JPH11296909A - Recording medium and master disk for manufacturing recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium which discriminates adjacent recording tracks even if a track pitch is made very narrow and also stably performs tracking servo. SOLUTION: When grooves are formed along a recording tack, they are formed so that wobbling grooves 6 and straight grooves 7 may describe a double helix. And, the widths of the grooves 6 and 7 are made different from each other so that the level of a push-pull signal obtained from light undergoing reflection diffraction by the grooves 6 can be different from the level of a push-pull signal obtained from light undergoing reflection diffraction by the grooves 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a recording medium having grooves formed along recording tracks. Further, the present invention relates to a recording medium manufacturing master used when manufacturing such a recording medium.

[0002]

2. Description of the Related Art As a recording medium, an optical disk formed in a disk shape and optically recorded and / or reproduced has been put to practical use. Such optical discs include a read-only optical disc in which embossed pits corresponding to data are formed in advance on a disc substrate, a magneto-optical disc for recording data using a magneto-optical effect, and a phase change of a recording film. There is a phase change type optical disk for recording data by utilizing the same.

[0003] Of these optical disks, writable optical disks such as magneto-optical disks and phase-change optical disks usually have grooves along recording tracks formed on the disk substrate. Here, the groove is a so-called guide groove formed along a recording track in order to mainly perform tracking servo. The portion between the grooves is called a land.

In an optical disk having a groove formed thereon, tracking servo is performed based on a push-pull signal obtained from light reflected and diffracted by the groove. Here, the push-pull signal is obtained by detecting the light reflected and diffracted by the groove by two photodetectors arranged symmetrically with respect to the track center, and taking the difference between the outputs from the two photodetectors. Is obtained by

[0005]

By the way, the demand for a higher recording density of a recording medium never stops.
It is desired that recording media such as optical disks have higher recording densities. In order to increase the recording density of the recording medium, for example, the track pitch may be reduced by reducing the interval between adjacent grooves. However, in the conventional recording medium, if the track pitch is too narrow, there are problems such as the inability to distinguish adjacent recording tracks and the inability to perform stable tracking servo.

The present invention has been proposed in view of the above-described conventional circumstances. Even if the track pitch is extremely narrow, it is possible to distinguish adjacent recording tracks and to stably record the tracks. It is an object to provide a recording medium capable of performing tracking servo. Another object of the present invention is to provide a master for manufacturing a recording medium capable of manufacturing such a recording medium.

[0007]

A recording medium according to the present invention is a recording medium in which a groove is formed along a recording track, wherein the first groove and the second groove are double spirals. It is formed so as to draw. The cross-sectional shape of the first groove is different from the cross-sectional shape of the second groove, and the level of the push-pull signal obtained from the light reflected and diffracted by the first groove is different from that of the second groove.
And the level of the push-pull signal obtained from the light reflected and diffracted by the groove is different. In order to make the cross-sectional shape of the first groove different from the cross-sectional shape of the second groove, for example, the width of the first groove may be different from the width of the second groove. .

In the above recording medium, the level of the push-pull signal obtained from the light reflected and diffracted by the first groove is different from the level of the push-pull signal obtained from the light reflected and diffracted by the second groove. The level of the push-pull signal obtained when the light spot is shifted to the side of the first groove is different from the level of the push-pull signal obtained when the light spot is shifted to the side of the second groove. Become. Therefore, in the recording medium according to the present invention, the recording track having the first groove on the left side and the second groove on the right side, the second groove on the left side, and the first track on the right side.
And the recording track having the groove can be determined by the push-pull signal.

In the recording medium, the first groove is a wobbling groove formed so that at least a part of the groove is meandering, and the second groove is a straight groove formed without meandering. You may. By making the groove meander as described above to form a wobbling groove, it is possible to add address information to the groove itself. In addition, when one groove is a wobbling groove and the other groove is a straight groove, it is easier to narrow the track than when both grooves are a wobbling groove. realizable.

In the recording medium, a peak value of a push-pull signal obtained from light reflected and diffracted by the first groove and a peak value of a push-pull signal obtained from light reflected and diffracted by the second groove are used. When the smaller peak value is P1 and the larger peak value is P2, P1 / P2 is preferably 0.83 or less. If P1 / P2 is 0.83 or less, the level of the push-pull signal obtained from the light reflected and diffracted by the first groove and the level of the push-pull signal obtained from the light reflected and diffracted by the second groove Can be sufficiently detected. Therefore, if P1 / P2 is 0.83 or less, a recording track with a first groove on the left and a second groove on the right, a recording track with a second groove on the left and a first groove on the right. Can be more reliably determined.

On the other hand, the master for manufacturing a recording medium according to the present invention is a master for manufacturing a recording medium used when manufacturing a recording medium in which grooves are formed along recording tracks. The first groove pattern and the second groove pattern are formed so as to draw a double spiral as an uneven pattern corresponding to the groove, and the width of the first groove pattern and the width of the second groove pattern are formed. The width is different.

Since the width of the first groove pattern and the width of the second groove pattern of the above-mentioned master for producing a recording medium are different, the recording media produced using this master for producing a recording medium have different widths. A first groove and a second groove are formed. In the recording medium in which a pair of grooves having different widths is formed, the level of the push-pull signal obtained from the light reflected and diffracted by the first groove and the light reflected and diffracted by the second groove are used. Since the level of the obtained push-pull signal is different, the level of the push-pull signal obtained when the light spot is shifted toward the first groove and the light spot is shifted toward the second groove. The level of the push-pull signal obtained sometimes differs. Therefore,
In this recording medium, the first groove is on the left and the second groove is on the right.
And the recording track having the second groove on the left and the first groove on the right can be determined by the push-pull signal.

In other words, according to the master for producing a recording medium, a recording track having a groove corresponding to the first groove pattern on the left side and a groove corresponding to the second groove pattern on the right side, and a recording track having a groove corresponding to the second groove pattern on the right side. A recording medium capable of discriminating, by a push-pull signal, a recording track having a groove corresponding to the second groove pattern and a recording track having a groove corresponding to the first groove pattern on the right side can be manufactured.

In the above-mentioned master for producing a recording medium, the first
The groove pattern of at least a part of the groove pattern is formed as an uneven pattern corresponding to a wobbling groove formed so as to meander, and the second groove pattern is formed as an uneven pattern corresponding to a straight groove formed without meandering. You may.

According to this master for manufacturing a recording medium, a recording medium having a wobbling groove and a straight groove can be manufactured. By making the groove meander to form a wobbling groove, address information can be added to the groove itself. According to the above-mentioned recording medium manufacturing master, the first groove pattern is an uneven pattern corresponding to the wobbling groove. A recording medium in which address information is added to the groove itself can be manufactured.

Moreover, when one groove is a wobbling groove and the other groove is a straight groove, it is easier to narrow the track than when both grooves are wobbling grooves. Therefore, according to the above-mentioned master for manufacturing a recording medium, in which the second groove pattern is a concavo-convex pattern corresponding to a straight groove, while adding address information to the groove itself,
The track pitch of the recording medium can be further reduced.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, a meandering groove is called wobbling, and a groove formed so as to wobble is called a wobbling groove. Also, a groove formed without meandering with respect to the wobbling groove is called a straight groove. Further, two grooves formed so as to draw a double spiral are collectively referred to as a double spiral groove.

<Magneto-Optical Disk> FIG. 1 is an enlarged cross-sectional view of a main part of a magneto-optical disk to which the present invention is applied.

The magneto-optical disk 1 is formed in a disk shape, and data is recorded using a magneto-optical effect. The magneto-optical disk 1 is made of polymethyl methacrylate (PMMA) or polycarbonate (PC).
A recording layer 3 on which magneto-optical recording is performed and a protective layer 4 for protecting the recording layer 3 are formed on a disk substrate 2 made of the same. Here, the recording layer 3 is formed by laminating, for example, a dielectric film made of SiN or the like, a perpendicular magnetic recording film made of a TeFeCo alloy or the like, a dielectric film made of SiN or the like, and a reflective film made of Al or the like. Become. The protective layer 4 is formed by, for example, spin-coating an ultraviolet curable resin on the recording layer 3. In the present invention, the recording layer 3 and the protective layer 4
Is arbitrary and is not limited to this example.

In this magneto-optical disk 1, as shown in FIG. 2 where a part of the recording area is enlarged, a part of the recording area is
A read-only area B1 in which C (Table Of Contents) information and the like are written in advance by the emboss pits 5, and the other area is an area B2 in which data can be written by magneto-optical recording.

The area B1 in which the TOC information and the like are written by the emboss pits 5 is a read-only data area, and in the following description, this data area is referred to as a read-only area B1. Further, an area B2 in which data can be written by magneto-optical recording is referred to as an area B2.
In the following description, it is referred to as a writable area B2.

In the magneto-optical disk 1, the emboss pits 5 formed in the read-only area B1 are, for example, 2-
A pit pattern subjected to eight modulations is formed in a single spiral shape. That is, TOC information and the like are written in the read-only area B1 by a pit row formed in a single spiral along the recording track.

On the other hand, in the writable area B2, the wobbling groove 6 and the straight groove 7 are formed in a double spiral shape.
Data is recorded by magneto-optical recording on a land between the straight groove 7 and the land. That is, FIG.
As shown in the figure, the portion between the wobbling groove 6 and the straight groove 7 and the inner circumferential side of the disk being the straight groove 7 becomes the first recording track TrackA where the information signal is recorded, and the wobbling groove 6 between the straight groove 7 and the wobbling groove 6 on the inner circumferential side of the disk is the second recording track TrackB where the information signal is recorded.
Becomes

Here, the wobbling groove 6 is ± 2.
It is formed so as to meander at a constant cycle with an amplitude of 0 nm. That is, in this magneto-optical disk 1, one of the grooves (that is, the wobbling groove 6) is set to ± 20.
By wobbling with an amplitude of nm, address information is added to the groove.

In this magneto-optical disk 1, the track pitch TPitch of the read-only area B1 is 0.95 μm.
Similarly, the track pitch TPitch of the writable area B2 is set to 0.95 μm.

Here, the track pitch TPitch of the read-only area B1 corresponds to the interval between the center positions of adjacent pit rows. That is, in the magneto-optical disk 1, the interval between the center positions of the adjacent pit rows is 0.95 μm. The track pitch of the writable area B2 corresponds to the interval between the center positions of the wobbling groove 6 and the straight groove 7. That is, in the magneto-optical disk 1, the interval between the center positions of the wobbling groove 6 and the straight groove 7 is 0.95 μm.

In the following description, the interval between the center positions of the adjacent straight grooves 7 is referred to as a track period TPeriod. The track period TPeriod is equivalent to twice the track pitch TPitch. In this magneto-optical disk 1, the track period TPeriod is:
It is 1.90 μm.

In the magneto-optical disk 1, an area between the read-only area B1 and the writable area B2 is called a transition area B3. And this magneto-optical disk 1
In this case, the interval between the read-only area B1 and the writable area B2 in the disk radial direction, that is, the width t1 of the transition area B3 is set within 20 μm. Thus, the transition region B3
Is sufficiently small, the recording / reproducing position shifts from the read-only area B1 to the writable area B2 at the time of recording / reproducing, or the recording / reproducing position changes from the writable area B2 to the read-only area B1. , It is possible to continuously perform stable recording and reproduction without losing the recording track.

In the magneto-optical disk 1 to which the present invention is applied, the wobbling groove 6 and the straight groove 7 are formed to have different widths. That is, in the magneto-optical disk 1, the cross-sectional shape of the wobbling groove 6 and the cross-sectional shape of the straight groove 7 are different. And like this,
By making the cross-sectional shape of the wobbling groove 6 different from the cross-sectional shape of the straight groove 7, in the magneto-optical disk 1, the level of the push-pull signal obtained from the light reflected and diffracted by the wobbling groove 6, The level of the push-pull signal obtained from the light reflected and diffracted by the groove 7 is made different.

Specifically, in this magneto-optical disk 1,
The smaller of the peak value of the push-pull signal obtained from the light reflected and diffracted by the wobbling groove 6 and the peak value of the push-pull signal obtained from the light reflected and diffracted by the second groove is P1 When the larger peak value is P2, P1 / P2 is 0.83 or less.

In this embodiment, the magneto-optical disk 1 in which the wobbling groove 6 and the straight groove 7 are formed is taken as an example. However, in the recording medium according to the present invention, the sectional shapes of the adjacent grooves are different. It should just be done. That is, the present invention is applicable to, for example, a recording medium in which only a wobbling groove is formed as a groove, a recording medium in which only a straight groove is formed as a groove, and the like.

<Laser Cutting Apparatus> When the above-described magneto-optical disc 1 is manufactured, a laser cutting apparatus is used for producing a master for producing a recording medium, which is the master of the magneto-optical disc 1. Hereinafter, an example of a laser cutting device used for manufacturing a master for manufacturing a recording medium will be described in detail with reference to FIG.

The laser cutting device 10 shown in FIG.
Is the photoresist 1 applied on the glass substrate 11
Exposure No. 2 to form a latent image. When a latent image is formed on the photoresist 12 by the laser cutting device 10, the glass substrate 11 coated with the photoresist 12 is attached to a rotary driving device provided on a movable optical table. When exposing the photoresist 12, the glass substrate 11 is driven to rotate by a rotation driving device as shown by an arrow C <b> 1 in the drawing so that the entire surface of the photoresist 12 is exposed in a desired pattern. Is translated by the moving optical table.

The laser cutting device 10 is capable of exposing the photoresist 12 with three exposure beams. The latent image corresponding to the embossed pit 5, the latent image corresponding to the wobbling groove 6, and the A latent image corresponding to the groove 7 is formed by each exposure beam. That is, in the laser cutting apparatus 10, a latent image corresponding to the embossed pit 5 is formed by the first exposure beam, a latent image corresponding to the wobbling groove 6 is formed by the second exposure beam, and the third exposure beam is formed. As a result, a latent image corresponding to the straight groove 7 is formed.

The laser cutting device 10 includes a light source 13 for emitting laser light and an electro-optic modulator (EO) for adjusting the light intensity of the laser light emitted from the light source 13.
M: Electro Optical Modulator 14, an analyzer 15 arranged on the optical axis of the laser light emitted from the electro-optic modulator 14, and the laser light transmitted through the analyzer 15 into reflected light and transmitted light. First beam splitter 16 for splitting
A second beam splitter 17 that divides the laser light transmitted through the first beam splitter 16 into reflected light and transmitted light, and converts the laser light transmitted through the second beam splitter 17 into reflected light and transmitted light. And a photodetector (PD: Ph) for detecting a laser beam transmitted through the third beam splitter 18.
An auto power controller (APC) 20 for applying a signal electric field to the electro-optic modulator 14 and adjusting the intensity of laser light emitted from the electro-optic modulator 14 is provided. ing.

In the laser cutting apparatus 10, the laser light emitted from the light source 13 is first given a predetermined light intensity by an electro-optic modulator 14 driven by a signal electric field applied from an auto power controller 20. And enters the analyzer 15. Here, analyzer 1
Reference numeral 5 denotes an analyzer that transmits only S-polarized light.
The laser beam transmitted through 5 becomes S-polarized light.

Although any light source can be used as the light source 13, a light source which emits a laser beam having a relatively short wavelength is preferable. Specifically, for example, the wavelength λ is 413 nm.
Kr laser that emits laser light of a wavelength of 442n
A He—Cd laser that emits m laser light is suitable as the light source 13.

The S-polarized laser light transmitted through the analyzer 15 is first split into reflected light and transmitted light by a first beam splitter 16, and further transmitted through the first beam splitter 16. The light is split into reflected light and transmitted light by the second beam splitter 17, and the laser light transmitted through the second beam splitter 17 is split into reflected light and transmitted light by the third beam splitter 18. Can be

In the laser cutting apparatus 10, the laser beam reflected by the first beam splitter 16 becomes the first exposure beam, and the laser beam reflected by the second beam splitter 17 becomes the second exposure beam. And the laser beam reflected by the third beam splitter 18 becomes a third exposure beam.

On the other hand, the laser light transmitted through the third beam splitter 18 has its light intensity detected by a photodetector 19, and a signal corresponding to the light intensity is transmitted from the photodetector 19 to an auto power controller 20. Then, in response to the signal sent from the photodetector 19, the auto power controller 20 applies the light to the electro-optic modulator 14 so that the light intensity detected by the photodetector 19 becomes constant at a predetermined level. Adjust the signal electric field. Thereby, automatic light amount control (APC: Auto Power Control) is performed so that the light intensity of the laser light emitted from the electro-optic modulator 14 becomes constant.
Is performed, and a stable laser beam with little noise is obtained.

The laser cutting device 10
Is a first modulation optical system 21 for modulating the light intensity of the laser light reflected by the first beam splitter 16.
And a second modulation optical system 22 for modulating the light intensity of the laser light reflected by the second beam splitter 17.
And a third modulation optical system 23 for modulating the light intensity of the laser beam reflected by the third beam splitter 18.
And an optical system 24 for re-combining the laser light subjected to the light intensity modulation by the first to third modulation optical systems 21, 22 and 23 and condensing the laser light on the photoresist 12. .

Then, the first exposure beam reflected by the first beam splitter 16 is guided to the first modulation optical system 21, where the light intensity is modulated by the first modulation optical system 21. Similarly, the second beam splitter 1
The second exposure beam reflected by 7 is guided to a second modulation optical system 22 and is subjected to light intensity modulation by the second modulation optical system 22. Similarly, the third exposure beam reflected by the third beam splitter 18 is:
The third modulation optical system 23 is guided to the third modulation optical system 23.
Performs light intensity modulation.

Then, the first exposure beam incident on the first modulation optical system 21 is condensed by a condenser lens 25 and is then subjected to an acousto-optic modulator (AOM).
, and the light intensity is modulated by the acousto-optic modulator 26 so as to correspond to a desired exposure pattern. Here, as the acousto-optic element used for the acousto-optic modulator 26, for example, an acousto-optic element made of tellurium oxide (TeO ₂ ) is suitable. Then, the first exposure beam, the light intensity of which has been modulated by the acousto-optic modulator 26, is collimated by the collimator lens 27 and then emitted from the first modulation optical system 21.

Here, a driving driver 28 for driving the acousto-optic modulator 26 is provided in the acousto-optic modulator 26.
Is attached. At the time of exposing the photoresist 12, a signal S1 corresponding to a desired exposure pattern is input to the driving driver 28, and the acousto-optic modulator 26 is driven by the driving driver 28 in accordance with the signal S1, and the first Light intensity modulation is performed on the exposure beam.

More specifically, for example, when a latent image of a pit pattern subjected to 2-8 modulation is formed on the photoresist 12, the modulation corresponding to the pit pattern subjected to 2-8 modulation is performed. The signal is input to the driving driver 28, and the acousto-optic modulator 26 is driven by the driving driver 28 according to the modulation signal. Thereby, 2-8
In order to correspond to the modulated pit pattern, the first
Is subjected to light intensity modulation.

The second exposure beam incident on the second modulation optical system 22 is condensed by a condenser lens 29 and then incident on an acousto-optic modulator 30. The light intensity is modulated so as to correspond to a desired exposure pattern. Here, as an acousto-optic element used for the acousto-optic modulator 30, for example, tellurium oxide (T
An acousto-optic device made of eO ₂ ) is preferred. And
The second exposure beam, the light intensity of which has been modulated by the acousto-optic modulator 30, is collimated by the collimator lens 31 and then emitted from the second modulation optical system 22.

Here, a driving driver 32 for driving the acousto-optic modulator 30 is provided in the acousto-optic modulator 30.
Is attached. At the time of exposing the photoresist, a signal S2 corresponding to a desired exposure pattern is input to the driving driver 32, and the acousto-optic modulator 30 is driven by the driving driver 32 according to the signal S2. Light intensity modulation is performed on the beam.

More specifically, for example, when a latent image having a groove pattern corresponding to the wobbling groove 6 having a constant depth is formed on the photoresist 12, a DC signal having a constant level is transmitted to the driving driver 32. The acousto-optic modulator 30 is driven by the driving driver 32 according to the input DC signal. Thereby, light intensity modulation is performed on the second exposure beam so as to correspond to a desired groove pattern.

The third exposure beam incident on the third modulating optical system 23 is condensed by a condensing lens 33 and then incident on an acousto-optic modulator 34. The light intensity is modulated so as to correspond to a desired exposure pattern. Here, as the acousto-optic element used for the acousto-optic modulator 34, for example, tellurium oxide (T
An acousto-optic device made of eO ₂ ) is preferred. And
The third exposure beam, the light intensity of which has been modulated by the acousto-optic modulator 34, is collimated by a collimator lens 35 and transmitted through a λ / 2 wavelength plate 36, whereby the polarization direction is rotated by 90 °. Then, the light is emitted from the third modulation optical system 23.

Here, a driving driver 37 for driving the acousto-optic modulator 34 is provided in the acousto-optic modulator 34.
Is attached. When the photoresist 12 is exposed, a signal S3 corresponding to a desired exposure pattern is input to the driver 37, and the driver 37 drives the acousto-optic modulator 34 according to the signal S3. Light intensity modulation is performed on the exposure beam.

Specifically, for example, when a latent image having a groove pattern corresponding to the straight groove 7 having a constant depth is formed in the photoresist 12, a DC signal of a constant level is transmitted to the driving driver 37. Input and the D
The acousto-optic modulator 34 is driven by the driving driver 37 according to the C signal. Thereby, light intensity modulation is performed on the third exposure beam so as to correspond to a desired groove pattern.

As described above, the first exposure beam is subjected to light intensity modulation by the first modulation optical system 21, and
Is subjected to light intensity modulation by the second modulation optical system 22, and the third exposure beam is modulated by the third modulation optical system 23.
Performs light intensity modulation. At this time, the first exposure beam emitted from the first modulation optical system 21 and the second exposure beam
The second exposure beam emitted from the modulation optical system 22 of
Although the third exposure beam emitted from the third modulation optical system 23 has been rotated by 90 ° by passing through the λ / 2 wavelength plate 36, the polarization direction is rotated by 90 °. It is polarized.

Then, the first exposure beam emitted from the first modulation optical system 21 is reflected by the mirror 40 and is guided horizontally and parallel on the moving optical table. Similarly, the second exposure beam emitted from the second modulation optical system 22 is reflected by the mirror 41 and is guided horizontally and parallel on the moving optical table. Similarly, the third exposure beam emitted from the third modulation optical system 23 is reflected by the mirror 42 and is guided horizontally and parallel on the moving optical table.

Then, the first light emitted from the first modulation optical system 21 and guided horizontally and in parallel on the movable optical table.
Is reflected by the mirror 43 and its traveling direction is bent by 90 °, and then enters the polarization beam splitter 45 via the half mirror 44. The second exposure beam emitted from the second modulation optical system 22 and guided horizontally and parallel to the moving optical table is transmitted to the deflection optical system 4.
6 after being optically deflected by the half mirror 44
Is reflected by the laser beam and the traveling direction is bent by 90 °, and then enters the polarization beam splitter 45. The third exposure beam emitted from the third modulation optical system 23 and guided horizontally and in parallel on the moving optical table directly enters the polarization beam splitter 45.

Here, the deflection optical system 46 is for performing optical deflection on the second exposure beam so as to correspond to wobbling of the wobbling groove. That is, the light emitted from the second modulation optical system 22 and the deflection optical system 4
The second exposure beam incident on the wedge prism 4
7 through an acousto-optic deflector (AOD: Acousto Optical
Deflector) 48 and is subjected to optical deflection by the acousto-optic deflector 48 so as to correspond to a desired exposure pattern. Here, as an acousto-optic element used for the acousto-optic deflector 48, for example, tellurium oxide (TeO
_The acousto-optic element consisting of ₂ ) is preferred. The second exposure beam that has been optically deflected by the acousto-optic deflector 48 passes through the wedge prism 49 to the deflection optical system 4.
6 is emitted.

The wedge prisms 47 and 49 allow the second exposure beam to be incident on the lattice plane of the acousto-optic device of the acousto-optic deflector 48 so as to satisfy the Bragg condition. The purpose of 48 is to prevent the beam horizontal height from changing even if the second exposure beam is optically deflected. In other words, the wedge prism 47, the acousto-optic deflector 48, and the wedge prism 49 are configured such that the grating surface of the acousto-optic element of the acousto-optic deflector 48 satisfies the Bragg condition with respect to the second exposure beam, and The second exposure beam emitted from 46 is arranged such that the beam horizontal height does not change.

Here, a driving driver 50 for driving the acousto-optic deflector 48 is provided in the acousto-optic deflector 48.
Is attached, and the driving driver 50 includes:
Voltage Controlled Oscilla (VCO)
tor) 51 is FM-modulated by a control signal S4 including address information and supplied. When the photoresist 12 is exposed, a signal corresponding to a desired exposure pattern is input from the voltage controlled oscillator 51 to the driving driver 50, and the driving driver 5
The acousto-optic deflector 48 is driven by 0, whereby the second exposure beam is optically deflected.

Specifically, for example, a frequency of 84.672
By wobbling the groove at kHz,
In a case where address information is added to a groove, for example, a high frequency signal having a center frequency of 224 MHz
The signal FM-modulated by the control signal of 4.672 kHz is
It is supplied from the voltage controlled oscillator 51 to the driving driver 50. In response to this signal, the driving driver 50 drives the acousto-optic deflector 48 to change the Bragg angle of the acousto-optic element of the acousto-optic deflector 48, thereby supporting wobbling at a frequency of 84.672 kHz. Optical deflection is performed on the second exposure beam.

The second exposure beam optically deflected by the deflection optical system 46 so as to correspond to the wobbling of the wobbling groove 6 is reflected by the half mirror 44 and proceeds as described above. The light is incident on the polarizing beam splitter 45 after being bent by 90 °.

Here, the polarization beam splitter 45
It reflects the polarized light and transmits the P-polarized light.
The first exposure beam emitted from the first modulation optical system 21 and the second exposure beam emitted from the second modulation optical system 22 and optically deflected by the deflection optical system 46 are S-polarized light. In addition, the third exposure beam emitted from the third modulation optical system 23 is P-polarized light. Therefore, the first and second exposure beams are reflected by the polarization beam splitter 45, and the third exposure beam passes through the polarization beam splitter 45. As a result, the first exposure beam emitted from the first modulation optical system 21, the second exposure beam emitted from the second modulation optical system 22 and optically deflected by the deflection optical system 46, The third exposure beam emitted from the third modulation optical system 23 is recombined with the third exposure beam so that the traveling directions are the same.

The first to third exposure beams recombined so that the traveling directions are the same direction and emitted from the polarizing beam splitter 45 are adjusted to a predetermined beam diameter by the magnifying lens 52, and then to the mirror 53. The light is reflected by the objective lens 54 and guided to the objective lens 54, and is focused on the photoresist 12 by the objective lens 54. This allows
The photoresist 12 is exposed, and a latent image is formed on the photoresist 12. At this time, as described above, the glass substrate 11 coated with the photoresist 12 is rotated by a rotary driving device as shown by an arrow C1 in the drawing so that the entire surface of the photoresist 12 is exposed in a desired pattern. , And is translated by a moving optical table. As a result, a latent image corresponding to the irradiation trajectory of the first to third exposure beams is formed over the entire surface of the photoresist 12.

The objective lens 54 for condensing the exposure beam on the photoresist 12 preferably has a large numerical aperture NA in order to form a finer pit pattern or groove pattern. Specifically, an objective lens having a numerical aperture NA of about 0.9 is suitable.

When irradiating the photoresist 12 with the first to third exposure beams as described above, the beam diameters of the first to third exposure beams are changed by the magnifying lens 52 as necessary. The effective numerical aperture for the objective lens 54 may be adjusted. Thereby, the spot diameters of the first to third exposure beams focused on the surface of the photoresist 12 can be changed.

The second exposure beam incident on the polarization beam splitter 45 is combined with the third exposure beam on the reflection surface of the polarization beam splitter 45. Here, the polarization beam splitter 45 is arranged such that the reflection surface of the deflection beam splitter forms an appropriate reflection angle with respect to the traveling direction of the light synthesized and emitted by the reflection surface.

More specifically, the reflection angle of the reflection surface of the polarizing beam splitter 54 is determined in such a manner that the spot corresponding to the second exposure beam and the spot corresponding to the third exposure beam in the radial direction of the glass substrate 11. The interval is the track pitch
Set to correspond to TPitch. This makes it possible to expose the portion corresponding to the wobbling groove 6 with the second exposure beam, and at the same time, to expose the portion corresponding to the straight groove 7 with the third exposure beam.

The laser cutting apparatus 10 as described above
Then, an optical system corresponding to a first exposure beam for forming a latent image corresponding to the embossed pit 5 and an optical system corresponding to a second exposure beam for forming a latent image corresponding to the wobbling groove 6 are provided. And an optical system corresponding to a third exposure beam for forming a latent image corresponding to the straight groove 7, so that only the laser cutting device 10 can be used to form a latent image corresponding to the embossed pit 5,
A latent image corresponding to the wobbling groove 6 and a latent image corresponding to the straight groove 7 can be collectively formed.

Moreover, the laser cutting device 10
Then, the irradiation position of the second exposure beam and the irradiation position of the third exposure beam are adjusted by adjusting the direction of the deflection beam splitter 45 for synthesizing the second exposure beam and the third exposure beam. It can be easily adjusted.

In the laser cutting apparatus 10, the spot diameters of the first to third exposure beams focused on the surface of the photoresist 12 can be easily changed by the magnifying lens 52. To make the width of the groove larger than the width of the groove,
It can be easily realized.

<Method of Manufacturing Magneto-Optical Disk> Next, a method of manufacturing the magneto-optical disk 1 shown in FIGS. 1 and 2 will be described in detail with a specific example.

When manufacturing the magneto-optical disk 1, first,
As a master step, a master for manufacturing a recording medium having a concavo-convex pattern corresponding to the embossed pit 5, the wobbling groove 6, and the straight groove 7 is manufactured.

In this mastering step, first, a disk-shaped glass substrate 11 whose surface is polished is washed and dried, and then a photoresist 12 as a photosensitive material is applied on the glass substrate 11. Next, the photoresist 12 is exposed by the laser cutting device 10 to form latent images corresponding to the emboss pits 5, the wobbling grooves 6, and the straight grooves 7 on the photoresist 12.

When a magneto-optical disk for evaluation described later is manufactured, a Kr laser emitting a laser beam having a wavelength λ of 413 nm is used as the light source 13 of the laser cutting device 10, and the first to third exposures are performed. The objective lens 54 for condensing the beam on the photoresist 12 has a numerical aperture NA of 0.9. A lens having a focal length of 80 mm was used as the magnifying lens.

When the photoresist 12 is exposed by the laser cutting device 10, first, the photoresist 12 is exposed by a first exposure beam to form a latent image corresponding to the embossed pit 5 on the photoresist 12. Then, by exposing the photoresist 12 with the second and third exposure beams, a latent image corresponding to the wobbling groove 6 and the straight groove 7 is formed on the photoresist 12.

When exposing the photoresist 12 with the first exposure beam, the second and third exposure beams are controlled by the acousto-optic modulators 30 and 34 so that the second and third exposure beams do not enter the photoresist 12. The third exposure beam is shielded. Conversely, when exposing the photoresist 12 with the second and third exposure beams, the first exposure beam is shielded by the acousto-optic modulator 26 so that the first exposure beam does not enter the photoresist 12. Keep it.

When a latent image corresponding to the embossed pits 5 is formed on the photoresist 12 by exposing the photoresist 12 with the first exposure beam, the first modulation optical system 21 converts the latent image to the first exposure beam. Then, light intensity modulation is performed. Specifically, for example, a modulation signal corresponding to a pit pattern subjected to 2-8 modulation is supplied to the driving driver 2.
8 and the driving driver 2 based on the modulated signal.
8 drives the acousto-optic modulator 26, whereby
Light intensity modulation is performed on the first exposure beam so as to correspond to the pit pattern subjected to the 2-8 modulation. Then, the first exposure beam having been subjected to the light intensity modulation is condensed on the photoresist 12 by the objective lens 54, thereby exposing the photoresist 12 to form a latent image corresponding to the embossed pit 5 into a photo. It is formed on a resist 12.

When the photoresist 12 is thus exposed to form a latent image corresponding to the embossed pit 5, the glass substrate 11 on which the photoresist 12 is applied is formed at a predetermined rotation speed. It is driven to rotate and is translated at a predetermined speed.

More specifically, when producing a magneto-optical disk for evaluation, which will be described later, the rotational speed of the glass substrate 11 is set to a linear speed between the light spot by the first exposure beam and the photoresist 12. 1.0 m / sec. Then, the glass substrate 11 is moved 0.9 times per rotation.
The glass substrate 11 was translated in the radial direction by a moving optical table by 5 μm (that is, the track pitch TPitch).

By exposing the photoresist 12 with the first exposure beam as described above, for example, 2-8
A latent image corresponding to the modulated pit pattern is formed on the photoresist 12 in a single spiral shape.

After the latent image corresponding to the emboss pit 5 is formed on the photoresist 12 as described above,
The photoresist 12 is exposed by the second and third exposure beams.
Are exposed to form latent images corresponding to the wobbling groove 6 and the straight groove 7 in the photoresist 1.
2 is formed.

When a latent image corresponding to the wobbling groove 6 is formed on the photoresist 12 by exposing the photoresist 12 with the second exposure beam, the second modulation beam is applied to the second exposure beam. The optical intensity modulation is performed by the system 22 and the optical deflection is performed by the optical deflection system 46.

More specifically, first, a DC signal of a fixed level is input to the driving driver 32, and the acousto-optic modulator 30 is driven by the driving driver 32 based on the DC signal. The light intensity modulation is performed on the second exposure beam so as to correspond to the pattern (1). Here, since the wobbling groove 6 is a continuous groove having a constant depth, while the latent image corresponding to the wobbling groove 6 is being formed, light is emitted so that the light intensity of the second exposure beam becomes constant. Apply intensity modulation.

Next, the second exposure beam subjected to the light intensity modulation by the second modulation optical system 22 is optically deflected by the deflection optical system 46. Specifically, a high frequency signal is FM-modulated from the voltage controlled oscillator 51 by a control signal and supplied to the driving driver 50, and the driving driver 50 drives the acousto-optical deflector 48 based on this signal, and The Bragg angle of the acousto-optic device of the acousto-optic deflector 48 is changed, and thereby the second exposure beam is optically deflected.

When a magneto-optical disk for evaluation described later is manufactured, a high frequency signal having a center frequency of 224 MHz is FM-modulated by a control signal having a frequency of 84.672 kHz.
The voltage-controlled oscillator 51 supplied the driving driver 50. Then, based on this signal, the driving driver 50
Drives the acousto-optic deflector 48 to change the Bragg angle of the acousto-optic element of the acousto-optic deflector 48, whereby the position of the light spot of the second exposure beam focused on the photoresist 12 is changed. , Frequency 84.672 kHz
Optical deflection was performed so as to vibrate in the radial direction of the glass substrate 11 at z and amplitude ± 20 nm.

Then, the second exposure beam having been subjected to the light intensity modulation and the optical deflection is condensed on the photoresist 12 by the objective lens 54, thereby exposing the photoresist 12 to the wobbling groove 6. A corresponding latent image is formed on the photoresist 12.

The photoresist 12 is exposed by the third exposure beam at the same time as the photoresist 12 is exposed by the second exposure beam, so that a latent image corresponding to the straight groove 7 is formed on the photoresist 12. I do.

When a latent image corresponding to the straight groove 7 is formed on the photoresist 12 by exposing the photoresist 12 with the third exposure beam, the third
Is subjected to light intensity modulation by the third modulation optical system 23.

Specifically, a constant level DC signal is input to the driving driver 37, and the acousto-optic modulator 34 is driven by the driving driver 37 based on the DC signal.
Thus, light intensity modulation is performed on the third exposure beam so as to correspond to the pattern of the straight groove 7. Here, since the straight groove 7 is a continuous groove having a constant depth, while the latent image corresponding to the straight groove 7 is being formed, the light is emitted so that the light intensity of the third exposure beam is constant. Apply intensity modulation.

Then, the third exposure beam subjected to the light intensity modulation as described above is condensed on the photoresist 12 by the objective lens 54, so that the photoresist 12
Is exposed to form a latent image corresponding to the straight groove 7 on the photoresist 12.

When the photoresist 12 is exposed to form latent images corresponding to the wobbling groove 6 and the straight groove 7, the photoresist 1 is exposed.
The glass substrate 11 coated with 2 is rotationally driven at a predetermined rotation speed and is translated at a predetermined speed.

More specifically, when producing a magneto-optical disk for evaluation, which will be described later, the rotation speed of the glass substrate 11 depends on the relative movement speed between the light spot by the second and third exposure beams and the photoresist 12. Was set to a linear velocity of 1.0 m / sec. Then, the glass substrate 11 was moved in parallel in the radial direction of the glass substrate 11 by a moving optical table by 1.90 μm per rotation (that is, by a track period TPeriod).

By exposing the photoresist 12 with the second and third exposure beams as described above, the latent image corresponding to the wobbling groove 6 and the latent image corresponding to the straight groove 7 are formed into a double spiral. Formed on photoresist 12.

When the photoresist 12 is exposed by the second and third exposure beams as described above, the level of the DC signal input to the driving drivers 32 and 37 is adjusted to adjust the level of the second exposure beam. The power is set to be different from the power of the third exposure beam. Thus, the width of the latent image corresponding to the wobbling groove 6 is different from the width of the latent image corresponding to the straight groove 7.

In the laser cutting apparatus 10, the distance between the spot corresponding to the second exposure beam and the spot corresponding to the third exposure beam in the radial direction of the glass substrate 11 corresponds to the track pitch TPitch. As described above, the reflection angle of the reflection surface of the polarization beam splitter 45 is set in advance.

By setting the reflection angle of the reflection surface of the polarization beam splitter 45 in this way, a latent image corresponding to the wobbling groove 6 is formed by the second exposure boom, and the latent image adjacent to the wobbling groove 6 is formed. A latent image corresponding to the straight groove 7 thus formed is formed by the third exposure beam. This means
In other words, the relative positioning between the wobbling groove 6 and the straight groove 7 can be realized by adjusting the direction of the deflection beam splitter 45.

After the latent image is formed on the photoresist 12 as described above, the glass substrate 11 is placed on a turntable of a developing machine such that the surface on which the photoresist 12 is coated is the upper surface. I do. Then, while rotating the glass substrate 11 by rotating the turntable, a developing solution is dropped on the photoresist 12 to perform a developing process, and the embossed pits 5, the wobbling groove 6, and the straight groove are formed on the glass substrate 11. 7
A concavo-convex pattern corresponding to is formed.

Next, a conductive film made of Ni or the like is formed on the concave / convex pattern by electroless plating, and then the glass substrate 11 on which the conductive film is formed is attached to an electroforming apparatus, and is then subjected to electroplating. A plating layer made of Ni or the like is formed on the conductive film so as to have a thickness of about 300 ± 5 μm. Thereafter, the plating layer is peeled off, and the peeled plating is washed with acetone or the like to remove the photoresist 12 remaining on the surface to which the uneven pattern has been transferred.

According to the above steps, a master for producing a recording medium made of plating on which the concavo-convex pattern formed on the glass substrate 11 has been transferred, that is, the concavo-convex pattern corresponding to the embossed pits 5, the wobbling grooves 6, and the straight grooves 7. The master for manufacturing a recording medium on which is formed is completed.

The recording medium producing master is a recording medium producing master to which the present invention is applied. That is, this master for manufacturing a recording medium is a master for manufacturing a recording medium used when manufacturing the magneto-optical disk 1 in which the wobbling groove 6 and the straight groove 7 are formed along the recording track. A first groove pattern which is an uneven pattern corresponding to 6 and a second groove pattern which is an uneven pattern corresponding to the straight groove 7 are formed in a double spiral shape. The first groove pattern and the second groove pattern are formed so that their widths are different from each other.

Next, as a transfer step, a disk substrate on which the surface shape of the above-mentioned master for producing a recording medium is transferred is manufactured by using a photopolymer method (so-called 2P method).

More specifically, first, a photopolymer is applied smoothly on the surface of the master for manufacturing a recording medium on which the concavo-convex pattern has been formed to form a photopolymer layer. The base plate is brought into close contact with the photopolymer layer while preventing dust from entering. Here, as the base plate, for example, a base plate made of polymethyl methacrylate (refractive index: 1.49) having a thickness of 1.2 mm is used.

Thereafter, the photopolymer is cured by irradiating ultraviolet rays, and then, the master for recording medium production is peeled off, thereby producing a disk substrate 2 on which the surface shape of the master for recording medium production is transferred.

Here, an example has been described in which the disk substrate 2 is manufactured by using the 2P method so that the concave and convex pattern formed on the master for manufacturing a recording medium is more accurately transferred to the disk substrate 2. When the disk substrate 2 is mass-produced, the disk substrate 2 is formed by injection molding using a transparent resin such as polymethyl methacrylate or polycarbonate.
Needless to say, it may be possible to produce

Next, as a film forming step, the recording layer 3 and the protective layer 4 are formed on the disk substrate 2 on which the surface shape of the recording medium manufacturing master has been transferred. Specifically, for example, first, a first dielectric film made of SiN or the like and a TeFeCo
A perpendicular magnetic recording film made of an alloy or the like and a second dielectric film made of SiN or the like are sequentially formed by sputtering,
Further, by forming a light reflecting film made of Al or the like on the second dielectric film by vapor deposition, the light reflecting film comprises a first dielectric film, a perpendicular magnetic recording film, a second dielectric film, and a light reflecting film. The recording layer 3 is formed. Thereafter, an ultraviolet curable resin is applied on the recording layer 3 by a spin coating method, and the ultraviolet curable resin is irradiated with ultraviolet light to be cured, thereby forming the protective layer 4.

Through the above steps, the magneto-optical disk 1 is completed.

<Evaluation of Magneto-Optical Disk> Next, a plurality of evaluation magneto-optical disks will be manufactured by the above-described manufacturing method, and the results of the evaluation will be described.

In evaluating the magneto-optical disk for evaluation, first, the power of the second exposure beam for forming a latent image corresponding to the wobbling groove 6 is set to 0.5 m.
A plurality of masters for producing a recording medium were produced by changing the value of W as a center. Here, the power of the third exposure beam for forming a latent image corresponding to the straight groove 7 is:
It was constant at 0.5 mW.

The width of the concavo-convex pattern corresponding to the wobbling groove 6 formed on the recording medium manufacturing master is determined by scanning electron microscope (SEM: Scanning Elect).
ronMicroscope). Table 1 shows the result of measurement of the relationship between the power of the second exposure beam and the width of the concavo-convex pattern corresponding to the wobbling groove 6.

[0108]

[Table 1]

From Table 1, it can be seen that the width of the concavo-convex pattern corresponding to the wobbling groove 6 changes by changing the power of the second exposure beam. This means that the width of the wobbling groove 6 of the magneto-optical disk 1 can be changed by changing the power of the second exposure beam.

Next, a magneto-optical disk for evaluation was produced by the 2P method using the above-mentioned master for producing a recording medium.
The push-pull signal was measured for those evaluation magneto-optical disks. Here, for the measurement of the push-pull signal, an optical pickup having a wavelength λ of the laser beam of 650 nm and a numerical aperture NA of the objective lens of 0.52 was used.

For each evaluation magneto-optical disk, a push-pull signal obtained from the light reflected and diffracted by the wobbling groove 6 and a push-pull signal obtained from the light reflected and diffracted by the straight groove 7 were measured. FIG. 4 shows the measurement results.

In FIG. 4, the vertical axis indicates the variation of the push-pull signal. Specifically, the vertical axis represents the peak value of the push-pull signal obtained from the light reflected and diffracted by the wobbling groove 6 and the peak value of the push-pull signal obtained from the light reflected and diffracted by the straight groove 7. The value of P1 / P2 is shown when the smaller peak value is P1 and the larger peak value is P2. The horizontal axis is the wobbling groove 6
The power of the second exposure beam for forming a latent image corresponding to.

From the results shown in FIG. 4, it is found that the value of P1 / P2 changes by changing the power of the second exposure beam. Here, changing the power of the second exposure beam means changing the width of the wobbling groove 6, as can be seen from the results shown in Table 1. From these facts, it can be seen that changing the width of the wobbling groove 6 changes the value of P1 / P2.

Then, the wobbling groove 6 and the straight groove 7 are distinguished by detecting the level of the push-pull signal for each evaluation magneto-optical disk having a different value of P1 / P2. The discrimination was made between the first recording track TrackA having the straight groove 7 and the second recording track TrackB having the wobbling groove 6 on the inner circumferential side of the disk.

As a result, in each evaluation magneto-optical disk in which the value of P1 / P2 is 0.83 or less, the level of the push-pull signal is detected so that the first recording track Track is detected.
A could be distinguished from the second recording track TrackB. From this, it was found that if the value of P1 / P2 is set to 0.83 or less, it is possible to distinguish the adjacent recording tracks TrackA and TrackB from the fluctuation of the push-pull signal.

That is, by making the width of the wobbling groove 6 and the width of the straight groove 7 different so that the value of P1 / P2 is 0.83 or less, in the conventional magneto-optical disk, adjacent recording tracks are formed. Even if the track is narrowed to such an extent that it cannot be distinguished, the adjacent recording tracks TrackA and TrackB can be determined from the fluctuation of the push-pull signal.

However, the fact that the value of P1 / P2 is small means that the level of the push-pull signal obtained from the light reflected and diffracted by one groove becomes small, so that the value of P1 / P2 is too large. If the size is reduced, the tracking servo may not be performed.

However, if the power of the second exposure beam is 90
In each of the evaluation magneto-optical disks manufactured by changing the values in the range of% to 110%, normal tracking servo was possible. Then, among the evaluation magneto-optical disks, among the evaluation magneto-optical disks having the smallest value of P1 / P2, the value of P1 / P2 was 0.4. From this, it can be said that if the value of P1 / P2 is at least 0.4 or more, tracking servo can be performed normally.

As described above, the value of P1 / P2 is 0.4
Wobbling groove 6 so that it is between
Also, it has been found that if the shape of the straight groove 7 is set, it is possible to realize both the determination of the adjacent recording tracks TrackA and TrackB and the stable tracking servo.

Incidentally, Japanese Patent Application Laid-Open No. 6-309672 discloses that
There is disclosed a method of performing tracking servo on two recording tracks by using one of two adjacent grooves. When this method is used, there is no need to perform tracking servo using the other groove. Therefore, when this method is used, P1
Even if the value of / P2 is less than 0.4, stable tracking servo can be realized. Therefore, P
The value of 1 / P2 does not necessarily have to be 0.4 or more.

By the way, in order to reduce the value of P1 / P2, as can be seen from the above-described experimental results, the width of one of the wobbling groove 6 and the straight groove 7 may be reduced. If the width of one of the wobbling groove 6 and the straight groove 7 is reduced, the width of the land becomes large as a result, and the recording track Trac is reduced.
The width of kA and TrackB becomes wider. And the recording track Tr
If the width of ackA and TrackB becomes wider, the recording track Track
The C / N of the reproduction signal detected from A and TrackB is improved. That is, reducing the width of either the wobbling groove 6 or the straight groove 7 so as to reduce the value of P1 / P2 has the advantage of improving the characteristics of the reproduced signal.

The present invention can be widely applied to a recording medium having grooves formed along recording tracks, and a recording medium manufacturing master used for manufacturing the recording medium, and is an object of the present invention. The recording medium may be, for example, a read-only recording medium, a recording medium capable of repeatedly rewriting data, or a recording medium in which data can be additionally written or cannot be erased.

The method of recording data is not particularly limited. For example, a recording medium to which the present invention is applied is a read-only optical recording medium in which data is written in advance by emboss pits or the like, a magneto-optical recording medium, or the like. Either a magneto-optical recording medium for recording data using the effect or a phase change recording medium for recording data using the phase change of the recording layer may be used.

The present invention can be widely applied to a recording medium having a groove formed in at least a part of a recording area, and a recording medium manufacturing master used for manufacturing the recording medium. That is, for example, a groove may be formed in the entire recording area, or an area in which data is recorded by embossed pits without forming a groove may exist in the recording area. .

[0125]

As is apparent from the above description, according to the present invention, even if the track pitch is extremely narrow, it is possible to distinguish adjacent recording tracks and to perform tracking servo stably. It is possible to provide a recording medium capable of performing the recording, and a recording medium production master capable of producing such a recording medium. Therefore, according to the present invention, it is possible to further narrow the track and achieve a higher recording density of the recording medium.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an enlarged main part of an example of a magneto-optical disk to which the present invention is applied.

FIG. 2 is an enlarged view showing a part of a recording area of a magneto-optical disk to which the present invention is applied.

FIG. 3 is a diagram showing an outline of an optical system of an example of a laser cutting apparatus used when producing a recording medium and a master for producing a recording medium according to the present invention.

FIG. 4 is a diagram showing the relationship between the power of a second exposure beam and the amount of fluctuation of a push-pull signal.

[Explanation of symbols]

Reference Signs List 1 magneto-optical disk, 2 disk substrate, 3 recording layer, 4 protective layer, 5 embossed pit, 6 wobbling groove, 7 straight groove, 21
First modulation optical system, 22 second modulation optical system, 23
Third modulation optical system, 46 deflection optical system

Claims (6)

[Claims] 1. A recording medium in which a groove is formed along a recording track, wherein the first groove and the second groove are formed so as to draw a double spiral. The cross-sectional shape of the first groove is different from the cross-sectional shape of the second groove. The level of the push-pull signal obtained from the light reflected and diffracted by the first groove, and the level of the push-pull signal reflected and diffracted by the second groove A recording medium characterized in that the level of the push-pull signal obtained from the reflected light is different. 2. The recording medium according to claim 1, wherein a width of said first groove is different from a width of said second groove. 3. The first groove is a wobbling groove formed at least partially so as to meander, and the second groove is a straight groove formed without meandering. The recording medium according to claim 1, wherein 4. A peak value of a push-pull signal obtained from light reflected and diffracted by the first groove, and
The smaller of the peak values of the push-pull signal obtained from the light reflected and diffracted by the groove
1. When the larger peak value is P2, P1 / P2
2. The recording medium according to claim 1, wherein is less than or equal to 0.83. 5. A recording medium manufacturing master used when manufacturing a recording medium in which a groove is formed along a recording track, wherein a concave and convex pattern corresponding to the groove includes a first groove pattern and a concave and convex pattern. A master for producing a recording medium, wherein a second groove pattern is formed so as to draw a double spiral, and a width of the first groove pattern is different from a width of the second groove pattern. 6. The first groove pattern is a concavo-convex pattern corresponding to a wobbling groove formed at least partially so as to meander, and the second groove pattern is a straight pattern formed without meandering. 6. The master for producing a recording medium according to claim 5, wherein the master has an uneven pattern corresponding to the groove.