JP2004095094A - Magnetic recording medium and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] At present, when the flying height of a magnetic head is narrowed, if unevenness due to uneven adhesion of a lubricant occurs on a lubricating film on the surface of a magnetic disk, the levitation of the magnetic head becomes unstable at a portion where the lubricating film is thick, and reliability is high. Causes a decline in sex.
In a magnetic recording medium in which at least a magnetic film, a protective film, and a lubricating film are sequentially formed on a non-magnetic substrate, the lubricating film has a main chain structure represented by a chemical formula (1).
X-CF2O- (CF2CF2O) m- (CFO) n-CF2-X (1)
(Where m and n are 0 or an integer of 1 or more, X is a terminal functional group, and the average molecular weight is 600 to 3500)
Wherein the bond ratio is 60% or more, the coverage ratio is 90% or more, the film thickness is 1.2 nm or less, and the unevenness of adhesion has no directionality.
[Selection diagram] Fig. 1

Description

−（ＣＨ２ＣＨ２Ｏ）ｐ−Ｈ又は−ＣＦ２ＣＨ２（ＯＣＨ２ＣＨ２）ｑ−ＯＨ（ｐ、ｑは整数である）　　（４）
のいずれか１種類で表される末端官能基Ｘを有する。
【００１４】
前記他の目的を達成するために、非磁性基板上に少なくとも磁性膜および保護膜を形成し、該磁性膜および保護膜が形成された非磁性基板の加熱温度と主鎖構造が化学式（１）
Ｘ−ＣＦ２Ｏ−（ＣＦ２ＣＦ２Ｏ）ｍ−（ＣＦＯ）ｎ−ＣＦ２−Ｘ　　　　　　　（１）
（ここでｍおよびｎは０または１以上の整数であり、Ｘは末端官能基であり、平均分子量は６００〜３５００である）
で表されるパーフルオロポリエーテルの潤滑剤の温度をそれぞれ一定に保持し、前記保護膜の上に蒸着法で潤滑膜を形成する。
【００１５】
前記潤滑膜の形成を大気中で行う。
【００１６】
前記潤滑膜形成時における非磁性基板および蒸着元の潤滑剤の温度は１００℃〜２００℃の範囲とする。
【００１７】
【発明の実施の形態】
本発明の実施例を図面を参照して詳細に説明する。図１に潤滑剤分子の磁気記録媒体表面における蒸発および付着の平衡状態に関する概念図を示す。蒸気となった潤滑剤分子は磁気記録媒体表面で蒸発と付着を繰り返している。潤滑剤分子が磁気記録媒体の保護膜に吸着しやすい官能基を有している場合、その官能基が保護膜表面に付着すると、その潤滑剤分子は蒸発しにくい。また、潤滑剤分子が付着している部分に蒸気中の潤滑剤分子は付着しにくく、付着したとしても蒸発しやすいため、すぐに蒸発する。すなわち、潤滑剤の末端官能基による保護膜表面へ付着している潤滑剤分子以外の分子は、蒸気と磁気記録媒体の温度がほぼ等しい場合には蒸発と付着がほぼ同じ確率で起こっていると推定される。このような平衡状態にあると磁気記録媒体表面には１分子層の潤滑膜が均一に形成される。温度の平衡状態が崩れている場合は、蒸発と付着の確率が等しくないため、潤滑膜は均一に形成されにくいと推定される。
【００１８】
このような平衡状態のもとで潤滑膜を形成するために、図２に示した設備を用意した。磁気記録媒体の例として磁気ディスクを用いて検討した実施例である。非磁性基板上に少なくとも磁性膜および保護膜が形成された磁気ディスク１は支持台２に支持され、潤滑剤塗布槽３と加熱処理槽４で処理される。
【００１９】
加熱処理槽４はヒータ６で温度制御されている。磁気ディスク１はまず加熱処理槽４へ搬送され、所定の温度まで加熱される。磁気ディスク１が所定の温度まで加熱されるとシャッター５が開き、磁気ディスク１は潤滑剤塗布槽３へ搬送され、シャッター５が閉まり密閉される。潤滑剤塗布槽３は潤滑剤８と潤滑剤８を保持する容器９を内部に持ち所定の温度に加熱して潤滑剤蒸気を発生させる機構である蒸発潤滑剤発生機構１０と配管されている。潤滑剤蒸気は潤滑剤塗布槽３の空気とともに循環される。配管には潤滑剤蒸気を循環させるポンプ１１やバルブ１２、１３が配置されており、潤滑剤蒸気の循環を制御する。蒸発潤滑剤発生機構１０や配管、潤滑剤塗布槽３はそれぞれ独立した加熱用のヒータ６を有しており、その温度は常に一定になるように制御される。潤滑剤塗布槽３には蒸気を循環させる攪拌ファン７が内蔵され、潤滑剤の付着むらに方向性が付かないように磁気ディスク１の面に対し渦巻状の空気流を送風する。潤滑剤塗布槽３に磁気ディスク１が入り、密閉されると、供給バルブ１３、排出バルブ１２を開きポンプ１１を駆動させ、蒸発潤滑剤発生機構１０で発生させた潤滑剤蒸気を槽内に循環させる。そのとき潤滑剤蒸気の温度と潤滑剤塗布槽３の温度、磁気ディスク１の加熱処理の温度は１５０±５℃以内になるように制御する。潤滑剤塗布槽３の外部よりエリプソメータで磁気ディスク１の潤滑膜の膜厚をモニタして、所定の厚さになったときに、供給バルブ１３を閉じ潤滑剤蒸気を排出する。その後、磁気ディスク１を取り出す。潤滑剤蒸気の密度は十分に小さいためエリプソメータで潤滑膜の膜厚を測定することが可能である。実際に製造する場合はエリプソメータで測定した潤滑膜厚が所定の膜厚になったときに磁気ディスク１を取り出すことも可能であり、膜厚の制御が簡単にできる。浸漬法などでは塗布中の膜厚をモニタすることは困難であり、この点でも本発明の潤滑剤塗布方法は優れている。
【００２０】
磁気ディスクとして、２．５インチサイズのガラス基板上にＮｉＴａ合金のシード膜を、ＣｒＴｉ合金下地膜、ＣｏＣｒＰｔ合金下部磁性膜、Ｒｕ中間膜、ＣｏＣｒＰｔＢ合金上部磁性膜を順次スパッタ成膜した後、イオンビーム法によりダイヤモンドライクカーボン（ＤＬＣ）膜を３．５ｎｍの厚さに形成した。その後、図２に示した加熱処理、潤滑剤塗布を行った。
【００２１】
加熱処理、潤滑剤塗布の標準温度は１５０℃である。加熱処理は３０分間行い、磁気ディスクの温度が１５０℃になることを確認した。使用した潤滑剤は化学式（１）の主鎖構造を持ち（パーフルオロポリエーテル）、末端官能基の構造が化学式（２）〜（４）で表されるアウジモント社製のフォンブリンＺ−ＤＯＬ、Ｚ−Ｔｅｔｒａｏｌ、Ｚ−ＤＯＬＴＸの３種類をそれぞれ塗布し比較した。それぞれの潤滑剤の平均分子量は２０００であり、重量平均分子量と数平均分子量の比は１．１以下になるように分子量を制御している。
Ｘ−ＣＦ２Ｏ−（ＣＦ２ＣＦ２Ｏ）ｍ−（ＣＦＯ）ｎ−ＣＦ２−Ｘ　　　　　　　　　　　　　　　　（１）
（ここでｍおよびｎは０または１以上の整数であり、Ｘは末端官能基であり、平均分子量は６００〜３５００である）
−ＣＨ２−ＯＨ　　　　　　　　　　　　　　　　　　　　　　　　　　（２）

−（ＣＨ２ＣＨ２Ｏ）ｐ−Ｈ又は−ＣＦ２ＣＨ２（ＯＣＨ２ＣＨ２）ｑ−ＯＨ（ｐ、ｑは整数である）　　（４）
まず、Ｚ−Ｔｅｔｒａｏｌを用いて磁気ディスクおよび潤滑剤蒸気の保持温度を同じ１５０℃としたとき、塗布時間に伴い、塗布される潤滑膜厚がどう変化するかを測定した。結果を図３に示す。比較例として、磁気ディスクの加熱工程での温度を１３０℃として潤滑剤蒸気と空気の温度を１５０℃にしたとき、および磁気ディスクの加熱工程での温度を１８０℃として潤滑剤蒸気と空気の温度を１５０℃にしたとき、の塗布時間と潤滑膜厚の関係を図４に示す。
【００２２】
図３と図４を比較すると明らかなように潤滑膜厚の時間変化は、実施例の場合が安定しており、比較例は時間とともに大きく変化する。大気中において数分程度の塗布時間で安定で均一な潤滑膜を形成できることが確認できた。そこで塗布時間を３分にしてそれぞれの温度条件で磁気ディスクに潤滑膜を形成した。そしてその磁気ディスクを潤滑剤の溶媒（スリーエム社製ＨＦＥ７１００）で常温でリンスしてボンド率を測定した。ボンド率はリンス後のエリプソメータで測定した潤滑膜厚とリンス前の潤滑膜厚との比率と定義している。また、フッ素コーティングを施したプローブを用いて原子間力顕微鏡（ＡＦＭ）で潤滑膜の膜厚と被覆率を測定した。その結果を表１に示す。
【００２３】
【表１】

ＡＦＭで測定した潤滑膜厚はエリプソメータで測定した膜厚とは異なり、潤滑膜の実際の膜厚を示しており、エリプソメータの膜厚は平均的な膜厚を示している。実施例の場合ボンド率は大きく、かつ被覆率も１００％に近いこと、またＡＦＭで測定した潤滑膜厚とエリプソメータで測定した潤滑膜厚とほぼ等しいことから、１分子層からなる潤滑膜となっていることがわかる。比較例１ではボンド率が著しく小さく、被覆率が１００％であることから１分子層ではなく多分子層の潤滑膜が形成されており、２分子層以上の潤滑剤が容易にリンスされることからボンド率が低下していると推定される。比較例２ではボンド率は大きいが、被覆率が実施例に比較して小さい。このことから、比較例２の潤滑膜はアイランド状に潤滑剤が付着していることがわかる。これらの結果より実施例では１分子層の潤滑膜が均一に分布しており潤滑膜としてヘッドの浮上性を阻害せず、優れた耐摩耗性を示すと考えられる。
【００２４】
次に加熱温度、潤滑剤蒸気の温度をパラメータとして検討を行った。温度を６０℃〜１６０℃まで変化させて潤滑膜厚が飽和する時間を測定した。使用した潤滑剤はＺ−Ｔｅｔｒａｏｌである。その結果を図５に示す。磁気ディスクの保持温度を上げるにつれて潤滑剤飽和時間は減少していく。特に１００℃以上では２００分以下と短時間となっており、製造に適している。温度を２００℃以上の高温にした場合は、潤滑剤が分解する恐れがあるため、１００℃〜２００℃が磁気ディスクの製造に適していると考えられる。
【００２５】
飽和した潤滑膜厚と磁気ディスクの保持温度との関係を図６に示す。飽和潤滑膜厚は温度とともに減少して、１３０℃〜１６０℃で１．２ｎｍ以下の一定膜厚（１．１ｎｍ）となる。これらの磁気ディスクをリンスしてそのボンド率と磁気ヘッドの浮上性を調査した。浮上性は浮上量８ｎｍのヘッドを磁気ディスク上で１０回シークした後、ヘッドに付着する潤滑剤の量を光学顕微鏡で観察して、多量に付着したものを×、少量付着したものを△、付着しなかったものを○とした。その結果を表２に示す。
【００２６】
【表２】

保持温度の増加に伴い、ボンド率は増加して、一緒に磁気ヘッドの浮上性も増加している。特にボンド率が６０％以上の保持温度１２０℃以上で処理を行った場合にヘッドの浮上性が良好であった。潤滑剤がＺ−ＤＯＬ、Ｚ−ＤＯＬＴＸの場合も１５０℃で潤滑剤を塗布してヘッドの浮上性を評価したところ良好な結果であった。
【００２７】
本実施例ではイオンビーム法で形成したＤＬＣ保護膜に対してＺ−ＤＯＬ、Ｚ−Ｔｅｔｒａｏｌ、Ｚ−ＤＯＬＴＸの潤滑剤を塗布した実施例を示したが、保護膜に窒素等のガスを添加した場合や、保護膜の成膜方式が異なる場合は、潤滑剤の付着性が異なるため、飽和潤滑膜厚やボンド率は変化すると考えられるため、前記実施例で示した最適な製造条件が全てについて当てはまるとは限らない。しかし、熱平衡な状態で潤滑剤を塗布することで、同様な効果を得ることが可能であると考えられる。
【００２８】
【発明の効果】
本発明により、潤滑膜を均一な厚さに形成できるので、信頼性の高い磁気ディスクを得ることができる。また潤滑膜形成装置の構造を複雑にしたり、潤滑膜形成時間を精密に制御する必要がなく、潤滑膜の製造方法を安価で簡単なものとすることができる。
【図面の簡単な説明】
【図１】磁気記録媒体表面における潤滑剤分子の蒸発および付着の平衡状態に関する概念図である。
【図２】本発明の１実施例による潤滑膜の形成方法を実現する製造装置の構成図である。
【図３】本発明の１実施例における潤滑剤の塗布時間に対する潤滑膜厚の変化を示す図である。
【図４】比較例における潤滑剤の塗布時間に対する潤滑膜厚の変化を示す図である。
【図５】磁気ディスクの加熱温度と潤滑膜厚飽和時間との関係を示す図である。
【図６】磁気ディスクの加熱温度と飽和潤滑膜厚との関係を示す図である。
【図７】従来の塗布方法により潤滑剤が塗布された磁気ディスクにおいて、潤滑剤の付着むら（斑）に方向性が生じている状態を示す平面図である。
【符号の説明】
１　　磁気ディスク　　　　　２　　支持台　　　　　　　３　　潤滑剤塗布槽
４　　加熱処理槽　　　　　　５　　シャッター　　　　　６　　加熱用ヒータ
７　　蒸気攪拌ファン　　　　８　　パーフルオロポリエーテル潤滑剤
９　　潤滑剤保持容器　　　　１０　　蒸発潤滑剤発生機構
１１　　循環用ポンプ　　　　　１２　　排出バルブ　　　　　　１３　　供給バルブ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic recording medium having a lubricating film used for a magnetic recording device and a method for manufacturing the magnetic recording medium, and more particularly to a structure of a lubricating film and a method for forming a lubricating film.
[0002]
[Prior art]
[Patent Document 1] "JP-A-2000-251251"
[Patent Document 2] "JP-A-06-195704"
[Patent Document 3] "JP-A-06-251365"
[Patent Document 4] "JP-A-10-320765"
[Patent Document 5] "JP-A-07-272268"
[Patent Document 6] "JP-A-08-287449"
[Patent Document 7] "JP-A-06-012658"
[Patent Document 8] "JP-A-08-306040"
The magnetic recording medium has a lubricating film formed on a non-magnetic substrate after at least a magnetic film and a protective film are formed thereon to improve the reliability thereof. Taking a magnetic disk as an example, a NiP plated substrate or a glass substrate is used as a nonmagnetic substrate, a Co alloy thin film is used as a magnetic film, and a carbon protective film is used as a protective film using a thin film forming technique such as a sputtering method. Generally, it is formed. As the lubricating film, a perfluoropolyether lubricant is generally used. In particular, a lubricating film having a polar group at the terminal of the lubricant is used for the purpose of enhancing the adsorptivity with the protective film. Further, as a method of applying the lubricating film, a dipping method, a spray method, a spin coating method, a vapor deposition method, and the like are generally used.
[0003]
JP-A-2000-251251 (Patent Document 1) and JP-A-06-195704 (Patent Document 2) disclose a method of forming a lubricating film by an immersion method. In the immersion method, a lubricant is dissolved in a solvent to form a lubricant solution, and a magnetic recording medium is immersed therein to form a lubricating film. Further, Japanese Patent Application Laid-Open No. 06-251365 (Patent Document 3) discloses a technique of heat-treating a magnetic recording medium after forming a lubricating film. Has been used as
[0004]
Techniques for forming a lubricating film by a vapor deposition method are disclosed in JP-A-10-320765 (Patent Document 4), JP-A-07-272268 (Patent Document 5), and JP-A-08-287449 (Patent Document 6). It is disclosed in, for example, Japanese Unexamined Patent Publication No. 06-012658 (Patent Document 7). In JP-A-10-320765 (Patent Document 4), lubrication is performed by disposing a magnetic recording medium and a lubricant in a closed container, heating the lubricant, evaporating the lubricant, and filling the closed container with a lubricant vapor. A method for forming a film is disclosed. Japanese Patent Laying-Open No. 07-272268 (Patent Document 5) similarly discloses a method of forming a lubricating film by heating and evaporating a lubricant in a vacuum vessel. Japanese Patent Application Laid-Open No. 08-287459 (Patent Document 6) discloses a method of applying ultrasonic vibration as a method of scattering and evaporating a lubricant. Japanese Patent Application Laid-Open No. 06-012658 (Patent Document 7) discloses a technique in which a magnetic recording medium and a lubricant are heated in an airtight container so that the temperature difference does not exceed 30 ° C. .
[0005]
As a further different technique, there is disclosed a technique of forming a lubricating film of a magnetic recording medium by performing gas phase polymerization from a gas serving as a lubricant material as described in JP-A-08-306040 (Patent Document 8). Have been.
[0006]
[Problems to be solved by the invention]
The problem to be solved by the present invention is as follows. In the method of forming a lubricating film by immersion coating in a lubricant solution, a large amount of solvent is used, so that the cost increases and the magnetic recording medium cannot be manufactured at low cost. Further, since the magnetic recording medium is immersed in the solution, there is a problem that the coating of the lubricating film is easily caused by the vibration of the solution. FIG. 7 shows a magnetic disk in which unevenness in the adhesion of lubricant has directional unevenness. When a step of heat-treating the magnetic recording medium is employed to make the coating spots on the lubricating film uniform, the manufacturing time becomes longer, and the equipment also needs to be prepared, and the magnetic recording medium cannot be manufactured at low cost. .
[0007]
Next, in the conventional vapor deposition method in which only the lubricating film is heated to form a lubricating film vapor and adhere to the magnetic recording medium, this becomes particularly remarkable when performed in a vacuum. The lubricating film becomes thick, and the lubricating film becomes uneven at a distant portion. This is because the density distribution of the vaporized lubricant molecules is not constant in the closed container. Further, when the temperature of the magnetic recording medium, the temperature of the lubricant, and the temperature in the closed container are different from each other, the following problem occurs. If the temperature of the magnetic recording medium is lower than the temperature of the lubricant, the rate at which the lubricant molecules adhere to the surface of the magnetic recording medium re-evaporate tends to be smaller than the rate at which the lubricant molecules adhere. The adhesion amount of the lubricating film tends to increase with time. Conversely, if the temperature of the magnetic recording medium is higher than the temperature of the lubricant, the rate at which the lubricant molecules adhere to the surface of the magnetic recording medium re-evaporate tends to be higher than the rate at which they adhere. The amount of adhesion of the lubricating film on the recording medium decreases with time, and tends to evaporate leaving the lubricating film strongly adsorbed on the surface of the protective film. For this reason, in order to eliminate the unevenness of the lubricating film and to manufacture the lubricating film to a constant value, the structure around the evaporation source and the structural design of the sealed container are complicated, and the time for forming the lubricating film is precisely controlled. It is necessary to control This is not preferable because the equipment becomes expensive and the product varies. Further, a heat treatment step may be required to eliminate unevenness of the lubricating film.
[0008]
The problem as a lubricating film is that the conventional coating method causes unevenness in the lubricating film. At present, when the flying height of the magnetic head is narrowed, the flying property of the magnetic head is not stabilized in a portion where the lubricating film is thick, and the reliability is reduced. Therefore, it is ideal that the lubricating film is ideally a one-molecule-layer uniform film. However, such a lubricating film cannot be formed by the conventional coating method because of the above-mentioned problem.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable magnetic recording medium in which the lubricating film of the magnetic recording medium has no unevenness in the direction of adhesion unevenness, thereby reducing thickness variations.
[0010]
Another object of the present invention is to provide a manufacturing method capable of producing a highly reliable magnetic recording medium without increasing the manufacturing cost.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, in a magnetic recording medium in which at least a magnetic film, a protective film, and a lubricating film are sequentially formed on a non-magnetic substrate, the lubricating film has a main chain structure represented by a chemical formula (1)
X-CF2O- (CF2CF2O) m- (CFO) n-CF2-X (1)
(Where m and n are 0 or an integer of 1 or more, X is a terminal functional group, and the average molecular weight is 600 to 3500)
Wherein the bond ratio is 60% or more, the coverage ratio is 90% or more, the film thickness is 1.2 nm or less, and the unevenness of adhesion has no directionality.
[0012]
The lubricating film is composed of one molecular layer.
[0013]
The perfluoropolyether has the chemical formulas (2), (3), and (4)
-CH2-OH (2)

-(CH2CH2O) p-H or -CF2CH2 (OCH2CH2) q-OH (p and q are integers) (4)
Has a terminal functional group X represented by any one of the above.
[0014]
In order to achieve the other object, at least a magnetic film and a protective film are formed on a non-magnetic substrate, and the heating temperature and the main chain structure of the non-magnetic substrate on which the magnetic film and the protective film are formed are represented by chemical formula (1).
X-CF2O- (CF2CF2O) m- (CFO) n-CF2-X (1)
(Where m and n are 0 or an integer of 1 or more, X is a terminal functional group, and the average molecular weight is 600 to 3500)
Is maintained at a constant temperature, and a lubricating film is formed on the protective film by a vapor deposition method.
[0015]
The formation of the lubricating film is performed in the atmosphere.
[0016]
The temperature of the non-magnetic substrate and the lubricant of the vapor deposition source during the formation of the lubricating film is in the range of 100 ° C. to 200 ° C.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram showing an equilibrium state of evaporation and adhesion of lubricant molecules on the surface of a magnetic recording medium. The vaporized lubricant molecules repeat evaporation and adhesion on the surface of the magnetic recording medium. When a lubricant molecule has a functional group which is easily adsorbed to a protective film of a magnetic recording medium, if the functional group adheres to the surface of the protective film, the lubricant molecule is less likely to evaporate. Further, the lubricant molecules in the vapor hardly adhere to the portion where the lubricant molecules are adhered, and even if they are adhered, the lubricant molecules are easily evaporated, and thus evaporate immediately. In other words, molecules other than the lubricant molecules adhering to the protective film surface due to the terminal functional groups of the lubricant are considered to have almost the same probability of evaporation and adhesion when the temperature of the vapor and the magnetic recording medium are almost equal. Presumed. In such an equilibrium state, a monomolecular lubricating film is uniformly formed on the surface of the magnetic recording medium. When the temperature equilibrium state is broken, it is estimated that the lubricating film is difficult to be formed uniformly because the probability of evaporation and adhesion is not equal.
[0018]
In order to form a lubricating film under such an equilibrium state, the equipment shown in FIG. 2 was prepared. This is an embodiment in which a study was conducted using a magnetic disk as an example of a magnetic recording medium. A magnetic disk 1 having at least a magnetic film and a protective film formed on a non-magnetic substrate is supported by a support 2 and processed in a lubricant coating tank 3 and a heat treatment tank 4.
[0019]
The temperature of the heat treatment tank 4 is controlled by a heater 6. The magnetic disk 1 is first transported to the heat treatment tank 4 and heated to a predetermined temperature. When the magnetic disk 1 is heated to a predetermined temperature, the shutter 5 opens, the magnetic disk 1 is transported to the lubricant coating tank 3, and the shutter 5 is closed and hermetically closed. The lubricant application tank 3 has a lubricant 8 and a container 9 for holding the lubricant 8 therein, and is connected to an evaporating lubricant generating mechanism 10 which is a mechanism for generating a lubricant vapor by heating to a predetermined temperature. The lubricant vapor is circulated together with the air in the lubricant application tank 3. A pump 11 and valves 12 and 13 for circulating the lubricant vapor are disposed in the piping, and control the circulation of the lubricant vapor. The evaporating lubricant generating mechanism 10, the piping, and the lubricant application tank 3 each have an independent heater 6 for heating, and the temperature thereof is controlled to be always constant. The lubricant application tank 3 has a built-in stirring fan 7 for circulating steam, and sends a spiral airflow to the surface of the magnetic disk 1 so that unevenness of the adhesion of the lubricant is not directed. When the magnetic disk 1 enters the lubricant application tank 3 and is sealed, the supply valve 13 and the discharge valve 12 are opened, the pump 11 is driven, and the lubricant vapor generated by the evaporation lubricant generation mechanism 10 is circulated in the tank. Let it. At this time, the temperature of the lubricant vapor, the temperature of the lubricant application tank 3, and the temperature of the heat treatment of the magnetic disk 1 are controlled to be within 150 ± 5 ° C. The thickness of the lubricating film of the magnetic disk 1 is monitored by an ellipsometer from the outside of the lubricant coating tank 3, and when the lubricating film reaches a predetermined thickness, the supply valve 13 is closed to discharge the lubricant vapor. After that, the magnetic disk 1 is taken out. Since the density of the lubricant vapor is sufficiently small, it is possible to measure the thickness of the lubricating film with an ellipsometer. In actual production, the magnetic disk 1 can be taken out when the lubricating film thickness measured by an ellipsometer reaches a predetermined film thickness, and the film thickness can be easily controlled. It is difficult to monitor the film thickness during application by the immersion method or the like, and the lubricant application method of the present invention is also excellent in this respect.
[0020]
As a magnetic disk, a NiTa alloy seed film, a CrTi alloy base film, a CoCrPt alloy lower magnetic film, a Ru intermediate film, and a CoCrPtB alloy upper magnetic film are sequentially formed on a 2.5-inch glass substrate by sputtering. A diamond-like carbon (DLC) film was formed to a thickness of 3.5 nm by a beam method. Thereafter, the heat treatment and the lubricant application shown in FIG. 2 were performed.
[0021]
The standard temperature for heat treatment and lubricant application is 150 ° C. The heat treatment was performed for 30 minutes, and it was confirmed that the temperature of the magnetic disk reached 150 ° C. The used lubricant has a main chain structure of chemical formula (1) (perfluoropolyether), and the structure of the terminal functional group is represented by chemical formulas (2) to (4). Three types of Z-Tetraol and Z-DOLTX were applied and compared. The average molecular weight of each lubricant is 2,000, and the molecular weight is controlled so that the ratio of the weight average molecular weight to the number average molecular weight is 1.1 or less.
X-CF2O- (CF2CF2O) m- (CFO) n-CF2-X (1)
(Where m and n are 0 or an integer of 1 or more, X is a terminal functional group, and the average molecular weight is 600 to 3500)
-CH2-OH (2)

-(CH2CH2O) p-H or -CF2CH2 (OCH2CH2) q-OH (p and q are integers) (4)
First, when the holding temperature of the magnetic disk and the lubricant vapor was set to the same 150 ° C. using Z-Tetraol, how the thickness of the applied lubricant changed with the application time was measured. The results are shown in FIG. As comparative examples, when the temperature in the heating step of the magnetic disk was 130 ° C. and the temperature of the lubricant vapor and air was 150 ° C., and the temperature in the heating step of the magnetic disk was 180 ° C. and the temperature of the lubricant vapor and air FIG. 4 shows the relationship between the application time and the lubricating film thickness when the temperature was set to 150 ° C.
[0022]
As is apparent from a comparison between FIG. 3 and FIG. 4, the time change of the lubricating film thickness is stable in the case of the example, and the comparative example changes greatly with time. It was confirmed that a stable and uniform lubricating film could be formed in a coating time of about several minutes in the atmosphere. Therefore, a lubricating film was formed on the magnetic disk under each temperature condition with the application time being 3 minutes. The magnetic disk was rinsed with a lubricant solvent (HFE7100 manufactured by 3M) at room temperature to measure the bond ratio. The bond ratio is defined as the ratio between the lubrication film thickness measured by an ellipsometer after rinsing and the lubrication film thickness before rinsing. The thickness and coverage of the lubricating film were measured by an atomic force microscope (AFM) using a probe coated with fluorine. Table 1 shows the results.
[0023]
[Table 1]

The lubricating film thickness measured by the AFM is different from the film thickness measured by the ellipsometer, and indicates the actual film thickness of the lubricating film, and the film thickness of the ellipsometer indicates the average film thickness. In the case of the embodiment, since the bond ratio is large and the coverage ratio is close to 100%, and since the lubricating film thickness measured by AFM is almost equal to the lubricating film thickness measured by ellipsometer, a lubricating film consisting of one molecular layer is obtained. You can see that it is. In Comparative Example 1, since the bond rate was extremely small and the coverage was 100%, a multi-layered lubricating film was formed instead of a monolayer, and the lubricant of two or more monolayers was easily rinsed. Therefore, it is estimated that the bond ratio has decreased. In Comparative Example 2, the bond ratio was large, but the coverage was small as compared with the examples. From this, it can be seen that the lubricant is attached to the lubricating film of Comparative Example 2 in an island shape. From these results, it is considered that in the examples, the lubricating film of one molecular layer is evenly distributed, does not hinder the floating of the head as a lubricating film, and exhibits excellent wear resistance.
[0024]
Next, the heating temperature and the temperature of the lubricant vapor were examined as parameters. The time at which the lubricating film thickness was saturated was measured by changing the temperature from 60 ° C to 160 ° C. The lubricant used was Z-Tetraol. The result is shown in FIG. As the holding temperature of the magnetic disk increases, the lubricant saturation time decreases. Particularly, when the temperature is 100 ° C. or more, the time is as short as 200 minutes or less, which is suitable for manufacturing. If the temperature is higher than 200 ° C., the lubricant may be decomposed, so that 100 ° C. to 200 ° C. is considered to be suitable for manufacturing a magnetic disk.
[0025]
FIG. 6 shows the relationship between the saturated lubricating film thickness and the magnetic disk holding temperature. The saturated lubricating film thickness decreases with temperature, and becomes a constant film thickness (1.1 nm) of 1.2 nm or less at 130 ° C. to 160 ° C. These magnetic disks were rinsed, and the bond ratio and flying property of the magnetic head were investigated. After the head having a flying height of 8 nm was sought 10 times on a magnetic disk, the amount of lubricant adhering to the head was observed with an optical microscope. Those that did not adhere were marked as ○. Table 2 shows the results.
[0026]
[Table 2]

As the holding temperature increases, the bond ratio increases, and the levitation of the magnetic head also increases. In particular, when the treatment was performed at a holding temperature of 120 ° C. or higher where the bond ratio was 60% or higher, the flying characteristics of the head were good. When the lubricant was Z-DOL or Z-DOLTX, the lubricant was applied at 150 [deg.] C. and the flying performance of the head was evaluated.
[0027]
In this embodiment, an example is shown in which a DLC protective film formed by an ion beam method is coated with a Z-DOL, Z-Tetraol, or Z-DOLTX lubricant, but a gas such as nitrogen is added to the protective film. In the case or when the film forming method of the protective film is different, since the adhesiveness of the lubricant is different, it is considered that the saturated lubricating film thickness and the bond ratio are changed. Not always. However, it is considered that a similar effect can be obtained by applying the lubricant in a state of thermal equilibrium.
[0028]
【The invention's effect】
According to the present invention, since a lubricating film can be formed with a uniform thickness, a highly reliable magnetic disk can be obtained. Further, there is no need to complicate the structure of the lubricating film forming apparatus or to precisely control the lubricating film forming time, so that the lubricating film manufacturing method can be inexpensive and simple.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing an equilibrium state of evaporation and adhesion of lubricant molecules on the surface of a magnetic recording medium.
FIG. 2 is a configuration diagram of a manufacturing apparatus for realizing a method of forming a lubricating film according to one embodiment of the present invention.
FIG. 3 is a diagram showing a change in a lubricant film thickness with respect to a lubricant application time in one example of the present invention.
FIG. 4 is a diagram showing a change in a lubricant film thickness with respect to a lubricant application time in a comparative example.
FIG. 5 is a diagram showing a relationship between a heating temperature of a magnetic disk and a lubrication film saturation time.
FIG. 6 is a diagram showing a relationship between a heating temperature of a magnetic disk and a saturated lubricating film thickness.
FIG. 7 is a plan view showing a state in which unevenness (spots) of adhesion of a lubricant has a direction on a magnetic disk to which a lubricant is applied by a conventional application method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Magnetic disk 2 Support stand 3 Lubricant application tank 4 Heat treatment tank 5 Shutter 6 Heater 7 Steam stirring fan 8 Perfluoropolyether lubricant 9 Lubricant holding container 10 Evaporation lubricant generation mechanism 11 Circulation pump 12 Discharge valve 13 Supply valve

Claims (7)

In a magnetic recording medium in which at least a magnetic film, a protective film, and a lubricating film are sequentially formed on a non-magnetic substrate, the lubricating film has a main chain structure represented by a chemical formula (1)
X-CF2O- (CF2CF2O) m- (CFO) n-CF2-X (1)
(Where m and n are 0 or an integer of 1 or more, X is a terminal functional group, and the average molecular weight is 600 to 3500)
Magnetic recording characterized by having a bond rate of 60% or more, a coverage of 90% or more, a film thickness of 1.2 nm or less, and non-uniformity in adhesion unevenness. Medium. 2. The magnetic recording medium according to claim 1, wherein the lubricating film is applied as a single molecular layer. The perfluoropolyether has the chemical formulas (2), (3), and (4)
-CH2-OH (2)

-(CH2CH2O) p-H or -CF2CH2 (OCH2CH2) q-OH (p and q are integers) (4)
The magnetic recording medium according to claim 1, further comprising a terminal functional group X represented by any one of the following. At least a magnetic film and a protective film are formed on a non-magnetic substrate, and the heating temperature and the main chain structure of the non-magnetic substrate on which the magnetic film and the protective film are formed are represented by chemical formula (1).
X-CF2O- (CF2CF2O) m- (CFO) n-CF2-X (1)
(Where m and n are 0 or an integer of 1 or more, X is a terminal functional group, and the average molecular weight is 600 to 3500)
Wherein the temperature of the lubricant of perfluoropolyether represented by the formula is maintained constant, and a lubricating film is formed on the protective film by a vapor deposition method. 5. The method according to claim 4, wherein the forming of the lubricating film is performed in the atmosphere. 6. The method according to claim 4, wherein the temperature of the nonmagnetic substrate and the lubricant at the time of forming the lubricating film is 100 ° C. to 200 ° C. The perfluoropolyether has the chemical formulas (2), (3), and (4)
-CH2-OH (2)

-(CH2CH2O) p-H or -CF2CH2 (OCH2CH2) q-OH (p and q are integers) (4)
7. The method for producing a magnetic recording medium according to claim 4, having a terminal functional group X represented by any one of the following.

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