WO2013183569A1 - Method for producing magnetic disk and glass substrate for information recording media - Google Patents

Method for producing magnetic disk and glass substrate for information recording media Download PDF

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Publication number
WO2013183569A1
WO2013183569A1 PCT/JP2013/065285 JP2013065285W WO2013183569A1 WO 2013183569 A1 WO2013183569 A1 WO 2013183569A1 JP 2013065285 W JP2013065285 W JP 2013065285W WO 2013183569 A1 WO2013183569 A1 WO 2013183569A1
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Prior art keywords
glass substrate
less
magnetic disk
glass
manufacturing
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PCT/JP2013/065285
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French (fr)
Japanese (ja)
Inventor
中島　哲也
知之 ▲辻▼村
学 西沢
小池　章夫
Original Assignee
旭硝子株式会社
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Application filed by 旭硝子株式会社 filed Critical 旭硝子株式会社
Priority to JP2014519971A priority Critical patent/JP5907259B2/en
Priority to CN201380029770.2A priority patent/CN104364212A/en
Priority to SG11201408098RA priority patent/SG11201408098RA/en
Publication of WO2013183569A1 publication Critical patent/WO2013183569A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
    • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
    • G11B5/7315—
    • 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
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
    • G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers

Definitions

  • the present invention relates to a method for manufacturing a magnetic disk and a glass substrate for an information recording medium, and more particularly to a method for manufacturing a magnetic disk for forming a magnetic recording layer at a high temperature and a glass substrate suitable for such a manufacturing method.
  • heat-assisted magnetic recording technology is attracting attention as a fusion technology of light and magnetism.
  • This is a technique in which a magnetic recording layer is irradiated with a laser beam or near-field light and recorded by applying an external magnetic field in a state where the coercive force is lowered in a locally heated portion, and the recorded magnetization is read by a GMR element or the like.
  • recording can be performed on a medium having a high holding force, the magnetic particles can be miniaturized while maintaining thermal stability.
  • silicon substrates are generally concerned with strength compared to glass substrates. Therefore, it is preferable to use a glass substrate also in the manufacture of a magnetic disk in which the magnetic recording layer is formed at a high temperature.
  • an object of the present invention is to provide a method for manufacturing such a magnetic disk and a method for manufacturing a glass substrate for an information recording medium suitable for such a manufacturing method.
  • the present invention is a method of manufacturing a magnetic disk including a step of forming a magnetic recording layer on a glass substrate having a temperature of 550 ° C. or higher,
  • the glass substrate is expressed in mole percentage, and SiO 2 is 60 to 75%, Al 2 O 3 is 7 to 17%, B 2 O 3 is less than 0 to less than 2%, and any one component of MgO, CaO, SrO and BaO More than 18% in total and 26% or less in total, the total content of the above 7 components is 95% or more, and any one or more of Li 2 O, Na 2 O and K 2 O is less than 1% in total Provided is a method for manufacturing a magnetic disk which contains or does not contain any of these three components.
  • the glass substrate contains 10.5 to 20% in total of one or more components of MgO and CaO in terms of mole percentage.
  • the present invention provides a method for producing the magnetic disk, wherein the glass substrate contains Al 2 O 3 in excess of 18% in terms of mass percentage.
  • the magnetic disk having a value obtained by dividing the content (molar percentage) of SiO 2 by the total amount RO of the contents (molar percentage) of MgO, CaO, SrO and BaO is 4.3 or less.
  • a manufacturing method is provided.
  • the present invention provides a method for manufacturing the magnetic disk, wherein a temperature T 2 at which the viscosity of the glass substrate is 10 2 dPa ⁇ s is 1710 ° C. or lower.
  • SiO 2 is 60 to 75%
  • Al 2 O 3 is 7 to 17%
  • B 2 O 3 is 0 to less than 2%
  • one or more components of MgO, CaO, SrO and BaO are contained.
  • the total content is more than 18% and 26% or less
  • the total content of the above seven components is 95% or more
  • any one or more of Li 2 O, Na 2 O and K 2 O is contained in less than 1% in total.
  • a glass substrate for an information recording medium which does not contain any of these three components.
  • the glass substrate for an information recording medium containing a total of 10.5 to 20% of any one component of MgO and CaO in terms of mole percentage.
  • the glass substrate for an information recording medium containing 6% or more of MgO in terms of mole percentage.
  • the glass substrate for an information recording medium wherein a value obtained by dividing the content (molar percentage) of SiO 2 by the total amount RO of the contents (molar percentage) of MgO, CaO, SrO, and BaO is 4.3 or less. provide.
  • the glass substrate for an information recording medium, wherein the information recording medium is a magnetic disk.
  • the inventions related to these glass substrates not only enable the substrate to be heated at a high temperature in the production of the magnetic disk for forming the magnetic recording layer, but also facilitate the production as described below. Is.
  • the glass having the composition shown in Example 14 of International Publication No. 2011/136027 has a low specific elastic modulus of 31.2 MNm ⁇ kg, and fluttering phenomenon easily occurs at the time of high-speed rotation of the disk and cannot cope with a high recording density. It became clear. Furthermore, it has been clarified that the glass having the above composition has insufficient acid resistance, and a phenomenon such as surface roughness is likely to occur after a polishing process or the like, and cannot cope with a high recording density. Further, it has also been clarified that the glass having the composition has insufficient alkali resistance, and a phenomenon such as surface roughness is likely to occur after a cleaning process or the like, and cannot cope with a high recording density.
  • the present inventors have found the facts as described above, have heat resistance applicable to the heat-assisted magnetic recording technology, have excellent mechanical properties, have excellent chemical durability, and have excellent solubility.
  • the present invention has led to the invention of the glass substrate of the present invention for the purpose of providing a glass substrate.
  • the present invention also includes a disk processing step for processing a glass plate into a glass disc, a wrapping step for wrapping the main surface of the glass disc, a main surface polishing step for polishing the main surface wrapped with the glass disc, and these A method for producing a glass substrate for an information recording medium comprising a washing step of washing a glass disc between or after these steps, wherein the glass plate is expressed in mole percentage, SiO 2 is 60 to 75%, 7 to 17% of Al 2 O 3 , 0 to less than 2% of B 2 O 3 , and any one or more of MgO, CaO, SrO and BaO in total including more than 18% and 26% or less, The total content is 95% or more, and any one or more of Li 2 O, Na 2 O and K 2 O is contained in total less than 1%, or none of these three components is contained.
  • a method for producing a glass substrate for an information recording medium is provided.
  • the glass disk may have a so-called donut shape having a hole in the center or may have no hole. Further, the end face is usually subjected to chamfering, and may be subjected to etching treatment or mirror polishing.
  • the downdraw method include a fusion method and a slit downdraw method.
  • a magnetic recording layer can be formed on a glass substrate at a high temperature, so that the recording density of the magnetic disk can be increased.
  • the glass substrate on which the magnetic recording layer is formed has a high specific elastic modulus and is less likely to cause surface roughness in a polishing process or a cleaning process. Can be obtained.
  • the glass substrate for an information recording medium of the present invention is a glass substrate that can form a magnetic recording layer at a high temperature and can increase the density of the magnetic disk.
  • the glass substrate for information recording medium of the present invention is less likely to cause surface roughness with respect to an acidic polishing slurry liquid (hereinafter referred to as acid solution) in the glass substrate polishing step or the like, and the glass substrate for information recording medium of the present invention. It becomes possible to manufacture a high recording density information recording medium with high productivity. If the glass substrate is prone to surface roughness with respect to the acid solution, an alternative to an acid solution having a high pH is required. In the polishing of a glass substrate using an acid solution having a high pH, the polishing rate decreases, and it takes time for a predetermined polishing amount, resulting in a decrease in productivity. Alternatively, the polishing time until surface roughness occurs is shortened and the predetermined surface roughness is not reached.
  • acid solution acidic polishing slurry liquid
  • the glass substrate for information recording medium of the present invention is less likely to cause surface roughness with respect to an alkaline liquid in a glass substrate cleaning process or the like, and a high recording density information recording medium is obtained by using the glass substrate for information recording medium of the present invention.
  • the glass substrate for information recording medium of the present invention is not only capable of forming a magnetic recording layer at a high temperature but also a glass substrate for information recording medium excellent in solubility, that is, mass productivity.
  • the material of the magnetic recording layer for use in the production method of the magnetic disk of the present invention is a FePt or SmCo 5 is typical.
  • the magnetic recording layer is formed on a glass substrate whose temperature is typically 550 ° C. or higher.
  • the temperature of the glass substrate is preferably 600 ° C. or higher or 650 ° C. or higher, as necessary.
  • the temperature of this glass substrate shall be 800 degrees C or less normally.
  • a layer such as an underlayer is formed between the glass substrate and the magnetic recording layer, and if necessary, a protective film or the like is formed on the magnetic recording layer. Layers are formed.
  • the temperature is 650 ° C. or higher so that deformation of the glass during formation is suppressed and the magnetic disk can be read and written normally. More preferably, it is 700 ° C. or higher, particularly preferably 750 ° C. or higher, and typically 800 ° C. or lower.
  • the temperature T 2 at which 10 2 dPa ⁇ s is obtained is preferably 1710 ° C. or lower. More preferably, it is 1700 degrees C or less, More preferably, it is 1680 degrees C or less.
  • the density of the glass of the present invention stabilizes the disk rotation, reduces the load on the rotary motor, reduces the power consumption, reduces the exhaust heat load due to the heat generated by the motor, and makes the glass less susceptible to damage. since preferably 2.7 g / cm 3 or less, typically is 2.62 g / cm 3 or less.
  • the specific elastic modulus of the substrate glass is preferably 32 MNm / kg or more in order to prevent a fluttering phenomenon during high-speed rotation and to cope with a high recording density. More preferably, it is 32.5 MNm / kg or more, More preferably, it is 33 MNm / kg or more.
  • the acid resistance index A of the substrate glass is preferably 0.025 nm / h or less in order to correspond to a high recording density without causing a phenomenon such as surface roughness in a polishing process or the like. More preferably, it is 0.02 nm / h or less.
  • the alkali resistance index B of the substrate glass is preferably 0.28 nm / h or less in order to cope with a high recording density without causing a phenomenon such as surface roughness in a cleaning process or the like. More preferably, it is 0.27 nm / h or less.
  • the acid resistance index A is determined by the following measurement method.
  • a measurement sample is obtained by mirror-polishing both surfaces of a glass plate having a thickness of 1 to 2 mm and a size of 4 cm square with colloidal silica and mirror-polishing end surfaces with cerium oxide abrasive grains. This is immersed in an aqueous HNO 3 solution having a pH of 2 (0.01 mol / liter) kept at room temperature for 3 hours.
  • the amount of Si eluted in the aqueous solution is analyzed by ICP mass spectrometry to obtain a measured value.
  • the etching rate of the glass is calculated from the following formula from the amount of eluted Si, the content of SiO 2 in the glass and the density of the glass.
  • the unit of the acid resistance index A is nm / h
  • L1 is the amount of the eluted Si per unit area of the glass plate
  • the unit is ⁇ g / cm 2
  • d is the density of the glass
  • the unit is g / cm 3
  • P SiO in the glass.
  • the unit of the mass percentage display content is 2.
  • the alkali resistance index B is determined by the following measurement method.
  • a measurement sample is obtained by mirror-polishing both surfaces of a glass plate having a thickness of 1 to 2 mm and a size of 4 cm square with colloidal silica and mirror-polishing end surfaces with cerium oxide abrasive grains. This is immersed in an aqueous NaOH solution having a pH of 12 (0.01 mol / liter) kept at room temperature for 3 hours while applying an ultrasonic wave of 100 kHz. The amount of Si eluted in the aqueous solution is analyzed by ICP mass spectrometry to obtain a measured value.
  • the etching rate of the glass is calculated from the following formula from the amount of eluted Si, the content of SiO 2 in the glass and the density of the glass.
  • the acid resistance index B is in units of nm / h
  • L2 is the amount of eluted Si per unit area of the glass plate
  • the unit is ⁇ g / cm 2
  • d is the density of the glass
  • the unit is g / cm 3
  • P is the SiO in the glass.
  • the unit of the mass percentage display content is 2.
  • composition of the glass of the present invention will be described using the mole percentage display content unless otherwise specified.
  • SiO 2 is an essential component. SiO 2 is 60% or more in order to keep basic chemical durability in order to reduce the weight of the substrate and make it difficult to be damaged. Preferably it is 63% or more, More preferably, it is 65% or more, More preferably, it is 66% or more. On the other hand, the viscosity of the glass is lowered, the solubility is made good, and it is made 75% or less in order to improve the chemical durability in the composition near the present invention. Preferably it is 71% or less, More preferably, it is 70% or less, More preferably, it is 69% or less.
  • Al 2 O 3 is an essential component.
  • Al 2 O 3 improves heat resistance, suppresses phase separation, maintains 7% or more to maintain the smoothness of the substrate surface after polishing and cleaning the substrate, and maintains resistance to scratches.
  • it is 9% or more, more preferably 11% or more, more preferably more than 12%, more preferably more than 12.5%.
  • Al 2 O 3 is made 17% or less in order to improve the glass solubility.
  • it is 16% or less, More preferably, it is 15% or less, More preferably, it is 14% or less.
  • the content of Al 2 O 3 is preferably greater than 18 wt%.
  • B 2 O 3 is not an essential component, but may be contained because it has an effect of improving the solubility and fragility of glass. Maintenance of acid-resistant, and less than 2% for the improvement of T A. Preferably it is 1.5% or less, More preferably, it is 1.0% or less, More preferably, it is 0.5% or less.
  • MgO, CaO, SrO and BaO are components that improve the solubility of the glass and improve the acid resistance and alkali resistance, and any one or more components must contain more than 18% in total (RO) amount. Preferably it is 18.5% or more, more preferably 19% or more.
  • the RO amount is set to 26% or less in order to improve devitrification characteristics and make it difficult to be damaged. Preferably it is 24% or less, more preferably 22% or less.
  • MgO + CaO is preferably 20% or less. More preferably, it is 18% or less.
  • the value obtained by dividing the content of SiO 2 (mole percentage) by the total amount RO of the contents of MgO, CaO, SrO and BaO (mole percentage) increases the specific elastic modulus and improves acid resistance and alkali resistance.
  • T 2 the temperature at which the viscosity becomes 10 2 dPa ⁇ s
  • it is preferably 4.3 or less. More preferably, it is 4.1 or less, More preferably, it is 3.9 or less.
  • MgO is a component that increases the Young's modulus and has the effect of increasing the rigidity of the glass. More preferably, it is 7% or more.
  • the glass of the present invention consists essentially of the above seven components, but may contain other components as long as the object of the present invention is not impaired. However, even in that case, the total content of these components is less than 5% for maintaining resistance to scratches, maintaining acid resistance, alkali resistance, and maintaining specific elasticity.
  • components other than the above seven components will be exemplarily described.
  • ZnO is a component having the same effect as MgO, CaO, SrO and BaO, and may be contained in a range of less than 5%.
  • the total content of ZnO and RO is preferably more than 18% and 26% or less.
  • Li 2 O since Na 2 O and K 2 O decreases the T A, it is preferable that the total content of these three components do not contain less than 1%, or substantially.
  • the total content thereof is preferably 3% or less. More preferably, it is 2% or less, particularly preferably 1% or less, and most preferably 0.3% or less.
  • SO 3 , F, Cl, As 2 O 3 , Sb 2 O 3, SnO 2 and the like are typical components as fining agents.
  • MgCa is the total content of MgO and CaO
  • RO is the total content of MgO, CaO, SrO and BaO.
  • the acid resistance index A was determined by the following measurement method.
  • a glass sample having a thickness of 1 to 2 mm and a size of 4 cm square was mirror-polished on both sides with colloidal silica, and the end surface was mirror-polished with cerium oxide abrasive grains as a measurement sample. This was immersed in an aqueous HNO 3 solution having a pH of 2 (0.01 mol / liter) kept at room temperature for 3 hours.
  • the amount of Si eluted in the aqueous solution was analyzed by ICP mass spectrometry to obtain a measured value.
  • the etching rate of the glass was calculated by the following formula from the amount of dissolved Si, the content of SiO 2 in the glass, and the density of the glass.
  • the unit of the acid resistance index A is nm / h
  • L1 is the amount of the eluted Si per unit area of the glass plate
  • the unit is ⁇ g / cm 2
  • d is the density of the glass
  • the unit is g / cm 3
  • P SiO in the glass.
  • the unit of the mass percentage display content is 2.
  • the alkali resistance index B was determined by the following measurement method.
  • a glass sample having a thickness of 1 to 2 mm and a size of 4 cm square was mirror-polished on both sides with colloidal silica, and the end surface was mirror-polished with cerium oxide abrasive grains as a measurement sample.
  • This was immersed in an aqueous NaOH solution having a pH of 12 (0.01 mol / liter) kept at room temperature for 3 hours while applying an ultrasonic wave of 100 kHz.
  • the amount of Si eluted in the aqueous solution was analyzed by ICP mass spectrometry to obtain a measured value.
  • the etching rate of the glass was calculated by the following formula from the amount of dissolved Si, the content of SiO 2 in the glass, and the density of the glass.
  • the unit of the alkali resistance index B is nm / h
  • L2 is the amount of the eluted Si per unit area of the glass plate
  • the unit is ⁇ g / cm 2
  • d is the density of the glass
  • the unit is g / cm 3
  • P is the SiO in the glass.
  • the unit of the mass percentage display content is 2.
  • Examples 1 to 6 are examples of the substrate glass used in the present invention.
  • Example 7 is a substrate glass for comparison.
  • the present invention can be used for manufacturing a magnetic disk and a glass substrate for an information recording medium.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Ceramic Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Glass Compositions (AREA)
  • Magnetic Record Carriers (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)

Abstract

The present invention provides a method for producing a magnetic disk, which is capable of forming a magnetic recording layer at high temperature. The present invention relates to a method for producing a magnetic disk, which comprises a step wherein a magnetic recording layer is formed on a glass substrate that is at a temperature of 550°C or more, and in which the glass substrate contains, in mol%, 60-75% of SiO2, 7-17% of Al2O3, 0% or more but less than 2% of B2O3, and one or more substances selected from among MgO, CaO, SrO and BaO in an amount of more than 18% but 26% or less in total, with the total of the above-mentioned seven components being 95% or more, while containing one or more substances selected from among Li2O, Na2O and K2O in an amount of less than 1% or not containing any of these three substances.

Description

磁気ディスクの製造方法および情報記録媒体用ガラス基板Manufacturing method of magnetic disk and glass substrate for information recording medium
　本発明は磁気ディスクの製造方法および情報記録媒体用ガラス基板に関し、特には高温で磁気記録層を形成する磁気ディスクの製造方法およびそのような製造方法に好適なガラス基板に関する。 The present invention relates to a method for manufacturing a magnetic disk and a glass substrate for an information recording medium, and more particularly to a method for manufacturing a magnetic disk for forming a magnetic recording layer at a high temperature and a glass substrate suitable for such a manufacturing method.
　近年、ハードディスクドライブの記録容量の増大に伴い、高記録密度化がハイペースで進行している。しかし、高記録密度化に伴い、磁性粒子の微細化が熱安定性を損ない、クロストークまたは再生信号のＳＮ比低下が問題となっている。 In recent years, with the increase in recording capacity of hard disk drives, higher recording density is progressing at a high pace. However, with the increase in recording density, miniaturization of magnetic particles impairs thermal stability, and there is a problem of crosstalk or a decrease in the S / N ratio of a reproduction signal.
　そこで、光と磁気の融合技術として熱アシスト磁気記録技術が注目されている。これは、磁気記録層にレーザ光または近接場光を照射して局所的に加熱した部分の保磁力を低下させた状態で外部磁界を印加して記録し、ＧＭＲ素子等で記録磁化を読み出す技術であり、高保持力媒体に記録できるため、熱安定性を保ちながら磁性粒子を微細化することが可能となる。 Therefore, heat-assisted magnetic recording technology is attracting attention as a fusion technology of light and magnetism. This is a technique in which a magnetic recording layer is irradiated with a laser beam or near-field light and recorded by applying an external magnetic field in a state where the coercive force is lowered in a locally heated portion, and the recorded magnetization is read by a GMR element or the like. In addition, since recording can be performed on a medium having a high holding force, the magnetic particles can be miniaturized while maintaining thermal stability.
　しかし、高保持力媒体を多層膜にして成膜するには、基板を十分に加熱する必要があり、高耐熱基板が求められる。 However, in order to form a high coercive force medium as a multilayer film, it is necessary to sufficiently heat the substrate, and a high heat-resistant substrate is required.
　また、垂直磁気記録方式においても高記録密度化の要求に応えるべく従来のものとは異なる磁気記録層が提案されているが、そのような磁気記録層の形成は基板を高温にして行う必要があることが多い。 Also in the perpendicular magnetic recording system, a magnetic recording layer different from the conventional one has been proposed to meet the demand for higher recording density, but such a magnetic recording layer needs to be formed at a high temperature. There are often.
　ところで、先に述べた熱アシスト磁気記録技術に対応できる基板としてシリコン基板が提案されている（特許文献１参照）。 Incidentally, a silicon substrate has been proposed as a substrate that can cope with the heat-assisted magnetic recording technique described above (see Patent Document 1).
日本国特開２００９－１９９６３３号公報Japanese Unexamined Patent Publication No. 2009-199633
　しかしながら、シリコン基板にはガラス基板に比べて一般的に強度の点で懸念がある。したがって、基板を高温にして磁気記録層を形成する磁気ディスクの製造においてもガラス基板を用いるようにすることが好ましい。 However, silicon substrates are generally concerned with strength compared to glass substrates. Therefore, it is preferable to use a glass substrate also in the manufacture of a magnetic disk in which the magnetic recording layer is formed at a high temperature.
　したがって、本発明はこのような磁気ディスクの製造方法およびそのような製造方法に好適な情報記録媒体用ガラス基板を製造する方法の提供を目的とする。 Therefore, an object of the present invention is to provide a method for manufacturing such a magnetic disk and a method for manufacturing a glass substrate for an information recording medium suitable for such a manufacturing method.
　本発明は、温度が５５０℃以上であるガラス基板の上に磁気記録層を形成する工程を含む磁気ディスクの製造方法であって、 The present invention is a method of manufacturing a magnetic disk including a step of forming a magnetic recording layer on a glass substrate having a temperature of 550 ° C. or higher,
　該ガラス基板がモル百分率表示で、ＳｉＯ２を６０～７５％、Ａｌ２Ｏ３を７～１７％、Ｂ２Ｏ３を０～２％未満、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯのいずれか１成分以上を合計で１８％超２６％以下含有し、上記７成分の含有量合計が９５％以上であり、Ｌｉ２Ｏ、Ｎａ２ＯおよびＫ２Ｏのいずれか１成分以上を合計で１％未満含有する、もしくはこれら３成分のいずれも含有しないものである磁気ディスクの製造方法を提供する。 The glass substrate is expressed in mole percentage, and SiO 2 is 60 to 75%, Al 2 O 3 is 7 to 17%, B 2 O 3 is less than 0 to less than 2%, and any one component of MgO, CaO, SrO and BaO More than 18% in total and 26% or less in total, the total content of the above 7 components is 95% or more, and any one or more of Li 2 O, Na 2 O and K 2 O is less than 1% in total Provided is a method for manufacturing a magnetic disk which contains or does not contain any of these three components.
　また、前記ガラス基板がモル百分率表示で、ＭｇＯおよびＣａＯのいずれか１成分以上を合計で１０．５～２０％含有する前記磁気ディスクの製造方法を提供する。 Also provided is a method for producing the magnetic disk, wherein the glass substrate contains 10.5 to 20% in total of one or more components of MgO and CaO in terms of mole percentage.
　また、前記ガラス基板がモル百分率表示で、ＭｇＯを６％以上含有する前記磁気ディスクの製造方法を提供する。 Also provided is a method for producing the magnetic disk, wherein the glass substrate is expressed in mole percentage and contains 6% or more of MgO.
　また、前記ガラス基板が、質量百分率表示でＡｌ２Ｏ３を１８％超含有する前記磁気ディスクの製造方法を提供する。 Further, the present invention provides a method for producing the magnetic disk, wherein the glass substrate contains Al 2 O 3 in excess of 18% in terms of mass percentage.
　また、前記ガラス基板が、ＳｉＯ２の含有量（モル百分率）を、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯの含有量（モル百分率）の合量ＲＯで除した値が４．３以下である前記磁気ディスクの製造方法を提供する。 The magnetic disk having a value obtained by dividing the content (molar percentage) of SiO 2 by the total amount RO of the contents (molar percentage) of MgO, CaO, SrO and BaO is 4.3 or less. A manufacturing method is provided.
　また、前記ガラス基板の粘度が１０２ｄＰａ・ｓとなる温度Ｔ２が１７１０℃以下である前記磁気ディスクの製造方法を提供する。 Further, the present invention provides a method for manufacturing the magnetic disk, wherein a temperature T 2 at which the viscosity of the glass substrate is 10 2 dPa · s is 1710 ° C. or lower.
　また、前記ガラス基板の徐冷点が６５０℃以上である前記磁気ディスクの製造方法を提供する。 Also provided is a method for producing the magnetic disk, wherein the glass substrate has an annealing point of 650 ° C. or higher.
　また、前記ガラス基板の比弾性率が３２ＭＮｍ・ｋｇ以上である前記磁気ディスクの製造方法を提供する。 Also provided is a method of manufacturing the magnetic disk, wherein the glass substrate has a specific elastic modulus of 32 MNm · kg or more.
　また、前記ガラス基板の耐酸性指標Ａが０．０２５ｎｍ／ｈ以下である前記磁気ディスクの製造方法を提供する。 Also provided is a method for producing the magnetic disk, wherein the acid resistance index A of the glass substrate is 0.025 nm / h or less.
　また、前記ガラス基板の耐アルカリ性指標Ｂが０．２８ｎｍ／ｈ以下である前記磁気ディスクの製造方法を提供する。 Also provided is a method for producing the magnetic disk, wherein the glass substrate has an alkali resistance index B of 0.28 nm / h or less.
　また、モル百分率表示で、ＳｉＯ２を６０～７５％、Ａｌ２Ｏ３を７～１７％、Ｂ２Ｏ３を０～２％未満、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯのいずれか１成分以上を合計で１８％超２６％以下含有し、上記７成分の含有量合計が９５％以上であり、Ｌｉ２Ｏ、Ｎａ２ＯおよびＫ２Ｏのいずれか１成分以上を合計で１％未満含有する、またはこれら３成分のいずれも含有しない情報記録媒体用ガラス基板を提供する。 In addition, in terms of mole percentage, SiO 2 is 60 to 75%, Al 2 O 3 is 7 to 17%, B 2 O 3 is 0 to less than 2%, and one or more components of MgO, CaO, SrO and BaO are contained. The total content is more than 18% and 26% or less, the total content of the above seven components is 95% or more, and any one or more of Li 2 O, Na 2 O and K 2 O is contained in less than 1% in total. Or a glass substrate for an information recording medium which does not contain any of these three components.
　また、モル百分率表示で、ＭｇＯおよびＣａＯのいずれか１成分以上を合計で１０．５～２０％含有する前記情報記録媒体用ガラス基板を提供する。 Also provided is the glass substrate for an information recording medium containing a total of 10.5 to 20% of any one component of MgO and CaO in terms of mole percentage.
　また、モル百分率表示で、ＭｇＯを６％以上含有する前記情報記録媒体用ガラス基板を提供する。 Also provided is the glass substrate for an information recording medium containing 6% or more of MgO in terms of mole percentage.
　また、質量百分率表示でＡｌ２Ｏ３を１８％超含有する前記情報記録媒体用ガラス基板を提供する。 Further, to provide a glass substrate for the information recording medium to 18% ultra containing Al 2 O 3 in mass percentage.
　また、ＳｉＯ２の含有量（モル百分率）を、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯの含有量（モル百分率）の合量ＲＯで除した値が４．３以下である前記情報記録媒体用ガラス基板を提供する。 The glass substrate for an information recording medium, wherein a value obtained by dividing the content (molar percentage) of SiO 2 by the total amount RO of the contents (molar percentage) of MgO, CaO, SrO, and BaO is 4.3 or less. provide.
　また、前記情報記録媒体が磁気ディスクである前記情報記録媒体用ガラス基板を提供する。 Also provided is the glass substrate for an information recording medium, wherein the information recording medium is a magnetic disk.
　本発明のうちこれらガラス基板に係る発明は、磁気記録層を形成する磁気ディスクの製造において基板を高温にできるようにするだけでなく、次に述べるように製造を容易にすることも目的とするものである。 Among the present inventions, the inventions related to these glass substrates not only enable the substrate to be heated at a high temperature in the production of the magnetic disk for forming the magnetic recording layer, but also facilitate the production as described below. Is.
　国際公開第２０１１／１３６０２７号には、耐熱性に優れるガラスの組成が開示されている。しかし、その実施例１４に示される組成のガラスは粘度が１０２ｄＰａ・ｓとなる温度Ｔ２が高いため、溶解性が悪くかつ泡などの欠点を除去しにくいことが明らかとなった。 International Publication No. 2011/136027 discloses a glass composition having excellent heat resistance. However, the glass viscosity of the composition indicated in the Example 14 for temperature T 2 is high as a 10 2 dPa · s, solubility becomes poor and clearly can be difficult to remove the drawbacks of such bubbles.
　また、国際公開第２０１１／１３６０２７号の実施例１４に示される組成のガラスは、比弾性率が３１．２ＭＮｍ・ｋｇと低く、ディスクの高速回転時にフラッタリング現象が起きやすく高記録密度に対応できないことが明らかとなった。さらに、該組成のガラスは、耐酸性が不十分であり、研磨工程等の後に面荒れなどの現象が起きやすく高記録密度に対応できないことも明らかとなった。また、該組成のガラスは、耐アルカリ性が不十分であり、洗浄工程等の後に面荒れなどの現象が起きやすく高記録密度に対応できないことも明らかとなった。 Further, the glass having the composition shown in Example 14 of International Publication No. 2011/136027 has a low specific elastic modulus of 31.2 MNm · kg, and fluttering phenomenon easily occurs at the time of high-speed rotation of the disk and cannot cope with a high recording density. It became clear. Furthermore, it has been clarified that the glass having the above composition has insufficient acid resistance, and a phenomenon such as surface roughness is likely to occur after a polishing process or the like, and cannot cope with a high recording density. Further, it has also been clarified that the glass having the composition has insufficient alkali resistance, and a phenomenon such as surface roughness is likely to occur after a cleaning process or the like, and cannot cope with a high recording density.
　本発明者は先に述べたような事実を見出し、熱アシスト磁気記録技術に適用できる耐熱性を持ち、優れた機械的特性を持ち、優れた化学耐久性を持ちながら、かつ溶解性にも優れたガラス基板の提供を目的とする本発明のガラス基板の発明をなすに至った。 The present inventors have found the facts as described above, have heat resistance applicable to the heat-assisted magnetic recording technology, have excellent mechanical properties, have excellent chemical durability, and have excellent solubility. The present invention has led to the invention of the glass substrate of the present invention for the purpose of providing a glass substrate.
　また、本発明は、ガラス板をガラス円板に加工する円板加工工程、ガラス円板の主表面をラッピングするラッピング工程、ガラス円板のラッピングされた主表面を研磨する主表面研磨工程およびこれら工程間、これら工程内またはこれら工程後においてガラス円板を洗浄する洗浄工程を含む情報記録媒体用ガラス基板の製造方法であって、ガラス板がモル百分率表示で、ＳｉＯ２を６０～７５％、Ａｌ２Ｏ３を７～１７％、Ｂ２Ｏ３を０～２％未満、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯのいずれか１成分以上を合計で１８％超２６％以下含有し、上記７成分の含有量合計が９５％以上であり、Ｌｉ２Ｏ、Ｎａ２ＯおよびＫ２Ｏのいずれか１成分以上を合計で１％未満含有する、もしくはこれら３成分のいずれも含有しないものである情報記録媒体用ガラス基板の製造方法を提供する。 The present invention also includes a disk processing step for processing a glass plate into a glass disc, a wrapping step for wrapping the main surface of the glass disc, a main surface polishing step for polishing the main surface wrapped with the glass disc, and these A method for producing a glass substrate for an information recording medium comprising a washing step of washing a glass disc between or after these steps, wherein the glass plate is expressed in mole percentage, SiO 2 is 60 to 75%, 7 to 17% of Al 2 O 3 , 0 to less than 2% of B 2 O 3 , and any one or more of MgO, CaO, SrO and BaO in total including more than 18% and 26% or less, The total content is 95% or more, and any one or more of Li 2 O, Na 2 O and K 2 O is contained in total less than 1%, or none of these three components is contained. A method for producing a glass substrate for an information recording medium is provided.
　前記情報記録媒体用ガラス基板の製造方法において、ガラス円板は中央に孔を有するいわゆるドーナツ形状のものでもよいし、孔を有さないものでもよい。また、端面については通常は面取り加工が行われる他、エッチング処理または鏡面研磨が行われることがある。 In the method for manufacturing a glass substrate for an information recording medium, the glass disk may have a so-called donut shape having a hole in the center or may have no hole. Further, the end face is usually subjected to chamfering, and may be subjected to etching treatment or mirror polishing.
　また、前記ガラス基板の徐冷点が６５０℃以上である前記情報記録媒体用ガラス基板の製造方法を提供する。 Also provided is a method for producing a glass substrate for an information recording medium, wherein the annealing point of the glass substrate is 650 ° C. or higher.
　また、フロート法またはダウンドロー法を用いて前記ガラス基板を製造する前記情報記録媒体用ガラス基板の製造方法を提供する。ダウンドロー法としては、例えば、フュージョン法およびスリットダウンドロー法が挙げられる。 Also provided is a method for producing a glass substrate for an information recording medium, wherein the glass substrate is produced using a float method or a downdraw method. Examples of the downdraw method include a fusion method and a slit downdraw method.
　また、前記情報記録媒体が磁気ディスクである前記情報記録媒体用ガラス基板の製造方法を提供する。 Also provided is a method for producing a glass substrate for an information recording medium, wherein the information recording medium is a magnetic disk.
　本発明の磁気ディスクの製造方法によれば、ガラス基板に高温で磁気記録層を形成することができるので磁気ディスクの高記録密度化が可能になる。また、本発明の磁気ディスクの製造方法によれば、磁気記録層を形成するガラス基板の比弾性率が高く、研磨工程または洗浄工程等での面荒れを起こしにくいことから、高記録密度に対応できる磁気ディスクを得ることができる。 According to the method for manufacturing a magnetic disk of the present invention, a magnetic recording layer can be formed on a glass substrate at a high temperature, so that the recording density of the magnetic disk can be increased. In addition, according to the method of manufacturing a magnetic disk of the present invention, the glass substrate on which the magnetic recording layer is formed has a high specific elastic modulus and is less likely to cause surface roughness in a polishing process or a cleaning process. Can be obtained.
　また、本発明の情報記録媒体用ガラス基板は、高温で磁気記録層を形成でき、磁気ディスクの高密度化を可能とするガラス基板である。 The glass substrate for an information recording medium of the present invention is a glass substrate that can form a magnetic recording layer at a high temperature and can increase the density of the magnetic disk.
　また、本発明の情報記録媒体用ガラス基板は、ガラス基板の研磨工程等での酸性の研磨スラリー液（以下、酸液という。）に対する面荒れを起こしにくく、本発明の情報記録媒体用ガラス基板を用いることにより高記録密度の情報記録媒体を生産性良く製造することが可能になる。ガラス基板が酸液に対して面荒れが起こしやすいと、ｐＨの大きい酸液への代替が必要となる。ｐＨの大きい酸液を使用したガラス基板の研磨では研磨速度が低下し所定の研磨量に要する時間がかかり生産性が低下する。あるいは面荒れを起こすまでの研磨時間が短くなり、所定の表面あらさに到達しなくなる。 In addition, the glass substrate for information recording medium of the present invention is less likely to cause surface roughness with respect to an acidic polishing slurry liquid (hereinafter referred to as acid solution) in the glass substrate polishing step or the like, and the glass substrate for information recording medium of the present invention. It becomes possible to manufacture a high recording density information recording medium with high productivity. If the glass substrate is prone to surface roughness with respect to the acid solution, an alternative to an acid solution having a high pH is required. In the polishing of a glass substrate using an acid solution having a high pH, the polishing rate decreases, and it takes time for a predetermined polishing amount, resulting in a decrease in productivity. Alternatively, the polishing time until surface roughness occurs is shortened and the predetermined surface roughness is not reached.
　また、本発明の情報記録媒体用ガラス基板は、ガラス基板の洗浄工程等でのアルカリ液に対する面荒れを起こしにくく、本発明の情報記録媒体用ガラス基板を用いることにより高記録密度の情報記録媒体を生産性良く製造することが可能になる。ガラス基板がアルカリ液に対して面荒れが起こしやすいと、ｐＨの小さいアルカリ液への代替が必要となる。ｐＨの小さいアルカリ液を使用したガラス基板の洗浄では洗浄力が低下し、所定の清浄度を有するまでの所要時間がかかり生産性が低下する。あるいは面荒れを起こすまでの時間が短くなり、所定の清浄度に到達しなくなる。 In addition, the glass substrate for information recording medium of the present invention is less likely to cause surface roughness with respect to an alkaline liquid in a glass substrate cleaning process or the like, and a high recording density information recording medium is obtained by using the glass substrate for information recording medium of the present invention. Can be manufactured with high productivity. If the glass substrate is prone to surface roughness with respect to the alkaline solution, an alternative to an alkaline solution having a low pH is required. Cleaning of a glass substrate using an alkaline solution having a low pH reduces the cleaning power, and takes a long time to obtain a predetermined cleanliness, resulting in a decrease in productivity. Or time until surface roughening will become short, and it will not reach predetermined cleanliness.
　また、本発明の情報記録媒体用ガラス基板は、高温で磁気記録層を形成できるだけでなく、溶解性すなわち量産性に優れた情報記録媒体用ガラス基板である。 The glass substrate for information recording medium of the present invention is not only capable of forming a magnetic recording layer at a high temperature but also a glass substrate for information recording medium excellent in solubility, that is, mass productivity.
　本発明の磁気ディスクの製造方法に用いる磁気記録層の材料としてはＦｅＰｔまたはＳｍＣｏ５が典型的である。 As the material of the magnetic recording layer for use in the production method of the magnetic disk of the present invention is a FePt or SmCo 5 is typical.
　前記磁気記録層は温度が典型的には５５０℃以上であるガラス基板の上に形成される。該ガラス基板の温度は必要に応じてたとえば６００℃以上または６５０℃以上にすることが好ましい。なお、該ガラス基板の温度は通常８００℃以下とする。 The magnetic recording layer is formed on a glass substrate whose temperature is typically 550 ° C. or higher. The temperature of the glass substrate is preferably 600 ° C. or higher or 650 ° C. or higher, as necessary. In addition, the temperature of this glass substrate shall be 800 degrees C or less normally.
　本発明の磁気ディスクの製造方法においては、必要に応じて、ガラス基板と磁気記録層の間に下地層などの層が形成され、また、必要に応じて、磁気記録層の上に保護膜などの層が形成される。 In the method for producing a magnetic disk of the present invention, if necessary, a layer such as an underlayer is formed between the glass substrate and the magnetic recording layer, and if necessary, a protective film or the like is formed on the magnetic recording layer. Layers are formed.
　本発明の磁気ディスクの製造方法で用いられるガラス基板を構成するガラス（以下、基板ガラスまたは本発明のガラスということがある。）および本発明のガラス基板の徐冷点ＴＡは、磁気記録層形成時のガラスの変形を抑止し磁気ディスクが正常に読み書きができるように６５０℃以上であることが好ましい。より好ましくは７００℃以上、特に好ましくは７５０℃以上であり、典型的には８００℃以下である。 Glass constituting the glass substrate used in the manufacturing method of the magnetic disk of the present invention (hereinafter sometimes referred to as a glass substrate glass or the present invention.) And annealing point T A of the glass substrate of the present invention, a magnetic recording layer It is preferable that the temperature is 650 ° C. or higher so that deformation of the glass during formation is suppressed and the magnetic disk can be read and written normally. More preferably, it is 700 ° C. or higher, particularly preferably 750 ° C. or higher, and typically 800 ° C. or lower.
　基板ガラスの粘度は、溶解性を良好なものとするために、１０２ｄＰａ・ｓとなる温度Ｔ２は１７１０℃以下であることが好ましい。より好ましくは１７００℃以下、さらに好ましくは１６８０℃以下である。 In order for the viscosity of the substrate glass to have good solubility, the temperature T 2 at which 10 2 dPa · s is obtained is preferably 1710 ° C. or lower. More preferably, it is 1700 degrees C or less, More preferably, it is 1680 degrees C or less.
　本発明のガラスの密度は、ディスク回転を安定化させ、回転モーターの負荷を軽減し、消費電力を小さくし、モーターの発熱による排熱の負荷を小さくするために、また、ガラスを傷つきにくくするため好ましくは２．７ｇ／ｃｍ３以下、典型的には２．６２ｇ／ｃｍ３以下である。 The density of the glass of the present invention stabilizes the disk rotation, reduces the load on the rotary motor, reduces the power consumption, reduces the exhaust heat load due to the heat generated by the motor, and makes the glass less susceptible to damage. since preferably 2.7 g / cm 3 or less, typically is 2.62 g / cm 3 or less.
　基板ガラスの比弾性率は、高速回転時にフラッタリング現象が起きにくく高記録密度に対応するため３２ＭＮｍ／ｋｇ以上であることが好ましい。より好ましくは３２．５ＭＮｍ／ｋｇ以上、さらに好ましくは３３ＭＮｍ／ｋｇ以上である。 The specific elastic modulus of the substrate glass is preferably 32 MNm / kg or more in order to prevent a fluttering phenomenon during high-speed rotation and to cope with a high recording density. More preferably, it is 32.5 MNm / kg or more, More preferably, it is 33 MNm / kg or more.
　基板ガラスの耐酸性指標Ａは、研磨工程等における面荒れなどの現象が起きずに高記録密度に対応するため０．０２５ｎｍ／ｈ以下であることが好ましい。より好ましくは０．０２ｎｍ／ｈ以下である。 The acid resistance index A of the substrate glass is preferably 0.025 nm / h or less in order to correspond to a high recording density without causing a phenomenon such as surface roughness in a polishing process or the like. More preferably, it is 0.02 nm / h or less.
　基板ガラスの耐アルカリ性指標Ｂは、洗浄工程等における面荒れなどの現象が起きずに高記録密度に対応するため０．２８ｎｍ／ｈ以下であることが好ましい。より好ましくは０．２７ｎｍ／ｈ以下である。 The alkali resistance index B of the substrate glass is preferably 0.28 nm / h or less in order to cope with a high recording density without causing a phenomenon such as surface roughness in a cleaning process or the like. More preferably, it is 0.27 nm / h or less.
　耐酸性指標Ａは以下の測定方法により決定する。
　厚さが１～２ｍｍ、大きさが４ｃｍ角のガラス板の両面をコロイダルシリカで鏡面研磨し、端面を酸化セリウム砥粒で鏡面研磨したものを測定サンプルとする。これを室温に保持したｐＨ＝２（０．０１モル／リットル）のＨＮＯ３水溶液に３時間浸漬する。前記水溶液中に溶出した溶出Ｓｉ量をＩＣＰ質量分析法で分析して測定値を得る。前記溶出Ｓｉ量、ガラス中のＳｉＯ２含有量およびガラスの密度から、ガラスのエッチング速度を下記式により算出する。
　耐酸性指標Ａ＝１０００×Ｌ１／［ｄ×Ｐ×（Ｓｉの原子量＝２８）／（ＳｉＯ２の分子量＝６０）］／３
　耐酸性指標Ａの単位はｎｍ／ｈ、Ｌ１はガラス板単位面積当たりの前記溶出Ｓｉ量で単位はμｇ／ｃｍ２、ｄはガラスの密度で単位はｇ／ｃｍ３、Ｐはガラス中のＳｉＯ２の質量百分率表示含有量で単位は質量％である。 The acid resistance index A is determined by the following measurement method.
A measurement sample is obtained by mirror-polishing both surfaces of a glass plate having a thickness of 1 to 2 mm and a size of 4 cm square with colloidal silica and mirror-polishing end surfaces with cerium oxide abrasive grains. This is immersed in an aqueous HNO 3 solution having a pH of 2 (0.01 mol / liter) kept at room temperature for 3 hours. The amount of Si eluted in the aqueous solution is analyzed by ICP mass spectrometry to obtain a measured value. The etching rate of the glass is calculated from the following formula from the amount of eluted Si, the content of SiO 2 in the glass and the density of the glass.
Acid resistance index A = 1000 × L1 / [d × P × (Si atomic weight = 28) / (SiO 2 molecular weight = 60)] / 3
The unit of the acid resistance index A is nm / h, L1 is the amount of the eluted Si per unit area of the glass plate, the unit is μg / cm 2 , d is the density of the glass, the unit is g / cm 3 , and P is SiO in the glass. The unit of the mass percentage display content is 2.
　耐アルカリ性指標Ｂは以下の測定方法により決定する。
　厚さが１～２ｍｍ、大きさが４ｃｍ角のガラス板の両面をコロイダルシリカで鏡面研磨し、端面を酸化セリウム砥粒で鏡面研磨したものを測定サンプルとする。これを室温に保持したｐＨ＝１２（０．０１モル／リットル）のＮａＯＨ水溶液に１００ｋＨｚの超音波を印加しながら３時間浸漬する。前記水溶液中に溶出した溶出Ｓｉ量をＩＣＰ質量分析法で分析して測定値を得る。前記溶出Ｓｉ量、ガラス中のＳｉＯ２含有量およびガラスの密度から、ガラスのエッチング速度を下記式により算出する。
　耐酸性指標Ｂ＝１０００×Ｌ２／［ｄ×Ｐ×（Ｓｉの原子量＝２８）／（ＳｉＯ２の分子量＝６０）］／３
　耐酸性指標Ｂの単位はｎｍ／ｈ、Ｌ２はガラス板単位面積当たりの前記溶出Ｓｉ量で単位はμｇ／ｃｍ２、ｄはガラスの密度で単位はｇ／ｃｍ３、Ｐはガラス中のＳｉＯ２の質量百分率表示含有量で単位は質量％である。 The alkali resistance index B is determined by the following measurement method.
A measurement sample is obtained by mirror-polishing both surfaces of a glass plate having a thickness of 1 to 2 mm and a size of 4 cm square with colloidal silica and mirror-polishing end surfaces with cerium oxide abrasive grains. This is immersed in an aqueous NaOH solution having a pH of 12 (0.01 mol / liter) kept at room temperature for 3 hours while applying an ultrasonic wave of 100 kHz. The amount of Si eluted in the aqueous solution is analyzed by ICP mass spectrometry to obtain a measured value. The etching rate of the glass is calculated from the following formula from the amount of eluted Si, the content of SiO 2 in the glass and the density of the glass.
Acid resistance index B = 1000 × L2 / [d × P × (Si atomic weight = 28) / (SiO 2 molecular weight = 60)] / 3
The acid resistance index B is in units of nm / h, L2 is the amount of eluted Si per unit area of the glass plate, the unit is μg / cm 2 , d is the density of the glass, the unit is g / cm 3 , and P is the SiO in the glass. The unit of the mass percentage display content is 2.
　次に本発明のガラスの組成について特に断らない限りモル百分率表示含有量を用いて説明する。 Next, the composition of the glass of the present invention will be described using the mole percentage display content unless otherwise specified.
　ＳｉＯ２は必須成分である。ＳｉＯ２は基板の軽量化のため、傷つきにくくするため、基礎的な化学的耐久性保持のために６０％以上である。好ましくは６３％以上、より好ましくは６５％以上、より好ましくは６６％以上である。一方、ガラスの粘性を下げ、溶解性を良好なものとし、本発明近傍組成での化学的耐久性の向上のために７５％以下とする。好ましくは７１％以下、より好ましくは７０％以下、より好ましくは６９％以下である。 SiO 2 is an essential component. SiO 2 is 60% or more in order to keep basic chemical durability in order to reduce the weight of the substrate and make it difficult to be damaged. Preferably it is 63% or more, More preferably, it is 65% or more, More preferably, it is 66% or more. On the other hand, the viscosity of the glass is lowered, the solubility is made good, and it is made 75% or less in order to improve the chemical durability in the composition near the present invention. Preferably it is 71% or less, More preferably, it is 70% or less, More preferably, it is 69% or less.
　Ａｌ２Ｏ３は必須成分である。Ａｌ２Ｏ３は耐熱性を向上させ、分相を抑制し、基板の研磨・洗浄後の基板表面の平滑さの維持のため、傷つきにくさの維持のために７％以上とする。好ましくは９％以上、より好ましくは１１％以上、より好ましくは１２％超、より好ましくは１２．５％超である。一方、ガラスの溶解性を良好なものとするためにＡｌ２Ｏ３は１７％以下とする。好ましくは１６％以下、より好ましくは１５％以下、より好ましくは１４％以下である。なお、Ａｌ２Ｏ３の含有量は１８質量％超であることが好ましい。 Al 2 O 3 is an essential component. Al 2 O 3 improves heat resistance, suppresses phase separation, maintains 7% or more to maintain the smoothness of the substrate surface after polishing and cleaning the substrate, and maintains resistance to scratches. Preferably it is 9% or more, more preferably 11% or more, more preferably more than 12%, more preferably more than 12.5%. On the other hand, Al 2 O 3 is made 17% or less in order to improve the glass solubility. Preferably it is 16% or less, More preferably, it is 15% or less, More preferably, it is 14% or less. Incidentally, the content of Al 2 O 3 is preferably greater than 18 wt%.
　Ｂ２Ｏ３は必須成分ではないが、ガラスの溶解性や傷つきやすさを改善する効果があり含有してもよい。耐酸性の維持、ＴＡの向上のため２％未満とする。好ましくは１．５％以下、より好ましくは１．０％以下、より好ましくは０．５％以下である。 B 2 O 3 is not an essential component, but may be contained because it has an effect of improving the solubility and fragility of glass. Maintenance of acid-resistant, and less than 2% for the improvement of T A. Preferably it is 1.5% or less, More preferably, it is 1.0% or less, More preferably, it is 0.5% or less.
　ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯはガラスの溶解性を改善し、耐酸性および耐アルカリ性を向上させる成分であり、いずれか１成分以上を合計（ＲＯ）量で１８％超含有しなければならない。好ましくは１８．５％以上、より好ましくは１９％以上である。一方、失透特性の向上、傷つきにくくするためにＲＯ量は２６％以下とする。好ましくは２４％以下、より好ましくは２２％以下である。 MgO, CaO, SrO and BaO are components that improve the solubility of the glass and improve the acid resistance and alkali resistance, and any one or more components must contain more than 18% in total (RO) amount. Preferably it is 18.5% or more, more preferably 19% or more. On the other hand, the RO amount is set to 26% or less in order to improve devitrification characteristics and make it difficult to be damaged. Preferably it is 24% or less, more preferably 22% or less.
　これら４成分の内ＭｇＯおよびＣａＯのいずれか１成分以上を１０．５％以上含有することが好ましい。溶解性を良好なものとするため、Ｔ２を低くする、傷つきにくくするためにＭｇＯおよびＣａＯの含有量の合計ＭｇＯ＋ＣａＯが１０．５％以上とすることが好ましい。より好ましくは１１％以上、さらに好ましくは１２％以上である。失透温度を低くし、成形を容易にするため、ＭｇＯ＋ＣａＯは２０％以下とすることが好ましい。より好ましくは１８％以下である。 Among these four components, it is preferable to contain 10.5% or more of any one of MgO and CaO. In order to improve the solubility, it is preferable that the total MgO + CaO content of MgO and CaO is 10.5% or more in order to reduce T 2 and to prevent damage. More preferably, it is 11% or more, More preferably, it is 12% or more. In order to lower the devitrification temperature and facilitate molding, MgO + CaO is preferably 20% or less. More preferably, it is 18% or less.
　ＳｉＯ２の含有量（モル百分率）を、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯの含有量（モル百分率）の合量ＲＯで除した値は、比弾性率を大きくし、耐酸性および耐アルカリ性を向上させ、粘度が１０２ｄＰａ・ｓとなる温度Ｔ２を低くするため４．３以下とすることが好ましい。より好ましくは４．１以下、さらに好ましくは３．９以下である。 The value obtained by dividing the content of SiO 2 (mole percentage) by the total amount RO of the contents of MgO, CaO, SrO and BaO (mole percentage) increases the specific elastic modulus and improves acid resistance and alkali resistance. In order to lower the temperature T 2 at which the viscosity becomes 10 2 dPa · s, it is preferably 4.3 or less. More preferably, it is 4.1 or less, More preferably, it is 3.9 or less.
　なお、ＭｇＯはヤング率を高くする成分であり、ガラスの剛性を高める効果があるため６％以上含有させることが好ましい。より好ましくは７％以上である。 Note that MgO is a component that increases the Young's modulus and has the effect of increasing the rigidity of the glass. More preferably, it is 7% or more.
　本発明のガラスは本質的に上記７成分からなるが、本発明の目的を損なわない範囲でその他の成分を含有してもよい。ただし、その場合であってもそれら成分の含有量の合計は、傷つきにくさの維持、耐酸性、耐アルカリ性の維持、比弾性の維持のため、５％未満である。以下では上記７成分以外の成分について例示的に説明する。 The glass of the present invention consists essentially of the above seven components, but may contain other components as long as the object of the present invention is not impaired. However, even in that case, the total content of these components is less than 5% for maintaining resistance to scratches, maintaining acid resistance, alkali resistance, and maintaining specific elasticity. Hereinafter, components other than the above seven components will be exemplarily described.
　ＺｎＯはＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯと同様の効果を奏する成分であり、５％未満の範囲で含有してもよい。ＺｎＯの含有量とＲＯの合計は１８％超２６％以下であることが好ましい。 ZnO is a component having the same effect as MgO, CaO, SrO and BaO, and may be contained in a range of less than 5%. The total content of ZnO and RO is preferably more than 18% and 26% or less.
　Ｌｉ２Ｏ、Ｎａ２ＯおよびＫ２ＯはＴＡを低下させるので、これら３成分の含有量の合計は１％未満、あるいは実質的に含有しないことが好ましい。 Li 2 O, since Na 2 O and K 2 O decreases the T A, it is preferable that the total content of these three components do not contain less than 1%, or substantially.
　ＶなどＴｉよりも原子番号が大きな原子の酸化物はガラスを傷つきやすくするおそれがあるので、これら酸化物を含有する場合にはそれらの含有量の合計は３％以下とすることが好ましい。より好ましくは２％以下、特に好ましくは１％以下、最も好ましくは０．３％以下である。 Since oxides having an atomic number larger than Ti, such as V, may easily damage the glass, when these oxides are contained, the total content thereof is preferably 3% or less. More preferably, it is 2% or less, particularly preferably 1% or less, and most preferably 0.3% or less.
　ＳＯ３、Ｆ、Ｃｌ、Ａｓ２Ｏ３、Ｓｂ２Ｏ３およびＳｎＯ２等は清澄剤として代表的な成分である。 SO 3 , F, Cl, As 2 O 3 , Sb 2 O 3, SnO 2 and the like are typical components as fining agents.
　表１中のＳｉＯ２～ＢａＯの欄にモル百分率表示で示す組成を有する７種のガラスを用意した。なお、表１中のＭｇＣａはＭｇＯおよびＣａＯの含有量の合計、ＲＯはＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯの含有量の合計である。これらガラスについて、密度ｄ（単位：ｇ／ｃｍ３）、徐冷点ＴＡ（単位：℃）、ヤング率Ｅ（単位：ＧＰａ）、比弾性率Ｅ／ｄ（単位：ＭＮｍ／ｋｇ）、粘度が１０４ｄＰａ・ｓとなる温度Ｔ４（単位：℃）、粘度が１０２ｄＰａ・ｓとなる温度Ｔ２（単位：℃）、失透温度（単位：℃）、耐酸性指標Ａ、耐アルカリ性指標Ｂを測定した。 Seven types of glasses having compositions shown in mole percentages in the columns of SiO 2 to BaO in Table 1 were prepared. In Table 1, MgCa is the total content of MgO and CaO, and RO is the total content of MgO, CaO, SrO and BaO. For these glasses, density d (unit: g / cm 3 ), annealing point T A (unit: ° C), Young's modulus E (unit: GPa), specific modulus E / d (unit: MNm / kg), viscosity temperature T 4 but which becomes 10 4 dPa · s (unit: ° C.), temperature T 2 at which the viscosity becomes 10 2 dPa · s (unit: ° C.), devitrification temperature (unit: ° C.), acid resistance index a, resistance The alkaline index B was measured.
　上記測定は次のようにして行った。
　密度：泡のないガラス２０～５０ｇについて、アルキメデス法にて測定した。
　徐冷点：ＪＩＳ　Ｒ３１０３（２００１年）に準じて測定した。
　ヤング率：厚さが５～１０ｍｍ、大きさが３ｃｍ×３ｃｍのガラス板について、超音波パルス法により測定した。
　比弾性率：上記で求めたヤング率を密度で除して求めた。
　Ｔ４、Ｔ２：回転粘度計により測定した。
　失透温度：ガラスを乳鉢で２ｍｍ程度のガラス粒に粉砕し、このガラス粒を白金ボートに並べて置き、温度傾斜炉中で２４時間熱処理した。結晶が析出しているガラス粒の温度の最高値を失透温度とした。 The above measurement was performed as follows.
Density: Measured by Archimedes method for 20 to 50 g of glass without bubbles.
Annealing point: Measured according to JIS R3103 (2001).
Young's modulus: A glass plate having a thickness of 5 to 10 mm and a size of 3 cm × 3 cm was measured by an ultrasonic pulse method.
Specific modulus: obtained by dividing the Young's modulus obtained above by the density.
T 4 , T 2 : Measured with a rotational viscometer.
Devitrification temperature: The glass was crushed into glass particles of about 2 mm in a mortar, and these glass particles were placed in a platinum boat and heat-treated in a temperature gradient furnace for 24 hours. The maximum value of the temperature of the glass grains on which the crystals were precipitated was defined as the devitrification temperature.
　耐酸性指標Ａは以下の測定方法により決定した。
　厚さが１～２ｍｍ、大きさが４ｃｍ角のガラス板の両面をコロイダルシリカで鏡面研磨し、端面を酸化セリウム砥粒で鏡面研磨したものを測定サンプルとした。これを室温に保持したｐＨ＝２（０．０１モル／リットル）のＨＮＯ３水溶液に３時間浸漬した。前記水溶液中に溶出した溶出Ｓｉ量をＩＣＰ質量分析法で分析して測定値を得た。前記溶出Ｓｉ量、ガラス中のＳｉＯ２含有量およびガラスの密度から、ガラスのエッチング速度を下記式により算出した。
　耐酸性指標Ａ＝１０００×Ｌ１／［ｄ×Ｐ×（Ｓｉの原子量＝２８）／（ＳｉＯ２の分子量＝６０）］／３
　耐酸性指標Ａの単位はｎｍ／ｈ、Ｌ１はガラス板単位面積当たりの前記溶出Ｓｉ量で単位はμｇ／ｃｍ２、ｄはガラスの密度で単位はｇ／ｃｍ３、Ｐはガラス中のＳｉＯ２の質量百分率表示含有量で単位は質量％である。 The acid resistance index A was determined by the following measurement method.
A glass sample having a thickness of 1 to 2 mm and a size of 4 cm square was mirror-polished on both sides with colloidal silica, and the end surface was mirror-polished with cerium oxide abrasive grains as a measurement sample. This was immersed in an aqueous HNO 3 solution having a pH of 2 (0.01 mol / liter) kept at room temperature for 3 hours. The amount of Si eluted in the aqueous solution was analyzed by ICP mass spectrometry to obtain a measured value. The etching rate of the glass was calculated by the following formula from the amount of dissolved Si, the content of SiO 2 in the glass, and the density of the glass.
Acid resistance index A = 1000 × L1 / [d × P × (Si atomic weight = 28) / (SiO 2 molecular weight = 60)] / 3
The unit of the acid resistance index A is nm / h, L1 is the amount of the eluted Si per unit area of the glass plate, the unit is μg / cm 2 , d is the density of the glass, the unit is g / cm 3 , and P is SiO in the glass. The unit of the mass percentage display content is 2.
　耐アルカリ性指標Ｂは以下の測定方法により決定した。
　厚さが１～２ｍｍ、大きさが４ｃｍ角のガラス板の両面をコロイダルシリカで鏡面研磨し、端面を酸化セリウム砥粒で鏡面研磨したものを測定サンプルとした。これを室温に保持したｐＨ＝１２（０．０１モル／リットル）のＮａＯＨ水溶液に１００ｋＨｚの超音波を印加しながら３時間浸漬した。前記水溶液中に溶出した溶出Ｓｉ量をＩＣＰ質量分析法で分析して測定値を得た。前記溶出Ｓｉ量、ガラス中のＳｉＯ２含有量およびガラスの密度から、ガラスのエッチング速度を下記式により算出した。
　耐アルカリ性指標Ｂ＝１０００×Ｌ２／［ｄ×Ｐ×（Ｓｉの原子量＝２８）／（ＳｉＯ２の分子量＝６０）］／３
　耐アルカリ性指標Ｂの単位はｎｍ／ｈ、Ｌ２はガラス板単位面積当たりの前記溶出Ｓｉ量で単位はμｇ／ｃｍ２、ｄはガラスの密度で単位はｇ／ｃｍ３、Ｐはガラス中のＳｉＯ２の質量百分率表示含有量で単位は質量％である。 The alkali resistance index B was determined by the following measurement method.
A glass sample having a thickness of 1 to 2 mm and a size of 4 cm square was mirror-polished on both sides with colloidal silica, and the end surface was mirror-polished with cerium oxide abrasive grains as a measurement sample. This was immersed in an aqueous NaOH solution having a pH of 12 (0.01 mol / liter) kept at room temperature for 3 hours while applying an ultrasonic wave of 100 kHz. The amount of Si eluted in the aqueous solution was analyzed by ICP mass spectrometry to obtain a measured value. The etching rate of the glass was calculated by the following formula from the amount of dissolved Si, the content of SiO 2 in the glass, and the density of the glass.
Alkali resistance index B = 1000 × L2 / [d × P × (Si atomic weight = 28) / (SiO 2 molecular weight = 60)] / 3
The unit of the alkali resistance index B is nm / h, L2 is the amount of the eluted Si per unit area of the glass plate, the unit is μg / cm 2 , d is the density of the glass, the unit is g / cm 3 , and P is the SiO in the glass. The unit of the mass percentage display content is 2.
　例１～６は本発明で用いられる基板ガラスの例である。例７は比較のための基板ガラスである。 Examples 1 to 6 are examples of the substrate glass used in the present invention. Example 7 is a substrate glass for comparison.
　本発明を特定の態様を用いて詳細に説明したが、本発明の意図と範囲を離れることなく様々な変更および変形が可能であることは、当業者にとって明らかである。なお本出願は、２０１２年６月５日付で出願された日本特許出願（特願２０１２－１２７８７２）に基づいており、その全体が引用により援用される。 Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention. Note that this application is based on a Japanese patent application filed on June 5, 2012 (Japanese Patent Application No. 2012-127872), which is incorporated by reference in its entirety.
　本発明は磁気ディスクおよび情報記録媒体用ガラス基板の製造に利用できる。 The present invention can be used for manufacturing a magnetic disk and a glass substrate for an information recording medium.

Claims (12)

  1. 　温度が５５０℃以上であるガラス基板の上に磁気記録層を形成する工程を含む磁気ディスクの製造方法であって、
    　該ガラス基板がモル百分率表示で、ＳｉＯ２を６０～７５％、Ａｌ２Ｏ３を７～１７％、Ｂ２Ｏ３を０～２％未満、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯのいずれか１成分以上を合計で１８％超２６％以下含有し、上記７成分の含有量合計が９５％以上であり、Ｌｉ２Ｏ、Ｎａ２ＯおよびＫ２Ｏのいずれか１成分以上を合計で１％未満含有する、またはこれら３成分のいずれも含有しないものである磁気ディスクの製造方法。     A method for manufacturing a magnetic disk comprising a step of forming a magnetic recording layer on a glass substrate having a temperature of 550 ° C. or higher,
    The glass substrate is expressed in mole percentage, and SiO 2 is 60 to 75%, Al 2 O 3 is 7 to 17%, B 2 O 3 is less than 0 to less than 2%, and any one component of MgO, CaO, SrO and BaO More than 18% in total and 26% or less in total, the total content of the above 7 components is 95% or more, and any one or more of Li 2 O, Na 2 O and K 2 O is less than 1% in total A method of manufacturing a magnetic disk that contains or does not contain any of these three components.
  2. 　前記ガラス基板がモル百分率表示で、ＭｇＯおよびＣａＯのいずれか１成分以上を合計で１０．５～２０％含有する請求項１に記載の磁気ディスクの製造方法。 2. The method of manufacturing a magnetic disk according to claim 1, wherein the glass substrate contains 10.5 to 20% in total of any one of MgO and CaO in terms of mole percentage.
  3. 　前記ガラス基板がモル百分率表示で、ＭｇＯを６％以上含有する請求項１または２に記載の磁気ディスクの製造方法。 3. The method of manufacturing a magnetic disk according to claim 1, wherein the glass substrate contains 6% or more of MgO in terms of mole percentage.
  4. 　前記ガラス基板が、質量百分率表示でＡｌ２Ｏ３を１８％超含有する請求項１～３のいずれか１項に記載の磁気ディスクの製造方法。 The method of manufacturing a magnetic disk according to any one of claims 1 to 3, wherein the glass substrate contains Al 2 O 3 in excess of 18% in terms of mass percentage.
  5. 　前記ガラス基板が、ＳｉＯ２の含有量（モル百分率）を、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯの含有量（モル百分率）の合量ＲＯで除した値が４．３以下である請求項１～４のいずれか１項に記載の磁気ディスクの製造方法。 The glass substrate has a value obtained by dividing the content (molar percentage) of SiO 2 by the total amount RO of the contents (molar percentage) of MgO, CaO, SrO, and BaO is 4.3 or less. The method for manufacturing a magnetic disk according to any one of the above.
  6. 　前記ガラス基板の比弾性率が３２ＭＮｍ・ｋｇ以上である請求項１～５のいずれか１項に記載の磁気ディスクの製造方法。 6. The method for manufacturing a magnetic disk according to claim 1, wherein the glass substrate has a specific elastic modulus of 32 MNm · kg or more.
  7. 　前記ガラス基板の耐酸性指標Ａが０．０２５ｎｍ／ｈ以下である請求項１～６のいずれか１項に記載の磁気ディスクの製造方法。 The method for manufacturing a magnetic disk according to any one of claims 1 to 6, wherein the acid resistance index A of the glass substrate is 0.025 nm / h or less.
  8. 　前記ガラス基板の耐アルカリ性指標Ｂが０．２８ｎｍ／ｈ以下である請求項１～７のいずれか１項に記載の磁気ディスクの製造方法。 The method of manufacturing a magnetic disk according to any one of claims 1 to 7, wherein the glass substrate has an alkali resistance index B of 0.28 nm / h or less.
  9. 　前記ガラス基板の粘度が１０２ｄＰａ・ｓとなる温度Ｔ２が１７１０℃以下である請求項１～８のいずれか１項に記載の磁気ディスクの製造方法。 The magnetic disk manufacturing method according to any one of the glass substrates with a viscosity of 10 2 claim temperature T 2 which is a dPa · s is 1710 ° C. or less 1-8.
  10. 　前記ガラス基板の徐冷点が６５０℃以上である請求項１～９のいずれか１項に記載の磁気ディスクの製造方法。 The method for manufacturing a magnetic disk according to any one of claims 1 to 9, wherein the glass substrate has an annealing point of 650 ° C or higher.
  11. 　モル百分率表示で、ＳｉＯ２を６０～７５％、Ａｌ２Ｏ３を７～１７％、Ｂ２Ｏ３を０～２％未満、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯのいずれか１成分以上を合計で１８％超２６％以下含有し、上記７成分の含有量合計が９５％以上であり、Ｌｉ２Ｏ、Ｎａ２ＯおよびＫ２Ｏのいずれか１成分以上を合計で１％未満含有する、またはこれら３成分のいずれも含有しない情報記録媒体用ガラス基板。 In terms of mole percentage, SiO 2 is 60 to 75%, Al 2 O 3 is 7 to 17%, B 2 O 3 is 0 to less than 2%, and any one or more of MgO, CaO, SrO and BaO in total More than 18% and not more than 26%, the total content of the seven components is 95% or more, and any one or more of Li 2 O, Na 2 O and K 2 O is contained in total less than 1%, or A glass substrate for information recording media that does not contain any of these three components.
  12. 　前記情報記録媒体が磁気ディスクである請求項１１に記載の情報記録媒体用ガラス基板。 The glass substrate for an information recording medium according to claim 11, wherein the information recording medium is a magnetic disk.
PCT/JP2013/065285 2012-06-05 2013-05-31 Method for producing magnetic disk and glass substrate for information recording media WO2013183569A1 (en)

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