlling the position of the magnetic head based on the tracking signal apparatus.