JP3912575B2 - Method for manufacturing glass substrate for magnetic recording medium, and method for manufacturing magnetic recording medium - Google Patents

Description

【００６０】
上記表にしめすように、浮上特性（ヘッドクラッシュやフライスティクション）も良好な磁気記録媒体が得られた。
【００６１】
（比較例１）
実施例１における化学強化後のケイフッ酸処理に変え、硫酸処理（濃度：１０重量％、時間：１００秒）に変えた以外は、実施例１と同様にして磁気記録媒体用基板、磁気記録媒体を作製した。その結果、Ｒｍａｘ＝６．１５ｎｍ、ＯＢＡ％３ｎｍ＝７２％となり、ＯＢＡ％３ｎｍ＝４０％±２０％の規格の範囲内に収めることができなかった。これは、ＡＦＭの測定バラツキの原因と考えられる異常突起が十分に除去できなかったことなどが原因で、ＯＢＡ％３ｎｍを制御できなかったと考えられる。尚、この得られた磁気記録媒体の摩擦係数を測定したところ、３．５となり３を超え、磁気ヘッドの吸着を回避することができなかった。
【００６２】
本発明は、上述の実施例に限定されるものではない。
【００６３】
例えば、ＯＢＡのスライスは３ｎｍに限られない。各種媒体に応じて適宜逮択される。
【００６４】
媒体の表面粗さを作る場所は、基板表面に限られない。例えば、下地層、保護層等にテクスチャーを形成してもよい。所定の表面粗さを形成する方法も、エッチング法に限らず、メカニカルテクスチャー、スパッタテクスチャー、レーザーテクスチャーや、微粒子を混在させこの微粒子によって所定の表面粗さにしても良い。但し、好ましくは、各突起の曲率半径等がほぼ同じとなるテクスチャー方法が好ましい。
【００６５】
表面状態を測定する手法として、ＡＦＭ（原子間力顕微鏡）の代わりに、ＳＴＭ（走査型トンネル顕微鏡）や、触針式表面粗さ計を用いることが可能である。但し、ＡＦＭ（原子間力顕微鏡）の場合は、比較的容易に、表面状態を正確に、高精度、高分解能で測定できる点で、他の測定方法に比べ優れている。
【００６６】
実施例２における潤滑剤も各種媒体によって適した潤滑剤が選定される。潤滑剤の形成方法もディップ法（浸漬法）に限らない。真空蒸着によって潤滑剤を形成しても良い。
【００６７】
本発明はＣＳＳ方式の磁気記録媒体に限らず、実施例７〜９に示すように磁気ヘッドの低浮上化がより進展するロードアンロード方式の磁気記録媒体におけるフライングスティクション（Flying Stiction）回避のための管理手法としても有効である。
また、ポリッシング工程後の表面粗さ制御工程における化学的処理工程に使用する薬液としてケイフッ酸に限らず、硫酸、燐酸、硝酸、フッ酸、ケイフッ酸のなかから選択される少なくとも１種の酸、又はアルカリを含む処理液で処理しても構わない。
【００６８】
基板の大ききも２．５インチに限らず、１インチ、３インチ、３．５インチなどの各種サイズに適用できる。
【００６９】
また、本発明は、磁気記録媒体用基板や磁気記録媒体に限らず、光ピックアップレンズなどが搭載されたヘッドスライダーを利用して記録再生する光磁気記録媒体用基板や光磁気記録媒体への適用もでき、それらの表面の管理手法としても有効である。
【００７０】
【発明の効果】
本発明によれば、Ｒｍａｘ１５ｎｍ以下（特にＲｍａｘ１０ｎｍ以下）の表面粗さを有する情報記録媒体用基板（磁気記録媒体用基板）及び情報記録媒体（磁気記録媒体）において、表面粗さに基づく摩擦係数を精度良く設計又は管理できる。
また、本発明によれば、Ｒｍａｘ１５ｎｍ以下（特にＲｍａｘ１０ｎｍ以下）の表面粗さを有する表面状態の管理において、ＡＦＭの測定バラツキの問題を解決できる。
【図面の簡単な説明】
【図１】ＡＦＭ測定によるＲｍａｘと摩擦係数との関係を表す図である。
【図２】ＡＦＭ測定によるＲａと摩擦係数との関係を表す図である。
【図３】ＡＦＭ測定によるＲｍａｘとグライドハイトとの関係を表す図である。
【図４】ＡＦＭ測定によるＢＡ％と真のピーク高さからの深さとの関係を説明するための図である。
【図５】ＯＢＡ％＠３ｎｍと摩擦係数との関係を表す図である。
【図６】潤滑剤を塗布した媒体におけるＯＢＡ％＠３ｎｍと摩擦係数との関係を表す図である。
【図７】最大突起高さ付近におけるＢＡ％とベアリング高さとの関係を表す図である。
【図８】オフセットベアリングエリアを説明するための図である。
【図９】ヘッドと突起との接触状態を説明するための図である。
【図１０】ＢＡ％＠４ｎｍと摩擦係数との関係を表す図である。
【図１１】磁気記録媒体の媒体設計から、磁気記録媒体用基板、及び磁気記録媒体の製造方法を説明するための図である。
【図１２】磁気記録媒体用基板、及び磁気記録媒体の製造方法を説明するための図である。
【図１３】化学強化処理後、ガラス基板の表面をケイフッ酸処理して得られた磁気記録媒体用ガラス基板のＲｍａｘとＯＢＡ％３ｎｍとの関係を示す図である。
【図１４】化学強化処理後、ガラス基板の表面を硫酸処理して得られた磁気記録媒体用ガラス基板のＲｍａｘとＯＢＡ％３ｎｍとの関係を示す図である。
【図１５】化学強化後のケイフッ酸による処理時間とＲａとの関係を示す図である。
【図１６】化学強化後のケイフッ酸による処理時間とＲｍａｘとの関係を示す図である。
【図１７】化学強化後のケイフッ酸による処理時間とＯＢＡ％３ｎｍとの関係を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a friction coefficient management method based on surface roughness, an information recording medium substrate, an information recording medium, a manufacturing method thereof, and the like.
[0002]
[Prior art]
There is a magnetic recording medium mounted on an HDD (hard disk drive) as an information recording medium. In recent years, the remarkable increase in recording capacity of HDDs has been realized, for example, by a reduction (lower gliding) of the gap between the head and the medium (the flying height of the head) during recording and reproduction. Although the reduction in the gap between the head and the medium is realized by an effort to smooth the surface of the medium, the smoothing of the surface of the medium, on the other hand, causes an adsorption problem between the head and the medium. Therefore, the design of the medium surface always suffers from the trade-off between low glide and avoidance of head adsorption.
In order to solve the contradictory problem of smoothing the surface of the media required for low glide and avoiding the tendency to adsorption (= tendency to increase the friction coefficient) due to smoothing, precise surface design is required. It is.
[0003]
Conventionally, surface roughness parameters such as Rmax and Ra by AFM (Atomic Force Microscope), normalized roughness Ra / Rmax, and the like have been used for shape management of the medium surface from the viewpoint of easy process feedback. It was.
[0004]
[Problems to be solved by the invention]
However, when the relationship between Rmax, Ra, Ra / Rmax measured by AFM and the friction coefficient was examined, in the low glide region (about 10 nm or less) where a more precise surface design is required, such a surface management method is too much. Was found to be too sensitive. FIGS. 1 and 2 show the relationship between the substrate surface roughness (Rmax (FIG. 1) and Ra (FIG. 2)) measured by AFM and the friction coefficient. Even if it is about 7.5 nm, the friction coefficient cannot be managed with parameters such as Rmax and Ra so that the friction coefficient has a width of about 0.7 to 2.2.
[0005]
On the other hand, a method for managing the friction coefficient by correlating the bearing area (bearing ratio) and the friction coefficient has been proposed. Specifically, in a magnetic recording medium in which a texture is formed on the surface of the medium, the texture (unevenness) is formed so that the bearing area at a depth of 20 nm from the highest surface is 20% or less, and the friction coefficient is specified to be small. A technique has been proposed (Japanese Patent Laid-Open No. 5-189756). The bearing area is the ratio of the area that appears when the irregularities in the measurement area are cut at an arbitrary contour surface (horizontal plane) to the measurement area, and is measured using an AFM (atomic force microscope) or the like. it can.
However, this technique mainly focuses on a magnetic recording medium in which the surface of an aluminum alloy substrate having a NiP film formed thereon is polished with loose abrasive grains and textured, and a bearing at a depth of 20 nm from the highest surface. Since the area is a parameter (that is, a magnetic recording medium having a rough surface (20 nm or more) is targeted), the magnetic recording medium having a surface roughness of Rmax 15 nm or less is quite useful as a friction coefficient management technique. There is no problem.
Such a technique is derived from an experiment and is not derived based on a theory such as a true contact area described later.
Further, for example, when the texture forming method is different, the total number of protrusions, the shape of the protrusions (the radius of curvature of the protrusions, the horizontal cross-sectional shape, the height of the protrusions), and the like are different. In this case, it can be said that the above technique is not at all useful as a management method of the friction coefficient of the medium surface since the coefficients are different.
[0006]
The present invention has been made under the above-mentioned background, and provides a novel surface management technique that enables accurate surface design even in a low glide region of about 10 nm or less, and is designed by this surface management technique. Another object of the present invention is to provide an information recording medium substrate (magnetic recording medium substrate), an information recording medium (magnetic recording medium), a manufacturing method thereof, and the like.
[0007]
[Means for Solving the Problems]
As a result of intensive studies on the frictional force acting on the magnetic head, the present inventor has found the following.
The frictional force acting on the magnetic head can be expressed by the following equation (1) because there is usually a lubricant or moisture in the air on the contact surface.
F = μN + F1 + F2 + F3 + ... (1)
In the above equation (1), F is the frictional force, μ is the coefficient of static friction, N is the normal drag, F1 is the meniscus force due to the lubricant, F2 is the meniscus force of moisture, and F3 is due to other substances (such as organic contamination). For example, adhesion force. The contact surface between the head (or the pad (pad) of the slider with pad for the purpose of reducing the contact area with the magnetic disk) and the surface of the medium with a certain surface roughness is uneven on the surface of the medium. Therefore, the true contact area is very small compared to the apparent contact area. When the load of the head is applied, the top of the projection is crushed by the pressure concentrated on the top of the projection, the real contact area increases, and the frictional force increases. However, there is no change in the apparent contact area. In the true contact surface, adhesion between the surfaces in contact with each other occurs, so as the true contact area increases, a large force (force to cut off frictional force) is required to separate (shear) the adhesion surface. . From the above, it can be said that it is μN∝true contact area.
Therefore, from the viewpoint of surface design, if a shape parameter representative of the true contact area between the magnetic head and the medium is extracted, it is theoretically assumed that the index is sensitive to friction.
[0008]
When the surface roughness obtained by precisely polishing the glass substrate surface is Rmax 15 nm or less, the true contact area between the magnetic head and the medium is proportional to the total number of protrusions that the head can contact (FIG. 9). When the relationship between the total number of protrusions at a predetermined depth from the maximum protrusion height to 4 nm in the 5 μm square AFM image and the friction coefficient is examined, the friction coefficient depends on the total number of protrusions (protrusion density) at the predetermined depth (proportional). ) However, since a certain amount of time is required to calculate the protrusion density from the AFM data, it is difficult to say that process feedback is easy, and it is not a parameter suitable for a process monitor. Therefore, it was examined whether the protrusion density at a predetermined depth could be directly represented by some AFM measurement value. Specifically, for example, when the relationship between the bearing area at the depth position from the maximum protrusion height (Rmax) to 4 nm in the 5 μm square (5 μm × 5 μm) AFM image and the total number of protrusions at the same depth position is examined, It was found that the bearing area at the predetermined depth position is proportional to the protrusion density at the predetermined depth. Further, when the relationship between the bearing area at the depth position from the maximum protrusion height (Rmax) to 4 nm in the 5 μm square AFM image and the friction coefficient was examined, the relationship of FIG. 10 was obtained, and the relationship at the predetermined depth position was obtained. It was found that the bearing area and the coefficient of friction have a correlation. The bearing area at the predetermined depth position can be easily obtained as an AFM measurement result, is easy to provide process feedback, and is a parameter suitable for process monitoring.
As described above, as a shape parameter representing the true contact area, for example, a magnetic recording medium having a surface roughness of Rmax 15 nm or less by using a bearing area in the vicinity of a depth of 4 nm from the maximum protrusion height (Rmax) as a parameter. It has been found that the coefficient of friction can be managed with respect to the above.
[0009]
However, when the bearing area is measured by AFM, there is a measurement variation in AFM itself. In addition, the presence of abnormal protrusions (irregular points) that do not affect the glide height and do not affect the friction coefficient, such as dust, may cause variations in AFM measurement. Because of these variations, Rmax by AFM measurement does not represent the true peak height. These variations are usually about 1 to 2 nm and have a great influence on a magnetic recording medium having a surface roughness (texture) of Rmax 15 nm or less. In particular, for a magnetic recording medium having a surface roughness (texture) of Rmax 10 nm or less, the influence of variation of 1 to 2 nm is extremely large. For example, if the maximum protrusion height is shifted by 1 to 2 nm, the slice level is also shifted by 1 to 2 nm, and the friction coefficient may not be managed in the bearing area corresponding to this slice level. Even if management is possible, the friction coefficient of the magnetic recording medium managed in this bearing area varies greatly (not optimal) because of the slicing level being inconsistent, and is insufficient as a friction coefficient management method. I found out.
[0010]
As a result of further research, when the bearing curve is repeatedly measured by AFM, the value of the bearing area at which the measured value of the bearing height starts to fluctuate near the maximum protrusion height (BA = 0%). It is found that the problem of AFM measurement variation can be solved by using various AFM measurement values excluding data from BA = 0% to the bearing area value where the bearing height measurement value starts to vary rapidly. It was.
For example, when a bearing curve is repeatedly measured with an AFM (Atomic Force Microscope) on a surface having a surface roughness of Rmax of about 15 nm or less, the bearing height is measured in the vicinity of the maximum protrusion height (BA = 0%). The bearing area value at which the value starts to fluctuate rapidly is obtained (0.5% in FIG. 7), and the corresponding bearing height (true peak height) is obtained from the bearing curve (FIG. 8). The bearing area at a predetermined depth (3 nm in FIG. 8) from this true peak, in other words, the bearing area (offset bearing area: OBA%) when the slice level is offset (subtracted) and the friction coefficient of the medium surface The correlation is examined by changing the predetermined depth, and the predetermined depth (predetermined slice level) at which the change amount of the bearing area corresponding to the change amount of the friction coefficient becomes large is obtained from the correlation. By managing the friction coefficient based on the correlation (for example, FIG. 5) between the bearing area value (offset bearing area value) and the friction coefficient at the predetermined slice level, the friction coefficient based on the surface roughness is accurately managed. I found out that I can do it.
Thus, by adopting OBA% as an index having high sensitivity to friction and adopting this OBA% as a process monitor index, the friction coefficient based on the surface roughness can be accurately managed.
Further, in designing the surface of the medium, the correlation between the formation condition for forming the surface state of the medium (the total number of protrusions, the curvature, etc.) and the OBA% is obtained in advance, so that the OBA% and the friction coefficient are obtained. Through the correlation, the friction coefficient based on the surface roughness can be designed with high accuracy, and a magnetic recording medium having a desired friction coefficient can be obtained by selecting the formation conditions.
[0011]
The present invention has the following configuration.
[0012]
(Configuration 1) An information recording medium substrate having a surface roughness of Rmax 15 nm or less,
The surface area of the substrate has a bearing area value (offset) from a bearing height (true peak height) corresponding to a bearing area value of 0.2% to 1.0% to a depth of 0.5 to 5 nm (predetermined slice level). A substrate for an information recording medium, wherein the bearing area value is 90% or less.
[0013]
(Configuration 2) An information recording medium substrate having a surface roughness of Rmax 15 nm or less,
When the surface of the substrate has a slice level corresponding to 20 to 45% of Rmax from a bearing height (true peak height) corresponding to a bearing area value of 0.2% to 1.0%, A substrate for an information recording medium, wherein a bearing area value (offset bearing area value) is 90% or less.
[0014]
(Structure 3) The information recording medium substrate according to Structure 1 or 2, wherein the information recording medium substrate is a glass substrate whose surface has been precisely polished and / or etched.
[0015]
(Configuration 4) An information recording medium having a surface roughness of Rmax 15 nm or less on the medium surface,
The surface of the information recording medium has a bearing area in a range of 0.5 to 5 nm (predetermined slice level) from a bearing height (true peak height) corresponding to a bearing area value of 0.2% to 1.0%. An information recording medium having a value (offset bearing area value) of 90% or less.
[0016]
(Configuration 5) An information recording medium having a surface roughness of Rmax 15 nm or less on the medium surface,
A depth corresponding to 20 to 45% of Rmax from a bearing height (true peak height) corresponding to a bearing area value of 0.2% to 1.0% is defined as a slice level. The information recording medium has a bearing area value (offset bearing area value) of 90% or less.
[0017]
(Structure 6) The information recording medium according to Structure 4 or 5, wherein a friction coefficient based on the surface roughness of the medium surface is 3 or less.
[0018]
(Configuration 7) The configurations 4 to 6 are characterized in that the correlation between the friction coefficient and the offset bearing area in the information recording medium formed with various lubricants is examined, and a lubricant that reduces the frictional force by the lubricant is employed. The information recording medium described.
[0019]
(Configuration 8) The lubricant is classified as PFPE (perfluoroalkyl polyether), includes an ether bond in the main chain, and-(OCF ₂ F ₂ ) M (OCF ₂ (8) The information recording medium according to (7), which is a lubricant having an n-linear structure and having a hydroxyl group as a terminal group.
[0020]
(Configuration 9) A step of immersing a glass substrate in a heated chemical strengthening treatment liquid, ion-exchanging ions on the surface of the glass substrate with ions in the chemical strengthening treatment liquid, and chemically strengthening the glass substrate;
And a step of treating the surface of the glass substrate pulled up from the chemical strengthening treatment liquid with a treatment liquid containing silicic acid, and a method for producing a glass substrate for an information recording medium.
[0021]
(Configuration 10) Polishing the surface of the glass substrate and immersing the glass substrate in a heated chemical strengthening treatment liquid, and ion-exchanging ions on the surface of the glass substrate with ions in the chemical strengthening treatment liquid to chemically strengthen the glass substrate. In the method for producing a glass substrate for information recording medium, comprising:
Having a step of controlling the surface of the glass substrate to a desired surface roughness by chemical treatment before the step of chemically strengthening,
And a step of treating the surface of the glass substrate pulled up from the chemical strengthening treatment liquid with a treatment liquid containing silicic acid, and a method for producing a glass substrate for an information recording medium.
[0022]
(Structure 11) In the structure 10, the chemical treatment is performed with a treatment liquid containing at least one acid selected from sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and silicofluoric acid, or an alkali. The manufacturing method of the glass substrate for information recording media of description.
[0023]
(Structure 12) The method for producing a glass substrate for an information recording medium according to any one of Structures 9 to 11, wherein the concentration of silicic acid is 0.01 to 10% by weight.
[0024]
(Structure 13) A method for producing an information recording medium, comprising forming at least a recording layer on the surface of the glass substrate for information recording medium obtained by Structures 9 to 12.
[0025]
(Configuration 14) A friction coefficient management method based on surface roughness on the surface of an information recording medium having a surface roughness of Rmax 15 nm or less,
When the bearing curve is repeatedly measured with an AFM (Atomic Force Microscope), the bearing area value at which the measured value of the bearing height starts to fluctuate near the maximum protrusion height (BA = 0%) is obtained. Find the bearing height (true peak height) corresponding to the bearing area value from the bearing curve,
The correlation between the bearing area at the predetermined depth from the true peak height and the friction coefficient based on the surface roughness is examined by changing the predetermined depth,
From the correlation, a predetermined depth (predetermined slice level) at which the amount of change in the bearing area corresponding to the amount of change in the friction coefficient is large is obtained,
A friction coefficient management method based on surface roughness, wherein friction coefficient management based on surface roughness is performed using a bearing area value (offset bearing area value) at the predetermined slice level.
[0026]
(Configuration 15) A friction coefficient management method based on surface roughness in an information recording medium having a surface roughness of Rmax 15 nm or less on the medium surface,
Friction based on surface roughness characterized in that the friction coefficient based on surface roughness is managed using a bearing area at a depth of 0.5 to 7 nm (slice level) from the maximum height (Rmax) measured by AFM measurement. Coefficient management technique.
[0027]
(Configuration 16) A friction coefficient management method based on surface roughness in an information recording medium having a surface roughness of Rmax 15 nm or less on the medium surface,
The friction coefficient based on the surface roughness is managed using the bearing area when the depth corresponding to 20 to 40% of Rmax is set as the slice level from the maximum height (Rmax) by AFM measurement. Friction coefficient management method based on surface roughness.
[0028]
(Configuration 17) An information recording medium manufacturing method for manufacturing an information recording medium having a desired medium surface based on the friction coefficient management method based on the surface roughness of configurations 14 to 16.
[0029]
(Configuration 18) In the method for manufacturing an information recording medium substrate for reflecting the surface of the information recording medium substrate on the surface of the information recording medium to obtain a desired medium surface, the friction coefficient based on the surface roughness of configurations 14 to 16 A method for manufacturing an information recording medium substrate, which manufactures an information recording medium substrate having a desired substrate surface based on the above management method.
[0030]
(Configuration 19) A method for managing a surface state of a substrate surface for an information recording medium having a surface roughness of Rmax 15 nm or less,
When the bearing curve is repeatedly measured with an AFM (Atomic Force Microscope), the bearing area value at which the measured value of the bearing height starts to fluctuate near the maximum protrusion height (BA = 0%) is obtained.
A surface state management method using various AFM measurement values excluding data from BA = 0% to a bearing area value at which the measurement value of the bearing height starts to vary rapidly.
[0031]
(Configuration 20) An information recording medium substrate manufacturing method for manufacturing an information recording medium substrate having a desired substrate surface based on the surface state management method of Configuration 19.
[0032]
(Configuration 21) A method for managing the surface state of an information recording medium surface having a surface roughness of Rmax 15 nm or less,
When the bearing curve is repeatedly measured with an AFM (Atomic Force Microscope), the bearing area value at which the measured value of the bearing height starts to fluctuate near the maximum protrusion height (BA = 0%) is obtained.
A surface state management method using various AFM measurement values excluding data from BA = 0% to a bearing area value at which the measurement value of the bearing height starts to vary rapidly.
[0033]
(Configuration 22) An information recording medium manufacturing method for manufacturing an information recording medium having a desired medium surface based on the surface state management method of Configuration 21.
[0034]
[Action]
According to Configuration 1, with respect to the surface of the information recording medium substrate (magnetic recording medium substrate), the bearing area value 0.2 where the measured value of the bearing height starts to vary rapidly from the experiment by the method of Configuration 14 described later. % To 1.0%, and 0.5 to 5 nm depth from the true peak height is determined as the slice level, and the bearing area value (offset bearing area value: OBA%) at this slice level is 90% or less. Thus, an information recording medium (magnetic recording medium) having a small friction coefficient (usually 3 or less) based on the surface roughness when it is used as an information recording medium (magnetic recording medium) can be obtained.
[0035]
Further, as in the configuration 2, the slice level depth in the configuration 1 is set to a slice level corresponding to 20 to 45% of Rmax, and the bearing area value (offset bearing area value: OBA%) in this slice level is used. Is set to 90% or less, an information recording medium (magnetic recording medium) having a small friction coefficient (usually 3 or less) based on the surface roughness when an information recording medium (magnetic recording medium) is obtained.
In particular, configurations 1 and 2 are suitable when the surface roughness of the information recording medium substrate (magnetic recording medium substrate) is Rmax 10 nm or less.
For an information recording medium substrate (magnetic recording medium substrate) with Rmax = 10 to 11 nm, for example, slice level = 4 nm (36 to 40% of Rmax) and OBA% = 70% or less are preferable. For an information recording medium substrate (magnetic recording medium substrate) of about Rmax = 7 to 8 nm, for example, slice level = 3 nm (38 to 43% of Rmax), OBA% = 90% or less (CSS magnetic system) In the case of a recording medium substrate, preferably 40% ± 20% (20-60%), and in the case of a load / unload type magnetic recording medium substrate, preferably 70% ± 20% (50-90%). . For an information recording medium substrate (magnetic recording medium substrate) of about Rmax = 5-6 nm, for example, slice level = 1.5-2 nm (25-40% of Rmax), OBA% = 80% or less ( In the case of a load / unload type magnetic recording medium substrate, 60% ± 20% (40 to 80%) is preferable. In addition, for an information recording medium substrate (magnetic recording medium substrate) having an extremely smooth Rmax of 3 nm or less, the slice level is 0.5 to 1.3 nm (20 to 43% of Rmax), for example. , OBA% = 90% or less (in the case of a substrate for a magnetic recording medium of a load / unload method, 70% ± 20% (50 to 90%) is preferable.
Note that the bearing area value at which the measured value of the bearing height starts to fluctuate rapidly may be about 0.5%, specifically 0.2 to 1.0%, preferably 0.3 to 0.7%. More preferably, it may be a value within the range of 0.4 to 0.6%.
[0036]
According to the configuration 3, the information recording medium substrate (magnetic recording medium substrate) is a glass substrate whose surface is precisely polished and / or etched. Magnetic recording medium substrate) can be obtained reliably and easily. As a specific manufacturing method of the etching process, means of configurations 9 to 12 described later can be given.
[0037]
According to configurations 4 and 5, as in configurations 1 and 2, the information recording medium (magnetic recording medium) has a surface roughness of Rmax 15 nm or less on the medium surface, and is based on the surface roughness (texture) of the medium surface. An information recording medium (magnetic recording medium) having a small friction coefficient (usually 3 or less) can be obtained.
In particular, configurations 4 and 5 are suitable for an information recording medium (magnetic recording medium) having a surface roughness of Rmax 10 nm or less on the surface of the information recording medium (magnetic recording medium surface).
In the case of an information recording medium (magnetic recording medium) having a surface roughness Rmax = 10 to 11 nm on the medium surface, for example, slice level = 4 nm (36 to 40% of Rmax) and OBA% = 70% or less. preferable. For an information recording medium (magnetic recording medium) of Rmax = 7 to 8 nm, for example, slice level = 3 nm (38 to 43% of Rmax), OBA% = 90% or less (in the case of a CSS type magnetic recording medium) In the case of a load / unload type magnetic recording medium, preferably 70% ± 20% (50-90%). For an information recording medium (magnetic recording medium) with Rmax = 5-6 nm, for example, slice level = 1.5-2 nm (25-40% of Rmax), OBA% = 80% or less (load unloading method) In the case of the above magnetic recording medium, 60% ± 20% (40 to 80%)) is preferable. In addition, in an information recording medium (magnetic recording medium) having a super-smooth Rmax of 3 nm or less, for example, slice level = 0.5 to 1.3 nm (20 to 43% of Rmax), OBA% = 90% or less (in the case of a load / unload type magnetic recording medium, preferably 70% ± 20% (50 to 90%).
Note that the bearing area value at which the measured value of the bearing height starts to fluctuate rapidly may be about 0.5%, specifically 0.2 to 1.0%, preferably 0.3 to 0.7%. More preferably, it may be a value within the range of 0.4 to 0.6%.
In order to obtain the medium surface of constitutions 4-6, the surface state of the medium surface is controlled by the substrate surface as in constitutions 1-3, and an underlayer, a magnetic layer, a protective layer, a lubricating layer, etc. are provided on the substrate surface. Examples thereof include a method for obtaining a desired medium surface by forming a film, and a method for obtaining a desired medium surface by controlling the surface state of any layer formed on the substrate. Examples of the method for controlling the surface state include mechanical treatment, chemical treatment, crystal grain growth by sputtering, and optical treatment such as laser light.
In addition, by using the glass substrate for information recording media (magnetic recording media) whose surface is precisely polished and / or etched as shown in the configuration 3, the information recording media (magnetic recording media) described in the configurations 4 to 6 are used. Is preferable because it is obtained reliably and easily. In addition, since there is no need to provide a layer for controlling the surface condition of the medium surface between the magnetic layer and the magnetic head, the spacing (flying height) between the magnetic recording medium and the magnetic head is reduced, and high recording density reproduction is achieved. Is preferable.
[0038]
According to Configuration 6, by defining the friction coefficient based on the surface roughness (texture) of the medium surface to be 3 or less, an information recording medium (magnetic recording medium) having a friction coefficient based on the surface roughness of 3 or less is ensured. Is obtained. The friction coefficient is preferably 2 or less, more preferably 1.5 or less.
[0039]
According to Configuration 7, the correlation between the friction coefficient and the offset bearing area in the information recording medium (magnetic recording medium) on which various types of lubricants are formed can be examined, and a lubricant that reduces the frictional force due to the lubricant can be selected. .
In addition, lubrication in which the frictional force due to the lubricant is reduced by performing the same evaluation on the surface formed with the lubricant using the friction coefficient management method based on the surface roughness described in the configurations 14 to 16. Needless to say, the agent can be selected.
[0040]
According to Configuration 8, the lubricant is classified as PFPE (perfluoroalkyl polyether), has an ether bond in the main chain, has a-(OCF2F2) m (OCF2) n-linear structure, and has a hydroxyl group as a terminal group. By using the agent, the frictional force due to the lubricant can be reliably reduced.
[0041]
Configurations 9 to 14 are specific methods for obtaining the information recording medium substrate (magnetic recording medium substrate) of configurations 1 to 3 and the information recording media (magnetic recording medium) of configurations 4 to 8. However, the information recording medium substrate (magnetic recording medium substrate) having the configurations 1 to 3 and the information recording medium (magnetic recording medium) having the configurations 4 to 8 are not limited by the following manufacturing method.
According to Configuration 9, a step of immersing a glass substrate in a heated chemical strengthening treatment liquid, chemically exchanging ions on the surface of the glass substrate with ions in the chemical strengthening treatment liquid, and chemically strengthening the glass substrate; And a step of treating the surface of the glass substrate pulled up from the surface with a treatment liquid containing silicic acid, it is possible to suppress variations in surface roughness and to control OBA% accurately. The inventors of the present invention have a measurement variation of the AFM itself when the bearing area is measured by the AFM (measurement variation due to an abnormal protrusion that does not affect the glide height and does not affect the friction coefficient). With regard to the chemically tempered glass substrate, the cause was investigated, and abnormal projections or the like causing measurement variations were often caused in the chemical strengthening treatment process, or the surface roughness was reduced by the chemical strengthening treatment process after precision polishing. It was found that the cause was an increase. And it was thought that OBA% can be controlled accurately by suppressing the cause of this measurement variation. By performing silicic acid treatment as a treatment after the chemical strengthening treatment, abnormal projections or the like causing the above-described measurement variation are removed, and OBA% can be strictly controlled.
Moreover, like the structure 10, it is preferable to control the glass substrate surface to a desired surface roughness by chemical treatment before the chemical strengthening step. When chemical treatment (excluding silicic acid treatment) that controls the surface roughness after chemical strengthening is performed, the chemical strengthening layer (compressive stress layer, tensile stress layer) is changed and the flatness of the substrate is deteriorated. It is not preferable because it causes.
As in Configuration 11, the chemical treatment is performed with a treatment solution containing at least one acid selected from sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and silicofluoric acid, or an alkali. The concentration of these acids and alkalis, the processing temperature, and the processing time are appropriately adjusted according to the surface state of the substrate to be obtained.
As in Structure 12, the silicic acid concentration in the silicic acid treatment after the chemical strengthening treatment is preferably 0.01 to 10% by weight. If the amount is less than 0.01% by weight, abnormal projections or the like that cause variation in AFM measurement may not be reliably removed. If the amount exceeds 10% by weight, the glass substrate surface is etched and before chemical strengthening treatment. This is not preferable because the surface state of the substrate surface controlled by chemical treatment changes or the surface roughness increases. Preferably, 0.05 to 7% by weight, and more preferably 0.1 to 5% by weight is preferable in terms of controllability.
Further, as in Configuration 13, by forming at least a recording layer (magnetic layer) on the surface of the glass substrate for information recording media (magnetic recording media) obtained by Configurations 9 to 12, a desired friction coefficient can be obtained. An information recording medium (magnetic recording medium) is obtained. The material of the magnetic layer in the present invention is not particularly limited. A known magnetic layer material can be used. In addition to the magnetic layer, an underlayer that improves the magnetic properties by controlling the crystal orientation of the magnetic layer, a protective layer that improves the corrosion resistance and mechanical durability of the magnetic recording medium, a lubricating layer that adjusts the friction coefficient, and an underlayer Alternatively, a seed layer for controlling the crystal grain size and grain size distribution of the magnetic layer can be formed. For these seed layer, underlayer, protective layer, and lubricating layer, known materials can be used.
[0042]
According to Configuration 14, since the correlation between the offset bearing area and the friction coefficient (for example, FIG. 5) is proportional and highly sensitive, an information recording medium (magnetic recording medium) is used by using the offset bearing area. The friction coefficient based on the surface roughness of the medium) surface can be designed or managed with high accuracy.
Particularly, in the configuration 14, when managing the friction coefficient based on the medium surface roughness of the information recording medium (magnetic recording medium), the information recording medium substrate (magnetic recording medium substrate) and the information recording medium (magnetic recording medium) It can be applied to surface roughness management, and is suitable for those whose surface roughness is Rmax 15 nm or less, and further Rmax 10 nm or less. According to Configuration 15, using the bearing area at a depth (slice level) of 0.5 to 7 nm from the maximum projection height (Rmax), and according to Configuration 16, from the maximum projection height (Rmax), Rmax Using the bearing area when the depth corresponding to 20 to 45% is set as the slice level, the friction coefficient based on the surface roughness is managed, and the surface roughness is influenced by the AFM measurement variation. It is possible to roughly design or manage the coefficient of friction based on
[0043]
According to the configuration 17, by manufacturing an information recording medium (magnetic recording medium) having a desired medium surface based on the friction coefficient management method based on the surface roughness of the configurations 14 to 16, a desired friction coefficient is obtained. An information recording medium (magnetic recording medium) having As a method for obtaining an information recording medium (magnetic recording medium) having a desired medium surface, the surface state of the medium surface is controlled by the substrate surface, and an underlayer, a recording layer (magnetic layer), a protective layer, a lubrication layer are provided on the substrate surface. Examples thereof include a method of obtaining a desired medium surface by forming a layer or the like, and a method of obtaining a desired medium surface by controlling the surface state of any layer formed on the substrate.
In particular, in order to reduce the spacing (flying height) between the information recording medium (magnetic recording medium) and the magnetic head and enable high recording density reproduction, it is preferable to control the surface of the substrate. In addition, it is preferable to apply to a method for manufacturing an information recording medium substrate (magnetic recording medium substrate) having a desired substrate surface based on the friction coefficient management technique based on the surface roughness of structures 14 to 16.
[0044]
According to configurations 19 and 21, as a method for managing the surface state of the information recording medium substrate (magnetic recording medium substrate) and the information recording medium (magnetic recording medium), the measured value of the bearing height is rapidly increased from BA = 0%. By using various AFM measurement values excluding data up to the bearing area value at which the variation starts, the problem of AFM measurement variation can be solved. For example, when OBA% is used, the friction coefficient based on the surface roughness can be designed or managed with high accuracy because it is hardly affected by variations in AFM measurement.
The various AFM measurement values referred to in the configurations 19 and 21 include Rmax, Ra, Ra / Rmax, BA% (bearing area) and the like in addition to OBA% (offset bearing area).
In addition, for example, by removing the data whose measurement values vary from the AFM measurement data, and using the data after this exclusion, the bearing curve, Rmax, Ra, Ra / Rmax, BA%, etc. are obtained, so that the AFM measurement variation is reduced. Effects can be excluded and accurate data can be obtained. These operations can be easily performed by setting in the AFM measuring apparatus.
As in Configuration 20, based on the surface state management method in Configuration 19, the desired friction coefficient can be obtained by applying it to a method for manufacturing an information recording medium substrate (magnetic recording medium substrate) having a desired substrate surface. An information recording medium substrate (magnetic recording medium substrate) for obtaining an information recording medium (magnetic recording medium) is obtained.
Further, as in Configuration 22, based on the management method of the surface state of Configuration 21, the information having a desired friction coefficient is applied to a method for manufacturing an information recording medium (magnetic recording medium) having a desired medium surface. A recording medium (magnetic recording medium) is obtained.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
From the medium design of the magnetic recording medium mounted on the hard disk drive of the present invention, a magnetic recording medium substrate and a method of manufacturing the magnetic recording medium will be described below.
FIG. 11 is a diagram for explaining a magnetic recording medium substrate and a method for manufacturing the magnetic recording medium from the medium design of the magnetic recording medium. FIG. 12 is a diagram for explaining a magnetic recording medium substrate and a method for manufacturing the magnetic recording medium.
In order to finally obtain a magnetic recording medium, as shown in FIG. 11, it is roughly divided into a medium design step (steps a to e), a magnetic recording medium substrate manufacturing step (step f), and a magnetic recording medium manufacturing step (step). It is manufactured via g).
[0046]
The medium (magnetic recording medium surface) design process is
a. Determining the relationship between the surface roughness (Rmax) of the surface of the medium (magnetic recording medium) and the flying height (glide height) of the magnetic head at which the magnetic head starts to contact the medium surface;
b. Determining the surface roughness (Rmax) of the medium surface to achieve a desired glide height from the relationship obtained in step a;
c. Determining the allowable range of the coefficient of friction on the medium surface according to the driving torque of the spindle motor of the hard disk drive;
d. Obtaining a correlation between the OBA% (offset bearing area) and the friction coefficient;
e. A step of determining an OBA% for obtaining a desired coefficient of friction from the correlation obtained in the step d;
Have
[0047]
The OBA% (offset bearing area) is a parameter for designing the medium surface and is a feature of the present invention, and is determined by the following steps (steps d-1 to d-4 shown in FIG. 11). The following steps are usually determined by preparing a plurality of samples (magnetic recording medium or magnetic recording medium substrate).
d-1. Determining the relationship between Rmax and bearing area by AFM;
d-2. Determining a true peak height according to the surface roughness of the medium (the bearing value at which the measured value of the bearing height begins to vary rapidly);
d-3. Determining the correlation between the depth from the true peak height determined in step d-2 and the bearing area, and determining a slice level at which the amount of change in the bearing area is increased;
d-4. Determining a bearing area value (OBA%: offset bearing area) at the slice level determined in step d-3;
Have
Incidentally, the friction coefficient and the surface roughness of the medium surface in the medium design process described above are often set to some extent tolerable by the hard disk drive manufacturer due to the relationship with the recording density. The medium manufacturer may omit the c process.
[0048]
Since the surface of the medium becomes OBA% determined by the medium design process, a substrate for a magnetic recording medium having the desired OBA% on the substrate surface is manufactured. The production process of the chemically tempered glass substrate for magnetic recording media of the present invention is shown below.
As shown in steps f-1 to f-8 in FIG. 12, the manufacturing process of the chemically strengthened glass substrate for a magnetic recording medium is as follows.
f-1. A step of examining the relationship between the manufacturing conditions of the chemically strengthened glass substrate for magnetic recording media and OBA% (omitted after the manufacturing conditions are determined);
f-2. A substrate molding process for molding a disk-shaped glass substrate;
f-3. A shape processing step that drills a central hole in a glass substrate and grinds the inner and outer circumferences of the disk-shaped substrate
f-4. Grinding process to wrap the main surface of the glass substrate;
f-5. A polishing step for polishing the main surface of the glass substrate (in addition, an end surface polishing step for polishing the end surface of the glass substrate may be included if necessary);
f-6. Chemical strengthening process to strengthen the glass substrate surface;
f-7. A process of treating the glass substrate after the chemical strengthening process with silicic acid,
f-8. Inspecting and packing the glass substrate;
Have
In addition, a cleaning process for cleaning the glass substrate is appropriately introduced between the processes as necessary. The manufacturing conditions in the above step f-1 include, for example, polishing conditions for polishing the substrate surface (abrasive species, abrasive particle size, pressure, time, polishing pad type, etc.), and substrate surface roughness. Chemical treatment conditions (chemical solution type, concentration, temperature, time), chemical strengthening treatment conditions (molten salt species, heating temperature, time) for chemically strengthening the glass substrate, silicic acid treatment conditions after chemical strengthening (concentration, temperature, Time). Since various conditions for these relationships are obtained in advance through experiments, the f-1 process may be omitted in the actual glass substrate manufacturing process. Further, in the f-2 process and the f-3 process, a donut-shaped substrate can be formed by direct pressing, and the f-2 process and the f-3 process can be performed in the same process.
The process for producing a chemically strengthened glass substrate according to the present invention is characterized by having a step of treating the surface of the glass substrate pulled up from the chemically strengthened treatment liquid with a treatment liquid containing silicic acid. By treating the surface of the glass substrate after the chemical strengthening treatment with a treatment liquid containing silicic acid, variation in surface roughness can be suppressed and OBA% can be controlled accurately. The silicic acid treatment can effectively remove the cause of measurement variation of the AFM itself (abnormal protrusions that do not affect the glide height and do not affect the coefficient of friction), and can be strictly removed. Can be controlled. FIG. 13 is a graph showing the relationship between Rmax and OBA% 3 nm of a glass substrate for magnetic recording medium obtained by the method for manufacturing a glass substrate for magnetic recording medium of the present invention (silicic acid treatment condition, concentration: 1.0% by weight). , Treatment time: 100 seconds, number of substrates 128), FIG. 14 shows the chemical strengthening treatment, and the surface of the glass substrate is treated with sulfuric acid (sulfuric acid treatment conditions, concentration: 10% by weight, treatment conditions: 100 seconds, number of substrates 128) It is a figure which shows the relationship between Rmax of a glass substrate for magnetic recording media obtained in this way, and OBA% 3nm. In FIGS. 13 and 14, the glass substrate for magnetic recording medium is manufactured so that OBA% 3 nm falls within the range of 20 to 40%. As can be seen from comparison between FIG. 13 and FIG. 14, in the case of FIG. 13, it is found that OBA% is approximately in the range of 3 nm = 20 to 40%, and is distributed in the vicinity of Rmax = 8 nm. . On the other hand, in the case of FIG. 14, it can be seen that OBA% 3 nm is not within the range of 20 to 40%, and Rmax is also widely distributed from about 5 nm to about 16 nm. Thus, it can be seen that the surface of the glass substrate after the chemical strengthening treatment is treated with silicic acid to effectively remove the cause of measurement variation of the AFM itself, and OBA% can be strictly controlled.
[0049]
Next, in order to obtain a magnetic recording medium, a magnetic layer or the like is formed on the glass substrate for a magnetic recording medium obtained by the above-described process to produce a magnetic recording medium. A typical magnetic recording medium manufacturing process will be described below.
The manufacturing process of the magnetic recording medium is as shown in steps g-1 to g-4 in FIG.
g-1. Forming a base layer on a glass substrate;
g-2. Forming a magnetic layer on the underlayer;
g-3. Forming a protective layer on the magnetic layer;
g-4. Forming a lubricating layer on the protective layer;
Have
The materials for the underlayer, magnetic layer, protective layer, and lubricating layer are not particularly limited. A seed layer may be provided between the glass substrate and the underlayer for the purpose of controlling the crystal grain size and grain size distribution of the underlayer and the magnetic layer. An intermediate layer for controlling the crystal orientation of the magnetic layer may be provided between the underlayer and the magnetic layer. The film thickness and composition of each of these layers are appropriately adjusted according to the required characteristics.
An example of manufacturing a magnetic recording medium substrate and a magnetic recording medium according to the above steps will be described below.
[0050]
Example 1
The following is an example of medium design when a 2.5 inch hard disk drive (4200 rpm) and a recording capacity of about 5 GB per medium are required.
(1) Design of Rmax defined by required glide height
In order to achieve the recording capacity of 5 GB, the flying height of the read / write (R / W) head needs to be reduced to about 20 nm because of the improvement of the S / N ratio and the narrowing of the track width. For this reason, the glide height must be reduced to about 8 to 10 nm. This means that contact between the head and the medium should not occur even with a head flying height of only 10 nm.
FIG. 3 is a graph showing the relationship between the surface roughness Rmax (measured by AFM) of the medium surface and the flying height (glide height) of the magnetic head at which the magnetic head starts to contact the medium surface. In order to achieve the glide height of 10 nm required from this graph, Rmax must be about 8 nm or less.
(2) Design of friction coefficient at Rmax defined in (1) above
The Rmax for achieving the required glide height was defined by (1) above. Under this restriction, a friction coefficient is designed to avoid magnetic head adsorption on the medium. The upper limit of the friction coefficient of the hard disk drive is defined by the driving torque of the spindle motor. When the friction is so large that it cannot be rotated by the driving torque, the magnetic head is attracted to the medium surface. In the model of the 4200 rpm motor in this embodiment, the upper limit of the friction coefficient is defined as 3 or less.
As described above, the OBA% for controlling the coefficient of friction represents the density of protrusions in a certain depth space, so that it is most sensitive to friction according to the specified Rmax. It is necessary to determine the slice position.
FIG. 4 shows various types of media having Rmax defined in the above (1) near 8 nm, and shows bearing curves in the media. The Rmax and Ra values of the respective media are substantially the same, but the bearing curves are greatly different. Therefore, the protrusion density, the protrusion shape, and the like are different, and consequently the friction coefficient is different. In distinguishing these media (coefficient of friction), the optimum slice level is set to a depth of 3 nm from the bearing height (true peak height) corresponding to the bearing area of 0.5%. The bearing area when the slice level is offset from the maximum protrusion height in this way is defined as an offset bearing area, and is denoted as OBA% @ 3 nm.
FIG. 5 represents the group shown in FIG. 2 expressed as OBA% @ 3 nm. With the introduction of OBA% @ 3 nm, it became possible to manage the friction coefficient, which was impossible with Rmax, Ra, and Rmax / Ra. The standard management is performed with OBA% @ 3nm = 40% ± 20% while ensuring a certain margin with respect to the regulation of the upper limit value <3 of the friction coefficient. Thereby, the friction coefficient is managed within a range of 0.5 to 2.5.
[0051]
In this embodiment, the surface roughness of the magnetic recording medium substrate is set so that the medium surface of the magnetic recording medium becomes Rmax and OBA% @ 3 nm = 40% ± 20% defined in (1) and (2) above. The magnetic recording medium is manufactured by forming the underlayer, the magnetic layer, the protective layer, and the lubricating layer on the substrate, with the above-described Rmax and OBA% @ 3 nm = 40% ± 20%. did.
[0052]
(3) Fabrication of magnetic recording medium substrate
A disk-shaped glass substrate was obtained by direct pressing the molten glass, and an aluminosilicate glass substrate having an outer diameter of 65 mmφ and an inner diameter of 20 mmφ was obtained through shape processing (drilling and chamfering) and end face polishing steps. Then, the glass substrate for magnetic recording media was produced through the lapping process, the polishing process, the chemical strengthening process, and the etching process by silicic acid.
Note that the surface roughness (measured by AFM) of the glass substrate after the polishing step was Rmax = 5.72 nm and Ra = 0.53 nm. The chemical strengthening conditions were carried out in a mixed molten salt of potassium nitrate and sodium nitrate at a processing temperature of 340 ° C. and a processing time of 2 hours. The silicic acid treatment conditions after chemical strengthening were as follows: concentration: 0.12 vol% The time was 100 seconds.
When the surface roughness of the obtained glass substrate was measured by AFM (atomic force microscope), it was Rmax = 6.92 nm, Ra = 0.79 nm, OBA% @ 3 nm = 41%.
[0053]
(4) Production of magnetic recording medium
A NiAl seed layer, a CrV underlayer, a CoCrPtTa magnetic layer, and a hydrogenated carbon protective layer are sequentially formed on both surfaces of the glass substrate for a magnetic recording medium obtained in (3) above using an in-line sputtering apparatus, and dip A perfluoropolyether liquid lubricant (Fonbrin: Zdol2000) was formed into a film by the method to prepare a magnetic recording medium.
When the surface roughness of the obtained magnetic recording medium was measured with an AFM (atomic force microscope), Rmax = 7.55 nm, Ra = 0.88 nm, OBA% @ 3 nm = 43%, and a friction coefficient of about 1.5. there were. The obtained magnetic recording medium had a TDFH of 8.4 nm. Thus, a magnetic recording medium within the design range was obtained.
Furthermore, when a CSS endurance test was conducted 100,000 times, no head crash or adsorption phenomenon occurred. Also, no head wear phenomenon was observed.
[0054]
In addition, when the reproducibility of repeated measurement (21 consecutive times) in the same measurement area was examined by AFM, the bearing area (BA% @ 4 nm) measured value at a depth of 4 nm from Rmax was 3.6 at 3σ and varied. On the other hand, the measured value of OBA% @ 4 nm was 1.8 at 3σ, and the variation was halved. That is, it can be seen that OBA% is less susceptible to variations in AFM measurement.
[0055]
(Example 2)
In the first embodiment, (1) under the constraint of Rmax defined by the glide height, (2) a medium surface having a good friction coefficient is designed, and (3) a magnetic material having a surface roughness obtained by the design. A recording medium substrate was prepared, and (4) a magnetic recording medium was prepared by forming at least a magnetic layer on the substrate.
That is, the first term (μN) represented on the right side is designed in the aforementioned frictional force formula F = μN + F1 + F2 + F3 +.
Here, in order to reduce the frictional force, it is also important to suppress the contribution of the second term (the meniscus force F1 caused by the lubricant) to be linearly coupled to a small value.
Therefore, in Example 2, by using the friction coefficient management method described above, the coating lubricant is optimized and a magnetic recording medium corresponding to higher recording density is produced.
[0056]
Specifically, the following two lubricants classified as PFPE (perfluoroalkyl polyether) were examined as lubricants. In both cases, the main chain contains an ether bond and has a-(OCF2F2) m (OCF2) n-linear structure.
(A) Zdol2000: terminal group = hydroxyl group, (b) AM3000: terminal group = piperonyl group FIG. 6 is a diagram showing the relationship between OBA% @ 3 nm and friction coefficient for both lubricants. As shown in the figure, it can be seen that (a) Zdol2000 can lower the friction coefficient (F1 is smaller) in the combination of the magnetic head and the medium in this embodiment.
Therefore, by producing a magnetic recording medium using the selected lubricant, a suitable magnetic recording medium corresponding to a higher recording density can be obtained.
[0057]
(Examples 3 to 6)
In Example 1, the substrate for magnetic recording medium and magnetic recording were the same as Example 1 except that chemical treatment with silicic acid was performed between the polishing process and the chemical strengthening process to control the surface roughness. A medium was made. In order to control the surface roughness, the glass substrate contains at least an alkali metal oxide and an alkaline earth oxide, and the alkaline earth oxide content is less than 3 mol% (specifically, SiO 2 ₂ : 58 to 75% by weight, Al ₂ O _Three : 5 to 23% by weight, Li ₂ O: 3 to 10% by weight, Na ₂ O: glass containing 4 to 13% by weight as a main component) was used. Silicic acid treatment conditions performed between the polishing step and the chemical strengthening step were as follows: concentration: 0.12 vol%, treatment time: 200 seconds. Moreover, the silicic acid treatment time after chemical strengthening was changed to 70 seconds (Example 3), 80 seconds (Example 4), 90 seconds (Example 5), and 100 seconds (Example 6), and the treatment time was changed. The change of surface roughness due to was investigated.
As a result, as shown in FIGS. 15 to 17, it can be seen that as the treatment time of the silicic acid treatment after chemical strengthening becomes longer, Ra is almost constant, but Rmax is lowered. From this, it is considered that the abnormal protrusion caused by the variation in AFM measurement is removed by the silicic acid treatment after chemical strengthening, Rmax is reduced, and as a result, OBA% can be controlled without variation. .
[0058]
(Examples 7 to 9)
Next, in Example 1, a substrate for a magnetic recording medium for a load / unload system and a magnetic recording medium were produced by appropriately adjusting the polishing conditions and the conditions for the silicic acid treatment after chemical strengthening. The magnetic recording media of Examples 7, 8, and 9 were produced by media design and friction coefficient management so that the recording capacities were 5 GB, 10 GB, and 15 GB, respectively.
Table 1 shows the surface states (surface roughness (Rmax, OBA%), slice level, and flying characteristics) of the magnetic recording medium substrates obtained in Examples 7 to 9.
[0059]
[Table 1]

[0060]
As shown in the above table, a magnetic recording medium having good flying characteristics (head crush and fly stiction) was obtained.
[0061]
(Comparative Example 1)
Substrate for magnetic recording medium and magnetic recording medium in the same manner as in Example 1 except that it was changed to silicic acid treatment after chemical strengthening in Example 1 and changed to sulfuric acid treatment (concentration: 10% by weight, time: 100 seconds). Was made. As a result, Rmax = 6.15 nm, OBA% 3 nm = 72%, and could not be within the range of the standard of OBA% 3 nm = 40% ± 20%. This is thought to be because OBA% 3 nm could not be controlled due to, for example, the abnormal protrusion that was considered to be the cause of AFM measurement variation not being sufficiently removed. When the coefficient of friction of the obtained magnetic recording medium was measured, it was 3.5 and exceeded 3, and it was not possible to avoid the adsorption of the magnetic head.
[0062]
The present invention is not limited to the embodiments described above.
[0063]
For example, the OBA slice is not limited to 3 nm. Arbitrated appropriately according to various media.
[0064]
The place for creating the surface roughness of the medium is not limited to the substrate surface. For example, you may form a texture in a base layer, a protective layer, etc. The method for forming the predetermined surface roughness is not limited to the etching method, and a mechanical texture, a sputter texture, a laser texture, or fine particles may be mixed to form a predetermined surface roughness using these fine particles. However, it is preferable to use a texture method in which the radius of curvature of each protrusion is substantially the same.
[0065]
As a method for measuring the surface state, an STM (scanning tunneling microscope) or a stylus type surface roughness meter can be used instead of AFM (atomic force microscope). However, the AFM (Atomic Force Microscope) is superior to other measurement methods in that the surface state can be measured accurately, with high accuracy and with high resolution, relatively easily.
[0066]
As the lubricant in Example 2, a suitable lubricant is selected depending on various media. The formation method of the lubricant is not limited to the dipping method (dipping method). The lubricant may be formed by vacuum deposition.
[0067]
The present invention is not limited to the CSS type magnetic recording medium, but avoids flying stiction in a load / unload type magnetic recording medium in which the lowering of the magnetic head is further advanced as shown in the seventh to ninth embodiments. It is also effective as a management method.
Further, the chemical solution used in the chemical treatment step in the surface roughness control step after the polishing step is not limited to silicic acid, but at least one acid selected from sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and silicic acid, Or you may process with the process liquid containing an alkali.
[0068]
The size of the substrate is not limited to 2.5 inches, but can be applied to various sizes such as 1 inch, 3 inches, and 3.5 inches.
[0069]
Further, the present invention is not limited to a magnetic recording medium substrate or a magnetic recording medium, but is applied to a magneto-optical recording medium substrate or a magneto-optical recording medium for recording / reproducing using a head slider on which an optical pickup lens or the like is mounted. It is also effective as a method for managing these surfaces.
[0070]
【The invention's effect】
According to the present invention, an information recording medium substrate (magnetic recording medium substrate) and an information recording medium (magnetic recording medium) having a surface roughness of Rmax 15 nm or less (particularly Rmax 10 nm or less) have a friction coefficient based on the surface roughness. Design or manage with high accuracy.
Further, according to the present invention, the problem of variation in AFM measurement can be solved in the management of a surface state having a surface roughness of Rmax 15 nm or less (particularly Rmax 10 nm or less).
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a relationship between Rmax and a friction coefficient by AFM measurement.
FIG. 2 is a diagram illustrating a relationship between Ra and a friction coefficient by AFM measurement.
FIG. 3 is a diagram showing a relationship between Rmax and glide height by AFM measurement.
FIG. 4 is a diagram for explaining the relationship between BA% by AFM measurement and the depth from the true peak height.
FIG. 5 is a diagram illustrating a relationship between OBA% @ 3 nm and a friction coefficient.
FIG. 6 is a diagram illustrating a relationship between OBA% @ 3 nm and a friction coefficient in a medium coated with a lubricant.
FIG. 7 is a diagram showing the relationship between BA% and the bearing height in the vicinity of the maximum protrusion height.
FIG. 8 is a diagram for explaining an offset bearing area.
FIG. 9 is a diagram for explaining a contact state between a head and a protrusion.
FIG. 10 is a diagram illustrating a relationship between BA% @ 4 nm and a friction coefficient.
FIG. 11 is a diagram for explaining a magnetic recording medium substrate and a method for manufacturing the magnetic recording medium, from the medium design of the magnetic recording medium.
FIG. 12 is a diagram for explaining a magnetic recording medium substrate and a method of manufacturing the magnetic recording medium.
FIG. 13 is a view showing the relationship between Rmax and OBA% 3 nm of a glass substrate for a magnetic recording medium obtained by subjecting the surface of a glass substrate to silicic acid treatment after chemical strengthening treatment.
FIG. 14 is a diagram showing the relationship between Rmax and OBA% 3 nm of a glass substrate for magnetic recording media obtained by subjecting the surface of a glass substrate to a sulfuric acid treatment after chemical strengthening treatment.
FIG. 15 is a diagram showing the relationship between Ra and the treatment time with silicic acid after chemical strengthening.
FIG. 16 is a graph showing the relationship between the treatment time with silicic acid after chemical strengthening and Rmax.
FIG. 17 is a diagram showing the relationship between the treatment time with silicic acid after chemical strengthening and OBA% 3 nm.

Claims (9)

A step of immersing the glass substrate in the heated chemical strengthening treatment liquid, ion-exchanging ions on the surface of the glass substrate with ions in the chemical strengthening treatment liquid, and chemically strengthening the glass substrate; the surface was closed and treating with a processing solution containing hydrosilicofluoric acid, the surface is precisely polished and etched, there in a magnetic recording medium for chemically strengthened glass substrate manufacturing method of Rmax has a surface roughness of less than 10nm And
Regarding a plurality of glass substrates for magnetic recording media obtained by the manufacturing method,
The measurement value of the offset bearing area (hereinafter referred to as “OBA% @”) is the measurement value of the bearing area at the slice level of 3 nm depth from the bearing height (true peak height) corresponding to the bearing value measurement of 0.5%. 3nm ") and the coefficient of friction based on surface roughness,
In addition, a correlation between the formation conditions in the manufacturing method for forming a desired substrate surface state and OBA% @ 3 nm is obtained in advance.
A glass substrate for a magnetic recording medium having a desired substrate surface is obtained by selecting the formation conditions through a correlation between the OBA% @ 3 nm and a friction coefficient. A method for producing a glass substrate for a medium. The method for producing a glass substrate for a magnetic recording medium according to claim 1 comprises:
Method of manufacturing a glass substrate for a magnetic recording medium according to claim 1, characterized in that before the step of chemical strengthening has a step of controlling the desired surface roughness by chemical treatment of the glass substrate surface.   The method for producing a glass substrate for a magnetic recording medium according to claim 1 or 2, wherein the chemically strengthened glass substrate for a magnetic recording medium has a surface roughness Rmax of 8 nm or less.   The magnetic treatment according to claim 2, wherein the chemical treatment is performed with a treatment solution containing at least one acid selected from sulfuric acid, phosphoric acid, nitric acid, hydrofluoric acid, and silicic hydrofluoric acid, or an alkali. A method for producing a glass substrate for a recording medium.   The method for producing a glass substrate for a magnetic recording medium according to any one of claims 1 to 4, wherein the concentration of the silicic acid is 0.01 to 10% by weight. By forming at least a magnetic layer on the surface of the chemically strengthened glass substrate for a magnetic recording medium obtained by the method for manufacturing a glass substrate for a magnetic recording medium according to any one of claims 1 to 5,
A magnetic recording medium having a magnetic layer formed on the surface of the chemically strengthened glass substrate for a magnetic recording medium, wherein a low-glide magnetic recording medium having a glide height of 10 nm or less is obtained. Method.   7. The method of manufacturing a magnetic recording medium according to claim 6, wherein a friction coefficient based on the surface roughness of the medium surface is 3 or less.   8. The lubricant according to claim 6 or 7, wherein a correlation between a coefficient of friction and a measured value of an offset bearing area in a magnetic recording medium formed with various lubricants is examined, and a lubricant that reduces a frictional force by the lubricant is employed. A method for producing the magnetic recording medium according to claim. The lubricant is classified as PFPE (perfluoroalkyl polyether), has an ether bond in the main chain, has a — (OCF ₂ F ₂ ) m (OCF ₂ ) n -linear structure, and has a hydroxyl group as a terminal group The method of manufacturing a magnetic recording medium according to claim 8, wherein the lubricant has a lubricant.

Images