US20120045971A1 - Method of manufacturing glass substrate for magnetic recording media - Google Patents

Method of manufacturing glass substrate for magnetic recording media Download PDF

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Publication number
US20120045971A1
US20120045971A1 US13/209,873 US201113209873A US2012045971A1 US 20120045971 A1 US20120045971 A1 US 20120045971A1 US 201113209873 A US201113209873 A US 201113209873A US 2012045971 A1 US2012045971 A1 US 2012045971A1
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Prior art keywords
diamond
glass substrate
lapping
polishing
pad
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English (en)
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Kazuyuki Haneda
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Resonac Holdings Corp
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Showa Denko KK
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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

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  • the present invention is related to a method of manufacturing a glass substrate for magnetic recording media.
  • the magnetic recording media used for a hard disk drive have significantly improved in recording density. Since the introduction of MR heads and of PRML technology, the areal recording density has further increased. Moreover, since the introduction of GMR heads or TMR heads, the areal recording density has continued to increase at a rate of about 1.5 times a year. However, in the future a higher lever of areal recording density will be required.
  • a substrate used for the magnetic recording media As a substrate for magnetic recording media, an aluminum substrate and a glass substrate are used conventionally. Of these, generally a glass substrate can be superior to aluminum substrate in hardness, surface smoothness, rigidity, and impact resistance. Therefore, a glass substrate has attracted growing attention as a substrate for magnetic recording media because it is expected to achieve a high recording density.
  • a disk-shaped glass substrate When manufacturing a glass substrate for magnetic recording media, a disk-shaped glass substrate can be obtained by cutting a large plate-shaped glass plate to a disk-shaped substrate or by press-molding molten glass directly on to the disk-shaped glass substrate using a mold. For surfaces and end faces of the obtained glass substrate, a lapping (grinding) process and polishing process are carried out.
  • a primary lapping process, secondary lapping process, primary polishing process, and secondary polishing process of a surface (data side) of a glass substrate are performed in this order.
  • a lapping process and polishing process on the inner and outer peripheral end faces of the substrate were performed.
  • Patent Literature 1 it is disclosed that when the primary lapping process using diamond pellets such as resin, metal and vitrified, and then the secondary lapping process using a diamond pad were performed, a substrate having surface smoothness and no defects such as scratches or grinding traces or aspiration traces can be manufactured, and it is also possible to decrease the process time.
  • cerium oxide chemical mechanical polishing has become a general technology.
  • cerium oxide is expensive; thus a technology requiring no, or very little, cerium oxide is preferable.
  • the object of the present invention is to provide a method of manufacturing a glass substrate for magnetic recording media which can produce glass substrates for magnetic recording media with high productivity, wherein the manufactured substrate has high surface smoothness and little waviness.
  • the present invention provides the following:
  • a method of manufacturing a glass substrate for magnetic recording media comprising:
  • the diamond pad on which a diamond abrasive was fixed using a binder the surface of the diamond pad has a structure in which plural tile-like projections having a flat top were provided in line;
  • the diamond pad used in the primary lapping process has an average diamond grain size of 4 to 12 ⁇ m, and a content of diamond grains in the projection of 5 to 70% by volume,
  • the diamond pad used in the secondary lapping process has an average diamond grain size of 1 to 5 ⁇ m, and a content of diamond grains in the projection of 5 to 80% by volume,
  • the diamond pad used in the tertiary lapping process has an average diamond grain size of 0.2 to 2 ⁇ m, and a content of diamond grains in the projection of 5 to 80% by volume, and
  • the silicon oxide is used as abrasive
  • the size of the projections of the diamond pad used in the primary, secondary and tertiary lapping process is 1.5 to 5 mm square with a height 0.2 to 3 mm, and the space between adjacent projections is 0.5 to 3 mm;
  • a method of manufacturing a glass substrate for magnetic recording media comprising:
  • the diamond pad on which diamond abrasive grain was fixed using binder is used, and the surface of the diamond pad has a structure in which plural tile-like projections having a flat top were provided in line;
  • the diamond pad used in the primary lapping process has an average diamond grain size of 3 to 12 ⁇ m, and a content of diamond grains in the projection of 5 to 70% by volume,
  • the diamond pad used in the secondary lapping process has an average diamond grain size of 0.2 to 5 ⁇ m, and a content of diamond grains in the projection of 5 to 80% by volume, and
  • the silicon oxide is used as abrasive
  • the size of the projections of the diamond pad used in primary, secondary and tertiary lapping process is 1.5 to 5 mm square with a height 0.2 to 3 mm, and the space between adjacent projections is 0.5 to 3 mm;
  • a glass substrates for magnetic recording media which has high surface smoothness and little waviness can be manufactured with high productivity.
  • FIG. 1 is a perspective view showing lapping operation for explaining the method of manufacturing a glass substrate for magnetic recording media according to the present invention.
  • FIG. 2A is a plan view showing an enlarged pad surface of diamond pad used in the lapping process.
  • FIG. 2B is a cross-section view showing an enlarged pad surface of diamond pad used in the lapping process.
  • FIG. 3 is a perspective view showing the inner and outer peripheral lapping process for explaining the method of manufacturing a glass substrate for magnetic recording media according to the present invention.
  • FIG. 4 is a perspective view showing the inner peripheral polishing process for explaining the method of manufacturing a glass substrate for magnetic recording media according to the present invention.
  • FIG. 5 is a perspective view showing the outer peripheral polishing process for explaining the method of manufacturing a glass substrate for magnetic recording media according to the present invention.
  • FIG. 6 is a perspective view showing a polishing process for explaining the method of manufacturing a glass substrate for magnetic recording media according to the present invention.
  • FIG. 7 is a perspective view showing another configuration example of a lapping or polishing machine used in the present invention.
  • a glass substrate for magnetic recording media manufactured by the method of the present invention is a disk-shaped glass substrate having a central aperture.
  • a magnetic recording media is formed by laminating a magnetic layer, protective layer and lubricant layer sequentially on the surface of the glass substrate.
  • writing or reading of information is performed for magnetic recording media by attaching a center of the magnetic recording media to an axis of a spindle motor, and making a magnetic head float and travel over the surfaces of the magnetic recording media which is rotated by the spindle motor.
  • the glass substrate for magnetic recording media for example, SiO 2 —Al 2 O 3 —R 2 O-based chemical glass (R represents at least one member selected from alkali metals.), SiO 2 —Al 2 O 3 —Li 2 O-based ceramic glass, SiO 2 —Al 2 O 3 —MgO—TiO 2 -based glass ceramics can be used.
  • lithium silicate, SiO 2 —-based crystal (quartz, cristobalite, and tridymite), cordierite, enstatite, aluminum magnesium titanate, spinel-based crystal ([Zn, and/or Mg] Al 2 O 4 , [Mg and/or Zn] 2 TiO 4 , as well as a solid solution between these two crystals), forsterite, Spodumene, a glass ceramic which includes solid solution crystals thereof as crystal phase can be suitably used as a glass substrate for magnetic recording medium.
  • a disk-shaped glass substrate which has a central aperture is obtained by cutting a glass substrate from a big glass plate, or directly pressing a glass substrate from melting glass by using a mold.
  • the method may further include a lapping process and polishing process for an inner and outer peripheral end face of the glass substrates.
  • a diamond pad to which diamond abrasive grain was fixed with binder is used.
  • the diamond pad is described below. Therefore, according to the present invention, with no use or less use of expensive cerium oxide slurry used in conventional polishing process, a polishing surface having little waviness and high surface smoothness can be obtained.
  • the polishing process using conventional cerium oxide slurry becomes unnecessary, and, as a result the two-step conventional polishing process can be changed to a one-step polishing process with use of silicon oxide slurry. Therefore, the method of the present invention reduces cost for polishing a glass substrate for magnetic recording media, and obtains high productivity.
  • primary lapping process, inner and outer peripheral lapping process, inner peripheral polishing process, second lapping process, tertiary lapping process, outer peripheral polishing process and primary polishing process are performed in this order.
  • this lapping machine 10 As the primary lapping process, a lapping machine 10 as shown in FIG. 1 is used, and a primary lapping process is carried out for surfaces except end face of the glass substrate W.
  • this lapping machine 10 includes a pair of upper and lower faceplates 11 and 12 , and several sheets of glass substrates are sandwiched between the faceplates 11 and 12 which are rotating in directions opposite to each other, and then both sides of the glass substrates W are lapped by grinding pads installed in the faceplates 11 and 12 .
  • the grinding pad used for the primary lapping process is a diamond pad 20 A to which diamond abrasive grain was fixed with binder (bond) as shown in FIGS. 2A and 2B .
  • the lapping surface 20 a has plural tile-like projections having a flat top which are installed in line.
  • the size S of the projections 21 of the diamond pad 20 A used in primary lapping process be 1.5 to 5 mm square with a height T 0.2 to 3 mm, and the space G between adjacent projections be 0.5 to 3 mm.
  • liquid coolant or lapping fluid can reach everywhere equally, and grinding dust can be discharged smoothly from a space interval of the projection 21 of the lap surface 20 a.
  • the diamond pad 20 A used in the primary lapping process have an average diamond grain size of 4 to 12 ⁇ m, and a content of diamond grains in the projection 21 of 5 to 70% by volume. It is more preferable that the diamond pad 20 A have a content of diamond grains of 20 to 30% by volume. This increases cost due to an increase in the process time when the diamond abrasive grain size and content are less than the above range. On the other hand, it becomes more difficult to obtain desired surface roughness when the diamond abrasive grain size and the content exceed the above range.
  • a binder of diamond pad 20 A for example, polyurethane resin, phenol-based resin, melamine-based resin, etc. can be used as a binder of diamond pad 20 A.
  • lapping machine 30 As the inner and outer peripheral lapping process, lapping machine 30 as shown in FIG. 3 is used, and lapping process is carried out for inner peripheral end surface of a central aperture of glass substrate W and outer peripheral end face of the glass substrate W.
  • the lapping machine 30 includes inner peripheral grindstone 31 and outer peripheral grindstone 32 .
  • the laminated substrates X is obtained by laminating plural pieces of glass substrates W in the state that the central apertures is matched each other wherein spacers (not shown) are sandwiched.
  • a polishing machine 40 as shown in FIG. 4 is used, and the polishing process is carried out for the inner peripheral end face of a central aperture of glass substrate W. That is, the polishing machine 40 has an inner peripheral polishing brush 41 , while rotating laminated substrates X around the axis, and the inner peripheral polishing brush 41 inserted in a central aperture of each glass substrate W is rotated in the direction opposite to that of the glass substrates W and moved vertically. At this time, polishing fluid is dropped to the inner peripheral polishing brush 41 . And then, the inner peripheral end face of glass substrates W is polished by the inner peripheral polishing brush 41 .
  • the polishing fluid for example, the slurried fluid obtained by dispersing silicon oxide (colloidal silica) or cerium oxide abrasive grain into water can be used.
  • the secondary lapping process like the primary lapping process, a lapping machine 10 as shown in FIG. 1 is used, and, the secondary lapping process is carried out for surfaces except end face of glass substrate W. That is, while sandwiching plural pieces of glass substrates W between a pair of upper and lower faceplates 11 and 12 , which are rotating in directions opposite to each other, both sides of these glass substrate W are lapped by a grinding pad installed in the faceplate 11 , 12 .
  • the grinding pad used for the secondary lapping process like the diamond pad 20 A as shown in FIGS. 2A and 2B , is a diamond pad 20 B to which diamond abrasive grain was fixed with binder (bond).
  • the lapping surface 20 a has plural tile-like projections having a flat top which are installed in line.
  • the size S of the projections 21 of the diamond pad 20 B used in secondary lapping process be 1.5 to 5 mm square with a height T 0.2 to 3 mm, and the space G between adjacent projections be 0.5 to 3 mm.
  • liquid coolant or lapping fluid can reach everywhere equally, and grinding dust can be discharged smoothly from an interval of the projection 21 of the lap surface 20 a.
  • the diamond pad 20 B used in the secondary lapping process have an average diamond grain size of 1 to 5 ⁇ m, and a content of diamond grains in the projection 21 of 5 to 80% by volume. It is more preferable that the content of diamond grains be 50 to 70% by volume. This increases cost due to an increase in the process time when the diamond abrasive grain size and content are less than the above range. On the other hand, it becomes more difficult to obtain desired surface roughness when the diamond abrasive grain size and content exceed the above range.
  • a binder of diamond pad 20 B for example, polyurethane resin, phenol-based resin, melamine-based resin, etc. can be used as a binder of diamond pad 20 B.
  • this lapping machine 10 As the tertiary lapping process, like the primary and secondary lapping processes, the lapping machine 10 as shown in FIG. 1 is used, and the tertiary lapping process is carried out for surfaces except for the end face of the glass substrate W.
  • this lapping machine 10 includes a pair of upper and lower faceplates 11 and 12 , several sheets of glass substrates sandwiched between the faceplates 11 and 12 which are rotating in directions opposite to each other, and both sides of the glass substrates W are lapped by grinding pads installed in the faceplates 11 and 12 .
  • the grinding pad used for the tertiary lapping process is a diamond pad 20 C to which diamond abrasive grain was fixed with binder (bond).
  • the lapping surface 20 a has plural tile-like projections having a flat top which are installed in line.
  • the size S of the projections 21 of the diamond pad 20 A used in tertiary lapping process be 1.5 to 5 mm square with a height T 0.2 to 3 mm, and the space G between adjacent projections be 0.5 to 3 mm.
  • liquid coolant or lapping fluid can reach everywhere equally, and grinding dust can be discharged smoothly from an interval of the projection 21 of the lap surface 20 a.
  • the diamond pad 20 A used in the tertiary lapping process have an average diamond grain size of 0.2 to 2 ⁇ m, and a content of diamond grains in the projection 21 of 5 to 80% by volume. It is more preferable that it have a content of diamond grains of 50 to 80% by volume. This increases cost due to increase the process time when diamond abrasive grain size and content are less than the above range. On the other hand, it becomes more difficult to obtain desired surface roughness when the diamond abrasive grain size and content exceed the above range.
  • a binder of diamond pad 20 C for example, polyurethane resin, phenol-based resin, melamine-based resin, etc. can be used as a binder of diamond pad 20 C.
  • a polishing machine 50 as shown in FIG. 5 is used, and the polishing process is carried out for the outer peripheral end face of the glass substrate W.
  • the polishing machine 50 has a rotating shaft 51 and outer peripheral polishing brush 52 .
  • the laminated substrates X is obtained by laminating plural pieces of glass substrates W in the state that the central apertures match each other wherein spacers (not shown) are sandwiched. While rotating laminated substrates X around the axis by the rotating shaft 51 inserted in a central aperture of each glass substrate W, the outer peripheral polishing brush 52 in contact with the surface of the outer peripheral end face of the glass substrates, is rotated in the direction opposite to that of the glass substrates W and moved vertically.
  • polishing fluid is dropped to the outer peripheral polishing brush 51 . And then, the outer peripheral end face of glass substrates W is polished by the outer peripheral polishing brush 51 . At the same time, the edge portion of the inner and outer peripheral end face, which was chamfered in the inner and outer peripheral lapping process, is polished.
  • the polishing fluid for example, the slurried fluid obtained by dispersing silicon oxide (colloidal silica) or cerium oxide abrasive grain into water can be used.
  • polishing machine 60 As primary polishing process, polishing machine 60 as shown in FIG. 6 is used, and primary polishing process is carried out for surfaces except for the end face of the glass substrate W. That is, while sandwiching plural pieces of glass substrates W between a pair of upper and lower faceplates 61 and 62 , which are rotating in directions opposite to each other, both sides of these glass substrates W are polished by the grinding pad installed in the faceplates 61 and 62 .
  • the grinding pad used for the primary polishing process is a hard polishing cloth made of urethane, for example.
  • polishing fluid is dropped to the glass substrates W.
  • the polishing fluid for example, the slurried fluid obtained by dispersing silicon oxide (colloidal silica) abrasive grain into water can be used.
  • the glass substrate W subjected to the lapping and polishing process is fed to the cleaning process and final inspection process.
  • a chemical cleaning method using cleaner (chemical) combined with an ultrasonic method is used to clean the glass substrate W and remove the abrasive, for example, used in the above step.
  • a laser optical inspection equipment for example, examination of the presence or absence of distortion or scratches on the surface of the glass substrate W can be performed.
  • diamond pads 20 A, 20 B, 20 C to which diamond abrasive grains as shown in FIGS. 2A and 2B were fixed to with binder in the primary, secondary and tertiary lapping process are used.
  • the lapping surface 20 a of the diamond pads 20 A, 20 B, 20 C has plural tile-like projections having a flat top which are installed in line.
  • the present invention by using such diamond pads 20 A, 20 B, 20 C, it is possible that while grinding dust is discharged smoothly from an interval of projection 21 of lapping surface 20 a , the surfaces except for the end face of the glass substrate W can be polished to smoothness.
  • a two-step conventional polishing process primary and secondary polishing processes
  • the application of expensive cerium oxide abrasive grain can be reduced.
  • the polishing process has a long process time in comparison with a lapping process, process time can be reduced.
  • primary lapping process, inner and outer peripheral lapping process, inner peripheral polishing process, second lapping process, outer peripheral polishing process and primary polishing process are performed in this order.
  • this lapping machine 10 As the primary lapping process, the lapping machine 10 as shown in FIG. 1 is used, and a primary lapping process is carried out for surfaces except for the end face of the glass substrate W.
  • this lapping machine 10 includes a pair of upper and lower faceplates 11 and 12 , several sheets of glass substrates sandwiched between the faceplates 11 and 12 which are rotating in directions opposite to each other, both sides of the glass substrates W are lapped by grinding pads installed in the faceplates 11 and 12 .
  • the grinding pad used for the primary lapping process is a diamond pad 20 D to which diamond abrasive grain was fixed with binder (bond).
  • the lapping surface 20 a has plural tile-like projections having a flat top which are installed in line.
  • the size S of the projections 21 of the diamond pad 20 D used in primary lapping process be 1.5 to 5 mm square with a height T 0.2 to 3 mm, and the space G between adjacent projections be 0.5 to 3 mm.
  • liquid coolant or lapping fluid can reach everywhere equally, and grinding dust can be discharged smoothly from an interval of the projection 21 of the lap surface 20 a.
  • the diamond pad 20 D used in the primary lapping process have an average diamond grain size of 3 to 10 ⁇ m, and a content of diamond grains in the projection 21 of 5 to 70% by volume. It is more preferable that it have a content of diamond grains of 20 to 30% by volume. This increases cost due to increase the process time when diamond abrasive grain size and content are less than the above range. On the other hand, it becomes more difficult to obtain desired surface roughness when the diamond abrasive grain size and content exceed the above range.
  • a binder of diamond pad 20 D for example, polyurethane resin, phenol-based resin, melamine-based resin, etc. can be used as a binder of diamond pad 20 D.
  • lapping machine 30 As the inner and outer peripheral lapping process, lapping machine 30 as shown in FIG. 3 is used, and lapping process is carried out for inner peripheral end surface of a central aperture of glass substrate W and outer peripheral end face of the glass substrate W.
  • the lapping machine 30 includes the inner peripheral grindstone 31 and outer peripheral grindstone 32 .
  • the laminated substrates X is obtained by laminating plural pieces of glass substrates W in the state that the central apertures match each other wherein spacers (not shown) is sandwiched.
  • the polishing machine 40 As the inner peripheral polishing process, using the polishing machine 40 as shown in FIG. 4 , and polishing process is carried out for the inner peripheral end face of a central aperture of the glass substrate W. That is, the polishing machine 40 has an inner peripheral polishing brush 41 , while rotating laminated substrates X around axis, and the inner peripheral polishing brush 41 inserted in a central aperture of each glass substrate W is rotated in the direction opposite to that of the glass substrates W and moved vertically. At this time, polishing fluid is dropped to inner peripheral polishing brush 41 . And then, the inner peripheral end face of glass substrates W is polished by the inner peripheral polishing brush 41 .
  • the polishing fluid for example, the slurried fluid obtained by dispersing silicon oxide (colloidal silica) or cerium oxide abrasive grain into water can be used.
  • the lapping machine 10 as shown in FIG. 1 is used, and, the secondary lapping process is carried out for surfaces except end face of glass substrate W. That is, while sandwiching plural pieces of glass substrates W between a pair of upper and lower faceplates 11 and 12 , which are rotating in directions opposite to each other, both sides of these glass substrate W are lapped by grinding pad installed in the faceplate 11 , 12 .
  • the grinding pad used for the secondary lapping process like the diamond pad 20 A as shown in FIGS. 2A and 2B , is a diamond pad 20 E to which diamond abrasive grain was fixed with binder (bond).
  • the lapping surface 20 a has plural tile-like projections having a flat top which are installed in line.
  • the size S of the projections 21 of the diamond pad 20 E used in the secondary lapping process be 1.5 to 5 mm square with a height T 0.2 to 3 mm, and the space G between adjacent projections be 0.5 to 3 mm.
  • liquid coolant or lapping fluid can reach everywhere equally, and grinding dust can be discharged smoothly from an interval of projection 21 of lap surface 20 a.
  • the diamond pad 20 E used in the secondary lapping process have an average diamond grain size of 0.2 to 2 ⁇ m, and a content of diamond grains in the projection 21 of 5 to 80% by volume. It is more preferable that it have a content of diamond grains of 50 to 70% by volume. This increases cost due to an increase in the process time when diamond abrasive grain size and content are less than the above range. On the other hand, it becomes more difficult to obtain desired surface roughness when the diamond abrasive grain size and content exceed the above range.
  • a binder of diamond pad 20 E for example, polyurethane resin, phenol-based resin, melamine-based resin, etc. can be used as a binder of diamond pad 20 E.
  • the polishing process is carried out for outer peripheral end face of glass substrate W.
  • the polishing machine 50 has a rotating shaft 51 and outer peripheral polishing brush 52 .
  • the laminated substrates X is obtained by laminating plural pieces of glass substrates W in the state that the central apertures match each other wherein spacers (not shown) are sandwiched. While rotating laminated substrates X around the axis by the rotating shaft 51 inserted in a central aperture of each glass substrate W, the outer peripheral polishing brush 52 in contact with the surface of the outer peripheral end face of the glass substrates, is rotated in the direction opposite to that of the glass substrates W and moved vertically.
  • polishing fluid is dropped to outer peripheral polishing brush 51 . And then, the outer peripheral end face of glass substrates W is polished by the outer peripheral polishing brush 51 . At the same time, the edge portion of the inner and outer peripheral end face, which was chamfered in the inner and outer peripheral lapping process, is polished.
  • the polishing fluid for example, the slurried fluid obtained by dispersing silicon oxide (colloidal silica) or cerium oxide abrasive grain into water can be used.
  • the polishing machine 60 as shown in FIG. 6 is used, and the primary polishing process is carried out for surfaces except end face of glass substrate W. That is, while sandwiching plural pieces of glass substrates W between a pair of upper and lower faceplates 61 , 62 , which are rotating in directions opposite to each other, both sides of these glass substrate W are polished by the grinding pad installed in the faceplates 61 , 62 .
  • the grinding pad used for the primary polishing process is a hard polishing cloth made of urethane, for example.
  • polishing fluid is dropped to the glass substrates W.
  • the polishing fluid for example, the slurried fluid obtained by dispersing silicon oxide (colloidal silica) abrasive grain into water can be used.
  • the glass substrate W subjected to the lapping and polishing process is fed to the cleaning process and final inspection process.
  • a chemical cleaning method using cleaner (chemical) combined with an ultrasonic method is used to clean the glass substrate W and remove the abrasive, for example, used in the above step.
  • the inspection process by using laser optical inspection equipment, for example, examination of the presence or absence of distortion or scratches on the surface of the glass substrate W.
  • diamond pads 20 D, 20 E to which diamond abrasive grain as shown in FIGS. 2A and 2B were fixed to with binder in the primary and secondary lapping process are used.
  • the lapping surface 20 a of the diamond pads 20 D, 20 E has plural tile-like projections having a flat top which are installed in line.
  • the present invention by using such diamond pads 20 D, 20 E, it is possible that while grinding dust is discharged smoothly from an interval of projection 21 of lap surface 20 a , the surfaces except of end face of the glass substrate W can be polished to smoothness.
  • two-steps conventional polishing process primary and secondary polishing processes
  • the application of expensive cerium oxide abrasive grain can be reduced.
  • the polishing process has a long process time in comparison with a lapping process, the process time can be reduced.
  • Lapping fluid used in each lapping process of the first and second embodiments, a commercial source can be used.
  • Lapping fluid by classifying roughly, includes water-based lapping fluid and oil-based lapping fluid.
  • the water-based lapping fluid contains pure water and a suitable amount of alcohol with addition of polyethylene glycol as a viscosity modifier, amine, and surfactant etc.
  • the oil-based lapping fluid contains oil with addition of an appropriate amount of stearic acid as an extreme pressure additive.
  • water-based Sabrelube 9016 manufactured by Chemetall
  • Chemetall water-based Sabrelube 9016
  • polishing auxiliaries and anticorrosive may be added to the lapping fluids used in each lapping process and polishing fluids used in polishing process in the first and the second embodiments.
  • polishing auxiliaries include an organic polymer having sulfonate group or carboxylic acid group at least. And an organic polymers containing sodium sulphonate or sodium carboxylate, having average molecular weight of 4000-10000, is preferable. Thus, it is possible to smooth surfaces of the glass substrate W in the above processes.
  • GEROPON SC/213 Product Name/Rhodia
  • GEROPON T/36 Product Name/Rhodia
  • GEROPON TA/10 Product Name/Rhodia
  • GEROPON TA/72 Product Name/Rhodia
  • New Karugen WG-5 Product Name/Takemoto Oil & Fat Corporation
  • Agurizoru G-200 Product Name/Kao Corporation
  • Demoru EP Powder Product Name/Kao Corporation
  • Demoru RNL Product Name/Kao Corporation
  • Isoban 600-SF35 Product name/Kuraray Ltd.
  • Polystar OM Product Name/NOF Corporation
  • Sokalan CP9 Product Name/BASF Japan (Ltd.)
  • Sokalan PA-15 Product Name/BA SF Japan Ltd.
  • Tokisanon GR-31A Product Name/Sanyo Chemical Industries, Corporation
  • the magnetic recording media manufactured using the glass substrate W generally includes corrosion-prone material such as Co, Ni and Fe in magnetic layer.
  • benzotriazole or a derivative thereof As a corrosion inhibitor, it is preferable to use benzotriazole or a derivative thereof.
  • benzotriazole for example, the compound obtained by substituting one, two or more hydrogen atoms of benzotriazole by a carboxyl group, methyl group, amino group, hydroxyl group.
  • 4-carboxy benzotriazole or a salt thereof, 7-carboxymethyl benzotriazole or a salt thereof, benzotriazole butyl ester, 1-hydroxymethyl benzotriazole, 1-hydroxybenzotriazole etc. can be used.
  • the addition amount of corrosion inhibitor the total amount of diamond slurry during use, it is preferable to use less than 1% by mass concerning to the total amount of diamond slurry during using, and 0.001% to 0.1% by mass is more preferable.
  • the polishing or lapping machine include a pair of lower faceplate 71 and upper faceplate 72 and plural carriers 73 which, for example, were placed at the surface of lower faceplate 71 which is opposed to the faceplate 72 as shown in FIG. 7 .
  • Glass substrates (not shown) are placed into a plural number of opening 74 (for example, 35 in the present embodiment) installed in each carrier 73 , and then the glass substrates are lapped by lapping pad or polished by polishing pad which are installed in the lower faceplate 71 and upper faceplate 72 .
  • the lower faceplate 71 and upper faceplate 72 can be rotated at the same central axis and in directions opposite to each other with the rotation movement of the rotation shafts 71 a and 72 a which are rotated by drive motor (not shown), wherein the rotation shafts 71 a and 72 a are placed at the center of the lower faceplate 71 and upper faceplate 72 .
  • a recess 75 for placing the plurality carriers 73 is provide on the surface of lower faceplate 71 wherein the surface is facing upper faceplate 72 .
  • a plural carrier 73 for example, it can be obtained by forming a disk made from epoxy resin which is strengthened by mixing aramid fiber and fiberglass. And these plural carriers 73 are placed around the axis 71 a in the inner wall of recess 75 .
  • a planet gears part 76 is installed in the periphery of each carrier 73 over the entire circumference.
  • a sun gear portion 77 which rotates with the rotation shaft 71 a while being intermeshed with the planetary gear carrier 76 of each 73 is provided in the periphery of the recess 75 .
  • the fixed gear portion 78 which is intermeshed with planetary gear 76 of each carrier 73 is provided.
  • the plural glass substrates held at the opening 75 of each carrier 73 can be lapped by the lapping pad or polished by the polishing pad placed at the lower faceplate 71 and upper faceplate 72 while being moved as planetary motion.
  • the glass substrate can be lapped or polished not only more accurately, but also quickly.
  • Example 1 firstly, a glass substrate (manufactured by Ohara, TS-10SX) having an outside diameter of 48 mm, center hole of 12 mm, thickness of 0.560 mm was used.
  • the primary lapping process is carried out by using a lapping machine including a pair of upper and lower faceplates. While several sheets of glass substrates are sandwiched between the faceplates which are rotating in directions opposite to each other, both sides of the glass substrates are lapped by lapping pads installed in the faceplates. At this time, Toraizakuto (Product Name/Manufactured by Sumitomo 3M) was used as the lapping pad of the primary lapping process.
  • the size of the projections of the lapping pad is 2.6 mm square with a height 2 mm, and the space between adjacent projections is 1 mm, the average particle size of the diamond grains is 9 ⁇ m, a content of diamond grains in the projection of 20%.
  • the lapping machine As the lapping machine, the four-way double-sided lapping machine (16B, manufactured by Hamai Co., Ltd) was used. The lapping process is carried out for 15 minutes, under the condition that rotational speed of the faceplate is 25 rpm, the processing pressure is 120 g/cm 2 .
  • As a lapping fluid Sabrelube 9016 (Manufactured by Chmetall) is used after diluted 1:10 in water, lapping amount per one side of the glass substrate was about 100 ⁇ m.
  • lapping machine including inner peripheral grindstone and outer peripheral grindstone was used.
  • the laminated substrates are obtained by laminating plural pieces of glass substrates in the state that the central apertures match each other wherein spacers are sandwiched. While rotating the laminated substrates around the axis, and inserting inner peripheral grindstone into a central aperture of glass substrates and putting glass substrates in a radial direction between outer peripheral grindstones which is placed on the periphery of each glass substrate, the inner peripheral grindstone and outer peripheral grindstone are rotated in the direction opposite to that of laminated substrates. And at the same time as grinding inner peripheral end face of the glass substrates by inner peripheral grindstone, outer peripheral end face of the glass substrates is lapped by peripheral grindstone.
  • the inner peripheral grindstone and outer peripheral grindstone use diamond grains with the average particle size of 10 ⁇ m.
  • the rotation speed of the inner peripheral grindstone and outer peripheral grindstone is 1200 rpm and 600 rpm, respectively, and processing was carried out for 30 seconds.
  • the inner peripheral polishing process using a polishing machine having an inner peripheral polishing brush, while laminated substrates are rotated around the axis, and the inner peripheral polishing brush inserted in a central aperture of each glass substrate is rotated in the direction opposite to that of the glass substrates and moved vertically, at the same time polishing fluid is dropped to inner peripheral polishing brush, the inner peripheral end face of glass substrates is polished by the inner peripheral polishing brush.
  • a nylon brush was used as the inner peripheral polishing brush.
  • the rotation speed of inner peripheral polishing brush is 300 rpm, and processing was carried out for 10 minutes
  • the secondary lapping process is carried out by using a lapping machine including a pair of upper and lower faceplates. While several sheets of glass substrates is sandwiched between the faceplates which are rotating in directions opposite to each other, both sides of the glass substrates are lapped by lapping pads installed in the faceplates. At this time, Toraizakuto (Product Name) manufactured by Sumitomo 3M was used as the lapping pad of the secondary lapping process.
  • the size of the projections 21 of the lapping pad is 2.6 mm square with a height 2 mm, and the space between adjacent projections is 1 mm, the average particle size of the diamond grains is 3 ⁇ m, a content of diamond grains in the projection of 50%.
  • the lapping machine As the lapping machine, the four-way double-sided lapping machine (16B, manufactured by Hamai Co., Ltd) was used. Lapping process is carried out for 10 minutes, under the condition that rotational speed of the faceplate is 25 rpm, the processing pressure is 120 g/cm 2 .
  • As a lapping fluid Sabrelube 9016 (Manufactured by Chmetall) is used after diluted 1:10 in water, lapping amount per one side of the glass substrate was about 30 ⁇ m.
  • the tertiary lapping process is carried out by using a lapping machine including a pair of upper and lower faceplates. While several sheets of glass substrates is sandwiched between the faceplates which are rotating in directions opposite to each other, both sides of the glass substrates are lapped by lapping pads installed in the faceplates. At this time, Toraizakuto (Product Name) manufactured by Sumitomo 3M was used as the lapping pad of the primary lapping process.
  • the size of the projections 21 of the lapping pad is 2.6 mm square with a height 2 mm, and the space between adjacent projections is 1 mm, the average particle size of the diamond grains is 0.5 ⁇ m, a content of diamond grains in the projection of 60%.
  • the lapping machine As the lapping machine, the four-way double-sided lapping machine (16B, manufactured by Hamai Co., Ltd) was used. Lapping process is carried out for 10 minutes, under the condition that rotational speed of the faceplate is 25 rpm, the processing pressure is 120 g/cm 2 .
  • As a lapping fluid Sabrelube 9016 (Manufactured by Chmetall) is used after diluted 1:10 in water, lapping amount per one side of the glass substrate was about 10 ⁇ m.
  • a polishing machine having an outer peripheral polishing brush was used.
  • the laminated substrates were obtained by laminating plural pieces of glass substrates in the state that the central apertures match each other wherein spacers are sandwiched. While rotating laminated substrates around the axis by the rotating shaft inserted in a central aperture of each glass substrate, the outer peripheral polishing brush in contact with the surface of the outer peripheral end face of the glass substrates, is rotated in the direction opposite to that of the glass substrates and moved vertically. At the same time polishing fluid is dropped to outer peripheral polishing brush, outer peripheral end face of glass substrates was polished by the outer peripheral polishing brush. In the case, a nylon brush was used as the outer peripheral polishing brush. The rotation speed of outer peripheral polishing brush is 300 rpm, and processing was carried out for 10 minutes
  • the polishing machine including a pair of upper and lower faceplates is used. While sandwiching plural pieces of glass substrates between a pair of upper and lower faceplates, which are rotating in directions opposite to each other, both sides of these glass substrate are polished by a polishing pad installed in the faceplates.
  • the polishing fluid is polishing slurry having silica content is 0.5 wt % by adding water to a silica abrasive polishing fluid having 40 wt % silica as solids content (0.08 ⁇ m average particle size, Compol, manufactured by Fujimi).
  • the polishing machine the four-way double-sided polishing machine (16B, manufactured by Hamai Co., Ltd) was used. Polishing process is carried out for 30 minutes, under the condition that rotational speed of the faceplate is 25 rpm, the processing pressure is 110 g/cm 2 , while the polishing liquid is supplied in a rate of 7 L/minutes. Polishing amount per one side of the glass substrate was about 2 ⁇ m.
  • the glass substrates obtained after the above processes were treated using chemical cleaning by the anionic surfactant combined with ultrasound treatment.
  • the glass substrates for magnetic recording media of Example 1 were obtained.
  • Example 2 the lapping processes of the glass substrates in Example 1 were changed to two-steps.
  • the lapping pad used in the primary lapping process lap of glass substrate, Toraizakuto (Product Name, Manufactured by Sumitomo 3M) was used.
  • the size of the projections of the lapping pad is 2.6 mm square with a height 2 mm, and the space between adjacent projections is 1 mm, the average particle size of the diamond grains is 4 ⁇ m, a content of diamond grains in the projection of 50%.
  • the lapping machine the four-way double-sided lapping machine (16B, manufactured by Hamai Co., Ltd) was used.
  • Lapping process is carried out for 10 minutes, under the condition that rotational speed of the faceplate is 25 rpm, the processing pressure is 120 g/cm 2 .
  • a lapping fluid Sabrelube 9016 (Manufactured by Chmetall) is used after diluted 1:10 in water, lapping amount per one side of the glass substrate was about 30 ⁇ m.
  • the secondary lapping process, the primary polishing process, and others were carried out as the same as in Example 1.
  • Comparative Example 1 the lapping process of glass substrates in Example 1 is changed to two-steps, and the polishing process was changed to two-steps.
  • the tertiary lapping process in Comparative Example 1 was not carried out, and two-step polishing processes were carried out under the following conditions
  • the polishing machine including a pair of upper and lower faceplates is used. While sandwiching plural pieces of glass substrates between a pair of upper and lower faceplates, which are rotating in directions opposite to each other, both sides of these glass substrate are polished by polishing pad installed in the faceplates.
  • the primary polishing pad Smoke Aid type (manufactured Filwel) was used.
  • the polishing fluid is polishing slurry having ceria content of 0.6 wt % obtained by adding water to ceria abrasive polishing fluid (SHOROX Tohoku Metal Chemical Co., Ltd., particle size 1.0 microns).
  • the polishing machine the four-way double-sided polishing machine (16B, manufactured by Hamai Co., Ltd) was used. Polishing process is carried out for 40 minutes, under the condition that rotational speed of the faceplate is 30 rpm, the processing pressure is 110 g/cm 2 , while the polishing liquid is supplied in a rate of 8 L/minutes. Polishing amount per one side of the glass substrate was about 15 ⁇ m.
  • the polishing machine including a pair of upper and lower faceplates is used. While sandwiching plural pieces of glass substrates between a pair of upper and lower faceplates, which are rotating in directions opposite to each other, both sides of these glass substrate are polished by polishing pad installed in the faceplates.
  • the primary polishing pad Smoke Aid type (manufactured Filwel) was used.
  • the polishing fluid is polishing slurry having ceria content of 0.6 wt % obtained by adding water to a commercially available ceria abrasive polishing fluid having ceria content of 12 wt % (SHOROX Tohoku Metal Chemical Co., Ltd., particle size 1.0 microns).
  • the polishing machine the four-way double-sided polishing machine (16B, manufactured by Hamai Co., Ltd) was used.
  • Polishing process is carried out for 30 minutes, under the condition that rotational speed of the faceplate is 25 rpm, the processing pressure is 110 g/cm 2 , while the polishing liquid is supplied in a rate of 8 L/minutes. Polishing amount per one side of the glass substrate was about 2

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
  • Surface Treatment Of Glass (AREA)
  • Polishing Bodies And Polishing Tools (AREA)
US13/209,873 2010-08-17 2011-08-15 Method of manufacturing glass substrate for magnetic recording media Abandoned US20120045971A1 (en)

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JP2010182330A JP5624829B2 (ja) 2010-08-17 2010-08-17 磁気記録媒体用ガラス基板の製造方法

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