WO2013001797A1 - Process for producing glass substrate for hdd, glass substrate for hdd, and magnetic recording medium for hdd - Google Patents

Process for producing glass substrate for hdd, glass substrate for hdd, and magnetic recording medium for hdd Download PDF

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Publication number
WO2013001797A1
WO2013001797A1 PCT/JP2012/004140 JP2012004140W WO2013001797A1 WO 2013001797 A1 WO2013001797 A1 WO 2013001797A1 JP 2012004140 W JP2012004140 W JP 2012004140W WO 2013001797 A1 WO2013001797 A1 WO 2013001797A1
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WO
WIPO (PCT)
Prior art keywords
glass substrate
chemical strengthening
hdd
tir
circumferential direction
Prior art date
Application number
PCT/JP2012/004140
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French (fr)
Japanese (ja)
Inventor
直之 福本
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コニカミノルタアドバンストレイヤー株式会社
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Filing date
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Application filed by コニカミノルタアドバンストレイヤー株式会社 filed Critical コニカミノルタアドバンストレイヤー株式会社
Priority to JP2013502723A priority Critical patent/JP5360331B2/en
Priority to CN201280042051.XA priority patent/CN103946920B/en
Publication of WO2013001797A1 publication Critical patent/WO2013001797A1/en

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
    • G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers
    • 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

Definitions

  • the present invention relates to a method for manufacturing a glass substrate for HDD, a glass substrate for HDD, and a magnetic recording medium for HDD.
  • a magnetic recording medium for HDD (hard disk drive) is known as a typical information recording medium having a recording layer utilizing properties such as magnetism, light, and magnetomagnetism.
  • an aluminum substrate has been widely used as an HDD substrate for manufacturing an HDD magnetic recording medium.
  • the surface smoothness is superior to that of the aluminum substrate and the surface defects are few, so that the flying height of the magnetic head can be reduced.
  • the proportion of using glass substrates as HDD substrates is increasing.
  • Magnetic recording media for HDDs mounted on mobile devices such as notebook personal computers require a substrate that is resistant to impacts.
  • a substrate that is resistant to impacts.
  • it is subjected to chemical strengthening treatment to provide impact resistance.
  • a glass substrate with improved resistance is often used.
  • DFH dynamic flying flying height
  • one aspect of the present invention is a method for manufacturing a glass substrate for HDD, which includes a chemical strengthening step of subjecting a glass substrate to chemical strengthening treatment by immersing the glass substrate in a chemical strengthening treatment solution, before and after the chemical strengthening step.
  • the increase in the TIR (totalHDDindicated runout) in the circumferential direction of the glass substrate is 0.5 ⁇ m or less.
  • Still another aspect of the present invention is an HDD magnetic recording medium manufactured by providing a recording layer on a main surface of the HDD glass substrate.
  • FIG. 1 is a manufacturing process diagram of a glass substrate for HDD according to an embodiment of the present invention.
  • FIG. 2 is a partial side view showing the configuration of the main part of the double-side grinding machine used in the first and second lapping processes.
  • FIG. 3 is a view taken along the line III-III in FIG. 2 and is a plan view of the lower surface plate and the carrier.
  • FIG. 4 is a longitudinal sectional view showing the configuration of the main part of the Oscar polisher used in the first polishing process.
  • FIG. 5A is a plan view of a lower polishing dish of an Oscar polishing machine in which a ring-shaped jig having a loosely fitted glass substrate is arranged, and FIG.
  • FIG. 5B is a view of the ring-shaped jig having a loosely fitted glass substrate. It is an expanded horizontal sectional view.
  • FIG. 6A, FIG. 6B, and FIG. 6C are plan views showing the operation of the Oscar polisher.
  • FIG. 7A is a perspective view of a carrier used to hold a glass substrate in the chemical strengthening process
  • FIG. 7B is a side view of the carrier.
  • FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D are flowcharts of the chemical strengthening process performed in the conventional chemical strengthening process.
  • FIG. 9A is a perspective view showing the surface shape of the glass substrate before chemical strengthening treatment
  • FIG. 9B is a perspective view showing the surface shape of the glass substrate after performing conventional chemical strengthening treatment. .
  • FIG. 10A is a height map of the main surface of the glass substrate before chemical strengthening treatment
  • FIG. 10B is a height map of the main surface of the glass substrate after conventional chemical strengthening treatment
  • FIG. c) It is explanatory drawing which compares and shows the TIR of the circumferential direction of the glass substrate before and behind a chemical strengthening process.
  • FIG. 11A, FIG. 11B, FIG. 11C, FIG. 11D, and FIG. 11E show chemical strengthening processes (specific examples) performed in the chemical strengthening process according to the embodiment of the present invention. It is a flowchart of method 1).
  • FIG. 12A, FIG. 12B, and FIG. 12C are elevation maps of the main surface of the glass substrate for explaining the action obtained by the specific method 1.
  • the present inventors In order to suppress the occurrence of head crashes, the present inventors have a sufficiently high rotational speed in the circumferential direction of the recording medium as compared with the moving speed at which the magnetic head moves in the radial direction of the recording medium during operation of the HDD. Noted that it is important to suppress fluctuations in the surface condition in the circumferential direction of the recording medium. From this point of view, it has been found that it is effective that the TIR (total indicated runout), which is an index of the flatness of the surface of the recording medium, is small in the circumferential direction of the recording medium. In addition, the present inventors have obtained the knowledge that the chemical strengthening treatment performed for improving impact resistance and the like deteriorates the TIR in the circumferential direction of the glass substrate, thereby completing the present invention.
  • the inventors of the present invention have the reason that the chemical strengthening treatment deteriorates the TIR in the circumferential direction of the glass substrate, such as temperature variation, concentration variation, or contamination of foreign substances in the chemical strengthening treatment solution in which the glass substrate is immersed. Since the environment is not uniform due to various factors, the present invention was completed with the knowledge that the surface shape of the glass substrate before and after the chemical strengthening treatment did not change uniformly.
  • Glass melting process First, in the glass melting step, a glass material is melted.
  • aluminosilicate glass and borosilicate glass are particularly preferable because they are excellent in impact resistance and vibration resistance.
  • the size of the glass substrate that is, the blank.
  • glass substrates having various sizes such as 2.5 inches, 1.8 inches, 1 inch, and 0.8 inches in outer diameter can be manufactured.
  • the thickness of the glass substrate There is no limitation on the thickness of the glass substrate.
  • glass substrates having various thicknesses such as 2 mm, 1 mm, 0.8 mm, and 0.63 mm can be manufactured.
  • the inner / outer diameter processing is performed by grinding the outer peripheral end surface and the inner peripheral end surface of the glass substrate with a drum-shaped grinding wheel using, for example, diamond.
  • both surfaces of the glass substrate are ground again to finely adjust the parallelism, flatness and thickness of the glass substrate.
  • a known grinding machine 10 called a double-side grinding machine using a planetary gear mechanism can be used.
  • the double-side grinding machine 10 includes a disk-shaped upper surface plate 11 and a lower surface plate 12 that are arranged vertically so as to be parallel to each other.
  • the upper and lower surface plates 11 and 12 rotate in opposite directions.
  • Diamond pellets 13 and 14 for grinding the main surface of the glass substrate are attached to the opposing surfaces of the upper and lower surface plates 11 and 12, respectively.
  • a plurality of carriers 17 are disposed between the upper and lower surface plates 11 and 12.
  • the weight of the surface plates 11 and 12 applied to the glass substrate and the rotational speed of the surface plates 11 and 12 are appropriately adjusted according to the desired grinding state.
  • the weight in the first and second wrapping steps is preferably 60 g / cm 2 (5.88 kPa) to 120 g / cm 2 (11.77 kPa).
  • the rotation speed of the surface plates 11 and 12 is preferably about 10 to 30 rpm, and the rotation speed of the upper surface plate 11 is preferably about 30 to 40% slower than the rotation speed of the lower surface plate 12. If the weight by the surface plates 11 and 12 is increased and the rotational speed of the surface plates 11 and 12 is increased, the grinding amount increases.
  • a cleaning step for removing the grinding liquid and glass powder remaining on the surface of the glass substrate after the first lapping step and / or after the second lapping step.
  • the surface roughness used in this embodiment is a value obtained by measuring a range of 1 ⁇ m ⁇ 1 ⁇ m using an atomic force microscope (Nanoscope manufactured by Digital Instruments).
  • the flatness used in the present embodiment is a value measured by a flatness measuring device, and the difference in height (Po ⁇ Vo value) between the highest position (Po) and the lowest position (Vo) on the surface of the glass substrate. It is.
  • the lower polishing dish 21 is rotated while supplying the polishing liquid with the glass substrate 80 as an object to be polished placed between the upper and lower polishing dishes 21 and 22.
  • the glass substrate 80 is polished by the upper and lower polishing dishes 21 and 22 by swinging left and right with respect to FIGS.
  • rotation of the glass substrate 80 can be promoted.
  • the glass substrate 80 having a concentric point target shape can be manufactured. That is, fluctuations in the surface state in the circumferential direction of the glass substrate 80 can be suppressed.
  • the glass substrate 80 having an outer diameter of 2.5 inches (63.5 mm) will be described as an example, but the size of the glass substrate 80 is not limited.
  • the upper and lower polishing dishes 21 and 22 have a diameter of 1000 mm, and elastic suedes (only the suede 24 of the lower polishing dish 21 is shown in FIG. 5A) are attached to the opposing surfaces. ing.
  • a glass substrate 80 is loosely fitted and held on a ring-shaped jig 23 (inner diameter 65 mm, outer diameter 67 mm, thickness 0.5 mm) manufactured from a resin material as shown in FIG. This is placed on the suede 24 of the lower polishing dish 21 for 100 sets.
  • the glass substrate 80 is sandwiched between the upper polishing dish 22 and the lower polishing dish 21 is rotated while supplying slurry containing cerium oxide or colloidal silica as abrasive grains (polishing material) as a polishing liquid. Is swung left and right with respect to FIGS. 4 to 6 within an arbitrary range. Thereby, the glass substrate 80 rotates within the ring-shaped jig 23 by the relative movement of the upper and lower polishing dishes 21 and 22, and both surfaces are polished in the circumferential direction.
  • a chemical strengthening layer (stress layer) is formed on the main surface, the outer peripheral end surface, and the inner peripheral end surface of the glass substrate by immersing the glass substrate in a chemical strengthening treatment solution. That is, a chemical strengthening process is performed on the glass substrate.
  • a chemical strengthening process is performed on the glass substrate.
  • the conventional chemical strengthening treatment is approximately as follows. First, as shown in FIG. 7A, a carrier 30 for holding a glass substrate 80 is used.
  • the carrier 30 is a container whose top and bottom are open, and a plurality of holding rods 31 are installed in parallel to each other.
  • the glass substrate 80 is held by the plurality of holding rods 31 at three points. Several tens of glass substrates 80 are arranged in parallel with each other with a slight gap and are simultaneously held by one carrier 30.
  • the glass substrate 80 held on the carrier 30 is preheated to 300 ° C. in the electric furnace 40.
  • a chemical strengthening treatment liquid prepared by mixing and dissolving potassium nitrate (60 mass%) and sodium nitrate (40 mass%) is prepared in a treatment liquid tank 50 and heated to 400 ° C. by a heater 51. To do.
  • the preheated glass substrate 80 is immersed in the chemical strengthening treatment solution for about 20 minutes, and a reinforcing layer is formed over the entire surface of the glass substrate 80.
  • FIG. 8C after the glass substrate 80 that has been subjected to the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes, FIG. As shown in FIG.
  • the surface shape of the glass substrate 80 before and after the chemical strengthening treatment is uniform. It does not change.
  • the glass substrate 80 having a substantially flat surface shape before the chemical strengthening treatment is deformed as shown in FIG. 9B. Become.
  • FIG. 10A is a height map of the main surface 81 (see FIG. 15) of the glass substrate 80 before the chemical strengthening treatment.
  • the flatness of the main surface 81 of the glass substrate 80 is relatively good before the chemical strengthening treatment. Therefore, as shown by a solid line (a) in FIG. 10C, the TIR in the circumferential direction of the main surface 81 of the glass substrate 80 is small.
  • FIG.10 (b) is a height map of the main surface 81 of the glass substrate 80 after the conventional chemical strengthening process.
  • the surface shape of the main surface 81 of the glass substrate 80 is distorted. Therefore, as indicated by a broken line (b) in FIG. 10C, the TIR in the circumferential direction of the main surface 81 of the glass substrate 80 increases.
  • the circumferential direction TIR in FIG. 10C is a value at a position indicated by a broken line in FIGS. 10A and 10B. Specifically, it is a value at a position of 0.75R from the center of the glass substrate 80, where R is the radius of the glass substrate 80.
  • the chemical strengthening treatment conventionally performed for improving the impact resistance of the glass substrate 80 deteriorates the TIR in the circumferential direction of the glass substrate 80.
  • the surface state in the circumferential direction of the glass substrate 80 greatly fluctuated, and head crushing due to poor tracking of the magnetic head was likely to occur.
  • the chemical strengthening process is intended to prevent the TIR in the circumferential direction of the glass substrate 80 from being deteriorated.
  • the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is set to 0.5 ⁇ m or less.
  • the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.3 ⁇ m or less. This is because the deterioration of the circumferential direction TIR of the glass substrate 80 due to the chemical strengthening process becomes more limited, and the occurrence of head crash due to the follow-up failure of the magnetic head is further suppressed.
  • the TIR in the circumferential direction of the glass substrate 80 is the TIR in the circumferential direction at a position of 0.75R from the center of the glass substrate 80, where R is the radius of the glass substrate 80.
  • the circumferential direction TIR in the same glass substrate has a correlation with the distance from the center of the glass substrate, and the circumferential direction TIR tends to increase as the distance from the center of the glass substrate increases.
  • the position of 0.75R from the center of the glass substrate 80 is a relatively outer position in the main surface 81 of the glass substrate 80 or the recording area of the recording medium. Therefore, by limiting the amount of increase in TIR in the circumferential direction at a position of 0.75R from the center of the glass substrate 80 to 0.5 ⁇ m or less or 0.3 ⁇ m or less, the outer peripheral end and the inner surface of the main surface 81 of the glass substrate 80 are reduced.
  • the glass substrate immersed in the chemical strengthening treatment liquid in the chemical strengthening step is as follows. It is possible to change the posture in the 80 chemical strengthening treatment liquid.
  • the glass substrate 80 held on the carrier 30 is preheated to 300 ° C. in the electric furnace 40.
  • a chemical strengthening treatment liquid prepared by mixing and dissolving potassium nitrate (60 mass%) and sodium nitrate (40 mass%) is prepared in a treatment liquid tank 50 and heated to 400 ° C. with a heater 51. To do.
  • the preheated glass substrate 80 is immersed in the chemical strengthening treatment solution for about 10 minutes (first immersion). After immersion for 10 minutes, the glass substrate 80 is taken out of the treatment liquid tank 50 together with the carrier 30, and all the glass substrates 80 are rotated by 90 ° with respect to the center of the glass substrate 80 as indicated by arrows in the figure.
  • the glass substrate 80 is immersed again in the chemical strengthening treatment liquid for about 10 minutes (second immersion).
  • the glass substrate 80 that has been subjected to the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes, and then FIG. 8 (e).
  • FIG. 11 (d) the glass substrate 80 that has been subjected to the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes, and then FIG. 8 (e).
  • the surface shape of the glass substrate 80 is changed into strain symmetrically through the center of the glass substrate 80 by the first immersion, as shown in FIG.
  • FIG. 12C since the orientation of the glass substrate 80 in the chemical strengthening treatment solution changed by 90 ° with respect to the center of the glass substrate 80 by the second immersion, these are combined, and as shown in FIG. Different shape changes will be canceled for each part of the surface.
  • the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 ⁇ m or less.
  • this example is a case where the surface shape of the glass substrate changes in line symmetry passing through the center of the glass substrate, that is, the surface shape of the glass substrate changes at two predetermined positions facing the glass substrate at 180 °.
  • the surface shape of the glass substrate changes only at a predetermined position
  • the glass substrate is rotated little by little at an angle smaller than 90 °, and each time the glass substrate is chemically strengthened. What is necessary is just to immerse in a liquid (for example, to immerse several times in total 3 times or more).
  • the temperature variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 ⁇ m or less. .
  • the temperature distribution of the chemical strengthening treatment liquid with respect to the glass substrate 80 can be made more uniform.
  • the glass substrate 80 after the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes.
  • FIG. 13C the glass substrate 80 after the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes.
  • the second specific method of setting the increase in TIR in the circumferential direction to 0.5 ⁇ m or less is intended to stabilize the chemical reaction in the ion exchange method.
  • a third specific method for setting the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step to 0.5 ⁇ m or less includes stirring the chemical strengthening treatment liquid in the chemical strengthening step. .
  • the concentration variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 ⁇ m or less. .
  • the heater 55 arranged in the circular hole at the center of the glass substrate 80 is circularly moved or rotated like a stirring bar as indicated by an arrow in the figure.
  • FIGS. 14A and 14B the periphery of the glass substrate 80 before and after the chemical strengthening treatment is obtained. Deterioration of the direction TIR is suppressed.
  • 14A is a height map of the main surface 81 of the glass substrate 80 before chemical strengthening treatment
  • FIG. 14B is the height map of the main surface 81 of the glass substrate 80 after chemical strengthening treatment according to 3 of this specific method. High and low map.
  • the flatness of the main surface 81 of the glass substrate 80 is well maintained before and after the chemical strengthening treatment.
  • the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 ⁇ m or less.
  • the third specific method of setting the amount of increase in TIR in the circumferential direction to 0.5 ⁇ m or less is intended to stabilize the chemical reaction in the ion exchange method.
  • a stirring rod having no heating function may be disposed in the circular hole in the center of the glass substrate 80.
  • the chemical strengthening treatment liquid is not limited to stirring in the circular hole in the central portion of the glass substrate 80, and the chemical strengthening treatment liquid is placed outside the circular hole in the central portion of the glass substrate 80, that is, around the glass substrate 80. You may stir. Further, the chemical strengthening treatment liquid may be stirred both inside and outside the circular hole at the center of the glass substrate 80.
  • a soft polishing pad having a hardness of about 65 to 80 (Asker-C), which is softer than the suede used in the first polishing step, is used.
  • Asker-C a soft polishing pad having a hardness of about 65 to 80
  • urethane foam or suede is preferably used as the polishing pad.
  • polishing liquid a slurry containing cerium oxide or the like similar to that in the first polishing step as abrasive grains (polishing material) can be used.
  • a polishing liquid having a finer grain size and less variation colloidal silica having an average particle size of 40 nm to 70 nm is preferably used as a polishing liquid in which slurry is dispersed in water as abrasive grains (abrasive).
  • the mixing ratio of water and abrasive grains is preferably about 1: 9 to 3: 7.
  • the weight applied to the glass substrate by the upper and lower surface plates is preferably 90 g / cm 2 (8.83 kPa) to 110 g / cm 2 (10.8 kPa). Further, the rotational speed of the upper and lower surface plates is preferably 15 rpm to 35 rpm, and the rotational speed of the upper surface plate is preferably about 30% to 40% slower than the rotational speed of the lower surface plate.
  • the flatness of the main surface of the glass substrate can be reduced to 3 ⁇ m or less, and the surface roughness Ra of the main surface of the glass substrate can be reduced to 0.1 nm.
  • the polishing amount in the second polishing step is preferably 2 ⁇ m to 5 ⁇ m. By setting the polishing amount within this range, it is possible to satisfactorily remove minute defects such as minute roughness and undulation generated on the surface of the glass substrate, or minute scratch marks generated in the previous steps.
  • the polishing step of polishing the surface of the glass substrate 80 after the chemical strengthening step the TIR in the circumferential direction of the final glass substrate 80 is further reduced. Therefore, the occurrence of head crash is further suppressed.
  • the cleaning process Next, in the cleaning process, the glass substrate after the second polishing process is scrubbed.
  • the cleaning method is not limited to scrub cleaning, and any cleaning method may be used as long as it can clean the surface of the glass substrate after the polishing process.
  • the drying process is a process of drying the surface of the glass substrate after removing the cleaning liquid remaining on the surface of the glass substrate using IPA (isopropyl alcohol) or the like.
  • IPA isopropyl alcohol
  • a water rinse cleaning process is performed on the glass substrate after scrub cleaning for 2 minutes to remove the cleaning liquid residue.
  • an IPA cleaning process is performed for 2 minutes, and water remaining on the surface of the glass substrate is removed by IPA.
  • the IPA vapor drying step is performed for 2 minutes, and the liquid IPA adhering to the surface of the glass substrate is dried while being removed by the IPA vapor.
  • the glass substrate drying process is not limited to this, and any drying method generally known as a glass substrate drying method such as spin drying or air knife drying may be used.
  • the glass substrate is visually inspected for the presence or absence of scratches, cracks, foreign matters, and the like. If visual discrimination is not possible, an inspection is performed using an optical surface analyzer (for example, “OSA6100” manufactured by KLA-TENCOL).
  • an optical surface analyzer for example, “OSA6100” manufactured by KLA-TENCOL.
  • Glass substrates that are determined to be non-defective in the inspection process are stored in a dedicated storage cassette and vacuum packed in a clean environment so that no foreign matter adheres to the surface, and then shipped as HDD glass substrates. .
  • the glass substrate for HDD manufactured as described above will be described.
  • the glass substrate 80 for HDD according to the present embodiment has a high quality in which the TIR in the circumferential direction is suppressed to a small value on the main surface 81 and the fluctuation of the surface state in the circumferential direction is suppressed.
  • This is a glass substrate for HDD.
  • the HDD magnetic recording medium according to the present embodiment is manufactured by providing a magnetic film as a recording layer on the main surface 81 of the HDD glass substrate 80.
  • the magnetic film may be formed directly or indirectly on the main surface 81.
  • the magnetic film may be formed on one side or both sides of the glass substrate 80.
  • a method for forming the magnetic film a conventionally known method can be used. For example, a method in which a thermosetting resin in which magnetic particles are dispersed is spin-coated on the glass substrate 80, or a method in which sputtering or electroless plating is used. And the like.
  • the film thickness by spin coating is about 0.3 ⁇ m to 1.2 ⁇ m
  • the film thickness by sputtering is about 0.01 ⁇ m to 0.08 ⁇ m
  • the film thickness by electroless plating is 0.01 ⁇ m to 0.1 ⁇ m. From the viewpoint of thinning and high density, film formation by sputtering or electroless plating is preferable.
  • the magnetic material used for the magnetic film is not particularly limited, and conventionally known materials can be used. Among them, a Co-based alloy or the like containing Ni and Cr as the basic material for adjusting the residual magnetic flux density is preferable in order to obtain high coercive force. Specifically, CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, CoNiPt, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, CoCrPtSiO, and the like whose main component is Co are preferable.
  • the magnetic film may be divided into a non-magnetic film (for example, Cr, CrMo, CrV, etc.) and may have a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa, etc.) designed to reduce noise.
  • a non-magnetic film for example, Cr, CrMo, CrV, etc.
  • a multilayer structure for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa, etc.
  • a ferrite type or iron-rare earth type a granular material having a structure in which magnetic particles such as Fe, Co, FeCo, and CoNiPt are dispersed in a nonmagnetic film made of SiO 2 , BN, etc. Good.
  • the magnetic film may be either an internal type or a vertical type recording format.
  • a lubricant may be thinly coated on the surface of the magnetic film.
  • the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.
  • an underlayer or a protective layer may be provided in addition to the magnetic film as the recording layer.
  • the underlayer in the HDD magnetic recording medium is selected according to the magnetic film.
  • the material for the underlayer include at least one material selected from the group consisting of nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.
  • Cr nonmagnetic metals
  • the underlayer is not limited to a single layer, and may have a multi-layer 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 can be used.
  • the protective layer is provided to prevent wear and corrosion of the magnetic film.
  • the protective layer 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 continuously formed by an in-line sputtering apparatus together with the underlayer and the magnetic film. Further, these protective layers may be a single layer, or may have a multilayer structure composed of the same or different layers.
  • Another protective layer may be formed on the protective layer or instead of the protective layer.
  • colloidal silica fine particles are dispersed and applied in a tetraalkoxysilane diluted with an alcohol solvent on the Cr layer, and further baked to obtain silicon dioxide (SiO 2 ).
  • a layer may be formed.
  • the HDD magnetic recording medium manufactured using the HDD glass substrate 80 preferably has a rotational speed of 7000 rpm or more when loaded in the hard disk drive.
  • the lapping process and the polishing process are performed in two steps.
  • the present invention is not limited to this and may be performed only once.
  • the chemical strengthening process was performed before the second polishing process, it may be performed after the second polishing process depending on the situation.
  • the outer peripheral end face and the inner peripheral end face other than the main surface of the glass substrate may be strengthened, or the glass substrate is subjected to HF immersion treatment as an edge mitigation treatment for scratches generated on the glass substrate. Also good.
  • the glass substrate for HDD according to the present embodiment is not limited to the use for manufacturing the magnetic recording medium for HDD, and can be used for the manufacture of, for example, a magneto-optical disk or an optical disk.
  • the method for manufacturing a glass substrate for HDD is a method for manufacturing a glass substrate for HDD that includes a chemical strengthening step in which the glass substrate 80 is subjected to a chemical strengthening treatment by immersing the glass substrate 80 in a chemical strengthening treatment solution.
  • the increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 ⁇ m or less.
  • the amount of increase in the TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 ⁇ m or less, the deterioration of the TIR in the circumferential direction of the glass substrate 80 due to the chemical strengthening treatment is extremely limited. It becomes the target. Therefore, the TIR in the circumferential direction of the glass substrate 80 after the chemical strengthening step is suppressed to a small value, the variation in the surface state in the circumferential direction of the glass substrate 80 is suppressed, and the occurrence of head crashes is suppressed.
  • the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.3 ⁇ m or less.
  • the deterioration of the TIR in the circumferential direction of the glass substrate 80 due to the chemical strengthening process is further limited. Therefore, the occurrence of head crash is further suppressed.
  • the amount of increase in TIR is set to 0.5 ⁇ m or less by changing the posture of the glass substrate 80 immersed in the chemical strengthening processing solution in the chemical strengthening processing solution.
  • the shape change that is different for each part of the surface of the glass substrate 80 that may occur when the posture of the glass substrate 80 is not changed is canceled by changing the posture of the glass substrate 80. Therefore, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 ⁇ m or less.
  • the increase in TIR is set to 0.5 ⁇ m or less by uniformizing the temperature distribution of the chemical strengthening treatment liquid.
  • the temperature variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 ⁇ m or less. .
  • the amount of increase in TIR is set to 0.5 ⁇ m or less by stirring the chemical strengthening treatment liquid.
  • the concentration variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 ⁇ m or less. .
  • the present embodiment includes a polishing step (second polishing step) for polishing the surface of the glass substrate 80 after the chemical strengthening step.
  • the TIR in the circumferential direction of the final glass substrate 80 is further reduced. Therefore, the occurrence of head crash is further suppressed.
  • the TIR in the circumferential direction of the glass substrate 80 is the TIR in the circumferential direction at a position of 0.75R from the center of the glass substrate 80, where R is the radius of the glass substrate 80.
  • the entire main surface 81 including the outer peripheral end and the inner peripheral end of the main surface 81 of the glass substrate 80, or the outer peripheral end and the inner peripheral end of the recording area of the recording medium are included.
  • the deterioration of the TIR in the circumferential direction becomes extremely limited, and the occurrence of head crashes is suppressed over a wide range.
  • the glass substrate 80 for HDD according to this embodiment is manufactured by the method for manufacturing the glass substrate for HDD.
  • the high-quality HDD glass substrate 80 is obtained in which the TIR in the circumferential direction is suppressed to a small value, and the fluctuation of the surface state in the circumferential direction is suppressed.
  • the HDD magnetic recording medium according to this embodiment is manufactured by providing a recording layer on the main surface 81 of the HDD glass substrate 80.
  • the HDD glass substrate 80 in which the circumferential TIR is suppressed to a small value and the fluctuation of the surface state in the circumferential direction is suppressed the occurrence of head crashes is suppressed.
  • a quality HDD magnetic recording medium is obtained.
  • the magnetic recording medium for HDD according to the present embodiment is preferably used for a hard disk drive having a rotational speed of 7000 rpm or more.
  • the present embodiment it is possible to obtain a high-quality HDD magnetic recording medium that is less likely to cause head crash due to poor tracking of the magnetic head even when rotated at a high speed of 7000 rpm or higher.
  • the glass substrate for HDD was manufactured according to the manufacturing process of FIG.
  • the total grinding amount in the first and second lapping steps was 0.1 mm.
  • the thickness of the glass substrate was 0.83 mm.
  • Example 1 the chemical strengthening treatment was performed as described with reference to FIGS. 11 (a), (b), (c), (d), and (e) (the chemical strengthening treatment according to the present invention). Specific method 1).
  • the number of glass substrates held by the carrier was 50 (25 ⁇ 2 rows).
  • Example 2 and 6 the chemical strengthening process was performed as described with reference to FIGS. 13A, 13B, 13C, and 13D (a specific method of the chemical strengthening process according to the present invention). 2).
  • the number of glass substrates held by the carrier was 50 (25 ⁇ 2 rows).
  • the chemical strengthening process was performed as described with reference to FIGS. 13A, 13B, 13C, and 13D (a specific method of the chemical strengthening process according to the present invention). 3).
  • the number of glass substrates held by the carrier was 50 (25 ⁇ 2 rows).
  • FIG. 13B only the heater 51 is left, and the plurality of heaters 52 to 54 arranged around the processing liquid tank 50 are omitted.
  • a stirring rod having no heating function was disposed in the circular hole at the center of the glass substrate 80.
  • the rotation speed of the stirring rod was 60 rpm.
  • the chemical strengthening treatment was performed as described with reference to FIGS. 13A, 13B, 13C, and 13D (a specific method of the chemical strengthening treatment according to the present invention). Combination of 2 and 3).
  • the number of glass substrates held by the carrier was 50 (25 ⁇ 2 rows).
  • FIG. 13B all the heaters 51 to 55 are used.
  • the heater 55 was rotated like a stirring rod. The rotation speed was 60 rpm.
  • Second polishing step The second polishing process was performed only in Comparative Example 2 and Examples 5 to 8. That is, both surfaces of the glass substrate were polished more precisely using a double-side polishing machine (manufactured by HAMAI).
  • a polishing pad made of urethane foam having a hardness of Asker-C and 70 degrees is used, and a polishing liquid is made by dispersing colloidal silica having an average particle diameter of 60 nm in water as abrasive grains (polishing material).
  • a slurry was used, and the mixing ratio of water and abrasive grains was 2: 8.
  • the weight was 90 g / cm 2 (8.83 kPa), the rotation speed of the upper surface plate was 20 rpm, and the rotation speed of the lower surface plate was 30 rpm.
  • the polishing amount in the first polishing step (Comparative Example 1, Examples 1 to 4) or the total polishing amount in the first and second polishing steps (Comparative Example 2 and Examples 5 to 8) are both 30 ⁇ m. did. As a result, the final glass substrate thickness was 0.8 mm.
  • the glass substrate was scrubbed.
  • a nonionic surfactant is used to increase the cleaning ability by diluting a mixture of potassium hydroxide (KOH) and sodium hydroxide (NaOH) at a mass ratio of 1: 1 as ultra-pure water (DI water).
  • the liquid obtained by adding the agent was used.
  • the cleaning liquid was supplied by spraying. After scrub cleaning, in order to remove the cleaning liquid remaining on the surface of the glass substrate, a water rinse cleaning process is performed in an ultrasonic bath for 2 minutes, an IPA cleaning process is performed in an ultrasonic bath for 2 minutes, and finally the glass substrate is cleaned with IPA vapor. The surface of was dried.
  • a magnetic film (recording layer) was provided on the main surface of the obtained glass substrate to obtain a magnetic recording medium (vertical recording format). That is, from the glass substrate side, a base layer made of Ni—Al (thickness of about 100 nm), a recording layer made of Co—Cr—Pt (thickness 20 nm), and a protective layer made of DLC (Diamond Like Carbon) (thickness 5 nm) are sequentially formed. Laminated. 100 magnetic recording media were manufactured for each of Comparative Examples 1 and 2 and Examples 1 to 8.
  • the number of follow-up defects is 0 (perfect quality product)
  • Number of follow-up failures is 1 (excellent product)
  • Number of follow-up failures is 2 to 4 (good product)
  • Number of follow-up failures is 5 to 9 (there is a variation in quality, but it cannot be used)
  • Number of follow-up defects is 10 or more (defective product)
  • Table 1 shows the TIR in the circumferential direction of the glass substrate before the chemical strengthening step, the increase in the TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step, the TIR in the circumferential direction of the glass substrate after the chemical strengthening step, and The TIR in the circumferential direction of the final glass substrate (the glass substrate after the chemical strengthening process in Comparative Example 1 and Examples 1 to 4 and the glass substrate after the second polishing process in Comparative Examples 2 and 5 to 8) is also shown. Indicated. These TIR values are the TIR values in the circumferential direction at a position of 0.75R from the center of the glass substrate, where R is the radius of the glass substrate.
  • the amount of increase in TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step was 0.5 ⁇ m or less (0.5 ⁇ m). ) Excellent head flying characteristics.
  • Examples 5 to 8 in which the second polishing process was performed after the chemical strengthening process were compared with Examples 1 to 4 in which the second polishing process was not performed, Examples 5 to 8 had a TIR in the circumferential direction of the final glass substrate. It was even smaller and more excellent in head flying characteristics.
  • the present invention has wide industrial applicability in the technical fields of a method for manufacturing a glass substrate for HDD, a glass substrate for HDD, and a magnetic recording medium for HDD.

Abstract

Provided is a process for producing a glass substrate for HDDs which inhibits head crushing even when used in a magnetic recording medium for HDDs that is to be mounted in an HDD equipped with a DFH head mechanism. Also provided are a glass substrate for HDDs and a magnetic recording medium for HDDs. The process for producing a glass substrate for HDDs includes a chemical strengthening step in which a glass substrate is chemically strengthened by immersing the glass substrate in a liquid for chemical strengthening. In the chemical strengthening step, the increase in the circumferential-direction TIR of the glass substrate through the chemical strengthening step is regulated to 0.5 µm or less by changing the attitude of the glass substrate within the chemical strengthening liquid in which the glass substrate is being immersed, and/or by flatting the temperature distribution of the chemical strengthening liquid, and/or by stirring the chemical strengthening liquid.

Description

ＨＤＤ用ガラス基板の製造方法、ＨＤＤ用ガラス基板、及びＨＤＤ用磁気記録媒体Manufacturing method of glass substrate for HDD, glass substrate for HDD, and magnetic recording medium for HDD
　本発明は、ＨＤＤ用ガラス基板の製造方法、ＨＤＤ用ガラス基板、及びＨＤＤ用磁気記録媒体に関する。 The present invention relates to a method for manufacturing a glass substrate for HDD, a glass substrate for HDD, and a magnetic recording medium for HDD.
　一般に、磁気、光、光磁気等の性質を利用した記録層を有する情報記録媒体の代表的なものにＨＤＤ（hard disk drive）用磁気記録媒体が知られている。ＨＤＤ用磁気記録媒体を製造するためのＨＤＤ用基板としては、従来、アルミニウム基板が広く用いられていた。しかし、近年、記録密度向上のための磁気ヘッド浮上量の低減の要請に伴い、アルミニウム基板よりも表面平滑性に優れ、しかも表面欠陥が少ないことから、磁気ヘッド浮上量の低減を図ることができるガラス基板をＨＤＤ用基板として用いる割合が増えている。 Generally, a magnetic recording medium for HDD (hard disk drive) is known as a typical information recording medium having a recording layer utilizing properties such as magnetism, light, and magnetomagnetism. Conventionally, an aluminum substrate has been widely used as an HDD substrate for manufacturing an HDD magnetic recording medium. However, in recent years, with the demand for reduction of the flying height of the magnetic head for improving the recording density, the surface smoothness is superior to that of the aluminum substrate and the surface defects are few, so that the flying height of the magnetic head can be reduced. The proportion of using glass substrates as HDD substrates is increasing.
　ノート型パーソナルコンピューター等のモバイル機器に搭載されるＨＤＤ用磁気記録媒体には、衝撃に強い基板が必要であるため、例えば特許文献１に開示されるように、化学強化処理を施して耐衝撃性を向上したガラス基板がよく用いられる。 Magnetic recording media for HDDs mounted on mobile devices such as notebook personal computers require a substrate that is resistant to impacts. For example, as disclosed in Patent Document 1, it is subjected to chemical strengthening treatment to provide impact resistance. A glass substrate with improved resistance is often used.
　ところで、昨今は高密度記録化が進行し、例えば２．５インチの記録媒体１枚で、記録容量が５００ＧＢ、面記録密度が６３０Ｇｂ／平方インチ以上というようなＨＤＤ用磁気記録媒体の出現が予想されている。それに伴い、ヘッド機構も改良が進み、ＤＦＨ（dynamic flying height）と称されるヘッド機構が知られている。ＤＦＨは、ヘッドの装着箇所に特殊な金属を用い、金属の熱膨張によってヘッドを記録媒体に対して微小距離で突出させる技術である。このようなＤＦＨヘッド機構では、ヘッドと記録媒体との間隙は数ｎｍ程度まで小さくなり、記録媒体の表面に対する磁気ヘッドの追従不良によるヘッドクラッシュ（head crash）が起き易くなる。 By the way, high-density recording has progressed recently, and for example, the appearance of a magnetic recording medium for HDD having a recording capacity of 500 GB and a surface recording density of 630 Gb / square inch or more with one 2.5-inch recording medium is expected. Has been. Accordingly, the head mechanism has also been improved, and a head mechanism called DFH (dynamic flying flying height) is known. DFH is a technique in which a special metal is used for the mounting position of the head, and the head protrudes from the recording medium at a minute distance by thermal expansion of the metal. In such a DFH head mechanism, the gap between the head and the recording medium is reduced to about several nanometers, and a head crash due to poor tracking of the magnetic head with respect to the surface of the recording medium is likely to occur.
特開２００１－１６７４２７号公報JP 2001-167427 A
　本発明の目的は、たとえＤＦＨヘッド機構を備えるＨＤＤに搭載されるような面記録密度が高いＨＤＤ用磁気記録媒体であっても、ヘッドクラッシュの発生が抑制されるＨＤＤ用ガラス基板の製造方法、その製造方法により製造されたＨＤＤ用ガラス基板、及びそのＨＤＤ用ガラス基板を用いたＨＤＤ用磁気記録媒体を提供することである。 An object of the present invention is to provide a method for manufacturing a glass substrate for an HDD in which the occurrence of head crashes is suppressed even if the magnetic recording medium for the HDD has a high surface recording density as mounted on an HDD having a DFH head mechanism. It is providing the glass substrate for HDD manufactured by the manufacturing method, and the magnetic recording medium for HDD using the glass substrate for HDD.
　すなわち、本発明の一局面は、ガラス基板を化学強化処理液に浸漬することによりガラス基板に化学強化処理を施す化学強化工程を含むＨＤＤ用ガラス基板の製造方法であって、化学強化工程の前後におけるガラス基板の周方向のＴＩＲ（total indicated runout）の増加量を０．５μｍ以下とすることを特徴とするＨＤＤ用ガラス基板の製造方法である。 That is, one aspect of the present invention is a method for manufacturing a glass substrate for HDD, which includes a chemical strengthening step of subjecting a glass substrate to chemical strengthening treatment by immersing the glass substrate in a chemical strengthening treatment solution, before and after the chemical strengthening step. The increase in the TIR (totalＨＤＤindicated runout) in the circumferential direction of the glass substrate is 0.5 μm or less.
　本発明の他の一局面は、前記ＨＤＤ用ガラス基板の製造方法により製造されたことを特徴とするＨＤＤ用ガラス基板である。 Another aspect of the present invention is a glass substrate for HDD manufactured by the method for manufacturing a glass substrate for HDD.
　本発明のさらに他の一局面は、前記ＨＤＤ用ガラス基板の主表面の上に記録層が設けられたことにより製造されたことを特徴とするＨＤＤ用磁気記録媒体である。 Still another aspect of the present invention is an HDD magnetic recording medium manufactured by providing a recording layer on a main surface of the HDD glass substrate.
　前記並びにその他の本発明の目的、特徴及び利点は、以下の詳細な記載と添付図面とから明らかになるであろう。 The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.
図１は、本発明の実施形態に係るＨＤＤ用ガラス基板の製造工程図である。FIG. 1 is a manufacturing process diagram of a glass substrate for HDD according to an embodiment of the present invention. 図２は、第１及び第２ラッピング工程で用いられる両面研削機の主要部の構成を示す部分側面図である。FIG. 2 is a partial side view showing the configuration of the main part of the double-side grinding machine used in the first and second lapping processes. 図３は、図２のＩＩＩ－ＩＩＩ線に沿う矢視図であって下定盤及びキャリアの平面図である。FIG. 3 is a view taken along the line III-III in FIG. 2 and is a plan view of the lower surface plate and the carrier. 図４は、第１ポリッシング工程で用いられるオスカー研磨機の主要部の構成を示す縦断面図である。FIG. 4 is a longitudinal sectional view showing the configuration of the main part of the Oscar polisher used in the first polishing process. 図５（ａ）は、ガラス基板を遊嵌合したリング状冶具が配置されたオスカー研磨機の下研磨皿の平面図、図５（ｂ）は、ガラス基板を遊嵌合したリング状冶具の拡大水平断面図である。FIG. 5A is a plan view of a lower polishing dish of an Oscar polishing machine in which a ring-shaped jig having a loosely fitted glass substrate is arranged, and FIG. 5B is a view of the ring-shaped jig having a loosely fitted glass substrate. It is an expanded horizontal sectional view. 図６（ａ）、図６（ｂ）、図６（ｃ）は、オスカー研磨機の動作を示す平面図である。FIG. 6A, FIG. 6B, and FIG. 6C are plan views showing the operation of the Oscar polisher. 図７（ａ）は、化学強化工程でガラス基板を保持するのに用いられるキャリヤの斜視図、図７（ｂ）は、キャリアの側面図である。FIG. 7A is a perspective view of a carrier used to hold a glass substrate in the chemical strengthening process, and FIG. 7B is a side view of the carrier. 図８（ａ）、図８（ｂ）、図８（ｃ）、図８（ｄ）は、従来の化学強化工程で行われる化学強化処理の流れ図である。FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D are flowcharts of the chemical strengthening process performed in the conventional chemical strengthening process. 図９（ａ）は、化学強化処理前のガラス基板の表面形状を示す斜視図、図９（ｂ）は、従来の化学強化処理を行った後のガラス基板の表面形状を示す斜視図である。FIG. 9A is a perspective view showing the surface shape of the glass substrate before chemical strengthening treatment, and FIG. 9B is a perspective view showing the surface shape of the glass substrate after performing conventional chemical strengthening treatment. . 図１０（ａ）は、化学強化処理前のガラス基板の主表面の高低マップ、図１０（ｂ）は、従来の化学強化処理を行った後のガラス基板の主表面の高低マップ、図１０（ｃ）は、化学強化処理前後のガラス基板の周方向のＴＩＲを比較して示す説明図である。10A is a height map of the main surface of the glass substrate before chemical strengthening treatment, FIG. 10B is a height map of the main surface of the glass substrate after conventional chemical strengthening treatment, and FIG. c) It is explanatory drawing which compares and shows the TIR of the circumferential direction of the glass substrate before and behind a chemical strengthening process. 図１１（ａ）、図１１（ｂ）、図１１（ｃ）、図１１（ｄ）、図１１（ｅ）は、本発明の実施形態に係る化学強化工程で行われる化学強化処理（具体的方法の１）の流れ図である。FIG. 11A, FIG. 11B, FIG. 11C, FIG. 11D, and FIG. 11E show chemical strengthening processes (specific examples) performed in the chemical strengthening process according to the embodiment of the present invention. It is a flowchart of method 1). 図１２（ａ）、図１２（ｂ）、図１２（ｃ）は、具体的方法の１で得られる作用を説明するためのガラス基板の主表面の高低マップである。FIG. 12A, FIG. 12B, and FIG. 12C are elevation maps of the main surface of the glass substrate for explaining the action obtained by the specific method 1. FIG. 図１３（ａ）、図１３（ｂ）、図１３（ｃ）、図１３（ｄ）は、本発明の実施形態に係る化学強化工程で行われる化学強化処理（具体的方法の２及び３）の流れ図である。FIGS. 13 (a), 13 (b), 13 (c), and 13 (d) show a chemical strengthening process (specific methods 2 and 3) performed in the chemical strengthening process according to the embodiment of the present invention. It is a flowchart. 図１４（ａ）、図１４（ｂ）は、具体的方法の２又は３で得られる作用を説明するためのガラス基板の主表面の高低マップである。FIG. 14A and FIG. 14B are elevation maps of the main surface of the glass substrate for explaining the action obtained by the specific method 2 or 3. 図１５は、本発明の実施形態に係るＨＤＤ用ガラス基板の斜視図である。FIG. 15 is a perspective view of a glass substrate for HDD according to an embodiment of the present invention.
　以下、図面を参照して、本発明の実施形態を説明する。ただし、本発明はこの実施形態に限定されるものではない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to this embodiment.
　本発明者等は、ＨＤＤの稼働中に磁気ヘッドが記録媒体の径方向に移動する移動速度に比べて、記録媒体の周方向の回転速度が十分大きいので、ヘッドクラッシュの発生を抑制するためには、記録媒体の周方向の表面状態の変動を抑制することが重要であることに着目した。そして、その観点から、記録媒体の表面の平坦度の指標であるＴＩＲ（total indicated runout）が記録媒体の周方向において小さいことが有効であることを見出した。その上で、本発明者等は、耐衝撃性の向上等のために行われる化学強化処理がガラス基板の周方向のＴＩＲを悪化させるという知見を得て本発明を完成した。 In order to suppress the occurrence of head crashes, the present inventors have a sufficiently high rotational speed in the circumferential direction of the recording medium as compared with the moving speed at which the magnetic head moves in the radial direction of the recording medium during operation of the HDD. Noted that it is important to suppress fluctuations in the surface condition in the circumferential direction of the recording medium. From this point of view, it has been found that it is effective that the TIR (total indicated runout), which is an index of the flatness of the surface of the recording medium, is small in the circumferential direction of the recording medium. In addition, the present inventors have obtained the knowledge that the chemical strengthening treatment performed for improving impact resistance and the like deteriorates the TIR in the circumferential direction of the glass substrate, thereby completing the present invention.
　さらに、本発明者等は、化学強化処理がガラス基板の周方向のＴＩＲを悪化させる原因が、ガラス基板を浸漬する化学強化処理液の温度バラツキや濃度バラツキあるいは異物の混入等、ガラス基板を取り巻く環境が様々な要因により一様でないから、化学強化処理の前後におけるガラス基板の表面形状が均一に変化しないためであるという知見を得て本発明を完成した。 Furthermore, the inventors of the present invention have the reason that the chemical strengthening treatment deteriorates the TIR in the circumferential direction of the glass substrate, such as temperature variation, concentration variation, or contamination of foreign substances in the chemical strengthening treatment solution in which the glass substrate is immersed. Since the environment is not uniform due to various factors, the present invention was completed with the knowledge that the surface shape of the glass substrate before and after the chemical strengthening treatment did not change uniformly.
　＜ＨＤＤ用ガラス基板の製造方法＞
　図１に示した工程図を参照して、ＨＤＤ用ガラス基板の製造方法を説明する。 <Method for producing glass substrate for HDD>
With reference to the process drawing shown in FIG. 1, the manufacturing method of the glass substrate for HDD is demonstrated.
　［ガラス溶融工程］
　まず、ガラス溶融工程では、ガラス素材を溶融する。ガラス基板の材料としては、例えば、ＳｉＯ２、Ｎａ２Ｏ、ＣａＯを主成分としたソーダライムガラス；ＳｉＯ２、Ａｌ２Ｏ３、Ｒ２Ｏ（Ｒ＝Ｋ、Ｎａ、Ｌｉ）を主成分としたアルミノシリケートガラス；ボロシリケートガラス；Ｌｉ２Ｏ－ＳｉＯ２系ガラス；Ｌｉ２Ｏ－Ａｌ２Ｏ３－ＳｉＯ２系ガラス；Ｒ’Ｏ－Ａｌ２Ｏ３－ＳｉＯ２系ガラス（Ｒ’＝Ｍｇ、Ｃａ、Ｓｒ、Ｂａ）等を使用することができる。これらのなかでも、アルミノシリケートガラスやボロシリケートガラスは、耐衝撃性や耐振動性に優れるため特に好ましい。 [Glass melting process]
First, in the glass melting step, a glass material is melted. As a material of the glass substrate, for example, soda lime glass mainly composed of SiO 2 , Na 2 O, CaO; mainly composed of SiO 2 , Al 2 O 3 , R 2 O (R = K, Na, Li) Aluminosilicate glass; borosilicate glass; Li 2 O—SiO 2 glass; Li 2 O—Al 2 O 3 —SiO 2 glass; R′O—Al 2 O 3 —SiO 2 glass (R ′ = Mg) , Ca, Sr, Ba) and the like can be used. Among these, aluminosilicate glass and borosilicate glass are particularly preferable because they are excellent in impact resistance and vibration resistance.
　［成型工程］
　次に、成型工程では、溶融したガラス素材を下型に流し込み、上型によってプレス成形して円板状のガラス基板（これをブランクという）を得る。なお、ブランクは、プレス成形によらず、例えばダウンドロー法やフロート法等で形成したシートガラスを研削砥石で切り出して作製してもよい。 [Molding process]
Next, in the molding step, the molten glass material is poured into the lower mold and press-molded with the upper mold to obtain a disk-shaped glass substrate (referred to as a blank). Note that the blank may be produced by cutting a sheet glass formed by, for example, a downdraw method or a float method with a grinding stone, without using press molding.
　ガラス基板、すなわちブランクの大きさに限定はない。例えば、外径が２．５インチ、１．８インチ、１インチ、０．８インチ等の種々の大きさのガラス基板を作製することができる。ガラス基板の厚みにも限定はない。例えば、２ｍｍ、１ｍｍ、０．８ｍｍ、０．６３ｍｍ等の種々の厚みのガラス基板を作製することができる。 There is no limitation on the size of the glass substrate, that is, the blank. For example, glass substrates having various sizes such as 2.5 inches, 1.8 inches, 1 inch, and 0.8 inches in outer diameter can be manufactured. There is no limitation on the thickness of the glass substrate. For example, glass substrates having various thicknesses such as 2 mm, 1 mm, 0.8 mm, and 0.63 mm can be manufactured.
　［熱処理工程］
　次に、熱処理工程では、プレス成型や切り出しによって作製されたガラス基板を耐熱部材のセッターと交互に積層し、高温の電気炉を通過させることにより、ガラス基板の反りの低減やガラスの結晶化を促進させる。 [Heat treatment process]
Next, in the heat treatment process, glass substrates produced by press molding or cutting are alternately stacked with heat-stable member setters and passed through a high-temperature electric furnace to reduce glass substrate warpage and glass crystallization. Promote.
　［第１ラッピング工程］
　次に、第１ラッピング工程では、ガラス基板の両表面を研削加工し、ガラス基板の平行度、平坦度及び厚みを予備調整する。 [First wrapping step]
Next, in the first lapping step, both surfaces of the glass substrate are ground and the parallelism, flatness, and thickness of the glass substrate are preliminarily adjusted.
　［コアリング加工工程］
　次に、コアリング加工工程では、第１ラッピング工程後のガラス基板の中心部に円形の穴を開ける。穴開けは、例えば、カッター部にダイヤモンド砥石等を備えたコアドリル等で研削することにより行うことができる。 [Coring process]
Next, in the coring process, a circular hole is formed in the center of the glass substrate after the first lapping process. The drilling can be performed, for example, by grinding with a core drill or the like provided with a diamond grindstone or the like in the cutter portion.
　［内・外径加工工程］
　次に、内・外径加工工程では、ガラス基板の外周端面及び内周端面を、例えばダイヤモンド等を用いた鼓状の研削砥石により研削することで内・外径加工する。 [Inner / outer diameter machining process]
Next, in the inner / outer diameter processing step, the inner / outer diameter processing is performed by grinding the outer peripheral end surface and the inner peripheral end surface of the glass substrate with a drum-shaped grinding wheel using, for example, diamond.
　［第２ラッピング工程］
　次に、第２ラッピング工程では、ガラス基板の両表面を再び研削加工し、ガラス基板の平行度、平坦度及び厚みを微調整する。 [Second wrapping step]
Next, in the second lapping step, both surfaces of the glass substrate are ground again to finely adjust the parallelism, flatness and thickness of the glass substrate.
　前記第１ラッピング工程及び前記第２ラッピング工程では、図２及び図３に示すように、遊星歯車機構を利用した両面研削機と称される公知の研削機１０が使用できる。両面研削機１０は、互いに平行になるように上下に配置された円盤状の上定盤１１と下定盤１２とを備えている。この上下の定盤１１，１２は互いに逆方向に回転する。この上下の定盤１１，１２の対向するそれぞれの面にガラス基板の主表面を研削するためのダイヤモンドペレット１３，１４が貼り付けられている。上下の定盤１１，１２の間に複数のキャリア１７が配設されている。各キャリア１７は、下定盤１２の回転軸の周囲に設けられたサンギア１５と、下定盤１２の外周に円環状に設けられたインターナルギア１６とに結合して回転する。各キャリア１７に複数の穴１８が形成されている。各穴１８にガラス基板が遊嵌合されて保持される。なお、ガラス基板は図２及び図３には図示されていないが、例えば図１５に符号８０が付されて図示されている。上下の定盤１１，１２、サンギア１５及びインターナルギア１６は、それぞれ別駆動で動作する。 In the first lapping step and the second lapping step, as shown in FIGS. 2 and 3, a known grinding machine 10 called a double-side grinding machine using a planetary gear mechanism can be used. The double-side grinding machine 10 includes a disk-shaped upper surface plate 11 and a lower surface plate 12 that are arranged vertically so as to be parallel to each other. The upper and lower surface plates 11 and 12 rotate in opposite directions. Diamond pellets 13 and 14 for grinding the main surface of the glass substrate are attached to the opposing surfaces of the upper and lower surface plates 11 and 12, respectively. A plurality of carriers 17 are disposed between the upper and lower surface plates 11 and 12. Each carrier 17 rotates in combination with a sun gear 15 provided around the rotation axis of the lower surface plate 12 and an internal gear 16 provided in an annular shape on the outer periphery of the lower surface plate 12. A plurality of holes 18 are formed in each carrier 17. A glass substrate is loosely fitted in each hole 18 and held. Although the glass substrate is not shown in FIGS. 2 and 3, for example, the glass substrate is shown with reference numeral 80 in FIG. The upper and lower surface plates 11, 12, the sun gear 15 and the internal gear 16 operate by separate driving.
　研削機１０の研削動作はおよそ次のようにして行われる。すなわち、上下の定盤１１，１２が互いに逆方向に回転すると、ダイヤモンドペレット１３，１４を介して上下の定盤１１，１２間に挟まれているキャリア１７は、複数のガラス基板を保持した状態で、自転しながら定盤１１，１２の回転中心に対して下定盤１２と同じ方向に公転する。このように動作している研削機１０に対して、上定盤１１のダイヤモンドペレット１３とガラス基板との間、及び、下定盤１２のダイヤモンドペレット１４とガラス基板との間に研削液を供給することにより、ガラス基板の研削が行われる。 The grinding operation of the grinding machine 10 is performed as follows. That is, when the upper and lower surface plates 11 and 12 rotate in opposite directions, the carrier 17 sandwiched between the upper and lower surface plates 11 and 12 via the diamond pellets 13 and 14 holds a plurality of glass substrates. Thus, while rotating, it revolves in the same direction as the lower surface plate 12 with respect to the rotation center of the surface plates 11 and 12. Grinding liquid is supplied between the diamond pellet 13 of the upper surface plate 11 and the glass substrate and between the diamond pellet 14 of the lower surface plate 12 and the glass substrate to the grinding machine 10 operating in this way. Thus, the glass substrate is ground.
　この両面研削機１０を使用する際、ガラス基板に加わる定盤１１，１２の加重及び定盤１１，１２の回転数を所望の研削状態に応じて適宜調整する。第１及び第２ラッピング工程における加重は、６０ｇ／ｃｍ２（５．８８ｋＰａ）から１２０ｇ／ｃｍ２（１１．７７ｋＰａ）とするのが好ましい。また、定盤１１，１２の回転数は、１０ｒｐｍから３０ｒｐｍ程度とし、上定盤１１の回転数を下定盤１２の回転数よりも３０％から４０％程度遅くするのが好ましい。定盤１１，１２による加重を大きくし、定盤１１，１２の回転数を速くすると、研削量は多くなる。しかし、加重が大きすぎると表面粗さが良好とならず、回転数が速すぎると平坦度が良好とならない。また、定盤１１，１２の加重を小さくし、定盤１１，１２の回転数を遅くすると、研削量が少なくなり、製造効率が低くなる。 When this double-side grinding machine 10 is used, the weight of the surface plates 11 and 12 applied to the glass substrate and the rotational speed of the surface plates 11 and 12 are appropriately adjusted according to the desired grinding state. The weight in the first and second wrapping steps is preferably 60 g / cm 2 (5.88 kPa) to 120 g / cm 2 (11.77 kPa). The rotation speed of the surface plates 11 and 12 is preferably about 10 to 30 rpm, and the rotation speed of the upper surface plate 11 is preferably about 30 to 40% slower than the rotation speed of the lower surface plate 12. If the weight by the surface plates 11 and 12 is increased and the rotational speed of the surface plates 11 and 12 is increased, the grinding amount increases. However, if the load is too large, the surface roughness will not be good, and if the rotational speed is too fast, the flatness will not be good. Further, if the weights of the surface plates 11 and 12 are reduced and the rotational speed of the surface plates 11 and 12 is decreased, the amount of grinding is reduced and the production efficiency is lowered.
　第２ラッピング工程を終えた時点で、ガラス基板の大きなうねり、欠け、ひび等の欠陥はほぼ除去される。また、ガラス基板の主表面の表面粗さは、Ｒａが０．２μｍから０．４μｍ程度とするのが好ましく、主表面の平坦度は、７～１０μｍが好ましい。このような面状態にしておくことで、次の第１ポリッシング工程での研磨を効率よく行うことができる。 When the second lapping process is completed, defects such as large waviness, chipping and cracking of the glass substrate are almost removed. The surface roughness of the main surface of the glass substrate is preferably Ra from about 0.2 μm to 0.4 μm, and the flatness of the main surface is preferably 7 to 10 μm. By maintaining such a surface state, it is possible to efficiently perform polishing in the next first polishing step.
　なお、第１ラッピング工程では、第２ラッピング工程を効率よく行うことができるように大まかにガラス基板の大きなうねり、欠け、ひび等を除去する。そのため、第２ラッピング工程では粗さが＃１３００メッシュから＃１７００メッシュ程度のダイヤモンドペレット１３，１４を使用し、第１ラッピング工程では粗さがそれより粗い＃８００メッシュから＃１２００メッシュ程度のダイヤモンドペレット１３，１４を使用するのが好ましい。第１ラッピング工程を終えた時点で、ガラス基板の主表面の表面粗さは、Ｒａが０．４μｍから０．８μｍ程度とするのが好ましく、主表面の平坦度は、１０～１５μｍが好ましい。 In the first lapping step, large waviness, chips, cracks, etc. of the glass substrate are roughly removed so that the second lapping step can be performed efficiently. Therefore, diamond pellets 13 and 14 having a roughness of about # 1300 mesh to # 1700 mesh are used in the second wrapping process, and diamond pellets having a roughness of about # 800 mesh to about # 1200 mesh are coarser in the first wrapping process. 13 and 14 are preferably used. When the first lapping step is completed, the surface roughness of the main surface of the glass substrate is preferably Ra from about 0.4 μm to 0.8 μm, and the flatness of the main surface is preferably 10 to 15 μm.
　また、第１ラッピング工程の後に、及び／又は、第２ラッピング工程の後に、ガラス基板の表面に残った研削液やガラス粉を除去するための洗浄工程を行うことが好ましい。 Further, it is preferable to perform a cleaning step for removing the grinding liquid and glass powder remaining on the surface of the glass substrate after the first lapping step and / or after the second lapping step.
　なお、本実施形態で用いる表面粗さは、原子間力顕微鏡（デジタルインスツルメンツ社製ナノスコープ）を用いて、１μｍ×１μｍの範囲を測定した値である。また、本実施形態で用いる平坦度は、平坦度測定装置で測定した値であり、ガラス基板の表面の最も高い位置（Ｐｏ）と最も低い位置（Ｖｏ）との高低差（Ｐｏ－Ｖｏ値）である。 In addition, the surface roughness used in this embodiment is a value obtained by measuring a range of 1 μm × 1 μm using an atomic force microscope (Nanoscope manufactured by Digital Instruments). The flatness used in the present embodiment is a value measured by a flatness measuring device, and the difference in height (Po−Vo value) between the highest position (Po) and the lowest position (Vo) on the surface of the glass substrate. It is.
　［端面研磨加工工程］
　次に、端面研磨加工工程では、第２ラッピング工程を終えたガラス基板の外周端面及び内周端面を、端面研磨機を用いて研磨加工する。 [End face polishing process]
Next, in the end face polishing process, the outer peripheral end face and the inner peripheral end face of the glass substrate after the second lapping process are polished using an end face polishing machine.
　［第１ポリッシング工程］
　次に、第１ポリッシング工程では、ガラス基板の両表面を研磨加工する。第１ポリッシング工程では、図４から図６に示すようなオスカー研磨機２０を用い、最終的に本実施形態に係るＨＤＤ用ガラス基板の形状を効率よく得ることができるようにガラス基板８０を研磨する。オスカー研磨機２０は、回転する下研磨皿２１と、下研磨皿２１の上方空間を水平方向（Ｘ←→Ｘ）に揺動する上研磨皿２２とを備えている。そして、上下の研磨皿２１，２２の間に、ガラス基板８０の外径よりも大きい内径を有するリング状冶具２３に収容されたガラス基板８０を配置して、ガラス基板８０を自転させながら、ガラス基板８０の両面を上下の研磨皿２１，２２で研磨する。 [First polishing step]
Next, in the first polishing step, both surfaces of the glass substrate are polished. In the first polishing step, the glass substrate 80 is polished so that the shape of the HDD glass substrate according to the present embodiment can be finally obtained efficiently by using an Oscar polishing machine 20 as shown in FIGS. To do. The Oscar polishing machine 20 includes a rotating lower polishing dish 21 and an upper polishing dish 22 that swings the upper space of the lower polishing dish 21 in the horizontal direction (X ← → X). The glass substrate 80 accommodated in the ring-shaped jig 23 having an inner diameter larger than the outer diameter of the glass substrate 80 is disposed between the upper and lower polishing dishes 21 and 22, and the glass substrate 80 is rotated while rotating the glass substrate 80. Both surfaces of the substrate 80 are polished by upper and lower polishing dishes 21 and 22.
　オスカー研磨機２０では、上下の研磨皿２１，２２の間に研磨対象物であるガラス基板８０を置いた状態で、研磨液を供給しながら、下研磨皿２１を自転させ、上研磨皿２２を図４から図６に関して左右に揺動させることで、ガラス基板８０が上下の研磨皿２１，２２により研磨される。条件によっては、ガラス基板８０の自転を促すことができる。その結果、同心円の点対象形状のガラス基板８０を製造することができる。すなわち、ガラス基板８０の周方向の表面状態の変動を抑制することができる。本実施形態では、外径が２．５インチ（６３．５ｍｍ）のガラス基板８０を例にして説明するが、ガラス基板８０の大きさに限定はない。 In the Oscar polishing machine 20, the lower polishing dish 21 is rotated while supplying the polishing liquid with the glass substrate 80 as an object to be polished placed between the upper and lower polishing dishes 21 and 22. The glass substrate 80 is polished by the upper and lower polishing dishes 21 and 22 by swinging left and right with respect to FIGS. Depending on conditions, rotation of the glass substrate 80 can be promoted. As a result, the glass substrate 80 having a concentric point target shape can be manufactured. That is, fluctuations in the surface state in the circumferential direction of the glass substrate 80 can be suppressed. In the present embodiment, the glass substrate 80 having an outer diameter of 2.5 inches (63.5 mm) will be described as an example, but the size of the glass substrate 80 is not limited.
　本実施形態では、上下の研磨皿２１，２２は直径が１０００ｍｍであり、対向するそれぞれの面に弾性に富むスウェード（図５（ａ）に下研磨皿２１のスウェード２４のみ図示）が貼り付けられている。図５（ｂ）に示すような樹脂材料で製造したリング状冶具２３（内径６５ｍｍ、外径６７ｍｍ、厚み０．５ｍｍ）にガラス基板８０を遊嵌合して保持する。これを１００セット下研磨皿２１のスウェード２４の上に置く。そして、上研磨皿２２でガラス基板８０を挟み込み、研磨液として、酸化セリウムやコロイダルシリカを砥粒（研磨材）として含有するスラリーを供給しながら、下研磨皿２１を自転させ、上研磨皿２２を任意の範囲で図４から図６に関して左右に揺動させる。これにより、ガラス基板８０は上下の研磨皿２１，２２の相対運動によってリング状冶具２３内で自転し、両表面が周方向に研磨される。 In the present embodiment, the upper and lower polishing dishes 21 and 22 have a diameter of 1000 mm, and elastic suedes (only the suede 24 of the lower polishing dish 21 is shown in FIG. 5A) are attached to the opposing surfaces. ing. A glass substrate 80 is loosely fitted and held on a ring-shaped jig 23 (inner diameter 65 mm, outer diameter 67 mm, thickness 0.5 mm) manufactured from a resin material as shown in FIG. This is placed on the suede 24 of the lower polishing dish 21 for 100 sets. Then, the glass substrate 80 is sandwiched between the upper polishing dish 22 and the lower polishing dish 21 is rotated while supplying slurry containing cerium oxide or colloidal silica as abrasive grains (polishing material) as a polishing liquid. Is swung left and right with respect to FIGS. 4 to 6 within an arbitrary range. Thereby, the glass substrate 80 rotates within the ring-shaped jig 23 by the relative movement of the upper and lower polishing dishes 21 and 22, and both surfaces are polished in the circumferential direction.
　［化学強化工程］
　（総論）
　次に、化学強化工程では、ガラス基板を化学強化処理液に浸漬することにより、ガラス基板の主表面、外周端面及び内周端面に化学強化層（応力層）を形成する。すなわち、ガラス基板に化学強化処理を施す。ガラス基板の主表面に化学強化層を形成することにより、ガラス基板の反りや主表面の粗面化を防止することができる。ガラス基板の外周端面及び内周端面に化学強化層を形成することにより、ガラス基板の耐衝撃性、耐振動性及び耐熱性等を向上させることができる。 [Chemical strengthening process]
(General)
Next, in the chemical strengthening step, a chemical strengthening layer (stress layer) is formed on the main surface, the outer peripheral end surface, and the inner peripheral end surface of the glass substrate by immersing the glass substrate in a chemical strengthening treatment solution. That is, a chemical strengthening process is performed on the glass substrate. By forming the chemical strengthening layer on the main surface of the glass substrate, warpage of the glass substrate and roughening of the main surface can be prevented. By forming the chemically strengthened layer on the outer peripheral end surface and the inner peripheral end surface of the glass substrate, the impact resistance, vibration resistance, heat resistance, and the like of the glass substrate can be improved.
　化学強化工程は、加熱された化学強化処理液にガラス基板を浸漬することによってガラス基板に含まれるリチウムイオン、ナトリウムイオン等のアルカリ金属イオンをそれよりイオン半径の大きなカリウムイオン等のアルカリ金属イオンで置換するイオン交換法により行われる。イオン半径の違いによって生じる歪みにより、イオン交換された領域に圧縮応力が発生し、ガラス基板の主表面、外周端面及び内周端面が応力層、すなわち化学強化層によって強化される。ガラス基板の表面が応力層で強化される結果、ガラス基板の耐衝撃性がより一層改善される。 In the chemical strengthening step, by immersing the glass substrate in a heated chemical strengthening solution, alkali metal ions such as lithium ions and sodium ions contained in the glass substrate are converted into alkali metal ions such as potassium ions having a larger ion radius. This is carried out by a replacement ion exchange method. Compressive stress is generated in the ion-exchanged region due to distortion caused by the difference in ion radius, and the main surface, outer peripheral end surface, and inner peripheral end surface of the glass substrate are strengthened by the stress layer, that is, the chemical strengthening layer. As a result of strengthening the surface of the glass substrate with the stress layer, the impact resistance of the glass substrate is further improved.
　化学強化処理液に特に制限はなく、公知の化学強化処理液を用いることができる。通常、カリウムイオンを含む溶融塩又はカリウムイオンとナトリウムイオンとを含む溶融塩を用いることが一般的である。カリウムイオンやナトリウムイオンを含む溶融塩としては、カリウムやナトリウムの硝酸塩、炭酸塩、硫酸塩やこれらの混合溶融塩が挙げられる。これらのなかでも、融点が低く、ガラス基板の変形を防止できるという観点から、硝酸塩を用いることが好ましい。 The chemical strengthening treatment liquid is not particularly limited, and a known chemical strengthening treatment liquid can be used. Usually, it is common to use a molten salt containing potassium ions or a molten salt containing potassium ions and sodium ions. Examples of the molten salt containing potassium ions and sodium ions include potassium and sodium nitrates, carbonates, sulfates, and mixed molten salts thereof. Among these, it is preferable to use nitrate from the viewpoint that the melting point is low and deformation of the glass substrate can be prevented.
　（従来の化学強化処理）
　従来の化学強化処理はおよそ次のようなものである。まず、図７（ａ）に示すように、ガラス基板８０を保持するためのキャリア３０が用いられる。キャリア３０は上下が開放した容器であり、複数の保持ロッド３１が相互に平行に架設されている。図７（ｂ）に示すように、ガラス基板８０は複数の保持ロッド３１に３点で保持される。１つのキャリア３０で数十枚のガラス基板８０が僅かな間隙で相互に平行に並べられて同時に保持される。 (Conventional chemical strengthening treatment)
The conventional chemical strengthening treatment is approximately as follows. First, as shown in FIG. 7A, a carrier 30 for holding a glass substrate 80 is used. The carrier 30 is a container whose top and bottom are open, and a plurality of holding rods 31 are installed in parallel to each other. As shown in FIG. 7B, the glass substrate 80 is held by the plurality of holding rods 31 at three points. Several tens of glass substrates 80 are arranged in parallel with each other with a slight gap and are simultaneously held by one carrier 30.
　図８（ａ）に示すように、キャリア３０に保持したガラス基板８０を電気炉４０で３００℃に予熱する。図８（ｂ）に示すように、硝酸カリウム（６０質量％）と硝酸ナトリウム（４０質量％）とを混合、溶解した化学強化処理液を処理液槽５０に用意し、ヒータ５１で４００℃に加熱する。予熱したガラス基板８０を化学強化処理液中に約２０分浸漬し、ガラス基板８０の全面に亘って強化層を形成する。図８（ｃ）に示すように、化学強化処理を終えたガラス基板８０を、ヒータ６１で７０℃に加温された温水槽６０に約１０分間浸漬して冷却した後、図８（ｄ）に示すように、温水槽６０から取り出す。 As shown in FIG. 8A, the glass substrate 80 held on the carrier 30 is preheated to 300 ° C. in the electric furnace 40. As shown in FIG. 8 (b), a chemical strengthening treatment liquid prepared by mixing and dissolving potassium nitrate (60 mass%) and sodium nitrate (40 mass%) is prepared in a treatment liquid tank 50 and heated to 400 ° C. by a heater 51. To do. The preheated glass substrate 80 is immersed in the chemical strengthening treatment solution for about 20 minutes, and a reinforcing layer is formed over the entire surface of the glass substrate 80. As shown in FIG. 8C, after the glass substrate 80 that has been subjected to the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes, FIG. As shown in FIG.
　このとき、化学強化処理液の温度バラツキや濃度バラツキあるいは異物の混入等、ガラス基板８０を取り巻く環境が様々な要因により一様でないため、化学強化処理の前後におけるガラス基板８０の表面形状が均一に変化しない。例えば、図９（ａ）に示すように、化学強化処理前は表面形状がほぼ平坦であったガラス基板８０が、図９（ｂ）に示すように、化学強化処理後は表面形状が歪となる。 At this time, since the environment surrounding the glass substrate 80 is not uniform due to various factors such as temperature variation and concentration variation of the chemical strengthening treatment liquid or mixing of foreign matters, the surface shape of the glass substrate 80 before and after the chemical strengthening treatment is uniform. It does not change. For example, as shown in FIG. 9A, the glass substrate 80 having a substantially flat surface shape before the chemical strengthening treatment is deformed as shown in FIG. 9B. Become.
　その結果、図１０（ａ）、（ｂ）、（ｃ）に示すように、化学強化処理後は、ガラス基板８０の周方向のＴＩＲが悪化する。図１０（ａ）は、化学強化処理前のガラス基板８０の主表面８１（図１５参照）の高低マップである。この図に示すように、化学強化処理前はガラス基板８０の主表面８１の平坦度が相対的に良好である。そのため、図１０（ｃ）に実線（ａ）で示すように、ガラス基板８０の主表面８１の周方向のＴＩＲは小さい。一方、図１０（ｂ）は、従来の化学強化処理後のガラス基板８０の主表面８１の高低マップである。この図に示すように、化学強化処理後はガラス基板８０の主表面８１の表面形状に歪が発生している。そのため、図１０（ｃ）に破線（ｂ）で示すように、ガラス基板８０の主表面８１の周方向のＴＩＲは大きくなる。 As a result, as shown in FIGS. 10A, 10B, and 10C, the TIR in the circumferential direction of the glass substrate 80 deteriorates after the chemical strengthening treatment. FIG. 10A is a height map of the main surface 81 (see FIG. 15) of the glass substrate 80 before the chemical strengthening treatment. As shown in this figure, the flatness of the main surface 81 of the glass substrate 80 is relatively good before the chemical strengthening treatment. Therefore, as shown by a solid line (a) in FIG. 10C, the TIR in the circumferential direction of the main surface 81 of the glass substrate 80 is small. On the other hand, FIG.10 (b) is a height map of the main surface 81 of the glass substrate 80 after the conventional chemical strengthening process. As shown in this figure, after the chemical strengthening treatment, the surface shape of the main surface 81 of the glass substrate 80 is distorted. Therefore, as indicated by a broken line (b) in FIG. 10C, the TIR in the circumferential direction of the main surface 81 of the glass substrate 80 increases.
　なお、図１０（ｃ）の周方向ＴＩＲは、図１０（ａ）及び図１０（ｂ）に破線で示す位置における値である。具体的には、ガラス基板８０の半径をＲとしたときに、ガラス基板８０の中心から０．７５Ｒの位置における値である。 In addition, the circumferential direction TIR in FIG. 10C is a value at a position indicated by a broken line in FIGS. 10A and 10B. Specifically, it is a value at a position of 0.75R from the center of the glass substrate 80, where R is the radius of the glass substrate 80.
　前記「ガラス基板の周方向のＴＩＲ」とは、例えば、ガラス基板の主表面に最適にフィットした平面を最小二乗法で求め、ガラス基板の主表面の高さを周方向に複数箇所測定し、高さが前記平面よりも上方にある最高点（Ｐ）と下方にある最低点（Ｖ）との差の絶対値（Ｐ－Ｖ値）をいう。 The “TIR in the circumferential direction of the glass substrate” means, for example, a plane that is optimally fitted to the main surface of the glass substrate by the least square method, and measures the height of the main surface of the glass substrate in a plurality of locations in the circumferential direction. The absolute value (P−V value) of the difference between the highest point (P) whose height is above the plane and the lowest point (V) below it.
　ガラス基板８０の主表面８１の周方向のＴＩＲは、例えば、白色光の干渉を利用して表面形状を測定する方式（例えば、Ｐｈａｓｅ　Ｓｈｉｆｔ　Ｔｅｃｈｎｏｌｏｇｙ社製の「Ｏｐｔｉｆｌａｔ」）や、被測定面に対して斜めにレーザー光を入射することで垂直入射方式に比べて高い反射率を得ることができ、粗い面形状においても測定が可能な方式（例えば、ＴＲＯＰＥＬ社製の「Ｆｌａｔ　Ｍａｓｔｅｒ　ＦＭ１００ＸＲＡ」）等により測定することができる。 The TIR in the circumferential direction of the main surface 81 of the glass substrate 80 is, for example, a method for measuring a surface shape using interference of white light (for example, “Optiflat” manufactured by Phase Shift Technology) or a surface to be measured. By applying laser light obliquely, it is possible to obtain a high reflectance compared to the vertical incidence method, and a method capable of measuring even with a rough surface shape (for example, “Flat Master FM100XRA” manufactured by TROPEL). Can be measured.
　このように、ガラス基板８０の耐衝撃性の向上等のために従来行われている化学強化処理がガラス基板８０の周方向のＴＩＲを悪化させていることが分かった。その結果、ガラス基板８０の周方向の表面状態が大きく変動し、磁気ヘッドの追従不良によるヘッドクラッシュが起き易くなっていた。 Thus, it has been found that the chemical strengthening treatment conventionally performed for improving the impact resistance of the glass substrate 80 deteriorates the TIR in the circumferential direction of the glass substrate 80. As a result, the surface state in the circumferential direction of the glass substrate 80 greatly fluctuated, and head crushing due to poor tracking of the magnetic head was likely to occur.
　（本実施形態の化学強化処理）
　そこで、本実施形態では、化学強化処理がガラス基板８０の周方向のＴＩＲを悪化させないようにすることを図っている。具体的には、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量を０．５μｍ以下とすることを図っている。 (Chemical strengthening treatment of this embodiment)
Therefore, in the present embodiment, the chemical strengthening process is intended to prevent the TIR in the circumferential direction of the glass substrate 80 from being deteriorated. Specifically, the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is set to 0.5 μm or less.
　これによれば、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量が０．５μｍ以下であるから、化学強化処理によるガラス基板８０の周方向ＴＩＲの悪化が極めて限定的となる。そのため、化学強化工程後のガラス基板８０の周方向のＴＩＲが小さい値に抑えられ、ガラス基板８０の周方向の表面状態の変動が抑制されて、磁気ヘッドの追従不良によるヘッドクラッシュの発生が抑制される。 According to this, since the amount of increase in the TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 μm or less, the deterioration in the circumferential direction TIR of the glass substrate 80 due to the chemical strengthening treatment is extremely limited. . Therefore, the TIR in the circumferential direction of the glass substrate 80 after the chemical strengthening process is suppressed to a small value, the fluctuation of the surface state in the circumferential direction of the glass substrate 80 is suppressed, and the occurrence of head crash due to the follow-up failure of the magnetic head is suppressed. Is done.
　本実施形態では、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量を０．３μｍ以下とすることが好ましい。化学強化処理によるガラス基板８０の周方向ＴＩＲの悪化がより一層限定的となり、磁気ヘッドの追従不良によるヘッドクラッシュの発生がより一層抑制されるからである。 In this embodiment, it is preferable that the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.3 μm or less. This is because the deterioration of the circumferential direction TIR of the glass substrate 80 due to the chemical strengthening process becomes more limited, and the occurrence of head crash due to the follow-up failure of the magnetic head is further suppressed.
　本実施形態では、ガラス基板８０の周方向のＴＩＲは、ガラス基板８０の半径をＲとしたときに、ガラス基板８０の中心から０．７５Ｒの位置における周方向のＴＩＲである。 In the present embodiment, the TIR in the circumferential direction of the glass substrate 80 is the TIR in the circumferential direction at a position of 0.75R from the center of the glass substrate 80, where R is the radius of the glass substrate 80.
　これによれば、次のような利点がある。すなわち、同一のガラス基板における周方向ＴＩＲはガラス基板の中心からの距離と相関関係にあり、ガラス基板の中心から外側に離れるほど周方向ＴＩＲは大きくなる傾向にある。そして、ガラス基板８０の中心から０．７５Ｒの位置は、ガラス基板８０の主表面８１ないし記録媒体の記録領域において相対的に外側の位置である。そのため、ガラス基板８０の中心から０．７５Ｒの位置における周方向のＴＩＲの増加量を０．５μｍ以下又は０．３μｍ以下に制限することによって、ガラス基板８０の主表面８１の外周端部及び内周端部を含めた主表面８１の全部、ないし記録媒体の記録領域の外周端部及び内周端部を含めた記録領域の全部においても、周方向ＴＩＲの悪化が極めて限定的となり、ヘッドクラッシュの発生が広範囲に亘って抑制されるという利点がある。 According to this, there are the following advantages. That is, the circumferential direction TIR in the same glass substrate has a correlation with the distance from the center of the glass substrate, and the circumferential direction TIR tends to increase as the distance from the center of the glass substrate increases. The position of 0.75R from the center of the glass substrate 80 is a relatively outer position in the main surface 81 of the glass substrate 80 or the recording area of the recording medium. Therefore, by limiting the amount of increase in TIR in the circumferential direction at a position of 0.75R from the center of the glass substrate 80 to 0.5 μm or less or 0.3 μm or less, the outer peripheral end and the inner surface of the main surface 81 of the glass substrate 80 are reduced. Deterioration in the circumferential direction TIR is extremely limited in the entire main surface 81 including the peripheral edge, or in the entire recording area including the outer peripheral edge and the inner peripheral edge of the recording area of the recording medium. There is an advantage that the occurrence of is suppressed over a wide range.
　（具体的方法の１）
　化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量を０．５μｍ以下とする１つ目の具体的方法としては、化学強化工程において、化学強化処理液に浸漬されているガラス基板８０の化学強化処理液中の姿勢を変えることが挙げられる。 (Specific method 1)
As a first specific method for setting the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step to 0.5 μm or less, the glass substrate immersed in the chemical strengthening treatment liquid in the chemical strengthening step is as follows. It is possible to change the posture in the 80 chemical strengthening treatment liquid.
　これによれば、次のような作用が得られる。すなわち、化学強化処理液中のガラス基板８０の姿勢を変えない場合は、ガラス基板８０を取り巻く環境が様々な要因により一様でないことに起因して、ガラス基板８０の表面の部位ごとに異なる形状変化が生じ得る。これに対し、化学強化処理液中のガラス基板８０の姿勢を変えることによって、このような部位ごとに異なる形状変化を打ち消すことができる。そのため、化学強化処理の前後におけるガラス基板８０の表面形状が均一に変化することとなって、ＴＩＲ増加量を容易に０．５μｍ以下とすることができる。 According to this, the following effects can be obtained. That is, when the posture of the glass substrate 80 in the chemical strengthening treatment liquid is not changed, the shape surrounding the glass substrate 80 is different for each part of the surface of the glass substrate 80 because the environment surrounding the glass substrate 80 is not uniform due to various factors. Changes can occur. On the other hand, by changing the posture of the glass substrate 80 in the chemical strengthening treatment liquid, it is possible to cancel the shape change that differs for each part. Therefore, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 μm or less.
　例えば、図１１（ａ）に示すように、キャリア３０に保持したガラス基板８０を電気炉４０で３００℃に予熱する。図１１（ｂ）に示すように、硝酸カリウム（６０質量％）と硝酸ナトリウム（４０質量％）とを混合、溶解した化学強化処理液を処理液槽５０に用意し、ヒータ５１で４００℃に加熱する。予熱したガラス基板８０を化学強化処理液中に約１０分浸漬する（１回目の浸漬）。１０分浸漬後、ガラス基板８０をキャリア３０ごと処理液槽５０から取り出し、全てのガラス基板８０を図中矢印で示すようにガラス基板８０の中心に関して９０°回転する。このようにガラス基板８０の姿勢を変えた後、図１１（ｃ）に示すように、再び化学強化処理液中に約１０分浸漬する（２回目の浸漬）。図１１（ｄ）に示すように、化学強化処理を終えたガラス基板８０を、ヒータ６１で７０℃に加温された温水槽６０に約１０分間浸漬して冷却した後、図８（ｅ）に示すように、温水槽６０から取り出す。 For example, as shown in FIG. 11 (a), the glass substrate 80 held on the carrier 30 is preheated to 300 ° C. in the electric furnace 40. As shown in FIG. 11 (b), a chemical strengthening treatment liquid prepared by mixing and dissolving potassium nitrate (60 mass%) and sodium nitrate (40 mass%) is prepared in a treatment liquid tank 50 and heated to 400 ° C. with a heater 51. To do. The preheated glass substrate 80 is immersed in the chemical strengthening treatment solution for about 10 minutes (first immersion). After immersion for 10 minutes, the glass substrate 80 is taken out of the treatment liquid tank 50 together with the carrier 30, and all the glass substrates 80 are rotated by 90 ° with respect to the center of the glass substrate 80 as indicated by arrows in the figure. After changing the attitude of the glass substrate 80 in this way, as shown in FIG. 11C, the glass substrate 80 is immersed again in the chemical strengthening treatment liquid for about 10 minutes (second immersion). As shown in FIG. 11 (d), the glass substrate 80 that has been subjected to the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes, and then FIG. 8 (e). As shown in FIG.
　こうすれば、図１２（ａ）に示すように、１回目の浸漬で、ガラス基板８０の中心を通る線対称にガラス基板８０の表面形状が歪に変化したものが、図１２（ｂ）に示すように、２回目の浸漬で、化学強化処理液中のガラス基板８０の姿勢がガラス基板８０の中心に関して９０°変わったため、これらが相まって、図１２（ｃ）に示すように、ガラス基板８０の表面の部位ごとに異なる形状変化が打ち消されることとなる。その結果、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量が０．５μｍ以下となる。 In this way, as shown in FIG. 12A, the surface shape of the glass substrate 80 is changed into strain symmetrically through the center of the glass substrate 80 by the first immersion, as shown in FIG. As shown in FIG. 12C, since the orientation of the glass substrate 80 in the chemical strengthening treatment solution changed by 90 ° with respect to the center of the glass substrate 80 by the second immersion, these are combined, and as shown in FIG. Different shape changes will be canceled for each part of the surface. As a result, the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 μm or less.
　なお、この例は、ガラス基板の表面形状がガラス基板の中心を通る線対称に変化する場合、つまりガラス基板の１８０°対向する所定の２箇所においてガラス基板の表面形状が変化する場合である。これに限らず、例えば、ガラス基板の表面形状が所定の１箇所のみにおいて変化するような場合は、ガラス基板を９０°より小さい角度で少しずつ回転して、その都度、ガラス基板を化学強化処理液中に浸漬すればよい（例えば全部で３回以上の複数回の浸漬を行う）。 In addition, this example is a case where the surface shape of the glass substrate changes in line symmetry passing through the center of the glass substrate, that is, the surface shape of the glass substrate changes at two predetermined positions facing the glass substrate at 180 °. For example, when the surface shape of the glass substrate changes only at a predetermined position, the glass substrate is rotated little by little at an angle smaller than 90 °, and each time the glass substrate is chemically strengthened. What is necessary is just to immerse in a liquid (for example, to immerse several times in total 3 times or more).
　この周方向のＴＩＲ増加量を０．５μｍ以下とする具体的方法の１は、化学強化処理によるガラス基板の形状変化を予め把握しておき、その形状変化に応じて、その形状変化を打ち消すように、化学強化処理を複数回に分けて行うことを趣旨とするものである。 One of the specific methods for setting the amount of increase in TIR in the circumferential direction to 0.5 μm or less is to grasp in advance the shape change of the glass substrate due to the chemical strengthening treatment, and to cancel the shape change according to the shape change. Furthermore, the purpose is to perform the chemical strengthening process in a plurality of times.
　なお、可能であれば、ガラス基板８０を処理液槽５０から取り出さずに、化学強化処理液中に浸漬したまま、姿勢を変えてもよい。 If possible, the posture may be changed while the glass substrate 80 is immersed in the chemical strengthening treatment liquid without being taken out of the treatment liquid tank 50.
　（具体的方法の２）
　化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量を０．５μｍ以下とする２つ目の具体的方法としては、化学強化工程において、化学強化処理液の温度分布を均一化することが挙げられる。 (Specific method 2)
As a second specific method of setting the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step to 0.5 μm or less, the temperature distribution of the chemical strengthening treatment liquid is made uniform in the chemical strengthening step. Can be mentioned.
　これによれば、ガラス基板８０を浸漬する化学強化処理液の温度バラツキが低減される。そのため、ガラス基板８０を取り巻く環境が一様となり、化学強化処理の前後におけるガラス基板８０の表面形状が均一に変化することとなって、ＴＩＲ増加量を容易に０．５μｍ以下とすることができる。 According to this, the temperature variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 μm or less. .
　例えば、図１３（ａ）に示すように、キャリア３０に保持したガラス基板８０を電気炉４０で３００℃に予熱する。図１３（ｂ）に示すように、硝酸カリウム（６０質量％）と硝酸ナトリウム（４０質量％）とを混合、溶解した化学強化処理液を処理液槽５０に用意し、ヒータ５１～５５で４００℃に加熱する。予熱したガラス基板８０を化学強化処理液中に約２０分浸漬する。このとき、複数のヒータ５１～５４を処理液槽５０の周囲に均等に配置することで、化学強化処理液の温度分布を均一化する。また、ガラス基板８０の中心部の円形穴の中に配置するヒータ５５を設けることで、ガラス基板８０に対する化学強化処理液の温度分布をより一層均一化できる。図１３（ｃ）に示すように、化学強化処理を終えたガラス基板８０を、ヒータ６１で７０℃に加温された温水槽６０に約１０分間浸漬して冷却した後、図１３（ｄ）に示すように、温水槽６０から取り出す。 For example, as shown in FIG. 13A, the glass substrate 80 held on the carrier 30 is preheated to 300 ° C. in the electric furnace 40. As shown in FIG. 13 (b), a chemical strengthening treatment liquid prepared by mixing and dissolving potassium nitrate (60 mass%) and sodium nitrate (40 mass%) is prepared in a treatment liquid tank 50, and heated at 400 ° C. with heaters 51 to 55. Heat to. The preheated glass substrate 80 is immersed in the chemical strengthening treatment liquid for about 20 minutes. At this time, by uniformly arranging the plurality of heaters 51 to 54 around the processing liquid tank 50, the temperature distribution of the chemical strengthening processing liquid is made uniform. Further, by providing the heater 55 disposed in the circular hole at the center of the glass substrate 80, the temperature distribution of the chemical strengthening treatment liquid with respect to the glass substrate 80 can be made more uniform. As shown in FIG. 13C, the glass substrate 80 after the chemical strengthening treatment is cooled by being immersed in a hot water tank 60 heated to 70 ° C. by a heater 61 for about 10 minutes. As shown in FIG.
　こうすれば、ガラス基板８０は、温度分布が均一化された化学強化処理液中に浸漬されたため、図１４（ａ）、（ｂ）に示すように、化学強化処理前後でガラス基板８０の周方向のＴＩＲが悪化することが抑制される。図１４（ａ）は、化学強化処理前のガラス基板８０の主表面８１の高低マップ、図１４（ｂ）は、この具体的方法の２による化学強化処理後のガラス基板８０の主表面８１の高低マップである。この図に示すように、化学強化処理の前後でガラス基板８０の主表面８１の平坦度が良好に維持されている。その結果、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量が０．５μｍ以下となる。 By so doing, since the glass substrate 80 is immersed in the chemical strengthening treatment liquid having a uniform temperature distribution, as shown in FIGS. 14A and 14B, the periphery of the glass substrate 80 before and after the chemical strengthening treatment is obtained. Deterioration of the direction TIR is suppressed. FIG. 14A is a height map of the main surface 81 of the glass substrate 80 before chemical strengthening treatment, and FIG. 14B is the height map of the main surface 81 of the glass substrate 80 after chemical strengthening treatment according to 2 of this specific method. High and low map. As shown in this figure, the flatness of the main surface 81 of the glass substrate 80 is well maintained before and after the chemical strengthening treatment. As a result, the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 μm or less.
　この周方向のＴＩＲ増加量を０．５μｍ以下とする具体的方法の２は、イオン交換法における化学反応の安定化を図ることを趣旨とするものである。 The second specific method of setting the increase in TIR in the circumferential direction to 0.5 μm or less is intended to stabilize the chemical reaction in the ion exchange method.
　なお、状況に応じて、ガラス基板８０の中心部の円形穴の中に配置するヒータ５５を省略してもよい。 In addition, you may abbreviate | omit the heater 55 arrange | positioned in the circular hole of the center part of the glass substrate 80 according to a condition.
　（具体的方法の３）
　化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量を０．５μｍ以下とする３つ目の具体的方法としては、化学強化工程において、化学強化処理液を攪拌することが挙げられる。 (Specific method 3)
A third specific method for setting the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step to 0.5 μm or less includes stirring the chemical strengthening treatment liquid in the chemical strengthening step. .
　これによれば、ガラス基板８０を浸漬する化学強化処理液の濃度バラツキが低減される。そのため、ガラス基板８０を取り巻く環境が一様となり、化学強化処理の前後におけるガラス基板８０の表面形状が均一に変化することとなって、ＴＩＲ増加量を容易に０．５μｍ以下とすることができる。 According to this, the concentration variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 μm or less. .
　例えば、前記図１３（ｂ）において、ガラス基板８０の中心部の円形穴の中に配置したヒータ５５を図中矢印で示すように攪拌棒のように円運動又は回転させる。 For example, in FIG. 13B, the heater 55 arranged in the circular hole at the center of the glass substrate 80 is circularly moved or rotated like a stirring bar as indicated by an arrow in the figure.
　こうすれば、ガラス基板８０は、濃度分布が均一化された化学強化処理液中に浸漬されたため、図１４（ａ）、（ｂ）に示すように、化学強化処理前後でガラス基板８０の周方向のＴＩＲが悪化することが抑制される。図１４（ａ）は、化学強化処理前のガラス基板８０の主表面８１の高低マップ、図１４（ｂ）は、この具体的方法の３による化学強化処理後のガラス基板８０の主表面８１の高低マップである。この図に示すように、化学強化処理の前後でガラス基板８０の主表面８１の平坦度が良好に維持されている。その結果、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量が０．５μｍ以下となる。 By so doing, since the glass substrate 80 is immersed in the chemical strengthening treatment liquid having a uniform concentration distribution, as shown in FIGS. 14A and 14B, the periphery of the glass substrate 80 before and after the chemical strengthening treatment is obtained. Deterioration of the direction TIR is suppressed. 14A is a height map of the main surface 81 of the glass substrate 80 before chemical strengthening treatment, and FIG. 14B is the height map of the main surface 81 of the glass substrate 80 after chemical strengthening treatment according to 3 of this specific method. High and low map. As shown in this figure, the flatness of the main surface 81 of the glass substrate 80 is well maintained before and after the chemical strengthening treatment. As a result, the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 μm or less.
　この周方向のＴＩＲ増加量を０．５μｍ以下とする具体的方法の３は、イオン交換法における化学反応の安定化を図ることを趣旨とするものである。 The third specific method of setting the amount of increase in TIR in the circumferential direction to 0.5 μm or less is intended to stabilize the chemical reaction in the ion exchange method.
　なお、状況に応じて、ガラス基板８０の中心部の円形穴の中に配置したヒータ５５に代えて、ガラス基板８０の中心部の円形穴の中に加熱機能のない攪拌棒を配置してもよい。また、ヒータ５１のみ残し、処理液槽５０の周囲に配置する複数のヒータ５２～５４を省略してもよい。また、ガラス基板８０の中心部の円形穴の中で化学強化処理液を攪拌することに限られず、ガラス基板８０の中心部の円形穴の外、つまりガラス基板８０の周囲で化学強化処理液を攪拌してもよい。また、ガラス基板８０の中心部の円形穴の中と外との両方で化学強化処理液を攪拌してもよい。 Depending on the situation, instead of the heater 55 disposed in the circular hole in the center of the glass substrate 80, a stirring rod having no heating function may be disposed in the circular hole in the center of the glass substrate 80. Good. Further, only the heater 51 may be left, and the plurality of heaters 52 to 54 disposed around the processing liquid tank 50 may be omitted. Further, the chemical strengthening treatment liquid is not limited to stirring in the circular hole in the central portion of the glass substrate 80, and the chemical strengthening treatment liquid is placed outside the circular hole in the central portion of the glass substrate 80, that is, around the glass substrate 80. You may stir. Further, the chemical strengthening treatment liquid may be stirred both inside and outside the circular hole at the center of the glass substrate 80.
　［第２ポリッシング工程］
　次に、第２ポリッシング工程では、化学強化工程後のガラス基板の両表面をさらに精密に研磨加工する。第２ポリッシング工程では、図２及び図３に示した、第１及び第２ラッピング工程で使用する両面研削機１０と類似の構成の両面研磨機を使用する。 [Second polishing step]
Next, in the second polishing step, both surfaces of the glass substrate after the chemical strengthening step are polished more precisely. In the second polishing process, a double-side polishing machine having a configuration similar to that of the double-side grinding machine 10 used in the first and second lapping processes shown in FIGS. 2 and 3 is used.
　第２ポリッシング工程では、ダイヤモンドペレット１３，１４に代えて、第１ポリッシング工程で使用するスウェードよりも軟らかい硬度６５から８０（Ａｓｋｅｒ－Ｃ）程度の軟質の研磨パッドを使用する。この研磨パッドは、例えば発泡ウレタンやスウェードを使用するのが好ましい。 In the second polishing step, instead of the diamond pellets 13 and 14, a soft polishing pad having a hardness of about 65 to 80 (Asker-C), which is softer than the suede used in the first polishing step, is used. For example, urethane foam or suede is preferably used as the polishing pad.
　研磨液としては、第１ポリッシング工程と同様の酸化セリウム等を砥粒（研磨材）として含有するスラリーを用いることができる。ただし、ガラス基板の表面をより滑らかにするために、砥粒の粒径がより細かくバラツキが少ない研磨液を用いるのが好ましい。例えば、平均粒径が４０ｎｍから７０ｎｍのコロイダルシリカを砥粒（研磨材）として水に分散させてスラリー状にしたものを研磨液として用いることが好ましい。水と砥粒との混合比率は、概ね１：９から３：７程度が好ましい。 As the polishing liquid, a slurry containing cerium oxide or the like similar to that in the first polishing step as abrasive grains (polishing material) can be used. However, in order to make the surface of the glass substrate smoother, it is preferable to use a polishing liquid having a finer grain size and less variation. For example, colloidal silica having an average particle size of 40 nm to 70 nm is preferably used as a polishing liquid in which slurry is dispersed in water as abrasive grains (abrasive). The mixing ratio of water and abrasive grains is preferably about 1: 9 to 3: 7.
　上下の定盤によるガラス基板への加重は、９０ｇ／ｃｍ２（８．８３ｋＰａ）から１１０ｇ／ｃｍ２（１０．８ｋＰａ）とするのが好ましい。また、上下の定盤の回転数は、１５ｒｐｍから３５ｒｐｍとし、上定盤の回転数を下定盤の回転数よりも３０％から４０％程度遅くするのが好ましい。 The weight applied to the glass substrate by the upper and lower surface plates is preferably 90 g / cm 2 (8.83 kPa) to 110 g / cm 2 (10.8 kPa). Further, the rotational speed of the upper and lower surface plates is preferably 15 rpm to 35 rpm, and the rotational speed of the upper surface plate is preferably about 30% to 40% slower than the rotational speed of the lower surface plate.
　第２ポリッシング工程の研磨条件を適宜調整することにより、ガラス基板の主表面の平坦度を３μｍ以下、ガラス基板の主表面の表面粗さＲａを０．１ｎｍまで小さくすることができる。 By appropriately adjusting the polishing conditions in the second polishing step, the flatness of the main surface of the glass substrate can be reduced to 3 μm or less, and the surface roughness Ra of the main surface of the glass substrate can be reduced to 0.1 nm.
　第２ポリッシング工程での研磨量は２μｍから５μｍとするのが好ましい。研磨量をこの範囲とすることにより、ガラス基板の表面に発生した微小な荒れやうねり、あるいはこれまでの工程で発生した微小なキズ痕といった微小欠陥を良好に除去することができる。 The polishing amount in the second polishing step is preferably 2 μm to 5 μm. By setting the polishing amount within this range, it is possible to satisfactorily remove minute defects such as minute roughness and undulation generated on the surface of the glass substrate, or minute scratch marks generated in the previous steps.
　このように、化学強化工程の後、ガラス基板８０の表面を研磨するポリッシング工程を含むことにより、最終のガラス基板８０の周方向のＴＩＲがより一層小さくなる。そのため、ヘッドクラッシュの発生がより一層抑制される。 Thus, by including the polishing step of polishing the surface of the glass substrate 80 after the chemical strengthening step, the TIR in the circumferential direction of the final glass substrate 80 is further reduced. Therefore, the occurrence of head crash is further suppressed.
　［洗浄工程］
　次に、洗浄工程では、第２ポリッシング工程後のガラス基板をスクラブ洗浄する。ただし、スクラブ洗浄に限られず、ポリッシング工程後のガラス基板の表面を清浄にできる洗浄方法であればいずれの洗浄方法でも構わない。 [Washing process]
Next, in the cleaning process, the glass substrate after the second polishing process is scrubbed. However, the cleaning method is not limited to scrub cleaning, and any cleaning method may be used as long as it can clean the surface of the glass substrate after the polishing process.
　スクラブ洗浄されたガラス基板に対して、必要により、超音波による洗浄及び乾燥処理が行われる。乾燥処理は、ガラス基板の表面に残る洗浄液をＩＰＡ（イソプロピルアルコール）等を用いて除去した後、ガラス基板の表面を乾燥させる処理である。例えば、スクラブ洗浄後のガラス基板に水リンス洗浄工程を２分間行ない、洗浄液の残渣を除去する。次に、ＩＰＡ洗浄工程を２分間行い、ガラス基板の表面に残る水をＩＰＡにより除去する。最後に、ＩＰＡ蒸気乾燥工程を２分間行い、ガラス基板の表面に付着している液状のＩＰＡをＩＰＡ蒸気により除去しつつ乾燥させる。 ガ ラ ス Ultrasonic cleaning and drying are performed on the scrubbed glass substrate, if necessary. The drying process is a process of drying the surface of the glass substrate after removing the cleaning liquid remaining on the surface of the glass substrate using IPA (isopropyl alcohol) or the like. For example, a water rinse cleaning process is performed on the glass substrate after scrub cleaning for 2 minutes to remove the cleaning liquid residue. Next, an IPA cleaning process is performed for 2 minutes, and water remaining on the surface of the glass substrate is removed by IPA. Finally, the IPA vapor drying step is performed for 2 minutes, and the liquid IPA adhering to the surface of the glass substrate is dried while being removed by the IPA vapor.
　ガラス基板の乾燥処理としてはこれに限定されるわけではなく、スピン乾燥、エアーナイフ乾燥等、ガラス基板の乾燥方法として一般的に知られたいずれの乾燥方法でも構わない。 The glass substrate drying process is not limited to this, and any drying method generally known as a glass substrate drying method such as spin drying or air knife drying may be used.
　［検査工程］
　次に、検査工程では、ガラス基板のキズ、割れ、異物の付着等の有無を目視にて検査する。目視では判別できない場合は、光学表面アナライザ（例えば、ＫＬＡ－ＴＥＮＣＯＬ社製の「ＯＳＡ６１００」）を用いて検査を行う。 [Inspection process]
Next, in the inspection process, the glass substrate is visually inspected for the presence or absence of scratches, cracks, foreign matters, and the like. If visual discrimination is not possible, an inspection is performed using an optical surface analyzer (for example, “OSA6100” manufactured by KLA-TENCOL).
　検査工程で良品と判別されたガラス基板は、異物等が表面に付着しないように、清浄な環境の中で、専用収納カセットに収納され、真空パックされた後、ＨＤＤ用ガラス基板として出荷される。 Glass substrates that are determined to be non-defective in the inspection process are stored in a dedicated storage cassette and vacuum packed in a clean environment so that no foreign matter adheres to the surface, and then shipped as HDD glass substrates. .
　＜ＨＤＤ用ガラス基板＞
　次に、前記のようにして製造されたＨＤＤ用ガラス基板について説明する。図１５に示すように、本実施形態に係るＨＤＤ用ガラス基板８０は、その主表面８１において、周方向のＴＩＲが小さい値に抑えられ、周方向の表面状態の変動が抑制された、高品質のＨＤＤ用ガラス基板である。 <Glass substrate for HDD>
Next, the glass substrate for HDD manufactured as described above will be described. As shown in FIG. 15, the glass substrate 80 for HDD according to the present embodiment has a high quality in which the TIR in the circumferential direction is suppressed to a small value on the main surface 81 and the fluctuation of the surface state in the circumferential direction is suppressed. This is a glass substrate for HDD.
　＜ＨＤＤ用磁気記録媒体＞
　次に、前記ＨＤＤ用ガラス基板８０を用いて製造されたＨＤＤ用磁気記録媒体について説明する。本実施形態に係るＨＤＤ用磁気記録媒体は、前記ＨＤＤ用ガラス基板８０の主表面８１の上に記録層としての磁性膜が設けられたことにより製造されたものである。磁性膜は主表面８１の上に直接に又は間接に形成されてよい。磁性膜はガラス基板８０の片面に又は両面に形成されてよい。 <Magnetic recording medium for HDD>
Next, an HDD magnetic recording medium manufactured using the HDD glass substrate 80 will be described. The HDD magnetic recording medium according to the present embodiment is manufactured by providing a magnetic film as a recording layer on the main surface 81 of the HDD glass substrate 80. The magnetic film may be formed directly or indirectly on the main surface 81. The magnetic film may be formed on one side or both sides of the glass substrate 80.
　磁性膜の形成方法としては従来公知の方法を用いることができ、例えば磁性粒子を分散させた熱硬化性樹脂をガラス基板８０上にスピンコートして形成する方法や、スパッタリングや無電解めっきにより形成する方法等が挙げられる。スピンコート法での膜厚は約０．３μｍ～１．２μｍ程度、スパッタリング法での膜厚は０．０１μｍ～０．０８μｍ程度、無電解めっき法での膜厚は０．０１μｍ～０．１μｍ程度であり、薄膜化及び高密度化の観点からは、スパッタリング法や無電解めっき法による膜形成が好ましい。 As a method for forming the magnetic film, a conventionally known method can be used. For example, a method in which a thermosetting resin in which magnetic particles are dispersed is spin-coated on the glass substrate 80, or a method in which sputtering or electroless plating is used. And the like. The film thickness by spin coating is about 0.3 μm to 1.2 μm, the film thickness by sputtering is about 0.01 μm to 0.08 μm, and the film thickness by electroless plating is 0.01 μm to 0.1 μm. From the viewpoint of thinning and high density, film formation by sputtering or electroless plating is preferable.
　磁性膜に用いる磁性材料としては特に限定はなく、従来公知のものが使用できる。なかでも、高い保持力を得るために結晶異方性の高いＣｏを基本材料とし、残留磁束密度を調整する目的でＮｉやＣｒを加えたＣｏ系合金等が好適である。具体的には、Ｃｏを主成分とするＣｏＰｔ、ＣｏＣｒ、ＣｏＮｉ、ＣｏＮｉＣｒ、ＣｏＣｒＴａ、ＣｏＰｔＣｒ、ＣｏＮｉＰｔ、ＣｏＮｉＣｒＰｔ、ＣｏＮｉＣｒＴａ、ＣｏＣｒＰｔＴａ、ＣｏＣｒＰｔＢ、ＣｏＣｒＰｔＳｉＯ等が好ましい。 The magnetic material used for the magnetic film is not particularly limited, and conventionally known materials can be used. Among them, a Co-based alloy or the like containing Ni and Cr as the basic material for adjusting the residual magnetic flux density is preferable in order to obtain high coercive force. Specifically, CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, CoNiPt, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, CoCrPtSiO, and the like whose main component is Co are preferable.
　磁性膜は、非磁性膜（例えば、Ｃｒ、ＣｒＭｏ、ＣｒＶ等）で分割し、ノイズの低減を図った多層構成（例えば、ＣｏＰｔＣｒ／ＣｒＭｏ／ＣｏＰｔＣｒ、ＣｏＣｒＰｔＴａ／ＣｒＭｏ／ＣｏＣｒＰｔＴａ等）としてもよい。 The magnetic film may be divided into a non-magnetic film (for example, Cr, CrMo, CrV, etc.) and may have a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa, etc.) designed to reduce noise.
　前記磁性材料の他、フェライト系や鉄－希土類系のものや、ＳｉＯ２、ＢＮ等からなる非磁性膜中に、Ｆｅ、Ｃｏ、ＦｅＣｏ、ＣｏＮｉＰｔ等の磁性粒子を分散させた構造のグラニュラー等でもよい。 In addition to the magnetic material, a ferrite type or iron-rare earth type, a granular material having a structure in which magnetic particles such as Fe, Co, FeCo, and CoNiPt are dispersed in a nonmagnetic film made of SiO 2 , BN, etc. Good.
　磁性膜は、内面型及び垂直型のいずれの記録形式であってもよい。 The magnetic film may be either an internal type or a vertical type recording format.
　磁気ヘッドの滑りをよくするために磁性膜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、例えば液体潤滑剤であるパーフロロポリエーテル（ＰＦＰＥ）をフレオン系等の溶媒で希釈したもの等が挙げられる。 ¡In order to improve the sliding of the magnetic head, a lubricant may be thinly coated on the surface of the magnetic film. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.
　本実施形態では、必要に応じて、記録層としての磁性膜の他に、下地層や保護層を設けてもよい。ＨＤＤ用磁気記録媒体における下地層は磁性膜に応じて選択される。下地層の材料としては、例えば、Ｃｒ、Ｍｏ、Ｔａ、Ｔｉ、Ｗ、Ｖ、Ｂ、Ａｌ、Ｎｉ等の非磁性金属からなる群より選ばれる少なくとも一種以上の材料が挙げられる。Ｃｏを主成分とする磁性膜の場合は、磁気特性の向上等の観点から、Ｃｒ単体やＣｒ合金であることが好ましい。下地層は単層とは限らず、同一又は異種の層を積層した複数層構造としても構わない。例えば、Ｃｒ／Ｃｒ、Ｃｒ／ＣｒＭｏ、Ｃｒ／ＣｒＶ、ＮｉＡｌ／Ｃｒ、ＮｉＡｌ／ＣｒＭｏ、ＮｉＡｌ／ＣｒＶ等の多層下地層とすることができる。 In this embodiment, if necessary, an underlayer or a protective layer may be provided in addition to the magnetic film as the recording layer. The underlayer in the HDD magnetic recording medium is selected according to the magnetic film. Examples of the material for the underlayer include at least one material selected from the group consisting of nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni. In the case of a magnetic film containing Co as a main component, it is preferable to use Cr alone or a Cr alloy from the viewpoint of improving magnetic characteristics. The underlayer is not limited to a single layer, and may have a multi-layer 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 can be used.
　保護層は、磁性膜の摩耗や腐食を防止するために設けられる。保護層としては、例えば、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、シリカ層等が挙げられる。これらの保護層は、下地層や磁性膜等と共に、インライン型スパッタ装置で連続して形成できる。また、これらの保護層は、単層としてもよく、あるいは、同一又は異種の層からなる多層構造としてもよい。 The protective layer is provided to prevent wear and corrosion of the magnetic film. Examples of the protective layer 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 continuously formed by an in-line sputtering apparatus together with the underlayer and the magnetic film. Further, these protective layers may be a single layer, or may have a multilayer structure composed of the same or different layers.
　前記保護層上に、あるいは前記保護層に代えて、他の保護層を形成してもよい。例えば、前記保護層に代えて、Ｃｒ層の上にテトラアルコキシ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、さらに焼成することにより、二酸化ケイ素（ＳｉＯ２）層を形成してもよい。 Another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, colloidal silica fine particles are dispersed and applied in a tetraalkoxysilane diluted with an alcohol solvent on the Cr layer, and further baked to obtain silicon dioxide (SiO 2 ). A layer may be formed.
　以上のように、基板として本実施形態に係るＨＤＤ用ガラス基板８０を用いて製造されたＨＤＤ用磁気記録媒体をＨＤＤに用いることで、ＨＤＤの高速回転時の磁気ヘッドの動作を安定にすることができる。 As described above, by using the HDD magnetic recording medium manufactured using the HDD glass substrate 80 according to the present embodiment as the substrate, the operation of the magnetic head at the time of high-speed rotation of the HDD can be stabilized. Can do.
　また、本実施形態に係るＨＤＤ用ガラス基板８０を用いて製造されたＨＤＤ用磁気記録媒体によれば、周方向のＴＩＲが小さい値に抑えられ、周方向の表面状態の変動が抑制されたＨＤＤ用ガラス基板８０が用いられているから、ヘッドクラッシュの発生が抑制された高品質のＨＤＤ用磁気記録媒体である。 Further, according to the HDD magnetic recording medium manufactured using the HDD glass substrate 80 according to the present embodiment, the TIR in the circumferential direction is suppressed to a small value, and fluctuations in the surface state in the circumferential direction are suppressed. Since the glass substrate 80 is used, it is a high quality HDD magnetic recording medium in which the occurrence of head crashes is suppressed.
　本実施形態においては、ＨＤＤ用ガラス基板８０を用いて製造されたＨＤＤ用磁気記録媒体は、ハードディスクドライブに装填されたときの回転数が７０００ｒｐｍ以上であることが好ましい。 In the present embodiment, the HDD magnetic recording medium manufactured using the HDD glass substrate 80 preferably has a rotational speed of 7000 rpm or more when loaded in the hard disk drive.
　これによれば、７０００ｒｐｍ以上の高速で回転されても磁気ヘッドの追従不良によるヘッドクラッシュが起き難い高品質のＨＤＤ用磁気記録媒体が実現することになる。 According to this, it is possible to realize a high-quality HDD magnetic recording medium that is less likely to cause head crash due to poor tracking of the magnetic head even when rotated at a high speed of 7000 rpm or more.
　なお、本実施形態では、ラッピング工程及びポリッシング工程は、２回に分けて行ったが、これに限らず、１回のみ行ってもよい。また、化学強化工程を第２ポリッシング工程の前に行ったが、状況に応じて第２ポリッシング工程の後に行ってもよい。 In the present embodiment, the lapping process and the polishing process are performed in two steps. However, the present invention is not limited to this and may be performed only once. Moreover, although the chemical strengthening process was performed before the second polishing process, it may be performed after the second polishing process depending on the situation.
　さらに、落下強度対策として、ガラス基板の主表面以外の外周端面や内周端面の強化を行ってもよいし、ガラス基板に生じたキズのエッジ緩和処理として、ガラス基板をＨＦ浸漬処理に供してもよい。 Furthermore, as measures against drop strength, the outer peripheral end face and the inner peripheral end face other than the main surface of the glass substrate may be strengthened, or the glass substrate is subjected to HF immersion treatment as an edge mitigation treatment for scratches generated on the glass substrate. Also good.
　本実施形態に係るＨＤＤ用ガラス基板は、ＨＤＤ用磁気記録媒体の製造用途に限定されるものではなく、例えば、光磁気ディスクや光ディスク等の製造用途にも用いることができる。 The glass substrate for HDD according to the present embodiment is not limited to the use for manufacturing the magnetic recording medium for HDD, and can be used for the manufacture of, for example, a magneto-optical disk or an optical disk.
　本実施形態の技術的特徴をまとめると下記のようになる。 The technical features of this embodiment are summarized as follows.
　本実施形態に係るＨＤＤ用ガラス基板の製造方法は、ガラス基板８０を化学強化処理液に浸漬することによりガラス基板８０に化学強化処理を施す化学強化工程を含むＨＤＤ用ガラス基板の製造方法であって、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量を０．５μｍ以下とすることを特徴とする。 The method for manufacturing a glass substrate for HDD according to the present embodiment is a method for manufacturing a glass substrate for HDD that includes a chemical strengthening step in which the glass substrate 80 is subjected to a chemical strengthening treatment by immersing the glass substrate 80 in a chemical strengthening treatment solution. The increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 μm or less.
　本実施形態によれば、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量が０．５μｍ以下であるから、化学強化処理によるガラス基板８０の周方向のＴＩＲの悪化が極めて限定的となる。そのため、化学強化工程後のガラス基板８０の周方向のＴＩＲが小さい値に抑えられ、ガラス基板８０の周方向の表面状態の変動が抑制されて、ヘッドクラッシュの発生が抑制される。 According to this embodiment, since the amount of increase in the TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.5 μm or less, the deterioration of the TIR in the circumferential direction of the glass substrate 80 due to the chemical strengthening treatment is extremely limited. It becomes the target. Therefore, the TIR in the circumferential direction of the glass substrate 80 after the chemical strengthening step is suppressed to a small value, the variation in the surface state in the circumferential direction of the glass substrate 80 is suppressed, and the occurrence of head crashes is suppressed.
　本実施形態においては、化学強化工程の前後におけるガラス基板８０の周方向のＴＩＲの増加量を０．３μｍ以下とすることが好ましい。 In the present embodiment, it is preferable that the amount of increase in TIR in the circumferential direction of the glass substrate 80 before and after the chemical strengthening step is 0.3 μm or less.
　本実施形態によれば、化学強化処理によるガラス基板８０の周方向のＴＩＲの悪化がより一層限定的となる。そのため、ヘッドクラッシュの発生がより一層抑制される。 According to the present embodiment, the deterioration of the TIR in the circumferential direction of the glass substrate 80 due to the chemical strengthening process is further limited. Therefore, the occurrence of head crash is further suppressed.
　本実施形態においては、化学強化工程では、化学強化処理液に浸漬されているガラス基板８０の化学強化処理液中の姿勢を変えることにより、ＴＩＲの増加量を０．５μｍ以下とする。 In the present embodiment, in the chemical strengthening step, the amount of increase in TIR is set to 0.5 μm or less by changing the posture of the glass substrate 80 immersed in the chemical strengthening processing solution in the chemical strengthening processing solution.
　本実施形態によれば、ガラス基板８０の姿勢を変えない場合に生じ得る、ガラス基板８０の表面の部位ごとに異なる形状変化が、ガラス基板８０の姿勢を変えることによって打ち消される。そのため、化学強化処理の前後におけるガラス基板８０の表面形状が均一に変化することとなって、ＴＩＲ増加量を容易に０．５μｍ以下とすることができる。 According to the present embodiment, the shape change that is different for each part of the surface of the glass substrate 80 that may occur when the posture of the glass substrate 80 is not changed is canceled by changing the posture of the glass substrate 80. Therefore, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 μm or less.
　本実施形態においては、化学強化工程では、化学強化処理液の温度分布を均一化することにより、ＴＩＲの増加量を０．５μｍ以下とする。 In the present embodiment, in the chemical strengthening step, the increase in TIR is set to 0.5 μm or less by uniformizing the temperature distribution of the chemical strengthening treatment liquid.
　本実施形態によれば、ガラス基板８０を浸漬する化学強化処理液の温度バラツキが低減される。そのため、ガラス基板８０を取り巻く環境が一様となり、化学強化処理の前後におけるガラス基板８０の表面形状が均一に変化することとなって、ＴＩＲ増加量を容易に０．５μｍ以下とすることができる。 According to this embodiment, the temperature variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 μm or less. .
　本実施形態においては、化学強化工程では、化学強化処理液を攪拌することにより、ＴＩＲの増加量を０．５μｍ以下とする。 In this embodiment, in the chemical strengthening step, the amount of increase in TIR is set to 0.5 μm or less by stirring the chemical strengthening treatment liquid.
　本実施形態によれば、ガラス基板８０を浸漬する化学強化処理液の濃度バラツキが低減される。そのため、ガラス基板８０を取り巻く環境が一様となり、化学強化処理の前後におけるガラス基板８０の表面形状が均一に変化することとなって、ＴＩＲ増加量を容易に０．５μｍ以下とすることができる。 According to the present embodiment, the concentration variation of the chemical strengthening treatment liquid in which the glass substrate 80 is immersed is reduced. Therefore, the environment surrounding the glass substrate 80 becomes uniform, the surface shape of the glass substrate 80 before and after the chemical strengthening process changes uniformly, and the TIR increase amount can be easily reduced to 0.5 μm or less. .
　本実施形態においては、化学強化工程の後、ガラス基板８０の表面を研磨するポリッシング工程（第２ポリッシング工程）を含む。 The present embodiment includes a polishing step (second polishing step) for polishing the surface of the glass substrate 80 after the chemical strengthening step.
　本実施形態によれば、最終のガラス基板８０の周方向のＴＩＲがより一層小さくなる。そのため、ヘッドクラッシュの発生がより一層抑制される。 According to this embodiment, the TIR in the circumferential direction of the final glass substrate 80 is further reduced. Therefore, the occurrence of head crash is further suppressed.
　本実施形態においては、ガラス基板８０の周方向のＴＩＲは、ガラス基板８０の半径をＲとしたときに、ガラス基板８０の中心から０．７５Ｒの位置における周方向のＴＩＲである。 In this embodiment, the TIR in the circumferential direction of the glass substrate 80 is the TIR in the circumferential direction at a position of 0.75R from the center of the glass substrate 80, where R is the radius of the glass substrate 80.
　本実施形態によれば、ガラス基板８０の主表面８１の外周端部及び内周端部を含めた主表面８１の全部、ないし記録媒体の記録領域の外周端部及び内周端部を含めた記録領域の全部において、周方向のＴＩＲの悪化が極めて限定的となり、ヘッドクラッシュの発生が広範囲に亘って抑制される。 According to the present embodiment, the entire main surface 81 including the outer peripheral end and the inner peripheral end of the main surface 81 of the glass substrate 80, or the outer peripheral end and the inner peripheral end of the recording area of the recording medium are included. In the entire recording area, the deterioration of the TIR in the circumferential direction becomes extremely limited, and the occurrence of head crashes is suppressed over a wide range.
　本実施形態に係るＨＤＤ用ガラス基板８０は、前記ＨＤＤ用ガラス基板の製造方法により製造されたことを特徴とする。 The glass substrate 80 for HDD according to this embodiment is manufactured by the method for manufacturing the glass substrate for HDD.
　本実施形態によれば、周方向のＴＩＲが小さい値に抑えられ、周方向の表面状態の変動が抑制された、高品質のＨＤＤ用ガラス基板８０が得られる。 According to the present embodiment, the high-quality HDD glass substrate 80 is obtained in which the TIR in the circumferential direction is suppressed to a small value, and the fluctuation of the surface state in the circumferential direction is suppressed.
　本実施形態に係るＨＤＤ用磁気記録媒体は、前記ＨＤＤ用ガラス基板８０の主表面８１の上に記録層が設けられたことにより製造されたことを特徴とする。 The HDD magnetic recording medium according to this embodiment is manufactured by providing a recording layer on the main surface 81 of the HDD glass substrate 80.
　本実施形態によれば、周方向のＴＩＲが小さい値に抑えられ、周方向の表面状態の変動が抑制されたＨＤＤ用ガラス基板８０が用いられているから、ヘッドクラッシュの発生が抑制された高品質のＨＤＤ用磁気記録媒体が得られる。 According to the present embodiment, since the HDD glass substrate 80 in which the circumferential TIR is suppressed to a small value and the fluctuation of the surface state in the circumferential direction is suppressed, the occurrence of head crashes is suppressed. A quality HDD magnetic recording medium is obtained.
　本実施形態に係るＨＤＤ用磁気記録媒体は、回転数が７０００ｒｐｍ以上のハードディスクドライブに用いられるものであることが好ましい。 The magnetic recording medium for HDD according to the present embodiment is preferably used for a hard disk drive having a rotational speed of 7000 rpm or more.
　本実施形態によれば、７０００ｒｐｍ以上の高速で回転されても磁気ヘッドの追従不良によるヘッドクラッシュが起き難い高品質のＨＤＤ用磁気記録媒体が得られる。 According to the present embodiment, it is possible to obtain a high-quality HDD magnetic recording medium that is less likely to cause head crash due to poor tracking of the magnetic head even when rotated at a high speed of 7000 rpm or higher.
　本実施形態によれば、記録媒体の表面に対する磁気ヘッドの追従不良によるヘッドクラッシュの発生が抑制されるＨＤＤ用ガラス基板８０の製造方法、その製造方法により製造されたＨＤＤ用ガラス基板８０、及びそのＨＤＤ用ガラス基板８０を用いたＨＤＤ用磁気記録媒体が提供されるから、ＤＦＨヘッド機構に対応でき、昨今の高密度記録化に寄与できる。 According to the present embodiment, a method for manufacturing an HDD glass substrate 80 in which the occurrence of a head crash due to a poor tracking of a magnetic head with respect to the surface of a recording medium is suppressed, an HDD glass substrate 80 manufactured by the manufacturing method, and its Since an HDD magnetic recording medium using the HDD glass substrate 80 is provided, it can be applied to the DFH head mechanism and can contribute to the recent high-density recording.
　以下、実施例及び比較例を通して、本発明をさらに詳しく説明する。ただし、本発明はこの実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail through examples and comparative examples. However, the present invention is not limited to this embodiment.
　＜ＨＤＤ用ガラス基板の製造＞
　図１の製造工程に従って、ＨＤＤ用ガラス基板を製造した。 <Manufacture of glass substrates for HDD>
The glass substrate for HDD was manufactured according to the manufacturing process of FIG.
　［１．ガラス溶融工程、成形工程］
　ガラス素材として、Ｔｇが４８０℃のアルミノシリケートガラスを用い、溶融したガラス素材をプレス成形して、外径が６８ｍｍ、厚みが０．９３ｍｍの円板状のガラス基板（ブランク）を作製した。 [1. Glass melting process, molding process]
An aluminosilicate glass having a Tg of 480 ° C. was used as the glass material, and the molten glass material was press-molded to produce a disk-shaped glass substrate (blank) having an outer diameter of 68 mm and a thickness of 0.93 mm.
　［２．熱処理工程］
　外形が７０ｍｍ、厚みが２ｍｍ、材質がアルミナのセッターとガラス基板とを交互に積層し、約４３０℃に設定された高温の電気炉を２時間かけて通過させることにより、ガラス基板の反りや内部応力を低減させた。 [2. Heat treatment process]
By alternately laminating setters and glass substrates with an outer shape of 70 mm, a thickness of 2 mm, and a material of alumina, and passing them through a high-temperature electric furnace set at about 430 ° C. over 2 hours, Stress was reduced.
　［３．第１ラッピング工程］
　ガラス基板の両表面を両面研削機（ＨＡＭＡＩ社製）を用いて研削加工した。研削条件として、ダイヤモンドペレットは＃１２００メッシュのものを用い、加重は１００ｇ／ｃｍ２（９．８１ｋＰａ）とし、上定盤の回転数は２０ｒｐｍとし、下定盤の回転数は３０ｒｐｍとした。 [3. First wrapping step]
Both surfaces of the glass substrate were ground using a double-side grinding machine (manufactured by HAMAI). As grinding conditions, diamond pellets of # 1200 mesh were used, the load was 100 g / cm 2 (9.81 kPa), the upper platen was rotated at 20 rpm, and the lower platen was rotated at 30 rpm.
　［４．コアリング加工工程］
　ダイヤモンド砥石を備えた円筒状のコアドリルを用いてガラス基板の中心部に直径が１８ｍｍの円形の穴を開けた。 [4. Coring process]
Using a cylindrical core drill equipped with a diamond grindstone, a circular hole having a diameter of 18 mm was formed in the center of the glass substrate.
　［５．内・外径加工工程］
　鼓状のダイヤモンド砥石を用いて、ガラス基板の外周端面及び内周端面を、外径６５ｍｍ、内径２０ｍｍに内・外径加工した。 [5. Inner / outer diameter machining process]
Using a drum-shaped diamond grindstone, the outer peripheral end surface and the inner peripheral end surface of the glass substrate were processed to have an inner diameter and an outer diameter of 65 mm and an inner diameter of 20 mm.
　［６．第２ラッピング工程］
　ガラス基板の両表面を両面研削機（ＨＡＭＡＩ社製）を用いて再び研削加工した。研削条件として、ダイヤモンドペレットは＃１７００メッシュのものを用い、加重は１００ｇ／ｃｍ２（９．８１ｋＰａ）とし、上定盤の回転数は２０ｒｐｍとし、下定盤の回転数は３０ｒｐｍとした。 [6. Second wrapping step]
Both surfaces of the glass substrate were ground again using a double-side grinding machine (manufactured by HAMAI). As grinding conditions, diamond pellets of # 1700 mesh were used, the load was 100 g / cm 2 (9.81 kPa), the upper platen was rotated at 20 rpm, and the lower platen was rotated at 30 rpm.
　第１及び第２ラッピング工程の合計の研削量は０．１ｍｍとした。その結果、ガラス基板の厚みは０．８３ｍｍとなった。 The total grinding amount in the first and second lapping steps was 0.1 mm. As a result, the thickness of the glass substrate was 0.83 mm.
　［７．端面研磨加工工程］
　ガラス基板を１００枚重ね、この状態で、ガラス基板の外周端面及び内周端面を、端面研磨機を用いて研磨加工した。研磨機のブラシ毛として、直径が０．２ｍｍのナイロン繊維を用いた。研磨液は、平均粒径が３μｍの酸化セリウムを砥粒（研磨材）として含有するスラリーを用いた。 [7. End polishing process]
100 glass substrates were stacked, and in this state, the outer peripheral end surface and the inner peripheral end surface of the glass substrate were polished using an end surface polishing machine. Nylon fiber having a diameter of 0.2 mm was used as the brush hair of the polishing machine. As the polishing liquid, a slurry containing cerium oxide having an average particle diameter of 3 μm as abrasive grains (abrasive material) was used.
　［８．第１ポリッシング工程］
　ガラス基板の両表面を図４から図６に示したようなオスカー研磨機を用いて周方向に研磨加工した。得られたガラス基板の周方向のＴＩＲ（化学強化工程前の周方向ＴＩＲ）は０．７μｍであった（表１参照）。このＴＩＲの値は、ガラス基板の半径をＲとしたときに、ガラス基板の中心から０．７５Ｒの位置における周方向のＴＩＲの値である。 [8. First polishing step]
Both surfaces of the glass substrate were polished in the circumferential direction using an Oscar polishing machine as shown in FIGS. The TIR (circumferential direction TIR before the chemical strengthening step) in the circumferential direction of the obtained glass substrate was 0.7 μm (see Table 1). This TIR value is a TIR value in the circumferential direction at a position of 0.75R from the center of the glass substrate, where R is the radius of the glass substrate.
　［９．化学強化工程］
　比較例１，２は、図８（ａ）、（ｂ）、（ｃ）、（ｄ）を参照して説明したように化学強化処理を行った（従来の化学強化処理）。キャリアのガラス基板保持枚数は５０枚（２５枚×２列）とした。 [9. Chemical strengthening process]
In Comparative Examples 1 and 2, the chemical strengthening process was performed as described with reference to FIGS. 8A, 8B, 8C, and 8D (conventional chemical strengthening process). The number of glass substrates held by the carrier was 50 (25 × 2 rows).
　実施例１，５は、図１１（ａ）、（ｂ）、（ｃ）、（ｄ）、（ｅ）を参照して説明したように化学強化処理を行った（本発明に係る化学強化処理の具体的方法の１）。キャリアのガラス基板保持枚数は５０枚（２５枚×２列）とした。 In Examples 1 and 5, the chemical strengthening treatment was performed as described with reference to FIGS. 11 (a), (b), (c), (d), and (e) (the chemical strengthening treatment according to the present invention). Specific method 1). The number of glass substrates held by the carrier was 50 (25 × 2 rows).
　実施例２，６は、図１３（ａ）、（ｂ）、（ｃ）、（ｄ）を参照して説明したように化学強化処理を行った（本発明に係る化学強化処理の具体的方法の２）。キャリアのガラス基板保持枚数は５０枚（２５枚×２列）とした。 In Examples 2 and 6, the chemical strengthening process was performed as described with reference to FIGS. 13A, 13B, 13C, and 13D (a specific method of the chemical strengthening process according to the present invention). 2). The number of glass substrates held by the carrier was 50 (25 × 2 rows).
　実施例３，７は、図１３（ａ）、（ｂ）、（ｃ）、（ｄ）を参照して説明したように化学強化処理を行った（本発明に係る化学強化処理の具体的方法の３）。キャリアのガラス基板保持枚数は５０枚（２５枚×２列）とした。ただし、図１３（ｂ）において、ヒータ５１のみ残し、処理液槽５０の周囲に配置する複数のヒータ５２～５４は省略した。また、ガラス基板８０の中心部の円形穴の中には、ヒータ５５ではなく、加熱機能のない攪拌棒を配置した。攪拌棒の回転数は６０ｒｐｍとした。 In Examples 3 and 7, the chemical strengthening process was performed as described with reference to FIGS. 13A, 13B, 13C, and 13D (a specific method of the chemical strengthening process according to the present invention). 3). The number of glass substrates held by the carrier was 50 (25 × 2 rows). However, in FIG. 13B, only the heater 51 is left, and the plurality of heaters 52 to 54 arranged around the processing liquid tank 50 are omitted. In addition, in the circular hole at the center of the glass substrate 80, not the heater 55 but a stirring rod having no heating function was disposed. The rotation speed of the stirring rod was 60 rpm.
　実施例４，８は、図１３（ａ）、（ｂ）、（ｃ）、（ｄ）を参照して説明したように化学強化処理を行った（本発明に係る化学強化処理の具体的方法の２と３の組み合わせ）。キャリアのガラス基板保持枚数は５０枚（２５枚×２列）とした。ただし、図１３（ｂ）において、ヒータ５１～５５を全て用いた。ヒータ５５を攪拌棒のように回転させた。回転数は６０ｒｐｍとした。 In Examples 4 and 8, the chemical strengthening treatment was performed as described with reference to FIGS. 13A, 13B, 13C, and 13D (a specific method of the chemical strengthening treatment according to the present invention). Combination of 2 and 3). The number of glass substrates held by the carrier was 50 (25 × 2 rows). However, in FIG. 13B, all the heaters 51 to 55 are used. The heater 55 was rotated like a stirring rod. The rotation speed was 60 rpm.
　［１０．第２ポリッシング工程］
　比較例２、実施例５～８のみ第２ポリッシング工程を行った。すなわち、ガラス基板の両表面を両面研磨機（ＨＡＭＡＩ社製）を用いてさらに精密に研磨加工した。研磨条件として、研磨パッドは、硬度がＡｓｋｅｒ－Ｃで７０度の発泡ウレタン製のものを用い、研磨液は、平均粒径が６０ｎｍのコロイダルシリカを砥粒（研磨材）として水に分散させてスラリー状にしたものを用い、水と砥粒との混合比率は、２：８とした。また、加重は９０ｇ／ｃｍ２（８．８３ｋＰａ）とし、上定盤の回転数は２０ｒｐｍとし、下定盤の回転数は３０ｒｐｍとした。 [10. Second polishing step]
The second polishing process was performed only in Comparative Example 2 and Examples 5 to 8. That is, both surfaces of the glass substrate were polished more precisely using a double-side polishing machine (manufactured by HAMAI). As polishing conditions, a polishing pad made of urethane foam having a hardness of Asker-C and 70 degrees is used, and a polishing liquid is made by dispersing colloidal silica having an average particle diameter of 60 nm in water as abrasive grains (polishing material). A slurry was used, and the mixing ratio of water and abrasive grains was 2: 8. The weight was 90 g / cm 2 (8.83 kPa), the rotation speed of the upper surface plate was 20 rpm, and the rotation speed of the lower surface plate was 30 rpm.
　第１ポリッシング工程の研磨量（比較例１、実施例１～４）、又は、第１及び第２ポリッシング工程の合計の研磨量（比較例２、実施例５～８）は、いずれも３０μｍとした。その結果、最終のガラス基板の厚みは０．８ｍｍとなった。 The polishing amount in the first polishing step (Comparative Example 1, Examples 1 to 4) or the total polishing amount in the first and second polishing steps (Comparative Example 2 and Examples 5 to 8) are both 30 μm. did. As a result, the final glass substrate thickness was 0.8 mm.
　［１１．洗浄工程］
　ガラス基板をスクラブ洗浄した。洗浄液として、水酸化カリウム（ＫＯＨ）と水酸化ナトリウム（ＮａＯＨ）とを質量比で１：１に混合したものを超純水（ＤＩ水）で希釈し、洗浄能力を高めるために非イオン界面活性剤を添加して得られた液体を用いた。洗浄液の供給は、スプレー噴霧によって行った。スクラブ洗浄後、ガラス基板の表面に残る洗浄液を除去するために、水リンス洗浄工程を超音波槽で２分間行い、ＩＰＡ洗浄工程を超音波槽で２分間行い、最後に、ＩＰＡ蒸気によりガラス基板の表面を乾燥させた。 [11. Cleaning process]
The glass substrate was scrubbed. A nonionic surfactant is used to increase the cleaning ability by diluting a mixture of potassium hydroxide (KOH) and sodium hydroxide (NaOH) at a mass ratio of 1: 1 as ultra-pure water (DI water). The liquid obtained by adding the agent was used. The cleaning liquid was supplied by spraying. After scrub cleaning, in order to remove the cleaning liquid remaining on the surface of the glass substrate, a water rinse cleaning process is performed in an ultrasonic bath for 2 minutes, an IPA cleaning process is performed in an ultrasonic bath for 2 minutes, and finally the glass substrate is cleaned with IPA vapor. The surface of was dried.
　＜ＨＤＤ用磁気記録媒体の製造＞
　得られたガラス基板の主表面の上に磁性膜（記録層）を設けて磁気記録媒体（垂直型記録形式）とした。すなわち、ガラス基板側から、Ｎｉ－Ａｌからなる下地層（厚み約１００ｎｍ）、Ｃｏ－Ｃｒ－Ｐｔからなる記録層（厚み２０ｎｍ）、ＤＬＣ（Ｄｉａｍｏｎｄ　Ｌｉｋｅ　Ｃａｒｂｏｎ）からなる保護層（厚み５ｎｍ）を順次積層した。磁気記録媒体は、比較例１，２及び実施例１～８のいずれも１００枚作製した。 <Manufacture of HDD magnetic recording media>
A magnetic film (recording layer) was provided on the main surface of the obtained glass substrate to obtain a magnetic recording medium (vertical recording format). That is, from the glass substrate side, a base layer made of Ni—Al (thickness of about 100 nm), a recording layer made of Co—Cr—Pt (thickness 20 nm), and a protective layer made of DLC (Diamond Like Carbon) (thickness 5 nm) are sequentially formed. Laminated. 100 magnetic recording media were manufactured for each of Comparative Examples 1 and 2 and Examples 1 to 8.
　＜ＨＤＤ用磁気記録媒体の評価＞
　作製した磁気記録媒体のヘッド浮上特性を評価した。すなわち、磁気記録媒体を７０００ｒｐｍで回転させ、この記録媒体に対し、ＤＦＨヘッド機構の磁気ヘッドを用いて、記録媒体の表面に対する磁気ヘッドの追従不良回数（記録媒体１枚あたりの全記録領域）を記録し、下記基準で評価した。追従不良回数が多いほど、ヘッドクラッシュやリードライトエラーが起き易いと判定される。結果を表１に示す。 <Evaluation of HDD magnetic recording media>
The head flying characteristics of the produced magnetic recording medium were evaluated. That is, the magnetic recording medium is rotated at 7000 rpm, and the magnetic head of the DFH head mechanism is used for this recording medium, and the number of follow-up failures of the magnetic head to the surface of the recording medium (total recording area per recording medium) Recorded and evaluated according to the following criteria. It is determined that head crashes and read / write errors are more likely to occur as the number of follow-up failures increases. The results are shown in Table 1.
　（評価基準）
◎◎：追従不良回数が０（申し分のない最優良品）
◎：追従不良回数が１（優良品）
○：追従不良回数が２～４（良品）
△：追従不良回数が５～９（品質にバラツキはあるが使用できないことはない）
×：追従不良回数が１０以上（不良品） (Evaluation criteria)
◎◎: The number of follow-up defects is 0 (perfect quality product)
◎: Number of follow-up failures is 1 (excellent product)
○: Number of follow-up failures is 2 to 4 (good product)
Δ: Number of follow-up failures is 5 to 9 (there is a variation in quality, but it cannot be used)
×: Number of follow-up defects is 10 or more (defective product)
　表１には、化学強化工程前のガラス基板の周方向のＴＩＲ、化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量、化学強化工程後のガラス基板の周方向のＴＩＲ、及び、最終のガラス基板（比較例１及び実施例１～４では化学強化工程後のガラス基板、比較例２及び実施例５～８では第２ポリッシング工程後のガラス基板）の周方向のＴＩＲを併せて示した。これらのＴＩＲの値は、ガラス基板の半径をＲとしたときに、ガラス基板の中心から０．７５Ｒの位置における周方向のＴＩＲの値である。 Table 1 shows the TIR in the circumferential direction of the glass substrate before the chemical strengthening step, the increase in the TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step, the TIR in the circumferential direction of the glass substrate after the chemical strengthening step, and The TIR in the circumferential direction of the final glass substrate (the glass substrate after the chemical strengthening process in Comparative Example 1 and Examples 1 to 4 and the glass substrate after the second polishing process in Comparative Examples 2 and 5 to 8) is also shown. Indicated. These TIR values are the TIR values in the circumferential direction at a position of 0.75R from the center of the glass substrate, where R is the radius of the glass substrate.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　＜結果の考察＞
　従来の化学強化処理を行った比較例１，２は、化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量が０．５μｍを超えており（０．７μｍ）、ヘッド浮上特性に劣っていた。 <Consideration of results>
In Comparative Examples 1 and 2 where the conventional chemical strengthening treatment was performed, the increase in TIR in the circumferential direction of the glass substrate before and after the chemical strengthening process exceeded 0.5 μm (0.7 μm), and the head flying characteristics were inferior. It was.
　本発明に係る化学強化処理の具体的方法の１を行った実施例１，５は、化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量が０．３μｍ以下であり（０．３μｍ）、ヘッド浮上特性により一層優れていた。 In Examples 1 and 5 in which the specific method 1 of the chemical strengthening treatment according to the present invention was performed, the increase in TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step was 0.3 μm or less (0.3 μm). ), The head flying characteristics were more excellent.
　本発明に係る化学強化処理の具体的方法の２を行った実施例２，６は、化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量が０．３μｍ以下であり（０．３μｍ）、ヘッド浮上特性により一層優れていた。 In Examples 2 and 6 in which the specific method 2 of the chemical strengthening treatment according to the present invention was performed, the increase in TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step was 0.3 μm or less (0.3 μm). ), The head flying characteristics were more excellent.
　本発明に係る化学強化処理の具体的方法の３を行った実施例３，７は、化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量が０．５μｍ以下であり（０．５μｍ）、ヘッド浮上特性に優れていた。 In Examples 3 and 7 in which the specific method 3 of the chemical strengthening treatment according to the present invention was performed, the amount of increase in TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step was 0.5 μm or less (0.5 μm). ) Excellent head flying characteristics.
　本発明に係る化学強化処理の具体的方法の２と３とを同時に行った実施例４，８は、化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量が０．３μｍ以下であり（０．２μｍ）、ヘッド浮上特性により一層優れていた。 In Examples 4 and 8 in which the specific methods 2 and 3 of the chemical strengthening treatment according to the present invention were performed simultaneously, the increase in TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step was 0.3 μm or less. (0.2 μm), which is more excellent in the head flying characteristics.
　化学強化工程の後、第２ポリッシング工程を行った実施例５～８と、行わなかった実施例１～４とを比べると、実施例５～８は、最終のガラス基板の周方向のＴＩＲがより一層小さくなり、ヘッド浮上特性により一層優れていた。 When Examples 5 to 8 in which the second polishing process was performed after the chemical strengthening process were compared with Examples 1 to 4 in which the second polishing process was not performed, Examples 5 to 8 had a TIR in the circumferential direction of the final glass substrate. It was even smaller and more excellent in head flying characteristics.
　この出願は、２０１１年６月３０日に出願された日本国特許出願特願２０１１－１４６２２９を基礎とするものであり、その内容は、本願に含まれるものである。 This application is based on Japanese Patent Application No. 2011-146229 filed on June 30, 2011, the contents of which are included in this application.
　本発明を表現するために、前述において図面を参照しながら実施形態を通して本発明を適切かつ十分に説明したが、当業者であれば前述の実施形態を変更及び／又は改良することは容易になし得ることであると認識すべきである。したがって、当業者が実施する変更形態又は改良形態が、請求の範囲に記載された請求項の権利範囲を離脱するレベルのものでない限り、当該変更形態又は当該改良形態は、当該請求項の権利範囲に包括されると解釈される。 In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized as gaining. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.
　本発明は、ＨＤＤ用ガラス基板の製造方法、ＨＤＤ用ガラス基板、及びＨＤＤ用磁気記録媒体の技術分野において、広範な産業上の利用可能性を有する。 The present invention has wide industrial applicability in the technical fields of a method for manufacturing a glass substrate for HDD, a glass substrate for HDD, and a magnetic recording medium for HDD.

Claims (10)

  1. 　ガラス基板を化学強化処理液に浸漬することによりガラス基板に化学強化処理を施す化学強化工程を含むＨＤＤ用ガラス基板の製造方法であって、
    　化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量を０．５μｍ以下とすることを特徴とするＨＤＤ用ガラス基板の製造方法。     A method for producing a glass substrate for HDD, comprising a chemical strengthening step of chemically strengthening a glass substrate by immersing the glass substrate in a chemical strengthening treatment liquid,
    The manufacturing method of the glass substrate for HDD characterized by making the increase amount of TIR of the circumferential direction of the glass substrate before and behind a chemical strengthening process into 0.5 micrometer or less.
  2. 　化学強化工程の前後におけるガラス基板の周方向のＴＩＲの増加量を０．３μｍ以下とすることを特徴とする請求項１に記載のＨＤＤ用ガラス基板の製造方法。 2. The method of manufacturing a glass substrate for HDD according to claim 1, wherein an increase in TIR in the circumferential direction of the glass substrate before and after the chemical strengthening step is 0.3 μm or less.
  3. 　化学強化工程では、化学強化処理液に浸漬されているガラス基板の化学強化処理液中の姿勢を変えることにより、ＴＩＲの増加量を０．５μｍ以下とすることを特徴とする請求項１に記載のＨＤＤ用ガラス基板の製造方法。 2. The increase in TIR is set to 0.5 μm or less by changing the posture of the glass substrate immersed in the chemical strengthening treatment solution in the chemical strengthening treatment solution in the chemical strengthening step. Manufacturing method of glass substrate for HDD.
  4. 　化学強化工程では、化学強化処理液の温度分布を均一化することにより、ＴＩＲの増加量を０．５μｍ以下とすることを特徴とする請求項１に記載のＨＤＤ用ガラス基板の製造方法。 The method for producing a glass substrate for HDD according to claim 1, wherein in the chemical strengthening step, the amount of increase in TIR is made 0.5 μm or less by uniformizing the temperature distribution of the chemical strengthening treatment liquid.
  5. 　化学強化工程では、化学強化処理液を攪拌することにより、ＴＩＲの増加量を０．５μｍ以下とすることを特徴とする請求項１に記載のＨＤＤ用ガラス基板の製造方法。 The method for producing a glass substrate for HDD according to claim 1, wherein in the chemical strengthening step, the amount of increase in TIR is set to 0.5 μm or less by stirring the chemical strengthening treatment liquid.
  6. 　化学強化工程の後、ガラス基板の表面を研磨するポリッシング工程を含むことを特徴とする請求項１から５のいずれか１項に記載のＨＤＤ用ガラス基板の製造方法。 The method for producing a glass substrate for HDD according to any one of claims 1 to 5, further comprising a polishing step of polishing the surface of the glass substrate after the chemical strengthening step.
  7. 　ガラス基板の周方向のＴＩＲは、ガラス基板の半径をＲとしたときに、ガラス基板の中心から０．７５Ｒの位置における周方向のＴＩＲであることを特徴とする請求項１から６のいずれか１項に記載のＨＤＤ用ガラス基板の製造方法。 7. The TIR in the circumferential direction of the glass substrate is a TIR in the circumferential direction at a position of 0.75R from the center of the glass substrate, where R is the radius of the glass substrate. The manufacturing method of the glass substrate for HDD of Claim 1.
  8. 　請求項１から７のいずれか１項に記載のＨＤＤ用ガラス基板の製造方法により製造されたことを特徴とするＨＤＤ用ガラス基板。 An HDD glass substrate manufactured by the method for manufacturing an HDD glass substrate according to any one of claims 1 to 7.
  9. 　請求項８に記載のＨＤＤ用ガラス基板の主表面の上に記録層が設けられたことにより製造されたことを特徴とするＨＤＤ用磁気記録媒体。 9. A magnetic recording medium for HDD, which is manufactured by providing a recording layer on the main surface of the glass substrate for HDD according to claim 8.
  10. 　回転数が７０００ｒｐｍ以上のハードディスクドライブに用いられるものであることを特徴とする請求項９に記載のＨＤＤ用磁気記録媒体。 The HDD magnetic recording medium according to claim 9, wherein the HDD magnetic recording medium is used for a hard disk drive having a rotational speed of 7000 rpm or more.
PCT/JP2012/004140 2011-06-30 2012-06-27 Process for producing glass substrate for hdd, glass substrate for hdd, and magnetic recording medium for hdd WO2013001797A1 (en)

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Citations (4)

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JP2007012247A (en) * 2005-06-03 2007-01-18 Hoya Corp Method of manufacturing glass substrate for magnetic disk and method of manufacturing magnetic disk
JP2008204521A (en) * 2007-02-19 2008-09-04 Hoya Corp Manufacturing method of glass substrate for magnetic disk and chemical strengthening device
WO2011096310A1 (en) * 2010-02-03 2011-08-11 コニカミノルタオプト株式会社 Glass substrate for information recording medium, method for producing glass substrate for information recording medium, and information recording medium
WO2011155132A1 (en) * 2010-06-09 2011-12-15 コニカミノルタオプト株式会社 Glass substrate, information-recording medium, and information disk device

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007012247A (en) * 2005-06-03 2007-01-18 Hoya Corp Method of manufacturing glass substrate for magnetic disk and method of manufacturing magnetic disk
JP2008204521A (en) * 2007-02-19 2008-09-04 Hoya Corp Manufacturing method of glass substrate for magnetic disk and chemical strengthening device
WO2011096310A1 (en) * 2010-02-03 2011-08-11 コニカミノルタオプト株式会社 Glass substrate for information recording medium, method for producing glass substrate for information recording medium, and information recording medium
WO2011155132A1 (en) * 2010-06-09 2011-12-15 コニカミノルタオプト株式会社 Glass substrate, information-recording medium, and information disk device

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