JP2004030844A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium of a metallic magnetic thin film type, the durability and the running performance of which can be enhanced. <P>SOLUTION: This invention provides the magnetic recording medium 10 wherein a magnetic layer 2 made of a ferromagnetic metallic thin film, and a carbon protective film 3 are sequentially formed on a nonmagnetic substrate 1, processing by aromatic amine, aromatic carboxylic acid, aromatic alcohol or ultraviolet ray radiation is applied to the surface of the carbon protective film 3 and the protection layer 3 holds a prescribed lubricant. <P>COPYRIGHT: (C)2004,JPO

Description

【０１５４】
【化４０】

【０１５５】
【化４１】

【０１５６】
【化４２】

【０１５７】
次に、このようにして得られた部分フッ化カルボン酸を下記〔化４３〕に示す様に、飽和脂肪族アルコールとほぼ等モル量反応させることって、最終的に、部分フッ化カルボン酸アルキルエステルが得られる。
【０１５８】
【化４３】

【０１５９】
ここで重要なのは上記部分フッ化カルボン酸アルキルエステルのアルコール部位のアルキル鎖が不飽和結合を含まないアルキル基から選ばれることである。このような不飽和結合を含まないエステルを用いることにより、長期間保存後においても、初期の潤滑特性を維持することができる。
【０１６０】
ここで、磁気記録媒体に使用される潤滑剤においては、〔化３７〕に示す末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、〔化３８〕に示す部分フッ化カルボン酸アルキルエステルとの混合比は、重量比で１０：９０〜９０：１０であるのが好ましく、さらには４０：６０〜６０：４０とすることが望ましい。上記範囲を超えると優れた潤滑効果が得られなくなる。
【０１６１】
また、磁気記録媒体において潤滑剤を最外層に保持させる方法としては、表面に潤滑剤をトップコートする方法が挙げられる。ここで、その塗布量は、０．０５ｍｇ／ｍ^２〜１００ｍｇ／ｍ^２であるのが好ましく、０．１ｍｇ／ｍ^２〜５０ｍｇ／ｍ^２であるのがより好ましい。塗布量が少なすぎると、摩擦係数の低下、耐磨耗性及び耐久性の向上という効果が表れず、また、塗布量が多すぎると、摺動部材と強磁性金属薄膜との間でハリツキ現象が起こり却って走行性が悪くなる。
【０１６２】
以上のように、本実施の形態に係る磁気記録媒体は、密着性や潤滑性の点で非常に優れた特性の潤滑剤の組み合わせを特定して用いているので、良好な走行性及び耐久性が確保されたものとなる。
また、この磁気記録媒体においては、保護層３の表面が芳香族アミンによりトップコートされているので、用いられる潤滑剤と、保護層３との密着性が向上し、更に良好な耐久性を実現することができる。
【０１６３】
また、この磁気記録媒体においては、磁性層２を強磁性金属薄膜としていることから、高密度記録、長時間記録にも充分対応可能である。
なお、本実施の形態に係る磁気記録媒体においては、必要に応じて、防錆剤を併用してもよい。防錆剤としては、通常この種の磁気記録媒体の防錆剤として使用されるものであれば何れも使用でき、例えばフェノール類、ナフトール類、キノン類、窒素原子を含む複素環化合物、酸素原子を含む複素環化合物、硫黄原子を含む複素環化合物等が挙げられる。
【０１６４】
また、本発明の磁気記録媒体においては、非磁性支持体１上の上記磁性層２が形成される面とは反対側の面に、いわゆるバックコート層を形成しても良い。このバックコート層は、結合剤樹脂と粉末成分とを有機溶媒に混合分散させたバックコート用塗料を非磁性支持体１に塗布することにより形成される。
【０１６５】
さらに上記のバックコート層には潤滑剤を併用してもよい。この場合バックコート層中に潤滑剤を内添する方法、あるいはバックコート層上に潤滑剤を被着する方法がある。いずれにしても潤滑剤としては、脂肪酸、脂肪酸エステル、脂肪酸アミド、金属石鹸、脂肪族アルコール、シリコーン系潤滑剤等、従来周知の潤滑剤が使用できる。
【０１６６】
以上のような本実施の形態に係る磁気記録媒体は、つぎのようにして作製される。
先ず、非磁性支持体１上に、例えば真空蒸着法により磁性層２となる強磁性金属薄膜を形成する。その後磁性層２上に、例えばプラズマＣＶＤ法により保護層３を形成する。さらに、この保護層３の表面に対して芳香族アミンによるトップコートを行う。そして、この保護層３上に、上述した潤滑剤を塗布して保護層３に潤滑剤を保持させて、目的とする磁気記録媒体１０が得られる。なお、必要に応じてバックコート層等を形成してもよい。
【０１６７】
磁性層２は、図３に示すような連続巻き取り式の真空蒸着装置４０によって形成することができる。
なお、磁性層２は上述した実施の形態Ａ−１と同様の工程により形成することができる。
【０１６８】
保護層３は、ＣＶＤ法により形成することができる。
ＣＶＤ法によって保護層３を形成する場合には、まず、真空容器中に炭化水素ガス、あるいは炭化水素と不活性ガスとの混合ガスを導入し、１０Ｐａ〜１００Ｐａ程度の圧力に保持した状態で、真空容器内に放電させて、炭化水素ガスのプラズマを発生させ、強磁性金属薄膜上に保護層３を形成する。放電形式としては、外部電極方式、内部電極方式のいずれでもよく、放電周波数については、実験的に決めることができる。また、強磁性金属薄膜が形成された非磁性支持体１側に配された電極に０〜−３ｋＶの電圧を印加することにより、保護層３の硬度の増大及び密着性を向上させることができる。
【０１６９】
保護層３の材料となる上記炭化水素としては、例えば、メタン、エタン、プロパン、ブタン、ペンタン、ヘキサン、ヘプタン、オクタン、エチレン、アセチレン、プロペン、ブテン、ペンテン、ベンゼンなどを用いることができる。
この保護層３は、スペーシングロスを少なく、かつ、強磁性金属薄膜の磨耗防止の効果を得られるよう、その厚さを３ｎｍ〜１５ｎｍ程度、特に５ｎｍ〜１０ｎｍ程度とすることが好ましい。
【０１７０】
ここでは、ＣＶＤ法により保護膜を形成する例について説明したが、保護層を形成する方法としては、この方法の他に、マグネトロンスパッタ法、イオンビームスパッタ法、イオンビームプレーティング法等の従来公知の薄膜形成方法を用いることができる。
そして、この例においては保護層３の表面に対して、特に芳香族アミンによるトップコートを行う。保護層３の表面を芳香族アミンによってトップコートすることにより、保護層３と潤滑剤との間の密着性の向上を図ることができる。
【０１７１】
〔実施の形態Ｂ−２〕
つぎに、本発明の実施の形態Ｂ−２に係る磁気記録媒体ついて説明する。本実施の形態に係る磁気記録媒体は、図１に示して説明した磁気記録媒体１０と同様に、非磁性支持体１上に磁性層２として強磁性金属薄膜、最外層として保護層３が順次形成されてなる構成を有しており、特に最外層となる保護層３表面に芳香族アミンによるトップコートが施され、さらに保護層３上に下記〔化４４〕で示される末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、下記〔化４５〕に示される部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤が保持されている。
【０１７２】
【化４４】
Ｒ_２ＯＯＣ−Ｒｆ’−ＣＯＯＲ_２
【０１７３】
但し、Ｒｆ’はパーフルオロポリエーテル鎖を表し、Ｒ_２は炭化水素基又はフッ化炭化水素基を表す。
【０１７４】
【化４５】
Ｃ_ｎＦ_２ｎ＋１（ＣＨ_２）_ｍＣＯＯＲ
【０１７５】
但し、Ｒは炭素数７〜２１のアルキル基を表し、ｍ、ｎはｍ＋ｎ≧８を満足する整数を表す。
【０１７６】
上記〔化４４〕に示される化合物及び上記〔化４５〕に示される化合物を含有する潤滑剤は、いわゆる厳しい使用条件下においても密着性や潤滑性が好適に保たれ、且つ長期に至り潤滑効果を持続する特性を有する。
なお、上記〔化４４〕及び上記〔化４５〕に示される潤滑剤が用いられた磁気記録媒体は、上記実施の形態Ｂ−１において説明した磁気記録媒体１０と略同様の構成を有するものであり、最外層に保持される潤滑剤のみが異なる例であり、その他の磁性層２や保護層３等の構成および製造方法については同様のものであるため、以下においては潤滑剤についてのみ説明する。
【０１７７】
上記〔化４４〕に示す末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物は、例えば、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとを、無水トルエン中でｐ−トルエンスルホン酸や濃硫酸等を触媒として反応させることによって得られる。
【０１７８】
ここで、上記末端にカルボキシル基を有するパーフルオロポリエーテルとしては、カルボキシル基を両末端に有するものが好ましく、具体的には、ＨＯＯＣ−ＣＦ_２（ＯＣ_２Ｆ_４）_ｍ　（ＯＣＦ_２）_ｊＯＣＦ_２−ＣＯＯＨ等が挙げられる。上記の末端にカルボキシル基を有するパーフルオロポリエーテルは、これらに限定されるものではない。なお、上記パーフルオロポリエーテル化学式中のｍ，ｊはいずれも１以上の整数を表す。
【０１７９】
また、上記末端にカルボキシル基を有するパーフルオロポリエーテルの分子量は、特に制約されるものではないが、実用的には６００〜５０００程度が好ましい。分子量が大きすぎると末端基の吸着基としての効果が薄れるとともに、パーフルオロポリエーテル鎖が大きくなる分、既存の炭化水素系溶媒に溶解しにくくなり、分子量が小さすぎると、パーフルオロポリエーテル鎖による潤滑効果が失われるためである。
【０１８０】
なお、上記末端にカルボキシル基を有するパーフルオロポリエーテルにおいては、パーフルオロポリエーテル鎖が部分水素化されてもよい。すなわち、パーフルオロポリエーテル鎖のフッ素原子の一部（５０％以下）を水素原子で置換しても良い。この場合にはパーフルオロポリエーテルとして部分水素化したパーフルオロポリエーテルを使用すればよい。
【０１８１】
一方、上記長鎖アルコールとしては、市販品、或いは合成品何れも使用可能である。また分子量が小さくなるに従って通常の有機溶媒に溶解し難くなることから、少なくともその１個のアルキル基の炭素数が６以上であることが好ましい。
【０１８２】
また、上述したように、本実施の形態で用いられる潤滑剤には、上記〔化４４〕に示す化合物の他に、上記〔化４５〕に示される部分フッ化カルボン酸アルキルエステルが含有される。上記〔化４５〕に示される部分フッ化カルボン酸アルキルエステルは、上記実施の形態Ｂ−１において説明した部分フッ化カルボン酸アルキルエステルと同様のものを適用できる。
【０１８３】
さらに、本例の磁気記録媒体に使用される潤滑剤においては、上記〔化４４〕に示す末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、上記〔化４５〕に示す部分フッ化カルボン酸アルキルエステルとの混合比は、重量比で１０：９０〜９０：１０であるのが好ましく、さらには４０：６０〜６０：４０とすることが望ましい。上記範囲を超えると優れた潤滑効果が得られなくなる。
【０１８４】
また、潤滑剤を保持させる方法としては、保護層３の表面に潤滑剤をトップコートする方法が挙げられる。塗布量は、０．０５ｍｇ／ｍ^２〜１００ｍｇ／ｍ^２であるのが好ましく、０．１ｍｇ／ｍ^２〜５０ｍｇ／ｍ^２であるのがより好ましい。塗布量が少なすぎると、摩擦係数の低下、耐磨耗性・耐久性の向上という効果が表れず、また、塗布量が多すぎると、摺動部材と強磁性金属薄膜との間でハリツキ現象が起こり、走行性が悪くなる。
【０１８５】
以上のように、本実施の形態に係る磁気記録媒体は、上述したような密着性や潤滑性の点で非常に優れた特性の潤滑剤の組み合わせを特定して用いているので、良好な走行性及び耐久性が確保されたものとなる。また、この磁気記録媒体においては、カーボンよりなる保護層３の表面が芳香族アミンによりトップコートされているので、用いられる潤滑剤と保護層との密着性が向上し、更に良好な耐久性を実現することができる。
【０１８６】
〔実施の形態Ｃ−１〕
次に、実施の形態Ｃ−１に係る磁気記録媒体について説明する。本実施の形態においては、上記実施の形態Ａ−１において説明した磁気記録媒体１０と同様に、非磁性支持体１上に磁性層２として強磁性金属薄膜、保護層３が順次形成されてなる構成を有するものとする。非磁性支持体１、磁性層２および保護層３の構成および製膜方法は上記実施の形態Ａ−１と同様のものとすることができる。
【０１８７】
この例における磁気記録媒体においては、特に保護層３の表面に、芳香族カルボン酸がトップコートされている。
芳香族カルボン酸としては、たとえばフタル酸、テレフタル酸、イソフタル酸、安息香酸、サリチル酸、没食子酸、ガロイル没食子酸、オピアン酸、バニリン酸、ピペロニル酸、ピペリン酸、カルミン酸、ヘスペリチン酸、ベンゼンヘキサカルボン酸、２−シクロヘキセン−１，２−ジカルボン酸、４−シクロヘキセン−１，２−ジカルボン酸、６−ヒドロキシ−５−イソプロピル−ｏ−トルイル酸、４−ヒドロキシ−３−メトキシケイ皮酸等を例示することができる。
【０１８８】
このような芳香族カルボン酸の塗布量としては、保護層３の表面における酸化度合いに依存して決定されることが好ましい。具体的な塗布量としては、０．０５ｍｇ／ｍ^２〜１００ｍｇ／ｍ^２であることが好ましく、更に、０．１ｍｇ／ｍ^２〜５０ｍｇ／ｍ^２であることがより好ましい。
【０１８９】
特に本実施の形態に係る磁気記録媒体おいては、保護層３上に芳香族カルボン酸からなるトップコートを介して、下記〔化４６〕に示す末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、下記〔化４７〕に示される部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤が、保持されている。
【０１９０】
【化４６】
Ｒ_１ＣＯＯＣＨ_２−Ｒｆ−ＣＨ_２ＯＣＯＲ_１
【０１９１】
但し、Ｒｆはパーフルオロポリエーテル鎖を表し、Ｒ_１は炭化水素基又はフッ化炭化水素基を表す。
【０１９２】
【化４７】
Ｃ_ｎＦ_２ｎ＋１（ＣＨ_２）_ｍＣＯＯＲ
【０１９３】
但し、Ｒは炭素数７〜２１のアルキル基を表し、ｍ、ｎはｍ＋ｎ≧８を満足する整数を表す。
【０１９４】
上記〔化４６〕に示される化合物及び上記〔化４７〕に示される化合物を含有する潤滑剤は、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、且つ長期に至り潤滑効果を持続する特性を有する。
【０１９５】
上記〔化４６〕に示す末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物は、例えば、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸クロリドとを、トルエン中で塩基を触媒として反応させることによって得られる。
【０１９６】
ここで、上記末端に水酸基を有するパーフルオロポリエーテルとしては、水酸基を両末端に有するものが好ましく、例えば、ＨＯ−ＣＨ_２ＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＨ_２−ＯＨ等が挙げられる。上記末端に水酸基を有するパーフルオロポリエーテルは、これらに限定されるものではない。なお、上記パーフルオロポリエーテル化学式中のｐ，ｑはいずれも１以上の整数を表す。
【０１９７】
また、この末端に水酸基を有するパーフルオロポリエーテルの分子量は、特に制約されるものではないが、実用的には６００〜５０００程度が好ましい。分子量が大きすぎると、末端基の吸着基としての効果が薄れると同時に、パーフルオロポリエーテル鎖が大きくなる分、既存の炭化水素系溶媒に溶解しにくくなり、逆に分子量が小さすぎると、パーフルオロポリエーテル鎖による潤滑効果が失われてしまうためである。
【０１９８】
なお、この末端に水酸基を有するパーフルオロポリエーテルにおいては、パーフルオロポリエーテル鎖が部分水素化されてもよい。すなわち、パーフルオロポリエーテル鎖のフッ素原子の一部（５０％以下）を水素原子で置換してもよい。この場合には、パーフルオロポリエーテルとして部分水素化したパーフルオロポリエーテルを使用すればよい。
【０１９９】
一方、上記長鎖カルボン酸クロリドとしては、市販品、或いは合成品何れも使用可能である。このように、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸クロリドとを反応させることにより、上記〔化４６〕に示すような、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物が合成される。
【０２００】
ここで、上記長鎖カルボン酸、つまり合成材料の長鎖カルボン酸クロリドのカルボン酸部分は、カルボン酸基を有する任意の構造で良く、例えば、分岐構造、異性体構造、脂環構造、不飽和結合の有無によらず選択することができる。また、この長鎖カルボン酸は、分子量に関しても任意であるが、分子量が小さくなるに伴って通常の炭化水素系の有機溶媒に溶解し難くなることから、少なくともアルキル基の炭素数が１０以上であることが望ましい。
【０２０１】
また、上述したように、本発明に用いられる上記潤滑剤には、上記〔化４６〕に示すエステル化合物の他に、上記〔化４７〕に示される部分フッ化カルボン酸アルキルエステルが含有される。この〔化４７〕に示す部分フッ化カルボン酸アルキルエステル中におけるＲの炭素数は７〜２１であることが望ましい。この炭素数が６以下であると潤滑効果が乏しく、また炭素数が２１を超えると有機溶剤への溶解性が低下するためである。上記化１０中のｍ，ｎに関してはｍ＋ｎ≧８を満たせば、特に制限はない。
【０２０２】
また、この部分フッ化カルボン酸アルキルエステルは、部分フッ化カルボン酸と飽和脂肪族アルコールとをほぼ等モル量で反応させることによって容易に合成することができる。
具体的に上記部分フッ化カルボン酸アルキルエステルの合成の具体的な反応式は、以下に示すようなものである。
【０２０３】
先ず、部分フッ化カルボン酸が次のようにして合成される。始めに、不飽和カルボン酸を出発原料として、下記〔化４８〕、〔化４９〕、〔化５０〕、および〔化５１〕に示す一連の反応を経ることにより部分フッ化カルボン酸が合成される。
詳しくは、下記〔化４８〕に示すように、不飽和カルボン酸がアルコールとエステル化反応して不飽和エステルとなる。その後、下記〔化４９〕に示すように、この不飽和エステルがフッ化炭素のヨウ化物と付加反応してフッ素及びヨウ素が付加される。そして、下記〔化５０〕に示すように、還元することによって部分フッ化エステルが生じる。その後、下記〔化５１〕に示すように、この部分フッ化エステルを加水分解することによって、最終的に部分フッ化カルボン酸が得られる。
【０２０４】
【化４８】

【０２０５】
【化４９】

【０２０６】
【化５０】

【０２０７】
【化５１】

【０２０８】
次に、このようにして得られた部分フッ化カルボン酸を下記〔化５２〕に示す様に、飽和脂肪族アルコールとほぼ等モル量反応させることって、最終的に部分フッ化カルボン酸アルキルエステルが得られる。
【０２０９】
【化５２】

【０２１０】
ここで上記部分フッ化カルボン酸アルキルエステルのアルコール部位のアルキル鎖は不飽和結合を含まないアルキル基から選定する。このような不飽和結合を含まないエステルを用いることにより、長期間保存後においても、初期の潤滑特性を維持することができる。
【０２１１】
磁気記録媒体に使用される潤滑剤においては、上記〔化４６〕に示す末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、上記〔化４７〕に示す部分フッ化カルボン酸アルキルエステルとの混合比は、重量比で１０：９０〜９０：１０であるのが好ましく、さらには４０：６０〜６０：４０とすることが望ましい。上記範囲を超えると優れた潤滑効果が得られなくなる。
【０２１２】
また、磁気記録媒体において潤滑剤を保持させる方法としては、表面に潤滑剤をトップコートする方法が挙げられる。塗布量は、０．０５ｍｇ／ｍ^２〜１００ｍｇ／ｍ^２であるのが好ましく、０．１ｍｇ／ｍ^２〜５０ｍｇ／ｍ^２であるのがより好ましい。塗布量が少なすぎると、摩擦係数の低下、耐磨耗性及び耐久性の向上という効果が表れず、また、塗布量が多すぎると、摺動部材と強磁性金属薄膜との間でハリツキ現象が起こり、却って走行性が悪くなるためである。
【０２１３】
以上のように、本実施の形態に係る磁気記録媒体は、上述したような、密着性や潤滑性の点で非常に優れた特性の潤滑剤の組み合わせを特定して用いているので、良好な走行性及び耐久性が確保されたものとなる。
また、この磁気記録媒体においては、カーボンよりなる保護層３が形成されているとともに、その表面が芳香族カルボン酸によりトップコートされているので、用いられる上記潤滑剤と、保護層３との密着性が向上し、更に良好な耐久性を実現することができる。
また、この磁気記録媒体においては、磁性層２を強磁性金属薄膜としていることから、高密度記録、長時間記録にも充分対応可能である。
【０２１４】
なお、本実施の形態に係る磁気記録媒体においては、必要に応じて、防錆剤を併用してもよい。防錆剤としては、通常この種の磁気記録媒体の防錆剤として使用されるものであれば何れも使用でき、例えばフェノール類、ナフトール類、キノン類、窒素原子を含む複素環化合物、酸素原子を含む複素環化合物、硫黄原子を含む複素環化合物等が挙げられる。
【０２１５】
また、本発明の磁気記録媒体においては、非磁性支持体１上の上記磁性層２が形成される面とは反対側の面に、いわゆるバックコート層を形成しても良い。このバックコート層は、結合剤樹脂と粉末成分とを有機溶媒に混合分散させたバックコート用塗料を非磁性支持体１に塗布することにより形成される。
【０２１６】
以上のように、本実施の形態に係る磁気記録媒体は、上述したような、密着性や潤滑性の点で非常に優れた特性の潤滑剤の組み合わせを特定して用いているので、良好な走行性及び耐久性が確保されたものとなる。
また、この磁気記録媒体においては、カーボンよりなる保護層３が形成されているとともに、その表面が芳香族カルボン酸によってトップコートされているので、用いられる潤滑剤と、保護層３との密着性が向上し、更に良好な耐久性を実現することができる。
【０２１７】
バックコート用塗料に使用される結合剤樹脂としては、例えば、塩化ビニル−酢酸ビニル系共重合体、塩化ビニル−塩化ビニリデン共重合体、塩化ビニル−アクリロニトリル共重合体、アクリル酸エステル−アクリロニトリル共重合体、熱可塑性ポリウレタンエラストマー、塩化ビニリデン−アクリロニトリル共重合体、ブタジエン−アクリロニトリル共重合体、ポリアミド樹脂、ポリビニルブチラール、セルロース誘導体、ポリエステル樹脂、フェノール樹脂、エポキシ樹脂、ポリウレタン硬化型樹脂、メラミン樹脂、アルキッド樹脂、シリコーン樹脂、エポキシ−ポリアミド樹脂、ニトロセルロース−メラミン樹脂、高分子量ポリエステル樹脂とイソシアネートプレポリマーの混合物、メタクリル酸塩共重合体とジイソシアネートプレポリマーの混合物、ポリエステルポリオールとポリイソシアネートとの混合物、尿素ホルムアルデヒド樹脂、低分子量グリコール／高分子量ジオール／トリフェニルメタントリイソシアネートとの混合物、ポリアミン樹脂及びこれらの混合物等が挙げられる。
あるいは、粉末成分の分散性の改善を図るために、親水性極性基を有する結合剤樹脂を使用してもよい。
【０２１８】
一方、上記粉末成分としては、導電性を付与するためのカーボン系微粉末や表面粗度のコントロール及び耐久性向上のために添加される無機顔料が挙げられる。上記カーボン系微粒子としては、例えば、ファーネスカーボン、チャネルカーボン、アセチレンカーボン、サーマルカーボン、ランプカーボン等が例示され、上記無機顔料としては、α−ＦｅＯＯＨ、α−Ｆｅ_２Ｏ_３、Ｃｒ_２Ｏ_３、ＴｉＯ_２、ＺｎＯ、ＳｉＯ、ＳｉＯ_２、ＳｉＯ_２・２Ｈ_２Ｏ、Ａｌ_２Ｏ_３、ＣａＣＯ_３、ＭｇＣＯ_３、Ｓｂ_２Ｏ_３等が挙げられる。
【０２１９】
さらに、上記バックコート用塗料の有機溶剤としては、例えば、アセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等のケトン系溶剤、酢酸メチル、酢酸エチル、酢酸ブチル、乳酸エチル、酢酸グリコールモノエチルエーテル等のエステル系溶剤、グリコールジメチルエーテル、グリコールモノエチルエーテル、ジオキサン等のグリコールエーテル系溶剤、ベンゼン、トルエン、キシレン等の芳香族炭化水素系溶剤、ヘキサン、ヘプタン等の脂肪族炭化水素溶媒、メチレンクロライド、エチレンクロライド、四塩化炭素、クロロホルム、エチレンクロロヒドリン、ジクロルベンゼン等の塩素化炭化水素系溶媒等、汎用の溶剤を用いることができる。
【０２２０】
さらに、上記のバックコート層には潤滑剤を併用してもよい。この場合、上記バックコート層中に潤滑剤を内添する方法、あるいはバックコート層上に潤滑剤を被着する方法がある。いずれにしても、上記潤滑剤としては、脂肪酸、脂肪酸エステル、脂肪酸アミド、金属石鹸、脂肪族アルコール、シリコーン系潤滑剤等、従来周知の潤滑剤が使用できる。
【０２２１】
以上のような本実施の形態に係る磁気記録媒体は、つぎのようにして作製される。
先ず、非磁性支持体１上に、例えば真空蒸着法により磁性層２となる強磁性金属薄膜を形成する。その後、この磁性層２上に、例えばプラズマＣＶＤ法により保護層３を形成する。さらに、この保護層３の表面に対して芳香族カルボン酸によるトップコートを行う。そして保護層３上に、上述の潤滑剤を保持させて、磁気記録媒体１０が得られる。なお必要に応じてバックコート層等を形成する。
【０２２２】
磁性層２は、図３に示した真空蒸着装置４０を用いて、上述した実施の形態Ａ−１における磁性層２と同様にして形成することができる。
【０２２３】
次に保護層３の形成方法について説明する。保護層３は、ＣＶＤ法により形成することができる。
ＣＶＤ法によって保護層３を形成する場合には、まず、真空容器中に炭化水素ガス、あるいは炭化水素と不活性ガスとの混合ガスを導入し、１０Ｐａ〜１００Ｐａ程度の圧力に保持した状態で、真空容器内に放電させて、炭化水素ガスのプラズマを発生させ、強磁性金属薄膜上に保護層３を形成する。放電形式としては、外部電極方式、内部電極方式のいずれでもよく、放電周波数については、実験的に決めることができる。また、強磁性金属薄膜が形成された非磁性支持体１側に配された電極に０〜−３ｋＶの電圧を印加することにより、保護層３の硬度の増大及び密着性を向上させることができる。
【０２２４】
保護層３の材料となる上記炭化水素としては、例えば、メタン、エタン、プロパン、ブタン、ペンタン、ヘキサン、ヘプタン、オクタン、エチレン、アセチレン、プロペン、ブテン、ペンテン、ベンゼンなどを用いることができる。
この保護層３は、スペーシングロスを少なく、かつ、強磁性金属薄膜の磨耗防止の効果を得られるよう、その厚さを３ｎｍ〜１５ｎｍ程度、特に５ｎｍ〜１０ｎｍ程度とすることが好ましい。
【０２２５】
ここでは、ＣＶＤ法により保護膜を形成する例について説明したが、保護層を形成する方法としては、この方法の他に、マグネトロンスパッタ法、イオンビームスパッタ法、イオンビームプレーティング法等の従来公知の薄膜形成方法を用いることができる。
そして、この例においては保護層３の表面に対して、特に芳香族カルボン酸によるトップコートを行う。保護層３の表面を芳香族カルボン酸によってトップコートすることにより、保護層３と潤滑剤との間の密着性の向上を図ることができる。
【０２２６】
〔実施の形態Ｃ−２〕
次に、本発明の実施の形態Ｃ−２に係る磁気記録媒体について説明する。本実施の形態に係る磁気記録媒体は、上述した実施の形態Ａ−１の磁気記録媒体１０と同様に、非磁性支持体１上に磁性層２として強磁性金属薄膜、保護層３が順次形成されてなる構成を有し、特に、保護層３表面に芳香族カルボン酸によるトップコートを介して、下記〔化５３〕で示される末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、下記〔化５４〕に示される部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤が保持されているものとする。
【０２２７】
【化５３】
Ｒ_２ＯＯＣ−Ｒｆ’−ＣＯＯＲ_２
【０２２８】
但し、Ｒｆ’はパーフルオロポリエーテル鎖を表し、Ｒ_２は炭化水素基又はフッ化炭化水素基を表す。
【０２２９】
【化５４】
Ｃ_ｎＦ_２ｎ＋１（ＣＨ_２）_ｍＣＯＯＲ
【０２３０】
但し、Ｒは炭素数７〜２１のアルキル基を表し、ｍ、ｎはｍ＋ｎ≧８を満足する整数を表す。
【０２３１】
上記〔化５３〕に示す化合物と上記〔化５４〕に示される化合物を含有する潤滑剤は、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、且つ長期に至り潤滑効果を持続する特性を有する。
【０２３２】
なお、上記潤滑剤が用いられる磁気記録媒体は、上記実施の形態Ｃ−１において説明した磁気記録媒体と略同様の構成を有するものであり、最外層に保持される潤滑剤のみが異なる例であり、その他の磁性層や保護層等は同じ構成を有している。そこで以下においては潤滑剤についてのみ説明する。
【０２３３】
上記〔化５３〕に示す末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物は、例えば、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとを、無水トルエン中でｐ−トルエンスルホン酸や濃硫酸等を触媒として反応させることによって得られる。
【０２３４】
ここで、上記末端にカルボキシル基を有するパーフルオロポリエーテルとしては、カルボキシル基を両末端に有するものが好ましく、具体的には、ＨＯＯＣ−ＣＦ_２（ＯＣ_２Ｆ_４）_ｍ　（ＯＣＦ_２）_ｊＯＣＦ_２−ＣＯＯＨ等が挙げられる。上記の末端にカルボキシル基を有するパーフルオロポリエーテルは、これらに限定されるものではない。なお、上記パーフルオロポリエーテル化学式中のｍ，ｊはいずれも１以上の整数を表す。
【０２３５】
また、上記末端にカルボキシル基を有するパーフルオロポリエーテルの分子量は、特に制約されるものではないが、実用的には６００〜５０００程度が好ましい。分子量が大きすぎると、末端基の吸着基としての効果が薄れるとともに、パーフルオロポリエーテル鎖が大きくなる分、既存の炭化水素系溶媒に溶解しにくくなり、分子量が小さすぎると、パーフルオロポリエーテル鎖による潤滑効果が失われてしまうためである。
【０２３６】
なお、上記末端にカルボキシル基を有するパーフルオロポリエーテルにおいては、パーフルオロポリエーテル鎖が部分水素化されてもよい。すなわち、パーフルオロポリエーテル鎖のフッ素原子の一部（５０％以下）を水素原子で置換しても良い。この場合には、パーフルオロポリエーテルとして部分水素化したパーフルオロポリエーテルを使用すればよい。
【０２３７】
一方、上記長鎖アルコールとしては、市販品、或いは合成品何れも使用可能である。また、その分子量が小さくなるに従って通常の有機溶媒に溶解し難くなることから、少なくともその１個のアルキル基の炭素数が６以上であることが好ましい。
【０２３８】
また、上述したように、本実施の形態で用いられる潤滑剤には、上記〔化５３〕に示す化合物の他に、上記〔化５４〕に示される部分フッ化カルボン酸アルキルエステルが含有される。上記〔化５４〕に示される部分フッ化カルボン酸アルキルエステルは、上記実施の形態Ｃ−１において説明した部分フッ化カルボン酸アルキルエステルと同様のものを使用することができる。
【０２３９】
さらに、本例の磁気記録媒体に使用される潤滑剤においては、上記〔化５３〕に示す末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、上記〔化５４〕に示す部分フッ化カルボン酸アルキルエステルとの混合比は、重量比で１０：９０〜９０：１０であるのが好ましく、さらには４０：６０〜６０：４０とすることが望ましい。上記範囲を超えると優れた潤滑効果が得られなくなる。
【０２４０】
また、潤滑剤を最外層に保持させる方法としては、保護層３の表面に潤滑剤をトップコートする方法が挙げられる。ここで、その塗布量は、０．０５ｍｇ／ｍ^２〜１００ｍｇ／ｍ^２であるのが好ましく、０．１ｍｇ／ｍ^２〜５０ｍｇ／ｍ^２であるのがより好ましい。この塗布量が少なすぎると、摩擦係数の低下、耐磨耗性・耐久性の向上という効果が表れず、また、塗布量が多すぎると、摺動部材と強磁性金属薄膜との間でハリツキ現象が起こり、却って走行性が悪くなる。
【０２４１】
以上のように、本実施の形態に係る磁気記録媒体は、密着性や潤滑性の点で非常に優れた特性の潤滑剤の組み合わせを特定して用いているので、良好な走行性及び耐久性が確保される。
また、カーボンよりなる保護層３の表面が芳香族カルボン酸によりトップコートされているので、用いられる潤滑剤と、保護層３との密着性が向上し、更に良好な耐久性を実現することができる。
【０２４２】
〔実施の形態Ｄ〕
次に、本発明の実施の形態Ｄに係る磁気記録媒体について説明する。本実施の形態に係る磁気記録媒体は、実施の形態Ａ−１において説明した図１の磁気記録媒体１０と同様に、非磁性支持体１上に磁性層２として強磁性金属薄膜、保護層３が順次形成されてなるものであり、保護層３の表面が、不活性ガス雰囲気中で紫外線照射処理されてなり、この保護層３上に、後述する潤滑剤が保持されているものとする。なお非磁性支持体１、磁性層２および保護層３の構成および製膜方法は上記実施の形態Ａ−１と同様のものとすることができる。
【０２４３】
本実施の形態に係る磁気記録媒体の保護層３の表面は、不活性ガス雰囲気中で紫外線が照射処理されているものとする。すなわち、潤滑剤層４を形成する前に、保護層３表面に不活性ガス雰囲気中で紫外線を照射する。保護層３の表面に紫外線を照射することにより、紫外線の光子エネルギーにより、炭素−炭素結合や炭素−水素結合が切断され、極性基が形成された状態となる。これにより保護層３と、保護層３上に保持される潤滑剤との間の密着性が向上し、潤滑剤の潤滑効果を長期間に亘って持続させることができる。
【０２４４】
また、保護層３の表面への紫外線照射は、不活性ガス雰囲気中で行われる。仮に、保護層３の表面への紫外線照射を大気中で行うと、紫外線によって発生するオゾン分子と、紫外線により生じた極性基とが結合してしまい、いわゆるウィークバウンダリーレアー化してしまう結果、保護層３と潤滑剤との吸着力が低下してしまう。言い換えると、保護層３に対する紫外線の照射を不活性ガス雰囲気中で行うことによって、保護層３表面に極性基を確実に形成することができ、保護層３と潤滑剤との吸着力を確実に向上させることができる。
なお、不活性ガスとしては、窒素、アルゴンおよび二酸化炭素を例示することができる。
【０２４５】
具体的に、紫外線としては、たとえば、低圧水銀ランプを使用して、波長が１８５ｎｍあるいは２５４ｎｍの紫外線を使用することが好ましい。波長が１８５ｎｍの紫外線では、光子エネルギーが１５５ｋｃａｌ／ｍｏｌとなり、波長が２５４ｎｍの紫外線では、光子エネルギーが１１３ｋｃａｌ／ｍｏｌとなる。このような低圧水銀ランプを使用することによって、保護層３に対して紫外線を効率よく照射することができる。
【０２４６】
また保護層３表面に紫外線を照射する際には、例えば図２に示すような紫外線照射装置２０が使用することができる。紫外線照射装置２０は、長尺状の被処理体２１を巻回してなる供給ロール２５および巻き取りロール２６と、供給ロール２５及び巻き取りロール２６との間に配設された紫外線処理部２７とを備えた構成を有している。
ここで、被処理体２１を供給ロール２５から巻き取りロール２６に向かって走行させるとともに、紫外線処理部２７に順次搬入する。紫外線処理部２７は、内部を密閉できる筐体２８内に配設された複数のガイドロール２９と、複数のガイドロール２９に架け合わされた被処理体２１、すなわち磁気記録媒体の保護層３に対向するように配設された複数の光源ランプ３０とを備えている。
また、紫外線処理部２７は、筐体２８にガス供給口２８ａ及びガス排出口２８ｂが形成されてなり、ガス供給口２８ａから不活性ガスを導入することによって、筐体２８内を不活性ガス雰囲気とすることができる。
【０２４７】
上述したような構成の紫外線照射装置２０では、筐体２８内を不活性ガス雰囲気とした状態で、順次走行する被処理体２１に対して、光源ランプ３０から紫外線を照射する。従って、この紫外線照射装置２０によれば、供給ロール２５から巻き取りロール２６に向かって被処理体２１を走行させることによって、保護層３に対して不活性ガス雰囲気中で紫外線を照射することができる。
【０２４８】
そして特に、本実施の形態に係る磁気記録媒体は、保護層３に下記〔化５５〕に示される末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、下記〔化５６〕に示される部分フッ化カルボン酸アルキルエステルを含有する潤滑剤が保持されているものである。
【０２４９】
【化５５】
Ｒ_１ＣＯＯＣＨ_２−Ｒｆ−ＣＨ_２ＯＣＯＲ_１
【０２５０】
但し、Ｒｆはパーフルオロポリエーテル鎖を表し、Ｒ_１は炭化水素基又はフッ化炭化水素基を表す。
【０２５１】
【化５６】
Ｃ_ｎＦ_２ｎ＋１（ＣＨ_２）_ｍＣＯＯＲ
【０２５２】
但し、Ｒは炭素数７〜２１のアルキル基を表し、ｍ、ｎはｍ＋ｎ≧８を満足する整数を表す。
【０２５３】
上記〔化５５〕に示される化合物及び上記〔化５６〕に示される化合物を有する潤滑剤は、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、且つ長期に至り潤滑効果を持続する特性を有するものである。
【０２５４】
上記〔化５５〕に示す末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物は、例えば、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸クロリドとを、トルエン中で塩基を触媒として反応させることによって得られる。
ここで、上記末端に水酸基を有するパーフルオロポリエーテルとしては、水酸基を両末端に有するものが好ましく、例えば、ＨＯ−ＣＨ_２ＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＨ_２−ＯＨ等が挙げられる。この末端に水酸基を有するパーフルオロポリエーテルは、これらに限定されるわけではない。なお、上記パーフルオロポリエーテル化学式中のｐ，ｑはいずれも１以上の整数を表す。
【０２５５】
また、この末端に水酸基を有するパーフルオロポリエーテルの分子量は、特に制約されるものではないが、実用的には６００〜５０００程度が好ましい。分子量が大きすぎると、末端基の吸着基としての効果が薄れると同時に、パーフルオロポリエーテル鎖が大きくなる分、既存の炭化水素系溶媒に溶解しにくくなる。逆に、分子量が小さすぎると、パーフルオロポリエーテル鎖による潤滑効果が失われてしまう。
【０２５６】
なお、この末端に水酸基を有するパーフルオロポリエーテルにおいては、パーフルオロポリエーテル鎖が部分水素化されてもよい。すなわち、パーフルオロポリエーテル鎖のフッ素原子の一部（５０％以下）を水素原子で置換してもよい。この場合には、パーフルオロポリエーテルとして部分水素化したパーフルオロポリエーテルを使用すればよい。
【０２５７】
一方、上記長鎖カルボン酸クロリドとしては、市販品、或いは合成品何れも使用可能である。このように、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸クロリドとを反応させることにより、上記〔化５５〕に示すような、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物が合成される。
【０２５８】
ここで、上記長鎖カルボン酸、つまり合成材料の長鎖カルボン酸クロリドのカルボン酸部分は、カルボン酸基を有する任意の構造で良く、例えば、分岐構造、異性体構造、脂環構造、不飽和結合の有無によらず選択することができる。また、この長鎖カルボン酸は、分子量に関しても任意であるが、分子量が小さくなるに伴って通常の炭化水素系の有機溶媒に溶解し難くなることから、少なくともアルキル基の炭素数が１０以上であることが好ましい。
【０２５９】
また、上述したように本実施の形態において用いられる潤滑剤には、上記〔化５５〕に示すエステル化合物の他に、上記〔化５６〕に示される部分フッ化カルボン酸アルキルエステル含有される。
この部分フッ化カルボン酸アルキルエステル中におけるＲの炭素数は７〜２１であることが好ましい。この炭素数が６以下であると潤滑効果が乏しく、また炭素数が２１を超えると有機溶剤への溶解性が低下する。上記〔化５６〕中のｍ、ｎに関しては、ｍ＋ｎ≧８を満たせば、特に制限はない。
【０２６０】
上記〔化５６〕に示される部分フッ化カルボン酸アルキルエステルは部分フッ化カルボン酸と飽和脂肪族アルコールとを、ほぼ等モル量で反応させることによって容易に合成することができる。
具体的には、上記部分フッ化カルボン酸アルキルエステルの合成の具体的な反応式は、以下に示すようなものである。
まず、部分フッ化カルボン酸は次のようにして合成される。初めに不飽和カルボン酸を出発原料として、上記〔化５７〕、〔化５８〕、〔化５９〕、および〔化６０〕に示す一連の反応を経ることにより部分フッ化カルボン酸が合成される。
【０２６１】
【化５７】

【０２６２】
【化５８】

【０２６３】
【化５９】

【０２６４】
【化６０】

【０２６５】
詳しくは、上記〔化５７〕に示すように、不飽和カルボン酸がアルコールとエステル化反応して不飽和エステルとなる。その後、上記〔化５８〕に示すように、この不飽和エステルがフッ化炭素のヨウ化物と付加反応して、フッ素およびヨウ素が付加される。そして上記〔化５９〕に示すように、還元反応することによって、部分フッ化エステルが生じる。その後、上記〔化６０〕に示すように、この部分フッ化エステルを加水分解することによって、最終的に部分フッ化カルボン酸が得られる。
【０２６６】
次にこのようにして得られた部分フッ化カルボン酸を、上記〔化６１〕に示すように、飽和脂肪族アルコールとほぼ等モル量反応させることによって、最終的に、部分フッ化カルボン酸アルキルエステルが得られる。
【０２６７】
【化６１】

【０２６８】
なお、ここで重要なのは上記部分フッ化カルボン酸アルキルエステルのアルコール部位のアルキル鎖が、不飽和結合を含まないアルキル基から選ばれることである。このような不飽和結合を含まないエステルを用いることにより、長期間の保存においても、初期の潤滑特性を維持することができる。
【０２６９】
さらに、磁気記録媒体に使用される潤滑剤においては、上記〔化５５〕に示される末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、上記〔化５６〕に示される部分フッ化カルボン酸アルキルエステルとの混合比は、重量比で１０：９０〜９０：１０であるのが好ましく、さらには４０：６０〜６０：４０とすることが望ましい。上記範囲を超えると優れた潤滑効果が得られなくなる。
【０２７０】
上記潤滑剤を最外層に保持させる方法としては、表面に潤滑剤をトップコートする方法が挙げられる。塗布量は、０．０５ｍｇ／ｍ^２〜１００ｍｇ／ｍ^２であるのが好ましく、０．１ｍｇ／ｍ^２〜５０ｍｇ／ｍ^２であるのがより好ましい。塗布量が少なすぎると、摩擦係数の低下、耐磨耗性及び耐久性の向上という効果が表れず、また、この塗布量が多すぎると、摺動部材と強磁性金属薄膜との間でハリツキ現象が起こり、却って走行性が悪くなる。
【０２７１】
以上のように、本実施の形態に係る磁気記録媒体は、上述したような密着性や潤滑性の点で非常に優れた特性の潤滑剤の組み合わせを特定して用いているので、良好な走行性及び耐久性が確保されたものとなる。
また、この磁気記録媒体においては、カーボンよりなる保護層３が形成されているとともに、その表面に紫外線が照射されているので、上記潤滑剤と、保護層３との密着性が向上し、更に良好な耐久性を実現することができる。
【０２７２】
また、この磁気記録媒体においては、磁性層２を強磁性金属薄膜としていることから、高密度記録、長時間記録にも充分対応可能である。
なお、本実施の形態に係る磁気記録媒体においては、必要に応じて、防錆剤を併用してもよい。防錆剤としては、通常この種の磁気記録媒体の防錆剤として使用されるものであれば何れも使用でき、例えばフェノール類、ナフトール類、キノン類、窒素原子を含む複素環化合物、酸素原子を含む複素環化合物、硫黄原子を含む複素環化合物等が挙げられる。
【０２７３】
また、本発明の磁気記録媒体においては、非磁性支持体１上の磁性層２が形成される面とは反対側の面に、いわゆるバックコート層を形成しても良い。このバックコート層は、結合剤樹脂と粉末成分とを有機溶媒に混合分散させたバックコート用塗料を非磁性支持体２に塗布することにより形成される。
【０２７４】
バックコート用塗料に使用される結合剤樹脂としては、例えば、塩化ビニル−酢酸ビニル系共重合体、塩化ビニル−塩化ビニリデン共重合体、塩化ビニル−アクリロニトリル共重合体、アクリル酸エステル−アクリロニトリル共重合体、熱可塑性ポリウレタンエラストマー、塩化ビニリデン−アクリロニトリル共重合体、ブタジエン−アクリロニトリル共重合体、ポリアミド樹脂、ポリビニルブチラール、セルロース誘導体、ポリエステル樹脂、フェノール樹脂、エポキシ樹脂、ポリウレタン硬化型樹脂、メラミン樹脂、アルキッド樹脂、シリコーン樹脂、エポキシ−ポリアミド樹脂、ニトロセルロース−メラミン樹脂、高分子量ポリエステル樹脂とイソシアネートプレポリマーの混合物、メタクリル酸塩共重合体とジイソシアネートプレポリマーの混合物、ポリエステルポリオールとポリイソシアネートとの混合物、尿素ホルムアルデヒド樹脂、低分子量グリコール／高分子量ジオール／トリフェニルメタントリイソシアネートとの混合物、ポリアミン樹脂及びこれらの混合物等が挙げられる。
【０２７５】
あるいは、粉末成分の分散性の改善を図るために、親水性極性基を有する結合剤樹脂を使用してもよい。
一方、上記粉末成分としては、導電性を付与するためのカーボン系微粉末や表面粗度のコントロール及び耐久性向上のために添加される無機顔料が挙げられる。上記カーボン系微粒子としては、例えば、ファーネスカーボン、チャネルカーボン、アセチレンカーボン、サーマルカーボン、ランプカーボン等が例示され、上記無機顔料としては、α−ＦｅＯＯＨ、α−Ｆｅ_２Ｏ_３、Ｃｒ_２Ｏ_３、ＴｉＯ_２、ＺｎＯ、ＳｉＯ、ＳｉＯ_２、ＳｉＯ_２・２Ｈ_２Ｏ、Ａｌ_２Ｏ_３、ＣａＣＯ_３、ＭｇＣＯ_３、Ｓｂ_２Ｏ_３等が挙げられる。
【０２７６】
さらに、上記バックコート用塗料の有機溶剤としては、例えば、アセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等のケトン系溶剤、酢酸メチル、酢酸エチル、酢酸ブチル、乳酸エチル、酢酸グリコールモノエチルエーテル等のエステル系溶剤、グリコールジメチルエーテル、グリコールモノエチルエーテル、ジオキサン等のグリコールエーテル系溶剤、ベンゼン、トルエン、キシレン等の芳香族炭化水素系溶剤、ヘキサン、ヘプタン等の脂肪族炭化水素溶媒、メチレンクロライド、エチレンクロライド、四塩化炭素、クロロホルム、エチレンクロロヒドリン、ジクロルベンゼン等の塩素化炭化水素系溶媒等、汎用の溶剤を用いることができる。
【０２７７】
さらに、上記のバックコート層には潤滑剤を併用してもよい。この場合、上記バックコート層中に潤滑剤を内添する方法、あるいはバックコート層上に潤滑剤を被着する方法がある。いずれにしても、上記潤滑剤としては、脂肪酸、脂肪酸エステル、脂肪酸アミド、金属石鹸、脂肪族アルコール、シリコーン系潤滑剤等、従来周知の潤滑剤が使用できる。
【０２７８】
本実施の形態に係る磁気記録媒体は、以下のようにして作製される。
先ず、非磁性支持体１上に、例えば真空蒸着法により磁性層２となる強磁性金属薄膜を形成する。その後、この磁性層２上に、例えばプラズマＣＶＤ法により保護層３を形成する。さらに、この保護層３の表面に対して紫外線照射を行う。そして、この保護層３上に、上述の潤滑剤をトップコートして保護層３に潤滑剤を保持させて、磁気記録媒体が得られる。なお、必要に応じてバックコート層等を形成してもよい。
【０２７９】
磁性層２は、図３に示した真空蒸着装置４０を用いて、上述した実施の形態Ａ−１の場合と同様にして形成することができる。
【０２８０】
次に、保護層３の形成方法について説明する。保護層３はＣＶＤ法により形成することができる。ＣＶＤ法によって保護層を形成する場合には、まず、真空容器中に炭化水素ガス、あるいは炭化水素と不活性ガスとの混合ガスを導入し、１０Ｐａ〜１００Ｐａ程度の圧力に保持した状態で、真空容器内に放電させて、炭化水素ガスのプラズマを発生させ、強磁性金属薄膜上に保護層３を形成する。放電形式としては、外部電極方式、内部電極方式のいずれでもよく、放電周波数については、実験的に決めることができる。また、強磁性金属薄膜が形成された非磁性支持体１側に配された電極に０〜−３ｋＶの電圧を印加することにより、保護層３の硬度の増大及び密着性を向上させることができる。
【０２８１】
保護層の材料となる上記炭化水素としては、例えば、メタン、エタン、プロパン、ブタン、ペンタン、ヘキサン、ヘプタン、オクタン、エチレン、アセチレン、プロペン、ブテン、ペンテン、ベンゼンなどを用いることができる。
保護層３は、スペーシングロスを少なく、かつ、強磁性金属薄膜の磨耗防止の効果を得られるよう、その厚さを３ｎｍ〜１５ｎｍ程度、特に５ｎｍ〜１０ｎｍ程度とすることが好ましい。
【０２８２】
ここでは、ＣＶＤ法により保護層３を形成する例について説明したが、保護層３を形成する方法としては、この方法の他に、マグネトロンスパッタ法、イオンビームスパッタ法、イオンビームプレーティング法等の従来公知の薄膜形成方法を用いることができる。
【０２８３】
そして、この保護層３の表面に対して、不活性ガス雰囲気中で紫外線照射処理を行う。保護層３の表面を紫外線照射処理することにより、保護層３と潤滑剤層４との間の密着性の向上が図られる。
【０２８４】
〔実施の形態Ｅ〕
次に、本発明の実施の形態Ｅに係る磁気記録媒体について説明する。本実施の形態に係る磁気記録媒体は、実施の形態Ａ−１において説明した図１の磁気記録媒体１０と同様に、非磁性支持体１上に磁性層２として強磁性金属薄膜、保護層３が順次形成されてなるものであり、保護層３の表面が、不活性ガス雰囲気中で紫外線照射処理されてなり、この保護層３上に、後述する潤滑剤が保持されているものとする。なお非磁性支持体１、磁性層２および保護層３の構成および製膜方法は上記実施の形態Ａ−１と同様のものとすることができる。
【０２８５】
本実施の形態に係る磁気記録媒体の保護層３の表面は、不活性ガス雰囲気中で紫外線が照射処理されているものとする。すなわち、潤滑剤層４を形成する前に、保護層３表面に不活性ガス雰囲気中で紫外線を照射する。保護層３の表面に紫外線を照射することにより、紫外線の光子エネルギーにより、炭素−炭素結合や炭素−水素結合が切断され、極性基が形成された状態となる。これにより保護層３と、保護層３上に保持される潤滑剤との間の密着性が向上し、潤滑剤の潤滑効果を長期間に亘って持続させることができる。
【０２８６】
また、保護層３の表面への紫外線照射は、不活性ガス雰囲気中で行われる。仮に、保護層３の表面への紫外線照射を大気中で行うと、紫外線によって発生するオゾン分子と、紫外線により生じた極性基とが結合してしまい、いわゆるウィークバウンダリーレアー化してしまう結果、保護層３と潤滑剤との吸着力が低下してしまう。言い換えると、保護層３に対する紫外線の照射を不活性ガス雰囲気中で行うことによって、保護層３表面に極性基を確実に形成することができ、保護層３と潤滑剤との吸着力を確実に向上させることができる。
なお、不活性ガスとしては、窒素、アルゴンおよび二酸化炭素を例示することができる。
【０２８７】
具体的に、紫外線としては、たとえば低圧水銀ランプを使用して、波長が１８５ｎｍあるいは２５４ｎｍの紫外線を使用することが好ましい。波長が１８５ｎｍの紫外線では、光子エネルギーが１５５ｋｃａｌ／ｍｏｌとなり、波長が２５４ｎｍの紫外線では、光子エネルギーが１１３ｋｃａｌ／ｍｏｌとなる。このような低圧水銀ランプを使用することによって、保護層３に対して紫外線を効率よく照射することができる。
【０２８８】
また保護層３表面に紫外線を照射する際には、例えば図２に示すような紫外線照射装置２０を適用できる。紫外線照射装置２０は、長尺状の被処理体２１を巻回してなる供給ロール２５および巻き取りロール２６と、供給ロール２５及び巻き取りロール２６との間に配設された紫外線処理部２７とを備えた構成を有している。
ここで、被処理体２１を供給ロール２５から巻き取りロール２６に向かって走行させるとともに、紫外線処理部２７に順次搬入する。紫外線処理部２７は、内部を密閉できる筐体２８内に配設された複数のガイドロール２９と、複数のガイドロール２９に架け合わされた被処理体２１、すなわち磁気記録媒体の保護層３に対向するように配設された複数の光源ランプ３０とを備えている。
また、紫外線処理部２７は、筐体２８にガス供給口２８ａ及びガス排出口２８ｂが形成されてなり、ガス供給口２８ａから不活性ガスを導入することによって、筐体２８内を不活性ガス雰囲気とすることができる。
【０２８９】
上述したような構成の紫外線照射装置２０では、筐体２８内を不活性ガス雰囲気とした状態で、順次走行する被処理体２１に対して、光源ランプ３０から紫外線を照射する。従って、この紫外線照射装置２０によれば、供給ロール２５から巻き取りロール２６に向かって被処理体２１を走行させることによって、保護層３に対して不活性ガス雰囲気中で紫外線を照射することができる。
【０２９０】
そして特に本実施の形態に係る磁気記録媒体は、保護層３に下記〔化６２〕に示される末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、下記〔化６３〕に示される部分フッ化カルボン酸アルキルエステルを含有する潤滑剤が保持されているものである。
【０２９１】
【化６２】
Ｒ_１ＯＯＣ−Ｒｆ−ＣＯＯＲ_１
【０２９２】
但し、Ｒｆはパーフルオロポリエーテル鎖を表し、Ｒ_１は炭化水素基又はフッ化炭化水素基を表す。
【０２９３】
【化６３】
Ｃ_ｎＦ_２ｎ＋１（ＣＨ_２）_ｍＣＯＯＲ
【０２９４】
但し、Ｒは炭素数７〜２１のアルキル基を表し、ｍ、ｎはｍ＋ｎ≧８を満足する整数を表す。
【０２９５】
上記〔化６２〕に示される化合物及び上記〔化６３〕に示される化合物を有する潤滑剤は、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、且つ長期に至り潤滑効果を持続する特性を有するものである。
【０２９６】
上記〔化６２〕に示す末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物は、例えば、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとを、無水トルエン中でｐ−トルエンスルホン酸や濃硫酸を触媒として反応させることによって得られる。
【０２９７】
ここで、上記末端にカルボキシル基を有するパーフルオロポリエーテルとしては、カルボキシル基を両末端に有するものが好ましく、例えば、ＨＯＯＣ−ＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＯＯＨ等が挙げられる。末端にカルボキシル基を有するパーフルオロポリエーテルは、これらに限定されるものではない。なお、上記パーフルオロポリエーテル化学式中のｐ，ｑはいずれも１以上の整数を表す。
【０２９８】
また、この末端にカルボキシル基を有するパーフルオロポリエーテルの分子量は、特に制約されるものではないが、実用的には６００〜５０００程度が好ましい。分子量が大きすぎると、末端基の吸着基としての効果が薄れると同時に、パーフルオロポリエーテル鎖が大きくなる分、既存の炭化水素系溶媒に溶解しにくくなる。逆に、分子量が小さすぎると、パーフルオロポリエーテル鎖による潤滑効果が失われてしまう。
【０２９９】
なお、この末端にカルボキシル基を有するパーフルオロポリエーテルにおいては、パーフルオロポリエーテル鎖が部分水素化されてもよい。すなわち、パーフルオロポリエーテル鎖のフッ素原子の一部（５０％以下）を水素原子で置換してもよい。この場合には、パーフルオロポリエーテルとして部分水素化したパーフルオロポリエーテルを使用すればよい。
【０３００】
一方、上記長鎖アルコールとしては、市販品、或いは合成品何れも使用可能である。このように、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとを反応させることにより、上記〔化６２〕に示すような、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物が合成される。
【０３０１】
上記長鎖アルコールは、分子量に関しても任意であるが、分子量が小さくなるに伴って通常の炭化水素系の有機溶媒に溶解し難くなることから、少なくともアルキル基の炭素数が６以上であることが好ましい。
【０３０２】
また、上述したように、本実施の形態に係る磁気記録媒体に適用される潤滑剤には、上記〔化６２〕に示すエステル化合物の他に、上記〔化６３〕に示される部分フッ化カルボン酸アルキルエステル含有される。
この〔化６３〕に示す部分フッ化カルボン酸アルキルエステル中におけるＲの炭素数は７〜２１であることが好ましい。この炭素数が６以下であると潤滑効果が乏しく、また炭素数が２１を超えると有機溶剤への溶解性が低下する。また、上記〔化６３〕中のｍ、ｎに関しては、ｍ＋ｎ≧８を満たせば、特に制限はない。
【０３０３】
また、上記〔化６３〕に示される部分フッ化カルボン酸アルキルエステルは部分フッ化カルボン酸と飽和脂肪族アルコールとを、ほぼ等モル量で反応させることによって容易に合成することができる。
具体的には、上記部分フッ化カルボン酸アルキルエステルの合成の具体的な反応式は、以下に示すようなものである。
【０３０４】
部分フッ化カルボン酸は次のようにして合成される。初めに不飽和カルボン酸を出発原料として、上記〔化６４〕、〔化６５〕、〔化６６〕および〔化６７〕に示す一連の反応を経ることにより、部分フッ化カルボン酸が合成される。
【０３０５】
【化６４】

【０３０６】
【化６５】

【０３０７】
【化６６】

【０３０８】
【化６７】

【０３０９】
詳しくは、上記〔化６４〕に示すように、不飽和カルボン酸がアルコールとエステル化反応して不飽和エステルとなる。その後、上記〔化６５〕に示すように、この不飽和エステルがフッ化炭素のヨウ化物と付加反応して、フッ素およびヨウ素が付加される。そして上記〔化６６〕に示すように、還元反応することによって、部分フッ化エステルが生じる。その後、上記〔化６７〕に示すように、この部分フッ化エステルを加水分解することによって、最終的に部分フッ化カルボン酸が得られる。
【０３１０】
次にこのようにして得られた部分フッ化カルボン酸を、下記〔化６８〕に示すように、飽和脂肪族アルコールとほぼ等モル量反応させることによって、最終的に、部分フッ化カルボン酸アルキルエステルが得られる。
【０３１１】
【化６８】

【０３１２】
なお、ここで重要なのは、上記部分フッ化カルボン酸アルキルエステルのアルコール部位のアルキル鎖が、不飽和結合を含まないアルキル基から選ばれることである。このような不飽和結合を含まないエステルを用いることにより、長期間の保存においても、初期の潤滑特性を維持することができる。
【０３１３】
さらに、磁気記録媒体に使用される潤滑剤においては、上記〔化６２〕に示される末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、上記〔化６３〕に示される部分フッ化カルボン酸アルキルエステルとの混合比は、重量比で１０：９０〜９０：１０、さらには４０：６０〜６０：４０とすることが望ましい。上記範囲を超えると優れた潤滑効果が得られなくなる。
【０３１４】
上記潤滑剤を最外層に保持させる方法としては、表面に潤滑剤をトップコートする方法が挙げられる。塗布量は、０．０５ｍｇ／ｍ^２〜１００ｍｇ／ｍ^２であるのが好ましく、０．１ｍｇ／ｍ^２〜５０ｍｇ／ｍ^２であるのがより好ましい。塗布量が少なすぎると、摩擦係数の低下、耐磨耗性及び耐久性の向上という効果が表れず、また、この塗布量が多すぎると、摺動部材と強磁性金属薄膜との間でハリツキ現象が起こり、却って走行性が悪くなる。
【０３１５】
以上のように、本実施の形態に係る磁気記録媒体は、上述したような、密着性や潤滑性の点で非常に優れた特性の潤滑剤の組み合わせを特定して用いているので、良好な走行性及び耐久性が確保されたものとなる。
また、この磁気記録媒体においては、カーボンよりなる保護層３が形成されているとともに、その表面に紫外線が照射されているので、上記潤滑剤と、保護層３との密着性が向上し、更に良好な耐久性を実現することができる。
【０３１６】
また、この磁気記録媒体においては、磁性層２を強磁性金属薄膜としていることから、高密度記録、長時間記録にも充分対応可能である。
なお、本実施の形態に係る磁気記録媒体においては、必要に応じて、防錆剤を併用してもよい。防錆剤としては、通常この種の磁気記録媒体の防錆剤として使用されるものであれば何れも使用でき、例えばフェノール類、ナフトール類、キノン類、窒素原子を含む複素環化合物、酸素原子を含む複素環化合物、硫黄原子を含む複素環化合物等が挙げられる。
【０３１７】
また、本発明の磁気記録媒体においては、非磁性支持体１上の磁性層２が形成される面とは反対側の面に、いわゆるバックコート層を形成しても良い。このバックコート層は、結合剤樹脂と粉末成分とを有機溶媒に混合分散させたバックコート用塗料を非磁性支持体１に塗布することにより形成される。
【０３１８】
バックコート用塗料に使用される結合剤樹脂としては、例えば、塩化ビニル−酢酸ビニル系共重合体、塩化ビニル−塩化ビニリデン共重合体、塩化ビニル−アクリロニトリル共重合体、アクリル酸エステル−アクリロニトリル共重合体、熱可塑性ポリウレタンエラストマー、塩化ビニリデン−アクリロニトリル共重合体、ブタジエン−アクリロニトリル共重合体、ポリアミド樹脂、ポリビニルブチラール、セルロース誘導体、ポリエステル樹脂、フェノール樹脂、エポキシ樹脂、ポリウレタン硬化型樹脂、メラミン樹脂、アルキッド樹脂、シリコーン樹脂、エポキシ−ポリアミド樹脂、ニトロセルロース−メラミン樹脂、高分子量ポリエステル樹脂とイソシアネートプレポリマーの混合物、メタクリル酸塩共重合体とジイソシアネートプレポリマーの混合物、ポリエステルポリオールとポリイソシアネートとの混合物、尿素ホルムアルデヒド樹脂、低分子量グリコール／高分子量ジオール／トリフェニルメタントリイソシアネートとの混合物、ポリアミン樹脂及びこれらの混合物等が挙げられる。
【０３１９】
あるいは、粉末成分の分散性の改善を図るために、親水性極性基を有する結合剤樹脂を使用してもよい。
一方、上記粉末成分としては、導電性を付与するためのカーボン系微粉末や表面粗度のコントロール及び耐久性向上のために添加される無機顔料が挙げられる。上記カーボン系微粒子としては、例えば、ファーネスカーボン、チャネルカーボン、アセチレンカーボン、サーマルカーボン、ランプカーボン等が例示され、上記無機顔料としては、α−ＦｅＯＯＨ、α−Ｆｅ_２Ｏ_３、Ｃｒ_２Ｏ_３、ＴｉＯ_２、ＺｎＯ、ＳｉＯ、ＳｉＯ_２、ＳｉＯ_２・２Ｈ_２Ｏ、Ａｌ_２Ｏ_３、ＣａＣＯ_３、ＭｇＣＯ_３、Ｓｂ_２Ｏ_３等が挙げられる。
【０３２０】
さらに、上記バックコート用塗料の有機溶剤としては、例えば、アセトン、メチルエチルケトン、メチルイソブチルケトン、シクロヘキサノン等のケトン系溶剤、酢酸メチル、酢酸エチル、酢酸ブチル、乳酸エチル、酢酸グリコールモノエチルエーテル等のエステル系溶剤、グリコールジメチルエーテル、グリコールモノエチルエーテル、ジオキサン等のグリコールエーテル系溶剤、ベンゼン、トルエン、キシレン等の芳香族炭化水素系溶剤、ヘキサン、ヘプタン等の脂肪族炭化水素溶媒、メチレンクロライド、エチレンクロライド、四塩化炭素、クロロホルム、エチレンクロロヒドリン、ジクロルベンゼン等の塩素化炭化水素系溶媒等、汎用の溶剤を用いることができる。
【０３２１】
さらに、上記のバックコート層には潤滑剤を併用してもよい。この場合、上記バックコート層中に潤滑剤を内添する方法、あるいはバックコート層上に潤滑剤を被着する方法がある。いずれにしても、上記潤滑剤としては、脂肪酸、脂肪酸エステル、脂肪酸アミド、金属石鹸、脂肪族アルコール、シリコーン系潤滑剤等、従来周知の潤滑剤が使用できる。
【０３２２】
本実施の形態に係る磁気記録媒体は、以下のようにして作製される。
先ず、非磁性支持体１上に、例えば真空蒸着法により磁性層２となる強磁性金属薄膜を形成する。その後、この磁性層２上に、例えばプラズマＣＶＤ法により保護層３を形成する。さらに、この保護層３の表面に対して紫外線照射を行う。そして、この保護層３上に、上述した潤滑剤をトップコートして保護層３に潤滑剤を保持させて、磁気記録媒体が得られる。なお、必要に応じてバックコート層等を形成してもよい。
【０３２３】
磁性層２は、図３に示した真空蒸着装置４０を用いて、上述した実施の形態Ａ−１の場合と同様にして形成することができる。
【０３２４】
次に、保護層３の形成方法について説明する。保護層３はＣＶＤ法により形成することができる。ＣＶＤ法によって保護層を形成する場合には、まず、真空容器中に炭化水素ガス、あるいは炭化水素と不活性ガスとの混合ガスを導入し、１０Ｐａ〜１００Ｐａ程度の圧力に保持した状態で、真空容器内に放電させて、炭化水素ガスのプラズマを発生させ、強磁性金属薄膜上に保護層３を形成する。放電形式としては、外部電極方式、内部電極方式のいずれでもよく、放電周波数については、実験的に決めることができる。また、強磁性金属薄膜が形成された非磁性支持体１側に配された電極に０〜−３ｋＶの電圧を印加することにより、保護層３の硬度の増大及び密着性を向上させることができる。
【０３２５】
保護層の材料となる上記炭化水素としては、例えば、メタン、エタン、プロパン、ブタン、ペンタン、ヘキサン、ヘプタン、オクタン、エチレン、アセチレン、プロペン、ブテン、ペンテン、ベンゼンなどを用いることができる。
保護層３は、スペーシングロスを少なく、かつ、強磁性金属薄膜の磨耗防止の効果を得られるよう、その厚さを３ｎｍ〜１５ｎｍ程度、特に５ｎｍ〜１０ｎｍ程度とすることが好ましい。
【０３２６】
ここでは、ＣＶＤ法により保護層３を形成する例について説明したが、保護層３を形成する方法としては、この方法の他に、マグネトロンスパッタ法、イオンビームスパッタ法、イオンビームプレーティング法等の従来公知の薄膜形成方法を用いることができる。
【０３２７】
そして、この保護層３の表面に対して不活性ガス雰囲気中で紫外線照射処理を行う。保護層３の表面を紫外線照射処理することにより、保護層３と潤滑剤層４との間の密着性の向上が図られる。
【０３２８】
【実施例】
以下、本発明の実施例について具体的な実験結果に基づいて説明する。
〔実験例Ａ１（実施例Ａ−１〜Ａ−８、比較例Ａ−１〜Ａ−１０）〕
本実験例では、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、パーフルオロカルボン酸エステルを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０３２９】
（サンプルの作製）
１　末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物の合成
先ず、末端に水酸基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＣＨ_２ＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＨ_２ＯＨ（但し、化学式中ｐ、ｑはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるトリエチルアミンを有機溶媒中に溶解させ、この溶液中に更にモル比で２倍等量のステアリン酸クロリドを３０分かけて滴下した。
滴下終了後１時間撹拌し、続いて３０分間加熱還流を行った。そして冷却した後、蒸留水、希塩酸水溶液の順で洗浄し、再度蒸留水により洗浄液が中性になるまで洗浄した。続いて有機溶媒を除去し、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製してエステル化合物を得た。ここで、このエステル化合物を化合物Ａ−１とする。
【０３３０】
次に、上記化合物Ａ−１と同様の合成方法によって、下記表１に示すような末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物である４種類の化合物Ａ−２〜Ａ−５を合成した。なお、表１中ｐ、ｑ、ｎは、１以上の整数をそれぞれ表す。
【０３３１】
【表１】

【０３３２】
２　サンプルテープの作製
次に磁気テープを以下のようにして作製した。先ず非磁性支持体である７．０μｍ厚のポリエチレンテレフタレートフィルムに、上述の真空蒸着装置を使用して斜め蒸着法によりＣｏを被着させ、磁性層となる強磁性金属薄膜を１８０ｎｍの厚さに形成した。
次に上記強磁性金属薄膜上に、エチレンとアルゴンの混合ガスの高周波プラズマにより、電極と、磁気記録媒体原反自身を対向電極として、原反に−１．５ｋＶの直流電圧を印加し、放電を行い、上記強磁性金属薄膜上に約８ｎｍの厚さのカーボン保護層を形成した。
次にポリエチレンテレフタレートフィルムの強磁性金属薄膜が形成された面とは反対側の面に、カーボン及びポリウレタン樹脂よりなる膜厚０．５μｍのバックコート層を形成した。
次に下記表２に示される芳香族アルコールをイソプロピルアルコールに溶解したものを、カーボン保護層上に塗布量が２ｍｇ／ｍ^２となるように塗布した。
【０３３３】
【表２】

【０３３４】
次に上記表２に示される化合物をそれぞれヘキサン溶媒に溶解したものを、上記カーボン保護層上に塗布量が５ｍｇ／ｍ^２となるように塗布して、１８種類の磁気記録媒体を得た。
そして、これら１８種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断して、実施例Ａ−１〜実施例Ａ−８及び比較例Ａ−１〜比較例Ａ−１０の１８種類のサンプルテープとした。
ただし比較例Ａ−３〜比較例Ａ−１０のサンプルテープについては、保護層の表面に芳香族アルコールを塗布しなかった。
【０３３５】
３　特性の評価
次に上記実施例Ａ−１〜実施例Ａ−８と比較例Ａ−１〜比較例Ａ−１０の１８種類のサンプルテープの特性を評価した。ここでは耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を評価した。これらを評価する際の環境条件としては、本発明者らが検討した上で、最も厳しい条件と思われる条件を採用した。
【０３３６】
１　摩擦係数の測定方法
摩擦係数の測定は、恒温槽中の環境条件を温度４０℃、湿度８０％ＲＨに制御して、この恒温槽中で各サンプルテープを１００パス走行させて測定することとした。なお、摩擦走行１００パス目の数値を摩擦係数とした。
２　スチル耐久性の測定方法
スチル耐久性の評価は、−５℃の恒温槽中で行い、市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用いて、各サンプルテープの再生出力が３ｄＢ落ちるまでの時間を測定して行った。
３　シャトル耐久性の測定方法
シャトル耐久性は、恒温槽中の環境条件を温度４０℃、湿度２０％ＲＨに制御して、この恒温槽中で市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用い、各サンプルテープを１００パスシャトル走行させ、１００パス走行後にその再生出力が初期出力から何ｄＢ落ちるかを測定して評価した。
【０３３７】
なお、これらの評価は潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の測定結果を下記表３に、３０日間保存した後の保存後の耐久性及び走行性の測定結果を下記表４にそれぞれ示す。
【０３３８】
【表３】

【０３３９】
【表４】

【０３４０】
表３及び表４の結果から、保護層表面を芳香族アルコールでトップコートし、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物とパーフルオロカルボン酸エステルとを組み合わせた潤滑剤を使用した実施例Ａ−１〜実施例Ａ−８のサンプルテープにおいては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０３４１】
一方、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物のみを含有する潤滑剤を用いた比較例Ａ−１及び比較例Ａ−２では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。
【０３４２】
また、保護層の表面に芳香族アルコールを塗布しなかった比較例Ａ−３〜比較例Ａ−１０では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった
【０３４３】
以上の結果より、保護層表面を芳香族アルコールで処理し、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、パーフルオロカルボン酸エステルとを組み合わせることにより、如何なる使用条件下においても優れた密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０３４４】
〔実験例Ａ２（実施例Ａ−９〜Ａ−１６、比較例Ａ−１１〜Ａ−２０）〕
本実験例においては、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、パーフルオロカルボン酸エステルを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０３４５】
（サンプルの作製）
１　末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物の合成
先ず、末端にカルボキシル基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＯＣＣＦ_２（ＯＣ_２Ｆ_４）_ｍ（ＯＣＦ_２）_ｊＯＣＦ_２ＣＯＯＨ（但し、化学式中ｍ、ｊはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるステアリルアルコールを無水トルエン中で少量のｐ−トルエンスルホン酸と濃硫酸を触媒として加熱還流させた。このとき、生成される水分を除去しながら行った。
反応終了後、トルエンを除去した後、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製して、その後溶媒を除去し、エステル化合物を得た。なお、ここで、このエステル化合物を化合物Ａ−６とする。
次に、上記化合物Ａ−６と同様な合成方法によって、下記表５に示すような末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物である４種類の化合物Ａ−７〜Ａ−１０を合成した。なお、表５中ｐ，ｑ、ｎは、１以上の整数をそれぞれ表す。
【０３４６】
【表５】

【０３４７】
２　サンプルテープの作製
まず上記実験例Ａ１と同様にして、非磁性支持体上に磁性層となる強磁性金属薄膜、カーボン保護層を形成し、バックコート層も形成した。さらに保護層表面に、下記表６に示されるような芳香族アルコールをイソプロピルアルコールに溶解したものを、塗布量が２ｍｇ／ｍ^２となるように塗布した。
【０３４８】
【表６】

【０３４９】
次に、前述の実験例Ａ１と同様にして、保護層表面に上記表６に示されるような潤滑剤をヘキサン溶媒に溶解したものを、塗布量が５ｍｇ／ｍ^２となるようにそれぞれ塗布して１８種類の磁気記録媒体を得た。
そして、これら１８種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断し、実施例Ａ−９〜実施例Ａ−１６及び比較例Ａ−１１〜比較例Ａ−２０の１８種類のサンプルテープを作製した。
ただし、比較例Ａ−１３〜比較例２０のサンプルテープについては、保護層の表面に芳香族アルコールを塗布しなかった。
【０３５０】
３　特性の評価
次に上記実施例Ａ−９〜実施例Ａ−１６と比較例Ａ−１１〜比較例Ａ−２０の１８種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を前述の実験例Ａ１と同様にして評価した。
【０３５１】
なお、これらの評価は、前述の実験例Ａ１と同様に潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の結果を表７、３０日間保存した後の保存後の耐久性及び走行性の結果を表８に示す。
【０３５２】
【表７】

【０３５３】
【表８】

【０３５４】
表７及び表８の結果から、保護層表面を芳香族アルコールでトップコートし、さらに潤滑剤として、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物とパーフルオロカルボン酸エステルとを組み合わせた潤滑剤を使用した実施例Ａ−９〜実施例Ａ−１６においては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０３５５】
一方、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物のみを含有する潤滑剤を用いた比較例Ａ−１１及び比較例Ａ−１２では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。
【０３５６】
また、保護層の表面に芳香族アルコールを塗布しなかった比較例Ａ−１３〜比較例Ａ−２０では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
以上の結果より、保護層表面を芳香族アルコールでトップコートし、さらに潤滑剤として、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、パーフルオロカルボン酸エステルとを組み合わせたものを用いることにより、如何なる使用条件下においても密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０３５７】
〔実験例Ｂ１（実施例Ｂ−１〜Ｂ−８、比較例Ｂ−１〜Ｂ−１３）〕
本実験例では、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、部分フッ化カルボン酸アルキルエステルを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０３５８】
（サンプルの作製）
１　末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物の合成
先ず、末端に水酸基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＣＨ_２ＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＨ_２ＯＨ（但し、化学式中ｐ、ｑはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるトリエチルアミンを有機溶媒中に溶解させ、この溶液中に更にモル比で２倍等量のステアリン酸クロリドを３０分かけて滴下した。
滴下終了後、１時間撹拌し、続いて３０分間加熱還流を行った。そして、冷却した後、蒸留水、希塩酸水溶液の順で洗浄し、再度蒸留水により洗浄液が中性になるまで洗浄した。続いて、有機溶媒を除去し、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製してエステル化合物を得た。ここで、このエステル化合物を化合物Ｂ−１とする。
次に、上記化合物Ｂ−１と同様の合成方法によって、下記表９に示すような末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物である４種類の化合物Ｂ−２〜Ｂ−５を合成した。なお、表９中ｐ、ｑ、ｎは、１以上の整数をそれぞれ表す。
【０３５９】
【表９】

【０３６０】
２　サンプルテープの作製
次に磁気テープを以下のようにして作製した。先ず非磁性支持体である７．０μｍ厚のポリエチレンテレフタレートフィルムに、上述の真空蒸着装置を使用して斜め蒸着法によりＣｏを被着させ、磁性層となる強磁性金属薄膜を１８０ｎｍの厚さに形成した。
次に上記強磁性金属薄膜上に、エチレンとアルゴンの混合ガスの高周波プラズマにより、電極と磁気記録媒体原反自身を対向電極として、原反に−１．５ｋＶの直流電圧を印加し、放電を行い、上記強磁性金属薄膜上に約８ｎｍの厚さのカーボン保護層を形成した。
次にポリエチレンテレフタレートフィルムの強磁性金属薄膜が形成された面とは反対側の面に、カーボン及びポリウレタン樹脂よりなる膜厚０．５μｍのバックコート層を形成した。
【０３６１】
次に下記表１０に示すように芳香族アミンをイソプロピルアルコールに溶解したものを、カーボン保護層上に塗布量が２ｍｇ／ｍ^２となるように塗布した。
次に下記表１０に示される化合物をそれぞれヘキサン溶媒に溶解したものを、上記カーボン保護層上に塗布量が５ｍｇ／ｍ^２となるように塗布して、２１種類の磁気記録媒体を得た。
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断して、実施例Ｂ−１〜実施例Ｂ−８及び比較例Ｂ−１〜比較例Ｂ−１３の２１種類のサンプルテープとした。
【０３６２】
ただし、比較例Ｂ−３〜比較例Ｂ−１０のサンプルテープについては、保護層の表面に芳香族アミンを塗布しなかった。さらに、比較例Ｂ−８〜比較例Ｂ−１０のサンプルテープについては、保護層を上述したようなプラズマＣＶＤ法によらず、マグネトロンスパッタ法により形成した。また、比較例Ｂ−１１〜比較例Ｂ−１３の潤滑剤に含有されている部分フッ化カルボン酸アルキルエステルは二重結合を有しているものとした。
【０３６３】
【表１０】

【０３６４】
３　特性の評価
次に上記実施例Ｂ−１〜実施例Ｂ−８と比較例Ｂ−１〜比較例Ｂ−１３の２１種類のサンプルテープの特性を評価した。ここでは耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を評価した。これらを評価する際の環境条件としては、本発明者らが検討した上で、最も厳しい条件と思われる条件を採用した。
【０３６５】
１　摩擦係数の測定方法
摩擦係数の測定は、恒温槽中の環境条件を温度４０℃、湿度８０％ＲＨに制御して、この恒温槽中で各サンプルテープを１００パス走行させて測定した。なお、摩擦走行１００パス目の数値を摩擦係数とした。
２　スチル耐久性の測定方法
スチル耐久性の評価は、−５℃の恒温槽中で行い、市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用いて、各サンプルテープの再生出力が３ｄＢ落ちるまでの時間を測定して行った。
３　シャトル耐久性の測定方法
シャトル耐久性は、恒温槽中の環境条件を温度４０℃、湿度２０％ＲＨに制御して、この恒温槽中で市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用い、各サンプルテープを１００パスシャトル走行させ、１００パス走行後にその再生出力が初期出力から何ｄＢ落ちるかを測定して評価した。
【０３６６】
これらの評価は、潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の測定結果を表１１、３０日間保存した後の保存後の耐久性及び走行性の測定結果を表１２に示す。
【０３６７】
【表１１】

【０３６８】
【表１２】

【０３６９】
表１１及び表１２の結果から、ＣＶＤ法により形成された保護層表面を芳香族アミンでトップコートし、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとを組み合わせた潤滑剤を使用した実施例Ｂ−１〜実施例Ｂ−８においては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０３７０】
一方、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物のみを含有する潤滑剤を用いた比較例Ｂ−１及び比較例Ｂ−２では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。
【０３７１】
また、保護層の表面に対して芳香族アミンを塗布しなかった比較例Ｂ−３〜比較例Ｂ−１０では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。さらに、保護層をＣＶＤ法ではなく、ＰＶＤ法であるマグネトロンスパッタ法により形成した場合にも、充分な耐久性は得られなかった。
さらに、実施例Ｂ−１と比較例Ｂ−１１〜比較例Ｂ−１３との比較結果から、飽和アルキル基を有するフッ化カルボン酸アルキルエステルを用いることにより、長期保存後も初期の特性を維持させることができることがわかった。
【０３７２】
以上の結果より、ＣＶＤ法により形成された保護層表面を芳香族アミンで処理し、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを組み合わせることにより、如何なる使用条件下においても優れた密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０３７３】
〔実験例Ｂ２（実施例Ｂ−９〜Ｂ−１６、比較例Ｂ−１４〜Ｂ−２６）〕
本実験例においては、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、部分フッ化カルボン酸アルキルエステルを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０３７４】
（サンプルの作製）
１　末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物の合成
先ず、末端にカルボキシル基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＯＣＣＦ_２（ＯＣ_２Ｆ_４）_ｍ（ＯＣＦ_２）_ｊＯＣＦ_２ＣＯＯＨ（但し、化学式中ｍ、ｊはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるステアリルアルコールを無水トルエン中で少量のｐ−トルエンスルホン酸と濃硫酸を触媒として加熱還流させた。このとき、生成される水分を除去しながら行った。
反応終了後、トルエンを除去した後、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製して、その後溶媒を除去し、エステル化合物を得た。なお、ここで、このエステル化合物を化合物Ｂ−６とする。
【０３７５】
次に、上記化合物Ｂ−６と同様な合成方法によって、下記表１３に示すような末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物である４種類の化合物Ｂ−７〜Ｂ−１０を合成した。なお、表１３中ｐ、ｑ、ｎは、１以上の整数をそれぞれ表す。
【０３７６】
【表１３】

【０３７７】
２　サンプルテープの作製
まず、前述の実験例Ｂ１と同様にして、非磁性支持体上に磁性層となる強磁性金属薄膜、カーボン保護層を形成し、バックコート層も形成した。さらに上記保護層の表面を、下記表１４に示すように芳香族アミンをイソプロピルアルコールに溶解したものを、カーボン保護層上に塗布量が２ｍｇ／ｍ^２となるように塗布した。
【０３７８】
次に前述の実験例Ｂ１と同様にして、保護層表面に下記表１４に示されるような潤滑剤をヘキサン溶媒に溶解したものを、塗布量が５ｍｇ／ｍ^２となるようにそれぞれ塗布して２１種類の磁気記録媒体を得た。
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断し、実施例Ｂ−９〜実施例Ｂ−１６及び比較例Ｂ−１４〜比較例Ｂ−２６の２１種類のサンプルテープを作製した。ただし、比較例Ｂ−１６〜比較例Ｂ−２０のサンプルテープについては、保護層の表面に芳香族アミンを塗布しなかった。さらに、比較例Ｂ−１８〜比較例Ｂ−２０のサンプルテープについては、保護層を上述したようなプラズマＣＶＤ法によらず、マグネトロンスパッタ法により形成した。
また、比較例Ｂ−２４〜比較例Ｂ−２６のフッ化カルボン酸アルキルエステルは二重結合を有しているものとした。
【０３７９】
【表１４】

【０３８０】
３　特性の評価
次に上記実施例Ｂ−９〜実施例Ｂ−１６と比較例Ｂ−１４〜比較例Ｂ−２６の２１種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を前述の実験例Ｂ１と同様にして評価した。
なお、これらの評価は、前述の実験例Ｂ１と同様に潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の結果を表１５、３０日間保存した後の保存後の耐久性及び走行性の結果を表１６に示す。
【０３８１】
【表１５】

【０３８２】
【表１６】

【０３８３】
表１５及び表１６の結果から、ＣＶＤ法により形成された保護層表面を芳香族アミンでトップコートし、さらに潤滑剤として末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物とフッ化カルボン酸アルキルエステルとを組み合わせた潤滑剤を使用した実施例Ｂ−９〜実施例Ｂ−１６においては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０３８４】
一方、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物のみを含有する潤滑剤を用いた比較例Ｂ−１４及び比較例Ｂ−１５では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。
また、保護層の表面に対して芳香族アミンを塗布しなかった比較例Ｂ−１６〜比較例Ｂ−２３では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
さらに、保護層をＣＶＤ法ではなく、ＰＶＤ法であるマグネトロンスパッタ法により形成した場合にも、充分な耐久性は得られなかった。
さらに、実施例Ｂ−９と比較例Ｂ−２４〜比較例Ｂ−２６との比較結果から、飽和アルキル基を有するフッ化カルボン酸アルキルエステルを用いることにより、長期保存後も初期の特性を維持させることができることがわかった。
【０３８５】
〔実験例Ｂ３（実施例Ｂ−１７〜Ｂ−２６、比較例Ｂ−２７〜Ｂ−３７）〕
１　末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物の合成法は前述実験Ｂ１と同様に行った。
２　サンプルテープの作製
まず、前述の実験例Ｂ１と同様にして、非磁性支持体上に磁性層となる強磁性金属薄膜、カーボン保護層をプラズマＣＶＤ法により形成し、バックコート層も形成した。
【０３８６】
次に下記表１７に示すように、芳香族アミンをイソプロピルアルコールに溶解したものを、カーボン保護層上に塗布量が２ｍｇ／ｍ^２となるように塗布した。次に下記表１７に示される化合物をヘキサン溶媒に溶解したものを、それぞれパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、化合物Ｂ−１〜Ｂ−５の重量比が９５：５〜５：９５、および化合物単独となるようにして、上記カーボン保護層上に塗布量が０．０３〜１２０ｍｇ／ｍ^２に塗布して、２１種類の磁気記録媒体を得た。
【０３８７】
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断して、実施例Ｂ−１７〜実施例Ｂ−２６及び比較例Ｂ−２７〜比較例Ｂ−３７の２１種類のサンプルテープとした。ただし、比較例Ｂ−３６〜比較例Ｂ−３７のサンプルテープについては、保護層の表面に芳香族アミンを塗布しなかった。
【０３８８】
【表１７】

【０３８９】
３　特性の評価
次に、上記実施例Ｂ−１７〜実施例Ｂ−２６と比較例Ｂ−２７〜比較例Ｂ−３７の２１種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を前述の実験例Ｂ１と同様にして評価した。
なお、これらの評価は、前述の実験例Ｂ１と同様に潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の結果を表１８、３０日間保存した後の保存後の耐久性及び走行性の結果を表１９に示す。
【０３９０】
【表１８】

【０３９１】
【表１９】

【０３９２】
上記表１８、表１９の結果から、ＣＶＤ法により形成された保護層表面を芳香族アミンでトップコートし、さらに潤滑剤として末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとの組み合わせにおいて、塗布量を０．１〜１００ｍｇ／ｍ^２、
上記エステル化合物と部分フッ化カルボン酸アルキルエステルとを重量比で、９０：１０〜１０：９０として適用することにより、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０３９３】
一方、比較例Ｂ−２７、Ｂ−２８、Ｂ−３５に示す様に、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとの組み合わせにおいて、塗布量を０．０１〜１００ｍｇ／ｍ^２以外の数値範囲で適用した場合においては、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
【０３９４】
また、末端に水酸基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物のみを含有する潤滑剤を用いた比較例Ｂ−３１、比較例Ｂ−３２、および部分フッ化カルボン酸アルキルエステルとの組み合わせにおいて、９０：１０〜１０：９０以外の数値範囲で適用した比較例Ｂ−２９、Ｂ−３０、Ｂ−３３、Ｂ−３４においては、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
【０３９５】
また、保護層の表面に対して芳香族アミンを塗布しなかった比較例Ｂ−３６、比較例Ｂ−３７では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
【０３９６】
以上の結果より、ＣＶＤ法により形成された保護層表面を芳香族アミンでトップコートし、さらに潤滑剤として、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物とフッ化カルボン酸アルキルエステルとを組み合わせて適用し、かつこの塗布量および重量比を最適化することにより、潤滑剤が如何なる使用条件下においても密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０３９７】
〔実験例Ｃ１（実施例Ｃ−１〜Ｃ−８、比較例Ｃ−１〜Ｃ−１３）〕
本実験例では、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、部分フッ化カルボン酸アルキルエステルを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０３９８】
（サンプルの作製）
１　末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物の合成
先ず、末端に水酸基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＣＨ_２ＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＨ_２ＯＨ（但し、化学式中ｐ、ｑはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるトリエチルアミンを有機溶媒中に溶解させ、この溶液中に更にモル比で２倍等量のステアリン酸クロリドを３０分かけて滴下した。
滴下終了後、１時間撹拌し、続いて３０分間加熱還流を行った。そして、冷却した後、蒸留水、希塩酸水溶液の順で洗浄し、再度蒸留水により洗浄液が中性になるまで洗浄した。続いて有機溶媒を除去し、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製してエステル化合物を得た。ここで、このエステル化合物を化合物Ｃ−１とする。
【０３９９】
次に、上記化合物Ｃ−１と同様な合成方法によって、下記表２０に示すような末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物である４種類の化合物Ｃ−２〜Ｃ−５を合成した。なお、表２０中ｐ、ｑ、ｎは、１以上の整数をそれぞれ表す。
【０４００】
【表２０】

【０４０１】
２　サンプルテープの作製
次に磁気テープを以下のようにして作製した。先ず非磁性支持体である７．０μｍ厚のポリエチレンテレフタレートフィルムに、上述の真空蒸着装置を使用して斜め蒸着法によりＣｏを被着させ、磁性層となる強磁性金属薄膜を１８０ｎｍの厚さに形成した。
次に上記強磁性金属薄膜上に、エチレンとアルゴンの混合ガスの高周波プラズマにより、電極と、磁気記録媒体原反自身を対向電極として、原反に−１．５ｋＶの直流電圧を印加し、放電を行い、上記強磁性金属薄膜上に約８ｎｍの厚さのカーボン保護層を形成した。
次にポリエチレンテレフタレートフィルムの強磁性金属薄膜が形成された面とは反対側の面に、カーボン及びポリウレタン樹脂よりなる膜厚０．５μｍのバックコート層を形成した。
【０４０２】
次に下記表２１に示すように、芳香族カルボン酸をイソプロピルアルコールに溶解したものを、カーボン保護層上に塗布量が２ｍｇ／ｍ^２となるように塗布した。
次に、下記表２１に示される化合物をそれぞれヘキサン溶媒に溶解したものを、上記カーボン保護層上に塗布量が５ｍｇ／ｍ^２となるように塗布して、２１種類の磁気記録媒体を得た。
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断して、実施例Ｃ−１〜実施例Ｃ−８及び比較例Ｃ−１〜比較例Ｃ−１３の２１種類のサンプルテープとした。
【０４０３】
ただし、比較例Ｃ−３〜比較例Ｃ−１０のサンプルテープについては、保護層の表面に、芳香族カルボン酸をトップコートしなかった。さらに、比較例Ｃ−８〜比較例Ｃ−１０のサンプルテープについては、保護層を上述したようなプラズマＣＶＤ法によらず、マグネトロンスパッタ法により形成した。
また、比較例Ｃ−１１〜比較例Ｃ−１３の部分フッ化カルボン酸アルキルエステルは二重結合を有しているものとした。
【０４０４】
【表２１】

【０４０５】
３　特性の評価
次に、上記実施例Ｃ−１〜実施例Ｃ−８と比較例Ｃ−１〜比較例Ｃ−１３の２１種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を評価した。これらを評価する際の環境条件としては、本発明者らが検討した上で、最も厳しい条件と思われる条件を採用した。
【０４０６】
１　摩擦係数の測定方法
摩擦係数の測定は、恒温槽中の環境条件を温度４０℃、湿度８０％ＲＨに制御して、この恒温槽中で各サンプルテープを１００パス走行させて測定した。なお、摩擦走行１００パス目の数値を摩擦係数とした。
２　スチル耐久性の測定方法
スチル耐久性の評価は、−５℃の恒温槽中で行い、市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用いて、各サンプルテープの再生出力が３ｄＢ落ちるまでの時間を測定して行った。
３　シャトル耐久性の測定方法
シャトル耐久性は、恒温槽中の環境条件を温度４０℃、湿度２０％ＲＨに制御して、この恒温槽中で市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用い、各サンプルテープを１００パスシャトル走行させ、１００パス走行後にその再生出力が初期出力から何ｄＢ落ちるかを測定して評価した。
【０４０７】
なお、これらの評価は、潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の測定結果を表２２、３０日間保存した後の保存後の耐久性及び走行性の測定結果を表２３に示す。
【０４０８】
【表２２】

【０４０９】
【表２３】

【０４１０】
表２２及び表２３の結果から、ＣＶＤ法により形成された保護層表面を芳香族カルボン酸でトップコートし、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとを組み合わせたものを使用した実施例Ｃ−１〜実施例Ｃ−８においては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０４１１】
一方、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物のみを含有する潤滑剤を用いた比較例Ｃ−１及び比較例Ｃ−２では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。
また、保護層の表面に対して芳香族カルボン酸をトップコートしなかった比較例Ｃ−３〜比較例Ｃ−１０では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
さらに、保護層をＣＶＤ法ではなく、ＰＶＤ法であるマグネトロンスパッタ法により形成した場合にも、充分な耐久性は得られなかった。
【０４１２】
さらに、実施例Ｃ−１と比較例Ｃ−１１〜比較例Ｃ−１３との比較結果から、不飽和結合を有さないフッ化カルボン酸アルキルエステルを用いることにより、長期保存後も初期の特性を維持させることができることがわかった。
【０４１３】
以上の結果より、ＣＶＤ法により形成された保護層表面を芳香族カルボン酸でトップコート処理し、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを組み合わせることにより、潤滑剤が如何なる使用条件下においても密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０４１４】
〔実験例Ｃ２（実施例Ｃ−９〜Ｃ−１６、比較例Ｃ−１４〜Ｃ−２６）〕
本実験例においては、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、部分フッ化カルボン酸アルキルエステルを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０４１５】
（サンプルの作製）
１　末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物の合成
先ず、末端にカルボキシル基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＯＣＣＦ_２（ＯＣ_２Ｆ_４）_ｍ（ＯＣＦ_２）_ｊＯＣＦ_２ＣＯＯＨ（但し、化学式中ｍ、ｊはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるステアリルアルコールを無水トルエン中で少量のｐ−トルエンスルホン酸と濃硫酸を触媒として加熱還流させた。このとき、生成される水分を除去しながら行った。
反応終了後、トルエンを除去した後、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製して、その後溶媒を除去し、エステル化合物を得た。なお、ここで、このエステル化合物を化合物Ｃ−６とする。
【０４１６】
次に上記化合物Ｃ−６と同様の合成方法によって、下記表２４に示すような末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物である４種類の化合物Ｃ−７〜Ｃ−１０を合成した。なお、表２４中ｐ、ｑ、ｎは、１以上の整数をそれぞれ表す。
【０４１７】
【表２４】

【０４１８】
２　サンプルテープの作製
まず、前述の実験例Ｃ１と同様にして、非磁性支持体上に磁性層となる強磁性金属薄膜、カーボン保護層をプラズマＣＶＤ法により形成し、バックコート層も形成した。さらに、上記保護層の表面を、下記表２５に示すように芳香族カルボン酸をイソプロピルアルコールに溶解したものを、カーボン保護層上に塗布量が２ｍｇ／ｍ^２となるように塗布した。
【０４１９】
次に、前述の実験例Ｃ１と同様にして、保護層表面に、下記表２５に示されるような潤滑剤をヘキサン溶媒に溶解したものを、塗布量が５ｍｇ／ｍ^２となるようにそれぞれ塗布して２１種類の磁気記録媒体を得た。
【０４２０】
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断し、実施例Ｃ−９〜実施例Ｃ−１６及び比較例Ｃ−１４〜比較例Ｃ−２６の２１種類のサンプルテープを作製した。ただし、比較例Ｃ−１６〜比較例２３のサンプルテープについては、保護層の表面に芳香族カルボン酸を塗布しなかった。
さらに、比較例１８〜比較例２０のサンプルテープについては、保護層を、上述したようなプラズマＣＶＤ法によらず、マグネトロンスパッタ法により形成した。
また、比較例２４〜比較例２６のフッ化カルボン酸アルキルエステルは二重結合を有しているものを適用した。
【０４２１】
【表２５】

【０４２２】
３　特性の評価
次に、上記実施例Ｃ−９〜実施例Ｃ−１６と比較例Ｃ−１４〜比較例Ｃ−２６の２１種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を前述の実験例Ｃ１と同様にして評価した。
なお、これらの評価は、前述の実験例Ｃ１と同様に潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の結果を表２６、３０日間保存した後の保存後の耐久性及び走行性の結果を表２７に示す。
【０４２３】
【表２６】

【０４２４】
【表２７】

【０４２５】
上記表２６及び表２７の結果から、ＣＶＤ法により形成された保護層表面を芳香族カルボン酸でトップコートし、さらに潤滑剤として、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物とフッ化カルボン酸アルキルエステルとを組み合わせた潤滑剤を使用した実施例Ｃ−９〜実施例Ｃ−１６においては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０４２６】
一方、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物のみを含有する潤滑剤を用いた比較例Ｃ−１４及び比較例Ｃ−１５では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。また、保護層の表面に対して芳香族カルボン酸を塗布しなかった比較例Ｃ−１６〜比較例Ｃ−２３では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。さらに保護層をＣＶＤ法ではなく、ＰＶＤ法であるマグネトロンスパッタ法により形成した場合にも、充分な耐久性は得られなかった。
さらに、実施例Ｃ−９と比較例Ｃ−２４〜比較例Ｃ−２６との比較結果から、不飽和結合を有さないフッ化カルボン酸アルキルエステルを用いることにより、長期保存後も初期の特性を維持させることができることがわかった。
【０４２７】
〔実験例Ｃ３（実施例Ｃ−１７〜Ｃ−２６、比較例Ｃ−２７〜Ｃ−３７）〕
１　末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物の合成法は前述した実験例Ｃ１と同様に行った。
【０４２８】
２　サンプルテープの作製
まず、前述の実験例Ｃ１と同様にして、非磁性支持体上に磁性層となる強磁性金属薄膜、カーボン保護層をプラズマＣＶＤ法により形成し、バックコート層も形成した。
次に、下記表２８に示すように、芳香族カルボン酸をイソプロピルアルコールに溶解したものを、カーボン保護層上に塗布量が２ｍｇ／ｍ^２となるように塗布した。
次に、下記表２８に示される化合物をそれぞれヘキサン溶媒に溶解したものを、上記カーボン保護層上に、塗布量を０．０３〜１２０ｍｇ／ｍ^２とし、かつ上記エステル化合物と部分フッ化カルボン酸アルキルエステルとの重量比を、それぞれ９５：５〜５：９５の範囲、あるいは単独で塗布して、２１種類の磁気記録媒体を得た。
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断して、実施例Ｃ−１７〜実施例Ｃ−２６及び比較例Ｃ−２７〜比較例Ｃ−３７の２１種類のサンプルテープとした。
【０４２９】
【表２８】

【０４３０】
３　特性の評価
次に、上記実施例Ｃ−１７〜実施例Ｃ−２６と比較例Ｃ−２７〜比較例Ｃ−３７の２１種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を前述の実験例Ｃ１と同様にして評価した。
なお、これらの評価は、前述の実験例Ｃ１と同様に潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の結果を表２９、３０日間保存した後の保存後の耐久性及び走行性の結果を表３０に示す。
【０４３１】
【表２９】

【０４３２】
【表３０】

【０４３３】
上記表２９、表３０の結果から、ＣＶＤ法により形成された保護層表面を芳香族カルボン酸でトップコートし、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとの組み合わせたものを使用し、この塗布量を０．１〜１００ｍｇ／ｍ^２とし、かつ末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとの重量比が９０：１０〜１０：９０であるものを適用した実施例Ｃ−１７〜実施例Ｃ−２６は、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０４３４】
一方、比較例Ｃ−２７、Ｃ−２８、Ｃ−３５〜Ｃ−３７に示す様に、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとの組み合わせた潤滑剤の塗布量が、０．１〜１〜１００ｍｇ／ｍ^２以外の数値範囲としたものは、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
【０４３５】
また、末端に水酸基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物のみを含有する潤滑剤を用いた比較例Ｃ−３１、比較例Ｃ−３２、および末端に水酸基を有するパーフルオロポリエーテルと部分フッ化カルボン酸アルキルエステルとの組み合わせにおいて、これらの重量比を９０：１０〜１０：９０以外の数値範囲としたものを適用した比較例Ｃ−２９、比較例Ｃ−３０、比較例Ｃ−３３、比較例Ｃ−３４においては、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
【０４３６】
以上の結果より、ＣＶＤ法により形成された保護層表面を芳香族カルボン酸でトップコートし、さらに潤滑剤として、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、フッ化カルボン酸アルキルエステルとを組み合わせたものを用い、かつ塗布量および重量比を最適化したことにより、潤滑剤が如何なる使用条件下においても密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０４３７】
〔実験例Ｄ（実施例Ｄ−１〜Ｄ−８、比較例Ｄ−１〜Ｄ−１３）〕
本実験例では、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、部分フッ化カルボン酸アルキルエステルを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０４３８】
（サンプルの作製）
１　末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物の合成
先ず、末端に水酸基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＣＨ_２ＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＨ_２ＯＨ（但し、化学式中ｐ、ｑはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるトリエチルアミンを有機溶媒中に溶解させ、この溶液中に更にモル比で２倍等量のステアリン酸クロリドを３０分かけて滴下した。
滴下終了後、１時間撹拌し、続いて３０分間加熱還流を行った。そして、冷却した後、蒸留水、希塩酸水溶液の順で洗浄し、再度蒸留水により洗浄液が中性になるまで洗浄した。続いて、有機溶媒を除去し、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製してエステル化合物を得た。ここで、このエステル化合物を化合物Ｄ−１とする。
【０４３９】
次に、上記化合物Ｄ−１と同様な合成方法によって、表３１に示すような末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物である４種類の化合物Ｄ−２〜Ｄ−５を合成した。なお、表３１中ｐ、ｑ、ｎは、１以上の整数をそれぞれ表す。
【０４４０】
【表３１】

【０４４１】
２　サンプルテープの作製
次に磁気テープを以下のようにして作製した。先ず非磁性支持体である７．０μｍ厚のポリエチレンテレフタレートフィルムに、上述の真空蒸着装置を使用して斜め蒸着法によりＣｏを被着させ、磁性層となる強磁性金属薄膜を１８０ｎｍの厚さに形成した。
次に、上記強磁性金属薄膜上に、エチレンとアルゴンの混合ガスの高周波プラズマにより、電極と、磁気記録媒体原反自身を対向電極として、原反に−１．５ｋＶの直流電圧を印加し、放電を行い、上記強磁性金属薄膜上に約８ｎｍの厚さのカーボン保護層を形成した。
次に、ポリエチレンテレフタレートフィルムの強磁性金属薄膜が形成された面とは反対側の面に、カーボン及びポリウレタン樹脂よりなる膜厚０．５μｍのバックコート層を形成した。
【０４４２】
次に、上記保護層の表面に、図２に示したような紫外線照射装置２０を用いて、下記表３２に示すような条件で紫外線照射を行った。なお、紫外線の波長は１８５ｎｍであり、紫外線の照射時間は磁気記録媒体のラインスピードで制御した。
次に、表３２に示される化合物をそれぞれヘキサン溶媒に溶解したものを、上記カーボン保護層上に塗布量が５ｍｇ／ｍ^２となるように塗布して、２１種類の磁気記録媒体を得た。
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断して、実施例Ｄ−１〜実施例Ｄ−８及び比較例Ｄ−１〜比較例Ｄ−１３の２１種類のサンプルテープとした。
【０４４３】
ただし、比較例Ｄ−３〜比較例Ｄ−１０のサンプルテープについては、保護層の表面に紫外線照射処理を行わなかった。また、比較例Ｄ−１１〜比較例Ｄ−１３の部分フッ化カルボン酸アルキルエステルは不飽和結合を有しているものとした。
【０４４４】
【表３２】

【０４４５】
３　特性の評価
次に上記実施例Ｄ−１〜実施例Ｄ−８と比較例Ｄ−１〜比較例Ｄ−１３の２１種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を評価した。これらを評価する際の環境条件としては、本発明者らが検討した上で、最も厳しい条件と思われる条件を採用した。
【０４４６】
１　摩擦係数の測定方法
摩擦係数の測定は、恒温槽中の環境条件を温度４０℃、湿度８０％ＲＨに制御して、この恒温槽中で各サンプルテープを１００パス走行させて測定した。なお、摩擦走行１００パス目の数値を摩擦係数とした。
２　スチル耐久性の測定方法
スチル耐久性の評価は、−５℃の恒温槽中で行い、市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用いて、各サンプルテープの再生出力が３ｄＢ落ちるまでの時間を測定して行った。
３　シャトル耐久性の測定方法
シャトル耐久性は、恒温槽中の環境条件を温度４０℃、湿度２０％ＲＨに制御して、この恒温槽中で市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用い、各サンプルテープを１００パスシャトル走行させ、１００パス走行後にその再生出力が初期出力から何ｄＢ落ちるかを測定して評価した。
【０４４７】
なお、これらの評価は、潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の測定結果を表３３、３０日間保存した後の保存後の耐久性及び走行性の測定結果を表３４に示す。
【０４４８】
【表３３】

【０４４９】
【表３４】

【０４５０】
上記表３３及び表３４の結果から、保護層表面を紫外線照射処理し、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとを組み合わせたものを使用した実施例Ｄ−１〜実施例Ｄ−８においては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０４５１】
一方、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物のみを含有する潤滑剤を用いた比較例Ｄ−１及び比較例Ｄ−２では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。
また、保護層の表面に紫外線を照射しなかった比較例Ｄ−３〜比較例Ｄ−１０では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
さらに、実施例Ｄ−１と比較例Ｄ−１１〜比較例Ｄ−１３との比較結果から、不飽和結合を有しない長鎖飽和脂肪酸を用いることにより、長期保存後も初期の特性を維持させることができることがわかった。
【０４５２】
以上の結果より、保護層表面に紫外線を照射し、さらに潤滑剤として、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとを組み合わせたものを用いることにより、潤滑剤が如何なる使用条件下においても密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０４５３】
〔実験例Ｅ（実施例Ｅ−１〜Ｅ−８、比較例Ｅ−１〜Ｅ−１３）〕
本実験例では、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤を使用した場合の効果を以下のようにして確認した。
【０４５４】
（サンプルの作製）
１　末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物の合成
先ず、末端にカルボキシル基を有するパーフルオロポリエーテルとして、分子量２０００のＨＯＯＣＣＦ_２（ＯＣ_２Ｆ_４）_ｐ（ＯＣＦ_２）_ｑＯＣＦ_２ＣＯＯＨ（但し、化学式中ｐ、ｑはそれぞれ１以上の整数を表す。）を用い、このパーフルオロポリエーテルとモル比で２倍等量となるステアリルアルコールを無水トルエン中で少量のｐ−トルエンスルホン酸と濃硫酸を触媒として加熱還流させた。このとき、生成される水分を除去しながら行った。
反応後トルエンを除去し、得られた化合物をシリカゲルカラムクロマトグラフィーを用いて精製して、その後溶媒を除去しエステル化合物を得た。なお、ここでこのエステル化合物を化合物Ｅ−１とする。
【０４５５】
次に上記化合物Ｅ−１と同様の合成方法によって、下記表３５に示すような末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物である４種類の化合物Ｅ−２〜Ｅ−５を合成した。なお、表３５中ｐ、ｑ、ｎは、１以上の整数をそれぞれ表す。
【０４５６】
【表３５】

【０４５７】
２　サンプルテープの作製
次に磁気テープを以下のようにして作製した。先ず非磁性支持体である７．０μｍ厚のポリエチレンテレフタレートフィルムに、上述の真空蒸着装置を使用して斜め蒸着法によりＣｏを被着させ、磁性層となる強磁性金属薄膜を１８０ｎｍの厚さに形成した。
次に上記強磁性金属薄膜上に、エチレンとアルゴンの混合ガスの高周波プラズマにより、電極と、磁気記録媒体原反自身を対向電極として、原反に−１．５ｋＶの直流電圧を印加し、放電を行い、上記強磁性金属薄膜上に約８ｎｍの厚さのカーボン保護層を形成した。
次にポリエチレンテレフタレートフィルムの強磁性金属薄膜が形成された面とは反対側の面に、カーボン及びポリウレタン樹脂よりなる膜厚０．５μｍのバックコート層を形成した。
【０４５８】
次に、上記保護層の表面に、図２に示したような紫外線照射装置２０を用いて、下記３６に示すような条件で紫外線照射処理を行った。なお紫外線の波長は１８５ｎｍであり、紫外線の照射時間は磁気記録媒体のラインスピードで制御した。
次に、表３６に示される化合物をそれぞれヘキサン溶媒に溶解したものを、上記カーボン保護層上に塗布量が５ｍｇ／ｍ^２となるように塗布して、２１種類の磁気記録媒体を得た。
そして、これら２１種類の磁気記録媒体をそれぞれ６．３５ｍｍ幅に裁断して、実施例Ｅ−１〜実施例Ｅ−８及び比較例Ｅ−１〜比較例Ｅ−１３の２１種類のサンプルテープとした。
ただし、比較例Ｅ−３〜比較例Ｅ−１０のサンプルテープについては、保護層の表面に紫外線照射処理を行わなかった。また、比較例Ｅ−１１〜比較例Ｅ−１３の部分フッ化カルボン酸アルキルエステルは不飽和結合を有しているものとした。
【０４５９】
【表３６】

【０４６０】
３　特性の評価
次に、上記実施例Ｅ−１〜実施例Ｅ−８と比較例Ｅ−１〜比較例Ｅ−１３の２１種類のサンプルテープの特性を評価した。ここでは、耐久性と走行性を評価することとし、具体的には摩擦係数、スチル耐久性及びシャトル耐久性を評価した。これらを評価する際の環境条件としては、本発明者らが検討した上で、最も厳しい条件と思われる条件を採用した。
【０４６１】
１　摩擦係数の測定方法
摩擦係数の測定は、恒温槽中の環境条件を温度４０℃、湿度８０％ＲＨに制御して、この恒温槽中で各サンプルテープを１００パス走行させて測定した。なお、摩擦走行１００パス目の数値を摩擦係数とした。
２　スチル耐久性の測定方法
スチル耐久性の評価は、−５℃の恒温槽中で行い、市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用いて、各サンプルテープの再生出力が３ｄＢ落ちるまでの時間を測定して行った。
３　シャトル耐久性の測定方法
シャトル耐久性は、恒温槽中の環境条件を温度４０℃、湿度２０％ＲＨに制御して、この恒温槽中で市販のデジタルビデオカムコーダー（ソニー社製、機種名：ＤＶＣ−ＶＸ１０００）を用い、各サンプルテープを１００パスシャトル走行させ、１００パス走行後にその再生出力が初期出力から何ｄＢ落ちるかを測定して評価した。
【０４６２】
なお、これらの評価は、潤滑剤を塗布した直後と、各サンプルテープを温度４５℃、湿度８０％ＲＨの環境下で３０日間保存した後に行った。潤滑剤を塗布した直後の初期の耐久性及び走行性の測定結果を下記表３７、３０日間保存した後の保存後の耐久性及び走行性の測定結果を下記表３８に示す。
【０４６３】
【表３７】

【０４６４】
【表３８】

【０４６５】
上記表３７及び表３８の結果から、保護層表面に紫外線照射処理を行い、さらに潤滑剤として、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と部分フッ化カルボン酸アルキルエステルとを組み合わせたものを使用した実施例Ｅ−１〜実施例Ｅ−８においては、何れも高温多湿、高温低湿或いは低温等の様々な使用条件下において摩擦係数、スチル耐久性及びシャトル耐久性の劣化が極めて少なく、非常に良好な結果が得られていることがわかった。
【０４６６】
一方、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物のみを含有する潤滑剤を用いた比較例Ｅ−１及び比較例Ｅ−２では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が非常に大きかった。
また、保護層の表面に紫外線照射処理を行わなかった比較例Ｅ−３〜比較例Ｅ−１０では、様々な使用条件下において摩擦係数やスチル耐久性、シャトル耐久性の劣化が大きく、良好な結果が得られなかった。
さらに、実施例Ｅ−１と比較例Ｅ−１１〜比較例Ｅ−１３との比較結果から、不飽和結合を有しない部分フッ化カルボン酸アルキルエステルを用いることにより、長期保存後も初期の特性を維持させることができることがわかった。
【０４６７】
以上の結果より、保護層表面に紫外線を照射し、さらに潤滑剤として、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを組み合わせたものを適用することにより、潤滑剤が如何なる使用条件下においても密着性や潤滑性が保たれ、且つ長期に亘り潤滑効果が持続するため、磁気記録媒体の良好な走行性及び耐久性が得られることがわかった。
【０４６８】
【発明の効果】
第１の発明の磁気記録媒体によれば、カーボン保護層の表面を芳香族アルコールによってトップコートし、カーボン保護層上に、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、パーフルオロカルボン酸エステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【０４６９】
第２の発明の磁気記録媒体によれば、カーボン保護層の表面を芳香族アルコールによってトップコートし、カーボン保護層上に、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、パーフルオロカルボン酸エステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【０４７０】
第３の発明の磁気記録媒体によれば、カーボン保護層の表面を芳香族アミンによってトップコートし、カーボン保護層上に、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【０４７１】
第４の発明の磁気記録媒体によれば、カーボン保護層の表面を芳香族アミンによってトップコートし、カーボン保護層上に、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【０４７２】
第５の発明の磁気記録媒体によれば、カーボン保護層の表面を芳香族カルボン酸によってトップコートし、カーボン保護層上に、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【０４７３】
第６の発明の磁気記録媒体によれば、カーボン保護層の表面を芳香族カルボン酸によってトップコートし、カーボン保護層上に、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と、部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【０４７４】
第７の発明の磁気記録媒体によれば、カーボン保護層の表面を、不活性ガス雰囲気中で紫外線照射処理し、保護層上に、末端に水酸基を有するパーフルオロポリエーテルと長鎖カルボン酸とのエステル化合物と部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【０４７５】
第８の発明の磁気記録媒体によれば、カーボン保護層の表面を、不活性ガス雰囲気中で紫外線照射処理し、保護層上に、末端にカルボキシル基を有するパーフルオロポリエーテルと長鎖アルコールとのエステル化合物と部分フッ化カルボン酸アルキルエステルとを含有する潤滑剤を保持させることにより、保護層と潤滑剤との密着性の向上が図られ、また、上記潤滑剤が最外層に保持されているので、如何なる使用条件下においても密着性や潤滑性が好適に保たれ、長期に亘って良好な走行性および耐久性が確保される。
【図面の簡単な説明】
【図１】本発明の磁気記録媒体の概略断面図を示す。
【図２】紫外線照射処理装置の概略図を示す。
【図３】磁性層を形成する際に用いる真空蒸着装置の一例の概略断面図を示す。
【符号の説明】
１……非磁性支持体、２……磁性層、３……保護層、４……潤滑剤層、１０……磁気記録媒体、２０……紫外線照射装置、２１……被処理体、２５……供給ロール、２６……巻き取りロール、２７……紫外線処理部、２８……筐体、２９……ガイドロール、４０……真空蒸着装置、４１……真空室、４２……冷却キャン、４３……蒸着源、４４……供給ロール、４５……巻き取りロール、４７，４８……ガイドロール、４９……電子ビーム発生源、５０……電子ビーム、５１……防着板、５２……シャッタ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic recording medium having a structure in which a ferromagnetic metal thin film is formed as a magnetic layer on a nonmagnetic support by a vacuum thin film forming technique.
[0002]
[Prior art]
Conventionally, as a magnetic recording medium, a magnetic layer is formed by applying a magnetic paint comprising a ferromagnetic powder such as an oxide magnetic powder or an alloy magnetic powder, a binder and an organic solvent on a non-magnetic support, So-called coating type magnetic recording media are widely used.
[0003]
On the other hand, as the demand for high recording density and long-time recording has increased, ferromagnetic metal materials such as Co, Co-Ni alloy, Co-Cr alloy, and Co-O have been plated or vacuum thin film forming technology (vacuum deposition method). A magnetic recording medium of a so-called ferromagnetic metal thin film type, in which a magnetic layer is formed by directly applying a magnetic layer to a non-magnetic support such as a polyester film or a polyimide film by a sputtering method, an ion plating method, or the like, is used. Have been. Such a ferromagnetic metal thin film type magnetic recording medium has been widely put into practical use in a consumer video format (8 mm Hi-8 format, DV format) or a professional video format (DVCAM).
[0004]
This ferromagnetic metal thin film type magnetic recording medium is superior in magnetic properties such as coercive force and squareness ratio as compared with a coating type magnetic recording medium, and is excellent not only in electromagnetic conversion characteristics in a short wavelength region but also in a magnetic layer. Since the thickness can be made extremely thin, magnetic demagnetization and thickness loss during reproduction are extremely small, and there is no need to mix a binder, which is a nonmagnetic material, in the magnetic layer. It has a number of advantages such as the ability to increase the packing density.
[0005]
In general, a magnetic recording medium is subjected to high-speed relative motion with a magnetic head in the process of recording / reproducing a signal, and at that time, it must be run smoothly and in a stable state. Further, it is better that the wear and damage to the magnetic head be as small as possible.
[0006]
However, in the magnetic recording medium of the ferromagnetic metal thin film type as described above, the surface smoothness of the magnetic layer is extremely good, and the substantial contact area with the magnetic head is increased. There are many drawbacks in durability, running property, and the like, which tend to cause cracking and increase the friction coefficient, and improvement of these has been a major issue.
[0007]
To cope with this, attempts have been made to improve durability and running properties by applying various lubricants to the surface of the magnetic layer and forming a lubricant layer, for example. As a lubricant used for such an application, for example, an organic fluorinated compound is known to be effective.
[0008]
In particular, Japanese Patent Application Laid-Open No. 05-93059 discloses a magnetic recording medium which exhibits a good lubricating effect under any use conditions by using an ester compound having a carboxyl group at a terminal as a lubricant.
Japanese Patent Application Laid-Open No. 05-194970 discloses a magnetic recording medium which realizes excellent durability and running properties by using an ester compound having a hydroxyl group at a terminal as a lubricant.
[0009]
[Problems to be solved by the invention]
By the way, in the above-described ferromagnetic metal thin film type magnetic recording medium, a carbon protective layer is generally formed on the magnetic layer in order to secure better durability. The ferromagnetic metal thin film type magnetic recording media used in the above-mentioned consumer video format DVC tapes and professional video format DVCAM tapes, and further in AIT tapes used in tape streamers, include: One in which a carbon protective layer is formed on a ferromagnetic metal thin film has been put to practical use. With the practical use of such a carbon protective layer, the durability is sufficiently ensured, and it is considered that the presence of this carbon protective layer will be indispensable in future magnetic recording media of the ferromagnetic metal thin film type.
[0010]
As the carbon protective layer, a DLC (Diamond Like Carbon) film is particularly applied, and a PVD (Physical Vapor Deposition) method such as a magnetron sputtering method or an ion beam sputtering method, or a CVD (Chemical Vapor Deposition) method is used. it can.
[0011]
However, the surface energy of the carbon protective layer formed by the CVD method is smaller than that of the carbon protective layer formed by the PVD method. Therefore, as described above, when an attempt is made to use a lubricant to improve the durability and running performance of the magnetic recording medium, the adsorptivity between the lubricant and the carbon protective layer is weak, and a stable and good lubricating effect is not exhibited. Therefore, it is necessary to design a lubricant in consideration of the existence of the carbon protective layer.
[0012]
Therefore, in the present invention, in view of the above-described circumstances, the effect of the lubricant is sufficiently exerted over a long period of time, and by improving the adhesion stability between the protective layer and the lubricant, excellent running performance and durability are achieved. It is an object to provide a realized magnetic recording medium.
[0013]
[Means for Solving the Problems]
In the first invention, there is provided a magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support, wherein the protective layer is top-coated with an aromatic alcohol on the surface. Is a lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid shown in the following [Chemical Formula 17] and a perfluorocarboxylic acid ester shown in the following [Chemical Formula 18]. The present invention provides a magnetic recording medium having the structure described above.
[0014]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0015]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0016]
Embedded image
C_nF_{2n + 1}COOR
[0017]
Here, n represents an integer of 6 to 10, and R represents an alkyl group of 9 to 25.
[0018]
According to a second aspect of the present invention, there is provided a magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support, wherein the protective layer is top-coated with an aromatic alcohol on a surface thereof. A lubricant containing an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the following [Chemical Formula 19] and a perfluorocarboxylic acid ester represented by the following [Chemical Formula 20] is most preferable. Provided is a magnetic recording medium configured to be held in an outer layer.
[0019]
Embedded image
R₂OOC-Rf'-COOR₂
[0020]
Here, Rf ′ represents a perfluoropolyether chain,₂Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0021]
Embedded image
C_nF_{2n + 1}COOR
[0022]
Here, n represents an integer of 6 to 10, and R represents an alkyl group of 9 to 25.
[0023]
According to a third aspect of the present invention, there is provided a magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support, wherein the protective layer is top-coated with an aromatic amine, A lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid shown in the following [Chemical Formula 21] and a partially fluorinated carboxylic acid alkyl ester shown in the following [Chemical Formula 22] And a magnetic recording medium configured to be held in the outermost layer.
[0024]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0025]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0026]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0027]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0028]
In a fourth aspect, there is provided a magnetic recording medium having a magnetic layer and a protective layer on a nonmagnetic support, wherein the protective layer is top-coated with an aromatic amine on the surface, and the protective layer has A lubricant containing an ester compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following [Chemical Formula 23] and a long-chain alcohol, and a partially fluorinated carboxylic acid alkyl ester represented by the following [Chemical Formula 24] And a magnetic recording medium configured to be held in the outermost layer.
[0029]
Embedded image
R₂OOC-Rf'-COOR₂
[0030]
Here, Rf ′ represents a perfluoropolyether chain,₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0031]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0032]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0033]
In a fifth aspect, there is provided a magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support, wherein the protective layer has a surface top-coated with an aromatic carboxylic acid. Is a lubricant containing an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid shown in the following [Chemical Formula 25] and an alkyl ester of a partially fluorinated carboxylic acid shown in the following [Chemical Formula 26]. Provides a magnetic recording medium configured to be held in the outermost layer.
[0034]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0035]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0036]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0037]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0038]
In a sixth aspect, the present invention provides a magnetic recording medium comprising a magnetic layer and a protective layer on a non-magnetic support, wherein the protective layer is top-coated with an aromatic carboxylic acid on the surface. Is a lubricant containing an ester compound of a perfluoropolyether having a carboxyl group at a terminal represented by the following [Chemical Formula 27] and a long-chain alcohol, and a partially fluorocarboxylic acid alkyl ester represented by the following [Chemical Formula 28]. Provides a magnetic recording medium configured to be held in the outermost layer.
[0039]
Embedded image
R₂OOC-Rf'-COOR₂
[0040]
Here, Rf ′ represents a perfluoropolyether chain,₂Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0041]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0042]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0043]
According to a seventh aspect of the present invention, there is provided a magnetic recording medium comprising a magnetic layer and a protective layer on a non-magnetic support, wherein the protective layer has a surface which is subjected to an ultraviolet irradiation treatment in an inert gas atmosphere. The layer contains an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid shown in the following [Chemical Formula 29], and an alkyl ester of a partially fluorinated carboxylic acid shown in the following [Chemical Formula 30]. Provided is a magnetic recording medium having a configuration in which a lubricant is held.
[0044]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0045]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0046]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0047]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0048]
According to an eighth aspect of the present invention, there is provided a magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support, wherein the protective layer has a surface subjected to ultraviolet irradiation treatment in an inert gas atmosphere to provide protection. The layer contains an ester compound of a perfluoropolyether having a carboxyl group at the terminal represented by the following [Chemical Formula 31] and a long-chain alcohol, and a partially fluorinated carboxylic acid alkyl ester represented by the following [Chemical Formula 32]. Provided is a magnetic recording medium having a configuration in which a lubricant is held.
[0049]
Embedded image
R₁OOC-Rf-COOR₁
[0050]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0051]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0052]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0053]
According to the magnetic recording medium of the first invention, the surface of the carbon protective layer is top-coated with an aromatic alcohol, and the compound represented by the above formula [17] and the compound represented by the formula [18] are formed on the carbon protective layer. By holding the lubricant containing, the adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0054]
According to the magnetic recording medium of the second invention, the surface of the carbon protective layer is top-coated with an aromatic alcohol, and the compound represented by the above formula [19] and the compound represented by the formula [20] are formed on the carbon protective layer. By holding the lubricant containing, the adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0055]
According to the magnetic recording medium of the third invention, the surface of the carbon protective layer is top-coated with an aromatic amine, and the compound represented by the above formula [21] and the compound represented by the formula [22] are formed on the carbon protective layer. By holding the lubricant containing, the adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0056]
According to the magnetic recording medium of the fourth invention, the surface of the carbon protective layer is top-coated with an aromatic amine, and the compound represented by the above formula [23] and the compound represented by the formula [24] are formed on the carbon protective layer. By holding the lubricant containing, the adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0057]
According to the magnetic recording medium of the fifth aspect, the surface of the carbon protective layer is top-coated with an aromatic carboxylic acid, and the compound represented by the above formula [25] and the compound represented by the formula [26] are formed on the carbon protective layer. By holding the lubricant containing the compound, the adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0058]
According to the magnetic recording medium of the sixth aspect, the surface of the carbon protective layer is top-coated with the aromatic carboxylic acid, and the compound represented by the above formula [27] and the compound represented by the formula [28] are formed on the carbon protective layer. By holding the lubricant containing the compound, the adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0059]
According to the magnetic recording medium of the seventh invention, the surface of the carbon protective layer is irradiated with ultraviolet light in an inert gas atmosphere, and the compound represented by the above [Chemical Formula 29] and [Chemical Formula 30] are formed on the protective layer. By holding a lubricant containing the compound shown, adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0060]
According to the magnetic recording medium of the eighth invention, the surface of the carbon protective layer is subjected to ultraviolet irradiation in an inert gas atmosphere, and the compound represented by the above [Chemical Formula 31] and [Chemical Formula 32] are formed on the protective layer. By holding a lubricant containing the compound shown, adhesion between the protective layer and the lubricant is improved. Further, since the lubricant is held in the outermost layer, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0061]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the magnetic recording medium of the present invention will be described.
The air recording medium is not limited to the examples shown below.
[0062]
As a matter common to the first to eighth inventions, FIG. 1 shows a schematic sectional view of an example of a magnetic recording medium 10. The magnetic recording medium 10 has a configuration in which a ferromagnetic metal thin film is formed as a magnetic layer 2 on a nonmagnetic support 1, and a protective layer 3 is formed on the magnetic layer 2. The lubricant layer 4 is formed on the surface of the protective layer 3 after a surface treatment as described later is performed.
FIG. 2 is a schematic diagram of an example of an ultraviolet irradiation device used when applying an ultraviolet irradiation process as a surface treatment of the protective layer 3, and FIG. 3 is a schematic diagram of a vacuum evaporation device for forming the magnetic layer 2. .
[0063]
[Embodiment A-1]
Examples of the nonmagnetic support 1 include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and vinyl such as polyvinyl chloride and polyvinylidene chloride. Examples thereof include plastics such as base resins, polycarbonates, polyimides, polyamides, and polyamideimides, light metals such as aluminum alloys and titanium alloys, and ceramics such as glass.
The form of the nonmagnetic support 1 may be any of a film, a sheet, a disk, a card, a drum, and the like.
[0064]
Further, the nonmagnetic support 1 may be formed with fine protrusions (not shown) such as fine protrusions, wrinkle protrusions, and granular protrusions on the surface in order to control the surface roughness.
Specifically, the mountain-like projections can be formed by, for example, internally adding inorganic fine particles having a particle size of about 50 to 300 nm when forming a polymer film constituting the nonmagnetic support 1, for example. , The height from the surface is 10 to 100 nm, and the density is about 1 × 10⁴[Pcs / mm²] To 1 × 10⁵[Pcs / mm²]. Calcium carbonate, silica, alumina and the like are preferable as the inorganic fine particles for forming the mountain-like projections.
[0065]
The wrinkle-like projections can be formed, for example, by applying a dilute solution of a resin using a specific mixed solvent on the nonmagnetic support 1 and drying the solution, and has a height of 0.01 to 10 μm, preferably, The thickness is set to 0.03 to 0.5 μm, and the shortest interval between the projections is set to about 0.1 to 20 μm.
[0066]
Examples of the resin for forming the wrinkled projections include, for example, polyethylene terephthalate, polyester such as polyethylene naphthalate, polyamide, polystyrene, polycarbonate, polyacrylate, polysulfone, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, and polyphenylene oxide. A simple substance, a mixture or a copolymer of phenoxy resin and the like can be mentioned, and those having a soluble solvent are suitable. Then, in a solution having a resin concentration of 1 to 1000 ppm obtained by dissolving these resins in the good solvent, a solvent which is a poor solvent for the resin and has a higher boiling point than the good solvent is 10 to 100 times the amount of the resin. By coating and drying the added solution on the surface of the non-magnetic support 1, a thin film having very fine wrinkle-like irregularities can be formed.
[0067]
The granular projections can be formed by adhering organic ultrafine particles such as an acrylic resin or inorganic fine particles such as silica or metal powder in a spherical or hemispherical shape. The height of the granular projections is 5 to 50 nm and the density is 1 × 10⁶[Pcs / mm²] To 5 × 10⁷[Pcs / mm²] Degree is preferred.
[0068]
By forming at least one of the above-mentioned protrusions on the non-magnetic support 1, the surface properties of the magnetic layer 2, that is, the ferromagnetic metal thin film can be controlled. By forming, the effect can be increased. In particular, by forming the wrinkle-like projections and the granular projections on the nonmagnetic support 1 on which the mountain-like projections are formed, the durability and running properties are remarkably improved. In this case, the total height of the projections is preferably in the range of 10 to 200 nm, and the density is 1 × 10 nm.⁵[Pcs / mm²] To 1 × 10⁷[Pcs / mm²] Is preferable.
[0069]
Next, the magnetic layer 2 will be described. Examples of a material for forming the ferromagnetic metal thin film to be the magnetic layer 2 include metals such as Fe, Co, and Ni, a Co—Ni alloy, a Co—Pt alloy, a Co—Ni—Pt alloy, a Fe—Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Fe-Co-B alloy, Co-Ni-Fe-B alloy, Co-Cr alloy, or a ferromagnetic metal material containing a metal such as Cr or Al And the like. In particular, when a Co—Cr alloy is used, a perpendicular magnetic film is formed.
[0070]
The magnetic layer 2 is formed as a continuous film by a vacuum thin film forming technique such as a vacuum deposition method, an ion plating method, and a sputtering method. Vacuum evaporation method is 1 × 10^-2~ 1 × 10^-6Under a vacuum of Pa, the ferromagnetic metal material is evaporated by resistance heating, high-frequency heating, electron beam heating, etc., and is deposited on the non-magnetic support 1. Generally, to obtain a high coercive force, So-called oblique evaporation, in which the ferromagnetic metal material is obliquely evaporated on the magnetic support 1, is used. Further, there is included a method in which vapor deposition is performed in an oxygen atmosphere to obtain a higher coercive force.
[0071]
The above-mentioned ion plating method is also a kind of the vacuum evaporation method, and 1 × 10^-2~ 1 × 10^-1DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of Pa to evaporate the ferromagnetic metal material during the discharge.
[0072]
The sputtering method is 1 × 10^-1A glow discharge is caused in an atmosphere containing argon gas of up to 1 × 10 Pa as a main component, and atoms of the target surface are knocked out by the generated argon gas ions. And a high-frequency sputtering method or a magnetron sputtering method using magnetron discharge. In the case of using this sputtering method, a base film of Cr, W, V, or the like may be formed in advance.
[0073]
In any of the above methods, a base metal layer of Bi, Sb, Pb, Sn, Ga, In, Cd, Ge, Si, Tl, or the like is previously formed on the nonmagnetic support 1 and is formed. By forming the film in a direction perpendicular to the surface of the nonmagnetic support 1, a magnetic layer 2 having no magnetic anisotropy orientation and excellent in-plane isotropy can be formed. It is preferable to use 10 as a magnetic disk.
The thickness of the ferromagnetic metal thin film formed by the above method is preferably 0.01 to 1 μm.
[0074]
The protective layer 3 is made of a carbon film, and is particularly preferably made of diamond-like carbon having relatively high hardness.
The protective layer 3 can be formed by, for example, a CVD method or the like. When the protective layer 3 is formed by the CVD method, for example, a hydrocarbon gas or a mixed gas of a hydrocarbon gas and an inert gas is introduced into a vacuum vessel, and the pressure is maintained at about 10 to 100 Pa. By discharging in the container, a plasma of hydrocarbon gas is generated, and a carbon thin film is formed on the magnetic layer 2.
The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency is experimentally determined. Further, by applying a voltage of 0 to -3 kV to an electrode disposed on the nonmagnetic support 1 side on which the ferromagnetic metal thin film is formed, the hardness of the protective layer 3 is increased, and the adhesion is improved. Or you can.
[0075]
As the above-mentioned hydrocarbon which is a material of the protective layer 3, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used.
[0076]
The protective layer 3 is preferably formed to a thickness of about 3 to 15 nm, particularly about 5 to 10 nm, so that the spacing loss is reduced and the effect of preventing the magnetic layer 2 from being worn is obtained.
[0077]
In this example, the surface of the protective layer 3 is top-coated with an aromatic alcohol. Specifically, examples of the aromatic alcohol include phenols and / or naphthols.
[0078]
Examples of phenols include dihydric phenols, alkylphenols, and nitrosophenols.
Examples of the dihydric phenol include pure phenols such as hydroquinone, resorcinol, and catechol, and alkylamino, nitro, and halogeno-substituted products thereof, for example, 2-methylhydroquinone, 4-methylresorcinol, 5-methylresorcinol, and 4-methylpyrocatechol. , 2,5-dimethylhydroquinone, 4,6-dimethylresorcinol, 2,5-dimethylresorcinol, 2-isopropyl-5-methylhydroquinone, 2-tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, -Tert-butylcatechol, 2-aminoresorcinol, 2-resorcinol, 2,5-dichlorohydroxyquinone and the like.
[0079]
The alkylphenol refers to an alkyl-substituted monohydric phenol, for example, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3-dimethylphenol 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4,6-trimethylphenol, 2,4,5-trimethylphenol, 5-isopropyl -2-methylphenol, p-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 4,4'-methylenebis-2,6-di-tert-butylphenol, 2,6-dimethyl-4 -Tert-butylphenol, 2,4,6-tri-tert-butyl Phenol, and the like.
[0080]
Examples of the nitrosophenol include 4-nitroso-2-methoxy-1-phenol, 4-nitroso-2-ethoxy-1-phenol, 6-nitroso-o-cresol, 4-nitroso-m-cresol, and o-nitrosophenol. Nitrosophenol, p-nitrosophenol, 2-nitrosoresorcin, 4-nitrosoresorcin and the like can be mentioned.
[0081]
As naphthols, α-naphthol, β-naphthol, 1,2-naphthalene diol, 1,3-naphthalene diol, 1,4-naphthalene diol, 1,5-naphthalene diol, 1,7-naphthalene diol, Pure naphthols such as 1,8-naphthalene diol, 2,3-naphthalene diol, 1,4,5-naphthalenetriol, 1,2,5,8-naphthalenetetraol and nitro, nitroso, amino, halogeno-substituted naphthols For example, 1-chloro-2-naphthol, 2,4-dichloro-1-naphthol, 1-nitro-2-naphthol, 1,6-dinitro-2-naphthol, 1-nitroso-2-naphthol, 2-nitroso -1-naphthol, 1-amino-2-naphthol and the like.
[0082]
It is preferable that the amount of the aromatic alcohol to be applied is determined depending on the degree of oxidation on the surface of the protective layer 3. The specific application amount is 0.05 mg / m²~ 100mg / m²And more preferably 0.1 mg / m²~ 50mg / m²Is more preferable.
[0083]
In particular, in the magnetic recording medium according to the present embodiment, perfluoropolyether having a hydroxyl group at a terminal represented by the following [Chemical Formula 33] and long-chain via a top coat made of an aromatic alcohol on the protective layer 3. It is assumed that a lubricant containing an ester compound with a carboxylic acid and a perfluorocarboxylic acid ester shown in the following [Formula 34] is held in the outermost layer.
[0084]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0085]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0086]
Embedded image
C_nF_{2n + 1}COOR
[0087]
Here, n represents an integer of 6 to 10, and R represents an alkyl group of 9 to 25.
[0088]
The lubricant containing the compound represented by the formula [33] and the compound represented by the formula [34] can maintain good adhesion and lubricity even under so-called severe use conditions, and can be lubricated for a long period of time. It has the property that the effect lasts.
[0089]
The ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid shown in the above [Formula 33] is, for example, a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid chloride in toluene. It is obtained by reacting with a base as a catalyst.
Here, as the perfluoropolyether having a hydroxyl group at a terminal, a perfluoropolyether having a hydroxyl group at both terminals is preferable. For example, HO-CH₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂—OH and the like.
The perfluoropolyether having a hydroxyl group at a terminal is, of course, not limited to these. In the above perfluoropolyether chemical formulas, p and q each represent an integer of 1 or more.
[0090]
The molecular weight of the perfluoropolyether having a hydroxyl group at the terminal is not particularly limited, but is preferably about 600 to 5000 for practical use.
If the molecular weight is too large, the effect of the terminal group as an adsorptive group is diminished, and at the same time, the perfluoropolyether chain becomes large, making it difficult to dissolve in existing hydrocarbon solvents. This is because the lubricating effect of the fluoropolyether chain is lost.
[0091]
In the perfluoropolyether having a hydroxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0092]
On the other hand, as the long-chain carboxylic acid chloride, any of commercial products and synthetic products can be used. By reacting the perfluoropolyether having a hydroxyl group at a terminal with a long-chain carboxylic acid chloride, a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid as shown in the above [Formula 33] Is synthesized.
[0093]
Here, the long-chain carboxylic acid, that is, the carboxylic acid portion of the long-chain carboxylic acid chloride of the synthetic material may have any structure having a carboxylic acid group, for example, a branched structure, an isomer structure, an alicyclic structure, and an unsaturated structure. It can be selected regardless of the presence or absence of the connection. The long-chain carboxylic acid is also optional in terms of molecular weight. However, it becomes difficult to dissolve in a normal hydrocarbon-based organic solvent as the molecular weight decreases, so that the alkyl group has at least 10 carbon atoms. Preferably, there is.
[0094]
Further, as described above, the lubricant used in the present example contains the perfluorocarboxylic acid ester represented by the above [Formula 34] in addition to the ester compound represented by the above [Formula 33].
[0095]
The perfluorocarboxylic acid ester represented by the above [Formula 34] can be easily synthesized by reacting a perfluorocarboxylic acid with a corresponding alcohol. The perfluorocarboxylic acid ester preferably has 6 to 10 carbon atoms in the perfluorocarboxylic acid moiety. When the number of carbon atoms is less than 6, the lubricating effect is insufficient. When the number of carbon atoms exceeds 10, solidification occurs in a low-temperature region, and as a result, the lubricating effect under low-temperature conditions decreases.
[0096]
The same applies to the carbon number of the alkyl group R in the ester portion, and the carbon number is preferably 9 to 25. When the number of carbon atoms is less than 9, the lubricating effect is insufficient, and when the number of carbon atoms exceeds 25, the lubricating effect under low temperature conditions is reduced.
What is important here is that the ester portion of the perfluorocarboxylic acid ester is selected from an alkyl group containing no unsaturated bond. The ester containing no unsaturated bond can maintain the initial lubricating properties even during long-term storage.
[0097]
Here, the lubricant used in the magnetic recording medium 10 includes an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid as shown in [Chemical Formula 33] and a perfluoropolyether as shown in [Chemical Formula 34]. The mixing ratio with the fluorocarboxylic acid ester is preferably from 10:90 to 90:10 by weight, and more preferably from 40:60 to 60:40. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0098]
In addition, as a method of retaining the lubricant in the outermost layer in the magnetic recording medium 10, a method of applying the lubricant to the surface is exemplified. Here, the coating amount is 0.05 mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable. If the coating amount is too small, the effect of lowering the friction coefficient and improve the abrasion resistance and durability will not be exhibited, and if the coating amount is too large, the cracking phenomenon will occur between the sliding member and the ferromagnetic metal thin film. The driving performance deteriorates.
[0099]
As described above, the magnetic recording medium 10 according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity as described above. The running performance and durability are secured.
Further, in the magnetic recording medium 10, the protective layer 3 made of carbon is formed, and the surface thereof is top-coated with an aromatic alcohol, so that the adhesion between the lubricant used and the protective layer 3 is improved. Thus, it is possible to improve the durability.
[0100]
Further, in the magnetic recording medium 10, since the magnetic layer 2 is formed of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording.
In the magnetic recording medium 10 according to the present embodiment, a rust preventive may be used in combination, if necessary. Any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium. Examples thereof include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, and oxygen atoms. And heterocyclic compounds containing a sulfur atom.
[0101]
In the magnetic recording medium 10 of the present invention, a so-called back coat layer may be formed on the surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer 2 is formed. The back coat layer is formed by applying a back coat paint in which a binder resin and a powder component are mixed and dispersed in an organic solvent to the nonmagnetic support 1.
[0102]
Here, as the binder resin used in the backcoat paint, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate- Acrylonitrile copolymer, thermoplastic polyurethane elastomer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, phenol resin, epoxy resin, polyurethane curable resin, melamine resin , Alkyd resin, silicone resin, epoxy-polyamide resin, nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylate copolymer and diisocyanate Mixtures of prepolymers, mixtures of polyester polyol and polyisocyanate, urea formaldehyde resin, mixture of a low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate, polyamine resin, and mixtures thereof.
Alternatively, a binder resin having a hydrophilic polar group may be used in order to improve the dispersibility of the powder component.
[0103]
On the other hand, examples of the powder component include carbon-based fine powder for imparting conductivity and inorganic pigments added for controlling surface roughness and improving durability. Examples of the carbon-based fine particles include furnace carbon, channel carbon, acetylene carbon, thermal carbon, and lamp carbon. Examples of the inorganic pigment include α-FeOOH and α-Fe.₂O₃, Cr₂O₃, TiO₂, ZnO, SiO, SiO₂, SiO₂・ 2H₂O, Al₂O₃, CaCO₃, MgCO₃, Sb₂O₃And the like.
[0104]
Further, as the organic solvent of the backcoat paint, for example, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl ether acetate. Solvent, glycol dimethyl ether, glycol monoethyl ether, glycol ether solvents such as dioxane, benzene, toluene, aromatic hydrocarbon solvents such as xylene, hexane, heptane and other aliphatic hydrocarbon solvents, methylene chloride, ethylene chloride, General-purpose solvents such as chlorinated hydrocarbon solvents such as carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene can be used.
[0105]
Further, a lubricant may be used in combination with the back coat layer. In this case, there is a method of internally adding a lubricant to the back coat layer or a method of applying a lubricant on the back coat layer. In any case, conventionally known lubricants such as fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, and silicone-based lubricants can be used as the lubricant.
[0106]
The magnetic recording medium 10 of the present invention as described above can be manufactured as follows. First, a ferromagnetic metal thin film serving as the magnetic layer 2 is formed on the nonmagnetic support 1 by, for example, a vacuum evaporation method. After that, the protective layer 3 is formed on the magnetic layer 2 by, for example, a plasma CVD method. Further, the surface of the protective layer 3 is subjected to a surface treatment with an aromatic alcohol. Then, the above-mentioned lubricant is top-coated on the protective layer 3 and the lubricant is held on the protective layer 3, whereby the intended magnetic recording medium 10 is obtained. It is needless to say that a back coat layer or the like may be formed as needed.
[0107]
More specifically, as a vacuum deposition apparatus for forming the magnetic layer 3, there is a continuous winding type vacuum deposition apparatus 40 as shown in FIG.
This vacuum deposition apparatus 40 is configured for so-called oblique deposition, and the inside thereof is, for example, 1 × 10^-3In a vacuum chamber 41 evacuated to about Pa, for example, a cooling can 42 that is cooled to about −20 ° C. and rotates in a counterclockwise direction as indicated by an arrow A in the drawing, and a ferromagnetic An evaporation source 43 for a metal thin film is provided.
[0108]
In the vacuum evaporation apparatus 40, a supply roll 44 and a take-up roll 45 in the drawing are also provided in the vacuum chamber 41, and the nonmagnetic support 1 is moved from the supply roll 44 in the direction indicated by the arrow B in the drawing. After traveling along the peripheral surface of the cooling can 42, it is taken up by a take-up roll 45.
[0109]
Guide rollers 47 # and 48 are disposed between the supply roll 44 and the cooling can 42 and between the cooling can 42 and the take-up roll 45, respectively. A predetermined tension is applied to the non-magnetic support 1 running along the take-up roll 45 so that the non-magnetic support 1 runs smoothly.
[0110]
The evaporation source 43 is a container such as a crucible in which a ferromagnetic metal material such as Co is contained. In this vacuum evaporation apparatus 40, an electron beam for heating and evaporating the ferromagnetic metal material of the evaporation source 43 A source 49 is also provided. In other words, the ferromagnetic metal material of the evaporation source 43 is acceleratedly irradiated with the electron beam 50 from the electron beam generation source 49, and is heated and evaporated as shown by the arrow C in the figure. Then, the ferromagnetic metal material is deposited on the nonmagnetic support 1 running along the peripheral surface of the cooling can 42 facing the evaporation source 43, and a ferromagnetic metal thin film is formed on the nonmagnetic support 1. .
[0111]
In the vacuum evaporation apparatus 40, a deposition-preventing plate 51 is provided between the deposition source 43 and the cooling can 42, and a shutter 52 is provided on the deposition-preventing plate 51 so as to be adjustable in position. To allow only vapor deposition particles incident at a predetermined angle to pass. Thus, the ferromagnetic metal thin film is formed by the oblique deposition method.
[0112]
Further, during the deposition of such a ferromagnetic metal thin film, oxygen gas is supplied to the vicinity of the surface of the non-magnetic support 1 through an oxygen gas inlet (not shown), whereby the magnetic properties, durability, and It is preferable to improve the weather resistance. In addition, in order to heat the evaporation source, known means such as a resistance heating means, a high-frequency heating means, and a laser heating means can be used in addition to the heating means using an electron beam as described above.
[0113]
Here, an example in which a ferromagnetic metal thin film made of Co is formed by an oblique evaporation method has been described. However, as a method of forming a ferromagnetic metal thin film, in addition to this method, a conventionally known method such as a vertical evaporation method or a sputtering method is used. The method of forming a thin film described above can be applied, and as the material of the ferromagnetic metal thin film, Ni, Fe, or an alloy thereof can be used in addition to Co. Further, the thickness of the ferromagnetic metal thin film at this time is preferably about 0.01 μm to 1 μm.
[0114]
Next, a method for forming the protective layer 3 will be described. The protective layer 3 is formed by, for example, a CVD method. When the protective layer 3 is formed by the CVD method, first, a hydrocarbon gas or a mixed gas of a hydrocarbon and an inert gas is introduced into a vacuum vessel, and the pressure is maintained at about 10 Pa to 100 Pa. The protective layer 3 is formed on the magnetic layer 2 by generating a plasma of a hydrocarbon gas by discharge in a vacuum vessel. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be experimentally determined.
In addition, by applying a voltage of 0 to -3 kV to the electrode disposed on the nonmagnetic support 1 side on which the magnetic layer 2 is formed, the hardness of the protective layer 3 can be increased and the adhesion can be improved.
[0115]
As the above-mentioned hydrocarbon which is a material for forming the protective layer 3, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used. . It is preferable that the protective layer 3 has a thickness of about 3 nm to 15 nm, particularly about 5 nm to 10 nm, so that the spacing loss is reduced and the effect of preventing the magnetic layer 2 from being worn is obtained.
[0116]
In the above description, an example in which the protective layer 3 is formed by the CVD method has been described. However, other known methods for forming the protective layer 3 include a magnetron sputtering method, an ion beam sputtering method, and an ion beam plating method. A thin film forming method can be used.
[0117]
Then, the surface of the protective layer 3 is top-coated with an aromatic alcohol, and the above-described lubricant is applied. By thus top-coating the surface of the protective layer 3 with the aromatic alcohol, the adhesion between the protective layer 3 and the lubricant layer 4 is improved.
[0118]
[Embodiment A-2]
Next, Embodiment A-2 of the magnetic recording medium of the present invention will be described. In this example, as in the case of the magnetic recording medium 10 described in the embodiment A-1, the ferromagnetic metal thin film and the protective layer 3 are sequentially formed as the magnetic layer 2 on the non-magnetic support 1. have. The magnetic recording medium according to the present embodiment has, in particular, a perfluoropolyether having a carboxyl group at a terminal represented by the following [Chemical Formula 35] as a lubricant layer 4 on the outermost protective layer 3. It is assumed that an ester compound with a long-chain alcohol and a lubricant containing a perfluorocarboxylic acid ester represented by the following [Formula 36] are held.
[0119]
Embedded image
R₂OOC-Rf'-COOR₂
[0120]
Here, Rf ′ represents a perfluoropolyether chain,₂Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0121]
Embedded image
C_nF_{2n + 1}COOR
[0122]
Here, n represents an integer of 6 to 10, and R represents an alkyl group of 9 to 25.
[0123]
The compound containing the compound represented by the above [Chemical formula 35] and the lubricant containing the compound represented by the above [Chemical formula 36] can maintain good adhesion and lubricity even under so-called severe use conditions, and lubricate for a long time. It has the property of maintaining the effect.
[0124]
The magnetic recording medium using the lubricant shown in the above [Formula 35] and the above [Formula 36] has substantially the same configuration as the magnetic recording medium described in the embodiment A-1. This is an example in which only the lubricant held in the outermost layer is different, and the other magnetic layers, protective layers, and the like have the same configuration. Therefore, in the following description, only the lubricant will be described, and description of other components will be omitted.
[0125]
The ester compound of a perfluoropolyether having a carboxyl group at the terminal and a long-chain alcohol shown in the above [Chemical Formula 35] is, for example, a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol in anhydrous toluene. It is obtained by reacting with p-toluenesulfonic acid or concentrated sulfuric acid as a catalyst.
[0126]
Here, as the perfluoropolyether having a carboxyl group at the terminal, a perfluoropolyether having a carboxyl group at both terminals is preferable. Specifically, HOOC-CF₂(OC₂F₄)_m(OCF₂)_jOCF₂—COOH and the like. The perfluoropolyether having a carboxyl group at the terminal is not limited to these. M and j in the chemical formula of perfluoropolyether each represent an integer of 1 or more.
[0127]
The molecular weight of the perfluoropolyether having a carboxyl group at the terminal is not particularly limited, but practically preferably about 600 to 5000. If the molecular weight is too large, the effect of the end group as an adsorbing group is diminished, and the perfluoropolyether chain becomes large, so that it becomes difficult to dissolve in existing hydrocarbon solvents. This is because the lubricating effect of the ether chain is lost.
[0128]
In the perfluoropolyether having a carboxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0129]
On the other hand, as the long-chain alcohol, either a commercial product or a synthetic product can be used. In addition, it is preferable that at least one of the alkyl groups has 6 or more carbon atoms because the molecular weight of the alkyl group becomes difficult to dissolve in an ordinary organic solvent as the molecular weight decreases.
[0130]
Further, as described above, the lubricant used in the present embodiment contains the perfluorocarboxylic acid ester represented by the above [Chemical Formula 36] in addition to the compound represented by the above [Chemical Formula 35]. As the perfluorocarboxylic acid ester represented by this [Chemical Formula 36], the same perfluorocarboxylic acid ester as applied in the above-mentioned Embodiment A-1 can be used.
[0131]
Further, in the lubricant used in the magnetic recording medium of the present example, an ester compound of a perfluoropolyether having a carboxyl group at a terminal shown in the above [Chemical Formula 35] and a long-chain alcohol; The mixing ratio with the perfluorocarboxylic acid ester shown is preferably from 10:90 to 90:10 by weight, and more preferably from 40:60 to 60:40. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0132]
Further, as a method of retaining the lubricant in the outermost layer, a method of top-coating the lubricant on the surface of the protective layer 3 may be mentioned. Here, the coating amount is 0.05 mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable.
If the coating amount is too small, the effect of lowering the friction coefficient and improving the abrasion resistance / durability will not be exhibited, and if the coating amount is too large, the sliding member and the ferromagnetic metal thin film will not have an effect. A cracking phenomenon occurs, leading to poor running performance.
[0133]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity, as described above. The running performance and durability are secured.
Further, in this magnetic recording medium, since the surface of the carbon protective layer 3 is top-coated with the aromatic alcohol, the adhesion between the lubricant and the protective layer 3 is improved, and more excellent durability is realized. be able to.
[0134]
[Embodiment B-1]
Next, a magnetic recording medium according to Embodiment B-1 will be described. In the present embodiment, a ferromagnetic metal thin film and a protective layer 3 are sequentially formed as a magnetic layer 2 on a nonmagnetic support 1, similarly to the magnetic recording medium 10 described in the embodiment A-1. It has a configuration. The configuration of the nonmagnetic support 1, the magnetic layer 2, and the protective layer 3 and the film forming method can be the same as those in Embodiment A-1.
[0135]
The surface of the protective layer 3 of the magnetic recording medium according to the present embodiment is top-coated with an aromatic amine.
By top-coating the surface of the protective layer 3 with an aromatic amine, the adhesion between the protective layer 3 and the lubricant is improved, and the lubricating effect of the lubricant can be maintained for a long time.
[0136]
Specific examples of the aromatic amine include aniline, N, N-dimethylaniline, o-phenylenediamine, m-phenylenediamine, thymylamine, pentachloroaniline, pentamethylaniline, 1-naphthylamine, 2-naphthylamine, and 1,2- Naphthalenediamine, 1,3-naphthalenediamine, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 1,7-naphthalenediamine, 2,3-naphthalenediamine, 1,2,3,4-tetrahydro-1- Examples thereof include naphthylamine, 5,6,7,8-tetrahydro-1-naphthylamine, and 5,6,7,8-tetrahydro-2-naphthylamine.
[0137]
It is preferable that the amount of the aromatic amine to be applied is determined depending on the degree of oxidation on the surface of the protective layer 3. The specific application amount is 0.05 mg / m²~ 100mg / m²And more preferably 0.1 mg / m²~ 50mg / m²Is more preferable.
[0138]
In particular, in the magnetic recording medium according to the present embodiment, a perfluoropolyether having a hydroxyl group at a terminal represented by the following [Chemical Formula 37] and a long-chain carboxylic acid are provided on the protective layer 3 via a top coat made of an aromatic amine. And a lubricant containing an ester compound of formula (1) and a partially fluorinated carboxylic acid alkyl ester shown in the following [Chemical Formula 38].
[0139]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0140]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0141]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0142]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0143]
The lubricant having the compound represented by the above [Chemical Formula 37] and the compound represented by the above [Chemical Formula 38] has good adhesion and lubricity even under so-called severe use conditions, and has a long term lubricating effect. It has lasting properties.
[0144]
The ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid shown in the above [Chemical Formula 37] is, for example, a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid chloride in toluene. It can be obtained by reacting with a base as a catalyst.
[0145]
Here, as the perfluoropolyether having a hydroxyl group at the terminal, one having a hydroxyl group at both terminals is preferable. For example, HO-CH₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂—OH and the like. The above-mentioned perfluoropolyether having a hydroxyl group at the terminal is not limited to these. In the above perfluoropolyether chemical formula, p and q each represent an integer of 1 or more.
[0146]
The molecular weight of the perfluoropolyether having a hydroxyl group at the terminal is not particularly limited, but is preferably about 600 to 5000 for practical use.
If the molecular weight is too large, the effect of the terminal group as an adsorptive group is diminished, and at the same time, the perfluoropolyether chain becomes large, so that it becomes difficult to dissolve in existing hydrocarbon solvents. Conversely, if the molecular weight is too small, the lubricating effect of the perfluoropolyether chain will be lost.
[0147]
In the perfluoropolyether having a hydroxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0148]
On the other hand, as the long-chain carboxylic acid chloride, either a commercial product or a synthetic product can be used. By reacting the perfluoropolyether having a hydroxyl group at the terminal with the long-chain carboxylic acid chloride, the perfluoropolyether having a hydroxyl group at the terminal and the long-chain carboxylic acid as shown in the above [Formula 37] Is synthesized.
[0149]
Here, the carboxylic acid portion of the long-chain carboxylic acid, that is, the carboxylic acid portion of the long-chain carboxylic acid chloride of the synthetic material, may have any structure having a carboxylic acid group, for example, a branched structure, an isomer structure, an alicyclic structure, It can be selected regardless of the presence or absence of unsaturated bonds. The long-chain carboxylic acid is also optional in terms of molecular weight. However, it becomes difficult to dissolve in a normal hydrocarbon-based organic solvent as the molecular weight decreases, so that the alkyl group has at least 10 carbon atoms. Preferably, there is.
[0150]
Further, as described above, the lubricant used in the present invention contains, in addition to the ester compound represented by the above formula [37], an alkyl ester of a partially fluorinated carboxylic acid represented by the above formula [38].
The carbon number of R in the partially fluorinated carboxylic acid alkyl ester shown in the above [Chemical Formula 38] is preferably 7 to 21. When the number of carbon atoms is 6 or less, the lubricating effect is poor, and when the number of carbon atoms exceeds 21, the solubility in an organic solvent decreases. There is no particular limitation on m and n in the above formula 10 as long as m + n ≧ 8 is satisfied.
[0151]
Further, the partially fluorinated carboxylic acid alkyl ester represented by the above [Chemical Formula 38] can be easily synthesized by reacting the partially fluorinated carboxylic acid with a saturated aliphatic alcohol in substantially equimolar amounts.
A specific reaction formula for synthesizing this partially fluorinated carboxylic acid alkyl ester is as shown below.
[0152]
First, a partially fluorinated carboxylic acid is synthesized through a series of reactions shown in the following [Chemical Formula 39], [Chemical Formula 40], [Chemical Formula 41], and [Chemical Formula 42] using an unsaturated carboxylic acid as a starting material. You.
Specifically, as shown in the following [Chemical Formula 39], the unsaturated carboxylic acid undergoes an esterification reaction with an alcohol to form an unsaturated ester. Then, as shown in the following [Formula 40], the unsaturated ester is subjected to an addition reaction with iodide of fluorocarbon to add fluorine and iodine. Then, as shown in the following [Formula 41], a partially fluorinated ester is generated by the reduction reaction. Then, as shown in the following [Formula 42], the partially fluorinated ester is hydrolyzed to finally obtain a partially fluorinated carboxylic acid.
[0153]
Embedded image

[0154]
Embedded image

[0155]
Embedded image

[0156]
Embedded image

[0157]
Next, the partially fluorinated carboxylic acid is finally reacted with a saturated aliphatic alcohol in an approximately equimolar amount as shown in the following [Chemical formula 43] to finally obtain the partially fluorinated carboxylic acid. An alkyl ester is obtained.
[0158]
Embedded image

[0159]
What is important here is that the alkyl chain at the alcohol site of the above-mentioned partially fluorinated carboxylic acid alkyl ester is selected from an alkyl group containing no unsaturated bond. By using such an ester containing no unsaturated bond, the initial lubricating properties can be maintained even after long-term storage.
[0160]
Here, in the lubricant used for the magnetic recording medium, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid represented by [Chemical Formula 37] and a partial fluorinated compound represented by [Chemical Formula 38] The mixing ratio with the carboxylic acid alkyl ester is preferably from 10:90 to 90:10 by weight, and more preferably from 40:60 to 60:40. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0161]
As a method for retaining the lubricant in the outermost layer in the magnetic recording medium, a method of top-coating the lubricant on the surface is exemplified. Here, the coating amount is 0.05 mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable. If the amount is too small, the effect of lowering the coefficient of friction and improve the abrasion resistance and durability will not be exhibited, and if the amount is too large, the sliding phenomenon between the sliding member and the ferromagnetic metal thin film will occur. The driving performance deteriorates.
[0162]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity. Is secured.
Further, in this magnetic recording medium, since the surface of the protective layer 3 is top-coated with an aromatic amine, the adhesion between the lubricant used and the protective layer 3 is improved, and further excellent durability is realized. can do.
[0163]
Further, in this magnetic recording medium, since the magnetic layer 2 is formed of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording.
In the magnetic recording medium according to the present embodiment, a rust preventive may be used in combination, if necessary. Any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium. Examples thereof include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, and oxygen atoms. And heterocyclic compounds containing a sulfur atom.
[0164]
In the magnetic recording medium of the present invention, a so-called back coat layer may be formed on the surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer 2 is formed. This back coat layer is formed by applying a back coat paint in which a binder resin and a powder component are mixed and dispersed in an organic solvent to the nonmagnetic support 1.
[0165]
Further, a lubricant may be used in combination with the above-mentioned back coat layer. In this case, there is a method of internally adding a lubricant to the back coat layer, or a method of applying a lubricant on the back coat layer. In any case, as the lubricant, a conventionally known lubricant such as a fatty acid, a fatty acid ester, a fatty acid amide, a metal soap, an aliphatic alcohol, and a silicone-based lubricant can be used.
[0166]
The magnetic recording medium according to the present embodiment as described above is manufactured as follows.
First, a ferromagnetic metal thin film serving as the magnetic layer 2 is formed on the nonmagnetic support 1 by, for example, a vacuum evaporation method. Thereafter, the protective layer 3 is formed on the magnetic layer 2 by, for example, a plasma CVD method. Further, the surface of the protective layer 3 is top-coated with an aromatic amine. Then, the above-described lubricant is applied on the protective layer 3 and the lubricant is held in the protective layer 3, whereby the intended magnetic recording medium 10 is obtained. In addition, you may form a back coat layer etc. as needed.
[0167]
The magnetic layer 2 can be formed by a continuous winding type vacuum evaporation apparatus 40 as shown in FIG.
Note that the magnetic layer 2 can be formed by the same steps as in Embodiment A-1 described above.
[0168]
The protective layer 3 can be formed by a CVD method.
When the protective layer 3 is formed by the CVD method, first, a hydrocarbon gas or a mixed gas of a hydrocarbon and an inert gas is introduced into a vacuum vessel, and the pressure is maintained at about 10 Pa to 100 Pa. The protective layer 3 is formed on the ferromagnetic metal thin film by causing discharge in a vacuum vessel to generate a plasma of a hydrocarbon gas. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be experimentally determined. Further, by applying a voltage of 0 to -3 kV to the electrode disposed on the nonmagnetic support 1 side on which the ferromagnetic metal thin film is formed, the hardness of the protective layer 3 can be increased and the adhesion can be improved. .
[0169]
As the above-mentioned hydrocarbon which is a material of the protective layer 3, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used.
This protective layer 3 preferably has a thickness of about 3 nm to 15 nm, particularly about 5 nm to 10 nm, so that the spacing loss is reduced and the effect of preventing the ferromagnetic metal thin film from being worn is obtained.
[0170]
Here, an example in which the protective film is formed by the CVD method has been described. However, as a method of forming the protective layer, in addition to this method, conventionally known methods such as a magnetron sputtering method, an ion beam sputtering method, and an ion beam plating method are used. Can be used.
Then, in this example, the surface of the protective layer 3 is top-coated particularly with an aromatic amine. By top-coating the surface of the protective layer 3 with an aromatic amine, the adhesion between the protective layer 3 and the lubricant can be improved.
[0171]
[Embodiment B-2]
Next, a magnetic recording medium according to Embodiment B-2 of the present invention will be described. In the magnetic recording medium according to the present embodiment, a ferromagnetic metal thin film as a magnetic layer 2 and a protective layer 3 as an outermost layer are sequentially formed on a non-magnetic support 1 in the same manner as the magnetic recording medium 10 described with reference to FIG. In particular, a top coat of an aromatic amine is applied to the surface of the protective layer 3 as the outermost layer, and a carboxyl group is added on the protective layer 3 at the terminal represented by the following formula. A lubricant containing an ester compound of a perfluoropolyether and a long-chain alcohol and a partially fluorinated carboxylic acid alkyl ester represented by the following [Formula 45] is retained.
[0172]
Embedded image
R₂OOC-Rf'-COOR₂
[0173]
Here, Rf ′ represents a perfluoropolyether chain,₂Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0174]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0175]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0176]
The lubricant containing the compound represented by the above [Formula 44] and the compound represented by the above [Chemical formula 45] can maintain good adhesion and lubricity even under so-called severe use conditions, and have a long-term lubricating effect. It has the property of lasting.
The magnetic recording medium using the lubricant shown in [Formula 44] and [Formula 45] has substantially the same configuration as the magnetic recording medium 10 described in Embodiment B-1. There is an example in which only the lubricant held in the outermost layer is different, and the other configurations and manufacturing methods of the magnetic layer 2 and the protective layer 3 are the same. Therefore, only the lubricant will be described below. .
[0177]
The ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the above [Formula 44] is, for example, a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol in anhydrous toluene. It can be obtained by reacting with p-toluenesulfonic acid or concentrated sulfuric acid as a catalyst.
[0178]
Here, as the perfluoropolyether having a carboxyl group at the terminal, a perfluoropolyether having a carboxyl group at both terminals is preferable. Specifically, HOOC-CF₂(OC₂F₄)_m(OCF₂)_jOCF₂—COOH and the like. The above-mentioned perfluoropolyether having a terminal carboxyl group is not limited to these. Note that m and j in the above chemical formula of perfluoropolyether each represent an integer of 1 or more.
[0179]
The molecular weight of the perfluoropolyether having a carboxyl group at the terminal is not particularly limited, but practically preferably about 600 to 5000. If the molecular weight is too large, the effect of the end group as an adsorptive group is diminished, and the perfluoropolyether chain becomes large, making it difficult to dissolve in existing hydrocarbon solvents.If the molecular weight is too small, the perfluoropolyether chain becomes small. This is because the lubrication effect due to is lost.
[0180]
In the perfluoropolyether having a carboxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0181]
On the other hand, as the long-chain alcohol, either a commercial product or a synthetic product can be used. In addition, since it becomes difficult to dissolve in a general organic solvent as the molecular weight becomes smaller, it is preferable that at least one alkyl group has 6 or more carbon atoms.
[0182]
Further, as described above, the lubricant used in the present embodiment contains, in addition to the compound shown in the above [Formula 44], a partially fluorinated carboxylic acid alkyl ester shown in the above [Formula 45]. . As the partially fluorinated carboxylic acid alkyl ester shown in the above [Formula 45], the same as the partially fluorinated carboxylic acid alkyl ester described in the above-mentioned Embodiment B-1 can be applied.
[0183]
Further, in the lubricant used for the magnetic recording medium of this example, an ester compound of a perfluoropolyether having a carboxyl group at a terminal shown in the above [Chemical Formula 44] and a long-chain alcohol; The mixing ratio with the indicated partially fluorinated carboxylic acid alkyl ester is preferably from 10:90 to 90:10 by weight, and more preferably from 40:60 to 60:40. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0184]
In addition, as a method of retaining the lubricant, a method of top-coating the surface of the protective layer 3 with the lubricant may be used. Application amount is 0.05mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable. If the amount of coating is too small, the effect of lowering the friction coefficient and improving the wear resistance and durability will not be exhibited, and if the amount of coating is too large, the shearing phenomenon will occur between the sliding member and the ferromagnetic metal thin film. Occurs, and the running performance deteriorates.
[0185]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity as described above. The durability and durability are secured. Further, in this magnetic recording medium, since the surface of the protective layer 3 made of carbon is top-coated with an aromatic amine, the adhesion between the lubricant used and the protective layer is improved, and the durability is further improved. Can be realized.
[0186]
[Embodiment C-1]
Next, a magnetic recording medium according to Embodiment C-1 will be described. In the present embodiment, a ferromagnetic metal thin film and a protective layer 3 are sequentially formed as a magnetic layer 2 on a nonmagnetic support 1, similarly to the magnetic recording medium 10 described in the embodiment A-1. It has a configuration. The configuration of the nonmagnetic support 1, the magnetic layer 2, and the protective layer 3 and the film forming method can be the same as those in Embodiment A-1.
[0187]
In the magnetic recording medium in this example, the surface of the protective layer 3 is particularly top-coated with an aromatic carboxylic acid.
Examples of the aromatic carboxylic acid include phthalic acid, terephthalic acid, isophthalic acid, benzoic acid, salicylic acid, gallic acid, galloyl gallic acid, opianic acid, vanillic acid, piperonylic acid, piperic acid, carminic acid, hesperitic acid, and benzenehexacarboxylic acid. Acid, 2-cyclohexene-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 6-hydroxy-5-isopropyl-o-toluic acid, 4-hydroxy-3-methoxycinnamic acid, etc. can do.
[0188]
It is preferable that the amount of the aromatic carboxylic acid to be applied is determined depending on the degree of oxidation on the surface of the protective layer 3. The specific application amount is 0.05 mg / m²~ 100mg / m²And more preferably 0.1 mg / m²~ 50mg / m²Is more preferable.
[0189]
In particular, in the magnetic recording medium according to the present embodiment, a long-chain perfluoropolyether having a hydroxyl group at the terminal represented by the following [Chemical Formula 46] is provided on the protective layer 3 via a top coat made of an aromatic carboxylic acid. A lubricant containing an ester compound with a carboxylic acid and a partially fluorinated carboxylic acid alkyl ester shown in the following [Chemical Formula 47] is retained.
[0190]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0191]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0192]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0193]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0194]
The lubricant containing the compound represented by the above [Chemical Formula 46] and the compound represented by the above [Chemical Formula 47] has good adhesion and lubricity under any use conditions, and has a long term lubricating effect. Has persistent properties.
[0195]
The ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid shown in the above [Chemical Formula 46] is, for example, a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid chloride in toluene. It is obtained by reacting with a base as a catalyst.
[0196]
Here, as the perfluoropolyether having a hydroxyl group at the terminal, one having a hydroxyl group at both terminals is preferable. For example, HO-CH₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂—OH and the like. The perfluoropolyether having a hydroxyl group at the terminal is not limited to these. In the above perfluoropolyether chemical formulas, p and q each represent an integer of 1 or more.
[0197]
The molecular weight of the perfluoropolyether having a hydroxyl group at the terminal is not particularly limited, but is preferably about 600 to 5000 for practical use. If the molecular weight is too large, the effect of the terminal group as an adsorptive group is diminished, and at the same time, the perfluoropolyether chain becomes large, making it difficult to dissolve in existing hydrocarbon solvents. This is because the lubricating effect of the fluoropolyether chain is lost.
[0198]
In the perfluoropolyether having a hydroxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0199]
On the other hand, as the long-chain carboxylic acid chloride, either a commercial product or a synthetic product can be used. Thus, by reacting the perfluoropolyether having a hydroxyl group at the terminal with the long-chain carboxylic acid chloride, the perfluoropolyether having a hydroxyl group at the terminal and the long-chain carboxylic acid as shown in the above [Formula 46] Is synthesized.
[0200]
Here, the long-chain carboxylic acid, that is, the carboxylic acid portion of the long-chain carboxylic acid chloride of the synthetic material may have any structure having a carboxylic acid group, for example, a branched structure, an isomer structure, an alicyclic structure, and an unsaturated structure. It can be selected regardless of the presence or absence of the connection. The long-chain carboxylic acid is also optional in terms of molecular weight. However, it becomes difficult to dissolve in a normal hydrocarbon-based organic solvent as the molecular weight decreases, so that the alkyl group has at least 10 carbon atoms. Desirably.
[0201]
Further, as described above, the lubricant used in the present invention contains, in addition to the ester compound represented by the above formula [46], an alkyl ester of a partially fluorinated carboxylic acid represented by the above formula [47]. . The number of carbon atoms of R in the partially fluorinated carboxylic acid alkyl ester represented by Chemical Formula 47 is desirably 7 to 21. When the number of carbon atoms is 6 or less, the lubricating effect is poor, and when the number of carbon atoms exceeds 21, the solubility in an organic solvent decreases. There is no particular limitation on m and n in the above formula 10 as long as m + n ≧ 8 is satisfied.
[0202]
Further, the partially fluorinated carboxylic acid alkyl ester can be easily synthesized by reacting the partially fluorinated carboxylic acid with a saturated aliphatic alcohol in substantially equimolar amounts.
Specifically, a specific reaction formula for the synthesis of the above-mentioned alkyl ester of partially fluorinated carboxylic acid is as shown below.
[0203]
First, a partially fluorinated carboxylic acid is synthesized as follows. First, a partially fluorinated carboxylic acid is synthesized through a series of reactions shown in the following [Chemical Formula 48], [Chemical Formula 49], [Chemical Formula 50], and [Chemical Formula 51] using an unsaturated carboxylic acid as a starting material. You.
Specifically, as shown in the following [Chemical Formula 48], the unsaturated carboxylic acid undergoes an esterification reaction with an alcohol to form an unsaturated ester. Thereafter, as shown in the following [Formula 49], the unsaturated ester is subjected to an addition reaction with iodide of fluorocarbon to add fluorine and iodine. Then, as shown in the following [Chemical Formula 50], the partial fluorinated ester is produced by the reduction. Thereafter, as shown in the following [Chemical formula 51], the partially fluorinated ester is hydrolyzed to finally obtain a partially fluorinated carboxylic acid.
[0204]
Embedded image

[0205]
Embedded image

[0206]
Embedded image

[0207]
Embedded image

[0208]
Next, the partially fluorinated carboxylic acid thus obtained is reacted with a saturated aliphatic alcohol in an approximately equimolar amount as shown in the following [Chemical Formula 52] to finally obtain the partially fluorinated alkyl carboxylate. An ester is obtained.
[0209]
Embedded image

[0210]
Here, the alkyl chain of the alcohol moiety of the above-mentioned partially fluorinated carboxylic acid alkyl ester is selected from an alkyl group containing no unsaturated bond. By using such an ester containing no unsaturated bond, the initial lubricating properties can be maintained even after long-term storage.
[0211]
In a lubricant used for a magnetic recording medium, an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid represented by the above [Chemical Formula 46] and a partially fluorinated carboxylic acid represented by the above [Chemical Formula 47] The mixing ratio with the acid alkyl ester is preferably from 10:90 to 90:10 by weight, and more preferably from 40:60 to 60:40. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0212]
Further, as a method of retaining the lubricant in the magnetic recording medium, a method of top-coating the lubricant on the surface may be mentioned. Application amount is 0.05mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable. If the amount is too small, the effect of lowering the coefficient of friction and improve the abrasion resistance and durability will not be exhibited, and if the amount is too large, the sliding phenomenon between the sliding member and the ferromagnetic metal thin film will occur. This results in worse running performance.
[0213]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity, as described above. The running performance and durability are secured.
Further, in this magnetic recording medium, the protective layer 3 made of carbon is formed, and the surface thereof is top-coated with an aromatic carboxylic acid. Properties can be improved, and more favorable durability can be realized.
Further, in this magnetic recording medium, since the magnetic layer 2 is formed of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording.
[0214]
In the magnetic recording medium according to the present embodiment, a rust preventive may be used in combination, if necessary. Any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium. Examples thereof include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, and oxygen atoms. And heterocyclic compounds containing a sulfur atom.
[0215]
In the magnetic recording medium of the present invention, a so-called back coat layer may be formed on the surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer 2 is formed. This back coat layer is formed by applying a back coat paint in which a binder resin and a powder component are mixed and dispersed in an organic solvent to the nonmagnetic support 1.
[0216]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity, as described above. The running performance and durability are secured.
Further, in this magnetic recording medium, the protective layer 3 made of carbon is formed, and the surface thereof is top-coated with the aromatic carboxylic acid. And improved durability can be realized.
[0219]
Examples of the binder resin used in the backcoat paint include a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrile copolymer, and an acrylate-acrylonitrile copolymer. Coalescence, thermoplastic polyurethane elastomer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, phenol resin, epoxy resin, polyurethane curable resin, melamine resin, alkyd resin , Silicone resin, epoxy-polyamide resin, nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylate copolymer and diisocyanate prepolymer Mixtures of mer, a mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, mixture of a low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate, polyamine resin, and mixtures thereof.
Alternatively, a binder resin having a hydrophilic polar group may be used in order to improve the dispersibility of the powder component.
[0218]
On the other hand, examples of the powder component include carbon-based fine powder for imparting conductivity and inorganic pigments added for controlling surface roughness and improving durability. Examples of the carbon-based fine particles include furnace carbon, channel carbon, acetylene carbon, thermal carbon, and lamp carbon. Examples of the inorganic pigment include α-FeOOH and α-Fe.₂O₃, Cr₂O₃, TiO₂, ZnO, SiO, SiO₂, SiO₂・ 2H₂O, Al₂O₃, CaCO₃, MgCO₃, Sb₂O₃And the like.
[0219]
Further, as the organic solvent of the backcoat paint, for example, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl ether acetate. Solvent, glycol dimethyl ether, glycol monoethyl ether, glycol ether solvents such as dioxane, benzene, toluene, aromatic hydrocarbon solvents such as xylene, hexane, heptane and other aliphatic hydrocarbon solvents, methylene chloride, ethylene chloride, General-purpose solvents such as chlorinated hydrocarbon solvents such as carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene can be used.
[0220]
Further, a lubricant may be used in combination with the back coat layer. In this case, there is a method of internally adding a lubricant to the back coat layer or a method of applying a lubricant on the back coat layer. In any case, conventionally known lubricants such as fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, and silicone-based lubricants can be used as the lubricant.
[0221]
The magnetic recording medium according to the present embodiment as described above is manufactured as follows.
First, a ferromagnetic metal thin film serving as the magnetic layer 2 is formed on the nonmagnetic support 1 by, for example, a vacuum evaporation method. Thereafter, a protective layer 3 is formed on the magnetic layer 2 by, for example, a plasma CVD method. Further, the surface of the protective layer 3 is top-coated with an aromatic carboxylic acid. Then, the above-mentioned lubricant is held on the protective layer 3, and the magnetic recording medium 10 is obtained. Note that a back coat layer or the like is formed as necessary.
[0222]
The magnetic layer 2 can be formed using the vacuum evaporation apparatus 40 shown in FIG. 3 in the same manner as the magnetic layer 2 in Embodiment A-1 described above.
[0223]
Next, a method for forming the protective layer 3 will be described. The protective layer 3 can be formed by a CVD method.
When the protective layer 3 is formed by the CVD method, first, a hydrocarbon gas or a mixed gas of a hydrocarbon and an inert gas is introduced into a vacuum vessel, and the pressure is maintained at about 10 Pa to 100 Pa. The protective layer 3 is formed on the ferromagnetic metal thin film by causing discharge in a vacuum vessel to generate a plasma of a hydrocarbon gas. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be experimentally determined. Further, by applying a voltage of 0 to -3 kV to the electrode disposed on the nonmagnetic support 1 side on which the ferromagnetic metal thin film is formed, the hardness of the protective layer 3 can be increased and the adhesion can be improved. .
[0224]
As the above-mentioned hydrocarbon which is a material of the protective layer 3, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used.
This protective layer 3 preferably has a thickness of about 3 nm to 15 nm, particularly about 5 nm to 10 nm, so that the spacing loss is reduced and the effect of preventing the ferromagnetic metal thin film from being worn is obtained.
[0225]
Here, an example in which the protective film is formed by the CVD method has been described. However, as a method of forming the protective layer, in addition to this method, conventionally known methods such as a magnetron sputtering method, an ion beam sputtering method, and an ion beam plating method are used. Can be used.
Then, in this example, the surface of the protective layer 3 is top-coated particularly with an aromatic carboxylic acid. By top-coating the surface of the protective layer 3 with an aromatic carboxylic acid, the adhesion between the protective layer 3 and the lubricant can be improved.
[0226]
[Embodiment C-2]
Next, a magnetic recording medium according to Embodiment C-2 of the present invention will be described. In the magnetic recording medium according to the present embodiment, a ferromagnetic metal thin film and a protective layer 3 are sequentially formed as a magnetic layer 2 on a nonmagnetic support 1, similarly to the magnetic recording medium 10 of Embodiment A-1 described above. In particular, a perfluoropolyether having a carboxyl group at the terminal represented by the following [Chemical Formula 53] and a long-chain alcohol through a top coat of an aromatic carboxylic acid on the surface of the protective layer 3 It is assumed that a lubricant containing an ester compound and a partially fluorinated carboxylic acid alkyl ester shown in the following [Formula 54] is held.
[0227]
Embedded image
R₂OOC-Rf'-COOR₂
[0228]
Here, Rf ′ represents a perfluoropolyether chain,₂Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0229]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0230]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0231]
The lubricant containing the compound represented by the above [Chemical Formula 53] and the compound represented by the above [Chemical Formula 54] can maintain good adhesion and lubricity under any use conditions, and maintain the lubricating effect for a long time. Have the property of
[0232]
The magnetic recording medium in which the lubricant is used has substantially the same configuration as the magnetic recording medium described in Embodiment C-1. In the example, only the lubricant held in the outermost layer is different. Yes, other magnetic layers, protective layers, and the like have the same configuration. Therefore, only the lubricant will be described below.
[0233]
The ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol shown in the above [Chemical Formula 53] can be obtained, for example, by mixing a perfluoropolyether having a carboxyl group at a terminal with a long-chain alcohol in anhydrous toluene. It can be obtained by reacting with p-toluenesulfonic acid or concentrated sulfuric acid as a catalyst.
[0234]
Here, as the perfluoropolyether having a carboxyl group at the terminal, a perfluoropolyether having a carboxyl group at both terminals is preferable. Specifically, HOOC-CF₂(OC₂F₄)_m(OCF₂)_jOCF₂—COOH and the like. The above-mentioned perfluoropolyether having a terminal carboxyl group is not limited to these. Note that m and j in the above chemical formula of perfluoropolyether each represent an integer of 1 or more.
[0235]
The molecular weight of the perfluoropolyether having a carboxyl group at the terminal is not particularly limited, but practically preferably about 600 to 5000. If the molecular weight is too large, the effect of the end group as an adsorbing group is diminished, and the perfluoropolyether chain becomes large, so that it becomes difficult to dissolve in existing hydrocarbon solvents.If the molecular weight is too small, the perfluoropolyether becomes too small. This is because the lubrication effect of the chains is lost.
[0236]
In the perfluoropolyether having a carboxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0237]
On the other hand, as the long-chain alcohol, either a commercial product or a synthetic product can be used. In addition, it is preferable that at least one of the alkyl groups has 6 or more carbon atoms because the molecular weight of the alkyl group becomes difficult to dissolve in an ordinary organic solvent as the molecular weight decreases.
[0238]
Further, as described above, the lubricant used in the present embodiment contains, in addition to the compound represented by the above formula [53], a partially fluorinated carboxylic acid alkyl ester represented by the above formula [54]. . As the partially fluorinated carboxylic acid alkyl ester shown in the above [Formula 54], the same as the partially fluorinated carboxylic acid alkyl ester described in the above-mentioned Embodiment C-1 can be used.
[0239]
Further, in the lubricant used for the magnetic recording medium of this example, an ester compound of a perfluoropolyether having a carboxyl group at a terminal shown in the above [Chemical Formula 53] and a long-chain alcohol, The mixing ratio with the indicated partially fluorinated carboxylic acid alkyl ester is preferably from 10:90 to 90:10 by weight, and more preferably from 40:60 to 60:40. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0240]
Further, as a method of retaining the lubricant in the outermost layer, a method of top-coating the lubricant on the surface of the protective layer 3 may be mentioned. Here, the coating amount is 0.05 mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable. If the coating amount is too small, the effect of lowering the friction coefficient and improving the abrasion resistance / durability will not be exhibited, and if the coating amount is too large, the shear between the sliding member and the ferromagnetic metal thin film will not occur. A phenomenon occurs, and the running performance worsens.
[0241]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity. Is secured.
Further, since the surface of the protective layer 3 made of carbon is top-coated with the aromatic carboxylic acid, the adhesiveness between the lubricant used and the protective layer 3 is improved, and further excellent durability can be realized. it can.
[0242]
[Embodiment D]
Next, a magnetic recording medium according to Embodiment D of the present invention will be described. The magnetic recording medium according to the present embodiment includes a ferromagnetic metal thin film and a protective layer 3 as a magnetic layer 2 on a nonmagnetic support 1, similarly to the magnetic recording medium 10 of FIG. 1 described in the embodiment A-1. Are sequentially formed, and the surface of the protective layer 3 is irradiated with ultraviolet rays in an inert gas atmosphere, and a lubricant described later is held on the protective layer 3. The configurations of the nonmagnetic support 1, the magnetic layer 2, and the protective layer 3 and the film forming method can be the same as those in Embodiment A-1.
[0243]
It is assumed that the surface of the protective layer 3 of the magnetic recording medium according to the present embodiment has been irradiated with ultraviolet rays in an inert gas atmosphere. That is, before forming the lubricant layer 4, the surface of the protective layer 3 is irradiated with ultraviolet rays in an inert gas atmosphere. By irradiating the surface of the protective layer 3 with ultraviolet rays, carbon-carbon bonds and carbon-hydrogen bonds are broken by the photon energy of the ultraviolet rays, so that a polar group is formed. Thereby, the adhesion between the protective layer 3 and the lubricant held on the protective layer 3 is improved, and the lubricating effect of the lubricant can be maintained for a long time.
[0244]
Irradiation of ultraviolet rays to the surface of the protective layer 3 is performed in an inert gas atmosphere. If the surface of the protective layer 3 is irradiated with ultraviolet rays in the air, the ozone molecules generated by the ultraviolet rays and the polar groups generated by the ultraviolet rays are combined to form a so-called weak boundary layer. The attraction between the layer 3 and the lubricant is reduced. In other words, by irradiating the protective layer 3 with ultraviolet rays in an inert gas atmosphere, a polar group can be reliably formed on the surface of the protective layer 3 and the adsorbing force between the protective layer 3 and the lubricant can be reliably increased. Can be improved.
In addition, examples of the inert gas include nitrogen, argon, and carbon dioxide.
[0245]
Specifically, for example, it is preferable to use a low-pressure mercury lamp and use ultraviolet light having a wavelength of 185 nm or 254 nm. In the case of ultraviolet light having a wavelength of 185 nm, the photon energy becomes 155 kcal / mol, and in the case of ultraviolet light having a wavelength of 254 nm, the photon energy becomes 113 kcal / mol. By using such a low-pressure mercury lamp, the protective layer 3 can be efficiently irradiated with ultraviolet rays.
[0246]
When irradiating the surface of the protective layer 3 with ultraviolet rays, for example, an ultraviolet irradiation device 20 as shown in FIG. 2 can be used. The ultraviolet irradiation device 20 includes a supply roll 25 and a take-up roll 26 which are formed by winding the long object 21, and an ultraviolet treatment unit 27 provided between the supply roll 25 and the take-up roll 26. Is provided.
Here, the target object 21 is caused to travel from the supply roll 25 toward the take-up roll 26 and is sequentially carried into the ultraviolet processing unit 27. The ultraviolet processing unit 27 faces a plurality of guide rolls 29 disposed in a housing 28 capable of sealing the inside, and the object to be processed 21 laid on the plurality of guide rolls 29, that is, the protection layer 3 of the magnetic recording medium. And a plurality of light source lamps 30 arranged in such a manner that
Further, the ultraviolet ray processing unit 27 is configured such that a gas supply port 28a and a gas discharge port 28b are formed in a housing 28, and an inert gas atmosphere is introduced into the housing 28 by introducing an inert gas from the gas supply port 28a. It can be.
[0247]
In the ultraviolet irradiation device 20 having the above-described configuration, the light source lamp 30 irradiates the processing target 21 that travels sequentially with the interior of the housing 28 in an inert gas atmosphere. Therefore, according to the ultraviolet irradiation device 20, the protective layer 3 can be irradiated with ultraviolet light in an inert gas atmosphere by running the object 21 from the supply roll 25 toward the take-up roll 26. it can.
[0248]
Particularly, in the magnetic recording medium according to the present embodiment, the protective layer 3 has an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid represented by the following [Chem. The lubricant containing the partially fluorinated carboxylic acid alkyl ester shown in [1] is retained.
[0249]
Embedded image
R₁COOCH₂-Rf-CH₂OCOR₁
[0250]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0251]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0252]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0253]
The lubricant having the compound represented by the above [Chemical Formula 55] and the compound represented by the above [Chemical Formula 56] can maintain good adhesion and lubricity under any use conditions, and maintain a lubricating effect for a long period of time. It has the following characteristics.
[0254]
The ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid shown in the above [Chemical Formula 55] is, for example, a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid chloride in toluene. It is obtained by reacting with a base as a catalyst.
Here, as the perfluoropolyether having a hydroxyl group at the terminal, one having a hydroxyl group at both terminals is preferable. For example, HO-CH₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂—OH and the like. The perfluoropolyether having a hydroxyl group at the terminal is not limited to these. In the above perfluoropolyether chemical formulas, p and q each represent an integer of 1 or more.
[0255]
The molecular weight of the perfluoropolyether having a hydroxyl group at the terminal is not particularly limited, but is preferably about 600 to 5000 for practical use. If the molecular weight is too large, the effect of the terminal group as an adsorptive group is diminished, and at the same time, the perfluoropolyether chain becomes large, so that it becomes difficult to dissolve in existing hydrocarbon solvents. Conversely, if the molecular weight is too small, the lubricating effect of the perfluoropolyether chain will be lost.
[0256]
In the perfluoropolyether having a hydroxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0257]
On the other hand, as the long-chain carboxylic acid chloride, either a commercial product or a synthetic product can be used. Thus, by reacting a perfluoropolyether having a hydroxyl group at a terminal with a long-chain carboxylic acid chloride, a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid as shown in the above [Formula 55] Is synthesized.
[0258]
Here, the long-chain carboxylic acid, that is, the carboxylic acid portion of the long-chain carboxylic acid chloride of the synthetic material may have any structure having a carboxylic acid group, for example, a branched structure, an isomer structure, an alicyclic structure, and an unsaturated structure. It can be selected regardless of the presence or absence of the connection. The long-chain carboxylic acid is also optional in terms of molecular weight. However, it becomes difficult to dissolve in a normal hydrocarbon-based organic solvent as the molecular weight decreases, so that the alkyl group has at least 10 carbon atoms. Preferably, there is.
[0259]
Further, as described above, the lubricant used in the present embodiment contains a partially fluorinated carboxylic acid alkyl ester represented by the above [Chemical Formula 56] in addition to the ester compound represented by the above [Chemical Formula 55].
The carbon number of R in the partially fluorinated carboxylic acid alkyl ester is preferably 7 to 21. When the number of carbon atoms is 6 or less, the lubricating effect is poor. When the number of carbon atoms exceeds 21, the solubility in the organic solvent is reduced. There is no particular limitation on m and n in the above [Formula 56] as long as m + n ≧ 8 is satisfied.
[0260]
The partially fluorinated carboxylic acid alkyl ester represented by the above [Formula 56] can be easily synthesized by reacting the partially fluorinated carboxylic acid with a saturated aliphatic alcohol in substantially equimolar amounts.
Specifically, a specific reaction formula for synthesizing the above-mentioned alkyl fluorinated carboxylate is as shown below.
First, a partially fluorinated carboxylic acid is synthesized as follows. First, a partially fluorinated carboxylic acid is synthesized through a series of reactions shown in the above [Chemical Formula 57], [Chemical Formula 58], [Chemical Formula 59], and [Chemical Formula 60] using an unsaturated carboxylic acid as a starting material. .
[0261]
Embedded image

[0262]
Embedded image

[0263]
Embedded image

[0264]
Embedded image

[0265]
Specifically, as shown in the above [Chemical Formula 57], the unsaturated carboxylic acid undergoes an esterification reaction with the alcohol to form an unsaturated ester. Thereafter, as shown in the above [Chemical Formula 58], the unsaturated ester undergoes an addition reaction with iodide of fluorocarbon to add fluorine and iodine. Then, as shown in the above [Chemical formula 59], a partially fluorinated ester is produced by a reduction reaction. Thereafter, as shown in the above [Chemical Formula 60], the partially fluorinated ester is hydrolyzed to finally obtain a partially fluorinated carboxylic acid.
[0266]
Next, the partially fluorinated carboxylic acid is finally reacted with a saturated aliphatic alcohol in an approximately equimolar amount as shown in the above [Chemical Formula 61] to finally obtain the partially fluorinated alkyl carboxylate. An ester is obtained.
[0267]
Embedded image

[0268]
What is important here is that the alkyl chain of the alcohol moiety of the above-mentioned partially fluorinated carboxylic acid alkyl ester is selected from an alkyl group containing no unsaturated bond. By using such an ester containing no unsaturated bond, the initial lubricating properties can be maintained even during long-term storage.
[0269]
Further, in a lubricant used for a magnetic recording medium, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid represented by the above [Chemical Formula 55]; The mixing ratio with the partially fluorinated carboxylic acid alkyl ester is preferably from 10:90 to 90:10 by weight, and more preferably from 40:60 to 60:40. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0270]
As a method of retaining the lubricant in the outermost layer, a method of top-coating the lubricant on the surface may be mentioned. Application amount is 0.05mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable. If the coating amount is too small, the effect of lowering the friction coefficient and improve the abrasion resistance and durability will not be exhibited, and if the coating amount is too large, the stiffness will occur between the sliding member and the ferromagnetic metal thin film. A phenomenon occurs, and the running performance worsens.
[0271]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity as described above. The durability and durability are secured.
Further, in this magnetic recording medium, since the protective layer 3 made of carbon is formed and the surface thereof is irradiated with ultraviolet rays, the adhesion between the lubricant and the protective layer 3 is improved. Good durability can be realized.
[0272]
Further, in this magnetic recording medium, since the magnetic layer 2 is formed of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording.
In the magnetic recording medium according to the present embodiment, a rust preventive may be used in combination, if necessary. Any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium. Examples thereof include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, and oxygen atoms. And heterocyclic compounds containing a sulfur atom.
[0273]
In the magnetic recording medium of the present invention, a so-called back coat layer may be formed on the surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer 2 is formed. The back coat layer is formed by applying a back coat paint in which a binder resin and a powder component are mixed and dispersed in an organic solvent to the nonmagnetic support 2.
[0274]
Examples of the binder resin used in the backcoat paint include a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrile copolymer, and an acrylate-acrylonitrile copolymer. Coalescence, thermoplastic polyurethane elastomer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, phenol resin, epoxy resin, polyurethane curable resin, melamine resin, alkyd resin , Silicone resin, epoxy-polyamide resin, nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylate copolymer and diisocyanate prepolymer Mixtures of mer, a mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, mixture of a low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate, polyamine resin, and mixtures thereof.
[0275]
Alternatively, a binder resin having a hydrophilic polar group may be used in order to improve the dispersibility of the powder component.
On the other hand, examples of the powder component include carbon-based fine powder for imparting conductivity and inorganic pigments added for controlling surface roughness and improving durability. Examples of the carbon-based fine particles include furnace carbon, channel carbon, acetylene carbon, thermal carbon, and lamp carbon. Examples of the inorganic pigment include α-FeOOH and α-Fe.₂O₃, Cr₂O₃, TiO₂, ZnO, SiO, SiO₂, SiO₂・ 2H₂O, Al₂O₃, CaCO₃, MgCO₃, Sb₂O₃And the like.
[0276]
Further, as the organic solvent of the backcoat paint, for example, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl ether acetate. Solvent, glycol dimethyl ether, glycol monoethyl ether, glycol ether solvents such as dioxane, benzene, toluene, aromatic hydrocarbon solvents such as xylene, hexane, heptane and other aliphatic hydrocarbon solvents, methylene chloride, ethylene chloride, General-purpose solvents such as chlorinated hydrocarbon solvents such as carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene can be used.
[0277]
Further, a lubricant may be used in combination with the back coat layer. In this case, there is a method of internally adding a lubricant to the back coat layer or a method of applying a lubricant on the back coat layer. In any case, conventionally known lubricants such as fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, and silicone-based lubricants can be used as the lubricant.
[0278]
The magnetic recording medium according to the present embodiment is manufactured as follows.
First, a ferromagnetic metal thin film serving as the magnetic layer 2 is formed on the nonmagnetic support 1 by, for example, a vacuum evaporation method. Thereafter, a protective layer 3 is formed on the magnetic layer 2 by, for example, a plasma CVD method. Further, the surface of the protective layer 3 is irradiated with ultraviolet rays. Then, the above-mentioned lubricant is top-coated on the protective layer 3 so that the protective layer 3 holds the lubricant, whereby a magnetic recording medium is obtained. In addition, you may form a back coat layer etc. as needed.
[0279]
The magnetic layer 2 can be formed using the vacuum evaporation apparatus 40 shown in FIG. 3 in the same manner as in the case of Embodiment A-1 described above.
[0280]
Next, a method for forming the protective layer 3 will be described. The protective layer 3 can be formed by a CVD method. When the protective layer is formed by the CVD method, first, a hydrocarbon gas or a mixed gas of a hydrocarbon and an inert gas is introduced into a vacuum vessel, and the pressure is maintained at about 10 Pa to 100 Pa. The protective layer 3 is formed on the ferromagnetic metal thin film by generating a plasma of a hydrocarbon gas by discharging the gas into the container. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be experimentally determined. Further, by applying a voltage of 0 to -3 kV to the electrode disposed on the nonmagnetic support 1 side on which the ferromagnetic metal thin film is formed, the hardness of the protective layer 3 can be increased and the adhesion can be improved. .
[0281]
As the above-mentioned hydrocarbon which is used as a material of the protective layer, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used.
It is preferable that the protective layer 3 has a thickness of about 3 nm to 15 nm, particularly about 5 nm to 10 nm, so as to reduce spacing loss and to obtain an effect of preventing abrasion of the ferromagnetic metal thin film.
[0282]
Here, an example in which the protective layer 3 is formed by the CVD method has been described. However, as a method of forming the protective layer 3, in addition to this method, a magnetron sputtering method, an ion beam sputtering method, an ion beam plating method, or the like may be used. A conventionally known thin film forming method can be used.
[0283]
Then, the surface of the protective layer 3 is subjected to an ultraviolet irradiation treatment in an inert gas atmosphere. By performing the ultraviolet irradiation treatment on the surface of the protective layer 3, the adhesion between the protective layer 3 and the lubricant layer 4 is improved.
[0284]
[Embodiment E]
Next, a magnetic recording medium according to Embodiment E of the present invention will be described. The magnetic recording medium according to the present embodiment includes a ferromagnetic metal thin film and a protective layer 3 as a magnetic layer 2 on a nonmagnetic support 1, similarly to the magnetic recording medium 10 of FIG. 1 described in the embodiment A-1. Are sequentially formed, and the surface of the protective layer 3 is irradiated with ultraviolet rays in an inert gas atmosphere, and a lubricant described later is held on the protective layer 3. The configurations of the nonmagnetic support 1, the magnetic layer 2, and the protective layer 3 and the film forming method can be the same as those in Embodiment A-1.
[0285]
It is assumed that the surface of the protective layer 3 of the magnetic recording medium according to the present embodiment has been irradiated with ultraviolet rays in an inert gas atmosphere. That is, before forming the lubricant layer 4, the surface of the protective layer 3 is irradiated with ultraviolet rays in an inert gas atmosphere. By irradiating the surface of the protective layer 3 with ultraviolet rays, carbon-carbon bonds and carbon-hydrogen bonds are broken by the photon energy of the ultraviolet rays, so that a polar group is formed. Thereby, the adhesion between the protective layer 3 and the lubricant held on the protective layer 3 is improved, and the lubricating effect of the lubricant can be maintained for a long time.
[0286]
Irradiation of ultraviolet rays to the surface of the protective layer 3 is performed in an inert gas atmosphere. If the surface of the protective layer 3 is irradiated with ultraviolet rays in the air, the ozone molecules generated by the ultraviolet rays and the polar groups generated by the ultraviolet rays are combined to form a so-called weak boundary layer. The attraction between the layer 3 and the lubricant is reduced. In other words, by irradiating the protective layer 3 with ultraviolet rays in an inert gas atmosphere, a polar group can be reliably formed on the surface of the protective layer 3 and the adsorbing force between the protective layer 3 and the lubricant can be reliably increased. Can be improved.
In addition, examples of the inert gas include nitrogen, argon, and carbon dioxide.
[0287]
Specifically, it is preferable to use, for example, a low-pressure mercury lamp and ultraviolet rays having a wavelength of 185 nm or 254 nm. In the case of ultraviolet light having a wavelength of 185 nm, the photon energy becomes 155 kcal / mol, and in the case of ultraviolet light having a wavelength of 254 nm, the photon energy becomes 113 kcal / mol. By using such a low-pressure mercury lamp, the protective layer 3 can be efficiently irradiated with ultraviolet rays.
[0288]
When irradiating the surface of the protective layer 3 with ultraviolet rays, for example, an ultraviolet irradiation device 20 as shown in FIG. 2 can be applied. The ultraviolet irradiation device 20 includes a supply roll 25 and a take-up roll 26 which are formed by winding the long object 21, and an ultraviolet treatment unit 27 provided between the supply roll 25 and the take-up roll 26. Is provided.
Here, the target object 21 is caused to travel from the supply roll 25 toward the take-up roll 26 and is sequentially carried into the ultraviolet processing unit 27. The ultraviolet processing unit 27 faces a plurality of guide rolls 29 disposed in a housing 28 capable of sealing the inside, and the object to be processed 21 laid on the plurality of guide rolls 29, that is, the protection layer 3 of the magnetic recording medium. And a plurality of light source lamps 30 arranged in such a manner that
Further, the ultraviolet ray processing unit 27 is configured such that a gas supply port 28a and a gas discharge port 28b are formed in a housing 28, and an inert gas atmosphere is introduced into the housing 28 by introducing an inert gas from the gas supply port 28a. It can be.
[0289]
In the ultraviolet irradiation device 20 having the above-described configuration, the light source lamp 30 irradiates the processing target 21 that travels sequentially with the interior of the housing 28 in an inert gas atmosphere. Therefore, according to the ultraviolet irradiation device 20, the protective layer 3 can be irradiated with ultraviolet light in an inert gas atmosphere by running the object 21 from the supply roll 25 toward the take-up roll 26. it can.
[0290]
In particular, the magnetic recording medium according to the present embodiment includes an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol represented by the following Chemical Formula 62 in the protective layer 3; In which a lubricant containing an alkyl ester of partially fluorinated carboxylic acid is held.
[0291]
Embedded image
R₁OOC-Rf-COOR₁
[0292]
Here, Rf represents a perfluoropolyether chain;₁Represents a hydrocarbon group or a fluorinated hydrocarbon group.
[0293]
Embedded image
C_nF_{2n + 1}(CH₂)_mCOOR
[0294]
Here, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.
[0295]
The lubricant having the compound represented by the above [Chemical Formula 62] and the compound represented by the above [Chemical Formula 63] maintains the adhesion and lubricity appropriately under any use conditions, and maintains the lubricating effect for a long time. It has the following characteristics.
[0296]
The ester compound of the perfluoropolyether having a carboxyl group at the terminal and the long-chain alcohol shown in the above [Formula 62] is, for example, a perfluoropolyether having a carboxyl group at the terminal and a long-chain alcohol in anhydrous toluene. It is obtained by reacting with p-toluenesulfonic acid or concentrated sulfuric acid as a catalyst.
[0297]
Here, as the perfluoropolyether having a carboxyl group at the terminal, a perfluoropolyether having a carboxyl group at both terminals is preferable. For example, HOOC-CF₂(OC₂F₄)_p(OCF₂)_qOCF₂COOH and the like. The perfluoropolyether having a terminal carboxyl group is not limited to these. In the above perfluoropolyether chemical formulas, p and q each represent an integer of 1 or more.
[0298]
The molecular weight of the perfluoropolyether having a carboxyl group at the terminal is not particularly limited, but practically preferably about 600 to 5000. If the molecular weight is too large, the effect of the terminal group as an adsorptive group is diminished, and at the same time, the perfluoropolyether chain becomes large, so that it becomes difficult to dissolve in existing hydrocarbon solvents. Conversely, if the molecular weight is too small, the lubricating effect of the perfluoropolyether chain will be lost.
[0299]
In the perfluoropolyether having a carboxyl group at the terminal, the perfluoropolyether chain may be partially hydrogenated. That is, a part (50% or less) of the fluorine atoms of the perfluoropolyether chain may be replaced with a hydrogen atom. In this case, a partially hydrogenated perfluoropolyether may be used as the perfluoropolyether.
[0300]
On the other hand, as the long-chain alcohol, either a commercial product or a synthetic product can be used. As described above, by reacting the perfluoropolyether having a carboxyl group at the terminal with the long-chain alcohol, the perfluoropolyether having a carboxyl group at the terminal and the long-chain alcohol as shown in the above [Chemical Formula 62] are obtained. Is synthesized.
[0301]
The long-chain alcohol is also optional in terms of molecular weight, but since it becomes difficult to dissolve in a normal hydrocarbon-based organic solvent as the molecular weight decreases, at least the alkyl group has at least 6 carbon atoms. preferable.
[0302]
Further, as described above, the lubricant applied to the magnetic recording medium according to the present embodiment includes, in addition to the ester compound represented by the above [Chemical Formula 62], the partially fluorinated carboxylic acid represented by the above [Chemical Formula 63]. Contains acid alkyl esters.
The carbon number of R in the partially fluorinated carboxylic acid alkyl ester represented by Chemical Formula 63 is preferably 7 to 21. When the number of carbon atoms is 6 or less, the lubricating effect is poor. When the number of carbon atoms exceeds 21, the solubility in the organic solvent is reduced. Further, m and n in the above [Chemical Formula 63] are not particularly limited as long as m + n ≧ 8 is satisfied.
[0303]
Further, the partially fluorinated carboxylic acid alkyl ester represented by the above [Chemical Formula 63] can be easily synthesized by reacting a partially fluorinated carboxylic acid with a saturated aliphatic alcohol in substantially equimolar amounts.
Specifically, a specific reaction formula for synthesizing the above-mentioned alkyl fluorinated carboxylate is as shown below.
[0304]
The partially fluorinated carboxylic acid is synthesized as follows. First, a partially fluorinated carboxylic acid is synthesized by using the unsaturated carboxylic acid as a starting material and undergoing a series of reactions shown in the above [Formula 64], [Formula 65], [Formula 66] and [Formula 67]. .
[0305]
Embedded image

[0306]
Embedded image

[0307]
Embedded image

[0308]
Embedded image

[0309]
Specifically, as shown in the above [Chemical Formula 64], the unsaturated carboxylic acid undergoes an esterification reaction with the alcohol to form an unsaturated ester. Thereafter, as shown in the above [Chemical formula 65], the unsaturated ester undergoes an addition reaction with iodide of fluorocarbon to add fluorine and iodine. Then, as shown in the above [Chemical Formula 66], a partially fluorinated ester is produced by a reduction reaction. Thereafter, as shown in the above [Chemical formula 67], the partially fluorinated ester is hydrolyzed to finally obtain a partially fluorinated carboxylic acid.
[0310]
Next, the partially fluorinated carboxylic acid thus obtained is reacted with a saturated aliphatic alcohol in an approximately equimolar amount as shown in the following [Chemical Formula 68] to finally obtain the partially fluorinated alkyl carboxylate. An ester is obtained.
[0311]
Embedded image

[0312]
What is important here is that the alkyl chain at the alcohol site of the above-mentioned partially fluorinated carboxylic acid alkyl ester is selected from an alkyl group containing no unsaturated bond. By using such an ester containing no unsaturated bond, the initial lubricating properties can be maintained even during long-term storage.
[0313]
Further, in the lubricant used for the magnetic recording medium, an ester compound of perfluoropolyether having a carboxyl group at a terminal represented by the above formula [Chem. 62] and a long-chain alcohol, and a lubricant represented by the above formula [Chem. 63] The mixing ratio with the partially fluorinated carboxylic acid alkyl ester is preferably from 10:90 to 90:10, more preferably from 40:60 to 60:40 by weight. If it exceeds the above range, an excellent lubricating effect cannot be obtained.
[0314]
As a method of retaining the lubricant in the outermost layer, a method of top-coating the lubricant on the surface may be mentioned. Application amount is 0.05mg / m²~ 100mg / m²Is preferably 0.1 mg / m²~ 50mg / m²Is more preferable. If the coating amount is too small, the effect of lowering the friction coefficient and improve the abrasion resistance and durability will not be exhibited, and if the coating amount is too large, the stiffness will occur between the sliding member and the ferromagnetic metal thin film. A phenomenon occurs, and the running performance worsens.
[0315]
As described above, the magnetic recording medium according to the present embodiment specifies and uses a combination of lubricants having extremely excellent characteristics in terms of adhesion and lubricity, as described above. The running performance and durability are secured.
Further, in this magnetic recording medium, since the protective layer 3 made of carbon is formed and the surface thereof is irradiated with ultraviolet rays, the adhesion between the lubricant and the protective layer 3 is improved. Good durability can be realized.
[0316]
Further, in this magnetic recording medium, since the magnetic layer 2 is formed of a ferromagnetic metal thin film, it can sufficiently cope with high-density recording and long-time recording.
In the magnetic recording medium according to the present embodiment, a rust preventive may be used in combination, if necessary. Any rust preventive can be used as long as it is generally used as a rust preventive for this type of magnetic recording medium. Examples thereof include phenols, naphthols, quinones, heterocyclic compounds containing a nitrogen atom, and oxygen atoms. And heterocyclic compounds containing a sulfur atom.
[0317]
In the magnetic recording medium of the present invention, a so-called back coat layer may be formed on the surface of the non-magnetic support 1 opposite to the surface on which the magnetic layer 2 is formed. This back coat layer is formed by applying a back coat paint in which a binder resin and a powder component are mixed and dispersed in an organic solvent to the nonmagnetic support 1.
[0318]
Examples of the binder resin used in the backcoat paint include a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinylidene chloride copolymer, a vinyl chloride-acrylonitrile copolymer, and an acrylate-acrylonitrile copolymer. Coalescence, thermoplastic polyurethane elastomer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative, polyester resin, phenol resin, epoxy resin, polyurethane curable resin, melamine resin, alkyd resin , Silicone resin, epoxy-polyamide resin, nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, methacrylate copolymer and diisocyanate prepolymer Mixtures of mer, a mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, mixture of a low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate, polyamine resin, and mixtures thereof.
[0319]
Alternatively, a binder resin having a hydrophilic polar group may be used in order to improve the dispersibility of the powder component.
On the other hand, examples of the powder component include carbon-based fine powder for imparting conductivity and inorganic pigments added for controlling surface roughness and improving durability. Examples of the carbon-based fine particles include furnace carbon, channel carbon, acetylene carbon, thermal carbon, and lamp carbon. Examples of the inorganic pigment include α-FeOOH and α-Fe.₂O₃, Cr₂O₃, TiO₂, ZnO, SiO, SiO₂, SiO₂・ 2H₂O, Al₂O₃, CaCO₃, MgCO₃, Sb₂O₃And the like.
[0320]
Further, as the organic solvent of the backcoat paint, for example, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl ether acetate. Solvent, glycol dimethyl ether, glycol monoethyl ether, glycol ether solvents such as dioxane, benzene, toluene, aromatic hydrocarbon solvents such as xylene, hexane, heptane and other aliphatic hydrocarbon solvents, methylene chloride, ethylene chloride, General-purpose solvents such as chlorinated hydrocarbon solvents such as carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene can be used.
[0321]
Further, a lubricant may be used in combination with the back coat layer. In this case, there is a method of internally adding a lubricant to the back coat layer or a method of applying a lubricant on the back coat layer. In any case, conventionally known lubricants such as fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, and silicone-based lubricants can be used as the lubricant.
[0322]
The magnetic recording medium according to the present embodiment is manufactured as follows.
First, a ferromagnetic metal thin film serving as the magnetic layer 2 is formed on the nonmagnetic support 1 by, for example, a vacuum evaporation method. Thereafter, a protective layer 3 is formed on the magnetic layer 2 by, for example, a plasma CVD method. Further, the surface of the protective layer 3 is irradiated with ultraviolet rays. Then, the above-mentioned lubricant is top-coated on the protective layer 3 so that the protective layer 3 holds the lubricant, whereby a magnetic recording medium is obtained. In addition, you may form a back coat layer etc. as needed.
[0323]
The magnetic layer 2 can be formed using the vacuum evaporation apparatus 40 shown in FIG. 3 in the same manner as in the case of Embodiment A-1 described above.
[0324]
Next, a method for forming the protective layer 3 will be described. The protective layer 3 can be formed by a CVD method. When the protective layer is formed by the CVD method, first, a hydrocarbon gas or a mixed gas of a hydrocarbon and an inert gas is introduced into a vacuum vessel, and the pressure is maintained at about 10 Pa to 100 Pa. The protective layer 3 is formed on the ferromagnetic metal thin film by generating a plasma of a hydrocarbon gas by discharging the gas into the container. The discharge type may be either an external electrode type or an internal electrode type, and the discharge frequency can be experimentally determined. Further, by applying a voltage of 0 to -3 kV to the electrode disposed on the nonmagnetic support 1 side on which the ferromagnetic metal thin film is formed, the hardness of the protective layer 3 can be increased and the adhesion can be improved. .
[0325]
As the above-mentioned hydrocarbon which is used as a material of the protective layer, for example, methane, ethane, propane, butane, pentane, hexane, heptane, octane, ethylene, acetylene, propene, butene, pentene, benzene and the like can be used.
It is preferable that the protective layer 3 has a thickness of about 3 nm to 15 nm, particularly about 5 nm to 10 nm, so as to reduce spacing loss and to obtain an effect of preventing abrasion of the ferromagnetic metal thin film.
[0326]
Here, an example in which the protective layer 3 is formed by the CVD method has been described. However, as a method of forming the protective layer 3, in addition to this method, a magnetron sputtering method, an ion beam sputtering method, an ion beam plating method, or the like may be used. A conventionally known thin film forming method can be used.
[0327]
Then, the surface of the protective layer 3 is subjected to an ultraviolet irradiation treatment in an inert gas atmosphere. By performing the ultraviolet irradiation treatment on the surface of the protective layer 3, the adhesion between the protective layer 3 and the lubricant layer 4 is improved.
[0328]
【Example】
Hereinafter, examples of the present invention will be described based on specific experimental results.
[Experimental example A1 (Examples A-1 to A-8, Comparative examples A-1 to A-10)]
In this experimental example, the effect of using an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a lubricant containing a perfluorocarboxylic acid ester was confirmed as follows.
[0329]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal hydroxyl group and long-chain carboxylic acid
First, HOCH having a molecular weight of 2000 was used as a perfluoropolyether having a hydroxyl group at a terminal.₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂Using OH (where p and q each represent an integer of 1 or more in the chemical formula), triethylamine, which is twice the molar amount of this perfluoropolyether in an organic solvent, is dissolved in an organic solvent. Further, stearic acid chloride in an amount twice as much as the molar ratio was added dropwise over 30 minutes.
After completion of the dropwise addition, the mixture was stirred for 1 hour, and then heated and refluxed for 30 minutes. After cooling, the resultant was washed with distilled water and a dilute aqueous hydrochloric acid solution in that order, and again washed with distilled water until the washing liquid became neutral. Subsequently, the organic solvent was removed, and the obtained compound was purified using silica gel column chromatography to obtain an ester compound. Here, this ester compound is referred to as compound A-1.
[0330]
Next, according to the same synthesis method as that of the compound A-1, the four types of compounds A-2 to 4 are ester compounds of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid as shown in Table 1 below. A-5 was synthesized. In Table 1, p, q, and n each represent an integer of 1 or more.
[0331]
[Table 1]

[0332]
2. Preparation of sample tape
Next, a magnetic tape was produced as follows. First, Co is applied to a 7.0 μm-thick polyethylene terephthalate film as a non-magnetic support by oblique evaporation using the above-described vacuum evaporation apparatus, and a ferromagnetic metal thin film serving as a magnetic layer is formed to a thickness of 180 nm. Formed.
Next, a DC voltage of -1.5 kV was applied to the ferromagnetic metal thin film by applying high-frequency plasma of a mixed gas of ethylene and argon to the electrode and the magnetic recording medium raw material as a counter electrode, thereby discharging the raw material. Was performed to form a carbon protective layer having a thickness of about 8 nm on the ferromagnetic metal thin film.
Next, a 0.5 μm-thick back coat layer made of carbon and polyurethane resin was formed on the surface of the polyethylene terephthalate film opposite to the surface on which the ferromagnetic metal thin film was formed.
Next, a solution obtained by dissolving an aromatic alcohol shown in Table 2 below in isopropyl alcohol was coated on the carbon protective layer at a coating amount of 2 mg / m 2.²It applied so that it might become.
[0333]
[Table 2]

[0334]
Next, each of the compounds shown in Table 2 above dissolved in a hexane solvent was coated on the carbon protective layer at a coating amount of 5 mg / m 2.²Thus, 18 types of magnetic recording media were obtained.
Each of these 18 types of magnetic recording media was cut into a 6.35 mm width, and 18 types of sample tapes of Examples A-1 to A-8 and Comparative Examples A-1 to A-10 were cut. did.
However, for the sample tapes of Comparative Examples A-3 to A-10, no aromatic alcohol was applied to the surface of the protective layer.
[0335]
3) Evaluation of characteristics
Next, the characteristics of the 18 types of sample tapes of Examples A-1 to A-8 and Comparative Examples A-1 to A-10 were evaluated. Here, the durability and running performance were evaluated, and specifically, the friction coefficient, still durability and shuttle durability were evaluated. As the environmental conditions for evaluating these, the inventors considered the conditions and adopted the conditions considered to be the most severe conditions.
[0336]
1. Measurement method of friction coefficient
The friction coefficient was measured by controlling the environmental conditions in the thermostat to a temperature of 40 ° C. and a humidity of 80% RH, and running each sample tape in this thermostat for 100 passes. In addition, the numerical value of the 100th pass of friction running was defined as the friction coefficient.
2. Measurement method of still durability
The evaluation of the still durability was performed in a -5 ° C. constant temperature bath, and the time until the reproduction output of each sample tape dropped by 3 dB using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: DVC-VX1000). Was measured.
3 Measurement method of shuttle durability
Shuttle durability was controlled by controlling the environmental conditions in a thermostat to a temperature of 40 ° C. and a humidity of 20% RH. Each sample tape was run for 100 pass shuttles, and after running for 100 passes, how many dB the reproduction output dropped from the initial output was measured and evaluated.
[0337]
These evaluations were performed immediately after the lubricant was applied and after each sample tape was stored for 30 days in an environment of a temperature of 45 ° C. and a humidity of 80% RH. The measurement results of the initial durability and running properties immediately after the application of the lubricant are shown in Table 3 below, and the measurement results of the durability and running properties after storage after storage for 30 days are shown in Table 4 below.
[0338]
[Table 3]

[0339]
[Table 4]

[0340]
From the results in Tables 3 and 4, the protective layer surface was top-coated with an aromatic alcohol, and further, as a lubricant, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a perfluorocarboxylic acid ester In the sample tapes of Examples A-1 to A-8 using a lubricant in combination with the above, the friction coefficient, still durability, and friction coefficient under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature It was found that the deterioration of shuttle durability was extremely small, and very good results were obtained.
[0341]
On the other hand, in Comparative Examples A-1 and A-2 using a lubricant containing only an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid, the friction coefficient was varied under various use conditions. And the durability of the still and shuttle durability was very large.
[0342]
Moreover, in Comparative Examples A-3 to A-10 in which the aromatic alcohol was not applied to the surface of the protective layer, the friction coefficient, still durability, and shuttle durability were greatly deteriorated under various use conditions, and were good. Results were not obtained
[0343]
From the above results, the protective layer surface is treated with an aromatic alcohol, and further, as a lubricant, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid, and a combination of a perfluorocarboxylic acid ester As a result, it was found that excellent running properties and durability of the magnetic recording medium were obtained because excellent adhesion and lubricity were maintained under any use conditions and the lubrication effect was maintained for a long period of time.
[0344]
[Experimental example A2 (Examples A-9 to A-16, Comparative examples A-11 to A-20)]
In this experimental example, the effect of using an ester compound of a perfluoropolyether having a carboxyl group at the end and a long-chain alcohol and a lubricant containing a perfluorocarboxylic acid ester was confirmed as follows. .
[0345]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal carboxyl group and long-chain alcohol
First, HOOCCF having a molecular weight of 2,000 was used as a perfluoropolyether having a carboxyl group at a terminal.₂(OC₂F₄)_m(OCF₂)_jOCF₂COOH (where m and j in the chemical formula each represent an integer of 1 or more) is used. A small amount of p-toluenesulfone is added to this perfluoropolyether in a molar amount twice as much as stearyl alcohol in anhydrous toluene. The mixture was heated to reflux using an acid and concentrated sulfuric acid as catalysts. At this time, the reaction was performed while removing generated water.
After completion of the reaction, toluene was removed, and the obtained compound was purified using silica gel column chromatography, and then the solvent was removed to obtain an ester compound. Here, this ester compound is referred to as compound A-6.
Next, according to the same synthesis method as that of the above-mentioned compound A-6, four kinds of compounds A-7 to 4 which are ester compounds of perfluoropolyether having a terminal carboxyl group and a long-chain alcohol as shown in Table 5 below. A-10 was synthesized. In Table 5, p, q, and n each represent an integer of 1 or more.
[0346]
[Table 5]

[0347]
2. Preparation of sample tape
First, a ferromagnetic metal thin film serving as a magnetic layer and a carbon protective layer were formed on a nonmagnetic support in the same manner as in Experimental Example A1, and a back coat layer was also formed. Further, on the surface of the protective layer, an aromatic alcohol as shown in the following Table 6 dissolved in isopropyl alcohol was applied at a coating amount of 2 mg / m 2.²It applied so that it might become.
[0348]
[Table 6]

[0349]
Next, in the same manner as in the above-mentioned Experimental Example A1, a solution in which a lubricant as shown in Table 6 above was dissolved in a hexane solvent was applied onto the surface of the protective layer at a coating amount of 5 mg / m 2.²Thus, 18 types of magnetic recording media were obtained.
Then, each of these 18 types of magnetic recording media was cut into a width of 6.35 mm, and 18 types of sample tapes of Examples A-9 to A-16 and Comparative Examples A-11 to A-20 were produced. did.
However, aromatic alcohol was not applied to the surface of the protective layer for the sample tapes of Comparative Examples A-13 to 20.
[0350]
3) Evaluation of characteristics
Next, the characteristics of the 18 types of sample tapes of Examples A-9 to A-16 and Comparative Examples A-11 to A-20 were evaluated. Here, the durability and the running property were evaluated. Specifically, the friction coefficient, the still durability, and the shuttle durability were evaluated in the same manner as in Experimental Example A1.
[0351]
These evaluations were performed immediately after the lubricant was applied in the same manner as in Experimental Example A1 and after each sample tape was stored for 30 days in an environment at a temperature of 45 ° C. and a humidity of 80% RH. Table 7 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 8 shows the results of the durability and running properties after storage after storage for 30 days.
[0352]
[Table 7]

[0353]
[Table 8]

[0354]
From the results shown in Tables 7 and 8, the protective layer surface was top-coated with an aromatic alcohol, and further, as a lubricant, an ester compound of perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol and a perfluorocarboxylic acid ester In Examples A-9 to A-16 using a lubricant in combination with the above, the friction coefficient, still durability and shuttle durability under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature It was found that there was very little deterioration of the sample and very good results were obtained.
[0355]
On the other hand, in Comparative Examples A-11 and A-12 using a lubricant containing only an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, the friction coefficient was varied under various use conditions. And the durability of the still and shuttle durability was very large.
[0356]
Further, in Comparative Examples A-13 to A-20 in which the aromatic alcohol was not applied to the surface of the protective layer, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various conditions of use, and were excellent. Results were not obtained.
From the above results, the protective layer surface was top-coated with an aromatic alcohol, and as a lubricant, an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, and a perfluorocarboxylic acid ester were combined. It can be seen that the use of a magnetic recording medium maintains good adhesion and lubricity under any use conditions and maintains the lubricating effect for a long period of time, so that good running properties and durability of the magnetic recording medium can be obtained. Was.
[0357]
[Experimental Example B1 (Examples B-1 to B-8, Comparative Examples B-1 to B-13)]
In this experimental example, the effect of using an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a lubricant containing a partially fluorinated carboxylic acid alkyl ester was confirmed as follows. did.
[0358]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal hydroxyl group and long-chain carboxylic acid
First, HOCH having a molecular weight of 2000 was used as a perfluoropolyether having a hydroxyl group at a terminal.₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂Using OH (where p and q each represent an integer of 1 or more in the chemical formula), triethylamine, which is twice the molar amount of this perfluoropolyether in an organic solvent, is dissolved in an organic solvent. Further, stearic acid chloride in an amount twice as much as the molar ratio was added dropwise over 30 minutes.
After the completion of the dropwise addition, the mixture was stirred for 1 hour, and then heated under reflux for 30 minutes. And after cooling, it wash | cleaned in order of distilled water and dilute hydrochloric acid aqueous solution, and wash | cleaned again with distilled water until the washing | cleaning liquid became neutral. Subsequently, the organic solvent was removed, and the obtained compound was purified using silica gel column chromatography to obtain an ester compound. Here, this ester compound is referred to as compound B-1.
Next, according to the same synthesis method as that of the above compound B-1, four types of compounds B-2 to 4 are ester compounds of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid as shown in Table 9 below. B-5 was synthesized. In Table 9, p, q, and n each represent an integer of 1 or more.
[0359]
[Table 9]

[0360]
2. Preparation of sample tape
Next, a magnetic tape was produced as follows. First, Co is applied to a 7.0 μm-thick polyethylene terephthalate film as a non-magnetic support by oblique evaporation using the above-described vacuum evaporation apparatus, and a ferromagnetic metal thin film serving as a magnetic layer is formed to a thickness of 180 nm. Formed.
Next, a DC voltage of -1.5 kV was applied to the ferromagnetic metal thin film by applying high-frequency plasma of a mixed gas of ethylene and argon to the raw material of the magnetic recording medium, using the electrode and the raw material of the magnetic recording medium as a counter electrode, to discharge. Then, a carbon protective layer having a thickness of about 8 nm was formed on the ferromagnetic metal thin film.
Next, a 0.5 μm-thick back coat layer made of carbon and polyurethane resin was formed on the surface of the polyethylene terephthalate film opposite to the surface on which the ferromagnetic metal thin film was formed.
[0361]
Next, as shown in Table 10 below, an aromatic amine dissolved in isopropyl alcohol was coated on the carbon protective layer at a coating amount of 2 mg / m 2.²It applied so that it might become.
Next, each of the compounds shown in Table 10 below dissolved in a hexane solvent was coated on the carbon protective layer at a coating amount of 5 mg / m 2.²To obtain 21 types of magnetic recording media.
Then, these 21 types of magnetic recording media were cut into 6.35 mm widths respectively, and 21 types of sample tapes of Example B-1 to Example B-8 and Comparative Example B-1 to Comparative Example B-13 were cut. did.
[0362]
However, for the sample tapes of Comparative Examples B-3 to B-10, no aromatic amine was applied to the surface of the protective layer. Further, with respect to the sample tapes of Comparative Examples B-8 to B-10, the protective layer was formed by the magnetron sputtering method instead of the plasma CVD method as described above. Further, the partially fluorinated carboxylic acid alkyl ester contained in the lubricants of Comparative Examples B-11 to B-13 had a double bond.
[0363]
[Table 10]

[0364]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples B-1 to B-8 and Comparative Examples B-1 to B-13 were evaluated. Here, the durability and running performance were evaluated, and specifically, the friction coefficient, still durability and shuttle durability were evaluated. As the environmental conditions for evaluating these, the inventors considered the conditions and adopted the conditions considered to be the most severe conditions.
[0365]
1. Measurement method of friction coefficient
The friction coefficient was measured by controlling the environmental conditions in the thermostat at a temperature of 40 ° C. and a humidity of 80% RH, and running each sample tape in this thermostat for 100 passes. In addition, the numerical value of the 100th pass of friction running was defined as the friction coefficient.
2. Measurement method of still durability
The evaluation of the still durability was performed in a -5 ° C. constant temperature bath, and the time until the reproduction output of each sample tape dropped by 3 dB using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: DVC-VX1000). Was measured.
3 Measurement method of shuttle durability
Shuttle durability was controlled by controlling the environmental conditions in a thermostat to a temperature of 40 ° C. and a humidity of 20% RH. Each sample tape was run for 100 pass shuttles, and after running for 100 passes, how many dB the reproduction output dropped from the initial output was measured and evaluated.
[0366]
These evaluations were performed immediately after the lubricant was applied and after each sample tape was stored for 30 days in an environment of a temperature of 45 ° C. and a humidity of 80% RH. Table 11 shows the measurement results of the initial durability and running properties immediately after the application of the lubricant, and Table 12 shows the measurement results of the durability and running properties after storage after storage for 30 days.
[0367]
[Table 11]

[0368]
[Table 12]

[0369]
From the results shown in Tables 11 and 12, the surface of the protective layer formed by the CVD method was top-coated with an aromatic amine, and further, as a lubricant, an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid. In Examples B-1 to B-8 using a lubricant in combination with a partially fluorinated carboxylic acid alkyl ester, the friction coefficient under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature It was found that the deterioration of the still durability and shuttle durability was extremely small, and very good results were obtained.
[0370]
On the other hand, in Comparative Examples B-1 and B-2 using a lubricant containing only an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid, the friction coefficient was varied under various use conditions. And the durability of the still and shuttle durability was very large.
[0371]
In Comparative Examples B-3 to B-10, in which the aromatic amine was not applied to the surface of the protective layer, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various use conditions. , Good results could not be obtained. Further, when the protective layer was formed by a magnetron sputtering method, which is a PVD method, instead of the CVD method, sufficient durability was not obtained.
Furthermore, from the results of comparison between Example B-1 and Comparative Examples B-11 to B-13, the initial characteristics are maintained even after long-term storage by using a fluorocarboxylic acid alkyl ester having a saturated alkyl group. It turns out that it can be done.
[0372]
From the above results, the surface of the protective layer formed by the CVD method was treated with an aromatic amine, and further, as a lubricant, an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid; By combining with a carboxylic acid alkyl ester, excellent adhesion and lubricity are maintained under any use conditions, and the lubricating effect is maintained for a long period of time. It turned out to be obtained.
[0373]
[Experimental example B2 (Examples B-9 to B-16, Comparative examples B-14 to B-26)]
In this experimental example, the effect of using an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, and a lubricant containing a partially fluorinated carboxylic acid alkyl ester as follows. confirmed.
[0374]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal carboxyl group and long-chain alcohol
First, HOOCCF having a molecular weight of 2,000 was used as a perfluoropolyether having a carboxyl group at a terminal.₂(OC₂F₄)_m(OCF₂)_jOCF₂COOH (where m and j in the chemical formula each represent an integer of 1 or more) is used. A small amount of p-toluenesulfone is added to this perfluoropolyether in a molar amount twice as much as stearyl alcohol in anhydrous toluene. The mixture was heated to reflux using an acid and concentrated sulfuric acid as catalysts. At this time, the reaction was performed while removing generated water.
After completion of the reaction, toluene was removed, and the obtained compound was purified using silica gel column chromatography, and then the solvent was removed to obtain an ester compound. Here, this ester compound is referred to as compound B-6.
[0375]
Next, according to the same synthesis method as that of the above compound B-6, four kinds of compounds B-7 to 4 which are ester compounds of perfluoropolyether having a terminal carboxyl group and a long-chain alcohol as shown in Table 13 below. B-10 was synthesized. In Table 13, p, q, and n each represent an integer of 1 or more.
[0376]
[Table 13]

[0377]
2. Preparation of sample tape
First, a ferromagnetic metal thin film serving as a magnetic layer and a carbon protective layer were formed on a nonmagnetic support in the same manner as in Experimental Example B1, and a back coat layer was also formed. Further, the surface of the protective layer was coated with an aromatic amine dissolved in isopropyl alcohol at a coating amount of 2 mg / m 2 as shown in Table 14 below.²It applied so that it might become.
[0378]
Next, in the same manner as in Experimental Example B1, a solution in which a lubricant as shown in Table 14 below was dissolved in a hexane solvent was applied to the surface of the protective layer at a coating amount of 5 mg / m 2.²Thus, 21 types of magnetic recording media were obtained.
Then, these 21 types of magnetic recording media were cut into 6.35 mm widths, respectively, to produce 21 types of sample tapes of Examples B-9 to B-16 and Comparative Examples B-14 to B-26. did. However, for the sample tapes of Comparative Examples B-16 to B-20, no aromatic amine was applied to the surface of the protective layer. Further, with respect to the sample tapes of Comparative Examples B-18 to B-20, the protective layer was formed by the magnetron sputtering method without using the plasma CVD method as described above.
In addition, the fluorinated carboxylic acid alkyl esters of Comparative Examples B-24 to B-26 had a double bond.
[0379]
[Table 14]

[0380]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples B-9 to B-16 and Comparative Examples B-14 to B-26 were evaluated. Here, the durability and the running property were evaluated. Specifically, the friction coefficient, the still durability, and the shuttle durability were evaluated in the same manner as in Experimental Example B1.
These evaluations were performed immediately after the lubricant was applied in the same manner as in Experimental Example B1 and after each sample tape was stored for 30 days in an environment at a temperature of 45 ° C. and a humidity of 80% RH. Table 15 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 16 shows the results of the durability and running properties after storage after storage for 30 days.
[0381]
[Table 15]

[0382]
[Table 16]

[0383]
From the results in Tables 15 and 16, the surface of the protective layer formed by the CVD method was top-coated with an aromatic amine, and an ester compound of a perfluoropolyether having a carboxyl group at a terminal as a lubricant and a long-chain alcohol was used as a lubricant. In Examples B-9 to B-16 in which a lubricant in combination with a fluorocarboxylic acid alkyl ester was used, the friction coefficient and the stillness under various use conditions such as high temperature and high humidity, high temperature and low humidity, and low temperature were all used. It was found that there was very little deterioration in durability and shuttle durability, and very good results were obtained.
[0384]
On the other hand, in Comparative Examples B-14 and B-15 using a lubricant containing only an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, the friction coefficient was varied under various use conditions. And the durability of the still and shuttle durability was very large.
In Comparative Examples B-16 to B-23 in which the aromatic amine was not applied to the surface of the protective layer, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various use conditions. , Good results could not be obtained.
Further, when the protective layer was formed by a magnetron sputtering method, which is a PVD method, instead of the CVD method, sufficient durability was not obtained.
Furthermore, from the comparison results of Example B-9 and Comparative Examples B-24 to B-26, the use of the fluorocarboxylic acid alkyl ester having a saturated alkyl group maintains the initial properties even after long-term storage. It turns out that it can be done.
[0385]
[Experimental example B3 (Examples B-17 to B-26, Comparative examples B-27 to B-37)]
The method for synthesizing an ester compound of a perfluoropolyether having a hydroxyl group at the 1-terminal and a long-chain carboxylic acid was performed in the same manner as in Experiment B1.
2. Preparation of sample tape
First, a ferromagnetic metal thin film serving as a magnetic layer and a carbon protective layer were formed on a nonmagnetic support by a plasma CVD method in the same manner as in Experimental Example B1, and a back coat layer was also formed.
[0386]
Next, as shown in Table 17 below, a solution obtained by dissolving an aromatic amine in isopropyl alcohol was applied onto the carbon protective layer at a coating amount of 2 mg / m 2.²It applied so that it might become. Next, the compounds shown in Table 17 below were dissolved in a hexane solvent, and the weight ratio of the ester compounds of perfluoropolyether and long-chain carboxylic acid to the compounds B-1 to B-5 was 95: 5 to 95: 5, respectively. 5:95, and a coating amount of 0.03 to 120 mg / m.²To obtain 21 types of magnetic recording media.
[0387]
Then, each of these 21 types of magnetic recording media was cut into a 6.35 mm width to obtain 21 types of sample tapes of Examples B-17 to B-26 and Comparative Examples B-27 to B-37. did. However, for the sample tapes of Comparative Examples B-36 to B-37, no aromatic amine was applied to the surface of the protective layer.
[0388]
[Table 17]

[0389]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples B-17 to B-26 and Comparative Examples B-27 to B-37 were evaluated. Here, the durability and the running property were evaluated. Specifically, the friction coefficient, the still durability, and the shuttle durability were evaluated in the same manner as in Experimental Example B1.
These evaluations were performed immediately after the lubricant was applied in the same manner as in Experimental Example B1 and after each sample tape was stored for 30 days in an environment at a temperature of 45 ° C. and a humidity of 80% RH. Table 18 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 19 shows the results of the durability and running properties after storage after storage for 30 days.
[0390]
[Table 18]

[0391]
[Table 19]

[0392]
From the results shown in Tables 18 and 19, the surface of the protective layer formed by the CVD method is top-coated with an aromatic amine, and an ester compound of a perfluoropolyether having a hydroxyl group at a terminal as a lubricant and a long-chain carboxylic acid And a partially fluorinated carboxylic acid alkyl ester in a combination amount of 0.1 to 100 mg / m²,
By applying the ester compound and the partially fluorinated carboxylic acid alkyl ester in a weight ratio of 90:10 to 10:90, the friction coefficient can be increased under various conditions of use such as high temperature and high humidity, high temperature and low humidity, or low temperature. It was found that deterioration in still durability and shuttle durability was extremely small, and very good results were obtained.
[0393]
On the other hand, as shown in Comparative Examples B-27, B-28 and B-35, in the combination of an ester compound of a perfluoropolyether having a hydroxyl group at a terminal with a long-chain carboxylic acid and a partially fluorinated carboxylic acid alkyl ester , The coating amount is 0.01 to 100 mg / m²When applied in a numerical range other than the above, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various use conditions, and good results were not obtained.
[0394]
Further, Comparative Examples B-31 and B-32 using a lubricant containing only an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain alcohol, and a partially fluorinated carboxylic acid alkyl ester were used. In Comparative Examples B-29, B-30, B-33, and B-34, which were applied in a numerical range other than 90:10 to 10:90 in the combination, the friction coefficient and the still durability under various use conditions were improved. Shuttle durability was greatly deteriorated, and good results were not obtained.
[0395]
In Comparative Examples B-36 and B-37 in which the aromatic amine was not applied to the surface of the protective layer, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various use conditions. , Good results could not be obtained.
[0396]
Based on the above results, the surface of the protective layer formed by the CVD method was top-coated with an aromatic amine, and further, as a lubricant, an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, and a fluorocarboxylic acid. By applying in combination with the acid alkyl ester and optimizing the coating amount and weight ratio, the adhesion and lubricity of the lubricant can be maintained under any use conditions, and the lubrication effect can be maintained for a long period of time. Therefore, it was found that good running properties and durability of the magnetic recording medium were obtained.
[0397]
[Experimental example C1 (Examples C-1 to C-8, Comparative examples C-1 to C-13)]
In this experimental example, the effect of using an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a lubricant containing a partially fluorinated carboxylic acid alkyl ester was confirmed as follows. did.
[0398]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal hydroxyl group and long-chain carboxylic acid
First, HOCH having a molecular weight of 2000 was used as a perfluoropolyether having a hydroxyl group at a terminal.₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂Using OH (where p and q each represent an integer of 1 or more in the chemical formula), triethylamine, which is twice the molar amount of this perfluoropolyether in an organic solvent, is dissolved in an organic solvent. Further, stearic acid chloride in an amount twice as much as the molar ratio was added dropwise over 30 minutes.
After the completion of the dropwise addition, the mixture was stirred for 1 hour, and then heated under reflux for 30 minutes. And after cooling, it wash | cleaned in order of distilled water and dilute hydrochloric acid aqueous solution, and wash | cleaned again with distilled water until the washing | cleaning liquid became neutral. Subsequently, the organic solvent was removed, and the obtained compound was purified using silica gel column chromatography to obtain an ester compound. Here, this ester compound is referred to as compound C-1.
[0399]
Next, according to a synthesis method similar to that of the above-mentioned compound C-1, four kinds of compounds C-2 to 4 are ester compounds of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid as shown in Table 20 below. C-5 was synthesized. In Table 20, p, q, and n each represent an integer of 1 or more.
[0400]
[Table 20]

[0401]
2. Preparation of sample tape
Next, a magnetic tape was produced as follows. First, Co is applied to a 7.0 μm-thick polyethylene terephthalate film as a non-magnetic support by oblique evaporation using the above-described vacuum evaporation apparatus, and a ferromagnetic metal thin film serving as a magnetic layer is formed to a thickness of 180 nm. Formed.
Next, a DC voltage of -1.5 kV was applied to the ferromagnetic metal thin film by applying high-frequency plasma of a mixed gas of ethylene and argon to the electrode and the magnetic recording medium raw material as a counter electrode, thereby discharging the raw material. Was performed to form a carbon protective layer having a thickness of about 8 nm on the ferromagnetic metal thin film.
Next, a 0.5 μm-thick back coat layer made of carbon and polyurethane resin was formed on the surface of the polyethylene terephthalate film opposite to the surface on which the ferromagnetic metal thin film was formed.
[0402]
Next, as shown in Table 21 below, a solution obtained by dissolving an aromatic carboxylic acid in isopropyl alcohol was coated on the carbon protective layer at a coating amount of 2 mg / m 2.²It applied so that it might become.
Next, each of the compounds shown in Table 21 below dissolved in a hexane solvent was coated on the carbon protective layer at a coating amount of 5 mg / m 2.²To obtain 21 types of magnetic recording media.
Then, each of these 21 types of magnetic recording media was cut into a 6.35 mm width, and 21 types of sample tapes of Examples C-1 to C-8 and Comparative Examples C-1 to C-13 were cut. did.
[0403]
However, for the sample tapes of Comparative Examples C-3 to C-10, the surface of the protective layer was not top-coated with the aromatic carboxylic acid. Further, with respect to the sample tapes of Comparative Examples C-8 to C-10, the protective layer was formed by the magnetron sputtering method instead of the plasma CVD method as described above.
Further, the partially fluorinated carboxylic acid alkyl esters of Comparative Examples C-11 to C-13 had a double bond.
[0404]
[Table 21]

[0405]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples C-1 to C-8 and Comparative Examples C-1 to C-13 were evaluated. Here, the durability and the running property were evaluated, and specifically, the coefficient of friction, still durability and shuttle durability were evaluated. As the environmental conditions for evaluating these, the inventors considered the conditions and adopted the conditions considered to be the most severe conditions.
[0406]
1. Measurement method of friction coefficient
The friction coefficient was measured by controlling the environmental conditions in the thermostat at a temperature of 40 ° C. and a humidity of 80% RH, and running each sample tape in this thermostat for 100 passes. In addition, the numerical value of the 100th pass of friction running was defined as the friction coefficient.
2. Measurement method of still durability
The evaluation of the still durability was performed in a -5 ° C. constant temperature bath, and the time until the reproduction output of each sample tape dropped by 3 dB using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: DVC-VX1000). Was measured.
3 Measurement method of shuttle durability
Shuttle durability was controlled by controlling the environmental conditions in a thermostat to a temperature of 40 ° C. and a humidity of 20% RH. Each sample tape was run for 100 pass shuttles, and after running for 100 passes, how many dB the reproduction output dropped from the initial output was measured and evaluated.
[0407]
These evaluations were performed immediately after the lubricant was applied and after each sample tape was stored for 30 days in an environment of a temperature of 45 ° C. and a humidity of 80% RH. Table 22 shows the measurement results of the initial durability and running properties immediately after the application of the lubricant, and Table 23 shows the measurement results of the durability and running properties after storage after storage for 30 days.
[0408]
[Table 22]

[0409]
[Table 23]

[0410]
From the results in Tables 22 and 23, the surface of the protective layer formed by the CVD method was top-coated with an aromatic carboxylic acid, and further, as a lubricant, an ester of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid. In Examples C-1 to C-8 using a combination of a compound and a partially fluorinated carboxylic acid alkyl ester, the coefficient of friction under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature It was found that the deterioration of the still durability and shuttle durability was extremely small, and very good results were obtained.
[0411]
On the other hand, in Comparative Examples C-1 and C-2 using a lubricant containing only an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid, the friction coefficient was changed under various use conditions. And the durability of the still and shuttle durability was very large.
Further, in Comparative Examples C-3 to C-10 in which the surface of the protective layer was not top-coated with an aromatic carboxylic acid, the friction coefficient, still durability, and shuttle durability deteriorated under various use conditions. And good results were not obtained.
Further, when the protective layer was formed by a magnetron sputtering method, which is a PVD method, instead of the CVD method, sufficient durability was not obtained.
[0412]
Furthermore, from the comparison results of Example C-1 and Comparative Examples C-11 to C-13, the use of the alkyl fluorinated carboxylate having no unsaturated bond enables the initial properties even after long-term storage. Was found to be able to be maintained.
[0413]
From the above results, the protective layer surface formed by the CVD method is top-coated with an aromatic carboxylic acid, and further, as a lubricant, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid, By combining with a partially fluorinated carboxylic acid alkyl ester, the lubricating agent maintains adhesion and lubricity under any use conditions and maintains a lubricating effect for a long period of time. And durability was obtained.
[0414]
[Experimental example C2 (Examples C-9 to C-16, Comparative examples C-14 to C-26)]
In this experimental example, the effect of using an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, and a lubricant containing a partially fluorinated carboxylic acid alkyl ester as follows. confirmed.
[0415]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal carboxyl group and long-chain alcohol
First, HOOCCF having a molecular weight of 2,000 was used as a perfluoropolyether having a carboxyl group at a terminal.₂(OC₂F₄)_m(OCF₂)_jOCF₂COOH (where m and j in the chemical formula each represent an integer of 1 or more) is used. A small amount of p-toluenesulfone is added to this perfluoropolyether in a molar amount twice as much as stearyl alcohol in anhydrous toluene. The mixture was heated to reflux using an acid and concentrated sulfuric acid as catalysts. At this time, the reaction was performed while removing generated water.
After completion of the reaction, toluene was removed, and the obtained compound was purified using silica gel column chromatography, and then the solvent was removed to obtain an ester compound. Here, this ester compound is referred to as compound C-6.
[0416]
Next, according to the same synthesis method as in the above-mentioned compound C-6, four kinds of compounds C-7 to C-4 which are ester compounds of perfluoropolyether having a terminal carboxyl group and a long-chain alcohol as shown in Table 24 below -10 was synthesized. In Table 24, p, q, and n each represent an integer of 1 or more.
[0417]
[Table 24]

[0418]
2. Preparation of sample tape
First, a ferromagnetic metal thin film serving as a magnetic layer and a carbon protective layer were formed on a non-magnetic support by a plasma CVD method in the same manner as in Experimental Example C1, and a back coat layer was also formed. Further, the surface of the protective layer was coated with an aromatic carboxylic acid dissolved in isopropyl alcohol at a coating amount of 2 mg / m 2 as shown in Table 25 below.²It applied so that it might become.
[0419]
Next, in the same manner as in the above-mentioned Experimental Example C1, a solution in which a lubricant as shown in Table 25 below was dissolved in a hexane solvent was applied onto the surface of the protective layer at a coating amount of 5 mg / m 2.²Thus, 21 types of magnetic recording media were obtained.
[0420]
Then, these 21 types of magnetic recording media were cut into 6.35 mm widths, respectively, to produce 21 types of sample tapes of Examples C-9 to C-16 and Comparative Examples C-14 to C-26. did. However, for the sample tapes of Comparative Examples C-16 to 23, no aromatic carboxylic acid was applied to the surface of the protective layer.
Further, with respect to the sample tapes of Comparative Examples 18 to 20, the protective layer was formed by the magnetron sputtering method instead of the plasma CVD method as described above.
In addition, as the fluorocarboxylic acid alkyl esters of Comparative Examples 24 to 26, those having a double bond were used.
[0421]
[Table 25]

[0422]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples C-9 to C-16 and Comparative examples C-14 to C-26 were evaluated. Here, the durability and the running property were evaluated. Specifically, the friction coefficient, the still durability, and the shuttle durability were evaluated in the same manner as in Experimental Example C1 described above.
These evaluations were performed immediately after the lubricant was applied in the same manner as in Experimental Example C1 and after each sample tape was stored for 30 days in an environment at a temperature of 45 ° C. and a humidity of 80% RH. Table 26 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 27 shows the results of the durability and running properties after storage after storage for 30 days.
[0423]
[Table 26]

[0424]
[Table 27]

[0425]
From the results in Tables 26 and 27 above, the surface of the protective layer formed by the CVD method was top-coated with aromatic carboxylic acid, and as a lubricant, a perfluoropolyether having a carboxyl group at the end and a long-chain alcohol were used. In Examples C-9 to C-16 using a lubricant in which an ester compound and a fluorocarboxylic acid alkyl ester were used in combination, all of the friction under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature was used. It was found that the deterioration of the coefficient, still durability and shuttle durability was extremely small, and very good results were obtained.
[0426]
On the other hand, in Comparative Examples C-14 and C-15 using a lubricant containing only an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, the friction coefficient was varied under various use conditions. And the durability of the still and shuttle durability was very large. Moreover, in Comparative Examples C-16 to C-23 in which the aromatic carboxylic acid was not applied to the surface of the protective layer, the friction coefficient, still durability, and shuttle durability deteriorated under various use conditions. Large and good results were not obtained. Further, even when the protective layer was formed by a magnetron sputtering method, which is a PVD method, instead of the CVD method, sufficient durability was not obtained.
Further, from the results of comparison between Example C-9 and Comparative Examples C-24 to C-26, the use of the alkyl fluorinated carboxylate having no unsaturated bond enables the initial properties even after long-term storage. Was found to be able to be maintained.
[0427]
[Experimental example C3 (Examples C-17 to C-26, Comparative examples C-27 to C-37)]
The method for synthesizing an ester compound of a perfluoropolyether having a hydroxyl group at the 1-terminal and a long-chain carboxylic acid was carried out in the same manner as in Experimental Example C1 described above.
[0428]
2. Preparation of sample tape
First, a ferromagnetic metal thin film serving as a magnetic layer and a carbon protective layer were formed on a non-magnetic support by a plasma CVD method in the same manner as in Experimental Example C1, and a back coat layer was also formed.
Next, as shown in Table 28 below, an aromatic carboxylic acid dissolved in isopropyl alcohol was coated on the carbon protective layer at a coating amount of 2 mg / m 2.²It applied so that it might become.
Next, a solution of each of the compounds shown in Table 28 below in a hexane solvent was coated on the carbon protective layer in an amount of 0.03 to 120 mg / m 2.²The weight ratio of the above-mentioned ester compound to the partially fluorinated carboxylic acid alkyl ester was in the range of 95: 5 to 5:95, respectively, or applied alone to obtain 21 types of magnetic recording media.
Then, each of these 21 types of magnetic recording media was cut into 6.35 mm widths, and 21 types of sample tapes of Examples C-17 to C-26 and Comparative Examples C-27 to C-37 were cut. did.
[0429]
[Table 28]

[0430]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples C-17 to C-26 and Comparative Examples C-27 to C-37 were evaluated. Here, the durability and the running property were evaluated. Specifically, the friction coefficient, the still durability, and the shuttle durability were evaluated in the same manner as in Experimental Example C1 described above.
These evaluations were performed immediately after the lubricant was applied in the same manner as in Experimental Example C1 and after each sample tape was stored for 30 days in an environment at a temperature of 45 ° C. and a humidity of 80% RH. Table 29 shows the results of the initial durability and running properties immediately after the application of the lubricant, and Table 30 shows the results of the durability and running properties after storage after storage for 30 days.
[0431]
[Table 29]

[0432]
[Table 30]

[0433]
From the results shown in Tables 29 and 30, the surface of the protective layer formed by the CVD method was top-coated with an aromatic carboxylic acid, and as a lubricant, a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid were used. A combination of an ester compound and a partially fluorinated carboxylic acid alkyl ester is used, and the coating amount is 0.1 to 100 mg / m²Example C wherein a weight ratio of an ester compound of a perfluoropolyether having a hydroxyl group at a terminal to a long-chain carboxylic acid and a partially fluorinated carboxylic acid alkyl ester is 90:10 to 10:90. In Examples -17 to C-26, the friction coefficient, still durability, and shuttle durability deteriorated very little under various use conditions such as high temperature and high humidity, high temperature and low humidity, and low temperature, and very good results were obtained. I knew it was being done.
[0434]
On the other hand, as shown in Comparative Examples C-27, C-28 and C-35 to C-37, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a partially fluorinated carboxylic acid alkyl ester Is 0.1 to 1 to 100 mg / m²Those having a numerical value range other than the above exhibited a large deterioration in the coefficient of friction, still durability, and shuttle durability under various use conditions, and did not provide good results.
[0435]
Comparative Examples C-31 and C-32 using a lubricant containing only an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain alcohol, and a perfluoropolyether having a hydroxyl group at a terminal Comparative Example C-29, Comparative Example C-30, Comparative Example C in which the weight ratio of these in the combination of and a partially fluorinated carboxylic acid alkyl ester was used in a numerical range other than 90:10 to 10:90. In -33 and Comparative Example C-34, the friction coefficient, still durability, and shuttle durability deteriorated greatly under various use conditions, and good results were not obtained.
[0436]
From the above results, the surface of the protective layer formed by the CVD method was top-coated with an aromatic carboxylic acid, and an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol was used as a lubricant. Adhesion and lubricity are maintained under any conditions of use, and the lubricating effect is maintained over a long period of time by using a combination with a carboxylic acid alkyl ester and optimizing the coating amount and weight ratio. , The good running property and durability of the magnetic recording medium can be obtained.
[0437]
[Experimental Example D (Examples D-1 to D-8, Comparative Examples D-1 to D-13)]
In this experimental example, the effect of using an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a lubricant containing a partially fluorinated carboxylic acid alkyl ester was confirmed as follows. did.
[0438]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal hydroxyl group and long-chain carboxylic acid
First, HOCH having a molecular weight of 2000 was used as a perfluoropolyether having a hydroxyl group at a terminal.₂CF₂(OC₂F₄)_p(OCF₂)_qOCF₂CH₂Using OH (where p and q each represent an integer of 1 or more in the chemical formula), triethylamine, which is twice the molar amount of this perfluoropolyether in an organic solvent, is dissolved in an organic solvent. Further, stearic acid chloride in an amount twice as much as the molar ratio was added dropwise over 30 minutes.
After the completion of the dropwise addition, the mixture was stirred for 1 hour, and then heated under reflux for 30 minutes. And after cooling, it wash | cleaned in order of distilled water and dilute hydrochloric acid aqueous solution, and wash | cleaned again with distilled water until the washing | cleaning liquid became neutral. Subsequently, the organic solvent was removed, and the obtained compound was purified using silica gel column chromatography to obtain an ester compound. Here, this ester compound is referred to as compound D-1.
[0439]
Next, according to the same synthesis method as that of the above-mentioned compound D-1, four kinds of compounds D-2 to D which are ester compounds of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid as shown in Table 31 -5 was synthesized. In Table 31, p, q, and n each represent an integer of 1 or more.
[0440]
[Table 31]

[0441]
2. Preparation of sample tape
Next, a magnetic tape was produced as follows. First, Co is applied to a 7.0 μm-thick polyethylene terephthalate film as a non-magnetic support by oblique evaporation using the above-described vacuum evaporation apparatus, and a ferromagnetic metal thin film serving as a magnetic layer is formed to a thickness of 180 nm. Formed.
Next, on the ferromagnetic metal thin film, a high-frequency plasma of a mixed gas of ethylene and argon was used to apply a DC voltage of -1.5 kV to the raw material, using the raw material of the magnetic recording medium itself as a counter electrode, Discharge was performed to form a carbon protective layer having a thickness of about 8 nm on the ferromagnetic metal thin film.
Next, on the surface of the polyethylene terephthalate film opposite to the surface on which the ferromagnetic metal thin film was formed, a back coat layer of carbon and polyurethane resin having a thickness of 0.5 μm was formed.
[0442]
Next, the surface of the protective layer was irradiated with ultraviolet rays using the ultraviolet ray irradiation device 20 as shown in FIG. 2 under the conditions shown in Table 32 below. The wavelength of the ultraviolet light was 185 nm, and the irradiation time of the ultraviolet light was controlled by the line speed of the magnetic recording medium.
Next, each of the compounds shown in Table 32 dissolved in a hexane solvent was coated on the carbon protective layer at a coating amount of 5 mg / m 2.²To obtain 21 types of magnetic recording media.
Then, each of these 21 types of magnetic recording media was cut into a 6.35 mm width, and 21 types of sample tapes of Example D-1 to Example D-8 and Comparative Example D-1 to Comparative Example D-13 were cut. did.
[0443]
However, with respect to the sample tapes of Comparative Examples D-3 to D-10, the surface of the protective layer was not subjected to the ultraviolet irradiation treatment. Further, the partially fluorinated carboxylic acid alkyl esters of Comparative Examples D-11 to D-13 had an unsaturated bond.
[0444]
[Table 32]

[0445]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples D-1 to D-8 and Comparative Examples D-1 to D-13 were evaluated. Here, the durability and the running property were evaluated, and specifically, the coefficient of friction, still durability and shuttle durability were evaluated. As the environmental conditions for evaluating these, the inventors considered the conditions and adopted the conditions considered to be the most severe conditions.
[0446]
1. Measurement method of friction coefficient
The friction coefficient was measured by controlling the environmental conditions in the thermostat at a temperature of 40 ° C. and a humidity of 80% RH, and running each sample tape in this thermostat for 100 passes. In addition, the numerical value of the 100th pass of friction running was defined as the friction coefficient.
2. Measurement method of still durability
The evaluation of the still durability was performed in a -5 ° C. constant temperature bath, and the time until the reproduction output of each sample tape dropped by 3 dB using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: DVC-VX1000). Was measured.
3 Measurement method of shuttle durability
Shuttle durability was controlled by controlling the environmental conditions in a thermostat to a temperature of 40 ° C. and a humidity of 20% RH. Each sample tape was run for 100 pass shuttles, and after running for 100 passes, how many dB the reproduction output dropped from the initial output was measured and evaluated.
[0447]
These evaluations were performed immediately after the lubricant was applied and after each sample tape was stored for 30 days in an environment of a temperature of 45 ° C. and a humidity of 80% RH. Table 33 shows the measurement results of the initial durability and running properties immediately after the application of the lubricant, and Table 34 shows the measurement results of the durability and running properties after storage after storage for 30 days.
[0448]
[Table 33]

[0449]
[Table 34]

[0450]
From the results shown in Tables 33 and 34, the surface of the protective layer was subjected to ultraviolet irradiation treatment, and further, as a lubricant, an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a partially fluoroalkyl carboxylate In Examples D-1 to D-8 using a combination of the above, the friction coefficient, still durability and shuttle durability under various use conditions such as high temperature and high humidity, high temperature and low humidity, or low temperature were all used. It was found that the deterioration was extremely small and very good results were obtained.
[0451]
On the other hand, in Comparative Examples D-1 and D-2 using a lubricant containing only an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid, the friction coefficient was changed under various use conditions. And the durability of the still and shuttle durability was very large.
Further, in Comparative Examples D-3 to D-10 in which the surface of the protective layer was not irradiated with ultraviolet rays, the friction coefficient, still durability, and shuttle durability were greatly deteriorated under various use conditions. Was not obtained.
Furthermore, from the comparison results of Example D-1 and Comparative Examples D-11 to D-13, by using a long-chain saturated fatty acid having no unsaturated bond, the initial properties are maintained even after long-term storage. I found that I could do it.
[0452]
From the above results, the protective layer surface was irradiated with ultraviolet light, and further, as a lubricant, a combination of an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid and a partially fluorinated carboxylic acid alkyl ester By using, the lubricant maintains the adhesion and lubricity under any use conditions, and since the lubrication effect is maintained for a long time, it is possible to obtain a good running property and durability of the magnetic recording medium. all right.
[0453]
[Experimental Example E (Examples E-1 to E-8, Comparative Examples E-1 to E-13)]
In this experimental example, the effect of using a lubricant containing an ester compound of a perfluoropolyether having a carboxyl group at the end and a long-chain alcohol, and a partially fluorinated carboxylic acid alkyl ester is as follows. confirmed.
[0454]
(Preparation of sample)
Synthesis of ester compound of perfluoropolyether having 1-terminal carboxyl group and long-chain alcohol
First, HOOCCF having a molecular weight of 2,000 was used as a perfluoropolyether having a carboxyl group at a terminal.₂(OC₂F₄)_p(OCF₂)_qOCF₂Using COOH (where p and q each represent an integer of 1 or more in the chemical formula), stearyl alcohol, which is twice the molar amount of this perfluoropolyether, is mixed with a small amount of p-toluenesulfone in anhydrous toluene. The mixture was heated to reflux using an acid and concentrated sulfuric acid as catalysts. At this time, the reaction was performed while removing generated water.
After the reaction, toluene was removed, and the obtained compound was purified using silica gel column chromatography, and then the solvent was removed to obtain an ester compound. Here, this ester compound is referred to as compound E-1.
[0455]
Next, according to the same synthesis method as that of the compound E-1, four kinds of compounds E-2 to E which are ester compounds of a perfluoropolyether having a terminal carboxyl group and a long-chain alcohol as shown in Table 35 below. -5 was synthesized. In Table 35, p, q, and n each represent an integer of 1 or more.
[0456]
[Table 35]

[0457]
2. Preparation of sample tape
Next, a magnetic tape was produced as follows. First, Co is applied to a 7.0 μm-thick polyethylene terephthalate film as a non-magnetic support by oblique evaporation using the above-described vacuum evaporation apparatus, and a ferromagnetic metal thin film serving as a magnetic layer is formed to a thickness of 180 nm. Formed.
Next, a DC voltage of -1.5 kV was applied to the ferromagnetic metal thin film by applying high-frequency plasma of a mixed gas of ethylene and argon to the electrode and the magnetic recording medium raw material as a counter electrode, thereby discharging the raw material. Was performed to form a carbon protective layer having a thickness of about 8 nm on the ferromagnetic metal thin film.
Next, a 0.5 μm-thick back coat layer made of carbon and polyurethane resin was formed on the surface of the polyethylene terephthalate film opposite to the surface on which the ferromagnetic metal thin film was formed.
[0458]
Next, the surface of the protective layer was subjected to an ultraviolet irradiation treatment using an ultraviolet irradiation apparatus 20 as shown in FIG. The wavelength of the ultraviolet light was 185 nm, and the irradiation time of the ultraviolet light was controlled by the line speed of the magnetic recording medium.
Next, each of the compounds shown in Table 36 dissolved in a hexane solvent was coated on the carbon protective layer at a coating amount of 5 mg / m 2.²To obtain 21 types of magnetic recording media.
Then, each of these 21 types of magnetic recording media was cut into a 6.35 mm width, and 21 types of sample tapes of Examples E-1 to E-8 and Comparative Examples E-1 to E-13 were cut. did.
However, with respect to the sample tapes of Comparative Examples E-3 to E-10, the surface of the protective layer was not subjected to the ultraviolet irradiation treatment. Further, the partially fluorinated carboxylic acid alkyl esters of Comparative Examples E-11 to E-13 had an unsaturated bond.
[0459]
[Table 36]

[0460]
3) Evaluation of characteristics
Next, the characteristics of the 21 types of sample tapes of Examples E-1 to E-8 and Comparative Examples E-1 to E-13 were evaluated. Here, the durability and the running property were evaluated, and specifically, the coefficient of friction, still durability and shuttle durability were evaluated. As the environmental conditions for evaluating these, the inventors considered the conditions and adopted the conditions considered to be the most severe conditions.
[0461]
1. Measurement method of friction coefficient
The friction coefficient was measured by controlling the environmental conditions in the thermostat at a temperature of 40 ° C. and a humidity of 80% RH, and running each sample tape in this thermostat for 100 passes. In addition, the numerical value of the 100th pass of friction running was defined as the friction coefficient.
2. Measurement method of still durability
The evaluation of the still durability was performed in a -5 ° C. constant temperature bath, and the time until the reproduction output of each sample tape dropped by 3 dB using a commercially available digital video camcorder (manufactured by Sony Corporation, model name: DVC-VX1000). Was measured.
3 Measurement method of shuttle durability
Shuttle durability was controlled by controlling the environmental conditions in a thermostat to a temperature of 40 ° C. and a humidity of 20% RH. Each sample tape was run for 100 pass shuttles, and after running for 100 passes, how many dB the reproduction output dropped from the initial output was measured and evaluated.
[0462]
These evaluations were performed immediately after the lubricant was applied and after each sample tape was stored for 30 days in an environment of a temperature of 45 ° C. and a humidity of 80% RH. The measurement results of the initial durability and running properties immediately after the application of the lubricant are shown in Table 37 below, and the measurement results of the durability and running properties after storage after storage for 30 days are shown in Table 38 below.
[0463]
[Table 37]

[0464]
[Table 38]

[0465]
From the results in Tables 37 and 38, the surface of the protective layer was subjected to ultraviolet irradiation treatment, and further, as a lubricant, an ester compound of perfluoropolyether having a terminal carboxyl group and a long-chain alcohol, and an alkyl partially fluorocarboxylate. In Examples E-1 to E-8 using a combination with an ester, the friction coefficient, still durability and shuttle durability under various use conditions such as high temperature and high humidity, high temperature and low humidity, and low temperature were all used. It was found that there was very little deterioration of the sample and very good results were obtained.
[0466]
On the other hand, in Comparative Examples E-1 and E-2 using a lubricant containing only an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, the friction coefficient was varied under various use conditions. And the durability of the still and shuttle durability was very large.
Further, in Comparative Examples E-3 to E-10 in which the surface of the protective layer was not subjected to the ultraviolet irradiation treatment, the friction coefficient, the still durability, and the shuttle durability were greatly deteriorated under various conditions of use, and the good results were obtained. No results were obtained.
Furthermore, from the results of comparison between Example E-1 and Comparative Examples E-11 to E-13, the use of a partially fluorinated carboxylic acid alkyl ester having no unsaturated bond enables the initial properties even after long-term storage. Was found to be able to be maintained.
[0467]
From the above results, the surface of the protective layer was irradiated with ultraviolet light, and further, as a lubricant, an ester compound of a perfluoropolyether having a carboxyl group at a terminal and a long-chain alcohol, and a partially fluorinated carboxylic acid alkyl ester were combined. By applying the lubricant, good adhesion and lubricity are maintained under any use condition of the lubricant, and the lubrication effect is maintained for a long period of time, so that good running property and durability of the magnetic recording medium can be obtained. I understand.
[0468]
【The invention's effect】
According to the magnetic recording medium of the first aspect, the surface of the carbon protective layer is top-coated with an aromatic alcohol, and an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid is formed on the carbon protective layer. And, by holding a lubricant containing a perfluorocarboxylic acid ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Adhesion and lubricity are suitably maintained even under use conditions, and good running properties and durability are secured over a long period of time.
[0469]
According to the magnetic recording medium of the second invention, the surface of the carbon protective layer is top-coated with an aromatic alcohol, and an ester compound of perfluoropolyether having a terminal carboxyl group and a long-chain alcohol on the carbon protective layer. And, by holding a lubricant containing a perfluorocarboxylic acid ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Adhesion and lubricity are suitably maintained even under use conditions, and good running properties and durability are secured over a long period of time.
[0470]
According to the magnetic recording medium of the third invention, the surface of the carbon protective layer is top-coated with an aromatic amine, and an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid is formed on the carbon protective layer. And, by holding a lubricant containing a partially fluorinated carboxylic acid alkyl ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Under any use conditions, the adhesion and lubricity are suitably maintained, and good running properties and durability are secured over a long period of time.
[0471]
According to the magnetic recording medium of the fourth aspect, the surface of the carbon protective layer is top-coated with an aromatic amine, and an ester compound of a perfluoropolyether having a terminal carboxyl group and a long-chain alcohol on the carbon protective layer. And, by holding a lubricant containing a partially fluorinated carboxylic acid alkyl ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0472]
According to the magnetic recording medium of the fifth invention, the surface of the carbon protective layer is top-coated with an aromatic carboxylic acid, and an ester of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid is formed on the carbon protective layer. By holding a compound and a lubricant containing a partially fluorinated carboxylic acid alkyl ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Therefore, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0473]
According to the magnetic recording medium of the sixth aspect, the surface of the carbon protective layer is top-coated with an aromatic carboxylic acid, and an ester of a perfluoropolyether having a terminal carboxyl group and a long-chain alcohol is formed on the carbon protective layer. By holding a compound and a lubricant containing a partially fluorinated carboxylic acid alkyl ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Therefore, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0474]
According to the magnetic recording medium of the seventh invention, the surface of the carbon protective layer is irradiated with ultraviolet light in an inert gas atmosphere, and a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid are formed on the protective layer. By holding the lubricant containing the ester compound and the partially fluorinated carboxylic acid alkyl ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Therefore, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are secured over a long period of time.
[0475]
According to the magnetic recording medium of the eighth invention, the surface of the carbon protective layer is irradiated with ultraviolet light in an inert gas atmosphere, and a perfluoropolyether having a terminal carboxyl group and a long-chain alcohol are formed on the protective layer. By holding a lubricant containing an ester compound and a partially fluorinated carboxylic acid alkyl ester, the adhesion between the protective layer and the lubricant is improved, and the lubricant is held in the outermost layer. Therefore, adhesion and lubricity are suitably maintained under any use conditions, and good running properties and durability are ensured for a long period of time.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a magnetic recording medium of the present invention.
FIG. 2 shows a schematic view of an ultraviolet irradiation apparatus.
FIG. 3 is a schematic sectional view of an example of a vacuum evaporation apparatus used for forming a magnetic layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic support, 2 ... Magnetic layer, 3 ... Protective layer, 4 ... Lubricant layer, 10 ... Magnetic recording medium, 20 ... Ultraviolet irradiation device, 21 ... Workpiece, 25 ... ... supply roll, 26 ... take-up roll, 27 ... ultraviolet ray processing unit, 28 ... housing, 29 ... guide roll, 40 ... vacuum evaporation apparatus, 41 ... vacuum chamber, 42 ... cooling can, 43 ... Evaporation source, 44 Supply roll, 45 Take-up roll, 47, 48 Guide roll, 49 Electron beam generation source, 50 Electron beam, 51 Anti-adhesion plate, 52 Shutter

Claims (43)

A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface that is top-coated with an aromatic alcohol,
The protective layer contains an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid shown in the following [Chemical Formula 1], and a perfluorocarboxylic acid ester shown in the following [Chemical Formula 2]. A magnetic recording medium comprising a lubricant held in an outermost layer.

(However, Rf represents a perfluoropolyether chain, and R ₁ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, n represents an integer of 6 to 10, and R represents an alkyl group of 9 to 25.) The mixing ratio between the ester compound of the perfluoropolyether having a hydroxyl group at the terminal represented by the above formula [1] and the long-chain carboxylic acid and the perfluorocarboxylic acid ester represented by the above formula [2] is 10% by weight. : 90 to 90:10. 2. The magnetic recording medium according to claim 1, wherein the number of carbon atoms of R in the perfluorocarboxylic acid ester represented by Chemical Formula 2 is 9 to 25. 2. The magnetic recording medium according to claim 1, wherein the magnetic layer is made of a ferromagnetic metal thin film. 2. The magnetic recording medium according to claim 1, wherein the protective layer is a carbon film. A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface that is top-coated with an aromatic alcohol,
The protective layer contains an ester compound of a perfluoropolyether having a terminal carboxyl group shown in the following [Chemical Formula 3] and a long-chain alcohol, and a perfluorocarboxylic acid ester shown in the following [Chemical Formula 4]. A magnetic recording medium comprising a lubricant held in an outermost layer.

(However, Rf ′ represents a perfluoropolyether chain, and R ₂ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, n represents an integer of 6 to 10, and R represents an alkyl group of 9 to 25.) The mixing ratio between the ester compound of the perfluoropolyether having a carboxyl group at the end represented by the above formula [Chemical Formula 3] and the long-chain alcohol and the perfluorocarboxylic acid ester represented by the formula [Chemical Formula 4] is 10% by weight. : 90 to 90:10. 7. The magnetic recording medium according to claim 6, wherein the number of carbon atoms of R in the perfluorocarboxylic acid ester represented by Chemical Formula 4 is 9 to 25. 7. The magnetic recording medium according to claim 6, wherein the magnetic layer is made of a ferromagnetic metal thin film. 2. The magnetic recording medium according to claim 1, wherein the protective layer is a carbon film. A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface top-coated with an aromatic amine,
The protective layer includes an ester compound of a perfluoropolyether having a terminal hydroxyl group and a long-chain carboxylic acid shown in the following [Chemical Formula 5] and a partially fluorinated carboxylic acid alkyl ester shown in the following [Chemical Formula 6]. A magnetic recording medium comprising a lubricant contained therein held in an outermost layer.

(However, Rf represents a perfluoropolyether chain, and R ₁ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.) The mixing ratio of the ester compound of the perfluoropolyether having a hydroxyl group at the terminal represented by the above formula [Chem. 5] and the long-chain carboxylic acid and the alkyl ester of the partially fluorinated carboxylic acid represented by the formula [Chem. The magnetic recording medium according to claim 11, wherein the ratio is 10:90 to 90:10. The total coating amount of the ester compound of the perfluoropolyether having a hydroxyl group at the end represented by the above formula [Chemical Formula 5] and the long-chain carboxylic acid and the partially fluorocarboxylic acid alkyl ester represented by the formula [Chemical Formula 6] is 0.1 the magnetic recording medium according to claim 11, characterized in that the -100 mg / ^{m 2.} The magnetic recording medium according to claim 11, wherein the magnetic layer is made of a ferromagnetic metal thin film. The magnetic recording medium according to claim 11, wherein the protective layer is a carbon film. The magnetic recording medium according to claim 11, wherein the protective layer is formed by a chemical vapor deposition method. A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface top-coated with an aromatic amine,
In the protective layer, an ester compound of a perfluoropolyether having a carboxyl group at a terminal shown in the following [Chemical Formula 7] and a long-chain alcohol, and an alkyl ester of a partially fluorinated carboxylic acid shown in the following [Chemical Formula 8] are used. A magnetic recording medium comprising a lubricant contained therein held in an outermost layer.

(However, Rf ′ represents a perfluoropolyether chain, and R ₁ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.) The mixing ratio of the ester compound of the perfluoropolyether having a carboxyl group at the terminal represented by the above formula [Chemical Formula 7] and the long-chain alcohol to the alkyl ester of the partially fluorinated carboxylic acid represented by the formula [Chem. The magnetic recording medium according to claim 17, wherein the ratio is from 10:90 to 90:10. 18. The magnetic recording medium according to claim 17, wherein the carbon number of R in the partially fluorinated carboxylic acid alkyl ester represented by Chemical Formula 8 is 7 to 21. 18. The magnetic recording medium according to claim 17, wherein the magnetic layer is made of a ferromagnetic metal thin film. The magnetic recording medium according to claim 17, wherein the protective layer is a carbon film. 18. The magnetic recording medium according to claim 17, wherein the protective layer is formed by a chemical vapor deposition method. A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface top-coated with an aromatic carboxylic acid,
The protective layer includes an ester compound of a perfluoropolyether having a hydroxyl group at a terminal represented by the following [Chemical Formula 9] and a long-chain carboxylic acid, and a partially fluorinated carboxylic acid alkyl ester represented by the following [Chemical Formula 10]. A magnetic recording medium comprising a lubricant contained therein held in an outermost layer.

(However, Rf represents a perfluoropolyether chain, and R ₁ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.) The mixing ratio of the ester compound of the perfluoropolyether having a hydroxyl group at the terminal shown in the above [Chemical Formula 9] and the long-chain carboxylic acid and the alkyl ester of the partially fluorinated carboxylic acid shown in the above [Chemical Formula 10] is represented by a weight ratio. 24. The magnetic recording medium according to claim 23, wherein the ratio is from 10:90 to 90:10. The total coating amount of the ester compound of a perfluoropolyether having a hydroxyl group at a terminal represented by the above formula [Chemical formula 9] and a long-chain carboxylic acid, and the alkyl ester of a partially fluorinated carboxylic acid represented by the formula [Chemical formula 10] is 0.1 the magnetic recording medium according to claim 23, characterized in that the -100 mg / ^{m 2.} The magnetic recording medium according to claim 23, wherein the magnetic layer is formed of a ferromagnetic metal thin film. The magnetic recording medium according to claim 23, wherein the protective layer is a carbon film. The magnetic recording medium according to claim 23, wherein the protective layer is formed by a chemical vapor deposition method. A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface top-coated with an aromatic carboxylic acid,
In the protective layer, an ester compound of a perfluoropolyether having a carboxyl group at a terminal shown in the following [Chemical Formula 11] and a long-chain alcohol, and a partially fluorinated carboxylic acid alkyl ester shown in the following [Chemical Formula 12] are used. A magnetic recording medium comprising a lubricant contained therein held in an outermost layer.

(However, Rf ′ represents a perfluoropolyether chain, and R ₂ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.) The mixing ratio of the ester compound of the perfluoropolyether having a carboxyl group at the end represented by the above formula [Chemical Formula 11] and the long-chain alcohol to the alkyl ester of the partially fluorinated carboxylic acid represented by the formula [Chem. 30. The magnetic recording medium according to claim 29, wherein the ratio is from 10:90 to 90:10. When the total coating amount of the ester compound of the perfluoropolyether having a carboxyl group at the terminal represented by the above formula [Chemical formula 11] and the long-chain alcohol, and the partially fluorinated carboxylic acid alkyl ester represented by the formula [Chemical formula 12] is 0.1 the magnetic recording medium according to claim 29, characterized in that the -100 mg / ^{m 2.} 30. The magnetic recording medium according to claim 29, wherein the carbon number of R in the partially fluorinated carboxylic acid alkyl ester represented by [Chemical Formula 12] is 7 to 21. 30. The magnetic recording medium according to claim 29, wherein the magnetic layer is made of a ferromagnetic metal thin film. The magnetic recording medium according to claim 29, wherein the protective layer is a carbon film. 30. The magnetic recording medium according to claim 29, wherein the protective layer is formed by a chemical vapor deposition method. A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface that is subjected to ultraviolet irradiation in an inert gas atmosphere,
The protective layer contains an ester compound of a perfluoropolyether having a hydroxyl group at a terminal and a long-chain carboxylic acid shown in the following [Chemical Formula 13], and a partially fluorinated carboxylic acid alkyl ester shown in the following [Chemical Formula 14]. A magnetic recording medium comprising a lubricant contained therein held in an outermost layer.

(However, Rf represents a perfluoropolyether chain, and R ₁ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.) The mixing ratio of the ester compound of the perfluoropolyether having a hydroxyl group at the terminal shown in the above [Chemical Formula 13] and the long-chain carboxylic acid and the alkyl ester of the partially fluorinated carboxylic acid shown in the above [Chemical Formula 14] is represented by a weight ratio. 37. The magnetic recording medium according to claim 36, wherein the ratio is from 10:90 to 90:10. 37. The magnetic recording medium according to claim 36, wherein the magnetic layer is made of a ferromagnetic metal thin film. The magnetic recording medium according to claim 36, wherein the protective layer is a carbon film. A magnetic recording medium having a magnetic layer and a protective layer on a non-magnetic support,
The protective layer has a surface that is subjected to ultraviolet irradiation in an inert gas atmosphere,
In the protective layer, an ester compound of a perfluoropolyether having a carboxyl group at a terminal shown in the following [Chemical Formula 15] and a long-chain alcohol, and an alkyl ester of a partially fluorinated carboxylic acid shown in the following [Chemical Formula 16] are used. A magnetic recording medium comprising a lubricant contained therein held in an outermost layer.

(However, Rf represents a perfluoropolyether chain, and R ₁ represents a hydrocarbon group or a fluorinated hydrocarbon group.)

(However, R represents an alkyl group having 7 to 21 carbon atoms, and m and n represent integers satisfying m + n ≧ 8.) The mixing ratio of the ester compound of the perfluoropolyether having a carboxyl group at the terminal shown in the above [Chemical Formula 15] and the long-chain alcohol, and the alkyl ester of the partially fluorinated carboxylic acid shown in the above [Chemical Formula 16] is represented by a weight ratio. The magnetic recording medium according to claim 40, wherein the ratio is from 10:90 to 90:10. The magnetic recording medium according to claim 40, wherein the magnetic layer is formed of a ferromagnetic metal thin film. The magnetic recording medium according to claim 40, wherein the protective layer is a carbon film.

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