WO2012132073A1 - Method for manufacturing glass substrate for information recording medium, and information recording medium - Google Patents

Method for manufacturing glass substrate for information recording medium, and information recording medium Download PDF

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Publication number
WO2012132073A1
WO2012132073A1 PCT/JP2011/072949 JP2011072949W WO2012132073A1 WO 2012132073 A1 WO2012132073 A1 WO 2012132073A1 JP 2011072949 W JP2011072949 W JP 2011072949W WO 2012132073 A1 WO2012132073 A1 WO 2012132073A1
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WIPO (PCT)
Prior art keywords
glass substrate
polishing
information recording
recording medium
processing
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PCT/JP2011/072949
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French (fr)
Japanese (ja)
Inventor
隆史 小松
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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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Priority to JP2013507042A priority Critical patent/JPWO2012132073A1/en
Publication of WO2012132073A1 publication Critical patent/WO2012132073A1/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

Definitions

  • the present invention relates to a method for manufacturing a glass substrate for information recording medium and an information recording medium, and in particular, includes a method for manufacturing a glass substrate for information recording medium used for manufacturing an information recording medium, and the glass substrate for information recording medium.
  • the present invention relates to an information recording medium.
  • An information recording medium such as a magnetic disk is mounted as a hard disk on a computer or the like.
  • An information recording medium is manufactured by forming a magnetic thin film layer including a recording layer using properties such as magnetism, light, or magnetomagnetism on the surface of a substrate. As the recording layer is magnetized by the magnetic head, predetermined information is recorded on the information recording medium.
  • the recording density of information recording media is improving year by year. Accordingly, high quality is required for the quality of substrates used for information recording media.
  • an aluminum substrate has been used as a substrate for an information recording medium.
  • the recording density is improved, it is gradually being replaced by a glass substrate that is superior in smoothness and strength of the substrate surface as compared with an aluminum substrate.
  • the method for producing a glass substrate for an information recording medium has a polishing step for ensuring high surface shape accuracy.
  • a polishing step for ensuring high surface shape accuracy.
  • two or more stages of polishing processes in which slurry and polishing pads having different processing capabilities are effectively combined are applied.
  • Conventional techniques for polishing a glass substrate have been proposed in, for example, Japanese Unexamined Patent Application Publication No. 2009-154232 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2008-142851 (Patent Document 2).
  • Patent Document 1 In the technique described in Japanese Patent Application Laid-Open No. 2009-154232 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2008-142851 (Patent Document 2), impurities such as agglomerated slurry are washed by cleaning the surface of the polishing pad used in the polishing process. Can be removed periodically from the surface of the polishing pad to prevent accumulation of impurities on the surface of the polishing pad.
  • the present invention has been made in view of the above problems, and its main purpose is to suppress the accumulation of impurities on the end face of the processing tool, and to reduce the generation of scratches and deposits on the main surface of the glass substrate. It is to provide a method for producing a glass substrate for an information recording medium.
  • the method for producing a glass substrate for information recording medium is a method for producing a glass substrate for information recording medium in which a magnetic recording layer is formed on the main surface of the glass substrate, the step of forming the glass substrate, The processing surface of a processing tool having a flat processing surface for grinding or polishing the surface and an end surface forming the periphery of the processing surface is brought into contact with the main surface, and the processing tool is slid relative to the main surface. And processing the main surface.
  • the end face is inclined at an angle greater than 90 ° with respect to the work surface.
  • the end face may form an angle of 95 ° to 170 ° with respect to the processed surface.
  • a part of the main surface may protrude from the processing surface.
  • the processing step may be a final polishing step of the main surface.
  • the processing surface and end surface of the processing tool may be cleaned after processing the main surface of the glass substrate once or a plurality of times.
  • An information recording medium includes a glass substrate obtained by any one of the above-described methods for producing a glass substrate for an information recording medium, and a magnetic recording layer formed on the surface of the glass substrate.
  • impurities such as agglomerated slurry can be prevented from accumulating on the end surface of the processing tool, and the generation of scratches and deposits on the main surface of the glass substrate can be reduced. Therefore, the yield of the glass substrate can be improved.
  • FIG. 1 is a perspective view showing a glass substrate 1 used for a magnetic disk 10 (see FIG. 2).
  • FIG. 2 is a perspective view showing a magnetic disk 10 provided with a glass substrate 1 as an information recording medium.
  • a glass substrate 1 (glass substrate for information recording medium) used for a magnetic disk 10 has an annular disk shape with a hole 1H formed in the center.
  • the circular disk-shaped glass substrate 1 has a front main surface 1A, a back main surface 1B, an inner peripheral end surface 1C, and an outer peripheral end surface 1D.
  • the size of the glass substrate 1 is not particularly limited, and is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch outer diameter.
  • the thickness of the glass substrate is, for example, 0.30 to 2.2 mm from the viewpoint of preventing breakage.
  • the glass substrate has an outer diameter of about 65 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm.
  • the thickness of the glass substrate 1 is a value calculated by averaging the values measured at a plurality of arbitrary points that are point targets on the glass substrate 1.
  • the magnetic disk 10 is configured by forming a magnetic film on the front main surface 1A of the glass substrate 1 and forming a magnetic thin film layer 2 including a magnetic recording layer.
  • the magnetic thin film layer 2 is formed only on the front main surface 1A, but the magnetic thin film layer 2 may also be formed on the back main surface 1B.
  • the magnetic thin film layer 2 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the front main surface 1A of the glass substrate 1 (spin coating method).
  • the magnetic thin film layer 2 may be formed on the front main surface 1A of the glass substrate 1 by a sputtering method, an electroless plating method, or the like.
  • the film thickness of the magnetic thin film layer 2 formed on the front main surface 1A of the glass substrate 1 is about 0.3 ⁇ m to 1.2 ⁇ m in the case of the spin coating method, about 0.04 ⁇ m to 0.08 ⁇ m in the case of the sputtering method, In the case of the electroless plating method, the thickness is about 0.05 ⁇ m to 0.1 ⁇ m. From the viewpoint of thinning and high density, the magnetic thin film layer 2 is preferably formed by sputtering or electroless plating.
  • the magnetic material used for the magnetic thin film layer 2 is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Co having high crystal anisotropy is basically used for the purpose of adjusting the residual magnetic flux density. A Co-based alloy to which Ni or Cr is added is suitable. Further, as a magnetic layer material suitable for heat-assisted recording, an FePt-based material may be used.
  • a lubricant may be thinly coated on the surface of the magnetic thin film layer 2 in order to improve the sliding of the magnetic recording head.
  • the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon.
  • an underlayer or a protective layer may be provided.
  • the underlayer in the magnetic disk 10 is selected according to the magnetic film.
  • the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.
  • the underlayer 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 may be used.
  • Examples of the protective layer for preventing wear and corrosion of the magnetic thin film layer 2 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus, such as an underlayer and a magnetic film. In addition, these protective layers may be a single layer, or may have a multilayer structure including the same or different layers.
  • Another protective layer may be formed on the protective layer or instead of the protective layer.
  • a tetraalkoxysilane is diluted with an alcohol-based solvent on a Cr layer, and then colloidal silica fine particles are dispersed and applied, followed by baking to form a silicon oxide (SiO 2 ) layer. It may be formed.
  • FIG. 3 is a flowchart showing a method for manufacturing the glass substrate 1 in the embodiment.
  • the glass substrate manufacturing method in the present embodiment includes a glass blank material preparation step (step S10), a glass substrate formation step (step S20), a polishing step (step S30), a chemical strengthening step (step S40), and a cleaning step ( Step S50).
  • a magnetic thin film forming step (step S60) may be performed on the glass substrate (corresponding to the glass substrate 1 in FIG. 1) obtained through the chemical strengthening treatment step (step S40).
  • the magnetic disk 10 is obtained by the magnetic thin film forming step (step S60).
  • the glass material constituting the glass substrate is melted (step S11).
  • general aluminosilicate glass is used as the glass material.
  • the aluminosilicate glass is composed of 58 mass% to 75 mass% SiO 2 , 5 mass% to 23 mass% Al 2 O 3 , 3 mass% to 10 mass% Li 2 O, and 4 mass% to 13 mass. % Na 2 O as a main component.
  • the molten glass material is poured onto the lower mold and then press-molded with the upper mold and the lower mold (step S12).
  • a disk-shaped glass blank (glass base material) is formed by press molding.
  • the glass blank material may be formed by cutting out sheet glass (sheet glass) formed by a downdraw method or a float method with a grinding wheel. Further, the glass material is not limited to aluminosilicate glass, and may be any material.
  • step S20 a lapping process is performed on both main surfaces of the press-molded glass blank material for the purpose of improving dimensional accuracy and shape accuracy (step).
  • step S21 Both main surfaces of a glass blank material are the main surfaces used as the front main surface 1A and the main surface used as the back main surface 1B in FIG. 1 through each process mentioned later (henceforth, both main surfaces) Also called).
  • the lapping process is performed using a double-sided lapping device using a planetary gear mechanism. Specifically, the lap surface plate is pressed from above and below both main surfaces of the glass blank material, the grinding liquid is supplied onto both main surfaces, the glass blank material and the lap surface plate are moved relative to each other, and the lap surface is moved. A polishing process is performed. By the lapping process, the approximate parallelism, flatness, thickness, and the like of the glass substrate are preliminarily adjusted, and a glass base material having an approximately flat main surface is obtained.
  • the surface accuracy of both surfaces of the glass substrate is 0 ⁇ m to 1 ⁇ m, You may finish to about 6 micrometers in surface roughness Rmax.
  • a coring (inner peripheral cut) process is performed on the center portion of the glass blank using a cylindrical diamond drill or the like (step S22).
  • a coring process is performed on the center portion of the glass blank using a cylindrical diamond drill or the like.
  • a predetermined chamfering process may be performed on the hole in the center.
  • step S30 Similar to step S21 described above, lap polishing is performed on both main surfaces of the glass substrate (step S31).
  • the coring step (step S22) fine scratches and protrusions formed on both main surfaces of the glass substrate are removed.
  • the outer peripheral end surface of the glass substrate is polished into a mirror surface by a brush (step S32).
  • the abrasive grains a slurry containing cerium oxide abrasive grains is used.
  • step S31 the warp of the glass substrate is corrected while removing scratches remaining on both main surfaces of the glass substrate in the lapping polishing process (step S31) (step S33).
  • a double-side polishing device using a planetary gear mechanism is used.
  • polishing is performed using a polishing pad such as hard velor, urethane foam, or pitch-impregnated suede.
  • abrasive general cerium oxide abrasive grains are used.
  • the glass substrate is subjected to polishing again, and minute defects and the like remaining on both main surfaces of the glass substrate are eliminated (step S34). Both main surfaces of the glass substrate are finished to have a mirror-like surface to form a desired flatness, and the warp of the glass substrate is eliminated.
  • a double-side polishing device using a planetary gear mechanism is used. For example, polishing is performed using a polishing pad which is a soft polisher made of suede or velor.
  • the polishing agent general colloidal silica finer than the cerium oxide used in the first polishing step is used.
  • FIG. 4 is a partial perspective view of a double-side polishing apparatus 1000 used in the polishing process
  • FIG. 5 is a partial cross-sectional view of the polishing pads 310 and 410.
  • a double-side polishing apparatus 1000 includes an upper surface plate (upper whetstone holding surface plate) 300, a lower surface plate (lower whetstone holding surface plate) 400, and a lower surface plate 400 of the upper surface plate 300.
  • the polishing pads 310 and 410 are an example of a processing tool for polishing both main surfaces of the glass substrate 1.
  • the upper surface plate 300 and the lower surface plate 400 rotate in directions opposite to each other with respect to the revolution direction of the carrier 500.
  • Carrier 500 is arranged in a gap formed between upper surface plate 300 and lower surface plate 400.
  • the disk-shaped glass substrate 1 is held by this carrier 500.
  • FIG. 4 a lower surface plate 400 that is one surface plate among the upper surface plate 300 and the lower surface plate 400 that is a pair of surface plates that sandwich the plurality of glass substrates 1 held by the carrier 500 is illustrated.
  • the upper surface plate 300 is not shown.
  • FIG. 5 the carrier 500 and the glass substrate 1 held by the carrier 500 are not shown.
  • the polishing pad 310 has a processed surface 311 that contacts the front main surface 1 ⁇ / b> A of the glass substrate 1.
  • the processing surface 311 is one surface of the annular pad-shaped polishing pad 310.
  • the processing surface 311 extends in a planar manner, and the planar shape is formed in an annular shape. With the processed surface 311 in contact with the front main surface 1A of the glass substrate 1, the front main surface 1A is polished by sliding the polishing pad 310 relative to the front main surface 1A.
  • An end surface 312 is provided on the periphery of the processing surface 311.
  • the planar shape of the boundary 313 between the processed surface 311 and the end surface 312 is circular.
  • the end surface 312 is formed in a conical surface shape.
  • the end surface 312 is provided so as to be inclined with respect to the processing surface 311 so as to form an angle ⁇ with the processing surface 311.
  • the polishing pad 410 has a processed surface 411 that contacts the back main surface 1B of the glass substrate 1.
  • the processing surface 411 is one surface of an annular plate-shaped polishing pad 410.
  • the processing surface 411 extends in a planar manner, and the planar shape is formed in an annular shape. With the processed surface 411 in contact with the back main surface 1B of the glass substrate 1, the back main surface 1B is polished by sliding the polishing pad 410 relative to the back main surface 1B.
  • An end face 412 is provided on the periphery of the processing surface 411.
  • the planar shape of the boundary 413 between the processed surface 411 and the end surface 412 is circular.
  • the end surface 412 is formed in a conical surface shape.
  • the end surface 412 is provided to be inclined with respect to the processing surface 411 so as to form an angle ⁇ with the processing surface 411.
  • the upper surface plate 300, the lower surface plate 400, and the polishing pads 310, 410 along the line passing through the center of the circle of the upper surface plate 300, the lower surface plate 400, and the polishing pads 310, 410 having an annular plate shape.
  • the cross section of is shown.
  • the processed surface 311 and the end surface 312 form an angle ⁇ .
  • the processed surface 411 and the end surface 412 form an angle ⁇ .
  • the angle ⁇ and the angle ⁇ may be equal to each other, or may be different from each other.
  • the angle ⁇ between the processed surface 311 and the end surface 312 and the angle ⁇ between the processed surface 411 and the end surface 412 are larger than 90 °.
  • the end faces 312 and 412 are inclined at an angle larger than 90 ° with respect to the processed surfaces 311 and 411.
  • the angles ⁇ and ⁇ each have an angle of 95 ° to 170 °.
  • the end surface 312 of the polishing pad 310 forms an angle of 95 ° or more and 170 ° or less with respect to the processing surface 311.
  • the end surface 412 of the polishing pad 410 forms an angle of 95 ° or more and 170 ° or less with respect to the processing surface 411.
  • the range of the angle ⁇ is defined as an average value of the angle formed by the processed surface 311 and the end surface 312 in the radial cross section of the annular plate-shaped polishing pad 310 over the entire circumference of the circle.
  • the range of the angle ⁇ is defined as an average value of the angle formed by the processing surface 411 and the end surface 412 in the radial cross section of the annular pad-shaped polishing pad 410 over the entire circumference of the circle. That is, if the angles ⁇ and ⁇ are the average in one circle of the polishing pads 310 and 410 within the above range, the angles ⁇ and ⁇ are outside the above range in one cross section along the radial direction of the polishing pads 310 and 410. It doesn't matter.
  • the surfaces of the polishing pads 310 and 410 may be cleaned.
  • the surface of the polishing pads 310 and 410 is cleaned by a carrier brush having hairs extending in a direction substantially perpendicular to the processing surfaces 311 and 411 or a high pressure supplied in a direction substantially perpendicular to the processing surfaces 311 and 411. It may be performed using water.
  • a carrier brush having hairs extending in a direction substantially perpendicular to the processing surfaces 311 and 411 or a high pressure supplied in a direction substantially perpendicular to the processing surfaces 311 and 411. It may be performed using water.
  • processing waste, aggregated abrasive grains, etc. existing on the surfaces of the polishing pads 310 and 410 or in the polishing pads 310 and 410 in the vicinity of the surfaces, etc. Can be removed to some extent.
  • the high-pressure water may be supplied in a direction inclined with respect to the processing surfaces 311 and 411.
  • the cleaning of the surfaces of the polishing pads 310 and 410 may be performed in any step in the polishing step (step S30), may be performed in any step in the polishing step (step S30), or You may perform after completion
  • the surfaces of the polishing pads 310 and 410 may be cleaned in the double-side polishing apparatus 1000.
  • the surfaces of the polishing pads 310 and 410 (that is, the processing surfaces 311 and 411 and the end surfaces 312 and 412) may be periodically cleaned every time one or a plurality of polishings are performed, or may be cleaned irregularly. May be.
  • the chemical strengthening layer is formed on both main surfaces of the glass substrate by immersing the glass substrate in the chemical strengthening treatment liquid (step S40).
  • a chemical strengthening treatment solution such as a solution for mixing potassium nitrate (70%) and sodium nitrate (30%) heated to 300 ° C. for 30 minutes, Perform chemical strengthening.
  • the alkali metal ions such as lithium ions and sodium ions contained in the glass substrate are replaced with alkali metal ions such as potassium ions having a larger ion radius than these ions (ion exchange method).
  • Compressive stress is generated in the ion-exchanged region due to the strain caused by the difference in ion radius, and both main surfaces of the glass substrate are strengthened.
  • a chemically strengthened layer may be formed in a range from the glass substrate surface to about 5 ⁇ m to improve the rigidity of the glass substrate. As described above, a glass substrate corresponding to the glass substrate 1 shown in FIG. 1 is obtained.
  • the glass substrate 1 may be further subjected to a polishing polishing process in which the machining allowance on both main surfaces is 0.1 ⁇ m or more and 0.5 ⁇ m or less.
  • a polishing polishing process in which the machining allowance on both main surfaces is 0.1 ⁇ m or more and 0.5 ⁇ m or less.
  • a chemical strengthening step may be performed between the first polishing step (rough polishing) and the second polishing step (precision polishing).
  • the glass substrate is cleaned (step S50).
  • the deposits attached to both main surfaces of the glass substrate are removed.
  • the number of deposits on the glass substrate surface is inspected using an optical defect inspection apparatus or the like.
  • the magnetic thin film layer 2 is formed by forming a magnetic film on both main surfaces (or one of the main surfaces) of the glass substrate (corresponding to the glass substrate 1 shown in FIG. 1) that has been subjected to the chemical strengthening treatment. Is done.
  • the magnetic thin film layer includes an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a protective layer made of a C system, and a lubrication made of an F system. It is formed by sequentially depositing layers. By forming the magnetic thin film layer, a perpendicular magnetic recording disk corresponding to the magnetic disk 10 shown in FIG. 2 can be obtained.
  • the magnetic disk in the present embodiment is an example of a perpendicular magnetic disk composed of a magnetic thin film layer.
  • the magnetic disk may be composed of a magnetic layer or the like as a so-called in-plane magnetic disk.
  • FIG. 6 to 9 are diagrams showing relative movement of the glass substrate 1 with respect to the polishing pads 310 and 410 when the glass substrate 1 is polished using the double-side polishing apparatus 1000.
  • FIG. When polishing the glass substrate 1, the upper surface plate 300 and the lower surface plate 400 rotate in opposite directions. For example, when viewed from above the double-side polishing apparatus 1000, the upper surface plate 300 rotates clockwise and the lower surface plate 400 rotates counterclockwise. At this time, the carrier 500 revolves while rotating. For example, the carrier 500 rotates around the circular center formed by the carrier 500 itself while revolving clockwise or counterclockwise around the rotation axis of the upper surface plate 300 and the lower surface plate 400.
  • the relative position of the glass substrate 1 held by the carrier 500 with respect to the polishing pads 310 and 410 changes. Specifically, the glass substrate 1 moves in the radial direction of the polishing pads 310 and 410 from the state in which the entire glass substrate 1 is sandwiched between the polishing pads 310 and 410 shown in FIG. Thus, as shown in FIG. 7, a part of the glass substrate 1 passes outside the polishing pads 310 and 410.
  • a part of the front main surface 1 ⁇ / b> A of the glass substrate 1 is disposed outside the processing surface 311 of the polishing pad 310, and a part of the back main surface 1 ⁇ / b> B of the glass substrate 1 is the polishing pad 410.
  • the front main surface 1A and the back main surface 1B of the glass substrate 1 pass outside the processed surfaces 311 and 411.
  • the glass substrate 1 is subjected to a so-called “overhang rotation” in which at least a part of the glass substrate 1 extends beyond the periphery of the upper surface plate 300 and the lower surface plate 400 to the outside and passes outside the upper surface plate 300 and the lower surface plate 400.
  • a part of the front main surface 1A of the glass substrate 1 protrudes from the processing surface 311 of the polishing pad 310, and a part of the back main surface 1B protrudes from the processing surface 411 of the polishing pad 410.
  • FIG. 10 is a plan view schematically showing a state in which a part of the glass substrate 1 protrudes from the processing surface 311 of the polishing pad 310.
  • FIG. 10 shows a state in which the glass substrate 1 protrudes most from the upper surface plate 300 and the lower surface plate 400 during the polishing of the glass substrate 1.
  • the distance H between the boundary 313 between the processing surface 311 and the end surface 312 of the polishing pad 310 and the outer peripheral portion of the glass substrate 1 is the maximum length that the glass substrate 1 protrudes from the surface plate during polishing processing. And is called the overhang length.
  • an abrasive is supplied to polish the glass substrate 1.
  • slurry 600 containing abrasive grains is used as the abrasive.
  • the slurry 600 supplied to the space between the polishing pads 310 and 410 becomes the end surface of the glass substrate 1 as shown in FIGS. Or it is pushed out of the space by the end face of the carrier 500 and then returned to the space again.
  • the slurry 600 contains impurities 601 such as agglomerated slurry.
  • impurities 601 such as agglomerated slurry.
  • the impurity 601 exists in the space between the polishing pads 310 and 410.
  • the glass substrate 1 moves in the radial direction of the polishing pads 310 and 410 as the carrier 500 rotates, the impurities 601 are also pushed out of the space by the end surface of the glass substrate 1 (FIG. 7).
  • the processing surface 311 and the end surface 312 have an angle greater than 90 °, more specifically, 95 ° to 170 °. Has an angle ⁇ . Therefore, the end surface 312 is inclined with respect to the processing surface 311.
  • the processed surface 411 and the end surface 412 have an angle greater than 90 °, more specifically, an angle ⁇ of 95 ° to 170 °. Therefore, the end surface 412 is inclined with respect to the processing surface 411. Therefore, the impurity 601 pushed out of the space between the polishing pads 310 and 410 as shown in FIG. 7 travels along the end surfaces 312 and 412 as shown in FIGS. You can return to the space between.
  • impurities 601 such as agglomerated slurry are polished when the glass substrate 1 is exposed to the outside of the surface plate and then reenters the surface plate. It is wiped by the end face of the pad and left on the end face. Therefore, impurities accumulate on the end surface of the polishing pad.
  • the accumulated impurities 601 are dried on the end face, the surface of the overhanging glass substrate 1 is scratched by the impurities 601 and causes the surface of the glass substrate 1 to be scratched.
  • the impurity 601 having a high viscosity due to a decrease in moisture adheres to the surface of the glass substrate 1, causing a protrusion to be formed on the surface of the glass substrate 1.
  • the glass substrate 1 is regarded as a defective product, and the final yield of the glass substrate 1 is reduced.
  • the end faces 312 and 412 of the polishing pads 310 and 410 are not perpendicular to the processing surfaces 311 and 411, and the end faces 312 and 412 are inclined.
  • the impurities 601 are again drawn into the space between the polishing pads 310 and 410.
  • the structure is easy. This suppresses the impurities 601 from being wiped by the end faces 312 and 412 when the glass substrate 1 rotates in an overhanging manner in the polishing process, and the impurities 601 remaining on the end faces 312 and 412. Therefore, accumulation of impurities 601 such as agglomerated slurry contained in the slurry 600 on the end surfaces 312 and 412 of the polishing pads 310 and 410 can be suppressed.
  • the angle ⁇ between the processing surface 311 and the end surface 312 of the polishing pad 310 and the angle ⁇ between the processing surface 411 and the end surface 412 of the polishing pad 410 are less than 95 °, impurities 601 such as agglomerated slurry are end surfaces. Since it is easy to accumulate in 312 and 412, the angle is preferably set to 95 ° or more. Further, if the angle ⁇ and the angle ⁇ are larger than 170 °, the area of the processing surfaces 311 and 411 used for polishing among the surfaces of the polishing pads 310 and 410 is reduced and the polishing efficiency is lowered. It is preferable to do this. More preferably, the angle ⁇ and the angle ⁇ are 110 ° or more and 150 ° or less as an average of one round of the polishing pads 310 and 410.
  • the polishing pads 310 and 410 formed in advance in a predetermined shape are attached to the upper surface plate 300 and the lower surface plate 400, respectively. May be formed.
  • the double-side polishing apparatus 1000 attaches a polishing pad material covering the entire surface of the upper surface plate 300 and the lower surface plate 400 to the upper surface plate 300 and the lower surface plate 400, respectively, and cuts the periphery of the polishing pad material into a predetermined shape. By doing so, it may be formed.
  • the impurities 601 are easily drawn into the polishing pads 310 and 410 from the end surfaces 312 and 412, and are not accumulated on the end surfaces 312 and 412. Accordingly, the above-described effect of improving the flatness of the substrate can be obtained, the accumulation of the impurities 601 on the end faces 312 and 412 can be suppressed, and the yield of the glass substrate 1 can be improved.
  • the surface of the polishing pads 310 and 410 may be cleaned using a carrier brush having resin bristles such as nylon or high-pressure water having a pressure of about 7 MPa in the polishing process of the glass substrate 1. Since the end surfaces 312 and 412 of the polishing pads 310 and 410 are inclined with respect to the processing surfaces 311 and 411, even if the impurities 601 remain on the end surfaces 312 and 412 during the polishing process, a carrier brush or high-pressure water is not washed. The impurities 601 are removed from the end faces 312 and 412 in contact with the end faces 312 and 412. Therefore, accumulation of the impurities 601 on the end faces 312 and 412 can be further suppressed.
  • a carrier brush having resin bristles such as nylon or high-pressure water having a pressure of about 7 MPa in the polishing process of the glass substrate 1. Since the end surfaces 312 and 412 of the polishing pads 310 and 410 are inclined with respect to the processing surfaces 311 and 411, even if the
  • the double-side polishing apparatus 1000 described above is used for polishing the glass substrate 1 in the second polishing polishing process (precision polishing) (step S34) which is the final polishing process among the polishing processes (step S30) shown in FIG. Is desirable.
  • the quality of the final glass substrate 1 can be ensured by reducing the deposits, so that the yield of the glass substrate 1 is surely obtained. Can be improved.
  • the polishing polishing process is further performed after the chemical strengthening process (step S40)
  • the polishing process after the chemical strengthening process (step S40) is not described in the second polishing process (step S34).
  • the glass substrate 1 may be polished using the double-side polishing apparatus 1000.
  • FIG. 11 is a diagram showing an evaluation result obtained by polishing the glass substrate 1 using the double-side polishing apparatus 1000 of the example and the comparative example.
  • an annular plate-shaped glass substrate 1 having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.8 mm was prepared, and the yield rate when 100 glass substrates 1 were polished was evaluated.
  • step S33 shows the conditions of the polishing pads 310 and 410 used in the first polishing step (step S33) shown in FIG. 3, and the conditions of the polishing pads 310 and 410 used in the second polishing step (step S34). , Is described. Under any of the conditions, 100 separate glass substrates prepared by the processing up to the previous step were used, processing was performed 15 times for each experimental level, and the processing content of the 15th time was taken as an example or a comparative example.
  • the first polishing step general hard urethane polishing pads 310 and 410 were used, and the type of slurry was cerium oxide slurry having a particle size of about 1.0 ⁇ m.
  • the angle formed between the processed surfaces 311 and 411 of the polishing pads 310 and 410 and the end surfaces 312 and 412 is 90 °.
  • the polishing pads 310 and 410 in which the angle between the processing surfaces 311 and 411 and the end surfaces 312 and 412 is 135 ° and the end surfaces 312 and 412 are inclined with respect to the processing surfaces 311 and 411 are used.
  • the glass substrate 1 was processed so as not to overhang the glass substrate 1 during processing. For each polishing, the surfaces of the polishing pads 310 and 410 were cleaned with a carrier brush.
  • the second polish polishing step general suede polishing pads 310 and 410 were used, and the type of slurry was silica slurry having a particle size of about 20 nm.
  • the angle formed between the processed surfaces 311 and 411 of the polishing pads 310 and 410 and the end surfaces 312 and 412 is 90 °.
  • the angle formed between the processed surfaces 311 and 411 and the end surfaces 312 and 412 is 135 °.
  • the angle formed between the processed surfaces 311 and 411 and the end surfaces 312 and 412 is 100 °.
  • the polishing pads 310 and 410 whose end faces 312 and 412 are inclined with respect to the processing surfaces 311 and 411 are used.
  • the glass substrate 1 was overhanged during the polishing process. The overhang length at this time was 1 mm.
  • the surfaces of the polishing pads 310 and 410 were cleaned with a carrier brush.
  • the yield rate of the glass substrate 1 was evaluated by visual inspection of the surface of the glass substrate 1 using a surface inspection device SSI-640 manufactured by System Seiko Co., Ltd. using a He—Ne laser light source.
  • a surface inspection device SSI-640 manufactured by System Seiko Co., Ltd. using a He—Ne laser light source.
  • defects generated on the surface of the glass substrate 1 such as convex portions (bumps), concave portions (pits), dust (particles), and scratches (scratches) are detected.
  • a defective product was detected when the number of detected defects exceeded a predetermined threshold.
  • the end surfaces 312 and 412 of the polishing pads 310 and 410 are inclined to form the glass substrate 1.
  • a significant improvement in the yield rate was observed.
  • the glass substrate 1 is compared with Example 1. It was confirmed that the yield rate was further improved.
  • the end surfaces 312 and 412 of the polishing pads 310 and 410 form a part of a conical surface, and the processing surfaces 311 and 411 and the end surfaces 312 and 412 are between them.
  • the example in which the circular boundaries 313 and 413 are formed has been described.
  • the shape of the end faces 312 and 412 is not limited to this example.
  • the end surface may be a curved surface represented by a partial shape of a spherical surface, a partial shape of a paraboloid, or the like.
  • the tangent plane to the curved surface at the boundary between the curved surface and the machining surface forms an angle that is not perpendicular to the machining surface, and the tangent plane is an angle larger than 90 ° with respect to the machining surface, preferably 95 ° or more.
  • An angle of 170 ° or less may be formed and inclined.
  • the polishing process which is a process of smoothing both the main surfaces 1A and 1B of the glass substrate 1 using the polishing pads 310 and 410, has been described.
  • the present invention may be applied not only to the polishing process but also to a grinding process which is a machining process with an improvement in dimensional accuracy of both the main surfaces 1A and 1B of the glass substrate 1, for example.

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  • Manufacturing Of Magnetic Record Carriers (AREA)

Abstract

Provided is a method for manufacturing a glass substrate for an information recording medium, whereby the accumulation of impurities on the end surface of a machining tool can be suppressed. A method for manufacturing a glass substrate for an information recording medium in which a magnetic recording layer is formed on the main surface of a glass substrate, the method comprising the steps of: forming a glass substrate; and bringing a machined surface (311) of a polishing pad (310) in contact with the main surface, the polishing pad having the flat machined surface (311) for polishing the main surface and an end surface (312) forming the peripheral edge of the machined surface (311), and sliding the polishing pad (310) against the main surface to machine the main surface. The end surface (312) is inclined at an angle greater than 90° relative to the machined surface (311).

Description

情報記録媒体用ガラス基板の製造方法および情報記録媒体Method for manufacturing glass substrate for information recording medium and information recording medium
　本発明は、情報記録媒体用ガラス基板の製造方法および情報記録媒体に関し、特に、情報記録媒体の製造に用いられる情報記録媒体用ガラス基板の製造方法、およびその情報記録媒体用ガラス基板を備えた情報記録媒体に関する。 The present invention relates to a method for manufacturing a glass substrate for information recording medium and an information recording medium, and in particular, includes a method for manufacturing a glass substrate for information recording medium used for manufacturing an information recording medium, and the glass substrate for information recording medium. The present invention relates to an information recording medium.
　磁気ディスクなどの情報記録媒体は、コンピュータなどにハードディスクとして搭載される。情報記録媒体は、基板の表面上に、磁気、光、または光磁気などの性質を利用した記録層を含む磁気薄膜層が形成されて製造される。記録層が磁気ヘッドによって磁化されることによって、所定の情報が情報記録媒体に記録される。 An information recording medium such as a magnetic disk is mounted as a hard disk on a computer or the like. An information recording medium is manufactured by forming a magnetic thin film layer including a recording layer using properties such as magnetism, light, or magnetomagnetism on the surface of a substrate. As the recording layer is magnetized by the magnetic head, predetermined information is recorded on the information recording medium.
　情報記録媒体は年々記録密度が向上している。それに伴い情報記録媒体に使用される基板の品質にも高い品質が要求されている。情報記録媒体用の基板としては、従来アルミニウム基板が用いられてきたが、記録密度の向上に伴い、アルミニウム基板に比較して基板表面の平滑性および強度に優れるガラス基板に徐々に置き換わりつつある。 The recording density of information recording media is improving year by year. Accordingly, high quality is required for the quality of substrates used for information recording media. Conventionally, an aluminum substrate has been used as a substrate for an information recording medium. However, as the recording density is improved, it is gradually being replaced by a glass substrate that is superior in smoothness and strength of the substrate surface as compared with an aluminum substrate.
　情報記録媒体用のガラス基板の製造方法では、高い表面形状精度を確保するための研磨工程を有している。ガラス基板の高精度な形状品質を達成するために、加工処理能力の異なるスラリーや研磨パッドを効果的に組み合わせた２段階以上の研磨工程が適用されている。従来のガラス基板の研磨に関する技術は、たとえば特開２００９－１５４２３２号公報（特許文献１）および特開２００８－１４２８５１号公報（特許文献２）に提案されている。 The method for producing a glass substrate for an information recording medium has a polishing step for ensuring high surface shape accuracy. In order to achieve highly accurate shape quality of the glass substrate, two or more stages of polishing processes in which slurry and polishing pads having different processing capabilities are effectively combined are applied. Conventional techniques for polishing a glass substrate have been proposed in, for example, Japanese Unexamined Patent Application Publication No. 2009-154232 (Patent Document 1) and Japanese Unexamined Patent Application Publication No. 2008-142851 (Patent Document 2).
特開２００９－１５４２３２号公報JP 2009-154232 A 特開２００８－１４２８５１号公報JP 2008-142851 A
　ガラス基板に求められる品質水準が高まるにつれて、基板表面のキズ・付着物を低減することが一層重要視されている。特に、ガラス基板の最終研磨時に生じるキズ・付着物は、その後の磁気薄膜層の形成工程において大きな問題となるため、ガラス基板の研磨加工中の不純物混入を低減することが求められている。 As the quality level required for glass substrates increases, it has become more important to reduce scratches and deposits on the substrate surface. In particular, scratches and deposits generated during the final polishing of the glass substrate become a serious problem in the subsequent formation process of the magnetic thin film layer. Therefore, it is required to reduce contamination of the glass substrate during polishing.
　特開２００９－１５４２３２号公報（特許文献１）および特開２００８－１４２８５１号公報（特許文献２）に記載の技術では、研磨加工で使用する研磨パッドの表面を洗浄し、凝集したスラリーなどの不純物を定期的に研磨パッドの表面から除去して、研磨パッドの表面への不純物の蓄積を防ぐことができる。しかし、この手法を研磨パッドの端面に適用するのは難しく、凝集したスラリーなどの不純物を研磨パッドの端面から取り除くのは困難であった。 In the technique described in Japanese Patent Application Laid-Open No. 2009-154232 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2008-142851 (Patent Document 2), impurities such as agglomerated slurry are washed by cleaning the surface of the polishing pad used in the polishing process. Can be removed periodically from the surface of the polishing pad to prevent accumulation of impurities on the surface of the polishing pad. However, it is difficult to apply this method to the end face of the polishing pad, and it is difficult to remove impurities such as agglomerated slurry from the end face of the polishing pad.
　本発明は上記の課題に鑑みてなされたものであり、その主たる目的は、加工工具の端面への不純物の蓄積を抑制でき、ガラス基板の主表面へのキズおよび付着物の発生を低減できる、情報記録媒体用ガラス基板の製造方法を提供することである。 The present invention has been made in view of the above problems, and its main purpose is to suppress the accumulation of impurities on the end face of the processing tool, and to reduce the generation of scratches and deposits on the main surface of the glass substrate. It is to provide a method for producing a glass substrate for an information recording medium.
　本発明に係る情報記録媒体用ガラス基板の製造方法は、ガラス基板の主表面に磁気記録層が形成される情報記録媒体用ガラス基板の製造方法であって、ガラス基板を形成する工程と、主表面を研削加工または研磨加工する平面状の加工表面と加工表面の周縁を形成する端面とを有する加工工具の加工表面を主表面に接触させ、加工工具を主表面に対して相対的に摺動させて、主表面を加工する工程と、を備える。端面は、加工表面に対して９０°より大きい角度を成して傾斜している。 The method for producing a glass substrate for information recording medium according to the present invention is a method for producing a glass substrate for information recording medium in which a magnetic recording layer is formed on the main surface of the glass substrate, the step of forming the glass substrate, The processing surface of a processing tool having a flat processing surface for grinding or polishing the surface and an end surface forming the periphery of the processing surface is brought into contact with the main surface, and the processing tool is slid relative to the main surface. And processing the main surface. The end face is inclined at an angle greater than 90 ° with respect to the work surface.
　上記方法において、端面は、加工表面に対して９５°以上１７０°以下の角度を形成してもよい。 In the above method, the end face may form an angle of 95 ° to 170 ° with respect to the processed surface.
　上記方法において、加工する工程において、主表面の一部が加工表面からはみ出してもよい。加工する工程は、主表面の最終研磨工程であってもよい。 In the above method, in the processing step, a part of the main surface may protrude from the processing surface. The processing step may be a final polishing step of the main surface.
　上記方法において、加工工具の加工表面と端面とは、ガラス基板の主表面を一回または複数回加工した後に洗浄されてもよい。 In the above method, the processing surface and end surface of the processing tool may be cleaned after processing the main surface of the glass substrate once or a plurality of times.
　本発明に係る情報記録媒体は、上記のいずれかの情報記録媒体用ガラス基板の製造方法によって得られたガラス基板と、ガラス基板の表面に形成された磁気記録層と、を備える。 An information recording medium according to the present invention includes a glass substrate obtained by any one of the above-described methods for producing a glass substrate for an information recording medium, and a magnetic recording layer formed on the surface of the glass substrate.
　本発明の情報記録媒体用ガラス基板の製造方法によると、凝集したスラリーなどの不純物が加工工具の端面に蓄積されるのを抑制でき、ガラス基板の主表面へのキズおよび付着物の発生を低減できるので、ガラス基板の歩留まりを向上させることができる。 According to the method for producing a glass substrate for an information recording medium of the present invention, impurities such as agglomerated slurry can be prevented from accumulating on the end surface of the processing tool, and the generation of scratches and deposits on the main surface of the glass substrate can be reduced. Therefore, the yield of the glass substrate can be improved.
実施の形態におけるガラス基板の製造方法によって得られるガラス基板を示す斜視図である。It is a perspective view which shows the glass substrate obtained by the manufacturing method of the glass substrate in embodiment. 実施の形態におけるガラス基板の製造方法によって得られるガラス基板を備えた磁気ディスクを示す斜視図である。It is a perspective view which shows the magnetic disc provided with the glass substrate obtained by the manufacturing method of the glass substrate in embodiment. 実施の形態におけるガラス基板の製造方法を示すフローチャート図である。It is a flowchart figure which shows the manufacturing method of the glass substrate in embodiment. 研磨工程に用いられる両面研磨装置の部分斜視図である。It is a fragmentary perspective view of the double-side polish apparatus used for a grinding | polishing process. 研磨パッドの部分断面図である。It is a fragmentary sectional view of a polishing pad. ガラス基板の研磨時の、研磨パッドに対するガラス基板の相対移動を示す第一の図である。It is a 1st figure which shows the relative movement of the glass substrate with respect to a polishing pad at the time of grinding | polishing of a glass substrate. ガラス基板の研磨時の、研磨パッドに対するガラス基板の相対移動を示す第二の図である。It is a 2nd figure which shows the relative movement of the glass substrate with respect to a polishing pad at the time of grinding | polishing of a glass substrate. ガラス基板の研磨時の、研磨パッドに対するガラス基板の相対移動を示す第三の図である。It is a 3rd figure which shows the relative movement of the glass substrate with respect to a polishing pad at the time of grinding | polishing of a glass substrate. ガラス基板の研磨時の、研磨パッドに対するガラス基板の相対移動を示す第四の図である。It is a 4th figure which shows the relative movement of the glass substrate with respect to a polishing pad at the time of grinding | polishing of a glass substrate. ガラス基板の一部が研磨パッドの加工表面からはみ出た状態を模式的に表す平面図である。It is a top view which represents typically the state where a part of glass substrate protruded from the process surface of the polishing pad. 実施例および比較例の両面研磨装置を用いてガラス基板を研磨加工した評価結果を示す図である。It is a figure which shows the evaluation result which grind | polished the glass substrate using the double-side polish apparatus of an Example and a comparative example.
　本発明に基づいた実施の形態について、以下、図面を参照しながら説明する。実施の形態の説明において、個数、量などに言及する場合、特に記載がある場合を除き、本発明の範囲は必ずしもその個数、量などに限定されない。実施の形態の説明において、同一の部品、相当部品に対しては、同一の参照番号を付し、重複する説明は繰り返さない場合がある。 Embodiments according to the present invention will be described below with reference to the drawings. In the description of the embodiments, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, or the like unless otherwise specified. In the description of the embodiments, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.
　［ガラス基板１・磁気ディスク１０］
　図１および図２を参照して、まず、本実施の形態に基づく情報記録媒体用ガラス基板の製造方法によって得られるガラス基板１、およびガラス基板１を備えた磁気ディスク１０について説明する。図１は、磁気ディスク１０（図２参照）に用いられるガラス基板１を示す斜視図である。図２は、情報記録媒体として、ガラス基板１を備えた磁気ディスク１０を示す斜視図である。 [Glass substrate 1 and magnetic disk 10]
With reference to FIG. 1 and FIG. 2, the glass substrate 1 obtained by the manufacturing method of the glass substrate for information recording media based on this Embodiment and the magnetic disc 10 provided with the glass substrate 1 are demonstrated first. FIG. 1 is a perspective view showing a glass substrate 1 used for a magnetic disk 10 (see FIG. 2). FIG. 2 is a perspective view showing a magnetic disk 10 provided with a glass substrate 1 as an information recording medium.
　図１に示すように、磁気ディスク１０に用いられるガラス基板１（情報記録媒体用ガラス基板）は、中心に孔１Ｈが形成された環状の円板形状を呈している。円形ディスク形状のガラス基板１は、表主表面１Ａ、裏主表面１Ｂ、内周端面１Ｃ、および外周端面１Ｄを有している。 As shown in FIG. 1, a glass substrate 1 (glass substrate for information recording medium) used for a magnetic disk 10 has an annular disk shape with a hole 1H formed in the center. The circular disk-shaped glass substrate 1 has a front main surface 1A, a back main surface 1B, an inner peripheral end surface 1C, and an outer peripheral end surface 1D.
　ガラス基板１の大きさは、特に制限はなく、たとえば外径０．８インチ、１．０インチ、１．８インチ、２．５インチ、または３．５インチなどである。ガラス基板の厚さは、破損防止の観点から、たとえば０．３０～２．２ｍｍである。本実施の形態におけるガラス基板の大きさは、外径が約６５ｍｍ、内径が約２０ｍｍ、厚さが約０．８ｍｍである。ガラス基板１の厚さとは、ガラス基板１上の点対象となる任意の複数の点で測定した値の平均によって算出される値である。 The size of the glass substrate 1 is not particularly limited, and is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch outer diameter. The thickness of the glass substrate is, for example, 0.30 to 2.2 mm from the viewpoint of preventing breakage. In the present embodiment, the glass substrate has an outer diameter of about 65 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm. The thickness of the glass substrate 1 is a value calculated by averaging the values measured at a plurality of arbitrary points that are point targets on the glass substrate 1.
　図２に示すように、磁気ディスク１０は、上記したガラス基板１の表主表面１Ａ上に磁性膜が成膜されて、磁気記録層を含む磁気薄膜層２が形成されることによって、構成される。図２中では、表主表面１Ａ上にのみ磁気薄膜層２が形成されているが、裏主表面１Ｂ上にも磁気薄膜層２が形成されていてもよい。 As shown in FIG. 2, the magnetic disk 10 is configured by forming a magnetic film on the front main surface 1A of the glass substrate 1 and forming a magnetic thin film layer 2 including a magnetic recording layer. The In FIG. 2, the magnetic thin film layer 2 is formed only on the front main surface 1A, but the magnetic thin film layer 2 may also be formed on the back main surface 1B.
　磁気薄膜層２は、磁性粒子を分散させた熱硬化性樹脂をガラス基板１の表主表面１Ａ上にスピンコートすることによって形成される（スピンコート法）。磁気薄膜層２は、ガラス基板１の表主表面１Ａに対してスパッタリング法、または無電解めっき法等により形成されてもよい。 The magnetic thin film layer 2 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the front main surface 1A of the glass substrate 1 (spin coating method). The magnetic thin film layer 2 may be formed on the front main surface 1A of the glass substrate 1 by a sputtering method, an electroless plating method, or the like.
　ガラス基板１の表主表面１Ａに形成される磁気薄膜層２の膜厚は、スピンコート法の場合は約０．３μｍ～１．２μｍ、スパッタリング法の場合は約０．０４μｍ～０．０８μｍ、無電解めっき法の場合は約０．０５μｍ～０．１μｍである。薄膜化および高密度化の観点からは、磁気薄膜層２はスパッタリング法または無電解めっき法によって形成されるとよい。 The film thickness of the magnetic thin film layer 2 formed on the front main surface 1A of the glass substrate 1 is about 0.3 μm to 1.2 μm in the case of the spin coating method, about 0.04 μm to 0.08 μm in the case of the sputtering method, In the case of the electroless plating method, the thickness is about 0.05 μm to 0.1 μm. From the viewpoint of thinning and high density, the magnetic thin film layer 2 is preferably formed by sputtering or electroless plating.
　磁気薄膜層２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が、高い保持力を得るために結晶異方性の高いＣｏを基本とし、残留磁束密度を調整する目的でＮｉやＣｒを加えたＣｏ系合金などが好適である。また、熱アシスト記録用に好適な磁性層材料として、ＦｅＰｔ系の材料が用いられてもよい。 The magnetic material used for the magnetic thin film layer 2 is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Co having high crystal anisotropy is basically used for the purpose of adjusting the residual magnetic flux density. A Co-based alloy to which Ni or Cr is added is suitable. Further, as a magnetic layer material suitable for heat-assisted recording, an FePt-based material may be used.
　また、磁気記録ヘッドの滑りをよくするために磁気薄膜層２の表面に潤滑剤を薄くコーティングしてもよい。潤滑剤としては、たとえば液体潤滑剤であるパーフロロポリエーテル（ＰＦＰＥ）をフレオン系などの溶媒で希釈したものが挙げられる。 Further, a lubricant may be thinly coated on the surface of the magnetic thin film layer 2 in order to improve the sliding of the magnetic recording head. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon.
　さらに、必要により下地層や保護層を設けてもよい。磁気ディスク１０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、たとえば、Ｃｒ、Ｍｏ、Ｔａ、Ｔｉ、Ｗ、Ｖ、Ｂ、Ａｌ、またはＮｉなどの非磁性金属から選ばれる少なくとも一種以上の材料が挙げられる。 Furthermore, if necessary, an underlayer or a protective layer may be provided. The underlayer in the magnetic disk 10 is selected according to the magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.
　また、下地層は単層とは限らず、同一または異種の層を積層した複数層構造としても構わない。たとえば、Ｃｒ／Ｃｒ、Ｃｒ／ＣｒＭｏ、Ｃｒ／ＣｒＶ、ＮｉＡｌ／Ｃｒ、ＮｉＡｌ／ＣｒＭｏ、ＮｉＡｌ／ＣｒＶ等の多層下地層としてもよい。 Also, 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 may be used.
　磁気薄膜層２の摩耗や腐食を防止する保護層としては、たとえば、Ｃｒ層、Ｃｒ合金層、カーボン層、水素化カーボン層、ジルコニア層、シリカ層などが挙げられる。これらの保護層は、下地層、磁性膜など共にインライン型スパッタ装置で連続して形成できる。また、これらの保護層は、単層としてもよく、あるいは、同一または異種の層からなる多層構成としてもよい。 Examples of the protective layer for preventing wear and corrosion of the magnetic thin film layer 2 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus, such as an underlayer and a magnetic film. In addition, these protective layers may be a single layer, or may have a multilayer structure including the same or different layers.
　上記保護層上に、あるいは上記保護層に替えて、他の保護層を形成してもよい。たとえば、上記保護層に替えて、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、さらに焼成して酸化ケイ素（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, instead of the protective layer, a tetraalkoxysilane is diluted with an alcohol-based solvent on a Cr layer, and then colloidal silica fine particles are dispersed and applied, followed by baking to form a silicon oxide (SiO 2 ) layer. It may be formed.
　［ガラス基板の製造方法］
　次に、図３に示すフローチャート図を用いて、本実施の形態におけるガラス基板（情報記録媒体用ガラス基板）の製造方法について説明する。図３は、実施の形態におけるガラス基板１の製造方法を示すフローチャート図である。 [Glass substrate manufacturing method]
Next, the manufacturing method of the glass substrate (glass substrate for information recording media) in this Embodiment is demonstrated using the flowchart figure shown in FIG. FIG. 3 is a flowchart showing a method for manufacturing the glass substrate 1 in the embodiment.
　本実施の形態におけるガラス基板の製造方法は、ガラスブランク材準備工程（ステップＳ１０）、ガラス基板形成工程（ステップＳ２０）、研磨工程（ステップＳ３０）、化学強化工程（ステップＳ４０）、および洗浄工程（ステップＳ５０）を備えている。化学強化処理工程（ステップＳ４０）を経ることによって得られたガラス基板（図１におけるガラス基板１に相当）に対して、磁気薄膜形成工程（ステップＳ６０）が実施されてもよい。磁気薄膜形成工程（ステップＳ６０）によって、磁気ディスク１０が得られる。 The glass substrate manufacturing method in the present embodiment includes a glass blank material preparation step (step S10), a glass substrate formation step (step S20), a polishing step (step S30), a chemical strengthening step (step S40), and a cleaning step ( Step S50). A magnetic thin film forming step (step S60) may be performed on the glass substrate (corresponding to the glass substrate 1 in FIG. 1) obtained through the chemical strengthening treatment step (step S40). The magnetic disk 10 is obtained by the magnetic thin film forming step (step S60).
　以下、これらの各ステップＳ１０～Ｓ６０の詳細について順に説明する、以下には、各ステップＳ１０～Ｓ６０間に適宜行なわれる簡易的な洗浄については記載していない。 Hereinafter, details of each of these steps S10 to S60 will be described in order. In the following, simple cleaning appropriately performed between each of steps S10 to S60 is not described.
　（ガラスブランク材準備工程）
　ガラスブランク材準備工程（ステップＳ１０）においては、ガラス基板を構成するガラス素材が溶融される（ステップＳ１１）。ガラス素材は、たとえば一般的なアルミノシリケートガラスが用いられる。アルミノシリケートガラスは、５８質量％～７５質量％のＳｉＯ２と、５質量％～２３質量％のＡｌ２Ｏ３と、３質量％～１０質量％のＬｉ２Ｏと、４質量％～１３質量％のＮａ２Ｏと、を主成分として含有する。溶融したガラス素材は、下型上に流し込まれた後、上型および下型によってプレス成形される（ステップＳ１２）。プレス成形によって、円盤状のガラスブランク材（ガラス母材）が形成される。 (Glass blank material preparation process)
In the glass blank material preparation step (step S10), the glass material constituting the glass substrate is melted (step S11). For example, general aluminosilicate glass is used as the glass material. The aluminosilicate glass is composed of 58 mass% to 75 mass% SiO 2 , 5 mass% to 23 mass% Al 2 O 3 , 3 mass% to 10 mass% Li 2 O, and 4 mass% to 13 mass. % Na 2 O as a main component. The molten glass material is poured onto the lower mold and then press-molded with the upper mold and the lower mold (step S12). A disk-shaped glass blank (glass base material) is formed by press molding.
　ガラスブランク材は、ダウンドロー法またはフロート法によって形成されたシートガラス（板ガラス）を、研削砥石で切り出すことによって形成されてもよい。またガラス素材も、アルミノシリケートガラスに限られるものではなく、任意の素材であってもよい。 The glass blank material may be formed by cutting out sheet glass (sheet glass) formed by a downdraw method or a float method with a grinding wheel. Further, the glass material is not limited to aluminosilicate glass, and may be any material.
　（ガラス基板形成工程）
　次に、ガラス基板形成工程（ステップＳ２０）においては、プレス成形されたガラスブランク材の両方の主表面に対して、寸法精度および形状精度の向上を目的として、ラップ研磨処理が施される（ステップＳ２１）。ガラスブランク材の両方の主表面とは、後述する各処理を経ることによって、図１における表主表面１Ａとなる主表面および裏主表面１Ｂとなる主表面のことである（以下、両主表面ともいう）。 (Glass substrate forming process)
Next, in the glass substrate forming step (step S20), a lapping process is performed on both main surfaces of the press-molded glass blank material for the purpose of improving dimensional accuracy and shape accuracy (step). S21). Both main surfaces of a glass blank material are the main surfaces used as the front main surface 1A and the main surface used as the back main surface 1B in FIG. 1 through each process mentioned later (henceforth, both main surfaces) Also called).
　ラップ研磨処理は、遊星歯車機構を利用した両面ラッピング装置を用いて行なわれる。具体的には、ガラスブランク材の両主表面に上下からラップ定盤を押圧させ、研削液を両主表面上に供給し、ガラスブランク材とラップ定盤とを相対的に移動させて、ラップ研磨処理が行なわれる。ラップ研磨処理によって、ガラス基板としてのおおよその平行度、平坦度、および厚みなどが予備調整され、おおよそ平坦な主表面を有するガラス母材が得られる。たとえば、粒度＃４００のアルミナ砥粒（粒径約４０～６０μｍ）を含有する研削液を用い、上定盤の荷重を１００ｋｇ程度に設定することによって、ガラス基板の両面を面精度０μｍ～１μｍ、表面粗さＲｍａｘで６μｍ程度に仕上げてもよい。 The lapping process is performed using a double-sided lapping device using a planetary gear mechanism. Specifically, the lap surface plate is pressed from above and below both main surfaces of the glass blank material, the grinding liquid is supplied onto both main surfaces, the glass blank material and the lap surface plate are moved relative to each other, and the lap surface is moved. A polishing process is performed. By the lapping process, the approximate parallelism, flatness, thickness, and the like of the glass substrate are preliminarily adjusted, and a glass base material having an approximately flat main surface is obtained. For example, by using a grinding fluid containing alumina abrasive grains having a particle size of # 400 (particle size of about 40 to 60 μm) and setting the load of the upper surface plate to about 100 kg, the surface accuracy of both surfaces of the glass substrate is 0 μm to 1 μm, You may finish to about 6 micrometers in surface roughness Rmax.
　ラップ研磨処理の後、円筒状のダイヤモンドドリルなどを用いて、ガラスブランク材の中心部に対してコアリング（内周カット）処理が施される（ステップＳ２２）。コアリング処理によって、中心部に孔の開いた円環状のガラス基板が得られる。中心部の孔に対しては、所定の面取り加工が施されてもよい。 After the lapping process, a coring (inner peripheral cut) process is performed on the center portion of the glass blank using a cylindrical diamond drill or the like (step S22). By the coring process, an annular glass substrate having a hole in the center is obtained. A predetermined chamfering process may be performed on the hole in the center.
　（研磨工程）
　次に、研磨工程（ステップＳ３０）においては、上述のステップＳ２１と同様に、ガラス基板の両主表面に対してラップ研磨処理が施される（ステップＳ３１）。コアリング工程（ステップＳ２２）においてガラス基板の両主表面に形成された微細なキズや突起物などが除去される。ラップ研磨処理の後、ガラス基板の外周端面がブラシによって鏡面状に研磨される（ステップＳ３２）。研磨砥粒としては、酸化セリウム砥粒を含むスラリーが用いられる。 (Polishing process)
Next, in the polishing step (step S30), similarly to step S21 described above, lap polishing is performed on both main surfaces of the glass substrate (step S31). In the coring step (step S22), fine scratches and protrusions formed on both main surfaces of the glass substrate are removed. After the lapping process, the outer peripheral end surface of the glass substrate is polished into a mirror surface by a brush (step S32). As the abrasive grains, a slurry containing cerium oxide abrasive grains is used.
　次に、第１ポリッシュ研磨工程（粗研磨）として、ラップ研磨工程（ステップＳ３１）においてガラス基板の両主表面に残留したキズを除去しつつ、ガラス基板の反りを矯正する（ステップＳ３３）。第１ポリッシュ研磨工程においては、遊星歯車機構を利用した両面研磨装置などが使用される。たとえば、硬質ベロア、ウレタン発泡、またはピッチ含浸スウェードなどの研磨パッドを用いて研磨が行なわれる。研磨剤としては、一般的な酸化セリウム砥粒が用いられる。 Next, as a first polishing polishing process (rough polishing), the warp of the glass substrate is corrected while removing scratches remaining on both main surfaces of the glass substrate in the lapping polishing process (step S31) (step S33). In the first polishing step, a double-side polishing device using a planetary gear mechanism is used. For example, polishing is performed using a polishing pad such as hard velor, urethane foam, or pitch-impregnated suede. As the abrasive, general cerium oxide abrasive grains are used.
　第２ポリッシュ研磨工程（精密研磨）においては、ガラス基板に研磨加工が再度実施され、ガラス基板の両主表面上に残留した微小欠陥等が解消される（ステップＳ３４）。ガラス基板の両主表面は鏡面状に仕上げられることによって所望の平坦度に形成され、ガラス基板の反りも解消される。第２ポリッシュ研磨工程においては、遊星歯車機構を利用した両面研磨装置などが使用される。たとえば、スウェードまたはベロアを素材とする軟質ポリッシャである研磨パッドを用いて研磨が行なわれる。研磨剤としては、第一ポリッシュ研磨工程で用いた酸化セリウムよりも微細な、一般的なコロイダルシリカが用いられる。 In the second polish polishing step (precision polishing), the glass substrate is subjected to polishing again, and minute defects and the like remaining on both main surfaces of the glass substrate are eliminated (step S34). Both main surfaces of the glass substrate are finished to have a mirror-like surface to form a desired flatness, and the warp of the glass substrate is eliminated. In the second polishing step, a double-side polishing device using a planetary gear mechanism is used. For example, polishing is performed using a polishing pad which is a soft polisher made of suede or velor. As the polishing agent, general colloidal silica finer than the cerium oxide used in the first polishing step is used.
　ここで、図４および図５を参照して、両面研磨装置１０００の構成について簡単に説明する。図４は、研磨工程に用いられる両面研磨装置１０００の部分斜視図、図５は、研磨パッド３１０，４１０の部分断面図である。 Here, the configuration of the double-side polishing apparatus 1000 will be briefly described with reference to FIGS. FIG. 4 is a partial perspective view of a double-side polishing apparatus 1000 used in the polishing process, and FIG. 5 is a partial cross-sectional view of the polishing pads 310 and 410.
　図４および図５を参照して、両面研磨装置１０００は、上定盤（上側砥石保持定盤）３００と、下定盤（下側砥石保持定盤）４００と、上定盤３００の下定盤４００に対向する側の下面に取り付けられた研磨パッド（上側研磨パッド）３１０と、下定盤４００の上定盤３００に対向する側の上面に取り付けられた研磨パッド（下側研磨パッド）４１０と、を備える。研磨パッド３１０，４１０は、ガラス基板１の両主表面を研磨加工するための加工工具の一例である。上定盤３００と下定盤４００とは、キャリア５００の公転方向に対して互いに反対方向に回転するようになっている。上定盤３００と下定盤４００との間に形成される隙間に、キャリア５００が配置される。ディスク状のガラス基板１は、このキャリア５００に保持される。 4 and 5, a double-side polishing apparatus 1000 includes an upper surface plate (upper whetstone holding surface plate) 300, a lower surface plate (lower whetstone holding surface plate) 400, and a lower surface plate 400 of the upper surface plate 300. A polishing pad (upper polishing pad) 310 attached to the lower surface of the lower surface plate 400, and a polishing pad (lower polishing pad) 410 attached to the upper surface of the lower surface plate 400 facing the upper surface plate 300. Prepare. The polishing pads 310 and 410 are an example of a processing tool for polishing both main surfaces of the glass substrate 1. The upper surface plate 300 and the lower surface plate 400 rotate in directions opposite to each other with respect to the revolution direction of the carrier 500. Carrier 500 is arranged in a gap formed between upper surface plate 300 and lower surface plate 400. The disk-shaped glass substrate 1 is held by this carrier 500.
　なお、図４では、キャリア５００に保持される複数のガラス基板１を挟持する一対の定盤である上定盤３００および下定盤４００のうち、一方の定盤である下定盤４００が図示され、上定盤３００は図示を省略されている。また図５では、キャリア５００とキャリア５００に保持されたガラス基板１とは、図示を省略されている。 In FIG. 4, a lower surface plate 400 that is one surface plate among the upper surface plate 300 and the lower surface plate 400 that is a pair of surface plates that sandwich the plurality of glass substrates 1 held by the carrier 500 is illustrated. The upper surface plate 300 is not shown. In FIG. 5, the carrier 500 and the glass substrate 1 held by the carrier 500 are not shown.
　図５に示すように、研磨パッド３１０は、ガラス基板１の表主表面１Ａに接触する加工表面３１１を有する。加工表面３１１は、円環板形状の研磨パッド３１０の一方の表面である。加工表面３１１は、平面的に延び、平面形状が円環状に形成されている。加工表面３１１をガラス基板１の表主表面１Ａに接触させた状態で、研磨パッド３１０を表主表面１Ａに対して相対的に摺動させることにより、表主表面１Ａが研磨加工される。加工表面３１１の周縁には、端面３１２が設けられている。加工表面３１１と端面３１２との境界３１３の平面形状は円形状である。端面３１２は、円錐面形状に形成されている。端面３１２は、加工表面３１１との間に角度αを形成するように、加工表面３１１に対して傾斜して設けられている。 As shown in FIG. 5, the polishing pad 310 has a processed surface 311 that contacts the front main surface 1 </ b> A of the glass substrate 1. The processing surface 311 is one surface of the annular pad-shaped polishing pad 310. The processing surface 311 extends in a planar manner, and the planar shape is formed in an annular shape. With the processed surface 311 in contact with the front main surface 1A of the glass substrate 1, the front main surface 1A is polished by sliding the polishing pad 310 relative to the front main surface 1A. An end surface 312 is provided on the periphery of the processing surface 311. The planar shape of the boundary 313 between the processed surface 311 and the end surface 312 is circular. The end surface 312 is formed in a conical surface shape. The end surface 312 is provided so as to be inclined with respect to the processing surface 311 so as to form an angle α with the processing surface 311.
　研磨パッド４１０は、ガラス基板１の裏主表面１Ｂに接触する加工表面４１１を有する。加工表面４１１は、円環板形状の研磨パッド４１０の一方の表面である。加工表面４１１は、平面的に延び、平面形状が円環状に形成されている。加工表面４１１をガラス基板１の裏主表面１Ｂに接触させた状態で、研磨パッド４１０を裏主表面１Ｂに対して相対的に摺動させることにより、裏主表面１Ｂが研磨加工される。加工表面４１１の周縁には、端面４１２が設けられている。加工表面４１１と端面４１２との境界４１３の平面形状は円形状である。端面４１２は、円錐面形状に形成されている。端面４１２は、加工表面４１１との間に角度βを形成するように、加工表面４１１に対して傾斜して設けられている。 The polishing pad 410 has a processed surface 411 that contacts the back main surface 1B of the glass substrate 1. The processing surface 411 is one surface of an annular plate-shaped polishing pad 410. The processing surface 411 extends in a planar manner, and the planar shape is formed in an annular shape. With the processed surface 411 in contact with the back main surface 1B of the glass substrate 1, the back main surface 1B is polished by sliding the polishing pad 410 relative to the back main surface 1B. An end face 412 is provided on the periphery of the processing surface 411. The planar shape of the boundary 413 between the processed surface 411 and the end surface 412 is circular. The end surface 412 is formed in a conical surface shape. The end surface 412 is provided to be inclined with respect to the processing surface 411 so as to form an angle β with the processing surface 411.
　図５には、円環板形状を有する上定盤３００、下定盤４００および研磨パッド３１０，４１０の、円の中心を通る線に沿う、上定盤３００、下定盤４００および研磨パッド３１０，４１０の断面が図示されている。円環板形状の研磨パッド３１０を当該円の径方向に切断した断面において、加工表面３１１と端面３１２とは、角度αを形成する。円環板形状の研磨パッド４１０を当該円の径方向に切断した断面において、加工表面４１１と端面４１２とは、角度βを形成する。角度αと角度βとは、相等しい角度であってもよく、または、互いに異なる角度であってもよい。 In FIG. 5, the upper surface plate 300, the lower surface plate 400, and the polishing pads 310, 410 along the line passing through the center of the circle of the upper surface plate 300, the lower surface plate 400, and the polishing pads 310, 410 having an annular plate shape. The cross section of is shown. In the cross section obtained by cutting the annular plate-shaped polishing pad 310 in the radial direction of the circle, the processed surface 311 and the end surface 312 form an angle α. In the cross section obtained by cutting the annular pad-shaped polishing pad 410 in the radial direction of the circle, the processed surface 411 and the end surface 412 form an angle β. The angle α and the angle β may be equal to each other, or may be different from each other.
　加工表面３１１と端面３１２との間の角度α、および、加工表面４１１と端面４１２との間の角度βは、９０°より大きい。端面３１２，４１２は、加工表面３１１，４１１に対して９０°より大きい角度を成して傾斜している。角度α，βはそれぞれ、９５°以上１７０°以下の角度を有する。研磨パッド３１０の端面３１２は、加工表面３１１に対して９５°以上１７０°以下の角度を形成する。研磨パッド４１０の端面４１２は、加工表面４１１に対して９５°以上１７０°以下の角度を形成する。 The angle α between the processed surface 311 and the end surface 312 and the angle β between the processed surface 411 and the end surface 412 are larger than 90 °. The end faces 312 and 412 are inclined at an angle larger than 90 ° with respect to the processed surfaces 311 and 411. The angles α and β each have an angle of 95 ° to 170 °. The end surface 312 of the polishing pad 310 forms an angle of 95 ° or more and 170 ° or less with respect to the processing surface 311. The end surface 412 of the polishing pad 410 forms an angle of 95 ° or more and 170 ° or less with respect to the processing surface 411.
　上記の角度αの範囲は、円環板形状の研磨パッド３１０の径方向断面において加工表面３１１と端面３１２とが成す角度の、円の全周における平均の値として、規定される。上記の角度βの範囲は、円環板形状の研磨パッド４１０の径方向断面において加工表面４１１と端面４１２とが成す角度の、円の全周における平均の値として、規定される。つまり、研磨パッド３１０，４１０の円の一周の平均で角度α，βが上記の範囲であれば、研磨パッド３１０，４１０の径方向に沿う一断面において角度α，βが上記の範囲を外れていても構わない。 The range of the angle α is defined as an average value of the angle formed by the processed surface 311 and the end surface 312 in the radial cross section of the annular plate-shaped polishing pad 310 over the entire circumference of the circle. The range of the angle β is defined as an average value of the angle formed by the processing surface 411 and the end surface 412 in the radial cross section of the annular pad-shaped polishing pad 410 over the entire circumference of the circle. That is, if the angles α and β are the average in one circle of the polishing pads 310 and 410 within the above range, the angles α and β are outside the above range in one cross section along the radial direction of the polishing pads 310 and 410. It doesn't matter.
　第２ポリッシュ研磨工程（ステップＳ３４）において、研磨パッド３１０，４１０の表面の洗浄が行なわれてもよい。研磨パッド３１０，４１０の表面の洗浄は、加工表面３１１，４１１に対して略垂直な方向に延びる毛を有するキャリアブラシ、または、加工表面３１１，４１１に対して略垂直な方向に供給される高圧水を用いて、行なわれてもよい。加工表面３１１，４１１と略垂直である方向から洗浄されることにより、研磨パッド３１０，４１０の表面上、または表面近傍の研磨パッド３１０，４１０の内部に存在する、加工屑や凝集した砥粒などをある程度取り除くことが可能になる。高圧水を用いて洗浄する場合、高圧水は加工表面３１１，４１１に対して傾斜した方向に供給されてもよい。 In the second polishing polishing step (step S34), the surfaces of the polishing pads 310 and 410 may be cleaned. The surface of the polishing pads 310 and 410 is cleaned by a carrier brush having hairs extending in a direction substantially perpendicular to the processing surfaces 311 and 411 or a high pressure supplied in a direction substantially perpendicular to the processing surfaces 311 and 411. It may be performed using water. By being cleaned from a direction substantially perpendicular to the processing surfaces 311 and 411, processing waste, aggregated abrasive grains, etc. existing on the surfaces of the polishing pads 310 and 410 or in the polishing pads 310 and 410 in the vicinity of the surfaces, etc. Can be removed to some extent. When cleaning with high-pressure water, the high-pressure water may be supplied in a direction inclined with respect to the processing surfaces 311 and 411.
　研磨パッド３１０，４１０の表面の洗浄は、研磨工程（ステップＳ３０）中の任意の工程において行なわれてもよく、研磨工程（ステップＳ３０）中の任意の工程間に行なわれてもよく、または、研磨工程（ステップＳ３０）の終了後に行なわれてもよい。ガラス基板の両主表面を一回または複数回研磨加工した後に、両面研磨装置１０００において研磨パッド３１０，４１０の表面の洗浄が行なわれてもよい。研磨パッド３１０，４１０の表面（すなわち、加工表面３１１，４１１および端面３１２，４１２）は、一回もしくは複数回の研磨を行なう毎に定期的に洗浄されてもよく、または、不定期的に洗浄されてもよい。 The cleaning of the surfaces of the polishing pads 310 and 410 may be performed in any step in the polishing step (step S30), may be performed in any step in the polishing step (step S30), or You may perform after completion | finish of a grinding | polishing process (step S30). After polishing both main surfaces of the glass substrate once or a plurality of times, the surfaces of the polishing pads 310 and 410 may be cleaned in the double-side polishing apparatus 1000. The surfaces of the polishing pads 310 and 410 (that is, the processing surfaces 311 and 411 and the end surfaces 312 and 412) may be periodically cleaned every time one or a plurality of polishings are performed, or may be cleaned irregularly. May be.
　（化学強化工程）
　ガラス基板が洗浄された後、化学強化処理液にガラス基板を浸漬することによって、ガラス基板の両主表面に化学強化層を形成する（ステップＳ４０）。ガラス基板が洗浄された後、３００℃に加熱された硝酸カリウム（７０％）と硝酸ナトリウム（３０％）との混合用液などの化学強化処理液中に、ガラス基板を３０分間浸漬することによって、化学強化を行なう。 (Chemical strengthening process)
After the glass substrate is washed, the chemical strengthening layer is formed on both main surfaces of the glass substrate by immersing the glass substrate in the chemical strengthening treatment liquid (step S40). After the glass substrate is washed, the glass substrate is immersed in a chemical strengthening treatment solution such as a solution for mixing potassium nitrate (70%) and sodium nitrate (30%) heated to 300 ° C. for 30 minutes, Perform chemical strengthening.
　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は、これらのイオンに比べて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によって置換される（イオン交換法）。イオン半径の違いによって生じる歪みより、イオン交換された領域に圧縮応力が発生し、ガラス基板の両主表面が強化される。たとえば、ガラス基板の両主表面において、ガラス基板表面から約５μｍまでの範囲に化学強化層を形成し、ガラス基板の剛性を向上させてもよい。以上のようにして、図１に示すガラス基板１に相当するガラス基板が得られる。 The alkali metal ions such as lithium ions and sodium ions contained in the glass substrate are replaced with alkali metal ions such as potassium ions having a larger ion radius than these ions (ion exchange method). Compressive stress is generated in the ion-exchanged region due to the strain caused by the difference in ion radius, and both main surfaces of the glass substrate are strengthened. For example, on both main surfaces of the glass substrate, a chemically strengthened layer may be formed in a range from the glass substrate surface to about 5 μm to improve the rigidity of the glass substrate. As described above, a glass substrate corresponding to the glass substrate 1 shown in FIG. 1 is obtained.
　ガラス基板１に対しては、両主表面上における取り代が０．１μｍ以上０．５μｍ以下のポリッシュ研磨処理がさらに施されてもよい。化学強化工程を経た後にガラス基板の主表面上に残留している付着物が除去されることによって、ガラス基板１を用いて製造される磁気ディスクにヘッドクラッシュが発生することが低減される。また、ポリッシュ研磨処理における両主表面上の取り代を０．１μｍ以上０．５μｍ以下とすることによって、化学強化処理によって発生した応力の不均一性が表面に現れることもなくなる。本実施の形態におけるガラス基板の製造方法としては、以上のように構成される。 The glass substrate 1 may be further subjected to a polishing polishing process in which the machining allowance on both main surfaces is 0.1 μm or more and 0.5 μm or less. By removing the deposits remaining on the main surface of the glass substrate after the chemical strengthening step, occurrence of head crashes in the magnetic disk manufactured using the glass substrate 1 is reduced. Further, by setting the machining allowance on both main surfaces in the polishing process to 0.1 μm or more and 0.5 μm or less, the unevenness of stress generated by the chemical strengthening process does not appear on the surface. The manufacturing method of the glass substrate in the present embodiment is configured as described above.
　なお、第１ポリッシュ研磨工程（粗研磨）と第２ポリッシュ研磨工程（精密研磨）との間に、化学強化工程を施してもかまわない。 Note that a chemical strengthening step may be performed between the first polishing step (rough polishing) and the second polishing step (precision polishing).
　（洗浄工程）
　次に、ガラス基板は洗浄される（ステップＳ５０）。ガラス基板の両主表面が洗剤、純水、オゾン、ＩＰＡ（イソプロピルアルコール）、またはＵＶ（ｕｌｔｒａｖｉｏｌｅｔ）オゾンなどによって洗浄されることによって、ガラス基板の両主表面に付着した付着物が除去される。 (Washing process)
Next, the glass substrate is cleaned (step S50). By cleaning both main surfaces of the glass substrate with detergent, pure water, ozone, IPA (isopropyl alcohol), UV (ultraviolet) ozone, or the like, the deposits attached to both main surfaces of the glass substrate are removed.
　その後、ガラス基板表面上の付着物の数が、光学式欠陥検査装置等を用いて検査される。 Thereafter, the number of deposits on the glass substrate surface is inspected using an optical defect inspection apparatus or the like.
　（磁気薄膜形成工程）
　化学強化処理が完了したガラス基板（図１に示すガラス基板１に相当）の両主表面（またはいずれか一方の主表面）に対し、磁性膜が形成されることにより、磁気薄膜層２が形成される。磁気薄膜層は、Ｃｒ合金からなる密着層、ＣｏＦｅＺｒ合金からなる軟磁性層、Ｒｕからなる配向制御下地層、ＣｏＣｒＰｔ合金からなる垂直磁気記録層、Ｃ系からなる保護層、およびＦ系からなる潤滑層が順次成膜されることによって形成される。磁気薄膜層の形成によって、図２に示す磁気ディスク１０に相当する垂直磁気記録ディスクを得ることができる。 (Magnetic thin film formation process)
The magnetic thin film layer 2 is formed by forming a magnetic film on both main surfaces (or one of the main surfaces) of the glass substrate (corresponding to the glass substrate 1 shown in FIG. 1) that has been subjected to the chemical strengthening treatment. Is done. The magnetic thin film layer includes an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a protective layer made of a C system, and a lubrication made of an F system. It is formed by sequentially depositing layers. By forming the magnetic thin film layer, a perpendicular magnetic recording disk corresponding to the magnetic disk 10 shown in FIG. 2 can be obtained.
　本実施の形態における磁気ディスクは、磁気薄膜層から構成される垂直磁気ディスクの一例である。磁気ディスクは、いわゆる面内磁気ディスクとして磁性層等から構成されてもよい。 The magnetic disk in the present embodiment is an example of a perpendicular magnetic disk composed of a magnetic thin film layer. The magnetic disk may be composed of a magnetic layer or the like as a so-called in-plane magnetic disk.
　（作用・効果）
　図６～図９は、両面研磨装置１０００を用いたガラス基板１の研磨時の、研磨パッド３１０，４１０に対するガラス基板１の相対移動を示す図である。ガラス基板１を研磨する際には、上定盤３００と下定盤４００とは、それぞれ反対方向に回転する。たとえば、両面研磨装置１０００の上方から見て、上定盤３００は時計方向に回転し、下定盤４００は半時計方向に回転する。このときキャリア５００は、自転しながら公転する。たとえばキャリア５００は、上定盤３００と下定盤４００との回転軸を中心に時計回りまたは反時計回りに公転しながら、キャリア５００自身が形成する円形状の中心回りに自転する。 (Action / Effect)
6 to 9 are diagrams showing relative movement of the glass substrate 1 with respect to the polishing pads 310 and 410 when the glass substrate 1 is polished using the double-side polishing apparatus 1000. FIG. When polishing the glass substrate 1, the upper surface plate 300 and the lower surface plate 400 rotate in opposite directions. For example, when viewed from above the double-side polishing apparatus 1000, the upper surface plate 300 rotates clockwise and the lower surface plate 400 rotates counterclockwise. At this time, the carrier 500 revolves while rotating. For example, the carrier 500 rotates around the circular center formed by the carrier 500 itself while revolving clockwise or counterclockwise around the rotation axis of the upper surface plate 300 and the lower surface plate 400.
　キャリア５００が自転することにより、キャリア５００に保持されているガラス基板１の、研磨パッド３１０，４１０に対する相対位置が変化する。具体的には、図６に示す研磨パッド３１０，４１０によってガラス基板１の全体が挟持された状態から、キャリア５００の自転に伴って研磨パッド３１０，４１０の径方向にガラス基板１が移動することで、図７に示すように、ガラス基板１の一部が研磨パッド３１０，４１０の外部を通過する。 When the carrier 500 rotates, the relative position of the glass substrate 1 held by the carrier 500 with respect to the polishing pads 310 and 410 changes. Specifically, the glass substrate 1 moves in the radial direction of the polishing pads 310 and 410 from the state in which the entire glass substrate 1 is sandwiched between the polishing pads 310 and 410 shown in FIG. Thus, as shown in FIG. 7, a part of the glass substrate 1 passes outside the polishing pads 310 and 410.
　図７に示す状態では、ガラス基板１の表主表面１Ａの一部は研磨パッド３１０の加工表面３１１の外側に配置されており、ガラス基板１の裏主表面１Ｂの一部は研磨パッド４１０の加工表面４１１の外側に配置されている。ガラス基板１の表主表面１Ａと裏主表面１Ｂとは、加工表面３１１，４１１の外側を通過する。ガラス基板１は、ガラス基板１の少なくとも一部が上定盤３００および下定盤４００の周縁を越えて外側にはみ出し上定盤３００および下定盤４００の外を通過する、いわゆる「オーバーハング回転」を行なう。このとき、ガラス基板１の表主表面１Ａの一部が研磨パッド３１０の加工表面３１１からはみ出し、裏主表面１Ｂの一部が研磨パッド４１０の加工表面４１１からはみ出した状態になる。 In the state shown in FIG. 7, a part of the front main surface 1 </ b> A of the glass substrate 1 is disposed outside the processing surface 311 of the polishing pad 310, and a part of the back main surface 1 </ b> B of the glass substrate 1 is the polishing pad 410. Arranged outside the processing surface 411. The front main surface 1A and the back main surface 1B of the glass substrate 1 pass outside the processed surfaces 311 and 411. The glass substrate 1 is subjected to a so-called “overhang rotation” in which at least a part of the glass substrate 1 extends beyond the periphery of the upper surface plate 300 and the lower surface plate 400 to the outside and passes outside the upper surface plate 300 and the lower surface plate 400. Do. At this time, a part of the front main surface 1A of the glass substrate 1 protrudes from the processing surface 311 of the polishing pad 310, and a part of the back main surface 1B protrudes from the processing surface 411 of the polishing pad 410.
　図１０は、ガラス基板１の一部が研磨パッド３１０の加工表面３１１からはみ出た状態を模式的に表す平面図である。ガラス基板１の研磨加工中に、ガラス基板１が上定盤３００および下定盤４００から最も大きくはみ出る状態が、図１０に図示されている。このときの、研磨パッド３１０の加工表面３１１と端面３１２との境界３１３と、ガラス基板１の外周部と、の間の距離Ｈが、研磨加工時にガラス基板１が定盤上からはみ出る最大長さであり、オーバーハング長と称する。 FIG. 10 is a plan view schematically showing a state in which a part of the glass substrate 1 protrudes from the processing surface 311 of the polishing pad 310. FIG. 10 shows a state in which the glass substrate 1 protrudes most from the upper surface plate 300 and the lower surface plate 400 during the polishing of the glass substrate 1. At this time, the distance H between the boundary 313 between the processing surface 311 and the end surface 312 of the polishing pad 310 and the outer peripheral portion of the glass substrate 1 is the maximum length that the glass substrate 1 protrudes from the surface plate during polishing processing. And is called the overhang length.
　図７に示す状態からキャリア５００が自転を続けることにより、図８に示すようにガラス基板１が研磨パッド３１０，４１０からはみ出る部分が減少し、さらに図９に示すようにガラス基板１の全体が研磨パッド３１０，４１０によって挟持された状態に戻る。 When the carrier 500 continues to rotate from the state shown in FIG. 7, the portion of the glass substrate 1 that protrudes from the polishing pads 310 and 410 is reduced as shown in FIG. 8, and the entire glass substrate 1 is further removed as shown in FIG. The state returned to the state sandwiched between the polishing pads 310 and 410 is restored.
　上述したように、ガラス基板１を研磨するために、研磨剤が供給される。研磨剤としては、研磨砥粒を含むスラリー６００が用いられる。研磨パッド３１０，４１０の径方向にガラス基板１が移動することにより、図６～図９に示すように、研磨パッド３１０，４１０の間の空間に供給されたスラリー６００が、ガラス基板１の端面またはキャリア５００の端面によって当該空間から押し出され、その後再び当該空間内へ戻される。 As described above, an abrasive is supplied to polish the glass substrate 1. As the abrasive, slurry 600 containing abrasive grains is used. As the glass substrate 1 moves in the radial direction of the polishing pads 310 and 410, the slurry 600 supplied to the space between the polishing pads 310 and 410 becomes the end surface of the glass substrate 1 as shown in FIGS. Or it is pushed out of the space by the end face of the carrier 500 and then returned to the space again.
　このスラリー６００には、凝集したスラリーなどの不純物６０１が含まれている。図６に示す、研磨パッド３１０，４１０によってガラス基板１の全体が挟持された状態では、不純物６０１は研磨パッド３１０，４１０の間の空間に存在する。キャリア５００の自転に伴って研磨パッド３１０，４１０の径方向にガラス基板１が移動することにより、不純物６０１もまた、ガラス基板１の端面によって当該空間から押し出される（図７）。 The slurry 600 contains impurities 601 such as agglomerated slurry. In the state where the entire glass substrate 1 is sandwiched between the polishing pads 310 and 410 shown in FIG. 6, the impurity 601 exists in the space between the polishing pads 310 and 410. When the glass substrate 1 moves in the radial direction of the polishing pads 310 and 410 as the carrier 500 rotates, the impurities 601 are also pushed out of the space by the end surface of the glass substrate 1 (FIG. 7).
　ここで、図５を参照して説明したように、本実施の形態の研磨パッド３１０において、加工表面３１１と端面３１２とは９０°より大きい角度、より具体的には９５°以上１７０°以下の角度αを有する。そのため、端面３１２は、加工表面３１１に対して傾斜している。かつ、研磨パッド４１０において、加工表面４１１と端面４１２とは９０°より大きい角度、より具体的には９５°以上１７０°以下の角度βを有する。そのため、端面４１２は、加工表面４１１に対して傾斜している。そのため、図７に示すように研磨パッド３１０，４１０の間の空間の外へ押し出された不純物６０１は、図８および図９に示すように、端面３１２，４１２を伝って、研磨パッド３１０，４１０の間の空間へ戻ることができる。 Here, as described with reference to FIG. 5, in the polishing pad 310 of the present embodiment, the processing surface 311 and the end surface 312 have an angle greater than 90 °, more specifically, 95 ° to 170 °. Has an angle α. Therefore, the end surface 312 is inclined with respect to the processing surface 311. In the polishing pad 410, the processed surface 411 and the end surface 412 have an angle greater than 90 °, more specifically, an angle β of 95 ° to 170 °. Therefore, the end surface 412 is inclined with respect to the processing surface 411. Therefore, the impurity 601 pushed out of the space between the polishing pads 310 and 410 as shown in FIG. 7 travels along the end surfaces 312 and 412 as shown in FIGS. You can return to the space between.
　研磨パッドの端面が加工表面に対して９０°の角度を形成する場合、ガラス基板１が定盤外部に露出し、その後定盤内に再進入する際に、凝集したスラリーなどの不純物６０１が研磨パッドの端面に拭われて端面上に残される。そのため、研磨パッドの端面上に、不純物が蓄積する。この蓄積された不純物６０１が端面上で乾燥すると、オーバーハングされたガラス基板１の表面が不純物６０１により引っ掻かれて、ガラス基板１の表面にキズが発生する原因となる。または、水分が減少し粘度の高くなった不純物６０１がガラス基板１の表面上に付着して、ガラス基板１の表面に突起部が形成される原因となる。これらのキズや付着物が発生すると、ガラス基板１は不良品とされるので、最終的なガラス基板１の歩留まりが低下する。 When the end surface of the polishing pad forms an angle of 90 ° with respect to the processing surface, impurities 601 such as agglomerated slurry are polished when the glass substrate 1 is exposed to the outside of the surface plate and then reenters the surface plate. It is wiped by the end face of the pad and left on the end face. Therefore, impurities accumulate on the end surface of the polishing pad. When the accumulated impurities 601 are dried on the end face, the surface of the overhanging glass substrate 1 is scratched by the impurities 601 and causes the surface of the glass substrate 1 to be scratched. Alternatively, the impurity 601 having a high viscosity due to a decrease in moisture adheres to the surface of the glass substrate 1, causing a protrusion to be formed on the surface of the glass substrate 1. When these scratches and deposits are generated, the glass substrate 1 is regarded as a defective product, and the final yield of the glass substrate 1 is reduced.
　これに対し、本実施の形態においては、研磨パッド３１０，４１０の端面３１２，４１２が加工表面３１１，４１１に対して垂直ではなく、端面３１２，４１２には傾斜が付けられている。端面３１２，４１２を積極的に傾斜させることにより、不純物６０１が研磨パッド３１０，４１０の間の空間の外へ押し出されても、再度研磨パッド３１０，４１０の間の空間内に不純物６０１が引き込まれ易い構成とされている。これにより、研磨工程においてガラス基板１がオーバーハング回転する際に不純物６０１が端面３１２，４１２で拭われて、不純物６０１が端面３１２，４１２上に残存することを抑制する。そのため、スラリー６００中に含まれる凝集したスラリーなどの不純物６０１が研磨パッド３１０，４１０の端面３１２，４１２に蓄積されることを、抑制することができる。 On the other hand, in the present embodiment, the end faces 312 and 412 of the polishing pads 310 and 410 are not perpendicular to the processing surfaces 311 and 411, and the end faces 312 and 412 are inclined. By positively inclining the end faces 312 and 412, even if the impurities 601 are pushed out of the space between the polishing pads 310 and 410, the impurities 601 are again drawn into the space between the polishing pads 310 and 410. The structure is easy. This suppresses the impurities 601 from being wiped by the end faces 312 and 412 when the glass substrate 1 rotates in an overhanging manner in the polishing process, and the impurities 601 remaining on the end faces 312 and 412. Therefore, accumulation of impurities 601 such as agglomerated slurry contained in the slurry 600 on the end surfaces 312 and 412 of the polishing pads 310 and 410 can be suppressed.
　その結果、端面３１２，４１２において不純物６０１が成長して増大することを回避できるので、研磨パッド３１０，４１０の端面３１２，４１２に蓄積した不純物６０１を原因として、ガラス基板１の表面にキズや付着物が発生することを抑制できる。したがって、研磨加工後のガラス基板１の良品の割合を向上できるので、ガラス基板１の歩留まりを向上させることができる。 As a result, it is possible to avoid the growth and increase of the impurities 601 on the end surfaces 312 and 412, so that the surface of the glass substrate 1 is scratched or damaged due to the impurities 601 accumulated on the end surfaces 312 and 412 of the polishing pads 310 and 410. Generation | occurrence | production of a kimono can be suppressed. Therefore, since the proportion of non-defective products of the glass substrate 1 after polishing can be improved, the yield of the glass substrate 1 can be improved.
　研磨パッド３１０の加工表面３１１と端面３１２との間の角度α、および、研磨パッド４１０の加工表面４１１と端面４１２との間の角度βは、９５°未満では凝集したスラリーなどの不純物６０１が端面３１２，４１２に蓄積し易くなるので、９５°以上とするのが好ましい。また、角度αおよび角度βは、１７０°より大きいと、研磨パッド３１０，４１０の表面のうち研磨に用いられる加工表面３１１，４１１の面積が減少して研磨効率が低下するので、１７０°以下とするのが好ましい。より好ましくは、角度αおよび角度βは、研磨パッド３１０，４１０の一周の平均で、１１０°以上１５０°以下である。 When the angle α between the processing surface 311 and the end surface 312 of the polishing pad 310 and the angle β between the processing surface 411 and the end surface 412 of the polishing pad 410 are less than 95 °, impurities 601 such as agglomerated slurry are end surfaces. Since it is easy to accumulate in 312 and 412, the angle is preferably set to 95 ° or more. Further, if the angle α and the angle β are larger than 170 °, the area of the processing surfaces 311 and 411 used for polishing among the surfaces of the polishing pads 310 and 410 is reduced and the polishing efficiency is lowered. It is preferable to do this. More preferably, the angle α and the angle β are 110 ° or more and 150 ° or less as an average of one round of the polishing pads 310 and 410.
　このような研磨パッド３１０，４１０が角度α，βを有する両面研磨装置１０００は、予め所定の形状に形成された研磨パッド３１０，４１０がそれぞれ上定盤３００、下定盤４００に貼着されることにより、形成されてもよい。または、両面研磨装置１０００は、上定盤３００、下定盤４００の全面を覆う研磨パッド素材を、上定盤３００および下定盤４００にそれぞれ貼り付け、当該研磨パッド素材の周縁を所定の形状に切断することにより、形成されてもよい。 In the double-side polishing apparatus 1000 in which the polishing pads 310 and 410 have the angles α and β, the polishing pads 310 and 410 formed in advance in a predetermined shape are attached to the upper surface plate 300 and the lower surface plate 400, respectively. May be formed. Alternatively, the double-side polishing apparatus 1000 attaches a polishing pad material covering the entire surface of the upper surface plate 300 and the lower surface plate 400 to the upper surface plate 300 and the lower surface plate 400, respectively, and cuts the periphery of the polishing pad material into a predetermined shape. By doing so, it may be formed.
　ガラス基板１の研磨加工時に、ガラス基板１の表面の一部が研磨パッド３１０，４１０の加工表面３１１，４１１の外側を通過し、ガラス基板１をオーバーハングさせることにより、研磨パッド３１０，４１０の偏磨耗を抑制でき、したがってガラス基板１の平坦度を向上させることができる。ガラス基板１をオーバーハングさせるとスラリー６００に含まれる不純物６０１が研磨パッド３１０，４１０の端面３１２，４１２上へ移動するが、端面３１２，４１２を加工表面３１１，４１１に対して傾斜させることにより、不純物６０１は端面３１２，４１２から研磨パッド３１０，４１０の内側へ容易に引き込まれ、端面３１２，４１２上へは蓄積されない。したがって、上述した基板平坦度を向上させる効果が得られるとともに、不純物６０１の端面３１２，４１２への蓄積を抑制し、ガラス基板１の歩留まりを向上することができる。 During polishing of the glass substrate 1, a part of the surface of the glass substrate 1 passes outside the processed surfaces 311, 411 of the polishing pads 310, 410 and overhangs the glass substrate 1, so that the polishing pads 310, 410 are overhanged. Uneven wear can be suppressed, and therefore the flatness of the glass substrate 1 can be improved. When the glass substrate 1 is overhanged, the impurities 601 contained in the slurry 600 move onto the end surfaces 312 and 412 of the polishing pads 310 and 410. By inclining the end surfaces 312 and 412 with respect to the processing surfaces 311 and 411, The impurities 601 are easily drawn into the polishing pads 310 and 410 from the end surfaces 312 and 412, and are not accumulated on the end surfaces 312 and 412. Accordingly, the above-described effect of improving the flatness of the substrate can be obtained, the accumulation of the impurities 601 on the end faces 312 and 412 can be suppressed, and the yield of the glass substrate 1 can be improved.
　研磨パッド３１０，４１０の表面の洗浄は、ガラス基板１の研磨工程内において、ナイロンなど樹脂製の毛を有するキャリアブラシ、または、７ＭＰａ程度の圧力の高圧水を用いて行なわれてもよい。研磨パッド３１０，４１０の端面３１２，４１２が加工表面３１１，４１１に対して傾斜を有することにより、研磨工程中に端面３１２，４１２に不純物６０１が残存したとしても、洗浄時にキャリアブラシまたは高圧水が端面３１２，４１２に接触して不純物６０１は端面３１２，４１２から除去される。そのため、端面３１２，４１２に不純物６０１が蓄積されることを、さらに抑制することができる。 The surface of the polishing pads 310 and 410 may be cleaned using a carrier brush having resin bristles such as nylon or high-pressure water having a pressure of about 7 MPa in the polishing process of the glass substrate 1. Since the end surfaces 312 and 412 of the polishing pads 310 and 410 are inclined with respect to the processing surfaces 311 and 411, even if the impurities 601 remain on the end surfaces 312 and 412 during the polishing process, a carrier brush or high-pressure water is not washed. The impurities 601 are removed from the end faces 312 and 412 in contact with the end faces 312 and 412. Therefore, accumulation of the impurities 601 on the end faces 312 and 412 can be further suppressed.
　上述した両面研磨装置１０００は、図３に示す研磨工程（ステップＳ３０）のうち、最終の研磨工程である第２ポリッシュ研磨工程（精密研磨）（ステップＳ３４）でのガラス基板１の研磨に使用されるのが望ましい。ガラス基板１の表面上の付着物が特に問題となる最終研磨工程で、付着物を低減させることにより、最終的なガラス基板１の品質を確保することができるので、確実にガラス基板１の歩留まりを向上することができる。化学強化工程（ステップＳ４０）を経た後にポリッシュ研磨処理がさらに施される場合には、第２ポリッシュ研磨工程（ステップＳ３４）ではなく、化学強化工程（ステップＳ４０）後のポリッシュ研磨処理において、上述した両面研磨装置１０００を使用してガラス基板１を研磨してもよい。 The double-side polishing apparatus 1000 described above is used for polishing the glass substrate 1 in the second polishing polishing process (precision polishing) (step S34) which is the final polishing process among the polishing processes (step S30) shown in FIG. Is desirable. In the final polishing step in which the deposits on the surface of the glass substrate 1 are particularly problematic, the quality of the final glass substrate 1 can be ensured by reducing the deposits, so that the yield of the glass substrate 1 is surely obtained. Can be improved. In the case where the polishing polishing process is further performed after the chemical strengthening process (step S40), the polishing process after the chemical strengthening process (step S40) is not described in the second polishing process (step S34). The glass substrate 1 may be polished using the double-side polishing apparatus 1000.
　以下、この発明の実施例について説明する。図１１は、実施例および比較例の両面研磨装置１０００を用いてガラス基板１を研磨加工した評価結果を示す図である。実施例および比較例では、外径φ６５ｍｍ、内径φ２０ｍｍ、板厚０．８ｍｍの円環板状のガラス基板１を準備し、１００枚のガラス基板１を研磨加工したときの歩留まり率について評価した。 Hereinafter, embodiments of the present invention will be described. FIG. 11 is a diagram showing an evaluation result obtained by polishing the glass substrate 1 using the double-side polishing apparatus 1000 of the example and the comparative example. In Examples and Comparative Examples, an annular plate-shaped glass substrate 1 having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.8 mm was prepared, and the yield rate when 100 glass substrates 1 were polished was evaluated.
　図１１には、図３に示す第１ポリッシュ研磨工程（ステップＳ３３）で使用した研磨パッド３１０，４１０の条件と、第２ポリッシュ研磨工程（ステップＳ３４）で使用した研磨パッド３１０，４１０の条件と、が記載されている。いずれの条件でも、前工程までの加工で作成された別個のガラス基板１００枚ずつを用い、それぞれの実験水準につき１５回の加工を行ない、１５回目の加工内容を実施例または比較例とした。 11 shows the conditions of the polishing pads 310 and 410 used in the first polishing step (step S33) shown in FIG. 3, and the conditions of the polishing pads 310 and 410 used in the second polishing step (step S34). , Is described. Under any of the conditions, 100 separate glass substrates prepared by the processing up to the previous step were used, processing was performed 15 times for each experimental level, and the processing content of the 15th time was taken as an example or a comparative example.
　第１ポリッシュ研磨工程では、一般的な硬質ウレタン製の研磨パッド３１０，４１０を用い、スラリーの種類は粒径約１．０μｍの酸化セリウムスラリーとした。実施例１～４および比較例１～２では、研磨パッド３１０，４１０の加工表面３１１，４１１と端面３１２，４１２とのなす角度が９０°である。一方実施例５では、加工表面３１１，４１１と端面３１２，４１２とのなす角度が１３５°であり、端面３１２，４１２が加工表面３１１，４１１に対して傾斜する研磨パッド３１０，４１０を使用した。第１ポリッシュ研磨工程では、加工中にガラス基板１をオーバーハングさせないように、ガラス基板１を加工した。一回の研磨毎に、キャリアブラシによる研磨パッド３１０，４１０の表面の洗浄を行なった。 In the first polishing step, general hard urethane polishing pads 310 and 410 were used, and the type of slurry was cerium oxide slurry having a particle size of about 1.0 μm. In Examples 1 to 4 and Comparative Examples 1 and 2, the angle formed between the processed surfaces 311 and 411 of the polishing pads 310 and 410 and the end surfaces 312 and 412 is 90 °. On the other hand, in Example 5, the polishing pads 310 and 410 in which the angle between the processing surfaces 311 and 411 and the end surfaces 312 and 412 is 135 ° and the end surfaces 312 and 412 are inclined with respect to the processing surfaces 311 and 411 are used. In the first polishing step, the glass substrate 1 was processed so as not to overhang the glass substrate 1 during processing. For each polishing, the surfaces of the polishing pads 310 and 410 were cleaned with a carrier brush.
　第２ポリッシュ研磨工程では、一般的なスウェード製の研磨パッド３１０，４１０を用い、スラリーの種類は粒径約２０ｎｍのシリカスラリーとした。比較例１～２では、研磨パッド３１０，４１０の加工表面３１１，４１１と端面３１２，４１２とのなす角度が９０°である。一方、実施例１，２および５では、加工表面３１１，４１１と端面３１２，４１２とのなす角度が１３５°である。また実施例３および４では、加工表面３１１，４１１と端面３１２，４１２とのなす角度が１００°である。このように実施例１～５ではそれぞれ、端面３１２，４１２が加工表面３１１，４１１に対して傾斜する研磨パッド３１０，４１０を使用した。実施例２，４および比較例２では、研磨加工中にガラス基板１をオーバーハングさせた。このときのオーバーハング長は１ｍｍとした。一回の研磨毎に、キャリアブラシによる研磨パッド３１０，４１０の表面の洗浄を行なった。 In the second polish polishing step, general suede polishing pads 310 and 410 were used, and the type of slurry was silica slurry having a particle size of about 20 nm. In Comparative Examples 1 and 2, the angle formed between the processed surfaces 311 and 411 of the polishing pads 310 and 410 and the end surfaces 312 and 412 is 90 °. On the other hand, in Examples 1, 2 and 5, the angle formed between the processed surfaces 311 and 411 and the end surfaces 312 and 412 is 135 °. In Examples 3 and 4, the angle formed between the processed surfaces 311 and 411 and the end surfaces 312 and 412 is 100 °. As described above, in Examples 1 to 5, the polishing pads 310 and 410 whose end faces 312 and 412 are inclined with respect to the processing surfaces 311 and 411 are used. In Examples 2 and 4 and Comparative Example 2, the glass substrate 1 was overhanged during the polishing process. The overhang length at this time was 1 mm. For each polishing, the surfaces of the polishing pads 310 and 410 were cleaned with a carrier brush.
　ガラス基板１の歩留まり率は、Ｈｅ－Ｎｅレーザ光源を用いたシステム精工社製表面検査装置ＳＳＩ－６４０を用いて、ガラス基板１の表面を外観検査することにより、評価した。表面検査装置では、凸部（バンプ）、凹部（ピット）、塵埃（パーティクル）および擦り傷（スクラッチ）などの、ガラス基板１の表面に発生する欠陥が検出される。検出された欠陥数が所定の閾値を超えたものを不良品とした。 The yield rate of the glass substrate 1 was evaluated by visual inspection of the surface of the glass substrate 1 using a surface inspection device SSI-640 manufactured by System Seiko Co., Ltd. using a He—Ne laser light source. In the surface inspection apparatus, defects generated on the surface of the glass substrate 1 such as convex portions (bumps), concave portions (pits), dust (particles), and scratches (scratches) are detected. A defective product was detected when the number of detected defects exceeded a predetermined threshold.
　計測の結果、図１１に示すように、比較例１では歩留まり率が「可」（Ｃ）レベルであり、比較例２では歩留まり率が「不良」（Ｄ）レベルであった。これに対し、実施例１～５では、ガラス基板１の歩留まり率は「優」（Ａ）または「良」（Ｂ）レベルであり、比較例と比べて実施例ではガラス基板１の歩留まり率が改善していた。実施例１，２と実施例３，４とを比較して、研磨パッド３１０，４１０の加工表面３１１，４１１と端面３１２，４１２とのなす角度が１３５°であるときに、より良い結果を得ることができた。 As a result of the measurement, as shown in FIG. 11, in Comparative Example 1, the yield rate was “OK” (C) level, and in Comparative Example 2, the yield rate was “Poor” (D) level. In contrast, in Examples 1 to 5, the yield rate of the glass substrate 1 is “excellent” (A) or “good” (B) level, and the yield rate of the glass substrate 1 is higher in the example than in the comparative example. It was improving. Comparing Examples 1 and 2 with Examples 3 and 4, better results are obtained when the angle formed between the processed surfaces 311 and 411 of the polishing pads 310 and 410 and the end surfaces 312 and 412 is 135 °. I was able to.
　実施例２，４および比較例２を比較して、研磨加工時にガラス基板１をオーバーハングさせる加工方法の場合、研磨パッド３１０，４１０の端面３１２，４１２に傾斜を付けることにより、ガラス基板１の歩留まり率の大幅な改善が見られた。また、実施例５に示すように、前加工である第１ポリッシュ研磨工程において、端面３１２，４１２を傾斜させた研磨パッド３１０，４１０を用いることにより、実施例１と比較してもガラス基板１の歩留まり率を一層改善することが確認された。 In the processing method in which the glass substrate 1 is overhanged during the polishing process by comparing the examples 2 and 4 and the comparative example 2, the end surfaces 312 and 412 of the polishing pads 310 and 410 are inclined to form the glass substrate 1. A significant improvement in the yield rate was observed. Further, as shown in Example 5, in the first polishing process, which is a pre-process, by using polishing pads 310 and 410 having inclined end faces 312 and 412, the glass substrate 1 is compared with Example 1. It was confirmed that the yield rate was further improved.
　なお、これまでの実施の形態および実施例の説明においては、研磨パッド３１０，４１０の端面３１２，４１２が円錐面の一部を形成し、加工表面３１１，４１１と端面３１２，４１２との間に円形状の境界３１３，４１３が形成される例について説明した。端面３１２，４１２の形状はこの例に限られるものではない。たとえば端面は、球面の一部形状、放物面の一部形状などに代表される、曲面であってもよい。この場合、当該曲面と加工表面との境界における曲面に対する接平面と、加工表面と、が垂直でない角度を形成し、当該接平面が加工表面に対して９０°より大きい角度、望ましくは９５°以上１７０°以下の角度を形成して、傾斜していればよい。 In the description of the embodiments and examples so far, the end surfaces 312 and 412 of the polishing pads 310 and 410 form a part of a conical surface, and the processing surfaces 311 and 411 and the end surfaces 312 and 412 are between them. The example in which the circular boundaries 313 and 413 are formed has been described. The shape of the end faces 312 and 412 is not limited to this example. For example, the end surface may be a curved surface represented by a partial shape of a spherical surface, a partial shape of a paraboloid, or the like. In this case, the tangent plane to the curved surface at the boundary between the curved surface and the machining surface forms an angle that is not perpendicular to the machining surface, and the tangent plane is an angle larger than 90 ° with respect to the machining surface, preferably 95 ° or more. An angle of 170 ° or less may be formed and inclined.
　また、これまでの実施の形態および実施例の説明においては、研磨パッド３１０，４１０を用いてガラス基板１の両主表面１Ａ，１Ｂを平滑化する加工である研磨処理について説明した。研磨処理に限らず、たとえばガラス基板１の両主表面１Ａ，１Ｂの寸法精度の向上を伴う機械加工である研削処理を行なう場合に、本願発明を適用してもよい。 In the description of the embodiments and examples so far, the polishing process, which is a process of smoothing both the main surfaces 1A and 1B of the glass substrate 1 using the polishing pads 310 and 410, has been described. The present invention may be applied not only to the polishing process but also to a grinding process which is a machining process with an improvement in dimensional accuracy of both the main surfaces 1A and 1B of the glass substrate 1, for example.
　以上のように本発明の実施の形態について説明を行なったが、今回開示された実施の形態および実施例はすべての点で例示であって、制限的なものではないと考えられるべきである。この発明の範囲は上記した説明ではなくて請求の範囲によって示され、請求の範囲と均等の意味、および範囲内でのすべての変更が含まれることが意図される。 As described above, the embodiment of the present invention has been described. However, it should be considered that the embodiment and the example disclosed this time are examples in all points and are not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
　１　ガラス基板、１Ａ　表主表面、１Ｂ　裏主表面、２　磁気薄膜層、１０　磁気ディスク、３００　上定盤、３１０，４１０　研磨パッド、３１１，４１１　加工表面、３１２，４１２　端面、３１３，４１３　境界、４００　下定盤、５００　キャリア、６００　スラリー、６０１　不純物、１０００　両面研磨装置、α，β　角度。 1 glass substrate, 1A front main surface, 1B back main surface, 2 magnetic thin film layer, 10 magnetic disk, 300 upper surface plate, 310, 410 polishing pad, 311, 411 processed surface, 312, 412 end surface, 313, 413 boundary, 400 lower surface plate, 500 carrier, 600 slurry, 601 impurities, 1000 double-side polishing machine, α, β angle.

Claims (6)

  1. 　ガラス基板（１）の主表面（１Ａ）に磁気記録層（２）が形成される情報記録媒体用ガラス基板の製造方法であって、
    　前記ガラス基板（１）を形成する工程（Ｓ２０）と、
    　前記主表面（１Ａ）を研削加工または研磨加工する平面状の加工表面（３１１）と前記加工表面（３１１）の周縁を形成する端面（３１２）とを有する加工工具（３１０）の前記加工表面（３１１）を前記主表面（１Ａ）に接触させ、前記加工工具（３１０）を前記主表面（１Ａ）に対して相対的に摺動させて、前記主表面（１Ａ）を加工する工程（Ｓ３４）と、を備え、
    　前記端面（３１２）は、前記加工表面（３１１）に対して９０°より大きい角度を成して傾斜している、情報記録媒体用ガラス基板の製造方法。     A method for producing a glass substrate for an information recording medium in which a magnetic recording layer (2) is formed on a main surface (1A) of a glass substrate (1),
    Forming the glass substrate (1) (S20);
    The processing surface (311) of the processing tool (310) having a flat processing surface (311) for grinding or polishing the main surface (1A) and an end surface (312) forming a peripheral edge of the processing surface (311) ( 311) is brought into contact with the main surface (1A), and the processing tool (310) is slid relative to the main surface (1A) to process the main surface (1A) (S34). And comprising
    The method for producing a glass substrate for an information recording medium, wherein the end surface (312) is inclined at an angle larger than 90 ° with respect to the processed surface (311).
  2. 　前記端面（３１２）は、前記加工表面（３１１）に対して９５°以上１７０°以下の角度を形成する、請求項１に記載の情報記録媒体用ガラス基板の製造方法。 The method for manufacturing a glass substrate for an information recording medium according to claim 1, wherein the end surface (312) forms an angle of 95 ° to 170 ° with respect to the processed surface (311).
  3. 　前記加工する工程（Ｓ３４）において、前記主表面（１Ａ）の一部が前記加工表面（３１１）からはみ出す、請求項１または請求項２に記載の情報記録媒体用ガラス基板の製造方法。 The method for producing a glass substrate for an information recording medium according to claim 1 or 2, wherein a part of the main surface (1A) protrudes from the processed surface (311) in the processing step (S34).
  4. 　前記加工する工程（Ｓ３４）は、前記主表面（１Ａ）の最終研磨工程である、請求項１から請求項３のいずれかに記載の情報記録媒体用ガラス基板の製造方法。 The method for producing a glass substrate for an information recording medium according to any one of claims 1 to 3, wherein the processing step (S34) is a final polishing step of the main surface (1A).
  5. 　前記加工表面（３１１）と前記端面（３１２）とは、前記主表面（１Ａ）を一回または複数回加工した後に洗浄される、請求項１から請求項４のいずれかに記載の情報記録媒体用ガラス基板の製造方法。 The information recording medium according to any one of claims 1 to 4, wherein the processed surface (311) and the end surface (312) are cleaned after the main surface (1A) is processed once or a plurality of times. Method for manufacturing glass substrate.
  6. 　請求項１から請求項５のいずれかに記載の情報記録媒体用ガラス基板の製造方法によって得られたガラス基板（１）と、
    　前記ガラス基板（１）の表面に形成された磁気記録層（２）と、を備える、情報記録媒体（１０）。     A glass substrate (1) obtained by the method for producing a glass substrate for an information recording medium according to any one of claims 1 to 5,
    An information recording medium (10) comprising: a magnetic recording layer (2) formed on the surface of the glass substrate (1).
PCT/JP2011/072949 2011-03-29 2011-10-05 Method for manufacturing glass substrate for information recording medium, and information recording medium WO2012132073A1 (en)

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