JP6423935B2 - Manufacturing method of glass substrate for information recording medium and polishing brush - Google Patents

Description

  The present invention relates to a glass substrate for information recording medium and a method for manufacturing the same, and in particular, a glass substrate for information recording medium mounted as part of an information recording medium in an information recording apparatus such as a hard disk drive (HDD) and the like. It relates to the manufacturing method.

  An information recording medium (magnetic disk) is mounted inside an information recording apparatus such as a hard disk drive. The information recording medium is manufactured by forming a magnetic recording layer for magnetic recording on the main surface of a disk-shaped glass substrate having a hole in the center.

  A glass substrate used for manufacturing an information recording medium is referred to as an information recording medium glass substrate (hereinafter also simply referred to as a glass substrate). The manufacturing method of the glass substrate for information recording media is disclosed by Unexamined-Japanese-Patent No. 2007-098484 (patent document 1) and Unexamined-Japanese-Patent No. 2007-245319 (patent document 2), for example.

JP 2007-098484 A JP 2007-245319 A

  With the expansion of usages and usage environments of computers and the like, demands for impact resistance required for information recording media (magnetic disks) and prevention of elution are also increasing year by year. When fine cracks are present on the inner peripheral end face of the information recording medium, the impact resistance of the information recording medium is lowered. In order to improve impact resistance, the inner peripheral end surface of the glass base plate constituting the information recording medium needs to be formed sufficiently smoothly by polishing.

  In general, in order to obtain high smoothness, the inner peripheral end surface of a glass substrate (glass base plate) is ground by grinding and then polished using a polishing slurry and a polishing brush. From the standpoint of improving production efficiency and the like, when performing polishing on the inner peripheral end surface of the glass base plate, the glass base plate is batch-polished in a state where a plurality of glass base plates are stacked. Sometimes.

  The present invention provides a method for manufacturing a glass substrate for an information recording medium in which inner peripheral end surfaces of a plurality of glass base plates are polished more smoothly even when the plurality of glass base plates are subjected to a batch polishing treatment. The purpose is to provide.

  The method for producing a glass substrate for an information recording medium according to the present invention includes a step of preparing a plurality of glass base plates having an inner peripheral end surface, and a bristle bundle made of a plurality of brush bristle members on the outer peripheral surface of the shaft member. A step of preparing a polishing brush planted in a spiral shape, and a plurality of the glass base plates, and then the inner peripheral end surfaces of the glass base plates and the brush bristles in a stacked state The step of disposing the polishing brush so that the front ends of the bundle face each other, and the polishing brush is rotated, and the inner peripheral end surfaces of the plurality of glass base plates in a stacked state Polishing the inner peripheral end face of the plurality of glass base plates by sliding a brush bristle bundle, and in a direction parallel to the rotation axis of the polishing brush, a plurality of the above The brush bristle The width of the region formed by the tips of each of the plurality of brush hair materials extending from the planting base is smaller than the width of the planting base in which the bristle material is planted on the shaft member. Further, it is planted on the shaft member.

  In a direction parallel to the rotation axis of the polishing brush, the plurality of brush bristle members have 95% or more of the plurality of brush bristle tips, and the plurality of the brush bristle members are arranged on the shaft member. ± 40 with respect to the center line in the width direction of the planting base extending in a direction perpendicular to the surface of the shaft center member when the width of the planting base in which the brush bristle material is planted is 100% as a standard. The shaft member is planted so as to be located within the range of%.

  Preferably, in a direction parallel to the rotation axis of the polishing brush, the plurality of brush bristle materials are planted on the shaft member so that the tips of the bristle bundles have an arc shape. Yes.

  According to the present invention, even when a plurality of glass base plates are subjected to a polishing process batchwise, the production of a glass substrate for an information recording medium in which the inner peripheral end surfaces of the plurality of glass base plates are polished more smoothly. You can get the method.

It is a perspective view which shows an information recording device provided with the glass substrate manufactured by using the manufacturing method of the glass substrate for information recording media in embodiment. It is a top view which shows the glass substrate manufactured by the manufacturing method of the glass substrate for information recording media in embodiment. It is arrow sectional drawing along the III-III line in FIG. It is a top view which shows the information recording medium provided with the glass substrate manufactured by the manufacturing method of the glass substrate for information recording media in embodiment. It is arrow sectional drawing along the VV line in FIG. It is a flowchart which shows the manufacturing method of the glass substrate for information recording media in embodiment. It is a perspective view which shows the brush for grinding | polishing used for the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is a side view which shows the brush for grinding | polishing used for the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is a side view which expands and shows typically the polishing brush used for the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in embodiment. It is a side view which expands and shows a mode that the end surface grinding | polishing process (inner peripheral end surface grinding | polishing process) of the manufacturing method of the glass substrate for information recording media in embodiment is implemented. It is a side view which expands and shows typically the polishing brush used for the end surface grinding | polishing process of the manufacturing method of the glass substrate for information recording media in a comparative example. It is a side view which expands and shows a mode that the end surface grinding | polishing process (inner peripheral end surface grinding | polishing process) of the manufacturing method of the glass substrate for information recording media in a comparative example is implemented. It is a figure which shows the conditions and result of the Example and comparative example regarding embodiment. It is a side view which shows typically the brush for grinding | polishing used for the comparative example 1 regarding embodiment. It is a side view which shows typically the brush for grinding | polishing used for the comparative example 2 regarding embodiment. It is a side view which shows typically the brush for grinding | polishing used for Example 1, 2 regarding embodiment. It is a side view which expands and shows typically the brush for grinding | polishing used for Example 1, 2 regarding embodiment. It is a side view which shows typically the brush for grinding | polishing used for the comparative example 3 regarding embodiment. It is a side view which shows typically the brush for grinding | polishing used for Example 3 regarding embodiment.

  Embodiments and examples based on the present invention will be described below with reference to the drawings. In the description of the embodiments and the examples, when the number, amount, and the like are referred to, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the description of the embodiment and each example, the same parts and corresponding parts are denoted by the same reference numerals, and redundant description may not be repeated.

[Embodiment]
(Information recording device 30)
First, the information recording device 30 will be described with reference to FIG. FIG. 1 is a perspective view showing the information recording apparatus 30. The information recording apparatus 30 includes the glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium (hereinafter also simply referred to as a glass substrate) in the embodiment as the information recording medium 10.

  Specifically, the information recording device 30 includes an information recording medium 10, a housing 20, a head slider 21, a suspension 22, an arm 23, a vertical shaft 24, a voice coil 25, a voice coil motor 26, a clamp member 27, and a fixing screw. 28. A spindle motor (not shown) is installed on the upper surface of the housing 20.

  An information recording medium 10 such as a magnetic disk is rotatably fixed to the spindle motor by a clamp member 27 and a fixing screw 28. The information recording medium 10 is rotationally driven by this spindle motor at, for example, several thousand rpm. Although details will be described later with reference to FIGS. 4 and 5, in the information recording medium 10, a chemically strengthened layer 12 (see FIG. 5) and a magnetic recording layer 14 (see FIGS. 4 and 5) are formed on the glass substrate 1. To be manufactured.

  The arm 23 is attached to be swingable about the vertical axis 24. A suspension 22 formed in a leaf spring (cantilever) shape is attached to the tip of the arm 23. A head slider 21 is attached to the tip of the suspension 22 so as to sandwich the information recording medium 10.

  A voice coil 25 is attached to the side of the arm 23 opposite to the head slider 21. The voice coil 25 is clamped by a magnet (not shown) provided on the housing 20. A voice coil motor 26 is constituted by the voice coil 25 and the magnet.

  A predetermined current is supplied to the voice coil 25. The arm 23 swings around the vertical axis 24 by the action of electromagnetic force generated by the current flowing through the voice coil 25 and the magnetic field of the magnet. As the arm 23 swings, the suspension 22 and the head slider 21 also swing in the direction of the arrow AR1. The head slider 21 reciprocates on the front and back surfaces of the information recording medium 10 in the radial direction of the information recording medium 10. A magnetic head (not shown) provided on the head slider 21 performs a seek operation.

  While the seek operation is performed, the head slider 21 receives a levitation force due to an air flow generated as the information recording medium 10 rotates. Due to the balance between the levitation force and the elastic force (pressing force) of the suspension 22, the head slider 21 travels with a constant flying height with respect to the surface of the information recording medium 10. By the traveling, the magnetic head provided on the head slider 21 can record and reproduce information (data) on a predetermined track in the information recording medium 10. The information recording apparatus 30 on which the glass substrate 1 is mounted as a part of the members constituting the information recording medium 10 is configured as described above.

(Glass substrate 1)
FIG. 2 is a plan view showing glass substrate 1 manufactured by the method for manufacturing a glass substrate for information recording medium according to the present embodiment. 3 is a cross-sectional view taken along the line III-III in FIG.

  As shown in FIGS. 2 and 3, the glass substrate 1 (glass substrate for information recording medium) used as a part of the information recording medium 10 (see FIGS. 4 and 5) has a main surface 2, a main surface 3, It has the inner peripheral end surface 4, the hole 5, and the outer peripheral end surface 6, and is formed in a disk shape as a whole. The hole 5 is provided so as to penetrate from one main surface 2 toward the other main surface 3. A chamfer 7 is formed between the main surface 2 and the inner peripheral end surface 4 and between the main surface 3 and the inner peripheral end surface 4. Between the main surface 2 and the outer peripheral end surface 6 and between the main surface 3 and the outer peripheral end surface 6, a chamfered portion 8 (chamfer portion) is formed.

  The size of the glass substrate 1 is, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch. The thickness of the glass substrate is, for example, 0.30 mm to 2.2 mm from the viewpoint of preventing breakage. In the present embodiment, the glass substrate has an outer diameter of about 64 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm. The thickness of the glass substrate is a value calculated by averaging the values measured at a plurality of arbitrary points that are point-symmetric on the glass substrate.

(Information recording medium 10)
FIG. 4 is a plan view showing an information recording medium 10 provided with a glass substrate 1 as an information recording medium. FIG. 5 is a cross-sectional view taken along the line VV in FIG.

  As shown in FIGS. 4 and 5, the information recording medium 10 includes a glass substrate 1, a chemical strengthening layer 12, and a magnetic recording layer 14. Chemical strengthening layer 12 is formed to cover main surfaces 2 and 3, inner peripheral end surface 4, and outer peripheral end surface 6 of glass substrate 1. The magnetic recording layer 14 is formed so as to cover a predetermined region on the main surfaces 2 and 3 of the chemical strengthening layer 12. By forming the chemical strengthening layer 12 on the inner peripheral end face 4 of the glass substrate 1, a hole 15 is formed inside the inner peripheral end face 4. The information recording medium 10 is fixed to a spindle motor provided on the housing 20 (see FIG. 1) using the holes 15.

  In the information recording medium 10 shown in FIG. 5, the magnetic recording layer 14 is formed on both (both sides) the chemical strengthening layer 12 formed on the main surface 2 and the chemical strengthening layer 12 formed on the main surface 3. Is formed. The magnetic recording layer 14 may be provided only on the chemical strengthening layer 12 (one side) formed on the main surface 2, or on the chemical strengthening layer 12 (one side) formed on the main surface 3. It may be provided.

  The magnetic recording layer 14 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the chemical strengthening layer 12 on the main surfaces 2 and 3 of the glass substrate 1 (spin coating method). The magnetic recording layer 14 may be formed by a sputtering method or an electroless plating method performed on the chemical strengthening layer 12 on the main surfaces 2 and 3 of the glass substrate 1.

  The film thickness of the magnetic recording layer 14 is about 0.3 μm to 1.2 μm in the case of spin coating, about 0.04 μm to 0.08 μm in the case of sputtering, and about 0.05 μm to about in the case of electroless plating. 0.1 μm. From the viewpoint of thinning and high density, the magnetic recording layer 14 is preferably formed by sputtering or electroless plating.

  As a magnetic material used for the magnetic recording layer 14, a Co-based alloy or the like containing Ni or Cr as a main component is added for the purpose of adjusting the residual magnetic flux density. Is preferably used.

  In order to improve the sliding of the magnetic head, the surface of the magnetic recording layer 14 may be thinly coated with a lubricant. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a solvent such as Freon.

  The magnetic recording layer 14 may be provided with an underlayer or a protective layer as necessary. The underlayer in the information recording medium 10 is selected according to the type of magnetic film. Examples of the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.

  The underlayer provided on the magnetic recording layer 14 is not limited to a single layer, and may have a multi-layer structure in which the same or different layers are stacked. For example, a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.

  Examples of the protective layer for preventing wear and corrosion of the magnetic recording layer 14 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, or a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus together with the underlayer and the magnetic film. These protective layers may be a single layer, or may have a multilayer structure composed of the same or different layers.

Another protective layer may be formed on the protective layer or instead of the protective layer. For example, in place of the protective layer, tetraalkoxylane is diluted with an alcohol-based solvent on a Cr layer, and then colloidal silica fine particles are dispersed and applied, followed by baking to form a silicon oxide (SiO ₂ ) layer. It may be formed.

(Glass substrate manufacturing method)
Next, the manufacturing method (S100) of the glass substrate (glass substrate for information recording media) in this Embodiment is demonstrated using the flowchart figure shown in FIG. The glass substrate manufacturing method (S100) in the present embodiment includes a glass base plate preparation step (S10), an alumina polishing step (S20), a coring step (S30), an end surface grinding step (S40), and an end surface polishing step ( S50), a lapping process (S60), a polishing process (S70), and a chemical strengthening process (S80).

  A magnetic recording layer deposition step (S200) is performed on the glass substrate obtained through the chemical strengthening step (S80). The information recording medium 10 (see FIGS. 4 and 5) is obtained through the magnetic recording layer deposition step (S200). Hereinafter, the detail of each process S10-S80 which comprises the manufacturing method (S100) of a glass substrate is demonstrated in order. In the following description, simple cleaning that is appropriately performed between the steps S10 to S80 may not be described in detail.

(S10: Glass base plate preparation process)
First, a predetermined number of substantially disk-shaped glass base plates constituting the glass substrate are prepared. The glass base plate can be obtained, for example, by directly pressing molten glass using an upper mold, a lower mold, and a body mold. At this time, instead of the direct press method, a disk-shaped glass base plate may be obtained by cutting out with a grinding wheel from a sheet glass formed by using a downdraw method or a float method.

(S20: Alumina polishing step)
Next, alumina polishing is performed on a predetermined number of glass base plates. The purpose of this alumina polishing treatment is to improve dimensional accuracy and shape accuracy. The alumina polishing process is performed using a lapping apparatus. By using alumina abrasive grains of particle size # 400, setting the load to about 100 kg and rotating the inner and outer rotation gears, both main surfaces of the glass base plate housed in the carrier are polished.

(S30: Coring process)
Next, using a cylindrical grindstone, holes are respectively formed in the central portions of a predetermined number of glass base plates. This hole corresponds to the hole 5 in FIGS. 2 and 3, and is used when the information recording medium 10 is fixed to the spindle motor.

(S40: End grinding process)
In the end face grinding step (S40), the inner peripheral end face and the outer peripheral end face of the predetermined number of glass base plates are ground using a grinding wheel, and further, a predetermined chamfering process is performed on the inner peripheral end face and the outer peripheral end face. To be implemented. By these processes, the inner peripheral end surface 4 of the glass base plate 1 is ground into a predetermined shape having a chamfered portion 7, and the outer peripheral end surface 6 of the glass base plate 1 is ground into a predetermined shape having a chamfered portion 8. Is done.

(S50: End face polishing step)
Next, an end surface polishing step (S50) using a polishing slurry such as cerium oxide is performed. The end surface polishing step (S50) includes an inner peripheral end surface polishing step (S51) and an outer peripheral end surface polishing step (S52).

  Referring to FIG. 7, a polishing brush 80 (abrasive member) is used in the inner peripheral end surface polishing step (S51). The polishing brush 80 is configured by a brush bristle bundle 81 made of a plurality of brush bristle materials being spirally planted on the outer peripheral surface of a cylindrical shaft center member 82. A further detailed configuration of the polishing brush 80 will be described later with reference to FIGS. 9 and 10.

  Referring to FIG. 8, the glass base plate 1 on which the inner peripheral end face 4 and the outer peripheral end face have been ground was overlapped in a block shape (block body 9), for example, 400 pieces each as shown in FIG. 8. In a state, it is fixed using a predetermined fixing jig (not shown). A spacer or the like may be provided between the adjacent glass base plates 1.

  After the plurality of glass base plates 1 are positioned and fixed, the polishing brush so that the inner peripheral end surfaces 4 of the plurality of glass base plates 1 in a stacked state and the tips of the brush bristle bundles 81 face each other. 80 is arranged inside the inner peripheral end face 4. In this state, the polishing brush 80 is rotated, and the brush bristle bundle 81 is slid with respect to the inner peripheral end surfaces 4 of the plurality of glass base plates 1 in a stacked state. The inner peripheral end face 4 is polished.

  Referring to FIG. 9, here, polishing brush 80 used in the inner peripheral end face polishing step (S51) in the present embodiment is configured as follows. As described above, the brush bristle bundle 81 of the polishing brush 80 includes a plurality of brush bristle materials 83 and 83. In the direction parallel to the rotation shaft 85 of the polishing brush 80, the plurality of brush bristle materials 83, 83 are arranged on the planting base R1 in which the plurality of brush bristle materials 83, 83 are planted on the shaft center member 82. The shaft center member 82 is planted so that the width W2 of the region R2 formed by the tips of each of the plurality of brush bristle materials 83, 83 extending from the planting base R1 is smaller than the width W1. Yes.

  Preferably, in the direction parallel to the rotation shaft 85 of the polishing brush 80, the plurality of brush bristle materials 83, 83 have a tip of the brush bristle material 83, 83 of 95% or more of the plural brush bristle members. Ranges Q and Q within ± 40% with respect to the center line 81C in the width direction of the planting base R1 extending in a direction perpendicular to the surface of the core member 82 (ranges when projected in a direction parallel to the center line 81C) It is good to be planted in the shaft center member 82 so that it may be located in the inside.

  Referring to FIG. 10, when polishing inner peripheral end surfaces 4 of a plurality of glass base plates 1 in an overlapped state using polishing brush 80, each of a plurality of brush bristle materials 83, 83 is used. The bristles contact the inner peripheral end surface 4 and the chamfered portion 7 of the glass base plate 1. When the bristles of each of the plurality of brush bristle materials 83, 83 are in contact with the inner peripheral end face 4 and the chamfered portion 7 of the glass base plate 1, they are concentrated in a narrow range, and the chamfered portions of the adjacent glass base plates 1. It becomes possible to apply a heavy load periodically between the sevens. Thereby, the sludge 88 (polishing waste) remaining between the chamfered portions 7 and 7 of the adjacent glass base plates 1 is effectively removed, and a good processing rate for the chamfered portion 7 is obtained. It is possible to secure.

  Referring to FIG. 11, on the other hand, in the polishing brush 80 </ b> Z in the comparative example, a plurality of brush bristle materials 83, 83 are planted so as to stand vertically with respect to the surface of the shaft center member 82. At the same time, they are arranged with substantially equal intervals.

  Referring to FIG. 12, when polishing inner peripheral end surfaces 4 of a plurality of glass base plates 1 in an overlapped state using polishing brush 80Z, brush bristle material 83 of polishing brush 80Z has an inner periphery. By abutting against the end face 4 and the chamfered portion 7, it spreads outward. The bristles of each of the plurality of brush bristle materials 83 and 83 do not concentrate in a narrow range when contacting the inner peripheral end surface 4 and the chamfered portion 7 of the glass base plate 1. A constant weak load is always applied between the chamfered portions 7, 7 of the adjacent glass base plates 1, and unlike the polishing brush 80 of the present embodiment, a strong load is periodically applied. I can't call it. As a result, it becomes difficult to effectively remove the sludge 88 (polishing waste) remaining between the chamfered portions 7 and 7 of the adjacent glass base plates 1.

  Therefore, according to the polishing brush 80 used in the method for manufacturing a glass substrate in the present embodiment, each of the bristles of the plurality of brush bristle materials 83, 83 has the inner peripheral end face 4 and the chamfer of the glass base plate 1. When contacting the part 7, it concentrates on a narrow range and it becomes possible to apply a heavy load regularly also between the chamfering parts 7 and 7 of the adjacent glass base plate 1. FIG. Thereby, the sludge 88 (polishing waste) remaining between the chamfered portions 7 and 7 of the adjacent glass base plates 1 is effectively removed, and a good processing rate for the chamfered portion 7 is obtained. It is possible to secure.

  For the outer peripheral end surface polishing step (S52), the same polishing brush 80 is used. In the outer peripheral end face polishing step (S52), the outer peripheral end face 6 is polished in a state where a plurality of glass base plates 1 are stacked, as in the inner peripheral end face polishing step (S51). In the end surface polishing step (S50), the polishing process may be performed in a state where the block body 9 (see FIG. 8) and the polishing brush 80 are completely immersed in the polishing liquid. The polishing treatment may be performed while the polishing slurry is poured (spread) between the outer peripheral end face 6 and the polishing brush 80.

(S60: Lapping process)
Referring to FIG. 6 again, after the glass base plate 1 (glass base plate 1) that has undergone the end face polishing step (S50) is washed, lapping is performed. After changing the grain size of the abrasive grains to a finer one, lapping using a lapping device is performed on the main surfaces 2 and 3 of the glass base plate 1.

(S70: Polishing process)
After the glass base plate 1 that has undergone the lapping step (S60) is washed, polishing is performed. Polishing is performed on the main surfaces 2 and 3 of the glass base plate 1 using a polishing apparatus (hard and soft polishing pads).

(S80: Chemical strengthening process)
Next, a chemical strengthening process is implemented to the glass base plate 1 which finished the washing | cleaning process. A chemical strengthening treatment tank is prepared, and a chemical strengthening liquid in which potassium nitrate (60%) and sodium nitrate (40%) are mixed is stored therein. While heating a chemical strengthening liquid to 300 to 400 degreeC, the glass base plate 1 after washing | cleaning is preheated to 200 to 300 degreeC.

  The glass base plate 1 is immersed in the chemical strengthening solution for 3 hours to 4 hours. Since the entire surface of the glass base plate 1 is chemically strengthened during the immersion, the plurality of glass base plates 1 are accommodated in a holder or the like so that the plurality of glass base plates 1 are held by the respective end faces. It is preferable to be immersed in a state.

  Alkali metal ions such as lithium ions and sodium ions contained in the glass base plate 1 are replaced with alkali metal ions such as potassium ions having a larger ion radius than these ions (ion exchange method). Compressive stress is generated in the ion-exchanged region due to the strain caused by the difference in ion radius, and both main surfaces of the glass base plate are strengthened.

  After the above steps are completed, the glass base plate 1 is ultrasonically cleaned using a high frequency of 950 kHz, or cleaned using an alkaline detergent so that the adhered matter remaining on the glass base plate 1 is eliminated. To do. Thereafter, the glass base plate 1 is dried using IPA vapor. Thus, the glass substrate in the present embodiment is obtained.

  Information recording such as a magnetic disk manufactured using the glass substrate 1 (see FIGS. 2 and 3) by removing the deposits remaining on the main surface of the glass substrate 1 after the chemical strengthening process. The occurrence of head crashes in the medium 10 (see FIGS. 4 and 5) is reduced. The glass substrate manufacturing method (S100) in the present embodiment is configured as described above.

(S200: Magnetic thin film formation process)
Magnetic recording layers are formed on both main surfaces (or one of the main surfaces) of the glass substrate that has been subjected to the chemical strengthening treatment. The magnetic recording layer includes, for example, an adhesion layer made of a Cr alloy, a soft magnetic layer made of a CoFeZr alloy, an orientation control underlayer made of Ru, a perpendicular magnetic recording layer made of a CoCrPt alloy, a protective layer made of a C system, and an F system. Are formed by sequentially forming the lubricating layer. By forming the magnetic recording layer, the information recording medium 10 shown in FIGS. 4 and 5 can be obtained.

(Action / Effect)
As described above, in the glass substrate manufacturing method according to the present embodiment, each of the bristles of the plurality of brush bristle materials 83 of the polishing brush 80 has the inner peripheral end face 4 and the chamfered chamfer of the glass base plate 1. When contacting the part 7, it concentrates on a narrow range and it becomes possible to apply a heavy load regularly also between the chamfering parts 7 and 7 of the adjacent glass base plate 1. FIG. Thereby, the sludge 88 (polishing waste) remaining between the chamfered portions 7 and 7 of the adjacent glass base plates 1 is effectively removed, and a good processing rate for the chamfered portion 7 is obtained. It is possible to secure.

[Experimental example]
Referring to FIG. 13, experiments were performed on Examples 1 to 3 based on the above embodiment and Comparative Examples 1 to 3 based on the above as an example. In Examples 1 to 3 and Comparative Examples 1 to 3, the glass base plate preparation process, the alumina polishing process for ensuring flatness, the coring process, and the end face grinding process are performed under the same conditions as in the above-described embodiment. is there.

  As polishing conditions for the inner peripheral end face in the inner peripheral end face polishing step, the number of processed sheets is 400 blocks 9, and the rotational speed of the polishing brush 80 having the spiral brush bristles 81 is set to 4000 rpm. The rotational speed of the block body 9 was set to 30 rpm. The inner diameter of the hole 5 of the glass base plate 1 is 20.01 mm, and the polishing time is 20 min. At the time of polishing, polishing slurry was poured between the inner peripheral end face 4 and the polishing brush 80. About the polishing brush used for the inner peripheral end surface polishing step, different ones were used in Examples 1 to 3 and Comparative Examples 1 to 3 as described later. In the outer peripheral end face polishing, brush polishing was used and cerium oxide was used. The concentration of cerium oxide was 15 wt%.

  In lapping, grinding with a double-side polishing machine and diamond sheet fixed abrasive was performed in common with Examples 1 to 3 and Comparative Examples 1 to 3. In the polishing process, in common with Examples 1-3 and Comparative Examples 1-3, as the first polishing process (P1), ceria abrasive grains and hard urethane pads are used, and the second polishing process (P2). ), Colloidal silica abrasive grains and hard suede pads were used. Thereafter, the obtained glass base plate 1 was chemically strengthened to obtain a glass substrate.

(Comparative Example 1)
With reference to FIGS. 13 and 14, the polishing brush used in Comparative Example 1 has a brush bristle material 83 with a length L of 4 mm, and the brush bristle material 83 has a planting range R of 1.5 mm. The bristle tip range Q of the brush bristle material 83 is 1.05 mm. The Q / R ratio calculated from the planting range R and the hair tip range Q is 70%. The bristle tip 81 has a radial tip shape.

(Comparative Example 2)
With reference to FIG. 13 and FIG. 15, the polishing brush used in Comparative Example 2 has a length L of the brush bristle material 83 of 4 mm, and a planting range R of the brush bristle material 83 is 1.5 mm, The bristle tip range Q of the brush bristle material 83 is 0.75 mm. The Q / R ratio calculated from the planting range R and the hair tip range Q is 50%. The bristle tip 81 has a flat tip shape.

Example 1
With reference to FIGS. 13, 16, and 17, in the polishing brush used in Example 1, the length L of the brush bristle material 83 is 4 mm, and the planting range R of the brush bristle material 83 is 1. The bristle tip range Q of the brush bristle material 83 is 0.60 mm. The Q / R ratio calculated from the planting range R and the hair tip range Q is 40%. The bristles of the bristle bundle 81 have a curl shape (arc shape) so as to draw an arc 89 (see FIG. 17).

(Example 2)
Referring to FIGS. 13, 16, and 17, similarly to Example 1, the polishing brush used in Example 2 has a length L of the brush bristle material 83 of 4 mm. The planting range R is 1.5 mm. In Example 2, the bristle tip range Q of the brush bristle material 83 is 0.45 mm. The Q / R ratio calculated from the planting range R and the hair tip range Q is 30%. As the hair tip shape of the bristle bundle 81, like the first embodiment, it has a curl shape (arc shape) so as to draw an arc 89 (see FIG. 17).

(Comparative Example 3)
With reference to FIG. 13 and FIG. 18, the polishing brush used in Comparative Example 3 has a length L of the brush bristle material 83 of 4 mm, and a planting range R of the brush bristle material 83 is 1.2 mm. The bristle tip range Q of the brush bristle material 83 is 0.60 mm. The Q / R ratio calculated from the planting range R and the hair tip range Q is 50%. The bristle tip 81 has a flat tip shape.

(Example 3)
With reference to FIG. 13 and FIG. 19, in the polishing brush used in Example 3, the length L of the brush bristle material 83 is 4 mm, the planting range R of the brush bristle material 83 is 1.5 mm, The bristle tip range Q of the brush bristle material 83 is 0.60 mm. The Q / R ratio calculated from the planting range R and the hair tip range Q is 40%. The bristle tip 81 has a flat tip shape.

  The chamfered portion 7 (the chamfer surface) of the inner peripheral end face 4 was inspected for the glass base plates 1 obtained in Examples 1 to 3 and Comparative Examples 1 to 3. As an inspection method, the chamfered portion 7 of the inner peripheral end face 4 is measured for roughness using an AFM (Dimension 3100 manufactured by Beco Co., Ltd. and measurement software NanoScope 7.2), and the value of the surface roughness Ra is 1.0 nm or more. The ratio of the glass base plate 1 is investigated, the case where the ratio of the corresponding glass base plate 1 is 10% or more is B evaluation, the case of less than 10% and 6% or more is A evaluation, and the case of less than 6% It was set as S evaluation.

  Further, the information recording medium 10 formed by subjecting the glass base plate 1 to film formation is incorporated into an actual information recording device 30 (hard disk drive), and 50 read / write tests are performed for each condition. It was confirmed.

  As shown in FIG. 13, as a result, in Examples 1 to 3, the state of the chamfered portion 7 was A evaluation or S evaluation, whereas in Comparative Examples 1 to 3, all were B evaluations. there were. Moreover, in Examples 1 and 2, evaluation better than Example 3 was obtained. When the bristles of the bristle bundle 81 are curled (arc-shaped), the tip of the brush bristle material 83 penetrates deeply between the chamfered portions 7 and 7 so that the chamfered portion 7 becomes uneven. It is thought that it was possible to polish without any problems.

  Moreover, in Comparative Examples 1, 2, and 3, due to insufficient polishing of the inner peripheral end face 4 of the glass base plate 1, an eluate is generated and adheres to the surface of the glass base plate 1, and after film formation It is considered that a defect occurred in the information recording medium 10 and an abnormality occurred in the recording characteristics.

  Further, in Comparative Example 3 in which the hair tip range Q was equal to that in Example 1 and the hair tip range Q was equal to the planting range R, an unfavorable result was obtained as compared with Example 1. This is considered to be a result of a decrease in the polishing rate because the bristles of the brush bristle material 83 fall in a specific direction when they hit the glass base plate 1.

  Moreover, in Example 3, the front-end | tip part as the bristle bundle 81 was made into the flat shape by the device of the planting method. The result of the end face inspection was A evaluation, but the recording characteristic test was slightly lower than Example 1. When the cause was investigated, in Example 3, the roughness of the chamfered portion 7 reached the acceptable level, but it was found that there was a variation in the values near the main surface and near the inner peripheral end surface 4. This is considered to be caused by the fact that the bristles of the brush bristle material 83 concentrated at the tip are better in the gap of the chamfered portion 7 in the first embodiment than in the third embodiment.

  Therefore, also from the result of this example, according to the polishing brush 80 in the above-described embodiment, the hair tips of the plurality of brush bristle materials 83, 83 of the polishing brush 80 are within the glass base plate 1. When contacting the peripheral end surface 4 and the chamfered portion 7, it is possible to concentrate in a narrow range and periodically apply a heavy load between the chamfered portions 7, 7 of the adjacent glass base plates 1. I understand. Thereby, sludge (polishing waste) remaining between the chamfered portions 7 and 7 of the adjacent glass base plates 1 is effectively removed, and a good processing rate for the chamfered portion 7 is secured. It turns out that it is possible to do.

  As mentioned above, although each embodiment and each Example based on this invention were described, each embodiment and each Example disclosed this time are illustrations in all points, and are not restrictive. The technical scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Glass substrate (glass base plate), 2, 3 Main surface, 4 Inner peripheral end surface, 5,15 hole, 6 Outer peripheral end surface, 7,8 Chamfer part, 9 Block body, 10 Information recording medium, 12 Chemical strengthening layer, 14 Magnetic recording layer, 20 Housing, 21 Head slider, 22 Suspension, 23 Arm, 24 Vertical axis, 25 Voice coil, 26 Voice coil motor, 27 Clamp member, 28 Fixing screw, 30 Information recording device, 80, 80Z For polishing Brush, 81 Brush bristle bundle, 81C Center line, 82 Axial member, 83 Brush bristle material, 85 Rotating shaft, 88 Sludge, 89 Arc, Q Tip range, R planting range, R1 planting base, R2 region.

Claims (4)

Preparing a plurality of glass base plates having an inner peripheral end surface;
A step of preparing a polishing brush in which a bristles made of a plurality of brush bristle materials are spirally planted on the outer peripheral surface of the shaft member;
After the plurality of glass base plates are stacked, the polishing brush is arranged so that the inner peripheral end surfaces of the plurality of glass base plates in the stacked state and the tip of the brush bristle bundle face each other. And a process of
By rotating the polishing brush and sliding the bristle bundle against the inner peripheral end surfaces of the plurality of glass base plates in a stacked state, Polishing the peripheral end surface, and
In a direction parallel to the rotational axis of the polishing brush, the plurality of brush bristle materials are compared with the width of the planting base in which the plurality of brush bristle materials are planted on the shaft center member. Planted on the shaft member so that the width of the region formed by the tips of each of the plurality of brush bristle members extending from the planting base is smaller;
The plurality of brush bristle materials have an arcuate shape in which the tips of the bristle bundles have an arcuate shape in which the central side portion in the parallel direction is located on the outside in the radial direction as compared to both outer side portions in the parallel direction. Are planted on the shaft member,
A method for producing a glass substrate for an information recording medium. Preparing a plurality of glass base plates having an inner peripheral end surface;
A step of preparing a polishing brush in which a bristles made of a plurality of brush bristle materials are spirally planted on the outer peripheral surface of the shaft member;
After the plurality of glass base plates are stacked, the polishing brush is arranged so that the inner peripheral end surfaces of the plurality of glass base plates in the stacked state and the tip of the brush bristle bundle face each other. And a process of
By rotating the polishing brush and sliding the bristle bundle against the inner peripheral end surfaces of the plurality of glass base plates in a stacked state, Polishing the peripheral end surface, and
In a direction parallel to the rotational axis of the polishing brush, the plurality of brush bristle materials are compared with the width of the planting base in which the plurality of brush bristle materials are planted on the shaft center member. Planted on the shaft member so that the width of the region formed by the tips of each of the plurality of brush bristle members extending from the planting base is smaller;
The plurality of brush bristle materials are planted on the shaft member so that the entire tip of the brush bristle bundle has a flat shape extending along the parallel direction ,
In a direction parallel to the rotation axis of the polishing brush, the plurality of brush bristle members have 95% or more of the plurality of brush bristle tips, and the plurality of the brush bristle members are disposed on the shaft member. ± 40 with respect to the center line in the width direction of the planting base extending in a direction perpendicular to the surface of the shaft center member when the width of the planting base in which the brush bristle material is planted is 100% as a standard. % Is planted in the shaft member so as to be within a range of within%.
A method for producing a glass substrate for an information recording medium. In the method for manufacturing a glass substrate for an information recording medium, the inner circumference of the plurality of glass base plates is rotated and slid with respect to the inner peripheral end surface of the plurality of glass base plates in an overlapped state. A polishing brush used in a step of polishing an end surface,
A bristles made of a plurality of brush bristles;
An axial member in which the brush bristle bundle is spirally planted on the outer peripheral surface,
In a direction parallel to the rotational axis of the polishing brush, the plurality of brush bristle materials are compared with the width of the planting base in which the plurality of brush bristle materials are planted on the shaft center member. Planted on the shaft member so that the width of the region formed by the tips of each of the plurality of brush bristle members extending from the planting base is smaller;
The plurality of brush bristle materials have an arcuate shape in which the tips of the bristle bundles have an arcuate shape in which the central side portion in the parallel direction is located on the outside in the radial direction as compared to both outer side portions in the parallel direction. Are planted on the shaft member,
Polishing brush. In the method for manufacturing a glass substrate for an information recording medium, the inner circumference of the plurality of glass base plates is rotated and slid with respect to the inner peripheral end surface of the plurality of glass base plates in an overlapped state. A polishing brush used in a step of polishing an end surface,
A bristles made of a plurality of brush bristles;
An axial member in which the brush bristle bundle is spirally planted on the outer peripheral surface,
In a direction parallel to the rotational axis of the polishing brush, the plurality of brush bristle materials are compared with the width of the planting base in which the plurality of brush bristle materials are planted on the shaft center member. Planted on the shaft member so that the width of the region formed by the tips of each of the plurality of brush bristle members extending from the planting base is smaller;
The plurality of brush bristle materials are planted on the shaft member so that the entire tip of the brush bristle bundle has a flat shape extending along the parallel direction ,
In a direction parallel to the rotation axis of the polishing brush, the plurality of brush bristle members have 95% or more of the plurality of brush bristle tips, and the plurality of the brush bristle members are disposed on the shaft member. ± 40 with respect to the center line in the width direction of the planting base extending in a direction perpendicular to the surface of the shaft center member when the width of the planting base in which the brush bristle material is planted is 100% as a standard. % Is planted in the shaft member so as to be within a range of within%.
Polishing brush.

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