JP2023117502A - Information recording medium - Google Patents

Abstract

To provide an information recording medium capable of obtaining satisfactory playback durability.SOLUTION: The information recording medium with at least four information layers and a cover layer are sequentially stacked on a substrate via an intermediate separation layer, in which information is recorded on the recording layer by irradiation with a laser beam of wavelength λ from the cover layer side or regenerate information from the recording layer. In the information recording medium, a phase adjustment film is formed on the laser beam irradiation side in contact with the first information layer, which is one of the information layers other than the information layer furthest from the substrate when viewed from the information layer, and further, a first intermediate separation layer is formed on the laser beam irradiation side in contact with the phase adjustment film.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to high-density information recording media on which information is recorded or reproduced by optical means.

Optical discs have so far evolved into CDs (Compact Discs), DVDs (Digital Versatile Discs), and BDs (Blu-ray (registered trademark) Discs). In recent years, archival discs, which have a higher recording density than BDs, have been developed, and a recording capacity of 500 gigabytes (GB) per disc has been achieved.

A 500GB archival disc has a structure in which two single-sided, three-layer discs (optical discs with three information layers on one side) that can store 250GB of information are stuck together, and each disc can record 500GB of information. It enables playback. That is, in this archival disc, the recording capacity per information layer is 83.3 GB.

In order to realize an archival disc with a capacity exceeding 500 GB, for example, a capacity of 1 TB, it is necessary to increase the number of information layers and increase the recording capacity per information layer. As a means of increasing the recording capacity per information layer, the track density (the number of tracks per unit length in the radial direction of the disc) is increased, the minimum pit length is shortened, and the size of the recording marks is reduced. A method of increasing the recording density is conceivable.

However, when the size of the recording mark is reduced, the signal becomes a high frequency signal and is affected by the system noise, and the S/N (S: signal, N: noise) of the disc decreases, and the reproduction durability (irradiating the reproduction light to the recording mark index that indicates the degree of deterioration in signal quality when the signal quality continues to deteriorate. In order to realize an archival disc with a capacity of 1 TB, good reproduction durability must be obtained even with minute recording marks.

Each information layer is composed of three types of thin films, which are called a first dielectric film, a recording film, and a second dielectric film in order from the far side to the near side when viewed from the laser beam irradiation surface. When the recording film is irradiated with a laser beam, the shape of the recording film is changed and a signal is recorded. Since the amount of light absorbed by the recording film contained in the information layer has a great effect on the initial characteristics and reproduction durability, conventionally, various compositions of the recording film have been studied in order to improve these characteristics (for example, See Patent Documents 1 and 2). However, in a 1 TB-capacity archival disc, it is difficult to obtain sufficient reproduction durability while maintaining good initial characteristics simply by optimizing the composition of the recording film. We investigated ways to improve the replay durability by means other than optimizing the composition.

JP 2018-106794 A WO2021/117470

The inventors focused on lowering the reproduction power as a means for improving the reproduction durability. The SNR of the signal is determined by the amount of light incident on the photodetector after the irradiated laser light is reflected by the information layer, that is, the product of the laser light intensity and the reflectance of the information layer. Therefore, in order to obtain a good SNR even at low reproduction power, it is necessary to increase the reflectance of the information layer, and the present inventors investigated increasing the reflectance of the information layer. Specifically, we optimized the design of the information recording medium by combining optical thin films and utilizing thin film interference to maximize the reflectance. As a result of examination, in an information recording medium in which at least four information layers and a cover layer are sequentially laminated on a substrate with an intermediate separation layer interposed therebetween, It was found that by providing a phase adjustment film with a low refractive index on the surface of the information layer, the reflectance can be increased by utilizing the interference effect of the thin film that constitutes the information layer. The information recording medium of the present invention makes it possible to reduce the reproduction power by efficiently reflecting the laser beam irradiated onto the information layer, thereby achieving excellent reproduction durability.

At least four information layers and a cover layer are sequentially laminated on the substrate via an intermediate separation layer, and information is recorded on the recording layer or information is read from the recording layer by irradiation of a laser beam having a wavelength of λ from the cover layer side. An information recording medium to be reproduced, wherein a phase adjustment film is formed on a laser beam irradiation side in contact with a first information layer which is one of the information layers other than the information layer farthest from the substrate, Further, a first intermediate separation layer is formed on the laser beam irradiation side in contact with the phase adjustment film, and the first information layer is arranged in the order of the first dielectric layer from the near side to the far side as viewed from the substrate. A film, a recording film _, and a second dielectric film are included in this order _. , the film thickness and refractive index of the phase control film are d _L and n _L , respectively, and the refractive index of the first intermediate separation layer is n _R , 0.5<=(2×d _A ×n _A ) /λ<=1.0, (2×d _L ×n _L )/λ is 0<(2×d _L ×n _L )/λ<0.75, and n _L <n _A and It is characterized in that _nL < _nR .

The information recording medium according to the embodiment of the present invention has an information layer exhibiting good reproduction durability, and enables realization of an information recording medium with high reliability and high recording density.

Sectional view of an information recording medium according to Embodiment 1 FIG. 4 is a diagram schematically showing that the laser beam 7 irradiated to the L0 layer 10 passes through the intermediate separation layer 2, enters the phase adjustment film 14, and is reflected or transmitted by the phase adjustment film 14 and the L0 layer 10; FIG. 4 is a diagram showing simulation results of the reflectance of the L0 layer 10 when the film thickness of the phase adjustment film 14 is changed; For various total film thicknesses d _A of the L0 layer 10, the ratio of the reflectance of the L0 layer 10 when the film thickness of the phase control film 14 is changed to the reflectance when the phase control film 14 is not formed is optically calculated. Figure showing simulation results Cross-sectional view of an information recording medium according to Embodiment 2 FIG. 4 is a diagram schematically showing that the laser beam 7 irradiated to the L3 layer 40 passes through the cover layer 5 and enters the phase adjustment film 14, and is reflected or transmitted by the phase adjustment film 14 and the L3 layer 40; FIG. 10 is a diagram showing simulation results of the reflectance of the L3 layer 40 when the film thickness of the phase adjustment film 14 is changed; For various total thicknesses d _B of the L3 layer 40, the ratio of the reflectance of the L3 layer 40 when the thickness of the phase adjustment film 14 is changed to the reflectance when the phase adjustment film 14 is not formed is optically calculated. Figure showing simulation results Cross-sectional view of an information recording medium according to Embodiment 3 FIG. 10 is a diagram showing results of evaluating the effective reflectance of the groove of the L0 layer 10 when the film thickness _dL of the phase adjustment film 14 is changed;

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid unnecessary verbosity in the following description and to facilitate understanding by those skilled in the art. It should be noted that the accompanying drawings and the following description are provided for a thorough understanding of the present disclosure by those skilled in the art and are not intended to limit the claimed subject matter.
(Embodiment 1)
FIG. 1 is a cross-sectional view of an information recording medium 100 according to the first embodiment.

The information recording medium 100 is a double-sided information recording medium in which an A-side information recording medium 101 and a B-side information recording medium 102 are bonded together. The A-side information recording medium 101 and the B-side information recording medium 102 each include an L0 layer 10, an L1 layer 20, and an L2 layer, which are sequentially laminated as information layers on the substrate 1 via intermediate separation layers 2, 3 and 4. 30 and an L3 layer 40 and a cover layer 5 is provided on the L3 layer 40 . In the L0 layer 10, a first dielectric film 11, a recording film 12, and a second dielectric film 13 are formed in this order from near to far when viewed from the substrate 1. FIG. The L1 layer 20, the L2 layer 30 and the L3 layer 40 have similar configurations. Furthermore, a phase adjustment film 14 is provided on the L0 layer 10 to increase the reflectance of the L0 layer 10 . The L1 layer 20, L2 layer 30 and L3 layer 40 are transmissive information layers. The A-side information recording medium 101 and the B-side information recording medium 102 are bonded together by a bonding layer 6 on the back surface of the substrate 1 (the side opposite to the surface having the information layer). The information recording medium 100 is irradiated with a laser beam 7 from the cover layer 5 side to record and reproduce information on each information layer. The laser light 7 is a blue-violet laser light having a wavelength of about 405 nm.

In the information recording medium 100, when the guide groove is formed in the substrate 1, the surface closer to the laser beam 7 is referred to as a "groove" in this specification for convenience, and the surface farther from the laser beam 7 is referred to as a "groove". is called "land" for convenience. By shortening the recording mark length and forming bits in both the groove and the land (land-groove recording), it is possible to increase the capacity per information layer.

Guide grooves may also be formed in the intermediate separation layers 2, 3 and 4, as will be described later. In particular, when land-groove recording is performed in the L1 layer 20, L2 layer 30 and L3 layer 40, it is preferable to form guide grooves in the intermediate separation layers 2, 3 and 4. FIG.

The effective reflectance of the four information layers can be adjusted by adjusting the reflectance of the L0 layer 10, L1 layer 20, L2 layer 30 and L3 layer 40 and the transmittance of the L1 layer 20, L2 layer 30 and L3 layer 40 respectively. You can control it. In this specification, the reflectance of each information layer measured with four information layers stacked is defined as the effective reflectance. Unless otherwise specified, reflectance measured without lamination is indicated unless "effective" is stated.

The functions, materials and thicknesses of the substrate 1, the intermediate separation layer 2, the intermediate separation layer 3, the intermediate separation layer 4, the cover layer 5 and the bonding layer 6 are described in detail below.

The substrate 1 is preferably a disk-shaped transparent substrate. The material of the substrate 1 can be, for example, resin such as polycarbonate, amorphous polyolefin, or polymethyl methacrylate, or glass. An uneven guide groove for guiding the laser light 7 may be formed on the surface of the substrate 1 on the L0 layer side, if necessary. The substrate 1 preferably has a thickness of about 0.5 mm and a diameter of about 120 mm. Further, when guide grooves are formed in the substrate 1, the step between the groove surface and the land surface is preferably 10 nm to 50 nm. Further, in Embodiment 1, the distance between grooves and lands is set to about 0.180 μm.

The intermediate separation layers 2, 3 and 4 are made of an acrylic resin such as a photocurable resin (especially an ultraviolet curable resin) or a slow-acting thermosetting resin, and the laser beam 7 efficiently passes through the L0 layer 10, the L1 layer 20 and the It is preferable that light absorption of the light of wavelength λ used for recording and reproduction is small so that it reaches the L2 layer 30 . The intermediate separation layers 2, 3 and 4 are used to distinguish the focus positions of the L0 layer 10, L1 layer 20, L2 layer 30 and L3 layer 40, and the thickness depends on the numerical aperture (NA) of the objective lens and the laser beam. It must be greater than or equal to the depth of focus ΔZ determined by the wavelength λ of 7. Assuming that the reference light intensity at the focal point is 80% of the no-aberration case, ΔZ can be approximated by equation (1).

また、Ｌ１層２０、Ｌ２層３０およびＬ３層４０における裏焦点の影響を防ぐために、中間分離層２、３および４の厚みは、それぞれ異なる値が好ましい。また、中間分離層２、３および４において、レーザ光７の入射側に凹凸の案内溝が形成されてもよい。

Also, in order to prevent the influence of the back focal point in the L1 layer 20, the L2 layer 30 and the L3 layer 40, the thicknesses of the intermediate separation layers 2, 3 and 4 are preferably different values. Further, in the intermediate separation layers 2, 3 and 4, uneven guide grooves may be formed on the incident side of the laser beam 7. FIG.

The cover layer 5 is made of, for example, a photocurable resin (particularly, an ultraviolet curable resin) or a slow-acting thermosetting resin, and preferably has a low light absorption with respect to the light of wavelength λ used for recording and reproduction. Also, for the cover layer 5, a resin such as polycarbonate, amorphous polyolefin, or polymethyl methacrylate, or glass may be used. When these materials are used, the cover layer 5, for example, a resin such as a photocurable resin (especially an ultraviolet curable resin) or a slow-acting thermosetting resin, is applied to the second dielectric film 43 of the L3 layer 40. It is formed by coating, spin-coating, and then curing. The thickness of the cover layer 5 is preferably about 35 μm to 75 μm, more preferably about 45 μm to 60 μm, which enables good recording/reproducing at NA=0.91.

The bonding layer 6 is made of, for example, a photocurable resin (in particular, an ultraviolet curable resin) or a slow-acting thermosetting resin, and bonds the A-side information recording medium 101 and the B-side information recording medium 102 together. . Also, the bonding layer 6 may be provided with a film for shielding the laser beam 7 . The thickness of the bonding layer 6 is preferably about 5 μm to 80 μm, more preferably about 20 μm to 50 μm.

When the information recording medium 100 has a thickness equivalent to the BD standard, the total thickness of the intermediate separation layers 2 to 4 and the cover layer 5 may be set to 100 μm. For example, the thickness of the intermediate separation layer 2 may be set to 15.5 μm, the thickness of the intermediate separation layer 3 to 19.5 μm, the thickness of the intermediate separation layer 4 to 11.5 μm, and the thickness of the cover layer 5 to 53.5 μm.

The readout durability of the information layer in the information recording medium 100 can be evaluated by continuously irradiating the laser beam 7 with the readout power to the recording marks previously recorded with the laser beam 7 with the optimum recording power. Specifically, it can be determined by the d-MLSE value after one million times (one million passes) of reproduction. If the d-MLSE value after 1,000,000 times of playback is 16.0% or less, it can be determined that 1,000,000 passes of playback were achieved with that playback power. Here, d-MLSE is an evaluation index of recorded signal quality and is an abbreviation for Distribution Derived-Maximum Likelihood Sequence Error Estimation.
<Method of Forming Information Recording Medium 100>
The A-side information recording medium 101 can be manufactured by the following procedures (1) to (8).
(1) A substrate 1 (for example, 0.5 mm thick and 120 mm in diameter) is placed in a film forming apparatus.
(2) forming the L0 layer 10; The first dielectric film 11, the recording film 12, and the second dielectric film 13, which constitute the L0 layer 10, can be formed by a sputtering method, which is one of vapor deposition methods.
First, a first dielectric film 11 is deposited. At this time, if a spiral guide groove is formed in the substrate 1, the first dielectric film 11 is formed on the guide groove side.

The first dielectric film 11 is formed by sputtering in a process gas atmosphere or a mixed gas atmosphere of a process gas and a reaction gas (for example, oxygen gas or nitrogen gas) using a sputtering target having a desired composition. can be formed. The process gas is, for example, Ar gas, Kr gas, or Xe gas, and Ar gas is advantageous in terms of cost. This applies to any sputtering where the atmosphere gas for sputtering is a process gas or a mixture thereof.

The target may comprise the oxide form, or may comprise the elemental metal or alloy form. When a target made of metal (including alloy) is used, oxide may be formed by reactive sputtering carried out in an atmosphere containing oxygen gas.

The specific resistance value of the target is preferably 1 Ω·cm or less. This facilitates DC sputtering.

The composition of the target may be adjusted so as to obtain the desired composition of the first dielectric film 11 .

For example, the composition of the target for forming the first dielectric film 11 is Zr—In—O,
Zr--Si--In--O, Zn--Zr--Sn--O, Ti--O, Nb--O and In--Sn--O are preferably used.

Alternatively, they preferably form oxides in the target, for example
ZrO ₂ —In ₂ O ₃ , ZrO ₂ —SiO ₂ —In ₂ O ₃ , ZnO—ZrO ₂ —SnO ₂ , TiO ₂ , Nb ₂ O ₅ , In ₂ O ₃ —SnO ₂ and the like are preferably used.

Subsequently, a recording film 12 is formed on the first dielectric film 11 . The recording film 12 is formed by sputtering in a process gas atmosphere or a mixed gas atmosphere of a process gas and a reaction gas using a target made of a metal alloy or a metal-oxide mixture, depending on its composition. can be formed. Since the thickness of the recording film 12 is thicker than the dielectric films such as the first dielectric film 11, considering productivity, the recording film 12 is formed by DC sputtering or pulse DC sputtering, which can be expected to have a higher film formation rate than RF sputtering. is preferably used for film formation. In order to contain a large amount of oxygen in the recording film 12, it is preferable to mix a large amount of oxygen gas into the atmospheric gas. The recording film 12 may be formed by performing multi-sputtering.

Specifically, when an alloy target or a mixture target is used for forming the recording film 12, the composition of the target is W--Cu--Ta--Mn--Ti--O, W--Cu--Ta--Zn--Mn--Ti--. O, W-Cu-Ta-Mn-Ti-Mg-O, W-Cu-Ta-Zn-Mn-Ti-Mg-O, W-Cu-Ta-Mn-Nb-O, W-Cu-Ta- Zn--Mn--Nb--O, W--Cu--Ta--Mn--Nb--Mg--O, W--Cu--Ta--Zn--Mn--Nb--Mg--O and the like.

Also, the recording film 12 may be composed of a laminated film of at least two kinds of recording film materials having different compositions.

The reflectance and recording sensitivity of the L0 layer 10 can be adjusted by changing the composition of the recording film material constituting the laminated film or the film thickness ratio of the laminated film.

Subsequently, a second dielectric film 13 is formed on the recording film 12 . The second dielectric film 13 can be formed by sputtering in a process gas atmosphere or a mixed gas atmosphere of a process gas and a reaction gas using a target corresponding to the composition of the second dielectric film 13 . Also, the second dielectric film 13 may be formed by performing multi-sputtering. The second dielectric film 13 can be formed using a target having a desired composition.

For example, as the target composition for forming the second dielectric film 13, Zr--In--O, Zr--Si--In--O, Zn--Zr--Sn--O, etc. are preferably used.

Alternatively, they preferably form oxides in the target, for example
ZrO ₂ —In ₂ O ₃ , ZrO ₂ —SiO ₂ —In ₂ O ₃ , ZnO—ZrO ₂ —SnO ₂ and the like are preferably used.
(3) Forming a phase control film 14 on the second dielectric film 13 . The phase control film 14 can be formed by sputtering in a process gas atmosphere or a mixed gas atmosphere of a process gas and a reaction gas using a target according to the composition of the phase control film 14 . Also, the phase adjustment film 14 may be formed by performing multi-sputtering. The phase control film 14 can be formed using a target having a desired composition.

For example, the target composition for forming the phase control film 14 is preferably SiO ₂ , MgF ₂ or the like.

Alternatively, the phase adjustment film 14 may be formed using a wet process such as a spin coating method, a self-assembled film method, or a Langmuir-Blodgett method.

For example, polytetrafluoroethylene or the like is preferably used as a material for forming the phase adjustment film 14 by spin coating.
(4) forming the intermediate isolation layer 2 on the phase control film 14; For the intermediate separation layer 2, a resin such as a photocurable resin (especially an ultraviolet curable resin) or a slow-acting thermosetting resin (for example, an acrylic resin) is applied onto the L0 layer 10 and spin-coated, and then the resin is cured. can be formed by When guide grooves are provided in the intermediate separation layer 2, a transfer substrate (mold) having grooves of a predetermined shape formed on the surface thereof is spin-coated in a state in which the resin is in close contact with the resin before curing, and then the resin is cured. Alternatively, the intermediate separation layer 2 may be formed by peeling the transfer substrate from the cured resin. In addition, the intermediate separation layer 2 may be formed in two steps. Specifically, the portion occupying most of the thickness is first formed by spin coating, and then the portion having the guide groove is formed by spin coating. It may be formed in combination with transfer using a transfer substrate.
(5) forming the L1 layer 20; Specifically, first, the first dielectric film 21 is formed on the intermediate isolation layer 2 . The first dielectric film 21 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.

A recording film 22 is then formed on the first dielectric film 21 . The recording film 22 can be formed by a method similar to that for the recording film 12 described above, using a target having a desired composition. Subsequently, a second dielectric film 23 is formed on the recording film 22 . The second dielectric film 23 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above. Subsequently, the intermediate separation layer 3 is formed on the second dielectric film 23. As shown in FIG. The intermediate separation layer 3 can be formed by the same method as the intermediate separation layer 2 described above.
(6) forming the L2 layer 30; Specifically, first, the first dielectric film 31 is formed on the intermediate isolation layer 3 . The first dielectric film 31 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.

A recording film 32 is then formed on the first dielectric film 31 . The recording film 32 can be formed using a target having a desired composition in the same manner as the recording film 12 described above. Subsequently, a second dielectric film 33 is formed on the recording film 32 . The second dielectric film 33 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above. Subsequently, an intermediate separation layer 4 is formed on the second dielectric film 33. As shown in FIG. The intermediate separation layer 4 can be formed in the same manner as the intermediate separation layers 2 and 3 described above.
(7) forming the L3 layer 40; The L3 layer 40 can be basically formed by the same method as the L1 layer 20 and the L2 layer 30 described above. First, a first dielectric film 41 is formed on the intermediate isolation layer 4 . The first dielectric film 41 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.

Subsequently, a recording film 42 is formed on the first dielectric film 41 . The recording film 42 can be formed using a target having a desired composition in the same manner as the recording film 12 described above. Subsequently, a second dielectric film 43 is formed on the recording film 42 . The second dielectric film 43 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above.

Any of the dielectric film, the recording film and the phase control film may be formed with a supply power of 10 W to 10 kW and a pressure of 0.01 Pa to 10 Pa in the deposition chamber during sputtering.

As for the target, if the powder or sintered body is in a crystalline phase, the oxide, nitride, oxynitride, and fluoride contained in the target can be examined by, for example, X-ray diffraction. The target texture may also include complex oxides, complex oxynitrides, mixed oxides, mixed oxynitrides, suboxides, high oxidation number oxides and oxyfluorides. This is about the targets for forming the first dielectric films 11, 21, 31, 41, the recording films 12, 22, 32, 42, the second dielectric films 13, 23, 33, 43 and the phase control film 14. applies similarly.
(8) Form the cover layer 5 on the second dielectric film 43 . The cover layer 5 is formed by applying a resin such as a photocurable resin (in particular, an ultraviolet curable resin) or a slow-acting thermosetting resin onto the second dielectric film 43, spin-coating the resin, and then curing the resin. can. Alternatively, the cover layer 5 may be formed by laminating a disk-shaped substrate 1 made of resin such as polycarbonate, amorphous polyolefin, or polymethyl methacrylate, or glass. Specifically, a resin such as a photocurable resin (particularly, an ultraviolet curable resin) or a slow-acting thermosetting resin is applied to the second dielectric film 43, and the substrate 1 is spun while the substrate 1 is in close contact with the applied resin. The cover layer 5 can be formed by coating to spread the resin uniformly and then curing the resin.

In addition to the sputtering method, a vacuum deposition method, an ion plating method, a chemical vapor deposition method (CVD method: Chemical Vapor Deposition), and a molecular beam epitaxy method (MBE method: Molecular Beam Epitaxy) can be used as a film forming method for each layer. It is also possible to use

Thus, the A-side information recording medium 101 can be manufactured. Also, if necessary, the substrate 1 and the L0 layer 10 may contain a disc identification code (for example, BCA (Burst Cutting Area)). For example, when attaching an identification code to the substrate 1 made of polycarbonate, the identification code can be attached by melting and vaporizing the polycarbonate using a CO ₂ laser or the like after molding the substrate 1 . Further, when attaching an identification code to the L0 layer 10, the identification code can be attached by recording on the recording film 12 using a semiconductor laser or the like, or by disassembling the recording film 12. FIG. The step of attaching an identification code to the L0 layer 10 may be performed after forming the phase control film 14, after forming the intermediate separation layer 2, after forming the cover layer 5, or after forming the bonding layer 6. FIG.

Similarly, the B-side information recording medium 102 can be manufactured. When guide grooves are provided on the substrate 1 of the B-side information recording medium 102, the rotating direction of the spiral may be opposite to or the same as that of the guide grooves of the substrate 1 of the A-side information recording medium 101 described above.

Finally, in the A-side information recording medium 101, the surface of the substrate 1 opposite to the surface on which the guide grooves are provided is uniformly coated with a photocurable resin (especially, an ultraviolet curable resin) to form a B-side information recording medium. The surface of substrate 1 102 opposite to the surface provided with the guide grooves is attached to the applied resin. After that, the bonding layer 6 is formed by irradiating the resin with light to cure it. Alternatively, a slow-curing photocurable resin is uniformly applied to the A-side information recording medium 101 and then exposed to light. good too. Thus, the information recording medium 100 having information layers on both sides according to the first embodiment can be manufactured.

Next, the L0 layer and phase adjustment film will be described in detail.
<Basic Configuration of L0 Layer and Phase Control Film>
The basic configuration of the L0 layer 10 including the first dielectric film 11, the recording film 12 and the second dielectric film 13, and the phase adjustment film 14 formed on the L0 layer 10 will be described. In the following description, the first dielectric film 11, the recording film 12 and the second dielectric film 13 are approximated as uniform media for ease of formulation.

When the film thickness and refractive index of the first dielectric film 11, the recording film 12, and the second dielectric film 13 are d _i and n _i (i=1, 2, 3), respectively, the total film of the L0 layer 10 is The thickness d _A and average refractive index n _A are expressed by equations (2) and (3).

Ｌ０層１０の反射特性は、第１誘電体膜１１、記録膜１２，第２誘電体膜１３および位相調整膜１４で生じる薄膜干渉の繰り返しを考慮することで計算できる。

The reflection characteristics of the L0 layer 10 can be calculated by considering repetition of thin film interference occurring in the first dielectric film 11, the recording film 12, the second dielectric film 13 and the phase adjustment film 14. FIG.

FIG. 2 schematically shows that the laser beam 7 irradiated to the L0 layer 10 passes through the intermediate separation layer 2, enters the phase adjustment film 14, and is reflected or transmitted by the phase adjustment film 14 and the L0 layer 10. It is a diagram. Let _nR be the refractive index of the intermediate separation layer 2 (medium 1), nL be the refractive index of the phase adjustment film 14 (medium 2), and _nL be the refractive index of the first dielectric film 11, the recording film 12, and the second dielectric film 13. Let n _A be the average refractive index of the L0 layer 10 (medium 3) composed of three types, and let n _S be the refractive index of the substrate 1 (medium 4). The film thickness of the phase adjustment film 14 is _dL , and the total film thickness of the first information layer 10 is _dA . Let θ ₁ be the incident angle of the laser beam that enters the phase adjustment film 14 through the intermediate separation layer 2 , and θ ₂ be the refraction angle. Let _θ3 be the refraction angle of the laser beam incident on the L0 layer 10 through the phase adjustment film 14 . Let r _{ij and} t _ij (i, j=1, 2, 3, 4 (i≠j)) be amplitude reflectance and amplitude transmittance when light is incident from medium i to medium j. The reflectivity R _L0 of the L0 layer 10 is expressed by equation (4) using Fresnel's formula.

Δ_２は、位相調整膜１４の中を１往復したときの位相差で、レーザ光７の波長をλとしたとき、式（５）で表される。

_Δ2 is the phase difference when making one round trip in the phase adjustment film 14, and is expressed by Equation (5) when the wavelength of the laser light 7 is λ.

δ_２は中間分離層２と位相調整膜１４との境界面および位相調整膜１４とＬ０層１０との境界面において生じる位相のずれを示している。屈折率の小さい媒質中を通った光が、屈折率の高い媒質に当たって反射される場合に、位相がπずれる。

_δ2 indicates the phase shift occurring at the interface between the intermediate separation layer 2 and the phase control film 14 and the interface between the phase control film 14 and the L0 layer 10 . When light passing through a medium with a low refractive index is reflected by a medium with a high refractive index, the phase shifts by π.

_r3 is the amplitude reflectance at the interface between the phase adjustment film 14 and the L0 layer 10, and is expressed by Equation (6).

Δ_３は、Ｌ０層１０を１往復したときの位相差で、レーザ光７の波長をλとしたとき、式（７）で表される。

_Δ3 is the phase difference when making one round trip in the L0 layer 10, and is expressed by the formula (7) when the wavelength of the laser light 7 is λ.

δ_３は位相調整膜１４とＬ０層１０との境界面およびＬ０層１０と基板１との境界面において生じる位相のずれを示している。
＜反射率を高くするための条件＞
レーザ光７は屈折率の低い媒質を通って、屈折率の高い媒質に当たって反射する場合、レーザ光７の位相がπずれる。この屈折率の異なる媒質の境界面で生じる位相のずれにより、反射率が最大となる条件が変化する。

δ ₃ indicates the phase shift occurring at the interface between the phase control film 14 and the L0 layer 10 and the interface between the L0 layer 10 and the substrate 1 .
<Conditions for increasing reflectance>
When the laser beam 7 passes through a medium with a low refractive index and is reflected by a medium with a high refractive index, the phase of the laser beam 7 is shifted by π. Due to the phase shift occurring at the interface between media with different refractive indices, the conditions for maximizing the reflectance change.

For example, the refractive index _nL of the phase adjustment film 14 is smaller than the refractive index _nR of the intermediate separation layer 2 and the average refractive index _nA of the L0 layer 10, and the average refractive index _nA of the L0 layer 10 is smaller than that of the substrate 1. When the refractive index is larger than _nS , the phase of the laser beam 7 is shifted by π when it passes through the phase adjustment film 14 and is reflected at the boundary surface with the L0 layer 10. The phase difference _Δ2 and the phase difference _Δ3 when making one round trip in the L0 layer 10 are expressed by equations (8) and (9), respectively.

位相差Δ_３がπの整数倍となるとき、式（４）中のｃоｓΔ_３は、ｃоｓΔ_３＝±１と一定の値を取るため、Ｌ０層１０の反射率は、位相差Δ_３に依存しない。このとき、位相差Δ_２が２πの整数倍となる条件で反射率が最大となり、反射率が最大値をとる位相調整膜１４の膜厚をｄ_{Ｌ（ＭＡＸ）}とすると、式（８）より、式（１０）が導出される。

When the phase difference Δ ₃ is an integral multiple of π, cos Δ ₃ in equation (4) takes a constant value of cos Δ ₃ =±1, so the reflectance of the L0 layer 10 depends on the phase difference Δ ₃ do not. At this time, when the reflectance is maximized under the condition that the phase difference _Δ2 is an integer multiple of 2π, and the film thickness of the phase adjustment film 14 at which the reflectance is maximized is dL _(MAX) , then from equation (8): , equation (10) is derived.

また、位相差Δ_２が（２ｐ＋１）π（ｐ＝０、１、２、３、・・・）となる場合に反射率が最小となり、反射率が最小値をとる位相調整膜１４の膜厚をｄ_{Ｌ（ＭＩＮ）}とすると、式（８）より、式（１１）が導出される。

In addition, when the phase difference _Δ2 is (2p+1)π (p=0, 1, 2, 3, . is dL _(MIN) , Equation (11) is derived from Equation (8).

式（１１）より、位相調整膜１４の屈折率ｎ_Ｌが、中間分離層２の屈折率ｎ_ＲおよびＬ０層１０の平均屈折率ｎ_Ａより小さい場合は、位相調整膜１４を形成しないときに反射率が最小値をとる。

From equation (11), when the refractive index _nL of the phase control film 14 is smaller than the refractive index _nR of the intermediate separation layer 2 and the average refractive index _nA of the L0 layer 10, when the phase control film 14 is not formed, Reflectance takes minimum value.

If the phase difference _Δ3 is not an integral multiple of π, the reflectance of the L0 layer ₁₀ changes depending on the value of cosΔ3 in equation (4). That is, the reflectance of the L0 layer 10 depends on the phase difference _Δ3 , and the film thickness _dL(MAX) of the phase adjustment film 14 with the maximum reflectance deviates from the formula (10). Assuming that this shift amount is Δd, the film thickness _dL(MAX) of the phase adjustment film 14 that maximizes the reflectance is expressed by Equation (12).

±Δｄの符号は、Δ_３の位相差によって決まり、（２ｑ－１）π＜Δ_３＜２ｑπ（ｑ＝０、±１、±２、±３、・・・）のときに－（マイナス）、２ｑπ＜Δ_３＜（２ｑ＋１）π（ｑ＝０、±１、±２、±３、・・・）のときに＋（プラス）となる。

The sign of ±Δd is determined by the phase difference of _Δ3 , and is − (minus) when (2q−1)π< _Δ3 <2qπ (q=0, ±1, ±2, ±3, . . . ) , 2qπ<Δ ₃ <(2q+1)π (q=0, ±1, ±2, ±3, . . . ).

On the other hand, when the refractive index _nL of the phase adjustment film 14 is larger than the refractive index _nR of the intermediate separation layer 2 and smaller than the average refractive index _nA of the first information layer 10, the laser light 7 passes through the intermediate separation layer 2. Since the phase of the laser beam 7 shifts by π when it is reflected at the interface with the phase adjustment film 14 through the phase adjustment film 14 and when it is reflected at the interface with the L0 layer 10 through the phase adjustment film 14, the phase difference _Δ2 is (2p+1)π (p=0, 1, 2, 3, . . . ), the reflectance is maximized. _L(MAX) is represented by Equation (13).

式（１３）より、位相調整膜１４の屈折率ｎ_Ｌが、中間分離層２の屈折率ｎ_Ｒより大きく、Ｌ０層１０の平均屈折率ｎ_Ａより小さい場合は、位相調整膜１４を形成しないときに反射率が最大値をとり、位相調整膜１４を形成すると反射率は低下する。
＜シミュレーション結果との比較＞
本発明者らは、Ｌ０層１０上に低屈折率の位相調整膜１４を形成することにより、Ｌ０層１０の反射率が向上することをシミュレーションによって確認した。

From equation (13), if the refractive index _nL of the phase control film 14 is greater than the refractive index _nR of the intermediate separation layer 2 and smaller than the average refractive index _nA of the L0 layer 10, the phase control film 14 is not formed. The reflectance sometimes takes a maximum value, and when the phase adjustment film 14 is formed, the reflectance decreases.
<Comparison with simulation results>
The inventors confirmed by simulation that the reflectance of the L0 layer 10 is improved by forming the phase adjustment film 14 with a low refractive index on the L0 layer 10 .

The results are described below. The following parameters were set for the calculation. The refractive index _nS of the substrate 1 was set to 1.62. The average refractive index n _A of the L0 layer 10 was set to 2.31. The refractive index _nL of the phase adjustment film 14 was set to 1.47. The refractive index n _R of the intermediate separation layer 2 was set to 1.52. A change in the reflectance of the L0 layer 10 when the film thickness _dA of the phase control film 14 is changed was calculated by optical simulation. In this simulation, the substrate 1 was a flat substrate, but it has been confirmed that the same results can be obtained with the substrate 1 having an uneven structure.

Since the incident angle of the laser beam 7 with which the information recording medium 100 is irradiated is approximately ±0.5°, θ ₁ =0° was set in this simulation.

FIG. 3 is a diagram showing simulation results of the reflectance of the L0 layer 10 when the film thickness of the phase adjustment film 14 is changed. Calculations were made with the total film thickness d _A of the L0 layer 10 being 64 nm. As shown in FIG. 3, the reflectance is increased by forming the phase adjustment film 14 with a low refractive index.

FIG. 4 shows the ratio of the reflectance of the L0 layer 10 when the thickness of the phase control film 14 is changed and the reflectance when the phase control film 14 is not formed at various total film thicknesses _dA of the L0 layer 10. is a diagram showing the result of optical simulation of . The total film thickness d _A of the L0 layer 10 was calculated under five conditions of 20 nm, 40 nm, 60 nm, 80 nm and 100 nm.

Total film thickness d _A is 20 nm, 40 nm (π<Δ ₃ <2π, i.e. 0<(2×d _A ×n _A )/λ<0.5) and 100 nm (3π<Δ ₃ <4π, i.e. 1.0 <(2×d _A ×n _A )/λ<1.5), the film thickness d _{A (MIN)} of the phase control film 14 having the minimum reflectance is shifted by 1 to 37 nm, and (2×d According to the condition of _A ×n _A )/λ, even if the phase adjustment film 14 is provided, the reflectance does not increase.

Although the configuration in which the phase adjustment film 14 is formed on the L0 layer 10 has been described in the first embodiment, the phase adjustment film 14 may be formed on the L1 layer 20 or the L2 layer 30. The same effect can be obtained even if
(Embodiment 2)
FIG. 5 is a cross-sectional view of the information recording medium 200 according to the second embodiment.

The information recording medium 200 is a double-sided information recording medium in which an A-side information recording medium 201 and a B-side information recording medium 202 are stuck together. The A-side information recording medium 201 and the B-side information recording medium 202 each include an L0 layer 10, an L1 layer 20, and an L2 layer, which are sequentially laminated as information layers on the substrate 1 via intermediate separation layers 2, 3 and 4. 30 and an L3 layer 40 , and a cover layer 5 is provided on the L3 layer 40 . In the L0 layer 10, a first dielectric film 11, a recording film 12, and a second dielectric film 13 are formed in this order from near to far when viewed from the substrate 1. FIG. The L1 layer 20, the L2 layer 30 and the L3 layer 40 have similar configurations. Furthermore, a phase adjustment film 14 is provided on the L3 layer 40 to increase the reflectance of the L3 layer 40 . The L1 layer 20, L2 layer 30 and L3 layer 40 are transmissive information layers. The A-side information recording medium 201 and the B-side information recording medium 202 are bonded together by a bonding layer 6 on the back surface of the substrate 1 (the side opposite to the surface having the information layer). The information recording medium 200 is irradiated with the laser beam 7 from the cover layer 5 side to record and reproduce information on each information layer.

The functions, materials and thicknesses of the substrate 1, the intermediate separation layer 2, the intermediate separation layer 3, the intermediate separation layer 4, the cover layer 5 and the bonding layer 6 are described in detail below.

Substrate 1 can be made of the same material as in the first embodiment, and has the same thickness as in the first embodiment.

The intermediate separation layers 2, 3 and 4 can be made of the same material as in the first embodiment, and have the same thickness as in the first embodiment.

The cover layer 5 can be made of the same material as in the first embodiment, and has the same thickness as in the first embodiment.

The bonding layer 6 can be made of the same material as in the first embodiment, and has the same thickness as in the first embodiment.

The read durability of the information layer in the information recording medium 200 can be evaluated by continuously irradiating the laser light 7 with the read power to the recording marks previously recorded with the laser light 7 with the optimum recording power. Specifically, it can be determined by the d-MLSE value after one million times (one million passes) of reproduction. If the d-MLSE value after 1,000,000 times of playback is 16.0% or less, it can be determined that 1,000,000 passes of playback were achieved with that playback power.
<Method of Forming Information Recording Medium 200>
The A-side information recording medium 201 can be manufactured by the following procedures (1) to (8).
(1) A substrate 1 (for example, 0.5 mm thick and 120 mm in diameter) is placed in a film forming apparatus.
(2) forming the L0 layer 10; The first dielectric film 11, the recording film 12, and the second dielectric film 13, which constitute the L0 layer 10, can be formed by a sputtering method, which is one of vapor deposition methods.
First, a first dielectric film 11 is deposited. At this time, if a spiral guide groove is formed in the substrate 1, the first dielectric film 11 is formed on the guide groove side.

The first dielectric film 11 can use the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.
Subsequently, a recording film 12 is formed on the first dielectric film 11 . The recording film 12 can be made of the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.

Subsequently, a second dielectric film 13 is formed on the recording film 12 . The second dielectric film 13 can use the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.
(3) forming the intermediate isolation layer 2 on the second dielectric film 13; The same material as in the first embodiment can be used for the intermediate separation layer 2, and the role and manufacturing method are also the same as in the first embodiment.
(4) forming the L1 layer 20; Specifically, first, the first dielectric film 21 is formed on the intermediate isolation layer 2 . The first dielectric film 21 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.

A recording film 22 is then formed on the first dielectric film 21 . The recording film 22 can be formed by a method similar to that for the recording film 12 described above, using a target having a desired composition. Subsequently, a second dielectric film 23 is formed on the recording film 22 . The second dielectric film 23 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above. Subsequently, the intermediate separation layer 3 is formed on the second dielectric film 23. As shown in FIG. The intermediate separation layer 3 can be formed by the same method as the intermediate separation layer 2 described above.
(5) forming the L2 layer 30; Specifically, first, the first dielectric film 31 is formed on the intermediate isolation layer 3 . The first dielectric film 31 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.
A recording film 32 is then formed on the first dielectric film 31 . The recording film 32 can be formed using a target having a desired composition in the same manner as the recording film 12 described above. Subsequently, a second dielectric film 33 is formed on the recording film 32 . The second dielectric film 33 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above. Subsequently, an intermediate separation layer 4 is formed on the second dielectric film 33. As shown in FIG. The intermediate separation layer 4 can be formed by the same method as the intermediate separation layers 2 and 3 described above.
(6) forming the L3 layer 40; The L3 layer 40 can be basically formed by the same method as the L2 layer 30 described above. First, a first dielectric film 41 is formed on the intermediate isolation layer 4 . The first dielectric film 41 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.

Subsequently, a recording film 42 is formed on the first dielectric film 41 . The recording film 42 can be formed using a target having a desired composition in the same manner as the recording film 12 described above. Subsequently, a second dielectric film 43 is formed on the recording film 42 . The second dielectric film 43 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above.
(7) Subsequently, the phase adjustment film 14 is formed on the second dielectric film 43 . The phase adjustment film 14 can use the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.

Any of the dielectric film, the recording film and the phase control film may be formed with a supply power of 10 W to 10 kW and a pressure of 0.01 Pa to 10 Pa in the deposition chamber during sputtering.

As for the target, if the powder or sintered body is in a crystalline phase, the oxide, nitride, oxynitride, and fluoride contained in the target can be examined by, for example, X-ray diffraction. The target texture may also include complex oxides, complex oxynitrides, mixed oxides, mixed oxynitrides, suboxides, high oxidation number oxides and oxyfluorides. This is about the targets for forming the first dielectric films 11, 21, 31, 41, the recording films 12, 22, 32, 42, the second dielectric films 13, 23, 33, 43 and the phase control film 14. applies similarly.
(8) Form the cover layer 5 on the phase control film 14 . The same material as in the first embodiment can be used for the cover layer 5, and the role and manufacturing method are also the same as in the first embodiment.

Thus, the A-side information recording medium 201 can be manufactured. Also, if necessary, the substrate 1 and the L0 layer 10 may contain a disc identification code (for example, BCA (Burst Cutting Area)). For example, when attaching an identification code to the substrate 1 made of polycarbonate, the identification code can be attached by melting and vaporizing the polycarbonate using a CO ₂ laser or the like after molding the substrate 1 . Further, when attaching an identification code to the L0 layer 10, the identification code can be attached by recording on the recording film 12 using a semiconductor laser or the like, or by disassembling the recording film 12. FIG. The step of attaching an identification code to the L0 layer 10 may be performed after forming the second dielectric film 13 , after forming the intermediate isolation layer 2 , after forming the cover layer 5 , or after forming the bonding layer 6 .

Similarly, the B-side information recording medium 202 can be manufactured. When guide grooves are provided in the substrate 1 of the B-side information recording medium 202, the rotating direction of the spiral may be opposite to or the same as that of the guide grooves of the substrate 1 of the A-side information recording medium 201 described above.

Finally, in the A-side information recording medium 201, the surface of the substrate 1 opposite to the surface on which the guide grooves are provided is uniformly coated with a photocurable resin (especially, an ultraviolet curable resin) to form a B-side information recording medium. The surface of the substrate 202 opposite to the surface provided with the guide grooves is attached to the applied resin. After that, the bonding layer 6 is formed by irradiating the resin with light to cure it. Alternatively, after uniformly coating the A-side information recording medium 201 with a slow curing photocurable resin, light is applied, and then the B-side information recording medium 202 is attached to form the bonding layer 6. good too. Thus, the information recording medium 200 having information layers on both sides according to the first embodiment can be manufactured. Next, the L3 layer and phase adjustment film will be described in detail.
<Basic Configuration of L3 Layer and Phase Control Film>
The basic configuration of the L3 layer 40 including the first dielectric film 41, the recording film 42 and the second dielectric film 43, and the phase adjustment film 14 formed between the L3 layer and the cover layer 5 will be described. In the following description, the first dielectric film 41, the recording film 42 and the second dielectric film 43 are approximated as uniform media for ease of formulation.

When the film thickness and refractive index of the first dielectric film 41, the recording film 42, and the second dielectric film 43 are respectively _dk and nk ( _k =4, 5, 6), the total film of the L3 layer 40 is The thickness d _B and average refractive index n _B are expressed by equations (14) and (15).

Ｌ３層４０の反射特性は、第１誘電体膜４１、記録膜４２、第２誘電体膜４３および位相調整膜１４で生じる薄膜干渉の繰り返しを考慮することで計算できる。

The reflection characteristics of the L3 layer 40 can be calculated by considering repetition of thin film interference occurring in the first dielectric film 41, the recording film 42, the second dielectric film 43 and the phase control film 14. FIG.

FIG. 6 is a diagram schematically showing that the laser beam 7 irradiated to the L3 layer 40 passes through the cover layer 5 and enters the phase adjustment film 14, and is reflected or transmitted by the phase adjustment film 14 and the L3 layer 40. is. Let _nC be the refractive index of the cover layer 5 (medium 5), _nL be the refractive index of the phase adjustment film 14 (medium 6), and three Let _nB be the average refractive index of the L3 layer 40 (medium 7) composed of the type, and let _nR be the refractive index of the intermediate separation layer 4 (medium 8). The film thickness of the phase control film 14 is _dL , and the total film thickness of the L3 layer 40 is _dB . Assume that the incident angle of the laser beam passing through the cover layer 5 and entering the phase adjustment film 14 is _θ5 , and the refraction angle is _θ6 . Let _θ7 be the refraction angle of the laser light incident on the L3 layer 40 through the phase adjustment film 14 . Let r _kl and t _kl (k, l=5, 6, 7, 8 (k≠l)) represent amplitude reflectance and amplitude transmittance when light is incident on medium l from medium k. The reflectivity R _L3 of the L3 layer 40 is expressed by equation (16) using Fresnel's formula.

Δ_６は、位相調整膜１４の中を１往復したときの位相差で、レーザ光７の波長をλとしたとき、式（１７）で表される。

_Δ6 is the phase difference when making one round trip in the phase adjustment film 14, and is expressed by the formula (17) when the wavelength of the laser light 7 is λ.

δ_６はカバー層５と位相調整膜１４との境界面および位相調整膜１４とＬ３層４０との境界面において生じる位相のずれを示している。

_δ6 indicates the phase shift occurring at the interface between the cover layer 5 and the phase control film 14 and the interface between the phase control film 14 and the L3 layer 40 .

_r7 is the amplitude reflectance at the interface between the phase control film 14 and the L3 layer 40, and is expressed by equation (18).

Δ_７は、Ｌ３層４０を１往復したときの位相差で、レーザ光７の波長をλとしたとき、式（１９）で表される。

_Δ7 is a phase difference when making one round trip in the L3 layer 40, and is expressed by Equation (19) when the wavelength of the laser light 7 is λ.

δ_７は位相調整膜１４とＬ３層４０との境界面およびＬ３層４０と中間分離層４との境界面において生じる位相のずれを示している。
＜反射率を高くするための条件＞
レーザ光７は屈折率の低い媒質を通って、屈折率の高い媒質に当たって反射する場合、レーザ光７の位相がπずれる。この屈折率の異なる媒質の境界面で生じる位相のずれにより、反射率が最大となる条件が変化する。

_δ7 indicates the phase shift occurring at the interface between the phase control film 14 and the L3 layer 40 and the interface between the L3 layer 40 and the intermediate separation layer 4 .
<Conditions for increasing reflectance>
When the laser beam 7 passes through a medium with a low refractive index and is reflected by a medium with a high refractive index, the phase of the laser beam 7 is shifted by π. Due to the phase shift occurring at the interface between media with different refractive indices, the conditions for maximizing the reflectance change.

For example, the refractive index _nL of the phase adjustment film 14 is smaller than the refractive index _nC of the cover layer 5 and the average refractive index _nB of the L3 layer 40, and the average refractive index _nB of the L3 layer 40 is less than the intermediate separation layer 4 When the refractive index n is larger than _L , the phase of the laser beam 7 shifts by π when it passes through the phase adjustment film 14 and is reflected at the boundary surface with the L3 layer 40. A phase difference Δ ₆ and a phase difference Δ ₇ when making one round trip in the L3 layer 40 are expressed by equations (20) and (21), respectively.

位相差Δ_７がπの整数倍となるとき、式（１６）中のｃоｓΔ_７は、ｃоｓΔ_７＝±１と一定の値を取るため、Ｌ３層４０の反射率は、位相差Δ_７に依存しない。このとき、位相差Δ_６が２πの整数倍となる条件で反射率が最大となり、反射率が最大値をとる位相調整膜１４の膜厚をｄ_{Ｌ（ＭＡＸ）}とすると、式（２０）より、式（２２）が導出される。

When the phase difference Δ ₇ is an integer multiple of π, cos Δ ₇ in equation (16) takes a constant value of cos Δ ₇ =±1, so the reflectance of the L3 layer 40 depends on the phase difference Δ ₇ . do not. At this time, the reflectance is maximized under the condition that the phase difference _Δ6 is an integer multiple of 2π, and the film thickness of the phase adjustment film 14 at which the reflectance is maximized is _dL(MAX). , Equation (22) is derived.

また、位相差Δ_６が（２ｐ＋１）π（ｐ＝０、１、２、３、・・・）となる場合に反射率が最小となり、反射率が最小値をとる位相調整膜１４の膜厚をｄ_{Ｌ（ＭＩＮ）}とすると、式（２０）より、式（２３）が導出される。

In addition, when the phase difference _Δ6 is (2p+1)π (p=0, 1, 2, 3, . is _dL(MIN) , Equation (23) is derived from Equation (20).

式（２３）より、位相調整膜１４の屈折率ｎ_Ｌが、中間分離層２の屈折率ｎ_ＲおよびＬ３層４０の平均屈折率ｎ_Ｂより小さい場合は、位相調整膜１４を形成しないときに反射率が最小値をとる。

(23), when the refractive index _nL of the phase control film 14 is smaller than the refractive index _nR of the intermediate separation layer 2 and the average refractive index _nB of the L3 layer 40, when the phase control film 14 is not formed, Reflectance takes minimum value.

If the phase difference _Δ7 is not an integer multiple of π, the reflectance of the L3 layer 40 changes depending on the value of cos _Δ7 in equation (16). That is, the reflectance of the L3 layer 40 depends on the phase difference _Δ7 , and the film thickness _dL(MAX) of the phase adjustment film 14 with the maximum reflectance deviates from the formula (22). Assuming that this shift amount is Δd, the film thickness _dL(MAX) of the phase adjustment film 14 that maximizes the reflectance is expressed by Equation (24).

±Δｄの符号は、Δ_７の位相差によって決まり、（２ｑ－１）π＜Δ_７＜２ｑπ（ｑ＝０、±１、±２、±３、・・・）のときに－（マイナス）、２ｑπ＜Δ_７＜（２ｑ＋１）π（ｑ＝０、±１、±２、±３、・・・）のときに＋（プラス）となる。

The sign of ±Δd is determined by the phase difference of _Δ7 , and is − (minus) when (2q−1)π< _Δ7 <2qπ (q=0, ±1, ±2, ±3, . . . ) , 2qπ<Δ ₇ <(2q+1)π (q=0, ±1, ±2, ±3, . . . ).

On the other hand, when the refractive index _nL of the phase control film 14 is larger than the refractive index _nC of the cover layer 5 and smaller than the average refractive index _nB of the L3 layer 40, the laser light 7 passes through the cover layer 5 and reaches the phase control film. 14 and when reflected at the boundary surface with the L3 layer 40 through the phase adjustment film 14, the phase difference Δ ₆ is (2p+1). The reflectance is maximized when π (p=0, 1, 2, 3, . . . ) _. is represented by the formula (25).

式（２５）より、位相調整膜１４の屈折率ｎ_Ｌが、カバー層５の屈折率ｎ_Ｃより大きく、Ｌ３層４０の平均屈折率ｎ_Ｂより小さい場合は、位相調整膜１４を形成しないときに反射率が最大値をとり、位相調整膜１４を形成すると反射率は低下する。
＜シミュレーション結果との比較＞
本発明者らは、Ｌ３層４０上に低屈折率の位相調整膜１４を形成することにより、Ｌ３層４０の反射率が向上することをシミュレーションによって確認した。

From equation (25), when the refractive index _nL of the phase control film 14 is greater than the refractive index _nC of the cover layer 5 and smaller than the average refractive index _nB of the L3 layer 40, the phase control film 14 is not formed. The reflectance reaches its maximum value at 100° C., and the reflectance decreases when the phase adjustment film 14 is formed.
<Comparison with simulation results>
The present inventors have confirmed by simulation that the reflectance of the L3 layer 40 is improved by forming the phase adjustment film 14 with a low refractive index on the L3 layer 40 .

The results are described below. The following parameters were set for the calculation. The refractive index _nR of the intermediate separation layer 4 was set to 1.52. The average refractive index _nB of the L3 layer 40 was set to 2.17. The refractive index _nL of the phase adjustment film 14 was set to 1.47. The refractive index n _C of the cover layer 5 was set to 1.56. A change in the reflectance of the L3 layer 40 when the film thickness d _B of the phase control film 14 is changed was calculated by optical simulation. In this simulation, the surface state of the intermediate isolation layer 4 was calculated as being flat, but it was confirmed that similar results could be obtained even when the intermediate isolation layer 4 has an uneven structure.

Since the incident angle of the laser beam 7 with which the information recording medium 200 is irradiated is approximately ±0.5°, θ ₅ =0° was set in this simulation.

FIG. 7 is a diagram showing simulation results of the reflectance of the L3 layer 40 when the film thickness of the phase adjustment film 14 is changed. Calculations were made with the total film thickness d _B of the L3 layer 40 being 78 nm. As can be seen from FIG. 7, the reflectance is increased by forming the phase adjustment film 14 with a low refractive index.

FIG. 8 shows the ratio of the reflectance of the L3 layer 40 when the film thickness of the phase control film 14 is changed and the reflectance when the phase control film 14 is not formed at various total film thicknesses d _B of the L3 layer 40. is a diagram showing the result of optical simulation of . The total film thickness _dB of the L3 layer 40 was calculated under five conditions of 20 nm, 40 nm, 60 nm, 80 nm and 100 nm.

Total film thickness d _B is 20 nm, 40 nm (π<Δ ₇ <2π, i.e. 0<(2×d _B ×n _B )/λ<0.5) and 100 nm (3π<Δ ₇ <4π, i.e. 1.0 <(2×d _B ×n _B )/λ<1.5), the film thickness d _{B (MIN)} of the phase control film 14 having the minimum reflectance is shifted by 1 to 50 nm, and (2×d It shows that the reflectance does not increase even if the phase adjustment film 14 is provided under the condition of _B ×n _B )/λ.
(Embodiment 3)
FIG. 9 is a cross-sectional view of an information recording medium 300 according to the third embodiment. The information recording medium 300 is a double-sided information recording medium in which an A-side information recording medium 301 and a B-side information recording medium 302 are bonded together. The A-side information recording medium 301 and the B-side information recording medium 302 each include an L0 layer 203, an L1 layer 20, and an L2 layer, which are sequentially laminated as information layers on the substrate 1 via intermediate separation layers 2, 3 and 4. 30 and an L3 layer 40 , and a cover layer 5 is provided on the L3 layer 40 . In the L0 layer 203, a first dielectric film 11, a recording film 12, and a second dielectric film 13 are formed in this order from near to far when viewed from the substrate 1. FIG. The L1 layer 20, the L2 layer 30 and the L3 layer 40 have similar configurations. A phase adjustment film 14 is provided on the L0 layer 303 to increase the reflectance of the L0 layer 303 . The L1 layer 20, L2 layer 30 and L3 layer 40 are transmissive information layers. Furthermore, the information recording medium 300 has a third dielectric film provided on the first dielectric film 11 of the L0 layer 20 . The A-side information recording medium 301 and the B-side information recording medium 302 are bonded together by a bonding layer 6 on the back surface of the substrate 1 (the side opposite to the surface having the information layer). The information recording medium 300 is irradiated with the laser beam 7 from the cover layer 5 side to record and reproduce information on each information layer.

The functions, materials and thicknesses of the substrate 1, the intermediate separation layer 2, the intermediate separation layer 3, the intermediate separation layer 4, the cover layer 5 and the bonding layer 6 are described in detail below.

Substrate 1 can be made of the same material as in the first embodiment, and has the same thickness as in the first embodiment.

The intermediate separation layers 2, 3 and 4 can be made of the same material as in the first embodiment, and have the same thickness as in the first embodiment.

The cover layer 5 can be made of the same material as in the first embodiment, and has the same thickness as in the first embodiment.

The bonding layer 6 can be made of the same material as in the first embodiment, and has the same thickness as in the first embodiment.

The reproduction durability of the information layer in the information recording medium 300 can be evaluated by continuously irradiating the laser beam 7 of reproduction power to the recording marks previously recorded with the laser beam 7 of optimum recording power. Specifically, it can be determined by the d-MLSE value after one million times (one million passes) of reproduction. If the d-MLSE value after 1,000,000 times of playback is 16.0% or less, it can be determined that 1,000,000 passes of playback were achieved with that playback power.
<Method of Forming Information Recording Medium 300>
The A-side information recording medium 301 can be manufactured by the following procedures (1) to (8).
(1) A substrate 1 (for example, 0.5 mm thick and 120 mm in diameter) is placed in a film forming apparatus. (2) forming the L0 layer 203; The first dielectric film 11, the third dielectric film 204, the recording film 12, and the second dielectric film 13, which constitute the L0 layer 203, can be formed by a sputtering method, which is one of vapor deposition methods. First, a first dielectric film 11 is deposited. At this time, if a spiral guide groove is formed in the substrate 1, the first dielectric film 11 is formed on the guide groove side.

The first dielectric film 11 can use the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.

Subsequently, a third dielectric film 204 is formed on the first dielectric film 11 . The third dielectric film 204 has a function of increasing the reflectance of the L0 layer 203. When the refractive index at 405 nm is 2.25 or more, the difference in refractive index from the recording film increases, and the L0 layer 203 reflects more. rate can be increased.

Specifically, it is preferable to use at least one material selected from TiO ₂ , Nb ₂ O ₅ and Bi ₂ O ₃ as the third dielectric film 203 , such as TiO ₂ , Nb ₂ O ₅ and Bi ₂ O ₃ . , TiO ₂ —Nb ₂ O ₅ , TiO ₂ —Bi ₂ O ₃ and the like can be used.

The third dielectric film 203 can be formed by performing sputtering in a process gas atmosphere or a mixed gas atmosphere of a process gas and a reaction gas using a target corresponding to the composition of the third dielectric film 203 . Also, the third dielectric film 203 may be formed by performing multi-sputtering. The third dielectric film 203 can be formed using a target with a desired composition.

Subsequently, the recording film 12 is formed on the third dielectric film 203 . The recording film 12 can be made of the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.

Subsequently, a second dielectric film 13 is formed on the recording film 12 . The second dielectric film 13 can use the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.
(3) Forming a phase control film 14 on the second dielectric film 13 . The phase adjustment film 14 can use the same material as in the first embodiment, and its role and manufacturing method are also the same as in the first embodiment.
(4) forming the intermediate isolation layer 2 on the phase control film 14; The same material as in the first embodiment can be used for the intermediate separation layer 2, and the role and manufacturing method are also the same as in the first embodiment.
(5) forming the L1 layer 20; Specifically, first, the first dielectric film 21 is formed on the intermediate isolation layer 2 . The first dielectric film 21 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.

A recording film 22 is then formed on the first dielectric film 21 . The recording film 22 can be formed by a method similar to that for the recording film 12 described above, using a target having a desired composition. Subsequently, a second dielectric film 23 is formed on the recording film 22 . The second dielectric film 23 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above. Subsequently, the intermediate separation layer 3 is formed on the second dielectric film 23. As shown in FIG. The intermediate separation layer 3 can be formed by the same method as the intermediate separation layer 2 described above.
(6) forming the L2 layer 30; Specifically, first, the first dielectric film 31 is formed on the intermediate isolation layer 3 . The first dielectric film 31 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.
A recording film 32 is then formed on the first dielectric film 31 . The recording film 32 can be formed using a target having a desired composition in the same manner as the recording film 12 described above. Subsequently, a second dielectric film 33 is formed on the recording film 32 . The second dielectric film 33 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above. Subsequently, an intermediate separation layer 4 is formed on the second dielectric film 33. As shown in FIG. The intermediate separation layer 4 can be formed by the same method as the intermediate separation layers 2 and 3 described above.
(7) forming the L3 layer 40; The L3 layer 40 can be basically formed by the same method as the L2 layer 30 described above. First, a first dielectric film 41 is formed on the intermediate isolation layer 4 . The first dielectric film 41 can be formed using a target having a desired composition in the same manner as the first dielectric film 11 described above.

Subsequently, a recording film 42 is formed on the first dielectric film 41 . The recording film 42 can be formed using a target having a desired composition in the same manner as the recording film 12 described above. Subsequently, a second dielectric film 43 is formed on the recording film 42 . The second dielectric film 43 can be formed using a target having a desired composition in the same manner as the second dielectric film 13 described above.

Any of the dielectric film, the recording film and the phase control film may be formed with a supply power of 10 W to 10 kW and a pressure of 0.01 Pa to 10 Pa in the deposition chamber during sputtering.

As for the target, if the powder or sintered body is in a crystalline phase, the oxide, nitride, oxynitride, and fluoride contained in the target can be examined by, for example, X-ray diffraction. The target texture may also include complex oxides, complex oxynitrides, mixed oxides, mixed oxynitrides, suboxides, high oxidation number oxides and oxyfluorides. This includes first dielectric films 11, 21, 31, 41, recording films 12, 22, 32, 42, second dielectric films 13, 23, 33, 43, third dielectric film 15 and phase control film 14. The same applies to targets for forming
(8) Form the cover layer 5 on the second dielectric film 43 . The same material as in the first embodiment can be used for the cover layer 5, and the role and manufacturing method are also the same as in the first embodiment.

Thus, the A-side information recording medium 101 can be manufactured. Also, if necessary, the substrate 1 and the L0 layer 203 may contain a disc identification code (eg, BCA (Burst Cutting Area)). For example, when attaching an identification code to the substrate 1 made of polycarbonate, the identification code can be attached by melting and vaporizing the polycarbonate using a CO ₂ laser or the like after molding the substrate 1 . When attaching an identification code to the L0 layer 203, the identification code can be attached by recording on the recording film 12 using a semiconductor laser or the like, or by disassembling the recording film 12. FIG. The step of attaching an identification code to the L0 layer 203 may be performed after forming the phase control film 14, after forming the intermediate separation layer 2, after forming the cover layer 5, or after forming the bonding layer 6. FIG.

Similarly, the B-side information recording medium 302 can be manufactured. When guide grooves are provided on the substrate 1 of the B-side information recording medium 302, the rotating direction of the spiral may be opposite to or the same as that of the guide grooves of the substrate 1 of the A-side information recording medium 301 described above.

Finally, in the A-side information recording medium 301, the surface of the substrate 1 opposite to the surface on which the guide grooves are provided is uniformly coated with a photocurable resin (particularly, an ultraviolet curable resin) to form a B-side information recording medium. The surface of the substrate 1 of 302 opposite to the surface provided with the guide grooves is attached to the applied resin. After that, the bonding layer 6 is formed by irradiating the resin with light to cure it. Alternatively, a slow curing photocurable resin is applied uniformly to the A-side information recording medium 301 and then exposed to light, and then the B-side information recording medium 302 is attached to form the bonding layer 6. good too. Thus, the information recording medium 300 having information layers on both sides according to the second embodiment can be manufactured.

Next, the technology of the present disclosure will be described in detail using examples.

More specific embodiments of the present invention will be described in more detail using examples.
(Example 1)
In this example, an example of the information recording medium 100 of Embodiment 1 will be described. A method for manufacturing the information recording medium 100 of this embodiment will be described below.

First, the configuration of the A-side information recording medium 101 will be described. As the substrate 1, a polycarbonate substrate (diameter 120 mm, thickness 0.5 mm) having spiral guide grooves (depth 30 nm, track pitch (land-groove distance) 0.18 μm) was prepared. An L0 layer 10 was formed on the substrate 1 . (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) as the first dielectric film 11 (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) of 12 nm and a recording film 12, a target consisting essentially of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O was used, and W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O was deposited to a thickness of 10 to 74 nm, and a second dielectric film was formed. Using a target consisting essentially of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) as 13, (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 10 nm was sequentially formed by a sputtering method.

Regarding the notation of the recording film 12, only the metal element ratio (atomic %) is described as the element ratio, and the subsequent elements are similarly described. For example, an oxide of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ (atomic %) is expressed as W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ -O.

The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power supply (6 kW). The second dielectric film 13 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).

Subsequently, a phase control film 14 was formed on the L0 layer 10 . As the phase control film 14, a SiO ₂ film having a thickness of 0 to 100 nm was formed by a sputtering method using a target made of SiO ₂ . The phase control film 14 was formed using a SiO ₂ target in an atmosphere of Ar+O ₂ (flow rate: 12+1.2 sccm) and an RF power source (1 kW).

Subsequently, an intermediate separation layer 2 having spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm) was formed on the phase adjustment film 14 . First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ as the recording film 22 in the embodiment of the present invention. Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 13 nm as the first dielectric film 41 and W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 was used to obtain W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O of 44 nm, and the second dielectric film 43 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 21 nm was sequentially formed by a sputtering method using a target composed of the following.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured by ultraviolet rays to form a cover layer 5 having a thickness of about 53.5 μm. .

Next, the configuration of the B-side information recording medium 102 will be described. As a substrate 1, a polycarbonate substrate (thickness: 0.5 mm) having spiral guide grooves (depth: 30 nm, track pitch (land-groove distance): 0.180 μm) was prepared. The direction of rotation of the spiral of the guide groove was opposite to that of the substrate 1 of the A-side information recording medium 101 described above. An L0 layer 10 was formed on the substrate 1 . As the first dielectric film 11, the first dielectric film 11 is substantially (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) ₁ ( _ZnO ) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) to 12 nm, and using a target consisting essentially of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ -O as the recording film 12, W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ -O to 10 to 10 nm. 74 nm, using a target consisting essentially of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) as the second dielectric film 13 , (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ A film of (In ₂ O ₃ ) ₅₀ (mol %) of 10 nm was sequentially formed by a sputtering method.
The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power source (6 kW). The second dielectric film 13 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).

Subsequently, a phase control film 14 was formed on the L0 layer 10 . As the phase control film 14, a SiO ₂ film having a thickness of 0 to 100 nm was formed by a sputtering method using a target made of SiO ₂ . The phase control film 14 was formed using a SiO ₂ target in an atmosphere of Ar+O ₂ (flow rate: 12+1.2 sccm) and an RF power source (1 kW).

Subsequently, an intermediate separation layer 2 was formed on the phase adjustment film 14 with spiral guide grooves (depth 33 nm, track pitch (land-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ as the recording film 22 in the embodiment of the present invention. Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).
An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 13 nm as the first dielectric film 41 and W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 was used to obtain W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O of 44 nm, and the second dielectric film 43 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 21 nm was sequentially formed by a sputtering method using a target composed of the following.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured with ultraviolet rays to form the cover layer 5 with a thickness of about 53.5 μm, thereby producing the B-side information recording medium 102 . .

Finally, the surface of the substrate 1 of the A-side information recording medium 101 opposite to the surface on which the guide grooves are provided is uniformly coated with an ultraviolet curing resin so that the guide grooves of the substrate 1 of the B-side information recording medium 102 are formed. A surface opposite to the provided surface was bonded, and the resin was cured by ultraviolet rays to form a bonding layer 6 (thickness: about 35 μm).

Thus, the information recording medium 100 of this example was produced.

Table 1 shows the refractive indices of the first dielectric film 11, the recording film 12, the second dielectric film 13, the phase adjustment film 14, the intermediate separation layer 2, and the substrate 1, which constitute the L0 layer .

本実施例の情報記録媒体１００の一例として、Ａ面情報記録媒体１０１およびＢ面情報記録媒体１０２の記録膜１２および位相調整膜１４の膜厚をそれぞれ、（記録膜１２の膜厚、位相調整膜１４の膜厚）＝（２５ｎｍ、１０ｎｍ）、（２５ｎｍ、２０ｎｍ）、（２５ｎｍ、４０ｎｍ）、（２５ｎｍ、６０ｎｍ）、（４２ｎｍ、５ｎｍ）、（４２ｎｍ、１０ｎｍ）、（４２ｎｍ、１５ｎｍ）、（４２ｎｍ、２０ｎｍ）、（４２ｎｍ、３０ｎｍ）、（４２ｎｍ、４０ｎｍ）、（４２ｎｍ、６０ｎｍ）、（４２ｎｍ、８０ｎｍ）、（４２ｎｍ、１００ｎｍ）、（６０ｎｍ、１０ｎｍ）、（６０ｎｍ、２０ｎｍ）、（６０ｎｍ、４０ｎｍ）、（６０ｎｍ、６０ｎｍ）とした情報記録媒体１００を作製した。これらのディスクＮｏ．を１－１～１－１７とする。比較例として、Ａ面情報記録媒体１０１およびＢ面情報記録媒体１０２の記録膜１２および位相調整膜１４の膜厚をそれぞれ、（記録膜１２の膜厚、位相調整膜１４の膜厚）＝（１０ｎｍ、１０ｎｍ）、（７４ｎｍ、１０ｎｍ）、（４２ｎｍ、０ｎｍ）としたディスクＮｏ．比較例１－１～１－３を作製した。

As an example of the information recording medium 100 of the present embodiment, the thicknesses of the recording film 12 and the phase adjustment film 14 of the A-side information recording medium 101 and the B-side information recording medium 102 are respectively set to (thickness of the recording film 12, phase adjustment Film thickness of film 14)=(25 nm, 10 nm), (25 nm, 20 nm), (25 nm, 40 nm), (25 nm, 60 nm), (42 nm, 5 nm), (42 nm, 10 nm), (42 nm, 15 nm), ( 42 nm, 20 nm), (42 nm, 30 nm), (42 nm, 40 nm), (42 nm, 60 nm), (42 nm, 80 nm), (42 nm, 100 nm), (60 nm, 10 nm), (60 nm, 20 nm), (60 nm, 40 nm) and (60 nm, 60 nm) were produced. These disk nos. are 1-1 to 1-17. As a comparative example, the thicknesses of the recording film 12 and the phase adjustment film 14 of the A-side information recording medium 101 and the B-side information recording medium 102 are respectively expressed as (thickness of the recording film 12, thickness of the phase adjustment film 14)=( 10 nm, 10 nm), (74 nm, 10 nm), (42 nm, 0 nm). Comparative Examples 1-1 to 1-3 were produced.

Disc No. 1-1 to 1-17 and Comparative Examples 1-1 to 1-3 were evaluated for reflectance and reproduction durability. The reflectance was evaluated using a Pulstec evaluation machine (ODU-1000). The reproduction durability was evaluated using an evaluation device manufactured in-house.

The wavelength of the laser beam 7 of the evaluation machine manufactured by Pulstec was 405 nm, the numerical aperture NA of the objective lens was 0.91, the linear velocity was 8.23 m/s, and the reflectance was measured with all information layers unrecorded. evaluated.

The wavelength of the laser beam 7 of the self-manufactured evaluation device was 405 nm, the numerical aperture NA of the objective lens was 0.91, and information was recorded on the grooves and lands. The recording linear velocity was 15.63 m/s and the reproducing linear velocity was 15.63 m/s. Information was recorded by multi-level recording in which a multi-level code was recorded. In multilevel recording, the recording depth is controlled to form a mark having a size corresponding to the value (level) of the multilevel code. Specifically, a quinary code was recorded, and the density was set to 125 GB per information layer. During reproduction, the difference in the size of the recording marks appears as the difference in the intensity of the reflected light (gradation). When a quinary code is recorded, gradations of reflected light corresponding to the quinary values are obtained. Signal quality was evaluated as d-MLSE (Distribution Derived-Maximum Likelihood Sequence Error Estimation).

Evaluation of the reproduction durability of the L0 layer 10 was carried out by multi-value recording random signals in adjacent grooves and lands, and recording the random signals in the groove located in the center of the recorded track and the lands on both sides at a linear velocity of 15.63 m/m. s, and subjected to waveform transparency processing (crosstalk cancellation processing) to minimize crosstalk from adjacent land tracks, and the absolute value of d-MLSE at the 1,000,000th repetition was used to determine the quality.

The reproduction power was set so that the reproduction light amount satisfied 0.117. For example, when the effective reflectance was 2.2%, the reproduction power was set to 5.3 mW. Here, the amount of reproduction light is the amount of light returned from the laser beam 7 irradiated to each information layer and reflected by each information layer. It can be obtained by dividing by 100 (effective reflectance R (%) x reproduction power Pr (mW)/100).

The d-MLSE value after 1 million times of playback is 15.0% or less ◎ (good), more than 15.0% and 16.0% or less ○ (practical level), more than 16.0% × (not practical).

The reason why the groove reproduction was evaluated instead of the land is that the groove has a lower reflectance than the land and requires a larger reproduction power, resulting in poor reproduction durability.

FIG. 10 and Table 2 show the results for the A-side information recording medium 101 .

FIG. 10 shows the results of evaluating the effective reflectance of the groove of the L0 layer 10 when the film thickness _dA of the phase control film 14 is changed when the film thickness of the recording film 12 is 42 nm. It was confirmed that the effective reflectance of the L0 layer 10 is increased by forming the phase control film 14 with a thickness of 5-100 nm.

Table 2 is a table showing the results of the reproduction durability of the L0 layer 10.

表２に示すように、ディスクＮｏ．１－１～１－１７において、比較例１－１～１－３と比較して、再生耐久性が良好な結果が得られた。具体的には、（２×ｄ_Ａ×ｎ_Ａ）／λが０．５以上１．０以下であり、Ｌ０層１０の上に位相調整膜１４を設け、位相調整膜１４の屈折率が平均屈折率ｎ_Ａおよび中間分離層２の屈折率ｎ_Ｒより小さく、且つ０＜（２×ｄ_L×ｎ_L）／λ＜０．７５の場合に、反射率が上昇して再生パワーが下がり、再生耐久性が向上することを確認できた。さらに、０．２０＜（２×ｄ_L×ｎ_L）／λ＜０．６０の場合には、さらなる効果があることも確認できた。なお、Ｂ面情報記録媒体１０２においても、同様の結果が得られた。
（実施例２）
本実施例では、実施の形態２の情報記録媒体２００の一例を説明する。以下、本実施例の情報記録媒体２００の製造方法である。

As shown in Table 2, disk No. In 1-1 to 1-17, better results were obtained in terms of reproduction durability than in Comparative Examples 1-1 to 1-3. Specifically, (2×d _A ×n _A )/λ is 0.5 or more and 1.0 or less, the phase adjustment film 14 is provided on the L0 layer 10, and the refractive index of the phase adjustment film 14 is average When the refractive index n _A is smaller than the refractive index n _R of the intermediate separation layer 2 and 0<(2×d _L ×n _L )/λ<0.75, the reflectance increases and the reproduction power decreases, It was confirmed that the playback durability was improved. Furthermore, it was also confirmed that there is a further effect when 0.20<(2×d _L ×n _L )/λ<0.60. Similar results were obtained for the B-side information recording medium 102 as well.
(Example 2)
In this example, an example of the information recording medium 200 of Embodiment 2 will be described. A method for manufacturing the information recording medium 200 of this embodiment will be described below.

First, the configuration of the A-side information recording medium 201 will be described. As the substrate 1, a polycarbonate substrate (diameter 120 mm, thickness 0.5 mm) having spiral guide grooves (depth 30 nm, track pitch (land-groove distance) 0.18 μm) was prepared. An L0 layer 10 was formed on the substrate 1 . (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) as the first dielectric film 11 (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) of 12 nm and a recording film 12, using a target consisting essentially of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O, W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O of 42 nm, and a second dielectric film 13; Using a _target consisting essentially of ( _ZrO2 ) ₂₅ ( _SiO2 ) _{25 ( In2O3} ) ₅₀ (mol%), ( _ZrO2 ) ₂₅ ( _SiO2 ) ₂₅ ( _In2O3 ) ₅₀ (mol%) %) was sequentially deposited by sputtering to a thickness of 10 nm.

The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power supply (6 kW). The second dielectric film 13 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).

Subsequently, an intermediate isolation layer 2 was formed on the L0 layer 10 with a spiral guide groove (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ as the recording film 22 in the embodiment of the present invention. Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3 kW).

An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . 8 to 13 nm of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) as the first dielectric film 41, and substantially W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O with a thickness of 28 to 57 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ as the second dielectric film 43 (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) films of 13 to 21 nm were successively formed by sputtering.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

Subsequently, a phase control film 14 was formed on the L3 layer 40 . As the phase control film 14, a SiO ₂ film having a thickness of 0 to 100 nm was formed by a sputtering method using a target made of SiO ₂ . The phase control film 14 was formed using a SiO ₂ target in an atmosphere of Ar+O ₂ (flow rate: 12+1.2 sccm) and an RF power source (1 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured by ultraviolet rays to form the cover layer 5 with a thickness of about 53.5 μm, thereby fabricating the A-side information recording medium 201 . .

Next, the configuration of the B-side information recording medium 202 will be described. As a substrate 1, a polycarbonate substrate (thickness: 0.5 mm) having spiral guide grooves (depth: 30 nm, track pitch (land-groove distance): 0.180 μm) was prepared. The direction of rotation of the spiral of the guide groove was opposite to that of the substrate 1 of the A-side information recording medium 201 described above. An L0 layer 10 was formed on the substrate 1 . As the first dielectric film 11, the first dielectric film 11 is substantially (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) ₁ ( _ZnO ) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) to 12 nm, using a target consisting essentially of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O as the recording film 12, W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O to 42 nm, Using a target substantially composed of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol % ₎ as _the second _dielectric film _{13 2} O ₃ ) ₅₀ (mol %) was deposited to a thickness of 10 nm by sputtering.

The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power source (6 kW). The second dielectric film 13 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).
Subsequently, an intermediate isolation layer 2 was formed on the L0 layer 10 with a spiral guide groove (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ as the recording film 22 in the embodiment of the present invention. Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3 kW).

An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . 8 to 13 nm of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) as the first dielectric film 41, and substantially W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O with a thickness of 28 to 57 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ as the second dielectric film 43 (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) films of 13 to 21 nm were successively formed by sputtering.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

Subsequently, a phase control film 14 was formed on the L3 layer 40 . As the phase control film 14, a SiO ₂ film having a thickness of 0 to 100 nm was formed by a sputtering method using a target made of SiO ₂ . The phase control film 14 was formed using a SiO ₂ target in an atmosphere of Ar+O ₂ (flow rate: 12+1.2 sccm) and an RF power source (1 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured by ultraviolet rays to form the cover layer 5 with a thickness of about 53.5 μm, thereby producing the B-side information recording medium 202 . .

Finally, the surface of the substrate 1 of the A-side information recording medium 201 opposite to the surface on which the guide grooves are provided is uniformly coated with an ultraviolet curing resin so that the guide grooves of the substrate 1 of the B-side information recording medium 202 are formed. A surface opposite to the provided surface was bonded, and the resin was cured by ultraviolet rays to form a bonding layer 6 (thickness: about 35 μm).

Thus, the information recording medium 200 of this example was produced.

Table 3 shows the refractive indices of the first dielectric film 41, the recording film 42, the second dielectric film 43, the phase adjustment film 14, the cover layer 5, and the intermediate separation layer 4, which constitute the L3 layer 40. .

本実施例の情報記録媒体２００の一例として、Ａ面情報記録媒体２０１およびＢ面情報記録媒体２０２の第１誘電体膜４１，記録膜４２、第２誘電体膜４３および位相調整膜１４の膜厚をそれぞれ、
（第１誘電体膜４１の膜厚、記録膜４２の膜厚、第２誘電体膜４３の膜厚、位相調整膜１４の膜厚）＝（８ｎｍ、２８ｎｍ、１３ｎｍ、１０ｎｍ）、（８ｎｍ、２８ｎｍ、１３ｎｍ、２０ｎｍ）、（８ｎｍ、２８ｎｍ、１３ｎｍ、４０ｎｍ）、（８ｎｍ、２８ｎｍ、１３ｎｍ、６０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、５ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、１０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、１５ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、２０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、３０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、４０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、６０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、８０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、１００ｎｍ）、（１３ｎｍ、５７ｎｍ、２１ｎｍ、１０ｎｍ）、（１３ｎｍ、５７ｎｍ、２１ｎｍ、２０ｎｍ）、（１３ｎｍ、５７ｎｍ、２１ｎｍ、４０ｎｍ）、（１３ｎｍ、５７ｎｍ、２１ｎｍ、６０ｎｍ）とした情報記録媒体２００を作製した。これらのディスクＮｏ．を２－１～２－１７とする。比較例として、Ａ面情報記録媒体２０１およびＢ面情報記録媒体２０２の第１誘電体膜４１，記録膜４２、第２誘電体膜４３および位相調整膜１４の膜厚をそれぞれ、
（第１誘電体膜４１の膜厚、記録膜４２の膜厚、第２誘電体膜４３の膜厚、位相調整膜１４の膜厚）＝（８ｎｍ、２４ｎｍ、１３ｎｍ、１０ｎｍ）、（１３ｎｍ、６２ｎｍ、２１ｎｍ、１０ｎｍ）、（１３ｎｍ、４４ｎｍ、２１ｎｍ、０ｎｍ）としたディスクＮｏ．比較例２－１～２－３を作製した。

As an example of the information recording medium 200 of this embodiment, the first dielectric film 41, the recording film 42, the second dielectric film 43, and the phase adjustment film 14 of the A-side information recording medium 201 and the B-side information recording medium 202 are shown. thickness, respectively,
(film thickness of first dielectric film 41, film thickness of recording film 42, film thickness of second dielectric film 43, film thickness of phase control film 14)=(8 nm, 28 nm, 13 nm, 10 nm), (8 nm, 28 nm, 13 nm, 20 nm), (8 nm, 28 nm, 13 nm, 40 nm), (8 nm, 28 nm, 13 nm, 60 nm), (13 nm, 44 nm, 21 nm, 5 nm), (13 nm, 44 nm, 21 nm, 10 nm), (13 nm, 44 nm, 21 nm, 15 nm), (13 nm, 44 nm, 21 nm, 20 nm), (13 nm, 44 nm, 21 nm, 30 nm), (13 nm, 44 nm, 21 nm, 40 nm), (13 nm, 44 nm, 21 nm, 60 nm), (13 nm, 44 nm, 21 nm, 80 nm), (13 nm, 44 nm, 21 nm, 100 nm), (13 nm, 57 nm, 21 nm, 10 nm), (13 nm, 57 nm, 21 nm, 20 nm), (13 nm, 57 nm, 21 nm, 40 nm), (13 nm, 57 nm, 21 nm, and 60 nm) were produced. These disk nos. are 2-1 to 2-17. As a comparative example, the film thicknesses of the first dielectric film 41, the recording film 42, the second dielectric film 43, and the phase adjustment film 14 of the A-side information recording medium 201 and the B-side information recording medium 202 are respectively
(film thickness of first dielectric film 41, film thickness of recording film 42, film thickness of second dielectric film 43, film thickness of phase control film 14)=(8 nm, 24 nm, 13 nm, 10 nm), (13 nm, 62 nm, 21 nm, 10 nm), (13 nm, 44 nm, 21 nm, 0 nm). Comparative Examples 2-1 to 2-3 were produced.

Disc No. Reflectance and reproduction durability were evaluated in 2-1 to 2-17 and Comparative Examples 2-1 to 2-3.
Disc No. In 2-1 to 2-17, the reflectance and reproduction durability were evaluated. The reflectance was evaluated using a Pulstec evaluation machine (ODU-1000). The reproduction durability was evaluated using an evaluation device manufactured in-house.

The wavelength of the laser beam 7 of the evaluation machine manufactured by Pulstec was 405 nm, the numerical aperture NA of the objective lens was 0.91, the linear velocity was 8.23 m/s, and the reflectance was measured with all information layers unrecorded. evaluated.

The wavelength of the laser beam 7 of the self-manufactured evaluation device was 405 nm, the numerical aperture NA of the objective lens was 0.91, and information was recorded on the grooves and lands. The recording linear velocity was 15.63 m/s and the reproducing linear velocity was 15.63 m/s. Information was recorded by multi-level recording in which a multi-level code was recorded. In multilevel recording, the recording depth is controlled to form a mark having a size corresponding to the value (level) of the multilevel code. Specifically, a quinary code was recorded, and the density was set to 125 GB per information layer. During reproduction, the difference in the size of the recording marks appears as the difference in the intensity of the reflected light (gradation). When a quinary code is recorded, gradations of reflected light corresponding to the quinary values are obtained. Signal quality was evaluated as d-MLSE (Distribution Derived-Maximum Likelihood Sequence Error Estimation).

The evaluation of the reproduction durability of the L3 layer 40 was carried out by multi-value recording random signals in adjacent grooves and lands, and recording the random signals in the groove located in the center of the recorded track and the lands on both sides at a linear velocity of 15.63 m/m. s, and subjected to waveform transparency processing (crosstalk cancellation processing) to minimize crosstalk from adjacent land tracks, and the absolute value of d-MLSE at the 1,000,000th repetition was used to determine the quality.

The reproduction power was set so that the reproduction light amount satisfied 0.117. For example, when the effective reflectance was 2.6%, the reproduction power was set to 4.5 mW.

The d-MLSE value after 1 million times of playback is 15.0% or less ◎ (good), 15.0% or more and 16.0% or less 〇 (practical level), 16.0% or more × (not practical).

The reason why the groove reproduction was evaluated instead of the land is that the groove has a lower reflectance than the land and requires a larger reproduction power, resulting in poor reproduction durability.

Table 4 shows the results of the reproduction durability of the L3 layer 40 in the A-side information recording medium 201 .

表４に示すように、ディスクＮｏ．２－１～２－１７において、比較例２－１～２－３と比較して、再生耐久性が良好な結果が得られた。具体的には、（２×ｄ_Ｂ×ｎ_Ｂ）／λが０．５以上１．０以下であり、Ｌ３層４０の上に位相調整膜１４を設け、位相調整膜１４の屈折率が平均屈折率ｎ_Ｂおよびカバー層５の屈折率ｎ_Ｃより小さく、且つ０＜（２×ｄ_L×ｎ_L）／λ＜０．７５の場合に、反射率が上昇して再生パワーが下がり、再生耐久性が向上することを確認できた。さらに、０．２０＜（２×ｄ_L×ｎ_L）／λ＜０．６０の場合には、さらなる効果があることも確認できた。なお、Ｂ面情報記録媒体２０２においても、同様の結果が得られた。
（実施例３）
本実施例では、実施の形態１の情報記録媒体１００の別の一例を説明する。以下、本実施例の情報記録媒体１００の製造方法である。

As shown in Table 4, disk No. In 2-1 to 2-17, better results in terms of reproduction durability were obtained than in Comparative Examples 2-1 to 2-3. Specifically, (2×d _B ×n _B )/λ is 0.5 or more and 1.0 or less, the phase adjustment film 14 is provided on the L3 layer 40, and the refractive index of the phase adjustment film 14 is the average When the refractive index n _B is smaller than the refractive index n _C of the cover layer 5 and 0<(2×d _L ×n _L )/λ<0.75, the reflectance increases, the reproduction power decreases, and the reproduction It was confirmed that the durability was improved. Furthermore, it was also confirmed that there is a further effect when 0.20<(2×d _L ×n _L )/λ<0.60. Similar results were obtained for the B-side information recording medium 202 as well.
(Example 3)
In this example, another example of the information recording medium 100 of Embodiment 1 will be described. A method for manufacturing the information recording medium 100 of this embodiment will be described below.

First, the configuration of the A-side information recording medium 101 will be described. As the substrate 1, a polycarbonate substrate (diameter 120 mm, thickness 0.5 mm) having spiral guide grooves (depth 30 nm, track pitch (land-groove distance) 0.18 μm) was prepared. An L0 layer 10 was formed on the substrate 1 . (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) as the first dielectric film 11 (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) of 12 nm and a recording film 12, using a target consisting essentially of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O, W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O of 42 nm, and a second dielectric film 13; Using a _target consisting essentially of ( _ZrO2 ) ₂₅ ( _SiO2 ) _{25 ( In2O3} ) ₅₀ (mol%), ( _ZrO2 ) ₂₅ ( _SiO2 ) ₂₅ ( _In2O3 ) ₅₀ (mol%) %) was sequentially deposited by sputtering to a thickness of 10 nm.

The total thickness d _A of the L0 layer 10 is 64 nm and the average refractive index n _A is 2.31. When the wavelength of the laser light 7 is λ=405 nm, (2×d _A ×n _A )/λ is 0.73.

The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power source (6 kW). The second dielectric film 13 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).

Subsequently, a phase control film 14 was formed on the L0 layer 10 . As the phase control film 14, a MgF ₂ film having a thickness of 5 to 100 nm was formed by a sputtering method using a target made of MgF ₂ . The phase control film 14 was formed using a MgF ₂ target in an Ar atmosphere (flow rate: 12 sccm) using an RF power source (0.5 kW). An intermediate isolation layer 2 having grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm) was formed. First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ as the recording film 22 in the embodiment of the present invention. Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 13 nm as the first dielectric film 41 and W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 was used to obtain W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O of 44 nm, and the second dielectric film 43 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 21 nm was sequentially formed by a sputtering method using a target composed of the following.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured by ultraviolet rays to form a cover layer 5 having a thickness of about 53.5 μm. .

Next, the configuration of the B-side information recording medium 102 will be described. As a substrate 1, a polycarbonate substrate (thickness: 0.5 mm) having spiral guide grooves (depth: 30 nm, track pitch (land-groove distance): 0.180 μm) was prepared. The direction of rotation of the spiral of the guide groove was opposite to that of the substrate 1 of the A-side information recording medium 101 described above. An L0 layer 10 was formed on the substrate 1 . As the first dielectric film 11, the first dielectric film 11 is substantially (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) ₁ ( _ZnO ) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) to 12 nm, using a target consisting essentially of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O as the recording film 12, W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ —O to 42 nm, Using a target substantially composed of (ZrO ₂ ) _{25 (} SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol % ₎ as _the second dielectric film _{13 2} O ₃ ) ₅₀ (mol %) was deposited to a thickness of 10 nm by sputtering.

The total thickness d _A of the L0 layer 10 is 64 nm and the average refractive index n _A is 2.31. When the wavelength of the laser light 7 is λ=405 nm, (2×d _A ×n _A )/λ is 0.73.

The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power supply (6 kW). The second dielectric film 13 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).

Subsequently, a phase control film 14 was formed on the L0 layer 10 . As the phase control film 14, a MgF ₂ film having a thickness of 5 to 100 nm was formed by a sputtering method using a target made of MgF ₂ . The phase control film 14 was formed using an MgF ₂ target in an Ar atmosphere (flow rate: 12 sccm) and an RF power source (0.5 kW).

Subsequently, an intermediate separation layer 2 was formed on the phase adjustment film 14 with spiral guide grooves (depth 33 nm, track pitch (land-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ as the recording film 22 in the embodiment of the present invention. Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 13 nm as the first dielectric film 41 and W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 was used to obtain W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O of 44 nm, and the second dielectric film 43 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 21 nm was sequentially formed by a sputtering method using a target composed of the following.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power source (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured with ultraviolet rays to form the cover layer 5 with a thickness of about 53.5 μm, thereby producing the B-side information recording medium 102 . .

Finally, the surface of the substrate 1 of the A-side information recording medium 101 opposite to the surface on which the guide grooves are provided is uniformly coated with an ultraviolet curing resin so that the guide grooves of the substrate 1 of the B-side information recording medium 102 are formed. A surface opposite to the provided surface was bonded, and the resin was cured by ultraviolet rays to form a bonding layer 6 (thickness: about 35 μm).

Thus, the information recording medium 100 of this example was produced.

Table 5 shows the refractive indices of the first dielectric film 11, the recording film 12, the second dielectric film 13, the phase adjustment film 14, the intermediate separation layer 2, and the substrate 1, which constitute the first information layer 10. there is

本実施例の情報記録媒体１００の一例として、Ａ面情報記録媒体１０１およびＢ面情報記録媒体１０２の位相調整膜１４の膜厚を５ｎｍ、１０ｎｍ、１５ｎｍ、２０ｎｍ、３０ｎｍ、４０ｎｍ、６０ｎｍ、８０ｎｍ、１００ｎｍとした情報記録媒体１００を作製した。これらのディスクＮｏ．を２－１～２－９とする。

As an example of the information recording medium 100 of the present embodiment, the film thickness of the phase adjustment film 14 of the A-side information recording medium 101 and the B-side information recording medium 102 is 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 60 nm, 80 nm, An information recording medium 100 with a thickness of 100 nm was produced. These disk nos. are 2-1 to 2-9.

Disc No. In 2-1 to 2-9, the reflectance and reproduction durability were evaluated. The reflectance was evaluated using a Pulstec evaluation machine (ODU-1000). The reproduction durability was evaluated using an evaluation device manufactured in-house.

The wavelength of the laser beam 7 of the evaluation machine manufactured by Pulstec was 405 nm, the numerical aperture NA of the objective lens was 0.91, the linear velocity was 8.23 m/s, and the reflectance was measured with all information layers unrecorded. evaluated.

The wavelength of the laser beam 7 of the self-manufactured evaluation device was 405 nm, the numerical aperture NA of the objective lens was 0.91, and information was recorded on the grooves and lands. The recording linear velocity was 15.63 m/s and the reproducing linear velocity was 15.63 m/s. Information was recorded by multi-level recording in which a multi-level code was recorded. In multilevel recording, the recording depth is controlled to form a mark having a size corresponding to the value (level) of the multilevel code. Specifically, a quinary code was recorded, and the density was set to 125 GB per information layer. During reproduction, the difference in the size of the recording marks appears as the difference in the intensity of the reflected light (gradation). When a quinary code is recorded, gradations of reflected light corresponding to the quinary values are obtained. Signal quality was evaluated as d-MLSE (Distribution Derived-Maximum Likelihood Sequence Error Estimation).

Evaluation of the reproduction durability of the L0 layer 10 was carried out by multi-value recording random signals in adjacent grooves and lands, and recording the random signals in the groove located in the center of the recorded track and the lands on both sides at a linear velocity of 15.63 m/m. s, and subjected to waveform transparency processing (crosstalk cancellation processing) to minimize crosstalk from adjacent land tracks, and the absolute value of d-MLSE at the 1,000,000th repetition was used to determine the quality.

The reproduction power was set so that the reproduction light amount satisfied 0.117. For example, when the effective reflectance was 2.2%, the reproduction power was set to 5.3 mW.

The d-MLSE value after 1 million times of playback is 15.0% or less ◎ (good), 15.0% or more and 16.0% or less 〇 (practical level), 16.0% or more × (not practical).

The reason why the groove reproduction was evaluated instead of the land is that the groove has a lower reflectance than the land and requires a larger reproduction power, resulting in poor reproduction durability.

Table 6 shows the results of the reproduction durability of the L0 layer 10 in the A-side information recording medium 101 .

ディスクＮｏ．２－１～２－９において、いずれも再生耐久性が良好な結果が得られた。具体的には、位相調整膜１４がＭｇＦ_２である場合でも、位相調整膜１４を設けるとともに、（２×ｄ_Ａ×ｎ_Ａ）／λが０．５以上１．０以下であり、位相調整膜１４の屈折率が平均屈折率ｎ_Ａおよび中間分離層２の屈折率ｎ_Ｒより小さく、且つ０＜（２×ｄ_L×ｎ_L）／λ＜０．７５の場合に、反射率が上昇して再生パワーが下がり、再生耐久性が向上することを確認できた。さらに、０．２０＜（２×ｄ_L×ｎ_L）／λ＜０．６０の場合には、さらなる効果があることも確認できた。Ｂ面情報記録媒体１０２においても、同様の結果が得られた。
（実施例４）
本実施例では、実施の形態２の情報記録媒体３００の一例を説明する。以下、本実施例の情報記録媒体３００の製造方法である。

Disc No. In 2-1 to 2-9, good results were obtained in terms of reproduction durability. Specifically, even when the phase adjustment film 14 is MgF ₂ , the phase adjustment film 14 is provided and (2×d _A ×n _A )/λ is 0.5 or more and 1.0 or less, and the phase adjustment film 14 is If the refractive index of the film 14 is smaller than the average refractive index n _A and the refractive index n _R of the intermediate separating layer 2, and 0<(2×d _L ×n _L )/λ<0.75, the reflectance increases. As a result, it was confirmed that the playback power decreased and the playback durability improved. Furthermore, it was also confirmed that there is a further effect when 0.20<(2×d _L ×n _L )/λ<0.60. Similar results were obtained for the B-side information recording medium 102 as well.
(Example 4)
In this example, an example of the information recording medium 300 of Embodiment 2 will be described. A method for manufacturing the information recording medium 300 of this embodiment will be described below.

First, the configuration of the A-side information recording medium 301 will be described. As the substrate 1, a polycarbonate substrate (diameter 120 mm, thickness 0.5 mm) having spiral guide grooves (depth 30 nm, track pitch (land-groove distance) 0.18 μm) was prepared. An L0 layer 203 was formed on the substrate 1 . (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) as the first dielectric film 11 (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol%) was added to 5 m, the third The dielectric film 204 was 7 nm thick, and the recording film 12 was formed by using a target substantially composed of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ -O, and W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ -O. 42 nm, using a target consisting essentially of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) as the second dielectric film 13 , (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ A film of (In ₂ O ₃ ) ₅₀ (mol %) of 10 nm was sequentially formed by a sputtering method.

The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The deposition of the third dielectric film 204 was performed in an Ar atmosphere (flow rate: 20 sccm) using a pulse DC power source (3 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power source (6 kW). The deposition of the second dielectric film 204 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).

Subsequently, a phase control film 14 was formed on the L0 layer 203 . As the phase control film 14, a _MgF2 film having a thickness of 10 nm was formed by a sputtering method using a _MgF2 target. The phase control film 14 was formed using a MgF ₂ target in an Ar atmosphere (flow rate: 12 sccm) using an RF power source (0.5 kW). An intermediate isolation layer 2 having grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm) was formed. First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ in the embodiment of the present invention as the recording film 22 Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 13 nm as the first dielectric film 41 and W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 was used to obtain W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O of 44 nm, and the second dielectric film 43 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 21 nm was sequentially formed by a sputtering method using a target composed of the following.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured by ultraviolet rays to form a cover layer 5 having a thickness of about 53.5 μm. .

Next, the configuration of the B-side information recording medium 302 will be described. As the substrate 1, a polycarbonate substrate (diameter 120 mm, thickness 0.5 mm) having spiral guide grooves (depth 30 nm, track pitch (land-groove distance) 0.18 μm) was prepared. An L0 layer 203 was formed on the substrate 1 . (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol %) as the first dielectric film 11 (ZnO) _48.4 (SnO ₂ ) _24.7 (ZrO ₂ ) _23.7 (MgO) _2.1 (Ga ₂ O ₃ ) _1.1 (mol%) was added to 5 m, the third The dielectric film 204 was 7 nm thick, and the recording film 12 was formed by using a target substantially composed of W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ -O, and W ₂₁ Cu ₁₇ Ta ₁₈ Zn ₄ Mn ₂₀ Ti ₂₀ -O. 42 nm, using a target consisting essentially of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) as the second dielectric film 13 , (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ A film of (In ₂ O ₃ ) ₅₀ (mol %) of 10 nm was sequentially formed by a sputtering method.

The first dielectric film 11 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (3.5 kW). The third dielectric film 15 was formed in an Ar atmosphere (flow rate: 20 sccm) using a pulse DC power source (3 kW). The recording film 12 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+36 sccm) using a pulse DC power supply (6 kW). The deposition of the second dielectric film 204 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (2.5 kW).

Subsequently, a phase control film 14 was formed on the L0 layer 203 . As the phase control film 14, a _MgF2 film having a thickness of 10 nm was formed by a sputtering method using a _MgF2 target. The phase adjustment film 14 was formed using an MgF ₂ target in an Ar atmosphere (flow rate: 12 sccm) and an RF power source (0.5 kW). An intermediate separation layer 2 having a depth of 33 nm and a track pitch (land-groove distance) of 0.180 μm was formed. First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin was cured with ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 2 was formed. The thickness of the intermediate separating layer 2 is approximately 15.5 μm.

Next, an L1 layer 20 was formed on the intermediate separation layer 2 . (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 16 nm as the first dielectric film 21 of the L1 layer 20, and substantially W ₃₂ Cu ₁₇ as the recording film 22 in the embodiment of the present invention. Using a target of Ta ₁₆ Zn ₁₇ Mn ₁₈ —O, W ₃₂ Cu ₁₇ Ta ₁₆ Zn ₁₇ Mn ₁₈ —O of 42 nm and substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ as the second dielectric film 23 Using a target of (In ₂ O ₃ ) ₅₀ (mol %), (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 14 nm was deposited sequentially by sputtering.

The first dielectric film 21 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The formation of the recording film 22 was performed using a pulse DC power supply (5.5 kW) in an atmosphere of mixed gas of Ar+O ₂ (flow rate: 12+38 sccm). The deposition of the second dielectric film 23 was performed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

Subsequently, an intermediate isolation layer 3 was formed on the L1 layer 20 with spiral guide grooves (depth 33 nm, track pitch (land-to-groove distance) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 3 was formed. The thickness of the intermediate separating layer 3 is approximately 19.5 μm.

An L2 layer 30 was formed on the intermediate separation layer 3 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 14 nm as the first dielectric film 31 and W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ -O as the recording film 32 was used to obtain W ₃₅ Cu ₁₄ Ta ₂₅ Zn ₁₁ Mn ₁₅ —O of 44 nm, and the second dielectric film 33 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 16 nm was sequentially formed by a sputtering method using a target composed of.

The first dielectric film 31 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power source (5 kW). The recording film 32 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 33 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power source (3 kW).

An intermediate isolation layer 4 was formed on the L2 layer 30 with a spiral guide groove (33 nm deep, track pitch (distance between land and groove) 0.180 μm). First, after spin-coating an ultraviolet curable resin that forms the thickness of the matrix, the resin is cured by ultraviolet light. Next, an ultraviolet curable resin for transferring the guide grooves is spin-coated, and a polycarbonate stamper substrate having guide grooves formed thereon is adhered thereon. After curing the resin with ultraviolet rays, the stamper substrate is peeled off. An intermediate separation layer 4 was formed. The thickness of the intermediate separating layer 4 is approximately 11.5 μm.

An L3 layer 40 was formed on the intermediate separation layer 4 . Target consisting of (ZrO ₂ ) ₂₅ (ZnO) ₅₀ (SnO ₂ ) ₂₅ (mol %) of 13 nm as the first dielectric film 41 and W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ -O as the recording film 42 was used to obtain W ₃₇ Cu ₁₂ Ta ₂₇ Zn ₁₁ Mn ₁₃ —O of 44 nm, and the second dielectric film 43 was substantially (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %). A film of (ZrO ₂ ) ₂₅ (SiO ₂ ) ₂₅ (In ₂ O ₃ ) ₅₀ (mol %) of 21 nm was sequentially formed by a sputtering method using a target composed of the following.

The first dielectric film 41 was formed in an Ar atmosphere (flow rate: 12 sccm) using a pulse DC power supply (4.8 kW). The recording film 42 was formed in a mixed gas atmosphere of Ar+O ₂ (flow rate: 12+48 sccm) using a pulse DC power supply (6 kW). The second dielectric film 43 was formed in an Ar atmosphere (flow rate: 12 sccm) using a DC power supply (3.5 kW).

After that, an ultraviolet curable resin was applied onto the second dielectric film 43 and spin-coated, and then the resin was cured with ultraviolet rays to form the cover layer 5 with a thickness of about 53.5 μm, thereby producing the B-side information recording medium 102 . .

Finally, the surface of the substrate 1 of the A-side information recording medium 301 opposite to the surface on which the guide grooves are provided is uniformly coated with an ultraviolet curing resin so that the guide grooves of the substrate 1 of the B-side information recording medium 302 are formed. A surface opposite to the provided surface was bonded, and the resin was cured by ultraviolet rays to form a bonding layer 6 (thickness: about 35 μm).

Thus, the information recording medium 300 of this example was produced.

As an example of the information recording medium 300 of the present embodiment, TiO ₂ , Nb ₂ O ₅ , (TiO ₂ ) ₈₀ (Bi _{2 O3} ) ₂₀ (mol%),
An information recording medium 300 was produced. These disk nos. are 4-1 to 4-3.

Disc No. Reflectance and reproduction durability were evaluated in 4-1 to 4-3 and Comparative Example 1-3. The reflectance was evaluated using a Pulstec evaluation machine (ODU-1000). The reproduction durability was evaluated using an evaluation device manufactured in-house.

The wavelength of the laser beam 7 of the evaluation machine manufactured by Pulstec was 405 nm, the numerical aperture NA of the objective lens was 0.91, the linear velocity was 8.23 m/s, and the reflectance was measured with all information layers unrecorded. evaluated.

The wavelength of the laser beam 7 of the self-manufactured evaluation device was 405 nm, the numerical aperture NA of the objective lens was 0.91, and information was recorded on the grooves and lands. The recording linear velocity was 15.63 m/s and the reproducing linear velocity was 15.63 m/s. Information was recorded by multi-level recording in which a multi-level code was recorded. In multilevel recording, the recording depth is controlled to form a mark having a size corresponding to the value (level) of the multilevel code. Specifically, a quinary code was recorded, and the density was set to 125 GB per information layer. During reproduction, the difference in the size of the recording marks appears as the difference in the intensity of the reflected light (gradation). When a quinary code is recorded, gradations of reflected light corresponding to the quinary values are obtained. Signal quality was evaluated as d-MLSE (Distribution Derived-Maximum Likelihood Sequence Error Estimation).

Evaluation of the reproduction durability of the L0 layer 203 was carried out by multi-value recording random signals in adjacent grooves and lands, and recording the random signals in the groove located in the center of the recorded track and the lands on both sides at a linear velocity of 15.63 m/m. s, and subjected to waveform transparency processing (crosstalk cancellation processing) to minimize crosstalk from adjacent land tracks, and the absolute value of d-MLSE at the 1,000,000th repetition was used to determine the quality.

The reproduction power was set so that the reproduction light amount satisfied 0.117. For example, when the effective reflectance was 2.2%, the reproduction power was set to 5.3 mW.

The d-MLSE value after 1 million times of playback is 15.0% or less ◎ (good), greater than 15.0 and 16.0% or less ○ (practical level), greater than 16.0% × ( impractical).

Table 7 shows the results for the A-side information recording medium 301 .

表７に示すように、ディスクＮｏ．４－１～４－３において、いずれも比較例１－３に対して反射率が上がり再生耐久性が良好な結果が得られ、本発明における第３誘電体膜２０４を設けることで、反射率が上昇して再生パワーが下がり、再生耐久性が向上することを確認できた。Ｂ面情報記録媒体３０２においても、同様の結果が得られた。

As shown in Table 7, disk No. In all of 4-1 to 4-3, the reflectance was higher than that of Comparative Example 1-3, and good results in reproduction durability were obtained. increased, the playback power decreased, and the playback durability improved. Similar results were obtained for the B-side information recording medium 302 as well.

Since the information recording medium of the present disclosure has an information layer with better reproduction durability, it is suitable for recording information at a high recording density and is useful for optical discs for recording large-capacity content. Specifically, it is useful for large-capacity, next-generation optical discs (for example, recording capacity of 1 TB) using a multilevel recording method, which has three or four information layers on both sides according to archival disc standards. .

1 substrates 2, 3, 4 intermediate separation layer 5 cover layer 6 bonding layer 7 laser beams 10, 20, 30, 40, 203 information layers 11, 21, 31, 41 first dielectric films 12, 22, 32, 42 Recording films 13, 23, 33, 43 Second dielectric film 14 Phase control films 100, 200, 300 Information recording media 101, 201, 301 A-side information recording media 102, 202, 302 B-side information recording media 304 Third dielectric Body membrane

Claims (6)

At least four information layers and a cover layer are sequentially laminated on a substrate via an intermediate separation layer, and information is recorded in the recording layer by irradiation with a laser beam having a wavelength of λ from the cover layer side, or the recording layer. An information recording medium for reproducing information from
A phase adjustment film is formed on the laser beam irradiation side in contact with a first information layer, which is one of the information layers other than the information layer farthest from the substrate, and the phase adjustment film is further provided with the phase adjustment film. A first intermediate separation layer is formed on the laser beam irradiation side in contact with the laser beam,
the first information layer includes a first dielectric film, a recording film, and a second dielectric film in this order from near to far when viewed from the substrate;
The total film thickness and average refractive index of the three thin films of the first dielectric film, the recording film, and the second dielectric film are d _A and n _A respectively, and the film thickness and refractive index of the phase control film are respectively 0.5<=(2* _dA * _nA )/[lambda]<=1.0, where _dL , _nL , the refractive index of the first intermediate separation layer is _nR , and (2* d _L ×n _L )/λ satisfies 0<(2×d _L ×n _L )/λ<0.75, and n _L <n _A and n _L <n _R. recoding media. At least four information layers and a cover layer are sequentially laminated on a substrate via an intermediate separation layer, and information is recorded in the recording layer by irradiation with a laser beam having a wavelength of λ from the cover layer side, or the recording layer. An information recording medium for reproducing information from
A phase adjustment film is formed on the laser beam irradiation side in contact with the first information layer, which is the farthest information layer as viewed from the substrate, and the cover is formed on the laser beam irradiation side in contact with the phase adjustment film. layers are formed
the first information layer includes a first dielectric film, a recording film, and a second dielectric film in this order from near to far when viewed from the substrate;
The overall film thickness and average refractive index of the three thin films of the first dielectric film, the recording film, and the second dielectric film are respectively d _B and n _B , and the film thickness and refractive index of the phase control film are respectively d _L , n _L , 0.5<=(2×d _B ×n _B )/λ<=1.0 when the refractive index of the cover layer is n _C , and (2×d _L ×n _L )/λ satisfies 0<(2×d _L ×n _L )/λ<0.75, and n _L < n _B and n _L < n _C. 3. The information recording medium according to claim 1, wherein 0.20<(2* _dL * _nL )/[lambda]<0.60. 3. The information recording medium according to claim 1, wherein the material of said phase control film is _SiO2 or _MgF2 . 3. The information recording medium according to claim 1, wherein in said at least one information layer, a third dielectric film is formed between said first dielectric film and said recording film. 6. The information recording medium according to claim ₅ , wherein said third dielectric _film contains at least one oxide selected from _TiO2 , _Nb2O5 and _Bi2O3 .

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