JPH06124492A - Disc-shaped recording medium - Google Patents

Abstract

PURPOSE:To obtain a system clock signal wherein a clock pulse whose S/N ratio is good can be always obtained and a jitter component is small. CONSTITUTION:The disk-shaped recording medium is provided with a data area in which an information signal is recorded and with a servo area in which servo information or the like is recorded in advance. Two servo marks 2 which are arranged zigzag around the center of a track and one clock mark 3 at the rear part of the servo area are formed in the servo area S. In a sample servo-type optical disk, the clock mark 3 is formed to be a radial belt-shaped pattern which is continued in the radial direction of the optical disk 1. Thereby, the amplitude of a clock pulse is not changed even in an off-track.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc-shaped recording medium represented by an optical disc and a magnetic disc, and more particularly to an improvement of a sample servo type disc-shaped recording medium.

[0002]

2. Description of the Related Art A technique of generating a system clock necessary for the operation of a disk drive device from a clock mark embedded on a disk has been put to practical use as a sample servo format in a magneto-optical disk, for example.

FIG. 24 shows the structure of a conventional sample servo type magneto-optical disk. The magneto-optical disk 101 of the sample servo system is provided with a data area 102 in which information signals are recorded and a servo area 103 in which servo information and the like are recorded in advance.
On 03, servo marks 104 and clock marks 105 are formed as so-called pre-pits.

Therefore, the spot Ls of the laser beam emitted from the reproducing head is the clock mark 10
The system clock signal can be obtained by multiplying the clock pulse obtained each time it passes over 5.

[0005]

By the way, since the clock mark 105 of the conventional disc-shaped recording medium is formed at the track center Tc, the reproduction output is the highest when the beam spot Ls is at the track center Tc. It is subject to modulation. Therefore, FIG.
In the middle, as shown by a, when the beam spot Ls is at the track center Tc, a clock pulse is obtained with the maximum S / N, but as shown by b in the figure, the beam spot Ls is off-track. Sometimes the S / N becomes worse.

FIG. 25 shows clock pulses Pc (a) when the beam spot Ls is at the track center Tc,
This shows the clock pulse Pc (b) when the beam spot Ls is off-track, and the S / N is worse as the clock pulse Pc (b) is off-track. If an attempt is made to obtain a system clock signal by multiplying such a signal having a poor S / N, there is a problem that the jitter component increases and control by the servo system becomes unstable.

As described above, the conventional sample servo disk has a big problem that the jitter component increases in the system clock signal when the beam spot Ls is off-track.

Therefore, the present invention has been proposed in view of such a conventional situation, and an object thereof is to provide a disk-shaped recording medium capable of always obtaining a clock pulse having a good S / N.

[0009]

In order to achieve the above object, the present invention provides a disc-shaped recording medium for obtaining system clock information by a clock mark 3, wherein the clock mark 3 is arranged in a radial direction of the disc-shaped recording medium. It is characterized in that it is formed as a continuous substantially radial pattern.

That is, according to the present invention, the clock mark 3 which has been formed as a prepit up to now is formed into a belt-shaped continuous pattern continuous in the radial direction of the disk-shaped recording medium, and the beam spot Ls and the magnetic head are on the disk-shaped recording medium. It is possible to detect under any condition at the best condition.

[0011]

In the disk-shaped recording medium 1 of the present invention, since the clock marks 3 are formed as a radial continuous pattern continuous in the radial direction of the disk 1, the reproducing head (magnetic head or beam spot Ls) is located at the track center Tc. The clock mark 3 is detected under the same condition even when it is in the off state or in the off-track state. That is, in the case of the optical disk 1, the clock mark 3 is detected by the entire range of the beam spot Ls of the reproducing laser beam, and in the case of the magnetic disk, the clock mark 3 is detected by the entire range of the track width in the magnetic gap of the magnetic head.

Therefore, the amplitude of the clock pulse Pc does not change even when the reproducing head is off-tracked. For example, a clock pulse with a good S / N can be obtained even during the seek of the reproducing head, and the system clock signal with a small jitter component is obtained. Is obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments in which the disk-shaped recording medium according to the present invention is applied to an optical disk and a magneto-optical disk will be described in detail below with reference to the drawings.

Example 1 First, an example in which the disk-shaped recording medium according to the present invention is applied to an optical disk of a sample servo system will be described. That is, in the optical disc 1 of this embodiment, as shown in FIG. 1, a data area D in which an information signal is recorded,
A servo area S in which servo information and the like are recorded in advance is provided.

In the servo area S, servo marks 2 and clock marks 3 are formed as so-called prepits. As shown in FIG. 2, these servo marks 2 and clock marks 3 are viewed from the transparent substrate 4 side by forming a concave portion 5 in a transparent substrate 4 at the time of molding and forming a reflective film 6 on the concave portion 5. It is sometimes formed as a substantially circular convex portion (servo mark 2) or a belt-shaped convex portion (clock mark 3).

Therefore, comparing the outputs of the reflected light generated by irradiating the reproducing laser light and irradiating the servo marks 2 arranged on both sides with the spot Ls of the laser beam across the track center Tc. The system clock signal can be obtained by multiplying the clock pulse obtained each time the spot Ls of the reproduction laser beam passes over the clock mark 3 by the tracking control by.

FIG. 3 is a block diagram for obtaining the system clock signal. The optical output reflected from the optical disk 1 is first converted into an electric signal by the head amplifier 11 and then amplified, and the servo mark is generated. Output fluctuations due to 2 and the clock mark 3 are recognized as the servo pulse Ps and the clock pulse Pc.

Next, peak detection is carried out by the peak detection circuit 12, and further the clock pit extraction circuit 13 at the subsequent stage.
At this time, the clock pit pulse P is extracted based on the peak detection pulse Pp from the peak detection circuit 12 and the clock pulse Pc from the head amplifier 11, and the extracted clock pit pulse P is multiplied by a multiplication means (for example, P
It is multiplied by LL) and converted into a system clock signal (servo clock, data clock).

In this embodiment, the clock mark 3 is formed as a radial strip pattern (see FIG. 1) continuous in the radial direction of the optical disc 1 by the reflective film 6 on the radial groove formed on the transparent substrate 4. Has been done. Therefore, the clock mark 3 is detected under the same condition whether the beam spot Ls is at the track center Tc or in a so-called off-track state which is off the track center Tc.

That is, for example, in FIG. 1, the beam spot Ls is located at the track center Tc (position a in the figure).
4 shows the signal waveform of the clock pulse Pc (a) obtained in the case of FIG. 4 and the signal waveform of the clock pulse Pc (B) obtained in the off-track state (position b in the figure).
Are almost equal, as shown in. This is because the size of the clock mark 3 entering the beam spot Ls is the same regardless of whether the beam spot Ls is in the track center Tc or in the off-track state, so that the light modulation received by the clock mark 3 is the same. This is because the degree of will be the same.

Thus, the optical disc 1 according to the present embodiment.
According to the above, since the clock mark 3 is formed as a substantially radial pattern continuous in the radial direction of the optical disc 1, a clock pulse with a good S / N can always be obtained, and a system clock signal with a small jitter component can be obtained. be able to. Further, since the amplitude of the clock pulse Pc does not change even when the beam spot Ls is off-track, a clock pulse with good S / N can be obtained even during the seek operation of the head.

Next, a method of manufacturing the optical disc 1 according to this embodiment will be described with reference to FIGS. Here, the apparatus shown in FIG. 5 shows a configuration of an optical recording apparatus (laser cutting apparatus) used for producing a master of the optical disc 1 which is a pre-stage of the stamper.

As shown in FIG. 5, this apparatus basically has a turntable 22 on which a smooth circular substrate 21 such as glass is placed, a gas laser light source 23 using a gas as an amplifying medium, An acousto-optic modulator (Acousto Optic Modulator; hereinafter simply referred to as AOM) 24 that intensity-modulates the laser beam L emitted from the gas laser light source 23 based on the ultrasonic wave W modulated by the recording pattern signal Sw. The mirror 26 is configured to guide the laser beam L whose intensity is modulated by the AOM 24 to the objective lens 25.

The substrate 21 is fixed on the turntable 22 by, for example, vacuum suction, and the turntable 22 is a spindle motor (not shown).
Is driven to rotate by, for example, CAV
It is designed to rotate in a (constant angular velocity) system. A photoresist film 27 is coated on the entire surface of the substrate 21. The objective lens 25 is arranged on the photoresist film 27 so as to face each other at a predetermined interval, and is moved in the radial direction of the substrate 21 together with the mirror 26 by a known moving mechanism mainly including a stepping motor. ing.

Here, when the photosensitive material of the photoresist film 27 is a positive type, the laser beam L is A
458 nm for r laser, 442 for He-Cd laser
The oscillation wavelength of nm is selected. Also, recently
A Kr laser having an oscillation wavelength near 400 nm may also be used. Further, these gas lasers 23 are emitted as a linearly polarized laser beam L through the Brewster window.

On the other hand, an ultrasonic wave generator 28 is connected to the AOM 24. The ultrasonic wave generator 28 outputs the generated ultrasonic wave to a recording pattern signal (photoresist film 27 is supplied to an input terminal). The recording pattern to be drawn is modulated on the basis of a signal Sw that is electrically converted. The ultrasonic wave W modulated by the ultrasonic generator 28 is
Supplied to the AOM 24.

The AOM 24 is composed of, for example, a TeO ₂ crystal, and uses a phase diffraction grating due to a change in the refractive index generated in the crystal by the ultrasonic wave supply from the ultrasonic wave generator 28, and the Bragg diffraction 1 The secondary diffracted light is used for signal recording. The intensity of the diffracted light is determined by the ultrasonic power, and the diffraction direction is determined by the carrier frequency.

The recording pattern signal Sw is created by the pattern generator 29. This pattern generator 29 is
The recording pattern signal Sw is created based on the clock signal Sc generated in L30. The PLL 30 uses the clock signal Sc based on the rotation timing signal St from the rotary encoder 31 attached to the spindle motor.
To generate.

Next, a method of manufacturing the master of the optical disc 1 according to this embodiment with the above laser cutting device will be described.

First, a smooth circular substrate 21 such as glass is polished, and a photoresist film 27 is applied on this substrate 21. After that, the substrate 21 is fixed on the turntable 22, and the substrate 21 is fixed by a spindle motor by the CAV method, for example.
To rotate. At this time, the objective lens 25 and the mirror 2
6 is moved in the radial direction of the substrate 21 and the laser spot Ls focused on the photoresist film 27 by the objective lens 25.
Are moved in one direction along the diameter of the substrate 21.

In this case, as shown in FIG. 6, the movement pitch d of the laser spot Ls is set so as not to move more than the diameter D of the laser spot Ls while the turntable 22 makes one rotation. For example, when using a spot Ls whose diameter D is 0.4 μm, the spot Ls is
0.3 in the radial direction of the substrate 21 per turntable turn.
Be prepared to send about μm.

On the other hand, the laser beam L is turned on / off by the AOM 24 in synchronization with the rotation of the turntable 22. Then, the laser beam L is irradiated to the photoresist film 27 each time the turntable 22 rotates by 1 / n, and the photoresist film 27 has n continuous laser beams in the radial direction of the substrate 21. A resist latent image of the radial clock mark 3 (n is an integer) is formed.

Subsequent operations are the same as in the conventional optical disk manufacturing method. After developing the photoresist film 27 on the substrate 21, a metal film is vapor-deposited on the entire surface including the remaining photoresist film 27 to form a master disc. To make. Then, a mother and a stamper are duplicated from this master, and a disk made of synthetic resin (see the transparent substrate 4 shown in FIG. 2) is molded from this stamper. After that, when the disc 4 is used as the optical disc 1, the optical disc 1 according to the present embodiment is completed by depositing a reflective film 6 of aluminum or the like on the surface of the disc 4 on which the clock mark 3 is formed.

Embodiment 2 Next, an embodiment in which the disk-shaped recording medium according to the present invention is applied to a sample servo type magneto-optical disk will be described with reference to FIGS. Since the entire track format of the magneto-optical disc 41 according to this embodiment is the same as that of the optical disc 1 described in the first embodiment, detailed description thereof will be omitted. As shown in FIG. 3, the clock marks 3 are formed in a substantially radial pattern continuous in the radial direction of the magneto-optical disc 41, as in the optical disc 1.

The examples shown in FIGS. 8 and 9 show an example in which a step is provided between the recording track 42 on which data is recorded and the clock mark 3. That is, FIG. 8 shows an example in which the clock mark 3 and the recording track 42 are convex portions and a concave portion is provided between the clock mark 3 and the recording track 42, and FIG. 9 shows an example in which only the clock mark 3 is a concave portion.

This magneto-optical disc 41 is manufactured by exposing a master disk through an exposure process and a developing process using the laser cutting apparatus shown in FIG. 5, and then duplicating a mother and a stamper based on the master disk. A disk 4 made of synthetic resin is molded. The process up to this point is the same as the manufacturing process of the optical disc 1.

Then, the disk 4 obtained as described above
8 is used as the magneto-optical disk 42, a magnetic film 43 is formed on the surface of the disk 4 on which the clock mark 3 is formed, as shown in FIGS. The magnetic film 43a in and the magnetic film 43b in the recess are magnetized by reversing the magnetization directions. As a method of magnetizing in this way, the magnetic films 43a and 4a of the convex portion and the concave portion are first formed by the head in which the current of level Ib is applied.
3b is magnetized and then a current of level −Iu (Ib> I
The magnetic film 43a of the convex portion may be magnetized in the opposite direction by the head in which u) is passed.

Alternatively, first, the rotation of the disk 4 is slowed to reduce the flying height of the head, and the magnetic films 43a and 43b of the convex portions and the concave portions are magnetized.
The magnetic field 43a of the convex portion may be magnetized in the direction opposite to the initial direction by increasing the speed of rotation of the head to increase the flying height of the head.

The above example shows an example in which a step is provided between the clock mark 3 and the recording track 42.
Also, as shown in FIG. 11, a so-called guard band GB may be provided by providing a step between adjacent recording tracks 42 as well. Also in this case, it can be manufactured in the same manner as the above example.

In the examples shown in FIGS. 7 to 11, the unevenness is formed on the disk 4 itself.
2 to 16, the disk 4 itself is not provided with irregularities, and the magnetic film 43 formed on the disk 4 is selectively removed by etching to form the clock mark 3 and the recording track 42. You may do it.

FIG. 13 shows an example in which the magnetic film 43 between the recording track 42 for recording data and the clock mark 3 is removed from the magnetic film 43, and FIG. 14 is shown in FIG.
An example in which the magnetic film 43 in the portion corresponding to the clock mark 3 is removed is shown. In addition, the example shown in FIG. 15 and FIG.
In the type shown in FIG. 13, an example in which the magnetic film 43 between the adjacent recording tracks 42 is removed and a so-called guard band GB is provided is shown. In these examples,
As a method of magnetizing the magnetic film 43, it is sufficient to magnetize the magnetic film 43 in one direction with a head in which a DC current is passed.

Next, a method for producing the magneto-optical disk 41 shown in FIG. 14 will be described with reference to FIGS. 17 to 22.

First, as shown in FIG. 17, the glass substrate 5
A mask master 54 in which a chrome layer 52 and a photoresist film 53 are sequentially laminated on 1 is prepared. Then, as shown in FIG.
By performing an exposure process using the laser cutting device shown by (1), a resist latent image of the clock mark 3 is formed on the photoresist film 53.

After that, as shown in FIG. 18, the photoresist film 53 is developed to dissolve the portion of the photoresist film 53 irradiated with the laser beam L, whereby the photoresist film 53 is removed.
A band-shaped opening 55 is formed along the shape of the clock mark 3. After that, as shown in FIG. 19, wet etching is performed to remove the chromium layer 52 exposed from the opening 55 by etching. After that, the upper photoresist film 53 is peeled off to complete the mask 56 of the chromium layer 52.

Next, as shown in FIG. 20, a magneto-optical disc master 58 in which the magnetic film 43 and the photoresist film 57 are sequentially laminated on the disc 4 is prepared. After that, a mask 56 is arranged on the photoresist film 57, and exposure is performed by the proximity method to form a resist latent image of the clock mark 3 on the photoresist film 57.

After that, as shown in FIG. 21, the photoresist film 57 is developed to dissolve the portion of the photoresist film 57 which is irradiated with the laser beam L, whereby the photoresist film 57 is removed.
A band-shaped opening 59 is formed along the shape of the clock mark 3. Then, as shown in FIG. 22, for example, wet etching is performed to remove the magnetic film 43 exposed from the opening 59 by etching. After that, the magneto-optical disk 41 shown in FIG. 14 is completed by peeling off the upper photoresist film 57.

As described above, in the magneto-optical disk 41 according to the present embodiment, the clock marks 3 are formed as a substantially radial pattern continuous in the radial direction of the magneto-optical disk 41, as in the optical disk 1. A clock pulse Pc having a good S / N can always be obtained, and a system clock signal with a small jitter component can be obtained. In addition, since the amplitude of the clock pulse Pc does not change even when the track is off-track, the S
It is possible to obtain a clock pulse Pc with a good / N.

As shown in FIG. 23, the optical disc 1
As a head feeding mechanism mounted in the recording / reproducing apparatus for the magneto-optical disk 41, a reproducing head (or recording head) 63 is provided at the tip of an arm 62 about a support shaft 61 as a rotation center via, for example, a gimbal spring. When the rotary actuator 64 is used, the movement path of the head 63 in the radial direction is centered on the support shaft 61, and the head 6 moves from this center.
Since it becomes an arc shape with the radius of curvature as the distance to 3,
The clock marks 3 of the optical disk 1 and the magneto-optical disk 41 may also be formed in a shape along the locus.

[0049]

As described above, according to the disc-shaped recording medium of the present invention, the clock marks, which have been formed as pre-pits, are formed as a continuous strip-shaped pattern continuous in the radial direction of the disc. Therefore, it is possible to always obtain a clock pulse with good S / N,
A system clock signal with less jitter component can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a track format of an embodiment (hereinafter, simply referred to as an optical disk according to an embodiment) in which a disk-shaped recording medium according to the present invention is applied to an optical disk of a sample servo system.

FIG. 2 is a sectional view taken along line AA in FIG. 1A.

FIG. 3 is a block diagram for obtaining a system clock signal from the optical disc according to the present embodiment.

FIG. 4 is a signal waveform diagram showing clock pulses when the beam spot is on-track and when it is off-track in the optical disc according to the present embodiment.

FIG. 5 is a configuration diagram showing an optical recording device (laser cutting device) used for producing a master disc of an optical disc according to the present embodiment.

FIG. 6 is a schematic diagram showing movement control of a beam spot in a laser cutting device.

FIG. 7 is a schematic diagram showing a main part of a track format of an embodiment (hereinafter, simply referred to as a magneto-optical disk according to the embodiment) in which the disk-shaped recording medium according to the present invention is applied to a sample servo type magneto-optical disk. Is.

FIG. 8 is a cross-sectional view of the magneto-optical disk according to the present embodiment, viewed from the line BB in FIG.

FIG. 9 is a cross-sectional view of another configuration example of the magneto-optical disk according to the present embodiment, viewed from the line BB in FIG. 7.

10 is a schematic diagram showing an example in which a guard band is provided in the magneto-optical disc shown in FIGS. 7 and 8. FIG.

11 is a cross-sectional view taken along the line C-C in FIG.

FIG. 12 is a schematic view showing an example in which the magneto-optical disk according to the present embodiment is configured by selectively removing the magnetic film by etching.

13 is a cross-sectional view of the magneto-optical disk shown in FIG. 12, taken along the line DD in FIG.

FIG. 14 is a cross-sectional view of another configuration example of the magneto-optical disk shown in FIG. 12, viewed from the line D-D.

FIG. 15 is a schematic view showing an example in which a guard band is provided in the magneto-optical disc shown in FIGS. 12 and 13.

16 is a sectional view taken along line EE in FIG.

FIG. 17 is a process step diagram showing a method of manufacturing the magneto-optical disc shown in FIGS. 12 and 14, showing an exposure process when forming a mask.

FIG. 18 is a process flow chart showing the method of manufacturing the magneto-optical disk shown in FIGS. 12 and 14 and showing the developing process when forming the mask.

FIG. 19 is a process flow chart showing a method of manufacturing the magneto-optical disk shown in FIGS. 12 and 14 and showing a completion stage of the mask.

20 shows a method of manufacturing the magneto-optical disk shown in FIGS. 12 and 14, and is a process step diagram showing an exposure process when the magneto-optical disk is formed using a mask.

FIG. 21 is a process step diagram showing the developing process for forming the magneto-optical disk, showing the method for manufacturing the magneto-optical disk shown in FIGS. 12 and 14;

22 shows a method of manufacturing the magneto-optical disk shown in FIGS. 12 and 14, and is a process step diagram showing a completion stage of the magneto-optical disk.

FIG. 23 is a schematic diagram showing a clock mark formation pattern when a rotary actuator is used as a head feed mechanism.

FIG. 24 is a schematic diagram showing a track format of a magneto-optical disk of a sample servo system according to a conventional example.

FIG. 25 is a signal waveform diagram showing clock pulses when the beam spot is on-track and when it is off-track in the magneto-optical disk according to the conventional example.

[Explanation of symbols]

 S Servo area D Data area 1 Optical disc 2 Servo mark 3 Clock mark Ls Beam spot Tc Track center 4 Transparent substrate (disc) 6 Reflective film 11 Head amplifier 12 Peak detection circuit 13 Clock pit extraction circuit 14 Multiplier (PLL) 21 Substrate 22 Turntable 23 Gas laser light source 24 AOM 25 Objective lens 27 Photoresist film 28 Ultrasonic wave generator 29 Pattern generator 30 PLL 31 Rotary encoder 41 Magneto-optical disk 42 Recording track 43 Magnetic film GB Guard band

Claims (4)

[Claims] 1. A disc-shaped recording medium for obtaining system clock information by clock marks, wherein the clock marks are formed as a substantially radial pattern continuous in the radial direction of the disc-shaped recording medium. . 2. The disc-shaped recording medium according to claim 1, wherein the disc-shaped recording medium is an optical disc, and the clock marks are formed as substantially radial recesses continuous in the radial direction of the disc-shaped recording medium. . 3. A disk-shaped recording medium is a magnetic disk, a magnetic layer is formed on the entire surface of a substrate, and clock marks are formed by a magnetic layer on a substantially radial concavo-convex portion continuous in the radial direction of the disk-shaped recording medium. A disc-shaped recording medium characterized by being provided. 4. The disk-shaped recording medium is a magnetic disk, and the clock mark is formed by a substantially radial magnetic layer continuous in the radial direction of the disk-shaped recording medium and separated from the recording magnetic layer. Disc-shaped recording medium.