JP4396230B2 - Optical recording method, master for manufacturing optical recording medium, and optical recording medium - Google Patents

Description

  The present invention relates to an optical recording method for forming (drawing) a recording pattern corresponding to an irradiation locus of laser light 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 also relates to an optical recording medium manufacturing master suitable for use in forming pits and grooves on an optical recording medium. Furthermore, the present invention relates to an optical recording method and an optical recording medium produced by an optical recording medium master.

  Optical recording media are pre-formed with discrete information patterns and tracking guide grooves (grooves) as preformats typified by CD (Compact Disc) and other reproduction-only optical discs and MD (Mini Disc) and the like. Various optical discs such as a writable optical disc have been proposed.

  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.

  Recently, recording media such as DVD-RW (Digital Versatile Disc-rewritable) have been remarkably developed, and a technology for controlling the shape of pits and grooves of such optical recording media with higher accuracy is desired.

  A DVD-RW format, which is an optical disc to which the present invention can be applied, will be described with reference to FIG. FIG. 1 is an enlarged view of a part of the DVD-RW format. The direction toward the right side as viewed in FIG. 1 is the direction toward the outer periphery of the disk, and the direction toward the left side is within the disk. It is a direction toward the circumferential side. FIG. 1 is a schematic diagram, and the number of tracks does not indicate the actual number.

The DVD-RW has a so-called readable embossed pit (hereinafter also abbreviated as REP) 1 in which information such as TOC (Table of Contents) information or a pulse signal having a predetermined period is recorded as information on the disc itself. And two types of pit areas, a so-called unreadable embossed pit (hereinafter sometimes abbreviated as URE) 2 in which copy protection information and the like are recorded, and a wobble groove 3 which is a data recording area Are formed on the substrate. As shown in FIG. 1, in the DVD-RW format, the area where the pits are formed and the wobble groove are mixed.

  The depth of the pits is preferably λ / 4 with respect to the wavelength λ of the reproduction light. Further, when forming the recording layer, the dielectric layer, etc., the direction along the recording track and the disc Since it is embedded in the radial direction, a certain depth is required. On the other hand, with respect to the groove, for example, when the recording layer is made of a phase change material, it has been found that the phase change signal improves jitter when the groove is made relatively shallow. Therefore, the leader emboss pit 1 is relatively deep and the groove 3 is relatively shallow.

  DVD-RW is a complex format and must satisfy many standards and characteristics. For example, in the readable emboss pit 1, it is necessary to obtain reproduction characteristics (jitter − ≦ 8.0%) and a sufficient push-pull signal amount (≧ 0.22). Further, it is necessary to obtain the recording / reproduction characteristics (recording jitter− ≦ 8.0%) of the wobble groove 3 as a recording area and a sufficient push-pull signal amount (≧ 0.22) of the wobble groove.

  In the following Patent Document 1, the above standards and characteristics are obtained by forming a readable embossed pit 1 having a deep U-shaped radial cross-sectional shape and a wobble groove 3 having a shallow U-shaped radial cross-sectional shape. It is disclosed that a push-pull signal amount sufficient to satisfy the above can be obtained.

JP 2002-22548 A

  However, the DVD-RW standard satisfies the standard in which the ratio (EPPr1) between the push-pull signal amount of the readable embossed pit 1 and the push-pull signal amount of the wobbled groove at a position of a radius of 25 mm is 3 dB or less. The push-pull signal amount needs to be stably increased, and the reproduction characteristics of the readable emboss pit 1 must be obtained. Unreachable embossed pits must also have a sufficient amount of push-pull signal and pit signal reproduction.

  Furthermore, in DVD-R and DVD-RW, a land pre-pit format in which pre-pits are provided in lands between adjacent grooves is employed. Land pre-pits (hereinafter sometimes abbreviated as LPP) are detected by reading a difference signal of a light receiving element divided into two in the disk radial direction. As a method for forming the land pre-pit, a method using a laser beam for forming a groove has been proposed.

  That is, the land prepit can be formed by temporarily displacing the laser beam for forming the groove to the outer peripheral side at the position where the land prepit is to be formed. In FIG. 1, reference numeral 4 indicates a trapezoidal wobble groove formed by changing the groove into a trapezoidal shape in this way. In order to reproduce the address information by the trapezoidal wobble groove 4, it is necessary to obtain a sufficient LPP signal amplitude and realize an LPP shape satisfying a PI (Parity Inner-code) error.

  The object of the present invention is to meet the standards of high-density optical discs such as DVD-RW by optimizing the depth and width of readable embossed pits, optimizing the shape of unreadable embossed pits, and optimizing the shape of LPP. A recording method, a master for manufacturing an optical recording medium, and an optical recording medium.

In order to solve the above-mentioned problem, the first aspect of the present invention is:
First and second embossed pits comprising a groove-like groove on the substrate and a plurality of pits discretely arranged in the circumferential direction, and a third formed in association with the groove to be wobbled An optical recording method for producing a master for producing a phase change optical recording medium in which a trapezoidal wobble groove is formed,
The third trapezoidal wobble groove of the phase change optical recording medium is configured as a trapezoidal wobble formed by protruding a part of the groove,
The length of the base of the third wobble is 6T-11T,
The depth of the third wobble is -3 nm to +4 nm of the recording area groove portion depth,
This is an optical recording method for producing a master for manufacturing a phase change optical recording medium so that the third wobble amplitude / track pitch ratio is 16.5-27.7%.

The second aspect of the present invention is:
First and second embossed pits comprising a groove-like groove on the substrate and a plurality of pits discretely arranged in the circumferential direction, and a third formed in association with the groove to be wobbled a production master of the phase-change optical recording medium for the production of trapezoidal phase-change optical recording medium and the wobble grooves are formed,
The third trapezoidal wobble groove of the phase change optical recording medium has a trapezoidal pit configuration formed by protruding a part of the groove,
The length of the base of the third wobble is 6T-11T,
The depth of the third wobble is -3 nm to +4 nm of the recording area groove portion depth,
The ratio of the amplitude of / track pitch of the third wobble is producing a master for the phase-change optical recording medium is 16.5-27.7%.

The third aspect of the present invention is:
First and second embossed pits comprising a groove-like groove on the substrate and a plurality of pits discretely arranged in the circumferential direction, and a third formed in association with the groove to be wobbled A phase change optical recording medium in which a trapezoidal wobble groove is formed,
The third trapezoidal wobble groove has a trapezoidal pit configuration formed by protruding a part of the groove,
The length of the base of the third wobble is 6T-11T,
The depth of the third wobble is -3 nm to +4 nm of the recording area groove portion depth,
The phase change optical recording medium has a third wobble amplitude / track pitch ratio of 16.5 to 27.7%.

  In the present invention, by optimizing the depth and width of the readable emboss pit REP, a sufficient push-pull signal amount of the readable emboss pit can be obtained to satisfy the EPPr1 standard and to satisfy the reproduction characteristics.

  The unreachable embossed pit URE can reduce a sufficient push-pull signal amount and unreachable embossed pit signal amplitude by optimizing the pit depth and increasing the pit duty (ratio).

  Furthermore, a trapezoidal wobble groove is used to reproduce the address information by the land prepit LPP. The trapezoidal wobble groove can be an optical system that uses only one exposure beam in an optical recording device, and the readable embossed pit, unreadable embossed pit, land prepit and groove are arranged along a series of spiral recording tracks. Can be formed. By making the wobble amplitude amount and the shape of the trapezoid wobble groove in the trapezoidal wobble groove appropriate, a sufficient LPP signal amplitude amount can be obtained, and the PI error after reproducing and recording the LPP address information can be satisfied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In order to manufacture the optical recording medium described above, it is necessary to prepare an optical recording medium manufacturing master serving as a master of the optical recording medium. For this purpose, a laser cutting device is used as an optical recording device. Hereinafter, an example of a laser cutting apparatus used for producing an optical recording medium manufacturing master will be described in detail with reference to FIG. Reference numeral 10 indicates an example of a laser cutting apparatus as a whole.

  In the manufacturing process of the optical recording medium, a laser beam emitted from the light source 11 is used when forming an optical recording medium manufacturing master for transferring each desired uneven pattern onto the surface of the optical recording medium substrate. The light source 11 is not particularly limited and may be appropriately selected and used, but a Kr laser that emits laser light having a wavelength λ of 351 nm is used.

  The laser beam emitted from the light source 11 advances straight as a parallel beam, is reflected by the mirror BS1, and is guided to the modulation optical system OM. In the modulation optical system OM, a condensing lens L1 is used to collect light on an acousto-optic modulator (AOM) 14, and the laser light intensity-modulated and diverged by the acousto-optic modulator 14 is collimated by the lens L2. It becomes a beam 12. The exposure beam emitted from the modulation optical system (OM) is reflected by the mirror M1 and guided horizontally and parallel onto the moving optical table 15.

  The exposure beam emitted from the modulation optical system OM, reflected by the mirror M1, and guided horizontally and parallel on the moving optical table 15 is optically deflected by the deflection optical system OD and then reflected by the mirror M2. Then, after the traveling direction is bent by 90 °, the light enters the polarization beam splitter PBS.

  Here, the deflection optical system OD is for applying an optical deflection to the exposure beam so as to correspond to the wobble of the wobble groove. That is, the exposure beam emitted from the modulation optical system OM and incident on the deflection optical system OD is incident on an acousto optical deflector (AOD) 48 via a wedge prism 47, and the acousto-optic deflector 48 Optical deflection is performed so as to correspond to a desired exposure pattern.

  Here, as the acoustooptic element used for the acoustooptic deflector 48, for example, an acoustooptic element made of tellurium oxide (TeO2) is suitable. The exposure beam optically deflected by the acousto-optic deflector 48 is emitted from the deflection optical system OD via the wedge prism 49.

  The wedge prisms 47 and 49 allow the exposure beam to be incident on the grating surface of the acoustooptic device of the acoustooptic deflector 48 so as to satisfy the Bragg condition, and the acoustooptic deflector 48 applies the exposure beam to the exposure beam. This is to prevent the beam horizontal height from changing even if optical deflection is applied. In other words, the wedge prism 47, the acoustooptic deflector 48, and the wedge prism 49 satisfy the Bragg condition for the second exposure beam of the acoustooptic element of the acoustooptic deflector 48, and the deflection optical system. It arrange | positions so that the beam horizontal height of the exposure beam radiate | emitted from OD may not change.

  Here, a driving driver 50 for driving the acousto-optic deflector 48 is attached to the acousto-optic deflector 48. The driving driver 50 includes a voltage controlled oscillator (VCO). A high frequency signal from 51 is phase-modulated and supplied by a control signal including address information. When the photoresist 32 is exposed, a signal corresponding to a desired exposure pattern is input from the voltage controlled oscillator 51 to the driving driver 50, and the acoustooptic deflector 48 is driven by the driving driver 50 in accordance with the signal. Thereby, an optical deflection is applied to the second exposure beam.

  As shown in the following Equation 1, the groove can be widened by performing multiple exposure with a period in which the spatial frequency of the wobble (deflection) frequency is smaller than the radius of the recording beam.

  v · 1 / f <D

    Here, v is the linear velocity, f is the wobble frequency, and D is the beam spot diameter on the glass master.

  For example, in the case of DVD-RW, if v = 3.49 m / s and D = 200 nm, f> 17.45 MHz. However, since the normal wobble (deflection) frequency is 5 MHz or less, when the linear velocity v of recording (cutting) is ¼, v = (3.49 / 4.0 = 0.8725) m / s, D = 200 nm, f> 4.363 MHz, so that the wobble (deflection) frequency is 5 MHz and sufficient multiple exposure is possible.

  Specifically, for example, in the case of recording readable embossed pits and unreadable embossed pits, the groove is formed at a linear velocity v = 0.8725 m / s and a frequency (140.7 / 4.0 = 35.175) kHz. Wobble. When adding clock information to the groove, for example, a high frequency signal having a center frequency of 224 MHz and a control signal having a frequency of 35.175 kHz are supplied from the voltage controlled oscillator 51 to the driving driver 50. In accordance with this signal, the acousto-optic deflector 48 is driven by the driving driver 50, and the Bragg angle of the acousto-optic element of the acousto-optic deflector 48 is changed, thereby corresponding to a wobble with a frequency of 35.175 kHz. As described above, optical deflection is applied to the second exposure beam.

  When recording the wobble groove of the data recording unit, multiple exposure is performed using a wobble clock signal with a linear velocity v = 0.8725 m / s, a frequency of 35.175 kHz, and a high frequency superimposed signal of 5 MHz. In this case, for example, a high frequency signal having a center frequency of 224 MHz and a control signal having a frequency of 35.175 kHz + 5 MHz are supplied from the voltage controlled oscillator 51 to the driving driver 50. In accordance with this signal, the acousto-optic deflector 48 is driven by the driving driver 50, and the Bragg angle of the acousto-optic element of the acousto-optic deflector 48 is changed, whereby a wobble with a frequency of 35.175 kHz + 5 MHz is supported. As described above, an optical deflection is applied to the exposure beam. The width of the wobbled groove can be widened by performing multiple exposure of the high frequency superimposed signal of 5 MHz.

  The trapezoidal wobbled groove LPP is obtained by superimposing an LPP trapezoidal signal on a wobble signal having a frequency of 35.175 kHz + 5 MHz.

    Then, by such a deflection optical system OD, the second exposure beam subjected to the optical deflection is formed so as to correspond to the wobble groove wobble of the readable emboss pit, the unread emboss pit, and the data recording unit. The second exposure beam is reflected by the wobble mirror M2 and the traveling direction is bent by 90 °, and then enters the polarization beam splitter PBS. The exposure beam is reflected by the PBS. Here, the polarization beam splitter PBS reflects S-polarized light and transmits P-polarized light.

  Then, the exposure beam recombined so that the traveling direction is the same direction and emitted from the polarization beam splitter PBS is made a predetermined beam diameter by the magnifying lens L3 and then reflected by the mirror M3 to the objective lens 54. Led. The objective lens 54 collects the light on the photoresist 32. As a result, the photoresist 32 is exposed and a latent image is formed on the photoresist 32.

  The glass substrate 31 on which the photoresist 32 is applied is rotationally driven and moved by a rotational drive device as indicated by an arrow M in the drawing so that the entire surface of the photoresist 32 is exposed in a desired pattern. It is translated by the optical table 15. As a result, a latent image corresponding to the exposure beam irradiation locus is formed over the entire surface of the photoresist 32.

This time, the numerical aperture NA of the objective lens 54 is set to 0.9. The acoustooptic element of acoustooptic modulator 14 was tellurium oxide (TeO ₂ ). A signal is supplied to the acousto-optic modulator 14 from the input terminal via the driver 13.

In the recording apparatus (cutting apparatus) of FIG. 2, exposure patterns corresponding to readable embossed pits, unreadable embossed pits, and land prepit grooves are formed by a single laser beam. That is, the EFM (Eight to Fourteen Modulation: 8-16 modulation) + signal is supplied to the acousto-optic modulator 14 when forming a readable embossed pit. When an unreadable embossed pit is formed, This is a modified EFM + signal obtained by uniformly extending the EFM + signal. When a groove is formed, it is a DC signal at a constant level. The laser light is intensity-modulated (ON / OFF) by the EFM + signal or the modified EFM + signal.

  In the recording apparatus and the recording method described above, 1) the depth of the readable embossed pit can be optimized by changing the thickness of the photoresist, and the width of the readable embossed pit is appropriate for the exposure beam on the photoresist. Optimization is possible by using a large diameter.

  2) In the shape of the unreadable embossed pit, the depth is optimized by changing the power of the exposure beam and the pit duty (ratio) by changing the value of the modified EFM + modulation 1 described later and the length of the modified pit signal uniformly. Is possible.

  3) The shape of the LPP can be optimized by the exposure beam power, the amplitude of the trapezoidal wobbled groove LPP, the length, and the trapezoidal shape. With the above-described method, a format suitable for DVD-RW can be provided.

  Next, the results of producing a plurality of evaluation optical disks using the optical recording apparatus or recording method as described above and evaluating them will be described.

  The photoresist surface formed on the glass plate surface is exposed according to the recording signal, and the recording signal (readable embossed pit, unreadable embossed pit, trapezoidal wobble groove) is recorded on the photoresist, and the thickness of the photoresist. Optical disc A (75 nm), optical disc B (80 nm), and optical disc C (85 nm) were produced. The readable embossed pit widths were optical disk A (297 nm), optical disk B (321 nm), and optical disk C (348 nm).

With the assumption that unreadable embossed pits do not read data, the negative edge of the pit was adjusted to the extent that it does not become RLL (Run Length Limited) violence, and the duty (ratio of pits) was improved to about 70% ( (Modified EFM + Modulation) 1 is used. The pit length or space length is normally defined as 3T at the shortest and 11T at the longest. To the extent that it does not become violence means to observe this rule. Here, T is the length of one clock cycle of the digital signal recorded on the disc. For example, 1T≈38 nsec. On the disc, 1T≈133 nm.

  (Modified EFM + Modulation) 1 is a process for reversing the ratio of pits and spaces with respect to a modified EFM signal in which the ratio of pits is smaller than that of spaces in order to obtain a sufficient push-pull signal amount. For example, a 3T pit and 8T space signal is converted into an 8T pit and 3T space signal to increase the pit ratio. The 10T pit and 6T space signals are converted into 11T pit and 5T space signals to increase the pit ratio.

  Furthermore, the duty (pit ratio) was improved to about 75% by using (deformed EFM + modulation) 2 in which the signal of (deformed EFM + modulation) 1 was increased by one. The amount to be lengthened is selected from 0, 1T, 1.5T, and 2T. Furthermore, the exposure power was appropriately changed, and three types of optical discs having different unreadable emboss pit depths were produced. This is an optical disc A (25 nm), an optical disc B (31 nm), and an optical disc C (38 nm).

  The groove portion which is a storage area has GR1 (radius 23.95-30 mm), GR2 (radius 30-35 mm), GR3 (radius 35-40 mm), GR4 (radius 40-45 mm), GR5 (radius 45-50 mm), The LPP shape was changed by dividing into 6 zones of GR6 (radius 50-58.6 mm). The LPP shape is a trapezoidal wobble groove 4 as shown in FIG. 1, and the length 6 and depth of the base (long side) of the trapezoid and the wobble amplitude 5 are changed. For example, the LPP shape was measured with an atomic force microscope (AFM).

  The LPP shape of the optical disc A is a trapezoid LPP wobble groove depth of 26 nm, an LPP wobble amplitude of 152 nm, and the base length of the trapezoid LPP wobble is 5T for GR1, 6T for GR2, 8T for GR3, 10T for GR4, and GR5 for 11T and GR6 were set to 12T. The depth of the groove portion which is a recording area was 25 nm. The trapezoidal wobble LPP had a base length of 1330 nm and an upper base length of 916 nm, and the rising and falling edges of the trapezoidal wobble were about 200 nm (1.5 T).

  The LPP shape of the optical disc B is LPP wobble amplitude 151 nm, trapezoid LPP wobble bottom length is 8T, trapezoid LPP wobble groove depth is GR1 is 20 nm, GR2 is 22 nm, GR3 is 25 nm, GR4 is 27 nm, GR5 Was 29 nm and GR6 was 31 nm. The depth of the groove portion which is a recording area was 25 nm.

  The LPP shape of the optical disk C was a trapezoidal LPP wobble with a base length of 8T, an LPP wobble groove depth of 25 nm, an LPP wobble amplitude of GRm, GR5 of 205 nm, and GR6 of 238 nm. The depth of the groove portion which is a recording area was 24 nm.

  Subsequently, the glass plate is placed on the turntable of the developing machine so that the photoresist is on top, and the glass plate is rotated with respect to the horizontal plane. Thereafter, a developing solution is dropped on the photoresist to develop the photoresist. Thereby, an uneven pattern based on the recording signal is formed on the signal forming surface of the glass plate. Thus, an optical disc master made of a glass plate and a concavo-convex pattern formed on the signal forming surface of the glass plate is produced.

  Next, a conductive film layer made of a nickel film is formed on the concave / convex pattern of the optical disk master by electroless plating 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 by electroplating so as to have a thickness of about 300 ± 5 μm. 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 to produce three types of stamper A, stamper B, and stamper C. .

  Using these three types of stampers, molding is performed on a transparent resin of PC (polycarbonate) to form three types of PC molded substrates on which minute irregularities (pits and groove patterns corresponding to signals) are transferred.

  Next, as a film forming process, a recording layer and a protective layer are formed on a disk substrate on which the surface shape of the master for producing an optical recording medium is transferred. Specifically, for example, first, a first dielectric film made of SiN or the like, a phase change recording film made of GeSbTe alloy or the like, and a second made of SiN or the like are formed on the surface of the disk substrate on which the concavo-convex pattern is formed. The first dielectric film, the phase change recording film, the first dielectric film, the phase change recording film, the first dielectric film, the phase change recording film, the second dielectric film, and the like. A recording layer composed of the dielectric film 2 and the light reflection film is formed. Thereafter, an ultraviolet curable resin is applied onto the recording layer by a spin coating method, and the ultraviolet curable resin is irradiated with ultraviolet rays to be cured, thereby forming a protective layer. The DVD-RW phase change optical discs A, B, and C are completed through the above steps.

  The results of producing optical disks A, B, and C and evaluating them will be described. Using each DVD-RW standard evaluation machine DDU-1000 (laser wavelength λ: 660 nm, objective lens numerical aperture NA: 0.60 optical pickup), the optical characteristics of readable embossed pits for each optical disk manufactured as described above. The signal characteristics of unreadable double embossed pits and the signal characteristics of wobble LPP were evaluated. Tracking was performed using a push-pull signal.

  Tables 1, 2, and 3 show signal characteristic evaluations of readable embossed pits, unreadable embossed pits, and LPP in optical disks A, B, and C, respectively. The meaning of each word in each table is as follows.

LPP Length: LPP base length [T], LPP Depth: LPP depth [nm], LPP
WobbleAmp: LPP wobble amplitude [nm], Zone: region, RE: readable embossed pit, URE: unreadable embossed pit, GR: groove, Radius: radius [mm].

PP before ・ ・ ・ Push-pull signal amount ((0.22-0.44) is in the proper range
Jitter ・ ・ ・ Reproduction characteristics [%] (less than 8.0% is appropriate)
LPPb ... LPP wobble amplitude / track pitch (0.18-0.27 is appropriate)
｜ EPPr1 | ・ ・ ・ Absolute value of EPPr1 [dB] (less than 3dB is appropriate)
｜ EPPr2 | ・ ・ ・ Absolute value [EPPr2] ratio of push-pull signal amount of URE and push-pull signal amount of wobble groove at radius 25mm [dB] (less than 3dB is appropriate)
PI Err. Av. ・ ・ ・ PI error (average value of errors during recording).

  In all readable embossed pits of optical discs A, B, and C, the reproduction jitter and | EPPr1 | satisfied the standard, and stable readable embossed pit reproduction was realized. When the readable embossed pit depth was 75-85 nm, stable readable embossed pit reproduction was achieved.

  In all unreadable embossed pits of optical discs A, B, and C, the | EPPr2 | standard was satisfied and stable tracking was realized. When the unreachable embossed pit depth is 25-38 nm, the | EPPr2 | standard and stable tracking were realized. When the EFM + signal was uniformly increased by 1.5T, and when it was increased by 2.5T, the | EPPr2 | standard and stable tracking were realized. Also, the EFM + signal was not reproduced in all unreadable embossed pits.

  In the LPP characteristics of the optical disc A, the base length of the trapezoidal LPP wobble satisfied the LPPb and PI error standards up to 6T-11T, and stable LPP reproduction was realized after recording.

  In the LPP characteristics of the optical disc B, when the trapezoidal LPP wobble groove depth was 22-29 nm, the LPPb and PI error standards were satisfied, and stable LPP reproduction was realized after recording. The depth of the groove part which is a recording area is 25 nm. When the depth of the LPP wobble groove was -3 nm to +4 nm of the recording area groove portion depth (19 nm to 31 nm), stable LPP reproduction was realized after recording.

  In the LPP characteristics of the optical disc C, when the LPP wobble amplitude was 122-205 nm, the LPPb and PI error standards were satisfied, and stable LPP reproduction was realized after recording.

  When the LPP wobble amplitude was normalized at a track pitch of 740 nm, the LPP wobble amplitude / track pitch was 16.5-27.7%. (122 nm / 740 nm = 16.5%, 205 nm / 740 nm = 27.7%)

  According to the present invention, a DVD-RW medium capable of reproducing the stable LPP signal after recording has been realized, with the | EPPr1 | standard and reproduction characteristics of readable embossed pits, tracking and reproduction of unreadable embossed pits disabled.

  The present invention is widely applicable to optical recording media in the LPP format of pits, grooves, and lands, and optical recording medium manufacturing masters used in the production thereof. The optical recording medium to be used may be, for example, a reproduction-only optical recording medium, an optical recording medium in which repetitive data can be rewritten, or an optical recording medium in which data can be additionally written but cannot be erased.

  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.

It is a basic diagram which shows an example of the format of the optical disk which can apply this invention. It is a basic diagram which shows the optical system about an example of the laser cutting apparatus used when producing the recording medium which concerns on this invention, and the original recording medium manufacture.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Readable embossed pit 2 Unreadable embossed pit 3 Groove 4 Trapezoidal wobble groove 5 LPP wobble amplitude 6 Length of base of trapezoid LPP wobble 10 Laser cutting device 11 Light source 13 Driver 31 Acoustooptic modulator (AOM)
32 Photoresist 47, 49 Wedge prism 51 Voltage controlled oscillator (VCO)
54 Objective lens OM Modulation optical system M1, M2, M3 Mirror L1, L2, L3 Lens BS1 Beam splitter PBS Polarized beam splitter

Claims (10)

First and second embossed pits comprising groove-shaped grooves on the substrate and a plurality of pits discretely arranged in the circumferential direction, and first grooves formed in association with the wobbling grooves. An optical recording method for producing a master for manufacturing a phase change optical recording medium in which three trapezoidal wobble grooves are formed,
The third trapezoidal wobble groove of the phase change optical recording medium is configured as a trapezoidal wobble formed by projecting a part of the groove,
The bottom length of the third wobble is 6T-11T,
The depth of the third wobble is -3 nm to +4 nm of the recording area groove portion depth,
An optical recording method for producing a master for manufacturing the phase-change optical recording medium such that a ratio of amplitude amount / track pitch of the third wobble is 16.5 to 27.7%. The optical recording method according to claim 1, wherein the master for manufacturing the phase change optical recording medium is prepared so that the depth of the first embossed pits of the phase change optical recording medium is 75 to 85 nm. Increasing the duty of the signals forming the second emboss pit of the phase change optical recording medium, further, so that long to one ratio with a predetermined value within a range of 2T the signal from 0, the phase change 2. The optical recording method according to claim 1, wherein a master for manufacturing an optical recording medium is prepared. First and second embossed pits comprising groove-shaped grooves on the substrate and a plurality of pits discretely arranged in the circumferential direction, and first grooves formed in association with the wobbling grooves. a third trapezoidal manufacturing a master for the phase-change optical recording medium for the wobbled groove to produce a phase change optical recording medium is formed,
The third trapezoidal wobble groove of the phase change optical recording medium is configured as a trapezoidal pit formed by protruding a part of the groove,
The bottom length of the third wobble is 6T-11T,
The depth of the third wobble is -3 nm to +4 nm of the recording area groove portion depth,
A master for producing a phase change optical recording medium , wherein the amplitude ratio / track pitch ratio of the third wobble is 16.5-27.7%. Manufacturing a master for the phase-change optical recording medium according to claim 4, wherein the depth of said first emboss pit of the phase change optical recording medium is 75-85Nm. 5. The duty of a signal forming the second emboss pit of the phase change optical recording medium is increased, and the signal is further increased by a predetermined value within a range of 0 to 2T. manufacturing a master for the phase-change optical recording medium. First and second embossed pits comprising groove-shaped grooves on the substrate and a plurality of pits discretely arranged in the circumferential direction, and first grooves formed in association with the wobbling grooves. A phase change optical recording medium formed with three trapezoidal wobble grooves,
The third trapezoidal wobble groove is configured as a trapezoidal pit formed by protruding a part of the groove,
The bottom length of the third wobble is 6T-11T,
The depth of the third wobble is -3 nm to +4 nm of the recording area groove portion depth,
A phase change optical recording medium in which the third wobble amplitude / track pitch ratio is 16.5 to 27.7%. 8. The phase change optical recording medium according to claim 7, wherein the first emboss pit has a depth of 75 to 85 nm. 8. The phase change optical recording medium according to claim 7, wherein the duty of the signal forming the second embossed pit is increased, and the signal is lengthened by a predetermined value within a range of 0 to 2T. 10. The phase change optical recording medium according to claim 9, wherein the second emboss pit has a depth of 25-38 nm.

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