JP2007051064A - Glass for magnetic disk substrate, glass substrate for magnetic disk and magnetic disk - Google Patents
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Abstract
【課題】充分な機械的強度があり、かつガラス基板上の金属磁性膜の腐食を改善する磁気ディスク基板用ガラスを提供する。
【解決手段】組成が質量％表示で実質的に、ＳｉＯ２ ５０〜６５、Ａｌ２Ｏ３ ５〜１５、Ｎａ２Ｏ ２〜７、Ｋ２Ｏ ４〜９、Ｎａ２Ｏ＋Ｋ２Ｏ ７〜１４、ＭｇＯ ０．５〜５、ＣａＯ ２〜８、ＭｇＯ＋ＣａＯ ２．５〜１０、ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ １２〜２５、ＺｒＯ２ １〜６、からなる磁気ディスク基板用ガラス。
【選択図】なしThe present invention provides a glass for a magnetic disk substrate that has sufficient mechanical strength and improves corrosion of a metal magnetic film on the glass substrate.
A substantially in composition by weight percentages, SiO 2 50~65, Al 2 O 3 5~15, Na 2 O 2~7, K 2 O 4~9, Na 2 O + K 2 O 7~14 , MgO 0.5-5, CaO 2-8, MgO + CaO 2.5-10, MgO + CaO + SrO + BaO 12-25, ZrO 2 1-6, glass for magnetic disk substrate.
[Selection figure] None
Description
本発明は磁気ディスク用ガラス基板、磁気ディスク基板用ガラスおよび磁気ディスクに関する。 The present invention relates to a glass substrate for a magnetic disk, glass for a magnetic disk substrate, and a magnetic disk.
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。
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。
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.
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.
これを回避するためにはアルカリ含有量のきわめて低いガラス、たとえばノンアルカリガラスを用いればよいことになる。
しかし、ノンアルカリガラスを用いたのでは、実用上充分な強度を得ることが難しい。これは、イオン交換強化処理を行えないためである。実用上充分な強度を得るために施すガラスの強化処理としては、風冷強化やイオン交換強化があるが、厚さの薄いディスク用ガラス基板においては、平坦性を保持するため、低温で行えるイオン交換強化処理を採用する必要がある。イオン交換処理とは、具体的には、Ｎａを含むガラスの転移温度以下の温度でガラス中のＮａ＋イオンをそれよりイオン半径の大きいＫ+ イオンと交換する処理である。
ガラスに含有されるアルカリは上記したようにイオン交換される成分であるから、ノンアルカリガラスはイオン交換強化の対策になり得ない。したがって低温型イオン交換処理を行う以上は基板ガラスはアルカリを含むガラスでなければならない。
In order to avoid this, glass having a very low alkali content, for example, non-alkali glass may be used.
However, when non-alkali glass is used, it is difficult to obtain a practically sufficient strength. This is because the ion exchange strengthening process cannot be performed. In order to maintain the flatness of thin glass glass substrates, there are ion-strengthening that can be performed at low temperatures for glass substrates for thin disks. It is necessary to adopt an exchange strengthening process. Specifically, the ion exchange treatment is a treatment for exchanging Na + ions in the glass with K + ions having a larger ion radius at a temperature lower than the transition temperature of the glass containing Na.
Since the alkali contained in the glass is a component that is ion-exchanged as described above, non-alkali glass cannot be a measure for strengthening ion exchange. Therefore, the substrate glass must be glass containing alkali as long as the low-temperature ion exchange treatment is performed.
前述のように磁気ディスクなどのガラス基板に要求される（１）多湿環境下またはエイジングによる磁性膜の劣化を生起させないこと、および（２）実用上充分な強度を有すること、は相反する性質であり、両者を満足することは難しい。
本発明の目的は、充分な機械的強度を得るためにイオン交換強化ができ、かつ従来のソーダライムガラスシリカ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ガラスおよびガラス基板を提供することにある。
As described above, required for glass substrates such as magnetic disks are contradictory to each other (1) not to cause deterioration of the magnetic film in a humid environment or due to aging, and (2) to have sufficient strength for practical use. Yes, it is difficult to satisfy both.
An object of the present invention is to provide a glass and a glass substrate that can enhance ion exchange to obtain sufficient mechanical strength and improve corrosion of a metal magnetic film on a glass substrate, which has been a problem with conventional soda lime glass silica Is to provide.
本発明は、組成が質量％表示で実質的に、ＳｉＯ２ ５０〜６５、Ａｌ２Ｏ３ ５〜１５、Ｎａ２Ｏ ２〜７、Ｋ２Ｏ ４〜９、Ｎａ２Ｏ＋Ｋ２Ｏ ７〜１４、ＭｇＯ ０．５〜５、ＣａＯ ２〜８、ＭｇＯ＋ＣａＯ ２．５〜１０、ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ １２〜２５、ＺｒＯ２ １〜６、からなる磁気ディスク基板用ガラスである。
また、前記磁気ディスク基板用ガラス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、前記磁気ディスク用ガラス基板の上に、順次、下地層、磁性層、保護層、潤滑層を設けてなる磁気ディスクである。
The present invention is substantially in the composition by weight percentages, SiO 2 50~65, Al 2 O 3 5~15, Na 2 O 2~7, K 2 O 4~9, Na 2 O + K 2 O 7~14 , MgO 0.5-5, CaO 2-8, MgO + CaO 2.5-10, MgO + CaO + SrO + BaO 12-25, ZrO 2 1-6, glass for magnetic disk substrate.
Moreover, it is a glass substrate for magnetic disks formed by chemically strengthening the glass for magnetic disk substrates.
Further, the magnetic disk has a base layer, a magnetic layer, a protective layer, and a lubricating layer sequentially provided on the magnetic disk glass substrate.
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、耐食性および耐エージング性がきわめて優れる。また、本発明のガラス基板はイオン交換強化の効果が充分に得られ、実際使用上充分な機械的強度を有する。さらに、本発明のガラスは、フロート法による成形にも適するものである。また、本発明のガラスは、加工性にも優れ、研磨した場合の速度は、通常のソーダライムシリカガラスと比べて１５〜５５％高い。したがって、生産性の点でも有利である。
なお、本発明のガラス基板は、比較的、ＣａＯの含有量が少ないことから、化学強化用の熔融硝酸カリウム塩にＣａＯが解けだしにくく、熔融硝酸カリウム塩の寿命が長くなる効果も有することが予想される。
The high-strength magnetic disk glass substrate of the present invention is extremely excellent in corrosion resistance and aging resistance as compared with a glass substrate using soda lime silica glass. Further, the glass substrate of the present invention has a sufficient ion exchange strengthening effect and has a mechanical strength sufficient for practical use. Furthermore, the glass of the present invention is suitable for forming by a float process. Moreover, the glass of this invention is excellent also in workability, and the speed | rate at the time of grinding | polishing is 15 to 55% higher than normal soda-lime silica glass. Therefore, it is advantageous in terms of productivity.
In addition, since the glass substrate of the present invention has a relatively low CaO content, it is expected that CaO is difficult to dissolve in the molten potassium nitrate salt for chemical strengthening and that the lifetime of the molten potassium nitrate salt is prolonged. The
本発明における磁気ディスク基板用ガラス（基板用ガラス）の各成分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、５０〜６５質量％とする。これが少ないと化学的耐久性が低下し、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５２〜６２質量％である。
Ａｌ２Ｏ３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５〜１５質量％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６〜９質量％、特に好ましくは６〜８質量％である。
Each component of the magnetic disk substrate glass (substrate glass) in the present invention will be described below.
SiO 2 is a glass network former, and in the present invention, it is 50 to 65% by mass. If the amount is too small, the chemical durability is lowered. If the amount is too large, melting tends to be difficult. More preferably, it is 52-62 mass%.
Al 2 O 3 improves the chemical durability of the glass and increases the ion exchange rate for replacing the alkali metal of the glass surface layer with an alkali metal having a larger ionic radius, thereby facilitating the formation of deep compressive stress. In the present invention, the content is 5 to 15% by mass. If this is too much, melting becomes difficult. More preferably, it is 6-9 mass%, Most preferably, it is 6-8 mass%.
Ｎａ２Ｏはガラス熔解時のフラックスとして作用するとともに、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、２〜７質量％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。
Ｋ２Ｏ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、Ｎａ２Ｏを一部置換することにより、Ｎａ２Ｏの添加量を低減させ、磁性膜の耐食性を高めうる。Ｋ２Ｏの添加量は４〜９質量％とする。Ｋ２Ｏが多くなり、Ｎａ２Ｏ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。Ｋ２Ｏ＋Ｎａ２Ｏは以上の観点で、７〜１４質量％とする。
Na 2 O acts as a flux at the time of glass melting and becomes a main component that is ion-exchanged at the time of chemical strengthening. In this invention, it is 2-7 mass%. 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, so that the corrosion resistance of the magnetic film may be deteriorated.
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. The amount of K 2 O added is 4 to 9% by mass. If K 2 O is increased and Na 2 O is relatively decreased, ion exchange itself is difficult to occur. K 2 O + Na 2 O in the above aspect, a 7 to 14 mass%.
ＭｇＯ、ＣａＯ、ＳｒＯおよびＢａＯはガラス熔解時のフラックスとしての作用があり、熔解を促進させるために添加される。これを超えると、ガラスの失透温度が高くなり、製板が困難になるおそれがある。
フロート法による成形を容易にするために、ＭｇＯは０．５〜５質量％とし、ＣａＯは２〜８質量％とし、またＭｇＯ＋ＣａＯは２．５〜１０質量％とする。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。失透温度をある程度低くすることはフロート法による成形性を確保するうえで重要である。つまり、フロート法成形は、粘度１０４ポイズ程度で行われるため、失透温度が１０４ポイズに相当する粘度を持つ温度より低いガラスでないとフロート法による成形が難しくなる。また、本発明において、ＣａＯは、後に述べる発明者らの実験によると、多すぎる場合に化学強化が入りにくくなる傾向がある。
MgO, CaO, SrO and BaO have a function as a flux at the time of glass melting, and are added to promote melting. If it exceeds this, the devitrification temperature of the glass becomes high, and there is a possibility that the plate making becomes difficult.
In order to facilitate forming by the float process, MgO is 0.5 to 5% by mass, CaO is 2 to 8% by mass, and MgO + CaO is 2.5 to 10% by mass. 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. Decreasing the devitrification temperature to some extent is important for securing the formability by the float process. That is, float molding, to be done at a viscosity of 10 4 poises about, the devitrification temperature is not lower glass than the temperature having a viscosity corresponding to 10 4 poise molding by a float process difficult. Moreover, in this invention, when CaO is too much according to the experiment of the inventors described later, when there is too much, there exists a tendency for chemical strengthening to become difficult to enter.
以上の観点から、ＭｇＯは、より好ましくは１〜３質量％である。またＣａＯは、より好ましくは２〜５．５質量％であり、特に好ましくは３〜５．５質量％である。さらに、ＭｇＯ＋ＣａＯは、より好ましくは４〜９質量％である。
ＳｒＯはフロート法による成形を容易にするためには、４〜１０質量％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る。より好ましくは６〜９質量％である。また、ＢａＯは５〜１２質量％とすることが好ましい。これも多すぎると、失透温度が高くなる。より好ましくは６〜１１質量％である。
From the above viewpoint, MgO is more preferably 1 to 3% by mass. Further, CaO is more preferably 2 to 5.5% by mass, and particularly preferably 3 to 5.5% by mass. Furthermore, MgO + CaO is more preferably 4 to 9% by mass.
SrO is preferably 4 to 10% by mass in order to facilitate molding by the float process. When this is too much, the devitrification temperature becomes high. More preferably, it is 6-9 mass%. Moreover, it is preferable that BaO shall be 5-12 mass%. If this amount is too large, the devitrification temperature becomes high. More preferably, it is 6-11 mass%.
ＺｒＯ２は化学的耐久性を向上させる効果がある。本発明では１〜６質量％とする。多すぎると、熔解性が低下するおそれがある。好ましくは２〜５質量％である。 ZrO 2 has the effect of improving chemical durability. In this invention, it is 1-6 mass%. If the amount is too large, the meltability may be lowered. Preferably it is 2-5 mass%.
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、Ａｓ２Ｏ３、Ｓｂ２Ｏ３、Ｐ２Ｏ５、Ｆ、Ｃｌ、ＳＯ３を合量で２質量％以下添加できる。また、ガラスの化学的耐久性向上のため、Ｌａ２Ｏ３、ＴｉＯ２、ＳｎＯ２、ＺｎＯを合量で５質量％以下添加できる。さらに、Ｆｅ２Ｏ３、ＣｏＯ、ＮｉＯ、Ｎｄ２Ｏ３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質量％以下が好ましい。なお、Ｋ２Ｏ、Ｎａ２Ｏなどのアルカリ成分は、この若干量をＬｉ２Ｏに置換できる。Ｌｉ２Ｏの含有量は１質量％以下が好ましい。 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 a total amount in order to improve the meltability, clarity, and moldability of the glass. 2 mass% or less can be added. In order to improve the chemical durability of the glass, La 2 O 3 , TiO 2 , SnO 2 and ZnO can be added in a total amount of 5% by mass or less. Further, the color tone of the glass can be adjusted by adding a coloring material such as Fe 2 O 3 , CoO, NiO, Nd 2 O 3 or the like. The total content of the coloring material is preferably 1% by mass or less. In addition, some amount of alkali 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 1% by mass or less.
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。 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.
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。 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.
また、磁気ディスク上に必要に応じて所定のテクスチャを形成するテクスチャ加工は、基板をドーナツ状に加工し、エッチング、研磨、洗浄した後、化学強化処理の前に行われる。テクスチャ加工は、フッ酸の液または蒸気を使用して行える。テクスチャ加工されたガラス基板は化学強化処理がなされる。 Further, the texture processing for forming a predetermined texture on the magnetic disk as needed is performed before the chemical strengthening process after processing the substrate into a donut shape, etching, polishing and cleaning. Texturing can be performed using hydrofluoric acid liquid or steam. The textured glass substrate is chemically strengthened.
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。
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。
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。
保護層としては、５〜１００ｎｍ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、３ｎｍ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。
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.
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.
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.
As the protective layer, a carbon or silica layer having a thickness of 5 to 100 nm can be used. In order to form a lubricating layer, a perfluoropolyether liquid lubricant having a thickness of about 3 nm can be used.
＜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。表１には比較例として通常のソーダライムシリカガラスも記載した（例５）。
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、歪点温度を表１に併記する。
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。
<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. Table 1 also shows ordinary soda lime silica glass as a comparative example (Example 5).
Devitrification temperature of the glass, 10 4 poise temperature, also shown 10 2 poise temperature, the strain point temperature 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.
＜ガラス基板の強度テスト＞
その後、上記ガラスディスク基板の各１０枚について化学強化処理を行った。すなわち、例１〜４については４８０℃の熔融硝酸カリウム塩に、また、例５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。また、例１については、別途、５００℃の熔融硝酸カリウム塩に１０時間浸漬し、化学強化処理を行ったところ、表面圧縮応力層の厚みは２０μｍとなった。
<Strength test of glass substrate>
Thereafter, chemical strengthening treatment was performed on each of the 10 glass disk substrates. That is, the chemical strengthening treatment was performed by immersing in a molten potassium nitrate salt at 480 ° C. for Examples 1 to 4 and in a molten potassium nitrate salt at 450 ° C. for Example 5 for 10 hours.
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. Moreover, about Example 1, when it separately immersed in 500 degreeC molten potassium nitrate salt for 10 hours and performed the chemical strengthening process, the thickness of the surface compressive-stress layer became 20 micrometers.
表１に示した結果からは、本発明の実施例にかかるガラス基板は１０μｍ以上の表面圧縮応力層を有し、かつＣａＯの含有量が５．５重量％未満のものは、１４μｍ以上の表面圧縮応力層を有することがわかる。すなわち、同条件で化学強化処理を行った場合、本発明においては、ＣａＯの含有量が少なくなると、表面の圧縮応力相の深さは深くなり、化学強化が入りやすくなる傾向がある。具体的には、前述したように、ＣａＯの含有量は２〜５．５重量％であることが好ましい。 From the results shown in Table 1, a glass substrate according to an example of the present invention has a surface compressive stress layer of 10 μm or more, and a CaO content of less than 5.5% by weight is a surface of 14 μm or more. It can be seen that it has a compressive stress layer. That is, when the chemical strengthening treatment is performed under the same conditions, in the present invention, when the CaO content decreases, the depth of the compressive stress phase on the surface becomes deep, and chemical strengthening tends to easily occur. Specifically, as described above, the CaO content is preferably 2 to 5.5% by weight.
前記ガラスディスク基板の未強化品および強化品についてディスクの外周全周を支持し、内周部に荷重をかける曲げ強度テストを各１０枚のディスクについて行い平均強度を求めた。
例５の曲げ強度は未強化品が１２．０ｋｇｆ／ｍｍ２、深さ２０μｍの圧縮応力層をもつ強化品が３４．１ｋｇｆ／ｍｍ２であった。これに対し、例１〜４未強化品は１５．５ｋｇｆ／ｍｍ２であり、例１のガラス基板に対して深さ２０μｍの圧縮応力層を形成した強化品は４３．６ｋｇｆ／ｍｍ２であった。
The unstrengthened product and the reinforced product of the glass disk substrate were subjected to a bending strength test in which the entire outer periphery of the disk was supported and a load was applied to the inner periphery, and the average strength was determined for each of the 10 disks.
The bending strength of Example 5 was 12.0 kgf / mm 2 for the unreinforced product and 34.1 kgf / mm 2 for the reinforced product having a compression stress layer with a depth of 20 μm. On the other hand, the unreinforced product of Examples 1 to 4 was 15.5 kgf / mm 2 , and the reinforced product in which a compressive stress layer having a depth of 20 μm was formed on the glass substrate of Example 1 was 43.6 kgf / mm 2. It was.
これらの結果によれば、本発明のガラス基板は従来のソーダライムシリカガラスからなる基板と遜色のない化学強化処理ができ、その強化処理後の強度も従来のソーダライムシリカガラスと同等以上のものであり、磁気記録媒体用として、実用上充分な強度を持つものと認められる。このことは、現在磁気ディスク基板として広く用いられているアルミニウムの降伏強度１０ｋｇｆ／ｍｍ２に比べて上記の曲げ強度がはるかに大きいことからも裏付けられる。 According to these results, the glass substrate of the present invention can be chemically strengthened in the same manner as a conventional soda lime silica glass substrate, and the strength after the strengthening treatment is equal to or higher than that of the conventional soda lime silica glass. Therefore, it is recognized that the magnetic recording medium has sufficient strength for practical use. This is supported by the fact that the bending strength is much higher than the yield strength of 10 kgf / mm 2 of aluminum, which is widely used at present as a magnetic disk substrate.
＜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５０ｎｍのＣｒからなる下地層を形成した後、厚さ約６０ｎｍのＣｏ−３０原子％Ｎｉ合金磁性層を形成し、その上に厚さ約３０ｎｍ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ところ、例５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５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。これに対し例１〜４のガラス基板からなる磁気記録媒体は未強化品を用いたもの、強化品を用いたものともに変色が認められなかった。
<Moisture resistance test of magnetic recording media>
After forming an underlayer made of Cr having a thickness of about 50 nm 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 60 nm is formed, A carbon protective film having a thickness of about 30 nm was formed thereon, and a perfluoropolyether liquid lubricant was applied thereon to obtain a magnetic recording medium.
When these were subjected to a moisture resistance test by holding them at 80 ° C. and 90% RH for 100 hours, the unreinforced magnetic recording medium made of the glass substrate of Example 5 was 2 to 2 from the inner and outer end faces of the disk. Discoloration was observed from the interface between the Co—Ni alloy layer and the glass over the range of 3 mm to the in-plane, and in the reinforced magnetic recording medium comprising the glass substrate of Example 5, discoloration was also observed over the range of 1 to 2 mm. In contrast, the magnetic recording media comprising the glass substrates of Examples 1 to 4 showed no discoloration in both the unreinforced product and the reinforced product.
＜研磨テスト＞
鋳鉄定盤を備えた両面研磨機を用いて、アルミナ・ジルコニア系の１５００番の研磨剤を用いて、加工圧６０ｇｆ／ｃｍ２で研磨すると、ソーダライムシリカガラスが厚み変化３．７８μｍ／分であったのに対し、例１のガラスは、厚み変化４．３５μｍ／分であった。
また、酸化セリウム含浸発泡ポリウレタンパッドを備えた両面研磨機を用いて酸化セリウムからなる研磨剤を用いて、加工圧１００ｇｆ／ｃｍ２で研磨すると、ソーダライムシリカガラスが厚み変化０．７４μｍ／分であったのに対し、例１のガラスは、厚み変化１．１５μｍ／分であった。
<Polishing test>
Using a double-side polishing machine equipped with a cast iron surface plate and polishing with an alumina / zirconia-based No. 1500 abrasive at a processing pressure of 60 gf / cm 2 , the soda lime silica glass has a thickness change of 3.78 μm / min. In contrast, the glass of Example 1 had a thickness change of 4.35 μm / min.
When a double-side polishing machine equipped with a cerium oxide-impregnated foamed polyurethane pad is used to polish at a processing pressure of 100 gf / cm 2 using a polishing agent made of cerium oxide, the soda lime silica glass has a thickness change of 0.74 μm / min. In contrast, the glass of Example 1 had a thickness change of 1.15 μm / min.
Claims (11)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| JP2006287485A JP2007051064A (en) | 1995-04-20 | 2006-10-23 | Glass for magnetic disk substrate, glass substrate for magnetic disk and magnetic disk |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9547495 | 1995-04-20 | ||
| JP2006287485A JP2007051064A (en) | 1995-04-20 | 2006-10-23 | Glass for magnetic disk substrate, glass substrate for magnetic disk and magnetic disk |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10033196A Division JPH092836A (en) | 1995-04-20 | 1996-04-22 | Glass substrate for magnetic disc and magnetic disc |
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| Application Number | Title | Priority Date | Filing Date |
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| JP2007125292A Division JP2007210885A (en) | 1995-04-20 | 2007-05-10 | Manufacturing method of glass substrate for magnetic disk |
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| JP2007051064A true JP2007051064A (en) | 2007-03-01 |
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| JP2006287485A Pending JP2007051064A (en) | 1995-04-20 | 2006-10-23 | Glass for magnetic disk substrate, glass substrate for magnetic disk and magnetic disk |
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| WO2011019010A1 (en) | 2009-08-10 | 2011-02-17 | Hoya株式会社 | Glass for magnetic recording medium substrate, magnetic recording medium substrate and method for producing same, and magnetic recording medium |
| WO2013047675A1 (en) * | 2011-09-29 | 2013-04-04 | セントラル硝子株式会社 | Chemically strengthened glass and method for producing same |
| JP5278633B1 (en) * | 2011-09-29 | 2013-09-04 | セントラル硝子株式会社 | Cover glass for display device and manufacturing method thereof |
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- 2006-10-23 JP JP2006287485A patent/JP2007051064A/en active Pending
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| WO2011019010A1 (en) | 2009-08-10 | 2011-02-17 | Hoya株式会社 | Glass for magnetic recording medium substrate, magnetic recording medium substrate and method for producing same, and magnetic recording medium |
| US8603653B2 (en) | 2009-08-10 | 2013-12-10 | Hoya Corporation | Glass for magnetic recording medium substrate, magnetic recording medium substrate and method of manufacturing the same, and magnetic recording medium |
| WO2013047675A1 (en) * | 2011-09-29 | 2013-04-04 | セントラル硝子株式会社 | Chemically strengthened glass and method for producing same |
| JP5267753B1 (en) * | 2011-09-29 | 2013-08-21 | セントラル硝子株式会社 | Chemically tempered glass and method for producing the same |
| JP5278633B1 (en) * | 2011-09-29 | 2013-09-04 | セントラル硝子株式会社 | Cover glass for display device and manufacturing method thereof |
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| US8885447B2 (en) | 2012-03-29 | 2014-11-11 | Hoya Corporation | Glass for magnetic recording medium substrate, glass substrate for magnetic recording medium, and their use |
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