WO2014115495A1 - Procédé de fabrication de substrat de verre pour disque dur - Google Patents

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

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Publication number
WO2014115495A1
WO2014115495A1 PCT/JP2014/000067 JP2014000067W WO2014115495A1 WO 2014115495 A1 WO2014115495 A1 WO 2014115495A1 JP 2014000067 W JP2014000067 W JP 2014000067W WO 2014115495 A1 WO2014115495 A1 WO 2014115495A1
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WIPO (PCT)
Prior art keywords
polishing
glass substrate
slurry
abrasive
particle size
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PCT/JP2014/000067
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English (en)
Japanese (ja)
Inventor
塚田　和也
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Hoya株式会社
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Publication of WO2014115495A1 publication Critical patent/WO2014115495A1/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

Definitions

  • the present invention relates to a method for manufacturing a glass substrate for a hard disk (magnetic information recording medium) used as a magnetic disk mounted on a hard disk (HDD).
  • a hard disk magnetic information recording medium
  • HDD hard disk
  • Glass substrates for magnetic information recording media such as HDDs are usually produced by performing a grinding process, a polishing process, a chemical strengthening process, etc. on a flat glass base plate obtained by a float method or a direct press method.
  • a one-stage or two-stage polishing process for finishing the surface depending on the surface quality is usually added.
  • a cerium oxide abrasive having a high polishing rate is generally used for the so-called rough polishing step that is first performed.
  • High-hardness polyurethane pads have been used in polishing processes that use cerium oxide to achieve a high rate, but there are defects that leave scratches and deep damage, making it a high-quality finish that meets the demands of high-density substrates. It was a high issue. Therefore, a suede-shaped pad having a feature including a foam layer designed to have a lower hardness than before has been introduced, and scratches and damage can be improved (for example, Patent Document 1).
  • Patent Document 2 a method of using a slurry in which the secondary particle size distribution of the polishing material is adjusted and no aggregation occurs (Patent Document 2), and oxidation as a polishing material.
  • Patent Document 3 A method of reducing the particle size and increasing the purity of cerium (Patent Document 3) has been reported.
  • polishing rate in order to shorten the manufacturing time, it is required to increase the polishing rate in order to obtain a desired polishing thickness (also referred to as polishing allowance) in a short period of time. It is required to adjust to the required surface roughness.
  • polishing allowance also referred to as polishing allowance
  • the polishing rate is increased with large abrasive particles, and the finished surface roughness is achieved with small abrasive particles.
  • the technology was examined. By using such an abrasive slurry, it became possible to adjust the desired polishing rate and the surface roughness after production to some extent.
  • the polishing rate is increased and the total manufacturing time is shortened. It became possible to improve the quality.
  • the above-mentioned problems are caused by the change in the particle size distribution of the abrasive particles as the polishing proceeds when the abrasive particles having different particle sizes are used.
  • a technique for maintaining the particle size distribution of each abrasive particle is not yet known.
  • the present invention has been made in view of such circumstances, and an object of the present invention is to provide an efficient method of manufacturing a glass substrate for a hard disk capable of ensuring quality capable of meeting the demand for higher density.
  • the method for manufacturing a glass substrate for hard disk includes a polishing step of polishing a glass substrate with a polishing slurry containing abrasive particles, and in the polishing step, An abrasive slurry A containing an abrasive particle group A having an average particle size and a dispersant optimal for the particle group A, an abrasive particle group B having an average particle size larger than the particle group A, and the particle group B Polishing is performed using a polishing slurry obtained by mixing polishing slurry B containing an optimal dispersant.
  • FIG. 1 is a view showing an example of a molding die for glass blanks and a press machine.
  • FIG. 2 is a perspective view of a rotary table on which a glass blank forming press is disposed.
  • the method for manufacturing a glass substrate for hard disk includes a polishing step of polishing the glass substrate with a polishing slurry containing abrasive particles, and in the polishing step, the glass substrate has a predetermined average particle diameter.
  • Abrasive slurry A containing an abrasive particle group A having and an optimal dispersant for the particle group A, an abrasive particle group B having an average particle size larger than the particle group A, and an optimal dispersant for the particle group B It grind
  • the inventor diligently studied the cause of the rate reduction when using a suede pad or the like for polishing, and found that the change in the particle size distribution accompanying the running of the abrasive was influencing, and further researching the present invention. Was completed.
  • the abrasive particles having at least two different particle size distributions are maintained by selecting optimum different dispersants, and by using a polishing slurry in which they are mixed, It is thought that the rate can be improved while maintaining the quality.
  • the manufacturing method of the glass substrate for hard disks of this invention is very useful on industrial use.
  • the manufacturing method of the glass substrate for hard disks according to the present embodiment includes at least the polishing step, the other steps are not particularly limited, and a step that can be used in a conventionally known manufacturing method is appropriately used. it can.
  • a melting process glass blanks manufacturing process
  • a disk processing process a rough grinding process (first grinding process), a fine grinding process (second grinding process), and a rough polishing process
  • Primary polishing step cleaning step, chemical strengthening step, mirror polishing step (secondary polishing step), and a method including a final cleaning step.
  • each said process may be performed in this order, and the order of a chemical strengthening process and a mirror polishing process (secondary polishing process) may be replaced.
  • a method including steps other than these may be used.
  • a heat treatment step, a shape processing step, a coring step, an end surface polishing step, and an inspection step may be performed.
  • the polishing step of the present embodiment may be performed in a rough polishing step (primary polishing step) or may be performed in a mirror polishing step (secondary polishing step). Furthermore, it is desirable to perform both in the rough polishing process and the mirror polishing process in order to achieve more effects.
  • each symbol indicates the following: 1 molding press, 2 upper press, 3 upper mold, 4 first molding surface, 5 lower mold, 6 second molding surface, 7 lower press machine, 8 rotary shaft, 9 rotary table, 21 outflow nozzle, 23 molten glass.
  • a glass material for example, a general aluminosilicate glass is used.
  • the aluminosilicate glass is composed of 58 mass% to 75 mass% SiO 2 , 5 mass% to 23 mass% Al 2 O 3 , 3 mass% to 10 mass% Li 2 O, and 4 mass% to 13 mass. % Na 2 O as a main component.
  • the glass material is not limited to aluminosilicate glass, and may be any material such as soda lime glass or borosilicate glass.
  • glass blanks which are intermediate molded bodies of glass substrates for hard disks, are produced by the direct press method. These glass blanks are generally manufactured by supplying molten glass and press-molding while cooling the molten glass.
  • heat treatment may be applied to correct the flatness of the glass blank and remove internal strain.
  • a coring process may be provided in order to obtain a donut-shaped substrate.
  • FIG. 1 is a schematic view of a mold and a press for producing the glass blanks of the present embodiment by press molding.
  • the press 1 for forming glass blanks is supplied with molten glass, and includes a lower mold 5 and a lower part 7 having a first molding surface 6 for pressurizing the supplied molten glass, and a lower mold 5. It has an upper die 3 and a press machine upper part 2 provided with a second molding surface 4 for pressurizing molten glass with one molding surface 6.
  • FIG. 2 is a perspective view showing a mechanism in which glass blanks are press-formed by the lower press 7 and the upper press 2 arranged on the rotary table.
  • the press machine lower part 7 is embedded in the rotary table 9 side by side in the circumferential direction.
  • the rotary table 9 is provided so as to be able to be driven to rotate around the rotary shaft 8 at a specific speed v (m / s).
  • the molten glass 23 is supplied to the lower mold 5 by the outflow nozzle 21 at a predetermined position on the turntable.
  • the lower mold 5 supplied with the molten glass 23 is transported by the rotary table together with the lower part 7 of the press machine, and the upper mold 3 installed on the upper part 2 of the press machine at another position is lowered to the position of the lower mold 5 to be melted. Pressurize the glass.
  • a plurality of heaters are installed inside the mold.
  • the heater is preferably arranged in one or more rounds and concentrically so as to be arranged at a uniform angle in the circumferential direction in terms of easy temperature control of the mold.
  • a plurality of heaters may or may not be arranged in the press machine lower part 7 in the same manner as the press machine upper part 2, but depending on the pressurizing time to be pressed, It is preferable that they are arranged.
  • the manufacture of the glass blanks in the present embodiment is mainly performed by a molten glass supply step for supplying molten glass to the first molding surface 6 formed on the lower mold 5 and a second molding surface formed on the upper mold 3. 4 and a pressurizing step of obtaining glass blanks by cooling the molten glass supplied to the first molding surface 6 while pressurizing it.
  • a predetermined rough surface is formed on the molding surface 6 of the lower die 5 and the molding surface 4 of the upper die 3 for the purpose of improving the grinding rate in the next grinding step and suppressing grinding variation, and pressurizes the glass blank surface.
  • the rough surface shape of the molding surface of each mold is transferred during the process.
  • the heat treatment step is a step aimed at correcting the flatness of glass blanks and removing internal strain.
  • a method of heat processing For example, the method of using a setter (alumina, zirconia, etc.) and stacking alternately with glass blanks, putting into a heat processing furnace, and applying heat can be employ
  • the temperature during the heat treatment can be performed in a temperature range from Tg to Tg + 100 (° C.) of the glass blank.
  • a coring process is a process of forming an inner hole (center hole) in the center part of the surface of the obtained glass blanks using a diamond core drill.
  • the center of the glass blanks is determined by this coring process.
  • a glass blank means the glass molding before finishing the coring process and performing the grinding process (1st grinding process) of the main plane mentioned later.
  • the glass blanks that have been subjected to the coring (inner peripheral cut) process are ground with a diamond grindstone on the inner peripheral end face and the outer peripheral end face that face the hole in the center portion.
  • chamfering is also performed. For example, in the case of a 2.5 inch hard disk, a predetermined chamfering process is performed after setting the outer diameter to 65 mm and the inner diameter (diameter of the circular hole 1H in the center) to 20 mm.
  • the surface roughness of the end face of the glass blanks at this time is about 2 ⁇ m in Rmax.
  • the grinding process is performed, for example, using a double-side grinding (lapping) device using a planetary gear mechanism. Specifically, the lapping platen is pressed from above and below on both main surfaces of the glass blanks obtained above, the grinding liquid is supplied onto both main surfaces, and the glass blanks and lapping platen are relatively moved. Thus, a grinding process is performed. By the grinding process, the approximate parallelism, flatness, thickness and the like of the glass substrate are preliminarily adjusted, and a glass substrate (glass base material) having a substantially flat main surface is obtained.
  • the grinding liquid for example, a grinding liquid containing alumina abrasive grains having a particle size of # 400 (particle size of about 40 to 60 ⁇ m) is used. By setting the upper surface plate load to about 100 kg, both surfaces of the glass blanks are faced. It may be finished to an accuracy of 0 ⁇ m to 1 ⁇ m and a surface roughness Rmax of about 6 ⁇ m.
  • grinding may be performed using a fixed abrasive type grinding pad in which diamond particles are supported on a resin, ceramic, or metal, which has the advantage of improving the balance between grinding speed and quality after grinding.
  • the particle diameter of diamond can be appropriately changed depending on the purpose, but the average particle diameter used in the first grinding is preferably 2 ⁇ m to 10 ⁇ m. If the diamond particle size is less than 2 ⁇ m for the first lapping, the processing speed is insufficient, and cracks generated on the main surface (upper and lower surfaces) of the glass substrate may not be removed. If the particle diameter of diamond exceeds 10 ⁇ m, there is a risk that cracks may occur on the main surfaces 2 and 3 of the glass substrate 1 due to diamond.
  • a diamond pad having a particle size smaller than that of the diamond particles used in the first grinding it is preferable to use a diamond pad having a particle size smaller than that of the diamond particles used in the first grinding, so that a surface suitable for polishing in the next step is used. Properties can be formed.
  • diamond particles having an average particle diameter of 1 ⁇ m to 5 ⁇ m are used. With the recent increase in density, the diamond particle diameter is becoming smaller, but a balance of workability is required, so 1.5 ⁇ m to 4 ⁇ m is more preferable.
  • the glass substrate main surface (upper and lower surfaces) is ground to a thickness of about 50 ⁇ m to 250 ⁇ m.
  • mirror polishing by brush polishing may be performed on the inner peripheral end surface of the glass substrate. Specifically, by supplying a polishing liquid containing an abrasive to the polishing brush, placing the polishing brush in contact with the inner peripheral end surface of the glass substrate, and then applying the polishing brush while rotating the glass substrate The inner peripheral end face of the glass substrate is polished.
  • abrasive cerium oxide is usually selected and supplied as a polishing liquid at an appropriate concentration.
  • the polishing brush a brush having an appropriate hardness and diameter is selected so that the polishing can be performed softly without damaging the end face.
  • an outer peripheral polishing step may be further performed.
  • mirror polishing by brush polishing is performed on the outer peripheral end surface of the glass substrate.
  • a polishing liquid containing an abrasive to the polishing brush, placing the polishing brush in contact with the outer peripheral end surface of the glass substrate, and applying the polishing brush while rotating the glass substrate, The outer peripheral end surface of the glass substrate is polished.
  • the abrasive and the polishing brush are selected in the same manner as the abrasive and the polishing brush used for polishing the inner peripheral end face of the glass substrate.
  • the polishing step is a step of polishing the glass substrate with a polishing slurry containing abrasive particles.
  • the glass substrate is divided into the abrasive particle group A having a predetermined average particle diameter and the particles.
  • a polishing slurry A containing the optimum dispersant for the group A, an abrasive particle group B having an average particle size larger than the particle group A, and a polishing slurry B containing the optimum dispersing agent for the particle group B are mixed. Polishing is performed using the resulting polishing slurry.
  • abrasive particle groups having different average particle diameters are prepared in advance, and the optimum dispersant (particle aggregation is controlled for each particle group to maintain the average particle diameter in the particle group.
  • a plurality of polishing slurries are prepared by mixing a dispersing agent that can be used, and a polishing slurry obtained by mixing them is used.
  • the polishing step of this embodiment using a polishing slurry in which abrasive particles having different particle size distributions are mixed is a rough polishing step (primary polishing). Step) or at least one of a mirror polishing step (secondary polishing step). Furthermore, it is desirable because a higher effect can be obtained by performing both in the rough polishing step and the mirror polishing step.
  • the abrasive particles contained in the polishing slurry are not particularly limited, but it is preferable to use particles having the same composition. That is, the polishing slurry preferably used in the present embodiment is a polishing slurry in which a plurality of abrasive particle groups having the same composition and different average particle sizes (particle size distribution) are mixed.
  • a polishing slurry C containing an abrasive particle group C having an average particle diameter intermediate between the particle group A and the particle group B, and a dispersing agent optimum for the particle group C is obtained by using the polishing slurry A and the polishing slurry as described above.
  • a polishing slurry mixed with B can also be used.
  • polishing slurry used in the polishing process of this embodiment will be described more specifically.
  • the abrasive can be appropriately selected depending on whether it is used for rough polishing or mirror polishing.
  • cerium oxide, zirconium oxide, zirconium silicate and the like are preferable for rough polishing; colloidal silica and the like are preferable for mirror polishing.
  • the average particle size in the slurry varies slightly depending on the type of abrasive used.
  • cerium oxide it is preferable to use about 0.5 to 2.5 ⁇ m.
  • a slurry in which these are dispersed in a solvent is preferable.
  • Neutral water and acidic / alkaline aqueous solution can be employ
  • a dispersant that is compatible with the distribution of particle groups is added.
  • the average particle diameter is less than 0.5 ⁇ m, the polishing pad tends to be unable to polish both main surfaces well. On the other hand, when the average particle diameter exceeds 2.5 ⁇ m, the polishing pad may deteriorate the flatness of the end face or cause scratches.
  • colloidal silica when colloidal silica is used, it is preferable to use a slurry obtained by dispersing colloidal silica having an average particle diameter of 10 to 80 nm in a solvent. Also in this case, it does not specifically limit as a solvent, Neutral water and acidic alkaline aqueous solution can be employ
  • a classifier is used to divide the particles into a group of particles having an average particle size (particle size distribution) on the large particle size side and a small particle size side, and according to the average particle size of each particle size distribution, a suitable dispersant and solvent are used.
  • a slurry small average particle size (small particle size): slurry A, large average particle size (large particle size): slurry B) is adjusted.
  • a suitable mixing ratio preferably 1: 1) and used for polishing.
  • the ratio of the slurry A containing the particle group on the small particle size side and the slurry B containing the particle group on the large particle size side in this embodiment is preferably in the range of 0.8 to 1.2 in A / B, 0.9 To 1.1 are more preferable. Further, when the intermediate particle group C is included, the ratio thereof is A: B: C and is mixed in the range of about 0.1 to 0.4: 0.2 to 0.7: 0.1 to 0.4. It is preferable.
  • the average particle size of the particle group B is larger than the average particle size of the particle group A, but the deviation of the average particle size of each particle group varies depending on the abrasive type. For example, in the case of cerium oxide, it can be set with a deviation of 0.3 to 0.7 ⁇ m.
  • the intermediate particle group C it is preferable to use intermediate particles separated from each of the particle groups A and B by at least 0.1 ⁇ m to 0.5 ⁇ m.
  • the group A and the group B are set with a difference of 20 to 60 nm.
  • the intermediate particle group C it is preferable to use intermediate particles separated from each of the particle groups A and B by at least 10 nm to 30 nm.
  • the dispersant used in this embodiment will be described.
  • polymer compounds having various functional groups are used.
  • the functional group carboxylic acid, carboxylate, sulfonic acid, sulfonate and the like are selected, and the counter cation forming the salt can be selected from alkali metal ions, ammonium and the like.
  • the polymer may be a copolymer.
  • the monomer type, the counter cation type, and the molecular weight of the polymer are appropriately selected so that the particle size distribution of each particle group described above can be maintained.
  • the dispersant suitable for the abrasive particle group A having a predetermined average particle size is selected to have a smaller molecular weight than the dispersant suitable for the abrasive particle group B having an average particle size larger than that of the particle group A.
  • the monomer structure preferably has a small number of functional groups (for example, one), and the functional group species may include a carboxylic acid or a salt thereof, but a sulfonic acid or a salt thereof is more preferable.
  • a dispersant having a relatively high molecular weight is preferably selected as the dispersant suitable for the abrasive particle group B having a large particle size distribution, and the monomer structure has a larger number of functional groups (for example, 2 or more). Liked. Moreover, as a kind of functional group, carboxylic acid or its salt is preferable.
  • a sulfonic acid polymer having a molecular weight in the range of 500 to 2000 can be selected as the dispersant for the particle group A, and a dispersant having a molecular weight of 10,000 to 20000, for example, can be selected.
  • a range of maleic acid polymers can be selected, but is not limited thereto.
  • a dispersant suitable for the intermediate particle group C is a polymer having a molecular weight located between the particle groups A and B in terms of molecular weight, and the molecular structure is a monomer having one functional group and two monomers having a functional group. And a copolymer thereof can be preferably used.
  • the rough polishing step is a step of polishing both the main surfaces of the glass substrate with a polishing slurry so that the surface roughness finally required in the subsequent mirror polishing step can be efficiently obtained. It does not specifically limit as a grinding
  • polishing pad used it is preferable to use a hard pad, for example, urethane foam is preferable because the shape change of the polishing surface increases when the hardness of the polishing pad decreases due to heat generated by polishing.
  • a suede pad can also be used for further quality improvement.
  • polishing slurry it is preferable to use the polishing slurry of the present embodiment as described above (especially, one using cerium oxide).
  • the polishing slurry of the present embodiment is used in the mirror polishing step described later, In this rough polishing step, a known polishing slurry used in normal rough polishing (cerium oxide having an average primary particle size of 0.5 to 2.5 ⁇ m, zirconium oxide, zirconium silicate is dispersed in a solvent. It is also possible to appropriately use a slurry).
  • the polishing rate can be kept high even if a suede pad with low hardness is used.
  • the supply amount of the polishing slurry is not particularly limited and is, for example, 5 to 10 L / min.
  • the polishing amount of the glass substrate in the rough polishing step is preferably about 20 to 40 ⁇ m.
  • the polishing amount of the glass substrate is less than 20 ⁇ m, there is a tendency that scratches and defects are not sufficiently removed.
  • the polishing amount of the glass substrate exceeds 40 ⁇ m, the glass substrate is polished more than necessary, and the production efficiency tends to decrease.
  • the glass substrate after the rough polishing step is preferably washed with a neutral detergent, pure water, IPA or the like.
  • a cleaning step may be provided, and the surface of the glass substrate 1 using a cleaning solution containing sulfuric acid and / or hydrofluoric acid for the purpose of removing any of the abrasive cerium oxide, zirconium oxide, or zirconium silicate in the previous step. Clean while etching.
  • a polishing slurry such as cerium oxide, zirconium oxide, or zirconium silicate adhering to the surface of the glass substrate is appropriately removed by a strongly acidic cleaning liquid such as sulfuric acid and / or hydrofluoric acid. Thereafter, the glass substrate 1 is cleaned using an acidic cleaning solution.
  • the cleaning liquid used in the cleaning step varies depending on the chemical resistance of the glass substrate 1, but a concentration of about 1% by mass to 30% by mass is preferable for sulfuric acid, and 0.2% by mass for hydrofluoric acid. A concentration of about 5% by mass is preferred. Cleaning using these cleaning liquids may be performed while applying ultrasonic waves in a cleaning machine in which an aqueous solution is stored.
  • the frequency of the ultrasonic wave used at this time is preferably 78 kHz or higher.
  • the mirror polishing process is a process of polishing both main surfaces of the glass substrate more precisely.
  • a double-side polishing machine similar to the double-side polishing machine used in the rough polishing process can be used.
  • the polishing pad is preferably a soft pad having a lower hardness than the polishing pad used in the rough polishing step, and for example, urethane foam or suede is preferably used.
  • the polishing slurry a slurry containing cerium oxide or the like similar to the rough polishing step can be used, but in order to make the surface of the glass substrate smoother, the polishing slurry has a finer grain size and less variation. Is preferably used. For example, it is preferable to use a slurry obtained by dispersing colloidal silica having an average primary particle size of 10 to 80 nm in a solvent to form a slurry.
  • a known polishing slurry preferably, colloidal silica used for normal mirror polishing is used in the mirror polishing step. Can be used as appropriate.
  • the polishing slurry according to the present embodiment as described above (particularly, using colloidal silica) in the mirror polishing step in addition to the rough polishing step. .
  • this embodiment it is possible to polish with high accuracy and provide high quality.
  • the supply amount of the polishing slurry is not particularly limited, and is, for example, 0.5 to 1 L / min.
  • the polishing amount in the mirror polishing step is preferably about 2 to 5 ⁇ m.
  • the obtained glass substrate can remove fine defects such as minute roughness and waviness generated on the surface of the glass substrate, or minute scratches generated in the previous process. Is done.
  • the glass substrate manufacturing method of the present embodiment can improve the flatness of the obtained glass substrate, and can manufacture a glass substrate on which the magnetic head can float more stably in the end region. .
  • this step by appropriately adjusting the polishing conditions in the mirror polishing step, the flatness of both main surfaces of the glass substrate is reduced to 2 ⁇ m or less, and the surface roughness Ra of both main surfaces of the glass substrate is reduced to 0.1 nm. be able to.
  • the chemical strengthening step is a step of immersing the glass substrate in a strengthening treatment liquid to improve the impact resistance, vibration resistance, heat resistance, and the like of the glass substrate.
  • the chemical strengthening step is a step of chemically strengthening the glass substrate.
  • the strengthening treatment liquid used for chemical strengthening include a mixed solution of potassium nitrate (60%) and sodium nitrate (40%).
  • Chemical strengthening can be performed by heating the strengthening treatment liquid to 300 to 400 ° C., preheating the glass substrate to 200 to 300 ° C., and immersing in the strengthening treatment liquid for 3 to 4 hours. In this immersion, it is preferable that the immersion is performed in a state of being housed in a holder that holds the end faces of the plurality of glass substrates so that both main surfaces of the glass substrate are chemically strengthened.
  • a standby process for waiting the glass substrate in the air and a water immersion process are adopted to remove the strengthening treatment liquid adhering to the surface of the glass substrate and to homogenize the surface of the glass substrate. It is preferable.
  • the chemically strengthened layer is formed uniformly, the compressive strain is uniform, deformation is difficult to occur, the flatness is good, and the mechanical strength is also good.
  • the waiting time and the water temperature in the water immersing step are not particularly limited. For example, it may be kept in the air for 1 to 60 seconds and immersed in water at about 35 to 100 ° C., and may be determined appropriately in consideration of production efficiency.
  • the final cleaning step is a step of cleaning and cleaning the glass substrate. It does not specifically limit as a washing
  • a cleaning liquid such as a detergent or pure water is used.
  • the pH of the cleaning solution used for scrub cleaning is preferably 9.0 or more and 12.2 or less. Within this range, the ⁇ potential can be easily adjusted and scrub cleaning can be performed efficiently.
  • both scrub cleaning with a detergent and scrub cleaning with pure water may be performed.
  • the glass substrate 1 By using a detergent and pure water, the glass substrate 1 can be more appropriately cleaned.
  • the glass substrate 1 may be further rinsed with pure water between scrub cleaning with a detergent and scrub cleaning with pure water.
  • the glass substrate may be further subjected to ultrasonic cleaning.
  • ultrasonic cleaning with chemical solution such as sulfuric acid aqueous solution, ultrasonic cleaning with pure water, ultrasonic cleaning with detergent, ultrasonic cleaning with IPA, and / or steam drying with IPA, etc. Further, it may be performed.
  • the cleaned glass substrate is subjected to ultrasonic cleaning and drying processes as necessary.
  • the drying step is a step of drying the surface of the glass substrate after removing the cleaning liquid remaining on the surface of the glass substrate with isopropyl alcohol (IPA) or the like.
  • IPA isopropyl alcohol
  • a water rinse cleaning process is performed on the glass substrate after scrub cleaning for 2 minutes to remove the cleaning liquid residue.
  • an IPA cleaning process is performed for 2 minutes, and water remaining on the surface of the glass substrate is removed by IPA.
  • the IPA vapor drying step is performed for 2 minutes, and the liquid IPA adhering to the surface of the glass substrate is dried while being removed by the IPA vapor.
  • the drying process of the glass substrate is not particularly limited, and for example, a known drying method such as spin drying or air knife drying can be employed.
  • the glass substrate that has undergone the final cleaning step may be further subjected to an inspection step before shipment.
  • the inspection step is a step of inspecting the glass substrate that has undergone the above-described steps for the presence or absence of scratches, cracks, foreign matters, and the like.
  • the inspection is performed visually or using an optical surface analyzer (for example, “OSA6100” manufactured by KLA-TENCOL).
  • OSA6100 manufactured by KLA-TENCOL
  • the method for manufacturing a glass substrate for hard disk includes a polishing step of polishing a glass substrate with a polishing slurry containing abrasive particles, and in the polishing step, An abrasive slurry A containing an abrasive particle group A having an average particle size and a dispersant optimal for the particle group A, an abrasive particle group B having an average particle size larger than the particle group A, and the particle group B Polishing is performed using a polishing slurry obtained by mixing polishing slurry B containing an optimal dispersant.
  • each abrasive particle Agglomeration changes the particle size distribution of the abrasive particles derived from each polishing slurry.
  • the particle size distribution in the mixed polishing slurry can be suppressed, and the quality of the polished surface is maintained.
  • the polishing rate can be stably maintained, it is possible to efficiently manufacture an excellent glass substrate.
  • the polishing slurry further includes an abrasive particle group C having an average particle diameter intermediate between the particle group A and the particle group B, and a dispersant optimal for the particle group C. It is more preferable to use a polishing slurry obtained by mixing the polishing slurry A and the polishing slurry B. With such a configuration, the particle distribution can have a shape more suitable for stabilizing the polishing rate, and the optimum particle size distribution can be maintained with higher accuracy, so that higher quality and higher rate can be provided.
  • the manufacturing method includes a rough polishing step and a mirror polishing step as the polishing step, and polishing is performed using the polishing slurry in at least one of the rough polishing step and the mirror polishing step.
  • the polishing process is performed in two stages, and at least one of them is used in the polishing slurry according to the present invention, leading to stabilization of the polishing rate of the applied process.
  • rough polishing is performed. It is considered that high quality can be obtained because the variation in the subsequent substrate removal is small and a more uniform surface state can be obtained, so that high-precision polishing is possible in the subsequent precision polishing step.
  • high surface quality can be obtained because the fluctuation of processing at the time of precision polishing is reduced and more precise conditions can be taken.
  • the manufacturing method it is preferable to polish using the polishing slurry in both the rough polishing step and the mirror polishing step. With such a configuration, it is possible to provide a higher-quality glass substrate suitable for high-density hard disk drives and media.
  • cerium oxide as abrasive particles in the rough polishing step.
  • Zirconium oxide, zircon, or the like may be used.
  • cerium oxide the effects of rate stabilization and reduction in machining allowance variation intended by the present invention can be exhibited more highly.
  • colloidal silica is suitable for obtaining higher surface quality.
  • the concentration of the abrasive component is 0.2 to 20% by mass in each of the polishing slurries.
  • a suede pad as a polishing pad in the rough polishing step.
  • the polishing quality is further improved, and by using the polishing slurry, the stability of the polishing rate can be obtained even if a suede pad is used.
  • Example 1 Glass melting process
  • each raw material was prepared and melted at 1500 ° C. using a platinum crucible.
  • a glass gob supplied to the center of the lower mold forming surface was used with an upper mold facing the lower mold, and a tungsten-based material was used for the upper mold and the lower mold.
  • the pressing time was 1 second, and butt molding was performed so that the thickness of the blanks after molding was uniform.
  • the plate thickness after molding was 1.1 mm on average.
  • the main surface (upper and lower surfaces) of the glass substrate was processed by using diamond grains made of acrylic resin as abrasive grains.
  • the diamond particle diameter was 4 ⁇ m.
  • the main surface (upper and lower surfaces) of the glass substrate was processed using a diamond-shaped diamond resin sheet.
  • a diamond particle diameter of 1.5 ⁇ m was used.
  • the glass substrate 1 main surface (upper and lower surfaces) was ground to about 250 ⁇ m.
  • a cerium oxide abrasive having an average particle size of 1.2 ⁇ m and a wide particle size distribution is applied to a classifier, and the cerium oxide abrasive having an average particle size of 0.95 ⁇ m and an average particle size of 0.4 ⁇ m is obtained. Abrasive and obtained.
  • the polishing slurry A and the slurry B were mixed one-on-one to obtain a polishing liquid used for rough polishing.
  • both main surfaces of 100 glass substrates were subjected to rough polishing using a double-side polishing machine (manufactured by Hamai Sangyo Co., Ltd., 16B type) using the above polishing liquid.
  • a suede urethane pad was used as the polishing pad.
  • the load was 120 g / cm 2 .
  • the supply amount of the polishing slurry was 10 L / min.
  • the polishing liquid is supplied from the slurry tank to the polishing machine, and the liquid used in the processing is discharged from the polishing machine and returned to the slurry tank at the same time, and is circulated through the slurry tank and used for processing.
  • the polishing time was set to 45 minutes.
  • polishing was performed continuously for 10 batches, with 100 glass substrates being polished per batch as one batch.
  • the polishing rate is derived by dividing by the polishing time, and is shown in Table 1 below.
  • chemical strengthening process chemical strengthening was performed on the glass substrate after the above steps. Specifically, first, a mixed melt obtained by melting a solid of potassium nitrate and sodium nitrate was prepared. In addition, this mixed melt is mixed so that the mixing ratio of potassium nitrate and sodium nitrate is 6: 4 by mass ratio. Then, this mixed melt was heated to 400 ° C., and the washed glass base plate was immersed in the heated mixed melt for 60 minutes.
  • the glass substrate was scrubbed.
  • a cleaning liquid a liquid obtained by diluting KOH and NaOH mixed at a mass ratio of 1: 1 with ultrapure water (DI water) and adding a nonionic surfactant to enhance the cleaning performance is obtained.
  • DI water ultrapure water
  • the cleaning liquid was supplied by spraying. After scrub cleaning, in order to remove the cleaning liquid remaining on the surface of the glass substrate, a water rinse cleaning process is performed in an ultrasonic bath for 2 minutes, an IPA cleaning process is performed in an ultrasonic bath for 2 minutes, and finally the glass substrate is cleaned with IPA vapor. The surface of was dried.
  • Example 2 A glass substrate was obtained in the same manner as in Example 1 except that the following polishing slurry was used in the rough polishing step.
  • a cerium oxide abrasive having an average particle size of 1.2 ⁇ m and a wide particle size distribution is applied to a classifier several times, and the cerium oxide abrasive having an average particle size of 0.98 ⁇ m and an oxidation of an average particle size of 0.67 ⁇ m.
  • a cerium oxide abrasive having a particle size distribution with a cerium abrasive and an average particle size of 0.37 ⁇ m was obtained.
  • a slurry was prepared with a concentration of 9% by mass. This is designated as slurry C.
  • the copolymer used here was a copolymer having a maleic acid / acrylic acid ratio lower than that used for 0.95 ⁇ m.
  • Slurry A ', Slurry B', and Slurry C were mixed so as to have the above mixing ratio to obtain a polishing liquid used for rough polishing.
  • Example 1 A glass substrate was obtained in the same manner as in Example 1 except that the following polishing slurry D was used in the rough polishing step.
  • a cerium oxide abrasive with an average particle size of 1.2 ⁇ m and a wide particle size distribution, a copolymer of maleic acid and acrylic acid (MW 12000) is added as a dispersant and neutral water is used as a dispersion medium.
  • a polishing slurry was prepared with a material concentration of 10% by mass. This was designated polishing slurry D.
  • Example 2 A glass substrate was obtained in the same manner as in Example 1 except that the following polishing slurry E was used in the rough polishing step.
  • a slurry prepared by using an acrylic acid polymer (MW 5000) as a dispersing agent to a polishing agent concentration of 10% by mass with respect to a cerium oxide abrasive having an average particle size of 1.2 ⁇ m and a wide particle size distribution. It was.
  • Slurries 1 and 2 were mixed so as to have the following silica ratio to obtain a polishing liquid used for precision polishing.
  • both main surfaces of the glass substrate were polished more precisely using a double-side polishing machine (manufactured by Hamai Sangyo Co., Ltd., 16B type).
  • the load was 120 g / cm 2 and the supply amount of the polishing slurry was 10 L / min.
  • 100 batches of glass substrates were processed as 10 batches.
  • the polishing liquid is supplied from the slurry tank to the polishing machine, and the liquid used in the processing is discharged from the polishing machine and returned to the slurry tank at the same time, and is circulated through the slurry tank and used for processing.
  • the polishing time was set to 30 minutes.
  • polishing rate was derived by dividing by 2 and is shown in Table 2 below.
  • Example 4 In the mirror polishing step, a glass substrate was obtained in the same manner as in Comparative Example 1 except that the following polishing slurry was used.
  • colloidal silica having an average primary particle size of 9 nm, colloidal silica having an average primary particle size of 20 nm, and colloidal silica having an average primary particle size of 35 nm are prepared.
  • Polishing slurries 1 ', 3, and 2' were mixed so as to have the following silica ratio to obtain a polishing liquid used for precision polishing.
  • Comparative Example 3 In the mirror polishing step, a glass substrate was obtained in the same manner as in Comparative Example 1 except that the following polishing slurry 4 was used.
  • Neutral water was used as a dispersion medium
  • the abrasive concentration was 20 mass%
  • the pH was adjusted with a liquid further containing sulfuric acid to obtain a polishing slurry 4.
  • Example 5 In the mirror polishing process, a glass substrate was obtained in the same manner as in Example 1 except that the polishing slurry of Example 3 was used.
  • the polishing rate was derived by dividing by the polishing time.
  • the thickness was measured using a Mitutoyo micrometer (measuring instrument).
  • polishing rate of mirror polishing and maximum thickness difference ⁇ t For the glass substrates obtained in Examples 3 to 4 and Comparative Example 3, the polishing rate after mirror polishing and the maximum thickness difference ⁇ t were evaluated. Polishing was performed continuously for 10 batches, with 100 batches of glass substrate polishing per batch.
  • the polishing rate was derived by dividing by the polishing time.
  • the thickness was measured using a Mitutoyo micrometer (measuring instrument). The results are shown in Table 2.
  • OSA defect count
  • defect inspection As the test apparatus, an optical defect inspection apparatus Candela-OSA6100 manufactured by KLA-Tencor was used.
  • the glass substrate obtained by the production method according to the present invention is excellent in rate stability in the rough polishing step, as compared with the glass substrate of the comparative example obtained by the conventional method.
  • the defect evaluation results also showed that there was very little variation in polishing allowance within one batch, and the final surface quality was excellent.
  • polishing rate was remarkably stabilized and the surface quality was excellent by using a slurry composed of three particle size distributions and each composed of a dispersing agent optimal for different distributions.
  • the rate stability in the precision polishing step is further improved, and the polishing allowance is reduced. It can be seen that the variation is further suppressed.
  • the degree of non-defective product by defect count is rank A, and there is no difference from the level where the present invention is applied to one process, but the non-defective product rate applied to both processes is 100-99%. It is found that the level is higher than the level (95 to 97%) of Examples 1 and 3 applied to No. 1, and the surface quality is also excellent.
  • the present invention has wide industrial applicability in the technical field of glass substrates for hard disks and their manufacturing methods.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

Abstract

Un aspect de la présente invention concerne un procédé de fabrication d'un substrat de verre pour disque dur, le procédé comprenant une étape de polissage destinée à polir le substrat de verre au moyen d'une boue de polissage contenant des particules abrasives, le procédé étant caractérisé en ce qu'une boue de polissage obtenue en mélangeant une boue de polissage (A), qui contient un groupe de particules abrasives (A) ayant un diamètre de particule moyen prescrit et un dispersant très adapté au groupe de particules (A), et une boue de polissage (B), qui contient un groupe de particules abrasives (B) ayant un diamètre de particule moyen plus élevé que celui du groupe de particules (A) et un dispersant très adapté au groupe de particules (B), est utilisée pour polir le substrat de verre lors de l'étape de polissage.
PCT/JP2014/000067 2013-01-23 2014-01-10 Procédé de fabrication de substrat de verre pour disque dur WO2014115495A1 (fr)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001288455A (ja) * 2000-02-03 2001-10-16 Kao Corp 研磨液組成物
JP2001323254A (ja) * 2000-05-12 2001-11-22 Kao Corp 研磨液組成物
JP2004253058A (ja) * 2003-02-20 2004-09-09 Kao Corp 研磨液組成物
JP2005187664A (ja) * 2003-12-25 2005-07-14 Fujimi Inc 研磨用組成物及びそれを用いた研磨方法
JP2007321159A (ja) * 2007-08-01 2007-12-13 Yamaguchi Seiken Kogyo Kk 硬脆材料用精密研磨組成物
JP2010192041A (ja) * 2009-02-18 2010-09-02 Fuji Electric Device Technology Co Ltd 磁気記録媒体用ガラス基板の製造方法、それが使用される磁気記録媒体用ガラス基板、および、垂直磁気記録媒体
JP2012209010A (ja) * 2011-03-15 2012-10-25 Asahi Glass Co Ltd 磁気記録媒体用ガラス基板の製造方法

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001288455A (ja) * 2000-02-03 2001-10-16 Kao Corp 研磨液組成物
JP2001323254A (ja) * 2000-05-12 2001-11-22 Kao Corp 研磨液組成物
JP2004253058A (ja) * 2003-02-20 2004-09-09 Kao Corp 研磨液組成物
JP2005187664A (ja) * 2003-12-25 2005-07-14 Fujimi Inc 研磨用組成物及びそれを用いた研磨方法
JP2007321159A (ja) * 2007-08-01 2007-12-13 Yamaguchi Seiken Kogyo Kk 硬脆材料用精密研磨組成物
JP2010192041A (ja) * 2009-02-18 2010-09-02 Fuji Electric Device Technology Co Ltd 磁気記録媒体用ガラス基板の製造方法、それが使用される磁気記録媒体用ガラス基板、および、垂直磁気記録媒体
JP2012209010A (ja) * 2011-03-15 2012-10-25 Asahi Glass Co Ltd 磁気記録媒体用ガラス基板の製造方法

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