JP5700015B2 - Glass substrate for magnetic recording media - Google Patents
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- JP5700015B2 JP5700015B2 JP2012219258A JP2012219258A JP5700015B2 JP 5700015 B2 JP5700015 B2 JP 5700015B2 JP 2012219258 A JP2012219258 A JP 2012219258A JP 2012219258 A JP2012219258 A JP 2012219258A JP 5700015 B2 JP5700015 B2 JP 5700015B2
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- 239000011521 glass Substances 0.000 title claims description 133
- 239000000758 substrate Substances 0.000 title claims description 131
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- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 12
- 229910052684 Cerium Inorganic materials 0.000 claims description 10
- 238000000550 scanning electron microscopy energy dispersive X-ray spectroscopy Methods 0.000 claims description 10
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 9
- 239000011591 potassium Substances 0.000 claims description 9
- 229910052700 potassium Inorganic materials 0.000 claims description 9
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- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 48
- 239000007788 liquid Substances 0.000 description 42
- 238000000034 method Methods 0.000 description 31
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- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 14
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 10
- 239000002270 dispersing agent Substances 0.000 description 9
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- 229910052845 zircon Inorganic materials 0.000 description 8
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 8
- 239000002253 acid Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- 229910052580 B4C Inorganic materials 0.000 description 4
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 description 4
- 229910003460 diamond Inorganic materials 0.000 description 4
- 239000010432 diamond Substances 0.000 description 4
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 4
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
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- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 150000002910 rare earth metals Chemical class 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
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- DRVWBEJJZZTIGJ-UHFFFAOYSA-N cerium(3+);oxygen(2-) Chemical class [O-2].[O-2].[O-2].[Ce+3].[Ce+3] DRVWBEJJZZTIGJ-UHFFFAOYSA-N 0.000 description 1
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- 239000002736 nonionic surfactant Substances 0.000 description 1
- OFNHPGDEEMZPFG-UHFFFAOYSA-N phosphanylidynenickel Chemical compound [P].[Ni] OFNHPGDEEMZPFG-UHFFFAOYSA-N 0.000 description 1
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Description
本発明は、磁気記録媒体用ガラス基板に関する。 The present invention relates to a glass substrate for a magnetic recording medium.
近年、磁気記録媒体、特に磁気ディスク装置においては、急激な高記録密度化が進んでいる。磁気ディスク装置では、高速回転する記録媒体（ディスク）上を、ヘッドを僅かに浮上させて走査することによってランダムアクセスを実現しており、高記録密度と高速アクセスを両立させるために、磁気ディスクとヘッドとの間隔（ヘッド浮上量）を小さくすること、磁気ディスクの回転数を上げること、が求められる。磁気ディスクの基材は、従来アルミニウム（Ａｌ）にニッケル−リン（Ｎｉ−Ｐ）メッキを施した基板が主流であったが、高剛性で高速回転させても変形しにくく、表面の平滑性が高いガラス基板が使われるようになってきている。 In recent years, magnetic recording media, particularly magnetic disk devices, have been rapidly increasing in recording density. In the magnetic disk device, random access is realized by scanning the recording medium (disk) rotating at high speed with the head slightly lifted, and in order to achieve both high recording density and high speed access, It is required to reduce the distance from the head (head flying height) and increase the rotational speed of the magnetic disk. Conventionally, the base material of magnetic disks is mainly aluminum (Al) plated with nickel-phosphorus (Ni-P), but it is highly rigid and difficult to deform even when rotated at high speed, and the surface is smooth. High glass substrates are being used.
このような磁気ディスク装置における高記録密度化に伴い、磁気記録媒体用ガラス基板への要求特性が年々厳しくなっている。特に、高記録密度を達成するために、ガラス基板の表面の異物や欠陥を低減して平滑性を向上させることは重要である。 With the increase in recording density in such a magnetic disk device, the required characteristics for a glass substrate for a magnetic recording medium are becoming stricter year by year. In particular, in order to achieve a high recording density, it is important to improve the smoothness by reducing foreign matters and defects on the surface of the glass substrate.
一般に、磁気記録媒体用ガラス基板を製造するには、板状ガラス等の原材から円盤形状の原基板を切り出し、中央部に円形の貫通孔を形成した後、ガラス基板の外周を構成する外周側面の角部分と、貫通孔の内壁を構成する内周側面の角部分との面取り加工を行う。その後、ガラス基板の内周および外周の側面と面取り部（以下、側面と面取り部と合わせて端面という。）の研磨（端面研磨）を行い、さらに対向する１対の主平面も研磨した後、洗浄工程を経て磁気記録媒体用ガラス基板を得る。 Generally, in order to manufacture a glass substrate for a magnetic recording medium, a disk-shaped original substrate is cut out from a raw material such as plate glass, a circular through-hole is formed in the center, and an outer periphery constituting the outer periphery of the glass substrate Chamfering is performed between the corner portion of the side surface and the corner portion of the inner peripheral side surface constituting the inner wall of the through hole. Then, after polishing (end surface polishing) of the inner and outer peripheral side surfaces and chamfered portions of the glass substrate (hereinafter referred to as end surfaces together with the side surfaces and chamfered portions), and also polishing a pair of opposing main planes, A glass substrate for a magnetic recording medium is obtained through a cleaning process.
このような磁気記録媒体用ガラス基板の製造において、ガラス基板の端面の研磨は、面取り加工等の際に端面に生じたキズやクラックを除去し、凹凸を平滑化して鏡面に仕上げるために行われる。ガラス基板の端面を平滑な鏡面に仕上げることにより、ガラス基板の機械的強度を向上させる、端面の凹凸に捕捉される異物を低減する、端面の凹凸がカセットや治具等の樹脂部材等を削って発生させるパーティクルを低減する、などの多くの効果がある。 In the production of such a glass substrate for magnetic recording media, polishing of the end surface of the glass substrate is performed in order to remove scratches and cracks generated on the end surface during chamfering and the like, smooth the unevenness, and finish the mirror surface. . Finishing the end surface of the glass substrate to a smooth mirror surface improves the mechanical strength of the glass substrate, reduces foreign matter trapped by the end surface unevenness, and the end surface unevenness scrapes resin members such as cassettes and jigs. There are many effects such as reducing the number of generated particles.
ガラス基板の端面の研磨が不十分である場合には、前記キズ等が端面（特に面取り部）に微小欠陥（潜傷）として残留することになる。そして、研磨後の洗浄等により、この微小欠陥がキズを中心に等方的にエッチングされて顕在化し、円形状または楕円形状のピット欠陥となる。このようなピット欠陥はその後の工程で異物を補足し、さらにその後の工程でその異物が排出されてガラス基板の表面に付着すると、情報記録媒体としての信頼性低下につながる。 When the end surface of the glass substrate is not sufficiently polished, the scratches or the like remain as minute defects (latent scratches) on the end surface (particularly the chamfered portion). Then, this fine defect is isotropically etched centering on the flaw by cleaning after polishing or the like, and becomes a pit defect having a circular or elliptical shape. Such a pit defect captures foreign matter in a subsequent process, and when the foreign matter is discharged and attached to the surface of the glass substrate in the subsequent process, the reliability of the information recording medium is reduced.
従来から、ガラス基板の端面を研磨し前記キズ等が存在する加工変質層を除去する技術として、酸化セリウム砥粒を用いて研磨する方法が提案されている（例えば、特許文献１参照。）。また、酸化セリウム砥粒を含有する研磨液と回転軸にブラシ毛が植毛された研磨ブラシを用いて、内周端面を研磨する方法も提案されている（例えば、特許文献２参照。）。砥粒を構成する酸化セリウムは、ガラス材料に対して化学的に強い相互作用を有するので、高い研磨速度（単位時間あたりの研磨量）の研磨が可能である。 Conventionally, a polishing method using cerium oxide abrasive grains has been proposed as a technique for removing a work-affected layer in which an end surface of a glass substrate is polished to remove the scratches (see, for example, Patent Document 1). In addition, a method of polishing an inner peripheral end surface using a polishing liquid containing cerium oxide abrasive grains and a polishing brush in which brush hairs are planted on a rotating shaft has been proposed (see, for example, Patent Document 2). Since cerium oxide constituting the abrasive grains has a chemically strong interaction with the glass material, polishing at a high polishing rate (polishing amount per unit time) is possible.
しかしながら、近時、産出国のレアアースに対する輸出規制などの影響により酸化セリウムの入手難や価格高騰が生じており、このような昨今の情勢から、砥粒である酸化セリウムの使用量をできるだけ低減することが求められている。 However, recently, cerium oxides have become difficult to obtain and prices have risen due to the effects of export restrictions on rare earths in the country of production. From such a recent situation, the amount of cerium oxide used as abrasive grains is reduced as much as possible. It is demanded.
また、酸化セリウムの残留による磁気記録媒体の欠陥を解消するためにも、酸化セリウム砥粒の使用量を抑えることが求められている。すなわち、酸化セリウムは、前記したようにガラスとの化学的親和力が大きいため、酸化セリウム粒子を用いて研磨したガラス基板では、表面に酸化セリウム粒子が強固に付着したり埋ったりするため、通常のアルカリ洗浄では酸化セリウム粒子を十分に除去することが難しかった。そのため、ガラス基板の表面に酸化セリウムが残留して、磁気記録媒体の欠陥となる問題が生じていた。さらに、表面に強固に付着した酸化セリウム粒子を除去するには、ガラス基板の表面を強酸やフッ素イオンを含有する洗浄液で洗浄する方法があるが、このような酸洗浄を行う方法では、工程上の負荷が大きいという問題があった。 Further, in order to eliminate defects in the magnetic recording medium due to residual cerium oxide, it is required to suppress the amount of cerium oxide abrasive grains used. That is, since cerium oxide has a large chemical affinity with glass as described above, in a glass substrate polished with cerium oxide particles, cerium oxide particles are firmly attached or buried on the surface. It was difficult to sufficiently remove cerium oxide particles by alkali cleaning. Therefore, cerium oxide remains on the surface of the glass substrate, resulting in a problem of a defect in the magnetic recording medium. Furthermore, in order to remove the cerium oxide particles firmly adhered to the surface, there is a method of cleaning the surface of the glass substrate with a cleaning solution containing a strong acid or a fluorine ion. There was a problem that the load of.
なお、ガラス基板の端面の研磨に関しては、主平面の研削（ラッピング）工程を間に挟んで前後２段階の端面研磨を行う方法も提案されている（例えば、特許文献３参照。）。すなわち、面取り加工後、研磨量の多い前段階の端面研磨を行い、次いで主平面の研削を行った後、研磨量がより少ない後段階の端面研磨を行うことで、面取り加工で発生した端面のキズが主平面の研削により伸長することを防ぐようにした技術が提案されている。 In addition, regarding the polishing of the end face of the glass substrate, there has also been proposed a method of performing end face polishing in two stages, front and rear, with a main surface grinding (lapping) step in between (see, for example, Patent Document 3). That is, after chamfering, end face polishing of the previous stage with a large amount of polishing is performed, then grinding of the main surface is performed, and then end face polishing of the lower stage with a smaller amount of polishing is performed, so that the end face generated in the chamfering process is Techniques have been proposed in which scratches are prevented from extending due to grinding of the main surface.
しかし、この方法においては、端面研磨に要する時間が長くなるため、面取り加工等により端面に生じたキズを短時間で除去し、平滑な鏡面を得ることが難しかった。また、砥粒として酸化セリウム粒子を使用する場合には、前記酸化セリウムに起因する異物付着の問題や、それを防止するための酸洗浄工程設置による工程負荷の問題が生じていた。 However, in this method, since the time required for end face polishing becomes long, it has been difficult to remove scratches generated on the end face by chamfering or the like in a short time to obtain a smooth mirror surface. In addition, when cerium oxide particles are used as the abrasive grains, the problem of foreign matter adhesion due to the cerium oxide and the process load problem due to the installation of an acid cleaning process to prevent it have occurred.
本発明は上記問題を解決するためになされたもので、面取り部等の端面にピット欠陥がない磁気記録媒体用ガラス基板を提供することを目的とする。また、ガラス基板の端面を、酸化セリウム砥粒の使用をできるだけ抑えながら、かつ高い研磨速度で研磨し、面取り部にピット欠陥のない磁気記録媒体用ガラス基板を得るための製造方法を提供することを目的とする。 The present invention has been made to solve the above problems, and an object of the present invention is to provide a glass substrate for a magnetic recording medium having no pit defects on the end face of a chamfered portion or the like. Further, to provide a manufacturing method for polishing the end face of a glass substrate at a high polishing rate while suppressing the use of cerium oxide abrasive grains as much as possible, and obtaining a glass substrate for a magnetic recording medium having no pit defect in a chamfered portion. With the goal.
本発明は、下記［１］〜［４］に示す磁気記録媒体用ガラス基板を提供する。 The present invention provides a glass substrate for a magnetic recording medium as shown in the following [1] to [4].
［１］中央部に貫通孔を有し、前記貫通孔を構成する内周側面と、外周側面、および互いに対向する１対の主平面を有する円盤形状のガラス基板において、前記内周側面および前記外周側面と前記主平面との交差部に、それぞれ内周面取り部および外周面取り部が形成された磁気記録媒体用ガラス基板であって、
前記内周面取り部は、ガラス基板の表面を５μｍエッチングしてから評価される、直径または長径の最大径が１０μｍ以上のピット欠陥数が５個／ｍｍ２以下であり、
前記内周面取り部は、ＳＥＭ−ＥＤＸを用いて該内周面取り部で測定されるセリウムのＬ線の強度を、前記ガラス基板に含まれるカリウムのＫ線、Ｌ線の強度（内部標準）で除した値が、０．３以下であることを特徴とする磁気記録媒体用ガラス基板。
[1] In a disk-shaped glass substrate having a through hole in the central portion and having an inner peripheral side surface forming the through hole, an outer peripheral side surface, and a pair of main planes facing each other, A glass substrate for a magnetic recording medium in which an inner peripheral chamfered portion and an outer peripheral chamfered portion are respectively formed at intersections between an outer peripheral side surface and the main plane,
The inner peripheral chamfer, the surface of the glass substrate is voted by 5μm etching state, and are maximum diameter 10μm or more pits number of defects having a diameter or major axis 5 / mm 2 or less,
The inner peripheral chamfered portion uses the SEM-EDX to measure the intensity of cerium L-line measured at the inner peripheral chamfered portion by the potassium K-line and L-line intensity (internal standard) contained in the glass substrate. The glass substrate for magnetic recording media , wherein the divided value is 0.3 or less .
［２］中央部に貫通孔を有し、前記貫通孔を構成する内周側面と、外周側面、および互いに対向する１対の主平面を有する円盤形状のガラス基板において、前記内周側面および前記外周側面と前記主平面との交差部に、それぞれ内周面取り部および外周面取り部が形成された磁気記録媒体用ガラス基板であって、
前記外周面取り部は、ガラス基板の表面を５μｍエッチングしてから評価される、直径または長径の最大径が１０μｍ以上のピット欠陥数が５個／ｍｍ２以下であり、
前記外周面取り部は、ＳＥＭ−ＥＤＸを用いて該外周面取り部で測定されるセリウムのＬ線の強度を、前記ガラス基板に含まれるカリウムのＫ線、Ｌ線の強度（内部標準）で除した値が、０．３以下であることを特徴とする磁気記録媒体用ガラス基板。
[2] In a disc-shaped glass substrate having a through hole in the center, and having an inner peripheral side surface that constitutes the through hole, an outer peripheral side surface, and a pair of main planes facing each other, A glass substrate for a magnetic recording medium in which an inner peripheral chamfered portion and an outer peripheral chamfered portion are respectively formed at intersections between an outer peripheral side surface and the main plane,
The outer circumferential chamfer, the surface of the glass substrate is voted by 5μm etched, the number pit defects of more than 10μm maximum diameter of the diameter or major axis Ri der 5 / mm 2 or less,
The outer peripheral chamfered portion was obtained by dividing the cerium L-line intensity measured by the outer peripheral chamfered portion using SEM-EDX by the potassium K-line and L-line intensities (internal standard) contained in the glass substrate. A glass substrate for a magnetic recording medium having a value of 0.3 or less .
［３］前記内周面取り部は、ＳＥＭ−ＥＤＸを用いて該内周面取り部で測定されるセリウムのＬ線の強度を、前記ガラス基板に含まれるカリウムのＫ線、Ｌ線の強度（内部標準）で除した値が、０．３以下である［２］に記載の磁気記録媒体用ガラス基板。 [3] The inner peripheral chamfered portion uses the SEM-EDX to measure the intensity of the cerium L-line measured by the inner peripheral chamfered portion, and the strength of the potassium K-line and L-line contained in the glass substrate (internal The glass substrate for magnetic recording media according to [2] , wherein a value divided by (standard) is 0.3 or less.
［４］前記外周面取り部は、ＳＥＭ−ＥＤＸを用いて該外周面取り部で測定されるセリウムのＬ線の強度を、前記ガラス基板に含まれるカリウムのＫ線、Ｌ線の強度（内部標準）で除した値が、０．３以下である［１］に記載の磁気記録媒体用ガラス基板。 [4] The outer peripheral chamfered portion uses the SEM-EDX to measure the intensity of the cerium L-line measured at the outer peripheral chamfered portion, and the strength of the potassium K-line and L-line contained in the glass substrate (internal standard). The glass substrate for magnetic recording media according to [1] , wherein the value divided by is 0.3 or less.
本発明によれば、砥粒としての酸化セリウム粒子の使用をできるだけ抑えながら、ガラス基板の端面を十分に高い研磨速度で効率的に研磨し、特に面取り部にピット欠陥がない磁気記録媒体用ガラス基板を得ることができる。そして、酸化セリウム砥粒の使用量の削減により、ガラス基板の端面への酸化セリウムの付着および酸化セリウムに起因する異物の付着を低減できる。また、付着した酸化セリウムを除去するための酸洗浄の工程をなくすことができるので、製造工程上の負荷をより低減できる。 According to the present invention, glass for a magnetic recording medium in which the end face of a glass substrate is efficiently polished at a sufficiently high polishing rate while suppressing the use of cerium oxide particles as abrasive grains as much as possible, and particularly there is no pit defect in the chamfered portion. A substrate can be obtained. And the reduction of the usage-amount of a cerium oxide abrasive grain can reduce the adhesion of the cerium oxide to the end surface of a glass substrate, and the adhesion of the foreign material resulting from a cerium oxide. In addition, since the acid cleaning step for removing the attached cerium oxide can be eliminated, the load on the manufacturing process can be further reduced.
以下、本発明を実施するための形態について説明するが、本発明は以下に記載される実施形態に限定されない。 Hereinafter, although the form for implementing this invention is demonstrated, this invention is not limited to embodiment described below.
［磁気記録媒体用ガラス基板の製造方法］
まず、製造される磁気記録媒体用ガラス基板を、図１に示す。図１に示す磁気記録媒体用ガラス基板１０は、中央部に断面形状が円形の貫通孔（以下、円孔という。）１１を有する円盤形状を有し、円孔１１の内壁面である内周側面１０１と、外周側面１０２、および対向する上下両側の主平面１０３ａ、１０３ｂからなる円盤形状を有している。そして、内周側面１０１と上下両主平面１０３ａ、１０３ｂとの交差部に内周面取り部１０４が形成されており、外周側面１０２と両主平面１０３ａ、１０３ｂとの交差部に外周面取り部１０５が形成されている。
[Method for producing glass substrate for magnetic recording medium]
First, the glass substrate for magnetic recording media manufactured is shown in FIG. A
このような磁気記録媒体用ガラス基板１０を製造する方法は、以下に示す（１）〜（５）の各工程を有する。
（１）中央部に円孔１１を有する円盤形状のガラス基板を形成する形状付与工程。
（２）ガラス基板の内周側面１０１および外周側面１０２と上下両主平面１０３ａ、１０３ｂとの交差部に、それぞれ内周面取り部１０４および外周面取り部１０５を形成する面取り工程。
（３）内周側面１０１と内周面取り部１０４（以下、内周側面と内周面取り部を合わせて内周端面と示す。）を研磨する内周端面研磨工程。
（４）外周側面１０２と外周面取り部１０５（以下、外周側面と外周面取り部を合わせて外周端面と示す。）を研磨する外周端面研磨工程。
（５）ガラス基板の上下両主平面１０３ａ、１０３ｂを研磨する主平面研磨工程。
The method for manufacturing such a glass substrate for
(1) A shape imparting step of forming a disk-shaped glass substrate having a
(2) A chamfering step of forming an inner peripheral chamfered portion 104 and an outer
(3) An inner peripheral end surface polishing step for polishing the inner
(4) An outer peripheral end surface polishing step for polishing the outer
(5) A main surface polishing step for polishing the upper and lower
前記（２）面取り工程の後、ガラス基板の上下両主平面１０３ａ、１０３ｂに研削（ラッピング）加工を行うことができる。また、各工程の間に、ガラス基板の洗浄（工程間洗浄）やガラス基板表面のエッチング（工程間エッチング）を実施してもよい。さらに、磁気記録媒体用ガラス基板に高い機械的強度が求められる場合は、ガラス基板の表面に強化層を形成する強化工程（例えば、化学強化工程）を、（５）主平面研磨工程の前、または（５）主平面研磨工程の後、あるいは（５）主平面研磨工程で多段階（２次〜３次）の研磨を行う場合は１次〜３次の研磨工程の間で実施してもよい。
After the (2) chamfering step, the upper and lower
この製造方法においては、（３）内周端面研磨工程と（４）外周端面研磨工程のうちの少なくとも一方の工程が、シリカ粒子、アルミナ粒子、ジルコニア粒子、ジルコン粒子、炭化ケイ素粒子、炭化ホウ素粒子およびダイヤモンド粒子からなる群より選ばれる１種以上であり、平均粒径が４μｍ〜２５μｍの第１の砥粒を含有する第１の研磨液を用いて端面（側面と面取り部）を研磨する第１の端面研磨工程（Ａ）と、第１の砥粒より平均粒径の小さい第２の砥粒を含有する第２の研磨液を用いて端面を研磨する第２の端面研磨工程（Ｂ）を備えており、（Ａ）第１の端面研磨工程次いで（Ｂ）第２の端面研磨工程の順で２段階の端面研磨を行う。 In this production method, at least one of (3) inner peripheral end surface polishing step and (4) outer peripheral end surface polishing step is performed by silica particles, alumina particles, zirconia particles, zircon particles, silicon carbide particles, boron carbide particles. And a first polishing liquid containing at least one selected from the group consisting of diamond particles and having an average particle size of 4 μm to 25 μm and polishing the end surfaces (side surfaces and chamfered portions). 1 end surface polishing step (A) and a second end surface polishing step (B) for polishing the end surface using a second polishing liquid containing second abrasive grains having an average particle size smaller than that of the first abrasive grains. (A) a first end surface polishing step, and then (B) a second end surface polishing step, followed by two stages of end surface polishing.
なお、本明細書において、平均粒径は、粒度分布の累積５０％点の粒子直径であるｄ50を示すものとする。粒径は、レーザー回折・散乱式等の粒度分布計を使用して測定した値である。 In the present specification, the average particle diameter indicates d50 which is the particle diameter at the 50% cumulative point of the particle size distribution. The particle size is a value measured using a particle size distribution analyzer such as a laser diffraction / scattering type.
以下、前記各工程について、さらに詳細に説明する。
＜（１）形状付与工程＞
フロート法、フュージョン法またはプレス成形法で成形されたガラス原基板を、中央部に円孔１１を有する円盤形状に加工する。ガラス原基板は、フロート法で成形されたものでも、フュージョン法またはプレス成形法で成形されたものでもよい。また、基板を構成するガラスは、アモルファスガラスでもよく、結晶化ガラスでもよい。
Hereinafter, each process will be described in more detail.
<(1) Shape imparting step>
An original glass substrate formed by a float method, a fusion method or a press forming method is processed into a disk shape having a
＜（２）面取り工程＞
中央部に円孔１１を有する円盤形状に加工されたガラス基板において、円孔１１の内壁面である内周側面１０１と上下両主平面１０３ａ、１０３ｂとの交差部に、所定の幅および角度で面取り加工を行い、内周面取り部１０４を形成する。また、前記ガラス基板の外周側面１０２と上下主平面１０３ａ、１０３ｂとの交差部にも、所定の幅および角度で面取り加工を行い、外周面取り部１０５を形成する。なお、この（２）面取り工程の後、ガラス基板の上下主平面１０３ａ、１０３ｂに研削加工を行ってもよい。
<(2) Chamfering process>
In a glass substrate processed into a disk shape having a
＜（３）内周端面研磨工程および（４）外周端面研磨工程＞
磁気記録媒体用ガラス基板の製造において、内周端面および外周端面の研磨は、面取り加工等の際に生じたキズ等が存在する領域である加工変質層を除去し、凹凸を平滑化して鏡面とする目的で行われる。ガラス基板の複数枚を積層し、研磨液と研磨ブラシを用いて内周端面および外周端面を研磨する。
<(3) Inner peripheral end face polishing step and (4) Outer peripheral end face polishing step>
In the production of a glass substrate for a magnetic recording medium, the polishing of the inner peripheral end face and the outer peripheral end face is performed by removing the work-affected layer, which is a region where scratches or the like generated during chamfering processing, etc. are present, and smoothing the unevenness. To be done. A plurality of glass substrates are laminated, and the inner peripheral end face and the outer peripheral end face are polished using a polishing liquid and a polishing brush.
（３）内周端面研磨工程と（４）外周端面研磨工程を行う順序は特に限定されず、どちらの研磨工程を先に行ってもよい。そして、（３）内周端面研磨工程と（４）外周端面研磨工程の少なくとも一方の工程において、以下に示す（Ａ）第１の端面研磨工程次いで（Ｂ）第２の端面研磨工程の順で２段階の端面研磨を行う。（３）内周端面研磨工程と（４）外周端面研磨工程の両方の工程で、（Ａ）第１の端面研磨工程と（Ｂ）第２の端面研磨工程（Ｂ）の２段階の端面研磨を行うことが好ましい。 The order in which (3) inner peripheral end surface polishing step and (4) outer peripheral end surface polishing step are performed is not particularly limited, and either polishing step may be performed first. Then, in at least one of the (3) inner peripheral end surface polishing step and (4) outer peripheral end surface polishing step, the following (A) first end surface polishing step and (B) second end surface polishing step are performed in this order. Two-stage end face polishing is performed. (3) Two stages of end face polishing: (A) first end face polishing process and (B) second end face polishing process (B) in both the inner peripheral end face polishing process and (4) outer peripheral end face polishing process. It is preferable to carry out.
なお、（３）内周端面研磨工程と（４）外周端面研磨工程の一方の工程が２段階の端面研磨を行わない場合には、その工程では、従来から公知の研磨液（例えば、平均粒径が１．３μｍの酸化セリウム砥粒を含有する研磨液）を使用して１段階の端面研磨を行うことができる。 When one of the (3) inner peripheral end surface polishing step and (4) outer peripheral end surface polishing step does not perform two-step end surface polishing, a conventionally known polishing liquid (for example, average grain size) One-step end face polishing can be performed using a polishing liquid containing a cerium oxide abrasive having a diameter of 1.3 μm.
「（Ａ）第１の端面研磨工程」
（Ａ）第１の端面研磨工程においては、シリカ粒子、アルミナ粒子、ジルコニア粒子、ジルコン粒子、炭化ケイ素粒子、炭化ホウ素粒子およびダイヤモンド粒子からなる群より選ばれる１種以上で平均粒径が４μｍ〜２５μｍの第１の砥粒を含有する第１の研磨液と、研磨ブラシを用いて端面研磨を行う。第１の砥粒としては、アルミナ粒子、ジルコニア粒子、およびジルコン粒子から選ばれる１種以上の粒子の使用が好ましく、特に、平均粒径が前記範囲内であるアルミナ粒子とジルコン粒子とを、所定の質量比（例えば５０：５０の質量比）で混合した砥粒の使用が好ましい。
“(A) First end face polishing step”
(A) In the first end face polishing step, the average particle size is 4 μm to 1 μm or more selected from the group consisting of silica particles, alumina particles, zirconia particles, zircon particles, silicon carbide particles, boron carbide particles and diamond particles. End face polishing is performed using a first polishing liquid containing first abrasive grains of 25 μm and a polishing brush. As the first abrasive grains, it is preferable to use one or more kinds of particles selected from alumina particles, zirconia particles, and zircon particles, and in particular, alumina particles and zircon particles having an average particle diameter within the above range are predetermined. It is preferable to use abrasive grains mixed at a mass ratio (for example, a mass ratio of 50:50).
（Ａ）第１の端面研磨工程における第１の砥粒として、前記したように酸化セリウム以外の粒子が使用されているので、端面研磨における酸化セリウムの使用量を低減することができ、レアアースの輸出規制に起因する原料の入手難や価格高騰に良好に対応できる。また、ガラス基板端面への酸化セリウムの付着量を低減できるので、酸化セリウムの残留によって生じる欠陥を抑制できる。さらに、酸化セリウムを除去するための酸洗浄工程をなくし、工程上の負荷を低減できる。 (A) Since particles other than cerium oxide are used as the first abrasive grains in the first end face polishing step as described above, the amount of cerium oxide used in end face polishing can be reduced, and rare earth It can cope with the difficulty in obtaining raw materials and price increases due to export restrictions. Moreover, since the adhesion amount of cerium oxide to the glass substrate end face can be reduced, defects caused by the remaining cerium oxide can be suppressed. Furthermore, the acid cleaning process for removing cerium oxide can be eliminated, and the load on the process can be reduced.
第１の砥粒の平均粒径は、研磨速度の向上とピット欠陥の抑制の両方の観点から、４μｍ〜２５μｍとする。第１の砥粒の平均粒径が４μｍ未満の場合には、（Ａ）第１の端面研磨工程における研磨速度が低くなり、後述する（Ｂ）第２の端面研磨工程と合わせた端面研磨工程全体に時間がかかり好ましくない。第１の砥粒の平均粒径が２５μｍを超える場合には、砥粒の分散安定性が悪くなるばかりでなく、第１の端面研磨工程（Ａ）においても研磨キズが生じやすくなる。第１の砥粒の平均粒径は、４μｍ〜１２μｍが好ましく、６μｍ〜１０μｍがさらに好ましい。 The average grain size of the first abrasive grains is 4 μm to 25 μm from the viewpoint of both improvement of the polishing rate and suppression of pit defects. When the average particle size of the first abrasive grains is less than 4 μm, (A) the polishing rate in the first end surface polishing step is reduced, and (B) the end surface polishing step combined with the second end surface polishing step described later. The whole process takes time and is not preferable. When the average particle size of the first abrasive grains exceeds 25 μm, not only the dispersion stability of the abrasive grains is deteriorated, but also polishing scratches are easily generated in the first end face polishing step (A). The average grain size of the first abrasive grains is preferably 4 μm to 12 μm, more preferably 6 μm to 10 μm.
第１の研磨液には、このような第１の砥粒の分散媒として水が含有される。水については特に制限はないが、他の成分に対する影響、不純物の混入、ｐＨ等への影響の少なさの点から、純水、超純水、イオン交換水等を使用することが好ましい。 The first polishing liquid contains water as a dispersion medium for such first abrasive grains. Although there is no restriction | limiting in particular about water, It is preferable to use a pure water, an ultrapure water, ion-exchange water etc. from the point of the influence with respect to another component, the mixing of an impurity, and the influence with little pH.
第１の研磨液における前記第１の砥粒の含有割合（濃度）は、管理のしやすさの点から、研磨液の比重を調整して管理される。第１の研磨液の比重は１．０５〜１．４５とすることが好ましい。１．０５〜１．３５の範囲がより好ましく、１．１５〜１．３５の範囲がさらに好ましい。研磨液の比重と研磨液中の砥粒の含有割合とは関連づけられており、比重の値から砥粒の含有割合を容易に求めることができる。そして、研磨液の比重に基づいて砥粒を補充することで、研磨液における砥粒の含有割合（濃度）を常に一定の範囲に保持し、被研磨部および研磨処理バッチ間での品質のばらつきを少なくすることができる。 The content ratio (concentration) of the first abrasive grains in the first polishing liquid is managed by adjusting the specific gravity of the polishing liquid from the viewpoint of ease of management. The specific gravity of the first polishing liquid is preferably 1.05 to 1.45. The range of 1.05-1.35 is more preferable, and the range of 1.15-1.35 is more preferable. The specific gravity of the polishing liquid and the content ratio of the abrasive grains in the polishing liquid are related, and the content ratio of the abrasive grains can be easily obtained from the value of the specific gravity. And by replenishing the abrasive grains based on the specific gravity of the polishing liquid, the content ratio (concentration) of the abrasive grains in the polishing liquid is always kept within a certain range, and the quality variation between the part to be polished and the polishing batch Can be reduced.
このように第１の砥粒の含有割合と密接な関係を有する第１の研磨液の比重が１．０５未満である場合には、研磨速度が低くなりすぎて、効率的な研磨を行うことが難しい。反対に、第１の研磨液の比重が１．４５を超える場合には、第１の砥粒の含有割合の上昇による研磨速度の上昇の度合いは飽和し、かえって砥粒の含有が多すぎて研磨液の粘度が高くなるため、研磨作業がしにくい。比重が１．０５〜１．４５の範囲であれば、十分に高い研磨速度が得られ、かつ研磨作業性が高い。 Thus, when the specific gravity of the first polishing liquid having a close relationship with the content ratio of the first abrasive grains is less than 1.05, the polishing rate becomes too low and efficient polishing is performed. Is difficult. On the other hand, when the specific gravity of the first polishing liquid exceeds 1.45, the degree of increase in the polishing rate due to the increase in the content ratio of the first abrasive grains is saturated, and the content of abrasive grains is too much. Since the viscosity of the polishing liquid increases, polishing work is difficult. When the specific gravity is in the range of 1.05 to 1.45, a sufficiently high polishing rate is obtained and the polishing workability is high.
第１の研磨液は、前記第１の砥粒と分散媒である水以外に他の成分を含有してもよい。含有可能な他の成分として、分散剤を挙げることができる。分散剤は、砥粒を純水等の分散媒中に安定的に分散させるために添加するものであり、陰イオン性、陽イオン性、ノニオン性、両性の界面活性剤や界面活性作用のある水溶性ポリマーを使用することができる。 The first polishing liquid may contain other components in addition to the first abrasive grains and water as a dispersion medium. A dispersing agent can be mentioned as another component which can be contained. The dispersant is added to stably disperse the abrasive grains in a dispersion medium such as pure water, and has an anionic, cationic, nonionic, amphoteric surfactant or surface active action. Water soluble polymers can be used.
分散剤を使用する場合、その添加割合は、第１の砥粒の質量に対して０．３〜５質量％とすることが好ましい。分散剤の添加割合がこの範囲より低いと、砥粒の分散性が不十分となることがある。また、分散剤の添加割合がこの範囲を超えると、研磨速度等に対して悪影響を与えるおそれがある。 When using a dispersing agent, it is preferable that the addition ratio shall be 0.3-5 mass% with respect to the mass of a 1st abrasive grain. When the addition ratio of the dispersant is lower than this range, the dispersibility of the abrasive grains may be insufficient. Moreover, when the addition ratio of the dispersing agent exceeds this range, there is a possibility of adversely affecting the polishing rate and the like.
（３）内周端面研磨工程および／または（４）外周端面研磨工程においては、このような（Ａ）第１の端面研磨工程に引き続いて後述する（Ｂ）第２の端面研磨工程を行うが、第１および第２の２段階の端面研磨における各段の研磨の程度（例えば、研磨量等）は、以下に示すようにすることが好ましい。すなわち、（Ａ）第１の端面研磨工程では、研磨の効率を第１の目的とし、面取り加工の際に生じたキズ等の加工変質層を高い研磨速度で取り除くため、研磨量も大きくする。そして、このような（Ａ）第１の端面研磨工程により、面取り加工の際に生じたキズ等の加工変質層が除去された端面を、後述する（Ｂ）第２の端面研磨工程において鏡面になるまで研磨する。 In (3) inner peripheral end surface polishing step and / or (4) outer peripheral end surface polishing step, (B) second end surface polishing step, which will be described later, is performed subsequently to (A) first end surface polishing step. The degree of polishing (for example, the polishing amount, etc.) at each stage in the first and second end face polishing is preferably as follows. That is, (A) In the first end face polishing step, the polishing efficiency is increased for the first purpose, and the process-affected layer such as scratches generated during the chamfering process is removed at a high polishing rate. Then, the end surface from which the work-affected layer such as scratches generated during the chamfering process is removed by the (A) first end surface polishing step is used as a mirror surface in the (B) second end surface polishing step described later. Polish until
「（Ｂ）第２の端面研磨工程）」
（Ｂ）第２の端面研磨工程においては、（Ａ）第１の端面研磨工程においてキズ等のある加工変質層が除去された後のガラス基板の端面（側面および面取り部）を、前記した第１の砥粒に比べて平均粒径が小さい第２の砥粒を含有する第２の研磨液を用いて、鏡面になるまで研磨する。
“(B) Second end face polishing step”
(B) In the second end surface polishing step, (A) the end surface (side surface and chamfered portion) of the glass substrate after removal of the damaged layer in the first end surface polishing step is removed. Polishing is performed until a mirror surface is obtained using a second polishing liquid containing second abrasive grains having an average grain size smaller than that of the first abrasive grains.
第２の砥粒は、シリカ粒子、アルミナ粒子、ジルコニア粒子、ジルコン粒子、酸化セリウム粒子、炭化ケイ素粒子、炭化ホウ素粒子およびダイヤモンド粒子からなる群より選ばれる１種または２種以上の粒子であることが好ましい。端面への酸化セリウムの付着および酸化セリウムに起因する異物の付着を防止するためには、第２の砥粒は、酸化セリウム粒子を除いた前記粒子群、すなわちシリカ粒子、アルミナ粒子、ジルコニア粒子、ジルコン粒子、炭化ケイ素粒子、炭化ホウ素粒子およびダイヤモンド粒子からなる群より選ばれる１種以上であることが好ましく、アルミナ粒子とジルコニア粒子のうちの少なくとも１種であることがさらに好ましい。（Ａ）第１の端面研磨工程だけでなく（Ｂ）第２の端面研磨工程においても、砥粒として酸化セリウム以外の粒子を使用した場合には、ガラス基板端面への酸化セリウムの付着や残留を完全に防止できるので、酸化セリウムの残留によって生じる欠陥を排除できる。また、レアアースの輸出規制に起因する原料の入手難や価格高騰に対応し、安価かつ安定的にガラス基板を研磨できる。さらに、酸化セリウムを除去するための酸洗浄工程を設ける必要がないので、ガラス基板製造における工程上の負荷を低減できる。 The second abrasive is one or more particles selected from the group consisting of silica particles, alumina particles, zirconia particles, zircon particles, cerium oxide particles, silicon carbide particles, boron carbide particles and diamond particles. Is preferred. In order to prevent adhesion of cerium oxide to the end face and adhesion of foreign matters due to cerium oxide, the second abrasive grains are the above particle group excluding cerium oxide particles, that is, silica particles, alumina particles, zirconia particles, It is preferably at least one selected from the group consisting of zircon particles, silicon carbide particles, boron carbide particles and diamond particles, and more preferably at least one of alumina particles and zirconia particles. (A) Not only in the first end surface polishing step, but also in (B) second end surface polishing step, when particles other than cerium oxide are used as the abrasive grains, adhesion or residual of cerium oxide on the glass substrate end surface Therefore, defects caused by residual cerium oxide can be eliminated. In addition, it is possible to polish the glass substrate stably at low cost in response to the difficulty in obtaining raw materials and price increases caused by rare earth export regulations. Furthermore, since it is not necessary to provide an acid cleaning step for removing cerium oxide, it is possible to reduce the process load in manufacturing the glass substrate.
第２の砥粒の平均粒径は、０．２μｍ以上４μｍ未満が好ましく、０．２μｍ〜２μｍがさらに好ましく、０．５μｍ〜１．５μｍが特に好ましい。第２の砥粒の平均粒径が０．２μｍ未満の場合には、研磨に時間がかかりすぎるおそれがある。第２の砥粒の平均粒径が４μｍ以上の場合には、端面を所望の研磨粗さ（鏡面）に研磨することが難しくなるおそれがある。 The average grain size of the second abrasive grains is preferably 0.2 μm or more and less than 4 μm, more preferably 0.2 μm to 2 μm, and particularly preferably 0.5 μm to 1.5 μm. When the average grain size of the second abrasive grains is less than 0.2 μm, it may take too much time for polishing. When the average grain size of the second abrasive grains is 4 μm or more, it may be difficult to polish the end surface to a desired polishing roughness (mirror surface).
第１の研磨液と同様に、第２の研磨液にも前記砥粒の分散媒として水が含有される。水については、特に制限はないが、他の成分に対する影響、不純物の混入、ｐＨ等への影響の少なさの点から、純水、超純水、イオン交換水等を使用することが好ましい。また、第２の研磨液の比重も、第１の研磨液と同様に１．０５〜１．４５の範囲とすることが好ましい。第２の研磨液の比重が１．０５未満である場合には、研磨速度が低くなりすぎるため、研磨効率が劣るおそれがある。反対に、第２の研磨液の比重が１．４５を超える場合には、第２の研磨液の粘度が高くなりすぎるため、研磨速度が低下し、研磨作業が難しくなるおそれがある。 Similar to the first polishing liquid, the second polishing liquid contains water as a dispersion medium for the abrasive grains. The water is not particularly limited, but it is preferable to use pure water, ultrapure water, ion-exchanged water, or the like from the viewpoint of influence on other components, mixing of impurities, and little influence on pH and the like. Also, the specific gravity of the second polishing liquid is preferably in the range of 1.05 to 1.45, similarly to the first polishing liquid. When the specific gravity of the second polishing liquid is less than 1.05, the polishing rate becomes too low, and the polishing efficiency may be inferior. On the other hand, when the specific gravity of the second polishing liquid exceeds 1.45, the viscosity of the second polishing liquid becomes too high, so that the polishing rate decreases and the polishing operation may become difficult.
さらに第２の研磨液は、前記第２の砥粒と水以外に分散剤を含有してもよい。分散剤としては、陰イオン性、陽イオン性、ノニオン性、両性の界面活性剤や界面活性作用のある水溶性ポリマーを使用することができる。 Furthermore, the second polishing liquid may contain a dispersant in addition to the second abrasive grains and water. As the dispersant, an anionic, cationic, nonionic or amphoteric surfactant or a water-soluble polymer having a surfactant activity can be used.
＜（５）主平面研磨工程＞
磁気記録媒体用ガラス基板の製造において、上下両主平面の研磨は、形状付与や面取り加工、主平面の研削等の際に生じたキズ等が存在する加工変質層を除去し、凹凸を平滑化して鏡面とする目的で行われる。（５）主平面研磨工程では、砥粒を含有する研磨液と発泡樹脂製等の研磨パッドとを使用し、両面研磨装置により上下両主平面の研磨を行うことが好ましい。
<(5) Main surface polishing step>
In the production of glass substrates for magnetic recording media, polishing of the upper and lower main planes removes the work-affected layer that has scratches and the like generated during shape imparting, chamfering, and grinding of the main plane, and smoothes the irregularities. This is done for the purpose of creating a mirror surface. (5) In the main surface polishing step, it is preferable to use a polishing liquid containing abrasive grains and a polishing pad made of foamed resin, etc., and to polish the upper and lower main surfaces with a double-side polishing apparatus.
所定の平均粒径の砥粒を使用して１次研磨のみを行ってもよいが、１次研磨を行った後、より粒径の小さい砥粒を使用して２次研磨を行ってもよい。また、２次研磨の後にさらに粒径の小さい砥粒を使用して３次研磨（仕上げ研磨）を行ってもよい。 Only primary polishing may be performed using abrasive grains having a predetermined average particle diameter, but secondary polishing may be performed using abrasive grains having a smaller particle diameter after performing primary polishing. . Further, after the secondary polishing, tertiary polishing (finish polishing) may be performed using abrasive grains having a smaller particle diameter.
主平面研磨用の砥粒としては、シリカ粒子、アルミナ粒子、ジルコニア粒子、ジルコン粒子、酸化セリウム粒子等を使用できる。これらの中でも酸化セリウム以外の粒子を使用した場合には、レアアースの輸出規制に起因する原料の入手難や価格高騰に対応し、安価かつ安定的にガラス基板を研磨できる。また、ガラス基板の主平面への酸化セリウムの付着も防止できるので、酸化セリウムの残留によって生じる欠陥をなくすことができるうえに、酸化セリウムを除去するための酸洗浄工程を設ける必要がないので、工程上の負荷を低減できる。 As abrasive grains for main surface polishing, silica particles, alumina particles, zirconia particles, zircon particles, cerium oxide particles and the like can be used. Among these, when particles other than cerium oxide are used, it is possible to polish the glass substrate stably at low cost in response to difficulty in obtaining raw materials and rising prices due to rare earth export regulations. Moreover, since it is possible to prevent adhesion of cerium oxide to the main plane of the glass substrate, it is possible to eliminate defects caused by residual cerium oxide, and it is not necessary to provide an acid cleaning step for removing cerium oxide. The load on the process can be reduced.
（５）主平面研磨工程の後は、ガラス基板の精密洗浄を行い、磁気記録媒体用ガラス基板を得る。そして、こうして得られた磁気記録媒体用ガラス基板の上に、磁性層などの薄膜が形成され、磁気ディスクが製造される。 (5) After the main surface polishing step, the glass substrate is precisely cleaned to obtain a glass substrate for a magnetic recording medium. A thin film such as a magnetic layer is formed on the glass substrate for magnetic recording medium thus obtained, and a magnetic disk is manufactured.
［磁気記録媒体用ガラス基板］
本発明の磁気記録媒体用ガラス基板は、図１に示す内周端面（内周側面１０１と内周面取り部１０４）と外周端面（外周側面１０２と外周面取り部１０５）のうちの少なくとも一方の端面に対して、前記（Ａ）第１の端面研磨工程と（Ｂ）第２の端面研磨工程を順に行い、鏡面になるまで研磨することにより得られるものであり、そのような２段階の研磨が行われた内周端面および／または外周端面の面取り部において、最大径１０μｍ以上のピット欠陥数が５個／ｍｍ２以下となっていることを特徴とする。面取り部の最大径１０μｍ以上のピット欠陥数は、３個／ｍｍ２以下が好ましく、１個／ｍｍ２以下がより好ましく、０個／ｍｍ２が特に好ましい。
[Glass substrate for magnetic recording media]
The glass substrate for a magnetic recording medium of the present invention has at least one end surface of the inner peripheral end surface (the inner
一般に、研磨ブラシを用いたガラス基板の端面研磨において、面取り部の研磨量は側面の研磨量に比べて少なくなるため、側面よりも面取り部に加工変質層が残留しやすい。ガラス基板の端面等の表面に残留する加工変質層は、ガラス基板の表面をエッチングすることにより、キズを中心に等方的にエッチングされて円形状または楕円形状のピット欠陥となり、光学顕微鏡等を用いて簡便に評価できるようになる。なお、面取り部の全周において、ピット欠陥の有無を確認するには、明視野方式ディテール可視化検査装置（Ｖｉｓｉｏｎ Ｐｓｙｔｅｃ社製、製品名：Ｍｉｃｒｏ‐Ｍａｘ ＶＭＩ‐２０００Ｐ）を用いるとよい。 Generally, in the end surface polishing of a glass substrate using a polishing brush, the amount of polishing of the chamfered portion is smaller than the amount of polishing of the side surface, so that the work-affected layer tends to remain in the chamfered portion rather than the side surface. The work-affected layer remaining on the surface such as the end face of the glass substrate is etched isotropically around the scratch by etching the surface of the glass substrate to form circular or elliptical pit defects. It becomes possible to evaluate simply by using. In order to confirm the presence or absence of pit defects all around the chamfered portion, it is preferable to use a bright field type detail visualization inspection device (product name: Micro-Max VMI-2000P, manufactured by Vision Psytec).
本発明の磁気記録媒体用ガラス基板では、面取り部の加工変質層などの欠陥がないため、ガラス基板の機械的強度の低下が抑えられる。また、面取り部の凹凸を平滑化して十分に鏡面に仕上げられているため、凹部に捕捉された異物が主平面の異物欠陥増加の原因となる問題がなくなる。さらに、酸化セリウムが付着した異物欠陥を低減、またはなくすことができる。 In the glass substrate for magnetic recording media of the present invention, since there is no defect such as a work-affected layer in the chamfered portion, a decrease in mechanical strength of the glass substrate can be suppressed. In addition, since the unevenness of the chamfered portion is smoothed and sufficiently mirror-finished, the problem that the foreign matter trapped in the concave portion causes an increase in foreign matter defects on the main plane is eliminated. Furthermore, foreign matter defects to which cerium oxide has adhered can be reduced or eliminated.
以下、本発明を実施例および比較例により具体的に説明する。以下の例において、例１〜例５および例８〜例２０は、内周端面の研磨を２段階で行った本発明の実施例であり、例６および例７は比較例である。また、例２１〜例２５および例２８〜例４０は、外周端面の研磨を２段階で行った本発明の実施例であり、例２６および例２７は比較例である。本発明は実施例に限定されるものではない。 Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following examples, Examples 1 to 5 and Examples 8 to 20 are examples of the present invention in which the inner peripheral end face was polished in two stages, and Examples 6 and 7 are comparative examples. Examples 21 to 25 and Examples 28 to 40 are examples of the present invention in which the outer peripheral end face was polished in two stages, and examples 26 and 27 are comparative examples. The present invention is not limited to the examples.
砥粒の平均粒径、研磨液の比重およびｐＨは、以下の装置により測定された値である。また、研磨速度および得られたガラス基板の端面の特性（ピット欠陥数および付着粒子数）は、下記の方法により測定し評価した。
［砥粒の平均粒径］
レーザー回折・散乱装置（日機装株式会社製：マイクロトラックＭＴ３３００）を使用して求めた。
［研磨液の比重］
横田計器製作所製の比重計を使用して測定した。
［研磨液のｐＨ］
横河電機株式会社製のｐＨメーターを使用し２５℃で測定した。
The average particle diameter of the abrasive grains, the specific gravity of the polishing liquid, and the pH are values measured by the following apparatus. Further, the polishing rate and the characteristics (number of pit defects and number of adhered particles) of the end face of the obtained glass substrate were measured and evaluated by the following methods.
[Average grain size of abrasive grains]
It was determined using a laser diffraction / scattering device (manufactured by Nikkiso Co., Ltd .: Microtrac MT3300).
[Specific gravity of polishing liquid]
Measurement was performed using a hydrometer made by Yokota Keiki Seisakusho.
[PH of polishing liquid]
Measurement was performed at 25 ° C. using a pH meter manufactured by Yokogawa Electric Corporation.
［研磨速度］
外周端面（外周側面および外周面取り部）については、（Ａ）第１の端面研磨工程後または（Ｂ）第２の端面研磨工程の前後において、外径測マイクロメータ（株式会社ミツトヨ社製：デジマチック標準外側マイクロメータ）を用いて研磨量（μｍ）を測定し、この測定値を研磨に要した時間（ｍｉｎ．）で除して求めた。
[Polishing speed]
For the outer peripheral end surfaces (outer peripheral side surface and outer peripheral chamfered portion), (A) after the first end surface polishing step or (B) before and after the second end surface polishing step, an outer diameter measuring micrometer (manufactured by Mitutoyo Corporation: Digi A polishing amount (μm) was measured using a standard outer micrometer), and this measured value was obtained by dividing by the time (min.) Required for polishing.
また、内周端面（内周側面と内周面取り部）については、（Ａ）第１の端面研磨工程または第２の端面研磨工程の前後において、ガラス基板中央部の円孔の直径を高精度２次元寸法測定機（キーエンス社製：ＶＭ８０４０）を用いて内周側面で測定し、研磨前後の円孔の直径差を用い、以下の式により内周端面の研磨量（μｍ）を計算した、そして、この計算値を研磨に要した時間（ｍｉｎ．）で除して研磨速度とした。
（内周端面の研磨量）＝［（研磨後ガラス基板の円孔の直径）−（研磨前ガラス基板の円孔の直径）］
In addition, for the inner peripheral end face (the inner peripheral side face and the inner peripheral chamfered portion), (A) the diameter of the circular hole in the central part of the glass substrate is highly accurate before and after the first end face polishing step or the second end face polishing step. Using a two-dimensional dimension measuring machine (manufactured by Keyence Corporation: VM8040), measured on the inner peripheral side surface, and using the difference in diameter of the circular holes before and after polishing, the polishing amount (μm) of the inner peripheral end surface was calculated by the following equation: The calculated value was divided by the time (min.) Required for polishing to obtain the polishing rate.
(Polishing amount of inner peripheral end face) = [(Diameter of circular hole in glass substrate after polishing) − (Diameter of circular hole in glass substrate before polishing)]
［ピット欠陥数］
ガラス基板の内周端面または外周端面を、フッ酸や硝酸等を含む酸性のエッチング溶液を用いて、ガラス基板を深さ方向に５μｍエッチングして加工変質層のキズを観察しやすいピット欠陥として、洗浄と乾燥を行った後、さらにピット欠陥数を評価しやすいサイズにガラス基板を切断した。こうして内周側面、内周面取り部、外周側面および外周面取り部をそれぞれ含むピット欠陥数観察試料を作製した。なお、ガラス基板の表面のエッチング量（深さ）は、端面研磨の研磨量の測定と同じ方法で測定した。
[Number of pit defects]
As the pit defect, the inner peripheral end surface or the outer peripheral end surface of the glass substrate is etched by 5 μm in the depth direction using an acidic etching solution containing hydrofluoric acid, nitric acid, etc., and the scratches on the work-affected layer are easily observed. After cleaning and drying, the glass substrate was cut to a size that facilitates evaluation of the number of pit defects. Thus, pit defect number observation samples each including an inner peripheral side surface, an inner peripheral chamfered portion, an outer peripheral side surface, and an outer peripheral chamfered portion were prepared. The etching amount (depth) on the surface of the glass substrate was measured by the same method as the measurement of the polishing amount for end face polishing.
ピット欠陥数は、レーザー顕微鏡（オリンパス社製、製品名：ＬＥＸＴ ＯＬＳ ３５００）を用いてカウントし評価した。各観察試料を試料台に付け、側面または面取り部の面がレーザー顕微鏡の対物レンズのレンズ面に対して平行となるように固定した。レーザー顕微鏡の対物レンズは２０倍を使用し、観察視野を６３５μｍ×４８０μｍとして、直径（または長径）が１０μｍ以上の円形状または楕円形状のピット欠陥の数をカウントした。そして、計測したピット欠陥数を観察面積で除した数値を算出した。この数値が５個／ｍｍ２以下のガラス基板を良品とする。 The number of pit defects was counted and evaluated using a laser microscope (manufactured by Olympus, product name: LEXT OLS 3500). Each observation sample was attached to a sample stage and fixed so that the side surface or the surface of the chamfered portion was parallel to the lens surface of the objective lens of the laser microscope. The objective lens of the laser microscope was 20 times, the observation field was 635 μm × 480 μm, and the number of circular or elliptical pit defects having a diameter (or major axis) of 10 μm or more was counted. Then, a numerical value obtained by dividing the measured number of pit defects by the observation area was calculated. A glass substrate having a numerical value of 5 pieces / mm 2 or less is regarded as a good product.
［付着粒子数］
内周面取り部または外周面取り部の各部をＳＥＭ−ＥＤＸ（装置名：日立製作所社製Ｓ４７００）を用いて観察し、酸化セリウム粒子の残渣状況（付着量）を調べた。すなわち、ＳＥＭ−ＥＤＸを用いて内周面取り部または外周面取り部の任意の８点を３０００倍に拡大表示し、観察視野領域の全面において、ＥＤＸの面分析によりセリウムの残渣を分析した。内周面取り部または外周面取り部のセリウムの残渣は、セリウムのＬ線の強度を、ガラス基板に含まれるカリウムのＫ線、Ｌ線の強度（内部標準）で除して評価した。そして、８箇所で測定した平均値を残留セリウム量とした。
[Number of adhered particles]
Each part of the inner peripheral chamfered portion or the outer peripheral chamfered portion was observed using SEM-EDX (device name: S4700, manufactured by Hitachi, Ltd.), and the residue state (adhesion amount) of the cerium oxide particles was examined. That is, arbitrary 8 points of the inner peripheral chamfered portion or the outer peripheral chamfered portion were magnified by 3000 times using SEM-EDX, and the cerium residue was analyzed by EDX surface analysis on the entire observation visual field region. The cerium residue in the inner peripheral chamfered portion or the outer peripheral chamfered portion was evaluated by dividing the strength of the cerium L-line by the strength of K-line and L-line (internal standard) of potassium contained in the glass substrate. And the average value measured in 8 places was made into the amount of residual cerium.
［例１］
フロート法で成形されたＳｉＯ２を主成分とするガラス板を、外径６５ｍｍ、内径２０ｍｍ、板厚０．６３５ｍｍの磁気記録媒体用ガラス基板が得られるような、中央部に円孔を有する円盤形状に加工した。
[Example 1]
A disk having a circular hole in the center so as to obtain a glass substrate for magnetic recording media having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.635 mm made of a glass plate mainly composed of SiO 2 formed by the float process. Processed into shape.
この中央部に円孔を有する円盤状ガラス基板の内周側面および外周側面を、最終製品である磁気記録媒体用ガラス基板としたときの面取り幅０．１５ｍｍ、面取り角度４５°となるように面取り加工した後、ガラス基板の上下主平面を、アルミナ砥粒（平均粒径７〜７．５μｍ）を用いて研削（ラッピング）した後、砥粒を洗浄・除去した。 Chamfering so that the inner peripheral side surface and the outer peripheral side surface of the disk-shaped glass substrate having a circular hole in the center portion have a chamfering width of 0.15 mm and a chamfering angle of 45 ° when the glass substrate for a magnetic recording medium as a final product is used. After processing, the upper and lower principal planes of the glass substrate were ground (wrapped) using alumina abrasive grains (average particle diameter of 7 to 7.5 μm), and then the abrasive grains were washed and removed.
次に、ガラス基板の内周端面（内周側面と内周面取り部）を、（Ａ）第１の端面研磨工程で、第１の研磨液と研磨ブラシとを用いて研磨し、内周側面と内周面取り部のキズ等のある加工変質層を除去した後、（Ｂ）第２の端面研磨工程で、第２の研磨液と研磨ブラシとを用い鏡面となるように研磨した。（Ａ）第１の端面研磨工程および（Ｂ）第１の端面研磨工程における研磨条件は、以下の通りであった。 Next, the inner peripheral end surface (the inner peripheral side surface and the inner peripheral chamfered portion) of the glass substrate is polished using the first polishing liquid and the polishing brush in the first end surface polishing step (A), and the inner peripheral side surface After removing the work-affected layer having scratches and the like on the inner peripheral chamfered portion, (B) in the second end surface polishing step, the second polishing liquid and a polishing brush were used to polish the surface to a mirror surface. The polishing conditions in (A) the first end surface polishing step and (B) the first end surface polishing step were as follows.
（Ａ）第１の端面研磨工程では、第１の研磨液として、平均粒径ｄ50が４μｍのアルミナ粒子と同じく平均粒径ｄ50が４μｍのジルコン粒子とを５０：５０の質量比で混合した混合砥粒と、水および公知の分散剤を含有する研磨液（比重１．２５）を使用し、１．０μｍ／ｍｉｎ．の研磨速度で３０分間研磨を行った。 (A) In the first end face polishing step, as the first polishing liquid, mixing of alumina particles having an average particle diameter d50 of 4 μm and zircon particles having an average particle diameter d50 of 4 μm in a mass ratio of 50:50 A polishing solution (specific gravity 1.25) containing abrasive grains, water and a known dispersant is used, and 1.0 μm / min. Polishing was performed at a polishing rate of 30 minutes.
（Ｂ）第２の端面研磨工程では、第２の研磨液として、砥粒である平均粒径ｄ50が１．２μｍの酸化セリウム粒子と水および公知の分散剤を含有する研磨液（比重１．３０）を使用し、１．４μｍ／ｍｉｎ．の研磨速度で内周端面が鏡面になるまで１５分間研磨を行った。内周端面研磨後のガラス基板は、砥粒を洗浄除去するため、超音波洗浄した。 (B) In the second end face polishing step, as the second polishing liquid, a polishing liquid containing cerium oxide particles having an average particle diameter d50 of 1.2 μm, water, and a known dispersant (specific gravity 1. 30) and 1.4 μm / min. Polishing was performed at a polishing rate of 15 minutes until the inner peripheral end surface became a mirror surface. The glass substrate after polishing the inner peripheral end face was subjected to ultrasonic cleaning in order to clean and remove the abrasive grains.
次に、こうして研磨が行われた後のガラス基板の内周端面（内周側面および内周面取り部）について、ピット欠陥数および付着粒子（酸化セリウム粒子）数を前記方法で測定した。測定結果をガラス基板の端面特性として表１に示す。 Next, the number of pit defects and the number of adhering particles (cerium oxide particles) were measured by the above method on the inner peripheral end face (inner peripheral side face and inner peripheral chamfered portion) of the glass substrate after being polished in this way. The measurement results are shown in Table 1 as the end face characteristics of the glass substrate.
端面加工後、両面研磨装置を用いてガラス基板の上下主平面を研磨した。上下主平面を研磨したガラス基板は、スクラブ洗浄、超音波洗浄を順次行い、イソプロピルアルコール蒸気により乾燥した。こうして、磁気記録媒体用ガラス基板を得た。 After the end face processing, the upper and lower main planes of the glass substrate were polished using a double-side polishing apparatus. The glass substrate whose upper and lower main surfaces were polished was sequentially scrubbed and ultrasonically cleaned and dried with isopropyl alcohol vapor. Thus, a glass substrate for a magnetic recording medium was obtained.
［例２〜例２０］
次に、（Ａ）第１の端面研磨工程と（Ｂ）第２の端面研磨工程の少なくとも一方における研磨液の組成を変えて内周端面の研磨を行った。すなわち、中央部に円孔を有する円盤形状に加工されたガラス基板の内周側面を、例１と同様に面取り加工した後、上下主平面を研削（ラッピング）した。次いで、得られたガラス基板の内周端面（内周側面と内周面取り部）を、（Ａ）第１の端面研磨工程で、表１および表２に示す砥粒を有する第１の研磨液を使用して同表に示す研磨速度で研磨した後、（Ｂ）第２の端面研磨工程で、表１および表２に示す砥粒を有する第２の研磨液を用いて同表に示す研磨速度で鏡面となるまで研磨した。
[Examples 2 to 20]
Next, the inner peripheral end face was polished while changing the composition of the polishing liquid in at least one of (A) the first end face polishing step and (B) the second end face polishing step. That is, the inner peripheral side surface of the glass substrate processed into a disk shape having a circular hole in the center was chamfered in the same manner as in Example 1, and then the upper and lower main planes were ground (lapped). Next, the inner peripheral end face (inner peripheral side face and inner peripheral chamfered portion) of the obtained glass substrate is (A) a first polishing liquid having abrasive grains shown in Table 1 and Table 2 in the first end face polishing step. After polishing at the polishing rate shown in the same table using (B), polishing shown in the same table using the second polishing liquid having the abrasive grains shown in Table 1 and Table 2 in the second end face polishing step Polished to a mirror surface at a speed.
こうして研磨が行われた後のガラス基板の内周端面（内周側面および内周面取り部）について、ピット欠陥数および付着粒子（酸化セリウム粒子）数を例１と同様に前記方法で測定した。測定結果を、ガラス基板の端面特性として表１および表２に示す。 The number of pit defects and the number of attached particles (cerium oxide particles) were measured in the same manner as in Example 1 for the inner peripheral end surface (inner peripheral side surface and inner peripheral chamfered portion) of the glass substrate after polishing. The measurement results are shown in Tables 1 and 2 as the end face characteristics of the glass substrate.
［例２１〜例４０］
例１と同様に面取り加工がなされたガラス基板の外周端面（外周側面と外周面取り部）を、（Ａ）第１の端面研磨工程で、表３および表４に示す砥粒を有する第１の研磨液を使用して同表に示す研磨速度で研磨した後、（Ｂ）第２の端面研磨工程で、表３および表４に示す砥粒を有する第２の研磨液を用いて同表に示す研磨速度で鏡面となるまで研磨した。
[Example 21 to Example 40]
The outer peripheral end face (outer peripheral side face and outer peripheral chamfered portion) of the glass substrate that has been chamfered in the same manner as in Example 1 is a (A) first end face polishing step that includes the abrasive grains shown in Table 3 and Table 4. After polishing at the polishing rate shown in the table using the polishing liquid, (B) In the second end face polishing step, the second polishing liquid having the abrasive grains shown in Table 3 and Table 4 is used. It grind | polished until it became a mirror surface with the grinding | polishing speed | rate shown.
こうして研磨が行われた後のガラス基板の外周端面（外周側面および外周面取り部）について、ピット欠陥数および付着粒子（酸化セリウム粒子）数を前記した方法で測定した。測定結果を、ガラス基板の端面特性として表３および表４に示す。 The number of pit defects and the number of adhering particles (cerium oxide particles) were measured by the method described above for the outer peripheral end surfaces (outer peripheral side surfaces and outer peripheral chamfered portions) of the glass substrate after being polished in this way. The measurement results are shown in Table 3 and Table 4 as the end face characteristics of the glass substrate.
表１〜表４からわかるように、内周端面研磨についての本発明の実施例である例１〜例５および例８〜例２０においては、研磨後のガラス基板の内周側面および内周面取り部にピット欠陥がほとんどなく、面取り加工等で生じたキズ等の加工変質層が完全に除去されている。また、外周端面研磨についての本発明の実施例である例２１〜例２５および例２８〜例４０においても、研磨後のガラス基板の外周側面および外周面取り部にピット欠陥がほとんどなく、面取り加工等で生じたキズ等の加工変質層が完全に除去されていることがわかる。すなわち、本発明の実施例である例１〜例５、例８〜例２５、例２８〜例４０においては、内周面取り部あるいは外周面取り部のピット欠陥数が５個／ｍｍ２以下のガラス基板が得られている。
さらに、これらの実施例の中でも、第２の砥粒として酸化セリウム以外の粒子を使用して（Ｂ）第２の端面研磨工程を行った例１４〜例２０例３４〜例４０においては、ガラス基板の端面への酸化セリウム粒子の付着・残留がないことがわかる。
As can be seen from Tables 1 to 4, in Examples 1 to 5 and Examples 8 to 20 which are examples of the present invention for inner peripheral end face polishing, the inner peripheral side surface and the inner peripheral chamfer of the polished glass substrate There are almost no pit defects in the portion, and the work-affected layer such as scratches caused by chamfering or the like is completely removed. Also in Examples 21 to 25 and Examples 28 to 40, which are examples of the present invention for polishing the outer peripheral end face, there are almost no pit defects on the outer peripheral side surface and the outer peripheral chamfered portion of the polished glass substrate, and chamfering and the like. It can be seen that the work-affected layer such as scratches generated in step 1 is completely removed. That is, in Examples 1 to 5, Examples 8 to 25, and Examples 28 to 40 which are examples of the present invention, the number of pit defects in the inner peripheral chamfered portion or the outer peripheral chamfered portion is 5 pieces / mm 2 or less. A substrate is obtained.
Further, among these examples, in Examples 14 to 20 and Examples 34 to 40, in which particles other than cerium oxide were used as the second abrasive grains (B) and the second end face polishing step was performed, It can be seen that there is no adhesion or residue of cerium oxide particles on the end face of the substrate.
これに対して、例６および例２６では、平均粒径が４μｍ未満の砥粒を使用して（Ａ）第１の端面研磨工程を行っているので、（Ａ）第１の端面研磨工程における研磨速度を十分に大きくすることができず、内周端面（内周側面と内周面取り部）および外周端面（外周側面と外周面取り部）における加工変質層（キズ等）の除去が十分にできていない。そのため、ガラス基板の内周端面あるいは外周端面にピット欠陥が数多く観察された。 On the other hand, in Example 6 and Example 26, since the (A) first end surface polishing step is performed using abrasive grains having an average particle size of less than 4 μm, (A) in the first end surface polishing step. The polishing rate cannot be increased sufficiently, and the work-affected layer (scratches, etc.) on the inner peripheral end face (inner peripheral side face and inner peripheral chamfered part) and outer peripheral end face (outer peripheral side face and outer peripheral chamfered part) can be removed sufficiently. Not. Therefore, many pit defects were observed on the inner peripheral end face or the outer peripheral end face of the glass substrate.
また、例７および例２７では、平均粒径が２５μｍを超える砥粒を使用して（Ａ）第１の端面研磨工程を行っているので、（Ａ）第１の端面研磨工程での研磨加工により研磨キズが発生する結果、ガラス基板の外周面取り部および内周面取り部だけでなく、外周側面および内周側面にもピット欠陥が数多く観察された。 Moreover, in Example 7 and Example 27, since the (A) 1st end surface grinding | polishing process is performed using the abrasive grain whose average particle diameter exceeds 25 micrometers, (A) The grinding | polishing process in a 1st end surface grinding | polishing process As a result of the generation of polishing scratches, many pit defects were observed not only on the outer peripheral chamfered portion and the inner peripheral chamfered portion of the glass substrate but also on the outer peripheral side surface and the inner peripheral side surface.
本発明によれば、砥粒としての酸化セリウム粒子の使用をできるだけ抑えながら、ガラス基板の端面を研磨し、端面にピット欠陥がなく高記録密度の実現が可能な磁気記録媒体用ガラス基板を生産性高く確実に得ることができる。 According to the present invention, while suppressing the use of cerium oxide particles as abrasive grains as much as possible, the end surface of a glass substrate is polished, and a glass substrate for a magnetic recording medium capable of realizing a high recording density without pit defects on the end surface is produced. Highly reliable and reliable.
１０…磁気記録媒体用ガラス基板、１１…円孔、１０１…内周側面、１０２…外周側面、１０３ａ，１０３ｂ…主平面、１０４…内周面取り部、１０５…外周面取り部。
DESCRIPTION OF
Claims (4)
前記内周面取り部は、ガラス基板の表面を５μｍエッチングしてから評価される、直径または長径の最大径が１０μｍ以上のピット欠陥数が５個／ｍｍ２以下であり、
前記内周面取り部は、ＳＥＭ−ＥＤＸを用いて該内周面取り部で測定されるセリウムのＬ線の強度を、前記ガラス基板に含まれるカリウムのＫ線、Ｌ線の強度（内部標準）で除した値が、０．３以下であることを特徴とする磁気記録媒体用ガラス基板。 In a disk-shaped glass substrate having a through hole in the central portion and having an inner peripheral side surface constituting the through hole, an outer peripheral side surface, and a pair of main planes facing each other, the inner peripheral side surface and the outer peripheral side surface A glass substrate for a magnetic recording medium in which an inner peripheral chamfered portion and an outer peripheral chamfered portion are respectively formed at intersections with the main plane,
The inner peripheral chamfer, the surface of the glass substrate is voted by 5μm etching state, and are maximum diameter 10μm or more pits number of defects having a diameter or major axis 5 / mm 2 or less,
The inner peripheral chamfered portion uses the SEM-EDX to measure the intensity of cerium L-line measured at the inner peripheral chamfered portion by the potassium K-line and L-line intensity (internal standard) contained in the glass substrate. The glass substrate for magnetic recording media , wherein the divided value is 0.3 or less .
前記外周面取り部は、ガラス基板の表面を５μｍエッチングしてから評価される、直径または長径の最大径が１０μｍ以上のピット欠陥数が５個／ｍｍ２以下であり、
前記外周面取り部は、ＳＥＭ−ＥＤＸを用いて該外周面取り部で測定されるセリウムのＬ線の強度を、前記ガラス基板に含まれるカリウムのＫ線、Ｌ線の強度（内部標準）で除した値が、０．３以下であることを特徴とする磁気記録媒体用ガラス基板。 In a disk-shaped glass substrate having a through hole in the central portion and having an inner peripheral side surface constituting the through hole, an outer peripheral side surface, and a pair of main planes facing each other, the inner peripheral side surface and the outer peripheral side surface A glass substrate for a magnetic recording medium in which an inner peripheral chamfered portion and an outer peripheral chamfered portion are respectively formed at intersections with the main plane,
The outer circumferential chamfer, the surface of the glass substrate is voted by 5μm etched, the number pit defects of more than 10μm maximum diameter of the diameter or major axis Ri der 5 / mm 2 or less,
The outer peripheral chamfered portion was obtained by dividing the cerium L-line intensity measured by the outer peripheral chamfered portion using SEM-EDX by the potassium K-line and L-line intensities (internal standard) contained in the glass substrate. A glass substrate for a magnetic recording medium having a value of 0.3 or less .
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