JP2006048785A - Method of manufacturing optical disk stamper, optical disk stamper and optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a reproduction characteristic of a wobbled groove and a characteristic of a fluctuation amount of a push-pull signal satisfactory by suppressing a height change in a land part at the time of manufacturing an optical disk stamper. <P>SOLUTION: An EOM (electro optic modulator) 15, a photodetector (PD) 16 and a light output control part (APC (auto power controller)) 17 make exposure per unit area of a laser beam emitted from a laser source 14 for oscillating a recording laser beam of quartic harmonic (λ=266 nm) of a YAG laser to be constant. An acousto-optic modulation deflector 22 optically deflects the laser beam and then is made incident on a beam expander (BEX) 26. Since the acousto-optic modulation deflector 22 forms respective wobbled grooves for a BCA (burs cutting area) area, a PIC (permanent information & control data) area and a data recording area, a record beam is deflected. Relative variation in height of a land part is not higher than 0.083 in the PIC area and is not higher than 0.047 in the data recording area. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing an optical disc stamper that can simplify a manufacturing process using a resist made of an inorganic material. Further, the present invention relates to an optical disc stamper obtained by simplifying the manufacturing process using a resist made of an inorganic material. Furthermore, the present invention relates to an optical disc created by an optical disc stamper.

  Today, various formats such as MD (Mini Disc), MO (Magneto Optical), DVD (Digital Versatile Disc), and Blu-ray Disc (registered trademark) have been proposed for optical disks used as information recording media. ing. The optical disk substrate used in any format is generally manufactured by injection molding of a resin material, and the price of the optical disk is reduced.

  In the injection molding of an optical disk substrate, in order to provide the optical disk with patterns such as grooves and pits, a stamper as an optical recording medium manufacturing master for transferring those patterns is disposed in the cavity of the injection molding apparatus.

  Here, an outline of a stamper manufacturing method will be described. First, a very thin photoresist (photosensitive agent) is applied onto a glass master by spin coating or the like, and exposure is performed with a laser of a cutting device while rotating the glass master. A latent image having a pattern corresponding to the groove or pit is formed on the photoresist film by exposure.

  Thereafter, a developing solution is dropped on the rotating glass master and developed to form an uneven resist pattern corresponding to the groove or pit of the optical disk on the glass master.

  Next, a stamper is obtained by depositing a metal such as nickel on the glass master by plating, peeling the metal, and performing trimming. The stamper is disposed in the cavity of the injection molding apparatus, and the resin is injected into the cavity, whereby the disk substrate is manufactured.

  Patent Document 1 below describes an exposure method in which an exposure beam is divided into two exposure beams and a deflection amount of each exposure beam is different when exposing a required pattern.

JP 2003-59052 A

  Conventionally, in each of the CD-R, CD-RW, DVD + RW, DVD-R, and DVD-RW formats, a groove recording format for recording in a wobbled groove has been proposed. In such an optical disc, the optimum format (groove width, track pitch, wobble format) differs depending on the type of the optical disc. Since the groove format is formed by the exposure beam, the groove width, track pitch, and wobble format are greatly affected by the spot diameter and wavelength of the exposure beam.

  In CD-R and CD-RW, a groove uneven pattern is recorded by a He-Cd laser (442 nm), the optimum groove width is 550 to 600 nm, and the track pitch is 1600 nm. DVD + RW, DVD-R, and DVD-RW of high-density optical discs are 4.7 GB, which is about 7.2 times the CD-R and CD-RW recording density, so the optimum groove width is 300 to 330 nm. The track pitch is 740 nm. By using a short wavelength Kr laser (413 nm), the spot diameter d of the exposure beam was reduced, and the optimum groove width of DVD + RW, DVD-R, and DVD-RW was realized. Recently, a Blu-ray Disc (hereinafter referred to as BD as appropriate) format has been proposed that is about 25 GB, which is about 5 times higher than DVD.

  The BD format is a high-density optical disc format having a recording capacity of about 25 Gbytes on a single layer on one side and about 50 Gbytes on two layers on one side. As a type of BD, a standard regarding a rewritable disc has already been proposed, and a standard for a recordable disc and a read-only disc has been studied.

In the BD format, the light source wavelength is set to 405 nm and the numerical aperture NA (Numerical Aperture) of the objective lens is increased to 0.85 in order to reduce the recording / reproducing beam spot diameter. In the CD (Compact Disc) standard, the light source wavelength is 780 nm, NA: 0.45, and the spot diameter is 2.11 μm. In the DVD (Digital Versatile Disc) standard, the light source wavelength is 650 nm, the NA is 0.6, and the spot diameter. : 1.32 μm. In the BD standard, the spot diameter can be narrowed down to 0.58 μm, which can be reduced to about 1/5 compared with DVD. Further, as a result of increasing the numerical aperture NA of the objective lens, the angle error (referred to as tilt margin) allowed for the tilt from 90 ° of the angle formed by the disk surface and the optical axis of the laser beam is reduced, so that information The cover layer covering the layer is thinned to 0.1 mm.

  FIG. 1 is a schematic diagram of a groove of a BD disc. The left side is the inner circumference side of the disc, and the right side is the outer circumference side of the disc. On the innermost side, there is a BCA (Burst Cutting Area) area 1, and the pits in the PIC (Permanent Information & Control Data) area 2 and the grooves in the data recording area 3 are wobble grooves formed so as to meander. FIG. 1 is a schematic diagram, and the number of tracks does not indicate the actual number.

  The inner peripheral BCA region 1 is formed by forming a group-like track with a radius r = 21.3 mm to 22.0 mm. The groove in the BCA region 1 is formed with a sufficiently large track pitch Tp = 2000 nm.

  In the PIC region 2, a group-like track is formed between radii r = 22.4 mm to 23.197 mm. In the PIC region 2, a rectangular wobble groove with a track pitch Tp = 350 nm is formed.

  The data area 3 is an area having a radius r = 23.235 mm to 58.017 mm, and a wobble groove is formed. The outer radius r = 58.17 mm to 58.6 mm is the lead-out area, and only the MSK sine wave wobble groove exists. The track pitch Tp = 320 nm. The track pitch is made relatively small in order to increase the data recording capacity. Note that data is actually recorded on the outer peripheral side from the radius r = 24 mm, and information and the like are recorded on the inner peripheral side from the radius r = 24 mm. In addition, the numerical value of a radial position is a thing in BD which has a capacity | capacitance of 23.3 GB.

  The grooves in the PIC area 2 and the data recording area 3 are wobble grooves formed by a superimposed signal of an MSK (Minimum Shift Keying) signal and an STW (Saw Tooth Wobble) signal. The MSK method is a wobble modulation method, in which addresses are concentrated and embedded at a specific position of a wobble composed of a sine wave.

  If information is concentrated and embedded in this way, it is affected when there is a defect in that portion, so the STW is multiplexed with the wobble of the MSK. The STW method is a method in which the wobble shape is a sawtooth wave shape, and address information “0” and “1” are determined by the direction of the teeth. The STW method has a feature that it is highly possible to repair even if a partial defect occurs because the same information is continuously arranged over a wide range. In the BD rewritable standard, it is possible to obtain address information having high resistance to errors by combining MSK and STW.

  The spot diameter d of the exposure beam is expressed by the following formula (1) by the wavelength λ of the exposure light source (laser) to be used and the numerical aperture NA of the objective lens for converging the light beam emitted from the light source on the photosensitive agent. .

  d = 1.22 X (λ / NA) (1)

  Table 1 summarizes the laser exposure wavelength (λ), track pitch (Tp), wobble amount (Wa), which is the amplitude in the disc radial direction, and the spot diameter (d) of the exposure beam in each of the above optical disc formats.

  As shown in Table 1, in a normal density optical disc of CD-R, CD-RW, DVD-R, DVD-RW, track pitch (Tp)> exposure beam diameter (d), and relatively easily, Each format (wobble groove) can be formed, and sufficient recording / reproduction characteristics and wobble reproduction characteristics can be obtained.

However, in a BD of a high-density optical disc, even when a 266 nm laser that is stable at a short wavelength is used, the track pitch Tp of the PIC region 2 is 350 nm and the track pitch Tp of the data recording unit 3 is 320 nm.
d (360 nm)> Tp (350 nm or 320 nm)
It becomes. That is, the exposure beam diameter (d)> track pitch Tp.

  From this relationship, the exposure beam leaks into the adjacent track. Depending on the phase relationship between adjacent wobble grooves, the wobble grooves may approach each other considerably, and the amount of leakage of the exposure beam to the adjacent track changes. Further, since the amount of leakage of the exposure beam into the land portion further changes due to wobble, the height of the land portion changes in the BD disc created in the steps of exposure, development, stamper creation, molding and the like.

  In the BD format, since the phase change recording film is used, if the groove depth is very shallow at about 23 nm and the land portion has a height change of about 2 to 3 nm, the height change amount is about 10%, and the wobble. It was difficult to obtain good reproduction characteristics with respect to the groove. Further, the change in the height of the land portion has a problem that the fluctuation of the push-pull signal used for the tracking servo is increased and the tracking servo becomes unstable.

  It is also conceivable to reduce the exposure beam diameter (d) by shortening the wavelength λ. For example, chemically amplified resists used in semiconductors for short-wavelength excimer lasers (wavelengths in the 200 nm range) react with amines in the air for chemical amplification in applications that require 1 to 3 hours, such as optical disk exposure. The reaction stability was impaired, and after development, the groove width change was large, the fluctuation of the push-pull signal was increased, and the tracking servo was made unstable.

  Accordingly, an object of the present invention is to provide an optical disc stamper manufacturing method, an optical disc stamper, and an optical disc stamper capable of suppressing a change in height of a land portion due to leakage of an exposure beam to an adjacent track or land during exposure for forming a wobble groove. To provide an optical disc.

In order to solve the above-described problem, a first aspect of the present invention includes a first region (rectangular wobble groove) having a wobble groove, the diameter of the exposure beam being larger than the pitch of the wobble groove, and the second In an optical disc stamper manufacturing method of an optical disc format having a region (superimposed wobble groove or sine wave wobble groove of sine wave and saw wave), wherein the pitch of the first region is larger than the pitch of the second region,
The land portion height change amount / average groove depth in the first region is approximately 0.083 or less, and the land portion height change amount / average groove depth in the second region is approximately 0.047. An optical disc stamper manufacturing method is characterized by the following.

The second aspect of the present invention includes a first region (rectangular wobble groove) having a wobble groove and a diameter of an exposure beam larger than the pitch of the wobble groove and a second region (superposition of a sawtooth wave and a sawtooth wave). In an optical disc stamper of an optical disc format having a wobble groove or a sine wave wobble groove), wherein the pitch of the first region is larger than the pitch of the second region,
The land portion height change amount / average groove depth in the first region is approximately 0.083 or less, and the land portion height change amount / average groove depth in the second region is approximately 0.047. An optical disc stamper characterized by the following.

The third aspect of the present invention includes a first region (rectangular wobble groove) having a wobble groove and a diameter of an exposure beam larger than the pitch of the wobble groove, and a second region (superposition of a sawtooth wave and a sine wave). In an optical disc of an optical disc format having a wobble groove or a sine wave wobble groove), wherein the pitch of the first area is larger than the pitch of the second area,
The land portion height change amount / average groove depth in the first region is approximately 0.083 or less, and the land portion height change amount / average groove depth in the second region is approximately 0.047. An optical disc characterized by the following.

According to a fourth aspect of the present invention, there are provided a first region (rectangular wobble groove) and a second region (sine wave and superposition of a sawtooth wave) having a wobble groove and having an exposure beam diameter larger than the pitch of the wobble groove. In an optical disc stamper manufacturing method of an optical disc format having a wobble groove or a sine wave wobble groove), wherein the pitch of the first region is larger than the pitch of the second region,
When the range of the wobble groove width change in the first region is 100%, the range of the wobble groove width change in the second region is 93.8% to 100%. The optical disc stamper manufacturing method is characterized in that the desired width is 98.1% to 100%.

According to a fifth aspect of the present invention, there are provided a first region (rectangular wobble groove) and a second region (sine wave and superposition of a sawtooth wave) having a wobble groove and the exposure beam diameter being larger than the pitch of the wobble groove. In an optical disc stamper of an optical disc format having a wobble groove or a sine wave wobble groove) and the pitch of the first area is larger than the pitch of the second area,
When the range of the wobble groove width change in the first region is 100%, the range of the wobble groove width change in the second region is 93.8% to 100%. An optical disc stamper characterized in that the desired width is 98.1% to 100%.

According to a sixth aspect of the present invention, there are provided a first region (rectangular wobble groove) and a second region (sine wave and superposition of a sawtooth wave) having a wobble groove and having an exposure beam diameter larger than the pitch of the wobble groove. In an optical disc of an optical disc format having a wobble groove or a sine wave wobble groove), wherein the pitch of the first area is larger than the pitch of the second area,
When the range of the wobble groove width change in the first region is 100%, the range of the wobble groove width change in the second region is 93.8% to 100%. In the case of a desired width, the optical disk is characterized by being 98.1% to 100%.

  According to the present invention, since the change in the height of the land portion of the wobble groove is suppressed, it is possible to obtain an optical disc having good recording / reproduction characteristics such as recording jitter, reproduction jitter, and push-pull signal characteristics. Further, no special one is required as the wavelength of the exposure beam and the type of resist, and the manufacturing cost can be relatively low.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A recording medium according to an embodiment is obtained by applying the present invention to a BD format as shown in FIG. In the BD, a groove track composed of an array of 2000 nm track pitch grooves in the BCA area 1, a groove track composed of a rectangular wobble groove array of 350 nm track pitch in the PIC area 2, and a 320 nm track pitch wobbling groove in the data recording area 3. The groove track is formed to be continuous in one spiral on the substrate surface.

  The BCA region 1 is formed with a radius r = 21.3 [mm] to 22.0 [mm], and the PIC region 2 is formed with a radius r = 22.4 [mm] to 23.2 [mm]. Thus, the data recording area 3 is formed with a radius r = 23.2 [mm] to 58.6 [mm].

  As described above, the BCA region non-wobble groove (2000 nm track pitch) can be formed relatively easily. According to the BD format standard, the rectangular wobble groove (350 nm track pitch) in the PIC area 2 must reproduce a rectangular signal of biphase modulation with a jitter of 4.5% or less.

  The wobble groove in the data recording area 3 must reproduce the wobble address information signal of each of the superimposed signals of the MSK of 956.522 [kHz] and the STW of the second harmonic wave. In order to reproduce each wobble address information signal, the secondary distortion of the wobble reproduction signal of MSK and STW must be -12 dB or less. Further, the track pitch of the data recording area 3 is as very small as 320 nm, and the fluctuation of the push-pull signal used for tracking servo must be 15% or less.

  In one embodiment, an exposure that can satisfy such characteristics is performed. In one embodiment, when forming a stamper for transferring each desired concavo-convex pattern onto the surface of a disk substrate in the manufacturing process of an optical disk, the laser intensity of the laser beam emitted from the light source is modulated by an APC (Auto Power Controller). For example, feedback control is performed on a device such as an EOM (Electro Optic Modulator), and the light output of the laser beam that passes through the EOM is linearly changed according to the linear velocity according to the radius, thereby making the exposure amount per unit area constant. Further, this is an example in which a shape pattern having a uniform groove width is formed using a stable novolac positive resist.

  First, an optical recording apparatus used in one embodiment will be described with reference to FIG. The laser cutting apparatus shown in FIG. 2 is for exposing a photoresist layer 11 formed on a glass master 10 to form a groove latent image on the photoresist layer 11.

  When forming a latent image on the photoresist layer 11, the glass master 10 is attached to a turntable 12 provided on the moving optical table 20. When the photoresist layer 11 is exposed, the turntable 12 is rotationally driven and translated by the moving optical table 20 so that the entire surface of the photoresist layer 11 is exposed in a desired pattern. . The Dallas master 10 is rotated at a constant linear velocity, for example.

  The recording laser light is generated from the laser light source 14. Any light source 14 can be used, but a light source that emits short-wavelength laser light is preferable. Specifically, for example, a laser source that oscillates a recording laser beam of the fourth harmonic (λ = 266 nm) of a YAG laser is used.

  The laser light emitted from the light source 14 travels straight as a parallel beam, enters the EOM 15 that is a modulator utilizing the electro-optic effect, and is intensity-modulated by the EOM 15. The laser beam whose intensity is modulated by the EOM 15 enters the beam splitter BS1 for optical path separation.

  A part of the laser light transmitted through the beam splitter BS1 enters a photodetector (PD) 16 disposed on the transmission optical path. The laser beam reflected by the beam splitter BS1 is further reflected by the mirror M2 and guided to the wobble optical system of the moving optical table 20.

The laser light incident on the photodetector 16 is converted into an electric signal by the photodetector 16, and an output signal of the photodetector 16 is supplied to an optical output control unit (APC) 17, and an output signal of the optical output control unit 17. Is supplied to the EOM 15 as a control signal. The EOM 15 modulates the intensity of the recording laser light emitted from the light source 14 in accordance with the signal electric field of the control signal supplied from the light output control unit 17.

  In this way, a part of the laser light is detected by the photodetector 16, and the optical output control unit 17 performs feedback control on the EOM 15 based on this, thereby stabilizing the optical output of the laser light that passes through the EOM 15. It is made to let you. By such a control system, the output of the reflected light of the beam splitter BS1 is also stable and can be recorded while the exposure amount per unit area is kept constant. The amount of change in exposure can be suppressed to within ± 2.0%, for example.

  The laser beam reflected by the mirror M2 and guided horizontally onto the moving optical table 20 is optically deflected by wedge prisms 21 and 23 and an acoustic optical modulator / acoustic deflector (AOM / AOD) 22. Is applied to the beam expander (BEX) 26.

  Two wedge prisms 21 and 23 and one acousto-optic modulator / acoustic deflector (AOM / AOD) 22 are arranged on the moving optical table 20. The wedge prisms 21 and 23 and the acousto-optic modulation deflector 22 are arranged so that the laser beam and the grating surface incident as parallel beams satisfy the Bragg condition and the beam horizontal height does not change. Yes. As the acoustooptic element used in the acoustooptic modulation deflector 22, tellurium oxide (TeO2) is suitable.

  The acousto-optic modulation deflector 22 is for applying an optical deflection to the laser beam so as to correspond to the wobble of the groove. That is, the laser light is incident on the acousto-optic modulation deflector 22 via the wedge prism 21 and is optically deflected by the acousto-optic modulation deflector 22 so as to correspond to a desired exposure pattern. The laser beam optically deflected by the acoustooptic modulation deflector 22 is emitted through the wedge prism 23.

A predetermined drive signal is supplied from the driver 24 to the acousto-optic modulation deflector 22. The driver 24 is supplied with a high-frequency signal from a voltage controlled oscillator (VCO) 25. A control signal is supplied to the voltage controlled oscillator 25.

  The control signal for the voltage controlled oscillator 25 is a zero-level direct current (DC) signal when forming a DC groove in the BCA region. In the case of forming a rectangular wobble groove in the PIC area, the control signal is a bi-phase modulated rectangular signal having a half frequency. In the case of forming a wobble groove in the data recording area, it is a superimposed signal of 478 [kHz] MSK of half frequency and STW of double wave. The superimposed signal of 478 [kHz] MSK and the second harmonic STW records wobble information of (MSK, STW) addresses.

  The acoustooptic modulation deflector 22 utilizes the fact that the first-order diffracted light intensity in Bragg diffraction is approximately proportional to the ultrasonic power, and modulates the ultrasonic power based on the recording signal to modulate the laser light. I do. In order to realize Bragg diffraction, the Bragg condition; 2 d sin θ = nλ (where d: lattice spacing, λ: laser beam wavelength, θ: angle between laser beam and lattice plane, n: integer) The positional relationship and attitude of the acousto-optic modulation deflector 22 with respect to the optical axis of the laser light are set.

  The laser light optically deflected by the wedge prisms 21 and 23 and the acoustooptic deflector 22 is incident on a beam expander (BEX) 26. The beam expander (BEX) 26 can convert the beam diameter. For example, the beam expander 26 expands the beam diameter (6 times, 4 times, 2 times).

  The laser light is enlarged to a predetermined beam diameter by a beam expander (BEX) 26, reflected by the mirror M 3, guided to the objective lens 27, and condensed on the photoresist layer 11 by the objective lens 27. The objective lens 27 for condensing the laser light on the photoresist layer 11 preferably has a large numerical aperture NA so that a finer groove pattern can be formed. An objective lens having an NA of about 0.9 is suitable.

  The photoresist layer 11 is exposed by laser light, and a latent image is formed on the photoresist layer 11. At this time, the glass master 10 coated with the photoresist layer 11 is driven to rotate by the turntable 12 and the moving optical table 20 so that the entire surface of the photoresist layer 11 is exposed in a desired pattern. As a result, 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 layer 11.

  In the optical recording apparatus described above, a groove track composed of a groove array of 2000 nm track pitch in the BCA area, a groove track composed of a rectangular wobble groove array of 350 nm track pitch in the PIC area, and a sine wave wobble in the data recording area. The groove track, which is the wobbling groove, is formed on the photoresist layer 11 on the glass master 10 as one spiral pattern.

  In order to form such a groove pattern, the feed pitch of the moving optical table 20 is set to BCA while controlling the rotational speed of the turntable 12 so that the linear velocity in the longitudinal direction of the track is 2.64 [m / s]. The exposure is performed at 2000 nm in the area, 350 nm in the PIC area, and 320 nm in the data recording area.

  In this optical recording apparatus, the position of the moving optical table 20 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 data recording as described above are performed. The latent image of each groove pattern in the region is exposed to the photoresist on the glass master 10. Further, it is possible to change the feed pitch of the moving optical table 20 by controlling the operations of the feed servo 33 and the air slider 32 with reference to the wavelength detected by the laser scale 31 (for example, 0.78 [μm]). It is said that.

  In one embodiment, the feed pitch is gradually changed. The feed pitch is 2000 nm during the BCA region (radius r = 21.3 mm to 22.0 mm), and the feed pitch is gradually increased from 2000 nm to 350 nm during the track pitch transition region (radius r = 22.0 mm to 22.4 mm). To change. 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.

  By the laser beam modulated and deflected as described above, a latent image of a groove in a desired BCA area, PIC area, and data recording area is formed on the photoresist layer 11 on the glass master 10.

  Subsequently, the photoresist 11 on the glass master 10 is subjected to development processing, and the exposed portion of the resist is dissolved for development. More specifically, an undeveloped glass master 10 is placed on a turntable of a developing machine (not shown), and a developer is dropped on the surface of the master 10 while rotating together with the turntable 12, and a photoresist layer on the surface of the master 11 is developed. As a result, the groove in the BCA area (2000 nm track pitch), the rectangular wobble groove in the PIC area (350 nm track pitch), and the wobbling groove in which the MSK and STW overlap in the data recording area are formed into one spiral. A patterned resist glass master can be obtained.

  Next, a conductive film layer made of a nickel film is formed on the concavo-convex pattern of the optical disk master by an electroless plating method or the like. The optical disk master on which the conductive film layer is formed is attached to an electroforming apparatus, and a nickel plating layer is formed on the conductive film layer to have a thickness of about 300 ± 5 [μm] by an electric plating method. Subsequently, the nickel plating layer is peeled off from the glass plate with the nickel plating layer with a cutter or the like, and the photoresist on the nickel plating layer signal forming surface is washed with acetone or the like.

  As an example, stamper A (BEX 6 times), stamper B (BEX 4 times), and stamper C (BEX 2 times) are manufactured. Further, a mother stamper A (BEX 6 times), a mother stamper B (BEX 4 times), and a mother stamper C (BEX 2 times) in which the unevenness is reversed are produced.

  Next, an evaluation disk is created. The manufacturing method is such that the mother stampers A, B, and C are made by injection molding using a transparent resin of polycarbonate (refractive index: 1.59) to form the disk substrates A, B, and C, and the groove uneven pattern formed on the signal forming surface is formed. Transcript.

As shown in FIG. 3, a light reflecting layer 42 made of an Al alloy or the like is formed on the signal forming surface of a 1.1 mm thick molded substrate 41. A first dielectric layer 43 made of SiO ₂ or the like on the light reflecting layer 42, a phase-change recording layer 44 made of GeSbTe alloy, a second dielectric layer 45 made of SiO ₂ or the like are sequentially formed by sputtering A recording layer comprising a light reflecting layer, a first dielectric layer, a phase change recording layer, and a second dielectric layer is formed.

  A PSA is applied to the second dielectric layer 43 by spin coating to a thickness of 20 nm, and a PSA + polycarbonate sheet cover layer 46 of PSA + polycarbonate sheet is formed by curing the PSA by applying pressure to a polycarbonate sheet having a thickness of 80 μm with a roller. It is formed. A recording / reproducing laser beam is irradiated from the cover layer 46 side. The BD format discs A, B, and C are completed through the above steps.

  The evaluation results of the disc created as described above will be described. As an example, the evaluation work of the optical disk A, the optical disk B, and the optical disk C is evaluated using a Blu-ray Disc evaluation machine equipped with an optical pickup (laser wavelength 406 nm, NA = 0.85). Recording and reproduction of data modulated by 1-7 modulation was performed on the wobble groove portion (recording area close to the reading surface) of the three types of optical discs A, B, and C, and the evaluation data is shown in Table 2 below.

In Table 2, G spec indicates a value within an allowable range defined by the standard. “Jitter”, the standard for the PIC area leading and jitter The “trailing” indicates in% how much the playback wobble signal rises and falls with respect to the reference window in terms of time. It is specified to be less than 4.5%.

In the data area (radius position 45mm), “NPPnorm min "," NPPnorm dev "," NWS “min” and “before CNR” are specified. "NPPnorm min "and" NPPnorm “dev” means the minimum value and amplitude fluctuation value of the normalized push-pull signal. "NPPnorm “min” must have a value in the range of 0.21 to 0.45, and “NPPnorm "dev" needs to be 0.15 or more. "NWS “min” means the minimum value of the normalized wobble signal. "NWS “min” needs to have a value in the range of 0.20 to 0.56. “Before CNR” means a CNR (carrier noise ratio) of a wobble signal. “Before CNR” should be high.

  “SHD / SHL” means second-order distortion of MSK and STW, and the standard requires that it be smaller than −12 dB. Furthermore, “Rec.Jitter” means recording jitter. According to the standard, the radial position (R) is required to be smaller than 6.5% at each position of 25 mm, 45 mm, and 55 mm.

  In the evaluation data shown in Table 2, the underlined data indicates values that do not satisfy the standard. As can be seen from Table 2, the optical disc A and the optical disc B have good reproduction jitter and recording jitter of the PIC wobble signal, and can realize good recording and reproduction characteristics. In addition, the amount of fluctuation of the push-pull signal is small and a stable tracking servo is realized. Further, the second order distortion (SHD / SHL) of MSK and STW sufficiently satisfies the standard, and it is possible to stably reproduce the wobble address information of the wobble groove.

  However, the optical disc C has poor reproduction jitter of the PIC wobble signal, the amplitude fluctuation value of the push-pull signal is outside the standard, and the secondary distortion of MSK and STW does not satisfy the standard.

The wobble groove shape of the optical disk was measured by an AFM (Atomic Force Microscope). The change in height of the land portion due to wobble was different in the above-described three types of optical disks. The wobble amplitude in the PIC region was ± 22 nm, and the wobble amplitude in MSK & STW was ± 11 nm. Table 3 below shows the measurement results of the change in height of the land portion due to wobble.

  From the measurement results shown in Table 3, the optical disk A and the optical disk can be obtained when the height change amount of the land portion due to wobble is within the allowable range of 1.9 nm or less for the PIC area and 1.1 nm or less for the data area (MSK & STW). In B, it can be seen that stable recording and reproduction is performed. The groove depth is 24 nm at the deep part (the part where the adjacent wobble is separated), and the shallow part (the part where the adjacent wobble approaches) is shallow by the height change amount of the land part due to the wobble. That is, in the portion where the groove depth of the optical disc B is shallow, the PIC area is 22.1 nm and the data portion is 22.9 nm. The average groove depth of the optical disc B is 23 nm in the PIC area and 23.5 nm in the data area.

  From the result of the evaluation described above, in order to perform stable recording / reproduction like the optical disc A and the optical disc B, the relationship of (the height change amount of the land portion due to wobble / the average groove depth) is expressed by the following formula ( It is necessary to satisfy what is shown in 2).

PIC region: 1.9 nm / 23 nm = 0.083
Data area: 1.1 nm / 23.5 nm = 0.047

  A laser light source of a fourth harmonic of a YAG laser having a wavelength of 266 nm, an objective lens having a numerical aperture NA = 0.9, and a stable novolac resist are used. The beam diameter of the 266 nm laser is 0.9 mm, and the beam expander BEX 26 expands the beam diameter by 6 times, 4 times, and 2 times, and the beam diameter before entering the objective lens 27 is 5 times. 4 mm, 3.6 mm, and 1.8 mm. The aperture of the objective lens 27 is 3.6 mm. When the expansion ratio of the beam expander BEX 26 is 6 times or 4 times and the beam diameter in front of the objective lens 27 is 5.4 mm or 3.6 mm, respectively, the reproduction jitter of the PIC wobble signal, MSK and STW 2 BD standards such as second order distortion (SHD / SHL) can be satisfied.

  That is, sufficient characteristics can be obtained when (the beam diameter before the objective lens / the aperture of the objective lens) has the following relationship.

  (5.4 to 3.6) mm / 3.6 mm = 1.5 to 1.0

  Furthermore, if the AOD frequency changes due to wobble due to the wobble asymmetry of the AOD constituting the acousto-optic modulation deflector 22 or the off-axis characteristics of the objective lens 27, it is emitted from the objective lens 27 as shown in FIG. The exposure power to be changed changes, and the groove width of the formed wobble groove changes. In the example of FIG. 4, the maximum exposure power is 0.287 mW at 224 MHz and 225 MHz. The power value is normalized by (exposure power / maximum exposure power) × 100 [%].

  The values corresponding to the power of FIG. 4 and the normalized power frequency are shown in Table 4 below.

  Focusing on the wobble asymmetry of the AOD and off-axis characteristics of the objective lens 27, three types of evaluation optical discs (disc D, disc E, and disc F) having different groove width changes are produced. The groove width change was evaluated, and the results of the evaluation are shown in Tables 5 and 6 below. Table 5 shows the groove width variation of the evaluation optical disk, and Table 6 shows the evaluation data.

  As an example, the change in AOD frequency due to wobble in the PIC area is ± 4 MHz, and the change in AOD frequency due to wobble in the data area MSK and STW is ± 2 MHz.

  In the case of the optical disc D, the center frequency is 224 MHz, the AOD frequency due to wobble in the PIC area is 220 MHz and 228 MHz, and the exposure power is 0.267 mW (93%) and 0.285 mW (99.3%), as a result. The groove width is 145 nm and 162 nm. In addition, the AOD frequency due to the wobble of the MSK and STW in the data area is 222 MHz and 226 MHz, and the exposure power is 0.281 mW (97.9%) and 0.286 mW (99.7%). As a result, the groove width As shown in Table 5, the changes are 154 nm and 164 nm.

Thus, in the case of the optical disk D in which the groove width changes, as can be seen from the underlined data in Table 6, the reproduction jitter and recording jitter of the PIC wobble signal are poor, and the push-pull signal fluctuation (NPPnorm dev), wobble secondary distortion (SHD / SHL) characteristics are poor and does not meet the standards.

  In the case of the optical disc E, the center frequency was set to 225 MHz. The frequency of AOD due to wobble in the PIC area is 221 MHz and 229 MHz, the exposure power is 0.275 mW (95.8%), 0.284 mW (99.0%), and as a result, the groove width is 151 nm and 161 nm. In addition, the AOD frequency due to the wobble of MSK and STW in the data area is 223 MHz and 227 MHz, and the exposure power is 0.285 mW (99.3%) and 0.286 mW (99.7%). As a result, the groove width is As shown in Table 5, the changes are 160 nm and 162 nm.

  In the case of the optical disk E in which the groove width changes in this way, the standard is sufficiently satisfied as can be seen from the data in Table 6. That is, the reproduction jitter and recording jitter of the PIC wobble signal are good, a good recording / reproduction characteristic can be realized, the fluctuation amount of the push-pull signal is small, a stable tracking servo can be realized, and the MSK and STW The secondary distortion (SHD / SHL) sufficiently satisfied the standard, and the wobble address information of the wobble groove could be stably reproduced.

  Further, in the case of the optical disk F, the center frequency is set to 226 MHz. The AOD frequency due to wobble in the PIC area is 222 MHz and 230 MHz, the exposure power is 0.281 mW (97.9%), and 0.283 mW (98.6%). As a result, the groove width is 155 nm and 160 nm. Also, the AOD frequency due to the MSK and STW wobbles in the data area is 224 MHz and 228 MHz, and the exposure power is 0.287 mW (100%) and 0.285 mW (99.3%), resulting in a change in groove width. As shown in Table 5, they are 158 nm and 161 nm.

  Thus, in the case of the optical disk F in which the groove width changes, as can be seen from the data in Table 6, the standard is sufficiently satisfied as in the optical disk E.

  Here, paying attention to the change in the groove width, when the fluctuation ratio of the groove width (smaller groove width / larger groove width) is obtained in the optical discs D, E, and F described above, the following table 7 is obtained. Become.

  From the above results, when the groove width change of the wobble in the PIC area is (93.8 to 100%), a characteristic that sufficiently satisfies the standard can be obtained. Further, when the groove width change of the wobbles of the MSK and STW in the data area is (98.1 to 100%), a characteristic that sufficiently satisfies the standard can be obtained.

As described above, one embodiment of the present invention uses a fourth-order harmonic laser light source of a YAG laser with a wavelength of 266 nm and an objective lens with a numerical aperture NA = 0.9 to optimize the wobble optical system according to the format. By using a stable novolak resist, the height change of the land due to wobble is made 1.9 nm or less, and the wobble reproduction characteristics (PIC)
Jitter, MSK & STW wobble reproduction) and push-pull signal fluctuation amounts can be achieved.

  The embodiment of the present invention has been specifically described above, but 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. For example, the numerical values given in the above-described embodiment are merely examples, and different numerical values may be used as necessary. Further, the configuration of the cutting device can be other than the configuration shown in FIG.

It is a basic diagram which shows the format of the high-density disk which can apply this invention. It is a basic diagram which shows an example of the optical recording apparatus (optical cutting apparatus) which can apply this invention. It is sectional drawing which shows the structure of the high density disk which can apply this invention. It is a graph which shows the change of the power with respect to the frequency of the acousto-optic deflector (AOD) which can be used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... BCA area | region 2 ... PIC area | region 3 ... Data recording area 10 ... Resist board | substrate 11 ... Resist layer 12 ... Turntable 13 ... Spindle servo 14 ... Laser light source 15 (EOM) ... Electro-optic modulator 16 (PD) ... Photo detector 20 ... Moving optical table 21, 23 ... Wedge prism 22 ... Acousto-optic deflector (AOD)
24 ... Driver 25 ... Voltage frequency controller (VCO)
26 (BEX) ··· Beam expander
27 ... Objective lens 30 ... Position sensor 31 ... Laser scale 32 ... Air slider 33 ... Feed servo

Claims (13)

A first area (rectangular wobble groove) having a wobble groove and a diameter of the exposure beam larger than the pitch of the wobble groove and a second area (overlapped wobble groove or sine wave wobble groove). In the optical disc stamper manufacturing method of the optical disc format, wherein the pitch of the first region is larger than the pitch of the second region,
The land portion height variation / average groove depth in the first region is approximately 0.083 or less, and the land portion height variation / average groove depth in the second region is approximately 0. 0.047 or less, a method of manufacturing an optical disc stamper. In claim 1,
A method of manufacturing an optical disc stamper, characterized in that a change in height of a land portion due to wobble in the first region is 1.9 nm or less. In claim 1,
A method of manufacturing an optical disc stamper, characterized in that a change in height of a land portion due to wobble in the second region is 1.1 nm or less. In claim 1,
A method for producing an optical disc stamper, comprising exposing a novolac positive resist with an exposure beam wavelength of 266 nm. A first area (rectangular wobble groove) having a wobble groove and a diameter of the exposure beam larger than the pitch of the wobble groove and a second area (overlapped wobble groove or sine wave wobble groove). An optical disc stamper having an optical disc format in which the pitch of the first region is larger than the pitch of the second region;
The land portion height variation / average groove depth in the first region is approximately 0.083 or less, and the land portion height variation / average groove depth in the second region is approximately 0. An optical disc stamper characterized by being 0.047 or less. In claim 5,
An optical disc stamper characterized in that a height change amount of a land portion due to wobble in the first region is 1.9 nm or less. In claim 5,
An optical disc stamper characterized in that a height change amount of a land portion due to wobble in the second region is 1.1 nm or less. A first area (rectangular wobble groove) having a wobble groove and a diameter of the exposure beam larger than the pitch of the wobble groove and a second area (overlapped wobble groove or sine wave wobble groove). An optical disc having an optical disc format in which the pitch of the first region is larger than the pitch of the second region;
The land portion height variation / average groove depth in the first region is approximately 0.083 or less, and the land portion height variation / average groove depth in the second region is approximately 0. .047 or less, an optical disc characterized by In claim 8,
An optical disc characterized in that the amount of change in height of a land portion due to wobble in the first region is 1.9 nm or less. In claim 8,
An optical disc characterized in that the amount of change in height of a land portion due to wobble in the second region is 1.1 nm or less. A first area (rectangular wobble groove) having a wobble groove and a diameter of the exposure beam larger than the pitch of the wobble groove and a second area (overlapped wobble groove or sine wave wobble groove). In the optical disc stamper manufacturing method of the optical disc format, wherein the pitch of the first region is larger than the pitch of the second region,
When the range of the wobble groove width change in the first region is set to a desired width of 100%, it is 93.8% to 100%. The range of the wobble groove width change in the second region is 100%. An optical disk stamper manufacturing method, wherein the desired width is 98.1% to 100%. A first area (rectangular wobble groove) having a wobble groove and a diameter of the exposure beam larger than the pitch of the wobble groove and a second area (overlapped wobble groove or sine wave wobble groove). An optical disc stamper having an optical disc format in which the pitch of the first region is larger than the pitch of the second region;
When the range of the wobble groove width change in the first region is set to a desired width of 100%, it is 93.8% to 100%. The range of the wobble groove width change in the second region is 100%. An optical disc stamper characterized by being 98.1% to 100% when% is a desired width. A first area (rectangular wobble groove) having a wobble groove and a diameter of the exposure beam larger than the pitch of the wobble groove and a second area (overlapped wobble groove or sine wave wobble groove). An optical disc having an optical disc format in which the pitch of the first region is larger than the pitch of the second region;
When the range of the wobble groove width change in the first region is set to a desired width of 100%, it is 93.8% to 100%. The range of the wobble groove width change in the second region is 100%. An optical disc characterized by being 98.1% to 100% when% is a desired width.

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