WO2014103985A1

WO2014103985A1 - Glass substrate for use in information recording medium, and manufacturing method and manufacturing device of glass substrate for use in information recording medium

Info

Publication number: WO2014103985A1
Application number: PCT/JP2013/084419
Authority: WO
Inventors: 小松　隆史
Original assignee: Hoya株式会社
Priority date: 2012-12-28
Filing date: 2013-12-24
Publication date: 2014-07-03
Also published as: CN104812531A; CN104812531B; JP5960288B2; JPWO2014103985A1

Abstract

A polishing process involves a process for arranging a glass substrate and a carrier between a sun gear (40) and an internal gear (50), and a process for polishing the surface of the glass substrate by rotating the carrier in a state in which the outer periphery of the carrier meshes with tooth surfaces (42, 52). All tooth surfaces (42) and/or all tooth surfaces (52) include recesses (41, 51) having a shape recessed from the tooth tips, and the outer periphery of the carrier meshes with the recesses (41, 51) when the carrier rotates. Defining DC (unit: m) as the pitch circle diameter of the carrier and d (unit: mm) as the recess depth of the recesses (41, 51) from the tooth tips, the relation holds that 0.24 ≦ d/DC ≦ 1.89.

Description

Information recording medium glass substrate, information recording medium glass substrate manufacturing method and manufacturing apparatus

The present invention relates to a glass substrate for information recording medium, a method for manufacturing a glass substrate for information recording medium, and a manufacturing apparatus.

An information recording medium is mounted on an information recording device such as a computer. In general, a glass substrate is used to manufacture an information recording medium. A magnetic thin film layer is formed on the glass substrate. Information can be recorded in the magnetic thin film layer by magnetizing the magnetic thin film layer with a magnetic head. In recent years, the recording density of information recording media tends to increase. For example, one 2.5 inch information recording medium having a recording capacity of 500 GB has been developed, and a glass substrate for an information recording medium having higher surface smoothness is required.

When manufacturing a glass substrate for information recording media, a double-side polishing apparatus is used to polish the surface of the glass substrate. The glass substrate is held by a carrier (also referred to as a polishing carrier) as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-006526 (Patent Document 1). With the glass substrate held by the carrier, the surface of the glass substrate is polished by the polishing pad of the double-side polishing apparatus.

JP 2008-006526 A

An object of the present invention is to provide a glass substrate for an information recording medium having higher surface smoothness, a manufacturing method thereof, and a manufacturing apparatus thereof.

The manufacturing method of the glass substrate for information recording media based on this invention is a manufacturing method of the glass substrate for information recording media provided with the grinding | polishing process of grind | polishing the surface of a glass substrate, Comprising: In the said grinding | polishing process, a glass substrate and a carrier are sun geared. And the step of disposing between the internal gear, and rotating the carrier using the sun gear and the internal gear in a state where the outer periphery of the carrier is engaged with the tooth surfaces of both the sun gear and the internal gear. Polishing the surface of the glass substrate by sliding the glass substrate against the polishing surface of the surface, all the tooth surfaces of the sun gear and / or all the tooth surfaces of the internal gear from the tooth tip Including a recess having a shape recessed in a direction perpendicular to the rotation axis of the carrier, wherein the carrier is in the recess. When the carrier rolls, the outer periphery of the carrier meshes, the pitch circle diameter of the carrier is DC (unit: m), and the depth of the recess from the tooth tip in the direction orthogonal to the rotation axis is d. Assuming (unit: mm), the relationship of 0.24 ≦ d / DC ≦ 1.89 is established.

Preferably, TA is a width dimension of the recess in a direction parallel to the rotation axis, and TA is a thickness dimension of the glass substrate in a direction parallel to the rotation axis. It is established.

Preferably, the concave portion forms one concave groove that is annularly continuous along the circumferential direction.

The glass substrate for information recording medium based on the present invention is manufactured using the above-described method for manufacturing a glass substrate for information recording medium based on the present invention.

An apparatus for producing a glass substrate for an information recording medium according to the present invention includes a polishing pad, a sun gear and an internal gear between which the glass substrate and a carrier are arranged, and the sun gear and the internal gear are both teeth of these. By rotating the carrier in a state where the outer periphery of the carrier is engaged with the surface, the glass substrate is brought into sliding contact with the polishing surface of the polishing pad to polish the surface of the glass substrate. And / or all the tooth surfaces of the internal gear include a recess having a shape that is recessed from a tooth tip in a direction perpendicular to the rotation axis of the carrier, and the carrier rotates when the carrier rotates. And the carrier has a pitch circle diameter of DC (unit: m) and is orthogonal to the rotational axis. The recess depth from the tooth tip of the recess in the direction d (unit: mm) When the relation 0.24 ≦ d / DC ≦ 1.89 is satisfied.

According to the present invention, a glass substrate for an information recording medium having higher surface smoothness, a manufacturing method thereof, and a manufacturing apparatus thereof can be obtained.

1 is a perspective view showing a glass substrate for information recording medium manufactured using the method for manufacturing a glass substrate for information recording medium in Embodiment 1. FIG. 1 is a perspective view showing a magnetic disk (information recording medium) including a glass substrate for information recording medium manufactured using the method for manufacturing a glass substrate for information recording medium in Embodiment 1. FIG. FIG. 3 is a flowchart showing a method for manufacturing the glass substrate for information recording medium in the first embodiment. It is a side view which shows the double-side polish apparatus used by 2nd polishing process S18 in Embodiment 1. FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. It is a figure which expands and shows the area | region enclosed by VI line | wire in FIG. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6. It is sectional drawing which shows a mode when the double-side polish apparatus used by 2nd polishing process S18 in Embodiment 1 is performing the polishing process. 5 is a cross-sectional view showing a double-side polishing apparatus used in a second polishing step S18 in the first embodiment. FIG. It is a perspective view which shows the tooth surface of the internal gear used for the double-side polish apparatus shown in FIG. FIG. 11 is a diagram schematically showing a state when the tooth surface of the internal gear is viewed from the direction of arrow XI in FIG. 10 (a diagram in which the tooth surface is developed in the circumferential direction). It is sectional drawing which shows a mode that the carrier has meshed | engaged with the internal gear of the double-side polish apparatus used by 2nd polishing process S18 in Embodiment 1. FIG. It is sectional drawing which shows a mode that the carrier has meshed | engaged with the internal gear of the double-side polish apparatus used at the 2nd polishing process in a comparative example. It is a figure (figure which developed a tooth surface in the peripheral direction) showing typically a tooth surface of an internal gear of a double-side polish device used at 2nd polish process S18 in Embodiment 2. It is a figure which shows the experimental condition and experimental result which concern on an experiment example.

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

[Embodiment 1]
1 and 2, a glass substrate 1G manufactured using the method for manufacturing a glass substrate for information recording medium according to the present embodiment, and a magnetic disk 1 including the glass substrate 1G (information recording medium) ).

(Glass substrate 1G)
As shown in FIG. 1, a glass substrate 1G (glass substrate for information recording medium) used for a magnetic disk 1 (see FIG. 2) has a disk shape with a hole 11 formed in the center. Glass substrate 1 G includes front main surface 14, back main surface 15, inner peripheral end surface 13, and outer peripheral end surface 12. A chamfer surface 13a having a tapered shape is provided on a portion of the inner peripheral end surface 13 on the front main surface 14 side, and a chamfer surface 13b having a tapered shape is provided on a portion on the back main surface 15 side of the inner peripheral end surface 13 (see FIG. 2).

The glass substrate 1G has a size of, for example, 0.8 inch, 1.0 inch, 1.8 inch, 2.5 inch, or 3.5 inch. The thickness of the glass substrate 1G is, for example, 0.30 mm to 2.2 mm. Glass substrate 1G in the present embodiment has an outer diameter of about 65 mm, an inner diameter of about 20 mm, and a thickness of about 0.8 mm. The thickness of the glass substrate 1G is a value calculated by averaging the values measured at a plurality of arbitrary points that are point-symmetric on the glass substrate 1G.

(Magnetic disk 1)
As shown in FIG. 2, the magnetic disk 1 includes a glass substrate 1 G and a magnetic thin film layer 16 (magnetic recording layer) formed on the front main surface 14. The magnetic thin film layer 16 in the present embodiment is formed only on the front main surface 14, but may be further formed on the back main surface 15. The magnetic thin film layer 16 is formed by spin-coating a thermosetting resin in which magnetic particles are dispersed on the front main surface 14 of the glass substrate 1G (spin coating method). The magnetic thin film layer 16 may be formed using a sputtering method or an electroless plating method.

The film thickness of the magnetic thin film layer 16 formed on the front main surface 14 of the glass substrate 1G is about 0.3 μm to about 1.2 μm in the case of the spin coating method, and about 0.04 μm to about 0.00 in the case of the sputtering method. In the case of electroless plating, the thickness is about 0.05 μm to about 0.1 μm. As the magnetic material used for forming the magnetic thin film layer 16, it is preferable to use Co having a high crystal anisotropy and a Co-based alloy with Ni or Cr added for the purpose of adjusting the residual magnetic flux density. An FePt-based material may be used as a magnetic material suitable for heat-assisted recording.

In order to improve the sliding with respect to the magnetic head, a thin lubricant may be coated on the surface of the magnetic thin film layer 16. Examples of the lubricant include those obtained by diluting perfluoropolyether (PFPE) with a freon-based solvent. You may provide a base layer and a protective layer as needed.

The underlayer 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 may have a single-layer structure or a multi-layer structure in which the same or different layers are stacked. Examples of the multilayer structure include Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, and NiAl / CrV.

Examples of the protective layer that prevents wear and corrosion of the magnetic thin film layer 16 include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer. These protective layers can be formed continuously with an in-line type sputtering apparatus, such as an underlayer and a magnetic film. These protective layers may have a single layer structure, or may have a multilayer structure in which the same or different layers are stacked.

Another protective layer may be formed on the protective layer or instead of the protective layer. For example, instead of the protective layer, while tetraalkoxysilane is diluted with an alcohol solvent, colloidal silica fine particles are dispersed and applied onto the Cr layer, and further baked to form a silicon oxide (SiO ₂ ) layer. You may form on it.

(Manufacturing method of glass substrate 1G)
With reference to FIG. 3, the manufacturing method of the glass substrate 1G which concerns on this Embodiment is demonstrated. The manufacturing method includes steps S10 to S19. In the glass melting step S10, the glass material is melted. In the molding step S11, the molten glass material is press-molded using the upper mold and the lower mold. A glass substrate is obtained by molding. The glass substrate may be cut out from the plate glass. The composition of the glass substrate is, for example, aluminosilicate glass.

In the first lapping step S12, lapping is performed on both main surfaces of the glass substrate using a double-sided lapping device having a planetary gear mechanism. The lap platen is pressed from above and below against the glass substrate, and the glass substrate and the lap platen are relatively moved while supplying abrasive grains and grinding liquid onto both main surfaces of the glass substrate. As the abrasive, alumina or the like is used. By the lapping process, a glass substrate having a substantially flat surface shape is obtained.

In the coring step S13, a hole is formed in the center of the glass substrate using a cylindrical diamond drill. Using a diamond grindstone, chamfering is performed on the inner peripheral end surface and the outer peripheral end surface of the glass substrate. In 2nd lapping process S14, the lapping process similar to 1st lapping process S12 is given to both main surfaces of a glass substrate. Fine irregularities formed on both main surfaces are removed.

In the outer periphery / inner periphery polishing step S15, mirror polishing is performed on the outer peripheral end surface and the inner peripheral end surface of the glass substrate using a brush. As the abrasive grains, for example, a slurry containing cerium oxide abrasive grains is used. In the first polishing step S16, both main surfaces of the glass substrate are polished using a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, for example, cerium oxide abrasive grains having an average particle diameter of about 1 μm are used. In the first and second lapping steps (S12, S14), scratches and warpage remaining on both main surfaces are corrected.

In the chemical strengthening step S17, compressive stress layers are formed on both main surfaces of the glass substrate. A mixed solution of potassium nitrate (70%) and sodium nitrate (30%) is heated to 300 ° C., and the glass substrate is immersed in the mixed solution for about 30 minutes. A compressive stress layer is formed, and both main surfaces and both end surfaces of the glass substrate are strengthened.

In the second polishing step S18 (polishing step), precision polishing is performed on both main surfaces of the glass substrate using a double-side polishing apparatus having a planetary gear mechanism. As the abrasive, for example, colloidal silica having an average particle diameter of about 20 nm is used. The micro-defects remaining on both main surfaces are eliminated, and both main surfaces are finished in a mirror shape. Fine warpage is also eliminated, and both main surfaces have a desired flatness. Further details of the second polishing step S18 will be described later with reference to FIG.

In the final cleaning step S19, both main surfaces and both end surfaces of the glass substrate are cleaned, and then the glass substrate is appropriately dried. The manufacturing method of the glass substrate for information recording media in this Embodiment is comprised as mentioned above. The glass substrate 1G shown in FIG. 1 is obtained by using this glass substrate manufacturing method. As described above, the magnetic disk 1 shown in FIG. 2 is obtained by forming the magnetic thin film layer on the glass substrate 1G.

(Second polishing step S18)
The double-side polishing apparatus 100 used in the second polishing step S18 will be described with reference to FIGS. As described above, in the second polishing step S18, precision polishing is performed on both main surfaces of the glass substrate using the double-side polishing apparatus 100 having a planetary gear mechanism. FIG. 4 is a side view showing the double-side polishing apparatus 100. FIG. 5 is a cross-sectional view taken along the line VV in FIG. FIG. 6 is an enlarged view showing a region surrounded by a VI line in FIG. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG.

As shown in FIG. 4, the double-side polishing apparatus 100 includes an upper surface plate 20, an upper polishing pad 21, a lower surface plate 30, and a lower polishing pad 31. The upper surface plate 20 and the lower surface plate 30 have a cylindrical shape. The upper polishing pad 21 is mounted on the lower surface on the side (glass substrate side) facing the lower surface plate 30 of the upper surface plate 20. The lower polishing pad 31 is mounted on the upper surface on the side (glass substrate side) facing the upper surface plate 20 of the lower surface plate 30. The lower surface of the upper surface plate 20 and the upper surface of the lower surface plate 30 are parallel to each other and rotate in opposite directions.

The upper polishing pad 21 and the lower polishing pad 31 are processed members for polishing both main surfaces of the glass substrate. For example, a polyurethane suede pad is used as the upper polishing pad 21 and the lower polishing pad 31. A surface of the upper polishing pad 21 facing the lower surface plate 30 forms an upper polishing surface 22. The surface of the lower polishing pad 31 facing the upper surface plate 20 forms a lower polishing surface 32.

As shown in FIGS. 5 and 6, a plurality of disk-shaped carriers 60 are arranged on the lower polishing surface 32 (see FIG. 5). The carrier 60 includes a holding portion 61 (see FIG. 6) having a plurality of circular holes, and a plurality of meshing teeth 62 are provided on the outer periphery of the carrier 60. The thickness of the carrier 60 is, for example, 650 μm. The plurality of meshing teeth 62 form a pitch circle 68 having a pitch circle diameter DC.

The glass substrate 1G is held in a circular hole provided in the holding unit 61 (see FIG. 6). The thickness of the glass substrate 1G is, for example, 810 μm. A sun gear 40 is provided at the center of the lower surface plate 30 (see FIG. 5). An internal gear 50 is provided coaxially with the sun gear 40 at the periphery of the lower surface plate 30 (see FIG. 5). The sun gear 40 and the internal gear 50 are thicker than the carrier 60 in a direction parallel to the rotation axis of the sun gear 40.

When the carrier 60 is disposed between the sun gear 40 and the internal gear 50, the meshing teeth 62 of the carrier 60 mesh with both the tooth surface 42 of the sun gear 40 and the tooth surface 52 of the internal gear 50. The carrier 60 is rotated using the sun gear 40 and the internal gear 50. In the present embodiment, when the sun gear 40 is driven to rotate, the carrier 60 revolves around the sun gear 40 while rotating.

7, the back main surface of the glass substrate 1G held by the carrier 60 is in contact with the lower polishing surface 32 of the lower polishing pad 31. In this state, the upper surface plate 20 moves downward along the vertical direction toward the lower surface plate 30 (see the white arrow). Thereafter, the upper polishing surface 22 of the upper polishing pad 21 comes into contact with the front main surface of the glass substrate 1 G held by the carrier 60.

As shown in FIG. 8, the glass substrate 1G is sandwiched between the upper polishing pad 21 and the lower polishing pad 31. The upper surface plate 20 and the lower surface plate 30 apply a predetermined stress to the glass substrate 1G in the thickness direction. Both main surfaces of the glass substrate 1G are pressed against the upper polishing surface 22 and the lower polishing surface 32.

In this state, while supplying a polishing liquid such as colloidal silica, the upper polishing surface 22 moves relative to the front main surface of the glass substrate 1G, and the lower polishing surface 32 moves relative to the back main surface of the glass substrate 1G. Moving. When the upper polishing surface 22 is in sliding contact with the front main surface of the glass substrate 1G, the front main surface of the glass substrate 1G is polished. When the lower polishing surface 32 is in sliding contact with the back main surface of the glass substrate 1G, the back main surface of the glass substrate 1G is polished. Both main surfaces of the glass substrate are polished simultaneously.

FIG. 9 is a cross-sectional view showing the double-side polishing apparatus 100, and shows a state when the carrier 60 (not shown) is removed from the sun gear 40 and the internal gear 50. FIG. As shown in FIG. 9, the tooth surface 42 of the sun gear 40 used in the double-side polishing apparatus 100 includes a recess 41. The recess 41 has a shape that is recessed from the tooth tip 43 of the tooth surface 42 in a direction orthogonal to the rotation axis of the sun gear 40 (or the rotation axis of the carrier). The recess 41 is recessed from the tooth tip 43 of the tooth surface 42 toward the inside in the radial direction of the sun gear 40, and the depth da of the recess 41 from the tooth tip 43 is, for example, 0.1 mm or more and 1.0 mm or less. is there. The dent depth da referred to here is the distance from the tooth tip 43 of the tooth surface 42 to the portion of the recess 41 that is located on the innermost side in the radial direction of the sun gear 40.

FIG. 10 is a perspective view showing the tooth surface 52 of the internal gear 50. In FIG. 10, for convenience of explanation, the carrier 60 is separated from the internal gear 50 and the carrier 60 is not engaged with the internal gear 50. FIG. 11 is a diagram schematically showing a state when the tooth surface 52 of the internal gear 50 is viewed from the direction of the arrow XI in FIG. 10 (a diagram in which the tooth surface 52 is developed in the circumferential direction).

9 to 11, the tooth surface 52 of the internal gear 50 used in the double-side polishing apparatus 100 includes a recess 51. The recess 51 has a shape that is recessed from the tooth tip 53 of the tooth surface 52 in a direction orthogonal to the rotation axis of the sun gear 40 (or the rotation axis of the carrier). The recess 51 is recessed from the tooth tip 53 of the tooth surface 52 toward the radially outer side of the internal gear 50, and the recess depth db (see FIG. 9) of the recess 51 from the tooth tip 53 is, for example, 0.1 mm. It is 1.0 mm or less. The dent depth db referred to here is the distance from the tooth tip 53 of the tooth surface 52 to the portion of the recess 51 located on the outermost side in the radial direction of the internal gear 50.

The concave portion 41 of the sun gear 40 and the concave portion 51 of the internal gear 50 are portions that mesh with the meshing teeth 62 provided on the outer periphery of the carrier 60 when the carrier 60 is disposed between the sun gear 40 and the internal gear 50. . The recess 41 is provided on all of the plurality of tooth surfaces 42 (sun gear teeth) provided on the outer periphery of the sun gear 40. The recess 51 is provided on all of the plurality of tooth surfaces 52 (internal gear teeth) provided on the outer periphery of the internal gear 50.

As described above with reference to FIG. 6, the plurality of meshing teeth 62 provided on the outer periphery of the carrier 60 form a pitch circle 68 having a pitch circle diameter DC. The pitch circle diameter DC (unit: m) and the recess depth da (unit: mm) provided in the recess 41 (see FIG. 9) are dimensions that satisfy the equation 0.24 ≦ da / DC ≦ 1.89. Have a relationship. The pitch circle diameter DC (unit: m) and the recess depth db (unit: mm) provided in the recess 51 (see FIG. 9) are dimensions that satisfy the equation 0.24 ≦ db / DC ≦ 1.89. Have a relationship.

FIG. 12 is a cross-sectional view showing a state where the meshing teeth 62 of the carrier 60 are meshed with the recess 51 of the internal gear 50 of the double-side polishing apparatus 100 used in the second polishing step S18. As described above, when the second polishing step S 18 is performed using the double-side polishing apparatus 100, the carrier 60 rotates with respect to the internal gear 50. When the carrier 60 is rotating, the meshing teeth 62 provided on the outer periphery of the carrier 60 mesh with the recess 51 of the internal gear 50.

On the other hand, when the second polishing step S18 is performed using the double-side polishing apparatus 100, the carrier 60 also rotates relative to the sun gear 40 (see FIG. 6 and the like). When the carrier 60 is rotating, the meshing teeth 62 provided on the outer periphery of the carrier 60 mesh with the recess 41 (see FIG. 9 and the like) of the sun gear 40.

The carrier 60 meshes with the recess 41 of the sun gear 40 on the sun gear 40 side as viewed from the carrier 60, and meshes with the recess 51 of the internal gear 50 on the internal gear 50 side when viewed from the carrier 60. The carrier 60 rotates and revolves in this state. In the direction parallel to the rotation axis of the sun gear 40, the movement of the carrier 60 is effectively restricted by the recesses 41 and 51 (the state of being positioned in the rotation axis direction is maintained).

Since the expressions 0.24 ≦ da / DC ≦ 1.89 and 0.24 ≦ db / DC ≦ 1.89 are satisfied, the carrier 60 is in a plane direction orthogonal to the rotation axis of the sun gear 40. It is possible to rotate and revolve with virtually no tilt while maintaining a conforming posture. Both main surfaces of the glass substrate 1G held by the carrier 60 can be effectively polished while receiving an appropriate and uniform pressing force from the upper polishing pad 21 and the lower polishing pad 31.

As shown in FIG. 12, when the width dimension of the recess 51 in the direction parallel to the rotation axis of the sun gear 40 is TA and the thickness dimension of the glass substrate 1G in the same direction is TB, the relationship of TA <TB is established. It is good to have. The width dimension TA of the recess 51 is larger than the width dimension of the meshing teeth 62 of the carrier 60. Since the relationship of TA <TB is established, unnecessary movement of the meshing teeth 62 of the carrier 60 in the vertical direction can be further suppressed. Although this feature has been described based on the internal gear 50, the same applies to the sun gear 40.

Suppose that the tooth surface 52 does not have the recess as described above as in the internal gear 50Z shown in FIG. In this case, the portion of the carrier 60 on the side of the meshing teeth 62 (the outer peripheral side of the carrier 60) is easy to move in the vertical direction because it forms a free end. In FIG. 13, when the carrier 60 is rotating, the position of the meshing teeth 62 is displaced upward, and the outer peripheral portion of the carrier 60 is curved. The meshing teeth 62 of the carrier 60 are not properly meshed with the tooth surfaces 52 of the internal gear 50Z, and an unnecessary moment may be applied to the glass substrate 1G.

If the glass substrate 1G is polished in this state, the upper polishing surface 22 of the upper polishing pad 21 and the lower polishing surface 32 of the lower polishing pad 31 may be damaged by contact with the carrier 60. When polishing is performed using the damaged upper polishing pad 21 and lower polishing pad 31, fine pits or deposits are formed as defects on both main surfaces of the glass substrate 1G. This defect induces read / write errors and head crashes when the glass substrate 1G is used as the magnetic disk 1.

Here, when 0.24> da / DC and 0.24> db / DC, the meshing position between the gears moves in the vertical direction, and the outer peripheral portion of the carrier 60 is easily curved. The polishing pad is scratched, making it difficult to obtain a high-quality glass substrate 1G. On the other hand, when da / DC> 1.89 and db / DC> 1.89, the carrier 60 can easily move in the polishing surface direction of the upper and lower surface plates, and perform uniform polishing on the glass substrate 1G. As a result, it becomes difficult to obtain a glass substrate 1G having high quality.

Therefore, in the present embodiment, the sun gear 40 is provided with the recess 41 and the internal gear 50 is provided with the recess 51, and 0.24 ≦ da / DC ≦ 1.89 and 0.24 ≦ db / DC ≦ 1.89. Is satisfied, the carrier 60 can rotate and revolve with substantially no inclination while maintaining the posture along the surface direction orthogonal to the rotation axis of the sun gear 40. . Both main surfaces of the glass substrate 1G held by the carrier 60 can be effectively polished while receiving an appropriate and uniform pressing force from the upper polishing pad 21 and the lower polishing pad 31.

There is no or almost no scratch on the upper polishing surface 22 of the upper polishing pad 21 and the lower polishing surface 32 of the lower polishing pad 31, and fine pits or deposits are formed as defects on both main surfaces of the glass substrate 1G. This is also effectively suppressed. Therefore, the glass substrate for information recording media manufactured by the manufacturing method and manufacturing apparatus of the glass substrate for information recording media in this Embodiment has higher surface smoothness.

In the present embodiment, the sun gear 40 is provided with the recess 41 and the internal gear 50 is provided with the recess 51. However, only the sun gear 40 is provided with the recess 41 and the internal gear 50 has the recess 51. Even if it is not provided, even if the sun gear 40 is not provided with the recess 41 and only the internal gear 50 is provided with the recess 51, substantially the same operations and effects can be obtained.

[Embodiment 2]
As in the internal gear 50 A shown in FIG. 14, the tooth surface 52 may be formed with one concave groove 55 that is annularly continuous along the circumferential direction. The concave groove 55 is formed with the same height position and the same width dimension in the direction parallel to the rotation axis of the sun gear 40 (the vertical direction in FIG. 14). In this case, the depth of the recess is a distance from the tooth surface of the internal gear 50 A to the surface of the recess groove 55 farthest in the direction perpendicular to the rotation axis of the sun gear 40. Also with this configuration, it is possible to obtain substantially the same operations and effects as in the first embodiment.

In the present embodiment, the description has been made based on the aspect in which the groove 55 is provided in the internal gear 50A. However, even if the groove is provided only in the sun gear and the groove is not provided in the internal gear, Even when the concave groove is not provided and the concave groove is provided only in the internal gear, substantially the same operations and effects can be obtained.

[Experimental example]
With reference to FIG. 15, the experiment example performed in relation to each of the above-described embodiments (second polishing step S18) will be described. The experimental examples included Examples 1 to 3 and Comparative Examples 1 to 3. In each example, a carrier having a pitch circle diameter of about 423 mm and a thickness of 650 μm and a glass substrate having an outer diameter of 65 mm and a thickness of 810 μm were prepared. Five carriers were used, and each carrier held 20 glass substrates, and a total of 100 glass substrates were polished simultaneously. A 16B double-side polishing machine manufactured by Hamai Sangyo Co., Ltd. was used as the polishing apparatus.

The yield was measured on 100 glass substrates obtained based on the production methods of Examples 1 to 3 and Comparative Examples 1 to 3. Yield is measured by measuring defects on both main surfaces of the cleaned glass substrate using SSI-640 (surface inspection device using He-Ne laser light source, manufactured by System Seiko Co., Ltd.). To do.

In Examples 1 to 3 and Comparative Examples 2 and 3, the sun gear 40 having the recess 41 and the internal gear 50 having the recess 51 were used. The width dimension (TA in FIG. 12) of the recess 51 in the direction parallel to the rotation axis of the sun gear 40 was 700 μm. The width dimension of the recess 41 in the same direction was also set to 700 μm. In Comparative Example 1, a sun gear that does not have the recess 41 and an internal gear that does not have the recess 51 are used.

In Examples 1 to 3, scratches may occur on the polishing pad when the expressions 0.24 ≦ da / DC ≦ 1.89 and 0.24 ≦ db / DC ≦ 1.89 are satisfied. It was found that the yield as the final product was also high. The sun gear 40 is provided with a recess 41, the internal gear 50 is provided with a recess 51, and the equations 0.24 ≦ da / DC ≦ 1.89 and 0.24 ≦ db / DC ≦ 1.89 are satisfied. Therefore, it is considered that the carrier 60 was able to rotate and revolve with substantially no inclination while maintaining the posture along the plane direction orthogonal to the rotation axis of the sun gear 40.

On the other hand, in Comparative Example 1, it was found that the polishing pad was scratched and the yield as the final product was low. In Comparative Example 2, 0.24> da / DC and 0.24> db / DC are satisfied, and the meshing position between the carrier 60 and the sun gear 40 and the meshing between the carrier 60 and the internal gear 50 are satisfied. This is probably because the position moves up and down and the outer peripheral portion of the carrier 60 tends to bend. A scratch was generated on the polishing pad, and in Comparative Example 3, da / DC> 1.89 and db / DC> 1.89, and a carrier crash occurred during the polishing operation, and proper polishing was performed. The process could not be performed.

Therefore, it was found that the glass substrate for information recording medium manufactured by the method and apparatus for manufacturing the glass substrate for information recording medium in each of the above-described embodiments has higher surface smoothness.

As mentioned above, although each embodiment and Example based on this invention were described, each embodiment and 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.

1 magnetic disk, 1G glass substrate, 11 holes, 12 outer peripheral end surface, 13 inner peripheral end surface, 13a, 13b chamfer surface, 14 front main surface, 15 back main surface, 16 magnetic thin film layer, 20 upper surface plate, 21 upper polishing pad 22 upper polishing surface, 30 lower surface plate, 31 lower polishing pad, 32 lower polishing surface, 40 sun gear, 41, 51 recess, 42, 52 tooth surface, 43, 53 tooth tip, 50, 50A, 50Z internal gear, 55 recess Groove, 60 carrier, 61 holding part, 62 meshing teeth, 68 pitch circle, 100 double-side polishing apparatus, DC pitch circle diameter, S10 glass melting process, S11 molding process, S12 first lapping process, S13 coring process, S14 second Lapping step, S15 outer / inner polishing step, S16 first polishing step, S17 chemistry Step, S18 second polishing step, S19 final wash step, TA width, TB thickness, da, db recess depth.

Claims

A method for producing a glass substrate for an information recording medium comprising a polishing step for polishing the surface of a glass substrate,
The polishing step includes
Placing the glass substrate and the carrier between the sun gear and the internal gear;
The carrier is rotated using the sun gear and the internal gear while the outer periphery of the carrier is engaged with the tooth surfaces of both the sun gear and the internal gear, and the glass substrate is slid against the polishing surface of the polishing pad. Polishing the surface of the glass substrate in contact with,
All the tooth surfaces of the sun gear and / or all the tooth surfaces of the internal gear include a recess having a shape recessed from a tooth tip in a direction perpendicular to the rotation axis of the carrier, and the carrier rotates in the recess. The outer circumference of the carrier meshes when
When the pitch circle diameter of the carrier is DC (unit: m), and the depth of the recess from the tooth tip in the direction orthogonal to the rotation axis is d (unit: mm),
The relationship 0.24 ≦ d / DC ≦ 1.89 is established,
A method for producing a glass substrate for an information recording medium.
If the width dimension of the recess in the direction parallel to the rotation axis is TA, and the thickness dimension of the glass substrate in the direction parallel to the rotation axis is TB,
TA <TB is established,
The manufacturing method of the glass substrate for information recording media of Claim 1.
The concave portion forms one concave groove that is annularly continuous along the circumferential direction.
The manufacturing method of the glass substrate for information recording media of Claim 1 or 2.
It manufactured using the manufacturing method of the glass substrate for information recording media in any one of Claim 1 to 3.
Glass substrate for information recording media.
A polishing pad;
A sun gear and an internal gear between which the glass substrate and the carrier are disposed,
The glass substrate is slidably contacted with the polishing surface of the polishing pad by rotating the carrier in a state where the sun gear and the internal gear mesh the outer periphery of the carrier with both tooth surfaces. The surface of the glass substrate is polished,
All the tooth surfaces of the sun gear and / or all the tooth surfaces of the internal gear include a recess having a shape recessed from a tooth tip in a direction perpendicular to the rotation axis of the carrier, and the carrier rotates in the recess. The outer circumference of the carrier meshes when
When the pitch circle diameter of the carrier is DC (unit: m), and the depth of the recess from the tooth tip in the direction orthogonal to the rotation axis is d (unit: mm),
The relationship 0.24 ≦ d / DC ≦ 1.89 is established,
Equipment for manufacturing glass substrates for information recording media.