JPH11203723A - Substrate for disk-like recording medium and disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise a disk recording density and to improve the reliability of a recorder using it by making at least a laser beam light wavelength be equal to or less than the length of the traveling direction of a floating type optical head and preventing the waviness of a substrate maximum amplitude from being equal to or more than the specified relative ratio length of the optical wavelength. SOLUTION: At the time of recording/reproducing information signals by near field recording, it is required to float the floating type optical head 20 from the magneto-optical recording layer of a magneto-optical disk 10 by a floating amount within the laser beam light wavelength λ/4. In this case, for a disk substrate, in an area for recording the signals of the magneto-optical disk 10 at least, the optical wavelength is equal to or less than the length of the traveling direction of the floating type optical head 20 and the maximum amplitude waviness of the substrate is prevented from being equal to or more than 1/4 of the optical wavelength. Thus, the floating type optical head 20 follows the large waviness and the inconvenience of colliding with the magneto- optical disk 10 is evaded. Also, for the disk substrate, heat-resistant thermoplastic norbornane resin without deformation is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-shaped recording medium substrate used for a disk-shaped recording medium on which recording and / or reproduction is performed using light, and a disk-shaped substrate using the disk-shaped recording medium substrate. The present invention relates to a disk device that performs recording and / or reproduction on a recording medium.

[0002]

2. Description of the Related Art Conventionally, disk-shaped recording media in which information signals are written or read using light, such as read-only optical disks, magneto-optical disks, and phase-change optical disks, have been widely used.

[0003] A disk device for recording and / or reproducing information signals on or from these disk-shaped recording media emits a laser beam from a semiconductor laser at the time of reproduction, for example, and uses the laser beam by an optical system. The information signal recorded on the disk-shaped recording medium is read out by irradiating the light with focusing on the signal recording surface of the mounted disk-shaped recording medium and detecting the reflected light.

[0004]

By the way, while a system for writing and reading information signals to and from a disk-shaped recording medium using such light has become widespread, a disk-shaped recording medium used in this system has been developed. Therefore, there is a demand for improvement in recording density and reliability.

[0005] However, in such a system, in order to improve the recording density, a floating type optical head which floats on a disk-shaped recording medium with a small flying height is employed as the optical head. There is a possibility that the optical recording medium collides with the disk-shaped recording medium, and such collision between the optical head and the disk-shaped recording medium has been a major factor that impairs the reliability of the disk-shaped recording medium.

Accordingly, the present invention provides a disk-shaped recording medium substrate capable of obtaining a high-density and highly reliable disk-shaped recording medium and a disk-shaped recording medium using the disk-shaped recording medium substrate. And / or to provide a disk device for performing reproduction.

[0007]

DISCLOSURE OF THE INVENTION A disk-shaped recording medium substrate according to the present invention has been developed in order to solve the above-described problems, and emits light from a light source while floating on the disk-shaped recording medium. In a disc-shaped recording medium substrate used for a disc-shaped recording medium in which an information signal is written or read by a floating optical head that irradiates and irradiates the disc-shaped recording medium, at least an area where a signal is recorded is provided. The wavelength is equal to or less than the length of the floating optical head in the traveling direction, and the maximum amplitude is 1/1 / the wavelength of the light.
It is characterized in that undulations of 4 or more are not formed.

By using the substrate for a disk-shaped recording medium as a substrate, the disk-shaped recording medium has at least a region where a signal is recorded, a wavelength of which is equal to or less than a length in a traveling direction of the flying optical head and a maximum. It is possible to provide a smooth flat surface having an amplitude of not less than 1/4 of the wavelength of the light to be used, and even if the floating type optical head is floated with a small floating amount, Collision can be avoided, and reliability can be improved and high-density recording can be performed.

In particular, in recent years, a system has been proposed in which a recording / reproducing method called near-field recording is used to reduce the spot diameter of a laser beam to achieve high-density recording on a disk-shaped recording medium.

[0010] This near-field recording utilizes leaked light whose spot is narrowed to 1 / n, which is obtained in a region very close to the lens when the laser beam passes through a lens having a high refractive index n. It performs recording and reproduction. At this time, leakage light having an output necessary for performing recording and reproduction is obtained when the distance from the lens is λ / 4.
To the extent.

Therefore, for example, when the wavelength λ of the light used for recording and / or reproducing on the disk-shaped recording medium is about 659 nm, it is necessary to fly up to achieve high-density recording by near-field recording. Type optical head is moved about 165 nm (λ) from the signal recording
It is necessary to perform recording and / or reproduction by levitating with a flying height within / 4).

At this time, if a swell having a wavelength shorter than the length of the flying optical head in the traveling direction is present in the area of the disk-shaped recording medium where the signal is recorded, the flying optical head cannot follow the swell. If the maximum amplitude of the undulation is about 165 nm (λ / 4) or more, the floating optical head collides with the disk-shaped recording medium, causing damage to the floating optical head or the disk-shaped recording medium itself. In some cases.

A region where a signal is recorded on a disk-shaped recording medium having a swell having a wavelength shorter than the length of the flying type optical head in the traveling direction and a maximum amplitude of about 165 nm or more extends over 4000 μm in an arbitrary direction. FIG. 1 shows the state of the surface of the disk-shaped recording medium obtained by scanning with the laser beam. FIG.
In the graph, the vertical axis represents the distance from the reference surface of the disk-shaped recording medium when the reference surface of the disk-shaped recording medium is set to 0, and the horizontal axis represents the scanned position.

In FIG. 1, the actual surface of the disk-shaped recording medium is represented by a solid line, and the average surface of the disk-shaped recording medium is represented by a virtual line (dashed line). The fine irregularities on the surface of the disk-shaped recording medium represented by solid lines are servo patterns formed in advance on the surface of the disk-shaped recording medium.

The floating optical head is shown by a broken line in FIG. The length of the flying optical head in the running direction is about 2 mm.

As shown in FIG. 1, in this disk-shaped recording medium, undulations having a maximum amplitude of 165 nm or more are formed in a region where the radial position is 3000 to 4000 μm. The wavelength of the undulation is shorter than the length of the flying optical head in the traveling direction. Therefore,
The flying type optical head cannot collaborate with the undulation and will collide.

In the disk-shaped recording medium using the disk-shaped recording medium substrate according to the present invention, at least a signal recording area is such that the wavelength is equal to or less than the length in the traveling direction of the flying optical head and the maximum amplitude is attained. Is a smooth plane having no undulation which is 1/4 or more of the wavelength of light. Therefore, even if recording and / or reproduction is performed by this near-field recording, collision with the optical head is avoided, and reliability is reduced. The recording density can be greatly improved without any loss.

The substrate for a disk-shaped recording medium according to the present invention is preferably formed by injection molding a resin.

The resin substrate for a disk-shaped recording medium is formed by injection-molding a resin to form a groove between a disk-shaped recording medium and a track having a concave portion for head positioning information and address information on the disk surface. It can be formed accurately and easily as a substrate for a disk-shaped recording medium having the above, and can be manufactured with higher productivity and lower cost than an aluminum substrate used for a hard disk or the like.

In this injection molding, it is desirable to use a molding die having a transfer pattern formed directly on the molding surface. As described above, by performing injection molding using the molding die in which the transfer pattern is directly formed on the molding surface, it is possible to suppress the occurrence of undulation having a large amplitude.

It is more preferable that the substrate for a disk-shaped recording medium according to the present invention is formed by injection molding of a thermoplastic norbornene resin.

As a material of a substrate for a disk-shaped recording medium,
For example, when polycarbonate, methyl methacrylate, or the like is used, the substrate for a disk-shaped recording medium may be greatly deformed due to moisture absorption, and is used for a disk-shaped recording medium that performs recording and / or reproduction by bringing an optical head close to the substrate. It is not always suitable as a material for the substrate. Also, even when using a low hygroscopic plastic material, polymethylpentene, polystyrene, etc.
Due to the crystallinity, the substrate for a disk-shaped recording medium may be deformed after molding, and there is a problem that heat resistance is insufficient.

On the other hand, when a thermoplastic norbornene-based resin is used as the material of the substrate for a disk-shaped recording medium, sufficient heat resistance is obtained, there is almost no deformation due to moisture absorption or crystallinity, and a floating optical system is used. An optimal substrate for a disk-shaped recording medium is obtained as a substrate for a disk-shaped recording medium on which recording and / or reproduction is performed with the head close to the recording medium.

Further, the disk device according to the present invention has a motor for rotating a disk-shaped recording medium, and a floating within a quarter of the wavelength of the light to be used on the disk-shaped recording medium rotated by the motor. A floating optical head that floats by an amount and writes or reads an information signal to or from the disk-shaped recording medium, and at least an area of the disk-shaped recording medium where a signal is recorded has a floating-type optical head. It is characterized in that no undulations are formed below the length of the optical head in the traveling direction and the maximum amplitude is not less than ４ of the wavelength of the light.

According to this disk device, the floating optical head floats on the disk-shaped recording medium rotated by the motor with a floating amount within one-fourth of the wavelength of the light to be used. Writing or reading of an information signal is performed on a recording medium.

At this time, at least the signal recording area of the disc-shaped recording medium has a wavelength equal to or less than the length in the traveling direction of the flying optical head and has a maximum amplitude equal to or more than １ ／ of the wavelength of the light. Is not formed,
Collision between the flying optical head and the disk-shaped recording medium is avoided, and highly reliable recording and / or reproduction can be performed.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

The substrate for a disk-shaped recording medium according to the present invention (hereinafter, referred to as a disk substrate) may be a read-only optical disk, a magneto-optical disk, a phase-change optical disk, or the like.
A substrate used for a disc-shaped recording medium on which recording and / or reproduction is performed using light, and at least a region of the disc-shaped recording medium where a signal is recorded has a length longer than the length of the flying optical head in the traveling direction. This is characterized in that no undulations are formed in which the wavelength is short and the maximum amplitude is 1/4 or more of the wavelength of the light.

This disk substrate is particularly suitable as a substrate for a disk-shaped recording medium on which an information signal is written or read by a method called near-field recording, in which recording and reproduction is performed by using near-field leakage light. It is.

In near-field recording, an optical head having a lens having a high refractive index n is brought close to a signal recording surface of a disk-shaped recording medium, and a spot diameter of 1 / n is formed on the signal recording surface of the disk-shaped recording medium. It is a system that irradiates a laser beam focused on, writes an information signal on a disk-shaped recording medium, or reads an information signal from a disk-shaped recording medium, and realizes high-density recording by reducing the spot diameter. is there.

When writing or reading an information signal by this near-field recording, the required output can be obtained only when the distance from the optical head is within １ ／ of the wavelength of the light used. It is.

Therefore, when writing or reading an information signal by near-field recording, the optical head is configured as a floating optical head using a floating head technology employed in a hard disk device or the like. The optical head is floated from the signal recording surface of the disk-shaped recording medium at a height within one-fourth of the wavelength of the light used to write or read information signals.

In the disk substrate according to the present invention, in a region where a signal is recorded, a swell in which the wavelength is shorter than the length of the floating optical head in the traveling direction and the maximum amplitude is 1/4 or more of the wavelength of the light. Since it is not formed, even if the information signal is written or read by near-field recording, collision with the flying optical head is avoided and reliability is improved.

Hereinafter, this disk substrate is molded using a resin, and is used as a substrate of a magneto-optical disk having a magneto-optical recording layer. An example in which writing or reading is performed will be described.

The magneto-optical disk 10 has a magneto-optical recording layer 12 formed on a disk substrate 11, as shown in FIG. 2, for example.

The magneto-optical recording layer 12 includes an Al reflecting film 13,
The first dielectric film 14, the recording film 15, and the second dielectric film 16 are sequentially laminated.

The recording film 15 is a film exhibiting a magneto-optical effect, and is made of, for example, rare earth elements such as Tb,
A Tb-Fe amorphous material using Fe as a transition metal is used.

The Al reflective film 13 is for improving the reflectivity of the magneto-optical recording layer 12.

Further, the first and second dielectric films 14 and 16
Is for improving the moisture resistance of the recording film 15 and preventing thermal deformation of the disk substrate 11 and for improving optical efficiency such as increasing light absorption by the recording film 15. Is, for example, ZnS-Si
An O ₂ -based material or the like is used.

The magneto-optical disk 10 includes a disk substrate 11
Each of the above-described films constituting the magneto-optical recording layer 12 is formed by, for example, sputtering or the like.

The magneto-optical disk 10 has a protective layer 17 for protecting the magneto-optical recording layer 12 on the magneto-optical recording layer 12 and a shock when a floating optical head comes into contact with the magneto-optical disk 10. It is desirable that a lubricant layer (not shown) be formed for relaxation.

The protective layer 17 is made of, for example, carbon or SiO ₂
Are formed on the magneto-optical recording layer 12 by sputtering or the like.

The lubricant layer is formed by applying, for example, perfluoropolyether on the protective layer 17 by spin coating or the like.

On the other hand, as shown in FIG. 3, the floating optical head 20 includes a prefocus lens 21 for condensing a laser beam emitted from a semiconductor laser, and a laser beam condensed by the prefocus lens 21. Further, two types of lenses, a focus lens 22 for forming a beam spot by narrowing down, are provided, and these are supported by a lens holder 23.

Of the two types of lenses, the focus lens 22 is formed by molding a material having a high refractive index into, for example, a hemispherical shape, and a circular plane is formed on the magneto-optical recording layer 1 of the magneto-optical disk 10.
It is supported by the lens holder 23 so as to face the surface on the second side.

The floating optical head 20 is provided with a thin-film coil 24 for modulating a magnetic field, which is located on the outer peripheral side of the focus lens 22 and supported by a lens holder 23. The floating optical head 20
Has a length L in the traveling direction of, for example, about 2 mm.

The floating optical head 20 configured as described above converges a laser beam emitted from a semiconductor laser while flying above the rotating magneto-optical disk 10 to perform magneto-optical recording on the magneto-optical disk 10. The layer 12 is irradiated. Also, in this floating optical head 20, during recording, the thin film coil 24 generates a magnetic field of a predetermined strength,
This magnetic field is applied to the portion of the magneto-optical recording layer 12 irradiated with the laser beam.

When the flying optical head 20 having such a configuration is used, recording and reproduction of information signals on the magneto-optical disk 10 can be performed by near-field recording. That is, the flying optical head 20 irradiates the magneto-optical recording layer 12 of the magneto-optical disk 10 with a laser beam transmitted through the focus lens 22 made of a material having a high refractive index n while being very close to the magneto-optical disk 10. Since the recording and reproduction of the information signal are performed, the leakage light whose spot is narrowed to 1 / n can be used for the recording and reproduction of the information signal.

More specifically, the wavelength is set to λ by using an optical system in which the objective lens is arranged at a certain distance from the disk.
When the laser beam is focused, the spot diameter of the laser beam becomes λ / NA (NA is the numerical aperture of the optical system),
When a laser beam having a wavelength of λ is condensed using the floating optical head 20, the diameter is 1 / n × λ / NA (n is the refractive index of the focus lens 22, NA is a floating optical head 20
Numerical aperture) and a focused laser beam spot can be obtained.

At this time, the leaked light having an output necessary for recording and reproducing the information signal is obtained in an area whose distance from the lens is about λ / 4.

Therefore, the floating type optical head 20
From the magneto-optical recording layer 12 of the magneto-optical disk 10
By performing recording and reproduction with respect to the magneto-optical disk 10 while flying with a flying height within the range, the objective lens is compared with a case where an optical system in which the objective lens is disposed at a certain distance from the disk is used. Can be improved up to about n times.

By the way, the disk substrate 11 may have undulation on the surface, reflecting the surface accuracy of the mold at the time of molding. The undulation of the disk substrate 11 appears as the undulation of the magneto-optical disk 10 as it is. Here, the undulation refers to the undulation of the surface of the disk substrate 11 that occurs during molding, and refers to the undulation of the surface of the disk substrate 11 where there are no foreign particles serving as nuclei.

As shown in FIG. 4, when the undulation of the magneto-optical disk 10 is a large undulation having a long wavelength b, the flying optical head 20 follows the undulation and moves on the magneto-optical disk 10. It floats with a predetermined flying height h.

However, as shown in FIG. 5, the flying optical head 20 cannot gradually follow the undulation as the wavelength b of the undulation of the magneto-optical disk 10 becomes shorter, and the flying height h fluctuates by Δh. Occurs. And
If the wavelength b of the undulation becomes shorter than the length L of the floating optical head 20 in the traveling direction, the floating optical head 20 cannot follow the undulation at all, and the fluctuation amount Δh of the floating amount h becomes the undulation. It becomes equal to the maximum amplitude a.

FIG. 6 shows the relationship between the waviness wavelength b of the magneto-optical disk 10 and the flying fluctuation amount Δh of the flying optical head 20. In FIG. 6, the vertical axis represents (floating fluctuation amount Δh of flying type optical head 20) / (maximum amplitude a of undulation of magneto-optical disk 10), and the horizontal axis represents (magnetic disk 10
Wavelength b) / (Length L in the running direction of the flying optical head 20) is shown.

As can be seen from FIG. 6, the magneto-optical disk 1
When the undulation wavelength b of 0 is sufficiently longer than the length L of the flying optical head 20 in the traveling direction, that is, (the undulation wavelength b of the magneto-optical disk 10) / (the traveling direction of the flying optical head 20) When the value of (length L) is large, the value of (floating fluctuation amount Δh of flying optical head 20) / (maximum amplitude a of undulation of magneto-optical disk 10) becomes small. The larger the value of (wavelength b of the undulation of the magneto-optical disk 10) / (length L of the flying optical head 20 in the running direction) becomes, the larger the (floating fluctuation amount Δ of the flying optical head 20).
h) / (the maximum amplitude a of the undulation of the magneto-optical disk 10) approaches 0, and the flying optical head 20 travels following the undulation of the magneto-optical disk 10.

On the other hand, when the undulation wavelength b of the magneto-optical disk 10 is equal to or less than the length L in the traveling direction of the flying optical head 20, that is, (wavelength b of undulation of the magneto-optical disk 10) / (floating optics Length L in the traveling direction of the head 20)
Is less than or equal to 1, the value of (floating fluctuation amount Δh of floating type optical head 20) / (maximum amplitude a of undulation of magneto-optical disk 10) is about 1, and floating type optical head 20 is It can be seen that the disk 10 does not follow the undulation at all.

When recording and reproducing an information signal on and from the magneto-optical disk 10 by near-field recording, in order to obtain an output required for recording and reproduction, as described above, the flying optical head 20 is used. By floating from the magneto-optical recording layer 12 of the magneto-optical disk 10 with a floating amount within λ / 4,
It is necessary to perform recording and reproduction on the magneto-optical disk 10.

At this time, the floating optical head 20 having a maximum amplitude of λ / 4 or more is recorded in the signal recording area of the magneto-optical disk 10.
If there is a swell that cannot be tracked at all, the swell causes the magneto-optical disk 10 and the floating type optical head 2.
0 collides with each other, resulting in damage to the magneto-optical disk 10 or the flying optical head 20.

Therefore, the disk substrate 11 has at least an area of the magneto-optical disk 10 where a signal is recorded where the wavelength is equal to or less than the length L in the traveling direction of the flying optical head 20 and the maximum amplitude is the wavelength of the laser beam. The swell that becomes 1/4 or more of the above is not formed.

Here, a method of manufacturing the disk substrate 11 according to the present invention will be described. This disk substrate 11
For example, a resin material is manufactured by, for example, injection molding using a molding die having a transfer pattern formed on a molding surface.

As the resin material used as the material of the disk substrate 11, a thermoplastic resin excellent in heat resistance, precision moldability, low hygroscopic deformation, high elastic modulus and the like is preferable.

More specifically, from the viewpoint of heat resistance, the glass transition temperature is 50 ° C. or higher, preferably 70 ° C. or higher, more preferably 100 ° C. or higher. 300 ° C or less, preferably 2
50 ° C. or less, more preferably 200 ° C. or less, and from the viewpoint of low moisture absorption, the water absorption (at 25 ° C., after immersion for 24 hours) is 0.2
% Or less, preferably 0.1% or less amorphous thermoplastic resin is preferable, and a thermoplastic norbornene-based resin is most preferable in terms of a good balance between them.

As shown in FIG. 7, for example, a molding die 50 used for injection molding of the disk substrate 11 includes a pair of fixed dies 51 and movable dies 52, and these fixed dies 51 and movable dies 52. And an annular mold (not shown) for molding the outer peripheral end of the disk substrate 11. The fixed mold 51, the movable mold 52, and the annular mold are cooled by a cooling mechanism (not shown).

When the movable mold 52 is brought into contact with the fixed mold 51, the molding die 50 has a cavity filled with a resin material therebetween. In the molding die 50, the opposing surfaces 51a, 52a of the fixed die 51 and the movable die 52 forming the cavities are disk forming surfaces, and these opposing surfaces 51a, 52a are formed.
For example, a transfer pattern corresponding to a desired track pattern or servo pattern is formed.

Here, a process of forming a transfer pattern on the opposing surfaces 51a and 52a of the fixed mold 51 and the movable mold 52 will be described.

First, as shown in FIG. 8, the opposite surfaces 51a, 52a on which the transfer patterns of the fixed mold 51 and the movable mold 52 are formed are subjected to a surface treatment such as plating or mirror finishing. , The respective opposing surfaces 51a, 52a
The holes, such as pinholes, gaps, etc. formed in the holes are filled.

Next, as shown in FIG. 9, each of the opposing surfaces 5 of the fixed mold 51 and the movable mold 52 having been subjected to the surface treatment.
A resist 53 is applied to 1a and 52a.

Next, as shown in FIG.
The opposite surfaces 51a and 52a of the fixed mold 51 and the movable mold 52 coated with are irradiated with laser light corresponding to the transfer pattern, and a predetermined portion of the resist is exposed.

Next, as shown in FIG. 11, the resist irradiated with the laser beam is developed and removed.

Next, as shown in FIG. 12, using the remaining resist as a mask, the opposing surfaces 51a and 52a of the fixed mold 51 and the movable mold 52 are coated with a gas such as argon ion. An etching process is performed.

Finally, as shown in FIG. 13, the resist used as the mask is washed and removed, and a desired transfer pattern is formed on the opposing surfaces 51a and 52a of the fixed mold 51 and the movable mold 52, respectively. .

The molding die 50 on which the transfer pattern is formed as described above is mounted on an injection molding apparatus (not shown). Then, when manufacturing the disk substrate 11, first,
The movable mold 52 is moved and abutted against the fixed mold 51 to form a cavity between the opposing surfaces 51a, 52a of the movable mold 52 and the fixed mold 51.

Next, the molten resin material is injected and filled into the cavity of the molding die 50 at a predetermined pressure. The resin material filled in the cavity is cooled and solidified in the cavity, so that the disk substrate 1
Molded as 1. At this time, the transfer patterns formed on the opposing surfaces 51a and 52a of the fixed mold 51 and the movable mold 52 are transferred to the surface of the disk substrate 11,
A desired track pattern or servo pattern is formed on the surface of the disk substrate 11.

The disk substrate 11 is manufactured as described above, so that the wavelength is at least equal to or less than the length of the flying optical head in the traveling direction at least in the region where the signal is recorded on the magneto-optical disk 10. It is possible to obtain a flat surface in which no undulation is formed in which the amplitude is at least １ ／ of the wavelength of the laser beam used.

Actually, an area to be a signal recording area of the disk substrate 11 manufactured as described above is
Scanning was performed at 0 μm, and the state of the undulation of the disk substrate 11 was examined. FIG. 14 shows the state of the surface of the disk substrate 11. In FIG. 14, the vertical axis indicates the distance of the surface of the disk substrate 11 from the reference surface when the reference surface of the disk substrate 11 is 0, and the horizontal axis indicates the position of the disk substrate 11 in the radial direction. .

In FIG. 14, the disk substrate 11
The actual surface of the disk substrate 1 is represented by a solid line.
The average plane of No. 1 is represented by a virtual line (dashed line). Fine irregularities on the surface of the disk substrate 11 represented by solid lines are servo patterns formed in advance on the surface of the disk substrate 11.

As shown in FIG. 14, no waviness of the disk substrate 11 having a wavelength equal to or shorter than the length of the floating optical head 20 in the traveling direction was observed. Although a large undulation having a wavelength sufficiently longer than the length of the floating optical head 20 in the traveling direction was confirmed, there is no problem since the floating optical head 20 follows the large undulation.
The length of the flying optical head 20 in the traveling direction is about 2
mm.

The magneto-optical disk 10 is manufactured by forming the magneto-optical recording layer 12 on the disk substrate 11, so that at least the signal recording area has a wavelength equal to or less than the length of the floating optical head in the running direction. In addition, it is possible to provide a smooth surface having no undulation with a maximum amplitude of 1/4 or more of the wavelength of the light. The inconvenience of colliding with the head 20 is avoided, and the reliability is improved.

The present invention has been described with reference to the magneto-optical recording layer 12.
An example in which the present invention is applied to the disk substrate 11 for the magneto-optical disk 10 having the structure described above is described. However, the present invention is not limited to this example, and a disk substrate for a read-only optical disk or a disk for a phase-change optical disk. It can also be applied to a substrate.

The magneto-optical disk 10 using the disk substrate 11 as described above is mounted on a disk device 30 as shown in FIGS. 15 and 16 for recording and reproducing. FIG. 15 is a block diagram showing a schematic configuration of the disk device 30, and FIG. 16 is a longitudinal sectional view of a main part of the disk device 30.

The disk drive 30 includes a spindle motor 31 for driving the magneto-optical disk 10 to rotate, a head mechanism 32 for writing or reading information signals to or from the magneto-optical disk 10 driven to rotate by the spindle motor 31. A signal processing unit 33 for generating an MO reproduction signal and a control signal based on a light receiving signal supplied from the head mechanism 32, and a system controller 34 for controlling operations of the spindle motor 31 and the head mechanism 32.

The spindle motor 31 controls the held magneto-optical disk 10 under the control of the system controller 34.
Is driven to rotate at a predetermined speed.

The head mechanism 32, as shown in FIG.
A floating optical head 20, a head drive unit 40 for driving the floating optical head 20, a laser beam that emits a laser beam toward the magneto-optical disk 10 and is reflected by the magneto-optical disk 10 (return light) And a light emitting / receiving section 44 for receiving the light.

As shown in FIG. 3, the floating type optical head 20 has a prefocus lens 21 and a focus lens 22 supported by a lens holder 23. Thin film coil 2
4 are provided. In addition, this floating type optical head 20
Is as described above, and the description is omitted here.

The head drive unit 40 is rotatably mounted on a rotation shaft 43 and has a floating optical head 2 at one end.
0, and a voice coil motor 42 provided on the other end of the support arm 41 to rotate the support arm 41.

When a predetermined current is supplied to the voice coil motor 42 under the control of the system controller 34, the head driving unit 40 rotates the support arm 41 about the rotation shaft 43 as the rotation center. Move
The floating optical head 20 attached to one end of the support arm 41 is lifted from the magneto-optical recording layer 12 of the rotating magneto-optical disk 10 by a predetermined amount.
0 in the radial direction.

The light-emitting / light-receiving section 44 is not shown, but
A semiconductor laser that emits a laser beam of a predetermined wavelength toward the magneto-optical recording layer 12 of the magneto-optical disk 10; a return light from the magneto-optical recording layer 12 of the magneto-optical disk 10 is received; And a photodetector that converts the received light signal to a signal processing unit 33. On the optical path of the laser beam emitted from the semiconductor laser, reflected by the magneto-optical recording layer 12 of the magneto-optical disk 10 and received by the photodetector, a mirror for reflecting the laser beam and bending the optical path as shown in FIG. Although not shown, optical elements such as a beam splitter 45 and 46 for separating a laser beam are arranged.

The signal processing section 33 generates an MO reproduction signal based on the light receiving signal supplied from the photodetector of the light emitting / receiving section 44 of the head mechanism 32, outputs this MO reproduction signal, and outputs a tracking error signal and the like. , And supplies the control signal to the system controller 34.

The system controller 34 controls the operation of the spindle motor 31 to rotate the magneto-optical disk 10 at a predetermined speed. Also, the system controller 34
Causes the head mechanism 32 to perform a recording operation based on a recording signal supplied from a device (not shown), and causes the head mechanism 32 to perform a reproducing operation. At this time, the system controller 34 causes the head mechanism 32 to perform tracking control based on the control signal supplied from the signal processing unit 33.

The disk device 30 configured as described above
In recording, the spindle motor 31 rotates the mounted magneto-optical disk 10 at a predetermined speed under the control of the system controller 34 during recording. In addition,
The semiconductor laser of the light receiving section 44 has a wavelength of, for example, 659 nm.
Out of the red laser beam.

The laser beam emitted from the semiconductor laser is bent by mirrors 45 and 46 and is incident on the floating optical head 20.

The flying type optical head 20 includes a head driving unit 4
0 on the rotating magneto-optical disk 10 supported by the support arm 41 of, for example, 165 nm from the magneto-optical recording layer 12.
The laser beam incident on the magneto-optical recording layer 12 of the magneto-optical disk 10 is converged and radiated to the magneto-optical recording layer 12 in a state where the laser beam floats with the flying height within the range. At this time, the surface of the magneto-optical disk 10
The wavelength is equal to or less than the length of the floating optical head 20 in the traveling direction,
In addition, since no waviness having a maximum amplitude of 165 nm or more is formed, the flying optical head 20
The inconvenience of colliding with the projection is avoided.

In the flying head 20, under the control of the system controller 34, the thin-film head 24 generates a magnetic field having an intensity corresponding to the recording signal, and this magnetic field is applied to a portion of the magneto-optical recording layer 12 where the laser beam is irradiated. Is applied.

As described above, the disk device 30
A predetermined information signal is recorded on the magneto-optical recording layer 12 of the magneto-optical disk 10. Note that, also at the time of this recording, tracking control is performed in the same manner as at the time of reproduction described later.

[0096] During playback, the disk device 30
Under the control of the system controller 34, the spindle motor 31 rotates the mounted magneto-optical disk 10 at a predetermined speed. The semiconductor laser of the light emitting / receiving unit 44 emits a red laser beam having a wavelength of, for example, 659 nm.

[0097] The laser beam emitted from the semiconductor laser is reflected by mirrors 45 and 46 and is incident on the floating optical head 20.

The flying type optical head 20 includes a head driving unit 4
0 on the rotating magneto-optical disk 10 supported by the support arm 41 of, for example, 165 nm from the magneto-optical recording layer 12.
The laser beam incident on the magneto-optical recording layer 12 of the magneto-optical disk 10 is converged and radiated to the magneto-optical recording layer 12 in a state where the laser beam floats with the flying height within the range.

At this time, since the surface of the magneto-optical disk 10 has no undulation whose wavelength is less than the length in the traveling direction of the floating optical head 20 and whose maximum amplitude is 165 nm or more, the floating optical head The inconvenience that the projection 20 collides with the projection of the magneto-optical disk 10 is avoided.

The laser beam applied to the magneto-optical recording layer 12 of the magneto-optical disk 10 is reflected by the magneto-optical recording layer 12 to become return light containing a signal component. Then, the return light passes through the floating optical head 20 and is reflected by the mirror 4.
The light is reflected at 5 and 46 and received by the photodetector of the light emitting / receiving unit 44.

The photo detector converts the received return light into an electric signal (light receiving signal) and supplies the electric signal to the signal processing unit 33.

The signal processing section 33 generates and outputs an MO reproduction signal based on the received light signal supplied from the photodetector, and generates a control signal such as a tracking error signal based on the received light signal supplied from the photodetector. The control signal is supplied to the system controller 34.

The system controller 34 controls the head driving unit 4 based on the control signal supplied from the signal processing unit 33.
0 by controlling the voice coil motor 43
The floating type optical head 20 supported by 1 is moved in the radial direction of the magneto-optical disk 10 to perform tracking control.

As described above, the disk device 30
The information signal recorded on the magneto-optical disk 10 is appropriately reproduced.

In the disk drive 30, the floating type optical head 20 floats within a range in which the distance between the magneto-optical disk 10 and the magneto-optical recording layer 12 is within １ ／ of the wavelength of the laser beam. 10 magneto-optical recording layers 12
Since the laser beam is applied to the optical disk 10, the spot diameter of the laser beam can be reduced, and an information signal can be recorded on the magneto-optical disk 10 at a high density. Magneto-optical disk 10
Can be reproduced.

In the disk device 30, a waviness is formed on the surface of the substrate so that the wavelength is equal to or less than the length of the flying optical head 20 in the traveling direction and the maximum amplitude is equal to or more than 1/4 of the wavelength of the laser beam. Since the recording and reproduction of the information signal are performed on the magneto-optical disk 10 using the disk substrate 11 which is not used, the floating type optical head 20 collides with the projection on the surface of the magneto-optical disk 10 and The inconvenience of causing damage to the optical head 20 or the magneto-optical disk 10 is avoided, and highly reliable recording and reproducing operations can be performed.

Although the above description has been made with reference to the disk device 30 for recording and reproducing data on and from the magneto-optical disk 10, the present invention is not limited to this example. Disk devices that perform playback
The present invention can also be applied to a disk device that performs recording and reproduction on a phase change optical disk.

[0108]

According to the substrate for a disk-shaped recording medium of the present invention, at least the region corresponding to the region where the signal of the disk-shaped recording medium is recorded has a wavelength not longer than the length of the flying optical head in the running direction. In addition, no swell having a maximum amplitude of 1/4 or more of the wavelength of the light used is formed. Therefore, a disc-shaped recording medium using this substrate avoids collision with the optical head and the like, and greatly improves reliability.

Further, the disc-shaped recording medium using this substrate is designed to perform recording and / or reproduction by causing the floating optical head to fly from the signal recording layer with a flying height of not more than 波長 of the wavelength of the light used. In any case, since collision with the floating optical head is avoided, high-density recording and / or reproduction can be performed.

Further, if the substrate for a disk-shaped recording medium is formed by injection molding a resin using a molding die having a transfer pattern formed on a molding surface, head positioning information and information can be obtained on the disk surface. Aluminum substrate which can be formed accurately and easily as a substrate for a disk-shaped recording medium provided with a concave portion for address information or a disk-shaped recording medium having grooves between tracks, and which is used for a hard disk or the like. It can be manufactured with high productivity and at low cost as compared with.

Further, in the disk device according to the present invention, in the area where the signal is recorded, the wavelength is equal to or less than the length in the traveling direction of the flying optical head and the maximum amplitude is １ ／ of the wavelength of the light used. Since the recording and reproduction of the information signal are performed on the disk-shaped recording medium in which the undulation is not formed as described above, the floating type optical head which floats with a floating amount within 1/4 of the wavelength of the light to be used. However, the inconvenience of colliding with the disk-shaped recording medium and causing damage to the floating optical head or the disk-shaped recording medium can be avoided, and highly reliable recording and reproducing operations can be performed.

Further, in this disk device, the floating optical head writes or reads an information signal on or from the disk-shaped recording medium while floating with a floating amount within １ ／ of the wavelength of the light to be used. Therefore, the spot diameter of light can be reduced, and information signals are recorded at a high density on the disk-shaped recording medium, or the information signals of the disk-shaped recording medium on which the information signals are recorded at a high density Can be played.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a state of undulation of a disk-shaped recording medium.

FIG. 2 is a longitudinal sectional view showing a main part of the magneto-optical disk.

FIG. 3 is a longitudinal sectional view showing a flying optical head that floats on a magneto-optical disk.

FIG. 4 is a diagram illustrating a state in which a flying optical head follows the undulation of a magneto-optical disk.

FIG. 5 is a diagram illustrating a state in which the flying optical head does not follow the undulation of the magneto-optical disk substrate.

FIG. 6 is a diagram illustrating the relationship between the wavelength of the undulation of the magneto-optical disk and the amount of fluctuation in the flying of the flying optical head.

FIG. 7 is a perspective view of a molding die used when manufacturing the disk substrate according to the present invention.

FIG. 8 is a diagram illustrating a step of performing a surface treatment on each of opposing surfaces of a fixed mold and a movable mold.

FIG. 9 is a diagram illustrating a step of applying a resist to each of the opposed surfaces of the fixed mold and the movable mold that have been subjected to the surface treatment.

FIG. 10 is a view for explaining a process of irradiating a laser beam corresponding to a transfer pattern to each of opposing surfaces of a fixed mold and a movable mold on which a resist is applied, thereby exposing the resist at a predetermined location. is there.

FIG. 11 is a diagram illustrating a process of developing and removing the exposed resist.

FIG. 12 is a diagram illustrating a process of performing an etching process on each of the opposing surfaces of the fixed mold and the movable mold using the resist remaining without being removed as a mask.

FIG. 13 is a view for explaining a step of cleaning and removing a resist used as a mask and forming a desired transfer pattern on each of opposing surfaces of a fixed mold and a movable mold.

FIG. 14 is a diagram illustrating a state of undulation of a disk substrate according to the present invention.

FIG. 15 is a block diagram illustrating a schematic configuration of an optical disk device.

FIG. 16 is a longitudinal sectional view showing a main part of the optical disk device.

[Explanation of symbols]

Reference Signs List 10 magneto-optical disk, 11 disk substrate, 12 magneto-optical disk layer, 17 protective layer, 20 floating optical head, 30 disk device, 31 spindle motor

Claims (7)

[Claims] The present invention is applied to a disk-shaped recording medium on which information signals are written or read by a floating-type optical head that focuses light from a light source and irradiates the disk-shaped recording medium while floating on the disk-shaped recording medium. In the disk-shaped recording medium substrate to be recorded, at least in a region where a signal is recorded, the wavelength is equal to or less than the length in the traveling direction of the floating optical head, and the maximum amplitude is equal to or more than ４ of the wavelength of the light. A substrate for a disk-shaped recording medium, wherein no waviness is formed. 2. The disc-shaped recording medium has a structure in which at least a signal recording layer and a protective layer are sequentially laminated on a substrate,
2. A disc-shaped recording medium on which information signals are written or read by irradiating the signal recording layer with light transmitted through the protective layer.
The substrate for a disk-shaped recording medium according to the above. 3. The disk-shaped recording medium substrate according to claim 1, wherein the substrate is formed by injection molding a resin using a molding die having a transfer pattern formed on a molding surface. 4. The substrate for a disk-shaped recording medium according to claim 3, wherein said resin is a thermoplastic norbornene-based resin. 5. A motor for rotationally driving a disk-shaped recording medium, and a disk floating on the disk-shaped recording medium rotationally driven by the motor with a floating amount within １ ／ of a wavelength of light to be used. A floating optical head that writes or reads an information signal to or from a disk-shaped recording medium, wherein at least a signal recording area of the disk-shaped recording medium has a wavelength that is equal to the length of the floating optical head in the traveling direction. A disk drive, wherein no waviness having a maximum amplitude of 1/4 or more of the wavelength of the light is formed. 6. The substrate of the disk-shaped recording medium is formed by injection-molding a resin using a molding die having a transfer pattern formed on a molding surface. Disk unit. 7. The disk device according to claim 5, wherein the substrate of the disk-shaped recording medium is made of a thermoplastic norbornene resin.