WO2010095466A1 - 情報記録媒体 - Google Patents
情報記録媒体 Download PDFInfo
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- WO2010095466A1 WO2010095466A1 PCT/JP2010/001147 JP2010001147W WO2010095466A1 WO 2010095466 A1 WO2010095466 A1 WO 2010095466A1 JP 2010001147 W JP2010001147 W JP 2010001147W WO 2010095466 A1 WO2010095466 A1 WO 2010095466A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2403—Layers; Shape, structure or physical properties thereof
- G11B7/24035—Recording layers
- G11B7/24038—Multiple laminated recording layers
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
- G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
- G11B7/2578—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
- G11B2007/24302—Metals or metalloids
- G11B2007/24312—Metals or metalloids group 14 elements (e.g. Si, Ge, Sn)
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
- G11B2007/24302—Metals or metalloids
- G11B2007/24314—Metals or metalloids group 15 elements (e.g. Sb, Bi)
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/242—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers
- G11B7/243—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of recording layers comprising inorganic materials only, e.g. ablative layers
- G11B2007/24302—Metals or metalloids
- G11B2007/24316—Metals or metalloids group 16 elements (i.e. chalcogenides, Se, Te)
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
- G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
- G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
- G11B2007/25715—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing oxygen
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
- G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
- G11B7/258—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers
- G11B7/259—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers based on silver
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/26—Apparatus or processes specially adapted for the manufacture of record carriers
- G11B7/266—Sputtering or spin-coating layers
Definitions
- the present invention relates to an information recording medium capable of optically recording, erasing, rewriting and / or reproducing information.
- the second dielectric layer, the recording layer, the first dielectric layer, and the reflective layer are arranged in this order from the light incident side. It is done.
- (ZnS) 80 (SiO 2 ) 20 (mol%) has been used as the material for the first and second dielectric layers.
- This material is an amorphous material, has low thermal conductivity, high transparency, and high refractive index.
- the film formation rate at the time of film formation is high, and mechanical properties and moisture resistance are excellent, it has been put into practical use as a material suitable for forming a dielectric layer.
- BD Blu-ray disc
- Zr—Cr—O a material containing ZrO 2 —Cr 2 O 3
- the rewriting is excellent over 10,000 times (for example, see Patent Document 2).
- This material is suitable for the interface layer because it does not contain S, has a high melting point, excellent heat resistance, and good adhesion to the recording layer.
- the semi-transparent information layer (L1) located in is composed of a very thin layer of about 6 nm for the recording layer and about 10 nm for the reflective layer, but is formed using Zr—Cr—O. It was possible to achieve 10,000 cycle performance by adopting the interface layer.
- next-generation DVD Digital Versatile Disc
- BD recorder with a built-in large-capacity hard disk and a large television with a built-in BD recorder have been released, and the spread of BD recorders and BD media has become widespread. Accelerating.
- the next theme of the BD medium is an increase in capacity. By increasing the capacity, it becomes possible to record a high-definition image on a BD medium for a longer time, or the BD medium can be used as a replaceable medium instead of a hard disk.
- a method for increasing the capacity there are a method for increasing the recording capacity per information layer and a method for increasing the number of layers (number of information layers). By combining the two, the capacity can be further increased.
- the inventor has worked on the development of a BD medium of 100 GB by combining both. Specifically, an information layer of 33.4 GB (25 GB conventionally) is developed per layer, and three layers are laminated. Increasing the recording capacity from 25 GB to 33.4 GB means that the recording density increases 1.34 times, and the recorded mark itself becomes smaller. Therefore, obtaining a signal amplitude equal to or greater than that of a conventional mark from a small mark is a technical problem.
- the transmittance of the information layer (L2) located closest to the light incident side must be higher than in the case of two layers.
- the L1 transmittance was optically designed at 50%.
- the L2 transmittance could be 56% or more and the L1 transmittance could be 50% or more.
- the L1 of the three layers must ensure a transmittance of 50% or more and obtain a good signal quality using the light transmitted through the L2, it requires a higher Rc than the L2.
- Rc By design, when Rc is increased, Ra also tends to increase, and as a result, Rc / Ra tends to decrease as in L2. Therefore, in order to increase the capacity, it is required to realize an information layer that can obtain both high transmittance and high reflectance ratio. That is, development of a film configuration capable of realizing such an information layer, specifically, development of a dielectric material used for a layer provided in contact with the recording layer is required.
- the information layer is required to have not only the above optical characteristics but also good repeated rewriting performance. Therefore, the layer provided in contact with the recording layer is also required to have good adhesion with the recording layer.
- the present invention solves the above-mentioned conventional problems, and can provide a large capacity by providing an information layer that can realize high transmittance and high reflectance ratio, and can also realize good repeated rewriting performance.
- An object is to provide an information recording medium.
- the information recording medium of the present invention is an information recording medium capable of recording or reproducing information by irradiation of light, and includes a dielectric layer b, a recording layer, and a dielectric layer a in this order from the light incident side,
- the dielectric layer a includes at least one element M selected from Al, Dy, Nb, Si, Ti and Y, Cr and O, and the dielectric layer b is selected from Zr and Hf. At least one element A, Cr, and O are included, and the dielectric layer a and the dielectric layer b are disposed in contact with the recording layer.
- a multilayer rewritable recording medium having a capacity of 33.4 GB or more per information layer can be realized.
- a large capacity information recording medium of 100 GB or more can be realized.
- FIG. 1 is a partial sectional view showing an example of the information recording medium of the present invention.
- FIG. 2 is a partial sectional view showing another example of the information recording medium of the present invention.
- FIG. 3 is a partial sectional view showing still another example of the information recording medium of the present invention.
- FIG. 4 is a partial sectional view showing still another example of the information recording medium of the present invention.
- the information recording medium of the present invention is an information recording medium capable of increasing the capacity by providing an information layer that can realize a high transmittance and a high reflectance ratio, and can also realize a good moisture resistance and repeated rewriting performance. It is an invention made for the purpose of providing.
- the present inventor has developed an information layer (L2) positioned closest to the light incident side in the three-layer BD medium and an information layer positioned in the middle (L2).
- L1 from the light incident side, the second dielectric layer, the second interface layer, the recording layer, the first interface layer, the first dielectric layer, the reflective layer, and the high refractive index layer are Optical design (calculation) was performed on the information layer having the configuration arranged in order. As a result, it was found that Rc / Ra can be increased by applying a relatively transparent material to the first interface layer. It has also been found that Rc / Ra can be further increased if a material having a refractive index smaller than that of the second interface layer is used for the first interface layer.
- L2 (test 2) in which Zr—Cr—O was applied to the second interface layer was prototyped and Rc / Ra was measured.
- test 2 was able to increase Rc / Ra.
- the extinction coefficient of the Zr—Cr—O interface layer with light having a wavelength of 405 nm is about 0.1.
- Rc / Ra can be increased by applying a dielectric material having a smaller extinction coefficient than Zr—Cr—O to the first interface layer.
- the Zr—Cr—O interface layer is an interface layer excellent in moisture resistance and repeated rewriting performance
- ZrO 2 is a transparent and thermally stable material
- Cr 2 O 3 is a chalcogen-based recording layer It is a material with excellent adhesion.
- the extinction coefficient of Cr 2 O 3 at a wavelength of 405 nm is as large as about 0.2, it cannot be used alone even if it has excellent adhesion. Since the supplemented adhesion deficiency of the ZrO 2 in Cr 2 O 3 added, simply measures that transparent by reducing the Cr 2 O 3, since lowering the adhesion, not taken. The same applies to the Hf—Cr—O interface layer.
- the present inventor has configured the information recording medium of the present invention, that is, an information recording medium capable of recording or reproducing information by light irradiation, from the light incident side, the dielectric layer b,
- the recording layer and the dielectric layer a are provided in this order, and the dielectric layer a includes at least one element M selected from Al, Dy, Nb, Si, Ti, and Y, Cr, and O,
- the dielectric layer b includes at least one element A selected from Zr and Hf, Cr, and O, and the dielectric layer a and the dielectric layer b are disposed in contact with the recording layer. Has reached the configuration.
- a dielectric material containing at least one element A selected from Zr and Hf, Cr and O which has both high heat resistance and excellent adhesion to the recording layer.
- a dielectric material containing at least one element M selected from Y, Cr, and O on an interface layer (dielectric layer a) located on the side opposite to the light incident side with respect to the recording layer Use.
- the dielectric layer a may contain a material represented by M c Cr d O 100-cd (atomic%).
- M c Cr d O 100-cd (atomic%) the subscripts c, d and 100-cd represent the composition ratio of M, Cr and O expressed in atomic%, where c and d are 12 ⁇ c ⁇ 40, 0 ⁇ d ⁇ 25, and 20 ⁇ (c + d) ⁇ 50.
- the element M included in the dielectric layer a may be at least one element selected from Al, Si, and Ti.
- M c Cr d O 100-cd (atomic%) is based on the total number of “M” atoms, “Cr” atoms, and “O” atoms (100 atomic%). It shows that the composition formula is expressed.
- the dielectric layer a is at least one selected from Al 2 O 3 , Dy 2 O 3 , Nb 2 O 5 , SiO 2 , TiO 2 and Y 2 O 3 .
- a material represented by (D) h (Cr 2 O 3 ) 100-h (mol%) may be included, including oxide D and Cr 2 O 3 .
- the subscripts h and 100-h indicate the composition ratio of D and Cr 2 O 3 expressed in mol%, where h is 50 ⁇ h ⁇ 100.
- the oxide D included in the dielectric layer a may be at least one oxide selected from Al 2 O 3 , SiO 2, and TiO 2 .
- (D) h (Cr 2 O 3 ) 100-h (mol%) is a mixture of h mol% of compound D and 100-h mol% of Cr 2 O 3. It shows that there is.
- the same notation method is used with the same meaning.
- the dielectric layer b may contain a material represented by A f Cr g O 100-fg (atomic%).
- a f Cr g O 100-fg (atomic%) the subscripts f, g and 100-f-g indicate the composition ratio of A, Cr and O expressed in atomic%, and f and g are 4 ⁇ f ⁇ 16, 21 ⁇ g ⁇ 35, and 30 ⁇ (f + g) ⁇ 50.
- the dielectric layer b is, Al, Dy, Nb, Si, further comprising at least any one element X selected from Ti and Y, A k Cr m X n O 100-kmn ( atomic% ) May be included.
- the subscripts k, m, n and 100-kmn are the compositions of A, Cr, X and O expressed in atomic%.
- K, m, and n satisfy 1 ⁇ k ⁇ 18, 3 ⁇ m ⁇ 35, 0 ⁇ n ⁇ 31, and 25 ⁇ (k + m + n) ⁇ 50.
- the element A contained in the dielectric layer b may be Zr, and the element X may be at least one element selected from Al, Dy, Si, and Ti.
- the dielectric layer b is one of the oxide AO 2 at least one selected from ZrO 2 and HfO 2, and a Cr 2 O 3, (AO 2 ) j ( Cr 2 O 3 ) 100-j (mol%) may be included.
- (AO 2 ) j (Cr 2 O 3 ) 100-j (mol%) the subscripts j and 100-j represent the composition ratio of AO 2 and Cr 2 O 3 expressed in mol%, j satisfies 20 ⁇ j ⁇ 60.
- the dielectric layer b further includes at least one oxide L selected from Al 2 O 3 , Dy 2 O 3 , Nb 2 O 5 , SiO 2 , TiO 2 and Y 2 O 3.
- a material represented by (AO 2 ) p (Cr 2 O 3 ) t (L) 100-pt (mol%) may be included.
- the subscripts p, t and 100- pt are AO 2 , Cr 2 expressed in mol%.
- the composition ratio of O 3 and L is shown, and p and t satisfy 20 ⁇ p ⁇ 60, 20 ⁇ t ⁇ 80, and 60 ⁇ (p + t) ⁇ 100.
- the oxide L included in the dielectric layer b may be at least one oxide selected from Al 2 O 3 , Dy 2 O 3 , SiO 2 and TiO 2 .
- a part of Cr contained in the dielectric layer a may be substituted with at least one element selected from Ga and In.
- a part of Cr 2 O 3 contained in the dielectric layer a is at least one selected from Ga 2 O 3 and In 2 O 3 It may be substituted with one oxide.
- a part of Cr contained in the dielectric layer b may be substituted with at least one element selected from Ga and In.
- a part of Cr 2 O 3 contained in the dielectric layer b is at least one selected from Ga 2 O 3 and In 2 O 3 It may be substituted with one oxide.
- the information recording medium of the present invention preferably satisfies na ⁇ nb, where na is the refractive index of the dielectric layer a and nb is the refractive index of the dielectric layer b.
- the information recording medium of the present invention includes N information layers, where N is an integer greater than or equal to 2, and the N information layers are arranged from the first information layer to the Nth in order from the side opposite to the light incident side.
- N is an integer greater than or equal to 2
- the recording layer, and the dielectric layer a may be included in this order.
- N may be 3.
- the recording layer may be formed of a material that causes a phase change by the light irradiation.
- the recording layer may contain Ge—Te and contain 40 atomic% or more of Ge, or contain at least one material selected from Sb—Ge and Sb—Te, and contain 70 atoms of Sb. % Or more may be included.
- FIG. 1 shows a partial cross section of the information recording medium 300.
- a first information layer 310, an intermediate layer 303, a second information layer 320, an intermediate layer 304, a third information layer 330, and a transparent layer 302 are arranged in this order on a substrate 301.
- the dielectric layer a and the dielectric layer b in the present invention are applied to all of the first information layer 310 to the third information layer 330, all the information layers are the information of the present invention. Although it corresponds to the Lth information layer of the recording medium, the present invention is not limited to this, and if at least one of the first information layer 310 to the third information layer 330 corresponds to the Lth information layer. Good.
- the second information layer 320 includes a dielectric layer 321, a reflective layer 322, a dielectric layer 323, an interface layer 324, a recording layer 325, an interface layer 326, and a dielectric layer 327 on one surface of the intermediate layer 303. It is formed by arranging in this order.
- the third information layer 330 includes a dielectric layer 331, a reflective layer 332, a dielectric layer 333, an interface layer 334, a recording layer 335, an interface layer 336, and a dielectric layer 337 on one surface of the intermediate layer 304. It is formed by arranging in order.
- information is recorded and reproduced by the laser beam 10 in the blue-violet region near the wavelength of 405 nm.
- the laser beam 10 is incident from the transparent layer 302 side.
- Information is recorded on and reproduced from the first information layer 310 by the laser light 10 that has passed through the third information layer 330 and the second information layer 320.
- Information is recorded on and reproduced from the second information layer 320 by the laser light 10 that has passed through the third information layer 330.
- information can be recorded / reproduced in three information layers, so that an information recording medium having a capacity of 100 GB can be obtained by setting the capacity per information layer to 33.4 GB, for example. .
- the effective reflectances of the three information layers are approximately equal. This is achieved by adjusting the reflectivity of the first, second and third information layers and the transmittance of the second and third information layers, respectively.
- a configuration designed to have an effective Rc of 2.2% and an effective Ra of 0.3% will be described as an example.
- the reflectance of each information layer measured in a state where three information layers are stacked is defined as an effective reflectance. Unless stated otherwise, unless stated as “effective”, it refers to the reflectance measured without lamination.
- Rc is the mirror reflectivity of the information layer when the recording layer is in the crystalline phase
- Ra is the mirror reflectivity of the information layer when the recording layer is in the amorphous phase.
- the effective Rc-g is, for example, 1.8%.
- the average value ((Tc + Ta) / 2) of the third information layer 330 is 56%
- the average value ((Tc + Ta) / 2) of the second information layer 320 is 50%
- the first information layer 310 has an Rc of 28%, Ra of 4%
- the second information layer 320 has an Rc of 7%
- the third information layer 330 has an Rc of 2.2%, It can be designed such that Ra is 0.3%.
- Tc is the transmittance of the information layer when the recording layer is in the crystalline phase
- Ta is the transmittance of the information layer when the recording layer is in the amorphous phase.
- Tc + Ta When (Tc + Ta) / 2 is 56%, for example, Tc may be 55% and Ta may be 57%. Alternatively, Tc may be 56% and Ta may be 57%. Tc and Ta are preferably close values, but may not be equal. In the following, when the transmittance of the information layer is simply referred to without specifying Tc and Ta, it means the average value of transmittance ((Tc + Ta) / 2).
- the substrate 301 mainly has a function as a support, is a disc, is transparent, and has a smooth surface.
- the material include a resin such as polycarbonate, amorphous polyolefin or polymethyl methacrylate (PMMA), or glass. In view of moldability, cost and mechanical strength, polycarbonate is preferably used.
- a substrate 301 having a thickness of about 1.1 mm and a diameter of about 120 mm is preferably used.
- An uneven guide groove for guiding the laser beam 10 may be formed on the surface of the substrate 301 on the side where the information layer 310 is formed.
- the surface on the side close to the laser beam 10 is referred to as a “groove surface” for convenience, and the surface on the side far from the laser beam 10 is referred to as “ Called “land surface”.
- the step between the groove surface and the land surface is preferably 10 nm or more and 30 nm or less. In Blu-ray Disc, recording is performed only on the groove surface, but the distance between the groove and the groove (from the center of the groove surface to the center of the groove surface) is preferably about 0.32 ⁇ m.
- the intermediate layer 303 has a function of separating the focal position of the laser beam 10 in the second information layer 320 and the focal position of the laser beam 10 in the first information layer 310, and the second information layer if necessary.
- a guide groove of the layer 320 may be formed.
- the intermediate layer 304 has a function of separating the focal position of the laser light 10 in the third information layer 330 and the focal position of the laser light 10 in the second information layer 320.
- Three guide grooves of the information layer 330 may be formed.
- the intermediate layers 303 and 304 can be formed of an ultraviolet curable resin. Moreover, you may have the structure by which the some resin layer was laminated
- the intermediate layers 303 and 304 are preferably transparent to the light of wavelength ⁇ to be recorded / reproduced so that the laser beam 10 efficiently reaches the first information layer 310 and the second information layer 320.
- the thicknesses of the intermediate layers 303 and 304 are (1) the depth of focus determined by the numerical aperture of the objective lens and the wavelength of the laser beam 10, and (2) the distance between the recording layer 315 and the recording layer 335 is the objective lens (3)
- the thickness of the transparent layer 302 and the thickness of the transparent layer 302 are preferably within the tolerance of the substrate thickness acceptable by the objective lens used.
- the distance from the surface of the transparent layer 302 to the recording layer 315 of the first information layer 310 is preferably 80 ⁇ m or more and 120 ⁇ m or less. Furthermore, the reproduction of signals from the first information layer 310, the second information layer 320, and the third information layer 330, and the recording / erasing / rewriting of signals to these information layers are mutually performed from other information layers. It is preferable that the film thicknesses of the intermediate layers 303 and 304 are different from each other so that the film can be satisfactorily performed without being affected by the above.
- the thickness of each intermediate layer is preferably selected in the range of 3 ⁇ m to 30 ⁇ m, and more preferably in the range of 10 ⁇ m to 30 ⁇ m.
- the film thicknesses of the intermediate layer 303, the intermediate layer 304, and the transparent layer 302 may be set so that the distance from the surface of the transparent layer 302 to the recording layer 315 is 100 ⁇ m.
- the intermediate layer 303 can be set to 25 ⁇ m
- the intermediate layer 304 can be set to 18 ⁇ m
- the transparent layer 302 can be set to 57 ⁇ m.
- it can also set in order like 16 micrometers, 24 micrometers, and 60 micrometers in order.
- the transparent layer 302 will be described.
- As a method of increasing the recording density of the information recording medium there is a method of increasing the numerical aperture NA of the objective lens so that the laser light can be narrowed down using a short wavelength laser light.
- NA numerical aperture
- the transparent layer 302 positioned on the side on which the laser beam 10 is incident is designed to be thinner than the substrate 301. According to this configuration, it is possible to obtain a large-capacity information recording medium 300 capable of higher density recording.
- the transparent layer 302 is disc-shaped, transparent, and has a smooth surface.
- the transparent layer 302 may be composed of, for example, a disk-shaped sheet and an adhesive layer, or may be composed of an ultraviolet curable resin.
- An uneven guide groove for guiding the laser beam 10 may be formed as necessary.
- the protective layer may be provided on the surface of the dielectric layer 337. Any configuration may be used, but the total thickness (for example, sheet thickness + adhesive layer thickness + protective layer thickness, or thickness of only the ultraviolet curable resin) is preferably 20 ⁇ m to 100 ⁇ m, and more preferably 30 ⁇ m to 80 ⁇ m.
- the sheet is preferably formed of a resin such as polycarbonate, amorphous polyolefin, or PMMA, and particularly preferably formed of polycarbonate. Further, since the transparent layer 302 is located on the laser beam 10 incident side, it is preferable that the birefringence in the short wavelength region is small optically.
- the third information layer 330 has the dielectric layer 331, the reflective layer 332, the dielectric layer 333, the interface layer 334, the recording layer 335, the interface layer 336, and the dielectric on one surface of the intermediate layer 304.
- the body layer 337 is formed by arranging in this order.
- the third information layer 330 is designed to have a high transmittance so that the laser light 10 can reach the first information layer 310 and the second information layer 320.
- Tc (%) is the light transmittance of the third information layer 330 when the recording layer 335 is in the crystalline phase, and the third information layer 330 when the recording layer 335 is in the amorphous phase.
- the light transmittance is Ta (%), it is preferably 53% ⁇ (Ta + Tc) / 2, and more preferably 56% ⁇ (Ta + Tc) / 2.
- the dielectric layer 331 has a function of increasing the light transmittance of the third information layer 330.
- the material is preferably transparent and has a refractive index of 2.4 or more with respect to the laser beam 10 having a wavelength of 405 nm.
- the refractive index of the dielectric layer 331 is small, the reflectance ratio Rc / Ra of the third information layer 330 is large, but the light transmittance is small.
- a refractive index of 2.4 or higher is preferable as a refractive index that provides a reflectance ratio of 4 or higher and a transmittance of 53% or higher. Therefore, if the refractive index is less than 2.4, the light transmittance of the third information layer 330 is reduced, and sufficient laser light 10 reaches the first information layer 310 and the second information layer 320. You may not get.
- a material of the dielectric layer 33 for example, a material containing at least one of ZrO 2 , Nb 2 O 5 , Bi 2 O 3 , CeO 2 , TiO 2 and WO 3 may be used.
- TiO 2 is preferably used because it has a high refractive index of 2.7 and excellent moisture resistance.
- ZrO 2, Nb 2 O 5 , Bi 2 O 3, CeO 2 at least any one of TiO 2 and WO 3 may be used a material containing more than 50 mol%.
- (ZrO 2 ) 80 (Cr 2 O 3 ) 20 (mol%), (Bi 2 O 3 ) 60 (SiO 2 ) 40 (mol%), (Bi 2 O 3 ) 60 (TeO 2 ) 40 (mol) %), (CeO 2 ) 50 (SnO 2 ) 50 (mol%), (TiO 2 ) 50 (HfO 2 ) 50 (mol%), (WO 3 ) 75 (Y 2 O 3 ) 25 (mol%), (Nb 2 O 5 ) 50 (MnO) 50 (mol%), (Al 2 O 3 ) 50 (TiO 2 ) 50 (mol%), or the like may be used.
- a material in which at least any two of ZrO 2 , Nb 2 O 5 , Bi 2 O 3 , CeO 2 , TiO 2 and WO 3 are mixed may be used.
- Bi 4 Ti 3 O 12 ((Bi 2 O 3 ) 40 (TiO 2 ) 60 (mol%)), Bi 2 Ti 4 O 11 ((Bi 2 O 3 ) 20 (TiO 2 ) 80 (mol%) ), Bi 12 TiO 20 ((Bi 2 O 3 ) 85.7 (TiO 2 ) 14.3 (mol%)), (WO 3 ) 50 (Bi 2 O 3 ) 50 (mol%), (TiO 2 ) 50 (Nb 2 O 5 ) 50 (mol%), (CeO 2 ) 50 (TiO 2 ) 50 (mol%), (ZrO 2 ) 50 (TiO 2 ) 50 (mol%), (WO 3 ) 67 (ZrO 2 ) 33 ( Mol%) and the like may be used.
- the thickness of the dielectric layer 331 is ⁇ / (8n 1 ) (nm) ( ⁇ is the wavelength of the laser beam 10, n 1 is the refractive index of the dielectric layer 331) and the vicinity thereof.
- the transmittance of the third information layer 330 is the maximum value.
- the reflectance contrast (Rc ⁇ Ra) / (Rc + Ra) takes a maximum value when the film thickness of the dielectric layer 331 is between ⁇ / (16n 1 ) and ⁇ / (4n 1 ). Therefore, the thickness of the dielectric layer 331 can be selected so that both are compatible, and is preferably 9 nm or more and 42 nm or less, more preferably 8 nm or more and 30 nm or less.
- the dielectric layer 331 may be composed of two or more layers.
- the reflective layer 332 optically increases the amount of light absorbed by the recording layer 335, or the difference in reflectance of the third information layer 330 between when the recording layer 335 is amorphous and when it is crystalline. It has a function to enlarge. In addition, it has the function of quickly diffusing heat generated in the recording layer 335 to rapidly cool the recording layer 335 and to make it amorphous easily. Further, the reflective layer 332 also has a function of protecting the multilayer film including the dielectric layers 333 to 337 from the usage environment.
- the reflective layer 332 has a function of quickly diffusing the heat of the recording layer 335. As described above, since the third information layer 330 requires high light transmittance, it is desirable that the light absorption by the reflective layer 332 be small. Therefore, the reflective layer 332 is preferably designed to be thin, and it is preferable to use a material having high thermal conductivity that can quickly diffuse heat even if it is thin.
- the reflective layer 332 preferably uses Ag or an Ag alloy.
- the Ag alloy for example, an alloy material such as Ag—Pd, Ag—Pd—Cu, Ag—Ga, Ag—Ga—Cu, Ag—Cu, or Ag—In—Cu may be used.
- a material obtained by adding a rare earth metal to Ag or Ag—Cu may be used.
- Ag—Pd—Cu, Ag—Ga—Cu, Ag—Cu, and Ag—In—Cu are preferably used because they have low light absorption, high thermal conductivity, and excellent moisture resistance.
- the film thickness is adjusted with the thickness of the recording layer, it is preferably 3 nm or more and 15 nm or less.
- the thickness is less than 3 nm, it is difficult to form a homogeneous thin film, the function of diffusing heat is reduced, and marks are hardly formed on the recording layer 335.
- the thickness is larger than 15 nm, the light transmittance of the third information layer 330 is less than 53%.
- the dielectric layers 333 and 337 have a function of adjusting Rc, Ra, Tc, and Ta of the third information layer 330 by adjusting the optical distance.
- the recording layer 335 has a function of increasing the light absorption efficiency and a function of protecting the recording layer 335 from moisture and the like.
- the film has high transparency with respect to the laser wavelength to be used and is excellent in heat resistance in addition to moisture resistance.
- oxides, sulfides, nitrides, carbides and fluorides, and mixtures thereof can be used as materials for the dielectric layers 333 and 337.
- oxides, sulfides, nitrides, carbides and fluorides, and mixtures thereof can be used as materials for the dielectric layers 333 and 337.
- oxides, sulfides, nitrides, carbides and fluorides, and mixtures thereof can be used as materials for the dielectric layers 333 and 337.
- oxides, sulfides, nitrides, carbides and fluorides, and mixtures thereof can be used as materials for the dielectric layers 333 and 337.
- oxides, sulfides, nitrides, carbides and fluorides, and mixtures thereof can be used as materials for the dielectric layers 333 and 337.
- oxides, sulfides, nitrides, carbides and fluorides, and mixtures thereof can be used as materials for the di
- nitride for example, AlN, BN, CrN, Ge 3 N 4 , HfN, NbN, Si 3 N 4 , TaN, TiN, VN and ZrN may be used.
- Al 4 C 3 , B 4 C, CaC 2 , Cr 3 C 2 , HfC, Mo 2 C, NbC, SiC, TaC, TiC, VC, W 2 C, WC, and ZrC may be used as the carbide. Good.
- fluoride for example, CaF 2 , CeF 3 , DyF 3 , ErF 3 , GdF 3 , HoF 3 , LaF 3 , MgF 2 , NdF 3 , YF 3 and YbF 3 may be used.
- Examples of the mixture include ZnS—SiO 2 , ZnS—SiO 2 —Ta 2 O 5 , ZnS—SiO 2 —LaF 3 , ZrO 2 —SiO 2 , ZrO 2 —Cr 2 O 3 , ZrO 2 —SiO 2 —Cr 2.
- O 3 ZrO 2 —Ga 2 O 3 , ZrO 2 —SiO 2 —Ga 2 O 3 , ZrO 2 —In 2 O 3, ZrO 2 —SiO 2 —In 2 O 3 and the like may be used.
- the dielectric layers 333 and 337 are made of at least one selected from oxides, sulfides and fluorides by 90 mol% or more. More preferably.
- a composite material or mixed material containing ZrO 2 has high transparency with respect to a wavelength near 405 nm and is excellent in heat resistance.
- the materials containing ZrO 2, in place of ZrO 2 CaO, MgO, may be used the added partially stabilized zirconia or stabilized zirconia any of Y 2 O 3 in ZrO 2.
- the HfO 2 to ZrO 2 and chemical properties are similar, may be used in place of ZrO 2.
- the dielectric layer 333 adjacent to the reflective layer 332 it is preferable to use Ag or an Ag alloy for the reflective layer 332, and thus it is more preferable that no sulfide is included.
- a more transparent material for the dielectric layer 337 located on the laser beam 10 incident side For example, ZnS—SiO 2 is a material that is amorphous, has low thermal conductivity, has high transparency and a high refractive index, has a high film formation rate during film formation, and has excellent mechanical properties and moisture resistance. Therefore, it is preferable as a material for the dielectric layer 337.
- As the dielectric layer 337 (ZnS) 80 (SiO 2 ) 20 (mol%) is particularly preferably used.
- the dielectric layer 333 or the dielectric layer 337 may be formed of two or more layers in which the above oxides or the like are stacked.
- the optical path length can be accurately determined by calculation based on, for example, the matrix method (for example, see Hiroshi Kubota “Wave Optics” Iwanami Shinsho, 1971, Chapter 3).
- the film thickness d can be determined from the optical path length nd.
- the third information layer 330 has a transmittance ((Tc + Ta) / 2) of 56%, a reflectance Rc of 2.2%, and a reflectance Ra of 0.3%. Designed to.
- the thickness of the dielectric layer 333 is preferably 20 nm or less, and more preferably 5 nm or more and 15 nm or less.
- the thickness of the dielectric layer 337 is preferably 15 nm or more and 60 nm or less, and more preferably 20 nm or more and 50 nm or less.
- the dielectric layer 333 and the dielectric layer 337 can be provided as necessary.
- the dielectric layer 333 is not necessarily provided.
- the dielectric layer 337 is not necessarily provided.
- the third information layer 330 has a configuration in which a dielectric layer 331, a reflective layer 332, an interface layer 334, a recording layer 335, an interface layer 336, and a dielectric layer 337 are arranged in this order on the intermediate layer 304.
- the dielectric layer 331, the reflective layer 332, the interface layer 334, the recording layer 335, and the interface layer 336 may be arranged in this order.
- the third information layer 330 has a configuration in which the dielectric layer 331, the reflective layer 332, the dielectric layer 333, the interface layer 334, the recording layer 335, and the interface layer 336 are arranged in this order on the intermediate layer 304. You may do it.
- Both the interface layer 334 and the interface layer 336 are provided in contact with the recording layer 335.
- the interface layer provided in contact with the recording layer 335 is required to at least be (1) high melting point and not melt during recording, and (2) good adhesion to the recording layer that is a chalcogenide material. The As described above, at the time of recording, the region where the recording mark is formed is heated to the melting point or higher and melted, so that the highest temperature is recorded during a series of recording and erasing operations.
- the interface layers 334 and 336 may have a nominal melting point of 1000 ° C. or more in order not to melt during recording. preferable. This is because a thin film of several nanometers may cause diffusion, decomposition, and melting at a temperature lower than the nominal melting point.
- na-ika refractive index of the interface layer 334
- ka extinction coefficient of the interface layer 3334
- the smaller the ka the larger the reflectance ratio Rc / Ra of the third information layer 330 can be. If na is small, the effect is greater.
- ka is preferably 0.07 or less, and more preferably 0.04 or less.
- na is more preferably relatively smaller than the refractive index nb of the interface layer 336.
- a material containing at least one element M selected from Al, Dy, Nb, Si, Ti, and Y, Cr, and O is used. Its composition can be expressed as M c Cr d O 100-cd (atomic%), and the subscripts c, d and 100-cd represent the composition ratio of M, Cr and O expressed in atomic%. Show. In this case, c and d preferably satisfy 12 ⁇ c ⁇ 40, 0 ⁇ d ⁇ 25, and 20 ⁇ (c + d) ⁇ 50. In this composition range, both high transparency and excellent adhesion to the chalcogenide recording film can be achieved.
- the interface layer 334 only needs to contain the elements M, Cr, and O, but preferably contains the elements M, Cr, and O as main components.
- the interface layer 334 may be substantially formed of the elements M, Cr, and O.
- the interface layer 334 includes the elements M, Cr, and O as main components when the total of all atoms included in the interface layer 334 is 100 atomic%. The total of these atoms is 90 atomic% or more, preferably 95 atomic% or more.
- the interface layer 334 is substantially formed of the elements M, Cr, and O.
- other components such as impurities may be mixed in a trace amount, but the total of the atoms of the elements M, Cr, and O Is 95 atomic% or more, preferably 98 atomic% or more.
- Specific materials include, for example, Al—Cr—O, Al—Dy—Cr—O, Al—Dy—Nb—Cr—O, Al—Dy—Si—Cr—O, and Al—Dy—Ti—Cr—O.
- a part of Cr contained in the material may be substituted with at least one element selected from Ga and In.
- Al—Cr—O may be Al—Cr—In—O, Al—Cr—Ga—O, or Al—Cr—In—Ga—O.
- Al—Si—Cr—O may be Al—Si—Cr—In—O, Al—Si—Cr—Ga—O, or Al—Si—Cr—In—Ga—O.
- Al—Ti—Cr—O may be Al—Ti—Cr—In—O, Al—Ti—Cr—Ga—O, or Al—Ti—Cr—In—Ga—O.
- the oxide of element M is transparent and has a high melting point. Therefore, it is preferable that the element M is contained in the interface layer 334 in an oxide state.
- the interface layer 334 includes at least one oxide D selected from Al 2 O 3 , Dy 2 O 3 , Nb 2 O 5 , SiO 2 , TiO 2, and Y 2 O 3. It's okay.
- the melting point and complex refractive index of each oxide D are as follows: Al 2 O 3 has a melting point of about 2000 ° C. and a complex refractive index of 1.66-i0.00, and Dy 2 O 3 has a melting point of 2000 ° C. and a complex refractive index.
- Nb 2 O 5 has a melting point of about 1500 ° C. and a complex refractive index of 2.51-i0.01
- SiO 2 has a melting point of about 1700 ° C. and a complex refractive index of 1.47-i0. 00
- TiO 2 has a melting point of about 1800 ° C. and a complex refractive index of 2.68-i0.01
- Y 2 O 3 has a melting point of about 2400 ° C. and a complex refractive index of 1.94-i0.01.
- fusing point is a solid literature value and a complex refractive index is an inventor's experimental value.
- the interface layer 334 may include a complex oxide of the element M, for example, a complex oxide of the oxide D.
- Al 6 Si 2 O 13 has a melting point of about 1900 ° C. and a complex refractive index of 1.59-i0.00
- Al 2 TiO 5 has a melting point of about 1900 ° C. and a complex refractive index of 2.17-i 0.01. is there.
- the interface layer 334 may include, as the element M oxide, a low oxide (an oxide having less oxygen than the stoichiometric composition) or a mixture other than the above-described compounds and composite oxides.
- the interface layer 334 includes a low oxide of the element M, a low oxide of Al, a low oxide of Dy, a low oxide of Nb, a low oxide of Si, a low oxide of Ti, and a low oxide of Y
- at least one selected from a low oxide of Al—Si and a low oxide of Al—Ti may be included.
- the interface layer 334 includes, for example, Al 2 O 3 —Dy 2 O 3 , Dy 2 O 3 —Nb 2 O 5 , Nb 2 O 5 — It may contain at least one selected from SiO 2 , SiO 2 —TiO 2 , TiO 2 —Y 2 O 3 and the like.
- the interface layer 334 As a material for the interface layer 334, it is preferable to use a material containing these oxides D and Cr.
- the composition is represented by (D) h (Cr 2 O 3 ) 100-h (mol%), and indicates the composition ratio of D and Cr 2 O 3 in which the suffixes h and 100-h are represented by mol%.
- H preferably satisfies 50 ⁇ h ⁇ 100.
- the oxide of Cr is preferably present as Cr 2 O 3 in the interface layer 334 and may be present as a low oxide of Cr 2 O 3 .
- the interface layer 334 may be formed of a material substantially represented by (D) h (Cr 2 O 3 ) 100-h (mol%).
- a mixture of oxide D and Cr 2 O 3 is used as the material of the interface layer 334, specifically, Al 2 O 3 —Cr 2 O 3 , Dy 2 O 3 —Cr 2 O 3 , Nb 2 O 5 -Cr 2 O 3, can be used SiO 2 -Cr 2 O 3, TiO 2 -Cr 2 O 3 and Y 2 O 3 -Cr 2 O 3 .
- a mixture of a composite oxide of oxide D and Cr 2 O 3 specifically, for example, Al 6 Si 2 O 13 —Cr 2 O 3 , Al 2 TiO 5 —Cr 2 O 3 is used. May be used.
- a mixture of the low oxide of element M and Cr 2 O 3 may be used.
- a mixture of oxide D and Cr 2 O 3 can also be used.
- the oxide D it is more preferable to include an Al oxide or an Al composite oxide in which oxygen vacancies are less likely to occur during thin film formation.
- Specific examples include Al 2 O 3 , Al 6 Si 2 O 13 , and Al 2 TiO 5 .
- a part of Cr 2 O 3 contained in the material may be substituted with at least one oxide selected from Ga 2 O 3 and In 2 O 3 .
- Al 2 O 3 —Cr 2 O 3 is replaced with Al 2 O 3 —Cr 2 O 3 —In 2 O 3 , Al 2 O 3 —Cr 2 O 3 —Ga 2 O 3 or Al 2 O 3 —Cr 2.
- O 3 —In 2 O 3 —Ga 2 O 3 may be used.
- Al 2 O 3 —SiO 2 —Cr 2 O 3 is replaced with Al 2 O 3 —SiO 2 —Cr 2 O 3 —In 2 O 3 or Al 2 O 3 —SiO 2 —Cr 2 O 3 —Ga 2 O. 3 or Al 2 O 3 —SiO 2 —Cr 2 O 3 —In 2 O 3 —Ga 2 O 3 may be used.
- Al 2 O 3 —TiO 2 —Cr 2 O 3 is replaced with Al 2 O 3 —TiO 2 —Cr 2 O 3 —In 2 O 3 , Al 2 O 3 —TiO 2 —Cr 2 O 3.
- the extinction coefficient ka is reduced without reducing the adhesion of the interface layer 334.
- the transparency can be increased and the refractive index na can be reduced.
- the total content of Ga 2 O 3 and In 2 O 3 in the interface layer 334 is preferably 30 mol% or less.
- the interface layer 336 (dielectric layer b)
- high heat resistance is required in addition to high melting point and adhesion.
- the semitransparent information layer such as the third information layer 330 or the second information layer 320
- the interface layer 336 needs a material having higher heat resistance than the interface layer 334.
- the order of forming the thin film layer is that the interface layer 336 is formed after the recording layer 335 is formed.
- a material for the interface layer 336 a material containing at least one element A selected from Zr and Hf, Cr, and O is used. Its composition can be expressed as A f Cr g O 100-fg (atomic%), and the subscripts f, g and 100-f-g represent the composition ratio of A, Cr and O expressed in atomic%. Show. In this case, it is preferable that f and g satisfy 4 ⁇ f ⁇ 16, 21 ⁇ g ⁇ 35, and 30 ⁇ (f + g) ⁇ 50. In this composition range, both excellent adhesion to the chalcogenide recording film and high heat resistance can be achieved.
- the interface layer 336 only needs to contain the elements A, Cr, and O, but preferably contains the elements A, Cr, and O as main components. In order to obtain the effect of the present invention more reliably, the interface layer 336 may be substantially formed of the elements A, Cr, and O. In this specification, the interface layer 336 includes the elements A, Cr, and O as main components when the total of all atoms included in the interface layer 336 is 100 atomic%. The total of these atoms is 90 atomic% or more, preferably 95 atomic% or more. Further, the interface layer 336 is substantially formed of the elements A, Cr, and O. For example, other components such as impurities may be mixed in a trace amount, but the total of the atoms of the elements A, Cr, and O Is 95 atomic% or more, preferably 98 atomic% or more.
- the interface layer 336 may further include at least one element X selected from Al, Dy, Nb, Si, Ti, and Y.
- the interface layer 336 is represented by A k Cr m X n O 100-kmn (atomic%), and the subscripts k, m, n, and 100- kmn are represented by atomic%, A,
- the composition ratio of Cr, X, and O is shown, and k, m, and n include a material that satisfies 1 ⁇ k ⁇ 18, 3 ⁇ m ⁇ 35, 0 ⁇ n ⁇ 31, and 25 ⁇ (k + m + n) ⁇ 50. Is preferred.
- the refractive index nb of the interface layer 336 can be adjusted.
- the interface layer 336 only needs to contain the elements A, Cr, elements X and O, but may contain the elements A, Cr, elements X and O as main components (elements A, Cr, elements X).
- the total of X and O atoms may be 90 atomic% or more, preferably 95 atomic% or more), and may be substantially formed from the elements A, Cr, elements X and O (element A, Cr, elements X and O).
- the total number of atoms is 95 atomic% or more, preferably 98 atomic% or more).
- Zr—Al—Cr—O may be Zr—Al—Cr—In—O, Zr—Al—Cr—Ga—O, or Zr—Al—Cr—In—Ga—O.
- Zr—Al—Si—Cr—O is replaced with Zr—Al—Si—Cr—In—O, Zr—Al—Si—Cr—Ga—O, or Zr—Al—Si—Cr—In—Ga—O. It is good.
- Zr—Al—Ti—Cr—O is replaced with Zr—Al—Ti—Cr—In—O, Zr—Al—Ti—Cr—Ga—O, or Zr—Al—Ti—Cr—In. It may be -Ga-O.
- the oxide of element A is transparent and has a high melting point. Therefore, it is preferable that the element A is contained in the interface layer 336 in an oxide state.
- the interface layer 336 may include at least one oxide AO 2 selected from ZrO 2 and HfO 2 .
- the oxide AO 2 include ZrO 2 , HfO 2, and ZrO 2 —HfO 2 .
- ZrO 2 has a melting point of about 2700 ° C. and a complex refractive index of 2.18-i0.01
- HfO 2 has a melting point of about 2800 ° C. and a complex refractive index of 2.14-i0.00.
- fusing point is a solid literature value and a complex refractive index is an inventor's experimental value.
- a material containing these oxides AO 2 and Cr oxide is preferably used as a material of the interface layer 336.
- the composition is represented by (AO 2 ) j (Cr 2 O 3 ) 100-j (mol%), and the composition of AO 2 and Cr 2 O 3 in which the subscripts j and 100-j are represented by mol%. It is more preferable that j represents a ratio, and j satisfies 20 ⁇ j ⁇ 60. Thereby, the lack of adhesion of ZrO 2 or HfO 2 can be supplemented with Cr 2 O 3 .
- the interface layer 336 may contain a material represented by (AO 2 ) j (Cr 2 O 3 ) 100-j (mol%), but substantially (AO 2 ) j (Cr 2 It may be formed from a material represented by O 3 ) 100-j (mol%). It is formed from a material substantially represented by (AO 2 ) j (Cr 2 O 3 ) 100-j (mol%) to oxidize oxides AO 2 and Cr 2 O 3 contained in the interface layer 336. It means that the total of the products is 95 mol% or more, preferably 98 mol% or more.
- the oxide of Cr is preferably present as Cr 2 O 3 in the interface layer 336 and may be present as a low oxide of Cr 2 O 3 .
- ZrO 2 is transparent, and according to the analysis of the present inventor, structural stability that no diffusion or decomposition occurs at least up to 1000 ° C. is obtained.
- HfO 2 having similar chemical properties to ZrO 2 has structural stability. However, since HfO 2 is expensive, it is more preferable to use ZrO 2 .
- the interface layer 336 As a material of the interface layer 336, as a mixture of the oxide of element A and the oxide of Cr, specifically, ZrO 2 —Cr 2 O 3 , HfO 2 —Cr 2 O 3 , ZrO 2 —HfO 2 — Cr 2 O 3 can be used.
- the oxide of element X is transparent and has a high melting point.
- the oxide of the element X may include at least one oxide L selected from Al 2 O 3 , Dy 2 O 3 , Nb 2 O 5 , SiO 2 , TiO 2 and Y 2 O 3 (melting point).
- the complex refractive index is the same as the description of the oxide D).
- the refractive index nb of the interface layer 336 can be adjusted.
- TiO 2 has a great effect of increasing the refractive index.
- the interface layer 336 may contain a material represented by (AO 2 ) p (Cr 2 O 3 ) t (L) 100-pt (mol%), but substantially (AO 2 ).
- p (Cr 2 O 3) t (L) 100-pt may also be formed from a material expressed with (mol%).
- the fact that it is formed from a material substantially represented by (AO 2 ) p (Cr 2 O 3 ) t (L) 100-pt (mol%) means that the oxides AO 2 and Cr 2 contained in the interface layer 336
- the sum of the oxides of O 3 and oxide L is 95 mol% or more, preferably 98 mol% or more.
- the oxide L includes at least one selected from Al 2 O 3 , Dy 2 O 3 , SiO 2 and TiO 2 having high transparency and an extinction coefficient of 0.02 or less.
- a part of Cr 2 O 3 contained in the material may be replaced with at least one oxide selected from Ga 2 O 3 and In 2 O 3 .
- ZrO 2 —Al 2 O 3 —Cr 2 O 3 is replaced with ZrO 2 —Al 2 O 3 —Cr 2 O 3 —Ga 2 O 3
- ZrO 2 —Al 2 O 3 —Cr 2 O 3 —In 2 O 3 —Ga 2 O 3 may be used.
- ZrO 2 —Al 2 O 3 —SiO 2 —Cr 2 O 3 is replaced with ZrO 2 —Al 2 O 3 —SiO 2 —Cr 2 O 3 —Ga 2 O 3 , ZrO 2 —Al 2 O 3 —SiO 2.
- ZrO 2 —Cr 2 O 3 —In 2 O 3 or ZrO 2 —Al 2 O 3 —SiO 2 —Cr 2 O 3 —Ga 2 O 3 —In 2 O 3 may be used.
- ZrO 2 —Al 2 O 3 —TiO 2 —Cr 2 O 3 is replaced with ZrO 2 —Al 2 O 3 —TiO 2 —Cr 2 O 3 —Ga 2 O 3 , ZrO 2 —Al 2 O. 3 -TiO 2 -Cr 2 O 3 -In 2 O 3 or ZrO 2 -Al 2 O 3 -TiO 2 -Cr 2 O 3 -Ga 2 O 3 -In 2 O 3 may be used.
- the extinction coefficient kb is maintained without deteriorating the adhesion and heat resistance of the interface layer 336.
- the transparency can be increased by reducing the size of the screen.
- the total content of Ga 2 O 3 and In 2 O 3 in the interface layer 336 is preferably 20 mol% or less. If the contents of Ga 2 O 3 and In 2 O 3 are excessively increased, the content of Cr 2 O 3 is decreased excessively, the heat resistance of the interface layer 336 is decreased, and a decrease in the number of rewrites may be started. Because there is.
- the complex refractive indexes of the interface layer 334 (dielectric layer a) and the interface layer 336 (dielectric layer b) are na-ika and nb-ikb (na: refractive index of the interface layer 334, ka: interface layer 334) More preferably, nb: refractive index of the interface layer 336, kb: extinction coefficient of the interface layer 336), and na ⁇ nb.
- the reflectance ratio Rc / Ra of the third information layer 330 can be further increased. Such a relationship can provide a greater effect especially in a semi-transparent information layer with low reflectance.
- the film thickness of the interface layer 334 is preferably 1 nm or more so that adhesion to the recording layer 335 can be secured and atomic diffusion from the other layers to the recording layer 335 can be suppressed.
- the thickness of the interface layer 334 is preferably 30 nm or less, more preferably 25 nm or less, in combination with the thickness of the dielectric layer 333. Since a highly transparent material is used for the interface layer 334, when the function of the dielectric layer 333 is also used, the thickness may be increased to 30 nm.
- the film thickness of the interface layer 336 is preferably 1 nm or more so that adhesion to the recording layer 335 can be secured and atomic diffusion from the other layers to the recording layer 335 can be suppressed. Moreover, it is preferable to make it thinner as the extinction coefficient kb is larger so as not to exert an optical influence.
- the thickness of the interface layer 336 is preferably 15 nm to 70 nm, more preferably 20 nm to 60 nm, combined with the thickness of the dielectric layer 337.
- the composition of the interface layers 334 and 336 and the dielectric layers 333 and 337 is analyzed by, for example, an X-ray microanalyzer (XMA), an electron beam microanalyzer (EPMA), or Rutherford backscattering analysis (RBS). Can do.
- XMA X-ray microanalyzer
- EPMA electron beam microanalyzer
- RBS Rutherford backscattering analysis
- the interface layers 334 and 336 and the dielectric layers 333 and 337 formed by sputtering include rare gases (Ar, Kr, Xe), moisture (O—H, H), organic matter (C) present in the sputtering atmosphere.
- Air N, O
- components metal of jigs placed in the sputtering chamber, and impurities (metals, semi-metals, semiconductors, dielectrics) contained in the target may inevitably be included.
- the method may detect these components.
- These components (other components other than the components specified as components included in the interface layer in the present invention) have an upper limit of 10 atomic percent when the total atoms contained in the interface layer and the dielectric layer are defined as 100 atomic percent. It may be contained as long as the components of the interface layer excluding other components satisfy the above-mentioned preferred composition ratio.
- the recording layer 335 is formed of a material that undergoes a phase change when irradiated with the laser beam 10, and includes, for example, at least one selected from Ge—Te, Sb—Ge, and Sb—Te. With this material configuration, for example, information can be recorded or reproduced on the third information layer 330 whose capacity is increased to 33.4 GB.
- a GeTe—Sb 2 Te 3 pseudo binary material a GeTe—Bi 2 Te 3 pseudo binary material, an Sb—Te eutectic material, or a Ge—Sb eutectic material can be used. These materials are phase change recording materials having both a high crystallization speed, a large optical change, and a high crystallization temperature.
- the crystallization speed is the relative speed of transition from the amorphous phase to the crystalline phase
- the optical change is the difference between the complex refractive index in the crystalline phase and the complex refractive index in the amorphous phase, the crystallization temperature and Is defined as the temperature at which the amorphous phase transitions to the crystalline phase.
- the GeTe—Sb 2 Te 3 pseudo-binary material includes GeTe containing Ge and Te 1: 1, and Sb 2 Te 3 containing Sb and Te 2: 3, and the crystal structure is a rock salt structure. . Since the rock salt structure has high objectivity, the time required for the reversible phase transition between the amorphous phase and the crystalline phase is shortened, that is, the crystallization rate is high. As the amount of Sb 2 Te 3 increases, the crystallization rate increases relatively.
- the Ge concentration in the GeTe—Sb 2 Te 3 pseudobinary material is preferably 40 atomic% to 48 atomic%.
- the GeTe-Bi 2 Te 3 pseudo-binary material includes GeTe containing Ge and Te 1: 1, and Bi 2 Te 3 containing Bi and Te 2: 3, and also has a rock salt type crystal structure. Have. Since Bi 2 Te 3 is easier to crystallize than Sb 2 Te 3 , the GeTe-Bi 2 Te 3 pseudobinary material has a higher crystallization rate than the GeTe-Sb 2 Te 3 pseudobinary material. . As the amount of Bi 2 Te 3 increases, the crystallization rate increases relatively.
- the GeTe—Bi 2 Te 3 pseudo-binary material is expressed by a composition ratio (atomic%), y (y satisfies 0 ⁇ y ⁇ 100) is used, and (Ge 0.5 Te 0.5 ) y (Bi 0.4 Te 0.6 ) Can be written as 100-y .
- sufficient signal quality may not be obtained if Ge is less than 40 atomic%.
- the Ge concentration range is large because the crystallization speed is high. If 99 ⁇ x, that is, if Ge is included more than 49.5%, the crystallization speed may be insufficient and sufficient rewriting performance may not be obtained. . Therefore, the Ge concentration in the GeTe—Bi 2 Te 3 pseudobinary material is preferably 40 atomic% or more and 49.5 atomic% or less.
- the recording layer 335 is formed by laminating a GeTe—Sb 2 Te 3 pseudo binary material or a GeTe—Bi 2 Te 3 pseudo binary material with Sn 50 Te 50 or Ge a Sn 50-a Te 50. It may be formed. Further, in order to improve the recording and storage reliability, a part of Sb or Bi may be replaced with at least one of Al, Ga, and In, or Al 2 Te 3 , Ga 2 Te 3.
- the recording layer 335 may be formed by laminating with In 2 Te 3 .
- a GeTe—Sb 2 Te 3 pseudo binary material and a GeTe—Bi 2 Te 3 pseudo binary material may be mixed and used as a GeTe—Sb 2 Te 3 —Bi 2 Te 3 material.
- a GeTe—Sb 2 Te 3 pseudobinary material and a GeTe—Bi 2 Te 3 pseudobinary material may be laminated and used. These effective elements may be used in combination.
- the Sb composition ratio can be arbitrarily determined as long as it is within an appropriate composition range, and has a high crystallization speed and a high crystallization temperature.
- Sb itself has a crystallinity that is stronger as it is crystallized in a thin film state even at room temperature, but a system to which Ge is added is preferably used because of poor recording storage reliability and small optical change. Since this system has a relatively high crystallization rate and a high crystallization temperature than the Sb—Te system, it is an excellent material in terms of storage reliability.
- the Sb concentration is preferably 60 atomic% or more. If the Sb concentration is less than 60 atomic%, the crystallization speed may be insufficient and sufficient rewriting performance may not be obtained. On the other hand, if the Sb concentration exceeds 90 atomic%, the record storage reliability may be lowered. Add at least one of Ag, In, Te, B, C, Si, and Zn at a composition ratio of 15 atomic% or less in order to increase the optical change or adjust the crystallization speed. May be.
- M1 represents at least one of Ag, In, N, Ge, B, C, Si, and Zn, and preferably satisfies 0.6 ⁇ z1 ⁇ 0.9 and 80 ⁇ z2 ⁇ 100. .
- the Sb—Te eutectic material can arbitrarily determine the Sb composition ratio within an appropriate composition range, and has a large crystallization speed and a high crystallization temperature.
- Sb itself has a crystallinity that is stronger as it is crystallized in a thin film state even at room temperature, a system to which Te is added is preferably used because of poor recording storage reliability and small optical change.
- an Sb concentration of 60 atomic% or more is preferable. When the Sb concentration is less than 60 atomic%, the crystallization speed is insufficient and sufficient rewriting performance cannot be obtained.
- the recording storage reliability is lowered.
- at least one of Ag, In, and Ge may be added at a composition ratio of 10 atomic% or less.
- at least one of B, C, Si, and Zn may be added at a composition ratio of 10 atomic% or less.
- M1 represents at least one of Ag, In, N, Ge, B, C, Si, and Zn, and preferably 0.6 ⁇ z3 ⁇ 0.9 and 80 ⁇ z4 ⁇ 100.
- composition of the recording layer 335 can be analyzed by, for example, high frequency inductively coupled plasma (ICP) emission spectroscopic analysis, X-ray microanalyzer (XMA), or electron beam microanalyzer (EPMA).
- ICP inductively coupled plasma
- XMA X-ray microanalyzer
- EPMA electron beam microanalyzer
- the recording layer 335 formed by sputtering has a rare gas (Ar, Kr, Xe), moisture (O—H, H), organic matter (C), air (N, O), sputtering chamber present in the sputtering atmosphere.
- the components (metals) of the jig placed on the metal and impurities (metals, metalloids, semiconductors, dielectrics) contained in the target may be inevitably contained. These are analyzed by ICP emission spectroscopic analysis, XMA, EPMA, etc. May be detected. These components (components other than the components specified above as components contained in the recording layer) may be contained up to 10 atomic percent when the total atoms contained in the recording layer are 100 atomic percent.
- the components of the recording layer excluding the other components satisfy the above-described preferable composition ratio. This applies similarly to recording layers 325 and 315 described later, and similarly applies to recording layers 415, 425, 435, 445, 215, 225, and 115 described in the following embodiments.
- the film thickness of the recording layer 335 is preferably 3 nm or more and 8 nm or less. If the thickness exceeds 8 nm, the light transmittance of the third information layer 330 decreases, and if it is less than 3 nm, the optical change of the recording layer 335 decreases. Since the crystallization speed decreases as the thickness of the recording layer decreases, the recording layer 335 preferably uses a composition ratio having a larger crystallization speed than the composition ratio used in the recording layer 325 or the recording layer 315.
- the second information layer 320 includes a dielectric layer 321, a reflective layer 322, a dielectric layer 323, an interface layer 324, a recording layer 325, an interface layer 326, and a dielectric layer 327 on one surface of the intermediate layer 303. It is formed by arranging in this order.
- the second information layer 320 is designed to have a high transmittance so that the laser light 10 can reach the first information layer 310.
- the light transmittance of the second information layer 320 when the recording layer 325 is in the crystalline phase is Tc (%), and the second information layer 320 when the recording layer 325 is in the amorphous phase.
- the light transmittance is Ta (%), it is preferably 47% ⁇ (Ta + Tc) / 2, and more preferably 50% ⁇ (Ta + Tc) / 2.
- the second information layer 320 may be designed such that the transmittance ((Tc + Ta) / 2) is 50%, the reflectance Rc is 7%, and the reflectance Ra is 1%.
- Tc + Ta) / 2 is 50%
- Tc may be 49% and Ta may be 51%.
- Tc may be 50% and Ta may be 52%.
- Tc and Ta are preferably close values, but they may not be equal.
- the dielectric layer 321 has a function similar to that of the dielectric layer 331, and preferred materials are also the same.
- the thickness of the dielectric layer 321 is preferably 10 nm or more and 30 nm or less so that a reflectance ratio of 4 or more and a transmittance of 47% or more can be obtained.
- the dielectric layer 321 may also be composed of two or more layers.
- the reflective layer 322 has a function similar to that of the reflective layer 332, and preferred materials are also the same.
- the film thickness is preferably 5 nm or more and 18 nm or less. If the thickness is less than 5 nm, the function of diffusing heat decreases, and it becomes difficult to form marks on the recording layer 325. On the other hand, if the thickness is larger than 18 nm, the transmittance of the second information layer 320 is less than 47%.
- the dielectric layers 323 and 327 have a function of adjusting Rc, Ra, Tc, and Ta of the second information layer 320 by adjusting the optical path length nd.
- the optical path lengths nd of the dielectric layer 323 and the dielectric layer 327 are strictly calculated by a matrix method so that 47% ⁇ (Ta + Tc) / 2, 7% ⁇ Rc, and Ra ⁇ 1.8% are satisfied. Can be determined.
- the thickness of the dielectric layer 327 is preferably 10 nm to 70 nm, more preferably 20 nm to 60 nm. is there.
- the thickness of the dielectric layer 323 is preferably 2 nm or more and 40 nm or less, and more preferably 5 nm or more and 30 nm or less.
- the material of the dielectric layers 323 and 327 can be selected from the materials of the dielectric layers 333 and 337 described above.
- the dielectric layers 323 and 327 may be provided as necessary, like the dielectric layers 333 and 337.
- the dielectric layer 323 is not necessarily provided.
- the dielectric layer 326 also has the function of the dielectric layer 327, the dielectric layer 327 is not necessarily provided. Is not necessarily provided.
- the interface layer 324 (dielectric layer a) and the interface layer 326 (dielectric layer b) have the same functions as the interface layers 334 and 336, and preferred materials are also the same.
- the film thickness of the interface layer 324 is preferably 1 nm or more so that adhesion to the recording layer 325 can be ensured and atomic diffusion from the other layers to the recording layer 325 can be suppressed.
- the thickness of the interface layer 324 is preferably 50 nm or less, more preferably 40 nm or less, combined with the dielectric layer 323. Since a highly transparent material is used for the interface layer 324, the interface layer 324 may be thickened to 50 nm in order to function as the dielectric layer 323.
- the thickness of the interface layer 326 is preferably 1 nm or more so that adhesion to the recording layer 325 can be secured and atomic diffusion from the other layers to the recording layer 325 can be suppressed.
- the thickness of the interface layer 326 is preferably 10 nm or more and 80 nm or less, and more preferably 20 nm or more and 70 nm or less, in combination with the thickness of the dielectric layer 327.
- the recording layer 325 has the same function as the recording layer 335. Further, since the second information layer 320 requires a transmittance of 47% or more, the thickness of the recording layer 325 is preferably 3 nm or more and 9 nm or less. When the thickness exceeds 9 nm, the light transmittance of the second information layer 320 decreases, and when it is less than 3 nm, the optical change of the recording layer 325 decreases. Since the crystallization speed of the recording layer decreases as the film thickness decreases, the recording layer 325 preferably uses a composition having a larger crystallization speed than the composition used for the recording layer 315.
- the reflective layer 312, the dielectric layer 313, the interface layer 314, the recording layer 315, the interface layer 316, and the dielectric layer 317 are arranged in this order on one surface of the substrate 301. Is formed by.
- the first information layer 310 information is recorded / reproduced by the laser beam 10 attenuated after passing through the third information layer 330 and the second information layer 320. Therefore, it is necessary to record within the output laser power range and to detect the signal with the reproduction power. Therefore, unlike the semi-transparent third information layer 330 and the second information layer 320, it is designed to have a high reflectance and a high light absorption rate. For example, to obtain an effective Rc-g of at least 1.5%, Rc-g is 19% or more, and Rc is about 24% or more.
- the reflective layer 312 has the same function as the reflective layer 332. However, since the first information layer 310 does not need to be translucent, the thickness of the reflective layer 312 can be increased, and the choice of preferred materials increases. For example, a metal selected from Al, Au, Ag, and Cu or an alloy thereof can be used. A material in which other elements are added to the above metal or alloy in order to improve its moisture resistance or adjust its thermal conductivity or optical properties (for example, light reflectance, light absorption or light transmittance). May be used.
- the additive elements are Mg, Ca, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru, Os, Co, Rh, Ni, Pd, Pt, Zn , B, Ga, In, C, Si, Ge, Sn, N, Sb, Bi, O, Te, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y And at least one selected from Lu is preferred. At this time, the addition concentration is preferably 3 atomic% or less.
- the reflection layer 312 has a small light absorption at the wavelength of the laser beam 10 used so as to increase the amount of light absorbed by the recording layer 315.
- a reflective layer 312 containing 97 atomic% or more of Ag is preferably used for the first information layer 310.
- alloy materials such as Ag—Pd, Ag—Cu, Ag—Bi, Ag—Ga—Cu, Ag—In—Sn, Ag—Pd—Cu, and Ag—Pd—Ti can be used. Of these, Ag—Pd—Cu is excellent in moisture resistance and is more preferably used.
- the reflective layer 312 may be formed of two or more layers.
- the substrate 301 may be a layer made of a dielectric material.
- the thickness of the reflective layer 312 is adjusted according to the linear velocity of the medium used and the composition of the recording layer 315, and is preferably 40 nm or more and 300 nm or less.
- the rapid cooling condition is insufficient, the heat of the recording layer is difficult to diffuse, and the recording layer is difficult to become amorphous.
- it is thicker than 300 nm the rapid cooling condition becomes excessive, the heat of the recording layer 315 is excessively diffused, and the recording sensitivity is deteriorated (that is, a larger laser power is required).
- the dielectric layer 313 and the dielectric layer 317 have the same functions as the dielectric layer 333 and the dielectric layer 337, respectively.
- a matrix method for example, “Wave Optics” Iwanami Shinsho, written by Hiroshi Kubota, for example
- Rc can be increased
- Rc / Ra can be increased
- Ac light absorption rate of the recording layer 315 in the crystalline phase
- the thickness of each layer is set so that the first information layer 310 satisfies 28% Rc and 4% Ra.
- the thickness of the dielectric layer 313 is preferably 30 nm or less, and more preferably 5 nm or more and 20 nm or less.
- the thickness of the dielectric layer 317 is preferably 30 nm to 130 nm, and more preferably 30 nm to 100 nm.
- the dielectric layer 313 and the dielectric layer 317 can be provided as necessary, similarly to the dielectric layer 333 and the dielectric layer 337.
- the dielectric layer 313 is not necessarily provided.
- the dielectric layer 313 is not necessarily provided.
- the layer 317 is not necessarily provided.
- the interface layer 314 (dielectric layer a) and the interface layer 316 (dielectric layer b) have the same functions as the interface layers 334 and 336, and preferred materials are also the same.
- the film thickness of the interface layer 314 is preferably 1 nm or more so that adhesion to the recording layer 315 can be ensured and atomic diffusion from the other layers to the recording layer 315 can be suppressed.
- the thickness of the interface layer 314 is preferably 40 nm or less, more preferably 5 nm or more and 30 nm or less, in combination with the dielectric layer 313. Since a highly transparent material is used for the interface layer 314, the interface layer 314 may be thickened to 40 nm in order to function as the dielectric layer 313.
- the film thickness of the interface layer 316 is preferably 1 nm or more so that adhesion to the recording layer 315 can be ensured and atomic diffusion from the other layers to the recording layer 315 can be suppressed. Moreover, it is preferable to make it thinner as the extinction coefficient is larger so as not to affect optically.
- the thickness of the interface layer 316 is preferably 30 nm to 140 nm, and more preferably 30 nm to 110 nm, in combination with the dielectric layer 317.
- the recording layer 315 has the same function as the recording layer 335, and preferred materials are also the same.
- the film thickness of the recording layer 315 is preferably 7 nm or more and 16 nm or less. If it exceeds 16 nm, the heat capacity increases and the laser power required for recording increases. In addition, the heat generated in the recording layer 315 is difficult to diffuse in the direction of the reflective layer 312 and it is difficult to form small recording marks necessary for high-density recording. If it is thinner than 7 nm, the reflectance Ra is increased, and Rc / Ra is decreased, making it difficult to obtain a good read signal.
- the dielectric layer a and the dielectric layer b in the present invention may be included in at least one information layer. Preferably, it is contained in a semitransparent information layer.
- the dielectric layer a and the dielectric layer b in the present invention may be applied to all of the included information layers. That is, the interface layers 334, 324, and 314 may correspond to the dielectric layer a in the present invention, and the interface layers 336, 326, and 316 may correspond to the dielectric layer b in the present invention.
- the dielectric layer a and the dielectric layer b are dielectric materials that exhibit excellent adhesion to the chalcogen-based recording layer, and can be a reversible phase change recording layer (rewritable type) or an irreversible phase. It can also be used together with a recording layer (recordable type) that can cause a change.
- An oxide containing at least one of them, a material in which two or more layers are stacked and alloyed or reacted at the time of recording, or an organic dye-based recording material may be used.
- the first information layer 310 does not necessarily include the dielectric layer a or the dielectric layer b. There is no need, for example, a read-only information layer may be used.
- the third information layer 330 includes the dielectric layer a and the dielectric layer b in the present invention
- the second information layer 320 and the first information layer 310 do not necessarily include the dielectric layer a or the dielectric layer b.
- the second information layer 320 may be a write-once information layer
- the first information layer 310 may be a read-only information layer.
- the read-only information layer includes a material containing at least one of a metal element, a metal alloy, a dielectric, a dielectric compound, a semiconductor element, and a metalloid element as a reflective layer on a pre-formed recording pit. Etc. may be formed.
- a reflective layer containing Ag or an Ag alloy may be formed, or the dielectric layer a or the dielectric layer b in the present invention may be formed.
- a magneto-optical recording layer may be formed on the first information layer 310.
- it may be an information recording medium including five or more information layers. The effects of the present invention can be obtained regardless of these modes.
- the information recording medium 300 can be either Constant Linear Velocity (CLV) with a constant linear velocity or Constant Angular Velocity (CAV) with a constant rotation speed.
- CLV Constant Linear Velocity
- CAV Constant Angular Velocity
- an optical system in which the numerical aperture NA of the objective lens is 0.85 is preferably used, but recording / reproduction may be performed using an optical system with NA> 1.
- NA the numerical aperture
- SIL solid immersion lens
- SIM solid immersion mirror
- the intermediate layer and the transparent layer may be formed with a thickness of 5 ⁇ m or less.
- the information recording medium 300 includes a first information layer 310, an intermediate layer 303, a second information layer 320, an intermediate layer 304, a third information layer 330, and a transparent layer 302 on a substrate 301 serving as a support. It is obtained by forming in order.
- the substrate 301 on which guide grooves (groove surface and land surface) are formed is placed in a sputtering apparatus, and a reflective layer 312, a dielectric layer 313, an interface layer 314, and a recording layer 315 are formed on the surface of the substrate 301 on which the guide grooves are formed.
- the interface layer 316 and the dielectric layer 317 are formed in this order.
- the first information layer 310 is formed on the substrate 301.
- the substrate 301 on which the first information layer 310 is formed is taken out from the sputtering apparatus, and the intermediate layer 303 is formed.
- the intermediate layer 303 is formed by the following procedure. First, an ultraviolet curable resin is applied to the surface of the dielectric layer 317 by, for example, spin coating. Next, the concavo-convex forming surface of the polycarbonate substrate having the concavo-convex complementary to the guide groove to be formed in the intermediate layer 303 is adhered to the ultraviolet curable resin. In this state, the resin is cured by irradiating ultraviolet rays, and then the polycarbonate substrate having unevenness is peeled off. Thereby, guide grooves having a shape complementary to the irregularities are formed in the ultraviolet curable resin, and the intermediate layer 303 having the guide grooves to be formed is formed.
- the shapes of the guide grooves formed on the substrate 301 and the guide grooves formed on the intermediate layer 303 may be the same or different.
- the intermediate layer 303 may be formed by forming a layer that protects the dielectric layer 317 with an ultraviolet curable resin and forming a layer having a guide groove thereon. In that case, the obtained intermediate layer 303 has a two-layer structure.
- the intermediate layer 303 may have a configuration in which three or more layers are stacked.
- the intermediate layer 303 may be formed by a printing method, an inkjet method, or a casting method.
- the substrate 301 formed up to the intermediate layer 303 is again placed in the sputtering apparatus, and the dielectric layer 321, the reflective layer 322, the dielectric layer 323, the interface layer 324, the recording layer are formed on the surface of the intermediate layer 303 having the guide groove. 325, the interface layer 326, and the dielectric layer 327 are formed in this order. As a result, the second information layer 320 is formed on the intermediate layer 303.
- the substrate 301 on which the second information layer 320 is formed is taken out from the sputtering apparatus, and the intermediate layer 304 is formed in the same manner as the intermediate layer 303.
- the substrate 301 formed up to the intermediate layer 304 is again placed in the sputtering apparatus, and the dielectric layer 331, the reflective layer 332, the dielectric layer 333, the interface layer 334, the recording layer are formed on the surface of the intermediate layer 304 having the guide groove. 335, the interface layer 336, and the dielectric layer 337 are formed in this order.
- the third information layer 330 is formed on the intermediate layer 304.
- the substrate 301 formed up to the third information layer 330 is taken out from the sputtering apparatus. Then, a transparent layer 302 is formed on the surface of the dielectric layer 337.
- the transparent layer 302 is formed by the following procedure.
- a transparent layer 302 having a target thickness can be formed by applying an ultraviolet curable resin to the surface of the dielectric layer 337 by, for example, a spin coating method and irradiating the ultraviolet ray to cure the resin.
- an ultraviolet curable resin is applied to the surface of the dielectric layer 337 by a spin coating method, a disk-shaped sheet is adhered to the applied ultraviolet curable resin, and the resin is cured by irradiating ultraviolet rays from the sheet side.
- the transparent layer 302 can also be formed.
- the transparent layer 302 can be formed by sticking a disk-shaped sheet having an adhesive layer.
- the transparent layer 302 may be composed of a plurality of layers having different physical properties, and the transparent layer 302 may be formed after providing another transparent layer on the surface of the dielectric layer 337. Alternatively, after forming the transparent layer 302 on the surface of the dielectric layer 337, another transparent layer may be formed on the surface of the transparent layer 302.
- the plurality of transparent layers may be different in viscosity, hardness, refractive index, and transparency. In this way, the transparent layer 302 is formed.
- the first information layer 310, the second information layer 320, and the third information layer 330 are initialized as necessary.
- Initialization is a step of crystallizing the amorphous recording layers 315, 325, and 335 by, for example, irradiating a semiconductor laser and raising the temperature to a crystallization temperature or higher.
- a good initialization can be performed.
- the initialization may be performed after the formation of the transparent layer 302 or may be performed before the formation.
- the recording layer 315 may be initialized after the first information layer 310 is formed, and the recording layer 325 may be initialized after the intermediate layer 303 and the second information layer 320 are formed.
- the effect of the present invention does not depend on the timing of performing initialization.
- the reflective layers 312, 322, and 332 are formed by sputtering a target containing a metal or alloy that constitutes the reflective layer. Sputtering may be performed using a direct current power source or a high frequency power source in a rare gas atmosphere or in a mixed gas atmosphere of oxygen gas and / or nitrogen gas and rare gas.
- the rare gas may be any of Ar gas, Kr gas, and Xe gas.
- the dielectric layers 313, 317, 321, 323, 327, 331, 333 and 337 are formed by sputtering a sputtering target containing an element, a mixture or a compound constituting the dielectric layer.
- Sputtering may be performed using a high-frequency power source in a rare gas atmosphere or in a mixed gas atmosphere of oxygen gas and / or nitrogen gas and rare gas. If possible, a DC power supply or a pulse generating DC power supply may be used.
- the rare gas may be any of Ar gas, Kr gas, and Xe gas.
- oxygen When forming a dielectric layer containing an oxide, oxygen may be deficient during sputtering. Therefore, use a target that suppresses oxygen deficiency, or use a small amount of oxygen gas of 10% or less as a rare gas.
- Sputtering may be performed in a mixed atmosphere.
- the interface layers 314, 316, 324, 326, 334, and 336 are formed by sputtering a sputtering target containing an element, a mixture, or a compound that constitutes the interface layer.
- Sputtering may be performed using a high-frequency power source in a rare gas atmosphere or in a mixed gas atmosphere of oxygen gas and / or nitrogen gas and rare gas. If possible, a DC power supply or a pulse generating DC power supply may be used.
- the rare gas may be any of Ar gas, Kr gas, and Xe gas.
- the material and composition of the sputtering target are determined so that the interface layer can be formed from the materials of the dielectric layer a and the dielectric layer b in the present invention.
- the composition of the sputtering target and the composition of the interface layer to be formed may not match, and in this case, the composition of the sputtering target can be adjusted to obtain the interface layer having the target composition.
- oxygen may be deficient in oxygen during sputtering, a target with suppressed oxygen deficiency may be used, or sputtering may be performed in an atmosphere in which a small amount of oxygen gas of 10% or less is mixed with a rare gas. .
- (Al 2 O 3 ) 70 (Cr 2 O 3 ) 30 (mol%) when an interface layer represented by (Al 2 O 3 ) 70 (Cr 2 O 3 ) 30 (mol%) is formed, (Al 2 O 3 ) 70 (Cr 2 O 3 ) 30 (mol%) Sputtering may be performed using a sputtering target represented in a rare gas atmosphere or an atmosphere in which a small amount of oxygen gas is mixed with a rare gas.
- the interface layer can also be formed by simultaneously sputtering each sputtering target of a single compound using a plurality of power supplies.
- the interface layer can also be formed by simultaneously sputtering a binary target, a ternary target, or the like in which two or more compounds are combined using a plurality of power supplies. Even when these sputtering targets are used, the sputtering may be performed in a rare gas atmosphere or a mixed gas atmosphere of oxygen gas and / or nitrogen gas and rare gas.
- the recording layers 315, 325 and 335 are formed by sputtering a sputtering target containing a material constituting the recording layer.
- Sputtering may be performed in a rare gas atmosphere or a mixed gas atmosphere of oxygen gas and / or nitrogen gas and rare gas using a direct current power source, a high frequency power source, or a pulse generation direct current power source.
- the rare gas may be any of Ar gas, Kr gas, and Xe gas.
- the composition of the sputtering target may not match the composition of the recording layer to be formed. In this case, the recording layer having the target composition can be obtained by adjusting the composition of the sputtering target.
- a recording layer having a target composition can be obtained by adjusting the output of each power source and controlling the composition.
- the target composition is adjusted by adjusting the flow rate and pressure of oxygen gas and nitrogen gas, the flow rate ratio and pressure ratio with noble gas. Recording layer can be obtained.
- a sputtering method is used as a method for forming each layer in this embodiment mode, the present invention is not limited to this, and a vacuum evaporation method, an ion plating method, a chemical vapor deposition (CVD) method, or a molecular beam is used. It is also possible to use an epitaxy (MBE) method or the like.
- the information recording medium 300 of Embodiment 1 can be manufactured.
- the information recording medium of the present invention can obtain the effect regardless of the structure of the information recording medium if the dielectric layer a and the dielectric layer b of the present invention are applied to the layer in contact with the recording layer.
- the transparent layer 302 is a transparent support substrate
- the third information layer 330, the intermediate layer 304, the second information layer 320, the intermediate layer 303, and the first information layer 310 are arranged in this order on the support substrate.
- the structure of the present invention can also be applied to a structure in which the substrate 312 is finally bonded with an ultraviolet curable resin or the like.
- the position where the substrate is bonded may be the position of any intermediate layer. The same applies to the following second to fourth embodiments.
- FIG. 2 shows a partial cross section of the information recording medium 400.
- the information recording medium 400 includes a first information layer 410, an intermediate layer 403, a second information layer 420, an intermediate layer 404, a third information layer 430, an intermediate layer 405, and a fourth information layer 440 on a substrate 401.
- the transparent layer 402 is formed by arrange
- positioning in order. That is, the information recording medium 400 of the present embodiment is an information recording medium including N information layers (N is an integer of 2 or more), and corresponds to the case where N 4.
- the dielectric layer a and the dielectric layer b in the present invention are applied to all of the first information layer 410 to the fourth information layer 440, all the information layers are the information of the present invention. Although it corresponds to the Lth information layer of the recording medium, the present invention is not limited to this, and at least one of the first information layer 410 to the fourth information layer 430 may correspond to the Lth information layer. .
- a reflective layer 412, a dielectric layer 413, an interface layer 414, a recording layer 415, an interface layer 416, and a dielectric layer 417 are arranged in this order on one surface of the substrate 401. Is formed by.
- the second information layer 420 includes a dielectric layer 421, a reflective layer 422, a dielectric layer 423, an interface layer 424, a recording layer 425, an interface layer 426, and a dielectric layer 427 on one surface of the intermediate layer 403. It is formed by arranging in this order.
- the third information layer 430 includes a dielectric layer 431, a reflective layer 432, a dielectric layer 433, an interface layer 434, a recording layer 435, an interface layer 436, and a dielectric layer 437 on one surface of the intermediate layer 404. It is formed by arranging in this order.
- the fourth information layer 440 includes a dielectric layer 441, a reflective layer 442, a dielectric layer 443, an interface layer 444, a recording layer 445, an interface layer 446, and a dielectric layer 447 on one surface of the intermediate layer 405. It is formed by arranging in this order.
- the first information layer 410 to the third information layer 430 correspond to the first information layer 310 to the third information layer 330 of Embodiment 1, and the arrangement order of each layer is the same, and the functions and materials are also the same. It is.
- the fourth information layer 440 also corresponds to the third information layer 330 of Embodiment 1, and the arrangement order of the layers is the same, and the functions and materials are the same.
- the film thickness of each layer may be optimized so as to satisfy a desired effective reflectance. As in the first embodiment, the thicknesses of the intermediate layers 403, 404, and 405 are optimized so that no interference occurs between the information during recording and reproduction.
- the dielectric layer a of the present invention corresponds to the interface layers 414, 424, 434, 444, and the dielectric layer b corresponds to the interface layers 416, 426, 436, 446. Even if the number of information layers increases, the effect of the present invention is the same as that of the first embodiment.
- the laser beam 10 is incident from the transparent layer 402 side.
- Information recording / reproduction with respect to the first information layer 410 is performed by the laser light 10 that has passed through the fourth information layer 440, the third information layer 430, and the second information layer 420.
- information can be recorded on each of the four recording layers.
- an information recording medium having a capacity of 133 GB, which is about 1.3 times that of the first embodiment, can be obtained by using a laser beam in a blue-violet region near a wavelength of 405 nm for recording and reproduction.
- the information recording medium 400 may also be used with CLV or CAV specifications.
- the configuration in which the dielectric layer a and the dielectric layer b in the present invention are applied to all of the first information layer 410 to the fourth information layer 440 has been described.
- the present invention is not limited to this.
- the dielectric layer a and the dielectric layer b in the present invention may be applied to at least one information layer. Preferably, it is contained in a semitransparent information layer.
- FIG. 3 shows a partial cross section of the information recording medium 200.
- N is an integer of 2 or more
- the dielectric layer a and the dielectric layer b are applied to both the first information layer 210 and the second information layer 220, all the information layers are included in the information recording medium of the present invention.
- the present invention is not limited to this, and at least one of the first information layer 210 and the second information layer 220 may correspond to the Lth information layer.
- a reflective layer 212, a dielectric layer 213, an interface layer 214, a recording layer 215, an interface layer 216, and a dielectric layer 217 are arranged in this order on one surface of the substrate 201. Is formed by.
- the second information layer 220 includes a dielectric layer 221, a reflective layer 222, a dielectric layer 223, an interface layer 224, a recording layer 225, an interface layer 226, and a dielectric layer 227 on one surface of the intermediate layer 203. It is formed by arranging in this order.
- the first information layer 210 and the second information layer 220 correspond to the first information layer 310 and the second information layer 320 of Embodiment 1, and the arrangement order of each layer is the same, and the functions and materials are the same. It is.
- the film thickness of each layer may be optimized so as to satisfy a desired effective reflectance.
- the thickness of the intermediate layer 203 is optimized so that no interference occurs between the information during recording and reproduction.
- the dielectric layer a of the present invention corresponds to the interface layers 214 and 224, and the dielectric layer b corresponds to the interface layers 216 and 226. Even if the number of information layers is reduced, the effect of the present invention is the same as that of the first embodiment.
- the laser beam 10 is incident from the transparent layer 202 side.
- Information recording / reproduction with respect to the first information layer 210 is performed by the laser beam 10 that has passed through the second information layer 220.
- information can be recorded in each of the two recording layers.
- an information recording medium having a capacity of 67 GB, which is approximately 0.67 times that of the first embodiment, can be obtained by using laser light in a blue-violet region near a wavelength of 405 nm for recording and reproduction.
- the information recording medium 200 may also be used with CLV or CAV specifications.
- the configuration in which the first information layer 210 and the second information layer 220 include the dielectric layer a and the dielectric layer b in the present invention has been described.
- the present invention is not limited to this.
- the dielectric layer a and the dielectric layer b in the present invention may be included in at least one information layer.
- it may be included in the second information layer 220 which is a translucent information layer.
- FIG. 4 shows a partial cross section of the information recording medium 100.
- the information recording medium 100 is formed by arranging an information layer 110 and a transparent layer 102 on a substrate 101 in this order.
- the information layer 110 includes a reflective layer 112, a dielectric layer 113, an interface layer 114, a recording layer 115, an interface layer 116, and a dielectric layer 117 arranged in this order on one surface of the substrate 101. Is formed.
- the information recording medium 100 can be used as a Blu-ray Disc having a capacity of 25 GB or more, for example, for recording and reproducing information with the laser beam 10 in the blue-violet region near the wavelength of 405 nm.
- the information recording medium 100 having this configuration is irradiated with the laser beam 10 from the transparent layer 102 side, thereby recording and reproducing information.
- the information layer 110 corresponds to the first information layer 310 of the first embodiment, the arrangement order of each layer is the same, and the function and material are also the same. What is necessary is just to optimize the film thickness of each layer so that a desired reflectance may be satisfy
- the dielectric layer a of the present invention corresponds to the interface layer 114, and the dielectric layer b corresponds to the interface layer 116. Even in an information recording medium composed of one information layer, the obtained effect of the present invention is the same as in the first embodiment.
- Example 1 In Example 1, for the materials used for the dielectric layer a and the dielectric layer b, the optical constant (complex refractive index) in light having a wavelength of 405 nm (dielectric layer a: na-ika (na: refractive index, ka: extinction) Attenuation coefficient) and dielectric layer b: nb-ikb (nb: refractive index, kb: extinction coefficient)) were experimentally investigated.
- the sample for calculating the optical constant was prepared by forming a dielectric layer having a thickness of about 20 nm on a quartz substrate by sputtering.
- Sample numbers 1-1 to 1-10 are materials for the dielectric layer a, and sample numbers 1-11 to 1-25 are materials for the dielectric layer b.
- a sample having a composition of (ZrO 2 ) 20 (Cr 2 O 3 ) 80 was prepared as a comparative example.
- each sample As the sputtering target, those having the same composition notation as the composition notation of each dielectric layer shown in (Table 1-1) to (Table 1-3) were used. For example, if the sample 1-1, (Al 2 O 3) 80 by (Cr 2 O 3) 20 sputtering a sputtering target, labeled (mol%) and, (Al 2 O 3) 80 (Cr 2 O 3 ) A dielectric layer a expressed as 20 (mol%) was formed.
- the sputtering target had a diameter of 200 mm and a thickness of 6 mm, and was attached to the cathode of an RF (high frequency) power source of the sputtering apparatus.
- a jig on which a quartz substrate (12 mm ⁇ 18 mm ⁇ 1.1 mm thickness) is set is mounted in a vacuum chamber so as to face the sputtering target, and a power of 3 kW is applied in an Ar gas atmosphere of 0.13 Pa.
- Each dielectric layer was deposited on a quartz substrate by sputtering.
- Table 1-1 shows the results of materials used as the dielectric layer a.
- Table 1-2 shows the results of materials used as the dielectric layer b.
- Table 1-3 shows the results of the material containing oxide L used as the dielectric layer b.
- the composition represented by (AO 2 ) p (Cr 2 O 3 ) t (L) 100-pt (mol%) converted to A k Cr m X n O 100-kmn (atomic%) is also described. .
- Sample numbers 1-12 to 1-15 were kb ⁇ 0.07, and were more preferable materials. As shown in Sample Nos. 1-12 and 1-13, when HfO 2 was included, kb was slightly reduced. Further, as shown in sample numbers 1-14 and 1-15, when replacing a part of Cr 2 O 3 by In 2 O 3 or Ga 2 O 3, kb is further reduced, decreased to 0.05 or less .
- the dielectric layer b Since the dielectric layer b requires high heat resistance in addition to excellent adhesion with the recording layer, it contains at least one element A selected from Zr and Hf, Cr, and O. In this composition, since the Cr concentration is higher than that of the dielectric layer a, the extinction coefficient of the dielectric layer b is larger than that of the dielectric layer a.
- Example 2 In Example 2, the information recording medium 300 of FIG. 1 was manufactured, and the relationship between the adhesion of the recording layer 325 and the material of the interface layer 324 (dielectric layer a) of the second information layer 320 was examined.
- the interface layer 326 corresponding to the dielectric layer b (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) having excellent adhesion to the recording layer 325 is used, and for the interface layer 324, (Al 2 O 3 ) h (Cr 2 O 3 ) 100-h (mol%) was used.
- each layer As the substrate 301, a polycarbonate substrate (diameter 120 mm, thickness 1.1 mm) on which guide grooves (depth 20 nm, groove-to-groove 0.32 ⁇ m) were formed was prepared and mounted in a sputtering apparatus. On the surface of the substrate 301 where the guide groove is formed, an Ag—Pd—Cu alloy is formed as a reflective layer 312 with a thickness of 100 nm, and a dielectric layer 313 is formed of (ZrO 2 ) 40 (SiO 2 ) 40 (Cr 2 O 3 ) 20 (mol%).
- (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) is 5 nm thick as the interface layer 314, and Ge 45 Sb 4 Te 51 (atomic%) is 12 nm thick as the recording layer 315.
- As the interface layer 316, (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) has a thickness of 5 nm, and as the dielectric layer 317, (ZnS) 80 (SiO 2 ) 20 (mol%) has a thickness of 60 nm. Laminated. Thus, the first information layer 310 was formed.
- an intermediate layer 303 having guide grooves was formed on the surface of the dielectric layer 317 to a thickness of 25 ⁇ m.
- Bi 4 Ti 3 O 12 is 20 nm thick as the dielectric layer 321
- Ag—Pd—Cu alloy is 9 nm thick as the reflective layer 322
- Al 2 O is used as the dielectric layer 323.
- 3 is 10 nm thick
- the interface layer 324 is 5 nm thick
- the recording layer 325 is Ge 45 Sb 3 In 1 Te 51 is 7 nm thick
- the interface layer 326 is (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%).
- the second information layer 320 was formed.
- the interface layer 324 was produced using the media sample numbers 2-1 to 2-7 shown in (Table 2). In Comparative Examples 2 to 4, the materials shown in (Table 2) were used.
- an intermediate layer 304 having a guide groove was formed on the surface of the dielectric layer 327 with a thickness of 18 ⁇ m.
- Bi 4 Ti 3 O 12 is 15 nm thick as the dielectric layer 331
- Ag—Pd—Cu alloy is 8 nm thick as the reflective layer 332
- Al 2 O is used as the dielectric layer 333.
- 3 is 6 nm thick
- (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) is 5 nm thick as the interface layer 334
- Ge 45 Bi 3 In 1 Te 51 is 6 nm thick as the recording layer 335.
- All the sputtering targets used had a round shape, a diameter of 200 mm, and a thickness of 6 mm.
- the dielectric layers 321 and 331 have a Bi 4 Ti 3 O 12 target of 2 kW using a high frequency power source in a mixed gas atmosphere in which the volume ratio of Ar gas and O 2 gas at a pressure of 0.13 Pa is 97: 3. Sputtered with output to form.
- the reflective layer 312 was formed by sputtering an Ag—Pd—Cu alloy target in an Ar gas atmosphere at a pressure of 0.2 Pa using a DC power source with an output of 2 kW.
- the reflective layers 322 and 332 were formed by sputtering an Ag—Pd—Cu alloy target in an Ar gas atmosphere at a pressure of 0.2 Pa using a direct current power source with an output of 200 W.
- the dielectric layer 313 is formed by using a (ZrO 2 ) 40 (SiO 2 ) 40 (Cr 2 O 3 ) 20 (mol%) target in an Ar gas atmosphere at a pressure of 0.13 Pa at a power of 3 kW using a high frequency power source. It was formed by sputtering.
- the dielectric layers 317, 327, and 337 are obtained by sputtering a (ZnS) 80 (SiO 2 ) 20 (mol%) target in an Ar gas atmosphere at a pressure of 0.13 Pa using a high frequency power source with an output of 2.5 kW. Formed.
- the interface layers 314, 316, 326, 334, and 336 are 3 kW of a (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) target using a high frequency power source in an Ar gas atmosphere at a pressure of 0.13 Pa. Sputtered with output.
- the interface layer 324 is formed by sputtering a sputtering target having the same composition notation as the composition of the interface layer 324 shown in (Table 2) in an Ar gas atmosphere at a pressure of 0.13 Pa and using a high frequency power source at an output of 3 kW. did.
- the recording layer 315 was formed by sputtering a Ge—Sb—Te alloy target in an Ar gas atmosphere at a pressure of 0.13 Pa using a pulse generation type DC power source with an output of 200 W.
- the recording layer 325 was formed by sputtering a Ge—Sb—In—Te alloy target in an Ar gas atmosphere at a pressure of 0.13 Pa using a pulse generation type DC power source with an output of 200 W.
- the recording layer 335 was formed by sputtering a Ge—Bi—In—Te alloy target in an Ar gas atmosphere at a pressure of 0.13 Pa using a pulse generation type DC power source with an output of 200 W.
- the substrate 301 having the third information layer 330 formed on the intermediate layer 304 was taken out of the sputtering apparatus. And the ultraviolet curable resin was apply
- the transparent layer 302 After the formation of the transparent layer 302, initialization was performed. Using a semiconductor laser having a wavelength of 810 nm, the recording layers 315, 325, and 335 of the information recording medium 300 were crystallized over almost the entire surface in an annular region having a radius of 22 to 60 mm.
- the intermediate layer 303 was formed by the following procedure. First, an ultraviolet curable resin was applied to the surface of the dielectric layer 317 by spin coating. Next, the unevenness forming surface of the polycarbonate substrate having unevenness (depth 20 nm, groove-to-groove 0.32 ⁇ m) complementary to the guide groove to be formed in the intermediate layer 303 was brought into close contact with the ultraviolet curable resin. In this state, the resin was cured by irradiating with ultraviolet rays, and then the polycarbonate substrate having unevenness was peeled off. As a result, a guide groove having the same shape as the substrate 301 was formed on the surface of the intermediate layer 303. The intermediate layer 304 was also formed on the surface of the dielectric layer 327 in the same procedure.
- the adhesion of the interface layer 324 in the second information layer 320 of the information recording medium 300 was evaluated based on the presence or absence of peeling under high temperature and high humidity conditions. Specifically, the initialized information recording medium 300 is left in a constant temperature and humidity chamber maintained at a temperature of 85 ° C. and a relative humidity of 85%, and after 50 hours, 100 hours, 200 hours, and 300 hours. The sample was taken out and visually examined using an optical microscope. When the reflected light is observed from the transparent layer 302 side through the third information layer 330, the peeling appears as round or elliptical interference fringes. As a matter of course, a sample without peeling is evaluated as having good adhesion, and a sample with peeling is evaluated as being poor in adhesion.
- ⁇ and ⁇ at each time of the adhesion verification test indicate that no peeling occurred and ⁇ represents that peeling occurred.
- x is peeled off in 50 hours
- ⁇ is peeled off in 50 hours (however, peeled off in 200 hours)
- ⁇ is not peeled off in 200 hours (however, 300 hours)
- ⁇ indicates no occurrence of peeling for 300 hours or more. If peeling does not occur in 200 hours, it can withstand practical use. Those in which peeling occurs in less than 50 hours are not practical. Even if peeling occurs in 200 hours, if peeling does not occur in 50 hours, the indoor environment can be used.
- the extinction coefficient ka is preferably 0.07 or less, and more preferably 0.04 or less. If it exceeds 0.1, the effect of increasing Rc / Ra cannot be obtained, which is not preferable. Therefore, x, ⁇ , ⁇ and ⁇ of evaluation are 0.1 ⁇ ka, ⁇ is 0.07 ⁇ ka ⁇ 0.1, ⁇ is 0.04 ⁇ ka ⁇ 0.07, and ⁇ is ka ⁇ 0. .04.
- x, ⁇ , and ⁇ are x evaluations for either adhesion or complex refractive index
- ⁇ is ⁇ evaluation for either adhesion or complex refractive index
- ⁇ is either adhesion or complex refractive index
- ⁇ is either adhesion or complex refractive index
- a comprehensive evaluation of ⁇ or ⁇ is practical, and the composition of the interface layer 324 for which ⁇ evaluation is obtained is more preferable.
- x does not endure practical use. Therefore, 50 ⁇ h ⁇ 100 is preferable in (Al 2 O 3 ) h (Cr 2 O 3 ) 100-h (mol%) (with emphasis on complex refractive index evaluation). More preferably, 50 ⁇ h ⁇ 80.
- Example 3 In Example 3, the information recording medium 300 shown in FIG. 1 was manufactured, and the adhesion relationship between the material of the interface layer 326 (dielectric layer b) of the second information layer 320 and the recording layer 325 was examined. Except for the interface layer 324 and the interface layer 326, the information recording medium 300 manufactured in Example 2 was used. In order to accurately investigate the adhesion between the interface layer 326 and the recording layer 325, the interface layer 324 corresponding to the dielectric layer a has (ZrO 2 ) 50 (Cr 2 ) that is superior in adhesion to the recording layer 325. O 3 ) 50 (mol%) was used. (ZrO 2 ) j (Cr 2 O 3 ) 100-j (mol%) was used for the interface layer 326. In either case, the film thickness was 5 nm.
- the interface layer 324 was formed by sputtering a (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) target in an Ar gas atmosphere at a pressure of 0.13 Pa using a high frequency power source at an output of 3 kW.
- the interface layer 326 was produced using the media sample numbers 3-1 to 3-7 shown in (Table 3). In Comparative Examples 5 and 6, the materials shown in (Table 3) were used. In either case, a sputtering target having the same composition notation as that of the interface layer 326 was formed by sputtering at a power of 3 kW using a high frequency power source in an Ar gas atmosphere having a pressure of 0.13 Pa. The comparative example was also formed under similar sputtering conditions.
- the adhesion was evaluated according to the adhesion evaluation method of Example 1.
- the complex refractive index was also calculated in the same manner as in Example 1.
- the definitions of x and ⁇ for each time of the adhesion verification test and x, ⁇ , ⁇ , and ⁇ for evaluation are the same as in Example 2.
- the interface layer 326 (dielectric layer b) has a larger extinction coefficient than the interface layer 324 (dielectric layer a). Therefore, the definition of the evaluation of the complex refractive index is different from that in Example 2, where x is 0.15 ⁇ kb, ⁇ is 0.10 ⁇ kb ⁇ 0.15, ⁇ is 0.05 ⁇ kb ⁇ 0.10, and ⁇ It is assumed that kb ⁇ 0.05.
- the definitions of x, ⁇ , and ⁇ in the comprehensive evaluation are the same as in Example 2.
- the complex refractive index was evaluated as ⁇ when the extinction coefficient k exceeded 0.1 when ZrO 2 was 30 mol% or less.
- Example 4 In Example 4, the information recording medium 300 of FIG. 1 was manufactured, and the relationship between the material of the interface layer 326 (dielectric layer b) of the second information layer 320 and the adhesion between the recording layer 325 was examined. Except for the interface layer 326, the information recording medium 300 manufactured in Example 3 was used. (AO 2 ) p (Cr 2 O 3 ) t (L) 100-pt (mol%) was used for the interface layer 326, and the film thickness was 5 nm.
- the interface layer 326 was produced using the media sample numbers 4-1 to 4-19 shown in (Table 4). In either case, a sputtering target having the same composition notation as that of the interface layer 326 was formed by sputtering at a power of 3 kW using a high frequency power source in an Ar gas atmosphere having a pressure of 0.13 Pa. Also in this example, the adhesion was evaluated according to the adhesion evaluation method of Example 1. The complex refractive index was also calculated in the same manner as in Example 1. The results of adhesion and complex refractive index are shown in (Table 4).
- media sample numbers 4-1 to 4-11 a material having a composition of (ZrO 2 ) p (Cr 2 O 3 ) t (TiO 2 ) 100-pt (mol%) was used for the interface layer 326.
- Media sample numbers 4-12 to 4-19 have a composition of (ZrO 2 ) 30 (Cr 2 O 3 ) 50 (L) 20 (mol%), and L contains Al 2 O 3 , Dy 2 O 3 , Nb 2 O 5 , SiO 2 , TiO 2 , Y 2 O 3 , Al 6 Si 2 O 13 , and Al 2 TiO 5 were used.
- media sample numbers 3-7 of Example 3 when comparing media sample numbers 3-7 of Example 3 with media sample numbers 4-5 and 4-10 of this example, these samples have a Cr 2 O 3 content of 30 mol% and an extinction coefficient of 0.04. However, media sample Nos. 3-7 were peeled off in 200 hours, whereas media samples Nos. 4-5 and 4-10 were not peeled off until 200 hours.
- Example 5 In Example 5, the information recording medium 300 of FIG. 1 is manufactured, and the material of the interface layer 324 (dielectric layer a) of the second information layer 320 and the material of the interface layer 326 (dielectric layer b) are combined. The optical characteristics and the recording / reproducing characteristics were examined in a configuration satisfying na ⁇ nb (na: refractive index of dielectric layer a, nb: refractive index of dielectric layer b). Except for the interface layer 324 and the interface layer 326, the information recording medium 300 manufactured in Example 2 was used.
- the interface layer 324 and the interface layer 326 are represented by the media sample numbers 5-1-1 to 5-1-15 and the media sample numbers 5-2-1 to 5 shown in (Table 5-1) to (Table 5-5). -3, media sample number 5-3-1, media sample number 5-4-1, and media sample numbers 5-5-1 to 5-5-5, respectively.
- the materials shown in Table 5-6 were used for the interface layer 324 and the interface layer 326 in Comparative Examples 7 to 10, respectively. In both cases, a sputtering target having the same composition notation as the interface notation of the interface layer 324 and the interface layer 326 was formed by sputtering at a power of 3 kW using a high frequency power source in an Ar gas atmosphere having a pressure of 0.13 Pa. Comparative examples 7 to 10 were also formed under similar sputtering conditions. The materials of the interface layer 324 and the interface layer 326 in each medium sample will be described below.
- (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) was used for the interface layer 326 and Al 2 was used for the interface layer 324.
- the Dy 2 O 3, Nb 2 O 5, SiO 2, TiO 2 and Y 2 O 80 mole% of at least one of oxide D is selected from 3 and Cr 2 O 3 containing materials 20 mol% Using.
- (ZrO 2 ) 50 (Cr 2 O 3 ) 50 (mol%) was used for the interface layer 326 and (Al 2 O 3 ) was used for the interface layer 324.
- a material in which a part of Cr 2 O 3 in 80 (Cr 2 O 3 ) 20 (mol%) was substituted with In 2 O 3 or Ga 2 O 3 was used.
- the interface layer 324 Al 2 O 3) 80 (Cr 2 O 3) 20 used (mol%), Al 2 O 3 in the interface layer 326, dy 2 O 3, Nb 2 O 5, SiO 2, and 25 mole% of at least one oxide L is selected from TiO 2 and Y 2 O 3, and the ZrO 2 25 mol%, Cr 2 O 3 50 mol % Containing material was used.
- a recording / reproduction evaluation method for the information recording medium 300 will be described.
- a spindle motor that rotates the information recording medium 300, an optical head that includes a semiconductor laser that emits laser light 10, and an objective lens that focuses the laser light 10 on a recording layer of the information recording medium 300;
- the recording / reproducing apparatus of the general structure equipped with these was used.
- information was recorded on the recording layer 325 of the second information layer 320 of the information recording medium 300.
- recording corresponding to a capacity of 33.4 GB was performed using a semiconductor laser having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.85. Recording was performed at a radius of 40 mm under the condition of a linear velocity of 7.4 m / sec. Reproduction evaluation of the recorded signal was performed by irradiating with a 1.0 mW laser beam under the condition of a linear velocity of 7.4 m / sec.
- CNR signal amplitude to noise ratio
- Repetitive rewrite performance was defined as the rewrite performance when the CNR decreased by 3 (dB) compared to the CNR of the signal recorded for the 11th time by alternately rewriting 3T and 8T.
- the adhesion was evaluated according to the adhesion evaluation method of Example 1. Regarding the evaluation criteria in the table, the case where peeling occurred in 50 hours was evaluated as x, the case where peeling did not occur in 50 hours (however, peeling occurred in 200 hours), and the case where peeling did not occur in 200 hours as ⁇ . .
- the reflectance ratio and transmittance of the second information layer 320 are determined by separately preparing a measurement medium in which the second information layer 320 and the transparent layer 302 are formed on the substrate 301 (which has not only a groove but also a mirror surface). And measured. Initialization was done only on one side. The transmittance was measured with a spectrophotometer at a wavelength of 405 nm. Since the transmittance Tc (the transmittance of the information layer when the recording layer is a crystalline phase) is lower than the Ta (the transmittance of the information layer when the recording layer is an amorphous phase), ( In Tables 5-1) to (Table 5-6), only the measured values of Tc are listed.
- Rc reflectance ratio
- Ra specular reflectivity when Ra is a crystalline phase
- Ra specular reflectivity when the recording layer is an amorphous phase
- the reflectivity ratio Rc / Ra is preferably 7 or more as a guideline for a value at which 3TCNR is 50 (dB) or more (in this embodiment, the design value of Rc is 7%, but 6%, 5% If the design value is lowered to%, Rc / Ra can be made larger, and the effect of the present invention can be obtained in this case as well.)
- the transmittance Tc is preferably 46% or more as a guide. If Tc is 46% or more, Ta can be obtained by 48% or more, so that 47% ⁇ (Ta + Tc) / 2 can be satisfied.
- the criteria for comprehensive evaluation are: Rc / Ra ⁇ 7, Tc ⁇ 46%, no peeling in 200 hours, repeated rewrite times ⁇ 10000, ⁇ 5.6 ⁇ Rc / Ra ⁇ 7, no peeling at 50 hours, peeling at 200 hours, 1000 ⁇ repetitive rewriting ⁇ 10000, if any one is true, ⁇ If any one of Rc / Ra ⁇ 5.6, Tc ⁇ 46%, occurrence of delamination in 50 hours, and repeated rewrite count ⁇ 1000, ⁇ , It was. Therefore, in all the samples shown in (Table 5-1) to (Table 5-5), the overall evaluation was “good”.
- the recording power (through the third information layer 330) was about 23 mW for all the media, and the erasing power was 7 mW for all the media. It was rank.
- Comparative Example 8 since the interface layer 326 was formed of a material containing Ti instead of at least one element selected from Zr and Hf, the heat resistance was insufficient, and the number of rewrites was only 500 times.
- the medium of Comparative Example 8 satisfied na ⁇ nb and was excellent in Rc / Ra and CNR, but unfortunately the heat resistance was insufficient and the repetition performance was poor.
- nb ⁇ na and Rc / Ra was as small as 4. Further, since (Al 2 O 3 ) 80 (Cr 2 O 3 ) 20 (mol%) was used for the interface layer 326, the heat resistance was insufficient, and the number of rewrites was only 1000 times. Similarly, in Comparative Example 10, since (ZrO 2 ) 50 (Ga 2 O 3 ) 50 was used for the interface layer 326, the heat resistance was insufficient and the number of rewritings was only 800 times.
- the material of the interface layer in contact with the recording layer is a combination of the materials of the dielectric layer a and the dielectric layer b limited in the information recording medium of the present invention.
- the semitransparent information layer it was possible to obtain performance superior to that of conventional information recording media.
- Example 6 In Example 6, as in Example 5, the information recording medium 300 of FIG. 1 was manufactured, and the material of the interface layer 324 (dielectric layer a) of the second information layer 320 and the interface layer 326 (dielectric layer b) were manufactured. The optical characteristics and the recording / reproducing characteristics were examined in a configuration satisfying na ⁇ nb (na: refractive index of dielectric layer a, nb: refractive index of dielectric layer b) in combination with the materials. Except for the interface layer 324 and the interface layer 326, the information recording medium 300 manufactured in Example 5 was used.
- the interface layer 324 and the interface layer 326 were produced using the media sample numbers 6-1 to 6-7 shown in (Table 6), respectively.
- (Al 2 O 3 ) 80 (Cr 2 O 3 ) 20 (mol%) is used for the interface layer 324, and
- (ZrO 2 ) j (Cr 2 O 3 ) 100-j (mol%) is used for the interface layer 326. Using.
- Example 7 In Example 7, the information recording medium 300 of FIG. 1 was manufactured, and all the interface layers included in the first information layer 310, the second information layer 320, and the third information layer 330 were formed on the dielectric according to the present invention. The material of layer a and dielectric layer b was applied.
- Rc of the first information layer 310 is about 28%
- Rc of the second information layer 320 is about 6%
- (Tc + Ta) / 2 is about 48%
- Rc of the third information layer 330 is about The design was such that 3% and (Tc + Ta) / 2 were about 59%.
- the first information layer 310 (Al 2 O 3 ) 70 (Cr 2 O 3 ) 30 (mol%) is used for the interface layer 314, and (ZrO 2 ) 25 (Cr 2 O 3 ) is used for the interface layer 316. 50 (SiO 2 ) 25 (mol%) was used.
- the thicknesses of the interface layers 314 and 316 were both 5 nm. The material and film thickness of each layer other than these were the same as in Example 5.
- the second information layer 320 For the second information layer 320, (Al 2 O 3 ) 80 (Cr 2 O 3 ) 20 (mol%) is used for the interface layer 324, and (ZrO 2 ) 25 (Cr 2 O 3 ) is used for the interface layer 326. 50 (SiO 2 ) 25 (mol%) was used. Both the interface layers 324 and 326 had a thickness of 5 nm.
- the dielectric layer 327 was made of (ZnS) 80 (SiO 2 ) 20 (mol%) and had a thickness of 38 nm. The material and film thickness of each layer other than these were the same as in Example 5.
- the dielectric layer 331 was made of Bi 4 Ti 3 O 12 and had a thickness of 18 nm. Further, (Al 2 O 3 ) 80 (Cr 2 O 3 ) 20 (mol%) is used for the interface layer 334, and (ZrO 2 ) 25 (Cr 2 O 3 ) 50 (SiO 2 ) 25 is used for the interface layer 336. Using (mol%), the film thicknesses of these interface layers were both 5 nm.
- the dielectric layer 337 was made of (ZnS) 80 (SiO 2 ) 20 (mol%) and had a thickness of 37 nm. The material and film thickness of each layer other than these were the same as in Example 5.
- the information recording medium of Example 7 was produced as described above.
- the reflectance (Rc, Ra), the reflectance ratio (Rc / Ra), the transmittance (Tc, Ta), and the average value of the transmittance ((Tc + Ta) / 2) of each information layer. was measured respectively.
- the complex refractive index of the interface layer of each information layer was also measured by the same method as in Example 1.
- the effective Rc and effective Ra of each information layer were measured to obtain the effective Rc / effective Ra.
- a recording / reproducing apparatus equipped with a semiconductor laser having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.85 was used as in Example 5.
- the laser beam is focused on the recording layer of the information layer to be measured of the information recording medium 300, the effective Rc is measured at the mirror surface of the initialization unit, and is effective at the mirror surface at the boundary between the initialization unit and the uninitialized unit. Ra was measured.
- the effective Rc and effective Ra of the first information layer 310 are determined by the laser light 10 that has passed through the transparent layer 302, the third information layer 330, the intermediate layer 304, the second information layer 320, and the intermediate layer 303 as the first information layer 310. Irradiates the layer 310, and detects the reflected laser light reflected by the first information layer 310 and passing through the intermediate layer 303, the second information layer 320, the intermediate layer 304, the third information layer 330, and the transparent layer 302. Is required. Similarly, the effective Rc and effective Ra of the second information layer 320 are obtained by irradiating the second information layer 320 with laser light that has passed through the transparent layer 302, the third information layer 330, and the intermediate layer 304.
- the effective Rc and effective Ra of the third information layer 330 are reflected by irradiating the third information layer 330 with the laser light that has passed through the transparent layer 302, reflected by the third information layer 330, and passed through the transparent layer 302. It is obtained by detecting the laser beam.
- the effective Ra of the second information layer 320 and the third information layer 330 was less than 0.2%, and the servo of the evaluator was unstable and could not be measured accurately.
- Rc / Ra exceeded 10.
- a high reflectance ratio Rc / Ra a high transmittance, and excellent adhesion , High CNR, and an excellent number of repetitions exceeding 10,000.
- Rc / Ra exceeded 11 in the second information layer 320 and the third information layer 330 which are translucent information layers.
- the dielectric layer a having both high transparency and excellent adhesion to the recording layer, and high heat resistance and the recording layer
- the dielectric layer b having excellent adhesion
- a translucent information layer having high reflectance ratio, high transmittance, and high rewriting performance can be realized.
- an information recording medium having a large capacity of 100 GB or more can be realized.
- the information recording medium of the present invention is useful for a rewritable multilayer Blu-ray Disc, a write-once multilayer Blu-ray Disc, etc. as a large-capacity optical information recording medium realized by providing an excellent dielectric layer.
- the information recording medium of the present invention can be recorded and reproduced by an optical system with NA> 1, for example, an optical system using SIL (solid immersion lens) or SIM (solid immersion mirror), as a large-capacity optical information recording medium. It is also useful for next-generation rewritable information recording media or next-generation rewritable multilayer information recording media.
Abstract
Description
本発明の実施の形態1として、情報記録媒体の一例を説明する。図1に、その情報記録媒体300の一部断面を示す。情報記録媒体300には、基板301上に、第1の情報層310、中間層303、第2の情報層320、中間層304、第3の情報層330および透明層302がこの順に配置されている。すなわち、本実施の形態の情報記録媒体300は、N個(Nは2以上の整数)の情報層を含む情報記録媒体であり、N=3の場合に相当する。本実施の形態では、第1の情報層310から第3の情報層330の全てに本発明における誘電体層aおよび誘電体層bが適用されているため、全ての情報層が本発明の情報記録媒体の第L情報層に相当するが、これに限定されず、第1の情報層310から第3の情報層330のうちの少なくともいずれか一つの情報層が第L情報層に相当すればよい。
本発明の実施の形態2として、情報記録媒体の一例を説明する。図2に、その情報記録媒体400の一部断面を示す。情報記録媒体400は、基板401上に、第1の情報層410、中間層403、第2の情報層420、中間層404、第3の情報層430、中間層405、第4の情報層440および透明層402が、順に配置されることによって形成されている。すなわち、本実施の形態の情報記録媒体400は、N個(Nは2以上の整数)の情報層を含む情報記録媒体であり、N=4の場合に相当する。本実施の形態では、第1の情報層410から第4の情報層440の全てに本発明における誘電体層aおよび誘電体層bが適用されているため、全ての情報層が本発明の情報記録媒体の第L情報層に相当するが、これに限定されず、第1の情報層410から第4の情報層430のうち少なくともいずれか一つの情報層が第L情報層に相当すればよい。
本発明の実施の形態3として、情報記録媒体の一例を説明する。図3に、その情報記録媒体200の一部断面を示す。情報記録媒体200は、基板201上に、第1の情報層210、中間層203、第2の情報層220および透明層202が、順に配置されることによって形成されている。すなわち、本実施の形態の情報記録媒体200は、N個(Nは2以上の整数)の情報層を含む情報記録媒体であり、N=2の場合に相当する。本実施の形態では、第1の情報層210および第2の情報層220の両方に誘電体層aおよび誘電体層bが適用されているため、全ての情報層が本発明の情報記録媒体の第L情報層に相当するが、これに限定されず、第1の情報層210および第2の情報層220の少なくともいずれか一つが第L情報層に相当すればよい。
本発明の実施の形態4として、情報記録媒体の一例を説明する。図4に、その情報記録媒体100の一部断面を示す。情報記録媒体100は、基板101上に情報層110および透明層102が、この順に配置されることによって形成されている。さらに、情報層110は、基板101の一方の表面上に、反射層112、誘電体層113、界面層114、記録層115、界面層116および誘電体層117が、この順に配置されることによって形成されている。
実施例1では、誘電体層aおよび誘電体層bに用いられる材料について、波長405nmの光における光学定数(複素屈折率)(誘電体層a:na-ika(na:屈折率、ka:消衰係数)、誘電体層b:nb-ikb(nb:屈折率、kb:消衰係数))を実験的に調べた。光学定数算出用の試料は、石英基板上に厚さ20nmほどの誘電体層をスパッタリングにより形成することによって、作製した。光学定数の算出に必要な膜厚は触針法により測定し、光学定数の算出にはエリプソメトリを用いた。試料番号1-1から1-10は誘電体層aの材料で、試料番号1-11から1-25は誘電体層bの材料である。比較例には、(ZrO2)20(Cr2O3)80組成の試料を準備した。
実施例2では、図1の情報記録媒体300を製造し、第2の情報層320の界面層324(誘電体層a)の材料と記録層325との密着性の関係を調べた。誘電体層bに相当する界面層326には、記録層325との密着性に優れた(ZrO2)50(Cr2O3)50(モル%)を用い、界面層324には(Al2O3)h(Cr2O3)100-h(モル%)を用いた。
実施例3では、図1の情報記録媒体300を製造し、第2の情報層320の界面層326(誘電体層b)の材料と記録層325との密着性の関係を調べた。界面層324および界面層326以外は、実施例2で製造した情報記録媒体300と同様とした。界面層326と記録層325との密着性を正確に調べるために、誘電体層aに相当する界面層324には、敢えて記録層325との密着性に優れた(ZrO2)50(Cr2O3)50(モル%)を用いた。界面層326には(ZrO2)j(Cr2O3)100-j(モル%)を用いた。いずれも膜厚は5nmとした。
実施例4では、図1の情報記録媒体300を製造し、第2の情報層320の界面層326(誘電体層b)の材料と記録層325との密着性との関係を調べた。界面層326以外は、実施例3で製造した情報記録媒体300と同様とした。界面層326には(AO2)p(Cr2O3)t(L)100-p-t(モル%)を用い、膜厚は5nmとした。
実施例5では、図1の情報記録媒体300を製造し、第2の情報層320の界面層324(誘電体層a)の材料と界面層326(誘電体層b)の材料とを組み合わせて、na<nb(na:誘電体層aの屈折率、nb:誘電体層bの屈折率)を満たす構成で、光学特性と記録再生特性とを調べた。界面層324および界面層326以外は、実施例2で製造した情報記録媒体300と同様とした。
5.6≦Rc/Ra<7、50時間で剥離無しで200時間では剥離発生、1000≦繰り返し書換回数<10000、のいずれか一つでも該当すれば△、
Rc/Ra<5.6、Tc<46%、50時間で剥離発生、繰り返し書換回数<1000のいずれか一つでも該当すれば×、
とした。よって、(表5-1)から(表5-5)に示す全ての試料において、総合評価は○となった。
実施例6では、実施例5同様、図1の情報記録媒体300を製造し、第2の情報層320の界面層324(誘電体層a)の材料と界面層326(誘電体層b)の材料とを組み合わせて、na<nb(na:誘電体層aの屈折率、nb:誘電体層bの屈折率)を満たす構成で、光学特性と記録再生特性とを調べた。界面層324および界面層326以外は、実施例5で製造した情報記録媒体300と同様とした。
その結果、界面層326の材料(ZrO2)j(Cr2O3)100-j(モル%)について、jが20≦j≦60を満たす場合に総合評価が○となり、より優れた性能が得られた。
実施例7では、図1の情報記録媒体300を製造し、第1の情報層310、第2の情報層320および第3の情報層330に含まれる界面層の全てに、本発明における誘電体層aおよび誘電体層bの材料を適用した。
Claims (24)
- 光の照射によって情報を記録または再生し得る情報記録媒体であって、
光の入射側から、誘電体層b、記録層および誘電体層aをこの順に備え、
前記誘電体層aが、Al、Dy、Nb、Si、TiおよびYより選ばれる少なくともいずれか一つの元素Mと、Crと、Oとを含み、
前記誘電体層bが、ZrおよびHfより選ばれる少なくともいずれか一つの元素Aと、Crと、Oとを含み、
前記誘電体層aおよび前記誘電体層bは、前記記録層に接して配置されている、
情報記録媒体。 - 前記誘電体層aが、式(1):
McCrdO100-c-d(原子%) (1)
で表される材料を含み、
前記式(1)において、添え字c、dおよび100-c-dは、原子%で表されるM、CrおよびOの組成比を示し、
cおよびdが、12<c<40、0<d≦25、且つ20<(c+d)<50を満たす、
請求項1に記載の情報記録媒体。 - 前記元素Mが、Al、SiおよびTiより選ばれる少なくともいずれか一つの元素である、
請求項1に記載の情報記録媒体。 - 前記誘電体層aに含まれるCrの一部が、GaおよびInより選ばれる少なくともいずれか一つの元素で置換されている、
請求項1に記載の情報記録媒体。 - 前記誘電体層aが、Al2O3、Dy2O3、Nb2O5、SiO2、TiO2およびY2O3より選ばれる少なくともいずれか一つの酸化物Dと、Cr2O3とを含む、式(2):
(D)h(Cr2O3)100-h(モル%) (2)
で表される材料を含み、
前記式(2)において、添え字hおよび100-hは、モル%で表されるDおよびCr2O3の組成比を示し、
hが、50≦h<100を満たす、
請求項2に記載の情報記録媒体。 - 前記酸化物Dが、Al2O3、SiO2およびTiO2より選ばれる少なくともいずれか一つの酸化物である、
請求項5に記載の情報記録媒体。 - 前記誘電体層aに含まれるCr2O3の一部が、Ga2O3およびIn2O3より選ばれる少なくともいずれか一つの酸化物で置換されている、
請求項5に記載の情報記録媒体。 - 前記誘電体層aにおけるGa2O3およびIn2O3の含有量の合計が、30モル%以下である、
請求項7に記載の情報記録媒体。 - 前記誘電体層bが、式(3):
AfCrgO100-f-g(原子%) (3)
で表される材料を含み、
前記式(3)において、添え字f、gおよび100-f-gは、原子%で表されるA、CrおよびOの組成比を示し、
fおよびgが、4<f<16、21<g<35、且つ30<(f+g)<50を満たす、請求項1に記載の情報記録媒体。 - 前記誘電体層bが、ZrO2およびHfO2より選ばれる少なくともいずれか一つの酸化物AO2と、Cr2O3とを含む、式(4):
(AO2)j(Cr2O3)100-j(モル%) (4)
で表される材料を含み、
前記式(4)において、添え字jおよび100-jは、モル%で表されるAO2およびCr2O3の組成比を示し、
jが、20≦j≦60を満たす、
請求項9に記載の情報記録媒体。 - 前記誘電体層bが、Al、Dy、Nb、Si、TiおよびYより選ばれる少なくともいずれか一つの元素Xをさらに含む、式(5):
AkCrmXnO100-k-m-n(原子%) (5)
で表される材料を含み、
前記式(5)において、添え字k、m、nおよび100-k-m-nは、原子%で表されるA、Cr、XおよびOの組成比を示し、
k、mおよびnが、1<k<18、3<m<35、0<n<31、且つ25<(k+m+n)<50を満たす、
請求項9に記載の情報記録媒体。 - 前記元素Xが、Al、Dy、SiおよびTiより選ばれる少なくともいずれか一つの元素である、
請求項11に記載の情報記録媒体。 - 前記誘電体層bに含まれるCrの一部が、GaおよびInより選ばれる少なくともいずれか一つの元素で置換されている、
請求項1に記載の情報記録媒体。 - 前記誘電体層bが、Al2O3、Dy2O3、Nb2O5、SiO2、TiO2およびY2O3より選ばれる少なくともいずれか一つの酸化物Lをさらに含む、式(6):
(AO2)p(Cr2O3)t(L)100-p-t(モル%) (6)
で表される材料を含み、
前記式(6)において、添え字p、tおよび100-p-tは、モル%で表されるAO2、Cr2O3およびLの組成比を示し、
pおよびtが、20≦p≦60、20≦t<80、且つ60≦(p+t)<100を満たす、
請求項10に記載の情報記録媒体。 - 前記元素AがZrである、
請求項1に記載の情報記録媒体。 - 前記酸化物Lが、Al2O3、Dy2O3、SiO2およびTiO2より選ばれる少なくともいずれか一つの酸化物である、
請求項14に記載の情報記録媒体。 - 前記誘電体層bに含まれるCr2O3の一部が、Ga2O3およびIn2O3より選ばれる少なくともいずれか一つの酸化物で置換されている、
請求項10に記載の情報記録媒体。 - 前記誘電体層bにおけるGa2O3およびIn2O3の含有量の合計が、20モル%以下である、
請求項17に記載の情報記録媒体。 - 前記誘電体層aの屈折率をna、前記誘電体層bの屈折率をnbとしたとき、na<nbを満たす、
請求項1に記載の情報記録媒体。 - N個の情報層を含み、前記Nは2以上の整数であって、前記N個の情報層を、光入射側と反対側から順に第1情報層から第N情報層としたとき、前記N個の情報層に含まれる第L情報層(Lは、1≦L≦Nを満たす少なくともいずれか一つの整数)が、前記光の入射側から、前記誘電体層b、前記記録層、前記誘電体層aをこの順に含む、
請求項1に記載の情報記録媒体。 - 前記Nが3である、
請求項20に記載の情報記録媒体。 - 前記記録層が、前記光の照射によって相変化を起こす材料によって形成されている、
請求項1に記載の情報記録媒体。 - 前記記録層がGe-Teを含み、且つGeを40原子%以上含む、
請求項22に記載の情報記録媒体。 - 前記記録層がSb-GeおよびSb-Teより選ばれる少なくともいずれか一つの材料を含み、且つSbを70原子%以上含む、
請求項22に記載の情報記録媒体。
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