JP4576721B2 - Biaxially oriented laminated thermoplastic film - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、二軸配向積層熱可塑性樹脂フィルム、例えば、磁気記録媒体用、コンデンサー用などの各種の工業材料用フィルムとして非常に適した二軸配向積層熱可塑性樹脂フィルムに関するものであり、特に、機械特性、耐摩耗性、寸法安定性を要求するコンピューター用磁気記録媒体基材として有用な二軸配向積層熱可塑性樹脂フィルムに関するものである。
【０００２】
【従来の技術】
磁気記録媒体用ベースフィルムとしては、出力性能や走行性を向上させるために、積層厚みと含有粒子の平均粒径との関係を規定した二軸配向フィルムが知られている（例えば特開平２−７７４３１号公報）。また、遮光性を付与するために偏平粒子を用いた二軸配向フィルムも知られている（例えば特開平６−３２２１４７号公報）。
【０００３】
しかし、上記のような従来の二軸配向フィルムでは、磁気記録媒体用ベースフィルムとして用いた場合、近年の工程速度の増速化や磁気記録テープの薄膜化に伴い、ベースフィルムの厚みが薄くなると、フィルムの機械強度や耐久性および走行性が不十分となることがある。また、近年の磁気記録テープの高密度化に伴って、記録された小さな磁区が周りの磁性体の影響を受けて不安定となり、基材フィルムが熱的な揺らぎを受け、寸法安定性が悪化し磁気記録テープのデータの信頼性が悪化するなどの問題が生じている。
【０００４】
【発明が解決しようとする課題】
本発明の課題は、かかる問題点を解決し、特に、コンピューター用高密度磁気記録テープの薄膜化に伴い要求が高まっている機械強度、走行性、熱寸法安定性に優れたフィルムを提供することにある。
【０００５】
【課題を解決するための手段】
上記課題を解決するために、本発明の二軸配向積層熱可塑性樹脂フィルムは、少なくとも１つの層（Ａ層）は、熱可塑性樹脂（Ａ）と板状不活性粒子（ＰA) を主たる成分からなり、Ａ層の少なくとも片面に熱可塑性樹脂（Ｂ）を主たる成分とするＢ層が積層された、２層以上の積層構造からなるフィルムであって、前記板状不活性粒子（ＰA) のアスペクト比（板面方向における平均粒径Ｄ／板面と垂直の方向における粒子の平均厚みｄｔ）が３〜１００、含有量が１〜８０重量％であることを特徴とするものからなる。
【０００６】
【発明の実施の形態】
以下、本発明について、望ましい実施の形態とともに詳細に説明する。
本発明の二軸配向積層熱可塑性樹脂フィルムは、２層以上の積層構造を有する。単層であると、例えば、磁気記録媒体用として用いる場合、走行性を向上させる目的で不活性粒子を含有させると、表面の突起の突起径や突起高さが不均一となり、表面性が著しく低下し、出力特性や耐摩耗性を良好にすることが出来ない。積層構成は２層以上であれば３層でも４層でも構わないが、本発明で目的とする機械強度、寸法安定性、走行性を良好に満足させるためには、とくに３層積層構成が好ましい。３層積層構成としては、熱可塑性樹脂Ｂ／熱可塑性樹脂Ａ／熱可塑性樹脂Ｂの構成や、熱可塑性樹脂Ｂ／熱可塑性樹脂Ａ／熱可塑性樹脂Ｃの構成を採ることができる。
【０００７】
本発明の二軸配向積層熱可塑性樹脂フィルムを構成する熱可塑性樹脂Ａ、Ｂ、Ｃは、特に限定されないが、ポリエステル、ポリオレフィン、ポリアミド、ポリイミド、ポリフェニレンスルフィドが好ましく例示される。各層を構成する熱可塑性樹脂Ａ、Ｂ、Ｃは同種でも異なる種類のものであっても構わない。また、本発明の目的を阻害しない範囲内で他種ポリマをブレンドしても構わないし、熱安定剤、酸化防止剤、紫外線吸収剤、帯電防止剤、難燃剤、顔料、染料、脂肪酸エステル、ワックスなどの有機滑剤や不活性粒子などが添加されてもよい。
【０００８】
本発明の二軸配向積層熱可塑性樹脂フィルムのＡ層に含有される粒子の粒形は板状形である。粒形が板状であると、ポリマの分子鎖に沿って粒子が配向し易くなるためかフィルムの機械強度と寸法安定性が向上する。含有粒子が球形や楕円形の粒子ではフィルムの機械強度が十分高められないので好ましくない。
【０００９】
本発明の二軸配向積層熱可塑性樹脂フィルムのＡ層に含有される板状不活性粒子（ＰA) のアスペクト比（板面方向における平均粒径Ｄ／板面と垂直の方向における粒子の平均厚みｄｔ）は、機械強度、寸法安定性の点から３〜１００である。好ましくは５〜８０の範囲であり、さらに好ましくは１０〜５０の範囲である。アスペクト比が本発明で規定した範囲外である、例えば球形粒子では、フィルムの機械強度、寸法安定性を向上させることが出来ない。また、アスペクト比が本発明における範囲よりも大きいと、粒子が凝集し、ポリマに沿って配向しにくくなり、機械強度や寸法安定性を向上させることができないので好ましくない。
【００１０】
板状不活性粒子としては特に限定されないが、タルク、マイカ、ガラスフレーク、板状アルミナ、シリカ、炭酸カルシウム、二酸化チタン、硫酸バリウム、石英粉、鱗片状黒鉛、フッ素雲母、リン酸カルシウム、酸化鉄等が例示される。中でも特に機械強度、寸法安定性の点から、モース硬度が６〜１０の範囲にある粒子が好ましい。モース硬度が６〜１０の粒子としては、シリカ、アルミナ、ジルコニア、二酸化チタン粒子等が例示されるが、本発明の効果を得るためには特に板状アルミナ粒子が好ましい。
【００１１】
板状不活性粒子の平均粒径（板面方向における平均粒径：つまり板の平均径）としては、０．１〜１０μｍが好ましく、更に好ましくは、０．３〜５μｍである。この平均粒径（板の径）が０．１μｍよりも小さいと、フィルム中で凝集し、均一な機械強度を得ることができない。また、上記平均粒径が上記範囲よりも大きいとフィルム自体の剛性が強くなりすぎ取り扱い性が悪化したり、粒子と基材との界面にできる空隙（ボイド）が大きくなりすぎて高い機械強度を得ることができない。
【００１２】
本発明においては、板状不活性粒子のＡ層中での含有量は、機械強度と寸法安定性の点から１〜８０重量％とされる。好ましくは５〜５０重量％であり、さらに好ましくは１０〜４０重量％である。板状不活性粒子の含有量が１重量％よりも少ないと機械強度と寸法安定性を共に満足させることができない。また、含有量が８０重量％よりも多くなるとフィルム自体が脆くなり好ましくない。
【００１３】
本発明の板状不活性粒子には、必要に応じて基材樹脂との親和性を高めるためやＡ層中での凝集状態をコントロールする目的で表面処理を施すことができる。
【００１４】
本発明の二軸配向積層熱可塑性樹脂フィルム全体に対するＡ層の厚み割合は、１〜９５％の範囲にあることが好ましく、より好ましくは５〜８０％の範囲である。Ａ層厚みの割合が上記範囲外であると、機械強度、寸法安定性および走行性の全てを向上させることができない。
【００１５】
本発明における熱可塑性樹脂Ｂからなる、Ｂ層の積層厚み（ｔB）は、表面性の点から板状不活性粒子Ａの厚み（ｄｔ）の０．５〜１００倍の範囲にあることが好ましい。より好ましくは１〜８０倍であり、さらに好ましくは２〜５０倍である。Ｂ層厚みが上記範囲よりも小さいとＡ層中に含有している粒子による表面突起がＢ層表面にトレースされ、表面粗さが大きくなり出力特性が悪化するため好ましくない。Ｂ層厚みが上記範囲より大きいと、Ａ層中に含有している粒子による表面突起がＢ層表面に全くトレースされず、磁気ヘッドに対する走行性が悪化する場合があるので好ましくない。Ｂ層厚みが上記範囲内であると、Ａ層表面の粗さが適度にＢ層表面にトレースされるので好ましい。
【００１６】
本発明におけるＢ層は粒子を含有している必要はないが、平均粒径が０．８μｍ以下の粒子であれば含有していても構わない。この場合、含有量は１重量％以下にすることが本発明の目的の点から望ましい。
【００１７】
本発明においてＣ層は、熱可塑性樹脂Ｃと不活性粒子（ＰB) を主成分とし、Ｃ層の積層厚みは耐摩耗性、走行性の点から０．１〜３μｍとされる。好ましくは、Ｃ層の積層厚みは０．５〜２μｍである。
【００１８】
不活性粒子（ＰB) としては特に限定されないが、酸化チタン、炭酸カルシウム、カオリン、タルク、コロイダルシリカ、ケイ酸アルミニウム粒子、リン酸カルシウム、硫酸バリウム、カーボンブラック、アルミナおよびジルコニア等の凝集粒子、架橋ポリスチレン、シリコーン、ポリイミドなどの架橋有機粒子、ポリエステル重合反応時に添加する触媒等によって析出する、いわゆる内部粒子や、界面活性剤などが好ましく例示される。また、含有粒子は１種類でもよいが２種類以上併用しても構わない。
【００１９】
含有する不活性粒子（ＰB) の平均粒径ｄBは、０．０５〜０．８μｍが好ましく、より好ましくは０．１〜０．６μｍである。含有量は０．０１〜１重量％が好ましく、より好ましくは０．１〜０．６重量％である。
【００２０】
不活性粒子（ＰB) としては、特に限定されないが粒径比（長径／短径）が１．０〜１．３の実質的に球形の粒子を用いることが好ましい。しかしながら、炭酸カルシウム粒子やアルミナのように粒形が不定形の粒子や凝集体であっても、含有量や粒径の調節、さらに、球形粒子との併用によって使いこなすことができる。また、粒径の相対標準偏差が０．６以下の粒度分布のシャープな粒子が好ましい。
【００２１】
本発明の二軸配向積層熱可塑性樹脂フィルムのヤング率は、長手方向、幅方向共に５ＧＰa以上２０ＧＰa以下であることが好ましい。より好ましくは、７〜１５ＧＰa、更に好ましくは８〜１２ＧＰaである。フィルムのヤング率を上記範囲内とすることによって、過酷な環境下での使用や磁気記録媒体の薄膜化に対応できる基材フィルムを、より容易に得ることができる。
【００２２】
本発明の二軸配向積層熱可塑性樹脂フィルムの長手方向の熱収縮率は、熱寸法安定性の点から０〜１．５％であることが好ましく、より好ましくは０〜１．２％である。熱収縮率をこの範囲内とすることによって、特に、データバックアップ用記録媒体としたときに、過酷な環境下の使用でも高い信頼性が得られ好ましい。
【００２３】
本発明の二軸配向積層熱可塑性樹脂フィルムの用途は、特に限定されないが、磁気記録媒体用、コンデンサー用などに用いられる。特に、データバックアップ用磁気記録媒体用基材として有効に用いることができる。
【００２４】
本発明に係るフィルムの製造方法の具体例について説明するが、本発明はこれに限定されるものではない。
本発明で用いる熱可塑性樹脂は公知の方法により得られるものを用いることができる。また、所定の熱可塑性樹脂に添加される板状不活性粒子（ＰA) 、不活性粒子（ＰB) は、樹脂製造工程における重合前、重合中、重合後のいずれの段階で添加してもよいが、例えば、熱可塑性樹脂としてポリエステルを用いる場合は、粒子をジオール成分にスラリーの形で混合、分散せしめて重合する方法、あるいはこのスラリーを熱可塑性樹脂に二軸ベント式押出機を用いて練り込む方法が例示される。また粒子スラリーを１８０〜２３０℃、特に１９０℃〜２１０℃の温度で３０分〜１２時間、好ましくは、２〜８時間熱処理する方法は本発明の効果をより一層高めるのに有効である。また、有機添加剤として、例えば、アルキルスルホン酸アルキル金属塩を用いる場合には、重合触媒を添加した後に添加し、所定の重合度が得られた時点で添加を終了する。高級エステルを添加する場合は、重合が完了する直前に、その重合最終段階における温度で、ポリマーを攪拌しながら添加するのが好ましい。
【００２５】
粒子および有機化合物の含有量を調節する方法としては、上記方法で高濃度マスターを作っておき、この高濃度の粒子および有機化合物マスターペレットを製膜時に粒子などを実質的に含有しないポリマーで希釈する方法を用いるのが好ましい。
【００２６】
次に、これらの粒子を含有する熱可塑性樹脂のペレットを必要に応じて十分乾燥した後、固有粘度が低下しないように窒素気流下あるいは真空下で２８０〜３２０℃に加熱された押出機に供給し、従来から行われている方法により製膜する。また、異物や変質ポリマーを除去するために各種のフィルター、例えば、焼結金属、多孔性セラミック、サンド、金網などの素材からなるフィルターを用いることが好ましい。フィルターの濾過精度は、使用する不活性粒子の粒径によって適宜選択することが好ましい。各層を構成する熱可塑性樹脂Ａ，Ｂ，Ｃ（Ａ，Ｂ，Ｃは同種、異種いずれでもよい）をそれぞれ十分乾燥した後、２台以上の溶融押出機にそれぞれ別に供給し、２または目的とする多層のマニホールドまたは合流ブロックを用いて、熱可塑性樹脂（Ａ）の少なくとも片面に熱可塑性樹脂（Ｂ）からなるポリマ層をポリマ管あるいは口金の段階で積層し、スリット状の口金から２層以上のシートを押し出し、静電印加キャスト法を用いて表面温度２０〜５０℃のキャスティングドラム上で冷却固化せしめて未延伸フィルムを作る。この場合、合流断面が矩形の合流ブロックを用いて積層する方法が、各種不活性粒子含有の熱可塑性樹脂層を薄く均一に積層するのに有効である。また、各層を構成するポリマ流路にスタティックミキサー、ギヤポンプを設置する方法、表面層の熱可塑性樹脂ＢおよびＣの溶融粘度をそれと接触する他層の熱可塑性樹脂Ａの溶融粘度よりも高くしておく方法は本発明の機械強度、熱寸法安定性を得るのに有効である。
【００２７】
次にこの未延伸フィルムを二軸延伸し、二軸配向せしめる。延伸方法としては、逐次二軸延伸法または同時二軸延伸法を用いることができる。例えば、最初に長手方向、次に幅方向の延伸を行う逐次二軸延伸法を用いる場合、長手方向の延伸倍率は、特に限定されないが、延伸速度５０００〜５００００％／分の速度で、総延伸倍率は３〜１０倍とするのが好ましく、さらに好ましくは３．５〜９倍の範囲である。延伸温度は、熱可塑性樹脂のガラス転移温度Ｔｇ以上、（ガラス転移温度Ｔｇ＋５０℃）以下の範囲が好ましい。
【００２８】
幅方向の延伸は、公知のテンターを用いて、延伸温度９０〜１６０℃、より好ましくは９５〜１５０℃の延伸温度で３〜１０倍、より好ましくは３．５〜９倍、幅方向の延伸速度は１０００〜３００００％／分の範囲で行うのが好ましい。
さらに必要に応じて、この二軸延伸フィルムを再度長手方向、幅方向の少なくとも一方向に延伸を行ってもよい。
【００２９】
次にこの延伸フィルムを熱処理する。この場合の熱処理温度は１７０〜２５０℃、より好ましくは１８０〜２３０℃で、処理時間は１〜３０秒が好ましい。
【００３０】
また、延伸法として同時二軸延伸法を用いる場合は、リニアモーターを利用した駆動方式によるテンターを用いて同時二軸延伸方法を用いることが好ましい。
同時二軸延伸温度としては、熱可塑性樹脂のガラス転移温度Ｔｇ以上、（ガラス転移温度Ｔｇ＋５０℃）以下であることが好ましい。延伸温度がこの範囲を大きく外れると、均一延伸ができなくなり厚み斑やフィルム破れが悪化し好ましくない。延伸倍率は、縦方向、横方向それぞれ３〜１０倍に延伸する。延伸速度としては特に限定されないが、２０００％／分〜５００００％／分が好ましい。
【００３１】
次にこの延伸フィルムを熱処理する。この場合の熱処理温度は１７０〜２５０℃、特に１８０〜２３０℃である。熱処理の時間は１〜３０秒の範囲が好適である。
【００３２】
この様にそれぞれの方法で二軸配向し熱処理を施したフィルムを室温まで徐冷しワインダーにて巻き取る。冷却方法は、２段階以上に分けて室温まで徐冷するのが好ましい。この時、長手方向、幅方向に０．５〜１０％程度のリラックス処理を行うことは、熱寸法安定性を本願の範囲内にするのに有効である。冷却温度としては、第１段目が［熱処理温度−２０℃］〜１２０℃であり、第２段目が［１段目の冷却温度−３０℃］〜４０℃の範囲内が好ましいが、これに限定されるものではない。
【００３３】
［物性の測定方法ならびに効果の評価方法］
（１）板状不活性粒子の板の平均粒径Ｄおよびアスペクト比（Ｄ／ｄｔ）
フィルムから熱可塑性樹脂をプラズマ低温灰化処理法で除去し粒子を露出させる。処理条件はポリマは灰化されるが粒子はダメージを受けない条件を選択する。板状粒子が含有されている層の上に他の層が積層されている場合は、片刃で積層部を削り取ってから、上記の方法で観察する。これをＳＥＭ（走査型電子顕微鏡）を用いて観察し、粒子の画像（粒子によってできる光の濃淡）をイメージアナライザーに結びつけて処理する。観察場所を変え粒子数１０００個以上について、個々の粒子の板面方向における直径を測定し、その平均値を板状不活性粒子の板の平均粒径Ｄとする。ＳＥＭの倍率としてはおおよそ２０００倍〜１０万倍くらいで妥当であると考えられるが、更に粒子が微細である場合は、倍率を適宜高倍率に変更し観察する。
【００３４】
粒子の平均厚みｄｔは、上記と同様に、ＳＥＭ写真から求めることもできるが、フィルムを平面に対して垂直に、厚さ１００ｎｍの超薄膜片として、透過型電子顕微鏡（ＴＥＭ）を用いて、板状不活性粒子の長径（上記の板の平均径Ｄに相当）と短径（粒子の厚み）を観察し、粒子１０００個以上について、粒子厚みに相当する値を求め、その平均値を不活性粒子の平均厚みｄｔとする。透過型電子顕微鏡の観察倍率は、適宜選択できるが、通常、２０００〜１０万倍程度である。以上の通り、板状不活性粒子の粒径（Ｄ）と厚み（ｄｔ）をそれぞれ求め、下記式よりアスペクト比を算出した。
アスペクト比＝Σ（Ｄ／ｄｔ）／Ｎ
Ｎ：粒子総個数
【００３５】
（２）球形および不定形の不活性粒子の平均粒径ｄB
フィルム断面を透過型電子顕微鏡（ＴＥＭ）を用い、フィルム中に含有されている粒子形状が板状以外の球形あるいは不定形の粒子を１万倍以上の倍率で観察し、粒子等価球直径を観察する。ＴＥＭの切片厚さは約１００nmとし、場所を変えて１００視野以上測定する。下記の式から体積平均径ｄBを求める。
ｄB＝Σｄｉ＊ＮＶi
ｄｉは粒径、ＮＶiはその体積分率である。
【００３６】
（３）粒子の含有量
積層部の粒子含有量は、フィルムを幅1/2インチにテープ状にスリットしたものを用い、フィルム表面に片刃を垂直に押しあて、さらに０．５ｍｍ押し込んだ状態で２０ｃｍ走行させる（走行張力：５００ｇ、走行速度：６．７ｃｍ／秒）。このとき片刃の先に付着したフィルム表面の削れ物を、ポリマは溶解し粒子は溶解しない溶媒を選択して溶解させ、粒子をポリマから遠心分離し、粒子の全体重量に対する比率（重量％）をもって粒子含有量とする。場合によっては赤外分光法の併用も有効である。
【００３７】
（４）フィルム積層厚み
２次イオン質量分析装置（ＳＩＭＳ）を用いて、表層から深さ５０００nmの範囲のフィルム中の粒子の内もっとも高濃度の粒子に起因する元素とポリエステルの炭素元素の濃度比（Ｍ+／Ｃ+）を粒子濃度とし、表面から深さ５０００ｎｍ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。本発明フィルムの場合は一旦極大値となった粒子濃度がまた減少し始める。この濃度分布曲線をもとに表層粒子濃度が極大値の１／２となる深さ（この深さは極大値となる深さよりも深い）を求め、これを積層厚さとした。条件は次の通りである。
(1) 測定装置
２次イオン質量分析装置（ＳＩＭＳ）
西独、ATOMIKA社製 A-DIDA3000
(2) 測定条件
１次イオン種 ：Ｏ2 +
１次イオン加速電圧：１２KV
１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 ：５．０×１０-9Torr
Ｅ−ＧＵＮ ：０．５KV−３．０A
【００３８】
なお、表層から深さ５０００nmの範囲に最も多く含有する粒子が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ＸＰＳ（Ｘ線光電子分光法）、ＩＲ（赤外分光法）などで上記同様のデプスプロファイルを測定し積層厚みを求めてもよいし、透過型電子顕微鏡（日立製Ｈ−６００型）を用いて、加速電圧１００ｋＶで、フィルム断面を、超薄切片法（ＲｕＯ4染色）で観察し、その界面をとらえ、その積層厚さを求めることもできる。倍率は、判定したい積層厚さによって選ぶことが通常であり、特に限定されないが、１万〜１００万倍が適当である。
【００３９】
（５）フィルムのヤング率
東洋ボールドウィン（株）の引っ張り試験機を用いて、温度２５℃、湿度６０％に調節された室温において、試長間１００ｍｍ、幅１０ｍｍの試料フィルムを引っ張り速度１０ｍｍ／分で引っ張った。得られた張力−歪み曲線の立ち上がりの直線部分の勾配からヤング率を求めた。
【００４０】
（６）熱収縮率
幅１０ｍｍにサンプリングして、２００ｍｍの間隔に標線をマークし、標線間を測定した後（Ｌ0）そのフィルムを１５０℃に制御したオーブンに無荷重で入れ、３０分処理した後取り出し、温度２５℃、湿度６５％雰囲気下に１時間、放置した後、標線間を測定し（Ｌ）、次式にて熱収縮率を求めた。
熱収縮率（％）＝｛（Ｌ0−Ｌ）／Ｌ0｝×１００
【００４１】
（７）耐久性
磁気テープの製造方法として、下記の磁性塗料をダイコーターにより乾燥カレンダ後の厚みが２μｍとなるように塗布し、磁場配向させ、乾燥させる。引き続き、上記支持体の反対側の面上に下記バックコート塗料を乾燥カレンダ後の厚さが０．７μｍとなるように塗布し、９０℃にて乾燥させバックコート層を形成した。
【００４２】
このようにして得られた磁気シートをカレンダー処理（温度７０℃、線圧１５０ｋｇ／ｃｍ）した後、コアに巻いた状態で６０℃４０％ＲＨ下４８時間エージングしたのち１／２インチ幅にスリットし、これを１００ｍ／分で走行させながら磁性層表面をセラミックホイール（回転速度＋１５０％、巻き付け角３０°）で研磨して、テープ長さ１２５ｍの磁気テープを作成した。この磁気テープをカートリッジに組み込んでコンピューター用テープを製造した。
【００４３】
〈磁性塗料〉
Ｃｏ含有強磁性Ｆｅ粒子 ：１００重量部
塩化ビニール系共重合体 ： １０重量部
（日本ゼオン製：ＭＲ１１０）
ポリウレタン樹脂 ： １０重量部
（東洋紡製：ＵＲ８２００）
α−アルミナ（１次径０．３μｍ） ： １０重量部
カーボンブラック（１次径２０ｎｍ）： ２重量部
メチルエチルケトン ： ７５重量部
トルエン ： ７５重量部
シクロヘキサノン ： ７５重量部
ポリイソシアネート ： ５重量部
ミリスチン酸 ： ２重量部
ブチルステアレート ： ４重量部
【００４４】
〈バックコート塗料〉
カーボンブラック（１次径２５ｎｍ）： ４０重量部
カーボンブラック（１次径７５ｎｍ）： ２重量部
ポリウレタン樹脂 ： ２０重量部
ポリイソシアネート ： ４重量部
ニトロセルロース ： ２０重量部
メチルエチルケトン ：１４０重量部
トルエン ：１４０重量部
シクロヘキサノン ：１４０重量部
ステアリン酸 ： １重量部
【００４５】
この磁気テープをＤＬＴ４０００ドライブを用いて、４０℃６５％ＲＨ環境下で４８時間、連続走行させ、ランダムデータ信号を記録し、ブロックエラーレート測定装置により、各コンピューター用テープのブロックエラーレートを１回走行後に対する４８時間後のエラーレートの上昇率を調べ、これで耐久性を評価した。
【００４６】
（８）出力特性
本発明のフィルムに連続真空蒸着装置を用いて、微量の酸素の存在下にコバルト・ニッケル合金（Ｎｉ20重量％）の厚み２００nmの蒸着層を設けた。さらに、蒸着層表面にカーボン保護膜を公知の手段で形成させた後、８ｍｍ幅にスリットし、パンケーキを作成した。次いで、このパンケーキから長さ２００ｍ分をカセットに組み込み、カセットテープとした。
【００４７】
このテープについて、市販のＨｉ８用ＶＴＲ（ＳＯＮＹ社製 EV-BS3000）を用いて、７ＭＨｚ±１ＭＨｚのＣ／Ｎの測定を行った このＣ／Ｎを比較例１の磁気テープと比較して
＋３ｄＢ以上 ：優
＋１〜＋３ｄＢ ：良
＋１ｄＢ未満 ：不良
と判定した。出力特性が比較例１の磁気テープと比較して、＋１ｄＢ以上あれば、デジタル記録方式の磁気テープとして充分使用できるレベルである。
【００４８】
（９）走行性
フィルムを幅１／２インチのテープ状にスリットしたものを、２５℃、６０％ＲＨ雰囲気で走行させ、初期の摩擦係数μｋを下記の式より求めた。
μｋ＝２／πｌｎ（Ｔ2／Ｔ1）
ここで、Ｔ1は入側張力、Ｔ2は出側張力である。ガイド径は６mmΦであり、ガイド材質はＳＵＳ２７（表面粗度０．２Ｓ）、巻き付け角は６０゜、走行速度は３．３ｃｍ／秒である。この測定によって得られたμｋが０．３以下の場合は滑り性：良好、０．３を越える場合は滑り性：不良と判定した。
【００４９】
【実施例】
次の実施例に基づき、本発明の実施形態を説明する。
実施例１
積層構成Ａ／Ｂの２層積層フィルムにおいて、Ａ層を構成する熱可塑性樹脂として公知の方法により得られたポリエチレンテレフタレート（以下、ＰＥＴという）に滑剤として平均粒径０．３μｍの板状アルミナ粒子（ＹＫＫ（株）製、板状アルミナ粒子“セラフ”）を３０重量％配合したポリマ（ポリマＡ）を作成した。Ｂ層を構成する熱可塑性樹脂として、公知の方法で作成した実質的に無粒子のＰＥＴを作成した（ポリマＢ）。押出機２台を用い、２８０℃に加熱された押出機Ｂには、ポリマＢを１８０℃で３時間真空乾燥した後に供給し、同じく２７０℃に加熱された押出機ＡにはポリマＡを１８０℃で３時間真空乾燥した後に供給し、２層積層するべくＴダイ中で合流させ（積層構成：Ａ／Ｂ）、表面温度２５℃のキャストドラムに静電荷を印加させながら密着冷却固化し、積層未延伸フィルムを作成した。
【００５０】
この未延伸フィルムをロール式延伸機にて長手方向に３段に分けて、温度９０℃で１．５倍、９２℃で２．２倍、さらに９３℃で１．３倍延伸し、続いて、テンターを用いて、幅方向に温度９８℃で３．８倍延伸した。続いてこのフィルムを長手方向、幅方向に１．０５倍ずつ微延伸しながら雰囲気温度２１０℃で５秒間熱処理し、冷却ゾーンにてリラックス率８％にて１５０℃で２秒、１００℃で３秒徐冷し、６０℃で１秒間熱処理を行い、Ａ層積層厚さ４μｍ、全厚さ６μｍの積層ポリエステルフィルムを得た。
この積層ポリエステルフィルムの特性は、表１に示したとおり、機械強度、熱寸法安定性、耐久性、出力特性、走行性に優れた特性を有していた。なお、表１においては、長手方向をＭＤ、幅方向をＴＤと略称してある。
【００５１】
実施例２
積層構成をＢ／Ａ／Ｃの３層積層とするフィルムにおいて、Ａ層を構成するポリマとして平均粒径０．６μｍの板状アルミナ粒子を１１重量％含有するＰＥＴと、下記の原料から重縮合したメソゲン基を有する共重合ポリエステル（メソゲン基含有量６０モル％）（表１では、ＬＣＰと略称してある。）を下記割合でブレンドしたポリマを用いた。
【００５２】
これらの原料を３台の押出機を用いて２８０℃、２７５℃、２８０℃で溶融押し出し、延伸条件を適宜変更してＢ／Ａ／Ｃの３層積層フィルムを作成した。なお、Ｂ層積層厚みは２．５μｍ、Ａ層積層厚み１μｍ、Ｃ層積層厚み２．５μｍであった。この積層ポリエステルフィルムの特性は、表１に示したとおり、機械強度、熱寸法安定性、耐久性、出力特性、走行性に優れた特性を有していた。
【００５３】
実施例３
実施例２で用いたポリマＡの板状粒子種、添加量、積層厚み比を表１の通り変更した以外は全て実施例２と同様にしてＢ／Ａ／Ｃの３層積層フィルムを作成した。
【００５４】
実施例４
積層構成をＢ／Ａ／Ｂの３層積層のフィルムにおいて、Ａ層を構成するポリマーを平均粒径０．６μｍの板状アルミナ粒子（ＹＫＫ（株）製、板状アルミナ粒子“セラフ”）を２０重量％配合したＰＥＴポリマ（ポリマＡ）を作成した。Ｂ層を構成する熱可塑性樹脂として、ポリエーテルイミド（ジーイープラスチックス社製“ウルテム１０１０”、以下ＰＥＩという）と公知の方法で得た平均粒径０．３μｍのコロイダルシリカ粒子を含有するＰＥＴを３５：６５の割合でブレンドしたポリマ（ポリマＤ）を用いた。押出機２台を用い、２８０℃に加熱された押出機Ｂには、ポリマＢを１８０℃で３時間真空乾燥した後に供給し、同じく２７０℃に加熱された押出機ＡにはポリマＡを１８０℃で３時間真空乾燥した後に供給し、３層積層するべくＴダイ中で合流させ（積層構成：Ｂ／Ａ／Ｂ）、表面温度２５℃のキャストドラムに静電荷を印加させながら密着冷却固化し、積層未延伸フィルムを作成した。
【００５５】
この未延伸フィルムをロール式延伸機にて長手方向に３段に分けて、温度９０℃で１．８倍、９２℃で２．０倍、さらに９３℃で１．３倍延伸し、続いて、テンターを用いて、幅方向に温度９８℃で４．０倍延伸した。定長下で温度２１０℃で１０秒間熱処理を行い、冷却ゾーンにてリラックス率８％にて１５０℃で３秒、１００℃で３秒徐冷を行い、Ｂ層積層厚さ１．５μｍ、全厚さ６μｍの積層ポリエステルフィルムを得た。
この積層ポリエステルフィルムの特性は、表１に示したとおり、機械強度、熱寸法安定性、耐久性、出力特性、走行性に優れた特性を有していた。
【００５６】
実施例５
Ｂ／Ａ／Ｄ／Ａ／Ｃの５層積層のフィルムにおいて、Ａ層ポリマを平均粒径０．６μｍの板状アルミナ粒子を１０重量％含有するＰＥＴポリマとした（ポリマＡ）。Ｂ層ポリマとして上記実施例４で用いたポリエーテルイミドとＰＥＴの割合を３５：６５の無粒子のＰＥＴ／ＰＥＩポリマを用いた（ポリマＢ）。Ｃ層ポリマとして、上記実施例２で用いたポリマＣを用いた。Ｄ層のポリマとしてＰＥＴリサイクルポリマを用いた。これらの４種類のポリマをそれぞれ乾燥し、４台の押出機に供給し、５層積層すべくＴダイ中で合流させ（積層構成：Ｂ／Ａ／Ｄ／Ａ／Ｃ）、表面温度２５℃のキャストドラムに静電荷を印加させながら密着冷却固化し、積層未延伸フィルムを作成した。
【００５７】
この未延伸フィルムをロール式延伸機にて長手方向に３段に分けて、温度９１℃で１．３倍、９２℃で２．３倍、さらに９３℃で１．３倍延伸し、続いて、テンターを用いて、幅方向に温度１００℃で４．２倍延伸した。定長下で温度２１０℃で１０秒間熱処理を行い、冷却ゾーンにてリラックス率１０％にて１５０℃で３秒、１００℃で３秒徐冷を行い、Ａ層積層厚さ各０．５μｍ、Ｂ層積層厚み０．５μｍ、Ｃ層積層厚さ１μｍ、全厚さ６μｍの積層ポリエステルフィルムを得た。
この積層ポリエステルフィルムの特性は、表１に示したとおり、機械強度、熱寸法安定性、耐久性、走行性に優れた特性を有していた。
【００５８】
実施例６
実施例１のポリマＡを平均粒径１０μｍの板状アルミナ粒子に変更し、含有量３重量％なるよう配合量を変更した。その他は実施例１と同様にしてＡ／Ｂの２層構成の、Ａ層厚み１μｍ、総厚み６μｍの積層フィルムを得た。
この積層ポリエステルフィルムの特性は、表１に示したとおり、機械強度、熱寸法安定性、耐久性、出力特性、走行性に優れた特性を有していた。
【００５９】
実施例７
Ｂ／Ａ／Ｃの３層積層において、Ａ層の熱可塑性樹脂Ａを公知の方法で得たポリエチレン２，６−ナフタレート（以下、ＰＥＮという）とし、平均粒径０．５μｍの板状アルミナ粒子を含有するＰＥＮペレットと適当量混合し、板状アルミナ粒子含有量を５重量％とした。Ｂ，Ｃ層ポリマは実施例２で用いたポリマＢおよびポリマＣを用いた。実施例１と同様に押出し、延伸条件を適宜変更してＢ、Ｃ層積層厚み２μｍ、Ａ層積層厚み１μｍの３層積層フィルムを作成した。
この積層ポリエステルフィルムの特性は、表１に示したとおり、機械強度、熱寸法安定性、耐久性、出力特性、走行性に優れた特性を有していた。
【００６０】
比較例１
上記実施例２で用いたポリマＡの粒子濃度を３０重量％に変更し、粒子含有量が２０重量％となるよう無粒子のＰＥＴペレットを用いて希釈し、実施例１と同様の延伸条件で総厚み６μｍの単層のフィルムを作成した。
【００６１】
比較例２
Ａ／Ｂの２層積層フィルムにおいて、Ａ層ポリマを平均粒径０．６μｍのシリカ粒子に変更した以外は実施例１と同様にしてＡ層積層厚み１μｍの２層積層フィルムを作成した。
【００６２】
比較例３
Ｂ／Ａ／Ｂの３層積層において、Ａ層ポリマを無粒子のＰＥＴとし、Ｂ層ポリマを実施例２で用いたポリマＣとして実施例３と同様に３層積層フィルムを作成した。
【００６３】
比較例４
実施例１のポリマＡに含有する粒子を平均粒径０．３μｍのα型アルミナ粒子に変更した以外は全て実施例１と同様にしてＡ層積層厚み４μｍ、総厚み６μｍの２層積層フィルムを得た。
【００６４】
比較例５
Ｂ／Ａ／Ｂの３層積層において、Ａ層ポリマを平均粒径２．５μｍの合成マイカ粒子を１０重量％含有するポリマとした。Ｂ層ポリマは比較例３で用いたポリマＣとして上記比較例３と同様にＡ層積層厚み２μｍ、総厚み６．０μｍの３層積層フィルムを得た。
【００６５】
【表１】
【発明の効果】
以上説明したように、本発明の二軸配向積層熱可塑性樹脂フィルムによれば、特に、高密度磁気記録テープの薄膜化に伴う機械強度、走行性、熱寸法安定性に優れたフィルムを提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biaxially oriented laminated thermoplastic resin film, for example, a biaxially oriented laminated thermoplastic resin film that is very suitable as a film for various industrial materials such as magnetic recording media and capacitors. The present invention relates to a biaxially oriented laminated thermoplastic resin film useful as a magnetic recording medium substrate for computers that requires mechanical properties, wear resistance, and dimensional stability.
[0002]
[Prior art]
As a base film for a magnetic recording medium, a biaxially oriented film that defines the relationship between the laminated thickness and the average particle diameter of the contained particles is known in order to improve output performance and runnability (for example, JP-A-2- 77431). Further, a biaxially oriented film using flat particles for imparting light shielding properties is also known (for example, JP-A-6-322147).
[0003]
However, when the conventional biaxially oriented film as described above is used as a base film for a magnetic recording medium, the thickness of the base film decreases as the process speed increases and the magnetic recording tape becomes thinner in recent years. The mechanical strength, durability, and running properties of the film may be insufficient. In addition, with the recent increase in the density of magnetic recording tape, the recorded small magnetic domains become unstable due to the influence of surrounding magnetic materials, the substrate film is subjected to thermal fluctuations, and the dimensional stability deteriorates. However, problems such as deterioration in the reliability of data on the magnetic recording tape have arisen.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to solve such problems, and in particular, to provide a film excellent in mechanical strength, running property and thermal dimensional stability, which has been increasingly demanded with the thinning of high-density magnetic recording tapes for computers. It is in.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, at least one layer (A layer) of the biaxially oriented laminated thermoplastic resin film of the present invention comprises a thermoplastic resin (A) and plate-like inert particles (PA), And a layered structure of two or more layers in which a B layer having a thermoplastic resin (B) as a main component is laminated on at least one side of the A layer, the plate-like inert particles (PAThe aspect ratio (average particle diameter D in the plate surface direction / average particle thickness dt in the direction perpendicular to the plate surface) is 3 to 100, and the content is 1 to 80% by weight. .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail together with preferred embodiments.
The biaxially oriented laminated thermoplastic resin film of the present invention has a laminated structure of two or more layers. If it is a single layer, for example, when it is used for a magnetic recording medium, if it contains inert particles for the purpose of improving running properties, the protrusion diameter and protrusion height of the protrusions on the surface will be uneven, and the surface properties will be remarkably high. The output characteristics and wear resistance cannot be improved. The laminated structure may be 3 or 4 as long as it is 2 or more. However, in order to satisfactorily satisfy the mechanical strength, dimensional stability, and runnability that are the object of the present invention, the 3 layer laminated structure is particularly preferable. . As a three-layer laminated structure, the structure of thermoplastic resin B / thermoplastic resin A / thermoplastic resin B and the structure of thermoplastic resin B / thermoplastic resin A / thermoplastic resin C can be adopted.
[0007]
The thermoplastic resins A, B, and C constituting the biaxially oriented laminated thermoplastic resin film of the present invention are not particularly limited, but preferred examples include polyester, polyolefin, polyamide, polyimide, and polyphenylene sulfide. The thermoplastic resins A, B, and C constituting each layer may be the same type or different types. Further, other kinds of polymers may be blended within the range not impairing the object of the present invention, and heat stabilizer, antioxidant, ultraviolet absorber, antistatic agent, flame retardant, pigment, dye, fatty acid ester, wax Organic lubricants such as and inert particles may be added.
[0008]
The particle shape of the particles contained in the A layer of the biaxially oriented laminated thermoplastic resin film of the present invention is a plate shape. If the particle shape is plate-like, the mechanical strength and dimensional stability of the film are improved because the particles are likely to be oriented along the polymer molecular chain. If the contained particles are spherical or elliptical, the mechanical strength of the film cannot be sufficiently increased, which is not preferable.
[0009]
Plate-like inert particles contained in the A layer of the biaxially oriented laminated thermoplastic resin film of the present invention (PAThe aspect ratio (average particle diameter D in the plate surface direction / average particle thickness dt in the direction perpendicular to the plate surface) is 3 to 100 in terms of mechanical strength and dimensional stability. Preferably it is the range of 5-80, More preferably, it is the range of 10-50. For example, spherical particles having an aspect ratio outside the range defined in the present invention cannot improve the mechanical strength and dimensional stability of the film. On the other hand, if the aspect ratio is larger than the range in the present invention, it is not preferable because the particles aggregate and become difficult to align along the polymer, and the mechanical strength and dimensional stability cannot be improved.
[0010]
The plate-like inert particles are not particularly limited, but include talc, mica, glass flakes, plate-like alumina, silica, calcium carbonate, titanium dioxide, barium sulfate, quartz powder, flaky graphite, fluoromica, calcium phosphate, iron oxide and the like. Illustrated. Among these, particles having a Mohs hardness in the range of 6 to 10 are particularly preferable from the viewpoint of mechanical strength and dimensional stability. Examples of particles having a Mohs hardness of 6 to 10 include silica, alumina, zirconia, and titanium dioxide particles. In order to obtain the effects of the present invention, plate-like alumina particles are particularly preferable.
[0011]
The average particle diameter of the plate-like inert particles (average particle diameter in the plate surface direction: that is, the average diameter of the plate) is preferably 0.1 to 10 μm, and more preferably 0.3 to 5 μm. When this average particle diameter (plate diameter) is smaller than 0.1 μm, the film aggregates in the film, and uniform mechanical strength cannot be obtained. Further, if the average particle size is larger than the above range, the rigidity of the film itself becomes too strong, the handleability deteriorates, or the voids formed at the interface between the particles and the substrate become too large, resulting in high mechanical strength. Can't get.
[0012]
In the present invention, the content of the plate-like inert particles in the layer A is 1 to 80% by weight from the viewpoint of mechanical strength and dimensional stability. Preferably it is 5 to 50 weight%, More preferably, it is 10 to 40 weight%. If the content of the plate-like inert particles is less than 1% by weight, both mechanical strength and dimensional stability cannot be satisfied. On the other hand, if the content exceeds 80% by weight, the film itself becomes brittle, which is not preferable.
[0013]
The plate-like inert particles of the present invention can be subjected to a surface treatment for the purpose of increasing the affinity with the base resin and controlling the aggregation state in the A layer as necessary.
[0014]
The thickness ratio of the A layer with respect to the entire biaxially oriented laminated thermoplastic resin film of the present invention is preferably in the range of 1 to 95%, more preferably in the range of 5 to 80%. When the ratio of the A layer thickness is out of the above range, all of the mechanical strength, dimensional stability, and runnability cannot be improved.
[0015]
The laminated thickness (tB) of the B layer made of the thermoplastic resin B in the present invention is preferably in the range of 0.5 to 100 times the thickness (dt) of the plate-like inert particles A from the viewpoint of surface properties. . More preferably, it is 1-80 times, More preferably, it is 2-50 times. If the thickness of the B layer is smaller than the above range, surface protrusions due to the particles contained in the A layer are traced on the surface of the B layer, and the surface roughness increases and the output characteristics are deteriorated. If the thickness of the B layer is larger than the above range, the surface protrusions due to the particles contained in the A layer are not traced on the surface of the B layer at all, which is not preferable because the running performance with respect to the magnetic head may be deteriorated. It is preferable that the thickness of the B layer is within the above range because the roughness of the surface of the A layer is appropriately traced on the surface of the B layer.
[0016]
The B layer in the present invention does not need to contain particles, but may contain particles having an average particle diameter of 0.8 μm or less. In this case, the content is desirably 1% by weight or less from the object of the present invention.
[0017]
In the present invention, the C layer comprises the thermoplastic resin C and inert particles (PB), And the thickness of the C layer is 0.1 to 3 μm from the viewpoint of wear resistance and runnability. Preferably, the lamination thickness of the C layer is 0.5 to 2 μm.
[0018]
Inert particles (PB) Is not particularly limited, such as titanium oxide, calcium carbonate, kaolin, talc, colloidal silica, aluminum silicate particles, calcium phosphate, barium sulfate, carbon black, aggregated particles such as alumina and zirconia, crosslinked polystyrene, silicone, polyimide, etc. Preferred examples include crosslinked organic particles, so-called internal particles that are precipitated by a catalyst added during the polyester polymerization reaction, surfactants, and the like. Further, the contained particles may be one type, but two or more types may be used in combination.
[0019]
Contains inert particles (PB) Is preferably 0.05 to 0.8 μm, more preferably 0.1 to 0.6 μm. The content is preferably 0.01 to 1% by weight, more preferably 0.1 to 0.6% by weight.
[0020]
Inert particles (PB) Is not particularly limited, but it is preferable to use substantially spherical particles having a particle size ratio (major axis / minor axis) of 1.0 to 1.3. However, even particles and agglomerates having an irregular particle shape such as calcium carbonate particles and alumina can be used by adjusting the content and particle size, and using them together with spherical particles. Further, a sharp particle having a particle size distribution with a relative standard deviation of the particle size of 0.6 or less is preferable.
[0021]
The Young's modulus of the biaxially oriented laminated thermoplastic resin film of the present invention is preferably 5 GPa or more and 20 GPa or less in both the longitudinal direction and the width direction. More preferably, it is 7-15 GPa, More preferably, it is 8-12 GPa. By setting the Young's modulus of the film within the above range, it is possible to more easily obtain a base film that can be used in harsh environments and can be made thin in magnetic recording media.
[0022]
The thermal contraction rate in the longitudinal direction of the biaxially oriented laminated thermoplastic resin film of the present invention is preferably 0 to 1.5%, more preferably 0 to 1.2% from the viewpoint of thermal dimensional stability. . By setting the thermal shrinkage rate within this range, it is preferable that high reliability can be obtained even when used in harsh environments, especially when a data backup recording medium is used.
[0023]
Although the use of the biaxially oriented laminated thermoplastic resin film of the present invention is not particularly limited, it is used for magnetic recording media, capacitors and the like. In particular, it can be effectively used as a base material for a magnetic recording medium for data backup.
[0024]
Although the specific example of the manufacturing method of the film which concerns on this invention is demonstrated, this invention is not limited to this.
As the thermoplastic resin used in the present invention, those obtained by a known method can be used. Further, plate-like inert particles (PA), Inert particles (PB) May be added at any stage before, during or after polymerization in the resin production process. For example, when using polyester as the thermoplastic resin, the particles are mixed with the diol component in the form of a slurry, Examples thereof include a method of dispersing and polymerizing, or a method of kneading this slurry into a thermoplastic resin using a biaxial vent type extruder. Moreover, the method of heat-treating the particle slurry at a temperature of 180 to 230 ° C., particularly 190 ° C. to 210 ° C. for 30 minutes to 12 hours, preferably 2 to 8 hours is effective for further enhancing the effect of the present invention. Further, for example, when an alkylsulfonic acid alkyl metal salt is used as the organic additive, it is added after the polymerization catalyst is added, and the addition is terminated when a predetermined degree of polymerization is obtained. When the higher ester is added, it is preferable to add the polymer with stirring at the temperature in the final stage of the polymerization immediately before the completion of the polymerization.
[0025]
As a method for adjusting the content of particles and organic compounds, a high-concentration master is prepared by the above method, and the high-concentration particles and organic compound master pellets are diluted with a polymer containing substantially no particles during film formation. It is preferable to use the method to do.
[0026]
Next, the pellets of the thermoplastic resin containing these particles are sufficiently dried as necessary, and then supplied to an extruder heated to 280 to 320 ° C. in a nitrogen stream or under vacuum so that the intrinsic viscosity does not decrease. And it forms into a film by the method currently performed conventionally. Moreover, it is preferable to use various types of filters, for example, filters made of materials such as sintered metal, porous ceramics, sand, and wire mesh, in order to remove foreign substances and denatured polymers. The filtration accuracy of the filter is preferably selected as appropriate depending on the particle size of the inert particles used. Each of the thermoplastic resins A, B, and C (A, B, and C may be the same type or different types) constituting each layer is sufficiently dried and then separately supplied to two or more melt extruders. Using a multilayer manifold or merging block, laminate a polymer layer made of thermoplastic resin (B) on at least one side of thermoplastic resin (A) at the stage of the polymer tube or die, and two or more layers from the slit-like die The sheet is extruded and cooled and solidified on a casting drum having a surface temperature of 20 to 50 ° C. by using an electrostatic application casting method to produce an unstretched film. In this case, the method of laminating using a confluence block having a rectangular confluence section is effective for thinly and uniformly laminating various kinds of inert particle-containing thermoplastic resin layers. Also, a static mixer, a method of installing a gear pump in the polymer flow path constituting each layer, and the melt viscosity of the thermoplastic resins B and C of the surface layer are made higher than the melt viscosity of the thermoplastic resin A of the other layer in contact therewith. This method is effective for obtaining the mechanical strength and thermal dimensional stability of the present invention.
[0027]
Next, this unstretched film is biaxially stretched to be biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. For example, when using a sequential biaxial stretching method in which stretching is first performed in the longitudinal direction and then in the width direction, the stretching ratio in the longitudinal direction is not particularly limited, but the total stretching is performed at a stretching speed of 5000 to 50000% / min. The magnification is preferably 3 to 10 times, and more preferably 3.5 to 9 times. The stretching temperature is preferably in the range of not less than the glass transition temperature Tg of the thermoplastic resin and not more than (glass transition temperature Tg + 50 ° C.).
[0028]
Stretching in the width direction is performed using a known tenter, stretching temperature of 90 to 160 ° C., more preferably 95 to 150 ° C., 3 to 10 times, more preferably 3.5 to 9 times, stretching in the width direction. The speed is preferably in the range of 1000 to 30000% / min.
Further, if necessary, the biaxially stretched film may be stretched again in at least one direction of the longitudinal direction and the width direction.
[0029]
Next, this stretched film is heat-treated. In this case, the heat treatment temperature is 170 to 250 ° C., more preferably 180 to 230 ° C., and the treatment time is preferably 1 to 30 seconds.
[0030]
Further, when the simultaneous biaxial stretching method is used as the stretching method, it is preferable to use the simultaneous biaxial stretching method by using a drive type tenter using a linear motor.
The simultaneous biaxial stretching temperature is preferably not less than the glass transition temperature Tg of the thermoplastic resin and not more than (glass transition temperature Tg + 50 ° C.). If the stretching temperature deviates greatly from this range, uniform stretching cannot be performed, and thickness spots and film tears are deteriorated, which is not preferable. The draw ratio is 3 to 10 times in the longitudinal direction and the transverse direction. Although it does not specifically limit as extending | stretching speed, 2000% / min-50000% / min are preferable.
[0031]
Next, this stretched film is heat-treated. In this case, the heat treatment temperature is 170 to 250 ° C, particularly 180 to 230 ° C. The heat treatment time is preferably in the range of 1 to 30 seconds.
[0032]
Thus, the film biaxially oriented and heat-treated by each method is gradually cooled to room temperature and wound with a winder. The cooling method is preferably gradually cooled to room temperature in two or more stages. At this time, performing a relaxation treatment of about 0.5 to 10% in the longitudinal direction and the width direction is effective for keeping the thermal dimensional stability within the scope of the present application. The cooling temperature is preferably in the range of [heat treatment temperature −20 ° C.] to 120 ° C. in the first stage and [cooling temperature in the first stage −30 ° C.] to 40 ° C. in the second stage. It is not limited to.
[0033]
[Methods for measuring physical properties and methods for evaluating effects]
(1) Average particle diameter D and aspect ratio (D / dt) of plate-like inert particles
The thermoplastic resin is removed from the film by a plasma low temperature ashing method to expose the particles. Processing conditions are selected so that the polymer is ashed but the particles are not damaged. When another layer is laminated on the layer containing the plate-like particles, the laminated part is scraped off with a single blade and then observed by the above method. This is observed using an SEM (scanning electron microscope), and an image of the particles (light density produced by the particles) is connected to an image analyzer for processing. The observation place is changed and the diameter in the plate surface direction of each particle is measured for 1000 or more particles, and the average value is defined as the average particle diameter D of the plate-like inert particles. It is considered that the magnification of SEM is about 2000 times to 100,000 times, but if the particles are finer, the magnification is appropriately changed to a high magnification and observed.
[0034]
The average thickness dt of the particles can be obtained from the SEM photograph in the same manner as described above, but the film is formed as an ultra-thin film piece with a thickness of 100 nm perpendicular to the plane using a transmission electron microscope (TEM). The long diameter (corresponding to the average diameter D of the above plate) and the short diameter (particle thickness) of the plate-like inert particles are observed, and a value corresponding to the particle thickness is obtained for 1000 or more particles. The average thickness dt of the inert particles is assumed. The observation magnification of the transmission electron microscope can be selected as appropriate, but is usually about 2000 to 100,000 times. As described above, the particle size (D) and thickness (dt) of the plate-like inert particles were determined, and the aspect ratio was calculated from the following formula.
Aspect ratio = Σ (D / dt) / N
N: Total number of particles
[0035]
(2) Average particle diameter dB of spherical and amorphous inert particles
Using a transmission electron microscope (TEM) to observe the cross section of the film, observe spherical or amorphous particles other than plate-like particles contained in the film at a magnification of 10,000 times or more, and observe the particle equivalent sphere diameter To do. The section thickness of the TEM is about 100 nm, and the measurement is performed at 100 fields or more at different locations. The volume average diameter dB is obtained from the following formula.
dB = Σdi * NVi
di is the particle size, and NVi is the volume fraction.
[0036]
(3) Particle content
The particle content of the laminated part was obtained by slitting the film in a tape shape with a width of 1/2 inch, using a single blade vertically pressed against the film surface, and further running for 20 cm (running tension: 500 g, travel speed: 6.7 cm / second). At this time, the scraped material on the film surface adhering to the tip of the single blade is dissolved by selecting a solvent in which the polymer dissolves and the particles do not dissolve, the particles are centrifuged from the polymer, and have a ratio (% by weight) to the total weight of the particles. The particle content. In some cases, combined use with infrared spectroscopy is also effective.
[0037]
(4) Film lamination thickness
Using a secondary ion mass spectrometer (SIMS), the concentration ratio of the element due to the highest concentration of particles in the film in the range of 5000 nm in depth from the surface layer to the carbon element of the polyester (M+/ C+) Is the particle concentration, and analysis in the thickness direction is performed from the surface to a depth of 5000 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 film of the present invention, the particle concentration once reached the maximum value starts to decrease again. Based on this concentration distribution curve, a depth at which the surface layer particle concentration becomes 1/2 of the maximum value (this depth is deeper than the depth at which the maximum value is reached) was obtained, and this was defined as the laminated thickness. The conditions are as follows.
(1) Measuring equipment
Secondary ion mass spectrometer (SIMS)
West Germany, ATOMIKA A-DIDA3000
(2) Measurement conditions
Primary ion species: O2 +
Primary ion acceleration voltage: 12KV
Primary ion current: 200nA
Raster area: 400 μm □
Analysis area: 30% gate
Measurement vacuum: 5.0 × 10-9Torr
E-GUN: 0.5KV-3.0A
[0038]
In addition, when the most contained particles in the depth range of 5000 nm from the surface layer are organic polymer particles, it is difficult to measure by SIMS, so XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy) while etching from the surface. ) Etc. may be used to measure the depth profile in the same manner as described above, and the thickness of the laminate may be obtained, or using a transmission electron microscope (Hitachi model H-600), the cross section of the film at an accelerating voltage of 100 kV ( RuOFourIt is also possible to obtain the stacking thickness by observing the interface by dyeing) and capturing the interface. The magnification is usually selected according to the thickness of the layer to be determined, and is not particularly limited, but 10,000 to 1,000,000 times is appropriate.
[0039]
(5) Young's modulus of the film
Using a tensile tester manufactured by Toyo Baldwin Co., Ltd., a sample film having a test length of 100 mm and a width of 10 mm was pulled at a pulling speed of 10 mm / min at room temperature adjusted to a temperature of 25 ° C. and a humidity of 60%. The Young's modulus was determined from the gradient of the rising straight portion of the obtained tension-strain curve.
[0040]
(6) Thermal shrinkage
Sampling to a width of 10 mm, marking marked lines at intervals of 200 mm, and measuring between marked lines (L0) The film was placed in an oven controlled at 150 ° C. under no load, treated for 30 minutes, taken out, left in an atmosphere of temperature 25 ° C. and humidity 65% for 1 hour, and measured between marked lines (L), The thermal contraction rate was calculated by the following formula.
Thermal contraction rate (%) = {(L0-L) / L0} × 100
[0041]
(7) Durability
As a method for producing a magnetic tape, the following magnetic coating is applied by a die coater so that the thickness after dry calendering is 2 μm, magnetically oriented and dried. Subsequently, the following back coat paint was applied onto the opposite surface of the support so that the thickness after dry calendering was 0.7 μm, and dried at 90 ° C. to form a back coat layer.
[0042]
The magnetic sheet thus obtained was calendered (temperature: 70 ° C., linear pressure: 150 kg / cm), then aged for 48 hours at 60 ° C. and 40% RH in a state of being wound around a core, and then slit to a 1/2 inch width. Then, the magnetic layer surface was polished with a ceramic wheel (rotation speed + 150%, winding angle 30 °) while running at 100 m / min, and a magnetic tape having a tape length of 125 m was prepared. The magnetic tape was incorporated into a cartridge to produce a computer tape.
[0043]
<Magnetic paint>
Co-containing ferromagnetic Fe particles: 100 parts by weight
Vinyl chloride copolymer: 10 parts by weight
(Nippon Zeon: MR110)
Polyurethane resin: 10 parts by weight
(Toyobo: UR8200)
α-alumina (primary diameter 0.3 μm): 10 parts by weight
Carbon black (primary diameter 20 nm): 2 parts by weight
Methyl ethyl ketone: 75 parts by weight
Toluene: 75 parts by weight
Cyclohexanone: 75 parts by weight
Polyisocyanate: 5 parts by weight
Myristic acid: 2 parts by weight
Butyl stearate: 4 parts by weight
[0044]
<Back coat paint>
Carbon black (primary diameter 25 nm): 40 parts by weight
Carbon black (primary diameter 75 nm): 2 parts by weight
Polyurethane resin: 20 parts by weight
Polyisocyanate: 4 parts by weight
Nitrocellulose: 20 parts by weight
Methyl ethyl ketone: 140 parts by weight
Toluene: 140 parts by weight
Cyclohexanone: 140 parts by weight
Stearic acid: 1 part by weight
[0045]
This magnetic tape is continuously run for 48 hours in a 40 ° C. and 65% RH environment using a DLT4000 drive, a random data signal is recorded, and the block error rate of each computer tape is once measured by a block error rate measuring device. The increase rate of the error rate after 48 hours with respect to after running was examined, and durability was evaluated with this.
[0046]
(8) Output characteristics
The film of the present invention was provided with a vapor deposition layer having a thickness of 200 nm of a cobalt-nickel alloy (Ni 20 wt%) in the presence of a small amount of oxygen using a continuous vacuum vapor deposition apparatus. Furthermore, after forming a carbon protective film on the surface of the vapor deposition layer by a known means, it was slit to a width of 8 mm to prepare a pancake. Next, a length of 200 m from this pancake was incorporated into a cassette to obtain a cassette tape.
[0047]
This tape was measured using a commercially available Hi8 VTR (EV-BS3000 manufactured by Sony Corporation), and the C / N of 7 MHz ± 1 MHz was measured. The C / N was compared with the magnetic tape of Comparative Example 1.
+3 dB or more: Excellent
+1 to +3 dB: good
<+1 dB: bad
It was determined. If the output characteristics are +1 dB or more compared with the magnetic tape of Comparative Example 1, it is a level that can be sufficiently used as a digital recording magnetic tape.
[0048]
(9) Driving performance
A film slit into a tape shape having a width of ½ inch was run in an atmosphere of 25 ° C. and 60% RH, and an initial friction coefficient μk was obtained from the following equation.
μk = 2 / πln (T2/ T1)
Where T1Is the entry side tension, T2Is the exit tension. The guide diameter is 6 mmΦ, the guide material is SUS27 (surface roughness 0.2S), the winding angle is 60 °, and the traveling speed is 3.3 cm / sec. When μk obtained by this measurement was 0.3 or less, it was determined that the slipperiness was good, and when it exceeded 0.3, the slipperiness was poor.
[0049]
【Example】
Based on the following examples, embodiments of the present invention will be described.
Example 1
A plate-like alumina particle having an average particle size of 0.3 μm as a lubricant to polyethylene terephthalate (hereinafter referred to as PET) obtained by a known method as a thermoplastic resin constituting the A layer in a two-layer laminated film having a laminated constitution A / B A polymer (Polymer A) containing 30% by weight (YKK Co., Ltd., plate-like alumina particles “Seraph”) was prepared. As a thermoplastic resin constituting the B layer, a substantially particle-free PET prepared by a known method was prepared (polymer B). Using two extruders, polymer B is supplied to extruder B heated to 280 ° C. after being vacuum-dried at 180 ° C. for 3 hours, and polymer A is supplied to extruder A that is also heated to 270 ° C. Supplyed after vacuum drying at 3 ° C. for 3 hours, merged in a T-die to laminate two layers (lamination configuration: A / B), solidified by cooling and solidifying while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C., A laminated unstretched film was created.
[0050]
This unstretched film is divided into three stages in the longitudinal direction by a roll-type stretching machine, stretched 1.5 times at a temperature of 90 ° C, 2.2 times at 92 ° C, and further 1.3 times at 93 ° C. Using a tenter, the film was stretched 3.8 times in the width direction at a temperature of 98 ° C. Subsequently, the film was heat-treated at an ambient temperature of 210 ° C. for 5 seconds while being finely stretched by 1.05 times in the longitudinal direction and the width direction, and in a cooling zone at a relaxation rate of 8% at 150 ° C. for 2 seconds and at 100 ° C. for 3 seconds. The film was gradually cooled for 2 seconds and heat treated at 60 ° C. for 1 second to obtain a laminated polyester film having a layer A laminate thickness of 4 μm and a total thickness of 6 μm.
As shown in Table 1, the characteristics of the laminated polyester film were excellent in mechanical strength, thermal dimensional stability, durability, output characteristics, and running characteristics. In Table 1, the longitudinal direction is abbreviated as MD and the width direction is abbreviated as TD.
[0051]
Example 2
In a film having a laminated structure of B / A / C three layers, polycondensation from PET containing 11% by weight of plate-like alumina particles having an average particle diameter of 0.6 μm as a polymer constituting the A layer and the following raw materials A polymer obtained by blending the copolymerized polyester having a mesogenic group (mesogen group content 60 mol%) (abbreviated as LCP in Table 1) at the following ratio was used.
[0052]
These raw materials were melt-extruded at 280 ° C., 275 ° C., and 280 ° C. using three extruders, and the stretching conditions were appropriately changed to prepare a B / A / C three-layer laminated film. The B layer stack thickness was 2.5 μm, the A layer stack thickness was 1 μm, and the C layer stack thickness was 2.5 μm. As shown in Table 1, the characteristics of the laminated polyester film were excellent in mechanical strength, thermal dimensional stability, durability, output characteristics, and running characteristics.
[0053]
Example 3
A B / A / C three-layer laminated film was prepared in the same manner as in Example 2 except that the plate A particle type, amount added, and lamination thickness ratio of Polymer A used in Example 2 were changed as shown in Table 1. .
[0054]
Example 4
In a three-layer film of B / A / B laminated structure, the polymer constituting the A layer is made of plate-like alumina particles having an average particle size of 0.6 μm (made by YKK, plate-like alumina particles “Seraph”). A 20% by weight blended PET polymer (Polymer A) was prepared. As a thermoplastic resin constituting the B layer, PET containing polyetherimide (“ULTEM 1010” manufactured by GE Plastics, hereinafter referred to as PEI) and colloidal silica particles having an average particle diameter of 0.3 μm obtained by a known method is used. A polymer (Polymer D) blended at a ratio of 35:65 was used. Using two extruders, polymer B is supplied to extruder B heated to 280 ° C. after being vacuum-dried at 180 ° C. for 3 hours, and polymer A is supplied to extruder A that is also heated to 270 ° C. Supplyed after vacuum drying at 3 ° C. for 3 hours, merged in a T-die to laminate 3 layers (lamination configuration: B / A / B), solidified by cooling while applying an electrostatic charge to a cast drum with a surface temperature of 25 ° C. Then, a laminated unstretched film was created.
[0055]
This unstretched film is divided into three stages in the longitudinal direction by a roll-type stretching machine, stretched 1.8 times at a temperature of 90 ° C, 2.0 times at 92 ° C, and further 1.3 times at 93 ° C. The film was stretched 4.0 times in the width direction at a temperature of 98 ° C. using a tenter. Heat treatment was performed for 10 seconds at a temperature of 210 ° C. under a constant length, and in the cooling zone, annealing was performed at 150 ° C. for 3 seconds and at 100 ° C. for 3 seconds at a relaxation rate of 8%. A laminated polyester film having a thickness of 6 μm was obtained.
As shown in Table 1, the characteristics of the laminated polyester film were excellent in mechanical strength, thermal dimensional stability, durability, output characteristics, and running characteristics.
[0056]
Example 5
In a five-layer film of B / A / D / A / C, the A layer polymer was a PET polymer containing 10% by weight of plate-like alumina particles having an average particle diameter of 0.6 μm (polymer A). As the B layer polymer, a particle-free PET / PEI polymer having a ratio of polyetherimide and PET used in Example 4 of 35:65 (polymer B) was used. As the C layer polymer, the polymer C used in Example 2 was used. A PET recycled polymer was used as the polymer for the D layer. Each of these four types of polymer is dried, supplied to four extruders, and merged in a T-die to laminate five layers (lamination configuration: B / A / D / A / C), surface temperature 25 ° C. While applying an electrostatic charge to the cast drum, it was closely cooled and solidified to produce a laminated unstretched film.
[0057]
This unstretched film is divided into three stages in the longitudinal direction by a roll-type stretching machine, stretched 1.3 times at a temperature of 91 ° C, 2.3 times at 92 ° C, and further 1.3 times at 93 ° C, Using a tenter, the film was stretched 4.2 times at a temperature of 100 ° C. in the width direction. Heat treatment was performed at a temperature of 210 ° C. for 10 seconds under a constant length, followed by slow cooling at 150 ° C. for 3 seconds and 100 ° C. for 3 seconds at a relaxation rate of 10%. A laminated polyester film having a B layer lamination thickness of 0.5 μm, a C layer lamination thickness of 1 μm, and a total thickness of 6 μm was obtained.
As shown in Table 1, the properties of the laminated polyester film were excellent in mechanical strength, thermal dimensional stability, durability, and running properties.
[0058]
Example 6
The polymer A of Example 1 was changed to plate-like alumina particles having an average particle diameter of 10 μm, and the blending amount was changed so that the content was 3% by weight. Others were obtained in the same manner as in Example 1 to obtain a laminated film having a two-layer structure of A / B and having an A layer thickness of 1 μm and a total thickness of 6 μm.
As shown in Table 1, the characteristics of the laminated polyester film were excellent in mechanical strength, thermal dimensional stability, durability, output characteristics, and running characteristics.
[0059]
Example 7
In the three-layer lamination of B / A / C, A-layer thermoplastic resin A is polyethylene 2,6-naphthalate (hereinafter referred to as PEN) obtained by a known method, and plate-like alumina particles having an average particle size of 0.5 μm An appropriate amount of the PEN pellets was mixed to make the plate-like alumina particle content 5% by weight. As the B and C layer polymers, the polymer B and the polymer C used in Example 2 were used. Extrusion was carried out in the same manner as in Example 1, and the stretching conditions were appropriately changed to prepare a three-layer laminated film having a B and C layer lamination thickness of 2 μm and an A layer lamination thickness of 1 μm.
As shown in Table 1, the characteristics of the laminated polyester film were excellent in mechanical strength, thermal dimensional stability, durability, output characteristics, and running characteristics.
[0060]
Comparative Example 1
The particle concentration of the polymer A used in Example 2 was changed to 30% by weight, diluted with particle-free PET pellets so that the particle content was 20% by weight, and the same stretching conditions as in Example 1 were used. A single-layer film having a total thickness of 6 μm was prepared.
[0061]
Comparative Example 2
A two-layer laminate film having an A layer laminate thickness of 1 μm was prepared in the same manner as in Example 1 except that the A / B two-layer laminate film was changed to silica particles having an average particle diameter of 0.6 μm.
[0062]
Comparative Example 3
In the three-layer lamination of B / A / B, a three-layer laminate film was prepared in the same manner as in Example 3 except that the A-layer polymer was non-particle PET and the B-layer polymer was the polymer C used in Example 2.
[0063]
Comparative Example 4
A two-layer laminated film having a layer A laminated thickness of 4 μm and a total thickness of 6 μm was obtained in the same manner as in Example 1 except that the particles contained in the polymer A of Example 1 were changed to α-type alumina particles having an average particle diameter of 0.3 μm. Obtained.
[0064]
Comparative Example 5
In the three-layer lamination of B / A / B, the A layer polymer was a polymer containing 10% by weight of synthetic mica particles having an average particle diameter of 2.5 μm. As the polymer C used in Comparative Example 3, a B-layer polymer was obtained in the same manner as in Comparative Example 3 to obtain a three-layer laminated film having an A layer laminated thickness of 2 μm and a total thickness of 6.0 μm.
[0065]
[Table 1]
【The invention's effect】
As described above, according to the biaxially oriented laminated thermoplastic resin film of the present invention, a film excellent in mechanical strength, running property, and thermal dimensional stability accompanying the thinning of the high-density magnetic recording tape is provided. be able to.
Claims (9)
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|---|---|---|---|
| JP2001023384A JP4576721B2 (en) | 2001-01-31 | 2001-01-31 | Biaxially oriented laminated thermoplastic film |
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| JP2004109355A (en) * | 2002-09-17 | 2004-04-08 | Yasuhiro Koike | Method for manufacturing optical material, optical material and optical element |
| JP2012072219A (en) * | 2010-09-28 | 2012-04-12 | Toray Ind Inc | Biaxially oriented polyester film |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03208639A (en) * | 1990-01-12 | 1991-09-11 | Toray Ind Inc | Biaxially oriented thermoplastic resin film |
| JPH05298672A (en) * | 1992-04-22 | 1993-11-12 | Toray Ind Inc | Audio tape |
| JPH05318577A (en) * | 1992-05-19 | 1993-12-03 | Teijin Ltd | Biaxially oriented polyester film for magnetic recording medium |
| JPH06234907A (en) * | 1993-02-10 | 1994-08-23 | Teijin Ltd | Polyester film |
| JPH11320793A (en) * | 1998-05-20 | 1999-11-24 | Toray Ind Inc | Biaxially oriented polyester film |
-
2001
- 2001-01-31 JP JP2001023384A patent/JP4576721B2/en not_active Expired - Lifetime
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03208639A (en) * | 1990-01-12 | 1991-09-11 | Toray Ind Inc | Biaxially oriented thermoplastic resin film |
| JPH05298672A (en) * | 1992-04-22 | 1993-11-12 | Toray Ind Inc | Audio tape |
| JPH05318577A (en) * | 1992-05-19 | 1993-12-03 | Teijin Ltd | Biaxially oriented polyester film for magnetic recording medium |
| JPH06234907A (en) * | 1993-02-10 | 1994-08-23 | Teijin Ltd | Polyester film |
| JPH11320793A (en) * | 1998-05-20 | 1999-11-24 | Toray Ind Inc | Biaxially oriented polyester film |
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