JP3575190B2 - Aromatic polyamide film and magnetic recording medium - Google Patents

Description

一般式（ＩＩ）で示される互いに異なった芳香核を有する構造単位からなるＢ群、
一般式（ＩＩ）
【化６】

及び、一般式（ＩＩＩ）で示される互いに異なった芳香核を有する構造単位からなるＣ群、
一般式（ＩＩＩ）
【化７】

（ここで、Ａｒ₁、Ａｒ₂、Ａｒ₃はパラ配向性の芳香核であり、各群の化合物はＲａ、Ｒｂ、Ｒｃで示されるニトロ基、シアノ基、炭素数１〜４のアルキル基、炭素数１〜３のアルコキシ基、トリアルキルシリル基、オキシアリール基、チオアリール基から選ばれる官能基で置換されていても構わない。ここで、ｋ、ｌ、ｍはそれぞれ０〜４の数である。また、Ａ群、Ｂ群は実質的に等モルである。）から少なくとも３種以上選択される構造単位（但し、基本芳香核を異にする少なくとも２種の構造単位は同じ群から選択される。）で示される構造単位を主たる構造単位とし、かつ隣接置換率が６０％以上である芳香族ポリアミドフィルムからなるフィルムであって、該フィルムの吸湿率が２．２％以下であることを特徴とする芳香族ポリアミドフィルムである。
【０００８】
【発明の実施の形態】
まず、本発明の芳香族ポリアミドは、上記の一般式（Ｉ）、一般式（ＩＩ）、一般式（ＩＩＩ ）の３群から少なくとも３種選択され、かつその内の少なくとも２種は同一群から選択された基本芳香核（官能基、置換基を除いた残りの部分として定義する。）を異にする構造単位からなる。かかる構成とすることでポリマの溶解性、ポリマ溶液の安定性が劇的に改善され、好ましく有機溶媒溶液系からの製膜が可能となる。この時、一般式（Ｉ）、一般式（ＩＩ）、一般式（ＩＩＩ ）の３群からは少なくとも４種以上、更に好ましくは５種以上選択されることが好ましく、また、２種以上の基本芳香核の異なる構造単位が選択される群は２群以上であることが好ましい。また、２種以上の基本芳香核の異なる構造単位が選択される群における各基本芳香核の存在割合（ＡＲ）は該群における基本芳香核の種類をＮ種とした時、
１／Ｎ×０．７≦ＡＲ≦１／Ｎ×１．３
好ましくは、
１／Ｎ×０．８≦ＡＲ≦１／Ｎ×１．２
更に好ましくは、
１／Ｎ×０．９≦ＡＲ≦１／Ｎ×１．１
であれば芳香族ポリアミドの溶解性、溶液の安定性に優れるばかりか機械特性にも優れたフィルムを得ることができる。
【０００９】
次に、Ａｒ_１ 、Ａｒ_２ 及びＡｒ_３ は互いに異なったパラ配向性芳香核である。ここで言うパラ配向性芳香核とは２価の結合鎖が互いに同軸あるいは平行にある芳香核で定義され、例えば、
【化８】

等を挙げることができるが、これに限定されるものではない。また、互いに異なったとは、基本芳香核または置換基の種類あるいは数を異にすると言う意味である。
【００１０】
Ａｒ_１ 、Ａｒ_２ 及びＡｒ_３ のパラ配向性は、力学的要求上必要な要因である。従って、本発明の芳香族ポリアミドフィルムにはこのような結合単位を６０モル％以上含有する。好ましくは７０モル％以上、更に好ましくは７５モル％以上含んでいることが好ましい。６０モル％未満であれば、成形物としたときに強度、伸度、剛性、耐熱性等のフィルムとしての十分な機能を全うできない。
【００１１】
本発明の芳香族ポリアミドは異なった基本芳香核を２種以上含有する。好ましくは３種以上、好ましくは４種以上である。これらの中でも基本芳香核の組み合わせとして、フェニレン基、ビフェニレン基、ナフチレン基から選ばれる少なくとも２種、特にビフェニレン基とフェニレン基の組み合わせは力学的特性、溶媒への溶解性に優れるので好ましい。
【００１２】
また、後述するように本発明においては、製膜溶液を好ましく有機溶媒溶液とすることができるが、一般式（Ｉ）で示される化合物として、３，３’−ジ置換−４，４’−ビフェニルジアミン及び／または２，２’−ジ置換−４，４’−ビフェニルジアミンと、２，５−ジ置換及び／または２，３−ジ置換パラフェニレンジアミンを用いたとき、ポリマーの溶解性は格段に改善されるので、ポリマー濃度を高めて生産性を改善できると共に製膜性に優れた溶液とすることができ、また、吸湿率も低く抑えることができるため好ましい。
【００１３】
さらに本発明の芳香族ポリアミドは、好ましく一般式（ＩＶ）で示されるＤ群の構造単位を含有することができる。
【００１４】
一般式（ＩＶ）
【化９】

（ここでＡｒ_４ 、Ａｒ_５ はパラ配向性の芳香核であり、Ｘ、Ｙは互いに同じか異なっていても良い−ＣＯ−または−ＮＨ−基。Ｚはブリッジ原子団。また、Ｒｄ、Ｒｅはニトロ基、シアノ基、炭素数１〜４のアルキル基、炭素数１〜３のアルコキシ基、トリアルキルシリル基、オキシアリール基、チオアリール基から選ばれる官能基であり、ｎ、ｐはそれぞれ０〜４の数である。この時、Ｘ、Ｙが共に−ＣＯ−の時はＡ群と（Ｂ群、Ｄ群）、Ｘ、Ｙが共に−ＮＨ−の時は（Ａ群、Ｄ群）とＢ群、互いに異なるときはＡ群、Ｂ群は実質的に等モルである。）
【００１５】
Ａｒ_４ 、Ａｒ_５ はパラ配向性の芳香核であり先述のＡｒ_１ 〜Ａｒ_３ と同様に定義される。
【００１６】
またＺはブリッジ原子団であって、１〜２個の橋かけ原子を有し、
−Ｏ−，−ＣＨ_２ −，−ＣＯ−，−ＳＯ_２ −，−Ｓ−，−Ｃ（ＣＨ_３ ）_２ −，−Ｃ（ＣＦ_３ ）_２ −
等から選ばれるが、これに限定されるものではない。
【００１７】
このＤ群の構造単位を含有した芳香族ポリアミドは、例えば有機溶媒溶液としたときの溶液の安定性に非常に優れ、製膜性が格段に改良されたものとなる。また、適度な柔軟性を付与することが可能であり、伸度特性を大きく改善できる。
【００１８】
しかしながら、先述のようにかかる構造単位の導入は成形体の機械特性をそこねることもあり、好ましくは、全芳香族ポリアミド構造単位の２〜４０％、より好ましくは５〜３０％、更に好ましくは１０〜２５％の範囲内で用いるのが良い。
【００１９】
また、本発明の芳香族ポリアミドの各芳香核は、芳香核の水素原子を置換する置換基Ｒａ、Ｒｂ、Ｒｃ、Ｒｄ、Ｒｅとして、ニトロ基、シアノ基、炭素数１〜４のアルキル基、炭素数１〜３のアルコキシ基、トリアルキルシリル基、オキシアリール基、チオアリール基から選ばれる置換基で置換されていると芳香族ポリアミドの溶解性、溶液の安定性に優れたものが得られ、かつ好ましく本発明の吸湿率を満足せしめるので好ましく用いられるが、吸湿率の低減には適度な大きさの官能基が好ましく、シアノ基、炭素数１〜４のアルキル基、炭素数１〜３のアルコキシ基、トリメチルシリル基から選ばれる官能基が好ましい。
【００２０】
また、本発明の芳香族ポリアミドの隣接置換率は、６０％以上、好ましくは７０％以上、更に好ましくは８０％以上であれば溶解性、溶液の安定性が向上するため製膜性が向上し、かつ、吸湿率を低減することができる。この隣接置換率Ｓ_０ は下式により定義され、使用する原料から確率的に求めることができる。また、ここで言う隣接とはアミド基が結合した芳香核炭素原子に隣接する芳香核炭素原子を指す。
【００２１】
Ｓ_０ ＝（隣接位に水素が置換していないアミド基の数）／（アミド基の総数）×１００（％） ………（式１）
【００２２】
本発明の芳香族ポリアミドフィルムは硫酸、発煙硫酸、トリフルオロメタンスルホン酸等の強酸に溶解させた製膜原液から得ても構わないが、本発明の芳香族ポリアミドは溶解性、溶液の安定性に優れることから有機溶媒溶液から得ることもできる。特に光学等方性を有する有機溶媒系溶液から得られるフィルムは優れた表面性を有するので工業的な利用価値が高く、複雑な製法によることもなくプロセス上にも好ましい。ここで用いられる有機溶媒は、該芳香族ポリアミドが溶解し、かつ安定な溶液を形成できれば特に制限はないが、Ｎ−メチルピロリドン、ジメチルアセトアミド、ジメチルホルムアミド、ヘキサメチルホスホルアミド等の非プロトン性有機極性溶媒が好ましく用いられる。もちろんこれら有機溶媒は混合溶媒であっても良い。
【００２３】
本発明の芳香族ポリアミドフィルムの吸湿率は２．２％以下である必要がある。好ましくは２．０％以下、更に好ましくは１．８％以下である。２．２％を越えるフィルムは湿度変化に伴う寸法や電気特性などの諸特性が大きく変動し磁気記録媒体、フレキシブルプリント基板用基材等において録再特性の劣化、耐久性の劣化、絶縁性能の劣化など製品としたときの安定性にかけるものとなる。また、蒸着あるいはスパッタリングなどで金属薄膜型磁性層を設けようと加熱・減圧した時、水蒸気が放出されて減圧が保てなかったりあるいは水蒸気が不純物ガスとして作用し、工程が不安定になり、また、金属薄膜層の品質も低下するため好ましくない。
【００２４】
本発明の芳香族ポリアミドは、一般式（Ｉ）、一般式（ＩＩ）、一般式（ＩＩＩ ）で表される繰り返し単位を６０モル％以上含むものであるが、目的に合わせ例えばアミド、エステルあるいはイミドの構造を有する構造単位が共重合、またはブレンドされていても差し支えない。もちろんこれら構造単位に含まれる芳香核にも、ニトロ基、シアノ基、炭素数１〜４のアルキル基、炭素数１〜３のアルコキシ基、トリアルキルシリル基、オキシアリール基、チオアリール基などの置換基を有していても構わない。また、その他構造単位に対する置換基としてハロゲンが使用されていてもかまわないが、先述のようにハロゲン原子の使用は地球環境上の問題あるいは製品性能への影響が懸念されるため、用いないことが好ましく、用いたとしても全芳香核の２０モル％未満、好ましくは１５モル％未満に止めることが好ましい。特に、一般式（Ｖ）および／または一般式（ＶＩ）で示される芳香族ポリイミドは、機械特性の改善に効果があり好ましく用いられる。
【００２５】
一般式（Ｖ）
【化１０】

一般式（ＶＩ）
【化１１】

ここでＡｒ_６ 、Ａｒ_８ は少なくとも１個の芳香環を含み、イミド環を形成する２つのカルボニル基は芳香環上の隣接する炭素原子に結合している。このＡｒ_６ は、芳香族テトラカルボン酸あるいはこの無水物に由来する。代表例としては次の様なものが挙げられる。
【００２６】
【化１２】

ここでＺ’は
−Ｏ−，−ＣＨ_２ −，−ＣＯ−，−ＳＯ_２ −，−Ｓ−，−Ｃ（ＣＨ_３ ）_２ −
等から選ばれるが、これに限定されるものではない。
【００２７】
また、Ａｒ_８ は無水カルボン酸あるいはこのハライドに由来する。Ａｒ_７ 、Ａｒ_９ は例えば
【化１３】

などが挙げられ、Ｘ’、Ｙ’は
−Ｏ−，−ＣＨ_２ −，−ＣＯ−，−ＳＯ_２ −，−Ｓ−，−Ｃ（ＣＨ_３ ）_２ −
等から選ばれるが、これに限定されるものではない。更にこれらの芳香環上の水素原子の一部が、ハロゲン基（特に塩素）、ニトロ基、炭素数１〜４のアルキル基（特にメチル基）、炭素数１〜３のアルコキシ基などの置換基で置換されているものも含み、また、重合体を構成するアミド結合中の水素が他の置換基によって置換されているものも含む。
【００２８】
本発明に用いられる芳香族ポリアミドには、成形体の物性を損なわない程度に粒子、滑剤、酸化防止剤その他の添加剤等がブレンドされていてもよい。
【００２９】
次に本発明の芳香族ポリアミドフィルムを製造する例を説明するが、本発明はこれに限定されるものではない。
【００３０】
芳香族ポリアミドを得る方法は例えば、低温溶液重合法、界面重合法、溶融重合法、固相重合法などが挙げられるが、低温溶液重合法つまり酸クロリドとジアミンから得る場合には、Ｎ−メチルピロリドン（ＮＭＰ）、ジメチルアセトアミド（ＤＭＡｃ）、ジメチルホルムアミド（ＤＭＦ）などの非プロトン性有機極性溶媒中で合成される。ポリマ溶液は、単量体として酸クロリドとジアミンを使用すると塩化水素が副生するが、これを中和する場合には水酸化カルシウム、炭酸カルシウム、炭酸リチウムなどの無機の中和剤、またエチレンオキサイド、プロピレンオキサイド、アンモニア、トリエチルアミン、トリエタノールアミン、ジエタノールアミンなどの有機の中和剤が使用される。また、イソシアネートとカルボン酸との反応は、非プロトン性有機極性溶媒中、触媒の存在下で行なわれる。
【００３１】
これらのポリマ溶液はそのまま成形体を得るための原液として使用してもよく、あるいはポリマを一度単離してから上記の有機溶媒や、硫酸等の無機溶媒に再溶解して原液を調製してもよい。
【００３２】
また、ポリマの固有粘度（ポリマ０．５ｇを硫酸中で１００ｍｌの溶液として３０℃で測定した値）は、０．５以上であることが好ましい。
【００３３】
成形体を得るための原液には溶解助剤として無機塩例えば塩化カルシウム、塩化マグネシウム、塩化リチウム、硝酸リチウムなどを添加する場合もある。原液中のポリマ濃度は好ましくは２〜４０重量％、更に好ましくは５〜３５重量％である。かかる範囲を下回れば吐出を大きく取る必要があり経済的に不利であり、越えれば吐出量あるいは溶液粘度の関係で薄もののフィルムを得ようとするときの困難性が高い。
【００３４】
また、必要に応じ例えばＳｉＯ_２ 、ＴｉＯ_２ 、ＴｉＮ、Ａｌ_２ Ｏ_３ 、ＺｒＯ_２ 、ゼオライト、その他の金属微粉末などの無機粒子や有機粒子等の粒子を含有量としてポリマ重量あたり０．０１〜５重量％、好ましくは０．０５〜３重量％添加する。
【００３５】
粒子の添加方法は特に制限はないが、凝集度を調整する場合は、例えば、粒子を予め１０ポイズ好ましくは１ポイズ以下の溶媒中に分散させる方法を挙げることができる。溶媒としては、製膜時に用いるものと同一であることが好ましいが、特に悪影響が見られないときには、他の溶媒を用いて差し支えない。また、これら溶媒には分散助剤等の添加物が分散に悪影響を及ぼさない範囲で用いられて構わない。粒子の分散には撹拌分散器、ボールミル、超音波分散器等を用い、好ましく、凝集度を調整する。
【００３６】
この分散された粒子は前記ポリマ溶液に混合するが、混合にあたっては重合前の溶媒に添加あるいは重合後に添加あるいはポリマ溶液調製時に添加してもよく、さらには吐出直前でも構わないが、原液中に均一に分散されていることが非常に重要である。
【００３７】
次にフィルム化について説明する。上記のように調製された製膜原液は、いわゆる溶液製膜法によりフィルム化が行なわれる。溶液製膜法には乾湿式法、乾式法、湿式法などがありいづれの方法で製膜されても差し支えないが、ここでは乾湿式法を例にとって説明する。
【００３８】
乾湿式法で製膜する場合は該原液を口金からドラム、エンドレスベルト等の支持体上に押し出して薄膜とし、次いでかかる薄膜層から溶媒を飛散させ薄膜が自己保持性をもつまで乾燥する。乾燥条件は例えば、室温〜２２０℃、６０分以内の範囲で行うことができる。またこの乾燥工程で用いられるドラム、エンドレスベルトの表面はなるだけ平滑であれば表面の平滑なフィルムが得られる。乾式工程を終えたフィルムは支持体から剥離されて湿式工程に導入され、脱塩、脱溶媒などが行なわれ、さらに延伸、乾燥、熱処理が行なわれてフィルムとなる。
【００３９】
この工程において湿式工程、延伸、熱処理工程は重要な役割を持つ。湿式工程を制御することで、緻密で吸湿率の低い好適なフィルムとすることができる。
【００４０】
この工程には水を脱溶媒としても構わないが、水と有機溶媒との混合媒を好ましく用いることができる。有機溶媒は水溶性であり、好ましくは重合溶媒同様、Ｎ−メチルピロリドン（ＮＭＰ）、ジメチルアセトアミド（ＤＭＡｃ）、ジメチルホルムアミド（ＤＭＦ）等の非プロトン性有機極性溶媒が好ましく、組成比を変化させた複数の浴を用いることが実用的である。また、温度は任意に選びうるが、４０℃以上であればより容易に目的を達することができる。
【００４１】
延伸は延伸倍率として面倍率で０．８〜８．０（面倍率とは延伸後のフィルム面積を延伸前のフィルムの面積で除した値で定義する。１以下はリラックスを意味する。）の範囲が通常用いられるが、本発明の吸湿率とするには結晶性を高めることが効果的であるので好ましくは１．３〜８．０、更に好ましくは１．４〜最大延伸倍率の８０％程度である。また、熱処理としては１５０℃〜５００℃、が通常用いられるが、本発明の吸湿率を達成するために、好ましくは２００℃〜４００℃、更に好ましくはＴｇ±４０℃の温度で数秒から数分間熱処理が好ましく実施される。さらに、延伸あるいは熱処理後のフィルムを徐冷する事は有効であり、５０℃／秒以下の速度で冷却する事が有効である。
【００４２】
また、本発明の芳香族ポリアミドフィルムの２０℃、相対湿度６０％における少なくとも一方向の引張りヤング率Ｅ２０が、Ｅ２０≧７．８４ＧＰａ、より好ましくはＥ２０≧８．８２ＧＰａ、更に好ましくはＥ２０≧９．８０ＧＰａであることが好ましい。
【００４３】
本発明の発明の芳香族ポリアミドフィルムは優れた機械特性を有しているので特に薄もののフィルムとしたときに他素材には見られない優れた効果を発揮する。好ましい厚みは０．５〜５０μｍ、より好ましくは１〜２０μｍ、更に好ましくは２〜１０μｍである。
【００４４】
本発明の芳香族ポリアミドフィルムはもちろん単層フィルムでも、積層フィルムであっても良い。積層フィルムとする時は、本発明の磁気記録媒体の基材フィルムと基層部（積層された本発明の基材フィルム以外のフィルム構成部分）は同じ種類でも異なるものでも良い。例えば２層の場合には、重合した芳香族ポリアミド溶液を二分し、それぞれ異なる粒子を添加した後、積層する。さらに３層以上の場合も同様である。これら積層の方法としては、周知の方法たとえば、口金内での積層、複合管での積層や、一旦１層を形成しておいてその上に他の層を形成する方法などがある。
【００４５】
また、本発明の芳香族ポリアミドフィルムから得られる成形体中に含まれる不純物として、トリクレンで抽出したときの抽出残渣は重量比にして０．２％以下、好ましくは０．１％以下であると成型時あるいは加工時あるいは使用時、ローラ、ガイドへの巻き付きなどの工程、使用上の不良要因を排除できるので好ましい。
【００４６】
また、成形体に含有される金属イオンとしては好ましくは３０００ｐｐｍ以下、更に好ましくは１００ｐｐｍ以下、特に好ましくは３０ｐｐｍ以下であれば接触部材の腐蝕等の影響を及ぼさない優れた成形体とできる。ここで言う金属イオンはイオン化された金属成分であって、外部粒子等の固形添加物を構成する金属成分は除かれる。
【００４７】
これは例えば溶媒を含めた原料の純度を高くすることはもちろんであるが、フィルム化の際重合溶媒及び無機塩を抽出する工程において表面に急激に緻密な層が形成されないようすることが好ましく、先述のように重合溶媒と同種の溶媒が凝固溶媒に対しある傾斜比をもって配合されてなる抽出槽を用いたり、抽出温度の調整例えば複数の抽出層で温度勾配を設けたりすること等は好適な方法である。
【００４８】
本発明は吸湿率が２．２％以下であるので、湿度による寸法変動などの影響が少ないために磁気記録媒体に好適である。磁気記録媒体とするにはこのフィルムに磁性層を形成する。記録方式としては任意であり、水平磁気記録、垂直磁気記録、光磁気記録など公知の記録方式をとることができる。磁性層を形成する方法は公知の方法、例えば、強磁性粉末を各種バインダーを用いて磁性塗料とし、基材フィルム上に塗布する湿式法、蒸着法、スパッタリング法、イオンプレーティング法などの乾式法があり、特に限定されるものではない。湿式法の場合にはグラビアロールを使用する方法が塗膜の均一性の点ではより好ましい。塗布後の乾燥温度は９０〜１５０℃が好ましい。また、カレンダ工程は２５℃〜１５０℃の範囲で行うのが好ましい。
【００４９】
磁気記録媒体は後述するように大容量化要求が高く、そのため磁性層としても塗布型磁性層から金属薄膜型磁性層を具した磁気記録媒体の要求が高まっている。本発明は吸湿率を小さくまた、蒸着などの高温にさらされる工程中、熱分解により腐食性物を生じるような官能基を制限しているので、金属薄膜型磁性層を具した磁気記録媒体においてその効果を顕著に発揮できる。
【００５０】
この金属薄膜型の磁性層としてはＣｏ、Ｆｅ、Ｎｉなどの金属の単体または合金やこれら単体または合金とＣｒ、Ｍｏ、Ｗ、Ｖ、Ｎｂ、Ｔｉ、Ｒｈ、Ｒｕ等との合金及びこれら金属あるいは合金の酸化物が例示でき、必要に応じ同種あるいは異種の磁性層を積層することもできる。また、これら磁性層の上には保護層あるいは潤滑層を好ましく形成することもできる。
【００５１】
また、特に、磁気記録媒体として厚みが６．５μｍ以下、幅が２．２〜１５ｍｍであって磁気記録媒体としたときの記録密度が１５キロバイト／ｍｍ^２ 以上（非圧縮時）であるテープ状磁気記録媒体としたときに、一層効果的に本発明の効果を利用した態様とできる。磁気テープの大容量化は支持体を薄くし長尺化する方法とトラック幅の狭幅化、記録波長の短波長化による単位面積あたりの記録容量を向上させる方法があり、これらは共用されることが多いが、本発明は吸湿率を抑えたことで湿度による寸法変化を抑制できたので、トラックのズレ、テープの伸びやたるみなどが生じ難く、記録位置精度が極めて高いので上記のような大容量化手段を好ましく採用する磁気テープ用ベースフィルムとして好ましく使用できる。記録密度としては好ましくは２５キロビット／ｍｍ^２ 以上、更に好ましくは３４キロビット／ｍｍ^２ 以上である。上限は特に無いが最終的に磁性層を構成する成分により規制される。また、フィルム厚みとしては好ましく４．５μｍ以下、更に好ましくは３．５μｍ以下である。下限はフィルムのヤング率と走行系の設計等にかかり、０．５μｍ程度である。薄膜化は好ましくパラ配向性芳香族ポリアミドとすれば達成できる。そして、上記高容量化対策の結果全体としての記憶容量としても１ＧＢ以上、好ましくは８ＧＢ以上、更に好ましくは１６ＧＢ以上、特に好ましくは３２ＧＢ以上とできる。全体の記憶容量は筐体サイズにもよるが上限は３００〜１０００ＧＢ程度である。
【００５２】
また、本発明のフィルムはもちろん単層フィルムでも用いられるが、積層フィルムであっても良い。また、各層を構成する成分は同じ種類であっても異なるものであっても良いが、積層フィルム全体として本願発明の要件を備えていることが好ましい。また、各層が粒子を含有していてもよく、粒子の種類、含有量等は本発明のフィルムに望ましく用いられるものを使用することが望ましい。また、内層部に用いる粒子の径が積層された本発明のフィルム中の粒子の径よりも大きいと、基材フィルム表面に適度のうねりを持たせる事ができテ−プ走行性がより一層良好となるので望ましく、ヘッドに対向する面に含有される粒子よりも反対面に含有される粒子の粒径及び／または含有量を大きくすることが走行性の点から見て好ましい。なお、積層構成については断面写真における粒子の深さ方向における分布あるいは断面のＸ線マイクロアナライザー分析、二次イオン質量分析法、あるいはエッチングしながらＥＳＣＡあるいは赤外線分光法等を用いたり、極めて薄層の場合には前記の方法の他表面写真を参酌し求めることができる。
【００５３】
また、本発明の芳香族ポリアミドフィルムの表面粗さとしてはＲｐで２〜５００ｎｍ、好ましくは３〜３００ｎｍ、Ｒａで０．１〜１００ｎｍ、好ましくは０．２〜５０ｎｍ、Ｒｚで２〜５００ｎｍ好ましくは３〜４００ｎｍであるように好ましく設計される。また、片面のみ磁性層を有する磁気記録媒体においてはその裏面は走行性の確保から適度にあれていることが好ましく、Ｒａとして０．５〜５０ｎｍ程度とすることが好ましい。なお、各パラメータの定義は例えば奈良治郎著「表面粗さ測定法」（総合技術センター、１９８３）に示されているものである。
【００５４】
本発明のフィルムの２００℃、１０分間での熱収縮率は５％以下が好ましく、より好ましくは２％以下であると温度変化によるテープの寸法変化、特に金属薄膜型磁性層形成時には高温度がかかることが多いので、上記熱収縮率を満足することで加工時の寸法変動、変形が小さくでき、良好な電磁変換特性を保てるので望ましい。
【００５５】
【実施例】
本発明の物性の測定方法、効果の評価方法は次の方法による。
【００５６】
（１）吸湿率
基材フィルム数グラムを真空乾燥器中で１００Ｐａ以下、１８０℃の条件下、恒量になるまで乾燥し、その重量をＷ１とする。次いで、該フィルムを２５℃、７５％ＲＨの環境下に４８時間置き、その後測定した重量をＷ２とする。吸湿率は
（Ｗ２−Ｗ１）／Ｗ１×１００（単位：％）
として求めた。
【００５７】
（２）強度、伸度、ヤング率
オリエンテック社製テンシロンを用い、試長５０ｍｍ、引張速度３００ｍｍ／分で実施した。
【００５８】
（３）隣接置換率
十分大きな相対粘度を有する芳香族ポリアミドの場合、投入原料の全てが反応したと見なし、投入原料の種類及び量から前記（式１）を用いて確率的な単純計算で求めた。また、フィルムが計算で求めた隣接置換率となっているかＣ１３ＮＭＲ及びＨ１ＮＭＲスペクトルによって確認を行った。
【００５９】
（４）トリクレン抽出率
試料である芳香族ポリアミドフィルム１０ｇをソックスレー抽出器を用い、２４時間抽出を行った。次いで抽出液をエバポレータを用いて溶媒を留去し残渣の重量を求め、次の式で抽出率を求めた。なお単位は％である。
【００６０】
トリクレン抽出率＝（残渣重量（ｇ）／成形体重量（ｇ））×１００
【００６１】
（５）金属イオン含有量
試料である芳香族ポリアミドフィルム２ｇを燃焼、灰化させ、硝酸、フッ化水素酸に溶解し、ついで希硝酸で定容化した。
【００６２】
次に、原子吸光分析装置を用い、予め作成した検量線に基づいて定量した。ここで、単位ｐｐｍは（μｇ／ｇ）である。また、外部添加粒子に起因する部分は計算から除いた。
【００６３】
（６）電磁変換特性
次にこのフィルムの製膜時の金属ベルトに接触しない側の表面に、次の組成からなる磁性塗料を調製し、グラビアロールで所定の塗布厚になるように塗布し、硬化した後、カレンダ処理を行った。磁性層の厚みは２μｍとした。
【００６４】
磁性粉（金属粉） ８０重量部
塩ビ系共重合体 １０重量部
ポリウレタン １０重量部
硬化剤 ５重量部
研磨剤 ５重量部
トルエン １００重量部
メチルエチルケトン １００重量部
【００６５】
この磁性層を塗布したフィルムを１／２インチ幅にスリットし、ＶＴＲカセットに組み込みＶＴＲテ−プとした。このテ−プに家庭用ＶＴＲを用いて２５℃、１０％ＲＨの環境下テレビ試験波形発生器によりＲＦ信号を入力した。このテープを２５℃、８０％ＲＨの環境下１週間保持後再生したときの画面下部変形量を求めた。変形量の大きなものほど特性が悪いことを意味し、１０以下であることが好ましい。
【００６６】
（７）耐久性
４５℃、８０％ＲＨの環境下、１００回繰り返し走行させた後の磁性面のすり傷や欠落及びテープおれの有無を観察し、次の３段階で評価した。
【００６７】
◎：まったくすり傷や欠落、テープおれが見られない。
○：極めて弱いすり傷やテープおれの発生が認められる。
×：きついすり傷や磁性層の欠落、テープおれが認められる。
【００６８】
実施例１〜７、比較例１〜４
以下の実施例あるいは比較例で用いた各原料の略記号はそれぞれ次の通りである。
【００６９】
芳香族ジアミン成分：
ＰＰＤ：パラフェニレンジアミン
ＤＰＸ：２，５ −ジメチルパラフェニレンジアミン
ＤＭＢ：３，３’−ジメチルベンジジン
ＤＯＢ：３，３’−ジメトキシベンジジン
ＤＰＥ：４，４’−ジアミノジフェニルメタン
ＴＤＭ：３，３’，５，５’−テトラメチル−４，４’−ジアミノジフェニルメタン
酸クロリド成分：
ＴＰＣ：テレフタル酸ジクロリド
ＭＰＣ：２−メチルテレフタル酸ジクロリド
ＮＰＣ：２，６−ナフタレンジカルボン酸ジクロリド
ＢＰＣ：４，４’− ビフェニルジカルボン酸ジクロリド
ＤＰＣ：４，４’− ジフェニルエーテルジカルボン酸ジクロリド
酸無水物成分：
ＰＡＨ：ピロメリット酸無水物
【００７０】
実施例１
脱水したＮ−メチルピロリドン（以下ＮＭＰと略す）に５０モル％のＤＭＢ、５０モル％のＤＰＸを溶解させ溶液を冷却する。ついで、１００モル％のＴＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。ポリマ濃度は７重量％であり、重合物は透明な溶液として得られた。また、２週間放置後も安定な溶液であった。
【００７１】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２８５℃で乾燥、熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み５μｍのフィルムを得た。このフィルムの吸湿率は１．５％、強度、伸度、ヤング率はそれぞれ４８０ＭＰａ、１８％、１３．７２ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２５ｐｐｍであった。
【００７２】
また、電磁変換特性、耐久性とも良好であった。
【００７３】
実施例２
ＮＭＰに４０モル％のＤＯＢ、４０モル％のＤＰＸ、２０モル％のＤＰＥを溶解させ溶液を冷却する。ついで、１００モル％のＴＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。ポリマ濃度は１２重量％であり、重合物は透明な溶液として得られた。また、２週間放置後も安定な溶液であった。
【００７４】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２８５℃で乾燥、２９５℃で熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み４．５μｍのフィルムを得た。このフィルムの吸湿率は１．７％、強度、伸度、ヤング率はそれぞれ５４０ＭＰａ、４２％、１２．２５ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２４ｐｐｍであった。
【００７５】
また、電磁変換特性、耐久性とも良好であった。
【００７６】
また、実施例２で得たフィルムに連続真空蒸着装置を用いて、表面にＣｏ−ＣｏＯ系薄膜を蒸着し、磁性層を形成した。次に蒸着層表面にカーボン保護膜、反対面にバックコート層を公知の手段により形成した。蒸着工程では全く問題なく磁性層を形成できた。また、このテープを６５℃、相対湿度９０％で７日間放置する強制劣化試験を行い、磁性層の残留磁化量を処理前後で比較してみると、殆ど劣化は認められず、高密度磁気記録に適した蒸着型磁性層を設けた磁気記録媒体に好適に使用しうることが判った。
【００７７】
参考例１
水浴のみを用い湿式工程を行った以外は実施例２と同様に重合・製膜を行いフィルムを得た。このフィルムの吸湿率は１．８％、強度、伸度、ヤング率はそれぞれ５１９ＭＰａ、４３％、１２．０４ＧＰａであった。また、トリクレン抽出率は０．３％、金属イオン含有量は１２０ｐｐｍであった。
【００７８】
また、電磁変換特性、耐久性ともまあ良好であったが、耐久性評価時にノイズが生ずる画質の劣化が認められた。
【００７９】
また、参考例１で得たフィルムに実施例２と同様にＣｏ−ＣｏＯ系薄膜を蒸着し、また、カーボン保護膜、バックコート層を形成した。蒸着工程ではほぼ問題なく磁性層を形成できた。しかしながら、このテープを実施例２同様の強制劣化試験を行い、磁性層の残留磁化量を処理前後で比較してみると、劣化が認められ、蒸着型磁性層を設けたタイプに使用するには信頼性に不安があることが判った。
【００８０】
参考例２
乾燥、熱処理を２７０℃で行い、延伸倍率を長手方向に１．１５倍、幅方向に１．２倍とした以外は実施例２と同様に重合・製膜を行いフィルムを得た。このフィルムの吸湿率は１．９％、強度、伸度、ヤング率はそれぞれ４９０ＭＰａ、４８％、１０．７８ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２４ｐｐｍであった。
【００８１】
また、電磁変換特性、耐久性ともまあ良好であったが実施例２を下回るものであった。
【００８２】
また、参考例２で得たフィルムに実施例２と同様にＣｏ−ＣｏＯ系薄膜を蒸着し、また、カーボン保護膜、バックコート層を形成した。蒸着工程ではほぼ問題なく磁性層を形成できた。しかしながら、このテープを実施例２同様の強制劣化試験を行い、磁性層の残留磁化量を処理前後で比較してみると、問題ないレベルであるが劣化が認められた。
【００８３】
実施例３
ＮＭＰに６０モル％のＤＯＢ、２０モル％のＤＰＸ、２０モル％のＤＰＥを溶解させ、溶液を冷却する。ついで、１００モル％のＴＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。ポリマ濃度は１０重量％であり、重合物は透明な溶液として得られた。また、２週間放置後も安定な溶液であった。
【００８４】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２８５℃で乾燥、３００℃で熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み８μｍのフィルムを得た。このフィルムの吸湿率は１．７％、強度、伸度、ヤング率はそれぞれ４４１ＭＰａ、３６％、９．３１ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２６ｐｐｍであった。
【００８５】
また、電磁変換特性、耐久性とも良好であった。
【００８６】
実施例４
ＮＭＰに４５モル％のＤＯＢ、４７モル％のＤＰＸ、８モル％のＴＤＭを溶解させ、溶液を冷却する。ついで、５０モル％のＴＰＣ、５０モル％のＮＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。ポリマ濃度は１２重量％であり、重合物は透明な溶液として得られた。また、２週間放置後も安定な溶液であった。
【００８７】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２８５℃で乾燥、２９５℃で熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み８μｍのフィルムを得た。このフィルムの吸湿率は１．５％、強度、伸度、ヤング率はそれぞれ５６８ＭＰａ、３５％、１３．２３ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２２ｐｐｍであった。
【００８８】
また、電磁変換特性、耐久性とも良好であった。
【００８９】
実施例５
ＮＭＰに４０モル％のＤＭＢ、４０モル％のＤＰＸ、２０モル％のＴＤＭを溶解させ、溶液を冷却する。ついで、１００モル％のＭＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。ポリマ濃度は１４重量％であり、重合物は透明な溶液として得られた。また、２週間放置後も安定な溶液であった。
【００９０】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２８０℃で乾燥、２９０℃で熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み８μｍのフィルムを得た。このフィルムの吸湿率は１．４％、強度、伸度、ヤング率はそれぞれ５２９ＭＰａ、４０％、１２．２５ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２０ｐｐｍであった。
【００９１】
また、電磁変換特性、耐久性とも良好であった。
【００９２】
実施例６
ＮＭＰに４０モル％のＤＯＢ、４０モル％のＰＰＤ、２０モル％のＤＰＥを溶解させ、溶液を冷却する。ついで、５０モル％のＭＰＣ、５０モル％のＢＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。ポリマ濃度は１２重量％であり、重合物は透明な溶液として得られた。また、２週間放置後も安定な溶液であった。
【００９３】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２８０℃で乾燥、２９０℃で熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み８μｍのフィルムを得た。このフィルムの吸湿率は１．９％、強度、伸度、ヤング率はそれぞれ５４９ＭＰａ、４５％、１２．７４ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２１ｐｐｍであった。
【００９４】
また、電磁変換特性、耐久性とも良好であった。
【００９５】
実施例７
ＮＭＰに５０モル％のＤＭＢ、５０モル％のＤＰＸを溶解させ、ついで５モル％のＰＡＨを加え３０分間撹拌し、ついで溶液を冷却する。次に、４０モル％のＭＰＣ、４５モル％のＢＰＣ、１０モル％のＤＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。ポリマ濃度は１２重量％であり、重合物は透明な溶液として得られた。また、２週間放置後も安定な溶液であった。
【００９６】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１８０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２７０℃で乾燥、熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み８μｍのフィルムを得た。このフィルムの吸湿率は１．９％、強度、伸度、ヤング率はそれぞれ５７８ＭＰａ、４２％、１４．２１ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２４ｐｐｍであった。
【００９７】
また、電磁変換特性、耐久性とも良好であった。
【００９８】
また、実施例７で得たフィルムに実施例２と同様にＣｏ−ＣｏＯ系薄膜を蒸着し、また、カーボン保護膜、バックコート層を形成した。蒸着工程ではほぼ問題なく磁性層を形成できた。蒸着工程では全く問題なく磁性層を形成できた。また、実施例２と同様の強制劣化試験を行い、磁性層の残留磁化量を処理前後で比較してみると、殆ど劣化は認められず、高密度磁気記録に適した蒸着型磁性層を設けた磁気記録媒体に好適に使用しうることが判った。
【００９９】
比較例１
ＮＭＰにポリマあたり５０重量％の臭化リチウムを溶解させ、次にＤＭＢ１００モル％を溶解し、溶液を冷却する。ついでＴＰＣ１００モル％を添加し反応を行った。生成物は重合開始後まもなく沈殿を生じ、フィルムを得ることができないものであった。
【０１００】
比較例２
ＮＭＰにポリマあたり５０重量％の臭化リチウムを溶解させ、次にＤＰＸ１００モル％を溶解し、溶液を冷却する。ついでＴＰＣ１００モル％を添加し反応を行った。生成物は重合開始後まもなく沈殿を生じ、成形体をえることができないものであった。
【０１０１】
比較例３
ＮＭＰにＤＭＢ５０モル％、ＰＰＤ５０モル％、ＤＰＥ２５モル％を溶解し溶液を冷却する。ついで１００モル％のＴＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。重合時において沈殿の生成なく重合を終了できたが、ポリマ濃度を７％としてもこの溶液は２週間放置後はゲル化する不安定な溶液であった。
【０１０２】
重合直後の溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２７０℃で乾燥、熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み８μｍのフィルムを得た。このフィルムの吸湿率は２．３％、強度、伸度、ヤング率はそれぞれ４２１ＭＰａ、４８％、８．５３ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は３５ｐｐｍであった。
【０１０３】
また、電磁変換特性、耐久性とも良好であった。
【０１０４】
比較例４
ＮＭＰにＤＭＢ４０モル％、ＰＰＤ４０モル％、ＤＰＥ２０モル％を溶解し溶液を冷却する。ついで１００モル％のＴＰＣを添加し２時間撹拌後水酸化リチウムで中和して重合物を得た。また、ポリマ濃度は８％でありこの溶液は２週間放置後は増粘したがなんとか製膜可能な溶液であった。
【０１０５】
この溶液に平均一次粒径１６ｎｍのシリカ粒子をポリマ当たり２重量％添加し、ついで５μｍカットのフィルターを通した後、ステンレスベルト上に流延し、１７０℃で２分間溶媒を蒸発後、自己支持性を得たフィルムをベルトから剥離して４０℃に保ったＮＭＰ／水比がそれぞれ３０／７０、２０／８０、１０／９０、０／１００の抽出浴中に順次導入して残存溶媒等を抽出し、ついで、テンター中で２７０℃で乾燥、熱処理を行った。この時長手方向に１．２５倍、幅方向に１．３倍延伸して、厚み８μｍのフィルムを得た。このフィルムの吸湿率は２．３％、強度、伸度、ヤング率はそれぞれ５１０ＭＰａ、３８％、１２．２５ＧＰａであった。また、トリクレン抽出率は０．１％以下、金属イオン含有量は２４ｐｐｍであった。
【０１０６】
また、電磁変換特性、耐久性とも良好であった。
【０１０７】
また、比較例４で得たフィルムに実施例２と同様にＣｏ−ＣｏＯ系薄膜を蒸着し、また、カーボン保護膜、バックコート層を形成した。蒸着工程では減圧操作が安定せず磁性層の形成は困難であった。また、微妙な圧変動があったため、形成された磁性層も組成が一定していないことが予測され、該フィルムを蒸着型磁性層を設けた磁気記録媒体とするには信頼性に問題のあることが判った。
【０１０８】
【表１】

【０１０９】
【発明の効果】
本発明の芳香族ポリアミドフィルムはその本来の優れた機械特性、耐熱性等の種々の性能を維持しつつ、特に芳香族ポリアミド本来の問題であった吸湿率を低減できるため、高密度磁気記録媒体やフレキシブルプリント配線板、感熱転写記録材、絶縁材をはじめとし、種々の用途における工業的利用価値は極めて高いものである。また、本発明の芳香族ポリアミドは好ましく有機溶媒系から得ることができ、その溶液の安定性にも優れるのでプロセス上の特別の操作を必要としない。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an aromatic polyamide film which is suitably used for applications requiring stability against changes in humidity, such as a magnetic recording medium.
[0002]
[Prior art]
Aromatic polyamide is a polymer useful as an industrial material because of its high heat resistance and electrical insulation. In particular, aromatic polyamides composed of para-oriented aromatic nuclei, such as polyparaphenylene terephthalamide (PPTA), provide molded articles having excellent strength and elastic modulus in addition to the above-mentioned properties due to their rigidity, and thus their utility value. Is expensive.
[0003]
On the other hand, in magnetic recording media applications for high-density, long-time recording and electronic circuit applications for high-density mounting, thinner base materials and stability against environmental changes are required.
[0004]
However, para-oriented aromatic polyamides such as PPTA have a high modulus of elasticity and can be obtained as a film having sufficient rigidity even if they are thin. The electrical characteristics fluctuate and do not have sufficient reliability. For example, Japanese Unexamined Patent Publication (Kokai) No. 1-207331 discloses a method for improving such characteristics. However, such a method requires a heat treatment at an extremely high temperature, and is too highly crystallized to be difficult to recycle. Is not preferred. In addition, aromatic polyamides such as PPTA have low solubility in solvents and dissolve only in very limited solvents such as sulfuric acid, so that there are great restrictions on processes. In particular, when the solution gives optical anisotropy, unless a special film-forming method is adopted, only a brittle film that can be easily torn is obtained and the process is extremely restricted.
[0005]
As an aromatic polyamide having a low moisture absorption and a high solubility in a solvent, Japanese Patent Publication No. 56-45421 proposes an aromatic polyamide in which a chlorine atom is introduced into an aromatic nucleus. However, such aromatic polyamides are expensive in the monomer used, and when heated, there is a concern that hydrogen chloride will be desorbed and the product performance will be affected, and there is a concern that film disposal and incineration will generate hydrogen chloride and dioxin during incineration. Environmentally unfavorable.
[0006]
[Problems to be solved by the invention]
The present invention solves such a problem, and does not impair the excellent heat resistance and mechanical properties of the aromatic polyamide, and has excellent solubility in a solvent and stability of a solution, and is preferably soluble in an organic solvent. It is another object of the present invention to provide an aromatic polyamide film having reduced moisture absorption.
[0007]
[Means for Solving the Problems]
That is, the present invention provides a group A comprising structural units having different aromatic nuclei represented by the general formula (I),
General formula (I)
Embedded image

A group B comprising structural units having different aromatic nuclei represented by the general formula (II),
General formula (II)
Embedded image

And a group C consisting of structural units having different aromatic nuclei represented by the general formula (III):
General formula (III)
Embedded image

(Where Ar ₁ , Ar _Two , Ar _Three Is a para-oriented aromatic nucleus, and the compounds in each group are a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a trialkylsilyl represented by Ra, Rb, and Rc. It may be substituted with a functional group selected from a group, an oxyaryl group and a thioaryl group. Here, k, l, and m are numbers from 0 to 4, respectively. The groups A and B are substantially equimolar. Or at least three structural units selected from the same group (provided that at least two structural units having different basic aromatic nuclei are selected from the same group). And the adjacent replacement ratio is 60% or more. A film comprising an aromatic polyamide film, wherein the film has a moisture absorption of 2.2% or less.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the aromatic polyamide of the present invention is selected from at least three types from among the three groups represented by the general formulas (I), (II) and (III), and at least two of them are selected from the same group. It consists of structural units that differ in the selected basic aromatic nucleus (defined as the remaining part excluding the functional groups and substituents). With this configuration, the solubility of the polymer and the stability of the polymer solution are dramatically improved, and a film can be preferably formed from an organic solvent solution system. At this time, it is preferable that at least 4 or more, more preferably 5 or more are selected from the three groups of the general formulas (I), (II) and (III). Preferably, two or more groups are selected from structural units having different aromatic nuclei. Further, the abundance ratio (AR) of each basic aromatic nucleus in a group in which two or more different structural units of the basic aromatic nucleus are selected, when the type of the basic aromatic nucleus in the group is N kinds,
1 / N × 0.7 ≦ AR ≦ 1 / N × 1.3
Preferably,
1 / N × 0.8 ≦ AR ≦ 1 / N × 1.2
More preferably,
1 / N × 0.9 ≦ AR ≦ 1 / N × 1.1
If this is the case, a film having not only excellent solubility of the aromatic polyamide and stability of the solution but also excellent mechanical properties can be obtained.
[0009]
Next, Ar ₁ , Ar ₂ And Ar ₃ Are different para-oriented aromatic nuclei. The para-oriented aromatic nucleus here is defined as an aromatic nucleus in which divalent bonding chains are coaxial or parallel to each other.
Embedded image

And the like, but are not limited thereto. Further, different from each other means that the kind or number of the basic aromatic nucleus or the substituent is different.
[0010]
Ar ₁ , Ar ₂ And Ar ₃ Is a necessary factor in mechanical requirements. Therefore, the aromatic polyamide film of the present invention contains such a bonding unit in an amount of 60 mol% or more. Preferably, the content is 70 mol% or more, more preferably 75 mol% or more. If the amount is less than 60 mol%, when formed into a molded product, the film cannot have sufficient functions such as strength, elongation, rigidity and heat resistance.
[0011]
The aromatic polyamide of the present invention contains two or more different basic aromatic nuclei. The number is preferably 3 or more, and more preferably 4 or more. Among them, as the combination of the basic aromatic nucleus, at least two kinds selected from a phenylene group, a biphenylene group, and a naphthylene group, particularly a combination of a biphenylene group and a phenylene group are preferable because of excellent mechanical properties and solubility in a solvent.
[0012]
Further, as described later, in the present invention, the film-forming solution can be preferably an organic solvent solution. However, as the compound represented by the general formula (I), 3,3′-disubstituted-4,4′- When using biphenyldiamine and / or 2,2′-disubstituted-4,4′-biphenyldiamine and 2,5-disubstituted and / or 2,3-disubstituted paraphenylenediamine, the solubility of the polymer is Since the solution is remarkably improved, the solution can be improved in productivity by increasing the polymer concentration, and a solution excellent in film forming property can be obtained, and the moisture absorption rate can be suppressed.
[0013]
Further, the aromatic polyamide of the present invention can preferably contain a structural unit of Group D represented by the general formula (IV).
[0014]
General formula (IV)
Embedded image

(Where Ar ₄ , Ar ₅ Is a para-oriented aromatic nucleus, and X and Y may be the same or different from each other, -CO- or -NH-. Z is a bridge atomic group. Rd and Re are functional groups selected from a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a trialkylsilyl group, an oxyaryl group, and a thioaryl group; , P are numbers from 0 to 4, respectively. At this time, when X and Y are both -CO-, group A and (group B and D), and when X and Y are both -NH- (group A and D) and group B, Is substantially equimolar for Group A and Group B. )
[0015]
Ar ₄ , Ar ₅ Is a para-oriented aromatic nucleus; ₁ ~ Ar ₃ Is defined similarly.
[0016]
Z is a bridging atomic group, having 1 to 2 bridging atoms,
-O-, -CH ₂ -, -CO-, -SO ₂ -, -S-, -C (CH ₃ ) ₂ −, −C (CF ₃ ) ₂ −
Etc., but is not limited to this.
[0017]
The aromatic polyamide containing the structural unit of Group D has, for example, extremely excellent solution stability when prepared as an organic solvent solution, and has a remarkably improved film-forming property. In addition, it is possible to impart appropriate flexibility, and the elongation characteristics can be greatly improved.
[0018]
However, as described above, the introduction of such a structural unit may impair the mechanical properties of the molded article, and is preferably 2 to 40%, more preferably 5 to 30%, even more preferably 10 to 30% of the wholly aromatic polyamide structural unit. It is good to use within the range of ２５25%.
[0019]
Further, each aromatic nucleus of the aromatic polyamide of the present invention is a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms as substituents Ra, Rb, Rc, Rd, Re for replacing a hydrogen atom of the aromatic nucleus, When substituted with a substituent selected from an alkoxy group having 1 to 3 carbon atoms, a trialkylsilyl group, an oxyaryl group and a thioaryl group, an aromatic polyamide having excellent solubility and solution stability can be obtained. It is preferably used because it satisfies the moisture absorption rate of the present invention, but a functional group having an appropriate size is preferable for reducing the moisture absorption rate, and is preferably a cyano group, an alkyl group having 1 to 4 carbon atoms, or a 1 to 3 carbon atoms. A functional group selected from an alkoxy group and a trimethylsilyl group is preferred.
[0020]
When the aromatic polyamide of the present invention has an adjacent substitution rate of 60% or more, preferably 70% or more, more preferably 80% or more, the solubility and the stability of the solution are improved, so that the film forming property is improved. In addition, the moisture absorption rate can be reduced. This adjacent replacement rate S ₀ Is defined by the following equation and can be stochastically determined from the raw materials used. The term “adjacent” as used herein refers to an aromatic nucleus carbon atom adjacent to an aromatic nucleus carbon atom to which an amide group is bonded.
[0021]
S ₀ = (Number of amide groups in which no hydrogen is substituted in the adjacent position) / (total number of amide groups) × 100 (%) (Formula 1)
[0022]
The aromatic polyamide film of the present invention may be obtained from a film-forming stock solution dissolved in a strong acid such as sulfuric acid, fuming sulfuric acid, and trifluoromethanesulfonic acid, but the aromatic polyamide of the present invention has high solubility and solution stability. Because of its superiority, it can be obtained from an organic solvent solution. In particular, a film obtained from an organic solvent-based solution having optical isotropy has excellent surface properties and thus has high industrial utility value, and is preferable in the process without using a complicated production method. The organic solvent used herein is not particularly limited as long as the aromatic polyamide can be dissolved and a stable solution can be formed, but aprotic solvents such as N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and hexamethylphosphoramide can be used. Organic polar solvents are preferably used. Of course, these organic solvents may be mixed solvents.
[0023]
It is necessary that the aromatic polyamide film of the present invention has a moisture absorption of 2.2% or less. Preferably it is 2.0% or less, more preferably 1.8% or less. When the film exceeds 2.2%, various characteristics such as dimensions and electrical characteristics are greatly changed due to a change in humidity, and the recording / reproducing characteristics are deteriorated, the durability is deteriorated, and the insulation performance is deteriorated in a magnetic recording medium, a substrate for a flexible printed circuit board, and the like. This will affect the stability of the product, such as deterioration. Also, when heating and depressurizing to provide a metal thin film type magnetic layer by vapor deposition or sputtering, etc., steam is released and the depressurization cannot be maintained, or steam acts as an impurity gas, and the process becomes unstable. However, it is not preferable because the quality of the metal thin film layer also deteriorates.
[0024]
The aromatic polyamide of the present invention contains 60 mol% or more of the repeating units represented by the general formulas (I), (II) and (III). Structural units having a structure may be copolymerized or blended. Of course, the aromatic nucleus contained in these structural units may also be substituted with a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a trialkylsilyl group, an oxyaryl group, a thioaryl group, or the like. It may have a group. In addition, halogen may be used as a substituent for other structural units.However, as described above, the use of halogen atoms is a concern not only for global environmental problems but also for product performance. Preferably, even if used, it is preferably less than 20 mol%, preferably less than 15 mol% of the total aromatic nucleus. In particular, the aromatic polyimide represented by the general formula (V) and / or the general formula (VI) is effective in improving mechanical properties and is preferably used.
[0025]
General formula (V)
Embedded image

General formula (VI)
Embedded image

Where Ar ₆ , Ar ₈ Contains at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring. This Ar ₆ Is derived from an aromatic tetracarboxylic acid or its anhydride. The following are typical examples.
[0026]
Embedded image

Where Z '
-O-, -CH ₂ -, -CO-, -SO ₂ -, -S-, -C (CH ₃ ) ₂ −
Etc., but is not limited to this.
[0027]
Also, Ar ₈ Is derived from carboxylic anhydride or this halide. Ar ₇ , Ar ₉ Is for example
Embedded image

X ′ and Y ′ are
-O-, -CH ₂ -, -CO-, -SO ₂ -, -S-, -C (CH ₃ ) ₂ −
Etc., but is not limited to this. Further, some of the hydrogen atoms on these aromatic rings may be substituted with a substituent such as a halogen group (especially chlorine), a nitro group, an alkyl group having 1 to 4 carbon atoms (especially a methyl group), or an alkoxy group having 1 to 3 carbon atoms. And those in which the hydrogen in the amide bond constituting the polymer is substituted by another substituent.
[0028]
The aromatic polyamide used in the present invention may be blended with particles, lubricants, antioxidants and other additives to such an extent that the physical properties of the molded article are not impaired.
[0029]
Next, an example of producing the aromatic polyamide film of the present invention will be described, but the present invention is not limited thereto.
[0030]
The method for obtaining an aromatic polyamide includes, for example, a low-temperature solution polymerization method, an interfacial polymerization method, a melt polymerization method, and a solid-phase polymerization method. It is synthesized in an aprotic organic polar solvent such as pyrrolidone (NMP), dimethylacetamide (DMAc), and dimethylformamide (DMF). When acid chloride and diamine are used as monomers in a polymer solution, hydrogen chloride is by-produced.When neutralizing this, an inorganic neutralizing agent such as calcium hydroxide, calcium carbonate, lithium carbonate, or ethylene is used. Organic neutralizing agents such as oxides, propylene oxide, ammonia, triethylamine, triethanolamine, diethanolamine and the like are used. The reaction between the isocyanate and the carboxylic acid is carried out in an aprotic organic polar solvent in the presence of a catalyst.
[0031]
These polymer solutions may be used as a stock solution for obtaining a molded body as it is, or the polymer solution may be isolated once and then the stock solution may be prepared by re-dissolving in the above organic solvent or an inorganic solvent such as sulfuric acid. Good.
[0032]
In addition, the intrinsic viscosity of the polymer (a value obtained by measuring 0.5 g of the polymer in sulfuric acid as a 100 ml solution at 30 ° C.) is preferably 0.5 or more.
[0033]
In some cases, an inorganic salt such as calcium chloride, magnesium chloride, lithium chloride, or lithium nitrate is added as a dissolution aid to the stock solution for obtaining a molded product. The polymer concentration in the stock solution is preferably from 2 to 40% by weight, more preferably from 5 to 35% by weight. Below this range, it is economically disadvantageous to have to take a large amount of discharge, and above this range, it is difficult to obtain a thin film due to the discharge amount or solution viscosity.
[0034]
If necessary, for example, SiO 2 ₂ , TiO ₂ , TiN, Al ₂ O ₃ , ZrO ₂ , Zeolite, and other fine metal powders, such as inorganic particles and organic particles, are added in an amount of 0.01 to 5% by weight, preferably 0.05 to 3% by weight, based on the weight of the polymer.
[0035]
The method of adding the particles is not particularly limited, but when adjusting the degree of aggregation, for example, a method in which the particles are dispersed in a solvent of 10 poise, preferably 1 poise or less can be mentioned. The solvent is preferably the same as that used at the time of film formation, but when no adverse effect is observed, another solvent may be used. Further, additives such as a dispersing aid may be used in these solvents as long as they do not adversely affect the dispersion. For dispersing the particles, a stirring disperser, a ball mill, an ultrasonic disperser or the like is used, and the degree of aggregation is preferably adjusted.
[0036]
The dispersed particles are mixed with the polymer solution, but may be added to the solvent before polymerization or added after polymerization or added at the time of preparing the polymer solution. It is very important that they are evenly dispersed.
[0037]
Next, film formation will be described. The film forming stock solution prepared as described above is formed into a film by a so-called solution film forming method. The solution film forming method includes a dry-wet method, a dry method, a wet method, and the like, and any method may be used. However, the dry-wet method will be described here as an example.
[0038]
When a film is formed by a dry-wet method, the undiluted solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and then the solvent is scattered from the thin film layer and dried until the thin film has a self-holding property. Drying can be performed, for example, at room temperature to 220 ° C. for 60 minutes or less. Further, if the surfaces of the drum and the endless belt used in this drying step are as smooth as possible, a film having a smooth surface can be obtained. The film after the dry process is peeled from the support, introduced into the wet process, subjected to desalting, solvent removal, and the like, and further stretched, dried, and heat-treated to form a film.
[0039]
In this process, the wet process, the stretching, and the heat treatment process play an important role. By controlling the wet process, a suitable film having a high density and a low moisture absorption rate can be obtained.
[0040]
In this step, water may be used as a solvent to remove the solvent, but a mixed medium of water and an organic solvent can be preferably used. The organic solvent is water-soluble, preferably an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), etc., like the polymerization solvent, and the composition ratio was changed. It is practical to use multiple baths. The temperature can be arbitrarily selected, but if the temperature is 40 ° C. or higher, the purpose can be more easily achieved.
[0041]
Stretching is a stretching ratio of 0.8 to 8.0 (area ratio is defined as a value obtained by dividing the area of the film after stretching by the area of the film before stretching. 1 or less means relaxation). Although the range is usually used, it is effective to increase the crystallinity in order to obtain the moisture absorption rate of the present invention. Therefore, the range is preferably 1.3 to 8.0, more preferably 1.4 to 80% of the maximum stretching ratio. It is about. As the heat treatment, 150 ° C. to 500 ° C. is usually used, but in order to achieve the moisture absorption of the present invention, preferably at 200 ° C. to 400 ° C., more preferably at a temperature of Tg ± 40 ° C. for several seconds to several minutes. Heat treatment is preferably performed. Further, it is effective to gradually cool the film after stretching or heat treatment, and it is effective to cool the film at a rate of 50 ° C./sec or less.
[0042]
Further, the tensile Young's modulus E20 in at least one direction at 20 ° C. and a relative humidity of 60% of the aromatic polyamide film of the present invention is E20 ≧ 7.84 GPa, more preferably E20 ≧ 8.82 GPa, and further preferably E20 ≧ 9. It is preferably 80 GPa.
[0043]
Since the aromatic polyamide film of the present invention has excellent mechanical properties, it exhibits an excellent effect not found in other materials, especially when the film is made thin. The preferred thickness is 0.5 to 50 μm, more preferably 1 to 20 μm, and still more preferably 2 to 10 μm.
[0044]
The aromatic polyamide film of the present invention may be a single-layer film or a laminated film. When forming a laminated film, the base film and the base layer portion (film components other than the laminated base film of the present invention) of the magnetic recording medium of the present invention may be the same type or different. For example, in the case of two layers, the polymerized aromatic polyamide solution is divided into two, and different particles are added to each other, followed by lamination. The same applies to the case of three or more layers. These laminating methods include well-known methods such as lamination in a die, lamination in a composite tube, and a method in which one layer is formed once and another layer is formed thereon.
[0045]
Further, as impurities contained in the molded product obtained from the aromatic polyamide film of the present invention, the extraction residue when extracted with trichlene is 0.2% or less by weight, preferably 0.1% or less. During molding, processing, or use, a process such as winding around a roller or a guide, or the like, is preferable because defects in use can be eliminated.
[0046]
Further, when the metal ions contained in the molded body are preferably 3000 ppm or less, more preferably 100 ppm or less, and particularly preferably 30 ppm or less, it is possible to obtain an excellent molded body which does not affect corrosion of the contact member. The metal ions referred to herein are ionized metal components, and exclude metal components constituting solid additives such as external particles.
[0047]
This is, of course, to increase the purity of the raw material including the solvent, for example, it is preferable to prevent the formation of a rapidly dense layer on the surface in the step of extracting the polymerization solvent and inorganic salt during film formation, It is preferable to use an extraction tank in which the same kind of solvent as the polymerization solvent is mixed with the coagulation solvent with a certain gradient ratio as described above, or to adjust the extraction temperature, for example, to provide a temperature gradient in a plurality of extraction layers. Is the way.
[0048]
Since the present invention has a moisture absorption of 2.2% or less, it is suitable for a magnetic recording medium because it has little influence of dimensional change due to humidity. To form a magnetic recording medium, a magnetic layer is formed on this film. The recording method is arbitrary, and a known recording method such as horizontal magnetic recording, vertical magnetic recording, and magneto-optical recording can be used. The method of forming the magnetic layer is a known method, for example, a dry method such as a wet method, a vapor deposition method, a sputtering method, and an ion plating method in which a ferromagnetic powder is formed into a magnetic paint using various binders and applied on a base film. There is no particular limitation. In the case of the wet method, a method using a gravure roll is more preferable from the viewpoint of the uniformity of the coating film. The drying temperature after application is preferably 90 to 150C. The calendering step is preferably performed at a temperature in the range of 25C to 150C.
[0049]
As will be described later, there is a high demand for a magnetic recording medium having a large capacity. Therefore, as a magnetic layer, a demand for a magnetic recording medium including a coating type magnetic layer and a metal thin film type magnetic layer is increasing. Since the present invention has a low moisture absorption rate and limits functional groups that generate corrosive substances by thermal decomposition during a process exposed to high temperatures such as vapor deposition, the present invention relates to a magnetic recording medium having a metal thin film type magnetic layer. The effect can be remarkably exhibited.
[0050]
Examples of the metal thin film type magnetic layer include simple substances or alloys of metals such as Co, Fe, and Ni, alloys of these simple substances or alloys with Cr, Mo, W, V, Nb, Ti, Rh, Ru, and the like; An oxide of an alloy can be exemplified, and magnetic layers of the same type or different types can be laminated as necessary. Further, a protective layer or a lubricating layer can be preferably formed on these magnetic layers.
[0051]
In particular, the magnetic recording medium has a thickness of 6.5 μm or less, a width of 2.2 to 15 mm, and a recording density of 15 kilobytes / mm when the magnetic recording medium is used. ² When the tape-shaped magnetic recording medium described above (when not compressed) is used, it is possible to more effectively utilize the effects of the present invention. To increase the capacity of a magnetic tape, there are a method of making the support thinner and making it longer, and a method of making the track width narrower and improving the recording capacity per unit area by shortening the recording wavelength, and these are shared. In many cases, the present invention was able to suppress the dimensional change due to humidity by suppressing the moisture absorption rate, so that the displacement of the track, the expansion or sagging of the tape is unlikely to occur, and the recording position accuracy is extremely high, so that It can be preferably used as a base film for a magnetic tape which preferably employs means for increasing the capacity. The recording density is preferably 25 kbit / mm ² And more preferably 34 kilobits / mm ² That is all. There is no particular upper limit, but it is finally regulated by the components constituting the magnetic layer. The thickness of the film is preferably 4.5 μm or less, more preferably 3.5 μm or less. The lower limit depends on the Young's modulus of the film and the design of the running system, and is about 0.5 μm. Thinning can be preferably achieved by using a para-oriented aromatic polyamide. As a result of the above measures for increasing the capacity, the storage capacity as a whole can be 1 GB or more, preferably 8 GB or more, more preferably 16 GB or more, particularly preferably 32 GB or more. Although the total storage capacity depends on the size of the housing, the upper limit is about 300 to 1000 GB.
[0052]
In addition, the film of the present invention may of course be used as a single-layer film, but may be a laminated film. The components constituting each layer may be the same or different, but it is preferable that the entire laminated film satisfies the requirements of the present invention. In addition, each layer may contain particles, and it is desirable to use those which are desirably used for the film of the present invention with respect to the type and content of the particles. Further, when the diameter of the particles used in the inner layer portion is larger than the diameter of the particles in the laminated film of the present invention, a moderate undulation can be provided on the base film surface, and the tape running property is further improved. Therefore, it is preferable from the viewpoint of running properties to increase the particle diameter and / or the content of the particles contained on the surface opposite to the surface facing the head. As for the lamination structure, the distribution of the particles in the cross-sectional photograph in the depth direction or the X-ray microanalyzer analysis of the cross section, secondary ion mass spectrometry, ESCA or infrared spectroscopy while etching, etc. In this case, it can be determined by referring to the surface photograph in addition to the above method.
[0053]
Further, the surface roughness of the aromatic polyamide film of the present invention is 2 to 500 nm in Rp, preferably 3 to 300 nm, 0.1 to 100 nm in Ra, preferably 0.2 to 50 nm, and 2 to 500 nm in Rz, preferably It is preferably designed to be 3-400 nm. In a magnetic recording medium having a magnetic layer only on one side, the back side is preferably appropriately adjusted to ensure running properties, and Ra is preferably about 0.5 to 50 nm. The definition of each parameter is, for example, the one shown in “Surface Roughness Measurement Method” by Jiro Nara (Tokyo Gijutsu Center, 1983).
[0054]
The heat shrinkage of the film of the present invention at 200 ° C. for 10 minutes is preferably 5% or less, and more preferably 2% or less, the dimensional change of the tape due to the temperature change, especially the high temperature when forming the metal thin film type magnetic layer. Since this is often the case, it is desirable to satisfy the above-mentioned heat shrinkage rate because dimensional fluctuation and deformation during processing can be reduced and good electromagnetic conversion characteristics can be maintained.
[0055]
【Example】
The method for measuring physical properties and the method for evaluating effects according to the present invention are as follows.
[0056]
(1) Moisture absorption rate
A few grams of the base film is dried in a vacuum dryer under a condition of 100 Pa or less and 180 ° C. until a constant weight is obtained, and the weight is W1. Next, the film is placed in an environment of 25 ° C. and 75% RH for 48 hours, and the measured weight is defined as W2. The moisture absorption rate is
(W2-W1) / W1 × 100 (unit:%)
Asked.
[0057]
(2) Strength, elongation, Young's modulus
The test was performed using Orientec Tensilon at a test length of 50 mm and a tensile speed of 300 mm / min.
[0058]
(3) Adjacent replacement rate
In the case of an aromatic polyamide having a sufficiently large relative viscosity, it was considered that all of the input raw materials had reacted, and it was determined by a stochastic simple calculation using the above (Equation 1) from the type and amount of the input raw materials. In addition, it was confirmed by C13NMR and H1NMR spectra whether the film had the adjacent substitution ratio obtained by calculation.
[0059]
(4) Tricrene extraction rate
10 g of an aromatic polyamide film as a sample was extracted for 24 hours using a Soxhlet extractor. Next, the solvent was distilled off from the extract using an evaporator, the weight of the residue was determined, and the extraction rate was determined by the following equation. The unit is%.
[0060]
Tricrene extraction rate = (residue weight (g) / molded body weight (g)) × 100
[0061]
(5) Metal ion content
2 g of an aromatic polyamide film as a sample was burned and ashed, dissolved in nitric acid and hydrofluoric acid, and then made constant in volume with diluted nitric acid.
[0062]
Next, quantification was performed using an atomic absorption spectrometer based on a calibration curve created in advance. Here, the unit ppm is (μg / g). In addition, a portion caused by the externally added particles was excluded from the calculation.
[0063]
(6) Electromagnetic conversion characteristics
Next, a magnetic paint having the following composition is prepared on the surface of the film that does not come into contact with the metal belt at the time of film formation, applied to a predetermined coating thickness with a gravure roll, cured, and then calendered. Was done. The thickness of the magnetic layer was 2 μm.
[0064]
Magnetic powder (metal powder) 80 parts by weight
PVC copolymer 10 parts by weight
10 parts by weight of polyurethane
5 parts by weight of curing agent
Abrasive 5 parts by weight
100 parts by weight of toluene
100 parts by weight of methyl ethyl ketone
[0065]
The film coated with the magnetic layer was slit into a 1/2 inch width and assembled into a VTR cassette to form a VTR tape. An RF signal was input to this tape using a home VTR by a television test waveform generator under an environment of 25 ° C. and 10% RH. The amount of deformation of the lower portion of the screen when the tape was reproduced after being held for one week in an environment of 25 ° C. and 80% RH was determined. The larger the deformation amount, the worse the characteristics are, and it is preferably 10 or less.
[0066]
(7) Durability
After repeated running 100 times in an environment of 45 ° C. and 80% RH, the magnetic surface was observed for scratches, omissions, and tapes, and evaluated by the following three steps.
[0067]
：: No scratches, omissions, or tape breaks were observed.
Good: Extremely weak scratches and tape breaks are observed.
×: Severe scratches, missing magnetic layer, and tape breaks are observed.
[0068]
Examples 1 to 7, Comparative Examples 1 to 4
Abbreviations of the respective raw materials used in the following Examples and Comparative Examples are as follows.
[0069]
Aromatic diamine component:
PPD: paraphenylenediamine
DPX: 2,5-dimethylparaphenylenediamine
DMB: 3,3'-dimethylbenzidine
DOB: 3,3'-dimethoxybenzidine
DPE: 4,4'-diaminodiphenylmethane
TDM: 3,3 ', 5,5'-tetramethyl-4,4'-diaminodiphenylmethane
Acid chloride component:
TPC: Terephthalic acid dichloride
MPC: 2-methylterephthalic acid dichloride
NPC: 2,6-naphthalenedicarboxylic dichloride
BPC: 4,4'-biphenyldicarboxylic acid dichloride
DPC: 4,4'-diphenyl ether dicarboxylic acid dichloride
Acid anhydride component:
PAH: pyromellitic anhydride
[0070]
Example 1
50 mol% of DMB and 50 mol% of DPX are dissolved in dehydrated N-methylpyrrolidone (hereinafter abbreviated as NMP), and the solution is cooled. Then, 100 mol% of TPC was added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 7% by weight and the polymer was obtained as a clear solution. Also, the solution was stable after standing for 2 weeks.
[0071]
To this solution, silica particles having an average primary particle size of 16 nm were added in an amount of 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction was performed, followed by drying and heat treatment at 285 ° C. in a tenter. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 5 μm. The moisture absorption of this film was 1.5%, and the strength, elongation, and Young's modulus were 480 MPa, 18%, and 13.72 GPa, respectively. The trichlene extraction rate was 0.1% or less, and the metal ion content was 25 ppm.
[0072]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0073]
Example 2
40 mol% of DOB, 40 mol% of DPX, and 20 mol% of DPE are dissolved in NMP, and the solution is cooled. Then, 100 mol% of TPC was added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 12% by weight and the polymer was obtained as a clear solution. Also, the solution was stable after standing for 2 weeks.
[0074]
To this solution, silica particles having an average primary particle size of 16 nm were added in an amount of 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction followed by drying at 285 ° C. in a tenter and heat treatment at 295 ° C. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 4.5 μm. The moisture absorption of this film was 1.7%, and the strength, elongation, and Young's modulus were 540 MPa, 42%, and 12.25 GPa, respectively. The trichlene extraction rate was 0.1% or less, and the metal ion content was 24 ppm.
[0075]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0076]
Further, a Co-CoO-based thin film was deposited on the surface of the film obtained in Example 2 using a continuous vacuum deposition apparatus to form a magnetic layer. Next, a carbon protective film was formed on the surface of the evaporation layer, and a back coat layer was formed on the opposite surface by a known means. The magnetic layer could be formed without any problem in the vapor deposition step. Further, when this tape was subjected to a forced deterioration test in which it was left at 65 ° C. and a relative humidity of 90% for 7 days, and the residual magnetization of the magnetic layer was compared before and after the treatment, almost no deterioration was observed. It can be suitably used for a magnetic recording medium provided with a vapor deposition type magnetic layer suitable for the above.
[0077]
Reference Example 1
Polymerization and film formation were performed in the same manner as in Example 2 except that the wet process was performed using only a water bath to obtain a film. The moisture absorption of this film was 1.8%, and the strength, elongation, and Young's modulus were 519 MPa, 43%, and 12.04 GPa, respectively. Further, the trichlene extraction rate was 0.3%, and the metal ion content was 120 ppm.
[0078]
In addition, although the electromagnetic conversion characteristics and the durability were fairly good, the deterioration of the image quality causing noise during the evaluation of the durability was recognized.
[0079]
Further, a Co—CoO-based thin film was deposited on the film obtained in Reference Example 1 in the same manner as in Example 2, and a carbon protective film and a back coat layer were formed. The magnetic layer could be formed with almost no problem in the vapor deposition process. However, when this tape was subjected to the same forced deterioration test as in Example 2 and the residual magnetization of the magnetic layer was compared before and after the treatment, deterioration was recognized. It turns out that there are concerns about reliability.
[0080]
Reference Example 2
Drying and heat treatment were performed at 270 ° C., and polymerization and film formation were carried out in the same manner as in Example 2 except that the stretching ratio was 1.15 times in the longitudinal direction and 1.2 times in the width direction, to obtain a film. This film had a moisture absorption of 1.9%, strength, elongation and Young's modulus of 490 MPa, 48% and 10.78 GPa, respectively. The trichlene extraction rate was 0.1% or less, and the metal ion content was 24 ppm.
[0081]
In addition, the electromagnetic conversion characteristics and the durability were fairly good, but were lower than those of Example 2.
[0082]
Further, a Co—CoO-based thin film was deposited on the film obtained in Reference Example 2 in the same manner as in Example 2, and a carbon protective film and a back coat layer were formed. The magnetic layer could be formed with almost no problem in the vapor deposition process. However, when this tape was subjected to the same forced deterioration test as in Example 2 and the residual magnetization amount of the magnetic layer was compared before and after the treatment, deterioration was recognized at a level that was no problem.
[0083]
Example 3
Dissolve 60 mol% DOB, 20 mol% DPX, 20 mol% DPE in NMP and cool the solution. Then, 100 mol% of TPC was added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 10% by weight and the polymer was obtained as a clear solution. Also, the solution was stable after standing for 2 weeks.
[0084]
To this solution, silica particles having an average primary particle size of 16 nm were added in an amount of 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction was performed, followed by drying at 285 ° C. in a tenter and heat treatment at 300 ° C. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 8 μm. The moisture absorption of this film was 1.7%, and the strength, elongation, and Young's modulus were 441 MPa, 36%, and 9.31 GPa, respectively. Moreover, the trichlene extraction rate was 0.1% or less, and the metal ion content was 26 ppm.
[0085]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0086]
Example 4
Dissolve 45 mol% DOB, 47 mol% DPX, 8 mol% TDM in NMP and cool the solution. Then, 50 mol% of TPC and 50 mol% of NPC were added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 12% by weight and the polymer was obtained as a clear solution. Also, the solution was stable after standing for 2 weeks.
[0087]
To this solution, silica particles having an average primary particle size of 16 nm were added in an amount of 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction followed by drying at 285 ° C. in a tenter and heat treatment at 295 ° C. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 8 μm. The moisture absorption of this film was 1.5%, and the strength, elongation, and Young's modulus were 568 MPa, 35%, and 13.23 GPa, respectively. The trichlene extraction rate was 0.1% or less, and the metal ion content was 22 ppm.
[0088]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0089]
Example 5
Dissolve 40 mol% DMB, 40 mol% DPX, 20 mol% TDM in NMP and cool the solution. Then, 100 mol% of MPC was added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 14% by weight and the polymer was obtained as a clear solution. Also, the solution was stable after standing for 2 weeks.
[0090]
To this solution, silica particles having an average primary particle size of 16 nm were added in an amount of 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction was followed by drying at 280 ° C. in a tenter and heat treatment at 290 ° C. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 8 μm. The moisture absorption of this film was 1.4%, and the strength, elongation, and Young's modulus were 529 MPa, 40%, and 12.25 GPa, respectively. Moreover, the trichlene extraction rate was 0.1% or less, and the metal ion content was 20 ppm.
[0091]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0092]
Example 6
Dissolve 40 mol% DOB, 40 mol% PPD, 20 mol% DPE in NMP and cool the solution. Then, 50 mol% of MPC and 50 mol% of BPC were added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 12% by weight and the polymer was obtained as a clear solution. Also, the solution was stable after standing for 2 weeks.
[0093]
To this solution, silica particles having an average primary particle size of 16 nm were added in an amount of 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction was followed by drying at 280 ° C. in a tenter and heat treatment at 290 ° C. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 8 μm. The moisture absorption of this film was 1.9%, and the strength, elongation, and Young's modulus were 549 MPa, 45%, and 12.74 GPa, respectively. Moreover, the trichlene extraction rate was 0.1% or less, and the metal ion content was 21 ppm.
[0094]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0095]
Example 7
Dissolve 50 mol% DMB and 50 mol% DPX in NMP, then add 5 mol% PAH, stir for 30 minutes, then cool the solution. Next, 40 mol% of MPC, 45 mol% of BPC, and 10 mol% of DPC were added, stirred for 2 hours, and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 12% by weight and the polymer was obtained as a clear solution. Also, the solution was stable after standing for 2 weeks.
[0096]
To this solution was added 2% by weight of silica particles having an average primary particle size of 16 nm per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 180 ° C. for 2 minutes to evaporate the solvent. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction was performed, followed by drying at 270 ° C. in a tenter and heat treatment. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 8 μm. The film had a moisture absorption of 1.9%, strength, elongation and Young's modulus of 578 MPa, 42% and 14.21 GPa, respectively. The trichlene extraction rate was 0.1% or less, and the metal ion content was 24 ppm.
[0097]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0098]
Further, a Co—CoO-based thin film was deposited on the film obtained in Example 7 in the same manner as in Example 2, and a carbon protective film and a back coat layer were formed. The magnetic layer could be formed with almost no problem in the vapor deposition process. The magnetic layer could be formed without any problem in the vapor deposition step. Further, when the same forced deterioration test as in Example 2 was performed and the residual magnetization of the magnetic layer was compared before and after the treatment, almost no deterioration was observed, and a deposition type magnetic layer suitable for high-density magnetic recording was provided. It can be suitably used for a magnetic recording medium.
[0099]
Comparative Example 1
Dissolve 50 wt% lithium bromide per polymer in NMP, then 100 mol% DMB and cool the solution. Next, 100 mol% of TPC was added to carry out a reaction. The product precipitates shortly after the start of polymerization, and a film cannot be obtained.
[0100]
Comparative Example 2
Dissolve 50 wt% lithium bromide per polymer in NMP, then 100 mol% DPX and cool the solution. Next, 100 mol% of TPC was added to carry out a reaction. The product was precipitated shortly after the start of the polymerization, and a molded product could not be obtained.
[0101]
Comparative Example 3
50 mol% of DMB, 50 mol% of PPD, and 25 mol% of DPE are dissolved in NMP, and the solution is cooled. Then, 100 mol% of TPC was added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. Although the polymerization could be completed without the formation of a precipitate during the polymerization, the solution was an unstable solution that gelled after standing for 2 weeks even when the polymer concentration was 7%.
[0102]
To the solution immediately after the polymerization, silica particles having an average primary particle size of 16 nm were added at 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The film having self-supporting properties was peeled off from the belt and introduced into an extraction bath with NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. Then, drying and heat treatment were performed at 270 ° C. in a tenter. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 8 μm. The moisture absorption of this film was 2.3%, and the strength, elongation, and Young's modulus were 421 MPa, 48%, and 8.53 GPa, respectively. The trichlene extraction rate was 0.1% or less, and the metal ion content was 35 ppm.
[0103]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0104]
Comparative Example 4
40 mol% of DMB, 40 mol% of PPD, and 20 mol% of DPE are dissolved in NMP, and the solution is cooled. Then, 100 mol% of TPC was added, and the mixture was stirred for 2 hours and neutralized with lithium hydroxide to obtain a polymer. The polymer concentration was 8%, and this solution was thickened after standing for 2 weeks, but was a solution that could be formed into a film.
[0105]
To this solution, silica particles having an average primary particle size of 16 nm were added at 2% by weight per polymer, and then passed through a 5 μm-cut filter, cast on a stainless steel belt, and evaporated at 170 ° C. for 2 minutes. The obtained film was peeled from the belt and introduced into an extraction bath having NMP / water ratios of 30/70, 20/80, 10/90 and 0/100, respectively, kept at 40 ° C. to remove residual solvent and the like. Extraction was performed, followed by drying at 270 ° C. in a tenter and heat treatment. At this time, the film was stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction to obtain a film having a thickness of 8 μm. The moisture absorption of this film was 2.3%, and the strength, elongation, and Young's modulus were 510 MPa, 38%, and 12.25 GPa, respectively. The trichlene extraction rate was 0.1% or less, and the metal ion content was 24 ppm.
[0106]
In addition, both the electromagnetic conversion characteristics and the durability were good.
[0107]
Further, a Co—CoO-based thin film was deposited on the film obtained in Comparative Example 4 in the same manner as in Example 2, and a carbon protective film and a back coat layer were formed. In the vapor deposition step, the decompression operation was not stable, and it was difficult to form a magnetic layer. Further, since there was a delicate pressure fluctuation, it is predicted that the composition of the formed magnetic layer is not constant, and there is a problem in reliability when the film is used as a magnetic recording medium provided with a vapor deposition type magnetic layer. It turns out.
[0108]
[Table 1]

[0109]
【The invention's effect】
The aromatic polyamide film of the present invention can maintain a variety of performances such as its original excellent mechanical properties and heat resistance, and can reduce the moisture absorption rate, which was an inherent problem of the aromatic polyamide film. It has extremely high industrial value in various applications, including flexible printed wiring boards, thermal transfer recording materials, and insulating materials. In addition, the aromatic polyamide of the present invention can be preferably obtained from an organic solvent system and has excellent stability of the solution, so that no special operation in the process is required.

Claims (9)

A group A comprising structural units having different aromatic nuclei represented by the general formula (I),
General formula (I)

A group B comprising structural units having different aromatic nuclei represented by the general formula (II),
General formula (II)

And a group C consisting of structural units having different aromatic nuclei represented by the general formula (III):
General formula (III)

(Here, Ar ₁ , Ar ₂ , and Ar ₃ are para-oriented aromatic nuclei, and the compounds in each group include nitro groups, cyano groups, alkyl groups having 1 to 4 carbon atoms represented by Ra, Rb, and Rc; It may be substituted with a functional group selected from an alkoxy group having 1 to 3 carbon atoms, a trialkylsilyl group, an oxyaryl group, and a thioaryl group, wherein k, l, and m are each a number of 0 to 4. Further, at least three or more structural units selected from the group A and the group B are substantially equimolar (provided that at least two structural units having different basic aromatic nuclei are selected from the same group). A) a film comprising an aromatic polyamide film having a structural unit represented by (a) as a main structural unit and having an adjacent substitution rate of 60% or more , wherein the film has a moisture absorption of 2.2% or less. Aromatic poly characterized by Bromide film. D group consisting of a structural unit represented by the general formula (IV),
General formula (IV)

(Where Ar ₄ and Ar ₅ are para-oriented aromatic nuclei, and X and Y may be the same or different from each other; —CO— or —NH—; Z is a bridge atomic group; and Rd, Re Is a functional group selected from a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a trialkylsilyl group, an oxyaryl group, and a thioaryl group. to 4 is a number.) structure units of which are selected from (wherein, X, Y are both -CO- group a and (B group when, D groups), X, Y is -NH-, both 2. The structural unit according to claim 1, further comprising: a structural unit consisting of (A group, D group) and B group, and when different from each other, A group and B group are substantially equimolar. Aromatic polyamide film. In group two or more structural units are selected, para orientation of the basic aromatic nucleus as phenylene group, biphenylene group, an aromatic polyamide film according to claim 1 or 2, wherein at least two are used among naphthylene group. In a group in which two or more types of structural units are selected, different aromatic nuclei having para-orientation include 3,3′-disubstituted-4,4′-biphenylene groups and / or 2,2′-disubstituted groups. The aromatic polyamide film according to any one of claims 1 to 3, wherein a 4,4'-biphenylene group and a 2,5-disubstituted and / or 2,3-disubstituted paraphenylene group are used. As the compound represented by the general formula (I), 3,3′-disubstituted-4,4′-biphenyldiamine and / or 2,2′-disubstituted-4,4′-biphenyldiamine and 2,5- The aromatic polyamide film according to any one of claims 1 to 4 , wherein a di-substituted and / or 2,3-di-substituted paraphenylenediamine is used. The aromatic polyamide film according to any one of claims 1 to 5 , wherein the aromatic polyamide film is formed from an optically isotropic organic solvent solution. The magnetic recording medium in which a magnetic layer is formed on at least one surface of the aromatic polyamide film according to any one of claims 1 to 6. The magnetic recording medium according to claim 7 , wherein the magnetic layer is a metal thin film type magnetic layer. Film thickness of 6.5μm or less, a tape width is 2.2Mm～15mm, claim 7 in which the recording density is 15 kilobytes / mm ² or more, wherein the recording capacity is a tape-like medium is 1GB or more Alternatively, the magnetic recording medium according to 8 .