WO2013190949A1

WO2013190949A1 - Recording medium and recording/reading device

Info

Publication number: WO2013190949A1
Application number: PCT/JP2013/064391
Authority: WO
Inventors: 松川　真; 智施神野; 信彦加藤
Original assignee: パイオニア株式会社
Priority date: 2012-06-18
Filing date: 2013-05-23
Publication date: 2013-12-27
Also published as: WO2013190626A1

Abstract

In a recording layer (11) there are laminated: a guide layer (12) onto which is directed a guiding laser beam (LB1) having a wavelength included in the range from 630 nm to 680 nm and a recording layer (13) onto which is directed a recording/reading laser beam (LB2) having a wavelength included in the range 400 nm to 410 nm. The recording layer has a laminated structure in which there are laminated a recording film (132) and dielectric films (131, 134). The refractive index of the dielectric films with respect to the guiding laser beam is no more than 2.2. The refractive index of the dielectric films with respect to the recording/reading laser beam is at least 1.85.

Description

Recording medium and recording / reproducing apparatus

The present invention relates to a technical field of a recording medium such as an optical disc having a large number of recording layers, and a recording / reproducing apparatus that performs at least one of a recording operation and a reproducing operation on such a recording medium.

As a recording medium including a large number of recording layers, for example, a recording medium having a plurality of recording layers that are actually targets of at least one of a recording operation and a reproducing operation, and a guide layer on which a tracking guide track is formed (for example, A so-called guide layer separation type optical disc) is known (see Patent Document 1). A recording / reproducing apparatus that performs at least one of a recording operation and a reproducing operation with respect to such a recording medium has a guide laser beam for reading the guide track of the guide layer, and at least one of the recording operation and the reproducing operation with respect to the recording layer. The recording / reproducing laser beam is irradiated. The recording / reproducing apparatus performs at least one of the recording operation and the reproducing operation by irradiating the recording layer with the recording / reproducing laser beam while performing tracking control based on the push-pull signal obtained from the return light of the guide laser beam.

In addition, Patent Document 2 is cited as a prior art document related to the present invention, although it is not a prior art document disclosing a guide layer separation type optical disc.

Japanese Patent No. 4037034 JP 2011-34611 A

By the way, in the guide layer separation type optical disc, the guide layer is located on the back side of the plurality of recording layers when viewed from the guide laser light emission side. For this reason, the guide laser beam passes through the plurality of recording layers before reaching the guide layer. For this reason, in order for the guide layer to be suitably irradiated with the guide laser beam, the transmittance of the guide laser beam in each of the plurality of recording layers is ensured (for example, the transmittance is a predetermined value (for example, 85%) or more). It is desirable to set On the other hand, a part of the guide laser beam is reflected by each of the plurality of recording layers. A part of the guide laser light reflected by each of the plurality of recording layers becomes so-called stray light. For this reason, the noise component resulting from stray light will be superimposed on the tracking error signal generated based on the return light of the guide laser light. As a result, there arises a technical problem that the signal quality of the tracking error signal is relatively deteriorated. In order to prevent such deterioration of the signal quality of the tracking error signal, the reflectance of the guide laser light in each of the plurality of recording layers is suppressed (for example, the reflectance is set to a predetermined value (for example, 10%) or less). ) Is desired.

On the other hand, in each of the plurality of recording layers, at least one of a recording operation and a reproducing operation is performed by a recording / reproducing laser beam having a wavelength different from the wavelength of the guide laser beam. In this case, in order for the recording / reproducing laser beam to be suitably irradiated to each of the plurality of recording layers, the transmittance of the recording / reproducing laser beam in each of the plurality of recording layers is ensured (for example, the transmittance is set to a predetermined value ( For example, it is desirable to set it to 80%) or higher. On the other hand, in order to suppress interference between a plurality of recording layers (for example, interference with other recording layers due to recording / reproducing laser light applied to one recording layer), each of the plurality of recording layers is suppressed. It is desirable to suppress the reflectance of the recording / reproducing laser beam in (for example, set the reflectance to a predetermined value (eg, 3%) or less).

In this way, the plurality of recording layers satisfy the condition that the guide laser light transmittance and the recording / reproducing laser light transmittance are ensured while the guide laser light reflectance and the recording / reproducing laser light reflectance are suppressed. It is desirable to satisfy. As a result, a recording / reproducing apparatus that performs at least one of a recording operation and a reproducing operation for a recording medium having a plurality of recording layers performs recording control using the return light of the guide laser light, and performs recording / reproducing laser light. At least one of the recording operation and the reproducing operation with respect to the plurality of recording layers used can be suitably performed (in other words, with high quality).

Incidentally, not only in a recording medium having a plurality of recording layers, but also in a recording medium having a guide layer and a single recording layer, the reflectance of the guide laser light and the reflectance of the recording / reproducing laser light are similarly suppressed. Thus, it goes without saying that it is desirable to satisfy the conditions of ensuring the transmittance of the guide laser beam and the transmittance of the recording / reproducing laser beam.

The present invention provides, for example, a recording medium including a recording layer that enables at least one of a recording operation and a reproducing operation to be suitably performed, and performs at least one of a recording operation and a reproducing operation on such a recording medium. It is an object to provide a recording / reproducing apparatus.

In order to solve the above problems, a recording medium includes a guide layer on which a guide track irradiated with guide laser light having a wavelength included in the range of 630 nm to 680 nm is formed, and a wavelength included in the range of 400 nm to 410 nm. A recording layer that is irradiated with a recording / reproducing laser beam, the recording layer comprising: (i) a recording film whose optical characteristics change by irradiation of the recording / reproducing laser beam; and (ii) a dielectric film. The dielectric film has a refractive index of 2.2 or less with respect to the guide laser beam, and the refractive index of the dielectric film with respect to the recording / reproducing laser beam is 1.85. That's it.

In order to solve the above problem, the recording / reproducing apparatus performs at least one of a recording operation and a reproducing operation with respect to the recording medium described above.

It is a typical perspective view which makes each layer easy to see by disassembling a plurality of layers constituting one optical disk at intervals in the stacking direction (vertical direction in FIG. 1). It is sectional drawing which shows the cross section of an optical disk with the irradiation aspect of a guide laser beam and a recording / reproducing laser beam. It is sectional drawing which shows each detailed structure of the some recording layer with which the optical disk of a present Example is provided. A correlation between the refractive index of a dielectric film composed of a mixture of TiO ₂ and SiO ₂ (that is, the refractive index with respect to the guide laser beam and the refractive index with respect to the recording / reproducing laser beam) and the SiO ₂ content is shown. It is a graph. It is a graph which shows the correlation between the refractive index of a dielectric film with respect to a recording / reproducing laser beam, a modulation degree, and modulation. It is sectional drawing which shows the recording layer of a 1st specific example. It is sectional drawing which shows the recording layer of a 2nd specific example. It is sectional drawing which shows the recording layer of a 3rd specific example. It is sectional drawing which shows the recording layer of a 4th example. It is sectional drawing which shows the recording layer of a 5th example. It is sectional drawing which shows the recording layer of a 1st comparative example. It is sectional drawing which shows the recording layer of a 2nd comparative example. It is sectional drawing which shows the recording layer of a 3rd comparative example. The characteristics of the recording layer of the first example, the characteristics of the recording layer of the second example, the characteristics of the recording layer of the third example, the characteristics of the recording layer of the fourth example, and the characteristics of the recording layer of the fifth example It is a table | surface which shows. It is a table | surface which shows the characteristic of the recording layer of a 1st comparative example, the characteristic of the recording layer of a 2nd comparative example, and the characteristic of the recording layer of a 3rd comparative example. It is a block diagram which shows the basic composition of a recording / reproducing apparatus. It is a block diagram which shows the structure of an optical pick-up.

Hereinafter, embodiments of the recording medium and the recording / reproducing apparatus will be described in order.

(Embodiment of recording medium)
<1>
The recording medium of the present embodiment has a guide layer on which a guide track is irradiated with a guide laser beam having a wavelength included in the range of 630 nm to 680 nm, and a recording / reproduction having a wavelength included in the range of 400 nm to 410 nm. A recording layer that is irradiated with a laser beam, and the recording layer is formed by stacking (i) a recording film whose optical characteristics are changed by irradiation of the recording / reproducing laser beam, and (ii) a dielectric film. The dielectric film has a refractive index of 2.2 or less with respect to the guide laser beam, and the refractive index of the dielectric film with respect to the recording / reproducing laser beam is 1.85 or more.

The recording medium of this embodiment includes a guide layer and a recording layer.

The guide layer is formed with a tracking guide track. Therefore, a recording / reproducing apparatus that performs at least one of a recording operation and a reproducing operation with respect to the recording medium (more specifically, with respect to a recording layer included in the recording medium) A push-pull signal corresponding to the positional relationship between the guide track and the beam spot of the guide laser light can be acquired based on the return light of the light (that is, the guide laser light reflected by the guide layer). As a result, the recording / reproducing apparatus can perform tracking control based on the push-pull signal.

The recording layer has a laminated structure in which a recording film and a dielectric film are laminated. Note that the recording film and the dielectric film may be laminated in this order when viewed from the laser beam emission side. Alternatively, the dielectric film and the recording film may be laminated in this order when viewed from the laser beam emission side.

The recording film is a film whose surface or internal optical characteristics change when irradiated with a recording / reproducing laser beam (for example, irradiated with a recording / reproducing laser beam focused on the recording film). . A place where the optical characteristic change occurs is treated as one of the so-called “mark part” and “space part”, and a part where the optical characteristic change does not occur is any of the so-called “mark part” or “space part”. By treating it as the other, data is recorded on the recording layer.

The dielectric film is a film for improving reliability with respect to power fluctuations in the recording film (that is, fluctuations in the power of the recording / reproducing laser beam irradiated on the recording film). The dielectric film may be used to protect the recording film in addition to or instead of improving the reliability against power fluctuations in the recording film.

Note that the wavelength of the guide laser light mainly used for tracking control is in the range of 630 nm to 680 nm. In other words, the wavelength λ1 of the guide laser light satisfies the condition of 630 nm ≦ λ1 ≦ 680 nm. That is, the guide laser beam may be substantially equivalent to the red laser beam. On the other hand, the wavelength of the recording / reproducing laser beam used mainly for at least one of the recording operation and the reproducing operation with respect to the recording layer is in the range of 400 nm to 410 nm. In other words, the wavelength λ2 of the recording / reproducing laser beam satisfies the condition of 400 nm ≦ λ2 ≦ 410 nm. That is, the recording / reproducing laser beam may be substantially equivalent to the blue laser beam.

The recording medium of this embodiment is particularly designed so that the refractive index of the dielectric film constituting the recording layer satisfies the following conditions. Specifically, the refractive index of the dielectric film with respect to the guide laser beam is designed to be 2.2 or less. In addition, the refractive index of the dielectric film with respect to the recording / reproducing laser beam is designed to be 1.85 or more.

By forming the recording layer from the dielectric film having such a refractive index, the recording layer (i-1) suppresses the reflectance of the guide laser beam (for example, the reflectance is a predetermined value (for example, 10 And (i-2) suppressing the reflectance of the recording / reproducing laser beam (for example, setting the reflectance to a predetermined value (for example, 3%) or less), while (ii-1) The transmittance of the guide laser beam is ensured (for example, the transmittance is set to a predetermined value (for example, 85%) or more), and (ii-2) the transmittance of the recording / reproducing laser beam is secured (for example, the transmittance is The condition of setting to a predetermined value (for example, 80% or more) can be satisfied. As a result, the recording / reproducing apparatus that performs at least one of the recording operation and the reproducing operation on the recording medium having such a recording layer uses the recording / reproducing laser beam while performing the tracking control using the return light of the guide laser beam. At least one of the recording operation and the reproducing operation with respect to the plurality of recording layers can be suitably performed (in other words, with high quality).

<2>
In another aspect of the recording medium of the present embodiment, the dielectric film includes at least one of an inorganic compound and a mixture of inorganic compounds.

According to this aspect, the dielectric film having the refractive index described above can be realized relatively easily by at least one of the inorganic compound and the mixture of inorganic compounds. Therefore, the various effects described above are suitably realized.

<3>
In the aspect of the recording medium in which the dielectric film includes at least one of an inorganic compound and a mixture of inorganic compounds as described above, the dielectric film includes (i) an oxide of Zn, an oxide of Ti, an oxide of Zr, or Sn. (Ii) Al nitride, or (iii) Zn sulfide.

According to this aspect, (i) oxidation of Zn oxide (ie ZnO), Ti oxide (ie TiO ₂ ), Zr oxide (ie ZrO ₂ ) or Sn (ie SnO ₂ ) The dielectric film having the above-described refractive index can be realized relatively easily by the material, (ii) Al nitride (ie, AlN), or (iii) Zn sulfide (ie, ZnS). Therefore, the various effects described above are suitably realized.

<4>
In the aspect of the recording medium in which the dielectric film includes at least one of an inorganic compound and a mixture of inorganic compounds as described above, the dielectric film includes (i) Zn oxide, Ti oxide, Zr oxide, Si And a mixture of at least two of (ii) Al nitride, and (iii) Zn sulfide.

According to this aspect, (i) Zn oxide (ie, ZnO), Ti oxide (ie, TiO ₂ ), Zr oxide (ie, ZrO ₂ ), Si oxide (ie, SiO ₂₎ ) And Sn (ie, SnO ₂ ), (ii) Al nitride (ie, AlN), and (iii) Zn sulfide (ie, ZnS). The dielectric film having the refractive index described above can be realized relatively easily. Therefore, the various effects described above are suitably realized.

<5>
In the aspect of the recording medium in which the dielectric film includes at least one of an inorganic compound and a mixture of inorganic compounds as described above, the dielectric film includes a mixture of TiO ₂ and SiO ₂ .

According to this aspect, the dielectric film having the above-described refractive index can be realized relatively easily by the mixture of TiO ₂ and SiO ₂ . Therefore, the various effects described above are suitably realized.

<6>
In the aspect of the recording medium in which the dielectric film includes a mixture of TiO ₂ and SiO ₂ as described above, the dielectric film includes 15 mol% or more and 59 mol% or less of SiO ₂ .

According to this aspect, the dielectric film having the above-described refractive index can be relatively easily made by the mixture of TiO ₂ and SiO ₂ (however, the mixture having a SiO ₂ content of 15 mol% or more and 59 mol% or less). Can be realized. Therefore, the various effects described above are suitably realized.

<7>
In another aspect of the recording medium of the present embodiment, the extinction coefficient of the dielectric film with respect to the guide laser beam is 0.05 or less, and the extinction coefficient of the dielectric film with respect to the recording / reproducing laser beam is 0. 05 or less.

According to this aspect, the absorption of the guide laser beam and the recording / reproducing laser beam in the dielectric film (in other words, the absorption of the guide laser beam and the recording / reproducing laser beam in the recording layer composed of the dielectric film) can be suppressed. it can. As a result, the recording layer can satisfy the conditions of ensuring the transmittance of the guide laser beam and the recording / reproducing laser beam while suppressing the reflectance of the guide laser beam and the recording / reproducing laser beam. As a result, the various effects described above are suitably realized.

<8>
In another aspect of the recording medium of the present embodiment, the modulation degree of the data recorded on the recording layer is 40% or more by changing the optical characteristics of the recording film by the irradiation of the recording / reproducing laser beam.

According to this aspect, the recording / reproducing apparatus that performs at least one of the recording operation and the reproducing operation with respect to the recording medium having such a recording layer performs the tracking control using the return light of the guide laser light, and performs the recording / reproducing laser beam. At least one of the recording operation and the reproducing operation with respect to a plurality of recording layers using can be performed suitably (in other words, with high quality). As a result, the various effects described above are suitably realized.

<9>
In another aspect of the recording medium of the present embodiment, the thickness of the dielectric film in the stacking direction is 20 nm or more and 110 nm or less.

According to this aspect, the dielectric film having the above-described refractive index can be realized relatively easily by the dielectric film having such a thickness (that is, the film thickness). Therefore, the various effects described above are suitably realized.

<10>
In another aspect of the recording medium of the present embodiment, the recording layer further includes another dielectric film disposed so as to sandwich the recording film between the recording film and the dielectric film.

According to this aspect, even if the recording layer further includes another dielectric film, the above-described various effects are suitably realized.

The other dielectric films, like the above-described dielectric film, improve reliability with respect to power fluctuations in the recording film (that is, fluctuations in the power of the recording / reproducing laser beam applied to the recording film). It may be a membrane. Alternatively, the other dielectric film may be a film for protecting the recording film.

Further, when the recording layer further includes another dielectric film, it is preferable that the other dielectric film is designed so as to satisfy the above-described conditions (that is, have the above-described characteristics). However, other dielectric films may be designed so as not to satisfy the above conditions.

<11>
In another aspect of the recording medium of the present embodiment, the recording layer further includes a light absorption film that forms the laminated structure together with the recording film and the dielectric film.

According to this aspect, even if the recording medium is further provided with the light absorbing film, the above-described various effects are suitably realized. The light absorbing film is a film mainly for absorbing recording / reproducing laser light and supplying necessary energy to the recording layer.

<12>
In another aspect of the recording medium of the present embodiment, the light absorption film is mainly composed of an oxide of Fe.

According to this aspect, the above-described light absorption film can be realized relatively easily by the oxide of Fe. Therefore, the various effects described above are suitably realized.

<13>
In another aspect of the recording medium of the present embodiment, the recording film contains Bi and O.

According to this aspect, the recording film described above can be realized relatively easily by Bi and O. Therefore, the various effects described above are suitably realized.

<14>
In another aspect of the recording medium of the present embodiment, a plurality of the recording layers are provided.

According to this aspect, even if the recording medium includes a plurality of recording layers, the various effects described above are preferably realized.

When the recording medium includes a plurality of recording layers, the dielectric film constituting each of the plurality of recording layers is designed so as to satisfy the above conditions (that is, have the above characteristics). It is preferable. However, while the dielectric film constituting a part of the plurality of recording layers satisfies the above conditions, the dielectric film constituting the other part of the plurality of recording layers You may design so that the above-mentioned conditions may not be satisfied.

(Embodiment of recording / reproducing apparatus)
<15>
The recording / reproducing apparatus of the present embodiment performs at least one of a recording operation and a reproducing operation on the recording medium of the present embodiment described above (including various aspects thereof).

The recording / reproducing apparatus of this embodiment (i-1) suppresses the reflectance of the guide laser beam (for example, sets the reflectance to a predetermined value (for example, 10%) or less) and (i-2) records / reproduces While suppressing the reflectance of the laser beam (for example, setting the reflectance to a predetermined value (for example, 3%) or less), (ii-1) ensuring the transmittance of the guide laser beam (for example, reducing the transmittance) (Ii-2) Conditions for ensuring the transmittance of the recording / reproducing laser beam (for example, setting the transmittance to a predetermined value (for example, 80%) or more) At least one of a recording operation and a reproducing operation can be performed on the recording layer that satisfies the above. As a result, the recording / reproducing apparatus of this embodiment preferably performs at least one of the recording operation and the reproducing operation with respect to the plurality of recording layers using the recording / reproducing laser beam while performing the tracking control using the return light of the guide laser beam. (In other words, high quality). Therefore, the various effects described above are suitably realized.

Incidentally, in response to various aspects that can be adopted by the recording medium of the present embodiment, the recording / reproducing apparatus of the present embodiment may also adopt various aspects.

Such an operation and other advantages of the present embodiment will be further clarified from examples described below.

As described above, the recording medium of the present embodiment includes a guide layer and a recording layer, and the dielectric film constituting the recording layer has a refractive index with respect to the guide laser beam of 2.2 or less and a recording / reproducing laser beam. The condition that the refractive index with respect to is 1.85 or more is satisfied. The recording / reproducing apparatus of this embodiment performs at least one of a recording operation and a reproducing operation with respect to the recording medium of this embodiment. Therefore, at least one of the recording operation and the reproducing operation with respect to the plurality of recording layers using the recording / reproducing laser beam is preferably performed (in other words, with high quality) while performing the tracking control using the return light of the guide laser beam. Can do.

Hereinafter, examples will be described with reference to the drawings.

(1) Configuration of Optical Disc First, the configuration of the optical disc 11 will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic perspective view in which a plurality of layers constituting one optical disk 11 are disassembled at intervals in the stacking direction (vertical direction in FIG. 1) to make each layer easy to see. FIG. FIG. 2 is a cross-sectional view showing a cross section of the optical disc 11 together with the irradiation modes of the guide laser beam LB1 and the recording / reproducing laser beam LB2.

As shown in FIG. 1, the optical disc 11 includes a single guide layer 12 and a plurality of (that is, two or more) recording layers 13. That is, the optical disk 11 is a so-called guide layer separation type optical disk. The optical disc 11 may include a single recording layer 13 instead of the plurality of recording layers 13.

When a recording operation on the optical disc 11 (particularly, a recording operation on a desired recording layer 13) is performed, the tracking guide laser beam LB1 focused on the guide layer 12 and the plurality of recording layers 13 are collected. The recording / reproducing laser beam LB2 emitted is simultaneously irradiated from the recording / reproducing apparatus 100. On the other hand, also when a reproducing operation on the optical disc 11 (particularly, a reproducing operation on a desired recording layer 13) is performed, the guide laser beam LB1 and the recording / reproducing laser beam LB2 are simultaneously irradiated from the recording / reproducing apparatus 100. . However, when a reproducing operation is performed on the optical disc 11, the recording / reproducing laser beam LB2 may be used for tracking (that is, the guide laser beam LB1 may not be used).

Note that the wavelength of the guide laser beam LB1 mainly used for tracking control is in the range of 630 nm to 680 nm. In other words, the wavelength λ1 of the guide laser beam LB1 satisfies the condition of 630 nm ≦ λ1 ≦ 680 nm. That is, the guide laser beam LB1 may be substantially equivalent to the red laser beam. However, the lower limit value of the wavelength λ1 of the guide laser beam LB1 is set in consideration of a predetermined margin (that is, an error that can be substantially regarded as 630 nm) α1 with respect to the above-described numerical value of “630 nm”. It may be set. Similarly, the upper limit value of the wavelength λ1 of the guide laser beam LB1 is set in consideration of a predetermined margin (substantially an error that can be regarded as 680 nm) β1 with respect to the numerical value of “680 nm” described above. May be. Therefore, the wavelength λ1 of the guide laser beam LB1 may satisfy the condition of 630 ± α1 nm ≦ λ1 ≦ 680 ± β1 nm.

Further, the wavelength of the recording / reproducing laser beam LB2 mainly used for at least one of the recording operation and the reproducing operation with respect to each of the plurality of recording layers 13 is in the range of 400 nm to 410 nm. In other words, the wavelength λ2 of the recording / reproducing laser beam LB2 satisfies the condition of 400 nm ≦ λ2 ≦ 410 nm. That is, the recording / reproducing laser beam LB2 may be substantially equivalent to the blue laser beam. However, the lower limit value of the wavelength λ2 of the recording / reproducing laser beam LB2 takes into account a predetermined margin (that is, an error that can be substantially regarded as 400 nm) α2 with respect to the numerical value of “400 nm” described above. May be set. Similarly, the upper limit value of the wavelength λ2 of the recording / reproducing laser beam LB2 is set in consideration of a predetermined margin (substantially an error that can be regarded as 410 nm) β2 with respect to the above-described numerical value of “410 nm”. It may be set. Therefore, the wavelength λ2 of the recording / reproducing laser beam LB2 may satisfy the condition of 400 ± α2 nm ≦ λ2 ≦ 410 ± β2 nm.

The optical disk 11 preferably adopts the CLV method. In the concentric or spiral guide track TR (specifically, a groove track GT and a land track LT described later), preformat information (for example, clock information, address information, recording start, etc.) conforms to the CLV system. Timing information, etc.) is recorded in advance.

The guide track TR formed on the guide layer 12 may be a single spiral. In this case, the groove track GT is preferably switched to the land track LT in a predetermined region of the guide layer 12. Similarly, the land track LT is preferably switched to the groove track GT in a predetermined region of the guide layer 12. However, the guide track TR may be a double spiral in which the groove track GT and the land track LT are separated.

As shown in FIG. 2, the recording / reproducing laser beam LB2 is focused on one desired recording layer 13 to be recorded or reproduced among the plurality of recording layers 13 stacked on the guide layer 12. The recording / reproducing laser beam LB2 is a blue laser beam having a relatively short wavelength, for example, like BD (Blu-ray (registered trademark) Disc: Blu-ray Disc). On the other hand, the guide laser beam LB1 is a red laser beam having a relatively long wavelength, for example, like DVD. The diameter of the beam spot formed on the guide layer 12 by the guide laser beam LB1 is, for example, about several times the diameter of the beam spot formed on the recording layer 13 by the recording / reproducing laser beam LB2.

Each of the plurality of recording layers 13 is a recording layer capable of optically recording and reproducing recording information independently. More specifically, each of the plurality of recording layers 13 is composed of, for example, a translucent thin film containing a two-photon absorption material. For example, as a two-photon absorption material, a fluorescent type using a fluorescent material in which the fluorescence intensity in a region where two-photon absorption occurs is changed, a refractive index changing type using a photorefractive material in which the refractive index is changed by electron localization, etc. However, it can be adopted. The use of photochromic compounds, bis (aralkylidene) cycloalkanone compounds, etc. is promising as refractive index changing type two-photon absorption materials.

The optical disk structure using a two-photon absorption material includes (i) a bulk type in which the entire optical disk 11 is made of a two-photon absorption material, and (ii) a recording layer 13 of a two-photon absorption material and a spacer layer 15 of another transparent material. There is a layer structure type in which are stacked alternately. The layer structure type has an advantage that focus control can be performed using light reflected at the interface between the recording layer 13 and the spacer layer 15. The bulk type has an advantage that the manufacturing cost can be suppressed because there are few multilayer film forming steps.

Each of the plurality of recording layers 13 may be, for example, a dye material in addition to the above-described two-photon absorption material, phase change material using an inorganic material, alloying type, and punching type. In each of the plurality of recording layers 13, the guide track TR is not formed in advance in an unrecorded state, and for example, the entire region is a mirror surface or a flat surface without unevenness.

(2) Detailed Configuration of Recording Layer Next, with reference to FIG. 3, the detailed configuration of each of the plurality of recording layers 13 included in the optical disc 11 of the present embodiment will be described. FIG. 3 is a cross-sectional view showing a detailed configuration of each of the plurality of recording layers 13 provided in the optical disc 11 of the present embodiment.

As shown in FIG. 3, the optical disc 11 includes a cover layer 14, a plurality of recording layers 13, a plurality of spacer layers 15, a guide layer 12, a 2P (Photo Polymer) layer 16, and a substrate 17. Yes. The plurality of recording layers 13 and the plurality of spacer layers 15 are arranged such that two adjacent recording layers 13 sandwich one spacer layer 15 therebetween. Note that the upper side of FIG. 3 is the emission side of the guide laser beam LB1 and the recording / reproducing laser beam LB2.

The cover layer 14 is a layer located on the outermost surface side of the optical disc 11 and is used to protect each layer formed on the lower layer side of the cover layer 14. The cover layer 14 has a thickness of 54 μm, for example. As the cover layer 14, a general cover layer may be used.

The spacer layer 15 is a member positioned between two adjacent recording layers 13 (in other words, a member for bonding the two adjacent recording layers 13 together). The total thickness of one recording layer 13 and one spacer layer 15 adjacent to each other is, for example, 12 μm or 16 μm. As the spacer layer 15, a general spacer layer may be used.

The 2P layer 16 is a member positioned between the plurality of recording layers 13 and the guide layer 12. The 2P layer 16 has a thickness of 146 μm, for example. The refractive index of the 2P layer 16 is 1.5, for example.

The substrate 17 is a member that is the basis of the optical disk 11. The material of the substrate 15 may be various materials such as glass, ceramics, and resin. As the resin constituting the substrate 15, polycarbonate resin, olefin resin, acrylic resin, epoxy resin, polystyrene resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, Urethane resin or the like may be used. Of these, polycarbonate resin and olefin resin are preferable from the viewpoint of ease of processing and molding. In this embodiment, polycarbonate resin is used.

Each of the plurality of recording layers 13 includes a dielectric film 131, a recording film 132, a light absorption film 133, and a dielectric film 134 as viewed from the emission side of the guide laser beam LB1 and the recording / reproducing laser beam LB2. Has a laminated structure. However, each of the plurality of recording layers 13 may not include any one of the dielectric film 131 and the dielectric film 134. Alternatively, each of the plurality of recording layers 13 may not include the light absorption film 133.

The dielectric film 131 functions as a film that improves the reliability against power fluctuations in the recording film 132 (that is, the power of the recording / reproducing laser beam LB2 when the recording film 132 is irradiated). Further, the dielectric film 131 may have a function of making it difficult for moisture in the substrate 17 or external moisture to reach the recording film 132 (that is, a function of suppressing alteration of the recording film 132). The characteristics of the dielectric film 131 will be described in detail later.

The recording film 132 functions as an inorganic reaction film, and is melted and mixed by the heat of the recording / reproducing laser beam LB2. As a result, the reflectance of the recording film 132 changes depending on whether or not the recording / reproducing laser beam LB2 is irradiated. As a main component of the recording film 132, Bi—O or Bi—MO (where M is Mg, Ca, Y, Dy, Ce, Tb, Ti, Zr, V, Nb, Ta, Mo, W, Mn, Fe, Zn, Al, In, Si, Ge, Sn, Sb, Li, Na, K, Sr, Ba, Sc, La, Nd, Sm, Gd, Ho, Cr, Co, Ni, Cu, Ga, Pb It is preferable that the main component is at least one element selected from among them. In this embodiment, for the sake of convenience of explanation, the description will be made using an example in which Bi—Ge—O is used as the main component of the recording film 132. The film thickness of the recording film 132 is 10 nm, for example. However, the film thickness of the recording film 133 may be any value other than 10 nm.

The light absorption film 133 has a function of supplying the necessary energy to the recording film 132 by absorbing the recording / reproducing laser beam LB2. As a main component of the light absorption film 133, Fe ₃ O ₄ is preferably used. However, instead of Fe ₃ O ₄ as the main component of the light absorption film, Fe ₂ O ₃ , FeO, CrO, Cr ₂ O ₃ , MnO, Mn ₂ O ₃ , MnO ₂ , V and ₂ O _3, VO ₂ _and, and V 2 _{O 5,} NiO and may be _Nd 2 _{O 3} and the like are used. The film thickness of the light absorption film 133 is 2 nm, for example. However, the film thickness of the light absorption film 133 may be any value other than 2 nm.

As described above, in this embodiment, a Bi-MO peroxide is used as the material of the recording film 132. The recording film 132 is formed by reactive sputtering. Since the light absorption film 133 may be oxidized during the formation of the recording film 132, it is preferable to use a material having light absorption characteristics in the oxide state as the material of the light absorption film 133.

The dielectric film 134 functions as a film that improves the reliability against the power fluctuation in the recording film 132 (that is, the power of the recording / reproducing laser beam LB2 when the recording film 132 is irradiated). In addition, the dielectric film 134 may have a function of making it difficult for moisture in the substrate 17 or external moisture to reach the recording film 132 (that is, a function of suppressing alteration of the recording film 132). The characteristics of the dielectric film 134 will be described later in detail.

(3) Characteristics of Dielectric Film Next, characteristics of the dielectric film 131 and the dielectric film 134 constituting the recording layer 13 will be described.

In the following description, the description will be focused on the characteristics of the dielectric film 131 in order to simplify the description. However, it goes without saying that the characteristics of the dielectric film 134 may match the characteristics of the dielectric film 131. However, some of the characteristics of the dielectric film 134 coincide with some of the characteristics of the dielectric film 131, while the other part of the characteristics of the dielectric film 134 is the other part of the characteristics of the dielectric film 131. Does not have to match. Alternatively, not all the characteristics of the dielectric film 134 need to match the characteristics of the dielectric film 131.

In addition, the dielectric film 131 constituting each of the plurality of recording layers 13 preferably has the following characteristics. That is, it is preferable that all the dielectric films 131 included in the optical disc 11 have the following characteristics. However, the dielectric film 131 that constitutes a part of the plurality of recording layers 13 has at least a part of the following characteristics, while the other part of the plurality of recording layers 13. The dielectric film 131 constituting the recording layer 13 may not have the following characteristics.

First, the dielectric film 131 has a characteristic that the refractive index with respect to the guide laser beam LB1 is 2.2 or less. The numerical value “2.2” corresponds to the upper limit value of the refractive index of the dielectric film 131 with respect to the guide laser beam LB1. On the other hand, a lower limit value of the refractive index of the dielectric film 131 with respect to the guide laser beam LB1 may be set. For example, the dielectric film 131 may have a characteristic that the refractive index with respect to the guide laser beam LB1 is 1.35 or more.

In addition, the dielectric film 131 has a characteristic that the refractive index with respect to the recording / reproducing laser beam LB2 is 1.85 or more. The numerical value “1.85” corresponds to the lower limit value of the refractive index of the dielectric film 131 with respect to the recording / reproducing laser beam LB2. On the other hand, an upper limit value of the refractive index of the dielectric film 131 with respect to the recording / reproducing laser beam LB2 may be set. For example, the dielectric film 131 may have a characteristic that the refractive index with respect to the recording / reproducing laser beam LB1 is 2.8 or less.

As a material of the dielectric film 131 having such a refractive index, Zn oxide (that is, ZnO), Ti oxide (that is, TiO ₂ ), Zr oxide (that is, ZrO ₂ ), Sn (that is, that is) , SnO ₂ ) oxide, Al nitride (ie, AlN), or Zn sulfide (ie, ZnS). In other words, the dielectric film 131 may be ZnO, TiO ₂ , ZrO ₂ , SnO ₂ , AlN or ZnS. Alternatively, the dielectric film 131 may contain ZnO, TiO ₂ , ZrO ₂ , SnO ₂ , AlN, or ZnS as part of its components.

Alternatively, as a material of the dielectric film 131 having such a refractive index, Zn oxide (that is, ZnO), Ti oxide (that is, TiO ₂ ), Zr oxide (that is, ZrO ₂ ), Si An example is a mixture of at least two of the following oxides (ie, SiO ₂ ), Sn (ie, SnO ₂ ) oxide, Al nitride (ie, AlN), and Zn sulfide (ie, ZnS). It is given as. In other words, the dielectric film 131 may be a mixture of at least two of ZnO, TiO ₂ , ZrO ₂ , SiO ₂ , SnO ₂ , AlN, and ZnS. Alternatively, the dielectric film 131 may contain at least one of ZnO, TiO ₂ , ZrO ₂ , SnO ₂ , AlN, and ZnS as a part of its components.

Specifically, for example, the dielectric film 131 made of ZnO has a refractive index with respect to the guide laser beam LB1 of 1.93 (that is, 2.2 or less) and a refractive index with respect to the recording / reproducing laser beam LB2. Is 2.06 (that is, 1.85 or more). Alternatively, for example, the dielectric film 131 made of AlN has a refractive index with respect to the guide laser beam LB1 of 1.90 (that is, 2.2 or less) and a refractive index with respect to the recording / reproducing laser beam LB2 of 1. The characteristic is 96 (that is, 1.85 or more). Alternatively, for example, the dielectric film 131 made of ZrO ₂ —Y ₂ O ₃ (where the weight percentage of Y ₂ O ₃ is 5 wt%) has a refractive index of 2.06 with respect to the guide laser beam LB1 (that is, And a refractive index with respect to the recording / reproducing laser beam LB2 is 2.11 (that is, 1.85 or more). Alternatively, for example, the dielectric film 131 made of a mixture of TiO ₂ and SiO ₂ (however, the content of SiO ₂ is 35 mol%) has a refractive index of 1.95 with respect to the guide laser beam LB1 (that is, And the refractive index with respect to the recording / reproducing laser beam LB2 is 2.08 (that is, 1.85 or more). Alternatively, for example, the dielectric film 131 made of a mixture of TiO ₂ and Al ₂ O ₃ (however, the content of Al ₂ O ₃ is 50 mol%) has a refractive index of 1.87 with respect to the guide laser beam LB1. (That is, 2.2 or less) and the refractive index with respect to the recording / reproducing laser beam LB2 is 1.91 (that is, 1.85 or more). Alternatively, for example, the dielectric film 131 made of a mixture of ZnS and SiO ₂ (however, the content of SiO ₂ is 20 mol%) has a refractive index of 2.14 with respect to the guide laser beam LB1 (that is, 2 And a refractive index with respect to the recording / reproducing laser beam LB2 is 2.36 (that is, 1.85 or more). Alternatively, for example, the dielectric film 131 made of a mixture of ZnO and SnO ₂ (however, the content of SnO ₂ is 30 mol%) has a refractive index of 2.01 with respect to the guide laser beam LB1 (that is, 2 And a refractive index with respect to the recording / reproducing laser beam LB2 is 2.195 (that is, 1.85 or more).

In the present embodiment, a mixture of TiO ₂ and SiO ₂ is preferably used as the material of the dielectric film 131. That is, the dielectric film 131 is preferably a mixture of TiO ₂ and SiO ₂ . In this case, in particular, the content of SiO ₂ is preferably 15 mol% or more and 59 mol% or less. In other words, it is preferable that the lower limit of the SiO ₂ content is 15 mol% and the upper limit of the SiO ₂ content is 59 mol%.

Here, referring to FIG. 4, when a mixture of TiO ₂ and SiO ₂ is used as the material of the dielectric film 131, it is preferable that the SiO ₂ content is 15 mol% or more and 59 mol% or less. Will be described. FIG. 4 shows the refractive index of the dielectric film 131 composed of a mixture of TiO ₂ and SiO ₂ (that is, the refractive index with respect to the guide laser beam LB1 and the refractive index with respect to the recording / reproducing laser beam LB2) and the SiO ₂ content rate. It is a graph which shows the correlation between.

As shown in FIG. 4, both the refractive index of the dielectric film 131 with respect to the guide laser beam LB1 and the refractive index of the dielectric film 131 with respect to the recording / reproducing laser beam LB2 increase the content of SiO ₂ in the dielectric film 131. Decreases as you go.

Here, when the content ratio of SiO ₂ becomes 15 mol%, the refractive index of the guide laser beam LB1 becomes 2.2. Therefore, in order to make the refractive index of the guide laser beam LB1 2.2 or less, the content of SiO ₂ is preferably 15 mol% or more.

In addition, when the content ratio of SiO ₂ reaches 59 mol%, the refractive index of the recording / reproducing laser beam LB2 becomes 1.85. Therefore, in order to set the refractive index of the recording / reproducing laser beam LB2 to 1.85 or more, the SiO ₂ content is preferably 59 mol% or less.

FIG. 4 is a graph obtained by connecting the sample values of the refractive index obtained through experiments by the inventors of the present application with an approximate curve. However, the accuracy of the sample value of the refractive index and the accuracy of the approximate curve may be affected. For this reason, the lower limit value of the content of SiO ₂ takes into account a predetermined margin (that is, an error that can be substantially regarded as 15 mol%) γ1 with respect to the numerical value of “15 mol%” described above. May be set. Similarly, the upper limit of the content rate of SiO ₂ is set in consideration of a predetermined margin (that is, an error that can be equated with 59 mol%) γ2 with respect to the numerical value of “59 mol%” described above. Also good. Accordingly, the content of SiO ₂ may be met 15 ± γ1mol% ≦ SiO ₂ content ratio ≦ 59 ± γ2mol% conditions.

Further, in order to realize the dielectric film 131 that satisfies the above-described refractive index condition, the dielectric film 131 has a characteristic that the extinction coefficient with respect to the guide laser beam LB1 is 0.05 or less. preferable. In other words, the upper limit value of the extinction coefficient of the dielectric film 131 with respect to the guide laser beam LB1 is preferably 0.05.

Further, in order to realize the dielectric film 131 that satisfies the above-described refractive index condition, the dielectric film 131 has a characteristic that the extinction coefficient with respect to the recording / reproducing laser beam LB2 is 0.05 or less. Is preferred. The upper limit value of the extinction coefficient of the dielectric film 131 with respect to the recording / reproducing laser beam LB2 is preferably 0.05.

The upper limit value of the extinction coefficient is based on the above-described numerical value of “0.05” after taking into account a predetermined margin (that is, an error that can be substantially regarded as 0.05) δ. It may be set. That is, the upper limit value of the extinction coefficient may be 0.05 ± δ.

Further, in order to realize the dielectric film 131 that satisfies the above-described refractive index condition, the thickness of the dielectric film 131 is preferably 20 nm or more and 110 nm. Preferably, in other words, it is preferable that the lower limit value of the film thickness of the dielectric film 131 is 20 nm and the upper limit value of the film thickness of the dielectric film 131 is 110 nm.

The lower limit value of the film thickness of the dielectric film 131 takes into account a predetermined margin (that is, an error that can be substantially regarded as 20 nm) φ1 with respect to the numerical value of “20 nm” described above. It may be set. Similarly, the upper limit value of the thickness of the dielectric film takes into account a predetermined margin (that is, an error that can be substantially regarded as 110 nm) φ2 with respect to the numerical value of “110 nm” described above. It may be set. Therefore, the dielectric film may satisfy the condition of 20 ± φ1 nm ≦ dielectric film thickness ≦ 110 nm ± φ2 nm.

The dielectric film 131 has a modulation degree of the recording layer 13 (that is, a modulation degree when data is recorded on the recording layer 13 by irradiation with the recording / reproducing laser beam LB2) of 40% or more. In other words, the lower limit value of the modulation degree of the recording layer 13 is preferably 40%.

Note that the lower limit value of the modulation degree is set in consideration of a predetermined margin (that is, an error that can be substantially regarded as 40%) ε with respect to the numerical value of “40%” described above. Also good. That is, the lower limit value of the modulation degree may be 40 ± ε%.

Here, when the refractive index of the dielectric film 131 with respect to the recording / reproducing laser beam LB2 is 1.85 or more, the modulation degree is often 40% or more. Here, a correlation between the refractive index of the dielectric film 131, the degree of modulation, and the modulation with respect to the recording / reproducing laser beam LB2 will be described with reference to FIG. FIG. 5 is a graph showing the correlation among the refractive index of the dielectric film 131, the degree of modulation, and the modulation with respect to the recording / reproducing laser beam LB2.

As shown in FIG. 5, as the refractive index of the dielectric film 131 with respect to the recording / reproducing laser beam LB2 increases, the degree of modulation also increases. Here, when the refractive index of the dielectric film 131 with respect to the recording / reproducing laser beam LB2 becomes 1.85, the modulation degree becomes 40%. Therefore, when the refractive index of the dielectric film 131 with respect to the recording / reproducing laser beam LB2 is 1.85 or more, the modulation degree is often 40% or more.

Each of the plurality of recording layers 13 having the dielectric film 131 having the characteristics described above suppresses the reflectance of the (i-1) guide laser beam LB1 (for example, the reflectance is a predetermined value (for example, 10%)). And (i-2) suppressing the reflectance of the recording / reproducing laser beam LB2 (for example, setting the reflectance to a predetermined value (for example, 3%) or less), while (ii-1) the guide The transmittance of the laser beam LB1 is secured (for example, the transmittance is set to a predetermined value (for example, 85%) or more) and (ii-2) the transmittance of the recording / reproducing laser beam LB2 is secured (for example, the transmittance) Is set to a predetermined value (for example, 80% or more)). The “reflectance” and “transmittance” here mean the reflectivity and transmittance in a state where the recording film 132 is not melted by the irradiation of the recording / reproducing laser beam LB2. As a result, the recording / reproducing apparatus 101 that performs at least one of the recording operation and the reproducing operation with respect to the optical disc 11 including the recording layer 13 performs the tracking control using the return light of the guide laser beam LB1, and performs the recording / reproducing laser beam. At least one of the recording operation and the reproducing operation with respect to the plurality of recording layers 13 using LB2 can be suitably performed (in other words, with high quality).

(4) Specific Example of Recording Layer Next, with reference to FIGS. 6 to 15, a specific example of the recording layer 13 is a comparative example including the dielectric film 131 and the dielectric film 134 that do not have the above-described characteristics. This will be explained in comparison with FIG. 6 is a cross-sectional view showing the recording layer 13a of the first specific example. FIG. 7 is a cross-sectional view showing the recording layer 13b of the second specific example. FIG. 8 is a cross-sectional view showing the recording layer 13c of the third specific example. FIG. 9 is a cross-sectional view showing the recording layer 13d of the fourth specific example. FIG. 10 is a cross-sectional view showing the recording layer 13e of the fifth specific example. FIG. 11 is a cross-sectional view showing the recording layer 13f of the first comparative example. FIG. 12 is a cross-sectional view showing the recording layer 13g of the second comparative example. FIG. 13 is a cross-sectional view showing the recording layer 13h of the third comparative example. FIG. 14 shows the characteristics of the recording layer 13a of the first specific example, the characteristics of the recording layer 13b of the second specific example, the characteristics of the recording layer 13c of the third specific example, the characteristics of the recording layer 13d of the fourth specific example, and the fifth It is a table | surface which shows the characteristic of the recording layer 13e of a specific example. FIG. 15 is a table showing characteristics of the recording layer 13g of the first comparative example, characteristics of the recording layer 13h of the second comparative example, and characteristics of the recording layer 13i of the third comparative example.

In the following, for the sake of simplicity of explanation, the explanation will be made using the optical disc 11 having only one recording layer 13. However, it goes without saying that each recording layer 13 can realize the characteristics shown in FIGS. 14 and 15 even when the optical disk 11 includes a plurality of recording layers 13.

(4-1) First Specific Example As shown in FIG. 6, the recording layer 13a of the first specific example includes a dielectric film 131 made of ZnO and having a film thickness of 40 nm, and a film made of BiGeO and having a film thickness. A recording film 132 having a thickness of 10 nm, a light absorption film 133 made of Fe ₃ O ₄ and a film thickness of 2 nm, and a dielectric film 134 made of ZnO and a film thickness of 34 nm. It has a structure.

The recording layer 13a of the first specific example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 uses a mixed gas having a gas pressure of 0.63 Pa composed of argon gas supplied at 85 sccm and oxygen gas supplied at 5 sccm as a sputtering gas, and has a high frequency input power of 500 W. It was formed by the RF sputtering method set to. The recording film 132 is formed by RF sputtering in which a high frequency input power is set to 150 W while using a mixed gas having a gas pressure of 0.58 Pa composed of argon gas supplied at 75 sccm and oxygen gas supplied at 15 sccm as a sputtering gas. Formed by law. The light absorbing film 133 is an RF in which a high frequency input power is set to 500 W while using a mixed gas having a gas pressure of 0.65 Pa composed of argon gas supplied at 90 sccm and oxygen gas supplied at 1 sccm as a sputtering gas. It was formed by sputtering.

As shown in FIG. 14, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13a of the first specific example has a refractive index of 1.93 with respect to the guide laser beam LB1 (that is, 2.2 or less). And the refractive index with respect to the recording / reproducing laser beam LB2 is 2.06 (that is, 1.85 or more). Further, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13a of the first specific example has an extinction coefficient of 0 (that is, 0.05 or less) with respect to the guide laser beam LB1, and recording / reproduction. The extinction coefficient with respect to the laser beam LB2 is 0.001 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation were measured when a recording operation was performed on the recording layer 13a of the first specific example. The recording operation was performed using a recording / reproducing laser LB2 having a wavelength of 405 nm that is irradiated onto the recording layer 13a through an optical system having an aperture ratio NA of 0.85. The recording operation was performed while performing tracking control based on the return light of the guide laser LB1 having a wavelength of 655 nm, which is irradiated to the guide layer 12 through an optical system having an aperture ratio NA of 0.60. In the recording operation, the linear velocity is 7.68 m / s, the channel clock frequency is 132 MHz, the data bit length is 87.39 nm, and the modulation method is 1-7 modulation (1-7PP modulation). Was done under certain conditions.

As a result, the recording layer 13a of the first specific example has (i-1) a reflectance of the guide laser beam LB1 of 6.1% (that is, 10% or less) and (i-2) a recording / reproducing laser. While the reflectance of the light LB2 is 1% (that is, 3% or less), (ii-1) the transmittance of the guide laser beam LB1 is 93.4% (that is, 85% or more). In addition, the condition that (ii-2) the transmittance of the recording / reproducing laser beam LB2 is 87.1% (that is, 80% or more) is satisfied. In addition, the modulation degree of the recording layer 13a of the first specific example satisfies the condition that it becomes 74.4% (that is, 40% or more).

(4-2) Second Specific Example As shown in FIG. 7, the recording layer 13b of the second specific example is composed of a mixture of TiO ₂ and SiO ₂ (however, the content of SiO ₂ is 35 mol%) and A dielectric film 131 having a thickness of 45 nm, a recording film 132 made of BiGeO and having a thickness of 10 nm, a light absorption film 133 made of Fe ₃ O ₄ and having a thickness of 2 nm, and TiO ₂ And a dielectric film 134 composed of a mixture of SiO ₂ and SiO ₂ (however, the content of SiO ₂ is 35 mol%) and having a film thickness of 35 nm.

The recording layer 13b of the second specific example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 is formed by an RF sputtering method in which a high-frequency input power is set to 750 W while using a gas having a gas pressure of 0.63 Pa composed of argon gas supplied at 90 sccm as a sputtering gas. It was. The recording film 132 and the light absorption film 133 were formed in the same manner as in the first specific example.

As shown in FIG. 14, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13b of the second specific example has a refractive index of 1.95 with respect to the guide laser beam LB1 (that is, 2.2 or less). And the refractive index with respect to the recording / reproducing laser beam LB2 is 2.08 (that is, 1.85 or more). In addition, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13b of the second specific example has an extinction coefficient of 0.001 (that is, 0.05 or less) with respect to the guide laser beam LB1. The extinction coefficient with respect to the recording / reproducing laser beam LB2 is 0.002 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation when the recording operation was performed on the recording layer 13b of the second specific example were measured. The recording operation was performed under the same conditions as in the first specific example.

As a result, the recording layer 13b of the second specific example has (i-1) a reflectivity of the guide laser beam LB1 of 6.6% (that is, 10% or less) and (i-2) a recording / reproducing laser. While the reflectance of the light LB2 is 1.1% (that is, 3% or less), (ii-1) the transmittance of the guide laser beam LB1 is 92.4% (that is, 85% or more). And (ii-2) the condition that the transmittance of the recording / reproducing laser beam LB2 is 88.6% (that is, 80% or more). In addition, the modulation degree of the recording layer 13b of the second specific example satisfies the condition that it becomes 65.5% (that is, 40% or more).

(4-3) Third Specific Example As shown in FIG. 8, the recording layer 13c of the third specific example is a mixture of TiO ₂ and Al ₂ O ₃ (however, the content of Al ₂ O ₃ is 50 mol%). A dielectric film 131 having a thickness of 46 nm, a recording film 132 having a thickness of 10 nm, and a light-absorbing film 133 having a thickness of 2 nm and made of Fe ₃ O _4. And a dielectric film 134 composed of a mixture of TiO ₂ and Al ₂ O ₃ (provided that the content of Al ₂ O ₃ is 50 mol%) and having a film thickness of 35 nm. ing.

The recording layer 13c of the third specific example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 was formed in the same manner as in the second specific example. The recording film 132 and the light absorption film 133 were formed in the same manner as in the first specific example.

As shown in FIG. 14, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13c of the third specific example has a refractive index of 1.87 with respect to the guide laser beam LB1 (that is, 2.2 or less). And the refractive index with respect to the recording / reproducing laser beam LB2 is 1.91 (that is, 1.85 or more). Further, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13c of the third specific example has an extinction coefficient with respect to the guide laser beam LB1 of 0.0028 (that is, 0.05 or less) and The extinction coefficient with respect to the recording / reproducing laser beam LB2 is 0.006 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation were measured when a recording operation was performed on the recording layer 13c of the third specific example. The recording operation was performed under the same conditions as in the first specific example.

As a result, in the recording layer 13c of the third specific example, (i-1) the reflectivity of the guide laser beam LB1 is 5.3% (that is, 10% or less), and (i-2) the recording / reproducing laser. While the reflectance of the light LB2 is 1.1% (that is, 3% or less), (ii-1) the transmittance of the guide laser beam LB1 is 93% (that is, 85% or more). And (ii-2) the condition that the transmittance of the recording / reproducing laser beam LB2 is 88.3% (that is, 80% or more) is satisfied. In addition, the modulation degree of the recording layer 13c of the third specific example satisfies the condition that it is 50.5% (that is, 40% or more).

(4-4) Fourth Specific Example As shown in FIG. 9, the recording layer 13d of the fourth specific example is composed of a mixture of ZnO and SnO ₂ (however, the content of SnO ₂ is 30 mol%) and is a film. A dielectric film 131 having a thickness of 42 nm, a recording film 132 made of BiGeO and having a thickness of 10 nm, a light absorption film 133 made of Fe ₃ O ₄ and having a thickness of 2 nm, ZnO and SnO ₂ and a dielectric film 134 having a film thickness of 35 nm, which is made of a mixture of ₂ (where the SnO ₂ content is 30 mol%).

The recording layer 13d of the fourth specific example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 has a high frequency input power of 500 W while using a mixed gas having a gas pressure of 0.63 Pa composed of argon gas supplied at 89 sccm and oxygen gas supplied at 1 sccm as the sputtering gas. It was formed by the RF sputtering method set to. The recording film 132 and the light absorption film 133 were formed in the same manner as in the first specific example.

As shown in FIG. 14, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13d of the fourth specific example has a refractive index of 2.01 with respect to the guide laser beam LB1 (that is, 2.2 or less). And the refractive index with respect to the recording / reproducing laser beam LB2 is 2.195 (that is, 1.85 or more). Further, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13d of the fourth specific example has an extinction coefficient of 0.0049 (that is, 0.05 or less) with respect to the guide laser beam LB1. The extinction coefficient with respect to the recording / reproducing laser beam LB2 is 0.0016 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation when the recording operation was performed on the recording layer 13d of the fourth specific example were measured. The recording operation was performed under the same conditions as in the first specific example.

As a result, the recording layer 13d of the fourth specific example has (i-1) the reflectance of the guide laser beam LB1 is 8% (that is, 10% or less) and (i-2) the recording / reproducing laser beam LB2. (Ii-1) The transmittance of the guide laser beam LB1 is 91.1% (that is, 85% or more). In addition, (ii-2) the condition that the transmittance of the recording / reproducing laser beam LB2 is 83.6% (that is, 80% or more) is satisfied. In addition, the degree of modulation of the recording layer 13d of the fourth specific example satisfies the condition that it becomes 73.2% (that is, 40% or more).

(4-5) Fifth Specific Example As shown in FIG. 10, the recording layer 13e of the fifth specific example includes a dielectric film 131 made of AlN (ie, Al nitride) and having a thickness of 50 nm. A recording film 132 made of BiGeO and having a thickness of 12.5 nm, a light absorption film 133 made of Fe ₃ O ₄ and having a thickness of 2 nm, and made of AlN and having a thickness of 35 nm It has a laminated structure in which a dielectric film 134 is laminated.

The recording layer 13e of the fifth specific example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 has a high frequency while using a mixed gas having a gas pressure of 0.43 Pa composed of argon gas supplied at 85.5 sccm and oxygen gas supplied at 4.5 sccm as a sputtering gas. It was formed by the RF sputtering method in which the input power was set to 700W. The recording film 132 is formed by RF sputtering in which a high frequency input power is set to 300 W while using a mixed gas having a gas pressure of 0.58 Pa composed of argon gas supplied at 60 sccm and oxygen gas supplied at 30 sccm as a sputtering gas. Formed by law. The light absorbing film 133 was formed in the same manner as in the first specific example.

As shown in FIG. 14, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13e of the fifth specific example has a refractive index with respect to the guide laser beam LB1 of 1.90 (that is, 2.2 or less). And the refractive index with respect to the recording / reproducing laser beam LB2 is 1.96 (that is, 1.85 or more). Further, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13e of the fifth specific example has an extinction coefficient with respect to the guide laser beam LB1 of 0.00 (that is, 0.05 or less) and The extinction coefficient with respect to the recording / reproducing laser beam LB2 is 0.00 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation when the recording operation was performed on the recording layer 13e of the fifth specific example were measured. The recording operation was performed under the same conditions as in the first specific example.

As a result, the recording layer 13e of the fifth specific example has (i-1) the reflectance of the guide laser beam LB1 is 4.46% (that is, 10% or less) and (i-2) the recording / reproducing laser. While the reflectance of the light LB2 is 1.5% (that is, 3% or less), (ii-1) the transmittance of the guide laser beam LB1 is 93.9% (that is, 85% or more). And (ii-2) the condition that the transmittance of the recording / reproducing laser beam LB2 is 87.4% (that is, 80% or more). In addition, the modulation degree of the recording layer 13e of the fifth specific example satisfies the condition that it is 86.1% (that is, 40% or more).

(4-6) First Comparative Example As shown in FIG. 11, the recording layer 13f of the first comparative example is composed of a dielectric film 131 made of SiN and having a film thickness of 53 nm, and a film made of BiGeO and having a film thickness. A recording film 132 having a thickness of 10 nm, a light absorption film 133 made of Fe ₃ O ₄ and having a thickness of 2 nm, and a dielectric film 134 made of SiN and having a thickness of 25 nm. It has a structure.

The recording layer 13f of the first comparative example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 uses a mixed gas having a gas pressure of 0.65 Pa composed of argon gas supplied at 85 sccm and nitrogen gas supplied at 5 sccm as a sputtering gas, and a high frequency input power of 400 W. It was formed by the RF sputtering method set to. The recording film 132 and the light absorption film 133 were formed in the same manner as in the first specific example.

As shown in FIG. 15, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13f of the first comparative example has a refractive index with respect to the guide laser beam LB1 of 1.71 (that is, 2.2 or less). ). However, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13f of the first comparative example has a refractive index of 1.81 with respect to the recording / reproducing laser beam LB2. That is, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13f of the first comparative example does not have a characteristic that the refractive index with respect to the recording / reproducing laser beam LB2 is 1.85 or more. In addition, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13f of the first comparative example has an extinction coefficient of 0 (that is, 0.05 or less) with respect to the guide laser beam LB1, and recording / reproduction. The extinction coefficient with respect to the laser beam LB2 is 0 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation were measured when a recording operation was performed on the recording layer 13f of the first comparative example. The recording operation was performed under the same conditions as in the first specific example.

As a result, the recording layer 13f of the first comparative example has (i-1) a reflectance of the guide laser beam LB1 of 3.9% (that is, 10% or less) and (i-2) a recording / reproducing laser. While the reflectance of the light LB2 is 1% (that is, 3% or less), (ii-1) the transmittance of the guide laser beam LB1 is 95.6% (that is, 85% or more). In addition, (ii-2) the condition that the transmittance of the recording / reproducing laser beam LB2 is 87.8% (that is, 80% or more) is satisfied. However, the modulation degree of the recording layer 13f of the first comparative example is 36.6%. That is, the condition that the modulation degree of the recording layer 13f of the first comparative example is 40% or more is not satisfied. Therefore, for the recording layer 13f of the first comparative example, at least one of the recording operation and the reproducing operation using the recording / reproducing laser beam LB2 is preferably performed while performing the tracking control using the return light of the guide laser beam LB1. (In other words, high quality) is not always possible.

(4-7) Second Comparative Example As shown in FIG. 12, the recording layer 13g of the second comparative example includes a dielectric film 131 made of TiO ₂ and a film thickness of 41 nm, and a film made of BiGeO. A recording film 132 having a thickness of 10 nm, a light absorption film 133 made of Fe ₃ O ₄ and having a thickness of 2 nm, and a dielectric film 134 made of TiO ₂ and having a thickness of 27.5 nm. It has a laminated structure.

The recording layer 13g of the second comparative example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 uses a mixed gas having a gas pressure of 0.63 Pa composed of argon gas supplied at 90 sccm and oxygen gas supplied at 1 sccm as a sputtering gas, and a high frequency input power of 500 W. It was formed by the RF sputtering method set to. The recording film 132 and the light absorption film 133 were formed in the same manner as in the first specific example.

As shown in FIG. 15, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13g of the second comparative example has a refractive index of 2.52 with respect to the recording / reproducing laser beam LB2 (that is, 1.85). It has the characteristics of However, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13g of the second comparative example has a refractive index of 2.35 with respect to the guide laser beam LB1. That is, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13g of the second comparative example does not have a characteristic that the refractive index with respect to the guide laser beam LB1 is 2.2 or less. In addition, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13g of the second comparative example has an extinction coefficient of 0 (that is, 0.05 or less) with respect to the guide laser beam LB1, and recording / reproduction. The extinction coefficient with respect to the laser beam LB2 is 0 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation when the recording operation was performed on the recording layer 13g of the second comparative example were measured. The recording operation was performed under the same conditions as in the first specific example.

As a result, the recording layer 13g of the second comparative example has (i-2) the reflectance of the recording / reproducing laser beam LB2 is 1.2% (that is, 3% or less), while (ii-2) The condition that the transmittance of the recording / reproducing laser beam LB2 is 89.1% (that is, 80% or more) is satisfied. In addition, the modulation degree of the recording layer 13g of the second comparative example satisfies the condition of 72.9% (that is, 40% or more). However, in the recording layer 13g of the second comparative example, (i-1) the reflectance of the guide laser beam LB1 is 15.1%, while (ii-1) the transmittance of the guide laser beam LB1 is 84.1. %become. That is, the recording layer 13g of the second comparative example has (i-1) the reflectance of the guide laser beam LB1 is 10% or less, while (ii-1) the transmittance of the guide laser beam LB1 is 85% or more. Does not satisfy the condition of becoming. Accordingly, at least one of the recording operation and the reproducing operation using the recording / reproducing laser beam LB2 is preferably performed on the recording layer 13g of the second comparative example while performing the tracking control using the return light of the guide laser beam LB1. (In other words, high quality) is not always possible.

(4-8) Third Comparative Example As shown in FIG. 13, the recording layer 13h of the third comparative example is composed of a dielectric film 131 made of SiO ₂ and having a film thickness of 25 nm, and a film made of BiGeO. A recording film 132 having a thickness of 10 nm, a light absorption film 133 made of Fe ₃ O ₄ and having a thickness of 2 nm, and a dielectric film 134 made of SiO ₂ and having a thickness of 25 nm are laminated. Have a laminated structure.

The recording layer 13h of the third comparative example was formed on the substrate 17 having a track pitch of 0.64 μm under the following conditions. Each of the

dielectric films

131 and 134 is formed by an RF sputtering method in which a high-frequency input power is set to 500 W while a gas having a gas pressure of 0.61 Pa composed of argon gas supplied at 90 sccm is used as a sputtering gas. It was. The recording film 132 was formed in the same manner as in the fifth specific example. The light absorbing film 133 was formed in the same manner as in the first specific example.

As shown in FIG. 15, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13h of the third comparative example has a refractive index with respect to the guide laser beam LB1 of 1.41 (that is, 2.2 or less). ). However, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13h of the third comparative example has a refractive index of 1.43 with respect to the recording / reproducing laser beam LB2. That is, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13h of the third comparative example does not have a characteristic that the refractive index with respect to the recording / reproducing laser beam LB2 is 1.85 or more. Further, each of the dielectric film 131 and the dielectric film 134 included in the recording layer 13h of the third comparative example has an extinction coefficient of 0.00 (that is, 0.05 or less) with respect to the guide laser beam LB1. The extinction coefficient with respect to the recording / reproducing laser beam LB2 is 0.00 (that is, 0.05 or less).

The reflectance, transmittance, and degree of modulation were measured when a recording operation was performed on the recording layer 13h of the third comparative example. The recording operation was performed under the same conditions as in the first specific example.

As a result, the recording layer 13h of the third comparative example has (i-1) a reflectance of the guide laser beam LB1 of 0.58% (that is, 10% or less) and (i-2) a recording / reproducing laser. While the reflectance of the light LB2 is 1.36% (that is, 3% or less), (ii-1) the transmittance of the guide laser beam LB1 is 98.8% (that is, 85% or more). And (ii-2) the condition that the transmittance of the recording / reproducing laser beam LB2 is 87.5% (that is, 80% or more). However, the modulation degree of the recording layer 13h of the third comparative example is 35.1%. That is, the condition that the modulation degree of the recording layer 13h of the third comparative example is 40% or more is not satisfied. Therefore, for the recording layer 13h of the third comparative example, at least one of the recording operation and the reproducing operation using the recording / reproducing laser beam LB2 is preferably performed while performing the tracking control using the return light of the guide laser beam LB1. (In other words, high quality) is not always possible.

(5) Recording / reproducing apparatus Next, with reference to FIG. 16, the recording / reproducing apparatus 101 of a present Example is demonstrated. FIG. 16 is a block diagram showing a basic configuration of the recording / reproducing apparatus 101.

As shown in FIG. 16, the recording / reproducing apparatus 101 is configured as a disk drive. The recording / reproducing apparatus 101 is connected to the host computer 201. The recording / reproducing apparatus 101 includes an optical pickup (PU: Pick Up) 102, a signal recording / reproducing unit 103, a spindle motor 104, a bus 106, a CPU (drive control unit) 111, a memory 112, and a data input / output unit 113.

Here, the configuration of the optical pickup 102 will be described in more detail with reference to FIG. FIG. 17 is a block diagram showing the configuration of the optical pickup 102.

As shown in FIG. 17, the optical pickup 102 includes a light source LD1 that is a red laser diode and a light source LD2 that is a blue laser diode. A guide laser beam LB1 is emitted from the light source LD1, and a recording / reproducing laser beam LB2 is emitted from the light source LD2.

The guide laser beam LB1 emitted from the light source LD1 is condensed on the guide layer 12 of the optical disc 11 through a deflection beam splitter (PBS), a quarter-wave plate (1/4 WP), an objective lens 102L, and the like. . The return light from the guide layer 12 of the guide laser beam LB1 is incident on the light receiving element PD1 through the objective lens 102L, the quarter-wave plate, the deflecting beam splitter, and the like.

The recording / reproducing laser beam LB2 emitted from the light source LD2 is recorded or reproduced from a plurality of recording layers 13 of the optical disc 11 through a deflection beam splitter (PBS), a quarter-wave plate, an objective lens 102L, and the like. The light is focused on a desired recording layer 13 as a target. The return light of the recording / reproducing laser beam LB2 is incident on the light receiving element PD2 via the objective lens 102L, a quarter-wave plate, a deflection beam splitter, and the like.

The light receiving elements PD1 and PD2 are typically light receiving elements such as a two-part or four-part CCD.

In FIG. 16 again, the host computer 201 includes an operation / display control unit 202, operation buttons 203, a display panel 204, a bus 206, a CPU 211, a memory 212, and a data input / output control unit 213. At the time of recording, recording data to be recorded is input from the data input / output control unit 213 to the recording / reproducing apparatus 101. At the time of reproduction, the recording data reproduced from the recording / reproducing apparatus 101 is output via the data input / output control unit 213.

The memory 112 and the memory 212 are (i) a computer program for controlling each element such as the CPU 111 in the recording / reproducing apparatus 101 and each element such as the CPU 211 in the host computer 201 so that a recording / reproducing operation described later is performed, And (ii) various data such as control data, in-process data, and processed data necessary for the recording / reproducing operation are appropriately used for temporarily or permanently storing the data via the bus 106, the bus 206, and the like.

Further, the present invention can be appropriately changed without departing from the gist or the idea of the invention that can be read from the claims and the entire specification, and a recording medium and a recording / reproducing apparatus accompanying such a change are also included in the present invention. Included in technical thought.

DESCRIPTION OF SYMBOLS 11 Optical disk 12 Guide layer 13 Recording layer 131 Dielectric layer 132 Recording film 133 Light absorption film 134 Dielectric film 14 Cover layer 15 Spacer layer 16 2P layer 17 Substrate LB1 Guide laser beam LB2 Recording / reproducing laser

Claims

A guide layer on which a guide track irradiated with guide laser light having a wavelength included in the range of 630 nm to 680 nm is formed;
And a recording layer irradiated with a recording / reproducing laser beam having a wavelength included in the range of 400 nm to 410 nm is laminated.
The recording layer has a laminated structure in which (i) a recording film whose optical characteristics are changed by irradiation with the recording / reproducing laser beam, and (ii) a dielectric film,
The refractive index of the dielectric film with respect to the guide laser light is 2.2 or less,
A recording medium, wherein a refractive index of the dielectric film with respect to the recording / reproducing laser beam is 1.85 or more.
The recording medium according to claim 1, wherein the dielectric film contains at least one of an inorganic compound and a mixture of inorganic compounds.
The dielectric film includes (i) Zn oxide, Ti oxide, Zr oxide or Sn oxide, (ii) Al nitride, or (iii) Zn sulfide. The recording medium according to claim 2.
The dielectric film comprises (i) Zn oxide, Ti oxide, Zr oxide, Si oxide and Sn oxide, (ii) Al nitride, and (iii) Zn sulfide. The recording medium according to claim 2, comprising a mixture of at least two of the recording medium.
The recording medium according to claim 2, wherein the dielectric film includes a mixture of TiO 2 and SiO 2 .
The recording medium according to claim 5, wherein the dielectric film contains 15 mol% or more and 59 mol% or less of SiO 2 .
The extinction coefficient of the dielectric film with respect to the guide laser light is 0.05 or less,
2. The recording medium according to claim 1, wherein an extinction coefficient of the dielectric film with respect to the recording / reproducing laser beam is 0.05 or less.
2. The recording medium according to claim 1, wherein the modulation degree of data recorded in the recording layer is 40% or more by changing optical characteristics of the recording film by irradiation with the recording / reproducing laser beam.
The recording medium according to claim 1, wherein the thickness of the dielectric film in the stacking direction is 20 nm or more and 110 nm or less.
The recording medium according to claim 1, wherein the recording layer further includes another dielectric film disposed so as to sandwich the recording film between the recording film and the dielectric film.
The recording medium according to claim 1, wherein the recording layer further includes a light absorbing film that forms the laminated structure together with the recording film and the dielectric film.
The recording medium according to claim 11, wherein the light absorbing film is mainly composed of an oxide of Fe.
The recording medium according to claim 1, wherein the recording film contains Bi and O.
The recording medium according to claim 1, comprising a plurality of the recording layers.
A recording / reproducing apparatus that performs at least one of a recording operation and a reproducing operation on the recording medium according to claim 1.