JP4081826B2 - Glass substrate for magnetic disk, magnetic disk and donut-shaped circular glass disk substrate - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は磁気ディスク用ガラス基板および磁気ディスクに関する。
【０００２】
【従来の技術】
磁気ディスクは、基板の上にスパッタ、メッキ、蒸着等のプロセスにより磁性膜および保護膜が形成されたものであり、一般にガラスは表面の平滑性に優れ、硬く、変形抵抗が大きく、かつ表面欠陥が少ない等の理由から高密度化に適した磁気ディスク用基板の材料として注目されている。
【０００３】
ガラス基板として比較的安価なアルカリを含むガラス、たとえばソーダライムシリカガラス、を用いた場合、特に多湿環境下やエイジング処理をした場合において磁性膜のピンホール部または磁性膜の周辺部など磁性膜が薄い部分またはガラスが露出した部分からアルカリイオンが析出し、これが引きがねとなって磁性膜が腐食または変色することが見出されている。
【０００４】
また、ガラス基板は従来のアルミニウム合金等の基板に比べ破壊強度が低い。従って、スピンドルへの装着その他取扱い時において形成されるわずかな傷の存在が破損につながる。
【０００５】
そのため、ガラス基板に化学強化を施し表面に圧縮応力層を形成することが行われているが、それだけでは不十分な場合が多い。
【０００６】
【発明が解決しようとする課題】
本発明の目的は、上記欠点を解決し、従来のソーダライムシリカガラスで問題となっていたガラス基板上の金属磁性膜の腐食を改善するとともに、傷がつきにくく破損しにくいガラス基板を提供することにある。
【０００７】
組成が重量％表示で、
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜１２、
Ｎａ2 Ｏ １〜 ７、
Ｋ2 Ｏ ９〜１６（９を除く）、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １０〜１７、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ ８〜１７、
ＺｒＯ2 ０．５〜 ５、
を含有し、ＺｎＯを含有しないガラス（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）を化学強化処理してなる磁気ディスク用ガラス基板である。
また、組成が重量％表示で、
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜１２、
Ｎａ2 Ｏ １〜 ７、
Ｋ2 Ｏ ９〜１６（９を除く）、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １０〜１７、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ ８〜１７、
ＺｒＯ2 ０．５〜 ５、
を含有し、ＺｎＯを含有しないドーナツ状円形ガラスディスク基板（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）である。
また、組成が重量％表示で、
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜１２、
Ｎａ2 Ｏ １〜 ４、
Ｋ2 Ｏ ９〜１６（９を除く）、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １０〜１７、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ ８〜１７、
ＺｒＯ2 ０．５〜 ５、
を含有するドーナツ状円形ガラスディスク基板（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）である。
【０００８】
【発明の実施の形態】
本発明におけるガラスの組成について以下に説明する。
ＳｉＯ2 はガラスのネットワークフォーマーであり、本発明では、６０〜７０重量％とする。これが少ないと傷がつきやすくなり、また化学的耐久性が低下する。多すぎると熔解が困難になる傾向がある。より好ましくは６２〜６８重量％である。
【０００９】
Ａｌ2 Ｏ3 はガラスの化学的耐久性を向上させるとともに、ガラス表層部のアルカリ金属をよりイオン半径の大きいアルカリ金属で置換するイオン交換の速度を増大させ、深い圧縮応力を形成させやすくする作用があり、本発明では１〜１２重量％とする。これが多すぎると、熔解が困難になる。より好ましくは７重量％以下である。
【００１０】
Ｎａ2 Ｏはガラス熔解時の粘性を下げ、溶解を促進するとともに、化学強化時にイオン交換される主たる成分となる。本発明では、１〜７重量％とする。これが多すぎると、化学的耐久性が低下するだけでなく、Ｎａ+ イオンがガラス基板表面へ多く析出するようになるため、磁性膜の耐食性が劣化するおそれがある。好ましくは４重量％以下である。
【００１１】
Ｋ2 Ｏの添加は化学強化時のイオン交換の速度を向上させる。また、Ｎａ2 Ｏを一部置換することにより、Ｎａ2 Ｏの添加量を低減させ、磁性膜の耐食性を高めうる。逆にＫ2 Ｏが多くなり、Ｎａ2 Ｏが相対的に少なくなりすぎると、イオン交換そのものが起こりにくくなる。本発明ではＫ2 Ｏの添加量は９〜１６重量％とする。イオン交換を容易にする観点で、Ｋ2 Ｏは好ましくは１２重量％以上、特に１３重量％以上である。また、Ｋ2 Ｏ＋Ｎａ2 Ｏは以上の観点で、１０〜１７重量％とする。
【００１２】
ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯはガラス熔解時の粘性を下げ、溶解しやすくするために合量で８重量％以上含有される。好ましくは合量で１３重量％以上である。他方、合量で１７重量％を超えるとガラスが傷つきやすくなり、また、失透温度が高くなる傾向がある。
【００１３】
フロート法による成形を容易にするためには、ＭｇＯは０．５〜９重量％、特に１〜７重量％とし、ＣａＯは０．５〜１０重量％、特には１〜８重量％とし、またＭｇＯ＋ＣａＯは５〜１３重量％、特には６〜１３重量％とすることが好ましい。これらが多すぎると、失透温度が高くなりフロート法による成形が困難になるおそれがある。
【００１４】
ＳｒＯは必須ではないが熔解性向上のために添加できる。フロート法による成形を容易にするためには、０〜５重量％、特には０〜３重量％とすることが好ましい。これが多すぎると失透温度が高くなり、ガラスが傷つきやすくなるおそれがある。
【００１５】
ＢａＯも必須ではないが熔解性向上のために添加でき、０〜２重量％とすることが好ましい。これも多すぎると、失透温度が高くなり、ガラスが傷つきやすくなるおそれがある。
【００１６】
ＺｒＯ2 は化学的耐久性を向上させる効果がある。本発明では０．５〜５重量％とする。化学的耐久性向上の点で、好ましくは２重量％以上含有する。一方多すぎると、熔解性が低下し、ガラスが傷つきやすくなるおそれがある。好ましくは４重量％以下である。
【００１７】
本発明によるガラス基板は上記成分以外に、ガラスの熔解性、清澄性、成形性を改善するため、Ａｓ2 Ｏ3 、Ｓｂ2 Ｏ3 、Ｐ2 Ｏ5 、Ｆ、Ｃｌ、ＳＯ3 を合量で２重量％以下添加できる。また、ガラスの化学的耐久性向上のため、Ｌａ2 Ｏ3 、ＴｉＯ2 、ＳｎＯ2 、Ｂ2 Ｏ3 を合量で５重量％以下添加できる。またＺｎＯも化学的耐久性向上のために添加できるが、フロート成形性を損なわないために１重量％以下とすることが好ましい。特に好ましくは、ＺｎＯは実質的には含有されない。
【００１８】
さらに、Ｆｅ2 Ｏ3 、ＣｏＯ、ＮｉＯ、Ｎｄ2 Ｏ3 、Ｓｅ等の着色材を添加してガラスの色調を調整できる。この着色材の含有量は合量で１重量％以下が好ましい。なお、Ｋ2 Ｏ、Ｎａ2 Ｏなどのアルカリ成分は、この若干量をＬｉ2 Ｏに置換できる。Ｌｉ2 Ｏの含有量は３重量％以下が好ましい。
【００１９】
本発明においてガラスの脆さを示す指標値としてはローンらによって提案された脆さ指標値Ｂを使用する（B.R.Lawn and D.B.Marshall, J.Am.Ceram.Soc.,62(7-8)347-350(1979) ）。ここで、脆さ指標値Ｂは材料のビッカース硬さＨV と破壊靱性値ＫC から数１により定義される。
【００２０】
【数１】
Ｂ＝ＨV ／ＫC （１）
【００２１】
本発明のガラスの脆さ指標値は７４００ｍ-1/2以下であることが好ましく、より好ましくは７３００ｍ-1/2以下である。
また、本発明のガラスは、化学強化が可能である。化学強化は通常、硝酸カリウム融液もしくは、硝酸カリウムと硝酸ナトリウムの混合融液にガラス板を浸漬することによって行われる。本発明のガラスにおいては化学強化によって、表面から５μｍ以上、特には１０μｍ以上の厚さの圧縮圧力層を生じさせることができる。
【００２２】
上述のように本発明のガラスは、傷がつきにくいうえ、従来の磁気ディスク用ガラスと同等以上の化学強化が可能であるため、製造工程中や、製品として使用中の破損おそれを大幅に減じることができる。
なお、本発明のガラスは典型的には密度が２．７ｇ／ｃｃ以下、特には２．６ｇ／ｃｃ以下である。このことも落下時の衝撃を小さくし、破損のおそれを小さくしている。
【００２３】
また、本発明のガラスの１つの重要な特徴として、フロート成形が可能なことがある。すなわち、フロート成形時の成形温度である１０4 ポイズの粘性を示す温度に比べて失透温度が低い。従って、失透などの不具合を生じることなく、フロート成形が可能である。
【００２４】
本発明のガラスは、たとえば、次のような方法で製造できる。すなわち、通常使用される各成分の原料を目標成分になるように調合し、これを熔解炉に連続的に投入し、１５００〜１６００℃に加熱して、熔融する。この熔融ガラスをフロート法により所定の板厚に成形し、徐冷後切断する。
【００２５】
本発明のガラス基板においては、所定のサイズに切断されたガラス板を化学強化処理する。化学強化処理は公知の方法で行えばよい。すなわち、４００〜５３０℃の硝酸カリウムまたはこれと硝酸ナトリウムとの混合液にガラス物品を２〜２０時間程度浸漬した後取り出し、徐冷することにより行える。
【００２６】
本発明の磁気ディスク用ガラス基板によって、磁気ディスクを形成するには、ガラス基板の上に順次、下地層、磁性層、保護層、潤滑層を設ければよい。
【００２７】
本発明で用いられる磁気記録層としての磁性層としては、Ｃｏ−Ｃｒ系、Ｃｏ−Ｃｒ−Ｐｔ系、Ｃｏ−Ｎｉ−Ｃｒ系、Ｃｏ−Ｎｉ−Ｃｒ−Ｐｔ系、Ｃｏ−Ｎｉ−Ｐｔ系、Ｃｏ−Ｃｒ−Ｔａ系などのＣｏ系合金を好ましく採用できる。耐久性や磁気特性を向上するために、磁性層の下に設けられる下地層としては、Ｎｉ層、Ｎｉ−Ｐ層、Ｃｒ層、ＳｉＯ2 層などを採用できる。
【００２８】
本発明では、Ｃｒ層、Ｃｒ合金層、他の材料からなる金属または合金層を磁性層の上または下に設けうる。
【００２９】
保護層としては、５０〜１０００Åの厚みのカーボンまたはシリカの層が使用でき、潤滑層を形成するためには、３０Å程度の厚みのパーフルオロポリエーテル系の液体潤滑剤が使用できる。
【００３０】
【実施例】
＜板状ガラスの作成＞
表１に示した例１〜４の４種類の組成について常法に従い調合・混合し、ガラスバッチを調製した。次いで容量約５００ｍｌのＰｔ−Ｒｈ１０％坩堝にガラスバッチを入れ１５００℃で均質化のため約１時間の撹拌を含め約４時間熔解し、カーボン板上に流し出して板状とし徐冷後、常法に従い切断・研磨して約１ｍｍ厚の板状ガラスサンプルを得た。なお、例１〜５は実施例であり、例６、７は比較例である。
【００３１】
これらのガラスの失透温度、１０4 ポイズの温度、１０2 ポイズの温度、歪点温度、脆さ指標値を測定し、表１に併記した。ついで例１〜５の板状ガラスサンプルを切断・研磨して外径６５ｍｍ、内径２０ｍｍ、厚さ０．６３５ｍｍのドーナツ状の円形ガラスディスク基板を各２０枚作成した。
【００３２】
脆さ指標値（単位：ｍ-1/2）は次のようにして求めた。脆さ指標値をガラスに適用する際の大きな問題は破壊靱性値ＫC が正確に評価しにくいことである。しかし、本出願人は、いくつかの手法を検討した結果、ビッカース圧子を押し込んだときにガラス表面に残る圧子の痕の大きさと痕の四隅から発生するクラックの長さとの関係から脆さを定量的に評価できることを見出している。その関係式は式（２）により定義される。ここで、Ｐはビッカース圧子の押し込み荷重でありａ、ｃは、それぞれ、ビッカース圧痕の対角長および四隅から発生するクラックの長さ（圧子の痕を含む対称な２つのクラックの全長）である。各種ガラスの表面に打ち込んだビッカース圧痕の寸法と数２を用いて、脆さ指標値を評価する。
【００３３】
【数２】
ｃ／ａ＝０．００５６Ｂ2/3 Ｐ1/6 （２）
【００３４】
例７のガラス基板は、脆さ指標値が７４００ｍ-1/2を超えるので、傷がつきやすく回転時に破損する確率が大きいことになる。
【００３５】
＜化学強化性テスト＞
上記ガラスディスクの基板各１０枚について化学強化処理を行った。すなわち、例１〜４および例７については４８０℃の熔融硝酸カリウム塩に、また、例６については４５０℃の熔融硝酸カリウム塩に、それぞれ１０時間浸漬し、化学強化処理を行った。上記各ガラスディスク基板について、東芝硝子製の主表面応力計ＦＳＷ−６０にて表面圧縮応力層の厚みを測定した結果を表１に併記する。表から明らかなように本発明によるガラス基板は１０μｍ以上の圧縮応力層を生じさせることができる。
【００３６】
＜磁気記録媒体の耐湿テスト＞
上記未強化品および強化品のそれぞれの主表面上にスパッタ法により厚さ約５００ÅのＣｒからなる下地層を形成した後、厚さ約６００ÅのＣｏ−３０原子％Ｎｉ合金磁性層を形成し、その上に厚さ約３００Åのカーボン保護膜を形成し、さらにその上にパーフルオロポリエーテル系の液体潤滑剤を塗布することにより磁気記録媒体を得た。これらについて８０℃、９０％ＲＨの雰囲気条件で１００時間保持することにより耐湿テストを実施した。
【００３７】
表より明らかなように、本発明によるガラス基板の脆さ指標値は、７４００ｍ-1/2以下であり、傷がつきにくい。そのため、スピンドルへの装着その他取扱い時においても傷がつきにくく回転時に破損が起こる等の問題がない。更に、例１〜５のガラス基板からなる磁気記録媒体は未強化品、強化品ともに変色が認められなかった。また、失透温度は、フロート法の成形粘度である１０4 ポイズに相当する温度よりも低く、フロート法による製造に好適であることがわかる。
【００３８】
一方、例６のガラス基板からなる未強化品磁気記録媒体はディスクの内周および外周の端面から２〜３ｍｍの範囲にわたってＣｏ−Ｎｉ合金層とガラスとの界面から面内にかけて変色が認められ、例６のガラス基板からなる強化品磁気記録媒体では同じく１〜２ｍｍの範囲にわたって変色が認められた。
【００３９】
【表１】
【発明の効果】
本発明の高強度な磁気ディスク用ガラス基板はソーダライムシリカガラスを使用したガラス基板に比べ、傷がつきにくく、耐食性および耐エージング性がきわめて優れる。さらに、本発明の磁気ディスク用ガラス基板は、フロート法による成形にも適するものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass substrate for a magnetic disk and a magnetic disk.
[0002]
[Prior art]
A magnetic disk has a magnetic film and a protective film formed on a substrate by processes such as sputtering, plating, and vapor deposition. Generally, glass has excellent surface smoothness, is hard, has high deformation resistance, and has surface defects. As a material for a magnetic disk substrate suitable for high density, it has been attracting attention for the reason that there are few.
[0003]
When a relatively inexpensive glass containing alkali, such as soda lime silica glass, is used as the glass substrate, the magnetic film such as the pinhole part of the magnetic film or the peripheral part of the magnetic film particularly in a humid environment or when subjected to an aging treatment. It has been found that alkali ions are deposited from a thin portion or a portion where the glass is exposed, and this acts as a trigger to corrode or discolor the magnetic film.
[0004]
Further, the glass substrate has a lower breaking strength than a conventional substrate made of an aluminum alloy or the like. Therefore, the presence of slight scratches formed during mounting on the spindle or other handling leads to breakage.
[0005]
Therefore, chemical strengthening is performed on the glass substrate to form a compressive stress layer on the surface, but this is often insufficient.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to solve the above drawbacks, as well as improves the corrosion of the metal magnetic film on a glass substrate which has been a problem in a conventional soda-lime-silica glass, provides hardly hardly damaged glass substrate to be scratched There is to do.
[0007]
The composition is expressed in weight% ,
SiO 2 60~70,
Al 2 O 3 1-12,
Na 2 O 1-7,
K 2 O 9-16 (excluding 9),
Na 2 O + K 2 O 10-17,
MgO + CaO + SrO + BaO 8-17,
ZrO 2 0.5-5,
Containing a glass substrate for a magnetic disk glass containing no ZnO (SiO 2 + Al 2 O 3 + ZrO 2 excluding those of 70 wt% or less) obtained by chemical strengthening processing.
Moreover, the composition is expressed in weight% ,
SiO 2 60~70,
Al 2 O 3 1-12,
Na 2 O 1-7,
K 2 O 9-16 (excluding 9),
Na 2 O + K 2 O 10-17,
MgO + CaO + SrO + BaO 8-17,
ZrO 2 0.5-5,
And a doughnut-shaped circular glass disk substrate that does not contain ZnO (excluding those in which SiO 2 + Al 2 O 3 + ZrO 2 is 70 wt% or less).
Moreover, the composition is expressed in weight% ,
SiO 2 60~70,
Al 2 O 3 1-12,
Na 2 O 1~ 4,
K 2 O 9-16 (excluding 9),
Na 2 O + K 2 O 10-17,
MgO + CaO + SrO + BaO 8-17,
ZrO 2 0.5-5,
Is you containing a donut-shaped circular glass disk substrate (SiO 2 + Al 2 O 3 + ZrO 2 excluding those of 70 wt% or less).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The composition of the glass in the present invention will be described below.
SiO 2 is a glass network former, and in the present invention, it is 60 to 70% by weight. If the amount is small, scratches are easily formed and chemical durability is lowered. If too much, melting tends to be difficult. More preferably, it is 62 to 68% by weight.
[0009]
Al 2 O 3 improves the chemical durability of the glass and increases the rate of ion exchange to replace the alkali metal on the glass surface layer with an alkali metal having a larger ion radius, thereby facilitating the formation of deep compressive stress. In the present invention, it is 1 to 12% by weight. If this is too much, melting becomes difficult. More preferably, it is 7% by weight or less.
[0010]
Na 2 O lowers the viscosity during glass melting, promotes melting, and becomes a main component that is ion-exchanged during chemical strengthening. In this invention, it is 1 to 7 weight%. If the amount is too large, not only the chemical durability is lowered, but a large amount of Na + ions are deposited on the surface of the glass substrate, which may deteriorate the corrosion resistance of the magnetic film. Preferably it is 4 weight% or less.
[0011]
The addition of K 2 O improves the rate of ion exchange during chemical strengthening. Also, by replacing part of the Na 2 O, to reduce the amount of Na 2 O, it may enhance the corrosion resistance of the magnetic film. Conversely, if K 2 O increases and Na 2 O decreases relatively relatively, ion exchange itself is difficult to occur. In the present invention, the amount of K 2 O added is 9 to 16% by weight. From the viewpoint of facilitating ion exchange, K 2 O is preferably 12% by weight or more, particularly 13% by weight or more. Further, K 2 O + Na 2 O in the above aspect, a 10 to 17 wt%.
[0012]
MgO, CaO, SrO and BaO are contained in a total amount of 8% by weight or more in order to lower the viscosity at the time of glass melting and to facilitate dissolution. The total amount is preferably 13% by weight or more. On the other hand, if the total amount exceeds 17% by weight, the glass tends to be damaged, and the devitrification temperature tends to increase.
[0013]
In order to facilitate forming by the float process, MgO is 0.5 to 9% by weight, particularly 1 to 7% by weight, CaO is 0.5 to 10% by weight, particularly 1 to 8% by weight, and MgO + CaO is preferably 5 to 13% by weight, particularly 6 to 13% by weight. When there are too many these, devitrification temperature becomes high and there exists a possibility that shaping | molding by a float process may become difficult.
[0014]
SrO is not essential, but can be added to improve meltability. In order to facilitate molding by the float process, it is preferably 0 to 5% by weight, particularly 0 to 3% by weight. If the amount is too large, the devitrification temperature becomes high and the glass may be easily damaged.
[0015]
BaO is not essential, but can be added to improve the meltability, and is preferably 0 to 2% by weight. If this amount is too large, the devitrification temperature becomes high and the glass may be easily damaged.
[0016]
ZrO 2 has the effect of improving chemical durability. In the present invention, the content is 0.5 to 5% by weight. From the viewpoint of improving chemical durability, the content is preferably 2% by weight or more. On the other hand, if the amount is too large, the meltability is lowered and the glass may be easily damaged. Preferably it is 4 weight% or less.
[0017]
In addition to the above components, the glass substrate according to the present invention contains As 2 O 3 , Sb 2 O 3 , P 2 O 5 , F, Cl and SO 3 in order to improve the meltability, clarity and formability of the glass. 2% by weight or less can be added. Further, in order to improve the chemical durability of the glass, La 2 O 3 , TiO 2 , SnO 2 , B 2 O 3 can be added in a total amount of 5% by weight or less. ZnO can also be added to improve chemical durability, but is preferably 1% by weight or less so as not to impair float moldability. Particularly preferably, ZnO is not substantially contained.
[0018]
Furthermore, the color tone of the glass can be adjusted by adding a colorant such as Fe 2 O 3 , CoO, NiO, Nd 2 O 3 , or Se. The total content of the coloring material is preferably 1% by weight or less. Note that some amount of alkaline components such as K 2 O and Na 2 O can be replaced with Li 2 O. The content of Li 2 O is preferably 3% by weight or less.
[0019]
In the present invention, the brittleness index value B proposed by Lorne et al. Is used as an index value indicating the brittleness of the glass (BRLawn and DBMarshall, J. Am. Ceram. Soc., 62 (7-8) 347-350. (1979)). Here, fragility index value B is defined by 1 the number of Vickers hardness H V and fracture toughness value K C of the material.
[0020]
[Expression 1]
B = H V / K C (1)
[0021]
The brittleness index value of the glass of the present invention is preferably 7400 m -1/2 or less, more preferably 7300 m -1/2 or less.
Further, the glass of the present invention can be chemically strengthened. Chemical strengthening is usually performed by immersing a glass plate in a potassium nitrate melt or a mixed melt of potassium nitrate and sodium nitrate. In the glass of the present invention, a compressed pressure layer having a thickness of 5 μm or more, particularly 10 μm or more can be generated from the surface by chemical strengthening.
[0022]
As described above, the glass of the present invention is not easily scratched and can be chemically strengthened at least as much as conventional glass for magnetic disks, thus greatly reducing the risk of breakage during the manufacturing process or in use as a product. be able to.
The glass of the present invention typically has a density of 2.7 g / cc or less, particularly 2.6 g / cc or less. This also reduces the impact when dropped and reduces the risk of breakage.
[0023]
One important feature of the glass of the present invention is that float forming is possible. That is, the devitrification temperature is lower than the temperature showing the viscosity of 10 4 poise, which is the molding temperature during float molding. Therefore, float forming is possible without causing problems such as devitrification.
[0024]
The glass of the present invention can be produced, for example, by the following method. That is, the raw material of each component normally used is mixed so that it may become a target component, this is continuously thrown into a melting furnace, and it heats to 1500-1600 degreeC and melts. The molten glass is formed into a predetermined plate thickness by a float method, and is cut after slow cooling.
[0025]
In the glass substrate of the present invention, the glass plate cut into a predetermined size is chemically strengthened. The chemical strengthening treatment may be performed by a known method. That is, it can be performed by immersing the glass article in potassium nitrate at 400 to 530 ° C. or a mixed solution of sodium nitrate and sodium nitrate for about 2 to 20 hours, then taking out and slowly cooling the glass article.
[0026]
In order to form a magnetic disk using the magnetic disk glass substrate of the present invention, an underlayer, a magnetic layer, a protective layer, and a lubricating layer may be sequentially provided on the glass substrate.
[0027]
As a magnetic layer as a magnetic recording layer used in the present invention, Co—Cr, Co—Cr—Pt, Co—Ni—Cr, Co—Ni—Cr—Pt, Co—Ni—Pt, Co-based alloys such as Co-Cr-Ta can be preferably used. In order to improve durability and magnetic characteristics, a Ni layer, a Ni—P layer, a Cr layer, a SiO 2 layer, or the like can be adopted as a base layer provided under the magnetic layer.
[0028]
In the present invention, a Cr layer, a Cr alloy layer, or a metal or alloy layer made of another material can be provided on or below the magnetic layer.
[0029]
As the protective layer, a carbon or silica layer having a thickness of 50 to 1000 mm can be used. In order to form a lubricating layer, a perfluoropolyether liquid lubricant having a thickness of about 30 mm can be used.
[0030]
【Example】
<Creation of plate glass>
The four compositions of Examples 1 to 4 shown in Table 1 were prepared and mixed according to a conventional method to prepare a glass batch. Next, a glass batch is put into a Pt-Rh 10% crucible with a capacity of about 500 ml, melted for about 4 hours including stirring for about 1 hour at 1500 ° C. for homogenization, poured out onto a carbon plate to form a plate, and gradually cooled. By cutting and polishing according to the method, a plate-like glass sample having a thickness of about 1 mm was obtained. Examples 1 to 5 are examples, and examples 6 and 7 are comparative examples.
[0031]
The devitrification temperature, the 10 4 poise temperature, the 10 2 poise temperature, the strain point temperature, and the brittleness index value of these glasses were measured and listed in Table 1. Next, the plate-shaped glass samples of Examples 1 to 5 were cut and polished to prepare 20 donut-shaped circular glass disk substrates each having an outer diameter of 65 mm, an inner diameter of 20 mm, and a thickness of 0.635 mm.
[0032]
The brittleness index value (unit: m −1/2 ) was determined as follows. A major problem in applying the brittleness index value to glass is that the fracture toughness value K C is difficult to accurately evaluate. However, as a result of studying several methods, the present applicant has quantified brittleness from the relationship between the size of the indenter mark remaining on the glass surface when the Vickers indenter is pushed in and the length of cracks generated from the four corners of the mark. Has been found that can be evaluated. The relational expression is defined by Expression (2). Here, P is the indentation load of the Vickers indenter, and a and c are the diagonal length of the Vickers indentation and the length of the crack generated from the four corners (the total length of two symmetrical cracks including the indenter trace), respectively. . The brittleness index value is evaluated by using the dimensions of Vickers indentation and the number 2 which are struck on the surface of various glasses.
[0033]
[Expression 2]
c / a = 0.0056B 2/3 P 1/6 (2)
[0034]
Since the glass substrate of Example 7 has a brittleness index value exceeding 7400 m −1/2 , the glass substrate is easily scratched and has a high probability of breaking during rotation.
[0035]
<Chemical strengthening test>
A chemical strengthening treatment was performed on each of the 10 substrates of the glass disk. In other words, Examples 1-4 and Example 7 were immersed in molten potassium nitrate at 480 ° C., and Example 6 was immersed in molten potassium nitrate at 450 ° C. for 10 hours to perform chemical strengthening treatment. Table 1 also shows the results of measuring the thickness of the surface compressive stress layer with the main surface stress meter FSW-60 manufactured by Toshiba Glass Co., Ltd. for each glass disk substrate. As is apparent from the table, the glass substrate according to the present invention can generate a compressive stress layer of 10 μm or more.
[0036]
<Moisture resistance test of magnetic recording media>
After forming a base layer made of Cr having a thickness of about 500 mm on the main surfaces of the unreinforced product and the reinforced product by sputtering, a Co-30 atomic% Ni alloy magnetic layer having a thickness of about 600 mm is formed, A carbon protective film having a thickness of about 300 mm was formed thereon, and a perfluoropolyether liquid lubricant was applied thereon to obtain a magnetic recording medium. These were subjected to a moisture resistance test by holding them at 80 ° C. and 90% RH for 100 hours.
[0037]
As is clear from the table, the brittleness index value of the glass substrate according to the present invention is 7400 m −1/2 or less, and is hardly scratched. Therefore, there are no problems such as damage to the spindle when it is mounted on the spindle or otherwise handled, and is not easily damaged. Further, the magnetic recording media comprising the glass substrates of Examples 1 to 5 showed no discoloration in both the unreinforced product and the reinforced product. Further, the devitrification temperature is lower than the temperature corresponding to 10 4 poise, which is the molding viscosity of the float process, and it can be seen that it is suitable for production by the float process.
[0038]
On the other hand, in the unreinforced product magnetic recording medium comprising the glass substrate of Example 6, discoloration was observed from the interface between the Co—Ni alloy layer and the glass to the in-plane over a range of 2 to 3 mm from the inner and outer end surfaces of the disk. In the reinforced magnetic recording medium comprising the glass substrate of Example 6, discoloration was also observed over the range of 1 to 2 mm.
[0039]
[ Table 1 ]
【The invention's effect】
The high-strength glass substrate for magnetic disk of the present invention is less likely to be scratched and has excellent corrosion resistance and aging resistance compared to a glass substrate using soda lime silica glass. Furthermore, the glass substrate for a magnetic disk of the present invention is also suitable for molding by a float method.
Claims (18)
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜１２、
Ｎａ2 Ｏ １〜 ７、
Ｋ2 Ｏ ９〜１６（９を除く）、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １０〜１７、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ ８〜１７、
ＺｒＯ2 ０．５〜 ５、
を含有し、ＺｎＯを含有しないガラス（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）を化学強化処理してなる磁気ディスク用ガラス基板。The composition is expressed in weight% ,
SiO 2 60~70,
Al 2 O 3 1-12,
Na 2 O 1-7,
K 2 O 9-16 (excluding 9),
Na 2 O + K 2 O 10-17,
MgO + CaO + SrO + BaO 8-17,
ZrO 2 0.5-5,
A glass substrate for a magnetic disk, which is obtained by chemically strengthening glass containing ZnO but excluding one containing 70% by weight or less of SiO 2 + Al 2 O 3 + ZrO 2 .
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜 ７、
Ｎａ2 Ｏ １〜 ７、
Ｋ2 Ｏ ９〜１６（９を除く）、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １０〜１７、
ＭｇＯ ０．５〜 ９、
ＣａＯ ０．５〜１０、
ＳｒＯ ０〜 ５、
ＢａＯ ０〜 ２、
ＭｇＯ＋ＣａＯ ５〜１３、
ＺｒＯ2 ０．５〜 ５、
を含有するもの（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）である請求項１、２または３記載の磁気ディスク用ガラス基板。The glass has a composition expressed by weight% ,
SiO 2 60~70,
Al 2 O 3 1-7,
Na 2 O 1-7,
K 2 O 9-16 (excluding 9),
Na 2 O + K 2 O 10-17,
MgO 0.5-9,
CaO 0.5-10,
SrO 0-5,
BaO 0-2,
MgO + CaO 5-13,
ZrO 2 0.5-5,
The content to shall (SiO 2 + Al 2 O 3 + ZrO 2 excluding those of 70 wt% or less) a glass substrate for a magnetic disk according to claim 1, 2 or 3 wherein.
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜 ７、
Ｎａ2 Ｏ １〜 ７、
Ｋ2 Ｏ １２〜１６、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １３〜１７、
ＭｇＯ １〜 ７、
ＣａＯ １〜 ８、
ＳｒＯ ０〜 ３、
ＢａＯ ０〜 ２、
ＭｇＯ＋ＣａＯ ６〜１３、
ＺｒＯ2 ０．５〜 ４、
を含有するもの（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）である請求項１、２、３または４記載の磁気ディスク用ガラス基板。The glass has a composition expressed by weight% ,
SiO 2 60~70,
Al 2 O 3 1-7,
Na 2 O 1-7,
K 2 O 12-16,
Na 2 O + K 2 O 13-17,
MgO 1-7,
CaO 1-8,
SrO 0-3,
BaO 0-2,
MgO + CaO 6-13,
ZrO 2 0.5-4,
The content to shall (SiO 2 + Al 2 O 3 + ZrO 2 excluding those of 70 wt% or less) a glass substrate for a magnetic disk according to claim 1, 2, 3 or 4, wherein.
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜１２、
Ｎａ2 Ｏ １〜 ７、
Ｋ2 Ｏ ９〜１６（９を除く）、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １０〜１７、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ ８〜１７、
ＺｒＯ2 ０．５〜 ５、
を含有し、ＺｎＯを含有しないドーナツ状円形ガラスディスク基板（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）。The composition is expressed in weight% ,
SiO 2 60~70,
Al 2 O 3 1-12,
Na 2 O 1-7,
K 2 O 9-16 (excluding 9),
Na 2 O + K 2 O 10-17,
MgO + CaO + SrO + BaO 8-17,
ZrO 2 0.5-5,
Containing, donut-shaped circular glass disc substrate which does not contain ZnO (SiO 2 + Al 2 O 3 + ZrO 2 excluding those of 70 wt% or less).
ＳｉＯ2 ６０〜７０、
Ａｌ2 Ｏ3 １〜１２、
Ｎａ2 Ｏ １〜 ４、
Ｋ2 Ｏ ９〜１６（９を除く）、
Ｎａ2 Ｏ＋Ｋ2 Ｏ １０〜１７、
ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ ８〜１７、
ＺｒＯ2 ０．５〜 ５、
を含有するドーナツ状円形ガラスディスク基板（ＳｉＯ2＋Ａｌ2 Ｏ3＋ＺｒＯ2が７０重量％以下のものを除く）。The composition is expressed in weight% ,
SiO 2 60~70,
Al 2 O 3 1-12,
Na 2 O 1~ 4,
K 2 O 9-16 (excluding 9),
Na 2 O + K 2 O 10-17,
MgO + CaO + SrO + BaO 8-17,
ZrO 2 0.5-5,
You containing a donut-shaped circular glass disk substrate (SiO 2 + Al 2 O 3 + ZrO 2 excluding those of 70 wt% or less).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31975296A JP4081826B2 (en) | 1996-11-29 | 1996-11-29 | Glass substrate for magnetic disk, magnetic disk and donut-shaped circular glass disk substrate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31975296A JP4081826B2 (en) | 1996-11-29 | 1996-11-29 | Glass substrate for magnetic disk, magnetic disk and donut-shaped circular glass disk substrate |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10158028A JPH10158028A (en) | 1998-06-16 |
| JP4081826B2 true JP4081826B2 (en) | 2008-04-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP31975296A Expired - Fee Related JP4081826B2 (en) | 1996-11-29 | 1996-11-29 | Glass substrate for magnetic disk, magnetic disk and donut-shaped circular glass disk substrate |
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| JP (1) | JP4081826B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE60006176T2 (en) | 1999-03-25 | 2004-04-22 | Central Glass Co., Ltd., Ube | Glass composition, glass object reinforced by ion exchange and process for its manufacture |
| JP3995902B2 (en) * | 2001-05-31 | 2007-10-24 | Ｈｏｙａ株式会社 | Glass substrate for information recording medium and magnetic information recording medium using the same |
| JPWO2004041740A1 (en) * | 2002-11-07 | 2006-03-09 | Hoya株式会社 | SUBSTRATE FOR INFORMATION RECORDING MEDIUM, INFORMATION RECORDING MEDIUM, AND ITS MANUFACTURING METHOD |
| JP4218839B2 (en) * | 2005-05-18 | 2009-02-04 | Ｈｏｙａ株式会社 | Glass substrate for information recording medium and magnetic information recording medium using the same |
| JP5904239B2 (en) * | 2009-04-02 | 2016-04-13 | 旭硝子株式会社 | Glass for information recording medium substrate, glass substrate for information recording medium and magnetic disk |
| JP5947364B2 (en) * | 2014-12-17 | 2016-07-06 | Hoya株式会社 | Glass substrate |
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