JP6170557B2 - Manufacturing method of glass substrate for magnetic disk, manufacturing method of magnetic disk, grinding wheel - Google Patents

Manufacturing method of glass substrate for magnetic disk, manufacturing method of magnetic disk, grinding wheel Download PDF

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JP6170557B2
JP6170557B2 JP2015524130A JP2015524130A JP6170557B2 JP 6170557 B2 JP6170557 B2 JP 6170557B2 JP 2015524130 A JP2015524130 A JP 2015524130A JP 2015524130 A JP2015524130 A JP 2015524130A JP 6170557 B2 JP6170557 B2 JP 6170557B2
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glass substrate
grinding
chamfered
grinding wheel
magnetic disk
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JPWO2014208718A1 (en
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広昭 小澤
広昭 小澤
政明 植田
政明 植田
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Hoya Corp
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
    • G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
    • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
    • C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass

Description

本発明は、磁気ディスク用ガラス基板の製造方法、磁気ディスクに関する。   The present invention relates to a method for manufacturing a glass substrate for a magnetic disk and a magnetic disk.

今日、パーソナルコンピュータ、あるいはＤＶＤ（Digital Versatile Disc）記録装置等には、データ記録のためにハードディスク装置(ＨＤＤ：Hard Disk Drive)が内蔵されている。特に、ノート型パーソナルコンピュータ等の可搬性を前提とした機器に用いられるハードディスク装置では、ガラス基板に磁性層が設けられた磁気ディスクが用いられ、磁気ディスクの面上を僅かに浮上させた磁気ヘッドで磁性層に磁気記録情報が記録され、あるいは読み取られる。この磁気ディスクの基板として、金属基板（アルミニウム基板）等に比べて塑性変形し難い性質を持つことから、ガラス基板が好適に用いられる。   2. Description of the Related Art Today, a personal computer, a DVD (Digital Versatile Disc) recording device, or the like has a built-in hard disk device (HDD: Hard Disk Drive) for data recording. In particular, in a hard disk device used in a portable computer such as a notebook personal computer, a magnetic disk in which a magnetic layer is provided on a glass substrate is used, and the magnetic head slightly floats above the surface of the magnetic disk. Thus, magnetic recording information is recorded on or read from the magnetic layer. As a substrate for this magnetic disk, a glass substrate is preferably used because it has a property that it is less likely to be plastically deformed than a metal substrate (aluminum substrate) or the like.

また、ハードディスク装置における記憶容量の増大の要請を受けて、磁気記録の高密度化が図られている。例えば、磁性層における磁化方向を基板の面に対して垂直方向にする垂直磁気記録方式を用いて、磁気記録情報エリア（記録ビット）の微細化が行われている。これにより、１枚のディスク基板における記憶容量を増大させることができる。さらに、記憶容量の一層の増大化のために、磁気ヘッドの記録再生素子部をさらに突き出すことによって磁気記録層との距離を極めて短くして、情報の記録再生の精度をより高める（Ｓ／Ｎ比を向上させる）ことも行われている。なお、このような磁気ヘッドの記録再生素子部の制御はＤＦＨ（Dynamic Flying Height)制御機構と呼ばれ、この制御機構を搭載した磁気ヘッドはＤＦＨヘッドと呼ばれている。このようなＤＦＨヘッドと組み合わされてＨＤＤに用いられる磁気ディスク用ガラス基板の主表面は、磁気ヘッドやそこからさらに突き出された記録再生素子部との衝突や接触を避けるために、極めて平滑な表面となるように作製されている。   Further, in response to a request for an increase in storage capacity in a hard disk device, the density of magnetic recording has been increased. For example, the magnetic recording information area (recording bit) is miniaturized by using a perpendicular magnetic recording method in which the magnetization direction in the magnetic layer is perpendicular to the surface of the substrate. Thereby, the storage capacity of one disk substrate can be increased. Furthermore, in order to further increase the storage capacity, the distance from the magnetic recording layer is extremely shortened by further protruding the recording / reproducing element portion of the magnetic head, thereby further improving the accuracy of information recording / reproducing (S / N). To improve the ratio). Such control of the recording / reproducing element portion of the magnetic head is called a DFH (Dynamic Flying Height) control mechanism, and a magnetic head equipped with this control mechanism is called a DFH head. The main surface of the magnetic disk glass substrate used in the HDD in combination with such a DFH head is an extremely smooth surface in order to avoid collision and contact with the magnetic head and the recording / reproducing element portion further protruding therefrom. It is produced to become.

磁気ディスク用ガラス基板を製造するときには、内孔が空けられた円板状のガラス基板の内周端部および外周端部に対して面取り加工が施される。すなわち、ガラス基板の主表面と側壁面との間に介在する面取面が形成される。面取面を形成することで、ガラス基板からの異物の発生を防止し、製造した磁気ディスクをＨＤＤに組み込んだときのヘッドクラッシュ障害やサーマルアスペリティ障害等の不具合を抑制できる。
円板状のガラス基板の端面研削方法として、外周部に溝部が形成された砥石を、回転する被加工物の回転軸に対して傾斜した回転軸の回りに回転駆動し、砥石の溝部を被加工物の外周部あるいは内周部に押圧することにより、被加工物の外周部あるいは内周部の端面研削を行う方法が知られている（下記特許文献１）。この端面研削方法によれば、面接触の状態で端面の研削が行われ、衝撃的に被加工物の外周部あるいは内周部に接触するのが緩和されるので、効率良く良好な表面品質が得られる、とされている。When manufacturing a glass substrate for a magnetic disk, chamfering is performed on an inner peripheral end and an outer peripheral end of a disk-shaped glass substrate having an inner hole. That is, a chamfered surface interposed between the main surface of the glass substrate and the side wall surface is formed. By forming the chamfered surface, generation of foreign matters from the glass substrate can be prevented, and problems such as a head crash failure and a thermal asperity failure when the manufactured magnetic disk is incorporated in the HDD can be suppressed.
As a method for grinding an end face of a disk-shaped glass substrate, a grindstone having a groove formed on the outer peripheral portion is rotationally driven around a rotation axis inclined with respect to a rotation axis of a rotating workpiece, and the grindstone groove is covered. A method is known in which end surface grinding of the outer peripheral portion or inner peripheral portion of the workpiece is performed by pressing the outer peripheral portion or inner peripheral portion of the workpiece (Patent Document 1 below). According to this end surface grinding method, the end surface is ground in the state of surface contact, and the contact with the outer peripheral portion or inner peripheral portion of the work piece is shocked, so that good surface quality is efficiently obtained. It is supposed to be obtained.

特開２０００−１６７７５３号公報JP 2000-167753 A

ところで、本願の発明者らが上記特許文献１に記載された端面研削方法に基づいて、内孔が空けられた円板状のガラス基板の端面研削を行ったところ、端面の表面品質が向上することが確認された一方で、一対の面取面（例えば外周端面の場合、外周の側壁面と一対の主表面との間にそれぞれ介在する面取面；内周端面も同様）の面取り角がそれぞれ異なるという問題が生ずることがわかった。磁気ディスク用ガラス基板の一対の面取面の面取り角がそれぞれ異なると、磁気ディスクをＨＤＤに組み込んで回転させたときにＨＤＤの筐体内の気流の乱れが発生してフラッタリングが生ずる原因となり好ましくない。また、ガラス基板上に成膜するために磁気ディスク用ガラス基板の外周端面を把持するときに、外周側の一対の面取面の面取り角がそれぞれ異なる場合には、精度良く把持できないことに起因して膜厚の制御の精度が低下する虞もある。   By the way, when the inventors of the present application perform end surface grinding of a disk-shaped glass substrate with an inner hole formed based on the end surface grinding method described in Patent Document 1, the surface quality of the end surface is improved. On the other hand, the chamfer angle of a pair of chamfered surfaces (for example, in the case of an outer peripheral end surface, a chamfered surface respectively interposed between the outer peripheral side wall surface and the pair of main surfaces; the same applies to the inner peripheral end surface) It turns out that there is a problem that they are different. If the chamfer angles of the pair of chamfered surfaces of the glass substrate for magnetic disk are different, it is preferable to cause fluttering due to turbulence of the air flow in the HDD housing when the magnetic disk is installed in the HDD and rotated. Absent. In addition, when gripping the outer peripheral end surface of the magnetic disk glass substrate for film formation on the glass substrate, if the chamfer angles of the pair of outer peripheral chamfer surfaces are different, the gripping cannot be accurately performed. As a result, the accuracy of film thickness control may be reduced.

そこで、本発明は、磁気ディスク用ガラス基板を製造する過程において円板状のガラス基板の端面を研削するときに、良好な端面品質を確保しつつ一対の面取面の面取り角を同一にすることを可能とした、磁気ディスク用ガラス基板の製造方法、磁気ディスクの製造方法、および研削砥石を提供することを目的とする。   Therefore, the present invention makes the chamfer angles of a pair of chamfered surfaces the same while ensuring good end surface quality when grinding the end surface of a disk-shaped glass substrate in the process of manufacturing a glass substrate for a magnetic disk. An object of the present invention is to provide a method for producing a glass substrate for a magnetic disk, a method for producing a magnetic disk, and a grinding wheel that make it possible.

本願発明者らは、溝部が形成された砥石を、ガラス基板の回転軸に対して傾斜した回転軸の回りに回転駆動し、砥石の溝部をガラス基板の外周部あるいは内周部に押圧することによるガラス基板の端面研削において、ガラス基板の一対の面取面が加工時に接触する砥石の溝部の一対の開口角を同じにした場合に、一対の面取面の面取り角が同じにならない原因について鋭意検討した。その結果、砥石の回転軸に対してガラス基板の回転軸が傾斜していることに起因して、一方の面取面と他方の面取面とで加工時の砥粒の作用が異なることで、加工後の面取り角が同じにならないことを突き止めた。   The inventors of the present application rotate the grindstone formed with the groove around the rotation axis inclined with respect to the rotation axis of the glass substrate, and press the groove of the grindstone against the outer peripheral portion or the inner peripheral portion of the glass substrate. About the cause of the chamfering angle of a pair of chamfered surfaces not being the same when grinding a pair of chamfered surfaces of a glass substrate with a pair of chamfered surfaces of a grindstone contacted at the time of processing. We studied diligently. As a result, due to the fact that the rotation axis of the glass substrate is inclined with respect to the rotation axis of the grindstone, the action of the abrasive grains during processing differs between one chamfered surface and the other chamfered surface. It was found that the chamfer angles after processing were not the same.

本発明の第１の観点は、中心に円孔が形成され、側壁面および主表面と側壁面との間に形成された面取面とを有する円板状ガラス基板の端面に対して、回転する研削砥石を用いて端面研削処理を行う磁気ディスク用ガラス基板の製造方法である。端面研削処理は、研削砥石の回転軸を、基板の主表面と直交する軸に対して傾斜させて、ガラス基板の一対の面取面を同時に研削するものである。研削砥石は、ガラス基板の面取面を研削する一対の面取面研削領域を有する溝形状を有する。一対の面取面研削領域は、ガラス基板の中心と研削砥石の回転軸とを結ぶ直線上に位置するガラス基板と研削砥石の接点を基準として、研削砥石の回転方向の前側（個々の砥粒が基準とする接点に近づく側）でガラス基板の面取面と接触する面取面研削領域（Ａ）と、研削砥石の回転方向の後側（個々の砥粒が基準とする接点から遠ざかる側）でガラス基板の面取面と接触する面取面研削領域（Ｂ）とからなり、面取面研削領域（Ａ）の開口角は、面取面研削領域（Ｂ）の開口角よりも小さいことを特徴とする。   According to a first aspect of the present invention, a circular hole is formed at the center, and the end surface of a disk-shaped glass substrate having a side wall surface and a chamfered surface formed between the main surface and the side wall surface is rotated. It is a manufacturing method of the glass substrate for magnetic discs which performs an end surface grinding process using the grinding wheel which performs. In the end face grinding process, a pair of chamfered surfaces of a glass substrate are ground simultaneously by inclining a rotation axis of a grinding wheel with respect to an axis orthogonal to the main surface of the substrate. The grinding wheel has a groove shape having a pair of chamfered surfaces for grinding the chamfered surface of the glass substrate. A pair of chamfered surface grinding regions is defined as a front side (individual abrasive grains) in the rotation direction of the grinding wheel with reference to a contact point between the glass substrate and the grinding wheel positioned on a straight line connecting the center of the glass substrate and the rotation axis of the grinding wheel. Chamfered surface grinding area (A) in contact with the chamfered surface of the glass substrate on the side closer to the reference contact, and the rear side in the rotation direction of the grinding wheel (the side on which each abrasive grain moves away from the reference contact) ) And a chamfered surface grinding region (B) in contact with the chamfered surface of the glass substrate, and the opening angle of the chamfered surface grinding region (A) is smaller than the opening angle of the chamfered surface grinding region (B). It is characterized by that.

上記磁気ディスク用ガラス基板の製造方法において、上記研削砥石の溝形状は、ガラス基板の側壁面を研削する側壁面研削領域をさらに有し、上記端面研削処理は、ガラス基板の側壁面と一対の面取面とを同時に研削してもよい。   In the method for manufacturing a glass substrate for a magnetic disk, the groove shape of the grinding wheel further includes a side wall surface grinding region for grinding the side wall surface of the glass substrate, and the end surface grinding treatment is performed in a pair with the side wall surface of the glass substrate. The chamfered surface may be ground simultaneously.

上記磁気ディスク用ガラス基板の製造方法において、磁気ディスク用ガラス基板の板厚が０．６３５ｍｍより小さくてもよい。   In the method for manufacturing a magnetic disk glass substrate, the thickness of the magnetic disk glass substrate may be smaller than 0.635 mm.

上記磁気ディスク用ガラス基板の製造方法において、上記磁気ディスク用ガラス基板は結晶化ガラスであることが好ましい。   In the method for manufacturing a glass substrate for a magnetic disk, the glass substrate for a magnetic disk is preferably crystallized glass.

本発明の第２の観点は、磁気ディスク用ガラス基板の製造方法によって作製された磁気ディスク用ガラス基板の主表面上に、磁性層を形成する処理を備えたことを特徴とする、磁気ディスクの製造方法である。   According to a second aspect of the present invention, there is provided a magnetic disk comprising a process for forming a magnetic layer on a main surface of a glass substrate for a magnetic disk manufactured by a method for manufacturing a glass substrate for a magnetic disk. It is a manufacturing method.

本発明の第３の観点は、中心に円孔が形成され、側壁面および主表面と側壁面との間に形成された面取面とを有する円板状ガラス基板の端面に対する端面研削処理において回転して使用される研削砥石である。この研削砥石は、円筒状又は円柱状の回転体からなり、当該回転体の周上に溝が形成されている。溝は、上記回転体の回転軸を含む面による断面視において、ガラス基板の側壁面と接触する側壁面研削面と、ガラス基板の側壁面を挟んで一方の面取面と接触する面取面研削面（Ａ）と、他方の面取面と接触する面取面研削面（Ｂ）とからなり、面取面研削面（Ａ）と面取面研削面（Ｂ）の、側壁面研削面からの開口角が異なることを特徴とする。   A third aspect of the present invention is an end surface grinding process for an end surface of a disk-shaped glass substrate having a circular hole at the center and having a side wall surface and a chamfered surface formed between the main surface and the side wall surface. It is a grinding wheel used by rotating. This grinding wheel is composed of a cylindrical or columnar rotating body, and a groove is formed on the circumference of the rotating body. The groove has a side wall surface ground surface that contacts the side wall surface of the glass substrate and a chamfer surface that contacts one of the chamfered surfaces across the side wall surface of the glass substrate in a cross-sectional view of the surface including the rotation axis of the rotating body. The side wall surface of the chamfered surface ground surface (A) and the chamfered surface ground surface (B) comprising a ground surface (A) and a chamfered surface ground surface (B) in contact with the other chamfered surface. The opening angle from is different.

上述した磁気ディスク用ガラス基板の製造方法、磁気ディスクの製造方法、および研削砥石によれば、磁気ディスク用ガラス基板を製造する過程において円板状のガラス基板の端面を研削するときに、良好な端面品質を確保しつつ一対の面取面の面取り角を同一にすることができる。   According to the method for manufacturing a magnetic disk glass substrate, the method for manufacturing a magnetic disk, and the grinding wheel described above, when grinding the end surface of a disk-shaped glass substrate in the process of manufacturing the magnetic disk glass substrate, The chamfer angles of the pair of chamfered surfaces can be made the same while ensuring the end surface quality.

実施形態の磁気ディスク用ガラス基板の外観形状を示す図。The figure which shows the external appearance shape of the glass substrate for magnetic discs of embodiment. 実施形態の磁気ディスク用ガラス基板の外周側の端部の拡大断面図。The expanded sectional view of the edge part of the outer peripheral side of the glass substrate for magnetic discs of embodiment. 円板状のガラス基板の内周端面の研削処理について示す図。The figure shown about the grinding process of the inner peripheral end surface of a disk-shaped glass substrate. 円板状のガラス基板の内周端面の研削処理時の、ガラス基板と研削砥石の接触面を示す図。The figure which shows the contact surface of a glass substrate and a grinding stone at the time of the grinding process of the internal peripheral end surface of a disk-shaped glass substrate. 研削砥石の溝部の開口角について説明する図。The figure explaining the opening angle of the groove part of a grinding wheel. 円板状のガラス基板の外周端面の研削処理について示す図。The figure shown about the grinding process of the outer peripheral end surface of a disk-shaped glass substrate.

以下、本実施形態の磁気ディスク用ガラス基板の製造方法について詳細に説明する。   Hereinafter, the manufacturing method of the glass substrate for magnetic disks of this embodiment is demonstrated in detail.

［磁気ディスク用ガラス基板］
本実施形態における磁気ディスク用ガラス基板の材料として、アルミノシリケートガラス、ソーダライムガラス、ボロシリケートガラスなどを用いることができる。特に、化学強化を施すことができ、また主表面の平坦度および基板の強度において優れた磁気ディスク用ガラス基板を作製することができるという点で、アルミノシリケートガラスを好適に用いることができる。[Magnetic disk glass substrate]
Aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used as the material for the magnetic disk glass substrate in the present embodiment. In particular, aluminosilicate glass can be suitably used in that it can be chemically strengthened and a glass substrate for a magnetic disk excellent in flatness of the main surface and strength of the substrate can be produced.

本実施形態の磁気ディスク用ガラス基板に用いられるガラス材料の組成を限定するものではないが、本実施形態のガラス基板は好ましくは、必須成分として、ＳｉＯ２、Ｌｉ２Ｏ、Ｎａ２Ｏ、ならびに、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯからなる群から選ばれる一種以上のアルカリ土類金属酸化物を含み、ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯの合計含有量に対するＣａＯの含有量のモル比（ＣａＯ／（ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ））が０．２０以下であって、ガラス転移温度が６５０℃以上であるアモルファスのアルミノシリケートガラスであってもよい。
また、酸化物基準の質量％で、ＳｉＯ２：４５．６０〜６０％、およびＡｌ２Ｏ３：７〜２０％、およびＢ２Ｏ３：１．００〜８％未満、およびＰ２Ｏ５：０．５０〜７％、およびＴｉＯ２：１〜１５％、およびＲＯの合計量：５〜３５％（ただしＲはＺｎおよびＭｇ）の各成分を含有し、ＣａＯの含有量が３．００％以下、ＢａＯの含有量が４％以下であり、ＰｂＯ成分、Ａｓ２Ｏ３成分およびＳｂ２Ｏ３成分およびＣｌ−、ＮＯ−、ＳＯ２−、Ｆ−成分を含有せず、主結晶相としてＲＡｌ２Ｏ４、Ｒ２ＴｉＯ４、（ただしＲはＺｎ、Ｍｇから選択される１種類以上）から選ばれる一種以上を含有し、主結晶相の結晶粒径が０．５ｎｍ〜２０ｎｍの範囲であり、結晶化度が１５％以下であり、比重が２．９５以下であることを特徴とする結晶化ガラスであってもよい。Although the composition of the glass material used for the glass substrate for magnetic disk of the present embodiment is not limited, the glass substrate of the present embodiment is preferably composed of SiO 2 , Li 2 O, Na 2 O, and And at least one alkaline earth metal oxide selected from the group consisting of MgO, CaO, SrO and BaO, and the molar ratio of the content of CaO to the total content of MgO, CaO, SrO and BaO (CaO / (MgO + CaO + SrO + BaO )) Is 0.20 or less, and an amorphous aluminosilicate glass having a glass transition temperature of 650 ° C. or more may be used.
Also, in terms of% by mass on the oxide basis, SiO 2: 45.60 to 60%, and Al 2 O 3: 7~20%, and B 2 O 3: less than 1.00 to 8%, and P 2 O 5 : 0.50 to 7%, and TiO 2 : 1 to 15%, and the total amount of RO: 5 to 35% (wherein R is Zn and Mg), and the content of CaO is 3.00 %, BaO content is 4% or less, PbO component, As 2 O 3 component and Sb 2 O 3 component and Cl − , NO − , SO 2− , F − component are not contained, and the main crystal phase RAl 2 O 4 , R 2 TiO 4 (where R is one or more selected from Zn and Mg), and the crystal grain size of the main crystal phase is in the range of 0.5 nm to 20 nm. The crystallinity is 15% or less and the specific gravity is 2.95 or less. It may be a crystallized glass characterized by the following.

図１Ａに、実施形態の磁気ディスク用ガラス基板の外観形状を示す。図１Ａに示すように、本実施形態における磁気ディスク用ガラス基板は、内孔２が形成された、ドーナツ型の薄板のガラス基板である。磁気ディスク用ガラス基板のサイズは問わないが、例えば、公称直径２．５インチの磁気ディスク用ガラス基板として好適である。
図１Ｂは、実施形態の磁気ディスク用ガラス基板の外周側の端部の断面を拡大して示す図である。図１Ｂに示すように、磁気ディスク用ガラス基板は、一対の主表面１ｐと、一対の主表面１ｐに対して直交する方向に沿って配置された側壁面１ｔと、一対の主表面１ｐと側壁面１ｔとの間に配置された一対の面取面１ｃとを有する。図示しないが、磁気ディスク用ガラス基板の内周側の端部についても同様に、側壁面と面取面が形成されている。側壁面１ｔを基準として各面取面１ｃのなす角度（面取り角）は基本的には同一であり、例えば１５〜７５度とすることが好ましい。この範囲内とすることで、磁気ディスク用ガラス基板を製造する過程や、その後の磁気ディスクやＨＤＤを製造する過程で基板の端部にキズが入ったり端部がカケたりすることを好適に防止することができる。面取り角は典型的には図示するように４５度である。なお、面取面は、断面視において円弧状に形成されていてもよい。FIG. 1A shows the appearance of the magnetic disk glass substrate of the embodiment. As shown in FIG. 1A, the glass substrate for a magnetic disk in the present embodiment is a donut-shaped thin glass substrate in which an inner hole 2 is formed. Although the size of the glass substrate for magnetic disks is not ask | required, for example, it is suitable as a glass substrate for magnetic disks with a nominal diameter of 2.5 inches.
FIG. 1B is an enlarged view showing a cross section of an end portion on the outer peripheral side of the glass substrate for magnetic disk of the embodiment. As shown in FIG. 1B, the magnetic disk glass substrate includes a pair of main surfaces 1p, side wall surfaces 1t arranged along a direction orthogonal to the pair of main surfaces 1p, and a pair of main surfaces 1p and sides. It has a pair of chamfered surfaces 1c arranged between the wall surface 1t. Although not shown, a side wall surface and a chamfered surface are similarly formed on the inner peripheral side end of the magnetic disk glass substrate. The angle (chamfer angle) formed by each chamfered surface 1c with respect to the side wall surface 1t is basically the same, and is preferably 15 to 75 degrees, for example. By making it within this range, it is preferable to prevent the edge of the substrate from being scratched or chipped in the process of manufacturing the magnetic disk glass substrate and the subsequent process of manufacturing the magnetic disk or HDD. can do. The chamfer angle is typically 45 degrees as shown. Note that the chamfered surface may be formed in an arc shape in a sectional view.

本実施形態の磁気ディスク用ガラス基板の板厚は、特に限定されるものではないが、例えば、公称２．５インチの磁気ディスク用ガラス基板の場合には、例えば０．８ｍｍ、０．６３５ｍｍであり、公称３．５インチの磁気ディスク用ガラス基板の場合には、例えば０．５ｍｍである。なお、磁気ディスク用ガラス基板は、一般には磁気ディスクに用いられた場合に、板厚が薄くなるほど回転時にバタつきやすく、フラッタリングが生じやすくなる。しかし、本実施形態の磁気ディスク用ガラス基板は、後述するように、一対の面取面が同一の角度となるように作製されるため、外周端部での気流の乱れが抑えられ、板厚を薄くした場合でもフラッタリングが抑制される。すなわち、本発明の効果がより発揮される観点から、本実施形態の磁気ディスク用ガラス基板の板厚は、０．６３５ｍｍより小さいことが好ましく、０．５ｍｍ以下であるとより好ましい。   The thickness of the magnetic disk glass substrate of the present embodiment is not particularly limited. For example, in the case of a magnetic disk glass substrate having a nominal size of 2.5 inches, the thickness is 0.8 mm or 0.635 mm, for example. In the case of a glass substrate for a nominal 3.5 inch magnetic disk, for example, it is 0.5 mm. In general, when a glass substrate for a magnetic disk is used for a magnetic disk, the thinner the plate thickness, the more easily flutters during rotation, and fluttering tends to occur. However, since the glass substrate for a magnetic disk of the present embodiment is manufactured so that a pair of chamfered surfaces have the same angle, as will be described later, the turbulence of the air flow at the outer peripheral edge is suppressed, and the plate thickness Fluttering is suppressed even when the thickness is made thinner. That is, from the viewpoint of further exerting the effect of the present invention, the thickness of the magnetic disk glass substrate of the present embodiment is preferably smaller than 0.635 mm, more preferably 0.5 mm or less.

［磁気ディスク用ガラス基板の製造方法］
以下、本実施形態の磁気ディスク用ガラス基板の製造方法について、処理毎に説明する。ただし、各処理の順番は適宜入れ替えてもよい。[Method of manufacturing glass substrate for magnetic disk]
Hereinafter, the manufacturing method of the glass substrate for magnetic disks of this embodiment is demonstrated for every process. However, the order of each process may be changed as appropriate.

（１）板状ガラスの成形および粗研削処理
例えばフロート法によって板状ガラスを形成した後、この板状ガラスから、磁気ディスク用ガラス基板の元となる所定形状のガラス素板が切り出される。フロート法の代わりに、例えば上型と下型を用いたプレス成形によってガラス素板を成形してもよい。なお、ガラス素板は、これらの方法に限らず、ダウンドロー法、リドロー法、フュージョン法などの公知の製造方法を用いて製造することもできる。
なお、ガラス素板の両主表面に対して、必要に応じて、粗研削処理を行ってもよい。(1) Molding and rough grinding of plate glass After forming a plate glass by, for example, the float method, a glass base plate having a predetermined shape that is a base of a glass substrate for a magnetic disk is cut out from the plate glass. Instead of the float process, the glass base plate may be formed by press molding using an upper mold and a lower mold, for example. In addition, a glass base plate can also be manufactured not only using these methods but using well-known manufacturing methods, such as a downdraw method, a redraw method, and a fusion method.
In addition, you may perform a rough grinding process with respect to both the main surfaces of a glass base plate as needed.

（２）形状加工処理
次に、形状加工処理が行われる。形状加工処理では、ガラスブランクの成形処理後、公知の加工方法を用いて円孔を形成することにより、円孔があいた円板状のガラス基板を得る。次いで、ガラス基板の端面研削処理を実施して所望の形状の面取面を形成する。つまり、ガラス基板の端部において、側壁面と主表面を繋ぐ面取面が形成される。(2) Shape processing processing Next, shape processing processing is performed. In the shape processing, after forming the glass blank, a circular hole is formed using a known processing method, thereby obtaining a disk-shaped glass substrate having a circular hole. Next, an end surface grinding process of the glass substrate is performed to form a chamfered surface having a desired shape. That is, a chamfered surface connecting the side wall surface and the main surface is formed at the end of the glass substrate.

以下、ガラス基板の内周端面の端面研削処理について、図２および図３を参照して説明する。本実施形態の端面研削処理では、総形砥石による研削加工に加えて、あるいは総形砥石による研削加工を経ずに、ガラス基板の端面に当接する砥石の軌跡が一定とならないように、ガラス基板の端面と砥石とを接触させる端面研削方法によって行われる。図２は、ガラス基板Ｇの内周端面の研削処理について示す図である。図３は、ガラス基板Ｇの内周端面の研削処理時の、ガラス基板Ｇと研削砥石５の接触面を示す図である。   Hereinafter, the end surface grinding process of the inner peripheral end surface of the glass substrate will be described with reference to FIGS. 2 and 3. In the end surface grinding process of the present embodiment, in addition to the grinding process with the general-purpose grindstone, or without the grinding process with the general-purpose grindstone, the trajectory of the grindstone contacting the end surface of the glass substrate is not constant. This is performed by an end surface grinding method in which the end surface of the steel is brought into contact with a grindstone. FIG. 2 is a diagram showing a grinding process for the inner peripheral end face of the glass substrate G. FIG. FIG. 3 is a diagram illustrating a contact surface between the glass substrate G and the grinding stone 5 during the grinding process of the inner peripheral end surface of the glass substrate G.

図３に示すように、ガラス基板Ｇの内周端面の研削加工に用いる研削砥石５は、全体が円柱状の回転体からなり、外周上に溝５０が形成されている。溝５０は、ガラス基板Ｇの内周側の側壁面と面取面Ｃ１,Ｃ２を同時に研削加工できるように形成されており、具体的には、溝５０は、側壁面研削領域５０ｔ及びその両側に存在する面取面研削領域５０ａ，５０ｂが周方向に設けられている。
ガラス基板の内周端面の加工では、研削砥石５に形成された溝５０の溝方向に対してガラス基板Ｇを傾けた状態、つまり研削砥石５の回転軸Ｌ５に対してガラス基板Ｇの回転軸Ｌ１を角度α（α＞０）だけ傾けた状態で、ガラス基板Ｇの内周端面に研削砥石５の溝５０を接触させながら、ガラス基板Ｇと研削砥石５の両方を回転させて研削加工を行う。すなわち、研削砥石５の溝５０とガラス基板Ｇがねじれの位置の関係となるように、ガラス基板Ｇに対して研削砥石５を傾斜させて研削加工を行う。これによって、ガラス基板Ｇの内周端面に当接する研削砥石５の溝５０の軌跡が一定とはならないで、研削砥石５の砥粒が基板端面に対してランダムな位置に当接、作用するため、深掘れなどによる基板へのダメージが少なく、研削加工面の表面粗さやその面内ばらつきも小さくなり、研削加工面をより高平滑に、すなわちより高い品質要求に応えられるレベルの品位に仕上げることができる。さらには砥石寿命の向上効果も有する。As shown in FIG. 3, the grinding wheel 5 used for grinding the inner peripheral end face of the glass substrate G is entirely composed of a cylindrical rotating body, and a groove 50 is formed on the outer periphery. The groove 50 is formed so that the inner peripheral side wall surface and the chamfered surfaces C1 and C2 of the glass substrate G can be ground simultaneously. Specifically, the groove 50 includes the side wall surface grinding region 50t and both sides thereof. Chamfered surface grinding regions 50a and 50b are provided in the circumferential direction.
In processing the inner peripheral end surface of the glass substrate, the glass substrate G is inclined with respect to the groove direction of the groove 50 formed in the grinding wheel 5, that is, the rotation axis of the glass substrate G with respect to the rotation axis L 5 of the grinding wheel 5. Grinding is performed by rotating both the glass substrate G and the grinding wheel 5 while contacting the groove 50 of the grinding wheel 5 with the inner peripheral end surface of the glass substrate G in a state where L1 is inclined by an angle α (α> 0). Do. That is, grinding is performed by inclining the grinding wheel 5 with respect to the glass substrate G so that the groove 50 of the grinding wheel 5 and the glass substrate G have a twisted positional relationship. Accordingly, the locus of the groove 50 of the grinding wheel 5 that contacts the inner peripheral end surface of the glass substrate G does not become constant, and the abrasive grains of the grinding wheel 5 contact and act on the substrate end surface at random positions. In addition, there is less damage to the substrate due to deep digging, etc., and the surface roughness and in-plane variation of the ground surface are also reduced, and the ground surface is finished to a higher level, that is, to a level that can meet higher quality requirements. Can do. Furthermore, it also has the effect of improving the wheel life.

また、図３に示すように、ガラス基板Ｇの内周端面の研削加工では、ガラス基板Ｇの側壁面と２つの面取面とを同時に研削する。図３において、研削砥石５の側壁面研削領域５０ｔおよび面取面研削領域５０ａ，５０ｂと、ガラス基板Ｇの端面とが接触する領域が、領域Ｔおよび領域Ｃａ，Ｃｂである。つまり、研削加工中において研削砥石５の溝５０とガラス基板Ｇの端面は面接触状態となる。そのため、ガラス基板Ｇに対する研削砥石５の接触長さ（切れ刃長さ）を伸ばして、砥粒の切れ味を持続させることができる。したがって、加工面品位にとって有利な微細砥粒砥石を用いて研削加工を行った場合にも安定した研削性を確保でき、塑性モード主体の研削加工による良好な研削面品位（鏡面品位）を安定的に得ることができる。しかも、研削砥石の切れ味を持続させ、塑性モードを実現する研削性を安定的に確保することで、ガラス基板の内周端面の面取り加工による良好な寸法形状精度を確保することができる。   Moreover, as shown in FIG. 3, in the grinding process of the inner peripheral end surface of the glass substrate G, the side wall surface and two chamfered surfaces of the glass substrate G are ground simultaneously. In FIG. 3, the regions where the side wall surface grinding region 50t and the chamfered surface grinding regions 50a, 50b of the grinding wheel 5 are in contact with the end surface of the glass substrate G are the region T and the regions Ca, Cb. That is, during the grinding process, the groove 50 of the grinding wheel 5 and the end face of the glass substrate G are in surface contact. Therefore, the contact length (cutting edge length) of the grinding wheel 5 with respect to the glass substrate G can be extended to maintain the sharpness of the abrasive grains. Therefore, stable grinding performance can be secured even when grinding is performed using a fine abrasive wheel that is advantageous for machining surface quality, and good grinding surface quality (mirror surface quality) by plastic mode-based grinding is stable. Can get to. In addition, by maintaining the sharpness of the grinding wheel and stably ensuring the grindability for realizing the plastic mode, it is possible to ensure good dimensional shape accuracy by chamfering the inner peripheral end face of the glass substrate.

上述の研削砥石５の溝方向に対するガラス基板Ｇの傾斜角度αは任意に設定することができるが、上述の作用効果をより良く発揮させるためには、例えば１〜１５度の範囲内とすることが好ましい。
上記端面研削加工で用いる研削砥石５としては、粗研削加工用には、例えば高剛性砥石であるダイヤモンド砥粒を電着ボンドで固めた所謂電着ボンド砥石が好適である。また、仕上げの精密研削加工用には、砥粒同士を結合するバインダーが例えばフェノール樹脂、ウレタン樹脂、ポリイミド樹脂、ポリエステル樹脂、フッ素樹脂等の樹脂材料であるレジンボンド砥石や、バインダーが例えば銅系合金、鋳鉄系合金、チタン系合金等の金属質結合剤であるメタルボンド砥石、バインダーがガラス質結合材であるビトリファイド砥石などが好適である。この中でも、砥石の硬度の調整が比較的容易なレジンボンド砥石が特に好適である。
また、砥粒の粒径としては、粗さを維持しながら砥石寿命に亘って研削性能を維持できるためには、例えば平均粒子径３０μｍ以下の砥粒が好適であるが、特に精密研削加工用には、平均粒子径３〜１５μｍの範囲内の砥粒が好適である。砥粒としては、例えばダイヤモンド砥粒が好適である。砥粒の粒径は、例えば電気抵抗試験法で測定することが可能である。
研削砥石５の周速度の好ましい例は、５００〜３０００ｍ／分、ガラス基板Ｇの周速度は、１〜３０ｍ／分程度である。また、ガラス基板Ｇの周速度に対する研削砥石５の周速度の比（周速度比）は、５０〜３００の範囲内であることが好ましい。The inclination angle α of the glass substrate G with respect to the groove direction of the grinding wheel 5 described above can be arbitrarily set, but in order to better exhibit the above-described effects, for example, within a range of 1 to 15 degrees. Is preferred.
As the grinding wheel 5 used in the end face grinding, a so-called electrodeposited bond grindstone in which diamond abrasive grains, which are high-rigidity grindstones are hardened by electrodeposition bond, is suitable for rough grinding. In addition, for finishing precision grinding, a resin bond grindstone in which the binder for bonding abrasive grains is a resin material such as phenol resin, urethane resin, polyimide resin, polyester resin, fluororesin, or the binder is copper-based, for example. A metal bond grindstone that is a metallic binder such as an alloy, cast iron alloy, or titanium alloy, and a vitrified grindstone whose binder is a vitreous binder are suitable. Among these, a resin bond grindstone in which the adjustment of the hardness of the grindstone is relatively easy is particularly suitable.
Further, as the grain size of the abrasive grains, for example, abrasive grains having an average grain diameter of 30 μm or less are suitable in order to maintain the grinding performance over the life of the grinding wheel while maintaining the roughness. For this, abrasive grains having an average particle diameter of 3 to 15 μm are suitable. As an abrasive grain, a diamond abrasive grain is suitable, for example. The particle size of the abrasive grains can be measured by, for example, an electrical resistance test method.
A preferable example of the peripheral speed of the grinding wheel 5 is 500 to 3000 m / min, and the peripheral speed of the glass substrate G is about 1 to 30 m / min. Further, the ratio of the peripheral speed of the grinding wheel 5 to the peripheral speed of the glass substrate G (peripheral speed ratio) is preferably in the range of 50 to 300.

図４は、研削砥石５の溝５０の開口角について説明する図であり、図３に示した研削砥石５のＡ部を拡大して示している。なお、図４に示す形状は、研削砥石５の回転軸Ｌ５を含む面による断面視において溝５０を拡大した場合の形状と同じである。図４に示すように、側壁面研削領域５０ｔに直交する面を基準にして面取面研削領域５０ａ，５０ｂの開口角をそれぞれθ１，θ２としたとき、図２に示す研削砥石の回転方向、および図３に示したガラス基板Ｇの回転軸Ｌ１の傾斜角度α（図３において、α＞０）の場合には、θ１＞θ２となっている。   FIG. 4 is a diagram for explaining the opening angle of the groove 50 of the grinding wheel 5, and shows an enlarged portion A of the grinding wheel 5 shown in FIG. 3. In addition, the shape shown in FIG. 4 is the same as the shape at the time of enlarging the groove | channel 50 in the cross sectional view by the surface containing the rotating shaft L5 of the grinding wheel 5. FIG. As shown in FIG. 4, when the opening angles of the chamfered surface grinding regions 50a and 50b are θ1 and θ2, respectively, with reference to a surface orthogonal to the side wall surface grinding region 50t, the rotation direction of the grinding wheel shown in FIG. In the case of the inclination angle α of the rotation axis L1 of the glass substrate G shown in FIG. 3 (α> 0 in FIG. 3), θ1> θ2.

θ１＞θ２とする理由は以下の通りである。図２に示す研削砥石の回転方向、および図３に示したガラス基板Ｇの回転軸Ｌ１の傾斜角度α（図３において、α＞０）の場合には、研削砥石５とガラス基板Ｇの接触領域Ｃａ，Ｃｂからわかるように、面取面研削領域５０ａは、ガラス基板Ｇの中心と研削砥石５の回転軸Ｌ５とを結ぶ直線上に位置するガラス基板Ｇと研削砥石５の接点を基準として、研削砥石５の回転方向の後側でガラス基板Ｇの面取面と接触する。面取面研削領域５０ｂは、その接点を基準として、研削砥石５の回転方向の前側でガラス基板Ｇの面取面と接触する。つまり、この例では、本発明の面取面研削領域（Ａ）は面取面研削領域５０ｂに対応し、本発明の面取面研削領域（Ｂ）は面取面研削領域５０ａに対応する。   The reason why θ1> θ2 is as follows. In the case of the rotation direction of the grinding wheel shown in FIG. 2 and the inclination angle α (α> 0 in FIG. 3) of the rotation axis L1 of the glass substrate G shown in FIG. As can be seen from the regions Ca and Cb, the chamfered surface grinding region 50a is based on the contact point between the glass substrate G and the grinding wheel 5 positioned on a straight line connecting the center of the glass substrate G and the rotation axis L5 of the grinding wheel 5. The chamfered surface of the glass substrate G is brought into contact with the rear side in the rotational direction of the grinding wheel 5. The chamfered surface grinding region 50b is in contact with the chamfered surface of the glass substrate G on the front side in the rotation direction of the grinding wheel 5 with the contact as a reference. That is, in this example, the chamfered surface grinding region (A) of the present invention corresponds to the chamfered surface grinding region 50b, and the chamfered surface grinding region (B) of the present invention corresponds to the chamfered surface grinding region 50a.

このとき、研削砥石５の回転方向の前側で（つまり、図３の面取面研削領域５０ｂの接触領域Ｃｂで）加工されるガラス基板Ｇの面取面Ｃ１には砥粒が食い込むように強く作用するために、面取面Ｃ１の面取り角は、面取面研削領域５０ｂの開口角θ２を超えた角度となる。他方、研削砥石５の回転方向の後側で（つまり、図３の面取面研削領域５０ａの接触領域Ｃａで）加工されるガラス基板Ｇの面取面Ｃ２には砥粒が比較的滑らかに作用するために、面取面Ｃ２の面取り角は、面取面研削領域５０ａの開口角θ１が転写される角度（すなわち、θ１と同一の角度）となる。そこで、研削砥石５の溝５０の開口角をθ１＞θ２に設定することで、端面研削処理後のガラス基板Ｇの面取面Ｃ１，Ｃ２の面取り角を一致させることができるようになる。なお、開口角θ１，θ２の差分は、ガラス基板Ｇの回転軸Ｌ１の傾斜角度α、研削砥石５の径等のファクタに基づいて、加工後の面取面Ｃ１，Ｃ２の面取り角が同一となるように適宜決定することができる。   At this time, the grindstone 5 is strong so that the abrasive grains bite into the chamfered surface C1 of the glass substrate G processed on the front side in the rotation direction of the grinding wheel 5 (that is, in the contact region Cb of the chamfered chamfered region 50b in FIG. 3). In order to act, the chamfering angle of the chamfered surface C1 is an angle exceeding the opening angle θ2 of the chamfered surface grinding region 50b. On the other hand, the abrasive grains are relatively smooth on the chamfered surface C2 of the glass substrate G processed on the rear side in the rotation direction of the grinding wheel 5 (that is, in the contact area Ca of the chamfered surface grinding area 50a in FIG. 3). In order to act, the chamfer angle of the chamfered surface C2 is an angle at which the opening angle θ1 of the chamfered surface grinding region 50a is transferred (that is, the same angle as θ1). Therefore, by setting the opening angle of the groove 50 of the grinding wheel 5 to θ1> θ2, the chamfering angles of the chamfered surfaces C1 and C2 of the glass substrate G after the end surface grinding process can be matched. The difference between the opening angles θ1 and θ2 is that the chamfering angles of the chamfered surfaces C1 and C2 after processing are the same based on factors such as the inclination angle α of the rotation axis L1 of the glass substrate G and the diameter of the grinding wheel 5. It can be determined as appropriate.

図４において、面取面研削領域５０ａの開口角θ１，面取面研削領域５０ｂの開口角θ２の関係をθ１＞θ２としたのは、図２に示す研削砥石の回転方向、および図３に示したガラス基板Ｇの回転軸Ｌ１の傾斜角度α（図３において、α＞０）の場合である。図２において研削砥石５の回転方向を逆転させた場合には、研削砥石５とガラス基板Ｇの接触領域Ｃａ，Ｃｂの研削砥石５の回転方向を基準とした前後関係も逆転するため、θ１＜θ２とするのがよい。また、図示しないが、図２に示す研削砥石の回転方向を変えない場合であっても、ガラス基板Ｇの回転軸Ｌ１の傾斜角度αを図３においてα＜０とする場合には、面取面研削領域５０ａ上の接触領域が面取面研削領域５０ｂの接触領域よりも研削砥石５の回転方向の前側となるため、θ１＜θ２とするのがよい。   In FIG. 4, the relationship between the opening angle θ1 of the chamfered surface grinding region 50a and the opening angle θ2 of the chamfered surface grinding region 50b is θ1> θ2 in the rotational direction of the grinding wheel shown in FIG. This is a case where the inclination angle α of the rotation axis L1 of the glass substrate G shown (α> 0 in FIG. 3). In FIG. 2, when the rotation direction of the grinding wheel 5 is reversed, the anteroposterior relationship with respect to the rotation direction of the grinding wheel 5 in the contact areas Ca and Cb between the grinding wheel 5 and the glass substrate G is also reversed. It is preferable to set θ2. Although not shown, even if the rotation direction of the grinding wheel shown in FIG. 2 is not changed, if the inclination angle α of the rotation axis L1 of the glass substrate G is α <0 in FIG. Since the contact area on the surface grinding area 50a is in front of the contact area of the chamfered surface grinding area 50b in the rotational direction of the grinding wheel 5, it is preferable that θ1 <θ2.

ガラス基板の外周端面の端面研削処理についても、内周端面と同様にして行うことができる。図５は、ガラス基板Ｇの外周端面の研削処理について示す図である。図５に示すように、外周端面の端面研削処理に使用される研削砥石７は、円筒状の回転体からなり、その内周上に溝が形成されている。図５に示すように、ガラス基板Ｇの外周端面の研削処理においても、内周端面の研削処理と同様に、研削砥石７の溝とガラス基板Ｇがねじれの位置の関係となるように、ガラス基板Ｇに対して研削砥石７を傾斜させて研削加工を行う。また、ガラス基板Ｇの外周端面の研削加工においても、内周端面の研削処理と同様に、ガラス基板Ｇの側壁面と２つの面取面とを同時に研削する。研削砥石７の溝方向に対するガラス基板Ｇの傾斜角度については、内周端面の研削処理と同様に、例えば１〜１５度の範囲内とすることが好ましい。
研削砥石７の溝の開口角は、図４に示したものと同様でよい。すなわち、ガラス基板Ｇの中心と研削砥石７の回転軸とを結ぶ直線上に位置するガラス基板Ｇと研削砥石７の接点を基準として、研削砥石７の回転方向の前側でガラス基板Ｇの面取面と接触する面取面研削領域（Ａ）と、研削砥石７の回転方向の後側でガラス基板Ｇの面取面と接触する面取面研削領域（Ｂ）とからなり、面取面研削領域（Ａ）の開口角は、面取面研削領域（Ｂ）の開口角よりも小さく設定されている。それによって、端面研削処理後のガラス基板Ｇの外周側の一対の面取面の面取り角を一致させることができるようになる。 The end face grinding of the outer peripheral end face of the glass substrate can be performed in the same manner as the inner peripheral end face. FIG. 5 is a diagram showing a grinding process of the outer peripheral end surface of the glass substrate G. As shown in FIG. 5, the grinding wheel 7 used for the end face grinding process of the outer peripheral end face is made of a cylindrical rotating body, and a groove is formed on the inner circumference thereof. As shown in FIG. 5, in the grinding process of the outer peripheral end face of the glass substrate G, as in the grinding process of the inner peripheral end face, the groove of the grinding wheel 7 and the glass substrate G are in a twisted positional relationship. Grinding is performed by inclining the grinding wheel 7 with respect to the substrate G. Moreover, also in the grinding process of the outer peripheral end surface of the glass substrate G, the side wall surface and two chamfered surfaces of the glass substrate G are ground simultaneously, similarly to the grinding process of the inner peripheral end surface. The inclination angle of the glass substrate G with respect to the groove direction of the grinding wheel 7 is preferably in the range of 1 to 15 degrees, for example, as in the grinding treatment of the inner peripheral end face.
The opening angle of the groove of the grinding wheel 7 may be the same as that shown in FIG. That is, the chamfering of the glass substrate G is performed on the front side in the rotation direction of the grinding wheel 7 with reference to the contact point between the glass substrate G and the grinding wheel 7 positioned on a straight line connecting the center of the glass substrate G and the rotation axis of the grinding wheel 7. A chamfered surface grinding region (A) that comes into contact with the surface and a chamfered surface grinding region (B) that comes into contact with the chamfered surface of the glass substrate G on the rear side in the rotational direction of the grinding wheel 7. The opening angle of the region (A) is set smaller than the opening angle of the chamfered surface grinding region (B). As a result, the chamfer angles of the pair of chamfered surfaces on the outer peripheral side of the glass substrate G after the end surface grinding process can be matched.

なお、上述した説明では、内周端面の研削砥石５が面取面研削領域５０ａ，５０ｂおよび側壁面研削領域５０ｔを有し、研削砥石５がガラス基板Ｇの内周端面の側壁面と一対の面取面とを同時に研削する場合について説明したが、研削砥石５は、一対の面取面を同時に研削し、そのときに側壁面を研削しないようにしてもよい。例えば、側壁面を先に研削する処理を別に行う場合には、研削砥石５を用いた研削処理は、一対の面取面を同時に研削することのみであってもよい。但し、上述したように、ガラス基板Ｇの内周端面の側壁面と一対の面取面とを同時に研削することによって、端面研削処理時間を短縮できる効果がある。
外周端面の場合についても同様のことが言える。In the above description, the grinding wheel 5 on the inner peripheral end surface has the chamfered surface grinding regions 50a and 50b and the side wall surface grinding region 50t, and the grinding wheel 5 is paired with the side wall surface on the inner peripheral end surface of the glass substrate G. Although the case where the chamfered surface is ground at the same time has been described, the grinding wheel 5 may grind the pair of chamfered surfaces at the same time and not grind the side wall surfaces at that time. For example, when the process of grinding the side wall surface first is performed separately, the grinding process using the grinding wheel 5 may be only grinding a pair of chamfered surfaces simultaneously. However, as described above, by grinding the side wall surface of the inner peripheral end surface of the glass substrate G and the pair of chamfered surfaces at the same time, there is an effect of shortening the end surface grinding time.
The same can be said for the outer peripheral end face.

（３）端面研磨処理
次にガラス基板の端面研磨処理が行われる。端面研磨処理は、研磨ブラシとガラス基板の端面との間に遊離砥粒を含む研磨液を供給して研磨ブラシとガラス基板とを相対的に移動させることにより研磨を行う処理である。端面研磨では、ガラス基板の内周端面および外周側端面を研磨対象とし、内周端面および外周側端面を鏡面状態にする。このとき、例えば酸化セリウム等の微粒子を遊離砥粒として含む研磨液が用いられる。端面研磨を行うことにより、ガラス基板の端面での塵等の異物粒子が付着した汚染、ダメージあるいはキズ等の損傷の除去を行うことができる。これにより、このガラス基板を用いて磁気ディスクを製造した場合であっても、サーマルアスペリティの発生を防止することができる。(3) End surface polishing process Next, the end surface polishing process of a glass substrate is performed. The end surface polishing process is a process for performing polishing by supplying a polishing liquid containing loose abrasive grains between the polishing brush and the end surface of the glass substrate and relatively moving the polishing brush and the glass substrate. In the end surface polishing, the inner peripheral end surface and the outer peripheral side end surface of the glass substrate are subjected to polishing, and the inner peripheral end surface and the outer peripheral side end surface are in a mirror state. At this time, for example, a polishing liquid containing fine particles such as cerium oxide as free abrasive grains is used. By performing the end surface polishing, it is possible to remove contamination such as dust, foreign matter particles such as dust on the end surface of the glass substrate, damage, or scratches. Thereby, even if it is a case where a magnetic disc is manufactured using this glass substrate, generation | occurrence | production of thermal asperity can be prevented.

（４）精研削処理
精研削処理では、遊星歯車機構を備えた両面研削装置を用いて円板状のガラス基板の主表面に対して研削加工を行う。両面研削装置は、上下一対の定盤（上定盤および下定盤）を有しており、上定盤および下定盤の間に、キャリアに装着された円板状のガラス基板が狭持される。そして、上定盤または下定盤のいずれか一方、または、双方を移動操作することにより、ガラス基板と各定盤とを相対的に移動させることで、ガラス基板の両主表面を研削することができる。(4) Fine grinding treatment In the fine grinding treatment, grinding is performed on the main surface of the disk-shaped glass substrate using a double-side grinding apparatus equipped with a planetary gear mechanism. The double-sided grinding apparatus has a pair of upper and lower surface plates (an upper surface plate and a lower surface plate), and a disk-shaped glass substrate mounted on a carrier is sandwiched between the upper surface plate and the lower surface plate. . Then, by moving the upper surface plate or the lower surface plate, or both of them, the main surface of the glass substrate can be ground by relatively moving the glass substrate and each surface plate. it can.

（５）第１研磨（主表面研磨）処理
次に、ガラス基板の主表面に第１研磨処理が施される。第１研磨処理では、遊星歯車機構を備えた両面研磨装置を用いてガラス基板の両側の主表面に対して研磨を行う。第１研磨処理では、例えば、酸化セリウム砥粒、あるいはジルコニア砥粒などの遊離砥粒と、樹脂ポリッシャが用いられる。第１研磨によって、例えば精研削処理を行った場合に主表面に残留したクラックや歪みを除去する。(5) First Polishing (Main Surface Polishing) Process Next, a first polishing process is performed on the main surface of the glass substrate. In the first polishing process, the main surfaces on both sides of the glass substrate are polished using a double-side polishing apparatus equipped with a planetary gear mechanism. In the first polishing process, for example, loose abrasive grains such as cerium oxide abrasive grains or zirconia abrasive grains and a resin polisher are used. The first polishing removes cracks and distortions remaining on the main surface when, for example, fine grinding is performed.

（６）化学強化処理
ガラス基板は適宜化学強化することができる。化学強化液として、例えば硝酸カリウム，硝酸ナトリウム、またはそれらの混合物を加熱して得られる溶融液を用いることができる。そして、ガラス基板を化学強化液に浸漬することによって、ガラス基板の表層にあるガラス組成中のリチウムイオンやナトリウムイオンが、それぞれ化学強化液中のイオン半径が相対的に大きいナトリウムイオンやカリウムイオンにそれぞれ置換されることで表層部分に圧縮応力層が形成され、ガラス基板が強化される。
化学強化処理を行うタイミングは、適宜決定することができるが、化学強化処理の後に研磨処理を行うようにすると、表面の平滑化とともに化学強化処理によってガラス基板の表面に固着した異物を取り除くことができるので特に好ましい。また、化学強化処理は、必要に応じて行われればよく、行われなくてもよい。(6) Chemical strengthening treatment The glass substrate can be appropriately chemically strengthened. As the chemical strengthening liquid, for example, a molten liquid obtained by heating potassium nitrate, sodium nitrate, or a mixture thereof can be used. Then, by immersing the glass substrate in the chemical strengthening solution, lithium ions and sodium ions in the glass composition on the surface of the glass substrate are converted into sodium ions and potassium ions having relatively large ion radii in the chemical strengthening solution, respectively. By replacing each, a compressive stress layer is formed in the surface layer portion, and the glass substrate is strengthened.
The timing of performing the chemical strengthening treatment can be determined as appropriate. However, if the polishing treatment is performed after the chemical strengthening treatment, the foreign matter fixed to the surface of the glass substrate by the chemical strengthening treatment can be removed together with the smoothing of the surface. This is particularly preferable because it can be performed. Further, the chemical strengthening treatment may be performed as necessary, and may not be performed.

（７）第２研磨（最終研磨）処理
次に、化学強化処理後のガラス基板に第２研磨が施される。第２研磨は、主表面の鏡面研磨を目的とする。第２研磨においても、第１研磨に用いる両面研磨装置と同様の構成を有する両面研磨装置が用いられる。第２研磨処理では、第１研磨処理よりも、遊離砥粒の粒子サイズと研磨パッドの樹脂ポリッシャの硬度を小さくすることが好ましい。このようにすることで、ガラス基板の表面粗さを極めて小さくすることができる。(7) Second Polishing (Final Polishing) Process Next, the second polishing is performed on the glass substrate after the chemical strengthening process. The second polishing is intended for mirror polishing of the main surface. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. In the second polishing process, it is preferable to make the particle size of the loose abrasive grains and the hardness of the resin polisher of the polishing pad smaller than in the first polishing process. By doing in this way, the surface roughness of a glass substrate can be made extremely small.

第２研磨処理に用いる遊離砥粒として、例えばコロイダルシリカ等の微粒子が用いられる。
第２研磨処理は、必ずしも必須な処理ではないが、ガラス基板の主表面の表面凹凸のレベルをさらに良好なものとすることができる点で実施することが好ましい。この後、洗浄を行うことによって、磁気ディスク用ガラス基板となる。
なお、第２研磨処理後のガラス基板の表面粗さの算術平均粗さＲａが０．１５ｎｍ以下となるようにガラス基板が研磨されることが、表面粗さの小さい磁気ディスク用ガラス基板を作製する点で好ましい。As the free abrasive grains used for the second polishing treatment, for example, fine particles such as colloidal silica are used.
The second polishing process is not necessarily an essential process, but it is preferable that the second polishing process is performed in that the level of surface irregularities on the main surface of the glass substrate can be further improved. Thereafter, by cleaning, a glass substrate for a magnetic disk is obtained.
Note that the glass substrate is polished so that the arithmetic average roughness Ra of the surface roughness of the glass substrate after the second polishing treatment is 0.15 nm or less, thereby producing a glass substrate for a magnetic disk having a small surface roughness. This is preferable.

なお、結晶化ガラスを作製する場合には、上述した各処理の途中で結晶化処理を行う。例えば、結晶化処理では、ガラス基板のそれぞれのガラス基板間にディスク状のセッターと呼ばれる板を挟んで、加熱炉に入れて熱処理を行う。セッターはセラミックス製としてもよい。熱処理では、例えば核形成温度で所定時間保持し、その後結晶成長温度で所定時間保持することによりガラス基板を結晶化させる。核形成温度および結晶成長の温度や時間は、ガラス基板のガラス組成によって適宜設定すればよい。加熱後の冷却では、ガラス基板に歪みや撓みが発生しないように、徐冷速度を調整することが好ましい。
結晶化したガラス基板は、例えば、粉末Ｘ線回折法で得られた回折強度分布を用いて結晶化の有無を判定することができる。なお、結晶相の平均結晶粒径は１０ｎｍ以下の結晶を析出させることが、ガラス基板の主表面の表面粗さを小さくして主表面を鏡面化させる点で好ましい。
結晶相は硬いため、研磨では加工し難い。平均結晶粒径が１０ｎｍを超えると、ガラス基板の主表面の研磨による加工時間が長くなり、また、研磨で取りきれない結晶相により表面粗さは無視できない大きさになる。また、結晶化処理後で、第２研磨処理前のガラス基板の表面粗さの算術平均粗さＲａは１ｎｍ以下であることが、第２研磨処理で取代量を小さくすることができる点で好ましい。
結晶化されたガラス（以降、結晶化ガラスという）は、非晶質のガラスを加熱することでガラス内部に結晶を析出させた構成の材料であり、非晶質のガラスとは区別され得る。結晶化ガラスは、内部に分散する結晶により、非晶質のガラスでは得られない特性を発揮する。例えば、ビッカース硬度、ヤング率、破壊靱性等の機械的強度、耐エッチング特性、熱膨張係数等の熱的特性について、結晶化ガラスは、非晶質ガラスでは実現しえない特性を発揮する。勿論、結晶化ガラスは紛体を焼結した構成のセラミックスとは異なる特性を発揮する。結晶化ガラスは、セラミックスと比較して、空孔が極めて少なく、緻密な構成を有する。
本実施形態においては、前記結晶化処理後のガラス基板のヤング率としては、１００ＧＰａ以上、より好ましくは１２０ＧＰａ以上であることが好ましい。こうすることで、抗折強度や耐衝撃性が高いガラス基板とすることができる。前記結晶化処理後のガラス基板の抗折強度は、耐衝撃性を向上させる観点から７ｋｇｆ以上であることが好ましく、特に８ｋｇｆ以上であることが好ましい。こうすることで、１００００ｒｐｍ以上の高速回転のＨＤＤ向けとして好適な磁気ディスク用ガラス基板とすることができる。In the case of producing crystallized glass, the crystallization process is performed in the middle of each process described above. For example, in the crystallization treatment, a plate called a disk-shaped setter is sandwiched between the glass substrates, and heat treatment is performed in a heating furnace. The setter may be made of ceramics. In the heat treatment, for example, the glass substrate is crystallized by holding at a nucleation temperature for a predetermined time and then holding at a crystal growth temperature for a predetermined time. The nucleation temperature and the crystal growth temperature and time may be appropriately set depending on the glass composition of the glass substrate. In cooling after heating, it is preferable to adjust the slow cooling rate so that the glass substrate is not distorted or bent.
The presence or absence of crystallization of the crystallized glass substrate can be determined using, for example, the diffraction intensity distribution obtained by the powder X-ray diffraction method. In addition, it is preferable to precipitate a crystal having an average crystal grain size of 10 nm or less in the crystal phase from the viewpoint of reducing the surface roughness of the main surface of the glass substrate and mirroring the main surface.
Since the crystal phase is hard, it is difficult to process by polishing. When the average crystal grain size exceeds 10 nm, the processing time by polishing the main surface of the glass substrate becomes long, and the surface roughness becomes a size that cannot be ignored due to the crystal phase that cannot be completely removed by polishing. In addition, it is preferable that the arithmetic average roughness Ra of the surface roughness of the glass substrate after the crystallization treatment and before the second polishing treatment is 1 nm or less in that the amount of machining allowance can be reduced by the second polishing treatment. .
Crystallized glass (hereinafter referred to as crystallized glass) is a material having a structure in which crystals are precipitated in glass by heating amorphous glass, and can be distinguished from amorphous glass. Crystallized glass exhibits characteristics that cannot be obtained with amorphous glass due to crystals dispersed inside. For example, with respect to mechanical properties such as Vickers hardness, Young's modulus, fracture toughness, and thermal properties such as etching resistance and thermal expansion coefficient, crystallized glass exhibits properties that cannot be realized with amorphous glass. Of course, crystallized glass exhibits different characteristics from ceramics having a structure in which powder is sintered. Crystallized glass has an extremely small number of pores and a dense structure as compared with ceramics.
In the present embodiment, the Young's modulus of the glass substrate after the crystallization treatment is preferably 100 GPa or more, more preferably 120 GPa or more. By carrying out like this, it can be set as a glass substrate with high bending strength and impact resistance. The bending strength of the glass substrate after the crystallization treatment is preferably 7 kgf or more, particularly preferably 8 kgf or more, from the viewpoint of improving impact resistance. By doing so, a glass substrate for a magnetic disk suitable for a high-speed rotation HDD of 10,000 rpm or more can be obtained.

［磁気ディスク］
磁気ディスクは、磁気ディスク用ガラス基板を用いて以下のようにして得られる。
磁気ディスクは、例えば磁気ディスク用ガラス基板（以下、単に「基板」という。）の主表面上に、主表面に近いほうから順に、少なくとも付着層、下地層、磁性層（磁気記録層）、保護層、潤滑層が積層された構成になっている。
例えば基板を、真空引きを行った成膜装置内に導入し、ＤＣマグネトロンスパッタリング法にてＡｒ雰囲気中で、基板の主表面上に付着層から磁性層まで順次成膜する。付着層としては例えばＣｒＴｉ、下地層としては例えばＣｒＲｕを用いることができる。磁性層としては、例えばＣｏＰｔ系合金を用いることができる。また、Ｌ１０規則構造のＣｏＰｔ系合金やＦｅＰｔ系合金を形成して熱アシスト磁気記録用の磁性層とすることもできる。上記成膜後、例えばＣＶＤ法によりＣ２Ｈ４を用いて保護層を成膜し、続いて表面に窒素を導入する窒化処理を行うことにより、磁気記録媒体を形成することができる。その後、例えばＰＦＰＥ（パーフルオロポリエーテル）をディップコート法により保護層上に塗布することにより、潤滑層を形成することができる。
作製された磁気ディスクは、好ましくは、ＤＦＨ(Dynamic Flying Height)コントロール機構を搭載した磁気ヘッドと、磁気ディスクを固定するためのスピンドルとを備えた、磁気記録再生装置としての磁気ディスクドライブ装置（ＨＤＤ(Hard Disk Drive)）に組み込まれる。[Magnetic disk]
A magnetic disk is obtained as follows using a magnetic disk glass substrate.
The magnetic disk is, for example, on the main surface of a glass substrate for magnetic disk (hereinafter simply referred to as “substrate”), in order from the closest to the main surface, at least an adhesion layer, an underlayer, a magnetic layer (magnetic recording layer), and a protective layer. A layer and a lubricating layer are laminated.
For example, the substrate is introduced into a film forming apparatus that has been evacuated, and a film is sequentially formed from an adhesion layer to a magnetic layer on the main surface of the substrate in an Ar atmosphere by a DC magnetron sputtering method. For example, CrTi can be used as the adhesion layer, and CrRu can be used as the underlayer. As the magnetic layer, for example, a CoPt alloy can be used. It is also possible to form a CoPt-based alloy and FePt based alloy L 10 regular structure and magnetic layer for heat-assisted magnetic recording. After the above film formation, a magnetic recording medium can be formed by forming a protective layer using, for example, C 2 H 4 by a CVD method and subsequently performing nitriding treatment for introducing nitrogen into the surface. Thereafter, for example, PFPE (perfluoropolyether) is applied on the protective layer by a dip coating method, whereby a lubricating layer can be formed.
The manufactured magnetic disk is preferably a magnetic disk drive device (HDD) as a magnetic recording / reproducing device, which includes a magnetic head equipped with a DFH (Dynamic Flying Height) control mechanism and a spindle for fixing the magnetic disk. (Hard Disk Drive)).

［実施例、比較例］
本実施形態の磁気ディスク用ガラス基板の製造方法の効果を確認した。使用したガラスの組成は、下記の通りである。
［ガラスの組成］
質量％表示で、ＳｉＯ２を６５．０８％、Ａｌ２Ｏ３を１５．１４％、Ｌｉ２Ｏを３．６１％、Ｎａ２Ｏを１０．６８％、Ｋ２Ｏを０．３５％、ＭｇＯを０．９９％、ＣａＯを２．０７％、ＺｒＯ２を１．９８％、Ｆｅ２Ｏ３を０．１０％、有する組成からなるアモルファスのアルミノシリケートガラスであり、ガラス転移温度が５１０℃である。[Examples and Comparative Examples]
The effect of the manufacturing method of the glass substrate for magnetic disks of this embodiment was confirmed. The composition of the used glass is as follows.
[Glass composition]
In terms of mass%, SiO 2 is 65.08%, Al 2 O 3 is 15.14%, Li 2 O is 3.61%, Na 2 O is 10.68%, K 2 O is 0.35%, An amorphous aluminosilicate glass having a composition having 0.99% MgO, 2.07% CaO, 1.98% ZrO 2 and 0.10% Fe 2 O 3 , and has a glass transition temperature of 510 ° C. It is.

［実施例、比較例のガラス基板の作製］
実施例、比較例の磁気ディスク用ガラス基板については、上記製造方法の各処理を順序通りに行うことで、内径が２０ｍｍ、外径が６５ｍｍ、厚さが０．８ｍｍの公称２．５インチサイズの磁気ディスク用ガラス基板を作製した。このとき、形状加工では、ガラス素板を切断し、円形の内孔（内径：２０ｍｍ）と円形の外形（外径：６５ｍｍ）を備えたドーナツ状の円板状ガラス基板を得た。このガラス基板の外周端部および内周端部に対して、図２〜図５に示した端面研削加工を施して、外周側の面取面および内周側の面取面を形成した。このとき、内周端面の研削では、α＝５度とし、外径１５ｍｍの研削砥石を使用した。外周端面の研削では、α＝５度とし、外径１００ｍｍの研削砥石を使用した。内周端面の研削、外周端面の研削共に、粒度＃４００の電着ダイヤモンド砥石、粒度＃２０００のレジンボンドダイヤモンド砥石を順に用いた。側壁面研削領域５０ｔ（図４参照）の幅は、１．０ｍｍとした。
表１、表２に示したように、実施例、比較例の磁気ディスク用ガラス基板を作製するに当たって、研削砥石の溝の開口角が異なる。なお、表１は内周側の端面研削の場合を、表２は外周側の端面研削の場合を、それぞれ示している。[Production of Glass Substrate for Examples and Comparative Examples]
About the glass substrate for magnetic disks of an Example and a comparative example, by performing each process of the said manufacturing method in order, an inner diameter is 20 mm, an outer diameter is 65 mm, thickness is a nominal 2.5 inch size of 0.8 mm. A magnetic disk glass substrate was prepared. At this time, in the shape processing, the glass base plate was cut to obtain a donut-shaped disk-shaped glass substrate having a circular inner hole (inner diameter: 20 mm) and a circular outer shape (outer diameter: 65 mm). The end surface grinding shown in FIGS. 2 to 5 was performed on the outer peripheral end portion and the inner peripheral end portion of the glass substrate to form an outer peripheral side chamfered surface and an inner peripheral side chamfered surface. At this time, in grinding the inner peripheral end face, α = 5 degrees and a grinding wheel having an outer diameter of 15 mm was used. In grinding of the outer peripheral end face, α = 5 degrees and a grinding wheel having an outer diameter of 100 mm was used. For the grinding of the inner peripheral end face and the outer peripheral end face, an electrodeposited diamond grindstone with a particle size of # 400 and a resin bond diamond grindstone with a particle size of # 2000 were used in this order. The width of the side wall surface grinding region 50t (see FIG. 4) was 1.0 mm.
As shown in Tables 1 and 2, when the glass substrates for magnetic disks of Examples and Comparative Examples are produced, the opening angles of the grooves of the grinding wheel are different. Table 1 shows the case of end face grinding on the inner peripheral side, and Table 2 shows the case of end face grinding on the outer peripheral side.

表１、表２において、ガラス基板の中心と研削砥石の回転軸とを結ぶ直線上に位置するガラス基板と研削砥石の接点を基準として、研削砥石の回転方向の前側でガラス基板の面取面と接触する面取面研削領域（Ａ）の開口角をθＡとし、研削砥石の回転方向の後側でガラス基板の面取面と接触する面取面研削領域（Ｂ）の開口角をθＢとする。面取面研削領域（Ａ）によって研削されるガラス基板の面取面の面取り角をΘＡとし、面取面研削領域（Ｂ）によって研削されるガラス基板の面取面の面取り角をΘＢとする。
表１、表２の面取り角をΘＡ、ΘＢは、端面研削加工直後の値である。In Table 1 and Table 2, the chamfered surface of the glass substrate on the front side in the rotation direction of the grinding wheel with reference to the contact point between the grinding wheel and the glass substrate located on the straight line connecting the center of the glass substrate and the rotation axis of the grinding wheel the aperture angle of the aperture angle and theta a, chamfered surface grinding region in contact with the chamfered surface of the glass substrate at the rear side of the rotational direction of the grinding wheel (B) of the chamfered surface grinding region contacting (a) and theta B. The chamfering angle of the chamfered surface of the glass substrate to be ground in the chamfered surface grinding region (A) is Θ A, and the chamfering angle of the chamfered surface of the glass substrate to be ground in the chamfered surface grinding region (B) is Θ B. And
In Tables 1 and 2, the chamfer angles Θ A and Θ B are values immediately after the end surface grinding.

Figure 0006170557
Figure 0006170557

Figure 0006170557
Figure 0006170557

端面研削加工の後に、端面研磨、主表面に対する第１研磨、第２研磨を行って、磁気ディスク用ガラス基板を作製したが、面取り角は、表１、表２に示した値と変わらなかった。
表１、表２の各実施例が示すように、外周端面および内周端面の研削では、砥石の開口角について、開口角θＡを開口角θＢよりも小さくすることで、端面研削後のガラス基板の一対の面取面の面取り角ΘＡ，ΘＢが同一となったことがわかる。After end face grinding, end face polishing, first polishing on the main surface, and second polishing were performed to produce a glass substrate for a magnetic disk, but the chamfer angle was not different from the values shown in Tables 1 and 2. .
As shown in Tables 1 and 2, in the grinding of the outer peripheral end face and the inner peripheral end face, the opening angle θ A of the grindstone is set to be smaller than the opening angle θ B so that the end face grinding is completed. It can be seen that the chamfer angles Θ A and Θ B of the pair of chamfered surfaces of the glass substrate are the same.

以上、本発明の磁気ディスク用ガラス基板、磁気ディスクの製造方法、および研削砥石について詳細に説明したが、本発明は上記実施形態に限定されず、本発明の主旨を逸脱しない範囲において、種々の改良や変更をしてもよいのは勿論である。   As described above, the glass substrate for magnetic disk, the method for manufacturing the magnetic disk, and the grinding wheel of the present invention have been described in detail. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention. Of course, improvements and changes may be made.

Claims (6)

中心に円孔が形成され、側壁面および主表面と側壁面との間に形成された面取面とを有する円板状ガラス基板の端面に対して、回転する研削砥石を用いて端面研削処理を行う磁気ディスク用ガラス基板の製造方法であって、
上記端面研削処理は、研削砥石の回転軸を、基板の主表面と直交する軸に対して傾斜させて、ガラス基板の一対の面取面を同時に研削するものであり、
上記研削砥石は、ガラス基板の面取面を研削する一対の面取面研削領域を有する溝形状を有し、
上記一対の面取面研削領域は、
ガラス基板の一方の面取面と接触する面取面研削領域（Ａ）と、ガラス基板の他方の面取面と接触する面取面研削領域（Ｂ）とを含み、
上記面取面研削領域（Ａ）の開口角は、上記面取面研削領域（Ｂ）の開口角よりも小さいことを特徴とする、
磁気ディスク用ガラス基板の製造方法。 An end surface grinding process using a rotating grinding wheel is performed on the end surface of a disk-shaped glass substrate having a circular hole formed in the center and having a side wall surface and a chamfered surface formed between the main surface and the side wall surface. A method of manufacturing a magnetic disk glass substrate, comprising:
The end face grinding process is to grind a pair of chamfered surfaces of a glass substrate at the same time by inclining a rotation axis of a grinding wheel with respect to an axis orthogonal to the main surface of the substrate,
The grinding wheel has a groove shape having a pair of chamfered surfaces for grinding a chamfered surface of a glass substrate,
The pair of chamfered surface grinding areas are
A chamfered surface grinding region (A) in contact with one chamfered surface of the glass substrate, and a chamfered surface ground region (B) in contact with the other chamfered surface of the glass substrate,
The opening angle of the chamfered surface grinding region (A) is smaller than the opening angle of the chamfered surface grinding region (B),
Manufacturing method of glass substrate for magnetic disk. 上記研削砥石の溝形状は、ガラス基板の側壁面を研削する側壁面研削領域をさらに有し、
上記端面研削処理は、ガラス基板の側壁面と一対の面取面とを同時に研削することを特徴とする、
請求項１に記載された磁気ディスク用ガラス基板の製造方法。 The groove shape of the grinding wheel further has a side wall surface grinding region for grinding the side wall surface of the glass substrate,
The end face grinding process is characterized in that the side wall surface of the glass substrate and the pair of chamfered surfaces are ground simultaneously.
The manufacturing method of the glass substrate for magnetic discs described in Claim 1. 上記磁気ディスク用ガラス基板の板厚が０．６３５ｍｍより小さいことを特徴とする、
請求項１又は２に記載された磁気ディスク用ガラス基板の製造方法。 The thickness of the magnetic disk glass substrate is smaller than 0.635 mm,
A method for producing a glass substrate for a magnetic disk according to claim 1 or 2. 上記一対の面取面研削領域は、
ガラス基板の中心点を起点として研削砥石の回転軸に直交する直線上に位置するガラス基板と研削砥石の接点を基準として、主に研削砥石の回転方向の前側でガラス基板の面取面と接触する面取面研削領域（Ａ）と、主に研削砥石の回転方向の後側でガラス基板の面取面と接触する面取面研削領域（Ｂ）とを含むことを特徴とする、
請求項１〜３のいずれかに記載された磁気ディスク用ガラス基板の製造方法。 The pair of chamfered surface grinding areas are
Contact the chamfered surface of the glass substrate mainly on the front side in the rotation direction of the grinding wheel with reference to the contact point between the grinding wheel and the glass substrate located on a straight line perpendicular to the rotation axis of the grinding wheel, starting from the center point of the glass substrate. A chamfered surface grinding region (A) to be performed, and a chamfered surface grinding region (B) mainly in contact with the chamfered surface of the glass substrate on the rear side in the rotational direction of the grinding wheel,
The manufacturing method of the glass substrate for magnetic discs in any one of Claims 1-3. 請求項１から４のいずれか１項に記載された磁気ディスク用ガラス基板の製造方法によって作製された磁気ディスク用ガラス基板の主表面上に、磁性層を形成する処理を備えたことを特徴とする、
磁気ディスクの製造方法。 A process for forming a magnetic layer on the main surface of the magnetic disk glass substrate produced by the method for producing a magnetic disk glass substrate according to any one of claims 1 to 4 is provided. To
A method of manufacturing a magnetic disk. 中心に円孔が形成され、側壁面および主表面と側壁面との間に形成された面取面とを有する円板状ガラス基板の端面に対する端面研削処理において回転して使用される研削砥石であって、
上記研削砥石は、円筒状又は円柱状の回転体からなり、当該回転体の周上に溝が形成されており、
上記溝は、上記回転体の回転軸を含む面による断面視において、ガラス基板の側壁面と接触する側壁面研削面と、ガラス基板の側壁面を挟んで一方の面取面と接触する面取面研削面（Ａ）と、他方の面取面と接触する面取面研削面（Ｂ）とからなり、
面取面研削面（Ａ）と面取面研削面（Ｂ）の、側壁面研削面からの開口角が異なることを特徴とする、研削砥石。 A grinding wheel used by rotating in an end surface grinding process for an end surface of a disk-shaped glass substrate having a circular hole in the center and having a side wall surface and a chamfered surface formed between the main surface and the side wall surface. There,
The grinding wheel is composed of a cylindrical or columnar rotating body, and a groove is formed on the periphery of the rotating body,
The groove has a side wall surface ground surface that contacts the side wall surface of the glass substrate and a chamfer surface that contacts one chamfered surface across the side wall surface of the glass substrate in a cross-sectional view of the surface including the rotation axis of the rotating body. It consists of a chamfered surface (A) and a chamfered chamfered surface (B) in contact with the other chamfered surface,
A grinding wheel characterized in that the chamfered surface (A) and the chamfered surface (B) have different opening angles from the side wall surface.
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