JP2004062991A - Disk substrate and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily measure eccentricity quantity in a state of a transparent substrate immediately after formation in an optical disk whose groove interval in a data region is ≤0.6μm. <P>SOLUTION: This disk has a plurality of grooves and is provided with a groove region in which these groove intervals are 0.6μm or less and a eccentricity measuring region consisting of a mirror region of a plane shape on a disk substrate. Width of the groove region and width of the mirror region are selected so that a plurality of grooves constituting the groove region can be tracked as if they are one groove in a conventional mechanical characteristic measuring device. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a disk substrate and an optical disk, in particular, an information signal portion and a light transmitting layer are sequentially provided on a disk substrate, and recording and recording of an information signal is performed by irradiating a laser beam from a side where the light transmitting layer is provided. It is suitable for application to an optical disc on which reproduction is performed.
[0002]
[Prior art]
In recent years, it has been desired to further increase the storage capacity of a storage medium (data storage medium). For this reason, studies are being actively conducted on optical discs, which are one of the most widespread storage media at present, for increasing the recording capacity by increasing the recording density.
[0003]
For example, as one method of realizing a higher density of an optical disk, a laser beam used for recording / reproducing an information signal is made shorter in wavelength, and a numerical aperture NA (numerical aperture) of an objective lens is made larger so that a beam is increased. A method for reducing the spot diameter has been proposed.
[0004]
For example, a CD (Compact Disc) optical system includes a semiconductor laser that outputs laser light with a wavelength of 780 nm or 830 nm and an objective lens with an NA of 0.45. An optical system of a DVD (Digital Versatile Disc) includes a semiconductor laser that outputs a laser beam having a wavelength of 660 nm and an objective lens with an NA of 0.6. With such an optical system, a DVD can achieve a recording capacity about eight times that of a CD.
[0005]
However, when the NA of such an objective lens is increased, aberration of light caused by the tilt of the disk increases, and the allowable amount of tilt (tilt) of the disk surface with respect to the optical axis of the optical pickup decreases. Problems arise. In order to solve this problem, it has been proposed to reduce the thickness of a substrate that transmits laser light. For example, a substrate having a thickness of 1.2 mm is used for a CD, whereas a substrate having a thickness of 0.6 mm is used for a DVD.
[0006]
In the future, in consideration of storing an HD (High Definition) image or the like on an optical disk, a capacity equivalent to that of a DVD will not be sufficient. Therefore, there is a demand for further shortening the wavelength of laser light used for recording / reproducing information signals, further increasing the NA of the objective lens, and further reducing the thickness of the substrate.
[0007]
Therefore, a light transmitting layer having a thickness of 0.1 mm is formed on the information signal portion formed on the substrate, and a laser beam having a wavelength of 405 nm is irradiated from the light transmitting layer side to an object having an NA of 0.85. There has been proposed a next-generation optical disk that irradiates an information signal portion via a lens to record / reproduce an information signal. As described above, this next-generation optical disk has a configuration in which laser light is incident not from the substrate side but from the light transmission layer side, so that the allowable amount of tilt is sufficiently large despite the high NA of 0.85. can do.
[0008]
In the production of this next-generation optical disk, it is required that warpage and eccentricity be further reduced as compared with conventional optical disks. For this reason, when manufacturing next-generation optical discs, in order to guarantee the mechanical properties of the final product, it is necessary to measure the mechanical properties at an earlier stage in the manufacturing process, that is, the transparent substrate immediately after molding, and to provide early feedback. It becomes important.
[0009]
Conventionally, as a device for measuring the inclination and eccentricity of a disk, a mechanical characteristic measuring device using an optical stylus method is widely known. In this mechanical characteristic measuring device, it is necessary to provide a pickup corresponding to the format of the optical disk for measuring the mechanical characteristics, that is, the thickness of the substrate and the light transmitting layer and the size of the track pitch. This is because, when measuring the mechanical characteristics of an optical disc using the optical stylus method, it is necessary to make the light collected by the pickup follow the groove.
[0010]
There has been proposed a method of measuring the mechanical characteristics of a next-generation optical disk using the mechanical characteristics measuring device using the optical stylus method. In this method, at least a reflective film and a light-transmitting layer having a thickness of 0.1 mm are formed on a disk substrate, and mechanical characteristics of the optical disk are measured by the above-described optical pickup. Thus, by forming at least the reflection film and the light transmitting layer having a thickness of 0.1 mm on the disk substrate, the optical pickup of the above-described format can measure the mechanical characteristics of the optical disk.
[0011]
However, when the mechanical characteristics of the disk substrate are measured in this manner, the measurement cannot be performed unless the light transmitting layer having a thickness of 0.1 mm is formed. As a result, feedback in manufacturing is delayed, and as a result, the productivity of the optical disc is reduced.
[0012]
In view of this, a method has been proposed in which a pickup that can focus laser light on a groove formed on a disk substrate in a state where a light transmission layer of 0.1 mm is not formed is provided, and is provided in a mechanical characteristic measuring device. . However, designing such a pickup for the purpose of merely measuring the mechanical properties of the transparent substrate and providing the pickup in the mechanical property measuring apparatus increases the cost of the manufacturing equipment.
[0013]
Therefore, there has been proposed a method of measuring the mechanical characteristics of a next-generation optical disk by using an optical disk mechanical characteristic measuring device using an optical style method which has been widely used in the past. This mechanical characteristic measuring device is used for measuring the amount of eccentricity of a disk substrate having a substrate thickness of 1.2 mm, and includes a semiconductor laser that outputs a laser having a wavelength of 680 nm and an objective lens having an NA of 0.55. It has. In the next-generation optical disk described above, a substrate having a thickness of about 1.1 mm is used. Therefore, by condensing the laser beam through the substrate, even with the conventional mechanical characteristic device, the amount of surface deviation and the inclination of the disk can be reduced. Can be measured.
[0014]
[Problems to be solved by the invention]
However, in the format of the above-described next-generation optical disc, the track pitch is 0.6 μm or less, so that the optical system provided in the conventional mechanical characteristic measuring device cannot obtain a tracking error signal of a sufficient magnitude. . That is, the conventional mechanical property measuring device cannot measure the amount of eccentricity.
[0015]
Accordingly, an object of the present invention is to provide a disk substrate and an optical disk that can easily measure the amount of eccentricity in a state of a transparent substrate immediately after molding in an optical disk having a groove interval of a data area of 0.6 μm or less. To provide.
[0016]
[Means for Solving the Problems]
The present inventor has conducted intensive studies in order to solve the above-mentioned problems of the conventional technology. The outline is described below.
[0017]
According to the knowledge of the present inventor, it is impossible to measure the amount of eccentricity of a disk substrate having a track pitch of 0.6 μm or less with a conventional mechanical characteristic measuring device because a disk substrate of this format has a sufficient size of tracking. This is because an error signal cannot be obtained.
[0018]
In order to solve the above-mentioned problem, the present inventor has proposed a method for obtaining a sufficiently large tracking error signal on a disk substrate having a track pitch of 0.6 μm or less using a conventional mechanical characteristic measuring apparatus. We worked diligently. As a result, an eccentricity measurement area for measuring eccentricity is provided, and a method of enlarging the groove interval only within this eccentricity area has been recalled.
[0019]
However, as a result of further study of this method by the present inventor, they found that this method had the following problems.
In general, when a narrow groove having a groove interval of 0.6 μm or less is formed in the data area, the wavelength of the exposure laser at the time of mastering must be shortened accordingly. For example, a laser having a wavelength of 266 nm is used.
However, when such a short-wavelength laser is used, if the track pitch is widened in the eccentricity measurement area, a groove width with respect to the track pitch is too narrow, so that a sufficient push-pull signal cannot be obtained, and further, a signal waveform is also reduced. It has been found that it has a problem of distortion.
[0020]
As a result of repeated studies as described above, the present inventor has determined that the eccentricity measurement includes a groove region in which one or more concentric grooves are formed, and a planar mirror region adjacent to the groove region. It has been recalled to provide the area on the disk substrate.
[0021]
The present invention has been devised based on the above study.
[0022]
Therefore, in order to solve the above-mentioned problem, the first invention of the present application provides a biased region in which one or two or more concentric grooves are formed and a planar mirror region are spatially alternately arranged. A disk substrate having a core measurement area.
[0023]
A second invention of the present application is a disk substrate having an eccentricity measurement area in which one or two or more grooves are formed and a planar mirror area are spatially alternately arranged;
An information signal portion formed on one main surface of the disk substrate;
An optical disc comprising a protective layer for protecting an information signal section.
[0024]
As described above, according to the present invention, the disk substrate has an eccentricity measurement in which one or two or more concentric grooves are formed and a mirror area on a plane is spatially alternately arranged. Because of the presence of the region, the groove region can be made to follow an optical pickup for measuring the mechanical characteristics of an optical disk having a groove having the same width as the groove region and a land having the same width as the mirror region. Therefore, a groove area and an eccentricity measurement area are provided using a mechanical property measuring device for measuring the mechanical properties of an optical disc having a groove having the same width as the groove area and a land having the same width as the mirror area. The eccentricity of the disk substrate can be measured.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.
[0026]
FIG. 1 shows an example of the configuration of an optical disk according to an embodiment of the present invention. FIG. 2 shows an example of the configuration of a substrate according to an embodiment of the present invention. FIG. 3 shows an example of the configuration of a sheet according to an embodiment of the present invention.
[0027]
As shown in FIG. 1, an optical disk according to an embodiment of the present invention mainly has an annular substrate 1 having a center hole 1b at the center and a planar annular light transmission having a through hole 2c at the center. And layer 2. The optical disc according to this embodiment is configured to record / reproduce an information signal by irradiating a substrate 1 with a laser beam from the side where the thin light transmitting layer 2 is provided. The light transmitting layer 2 is formed by bonding the sheet 4 shown in FIG. 3 to one main surface of the substrate 1 shown in FIG. 1 on which the information signal portion 1c is formed.
[0028]
Also, as shown in FIG. 1, a clamp area 3 for mounting the optical disk on the spindle motor is set near the center hole 1b of the optical disk. The inner diameter of the clamp region 3 is selected from 22 mm to 24 mm, for example, 23 mm. The outer diameter of the clamp area 3 is selected from 32 mm to 34 mm, for example, 33 mm.
[0029]
As shown in FIG. 2, the substrate 1 has a center hole 1b formed in the center and a land and a groove formed on one main surface, and a disk substrate 1a formed on one main surface of the disk substrate 1a. And an information signal section 1c. A data area and an eccentricity measurement area are set in the area where the land and the groove are formed. In one embodiment of the present invention, on one main surface of the disk substrate 1a, a portion closer to the incident light is referred to as a groove, and a portion formed between the grooves is referred to as a land.
[0030]
The thickness of the disk substrate 1a is selected from 0.6 mm to 1.2 mm, for example, 1.1 mm. The diameter (outer diameter) of the disk substrate 1a is, for example, 120 mm, and the opening diameter (inner diameter) of the center hole 1b is, for example, 15 mm. In the data area, data is recorded on one or both of the groove and the land. This time we chose the method of recording on the groove. The distance (track pitch) between grooves formed in the data area was set to 0.32 μm. The width of the groove formed in the data area is selected in consideration of signal characteristics, but is set to 0.22 μm (half width) this time.
[0031]
The disk substrate 1a is made of, for example, a material that can transmit laser light used for measuring at least the mechanical characteristics of the disk substrate 1a. As a material forming the disk substrate 1a, a low water-absorbing resin such as polycarbonate (PC) or a cycloolefin polymer (for example, ZEONEX (registered trademark)) is used.
[0032]
The information signal section 1c is provided with a reflective film, a film made of a magneto-optical material, a film made of a phase change material, an organic dye film, or the like. Specifically, when the optical disc as a final product is a read-only type (ROM (Read Only Memory)) optical disc, the information signal unit 1c has at least a reflective layer made of, for example, Al, an Al alloy, or an Ag alloy. It is configured by providing a single-layer film or a laminated film. When the optical disc as a final product is a rewritable optical disc, the information signal portion 1c is made of a film made of a magneto-optical material such as a TbFeCo-based alloy, a TbFeCoSi-based alloy, or a TbFeCoCr-based alloy, a GeSbTe alloy, a GeInSbTe. A single-layer film or a laminated film having at least a film made of an alloy or a phase change material such as an AgInSbTe alloy is provided. When the optical disc as the final product is a write-once optical disc, the information signal portion 1c is formed of a film made of a phase change material such as a GeTe material or a film made of an organic dye material such as a cyanine dye or a phthalocyanine dye. It is composed of at least a single layer film or a laminated film.
[0033]
An eccentricity measurement area is formed on one main surface of the disk substrate 1a on which the unevenness is formed. The eccentricity measurement area is an area for measuring the amount of eccentricity of the optical disk, specifically, an area for measuring the amount of eccentricity of the optical disk using a conventional optical disk mechanical characteristic measuring device. In one embodiment of the present invention, the conventional mechanical characteristic measuring device is a mechanical characteristic measuring device for measuring the mechanical characteristics of an optical disk (for example, a compact disk) having a substrate thickness of 1.2 mm. This is a mechanical property measuring device having an optical system including a semiconductor laser that outputs a laser beam of 680 nm and an objective lens with an NA of 0.55.
[0034]
FIG. 4 shows a plan view of an eccentricity measurement area formed on one main surface of the disk substrate 1a. As shown in FIG. 4, the eccentricity measurement area is configured by spatially alternately arranging groove areas in which a plurality of grooves are formed and mirror areas on a plane. The width of the eccentricity measurement area is selected to be equal to or larger than the maximum value of the amount of eccentricity generated in the replica substrate manufacturing process. Conventionally, the maximum value of the amount of eccentricity generated in the process of manufacturing a replica substrate is about 30 μm, and thus the width of the eccentricity measurement region is selected in the range of 30 μm to 3 mm, for example, 100 μm.
[0035]
One or two or more concentric grooves are formed concentrically around the center hole 1b in the groove region. By forming the grooves concentrically in this manner, the conventional mechanical characteristic measuring device can obtain a tracking error signal (push-pull signal) of a sufficient magnitude. That is, the conventional mechanical characteristic measuring device can perform an appropriate tracking operation.
[0036]
Repetition interval d ₂ between the groove area and the mirror area is selected according to the optical system of the mechanical characteristic measuring apparatus. When using the mechanical characteristic measuring apparatus having the above-described optical systems, repetition interval d ₂ between the groove area and the mirror area is selected from a range of 0.7Myuemu～2.5Myuemu, it is selected to be, for example, 1.6 [mu] m. If repetition interval d ₂ is 0.7μm or more, the machine characteristic measuring apparatus having the optical system described above, it is possible to obtain a sufficient magnitude of the tracking error signal (push-pull signal). That is, a stable tracking operation can be performed. Further, if the repetition interval d ₂ is at 2.5μm or less, a mechanical characteristic measuring apparatus having an optical system described above can be obtained without distortion tracking error signal (push-pull signal).
[0037]
The width of the groove region is selected according to the optical system of the mechanical property device that measures the mechanical properties of the optical disc. When measuring the mechanical characteristics of the optical disk using the above-described conventional mechanical characteristic measuring device, any width may be selected as long as a sufficiently large push-pull signal without distortion can be obtained. Normally, the above characteristics can be satisfied if the interval between the groove regions is in the range of 0.2 to 0.8. In particular, when the interval between the groove areas is set to about half, the amplitude of the push-pull signal is maximized, and the distortion is suppressed. If the interval between the groove regions is 1.6 μm, the width of the groove region is selected to be, for example, 0.8 μm.
[0038]
The mirror area formed adjacent to the groove area is a planar area where no groove is formed. The width of the mirror region is selected according to the optical system of the mechanical characteristic device for measuring the mechanical characteristics of the optical disk. When measuring the mechanical characteristics of the optical disk using the above-described conventional mechanical characteristic measuring device, any width may be selected as long as a sufficiently large push-pull signal without distortion can be obtained. Normally, the above characteristics can be satisfied if the interval between the groove regions is in the range of 0.2 to 0.8. In particular, when the interval between the groove areas is set to about half, the amplitude of the push-pull signal is maximized, and the distortion is suppressed. If the interval between the groove regions is 1.6 μm, the width of the mirror region is selected to be, for example, 0.8 μm.
[0039]
It is not preferable to form the groove intermittently in a spiral shape. This is because if the groove is formed spirally and intermittently, the push-pull signal is disturbed at the joint, and tracking is not stably performed.
[0040]
The interval between the grooves in the groove region does not need to be selected to be the same as the interval (track pitch) between the grooves in the data region, but is at least equal to or less than the diffraction limit of the optical system in the above-described conventional mechanical characteristic measuring device. Is preferred. Conversely, if the interval between the grooves in the groove area is short, there is a problem that the time for cutting becomes long. Specifically, the distance _{d 1} of the groove is selected from a range of 0.05Myuemu～0.6Myuemu, it is selected to be, for example, 0.1 [mu] m.
[0041]
In the optical system of the above-described conventional mechanical characteristic measuring apparatus, the track pitch of 0.6 μm is almost at the diffraction limit. Therefore, in the conventional mechanical characteristic measuring device, each groove in the groove area is not identified, and a plurality of grooves constituting the groove area are identified as if they were one groove.
[0042]
As shown in FIG. 3, a sheet 4 used for forming the light transmitting layer 2 according to the embodiment includes a light transmitting sheet 2a and a pressure-sensitive adhesive ( And PSA). As in the case of the substrate 1, the sheet 4 has a structure punched out in a plane annular shape, and has a through hole 2c in the center. The diameter (outer diameter) of the sheet 4 is selected to be substantially the same as or smaller than the outer diameter of the substrate 1, and is, for example, 120 mm. On the other hand, the diameter (inner diameter) of the through-hole 2c is selected from a range equal to or larger than the opening diameter of the center hole 1b and equal to or smaller than the innermost diameter (eg, 23 mm diameter) of the clamp area 3, and is set to, for example, 23 mm. The thickness of the sheet 4 is, for example, 100 μm.
[0043]
The light-transmitting sheet 2a of the sheet 4 is made of, for example, a light-transmitting thermoplastic resin which satisfies at least optical characteristics capable of transmitting laser light used for recording / reproducing. The thermoplastic resin is selected from materials having physical properties such as heat-resistant dimensional stability, coefficient of thermal expansion, or coefficient of hygroscopic expansion close to the disk substrate 1a. Specifically, for example, polycarbonate (PC) or polymethyl methacrylate ( Methacrylic resin such as poly (methyl methacrylate). Further, the thickness of the light transmitting sheet 2a is preferably selected from the range of 60 μm to 100 μm, and more preferably selected from the range of 70 μm to 100 μm. In this embodiment, considering that the light-transmitting sheet 2a is bonded to one main surface of the substrate 1 via an adhesive layer 2b made of a pressure-sensitive adhesive (PSA), the light-transmitting sheet 2a The thickness is selected to be, for example, 70 μm. The thickness of the light transmitting sheet 2a is determined in consideration of the wavelength of laser light used for recording / reproducing information signals and the desired thickness of the light transmitting layer 2.
[0044]
The PSA forming the adhesive layer 2b is, for example, methacrylic resin. The thickness of the adhesive layer 2b is, for example, 30 μm, but the thickness of the adhesive layer 2b and the material used as the pressure-sensitive adhesive include the desired film thickness of the light transmitting layer 2 and the recording of information signals. / Determined in consideration of the wavelength of laser light used for reproduction.
[0045]
FIG. 5 is a cross-sectional view showing an image during reproduction of the optical disc according to the embodiment of the present invention. As shown in FIG. 5, in the optical disc according to the embodiment of the present invention, the information signal portion 1c is irradiated with laser light from the side where the thin light transmitting layer 2 is provided on the substrate 1, thereby recording the information signal. / Reproduction is performed.
[0046]
FIG. 6 is a sectional view showing an image at the time of measuring the mechanical characteristics of the optical disc according to the embodiment of the present invention. As shown in FIG. 6, in the disk substrate according to one embodiment of the present invention, the mechanical properties of the disk substrate are measured by irradiating a laser beam from a surface opposite to one main surface on which the unevenness is formed. Is done.
[0047]
According to the embodiment of the present invention, the following effects can be obtained.
A data area having a groove interval in the range of 0.2 μm to 0.6 μm, a plurality of grooves, and a groove area having the same groove interval as the data area; and a planar mirror adjacent to the groove area. Since the disk substrate 1a is provided with an eccentricity measurement region including a region, a conventional mechanical characteristic measuring device for measuring mechanical characteristics of an optical disk having a substrate thickness of 1.2 mm, specifically, a laser having a wavelength of 680 nm A narrow track pitch having a groove interval in a range of 0.2 μm to 0.6 μm using a mechanical property measuring apparatus having an optical system including a semiconductor laser that outputs light and an objective lens having an NA of 0.55. It is possible to measure the amount of eccentricity of a format optical disc. Therefore, the amount of eccentricity can be measured in the state of the disk substrate 1a where the light transmission layer 2 is not formed, so that an optical disk can be manufactured by an efficient production system.
[0048]
As described above, one embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.
[0049]
For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as needed.
[0050]
In the above-described embodiment, an example has been described in which the distance between the grooves formed in the eccentricity measurement area and the distance between the grooves formed in the data area are different, but the groove formed in the eccentricity measurement area is different. The distance between them and the distance between the grooves formed in the data area may be the same.
[0051]
【The invention's effect】
As described above, according to the present invention, the disk substrate has the eccentricity measurement area in which the groove area in which one or two or more grooves are formed and the mirror area on the plane are spatially alternately arranged. Accordingly, the groove area can be made to follow an optical pickup for measuring the mechanical characteristics of an optical disk having a groove having the same width as the groove area and a land having the same width as the mirror area. Therefore, a groove area and an eccentricity measurement area are provided by using a mechanical property measuring device for measuring mechanical properties of an optical disc having a groove having the same width as the groove area and a land having the same width as the mirror area. The eccentricity of the disk substrate can be measured.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a structure of an optical disc according to an embodiment of the present invention.
FIG. 2 is a sectional view showing a configuration of a substrate according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a configuration of a sheet according to an embodiment of the present invention.
FIG. 4 is a plan view of an eccentricity measurement area provided on a replica substrate according to an embodiment of the present invention.
FIG. 5 is a cross-sectional view showing an image when data is reproduced from the optical disc according to the embodiment of the present invention.
FIG. 6 is a sectional view showing an image at the time of measuring the mechanical characteristics of the optical disc according to the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Substrate, 1a ... Disk substrate, 1b ... Center hole, 1c ... Information signal part, 2 ... Light transmission layer, 2a ... Light transmission sheet, 2b ... Adhesion Layer, 3 ... Clamping area, 4 ... Sheet

Claims (15)

A disk substrate having an eccentricity measurement area in which one or two or more concentric grooves are formed and a planar mirror area are spatially alternately arranged. 2. The disk substrate according to claim 1, wherein the widths of the groove area and the mirror area are selected according to an optical system used for measuring the amount of eccentricity. 2. The disk substrate according to claim 1, wherein an interval between the grooves is 0.05 μm or more and 0.6 μm or less. 4. The disk substrate according to claim 3, wherein a repetition interval of the groove area or the mirror area is 0.7 μm or more and 2.5 μm or less. 4. The disk substrate according to claim 3, wherein a width of the groove area is in a range of 0.2 to 0.8 of a repetition interval of the groove area or the mirror area. 4. The disk substrate according to claim 3, wherein the width of the groove area is approximately half the repetition interval of the groove area or the mirror area. 4. The disk substrate according to claim 3, wherein the width of the eccentricity measurement area is 30 μm or more and 3 mm or less. A disk substrate having an eccentricity measurement region in which one or more concentric grooves are formed, and a planar mirror region are spatially alternately arranged;
An information signal portion formed on one main surface of the disk substrate;
An optical disc, comprising: a protection layer for protecting the information signal section. 9. The optical disk according to claim 8, wherein the widths of the groove area and the mirror area are selected according to an optical system used for measuring the amount of eccentricity. 9. The optical disk according to claim 8, wherein the protection layer has a light-transmitting property, and recording and / or reproduction of an information signal is performed by irradiating a laser beam from a side on which the protection layer is provided. . 9. The optical disk according to claim 8, wherein the groove interval is 0.05 μm or more and 0.6 μm or less. 12. The optical disk according to claim 11, wherein a repetition interval of the groove area or the mirror area is 0.7 μm or more and 2.5 μm or less. 12. The optical disk according to claim 11, wherein a width of the groove area is in a range of 0.2 to 0.8 of a repetition interval of the groove area or the mirror area. 12. The optical disk according to claim 11, wherein a width of the groove area is approximately half of a repetition interval of the groove area or the mirror area. 11. The optical disk according to claim 10, wherein the width of the eccentricity measurement area is 30 μm or more and 3 mm or less.

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