JP3946386B2 - Lubricant and magnetic recording medium using the same - Google Patents

Description

〔式中、Ｒｆはフツ化炭素基、Ｒ¹ は炭化水素基、Ａ¹ ，Ａ² は下記の式；

で示される有機基であつて、Ｒは、一般式（１）ではＡ¹ ，Ａ² のうちの一方が炭化水素基、他方が水素原子または炭化水素基、一般式（２），（３）では炭化水素基、ｍ，ｎ，ｋは０または１である〕
のいずれかの式で表されるフツ化カルボン酸からなる潤滑剤（請求項１〜４）と、非磁性支持体の少なくとも片面に磁性層を有する磁気記録媒体において、磁性層がその内部または表面に上記構成の潤滑剤を有することを特徴とする磁気記録媒体（請求項５〜７）とに係るものである。
【００１０】
【発明の実施の形態】
本発明に用いられるフツ化カルボン酸は、前記の一般式（１）〜（３）のいずれかの式で表される化学構造を有するもので、分子内に２個のカルボキシル基を有するか、またはカルボキシル基と水酸基をそれぞれ１個ずつ有することから、強磁性金属薄膜やその保護膜表面およびヘツド表面に吸着して安定に存在でき、とくに低温・低湿のような過酷な環境下でも摺動面から排除されることなく安定に存在でき、そのため、フツ化炭素基の潤滑性能に基づく良好な摺動特性が確保されて、ヘツド媒体間の摩耗によるヘツド汚れやドロツプアウトを低減し、磁気記録媒体の耐久性および走行性を大きく向上する。
【００１１】
このようなフツ化カルボン酸を示す一般式（１）〜（３）中、Ｒｆは、表面エネルギ―を低減して良好な潤滑特性を付与するためのフツ化炭素基であり、上記効果をよりよく発揮させるため、Ｆ（ＣＦ₂ ）ｐ−（ｐは整数である）を主成分としたものが好ましい。また、構成炭素数は、２〜５０、好ましくは４〜３０、より好ましくは６〜２０であるのがよい。２未満ではフツ素独特の潤滑性を発揮できず、磁気記録媒体として十分な耐久性を得られず、５０を超えると上記効果が飽和し、また潤滑剤の粘度が上昇するなどの問題を生じやすい。
【００１２】
また、一般式（１）〜（３）中、Ｒ¹ は炭素数が通常１〜２６の炭化水素基であり、飽和または不飽和、直鎖または分岐鎖や環状であつてもよい。このような炭化水素基の存在で、フツ化炭素基（Ｒｆ）とエステル結合との距離を隔てて、上記エステル結合の安定性を確保して、フツ化カルボン酸の加水分解性を防ぎ、その分解物がヘツド汚れなどの原因となるのを防止する。
【００１３】
さらに、Ａ¹ ，Ａ² を構成するＲは、一般式（１）ではＡ¹ ，Ａ² のうちの一方が炭化水素基、他方が水素原子または炭化水素基であり、また一般式（２），（３）では炭化水素基である。上記の炭化水素基は、飽和または不飽和、直鎖または分岐鎖や環状であつてもよいが、とくに飽和直鎖炭化水素基であるのが好ましい。炭化水素基の炭素数は、摩擦係数や粘度特性の面より、通常１〜２６の範囲とされるが、非フツ素系溶剤に対する溶解性を高めるため、好ましくは８以上であるのがよく、とくに好ましくは１２〜１８である。
【００１４】
なお、上記のＲ¹ ，Ａ¹ ，Ａ² を構成する炭化水素基には、炭素および水素以外の構成元素として、窒素、酸素、燐などの他の元素を含ませて、高荷重下での摺動特性をより向上させるようにしてもよい。
【００１５】
このように構成されるフツ化カルボン酸は、環境にやさしい非フツ素系溶剤に可溶であり、上記溶剤で塗布、浸漬、噴霧などの操作を行えるという特徴を備えている。環境にやさしい非フツ素系溶剤としては、炭化水素系溶剤、ケトン系溶剤、アルコ―ル系溶剤、エステル系溶剤などの汎用溶剤があり、具体的には、ヘキサン、ヘプタン、オクタン、デカン、ドデカン、ベンゼン、トルエン、キシレン、シクロヘキサン、メチルエチルケトン、メチルイソブチルケトン、メタノ―ル、エタノ―ル、イソプロパノ―ル、ジエチルエ―テル、テトラヒドロフラン、ジオキサン、シクロヘキサノンなどを挙げることができる。
【００１６】
本発明において、上記のフツ化カルボン酸は、いかなる方法で合成されたものであつてもよい。工業的に有効な合成法の一例を示すと、Ｒｆ−Ｒ¹ −ＣＨ（ＯＨ）−ＣＨ₂ ＯＨで表されるフツ化アルコ―ル１モルに対して、無水コハク酸、アルキル無水コハク酸、アルキル無水チオリンゴ酸などのカルボン酸成分を２モル反応させることにより、一般式（１）で表されるフツ化カルボン酸を、また、上記カルボン酸成分を１モル反応させることにより、一般式（２）または（３）で表されるフツ化カルボン酸を、それぞれ容易に合成できる。後者の場合、一般式（２）で表されるものと一般式（３）で表されるものとが混在したフツ化カルボン酸が得られるが、本発明では、この混在物をそのまま使用できる。また、カルボン酸成分として上記のような酸無水物を使用すると、上記の一般式（１）〜（３）におけるＡ¹ ，Ａ² として、通常ｍ＝０でｎ＝１であるものとｍ＝１でｎ＝０であるものとが混在したフツ化カルボン酸が得られるが、本発明では、この混在物をそのまま使用できるものである。
【００１７】
本発明においては、このようなフツ化カルボン酸を潤滑剤として使用することを特徴としているが、その際、必要によりこれ以外の潤滑剤を併用してもよい。たとえば脂肪酸またはその金属塩、脂肪族エステル、脂肪族アミド、脂肪族アルコ―ル、脂肪族アミン、モノサルフアイド、パラフイン類、シリコ―ン化合物、脂肪酸とフツ化アルコ―ルとのエステル、パ―フロロポリエ―テル、ポリテトラフルオロエチレンなど、一般に使用される各種潤滑剤を併用することができる。これら潤滑剤の使用量は、本発明のフツ化カルボン酸１モルに対して、０．０１〜１００モル、好ましくは０．１〜１０モルとなる割合とするのがよい。また、上記潤滑剤のほか、トリオレイルホスフエ―トなどのリン系極圧剤、二硫化ベンジルなどの硫黄系極圧剤、臭化アリルなどのハロゲン系極圧剤、ジイソブチルジチオリン酸亜鉛などの有機金属系極圧剤などを併用してもよい。
【００１８】
本発明の磁気記録媒体は、非磁性支持体の少なくとも片面に磁性層を有して、この磁性層がその内部または表面に上記のフツ化カルボン酸からなる潤滑剤を有することを特徴としたものである。上記の潤滑剤を磁性層の内部または表面に設けるには、上記潤滑剤を前記した非フツ素系溶剤からなる汎用溶剤に溶解させ、この溶液を非磁性支持体の少なくとも片面に形成された磁性層の上に、塗布または噴霧して乾燥するか、上記の溶液中に磁性層を浸漬して乾燥すればよい。磁性層の種類に応じた適宜の方法を使用できる。
【００１９】
磁性層が強磁性金属薄膜からなる場合、その薄膜上に、真空蒸着、スパツタリング、プラズマなどにより、炭素（ダイヤモンド状あるいはアモルフアス状）、、窒化炭素、酸化硅素、酸化ジルコニウム、酸化クロムを主成分とする保護膜や、有機化合物などからなる保護膜を設けるようにしてもよい。また、それらにフツ素、窒素、硅素などを含ませた保護膜を設けてもよい。さらに、強磁性金属塗膜は、表面に微量の水分が付着したものであつてもよいし、ベンゾトリアゾ―ル系などの防錆剤を塗布したものであつてもよい。
【００２０】
また、炭素保護膜などの表面に酸素およびアンモニアプラズマ処理などを施してもよい。プラズマ処理を施すことにより、保護膜表面を清浄化しつつ、プラズマ中の化学活性種を堆積させることができ、保護膜の硬度を低下させることなく潤滑剤をより安定に存在させることが可能となる。また、グロ―放電処理、紫外線照射処理、熱処理などを行うことによつても、潤滑剤を安定に存在させることが可能である。これらの処理は、潤滑剤を付着させる前に行つてもよいし、潤滑剤を付着させたのちに行つてもよく、また潤滑剤を付着させたのち、余分な潤滑剤を溶剤などで洗浄したのちに行つてもよい。
【００２１】
強磁性金属薄膜上への潤滑剤の塗布量は、薄膜表面に対し０．５〜２０mg／m²の範囲とするのが好ましい。潤滑剤の塗布量が過少では、薄膜表面に潤滑剤を均一に付着させにくく、スチル耐久性を十分に向上させることができない。また、潤滑剤の塗布量が過多となると、磁気ヘツドと強磁性金属薄膜とが貼り付いたりするため、好ましくない。潤滑剤の塗布量は、Ｘ線光電子分光法および液体カラムクロマトグラフイなどにより、求めることができる。
【００２２】
本発明の磁気記録媒体において、非磁性支持体には、ポリエチレンテレフタレ―ト、ポリエチレンナフタレ―ト、ポリカ―ボネ―ト、ポリアミド、ポリイミド、ポリ塩化ビニルなどのプラスチツク、ガラス、アルミニウム合金、チタン合金などが好適に使用される。この非磁性支持体は、テ―プ、シ―ト、デイスク、カ―ドなどのいずれの形態でもよく、表面に突起を設けたものでもよい。
【００２３】
強磁性金属薄膜型の磁気記録媒体では、上記の非磁性支持体の片面または両面に、Ｃｏ、Ｎｉ、Ｆｅ、Ｃｏ−Ｎｉ、Ｃｏ−Ｃｒ、Ｃｏ−Ｐ、Ｃｏ−Ｎｉ−Ｐ、Ｆｅ−Ｃｏ−Ｂ、Ｆｅ−Ｃｏ−Ｎｉ、Ｃｏ−Ｎｉ−Ｆｅ−Ｂ、Ｆｅ−Ｎｉ、Ｆｅ−Ｃｏ、Ｃｏ−Ｐｔ、Ｃｏ−Ｎｉ−Ｐｔまたはこれらに酸素を加えたものなどからなる種々の強磁性材が、真空蒸着、イオンプレ―テイング、スパツタリング、メツキなどの方法で、薄膜形成される。このように形成される強磁性金属薄膜の膜厚は、通常０．０３〜１μｍの範囲にあるのが好ましい。
【００２４】
本発明の磁気記録媒体において、非磁性支持体の一面側のみに磁性層を形成したものでは、その反対面側にバツクコ―ト層を設けてもよい。このバツクコ―ト層は、カ―ボンブラツク、ベンガラ、炭酸カルシウム、硫酸バリウムなどの非磁性粉を、塩化ビニル−酢酸ビニル系共重合体、ポリエステル系樹脂、ポリウレタン系樹脂、ニトロセルロ―ス系樹脂、繊維素系樹脂などの結合剤樹脂および有機溶剤とともに混合分散して、バツクコ―ト層用塗料を調製し、この塗料を非磁性支持体の反対面側に塗布、乾燥して形成される。
【００２５】
【実施例】
つぎに、本発明の実施例を記載して、より具体的に説明する。ただし、本発明は、以下の実施例によりなんら限定されるものではない。
【００２６】
実施例１
式：Ｆ（ＣＦ₂ ）₆ −ＣＨ₂ −ＣＨ（ＯＨ）−ＣＨ₂ ＯＨで表されるフツ化ジアルコ―ル１モルと、ｎ−オクタデシル無水コハク酸２モルとを、撹拌翼を備えたフラスコに仕込み、窒素気流下、１００℃で１２時間反応させた。反応終了後、反応混合物をフツ素系溶剤（３Ｍ社製の「ＦＣ７７」）に溶解し、１０℃に冷却して、未反応のフツ化ジアルコ―ルを除去した。また、反応物をベンゼン溶液として同様の処理により、未反応のｎ−オクタデシル無水コハク酸を除去して、フツ化カルボン酸からなる潤滑剤を得た。この潤滑剤は、図１に示す赤外分光スペクトルで、１，７４０cm^-1付近にエステル結合、１，７００cm^-1付近にカルボン酸由来のピ―クがみられ、前式の一般式（１）（式中、Ｒｆ，Ｒ¹ は上記のフツ化ジアルコ―ルに由来する基、Ａ¹ ，Ａ² におけるＲはｎ−オクタンデシル基、ｋは０である）で表されるフツ化カルボン酸であることを確認した。
【００２７】
実施例２
実施例１と同じフツ化アルコ―ル１モルと、ｎ−オクチル無水コハク酸２モルとを、撹拌翼を備えたフラスコに仕込み、窒素気流下、１００℃で１２時間反応させた。反応終了後、反応混合物を実施例１と同じフツ素系溶剤に溶解し、１０℃に冷却して、未反応のフツ化ジアルコ―ルを除去した。さらに、反応物をベンゼン溶液として同様の処理により、未反応のｎ−オクチル無水コハク酸を除去して、フツ化カルボン酸からなる潤滑剤を得た。この潤滑剤は、赤外分光スペクトルにより、実施例１と同様の一般式（１）で表されるフツ化カルボン酸（ただし、Ｒはｎ−オクチル基である）であることを確認した。
【００２８】
実施例３
実施例１と同じフツ化ジアルコ―ル１モルと、ｉｓｏ−オクタデシル無水コハク酸２モルとを、撹拌翼を備えたフラスコに仕込み、窒素気流下、１００℃で１２時間反応させた。反応終了後、反応混合物を実施例１と同じフツ素系溶剤に溶解し、１０℃に冷却して、未反応の上記フツ化ジアルコ―ルを除去した。さらに、反応物をベンゼン溶液として同様の処理により、未反応のｉｓｏ−オクタデシル無水コハク酸を除去して、フツ化カルボン酸からなる潤滑剤を得た。この潤滑剤は、赤外分光スペクトルにより、実施例１と同様の一般式（１）で表されるフツ化カルボン酸（ただし、Ｒはｉｓｏ−オクタデシル基である）であることを確認した。
【００２９】
実施例４
実施例１と同じフツ化ジアルコ―ル１モルと、オクタデセニル無水コハク酸２モルとを、撹拌翼を備えたフラスコに仕込み、窒素気流下、１００℃で１２時間反応させた。反応終了後、反応混合物を実施例１と同じフツ素系溶剤に溶解し、１０℃に冷却して、未反応の上記フツ化ジアルコ―ルを除去した。さらに、反応物をベンゼン溶液として同様の処理により、未反応のオクタデセニル無水コハク酸を除去して、フツ化カルボン酸からなる潤滑剤を得た。この潤滑剤は、赤外分光スペクトルにより、実施例１と同様の一般式（１）で表されるフツ化カルボン酸（ただし、Ｒはオクタデセニル基である）であることを確認した。
【００３０】
実施例５
実施例１と同じフツ化ジアルコ―ル１モルと、ｎ−オクタデシル無水チオリンゴ酸２モルとを、撹拌翼を備えたフラスコに仕込み、窒素気流下、１００℃で１２時間反応させた。反応終了後、反応混合物を実施例１と同じフツ素系溶剤に溶解し、１０℃に冷却して、未反応の上記フツ化ジアルコ―ルを除去した。さらに、反応物をベンゼン溶液として同様の処理により、未反応のｎ−オクタデシル無水チオリンゴ酸を除去して、フツ化カルボン酸からなる潤滑剤を得た。この潤滑剤は、赤外分光スペクトルにより、実施例１と同様の一般式（１）で表されるフツ化カルボン酸（ただし、Ｒはｎ−オクタデシル基、ｋは１である）であることを確認した。
【００３１】
実施例６
実施例１と同じフツ化ジアルコ―ル１モルと、ｎ−オクタデシル無水コハク酸１モルとを、撹拌翼を備えたフラスコに仕込み、窒素気流下、１００℃で１２時間反応させた。反応終了後、反応混合物を実施例１と同じフツ素系溶剤に溶解し、１０℃に冷却して、未反応の上記フツ化ジアルコ―ルを除去した。さらに、反応物をベンゼン溶液として同様の処理により、未反応のｎ−オクタデシル無水コハク酸を除去して、フツ化カルボン酸からなる潤滑剤を得た。この潤滑剤は、赤外分光スペクトルおよび核磁気共鳴スペクトルにより、一般式（２），（３）で表されるフツ化カルボン酸の混合物（ただし、Ｒはｎ−オクタデシル基である）であることを確認した。また、上記混合物の比は、一般式（２）：一般式（３）＝９：１（重量比）であることを確認した。
【００３２】
実施例７
実施例１と同じフツ化ジアルコ―ル１モルと、ｎ−オクタデシル無水コハク酸１モルとを、撹拌翼を備えたフラスコに仕込み、窒素気流下、１８０℃で１２時間反応させた。反応終了後、反応混合物を実施例１と同じフツ素系溶剤に溶解し、１０℃に冷却して、未反応の上記フツ化ジアルコ―ルを除去した。さらに、反応物をベンゼン溶液として同様の処理により、未反応のｎ−オクタデシル無水コハク酸を除去して、フツ化カルボン酸からなる潤滑剤を得た。この潤滑剤は、赤外分光スペクトルおよび核磁気共鳴スペクトルにより、一般式（２），（３）で表されるフツ化カルボン酸の混合物（ただし、Ｒはｎ−オクタデシル基である）であることを確認した。また、上記混合物の比は、一般式（２）：一般式（３）＝７：３（重量比）であることを確認した。
【００３３】
比較例１
式；ＨＯＣＨ₂ ＣＦ₂ （ＯＣ₂ Ｆ₄ ）ｐ（ＯＣＦ₂ ）ｑＯＣＦ₂ ＣＨ₂ ＯＨ（ｐ，ｑは整数である）で表されるフツ化ジアルコ―ル（アウジモント社製の「ＦＯＮＢＬＩＮ Ｚ ＤＯＬ」、平均分子量２，０００）を使用し、これをそのまま潤滑剤とした。
【００３４】
比較例２
比較例１と同じフツ化ジアルコ―ル１モルと、ｎ−オクタデシル無水コハク酸２モルとを、実施例１と同様に反応させて、フツ化ジカルボン酸からなる潤滑剤を得た。
【００３５】
比較例３
式：Ｆ（ＣＦ₂ ）₈ ＣＨ₂ ＣＨ₂ ＯＨで表されるフツ化モノアルコ―ル１モルと、ｎ−オクタデシル無水コハク酸１モルとを、実施例１と同様に反応させて、式；Ｆ（ＣＦ₂ ）₈ ＣＨ₂ ＣＨ₂ ＯＣＯＣＨ₂ ＣＨ（ＣＯＯＨ）（ＣＨ₂ ）₁₈Ｈで表されるフツ化モノカルボン酸からなる潤滑剤を得た。
【００３６】
比較例４
式：Ｆ（ＣＦ₂ ）₈ ＣＨ₂ ＣＨ₂ ＯＨで表されるフツ化モノアルコ―ル２モルと、デカンジカルボン酸１モルとを反応させ、式：Ｆ（ＣＦ₂ ）₈ ＣＨ₂ ＣＨ₂ ＯＣＯ（ＣＨ₂ ）₁₀ＣＯＯＣＨ₂ ＣＨ₂ （ＣＦ₂ ）₈ Ｆで表されるフツ化ジエステルからなる潤滑剤を得た。
【００３７】
以上の実施例１〜７および比較例１〜４の各潤滑剤について、非フツ素系溶剤に対する溶解性を、以下の方法により、調べた。すなわち、非フツ素系溶剤としてメチルイソブチルケトン：イソプロピルアルコ―ル＝３：１（重量比）を使用し、各潤滑剤をこの溶剤に少量ずつ加えてよく撹拌し、０．０５重量％以上溶解するものを〇、それ以下のものを×、と評価した。
【００３８】
その結果、実施例１〜７および比較例２〜４の各潤滑剤はいずれも○、比較例１の潤滑剤は×、であつた。この結果からも明らかなように、実施例１〜７および比較例２〜４の各潤滑剤は、非フツ素系溶剤に対する溶解性にすぐれており、上記溶剤で塗布などの作業を行えることから、環境にやさしい潤滑剤であることがわかつた。これに対して、比較例１の潤滑剤は、非フツ素系溶剤に対する溶解性に劣つており、環境悪化の原因となるフツ素系溶剤を使用して塗布などの作業を行う必要があることがわかつた。
【００３９】
実施例８〜１４
非磁性支持体として、厚さが６μｍのポリエチレンテレフタレ―トフイルムを使用し、このフイルム上に、Ｃｏを酸素雰囲気下で斜め蒸着して、厚さが０．１５μｍのＣｏ−Ｏからなる強磁性金属薄膜を形成した。しかるのち、１３．５６ＭＨｚのＲＦを用い、モノマ―ガスとしてエチレン、キヤリアガスとして水素を用いて、プラズマ重合法により、上記の強磁性金属薄膜上に厚さが１０ｎｍのＤＬＣ（ダイアモンド状カ―ボン）保護膜を形成した。この保護膜の形成後、幅が８mmとなるように切断して、テ―プを作製した。
【００４０】
つぎに、実施例１〜７の各潤滑剤を、それぞれ、ｎ−ヘキサン：メチルエチルケトン：イソプロピルアルコ―ル＝５：３：２（重量比）の混合溶剤に、０．２重量％濃度となるように溶解させて、潤滑剤溶液を調製した。この潤滑剤溶液中に、上記のテ―プを浸漬塗布したのち、乾燥して、ＤＬＣ保護膜上に各潤滑剤被膜を有する７種のビデオテ―プをそれぞれ作製した。
【００４１】
比較例５〜８
潤滑剤として、比較例１〜４の各潤滑剤を使用した以外は、実施例８〜１４と同様にして、４種のビデオテ―プを作製した。なお、比較例１の潤滑剤では、潤滑剤溶液の調製に際し、パ―フロロオクタンを使用した。
【００４２】
以上の実施例８〜１４および比較例５〜８の各ビデオテ―プについて、潤滑性の評価として、摩擦係数、スチル耐久性およびヘツド汚れを、下記の方法により調べた。これらの結果は、表１に示されるとおりであつた。
【００４３】
＜摩擦係数＞
２０℃，５０％ＲＨの雰囲気下、摺動速度１ｍ／分、摺動距離５cm、テ―プ張力２０ｇｆの条件で、対ステンレスピンに往復摺動試験を行い、１００往復目の摩擦係数を求めた。
【００４４】
＜スチル耐久性＞
−５℃，２５％ＲＨの雰囲気下、直径４cmの８mm用シリンダに２２０°の巻き付け角でセツトし、テ―プ／磁気ヘツド間相対速度１１．３ｍ／秒、テ―プ張力１２．５ｇｆの条件で、波長１．６μｍの正弦波を記録し、スチルモ―ドで再生出力を測定した。スチル寿命は、再生出力が初期値から１／２低下するまでの時間とした。
【００４５】
＜ヘツド汚れ＞
各ビデオテ―プ５０ｍを、−５℃，２５％ＲＨの雰囲気下、８mmＶＴＲ〔ソニ―（株）ＥＶ−Ｓ９００〕で１００回繰り返し走行させたのち、磁気ヘツドの汚れを顕微鏡で調べた。ヘツド汚れの評価は、以下の３段階で行つた。
〇：ヘツド汚れがみられない
△：ヘツド汚れが少しみられる
×：ヘツド汚れがたくさんみられる
【００４６】
表１

【００４７】
上記の結果より明らかなように、実施例８〜１４の各ビデオテ―プは、摩擦係数が低くて、スチル寿命が長く、しかもヘツド汚れが少ないことがわかる。これに対し、比較例５のビデオテ―プは、上記同様の潤滑性を示すが、潤滑剤溶液の調製に際して、フツ素系溶剤を用いる必要があるため、環境悪化の原因となり、好ましくない。また、比較例６のビデオテ―プは、用いる潤滑剤の非フツ素系溶剤に対する溶解性は良好であるが、ヘツド汚れが大きく、さらに、比較例７，８の各ビデオテ―プは、スチル寿命が短く、ヘツド汚れも大きい。
【００４８】
【発明の効果】
以上のように、本発明では、分子内にフツ化炭素基および炭化水素基とともに２個のカルボキシル基またはカルボキシル基と水酸基をそれぞれ１個有する特定のフツ化カルボン酸を使用したことにより、高温・低温、高湿・低湿のあらゆる環境下において、高速・低速、高負荷・低負荷にかかわらず接触する２固体間を低摩擦、低摩耗で摺動させることができ、かつ非フツ素系溶剤に可溶である環境にやさしい潤滑剤を提供できる。また、この潤滑剤を磁気記録媒体用に使用することにより、耐久性および走行性にすぐれた磁気記録媒体を提供できる。
【図面の簡単な説明】
【図１】実施例１で得たフツ化カルボン酸からなる潤滑剤の赤外分光スペクトルを示す特性図である。[0001]
BACKGROUND OF THE INVENTION
The present invention is an environmentally friendly lubrication that slides between two contacting solids with low friction and low wear regardless of high speed / low speed, high load / low load in any environment of high temperature / low temperature, high humidity / low humidity. The present invention relates to an agent and a magnetic recording medium using the same.
[0002]
[Prior art]
For the purpose of extending the period of use of equipment and devices by sliding between two contacting solids with low friction and low wear, the solid surface has been hardened and a lubricant has been developed. Particularly in the field of office automation equipment, there is a strong demand for size reduction, and a precise mechanism is adopted year after year for the sliding part. In future equipment in which precision parts slide continuously or intermittently in a wide range of environments, friction and wear at the start, end, or slide will be reduced more than ever, and motors, etc. It is necessary to reduce the load.
[0003]
Until now, in the protective lubrication system, a hard and hard-wearing surface layer is provided at the sliding part, and grease, oily semi-solid or liquid lubricant has been used as the lubricant. However, in precision equipment that requires smoothing of the contact area, there is still a lubricant that slides between two contacting solids with low friction and low wear regardless of high speed / low speed, high load / low load. In fact, the problem is that it has not been possible to avoid problems such as starting failure and accidental sudden increase in frictional force during sliding.
[0004]
For example, in a ferromagnetic metal thin film type magnetic recording medium produced by depositing a ferromagnetic metal or an alloy thereof on a nonmagnetic support by vacuum deposition or the like, the magnetic layer of the magnetic layer is smaller than that of a coating type magnetic recording medium. Easy to achieve high coercive force and thin film, excellent in high density recording characteristics, but does not use tough binder resin, and has good surface smoothness of ferromagnetic metal thin film and protective film usually provided on it For this reason, the coefficient of friction with the magnetic head is large, so that the magnetic head is likely to be worn or damaged, resulting in inferior durability and running performance.
[0005]
For such problems, JP-A-3-254419, JP-A-4-270243, JP-A-4-274018, JP-A-5-77818, JP-A-6-293703, JP-A-7-118204, In each publication such as Kaihei 7-216375, JP-A-7-225941, and JP-A-7-324061, as a lubricant for a magnetic recording medium, “FOMBLIN Z DOL”, “FONBLIN AM 2001” manufactured by Augmont, etc. By using various lubricants such as perfluoropolyether lubricants, carboxylic acid lubricants, partially fluorinated ester lubricants, etc., and making these lubricants present on the ferromagnetic metal thin film, they are durable. To improve performance and running performance is being studied.
[0006]
However, even if such a lubricant is used, the problem of magnetic head contamination and dropout has not been solved yet, and durability and running performance under severe environments such as low temperature and low humidity are still insufficient. .
[0007]
[Problems to be solved by the invention]
In light of the above-described conventional circumstances, the present invention is applicable to high-speed / low-speed, high-load / low-load in any high-temperature / low-temperature / high-humidity / low-humidity environment, even in future precision equipment where smoothing of the contact area is progressing. By sliding the two solids in contact with each other with low friction and low wear, and obtaining an environmentally friendly lubricant, by using this lubricant, a magnetic recording medium with excellent durability and running properties can be obtained. The purpose is that.
[0008]
[Means for Solving the Problems]
As a result of intensive studies on the above object, the present inventors have found that, according to a specific fluorocarboxylic acid having two carboxyl groups or one carboxyl group and one hydroxyl group together with a hydrocarbon group in the molecule, Operations such as coating, dipping, and spraying with fluorine-based solvents are possible, environmental damage due to the use of fluorine-based solvents is not caused, and it can be used as an environmentally friendly lubricant. It can slide between two contacting solids with low friction and low wear regardless of whether it is high speed / low speed, high load / low load in the environment. Knowing that a highly improved magnetic recording medium can be obtained, the present invention has been completed.
[0009]
That is, the present invention provides the following general formulas (1) to (3);

[Wherein Rf is a fluorocarbon group, R ¹ is a hydrocarbon group, A ¹ and A ² are the following formulas;

In it shall apply an organic group represented, R represents the general formula (1) in A ^1, while a hydrocarbon group of A ^2, the other is a hydrogen atom or a hydrocarbon group, the general formula (2), (3) Is a hydrocarbon group, m, n, and k are 0 or 1.]
In a magnetic recording medium having a lubricant comprising a fluorinated carboxylic acid represented by any one of the formulas (Claims 1 to 4) and a magnetic layer on at least one surface of a nonmagnetic support, the magnetic layer And a magnetic recording medium (claims 5 to 7), characterized by having the above-structured lubricant.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The fluorinated carboxylic acid used in the present invention has a chemical structure represented by any one of the general formulas (1) to (3), and has two carboxyl groups in the molecule. Or, since it has one carboxyl group and one hydroxyl group, it can be stably adsorbed on the surface of the ferromagnetic metal thin film, its protective film, and the head, and even in harsh environments such as low temperature and low humidity Therefore, good sliding characteristics based on the lubrication performance of the fluorocarbon group can be ensured, head contamination and dropout due to wear between the head media can be reduced, and magnetic recording media Durability and running performance are greatly improved.
[0011]
In the general formulas (1) to (3) showing such a fluorinated carboxylic acid, Rf is a fluorinated carbon group for reducing surface energy and imparting good lubricating properties, and the above effects are further improved. for better _{exerted, F (CF 2) p- (} p is an integer) preferably one composed mainly of. In addition, the number of constituent carbon atoms is 2 to 50, preferably 4 to 30, and more preferably 6 to 20. If it is less than 2, the lubricity peculiar to fluorine cannot be exhibited, and sufficient durability as a magnetic recording medium cannot be obtained, and if it exceeds 50, the above effects are saturated and the viscosity of the lubricant increases. Cheap.
[0012]
In general formulas (1) to (3), R ¹ is usually a hydrocarbon group having ^{1 to} 26 carbon atoms, and may be saturated or unsaturated, linear, branched or cyclic. In the presence of such a hydrocarbon group, the distance between the fluorocarbon group (Rf) and the ester bond is separated, the stability of the ester bond is ensured, and the hydrolyzability of the fluorocarboxylic acid is prevented. Prevent decomposition products from causing head contamination.
[0013]
Further, R constituting A ¹ and A ² is represented by the general formula (1) in which ^one of A ¹ and A ² is a hydrocarbon group, the other is a hydrogen atom or a hydrocarbon group, and the general formula (2) , (3) is a hydrocarbon group. The above hydrocarbon group may be saturated or unsaturated, linear, branched or cyclic, but is preferably a saturated linear hydrocarbon group. The number of carbon atoms of the hydrocarbon group is usually in the range of 1 to 26 in terms of the coefficient of friction and viscosity characteristics, but in order to increase the solubility in non-fluorinated solvents, it is preferably 8 or more. Especially preferably, it is 12-18.
[0014]
The hydrocarbon groups constituting the above R ¹ , A ¹ , and A ² contain other elements such as nitrogen, oxygen, and phosphorus as constituent elements other than carbon and hydrogen, and can be used under a high load. You may make it improve a sliding characteristic more.
[0015]
The fluorinated carboxylic acid constituted in this way is soluble in an environment-friendly non-fluorinated solvent, and has such a feature that operations such as coating, dipping and spraying can be performed with the solvent. Environmentally friendly non-fluorinated solvents include general-purpose solvents such as hydrocarbon solvents, ketone solvents, alcohol solvents, and ester solvents. Specific examples include hexane, heptane, octane, decane, and dodecane. Benzene, toluene, xylene, cyclohexane, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropanol, diethyl ether, tetrahydrofuran, dioxane, cyclohexanone and the like.
[0016]
In the present invention, the above fluorinated carboxylic acid may be synthesized by any method. An example of an industrially effective synthesis method is as follows: succinic anhydride, alkyl succinic anhydride, 1 mol of fluoride alcohol represented by Rf—R ¹ —CH (OH) —CH ₂ OH, By reacting 2 moles of a carboxylic acid component such as an alkyl thiomalic anhydride, the fluorinated carboxylic acid represented by the general formula (1) is reacted with 1 mole of the carboxylic acid component. ) Or (3) can be easily synthesized. In the latter case, a fluorocarboxylic acid in which the compound represented by the general formula (2) and the compound represented by the general formula (3) are mixed is obtained. In the present invention, this mixture can be used as it is. Further, when an acid anhydride as described above is used as the carboxylic acid component, as A ¹ and A ² in the above general formulas (1) to (3), m = 0 usually and n = 1 and m = 1 and n = 0 are obtained, but in the present invention, this mixture can be used as it is.
[0017]
In the present invention, such a fluorinated carboxylic acid is used as a lubricant, but other lubricants may be used in combination as necessary. For example, fatty acids or metal salts thereof, aliphatic esters, aliphatic amides, aliphatic alcohols, aliphatic amines, monosulfides, paraffins, silicone compounds, esters of fatty acids and fluorinated alcohols, Various commonly used lubricants such as fluoropolyether and polytetrafluoroethylene can be used in combination. The amount of the lubricant used is 0.01 to 100 mol, preferably 0.1 to 10 mol, per 1 mol of the fluorinated carboxylic acid of the present invention. In addition to the above lubricants, phosphorus-based extreme pressure agents such as trioleyl phosphate, sulfur-based extreme pressure agents such as benzyl disulfide, halogen-based extreme pressure agents such as allyl bromide, zinc diisobutyldithiophosphate, etc. An organometallic extreme pressure agent or the like may be used in combination.
[0018]
The magnetic recording medium of the present invention is characterized in that it has a magnetic layer on at least one surface of a non-magnetic support, and this magnetic layer has a lubricant composed of the above-mentioned fluorinated carboxylic acid inside or on its surface. It is. In order to provide the lubricant inside or on the surface of the magnetic layer, the lubricant is dissolved in a general-purpose solvent composed of the above-mentioned non-fluorine-based solvent, and this solution is formed on at least one surface of the nonmagnetic support. The layer may be applied or sprayed on the layer and dried, or the magnetic layer may be immersed in the above solution and dried. An appropriate method according to the type of the magnetic layer can be used.
[0019]
When the magnetic layer is made of a ferromagnetic metal thin film, the main component is carbon (diamond or amorphous), carbon nitride, silicon oxide, zirconium oxide, or chromium oxide by vacuum deposition, sputtering or plasma. A protective film made of an organic compound or the like may be provided. In addition, a protective film containing fluorine, nitrogen, silicon, or the like may be provided. Further, the ferromagnetic metal coating film may be one having a minute amount of moisture attached to the surface, or one coated with a rust preventive such as benzotriazole.
[0020]
Further, the surface of the carbon protective film or the like may be subjected to oxygen and ammonia plasma treatment. By performing the plasma treatment, it is possible to deposit the chemically active species in the plasma while cleaning the surface of the protective film, and it is possible to make the lubricant exist more stably without reducing the hardness of the protective film. . Further, the lubricant can be stably present also by performing glow discharge treatment, ultraviolet irradiation treatment, heat treatment, and the like. These treatments may be performed before the lubricant is applied, or may be performed after the lubricant is applied, and after the lubricant is applied, the excess lubricant is washed with a solvent or the like. You may go later.
[0021]
The amount of lubricant applied to the ferromagnetic metal thin film is preferably in the range of 0.5 to 20 mg / m ² with respect to the thin film surface. If the coating amount of the lubricant is too small, it is difficult to uniformly apply the lubricant to the surface of the thin film, and the still durability cannot be sufficiently improved. Also, if the amount of lubricant applied is excessive, the magnetic head and the ferromagnetic metal thin film may stick together, which is not preferable. The amount of lubricant applied can be determined by X-ray photoelectron spectroscopy and liquid column chromatography.
[0022]
In the magnetic recording medium of the present invention, the nonmagnetic support includes polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyamide, polyimide, polyvinyl chloride and other plastics, glass, aluminum alloy, titanium An alloy or the like is preferably used. The nonmagnetic support may be in any form such as a tape, a sheet, a disk, and a card, and may have a protrusion on the surface.
[0023]
In the ferromagnetic metal thin film type magnetic recording medium, Co, Ni, Fe, Co—Ni, Co—Cr, Co—P, Co—Ni—P, Fe—Co are provided on one or both sides of the nonmagnetic support. -B, Fe-Co-Ni, Co-Ni-Fe-B, Fe-Ni, Fe-Co, Co-Pt, Co-Ni-Pt or various ferromagnetic materials made by adding oxygen to them However, a thin film is formed by methods such as vacuum deposition, ion plating, sputtering, and plating. The thickness of the ferromagnetic metal thin film thus formed is preferably in the range of 0.03 to 1 μm.
[0024]
In the magnetic recording medium of the present invention, when a magnetic layer is formed only on one side of the nonmagnetic support, a back coat layer may be provided on the opposite side. This back coat layer is made of non-magnetic powder such as carbon black, bengara, calcium carbonate, barium sulfate, vinyl chloride-vinyl acetate copolymer, polyester resin, polyurethane resin, nitrocellulose resin, fiber It is formed by mixing and dispersing together with a binder resin such as a base resin and an organic solvent to prepare a coating layer for the backcoat layer, and applying and drying the coating material on the opposite side of the nonmagnetic support.
[0025]
【Example】
Next, examples of the present invention will be described in more detail. However, the present invention is not limited to the following examples.
[0026]
Example 1
A flask equipped with a stirring blade containing 1 mol of fluorinated dialkol represented by the formula F (CF ₂ ) ₆ —CH ₂ —CH (OH) —CH ₂ OH and ₂ mol of n-octadecyl succinic anhydride. And allowed to react at 100 ° C. for 12 hours under a nitrogen stream. After completion of the reaction, the reaction mixture was dissolved in a fluorine-based solvent (“FC77” manufactured by 3M) and cooled to 10 ° C. to remove unreacted dial fluoride fluoride. Further, the reaction product was treated as a benzene solution by the same treatment to remove unreacted n-octadecyl succinic anhydride to obtain a lubricant composed of a fluorinated carboxylic acid. The lubricant, the infrared spectrum shown in Figure 1, 1,740Cm ^-1 around the ester bond, 1,700Cm ^-1 peak derived from the carboxylic acid in the vicinity - Kugami is, Equation formula (1 ) (Wherein Rf and R ¹ are groups derived from the above-mentioned dialcide fluoride, R in A ¹ and A ² is an n-octanedecyl group, and k is 0) It was confirmed that.
[0027]
Example 2
1 mol of the same alcohol fluoride as in Example 1 and 2 mol of n-octyl succinic anhydride were charged into a flask equipped with a stirring blade and reacted at 100 ° C. for 12 hours in a nitrogen stream. After completion of the reaction, the reaction mixture was dissolved in the same fluorine-based solvent as in Example 1 and cooled to 10 ° C. to remove unreacted dial fluoride fluoride. Furthermore, unreacted n-octyl succinic anhydride was removed by the same treatment using the reaction product as a benzene solution to obtain a lubricant comprising a fluorinated carboxylic acid. This lubricant was confirmed to be a fluorocarboxylic acid represented by the same general formula (1) as in Example 1 (provided that R is an n-octyl group) by infrared spectroscopy.
[0028]
Example 3
The same 1 mol of dialcohol fluoride as in Example 1 and 2 mol of iso-octadecyl succinic anhydride were charged into a flask equipped with a stirring blade and reacted at 100 ° C. for 12 hours in a nitrogen stream. After completion of the reaction, the reaction mixture was dissolved in the same fluorine-based solvent as in Example 1 and cooled to 10 ° C. to remove the unreacted dial fluoride fluoride. Furthermore, unreacted iso-octadecyl succinic anhydride was removed by the same treatment using the reaction product as a benzene solution to obtain a lubricant comprising a fluorinated carboxylic acid. This lubricant was confirmed by infrared spectroscopy to be a fluorinated carboxylic acid represented by the same general formula (1) as in Example 1 (where R is an iso-octadecyl group).
[0029]
Example 4
The same dial fluoride fluoride as in Example 1 and 2 mol of octadecenyl succinic anhydride were charged into a flask equipped with a stirring blade and allowed to react at 100 ° C. for 12 hours in a nitrogen stream. After completion of the reaction, the reaction mixture was dissolved in the same fluorine-based solvent as in Example 1 and cooled to 10 ° C. to remove the unreacted dial fluoride fluoride. Further, the reaction product was treated as a benzene solution by the same treatment to remove unreacted octadecenyl succinic anhydride to obtain a lubricant composed of a fluorinated carboxylic acid. This lubricant was confirmed by infrared spectroscopy to be a fluorinated carboxylic acid represented by the same general formula (1) as in Example 1 (where R is an octadecenyl group).
[0030]
Example 5
The same dial fluoride fluoride as in Example 1 and 2 mol of n-octadecyl thiomalic anhydride were charged into a flask equipped with a stirring blade and allowed to react at 100 ° C. for 12 hours in a nitrogen stream. After completion of the reaction, the reaction mixture was dissolved in the same fluorine-based solvent as in Example 1 and cooled to 10 ° C. to remove the unreacted dial fluoride fluoride. Furthermore, unreacted n-octadecyl thiomalic anhydride was removed by the same treatment using the reaction product as a benzene solution to obtain a lubricant composed of a fluorinated carboxylic acid. This lubricant is a fluorocarboxylic acid represented by the same general formula (1) as in Example 1 (wherein R is an n-octadecyl group and k is 1) by infrared spectroscopy. confirmed.
[0031]
Example 6
The same dial fluoride fluoride as in Example 1 and 1 mol of n-octadecyl succinic anhydride were charged into a flask equipped with a stirring blade and reacted at 100 ° C. for 12 hours in a nitrogen stream. After completion of the reaction, the reaction mixture was dissolved in the same fluorine-based solvent as in Example 1 and cooled to 10 ° C. to remove the unreacted dial fluoride fluoride. Furthermore, unreacted n-octadecyl succinic anhydride was removed by the same treatment using the reaction product as a benzene solution to obtain a lubricant composed of a fluorinated carboxylic acid. This lubricant is a mixture of fluorinated carboxylic acids represented by the general formulas (2) and (3) (where R is an n-octadecyl group) by infrared spectroscopy and nuclear magnetic resonance spectra. It was confirmed. Moreover, it confirmed that ratio of the said mixture was General formula (2): General formula (3) = 9: 1 (weight ratio).
[0032]
Example 7
The same dial fluoride fluoride as in Example 1 and 1 mol of n-octadecyl succinic anhydride were charged into a flask equipped with a stirring blade and reacted at 180 ° C. for 12 hours in a nitrogen stream. After completion of the reaction, the reaction mixture was dissolved in the same fluorine-based solvent as in Example 1 and cooled to 10 ° C. to remove the unreacted dial fluoride fluoride. Furthermore, unreacted n-octadecyl succinic anhydride was removed by the same treatment using the reaction product as a benzene solution to obtain a lubricant composed of a fluorinated carboxylic acid. This lubricant is a mixture of fluorinated carboxylic acids represented by the general formulas (2) and (3) (where R is an n-octadecyl group) by infrared spectroscopy and nuclear magnetic resonance spectra. It was confirmed. Moreover, it confirmed that ratio of the said mixture was General formula (2): General formula (3) = 7: 3 (weight ratio).
[0033]
Comparative Example 1
Formula HOCH ₂ CF ₂ (OC ₂ F ₄ ) p (OCF ₂ ) qOCF ₂ CH ₂ OH (p and q are integers) Fluorinated dial alcohol (“FONBLIN Z DOL” manufactured by Augmont) And an average molecular weight of 2,000) was used as a lubricant as it was.
[0034]
Comparative Example 2
In the same manner as in Example 1, 1 mol of the fluorinated dialcohol as in Comparative Example 1 and 2 mol of n-octadecyl succinic anhydride were reacted to obtain a lubricant composed of a fluorinated dicarboxylic acid.
[0035]
Comparative Example 3
A compound represented by the formula: F (CF ₂ ) ₈ CH ₂ CH ₂ OH is reacted in the same manner as in Example 1 with 1 mole of monoalkyl fluoride and 1 mole of n-octadecyl succinic anhydride. A lubricant composed of a fluorinated monocarboxylic acid represented by (CF ₂ ) ₈ CH ₂ CH ₂ OCOCH ₂ CH (COOH) (CH ₂ ) ₁₈ H was obtained.
[0036]
Comparative Example 4
A formula: F (CF ₂ ) ₈ CH ₂ CH ₂ OCO (formula: F (CF ₂ ) ₈ CH ₂ CH ₂ OH is reacted with 2 mol of a monofluorinated fluoride represented by 1 mol of decanedicarboxylic acid. A lubricant composed of a fluorinated diester represented by CH ₂ ) ₁₀ COOCH ₂ CH ₂ (CF ₂ ) ₈ F was obtained.
[0037]
About each lubricant of the above Examples 1-7 and Comparative Examples 1-4, the solubility with respect to a non-fluorine type solvent was investigated with the following method. In other words, methyl isobutyl ketone: isopropyl alcohol = 3: 1 (weight ratio) was used as a non-fluorine solvent, and each lubricant was added to this solvent in small portions and stirred well to dissolve 0.05% by weight or more. The ones to be evaluated were rated as ◯ and the ones below were evaluated as ×.
[0038]
As a result, each of the lubricants of Examples 1 to 7 and Comparative Examples 2 to 4 was ○, and the lubricant of Comparative Example 1 was ×. As is clear from this result, each of the lubricants of Examples 1 to 7 and Comparative Examples 2 to 4 has excellent solubility in non-fluorine solvents, and can perform operations such as coating with the above solvents. I have found that this is an environmentally friendly lubricant. On the other hand, the lubricant of Comparative Example 1 has poor solubility in non-fluorine solvents, and it is necessary to perform operations such as application using a fluorine solvent that causes environmental deterioration. Gawakuta.
[0039]
Examples 8-14
As a non-magnetic support, a polyethylene terephthalate film having a thickness of 6 μm is used, and Co is obliquely deposited on the film in an oxygen atmosphere to form a ferromagnetic material composed of Co—O having a thickness of 0.15 μm. A metal thin film was formed. After that, DLC (diamond carbon) having a thickness of 10 nm is formed on the above ferromagnetic metal thin film by plasma polymerization using 13.56 MHz RF, ethylene as monomer gas and hydrogen as carrier gas. A protective film was formed. After the formation of this protective film, the tape was cut so as to have a width of 8 mm.
[0040]
Next, each of the lubricants of Examples 1 to 7 is 0.2% by weight in a mixed solvent of n-hexane: methyl ethyl ketone: isopropyl alcohol = 5: 3: 2 (weight ratio). To obtain a lubricant solution. The tape was dip-coated in this lubricant solution and then dried to prepare 7 types of video tapes each having a lubricant film on the DLC protective film.
[0041]
Comparative Examples 5-8
Four types of video tapes were produced in the same manner as in Examples 8 to 14 except that each lubricant of Comparative Examples 1 to 4 was used as the lubricant. In the lubricant of Comparative Example 1, perfluorooctane was used when preparing the lubricant solution.
[0042]
For each of the video tapes of Examples 8 to 14 and Comparative Examples 5 to 8, the friction coefficient, the still durability, and the head dirt were examined by the following methods as the evaluation of lubricity. These results were as shown in Table 1.
[0043]
<Friction coefficient>
A reciprocating sliding test is performed on a stainless steel pin under the conditions of a sliding speed of 1 m / min, a sliding distance of 5 cm, and a tape tension of 20 gf in an atmosphere of 20 ° C. and 50% RH, and the friction coefficient at the 100th reciprocation is obtained. It was.
[0044]
<Still durability>
In an atmosphere of -5 ° C and 25% RH, set at a wrapping angle of 220 ° on an 8 mm cylinder with a diameter of 4 cm, with a tape / magnetic head relative speed of 11.3 m / sec and a tape tension of 12.5 gf. Under the conditions, a sine wave with a wavelength of 1.6 μm was recorded, and the reproduction output was measured in still mode. The still life was defined as the time required for the reproduction output to decrease by 1/2 from the initial value.
[0045]
<Head dirt>
Each video tape 50 m was repeatedly run 100 times in an 8 mm VTR [Sony Corporation EV-S900] in an atmosphere of −5 ° C. and 25% RH, and then the contamination of the magnetic head was examined with a microscope. The head dirt was evaluated in the following three stages.
◯: No head dirt is observed Δ: Some head dirt is seen ×: Many head dirt is seen [0046]
Table 1

[0047]
As is apparent from the above results, each of the video tapes of Examples 8 to 14 has a low coefficient of friction, a long still life, and little head contamination. On the other hand, the video tape of Comparative Example 5 shows the same lubricity as described above, but it is not preferable because a fluorine-based solvent needs to be used in preparing the lubricant solution, which causes environmental deterioration. Further, the video tape of Comparative Example 6 has good solubility in the non-fluorinated solvent of the lubricant used, but has a large head dirt, and each Video Tape of Comparative Examples 7 and 8 has a still life. Is short and the head is dirty.
[0048]
【The invention's effect】
As described above, in the present invention, the use of a specific fluorine-containing carboxylic acid having two carboxyl groups or one carboxyl group and one hydroxyl group together with a fluorine carbon group and a hydrocarbon group in the molecule, Can be slid with low friction, low wear between two contacting solids regardless of high speed / low speed, high load / low load in any environment of low temperature, high humidity / low humidity, and non-fluorine solvent An environmentally friendly lubricant that is soluble can be provided. Further, by using this lubricant for a magnetic recording medium, it is possible to provide a magnetic recording medium excellent in durability and running performance.
[Brief description of the drawings]
1 is a characteristic diagram showing an infrared spectrum of a lubricant comprising a fluorinated carboxylic acid obtained in Example 1. FIG.

Claims (7)

The following general formulas (1) to (3);

[Wherein Rf is a fluorocarbon group, R ¹ is a hydrocarbon group, A ¹ and A ² are the following formulas;

In it shall apply an organic group represented, R represents the general formula (1) in A ^1, while a hydrocarbon group of A ^2, the other is a hydrogen atom or a hydrocarbon group, the general formula (2), (3) Is a hydrocarbon group, m, n, and k are 0 or 1.]
A lubricant comprising a fluorinated carboxylic acid represented by any one of the formulas: _2. The lubricant according to claim 1, wherein, in the general formulas (1) to (3), Rf is a fluorocarbon group whose main component is F (CF ₂ ) p- (p is an integer). In the general formula (1) to (3), lubricant of claim 1 R constituting the A ^1, A ² is a hydrocarbon group having 8 or more carbon atoms. The lubricant according to claim 1, wherein the fluorinated carboxylic acid represented by any one of the general formulas (1) to (3) is soluble in a non-fluorinated solvent. A magnetic recording medium having a magnetic layer on at least one surface of a nonmagnetic support, wherein the magnetic layer has the lubricant according to any one of claims 1 to 4 inside or on the surface thereof. 6. The magnetic recording medium according to claim 5, wherein the magnetic recording medium has a thin magnetic layer of ferromagnetic metal, and the amount of lubricant applied is 0.5 to 20 mg / m < ² >. 7. The magnetic recording medium according to claim 6, further comprising a protective film mainly composed of carbon, carbon nitride, silicon oxide, zirconium oxide or chromium oxide on the ferromagnetic metal thin film type magnetic layer.

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