JP2004310899A - Support base for magnetic recording medium - Google Patents
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- JP2004310899A JP2004310899A JP2003102563A JP2003102563A JP2004310899A JP 2004310899 A JP2004310899 A JP 2004310899A JP 2003102563 A JP2003102563 A JP 2003102563A JP 2003102563 A JP2003102563 A JP 2003102563A JP 2004310899 A JP2004310899 A JP 2004310899A
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、ポリエステルフイルムの表面にガスバリア層を設けた磁気記録媒体用支持体に関し、さらに詳しくは、寸法安定性に優れながらもスリット性に優れたポリエステルフイルムの表面にガスバリア層を設けた磁気記録媒体用支持体、特にリニア記録方式のデータストレージテープ用磁気記録媒体用支持体に関する。
【０００２】
【従来の技術】
ポリエステルフィルムは優れた熱、機械特性から磁気記録媒体用、電気絶縁用など広い分野で用いられている。中でも、磁気記録媒体用、特にデータストレージ用途においては、テープの高密度化、高容量化に伴ってベースフィルムへの特性要求も厳しいものとなっている。ＱＩＣ、ＤＬＴ、更に高容量のスーパーＤＬＴ、ＬＴＯ等、リニアトラック方式を採用するデータストレージ用途では、テープの高容量化を実現するために、線記録密度のアップ、トラック密度のアップ、テープの長尺化がなされており、平坦化、薄手化、高強度化、高寸法安定化が要求されている。
【０００３】
そこで、特開平１１−４８４３４号公報（特許文献１）や特開平１１−１３４６３９号公報（特許文献２）では、ポリエステル系プラスチックフィルムの両面に、金属、半金属および合金並びにこれらの酸化物および複合物から選ばれた金属材料からなる強化膜を設けて、支持体の薄膜化による剛性低下を補う、特に幅方向のヤング率が高い磁気記録媒体用支持体が提案されている。
【０００４】
しかしながら、これらの支持体を用いた磁気記録媒体は、走行耐久性および高温、高湿度環境下での記録再生性能にばらつきが生じやすく、工業製品としては必ずしも満足しないことが特開２００２−２６９７２５号公報（特許文献３）で開示されている。そして、これらの問題に対して、特許文献３では、ポリエステルフィルムの片側の表面Ｂ上に金属、半金属および合金並びにこれらの酸化物および複合物から選ばれた金属材料からなる強化膜を設け、かつ他方の表面ＡのＲａが１〜５ｎｍ、支持体の厚さが２〜６μｍ、長手方向のヤング率が５ＧＰａ以上、幅方向のヤング率が７．５ＧＰａ以上、すなわち幅方向のヤング率が極めて高い、湿度膨張係数が−１０〜１０ｐｐｍ／％ＲＨ、温度膨張係数が−１０〜１０ｐｐｍ／％ＲＨである支持体が提案されている。そして、特許文献３では、支持体の湿度膨張係数を−１０〜１０ｐｐｍ／％ＲＨにするために、強化膜として、温度膨張係数が小さい、防湿性の材料を選び、膜厚を５０ｎｍ以上に調整することも開示されている。
【０００５】
しかしながら、本発明者らが検討したところ、これらのフィルムをリニアトラック方式の磁気記録媒体のベースフィルムとして用いると、フィルムを製膜方向にスリットする際に、強化膜の存在によって切断面が乱れてしまう。そして、リニア方式の磁気記録媒体では、データトラックの位置検出を確認するためのサーボトラックが切断面を基準として形成されるため、サーボトラックの位置が乱れるという致命的な欠陥があることをを見出した。
【０００６】
【特許文献１】
特開平１１−４８４３４号公報
【特許文献２】
特開平１１−１３４６３９号公報
【特許文献３】
特開２００２−２６９７２５号公報
【０００７】
【発明が解決しようとする課題】
本発明の課題は、上記従来技術が有する問題を解決し、寸法安定性に優れながらも優れたスリット性も兼備するポリエステルフイルムの表面にガスバリア層を設けた磁気記録媒体用支持体を提供することにある。
【０００８】
【課題を解決するための手段】
本発明によれば、本発明の目的は、ポリエステルフイルムと、その両面に設けられたガスバリア層とからなる支持体であって、支持体は長手方向のヤング率が８ＧＰａ以上、幅方向のヤング率が６ＧＰａ以上および長手方向のヤング率が幅方向のヤング率よりも１ＧＰａ以上大きく、それぞれのガスバリア層の厚みは、ポリエステルフィルムの厚みを基準として、１〜５．０％の範囲にある磁気記録媒体用支持体によって達成される。
【０００９】
また、本発明はその好ましい態様として（１）前記ガスバリア層が、金属、半金属及び合金並びにこれらの酸化物及び複合物から選ばれた材料からなること、（２）支持体の幅方向の湿度膨張係数が０〜１０ｐｐｍ／％ＲＨで、幅方向の温度膨張係数が−１０〜１０ｐｐｍ／℃であること、（３）フィルムの長手方向に、フィルムの厚み方向の単位断面積１ｍｍ２あたりに２．７ｋｇの荷重を負荷して、４９℃および９０％ＲＨの雰囲気下で７２時間処理した時の、幅方向の寸法変化率（αｗ）が０．４％以下であること、（４）支持体の長手方向と幅方向のヤング率の和を、ポリエステルフィルムの長手方向と幅方向のヤング率の和で割った値が、１．０〜３．０の範囲にあること、（５）ポリエステルがポリエチレンテレフタレートまたはポリエチレン−２、６−ナフタレートであること、（６）支持体の厚みが２〜１０μｍの範囲にあること、および（７）リニア記録方式の磁気記録媒体用に用いられることのいずれかを具備する磁気記録媒体用支持体も包含するものである。
【００１０】
さらにまた、本発明によれば、ポリエステルフイルムおよびその両面に設けられたガスバリア層からなる支持体と該支持体の一方の表面に設けられた磁性層とからなる磁気記録媒体であって、それぞれのガスバリア層の厚みは、ポリエステルフィルムの厚みを基準として、０．２〜２．０％の範囲であり、かつ長手方向のヤング率が８ＧＰａ以上、幅方向のヤング率が６ＧＰａ以上および長手方向のヤング率が幅方向のヤング率よりも１ＧＰａ以上大きい磁気記録媒体も提供される。
【００１１】
【発明の実施の形態】
＜ポリエステル＞
本発明におけるポリエステルとしては、例えばポリエチレンテレフタレート、ポリエチレンイソフタレート、ポリブチレンテレフタレート、ポリエチレン―２，６―ナフタレート、ポリエチレン―α、β―ビス（２―クロルフェノキシ）エタン―４，４′―ジカルボキシレート等が挙げられる。これらのポリエステルは、繰返し単位が、他の第３成分に変更された共重合体でも、ブレンド体であってもよい。これらポリエステルの中でも、強度を比較的高く発現させやすいことから、ポリエチレンテレフタレートあるいはポリエチレン―２，６―ナフタレートが好ましく、特に高強度化という観点から、ポリエチレン―２，６―ナフタレートが最も好ましい。もちろん、ここでいうポリエチレン―２，６―ナフタレートは、単独でも、他のポリエステルとの共重合体や、２種以上のポリエステルの混合体であってもかまわない。具体的には、その繰返し構造単位が実質的にエチレン―２，６―ナフタレートのみならず、繰返し構造単位を基準として、好ましくは１０モル％以下、さらに好ましくは５モル％以下が他の第３成分であるポリエチレン―２，６―ナフタレート共重合体及びポリマー混合物であってもよい。また、ポリエチレンテレフタレートにポリイミドなどの機能剤を添加して、強度を向上させたポリエチレンテレフタレートも好ましい。
【００１２】
ポリエチレン―２，６―ナフタレートは、そのポリマーの固有粘度の下限が０．４０以上であることが好ましく、一方上限は０．８０以下であることが好ましい。固有粘度が下限未満だと工程切断が多発しやすく、一方固有粘度が上限を超えると重合時の生産性が低下することがある。
【００１３】
本発明で使用するポリエステルは、特にその製法を限定されず、それ自体公知の方法を任意に採用することができる。例えば、ポリエチレン―２，６―ナフタレートの場合酸成分のエステル形成性誘導体、例えば、ジ低級アルキル―２，６―ナフタレートとエチレングリコールとをエステル交換反応させてから重縮合反応させることで製造でき、通常これらの反応は触媒の存在下で反応させる。
【００１４】
本発明で使用するポリエステルには、製膜時のフィルムの巻取り性や、フィルムの搬送性等を良くするため、滑剤として有機又は無機の不活性粒子を含有させてもよい。
【００１５】
＜ポリエステルフィルム＞
本発明の支持体を構成するポリエステルフィルムは、少なくとも一方の表面、すなわち磁性層が形成される側の表面は、表面粗さ（Ｒａ）が０．１〜１０ｎｍ、更には０．５〜５ｎｍであることが好ましい。この表面粗さが上限を越えると、磁気テープとしたとき磁性層面が粗化し、電磁変換特性が低下するので好ましくない。一方、この表面粗さが下限未満の場合、フィルム―フィルム間の滑り性が低下し、フィルムの巻取り性が悪化するので好ましくない。このような表面粗さ（Ｒａ）は、フィルムを構成するポリエステルに、不活性微粒子を含有させたり、微細凹凸を形成する表面処理例えば易滑塗剤のコーティング処理によって調整することができる。不活性粒子としては、例えば周期律表第ＩＩＡ、第ＩＩＢ、第ＩＶＡ、第ＩＶＢの元素を含有する無機微粒子（例えば、カオリン、アルミナ、酸化チタン、炭酸カルシウム、二酸化ケイ素など）、シリコーン樹脂、架橋ポリスチレン等の如き耐熱性の高い高分子よりなる微粒子などが挙げられる。不活性粒子をフィルムを構成するポリエステルに含有させる場合、粒子の平均粒径は０．０５〜１．０μｍ、更には０．１〜０．８μｍであることが好ましく、また添加量は、不活性粒子が添加されるポリエステルの重量を基準として、０．０５〜０．５重量％（対ポリマー）、さらには０．１〜０．３重量％（対ポリマー）であることが好ましい。また、平均粒径の異なる２種類以上の不活性粒子を用いてもよい。
【００１６】
また、前記ポリエステルフィルムの他方の表面、すなわち磁性層が形成されない側の表面は、表面粗さ（Ｒａ）が５〜３０ｎｍ、更には５〜１５ｎｍの範囲であることが好ましい。Ｒａが下限未満であると、フィルム製造時の巻取り性が悪く、巻き姿の良い製品を得ることが困難である。また、Ｒａが上限を超えると磁性面の粗さに影響し、電磁変換特性が低下するので好ましくない。
【００１７】
本発明におけるポリエステルフィルムは、ガスバリア層を形成した支持体の状態で、縦方向のヤング率が８ＧＰａ以上、横方向のヤング率が６ＧＰａ以上となるものであれば特に制限されない。好ましくは、支持体を形成する前のポリエステルフィルムのヤング率は、縦方向が９ＧＰａ以上、さらに１０ＧＰａ以上、横方向のヤング率が７ＧＰａ以上、さらに８ＧＰａ以上であることが好ましい。ポリエステルフィルムの縦方向または横方向のヤング率が下限未満だと、支持体の縦方向のヤング率を８ＧＰａ以上または横方向のヤング率を７ＧＰａ以上とすることが困難となり、スリット性の劣るような過度に厚いガスバリア層を形成しなくてはならなくなることがある。
【００１８】
また、支持体を形成する前のポリエステルフィルムは、縦方向のヤング率が、横方向のヤング率よりも１ＧＰａ以上大きいことが必要である。縦方向のヤング率が、横方向のヤング率よりも１ＧＰａ以上大きい、好ましくは２ＧＰａ以上、さらに好ましくは３ＧＰａ以上大きいと、分子鎖が縦方向により配向しており、縦方向、すなわち製膜方向のスリット性が向上し、ガスバリア層によるスリット性の低下を補うことができる。
【００１９】
さらにまた、支持体の縦方向のヤング率と横方向のヤング率の和を、支持体を形成する前のポリエステルフィルムの縦方向のヤング率と横方向のヤング率の和で割った値（以下、ヤング率比と称することがある。）は、１．１〜３の範囲であることが好ましい。ヤング率比が、上記範囲内だと、ポリエステルフィルムのヤング率を損なうことなく、しかもガスバリア層によるスリット性の低下が小さくなる。さらに好ましいヤング率比は、１．２〜３．０、特に１．５〜３．０の範囲である。
【００２０】
＜ガスバリア層＞
ガスバリア層の材料としては、特に制限されないが、Ａｌ、Ｃｕ、Ｚｎ、Ｓｎ、Ｎｉ、Ａｇ、Ｃｏ、Ｆｅ、Ｍｎなどの金属、Ｓｉ、Ｇｅ、Ａｓ、Ｓｃ、Ｓｂなどの半金属、これらの金属及び半金属の合金、それらの複合物であるＦｅ−Ｃｏ、Ｆｅ−Ｎｉ、Ｃｏ−Ｎｉ、Ｆｅ−Ｃｏ−Ｎｉ、Ｆｅ−Ｃｕ、Ｃｏ−Ｃｕ、Ｃｏ−Ａｕ、Ｃｏ−Ｙ、Ｃｏ−Ｌａ、Ｃｏ−Ｐｒ、Ｃｏ−Ｇｄ、Ｃｏ−Ｓｍ、Ｃｏ−Ｐｔ、Ｎｉ−Ｃｕ、Ｍｎ−Ｂｉ、Ｍｎ−Ｓｂ、Ｍｎ−Ａｌ、Ｆｅ−Ｃｒ、Ｃｏ−Ｃｒ、Ｎｉ−Ｃｒ、Ｆｅ−Ｃｏ−Ｃｒ、Ｎｉ−Ｃｏ−Ｃｒ、Ｆｅ−Ｓｉ−Ｏ、Ｓｉ−Ｃ、Ｓｉ−Ｎ、Ｃｕ−Ａｌ−Ｏ、Ｓｉ−Ｎ−Ｏ、Ｓｉ−Ｃ−Ｏ等、また、これらの金属、半金属および合金の酸化物（例えば、酸化ケイ素、酸化アルミニウム、窒化珪素など）などが好ましく挙げられる。これらの中でも、ガス、特に水分のバリヤ性に優れる酸化ケイ素、酸化アルミニウム、窒化珪素らなる群より選ばれた少なくとも１種から形成されるガスバリア層が好ましい。
【００２１】
本発明におけるガスバリア層は、ポリエステルフィルムの両面に設けられていることが必要である。ガスバリア層が片面だけだと、ポリエステルフィルムの一方の表面から侵入するガスの量は低減できるが、他方の表面はポリエステルフィルムが露出しており、ポリエステルフィルムへのガスの侵入量はほとんど低減できない。
【００２２】
また、ポリエステルフィルムの両面にそれぞれ設けられるガスバリア層の厚みは、ポリエステルフィルムの厚みを基準として、１．０〜５．０％（以下、ガスバリア層の厚み比と称する。）の範囲である。ガスバリア層の厚み比が下限未満だと、ガスバリア層が薄すぎて、十分なガスバリア効果が得られなかったり、また、ポリエステルフィルムの変形に追従できずに亀裂が生じたりする。一方、ガスバリア層の厚み比が上限を超えると、ガスバリア層が厚くなりすぎて、支持体をスリットする際に、切断面が乱れてしまう。好ましいガスバリア層の厚み比は、１．２〜４．５％、さらに１．５〜４．０％の範囲である。本発明では、ポリエステルフィルムの両面にガスバリア層を設けるため、このように厚みの薄いガスバリア層でも、十分なガスバリア効果が得られる。このようなガスバリア層は、好ましくは真空蒸着法、スパッタリング法、イオンプレーティング法等によってポリエステルフィルムの表面に形成される。
【００２３】
＜支持体＞
本発明の支持体は、少なくとも一方の表面、すなわち磁性層が形成される側の表面は、表面粗さ（Ｒａ）が、０．１〜１０ｎｍ、更には０．５〜５ｎｍであることが好ましい。この表面粗さが上限を越えると、磁気テープとしたとき磁性層面が粗化し、電磁変換特性が低下するので好ましくない。一方、この表面粗さが下限未満の場合、フィルム―フィルム間の滑り性が低下し、フィルムの巻取り性が悪化するので好ましくない。このような表面粗さは、前述のポリエステルフィルムの表面粗さを調整することで達成できる。
【００２４】
本発明の支持体は、縦方向のヤング率が８ＧＰａ以上、好ましくは９ＧＰａ以上、横方向のヤング率が６ＧＰａ以上、好ましくは７ＧＰａ以上である。縦方向のヤング率が上記の範囲より低いと、テープの長手方向の張力変化による幅方向の寸法変化が悪くなり、また横方向のヤング率が上記の範囲より低いと、温湿度変化によるテープの幅方向の寸法変化が悪くなり、トラックずれが発生する。また、本発明の支持体は、縦方向のヤング率が、横方向のヤング率よりも１ＧＰａ以上大きいことが必要である。好ましくは縦方向のヤング率が、横方向のヤング率よりも２ＧＰａ以上、さらに３ＧＰａ以上である。縦方向のヤング率が、横方向のヤング率が横方向のヤング率よりも１ＧＰａ以上大きいと、支持体を構成するポリエステルフィルム中の分子鎖が縦方向により配向しており、縦方向、すなわち製膜方向のスリット性が向上し、ガスバリア層によるスリット性の低下を補うことができる。さらに、縦方向のヤング率が、横方向のヤング率よりも２ＧＰａ以上、さらに３ＧＰａ以上であると、より支持体を構成するポリエステルフィルム中の分子鎖が縦方向により配向しており、縦方向、すなわち製膜方向のスリット性が向上し、ガスバリア層によるスリット性の低下を補うことができる。
【００２５】
本発明の支持体は、幅方向の湿度膨張係数が０〜１０ｐｐｍ／％ＲＨである。湿度膨張係数が、本発明の範囲を外れると、湿度変化による寸法変化が大きくなり、トラックがずれが発生してエラーとなる。このような湿度膨張係数は、ヤング率を上記範囲内にしつつ、ポリエステルフィルムの両面にガスバリア層を設けることによって調整できる。
【００２６】
本発明の支持体は、幅方向の温度膨張係数が−１０〜１０ｐｐｍ／℃である。温度膨張係数が−１０ｐｐｍ／℃より小さい、または１０ｐｐｍ／℃より大きいと、温度変化による寸法変化が大きくなり、トラックがずれが発生し、エラーとなる。このような温度膨張係数は、ヤング率を上記範囲内にしつつ、熱固定処理によって熱寸法安定性を付与し、かつポリエステルフィルムの両面に形成するガスバリア層として、温度による寸法変化の小さい材料を選択することによって調整できる。
【００２７】
本発明の支持体は、長手方向に荷重下の幅方向の寸法変化が０．４％以下である。ここでいう長手方向荷重下の幅方向の寸法変化（αｗ）とは、温度２３℃、湿度５０％の雰囲気下でフィルムの幅（Ｌ１）をまず測定し、その後、該フィルムを、４９℃（１２０°Ｆ）×９０％ＲＨの高温高湿下で、片側（もう一方は固定）に単位断面積１ｍｍ２あたり２．７ｋｇの重りをつけ、７２ｈｒ（３日間）処理した後、重りを取り外して、温度２３℃、湿度５０％の雰囲気下で２４ｈｒ調湿した状態で測定されるフィルムの幅（Ｌ２）を測定し、Ｌ１からＬ２を差し引いた値をＬ１で割った値である。長手方向荷重下の幅方向の寸法変化が、０．４％より大きいと、トラックがずれが発生し、エラーとなる。このような長手方向荷重下の幅方向の寸法変化は、ヤング率を上記範囲内にしつつ、ポリエステルフィルムの両面にガスバリア層を設け、かつガスバリア層として、温度による寸法変化の小さい材料を選択することによって調整できる。
【００２８】
＜製造方法＞
本発明の支持体は、以下のような方法で製造することができる。
先ずポリエステルフィルムが単層フィルムの場合は、高濃度の不活性粒子を含有するポリエステルペレットと不活性粒子を含有しないポリエステルペレットとを所定の割合で混合し、乾燥後、溶融温度２８０℃〜３３０℃で押出し機よりＴダイを経て押出し、冷却ドラム上に流延し冷却固化して未延伸フィルムを作成する。ポリエチレン―２，６―ナフタレートフィルムの場合、この未延伸フィルムを縦方向に１００〜１７０℃の温度で５〜８倍の倍率で延伸し、次いで上記延伸方向と直角方向に１１５〜１８０℃の温度で４〜７倍の倍率で延伸する。または必要に応じて縦また横方向の延伸を２段階以上に分割実施してもよい（縦多段延伸、縦−横−縦の３段延伸、縦−横−縦−横の４段延伸等）。また同時二軸延伸にて実施してもよい。このようにして全延伸倍率は、面積延伸倍率として１０〜６０倍、更には２０〜５０倍が好ましい。この際、ポリエステルフィルムによるスリット性向上効果を発現させるため、縦方向の延伸倍率から横方向の延伸倍率を差し引いた値は０．５倍以上あることが好ましい。また二軸配向フィルムは１８０〜２５０℃の温度で熱固定することが好ましく、更には２００〜２３０℃で熱固定するのが好ましく、熱固定時間は１〜６０秒が好ましい。
【００２９】
支持体を構成するポリエステルフィルムが積層フィルムの場合は、２台の押出し機を用い、２層またはそれ以上の層を押出せる多層ダイから未延伸フィルムを押出せばよく、その後の工程は、上記単層フィルムと同様な操作を繰り返せばよい。
【００３０】
このようにして得られたポリエステルフィルムの両表面に、前述のガスバリア層を、真空蒸着法、スパッタリング法またはイオンプレーティング法等によって形成することで、本発明の支持体は製造できる。
【００３１】
＜磁気記録媒体＞
本発明の支持体は、寸法安定性に優れながらも優れたスリット性も兼備するポリエステルフイルムの表面にガスバリア層を設けた磁気記録媒体用支持体であることから、高密度磁気記録媒体、特にディジタル記録型磁気機記録媒体のベースフィルムとして好ましく用いられる。
【００３２】
本発明の磁気記録媒体は、上記本発明の支持体の片側表面（積層の場合は平坦側表面）に、磁性層を塗布、あるいは真空蒸着、スパッタリング、イオンプレーティング等の方法により、鉄、コバルト、クロム又はこれらを主成分とする合金もしくは酸化物より成る強磁性金属薄膜層を形成し、またその表面に、目的、用途、必要に応じてダイアモンドライクカーボン（ＤＬＣ）等の保護層、含フッ素カルボン酸系潤滑層を順次設け、更に磁性層と反対側の表面にバックコート層を設けることにより、形成される。
【００３３】
【実施例】
以下、実施例に基づいて本発明をさらに説明する。尚、本発明における種々の物性値及び特性は、以下のようにして測定されたものであり、かつ定義される。
（１）ヤング率
東洋ボールドウイン（株）の引張試験機「テンシロン」を用いて、温度２０℃、湿度５０％に調節された室内において、フィルムを試料幅１０ｍｍ、長さ１５ｃｍに切り、チャック間１００ｍｍにして引張速度１０ｍｍ／分、チャート速度５００ｍｍ／分で引張り、得られる荷重―伸び曲線の立ち上り部の接線よりヤング率を計算する。
（２）表面粗さ（Ｒａ）
小坂研究所（株）製の触針式表面粗さ計（サーフコーダ３０Ｃ）を用いて針の半径２μｍ、触針用３０ｍｇの条件下でチャート（フィルム表面粗さ曲線）をかかせる。フィルム表面粗さ曲線から、その中心線の方向に測定長さＬの部分を抜き取り、この抜き取り部分の中心線をＸ軸とし、縦倍率の方向をＹ軸として、粗さ曲線をＹ＝ｆ（Ｘ）で表したとき、次式で与えられるＲａ（μｍ）をフィルム平均粗さとして定義する。
【００３４】
【数１】
本発明では、測定長を１．２５ｍｍとし、カットオフ値を０．０８ｍｍとして、５回測定した平均値をＲａとする。
（３）不活性粒子の平均粒径
島津製作所製ＣＰ―５０型セントリフュグルパーティクルサイズアナライザー（Ｃｅｎｔｒｉｆｕｇａｌ Ｐａｒｔｉｃｌｅ Ｓｉｚｅ Ａｎａｌｙｚｅｒ）を用いて測定する。得られる遠心沈降曲線をもとに算出する各粒径の粒径とその存在量との累積曲線から、５０マスパーセント（ｍａｓｓ ｐｅｒｃｅｎｔ）に相当する粒径を読み取り、この値を上記平均粒径とする。
（４）長手方向荷重下の幅方向の寸法変化（αｗ）
温度２３℃、湿度５０％の雰囲気下において、１２．６５ｍｍ（１／２インチ）にスリットしたフィルムを図１に示す通りにセットする。なお、１２．６５ｍｍにスリットしたサンプルは検出器にて幅寸法が測定できるようにするため、あらかじめ表面にスパッタによって金を蒸着しておく。この状態でフィルムの片側（もう一方は固定）に２２ＭＰａの重りをつけ、そのときのフィルムの幅（Ｌ１）をキーエンス製レーザー外径測定器（本体：３１００型、センサー：３０６０型）にて測定する。
【００３６】
その後、４９℃（１２０°Ｆ）×９０％ＲＨの高温高湿下で、片側（もう一方は固定）に単位断面積１ｍｍ２あたり２．７ｋｇの重りをつけ、７２ｈｒ（３日間）処理した後、重りを取り外し、温度２３℃、湿度５０％の雰囲気下で２４ｈｒ調湿した後、再び、フィルムの片側（もう一方は固定）に２２ＭＰａの重りをつけ、そのときのフィルムの幅（Ｌ２）をキーエンス製レーザー外径測定器（本体：３１００型、センサー：３０６０型）にて測定する。
【００３７】
上記で測定した温湿度処理前後の寸法より、荷重下温湿度処理前後の幅寸法変化（αＷ）は、次式より算出する。
【００３８】
【数２】
αＷ＝｛（Ｌ１−Ｌ２）×／Ｌ１｝×１００（％）
（５）温度膨張係数（αｔ）
フィルムサンプルをフィルム横方向に長さ１５ｍｍ、幅５ｍｍに切り出し、真空理工製 ＴＭＡ３０００にセットし、窒素雰囲気下、６０℃で３０分前処理し、その後室温まで降温させる。その後２５℃から７０℃まで２℃／分で昇温し、各温度でのサンプル長を測定し、次式より温度膨張係数（αｔ）を算出する。
【００３９】
【数３】
αｔ＝｛（Ｌ２−Ｌ１）／（Ｌ１×ΔＴ）｝×１０６＋０．５
ここで、上記式中の、Ｌ１は４０℃時のサンプル長（ｍｍ）、Ｌ２は６０℃時のサンプル長（ｍｍ）、ΔＴは２０（＝６０−４０℃）℃、および０．５は石英ガラスの温度膨張係数に１０６を掛けた値である。
（６）湿度膨張係数（αｈ）
フィルムサンプルをフィルム横方向に長さ１５ｍｍ、幅５ｍｍに切り出し、真空理工製ＴＭＡ３０００にセットし、窒素雰囲気下から、湿度３０％ＲＨ、及び湿度７０％ＲＨの一定に保ち、その時のサンプルの長さを測定し、次式にて湿度膨張係数を算出する。
【００４０】
【数４】
αｈ＝｛（Ｌ２−Ｌ１）×／（Ｌ１×ΔＨ）｝×１０６
ここで、上記式中のＬ１は湿度３０％ＲＨ時のサンプル長（ｍｍ）、Ｌ２は湿度７０％ＲＨ時のサンプル長（ｍｍ）およびΔＨは４０（＝７０−３０％ＲＨ）％ＲＨである。
（７）トラックずれ（エラーレート）
メディアロジック社製ＭＬ４５００Ｂ、ＱＩＣ用システムを用いて、下記条件にてエラーレートを測定する。
【００４１】
Ｃｕｒｒｅｎｔ ＝１５．４２ｍＡ
Ｆｒｅｑｕｅｎｃｙ ：０．２５ＭＨｚ
Ｌｏｃａｔｉｏｎ＝０
Ｔｈｒｅｓｈｏｌｄ ：４０．０
Ｂａｄ／Ｇｏｏｄ／ＭＡＸ：１：１：１
Ｔｒａｃｋｓ：２８
なお、エラーレート数は、測定したトラック数（＝２８）の平均値で表わす。
【００４２】
条件１および条件２の測定は次のように行う。
条件１：１０℃、１０％ＲＨの温湿度下で記録した後４５℃、８０％ＲＨの温湿度下で再生し、温湿度変化によるトラックずれ量を測定する。
条件２：２３℃、５０％ＲＨの温湿度下で記録した後４０℃、６０％ＲＨの温湿度下で６０時間繰り返し走行させ、２３℃、５０％ＲＨの温湿度下に戻し、２４時間保持した後、記録を再生し、比較的高温高湿度下での走行による幅収縮によるトラックずれ量を測定する。
【００４３】
評価基準は次の通りである。
◎：エラーレート無し
○：エラーレートは有るが、実用上問題無し
×：エラーレートが多く、実用上問題あり
（８）電磁変換特性
メディアロジック社製ＭＬ４５００Ｂ、ＱＩＣ用システムを用いて測定した。なお、評価は、実施例１のサンプルのＳ／Ｎを０ｄＢとし、下記基準で相対評価した。
◎：＋１ｄＢ以上
○：−１ｄＢ〜＋１ｄＢ未満
×：−１ｄＢ未満
【００４４】
（９）ポリエステルフィルムおよびガスバリア層の厚み
フィルム全体の厚みはマイクロメーターにてランダムに１０点測定し、その平均値を用いる。ポリエステルフィルムが２つ以上の層からなる積層フィルムである場合、各層の厚みについては、薄いポリエステル層の層厚みを下記に述べる方法にて測定し、厚いポリエステル層の層厚みは、全厚みより皮膜層および薄いポリエステル層の層厚を引き算して求める。すなわち、二次イオン質量分析装置（ＳＩＭＳ）を用いて、被覆層を除いた表層から深さ５，０００ｎｍの範囲のフィルム中の粒子の内最も高濃度の粒子に起因する金属元素（Ｍ＋）とポリエステルの炭化水素（Ｃ＋）の濃度比（Ｍ＋／Ｃ＋）を粒子濃度とし、表面から深さ５，０００ｎｍまで厚さ方向の分析を行う。表層では表面という界面のために粒子濃度は低く、表面から遠ざかるにつれて粒子濃度は高くなる。本発明の場合、粒子濃度は一旦安定値１になったのち、上昇して安定値２になる場合と、単調に減少する場合とがある。この分布曲線をもとに、前者の場合は、（安定値１＋安定値２）／２の粒子濃度を与える深さをもって、また後者の場合は粒子濃度が安定値１の１／２になる深さ（この深さは安定値１を与える深さよりも深い）をもって、薄いポリエステル層の厚み（μｍ）とする。
【００４５】
測定条件は、以下のとおりである。
（ａ）測定装置
二次イオン質量分析装置（ＳＩＭＳ）；パーキン・エルマー株式会社
（ＰＥＲＫＩＮ ＥＬＭＥＲ ＩＮＣ．）製、「６３００」
（ｂ）測定条件
一次イオン種：Ｏ２ ＋
一次イオン加速電圧：１２ＫＶ
一次イオン電流：２００ｎＡ
ラスター領域：４００μｍ□
分析領域：ゲート３０％
測定真空度：６．０×１０−９Ｔｏｒｒ
Ｅ−ＧＵＮＮ：０．５ＫＶ−３．０Ａ
【００４６】
なお、表層から５，０００ｎｍの範囲に最も多く存在する粒子がシリコーン樹脂以外の有機高分子粒子の場合はＳＩＭＳでは測定が難しいので、表面からエッチングしながらＦＴ−ＩＲ（フーリエトランスフォーム赤外分光法）、粒子によってはＸＰＳ（Ｘ線光電分光法）などで上記同様の濃度分布曲線を測定し、層厚（μｍ）を求める。
【００４７】
また、ガスバリア層の厚みは、フィルムの小片をエポキシ樹脂にて固定成形し、ミクロトームにて約６００オングストロームの厚みの超薄切片（フィルムの流れ方向に平行に切断する）を作成した。この試料を透過型電子顕微鏡（株式会社日立製作所製：Ｈ−８００型）にて観察し、ガスバリア層の境界面を探して厚み（ｎｍ）を求める。
（１０）スリット性
温度２３℃、湿度５０％の雰囲気下において、１２．６５ｍｍ（１／２インチ）にスリットしたフィルムを図１に示す通りにセットする。この状態でフィルムの片側（もう一方は固定）に１０ＭＰａの重りをつけ、そのときのフィルムの幅（Ｌ）をキーエンス製レーザー外径測定器（本体：３１００型、センサー：３０６０型）にて、長手方向に０．１ｍｍ間隔で測定する。
【００４８】
そして、得られた幅（Ｌ）の最大値と最小値の差を、幅の変化量（△Ｌ）として算出し、以下の基準にて評価する。
◎：０．２μｍ未満
○：０，２μｍ以上０．５μｍ未満
×：０．５μｍ以上
【００４９】
［実施例１］
平均粒径０．５μｍのシリコーン粒子を０．０２重量％、平均粒径０．１μｍの球状シリカ粒子を０．３０重量％含有した固有粘度（オルソクロロフェノール、３５℃）０．６０のポリエチレン―２，６―ナフタレートを１８０℃で５時間乾燥した後、押出機ホッパーに供給し、３００℃で溶融し、Ｔ型押出ダイを用いて、表面仕上げ０．３Ｓ、表面温度６０℃に保持したキャスティングドラム上で急冷固化せしめて、未延伸フィルムを得た。
【００５０】
このようにして得られた未延伸フィルムを１２０℃にて予熱し、更に低速、高速のロール間で１４ｍｍ上方より８３０℃の表面温度の赤外線ヒーターにて加熱して５．４倍に延伸し、急冷し、続いてステンターに供給し、１２５℃にて横方向に４．８倍延伸した。さらに引き続いて２２５℃で３秒間熱固定し、厚み４．５μｍの二軸配向フィルムを得た。得られたフィルムのヤング率は縦方向８ＧＰａ 、横方向７ＧＰａであった。得られたフィルムロールの両面にスパッターにてＡｕの膜を厚さ１５０ｎｍでそれぞれ形成し、支持体を作成した。得られた支持体のヤング率は縦方向８ＧＰａ 、横方向６ＧＰａであった。
【００５１】
一方、下記に示す組成物をボールミルに入れ、１６時間混練、分散した後、イソシアネート化合物（バイエル社製のデスモジュールＬ）５重量部を加え、１時間高速剪断分散して磁性塗料とした。
磁性塗料の組成：
針状Ｆｅ粒子 １００重量部
塩化ビニル―酢酸ビニル共重合体 １５重量部
（積水化学製エスレック７Ａ）
熱可塑性ポリウレタン樹脂 ５重量部
酸化クロム ５重量部
カーボンブラック ５重量部
レシチン ２重量部
脂肪酸エステル １重量部
トルエン ５０重量部
メチルエチルケトン ５０重量部
シクロヘキサノン ５０重量部
【００５２】
この磁性塗料を上述のポリエチレン―２，６―ナフタレートフイルムの片面に塗布厚さ０．５μｍとなるように塗布し、次いで２５００ガウスの直流磁場中で配向処理を実施し、１００℃で加熱乾燥後、スーパーカレンダー処理（線圧２００ｋｇ／ｃｍ、温度８０℃）をして巻き取った。この巻き取ったロールを５５℃のオーブン中に３日間放置した。
【００５３】
さらに下記組成のバックコート層塗料を厚さ１μｍに塗布し、乾燥させ、さらに６．３５ｍｍ（＝１′／４）に裁断し、磁気テープを得た。
バックコート層塗料の組成：
カーボンブラック １００重量部
熱可塑性ポリウレタン樹脂 ６０重量部
イソシアネート化合物 １８重量部
（日本ポリウレタン工業社製コロネートＬ）
シリコーンオイル ０．５重量部
メチルエチルケトン ２５０重量部
トルエン ５０重量部
得られた支持体およびテープの特性を表１に示す。この表から明らかなように、エラーレートが少なく、出力特性も良好であった。
【００５４】
［実施例２］
平均粒径０．１μｍの球状シリカ粒子を０．１重量％含有したＡ層用の固有粘度（オルソクロロフェノール、３５℃）０．６０のポリエチレン―２，６―ナフタレート、平均粒径０．３μｍの球状シリカ粒子を０．１５重量％、平均粒径０．１μｍの球状シリカ粒子を０．１５重量％含有したＢ層用の固有粘度（オルソクロロフェノール、３５℃）０．６０のポリエチレン―２，６―ナフタレートを１８０℃で５時間乾燥した後、別の押出機ホッパーに供給し、溶融温度３００℃で溶融し、マルチマニホールド型共押出しダイを用いてＡ層とＢ層を積層し、表面仕上げ０．３Ｓ、表面温度６０℃に保持したキャスティングドラム上で急冷固化せしめて、未延伸フィルムを得た。
【００５５】
このようにして得られた未延伸フィルムを１２０℃にて予熱し、更に低速、高速のロール間で１４ｍｍ上方より８３０℃の表面温度の赤外線ヒーターにて加熱して５．９倍に延伸し、急冷し、続いてステンターに供給し、１２５℃にて横方向に４．５倍、さらに１７０℃にて横方向に１．１５倍に延伸し、トータル５．２倍延伸した。さらに引き続いて２２５℃で３秒間熱固定し、厚み４．５μｍの二軸配向フィルムを得た。得られたフィルムロールの両面にアルミニウムの真空蒸着を、酸素を導入しながら行ない、酸化アルミニウム強化膜をそれぞれ形成し支持体を作成した。得られた支持体のヤング率は縦方向９ＧＰａ 、横方向７ＧＰａであった。
【００５６】
以下は実施例１と同様の方法で熱処理後、実施例１と同じ磁性塗料をＡ層面に、反対面のＢ層面に実施例１と同じバックコートを塗布し、磁気テープを得て評価した。得られた支持体およびテープの特性を表１に示す。この表から明らかなように、エラーレートが少なく、出力特性も良好であった。
【００５７】
［実施例３］
平均粒径０．１μｍの球状シリカ粒子を０．０１重量％含有したＡ層用の固有粘度（オルソクロロフェノール、３５℃）０．６０のポリエチレン―２，６―ナフタレート、平均粒径０．３μｍのシリコーン粒子を０．１重量％、平均粒径０．１μｍの球状シリカ粒子を０．１５重量％含有したＢ層用の固有粘度（オルソクロロフェノール、３５℃）０．６０のポリエチレン―２，６―ナフタレートを１８０℃で５時間乾燥した後、別の押出機ホッパーに供給し、溶融温度３００℃で溶融し、マルチマニホールド型共押出しダイを用いてＡ層とＢ層を積層し、表面仕上げ０．３Ｓ、表面温度６０℃に保持したキャスティングドラム上で急冷固化せしめて、未延伸フィルムを得た。
【００５８】
このようにして得られた未延伸フィルムを１２０℃にて予熱し、更に低速、高速のロール間で１４ｍｍ上方より８３０℃の表面温度の赤外線ヒーターにて加熱して２．３倍に延伸し、急冷し、続いてステンターに供給し、１２５℃にて横方向に５．０倍に延伸し、１６０℃で３秒間熱固定した後、１４０℃にて予熱し、更に低速、高速のロール間で１４ｍｍ上方より８３０℃の表面温度の赤外線ヒーターにて加熱して３．１倍に延伸し、急冷し、続いてステンターに供給し、１７０℃にて横方向に１．３倍に延伸し、２１５℃で３秒間熱固定した後、厚み４．５μｍの二軸配向フィルムを得た。得られたフィルムロールの両面にシリカ膜をそれぞれ真空蒸着し、支持体を作成した。得られた支持体のヤング率は縦方向１１ＧＰａ 、横方向８ＧＰａであった。得られた支持体およびテープの特性を表１に示す。この表から明らかなように、エラーレートが少なく、出力特性も良好であった。
【００５９】
［比較例１］
スパッターにてＡｕの膜を形成しなかった以外は実施例１と同様にして厚み４．５μｍの二軸配向フィルムを得た。また磁気テープは実施例１と同様にして得た。得られた支持体およびテープの特性を表１に示す。
【００６０】
［比較例２］
平均粒径０．８μｍのシリコーン粒子を０．１重量％含有した固有粘度（オルソクロロフェノール、３５℃）０．６０のポリエチレン―２，６―ナフタレートを１８０℃で５時間乾燥した後、押出機ホッパーに供給し、３００℃で溶融し、Ｔ型押出ダイを用いて、表面仕上げ０．３Ｓ、表面温度６０℃に保持したキャスティングドラム上で急冷固化せしめて、未延伸フィルムを得た。
【００６１】
このようにして得られた未延伸フィルムを１２０℃にて予熱し、更に低速、高速のロール間で１４ｍｍ上方より８３０℃の表面温度の赤外線ヒーターにて加熱して４．０倍に延伸し、急冷し、続いてステンターに供給し、１２５℃にて横方向に５．４倍延伸した。さらに引き続いて２２５℃で３秒間熱固定し、スパッターにてＡｕの膜を形成しなかった以外は実施例１と同様にして厚み４．５μｍの二軸配向フィルムを得た。得られたフィルムのヤング率は縦方向６ＧＰａ 、横方向９ＧＰａであった。そして、該二軸配向フィルムに直接実施例１と同様にして磁性層を設け磁気テープを得た。得られた支持体およびテープの特性を表１に示す。
【００６２】
［比較例３］
２軸配向フィルムの縦方向および幅方向のヤング率を表１に示すように変更した以外は実施例２と同様な操作を繰り返した。得られた支持体およびテープの特性を表１に示す。
【００６３】
【表１】
【発明の効果】
本発明によれば、ポリエステルフイルムにガスバリア層を設ける際に、ガスバリア層としてポリエステルフィルムの厚みに対して１〜５％の薄いガスバリア層を選択し、それをポリエステルフイルムの片面だけでなく両面に形成し、かつ支持体の長手方向のヤング率を８ＧＰａ以上、幅方向のヤング率を６ＧＰａ以上および長手方向のヤング率を幅方向のヤング率よりも１ＧＰａ以上大きくすること、すなわち、これら３つの要件が有機的に結合することにより、寸法安定性に優れながらもスリット性も兼備する磁気記録媒体用支持体が提供される。
【００６５】
そして、本発明の支持体をベースフィルムとして磁気記録媒体に用いると、トラックずれによるエラーレート発生がなく、出力特性に優れ、長時間使用に耐えるデジタルデータストレージテープとして有用な磁気記録媒体を得ることができる。
【図面の簡単な説明】
【図１】フィルム縦方向荷重印加後の幅方向の残留収縮（αＷ）を測定する装置の説明図である。
【符号の説明】
１ 試料
２ 荷重
３ 光センサー ＬＳ−３０３６ 受光部
４ 光センサー ＬＳ−３０３６ 発光部
５ レーザー光
６ ガラス板
７ 計測器 ＬＳ３１００
８ アナログ／デジタル変換器 ＨＰ３４５７Ａ
９ パーソナルコンピューター[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a support for a magnetic recording medium provided with a gas barrier layer on the surface of a polyester film, and more particularly, to a magnetic recording medium provided with a gas barrier layer on the surface of a polyester film having excellent dimensional stability and excellent slitting properties. The present invention relates to a support for a medium, and particularly to a support for a magnetic recording medium for a data storage tape of a linear recording system.
[0002]
[Prior art]
Polyester films are used in a wide range of fields such as for magnetic recording media and electrical insulation due to their excellent heat and mechanical properties. Above all, in magnetic recording media, especially in data storage applications, the demands on the characteristics of the base film have become strict with the increase in density and capacity of tapes. For data storage applications that use the linear track system, such as QIC, DLT, and even higher-capacity super DLT, LTO, etc., to achieve higher tape capacity, increase the linear recording density, increase the track density, and increase the tape length. As the length is reduced, flattening, thinning, high strength, and high dimensional stability are required.
[0003]
Therefore, JP-A-11-48434 (Patent Document 1) and JP-A-11-134439 (Patent Document 2) disclose, on both surfaces of a polyester-based plastic film, metals, metalloids, alloys, oxides and composites thereof. There has been proposed a support for a magnetic recording medium having a high Young's modulus in the width direction, in particular, providing a reinforcing film made of a metal material selected from materials to compensate for a decrease in rigidity due to the thinning of the support.
[0004]
However, magnetic recording media using these supports tend to vary in running durability and recording / reproducing performance under high-temperature, high-humidity environments, and are not always satisfactory as industrial products. It is disclosed in the official gazette (Patent Document 3). To solve these problems, Patent Document 3 discloses that a reinforcing film made of a metal material selected from metals, metalloids, alloys, and oxides and composites thereof is provided on one surface B of a polyester film. And Ra of the other surface A is 1 to 5 nm, the thickness of the support is 2 to 6 μm, the Young's modulus in the longitudinal direction is 5 GPa or more, and the Young's modulus in the width direction is 7.5 GPa or more. A support having a high humidity expansion coefficient of -10 to 10 ppm /% RH and a temperature expansion coefficient of -10 to 10 ppm /% RH has been proposed. In Patent Document 3, in order to make the humidity expansion coefficient of the support -10 to 10 ppm /% RH, a moisture-proof material having a small temperature expansion coefficient is selected as the reinforcing film, and the film thickness is adjusted to 50 nm or more. Is also disclosed.
[0005]
However, the present inventors have studied that when these films are used as a base film of a linear track type magnetic recording medium, when the film is slit in the film forming direction, the cut surface is disturbed by the presence of the reinforcing film. I will. And, in the magnetic recording medium of the linear system, since the servo track for confirming the detection of the position of the data track is formed based on the cut surface, it has been found that there is a fatal defect that the position of the servo track is disturbed. Was.
[0006]
[Patent Document 1]
JP-A-11-48434
[Patent Document 2]
JP-A-11-134639
[Patent Document 3]
JP-A-2002-269725
[0007]
[Problems to be solved by the invention]
An object of the present invention is to solve the problems of the prior art and to provide a magnetic recording medium support having a gas barrier layer provided on the surface of a polyester film having excellent dimensional stability and also having excellent slitting properties. It is in.
[0008]
[Means for Solving the Problems]
According to the present invention, an object of the present invention is a support comprising a polyester film and gas barrier layers provided on both surfaces thereof, wherein the support has a Young's modulus in a longitudinal direction of 8 GPa or more and a Young's modulus in a width direction. Is a magnetic recording medium whose Young's modulus in the longitudinal direction is 6 GPa or more and the Young's modulus in the longitudinal direction is 1 GPa or more larger than the Young's modulus in the width direction, and the thickness of each gas barrier layer is in the range of 1 to 5.0% based on the thickness of the polyester film. Achieved by the support.
[0009]
In a preferred embodiment of the present invention, (1) the gas barrier layer is made of a material selected from metals, metalloids and alloys, and oxides and composites thereof; and (2) humidity in the width direction of the support. The expansion coefficient is 0 to 10 ppm /% RH, and the temperature expansion coefficient in the width direction is -10 to 10 ppm / ° C. (3) In the longitudinal direction of the film, the unit cross-sectional area in the thickness direction of the film is 1 mm.2The dimensional change rate (αw) in the width direction is 0.4% or less when a load of 2.7 kg is applied thereto and treated in an atmosphere of 49 ° C. and 90% RH for 72 hours; A) a value obtained by dividing the sum of the Young's modulus in the longitudinal direction and the width direction of the support by the sum of the Young's modulus in the longitudinal direction and the width direction of the polyester film is in the range of 1.0 to 3.0; ) The polyester is polyethylene terephthalate or polyethylene-2,6-naphthalate, (6) the thickness of the support is in the range of 2 to 10 µm, and (7) the recording medium is used for a linear recording type magnetic recording medium. And a support for a magnetic recording medium having any of the above.
[0010]
Still further, according to the present invention, there is provided a magnetic recording medium comprising a support comprising a polyester film and a gas barrier layer provided on both surfaces thereof, and a magnetic layer provided on one surface of the support. The thickness of the gas barrier layer is in the range of 0.2 to 2.0% based on the thickness of the polyester film, and has a Young's modulus in the longitudinal direction of 8 GPa or more, a Young's modulus in the width direction of 6 GPa or more, and a Young's modulus in the longitudinal direction. A magnetic recording medium having a modulus greater than the Young's modulus in the width direction by 1 GPa or more is also provided.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
<Polyester>
Examples of the polyester in the present invention include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate And the like. These polyesters may be a copolymer in which the repeating unit is changed to another third component, or may be a blend. Among these polyesters, polyethylene terephthalate or polyethylene-2,6-naphthalate is preferred because of relatively high strength, and polyethylene-2,6-naphthalate is particularly preferred from the viewpoint of increasing strength. Needless to say, the polyethylene-2,6-naphthalate mentioned here may be a single substance, a copolymer with another polyester, or a mixture of two or more polyesters. Specifically, the repeating unit is substantially not only ethylene-2,6-naphthalate, but preferably 10 mol% or less, more preferably 5 mol% or less, based on the repeating structural unit. The component may be a polyethylene-2,6-naphthalate copolymer or a polymer mixture. Further, polyethylene terephthalate obtained by adding a functional agent such as polyimide to polyethylene terephthalate to improve the strength is also preferable.
[0012]
As for polyethylene-2,6-naphthalate, the lower limit of the intrinsic viscosity of the polymer is preferably 0.40 or more, while the upper limit is preferably 0.80 or less. If the intrinsic viscosity is less than the lower limit, process cutting is likely to occur frequently, while if the intrinsic viscosity exceeds the upper limit, productivity during polymerization may be reduced.
[0013]
The production method of the polyester used in the present invention is not particularly limited, and any method known per se can be adopted. For example, in the case of polyethylene-2,6-naphthalate, an ester-forming derivative of an acid component, for example, can be produced by subjecting a di-lower alkyl-2,6-naphthalate and ethylene glycol to a transesterification reaction followed by a polycondensation reaction, Usually, these reactions are carried out in the presence of a catalyst.
[0014]
The polyester used in the present invention may contain organic or inorganic inert particles as a lubricant in order to improve the film winding property during film formation, the film transport property, and the like.
[0015]
<Polyester film>
At least one surface of the polyester film constituting the support of the present invention, that is, the surface on the side on which the magnetic layer is formed, has a surface roughness (Ra) of 0.1 to 10 nm, more preferably 0.5 to 5 nm. Preferably, there is. If the surface roughness exceeds the upper limit, the surface of the magnetic layer becomes rough when a magnetic tape is used, and electromagnetic conversion characteristics are undesirably reduced. On the other hand, if the surface roughness is less than the lower limit, the slipperiness between the film and the film is reduced, and the winding property of the film is undesirably deteriorated. Such surface roughness (Ra) can be adjusted by adding inert fine particles to the polyester constituting the film or by performing a surface treatment for forming fine irregularities, for example, a coating treatment with an easy-to-use lubricant. As the inert particles, for example, inorganic fine particles (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.) containing elements of Periodic Tables IIA, IIB, IVA, IVB, silicone resin, crosslinked Fine particles made of a polymer having high heat resistance such as polystyrene are exemplified. When the inert particles are contained in the polyester constituting the film, the average particle diameter of the particles is preferably from 0.05 to 1.0 μm, more preferably from 0.1 to 0.8 μm, and the amount added is inert. It is preferably from 0.05 to 0.5% by weight (based on the polymer), more preferably from 0.1 to 0.3% by weight (based on the polymer), based on the weight of the polyester to which the particles are added. Further, two or more types of inert particles having different average particle sizes may be used.
[0016]
The other surface of the polyester film, that is, the surface on which the magnetic layer is not formed, preferably has a surface roughness (Ra) of 5 to 30 nm, more preferably 5 to 15 nm. When Ra is less than the lower limit, the winding property during film production is poor, and it is difficult to obtain a product with good winding appearance. On the other hand, if Ra exceeds the upper limit, the roughness of the magnetic surface is affected, and the electromagnetic conversion characteristics are deteriorated.
[0017]
The polyester film in the present invention is not particularly limited as long as it has a Young's modulus of 8 GPa or more in the vertical direction and 6 GPa or more in the horizontal direction in the state of the support on which the gas barrier layer is formed. Preferably, the Young's modulus of the polyester film before forming the support is 9 GPa or more in the longitudinal direction, more preferably 10 GPa or more, and the Young's modulus in the horizontal direction is 7 GPa or more, and more preferably 8 GPa or more. When the longitudinal or transverse Young's modulus of the polyester film is less than the lower limit, it is difficult to make the longitudinal Young's modulus of the support 8 GPa or more or the transverse Young's modulus 7 GPa or more, and the slitting property is poor. It may be necessary to form an excessively thick gas barrier layer.
[0018]
Further, the polyester film before forming the support needs to have a Young's modulus in the longitudinal direction larger than that in the transverse direction by 1 GPa or more. When the Young's modulus in the vertical direction is larger than the Young's modulus in the horizontal direction by 1 GPa or more, preferably 2 GPa or more, and more preferably 3 GPa or more, the molecular chains are oriented more in the vertical direction, and in the vertical direction, that is, in the film forming direction. The slit property is improved, and a decrease in the slit property due to the gas barrier layer can be compensated.
[0019]
Furthermore, the value obtained by dividing the sum of the longitudinal Young's modulus and the transverse Young's modulus of the support by the sum of the longitudinal Young's modulus and the transverse Young's modulus of the polyester film before forming the support (hereinafter referred to as “the Young's modulus”). , May be referred to as the Young's modulus ratio). When the Young's modulus ratio is within the above range, a decrease in the slit property due to the gas barrier layer is reduced without impairing the Young's modulus of the polyester film. A more preferable Young's modulus ratio is in the range of 1.2 to 3.0, particularly 1.5 to 3.0.
[0020]
<Gas barrier layer>
The material of the gas barrier layer is not particularly limited, but includes metals such as Al, Cu, Zn, Sn, Ni, Ag, Co, Fe, and Mn; semimetals such as Si, Ge, As, Sc, and Sb; And metalloid alloys, their composites Fe-Co, Fe-Ni, Co-Ni, Fe-Co-Ni, Fe-Cu, Co-Cu, Co-Au, Co-Y, Co-La, Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-Cu, Mn-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr, Ni-Co-Cr, Fe-Si-O, Si-C, Si-N, Cu-Al-O, Si-NO, Si-CO, etc. Oxides (eg, silicon oxide, aluminum oxide, silicon nitride, etc.) It may preferably be mentioned. Among these, a gas barrier layer formed of at least one selected from the group consisting of silicon oxide, aluminum oxide, and silicon nitride, which is excellent in barrier properties of gas, particularly moisture, is preferable.
[0021]
The gas barrier layer in the present invention needs to be provided on both sides of the polyester film. If the gas barrier layer is only on one side, the amount of gas entering from one surface of the polyester film can be reduced, but the polyester film is exposed on the other surface, and the amount of gas entering the polyester film can hardly be reduced.
[0022]
The thickness of the gas barrier layer provided on each side of the polyester film is in the range of 1.0 to 5.0% (hereinafter referred to as the gas barrier layer thickness ratio) based on the thickness of the polyester film. If the thickness ratio of the gas barrier layer is less than the lower limit, the gas barrier layer is too thin to obtain a sufficient gas barrier effect, and cracks occur because the polyester film cannot follow the deformation of the polyester film. On the other hand, when the thickness ratio of the gas barrier layer exceeds the upper limit, the gas barrier layer becomes too thick, and the cut surface is disturbed when slitting the support. The preferred thickness ratio of the gas barrier layer is in the range of 1.2 to 4.5%, and more preferably 1.5 to 4.0%. In the present invention, since a gas barrier layer is provided on both sides of the polyester film, a sufficient gas barrier effect can be obtained even with such a thin gas barrier layer. Such a gas barrier layer is preferably formed on the surface of the polyester film by a vacuum deposition method, a sputtering method, an ion plating method, or the like.
[0023]
<Support>
In the support of the present invention, at least one surface, that is, the surface on which the magnetic layer is formed, preferably has a surface roughness (Ra) of 0.1 to 10 nm, more preferably 0.5 to 5 nm. . If the surface roughness exceeds the upper limit, the surface of the magnetic layer becomes rough when a magnetic tape is used, and electromagnetic conversion characteristics are undesirably reduced. On the other hand, if the surface roughness is less than the lower limit, the slipperiness between the film and the film is reduced, and the winding property of the film is undesirably deteriorated. Such surface roughness can be achieved by adjusting the surface roughness of the aforementioned polyester film.
[0024]
The support of the present invention has a Young's modulus in the vertical direction of 8 GPa or more, preferably 9 GPa or more, and a Young's modulus in the horizontal direction of 6 GPa or more, preferably 7 GPa or more. When the Young's modulus in the longitudinal direction is lower than the above range, the dimensional change in the width direction due to the change in the tension in the longitudinal direction of the tape becomes worse. The dimensional change in the width direction is deteriorated, and a track shift occurs. Further, the support of the present invention is required to have a Young's modulus in the vertical direction larger than that in the horizontal direction by 1 GPa or more. Preferably, the Young's modulus in the vertical direction is 2 GPa or more, more preferably 3 GPa or more, than the Young's modulus in the horizontal direction. When the Young's modulus in the vertical direction is 1 GPa or more greater than the Young's modulus in the horizontal direction, the molecular chains in the polyester film constituting the support are oriented more in the vertical direction, and The slit property in the film direction is improved, and a decrease in the slit property due to the gas barrier layer can be compensated. Furthermore, when the Young's modulus in the vertical direction is 2 GPa or more, more preferably 3 GPa or more than the Young's modulus in the horizontal direction, the molecular chains in the polyester film constituting the support are more oriented in the vertical direction, That is, the slit property in the film forming direction is improved, and the decrease in the slit property due to the gas barrier layer can be compensated.
[0025]
The support of the present invention has a coefficient of humidity expansion in the width direction of 0 to 10 ppm /% RH. When the coefficient of humidity expansion is out of the range of the present invention, a dimensional change due to a change in humidity becomes large, and a track shift occurs to cause an error. Such a humidity expansion coefficient can be adjusted by providing a gas barrier layer on both surfaces of the polyester film while keeping the Young's modulus within the above range.
[0026]
The support of the present invention has a temperature expansion coefficient in the width direction of −10 to 10 ppm / ° C. If the coefficient of thermal expansion is smaller than -10 ppm / ° C. or larger than 10 ppm / ° C., a dimensional change due to a temperature change becomes large, a track shift occurs, and an error occurs. Such a thermal expansion coefficient, while keeping the Young's modulus within the above range, imparts thermal dimensional stability by heat setting treatment, and selects a material having a small dimensional change due to temperature as a gas barrier layer formed on both surfaces of the polyester film. Can be adjusted.
[0027]
In the support of the present invention, the dimensional change in the width direction under a load in the longitudinal direction is 0.4% or less. Here, the dimensional change (αw) in the width direction under the load in the longitudinal direction refers to the width (Lw) of the film in an atmosphere at a temperature of 23 ° C. and a humidity of 50%.1) Is measured first, and then the film is placed on one side (the other is fixed) in a unit cross-sectional area of 1 mm under high temperature and high humidity of 49 ° C. (120 ° F.) × 90% RH.2After applying 2.7 kg of weight per 72 hours (3 days), the weight was removed, and the film width (L) measured in a state where the humidity was adjusted in an atmosphere of a temperature of 23 ° C. and a humidity of 50% for 24 hours was measured.2) And measure L1To L2L is the value obtained by subtracting1Divided by. If the dimensional change in the width direction under the load in the longitudinal direction is larger than 0.4%, a track shift occurs and an error occurs. Such a dimensional change in the width direction under a longitudinal load is to provide a gas barrier layer on both sides of the polyester film while keeping the Young's modulus within the above range, and select a material having a small dimensional change due to temperature as the gas barrier layer. Can be adjusted by
[0028]
<Production method>
The support of the present invention can be produced by the following method.
First, when the polyester film is a single-layer film, a polyester pellet containing a high concentration of inert particles and a polyester pellet containing no inert particles are mixed at a predetermined ratio, and after drying, a melting temperature of 280 ° C. to 330 ° C. And extruded through a T-die from an extruder, cast on a cooling drum, cooled and solidified to form an unstretched film. In the case of a polyethylene-2,6-naphthalate film, the unstretched film is stretched in the machine direction at a temperature of 100 to 170 ° C. at a magnification of 5 to 8 times, and then stretched at a temperature of 115 to 180 ° C. in a direction perpendicular to the stretching direction. Stretch at 4 to 7 times magnification at temperature. Or, if necessary, the stretching in the vertical and horizontal directions may be performed in two or more stages (multi-stage stretching, three-stage stretching in the vertical-horizontal-vertical direction, four-stage stretching in the vertical-horizontal-vertical-horizontal direction, etc.) . Moreover, you may implement by simultaneous biaxial stretching. Thus, the total stretching ratio is preferably 10 to 60 times, more preferably 20 to 50 times as the area stretching ratio. At this time, it is preferable that the value obtained by subtracting the stretching ratio in the horizontal direction from the stretching ratio in the vertical direction is 0.5 times or more in order to exhibit the effect of improving the slitting property of the polyester film. The biaxially oriented film is preferably heat-set at a temperature of 180 to 250 ° C, more preferably at 200 to 230 ° C, and the heat-setting time is preferably 1 to 60 seconds.
[0029]
When the polyester film constituting the support is a laminated film, the unstretched film may be extruded from a multilayer die capable of extruding two or more layers by using two extruders. What is necessary is just to repeat the same operation as a monolayer film.
[0030]
The support of the present invention can be manufactured by forming the above-described gas barrier layer on both surfaces of the polyester film thus obtained by a vacuum evaporation method, a sputtering method, an ion plating method, or the like.
[0031]
<Magnetic recording medium>
The support of the present invention is a support for a magnetic recording medium in which a gas barrier layer is provided on the surface of a polyester film having excellent dimensional stability and also excellent slitting properties. It is preferably used as a base film of a recording type magnetic machine recording medium.
[0032]
The magnetic recording medium of the present invention may be formed by coating a magnetic layer on one surface (flat surface in the case of lamination) of the support of the present invention, or by using a method such as vacuum evaporation, sputtering, or ion plating. , Or a ferromagnetic metal thin film layer made of chromium or an alloy or oxide containing these as a main component, and on its surface, a protective layer such as diamond-like carbon (DLC) if necessary, a fluorine-containing layer. It is formed by sequentially providing a carboxylic acid-based lubricating layer and further providing a back coat layer on the surface opposite to the magnetic layer.
[0033]
【Example】
Hereinafter, the present invention will be further described based on examples. The various physical properties and characteristics in the present invention are measured and defined as follows.
(1) Young's modulus
Using a tensile tester “Tensilon” manufactured by Toyo Baldwin Co., Ltd., in a room adjusted to a temperature of 20 ° C. and a humidity of 50%, a film is cut into a sample having a width of 10 mm and a length of 15 cm. It is pulled at a chart speed of 500 mm / min at a speed of 10 mm / min, and the Young's modulus is calculated from the tangent at the rising portion of the obtained load-elongation curve.
(2) Surface roughness (Ra)
Using a stylus type surface roughness meter (Surfcoder 30C) manufactured by Kosaka Laboratory Co., Ltd., a chart (film surface roughness curve) is applied under the conditions of a needle radius of 2 μm and a stylus of 30 mg. From the film surface roughness curve, a portion of the measured length L is extracted in the direction of the center line, the center line of the extracted portion is set as the X axis, the direction of the vertical magnification is set as the Y axis, and the roughness curve is expressed as Y = f ( When represented by X), Ra (μm) given by the following equation is defined as the film average roughness.
[0034]
(Equation 1)
In the present invention, the measurement length is 1.25 mm, the cutoff value is 0.08 mm, and the average value measured five times is Ra.
(3) Average particle size of inert particles
The measurement is performed using a Shimadzu Corporation CP-50 type centrifugal particle size analyzer (Centrifugal Particle Size Analyzer). From the cumulative curve of the particle size of each particle size and its abundance calculated based on the obtained centrifugal sedimentation curve, the particle size corresponding to 50 mass percent was read, and this value was defined as the average particle size. I do.
(4) Dimensional change in width direction under longitudinal load (αw)
Under an atmosphere of a temperature of 23 ° C. and a humidity of 50%, a film slit to 12.65 mm (１ ／ inch) is set as shown in FIG. In addition, in order to measure the width dimension of the sample slit to 12.65 mm with a detector, gold is vapor-deposited on the surface in advance by sputtering. In this state, a 22 MPa weight is attached to one side of the film (the other is fixed), and the width of the film (L1) Is measured with a Keyence laser diameter measuring instrument (body: 3100 type, sensor: 3060 type).
[0036]
Then, under high temperature and high humidity of 49 ° C. (120 ° F.) × 90% RH, the unit cross-sectional area is 1 mm on one side (the other is fixed).2After applying a 2.7 kg weight per 72 hr (for 3 days), remove the weight, adjust the humidity for 24 hr in an atmosphere of a temperature of 23 ° C. and a humidity of 50%, and then again on one side of the film (the other is fixed). With a 22MPa weight, and then the width of the film (L2) Is measured with a Keyence laser diameter measuring instrument (body: 3100 type, sensor: 3060 type).
[0037]
From the dimensions before and after the temperature and humidity treatment measured above, the width dimension change (αW) before and after the temperature and humidity treatment under load is calculated by the following equation.
[0038]
(Equation 2)
αW = ｛(L1-L2) × / L1｝ × 100 (%)
(5) Thermal expansion coefficient (αt)
A film sample is cut out to a length of 15 mm and a width of 5 mm in the lateral direction of the film, set on a TMA3000 manufactured by Vacuum Riko, pretreated at 60 ° C. for 30 minutes in a nitrogen atmosphere, and then cooled to room temperature. Thereafter, the temperature is raised from 25 ° C. to 70 ° C. at a rate of 2 ° C./min, the sample length at each temperature is measured, and the thermal expansion coefficient (αt) is calculated from the following equation.
[0039]
(Equation 3)
αt = ｛(L2-L1) / (L1× ΔT)｝ × 106+0.5
Here, L in the above equation1Is the sample length (mm) at 40 ° C., L2Is the sample length (mm) at 60 ° C., ΔT is 20 (= 60−40 ° C.) ° C., and 0.5 is the coefficient of thermal expansion of quartz glass by 106Multiplied by.
(6) Humidity expansion coefficient (αh)
A film sample was cut out to a length of 15 mm and a width of 5 mm in the lateral direction of the film, set on a TMA3000 manufactured by Vacuum Riko, and kept at a constant humidity of 30% RH and 70% RH under a nitrogen atmosphere. Is measured, and the humidity expansion coefficient is calculated by the following equation.
[0040]
(Equation 4)
αh = ｛(L2-L1) × / (L1× ΔH)｝ × 106
Here, L in the above equation1Is the sample length (mm) at a humidity of 30% RH, L2Is the sample length (mm) at a humidity of 70% RH and ΔH is 40 (= 70−30% RH)% RH.
(7) Track deviation (error rate)
The error rate is measured under the following conditions using a system for QIC, ML4500B manufactured by MediaLogic.
[0041]
Current = 15.42 mA
Frequency: 0.25 MHz
Location = 0
Threshold: 40.0
Bad / Good / MAX: 1: 1: 1
Tracks: 28
The number of error rates is represented by an average value of the measured number of tracks (= 28).
[0042]
The conditions 1 and 2 are measured as follows.
Condition 1: Recording is performed at 10 ° C. and 10% RH and then reproduced at 45 ° C. and 80% RH, and the track shift due to the change in temperature and humidity is measured.
Condition 2: After recording at a temperature of 23 ° C. and a humidity of 50% RH, the vehicle is repeatedly run at a temperature of 40 ° C. and a humidity of 60% RH for 60 hours, returned to a temperature of 23 ° C. and a humidity of 50% RH, and maintained for 24 hours. After that, the recording is reproduced, and the track shift amount due to the width shrinkage due to running at a relatively high temperature and high humidity is measured.
[0043]
The evaluation criteria are as follows.
◎: No error rate
○: There is an error rate, but there is no practical problem
×: High error rate, practically problematic
(8) Electromagnetic conversion characteristics
The measurement was performed using a ML4500B manufactured by Medialogic, a system for QIC. The evaluation was performed with the S / N of the sample of Example 1 set to 0 dB and relative evaluation was performed according to the following criteria.
◎: +1 dB or more
：: -1 dB to less than +1 dB
×: less than -1 dB
[0044]
(9) Thickness of polyester film and gas barrier layer
The thickness of the entire film is randomly measured at 10 points with a micrometer, and the average value is used. When the polyester film is a laminated film composed of two or more layers, for the thickness of each layer, measure the layer thickness of the thin polyester layer by the method described below. Determined by subtracting the layer thickness of the layer and the thin polyester layer. That is, using a secondary ion mass spectrometer (SIMS), the metal element (M +) originating from the particles having the highest concentration among the particles in the film having a depth of 5,000 nm from the surface layer excluding the coating layer is used. The concentration ratio (M + / C +) of the hydrocarbon (C +) of the polyester is defined as the particle concentration, and the analysis is performed in the thickness direction from the surface to a depth of 5,000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, the particle concentration once reaches a stable value of 1 and then increases to a stable value of 2, or monotonously decreases. Based on this distribution curve, in the former case, the depth gives a particle concentration of (stable value 1 + stable value 2) / 2, and in the latter case, the depth at which the particle concentration becomes 1/2 of the stable value 1 The thickness (the depth is greater than the depth that gives a stable value of 1) is defined as the thickness (μm) of the thin polyester layer.
[0045]
The measurement conditions are as follows.
(A) Measuring device
Secondary ion mass spectrometer (SIMS); Perkin-Elmer Co., Ltd.
(PERKIN ELMER INC.), “6300”
(B) Measurement conditions
Primary ion species: O2 +
Primary ion acceleration voltage: 12 KV
Primary ion current: 200 nA
Raster area: 400 μm □
Analysis area: gate 30%
Measurement vacuum degree: 6.0 × 10-9Torr
E-GUNN: 0.5KV-3.0A
[0046]
In the case where the most abundant particles in the range of 5,000 nm from the surface layer are organic polymer particles other than silicone resin, it is difficult to measure by SIMS. Therefore, FT-IR (Fourier transform infrared spectroscopy) is performed while etching from the surface. ), Depending on the particles, the same concentration distribution curve as above is measured by XPS (X-ray photoelectric spectroscopy) or the like, and the layer thickness (μm) is determined.
[0047]
The thickness of the gas barrier layer was determined by molding a small piece of the film with an epoxy resin and forming an ultrathin section (cut in parallel to the film flow direction) with a thickness of about 600 angstroms using a microtome. The sample is observed with a transmission electron microscope (H-800, manufactured by Hitachi, Ltd.), and the thickness (nm) is determined by searching for the boundary surface of the gas barrier layer.
(10) Slit properties
Under an atmosphere of a temperature of 23 ° C. and a humidity of 50%, a film slit to 12.65 mm (１ ／ inch) is set as shown in FIG. In this state, a 10 MPa weight is attached to one side of the film (the other is fixed), and the width (L) of the film at that time is measured with a Keyence laser outer diameter measuring device (body: 3100 type, sensor: 3060 type). Measure at 0.1 mm intervals in the longitudinal direction.
[0048]
Then, the difference between the maximum value and the minimum value of the obtained width (L) is calculated as the width change amount (ΔL), and evaluated based on the following criteria.
◎: less than 0.2 μm
：: 0.2 μm or more and less than 0.5 μm
×: 0.5 μm or more
[0049]
[Example 1]
Polyethylene having an intrinsic viscosity of 0.60 (orthochlorophenol, 35 ° C.) containing 0.02% by weight of silicone particles having an average particle size of 0.5 μm and 0.30% by weight of spherical silica particles having an average particle size of 0.1 μm After drying 2,6-naphthalate at 180 ° C. for 5 hours, it is supplied to an extruder hopper, melted at 300 ° C., and subjected to casting using a T-type extrusion die with a surface finish of 0.3 S and a surface temperature of 60 ° C. It was quenched and solidified on a drum to obtain an unstretched film.
[0050]
The unstretched film thus obtained was preheated at 120 ° C., further stretched 5.4 times by heating with an infrared heater having a surface temperature of 830 ° C. from 14 mm above between low-speed and high-speed rolls, It was quenched and then supplied to a stenter and stretched 4.8 times in the transverse direction at 125 ° C. Subsequently, the film was heat-set at 225 ° C. for 3 seconds to obtain a biaxially oriented film having a thickness of 4.5 μm. The resulting film had a Young's modulus of 8 GPa in the vertical direction and 7 GPa in the horizontal direction. An Au film was formed on both surfaces of the obtained film roll by sputtering to a thickness of 150 nm, respectively, to prepare a support. The resulting support had a Young's modulus of 8 GPa in the vertical direction and 6 GPa in the horizontal direction.
[0051]
On the other hand, the composition shown below was put into a ball mill, kneaded and dispersed for 16 hours, and then 5 parts by weight of an isocyanate compound (Desmodur L manufactured by Bayer AG) was added, followed by high-speed shearing and dispersion for 1 hour to obtain a magnetic paint.
Composition of magnetic paint:
Acicular Fe particles 100 parts by weight
15 parts by weight of vinyl chloride-vinyl acetate copolymer
(Eslec 7A manufactured by Sekisui Chemical)
5 parts by weight of thermoplastic polyurethane resin
Chromium oxide 5 parts by weight
5 parts by weight carbon black
Lecithin 2 parts by weight
1 part by weight of fatty acid ester
50 parts by weight of toluene
50 parts by weight of methyl ethyl ketone
Cyclohexanone 50 parts by weight
[0052]
This magnetic paint is applied to one side of the above-mentioned polyethylene-2,6-naphthalate film so as to have a coating thickness of 0.5 μm, then subjected to an orientation treatment in a DC magnetic field of 2500 gauss, and dried by heating at 100 ° C. Thereafter, the resultant was subjected to a super calender treatment (linear pressure: 200 kg / cm, temperature: 80 ° C.) and wound up. The wound roll was left in an oven at 55 ° C. for 3 days.
[0053]
Further, a back coat layer paint having the following composition was applied to a thickness of 1 μm, dried, and further cut into 6.35 mm (= 1 ′ / 4) to obtain a magnetic tape.
Backcoat layer paint composition:
100 parts by weight of carbon black
60 parts by weight of thermoplastic polyurethane resin
18 parts by weight of isocyanate compound
(Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.)
0.5 parts by weight of silicone oil
250 parts by weight of methyl ethyl ketone
50 parts by weight of toluene
Table 1 shows the properties of the obtained support and tape. As is clear from this table, the error rate was low and the output characteristics were good.
[0054]
[Example 2]
Polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.60 (orthochlorophenol, 35 ° C.) for layer A containing 0.1% by weight of spherical silica particles having an average particle diameter of 0.1 μm, and an average particle diameter of 0.3 μm Polyethylene-2 having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.60 containing 0.15% by weight of spherical silica particles of 0.15% by weight and 0.15% by weight of spherical silica particles having an average particle diameter of 0.1 μm , 6-Naphthalate was dried at 180 ° C. for 5 hours, fed to another extruder hopper, melted at a melting temperature of 300 ° C., and layer A and layer B were laminated using a multi-manifold type coextrusion die. It was quenched and solidified on a casting drum maintained at a finish of 0.3 S and a surface temperature of 60 ° C. to obtain an unstretched film.
[0055]
The unstretched film thus obtained was preheated at 120 ° C., further stretched 5.9 times by heating with an infrared heater having a surface temperature of 830 ° C. from 14 mm above between low-speed and high-speed rolls, After quenching, it was supplied to a stenter and stretched 4.5 times in the horizontal direction at 125 ° C. and further 1.15 times in the horizontal direction at 170 ° C., for a total of 5.2 times. Subsequently, the film was heat-set at 225 ° C. for 3 seconds to obtain a biaxially oriented film having a thickness of 4.5 μm. Aluminum was vacuum-deposited on both sides of the obtained film roll while introducing oxygen to form aluminum oxide reinforced films, respectively, to prepare a support. The resulting support had a Young's modulus of 9 GPa in the vertical direction and 7 GPa in the horizontal direction.
[0056]
After the heat treatment was performed in the same manner as in Example 1, the same magnetic paint as in Example 1 was applied to the A layer surface, and the opposite back layer B layer was coated with the same back coat as in Example 1, and a magnetic tape was obtained and evaluated. Table 1 shows the properties of the obtained support and tape. As is clear from this table, the error rate was low and the output characteristics were good.
[0057]
[Example 3]
Polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.60 (orthochlorophenol, 35 ° C.) for layer A containing 0.01% by weight of spherical silica particles having an average particle diameter of 0.1 μm, and an average particle diameter of 0.3 μm 0.1% by weight of silicone particles of 0.1% by weight and 0.15% by weight of spherical silica particles having an average particle diameter of 0.1 μm. After 6-naphthalate is dried at 180 ° C for 5 hours, it is supplied to another extruder hopper, melted at a melting temperature of 300 ° C, and the layers A and B are laminated using a multi-manifold type coextrusion die, and the surface is finished. It was quenched and solidified on a casting drum maintained at 0.3 S and a surface temperature of 60 ° C. to obtain an unstretched film.
[0058]
The unstretched film thus obtained was preheated at 120 ° C., further stretched 2.3 times by heating with an infrared heater having a surface temperature of 830 ° C. from 14 mm above between low-speed and high-speed rolls, After quenching, it is supplied to a stenter, stretched 5.0 times in the transverse direction at 125 ° C., heat-set at 160 ° C. for 3 seconds, preheated at 140 ° C., and further between low-speed and high-speed rolls. It is heated by an infrared heater having a surface temperature of 830 ° C. from above 14 mm and stretched 3.1 times, quenched, and subsequently supplied to a stenter, and stretched 1.3 times in the horizontal direction at 170 ° C. After heat setting at 3 ° C. for 3 seconds, a biaxially oriented film having a thickness of 4.5 μm was obtained. A silica film was vacuum-deposited on both sides of the obtained film roll to form a support. The resulting support had a Young's modulus of 11 GPa in the vertical direction and 8 GPa in the horizontal direction. Table 1 shows the properties of the obtained support and tape. As is clear from this table, the error rate was low and the output characteristics were good.
[0059]
[Comparative Example 1]
A biaxially oriented film having a thickness of 4.5 μm was obtained in the same manner as in Example 1 except that the Au film was not formed by a sputter. The magnetic tape was obtained in the same manner as in Example 1. Table 1 shows the properties of the obtained support and tape.
[0060]
[Comparative Example 2]
After drying polyethylene-2,6-naphthalate having an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.60 containing 0.1% by weight of silicone particles having an average particle diameter of 0.8 µm at 180 ° C for 5 hours, the extruder is used. It was supplied to a hopper, melted at 300 ° C., and quenched and solidified on a casting drum maintained at a surface finish of 0.3 S and a surface temperature of 60 ° C. using a T-shaped extrusion die to obtain an unstretched film.
[0061]
The unstretched film thus obtained was preheated at 120 ° C., further stretched 4.0 times by heating with an infrared heater having a surface temperature of 830 ° C. from 14 mm above between low-speed and high-speed rolls, It was quenched and then supplied to a stenter and stretched 5.4 times in the transverse direction at 125 ° C. Subsequently, heat fixation was performed at 225 ° C. for 3 seconds, and a biaxially oriented film having a thickness of 4.5 μm was obtained in the same manner as in Example 1 except that an Au film was not formed by sputtering. The Young's modulus of the obtained film was 6 GPa in the vertical direction and 9 GPa in the horizontal direction. Then, a magnetic layer was provided directly on the biaxially oriented film in the same manner as in Example 1 to obtain a magnetic tape. Table 1 shows the properties of the obtained support and tape.
[0062]
[Comparative Example 3]
The same operation as in Example 2 was repeated except that the Young's modulus in the longitudinal direction and the width direction of the biaxially oriented film was changed as shown in Table 1. Table 1 shows the properties of the obtained support and tape.
[0063]
[Table 1]
【The invention's effect】
According to the present invention, when providing a gas barrier layer on a polyester film, a gas barrier layer having a thickness of 1 to 5% with respect to the thickness of the polyester film is selected as the gas barrier layer, and the gas barrier layer is formed not only on one side but also on both sides of the polyester film. And, the Young's modulus in the longitudinal direction of the support is 8 GPa or more, the Young's modulus in the width direction is 6 GPa or more, and the Young's modulus in the longitudinal direction is 1 GPa or more greater than the Young's modulus in the width direction. By being organically bonded, a support for a magnetic recording medium having excellent dimensional stability and also having slit properties is provided.
[0065]
When the support of the present invention is used as a base film in a magnetic recording medium, an error rate does not occur due to track deviation, the output characteristics are excellent, and a magnetic recording medium useful as a digital data storage tape that can be used for a long time can be obtained. Can be.
[Brief description of the drawings]
FIG. 1 is an explanatory view of an apparatus for measuring a residual shrinkage (αW) in a width direction after application of a load in a longitudinal direction of a film.
[Explanation of symbols]
1 sample
2 load
3 Light sensor LS-3036 Light receiving part
4 Light sensor LS-3036 Light emitting unit
5 Laser light
6 glass plate
7 Measuring instrument LS3100
8 analog / digital converter HP3457A
9 Personal computer
Claims (9)
支持体は長手方向のヤング率が８ＧＰａ以上、幅方向のヤング率が６ＧＰａ以上および長手方向のヤング率が幅方向のヤング率よりも１ＧＰａ以上大きく、
それぞれのガスバリア層の厚みは、ポリエステルフィルムの厚みを基準として、１〜５．０％の範囲にあることを特徴とする磁気記録媒体用支持体。A support comprising a polyester film and gas barrier layers provided on both surfaces thereof,
The support has a Young's modulus in the longitudinal direction of 8 GPa or more, a Young's modulus in the width direction of 6 GPa or more, and a Young's modulus in the longitudinal direction of 1 GPa or more larger than the Young's modulus in the width direction,
A support for a magnetic recording medium, wherein the thickness of each gas barrier layer is in the range of 1 to 5.0% based on the thickness of the polyester film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003102563A JP2004310899A (en) | 2003-04-07 | 2003-04-07 | Support base for magnetic recording medium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2003102563A JP2004310899A (en) | 2003-04-07 | 2003-04-07 | Support base for magnetic recording medium |
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| Publication Number | Publication Date |
|---|---|
| JP2004310899A true JP2004310899A (en) | 2004-11-04 |
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ID=33465956
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|---|---|---|---|
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007157244A (en) * | 2005-12-06 | 2007-06-21 | Toray Ind Inc | Support for magnetic recording medium and magnetic recording medium |
| JP2007226943A (en) * | 2006-01-24 | 2007-09-06 | Toray Ind Inc | Base for magnetic recording medium and magnetic recording medium thereof |
-
2003
- 2003-04-07 JP JP2003102563A patent/JP2004310899A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007157244A (en) * | 2005-12-06 | 2007-06-21 | Toray Ind Inc | Support for magnetic recording medium and magnetic recording medium |
| JP2007226943A (en) * | 2006-01-24 | 2007-09-06 | Toray Ind Inc | Base for magnetic recording medium and magnetic recording medium thereof |
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