JP5305698B2 - Method for manufacturing glass substrate for magnetic disk, method for manufacturing magnetic disk, and glass substrate for magnetic disk - Google Patents

Description

  The present invention relates to a method of manufacturing a glass substrate for a magnetic disk, a method of manufacturing a magnetic disk using such a glass substrate, and a glass substrate for a magnetic disk.

  In the grinding process in the manufacturing process of a glass substrate for magnetic disks, conventionally, lapping is performed by using a cast iron surface plate and grinding while supplying a grinding liquid (slurry) containing loose abrasive grains between the glass substrate and the surface plate. Has been done. At this time, the smoothness of the ground surface of the surface plate decreases as grinding is performed.

  When correcting a ground surface with reduced smoothness as described above, typically, a planetary gear-type surface plate is used, and a correction ring is sandwiched between the upper surface plate and the lower surface plate, in the same manner as in the grinding process. The surface plate was shaved by supplying pressure to the surface plate while supplying free abrasive grains, and the smoothness of the surface plate was recovered. The facets generated when the surface plate is shaved by such correction are not discharged from the surface plate and function as a grindstone. That is, the smoothness of the surface plate is corrected by using the facets and loose abrasive grains.

  A method such as lapping that repeats grinding and correction as described above is called a loose abrasive method. However, grinding using the loose abrasive method has problems such as long processing time, poor efficiency, and sagging at the edges. On the other hand, in recent years, the accuracy required for grinding with a surface plate has increased, and it has become necessary to improve the smoothness of glass substrates more than ever.

  Due to these circumstances, the loose abrasive method such as lapping has been replaced by a fixed abrasive method that has been developed in recent years, using a surface plate in which fine resinoid bond diamond containing fine diamond is affixed to the grinding surface as fixed abrasive. (Patent Documents 1 to 3).

  However, even when the main surface of the glass substrate is ground using the surface plate of the fixed abrasive method, as the grinding is continued, the abrasive grains fall off and the smoothness of the ground surface is gradually lowered, and gradually to the glass substrate. There is a drawback that smoothness cannot be imparted. Specifically, undulation is formed on the ground surface of the surface plate.

In order to correct such undulation, there is a method for correcting the smoothness of the surface grinding surface using a grindstone. Specifically, the facet generated when the grindstone is shaved acts as an abrasive and corrects the smoothness of the surface plate to which fixed abrasive grains containing diamond particles are attached (Patent Document 4).
JP-A-2005-202997 JP 2001-191247 A Japanese Patent No. 2977508 JP 2000-153458 A

  However, when the smoothness of the surface plate is corrected using a grindstone, undulation having a shape wavelength larger than that generated by the grinding process of the glass substrate is generated. This is because the grindstone has the same thickness as the cast iron correction ring and is strong against bending. Although the smoothness of the surface plate is improved as the shape wavelength of the undulation generated is larger than before correction, the undulation still remains. Unless this undulation is corrected, the surface plate cannot impart smoothness to the glass substrate in the grinding process.

  In view of such problems, the present invention is a method for producing a magnetic disk glass substrate that is excellent in smoothness by efficiently and accurately correcting the undulation of a surface plate to which fixed abrasive grains are bonded. It is an object of the present invention to provide a manufacturing method, a magnetic disk manufacturing method for manufacturing a magnetic disk from such a glass substrate, and a magnetic disk glass substrate excellent in smoothness.

  In order to solve the above-described problem, the method for manufacturing a glass substrate for a magnetic disk according to the present invention is a grinding method in which a main surface of a glass substrate is ground using a surface plate in which fixed abrasive grains containing diamond particles are arranged on a grinding surface. And a correction step in which the correction surface of the correction member whose correction surface is made of a glass material and the ground surface of the surface plate are pressed against each other and slid after the grinding step. This improves the smoothness of the ground surface of the surface plate.

  Another method of manufacturing a glass substrate for a magnetic disk according to the present invention is to grind the main surface of a glass substrate using a surface plate in which fixed abrasive grains including diamond particles are arranged on a grinding surface in order to solve the above-described problems. And after the grinding process, the correction surface of the correction member whose correction surface is made of a glass material and the grinding surface of the surface plate are pressed against each other and slid, and the grinding surface of the surface plate is cooled with coolant. It is good to include the correction process which removes the facet which arises during a correction process from the grinding surface by supplying and circulating coolant and filtering.

  The reason for removing the facets in this way is as follows. In other words, if there is a face in the coolant that circulates between the coolant container and the surface plate, moisture will evaporate in the middle of the flow, or waves may be generated, agglomerating and forming foreign objects. It is because there is a possibility of causing.

  The correction process described above may be performed using a planetary gear system.

  Further, prior to the above-described grinding step, a fixed abrasive grain disposing step of disposing fixed abrasive grains containing diamond particles on the ground surface of the surface plate, a ground surface of the surface plate, and a thicker correction surface than the glass substrate An initial correction step in which a correction surface of a metal correction member made of a material is slid while being pressed against each other while supplying a grinding liquid containing loose abrasive grains, a grinding surface of the surface plate, a dummy glass, It is good to include the smoothness preparation process which presses and mutually slides.

  As described above, when the smoothness of the surface plate is corrected using the metallic correction member and the grinding fluid containing loose abrasive grains, the actual grinding is different from the case where the correction is performed using the correction member and the coolant. Smoothness that can be used in the process cannot be obtained. However, immediately after fixing the fixed abrasive grains containing diamond particles to the surface plate, the smoothness is particularly inferior, so it is possible to take a large machining allowance of about several hundreds μm, although it is a rough correction, The smoothness of the entire platen can be improved.

  Thereafter, in order to prepare such smoothness that can be used in an actual grinding process, the dummy glass may be ground to reduce the roughness. Thus, by combining the correction of the large machining allowance and the modification of the small machining allowance, the undulation of the surface plate can be corrected efficiently in the present invention.

  The method of manufacturing a magnetic disk according to the present invention is characterized in that it is manufactured by forming at least a magnetic layer on a glass substrate manufactured by any one of the methods described above.

  The magnetic layer described above may include a perpendicular magnetic recording layer made of a CoCrPt-based alloy.

  A glass substrate for a magnetic disk according to the present invention is manufactured using the above-described magnetic disk manufacturing method, and is a glass substrate for a magnetic disk compatible with a DFH (Dynamic Flying Height) head.

  According to the present invention, a glass substrate for a magnetic disk excellent in smoothness is manufactured by accurately and effectively correcting the undulation of a surface plate to which a fixed abrasive is attached, and a magnetic disk is manufactured from the glass substrate. Is possible.

  Embodiments of a method for manufacturing a magnetic disk glass substrate and a method for manufacturing a magnetic disk according to the present invention will now be described in detail with reference to the accompanying drawings. In the figure, elements not directly related to the present invention are not shown. Similar elements are denoted by the same reference numerals.

  FIG. 1 is a view showing a glass substrate carrier included in a surface plate to which an embodiment of the present invention is applied. The glass substrate 100 is held on the lower surface plate 10 by a carrier 110 having a gear on the outer periphery, and the carrier 110 is engaged with the sun gear 120 and the internal gear 130. By rotating the sun gear 120 in the arrow direction, each carrier 110 revolves while rotating as a planetary gear in each arrow direction.

  5A is a cross-sectional view taken along line AA of the carrier 110 in FIG. 1. The upper surface plate 140 is movable in the vertical direction with respect to the lower surface plate 10, and the glass substrate 100 is sandwiched between the carrier 110 from above and below. This shows the state of grinding. As shown in FIG. 5 (a), the upper surface plate 140 and the lower surface plate 10 are each provided with fixed abrasive grains 150 containing diamond particles on the grinding surface, and the surface plate 200 is rotated to rotate the glass. The main surface of the substrate 100 is ground.

  The fixed abrasive 150 including diamond particles may be formed into a pellet by bonding a plurality of diamond particles as shown in FIG. 5A with a resin, or as shown in FIG. Alternatively, a diamond sheet 160 may be used that is bonded in a planar manner to the upper and lower surface plates 140 and 10 by adhesion using a resin or electrodeposition.

  As grinding is continued, undulation with a half wavelength of 60 to 70 mm is generated on the ground surface of the surface plate to which the fixed abrasive 150 containing diamond particles or the diamond sheet 160 is fixed. When the glass substrate is ground in a state where the undulation remains, the smoothness of the glass substrate (the difference in height of the entire main surface of the substrate) is deteriorated.

  Therefore, an object of the embodiment of the present invention is to smooth the ground surface of the surface plate on which the fixed abrasive grains 150 and 160 are provided, as will be described later. In the case where the pellet-shaped fixed abrasive 150 is used, smoothing means that the height is uniform with respect to the lower surface plate, and that the upper and lower surface plates are parallel and flat. In the case of the diamond sheet 160, it means that the ground surface is smoothed.

  In order to perform such correction, it is necessary to correct the undulation generated on the surface plate using a correction member. Any material can be used for the correction member as long as it can correct the undulation, but a glass material is preferable.

  FIG. 2 is a view showing a glass correction ring which is an example of a correction member used in the embodiment of the present invention. Each of the glass correction rings 202A and 202B shown in FIGS. 2A and 2B has a configuration that can replace the carrier 110 shown in FIG. That is, it may be held by carriers 210A and 210B having gears on the outer periphery, and glass may be attached to the top and bottom of metal cores 220A and 220B. Or although not shown, it is good also as plate-like glass without a core material. Here, the glass material which comprises the correction surface of a glass correction ring may be the same as that of the glass substrate 100 which is a process target, and may differ.

  The glass 230A in FIG. 2A is a rectangular glass attached along the circumference of the carrier 210A. The central portion of the carrier 210A is a circular cavity, and no glass is pasted thereon. The glass 230B in FIG. 2B is also obtained by pasting rectangular glass into two inner and outer circles at a finer pitch along the circumference of the carrier 210B. The glass affixed along the inner circle is shaped as if it had been eroded by a central cavity having a generally square shape with trimmed corners.

  As shown in FIGS. 2A and 2B, the glass of the glass correction rings 202A and 202B is disposed along the circumference of the carrier, and the entire carrier is not covered with the glass. This is because when the entire carrier is made of glass, the frictional force becomes too large when it comes into contact with the surface plate, and the glass correction ring cannot be rotated relative to the surface plate, improving the smoothness of the ground surface of the surface plate. This is because the purpose cannot be achieved. There is also the advantage of saving glass and other material costs since the entire carrier need not be coated with glass.

  FIG. 3 is a view showing that the glass correction ring shown in FIG. 2 can be replaced with the carrier shown in FIG. When the glass substrate 100 is ground, each carrier 110 is used as a planetary gear. When the smoothness of the surface plate is corrected, any one of the glass correction rings 202A and 202B shown in FIGS. Can be planetary gears. In FIG. 3, as a representative, the carrier 110 is replaced with a glass correction ring 202A.

  FIG. 4 is a diagram showing the result of the replacement shown in FIG. FIG. 4A is a view in which the carrier 110 is replaced with the glass correction ring 202A shown in FIG. 2A, and FIG. 4B is a view in which the carrier 110 is replaced with the glass correction ring 202B shown in FIG. FIG. In this way, the carrier 110 of the glass substrate 100 to be ground is replaced with the glass correction ring 202A or 202B, and the surface plate is rotated in the same manner as when the glass substrate 100 is ground. The ground surface is shaved by the glass correction ring 202A or 202B, and the smoothness is corrected.

  5 shows a cross-sectional view of the surface plate 200, FIG. 5 (a) is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 5 (b) is a cross-sectional view taken along the line XX in FIG. At the time of grinding the glass substrate 100, as shown in FIG. 5A, a carrier 110 is sandwiched between upper and lower surface plates 140, 110, and a ground surface provided with fixed abrasive grains 150 including diamond particles, The glass substrate 100 is ground by sliding the main surface against each other.

  On the other hand, when correcting the smoothness of the ground surface of the surface plate 200, as shown in FIG. 5B, the correction ring 202A replaced with the carrier 110 is sandwiched between the upper and lower surface plates 140 and 110 in the same manner as during grinding. Slide against each other. As a result, the fixed abrasive grains 150 on the grinding surface are shaved and their heights become uniform. That is, the smoothness of the ground surface, which has been reduced in the grinding process, is corrected, and the smoothness of the ground surface is restored to a state where the smoothness can be imparted to the glass substrate 100 to be ground during grinding.

  FIG. 6 is a YY cross-sectional view of FIG. In FIG. 6, a diamond sheet 160 that is bonded in a planar manner to the upper and lower surface plates 140 and 10 is used instead of the pellet-shaped fixed abrasive 150.

  5B and 6B, among the glass correction rings 202A and 202B, the glasses 230A and 230B constituting the correction surface have a thickness equal to or greater than that of the glass substrate 100 shown in FIG. 5A. .

  The reason for having such a thickness is to increase the correction capability of the correction rings 202A and 202B. In the case of a double-side polishing machine such as the upper and lower surface plates 140 and 10, the processing is easier because the bending strength increases as the thickness of the object to be processed sandwiched between them increases. The same applies when the upper and lower surface plates 140 and 10 are corrected by the correction rings 202A and 202B. The thicker the correction rings, the higher the correction capability. That is, undulation generated by processing a thin workpiece such as the glass substrate 100 can be reduced by processing a thicker target than the workpiece.

  The correction surface of the glass correction ring 202A or 202B made of such a glass material and the grinding surfaces of the upper and lower surface plates 10 and 140 are slid while being pressed against each other while supplying the coolant. Thus, the smoothness of the ground surfaces of the upper and lower surface plates 140 and 10 can be enhanced.

  If the glass correction rings 202A and 202B are used, it is possible to improve the smoothness of the surface plate by correcting the undulation of a half wavelength of 60 to 70 mm. The flatness of the correction surfaces of the glass correction rings 202A and 202B (measurement area of 8 mm is measured using a stylus type surface roughness measuring device) is preferably 0.2 μm or less, and more preferably 0.1 μm or less.

  As described above, it is preferable that the glass correction ring has a thickness equal to or larger than that of the glass substrate 100 in order to correct the undulation of the surface plate.

  FIG. 7 is an overall view of the grinding apparatus when the surface plate is corrected using the correction ring shown in FIG. The grinding apparatus 300 sandwiches the internal gear 130 between the lower surface plate 10 and the upper surface plate 140 from above and below. In the internal gear 130, the carrier 110 is held at the time of grinding, and the glass correction ring 202A or 202B is held at the time of correcting the smoothness of the surface plate. In FIG. 7, a diamond surface 160 is used as a ground surface, which is planarly bonded to the upper and lower surface plates 140 and 10.

  In either the grinding process or the correction process, as described above, the carrier 110 having a gear on the outer periphery or the glass correction ring 202A or 202B is held as a planetary gear in the internal gear 130, and the sun gear 120 is rotated. Thus, the main surface of the glass substrate or the correction surface of the glass correction ring 202A or 202B and the grinding surfaces of the upper and lower surface plates 10 and 140 are pressed against each other and slid while supplying the coolant.

  In the correction process, the coolant 310 in the container 302 is supplied into the surface plate 200 by the pump 320 and circulated. In this correction process, the facets from which the grinding surfaces of the upper and lower surface plates 10 and 140 that are generated during the process are cut are removed from the grinding surface of the surface plate 200. Specifically, when the coolant 310 is circulated, the coolant is filtered by the filter 330 provided in the lower surface plate 10, and the facet is retained in the filter 330.

  In this correction process, the machining allowance of the pellet-shaped fixed abrasive 150 or the diamond sheet 160 provided on the grinding surfaces of the upper and lower surface plates 10 and 140 is preferably 5 to 30 μm.

  FIG. 8 is a flowchart showing the flow of processing according to the embodiment of the present invention. When grinding a glass substrate, first, a fixed abrasive grain arranging step is carried out in which the fixed abrasive grains 150 or 160 containing diamond particles are arranged on the grinding surface of the surface plate (step S400).

  Next, the ground surface of the surface plate 200 and the correction surface of the metal correction member, which is thicker than the glass substrate and the correction surface is made of a metal material, are pressed against each other while supplying a grinding liquid containing loose abrasive grains. Then, an initial correction step of sliding is performed (step S410).

  Although the illustration of the initial correction process is omitted, this process can be executed in the same manner as shown in FIG. The reason for performing the initial correction process is that the smoothness of the ground surface of the surface plate 200 is particularly deteriorated immediately after the fixed abrasive grains 150 or 160 containing diamond particles are fixed to the surface plate 200. At this time, the undulation generated on the ground surface of the surface plate 200 is a undulation having a larger shape wavelength than that of the undulation (half wavelength 60 to 70 mm) which is corrected by a subsequent glass ring correction. There is a need to.

  Therefore, in this case, it is preferable to correct using a cast iron correction ring and a slurry containing loose abrasive grains (for example, a particle size of 8 to 15 μm) instead of the glass correction ring in the embodiment of the present invention. . When such a cast iron correction ring and a slurry containing loose abrasive grains are used, it is possible to correct the undulation component of a larger shape wavelength by a machining allowance of about several hundred μm, which is larger than that at the time of correction by the glass correction ring. Because it can.

  Thus, when the smoothness of the surface plate 200 is initially corrected using a metal correction ring such as cast iron and a grinding liquid containing loose abrasive grains, correction is performed using the glass correction rings 202A and 202B and the coolant 310. Unlike the case, the smoothness that can be used in the actual grinding process is not obtained.

  In other words, the correction when the glass correction rings 202A and 202B and the coolant 310 are used, and the correction when the slurry including the cast iron correction ring and loose abrasive grains are used, the shape wavelength to be corrected and the fixed wavelength after correction. The roughness of the board is different.

  Therefore, in order to obtain smoothness that can be used in the actual grinding process, the dummy glass is ground after the initial correction to reduce the roughness (step S420).

  Then, a grinding process is performed and the main surface of several tens batches of glass substrates is ground (step S430). After the grinding process, in order to correct the smoothness of the surface plate 200 that has been lowered in the grinding process, correction of the surface plate is performed using the glass correction rings 202A and 202B and the coolant 310 between the batches of the glass substrates to be ground. (Step S440). At this time, the half-waves to be corrected have a half wavelength of 60 to 70 mm, and the machining allowance is preferably 5 to 30 μm.

[Example]
Embodiments of a method for manufacturing a magnetic disk glass substrate and a method for manufacturing a magnetic disk to which the present invention is applied will be described below. This glass substrate for magnetic disk and magnetic disk are 0.8 inch type disk (inner diameter 6 mm, outer diameter 21.6 mm, plate thickness 0.381 mm), 1.0 inch type disk (inner diameter 7 mm, outer diameter 27.4 mm, It is manufactured as a magnetic disk having a predetermined shape such as a plate thickness of 0.381 mm) and a 1.8 inch type magnetic disk (inner diameter of 12 mm, outer diameter of 48 mm, plate thickness of 0.508 mm). Further, it may be manufactured as a 2.5 inch type disc or a 3.5 inch type disc.

(1) Shape processing step and lapping step In the method for manufacturing a magnetic disk glass substrate according to this example, first, the surface of the plate-like glass is lapped (ground) to obtain a glass base material. Cut the glass disc. Various plate glasses can be used as the plate glass. This plate-like glass can be manufactured by using a known manufacturing method such as a press method, a float method, a downdraw method, a redraw method, or a fusion method using a molten glass as a material. Of these, plate glass can be produced at low cost by using the pressing method. As the material of the plate glass, amorphous glass or glass ceramics (crystallized glass) can be used. As the material for the plate glass, aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used. In particular, as an amorphous glass, an aluminosilicate glass can be preferably used in that it can be chemically strengthened and a magnetic disk substrate excellent in flatness of the main surface and substrate strength can be supplied.

In this example, the melted aluminosilicate glass was molded into a disk shape by direct pressing using an upper mold, a lower mold, and a barrel mold to obtain an amorphous plate glass. As the aluminosilicate _glass, SiO 2: 58 to 75 _{wt%, Al} 2 O 3: _{5~23 wt%,} Li 2 O: 3 to 10 _wt%, Na 2 O: 4 to 13 principal component weight% Chemically strengthened glass contained as

  Next, both main surfaces of the plate glass were lapped to form a disk-shaped glass base material. This lapping process was performed using alumina free abrasive grains with a double-sided lapping apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed from above and below on both sides of the plate glass, a grinding liquid containing free abrasive grains is supplied onto the main surface of the plate glass, and these are moved relatively to perform lapping. went. By this lapping process, a glass base material having a flat main surface was obtained.

(2) Cutting process (coring, forming, chamfering)
Next, the glass base material was cut using a diamond cutter, and a disk-shaped glass substrate was cut out from the glass base material. Next, using a cylindrical diamond drill, an inner hole was formed in the center of the glass substrate to obtain an annular glass substrate (coring). Then, the inner peripheral end face and the outer peripheral end face were ground with a diamond grindstone and subjected to predetermined chamfering (forming, chamfering).

(3) Grinding process by fixed abrasive method Next, grinding was performed on both main surfaces of the obtained glass substrate. The specific procedure is as shown in the flowchart of FIG. By performing this grinding process, it is possible to remove in advance the fine unevenness formed on the main surface in the cutting process and end face polishing process, which are the previous processes, and the subsequent polishing process for the main surface can be performed in a short time. Can be completed.

  FIG. 9 is a graph showing the surface plate cross-sectional profile of the comparative example along the time series, which is a comparison object of the embodiment of the present invention, and FIG. 10 shows the surface plate cross-sectional profile of the embodiment of the present invention along the time series. It is a graph shown. Here, the profile is a comparison of the height of the ground surface of the upper surface plate 140 with a predetermined reference height of 0 micron.

  FIG. 9A shows a platen cross-sectional profile after initial correction by a cast iron correction ring immediately after fixing fixed abrasive grains 150 or 160 containing diamond particles to the platen 200 in the comparative example. This is equivalent to the state after step 410 in FIG. 8 showing the flowchart of the embodiment of the present invention is executed. This profile is distributed above and below the reference height of 0 micron, and discontinuous points are scattered.

  In the comparative example, the profile after grinding 50 batches of glass substrates from the state of FIG. 9A is shown in FIG. It can be seen that the ground surface is sharpened and has a severely wavy profile, and the smoothness is significantly reduced. The flatness of these 50 batches of glass substrates was 3 μm (measurement area of 8 mm was measured using a stylus type surface roughness measuring apparatus). And after that, as a result of searching 50 batches of glass substrates, the flatness of the glass substrate became 10 micrometers.

  On the other hand, FIG. 10A shows a surface plate cross-sectional profile after the initial correction (step S410) and dummy glass grinding (step S420) of FIG. 8 in the embodiment of the present invention. When FIG. 10 (a) and FIG. 9 (a) are compared as the state immediately before the grinding process of the glass substrate 100, the embodiment of the present invention has less difference between the maximum value and the minimum value, and is a discontinuous point. Clearly, the smoothness of the cross section of the surface plate is excellent.

  FIG. 10B shows a profile after grinding 20 batches of glass substrates from the state of FIG. 10A in this embodiment, that is, a cross-sectional profile of the surface plate after the grinding step (step S430) of FIG. . Although the ground surface is shaved and the smoothness is lowered, the smoothness is clearly superior when compared with FIG. 9B showing the state after grinding in the comparative example.

  FIG.10 (c) shows the surface plate cross-sectional profile after performing the correction process by a glass correction ring, ie, the correction process (step S440) of FIG. 8, for 30 minutes from the state of FIG.10 (b) in a present Example. . It can be seen that the wave of the profile disappears, the difference between the maximum value and the minimum value decreases, and the smoothness is restored.

  FIG. 10 (d) shows the profile after grinding 50 batches of glass substrates from the state of FIG. 10 (c), that is, after the grinding step (step S430) in FIG. The board cross section profile is shown. The flatness of the glass substrates after grinding of all 50 batches is 3 μm or less, and the smoothness of the glass substrates is excellent even when compared with the comparative example. Thereafter, steps S440 and S430 may be alternately repeated.

(4) End surface grinding | polishing process Next, mirror polishing was performed with the brush grinding | polishing method about the outer peripheral end surface of the glass substrate. At this time, as the abrasive grains, a slurry (free abrasive grains) containing cerium oxide abrasive grains was used.

  And the glass substrate which finished the end surface grinding | polishing process was washed with water. By this end face polishing step, the end face of the glass substrate was processed into a mirror state that can prevent the precipitation of sodium and potassium. In particular, the inner peripheral end face was in a good state without a decrease in tolerance and roundness of the inner hole even when a large number of about 200 to 300 sheets were laminated and polished.

(5) Main surface polishing step As the main surface polishing step, first, a first polishing step was performed. This first polishing step is mainly intended to remove scratches and distortions remaining on the main surface in the lapping step described above. In the first polishing step, the main surface was polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, cerium oxide abrasive grains were used.

  The glass substrate which finished this 1st grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA (isopropyl alcohol) one by one, and was wash | cleaned.

  Next, a second polishing step was performed as the main surface polishing step. The purpose of this second polishing step is to finish the main surface into a mirror surface. In the second polishing step, mirror polishing of the main surface was performed using a soft foamed resin polisher by a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, cerium oxide abrasive grains finer than the cerium oxide abrasive grains used in the first polishing step were used.

  The glass substrate which finished this 2nd grinding | polishing process was immersed in each washing tank of neutral detergent, a pure water, and IPA (isopropyl alcohol) sequentially, and was wash | cleaned. Note that ultrasonic waves were applied to each cleaning tank.

(6) Chemical strengthening process Next, the glass substrate was chemically strengthened. For chemical strengthening, first prepare a powdered chemical strengthening salt mixed with potassium nitrate (60%) and sodium nitrate (40%) as a solid chemical strengthening salt, put it into a salt charging container, and heat it with an electromagnetic wave generator. Melted.

  Thus, lithium ions and sodium ions in the glass substrate were replaced with sodium ions and potassium ions in the chemical strengthening solution, respectively, and the glass substrate was strengthened.

  The glass substrate that had been subjected to the chemical strengthening treatment was immersed in a 20 ° C. water bath and rapidly cooled, and maintained for about 10 minutes. And the glass substrate which finished quenching was immersed in the concentrated sulfuric acid heated at about 40 degreeC, and was wash | cleaned. Further, the glass substrate after the sulfuric acid cleaning was cleaned by immersing in a cleaning bath of pure water and IPA (isopropyl alcohol) sequentially.

  As described above, a flat and smooth, high-rigidity glass substrate for a magnetic disk is obtained by performing a lapping process, a cutting process, a grinding process, an end face polishing process, first and second polishing processes, and a chemical strengthening process. Obtained.

(7) Magnetic disk manufacturing process On both surfaces of the glass substrate obtained through the above-described processes, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoTaZr-based alloy, an underlayer made of Ru, and a CoCrPt group on the surface of the glass substrate A perpendicular magnetic recording disk was manufactured by sequentially forming a perpendicular magnetic recording layer made of an alloy, a protective layer made of hydrogenated carbon, and a lubricating layer made of perfluoropolyether. Although this configuration is an example of a configuration of a perpendicular magnetic disk, a magnetic layer or the like may be configured as an in-plane magnetic disk.

  The glass substrate for a magnetic disk manufactured using the above-described magnetic disk manufacturing method is a glass substrate for a magnetic disk compatible with a DFH (Dynamic Flying Height) head.

  In recent years, a technique called DFH (Dynamic Flying Height) has been developed as one of the techniques for stabilizing control of the flying height of the magnetic head and further reducing the flying height. A heater element is embedded in the magnetic head, and the heater element generates heat during operation of the magnetic head. The heat causes the magnetic head to thermally expand and slightly protrude toward the magnetic disk. As a result, the magnetic spacing, which is the magnetic gap between the magnetic head and the main surface of the magnetic disk, can be reduced only at that time. That is, DFH is a technology that can reduce the flying height of a magnetic head from a magnetic disk.

  Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention is applicable to a method for manufacturing a glass substrate for a magnetic disk, a method for manufacturing a magnetic disk using such a glass substrate, and a glass substrate for a magnetic disk.

It is a figure which shows the carrier of the glass substrate to which embodiment of this invention is applied. It is a figure which shows the glass correction ring which is an example of the correction member used for embodiment of this invention. FIG. 3 is a view showing that the glass correction ring shown in FIG. 2 can be replaced with the carrier shown in FIG. 1. The results of the replacement shown in FIG. 3 are shown, and (a) and (b) are diagrams in which the carrier is replaced with the glass correction ring shown in FIGS. 2 (a) and 2 (b), respectively. The cross section of a surface plate is shown, (a) is AA sectional drawing of FIG. 1, (b) is XX sectional drawing of Fig.4 (a). It is YY sectional drawing of FIG.4 (b). FIG. 5 is an overall view of a grinding apparatus when a surface plate is corrected using the correction ring shown in FIG. 4. It is a flowchart which shows the flow of the process of embodiment of this invention. It is a graph which shows the surface plate cross-sectional profile of the comparative example which is a comparison object of the Example of this invention along a time series. It is a graph which shows the surface plate cross-sectional profile of the Example of this invention along a time series.

Explanation of symbols

10 Lower surface plate 140 Upper surface plate 150 Fixed abrasive 160 Diamond sheet 200 Surface plate 202A, 202B Glass correction ring 210A, 210B Carrier 230A, 230B Glass 310 Coolant

Claims (9)

A fixed abrasive grain deployment step of deploying fixed abrasive grains containing diamond particles on the grinding surface of the surface plate;
Slide the grinding surface of the surface plate and the correction surface of the metal correction member, which is thicker than the glass substrate and the correction surface is made of a metal material, while pressing each other while supplying a grinding liquid containing loose abrasive grains. An initial correction process,
After the initial correction step, a grinding step of grinding the main surface of the glass substrate using a surface plate provided with fixed abrasive grains containing diamond particles on the grinding surface;
After the grinding step, the correction surface includes a correction surface of a correction member made of a glass material and a correction step in which the grinding surface of the surface plate is pressed against each other and slid.
In the grinding step, using a carrier that holds a plurality of the glass substrates, the main surface of the glass substrate is ground,
The method of manufacturing a glass substrate for a magnetic disk, wherein the correction member used in the correction step has a size that can replace the carrier. A fixed abrasive grain deployment step of deploying fixed abrasive grains containing diamond particles on the grinding surface of the surface plate;
Slide the grinding surface of the surface plate and the correction surface of the metal correction member, which is thicker than the glass substrate and the correction surface is made of a metal material, while pressing each other while supplying a grinding liquid containing loose abrasive grains. An initial correction process,
After the initial correction step, a grinding step of grinding the main surface of the glass substrate using a surface plate provided with fixed abrasive grains containing diamond particles on the grinding surface;
After the grinding step, the correction surface of the correction member whose correction surface is made of a glass material and the grinding surface of the surface plate are pressed against each other and slid, and the coolant is supplied to the grinding surface of the surface plate. And a correction step of removing facets generated during the correction step from the ground surface by circulating and filtering the coolant,
In the grinding step, using a carrier that holds a plurality of the glass substrates, the main surface of the glass substrate is ground,
The method of manufacturing a glass substrate for a magnetic disk, wherein the correction member used in the correction step has a size that can replace the carrier.   3. The method for manufacturing a glass substrate for a magnetic disk according to claim 1, wherein in the correction step, undulation having a half wavelength of 60 to 70 mm generated on the ground surface by the grinding step is reduced.   4. The magnetic disk according to claim 1, wherein the correction member is configured such that a glass material constituting the correction surface is disposed along a circumference of the correction member. 5. A method for producing a glass substrate.   5. The method of manufacturing a glass substrate for a magnetic disk according to claim 1, wherein the correcting step is performed using a planetary gear system. Before the grinding process,
The glass substrate for a magnetic disk according to any one of claims 1 to 5, further comprising a smoothness preparation step in which the ground surface of the surface plate and the dummy glass are pressed against each other and slid. Production method.   A method for producing a magnetic disk, comprising forming at least a magnetic layer on a glass substrate produced by using the production method according to claim 1.   8. The method of manufacturing a magnetic disk according to claim 7, wherein the magnetic layer includes a perpendicular magnetic recording layer made of a CoCrPt-based alloy.   7. A magnetic disk glass substrate manufactured by the method for manufacturing a magnetic disk according to claim 1, wherein the glass substrate is a magnetic disk for a DFH (Dynamic Flying Height) head. Glass substrate.

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