JP2001229577A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high recording density and to stably and surely record and reproduce. SOLUTION: A land part 6 and a groove part 7 are formed along the recording track on the face of a disk substrate 2 where first and second signal recording layers 3, 4 are to be formed. The land part 6 is formed wider than the groove part 7. Recording and reproducing is carried out at the position of the land part 6 and the groove part 7 along the recording track.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium in which a signal recording layer is provided on a substrate and an information signal is recorded and / or reproduced by irradiating the signal recording layer with a light beam. .

[0002]

2. Description of the Related Art An optical recording medium is formed in a disk shape with a signal recording layer. By irradiating the signal recording layer with a light beam, recording and / or reproduction of an information signal (hereinafter referred to as an information signal) is performed. , Recording and reproduction).

As such an optical recording medium, for example,
An optical disk CD that can be used for a so-called compact disk recordable system and can additionally record information signals
There is R (CD-Recordable). In the CD-R, a signal recording layer on which an information signal is recorded is formed of an organic dye-based material, a recording mark is written by irradiating a light beam, and the reflectance of the signal recording layer is determined by the presence or absence of the recording mark. Is changed, the recording is performed, and the recorded signal is reproduced by detecting the reflectance of the signal reflection layer to detect the presence or absence of a recording mark.

As an optical recording medium, for example, a mini disc (MD) or an MO (Magneto-Optica) is used.
l) Magneto-optical disk, such as a disk, which performs recording and reproduction on the signal recording layer using the magneto-optical effect, and CD
A phase change optical disk, such as a RW (CD-Rewritable), in which a recording signal can be rewritten by utilizing a phase change of a signal recording layer, has been put to practical use.

Further, as an optical recording medium, for example, a CD (Compact Disc) or a CD which has been widely used in the past,
There is a read-only optical disk such as a ROM (CD-Read Only Memory) in which a concavo-convex pattern corresponding to an information signal to be recorded is previously formed on a disk substrate. In such a read-only optical disk, a light reflection layer is provided on a disk substrate, and a reflected signal of an irradiated light beam is detected to detect a concavo-convex pattern and reproduce a recorded signal. That is, the concavo-convex pattern formed on the disk substrate has a function as a signal recording layer for recording information signals.

Meanwhile, in the above-mentioned optical recording medium, a method of forming a predetermined groove shape along the recording track has been proposed in order to realize tracking servo for irradiating a light beam along the recording track. And
Has been put to practical use. Such a groove shape is formed in a spiral shape or concentric shape, and the concave portion and the convex portion viewed from the light beam irradiation side are called a land portion and a groove portion, respectively. Then, for example, a recording track is formed along a groove that is convex when viewed from the light beam irradiation side, and information signals are recorded and reproduced on the recording track.

In the field of recording / reproducing, it is strongly desired to reduce the size, weight and capacity of recording media and recording / reproducing devices, and to achieve high recording densities of optical recording media. Is becoming important. Therefore, in the optical recording medium, as described above, of the groove formed along the recording track, not only recording / reproducing is performed on only one of the irregularities but also on both the land portion and the groove portion. A so-called land-groove recording method for performing recording and reproduction by using a conventional method has been proposed.

[0008] In the optical recording medium, it has been proposed to perform recording and reproduction by, for example, a magnetic super-resolution method in order to achieve a high recording density. In the magnetic super-resolution method, a first magnetic layer on which a magnetic signal corresponding to an information signal is recorded is provided as a signal recording layer of an optical recording medium, and a first magnetic layer is irradiated with a light beam and heated to form a first magnetic layer. And a second magnetic layer to which a magnetic signal recorded on the magnetic layer is transferred.
Then, at the time of reproduction, the magnetic signal transferred to the second magnetic layer is read. Thereby, even when a magnetic signal smaller than the spot diameter of the light beam is recorded on the first magnetic layer, only the magnetic signal transferred to the second magnetic layer can be detected, and the density can be increased. The recorded magnetic signal can be reliably reproduced.

[0009]

By the way, in the above-mentioned land / groove recording method, the width of each of the land and the groove is set so that the same recording / reproducing characteristics can be obtained in both the land and the groove. It is formed to have the same diameter as the spot diameter of a light beam used for recording and reproduction.

However, when the recording mark recorded on the signal recording layer is made smaller than the spot diameter of the light beam as in the above-described magnetic super-resolution method, the land / groove recording method is applied to the land portion. If recording is performed on both the land portion and the groove portion, there is a problem that the recording and reproduction characteristics are different between the land portion and the groove portion. Therefore, in the land groove recording method,
By making the recording track narrow and making the size of the information signal to be recorded on the signal recording layer smaller than the spot diameter of the light beam, stable and reliable recording and reproduction can be performed when further increasing the density. Becomes extremely difficult.

Accordingly, the present invention provides an optical recording medium capable of performing stable and reliable recording / reproduction even in a case where the recording density is further increased in the land / groove recording method. Aim.

[0012]

An optical recording medium according to the present invention has a signal recording layer on a substrate, and irradiates the signal recording layer with a light beam to record and / or reproduce information signals. Is performed on the optical recording medium. The signal recording layer has a width smaller than the spot diameter of the light beam,
A land portion that is a concave portion as viewed from the side irradiated with the light beam and a groove portion that is a convex portion are formed along a recording track, and both the land portion and the groove portion are formed. Recording and / or reproduction of the information signal is performed. The land is formed wider than the groove.

In the optical recording medium configured as described above, the recording and reproducing characteristics of the information signal recorded on the recording track can be made substantially the same between the land portion and the groove portion.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, as an example of an optical recording medium to which the present invention is applied, a magneto-optical disc 1 on which recording and reproduction are performed by a magnetic super-resolution method as shown in FIGS. 1 and 2 will be described. However, the present invention is not limited to application to an optical recording medium in which recording and reproduction are performed by a magnetic super-resolution method, and recording and reproduction of an information signal can be performed by irradiating a signal recording layer with a light beam. It can be widely applied to optical recording media to be performed.

Specifically, for example, a write-once optical disc in which a signal recording layer is formed of an organic dye-based material,
A magneto-optical disk that performs recording and reproduction on the signal recording layer using the magneto-optical effect, a phase-change optical disk that performs recording and reproduction using the phase change of the signal recording layer, and a concavo-convex pattern formed on the disk substrate is an information signal. The present invention can be applied to a read-only optical disk or the like having a function as a signal recording layer for recording data.

In the following, as an example of an optical recording medium to which the present invention is applied, a magneto-optical disk 1 in which recording and reproduction are performed on a signal recording layer by a magnetic super-resolution method utilizing a magneto-optical effect will be described. The present invention can be applied to, for example, a super-resolution optical recording medium using a heat distribution of a transmitted light amount in a phase change optical disk.

As shown in FIGS. 1 and 2, a magneto-optical disk 1 to which the present invention is applied is formed in a substantially disk shape by using a resin material such as polymethyl methacrylate (PMMA) or polycarbonate (PC). Disk substrate 2
Is provided. In addition, for example, GdF
a first signal recording layer 3 made of eCo, a second signal recording layer 4 made of TbFeCo, for example,
A protective layer 5 formed by spin-coating an ultraviolet curable resin or the like is sequentially formed. FIG. 1 is a perspective view schematically showing the magneto-optical disk 1, and FIG. 2 is an enlarged sectional view of a main part schematically showing a laminated structure of the magneto-optical disk 1.

The disc substrate 2 has a center hole 2a formed at the center thereof. Magneto-optical disk 1
When recording / reproducing is performed by the recording / reproducing device, the is supported and fixed to a rotation drive mechanism of the recording / reproducing device in the vicinity of the center hole 2a and is driven to rotate at a predetermined speed. The disk substrate 2 has a light-transmitting property with respect to a light beam used for recording and reproduction. Then, a light beam is incident from the main surface 1b of the disk substrate 2 on which the respective layers are not stacked.

In the disk substrate 2, a concave / convex shape as a guide groove is formed in a predetermined concave / convex pattern on a main surface 2c on a side on which each layer is not laminated. This concavo-convex pattern is formed in a spiral or concentric shape on the main surface 2c of the disk substrate 2, and a portion that is concave when viewed from the side where the light beam is incident is the land portion 6 and is convex. The portion is a groove portion 7. In the magneto-optical disk 1, recording tracks are formed along the groove shapes of the land portions 6 and the groove portions 7, and recording on the first and second signal recording layers 3 and 4 is performed along the recording tracks. The reproduction is performed.

The land portion 6 and the groove portion 7 are formed to have a width smaller than the spot diameter of the light beam irradiated at the time of recording / reproducing on the first and second signal recording layers 3 and 4. Specifically, for example, the wavelength of the light beam irradiated from the disk substrate 2 side to the magneto-optical disk 1 whose disk substrate 2 has a thickness of 1.2 mm is 680.
Assuming that an objective lens having a numerical aperture NA of 0.55 is used, the spot diameter of the light beam irradiated on the first and second signal recording layers 3 and 4 serving as signal recording surfaces is as follows. It is about 0.9 μm. In this case, the land portions 6 and the groove portions 7 are formed to have a thickness of, for example, about 0.725 μm and 0.588 μm, respectively.

In general, the spot diameter of a light beam used for recording and reproduction on an optical recording medium is proportional to a value obtained by dividing the wavelength λ of the light beam by the numerical aperture NA of the objective lens. The wavelength λ of the light beam depends on, for example, the material of the signal recording layer for recording the information signal and the transmission characteristics of the semiconductor laser element. It is regulated by the thickness of the substrate, the distance at the time of recording / reproducing between the optical head equipped with the objective lens and the optical recording medium, and the like. for that reason,
There is a limit to the wavelength λ of the light beam and the numerical aperture NA of the objective lens that can be used for recording and reproduction, and there is a limit to reducing the spot diameter of the light beam. Therefore, there is a limit to reducing the size of the recording mark to be recorded on the signal recording layer, and it has been difficult to achieve a high recording density.

However, in the magneto-optical disk 1 to which the present invention is applied, the land 6 and the groove 7 are formed with a width smaller than the spot diameter of the light beam, so that the second signal recording layer 4 The recorded magnetic signal can be reduced. That is, the width of the magnetic signal recorded on the second signal recording layer 4 in the track direction is regulated by the width of the land 6 and the groove 7, so that the width of the land 6 and the groove 7 is reduced. By doing so, it is possible to form a magnetic signal with high density,
As a result, it is possible to increase the recording density and capacity of the magneto-optical disk 1.

Incidentally, in the magneto-optical disk 1, the width of the land 6 is larger than the width of the groove 7. As a result, as will be described later in detail, the recording and reproducing characteristics of the recording marks to be recorded on the recording tracks can be made equal, and a stable and reliable recording and reproducing operation can be performed.

The land portion 6 and the groove portion 7
May be formed in a meandering (wobbling) manner at a predetermined period, and a wobble signal may be recorded in advance in this wobbling. The wobble signal may be, for example, a signal obtained by FM-modulating sector information including absolute time information and address information of a recording track. In the magneto-optical disk 1, recording and reproduction are performed while detecting wobble signals recorded in the uneven shape of the land portion 6 and the groove portion 7 as described above, so that the recording and reproduction head can access an arbitrary recording track. Can be facilitated.

The first and second signal recording layers 3 and 4 have a function as signal recording layers in the magneto-optical disk 1, and record and reproduce information signals by a so-called magnetic super-resolution method. That is, at the time of recording, an external magnetic field corresponding to the information signal is applied by the recording / reproducing device, so that a magnetic signal corresponding to the information signal is recorded on the second signal recording layer 4 as a recording mark. At the time of reproduction, a predetermined area in the first signal recording layer 3 is heated by irradiating a light beam, so that the second area
The magnetic signal recorded on the signal recording layer 4 is transferred to the first signal recording layer 3, and the transferred magnetic signal is detected by the magnetic head.

That is, in the magneto-optical disk 1,
The second signal recording layer 4 has a function as a recording state holding layer for holding a magnetic signal recorded according to the information signal, and the first signal recording layer 3 functions as a second signal at the time of reproduction. It has a function as a reproducing layer from which a magnetic signal held in the recording layer 4 is transferred and read. The magneto-optical disk 1
Since the recording and reproduction of the information signal is performed by the magnetic super-resolution method in this way, a minute magnetic signal is formed on the second signal recording layer 4 to increase the recording density.
The capacity can be increased, and the magnetic signal transferred to the first signal recording layer 3 can be reliably and stably read during reproduction.

In the magneto-optical disk 1, between the first signal recording layer 3 and the second signal recording layer 4, the magnetic coupling between the first and second signal recording layers 4 is established. For the purpose of control, an intermediate layer made of, for example, GdFe may be formed. Further, between the second signal recording layer 4 and the protective layer 5, for the purpose of improving the utilization efficiency of the light beam used for recording / reproduction or diffusing the heat generated by the irradiation of the light beam, for example, Cu, Al, Ag, Au
A light reflection layer formed by the above method may be formed.
In the magneto-optical disk 1, a dielectric layer or the like may be formed between the layers.

When manufacturing the magneto-optical disk 1 to which the present invention described above is applied, the land 6 and the groove 7 are formed by performing injection molding or the like using a stamper serving as the master. Then, the first signal recording layer 3, the second signal recording layer 4, and the protective layer 5 are sequentially formed as a thin film on the disk substrate 2.
Hereinafter, an example of a laser cutting apparatus for producing a stamper used when producing the disk substrate 2 will be described.

The laser cutting device 20 shown in FIG.
Is a device for exposing a photoresist layer 22 applied on a glass substrate 21 to form a latent image. When a latent image is formed on the photoresist layer 22 by the laser cutting device 20, the glass substrate 21 coated with the photoresist layer 22 is attached to a rotation driving device provided on a moving optical table. When the photoresist layer 22 is exposed, the glass substrate 21 corresponds to the concavo-convex pattern (spiral shape or concentric shape) of the land portion 6 and the groove portion 7 formed on the disk substrate 1 over the entire surface of the photoresist layer 22. In such a manner that the exposure is performed in the set pattern, it is rotationally driven by a rotary driving device as shown by an arrow A in the figure, and is translated in a radial direction by an optical moving table.

The laser cutting device 20 includes a light source 23 for emitting laser light, and an electro-optical modulator (EO) for adjusting the light intensity of the laser light emitted from the light source 23.
M: Electro Optical Modulator) 24, a beam splitter 25 for splitting a laser beam emitted from the electro-optic modulator 24 into reflected light and transmitted light, and a beam splitter 2
Photodetector (PD: Photodetector) 26 for detecting the laser beam that has passed through 5, and electro-optic modulator 24
And an auto power controller (APC) 27 for adjusting the intensity of the laser beam emitted from the electro-optic modulator 24 by applying a signal electric field thereto.

In the laser cutting device 20, the laser light emitted from the light source 23 is first given a predetermined light intensity by an electro-optic modulator 24 driven by a signal electric field applied from an auto power controller 27. .

Although any light source can be used as the light source 23, 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 23.

Then, the laser light emitted from the electro-optic modulator 24 is divided into reflected light and transmitted light by the beam splitter 25. The laser beam reflected by the beam splitter 25 becomes an exposure beam for exposing the photoresist layer 22.

Here, the light intensity of the laser light transmitted through the beam splitter 25 is detected by the photodetector 26, and a signal corresponding to the light intensity is sent from the photodetector 26 to the auto power controller 27. Then, in response to the signal transmitted from the photodetector 26, the auto power controller 27 applies the light to the electro-optic modulator 24 so that the light intensity detected by the photodetector 26 becomes constant at a predetermined level. Adjust the signal electric field. As a result, automatic power control (APC: Auto Power Control) is performed so that the light intensity of the laser light emitted from the electro-optic modulator 24 becomes constant, and a stable laser light with little noise is obtained.

On the other hand, the exposure beam reflected by the beam splitter 25 is guided to a modulation optical system 31 for modulating the light intensity of the exposure beam.
1 performs light intensity modulation.

The exposure beam incident on the modulation optical system 31 is
After being condensed by the condenser lens 32, the light is incident on an acousto-optic modulator (AOM) 33, and the light intensity is modulated by the acousto-optic modulator 33 so as to correspond to a desired exposure pattern. Then, the exposure beam whose light intensity has been modulated by the acousto-optic modulator 33 is collimated by the collimator lens 34 and then emitted from the modulation optical system 31.

Here, a driving driver 35 for driving the acousto-optic modulator 33 is provided in the acousto-optic modulator 33.
Is attached. Then, the photoresist layer 22
At the time of exposure, a signal S1 corresponding to a desired exposure pattern
Is input to the driving driver 35, the acousto-optic modulator 33 is driven by the driving driver 35 according to the signal S1, and light intensity modulation is performed on the exposure beam.

More specifically, when a latent image having a concavo-convex pattern corresponding to the groove portion 7 having a constant depth is formed on the photoresist layer 22, a DC signal having a constant level is input to the driving driver 35, and The acousto-optic modulator 33 is driven by the driving driver 35 according to the DC signal. Thereby, light intensity modulation is performed on the exposure beam so as to correspond to a desired concavo-convex pattern.

As described above, the light intensity of the exposure beam is modulated by the modulation optical system 31. Then, the exposure beam emitted from the modulation optical system 31 is reflected by the mirror 36 and is guided horizontally and parallel on the moving optical table.

The exposure beam guided horizontally and parallel on the moving optical table is optically deflected by the deflection optical system 37. Here, the deflection optical system 37 is for performing optical deflection on the exposure beam. That is, when a latent image corresponding to the land 6 and the groove 7 formed on the disk substrate 2 of the magneto-optical disk 1 to which the present invention is applied, the deflection optical system 37 forms
The exposure beam is optically deflected so as to correspond to the concavo-convex shape of the land portion 6 and the groove portion 7, and the photoresist layer 22 is exposed by the optically deflected exposure beam.

That is, the exposure beam emitted from the modulation optical system 31 and made incident on the deflection optical system 37 passes through a wedge prism 38 and an acousto-optic deflector (AOD: Acousto Optic).
calDeflector) 39, and this acousto-optic deflector 39
Thus, optical deflection is performed so as to correspond to a desired exposure pattern. The exposure beam optically deflected by the acousto-optic deflector 39 is applied to the wedge prism 4.
The light is emitted from the deflection optical system 37 through the optical element 0.

Here, the acousto-optic deflector 39 has a driving driver 41 for driving the acousto-optic deflector 39.
Is attached. Then, the photoresist layer 22
At the time of exposure, a signal S2 corresponding to a desired exposure pattern
Is input to the driving driver 41, and the acousto-optic deflector 39 is driven by the driving driver 41 in accordance with the signal S2, and the exposure beam is optically deflected.

The exposure beam optically deflected by the deflection optical system 37 is transmitted to the magnifying lens 42.
Then, the beam is made to have a predetermined beam diameter, is reflected by a mirror 43, is guided to an objective lens 44, and is condensed on the photoresist layer 22 by the objective lens 44.
As a result, the photoresist layer 22 is exposed, and a latent image is formed on the photoresist layer 22.

At this time, the glass substrate 21 on which the photoresist layer 22 is applied is indicated by an arrow A in the figure so that the entire surface of the photoresist layer 22 is exposed in a desired pattern as described above. As described above, and is translated by the moving optical table while being rotationally driven by the rotational driving device. As a result, a latent image corresponding to the irradiation locus of the exposure beam is formed over the entire surface of the photoresist layer 22.

Next, a method for manufacturing the magneto-optical disk 1 to which the present invention is applied will be described in detail with specific examples.

When manufacturing the magneto-optical disk 1 to which the present invention is applied, first, as a master disk process, a stamper having a concavo-convex pattern corresponding to the land portions 6 and the groove portions 7 formed on the disk substrate 2 is manufactured.

In this mastering step, first, a disk-shaped glass substrate whose surface has been polished is washed and dried, and thereafter,
On this glass substrate, a photoresist layer as a photosensitive material is applied. Next, the photoresist layer is exposed by the above-described laser cutting device 20 to form a latent image corresponding to the land portion 6 and the groove portion 7 formed on the disk substrate 2 in the photoresist layer.

At this time, the exposure beam is optically deflected by the deflection optical system 37 of the laser cutting device 20 so as to correspond to the signal to be recorded. This allows
A latent image corresponding to the land 6 and the groove 7 is formed on the photoresist layer.

When exposing the photoresist layer to form a latent image corresponding to the land portion 6 and the groove portion 7,
A glass substrate coated with a photoresist layer is
The motor is driven to rotate at a predetermined rotation speed and is translated in a radial direction at a predetermined speed. Specifically, for example,
By adjusting the rotation speed of the glass substrate and the moving speed in the radial direction, the track pitch in the land portion 6 and the groove portion 7 is set to be about 1.3 μm.

After the latent image is formed on the photoresist layer as described above, the glass substrate is placed on a turntable of a developing machine such that the surface on which the photoresist layer is coated is the upper surface. Place. Then, while rotating the glass substrate by rotating the turntable, a developing solution is dropped on the photoresist layer and subjected to a developing process, so that a concavo-convex pattern corresponding to the land portion 6 and the groove portion 7 is formed on the glass substrate. To form

Next, a conductive film made of Ni or the like is formed on the concavo-convex pattern by electroless plating, and then the glass substrate on which the conductive film is formed is attached to an electroforming apparatus.
A plating layer made of Ni or the like is formed on the conductive film by electroplating 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 layer remaining on the surface to which the uneven pattern has been transferred.

According to the above steps, an original master for producing an optical recording medium, ie, an uneven pattern corresponding to the land portion 6 and the groove portion 7 was formed by plating the uneven pattern formed on the glass substrate. The stamper is completed.

Next, as a transfer step, the disk substrate 2 on which the surface shape of the stamper is transferred by the photopolymer method (so-called 2P method) is manufactured.

More specifically, first, a photopolymer is applied smoothly onto the surface of the stamper on which the concavo-convex pattern is formed to form a photopolymer layer, and then no bubbles or dust enter the photopolymer layer. The base plate is brought into close contact with the photopolymer layer. Here, as the base plate, for example, a base plate made of polymethyl methacrylate having a thickness of 1.2 mm is used.

Thereafter, the photopolymer is cured by irradiating ultraviolet rays, and then the stamper is peeled off.
The disk substrate 2 on which the surface shape of the stamper is transferred is manufactured.

Here, an example has been described in which the disk substrate 2 is manufactured using the 2P method so that the concavo-convex pattern formed on the stamper is more accurately transferred to the disk substrate 2. In the case of mass production, it goes without saying that it may be manufactured by injection molding using a transparent resin such as polymethyl methacrylate or polycarbonate.

Next, as a film forming step, a first signal recording layer 3, a second signal recording layer 4, and a protective layer 5 are sequentially formed on the disk substrate 2 on which the surface shape of the stamper has been transferred. Form. Specifically, for example, first, by sputtering using a predetermined target material on the surface of the disk substrate 2 on which the uneven pattern is formed, Gd
A first signal recording layer 3 made of FeCo;
Second signal recording layer 4 made of TbFeCo
Are formed into a thin film. Thereafter, an ultraviolet curable resin is applied on the second signal recording layer 4 by a spin coating method, and the ultraviolet curable resin is irradiated with ultraviolet light to be cured, thereby forming the protective layer 5.

Through the above steps, the magneto-optical disk 1 to which the present invention is applied is completed. That is, as described above, by using the stamper on which the concavo-convex pattern corresponding to the land portion 6 and the groove portion 7 formed on the disc substrate 2 is formed, the magneto-optical disc 1 to which the present invention is applied is used.
Can be produced.

<Experimental Example> A description will be given below of the result of actually manufacturing the above-described magneto-optical disk 1 and measuring the recording and reproducing characteristics thereof.

EXPERIMENTAL EXAMPLE 1 First, as experimental example 1, the depth of the groove portion 7 in the disk substrate 2 was set to 70 nm, and the ratio of the width of the land portion 6 and the width of the groove portion 7 was slightly changed. 1 was produced. At this time, the disk substrate 2 is 1.2 mm thick by the 2P method using the stamper as described above.
The width of the land portion 6 and the groove portion 7 is
They were fabricated so as to be about 0.7 μm and about 0.6 μm, respectively.

When measuring the ratio of the width of the land portion 6 to the width of the groove portion 7, the irradiated light beam is reflected and returned according to the width of the land portion 6 and the groove portion 7. Since the amount of light changes, the ratio of the amount of reflected light is defined as the ratio of the width of the land 6 to the width of the groove 7.
However, for example, the widths of the land portion 6 and the groove portion 7 are directly measured by various optical microscopes or electron microscopes, and the like.
The ratio may be calculated.

The lands 6 and grooves 7 of the plurality of magneto-optical disks 1 manufactured as described above are
A light beam having a wavelength λ of 680 nm has a numerical aperture NA of 0.2.
Recording and reproduction were performed by irradiating with an objective lens of 55, and the CN ratio at the time of reproduction in the land portion 6 and the groove portion 7 was measured.

Experimental Example 2 Next, as Experimental Example 2, except that the depth of the groove portion 7 in the disk substrate 2 was set to 60 nm,
A plurality of magneto-optical disks 1 were produced in the same manner as described above. Then, an experiment example 1 was performed on these plurality of magneto-optical disks 1.
Recording and reproduction were performed in the same manner as in the above case, and the CN ratio at the time of reproduction was measured in the land 6 and the groove 7, respectively.

Experimental Example 3 Next, as Experimental Example 3, except that the depth of the groove portion 7 in the disk substrate 2 was set to 50 nm,
A plurality of magneto-optical disks 1 were produced in the same manner as described above. Then, an experiment example 1 was performed on these plurality of magneto-optical disks 1.
Recording and reproduction were performed in the same manner as in the above case, and the CN ratio at the time of reproduction was measured in the land 6 and the groove 7, respectively.

FIG. 4 shows the results measured in Experimental Examples 1 to 3 as described above. As is clear from the results shown in FIG.
It can be seen that the CN ratio in the land portion 6 is improved and the CN ratio in the groove portion 7 is degraded as the land portion 6 becomes wider than the groove portion 7. . Therefore, the land 6 and the groove 7
In order to make the recording / reproducing characteristics at the same level, it is optimal to set the width of the land portion 6 and the groove portion 7 at a point where the CN ratio curve intersects the land portion 6 and the groove portion 7. .

As described above, the land portion 6 and the groove portion 7
It can be seen that the point where the curves of the CN ratio intersect with each other is at a position where the width ratio is 1.0 or more, regardless of the depth of the groove portion 7. Therefore, the magneto-optical disk 1 to which the present invention is applied
By making the width of the land 6 wider than the width of the groove 7, the recording and reproduction characteristics of the land 6 and the groove 7 can be made equal.
It is clear that good recording and reproduction can be performed on the recording tracks located at both the land 6 and the groove 7.

Experimental Example 4 Next, in Experimental Example 4, the ratio of the width of the land 6 to the width of the groove 7 was 1.0, and the depth of the groove 7 in the disk substrate 2 was 60 nm. A magneto-optical disk 1 was manufactured in the same manner as in Experimental Example 1 described above. The land 6 and the groove 7 of the magneto-optical disk 1
Recording and reproduction were performed by irradiating a light beam having a wavelength λ of 680 nm with an objective lens having a numerical aperture NA of 0.55. At this time, the irradiation power of the light beam at the time of recording and the irradiation power of the light beam at the time of reproduction were changed, and the byte error rate at the time of reproduction was measured at the land 6 and the groove 7, respectively. FIG. 5 shows a measurement result of the byte error rate in the land portion 6 and FIG. 6 shows a measurement result of the groove portion 7.

Experimental Example 5 Next, in Experimental Example 5, except that the ratio of the width of the land 6 to the width of the groove 7 was set to 1.05,
A magneto-optical disk 1 was produced in the same manner as described above, and recording and reproduction were performed. At this time, the irradiation power of the light beam at the time of recording and the irradiation power of the light beam at the time of reproduction are changed so that the byte error rate at the time of reproduction is reduced.
And the groove portion 7 were measured. FIG. 7 shows the measurement result of the byte error rate in the land section 6, and FIG. 8 shows the measurement result in the groove section 7.

Experimental Example 6 Next, in Experimental Example 6, except that the ratio of the width of the land portion 6 to the width of the groove portion 7 was set to 1.10.
A magneto-optical disk 1 was produced in the same manner as described above, and recording and reproduction were performed. At this time, the irradiation power of the light beam at the time of recording and the irradiation power of the light beam at the time of reproduction are changed so that the byte error rate at the time of reproduction is reduced.
And the groove portion 7 were measured. FIG. 9 shows a measurement result of the byte error rate in the land portion 6 and FIG. 10 shows a measurement result of the groove portion 7.

As is clear from the results of Experimental Examples 4 to 6 shown in FIGS. 5 to 10, in the case of Experimental Example 4 in which the land 6 and the groove 7 have the same width, It can be seen that the byte error rate characteristics of the section 6 and the groove section 7 are significantly different, and the same recording / reproducing characteristics cannot be obtained. As shown in FIGS. 7 and 8, the ratio of the width of the land 6 to the width of the groove 7 is 1.05.
When the land 6 is formed to be wide, equivalent byte error rate characteristics can be obtained in the land 6 and the groove 7, and the same recording / reproducing characteristics can be obtained at the positions of the land 6 and the groove 7, respectively. It can be seen that it can be obtained.

Also, as shown in FIGS. 9 and 10, even when the land 6 is formed so as to be wider than the groove 7, the byte error between the land 6 and the groove 7 can be prevented. The result is that the rate characteristics are significantly different, indicating that it is difficult to obtain the same recording and reproduction characteristics.

[0072]

As described above, in the optical recording medium according to the present invention, since the lands are formed wider than the grooves, the widths of these lands and grooves are used for recording and reproduction. Even if the spot diameter is smaller than the spot diameter of the light beam, the recording and reproducing characteristics of the information signal recorded on the recording track can be made substantially the same between the land portion and the groove portion. As a result, information signals can be recorded on a recording track at a high density, a large capacity can be achieved, and stable and reliable recording and reproduction can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a magneto-optical disk shown as one configuration example of an optical recording medium to which the present invention is applied.

FIG. 2 is an enlarged sectional view of a main part showing a laminated structure of the magneto-optical disk.

FIG. 3 is a schematic configuration diagram showing a laser cutting device used when manufacturing the magneto-optical disk.

FIG. 4 is a view showing a result of measuring a CN ratio at the time of reproduction when the width of a land portion and a groove portion of the magneto-optical disk is changed.

FIG. 5 is a diagram for explaining the recording / reproducing characteristics of the magneto-optical disk, wherein the ratio of the width of the land portion and the groove portion is 1.
It is a figure which shows the byte error rate characteristic in the land part when it is set to 00.

FIG. 6 is a diagram for explaining the recording / reproducing characteristics of the magneto-optical disk, wherein the ratio of the width of the land portion and the groove portion is 1.
It is a figure showing the byte error rate characteristic in the groove part when it is set to 00.

FIG. 7 is a diagram for explaining the recording / reproducing characteristics of the magneto-optical disk, wherein the ratio of the width of the land portion and the groove portion is 1.
It is a figure which shows the byte error rate characteristic in the land part when it is set to 05.

FIG. 8 is a diagram for explaining the recording / reproducing characteristics of the magneto-optical disk, wherein the ratio of the width of the land portion and the groove portion is 1.
It is a figure which shows the byte error rate characteristic in the groove part at 05.

FIG. 9 is a diagram for explaining the recording / reproducing characteristics of the magneto-optical disk, where the ratio of the width of the land portion and the groove portion is 1.
It is a figure which shows the byte error rate characteristic in the land part when it is set to 10.

FIG. 10 is a diagram for explaining the recording / reproducing characteristics of the magneto-optical disk, and is a diagram showing a byte error rate characteristic in the groove portion when the width ratio between the land portion and the groove portion is 1.10. .

[Explanation of symbols]

Reference Signs List 1 magneto-optical disk, 2 disk substrate, 3 first signal recording layer, 4 second signal recording layer, 5 protective layer, 6 land portion, 7 groove portion

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshihisa Chiba 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hiroyuki Takemoto 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 5D029 WA27 WA29 WB11 WC10 WD10 5D075 EE03 FF12 FG18 5D090 AA01 BB10 CC01 CC04 FF15 GG07

Claims (2)

[Claims] An optical recording medium comprising: a signal recording layer on a substrate; and irradiating the signal recording layer with a light beam to record and / or reproduce an information signal. The layer has a land smaller in width than the spot diameter of the light beam and has a concave portion as viewed from the side irradiated with the light beam and a groove portion which is a convex portion in the recording track. The recording and / or reproduction of the information signal is performed on both the land portion and the groove portion, and the land portion is formed wider than the groove portion. Optical recording medium. 2. A signal recording layer comprising: a first magnetic layer on which a magnetic signal according to an information signal is recorded; and a signal beam, which is irradiated with a light beam and heated to thereby record on the first magnetic layer. 2. The optical recording medium according to claim 1, further comprising: a second magnetic layer to which the transferred magnetic signal is transferred.