WO2023100893A1 - 磁気記録媒体用ガラス基板、磁気記録媒体用ガラスディスク、磁気記録媒体及びガラスディスクの製造方法 - Google Patents

磁気記録媒体用ガラス基板、磁気記録媒体用ガラスディスク、磁気記録媒体及びガラスディスクの製造方法 Download PDF

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Publication number
WO2023100893A1
WO2023100893A1 PCT/JP2022/044030 JP2022044030W WO2023100893A1 WO 2023100893 A1 WO2023100893 A1 WO 2023100893A1 JP 2022044030 W JP2022044030 W JP 2022044030W WO 2023100893 A1 WO2023100893 A1 WO 2023100893A1
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Prior art keywords
magnetic recording
recording medium
glass
glass substrate
medium according
Prior art date
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Ceased
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PCT/JP2022/044030
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English (en)
French (fr)
Japanese (ja)
Inventor
晋吉 三和
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Nippon Electric Glass Co Ltd
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Nippon Electric Glass Co Ltd
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Publication date
Application filed by Nippon Electric Glass Co Ltd filed Critical Nippon Electric Glass Co Ltd
Priority to US18/706,446 priority Critical patent/US20250263325A1/en
Priority to JP2023565025A priority patent/JPWO2023100893A1/ja
Priority to CN202280077269.2A priority patent/CN118284935A/zh
Publication of WO2023100893A1 publication Critical patent/WO2023100893A1/ja
Anticipated expiration legal-status Critical
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    • 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
    • G11B5/739—Magnetic recording media substrates
    • G11B5/73911—Inorganic substrates
    • G11B5/73921—Glass or ceramic substrates
    • 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
    • C03C3/093—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium containing zinc or zirconium
    • 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
    • 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
    • G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers

Definitions

  • the present invention relates to a glass substrate for a magnetic recording medium, a glass disk for a magnetic recording medium, a magnetic recording medium, and a method for manufacturing a glass disk.
  • a magnetic recording device includes a magnetic recording medium in which a magnetic layer is formed on a magnetic recording medium disk, and information can be recorded using the magnetic layer.
  • a magnetic recording medium in which a magnetic layer is formed on a magnetic recording medium disk, and information can be recorded using the magnetic layer.
  • aluminum alloy disks have been used as disks for magnetic recording media used in magnetic recording devices.
  • Glass discs which have excellent properties, are also used.
  • HAMR energy-assisted magnetic recording method
  • an ordered alloy having a large magnetic anisotropy coefficient Ku (hereinafter referred to as "high Ku") is used as the magnetic material of the magnetic layer.
  • the base material including the glass disk is heat-treated at a high temperature of 600 to 800° C. during or before and after the film formation of the magnetic layer. do.
  • the substrate including the glass disk is irradiated with a laser after the magnetic layer is formed. Such heat treatment and laser irradiation also have the purpose of increasing the annealing temperature and coercive force of the magnetic layer containing the FePt-based alloy or the like.
  • glass disks for magnetic recording media are required to have high rigidity (Young's modulus) so as not to cause large deformation during high-speed rotation.
  • a magnetic recording medium comprising a glass disk
  • information is written and read along the direction of rotation while the medium is rotated around the central axis at high speed and the magnetic head is moved in the radial direction.
  • the rotational speed for increasing the writing speed and reading speed has been increasing from 5400 rpm to 7200 rpm and further to 10000 rpm. Since positions for recording information are assigned, if the glass disk is deformed during rotation, the position of the magnetic head will be shifted, making accurate reading difficult.
  • the DFH mechanism is a mechanism in which a heating portion such as a very small heater is provided in the vicinity of the recording/reproducing element portion of the magnetic head, and only the periphery of the element portion is thermally expanded toward the medium surface direction.
  • the magnetic head since the gap between the recording/reproducing element portion of the magnetic head and the surface of the magnetic recording medium is extremely small, for example, 2 nm or less, the magnetic head may collide with the surface of the magnetic recording medium even with a slight impact. be. This tendency becomes more conspicuous as the rotation speed increases. Therefore, during high-speed rotation, it is important to prevent the deflection and fluttering of the glass disk, which cause this collision.
  • glass disks for magnetic recording media are also required to have an appropriate coefficient of thermal expansion in order to improve the reliability of recording and reproduction of magnetic recording media.
  • an HDD (hard disk drive) incorporating a magnetic recording medium has a structure in which the central portion is pressed by the spindle of a spindle motor to rotate the magnetic recording medium itself. Therefore, if the difference in thermal expansion coefficient between the glass disk and the spindle material is too large, the magnetic recording medium will be deformed due to the difference in thermal expansion and contraction between them due to ambient temperature changes. If such a phenomenon occurs, the written information cannot be read by the magnetic head, and there is a possibility that the reliability of recording and reproduction may be impaired. Therefore, it is desirable that the glass disk for magnetic recording media has a coefficient of thermal expansion that matches the coefficient of thermal expansion of the spindle material (for example, stainless steel) as much as possible.
  • the spindle material for example, stainless steel
  • the present invention has been made in view of the above circumstances, and its object is to prevent bending and fluttering during high-speed rotation, reduce the amount of deformation when placed horizontally, and furthermore, The object is to create a glass disk for magnetic recording media that matches the coefficient of thermal expansion of the material (such as stainless steel).
  • the present inventor found that the above technical problems can be solved by limiting the various properties of the glass substrate (original glass plate) before being processed into a glass disk within a predetermined range. , is proposed as the present invention. That is, the glass substrate for a magnetic recording medium of the present invention has an average linear thermal expansion coefficient of 30 ⁇ 10 ⁇ 7 /° C. to 70 ⁇ 10 ⁇ 7 /° C. in a temperature range of 30° C. to 380° C. and a Young's modulus of 80 GPa. It is characterized by having a specific Young's modulus of 30 GPa/g ⁇ cm ⁇ 3 or more and a strain point of 700° C. or more.
  • the "average linear thermal expansion coefficient in the temperature range of 30° C. to 380° C.” can be measured with a dilatometer.
  • Stress point refers to a value measured according to the ASTM C336 method.
  • Young's modulus can be measured by a well-known resonance method.
  • the “specific Young's modulus” is a value obtained by dividing the Young's modulus by the density, and the density can be measured by, for example, the well-known Archimedes method.
  • the glass substrate for a magnetic recording medium of the present invention has an average coefficient of linear thermal expansion of 30 ⁇ 10 -7 /°C or higher in the temperature range of 30°C to 380°C.
  • the Young's modulus of the glass substrate for magnetic recording media of the present invention is regulated to 80 GPa or more. This makes it difficult for the glass disk to bend or flutter during high-speed rotation, thereby preventing collision between the information recording medium and the magnetic head.
  • the glass substrate for a magnetic recording medium of the present invention has a specific Young's modulus of 30 GPa/g ⁇ cm ⁇ 3 or more. In this way, even when the glass disk is made thin, the glass disk is less likely to bend or flutter, and damage due to collision between the information recording medium and the magnetic head or peripheral parts can be prevented.
  • the strain point of the glass substrate for a magnetic recording medium of the present invention is regulated to 700°C or higher. In this way, even if heat treatment is performed at a high temperature, the glass disk is not deformed, and deformation of the glass disk can be prevented when manufacturing a magnetic recording medium using the energy-assisted magnetic recording method (HAMR).
  • HAMR energy-assisted magnetic recording method
  • the glass substrate for a magnetic recording medium of the present invention has a glass composition of 55% to 65% by mass of SiO 2 , 15% to 25% of Al 2 O 3 , and 2% to 5.5% of B 2 O 3 . , MgO 0.1% to 10%, CaO 0.1% to 10%, SrO 0% to 10%, BaO 0% to 10%, and ZrO 2 0% to 1%.
  • the glass substrate for a magnetic recording medium of the present invention preferably has a crack generation rate of 50% or less when indented with a Vickers indenter with a load of 500 g.
  • the "crack occurrence rate” is a value measured as follows. First, in a constant temperature and humidity chamber maintained at a humidity of 30% and a temperature of 25°C, a Vickers indenter set to a load of 500 g was driven into the glass surface for 15 seconds, and after 15 seconds, the number of cracks generated from the four corners of the indentation was counted.
  • the Vickers indenter can be implanted by a fully automatic Vickers hardness tester (for example, FLC-50VX manufactured by Futuretech). However, since the crack generation rate varies depending on the moisture content of the glass surface, the glass should be annealed for at least 1 hour in the temperature range of (Ps-350°C) to (Ps-10°C) before measurement. It is desirable to cancel differences in surface moisture conditions. In addition, Ps points out a strain point.
  • the glass substrate for a magnetic recording medium of the present invention preferably has a Vickers hardness of 640 or higher. By doing so, the main surface is less likely to be finely scratched. As a result, the surface accuracy of the magnetic recording medium can be maintained.
  • Vickers hardness refers to a value measured by pressing a Vickers indenter with a load of 100 g using a Vickers hardness tester.
  • the content of Na 2 O in the glass composition is preferably less than 0.1% by mass. Thereby, the performance of the magnetic layer formed on the surface of the glass disk can be maintained.
  • the glass substrate for a magnetic recording medium of the present invention preferably has a ⁇ -OH of 0.30/mm or less.
  • the glass substrate for a magnetic recording medium of the present invention preferably has an average roughness Ra of 2.0 nm or less on the main surface.
  • the "surface roughness Ra of the main surface” refers to the surface roughness Ra of both surfaces excluding the end surfaces, and can be measured with an atomic force microscope (AFM), for example.
  • the glass substrate for a magnetic recording medium of the present invention is finally processed into a disk shape by processing steps such as cutting and polishing, and the surface roughness and Ra of the glass disk are similarly 2.0 nm or less. is desirable. This makes it easier to obtain a highly accurate glass surface.
  • the glass substrate for a magnetic recording medium of the present invention preferably has an optical path length of 0.7 mm and an average linear transmittance of 70% or more in a wavelength range of 350 nm to 1500 nm.
  • the magnetic layer is sufficiently irradiated with the laser beam when laser irradiation is performed to increase Ku, so that the recording density of the magnetic recording medium can be efficiently increased.
  • the "average linear transmittance at an optical path length of 0.7 mm and a wavelength range of 350 nm to 1500 nm" can be measured with a commercially available spectrophotometer, for example, Shimadzu UV-3100 spectrophotometer, or Hitachi U -4000 or the like can be used.
  • the glass substrate for a magnetic recording medium of the present invention preferably has a substantially rectangular shape of 500 mm square or more and a thickness of 0.7 mm or less. In this way, a plurality of glass discs can be obtained from one glass substrate, thereby improving the productivity of the glass discs.
  • the main surface of the glass substrate for a magnetic recording medium of the present invention is essentially a fire-polished surface.
  • the glass disk for a magnetic recording medium of the present invention is preferably produced from the above glass substrate for a magnetic recording medium.
  • the glass disk for a magnetic recording medium of the present invention has an average linear thermal expansion coefficient of 30 ⁇ 10 ⁇ 7 /° C. to 70 ⁇ 10 ⁇ 7 /° C. in a temperature range of 30° C. to 380° C. and a Young's modulus of 80 GPa. It is characterized by having a specific Young's modulus of 30 GPa/g ⁇ cm ⁇ 3 or more and a strain point of 700° C. or more.
  • the glass disk for a magnetic recording medium of the present invention has a glass composition of 55% to 65% by mass of SiO 2 , 15% to 25% of Al 2 O 3 , and 2% to 5.5% of B 2 O 3 . , MgO 0.1% to 10%, CaO 0.1% to 10%, SrO 0% to 10%, BaO 0% to 10%, and ZrO 2 0% to 1%.
  • the magnetic recording medium of the present invention preferably includes the glass disk for a magnetic recording medium.
  • a method for producing a glass disk of the present invention is a method for producing a glass disk by processing a glass substrate for a magnetic recording medium to obtain a glass disk, wherein the glass substrate for a magnetic recording medium is the above glass substrate for a magnetic recording medium. is preferred.
  • FIG. 4 is an upper perspective view for showing the shape of a glass disk
  • the average linear thermal expansion coefficient in the temperature range of 30° C. to 380° C. is 30 ⁇ 10 ⁇ 7 /° C. to 70 ⁇ 10 ⁇ 7 /° C. or more, preferably 31 ⁇ 10 ⁇ 7 /°C to 70 ⁇ 10 ⁇ 7 /°C, 32 ⁇ 10 ⁇ 7 /°C to 65 ⁇ 10 ⁇ 7 /°C, 33 ⁇ 10 ⁇ 7 /°C to 60 ⁇ 10 ⁇ 7 /°C, 34 ⁇ 10 ⁇ 7 /°C to 55 x 10 -7 /°C, 35 x 10 -7 /°C to 45 x 10 -7 /°C, especially 35 x 10 -7 /°C to 40 x 10 -7 /°C.
  • the average coefficient of linear thermal expansion in the temperature range of 30 to 380°C is out of the above range, the difference in thermal expansion coefficient between the glass disk and the spindle material will increase. become difficult to match. As a result, the magnetic recording medium is likely to be deformed, and the reliability of recording and reproduction of the magnetic recording medium is likely to be lowered.
  • the Young's modulus of the glass substrate for a magnetic recording medium of the present invention is 80 GPa or higher, preferably 81 GPa or higher, more preferably 82 GPa or higher, and particularly preferably 83 GPa to 120 GPa. If the Young's modulus is too low, the glass disk tends to flex and flutter during high-speed rotation, and the information recording medium tends to collide with the magnetic head.
  • the specific Young's modulus is 30 GPa/g ⁇ cm ⁇ 3 or more, preferably 31 GPa/g ⁇ cm ⁇ 3 or more, 32 GPa/g ⁇ cm ⁇ 3 or more, particularly 33 GPa/g. ⁇ cm ⁇ 3 or more. If the specific Young's modulus is too low, the glass disk is likely to bend or flutter when the thickness of the glass disk is reduced, so that the information recording medium and the magnetic head are likely to collide.
  • the glass substrate for a magnetic recording medium of the present invention has a strain point of 700°C or higher, preferably 710°C or higher, particularly 720°C or higher. If the strain point is too low, the glass disk is likely to be deformed by heat treatment at high temperatures.
  • the glass substrate for a magnetic recording medium (and the glass disk for a magnetic recording medium) of the present invention has a glass composition of 55% to 65% by mass of SiO 2 , 15% to 25% of Al 2 O 3 and B 2 O 3 .
  • Contains 2%-5.5%, MgO 0.1%-10%, CaO 0.1%-10%, SrO 0%-10%, BaO 0%-10%, ZrO 2 0%-1% is preferred.
  • the reasons for limiting the content of each component as described above are as follows.
  • % display represents the mass % except when there is particular notice.
  • SiO2 is a component that forms the network of glass.
  • the content of SiO 2 is preferably 55%-65%, 56%-64%, 57%-63%, 58%-63%, 59%-62.5%. If the SiO 2 content is too low, vitrification becomes difficult and the heat resistance tends to decrease. In addition, the liquidus viscosity increases, making down-draw molding difficult. In addition, the density increases, and the specific Young's modulus tends to decrease. On the other hand, if the content of SiO 2 is too high, the viscosity of the glass melt increases, and the meltability and moldability tend to deteriorate. Also, the liquidus temperature rises, making molding difficult. Also, the coefficient of thermal expansion becomes too low.
  • Al 2 O 3 is a component that increases the Young's modulus, raises the strain point and the annealing point, and enhances the heat resistance.
  • the content of Al 2 O 3 is preferably 15% to 25%, 16% to 24%, 17% to 23%, 18% to 22%, especially 18% to 21%. If the content of Al 2 O 3 is too small, the Young's modulus is lowered, and the heat resistance and slow cooling tend to be lowered. On the other hand, if the content of Al 2 O 3 is too high, the liquidus temperature will decrease, making it difficult to mold by the overflow downdraw method.
  • B 2 O 3 is a component that forms a network of glass to enhance the solubility and lowers the liquidus temperature to enhance devitrification resistance. It is also a component that enhances scratch resistance.
  • the content of B 2 O 3 is preferably 2% to 5.5%, 2.2% to 5%, especially 2.5% to 5%. If the content of B 2 O 3 is too small, the scratch resistance is lowered and the liquidus temperature is lowered, making molding by the overflow downdraw method difficult. In addition, the glass becomes brittle, and defects such as chipping tend to occur during processing such as cutting and polishing. On the other hand, if the content of B 2 O 3 is too large, the Young's modulus is lowered, the rigidity is lowered, the strain point and the annealing point are lowered, and the heat resistance tends to be lowered.
  • MgO is a component that greatly increases the Young's modulus, and is also a component that lowers the high-temperature viscosity and improves meltability and moldability.
  • the content of MgO is preferably 0.1% to 10%, 0.5% to 9%, 0.5% to 8%, 0.5% to 7%, 1% to 6.5%, especially 1 .5% to 6%. If the content of MgO is too low, the Young's modulus and solubility are lowered, and the scratch resistance tends to be lowered. On the other hand, if the content of MgO is too high, the liquidus temperature rises and the liquidus viscosity drops, so the devitrification resistance tends to drop.
  • B 2 O 3 +MgO total amount of B 2 O 3 and MgO is preferably 5% to 10%, 5% to 9%, 5% to 8.5%, especially 5% to 8%. By doing so, it becomes easier to achieve both a high strain point and high scratch resistance.
  • CaO is a component that increases Young's modulus, lowers high-temperature viscosity, and enhances meltability and moldability.
  • the content of CaO is preferably 0.1% to 10%, 1% to 12%, 2% to 10%, especially 3% to 7%. If the content of CaO is too low, it will be difficult to obtain the above effects. On the other hand, if the CaO content is too high, the devitrification resistance tends to decrease.
  • the mass % ratio (B 2 O 3 +MgO)/CaO (value obtained by dividing the total amount of B 2 O 3 and MgO by CaO) is preferably 1.0 to 2.0, particularly 1.0 to 1.8. be. By doing so, it becomes easier to achieve both a high strain point and high devitrification resistance.
  • SrO is a component that lowers high-temperature viscosity and improves meltability and moldability. SrO is also preferably 0% to 10%, 0.1% to 8%, 0.5% to 6%, especially 1.5% to 6%. If the SrO content is too high, the devitrification resistance tends to decrease, and the density increases, which tends to decrease the specific Young's modulus.
  • BaO is a component that slightly lowers high-temperature viscosity and increases meltability. In addition, since it stabilizes the glass, it has the effect of lowering the liquidus temperature and increasing the liquidus viscosity. BaO is preferably 0% to 10%, 0.1% to 10%, 0.5% to 8%, especially 0.5% to 7%. If the BaO content is too high, the density increases and the specific Young's modulus tends to decrease.
  • ZrO 2 is a component that increases the Young's modulus, but if its content is too high, the devitrification resistance tends to decrease. Moreover, since the raw material is expensive, there is a possibility that the manufacturing cost will rise.
  • the content of ZrO 2 is preferably 0-1%, especially 0.01%-1%.
  • ingredients for example, the following ingredients may be added.
  • ZnO is a component that lowers high-temperature viscosity and significantly increases meltability.
  • the content of ZnO is preferably 0% to 7%, 0.1% to 5%, especially 0.5% to 3%. If the ZnO content is too low, it will be difficult to obtain the above effects. If the content of ZnO is too large, the glass tends to devitrify, and the strain point is lowered, which tends to lower the heat resistance.
  • TiO 2 is a component that enhances water resistance and weather resistance, and is a component that colors the glass.
  • the content of TiO 2 is therefore preferably between 0% and 0.5%, in particular between 0.005% and less than 0.1%.
  • Y 2 O 3 and La 2 O 3 are components that increase Young's modulus, but if the total amount of these components is too large, the devitrification resistance tends to decrease. Moreover, since the raw material is expensive, there is a possibility that the manufacturing cost will rise. Furthermore, there is a risk that the density will increase and the specific Young's modulus will decrease.
  • the total amount and individual content of these components are preferably 5% or less, 3% or less, 1% or less, and particularly preferably less than 0.1%.
  • Li 2 O, Na 2 O and K 2 O are components that lower high-temperature viscosity and improve meltability and moldability, but also lower water resistance and weather resistance.
  • the total and individual contents of Li 2 O, Na 2 O and K 2 O are preferably between 0.005% and 0.2%, between 0.01% and 0.1%, especially between 0.01% and 0.01%. less than 1%. If the contents of Li 2 O, Na 2 O and K 2 O are too high, the performance of the magnetic layer formed on the surface of the glass disk tends to deteriorate.
  • one or more selected from the group of SnO 2 , Cl, SO 3 and CeO 2 may be added at 0.05% to 0.5%. good.
  • Fe 2 O 3 is a component that is inevitably mixed into glass raw materials as an impurity, and is a coloring component. Therefore, the content of Fe 2 O 3 is preferably 0.5% or less, 0.001% to 0.1%, 0.005% to 0.07%, 0.008% to 0.03%, especially 0.008% to 0.025%. If the Fe 2 O 3 content is too high, the average linear transmittance in the wavelength range of 350 to 1500 nm tends to decrease.
  • the glass composition preferably does not substantially contain As2O3 , Sb2O3 , PbO, Bi2O3 and F.
  • substantially does not contain means that although the specified component is not actively added as a glass component, it is allowed to be mixed as an impurity. It means that the content is less than 0.05%.
  • the glass substrate for magnetic recording media (and the glass disk for magnetic recording media) of the present invention preferably has the following properties.
  • the crack generation rate when indented with a Vickers indenter with a load of 500 g is preferably 50% or less, 40% or less, 30% or less, and particularly preferably 20% or less. If the crack generation rate is too high, cracks are likely to occur on the end face of the magnetic recording medium (glass disk), and the magnetic recording medium (glass disk) is likely to be damaged.
  • the Vickers hardness is preferably 640 or higher, further 650 or higher, particularly 660 or higher. If the Vickers hardness is too low, the main surface is likely to be finely scratched, and the average surface roughness Ra may increase.
  • the liquidus temperature is preferably 1300° C. or lower, 1280° C. or lower, 1260° C. or lower, 1250° C. or lower, 1240° C. or lower, particularly 1230° C. or lower.
  • the liquidus viscosity is preferably 10 3.8 dPa ⁇ s or more, 10 4.4 dPa ⁇ s or more, 10 4.6 dPa ⁇ s or more, 10 4.8 dPa ⁇ s or more, particularly 10 5.0 dPa ⁇ s or more. s or more. This makes it difficult for devitrified crystals to precipitate during molding and facilitates molding into a plate by an overflow down-draw method or the like.
  • the "liquidus temperature” refers to the glass powder that passes through a 30-mesh (500 ⁇ m) standard sieve and remains on the 50-mesh (300 ⁇ m) sieve.
  • the "liquidus viscosity”, which can be calculated by measuring the temperature at which is precipitated, refers to the viscosity of the glass at the liquidus temperature, and can be measured by the platinum ball pull-up method.
  • the average in-line transmittance at an optical path length of 0.7 mm and a wavelength range of 350 nm to 1500 nm is preferably 70% or more, 80% or more, particularly 90% or more. If the average in-line transmittance in the optical path length of 0.7 mm and the wavelength range of 350 to 1500 nm is too low, the magnetic layer is not sufficiently irradiated with the laser light, making it difficult to increase Ku of the magnetic layer.
  • ⁇ -OH is preferably 0.30/mm or less, 0.25/mm or less, 0.20/mm or less, particularly 0.15/mm or less. If the ⁇ -OH is too large, the strain point and annealing point may be lowered, and the heat resistance may be lowered. If the ⁇ -OH is extremely lowered, it becomes necessary to introduce nitrogen into the melting atmosphere or introduce a dry component such as chlorine, which increases the cost of melting equipment and operation. Therefore, ⁇ -OH is preferably 0.05/mm or more.
  • Methods for reducing ⁇ -OH include the following methods. (1) Select raw materials with low water content. (2) Adding components (Cl, SO 3, etc.) that lower ⁇ -OH into the glass. (3) Reduce the moisture content in the furnace atmosphere. For example, introducing nitrogen into the melting atmosphere. (4) N2 bubbling in the molten glass; (5) Use a small melting furnace. (6) Increase the flow rate of molten glass. (7) Adopt an electric melting method.
  • ⁇ -OH refers to the value obtained by measuring the transmittance using FT-IR and using the following formula.
  • the average roughness Ra of the main surface is preferably 2.0 nm or less, 1.0 nm or less, 0.7 nm or less, 0.5 nm or less, and particularly 0.2 nm or less. If the average roughness Ra of the main surface is too large, improvement in magnetic properties cannot be expected even if the bit size is reduced for higher recording density.
  • the plate thickness is preferably 1.5 mm or less, 1.0 mm or less, 0.2 to 0.7 mm, particularly 0.3 to 0.6 mm. If the plate thickness is too thick, the plate must be mechanically or chemically polished to the desired plate thickness, and the plate must be polished to the desired plate thickness, which may increase the processing cost.
  • the glass substrate for a magnetic recording medium of the present invention is desirably molded by an overflow down-draw method or a slit down-draw method. Further, it is preferable that the main surface is substantially a fire-polished surface (the effective surface on which the magnetic layer is formed is the fire-polished surface). By doing so, the main surface of the glass substrate becomes smooth, fine cracks on the main surface are reduced, and mechanical properties and strength are improved. Furthermore, chipping or the like is less likely to occur when processed into a glass disk in a processing step.
  • the glass substrate for a magnetic recording medium of the present invention has a rectangular shape and undergoes processing steps such as polishing and cutting, and finally has a disk shape, that is, a disk shape with a circular opening formed in the center. It becomes a shape (see FIG. 1) and is made into a glass disk. This glass disk is then mounted on a magnetic recording device.
  • the shape of the glass disc is shown in FIG.
  • the size of the glass substrate is preferably 500 mm square or more, especially 1000 mm square or more. As the size increases, a large number of glass disks can be obtained from one glass substrate, which improves the productivity of glass disks.
  • Table 1 shows examples of the present invention.
  • a glass batch prepared by mixing glass raw materials so as to have the glass composition shown in the table was placed in a platinum crucible, then melted at 1500° C. to 1700° C. for 24 hours, refined and homogenized.
  • the glass batch was melted, it was homogenized by stirring using a platinum stirrer.
  • the molten glass was poured onto a carbon plate, shaped into a plate, and then slowly cooled at a temperature near the annealing point for 30 minutes.
  • ⁇ -OH average linear thermal expansion coefficient CTE in the temperature range of 30 ° C. to 380 ° C. 30 ° C. to 380 ° C.
  • ⁇ -OH is measured by the above method.
  • Average coefficient of linear thermal expansion CTE in the temperature range of 30° C. to 380 ° C. 30° C. to 380° C. is a value measured with a dilatometer.
  • the density ⁇ is a value measured by the Archimedes method.
  • strain point Ps, annealing point Ta, and softening point Ts are values measured based on the methods of ASTM C336 and C338.
  • the temperatures at high-temperature viscosities of 10 4.0 dPa ⁇ s, 10 3.0 dPa ⁇ s, and 10 2.5 dPa ⁇ s are values measured by the platinum ball pull-up method.
  • Young's modulus and specific Young's modulus refer to values measured by the resonance method.
  • the liquidus temperature TL is obtained by pulverizing each sample, passing through a 30-mesh (500 ⁇ m) standard sieve, placing the glass powder remaining on the 50-mesh (300 ⁇ m) in a platinum boat, and adjusting the temperature from 1100° C. to 1350° C. After being held in the gradient furnace for 24 hours, the platinum boat was taken out, and the temperature was such that devitrified crystals (crystal foreign matter) were observed in the glass.
  • the liquidus viscosity log ⁇ is a value obtained by measuring the viscosity of the glass at the liquidus temperature TL by the platinum ball pull-up method.
  • the crack incidence rate and Vickers hardness are the values measured by the above method.
  • sample no. 1 to 5 are average linear thermal expansion coefficient CTE in the temperature range of 30 ° C. to 380 ° C. 30 ° C. to 380 ° C. is 35 ⁇ 10 -7 / ° C. to 38 ⁇ 10 -7 / ° C., Young's modulus is 80 GPa or more, specific Young Since it has a modulus of 31.4 GPa/g ⁇ cm ⁇ 3 or higher and a strain point of 710° C. or higher, it is suitable as a glass substrate for magnetic recording media.
  • Sample No. in the table A glass batch prepared by mixing glass raw materials so as to have a glass composition of 1 to 5 is put into a melting kiln, then melted at 1500 ° C. to 1700 ° C. for 24 hours, clarified and homogenized to a thickness of 0.7 mm. It was molded into a plate shape by the overflow down-draw method.
  • the surface roughness Ra of the main surface of the obtained glass substrate was measured with an atomic force microscope (AFM), it was 0.10 nm to 0.20 nm.
  • AFM atomic force microscope
  • the average linear transmittance of the obtained glass substrate at an optical path length of 0.7 mm and a wavelength range of 350 nm to 1500 nm was measured with a spectrophotometer UV-3100 manufactured by Shimadzu Corporation, and all of them were 90% or more. After that, these glass substrates were processed into glass disks by performing processing steps such as a polishing step and a cutting step.

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  • Chemical Kinetics & Catalysis (AREA)
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PCT/JP2022/044030 2021-12-01 2022-11-29 磁気記録媒体用ガラス基板、磁気記録媒体用ガラスディスク、磁気記録媒体及びガラスディスクの製造方法 Ceased WO2023100893A1 (ja)

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US18/706,446 US20250263325A1 (en) 2021-12-01 2022-11-29 Glass substrate for magnetic recording medium, glass disk for magnetic recording medium, method for manufacturing magnetic recording medium, and method for manufacturing glass disk
JP2023565025A JPWO2023100893A1 (https=) 2021-12-01 2022-11-29
CN202280077269.2A CN118284935A (zh) 2021-12-01 2022-11-29 磁记录介质用玻璃基板、磁记录介质用玻璃盘、磁记录介质和玻璃盘的制造方法

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Publication number Priority date Publication date Assignee Title
WO2025143137A1 (ja) * 2023-12-27 2025-07-03 Hoya株式会社 情報記録媒体用ディスク

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017052661A (ja) * 2015-09-08 2017-03-16 旭硝子株式会社 磁気記録媒体用ガラス、磁気記録媒体用化学強化ガラス、磁気記録媒体用ガラス基板、及び磁気記録媒体
WO2020032146A1 (ja) * 2018-08-07 2020-02-13 Hoya株式会社 磁気ディスク用基板及び磁気ディスク
WO2020256945A1 (en) * 2019-06-19 2020-12-24 Corning Incorporated Yttria-containing glass substrate
JP2021075407A (ja) * 2019-11-05 2021-05-20 日本電気硝子株式会社 紫外線透過ガラス
JP2021086643A (ja) * 2019-11-25 2021-06-03 日本電気硝子株式会社 磁気記録媒体用ガラス基板及びそれを用いた磁気記録装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017052661A (ja) * 2015-09-08 2017-03-16 旭硝子株式会社 磁気記録媒体用ガラス、磁気記録媒体用化学強化ガラス、磁気記録媒体用ガラス基板、及び磁気記録媒体
WO2020032146A1 (ja) * 2018-08-07 2020-02-13 Hoya株式会社 磁気ディスク用基板及び磁気ディスク
WO2020256945A1 (en) * 2019-06-19 2020-12-24 Corning Incorporated Yttria-containing glass substrate
JP2021075407A (ja) * 2019-11-05 2021-05-20 日本電気硝子株式会社 紫外線透過ガラス
JP2021086643A (ja) * 2019-11-25 2021-06-03 日本電気硝子株式会社 磁気記録媒体用ガラス基板及びそれを用いた磁気記録装置

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2025143137A1 (ja) * 2023-12-27 2025-07-03 Hoya株式会社 情報記録媒体用ディスク

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