WO2014136751A1 - Glass substrate for information recording media, and information recording medium - Google Patents

Glass substrate for information recording media, and information recording medium Download PDF

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Publication number
WO2014136751A1
WO2014136751A1 PCT/JP2014/055396 JP2014055396W WO2014136751A1 WO 2014136751 A1 WO2014136751 A1 WO 2014136751A1 JP 2014055396 W JP2014055396 W JP 2014055396W WO 2014136751 A1 WO2014136751 A1 WO 2014136751A1
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WO
WIPO (PCT)
Prior art keywords
glass substrate
information recording
recording medium
glass
sio
Prior art date
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PCT/JP2014/055396
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French (fr)
Japanese (ja)
Inventor
大士 梶田
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Hoya株式会社
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Publication date
Application filed by Hoya株式会社 filed Critical Hoya株式会社
Priority to JP2015504317A priority Critical patent/JP6029740B2/en
Publication of WO2014136751A1 publication Critical patent/WO2014136751A1/en

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    • 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
    • C03C3/095—Glass compositions containing silica with 40% to 90% silica, by weight containing rare earths
    • 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
    • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
    • C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions
    • C03C21/002—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions to perform ion-exchange between alkali ions
    • 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
    • G11B5/62—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

Definitions

  • the present invention relates to a glass substrate for an information recording medium and an information recording medium mounted as part of the information recording medium in an information recording apparatus such as a hard disk drive (HDD).
  • HDD hard disk drive
  • Patent Document 1 Japanese Patent Laid-Open No. 2005-015328
  • Patent Document 2 Japanese Patent Laid-Open No. 2005-314159
  • the Tg which is an index of heat resistance of the glass substrate, is improved to 600 ° C. or higher.
  • a high-temperature heat treatment at about 600 ° C. is performed during the film formation of the Fe—Pt magnetic material on the glass substrate.
  • the present invention has been made to solve the above-described problems, and suppresses deformation of the glass substrate and suppresses diffusion of Li from the glass substrate during film formation of the magnetic recording medium and high-temperature annealing.
  • a glass substrate for an information recording medium and an information recording medium are provided.
  • the glass substrate for information recording medium is a glass substrate for heat assist recording.
  • the information recording medium according to the present invention has a magnetic recording layer on the glass substrate for information recording medium described above.
  • the glass substrate for an information recording medium and the information recording capable of suppressing the deformation of the glass substrate and suppressing the diffusion of Li from the glass substrate at the time of film formation and high temperature annealing of the magnetic recording medium.
  • a medium can be provided.
  • FIG. 2 is a perspective view showing an information recording device 30.
  • FIG. It is a top view which shows the glass substrate 1 manufactured by the manufacturing method of the glass substrate for information recording media based on this Embodiment.
  • FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2.
  • FIG. 5 is a cross-sectional view taken along line VV in FIG. 4.
  • FIG. 1 is a perspective view showing the information recording apparatus 30.
  • the information recording apparatus 30 includes the glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium (hereinafter also simply referred to as a glass substrate) in the embodiment as the information recording medium 10.
  • the information recording device 30 includes an information recording medium 10, a housing 20, a head slider 21, a suspension 22, an arm 23, a vertical shaft 24, a voice coil 25, a voice coil motor 26, a clamp member 27, and a fixing screw. 28.
  • a spindle motor (not shown) is installed on the upper surface of the housing 20.
  • An information recording medium 10 such as a magnetic disk is rotatably fixed to the spindle motor by a clamp member 27 and a fixing screw 28.
  • the information recording medium 10 is rotationally driven by this spindle motor at, for example, several thousand rpm.
  • a compression stress layer 12 see FIG. 5
  • a magnetic recording layer 14 see FIGS. 4 and 5 are formed on the glass substrate 1. To be manufactured.
  • the arm 23 is attached so as to be swingable around the vertical axis 24.
  • a suspension 22 formed in a leaf spring (cantilever) shape is attached to the tip of the arm 23.
  • a head slider 21 is attached to the tip of the suspension 22 so as to sandwich the information recording medium 10.
  • a voice coil 25 is attached to the opposite side of the arm 23 from the head slider 21.
  • the voice coil 25 is clamped by a magnet (not shown) provided on the housing 20.
  • a voice coil motor 26 is constituted by the voice coil 25 and the magnet.
  • a predetermined current is supplied to the voice coil 25.
  • the arm 23 swings around the vertical axis 24 by the action of electromagnetic force generated by the current flowing through the voice coil 25 and the magnetic field of the magnet.
  • the suspension 22 and the head slider 21 also swing in the direction of the arrow AR1.
  • the head slider 21 reciprocates on the front and back surfaces of the information recording medium 10 in the radial direction of the information recording medium 10.
  • a magnetic head (not shown) provided on the head slider 21 performs a seek operation.
  • the head slider 21 While the seek operation is performed, the head slider 21 receives a levitation force due to the air flow generated as the information recording medium 10 rotates. Due to the balance between the levitation force and the elastic force (pressing force) of the suspension 22, the head slider 21 travels with a constant flying height with respect to the surface of the information recording medium 10. By the traveling, the magnetic head provided on the head slider 21 can record and reproduce information (data) on a predetermined track in the information recording medium 10.
  • the information recording apparatus 30 on which the glass substrate 1 is mounted as a part of the members constituting the information recording medium 10 is configured as described above.
  • FIG. 2 is a plan view showing glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium according to the present embodiment.
  • 3 is a cross-sectional view taken along the line III-III in FIG.
  • the glass substrate 1 (glass substrate for information recording medium) used as a part of the information recording medium 10 (see FIGS. 4 and 5) has a main surface 2, a main surface 3, It has the inner peripheral end surface 4, the hole 5, and the outer peripheral end surface 6, and is formed in a disk shape as a whole.
  • the hole 5 is provided so as to penetrate from one main surface 2 toward the other main surface 3.
  • a chamfer 7 is formed between the main surface 2 and the inner peripheral end surface 4 and between the main surface 3 and the inner peripheral end surface 4.
  • a chamfered portion 8 (chamfer portion) is formed between the main surface 2 and the outer peripheral end surface 6 and between the main surface 3 and the outer peripheral end surface 6, a chamfered portion 8 (chamfer portion) is formed.
  • the size of the glass substrate 1 is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch. It is possible to make the size smaller than this or larger than this.
  • the thickness of the glass substrate is, for example, 0.30 mm to 2.2 mm from the viewpoint of preventing breakage.
  • the glass substrate has an outer diameter of about 64 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm.
  • the thickness of the glass substrate is a value calculated by averaging the values measured at a plurality of arbitrary points to be pointed on the glass substrate. From the viewpoint of increasing the hardness of the glass substrate, the Vickers hardness of the glass substrate 1 is preferably 610 kg / mm 2 or more.
  • FIG. 4 is a plan view showing an information recording medium 10 provided with a glass substrate 1 as an information recording medium.
  • FIG. 5 is a cross-sectional view taken along the line VV in FIG.
  • the information recording medium 10 includes a glass substrate 1, a compressive stress layer 12, and a magnetic recording layer 14.
  • the compressive stress layer 12 is formed so as to cover the main surfaces 2 and 3, the inner peripheral end face 4, and the outer peripheral end face 6 of the glass substrate 1.
  • the magnetic recording layer 14 is formed so as to cover a predetermined region on the main surfaces 2 and 3 of the compressive stress layer 12.
  • the magnetic recording layer 14 is formed on both the compressive stress layer 12 formed on the main surface 2 and the compressive stress layer 12 formed on the main surface 3 (both sides). Is formed.
  • the magnetic recording layer 14 may be provided only on the compression stress layer 12 (one side) formed on the main surface 2, or on the compression stress layer 12 (one side) formed on the main surface 3. It may be provided.
  • the magnetic recording layer 14 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the compressive stress layer 12 on the main surfaces 2 and 3 of the glass substrate 1 (spin coating method).
  • the magnetic recording layer 14 may be formed by a sputtering method or an electroless plating method performed on the compressive stress layer 12 on the main surfaces 2 and 3 of the glass substrate 1.
  • the thickness of the magnetic recording layer 14 is about 0.3 ⁇ m to 1.2 ⁇ m for the spin coating method, about 0.04 ⁇ m to 0.08 ⁇ m for the sputtering method, and about 0.05 ⁇ m to about the electroless plating method. 0.1 ⁇ m. From the viewpoint of thinning and high density, the magnetic recording layer 14 is preferably formed by sputtering or electroless plating.
  • a Co-based alloy or the like containing Ni or Cr as a main component is added for the purpose of adjusting the residual magnetic flux density. Is preferably used.
  • Fe—Pt magnetic materials have been used as magnetic layer materials suitable for heat-assisted recording.
  • the surface of the magnetic recording layer 14 may be thinly coated with a lubricant.
  • a lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon.
  • the magnetic recording layer 14 may be provided with a base layer or a protective layer as necessary.
  • the underlayer in the information recording medium 10 is selected according to the type of magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.
  • the underlayer provided on the magnetic recording layer 14 is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked.
  • a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.
  • Examples of the protective layer for preventing wear and corrosion of the magnetic recording layer 14 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus together with the underlayer and the magnetic film. These protective layers may be a single layer, or may have a multilayer structure composed of the same or different layers.
  • protective layers may be formed on the protective layer or instead of the protective layer.
  • colloidal silica fine particles are dispersed and coated on a Cr layer with tetraalkoxylane diluted with an alcohol solvent, and then fired to form a silicon oxide (SiO2) layer. May be.
  • the glass substrate manufacturing method S100 in the present embodiment includes a plate-like glass forming step S10, a cut-out forming step S20, a blasting step S30, a lapping step S40, an end surface polishing step S50, a rough polishing step S60, a cleaning step S65, and a chemical strengthening step. S70, precision polishing process S80, and scrub cleaning process S90 are provided.
  • the magnetic thin film forming step S200 is performed on the glass substrate obtained through the scrub cleaning step S90. Through the magnetic thin film forming step S200, the information recording medium 10 (see FIGS. 4 and 5) is obtained.
  • the details of the steps S10 to S90 constituting the glass substrate manufacturing method S100 will be described in order.
  • a glass sheet is manufactured using a known glass forming method such as a direct press method, a float method, a down draw method, a redraw method, or a fusion method using a molten glass as a material.
  • a known glass forming method such as a direct press method, a float method, a down draw method, a redraw method, or a fusion method using a molten glass as a material.
  • the blended raw material is put into a platinum crucible in an electric furnace heated to 1300 to 1550 ° C., etc., melted and clarified, stirred and homogenized, cast into a preheated mold, and gradually cooled into a glass block.
  • the direct press method can be directly molded from a melted glass into a target glass molded product, and is therefore suitable for producing a large amount of sheet glass having the same shape.
  • molten glass is supplied to a press mold and pressed with a press mold while the glass is in a softened state to form a sheet glass. After being held for 1 to 3 hours at a temperature near the glass transition point, it is gradually cooled.
  • the glass substrate 1 has a Vickers hardness of 610 kg / mm 2 or more.
  • a material of the glass substrate for example, amorphous glass or crystallized glass can be used.
  • chemical strengthening can be appropriately performed, and a glass substrate for an information recording medium excellent in flatness of the main surface and substrate strength can be provided.
  • blasting step S30 a plurality of particles (abrasive grains) 200 are sprayed on the main surfaces 2 and 3 of the glass substrate 1 formed by the plate-like glass forming step S10, whereby the main of the glass substrate (glass substrate precursor) 1 is obtained. Surfaces 2 and 3 are ground (first grinding step).
  • the average Ra of the glass substrate 1 is set to about 2.0 ⁇ m.
  • lapping step S40 In the lapping step (second grinding step) S40, lapping (second grinding) is performed on the main surface of the glass substrate 1 using a lapping machine (not shown). Both main surfaces of the glass substrate 1 are ground by the lapping machine.
  • End face polishing step S50 In the end surface polishing step S50, the inner peripheral end surface and the outer peripheral end surface of the glass substrate 1 are polished using a polishing brush having a spiral brush bristle material. While supplying the polishing slurry between the polishing brush and each end surface of the glass substrate 1, the polishing brush is rotated in contact with each end surface. With the glass substrate 1 immersed in the polishing liquid, the polishing brush may be rotated in contact with each end face.
  • the glass substrate 1 whose inner peripheral end face and outer peripheral end face are polished has its main surfaces 2 and 3 polished roughly in a plurality of times.
  • the main surfaces 2 and 3 are polished in two steps of the first and second rough polishing steps.
  • the first rough polishing step is mainly intended to remove scratches and distortions remaining on the main surfaces 2 and 3 in the lapping step, and the second rough polishing step The purpose is to finish the main surfaces 2 and 3 in a mirror shape.
  • the glass substrate 1 is subjected to a cleaning process using an acidic cleaning liquid.
  • the purpose of this cleaning treatment is to remove from the surface of the glass substrate 1 any of cerium oxide, zirconium oxide, or zirconium silicate used as a polishing slurry in the rough polishing step S60, which is the previous step.
  • the surface of the glass substrate 1 is etched using a cleaning liquid containing sulfuric acid and / or hydrofluoric acid. Wash.
  • the polishing slurry such as cerium oxide, zirconium oxide, or zirconium silicate adhering to the surface of the glass substrate 1 is appropriately removed by a strongly acidic cleaning liquid such as sulfuric acid and / or hydrofluoric acid. Thereafter, the glass substrate 1 is cleaned using an acidic cleaning solution.
  • the cleaning liquid used in the cleaning step S65 varies depending on the chemical resistance of the glass substrate 1, but a concentration of about 1% to 30% is preferable for sulfuric acid, and 0.2% to 5% for hydrofluoric acid. A concentration of about is preferred. Cleaning using these cleaning liquids may be performed while applying ultrasonic waves in a cleaning machine in which an aqueous solution is stored.
  • the frequency of the ultrasonic wave used at this time is preferably 78 kHz or higher.
  • the glass substrate 1 is chemically strengthened.
  • the chemical strengthening liquid for example, a mixed liquid of potassium nitrate (50 wt%) and sodium sulfate (50 wt%) can be used.
  • the chemical strengthening liquid is heated to, for example, 300 ° C. to 480 ° C.
  • the cleaned glass substrate 1 is preheated to 300 ° C. to 480 ° C., for example.
  • the glass substrate 1 is immersed in the chemical strengthening solution for 3 hours to 4 hours, for example.
  • the plurality of glass substrates 1 can be held in their respective holders so that the entire main surfaces 2 and 3 of the glass substrate 1 are chemically strengthened. preferable.
  • alkali metal ions lithium ions and sodium ions
  • salts sodium ions
  • potassium ions potassium ions
  • the surface of the glass substrate 1 is strengthened by the formation of the compressive stress layer, and the glass substrate 1 has good impact resistance.
  • the glass substrate 1 subjected to the chemical strengthening treatment is appropriately washed.
  • the glass substrate 1 is further cleaned using pure water or IPA (isopropyl alcohol) after being cleaned with sulfuric acid. Thereafter, the chemically strengthened layer may be removed.
  • IPA isopropyl alcohol
  • precision polishing step S80 After the chemical strengthening step S70, a precision polishing process is performed on the glass substrate 1.
  • the precision polishing step S80 is intended to finish the main surface of the glass substrate 1 in a mirror shape.
  • the precision polishing step S80 similarly to the rough polishing step S60 described above, the glass substrate 1 is precisely polished using a double-side polishing machine (see FIG. 11).
  • the composition of the polishing abrasive grains contained in the polishing liquid (slurry) used and the polishing pad used are different.
  • the grain size of the abrasive grains in the polishing liquid supplied to the main surfaces 2 and 3 of the glass substrate 1 on which the compressive stress layer is formed is made smaller than in the rough polishing step S60. Soften the hardness.
  • the polishing pad used in the precision polishing step S80 is, for example, a soft foam resin polisher.
  • the precision polishing step S80 uses loose abrasive grains, and includes a first polishing step with abrasive grains mainly composed of Ce and a second polishing step of polishing with abrasive grains mainly composed of Si.
  • the glass substrate 1 may be temporarily stored in water after being removed from the polishing pad of the double-side polishing machine. By storing in water, it is possible to reduce the amount of foreign matter such as polishing wrinkles or loose abrasive grains adhering to the glass substrate 1 after precision polishing while preventing the surface of the glass substrate 1 from drying after precision polishing. After the glass substrate 1 is stored in water for a predetermined time, the glass substrate 1 is set in a scrub cleaning device and scrub cleaning is performed on the glass substrate 1.
  • a cleaning liquid such as a detergent or pure water is used.
  • the pH of the cleaning solution used for scrub cleaning is preferably 9.0 or more and 12.2 or less. Within this range, the ⁇ potential can be easily adjusted and scrub cleaning can be performed efficiently.
  • both scrub cleaning with a detergent and scrub cleaning with pure water may be performed.
  • the glass substrate 1 By using a detergent and pure water, the glass substrate 1 can be more appropriately cleaned.
  • the glass substrate 1 may be further rinsed with pure water between scrub cleaning with a detergent and scrub cleaning with pure water.
  • the glass substrate 1 may be further subjected to ultrasonic cleaning.
  • ultrasonic cleaning with chemical solution such as sulfuric acid aqueous solution, ultrasonic cleaning with pure water, ultrasonic cleaning with detergent, ultrasonic cleaning with IPA, and / or steam drying with IPA, etc. Further, it may be performed.
  • the manufacturing method S100 of the glass substrate 1 in the present embodiment is configured as described above. By using manufacturing method S100 of glass substrate 1, glass substrate 1 of this embodiment shown in Drawing 2 and Drawing 3 can be obtained.
  • Magnetic thin film forming step S200 A magnetic recording layer is formed on the main surfaces 2 and 3 (or one of the main surfaces 2 and 3) of the glass substrate 1 after the scrub cleaning process is completed.
  • the magnetic recording layer includes, for example, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a protective layer made of a C system, and an F system.
  • an adhesion layer made of a Cr alloy
  • a soft magnetic layer made of a CoFeZr alloy
  • an orientation control underlayer made of Ru
  • a perpendicular magnetic recording layer made of a CoCrPt alloy
  • a protective layer made of a C system
  • F system an F system
  • the glass substrate 1 for an information recording medium used in the embodiment according to the present invention will be described in more detail.
  • the glass substrate 1 in the present embodiment is displayed in mol%, SiO 2 : 56 to 71%, Al 2 O 3 : 5 to 15%, B 2 O 3 : 0 to 3% Li 2 O: 0.1 to 6%, Na 2 O: 0.1 to 4%, K 2 O: 0-2%, MgO: 3 to 13%, CaO: 4-21%, SrO: 0 to 3%, BaO: 0 to 3%, ZnO: 0 to 3%, ZrO 2 : 0 to 3%, CeO 2 : 0-2%, SnO 2 : 0-2%, TiO 2 : 0-5%, and Nb 2 O 5 : 0 to 3%, And a content range of SiO 2 + Al 2 O 3 + B 2 O 3 : 64 to 80%, Li 2 O + Na 2 O + K 2 O: 0.2-6% MgO + CaO + SrO + BaO + ZnO: 14 to 28%, (Nb 2 O 5 + TiO 2
  • % indicating a glass composition indicates “mol%” unless otherwise specified.
  • An addition notation of a chemical formula such as “SiO 2 + Al 2 O 3 + B 2 O 3 ” indicates the total amount of components represented by such chemical formula.
  • SiO 2 + Al 2 O 3 + B 2 O 3 indicates the total amount of SiO 2 , Al 2 O 3 and B 2 O 3 .
  • the glass composition is preferably composed of only the components shown above except for inevitable impurities.
  • the deformation of the glass substrate 1 and the diffusion of Li from the glass substrate 1 can be suppressed during the formation of the magnetic recording medium and the high-temperature annealing.
  • the glass substrate for information recording medium of the present embodiment showing the above characteristics is particularly suitable as a glass substrate for heat-assisted recording.
  • Thermally assisted recording performs information recording while locally heating a magnetic recording medium.
  • the use of the above-described Fe—Pt magnetic material is required to realize high-density recording. This is because the glass substrate is required to have particularly high heat resistance.
  • SiO 2 is an important component for forming a glass network structure.
  • such SiO 2 is 56 to 71% (the expression of such a numerical range in this embodiment means that the lower limit value and the upper limit value are included in the range. Therefore, “56 “ ⁇ 71%” means “56% or more and 71% or less”).
  • the content of SiO 2 is less than 56%, glass formation becomes difficult, and chemical durability may be deteriorated. On the other hand, if it exceeds 71%, the meltability deteriorates. Therefore, the content range of SiO 2 needs to be in the range of 56 to 71%. Among these, the range of 58 to 69% is preferable.
  • Al 2 O 3 is an important component that forms a network structure together with SiO 2 , and has a function of improving not only heat resistance but also ion exchange performance.
  • the content of Al 2 O 3 is less than 5%, chemical durability and ion exchange performance may be deteriorated. Conversely, if it exceeds 15%, the ion exchange performance is lowered, and the meltability is further deteriorated. For this reason, the content range of Al 2 O 3 needs to be 5 to 15%. Among them, the range of 7 to 13% is preferable.
  • B 2 O 3 is a component that forms a network structure with SiO 2 , and has a function of lowering the melting temperature, so is contained as necessary. If it exceeds 3%, Tg (glass transition point), which is an index of heat resistance, is lowered. Therefore, the content of B 2 O 3 needs to be in the range of 0 to 3%. Among these, the range is preferably 0 to 2%.
  • the total amount of SiO 2 + Al 2 O 3 + B 2 O 3 was 64 to 80%. These are important components for forming a glass network structure, and if it is less than 65%, glass formation becomes difficult. On the other hand, if it exceeds 80%, the viscosity is too high and the meltability deteriorates. Among these, the range is preferably 66 to 78%.
  • Li 2 O is a component necessary for improving chemical durability and further improving meltability.
  • the content of Li 2 O is less than 0.1%, the effect of suppressing the dissolution of Li and the effect of improving the meltability cannot be obtained sufficiently.
  • the Li 2 O content needs to be in the range of 0.1 to 6%. Among these, the range is preferably 0.2 to 5%.
  • Na 2 O is a component necessary for improving the meltability.
  • the content of Na 2 O is less than 0.1%, the viscosity increases, the liquidus temperature rises, and the meltability deteriorates. Conversely, if it exceeds 4%, the chemical durability is lowered. Therefore, the content of Na 2 O needs to be in the range of 0.1 to 4%. Among these, the range is preferably 0.2 to 3%.
  • K 2 O Since K 2 O has the effect of improving the meltability, it may be contained as necessary. When the content of K 2 O exceeds 2%, Tg is lowered and chemical durability is also deteriorated. Therefore, the content range of K 2 O is set to 0 to 2%. Among these, the range is preferably 0 to 1%.
  • the total amount of Li 2 O + Na 2 O + K 2 O was in the range of 0.2 to 6%. If the total amount is less than 0.2%, a sufficient improvement effect of meltability cannot be obtained. On the other hand, if the total amount exceeds 6%, Tg decreases, sufficient heat resistance cannot be obtained, and chemical durability deteriorates. More preferably, it is in the range of 0.4 to 5.5%.
  • MgO has the effect of improving heat resistance and improving meltability. If the content of MgO is less than 3%, the effect of improving the heat resistance and the effect of improving the meltability cannot be obtained. Conversely, if the content exceeds 13%, the glass structure becomes unstable and the devitrification resistance is reduced. It becomes worse and it becomes difficult to mold. Therefore, the MgO content range is set to 3 to 13%. Among these, the range of 5 to 11% is preferable.
  • CaO has the effect of improving the meltability and maintaining the Tg. If the content of CaO is less than 4%, the effect of improving the meltability and the effect of maintaining Tg cannot be obtained sufficiently. Conversely, if the content exceeds 21%, the glass structure becomes unstable and the chemical durability is improved. It will get worse. Therefore, the CaO content range is set to 4 to 21%. Among these, the range of 6 to 19% is preferable.
  • the SrO content range is set to a range of 0 to 3%. Among these, the range is preferably 0 to 2%.
  • BaO has the effect of improving the meltability and also has the effect of maintaining Tg, so it is contained as necessary.
  • the content range of BaO is set to 0 to 3%. Among these, the range is preferably 0 to 2%.
  • the content range of ZnO is set to 0 to 3%. Among these, the range is preferably 0 to 2%.
  • the total amount of MgO + CaO + SrO + BaO + ZnO was in the range of 14 to 28%. If it is less than 14%, the effects of improving Young's modulus and improving meltability cannot be obtained sufficiently. On the contrary, when the total amount exceeds 28%, the chemical durability deteriorates. More preferably, it is in the range of 16 to 26%.
  • TiO 2 has the effect of softening high temperature viscosity and improving chemical durability. If the content of TiO 2 exceeds 5%, the glass structure becomes unstable, devitrification resistance deteriorates, and molding becomes difficult. Therefore, the content range of TiO 2 is set to a range of 0 to 5%. Among these, the range of 0 to 4% is preferable.
  • Nb 2 O 5 has the effect of improving the chemical durability while improving the meltability.
  • the content range of Nb 2 O 5 is set to 0 to 3%. Among these, the range is preferably 0 to 2%.
  • the content range was set to 0 to 3%. Among these, the range is preferably 0 to 2%.
  • CeO 2 and SnO 2 play a role as a clarifying agent, and may be contained as necessary.
  • the content range was set to 0 to 2%.
  • the range is preferably 0 to 1%.
  • the raw material that plays a role as a fining agent such as Sb 2 O 3, and it may be contained in the range of 0 to 2%.
  • (Nb 2 O 5 + TiO 2 ) / SiO 2 is preferably in the range of 0.01 to 0.06. If the ratio is less than 0.01, the chemical durability is deteriorated. If the ratio exceeds 0.06, the chemical durability is adversely affected.
  • the durability as a skeleton is greatly improved by entering a part of the network structure of the glass, and the diffusion rate of Li ions in the glass is also suppressed. Therefore, the diffusion to the magnetic thin film is suppressed.
  • a desirable range is from 0.012 to 0.05. Nb 2 O 5 and TiO 2 do not have these effects unless one of them is essential.
  • Li 2 O / (Li 2 O + Na 2 O + K 2 O) is preferably in the range of 0.30 to 0.99. If the amount is less than 0.03, the Li elution amount is deteriorated. Therefore, it is essential to contain Li 2 O in a predetermined amount or more. On the other hand, when only Li 2 O is contained at 1.00, elution of Na and K deteriorates. By containing Li 2 O / (Li 2 O + Na 2 O + K 2 O) at a predetermined ratio, a synergistic effect with Nb 2 O 5 and TIO 2 is shown, and the Li diffusion rate is suppressed. A desirable range is from 0.50 to 0.95.
  • FIG. 7 to FIG. 9 show the glass compositions in each example and each comparative example.
  • a predetermined amount of raw material powder is weighed into a platinum crucible and mixed so as to have the glass composition described in Examples 1 to 15. Then, it melt
  • the stirring blade was taken out and allowed to stand for 3 hours, and then the melt was poured into a mold to obtain a glass block. Thereafter, the glass block was held in the vicinity of the glass transition point of each glass for 2 hours, and then slowly cooled to remove strain.
  • the obtained glass block was sliced into a 2.5-inch disk shape having a thickness of about 1.0 mm, and the inner and outer circumferences were concentrically cut out using a cutter to obtain a disk-shaped glass substrate. Rough polishing and polishing were performed on both surfaces of the glass substrate.
  • the glass substrate was washed to produce a glass substrate for an information recording medium having a thickness of 0.8 mm shown in each example and each comparative example.
  • the following physical property evaluation was performed on the produced glass substrate for an information recording medium.
  • Glass material physical properties were measured by the following methods, respectively.
  • ⁇ Glass transition point (Tg)> Using a differential heat measuring device (trade name: EXSTAR6000, manufactured by Seiko Instruments Inc.), heating and measuring a glass sample adjusted to a powder form in a temperature range of room temperature to 900 ° C. at a rate of temperature increase of 10 ° C./min. was used to measure the glass transition point.
  • EXSTAR6000 differential heat measuring device
  • ⁇ Li elution amount> The surface of the glass substrate was polished with cerium oxide to obtain a smooth surface with an Ra value of 2 nm or less. Thereafter, the surface of the glass substrate was washed and immersed in 50 ml of RO water at 80 ° C. for 24 hours. Thereafter, the eluate was analyzed and calculated using an ICP emission spectroscopic analyzer.
  • ⁇ Heat resistance test> An Fe—Pt alloy film was formed on a glass substrate, and then judged by the flatness after heat treatment at 600 ° C. ⁇ 1 hour. The flatness was measured using a white light interference type surface shape measuring instrument (Optiflat (manufactured by Phase Shift Technology)). The glass substrate of each example had a flatness before heat treatment of about 2.0 to 2.3 mm.
  • HDD test> An Fe—Pt alloy film was formed on a glass substrate, then heat-treated at 600 ° C. for 1 hour, and then evaluated by the number of reading errors when operating at 15000 rpm. The evaluation was performed 100 sheets in each example and each comparative example, and the total number of errors in the hard disk drive (HDD) test is shown in FIGS. The mol% values shown in FIGS. 7 to 9 are rounded off to the first decimal place and used to the first decimal place as significant figures.
  • the number of errors in the hard disk drive (HDD) test shown in FIGS. 7 to 9 the number of errors is evaluated as 0 to 2 times “A”, the number of errors is evaluated as 3 to 5 times “B”, and the number of errors is The evaluation “C” was 6 times or more.
  • the glass substrate for hard disk drive (HDD) in each example is different from the glass substrate for HDD in each comparative example in the formation of the magnetic recording medium and the glass substrate during high-temperature annealing. No deformation has occurred. Furthermore, each glass component is contained in a predetermined ratio, and both (Nb 2 O 5 + TiO 2 ) / SiO 2 and Li 2 O / (Li 2 O + Na 2 O + K 2 O) are within a predetermined range. As a result, it was possible to obtain a good SNR characteristic by containing Li ions and suppressing the diffusion of Li, and as a result, excellent evaluation was obtained in a hard disk drive (HDD) test.

Abstract

This glass substrate for information recording media contains, in mol%, 56-71% of SiO2, 5-15% of Al2O3, 0-3% of B2O3, 0.1-6% of Li2O, 0.1-4% of Na2O, 0-2% of K2O, 3-13% of MgO, 4-21% of CaO, 0-3% of SrO, 0-3% of BaO, 0-3% of ZnO, 0-3% ZrO2, 0-2% of CeO2, 0-2% of SnO2, 0-5% of TiO2 and 0-3% of Nb2O5, while satisfying the following glass composition ratios, SiO2 + Al2O3 +B2O3 being 64-80%, Li2O + Na2O + K2O being 0.2-6%, MgO + CaO + SrO + BaO + ZnO being 14-28%, (Nb2O5 + TiO2)/SiO2 = 0.01-0.06 and Li2O/(Li2O + Na2O + K2O) = 0.30-0.99.

Description

情報記録媒体用ガラス基板および情報記録媒体Glass substrate for information recording medium and information recording medium
　本発明は、ハードディスクドライブ（ＨＤＤ：Hard　Disk　Drive）などの情報記録装置に情報記録媒体の一部として搭載される情報記録媒体用ガラス基板および情報記録媒体に関する。 The present invention relates to a glass substrate for an information recording medium and an information recording medium mounted as part of the information recording medium in an information recording apparatus such as a hard disk drive (HDD).
　近年、ＨＤＤの記憶容量が飛躍的に増大することに伴い、１ビットに費やす媒体の記録面積を小さくしていくことが必要不可欠となっている。それに比例させて記録用の磁性粒子サイズも微細化しなければならない。しかし、微細化により記録した磁化の向きを一方向に保つエネルギーが小さくなり、熱エネルギーの影響を受けやすい。磁化の向きを安定させるため、現在磁性材料として広く使用されているＣｏＣｒ系合金から、保磁力の高いＦｅ－Ｐｔ系磁性材料に媒体を変える必要性がある。 In recent years, as the storage capacity of HDDs has increased dramatically, it has become indispensable to reduce the recording area of the medium spent for one bit. In proportion to this, the size of magnetic particles for recording must be reduced. However, the energy for maintaining the direction of magnetization recorded in one direction is reduced by miniaturization, and it is easily affected by thermal energy. In order to stabilize the magnetization direction, there is a need to change the medium from a CoCr-based alloy, which is currently widely used as a magnetic material, to an Fe—Pt-based magnetic material having a high coercive force.
　しかし、Ｆｅ－Ｐｔ系磁性材料の成膜では、Ｆｅ、Ｐｔ原子の配列が不規則になり、高い保磁力が得られない。規則化して高い保磁力を得るには、Ｆｅ－Ｐｔ系磁性材料に対し、約６００℃での高温熱処理を施すことが必要不可欠となる。このため、Ｆｅ－Ｐｔ系磁性材料が成膜されるガラス基板においても、高い耐熱性が要求される。 However, in the film formation of the Fe—Pt magnetic material, the arrangement of Fe and Pt atoms becomes irregular, and a high coercive force cannot be obtained. In order to obtain a high coercive force by ordering, it is indispensable to subject the Fe—Pt magnetic material to a high temperature heat treatment at about 600 ° C. For this reason, high heat resistance is required even for a glass substrate on which a Fe—Pt magnetic material is formed.
　一般に、高い耐熱性を有するガラス基板としては、種々のガラス組成のものが提案されている（特開２００５－０１５３２８号公報（特許文献１）、特開２００５－３１４１５９号公報（特許文献２））。 In general, as glass substrates having high heat resistance, those having various glass compositions have been proposed (Japanese Patent Laid-Open No. 2005-015328 (Patent Document 1) and Japanese Patent Laid-Open No. 2005-314159 (Patent Document 2)). .
特開２００５－０１５３２８号公報JP 2005-015328 A 特開２００５－３１４１５９号公報JP 2005-314159 A
　上述したように、Ｆｅ－Ｐｔ系磁性材料に対し、約６００℃での高温熱処理を施すことが必要不可欠となるため、ガラス基板の耐熱性の指標となるＴｇを６００℃以上まで向上させて、ガラス基板へのＦｅ－Ｐｔ系磁性材料の成膜時に約６００℃での高温熱処理を施している。 As described above, since it is indispensable to perform high-temperature heat treatment at about 600 ° C. on the Fe—Pt magnetic material, the Tg, which is an index of heat resistance of the glass substrate, is improved to 600 ° C. or higher. A high-temperature heat treatment at about 600 ° C. is performed during the film formation of the Fe—Pt magnetic material on the glass substrate.
　その結果、ガラス基板の変形はなかったが、そのガラス基板を用いて製造された情報記録媒体（磁気ディスク）の電磁変換特性の低下が避けられなかった。原因を調査した結果、６００℃での高温熱処理によってガラス成分中のＬｉイオンが磁性膜内まで拡散して、電磁変換特性に影響を及ぼしていることが明確になってきた。 As a result, the glass substrate was not deformed, but the electromagnetic conversion characteristics of the information recording medium (magnetic disk) manufactured using the glass substrate were inevitably deteriorated. As a result of investigating the cause, it has become clear that Li ions in the glass component are diffused into the magnetic film by high-temperature heat treatment at 600 ° C. and affect the electromagnetic conversion characteristics.
　高保磁力のＦｅ－Ｐｔ系の磁性材料を成膜する際に、ガラス基板のＴｇ（ガラス転移点特権）が６００℃以下では、耐熱性が低いことで変形が発生する。Ｔｇを低下させるＬｉ２Ｏの含有量を抑制し、Ｔｇ＞６００℃の耐熱性を確保しても、６００℃のアニールによってガラス成分中のＬｉイオンの磁性膜内への拡散は避けられなかった。 When a high coercive force Fe—Pt magnetic material is formed, if the glass substrate has a Tg (privilege of glass transition temperature) of 600 ° C. or lower, deformation occurs due to low heat resistance. Even if the content of Li 2 O that lowers Tg is suppressed and heat resistance of Tg> 600 ° C. is ensured, diffusion of Li ions in the glass component into the magnetic film is unavoidable by annealing at 600 ° C. .
　一方、Ｌｉ２Ｏ含有量を０にすると、ガラス骨格全体としての化学的耐久性が悪化し、Ｎａ、Ｋイオンの溶出が悪化する。アルカリ酸化物の含有量を０にすると、溶融・成形性が極端に悪化し、ガラス基板の生産が困難となる。 On the other hand, when the Li 2 O content is 0, the chemical durability of the entire glass skeleton is deteriorated, and the elution of Na and K ions is deteriorated. When the content of the alkali oxide is 0, melting / formability is extremely deteriorated, and it becomes difficult to produce a glass substrate.
　したがって、この発明は、上記課題を解決するためになされたものであり、磁気記録媒体の成膜および高温アニール時に、ガラス基板の変形を抑制するとともに、ガラス基板からのＬｉの拡散を抑制することを可能とする情報記録媒体用ガラス基板および情報記録媒体を提供する。 Accordingly, the present invention has been made to solve the above-described problems, and suppresses deformation of the glass substrate and suppresses diffusion of Li from the glass substrate during film formation of the magnetic recording medium and high-temperature annealing. Provided are a glass substrate for an information recording medium and an information recording medium.
　本発明に基づいた情報記録媒体用ガラス基板においては、
　ｍｏｌ％表示で、
ＳｉＯ２：５６～７１％、
Ａｌ２Ｏ３：５～１５％、
Ｂ２Ｏ３：０～３％、
Ｌｉ２Ｏ：０．１～６％、
Ｎａ２Ｏ：０．１～４％、
Ｋ２Ｏ：０～２％、
ＭｇＯ：３～１３％、
ＣａＯ：４～２１％、
ＳｒＯ：０～３％、
ＢａＯ：０～３％、
ＺｎＯ：０～３％、
ＺｒＯ２：０～３％、
ＣｅＯ２：０～２％、
ＳｎＯ２：０～２％、
ＴｉＯ２：０～５％、および、
Ｎｂ２Ｏ５：０～３％、
となる含有範囲を有し、かつ、
ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３：６４～８０％、
Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ：０．２～６％、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ＋ＺｎＯ：１４～２８％、
（Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２＝０．０１～０．０６、および、
Ｌｉ２Ｏ／（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）＝０．３０～０．９９、
というガラス組成比率を満足する。 In the glass substrate for information recording medium based on the present invention,
In mol% display
SiO 2 : 56 to 71%,
Al 2 O 3 : 5 to 15%,
B 2 O 3 : 0 to 3%
Li 2 O: 0.1 to 6%,
Na 2 O: 0.1 to 4%,
K 2 O: 0-2%,
MgO: 3 to 13%,
CaO: 4-21%,
SrO: 0 to 3%,
BaO: 0 to 3%,
ZnO: 0 to 3%,
ZrO 2 : 0 to 3%,
CeO 2 : 0-2%,
SnO 2 : 0-2%,
TiO 2 : 0-5%, and
Nb 2 O 5 : 0 to 3%,
And a content range of
SiO 2 + Al 2 O 3 + B 2 O 3 : 64 to 80%,
Li 2 O + Na 2 O + K 2 O: 0.2-6%
MgO + CaO + SrO + BaO + ZnO: 14 to 28%,
(Nb 2 O 5 + TiO 2 ) / SiO 2 = 0.01 to 0.06, and
Li 2 O / (Li 2 O + Na 2 O + K 2 O) = 0.30 to 0.99,
The glass composition ratio is satisfied.
　他の形態における情報記録媒体用ガラス基板においては、
　ｍｏｌ％表示で、
ＳｉＯ２：５８～６９％、
Ａｌ２Ｏ３：７～１３％、
Ｂ２Ｏ３：０～２％、
Ｌｉ２Ｏ：０．２～５％、
Ｎａ２Ｏ：０．２～３％、
Ｋ２Ｏ：０～１％、
ＭｇＯ：５～１１％、
ＣａＯ：６～１９％、
ＳｒＯ：０～２％、
ＢａＯ：０～２％、
ＺｎＯ：０～２％、
ＺｒＯ２：０～２％、
ＣｅＯ２：０～１％、
ＳｎＯ２：０～１％、
ＴｉＯ２：０～４％、
Ｎｂ２Ｏ５：０～２％、
となる含有範囲を有し、かつ、ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３：６６～７８％、
Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ：０．４～５．５％、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ＋ＺｎＯ：１６～２６％、
（Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２＝０．０１２～０．０５、および、
Ｌｉ２Ｏ/（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）＝０．５０～０．９５、
というガラス組成比率を満足する。 In the glass substrate for information recording media in other forms,
In mol% display
SiO 2 : 58 to 69%,
Al 2 O 3 : 7 to 13%,
B 2 O 3 : 0 to 2%
Li 2 O: 0.2 to 5%,
Na 2 O: 0.2-3%,
K 2 O: 0 to 1%,
MgO: 5 to 11%,
CaO: 6-19%,
SrO: 0-2%,
BaO: 0-2%,
ZnO: 0-2%,
ZrO 2 : 0 to 2%,
CeO 2 : 0 to 1%,
SnO 2 : 0 to 1%
TiO 2 : 0 to 4%,
Nb 2 O 5 : 0 to 2%,
And a content range of SiO 2 + Al 2 O 3 + B 2 O 3 : 66 to 78%,
Li 2 O + Na 2 O + K 2 O: 0.4 to 5.5%,
MgO + CaO + SrO + BaO + ZnO: 16 to 26%,
(Nb 2 O 5 + TiO 2 ) / SiO 2 = 0.012 to 0.05, and
Li 2 O / (Li 2 O + Na 2 O + K 2 O) = 0.50-0.95,
The glass composition ratio is satisfied.
　他の形態における情報記録媒体用ガラス基板においては、当該情報記録媒体用ガラス基板は、熱アシスト記録用のガラス基板である。 In the glass substrate for information recording medium in another form, the glass substrate for information recording medium is a glass substrate for heat assist recording.
　本発明に基づいた情報記録媒体においては、上述のいずれかに記載の情報記録媒体用ガラス基板上に磁気記録層を有する。 The information recording medium according to the present invention has a magnetic recording layer on the glass substrate for information recording medium described above.
　本発明によれば、磁気記録媒体の成膜および高温アニール時に、ガラス基板の変形を抑制するとともに、ガラス基板からのＬｉの拡散を抑制することを可能とする情報記録媒体用ガラス基板および情報記録媒体を提供することが可能となる。 According to the present invention, the glass substrate for an information recording medium and the information recording capable of suppressing the deformation of the glass substrate and suppressing the diffusion of Li from the glass substrate at the time of film formation and high temperature annealing of the magnetic recording medium. A medium can be provided.
情報記録装置３０を示す斜視図である。2 is a perspective view showing an information recording device 30. FIG. 本実施の形態に基づく情報記録媒体用ガラス基板の製造方法によって製造されるガラス基板１を示す平面図である。It is a top view which shows the glass substrate 1 manufactured by the manufacturing method of the glass substrate for information recording media based on this Embodiment. 図２中のＩＩＩ－ＩＩＩ線に沿った矢視断面図である。FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. 情報記録媒体としてガラス基板１を備えた情報記録媒体１０を示す平面図である。It is a top view which shows the information recording medium 10 provided with the glass substrate 1 as an information recording medium. 図４中のＶ－Ｖ線に沿った矢視断面図である。FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. ガラス基板の製造方法を示すフローチャートである。It is a flowchart which shows the manufacturing method of a glass substrate. 実施例１から実施例８のＨＤＤテストの評価を示す図である。It is a figure which shows evaluation of the HDD test of Example 1-8. 実施例９から実施例１５のＨＤＤテストの評価を示す図である。It is a figure which shows evaluation of the HDD test of Example 9-15. 比較例１から比較例７のＨＤＤテストの評価を示す図である。It is a figure which shows evaluation of the HDD test of the comparative example 1 to the comparative example 7. FIG.
　本発明に基づいた実施の形態および各実施例について、以下、図面を参照しながら説明する。実施の形態および各実施例の説明において、個数、量などに言及する場合、特に記載がある場合を除き、本発明の範囲は必ずしもその個数、量などに限定されない。実施の形態および各実施例の説明において、同一の部品、相当部品に対しては、同一の参照番号を付し、重複する説明は繰り返さない場合がある。 Embodiments and examples based on the present invention will be described below with reference to the drawings. In the description of the embodiments and the examples, when the number, amount, and the like are referred to, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the description of the embodiment and each example, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.
　［実施の形態］
　（情報記録装置３０）
　図１を参照して、まず、情報記録装置３０について説明する。図１は、情報記録装置３０を示す斜視図である。情報記録装置３０は、実施の形態における情報記録媒体用ガラス基板（以下、単にガラス基板ともいう）の製造方法によって製造されたガラス基板１を、情報記録媒体１０として備える。 [Embodiment]
(Information recording device 30)
First, the information recording device 30 will be described with reference to FIG. FIG. 1 is a perspective view showing the information recording apparatus 30. The information recording apparatus 30 includes the glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium (hereinafter also simply referred to as a glass substrate) in the embodiment as the information recording medium 10.
　具体的には、情報記録装置３０は、情報記録媒体１０、筐体２０、ヘッドスライダー２１、サスペンション２２、アーム２３、垂直軸２４、ボイスコイル２５、ボイスコイルモーター２６、クランプ部材２７、および固定ネジ２８を備える。筐体２０の上面上には、スピンドルモーター（図示せず）が設置される。 Specifically, the information recording device 30 includes an information recording medium 10, a housing 20, a head slider 21, a suspension 22, an arm 23, a vertical shaft 24, a voice coil 25, a voice coil motor 26, a clamp member 27, and a fixing screw. 28. A spindle motor (not shown) is installed on the upper surface of the housing 20.
　磁気ディスクなどの情報記録媒体１０は、クランプ部材２７および固定ネジ２８によって、上記のスピンドルモーターに回転可能に固定される。情報記録媒体１０は、このスピンドルモーターによって、たとえば数千ｒｐｍの回転数で回転駆動される。詳細は図４および図５を参照して後述されるが、情報記録媒体１０は、ガラス基板１に圧縮応力層１２（図５参照）および磁気記録層１４（図４および図５参照）が形成されることによって製造される。 An information recording medium 10 such as a magnetic disk is rotatably fixed to the spindle motor by a clamp member 27 and a fixing screw 28. The information recording medium 10 is rotationally driven by this spindle motor at, for example, several thousand rpm. Although details will be described later with reference to FIGS. 4 and 5, in the information recording medium 10, a compression stress layer 12 (see FIG. 5) and a magnetic recording layer 14 (see FIGS. 4 and 5) are formed on the glass substrate 1. To be manufactured.
　アーム２３は、垂直軸２４回りに揺動可能に取り付けられる。アーム２３の先端には、板バネ（片持ち梁）状に形成されたサスペンション２２が取り付けられる。サスペンション２２の先端には、ヘッドスライダー２１が情報記録媒体１０を挟み込むように取り付けられる。 The arm 23 is attached so as to be swingable around the vertical axis 24. A suspension 22 formed in a leaf spring (cantilever) shape is attached to the tip of the arm 23. A head slider 21 is attached to the tip of the suspension 22 so as to sandwich the information recording medium 10.
　アーム２３のヘッドスライダー２１とは反対側には、ボイスコイル２５が取り付けられる。ボイスコイル２５は、筐体２０上に設けられたマグネット（図示せず）によって挟持される。ボイスコイル２５およびこのマグネットにより、ボイスコイルモーター２６が構成される。 A voice coil 25 is attached to the opposite side of the arm 23 from the head slider 21. The voice coil 25 is clamped by a magnet (not shown) provided on the housing 20. A voice coil motor 26 is constituted by the voice coil 25 and the magnet.
　ボイスコイル２５には所定の電流が供給される。アーム２３は、ボイスコイル２５に流れる電流と上記マグネットの磁場とにより発生する電磁力の作用によって、垂直軸２４回りに揺動する。アーム２３の揺動によって、サスペンション２２およびヘッドスライダー２１も矢印ＡＲ１方向に揺動する。ヘッドスライダー２１は、情報記録媒体１０の表面上および裏面上を、情報記録媒体１０の半径方向に往復移動する。ヘッドスライダー２１に設けられた磁気ヘッド（図示せず）はシーク動作を行なう。 A predetermined current is supplied to the voice coil 25. The arm 23 swings around the vertical axis 24 by the action of electromagnetic force generated by the current flowing through the voice coil 25 and the magnetic field of the magnet. As the arm 23 swings, the suspension 22 and the head slider 21 also swing in the direction of the arrow AR1. The head slider 21 reciprocates on the front and back surfaces of the information recording medium 10 in the radial direction of the information recording medium 10. A magnetic head (not shown) provided on the head slider 21 performs a seek operation.
　当該シーク動作が行なわれる一方で、ヘッドスライダー２１は、情報記録媒体１０の回転に伴って発生する空気流により、浮揚力を受ける。当該浮揚力とサスペンション２２の弾性力（押圧力）とのバランスによって、ヘッドスライダー２１は情報記録媒体１０の表面に対して一定の浮上量で走行する。当該走行によって、ヘッドスライダー２１に設けられた磁気ヘッドは、情報記録媒体１０内の所定のトラックに対して情報（データ）の記録および再生を行なうことが可能となる。ガラス基板１が情報記録媒体１０を構成する部材の一部として搭載される情報記録装置３０は、以上のように構成される。 While the seek operation is performed, the head slider 21 receives a levitation force due to the air flow generated as the information recording medium 10 rotates. Due to the balance between the levitation force and the elastic force (pressing force) of the suspension 22, the head slider 21 travels with a constant flying height with respect to the surface of the information recording medium 10. By the traveling, the magnetic head provided on the head slider 21 can record and reproduce information (data) on a predetermined track in the information recording medium 10. The information recording apparatus 30 on which the glass substrate 1 is mounted as a part of the members constituting the information recording medium 10 is configured as described above.
　（ガラス基板１）
　図２は、本実施の形態に基づく情報記録媒体用ガラス基板の製造方法によって製造されるガラス基板１を示す平面図である。図３は、図２中のＩＩＩ－ＩＩＩ線に沿った矢視断面図である。 (Glass substrate 1)
FIG. 2 is a plan view showing glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium according to the present embodiment. 3 is a cross-sectional view taken along the line III-III in FIG.
　図２および図３に示すように、情報記録媒体１０（図４および図５参照）にその一部として用いられるガラス基板１（情報記録媒体用ガラス基板）は、主表面２、主表面３、内周端面４、孔５、および外周端面６を有し、全体として円盤状に形成される。孔５は、一方の主表面２から他方の主表面３に向かって貫通するように設けられる。主表面２と内周端面４との間、および、主表面３と内周端面４との間には、面取部７がそれぞれ形成される。主表面２と外周端面６との間、および、主表面３と外周端面６との間には、面取部８（チャンファー部）が形成される。 As shown in FIGS. 2 and 3, the glass substrate 1 (glass substrate for information recording medium) used as a part of the information recording medium 10 (see FIGS. 4 and 5) has a main surface 2, a main surface 3, It has the inner peripheral end surface 4, the hole 5, and the outer peripheral end surface 6, and is formed in a disk shape as a whole. The hole 5 is provided so as to penetrate from one main surface 2 toward the other main surface 3. A chamfer 7 is formed between the main surface 2 and the inner peripheral end surface 4 and between the main surface 3 and the inner peripheral end surface 4. Between the main surface 2 and the outer peripheral end surface 6 and between the main surface 3 and the outer peripheral end surface 6, a chamfered portion 8 (chamfer portion) is formed.
　ガラス基板１の大きさは、たとえば０．８インチ、１．０インチ、１．８インチ、２．５インチ、または３．５インチである。これ以下、または、これ以上のインチサイズとすること可能である。ガラス基板の厚さは、破損防止の観点から、たとえば０．３０ｍｍ～２．２ｍｍである。本実施の形態におけるガラス基板の大きさは、外径が約６４ｍｍ、内径が約２０ｍｍ、厚さが約０．８ｍｍである。ガラス基板の厚さとは、ガラス基板上の点対象となる任意の複数の点で測定した値の平均によって算出される値である。ガラス基板の高硬度化の観点から、ガラス基板１のビッカース硬度は、６１０ｋｇ／ｍｍ２以上であるとよい。 The size of the glass substrate 1 is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch. It is possible to make the size smaller than this or larger than this. The thickness of the glass substrate is, for example, 0.30 mm to 2.2 mm from the viewpoint of preventing breakage. In the present embodiment, the glass substrate has an outer diameter of about 64 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm. The thickness of the glass substrate is a value calculated by averaging the values measured at a plurality of arbitrary points to be pointed on the glass substrate. From the viewpoint of increasing the hardness of the glass substrate, the Vickers hardness of the glass substrate 1 is preferably 610 kg / mm 2 or more.
　（情報記録媒体１０）
　図４は、情報記録媒体としてガラス基板１を備えた情報記録媒体１０を示す平面図である。図５は、図４中のＶ－Ｖ線に沿った矢視断面図である。 (Information recording medium 10)
FIG. 4 is a plan view showing an information recording medium 10 provided with a glass substrate 1 as an information recording medium. FIG. 5 is a cross-sectional view taken along the line VV in FIG.
　図４および図５に示すように、情報記録媒体１０は、ガラス基板１と、圧縮応力層１２と、磁気記録層１４とを含む。圧縮応力層１２は、ガラス基板１の主表面２，３、内周端面４、および外周端面６を覆うように形成される。磁気記録層１４は、圧縮応力層１２の主表面２，３上の所定の領域を覆うように形成される。ガラス基板１の内周端面４上に圧縮応力層１２が形成されることによって、内周端面４の内側に孔１５が形成される。孔１５を利用して、情報記録媒体１０は筐体２０（図１参照）上に設けられたスピンドルモーターに対して固定される。 4 and 5, the information recording medium 10 includes a glass substrate 1, a compressive stress layer 12, and a magnetic recording layer 14. The compressive stress layer 12 is formed so as to cover the main surfaces 2 and 3, the inner peripheral end face 4, and the outer peripheral end face 6 of the glass substrate 1. The magnetic recording layer 14 is formed so as to cover a predetermined region on the main surfaces 2 and 3 of the compressive stress layer 12. By forming the compressive stress layer 12 on the inner peripheral end face 4 of the glass substrate 1, a hole 15 is formed inside the inner peripheral end face 4. The information recording medium 10 is fixed to a spindle motor provided on the housing 20 (see FIG. 1) using the holes 15.
　図５に示す情報記録媒体１０においては、主表面２上に形成された圧縮応力層１２と主表面３上に形成された圧縮応力層１２との双方（両面）の上に、磁気記録層１４が形成されている。磁気記録層１４は、主表面２上に形成された圧縮応力層１２の上（片面）にのみ設けられていてもよく、主表面３上に形成された圧縮応力層１２の上（片面）に設けられていてもよい。 In the information recording medium 10 shown in FIG. 5, the magnetic recording layer 14 is formed on both the compressive stress layer 12 formed on the main surface 2 and the compressive stress layer 12 formed on the main surface 3 (both sides). Is formed. The magnetic recording layer 14 may be provided only on the compression stress layer 12 (one side) formed on the main surface 2, or on the compression stress layer 12 (one side) formed on the main surface 3. It may be provided.
　磁気記録層１４は、磁性粒子を分散させた熱硬化性樹脂をガラス基板１の主表面２，３上の圧縮応力層１２にスピンコートすることによって形成される（スピンコート法）。磁気記録層１４は、ガラス基板１の主表面２，３上の圧縮応力層１２に対して実施されるスパッタリング法または無電解めっき法等により形成されてもよい。 The magnetic recording layer 14 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the compressive stress layer 12 on the main surfaces 2 and 3 of the glass substrate 1 (spin coating method). The magnetic recording layer 14 may be formed by a sputtering method or an electroless plating method performed on the compressive stress layer 12 on the main surfaces 2 and 3 of the glass substrate 1.
　磁気記録層１４の膜厚は、スピンコート法の場合は約０．３μｍ～１．２μｍ、スパッタリング法の場合は約０．０４μｍ～０．０８μｍ、無電解めっき法の場合は約０．０５μｍ～０．１μｍである。薄膜化および高密度化の観点からは、磁気記録層１４はスパッタリング法または無電解めっき法によって形成されるとよい。 The thickness of the magnetic recording layer 14 is about 0.3 μm to 1.2 μm for the spin coating method, about 0.04 μm to 0.08 μm for the sputtering method, and about 0.05 μm to about the electroless plating method. 0.1 μm. From the viewpoint of thinning and high density, the magnetic recording layer 14 is preferably formed by sputtering or electroless plating.
　磁気記録層１４に用いる磁性材料としては、高い保持力を得る目的で結晶異方性の高いＣｏを主成分とし、残留磁束密度を調整する目的でＮｉまたはＣｒを加えたＣｏ系合金などを付加的に用いることが好適である。近年では、熱アシスト記録用に好適な磁性層材料として、Ｆｅ－Ｐｔ系磁性材料が用いられるようになってきている。 As a magnetic material used for the magnetic recording layer 14, a Co-based alloy or the like containing Ni or Cr as a main component is added for the purpose of adjusting the residual magnetic flux density. Is preferably used. In recent years, Fe—Pt magnetic materials have been used as magnetic layer materials suitable for heat-assisted recording.
　磁気ヘッドの滑りをよくするために、磁気記録層１４の表面に潤滑剤を薄くコーティングしてもよい。潤滑剤としては、たとえば液体潤滑剤であるパーフロロポリエーテル（ＰＦＰＥ）をフレオン系などの溶媒で希釈したものが挙げられる。 In order to improve the sliding of the magnetic head, the surface of the magnetic recording layer 14 may be thinly coated with a lubricant. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon.
　磁気記録層１４には、必要に応じて下地層または保護層を設けてもよい。情報記録媒体１０における下地層は、磁性膜の種類に応じて選択される。下地層の材料としては、たとえば、Ｃｒ、Ｍｏ、Ｔａ、Ｔｉ、Ｗ、Ｖ、Ｂ、Ａｌ、またはＮｉなどの非磁性金属から選ばれる少なくとも一種以上の材料が挙げられる。 The magnetic recording layer 14 may be provided with a base layer or a protective layer as necessary. The underlayer in the information recording medium 10 is selected according to the type of magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.
　磁気記録層１４に設ける下地層は、単層に限らず、同一または異種の層を積層した複数層構造としても構わない。たとえば、Ｃｒ／Ｃｒ、Ｃｒ／ＣｒＭｏ、Ｃｒ／ＣｒＶ、ＮｉＡｌ／Ｃｒ、ＮｉＡｌ／ＣｒＭｏ、または、ＮｉＡｌ／ＣｒＶ等の多層下地層としてもよい。 The underlayer provided on the magnetic recording layer 14 is not limited to a single layer, and may have a multilayer structure in which the same or different layers are stacked. For example, a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.
　磁気記録層１４の摩耗および腐食を防止する保護層としては、たとえば、Ｃｒ層、Ｃｒ合金層、カーボン層、水素化カーボン層、ジルコニア層、またはシリカ層が挙げられる。これらの保護層は、下地層および磁性膜など共にインライン型スパッタ装置で連続して形成されることができる。これらの保護層は、単層としてもよく、または、同一若しくは異種の層からなる多層構成としてもよい。 Examples of the protective layer for preventing wear and corrosion of the magnetic recording layer 14 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus together with the underlayer and the magnetic film. These protective layers may be a single layer, or may have a multilayer structure composed of the same or different layers.
　上記保護層上に、あるいは上記保護層に代えて、他の保護層を形成してもよい。たとえば、上記保護層に代えて、Ｃｒ層の上にテトラアルコキシランをアルコール系の溶媒で希釈した中に、コロイダルシリカ微粒子を分散して塗布し、さらに焼成して酸化ケイ素（ＳｉＯ２）層を形成してもよい。 Other protective layers may be formed on the protective layer or instead of the protective layer. For example, instead of the protective layer, colloidal silica fine particles are dispersed and coated on a Cr layer with tetraalkoxylane diluted with an alcohol solvent, and then fired to form a silicon oxide (SiO2) layer. May be.
　（ガラス基板の製造方法）
　次に、図６に示すフローチャート図を用いて、本実施の形態におけるガラス基板（情報記録媒体用ガラス基板）の製造方法Ｓ１００について説明する。本実施の形態におけるガラス基板の製造方法Ｓ１００は、板状ガラス成形工程Ｓ１０、切り出し成形工程Ｓ２０、ブラスト工程Ｓ３０、ラッピング工程Ｓ４０、端面研磨工程Ｓ５０、粗研磨工程Ｓ６０、洗浄工程Ｓ６５、化学強化工程Ｓ７０、精密研磨工程Ｓ８０、および、スクラブ洗浄工程Ｓ９０を備える。 (Glass substrate manufacturing method)
Next, the manufacturing method S100 of the glass substrate (glass substrate for information recording media) in this Embodiment is demonstrated using the flowchart figure shown in FIG. The glass substrate manufacturing method S100 in the present embodiment includes a plate-like glass forming step S10, a cut-out forming step S20, a blasting step S30, a lapping step S40, an end surface polishing step S50, a rough polishing step S60, a cleaning step S65, and a chemical strengthening step. S70, precision polishing process S80, and scrub cleaning process S90 are provided.
　スクラブ洗浄工程Ｓ９０を経ることによって得られたガラス基板に対して、磁気薄膜形成工程Ｓ２００が実施される。磁気薄膜形成工程Ｓ２００を経ることによって、情報記録媒体１０（図４および図５参照）が得られる。以下、ガラス基板の製造方法Ｓ１００を構成する各工程Ｓ１０～Ｓ９０の詳細について順に説明する。 The magnetic thin film forming step S200 is performed on the glass substrate obtained through the scrub cleaning step S90. Through the magnetic thin film forming step S200, the information recording medium 10 (see FIGS. 4 and 5) is obtained. Hereinafter, the details of the steps S10 to S90 constituting the glass substrate manufacturing method S100 will be described in order.
　（板状ガラス成形工程Ｓ１０）
　まず、板状ガラス成形工程Ｓ１０において、溶融ガラスを材料として、ダイレクトプレス法、フロート法、ダウンドロー法、リドロー法、またはフュージョン法など、公知の成形方法を用いて、板状ガラスを製造する。 (Plate-shaped glass forming step S10)
First, in the glass sheet forming step S10, a glass sheet is manufactured using a known glass forming method such as a direct press method, a float method, a down draw method, a redraw method, or a fusion method using a molten glass as a material.
　溶融ガラスを構成する各成分の原料として、各々相当する酸化物、炭酸塩、硝酸塩、水酸化物等が使用され、所望の割合に秤量され、粉末で充分に混合して調合原料とされる。調合原料が、例えば１３００～１５５０℃に加熱された電気炉中の白金坩堝等に投入され、溶融清澄後、撹拌均質化して予め加熱された鋳型に鋳込まれ、徐冷してガラスブロックとされる。 As raw materials for each component constituting the molten glass, corresponding oxides, carbonates, nitrates, hydroxides and the like are used, respectively, weighed to a desired ratio, and thoroughly mixed with powder to obtain a blended raw material. For example, the blended raw material is put into a platinum crucible in an electric furnace heated to 1300 to 1550 ° C., etc., melted and clarified, stirred and homogenized, cast into a preheated mold, and gradually cooled into a glass block. The
　ダイレクトプレス法は、溶解したガラスから目的とするガラス成形品に直接的に成形できるため、同一の形状を有する板状ガラスを多量に生産する場合に好適である。ダイレクトプレス法では、溶融ガラスをプレス成形型に供給し、このガラスが軟化状態にある間にプレス成形型でプレスして板状ガラスを成形する。ガラス転移点付近の温度で、１～３時間保持された後に徐冷される。 The direct press method can be directly molded from a melted glass into a target glass molded product, and is therefore suitable for producing a large amount of sheet glass having the same shape. In the direct press method, molten glass is supplied to a press mold and pressed with a press mold while the glass is in a softened state to form a sheet glass. After being held for 1 to 3 hours at a temperature near the glass transition point, it is gradually cooled.
　ガラス基板１のビッカース硬度は、６１０ｋｇ／ｍｍ２以上である。ガラス基板の材質としては、たとえばアモルファスガラス、結晶化ガラスを利用できる。アモルファスガラスを用いる場合、化学強化を適切に施すことができるとともに、主表面の平坦性および基板強度において優れた情報記録媒体用ガラス基板を提供することが可能となる。 The glass substrate 1 has a Vickers hardness of 610 kg / mm 2 or more. As a material of the glass substrate, for example, amorphous glass or crystallized glass can be used. When amorphous glass is used, chemical strengthening can be appropriately performed, and a glass substrate for an information recording medium excellent in flatness of the main surface and substrate strength can be provided.
　（切り出し成形工程Ｓ２０）
　再び、図６を参照して、切り出し成形工程Ｓ２０においては、円筒状のダイヤモンドドリルを用いて、このガラス基板の中心部に内孔を形成し、円環状のガラス基板を成形する（コアリング加工）。その後、内周端面および外周端面をダイヤモンド砥石によって研削し、所定の面取り加工を施す（フォーミング、チャンファリング）。 (Cut-out molding step S20)
Referring to FIG. 6 again, in the cut-out forming step S20, an inner hole is formed in the center of the glass substrate using a cylindrical diamond drill, and an annular glass substrate is formed (coring process). ). Thereafter, the inner peripheral end face and the outer peripheral end face are ground with a diamond grindstone and subjected to predetermined chamfering (forming, chamfering).
　（ブラスト工程Ｓ３０）
　ブラスト工程Ｓ３０においては、板状ガラス成形工程Ｓ１０よって形成されたガラス基板１の主表面２，３に複数の粒子（砥粒）２００を吹き付けることによって、ガラス基板（ガラス基板前駆体）１の主表面２，３の研削を行なう（第１研削工程）。このブラスト工程Ｓ３０により、たとえば、ガラス基板１の平均Ｒａは、２．０μｍ程度とされる。 (Blasting process S30)
In the blasting step S30, a plurality of particles (abrasive grains) 200 are sprayed on the main surfaces 2 and 3 of the glass substrate 1 formed by the plate-like glass forming step S10, whereby the main of the glass substrate (glass substrate precursor) 1 is obtained. Surfaces 2 and 3 are ground (first grinding step). By this blasting step S30, for example, the average Ra of the glass substrate 1 is set to about 2.0 μm.
　（ラッピング工程Ｓ４０）
　ラッピング工程（第２研削工程）Ｓ４０においては、ラッピンマシーン（図示省略）を用いて、ガラス基板１の主表面にラッピング（第２研削）を施す。ラッピンマシーンにより、ガラス基板１の両主表面が研削される。 (Lapping step S40)
In the lapping step (second grinding step) S40, lapping (second grinding) is performed on the main surface of the glass substrate 1 using a lapping machine (not shown). Both main surfaces of the glass substrate 1 are ground by the lapping machine.
　（端面研磨工程Ｓ５０）
　端面研磨工程Ｓ５０においては、ガラス基板１の内周端面および外周端面が、螺旋状のブラシ毛材を有する研磨ブラシを用いて研磨される。研磨ブラシとガラス基板１の各端面との間に研磨スラリーを供給しつつ、研磨ブラシを各端面に当接させた状態で回転させる。ガラス基板１を研磨液の中に浸漬した状態で、研磨ブラシを各端面に当接させた状態で回転させてもよい。 (End face polishing step S50)
In the end surface polishing step S50, the inner peripheral end surface and the outer peripheral end surface of the glass substrate 1 are polished using a polishing brush having a spiral brush bristle material. While supplying the polishing slurry between the polishing brush and each end surface of the glass substrate 1, the polishing brush is rotated in contact with each end surface. With the glass substrate 1 immersed in the polishing liquid, the polishing brush may be rotated in contact with each end face.
　（粗研磨工程Ｓ６０）
　内周端面および外周端面が研磨されたガラス基板１は、複数回に分けて主表面２，３が粗く研磨される。たとえば、第１および第２粗研磨工程の２回にわけて、主表面２，３が研磨される。徐々にガラス基板１の仕上がり精度を高めることにより、平滑性および平坦性の高い表面を有するガラス基板１を得ることができる。２回に分けて粗研磨を行なう場合、第１粗研磨工程は、前述のラッピング工程において主表面２，３に残留したキズおよび歪みを除去することを主たる目的とし、第２粗研磨工程は、主表面２，３を鏡面状に仕上げることを目的としている。 (Rough polishing step S60)
The glass substrate 1 whose inner peripheral end face and outer peripheral end face are polished has its main surfaces 2 and 3 polished roughly in a plurality of times. For example, the main surfaces 2 and 3 are polished in two steps of the first and second rough polishing steps. By gradually increasing the finishing accuracy of the glass substrate 1, the glass substrate 1 having a highly smooth and flat surface can be obtained. When performing rough polishing in two steps, the first rough polishing step is mainly intended to remove scratches and distortions remaining on the main surfaces 2 and 3 in the lapping step, and the second rough polishing step The purpose is to finish the main surfaces 2 and 3 in a mirror shape.
　（洗浄工程Ｓ６５）
　粗研磨工程Ｓ６０の後、ガラス基板１に対して酸性の洗浄液を用いた洗浄処理が実施される。この洗浄処理は、前工程である粗研磨工程Ｓ６０において研磨スラリーとして使用されていた酸化セリウム、酸化ジルコニウム、またはケイ酸ジルコニウムのいずれかを、ガラス基板１の表面から除去することを目的としている。 (Washing step S65)
After the rough polishing step S60, the glass substrate 1 is subjected to a cleaning process using an acidic cleaning liquid. The purpose of this cleaning treatment is to remove from the surface of the glass substrate 1 any of cerium oxide, zirconium oxide, or zirconium silicate used as a polishing slurry in the rough polishing step S60, which is the previous step.
　具体的には、粗研磨工程Ｓ６０において使用した研磨パッドから粗研磨後のガラス基板１を取り外した後、硫酸およびまたはフッ化水素酸などを含む洗浄液を用いてガラス基板１の表面をエッチングしながら洗浄する。ガラス基板１の表面に付着していた酸化セリウム、酸化ジルコニウム、またはケイ酸ジルコニウムなどの研磨スラリーは、硫酸およびまたはフッ化水素酸などの強酸性の洗浄液によって適切に除去される。その後、ガラス基板１は酸性の洗浄液を用いて洗浄される。 Specifically, after removing the glass substrate 1 after the rough polishing from the polishing pad used in the rough polishing step S60, the surface of the glass substrate 1 is etched using a cleaning liquid containing sulfuric acid and / or hydrofluoric acid. Wash. The polishing slurry such as cerium oxide, zirconium oxide, or zirconium silicate adhering to the surface of the glass substrate 1 is appropriately removed by a strongly acidic cleaning liquid such as sulfuric acid and / or hydrofluoric acid. Thereafter, the glass substrate 1 is cleaned using an acidic cleaning solution.
　洗浄工程Ｓ６５において用いられる洗浄液は、ガラス基板１の耐化学性によっても異なるが、硫酸であれば１％～３０％程度の濃度が好ましく、フッ化水素酸であれば０．２％～５％程度の濃度が好ましい。これらの洗浄液を用いた洗浄は、水溶液が貯留された洗浄機の中で超音波を印加しながら行なわれるとよい。この際に用いられる超音波の周波数は、７８ｋＨｚ以上であることが好ましい。 The cleaning liquid used in the cleaning step S65 varies depending on the chemical resistance of the glass substrate 1, but a concentration of about 1% to 30% is preferable for sulfuric acid, and 0.2% to 5% for hydrofluoric acid. A concentration of about is preferred. Cleaning using these cleaning liquids may be performed while applying ultrasonic waves in a cleaning machine in which an aqueous solution is stored. The frequency of the ultrasonic wave used at this time is preferably 78 kHz or higher.
　（化学強化工程Ｓ７０）
　洗浄工程Ｓ６５の後、ガラス基板１は化学強化される。化学強化液としては、たとえば硝酸カリウム（５０ｗｔ％）と硫酸ナトリウム（５０ｗｔ％）との混合液を用いることができる。化学強化液は、たとえば３００℃～４８０℃に加熱される。洗浄したガラス基板１は、たとえば３００℃～４８０℃に予熱される。ガラス基板１は、化学強化液中にたとえば３時間～４時間浸漬される。 (Chemical strengthening step S70)
After the cleaning step S65, the glass substrate 1 is chemically strengthened. As the chemical strengthening liquid, for example, a mixed liquid of potassium nitrate (50 wt%) and sodium sulfate (50 wt%) can be used. The chemical strengthening liquid is heated to, for example, 300 ° C. to 480 ° C. The cleaned glass substrate 1 is preheated to 300 ° C. to 480 ° C., for example. The glass substrate 1 is immersed in the chemical strengthening solution for 3 hours to 4 hours, for example.
　浸漬の際には、ガラス基板１の主表面２，３の全体が化学強化されるように、複数のガラス基板１が各々の端面で保持されるように、ホルダーに収納した状態で行なうことが好ましい。ガラス基板１を化学強化液中に浸漬することによって、ガラス基板１の表層のアルカリ金属イオン（リチウムイオンおよびナトリウムイオン）が、化学強化液中のイオン半径が相対的に大きい化学強化塩（ナトリウムイオンおよびカリウムイオン）に置換される。これにより、ガラス基板１の表層にはたとえば５０μｍ～２００μｍの厚さを有する圧縮応力層が形成される。 When dipping, the plurality of glass substrates 1 can be held in their respective holders so that the entire main surfaces 2 and 3 of the glass substrate 1 are chemically strengthened. preferable. By immersing the glass substrate 1 in the chemical strengthening solution, alkali metal ions (lithium ions and sodium ions) on the surface layer of the glass substrate 1 are chemically strengthened salts (sodium ions) having a relatively large ion radius in the chemical strengthening solution. And potassium ions). As a result, a compressive stress layer having a thickness of, for example, 50 μm to 200 μm is formed on the surface layer of the glass substrate 1.
　圧縮応力層の形成によってガラス基板１の表面が強化され、ガラス基板１は、良好な耐衝撃性を有することとなる。化学強化処理されたガラス基板１は、適宜洗浄される。たとえば、ガラス基板１は、硫酸で洗浄された後に、純水またはＩＰＡ（イソプロピルアルコール）等を用いてさらに洗浄される。その後、化学強化層を除去してもよい。 The surface of the glass substrate 1 is strengthened by the formation of the compressive stress layer, and the glass substrate 1 has good impact resistance. The glass substrate 1 subjected to the chemical strengthening treatment is appropriately washed. For example, the glass substrate 1 is further cleaned using pure water or IPA (isopropyl alcohol) after being cleaned with sulfuric acid. Thereafter, the chemically strengthened layer may be removed.
　（精密研磨工程Ｓ８０）
　化学強化工程Ｓ７０の後、ガラス基板１に対して精密研磨処理が実施される。精密研磨工程Ｓ８０は、ガラス基板１の主表面を鏡面状に仕上げることを目的としている。精密研磨工程Ｓ８０では、上述の粗研磨工程Ｓ６０と同様に、両面研磨機（図１１参照）を用いてガラス基板１に対する精密研磨が行なわれる。 (Precision polishing step S80)
After the chemical strengthening step S70, a precision polishing process is performed on the glass substrate 1. The precision polishing step S80 is intended to finish the main surface of the glass substrate 1 in a mirror shape. In the precision polishing step S80, similarly to the rough polishing step S60 described above, the glass substrate 1 is precisely polished using a double-side polishing machine (see FIG. 11).
　精密研磨工程Ｓ８０と上記の粗研磨工程Ｓ６０とでは、使用される研磨液（スラリー）に含有される研磨砥粒、および、使用される研磨パッドの組成が異なる。精密研磨工程Ｓ８０では、粗研磨工程Ｓ６０よりも、圧縮応力層が形成されたガラス基板１の主表面２，３に供給される研磨液中の研磨砥粒の粒径を小さくし、研磨パッドの硬さを柔らかくする。 In the fine polishing step S80 and the rough polishing step S60, the composition of the polishing abrasive grains contained in the polishing liquid (slurry) used and the polishing pad used are different. In the precision polishing step S80, the grain size of the abrasive grains in the polishing liquid supplied to the main surfaces 2 and 3 of the glass substrate 1 on which the compressive stress layer is formed is made smaller than in the rough polishing step S60. Soften the hardness.
　精密研磨工程Ｓ８０に用いられる研磨パッドとしては、たとえば軟質発泡樹脂ポリッシャーである。精密研磨工程Ｓ８０においては、遊離砥粒が用いられ、Ｃｅを主成分とする砥粒で第１研磨工程と、Ｓｉを主成分とする砥粒で研磨する第２研磨工程とを含む。 The polishing pad used in the precision polishing step S80 is, for example, a soft foam resin polisher. The precision polishing step S80 uses loose abrasive grains, and includes a first polishing step with abrasive grains mainly composed of Ce and a second polishing step of polishing with abrasive grains mainly composed of Si.
　（スクラブ洗浄工程Ｓ９０）
　精密研磨工程Ｓ８０の後、ガラス基板１に対してスクラブ洗浄処理が実施される。具体的には、精密研磨工程Ｓ８０において使用した研磨パッドから精密研磨後のガラス基板１を取り外した後、ガラス基板１の表面に洗浄液を供給しつつ、圧縮応力層が形成されたガラス基板１の表面に対してスクラブ洗浄装置を用いてスクラブ洗浄を行なう。 (Scrub cleaning step S90)
After the precision polishing step S80, a scrub cleaning process is performed on the glass substrate 1. Specifically, the glass substrate 1 after the precision polishing is removed from the polishing pad used in the precision polishing step S80, and then the cleaning liquid is supplied to the surface of the glass substrate 1 while the compression stress layer is formed. Scrub cleaning is performed on the surface using a scrub cleaning device.
　ガラス基板１は、両面研磨機の研磨パッドから取り外された後、一時的に水中保管されてもよい。水中保管により、精密研磨後にガラス基板１の表面が乾燥することを防ぎつつ、精密研磨後のガラス基板１に付着している研磨滓または遊離砥粒等の異物の量を低減することができる。所定の時間だけガラス基板１を水中保管した後、ガラス基板１をスクラブ洗浄装置にセットし、ガラス基板１に対するスクラブ洗浄を行なう。 The glass substrate 1 may be temporarily stored in water after being removed from the polishing pad of the double-side polishing machine. By storing in water, it is possible to reduce the amount of foreign matter such as polishing wrinkles or loose abrasive grains adhering to the glass substrate 1 after precision polishing while preventing the surface of the glass substrate 1 from drying after precision polishing. After the glass substrate 1 is stored in water for a predetermined time, the glass substrate 1 is set in a scrub cleaning device and scrub cleaning is performed on the glass substrate 1.
　スクラブ洗浄としては、たとえば、洗剤または純水等の洗浄液が用いられる。スクラブ洗浄に用いられる洗浄液のｐＨは、９．０以上１２．２以下であるとよい。この範囲内であれば、ζ電位を容易に調整でき、効率的にスクラブ洗浄を行なうことが可能となる。スクラブ洗浄としては、洗剤によるスクラブ洗浄と、純水によるスクラブ洗浄との双方を行なってもよい。洗剤および純水を用いることによって、より適切にガラス基板１を洗浄できる。洗剤によるスクラブ洗浄と純水によるスクラブ洗浄との間に、ガラス基板１を純水でさらにリンス処理してもよい。 As the scrub cleaning, for example, a cleaning liquid such as a detergent or pure water is used. The pH of the cleaning solution used for scrub cleaning is preferably 9.0 or more and 12.2 or less. Within this range, the ζ potential can be easily adjusted and scrub cleaning can be performed efficiently. As scrub cleaning, both scrub cleaning with a detergent and scrub cleaning with pure water may be performed. By using a detergent and pure water, the glass substrate 1 can be more appropriately cleaned. The glass substrate 1 may be further rinsed with pure water between scrub cleaning with a detergent and scrub cleaning with pure water.
　スクラブ洗浄を行なった後に、ガラス基板１に対して超音波洗浄をさらに行なってもよい。洗剤および純水によるスクラブ洗浄を行なった後に、硫酸水溶液等の薬液による超音波洗浄、純水による超音波洗浄、洗剤による超音波洗浄、ＩＰＡによる超音波洗浄、およびまたは、ＩＰＡによる蒸気乾燥等を更に行なってもよい。 After the scrub cleaning, the glass substrate 1 may be further subjected to ultrasonic cleaning. After scrub cleaning with detergent and pure water, ultrasonic cleaning with chemical solution such as sulfuric acid aqueous solution, ultrasonic cleaning with pure water, ultrasonic cleaning with detergent, ultrasonic cleaning with IPA, and / or steam drying with IPA, etc. Further, it may be performed.
　本実施の形態におけるガラス基板１の製造方法Ｓ１００としては、以上のように構成される。ガラス基板１の製造方法Ｓ１００を使用することによって、図２および図３に示す本実施の形態のガラス基板１を得ることができる。 The manufacturing method S100 of the glass substrate 1 in the present embodiment is configured as described above. By using manufacturing method S100 of glass substrate 1, glass substrate 1 of this embodiment shown in Drawing 2 and Drawing 3 can be obtained.
　（磁気薄膜形成工程Ｓ２００）
　スクラブ洗浄処理が完了したガラス基板１の主表面２，３（またはいずれか一方の主表面２，３）に対し、磁気記録層が形成される。磁気記録層は、たとえば、Ｃｒ合金からなる密着層、ＣｏＦｅＺｒ合金からなる軟磁性層、Ｒｕからなる配向制御下地層、ＣｏＣｒＰｔ合金からなる垂直磁気記録層、Ｃ系からなる保護層、およびＦ系からなる潤滑層が順次成膜されることによって形成される。磁気記録層の形成によって、図４および図５に示す情報記録媒体１０を得ることができる。 (Magnetic thin film forming step S200)
A magnetic recording layer is formed on the main surfaces 2 and 3 (or one of the main surfaces 2 and 3) of the glass substrate 1 after the scrub cleaning process is completed. The magnetic recording layer includes, for example, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a protective layer made of a C system, and an F system. Are formed by sequentially forming the lubricating layer. By forming the magnetic recording layer, the information recording medium 10 shown in FIGS. 4 and 5 can be obtained.
　以下、本発明に係る実施の形態に用いられる情報記録媒体用のガラス基板１について、さらに詳細に説明する。 Hereinafter, the glass substrate 1 for an information recording medium used in the embodiment according to the present invention will be described in more detail.
　＜ガラス基板１＞
　本実施の形態におけるガラス基板１は、ｍｏｌ％表示で、
ＳｉＯ２：５６～７１％、
Ａｌ２Ｏ３：５～１５％、
Ｂ２Ｏ３：０～３％、
Ｌｉ２Ｏ：０．１～６％、
Ｎａ２Ｏ：０．１～４％、
Ｋ２Ｏ：０～２％、
ＭｇＯ：３～１３％、
ＣａＯ：４～２１％、
ＳｒＯ：０～３％、
ＢａＯ：０～３％、
ＺｎＯ：０～３％、
ＺｒＯ２：０～３％、
ＣｅＯ２：０～２％、
ＳｎＯ２：０～２％、
ＴｉＯ２：０～５％、および、
Ｎｂ２Ｏ５：０～３％、
となる含有範囲を有し、かつ
ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３：６４～８０％、
Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ：０．２～６％、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ＋ＺｎＯ：１４～２８％、
（Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２＝０．０１～０．０６、および、
Ｌｉ２Ｏ／（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）＝０．３０～０．９９、というガラス組成比率を満足する。 <Glass substrate 1>
The glass substrate 1 in the present embodiment is displayed in mol%,
SiO 2 : 56 to 71%,
Al 2 O 3 : 5 to 15%,
B 2 O 3 : 0 to 3%
Li 2 O: 0.1 to 6%,
Na 2 O: 0.1 to 4%,
K 2 O: 0-2%,
MgO: 3 to 13%,
CaO: 4-21%,
SrO: 0 to 3%,
BaO: 0 to 3%,
ZnO: 0 to 3%,
ZrO 2 : 0 to 3%,
CeO 2 : 0-2%,
SnO 2 : 0-2%,
TiO 2 : 0-5%, and
Nb 2 O 5 : 0 to 3%,
And a content range of SiO 2 + Al 2 O 3 + B 2 O 3 : 64 to 80%,
Li 2 O + Na 2 O + K 2 O: 0.2-6%
MgO + CaO + SrO + BaO + ZnO: 14 to 28%,
(Nb 2 O 5 + TiO 2 ) / SiO 2 = 0.01 to 0.06, and
The glass composition ratio of Li 2 O / (Li 2 O + Na 2 O + K 2 O) = 0.30 to 0.99 is satisfied.
　本実施の形態においては、ガラス組成を示す「％」表示は特に断らない限り「ｍｏｌ％」を示すものとする。「ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３」等のような化学式の加算表記は、そのような化学式で示される成分の合計量を示すものとする。たとえば、「ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３」とはＳｉＯ２とＡｌ２Ｏ３とＢ２Ｏ３との合計量を示す。 In the present embodiment, “%” indicating a glass composition indicates “mol%” unless otherwise specified. An addition notation of a chemical formula such as “SiO 2 + Al 2 O 3 + B 2 O 3 ” indicates the total amount of components represented by such chemical formula. For example, “SiO 2 + Al 2 O 3 + B 2 O 3 ” indicates the total amount of SiO 2 , Al 2 O 3 and B 2 O 3 .
　当該ガラス組成は、不可避不純物を除き上記に示された成分のみで構成されることが好ましい。 The glass composition is preferably composed of only the components shown above except for inevitable impurities.
　上記ガラス基板１を用いることで、磁気記録媒体の成膜および高温アニール時に、ガラス基板１の変形を抑制するとともに、ガラス基板１からのＬｉの拡散を抑制することを可能とする。 By using the glass substrate 1, the deformation of the glass substrate 1 and the diffusion of Li from the glass substrate 1 can be suppressed during the formation of the magnetic recording medium and the high-temperature annealing.
　上記のような特性を示す本実施の形態の情報記録媒体用ガラス基板は、特に熱アシスト記録用のガラス基板として好適である。熱アシスト記録は、磁気記録媒体を局所的に加熱しながら情報記録を行なうものであるが、特に高密度記録を実現するために上記のようなＦｅ－Ｐｔ系磁性材料の使用が要求されることから、ガラス基板に対しても特に高い耐熱性が要求されるためである。 The glass substrate for information recording medium of the present embodiment showing the above characteristics is particularly suitable as a glass substrate for heat-assisted recording. Thermally assisted recording performs information recording while locally heating a magnetic recording medium. In particular, the use of the above-described Fe—Pt magnetic material is required to realize high-density recording. This is because the glass substrate is required to have particularly high heat resistance.
　＜ガラス組成＞
　本発明のガラス組成を構成する各構成成分について以下説明する。 <Glass composition>
Each component which comprises the glass composition of this invention is demonstrated below.
　ＳｉＯ２は、ガラスの網目構造を形成する重要な成分である。本発明のガラス組成では、このようなＳｉＯ２を５６～７１％（本実施の形態におけるこのような数値範囲の表記は下限値および上限値がその範囲に含まれることを意味する。よって「５６～７１％」とは「５６％以上７１％以下」を示す）の範囲で含有する。 SiO 2 is an important component for forming a glass network structure. In the glass composition of the present invention, such SiO 2 is 56 to 71% (the expression of such a numerical range in this embodiment means that the lower limit value and the upper limit value are included in the range. Therefore, “56 “˜71%” means “56% or more and 71% or less”).
　ＳｉＯ２の含有量が５６％未満では、ガラス形成が困難となり、化学的耐久性が悪化する恐れがある。逆に７１％を超えると溶融性が悪化してしまう。そのためＳｉＯ２の含有範囲は５６～７１％の範囲とすることが必要である。その中でも好ましくは５８～６９％の範囲である。 If the content of SiO 2 is less than 56%, glass formation becomes difficult, and chemical durability may be deteriorated. On the other hand, if it exceeds 71%, the meltability deteriorates. Therefore, the content range of SiO 2 needs to be in the range of 56 to 71%. Among these, the range of 58 to 69% is preferable.
　Ａｌ２Ｏ３は、ＳｉＯ２と共に網目構造を形成する重要な成分であり、耐熱性を向上させるだけではなく、イオン交換性能を向上させる働きを有している。Ａｌ２Ｏ３の含有量が５％より少ないと、化学的耐久性、イオン交換性能が低下する恐れがある。逆に１５％を超えると、イオン交換性能が低下し、更に溶融性が悪化してしてしまう。このためＡｌ２Ｏ３の含有範囲は５～１５％の範囲とすることが必要である。その中でも好ましくは７～１３％の範囲である。 Al 2 O 3 is an important component that forms a network structure together with SiO 2 , and has a function of improving not only heat resistance but also ion exchange performance. When the content of Al 2 O 3 is less than 5%, chemical durability and ion exchange performance may be deteriorated. Conversely, if it exceeds 15%, the ion exchange performance is lowered, and the meltability is further deteriorated. For this reason, the content range of Al 2 O 3 needs to be 5 to 15%. Among them, the range of 7 to 13% is preferable.
　Ｂ２Ｏ３は、ＳｉＯ２と共に網目構造を形成する成分であり、溶融温度を低下させる働きを有しているので必要に応じて含有させる。３％を超えると、耐熱性の指標となるＴｇ（ガラス転移点）が低下してしまう。このためＢ２Ｏ３の含有量は０～３％の範囲とすることが必要である。その中でも好ましくは０～２％の範囲である。 B 2 O 3 is a component that forms a network structure with SiO 2 , and has a function of lowering the melting temperature, so is contained as necessary. If it exceeds 3%, Tg (glass transition point), which is an index of heat resistance, is lowered. Therefore, the content of B 2 O 3 needs to be in the range of 0 to 3%. Among these, the range is preferably 0 to 2%.
　ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３は、総量で６４～８０％とした。これらはガラスの網目構造を形成する重要な成分であり、６５％より少ないとガラス形成が困難となる。逆に８０％を超えると粘度が高くすぎて溶融性が悪化してしまう。その中でも好ましくは６６～７８％の範囲である。 The total amount of SiO 2 + Al 2 O 3 + B 2 O 3 was 64 to 80%. These are important components for forming a glass network structure, and if it is less than 65%, glass formation becomes difficult. On the other hand, if it exceeds 80%, the viscosity is too high and the meltability deteriorates. Among these, the range is preferably 66 to 78%.
　Ｌｉ２Ｏは、化学的耐久性を向上させ、更に溶融性を向上させるのに必要な成分である。Ｌｉ２Ｏの含有量が０．１％より少ないと、Ｌｉ溶出の抑制効果と溶融性を向上させる効果が十分に得られない。逆に６％を超えると、Ｔｇが低下し、Ｌｉ溶出が悪化してしまう。そのため、Ｌｉ２Ｏの含有量は０．１～６％の範囲とすることが必要である。その中でも好ましくは０．２～５％の範囲である。 Li 2 O is a component necessary for improving chemical durability and further improving meltability. When the content of Li 2 O is less than 0.1%, the effect of suppressing the dissolution of Li and the effect of improving the meltability cannot be obtained sufficiently. Conversely, when it exceeds 6%, Tg will fall and Li elution will deteriorate. Therefore, the Li 2 O content needs to be in the range of 0.1 to 6%. Among these, the range is preferably 0.2 to 5%.
　Ｎａ２Ｏは、溶融性を向上させるために必要な成分である。Ｎａ２Ｏの含有量が０．１％より少ないと、粘度が高くなり液相温度が上昇して溶融性が悪化する。逆に４％を超えると、化学的耐久性が低下してしまう。そのためＮａ２Ｏの含有量は０．１～４％の範囲とすることが必要である。その中でも好ましくは０．２～３％の範囲である。 Na 2 O is a component necessary for improving the meltability. When the content of Na 2 O is less than 0.1%, the viscosity increases, the liquidus temperature rises, and the meltability deteriorates. Conversely, if it exceeds 4%, the chemical durability is lowered. Therefore, the content of Na 2 O needs to be in the range of 0.1 to 4%. Among these, the range is preferably 0.2 to 3%.
　Ｋ２Ｏは溶融性を改善する効果を持っているので、必要に応じて含有させて良い。Ｋ２Ｏの含有量が２％を超えるとＴｇが低下し、化学的耐久性も悪化してしまう。そのためＫ２Ｏの含有範囲は０～２％の範囲とした。その中でも好ましくは０～１％の範囲である。 Since K 2 O has the effect of improving the meltability, it may be contained as necessary. When the content of K 2 O exceeds 2%, Tg is lowered and chemical durability is also deteriorated. Therefore, the content range of K 2 O is set to 0 to 2%. Among these, the range is preferably 0 to 1%.
　Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏは、総量を０．２～６％の範囲とした。この総量が０．２％より少ないと溶融性の十分な改善効果が得られない。逆に総量が６％を超えるとＴｇが低下し十分な耐熱性が得られず、化学的耐久性が悪化する。より好ましくは０．４～５．５％の範囲である。 The total amount of Li 2 O + Na 2 O + K 2 O was in the range of 0.2 to 6%. If the total amount is less than 0.2%, a sufficient improvement effect of meltability cannot be obtained. On the other hand, if the total amount exceeds 6%, Tg decreases, sufficient heat resistance cannot be obtained, and chemical durability deteriorates. More preferably, it is in the range of 0.4 to 5.5%.
　ＭｇＯは、耐熱性を向上すると共に溶融性を改善する効果を持っている。ＭｇＯの含有量が３％未満では、耐熱性を向上する効果と溶融性を改善する効果が得られず、逆に含有量が１３％を超えるとガラス構造が不安定となり、耐失透性が悪化してしまい成形困難となる。そのためＭｇＯの含有範囲は３～１３％の範囲とした。その中でも好ましくは５～１１％の範囲である。 MgO has the effect of improving heat resistance and improving meltability. If the content of MgO is less than 3%, the effect of improving the heat resistance and the effect of improving the meltability cannot be obtained. Conversely, if the content exceeds 13%, the glass structure becomes unstable and the devitrification resistance is reduced. It becomes worse and it becomes difficult to mold. Therefore, the MgO content range is set to 3 to 13%. Among these, the range of 5 to 11% is preferable.
　ＣａＯは溶融性を改善する効果を持つと共に、Ｔｇを維持する効果を持っている。ＣａＯの含有量が４％未満では溶融性を改善する効果とＴｇを維持する効果が十分に得られず、逆に含有量が２１％を超えるとガラス構造が不安定となり、化学的耐久性が悪化してしまう。そのためＣａＯの含有範囲は４～２１％の範囲とした。その中でも好ましくは６～１９％の範囲である。 CaO has the effect of improving the meltability and maintaining the Tg. If the content of CaO is less than 4%, the effect of improving the meltability and the effect of maintaining Tg cannot be obtained sufficiently. Conversely, if the content exceeds 21%, the glass structure becomes unstable and the chemical durability is improved. It will get worse. Therefore, the CaO content range is set to 4 to 21%. Among these, the range of 6 to 19% is preferable.
　ＳｒＯは溶融性を改善する効果を持つと共に、Ｔｇを維持する効果を持っているので必要に応じて含有させる。ＳｒＯの含有量が３％を超えると耐失透性が悪化してしまい成形困難となる。そのためＳｒＯの含有範囲は０～３％の範囲とした。その中でも好ましくは０～２％の範囲である。 SrO has the effect of improving meltability and also has the effect of maintaining Tg, so it is contained as necessary. When the content of SrO exceeds 3%, the devitrification resistance is deteriorated and molding becomes difficult. Therefore, the SrO content range is set to a range of 0 to 3%. Among these, the range is preferably 0 to 2%.
　ＢａＯは溶融性を改善する効果を持つと共に、Ｔｇを維持する効果を持っているので必要に応じて含有させる。ＢａＯの含有量が３％を超えると耐失透性が悪化してしまい成形困難となる。そのためＢａＯの含有範囲は０～３％の範囲とした。その中でも好ましくは０～２％の範囲である。 BaO has the effect of improving the meltability and also has the effect of maintaining Tg, so it is contained as necessary. When the content of BaO exceeds 3%, devitrification resistance deteriorates and molding becomes difficult. Therefore, the content range of BaO is set to 0 to 3%. Among these, the range is preferably 0 to 2%.
　ＺnＯは化学的耐久性を向上させると共に溶融性を改善する効果を持つので必要に応じて含有させる。ＺnＯの含有量が３％を超えるとガラス構造が不安定となり、耐失透性が悪化してしまう。そのためＺnＯの含有範囲は０～３％の範囲とした。その中でも好ましくは０～２％の範囲である。 ZnO is added as necessary because it has the effect of improving chemical durability and improving melting properties. If the ZnO content exceeds 3%, the glass structure becomes unstable, and the devitrification resistance deteriorates. Therefore, the content range of ZnO is set to 0 to 3%. Among these, the range is preferably 0 to 2%.
　ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ＋ＺｎＯの総量は、１４～２８％の範囲とした。１４％より少ないとヤング率の向上と溶融性向上の効果が十分に得られない。逆に総量が２８％を超えると化学的耐久性が悪化する。より好ましくは１６～２６％の範囲である。 The total amount of MgO + CaO + SrO + BaO + ZnO was in the range of 14 to 28%. If it is less than 14%, the effects of improving Young's modulus and improving meltability cannot be obtained sufficiently. On the contrary, when the total amount exceeds 28%, the chemical durability deteriorates. More preferably, it is in the range of 16 to 26%.
　ＴｉＯ２は高温粘性を軟化させると共に化学的耐久性を向上する効果を持っている。ＴｉＯ２の含有量が５％を超えるとガラス構造が不安定となり、耐失透性が悪化してしまい成形困難となる。そのためＴｉＯ２の含有範囲は０～５％の範囲とした。その中でも好ましくは０～４％の範囲である。 TiO 2 has the effect of softening high temperature viscosity and improving chemical durability. If the content of TiO 2 exceeds 5%, the glass structure becomes unstable, devitrification resistance deteriorates, and molding becomes difficult. Therefore, the content range of TiO 2 is set to a range of 0 to 5%. Among these, the range of 0 to 4% is preferable.
　Ｎｂ２Ｏ５は、溶融性を向上させると共に、化学的耐久性を向上する効果を持っている。Ｎｂ２Ｏ５の含有量が３％を超えると、液相温度が上昇し耐失透性が悪化してしまう。そのためＮｂ２Ｏ５の含有範囲は０～３％の範囲とした。その中でも好ましくは０～２％の範囲である。 Nb 2 O 5 has the effect of improving the chemical durability while improving the meltability. When the content of Nb 2 O 5 exceeds 3%, the liquidus temperature rises and the devitrification resistance deteriorates. Therefore, the content range of Nb 2 O 5 is set to 0 to 3%. Among these, the range is preferably 0 to 2%.
　ＺｒＯ２はガラスの耐熱性を向上する効果があるので、必要に応じて含有させても良い。ただし、含有量が３％を超えると耐失透性が悪化してしまい、ガラス化が困難となる。そのため含有範囲は０～３％の範囲とした。その中でも好ましくは０～２％の範囲である。 Since ZrO 2 has an effect of improving the heat resistance of the glass, it may be contained as necessary. However, if the content exceeds 3%, the devitrification resistance deteriorates, and vitrification becomes difficult. Therefore, the content range was set to 0 to 3%. Among these, the range is preferably 0 to 2%.
　ＣｅＯ２およびＳｎＯ２は清澄剤としての役割を果たすので、必要に応じて含有させて良い。それぞれ含有量が２％を超えると耐失透性が悪化してしまい、ガラス化が困難となる。そのため含有範囲は０～２％の範囲とした。その中でも好ましくは０～１％の範囲である。これら２つ以外でも、Ｓｂ２Ｏ３等の清澄剤としての役割を果たす原料に制限は無く、０～２％の範囲で含有させても良い。 CeO 2 and SnO 2 play a role as a clarifying agent, and may be contained as necessary. When each content exceeds 2%, devitrification resistance deteriorates and vitrification becomes difficult. Therefore, the content range was set to 0 to 2%. Among these, the range is preferably 0 to 1%. In addition to these two, there is no limitation on the raw material that plays a role as a fining agent such as Sb 2 O 3, and it may be contained in the range of 0 to 2%.
　（Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２は、０．０１～０．０６の範囲とすることが望ましい。比率が０．０１未満では化学的耐久性が悪化してしまい、比率が０．０６を超えると、逆に化学的耐久性が悪化してしまう。（Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２を所定の比率で含有させることでガラスの網目構造の一部に入り骨格としての耐久性が大きく向上し、ガラスのＬｉイオンの拡散速度も抑制することで、磁気薄膜への拡散を抑制する。望ましい範囲は、０．０１２～０．０５の範囲である。Ｎｂ２Ｏ５とＴｉＯ２は、どちらか一方を必須で含有しない限り、これらの効果は得られない。 (Nb 2 O 5 + TiO 2 ) / SiO 2 is preferably in the range of 0.01 to 0.06. If the ratio is less than 0.01, the chemical durability is deteriorated. If the ratio exceeds 0.06, the chemical durability is adversely affected. By containing (Nb 2 O 5 + TiO 2 ) / SiO 2 at a predetermined ratio, the durability as a skeleton is greatly improved by entering a part of the network structure of the glass, and the diffusion rate of Li ions in the glass is also suppressed. Therefore, the diffusion to the magnetic thin film is suppressed. A desirable range is from 0.012 to 0.05. Nb 2 O 5 and TiO 2 do not have these effects unless one of them is essential.
　Ｌｉ２Ｏ／（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）は、０．３０～０．９９の範囲とすることが望ましい。０．０３未満ではＬｉ溶出量が悪化してしまうので、所定の量以上のＬｉ２Ｏ含有を必須とする。逆に、１．００でＬｉ２Ｏのみ含有した場合は、Ｎａ、Ｋの溶出が悪化してしまう。Ｌｉ２Ｏ／（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）を所定の比率で含有することで、Ｎｂ２Ｏ５、ＴＩＯ２との相乗効果を示してＬｉ拡散速度が抑制される。望ましい範囲は、０．５０～０．９５の範囲である。 Li 2 O / (Li 2 O + Na 2 O + K 2 O) is preferably in the range of 0.30 to 0.99. If the amount is less than 0.03, the Li elution amount is deteriorated. Therefore, it is essential to contain Li 2 O in a predetermined amount or more. On the other hand, when only Li 2 O is contained at 1.00, elution of Na and K deteriorates. By containing Li 2 O / (Li 2 O + Na 2 O + K 2 O) at a predetermined ratio, a synergistic effect with Nb 2 O 5 and TIO 2 is shown, and the Li diffusion rate is suppressed. A desirable range is from 0.50 to 0.95.
　（実施例１～１５、および、比較例１～７）
　図７から図９に、各実施例および各比較例におけるガラス組成を示す。実施例１～１５に記載のガラス組成となるように、所定量の原料粉末を白金るつぼに秤量して入れ、混合する。その後、電気炉中で１５００℃で溶解した。原料が充分に溶解したのち、白金製の撹拌羽をガラス融液に挿入し、１時間撹拌した。 (Examples 1 to 15 and Comparative Examples 1 to 7)
FIG. 7 to FIG. 9 show the glass compositions in each example and each comparative example. A predetermined amount of raw material powder is weighed into a platinum crucible and mixed so as to have the glass composition described in Examples 1 to 15. Then, it melt | dissolved at 1500 degreeC in the electric furnace. After the raw materials were sufficiently dissolved, a platinum stirring blade was inserted into the glass melt and stirred for 1 hour.
　その後、撹拌羽を取り出し、３時間静置した後、金型に融液を流しこむことによってガラスブロックを得た。その後、各ガラスのガラス転移点付近でガラスブロックを２時間保持した後、徐冷して歪取りを行なった。 Thereafter, the stirring blade was taken out and allowed to stand for 3 hours, and then the melt was poured into a mold to obtain a glass block. Thereafter, the glass block was held in the vicinity of the glass transition point of each glass for 2 hours, and then slowly cooled to remove strain.
　得られたガラスブロックを、厚み約１.０ｍｍの２．５インチの円盤形状にスライスし、内周、外周を同心円としてカッターを用いて切り出し、円盤形状のガラス基板とした。ガラス基板の両面に対して粗研磨および研磨を行なった。 The obtained glass block was sliced into a 2.5-inch disk shape having a thickness of about 1.0 mm, and the inner and outer circumferences were concentrically cut out using a cutter to obtain a disk-shaped glass substrate. Rough polishing and polishing were performed on both surfaces of the glass substrate.
　その後、ガラス基板の洗浄を行なうことにより各実施例および各比較例に示す、厚みが０．８ｍｍである情報記録媒体用ガラス基板を作製した。この作製した情報記録媒体用ガラス基板について下記物性評価を行なった。 Thereafter, the glass substrate was washed to produce a glass substrate for an information recording medium having a thickness of 0.8 mm shown in each example and each comparative example. The following physical property evaluation was performed on the produced glass substrate for an information recording medium.
　ガラスの材料物性測定（ガラス転移点Ｔｇ、Ｓｉ溶出量、高温粘性）は、それぞれ下記の方法で測定を実施した。 Glass material physical properties (glass transition point Tg, Si elution amount, high temperature viscosity) were measured by the following methods, respectively.
　＜ガラス転移点（Ｔｇ）＞
　示差熱測定装置（商品名：EXSTAR6000、セイコーインスツルメンツ社製）を用いて、室温～９００℃の温度範囲を１０℃／ｍｉｎの昇温速度で、粉末状に調整したガラス試料を加熱し測定することにより、ガラス転移点を測定した。 <Glass transition point (Tg)>
Using a differential heat measuring device (trade name: EXSTAR6000, manufactured by Seiko Instruments Inc.), heating and measuring a glass sample adjusted to a powder form in a temperature range of room temperature to 900 ° C. at a rate of temperature increase of 10 ° C./min. Was used to measure the glass transition point.
　＜Ｌｉ溶出量＞
　ガラス基板の表面を酸化セリウムで研磨して、Ｒａ値が２ｎｍ以下の平滑面とした。その後、ガラス基板の表面を洗浄し、８０℃のＲＯ水５０ｍｌ中に２４時間浸漬した。その後、ＩＣＰ発光分光分析装置で溶出液を分析し算出した。 <Li elution amount>
The surface of the glass substrate was polished with cerium oxide to obtain a smooth surface with an Ra value of 2 nm or less. Thereafter, the surface of the glass substrate was washed and immersed in 50 ml of RO water at 80 ° C. for 24 hours. Thereafter, the eluate was analyzed and calculated using an ICP emission spectroscopic analyzer.
　＜耐熱テスト＞
　ガラス基板にＦｅ－Ｐｔ合金を成膜し、その後６００℃×１時間で熱処理した後の平坦度で判断した。平坦度は、白色光干渉式表面形状測定機（Optiflat（Phase　Shift　Technology社製））を用いて測定した。各実施例のガラス基板は、熱処理前の平坦度は、２．０Å～２．３Å程度であった。 <Heat resistance test>
An Fe—Pt alloy film was formed on a glass substrate, and then judged by the flatness after heat treatment at 600 ° C. × 1 hour. The flatness was measured using a white light interference type surface shape measuring instrument (Optiflat (manufactured by Phase Shift Technology)). The glass substrate of each example had a flatness before heat treatment of about 2.0 to 2.3 mm.
　＜ハードディスクドライブ（ＨＤＤ）テスト＞
　ガラス基板にＦｅ－Ｐｔ合金を成膜し、その後６００℃×１時間で熱処理した後に、１５０００ｒｐｍで動作させた際の読み取りエラー回数で評価した。評価は各実施例、各比較例で１００枚ずつ行ない、そのハードディスクドライブ（ＨＤＤ）テストのエラー回数の総数を、図７～図９に示した。図７～図９に示すｍｏｌ％の値は、小数第２位を四捨五入して小数点以下１桁までを有効数字として用いる。 <Hard disk drive (HDD) test>
An Fe—Pt alloy film was formed on a glass substrate, then heat-treated at 600 ° C. for 1 hour, and then evaluated by the number of reading errors when operating at 15000 rpm. The evaluation was performed 100 sheets in each example and each comparative example, and the total number of errors in the hard disk drive (HDD) test is shown in FIGS. The mol% values shown in FIGS. 7 to 9 are rounded off to the first decimal place and used to the first decimal place as significant figures.
　図７～図９に示す、ハードディスクドライブ（ＨＤＤ）テストのエラー回数に関して、エラー回数が０回～２回を評価「Ａ」、エラー回数が３回～５回を評価「Ｂ」、エラー回数が６回以上を評価「Ｃ」とした。 Regarding the number of errors in the hard disk drive (HDD) test shown in FIGS. 7 to 9, the number of errors is evaluated as 0 to 2 times “A”, the number of errors is evaluated as 3 to 5 times “B”, and the number of errors is The evaluation “C” was 6 times or more.
　図７～図９より明らかなように、各実施例のハードディスクドライブ（ＨＤＤ）用のガラス基板は、各比較例のＨＤＤ用ガラス基板に比べ、磁気記録媒体の成膜および高温アニール時にガラス基板の変形が発生していない。さらに、各ガラス成分を所定の割合で含有させて、かつ、（Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２、および、Ｌｉ２Ｏ／（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）の両方を所定の範囲とすることで、Ｌｉイオンを含有し、かつ、Ｌｉの拡散を抑制して良好なＳＮＲ特性を得ることを可能とし、その結果、ハードディスクドライブ（ＨＤＤ）テストで優れた評価が得られた。 As is apparent from FIGS. 7 to 9, the glass substrate for hard disk drive (HDD) in each example is different from the glass substrate for HDD in each comparative example in the formation of the magnetic recording medium and the glass substrate during high-temperature annealing. No deformation has occurred. Furthermore, each glass component is contained in a predetermined ratio, and both (Nb 2 O 5 + TiO 2 ) / SiO 2 and Li 2 O / (Li 2 O + Na 2 O + K 2 O) are within a predetermined range. As a result, it was possible to obtain a good SNR characteristic by containing Li ions and suppressing the diffusion of Li, and as a result, excellent evaluation was obtained in a hard disk drive (HDD) test.
　今回開示された実施の形態および実施例はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて請求の範囲によって示され、請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
　１　ガラス基板、２，３　主表面、４　内周端面、５，１５　孔、６　外周端面、１０　情報記録媒体、１２　圧縮応力層、１４　磁気記録層、２０　筐体、２１　ヘッドスライダー、２２　サスペンション、２３　アーム、２４　垂直軸、２５　ボイスコイル、２６　ボイスコイルモーター、２７　クランプ部材、２８　固定ネジ、３０　情報記録装置。 DESCRIPTION OF SYMBOLS 1 Glass substrate, 2, 3 Main surface, 4 Inner peripheral end surface, 5,15 hole, 6, Outer peripheral end surface, 10 Information recording medium, 12 Compression stress layer, 14 Magnetic recording layer, 20 Housing, 21 Head slider, 22 Suspension, 23 arm, 24 vertical axis, 25 voice coil, 26 voice coil motor, 27 clamp member, 28 fixing screw, 30 information recording device.

Claims (4)

  1. 　ｍｏｌ％表示で、
    ＳｉＯ２：５６～７１％、
    Ａｌ２Ｏ３：５～１５％、
    Ｂ２Ｏ３：０～３％、
    Ｌｉ２Ｏ：０．１～６％、
    Ｎａ２Ｏ：０．１～４％、
    Ｋ２Ｏ：０～２％、
    ＭｇＯ：３～１３％、
    ＣａＯ：４～２１％、
    ＳｒＯ：０～３％、
    ＢａＯ：０～３％、
    ＺｎＯ：０～３％、
    ＺｒＯ２：０～３％、
    ＣｅＯ２：０～２％、
    ＳｎＯ２：０～２％、
    ＴｉＯ２：０～５％、および、
    Ｎｂ２Ｏ５：０～３％、
    となる含有範囲を有し、かつ、
    ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３：６４～８０％、
    Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ：０．２～６％、
    ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ＋ＺｎＯ：１４～２８％、
    （Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２＝０．０１～０．０６、および、
    Ｌｉ２Ｏ／（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）＝０．３０～０．９９、
    というガラス組成比率を満足する、情報記録媒体用ガラス基板。     In mol% display
    SiO 2 : 56 to 71%,
    Al 2 O 3 : 5 to 15%,
    B 2 O 3 : 0 to 3%
    Li 2 O: 0.1 to 6%,
    Na 2 O: 0.1 to 4%,
    K 2 O: 0-2%,
    MgO: 3 to 13%,
    CaO: 4-21%,
    SrO: 0 to 3%,
    BaO: 0 to 3%,
    ZnO: 0 to 3%,
    ZrO 2 : 0 to 3%,
    CeO 2 : 0-2%,
    SnO 2 : 0-2%,
    TiO 2 : 0-5%, and
    Nb 2 O 5 : 0 to 3%,
    And a content range of
    SiO 2 + Al 2 O 3 + B 2 O 3 : 64 to 80%,
    Li 2 O + Na 2 O + K 2 O: 0.2-6%
    MgO + CaO + SrO + BaO + ZnO: 14 to 28%,
    (Nb 2 O 5 + TiO 2 ) / SiO 2 = 0.01 to 0.06, and
    Li 2 O / (Li 2 O + Na 2 O + K 2 O) = 0.30 to 0.99,
    A glass substrate for an information recording medium that satisfies the glass composition ratio.
  2. 　ｍｏｌ％表示で、
    ＳｉＯ２：５８～６９％、
    Ａｌ２Ｏ３：７～１３％、
    Ｂ２Ｏ３：０～２％、
    Ｌｉ２Ｏ：０．２～５％、
    Ｎａ２Ｏ：０．２～３％、
    Ｋ２Ｏ：０～１％、
    ＭｇＯ：５～１１％、
    ＣａＯ：６～１９％、
    ＳｒＯ：０～２％、
    ＢａＯ：０～２％、
    ＺｎＯ：０～２％、
    ＺｒＯ２：０～２％、
    ＣｅＯ２：０～１％、
    ＳｎＯ２：０～１％、
    ＴｉＯ２：０～４％、
    Ｎｂ２Ｏ５：０～２％、
    となる含有範囲を有し、かつ、
    ＳｉＯ２＋Ａｌ２Ｏ３＋Ｂ２Ｏ３：６６～７８％、
    Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ：０．４～５．５％、
    ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ＋ＺｎＯ：１６～２６％、
    （Ｎｂ２Ｏ５＋ＴｉＯ２）／ＳｉＯ２＝０．０１２～０．０５、および、
    Ｌｉ２Ｏ/（Ｌｉ２Ｏ＋Ｎａ２Ｏ＋Ｋ２Ｏ）＝０．５０～０．９５、というガラス組成比率を満足する、請求項１に記載の情報記録媒体用ガラス基板。     In mol% display
    SiO 2 : 58 to 69%,
    Al 2 O 3 : 7 to 13%,
    B 2 O 3 : 0 to 2%
    Li 2 O: 0.2 to 5%,
    Na 2 O: 0.2-3%,
    K 2 O: 0 to 1%,
    MgO: 5 to 11%,
    CaO: 6-19%,
    SrO: 0-2%,
    BaO: 0-2%,
    ZnO: 0-2%,
    ZrO 2 : 0 to 2%,
    CeO 2 : 0 to 1%,
    SnO 2 : 0 to 1%
    TiO 2 : 0 to 4%,
    Nb 2 O 5 : 0 to 2%,
    And a content range of
    SiO 2 + Al 2 O 3 + B 2 O 3 : 66 to 78%,
    Li 2 O + Na 2 O + K 2 O: 0.4 to 5.5%,
    MgO + CaO + SrO + BaO + ZnO: 16 to 26%,
    (Nb 2 O 5 + TiO 2 ) / SiO 2 = 0.012 to 0.05, and
    2. The glass substrate for an information recording medium according to claim 1, wherein a glass composition ratio of Li 2 O / (Li 2 O + Na 2 O + K 2 O) = 0.50 to 0.95 is satisfied.
  3. 　当該情報記録媒体用ガラス基板は、熱アシスト記録用のガラス基板である、請求項１または２に記載の情報記録媒体用ガラス基板。 The glass substrate for information recording medium according to claim 1 or 2, wherein the glass substrate for information recording medium is a glass substrate for heat-assisted recording.
  4. 　請求項１～３のいずれか１項に記載の情報記録媒体用ガラス基板上に磁気記録層を有する情報記録媒体。 An information recording medium having a magnetic recording layer on the glass substrate for information recording medium according to any one of claims 1 to 3.
PCT/JP2014/055396 2013-03-05 2014-03-04 Glass substrate for information recording media, and information recording medium WO2014136751A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019055911A (en) * 2014-10-08 2019-04-11 コーニング インコーポレイテッド Glass and glass ceramic having metal oxide density gradient
WO2023235211A1 (en) * 2022-05-31 2023-12-07 Corning Incorporated Ion exchangeable yellow glass articles

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000357318A (en) * 1999-04-13 2000-12-26 Asahi Glass Co Ltd Glass for substrate of information recording medium and glass substrate for information recording medium
JP2001172043A (en) * 1999-12-20 2001-06-26 Asahi Glass Co Ltd Glass used for substrate of data recording medium, and glass substrate of data recording medium
WO2012057338A1 (en) * 2010-10-29 2012-05-03 Hoya株式会社 Glass substrate for use in magnetic storage medium, magnetic storage medium, and glass substrate blank for use in magnetic storage medium

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000357318A (en) * 1999-04-13 2000-12-26 Asahi Glass Co Ltd Glass for substrate of information recording medium and glass substrate for information recording medium
JP2001172043A (en) * 1999-12-20 2001-06-26 Asahi Glass Co Ltd Glass used for substrate of data recording medium, and glass substrate of data recording medium
WO2012057338A1 (en) * 2010-10-29 2012-05-03 Hoya株式会社 Glass substrate for use in magnetic storage medium, magnetic storage medium, and glass substrate blank for use in magnetic storage medium

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019055911A (en) * 2014-10-08 2019-04-11 コーニング インコーポレイテッド Glass and glass ceramic having metal oxide density gradient
WO2023235211A1 (en) * 2022-05-31 2023-12-07 Corning Incorporated Ion exchangeable yellow glass articles

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