WO2025239331A1 - Disque magnétique, substrat de disque magnétique, et utilisation d'un substrat de disque magnétique, et procédé de fabrication de disque magnétique - Google Patents

Disque magnétique, substrat de disque magnétique, et utilisation d'un substrat de disque magnétique, et procédé de fabrication de disque magnétique

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Publication number
WO2025239331A1
WO2025239331A1 PCT/JP2025/017254 JP2025017254W WO2025239331A1 WO 2025239331 A1 WO2025239331 A1 WO 2025239331A1 JP 2025017254 W JP2025017254 W JP 2025017254W WO 2025239331 A1 WO2025239331 A1 WO 2025239331A1
Authority
WO
WIPO (PCT)
Prior art keywords
magnetic disk
substrate
straightness
heating
mol
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2025/017254
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English (en)
Japanese (ja)
Inventor
伸二 江田
ヴー クアン ズン
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hoya Corp
Original Assignee
Hoya Corp
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Filing date
Publication date
Application filed by Hoya Corp filed Critical Hoya Corp
Publication of WO2025239331A1 publication Critical patent/WO2025239331A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
    • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/097—Glass compositions containing silica with 40% to 90% silica, by weight containing phosphorus, niobium or tantalum
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/64—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
    • G11B5/65—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent characterised by its composition
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
    • G11B5/82—Disk carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers

Definitions

  • This disclosure relates to magnetic disks, magnetic disk substrates, uses of magnetic disk substrates, and methods for manufacturing magnetic disks.
  • HAMR heat-assisted magnetic recording
  • a sputtering method is used, but this method has the problem of the magnetic disk substrate deforming due to exposure to high temperature conditions. For this reason, a magnetic disk that is less likely to deform is desired.
  • the present disclosure therefore aims to provide a magnetic disk, a magnetic disk substrate, a use of the magnetic disk substrate, and a method for manufacturing a magnetic disk that are suitable for use in thermally assisted magnetic recording.
  • One embodiment of the present disclosure is a magnetic disk, a substrate having a pair of main surfaces and an outer peripheral edge surface; a magnetic layer having an L10 structure on the pair of main surfaces and the outer peripheral end surface of the substrate, The magnetic disk is heated under the following heating conditions, and then the straightness measured under the following measuring conditions is 90 ⁇ m or less.
  • One embodiment of the present disclosure is a magnetic disk substrate having a pair of main surfaces and an outer peripheral end surface, The magnetic disk substrate is heated under the following heating conditions, and then the straightness measured under the following measuring conditions is 90 ⁇ m or less.
  • One embodiment of the present disclosure is a method for manufacturing a magnetic disk, comprising: a step of heating the substrate until the substrate surface temperature reaches 600 to 780°C, and then forming a magnetic layer having an L10 structure;
  • the method relates to a magnetic disk manufacturing method in which the substrate is a magnetic disk substrate having a pair of main surfaces and an outer peripheral end surface, and after heating the magnetic disk substrate under the following heating conditions, the magnetic disk substrate has a straightness of 90 ⁇ m or less as measured under the following measuring conditions.
  • the surface temperature of the magnetic disk is heated from room temperature to 600° C. in 25 seconds, then heated to 700° C. in 35 seconds, and then cooled to room temperature in 120 seconds.
  • the maximum valley depth Sv is measured in three directions, each oriented 120 degrees apart, over a measurement range of at least 88 mm in length using a surface roughness measuring device, and the number average value of the maximum valley depth Sv is determined as the straightness value.
  • This embodiment provides a magnetic disk, magnetic disk substrate, use of the magnetic disk substrate, and method for manufacturing a magnetic disk that are suitable for use in thermally assisted magnetic recording.
  • FIG. 1 is a perspective view showing the appearance of a magnetic disk according to this embodiment.
  • FIG. 2 is a cross-sectional view of the magnetic disk according to this embodiment.
  • FIG. 3 is a front view showing the measurement points of the straightness of the magnetic disk according to this embodiment.
  • FIG. 4 is a diagram showing a temperature rise program for the heating test.
  • the magnetic disk according to this embodiment is a substrate having a pair of main surfaces and an outer peripheral edge surface; a magnetic layer having an L10 structure on the pair of main surfaces and the outer peripheral end surface of the substrate, The magnetic disk is heated under the following conditions, and then the straightness measured under the following conditions is 90 ⁇ m or less. According to the above configuration, it is possible to provide a magnetic disk suitable for use in thermally assisted magnetic recording.
  • Heating conditions The surface temperature of the magnetic disk is heated from room temperature to 600° C. in 25 seconds, then heated to 700° C. in 35 seconds, and then cooled to room temperature in 120 seconds.
  • the straightness can be measured by the following method.
  • the maximum valley depth Sv is measured in three directions, each oriented 120 degrees apart, over a measurement range of at least 88 mm in length using a surface roughness measuring device, and the number average value of the maximum valley depth Sv is determined as the straightness value.
  • the straightness is measured in a measurement range of at least 88 mm in length.
  • the measurement position on the magnetic disk can be a measurement range on a straight line of 88 mm in length shown by the dotted line in Figure 3.
  • the straightness is measured by measuring the maximum valley depth Sv in three directions that are 120 degrees apart as shown in Figure 3, and the number average of the measured values is taken as the straightness.
  • a product named "Surftest-VS2100" manufactured by Mitutoyo Corporation can be used as the surface roughness measuring instrument.
  • the magnetic disk according to this embodiment has a straightness of 90 ⁇ m or less when measured after heating under the above conditions (hereinafter simply referred to as "straightness after heating").
  • the straightness after heating is preferably 80 ⁇ m or less, more preferably 70 ⁇ m or less, and even more preferably 60 ⁇ m or less.
  • the lower limit of the straightness after heating is not particularly limited, but is, for example, 20 ⁇ m or more. To obtain this straightness, the above-mentioned range can be achieved, for example, by adjusting the glass transition temperature, thermal expansion coefficient, specific elastic modulus, etc.
  • the composition of the material of the magnetic disk used by adjusting the plate thickness of the magnetic disk, or by changing the manufacturing method (for example, a method in which molten glass is molded into a sheet and rapidly cooled to obtain plate glass, which is then processed into the shape of the substrate, or by using a down-draw method when molding into a sheet).
  • the straightness value after heating is also affected by the thickness of the substrate, and the rate at which straightness increases as the substrate thickness is reduced varies depending on the material. It is preferable for the increase in straightness value after heating to be small even when the substrate thickness is reduced.
  • the product of the straightness ( ⁇ m) of a glass substrate after heating and the substrate thickness (mm) is preferably 50.0 ( ⁇ m ⁇ mm) or less, more preferably 40.0 ( ⁇ m ⁇ mm) or less, and even more preferably 35.0 ( ⁇ m ⁇ mm) or less.
  • the magnetic disk according to this embodiment preferably has a change in straightness between before and after heating under the above conditions (hereinafter simply referred to as "change in straightness") of 10 to 80 ⁇ m.
  • change in straightness a change in straightness between before and after heating under the above conditions
  • the amount of change in straightness is preferably 15 to 75 ⁇ m, more preferably 15 to 70 ⁇ m, even more preferably 15 to 60 ⁇ m, and still more preferably 15 to 50 ⁇ m.
  • the magnetic disk according to this embodiment preferably has a straightness of 30 ⁇ m or less before heating (hereinafter also referred to as "straightness before heating").
  • the straightness before heating is preferably 20 ⁇ m or less, more preferably 15 ⁇ m or less, even more preferably 10 ⁇ m or less, and even more preferably 5 ⁇ m or less.
  • the lower limit of the straightness before heating is not particularly limited, but is, for example, 1 ⁇ m or more.
  • FIG. 1 is an external perspective view of a magnetic disk 21 according to this embodiment.
  • the magnetic disk 21 is annular in shape and has a spindle hole 215.
  • the magnetic disk 21 has main surfaces 216 that face each other.
  • the pair of main surfaces are approximately parallel.
  • approximately parallel means that the parallelism is, for example, 5 ⁇ m or less.
  • the magnetic disk 21 has an outer peripheral end surface 217 that connects the pair of main surfaces.
  • the magnetic disk 21 also has an inner peripheral end surface 218 that connects the pair of main surfaces.
  • the magnetic disk 21 includes a substrate 211 and a magnetic layer 214 containing a magnetic material containing an L1 0 -FePt alloy.
  • the magnetic disk 21 may further include a first underlayer 213 containing MgO.
  • the magnetic disk 21 may also further include a second underlayer 212 containing a Cr alloy.
  • the magnetic layer 214 may be a single layer, or may have a multi-layer laminate structure.
  • the magnetic disk 21 may have a protective layer 215 and a lubricating layer 216.
  • a soft magnetic layer and a heat sink layer may be added as appropriate.
  • the magnetic disk substrate (hereinafter simply referred to as "substrate”) according to this embodiment preferably has a thickness of 0.2 to 0.6 mm.
  • the thickness of the substrate is preferably 0.30 to 0.55 mm, more preferably 0.35 to 0.50 mm, and even more preferably 0.41 to 0.45 mm.
  • Substrate materials include, for example, metal materials such as stainless steel, titanium, aluminum, and aluminum alloys, ceramics, and glass. Of these, glass substrates are preferred.
  • the glass composition of the glass substrate preferably contains 55 to 80 mol% of SiO2 , 5 to 25 mol% of Al2O3 , 0 to 8 mol% of B2O3 , 0 to 5 mol% of P2O5 , 5 to 25 mol% of MO (MO is at least one selected from MgO, CaO, SrO, and BaO, and the content thereof is the total content of MgO, CaO, SrO, and BaO), and 0 to 15 mol% of M2O ( M2O is at least one selected from Li2O , Na2O , and K2O , and the content thereof is the total content of Li2O , Na2O , and K2O ).
  • MO is at least one selected from MgO, CaO, SrO, and BaO, and the content thereof is the total content of MgO, CaO, SrO, and BaO
  • M2O is at least one selected from Li2O , Na2O , and K2O
  • the preferred content of each component in the glass composition of the glass substrate is as follows:
  • SiO2 is a network-forming component of glass. From the viewpoint of enhancing the stability of the glass and improving the meltability during production, the content of SiO2 is preferably 55 to 80 mol%, more preferably 57 to 75 mol%, and even more preferably 60 to 70 mol%.
  • the content of Al 2 O 3 is preferably 5 to 25 mol %, more preferably 10 to 20 mol %, and even more preferably 12 to 18 mol %, from the viewpoint of improving the heat resistance and stability of the glass.
  • B 2 O 3 is a component that forms a network of glass.
  • the content of B 2 O 3 is preferably 0 to 8 mol %, more preferably 0 to 1.5 mol %, and even more preferably 0.1 to 0.8 mol %.
  • the content of P 2 O 5 is preferably 0 to 5 mol %, more preferably 0 to 3 mol %, and even more preferably 0.1 to 3 mol %.
  • MO is at least one selected from MgO, CaO, SrO, and BaO, and its content is the total content of MgO, CaO, SrO, and BaO.
  • the content of MO is preferably 5 to 25 mol%, more preferably 6 to 20 mol%, and even more preferably 14 to 18 mol%.
  • the content of MgO is preferably 3 to 20 mol %, more preferably 4 to 19 mol %, and even more preferably 8 to 18 mol %.
  • the CaO content is preferably 0 to 10 mol%, more preferably 0 to 8 mol%, and even more preferably 0 to 6 mol%.
  • the SrO content is preferably 0 to 5 mol%, more preferably 0 to 3 mol%, and even more preferably 0 to 1.5 mol%.
  • the BaO content is preferably 0 to 5 mol%, more preferably 0 to 4 mol%, and even more preferably 0 to 1.5 mol%.
  • M 2 O is at least one selected from Li 2 O, Na 2 O, and K 2 O, and the content thereof is the total value of Li 2 O, Na 2 O, and K 2 O.
  • the content of M 2 O is preferably 0 to 15 mol %, more preferably 0 to 10 mol %, and even more preferably 0.01 to 9 mol %.
  • the content of Li 2 O is preferably 0 to 5 mol %, more preferably 0 to 7 mol %, and even more preferably 0.01 to 6 mol %.
  • the content of Na 2 O is preferably 0 to 10 mol %, more preferably 0 to 7 mol %, and even more preferably 0.01 to 5 mol %.
  • the content of K 2 O is preferably 0 to 3 mol %, more preferably 0 to 1 mol %, and even more preferably 0 to 0.3 mol %.
  • the glass composition is expressed as a glass composition based on oxides.
  • glass composition based on oxides means a glass composition obtained by converting the glass raw materials into oxides that are present in the glass after being completely decomposed during melting.
  • the glass composition in the present disclosure can be determined by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Quantitative analysis is performed for each element using ICP-AES. The analytical values are then converted into oxide notation.
  • the analytical values obtained by ICP-AES may contain a measurement error of, for example, about ⁇ 5% of the analytical value. Therefore, the oxide notation values converted from the analytical values may also contain an error of about ⁇ 5%.
  • a content of 0 mol% of a constituent component means that the constituent component is substantially absent, and indicates that the content of the constituent component is at or below the impurity level, for example, less than 0.01 mol%.
  • the magnetic disk substrate according to this embodiment has a straightness of 90 ⁇ m or less when measured after heating under the above conditions (hereinafter simply referred to as "straightness after heating"). By having this straightness, a magnetic disk substrate suitable for use in thermally assisted magnetic recording can be obtained.
  • the straightness after heating is preferably 80 ⁇ m or less, more preferably 70 ⁇ m or less, and even more preferably 60 ⁇ m or less.
  • the lower limit of the straightness after heating is not particularly limited, but is, for example, 20 ⁇ m or more.
  • the magnetic disk substrate according to this embodiment preferably has a change in straightness between before and after heating under the above conditions (hereinafter simply referred to as "change in straightness") of 80 ⁇ m or less.
  • change in straightness is preferably 70 ⁇ m or less, more preferably 60 ⁇ m or less, even more preferably 50 ⁇ m or less, and even more preferably 40 ⁇ m or less.
  • the lower limit of the change in straightness is not particularly limited, but is, for example, 20 ⁇ m or more.
  • the magnetic disk substrate according to this embodiment preferably has a straightness of 50 ⁇ m or less before heating (hereinafter also referred to as "straightness before heating").
  • the straightness before heating is preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less, even more preferably 20 ⁇ m or less, and even more preferably 15 ⁇ m or less.
  • the lower limit of the straightness before heating is not particularly limited, but is, for example, 20 ⁇ m or more.
  • the Young's modulus of the substrate is preferably 80 GPa or more, more preferably 80 to 110 GPa, and even more preferably 85 to 105 GPa.
  • the glass transition temperature of the substrate is preferably 700°C or higher, more preferably 710 to 850°C, and even more preferably 720 to 840°C.
  • the thermal expansion coefficient of the substrate at 100 to 300° C. (unit: ⁇ 10 ⁇ 7 /K) is preferably 10 to 110, more preferably 25 to 98, and even more preferably 30 to 55.
  • the value of the specific elastic modulus E/d of the substrate is preferably 31.0 ⁇ 10 6 m 2 /s 2 or more, more preferably 31.5 ⁇ 10 6 m 2 /s 2 or more, and preferably 34.0 ⁇ 10 6 m 2 /s 2 or more.
  • the substrate has a specific elastic modulus E/d within this range, impact resistance is further improved.
  • the substrate has a thickness of 0.51 mm or less, the above-mentioned effect is more pronounced when the substrate has a specific elastic modulus E/d within the above-mentioned range.
  • the specific elastic modulus E/d means the value obtained by dividing Young's modulus by specific gravity.
  • the magnetic disk 21 includes a magnetic layer 214.
  • the magnetic disk 21 may have, for example, a second underlayer 212 containing a Cr alloy, a first underlayer 213 containing MgO, the magnetic layer 214, a protective layer 215, and a lubricating layer 216 stacked on the main surface of a smoothly polished glass substrate in this order from the closest to the main surface.
  • the second underlayer may be made of, for example, a Cr alloy, more specifically, CrTi, CrB, etc.
  • the thickness of the second underlayer may be, for example, 1 to 30 nm.
  • the first underlayer may be made of a material containing, for example, Ru or MgO, and preferably contains MgO. By using a first underlayer containing MgO, it becomes easier to form an L1 0 -FePt alloy when forming the magnetic layer.
  • the thickness of the first underlayer may be, for example, 5 to 30 nm.
  • the first and second underlayers are formed sequentially on the main surfaces of the glass substrate, for example, by placing the glass substrate in a vacuum-drawn film-forming apparatus and depositing them sequentially on the main surfaces of the glass substrate in an Ar atmosphere using DC (Direct Current) magnetron sputtering.
  • DC Direct Current
  • the magnetic layer preferably has an L10 structure to achieve ultra-high recording density on magnetic disks. It has a granular structure including magnetic grains containing an FePt alloy and grain boundary portions.
  • the grain boundary portions contain non-magnetic materials such as C, B, BN, Al2O3 , SiO2 , TiO2 , and Cr2O3 .
  • the granular structure is also called a granular structure.
  • the magnetic material is not limited to a ferromagnetic material, but may also be an alternating magnetic material. Using an alternating magnetic material eliminates the influence of external magnetic fields, allowing the grain size of the magnetic material to be 10 nm or less, preferably 4 nm or less, and more preferably 2 nm or less, thereby further improving recording density.
  • the magnetic layer is preferably composed of an L1 0 -FePt alloy material.
  • “based" means to contain.
  • Specific examples of the L1 0 -FePt alloy material that constitutes the magnetic layer include FePt and FePtAg (FePt alloyed with Ag) containing C (carbon), and FePt and FePtAg (FePt alloyed with Ag) containing Si (silicon).
  • magnetic materials having an L1 0 structure can be composed of rare earth magnet materials such as CoPt alloys, Nd 2 Fe 14 B, and SnCo 5 , in addition to FePt alloys.
  • the magnetic layer preferably has a composition represented by formula (1).
  • (Fe x Pt 1-x ) 1-z Ag z -C v ...(1) (wherein 0.4 ⁇ x ⁇ 0.55, 0 ⁇ z ⁇ 0.2, 0 ⁇ v ⁇ 50 vol% (preferably 30 vol% ⁇ v ⁇ 50 vol%), and (Fe x Pt 1-x ) 1-z Ag z is (100 ⁇ v) vol%.)
  • the composition Fe:Pt By setting the composition Fe:Pt to be close to 1:1, the order-disorder transformation temperature of the L1 0 type/A1 phase becomes the highest, and a high driving force for the L1 0 order can be obtained.
  • the C in the FePt--C layer or FePtAg--C layer phase-separates from the FePt or FePtAg to form a non-magnetic matrix with a granular structure.
  • the magnetic grains containing the L1 0 -FePt alloy are preferably island-shaped magnetic grains.
  • the grain size of the magnetic grains is preferably smaller. To obtain magnetic grains with a small grain size, it is sufficient to form a thin film with a thickness of, for example, 20 nm or less.
  • an alloy target containing the above materials is prepared as the non-magnetic material that constitutes the grain boundary portion.
  • simultaneous sputtering is performed, the respective targets are prepared and films are formed simultaneously.
  • simultaneous sputtering may be performed using two targets: an FePt alloy and a compound that will become the non-magnetic matrix.
  • the volume fraction of the non-magnetic matrix can be changed by controlling the deposition rate.
  • simultaneous sputtering (co-sputtering) of FePt and C can be employed.
  • a preferred method is to use an FePt alloy target and a C target, and to control the power of the C target during FePt sputtering to change the film deposition rate of C, as shown in the examples.
  • the thickness of the magnetic layer may be, for example, 1 to 20 nm.
  • An auxiliary recording layer may also be provided above or below the magnetic layer.
  • the magnetic recording layer can achieve high heat resistance in addition to high-density recording, low noise, and coercive force control.
  • the composition of the auxiliary recording layer can be, for example, a ferromagnetic alloy containing FePt with an A1 structure. Instead of forming a ferromagnetic layer, a portion of an FePt magnetic material having an L1 0 structure can be disordered into an A1 structure by ion irradiation or plasma damage, thereby controlling the coercive force.
  • the thickness of the auxiliary recording layer is preferably about 0 to 10 nm.
  • the auxiliary recording layer can be formed, for example, by sputtering.
  • an exchange coupling control layer may be provided between the magnetic layer and the auxiliary recording layer.
  • the exchange coupling control layer may be made of, for example, Ru or a Ru alloy.
  • the thickness of the exchange coupling control layer is preferably approximately 0 to 10 nm.
  • the exchange coupling control layer can be formed, for example, by sputtering.
  • a carbon-based protective layer is preferable as the material for the protective layer.
  • the protective layer can be formed, for example, by depositing the protective layer using C 2 H 4 by a chemical vapor deposition (CVD) method, and then performing a nitriding process in the same chamber to introduce nitrogen into the surface.
  • CVD chemical vapor deposition
  • the thickness of the protective layer can be, for example, 3 to 7 nm.
  • the lubricating layer may contain PFPE (polyfluoropolyether).
  • the lubricating layer can be formed, for example, by applying PFPE (polyfluoropolyether) to the protective layer using a dip coating method.
  • the method for manufacturing a magnetic disk includes the steps of: The method includes a step of heating the substrate until the substrate surface temperature reaches 600 to 780° C., and then forming a magnetic layer having an L10 structure.
  • the substrate here is a magnetic disk substrate having a pair of main surfaces and an outer peripheral end surface, and after heating the magnetic disk substrate under the aforementioned heating conditions, the straightness measured under the aforementioned measurement conditions is 90 ⁇ m or less.
  • the magnetic layer formation process it is preferable to form the magnetic layer on the substrate by sputtering.
  • sputtering process various types of equipment and conditions can be used as appropriate, including known methods.
  • DC magnetron sputtering is particularly preferable, as it allows for uniform film formation.
  • an alloy having an ordered L10 structure with high uniaxial magnetic anisotropy In order to form an alloy with high coercivity for a magnetic disk, it is preferable to produce an alloy having an ordered L10 structure with high uniaxial magnetic anisotropy. In this embodiment, in order to grow FePt alloy particles having a highly ordered L10 structure in an island shape, it is preferable to maintain the substrate temperature at 650°C or higher during sputtering film formation.
  • simultaneous sputtering may be performed using separate targets of Fe and Pt that make up an FePt alloy, or separate targets of Fe, Pt, and Ag that make up an FePtAg alloy, or sputtering may be performed using an FePt alloy target or FePtAg alloy target whose composition has been preliminarily adjusted.
  • the alloy target mainly composed of Fe and Pt is preferably prepared so that the composition of Fe and Pt in the magnetic layer to be formed is close to 1:1, specifically, Fe x Pt 1-x , where x is 0.4 ⁇ x ⁇ 0.55. Furthermore, when separate targets of Fe and Pt are used, the film formation rate can be made approximately 1:1 by controlling the power input to each target.
  • the substrate may be heat-treated (annealed) if necessary.
  • the annealing temperature is preferably 300 to 700°C.
  • a magnetic disk a substrate having a pair of main surfaces and an outer peripheral edge surface; a magnetic layer having an L10 structure on the pair of main surfaces and the outer peripheral end surface of the substrate,
  • the magnetic disk is heated under the following heating conditions, and then the straightness measured under the following measuring conditions is 90 ⁇ m or less.
  • Heating conditions The surface temperature of the magnetic disk is heated from room temperature to 600° C. in 25 seconds, then heated to 700° C. in 35 seconds, and then cooled to room temperature in 120 seconds.
  • the maximum valley depth Sv is measured in three directions, each oriented 120 degrees apart, within a measurement range of at least 88 mm in length using a surface roughness measuring device, and the number average value of the maximum valley depth Sv is determined as the straightness value.
  • ⁇ 4> The magnetic disk according to any one of ⁇ 1> to ⁇ 3>, wherein the change in straightness before and after heating under the heating conditions is 15 to 70 ⁇ m.
  • ⁇ 5> The magnetic disk according to any one of ⁇ 1> to ⁇ 4>, wherein the magnetic layer has a granular structure including magnetic grains containing an L1 0 -FePt alloy and grain boundary portions.
  • ⁇ 6> The magnetic disk according to any one of ⁇ 1> to ⁇ 5>, further comprising a first underlayer containing MgO on the pair of main surfaces and the outer peripheral end face of the substrate.
  • ⁇ 7> The magnetic disk according to any one of ⁇ 1> to ⁇ 6>, further comprising a second underlayer containing a Cr alloy on the pair of main surfaces and the outer peripheral end face of the substrate.
  • ⁇ 8> The magnetic disk according to any one of ⁇ 1> to ⁇ 7>, wherein the substrate is a glass substrate.
  • the substrate is ⁇ 8> A magnetic disk according to any one of ⁇ 1> to ⁇ 8>, containing 55 to 80 mol% of SiO2, 5 to 25 mol% of Al2O3 , 0 to 8 mol% of B2O3 , 0 to 5 mol% of P2O5 , 5 to 25 mol% of MO (MO is at least one selected from MgO, CaO, SrO, and BaO, and the content thereof is the total value of the contents of MgO, CaO, SrO, and BaO), and 0 to 15 mol% of M2O ( M2O is at least one selected from Li2O , Na2O , and K2O , and the content thereof is the total value of Li2O , Na2O , and K2O ).
  • MO is at least one selected from MgO, CaO, SrO, and BaO, and the content thereof is the total value of the contents of MgO, CaO, SrO, and BaO
  • M2O
  • ⁇ 10> The magnetic disk according to any one of ⁇ 1> to ⁇ 9>, wherein the substrate has a thickness of 0.2 to 0.6 mm.
  • ⁇ 11> The magnetic disk according to any one of ⁇ 1> to ⁇ 10>, wherein the substrate has a Young's modulus of 80 GPa or more.
  • ⁇ 12> The magnetic disk according to any one of ⁇ 1> to ⁇ 11>, wherein the substrate has a glass transition temperature of 700° C. or higher.
  • ⁇ 13> A magnetic disk substrate having a pair of main surfaces and an outer peripheral end surface, The magnetic disk substrate is heated under the following heating conditions, and then the straightness measured under the following measuring conditions is 90 ⁇ m or less.
  • the surface temperature of the magnetic disk is heated from room temperature to 600° C. in 25 seconds, then heated to 700° C. in 35 seconds, and then cooled to room temperature in 120 seconds.
  • the maximum valley depth Sv is measured in three directions, each oriented 120 degrees apart, within a measurement range of at least 88 mm in length using a surface roughness measuring device, and the number average value of the maximum valley depth Sv is determined as the straightness value.
  • ⁇ 15> ⁇ 13> or ⁇ 14> wherein the magnetic disk substrate has a straightness of 80 ⁇ m or less as measured under the measurement conditions after heating the magnetic disk under the heating conditions.
  • ⁇ 16> ⁇ 16> The magnetic disk substrate according to any one of ⁇ 13> to ⁇ 15>, wherein the change in straightness before and after heating under the heating conditions is 15 to 70 ⁇ m.
  • ⁇ 17> The magnetic disk substrate according to any one of ⁇ 13> to ⁇ 16>, wherein the substrate is made of glass.
  • the substrate is ⁇ 13> - ⁇ 17>
  • the magnetic disk substrate contains 55 to 80 mol% of SiO2 , 5 to 25 mol% of Al2O3 , 0 to 8 mol% of B2O3 , 5 to 25 mol% of MO (MO is at least one selected from MgO, CaO, SrO, and BaO, and the content is the total value of the contents of MgO, CaO, SrO , and BaO ), and 0 to 15 mol% of M2O ( M2O is at least one selected from Li2O , Na2O , and K2O , and the content is the total value of Li2O , Na2O, and K2O).
  • ⁇ 19> The magnetic disk substrate according to any one of ⁇ 13> to ⁇ 18>, wherein the substrate has a thickness of 0.2 to 0.6 mm.
  • ⁇ 20> The magnetic disk substrate according to any one of ⁇ 13> to ⁇ 19>, wherein the substrate has a Young's modulus of 80 GPa or more.
  • ⁇ 21> The magnetic disk substrate according to any one of ⁇ 13> to ⁇ 20>, wherein the substrate has a glass transition temperature of 700° C. or higher.
  • ⁇ 22> The magnetic disk substrate according to any one of ⁇ 13> to ⁇ 21>, which is for thermally assisted recording.
  • a method for manufacturing a magnetic disk comprising: a step of heating the substrate until the substrate surface temperature reaches 600 to 780°C, and then forming a magnetic layer having an L10 structure; The method for manufacturing a magnetic disk, wherein the substrate is a magnetic disk substrate having a pair of main surfaces and an outer peripheral end surface, and after heating the magnetic disk substrate under the following heating conditions, the magnetic disk substrate has a straightness of 90 ⁇ m or less as measured under the following measurement conditions. (Heating conditions) The surface temperature of the magnetic disk is heated from room temperature to 600° C.
  • the maximum valley depth Sv is measured in three directions, each oriented 120 degrees apart, within a measurement range of at least 88 mm in length using a surface roughness measuring device, and the number average value of the maximum valley depth Sv is determined as the straightness value.
  • the method for producing a magnetic disk according to ⁇ 24> wherein the change in straightness before and after heating under the heating conditions is 10 to 80 ⁇ m.
  • ⁇ 27> ⁇ 27> The method for manufacturing a magnetic disk according to any one of ⁇ 24> to ⁇ 26>, wherein the change in straightness before and after heating under the heating conditions is 15 to 70 ⁇ m.
  • the straightness was measured using a surface roughness measuring instrument (product name "Surftest-VS2100” manufactured by Mitutoyo Corporation). The measurement was performed in a measurement range on a straight line of 88 mm in length shown by the dotted line in Figure 3. Measurement was performed in three directions, each 120 degrees apart, and the number average of the measured values was taken as the straightness.
  • a magnetic disk (substrate) is placed between two ceramic panel heaters, and the substrate is left in place for 60 seconds, after which it is removed.
  • Four cartridge heaters 500 W were inserted into one ceramic panel (AIN (aluminum nitride)). Two such panels were prepared, and the heater panel surfaces were spaced 18 mm apart.
  • a thermocouple (Cerathermo Thermocouple Type K, wire diameter ⁇ 0.1) placed on the magnetic disk surface was used to adjust the panel temperature so that the disk surface reached a predetermined temperature, and non-contact heating was performed in the atmosphere.
  • the magnetic disk was heated to 700°C in 60 seconds, as shown in the graph below, and then the magnetic disk was removed. As shown in Figure 4, the magnetic disk was heated from room temperature to 600°C in 25 seconds, and then heated to 700°C in 35 seconds. It was then cooled to room temperature over 120 seconds.
  • the Young's modulus E of the substrate was measured based on JIS R1602: 1995.
  • a test piece for measurement was cut out from the magnetic disk as a rectangular parallelepiped having a length of 50 mm, a width of 10 mm, and a thickness the same as that of the magnetic disk, and the measurement was performed at room temperature.
  • ⁇ Glass transition temperature> Using a thermomechanical analyzer, a graph was created from the amount of change in the probe position due to thermal expansion caused by a temperature rise, and the glass transition temperature was read from the change in the slope of the graph.
  • the thermal expansion coefficient of the substrate was determined by measuring the change in length of a sample cut out from the magnetic disk to a size of 50 mm in length and 10 mm in width, using a thermal dilatometer based on laser interferometry, over a specified temperature range, and using this as the average linear expansion coefficient value from 100 to 300°C.
  • Magnetic disk substrate diameter 97 mm, inner diameter 25 mm, plate thickness 0.5 mm or 0.43 mm
  • Thickness t Thickness of the glass substrate (mm) Straightness before heating C1: Straightness before heating ( ⁇ m) Straightness after heating C2: Straightness after heating ( ⁇ m) Change in straightness before and after heating dC: Change in straightness C2-C1 ( ⁇ m) (magnetic disk substrate)
  • SU-1 Glass substrate (a 0.43 mm thick glass substrate was obtained using alkali-containing glass having a glass transition temperature of 752°C, a thermal expansion coefficient at 100 to 300°C of 43 (10 -7 /K), a Young's modulus of 90 (GPa), and a specific elastic modulus of 36.1 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 16.3 ( ⁇ m ⁇ mm).
  • the alkali-containing glass used had a B 2 O 3 content of 0 mol %, a total MgO and CaO content of 18.5 mol %, a Li 2 O content of 1.0 mol %, and a Na 2 O content of 3.0 mol %).
  • SU-2 Glass substrate (a 0.43 mm thick glass substrate was obtained using alkali-containing glass having a glass transition temperature of 737°C, a thermal expansion coefficient at 100 to 300°C of 43 (10 -7 /K), a Young's modulus of 93 (GPa), and a specific elastic modulus of 36.8 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 25.4 ( ⁇ m ⁇ mm).
  • the alkali-containing glass used had a B 2 O 3 content of 0.3 mol %, a total content of MgO and CaO of 16.5 mol %, a Li 2 O content of 0.8 mol %, and a Na 2 O content of 3.0 mol %).
  • SU- 3 Glass substrate (a 0.50 mm thick glass substrate was obtained using alkali-free glass formed by down-drawing, which had a glass transition temperature of 810°C, a thermal expansion coefficient at 100 to 300°C of 39 (10 -7 /K), a Young's modulus of 83 (GPa), and a specific elastic modulus of 31.4 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 29.5 ( ⁇ m ⁇ mm).
  • the alkali-free glass used had a B 2 O 3 content of 0.8 mol %, a total content of MgO and CaO of 11.0 mol %, and a Li 2 O and Na 2 O content of 0 mol %).
  • SU- 4 Glass substrate (a glass substrate having a thickness of 0.50 mm was obtained using a down-drawn alkali-free glass having a glass transition temperature of 805°C, a thermal expansion coefficient at 100 to 300°C of 34 (10 -7 /K), a Young's modulus of 83 (GPa), and a specific elastic modulus of 31.5 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 34.5 ( ⁇ m ⁇ mm).
  • SU-5 Glass substrate (a glass substrate having a thickness of 0.50 mm was obtained using alkali-containing glass having a glass transition temperature of 710°C, a thermal expansion coefficient of 45 (10 -7 /K) at 100 to 300°C, a Young's modulus of 98 (GPa), and a specific elastic modulus of 38.2 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 35.0 ( ⁇ m ⁇ mm).
  • SU-6 Glass substrate (a 0.43 mm thick glass substrate was obtained using alkali-containing glass having a glass transition temperature of 727°C, a thermal expansion coefficient at 100 to 300°C of 45 (10 -7 /K), a Young's modulus of 96 (GPa), and a specific elastic modulus of 37.9 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 33.5 ( ⁇ m ⁇ mm).
  • the alkali-containing glass used had a B 2 O 3 content of 1.5 mol %, a total MgO and CaO content of 21.5 mol %, a Li 2 O content of 0.5 mol %, and a Na 2 O content of 2.5 mol %).
  • SU-7 Glass substrate (a glass substrate having a thickness of 0.43 mm was obtained using alkali-free glass formed by down-drawing, which had a glass transition temperature of 810°C, a thermal expansion coefficient at 100 to 300°C of 39 (10 -7 /K), a Young's modulus of 83 (GPa), and a specific elastic modulus of 31.4 ( 10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 35.7 ( ⁇ m ⁇ mm).
  • SU-8 Glass substrate (a glass substrate having a thickness of 0.43 mm was obtained using alkali-free glass formed by down-drawing, which had a glass transition temperature of 805°C, a thermal expansion coefficient at 100 to 300°C of 34 (10 -7 /K), a Young's modulus of 83 (GPa), and a specific elastic modulus of 31.5 ( 10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 37.4 ( ⁇ m ⁇ mm).
  • SU-9 Glass substrate (a glass substrate having a thickness of 0.50 mm was obtained using alkali-free glass formed by the float method, which had a glass transition temperature of 782°C, a thermal expansion coefficient at 100 to 300°C of 35 (10 -7 /K), a Young's modulus of 85 (GPa), and a specific elastic modulus of 32.8 ( 10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 42.5 ( ⁇ m ⁇ mm).
  • SU-10 Glass substrate (a glass substrate having a thickness of 0.43 mm was obtained using alkali-containing glass having a glass transition temperature of 710°C, a thermal expansion coefficient of 45 (10 -7 /K) at 100 to 300°C, a Young's modulus of 98 (GPa), and a specific elastic modulus of 38.2 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 44.3 ( ⁇ m ⁇ mm).
  • SU-11 Glass substrate (a glass substrate having a thickness of 0.43 mm was obtained using alkali-free glass formed by the float method, which had a glass transition temperature of 782°C, a thermal expansion coefficient at 100 to 300°C of 35 (10 -7 /K), a Young's modulus of 85 (GPa), and a specific elastic modulus of 32.8 ( 10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 51.2 ( ⁇ m ⁇ mm).
  • SU-12 Glass substrate (a glass substrate having a thickness of 0.50 mm was obtained using alkali-free glass formed by down-drawing, which had a glass transition temperature of 780°C, a thermal expansion coefficient at 100 to 300°C of 36 (10 -7 /K), a Young's modulus of 84 (GPa), and a specific elastic modulus of 33.1 ( 10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 58.0 ( ⁇ m ⁇ mm).
  • SU-13 Glass substrate (a glass substrate having a thickness of 0.43 mm was obtained using alkali-free glass formed by down-drawing, which had a glass transition temperature of 780°C, a thermal expansion coefficient at 100 to 300°C of 36 (10 -7 /K), a Young's modulus of 84 (GPa), and a specific elastic modulus of 33.1 ( 10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 56.3 ( ⁇ m ⁇ mm).
  • SU-14 Glass substrate (a glass substrate having a thickness of 0.50 mm was obtained using alkali-containing glass having a glass transition temperature of 691°C, a thermal expansion coefficient of 51 (10 -7 /K) at 100 to 300°C, a Young's modulus of 95 (GPa), and a specific elastic modulus of 36.6 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 138.0 ( ⁇ m ⁇ mm).
  • SU-15 Glass substrate (a glass substrate having a thickness of 0.43 mm was obtained using alkali-containing glass having a glass transition temperature of 691°C, a thermal expansion coefficient of 51 (10 -7 /K) at 100 to 300°C, a Young's modulus of 95 (GPa), and a specific elastic modulus of 36.6 (10 6 m 2 /s 2 ).
  • the product of the straightness C2 ( ⁇ m) of the glass substrate after heating and the thickness (mm) of the substrate was 164.7 ( ⁇ m ⁇ mm).
  • the value of C2 x t is 34.0 ( ⁇ m/mm) or less.
  • the change in straightness dC before and after heating tends to increase, but for substrates with a C2 x t value of 34.0 ( ⁇ m/mm) or less, the change in straightness dC before and after heating can be kept sufficiently small even if the thickness is 0.43 mm or less.
  • all of the magnetic disk substrates in each example contained 55 to 80 mol% SiO2 , 5 to 25 mol % Al2O3 , 0 to 8 mol% B2O3 , 0 to 5 mol% P2O5 , 5 to 25 mol% MO (MO is at least one selected from MgO, CaO, SrO and BaO, and its content is the total content of MgO, CaO, SrO and BaO), and 0 to 15 mol% M2O ( M2O is at least one selected from Li2O , Na2O and K2O , and its content is the total value of Li2O , Na2O and K2O ).
  • MO is at least one selected from MgO, CaO, SrO and BaO, and its content is the total content of MgO, CaO, SrO and BaO
  • M2O is at least one selected from Li2O , Na2O and K2O , and its content is the total value of Li2O , Na2O
  • the magnetic disk substrates of Examples 1, 2, 3, and 6 contained 0 to 15 mol % M2O and 5 to 25 mol % MO. Furthermore, in these magnetic disk substrates, the B2O3 content was 0 to 1.5 mol %, and the total content of MgO and CaO was 5.0 to 25.0 mol %. Because these magnetic disk substrates have a low B2O3 content , they are preferable because they can reduce the change in straightness dC after heating even if the plate thickness is small.

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Abstract

La présente divulgation concerne un disque magnétique qui est approprié pour être utilisé dans un enregistrement magnétique assisté thermiquement, un substrat de disque magnétique, l'utilisation du substrat de disque magnétique, et un procédé de fabrication du disque magnétique.　La présente divulgation concerne un disque magnétique qui comprend : un substrat comprenant une paire de surfaces principales et une surface d'extrémité circonférentielle externe ; et une couche magnétique présentant une structure L10 sur la paire de surfaces principales et la surface d'extrémité circonférentielle externe du substrat. La rectitude du disque magnétique mesurée dans la condition de mesure suivante après chauffage du disque magnétique dans la condition de chauffage suivante est inférieure ou égale à 90 µm. (condition de chauffage) Le disque magnétique est chauffé de sorte que la température de surface atteigne 600 °C à partir de la température ambiante en 25 secondes, puis est chauffé de sorte que la température de surface atteigne 700 °C en 35 secondes, puis est refroidi de sorte que la température de surface atteigne la température ambiante en 120 secondes. (condition de mesure de rectitude) Au moyen d'un dispositif de mesure de rugosité de surface, les valeurs des profondeurs de vallée maximales Sv sont mesurées dans une plage de mesure d'au moins 88 mm de longueur dans trois directions qui sont différentes les unes des autres de 120°, et la valeur moyenne en nombre des profondeurs de vallée maximales Sv sont obtenues en tant que valeur de rectitude.
PCT/JP2025/017254 2024-05-15 2025-05-12 Disque magnétique, substrat de disque magnétique, et utilisation d'un substrat de disque magnétique, et procédé de fabrication de disque magnétique Pending WO2025239331A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004062995A (ja) * 2002-07-29 2004-02-26 Fuji Electric Holdings Co Ltd 垂直磁気記録媒体用基板およびその製造方法並びに垂直磁気記録媒体およびその製造方法
JP2016216355A (ja) * 2011-04-21 2016-12-22 Hoya株式会社 ガラスブランク
JP2019160384A (ja) * 2018-03-09 2019-09-19 株式会社Uacj 磁気ディスク用基板及びその製造方法、並びに、当該磁気ディスク用基板を用いた磁気ディスク
WO2023282262A1 (fr) * 2021-07-05 2023-01-12 Hoya株式会社 Plaque de verre, verre en forme de disque, substrat de verre de disque magnétique et procédé de fabrication de plaque de verre

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004062995A (ja) * 2002-07-29 2004-02-26 Fuji Electric Holdings Co Ltd 垂直磁気記録媒体用基板およびその製造方法並びに垂直磁気記録媒体およびその製造方法
JP2016216355A (ja) * 2011-04-21 2016-12-22 Hoya株式会社 ガラスブランク
JP2019160384A (ja) * 2018-03-09 2019-09-19 株式会社Uacj 磁気ディスク用基板及びその製造方法、並びに、当該磁気ディスク用基板を用いた磁気ディスク
WO2023282262A1 (fr) * 2021-07-05 2023-01-12 Hoya株式会社 Plaque de verre, verre en forme de disque, substrat de verre de disque magnétique et procédé de fabrication de plaque de verre

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