JP2005203050A - Recording method of optical master disk, manufacturing method of optical master disk, optical master disk, and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dispense with preparation of a mother stamper and to reduce the disk manufacturing cost in a process for manufacturing the optical disk. <P>SOLUTION: A desired groove shape is exposed on a photoresist 11 applied on an etching layer of a metal substrate 12 by using a laser cutting device. After plasma etching is performed at the part of the surface of the etching layer of the metal substrate 12 exposed by exposure/development to form a groove Gv, remaining photoresist 11 is removed by O<SB>2</SB>ashing. The metal substrate 12 on which a rugged pattern corresponding to the groove Gv is formed is directly used as a stamper and injection molding is performed by using a polycarbonate resin to form a disk substrate 13. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  For example, the present invention provides a recording on an optical disc master that forms (draws) a recording pattern in accordance with a laser beam irradiation locus on a photoresist film or the like by irradiating a photoresist film or the like formed on one surface with laser light, for example. The present invention relates to a method and a method for manufacturing an optical disc master. The present invention also relates to an optical disc master suitable for use in forming a groove on an optical disc. Furthermore, the present invention relates to an optical disc produced from an optical disc master.

  Conventional recordable disc-shaped recording media include MD (Mini Disc), CD (Compact Disc) -R (Recordable), CD-RW (ReWritable), DVD (Digital Versatile Disc) + RW (ReWritable), DVD-R ( Recordable) and DVD-RW (ReWritable) have been proposed. In the format of these disc-shaped recording media, a groove recording format for recording in a groove is adopted.

  Such various optical disc manufacturing processes generally include a step of producing a metal master called a stamper having a surface shape corresponding to a desired uneven pattern such as pits and grooves, and the surface shape of the stamper on the disk substrate. And a film forming process for forming a recording layer and a protective layer.

  In the master manufacturing process, after cleaning and drying the glass substrate whose surface has been polished, a photoresist, which is a photosensitive material, is applied to the glass substrate, and the photoresist is irradiated with laser light to form a pattern of pits and grooves. In general, a method of exposing is used. By developing the latent image formed on the photoresist by this exposure, a concavo-convex pattern corresponding to the pattern of pits and grooves is formed on the photoresist, which is further transferred to the metal surface to form a stamper. In such a method of recording a concavo-convex pattern by exposure with laser light, it is required to transfer the pattern to the photoresist surface on the order of submicrons.

  In each ISO (International Organization for Standardizaiton) magneto-optical (MO) disk format, a land recording format for recording on a land (between grooves) has been proposed. In a DVD-RAM (Digital Versatile Disc-Randaom Access Memory) or the like, as one method for realizing a higher density of an optical disc, recording is performed both in the groove and between the grooves (land), thereby reducing the track density. A method (land / groove recording) has been proposed to increase the density by doubling. Here, the groove is a so-called guide groove formed along the recording track so that tracking servo can be performed mainly. A portion near the optical pickup (reading surface) is called a groove, and a far portion is called a land. A portion between the grooves is called a land.

However, in land / groove recording such as DVD-RAM, there is a disadvantage that optimum recording cannot be performed unless the focus point is changed between land recording and groove recording. Also, ISO (International Symposium on Optical Memory) 2000 Simulation
Of Heat Generation And Conduction On Land / Groove Disc, there is a report that the recording beam shape is different between land recording and groove recording, and it is difficult to make the land recording / reproducing characteristics and the groove recording / reproducing characteristics the same.

  In addition, in an optical disc used in DVR (Digital Video Recorder), the recording / reproducing characteristics near the reading surface (land) are good, but the recording / reproducing characteristics far from the reading surface (groove) are not good. The result is obtained. In order to perform recording / reproduction on both the groove and land tracks, it was necessary to make the recording / reproduction characteristics of both tracks good and uniform.

  Furthermore, even if the beam spot of the laser beam is reduced, the range of heat propagation is not so narrow, so the influence of heat propagation to adjacent tracks is increased by reducing the track pitch. As a result, there is a possibility that the data of the adjacent track is erased during recording.

  For the above reasons, in a high-density optical disc such as Blu-ray Disc (trademark), a groove is formed in a portion near the optical pickup, and a land is formed in a far portion to perform groove recording. FIG. 1 schematically shows a part of the vicinity of a boundary between a lead-in area and a data recording area in a high-density optical disc format such as a Blu-ray Disc format.

  As shown in FIG. 1, the left side is the inner circumference side of the disk, and the right side is the outer circumference side of the disk. In the Blu-ray Disc, the pit in the PIC (Permanent Information & Control Data) area 2 and the groove in the data recording area 3 are wobble grooves formed to meander. FIG. 1 is a schematic diagram, and the number of tracks does not indicate the actual number.

  The groove in the inner peripheral BCA (Burst Cutting Area) region 1 is a groove having a track pitch Tp1 of 2000 nm. The groove in the PIC area 2 is a rectangular wobble groove with a track pitch Tp2 of 350 nm. The groove in the PIC area 2 and the data recording area 3 is a wobble groove formed by a superimposed signal of an MSK (Minimum Shift Keying) signal having a track pitch Tp3 of 320 nm and an STW (Saw Tooth Wobble) signal.

  FIG. 2 shows a method for producing a Blu-ray Disc. By using a laser cutting apparatus and irradiating the photoresist 42 on the glass master 41 with laser light, latent images of grooves and pits are formed. As shown in FIG. 2A, a development process is performed on the glass master 41, and the exposed portion of the photoresist 42 is dissolved and developed. As a result, the photoresist 42 is a positive type, so that the recess groove is patterned. A glass master is obtained.

  Next, an optical disc master in which a conductive film layer made of a nickel film is formed on the concave groove pattern of the resist glass master by electroless plating or the like is attached to an electroforming apparatus, and nickel plating is applied on the conductive film layer by an electroplating method. A layer is formed to produce a master stamper 43 having a convex groove pattern. Further, as shown in FIG. 2B, a mother stamper (concave groove pattern) 44 in which the concavities and convexities are reversed based on the master stamper 43 is produced.

  Next, as a method for producing an optical disc, a disc substrate 45 is produced by injection molding using a mother stamper 44 and a polycarbonate (refractive index 1.59) transparent resin. The concave / convex pattern of the groove Gv is transferred to the signal forming surface of the disk substrate 45. Thereafter, a reflective layer, a second dielectric layer, a recording layer 46, and a first dielectric layer are formed on the signal forming surface (convex groove pattern), and a 0.1 mm cover layer 47 is formed on the recording layer 46. Form. Through the above steps, a high-density phase change optical disk such as Blu-ray is completed.

  As described above, by fabricating the mother stamper 44 that is a replica stamper of the master stamper 43, the concave / convex pattern of the groove can be reversed, and the side closer to the optical pickup 48 (reading surface) as shown in FIG. 2C. Grooves Gv protruding in the shape can be formed. With this technique, the groove reproduction characteristic and the wobble characteristic can be improved.

  In the following Patent Document 1, it is proposed that a chromium (Cr) layer is provided between a glass master and a photoresist, and that the recesses are patterned in the chromium layer by etching using the photoresist with irregularities as a mask. Yes. It is described that this makes it possible to form a glass master having pits having a width smaller than the spot diameter of the laser beam, and to realize high-density recording of an optical disc.

Japanese Patent No. 2754785

  As described above, since the master stamper 43 obtained by plating from the glass master has the irregularities reversed, the mother stamper 44 having the irregularities reversed again by the plating process is created from the master stamper 43, and the mother stamper is A desired disk substrate 45 is obtained by injection molding. Thus, the necessity of the mother stamper 44 has a problem of increasing the manufacturing cost of the optical disc.

  This problem can be solved by using a negative type resist material instead of a positive type. However, at present, a negative resist material having a resolution equivalent to that of a positive type resist material that is normally used is obtained. It is not done.

  Accordingly, an object of the present invention is to provide an optical disc master recording method, an optical disc master manufacturing method, an optical disc master, and an optical disc having good groove recording / reproducing characteristics and wobble characteristics without producing a mother stamper.

In order to achieve the above-described problem, a first aspect of the present invention is a method of recording an optical disc master used when manufacturing an optical disc having a wobble groove having a convex shape with respect to a reading surface,
A recording method for an optical disc master, wherein a resist on a metal substrate is exposed corresponding to a wobble groove, an exposed portion is removed, and an opening corresponding to the groove of the resist is generated on the metal substrate.

A second aspect of the present invention is a method of manufacturing an optical disc master used when manufacturing an optical disc having a wobble groove having a convex shape with respect to a reading surface,
A coating process for coating a resist on the etching layer on the metal substrate;
An exposure process for forming a latent image of the groove on the resist;
Developing the resist and removing the resist corresponding to the groove;
An etching step of etching the etching layer using a resist as a mask;
And a removing process for removing the remaining resist.

A third aspect of the present invention is an optical disc master used when manufacturing an optical disc having a wobble groove having a convex shape with respect to a reading surface,
Forming a latent image of the groove in the resist, developing the resist, removing the resist corresponding to the groove,
An optical disk master having a groove corresponding to a groove formed by etching an etching layer on a metal substrate using a resist as a mask.

A fourth aspect of the present invention is an optical disc having a wobble groove having a convex shape with respect to a reading surface,
A recording film is formed on a disk substrate molded by an optical disk master, and a cover layer is provided on the recording film.
The optical disc master is
Forming a latent image of the groove in the resist, developing the resist, removing the resist corresponding to the groove,
An optical disc using an optical disc master in which a groove corresponding to a groove is formed by etching an etching layer on a metal substrate using a resist as a mask.

  In the present invention, for example, a metal master having a groove formed by plasma etching is used as a stamper. According to the present invention, it is not necessary to create a mother stamper by forming a disk substrate using a metal master as a stamper. Thereby, the cost of manufacturing the disk can be reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In one embodiment, the present invention is applied to a Blu-ray Disc as shown in FIG. A groove track composed of a groove array of 2000 nm track pitch Tp1 in the BCA area 1, a groove track composed of a rectangular wobble groove array of 350 nm track pitch Tp2 in the PIC area 2, and a groove which is a wobbling groove in the data recording area 3 A track is formed on the substrate surface so as to be continuous in one spiral. The BCA area has a radius r = 21.3 mm to 22.0 mm, the PIC area has a radius r = 22.4 mm to 23.2 mm, and the data recording area has a radius r = 23.2 mm to 58.5 mm. It is formed.

  The track pitch Tp3 of the groove in the data recording area 3 is 320 nm. This is to make it possible to obtain a large capacity capable of recording / reproducing for a longer time by narrowing the pitch. On the other hand, the groove track pitch Tp1 of the BCA region 1 is 2000 nm, which is sufficiently wide. The track pitch Tp2 of the groove in the PIC area 2 is 350 nm, and the PIC area 2 is a groove track made up of an array of rectangular wobble grooves.

  When manufacturing the optical disc described above, it is necessary to produce an optical disc master serving as an optical disc master, and a laser cutting device is used for this purpose. Hereinafter, an example of a laser cutting apparatus used for producing an optical disc master will be described with reference to FIG.

  The laser cutting apparatus 20 shown in FIG. 3 is for exposing a positive type photoresist 28 applied on the metal master 17 to form a latent image of the groove on the photoresist 28. When forming a latent image on the photoresist 28, the metal master disk 17 coated with the photoresist 28 is attached to a rotation driving device 16 provided on the moving optical table 27. When the photoresist 28 is exposed, the metal master 17 is rotated by the rotation driving device 16 and parallel by the moving optical table 27 so that the entire surface of the photoresist 28 is exposed in a desired pattern. Moved.

  The laser cutting device 20 includes a light source 21 that emits laser light, a rotary drive device 16, a spindle servo 18, a drive driver 25, a position sensor 30, a laser scale 31, an air slider 32, and a feed servo 33. And a beam expander 34.

  The laser light emitted from the light source 21 is reflected by the mirror M1 and the mirror M2 and guided horizontally and in parallel on the moving optical table 27.

  An arbitrary light source 21 can be used, but a light source that emits a laser beam with a short wavelength is preferable. Specifically, for example, a Kr laser that emits laser light having a wavelength λ of 266 nm is suitable.

  The laser beam reflected by the mirror M2 and guided horizontally onto the moving optical table 27 is incident on the beam expander (BEX) 34 after being optically deflected by the wedge prism 23 and the acousto-optic deflector 24.

An acousto-optic deflector (AOD: Acousto Optical Deflector) 24 is for applying an optical deflection to the laser beam so as to correspond to the wobble of the groove. In other words, the laser light is incident on the acousto-optic deflector 24 via the wedge prism 23, and the acousto-optic deflector 24 performs optical deflection so as to correspond to a desired exposure pattern. Here, as the acoustooptic element used in the acoustooptic deflector 24, for example, an acoustooptic element made of tellurium oxide (TeO ₂ ) is suitable. The laser beam optically deflected by the acoustooptic deflector 24 is emitted through the wedge prism 23.

  The wedge prism 23 allows laser light to be incident on the grating surface of the acoustooptic device of the acoustooptic deflector 24 so as to satisfy the Bragg condition. This is for deflecting and changing the horizontal height of the beam.

  Here, a driving driver 25 for driving is connected to the acousto-optic deflector 24. A high-frequency signal from a voltage controlled oscillator (VCO) 29 is supplied to the driving driver 25 together with a DC voltage. A control signal is supplied to the voltage controlled oscillator 29. Then, the acousto-optic deflector 24 is driven by the driver 25 for driving, and thereby optical deflection is applied to the laser light.

  As a control signal supplied to the voltage controlled oscillator 29, specifically, for example, when forming a groove in the BCA region 1, it is a zero level direct current (DC) signal, and when forming a rectangular wobble groove in the PIC region 2. Is a rectangular signal of biphase modulation. When the wobble groove of the data recording area 3 is formed, it is a superposition signal of an MSK signal of 956.5 kHz and an STW signal of 1923 kHz.

  The laser beam optically deflected by the wedge prism 23 and the acoustooptic deflector 24 is incident on a beam expander (BEX) 34. The beam expander (BEX) 34 can convert the beam diameter.

  The laser beam is made a predetermined beam diameter by a beam expander (BEX) 34, reflected by a mirror M 3, guided to the objective lens 26, and condensed on the photoresist 28 by the objective lens 26.

  The photoresist 28 is exposed by laser light, and a latent image is formed on the photoresist 28. At this time, the metal master disk 17 coated with the photoresist 28 is rotationally driven by the rotation driving device 16 and is also moved by the moving optical table 27 so that the entire surface of the photoresist 28 is exposed in a desired pattern. The laser beam is moved in the radial direction. As a result, a latent image corresponding to the laser beam irradiation locus is formed over the entire surface of the photoresist 28. In one embodiment of the present invention, the rotational speed of the rotary drive device 16 is controlled so that the linear velocity in the longitudinal direction of the track is 5.28 m / s.

  The moving optical table 27 is exposed at a feed pitch of 2000 nm in the BCA area, 350 nm in the PIC area, and 320 nm in the data recording area. In this laser cutting apparatus 20, the position of the moving optical table 27 is detected by the position sensor 30, and exposure is performed at a timing and a pitch corresponding to each area, and the BCA area, the PIC area, and The latent image of the groove pattern in the data recording area can be exposed to the photoresist 28 on the metal master 17. Further, it is possible to change the feed pitch of the moving optical table 27 instantaneously by controlling the operations of the feed servo 33 and the air slider 32 on the basis of the wavelength detected by the laser scale 31 (for example, 0.78 μm). is there.

  The feed pitch is 2000 nm during the BCA region 1 (radius r = 21.3 mm to 22.0 mm), and the feed pitch is changed from 2000 nm to 350 nm during the track pitch transition region (radius r = 22.0 mm to 22.4 mm). Change gradually. The feed pitch is 350 nm in the PIC region 2 (radius r = 22.4 mm to 23.2 mm), and the feed pitch is gradually changed from 350 nm to 320 nm in the track pitch transition region (radius r = 23.2 mm). The data recording area 3 (radius r = 23.2 mm to 58.5 mm) is formed at a feed pitch of 320 nm.

  Note that the objective lens 26 for condensing the laser light on the photoresist 28 preferably has a large numerical aperture NA so that a finer groove pattern can be formed. An objective lens having a number NA of about 0.9 is suitable.

  After the latent image is formed on the photoresist 28, the metal master 17 is placed on the turntable of the developing machine so that the surface coated with the photoresist 28 is the upper surface. Then, while rotating the turntable, the developer is dropped on the photoresist 28 while rotating the metal master 17, and the development process is performed on the metal master 17, so that the groove of the BCA region 1 and the PIC region 2 are formed on the metal master 17. Concave and convex patterns corresponding to the rectangular wobbling groove and the wobbling groove in the data recording area 3 are formed.

  Here, an example of a metal master forming method using the laser cutting device 20 will be described with reference to FIG. FIG. 4 is a schematic view showing a method for manufacturing a metal master of an optical disk according to the present invention, and shows a cross-sectional view of the master in the process of forming a metal master.

  In one embodiment of the present invention, a metal substrate 12 having a structure in which a film is formed by sputtering an etching layer with a thickness of 200 nm in advance on an aluminum (Al) substrate for a hard disk is used. Here, tungsten (W), titanium (Ti), molybdenum (Mo), or the like is used as the etching layer. By etching the etching layer, a metal master having a concavo-convex pattern is obtained.

  First, as shown in FIG. 4A, after applying the photoresist 11 on the metal substrate 12 with a thickness of, for example, 50 nm, the region where the groove shape is to be formed, that is, the region where the groove on the surface of the photoresist 11 is to be formed. Then, a laser power for exposing the surface of the metal substrate 12, for example, a laser beam of about 0.25 mj / m, is irradiated to form a latent image for the concave groove on the photoresist 11.

  By dissolving the formed latent image portion with a developing solution, a metal substrate 12 having a photoresist 11 with unevenness formed on one surface is formed.

Next, the first plasma etching is performed on the coated surface of the photoresist 11 using the photoresist 11 as a mask in a gas atmosphere such as CHF ₃ gas. As a result, in the groove portion where the surface of the metal substrate 12 is exposed, etching proceeds and a groove is formed on the metal substrate 12. Etching is not performed in other regions because the photoresist serves as a mask. At this time, the etching amount in the groove portion is about 25 nm. As shown in FIG. 4B, a groove Gv is formed in the metal substrate 12 by etching.

Finally, as shown in FIG. 4C, the photoresist 11 is completely removed from the metal substrate 12 by O ₂ ashing to obtain the metal substrate 12 of the optical disk having the groove Gv having a depth of about 25 nm. Since the groove shape thus obtained is obtained by plasma etching, the cross section is not V-shaped but U-shaped. As described above, the metal substrate 12 on which the concave / convex pattern corresponding to the groove Gv in each region is formed is completed.

  An optical disk is produced by directly using a metal substrate 12 having a concavo-convex pattern as a stamper, and producing a disk substrate 13 having a thickness of 1.1 mm and a diameter of 120 mm by injection molding with a transparent resin of polycarbonate (refractive index 1.59). To do. Of course, a transparent resin such as polymethyl methacrylate may be used as the material of the disk substrate 13. Further, a disk substrate may be produced by using a photopolymerization method (photo polymerization method, so-called 2P method). At this time, as shown in FIG. 4C, the uneven pattern which is the surface shape of the metal substrate 12 is transferred to the signal forming surface of the disk substrate 13.

Next, as a film forming process, a recording layer and a cover layer are formed on the disk substrate 13 to which the surface shape of the metal substrate 12 is transferred in the same manner as in the conventional optical disk manufacturing method. Specifically, for example, first, a light reflecting film made of a silver alloy or the like (AgNdCu), a mixture of zinc sulfide and silicon oxide (ZnS · A first dielectric film made of SiO2), a phase change recording layer made of germanium / antimony / tellurium alloy (GeSbTe), etc., a mixture of zinc sulfide and silicon oxide (ZnS / SiO2)
) Etc. are formed in the order of the second dielectric film.

  As a result, a recording layer composed of the second dielectric film, the phase change recording layer, the first dielectric film, and the light reflecting film is formed on the disk substrate 13. Thereafter, an adhesive sheet (PSA) having a thickness of about 0.1 mm is bonded to the recording layer so as to substantially cover the entire substrate, thereby forming a cover layer. The optical disc is completed through the above steps.

  As another method, the cover layer can be formed by applying an ultraviolet curable resin smoothly by a spin coat method or the like, and irradiating the ultraviolet curable resin with ultraviolet rays and curing it.

  Next, a plurality of evaluation optical disks are produced by the manufacturing method as described above, and the results of the evaluation are described. The evaluation work is performed using a Blu-ray Disc evaluator equipped with an optical pickup (wavelength λ = 406 nm, NA = 0.85).

  As an optical disk for evaluation, an optical disk manufactured using tungsten (W) as an etching layer of a metal substrate is optical disk A, an optical disk manufactured using titanium (Ti) as an etching layer is optical disk B, and molybdenum (Mo) is used as an etching layer. The optical disc produced using () is designated as optical disc C. The thickness of each disk substrate is 1.1 mm, and the thickness of the cover layer is 0.1 mm.

  In the evaluation work, recording and reproduction are performed with 1-7 modulation (RLL (1, 7)) on the wobble groove portion (recording area close to the reading surface) of the above three types of optical disks, and the recording / reproduction characteristics are evaluated.

  The jitters of optical disc A, optical disc B, and optical disc C are 7.9%, 8.1%, and 8.0%, respectively, and good recording / reproduction characteristics can be realized. Furthermore, the wobble address information of the wobble groove can be stably reproduced. Further, the reproduction of the wobble signal of the rectangular wobble groove of the PIC can be reproduced with a jitter of about -3.4%, and good reproduction characteristics can be realized.

  Using a groove recording format in which a rectangular wobble groove in the PIC area and a wobble groove formed by superimposing an MSK signal and an STW signal are used, and a high density equivalent to the track density of land / groove recording is achieved (the above groove When recording density is doubled, the recording density equivalent to land / groove recording can be realized without changing the focus point. When recording / reproducing is performed only on the recording area close to the reading surface, the recording / reproducing characteristics of the groove recording format can be made equal to the recording / reproducing characteristics of the land / groove recording format.

  As described above, by using a metal master obtained by plasma etching as a stamper without using a mother stamper, good reproduction of a PIC wobble signal of a rectangular wobble groove of PIC, good recording / reproduction characteristics and wobble of a wobble groove portion are achieved. Address information can be reproduced stably, and the recording density can be greatly improved.

  The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications can be made without departing from the gist of the present invention. The present invention is widely applicable to an optical recording medium in which grooves are formed along a recording track, and an optical recording medium manufacturing master used for manufacturing the optical recording medium, and is an object of the present invention. The optical recording medium may be, for example, a read-only optical recording medium, an optical recording medium in which data can be rewritten repeatedly, or an optical recording medium in which data can be additionally written or cannot be erased.

It is a basic diagram which shows typically an example of the format of the high-density optical disk which can apply this invention. It is a basic diagram which shows an example of the manufacturing method of the conventional high density optical disk. It is a basic diagram which shows the structure of an example of the laser cutting apparatus used when producing the optical disk and optical disk master concerning this invention. It is a basic diagram used for description of one Embodiment of the manufacturing method of the master of the optical disk based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 BCA area | region 2 PIC area | region 3 Data recording area Gv Groove 11 Photoresist 12 Metal substrate 13 Disc substrate 16 Rotation drive device 17 Metal master disk 18 Spindle servo 21 Light source

Claims (6)

A method for recording an optical disc master used when manufacturing an optical disc having a convex wobble groove with respect to a reading surface,
A method for recording an optical disc master, comprising: exposing a resist on a metal substrate corresponding to the wobble groove; removing an exposed portion; and generating an opening on the metal substrate corresponding to the groove of the resist. In claim 1,
The method for recording an optical disc master, wherein the metal substrate has an etching layer on the metal substrate. A method of manufacturing an optical disc master used when manufacturing an optical disc having a convex wobble groove with respect to a reading surface,
A coating process for coating a resist on the etching layer on the metal substrate;
An exposure step of forming a latent image of the groove on the resist;
A development step of developing the resist and removing the resist in a portion corresponding to the groove;
An etching step of etching the etching layer using the resist as a mask;
And a removing step of removing the remaining resist. An optical disc master used when manufacturing an optical disc having a wobble groove having a convex shape with respect to a reading surface,
Forming a latent image of the groove in the resist, developing the resist, removing the resist corresponding to the groove;
An optical disc master in which a groove corresponding to the groove is formed by etching an etching layer on a metal substrate using the resist as a mask. An optical disc having a wobble groove convex to the reading surface,
A recording film is formed on a disk substrate molded by an optical disk master, and a cover layer is provided on the recording film.
The above optical disc master is
Forming a latent image of the groove in the resist, developing the resist, removing the resist corresponding to the groove;
An optical disk comprising: an optical disk master in which a concave groove corresponding to the groove is formed by etching an etching layer on a metal substrate using the resist as a mask. In claim 5,
An optical disc, wherein NA is 0.85 or more, where NA is the numerical aperture of an objective lens used for recording or reproduction.

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