WO2016060169A1 - Method for manufacturing substrate for magnetic disc - Google Patents
Method for manufacturing substrate for magnetic disc Download PDFInfo
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- WO2016060169A1 WO2016060169A1 PCT/JP2015/079066 JP2015079066W WO2016060169A1 WO 2016060169 A1 WO2016060169 A1 WO 2016060169A1 JP 2015079066 W JP2015079066 W JP 2015079066W WO 2016060169 A1 WO2016060169 A1 WO 2016060169A1
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- Prior art keywords
- polishing
- magnetic disk
- slurry
- filter
- substrate
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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
Definitions
- the present invention relates to a method for manufacturing a magnetic disk substrate having a polishing process.
- a personal computer, a notebook personal computer, a DVD (Digital Versatile Disc) recording device and the like have a built-in hard disk device for data recording.
- a hard disk device used in a portable computer such as a notebook personal computer
- a magnetic disk in which a magnetic layer is provided on a glass substrate is used, and the magnetic head slightly floats above the surface of the magnetic disk.
- Magnetic recording information is recorded on or read from the magnetic layer by a (DFH (Dynamic Flying Height) head).
- a glass substrate is preferably used because it has a property that it is less likely to undergo plastic deformation than a metal substrate or the like. In order to stably read and write magnetic recording information by the magnetic head, it is required to make the surface irregularities of the magnetic disk glass substrate as small as possible.
- the glass substrate is subjected to a polishing process.
- An abrasive containing fine abrasive grains such as silica (SiO 2 ) is used for precise polishing for making a glass substrate into a final product.
- an abrasive is used as a polishing agent in a predetermined size by performing a filtering treatment or centrifugal separation.
- polishing circulating the slurry containing a silica abrasive grain at the time of a grinding
- a mirror polishing process using silica abrasive grains on the main surface of the glass substrate is performed.
- a method of manufacturing a glass substrate for a magnetic disk using a polishing liquid (including silica abrasive grains) after filtering using a filter having a minimum trapped particle diameter of 1 ⁇ m or less is known (Patent Literature). 1).
- the glass substrate after the mirror polishing process is cleaned with a cleaning liquid in order to remove foreign matters such as abrasive grains adhering to the surface (final cleaning process).
- Patent Document 2 attempts to filter the slurry with a filter using polyethersulfone (PES).
- PES polyethersulfone
- foreign matters derived from the slurry containing silica abrasive grains used for the polishing process may adhere to the main surface of the magnetic disk substrate after the mirror polishing process.
- these foreign substances there are plate-shaped foreign substances (hereinafter referred to as plate-like foreign substances) having an extremely flat shape.
- plate-like foreign substances having an extremely flat shape.
- the magnetic layer is formed on the main surface with the plate-like foreign material remaining on the main surface of the magnetic disk substrate, surface irregularities are formed on the surface of the magnetic disk. If the magnetic recording information on the magnetic disk is read / written by a magnetic head having a very short flying distance, the magnetic head may collide with the surface irregularities. Since the plate-like foreign matter has a large adhesion area with the magnetic disk substrate, it cannot be easily removed with a cleaning solution having a low etching power.
- the plate-like foreign matter is a foreign matter having an irregular shape larger than the average particle diameter (d50) of the substantially spherical silica abrasive grains, and is considered to be removed by a filter.
- the average particle diameter indicates a median diameter measured based on a volume distribution using a laser diffraction / scattering method.
- the filter was clogged with silica abrasive grains, and foreign matters could not be efficiently removed from the slurry.
- an object of the present invention is to provide a method for manufacturing a magnetic disk substrate that can improve the yield after polishing of the magnetic disk substrate by removing foreign substances contained in the polishing liquid.
- the present inventor examined the cause of the silica abrasive grains being easily clogged in a filter using polyethersulfone. As a result, since the surface of the silica particles is hydrophilic, it is found that the silica particles are likely to adhere to the hydrophilic polyethersulfone, and it is also found that the smaller the silica particles are, the more difficult it is to leave after the adhesion. Was invented.
- a first aspect of the present invention is a method of manufacturing a magnetic disk substrate, By sandwiching the substrate between a pair of polishing pads, supplying a polishing liquid containing abrasive grains between the polishing pad and the substrate, and sliding the polishing pad and the glass substrate relatively, the magnetic disk Including a polishing process for polishing both main surfaces of the substrate;
- the abrasive is colloidal silica having an average particle size of 40 nm or less
- the polishing liquid is obtained by subjecting the abrasive grains and a slurry containing large diameter particles having a larger particle diameter than the average particle diameter of the abrasive grains to a removal treatment to remove the large diameter particles,
- the removal treatment is characterized in that the slurry is passed through a filter made of a hydrophobic polymer material and having an opening diameter of 100 nm or less.
- a filter made of a hydrophobic polymer material is hard to adhere abrasive grains contained in the slurry and particles larger than the average particle diameter of the abrasive grains, the filter is not easily clogged even when the slurry is passed through the filter. For this reason, particles larger than the average particle diameter of the abrasive grains can be efficiently removed as a filtration residue.
- the colloidal silica concentration in the slurry is preferably 30% by weight or less and passed through the filter.
- the pH of the slurry is adjusted to an alkaline range of 8 to 13 and passed through the filter.
- the hydrophobic polymer material is preferably polyvinylidene fluoride (PVDF).
- the filter is preferably a hydrophobic polymer film formed into a porous film by a phase transition method.
- the above manufacturing method is optimal when polishing is performed using colloidal silica obtained using water glass and an ion exchange resin.
- the magnetic disk substrate has a disk shape and a ring shape in which a circular center hole concentric with the outer periphery is cut out.
- a magnetic disk is formed by forming magnetic layers (recording areas) in the annular areas on both sides of the magnetic disk substrate.
- a glass substrate, an aluminum alloy substrate having a NiP alloy film formed on the surface, or the like can be used as the magnetic disk substrate.
- a mirror polishing process is performed before the magnetic layer is formed.
- the main surface of the magnetic disk substrate is polished using a double-side polishing apparatus equipped with a planetary gear mechanism. Specifically, the main surface on both sides of the magnetic disk substrate is polished while holding the outer peripheral side end face of the magnetic disk substrate in the holding hole provided in the holding member of the double-side polishing apparatus.
- the double-side polishing apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and an annular plate-shaped polishing pad (for example, as a whole on the upper surface of the lower surface plate and the bottom surface of the upper surface plate) Resin polisher) is attached.
- a polishing liquid that contains colloidal silica (silica abrasive grains) as free abrasive grains is preferable as the polishing liquid used for the mirror polishing process.
- Colloidal silica contained in the polishing liquid used for the mirror polishing treatment can be produced by a sol-gel method using tetramethyl orthosilicate, tetraethyl orthosilicate or the like as a raw material, or an ion exchange method using water glass as a raw material. Among these, it is preferable to manufacture by an ion exchange method from a cost viewpoint.
- silica sand and an alkali agent for example, Na 2 CO 3 , NaHCO 3 , NaOH, K 2 CO 3 , KHCO 3 , KOH, etc.
- an alkali agent for example, Na 2 CO 3 , NaHCO 3 , NaOH, K 2 CO 3 , KHCO 3 , KOH, etc.
- water glass is mixed with a proton-type cation exchange resin to lower the pH of the aqueous silicate solution.
- the slurry containing colloidal silica thus generated may contain large-sized particles (coarse particles, plate-like substances, etc.) having a large particle size that are inappropriate for use as abrasive grains.
- the average particle diameter of colloidal silica suitable as abrasive grains is 60 nm or less, preferably 10 to 60 nm, more preferably 20 to 50 nm, whereas large diameters inappropriate for use as abrasive grains.
- the particle diameter of the particles is 2 times or more of the average particle diameter, and more inappropriate is 5 times or more.
- the particle size of large particles is 200 nm to 1 ⁇ m.
- the slurry containing colloidal silica produced in this way may contain a plate-like substance derived from raw material silica sand.
- This plate-like substance is a silicate crystal containing aluminum, and this crystal is a layered layered silicate (for example, a layered clay mineral such as montmorillonite, saponite, and kaolinite).
- This plate-like material has a very flat shape. When such a plate-like substance adheres to a precisely polished surface, it is easy to adhere, and thus it becomes difficult to clean. Therefore, this plate-like substance is a foreign substance to the slurry containing colloidal silica (hereinafter referred to as a plate-like foreign substance). Called).
- This plate-like foreign material remains without melting even when silica sand and an alkali agent are mixed and melted, and contains colloidal silica produced from water glass in water glass obtained by dissolving the melt in water. It remains in the slurry.
- the plate-like foreign matter among the large-diameter particles, particles having a maximum length of 5 times or more the thickness are plate-like foreign matters.
- the maximum length of the plate-like foreign material is 50 nm to 1 ⁇ m, preferably 70 nm to 300 nm, more preferably 130 to 240 nm, and the thickness is 1 to 25 nm, preferably 1 to 5 nm.
- the maximum length of the plate-like foreign material refers to the length of the longest side of the cuboid frame that circumscribes the plate-like foreign material
- the thickness of the plate-like foreign material refers to the length of the shortest side of the cuboid frame.
- the length of the long side of the rectangle circumscribing the outline of the plate-like foreign substance is the maximum length, and the maximum height of the plate-like foreign substance is the thickness. Can do.
- the removal process described below is performed in advance.
- a removal process is a process which removes the particle
- a microfiltration membrane made of a hydrophobic polymer material and having an opening diameter of 100 nm or less can be used.
- the hydrophobic polymer material is a material made of a polymer having a small polarity and hardly forming a hydrogen bond with water.
- a filter made of a hydrophobic polymer material is hard to adhere abrasive grains contained in the slurry or particles larger than the average particle diameter of the abrasive grains, the filter is not easily clogged even when the slurry is passed through the filter. For this reason, particles larger than the average particle diameter of the abrasive grains can be efficiently removed as a filtration residue.
- a hydrophobic polymer material for example, a material having a water contact angle (85 to 125 °) can be used.
- the opening diameter is a diameter of a circle inscribed in the opening.
- the shape of the opening of the filter can be measured with a scanning electron microscope (SEM) to obtain the opening diameter of the opening.
- hydrophobic polymer material used for the microfiltration membrane for example, polypropylene, polyethylene, fluororesin, or the like can be used.
- fluororesin include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinyl fluoride (PVF), and polyfluoride.
- PTFE polytetrafluoroethylene
- PFA perfluoroalkoxyalkane
- FEP perfluoroethylene propene copolymer
- ETFE ethylene-tetrafluoroethylene copolymer
- PVDF vinylidene
- PCTFE polychlorotrifluoroethylene
- ECTFE ethylene-chlorotrifluoroethylene copolymer
- a fluororesin having high water repellency it is preferable to use a fluororesin having high water repellency.
- a fluororesin having high water repellency By using a highly water-repellent fluororesin, the contact area between the filter and the slurry is reduced, so that clogging of the filter can be further reduced.
- any method such as natural filtration by gravity, vacuum filtration (suction filtration), pressure filtration, centrifugal filtration, or cross flow ultrafiltration can be used.
- a microfiltration membrane made of a hydrophobic polymer material may be used as a porous membrane filter, or a non-woven filter membrane made of a hydrophobic polymer fiber. Moreover, it is good also as a plate-shaped filtration board by compression-molding a film-form filter material. Moreover, it is good also as a hollow fiber membrane shape, a spiral membrane shape, and a tubular membrane shape, and it can select suitably according to the filtration method.
- the flatness of the opening provided in the hydrophobic polymer film is preferably smaller than 0.3, and the opening is most preferably a perfect circle (the flatness is 0).
- a hydrophobic polymer film having a small aperture flatness can be produced by, for example, a phase transition method.
- a hydrophobic polymer film formed into a porous film by a phase transition method has an opening with an extremely small flatness. Specifically, in the phase transition method, first, a solution in which a polymer material that is a material of the hydrophobic polymer film is dissolved in a solvent is applied to the support plate. Next, the support plate coated with the solution is immersed in a non-solvent such as water. Then, the polymer in the solution applied to the support plate is deposited on the support plate, and a solid-phase porous film is formed on the support plate.
- the solvent can be appropriately selected from those that dissolve the polymer material that is the material of the hydrophobic polymer membrane.
- the non-solvent can be appropriately selected from those in which the polymer material used as the material of the hydrophobic polymer film is hardly soluble or insoluble and does not mix with the solvent.
- PVDF can be selected as the material for the hydrophobic polymer membrane
- triethyl phosphate (TEP) can be selected as the solvent
- water deionized water
- the concentration of colloidal silica in the slurry is 30 wt% or less, preferably 5 to 25 wt%, and passed through the filter.
- the filter passage amount per unit time was 800 liters, whereas at 25% by weight 430 liters, It is confirmed that 30% by weight is 150 liters, 35% by weight is 30 liters, and 40% by weight is 10 liters.
- the filter treatment is performed in a state where the concentration of colloidal silica in the slurry is diluted as much as possible within the range of the concentration of colloidal silica used for the second polishing treatment. Specifically, when the concentration of colloidal silica used for the second polishing treatment is 20% by weight or less, the filter treatment is performed with the concentration of colloidal silica in the slurry diluted to about 20 to 25% by weight.
- the pH of the slurry In order to improve the dispersibility of the abrasive grains in the slurry, it is preferable to adjust the pH of the slurry to an alkaline range of 8 to 13 and pass it through a filter.
- the filter passage amount By adjusting the pH of the slurry to the alkaline side, the filter passage amount is relatively increased, and by adjusting the pH to the acidic side, the filter permeation amount is relatively decreased.
- a treatment for reducing the surface charge of the colloidal silica in order to agglomerate the colloidal silica in the obtained polishing liquid.
- a treatment for reducing the surface charge of colloidal silica there is a method of adjusting the pH of the polishing liquid to an acidity of 1 or more and 5 or less.
- an additive for reducing the surface charge of colloidal silica in the polishing liquid for example, sulfuric acid compounds such as K 2 SO 4 and Na 2 SO 4 , phosphoric acid compounds such as K 3 PO 4 and Na 3 PO 4 , NaNO 3 and the like) Of nitric acid compound
- sulfuric acid compounds such as K 2 SO 4 and Na 2 SO 4
- phosphoric acid compounds such as K 3 PO 4 and Na 3 PO 4 , NaNO 3 and the like
- nitric acid compound is preferably added. If the surface charge of the colloidal silica is reduced before the removal treatment, the adsorbent with a positive surface charge is less likely to adhere to coarse particles and plate-like foreign matter, and the coarse particles and plate-like foreign matter can be removed from the slurry. It becomes difficult.
- the mirror polishing process performed using colloidal silica from which the plate-like foreign material has been removed in advance as free abrasive grains is suitable for the mirror polishing process of the glass substrate.
- the glass used for the magnetic disk glass substrate include aluminosilicate glass, soda lime glass, and borosilicate glass.
- aluminosilicate glass can be suitably used in that it can be chemically strengthened and a glass substrate for a magnetic disk excellent in the flatness of the main surface and the strength of the substrate can be produced.
- the manufacturing method of the glass substrate for magnetic discs is demonstrated.
- a magnetic disk glass blank (hereinafter simply referred to as a glass blank) is a material for a disk-shaped magnetic disk glass substrate having a pair of main surfaces, and is a form before a center hole is cut out.
- a hole is made in the central portion of the produced glass blank to produce a ring-shaped (annular) glass substrate.
- shape processing is performed on the glass substrate with holes.
- end face polishing is performed on the glass substrate that has been processed into a shape.
- grinding with fixed abrasive is performed on the glass substrate on which the end face has been polished.
- first polishing is performed on the main surface of the glass substrate.
- chemical strengthening is performed on the glass substrate as necessary.
- second polishing is performed on the glass substrate.
- a glass substrate for magnetic disk is obtained through a cleaning process.
- a glass substrate having a circular central hole can be obtained by forming a circular hole on a glass blank using a core drill or the like.
- (C) Shape processing In the shape processing, chamfering is performed on the edge of the glass substrate after the circular hole is formed.
- (D) End surface polishing process In the end surface polishing process, mirror finishing is performed on the inner end face and the outer peripheral end face of the glass substrate by brush polishing. At this time, an abrasive slurry containing particles such as cerium oxide as free abrasive grains is used.
- the main surface of the glass substrate is ground using a double-side grinding apparatus having a planetary gear mechanism. Specifically, the main surface on both sides of the glass substrate is ground while holding the outer peripheral side end face of the glass substrate generated from the glass blank in the holding hole provided in the holding member of the double-side grinding apparatus.
- the double-sided grinding apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and a glass substrate is sandwiched between the upper surface plate and the lower surface plate. Then, by moving one or both of the upper surface plate and the lower surface plate and relatively moving the glass substrate and each surface plate, both main surfaces of the glass substrate can be ground.
- a glass substrate is polished using a double-side polishing apparatus having a configuration similar to that of a double-side grinding apparatus while applying a polishing liquid containing loose abrasive grains to the double-side polishing apparatus.
- the free abrasive grains for example, cerium oxide abrasive grains, aluminum oxide abrasive grains, zirconia abrasive grains, etc. (particle size: diameter of about 1 to 2 ⁇ m) are used.
- the glass substrate is sandwiched between a pair of upper and lower surface plates.
- An annular flat polishing pad (for example, a resin polisher) is attached to the upper surface of the lower surface plate and the bottom surface of the upper surface plate as a whole. While supplying the polishing liquid between the main surface of the glass substrate and the polishing pad, the glass substrate and the polishing pad move relatively by moving either the upper surface plate, the lower surface plate, or both. Then, both main surfaces of the glass substrate are polished.
- a resin polisher for example, a resin polisher
- the glass substrate is chemically strengthened by immersing the glass substrate in a chemical strengthening solution.
- a chemical strengthening liquid for example, a mixed melt of potassium nitrate and sodium nitrate can be used. The chemical strengthening process may not be performed.
- the second polishing treatment is intended for mirror polishing of the main surface. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. The machining allowance by the second polishing is, for example, about 1 ⁇ m.
- the second polishing process is different from the first polishing process in that the type and particle size of the free abrasive grains are different and the hardness of the resin polisher is different.
- a polishing liquid obtained by performing the above-described removal process and containing colloidal silica as free abrasive grains is used.
- the roughness (Ra) of the main surface can be set to 0.15 nm or less and the micro waveness of the main surface can be set to 0.1 nm or less.
- a multi-stage polishing process may be performed using a plurality of types of polishing abrasive grains.
- the polishing process before performing the polishing process using a polishing liquid containing colloidal silica as free abrasive grains, the polishing process may be performed using a polishing liquid containing cerium oxide (CeO 2 ) as free abrasive grains.
- a final polishing process may be performed using a polishing liquid containing colloidal silica as free abrasive grains.
- the glass substrate becomes a glass substrate for a magnetic disk before the surface of the glass substrate is cleaned using an alkaline cleaning liquid and the magnetic layer is formed.
- an alkaline cleaning liquid in which the difference in surface roughness Ra between the glass substrate before and after the cleaning process is 0.05 nm or less. Since plate-like foreign substances adhering to the glass substrate are difficult to remove, an alkaline cleaning liquid having a high cleaning power has been conventionally used. For this reason, the alkaline cleaning liquid having a strong cleaning power is likely to act on the main surface of the glass substrate having no plate-like foreign matter and roughen the main surface.
- an alkaline cleaning liquid having a weaker cleaning power than that of the prior art that is, an alkaline cleaning liquid that makes the difference in the surface roughness Ra of the glass substrate before and after the cleaning process 0.05 nm or less can be used.
- Ra is the surface roughness specified in JIS B0601. This surface roughness is obtained based on data obtained by measuring a range of 1 ⁇ m ⁇ 1 ⁇ m with a resolution of 256 ⁇ 256 pixels using an atomic force microscope (AFM).
- the cleaning treatment is preferably non-scrub cleaning in which the glass substrate is immersed in or brought into contact with the cleaning liquid in terms of not causing scratches on the glass substrate.
- scrub cleaning is performed to remove the plate-like foreign matter by rubbing the glass substrate with a brush or a cleaning pad in order to remove the plate-like foreign matter firmly attached to the glass substrate.
- this scrub cleaning tends to damage the main surface of the glass substrate.
- since it polishes using the slurry containing the silica abrasive grain which performed the removal process mentioned above a plate-shaped foreign material does not adhere to a glass substrate. For this reason, it is not necessary to perform scrub cleaning as in the past. For this reason, in this embodiment, unnecessary scratches are not applied to the main surface of the glass substrate by performing non-scrub cleaning in which the glass substrate is immersed in or brought into contact with the cleaning liquid.
- the glass substrate is used as the magnetic disk substrate, but the present invention can also be applied to an aluminum alloy substrate.
- an aluminum alloy substrate an aluminum alloy substrate obtained by rolling an aluminum alloy and forming a NiP plating film on the surface of the aluminum alloy substrate cut into a disk shape is used, and the NiP plating film surface is polished using a polishing pad.
- a magnetic disk using an aluminum alloy substrate is obtained by laminating a soft magnetic layer, a nonmagnetic underlayer, a perpendicular magnetic recording layer, a protective layer, a lubricating layer, and the like on an aluminum alloy substrate.
- the same polishing pad used in the polishing step of the glass substrate can be used as the polishing pad used in the polishing step.
- the molten aluminum alloy is cast, rolled, cut out as a disk-shaped aluminum alloy base plate, and processed to a predetermined size by grinding the main surface and the end face.
- the surface of the aluminum alloy base plate is subjected to NiP plating film formation with a thickness of 5 to 30 ⁇ m to obtain an aluminum alloy substrate.
- the main surface of the aluminum alloy substrate subjected to NiP plating is polished using a polishing pad to reduce microwaviness.
- the polishing process is usually performed in two stages by changing the type and particle size of the abrasive grains.
- a slurry containing aluminum oxide abrasive grains having an average particle diameter of 0.3 to 3 ⁇ m is used.
- an aluminum alloy substrate is sandwiched between the polishing pads subjected to the opening treatment using a slurry containing colloidal silica abrasive grains having an average particle size of 40 nm or less, preferably 5 to 40 nm, and relatively slid. Reduces scratches and undulations on the NiP plating surface.
- a cleaning process is performed in order to remove particles such as abrasive grains and polishing residue adhering to the substrate surface after the polishing process.
- a polishing liquid containing colloidal silica as free abrasive grains obtained by performing the above-described removal treatment can be used.
- PVDF polyvinylidene fluoride
- a porous film of polyethersulfone (PES) prepared by a phase transition method was prepared and used as a filter.
- the opening diameter of the prepared porous membrane is as shown in Table 1.
- the colloidal silica concentration in the slurry was adjusted to 30% by weight or less, and the pH of the slurry was adjusted to 10 to pass through the filter.
- the filter was clogged and could not pass through the filter. For this reason, the subsequent processing cannot be performed in the comparative example, and the subsequent processing is performed only in the example.
- the pH of the filtrate that passed through the filter in the separation process was adjusted to 3, and this was used as a polishing liquid to perform mirror polishing of the glass substrate.
- the main surface of the glass substrate was polished by moving the polishing pad relative to the main surface of the glass substrate.
- the main surface of the cleaned and dried glass substrate was subjected to detection of foreign matters or defects using a laser type surface inspection apparatus.
- the laser threshold is set to a range in which the number of detected foreign matters or defects is 20 or less, and the detected foreign matter or defects are measured using an SEM (scanning electron microscope) or AFM (atomic force microscope).
- a foreign material having a major axis of 100 nm or more is a layered flat foreign material (a plate-like foreign material made of layered silicate).
- a layered flat foreign material a plate-like foreign material made of layered silicate.
- a plurality of layered flat foreign matters were attached to the main surfaces of the front and back surfaces of the glass substrate (two pieces). / More than one layered flat foreign material is attached).
- the number of foreign matters per 100 glass substrates is 2 or less, and the filtrate obtained by passing the slurry through a filter made of a hydrophobic polymer material is suitable as a polishing liquid. I understand.
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- Manufacturing Of Magnetic Record Carriers (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
Abstract
To improve yield after polishing of a substrate for a magnetic disc. In the present invention, a slurry comprising a hydrophobic macromolecular material is passed through a filter having openings 100 nm or less in diameter, the slurry being the raw material for a polishing solution used in polishing the main surface of a substrate. Polishing is carried out by using the polishing solution after removing, using the filter, particles contained in the slurry that have a grain diameter greater than the average grain diameter of an abrasive grain.
Description
本発明は、研磨処理を有する磁気ディスク用基板の製造方法に関する。
The present invention relates to a method for manufacturing a magnetic disk substrate having a polishing process.
今日、パーソナルコンピュータ、ノート型パーソナルコンピュータ、DVD(Digital Versatile Disc)記録装置等には、データ記録のためにハードディスク装置が内蔵されている。特に、ノート型パーソナルコンピュータ等の可搬性を前提とした機器に用いられるハードディスク装置では、ガラス基板に磁性層が設けられた磁気ディスクが用いられ、磁気ディスクの面上を僅かに浮上させた磁気ヘッド(DFH(Dynamic Flying Height)ヘッド)で磁性層に磁気記録情報が記録され、あるいは読み取られる。この磁気ディスクの基板には、金属基板等に比べて塑性変形をしにくい性質を持つことから、ガラス基板が好適に用いられている。磁気ヘッドによる磁気記録情報の読み書きを安定して行うために、磁気ディスク用ガラス基板の表面凹凸は可能な限り小さくすることが求められる。
Today, a personal computer, a notebook personal computer, a DVD (Digital Versatile Disc) recording device and the like have a built-in hard disk device for data recording. In particular, in a hard disk device used in a portable computer such as a notebook personal computer, a magnetic disk in which a magnetic layer is provided on a glass substrate is used, and the magnetic head slightly floats above the surface of the magnetic disk. Magnetic recording information is recorded on or read from the magnetic layer by a (DFH (Dynamic Flying Height) head). As the substrate of this magnetic disk, a glass substrate is preferably used because it has a property that it is less likely to undergo plastic deformation than a metal substrate or the like. In order to stably read and write magnetic recording information by the magnetic head, it is required to make the surface irregularities of the magnetic disk glass substrate as small as possible.
磁気ディスク用ガラス基板の表面凹凸を小さくするために、ガラス基板の研磨処理が行われる。ガラス基板を最終製品とするための精密な研磨に、シリカ(SiO2)等の微細な研磨砥粒を含む研磨剤が用いられる。このような研磨剤は、研磨処理後のガラス基板の表面品質を高めるために、フィルタリング処理や遠心分離を行なうことで所定のサイズに揃えて研磨剤として用いられる。また、研磨処理時、シリカ砥粒を含むスラリーを循環させながら研磨に用いる場合、研磨に使用したスラリーをフィルタリングしたのち、研磨に再使用する。
例えば、研磨工程の最終工程において、ガラス基板の主表面のシリカ砥粒を用いた鏡面研磨処理が行われる。この鏡面研磨処理において、最小捕捉粒子径が1μm以下のフィルタを使用してフィルタリングした後の研磨液(シリカ砥粒を含む)を用いる磁気ディスク用ガラス基板の製造方法が知られている(特許文献1)。鏡面研磨処理後のガラス基板は、表面に付着した砥粒等の異物を除去するために、洗浄液で洗浄される(最終洗浄処理)。 In order to reduce the surface unevenness of the magnetic disk glass substrate, the glass substrate is subjected to a polishing process. An abrasive containing fine abrasive grains such as silica (SiO 2 ) is used for precise polishing for making a glass substrate into a final product. In order to improve the surface quality of the glass substrate after the polishing treatment, such an abrasive is used as a polishing agent in a predetermined size by performing a filtering treatment or centrifugal separation. Moreover, when using for grinding | polishing, circulating the slurry containing a silica abrasive grain at the time of a grinding | polishing process, after filtering the slurry used for grinding | polishing, it reuses for grinding | polishing.
For example, in the final process of the polishing process, a mirror polishing process using silica abrasive grains on the main surface of the glass substrate is performed. In this mirror polishing process, a method of manufacturing a glass substrate for a magnetic disk using a polishing liquid (including silica abrasive grains) after filtering using a filter having a minimum trapped particle diameter of 1 μm or less is known (Patent Literature). 1). The glass substrate after the mirror polishing process is cleaned with a cleaning liquid in order to remove foreign matters such as abrasive grains adhering to the surface (final cleaning process).
例えば、研磨工程の最終工程において、ガラス基板の主表面のシリカ砥粒を用いた鏡面研磨処理が行われる。この鏡面研磨処理において、最小捕捉粒子径が1μm以下のフィルタを使用してフィルタリングした後の研磨液(シリカ砥粒を含む)を用いる磁気ディスク用ガラス基板の製造方法が知られている(特許文献1)。鏡面研磨処理後のガラス基板は、表面に付着した砥粒等の異物を除去するために、洗浄液で洗浄される(最終洗浄処理)。 In order to reduce the surface unevenness of the magnetic disk glass substrate, the glass substrate is subjected to a polishing process. An abrasive containing fine abrasive grains such as silica (SiO 2 ) is used for precise polishing for making a glass substrate into a final product. In order to improve the surface quality of the glass substrate after the polishing treatment, such an abrasive is used as a polishing agent in a predetermined size by performing a filtering treatment or centrifugal separation. Moreover, when using for grinding | polishing, circulating the slurry containing a silica abrasive grain at the time of a grinding | polishing process, after filtering the slurry used for grinding | polishing, it reuses for grinding | polishing.
For example, in the final process of the polishing process, a mirror polishing process using silica abrasive grains on the main surface of the glass substrate is performed. In this mirror polishing process, a method of manufacturing a glass substrate for a magnetic disk using a polishing liquid (including silica abrasive grains) after filtering using a filter having a minimum trapped particle diameter of 1 μm or less is known (Patent Literature). 1). The glass substrate after the mirror polishing process is cleaned with a cleaning liquid in order to remove foreign matters such as abrasive grains adhering to the surface (final cleaning process).
また、研磨処理前に、シリカ砥粒を含むスラリーをフィルタリングすることで、スラリーから異物を除去することも試みられている。例えば、特許文献2では、ポリエーテルサルフォン(PES)を用いたフィルタでスラリーをフィルタリングすることが試みられている。
Also, it has been attempted to remove foreign matters from the slurry by filtering the slurry containing silica abrasive grains before the polishing treatment. For example, Patent Document 2 attempts to filter the slurry with a filter using polyethersulfone (PES).
研磨処理後の最終洗浄処理において、磁気ディスク用ガラス基板の表面から砥粒等の異物を除去するためにエッチング力の高い洗浄液を用いると、磁気ディスク用ガラス基板が洗浄液によりエッチングされ、主表面に僅かな凹凸が形成される。この僅かな凹凸は、従来の磁気ヘッドの浮上距離よりも充分に小さく、かつては無視できる範囲であった。
In the final cleaning process after the polishing process, when a cleaning liquid having a high etching power is used to remove foreign substances such as abrasive grains from the surface of the magnetic disk glass substrate, the magnetic disk glass substrate is etched by the cleaning liquid, Slight irregularities are formed. This slight unevenness was sufficiently smaller than the flying distance of the conventional magnetic head and was once negligible.
しかし、近年、磁気ディスクの記録密度の増加に伴い、微弱な磁界の読み取りおよび記録を確実に行うために、磁気ヘッドの磁気ディスク表面からの浮上距離を極めて小さくすることが行われている。このため、エッチングによる僅かな凹凸が無視できなくなってきた。そこで、従来よりもエッチング力の低い洗浄液を用いて、磁気ディスク用基板の最終洗浄処理を行うことが試みられている。
However, in recent years, as the recording density of the magnetic disk increases, in order to reliably read and record a weak magnetic field, the flying distance of the magnetic head from the magnetic disk surface has been extremely reduced. For this reason, slight unevenness due to etching cannot be ignored. Therefore, it has been attempted to perform a final cleaning process on the magnetic disk substrate by using a cleaning liquid having a lower etching power than conventional ones.
一方、鏡面研磨処理後の磁気ディスク用基板の主表面には、研磨処理に用いるシリカ砥粒を含むスラリーに由来する異物が付着する場合がある。この異物の中には、極めて平たい形をした板状の異物(以下、板状異物という)がある。板状異物が磁気ディスク用基板の主表面に残存した状態で主表面に磁性層を形成すると、磁気ディスクの面上に表面凹凸が形成される。この磁気ディスクの磁気記録情報の読み書きを、極めて浮上距離の短い磁気ヘッドで行うと、磁気ヘッドがこの表面凹凸に衝突するおそれがある。この板状異物は、磁気ディスク用基板との付着面積が大きいため、エッチング力の低い洗浄液では容易に除去することができない。
On the other hand, foreign matters derived from the slurry containing silica abrasive grains used for the polishing process may adhere to the main surface of the magnetic disk substrate after the mirror polishing process. Among these foreign substances, there are plate-shaped foreign substances (hereinafter referred to as plate-like foreign substances) having an extremely flat shape. When the magnetic layer is formed on the main surface with the plate-like foreign material remaining on the main surface of the magnetic disk substrate, surface irregularities are formed on the surface of the magnetic disk. If the magnetic recording information on the magnetic disk is read / written by a magnetic head having a very short flying distance, the magnetic head may collide with the surface irregularities. Since the plate-like foreign matter has a large adhesion area with the magnetic disk substrate, it cannot be easily removed with a cleaning solution having a low etching power.
上記の板状異物は、概略球形状のシリカ砥粒の平均粒子径(d50)より大きな異形状の異物であるため、フィルタにより除去できるとも考えられる。ここで、平均粒子径とは、レーザー回折・散乱法を用いた体積分布に基づいて測定されるメディアン径を示す。
しかし、ポリエーテルサルフォンを用いたフィルタでスラリーを濾過すると、シリカ砥粒によるフィルタの目詰まりが生じ、スラリーから効率よく異物を除去することができなかった。 The plate-like foreign matter is a foreign matter having an irregular shape larger than the average particle diameter (d50) of the substantially spherical silica abrasive grains, and is considered to be removed by a filter. Here, the average particle diameter indicates a median diameter measured based on a volume distribution using a laser diffraction / scattering method.
However, when the slurry was filtered with a filter using polyethersulfone, the filter was clogged with silica abrasive grains, and foreign matters could not be efficiently removed from the slurry.
しかし、ポリエーテルサルフォンを用いたフィルタでスラリーを濾過すると、シリカ砥粒によるフィルタの目詰まりが生じ、スラリーから効率よく異物を除去することができなかった。 The plate-like foreign matter is a foreign matter having an irregular shape larger than the average particle diameter (d50) of the substantially spherical silica abrasive grains, and is considered to be removed by a filter. Here, the average particle diameter indicates a median diameter measured based on a volume distribution using a laser diffraction / scattering method.
However, when the slurry was filtered with a filter using polyethersulfone, the filter was clogged with silica abrasive grains, and foreign matters could not be efficiently removed from the slurry.
そこで、本発明は、研磨液に含まれる異物を除去することで、磁気ディスク用基板の研磨処理後の歩留まりを向上させることができる磁気ディスク用基板の製造方法を提供することを目的とする。
Therefore, an object of the present invention is to provide a method for manufacturing a magnetic disk substrate that can improve the yield after polishing of the magnetic disk substrate by removing foreign substances contained in the polishing liquid.
本発明者は、ポリエーテルサルフォンを用いたフィルタにおいて、シリカ砥粒の目詰まりがし易い原因を検討した。その結果、シリカ粒子の表面は親水性であるため、親水性のポリエーテルサルフォンにシリカ粒子が付着しやすいことを見出し、また、小さいシリカ粒子ほど付着した後に離れにくいことも見出し、以下の方法を発明した。
The present inventor examined the cause of the silica abrasive grains being easily clogged in a filter using polyethersulfone. As a result, since the surface of the silica particles is hydrophilic, it is found that the silica particles are likely to adhere to the hydrophilic polyethersulfone, and it is also found that the smaller the silica particles are, the more difficult it is to leave after the adhesion. Was invented.
上記課題を解決するため、本発明の第1の態様は、磁気ディスク用基板の製造方法であって、
一対の研磨パッドで基板を挟み、前記研磨パッドと前記基板の間に砥粒を含む研磨液を供給して、前記研磨パッドと前記ガラス基板を相対的に摺動させることにより、前記磁気ディスク用基板の両主表面を研磨する研磨処理を含み、
前記砥粒は平均粒径40nm以下のコロイダルシリカであり、
前記研磨液は、前記砥粒および前記砥粒の平均粒径よりも大きな粒径の大径粒子を含むスラリーに前記大径粒子を除去する除去処理を施すことによって得られ、
前記除去処理は、疎水性高分子材料からなり、開口径が100nm以下であるフィルタに前記スラリーを通す処理であることを特徴とする。 In order to solve the above problems, a first aspect of the present invention is a method of manufacturing a magnetic disk substrate,
By sandwiching the substrate between a pair of polishing pads, supplying a polishing liquid containing abrasive grains between the polishing pad and the substrate, and sliding the polishing pad and the glass substrate relatively, the magnetic disk Including a polishing process for polishing both main surfaces of the substrate;
The abrasive is colloidal silica having an average particle size of 40 nm or less,
The polishing liquid is obtained by subjecting the abrasive grains and a slurry containing large diameter particles having a larger particle diameter than the average particle diameter of the abrasive grains to a removal treatment to remove the large diameter particles,
The removal treatment is characterized in that the slurry is passed through a filter made of a hydrophobic polymer material and having an opening diameter of 100 nm or less.
一対の研磨パッドで基板を挟み、前記研磨パッドと前記基板の間に砥粒を含む研磨液を供給して、前記研磨パッドと前記ガラス基板を相対的に摺動させることにより、前記磁気ディスク用基板の両主表面を研磨する研磨処理を含み、
前記砥粒は平均粒径40nm以下のコロイダルシリカであり、
前記研磨液は、前記砥粒および前記砥粒の平均粒径よりも大きな粒径の大径粒子を含むスラリーに前記大径粒子を除去する除去処理を施すことによって得られ、
前記除去処理は、疎水性高分子材料からなり、開口径が100nm以下であるフィルタに前記スラリーを通す処理であることを特徴とする。 In order to solve the above problems, a first aspect of the present invention is a method of manufacturing a magnetic disk substrate,
By sandwiching the substrate between a pair of polishing pads, supplying a polishing liquid containing abrasive grains between the polishing pad and the substrate, and sliding the polishing pad and the glass substrate relatively, the magnetic disk Including a polishing process for polishing both main surfaces of the substrate;
The abrasive is colloidal silica having an average particle size of 40 nm or less,
The polishing liquid is obtained by subjecting the abrasive grains and a slurry containing large diameter particles having a larger particle diameter than the average particle diameter of the abrasive grains to a removal treatment to remove the large diameter particles,
The removal treatment is characterized in that the slurry is passed through a filter made of a hydrophobic polymer material and having an opening diameter of 100 nm or less.
疎水性高分子材料からなるフィルタには、スラリー中に含まれる砥粒や砥粒の平均粒径よりも大きな粒子が付着しにくいため、このフィルタにスラリーを通してもフィルタの目詰まりが生じにくい。このため、砥粒の平均粒径よりも大きな粒子を濾過残渣として効率よく除去することができる。
Since a filter made of a hydrophobic polymer material is hard to adhere abrasive grains contained in the slurry and particles larger than the average particle diameter of the abrasive grains, the filter is not easily clogged even when the slurry is passed through the filter. For this reason, particles larger than the average particle diameter of the abrasive grains can be efficiently removed as a filtration residue.
前記スラリー中のコロイダルシリカの濃度を30重量%以下にして前記フィルタに通すことが好ましい。
The colloidal silica concentration in the slurry is preferably 30% by weight or less and passed through the filter.
前記スラリーのpHを8以上13以下のアルカリ性の範囲に調整して前記フィルタに通すことが好ましい。
It is preferable that the pH of the slurry is adjusted to an alkaline range of 8 to 13 and passed through the filter.
前記疎水性高分子材料はポリフッ化ビニリデン(PVDF)であることが好ましい。
The hydrophobic polymer material is preferably polyvinylidene fluoride (PVDF).
前記フィルタは、相転移法により多孔質膜状に形成された疎水性高分子膜であることが好ましい。
The filter is preferably a hydrophobic polymer film formed into a porous film by a phase transition method.
上記の製造方法は、水ガラスとイオン交換樹脂を用いて得られるコロイダルシリカを用いて研磨処理を行う場合に最適である。
The above manufacturing method is optimal when polishing is performed using colloidal silica obtained using water glass and an ion exchange resin.
前記フィルタに前記スラリーを通して得られる研磨液のpHを、研磨処理を行う前に、酸性に調整することが好ましい。
It is preferable to adjust the pH of the polishing liquid obtained by passing the slurry through the filter to acidity before performing the polishing treatment.
上述の磁気ディスク用基板の製造方法によれば、研磨処理に用いるシリカ砥粒から板状異物のような異物を除去することができる。このため、磁気ディスク用基板の主表面に板状異物が付着せず、磁気ディスク用基板の研磨処理後の歩留まりを向上させることができる。
According to the method for manufacturing a magnetic disk substrate described above, foreign matters such as plate-like foreign matters can be removed from the silica abrasive grains used in the polishing process. For this reason, plate-like foreign substances do not adhere to the main surface of the magnetic disk substrate, and the yield after the polishing process of the magnetic disk substrate can be improved.
以下、本発明の実施形態に係る磁気ディスク用基板の製造方法について説明する。
(磁気ディスク用基板)
まず、磁気ディスク用基板について説明する。磁気ディスク用基板は、円板形状であって、外周と同心の円形の中心孔がくり抜かれたリング状である。磁気ディスク用基板の両面の円環状領域に磁性層(記録領域)が形成されることで、磁気ディスクが形成される。磁気ディスク用基板として、ガラス基板や、表面にNiP合金膜が形成されたアルミニウム合金基板等を用いることができる。 Hereinafter, a method for manufacturing a magnetic disk substrate according to an embodiment of the present invention will be described.
(Magnetic disk substrate)
First, the magnetic disk substrate will be described. The magnetic disk substrate has a disk shape and a ring shape in which a circular center hole concentric with the outer periphery is cut out. A magnetic disk is formed by forming magnetic layers (recording areas) in the annular areas on both sides of the magnetic disk substrate. As the magnetic disk substrate, a glass substrate, an aluminum alloy substrate having a NiP alloy film formed on the surface, or the like can be used.
(磁気ディスク用基板)
まず、磁気ディスク用基板について説明する。磁気ディスク用基板は、円板形状であって、外周と同心の円形の中心孔がくり抜かれたリング状である。磁気ディスク用基板の両面の円環状領域に磁性層(記録領域)が形成されることで、磁気ディスクが形成される。磁気ディスク用基板として、ガラス基板や、表面にNiP合金膜が形成されたアルミニウム合金基板等を用いることができる。 Hereinafter, a method for manufacturing a magnetic disk substrate according to an embodiment of the present invention will be described.
(Magnetic disk substrate)
First, the magnetic disk substrate will be described. The magnetic disk substrate has a disk shape and a ring shape in which a circular center hole concentric with the outer periphery is cut out. A magnetic disk is formed by forming magnetic layers (recording areas) in the annular areas on both sides of the magnetic disk substrate. As the magnetic disk substrate, a glass substrate, an aluminum alloy substrate having a NiP alloy film formed on the surface, or the like can be used.
本実施形態においては、磁性層を形成する前に、鏡面研磨処理が行われる。鏡面研磨処理では、遊星歯車機構を備えた両面研磨装置を用いて、磁気ディスク用基板の主表面に対して研磨処理を行う。具体的には、磁気ディスク用基板の外周側端面を、両面研磨装置の保持部材に設けられた保持孔内に保持しながら磁気ディスク用基板の両側の主表面の研磨を行う。両面研磨装置は、上下一対の定盤(上定盤および下定盤)を有しており、下定盤の上面及び上定盤の底面には、全体として円環形状の平板の研磨パッド(例えば、樹脂ポリッシャ)が取り付けられている。磁気ディスク用基板の主表面と研磨パッドとの間に研磨液を供給しながら、上定盤または下定盤のいずれか一方、または、双方を移動させることで、磁気ディスク用基板と研磨パッドとが相対的に移動し、磁気ディスク用基板の両主表面が研磨される。
In this embodiment, a mirror polishing process is performed before the magnetic layer is formed. In the mirror polishing process, the main surface of the magnetic disk substrate is polished using a double-side polishing apparatus equipped with a planetary gear mechanism. Specifically, the main surface on both sides of the magnetic disk substrate is polished while holding the outer peripheral side end face of the magnetic disk substrate in the holding hole provided in the holding member of the double-side polishing apparatus. The double-side polishing apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and an annular plate-shaped polishing pad (for example, as a whole on the upper surface of the lower surface plate and the bottom surface of the upper surface plate) Resin polisher) is attached. While supplying the polishing liquid between the main surface of the magnetic disk substrate and the polishing pad, either or both of the upper surface plate and the lower surface plate are moved, so that the magnetic disk substrate and the polishing pad are moved. The two main surfaces of the magnetic disk substrate are polished relative to each other.
本実施形態においては、鏡面研磨処理に用いる研磨液として、コロイダルシリカ(シリカ砥粒)を遊離砥粒として含む研磨液が好ましい。
鏡面研磨処理に用いる研磨液に含まれるコロイダルシリカは、オルトケイ酸テトラメチル、オルトケイ酸テトラエチル等を原料とするゾルゲル法、水ガラスを原料とするイオン交換法により製造することができる。この中でも、コスト面からイオン交換法により製造することが好ましい。
具体的には、ケイ砂とアルカリ剤(例えばNa2CO3、NaHCO3、NaOH、K2CO3、KHCO3、KOH等)とを混合し、加熱して熔融することでケイ酸塩を生成する。次に、得られたケイ酸塩を、必要に応じて冷却した後、水に溶解させることでケイ酸塩水溶液(水ガラス)を生成する。この水ガラスにプロトン型陽イオン交換樹脂を混合してケイ酸塩水溶液のpHを下げる。その後、所定の時間、所定の温度の加熱処理を行うことで、ケイ酸塩水溶液中でシラノール基同士の縮重合が促進され、コロイダルシリカが生成され、コロイダルシリカを砥粒として含むスラリーが得られる。 In the present embodiment, a polishing liquid that contains colloidal silica (silica abrasive grains) as free abrasive grains is preferable as the polishing liquid used for the mirror polishing process.
Colloidal silica contained in the polishing liquid used for the mirror polishing treatment can be produced by a sol-gel method using tetramethyl orthosilicate, tetraethyl orthosilicate or the like as a raw material, or an ion exchange method using water glass as a raw material. Among these, it is preferable to manufacture by an ion exchange method from a cost viewpoint.
Specifically, silica sand and an alkali agent (for example, Na 2 CO 3 , NaHCO 3 , NaOH, K 2 CO 3 , KHCO 3 , KOH, etc.) are mixed and heated to melt to produce silicate. To do. Next, the obtained silicate is cooled as necessary, and then dissolved in water to produce an aqueous silicate solution (water glass). The water glass is mixed with a proton-type cation exchange resin to lower the pH of the aqueous silicate solution. Thereafter, by performing a heat treatment at a predetermined temperature for a predetermined time, the condensation polymerization of silanol groups in the silicate aqueous solution is promoted, colloidal silica is generated, and a slurry containing colloidal silica as abrasive grains is obtained. .
鏡面研磨処理に用いる研磨液に含まれるコロイダルシリカは、オルトケイ酸テトラメチル、オルトケイ酸テトラエチル等を原料とするゾルゲル法、水ガラスを原料とするイオン交換法により製造することができる。この中でも、コスト面からイオン交換法により製造することが好ましい。
具体的には、ケイ砂とアルカリ剤(例えばNa2CO3、NaHCO3、NaOH、K2CO3、KHCO3、KOH等)とを混合し、加熱して熔融することでケイ酸塩を生成する。次に、得られたケイ酸塩を、必要に応じて冷却した後、水に溶解させることでケイ酸塩水溶液(水ガラス)を生成する。この水ガラスにプロトン型陽イオン交換樹脂を混合してケイ酸塩水溶液のpHを下げる。その後、所定の時間、所定の温度の加熱処理を行うことで、ケイ酸塩水溶液中でシラノール基同士の縮重合が促進され、コロイダルシリカが生成され、コロイダルシリカを砥粒として含むスラリーが得られる。 In the present embodiment, a polishing liquid that contains colloidal silica (silica abrasive grains) as free abrasive grains is preferable as the polishing liquid used for the mirror polishing process.
Colloidal silica contained in the polishing liquid used for the mirror polishing treatment can be produced by a sol-gel method using tetramethyl orthosilicate, tetraethyl orthosilicate or the like as a raw material, or an ion exchange method using water glass as a raw material. Among these, it is preferable to manufacture by an ion exchange method from a cost viewpoint.
Specifically, silica sand and an alkali agent (for example, Na 2 CO 3 , NaHCO 3 , NaOH, K 2 CO 3 , KHCO 3 , KOH, etc.) are mixed and heated to melt to produce silicate. To do. Next, the obtained silicate is cooled as necessary, and then dissolved in water to produce an aqueous silicate solution (water glass). The water glass is mixed with a proton-type cation exchange resin to lower the pH of the aqueous silicate solution. Thereafter, by performing a heat treatment at a predetermined temperature for a predetermined time, the condensation polymerization of silanol groups in the silicate aqueous solution is promoted, colloidal silica is generated, and a slurry containing colloidal silica as abrasive grains is obtained. .
このように生成されたコロイダルシリカを含むスラリーには、研磨砥粒として用いるのには不適切な、粒子径が大きい大径粒子(粗大粒子、板状物質等)が含まれる場合がある。具体的には、研磨砥粒として適したコロイダルシリカの平均粒子径が60nm以下、好ましくは10~60nm、より好ましくは20~50nmであるのに対し、砥粒として用いるのに不適切な大径粒子の粒子径は平均粒子径の2倍以上、より不適切なものは5倍以上である。例えば、大径粒子の粒子径は200nm~1μmである。
また、このように生成されたコロイダルシリカを含むスラリーには、原料のケイ砂に由来する、板状物質が混在している場合がある。この板状物質はアルミニウムを含むケイ酸塩の結晶であり、この結晶は層状を成す層状ケイ酸塩(例えばモンモリロナイト、サポナイト、カオリナイトなどの層状粘土鉱物)である。この板状物質は、極めて平たい形をしている。このような板状物質が精密に研磨された表面に付着した場合、密着しやすいため、洗浄することが困難になるため、この板状物質はコロイダルシリカを含むスラリーに対する異物(以下、板状異物と称する)とみなされる。
この板状異物は、ケイ砂とアルカリ剤とを混合して熔融しても熔けることなく残存し、熔融物を水に溶解させて得られる水ガラス内、水ガラスから製造されるコロイダルシリカを含むスラリー内にも残存する。 The slurry containing colloidal silica thus generated may contain large-sized particles (coarse particles, plate-like substances, etc.) having a large particle size that are inappropriate for use as abrasive grains. Specifically, the average particle diameter of colloidal silica suitable as abrasive grains is 60 nm or less, preferably 10 to 60 nm, more preferably 20 to 50 nm, whereas large diameters inappropriate for use as abrasive grains. The particle diameter of the particles is 2 times or more of the average particle diameter, and more inappropriate is 5 times or more. For example, the particle size of large particles is 200 nm to 1 μm.
Moreover, the slurry containing colloidal silica produced in this way may contain a plate-like substance derived from raw material silica sand. This plate-like substance is a silicate crystal containing aluminum, and this crystal is a layered layered silicate (for example, a layered clay mineral such as montmorillonite, saponite, and kaolinite). This plate-like material has a very flat shape. When such a plate-like substance adheres to a precisely polished surface, it is easy to adhere, and thus it becomes difficult to clean. Therefore, this plate-like substance is a foreign substance to the slurry containing colloidal silica (hereinafter referred to as a plate-like foreign substance). Called).
This plate-like foreign material remains without melting even when silica sand and an alkali agent are mixed and melted, and contains colloidal silica produced from water glass in water glass obtained by dissolving the melt in water. It remains in the slurry.
また、このように生成されたコロイダルシリカを含むスラリーには、原料のケイ砂に由来する、板状物質が混在している場合がある。この板状物質はアルミニウムを含むケイ酸塩の結晶であり、この結晶は層状を成す層状ケイ酸塩(例えばモンモリロナイト、サポナイト、カオリナイトなどの層状粘土鉱物)である。この板状物質は、極めて平たい形をしている。このような板状物質が精密に研磨された表面に付着した場合、密着しやすいため、洗浄することが困難になるため、この板状物質はコロイダルシリカを含むスラリーに対する異物(以下、板状異物と称する)とみなされる。
この板状異物は、ケイ砂とアルカリ剤とを混合して熔融しても熔けることなく残存し、熔融物を水に溶解させて得られる水ガラス内、水ガラスから製造されるコロイダルシリカを含むスラリー内にも残存する。 The slurry containing colloidal silica thus generated may contain large-sized particles (coarse particles, plate-like substances, etc.) having a large particle size that are inappropriate for use as abrasive grains. Specifically, the average particle diameter of colloidal silica suitable as abrasive grains is 60 nm or less, preferably 10 to 60 nm, more preferably 20 to 50 nm, whereas large diameters inappropriate for use as abrasive grains. The particle diameter of the particles is 2 times or more of the average particle diameter, and more inappropriate is 5 times or more. For example, the particle size of large particles is 200 nm to 1 μm.
Moreover, the slurry containing colloidal silica produced in this way may contain a plate-like substance derived from raw material silica sand. This plate-like substance is a silicate crystal containing aluminum, and this crystal is a layered layered silicate (for example, a layered clay mineral such as montmorillonite, saponite, and kaolinite). This plate-like material has a very flat shape. When such a plate-like substance adheres to a precisely polished surface, it is easy to adhere, and thus it becomes difficult to clean. Therefore, this plate-like substance is a foreign substance to the slurry containing colloidal silica (hereinafter referred to as a plate-like foreign substance). Called).
This plate-like foreign material remains without melting even when silica sand and an alkali agent are mixed and melted, and contains colloidal silica produced from water glass in water glass obtained by dissolving the melt in water. It remains in the slurry.
板状異物は、大径粒子のうち、最大長さが厚さの5倍以上の粒子が板状異物である。例えば板状異物の最大長さは50nm~1μm、好ましくは70nm~300nm、さらに好ましくは130~240nm厚みは1~25nm、好ましくは1~5nmである。
ここで、板状異物の最大長さは、板状異物に外接する直方体枠の最も長い辺の長さをいい、板状異物の厚さはこの直方体枠の最も短い辺の長さをいう。ガラス基板に付着した板状異物をSEMやAFMで観察したとき、板状異物の輪郭線と外接する長方形の長辺の長さを最大長さ、板状異物の最大高さを厚さとすることができる。
本実施形態では、あらかじめ以下に説明する除去処理を行う。 As for the plate-like foreign matter, among the large-diameter particles, particles having a maximum length of 5 times or more the thickness are plate-like foreign matters. For example, the maximum length of the plate-like foreign material is 50 nm to 1 μm, preferably 70 nm to 300 nm, more preferably 130 to 240 nm, and the thickness is 1 to 25 nm, preferably 1 to 5 nm.
Here, the maximum length of the plate-like foreign material refers to the length of the longest side of the cuboid frame that circumscribes the plate-like foreign material, and the thickness of the plate-like foreign material refers to the length of the shortest side of the cuboid frame. When observing a plate-like foreign substance attached to a glass substrate with SEM or AFM, the length of the long side of the rectangle circumscribing the outline of the plate-like foreign substance is the maximum length, and the maximum height of the plate-like foreign substance is the thickness. Can do.
In this embodiment, the removal process described below is performed in advance.
ここで、板状異物の最大長さは、板状異物に外接する直方体枠の最も長い辺の長さをいい、板状異物の厚さはこの直方体枠の最も短い辺の長さをいう。ガラス基板に付着した板状異物をSEMやAFMで観察したとき、板状異物の輪郭線と外接する長方形の長辺の長さを最大長さ、板状異物の最大高さを厚さとすることができる。
本実施形態では、あらかじめ以下に説明する除去処理を行う。 As for the plate-like foreign matter, among the large-diameter particles, particles having a maximum length of 5 times or more the thickness are plate-like foreign matters. For example, the maximum length of the plate-like foreign material is 50 nm to 1 μm, preferably 70 nm to 300 nm, more preferably 130 to 240 nm, and the thickness is 1 to 25 nm, preferably 1 to 5 nm.
Here, the maximum length of the plate-like foreign material refers to the length of the longest side of the cuboid frame that circumscribes the plate-like foreign material, and the thickness of the plate-like foreign material refers to the length of the shortest side of the cuboid frame. When observing a plate-like foreign substance attached to a glass substrate with SEM or AFM, the length of the long side of the rectangle circumscribing the outline of the plate-like foreign substance is the maximum length, and the maximum height of the plate-like foreign substance is the thickness. Can do.
In this embodiment, the removal process described below is performed in advance.
(除去処理)
除去処理は、スラリーをフィルタに通すことで、スラリーに含まれ砥粒の平均粒径よりも大きな粒径の粒子を濾過残渣として除去する処理である。
フィルタとして、疎水性高分子材料からなり、開口径が100nm以下である精密濾過膜を用いることができる。ここで、疎水性高分子材料とは、極性が小さく、水と水素結合を形成しにくい高分子からなる材料である。疎水性高分子材料からなるフィルタには、スラリー中に含まれる砥粒や砥粒の平均粒径よりも大きな粒子が付着しにくいため、このフィルタにスラリーを通してもフィルタの目詰まりが生じにくい。このため、砥粒の平均粒径よりも大きな粒子を濾過残渣として効率よく除去することができる。
このような疎水性高分子材料として、例えば水の接触角が(85~125°)の材料を用いることができる。
ここで、開口径とは、開口に内接する円の直径である。例えば走査型電子顕微鏡(SEM: Scanning Electron Microscope)によりフィルタの開口の形状を計測し、開口の開口径を求めることができる。 (Removal process)
A removal process is a process which removes the particle | grains larger than the average particle diameter of an abrasive grain contained in a slurry as a filtration residue by letting a slurry pass a filter.
As the filter, a microfiltration membrane made of a hydrophobic polymer material and having an opening diameter of 100 nm or less can be used. Here, the hydrophobic polymer material is a material made of a polymer having a small polarity and hardly forming a hydrogen bond with water. Since a filter made of a hydrophobic polymer material is hard to adhere abrasive grains contained in the slurry or particles larger than the average particle diameter of the abrasive grains, the filter is not easily clogged even when the slurry is passed through the filter. For this reason, particles larger than the average particle diameter of the abrasive grains can be efficiently removed as a filtration residue.
As such a hydrophobic polymer material, for example, a material having a water contact angle (85 to 125 °) can be used.
Here, the opening diameter is a diameter of a circle inscribed in the opening. For example, the shape of the opening of the filter can be measured with a scanning electron microscope (SEM) to obtain the opening diameter of the opening.
除去処理は、スラリーをフィルタに通すことで、スラリーに含まれ砥粒の平均粒径よりも大きな粒径の粒子を濾過残渣として除去する処理である。
フィルタとして、疎水性高分子材料からなり、開口径が100nm以下である精密濾過膜を用いることができる。ここで、疎水性高分子材料とは、極性が小さく、水と水素結合を形成しにくい高分子からなる材料である。疎水性高分子材料からなるフィルタには、スラリー中に含まれる砥粒や砥粒の平均粒径よりも大きな粒子が付着しにくいため、このフィルタにスラリーを通してもフィルタの目詰まりが生じにくい。このため、砥粒の平均粒径よりも大きな粒子を濾過残渣として効率よく除去することができる。
このような疎水性高分子材料として、例えば水の接触角が(85~125°)の材料を用いることができる。
ここで、開口径とは、開口に内接する円の直径である。例えば走査型電子顕微鏡(SEM: Scanning Electron Microscope)によりフィルタの開口の形状を計測し、開口の開口径を求めることができる。 (Removal process)
A removal process is a process which removes the particle | grains larger than the average particle diameter of an abrasive grain contained in a slurry as a filtration residue by letting a slurry pass a filter.
As the filter, a microfiltration membrane made of a hydrophobic polymer material and having an opening diameter of 100 nm or less can be used. Here, the hydrophobic polymer material is a material made of a polymer having a small polarity and hardly forming a hydrogen bond with water. Since a filter made of a hydrophobic polymer material is hard to adhere abrasive grains contained in the slurry or particles larger than the average particle diameter of the abrasive grains, the filter is not easily clogged even when the slurry is passed through the filter. For this reason, particles larger than the average particle diameter of the abrasive grains can be efficiently removed as a filtration residue.
As such a hydrophobic polymer material, for example, a material having a water contact angle (85 to 125 °) can be used.
Here, the opening diameter is a diameter of a circle inscribed in the opening. For example, the shape of the opening of the filter can be measured with a scanning electron microscope (SEM) to obtain the opening diameter of the opening.
精密濾過膜に用いる疎水性高分子材料として、例えば、ポリプロピレン、ポリエチレン、フッ素樹脂等を用いることができる。フッ素樹脂として、例えば、ポリテトラフルオロエチレン(PTFE)、パーフルオロアルコキシアルカン(PFA)、パーフルオロエチレンプロペンコポリマー(FEP)、エチレン-テトラフルオロエチレンコポリマー(ETFE)、ポリフッ化ビニル(PVF)、ポリフッ化ビニリデン(PVDF)、ポリクロロトリフルオロエチレン(PCTFE)、エチレン-クロロトリフルオロエチレンコポリマー(ECTFE)等を用いることができる。この中でも、撥水性の高いフッ素樹脂を用いることが好ましい。撥水性の高いフッ素樹脂を用いることで、フィルタとスラリーとの接触面積が低減されるため、フィルタの目詰まりをさらに低減することができる。
As the hydrophobic polymer material used for the microfiltration membrane, for example, polypropylene, polyethylene, fluororesin, or the like can be used. Examples of the fluororesin include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylene propene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinyl fluoride (PVF), and polyfluoride. Vinylidene (PVDF), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), or the like can be used. Among these, it is preferable to use a fluororesin having high water repellency. By using a highly water-repellent fluororesin, the contact area between the filter and the slurry is reduced, so that clogging of the filter can be further reduced.
濾過方法として、重力による自然濾過、減圧濾過(吸引濾過)、加圧濾過、遠心濾過、クロスフロー方式の限外濾過等の任意の方法を用いることができる。
As a filtration method, any method such as natural filtration by gravity, vacuum filtration (suction filtration), pressure filtration, centrifugal filtration, or cross flow ultrafiltration can be used.
疎水性高分子材料からなる精密濾過膜を、多孔性のメンブレンフィルタとしてもよいし、疎水性高分子繊維からなる不織布状の濾過膜としてもよい。また、膜状の濾過材を圧縮成型して板状の濾過板としてもよい。また、中空糸膜形状、スパイラル膜形状、チューブラー膜形状としてもよく、濾過方法に応じて適宜選択することができる。
A microfiltration membrane made of a hydrophobic polymer material may be used as a porous membrane filter, or a non-woven filter membrane made of a hydrophobic polymer fiber. Moreover, it is good also as a plate-shaped filtration board by compression-molding a film-form filter material. Moreover, it is good also as a hollow fiber membrane shape, a spiral membrane shape, and a tubular membrane shape, and it can select suitably according to the filtration method.
本実施形態においては、疎水性高分子膜に設けられた開口の扁平率が0.3よりも小さいことが好ましく、開口が真円(扁平率が0)であることが最も好ましい。開口の扁平率が小さい疎水性高分子膜は、例えば相転移法により作成することができる。相転移法により多孔質膜状に形成された疎水性高分子膜は、扁平率が極めて小さい開口を有する。
相転移法では、具体的には、まず、疎水性高分子膜の材料となる高分子材料を溶媒に溶解させた溶液を、支持板に塗布する。次に、溶液が塗布された支持板を水等の非溶媒に浸漬する。すると、支持板に塗布された溶液中のポリマーが支持板に析出し、固相の多孔質膜が支持板上に形成される。 In the present embodiment, the flatness of the opening provided in the hydrophobic polymer film is preferably smaller than 0.3, and the opening is most preferably a perfect circle (the flatness is 0). A hydrophobic polymer film having a small aperture flatness can be produced by, for example, a phase transition method. A hydrophobic polymer film formed into a porous film by a phase transition method has an opening with an extremely small flatness.
Specifically, in the phase transition method, first, a solution in which a polymer material that is a material of the hydrophobic polymer film is dissolved in a solvent is applied to the support plate. Next, the support plate coated with the solution is immersed in a non-solvent such as water. Then, the polymer in the solution applied to the support plate is deposited on the support plate, and a solid-phase porous film is formed on the support plate.
相転移法では、具体的には、まず、疎水性高分子膜の材料となる高分子材料を溶媒に溶解させた溶液を、支持板に塗布する。次に、溶液が塗布された支持板を水等の非溶媒に浸漬する。すると、支持板に塗布された溶液中のポリマーが支持板に析出し、固相の多孔質膜が支持板上に形成される。 In the present embodiment, the flatness of the opening provided in the hydrophobic polymer film is preferably smaller than 0.3, and the opening is most preferably a perfect circle (the flatness is 0). A hydrophobic polymer film having a small aperture flatness can be produced by, for example, a phase transition method. A hydrophobic polymer film formed into a porous film by a phase transition method has an opening with an extremely small flatness.
Specifically, in the phase transition method, first, a solution in which a polymer material that is a material of the hydrophobic polymer film is dissolved in a solvent is applied to the support plate. Next, the support plate coated with the solution is immersed in a non-solvent such as water. Then, the polymer in the solution applied to the support plate is deposited on the support plate, and a solid-phase porous film is formed on the support plate.
溶媒は疎水性高分子膜の材料となる高分子材料を溶解するものから適宜選択することができる。非溶媒は疎水性高分子膜の材料となる高分子材料が難溶あるいは不溶であり、かつ、溶媒と混合しないものから、適宜選択することができる。
例えば、疎水性高分子膜の材料としてPVDFを選択し、溶媒としてトリエチルホスフェート(TEP)を選択し、非溶媒として水(脱イオン水)を選択することができる。 The solvent can be appropriately selected from those that dissolve the polymer material that is the material of the hydrophobic polymer membrane. The non-solvent can be appropriately selected from those in which the polymer material used as the material of the hydrophobic polymer film is hardly soluble or insoluble and does not mix with the solvent.
For example, PVDF can be selected as the material for the hydrophobic polymer membrane, triethyl phosphate (TEP) can be selected as the solvent, and water (deionized water) can be selected as the non-solvent.
例えば、疎水性高分子膜の材料としてPVDFを選択し、溶媒としてトリエチルホスフェート(TEP)を選択し、非溶媒として水(脱イオン水)を選択することができる。 The solvent can be appropriately selected from those that dissolve the polymer material that is the material of the hydrophobic polymer membrane. The non-solvent can be appropriately selected from those in which the polymer material used as the material of the hydrophobic polymer film is hardly soluble or insoluble and does not mix with the solvent.
For example, PVDF can be selected as the material for the hydrophobic polymer membrane, triethyl phosphate (TEP) can be selected as the solvent, and water (deionized water) can be selected as the non-solvent.
上記のフィルタにスラリーを通すことで、スラリーに含まれ砥粒の平均粒径よりも大きな粒径の粒子を濾過残渣として除去することができる。ここで、スラリーの濾過を効率よく行うために、スラリー中のコロイダルシリカの濃度を30重量%以下、好ましくは5~25重量%にしてフィルタに通すことが好ましい。コロイダルシリカの濃度を調整してフィルタに通したところ、コロイダルシリカの濃度が20重量%の場合には単位時間当たりのフィルタ通過量が800リットルであるのに対して、25重量%では430リットル、30重量%では150リットル、35重量%では30リットル、40重量%では10リットルとなり、コロイダルシリカの濃度が増加するにつれて急激にフィルタの通過量が減少し、フィルタの目詰まりを生じることが確認された。このため、第2研磨処理に用いるコロイダルシリカの濃度の範囲でできるだけスラリー中のコロイダルシリカの濃度を希釈した状態でフィルタ処理を行うことが好ましい。具体的には、第2研磨処理に用いるコロイダルシリカの濃度を20重量%以下として用いる場合、スラリー中のコロイダルシリカの濃度を20~25重量%程度に希釈した状態でフィルタ処理を行う。
By passing the slurry through the filter, particles having a particle size larger than the average particle size of the abrasive grains contained in the slurry can be removed as a filtration residue. Here, in order to efficiently filter the slurry, it is preferable that the concentration of colloidal silica in the slurry is 30 wt% or less, preferably 5 to 25 wt%, and passed through the filter. When the colloidal silica concentration was adjusted and passed through the filter, when the colloidal silica concentration was 20% by weight, the filter passage amount per unit time was 800 liters, whereas at 25% by weight 430 liters, It is confirmed that 30% by weight is 150 liters, 35% by weight is 30 liters, and 40% by weight is 10 liters. As the colloidal silica concentration increases, the amount of filter passage decreases rapidly, causing clogging of the filter. It was. For this reason, it is preferable to perform the filter treatment in a state where the concentration of colloidal silica in the slurry is diluted as much as possible within the range of the concentration of colloidal silica used for the second polishing treatment. Specifically, when the concentration of colloidal silica used for the second polishing treatment is 20% by weight or less, the filter treatment is performed with the concentration of colloidal silica in the slurry diluted to about 20 to 25% by weight.
また、砥粒のスラリー中での分散性を高めるために、スラリーのpHを8以上13以下のアルカリ性の範囲に調整してフィルタに通すことが好ましい。スラリーのpHをアルカリ性側に調整することで相対的にフィルタ通過量は増加し、pHを酸性側に調整することで相対的にフィルタ透過量は減少する。そのため、フィルタの目詰まりを防止するとともに、板状異物をコロイダルシリカ砥粒の研磨スラリーから好適に除去するために、スラリーのpHを8~13のアルカリ性の範囲に調整することが好ましい。
In order to improve the dispersibility of the abrasive grains in the slurry, it is preferable to adjust the pH of the slurry to an alkaline range of 8 to 13 and pass it through a filter. By adjusting the pH of the slurry to the alkaline side, the filter passage amount is relatively increased, and by adjusting the pH to the acidic side, the filter permeation amount is relatively decreased. For this reason, it is preferable to adjust the pH of the slurry to an alkaline range of 8 to 13 in order to prevent clogging of the filter and to suitably remove the plate-like foreign matters from the polishing slurry of colloidal silica abrasive grains.
上記の除去処理を行った後、得られた研磨液中のコロイダルシリカを凝集させるために、コロイダルシリカの表面電荷を減少させる処理を行うことが好ましい。コロイダルシリカを凝集させることで、研磨レートを高めるとともに、研磨処理後のガラス基板の表面凹凸を小さくすることができる。
コロイダルシリカの表面電荷を減少させる方法として、研磨液のpHを1以上5以下の酸性に調整する方法がある。
あるいは、研磨液中のコロイダルシリカの表面電荷を減少させる添加剤(例えば、K2SO4,Na2SO4等の硫酸化合物、K3PO4,Na3PO4等の燐酸化合物、NaNO3等の硝酸化合物)を添加することが好ましい。除去処理を行う前にコロイダルシリカの表面電荷を減少させると、表面電荷が正である吸着材が粗大粒子や板状異物に付着しにくくなり、粗大粒子や板状異物をスラリーから除去することが困難になる。 After performing the above removal treatment, it is preferable to perform a treatment for reducing the surface charge of the colloidal silica in order to agglomerate the colloidal silica in the obtained polishing liquid. By aggregating colloidal silica, it is possible to increase the polishing rate and reduce the surface roughness of the glass substrate after the polishing treatment.
As a method of reducing the surface charge of colloidal silica, there is a method of adjusting the pH of the polishing liquid to an acidity of 1 or more and 5 or less.
Alternatively, an additive for reducing the surface charge of colloidal silica in the polishing liquid (for example, sulfuric acid compounds such as K 2 SO 4 and Na 2 SO 4 , phosphoric acid compounds such as K 3 PO 4 and Na 3 PO 4 , NaNO 3 and the like) Of nitric acid compound) is preferably added. If the surface charge of the colloidal silica is reduced before the removal treatment, the adsorbent with a positive surface charge is less likely to adhere to coarse particles and plate-like foreign matter, and the coarse particles and plate-like foreign matter can be removed from the slurry. It becomes difficult.
コロイダルシリカの表面電荷を減少させる方法として、研磨液のpHを1以上5以下の酸性に調整する方法がある。
あるいは、研磨液中のコロイダルシリカの表面電荷を減少させる添加剤(例えば、K2SO4,Na2SO4等の硫酸化合物、K3PO4,Na3PO4等の燐酸化合物、NaNO3等の硝酸化合物)を添加することが好ましい。除去処理を行う前にコロイダルシリカの表面電荷を減少させると、表面電荷が正である吸着材が粗大粒子や板状異物に付着しにくくなり、粗大粒子や板状異物をスラリーから除去することが困難になる。 After performing the above removal treatment, it is preferable to perform a treatment for reducing the surface charge of the colloidal silica in order to agglomerate the colloidal silica in the obtained polishing liquid. By aggregating colloidal silica, it is possible to increase the polishing rate and reduce the surface roughness of the glass substrate after the polishing treatment.
As a method of reducing the surface charge of colloidal silica, there is a method of adjusting the pH of the polishing liquid to an acidity of 1 or more and 5 or less.
Alternatively, an additive for reducing the surface charge of colloidal silica in the polishing liquid (for example, sulfuric acid compounds such as K 2 SO 4 and Na 2 SO 4 , phosphoric acid compounds such as K 3 PO 4 and Na 3 PO 4 , NaNO 3 and the like) Of nitric acid compound) is preferably added. If the surface charge of the colloidal silica is reduced before the removal treatment, the adsorbent with a positive surface charge is less likely to adhere to coarse particles and plate-like foreign matter, and the coarse particles and plate-like foreign matter can be removed from the slurry. It becomes difficult.
上記の板状異物は、特にガラス基板の主表面に付着すると、その後の洗浄処理等で除去することは難しくなる。このため、あらかじめ板状異物を除去したコロイダルシリカを遊離砥粒に用いて行う鏡面研磨処理は、ガラス基板の鏡面研磨処理に好適である。磁気ディスク用ガラス基板に用いるガラスとして、具体的には、アルミノシリケートガラス、ソーダライムガラス、ボロシリケートガラス等が挙げられる。特に、化学強化を施すことができ、また主表面の平面度及び基板の強度において優れた磁気ディスク用ガラス基板を作製することができるという点で、アルミノシリケートガラスを好適に用いることができる。
ここで、磁気ディスク用ガラス基板の製造方法について説明する。 In particular, when the plate-like foreign material adheres to the main surface of the glass substrate, it is difficult to remove it by a subsequent cleaning process or the like. For this reason, the mirror polishing process performed using colloidal silica from which the plate-like foreign material has been removed in advance as free abrasive grains is suitable for the mirror polishing process of the glass substrate. Specific examples of the glass used for the magnetic disk glass substrate include aluminosilicate glass, soda lime glass, and borosilicate glass. In particular, aluminosilicate glass can be suitably used in that it can be chemically strengthened and a glass substrate for a magnetic disk excellent in the flatness of the main surface and the strength of the substrate can be produced.
Here, the manufacturing method of the glass substrate for magnetic discs is demonstrated.
ここで、磁気ディスク用ガラス基板の製造方法について説明する。 In particular, when the plate-like foreign material adheres to the main surface of the glass substrate, it is difficult to remove it by a subsequent cleaning process or the like. For this reason, the mirror polishing process performed using colloidal silica from which the plate-like foreign material has been removed in advance as free abrasive grains is suitable for the mirror polishing process of the glass substrate. Specific examples of the glass used for the magnetic disk glass substrate include aluminosilicate glass, soda lime glass, and borosilicate glass. In particular, aluminosilicate glass can be suitably used in that it can be chemically strengthened and a glass substrate for a magnetic disk excellent in the flatness of the main surface and the strength of the substrate can be produced.
Here, the manufacturing method of the glass substrate for magnetic discs is demonstrated.
(磁気ディスク用ガラス基板の製造方法)
先ず、磁気ディスク用ガラスブランクをプレス成形により作製する。磁気ディスク用ガラスブランク(以降、単にガラスブランクという)は、一対の主表面を有する円板状の磁気ディスク用ガラス基板の素材であって、中心孔がくり抜かれる前の形態である。
次に、作製されたガラスブランクの中心部分に孔をあけ、リング形状(円環状)のガラス基板を作製する。次に、穴をあけたガラス基板に対して形状加工を行う。次に、形状加工されたガラス基板に対して端面研磨を行う。次に、端面研磨の行われたガラス基板に、固定砥粒による研削を行う。次に、ガラス基板の主表面に第1研磨を行う。次に、ガラス基板に対して必要に応じて化学強化を行う。その後、ガラス基板に対して第2研磨(鏡面研磨)を行う。第2研磨後、洗浄処理を経て、磁気ディスク用ガラス基板が得られる。
以下、各処理について、さらに説明する。 (Method for producing glass substrate for magnetic disk)
First, a glass blank for a magnetic disk is produced by press molding. A magnetic disk glass blank (hereinafter simply referred to as a glass blank) is a material for a disk-shaped magnetic disk glass substrate having a pair of main surfaces, and is a form before a center hole is cut out.
Next, a hole is made in the central portion of the produced glass blank to produce a ring-shaped (annular) glass substrate. Next, shape processing is performed on the glass substrate with holes. Next, end face polishing is performed on the glass substrate that has been processed into a shape. Next, grinding with fixed abrasive is performed on the glass substrate on which the end face has been polished. Next, the first polishing is performed on the main surface of the glass substrate. Next, chemical strengthening is performed on the glass substrate as necessary. Thereafter, second polishing (mirror polishing) is performed on the glass substrate. After the second polishing, a glass substrate for magnetic disk is obtained through a cleaning process.
Hereinafter, each process will be further described.
先ず、磁気ディスク用ガラスブランクをプレス成形により作製する。磁気ディスク用ガラスブランク(以降、単にガラスブランクという)は、一対の主表面を有する円板状の磁気ディスク用ガラス基板の素材であって、中心孔がくり抜かれる前の形態である。
次に、作製されたガラスブランクの中心部分に孔をあけ、リング形状(円環状)のガラス基板を作製する。次に、穴をあけたガラス基板に対して形状加工を行う。次に、形状加工されたガラス基板に対して端面研磨を行う。次に、端面研磨の行われたガラス基板に、固定砥粒による研削を行う。次に、ガラス基板の主表面に第1研磨を行う。次に、ガラス基板に対して必要に応じて化学強化を行う。その後、ガラス基板に対して第2研磨(鏡面研磨)を行う。第2研磨後、洗浄処理を経て、磁気ディスク用ガラス基板が得られる。
以下、各処理について、さらに説明する。 (Method for producing glass substrate for magnetic disk)
First, a glass blank for a magnetic disk is produced by press molding. A magnetic disk glass blank (hereinafter simply referred to as a glass blank) is a material for a disk-shaped magnetic disk glass substrate having a pair of main surfaces, and is a form before a center hole is cut out.
Next, a hole is made in the central portion of the produced glass blank to produce a ring-shaped (annular) glass substrate. Next, shape processing is performed on the glass substrate with holes. Next, end face polishing is performed on the glass substrate that has been processed into a shape. Next, grinding with fixed abrasive is performed on the glass substrate on which the end face has been polished. Next, the first polishing is performed on the main surface of the glass substrate. Next, chemical strengthening is performed on the glass substrate as necessary. Thereafter, second polishing (mirror polishing) is performed on the glass substrate. After the second polishing, a glass substrate for magnetic disk is obtained through a cleaning process.
Hereinafter, each process will be further described.
(a)プレス成形処理
溶融ガラス流の先端部を切断した溶融ガラスの塊を一対の金型のプレス成形面の間に挟みこみ、プレスしてガラスブランクを成形する。所定時間プレスを行った後、金型を開いてガラスブランクが取り出される。 (A) Press molding process The lump of the molten glass which cut | disconnected the front-end | tip part of the molten glass flow is pinched | interposed between the press molding surfaces of a pair of metal molds, and is pressed to form a glass blank. After pressing for a predetermined time, the mold is opened and the glass blank is taken out.
溶融ガラス流の先端部を切断した溶融ガラスの塊を一対の金型のプレス成形面の間に挟みこみ、プレスしてガラスブランクを成形する。所定時間プレスを行った後、金型を開いてガラスブランクが取り出される。 (A) Press molding process The lump of the molten glass which cut | disconnected the front-end | tip part of the molten glass flow is pinched | interposed between the press molding surfaces of a pair of metal molds, and is pressed to form a glass blank. After pressing for a predetermined time, the mold is opened and the glass blank is taken out.
(b)円孔形成処理
ガラスブランクに対してコアドリル等を用いて円孔を形成することにより円形状の中央孔があいたガラス基板を得ることができる。 (B) Circular hole formation treatment A glass substrate having a circular central hole can be obtained by forming a circular hole on a glass blank using a core drill or the like.
ガラスブランクに対してコアドリル等を用いて円孔を形成することにより円形状の中央孔があいたガラス基板を得ることができる。 (B) Circular hole formation treatment A glass substrate having a circular central hole can be obtained by forming a circular hole on a glass blank using a core drill or the like.
(c)形状加工処理
形状加工処理では、円孔形成後のガラス基板の端部に対する面取り加工を行う。 (C) Shape processing In the shape processing, chamfering is performed on the edge of the glass substrate after the circular hole is formed.
形状加工処理では、円孔形成後のガラス基板の端部に対する面取り加工を行う。 (C) Shape processing In the shape processing, chamfering is performed on the edge of the glass substrate after the circular hole is formed.
(d)端面研磨処理
端面研磨処理では、ガラス基板の内側端面及び外周側端面に対して、ブラシ研磨により鏡面仕上げを行う。このとき、酸化セリウム等の粒子を遊離砥粒として含む砥粒スラリーが用いられる。 (D) End surface polishing process In the end surface polishing process, mirror finishing is performed on the inner end face and the outer peripheral end face of the glass substrate by brush polishing. At this time, an abrasive slurry containing particles such as cerium oxide as free abrasive grains is used.
端面研磨処理では、ガラス基板の内側端面及び外周側端面に対して、ブラシ研磨により鏡面仕上げを行う。このとき、酸化セリウム等の粒子を遊離砥粒として含む砥粒スラリーが用いられる。 (D) End surface polishing process In the end surface polishing process, mirror finishing is performed on the inner end face and the outer peripheral end face of the glass substrate by brush polishing. At this time, an abrasive slurry containing particles such as cerium oxide as free abrasive grains is used.
(e)研削処理
固定砥粒による研削処理では、遊星歯車機構を備えた両面研削装置を用いて、ガラス基板の主表面に対して研削加工を行う。具体的には、ガラスブランクから生成されたガラス基板の外周側端面を、両面研削装置の保持部材に設けられた保持孔内に保持しながらガラス基板の両側の主表面の研削を行う。両面研削装置は、上下一対の定盤(上定盤および下定盤)を有しており、上定盤および下定盤の間にガラス基板が狭持される。そして、上定盤または下定盤のいずれか一方、または、双方を移動操作させ、ガラス基板と各定盤とを相対的に移動させることにより、ガラス基板の両主表面を研削することができる。 (E) Grinding process In the grinding process using the fixed abrasive grains, the main surface of the glass substrate is ground using a double-side grinding apparatus having a planetary gear mechanism. Specifically, the main surface on both sides of the glass substrate is ground while holding the outer peripheral side end face of the glass substrate generated from the glass blank in the holding hole provided in the holding member of the double-side grinding apparatus. The double-sided grinding apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and a glass substrate is sandwiched between the upper surface plate and the lower surface plate. Then, by moving one or both of the upper surface plate and the lower surface plate and relatively moving the glass substrate and each surface plate, both main surfaces of the glass substrate can be ground.
固定砥粒による研削処理では、遊星歯車機構を備えた両面研削装置を用いて、ガラス基板の主表面に対して研削加工を行う。具体的には、ガラスブランクから生成されたガラス基板の外周側端面を、両面研削装置の保持部材に設けられた保持孔内に保持しながらガラス基板の両側の主表面の研削を行う。両面研削装置は、上下一対の定盤(上定盤および下定盤)を有しており、上定盤および下定盤の間にガラス基板が狭持される。そして、上定盤または下定盤のいずれか一方、または、双方を移動操作させ、ガラス基板と各定盤とを相対的に移動させることにより、ガラス基板の両主表面を研削することができる。 (E) Grinding process In the grinding process using the fixed abrasive grains, the main surface of the glass substrate is ground using a double-side grinding apparatus having a planetary gear mechanism. Specifically, the main surface on both sides of the glass substrate is ground while holding the outer peripheral side end face of the glass substrate generated from the glass blank in the holding hole provided in the holding member of the double-side grinding apparatus. The double-sided grinding apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and a glass substrate is sandwiched between the upper surface plate and the lower surface plate. Then, by moving one or both of the upper surface plate and the lower surface plate and relatively moving the glass substrate and each surface plate, both main surfaces of the glass substrate can be ground.
(f)第1研磨処理
第1研磨は、例えば固定砥粒による研削を行った場合に主表面に残留したキズや歪みの除去、あるいは微小な表面凹凸(マイクロウェービネス、粗さ)の調整を目的とする。 (F) First polishing treatment In the first polishing, for example, when grinding with fixed abrasive grains is performed, scratches and distortions remaining on the main surface are removed, or fine surface irregularities (microwaveness, roughness) are adjusted. Objective.
第1研磨は、例えば固定砥粒による研削を行った場合に主表面に残留したキズや歪みの除去、あるいは微小な表面凹凸(マイクロウェービネス、粗さ)の調整を目的とする。 (F) First polishing treatment In the first polishing, for example, when grinding with fixed abrasive grains is performed, scratches and distortions remaining on the main surface are removed, or fine surface irregularities (microwaveness, roughness) are adjusted. Objective.
第1研磨処理では、両面研削装置と同様の構成を備えた両面研磨装置を用い、遊離砥粒を含んだ研磨液を両面研磨装置に与えながらガラス基板が研磨される。遊離砥粒として、例えば、酸化セリウム砥粒、酸化アルミニウム砥粒あるいはジルコニア砥粒など(粒子サイズ:直径1~2μm程度)が用いられる。両面研磨装置も、両面研削装置と同様に、上下一対の定盤の間にガラス基板が狭持される。下定盤の上面及び上定盤の底面には、全体として円環形状の平板の研磨パッド(例えば、樹脂ポリッシャ)が取り付けられている。ガラス基板の主表面と研磨パッドとの間に研磨液を供給しながら、上定盤または下定盤のいずれか一方、または、双方を移動させることで、ガラス基板と研磨パッドとが相対的に移動し、ガラス基板の両主表面が研磨される。
In the first polishing process, a glass substrate is polished using a double-side polishing apparatus having a configuration similar to that of a double-side grinding apparatus while applying a polishing liquid containing loose abrasive grains to the double-side polishing apparatus. As the free abrasive grains, for example, cerium oxide abrasive grains, aluminum oxide abrasive grains, zirconia abrasive grains, etc. (particle size: diameter of about 1 to 2 μm) are used. In the double-side polishing apparatus, similarly to the double-side grinding apparatus, the glass substrate is sandwiched between a pair of upper and lower surface plates. An annular flat polishing pad (for example, a resin polisher) is attached to the upper surface of the lower surface plate and the bottom surface of the upper surface plate as a whole. While supplying the polishing liquid between the main surface of the glass substrate and the polishing pad, the glass substrate and the polishing pad move relatively by moving either the upper surface plate, the lower surface plate, or both. Then, both main surfaces of the glass substrate are polished.
(g)化学強化処理
化学強化処理では、ガラス基板を化学強化液に浸漬することによって、ガラス基板を化学強化する。化学強化液として、例えば硝酸カリウムと硝酸ナトリウムの混合熔融液等を用いることができる。なお、化学強化処理は実施しなくてもよい。 (G) Chemical strengthening treatment In the chemical strengthening treatment, the glass substrate is chemically strengthened by immersing the glass substrate in a chemical strengthening solution. As the chemical strengthening liquid, for example, a mixed melt of potassium nitrate and sodium nitrate can be used. The chemical strengthening process may not be performed.
化学強化処理では、ガラス基板を化学強化液に浸漬することによって、ガラス基板を化学強化する。化学強化液として、例えば硝酸カリウムと硝酸ナトリウムの混合熔融液等を用いることができる。なお、化学強化処理は実施しなくてもよい。 (G) Chemical strengthening treatment In the chemical strengthening treatment, the glass substrate is chemically strengthened by immersing the glass substrate in a chemical strengthening solution. As the chemical strengthening liquid, for example, a mixed melt of potassium nitrate and sodium nitrate can be used. The chemical strengthening process may not be performed.
(h)第2研磨(鏡面研磨)処理
第2研磨処理は、主表面の鏡面研磨を目的とする。第2研磨においても、第1研磨に用いる両面研磨装置と同様の構成を有する両面研磨装置が用いられる。第2研磨による取り代は、例えば1μm程度である。第2研磨処理が第1研磨処理と異なる点は、遊離砥粒の種類及び粒子サイズが異なることと、樹脂ポリッシャの硬度が異なることである。 (H) Second polishing (mirror polishing) treatment The second polishing treatment is intended for mirror polishing of the main surface. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. The machining allowance by the second polishing is, for example, about 1 μm. The second polishing process is different from the first polishing process in that the type and particle size of the free abrasive grains are different and the hardness of the resin polisher is different.
第2研磨処理は、主表面の鏡面研磨を目的とする。第2研磨においても、第1研磨に用いる両面研磨装置と同様の構成を有する両面研磨装置が用いられる。第2研磨による取り代は、例えば1μm程度である。第2研磨処理が第1研磨処理と異なる点は、遊離砥粒の種類及び粒子サイズが異なることと、樹脂ポリッシャの硬度が異なることである。 (H) Second polishing (mirror polishing) treatment The second polishing treatment is intended for mirror polishing of the main surface. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. The machining allowance by the second polishing is, for example, about 1 μm. The second polishing process is different from the first polishing process in that the type and particle size of the free abrasive grains are different and the hardness of the resin polisher is different.
第2研磨処理では、上述した除去処理を行って得られた、コロイダルシリカを遊離砥粒として含む研磨液が用いられる。
第2研磨処理を実施することで、主表面の粗さ(Ra)を0.15nm以下かつ主表面のマイクロウェービネスを0.1nm以下とすることができる。
なお、第2研磨処理において、複数種類の研磨砥粒を用いて多段階の研磨処理を行ってもよい。例えば、コロイダルシリカを遊離砥粒として含む研磨液を用いて研磨処理を行う前に、酸化セリウム(CeO2)を遊離砥粒として含む研磨液を用いて研磨処理を行ってもよい。また、コロイダルシリカを遊離砥粒として含む研磨液を用いて研磨処理を行った後に、さらにコロイダルシリカを遊離砥粒として含む研磨液を用いて仕上げの研磨処理を行ってもよい。 In the second polishing process, a polishing liquid obtained by performing the above-described removal process and containing colloidal silica as free abrasive grains is used.
By performing the second polishing treatment, the roughness (Ra) of the main surface can be set to 0.15 nm or less and the micro waveness of the main surface can be set to 0.1 nm or less.
In the second polishing process, a multi-stage polishing process may be performed using a plurality of types of polishing abrasive grains. For example, before performing the polishing process using a polishing liquid containing colloidal silica as free abrasive grains, the polishing process may be performed using a polishing liquid containing cerium oxide (CeO 2 ) as free abrasive grains. Moreover, after performing the polishing process using a polishing liquid containing colloidal silica as free abrasive grains, a final polishing process may be performed using a polishing liquid containing colloidal silica as free abrasive grains.
第2研磨処理を実施することで、主表面の粗さ(Ra)を0.15nm以下かつ主表面のマイクロウェービネスを0.1nm以下とすることができる。
なお、第2研磨処理において、複数種類の研磨砥粒を用いて多段階の研磨処理を行ってもよい。例えば、コロイダルシリカを遊離砥粒として含む研磨液を用いて研磨処理を行う前に、酸化セリウム(CeO2)を遊離砥粒として含む研磨液を用いて研磨処理を行ってもよい。また、コロイダルシリカを遊離砥粒として含む研磨液を用いて研磨処理を行った後に、さらにコロイダルシリカを遊離砥粒として含む研磨液を用いて仕上げの研磨処理を行ってもよい。 In the second polishing process, a polishing liquid obtained by performing the above-described removal process and containing colloidal silica as free abrasive grains is used.
By performing the second polishing treatment, the roughness (Ra) of the main surface can be set to 0.15 nm or less and the micro waveness of the main surface can be set to 0.1 nm or less.
In the second polishing process, a multi-stage polishing process may be performed using a plurality of types of polishing abrasive grains. For example, before performing the polishing process using a polishing liquid containing colloidal silica as free abrasive grains, the polishing process may be performed using a polishing liquid containing cerium oxide (CeO 2 ) as free abrasive grains. Moreover, after performing the polishing process using a polishing liquid containing colloidal silica as free abrasive grains, a final polishing process may be performed using a polishing liquid containing colloidal silica as free abrasive grains.
(i)洗浄処理
第2研磨処理の後、ガラス基板は、アルカリ洗浄液を用いてガラス基板の表面が洗浄され、磁性層が形成される前の磁気ディスク用ガラス基板となる。
このとき、洗浄処理では、洗浄処理前後のガラス基板の表面粗さRaの差が0.05nm以下にするアルカリ洗浄液を用いることが好ましい。ガラス基板に付着する板状異物は、除去し難いため、従来、洗浄力の高いアルカリ洗浄液を従来用いていた。このため、洗浄力の強いアルカリ洗浄液は、板状異物のないガラス基板の主表面に作用して主表面を荒らし易い。しかし、本実施形態では、上述した除去処理を施したシリカ砥粒を用いて研磨処理を行うので、ガラス基板には板状異物は付着しない。このため、本実施形態では、従来に比べて洗浄力の弱いアルカリ洗浄液、すなわち、洗浄処理前後のガラス基板の表面粗さRaの差を0.05nm以下にするアルカリ洗浄液を用いることができる。なお、Raは、JIS B0601に規定される表面粗さである。この表面粗さは、原子間力顕微鏡(AFM)を用いて1μm×1μmの範囲を256×256ピクセルの解像度で測定したデータに基づいて得られるものである。 (I) Cleaning Process After the second polishing process, the glass substrate becomes a glass substrate for a magnetic disk before the surface of the glass substrate is cleaned using an alkaline cleaning liquid and the magnetic layer is formed.
At this time, in the cleaning process, it is preferable to use an alkaline cleaning liquid in which the difference in surface roughness Ra between the glass substrate before and after the cleaning process is 0.05 nm or less. Since plate-like foreign substances adhering to the glass substrate are difficult to remove, an alkaline cleaning liquid having a high cleaning power has been conventionally used. For this reason, the alkaline cleaning liquid having a strong cleaning power is likely to act on the main surface of the glass substrate having no plate-like foreign matter and roughen the main surface. However, in this embodiment, since the polishing process is performed using the silica abrasive grains subjected to the above-described removal process, no plate-like foreign matter adheres to the glass substrate. For this reason, in the present embodiment, an alkaline cleaning liquid having a weaker cleaning power than that of the prior art, that is, an alkaline cleaning liquid that makes the difference in the surface roughness Ra of the glass substrate before and after the cleaning process 0.05 nm or less can be used. Note that Ra is the surface roughness specified in JIS B0601. This surface roughness is obtained based on data obtained by measuring a range of 1 μm × 1 μm with a resolution of 256 × 256 pixels using an atomic force microscope (AFM).
第2研磨処理の後、ガラス基板は、アルカリ洗浄液を用いてガラス基板の表面が洗浄され、磁性層が形成される前の磁気ディスク用ガラス基板となる。
このとき、洗浄処理では、洗浄処理前後のガラス基板の表面粗さRaの差が0.05nm以下にするアルカリ洗浄液を用いることが好ましい。ガラス基板に付着する板状異物は、除去し難いため、従来、洗浄力の高いアルカリ洗浄液を従来用いていた。このため、洗浄力の強いアルカリ洗浄液は、板状異物のないガラス基板の主表面に作用して主表面を荒らし易い。しかし、本実施形態では、上述した除去処理を施したシリカ砥粒を用いて研磨処理を行うので、ガラス基板には板状異物は付着しない。このため、本実施形態では、従来に比べて洗浄力の弱いアルカリ洗浄液、すなわち、洗浄処理前後のガラス基板の表面粗さRaの差を0.05nm以下にするアルカリ洗浄液を用いることができる。なお、Raは、JIS B0601に規定される表面粗さである。この表面粗さは、原子間力顕微鏡(AFM)を用いて1μm×1μmの範囲を256×256ピクセルの解像度で測定したデータに基づいて得られるものである。 (I) Cleaning Process After the second polishing process, the glass substrate becomes a glass substrate for a magnetic disk before the surface of the glass substrate is cleaned using an alkaline cleaning liquid and the magnetic layer is formed.
At this time, in the cleaning process, it is preferable to use an alkaline cleaning liquid in which the difference in surface roughness Ra between the glass substrate before and after the cleaning process is 0.05 nm or less. Since plate-like foreign substances adhering to the glass substrate are difficult to remove, an alkaline cleaning liquid having a high cleaning power has been conventionally used. For this reason, the alkaline cleaning liquid having a strong cleaning power is likely to act on the main surface of the glass substrate having no plate-like foreign matter and roughen the main surface. However, in this embodiment, since the polishing process is performed using the silica abrasive grains subjected to the above-described removal process, no plate-like foreign matter adheres to the glass substrate. For this reason, in the present embodiment, an alkaline cleaning liquid having a weaker cleaning power than that of the prior art, that is, an alkaline cleaning liquid that makes the difference in the surface roughness Ra of the glass substrate before and after the cleaning process 0.05 nm or less can be used. Note that Ra is the surface roughness specified in JIS B0601. This surface roughness is obtained based on data obtained by measuring a range of 1 μm × 1 μm with a resolution of 256 × 256 pixels using an atomic force microscope (AFM).
また、洗浄処理は、ガラス基板を洗浄液に浸すあるいは接触させる非スクラブ洗浄であることが、ガラス基板に傷を作らない点で好ましい。従来の洗浄処理では、ガラス基板に強固に付着した板状異物を除去するために、ブラシや洗浄パッドでガラス基板を擦って、板状異物を除去するスクラブ洗浄を行なっていた。しかし、このスクラブ洗浄では、ガラス基板の主表面に傷を付け易い。本実施形態では、上述した除去処理を施したシリカ砥粒を含んだスラリーを用いて研磨するので、ガラス基板には板状異物が付着しない。このため、従来のようにスクラブ洗浄をしなくてもよい。このため、本実施形態では、ガラス基板を洗浄液に浸すあるいは接触させる非スクラブ洗浄をすることにより、不要な傷をガラス基板の主表面に付けることがなくなる。
In addition, the cleaning treatment is preferably non-scrub cleaning in which the glass substrate is immersed in or brought into contact with the cleaning liquid in terms of not causing scratches on the glass substrate. In the conventional cleaning process, scrub cleaning is performed to remove the plate-like foreign matter by rubbing the glass substrate with a brush or a cleaning pad in order to remove the plate-like foreign matter firmly attached to the glass substrate. However, this scrub cleaning tends to damage the main surface of the glass substrate. In this embodiment, since it polishes using the slurry containing the silica abrasive grain which performed the removal process mentioned above, a plate-shaped foreign material does not adhere to a glass substrate. For this reason, it is not necessary to perform scrub cleaning as in the past. For this reason, in this embodiment, unnecessary scratches are not applied to the main surface of the glass substrate by performing non-scrub cleaning in which the glass substrate is immersed in or brought into contact with the cleaning liquid.
以上磁気ディスク用基板としてガラス基板を用いて説明してきたが、本発明はアルミニウム合金基板にも適用することができるものである。アルミニウム合金基板の場合には、アルミニウム合金を圧延し、円板状に切り出したアルミニウム合金素板の表面にNiPめっきを成膜したアルミニウム合金基板を用い、NiPめっき膜表面を研磨パッドを用いて研磨することとなる。アルミニウム合金基板を用いた磁気ディスクは軟磁性層、非磁性下地層、垂直磁気記録層、保護層および潤滑層等がアルミニウム合金基板に積層して得られるものである。
As described above, the glass substrate is used as the magnetic disk substrate, but the present invention can also be applied to an aluminum alloy substrate. In the case of an aluminum alloy substrate, an aluminum alloy substrate obtained by rolling an aluminum alloy and forming a NiP plating film on the surface of the aluminum alloy substrate cut into a disk shape is used, and the NiP plating film surface is polished using a polishing pad. Will be. A magnetic disk using an aluminum alloy substrate is obtained by laminating a soft magnetic layer, a nonmagnetic underlayer, a perpendicular magnetic recording layer, a protective layer, a lubricating layer, and the like on an aluminum alloy substrate.
具体的には、以下の各処理工程を経て製造されるところ、研磨処理工程において用いられる研磨パッドはガラス基板の研磨工程において用いられる研磨パッドと同じものを用いることができる。
溶解したアルミニウム合金を鋳造し、圧延した後に円板状のアルミニウム合金素板として切り出し、主表面および端面を研削処理することにより所定の寸法に加工する。その後、アルミニウム合金素板の表面に5~30μmの厚さでNiPめっき成膜処理を施し、アルミニウム合金基板とする。続いて、NiPめっきを施したアルミニウム合金基板の主表面を研磨パッドを用いて研磨処理することで微小うねりを低減する。研磨処理は通常、研磨砥粒の種類および粒径を変えて2段階で行われ、第1研磨処理では平均粒径が0.3~3μmの酸化アルミニウム砥粒を含有したスラリーを用い、第2研磨処理では平均粒径が40nm以下、好ましくは5~40nmのコロイダルシリカ砥粒を含有したスラリーを用いて、それぞれ開口処理を施した研磨パッド間に挟み込み相対的に摺動させることでアルミニウム合金基板表面のNiPめっき表面の傷やうねりを低減する。さらに、第1研磨処理の後および第2研磨処理の後には研磨処理後に基板表面に付着する研磨砥粒や研磨カス等のパーティクルを除去するため洗浄処理が行われる。この第2研磨処理において、上述した除去処理を行って得られた、コロイダルシリカを遊離砥粒として含む研磨液を用いることができる。 Specifically, when manufactured through the following respective processing steps, the same polishing pad used in the polishing step of the glass substrate can be used as the polishing pad used in the polishing step.
The molten aluminum alloy is cast, rolled, cut out as a disk-shaped aluminum alloy base plate, and processed to a predetermined size by grinding the main surface and the end face. After that, the surface of the aluminum alloy base plate is subjected to NiP plating film formation with a thickness of 5 to 30 μm to obtain an aluminum alloy substrate. Subsequently, the main surface of the aluminum alloy substrate subjected to NiP plating is polished using a polishing pad to reduce microwaviness. The polishing process is usually performed in two stages by changing the type and particle size of the abrasive grains. In the first polishing process, a slurry containing aluminum oxide abrasive grains having an average particle diameter of 0.3 to 3 μm is used. In the polishing treatment, an aluminum alloy substrate is sandwiched between the polishing pads subjected to the opening treatment using a slurry containing colloidal silica abrasive grains having an average particle size of 40 nm or less, preferably 5 to 40 nm, and relatively slid. Reduces scratches and undulations on the NiP plating surface. Further, after the first polishing process and after the second polishing process, a cleaning process is performed in order to remove particles such as abrasive grains and polishing residue adhering to the substrate surface after the polishing process. In this second polishing treatment, a polishing liquid containing colloidal silica as free abrasive grains obtained by performing the above-described removal treatment can be used.
溶解したアルミニウム合金を鋳造し、圧延した後に円板状のアルミニウム合金素板として切り出し、主表面および端面を研削処理することにより所定の寸法に加工する。その後、アルミニウム合金素板の表面に5~30μmの厚さでNiPめっき成膜処理を施し、アルミニウム合金基板とする。続いて、NiPめっきを施したアルミニウム合金基板の主表面を研磨パッドを用いて研磨処理することで微小うねりを低減する。研磨処理は通常、研磨砥粒の種類および粒径を変えて2段階で行われ、第1研磨処理では平均粒径が0.3~3μmの酸化アルミニウム砥粒を含有したスラリーを用い、第2研磨処理では平均粒径が40nm以下、好ましくは5~40nmのコロイダルシリカ砥粒を含有したスラリーを用いて、それぞれ開口処理を施した研磨パッド間に挟み込み相対的に摺動させることでアルミニウム合金基板表面のNiPめっき表面の傷やうねりを低減する。さらに、第1研磨処理の後および第2研磨処理の後には研磨処理後に基板表面に付着する研磨砥粒や研磨カス等のパーティクルを除去するため洗浄処理が行われる。この第2研磨処理において、上述した除去処理を行って得られた、コロイダルシリカを遊離砥粒として含む研磨液を用いることができる。 Specifically, when manufactured through the following respective processing steps, the same polishing pad used in the polishing step of the glass substrate can be used as the polishing pad used in the polishing step.
The molten aluminum alloy is cast, rolled, cut out as a disk-shaped aluminum alloy base plate, and processed to a predetermined size by grinding the main surface and the end face. After that, the surface of the aluminum alloy base plate is subjected to NiP plating film formation with a thickness of 5 to 30 μm to obtain an aluminum alloy substrate. Subsequently, the main surface of the aluminum alloy substrate subjected to NiP plating is polished using a polishing pad to reduce microwaviness. The polishing process is usually performed in two stages by changing the type and particle size of the abrasive grains. In the first polishing process, a slurry containing aluminum oxide abrasive grains having an average particle diameter of 0.3 to 3 μm is used. In the polishing treatment, an aluminum alloy substrate is sandwiched between the polishing pads subjected to the opening treatment using a slurry containing colloidal silica abrasive grains having an average particle size of 40 nm or less, preferably 5 to 40 nm, and relatively slid. Reduces scratches and undulations on the NiP plating surface. Further, after the first polishing process and after the second polishing process, a cleaning process is performed in order to remove particles such as abrasive grains and polishing residue adhering to the substrate surface after the polishing process. In this second polishing treatment, a polishing liquid containing colloidal silica as free abrasive grains obtained by performing the above-described removal treatment can be used.
以下、本発明の実施例および比較例について説明する。
(コロイダルシリカの作成)
ケイ砂と炭酸ナトリウムとを原料としてイオン交換法によりコロイダルシリカを含むスラリーを得た。コロイダルシリカの平均粒子径は表1に示す通りである。 Examples of the present invention and comparative examples will be described below.
(Creation of colloidal silica)
A slurry containing colloidal silica was obtained by an ion exchange method using silica sand and sodium carbonate as raw materials. The average particle diameter of colloidal silica is as shown in Table 1.
(コロイダルシリカの作成)
ケイ砂と炭酸ナトリウムとを原料としてイオン交換法によりコロイダルシリカを含むスラリーを得た。コロイダルシリカの平均粒子径は表1に示す通りである。 Examples of the present invention and comparative examples will be described below.
(Creation of colloidal silica)
A slurry containing colloidal silica was obtained by an ion exchange method using silica sand and sodium carbonate as raw materials. The average particle diameter of colloidal silica is as shown in Table 1.
(除去処理)
実施例では、相転移法により作成されたポリフッ化ビニリデン(PVDF)の多孔質膜を用意し、これをフィルタとして用いた。用意した多孔質膜の開口径は表1に示す通りである。
上記のスラリー中のコロイダルシリカの濃度を30重量%以下に調整するとともに、スラリーのpHを10に調整してフィルタに通した。 (Removal process)
In Examples, a porous film of polyvinylidene fluoride (PVDF) prepared by a phase transition method was prepared and used as a filter. The opening diameter of the prepared porous membrane is as shown in Table 1.
The concentration of colloidal silica in the slurry was adjusted to 30% by weight or less, and the pH of the slurry was adjusted to 10 and passed through a filter.
実施例では、相転移法により作成されたポリフッ化ビニリデン(PVDF)の多孔質膜を用意し、これをフィルタとして用いた。用意した多孔質膜の開口径は表1に示す通りである。
上記のスラリー中のコロイダルシリカの濃度を30重量%以下に調整するとともに、スラリーのpHを10に調整してフィルタに通した。 (Removal process)
In Examples, a porous film of polyvinylidene fluoride (PVDF) prepared by a phase transition method was prepared and used as a filter. The opening diameter of the prepared porous membrane is as shown in Table 1.
The concentration of colloidal silica in the slurry was adjusted to 30% by weight or less, and the pH of the slurry was adjusted to 10 and passed through a filter.
比較例では、相転移法により作成されたポリエーテルサルフォン(PES)の多孔質膜を用意し、これをフィルタとして用いた。用意した多孔質膜の開口径は表1に示す通りである。
比較例においても、上記のスラリー中のコロイダルシリカの濃度を30重量%以下に調整するとともに、スラリーのpHを10に調整してフィルタに通そうとした。しかし、フィルタの目詰まりが生じ、フィルタに通すことができなかった。
このため、比較例では以後の処理を行うことができず、実施例のみで以後の処理を行った。 In the comparative example, a porous film of polyethersulfone (PES) prepared by a phase transition method was prepared and used as a filter. The opening diameter of the prepared porous membrane is as shown in Table 1.
Also in the comparative example, the colloidal silica concentration in the slurry was adjusted to 30% by weight or less, and the pH of the slurry was adjusted to 10 to pass through the filter. However, the filter was clogged and could not pass through the filter.
For this reason, the subsequent processing cannot be performed in the comparative example, and the subsequent processing is performed only in the example.
比較例においても、上記のスラリー中のコロイダルシリカの濃度を30重量%以下に調整するとともに、スラリーのpHを10に調整してフィルタに通そうとした。しかし、フィルタの目詰まりが生じ、フィルタに通すことができなかった。
このため、比較例では以後の処理を行うことができず、実施例のみで以後の処理を行った。 In the comparative example, a porous film of polyethersulfone (PES) prepared by a phase transition method was prepared and used as a filter. The opening diameter of the prepared porous membrane is as shown in Table 1.
Also in the comparative example, the colloidal silica concentration in the slurry was adjusted to 30% by weight or less, and the pH of the slurry was adjusted to 10 to pass through the filter. However, the filter was clogged and could not pass through the filter.
For this reason, the subsequent processing cannot be performed in the comparative example, and the subsequent processing is performed only in the example.
(ガラス基板の研磨処理)
次に、分離処理でフィルタを通過した濾液のpHを3に調整し、これを研磨液として用いて、ガラス基板の鏡面研磨処理を行った。ガラス基板の主表面とポリウレタン製の研磨パッドとの間に、上記の研磨液を供給しながら、研磨パッドをガラス基板の主表面に対して相対移動させることでガラス基板の主表面を研磨した。
上述した磨処理後、洗浄、乾燥したガラス基板の主表面について、レーザー式の表面検査装置を用いて異物又は欠陥の検出を行った。レーザーの閾値を異物又は欠陥の検出数が20個以下となる範囲に設定し、検出された異物又は欠陥について、SEM(走査型電子顕微鏡)又はAFM(原子間力顕微鏡)を用いて、長径が100nm以上となる異物の数をカウントした。次に断面TEM(透過型電子顕微鏡)を用いて、長径が100nm以上の異物に対して、層状の平板異物(層状ケイ酸塩からなる板状異物)であるか否かを確認した。フィルタによる除去処理を行っていないイオン交換法によるシリカを含んだスラリーで研磨したガラス基板では、ガラス基板の表裏の主表面に複数の層状平板異物が付着していることが確認された(2個/枚以上の層状平板異物が付着している)。一方、イオン交換法によるシリカを含んだスラリーについてフィルタによる異物の除去処理を行った後に基板を研磨した場合には、ガラス基板の表裏の主表面に付着した層状平板異物は検出されなかった(基板主表面には層状平板異物の付着がない)。 (Glass substrate polishing process)
Next, the pH of the filtrate that passed through the filter in the separation process was adjusted to 3, and this was used as a polishing liquid to perform mirror polishing of the glass substrate. While supplying the above polishing liquid between the main surface of the glass substrate and the polyurethane polishing pad, the main surface of the glass substrate was polished by moving the polishing pad relative to the main surface of the glass substrate.
After the above-described polishing treatment, the main surface of the cleaned and dried glass substrate was subjected to detection of foreign matters or defects using a laser type surface inspection apparatus. The laser threshold is set to a range in which the number of detected foreign matters or defects is 20 or less, and the detected foreign matter or defects are measured using an SEM (scanning electron microscope) or AFM (atomic force microscope). The number of foreign matters that were 100 nm or more was counted. Next, using a cross-sectional TEM (transmission electron microscope), it was confirmed whether or not a foreign material having a major axis of 100 nm or more is a layered flat foreign material (a plate-like foreign material made of layered silicate). In a glass substrate polished with a slurry containing silica by an ion exchange method that has not been subjected to removal treatment by a filter, it was confirmed that a plurality of layered flat foreign matters were attached to the main surfaces of the front and back surfaces of the glass substrate (two pieces). / More than one layered flat foreign material is attached). On the other hand, when the substrate was polished after removing the foreign matter using a filter for the slurry containing silica by the ion exchange method, the layered flat foreign matter adhering to the front and back main surfaces of the glass substrate was not detected (substrate There is no adhesion of layered flat foreign material on the main surface).
次に、分離処理でフィルタを通過した濾液のpHを3に調整し、これを研磨液として用いて、ガラス基板の鏡面研磨処理を行った。ガラス基板の主表面とポリウレタン製の研磨パッドとの間に、上記の研磨液を供給しながら、研磨パッドをガラス基板の主表面に対して相対移動させることでガラス基板の主表面を研磨した。
上述した磨処理後、洗浄、乾燥したガラス基板の主表面について、レーザー式の表面検査装置を用いて異物又は欠陥の検出を行った。レーザーの閾値を異物又は欠陥の検出数が20個以下となる範囲に設定し、検出された異物又は欠陥について、SEM(走査型電子顕微鏡)又はAFM(原子間力顕微鏡)を用いて、長径が100nm以上となる異物の数をカウントした。次に断面TEM(透過型電子顕微鏡)を用いて、長径が100nm以上の異物に対して、層状の平板異物(層状ケイ酸塩からなる板状異物)であるか否かを確認した。フィルタによる除去処理を行っていないイオン交換法によるシリカを含んだスラリーで研磨したガラス基板では、ガラス基板の表裏の主表面に複数の層状平板異物が付着していることが確認された(2個/枚以上の層状平板異物が付着している)。一方、イオン交換法によるシリカを含んだスラリーについてフィルタによる異物の除去処理を行った後に基板を研磨した場合には、ガラス基板の表裏の主表面に付着した層状平板異物は検出されなかった(基板主表面には層状平板異物の付着がない)。 (Glass substrate polishing process)
Next, the pH of the filtrate that passed through the filter in the separation process was adjusted to 3, and this was used as a polishing liquid to perform mirror polishing of the glass substrate. While supplying the above polishing liquid between the main surface of the glass substrate and the polyurethane polishing pad, the main surface of the glass substrate was polished by moving the polishing pad relative to the main surface of the glass substrate.
After the above-described polishing treatment, the main surface of the cleaned and dried glass substrate was subjected to detection of foreign matters or defects using a laser type surface inspection apparatus. The laser threshold is set to a range in which the number of detected foreign matters or defects is 20 or less, and the detected foreign matter or defects are measured using an SEM (scanning electron microscope) or AFM (atomic force microscope). The number of foreign matters that were 100 nm or more was counted. Next, using a cross-sectional TEM (transmission electron microscope), it was confirmed whether or not a foreign material having a major axis of 100 nm or more is a layered flat foreign material (a plate-like foreign material made of layered silicate). In a glass substrate polished with a slurry containing silica by an ion exchange method that has not been subjected to removal treatment by a filter, it was confirmed that a plurality of layered flat foreign matters were attached to the main surfaces of the front and back surfaces of the glass substrate (two pieces). / More than one layered flat foreign material is attached). On the other hand, when the substrate was polished after removing the foreign matter using a filter for the slurry containing silica by the ion exchange method, the layered flat foreign matter adhering to the front and back main surfaces of the glass substrate was not detected (substrate There is no adhesion of layered flat foreign material on the main surface).
〔ガラス基板主表面の異物の評価〕
研磨処理後、洗浄、乾燥したガラス基板の主表面について、レーザー式の表面検査装置とSEM、AFMを用いて異物の検出と同定を行った。同じ条件で製造したガラス基板100枚について、1枚あたり1ポイントずつ異物を検出、同定し、合計100ポイントにおける当たりの異物の数が0個の場合をA、1~2個の場合をB、3~10個の場合をC、11個以上の場合をDと評価した。評価がA、B又はCであれば研磨液として使用可能である。
結果を表1に示す。 [Evaluation of foreign substances on the main surface of the glass substrate]
After the polishing treatment, the main surface of the cleaned and dried glass substrate was subjected to detection and identification of foreign matter using a laser type surface inspection apparatus, SEM, and AFM. For 100 glass substrates manufactured under the same conditions, 1 point of foreign matter is detected and identified for each piece, A for the case where the total number of foreign matters per 100 points is 0, B for 1 to 2 cases, The case of 3 to 10 was evaluated as C, and the case of 11 or more was evaluated as D. If the evaluation is A, B or C, it can be used as a polishing liquid.
The results are shown in Table 1.
研磨処理後、洗浄、乾燥したガラス基板の主表面について、レーザー式の表面検査装置とSEM、AFMを用いて異物の検出と同定を行った。同じ条件で製造したガラス基板100枚について、1枚あたり1ポイントずつ異物を検出、同定し、合計100ポイントにおける当たりの異物の数が0個の場合をA、1~2個の場合をB、3~10個の場合をC、11個以上の場合をDと評価した。評価がA、B又はCであれば研磨液として使用可能である。
結果を表1に示す。 [Evaluation of foreign substances on the main surface of the glass substrate]
After the polishing treatment, the main surface of the cleaned and dried glass substrate was subjected to detection and identification of foreign matter using a laser type surface inspection apparatus, SEM, and AFM. For 100 glass substrates manufactured under the same conditions, 1 point of foreign matter is detected and identified for each piece, A for the case where the total number of foreign matters per 100 points is 0, B for 1 to 2 cases, The case of 3 to 10 was evaluated as C, and the case of 11 or more was evaluated as D. If the evaluation is A, B or C, it can be used as a polishing liquid.
The results are shown in Table 1.
実施例1~6のガラス基板についてはガラス基板100枚当たりの異物数が2個以下であり、スラリーを疎水性高分子材料からなるフィルタに通過させて得られる濾液は研磨液として好適であることがわかる。
Regarding the glass substrates of Examples 1 to 6, the number of foreign matters per 100 glass substrates is 2 or less, and the filtrate obtained by passing the slurry through a filter made of a hydrophobic polymer material is suitable as a polishing liquid. I understand.
以上、本発明の磁気ディスク用基板の製造方法について詳細に説明したが、本発明は上記実施形態に限定されず、本発明の主旨を逸脱しない範囲において、種々の改良や変更をしてもよいのはもちろんである。
As mentioned above, although the manufacturing method of the substrate for magnetic disks of this invention was demonstrated in detail, this invention is not limited to the said embodiment, You may make various improvement and change in the range which does not deviate from the main point of this invention. Of course.
Claims (7)
- 磁気ディスク用基板の製造方法であって、
一対の研磨パッドで基板を挟み、前記研磨パッドと前記基板の間に砥粒を含む研磨液を供給して、前記研磨パッドと前記ガラス基板を相対的に摺動させることにより、前記磁気ディスク用基板の両主表面を研磨する研磨処理を含み、
前記砥粒は平均粒径40nm以下のコロイダルシリカであり、
前記研磨液は、前記砥粒および前記砥粒の平均粒径よりも大きな粒径の大径粒子を含むスラリーに前記大径粒子を除去する除去処理を施すことによって得られ、
前記除去処理は、疎水性高分子材料からなり、開口径が100nm以下であるフィルタに前記スラリーを通す処理である、ことを特徴とする磁気ディスク用基板の製造方法。 A method for manufacturing a magnetic disk substrate, comprising:
By sandwiching the substrate between a pair of polishing pads, supplying a polishing liquid containing abrasive grains between the polishing pad and the substrate, and sliding the polishing pad and the glass substrate relatively, the magnetic disk Including a polishing process for polishing both main surfaces of the substrate;
The abrasive is colloidal silica having an average particle size of 40 nm or less,
The polishing liquid is obtained by subjecting the abrasive grains and a slurry containing large diameter particles having a larger particle diameter than the average particle diameter of the abrasive grains to a removal treatment to remove the large diameter particles,
The method for producing a substrate for a magnetic disk, wherein the removing process is a process of passing the slurry through a filter made of a hydrophobic polymer material and having an opening diameter of 100 nm or less. - 前記スラリー中のコロイダルシリカの濃度を30重量%以下にして前記フィルタに通す、請求項1に記載の磁気ディスク用基板の製造方法。 2. The method of manufacturing a magnetic disk substrate according to claim 1, wherein the concentration of colloidal silica in the slurry is set to 30% by weight or less and passed through the filter.
- 前記スラリーのpHを8以上13以下のアルカリ性の範囲に調整して前記フィルタに通す、請求項1又は2に記載の磁気ディスク用基板の製造方法。 3. The method of manufacturing a magnetic disk substrate according to claim 1, wherein the pH of the slurry is adjusted to an alkaline range of 8 to 13 and passed through the filter.
- 前記疎水性高分子材料はポリフッ化ビニリデン(PVDF)である、請求項1~3のいずれか一項に記載の磁気ディスク用基板の製造方法。 The method for manufacturing a magnetic disk substrate according to any one of claims 1 to 3, wherein the hydrophobic polymer material is polyvinylidene fluoride (PVDF).
- 前記フィルタは、相転移法により多孔質膜状に形成された疎水性高分子膜である、請求項1~4のいずれか一項に記載の磁気ディスク用基板の製造方法。 The method for manufacturing a magnetic disk substrate according to any one of claims 1 to 4, wherein the filter is a hydrophobic polymer film formed into a porous film by a phase transition method.
- 前記コロイダルシリカは、水ガラスとイオン交換樹脂を用いて得られる、請求項1~5のいずれか一項に記載の磁気ディスク用基板の製造方法。 6. The method for producing a magnetic disk substrate according to claim 1, wherein the colloidal silica is obtained using water glass and an ion exchange resin.
- 前記フィルタに前記スラリーを通して得られる研磨液のpHを、研磨処理を行う前に、酸性に調整する、請求項1~6のいずれか一項に記載の磁気ディスク用基板の製造方法。 The method for producing a magnetic disk substrate according to any one of claims 1 to 6, wherein the pH of the polishing liquid obtained by passing the slurry through the filter is adjusted to be acidic before performing the polishing treatment.
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