JP4529945B2 - Optical disc recording medium and reproducing method thereof - Google Patents

Description

The present invention relates to an optical disc recording medium in which two recording layers are laminated on a substrate and a reproducing method thereof, and the recording layer farther from the incident side of the reproducing laser beam when the reproducing laser beam is irradiated from the recording layer side. The present invention relates to an optical disc recording medium capable of stably reproducing information recorded on the recording medium and a reproducing method thereof.

  As optical discs, CDs and DVDs are widely used, but HD-DVDs (High Density Digital Versail Discs) and BDs (Blue ray Discs) that use blue-violet lasers have been developed, and commercialization has started in part. . As the types of optical discs increase, the demand for practical application of hybrid optical disc recording media has increased. CD / DVD optical discs already having a CD recording layer and a DVD recording layer, a DVD recording layer, and an HD-DVD recording layer DVD / HD-DVD optical discs having a DVD, a DVD / BD optical disc having a DVD recording layer and a BD recording layer are commercially available.

Non-Patent Document 1 describes an optical disc in which a BD recording layer is formed on a disc substrate having DVD pits formed on the surface thereof.
The optical disk described in Non-Patent Document 1 has a configuration in which a pit for DVD is formed on the surface of a disk-shaped disk substrate having a center hole, and a recording layer for BD is laminated on the pit for DVD. A lead-in area and a data area are sequentially formed along the radial direction. The lead-in area includes a first lead-in area having pits with a wide track pitch, and a second lead having a pit with a track pitch narrower than the track pitch of the first lead-in area outside the first lead-in area. In region is formed. In the data area, pits having the same track pitch as the second lead-in area are formed.

In Non-Patent Document 2, the track pitch of pits recorded in the first lead-in area in the lead-in area of the BD recording layer is 0.35 μm, and the second lead-in area and the data area The track pitch of the recorded pits is 0.32 μm.
BD-Hybrid Standard (Figure2-3 Example) BD-ROM standard (3.2.2 Track pitch)

  By the way, when the reproduction laser beam is incident from the BD recording layer side and the DVD pit in the lead-in area is reproduced across the first and second lead-in areas, the reproduction laser light is incident from the first lead-in area. Thus, the light transmission amount of the reproduction laser light reaching the DVD pit differs from the light transmission amount of the reproduction laser light incident from the second lead-in region and reaching the DVD pit.

For this reason, the reproduction signal, the focus error signal, and the tracking error signal obtained by detecting the return light of the reproduction laser beam reflected by the DVD pits become unstable. This causes a problem that stable reproduction cannot be performed.
A similar problem occurs when there is an eccentricity between the BD recording layer and the DVD pit.

  Therefore, the present invention has been made to solve the above-described problems, and has two recording layers, and the track pitch is close to the recording layer closer to the reproducing laser beam incident side. An optical disk recording medium capable of stably reproducing a recording layer on a far side when viewed from the incident side of a reproduction laser beam when reproducing an optical disk recording medium having two areas in which different pits are recorded, and a reproducing method thereof The purpose is to provide.

According to a first aspect of the present invention, a recording layer is formed on a substrate, and further along the radial direction of the substrate, the first track pitch is formed on either side of the substrate surface or the recording layer facing each other. The first pit is recorded and the area on the recording layer is the second area with the second track pitch and the third area with the third track pitch narrower than the second track pitch. And a second area in which three pits are recorded, the width of the second pit is equal to the third pit, and the slope of the inclined portion of the second pit with respect to the substrate Provided is an optical disk recording medium characterized in that an inclination angle is smaller than that of the third pit.
According to a second aspect of the present invention, a recording layer is formed on a substrate, and a first pit is formed at a first track pitch on either side of the substrate surface or the recording layer facing each other along the radial direction of the substrate. And a third pit with a third track pitch narrower than the second track pitch and a first area where the second pit is recorded at a second track pitch in the area on the recording layer In the optical disk recording medium having the second area on which is recorded, the shape of the second pit is larger than that of the third pit, and the inclination angle of the inclined portion of the second pit with respect to the substrate Provides an optical disk recording medium characterized by being equal to the third pit .

According to the present invention, the width of the second pit is equal to the third pit, and the inclination angle of the inclined portion of the second pit with respect to the substrate is smaller than the third pit, or the second pit Is larger than the third pit, and the inclination angle of the inclined portion of the second pit with respect to the substrate is equal to the third pit, so that the information recorded as the first pit can be stabilized. Can play.
In addition, the information is reproduced from the first pit after adjusting the equalizer characteristics while avoiding the region where the reproduction laser beam crosses the boundary between the first region and the second region of the recording layer. Good reproduction signals, focus error signals and tracking error signals can be obtained, and stable reproduction can be achieved.

Hereinafter, an optical disk recording medium and a reproducing method thereof according to each embodiment of the present invention will be described with reference to FIGS.
First, a first embodiment will be described with reference to FIGS.
FIG. 1 is a sectional view showing an optical disk recording medium according to the first embodiment of the present invention. FIG. 2 is an enlarged view showing pits recorded in the first and second lead-in areas of the BD recording layer. FIG. 3 is a view showing a cutting device. FIG. 4 is a diagram showing the relationship between the numerical aperture NA of the recording lens and the light transmittance at which the reproduction laser light passes through the BD recording layer.

As shown in FIGS. 1A and 1B, the optical disk recording medium 1 according to the first embodiment has a track pitch of 0.74 μm on a disk-shaped first disk substrate 2 having a center hole 2A. The DVD pit 3 is formed, and the BD recording layer 4 and the protective layer 5 are sequentially stacked on the DVD pit 3.
Furthermore, a lead-in area 6 and a data area 7 are formed outside the lead-in area 6 in the radial direction of the optical disc recording medium 1.

The lead-in area 6 includes a first lead-in area 6A in which essential information for recording and reproduction is stored from the inner periphery side toward the outer periphery side, and a second lead-in area 6B in which additional information is stored. Consists of.
Pits 8 are recorded at a track pitch of 0.35 μm in the first lead-in area 6A of the recording layer 4 for BD, and pits 9 are recorded at a track pitch of 0.32 μm in the second lead-in area 6B. Yes. In the data area 7 of the BD recording layer 4, pits 10 are recorded at the same track pitch of 0.32 μm as that of the second lead-in area 6B.

The areas of the DVD pit 3 and the BD recording layer 4 other than the DVD pit 3 and pits 8 to 10 recorded in the lead-in area 6 and the data area 7 serve as a mirror surface P that transmits the reproduction laser beam. Yes. The widths of the pit 8 and the pit 9 are the same. The linear recording densities of the pits 8 to 10 recorded in the first and second lead-in areas 6A and 6B and the data area 7 of the BD recording layer 4 are the same.
Hereinafter, the pit width refers to the distance between the centers of the inclined portions 8A and 8A sandwiching the bottom portion 8B of the pit 8 and the distance between the centers of the inclined portions 9A and 9A sandwiching the bottom portion 9B of the pit 9.

As shown in FIG. 2A, the angle formed by the inclined portion 8A of the pit 8 recorded in the first lead-in area 6A of the BD recording layer 4 with respect to the bottom portion 8B is 41 ° to 43 °. . As shown in FIG. 2B, the angle formed by the inclined portion 9A of the pit 9 recorded in the second lead-in area 6B with respect to the bottom portion 9B is 45 °. Thus, the inclined portion 9A of the pit 9 has a steeper inclination angle than the inclined portion 8A of the pit 8.
Hereinafter, the inclination angle of the inclined portion of the pit refers to the inclination angle of the inclined portion with respect to the bottom portion of the pit.

Here, the reason why the inclination angle of the inclined portion 9A of the pit 9 is steeper than that of the inclined portion 8A of the pit 8 will be described.
Since the track pitch of the first lead-in area 6A is wider than that of the second lead-in area 6B, when pits having the same shape are recorded, the density of the pits 8 recorded in the first lead-in area 6A Is lower than the density of the pits 9 recorded in the second lead-in area 6B. Therefore, when information is reproduced by detecting the DVD pit 3, the transmission amount of the reproduction laser light transmitted through the DVD recording layer 4 is the first lead-in area in the second lead-in area 6 B. Since the area of the mirror surface P through which the reproduction laser beam is transmitted is smaller than 6A, it becomes smaller.

  For this reason, the pit 9 recorded in the second lead-in area 6B is made so that the reproduction laser beam reflected by the inclined portion 8A of the pit 8 becomes larger than the reproduction laser beam reflected by the inclined portion 9A of the pit 9. The inclination angle of the inclined portion 9A is made steeper than the inclination angle of the inclined portion 8A of the pit 8 recorded in the first lead-in area 6A, so that the first and second lead-in areas 6A, 6B of the BD recording layer 4 are obtained. The amount of light transmitted through the reproduction laser beam that passes through is made equal.

Next, a method for producing an optical disk in which pits 8 to 10 are formed on the BD recording layer 4 will be described with reference to FIG.
FIG. 3 is a view showing a cutting device for producing a glass master.
First, the configuration of the cutting device 11 will be described.
The cutting device 11 includes a gas laser 13 for exposing a glass master 12 coated with a photoresist on a glass substrate, and an optical modulator 14 that modulates laser light emitted from the gas laser 13 by a recording signal supplied from the outside. A beam expander 15 that enlarges the beam diameter of the laser light modulated by the light modulator 14 to obtain cutting light, a variable diaphragm 16 that narrows the diameter of the cutting light emitted from the beam expander 15, and a variable The reflecting mirror 17 is configured to reflect the cutting light focused by the diaphragm 16, and the recording lens 18 is used to collect the cutting light reflected by the reflecting mirror 17 on the glass master 12.

Next, a method for forming a photoresist pattern with different diameters by exposing the photoresist of the glass master 12 with cutting light will be described.
A laser beam is emitted from the gas laser 13, the laser beam is modulated by the optical modulator 14, and then the beam diameter of the laser beam is expanded by the beam expander 15. Next, the beam diameter of the laser beam expanded by the beam expander 15 is narrowed by the variable diaphragm 16, reflected by the reflection mirror 17, and further cut by exposing the photoresist on the glass master 12 with the recording lens 18. To form a photoresist pattern.

  At this time, the photoresist patterns corresponding to the pits 8 to 10 respectively recorded in the first and second lead-in areas 6A and 6B of the BD recording layer 4 in the optical disc recording medium 1 described above are obtained from the variable diaphragm 16. It can be formed by changing the aperture. That is, the photoresist pattern corresponding to the pits 8 changes the aperture of the variable diaphragm 16 so that the numerical aperture of the recording lens 18 is 0.7, and the photoresist patterns corresponding to the pits 9 and 10 are The numerical aperture of the recording lens 18 is set to 0.9 by changing the diaphragm of the variable diaphragm 16.

Next, the glass master 12 having a photoresist pattern corresponding to the pits 8 to 10 is developed.
The sidewall of the groove of the photoresist pattern becomes steeper as the numerical aperture of the recording lens 18 is larger, so that the one formed with the numerical aperture 0.9 becomes steeper than the one formed with the numerical aperture 0.7.
Next, a stamper (not shown) is produced by electroforming using the glass master 12. Next, using this stamper (not shown), transfer is performed by injection molding onto the disk substrate 2 on which the BD recording layer 4 has been previously formed, and the optical disk recording medium 1 shown in FIG. 1 is manufactured.
At this time, the pits 8 to 10 recorded on the optical disc recording medium 1 have the same shape as the photoresist pattern formed on the glass master 12.

  That is, the pit 8 shown in FIG. 2A is a BD recording of the optical disk recording medium 1 obtained from the glass master 12 produced by using the cutting device 11 of the recording lens 18 having a numerical aperture NA of 0.7. The pit 9 recorded in the layer 4 and shown in FIG. 2B is obtained by using the cutting device 11 of the recording lens 18 having a numerical aperture NA larger than 0.7 and a numerical aperture NA of 0.9. It is recorded on the BD recording layer 4 of the optical disc recording medium 1 obtained from the produced glass master 12. The inclination angle of the inclined portion 9A of the pit 9 is steeper than the inclination angle of the inclined portion 8A of the pit 8.

Here, when reproducing the pit for DVD using the reproduction laser beam on the optical disk recording medium 1 manufactured as described above, the numerical aperture NA of the recording lens 18 used in the cutting device 11 and the reproduction laser beam are The relationship with the light transmittance transmitted through the BD recording layer 4 was examined. The result is shown in FIG.
In FIG. 4, the horizontal axis represents the numerical aperture NA of the recording lens 18, and the vertical axis represents the light transmittance (%) at which the reproduction laser beam passes through the BD recording layer 4.
As shown in FIG. 4, the optical disk recording medium 1 obtained from the glass master 12 produced using the recording lens 18 having a large numerical aperture NA is made by using the recording lens 18 having a smaller numerical aperture NA. Compared with the optical disc recording medium 1 obtained from the master 12, the light transmittance at which the reproduction laser light passes through the BD recording layer 4 tends to increase.

  Since the area of the inclined portion 8A of the pit 8 irradiated by the reproduction laser beam is larger than that of the inclined portion 9A of the pit 9, the reproduction laser beam is reflected by the inclined portion 8A of the pit 8 rather than the inclined portion 9A of the pit 9. The rate increases. That is, the light transmission amount of the reproduction laser beam is greater in the pit 9 than in the pit 8. In this manner, the amount of light transmitted through the pit 9 recorded in the second lead-in area 6B is made larger than that of the pit 8 recorded in the first lead-in area 6A, and the BD recording is performed. It is possible to make the light transmission amounts of the reproduction laser beams transmitted through the first and second lead-in regions 6A and 6B of the layer 4 substantially equal. For this reason, even when the reproduction laser beam straddles the first and second lead-in areas 6A and 6B, the reproduction laser beam that irradiates the DVD pit 3 through the first and second lead-in areas 6A and 6B. The change in the amount of light transmission can be kept small.

  As described above, the slope 9A of the pit 9 recorded in the second lead-in area 6B in the BD recording layer 4 is steeper than the slope 8A of the pit 8 recorded in the first lead-in area 6A. Since the angle is set, when the DVD pit 3 is reproduced, it is possible to suppress a change in the light transmission amount of the reproduction laser light transmitted through the first lead-in area 6A and the second lead-in area 6B. Therefore, stable reproduction of the optical disk recording medium 1, focus error servo control, and tracking error servo control can be performed.

Next, a second embodiment will be described with reference to FIGS.
FIG. 5 is an enlarged plan view of the vicinity of the lead-in area of the optical disk recording medium according to the second embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the recording power for irradiating the photoresist on the glass master and the light transmittance at which the reproduction laser beam passes through the BD recording layer.
As shown in FIG. 5, in the optical disk recording medium 19 according to the second embodiment, the shape of the pits 8 recorded in the first lead-in area 6A of the BD recording layer 4 is the second lead-in area 6B. And the inclination angle of the inclined portion of the pit 8 with respect to the disk substrate 2 is equal to that of the pit 9, and the others are the same.

Here, the relationship between the recording power of the cutting light that irradiates the photoresist of the glass master 12 and the light transmittance at which the reproduction laser light passes through the BD recording layer 4 was examined.
In the case of BD, since the target of the reproduction signal obtained from the pit and other aspects is defined as -10% to + 15%, the recording power is within the range that satisfies this when cutting. It is necessary to change In consideration of the above, the glass master 12 is manufactured by setting the recording power of the cutting light to 0.95 times and 1.05 times the standard recording power, and the optical disk recording medium 1 is manufactured using the glass master 12. Produced. At this time, the numerical aperture of the recording lens 18 is 0.9. The result is shown in FIG.

In FIG. 6, the horizontal axis represents the recording power (relative value) of the cutting light, and the vertical axis represents the light transmittance (%) at which the reproduction laser light passes through the BD recording layer 4. In FIG. 6, the recording power on the vertical axis represents a relative value when the standard recording power is 1.
As shown in FIG. 6, the light transmittance of the reproduction laser beam transmitted through the BD recording layer 4 tends to decrease as the recording power of the cutting light increases.

  The pit 8 shown in FIG. 5A is obtained from the glass master 12 produced by cutting with a cutting power of 1.05 times the standard recording power using the cutting device 11. The pit 9 shown in FIG. 4B is produced by cutting with a cutting power of 0.95 times the standard standard recording power using the cutting device 11. In general, since the shape of the pits becomes larger as the recording power increases, the shape of the pits 8 becomes larger than the pits 9.

  According to the second embodiment, in addition to the effects of the first embodiment, the light transmission amount of the reproduction laser light that passes through the first and second lead-in areas 6A and 6B of the BD recording layer 4 is set. Since the optical disk recording medium 1 can be obtained using the glass master 12 produced only by changing the recording power in order to make them substantially equal, the productivity is improved.

Next, a third embodiment will be described with reference to FIG.
FIG. 7 is a diagram showing an optical disc recording / reproducing apparatus.
First, an optical disk recording / reproducing apparatus 20 that records or reproduces the optical disk recording medium 1 will be described.
As shown in FIG. 7, the optical disc recording / reproducing apparatus 20 includes a spindle motor 21 for rotating the optical disc recording medium 1 and an optical pickup 22 for recording information on the optical disc recording medium 1 as pits or reproducing the information. A recording encoding circuit 23 that encodes a recording signal supplied from the outside, and a laser driver that modulates the laser light emitted from the optical pickup 22 based on the recording signal encoded by the recording encoding circuit 23 24.

  Here, the optical pickup 22 is configured to output a laser beam having a wavelength of 420 to 430 nm or a laser beam having a wavelength of 630 to 650 nm, and a laser beam emitted from the semiconductor laser element 22A to each recording layer of the optical disc recording medium 1. Objective lens 22B for condensing light and optical detector 22C for detecting return light from optical disk recording medium 1.

  Further, the optical disc recording / reproducing apparatus 20 emits a reproduction laser beam from the semiconductor laser element 22A in the optical pickup 22 to the BD recording layer 4 or the DVD pit 3 of the optical disc recording medium 1, and the return light reflected here. Is amplified by the head amplifier 25, the equalizer 26 for equalizing the signal amplified by the head amplifier 25 to a predetermined value, and the head amplifier 25. A reproduction detection circuit 27 for detecting a reproduction signal from the received signal, and a focus error signal and a tracking error signal are generated based on the signal that is equalized by the equalizer 26 or the signal amplified by the head amplifier 25 A servo circuit 28 for performing the servo operation of the optical pickup 22 and a control signal for controlling the whole are provided. Obtain and a system controller 29.

Next, a recording method of the optical disc recording medium 1 will be described.
Based on an instruction signal from the system controller 29, a recording signal is supplied from the outside to the recording encoding circuit 23 and encoded, and then the encoded recording signal is used to transfer the recording signal from the laser driver 24 to the optical disc recording medium 1. A strategy for recording is output to the optical pickup 22. The laser light having a wavelength of 420 to 430 nm or 630 to 650 nm emitted from the semiconductor laser element 22A in the optical pickup 22 is modulated based on the strategy, and this modulated laser light is recorded on the optical disk by the objective lens 22C of the optical pickup 22. Irradiation from the protective layer 5 side of the medium 1 is focused on the BD recording layer 4 or the DVD pit 3 to record pits as information.

Next, a reproducing method of the optical disc recording medium 1 according to the third embodiment will be described.
Before reproducing the optical disk recording medium 1, initial adjustment is performed by the equalizer 26 so that a stable reproduction signal can be obtained while avoiding the boundary area between the first lead-in area 6A and the second lead-in area 6B.
Based on an instruction signal from the system controller 29, a laser beam having a wavelength of 420 to 430 nm or 630 to 650 nm is emitted from the semiconductor laser element 22A in the optical pickup 22, and the protective layer of the optical disc recording medium 1 is passed through the objective lens 22C. 5 is incident on the BD recording layer 4 or the DVD pit 3 of the optical disc recording medium 1.

  The return light reflected by the BD recording layer 4 or the DVD pit 3 is incident on the photodetector 22C through the objective lens 22B. The return light incident on the photodetector 22C is photoelectrically converted into an electric signal and then amplified by the head amplifier 25. Next, the electrical signal amplified by the head amplifier 25 is equalized and adjusted to a predetermined value by the equalizer 26. The reproduction signal, the focus error signal and the tracking error signal are detected from the electric signal equalized by the reproduction detection circuit 27 to reproduce and track the information recorded on the BD recording layer 4 or the DVD pit 3 of the optical disc recording medium 1. Servo control and focus servo control are performed. The equalization adjustment is performed using a reproduction signal obtained from a reference area in which a fixed pattern such as the shortest pit or the longest pit is recorded. In addition, the calibration performed in association with the recording / reproducing of the optical disc is performed by detecting the RF output, jitter, and the like of the calibration area prepared in advance.

  As described above, equalization adjustment is performed by the equalizer 26 so as to obtain a stable reproduction signal while avoiding the boundary area between the first lead-in area 6A and the second lead-in area 6B before reproducing the optical disk recording medium 1. Therefore, a highly accurate reproduction signal, focus error signal, and tracking error signal can be obtained, and stable reproduction of the pit 3 for DVD can be achieved.

It is sectional drawing which shows the optical disk recording medium in the 1st Embodiment of this invention. FIG. 4 is an enlarged view showing pits recorded in first and second lead-in areas of a BD recording layer. It is a figure which shows a cutting device. It is a figure which shows the relationship between numerical aperture NA of a recording lens, and the light transmittance which the reproduction | regeneration laser beam permeate | transmits the recording layer for BD. It is an enlarged plan view of the vicinity of the lead-in area of the optical disk recording medium in the second embodiment of the present invention. It is a figure which shows the relationship between the recording power which irradiates the photoresist of a glass original disc, and the light transmittance which a reproduction | regeneration laser beam permeate | transmits the recording layer for BD. It is a figure which shows an optical disk recording / reproducing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,19 ... Optical disk recording medium, 2 ... 1st disk substrate, 3 ... DVD pit, 4 ... BD recording layer, 5 ... Protective layer, 6 ... Lead-in area, 6A ... 1st lead-in area, 6B ... 1st 2 lead-in area, 7 ... data area, 8, 9, 10 ... pit, 11 ... cutting device, 12 ... glass master, 13 ... gas laser, 14 ... light modulator, 15 ... beam expander, 16 ... variable aperture, DESCRIPTION OF SYMBOLS 17 ... Reflection mirror, 18 ... Recording lens, 20 ... Optical disk recording / reproducing apparatus, 21 ... Spindle motor, 22 ... Optical pick-up, 23 ... Recording encoding circuit, 24 ... Laser driver, 25 ... Head amplifier, 26 ... Equalizer, 27 ... Reproduction detection circuit, 28 ... servo circuit, 29 ... system controller

Claims (2)

A recording layer is formed on the substrate, and first pits are recorded at a first track pitch on either side of the substrate surface or the recording layer facing each other along the radial direction of the substrate, and The area on the recording layer is the first area where the second pit is recorded at the second track pitch, and the third pit is recorded at the third track pitch narrower than the second track pitch. In an optical disk recording medium having two areas,
An optical disc recording medium characterized in that the width of the second pit is equal to that of the third pit, and the inclination angle of the inclined portion of the second pit with respect to the substrate is smaller than that of the third pit. . A recording layer is formed on the substrate, and first pits are recorded at a first track pitch on either side of the substrate surface or the recording layer facing each other along the radial direction of the substrate, and The area on the recording layer is the first area where the second pit is recorded at the second track pitch, and the third pit is recorded at the third track pitch narrower than the second track pitch. In an optical disk recording medium having two areas,
An optical disc recording medium characterized in that the shape of the second pit is larger than that of the third pit, and the inclination angle of the inclined portion of the second pit with respect to the substrate is equal to that of the third pit. .

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