JPH113547A - Optical disc manufacturing method - Google Patents

Abstract

(57) Abstract: Provided is a method of manufacturing an optical disk for recording information on grooves and lands that can accurately obtain address information without crosstalk. SOLUTION: A groove 4 formed in a spiral or concentric shape and serving as a recording track for recording information, a land 1 between the grooves also serving as a recording track for recording information, and address information of the recording track are recorded. First and second uneven pit rows 4a, 4a,
4b, comprising the steps of:
The light beams 31a, 3 from separate light beam irradiation means correspond to the pit row 4a and the second pit row 4b, respectively.
1b is irradiated on the photoresist on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk such as a magneto-optical disk in which address information has been recorded in advance by using pit rows having irregularities.

[0002]

2. Description of the Related Art Conventionally, in an optical memory for recording / reproducing information using light, a recording film composed of a perpendicular magnetization film is used as a recording medium, and a magnetic field is applied while irradiating a laser beam, thereby forming a light spot inside an optical spot. A magneto-optical disk for recording information by making the magnetization upward or downward has been put to practical use.

[0003] As shown in FIG.
The grooves 51 are provided so that the light spot 55 can accurately follow the lands 52 between the grooves 51. Address information is recorded on the land 52 by pits 53..., So that the address information of the track scanned by the light spot 55 can be obtained.

Recording and reproduction of information are performed on tracks corresponding to the lands 52. The track pitch is set to about the diameter of the light spot 55,
Is determined by the wavelength of the laser light and the numerical aperture of the objective lens that converges the laser light to the light spot 55. The wavelength of the laser light is usually 780 to 830 n
m, and the numerical aperture of the objective lens is 0.45 to 0.6. Therefore, the diameter of the light spot 55 ranges from 1.2 to 1..
4 μm, and the track pitch is set to 1.4 to 1.6 μm. Therefore, the size of the recording domain 54 whose magnetization is upward or downward is at least 0.8 μm.
About.

As shown in FIG. 9, a magneto-optical disk having flat mirror portions 62 is also known. Grooves 61 are not formed in the mirror portions 62 but pits 63 are formed. The light spot 55 tracks the groove 61, and the address information of the track scanned by the light spot 55 is reproduced from the pits 63. Also in this magneto-optical disk, the size of the recording domains 64 on the groove 61 is
The minimum is about 0.8 μm.

In recent years, the recording film of a magneto-optical disk has a multi-layer structure, so that the recording film has a magnetic super-resolution (Magnet).
ic Super Resolution, thereby forming a recording domain much smaller than the size of the light spot 55 to improve the recording density. Using this magnetic super-resolution,
It is possible to stably form the recording domain having the above-mentioned half size, and it is possible to reduce the track pitch to about half the above-mentioned 0.8 μm. The density can be dramatically improved. This magnetic super-resolution is described in, for example, Journal of the Japan Society of Applied Magnetics, Vol. 15, No. 5, 1991 pp. 8
38-845 is detailed.

[0007]

However, in the above-mentioned conventional configuration, when the track pitch is reduced to １ ／, the size of the pits 53 is also reduced to ト ラ ッ ク. Therefore, pit 5
3 is weak.

Further, since the distance between the pits 53 of adjacent tracks is also reduced to 1/2, there is a problem that crosstalk easily occurs and accurate address information cannot be obtained.

[0009]

According to a first aspect of the present invention, there is provided a manufacturing method of a groove formed spirally or concentrically and serving as a recording track for recording information, and a groove serving as a recording track for recording information. A method for manufacturing an optical disc, comprising: a land between the first and second pits, and first and second concavo-convex pit rows not radially adjacent to each other for recording address information of a recording track, wherein the first pit row and the second pit row are provided. The method is characterized in that light beams from separate light beam irradiation means are applied to the photoresist on the substrate corresponding to the rows.

According to a second aspect of the present invention, there is provided a method of manufacturing an optical disk according to the first aspect.
A first light beam is radiated at a first intensity corresponding to the groove, and a first light beam is radiated at a lower intensity than the first intensity corresponding to a first uneven pit row. It is characterized in that a second light beam is irradiated corresponding to the uneven pit row.

According to a third aspect of the present invention, there is provided the optical disk manufacturing method according to the first aspect.
A first light beam and a second light beam are irradiated adjacent to each other corresponding to the groove, and a first light beam is irradiated corresponding to the first uneven pit row. It is characterized in that a second light beam is irradiated corresponding to the pit row.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a magneto-optical disk according to this embodiment.
As shown in FIG. 1, spiral or concentric grooves 1 are provided. The grooves 1 are interrupted every time the circuit goes around, and the interrupted portions are flat mirror portions 3. The width of the groove 1 and the width of the land 2 between the grooves 1 are set to be equal to each other and equal to the track pitch.

In each mirror section 3, pits 4a... (First pit row) on which address information is recorded are formed.
A pit 4b (second pit row) on which address information is recorded is formed in a portion of each land 2 near the mirror portion 3. Therefore, the pits 4a ... and 4b ... are arranged in different radial directions.

In the above configuration, information is recorded on tracks on grooves 1 and lands 2. Whether the light spot 6 follows the track on the groove 1 or the track on the land 2 can be easily selected by inverting the polarity of the tracking signal. The tracking signal is obtained by, for example, a push-pull method.

When the light spot 6 scans the tracks on the grooves 1, the address information is obtained from the pits 4a. On the other hand, when the light spot 6 scans the tracks on the lands 2, the address information is obtained from the pits 4b.

As described above, in the magneto-optical disk of the present embodiment, the pits 4a... 4b are arranged in different radial directions so as not to be adjacent to each other.
Are not simultaneously irradiated on the pits 4a... And 4b. Therefore, crosstalk hardly occurs, and accurate address information is required.

When information is recorded by using the magnetic super-resolution effect, the diameter of the recording domain 5 can be set to about 0.4 μm.
Therefore, when the track width is set to 0.8 μm (that is, both the width of the groove 1 and the width of the land 2 are set to 0.8 μm).
m), recording and reproduction can be easily performed. Further, since the track pitch can be reduced to half of 0.8 μm from the conventional 1.6 μm, the recording density can be greatly improved. Moreover, accurate address information can be obtained.

When the wavelength of the laser beam used for recording and reproduction is shortened, the track pitch can be further reduced.
For example, the wavelength of the laser light is changed from 830 nm to 458 nm.
, The track pitch can be increased by (458/830) times. That is, the recording density can be almost doubled.

In the above embodiment, when the magneto-optical disk is divided into a plurality of sectors and the storage area of the magneto-optical disk is managed by the tracks and the sectors, each time the groove 1 makes one round, the same number of mirror units as the number of sectors is provided. 3 are provided, and pits 4a and 4b are formed for each mirror portion 3.

When the storage area of the magneto-optical disk is managed in units of a plurality of tracks, the groove 1 has n
One mirror section 3 may be provided for each rotation (n> 1), and pits 4a and 4b may be formed for each mirror section 3.

Furthermore, the magneto-optical disk may be divided into a plurality of ring-shaped zones, and the number of sectors per track may be changed for each zone.

The pits 4a may be arranged in the same radial direction or may be arranged in different radial directions. The same applies to the pit 4b.

Incidentally, inside (the center side of the magneto-optical disk) or outside (outer edge side of the magneto-optical disk) the pits 4a.
Or the groove 1 is not preferable in order to obtain accurate address information and a tracking signal.

That is, with such an arrangement, the first
Then, crosstalk occurs in the address signal. Second, when the light spot 6 scans a track on the land 2, when the pits 4b appear, the polarity of the tracking signal is inverted. For this reason, tracking becomes unstable.

The second embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as the members shown in the drawings of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The magneto-optical disk of this embodiment is different from the above-described embodiment in that pits 4b for recording address information are formed in portions of each land 2 remote from the mirror portion 3. .

Thus, crosstalk between the pits 4a... 4b becomes more unlikely, and more accurate address information is required.

The following will describe a third embodiment of the present invention with reference to FIG. For convenience of explanation, members having the same functions as the members shown in the drawings of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The magneto-optical disk according to the present embodiment has a point that the width of the groove portion 1a adjacent to the pits 4b is reduced.
This is different from the first and second embodiments. In addition,
The groove portion 1a does not necessarily need to be connected to the groove 1.

When the width of the groove 1 and the width of the land 2 are each set to 0.8 μm, the width of the groove portion 1a is set to 0.4 to 0.5 μm.

As a result, compared to the above embodiment,
The amount of reflected light when the light spot 6 is irradiated on the land 2 where the pits 4b.
Since the difference from the amount of reflected light when irradiating a portion where b is not formed increases, more accurate address information can be obtained from the pits 4b.

In order to give priority to the signal quality from the pits 4b, it is better that the width of the groove portion 1a is narrow (for example, 0.3 to 0.4 μm), and the light from the recording domain to be recorded on the groove 1 is good. To give priority to the signal quality of the magnetic signal, it is better that the width of the groove portion 1a is wide (for example, 0.4 to 0.4).
0.6 μm). Therefore, as described above, when the width of the groove portion 1a is set to 0.4 to 0.5 μm, both signal qualities can be satisfied.

In the first to third embodiments, the width of the groove 1 is equal to the width of the land 2. Therefore, even when the light spot 6 scans the track on the groove 1, the track on the land 2 is Also when scanning, the amount of reflected light is equal. Therefore, no matter which track is scanned, a reproduced signal having substantially the same magnitude can be obtained. For this reason, the processing circuit for the reproduction signal can be simplified.

By the way, in order to obtain a strong track cross signal, the width of the groove 1 and the width of the land 2 may be made different to some extent. Here, the track cross signal is a signal indicating a change in the amount of reflected light when the light spot 6 crosses the track. The direction of movement of the light spot 6 can be detected from the phase difference between the track cross signal and a track error signal indicating a deviation between the center of the light spot 6 and the center of the track, and a target track can be accessed.

However, the width of the groove 1 and the land 2
If the width of the signal is too different, a strong track cross signal can be obtained, but the quality of the reproduced signal deteriorates.

For example, the sum of the width of the groove 1 and the width of the land 2 is 1.6 μm (that is, the track pitch is 0.8 μm).
m), the wavelength of the laser light is 780 nm, and the N of the objective lens is
When A is 0.55, when the width of the groove 1 or the width of the land 2 is less than 0.4 μm, the difference between the reflectance from the track on the groove 1 and the reflectance from the track on the land 2 increases. . That is, the amount of reflected light from a narrow track is significantly reduced.

On the other hand, if the width of the groove 1 or the width of the land 2 is 0.7 to 0.8 μm, a strong track cross signal cannot be obtained. Therefore, in order to obtain an appropriate reproduction signal and an appropriate track cross signal, it is preferable to set the width of the groove 1 or the land 2 to 0.4 to 0.7 μm.

More generally, the width of the groove 1 or the width of the land 2 is less than approximately 30% of the diameter of the light spot 6 (780 nm / 0.55 × 0.3 = 0.42 μm in the above example). Then, the difference in reflectance increases. The width of the groove 1 or the width of the land 2 is about 45% of the sum of the width of the groove 1 and the width of the land 2 (that is, twice the track pitch).
If it exceeds (1.6 μm × 0.45 = 0.72 μm in the above example), the track cross signal will be significantly reduced.

Therefore, in order to obtain an appropriate reproduction signal and an appropriate track cross signal, the width of the groove 1 or the width of the land 2 must be 30% or more of the diameter of the light spot 6.
It is preferable to set it to 45% or less, which is twice the track pitch.

The mastering process for the three types of magneto-optical disks shown in the first to third embodiments will be described below with reference to FIG.

First, a photoresist 8 is applied to one surface of a quartz glass substrate 7 (FIG. 7A). Then, the laser beam is converged on the photoresist 8, and the photoresist 8 is exposed to a desired pattern of the grooves 1 and the pits 4a, 4b. When this is developed to remove unnecessary photoresist 8, photoresist 8a having a desired pattern remains on substrate 7 (FIG. 9B).

Next, the substrate 7 is dry-etched using the photoresists 8a as a mask (FIG. 3 (c)). For example, CF ₄ is used as an etching gas. After the etching, the photoresists 8a are removed (FIG. 4D), and a metal layer 9 made of Ni is formed by electroforming (FIG. 3E). When this is peeled off, a stamper made of the metal layer 9 is obtained (FIG. 6F).

By molding plastic such as polycarbonate using the stamper, a substrate for a magneto-optical disk having desired grooves 1 and pits 4a and 4b is manufactured. When a recording medium is formed on this substrate, the above-described magneto-optical disk is obtained.

FIG. 5 shows an example of a recording apparatus used in the step of exposing the photoresist 8 to patterns of the groove 1 and the pits 4a, 4b,.

The recording apparatus includes a laser light source 11a for exposing the photoresist 8 and a laser light source 11b for focusing the objective lens 10. As the laser light source 11a, for example, an argon laser is used, and as the laser light source 11b, for example, a He-Ne laser is used.

The laser light from the laser light source 11a is
After the optical noise is reduced by the noise suppression device 12 a, the light is reflected by the mirrors 19 and 20 and enters the beam splitter 21. Laser beam splitter 2
The light is divided into two parts, one of which is incident on the optical modulator 18a, and the other is reflected by the mirror 24b and is incident on the optical modulator 18b. As the optical modulators 18a and 18b, for example, acousto-optic devices can be used. In that case, the convex lenses 22 for convergence are respectively provided before and after the optical modulators 18a and 18b.
-It is necessary to arrange 22.

The light beam that has passed through the light modulator 18a enters the light deflector 23a, and is reflected at right angles by a mirror 24a. On the other hand, the light beam that has passed through the light modulator 18b enters the optical deflector 23b, and then enters the (1/2) wavelength plate 25, and the polarization plane is rotated by 90 degrees. Optical deflectors 23a and 23
As b, for example, an element whose traveling direction can be changed by using an electro-optic effect or an acousto-optic effect can be used.

After these light beams are recombined by the polarizing prism 26, they are expanded to an appropriate light beam diameter by the beam expander 27, reflected by the dichroic mirror 15, and incident on the objective lens 10. And the objective lens 1
0 causes light spot 3 on photoresist 8 on substrate 7
1a and 31b (to be described later) are converged.

The light modulators 18a and 18b are controlled by drivers 28a and 28b, respectively. The light deflectors 23a and 23b are provided with drivers 29a and 29
b.

On the other hand, after the laser light from the laser light source 11b is reduced in optical noise by the noise suppression device 12b, the polarization beam splitter 13, (1/4)
The light passes through the wave plate 14 and the dichroic mirror 15 and is converged on the photoresist 8 on the substrate 7 by the objective lens 10.

The reflected light is condensed by an objective lens 10, passes through a dichroic mirror 15, a (１ ／) wavelength plate 14, and a polarizing beam splitter 13, and is subjected to four-division light detection by an objective lens 16 and a cylindrical lens 17. Vessel 1
8 converged. A focus servo signal is generated based on a signal from the photodetector 18, and a focus servo system (not shown) drives the objective lens 10 in a focus direction. Thereby, the spindle motor 3
The objective lens 10 is always focused on the photoresist 8 on the substrate 7 rotating at zero.

The method of exposing the photoresist 8 by the recording apparatus will be described below with reference to FIG.

First, in order to arrange the light spots 31a and 31b at a distance equal to the track pitch in the radial direction as shown in FIG.
The DC voltage applied to the optical deflectors 23a and 23b from the a.29b and the setting angles of the mirrors 24a and 24b are adjusted.

Then, the photoresist 8 is exposed to the pattern of the groove 1, the pits 4a,..., The groove portion 1a, and the groove 1 by the light spot 31a in the right direction of FIG. Strength I
₁ is controlled by the driver 28a as shown in FIG.

That is, the photoresist 8 is transferred to the groove 1
The light intensity I ₁ is set to the high level P ₁ when exposing to the pattern of the pits 4 a. The light intensity I ₁ is set to the low level P ₄ when exposing to the pattern of the pits 4 a. when to be set the light intensity I ₁ at the low level P _2. When not sensitive photoresist 8, the light intensity I ₁ to zero. Thus, by changing the light intensity I _1, the size of the exposed portions of the photoresist 8 is controlled.

On the other hand, the light spot 31b causes the pit 4b to extend in parallel with the groove 1a as shown in FIG.
In order to expose the photoresist 8 to the pattern of..., The light intensity I ₂ of the light spot 31b is controlled by the driver 28b as shown in FIG.

That is, the photoresist 8 is replaced with the pits 4b.
When it made sensitive to ... pattern, setting the light intensity I ₂ at the low level P _3. When not sensitive photoresist 8, the light intensity I ₂ to zero.

Another method for exposing the photoresist 8 by the above recording apparatus will be described below with reference to FIG.

This method is different from the above method in that the groove 1 is formed using two light spots 31a and 31b.

First, the light spots 31a and 31b are moved in the radial direction by one-fourth of the track pitch as shown in FIG.
In order to dispose them at a distance equal to 2, the DC voltage applied to the optical deflectors 23a and 23b from the drivers 29a and 29b and the setting angles of the mirrors 24a and 24b are adjusted.

Then, the light spot 31a is used to form a photoresist 8 in a pattern on one side of the groove 1 (upper side in the figure), pits 4a,..., A groove portion 1b, and one side of the groove 1 in the right direction of FIG. in order to sensitize the light intensity I ₁ of the light spot 31a it is, by the driver 28a, is controlled as shown in FIG. (b).

That is, the photoresist 8 is transferred to the groove 1
When is the exposed to one side of the pattern, the light intensity I ₁ is set to level P _5, when made sensitive to the pit 4a ... pattern, sets the light intensity I ₁ to level P _7, the groove 1
When exposing to the pattern b, the light intensity I _{1 is changed} to the level P ₆
Set to. When not sensitive photoresist 8, the light intensity I ₁ to zero. Thus, by changing the light intensity I _1, the size of the exposed portions of the photoresist 8 is controlled.

[0064] Also, pits 4a ..., when for sensitizing the photoresist 8 on the pattern of the groove portion 1b, and the voltage applied from the driver 29a to the light deflector 23a, as shown in FIG. 2 (d), only V ₁ shift Then, the light spot 31a is set at the center of the groove 1 in the width direction.

On the other hand, the light spot 31b exposes the photoresist 8 to a pattern of pits 4b in parallel with the groove 1b on one side (lower side in the figure) of the groove 1 as shown in FIG. Therefore, the light spot 31
b is the light intensity I _2, by the driver 28b, is controlled as shown in FIG. (c).

That is, the photoresist 8 is transferred to the groove 1
, The light intensity I ₁ is set to the level P5, and the photoresist 8 is exposed to the pits 4b.
When to be exposed to the pattern, the light intensity I ₂ level P9
Set to. When not sensitive photoresist 8, the light intensity I ₂ to zero.

[0067] Further, when for sensitizing the photoresist 8 on the pit 4b ... pattern, the voltage applied from the driver 29b to the optical deflector 23b, as shown in FIG. (E), is shifted by V _2, the light spot 31b to Land 2
At the center in the width direction.

In the present method, when the width of the groove portion 1b and the diameter of the pits 4a and 4b are equal to half of the width of the groove 1, P ₅ , P ₆ , P ₇ and P ₉ may be set to the same value. Therefore, the light intensities I ₁ and I ₂ of the light spots 31a and 31b can be set to two levels. This facilitates control as compared to the above method.

In the above, the method for exposing the photoresist 8 by the above-described recording device has been described by taking the magneto-optical disk of the third embodiment as an example. However, the method has been described in the first and second embodiments. It can also be applied to magneto-optical disks.

In the above embodiments, the magneto-optical disk and the method of manufacturing the same have been described. However, the present invention can be widely applied to an optical disk having pits 4a,...

[0071]

According to the structure of the present invention, since two light beams are used, it is possible to easily manufacture an optical disk which is less likely to cause crosstalk and which can accurately obtain address information with a simple apparatus structure. It is possible to do.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a magneto-optical disk according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a schematic configuration of a magneto-optical disk according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a schematic configuration of a magneto-optical disk according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a mastering process of a substrate used in the magneto-optical disk of FIGS. 1 to 3;

5 is a block diagram schematically showing a recording apparatus used in a photoresist exposure step of the mastering process of FIG.

FIG. 6 is an explanatory view showing a method for exposing a photoresist by the recording apparatus of FIG. 5;

FIG. 7 is an explanatory view showing another method for exposing a photoresist by the recording apparatus of FIG. 5;

FIG. 8 is an explanatory diagram showing a schematic configuration of a conventional magneto-optical disk.

FIG. 9 is an explanatory diagram showing a schematic configuration of another conventional magneto-optical disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Groove 1a Groove part 2 Land 3 Mirror part (broken part of groove) 4a Pit (first uneven pit row) 4b Pit (second uneven pit row) 5 Recording domain 6 Light spot 31a Light spot 31b Light spot

Claims (3)

[Claims] 1. A groove formed spirally or concentrically as a recording track for recording information, a land between the grooves also serving as a recording track for recording information, and a radius for recording address information of the recording track. A method for manufacturing an optical disc, comprising: a first and a second concavo-convex pit row that are not adjacent to each other in a direction. Irradiating the photoresist on the substrate with the light beam. 2. The method for manufacturing an optical disk according to claim 1, wherein a first light beam is irradiated at a first intensity corresponding to the groove, and a first light beam is irradiated corresponding to the first uneven pit row. The first light beam
A method for manufacturing an optical disk, comprising: irradiating with an intensity lower than the intensity, and irradiating a second light beam corresponding to the second uneven pit row. 3. The method for manufacturing an optical disk according to claim 1, wherein a first light beam and a second light beam are irradiated adjacent to each other in correspondence with the groove, so that the first uneven pit row is formed. A method for manufacturing an optical disk, comprising: irradiating a first light beam correspondingly, and irradiating a second light beam corresponding to a second concavo-convex pit row.