WO2007125872A1

WO2007125872A1 - Optical recording disc and optical recording system using same

Info

Publication number: WO2007125872A1
Application number: PCT/JP2007/058753
Authority: WO
Inventors: Katsuyuki Takahashi; Naoyasu Miyagawa
Original assignee: Panasonic Corporation
Priority date: 2006-04-24
Filing date: 2007-04-23
Publication date: 2007-11-08
Also published as: JP2009163780A

Abstract

An optical recording disc is provided with a supporting substrate and a plurality of optical function layers formed on the supporting substrate. Information can be recorded and/or reproduced by irradiating the optical function layers with laser beams from the direction opposite to the supporting substrate. The optical function layers include at least an optical function layer (L0) close to the supporting substrate, and an optical function layer (L1) closer to a laser beam entrance face than the optical function layer (L0). The optical recording disc having excellent tracking performance and recording/reproducing performance is provided bymaking the width of a groove on the optical function layer (L0) narrower than that of a groove on the optical function layer (L1).

Description

Specification

Optical recording disk and optical recording system using the same

Technical field

The present invention relates to an optical recording disk suitable for high-density and large-capacity recording / reproduction and an optical recording system using the same.

Background art

In recent years, the amount of information that can be recorded on one optical recording medium has increased significantly. In the case of DVD-format media such as DVD-R, DVD-RAM, DVD-RW, etc., which are rapidly spreading at present, the disc is 4.7 GB, which is about 7 times that of CD-R and CD-RW. It is. The Blu-Ray (hereinafter referred to as BD) format, which has been recently standardized, is 25 GB for a single-layer disc and 50 GB for a double-layer disc, and a double-layer disc can record about 10 times the information of a DVD. . This means that the digital and IB Vision can be recorded for more than 4 hours.

[0003] In order to achieve this performance, recording material technology that realizes good recording performance with high density as well as advancement in optical recording drive technology including optical pickups that record and reproduce minute marks! In addition, progress is required in process technology that realizes multi-layering, as well as master technology and molding technology that stably realize fine tracks. In order to establish the format, it is necessary to consider the performance margin of the entire system.

[0004] Further, in order to further increase the capacity, proposals for further multilayering have been made. In order to instantly determine which layer of the multilayer disc is focused! /, By changing the width and depth of the group so that it is larger in the layer far from the laser incident surface, A method to detect which layer is focused! / Is proposed.

[0005] In addition, when performing multi-layering, it is necessary to stabilize the tracking operation that is performed only by the focus operation described above. In Patent Document 2, the laser incident surface force due to uneven thickness of the intermediate layer of the multi-layer disc is far. In order to prevent degradation of the SZN ratio of the tracking signal in the recording layer, a method for stabilizing the tracking operation by increasing the depth of the group and increasing the output has been proposed. [0006] Also, in Patent Document 3, the depth Gd of each groove is 15 nm or more and 25 nm or less on one main surface of the support substrate of the optical recording disk, and the half width Gw of the group is There has been proposed a method of stabilizing the tracking operation by forming groups and lands alternately so that the thickness is 150 nm or more and 230 nm or less and the recording layer contains an inorganic element.

Here, the structure of the conventional optical recording disk as described above will be specifically described. FIG. 12 is a cross-sectional view of a conventional dual-layer optical recording disk. For example, in the case of a BD double-layer disc, a rear layer 103, an intermediate layer 101, a front layer 104, and a cover layer 102 are formed on a substrate 100 as shown in FIG. In the front layer 104, which is the front layer, when the recording layer thickness S is 10 nm, the transparent layer through which the laser beam LB passes, that is, the cover layer 102 is as thin as 75 m. Changes less, and signal degradation due to optical aberrations during disc tilt is small.

[0008] On the other hand, in the rear layer 103, which is the inner layer, when the recording layer thickness is lOnm, the thickness of the transparent layer through which the laser beam LB passes (the thickness of the cover layer 102 and the intermediate layer 101) is about 100 m, the change in the jitter of the playback signal with respect to the disc tilt increases, and the signal degradation due to aberrations during disc tilt is large, so the necessary margin (jitter value less than the predetermined value for the predetermined tilt width) is secured. I can't do that.

[0009] Therefore, by designing the two-layer optical recording disk by increasing the recording layer of the rear layer 103 so that the degree of modulation of the rear layer 103 is larger than that of the front layer 104, the signal of the rear layer 103 can be designed. The required amplitude can be secured by increasing the amplitude.

[0010] On the other hand, in order for an optical recording disk to exhibit stable performance, the servo must be stable. One element of this servo is the tracking performance, and it is important that the change of the push-pull signal (hereinafter referred to as “PPnor malj t \”) normalized by the reflection level before and after recording is small! is there.

[0011] However, when the recording layer of the rear layer 103 is thickened to increase the modulation degree, the ratio of PPnormal before and after recording (hereinafter referred to as “PPr”) increases, which is sufficient for an optical recording drive. There was a problem that tracking control was not possible. Another problem is that if the recording layer is made thin like the front layer 104, the degree of modulation becomes too small and the recording / reproducing characteristics become insufficient. Patent Document 1: JP 2002-117591

Patent Document 2: Japanese Patent Laid-Open No. 2003-196885

Patent Document 3: Japanese Patent Laid-Open No. 2004-327016

Disclosure of the invention

The present invention provides an optical recording disc that can stabilize the tracking performance even when the recording layer is thick and can realize good recording and reproducing characteristics even when the recording layer is thin. Is intended to provide.

[0013] An optical recording disk according to one aspect of the present invention includes a support substrate and a plurality of optical functional layers formed on the support substrate, and the laser beam is emitted from a direction opposite to the support substrate. An optical recording disk on which information is recorded and / or reproduced by irradiating the functional layer, wherein the plurality of optical functional layers include a support substrate side optical functional layer close to the support substrate and the support At least an incident surface side optical functional layer closer to the incident surface of the laser beam than the substrate side optical functional layer, and the width of the dimple of the support substrate side optical functional layer is the incident surface side optical functional layer Narrower than the width of the group.

[0014] With the above configuration, even when the recording layer is thick, the ratio of PPnormal before and after recording can be reduced, so that tracking performance can be stabilized, and even when the recording layer is thin, modulation can be performed. Therefore, it is possible to provide an optical recording disk capable of realizing good recording / reproducing characteristics.

Brief Description of Drawings

FIG. 1 is a cross-sectional view of a two-layer optical recording disk according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining definitions of a group width and a group depth.

FIG. 3 is a schematic diagram for explaining a state in which recording / reproduction is performed on the two-layer optical recording disk shown in FIG. 1 using a laser beam.

FIG. 4 is a diagram showing a relationship between disc tilt and jitter of an optical functional layer of an optical recording disc.

FIG. 5 is a diagram showing the relationship between the thickness of a recording layer of an optical recording disk and the degree of modulation.

FIG. 6 is a schematic diagram for explaining a tracking servo signal extraction method of the optical recording system of the present embodiment. FIG. 7 is a diagram showing the relationship between the group phase difference and the SUM and PP signals.

FIG. 8 is a diagram showing the relationship between the recording layer thickness and PPr.

FIG. 9 is a cross-sectional view of a four-layer optical recording disk in one embodiment of the present invention.

FIG. 10 is a diagram showing the relationship between the group width, PPr, and modulation factor in the thickness of each recording layer of the four-layer optical recording disk in one embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the group width and PPnormal at each group depth of the four-layer optical recording disk in the embodiment of the present invention.

FIG. 12 is a cross-sectional view of a conventional dual-layer optical recording disk.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a two-layer optical recording disk according to an embodiment of the present invention.

A two-layer optical recording disk shown in FIG. 1 includes a support substrate 1, an L0 optical functional layer 10, an intermediate layer 2,

L1 optical functional layer 15 and cover layer 5 are provided. Here, the L0 optical functional layer 10 includes an L0 reflection layer 6, an L0 back side dielectric layer 7, an L0 recording layer 8, and an L0 front side dielectric layer 9. The L1 optical functional layer 15 includes an L1 reflective layer 11, an L1 back side dielectric layer 12, an L1 recording layer 13, and an L1 front side dielectric layer.

The support substrate 1 is a transparent substrate made of polycarbonate having a thickness of 1.1 mm and having tracking grooves (groups). The support substrate is not particularly limited to this example, and various substrates can be used.

[0019] On the support substrate 1, as an L0 optical functional layer 10, an L0 reflective layer 6 with a film thickness of 40 nm that also has an Ag alloy force, an L0 back dielectric layer 7 with a film thickness of 30 nm that has a ZnS-SiO force, Te— Pd—O

2

L0 recording layer 8 with a thickness of 20 nm and ZnS—SiO force 40 nm before L0

2

The side dielectric layer 9 is sequentially formed by vacuum sputtering. Thereafter, an intermediate layer 2 made of an ultraviolet curable resin and having a film thickness of 25 m is provided, and a groove (group) for tracking is formed on the surface by a transfer method.

[0020] Further, as the L1 optical functional layer 15, an L1 reflective layer 11 having a film thickness of 6 nm that also has an Ag alloy force, an L1 back dielectric layer 12 having a film thickness of 15 nm that also has a Zn S-SiO force, and Te-Pd-O Main film

2

10nm thick L1 recording layer 13 and 20nm thick L1 front dielectric consisting of ZnS-SiO The layer 14 is sequentially formed on the intermediate layer 2 by vacuum sputtering. Thereafter, a cover layer 5 having a film thickness of 75 μm made of an ultraviolet curable resin is formed.

Note that the LO recording layer 8 preferably contains at least one selected from the group consisting of Te, Pd, and O force as a main component, which is preferably an inorganic write-once recording material. In this case, good recording / reproducing characteristics can be realized. The other recording layers are the same as described above.

Here, the width of the group and the depth of the group will be described in detail. FIG. 2 is a cross-sectional view for explaining the definition of the group width and the group depth. In FIG. 2, the L0 optical functional layer 10 will be described as an example, but the same applies to the L1 optical functional layer 15 and the like.

As shown in FIG. 2, the group depth Gd in the present embodiment means the height of the step at the boundary between the intermediate layer 2 and the L0 optical functional layer 10, and the group width Gw Means the width of the group at the depth of 1Z2 of the depth Gd of the groove. In the present embodiment, the group is formed in accordance with the track pitch, and the track pitch can be arbitrarily set within the range of 0.31 m or more and 0.33 μm or less. If it is, 0.32 m can be used.

Next, a recording / reproducing operation by the optical recording system for the dual-layer optical recording disk configured as described above will be described. FIG. 3 is a schematic diagram for explaining a state in which recording / reproduction is performed on the double-layered optical recording disk shown in FIG. 1 using a laser beam.

As shown in FIG. 3, the optical recording system 50 is configured as, for example, an optical recording drive, and includes an optical pickup 52 having a semiconductor laser that emits a laser beam LB. The laser beam LB is an optical recording drive. The light is converged by the objective lens 51 provided in the pickup 52 and guided to the two-layer optical recording disk. At this time, the laser beam LB is transmitted from the cover layer 5 side to the front optical functional layer (incident surface side optical functional layer) L1 optical functional layer 15 or rear optical functional layer (supporting substrate side optical functional layer). The L0 optical functional layer 10 is irradiated, and the focus servo of the objective lens 51 is applied using the reflected light from the L1 optical functional layer 15 or the L0 optical functional layer 10, and the L1 optical functional layer 10 Push-pull for functional layer 15 or L0 optical functional layer 10 group (convex part as seen from laser beam LB incident side) Tracking servo is applied by the method, and information is recorded and reproduced. The tracking method is not particularly limited to the above example, and other methods may be used.

Here, the wavelength of the laser beam LB is preferably in the range of not less than 400 nm and not more than 410 nm. In this case, information can be recorded and reproduced with high density and stability. The NA of the objective lens 51 that is an optical system for converging the laser beam LB is preferably in the range of 0.84 or more and 0.86 or less. In this case, information can be recorded and reproduced with high density and stability.

FIG. 4 is a diagram showing the relationship between the disc tilt and jitter of the optical functional layer of the optical recording disc, and the thin line in the figure indicates that the thickness of the LO recording layer 8 of the optical functional layer 10 is lOnm. Shows the relationship between disc tilt and jitter in the case of, and the broken line shows the relationship between disc tilt and jitter when the thickness of the L1 recording layer 13 of the optical functional layer 15 is lOnm, and the thick line shows the optical function. The relationship between disc tilt and jitter when the thickness of the L0 recording layer 8 of the active layer 10 is 20 nm is shown.

[0028] In Fig. 4, when both the L1 recording layer 13 and the L0 recording layer 8 have a small modulation degree, that is, when the thickness of the L1 recording layer 13 and the L0 recording layer 8 is lOnm, the L1 recording layer 13 (broken line) shows that when the range between the two vertical broken lines in the figure is the working tilt range, the jitter of the playback signal for the tilt within this range is less than the allowable jitter value shown by the horizontal broken line. The force to secure the jitter margin for the required tilt In the L0 recording layer 8 (thin line), the jitter of the playback signal exceeds the allowable jitter value shown by the horizontal broken line at both ends of the used tilt range. Jitter margin can be secured.

The reason for this is that in the L1 recording layer 13, the thickness of the cover layer 5, which is the incident-side transparent layer, is as thin as 75 μm, and the optical aberration due to tilting is small, so that the deterioration of jitter is small. In contrast, in the L0 recording layer 8, the incident-side transparent layer (intermediate layer 2 + cover layer 5) is as thick as 100 / zm, and the optical aberration due to tilt is large, so that the jitter is greatly deteriorated. .

Here, in order to secure a jitter margin with respect to the tilt of the L0 recording layer 8, it is effective to reduce the thickness of the incident-side transparent layer. However, the L0 recording layer 8 and the L1 recording layer 13 are effective. When approaching, signal quality degradation due to interlayer crosstalk occurs, so a certain interlayer distance is required, and the thickness of the incident-side transparent layer cannot be reduced. While pushing Even when the side transparent layer is thick, the margin can be maintained by increasing the thickness of the recording layer as described below.

FIG. 5 is a diagram showing the relationship between the thickness of the recording layer of the optical recording disk and the degree of modulation. As shown in FIG. 5, the modulation degree increases by increasing the thickness of the recording layer containing Te—Pd—O as the main component. Accordingly, when the thickness of the LO recording layer 8 is 20 nm, the degree of modulation increases and the SZN ratio can be improved. As a result, as shown by the thick line in FIG. 4, the jitter can be reduced as a whole, so that even if the incident-side transparent layer is thick like the LO recording layer 8, the jitter margin for the required tilt range can be obtained. Can be secured.

[0032] Further, from FIG. 5, when the minimum allowable value of the modulation degree is set to 0.4, when the thickness of the recording layer is less than 9 nm, the minimum allowable value cannot be satisfied and the recording layer is very If it is thin, the degree of modulation becomes small, and it can be seen that the recording / reproducing performance may not be secured. Therefore, when the minimum allowable modulation factor is set to 0.4, the thickness of the recording layer is preferably 9 nm or more, more preferably lOnm or more. In this embodiment, as shown in FIG. 4, the thickness of the L1 recording layer 13 is set to lOnm, the thickness of the L0 recording layer 8 is set to 20 nm, and a margin of jitter with respect to the necessary tilt is secured. Yes.

[0033] Further, the L0 recording layer 8 is preferably within 105 μm from the surface of the cover layer 5 which is a laser incident surface. In this case, the optical aberration due to the disc tilt of the L0 recording layer 8 can be limited to a predetermined range, and a jitter margin for the necessary tilt range can be secured.

[0034] Next, the tracking servo performance when the above-mentioned double-layer optical recording disk is used will be described. FIG. 6 is a schematic diagram for explaining a tracking servo signal extraction method of the optical recording system of the present embodiment. In FIG. 6, for the sake of clarity, only the part related to the tracking servo in the optical recording system is shown, and the other parts are not shown.

In FIG. 6, the land LT and the group GT are alternately formed on the recording layer (L0 recording layer 8 or L1 recording layer 13) of the double-layered optical recording disk, and the recording layer strength is reduced. The reflected light RB is collected by the quadrant detector 61, and of the electric signals A to D from the light receiving areas 61a to 61d of the quadrant detector 61 excited by the reflected light RB, the electric signals from the light receiving areas 61a and 61b. The signals A and B are input to the adder 62, and the electric signals C and D from the light receiving areas 61c and 61d are input to the calorie calculator 63. The adder 62 adds the electrical signals A and B and outputs the result to the adder 64 and the subtractor 66, and the adder 63 adds the electrical signals C and D and outputs the result to the adder 64 and the subtractor 66.

Adder 64 adds all signals A to D, and the added signal is input to signal demodulation circuit 65 as a SUM signal (A + B + C + D). The subtractor 66 subtracts the electric signal (C + D) on the other side from the electric signal (A + B) on one side along the groove by the group GT, and the subtracted signal is PP (push-pull signal). ) Signal is input to tracking servo circuit 67. In this embodiment, during tracking servo operation, a normalized PP signal (hereinafter, rppnor malj t) is created by dividing the PP signal by the SUM signal by a divider (not shown) and performing normalization. The difference in the reflection level of the layered optical recording disk is canceled.

FIG. 7 is a diagram showing the relationship between the phase difference of the group (the optical groove depth of the group that takes into account the refractive index), the SUM signal, and the PP signal. The SUM signal indicated by the broken line in Fig. 7 is maximum when the phase difference of the group is zero, and is minimum when the phase difference of the group is λΖ4. In addition, the ΡΡ signal indicated by the solid line in FIG. 7 is maximum when the group phase difference is λ Ζ8, and is minimum when the group phase difference is zero or λ Ζ4.

[0038] The phase difference of a group of commonly used two-layer optical recording discs is about Z10 in an unrecorded state. If the group phase difference does not change after recording, the SUM signal PPnormal does not change because the ratio of と and ΡΡ signal does not change. However, in practice, PPnormal often increases after recording. This is because the refractive index of the recording layer decreases after recording and the phase difference of the group with respect to the land increases. Moreover, the possibility of substrate deformation due to the heating temperature during recording is also conceivable.

[0039] The increase in the phase difference of the above group will be described with reference to FIG. 7. When the phase difference of the group in the unrecorded state is the line LN, the group position is positioned at the position of the line LE or LF after recording. The phase difference has moved. This increases the ratio of PP signal to SUM signal and increases PPnormal. Here, the ratio of PPnormal after recording to PPnormal when unrecorded is PPr (= (PPnormal after recording) / (unrecorded) PPnormal))), and if PPnormal increases after recording, PPr will exceed 1.

FIG. 8 is a diagram showing the relationship between the thickness of the recording layer and PPr. As shown in Fig. 8, it can be seen that PPr tends to increase as the recording layer becomes thicker. This indicates that if other conditions are the same, the PPr increases in the optical functional layer 10 that is the thick rear layer of the recording layer, which affects the tracking performance.

For this reason, in the present embodiment, the group width and depth are optimized as described below, and good tracking performance is realized even when the recording layer is thick. In the following description, since the same measurement results were obtained with the above-described two-layer optical recording disk and the multilayered four-layer optical recording disk, the four-layer optical recording disk shown in FIG. An example will be described.

FIG. 9 is a cross-sectional view of a four-layer optical recording disk according to an embodiment of the present invention. The four-layer type optical recording disk shown in FIG. 9 has a support substrate 1, L0 optical functional layer 10, intermediate layer 2, L1 optical functional layer 15, intermediate layer 3, L2 optical functional layer 19, intermediate layer 4, L3. An optical functional layer 23 and a cover layer 5 are provided. The arrow LI in the figure indicates the direction of incidence of the laser beam.

Here, the L0 optical functional layer 10 is composed of the L0 reflection layer 6, the L0 back side dielectric layer 7, the L0 recording layer 8, and the L0 front side dielectric layer 9. The L1 optical functional layer 15 includes an L1 reflection layer 11, an L1 back side dielectric layer 12, an L1 recording layer 13, and an L1 front side dielectric layer 14. The L2 optical functional layer 19 includes an L2 back side dielectric layer 16, an L2 recording layer 17, and an L2 front side dielectric layer 18. The L3 optical functional layer 23 includes an L3 back side dielectric layer 20, an L3 recording layer 21, and an L3 front side dielectric layer 22.

[0045] On the support substrate 1, as the L0 optical functional layer 10, a 40 nm thick L0 reflective layer 6 made of an Ag alloy carrier, a 30 nm thick L0 back side dielectric layer 7 made of ZnS-SiO force, Te—Pd—O

2

L0 recording layer 8 with a thickness of 20 nm and ZnS—SiO force 40 nm before L0 The side dielectric layer 9 is sequentially formed by vacuum sputtering. Thereafter, an intermediate layer 2 made of an ultraviolet curable resin and having a thickness of about 20 m is provided, and a tracking groove (group) is formed on the surface by a transfer method.

[0046] On the intermediate layer 2, as an L1 optical functional layer 15, an L1 reflective layer 11 having a film thickness of 6 nm that also has an Ag alloy force, an L1 back dielectric layer 12 having a film thickness of 15 nm that also has a ZnS-SiO force, Te — Pd— O

2

10 nm thick L1 recording layer 13 as the main component and 20 nm thick LI with ZnS-SiO force

2

The front dielectric layer 14 is sequentially formed by vacuum sputtering. Thereafter, an intermediate layer 3 made of an ultraviolet curable resin and having a thickness of about 20 m is provided, and a groove (group) for tracking is formed on the surface by a transfer method.

[0047] Further, on the intermediate layer 3, as the L2 optical functional layer 19, a film thickness of 15 nm also having a ZnS-SiO force

2

The L2 back side dielectric layer 16, the L2 recording layer 17 with a thickness of 8 nm mainly composed of Te—Pd—O, and the L2 front side dielectric layer 18 with a thickness of 15 nm consisting of ZnS—SiO By sputtering

2

Films are sequentially formed. Thereafter, an intermediate layer 4 made of an ultraviolet curable resin and having a thickness of about 20 m is provided, and a tracking groove (group) is formed on the surface by a transfer method.

[0048] Furthermore, as the L3 optical functional layer 23, the L3 back side dielectric having a thickness of 5 nm, which also has ZnS-SiO force.

2

Body layer 20, 6 nm thick L3 recording layer 21 mainly composed of Te—Pd—O, and ZnS—SiO?

The dielectric layer 22 on the front side of the L3 having a thickness of 15 nm is sequentially formed on the intermediate layer 4 by vacuum sputtering. Thereafter, a cover layer 5 made of an ultraviolet curable resin and having a thickness of about 40 / zm is formed.

In the four-layer optical recording disk of one embodiment of the present invention, as described above, the thickness of the L0 recording layer 8 is 20 nm, the thickness of the L1 recording layer 13 is 10 nm, and the thickness of the L2 recording layer 17 The thickness of the L3 recording layer 21 is 6 nm, and the reflectance from the optical functional layers 10, 15, 19, 23 to the outside of the disc is within ± 20% of the average of each layer. And each optical functional layer 10, 15, 1

9 and 23 recording sensitivity Each optical functional layer within ± 20% of the average of each layer

10, 15, 19, and 23 were formed. In addition, the thickness of each of the intermediate layers 2, 3, and 4 may be changed little by little so that the plurality of layers are not focused.

[0050] In order to study the optimum group width and depth, etc., the inventors of the present invention have 140, 160, 180, 200, 220, 240, and 260 nm as the group width of each layer. The above four-layer type optical recording disk and double-layer type optical recording disk were created in six types of 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, and 24 nm as types and group depths. — Using 1000, we measured the recording and playback characteristics of each optical recording disk. Jitter measurement was performed using PULSTEC's SignalDetector and YOKO GAWA's time interval analyzer TA720 !, and LEQ-Gain was set to 7. OdB. These measurement results will be described in detail below.

[0051] It should be noted that the measurement results of PPr and modulation degree with respect to the group width of the L0 optical functional layer 10 and the L1 optical functional layer 15 of the two-layer optical recording disk shown in FIG. The measurement results were almost the same as the measurement results of the L0 optical functional layer 10 and the L1 optical functional layer 15 of the four-layer optical recording disk described below. Only the optical recording disk will be described in detail.

FIG. 10 is a diagram showing the relationship between the group width, the PPr, and the modulation degree in the thickness of each recording layer of the four-layer optical recording disk in one embodiment of the present invention. 4 is a table showing the measurement results of PPr and modulation degree with respect to the width of the group in the thickness of each recording layer.

[0053] [Table 1]

[0054] From FIG. 10 and Table 1, it can be seen that PPr correlates with the width of the group not only with the thickness of the recording layer. This is because the optical phase change after recording can be suppressed by narrowing the group width, and the recording layer (L0 recording layer 8: 20 nm) is thick like the L0 optical functional layer 10. If this is the case, the PPr can be kept small by narrowing the group width. it can.

[0055] It can also be seen that the degree of modulation also has a correlation with the width of the group that depends on only the thickness of the recording layer. This is because the width of the recording mark can be increased by increasing the width of the group, such as L1 optical functional layer 15, L2 optical functional layer 19, and L3 optical functional layer 23. When the recording layer (L1 recording layer 13: 10 nm, L2 recording layer 17: 8 nm, L3 recording layer 21: 6 nm) is thin V, the modulation factor can be compensated for by widening the group width.

FIG. 11 is a diagram showing the relationship between the group width and PPnormal at each group depth of the four-layer optical recording disk according to one embodiment of the present invention, and Table 2 shows each group depth. It is a table | surface which shows the measurement result of PPnormal with respect to the width | variety of the group in.

is doing.

[0057] [Table 2]

[0058] From FIG. 11 and Table 2, it can be seen that PPnormal decreases with a peak at 160 nm where the width of the group is 1Z2 of the track pitch. PPnormal is also correlated with the depth of the group, and it can be seen that PPnormal can be increased by increasing the depth of the group. Therefore, the recording layer (L1 recording layer 13: 10 nm, L2 recording layer 17: 8 nm, L3 recording layer 21: 6 nm) like L1 optical functional layer 15, L2 optical functional layer 19, L3 optical functional layer 23 When the width of the group is widened to compensate for the degree of modulation when PP is thin, PPnormal decreases, so it is effective to increase PPnormal by increasing the group depth.

[0059] For example, the L0 optical functional layer 10 group width is 165 nm, the L1 optical functional layer 15 group width is 190 nm, the L2 optical functional layer 19 group width is 205 nm, and the L3 optical functional layer 10 group width is 205 nm. When the width of the functional layer 23 group is 225 nm, the depth of the LO optical functional layer 10 group is 18 nm, the depth of the L1 optical functional layer 15 group is 20 nm, and the depth of the L2 optical functional layer 19 group If the depth is 22 nm and the depth of the L3 optical functional layer 23 group is 24 nm, the PPnormal of each layer is almost the same value (about approximately as shown in point PPO, point PP1, point PP2, and point PP3 in Figure 11). 0.25) and stable tracking servo can be realized.

[0060] Table 3 is a table showing measurement results of recording / reproducing jitter with respect to the group depth and group width of each optical functional layer of the four-layer optical recording disk according to one embodiment of the present invention.

[0061] [Table 3]

[0062] From Table 3, it can be seen that the jitter tends to deteriorate as the group width is narrowed. This is because when the width of the group becomes narrower, the width of the recording mark also becomes narrower, and the side surface of the group that generates the main component of the media noise approaches the center of the beam spot (where the light intensity is the highest). This is because the SZN ratio of the playback signal becomes worse.

[0063] Also, from Table 3, it can be seen that the jitter deteriorates even if the group width becomes too wide. . This is because the side part of the adjacent track exerts a force on a part of the beam spot, so that the crosstalk of the wobble (meandering) signal of the adjacent track increases and the adjacent recording mark also approaches, so the crosstalk increases. Because.

[0064] Further, it can be seen from Table 3 that the above-mentioned influence increases as the depth of the group increases, so that the jitter tends to deteriorate. For this reason, considering the performance margin of the entire optical recording system, the practical group depth is preferably 26 nm or less.

[0065] Considering the performance margin of the entire optical recording system and the like, generally, if the jitter value is 6.5% or less in the LO optical functional layer 10, the L1 optical functional layer 15, L2 optical In the functional layer 19 and the L3 optical functional layer 23, 8.5% or less is satisfactory. In addition, PPr is good if it is 1.25 or less, good if the degree of modulation is 0.4 or more, and good if PPnormal is 0.21 or more.

[0066] From FIG. 10 and FIG. 11 and Tables 1 to 3, in order to satisfy the above numerical values, in the L0 optical functional layer 10, the group width is preferably in the range of 140 nm to 190 nm. Good. This is because if it is less than 140 mn, the jitter is less than 6.5%, and if it exceeds 190 nm, PPr exceeds 1.25, which is not preferable. Furthermore, considering the margin, in the L0 optical functional layer 10, the group width is more preferably 165 nm, more preferably in the range of 140 nm or more and 180 nm or less.

[0067] Similarly, in the L1 optical functional layer 15, the width of the group is preferably in the range of 160 nm or more and 220 nm or less. This is because when the degree of modulation is less than 160 mn, the degree of modulation is less than 0.4, and when it exceeds 220 nm, PPr exceeds 1.25, which is not preferable. Further, considering the margin, in the L1 optical functional layer 15, the group width is more preferably 190 nm, more preferably in the range of 170 nm to 210 nm.

[0068] Similarly, in the L2 optical functional layer 19, the group width is preferably in the range of 180 nm or more and 235 nm or less. This is because when the degree of modulation is less than 180 mn, the degree of modulation is less than 0.4, and when it exceeds 235 nm, PPr exceeds 1.25, which is not preferable. Further, considering the margin, in the L2 optical functional layer 19, the group width is more preferably 205 nm, more preferably in the range of 190 nm to 225 nm. [0069] Similarly, in the L3 optical functional layer 23, the group width is preferably in the range of 200 nm to 250 nm. This is because when the degree of modulation is less than 200 mn, the degree of modulation is less than 0.4, and when it exceeds 250 nm, PPr exceeds 1.25, which is not preferable. Further, considering the margin, in the L3 optical functional layer 23, the group width is more preferably in the range of 210 nm to 240 nm, and more preferably 225 nm.

[0070] From FIG. 10 and FIG. 11 and Tables 1 to 3, in order to satisfy the above numerical values, in the LO optical functional layer 10, when the group width is in the range of 140 nm or more and 190 nm or less, Since PPnormal is less than 0.21 if it is less than 14 nm, the depth of the group is preferably in the range of 14 nm or more and 26 nm or less. Furthermore, considering the margin, it is in the range of 16 nm or more and 20 nm or less. More preferably, it is 18 nm.

Similarly, in the L1 optical functional layer 15, when the group width is in the range of 160 nm or more and 220 nm or less, the PPnormal is less than 0.21 when the width is less than 15 nm, so the depth of the group is 15 nm. More preferably, the range is 26 nm or less, and considering the margin, the range of 18 nm or more and 22 nm or less is more preferable, and 20 nm is more preferable.

[0072] Similarly, in the L2 optical functional layer 19, when the group width is in the range of 180 nm or more and 235 nm or less, the PPnormal is less than 0.21 when the group width is less than 16 nm. The range of 26 nm or less is preferable, and considering the margin, the range of 20 nm to 24 nm is more preferable, and 22 nm is even more preferable.

[0073] Similarly, in the L3 optical functional layer 23, when the group width is in the range of 200 nm or more and 250 nm or less, the PPnormal is less than 0.21 when the width is less than 18 nm. The range of 26 nm or less is preferable, and considering the margin, the range of 22 nm or more and 26 nm or less is more preferable, more preferably 24 nm.

[0074] As described above, according to the present embodiment, the L1 optical functional layer 15, the L1 optical functional layer 15, and the L1 optical functional layer 15, Like the L2 optical functional layer 19 and the L3 optical functional layer 23, the incident surface force of the laser beam is close Since the loop width is wide, PPr can be kept small, and the modulation factor can be secured.

As a result, even when the incident surface force of the laser beam is far and the recording layer is thick like the optical functional layer 10, the PPnormal ratio (PPr) before and after recording can be reduced, so that the tracking performance is improved. It can be stabilized, and even if the recording layer is thin, such as the optical functional layer 15, the L2 optical functional layer 19, and the L3 optical functional layer 23, the required modulation degree is required. Therefore, a multilayer optical recording disk having good recording / reproducing characteristics can be realized.

In the above, the force described for the two-layer or four-layer optical recording disk The number of optical functional layers (recording layers) of the optical recording disk to which the present invention is applied is not particularly limited to the above example. Even if the optical recording disk has three or more layers, the width of the optical functional layer group on the support substrate side is the optical surface on the incident surface side in at least one set of optical functional layers. If the width of the functional layer group is narrower, the same effect can be obtained.

[0077] The above embodiment power is also summarized as follows. That is, the optical recording disk according to the present invention includes a support substrate and a plurality of optical functional layers formed on the support substrate, and a laser beam is applied to the optical functional layer from a direction opposite to the support substrate. An optical recording disk on which information is recorded and Z or reproduced by irradiation, wherein the plurality of optical functional layers include a support substrate side optical functional layer close to the support substrate and the support substrate side optical function layer. At least an incident surface side optical functional layer closer to the laser beam incident surface than the functional layer, and the width of the support substrate side optical functional layer group is greater than the width of the incident surface side optical functional layer group. Narrow,.

In this optical recording disk, the optical phase change after recording can be suppressed by narrowing the width of the support substrate side optical functional layer group, so that the PPnormal ratio before and after recording is reduced. In addition, since the width of the recording mark can be increased by increasing the width of the groove of the incident surface side optical functional layer, the degree of modulation can be increased. As a result, even when the recording layer is thick like the support substrate side optical functional layer, the PPnormal ratio before and after recording can be reduced, so that the tracking performance can be stabilized and the incident surface side optical Like the functional layer, the recording layer Even when it is thin, the degree of modulation can be increased, so that good recording and reproduction characteristics can be realized.

[0079] The thickness of the recording layer of the support substrate side optical functional layer is preferably larger than the thickness of the recording layer of the incident surface side optical functional layer. In this case, the degree of modulation of the reproduction signal from the recording layer of the support substrate side optical functional layer can be increased.

[0080] The modulation degree of the reproduction signal from the recording layer of the support substrate side optical functional layer is preferably larger than the modulation degree of the reproduction signal of the recording layer force of the incident surface side optical functional layer. In this case, it is possible to realize good recording / reproduction characteristics for the support substrate side optical functional layer.

[0081] It is preferable that the depth of the group of the support substrate side optical functional layer is shallower than the depth of the group of the incident surface side optical functional layer. In this case, PPnormal decreases when the width of the group of the optical surface layer on the incident surface side is increased in order to increase the degree of modulation, but the PPnormal increases by increasing the group depth of the optical surface layer on the incident surface side. And PPno rmal can be set to an appropriate value.

[0082] The recording layer of the support substrate side optical functional layer is preferably within 105 m from the laser incident surface. In this case, the optical aberration due to the disc tilt of the optical function layer on the support substrate side can be limited to a predetermined range, and a margin of jitter with respect to the necessary tilt range can be ensured.

[0083] The recording layer of the support substrate side optical functional layer is preferably made of an inorganic write-once recording material, and preferably contains at least one selected from the group consisting of Te, Pd, and O force as a main component. preferable. In this case, good recording / reproducing characteristics can be realized.

[0084] The width of the group of the plurality of optical functional layers is preferably close to the support substrate and narrower as the optical functional layer. In this case, the closer to the support substrate, the narrower the group width, the optical phase change after recording can be suppressed, so that PPr can be reduced. In addition, by increasing the width of the group sequentially as the support substrate force increases, the width of the recording mark can be increased, so that the degree of modulation can be increased.

[0085] The thickness of the recording layer of the plurality of optical functional layers is close to that of the support substrate, and the optical function It is preferable that the layer is thicker. In this case, the modulation degree of the reproduction signal can be increased by increasing the thickness of the recording layer as it is closer to the support substrate.

[0086] The degree of modulation of the reproduction signal from the recording layers of the plurality of optical functional layers is preferably larger as the optical functional layer is closer to the support substrate. In this case, by increasing the degree of modulation of the reproduction signal from the recording layer as it is closer to the support substrate, good recording / reproduction characteristics can be realized for all the optical functional layers.

[0087] The depth of the group of the plurality of optical functional layers is preferably shallower as the optical functional layer is closer to the support substrate. In this case, when the width of the optical functional layer group is gradually increased as the distance from the support substrate increases in order to increase the degree of modulation, the force that decreases the PPnormal is gradually increased. It can be deepened to increase PPnormal, and PPnormal can be set to an appropriate value for all optical functional layers.

[0088] A first group is formed on one main surface of the support substrate, and the support substrate side optical functional layer is formed on the one main surface of the support substrate on which the first group is formed. A first optical functional layer formed and including at least a first recording layer, further comprising a light transmissive layer formed on the first optical functional layer, wherein the first transmissive layer comprises: A second group is formed on a surface opposite to the optical functional layer, and the incident surface side optical functional layer is formed on the light transmission layer on which the second group is formed, and at least a second group is formed. The second optical functional layer including the recording layer is preferable. The track pitch of the first and second optical functional layers is in the range of 0.31 μm or more and 0.33 μm or less, and the width of the group of the first optical functional layers is 140 nm. The depth of the first optical functional layer group is more preferably in the range of 190 nm or less and the width of the second optical functional layer group is more preferably in the range of 160 nm or more and 220 nm or less. More preferably, the depth of the group of the second optical functional layer is in the range of 15 nm to 26 nm.

[0089] In this case, a two-layer optical recording disk is constituted by the first and second optical functional layers, and the tracking performance can be stabilized even when the recording layer is thick. Even if it is thin, a two-layer optical recording disk that can realize good recording and reproduction characteristics Can be provided.

[0090] The plurality of optical functional layers include first to fourth optical functional layers, a first group is formed on one main surface of the support substrate, and the first optical functional layer Is an optical functional layer that is formed on the one main surface of the support substrate on which the first group is formed and includes at least a first recording layer, on the first optical functional layer A first light transmission layer formed; a second group formed on a surface of the first light transmission layer opposite to the first optical functional layer; and the second optical transmission layer The functional layer is an optical functional layer that is formed on the first light transmission layer in which the second group is formed and includes at least a second recording layer, and on the second optical functional layer A second light transmission layer formed, and a third light transmission layer on a surface opposite to the second optical functional layer of the second light transmission layer. A group is formed, and the third optical functional layer is an optical functional layer formed on the second light transmission layer formed with the third group and including at least a third recording layer. A third light transmission layer formed on the third optical function layer, and a fourth light transmission layer on a surface opposite to the third optical function layer of the third light transmission layer. The fourth optical functional layer is an optical functional layer formed on the third light transmission layer formed with the fourth group and including at least a fourth recording layer. Yes, the width of the first optical functional layer group is smaller than the width of the second optical functional layer group, and the width of the second optical functional layer group is the third optical functional layer. The width of the group of the third optical functional layer, which is narrower than the width of the group of, is the width of the group of the fourth optical functional layer. Narrow is preferred.

[0091] Further, the plurality of optical functional layers include first to fourth optical functional layers, a first group is formed on one main surface of the support substrate, and the first optical layer is formed. The functional layer is an optical functional layer that is formed on the one main surface of the support substrate on which the first group is formed, and includes at least the first recording layer. A first light-transmitting layer formed on the optical functional layer; and a second group is formed on a surface of the first light-transmitting layer opposite to the first optical functional layer. And the second optical functional layer is an optical functional layer formed on the first light transmission layer in which the second group is formed and including at least a second recording layer, A second optical layer formed on the second optical functional layer. A light transmission layer, a third group is formed on a surface of the second light transmission layer opposite to the second optical function layer, and the third optical function layer includes the first optical function layer. 3 is an optical functional layer formed on the second light transmission layer on which the third groove is formed, and includes at least a third recording layer, and is formed on the third optical functional layer. 3, and a fourth group is formed on the surface of the third light transmissive layer opposite to the third optical functional layer, and the fourth optical functional layer. Is an optical functional layer formed on the third light transmission layer in which the fourth group is formed and including at least a fourth recording layer, and the first to fourth optical functional layers The track pitch is in the range of 0.311 to 0.33 m, and the width of the first optical functional layer group is in the range of 140 nm to 19 Onm. The width of the second optical functional layer group is in the range of 160 nm to 220 nm, and the width of the third optical functional layer group is in the range of 180 nm to 235 nm, The width of the fourth optical functional layer group is preferably in the range of 200 nm to 250 nm, and the depth of the first optical functional layer group is in the range of 14 nm to 26 nm, The groove depth of the second optical functional layer is in the range of 15 nm to 26 nm, and the depth of the groove of the third optical functional layer is in the range of 16 nm to 26 nm. The depth of the group of the fourth optical functional layer is more preferably in the range of 18 nm or more and 26 nm or less.

[0092] In the above case, a four-layer optical recording disk is constituted by the first to fourth optical functional layers. Even when the recording layer is thick, the tracking performance can be stabilized and the recording layer It is possible to provide a four-layer optical recording disk capable of realizing good recording / reproducing characteristics even when it is thin.

[0093] An optical recording system according to the present invention is an optical recording system that records and / or reproduces information by focusing laser light on the optical recording disk, and performs tracking by a push-pull method.

In this optical recording system, when information is recorded and Z or reproduced by converging the laser beam on the optical recording disk, tracking is performed by a push-pull method, so that it is stable. Tracking control can be realized.

[0095] An optical recording system according to the present invention focuses laser light on the optical recording disk. The optical recording system records and / or reproduces information according to the above, and the wavelength of the laser beam is in the range of 400 nm or more and 410 nm or less.

In this optical recording system, when information is recorded and / or reproduced by converging laser light on the optical recording disk, laser light having a wavelength in the range of 400 nm to 410 nm is used. Since it is used, information can be recorded and Z or reproduced with high density and stability.

[0097] An optical recording system according to the present invention is an optical recording system for recording and / or reproducing information by converging a laser beam on the optical recording disk, and an optical system for converging the laser beam. The NA of the system is in the range from 0.84 to 0.86.

In this optical recording system, when information is recorded and Z or reproduced by focusing the laser beam on the optical recording disk, NA in the range of 0.84 to 0.86 is used. Since the laser beam is converged using the optical system, information can be recorded and Z or reproduced with high density and stability.

Industrial applicability

[0099] The present invention is a technique relating to the parameters of the substrate and group shape of a high-density and multi-layer optical recording disk, and can stabilize the tracking performance even when the recording layer is thick. Even when the recording layer is thin, good recording / reproducing characteristics can be realized, so that it is useful as an optical recording disk suitable for high-density and large-capacity recording / reproducing and an optical recording system using the same.

Claims

The scope of the claims

[1] A support substrate and a plurality of optical functional layers formed on the support substrate, and information is recorded by irradiating the optical functional layer with the support substrate and a reverse force laser beam. And Z or an optical recording disc to be reproduced,

The plurality of optical functional layers include at least a support substrate side optical functional layer close to the support substrate, and an incident surface side optical functional layer closer to a laser beam incident surface than the support substrate side optical functional layer. ,

The optical recording disk according to claim 1, wherein a width of the group of the support substrate side optical functional layer is narrower than a width of the group of the incident surface side optical functional layer.

2. The optical recording disk according to claim 1, wherein the thickness of the recording layer of the support substrate side optical functional layer is larger than the thickness of the recording layer of the incident surface side optical functional layer.

3. The modulation degree of the reproduction signal from the recording layer of the support substrate side optical functional layer is larger than the modulation degree of the reproduction signal from the recording layer of the incident surface side optical functional layer. The optical recording disk according to 1 or 2.

[4] The optical recording according to any one of [1] to [3], wherein the depth of the group of the support substrate side optical functional layer is shallower than the depth of the group of the incident surface side optical functional layer. disk.

[5] The optical recording disk according to any one of [1] to [4], wherein the recording layer of the support substrate side optical functional layer is within 105 μm from the laser incident surface.

6. The optical recording disk according to any one of claims 1 to 5, wherein the recording layer of the support substrate side optical functional layer is made of an inorganic write-once recording material.

7. The recording layer of the support substrate side optical functional layer contains at least one selected from the group consisting of Te, Pd, and O as a main component. Optical recording disc.

8. The optical recording disk according to any one of claims 1 to 7, wherein a width of the group of the plurality of optical functional layers is close to the support substrate and is narrower as the optical functional layer.

9. The optical recording disk according to claim 1, wherein the recording layers of the plurality of optical functional layers are close to the support substrate and thicker as the optical functional layer. . [10] The degree of modulation of the reproduction signal from the recording layers of the plurality of optical functional layers is closer to the support substrate and larger as the optical functional layer, The optical recording disc described.

11. The optical recording disk according to claim 1, wherein the depth of the group of the plurality of optical functional layers is shallower as the optical functional layer is closer to the support substrate.

[12] A first group is formed on one main surface of the support substrate,

The support substrate side optical functional layer is formed on the one main surface of the support substrate on which the first group is formed, and includes a first optical functional layer including at least a first recording layer. And

A light transmission layer formed on the first optical functional layer;

A second group is formed on a surface of the light transmission layer opposite to the first optical functional layer;

The incident surface side optical functional layer is a second optical functional layer which is formed on the light transmission layer in which the second group is formed and includes at least a second recording layer. Claims 1 to: The optical recording disk according to any one of L1.

[13] The track pitch of the first and second optical functional layers is in a range from 0.31 m to 0.33 μm,

The width of the group of the first optical functional layer is in the range of 140 nm or more and 190 nm or less,

13. The optical recording disk according to claim 12, wherein the width of the group of the second optical functional layer is in a range of 160 nm or more and 220 nm or less.

[14] The depth of the group of the first optical functional layer is in the range of 14 nm to 26 nm, and the depth of the group of the second optical functional layer is in the range of 15 nm to 26 nm. 14. The optical recording disk according to claim 13, wherein:

[15] The plurality of optical functional layers include first to fourth optical functional layers,

A first group is formed on one main surface of the support substrate;

The first optical functional layer is formed in front of the support substrate on which the first group is formed. An optical functional layer formed on one main surface and including at least a first recording layer, further comprising a first light transmission layer formed on the first optical functional layer, A second group is formed on the surface of the light transmitting layer opposite to the first optical functional layer,

The second optical functional layer is an optical functional layer formed on the first light transmission layer in which the second group is formed and including at least a second recording layer,

A second light transmission layer formed on the second optical function layer; and a third group on a surface of the second light transmission layer opposite to the second optical function layer. Formed,

The third optical functional layer is an optical functional layer formed on the second light transmission layer in which the third group is formed and including at least a third recording layer,

A third light transmission layer formed on the third optical function layer; and a fourth group on a surface of the third light transmission layer opposite to the third optical function layer. Formed,

The fourth optical functional layer is an optical functional layer formed on the third light transmission layer in which the fourth group is formed and including at least a fourth recording layer,

The width of the group of the first optical functional layer is narrower than the width of the group of the second optical functional layer, and the width of the group of the second optical functional layer is the double of the third optical functional layer. The width of the group of the third optical functional layer narrower than the width of the first optical functional layer is narrower than the width of the group of fourth optical functional layer. Optical recording disc.

The plurality of optical functional layers include first to fourth optical functional layers,

A first group is formed on one main surface of the support substrate;

The first optical functional layer is an optical functional layer formed on the one main surface of the support substrate on which the first group is formed and including at least a first recording layer, A first light transmission layer formed on the first optical functional layer, and a second group on a surface of the first light transmission layer opposite to the first optical functional layer; Formed, The second optical functional layer is an optical functional layer formed on the first light transmission layer in which the second group is formed and including at least a second recording layer,

The track pitch of the first to fourth optical functional layers is in the range of 0.31 m or more and 0.33 μm or less,

The width of the group of the second optical functional layer is in the range of 160 nm or more and 220 nm or less,

The width of the group of the third optical functional layer is in a range of 180 nm or more and 235 nm or less,

16. The optical recording disk according to claim 1, wherein the width of the group of the fourth optical functional layer is in the range of 200 nm or more and 250 nm or less. The depth of the first optical functional layer group is in the range of 14 nm to 26 nm, and the depth of the second optical functional layer group is in the range of 15 nm to 26 nm,

The depth of the group of the third optical functional layer is in the range of 16 nm to 26 nm, 17. The optical recording disk according to claim 16, wherein the depth of the group of the fourth optical functional layer is in the range of 18 nm or more and 26 nm or less.

[18] An optical recording system for recording and / or reproducing information by converging a laser beam on the optical recording disk according to any one of claims 1 to 17,

An optical recording system that performs tracking by a push-pull method.

[19] An optical recording system for recording and / or reproducing information by converging a laser beam on the optical recording disk according to any one of claims 1 to 17,

An optical recording system characterized in that the wavelength of the laser beam is in the range of not less than 400 nm and not more than 410 nm.

[20] An optical recording system for recording and / or reproducing information by converging a laser beam on the optical recording disk according to any one of claims 1 to 17,

The optical recording system characterized in that the NA of the optical system for converging the laser light is in the range of 0.84 to 0.86.