WO2011021478A1 - Method for manufacturing glass substrate, glass substrate, method for manufacturing magnetic recording medium, and magnetic recording medium - Google Patents

Method for manufacturing glass substrate, glass substrate, method for manufacturing magnetic recording medium, and magnetic recording medium Download PDF

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Publication number
WO2011021478A1
WO2011021478A1 PCT/JP2010/062588 JP2010062588W WO2011021478A1 WO 2011021478 A1 WO2011021478 A1 WO 2011021478A1 JP 2010062588 W JP2010062588 W JP 2010062588W WO 2011021478 A1 WO2011021478 A1 WO 2011021478A1
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Prior art keywords
glass substrate
polishing
manufacturing
recording medium
magnetic recording
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PCT/JP2010/062588
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French (fr)
Japanese (ja)
Inventor
慎一 佐伯
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コニカミノルタオプト株式会社
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Priority to JP2011527621A priority Critical patent/JPWO2011021478A1/en
Publication of WO2011021478A1 publication Critical patent/WO2011021478A1/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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/042—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C15/00—Surface treatment of glass, not in the form of fibres or filaments, by etching
    • C03C15/02—Surface treatment of glass, not in the form of fibres or filaments, by etching for making a smooth surface
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C19/00—Surface treatment of glass, not in the form of fibres or filaments, by mechanical means

Definitions

  • the present invention relates to a glass substrate manufacturing method, a glass substrate, a magnetic recording medium manufacturing method, and a magnetic recording medium.
  • Such a glass substrate such as a magnetic disk is manufactured by polishing the glass substrate called a blank material.
  • a glass substrate blade material
  • a method of manufacturing by press molding, a method of cutting and manufacturing a plate glass manufactured by a float method, and the like are known. If the glass substrate is cut into a certain shape, the surface has large irregularities, and it is necessary to polish the surface. Also, a technique for polishing with higher accuracy is required because of the demand for higher density.
  • the glass surface finishing process is performed in the order of a first polishing process and a second polishing process (see, for example, Patent Document 1 and Patent Document 2).
  • the first polishing process and the second polishing process are so-called polishing processes. After removing scratches and defects in the first polishing process to make the surface of the glass substrate have a predetermined surface roughness, Polish the surface more precisely.
  • a method of polishing using a polishing liquid containing an abrasive is used in both the first polishing step and the second polishing step.
  • the present invention has been made in view of the above problems, and a glass substrate manufacturing method capable of efficiently manufacturing a glass substrate having high smoothness, and a magnetic recording medium having high smoothness can be efficiently manufactured.
  • An object of the present invention is to provide a method for manufacturing a magnetic recording medium.
  • the present invention has the following features.
  • a method for producing a magnetic recording medium comprising a step of forming a magnetic film on a surface of a glass substrate produced using the method for producing a glass substrate according to 1 above.
  • the step of immersing in acid or alkali, the rinsing step, and the second polishing step are performed in this order, so that the substrate surface is hydrated before the second polishing step.
  • the processing stability of the entire surface of the substrate is improved.
  • the polishing liquid spreads uniformly over the entire surface of the glass substrate with improved processing stability polishing with high smoothness is possible in a short time.
  • FIG. 1 is a diagram showing an overall configuration of a glass substrate 1 according to the present invention.
  • the glass substrate 1 has a donut-shaped disk shape with a hole 5 formed in the center.
  • 10t is an outer peripheral end surface
  • 20t is an inner peripheral end surface
  • 7a is a front main surface
  • 7b is a back main surface.
  • FIG. 2 is a perspective view of a magnetic disk as an example of a magnetic recording medium according to the present invention.
  • the magnetic disk D has a magnetic film 2 directly formed on the surface of a circular glass substrate 1.
  • the magnetic film 2 can also be provided on the back main surface 7b.
  • FIG. 3 is a manufacturing process diagram of an example of a method for manufacturing a glass substrate according to the present invention.
  • the manufacturing process of the present embodiment is characterized in that after performing the first polishing process, before performing the second polishing process, an acid or alkali solution dipping process and a rinsing process are performed in this order.
  • the manufacturing process of the glass substrate of this embodiment is demonstrated in detail using FIG.
  • the glass substrate of the present invention is not limited to a magnetic recording medium, and can be used for a magneto-optical disk, an optical disk, and the like.
  • ⁇ Manufacturing process of glass substrate> There is no particular limitation on the size of the glass substrate. For example, there are glass substrates of various sizes such as an outer diameter of 2.5 inches, 1.8 inches, 1 inch, and 0.8 inches. Further, the thickness of the glass substrate is not limited, and there are glass substrates having various thicknesses such as 2 mm, 1 mm, and 0.63 mm.
  • Glass melting process First, the glass material is melted.
  • soda lime glass mainly composed of SiO 2 , Na 2 O, CaO
  • aluminosilicate glass and borosilicate glass are particularly preferable because they are excellent in impact resistance and vibration resistance.
  • the disc-shaped blank material may be manufactured by cutting a sheet glass formed by, for example, a downdraw method or a float method with a grinding stone, without using press molding.
  • the press-formed blank is drilled at the center with a core drill or the like having a diamond grindstone or the like at the cutter.
  • both surfaces of the glass substrate are lapped to preliminarily adjust the overall shape of the glass substrate, that is, the parallelism, flatness, and thickness of the glass substrate.
  • the inner and outer diameters are processed by grinding the outer peripheral end surface and the inner peripheral end surface of the glass substrate with a grinding wheel such as a drum-like diamond.
  • a grinding wheel such as a drum-like diamond.
  • the outer diameter and roundness of the glass substrate, the inner diameter of the hole, and the concentricity of the glass substrate and the hole are finely adjusted. For example, a 45 ° chamfer of about 0.1 mm to 0.2 mm is performed.
  • the order from the first lapping process after the coring process to the outer peripheral end face machining process is not limited to that shown in FIG. 3 and can be changed as appropriate according to the situation.
  • the lapping process may be performed first, and then the inner / outer diameter machining process, the inner circumference, and the outer circumference end face machining process may be performed.
  • a second lapping step, an inner circumference and an outer circumference end face machining step may be performed.
  • a polishing machine for lapping a glass substrate in the first and second lapping steps will be described.
  • the double-side polishing machine includes a disk-shaped upper surface plate and a lower surface plate that are arranged vertically so as to be parallel to each other, and rotate in opposite directions.
  • a plurality of diamond pellets for wrapping the main surface of the glass substrate are attached to the opposing surfaces of the upper and lower surface plates.
  • Between the upper and lower surface plates there are a plurality of carriers that rotate in combination with an internal gear provided in an annular shape on the outer periphery of the lower surface plate and a sun gear provided around the rotation axis of the lower surface plate.
  • the carrier is provided with a plurality of holes, and a glass substrate is fitted into the holes.
  • the upper and lower surface plates, the internal gear, and the sun gear can be operated by separate driving.
  • the lapping operation of the polishing machine is such that the upper and lower surface plates rotate in opposite directions, and the carrier sandwiched between the surface plates through the diamond pellets rotates with the surface plate holding a plurality of glass substrates. Revolves in the same direction as the lower surface plate relative to the center of rotation.
  • the glass substrate can be lapped by supplying the grinding liquid between the upper surface plate and the glass substrate, and the lower surface plate and the glass substrate.
  • the processing pressure of the surface plate applied to the glass substrate and the rotation speed of the surface plate are adjusted as appropriate according to the desired lapping state.
  • the processing pressure in the first and second lapping steps is preferably 5884 Pa to 11768 Pa.
  • the rotation speed of the surface plate is preferably about 5 to 30 rpm, and the rotation speed of the upper surface plate is preferably about 30 to 40% slower than the lower surface rotation speed. If the processing pressure by the surface plate is increased and the rotation speed of the surface plate is increased, the lapping amount increases. However, if the processing pressure is increased too much, the surface roughness will not be good, and if the rotation speed is too high, the flatness will be increased. Is not good. Further, when the processing pressure is small and the rotation speed of the surface plate is slow, the amount of lapping is small and the production efficiency is lowered.
  • the surface roughness of the main surface of the glass substrate is Rz (maximum height roughness) of 2 ⁇ m to 4 ⁇ m, Ra (arithmetic)
  • the average roughness is preferably about 0.2 ⁇ m to 0.4 ⁇ m.
  • the surface roughness at the time when the first lapping step is completed is preferably such that Rz is 4 ⁇ m to 8 ⁇ m and Ra is about 0.4 ⁇ m to 0.8 ⁇ m.
  • the inner and outer end faces of the glass substrate are polished by brushing in the inner and outer end face processing steps.
  • the brush is preferably made of nylon, polypropylene or the like having a diameter of about 0.2 to 0.3 mm.
  • the polishing liquid is preferably cerium oxide having a particle size of about several ⁇ m.
  • the surface roughness of the inner and outer end faces is preferably such that Rz is 0.2 ⁇ m to 0.4 ⁇ m and Ra is about 0.02 ⁇ m to 0.04 ⁇ m.
  • the shape of the end surface of the glass substrate that has undergone the inner and outer diameter processing steps and the inner and outer peripheral end surface processing steps is such that the corner formed by the main surface and the end surface is removed, and the position is about 0.2 mm to 0.5 mm from the outer peripheral end surface. From the main surface.
  • Ra absolute mean roughness
  • Rz maximum height roughness
  • the diamond pellet and the grinding liquid are used when polishing the glass substrate.
  • a polishing method by attaching a pad to the polishing surface of the upper and lower surface plates and supplying the polishing liquid.
  • the abrasive include cerium oxide, zirconium oxide, aluminum oxide, manganese oxide, colloidal silica, and diamond. These are dispersed in water and used as a slurry.
  • the pad is divided into a hard pad and a soft pad, but can be appropriately selected and used as necessary.
  • the hard pad include pads made of hard velor, urethane foam, pitch-containing suede, etc.
  • examples of the soft pad include pads made of suede, velor, etc.
  • the polishing method using a pad and an abrasive can correspond to rough polishing to precision polishing by changing the particle size of the abrasive and the type of pad. Therefore, in the first lapping step and the second lapping step, the abrasive, the particle size of the abrasive, and the pad are appropriately combined so that the above-mentioned surface roughness can be obtained by efficiently removing large undulations, chips, cracks, etc. Can respond.
  • polishing machines used in the first lapping process and the second lapping process have the same configuration, but it is preferable to perform polishing using different polishing machines prepared for each process. This is because the dedicated diamond pellets are pasted, so that the replacement is a large-scale operation, and complicated operations such as resetting the polishing conditions are required, resulting in a reduction in manufacturing efficiency.
  • the glass substrate is immersed in a chemical strengthening solution to form a chemically strengthened layer on the glass substrate.
  • a chemical strengthening solution By forming the chemical strengthening layer, impact resistance, vibration resistance, heat resistance and the like can be improved.
  • alkali metal ions such as lithium ions and sodium ions contained in the glass substrate are converted into alkali ions such as potassium ions having a larger ion radius. This is performed by the ion exchange method for substitution. Compressive stress is generated in the ion-exchanged region due to the distortion caused by the difference in ion radius, and the surface of the glass substrate is strengthened.
  • the chemical strengthening treatment liquid is not particularly limited, and a known chemical strengthening treatment liquid can be used. Usually, it is common to use a molten salt containing potassium ions or a molten salt containing potassium ions and sodium ions. Examples of the molten salt containing potassium ions and sodium ions include potassium and sodium nitrates, carbonates, sulfates, and mixed molten salts thereof. Among these, from the viewpoint that the melting point is low and deformation of the glass substrate can be prevented, it is preferable to use nitrate.
  • the chemical strengthening solution is heated to a temperature higher than the temperature at which the above components melt.
  • the heating temperature of the chemical strengthening treatment liquid is preferably lower than the glass transition point (Tg) of the glass substrate, more preferably lower than the glass transition point ⁇ 50 ° C.
  • the glass substrate is placed in a preheating tank prior to immersion in the chemical strengthening treatment liquid. You may have the preheating process heated to predetermined temperature.
  • the thickness of the chemically strengthened layer is preferably in the range of about 5 ⁇ m to 15 ⁇ m in view of improving the strength of the glass substrate and shortening the polishing process time.
  • the thickness of the reinforcing layer is within this range, a glass substrate having good impact resistance, which is flatness and mechanical strength, can be obtained.
  • the shape of the outer peripheral edge of the front main surface 7a after the chemical strengthening process is almost the same as that before the chemical strengthening process, and the above-mentioned chemical strengthening layer of about 5 ⁇ m to 15 ⁇ m is almost uniformly placed on the entire surface of the glass substrate. It becomes.
  • polishing process Next, the polishing process will be described.
  • the surface of the glass substrate is precisely finished, and the shape of the outer peripheral end of the main surface is polished to a desired shape.
  • polishing can be done.
  • the polishing method uses a polishing machine having the same configuration as the polishing machine used in the first and second lapping processes, except that a pad and a polishing liquid are used instead of the diamond pellets and the grinding liquid used in the lapping process. .
  • the pad is a hard pad having a hardness A of about 80 to 90, and it is preferable to use, for example, urethane foam.
  • the abrasive is preferably used in the form of a slurry by dispersing cerium oxide, colloidal silica, zirconium oxide, titanium oxide, manganese oxide or the like having a particle size of 0.6 ⁇ m to 2.5 ⁇ m in water.
  • the mixing ratio of water and abrasive is preferably about 1: 1 to 4: 1.
  • the processing pressure on the glass substrate by the surface plate is preferably 8826 Pa to 10787 Pa.
  • the processing pressure applied to the glass substrate by the surface plate greatly affects the shape of the outer peripheral edge. As the processing pressure is increased, the inner side of the outer peripheral end tends to decrease and increase toward the outer side. Further, when the processing pressure is reduced, the outer peripheral end portion tends to be close to a flat surface and the surface sagging increases. The processing pressure can be determined while observing such a tendency.
  • the rotation speed of the surface plate is changed from 20 rpm to 60 rpm so that the flatness obtained until the chemical strengthening process is maintained and the surface roughness is further improved, and the rotation speed of the upper surface plate is set from the lower surface plate rotation speed. It is preferable to slow by 30% to 40%.
  • the polishing amount is preferably 30 ⁇ m to 40 ⁇ m according to the above polishing conditions. If it is less than 30 ⁇ m, scratches and defects cannot be removed sufficiently. If it exceeds 40 ⁇ m, the surface roughness can be in the range of Rz from 0.2 nm to 30 nm and Ra from 0.5 nm to 2 nm. However, polishing is performed more than necessary, and the production efficiency decreases.
  • a modification treatment is performed in which the glass substrate is immersed in an acid or alkali solution to remove a hydrated layer or a work-affected layer on the surface of the glass substrate.
  • the entire surface of the glass substrate can be uniformly and stably polished in the second polishing step.
  • the acid or alkali used in this step is not particularly limited, and for example, an acid such as HF or H 2 SO 4 or an alkaline solution such as NaOH or KOH can be used.
  • the temperature of the acid or alkali solution is preferably 20 ° C. to 40 ° C., and the immersion time is preferably in the range of 60 sec to 300 sec.
  • the glass substrate is immersed in pure water or the like to remove the acid or alkali solution attached to the glass substrate.
  • the second polishing step is a step of polishing the surface of the glass substrate after the first polishing step more precisely.
  • the pad used in the second polishing step is a soft pad having a hardness of about 65 to 80 (Asker-C) that is softer than the pad used in the first polishing step.
  • Asker-C urethane foam or suede is preferably used.
  • As the abrasive cerium oxide, colloidal silica, zirconium oxide, titanium oxide, manganese oxide, and the like similar to those in the first polishing step can be used. However, in order to make the surface of the glass substrate smoother, the particle size is finer. It is preferable to use an abrasive with little variation.
  • An abrasive having an average particle size of 10 nm to 100 nm is dispersed in water to form a slurry and used as a polishing liquid.
  • the mixing ratio of water and abrasive is preferably about 3: 1 to 20: 1.
  • the glass substrate before the second polishing step, the glass substrate is immersed in an acid or alkali solution to remove the hydrated layer or the work-affected layer on the surface of the glass substrate. Compared to immediately after the first polishing step, it is greatly improved.
  • the polishing liquid spreads uniformly on the surface of the glass substrate, and uniform polishing characteristics are obtained over the entire surface of the glass substrate.
  • the processing pressure on the glass substrate by the surface plate is preferably 8826 Pa to 10787 Pa.
  • the processing pressure applied to the glass substrate by the surface plate greatly affects the shape of the outer peripheral edge as in the first polishing step, but the shape cannot be changed as efficiently as the first polishing step because the polishing rate is slow.
  • the change in the shape of the outer peripheral end due to the adjustment of the processing pressure is the same as in the first polishing step, and when the processing pressure is increased, the inner side of the outer peripheral end tends to decrease and increase toward the outside. Further, when the processing pressure is reduced, the outer peripheral end portion tends to be close to a flat surface and the surface sagging increases. In order to obtain the shape of the outer peripheral end, the processing pressure can be determined while observing such a tendency.
  • the rotation speed of the surface plate is preferably 5 to 50 rpm, and the rotation speed of the upper surface plate is preferably 30% to 40% slower than the rotation speed of the lower surface plate.
  • the polishing conditions in the second polishing step are adjusted to obtain a desired shape of the outer peripheral edge, and the surface roughness Ra can be 0.15 nm or less.
  • the polishing amount is preferably 2 ⁇ m to 5 ⁇ m. When the polishing amount is within this range, minute defects such as minute roughness and undulation generated on the surface and minute scratches generated in the process so far can be efficiently removed.
  • the manufacturing method of the glass substrate for information recording media you may have various processes other than the above. For example, an annealing process for relaxing internal strain of the glass substrate, a heat shock process for confirming the reliability of the strength of the glass substrate, various inspection / evaluation processes, and the like may be included.
  • the polishing machine used in the first polishing process it is preferable not to use the polishing machine used in the first polishing process as it is, but to polish using another polishing machine that has the same configuration but is prepared for each process. . This is because, if the polishing machine used in the first polishing step is used as it is, the polishing accuracy in the second polishing step decreases due to the abrasive remaining in the first polishing step, and the polishing conditions are reset. This is because work is required and the production efficiency is lowered.
  • a conventionally known method can be used as a method for forming the magnetic film 2.
  • a method in which a thermosetting resin in which magnetic particles are dispersed is spin-coated on a substrate, or a method in which sputtering or electroless plating is used. The method of doing is mentioned.
  • the film thickness by spin coating is about 0.3 ⁇ m to 1.2 ⁇ m
  • the film thickness by sputtering is about 0.04 ⁇ m to 0.08 ⁇ m
  • the film thickness by electroless plating is 0.05 ⁇ m to 0.1 ⁇ m. From the viewpoint of thinning and densification, film formation by sputtering and electroless plating is preferable.
  • the magnetic material used for the magnetic film is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Ni having a high crystal anisotropy is basically used, and Ni or A Co-based alloy to which Cr is added is suitable. Specific examples include CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, and CoNiPt containing Co as a main component, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, and CoCrPtSiO.
  • the magnetic film may have a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa) that is divided by a nonmagnetic film (for example, Cr, CrMo, CrV, etc.) to reduce noise.
  • a nonmagnetic film for example, Cr, CrMo, CrV, etc.
  • granular materials such as ferrite, iron-rare earth, and non-magnetic films made of SiO 2 , BN, etc. are dispersed with magnetic particles such as Fe, Co, FeCo, CoNiPt, etc. Also good.
  • the magnetic film may be of any recording type of inner surface type and vertical type.
  • a lubricant may be thinly coated on the surface of the magnetic film in order to improve the sliding of the magnetic head.
  • the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.
  • an underlayer or a protective layer may be provided.
  • the underlayer in the magnetic disk 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.
  • Cr alone or a Cr alloy is preferable from the viewpoint of improving magnetic characteristics.
  • the underlayer is not limited to a single layer, and may have a multi-layer structure in which the same or different layers are stacked.
  • 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 that prevents wear and corrosion of the magnetic film 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.
  • these protective layers may be a single layer, or may have a multilayer structure including the same or different layers. Note that another protective layer may be formed on the protective layer or instead of the protective layer.
  • tetraalkoxysilane is diluted with an alcohol solvent on the Cr layer, and then colloidal silica fine particles are dispersed and applied, and then baked to form a silicon dioxide (SiO 2 ) layer. It may be formed.
  • Example 10 The glass substrates of Examples 1 to 12 were produced as follows.
  • Aluminosilicate glass (Tg: 500 ° C.) was used as a glass material, and 1200 pieces of blank materials were produced by press molding the molten glass.
  • Example 1 (Acid or alkaline solution dipping process)
  • glass substrates were immersed in 25 ° C. solutions of HF having different concentrations for 120 seconds.
  • the concentration of the HF solution was 0.1% by mass in Example 1, 0.3% by mass in Example 2, 0.5% by mass in Example 3, 1.0% by mass in Example 4, and Example 5 Then, it was 1.5 mass%.
  • each glass substrate was immersed in a solution of NaOH having a different concentration at 25 ° C. for 120 seconds.
  • the concentration of the NaOH solution was 0.1% by weight in Example 6, 0.3% by weight in Example 7, 0.5% by weight in Example 8, 1.0% by weight in Example 9, and Example 10 Was 2.0 mass%, Example 11 was 3.0 mass%, and Example 12 was 5.0 mass%.
  • polishing step A suede pad manufactured by FILWEL was used, and cerium oxide and colloidal silica were used as the abrasive.
  • the polishing conditions were pad hardness 80 (Asker-C), abrasive particle size 30 (nm), rotation speed 30 (rpm), and processing pressure 10787 (Pa).
  • the polishing rate was determined from the polishing amount when the glass substrates of Examples 1 to 12 were polished for a predetermined time. Next, polishing was performed by obtaining a processing time for the polishing amount to be a target of 2 ⁇ m from the polishing rates of Examples 1 to 12.
  • the target polishing amount of the comparative example is also 2 ⁇ m.
  • the processing time was set to 33.4 minutes from the polishing rate under the conditions of the comparative example obtained by conducting an experiment in advance.
  • the temperature conditions and the like in each step are the same as those in Example 1.
  • 100 glass substrates were produced.
  • the polishing rate was obtained from the polishing amount when the glass substrate was polished for a predetermined time in the second polishing step.
  • the surface roughness Ra was measured using an atomic force microscope (AFM) based on JIS B0601: 2001.
  • the number of surface defects was determined by irradiating the surface of the glass substrate with laser using OSA (Optical Surface Analyzer) and detecting the surface defects from scattering.
  • the detection sensitivity was set to 0.08 ⁇ m, and the number of defects having a size of 0.1 ⁇ m or more on the substrate surface was evaluated.
  • Waviness Wa was measured using a multi-function disk interferometer (Optiflat Phase Shift Technology Inc.), and the entire surface of the glass substrate was measured.
  • the measurement principle is a method of measuring a subtle shape change of the surface by irradiating the surface of the glass substrate with white light and measuring an intensity change of interference between the reference light and the measurement light having different phases.
  • the obtained measurement data was cut off with a period of 5 mm or more to obtain a waviness Wa.
  • Table 1 shows the average values of the measurement results obtained by measuring the polishing rate, surface roughness, waviness Wa and the number of surface defects on the surface of each of the 100 glass substrates prepared in Examples 1 to 12.
  • the polishing rate is described as a ratio with the polishing rate of the comparative example being 0.06 ⁇ m / min as 1.
  • Table 2 shows the average values of the measurement results obtained by measuring the polishing rate, surface roughness, waviness Wa and the number of surface defects on the surface of each of 100 glass substrates prepared in Comparative Examples.
  • the polishing rate of the comparative example is 0.06 ⁇ m / min.
  • polishing rates of Examples 1 to 12 are all higher than the polishing rate of the comparative example, and each example can shorten the processing time of the second polishing step compared to the comparative example.
  • Example 1 the number of surface defects was smaller than that of the comparative example. Further, in Examples 1 and 2, the waviness Wa and the surface roughness Ra are both smaller than the waviness Wa and the surface roughness Ra of the comparative example, and can be processed into a surface state having higher smoothness than the comparative example.
  • the waviness Wa is in the range of 0.32 nm to 0.38 nm
  • the surface roughness Ra is in the range of 0.12 nm to 0.14 nm
  • the waviness Wa of the comparative example is 0.36 nm.
  • the roughness Ra was approximately equivalent to 0.12 nm.
  • a glass substrate manufacturing method capable of efficiently manufacturing a glass substrate having high smoothness, and a magnetism capable of efficiently manufacturing a magnetic recording medium having high smoothness.
  • a method for manufacturing a recording medium can be provided.

Abstract

Disclosed is a method for manufacturing a glass substrate, which has a step of immersing the glass substrate in an acid or alkaline solution, and a rinse step wherein the glass substrate, which has been subjected to the immersing step, is cleaned. In the method, after performing a first polishing step, the immersion step, the rinse step, and a second polishing step are performed in this order. Thus, the glass substrate having high smoothness can be efficiently manufactured.

Description

ガラス基板の製造方法、ガラス基板、磁気記録媒体の製造方法および磁気記録媒体Glass substrate manufacturing method, glass substrate, magnetic recording medium manufacturing method, and magnetic recording medium
　本発明は、ガラス基板の製造方法、ガラス基板、磁気記録媒体の製造方法および磁気記録媒体に関する。 The present invention relates to a glass substrate manufacturing method, a glass substrate, a magnetic recording medium manufacturing method, and a magnetic recording medium.
　従来、コンピュータ等に用いられる情報記録媒体として磁気ディスクがある。磁気ディスク用基板としては、アルミニウム基板が一般的に用いられてきた。しかし、近年、記録密度向上のための磁気ヘッド浮上量の低減の要請に伴い、アルミニウム基板よりも表面の平滑性に優れ、しかも表面欠陥が少ないことから磁気ヘッド浮上量の低減を図ることができるガラス基板を磁気ディスク用基板として用いる割合が増えてきている。 Conventionally, there is a magnetic disk as an information recording medium used for a computer or the like. As a magnetic disk substrate, an aluminum substrate has been generally used. However, in recent years, with the demand for a reduction in the flying height of the magnetic head for improving the recording density, the surface smoothness is superior to that of an aluminum substrate and the surface defects are few, so that the flying height of the magnetic head can be reduced. The proportion of using glass substrates as magnetic disk substrates is increasing.
　このような磁気ディスク等のガラス基板は、ブランク材と呼ばれるガラス基板に研磨加工等を施すことによって製造される。ガラス基板（ブランク材）は、プレス成形によって製造する方法や、フロート法等によって作製された板ガラスを切断して製造する方法等が知られている。一定の形状に切り出されたガラス基板のままでは表面の凹凸が大きく、表面研磨を行う必要があり、また、高密度化の要請からより高精度に研磨する技術が求められている。 Such a glass substrate such as a magnetic disk is manufactured by polishing the glass substrate called a blank material. As for a glass substrate (blank material), a method of manufacturing by press molding, a method of cutting and manufacturing a plate glass manufactured by a float method, and the like are known. If the glass substrate is cut into a certain shape, the surface has large irregularities, and it is necessary to polish the surface. Also, a technique for polishing with higher accuracy is required because of the demand for higher density.
　従来、よく知られているように、ガラスの表面仕上げの工程は、第１研磨工程、第２研磨工程の順に行われる（例えば、特許文献１、特許文献２参照）。 Conventionally, as is well known, the glass surface finishing process is performed in the order of a first polishing process and a second polishing process (see, for example, Patent Document 1 and Patent Document 2).
　第１研磨工程、第２研磨工程はいわゆる研磨工程であり、第１研磨工程でキズや欠陥を除去してガラス基板の表面を所定の面粗さにした後、第２研磨工程でガラス基板の表面をさらに精密に研磨する。近年、ガラス基板には非常に高いレベルの平滑性が要求されるため、第１研磨工程、第２研磨工程ではともに研磨剤を含む研磨液を用いて研磨する方法が用いられている。 The first polishing process and the second polishing process are so-called polishing processes. After removing scratches and defects in the first polishing process to make the surface of the glass substrate have a predetermined surface roughness, Polish the surface more precisely. In recent years, since glass substrates are required to have a very high level of smoothness, a method of polishing using a polishing liquid containing an abrasive is used in both the first polishing step and the second polishing step.
特開平５－８９４５９号公報Japanese Patent Laid-Open No. 5-89459 特開平１１－１５４３２５号公報JP-A-11-154325
　しかしながら、特許文献１、特許文献２に開示されている従来の研磨工程では、高いレベルの平滑性を有するガラス基板を効率的に製造することが非常に困難になってきた。 However, in the conventional polishing processes disclosed in Patent Document 1 and Patent Document 2, it has become very difficult to efficiently manufacture a glass substrate having a high level of smoothness.
　本発明は上記課題に鑑みてなされたものであり、平滑性の高いガラス基板を効率的に製造することができるガラス基板の製造方法、平滑性の高い磁気記録媒体を効率的に製造することができる磁気記録媒体の製造方法を提供することを目的とする。 The present invention has been made in view of the above problems, and a glass substrate manufacturing method capable of efficiently manufacturing a glass substrate having high smoothness, and a magnetic recording medium having high smoothness can be efficiently manufactured. An object of the present invention is to provide a method for manufacturing a magnetic recording medium.
　上記の課題を解決するために、本発明は以下の特徴を有するものである。 In order to solve the above problems, the present invention has the following features.
　１．研磨剤を含む研磨液を用いてガラス基板の表面を研磨する第１研磨工程と第２研磨工程とを有するガラス基板の製造方法において、
　前記ガラス基板を酸またはアルカリの溶液に浸漬する酸またはアルカリ溶液浸漬工程と、
　前記酸またはアルカリ溶液浸漬工程を終えたガラス基板に付着した酸またはアルカリ溶液を除去するリンス工程と、
　を有し、
　前記第１研磨工程を行った後、前記酸またはアルカリ溶液浸漬工程と前記リンス工程と前記第２研磨工程とをこの順に行うことを特徴とするガラス基板の製造方法。 1. In the method for manufacturing a glass substrate having a first polishing step and a second polishing step for polishing the surface of the glass substrate using a polishing liquid containing an abrasive,
An acid or alkali solution immersing step of immersing the glass substrate in an acid or alkali solution;
A rinsing step for removing the acid or alkali solution attached to the glass substrate after the acid or alkali solution immersion step;
Have
After the said 1st grinding | polishing process, the said acid or alkali solution immersion process, the said rinse process, and the said 2nd grinding | polishing process are performed in this order.
　２．前記浸漬工程に用いられる酸はフッ化水素であることを特徴とする前記１に記載のガラス基板の製造方法。 2. 2. The method for producing a glass substrate according to 1 above, wherein the acid used in the dipping step is hydrogen fluoride.
　３．前記浸漬工程に用いられるアルカリは水酸化ナトリウムであることを特徴とする前記１に記載のガラス基板の製造方法。 3. 2. The method for producing a glass substrate according to 1 above, wherein the alkali used in the dipping step is sodium hydroxide.
　４．前記第２研磨工程における研磨量は２μｍから５μｍであることを特徴とする前記１から３のいずれか１項に記載のガラス基板の製造方法。 4. 4. The method for manufacturing a glass substrate according to any one of 1 to 3, wherein a polishing amount in the second polishing step is 2 μm to 5 μm.
　５．化学強化液にガラス基板を浸漬してガラス基板に化学強化層を形成する化学強化工程を更に有することを特徴とする前記１から４のいずれか１項に記載のガラス基板の製造方法。 5. 5. The method for producing a glass substrate according to any one of 1 to 4, further comprising a chemical strengthening step of immersing the glass substrate in a chemical strengthening solution to form a chemical strengthening layer on the glass substrate.
　６．前記１から５のいずれか１項に記載のガラス基板の製造方法を用いて製造されたことを特徴とするガラス基板。 6. A glass substrate manufactured using the method for manufacturing a glass substrate according to any one of 1 to 5 above.
　７．前記１に記載のガラス基板の製造方法を用いて製造したガラス基板の表面に磁性膜を形成する工程を有することを特徴とする磁気記録媒体の製造方法。 7. A method for producing a magnetic recording medium, comprising a step of forming a magnetic film on a surface of a glass substrate produced using the method for producing a glass substrate according to 1 above.
　８．前記７に記載の磁気記録媒体の製造方法を用いて製造されたことを特徴とする磁気記録媒体。 8. 8. A magnetic recording medium manufactured using the method for manufacturing a magnetic recording medium according to 7.
　本発明によれば、第１研磨工程を行った後、酸またはアルカリに浸漬する工程とリンス工程と第２研磨工程とをこの順に行うので、第２研磨工程を行う前に基板表面の水和層や加工変質層が除去され、基板全面の加工安定性が向上する。第２研磨工程では加工安定性が向上したガラス基板の全面に均一に研磨液が広がるので短時間で平滑度の高い研磨が可能になる。 According to the present invention, after performing the first polishing step, the step of immersing in acid or alkali, the rinsing step, and the second polishing step are performed in this order, so that the substrate surface is hydrated before the second polishing step. Thus, the processing stability of the entire surface of the substrate is improved. In the second polishing step, since the polishing liquid spreads uniformly over the entire surface of the glass substrate with improved processing stability, polishing with high smoothness is possible in a short time.
　したがって、平滑性の高いガラス基板を効率的に製造することができるガラス基板の製造方法、および平滑性の高い磁気記録媒体を効率的に製造することができる磁気記録媒体の製造方法を提供することができる。 Accordingly, it is possible to provide a method for producing a glass substrate capable of efficiently producing a glass substrate having high smoothness, and a method for producing a magnetic recording medium capable of efficiently producing a magnetic recording medium having high smoothness. Can do.
ガラス基板の全体構成を示す図である。It is a figure which shows the whole structure of a glass substrate. ガラス基板の表主表面の上に磁性膜を備えている磁気記録媒体の例を示す図である。It is a figure which shows the example of the magnetic recording medium provided with the magnetic film on the front main surface of a glass substrate. ガラス基板の製造における工程を説明する製造工程図である。It is a manufacturing process figure explaining the process in manufacture of a glass substrate.
　本発明を図示の実施の形態に基づいて説明するが、本発明は該実施の形態に限らない。 The present invention will be described based on the illustrated embodiment, but the present invention is not limited to the embodiment.
　図１は、本発明に係るガラス基板１の全体構成を示す図である。図１に示す様に、ガラス基板１は、中心に孔５が形成されたドーナツ状の円板形状をしている。１０ｔは外周端面、２０ｔは内周端面、７ａは表主表面、７ｂは裏主表面を示している。 FIG. 1 is a diagram showing an overall configuration of a glass substrate 1 according to the present invention. As shown in FIG. 1, the glass substrate 1 has a donut-shaped disk shape with a hole 5 formed in the center. 10t is an outer peripheral end surface, 20t is an inner peripheral end surface, 7a is a front main surface, and 7b is a back main surface.
　図２は、本発明に係る磁気記録媒体の一例である磁気ディスクの斜視図である。磁気ディスクＤは、円形のガラス基板１の表面に磁性膜２が直接形成されている。なお、磁性膜２は裏主表面７ｂの上にも設けることができる。 FIG. 2 is a perspective view of a magnetic disk as an example of a magnetic recording medium according to the present invention. The magnetic disk D has a magnetic film 2 directly formed on the surface of a circular glass substrate 1. The magnetic film 2 can also be provided on the back main surface 7b.
　図３は、本発明に係るガラス基板の製造方法の一例の製造工程図である。 FIG. 3 is a manufacturing process diagram of an example of a method for manufacturing a glass substrate according to the present invention.
　本実施形態の製造工程では、第１研磨工程を行った後、第２研磨工程を行う前に、酸またはアルカリ溶液浸漬工程とリンス工程とをこの順に行っている点が特徴である。図３を用いて、本実施形態のガラス基板の製造工程について詳しく説明する。 The manufacturing process of the present embodiment is characterized in that after performing the first polishing process, before performing the second polishing process, an acid or alkali solution dipping process and a rinsing process are performed in this order. The manufacturing process of the glass substrate of this embodiment is demonstrated in detail using FIG.
　なお、本発明のガラス基板は、磁気記録媒体に限定されるものではなく、光磁気ディスクや光ディスクなどにも用いることができる。 The glass substrate of the present invention is not limited to a magnetic recording medium, and can be used for a magneto-optical disk, an optical disk, and the like.
　＜ガラス基板の製造工程＞
　ガラス基板の大きさに特に限定はない。例えば、外径が２．５インチ、１．８インチ、１インチ、０．８インチなど種々の大きさのガラス基板がある。また、ガラス基板の厚みにも限定はなく、２ｍｍ、１ｍｍ、０．６３ｍｍなど種々の厚みのガラス基板がある。 <Manufacturing process of glass substrate>
There is no particular limitation on the size of the glass substrate. For example, there are glass substrates of various sizes such as an outer diameter of 2.5 inches, 1.8 inches, 1 inch, and 0.8 inches. Further, the thickness of the glass substrate is not limited, and there are glass substrates having various thicknesses such as 2 mm, 1 mm, and 0.63 mm.
　（ガラス溶融工程）
　最初に、ガラス素材を溶融する。 (Glass melting process)
First, the glass material is melted.
　ガラス基板の材料としては特に制限はない。例えば、ＳｉＯ２、Ｎａ２Ｏ、ＣａＯを主成分としたソーダライムガラス；ＳｉＯ２、Ａｌ２Ｏ３、Ｒ２Ｏ（Ｒ＝Ｋ、Ｎａ、Ｌｉ）を主成分としたアルミノシリケートガラス；ボロシリケートガラス；Ｌｉ２Ｏ－ＳｉＯ２系ガラス；Ｌｉ２Ｏ－Ａｌ２Ｏ３－ＳｉＯ２系ガラス；Ｒ’Ｏ－Ａｌ２Ｏ３－ＳｉＯ２系ガラス（Ｒ’＝Ｍｇ、Ｃａ、Ｓｒ、Ｂａ）などを使用することができる。中でも、アルミノシリケートガラスやボロシリケートガラスは、耐衝撃性や耐振動性に優れるため特に好ましい。 There is no restriction | limiting in particular as a material of a glass substrate. For example, soda lime glass mainly composed of SiO 2 , Na 2 O, CaO; aluminosilicate glass mainly composed of SiO 2 , Al 2 O 3 , R 2 O (R = K, Na, Li); borosilicate Glass; Li 2 O—SiO 2 glass; Li 2 O—Al 2 O 3 —SiO 2 glass; R′O—Al 2 O 3 —SiO 2 glass (R ′ = Mg, Ca, Sr, Ba) Etc. can be used. Among these, aluminosilicate glass and borosilicate glass are particularly preferable because they are excellent in impact resistance and vibration resistance.
　（プレス成形工程）
　溶融ガラスを下型に流し込み、上型によってプレス成形して円板状のブランク材を得る。なお、円板状のブランク材は、プレス成形によらず、例えばダウンドロー法やフロート法で形成したシートガラスを研削砥石で切り出して作製してもよい。 (Press molding process)
Molten glass is poured into the lower mold and press-molded with the upper mold to obtain a disk-shaped blank. Note that the disc-shaped blank material may be manufactured by cutting a sheet glass formed by, for example, a downdraw method or a float method with a grinding stone, without using press molding.
　（コアリング加工工程）
　プレス成形したブランク材は、カッター部にダイヤモンド砥石等を備えたコアドリル等で中心部に孔を開ける。 (Coring process)
The press-formed blank is drilled at the center with a core drill or the like having a diamond grindstone or the like at the cutter.
　（第１ラッピング工程）
　次に、ガラス基板の両表面をラッピング加工し、ガラス基板の全体形状、すなわちガラス基板の平行度、平坦度および厚みを予備調整する。 (First lapping process)
Next, both surfaces of the glass substrate are lapped to preliminarily adjust the overall shape of the glass substrate, that is, the parallelism, flatness, and thickness of the glass substrate.
　（内・外径加工工程）
　次に、ガラス基板の外周端面および内周端面を、例えば鼓状のダイヤモンド等の研削砥石により研削することで内・外径加工する。この内・外径加工により、ガラス基板の外径寸法および真円度、孔の内径寸法、並びにガラス基板と孔との同心度を微調整し、また、ガラス基板の内・外周角部を、例えば、０．１ｍｍから０．２ｍｍ程度の４５°の面取りをする。 (Inner / outer diameter machining process)
Next, the inner and outer diameters are processed by grinding the outer peripheral end surface and the inner peripheral end surface of the glass substrate with a grinding wheel such as a drum-like diamond. By this inner / outer diameter processing, the outer diameter and roundness of the glass substrate, the inner diameter of the hole, and the concentricity of the glass substrate and the hole are finely adjusted. For example, a 45 ° chamfer of about 0.1 mm to 0.2 mm is performed.
　（内周端面加工工程）
　この後、ガラス基板の内周端面を、研磨液を使用したブラシ研磨により面取り部の角部を曲面とし、また微細なキズ等を除去する。 (Inner peripheral end face machining process)
Thereafter, the corners of the chamfered portion are curved by brush polishing using a polishing liquid on the inner peripheral end surface of the glass substrate, and fine scratches and the like are removed.
　（第２ラッピング工程）
　次に、ガラス基板の両表面を再びラッピング加工して、ガラス基板の平行度、平坦度および厚みを微調整する。 (Second wrapping process)
Next, the both surfaces of the glass substrate are lapped again to finely adjust the parallelism, flatness and thickness of the glass substrate.
　（外周端面加工工程）
　そして、ガラス基板の外周端面を、研磨液を使用したブラシ研磨により面取り部の角部を曲面とし、また微細なキズ等を除去する。 (Outer peripheral end face machining process)
And the corner | angular part of a chamfering part is made into a curved surface by brush grinding | polishing which uses polishing liquid for the outer peripheral end surface of a glass substrate, and a fine crack etc. are removed.
　なお、コアリング加工以降の第１ラッピング工程から外周端面加工工程までの順序は、図３に示したものに限定されず、状況に応じて適宜変更することができる。例えば、ラッピング工程を一つにして最初に行い、その後、内・外径加工工程、内周、外周端面加工工程を行っても良い。また、第１ラッピング工程、内・外径加工工程の後、第２ラッピング工程、内周、外周端面加工工程を行っても良い。 In addition, the order from the first lapping process after the coring process to the outer peripheral end face machining process is not limited to that shown in FIG. 3 and can be changed as appropriate according to the situation. For example, the lapping process may be performed first, and then the inner / outer diameter machining process, the inner circumference, and the outer circumference end face machining process may be performed. Further, after the first lapping step and the inner / outer diameter machining step, a second lapping step, an inner circumference and an outer circumference end face machining step may be performed.
　第１及び第２ラッピング工程にてガラス基板をラッピングする研磨機について説明する。研磨機は、両面研磨機と呼ばれる公知の研磨機を使用できる。両面研磨機は、互いに平行になるように上下に配置された円盤状の上定盤と下定盤とを備えており、互いに逆方向に回転する。この上下の定盤の対向するそれぞれの面にガラス基板の主表面をラッピングするための複数のダイヤモンドペレットが貼り付けてある。上下の定盤の間には、下定盤の外周に円環状に設けてあるインターナルギアと下定盤の回転軸の周囲に設けてある太陽ギアとに結合して回転する複数のキャリアがある。このキャリアには、複数の穴が設けてあり、この穴にガラス基板をはめ込んで配置する。上下の定盤、インターナルギア及び太陽ギアは別駆動で動作することができる。 A polishing machine for lapping a glass substrate in the first and second lapping steps will be described. As the polishing machine, a known polishing machine called a double-side polishing machine can be used. The double-side polishing machine includes a disk-shaped upper surface plate and a lower surface plate that are arranged vertically so as to be parallel to each other, and rotate in opposite directions. A plurality of diamond pellets for wrapping the main surface of the glass substrate are attached to the opposing surfaces of the upper and lower surface plates. Between the upper and lower surface plates, there are a plurality of carriers that rotate in combination with an internal gear provided in an annular shape on the outer periphery of the lower surface plate and a sun gear provided around the rotation axis of the lower surface plate. The carrier is provided with a plurality of holes, and a glass substrate is fitted into the holes. The upper and lower surface plates, the internal gear, and the sun gear can be operated by separate driving.
　研磨機のラッピング動作は、上下の定盤が互いに逆方向に回転し、ダイヤモンドペレットを介して定盤に挟まれているキャリアは、複数のガラス基板を保持した状態で、自転しながら定盤の回転中心に対して下定盤と同じ方向に公転する。このような動作している研磨機において、研削液を上定盤とガラス基板及び下定盤とガラス基板との間に供給することでガラス基板のラッピングを行うことができる。 The lapping operation of the polishing machine is such that the upper and lower surface plates rotate in opposite directions, and the carrier sandwiched between the surface plates through the diamond pellets rotates with the surface plate holding a plurality of glass substrates. Revolves in the same direction as the lower surface plate relative to the center of rotation. In the polishing machine operating in this manner, the glass substrate can be lapped by supplying the grinding liquid between the upper surface plate and the glass substrate, and the lower surface plate and the glass substrate.
　この両面研磨機を使用する際、ガラス基板に加わる定盤の加工圧力及び定盤の回転数を所望のラッピング状態に応じて適宜調整する。第１及び第２ラッピング工程における加工圧力は、５８８４Ｐａから１１７６８Ｐａとするのが好ましい。また、定盤の回転数は、５ｒｐｍから３０ｒｐｍ程度とし、上の定盤の回転数を下の定盤回転数より３０％から４０％程度遅くするのが好ましい。定盤による加工圧力を大きくし、定盤の回転数を速くするとラッピング量は多くなるが、加工圧力を大きくしすぎると面粗さが良好とならず、また、回転数が速すぎると平坦度が良好とならない。また加工圧力が小さく定盤の回転数が遅いとラッピング量が少なく製造効率が低くなる。 When using this double-side polishing machine, the processing pressure of the surface plate applied to the glass substrate and the rotation speed of the surface plate are adjusted as appropriate according to the desired lapping state. The processing pressure in the first and second lapping steps is preferably 5884 Pa to 11768 Pa. Further, the rotation speed of the surface plate is preferably about 5 to 30 rpm, and the rotation speed of the upper surface plate is preferably about 30 to 40% slower than the lower surface rotation speed. If the processing pressure by the surface plate is increased and the rotation speed of the surface plate is increased, the lapping amount increases. However, if the processing pressure is increased too much, the surface roughness will not be good, and if the rotation speed is too high, the flatness will be increased. Is not good. Further, when the processing pressure is small and the rotation speed of the surface plate is slow, the amount of lapping is small and the production efficiency is lowered.
　第２ラッピング工程を終えた時点で、大きなうねり、欠け、ひび等の欠陥は除去され、ガラス基板の主表面の面粗さは、Ｒｚ（最大高さ粗さ）が２μｍから４μｍ、Ｒａ（算術平均粗さ）が０．２μｍから０．４μｍ程度とするのが好ましい。このような面状態にしておくことで、次の化学強化工程を経て第１研磨工程で研磨を効率よく行うことができる。 Upon completion of the second lapping step, defects such as large waviness, chipping and cracks are removed, and the surface roughness of the main surface of the glass substrate is Rz (maximum height roughness) of 2 μm to 4 μm, Ra (arithmetic) The average roughness is preferably about 0.2 μm to 0.4 μm. By setting it as such a surface state, it can polish efficiently by a 1st grinding | polishing process through the following chemical strengthening process.
　尚、第１ラッピング工程では、第２ラッピング工程を効率よく行うことができるように大まかに大きなうねり、欠け、ひびを効率よく除去する。このため、第２ラッピングで使用する粗さ＃１３００メッシュから＃１７００メッシュより粗い＃８００メッシュから＃１２００メッシュ程度のダイヤモンドペレットを使用するのが好ましい。第１ラッピング工程が完了した時点での面粗さは、Ｒｚが４μｍから８μｍで、Ｒａが０．４μｍから０．８μｍ程度とするのが好ましい。 In the first wrapping step, roughly large undulations, chips and cracks are efficiently removed so that the second wrapping step can be performed efficiently. For this reason, it is preferable to use diamond pellets of # 800 mesh to # 1200 mesh which are coarser than # 1300 mesh to # 1700 mesh used in the second wrapping. The surface roughness at the time when the first lapping step is completed is preferably such that Rz is 4 μm to 8 μm and Ra is about 0.4 μm to 0.8 μm.
　ガラス基板の内周、外周の端面は、内周及び外周端面加工工程でブラシ研磨によるポリッシング加工を行う。ブラシは、φ０．２からφ０．３ｍｍ程度のナイロン、ポリプロピレン等を使用するのが好ましい。また、研磨液は、粒径が数μｍ程度の酸化セリウムが好ましい。ブラシ研磨の結果、内周、外周の端面の面粗さは、Ｒｚが０．２μｍから０．４μｍで、Ｒａが０．０２μｍから０．０４μｍ程度とするのが好ましい。内・外径加工工程及び内周及び外周端面加工工程を経たガラス基板の端面の形状は、主表面と端面とが成す角部が取り除かれ、外周端面から０．２ｍｍから０．５ｍｍ程度の位置から主表面よりダレた状態となる。 The inner and outer end faces of the glass substrate are polished by brushing in the inner and outer end face processing steps. The brush is preferably made of nylon, polypropylene or the like having a diameter of about 0.2 to 0.3 mm. The polishing liquid is preferably cerium oxide having a particle size of about several μm. As a result of brush polishing, the surface roughness of the inner and outer end faces is preferably such that Rz is 0.2 μm to 0.4 μm and Ra is about 0.02 μm to 0.04 μm. The shape of the end surface of the glass substrate that has undergone the inner and outer diameter processing steps and the inner and outer peripheral end surface processing steps is such that the corner formed by the main surface and the end surface is removed, and the position is about 0.2 mm to 0.5 mm from the outer peripheral end surface. From the main surface.
　ここで、Ｒａ（算術平均粗さ）、Ｒｚ（最大高さ粗さ）は、ＪＩＳ　Ｂ０６０１：２００１で規定されている。これらは、原子間力顕微鏡（ＡＦＭ）等により測定することができる。これら規定及び測定方法は、以降で記述されるＲａ、Ｒｚについても同じく適用する。 Here, Ra (arithmetic mean roughness) and Rz (maximum height roughness) are defined in JIS B0601: 2001. These can be measured by an atomic force microscope (AFM) or the like. These rules and measurement methods also apply to Ra and Rz described below.
　上記の例では、ガラス基板を研磨する際にダイヤモンドペレットと研削液を用いているが、上下の定盤の研磨面にパッドを貼り付け、研磨液を供給して研磨する方法とすることもできる。研磨剤としては、例えば、酸化セリウム、酸化ジルコニウム、酸化アルミニウム、酸化マンガン、コロイダルシリカ、ダイヤモンドなどが挙げられる。これらを水で分散化してスラリー状として使用する。パッドは硬質パッドと軟質パッドとに分けられるが、必要に応じて適宜選択して用いることができる。硬質パッドとしては、硬質ベロア、ウレタン発泡、ピッチ含有スウェード等を素材とするパッドが挙げられ、軟質パッドとしては、スウェードやベロア等を素材とするパッドが挙げられる。 In the above example, the diamond pellet and the grinding liquid are used when polishing the glass substrate. However, it is also possible to apply a polishing method by attaching a pad to the polishing surface of the upper and lower surface plates and supplying the polishing liquid. . Examples of the abrasive include cerium oxide, zirconium oxide, aluminum oxide, manganese oxide, colloidal silica, and diamond. These are dispersed in water and used as a slurry. The pad is divided into a hard pad and a soft pad, but can be appropriately selected and used as necessary. Examples of the hard pad include pads made of hard velor, urethane foam, pitch-containing suede, etc., and examples of the soft pad include pads made of suede, velor, etc.
　パッドと研磨剤を使用する研磨方法は、研磨剤の粒度やパッドの種類を変えて、粗研磨から精密研磨まで対応することができる。よって、第１ラッピング工程と第２ラッピング工程で、効率よく大きなうねり、欠け、ひび等を除去し上記の面粗さを得ることができる様に研磨剤、研磨剤の粒度、パッドを適宜組み合わせて対応することができる。 The polishing method using a pad and an abrasive can correspond to rough polishing to precision polishing by changing the particle size of the abrasive and the type of pad. Therefore, in the first lapping step and the second lapping step, the abrasive, the particle size of the abrasive, and the pad are appropriately combined so that the above-mentioned surface roughness can be obtained by efficiently removing large undulations, chips, cracks, etc. Can respond.
　また、第１及び第２ラッピング工程の後、ガラス基板の表面に残った研磨剤やガラス粉を除去するための洗浄工程を行うことが好ましい。 Further, it is preferable to perform a cleaning process for removing the abrasive and glass powder remaining on the surface of the glass substrate after the first and second lapping processes.
　尚、第１ラッピング工程及び第２ラッピング工程で使用する研磨機は、同一構成ではあるがそれぞれの工程専用に用意された別の研磨機を用いて研磨加工を行うのが好ましい。これは、専用のダイヤモンドペレットを貼り付けているため交換が大掛かりな作業となり、また、研磨条件を再設定する等の煩雑な作業が必要となり、製造効率が低下するためである。 Note that the polishing machines used in the first lapping process and the second lapping process have the same configuration, but it is preferable to perform polishing using different polishing machines prepared for each process. This is because the dedicated diamond pellets are pasted, so that the replacement is a large-scale operation, and complicated operations such as resetting the polishing conditions are required, resulting in a reduction in manufacturing efficiency.
　（化学強化工程）
　次に、化学強化液にガラス基板を浸漬してガラス基板に化学強化層を形成する。化学強化層を形成することで耐衝撃性、耐振動性及び耐熱性等を向上させることができる。 (Chemical strengthening process)
Next, the glass substrate is immersed in a chemical strengthening solution to form a chemically strengthened layer on the glass substrate. By forming the chemical strengthening layer, impact resistance, vibration resistance, heat resistance and the like can be improved.
　化学強化工程は、加熱された化学強化処理液にガラス基板を浸漬することによってガラス基板に含まれるリチウムイオン、ナトリウムイオン等のアルカリ金属イオンをそれよりイオン半径の大きなカリウムイオン等のアルカリ金属イオンによって置換するイオン交換法によって行われる。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、ガラス基板の表面が強化される。 In the chemical strengthening step, by immersing the glass substrate in a heated chemical strengthening solution, alkali metal ions such as lithium ions and sodium ions contained in the glass substrate are converted into alkali ions such as potassium ions having a larger ion radius. This is performed by the ion exchange method for substitution. Compressive stress is generated in the ion-exchanged region due to the distortion caused by the difference in ion radius, and the surface of the glass substrate is strengthened.
　化学強化処理液に特に制限はなく、公知の化学強化処理液を用いることができる。通常、カリウムイオンを含む溶融塩又はカリウムイオンとナトリウムイオンを含む溶融塩を用いることが一般的である。カリウムイオンやナトリウムイオンを含む溶融塩としては、カリウムやナトリウムの硝酸塩、炭酸塩、硫酸塩やこれらの混合溶融塩が挙げられる。中でも、融点が低く、ガラス基板の変形を防止できるという観点からは、硝酸塩を用いることが好ましい。 The chemical strengthening treatment liquid is not particularly limited, and a known chemical strengthening treatment liquid can be used. Usually, it is common to use a molten salt containing potassium ions or a molten salt containing potassium ions and sodium ions. Examples of the molten salt containing potassium ions and sodium ions include potassium and sodium nitrates, carbonates, sulfates, and mixed molten salts thereof. Among these, from the viewpoint that the melting point is low and deformation of the glass substrate can be prevented, it is preferable to use nitrate.
　化学強化処理液は、上記の成分が融解する温度よりも高温になるよう加熱される。一方、化学強化処理液の加熱温度が高すぎると、ガラス基板の温度が上がりすぎ、ガラス基板の変形を招く恐れがある。このため、化学強化処理液の加熱温度はガラス基板のガラス転移点（Ｔｇ）よりも低い温度が好ましく、ガラス転移点－５０℃よりも低い温度とすることが更に好ましい。 The chemical strengthening solution is heated to a temperature higher than the temperature at which the above components melt. On the other hand, when the heating temperature of the chemical strengthening treatment liquid is too high, the temperature of the glass substrate is excessively increased, and the glass substrate may be deformed. For this reason, the heating temperature of the chemical strengthening treatment liquid is preferably lower than the glass transition point (Tg) of the glass substrate, more preferably lower than the glass transition point −50 ° C.
　なお、加熱された化学強化処理液に浸漬される際の熱衝撃によるガラス基板の割れや微細なクラックの発生を防止するため、化学強化処理液への浸漬に先立って、予熱槽でガラス基板を所定温度に加熱する予熱工程を有していても良い。 In addition, in order to prevent the occurrence of cracks and fine cracks in the glass substrate due to thermal shock when immersed in the heated chemical strengthening treatment liquid, the glass substrate is placed in a preheating tank prior to immersion in the chemical strengthening treatment liquid. You may have the preheating process heated to predetermined temperature.
　化学強化層の厚みとしては、ガラス基板の強度向上と研磨工程の時間の短縮との兼ね合いから、５μｍ～１５μｍ程度の範囲が好ましい。強化層の厚みがこの範囲の場合、平坦度、機械的強度である耐衝撃性が良好なガラス基板とすることができる。 The thickness of the chemically strengthened layer is preferably in the range of about 5 μm to 15 μm in view of improving the strength of the glass substrate and shortening the polishing process time. When the thickness of the reinforcing layer is within this range, a glass substrate having good impact resistance, which is flatness and mechanical strength, can be obtained.
　化学強化工程後の表主表面７ａの外周端部の形状は、化学強化工程前とほとんど変わらず、上記の５μｍ～１５μｍ程度の化学強化層がガラス基板の表面全体にほぼ一様に載った状態となる。 The shape of the outer peripheral edge of the front main surface 7a after the chemical strengthening process is almost the same as that before the chemical strengthening process, and the above-mentioned chemical strengthening layer of about 5 μm to 15 μm is almost uniformly placed on the entire surface of the glass substrate. It becomes.
　（第１研磨工程）
　次に、研磨工程に関して説明する。研磨工程では、ガラス基板の表面を精密に仕上げると伴に主表面の外周端部の形状を所望の形状に研磨する。 (First polishing process)
Next, the polishing process will be described. In the polishing step, the surface of the glass substrate is precisely finished, and the shape of the outer peripheral end of the main surface is polished to a desired shape.
　まず、第１研磨工程では、第２研磨工程で最終的に必要とされる面粗さを効率よく得ることができるように、面粗さを向上させるとともに最終的に所望の形状を効率よく得ることができる研磨を行う。 First, in the first polishing step, the surface roughness is improved and finally a desired shape is efficiently obtained so that the surface roughness finally required in the second polishing step can be efficiently obtained. Polishing can be done.
　研磨の方法は、ラッピング工程で使用したダイヤモンドペレットと研削液に代えて、パッドと研磨液を使用する以外は第１及び第２ラッピング工程で使用した研磨機と同一の構成の研磨機を使用する。 The polishing method uses a polishing machine having the same configuration as the polishing machine used in the first and second lapping processes, except that a pad and a polishing liquid are used instead of the diamond pellets and the grinding liquid used in the lapping process. .
　パッドは硬度Ａで８０から９０程度の硬質パッドで例えば発泡ウレタンを使用するのが好ましい。パッドの硬度が研磨による発熱により柔らかくなると研磨面の形状変化が大きくなるため硬質パッドを用いるのが好ましい。研磨剤は、粒径が０．６μｍから２．５μｍの酸化セリウム、コロイダルシリカ、酸化ジルコニウム、酸化チタニウム、酸化マンガン等を水に分散させてスラリー状にして用いるのが好ましい。水と研磨剤との混合比率は、概ね１：１から４：１程度が好ましい。 The pad is a hard pad having a hardness A of about 80 to 90, and it is preferable to use, for example, urethane foam. When the pad hardness becomes soft due to heat generated by polishing, the shape change of the polished surface increases, so it is preferable to use a hard pad. The abrasive is preferably used in the form of a slurry by dispersing cerium oxide, colloidal silica, zirconium oxide, titanium oxide, manganese oxide or the like having a particle size of 0.6 μm to 2.5 μm in water. The mixing ratio of water and abrasive is preferably about 1: 1 to 4: 1.
　定盤によるガラス基板への加工圧力は、８８２６Ｐａから１０７８７Ｐａとするのが好ましい。定盤によるガラス基板への加工圧力は、外周端部の形状に大きく影響する。加工圧力を大きくしていくと、外周端部の内側が下がり外側に向かって上がる傾向を示す。また、加工圧力を小さくしていくと、外周端部は平面に近くなるとともに面ダレが大きくなる傾向を示す。こうした傾向を観察しながら加工圧力を決めることができる。 The processing pressure on the glass substrate by the surface plate is preferably 8826 Pa to 10787 Pa. The processing pressure applied to the glass substrate by the surface plate greatly affects the shape of the outer peripheral edge. As the processing pressure is increased, the inner side of the outer peripheral end tends to decrease and increase toward the outer side. Further, when the processing pressure is reduced, the outer peripheral end portion tends to be close to a flat surface and the surface sagging increases. The processing pressure can be determined while observing such a tendency.
　また、化学強化工程までに得た平坦度を維持し、さらに面粗さを向上させるように定盤の回転数を２０ｒｐｍから６０ｒｐｍとし、上の定盤の回転数を下の定盤回転数より３０％から４０％遅くするのが好ましい。 In addition, the rotation speed of the surface plate is changed from 20 rpm to 60 rpm so that the flatness obtained until the chemical strengthening process is maintained and the surface roughness is further improved, and the rotation speed of the upper surface plate is set from the lower surface plate rotation speed. It is preferable to slow by 30% to 40%.
　上記の研磨条件により研磨量を３０μｍから４０μｍとするのが好ましい。３０μｍ未満では、キズや欠陥を十分に除去ができない。また４０μｍを超える場合は、面粗さをＲｚが０．２ｎｍから３０ｎｍ、Ｒａが０．５ｎｍから２ｎｍの範囲とすることができるが、必要以上に研磨を行うことになり製造効率が低下する。 The polishing amount is preferably 30 μm to 40 μm according to the above polishing conditions. If it is less than 30 μm, scratches and defects cannot be removed sufficiently. If it exceeds 40 μm, the surface roughness can be in the range of Rz from 0.2 nm to 30 nm and Ra from 0.5 nm to 2 nm. However, polishing is performed more than necessary, and the production efficiency decreases.
　（酸またはアルカリ溶液浸漬工程）
　第２研磨工程の前に、酸またはアルカリ溶液にガラス基板を浸漬してガラス基板表面の水和層や加工変質層を除去する改質処理を行う。この改質処理により、第２研磨工程においてガラス基板表面を全体に均質かつ安定に研磨できる。 (Acid or alkaline solution dipping process)
Prior to the second polishing step, a modification treatment is performed in which the glass substrate is immersed in an acid or alkali solution to remove a hydrated layer or a work-affected layer on the surface of the glass substrate. By this modification treatment, the entire surface of the glass substrate can be uniformly and stably polished in the second polishing step.
　本工程に用いる酸またはアルカリは特に限定されるものではなく、例えばＨＦ、Ｈ２ＳＯ４などの酸や、ＮａＯＨ、ＫＯＨなどのアルカリ溶液を用いることができる。酸またはアルカリ溶液の温度は２０℃～４０℃、浸漬時間は６０ｓｅｃ～３００ｓｅｃの範囲にすることが好ましい。 The acid or alkali used in this step is not particularly limited, and for example, an acid such as HF or H 2 SO 4 or an alkaline solution such as NaOH or KOH can be used. The temperature of the acid or alkali solution is preferably 20 ° C. to 40 ° C., and the immersion time is preferably in the range of 60 sec to 300 sec.
　（リンス工程）
　純水などにガラス基板を浸漬して、ガラス基板に付着した酸またはアルカリ溶液を除去する。 (Rinse process)
The glass substrate is immersed in pure water or the like to remove the acid or alkali solution attached to the glass substrate.
　（第２研磨工程）
　第２研磨工程は、第１研磨工程後のガラス基板の表面を更に精密に研磨する工程である。第２研磨工程で使用するパッドは、第１研磨工程で使用するパッドより柔らかい硬度６５から８０（Ａｓｋｅｒ－Ｃ）程度の軟質パッドで、例えば発泡ウレタンやスウェードを使用するのが好ましい。研磨剤としては、第１研磨工程と同様の酸化セリウム、コロイダルシリカ、酸化ジルコニウム、酸化チタニウム、酸化マンガン等を用いることができるが、ガラス基板の表面をより滑らかにするため、粒径がより細かくバラツキが少ない研磨剤を用いるのが好ましい。粒径の平均粒子径が１０ｎｍから１００ｎｍの研磨剤を水に分散させてスラリー状にして研磨液として用い、水と研磨剤との混合比率は、３：１から２０：１程度が好ましい。 (Second polishing step)
The second polishing step is a step of polishing the surface of the glass substrate after the first polishing step more precisely. The pad used in the second polishing step is a soft pad having a hardness of about 65 to 80 (Asker-C) that is softer than the pad used in the first polishing step. For example, urethane foam or suede is preferably used. As the abrasive, cerium oxide, colloidal silica, zirconium oxide, titanium oxide, manganese oxide, and the like similar to those in the first polishing step can be used. However, in order to make the surface of the glass substrate smoother, the particle size is finer. It is preferable to use an abrasive with little variation. An abrasive having an average particle size of 10 nm to 100 nm is dispersed in water to form a slurry and used as a polishing liquid. The mixing ratio of water and abrasive is preferably about 3: 1 to 20: 1.
　本発明では第２研磨工程の前に、酸またはアルカリ溶液にガラス基板を浸漬してガラス基板表面の水和層や加工変質層を除去しているので、ガラス基板表面全面の加工安定性が第１研磨工程の直後に比べて大幅に向上している。 In the present invention, before the second polishing step, the glass substrate is immersed in an acid or alkali solution to remove the hydrated layer or the work-affected layer on the surface of the glass substrate. Compared to immediately after the first polishing step, it is greatly improved.
　そのため第２研磨工程を始めるとすぐに研磨液は、ガラス基板の表面に一様に広がり、ガラス基板表面の全面にわたって均一な研磨特性が得られる。 Therefore, as soon as the second polishing step is started, the polishing liquid spreads uniformly on the surface of the glass substrate, and uniform polishing characteristics are obtained over the entire surface of the glass substrate.
　定盤によるガラス基板への加工圧力は、８８２６Ｐａから１０７８７Ｐａが好ましい。定盤によるガラス基板への加工圧力は、第１研磨工程と同様に外周端部の形状に大きく影響するが、研磨速度が遅いため第１研磨工程ほど効率的に形状を変化させることはできない。加工圧力の加減による外周端部の形状の変化は、第１研磨工程と同様であり、加工圧力を大きくしていくと、外周端部の内側が下がり外側に向かって上がる傾向を示す。また、加工圧力を小さくしていくと、外周端部は平面に近くなるとともに面ダレが大きくなる傾向を示す。外周端部の形状を得るために、こうした傾向を観察しながら加工圧力を決めることができる。定盤の回転数を５ｒｐｍから５０ｒｐｍとし、上定盤の回転数を下定盤の回転数より３０％から４０％遅くするのが好ましい。 The processing pressure on the glass substrate by the surface plate is preferably 8826 Pa to 10787 Pa. The processing pressure applied to the glass substrate by the surface plate greatly affects the shape of the outer peripheral edge as in the first polishing step, but the shape cannot be changed as efficiently as the first polishing step because the polishing rate is slow. The change in the shape of the outer peripheral end due to the adjustment of the processing pressure is the same as in the first polishing step, and when the processing pressure is increased, the inner side of the outer peripheral end tends to decrease and increase toward the outside. Further, when the processing pressure is reduced, the outer peripheral end portion tends to be close to a flat surface and the surface sagging increases. In order to obtain the shape of the outer peripheral end, the processing pressure can be determined while observing such a tendency. The rotation speed of the surface plate is preferably 5 to 50 rpm, and the rotation speed of the upper surface plate is preferably 30% to 40% slower than the rotation speed of the lower surface plate.
　上記の様に第２研磨工程での研磨条件を調整して所望の外周端部の形状を得るとともに、面粗さをＲａが０．１５ｎｍ以下にすることができる。 As described above, the polishing conditions in the second polishing step are adjusted to obtain a desired shape of the outer peripheral edge, and the surface roughness Ra can be 0.15 nm or less.
　研磨量は２μｍから５μｍとするのが好ましい。研磨量をこの範囲とすると、表面に発生した微小な荒れやうねり、これまでの工程で生じた微小な傷痕といった微小な欠陥を効率良く除去することができる。 The polishing amount is preferably 2 μm to 5 μm. When the polishing amount is within this range, minute defects such as minute roughness and undulation generated on the surface and minute scratches generated in the process so far can be efficiently removed.
　（洗浄工程）
　（検査工程）
　第２研磨工程の終了後、ガラス基板の洗浄及び検査を行い、ガラス基板が完成する。 (Washing process)
(Inspection process)
After completion of the second polishing step, the glass substrate is cleaned and inspected to complete the glass substrate.
　なお、情報記録媒体用ガラス基板の製造方法においては、上記以外の種々の工程を有していても良い。例えば、ガラス基板の内部歪みを緩和するためのアニール工程、ガラス基板の強度の信頼性確認のためのヒートショック工程、種々の検査・評価工程等を有していても良い。 In addition, in the manufacturing method of the glass substrate for information recording media, you may have various processes other than the above. For example, an annealing process for relaxing internal strain of the glass substrate, a heat shock process for confirming the reliability of the strength of the glass substrate, various inspection / evaluation processes, and the like may be included.
　また、第２研磨工程では、第１研磨工程で使用した研磨機をそのまま用いるのではなく、同一構成ではあるがそれぞれの工程専用に用意された別の研磨機を用いて研磨を行うのが好ましい。これは、第１研磨工程で使用した研磨機をそのまま用いると第１研磨工程で残留した研磨剤等により第２研磨工程での研磨精度が低下したり、研磨条件を再設定する等の煩雑な作業が必要となり、製造効率が低下したりするためである。 In the second polishing step, it is preferable not to use the polishing machine used in the first polishing process as it is, but to polish using another polishing machine that has the same configuration but is prepared for each process. . This is because, if the polishing machine used in the first polishing step is used as it is, the polishing accuracy in the second polishing step decreases due to the abrasive remaining in the first polishing step, and the polishing conditions are reset. This is because work is required and the production efficiency is lowered.
　（磁性膜形成工程）
　次に、ガラス基板に設ける磁性膜２について説明する。以下、図２に基づき磁性膜２を設けた磁気記録媒体Ｄについて説明する。 (Magnetic film forming process)
Next, the magnetic film 2 provided on the glass substrate will be described. Hereinafter, the magnetic recording medium D provided with the magnetic film 2 will be described with reference to FIG.
　磁性膜２の形成方法としては従来の公知の方法を用いることができ、例えば磁性粒子を分散させた熱硬化性樹脂を基板上にスピンコートして形成する方法や、スパッタリング、無電解めっきにより形成する方法が挙げられる。スピンコート法での膜厚は約０．３μｍ～１．２μｍ程度、スパッタリング法での膜厚は０．０４μｍ～０．０８μｍ程度、無電解めっき法での膜厚は０．０５μｍ～０．１μｍ程度であり、薄膜化および高密度化の観点からはスパッタリング法および無電解めっき法による膜形成が好ましい。 As a method for forming the magnetic film 2, a conventionally known method can be used. For example, a method in which a thermosetting resin in which magnetic particles are dispersed is spin-coated on a substrate, or a method in which sputtering or electroless plating is used. The method of doing is mentioned. The film thickness by spin coating is about 0.3 μm to 1.2 μm, the film thickness by sputtering is about 0.04 μm to 0.08 μm, and the film thickness by electroless plating is 0.05 μm to 0.1 μm. From the viewpoint of thinning and densification, film formation by sputtering and electroless plating is preferable.
　磁性膜に用いる磁性材料としては、特に限定はなく従来公知のものが使用できるが、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。具体的には、Ｃｏを主成分とするＣｏＰｔ、ＣｏＣｒ、ＣｏＮｉ、ＣｏＮｉＣｒ、ＣｏＣｒＴａ、ＣｏＰｔＣｒ、ＣｏＮｉＰｔや、ＣｏＮｉＣｒＰｔ、ＣｏＮｉＣｒＴａ、ＣｏＣｒＰｔＴａ、ＣｏＣｒＰｔＢ、ＣｏＣｒＰｔＳｉＯなどが挙げられる。磁性膜は、非磁性膜（例えば、Ｃｒ、ＣｒＭｏ、ＣｒＶなど）で分割しノイズの低減を図った多層構成（例えば、ＣｏＰｔＣｒ／ＣｒＭｏ／ＣｏＰｔＣｒ、ＣｏＣｒＰｔＴａ／ＣｒＭｏ／ＣｏＣｒＰｔＴａなど）としてもよい。上記の磁性材料の他、フェライト系、鉄－希土類系や、ＳｉＯ２、ＢＮなどからなる非磁性膜中にＦｅ、Ｃｏ、ＦｅＣｏ、ＣｏＮｉＰｔ等の磁性粒子を分散された構造のグラニュラーなどであってもよい。また、磁性膜は、内面型および垂直型のいずれの記録形式であってもよい。 The magnetic material used for the magnetic film is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Ni having a high crystal anisotropy is basically used, and Ni or A Co-based alloy to which Cr is added is suitable. Specific examples include CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, and CoNiPt containing Co as a main component, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, and CoCrPtSiO. The magnetic film may have a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa) that is divided by a nonmagnetic film (for example, Cr, CrMo, CrV, etc.) to reduce noise. In addition to the above magnetic materials, granular materials such as ferrite, iron-rare earth, and non-magnetic films made of SiO 2 , BN, etc. are dispersed with magnetic particles such as Fe, Co, FeCo, CoNiPt, etc. Also good. Further, the magnetic film may be of any recording type of inner surface type and vertical type.
　また、磁気ヘッドの滑りをよくするために磁性膜の表面に潤滑剤を薄くコーティングしてもよい。潤滑剤としては、例えば液体潤滑剤であるパーフロロポリエーテル（ＰＦＰＥ）をフレオン系などの溶媒で希釈したものが挙げられる。 In addition, a lubricant may be thinly coated on the surface of the magnetic film in order to improve the sliding of the magnetic head. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.
　さらに必要により下地層や保護層を設けてもよい。磁気ディスクにおける下地層は磁性膜に応じて選択される。下地層の材料としては、例えば、Ｃｒ、Ｍｏ、Ｔａ、Ｔｉ、Ｗ、Ｖ、Ｂ、Ａｌ、Ｎｉ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。Ｃｏを主成分とする磁性膜の場合には、磁気特性向上等の観点からＣｒ単体やＣｒ合金であることが好ましい。また、下地層は単層とは限らず、同一又は異種の層を積層した複数層構造としても構わない。例えば、Ｃｒ／Ｃｒ、Ｃｒ／ＣｒＭｏ、Ｃｒ／ＣｒＶ、ＮｉＡｌ／Ｃｒ、ＮｉＡｌ／ＣｒＭｏ、ＮｉＡｌ／ＣｒＶ等の多層下地層としてもよい。 Further, if necessary, an underlayer or a protective layer may be provided. The underlayer in the magnetic disk 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. In the case of a magnetic film containing Co as a main component, Cr alone or a Cr alloy is preferable from the viewpoint of improving magnetic characteristics. Further, 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.
　磁性膜の摩耗や腐食を防止する保護層としては、例えば、Ｃｒ層、Ｃｒ合金層、カーボン層、水素化カーボン層、ジルコニア層、シリカ層などが挙げられる。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、同一又は異種の層からなる多層構成としてもよい。なお、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。例えば、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、さらに焼成して二酸化ケイ素（ＳｉＯ２）層を形成してもよい。 Examples of the protective layer that prevents wear and corrosion of the magnetic film 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. Note that another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, tetraalkoxysilane is diluted with an alcohol solvent on the Cr layer, and then colloidal silica fine particles are dispersed and applied, and then baked to form a silicon dioxide (SiO 2 ) layer. It may be formed.
　［実施例］
　実施例１～１２のガラス基板を以下のように作製した。 [Example]
The glass substrates of Examples 1 to 12 were produced as follows.
　（ガラス基板の作製）
　図３で説明した製造工程図に従って、実施例１～１２のガラス基板を各１００枚作製した。 (Production of glass substrate)
100 glass substrates of Examples 1 to 12 were produced according to the manufacturing process diagram described in FIG.
　ガラス材料としてアルミノシリケートガラス（Ｔｇ：５００℃）を用い、溶融ガラスをプレス成形してブランク材を１２００枚作製した。内外周加工工程、ラッピング工程を経て、外径６５ｍｍ、内径２０ｍｍのガラス基板とした。ガラス基板の厚みは０．６４ｍｍとした。 Aluminosilicate glass (Tg: 500 ° C.) was used as a glass material, and 1200 pieces of blank materials were produced by press molding the molten glass. A glass substrate having an outer diameter of 65 mm and an inner diameter of 20 mm was obtained through an inner and outer peripheral processing step and a lapping step. The thickness of the glass substrate was 0.64 mm.
　（化学強化工程）
　加熱した化学強化処理液にガラス基板を浸漬した。化学強化処理液にはカリウムの硝酸塩を用いた。 (Chemical strengthening process)
The glass substrate was immersed in the heated chemical strengthening treatment liquid. Potassium nitrate was used for the chemical strengthening treatment solution.
　（第１研磨工程）
　ニッタ・ハース社製のウレタンパッドを用い、研磨剤としては、酸化セリウムを用いた。研磨条件は、パッドの硬度７６（硬度Ａ）、研磨剤の粒径０．６（μｍ）、回転数３０（ｒｐｍ）、加工圧力１０７８７（Ｐａ）とした。 (First polishing process)
A urethane pad manufactured by Nitta Haas was used, and cerium oxide was used as an abrasive. The polishing conditions were pad hardness 76 (hardness A), abrasive particle size 0.6 (μm), rotation speed 30 (rpm), and processing pressure 10787 (Pa).
　（酸またはアルカリ溶液浸漬工程）
　実施例１～５では、ガラス基板を濃度の異なるＨＦの２５℃の溶液にそれぞれ１２０秒浸漬した。ＨＦの溶液の濃度は、実施例１では０．１質量％、実施例２では０．３質量％、実施例３では０．５質量％、実施例４では１．０質量％、実施例５では１．５質量％とした。 (Acid or alkaline solution dipping process)
In Examples 1 to 5, glass substrates were immersed in 25 ° C. solutions of HF having different concentrations for 120 seconds. The concentration of the HF solution was 0.1% by mass in Example 1, 0.3% by mass in Example 2, 0.5% by mass in Example 3, 1.0% by mass in Example 4, and Example 5 Then, it was 1.5 mass%.
　実施例６～１２では、ガラス基板を濃度の異なるＮａＯＨの２５℃の溶液にそれぞれ１２０秒浸漬した。ＮａＯＨの溶液の濃度は、実施例６では０．１質量％、実施例７では０．３質量％、実施例８では０．５質量％、実施例９では１．０質量％、実施例１０では２．０質量％、実施例１１では３．０質量％、実施例１２では５．０質量％とした。 In Examples 6 to 12, each glass substrate was immersed in a solution of NaOH having a different concentration at 25 ° C. for 120 seconds. The concentration of the NaOH solution was 0.1% by weight in Example 6, 0.3% by weight in Example 7, 0.5% by weight in Example 8, 1.0% by weight in Example 9, and Example 10 Was 2.0 mass%, Example 11 was 3.0 mass%, and Example 12 was 5.0 mass%.
　（リンス工程）
　純水にガラス基板を浸漬して、ガラス基板に付着した酸またはアルカリ溶液を除去した。 (Rinse process)
The glass substrate was immersed in pure water to remove the acid or alkali solution adhering to the glass substrate.
　（第２研磨工程）
　ＦＩＬＷＥＬ社製のスウェードパッドを用い、研磨剤としては、酸化セリウムおよびコロイダルシリカを用いた。研磨条件は、パッドの硬度８０（Ａｓｋｅｒ－Ｃ）、研磨剤の粒径３０（ｎｍ）、回転数３０（ｒｐｍ）、加工圧力１０７８７（Ｐａ）とした。 (Second polishing step)
A suede pad manufactured by FILWEL was used, and cerium oxide and colloidal silica were used as the abrasive. The polishing conditions were pad hardness 80 (Asker-C), abrasive particle size 30 (nm), rotation speed 30 (rpm), and processing pressure 10787 (Pa).
　実施例１～１２のガラス基板について所定時間の研磨を行ったときの研磨量から研磨レートを求めた。次に、実施例１～１２の研磨レートから研磨量が目標の２μｍになる加工時間を求めて研磨を行った。 The polishing rate was determined from the polishing amount when the glass substrates of Examples 1 to 12 were polished for a predetermined time. Next, polishing was performed by obtaining a processing time for the polishing amount to be a target of 2 μm from the polishing rates of Examples 1 to 12.
　［比較例］
　比較例では、第１研磨工程までの工程は実施例と同じ順に行い、第１研磨工程の後第２研磨工程を続けて行った。 [Comparative example]
In the comparative example, the steps up to the first polishing step were performed in the same order as in the example, and the second polishing step was continued after the first polishing step.
　比較例の目標の研磨量も２μｍである。予め実験を行って求めた比較例の条件での研磨レートから加工時間を３３．４分とした。各工程における温度条件等は実施例１と同じ条件である。比較例ではガラス基板を１００枚作製した。 The target polishing amount of the comparative example is also 2 μm. The processing time was set to 33.4 minutes from the polishing rate under the conditions of the comparative example obtained by conducting an experiment in advance. The temperature conditions and the like in each step are the same as those in Example 1. In the comparative example, 100 glass substrates were produced.
　［測定方法］
　研磨レートは、第２研磨工程でガラス基板に所定時間の研磨を行ったときの研磨量から求めた。 [Measuring method]
The polishing rate was obtained from the polishing amount when the glass substrate was polished for a predetermined time in the second polishing step.
　面粗さＲａは、ＪＩＳ　Ｂ０６０１：２００１に基づいて、原子間力顕微鏡（ＡＦＭ）を用いて測定した。 The surface roughness Ra was measured using an atomic force microscope (AFM) based on JIS B0601: 2001.
　表面欠陥数は、ＯＳＡ（Ｏｐｔｉｃａｌ　Ｓｕｒｆａｃｅ　Ａｎａｌｙｚｅｒ）を用いガラス基板表面にレーザを照射して、散乱から表面欠陥を検出した。検出感度は０．０８μｍに設定し、基板表面の０．１μｍ以上のサイズの欠陥数を評価した。 The number of surface defects was determined by irradiating the surface of the glass substrate with laser using OSA (Optical Surface Analyzer) and detecting the surface defects from scattering. The detection sensitivity was set to 0.08 μm, and the number of defects having a size of 0.1 μm or more on the substrate surface was evaluated.
　うねりＷａの測定は、多機能ディスク用干渉計（オプティフラット　Ｐｈａｓｅ　Ｓｈｉｆｔ　Ｔｅｃｈｎｏｌｏｇｙ．Ｉｎｃ．製）を用いて行い、ガラス基板表面の全面を測定した。測定原理は、ガラス基板の表面に白色光を照射し、位相の異なる参照光と測定光の干渉の強度変化を測定することで、表面の微妙な形状変化を測定する方法である。得られた測定データを５ｍｍ以上の周期をカットオフし、うねりＷａとした。 Waviness Wa was measured using a multi-function disk interferometer (Optiflat Phase Shift Technology Inc.), and the entire surface of the glass substrate was measured. The measurement principle is a method of measuring a subtle shape change of the surface by irradiating the surface of the glass substrate with white light and measuring an intensity change of interference between the reference light and the measurement light having different phases. The obtained measurement data was cut off with a period of 5 mm or more to obtain a waviness Wa.
　［測定結果］
　実施例１～１２で作製した各１００枚のガラス基板表面の研磨レート、面粗さ、うねりＷａ、表面欠陥数をそれぞれ測定した測定結果の平均値を表１に示す。研磨レートは、比較例の研磨レート０．０６μｍ／ｍｉｎを１としてその比を記載している。 [Measurement result]
Table 1 shows the average values of the measurement results obtained by measuring the polishing rate, surface roughness, waviness Wa and the number of surface defects on the surface of each of the 100 glass substrates prepared in Examples 1 to 12. The polishing rate is described as a ratio with the polishing rate of the comparative example being 0.06 μm / min as 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　比較例で作製した各１００枚のガラス基板表面の研磨レート、面粗さ、うねりＷａ、表面欠陥数をそれぞれ測定した測定結果の平均値を表２に示す。比較例の研磨レート０．０６μｍ／ｍｉｎを１としている。 Table 2 shows the average values of the measurement results obtained by measuring the polishing rate, surface roughness, waviness Wa and the number of surface defects on the surface of each of 100 glass substrates prepared in Comparative Examples. The polishing rate of the comparative example is 0.06 μm / min.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　実施例１～１２の研磨レートは、何れも比較例の研磨レートよりも高く、各実施例は比較例より第２研磨工程の加工時間を短縮できる。 The polishing rates of Examples 1 to 12 are all higher than the polishing rate of the comparative example, and each example can shorten the processing time of the second polishing step compared to the comparative example.
　また、実施例１～１２では、何れも比較例より表面欠陥数が少なかった。更に、実施例１、２では、うねりＷａ、面粗さＲａとも、比較例のうねりＷａ、面粗さＲａより小さくなり、比較例に比べ平滑性の高い表面状態に加工することができる。 In Examples 1 to 12, the number of surface defects was smaller than that of the comparative example. Further, in Examples 1 and 2, the waviness Wa and the surface roughness Ra are both smaller than the waviness Wa and the surface roughness Ra of the comparative example, and can be processed into a surface state having higher smoothness than the comparative example.
　実施例３、４、実施例７～１１では、うねりＷａは０．３２ｎｍ～０．３８ｎｍ、面粗さＲａは０．１２ｎｍ～０．１４ｎｍの範囲であり、比較例のうねりＷａ０．３６ｎｍ、面粗さＲａ０．１２ｎｍとほぼ同等であった。 In Examples 3 and 4, and Examples 7 to 11, the waviness Wa is in the range of 0.32 nm to 0.38 nm, the surface roughness Ra is in the range of 0.12 nm to 0.14 nm, and the waviness Wa of the comparative example is 0.36 nm. The roughness Ra was approximately equivalent to 0.12 nm.
　これらから、実施例３、４、実施例７～１１の条件でガラス基板を製造すると、比較例より高い研磨レートで、比較例より表面欠陥数が少なく、比較例と同等程度のうねりＷａ、面粗さＲａの表面状態に加工することができる。 From these, when a glass substrate is manufactured under the conditions of Examples 3 and 4 and Examples 7 to 11, the number of surface defects is smaller than that of the comparative example at a higher polishing rate than that of the comparative example, and the waviness Wa and the surface are comparable to those of the comparative example. It can be processed into a surface state of roughness Ra.
　以上このように、本発明によれば、平滑性の高いガラス基板を効率的に製造することができるガラス基板の製造方法、および平滑性の高い磁気記録媒体を効率的に製造することができる磁気記録媒体の製造方法を提供することができる。 As described above, according to the present invention, a glass substrate manufacturing method capable of efficiently manufacturing a glass substrate having high smoothness, and a magnetism capable of efficiently manufacturing a magnetic recording medium having high smoothness. A method for manufacturing a recording medium can be provided.
　１　ガラス基板
　２　磁性膜
　５　孔
　７ａ　表主表面
　７ｂ　裏主表面
　１０ｔ　外周端面
　２０ｔ　内周端面
　Ｄ　磁気ディスク DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Magnetic film 5 Hole 7a Front main surface 7b Back main surface 10t Outer peripheral end surface 20t Inner peripheral end surface D Magnetic disk

Claims (8)

  1. 　研磨剤を含む研磨液を用いてガラス基板の表面を研磨する第１研磨工程と第２研磨工程とを有するガラス基板の製造方法において、
    　前記ガラス基板を酸またはアルカリの溶液に浸漬する酸またはアルカリ溶液浸漬工程と、
    　前記酸またはアルカリ溶液浸漬工程を終えたガラス基板に付着した酸またはアルカリ溶液を除去するリンス工程と、
    　を有し、
    　前記第１研磨工程を行った後、前記酸またはアルカリ溶液浸漬工程と前記リンス工程と前記第２研磨工程とをこの順に行うことを特徴とするガラス基板の製造方法。     In the method for manufacturing a glass substrate having a first polishing step and a second polishing step for polishing the surface of the glass substrate using a polishing liquid containing an abrasive,
    An acid or alkali solution immersing step of immersing the glass substrate in an acid or alkali solution;
    A rinsing step for removing the acid or alkali solution attached to the glass substrate after the acid or alkali solution immersion step;
    Have
    After the said 1st grinding | polishing process, the said acid or alkali solution immersion process, the said rinse process, and the said 2nd grinding | polishing process are performed in this order.
  2. 　前記浸漬工程に用いられる酸はフッ化水素であることを特徴とする請求項１に記載のガラス基板の製造方法。 The method for producing a glass substrate according to claim 1, wherein the acid used in the dipping step is hydrogen fluoride.
  3. 　前記浸漬工程に用いられるアルカリは水酸化ナトリウムであることを特徴とする請求項１に記載のガラス基板の製造方法。 The method for producing a glass substrate according to claim 1, wherein the alkali used in the dipping step is sodium hydroxide.
  4. 　前記第２研磨工程における研磨量は２μｍから５μｍであることを特徴とする請求項１から３のいずれか１項に記載のガラス基板の製造方法。 The method for producing a glass substrate according to any one of claims 1 to 3, wherein a polishing amount in the second polishing step is 2 to 5 µm.
  5. 　化学強化液にガラス基板を浸漬してガラス基板に化学強化層を形成する化学強化工程を更に有することを特徴とする請求項１から４のいずれか１項に記載のガラス基板の製造方法。 The method for producing a glass substrate according to any one of claims 1 to 4, further comprising a chemical strengthening step of immersing the glass substrate in a chemical strengthening solution to form a chemically strengthened layer on the glass substrate.
  6. 　請求項１から５のいずれか１項に記載のガラス基板の製造方法を用いて製造されたことを特徴とするガラス基板。 A glass substrate manufactured using the method for manufacturing a glass substrate according to any one of claims 1 to 5.
  7. 　請求項１に記載のガラス基板の製造方法を用いて製造したガラス基板の表面に磁性膜を形成する工程を有することを特徴とする磁気記録媒体の製造方法。 A method for producing a magnetic recording medium, comprising a step of forming a magnetic film on a surface of a glass substrate produced using the method for producing a glass substrate according to claim 1.
  8. 　請求項７に記載の磁気記録媒体の製造方法を用いて製造されたことを特徴とする磁気記録媒体。 A magnetic recording medium manufactured using the method for manufacturing a magnetic recording medium according to claim 7.
PCT/JP2010/062588 2009-08-17 2010-07-27 Method for manufacturing glass substrate, glass substrate, method for manufacturing magnetic recording medium, and magnetic recording medium WO2011021478A1 (en)

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JP2012218995A (en) * 2011-04-12 2012-11-12 Asahi Glass Co Ltd Method for manufacturing tempered glass plate and cover glass, and cover glass
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JP2016147789A (en) * 2015-02-13 2016-08-18 日本電気硝子株式会社 Glass article and method for producing the same
JP2019012183A (en) * 2017-06-30 2019-01-24 クアーズテック株式会社 Substrate for photo-mask, and manufacturing method therefor

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