WO2013146090A1 - Procédé de fabrication de substrat de verre pour disque magnétique - Google Patents

Procédé de fabrication de substrat de verre pour disque magnétique Download PDF

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Publication number
WO2013146090A1
WO2013146090A1 PCT/JP2013/055593 JP2013055593W WO2013146090A1 WO 2013146090 A1 WO2013146090 A1 WO 2013146090A1 JP 2013055593 W JP2013055593 W JP 2013055593W WO 2013146090 A1 WO2013146090 A1 WO 2013146090A1
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WO
WIPO (PCT)
Prior art keywords
polishing
glass substrate
base plate
zirconia
magnetic disk
Prior art date
Application number
PCT/JP2013/055593
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English (en)
Japanese (ja)
Inventor
京介 飯泉
田村　健
Original Assignee
Hoya株式会社
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Filing date
Publication date
Application filed by Hoya株式会社 filed Critical Hoya株式会社
Priority to CN201380009608.4A priority Critical patent/CN104137181A/zh
Publication of WO2013146090A1 publication Critical patent/WO2013146090A1/fr

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
    • G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/042—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor
    • B24B37/044—Lapping machines or devices; Accessories designed for working plane surfaces operating processes therefor characterised by the composition of the lapping agent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories
    • B24B37/04—Lapping machines or devices; Accessories designed for working plane surfaces
    • B24B37/07—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool
    • B24B37/08—Lapping machines or devices; Accessories designed for working plane surfaces characterised by the movement of the work or lapping tool for double side lapping
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1409—Abrasive particles per se
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1436—Composite particles, e.g. coated particles
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1454—Abrasive powders, suspensions and pastes for polishing

Definitions

  • the present invention relates to a method for producing a glass substrate for a magnetic disk.
  • a personal computer or a DVD (Digital Versatile Disc) recording device has a built-in hard disk device (HDD: Hard Disk Drive) for data recording.
  • HDD Hard Disk Drive
  • 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.
  • a glass substrate is preferably used because it has a property that it is less likely to be plastically deformed than a metal substrate (aluminum substrate) or the like.
  • the density of magnetic recording has been increased.
  • the magnetic recording information area (recording bit) is miniaturized by using a perpendicular magnetic recording method in which the magnetization direction in the magnetic layer is perpendicular to the surface of the substrate.
  • the storage capacity of one disk substrate can be increased.
  • the distance from the magnetic recording layer is extremely shortened by further protruding the recording / reproducing element portion of the magnetic head, thereby further improving the accuracy of information recording / reproducing (S / N). To improve the ratio).
  • Such control of the recording / reproducing element portion of the magnetic head is called a DFH (Dynamic Flying Height) control mechanism, and a magnetic head equipped with this control mechanism is called a DFH head.
  • DFH Dynamic Flying Height
  • a magnetic head equipped with this control mechanism is called a DFH head.
  • the surface irregularity of the substrate is extremely small in order to avoid collision and contact with the magnetic head and the recording / reproducing element portion protruding further therefrom. It is made to be smaller.
  • the main surface of the plate-like glass material that has become flat after press molding is ground on the main surface, and the grinding process remains on the main surface.
  • a main surface polishing step is included for the purpose of removing scratches and distortions.
  • abrasive grains such as cerium oxide (cerium dioxide), silicon dioxide, zirconium dioxide (zirconia) as an abrasive are known.
  • Patent Document 1 discloses a method of polishing a glass substrate for a magnetic disk using a polishing liquid in which calcium aluminate, magnesium sulfate, magnesium chloride or the like is added to zirconia abrasive grains.
  • a magnetic layer was formed on a glass substrate made of zirconia as a polishing material for loose abrasive grains on a glass base plate, a magnetic disk was prepared, and a glide test was performed using a glide head. Compared to a glass substrate produced using an abrasive, a decrease in yield (that is, an increase in defect occurrence rate) was observed. The glide inspection is to determine whether or not the magnetic head can stably operate with a predetermined flying height with respect to the magnetic disk.
  • a glide head equipped with a piezoelectric element or the like is caused to fly with a predetermined flying height with respect to the main surface of the magnetic disk, and whether or not there is a collision between the glide head and a projection such as a foreign object on the main surface of the magnetic disk.
  • the detection is performed by a piezoelectric element or the like.
  • the present invention manufactures a magnetic disk glass substrate in which foreign substances are unlikely to remain on the glass substrate when the magnetic disk glass substrate is manufactured by polishing using zirconia abrasive as an abrasive for free abrasive grains.
  • An object of the present invention is to provide a method for manufacturing a glass substrate for a magnetic disk.
  • the inventors of the present application have conducted intensive studies in order to investigate the cause of the decrease in yield due to the above glide inspection.
  • the main surface of the glass substrate has zirconia particles adhering to the main surface during the formation of the magnetic layer, even after the main surface is sufficiently cleaned and the particles are removed after polishing with a mirror finish.
  • minute convex portions are formed on the surface of the magnetic disk. And this minute convex part causes troubles, such as a head crash trouble and a thermal asperity trouble.
  • the zirconia particles adhering to the main surface of the glass substrate are also derived from zirconia abrasive grains used for polishing or a part thereof, which are attached to the outer peripheral surface and inner peripheral surface of the glass substrate. It was.
  • cleaning method which removes effectively the zirconia particle adhering to the glass substrate is not established.
  • the inventors of the present application consider the reason why zirconia particles may adhere to the main surface when the magnetic layer is formed even if the main surface is sufficiently washed and particles are removed. Yes. In other words, even if zirconia particles remain on the glass base plate by main surface polishing with zirconia abrasive grains, the zirconia particles remaining on the main surface are removed by final polishing on the main surface, but on the side wall surface of the glass base plate. Residual or adhered zirconia particles are not removed by subsequent cleaning of the glass base plate.
  • the zirconia particles adhere to the side wall surface of the glass base plate by the glass base plate contacting the carrier during polishing. Conceivable. And in the process after the main surface grinding
  • zirconia particles are detached from the side wall surface when the outer side wall surface is gripped in the film forming process on the magnetic disk glass substrate, or from the outer side wall surface in the magnetic disk glass substrate cleaning process. It is also possible that the particles are detached.
  • the inventors of the present application make the zirconia particles used as polishing abrasive grains in the polishing step into a shape that is difficult to adhere to the side wall surface of the glass base plate, thereby forming the side wall surface of the glass base plate. It has been found that the amount of zirconia particles remaining after being fixed is reduced, whereby zirconia is less likely to adhere to the main surface in a later step. Specifically, it has been found that by making the primary particles of zirconia particles rounded, the zirconia particles are difficult to adhere to the side wall surface of the glass substrate. Then, one of the measures for making the primary particles of the zirconia particles rounded is to manufacture the zirconia particles by a wet method, and the invention of the embodiment described below is conceived. It came.
  • a doughnut-shaped glass substrate having at least a pair of main surfaces and two side wall surfaces constituting an inner hole and an outer shape is attached to a polishing platen while being held by a carrier.
  • Manufacturing a glass substrate for a magnetic disk having a polishing step of polishing the glass substrate by planetary gear motion of the carrier while sandwiching the pair of main surfaces with the polishing pad provided and supplying a polishing liquid to the pair of main surfaces The method is characterized in that the polishing liquid contains zirconia particles produced by a wet method as abrasive grains.
  • the zirconia particles are preferably formed by agglomeration of primary particles having a particle size in the range of 70 to 200 nm.
  • the BET specific surface area of the zirconia particles is preferably in the range of 4 to 15 m 2 / g.
  • the average particle diameter (D50) of the zirconia particles is in the range of 0.2 to 0.6 ⁇ m.
  • X1 / X2 is 1. It is preferably 0 to 1.3.
  • the surface roughness of the end face of the carrier that contacts the side wall surface of the glass substrate is preferably 5 ⁇ m or less.
  • the surface roughness of the side wall surface of the glass substrate before being polished with the polishing liquid having zirconia particles is 0.1 ⁇ m or less in terms of arithmetic average roughness Ra. Is preferred.
  • the glass substrate for magnetic disk preferably has a diameter larger than 2.5 inches and a plate thickness of 0.6 mm or less.
  • the fracture toughness value K 1c of the glass substrate is 0.7 [MPa / m 1/2 ] or more as measured by a Vickers hardness meter. It is preferable to have a chemical strengthening step for chemically strengthening the glass substrate.
  • polishing apparatus double-side polish apparatus used at a 1st grinding
  • polishing process The figure which shows typically the zirconia particle (secondary particle) of embodiment.
  • zirconia particles produced by a wet method schematically showing the state when the zirconia particles are acting in the polishing process between the main surface of the glass base plate and the polishing pad (this polishing step)
  • zirconia particles produced by a dry method unlike the polishing step.
  • Aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used as the material for the magnetic disk glass substrate in the present embodiment.
  • 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. More preferably, it is an amorphous aluminosilicate glass.
  • the composition of the glass substrate for a magnetic disk of this embodiment is not limited, the glass substrate of this embodiment is preferably converted to an oxide standard and expressed in mol%, SiO 2 is 50 to 75%, Al 2 to O 3 to 1 to 15%, at least one component selected from Li 2 O, Na 2 O and K 2 O in total 5 to 35%, selected from MgO, CaO, SrO, BaO and ZnO 0-20% in total of at least one component, and at least one selected from ZrO 2 , TiO 2 , La 2 O 3 , Y 2 O 3 , Ta 2 O 5 , Nb 2 O 5 and HfO 2 An amorphous aluminosilicate glass having a composition having a total of 0 to 10% of components.
  • the glass substrate for magnetic disk in this embodiment is an annular thin glass substrate.
  • the size of the glass substrate for magnetic disks is not ask
  • a glass gob made of molten glass is supplied onto a lower mold that is a receiving gob forming mold, and an upper mold that is a lower mold and an opposing gob forming mold is used.
  • Glass gob is press molded. More specifically, after a glass gob made of molten glass is supplied onto the lower mold, the lower surface of the upper mold cylinder and the upper surface of the lower mold cylinder are brought into contact with each other, and the upper mold and the upper mold mold are slid. Form a thin glass blank forming space outside the moving surface and the sliding surface of the lower mold and the lower mold body, and lower the upper mold to perform press molding. To rise.
  • the glass base plate used as the origin of the glass substrate for magnetic discs is shape
  • a glass base plate can be manufactured using not only the method mentioned above but well-known manufacturing methods, such as a downdraw method, a redraw method, and a fusion method.
  • lapping processing using alumina-based loose abrasive grains is performed on both main surfaces of the glass base plate cut into a predetermined shape, if necessary.
  • the lapping platen is pressed on both sides of the glass base plate from above and below, a grinding liquid (slurry) containing free abrasive grains is supplied onto the main surface of the glass base plate, and these are moved relatively.
  • a grinding liquid (slurry) containing free abrasive grains is supplied onto the main surface of the glass base plate, and these are moved relatively. Perform lapping.
  • a glass base plate is shape
  • a chamfering step of forming a chamfered portion at the ends (outer peripheral end and inner peripheral end) is performed.
  • the outer peripheral end and the inner peripheral end of the annular glass base plate are chamfered with, for example, a metal bond grindstone using diamond abrasive grains to form a chamfered portion.
  • end face polishing (edge polishing) of an annular glass base plate is performed.
  • the inner peripheral side wall surface (end surface) and the outer peripheral side wall surface (end surface) of the glass base plate are mirror-finished by brush polishing.
  • a slurry containing fine particles such as cerium oxide as free abrasive grains is used.
  • the end face polishing step is performed before the first polishing step. It is preferable to carry out. For example, it is preferable to perform the end surface polishing so that the arithmetic average roughness Ra of the end surface of the glass base plate after the end surface polishing step is 0.1 ⁇ m or less.
  • the double-sided grinding apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and an annular glass base plate is sandwiched between the upper surface plate and the lower surface plate. Then, by moving both the upper surface plate and the lower surface plate, or both of them, the main surface of the glass base plate is ground by relatively moving the glass base plate and each surface plate. be able to.
  • polishing (main surface grinding
  • polishing is given to the main surface of the ground glass base plate.
  • the machining allowance by the first polishing is, for example, about several ⁇ m to 50 ⁇ m.
  • FIG. 1 is an exploded perspective view of a polishing apparatus (double-side polishing apparatus) used in the first polishing step.
  • FIG. 2 is a cross-sectional view of a polishing apparatus (double-side polishing apparatus) used in the first polishing process. Note that the same configuration as this polishing apparatus can be applied to a grinding apparatus used in the above-described grinding process.
  • the polishing apparatus has a pair of upper and lower surface plates, that is, an upper surface plate 40 and a lower surface plate 50.
  • An annular glass base plate G is sandwiched between the upper surface plate 40 and the lower surface plate 50, and either one or both of the upper surface plate 40 and the lower surface plate 50 are moved to operate the glass base plate G. By moving the surface plates relative to each other, both main surfaces of the glass base plate G can be polished.
  • an annular flat polishing pad 10 is attached to the upper surface of the lower platen 50 and the bottom surface of the upper platen 40 as a whole.
  • the carrier 30 includes a tooth portion 31 that is provided on the outer peripheral portion and meshes with the sun gear 61 and the internal gear 62, and one or a plurality of holes 32 that accommodate and hold the glass base plate G.
  • the sun gear 61, the internal gear 62 provided on the outer edge, and the disk-shaped carrier 30 constitute a planetary gear mechanism centered on the central axis CTR as a whole.
  • the disc-shaped carrier 30 meshes with the sun gear 61 on the inner peripheral side and meshes with the internal gear 62 on the outer peripheral side, and accommodates and holds one or more glass base plates G (workpieces).
  • the carrier 30 revolves while rotating as a planetary gear, and the glass base plate G and the lower surface plate 50 are relatively moved.
  • the sun gear 61 rotates in the CCW (counterclockwise) direction
  • the carrier 30 rotates in the CW (clockwise) direction
  • the internal gear 62 rotates in the CCW direction.
  • relative movement occurs between the polishing pad 10 and the glass base plate G.
  • the glass base plate G and the upper surface plate 40 may be relatively moved.
  • the upper surface plate 40 is pressed against the glass base plate G (that is, in the vertical direction) with a predetermined load, and the polishing pad 10 is pressed against the glass base plate G.
  • a polishing liquid (slurry) is supplied between the glass base plate G and the polishing pad 10 from the polishing liquid supply tank 71 via one or a plurality of pipes 72 by a pump (not shown).
  • the main surface of the glass base plate G is polished by the abrasive contained in the polishing liquid.
  • the polishing liquid used for polishing the glass base plate G is discharged from the upper and lower surface plates, returned to the polishing liquid supply tank 71 by a filter and a return pipe (not shown), and reused.
  • the load of the upper surface plate 40 applied to the glass base plate G is adjusted for the purpose of setting a desired polishing load on the glass base plate G.
  • Load, 50 g / cm 2 or more is preferred from the viewpoint of high polishing rate achieved, more preferably 70 g / cm 2 or more, 90 g / cm 2 or more is more preferable.
  • the polishing load is preferably 180 g / cm 2 or less, more preferably 160 g / cm 2 or less, and even more preferably 140 g / cm 2 or less. That is, the load is preferably 50 g / cm 2 to 180 g / cm 2, more preferably 70 g / cm 2 to 160 g / cm 2, and still more preferably 90 g / cm 2 to 140 g / cm 2 .
  • the supply rate of the polishing liquid during polishing processing varies depending on the polishing pad 10, the composition and concentration of the polishing liquid, and the size of the glass base plate G, but is preferably 500 to 5000 ml / min, more preferably from the viewpoint of improving the polishing rate. Is 1000 to 4500 ml / min, more preferably 1500 to 4000 ml / min.
  • the rotation speed of the polishing pad 10 is preferably 10 to 50 rpm, more preferably 20 to 40 rpm, and further preferably 25 to 35 rpm.
  • polishing liquid used in the polishing apparatus of FIG. 1 contains zirconia (ZrO 2 ) particles produced by a wet method rather than a dry method as abrasive grains.
  • the dry method is a method of producing by pulverized product of zirconia or desiliconized zirconia obtained by electrofusion method, pulverized product of baderite or the like.
  • the electrofusion method is a process in which zircon sand, badelite or the like is heated to about 2,700 ° C. to evaporate silicon to lower the silicon concentration and improve the zirconium concentration.
  • Desiliconized zirconia is a powder in which the silicon concentration is reduced by electrofusion.
  • Badelite is a natural mineral, and is a relatively high purity zirconia having a low silicon concentration at the time of the natural mineral.
  • the wet method produces a solution in which a compound containing zirconium is dissolved in a chemical, and crystal growth is performed in the solution to produce a sol containing zirconium, which is then fired to produce zirconium. It is a manufacturing method to do.
  • a zirconia powder is generally produced through the following steps (I) to (V).
  • Flotation process Zircon concentrate by selecting ilmenite, rutile, and monazite using specific gravity ore, using the difference in specific gravity, removing silica sand, and using the difference in specific gravity, magnetism, and conductivity.
  • Zircon sand Caustic soda melting step: Silica is separated by melting zircon sand with caustic soda.
  • Hydrochloric acid decomposition step Decompose and concentrate with hydrochloric acid to produce zirconium oxychloride (ZrOCl 2 ⁇ 8H 2 O).
  • a pulverizing step of pulverizing zirconia with any of a ball mill, a jet mill, and a bead mill, or a combination thereof, is performed in order to produce powdered zirconia.
  • the mill used in the pulverization process and its setting vary depending on the target particle size of zirconia and the like.
  • the zirconia produced by the dry method causes intragranular cracking of zirconia in the pulverization step, and becomes particles having a sharp tip.
  • zirconia produced by a wet method is cut at the interface between primary particles with little intragranular cracking in the pulverization process (that is, it becomes a grain boundary crack), and the tip is as in the dry method. Are sharp and few sharp particles are formed.
  • the zirconia particles used as abrasive grains take the form of secondary particles (aggregates of primary particles), and the secondary particles (made by a wet method) are schematically shown in FIG. Show.
  • zirconia particles as abrasive grains take the form of an aggregate of a plurality of primary particles.
  • the shape of primary particles of zirconia particles produced by a wet method is rounded as a whole.
  • FIG. 4 is a diagram illustrating a state in which the glass base plate G is accommodated in the hole 32 of the carrier 30.
  • FIG. 4 in a state where the glass base plate G is accommodated in the carrier 30 of the polishing apparatus, in order to enable the glass base plate G to be detached from the carrier 30, between the carrier 30 and the glass base plate G. Is provided with a slight gap CL in the horizontal direction (that is, the direction parallel to the main surface of the glass base plate G).
  • D2> D1 is established when the outer diameter of the glass base plate G to be polished is D1 and the diameter of the hole 32 of the carrier 30 (the diameter of the contact surface with which the glass base plate abuts) is D2.
  • the gap CL between the side wall surface Gt of the glass base plate G and the side wall surface 30t that forms the hole 32 of the carrier 30 has an abrasive of zirconia (ZrO 2 ) in the polishing liquid. Grain comes in.
  • the glass base plate G moves in an unconstrained state in the hole 32 of the carrier 30 in a direction parallel to the main surface while being subjected to a load by the surface plate in the thickness direction.
  • the side wall surface Gt of the glass base plate G is brought into contact with the side wall surface 30t forming the hole 32, and the zirconia abrasive grains that have entered the gap CL are pressed against the side wall surface Gt of the glass base plate G.
  • FIG. 5 schematically shows a state when the zirconia particles (secondary particles) are pressed against the side wall surface Gt of the glass base plate G.
  • zirconia particles manufactured by a wet method main polishing
  • the case of the zirconia particle manufactured by the dry method different from this polishing process is shown.
  • the figure in the case of zirconia particles produced by a dry process is shown for comparison.
  • the zirconia abrasive grains used in this polishing step are manufactured by a wet method, the primary particles are rounded, and are the main forms during polishing. The surface of some secondary particles is also rounded. Therefore, even if the zirconia abrasive grains are pressed against the side wall surface Gt of the glass base plate G, the side wall surface Gt is hardly pierced and the possibility that zirconia particles remain on the side wall surface Gt after polishing is low. Since the side wall surface Gt is hardly scratched, scratches due to polishing are less likely to occur. On the other hand, in the case of the zirconia particles manufactured by the dry method (lower part of FIG.
  • the side wall surface Gt is easily pierced and then polished on the side wall surface Gt. There is a high possibility that zirconia particles remain, and the side wall surface Gt may be scratched during polishing, and scratches due to polishing are likely to occur.
  • FIG. 6 schematically shows a state in which zirconia particles (secondary particles) are acting in the polishing process between the main surface Gp of the glass base plate G and the polishing pad 10.
  • zirconia particles manufactured in in the case of the main polishing step
  • the case of the zirconia particles manufactured by the dry method is different from the main polishing step.
  • the figure in the case of zirconia particles produced by a dry process is shown for comparison. It is the individual primary particles constituting the zirconia particles that are in the form of secondary particles that contribute to the polishing by contacting with the main surface Gp of the glass base plate G during the polishing process.
  • the zirconia abrasive grains used in this polishing step are manufactured by a wet method, the primary particles are rounded, and therefore scratches are less likely to occur due to contact with the main surface Gp.
  • the shape of the primary particles that contact the main surface Gp has many sharp points such as rocks. The main surface Gp is easily scratched, and scratches due to polishing are likely to occur.
  • the zirconia particles as the abrasive grains are preferably formed by agglomeration of primary particles having a particle size in the range of 70 to 200 nm.
  • FIG. 7 A method for measuring primary particles is shown in FIG. As shown in FIG. 7, the zirconia abrasive grains were observed with an SEM (scanning electron microscope) at a magnification of, for example, 30,000 to 100,000 times, and the major axis length (X1) of the primary particles and the minor axis length were observed.
  • the average value of (X2) ((X1 + X2) / 2) is defined as the primary particle diameter.
  • the major axis and the minor axis are assumed to be orthogonal.
  • the aspect ratio (X1 ⁇ X2 in FIG. 6) of the primary particles of the present embodiment is 1.0 to 1.3, and has a rounded shape as a whole.
  • the BET specific surface area is known as an index having a certain correlation with the primary particle diameter of the abrasive grains.
  • the BET specific surface area of the primary particles of the abrasive grains may be in the range of 4 to 15 m 2 / g. preferable.
  • the BET specific surface area can be measured by a BET single point method by a gas adsorption method using a flow type specific surface area measuring device.
  • zirconia fine particles that are sufficiently small not to contribute to the polishing ability may be contained, but the BET specific surface area can also be increased by increasing the amount of the fine particles. In this case, the BET specific surface area can be changed without changing the primary particle diameter of the zirconia particles contributing to the polishing ability.
  • Secondary particle size of the abrasive grains (hereinafter referred to as “secondary particle size”) Regarding the secondary particle diameter of zirconia abrasive grains, which is the main form at the time of polishing, the lower limit value and the upper limit value are determined by the same idea as the primary particle diameter described above. In addition, when the secondary particle diameter is too large, there is a possibility that the polishing rate may be lowered by reducing the number of secondary particles acting on the polishing under a certain slurry concentration. Therefore, the lower limit value and the upper limit value of the secondary particles are determined from the viewpoint that the polishing action functions effectively (that is, the polishing rate is ensured) and scratches can be reduced.
  • the secondary particle diameter (average particle diameter D50) of the abrasive grains is preferably in the range of 0.2 to 0.6 ⁇ m.
  • the preferable particle diameter range is a value in a state where the zirconia abrasive grains are scattered by the polishing process. Become a range. That is, zirconia is generally used for ceramics, electronic materials, and refractory applications.
  • the secondary particle diameter can be intentionally increased to about several tens of ⁇ m by using spray drying or the like in the drying step.
  • intentionally increasing the secondary particle diameter is called granulation, but the granulated zirconia is easily broken by polishing.
  • zirconia is aggregated with a weak cohesive force due to moisture aggregation or the like, the aggregated zirconia is easily broken by polishing.
  • the average particle size (D50) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size.
  • the surface roughness (Ra) of the side wall surface of the glass base plate before the first polishing is preferably 0.1 ⁇ m or less, and more preferably 0.05 ⁇ m or less.
  • the surface roughness (Ra) here can be measured with a stylus roughness meter. Since the surface roughness of the side wall surface of the glass base plate G is so small, the contact area with the carrier 30 can be increased, and the number of abrasive grains entering between the glass base plate G and the carrier 30 increases. And since force will be disperse
  • the surface roughness of the end surface (wall surface facing the side wall surface of the glass base plate G) in the hole 32 of the carrier 30 that is in contact with the side wall surface of the glass base plate G is 5 ⁇ m or less, preferably 3 ⁇ m or less.
  • the surface roughness (Ra) wrinkle here can be measured by moving the needle in the circumferential direction with respect to the end face of the hole 32 using a stylus type roughness meter.
  • the contact area with the glass base plate G can be increased, so that the number of abrasive grains entering between them increases, and more Since the force is dispersed in the abrasive grains, the zirconia particles are less likely to pierce the side wall surface of the glass base plate G. Further, if the roughness of the end surface of the hole 32 of the carrier 30 is small, scratches are less likely to enter the glass base plate G when the end surface comes into contact with the glass base plate G. Therefore, the zirconia abrasive grains captured by the scratches By reducing the number, the probability of piercing the side wall surface of the glass base plate G can be reduced indirectly. While the first polishing is performed, the side wall surface of the glass base plate G is prevented from being excessively roughened, and the zirconia abrasive grains are difficult to adhere to the side wall surface of the glass base plate G.
  • the manufacturing method of this embodiment is suitable for manufacturing a glass substrate for a magnetic disk having a diameter larger than 2.5 inch size and a plate thickness of 0.6 mm or less.
  • a glass substrate for a magnetic disk has a higher aspect ratio (diameter / plate thickness) than the conventional one. For this reason, since the plate
  • zirconia particles are likely to adhere to the side wall surface of the glass base plate, and the proportion of zirconia particles attached to the side wall surface of the glass base plate tends to be relatively high.
  • the secondary particles which are the main forms of zirconia abrasive grains, are rounded, the surfaces thereof are rounded. Even if the abrasive grains are pressed against the side wall surface Gt of the glass base plate G, the occurrence of such a problem can be suppressed because the side wall surface Gt is rarely pierced.
  • the roughness (Ra) of the main surface of the glass base plate is set to 0.5 nm or less and the micro waveness (MW- Polishing is performed so that Rq) is 0.5 nm or less.
  • the micro waveness can be expressed by an RMS (Rq) value calculated as a roughness of a wavelength band of 100 to 500 ⁇ m in an area having a radius of 14.0 to 31.5 mm on the entire main surface. It can be measured using a surface profile measuring machine.
  • the roughness of the main surface is expressed by an arithmetic average roughness Ra defined by JIS B0601: 2001.
  • the roughness is 0.006 ⁇ m or more and 200 ⁇ m or less, for example, the roughness is measured with a stylus type roughness measuring machine, and JIS B0633: It can be calculated by the method defined in 2001.
  • the roughness can be measured by a scanning probe microscope (atomic force microscope; AFM) and calculated by a method defined in JIS R1683: 2007.
  • AFM atomic force microscope
  • JIS R1683 it is possible to use the arithmetic average roughness Ra when measured at a resolution of 256 ⁇ 256 pixels in a measurement area of 1 ⁇ m ⁇ 1 ⁇ m square.
  • the glass base plate after the first polishing is chemically strengthened.
  • the chemical strengthening solution for example, a mixed solution of potassium nitrate (60% by weight) and sodium sulfate (40% by weight) can be used.
  • the chemical strengthening liquid is heated to, for example, 300 ° C. to 400 ° C., and after the cleaned glass base plate is preheated to, for example, 200 ° C. to 300 ° C., the glass base plate is placed in the chemical strengthening liquid, for example, 1 Soak for 5 to 5 hours.
  • the immersion is preferably performed in a state of being housed in a holder so that the plurality of glass base plates are held by the side wall surfaces so that the entire main surfaces of both glass base plates are chemically strengthened.
  • the glass base plate is strengthened.
  • the chemically strengthened glass base plate is washed. For example, after washing with sulfuric acid, it is washed with pure water or the like.
  • the glass substrate that has been chemically strengthened and sufficiently cleaned is subjected to final polishing.
  • the machining allowance by the final polishing is 5 ⁇ m or less.
  • the polishing apparatus used in the first polishing is used.
  • the difference from the first polishing is that the type and particle size of the free abrasive grains are different and the hardness of the resin polisher is different.
  • the free abrasive grains used in the final polishing for example, fine particles (particle size: diameter of about 10 to 50 nm) such as colloidal silica made turbid in the slurry are used.
  • a glass substrate for a magnetic disk can be obtained by washing the polished glass base plate with a neutral detergent, pure water, IPA or the like.
  • the order of a process is not restricted to the order mentioned above.
  • particles such as colloidal silica are supplied between the glass base plate and the hole of the carrier, whereby the side wall surface of the glass base plate is polished and adhered to the side wall surface.
  • the zirconia particles that may be removed may be removed.
  • the fracture toughness value K 1c of the glass base plate after chemical strengthening is 0.7 [MPa / m 1/2 ] or more as measured by a Vickers hardness meter.
  • the compressed layer formed on the side wall surface of the glass base plate by chemical strengthening is used to make the zirconia abrasive grains, which are abrasive grains in the first polishing step, which is a subsequent step, of the glass base plate. It can function as a sticking prevention layer for preventing sticking to the side wall surface.
  • the chemical strengthening treatment conditions such that the fracture toughness value K 1c of the glass base plate after chemical strengthening is 0.7 [MPa / m 1/2 ] or more as measured by a Vickers hardness meter are, for example, in advance It may be determined by changing various chemical treatment conditions.
  • the fracture toughness value K 1c is more preferably 1.0 [MPa / m 1/2 ] or more. Moreover, it is still more preferable in it being 1.3 [MPa / m 1/2 ] or more. Fracture toughness value K 1c is preferably higher, the upper limit of the fracture toughness value K 1c is not particularly provided.
  • the fracture toughness value K 1c is a sharp diamond indenter of known Vickers hardness meter can be measured by the method of pushing the glass workpiece. That is, the fracture toughness value K1c is obtained by the following equation from the size of the indentation of the indenter remaining on the glass base plate when the Vickers indenter is pushed in and the length of the crack generated from the corner of the indentation.
  • P is the indentation load [N] of the Vickers indenter
  • a is the length [m] half of the diagonal length of the Vickers indentation.
  • E is the Young's modulus [Pa] of the glass base plate
  • C is the length [m] that is half the length of the string.
  • the chemical strengthening treatment conditions include the type of chemical strengthening solution (for example, the mixing ratio of potassium nitrate and sodium sulfate), the temperature of the chemical strengthening solution, the chemical strengthening treatment time, and the like. It is also possible to select a glass composition of the glass base plate such that the fracture toughness value K 1c of the glass base plate after chemical strengthening is 0.7 [MPa / m 1/2 ] or more as described above.
  • the main surface of the glass base plate is a measurement target of the fracture toughness value K1c , but the chemical strengthening is performed because the side wall surface of the end face of the glass base plate is chemically strengthened in the same manner as the main surface.
  • fracture toughness K 1c of the side wall surface of the glass workpiece is the same as the measurement results of fracture toughness K 1c of the main surface can be replaced by fracture toughness K 1c of the main surface.
  • a magnetic disk is obtained as follows using a magnetic disk glass substrate.
  • the magnetic disk is, for example, on the main surface of a glass substrate for magnetic disk (hereinafter simply referred to as “substrate”), in order from the closest to the main surface, at least an adhesion layer, an underlayer, a magnetic layer (magnetic recording layer), and a protective layer.
  • a layer and a lubricating layer are laminated.
  • the substrate is introduced into a film forming apparatus that has been evacuated, and a film is sequentially formed from an adhesion layer to a magnetic layer on the main surface of the substrate in an Ar atmosphere by a DC magnetron sputtering method.
  • a magnetic recording medium can be formed by forming a protective layer using, for example, C 2 H 4 by a CVD method and subsequently performing nitriding treatment for introducing nitrogen into the surface. Thereafter, for example, PFPE (perfluoropolyether) is applied on the protective layer by a dip coating method, whereby a lubricating layer can be formed.
  • the produced magnetic disk is preferably incorporated in an HDD (Hard Disk Drive) as a magnetic recording / reproducing apparatus together with a magnetic head equipped with a DFH (Dynamic Flying Height) control mechanism.
  • HDD Hard Disk Drive
  • DFH Dynamic Flying Height
  • a 2.5-inch magnetic disk was produced from the manufactured glass substrate for magnetic disk.
  • the produced glass substrate for a magnetic disk is an amorphous aluminosilicate glass having the following composition.
  • Glass composition Converted to oxide basis, expressed in mol%, SiO 2 is 50 to 75%, Al 2 O 3 is 1 to 15%, at least one component selected from Li 2 O, Na 2 O and K 2 O 5 to 35% in total, 0 to 20% in total of at least one component selected from MgO, CaO, SrO, BaO and ZnO, and ZrO 2 , TiO 2 , La 2 O 3 , Y 2 O 3 , Amorphous aluminosilicate glass having a composition having a total of 0 to 10% of at least one component selected from Ta 2 O 5 , Nb 2 O 5 and HfO 2
  • each process of the manufacturing method of the glass substrate for magnetic disks of this embodiment was performed in order.
  • a press molding method used in the method for producing a glass substrate for a magnetic disk described in JP 2011-138589 A was used.
  • lapping alumina-based free abrasive grains having an average particle diameter of 20 ⁇ m were used.
  • a plurality of glass base plates laminated with a spacer interposed between the glass base plates is polished using cerium oxide having an average particle size (D50) of 1.0 ⁇ m as free abrasive grains. Polished with a brush.
  • D50 average particle size
  • the diamond sheet was ground using a grinding device that was bonded to the upper surface plate and the lower surface plate.
  • polishing was performed for 60 minutes using the polishing apparatus of FIGS. Detailed polishing conditions are as shown below.
  • the chemical strengthening of (7) a liquid mixture of potassium nitrate (60% by weight) and sodium nitrate (40% by weight) is used as the chemical strengthening liquid, the temperature of the chemical strengthening liquid is set to 350 ° C., and preheated to 200 ° C. in advance. The glass base plate was immersed in the chemical strengthening solution for 4 hours.
  • polishing was performed for a predetermined time using colloidal silica having a particle diameter of 10 to 50 ⁇ m using another polishing apparatus similar to that shown in FIGS. Thereby, arithmetic mean roughness Ra (JIS B0601: 2001) of the main surface was made into 0.15 nm or less.
  • the glass substrate after the final polishing was cleaned using a neutral cleaning solution and an alkaline cleaning solution. This obtained the glass substrate for magnetic discs.
  • Polishing pad Hard urethane pad (JIS-A hardness: 80-100) Polishing load: 120 g / cm 2 ⁇ Surface plate speed: 30 rpm Polishing fluid supply flow rate: 3000 L / min Polishing liquid: containing 10% by weight of zirconia (ZrO 2 ) abrasive grains. All the zirconia abrasive grains of the examples were prepared by a wet method. The zirconia abrasive grains of the comparative example were produced by a dry method.
  • the setting of the zirconia abrasive grains in the first polishing of (6) was changed to evaluate the polishing rate in the polishing process and the presence or absence of scratches on the glass base plate after the polishing process.
  • the results shown in Table 1 and Table 2 were obtained.
  • the said evaluation was performed about what wash
  • the secondary particle diameter (average particle diameter D50) of the zirconia abrasive grains was measured by a light scattering method using a particle diameter / particle size distribution measuring apparatus.
  • the average particle size D50 is the particle size at which the cumulative volume frequency is 50% when the total volume frequency is determined with the total volume of the powder population in the particle size distribution measured by the light scattering method as 100%. is there.
  • the primary particle diameter was measured by a method as shown in FIG. 7 with zirconia abrasive grains magnified 30,000 to 100,000 times with a scanning electron microscope. Further, the BET specific surface area was measured by a BET single point method by a gas adsorption method using a fluid specific surface area measuring device.
  • polishing rate evaluation criteria The polishing rate was evaluated based on the following criteria by measuring the polishing rate of the first batch. ⁇ , ⁇ or ⁇ is acceptable. ⁇ : Greater than 1.8 ⁇ m / min ⁇ : Greater than 1.6 ⁇ m / min, 1.8 ⁇ m / min or less ⁇ : Greater than 1.4 ⁇ m / min, 1.6 ⁇ m / min or less X: 1.4 ⁇ m / min or less
  • a magnetic disk was manufactured by laminating an adhesion layer, an underlayer, a magnetic layer (magnetic recording layer), a protective layer, and a lubricating layer on the glass substrates for magnetic disks of Examples 1 to 13 and Comparative Example, and a glide head.
  • the glide test was performed with the flying height of 7 nm set to 7 nm.
  • the yield inspection pass rate
  • the yield was lower than 90%, which was unacceptable.
  • the defect position detected by the glide inspection was observed by SEM / EDX, a foreign matter was found.
  • composition analysis of the found foreign matter revealed that it was a foreign matter derived from a zirconia abrasive. That is, it is considered that the zirconia particles used in the polishing step were found as foreign substances by attaching to the glass base plate during the polishing process.
  • the order of the steps is (7) chemical strengthening, (6) first polishing, (8) second polishing, not (6) first polishing, (7) chemical strengthening, and (8) second polishing.
  • the glass substrate for magnetic disks was produced by changing the above. At this time, the manufacturing method of zirconia abrasive grains in the first polishing and the primary particle diameter and secondary particle diameter D50 of the zirconia abrasive grains were the same as those in Example 3 in Table 1. Further, the glass substrate for a magnetic disk with various changes in the fracture toughness value K 1c was prepared as shown in Table 3 below by appropriately changing the strengthening temperature and the immersion time in the chemical strengthening step (Example 14 in Table 3). 15). Table 3 shows the evaluation results of the glass base plate after the first polishing at this time.
  • the production method of the zirconia abrasive grains, the primary particle diameter of the zirconia abrasive grains, and the secondary particle diameter D50 are the same as those in Example 8 of Table 1, and carriers having different surface roughness of the end faces are used in the polishing apparatus for the first polishing.
  • first polishing was performed to produce glass substrates for magnetic disks (Examples 16 to 18 in Table 4).
  • the order of the steps was (6) first polishing, (7) chemical strengthening, and (8) second polishing in this order to produce a magnetic disk glass substrate.
  • Table 4 shows the evaluation results of the glass base plate after the first polishing at this time.
  • the scratch evaluation was good when the surface roughness Ra of the end face of the carrier was 5 ⁇ m or less, and even better when it was 3 ⁇ m or less. This is because, as the surface roughness of the end face of the carrier is smaller, the number of zirconia abrasive grains entering between the glass base plate and the carrier increases, and the force is dispersed to more abrasive grains. This is considered to be because it is difficult to pierce the side wall surface of the glass base plate.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Magnetic Record Carriers (AREA)

Abstract

L'invention fournit un procédé de fabrication de substrat de verre pour disque magnétique selon lequel des défaillances telles qu'un problème d'écrasement de tête, d'aspérités thermiques, ou similaire, sont peu susceptibles de se produire, lors de la fabrication d'un substrat de verre pour disque magnétique en effectuant un polissage à l'aide d'un grain d'abrasif de zircone en tant que grain d'abrasif de polissage à l'état libre. Plus précisément, le procédé de l'invention comporte une étape de polissage au cours de laquelle dans un état de maintien par un support d'un substrat de verre de forme annulaire qui possède au moins une paire de surfaces principales, et de faces paroi latérale configurant un orifice interne et un contour, tandis que ladite paire de surfaces principales est enserrée par un tampon à polir installé sur une platine de polissage, et est alimenté en liquide de polissage, ledit substrat de verre est poli par fonctionnement d'une roue planétaire dudit support. Ledit liquide de polissage est caractéristique en ce qu'il comprend des particules de zircone fabriquées par un procédé par voie humide en tant que grain d'abrasif de polissage.
PCT/JP2013/055593 2012-03-30 2013-02-28 Procédé de fabrication de substrat de verre pour disque magnétique WO2013146090A1 (fr)

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WO2019066086A1 (fr) * 2017-09-29 2019-04-04 Hoya株式会社 Élément d'espacement en verre et dispositif de d'entraînement de disque dur
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JPH10121034A (ja) * 1996-03-18 1998-05-12 Showa Denko Kk 磁気ディスク基板の研磨用組成物
WO2006123562A1 (fr) * 2005-05-20 2006-11-23 Nissan Chemical Industries, Ltd. Procédé servant à produire une composition de polissage
JP2011134367A (ja) * 2009-12-22 2011-07-07 Asahi Glass Co Ltd データ記憶媒体用ガラス基板の製造方法及びガラス基板
WO2012029857A1 (fr) * 2010-08-31 2012-03-08 Hoya株式会社 Procédé pour la production de substrat en verre pour disques magnétiques, et procédé pour la production de disque magnétique
JP5126401B1 (ja) * 2011-09-28 2013-01-23 旭硝子株式会社 磁気記録媒体用ガラス基板

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JP2008006526A (ja) * 2006-06-28 2008-01-17 Konica Minolta Opto Inc 研磨キャリア
CN101542606B (zh) * 2007-05-30 2012-06-20 东洋钢钣株式会社 磁盘用玻璃基板的表面加工方法和磁盘用玻璃基板

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JPH10121034A (ja) * 1996-03-18 1998-05-12 Showa Denko Kk 磁気ディスク基板の研磨用組成物
WO2006123562A1 (fr) * 2005-05-20 2006-11-23 Nissan Chemical Industries, Ltd. Procédé servant à produire une composition de polissage
JP2011134367A (ja) * 2009-12-22 2011-07-07 Asahi Glass Co Ltd データ記憶媒体用ガラス基板の製造方法及びガラス基板
WO2012029857A1 (fr) * 2010-08-31 2012-03-08 Hoya株式会社 Procédé pour la production de substrat en verre pour disques magnétiques, et procédé pour la production de disque magnétique
JP5126401B1 (ja) * 2011-09-28 2013-01-23 旭硝子株式会社 磁気記録媒体用ガラス基板

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