WO2012090655A1

WO2012090655A1 - Method for producing glass substrate

Info

Publication number: WO2012090655A1
Application number: PCT/JP2011/078156
Authority: WO
Inventors: 河合　秀樹; 達久加藤; 遠藤　毅; 小松　隆史
Original assignee: コニカミノルタオプト株式会社
Priority date: 2010-12-28
Filing date: 2011-12-06
Publication date: 2012-07-05
Also published as: JPWO2012090655A1

Abstract

Provided is a method for producing a glass substrate comprising a polishing step which repeatedly uses a polished surface (24) of a polishing pad (20A) in which a plurality of openings (27) are formed on the polished surface (24) to perform a polishing process to each of a plurality of glass substrates, and which performs a dressing process to the polished surface (24) every time the polished surface (24) has been used for a predetermined number of times, wherein at the start of use of the polished surface (24), a first average area of the plurality of openings (27) is defined based on the area of each of the plurality of openings (27), and every time a dressing process is performed on the polished surface (24), a second average area of the plurality of openings (27) is defined based on the area of each of the plurality of openings (27), thereby an average value is defined based on the first average area and the second average area after the polishing process. The first average area and the second average area after the polishing process are within the range of 64% to 144% with respect to the above average value.

Description

Manufacturing method of glass substrate

The present invention relates to a method for manufacturing a glass substrate, and more particularly to a method for manufacturing a glass substrate used for manufacturing an information recording medium.

Information recording devices such as HDD (Hard Disk Drive) incorporate a disk-shaped information recording medium such as a magnetic disk or a magneto-optical disk. The information recording medium is manufactured from a glass substrate for information recording medium (hereinafter also referred to as a glass substrate). A magnetic thin film layer including a recording layer using properties such as magnetism, light, or magnetomagnetism is formed on the main surface of the glass substrate. When the recording layer is magnetized by the magnetic head, predetermined information is recorded on an information recording medium such as a magnetic disk.

In the manufacturing method of the glass substrate for information recording media, the polishing process is performed on the main surface of the glass substrate using a polishing pad before the chemical strengthening process is performed on the main surface of the glass substrate. (See JP 2010-082721 (Patent Document 1), JP 2005-149668 (Patent Document 2), and JP 2009-101504 (Patent Document 3)). Generally, in the above-described polishing treatment for the main surface, the rough polishing step and the precision polishing step are performed in this order.

First, in the rough polishing step, cerium oxide is supplied as a slurry (polishing liquid) to the main surface of the glass substrate. The main surface of the glass substrate is relatively rough polished using a hard urethane pad or the like. Through the rough polishing step, the parallelism, flatness, thickness, etc. of the main surface of the glass substrate are adjusted.

Next, in the precision polishing step, colloidal silica is supplied as a slurry to the main surface of the glass substrate. The main surface of the glass substrate is polished relatively accurately using a soft foamed urethane pad or the like. By passing through the precision polishing step, the unevenness of the main surface becomes uniform, and the parallelism and flatness of the main surface of the glass substrate are further increased.

Referring to FIG. 14, a general polishing pad 20 used in the precision polishing process will be described. A polishing pad 20 for polishing both main surfaces of a glass substrate (not shown) includes a polishing layer 22 fixed on a predetermined surface plate (not shown). The polishing layer 22 is made of, for example, a foamed resin. The polishing layer 22 has a polishing surface 24 and a plurality of foam pores 26. An opening 27 is exposed from the upper end of the foaming pore 26 toward the polishing surface 24.

In a general precision polishing process, the polishing surface 24 of the polishing pad 20 is pressed against the main surface of the glass substrate. The main surface of the glass substrate is polished by the polishing surface 24 while colloidal silica or the like is supplied between the glass substrate and the polishing surface 24. By passing through the precision polishing step, the smoothness and flatness of the main surface of the glass substrate are adjusted.

Here, an information recording medium such as a magnetic disk rotates at high speed inside an information recording apparatus such as an HDD. For recording and reproducing information, a magnetic head flies over a magnetic recording layer formed on the surface of the information recording medium. In recent years, as the recording density increases, the distance (DFH: Dynamic Flying Height) between the magnetic head and the information recording medium (magnetic thin film layer) tends to decrease. In order to suppress contact between the magnetic thin film layer formed on the main surface of the glass substrate and the magnetic head (so-called head crush phenomenon), the demand for smoothness and flatness of the main surface of the glass substrate is increasing. .

JP 2010-082721 A JP 2005-149668 A JP 2009-101504 A

Referring to FIG. 14, the polishing surface 24 of the polishing pad 20 is gradually worn down by being repeatedly used to polish the main surface of the glass substrate. The position of the polishing surface 24 gradually recedes (towards the upper side in FIG. 14). The polishing surface 24 is dressed each time it is used for polishing a predetermined number of glass substrates. For example, after the polishing surface 24 is worn down and the polishing surface 24 reaches (retracts) slightly from the state shown in FIG. 14 to the position indicated by the dotted line R1, the dressing process is performed on the polishing surface 24. By the dressing process, the polished surface 24 exhibits a flat surface along the dotted line R1.

The polished surface 24 is regenerated to a good surface roughness and is again used for polishing the glass substrate. After the polishing surface 24 is worn down and the polishing surface 24 reaches a position just before the position indicated by the dotted line R2, the dressing process is performed on the polishing surface 24 again. By the dressing process, the polishing surface 24 exhibits a flat surface along the dotted line R2. Thereafter, the polishing surface 24 is again subjected to polishing of the glass substrate.

After the polishing surface 24 is worn down and the polishing surface 24 reaches a position just before the position indicated by the dotted line R3, the polishing surface 24 is dressed again. The polishing surface 24 presents a flat surface along the dotted line R3, and the polishing surface 24 is again used for polishing the glass substrate. By periodically dressing the polishing surface 24, the surface roughness of the polishing surface 24 is maintained in a good state. For convenience, the interval between the dotted line R1 and the dotted line R2 and the interval between the dotted line R2 and the dotted line R3 are illustrated widely, but in actuality, these intervals are several μm.

Here, Japanese Patent Laid-Open No. 2005-149668 (Patent Document 2) discloses an invention relating to a polishing surface in an initial state (at the start of use of the polishing pad), but does not mention changes in the state of the polishing surface. Absent. Japanese Patent Laying-Open No. 2010-082721 (Patent Document 1) does not mention a change in the opening diameter. Japanese Patent Laying-Open No. 2009-101504 (Patent Document 3) describes the effect of changing the aperture diameter, but does not refer to the minute waviness of the substrate. In the conventional method for manufacturing a glass substrate, the area of the opening of the foam pore, the area occupation ratio of the opening with respect to the polished surface, or the like greatly varies depending on the state change of the polished surface. Irregularities such as micro swells occurred on the main surface of the glass substrate, and the quality of the glass substrate varied.

The present invention has been made in view of the above circumstances, and provides a method for manufacturing a glass substrate capable of reducing quality variations such as a microwaviness shape on the main surface of the glass substrate for information recording media. For the purpose.

The manufacturing method of the glass substrate based on this invention uses the polishing pad in which the several opening part was formed in the grinding | polishing surface, the preparatory process which prepares several glass substrate, and the said grinding | polishing surface of the said polishing pad repeatedly. A polishing step of performing a polishing process on each of the plurality of glass substrates and dressing the polishing surface every time the polishing surface is used a predetermined number of times, and at the start of use of the polishing surface Based on the area of each of the plurality of openings at the start of use of the polishing surface, a first average area of the plurality of openings at the start of use of the polishing surface is defined, and the dress on the polishing surface Each time processing is performed, the second of the plurality of openings each time the dressing is performed is based on the area of each of the plurality of openings when the dressing is performed. An average area is defined, and based on the first average area and the second average area through the polishing process, an average value of the first average area and the second average area through the polishing process is defined, The first average area and the second average area through the polishing step are within a range of 64% to 144% with respect to the average value of the first average area and the second average area through the polishing step. It is.

Preferably, the polishing pad prepared in the preparation step includes a resin layer constituting the polishing surface, and in the preparation step, a plurality of the above-described molds are used by using a molding die having a plurality of uneven patterns. By transferring the concavo-convex pattern to the resin layer, the polishing pad having the plurality of openings formed in the polishing surface is prepared.

Preferably, the polishing pad prepared in the preparation step includes a resin layer constituting the polishing surface, and in the preparation step, a portion of the resin layer corresponding to the opening is subjected to thermal processing. Thus, the polishing pad having the plurality of openings formed in the polishing surface is prepared.

Preferably, the polishing pad prepared in the preparation step includes a resin layer constituting the polishing surface, and in the preparation step, machining is performed on a portion of the resin layer corresponding to the opening. Thus, the polishing pad having the plurality of openings formed in the polishing surface is prepared.

Preferably, at the start of use of the polishing surface and each time the dressing is performed on the polishing surface, an average between adjacent openings among the plurality of openings formed in the polishing surface An interval value is defined, and the average interval value is in the range of 5 μm to 100 μm.

Preferably, the total area of the plurality of openings formed in the polishing surface is defined at the start of use of the polishing surface and each time the dressing is performed on the polishing surface, and the use of the polishing surface The total area at the start and every time the dressing is performed on the polished surface is in the range of 20% to 60% with respect to the area of the polished surface.

Preferably, the average value of the first average area and the second average area through the polishing step is not less than 0.25π × 10 ⁻¹² (m ² ) and not more than 1.00π × 10 ⁻⁸ (m ² ). Within range.

According to the present invention, it is possible to obtain a glass substrate manufacturing method capable of reducing quality variations such as a fine waviness shape on the main surface of a glass substrate for an information recording medium.

It is a perspective view which shows the glass substrate manufactured by the manufacturing method of the glass substrate in embodiment. It is a perspective view which shows the magnetic disc manufactured by forming a magnetic thin film layer in the main surface of the glass substrate manufactured by the manufacturing method of the glass substrate in embodiment. It is a figure which shows each process of the manufacturing method of the glass substrate in embodiment. It is a bottom view which shows the polishing pad used for the manufacturing method of the glass substrate in embodiment. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. It is a bottom view of the polishing pad for demonstrating the space | interval of adjacent opening parts. It is a bottom view which shows the 1st modification of the polishing pad which can be used for the manufacturing method of the glass substrate in embodiment. It is a bottom view which shows the 2nd modification of the polishing pad which can be used for the manufacturing method of the glass substrate in embodiment. It is a top view which shows the stamper used for the manufacturing method of the polishing pad used for the manufacturing method of the glass substrate in embodiment. It is sectional drawing which shows a mode that the said polishing pad is produced using the stamper used for the manufacturing method of the polishing pad used for the manufacturing method of the glass substrate in embodiment. It is sectional drawing which shows the 1st modification of the manufacturing method of the polishing pad which can be used for the manufacturing method of the glass substrate in embodiment. It is sectional drawing which shows the 2nd modification of the manufacturing method of the polishing pad which can be used for the manufacturing method of the glass substrate in embodiment. It is a figure which shows each characteristic of the polishing pad regarding an Example and a comparative example. It is sectional drawing which shows the general polishing pad used for the precision grinding | polishing process of the manufacturing method of a glass substrate.

Embodiments and examples based on the present invention will be described below with reference to the drawings. In the description of each embodiment and each example, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the description of each 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]
(Glass substrate 1 / magnetic disk 10)
With reference to FIG. 1 and FIG. 2, the glass substrate 1 obtained by the manufacturing method of the glass substrate for information recording media based on Embodiment and the magnetic disk 10 provided with the glass substrate 1 are demonstrated first. FIG. 1 is a perspective view showing a glass substrate 1 used for a magnetic disk 10 (see FIG. 2). FIG. 2 is a perspective view showing a magnetic disk 10 as an information recording medium provided with the glass substrate 1.

As shown in FIG. 1, a glass substrate 1 (glass substrate for information recording medium) used for a magnetic disk 10 has an annular disk shape with a hole 1H formed in the center. The glass substrate 1 has a front main surface 1A, a back main surface 1B, an inner peripheral end surface 1C, and an outer peripheral end surface 1D. A chemical strengthening layer (not shown) is formed on the front main surface 1A, the back main surface 1B, the inner peripheral end surface 1C, and the outer peripheral end surface 1D.

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 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 to be pointed on the glass substrate.

As shown in FIG. 2, the magnetic disk 10 is configured by forming a magnetic thin film layer 2 on the front main surface 1A of the glass substrate 1 described above. In FIG. 2, the magnetic thin film layer 2 is formed only on the front main surface 1A, but the magnetic thin film layer 2 may also be formed on the back main surface 1B.

In order to improve the sliding of the magnetic head, the surface of the magnetic thin film layer 2 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.

If necessary, an underlayer or a protective layer may be provided. The underlayer in the magnetic disk 10 is selected according to the 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 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 thin film layer 2 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. In addition, these protective layers may be a single layer, or may have a multilayer structure including 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 of the glass substrate (glass substrate for information recording media) in this Embodiment is demonstrated using the flowchart figure shown in FIG.

The manufacturing method of the glass substrate in the present embodiment includes a rough lapping step (step S10), a shape processing step (step S20), a roughening step (step S30), a fine lapping step (step S40), and an end surface polishing step (step). S50), a main surface polishing step (step S60), and a chemical strengthening step (step S70). A magnetic thin film forming step (step S80) is performed on the glass substrate (corresponding to the glass substrate 1 in FIG. 1) obtained through the chemical strengthening treatment step (step S70). can get.

Hereinafter, the details of each of these steps S10 to S80 will be described in order. In the following, simple cleaning appropriately performed between each of steps S10 to S80 will not be described.

In the rough lapping process (step S10), for example, a glass substrate having a diameter of 66 mmφ and a thickness of 1.2 mm is prepared. The glass substrate is manufactured by directly pressing a molten glass using an upper mold, a lower mold, and a copper mold. The material of the glass substrate is, for example, aluminosilicate glass. The glass substrate may be manufactured by cutting out from a sheet-like glass formed by a downdraw method or a float method using a grinding wheel.

* Rough lapping is applied to the prepared glass substrate. This rough lapping process improves the dimensional accuracy and shape accuracy of the glass substrate. This rough lapping process is performed using a double-sided lapping apparatus. The abrasive used is, for example, alumina having a particle size of # 400 (particle size of about 40 μm to 60 μm). The load of the upper surface plate is set to about 100 kg with respect to the glass substrate accommodated in the carrier of the double-side wrapping apparatus. By polishing with a double-sided lapping device, both main surfaces of the glass substrate are finished with a surface accuracy of 0 μm to 1 μm and a surface roughness Rmax of about 6 μm.

In the shape processing step (step S20), the outer peripheral end surface and the inner peripheral end surface of the glass substrate are ground. The outer diameter of the glass substrate is 65 mm, and the inner diameter (the diameter of the hole 1H in the central portion) is 20 mm. The surface roughness Rmax of the outer peripheral end face and the inner peripheral end face of the glass substrate is finished to about 2 μm, for example. At this time, chamfering may be performed on the outer peripheral end surface and the inner peripheral end surface of the glass substrate.

In the roughening step (step S30), a flat polishing machine is used. A plane polishing machine mechanically polishes a glass substrate using loose abrasive grains. The entire surface of the glass substrate is finished to a substantially uniform surface roughness (Ra = about 0.01 μm to 0.4 μm). The surface roughness set in the roughening step may be determined in relation to the particle size of the fixed abrasive used in the fine lapping step described below.

In the fine wrapping process (step S40), a wrapping apparatus is used. The lapping apparatus grinds both main surfaces of the roughened glass substrate using a fixed abrasive polishing pad such as a diamond sheet. Both main surfaces of the glass substrate are finished to have a surface roughness Ra of 0.1 μm or less and a flatness of 7 μm or less.

Since both main surfaces of the glass substrate are roughened in advance in the above-described roughening step (step S30), the fine fixed abrasive grains are caught by both main surfaces of the glass substrate through the fine lapping step. Formed. Generation | occurrence | production of the malfunction that a fixed abrasive grain slips on the main surface of a glass substrate is suppressed. For this reason, the processing rate in the fine lapping process can be set to a high value from the start of polishing on both main surfaces of the glass substrate.

In the end surface polishing step (step S50), a brush is used. With the glass substrate rotated, the outer peripheral end surface and the inner peripheral end surface of the glass substrate are polished with a brush. The glass substrate is finished to have a surface roughness Rmax of about 0.4 μm and a surface roughness Ra of about 0.1 μm on the outer peripheral end surface and the inner peripheral end surface. After the end face polishing process is completed, the glass substrate is washed with water.

The main surface polishing step (step S60) includes a rough polishing step (step S61) and a fine polishing step (step S62). First, a rough polishing process (step S61) is performed. In the rough polishing process (step S61), the scratches and distortion remaining in the fine lapping process (step S40) are removed. A double-side polishing apparatus using a suede pad polishes both main surfaces of the glass substrate. As the slurry (abrasive), cerium oxide having CeO ₂ / TREO of 99 mass% or more and a total mass of the alkaline earth metal content of 10 mass ppm or less is used.

Next, a precision polishing step (step S62) is performed. Here, both main surfaces of the glass substrate are polished with high accuracy using a soft polishing pad 20A described later. As the slurry (polishing agent), silica abrasive grains having a particle diameter smaller than that of cerium oxide used in the above-described rough polishing step (step S61) are used. Details of the polishing pad 20A will be described later with reference to FIGS.

In the chemical strengthening process (step S70), the chemical strengthening process is performed on the glass substrate on which the main surface polishing process (step S60) is completed. Ions that are present on the surface (surface layer) of the glass substrate (when the glass substrate is an aluminosilicate glass, Li ⁺ and Na ⁺ ) are ions having a larger ion radius (Na ⁺ and K ⁺ ) Is ion exchanged.

Compressive stress is generated on the surface of the glass substrate (from both main surfaces of the glass substrate to a depth of about 5 μm, for example) by the ion exchange. The surface of the glass substrate is strengthened by the generation of the compressive stress, and the rigidity as the glass substrate is improved. The manufacturing method of the glass substrate in the present embodiment is configured as described above.

In the magnetic thin film forming step (step S80), the magnetic thin film layer is formed on both main surfaces (or one of the main surfaces) of the glass substrate (corresponding to the glass substrate 1 shown in FIG. 1) on which the chemical strengthening process has been completed. It is formed. The magnetic thin film layer includes 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 a lubrication made of an F system. It is formed by sequentially depositing layers. By forming the magnetic thin film layer, a perpendicular magnetic recording disk corresponding to the magnetic disk 10 shown in FIG. 2 can be obtained.

The magnetic disk in the present embodiment is an example of a perpendicular magnetic disk composed of a magnetic thin film layer. The magnetic disk may be composed of a magnetic layer or the like as a so-called in-plane magnetic disk.

(Polishing pad 20A)
With reference to FIG. 4 and FIG. 5, the polishing pad 20A used for the manufacturing method of the glass substrate in this Embodiment is demonstrated. FIG. 4 is a bottom view showing the polishing pad 20A (the polishing surface 24 thereof). 5 is a cross-sectional view taken along line VV in FIG. The polishing pad 20A is used for polishing both main surfaces of the glass substrate in the above-described precision polishing step (step S62).

The polishing pad 20A includes a polishing layer 22 fixed on a predetermined surface plate (not shown). The polishing layer 22 is made of, for example, a resin. A plurality of openings 27 are formed in the polishing surface 24. The polishing surface 24 of the polishing pad 20A is used repeatedly in order to perform the polishing process on each of the plurality of glass substrates. The polishing surface 24 gradually wears down, and the position of the polishing surface 24 gradually recedes (toward the upper side in FIG. 5). Each time the polishing surface 24 is used a predetermined number of times, the polishing surface 24 is dressed.

For example, after the polishing surface 24 is worn down and the polishing surface 24 reaches (retreats) slightly from the state shown in FIG. 5 to the position indicated by the dotted line R1, the dressing process is performed on the polishing surface 24. By the dressing process, the polished surface 24 exhibits a flat surface along the dotted line R1. The polished surface 24 is regenerated to have a good surface roughness and is again used for polishing the glass substrate. In the polishing pad 20A, the polishing surface 24 is scraped off by, for example, about several μm by one dressing process.

Similarly, after the polishing surface 24 reaches slightly before the position indicated by the dotted line R2, the polishing surface 24 is dressed. The polishing surface 24 presents a flat surface along the dotted line R2, and the polishing surface 24 is again used for polishing the glass substrate. Further, after the polishing surface 24 reaches a position just before the position indicated by the dotted line R3, the polishing surface 24 is dressed. The polishing surface 24 presents a flat surface along the dotted line R3, and the polishing surface 24 is again used for polishing the glass substrate.

By periodically dressing the polishing surface 24, the surface roughness of the polishing surface 24 is maintained in a good state. In the polishing pad 20A, this dressing is repeated, for example, about 100 times while the polishing surface 24 is used for polishing the glass substrate. For convenience, the interval between the dotted line R1 and the dotted line R2 and the interval between the dotted line R2 and the dotted line R3 are illustrated widely, but in actuality, these intervals are several μm.

Here, the polishing pad 20 </ b> A at the start of use of the polishing surface 24 (state shown in FIG. 5) starts using the polishing surface 24 based on the area of each of the plurality of openings 27 at the start of use of the polishing surface 24. It has an average area A ₁ (first average area) of the plurality of openings 27 at the time. In other words, the average and the area A _1, a value obtained by averaging all the area of the opening 27 in the polishing surface 24 at the start of use time (the state shown in FIG. 5) of the polishing surface 24.

It is assumed that the use of the polishing surface 24 (that is, the polishing process) is started, and that the polishing surface 24 exhibits a flat surface along the dotted line R1 by dressing performed thereafter. The polishing pad 20A in this case is based on the area of each of the plurality of openings 27 in the polishing surface 24 along the dotted line R1, and the average area B ₁ (the plurality of openings 27 in the polishing surface 24 along the dotted line R1). Second average area). The average and the area B _1, a value obtained by averaging all the area of the opening 27 in the polishing surface 24 along the dotted line R1.

Thereafter, it is assumed that the polishing surface 24 exhibits a flat surface along the dotted line R2 by dressing. In this case, the polishing pad 20A is based on the area of each of the plurality of openings 27 in the polishing surface 24 along the dotted line R2, and the average area B ₂ of the plurality of openings 27 in the polishing surface 24 along the dotted line R2 ( Other second average area). The average and the area B _2, a value obtained by averaging all the area of the opening 27 in the polishing surface 24 along the dotted line R2.

Further, after that, it is assumed that the polishing surface 24 exhibits a flat surface along the dotted line R3 by dressing. In this case, the polishing pad 20A is based on the area of each of the plurality of openings 27 in the polishing surface 24 along the dotted line R3, and the average area B ₃ of the plurality of openings 27 in the polishing surface 24 along the dotted line R3 ( Furthermore, it has another second average area). The average area B _3, a value obtained by averaging all the area of the opening 27 in the polishing surface 24 along the dotted line R3.

While the polishing pad 20A is used (polishing step is performed), every time dressing is performed on the polishing surface 24, an average area (like the above average areas B ₁ , B ₂ , B ₃ ) The second average area) is obtained sequentially. Based on the average area A ₁ at the start of use and the average areas B ₁ , B ₂ , B ₃ ... Through the polishing process, the average value D is calculated by averaging these. The average value D is a value obtained by averaging the average area A ₁ at the start of use and the average areas B ₁ , B ₂ , B ₃ .

Here, in polishing pad 20A used in the glass substrate manufacturing method of the present embodiment, average area A ₁ at the start of use and average areas B ₁ , B ₂ , B ₃ . Each value is in the range of 64% to 144% with respect to the averaged value (average value D). The plurality of openings 27 formed in the polishing pad 20A used in the glass substrate manufacturing method in the present embodiment are formed so as to satisfy the conditions.

Preferably, each of the average area A ₁ at the start of use and the average areas B ₁ , B ₂ , B ₃ ... Through the polishing process is averaged with respect to the average value (average value D). It is good that it is in the range of 72% or more and 132% or less. More preferably, each of the average area A ₁ at the start of use and the average areas B ₁ , B ₂ , B ₃ ... Through the polishing process is compared with the average value (average value D). It is good to be in the range of 81% or more and 121% or less.

When the plurality of openings 27 do not satisfy these conditions (that is, when the change in the cross-sectional area of the plurality of openings 27 each time dressing is performed on the polishing surface 24 is large), the openings 27 are formed. The elasticity of the polishing layer 22 in the vertical direction changes greatly each time dressing is performed on the polishing surface 24. Along with a large change in the elasticity of the polishing layer 22 in the vertical direction, irregularities of the shape such as micro-waviness occur on the main surface of the glass substrate to be polished, and the quality of the glass substrate after the precision polishing process varies. Arise.

Because the plurality of openings 27 satisfy the above conditions, the polishing characteristics of the polishing surface 24 with respect to the main surface of the glass substrate become substantially uniform at the start of use and whenever dressing is performed. Even if the polishing surface 24 of the polishing pad 20A is repeatedly subjected to dressing processing, irregularities such as micro swell are hardly generated on the main surface of the glass substrate to be polished, and the precision polishing step (step S62) is performed. Variations in the quality of the passed glass substrate are also suppressed.

When the opening 27 is circular, the above condition can be converted into a radius. That is, the average value D calculated from the average area is converted into a radius to obtain the average value r. With respect to this average value r, the plurality of openings 27 are arranged such that the average radius of the plurality of openings 27 at the start of use and every time dressing is performed is in the range of 80% to 120%. It may be formed.

Preferably, the plurality of openings 27 have an average radius within the range of 85% or more and 115% or less at the start of use and every time dressing is performed with respect to the average value r. An opening 27 may be formed. More preferably, with respect to the average value r, the plurality of openings are arranged such that the average radius of the plurality of openings 27 at the start of use and every time dressing is performed is in the range of 90% to 110%. A portion 27 may be formed.

Further, the average value D, which is an average value of the average area A ₁ at the start of use and the average areas B ₁ , B ₂ , B ₃ ... Through the polishing process, is 0.25π × 10 ⁻¹² (m ² ). It is preferable to be within the range of 1.00π × 10 ⁻⁸ (m ² ) or less. Preferably, the average value D is in the range of 6.25π × 10 ⁻¹² (m ² ) or more and 0.25π × 10 ⁻⁸ (m ² ) or less. More preferably, the average value D is in the range of 0.25π × 10 ⁻¹⁰ (m ² ) to 0.04π × 10 ⁻⁸ (m ² ).

When the average value D is less than 0.25π × 10 ⁻¹² (m ² ), the agglomerated slurry is clogged in the opening 27, and the abrasion of the polishing surface 24 is difficult to be performed in an equilibrium (uniform) manner. When the average value D is larger than 1.00π × 10 ⁻⁸ (m ² ), there is a risk that the fine waviness on the surface of the glass substrate to be polished increases.

When the opening 27 is circular, the above area condition can be converted into a diameter. That is, the average value D calculated from the above average area is converted into a diameter to obtain the average value d. The plurality of openings 27 may be formed so that the average value d is in the range of 1 μm to 200 μm. Preferably, a plurality of openings 27 are formed so that the average value d is in the range of 5 μm to 100 μm. More preferably, the plurality of openings 27 may be formed so that the average value d is in the range of 10 μm to 40 μm.

Here, referring to FIG. 5, among the plurality of openings 27, intervals E1, E2, E3,... Defined between adjacent openings 27 (values at the start of use and every dressing) The average value (average interval value) is preferably in the range of 5 μm to 100 μm. In other words, the intervals E1, E2, E3,... Are the wall thicknesses of the polishing layer 22 positioned between the adjacent openings 27. Referring to FIG. 6, the “interval between adjacent openings 27” referred to here is the polishing surface 24 (polishing) by a line segment connecting the area centroids 27 </ b> G in the cross-sectional shape of each

opening

27, 27. Layer 22) is the length of the cut (shown by line segments E10, E11, E12 in FIG. 6). Referring to FIG. 5 again, preferably, among the plurality of openings 27, the average value (average interval value) of the intervals E1, E2, E3,. It is good in the range of 10 micrometers or more and 50 micrometers or less.

When the average value (average interval value) is less than 5 μm, the wall thickness of the polishing layer 22 that forms the opening 27 becomes thin, and the polishing layer 22 that forms the opening 27 easily falls during the precision polishing step. Become. When the average value (average interval value) is larger than 100 μm, the frictional force generated between the polishing surface 24 and the main surface of the glass substrate is increased, and the main surface of the glass substrate is not easily polished.

Further, the total area of the plurality of openings 27 in the polishing surface 24 is obtained at the start of use of the polishing surface 24 and each time dressing is performed on the polishing surface 24. The total area is preferably in the range of 20% to 60% with respect to the area of the polishing surface 24 at the start of use of the polishing surface 24 and each time dressing is performed on the polishing surface 24.

In other words, at the start of use of the polishing surface 24 and each time dressing is performed on the polishing surface 24, the area occupancy ratio of the plurality of openings 27 to the polishing surface 24 is in the range of 20% or more and 60% or less. Good. In addition, Preferably, the said area occupation rate is good in the range of 25% or more and 40% or less. When the area occupancy is less than 20%, the frictional force generated between the polishing surface 24 and the main surface of the glass substrate increases, and smooth polishing becomes difficult, which may lead to damage to the pad or the glass substrate. is there. When the area occupancy is larger than 60%, the wall thickness of the polishing layer 22 forming the opening 27 becomes thin, and the abrasion of the polishing surface 24 is hardly performed in a balanced (uniform) manner.

As described above, when the polishing pad 20A is used in the precision polishing step (step S62), the polishing characteristics of the polishing surface 24 with respect to the main surface of the glass substrate at the start of use and every time dressing is performed are as follows. It becomes almost uniform. Even if the dressing process is repeatedly performed on the polishing pad 20A, irregularities of the shape such as microwaviness hardly occur on the main surface of the glass substrate to be polished, and the glass substrate that has undergone the precision polishing step (step S62) Variations in quality are also suppressed.

[Modification of Embodiment]
In the method for manufacturing a glass substrate in the above-described embodiment (see FIG. 4), a polishing pad 20A in which a plurality of openings 27 having substantially the same area are regularly arranged in the polishing surface 24 is prepared. . The planar shape of the plurality of openings 27 is a perfect circle.

Referring to FIG. 7, the shape of the plurality of openings 27 may be an isosceles triangle as in the polishing pad 20B. The shape of the plurality of openings 27 is not limited to an isosceles triangle, and may be any shape (such as an ellipse, a polygon, and an array). The shape of the plurality of openings 27 may be non-uniform.

Since the plurality of openings 27 satisfy the conditions described in the above embodiment, the polishing characteristics of the polishing surface 24 with respect to the main surface of the glass substrate at the start of use and every time dressing is performed are: It becomes almost uniform. As a result, even when the dressing process is repeatedly performed on the polishing pad 20B, irregularities such as microwaviness are hardly generated on the main surface of the glass substrate to be polished, and the precision polishing process (step S62) is performed. Variations in the quality of the glass substrate are also suppressed.

Referring to FIG. 8, the size of the plurality of openings 27 may be different from each other as in the polishing pad 20C. Even if the sizes of the plurality of openings 27 are not uniform, the plurality of openings 27 satisfy the conditions described in the above embodiment, so that at the start of use and every time dressing is performed. The polishing characteristics of the polishing surface 24 with respect to the main surface of the glass substrate are substantially uniform. As a result, even when the dressing process is repeatedly performed on the polishing pad 20C, irregularities such as micro waviness are hardly generated on the main surface of the glass substrate to be polished, and the precision polishing process (step S62) is performed. Variations in the quality of the glass substrate are also suppressed.

(Manufacturing method of polishing pad 20A)
FIG. 9 is a bottom view showing the stamper 30 used for manufacturing the polishing pad 20A. FIG. 10 is a cross-sectional view showing how the polishing pad 20A is manufactured using the stamper 30. As shown in FIG. When manufacturing the polishing pad 20A (not shown), a stamper 30 (molding die) in which a plurality of projections 37 are provided on the flat surface 34 is prepared. The stamper 30 is made of stainless steel, for example. The uneven pattern shape of the plurality of protrusions 37 corresponds to the shape of the plurality of openings 27 formed in the polishing pad 20A.

As shown in FIG. 10, a resin (material constituting the polishing layer 22) melted so as to be deformable by being heated to a predetermined temperature is poured into the mold 39. The molten resin is cured by heat removal between the mold 39 and the stamper 30. By the curing, a polishing pad 20A (see FIG. 5) in which a plurality of openings 27 are transferred from a plurality of protrusions 37 of the stamper 30 is manufactured.

Referring to FIG. 11, as a manufacturing method of polishing pad 20A, thermal processing using laser oscillator 40 or the like may be performed on polishing layer 22. As the thermal processing, electric discharge processing using an electrode having a predetermined electrode shape may be performed. Also in this case, the polishing layer 22 is composed of a resin layer such as urethane. By the thermal processing, a part of the polishing layer 22 is melted, and a plurality of openings 27 are formed. The shape of the plurality of openings 27 is not limited to a circle as in the above-described polishing pad 20B (see FIG. 7), and can be formed into an arbitrary shape by thermal processing. The size of the plurality of openings 27 is not limited to the same as the above-described polishing pad 20C (see FIG. 8), and can be formed in any size by thermal processing.

Referring to FIG. 12, as a method of manufacturing polishing pad 20A, machining (grinding) using a drill 50 or the like may be performed on polishing layer 22. Also in this case, the polishing layer 22 is composed of a resin layer such as urethane. By the machining, a part of the polishing layer 22 is scraped off, and a plurality of openings 27 are formed. The shape of the plurality of openings 27 is not limited to a circle like the above-described polishing pad 20B (see FIG. 7), and can be formed into an arbitrary shape by machining. The size of the plurality of openings 27 is not limited to the same as the above-described polishing pad 20C (see FIG. 8), and can be formed to an arbitrary size by machining.

[Examples and Comparative Examples]
Hereafter, with reference to FIG. 13, the Example performed based on this invention and the comparative example regarding the said Example are each demonstrated. Here, 13 types of polishing pads as Examples 1 to 13 and 1 type of polishing pad as Comparative Example 1 were prepared in order to perform a precise polishing process on a glass substrate. The polishing pad in Comparative Example 1 corresponds to the polishing pad 20 described with reference to FIG. 14 at the beginning.

The polishing surface of each polishing pad in Examples 1 to 10, 13 and Comparative Example 1 was a circular one having an outer diameter of 1200 mmφ. The polishing surface of each polishing pad in Examples 11 and 12 was a square type having four sides of 20 mm and 15 mm, respectively. In each of the polishing pads in Examples 1 to 13 and Comparative Example 1, a polishing layer having a thickness in the range of 540 μm to 650 μm was used. The depth of the plurality of openings formed in the polished surface is greater than 200 μm in the direction perpendicular to the polished surface. Note that the outer diameter, the thickness of the polishing layer, and the depth of the opening are not limited to the above values in the present invention.

Using the polishing pads in Examples 1 to 13 and Comparative Example 1, precision polishing was performed on the main surface of the glass substrate. At this time, each polishing pad was attached to a general 16B double-side polishing apparatus. The polishing time for the glass substrate was 20 minutes. In one polishing process, 100 glass substrates were collectively subjected to precision polishing treatment one by one. Each time the two main surfaces of one glass substrate were subjected to precision polishing, dressing was performed once on the polishing surface of the polishing pad. Various processing conditions in the precision polishing treatment were fixed. The apparatus used for polishing may be a smaller apparatus than the present embodiment, such as 9B type.

In dressing, a grinding stone made of diamond pellets was placed on the polishing surface of the polishing pad, and a load was applied to uniformly polish the polishing surface. In one dressing process, the polishing surface was polished so that the polishing surface was retracted by about 2 μm. As a result, the dressing process is performed 100 times, so that the polished surface after the precision polishing process for the 100 glass substrates is retracted by 200 μm as compared with the start of use.

Here, as shown in FIG. 13, each of the polishing pads in Examples 1 to 13 has an average radius r of a plurality of openings defined at the start of use and each time dressing is performed. Is set to be in the range of 80% to 120%. Specifically, in Examples 1 to 9, the average radius is in the range of 82% to 118%, and in Example 10, the average radius is in the range of 97% to 106%. In Example 11, the average radius is in the range of 96% to 116%, and in Example 12, the average radius is in the range of 97% to 105%. In Example 13, those having an average radius in the range of 89% to 118% were used.

That is, the plurality of openings formed in the polishing pads in Examples 1 to 13 are the same as the conditions described in the above-described embodiment (the average value r is a plurality of openings at the start of use and each time dressing is performed. The average radius of the openings 27 is in the range of 80% to 120%.

On the other hand, in the polishing pad in Comparative Example 1, the average radius of the opening defined at the start of use and every time dressing is performed is in the range of 57% to 167% with respect to the average value r. It is set to become. The plurality of openings formed in the polishing pad in Comparative Example 1 are the same as the conditions described in the above-described embodiment (the plurality of openings 27 at the start of use and each time dressing is performed on the average value r). In the range of 80% or more and 120% or less).

(Contrast with Examples 1 to 10, 13 and Comparative Example 1)
A magnetic film was formed on each of 100 glass substrates subjected to precision polishing using each of the polishing pads in Examples 1 to 10, 13 and Comparative Example 1. Glide inspection was performed on each of 100 glass substrates on which magnetic films were formed, and dressing was performed 100 times at the start of use of the polishing pad (hereinafter also referred to as before use) and on the polishing pad. The glide test yield of the glass substrate after (hereinafter also referred to as after use) was measured.

Here, the glide test yield (also referred to as the glide test pass rate) is a test in which a projection having a predetermined height or more existing on the surface of the magnetic film is detected over the entire circumference with a magnetic head that floats at a constant height. The probability of passing the glide test is shown.

In the polishing pad of Example 1, the glide test yield before using the polishing pad was 93%, and the glide test yield after using the polishing pad was 91%. The difference in glide test yield before use and after use is 2%. In the polishing pad of Example 1, it turns out that the quality in the main surface of a glass substrate is maintained in the fixed range both before and after use.

Similarly, in Examples 2 to 10 and 13, the difference in the glide inspection yield before use and after use is 13% of Example 7 at the maximum. Also in the polishing pads of Examples 2 to 10 and 13, it can be seen that the quality on the main surface of the glass substrate is maintained within a certain range both before and after use.

On the other hand, in the polishing pad of Comparative Example 1, the glide inspection yield before use of the polishing pad was 96%, and the glide inspection yield after use of the polishing pad was 72%. The difference in the glide test yield before use and after use is 24%. In the polishing pad of Comparative Example 1, the quality on the main surface of the glass substrate is not maintained within a certain range, and it can be seen that there is a variation in the quality of the microwaviness component and the like on the main surface of the glass substrate. .

The glass substrates that failed the glide test were inspected from 100 glass substrates that had been subjected to precision polishing using the polishing pad in Comparative Example 1. An optical surface analyzer (OSA (Optical Surface Analyzer), KLA-TENCOL, OSA6100) was used for the inspection, and the spatial frequency used for the analysis was set to 200 μm or more and 1000 μm or less. As a result, in these glass substrates that were rejected, the minute waviness component exceeded a predetermined reference value. From this, in order to reduce the quality variation such as the micro-waviness component on the main surface of the glass substrate, the average radius of the opening defined respectively at the start of use and every time dressing is performed, It can be seen that the average value r is preferably set to be in the range of 80% to 120%.

(Comparison between Examples 10 to 13 and Comparative Example 1)
Here, the polishing pads in Examples 10 and 13 were produced using the stamper 30 shown in FIGS. The stamper 30 is made of stainless steel, and the outer shapes of the plurality of protrusions 37 as the concavo-convex pattern are each cylindrical. The protruding heights of the plurality of protrusions 37 from the flat surface 34 are each about 250 μm. Each of the plurality of protrusions 37 has a diameter of about 80 μm, and has a shape with a minute taper corresponding to the shape of the opening formed in the polishing pad. The interval (pitch) between the plurality of protrusions 37 is 180 μm.

The polishing pad in Example 11 was produced by the method shown in FIG. Specifically, a 20 mm square non-foamed urethane sheet is produced by a known method, and a laser processing with an excimer laser is performed so that the depth from the polished surface is 300 μm, the diameter is 90 μm, and the interval (pitch) is 200 μm. A cylindrical recess was formed (both designed values). The recess forms an opening in the polishing surface. The concave portion may be formed by other means such as electric discharge machining using an electrode having a predetermined electrode shape.

The polishing pad in Example 12 was produced by the method shown in FIG. Specifically, a 15 mm square non-foamed urethane sheet is produced by a known method, and a depth of 300 μm from the polished surface, a diameter of 90 μm, and an interval (pitch) of 200 μm are obtained by machining with a drilling machine. A cylindrical recess was formed (both designed values). The recess forms an opening in the polishing surface.

On the other hand, the polishing pad in Comparative Example 1 was prepared by buffing the pad surface using a known method (for example, Japanese Patent Application Laid-Open No. 2010-082721) so that the foamed pore has an opening in the polishing surface. .

For each of the polishing pads in Examples 10 to 13 and Comparative Example 1, the interval between adjacent openings (the wall thickness of the polishing layer positioned between adjacent openings) is set at the start of use and dressing. Was measured every 10 times, and the average value (average interval value) was calculated. In addition, the space | interval of adjacent opening parts is measured as an average value in a 500 micrometers square surface. As a result, the average value (average interval value) was 100 μm to 106 μm in Examples 10 to 13 and 22 μm in Comparative Example 1.

For each of the polishing pads in Examples 10 to 13 and Comparative Example 1, the area occupation ratio of the plurality of openings to the polishing surface was measured at the start of use and every time dressing was performed 10 times, and the average of these was measured. The value was calculated. This area occupancy was measured as an average value in a 500 μm square plane. As a result, the average value of the area occupancy ratio of the openings was 35% to 38% in Examples 10 to 13 and 35% in Comparative Example 1.

For each of the polishing pads in Examples 10 to 13 and Comparative Example 1, the average diameter of the plurality of openings was measured at the start of use and every time dressing was performed 10 times, and the average value was calculated. . The average diameter of the plurality of openings was measured as an average value in a 500 μm square plane. As a result, the average value of the diameters of the plurality of openings was 81 to 95 μm in Examples 10 to 13 and 18 μm in Comparative Example 1.

According to the comparison between Examples 10 to 13 and Comparative Example 1, according to the polishing pad manufacturing method described in the above embodiment, a plurality of openings respectively defined at the start of use and each time dressing is performed. It can be seen that the average radius of the portion can be set to be in the range of 80% to 120% with respect to the average value r.

As mentioned above, although 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.

1 glass substrate, 1A front main surface, 1B back main surface, 1C inner peripheral end surface, 1D outer peripheral end surface, 1H hole, 2 magnetic thin film layer, 10 magnetic disk, 20, 20A-20C polishing pad, 22 polishing layer (resin layer) , 24 polished surface, 26 foam pores, 27 openings, 30 stamper (molding die), 34 flat surface, 37 protrusions, 39 frame, 40 laser oscillator, 50 drill, E1-E3 spacing, R1-R3 dotted line .

Claims

A preparation step of preparing a polishing pad (20A) having a plurality of openings (27) formed in a polishing surface (24), and a plurality of glass substrates (1);
The polishing surface (24) of the polishing pad (20A) is repeatedly used to polish each of the plurality of glass substrates (1), and the polishing surface (24) is used a predetermined number of times. A polishing step for dressing the polishing surface (24) every time,
At the start of use of the polishing surface (24), the plurality of at the start of use of the polishing surface (24) based on the area of each of the plurality of openings (27) at the start of use of the polishing surface (24). A first average area of the opening (27) of
Each time the dressing is performed on the polished surface (24), the dressing is performed based on the area of each of the plurality of openings (27) each time the dressing is performed. A second average area of the plurality of openings (27) in each is defined;
Based on the first average area and the second average area through the polishing process, an average value of the first average area and the second average area through the polishing process is defined,
The first average area and the second average area through the polishing step are in the range of 64% to 144% with respect to the average value of the first average area and the second average area through the polishing step. Is within,
A method for producing a glass substrate.
The polishing pad (20A) prepared in the preparation step includes a resin layer (22) constituting the polishing surface (24),
In the preparation step, by using a molding die (30) having a plurality of concavo-convex patterns, a plurality of the concavo-convex patterns are transferred to the resin layer (22), whereby the polishing surface (24) is transferred. The polishing pad (20A) in which a plurality of the openings (27) are formed is prepared.
The manufacturing method of the glass substrate of Claim 1.
The polishing pad (20A) prepared in the preparation step includes a resin layer (22) constituting the polishing surface (24),
In the preparatory step, a plurality of openings (27) are formed in the polishing surface (24) by subjecting a portion of the resin layer (22) corresponding to the openings (27) to thermal processing. The polished polishing pad (20A) is prepared,
The manufacturing method of the glass substrate of Claim 1.
The polishing pad (20A) prepared in the preparation step includes a resin layer (22) constituting the polishing surface (24),
In the preparatory step, a plurality of openings (27) are formed in the polishing surface (24) by machining a portion of the resin layer (22) corresponding to the openings (27). The polished polishing pad (20A) is prepared,
The manufacturing method of the glass substrate of Claim 1.
Next to the plurality of openings (27) formed in the polishing surface (24) at the start of use of the polishing surface (24) and each time the dressing is performed on the polishing surface (24). An average spacing value between the matching openings (27) is defined;
The average interval value is in the range of 5 μm to 100 μm.
The manufacturing method of the glass substrate in any one of Claim 1 to 4.
The total area of the plurality of openings (27) formed in the polishing surface (24) at the start of use of the polishing surface (24) and each time the dressing is performed on the polishing surface (24). Is defined,
The total area at the start of use of the polishing surface (24) and each time the dressing is performed on the polishing surface (24) is 20% or more and 60% or less with respect to the area of the polishing surface (24). Is in range,
The manufacturing method of the glass substrate in any one of Claim 1 to 5.
The average value of the first average area and the second average area through the polishing step is within a range of 0.25π × 10 −12 (m 2 ) to 1.00π × 10 −8 (m 2 ). is there,
The manufacturing method of the glass substrate in any one of Claim 1 to 6.