JP3942211B2 - Biaxially oriented laminated polyester film for magnetic recording media - Google Patents

Description

【００４５】
［但し、Ｃ_A はポリエステルＡ１層、Ａ２層中の平均粒径０．４μｍ以上の不活性粒子の含有量（重量％）、
Ｃ_B はポリエステルＢ層中の平均粒径０．４μｍ以上の不活性粒子の含有量（重量％）、
ｄ_A はポリエステルフイルムＡ１層及びＡ２層の総厚み（μｍ）、
ｄ_B はポリエステルフイルムＢ層の厚み（μｍ）、
Ｒは０．３〜０．０７の数値
である。］
【００４６】
上記式においてＲ（値）が０．７を超えたり、０．３未満であると、回収フイルムを使用したときのポリエステルＢ層の平均粒径が０．４μｍ以上の不活性粒子の含有量の変動が大きくなり、その結果ポリエステルＡ１層及びＡ２層表面の粗さも変動が大きくなるので、好ましくない。好ましいＲ（値）は０．４〜０．６である。また平均粒径が０．４μｍ未満の小粒径不活性粒子は、ポリエステルＢ層に含有されていてもポリエステルＡ１層及びＡ２層の表面へ与える影響は小さい。
【００４７】
本発明の二軸配向積層ポリエステルフイルムは、巻き取り速度２００ｍ／分における巻き取り性指数が１００以下であることが好ましい。巻き取り性指数が１００以下であると、高速デュプリケータ用ベースフイルムとして使用する際、巻き取り性に対する改善効果が顕著であるので好ましい。他方、巻き取り性指数が１００より大きいと高速で巻き取った際、フイルムロールの端面が不揃いになるなどして巻き形状が悪化したり、ひどい場合には巻き取り中に巻きくずれたりするので好ましくない。巻き取り速度２００ｍ／分における巻き取り性指数は、より好ましくは８５以下であり、特に好ましくは７０以下である。
【００４８】
さらに、本発明の二軸配向積層ポリエステルフイルムは、フイルムの総厚みが５〜２５μｍであることが好ましく、１０〜２０μｍであることが更に好ましい。
【００４９】
また、フイルムの縦方向のヤング率は４００ｋｇ／ｍｍ² 以上、更には４５０ｋｇ／ｍｍ² 以上であることが好ましい。また横方向のヤング率は５００ｋｇ／ｍｍ² 以上、更には６００ｋｇ／ｍｍ² 以上であることが好ましい。縦、横方向のヤング率が上記範囲にあると、長時間テープ用としての薄膜化にも十分対応し得るので好ましい。
【００５０】
本発明の二軸配向積層ポリエステルフイルムは、磁気記録媒体製造の際には、ポリエステルＡ１層の表面に磁性層を設けるようにして使用される。こうすることにより、優れた電磁変換特性、耐削れ性、走行耐久性、巻き取り性を同時に満足する磁気記録媒体を製造することができる。
【００５１】
本発明の二軸配向積層ポリエステルフイルムは、基本的には従来から知られている、あるいは当業界に蓄積されている方法で得ることができる。例えば、先ず積層未延伸フイルムを製造し、次いで該フイルムを二軸配向させることで得ることができる。この積層未延伸フイルムは、従来から蓄積された積層フイルムの製造法で製造することができる。例えば、表面を形成するフイルム層（ポリエステルＡ１、Ａ２層）と、芯層を形成するフイルム層（ポリエステルＢ層）とを、溶融状態又は冷却固化された状態で積層する方法を用いることができる。さらに具体的には、例えば共押出し、エクストルージョンラミネート等の方法で製造できる。
【００５２】
上述の方法で積層された未延伸フイルムは、更に従来から蓄積された二軸配向フイルムの製造法に準じて、二軸配向フイルムとすることができる。例えば、積層未延伸フイルムを一軸方向（縦方向又は横方向）に（Ｔｇ−１０）〜（Ｔｇ＋７０）℃の温度（但し、Ｔｇ：ポリエステルのガラス転移温度）で２．５〜８．０倍の倍率で延伸し、次いで上記延伸方向と直角方向（一段目延伸が縦方向の場合には、二段目延伸は横方向となる）にＴｇ（℃）〜（Ｔｇ＋７０）℃の温度で２．５〜８．０倍の倍率で延伸することで製造できる。この場合、面積延伸倍率は９〜３２倍、更には１２〜２８倍にするのが好ましい。延伸手段は同時二軸延伸、逐次二軸延伸のいずれでもよい。更に、二軸配向フイルムは、（Ｔｇ＋７０）℃〜Ｔｍ（℃）の温度で熱固定することができる。例えば積層ポリエチレンテレフタレートフイルムについては１９０〜２３０℃で熱固定することが好ましい。熱固定時間は、例えば１〜６０秒である。
【００５３】
本発明の二軸配向積層ポリエステルフイルムは、ポリエステルＡ１層及びＡ２層をポリエステルＢ層の両側に積層した３層構成の積層ポリエステルフイルムとし、両最外層の厚み及び表面性を特定範囲としたため、高速デュプリケータ用磁気記録媒体のベースフイルムとして要求される巻き取り性、ベース面の平坦性、耐削れ性、電磁変換特性の向上の点で、優れた性能を有しており、また安価な製造コストで製造し得る極めてトータルパフォーマンスに優れたものであり、磁気記録媒体用ベースフイルムとして特に有用なものである。
【００５４】
なお、本発明における種々の物性値および特性は以下の如くして測定されたものであり、かつ定義される。
【００５５】
（１）粒子の平均粒径（ＤＰ）
島津製作所（株）製ＣＰ―５０型セントリフュグル パーティクル サイズ アナライザー（Centrifugal Particle Size Analyzer）を用いて測定する。得られる遠心沈降曲線を基に算出した各粒径の粒子とその存在量との積算曲線から、５０マスパーセントに相当する粒径を読み取り、この値を上記平均粒径とする（Book「粒度測定技術」日刊工業新聞発行、１９７５年、頁２４２〜２４７参照）。
【００５６】
（２）粒子の見掛けのヤング率
島津製作所（株）製超微小圧縮試験機ＭＣＴＭ―２０１を用いてダイヤモンド圧子を一定負荷速度（２９ｍｇｆ／秒）で降下させ、粒子１個に外力をかける。そして、粒子が破壊されたときの荷重Ｐ（ｋｇｆ）、粒子が破壊されたときの圧子の変位Ｚ（ｍｍ）、粒子の粒径ｄ（ｍｍ）から下記式に従って見掛けのヤング率Ｙを求め、同様の操作を１０回行ない、１０回の平均値をもって粒子の見掛けのヤング率とする。
【００５７】
【数１７】
Ｙ＝２．８Ｐ／πｄＺ
【００５８】
（３）粒子の平均凝集度
粒子を含有したフイルムを断面方向に厚さ１００ｎｍの徴薄切片とし、透過電子顕微鏡（例えば日本電子製ＪＥＭ―１２００ＥＸ）を用いて、１０万倍程度の倍率で粒子を観察すると、これ以上粒子を分割できない最小の粒子（一次粒子）を観察できる。この観察写真より１００個の粒子について、特に凝集粒子（二次粒子）についてはいくつの一次粒子からできているか数え、一次粒子の総和を測定した粒子の数で割った値を平均凝集度とする。
【００５９】
（４）三次元中心面平均粗さ（ＳＲａ）、三次元十点平均粗さ（ＳＲｚ）
三次元粗さ測定機（小坂研究所製ＳＥ―３ＣＫ）を用いて、針径２μｍＲ、針圧３０ｍｇ、測定長１ｍｍ、サンプリングピッチ２μｍ、カットオフ０．２５ｍｍ、縦方向拡大率２万倍、横方向拡大率２００倍、走査本数１００本の条件にてフイルム表面の三次元表面プロファイルをイメージさせる。得られたプロファイルから中心面上に面積Ｓ_M の部分を抜き取り、この抜き取り部分の中心面上に直交座標軸、Ｘ軸、Ｙ軸を置き、中心面に直交する軸をＺ軸として、次式により与えられる値をＳＲａとする。
【００６０】
【数１８】

【００６１】
また、ＳＲｚについては、プロファイルから基準面積分だけ抜き取った部分の平均線に平行な平面のうち高い方から１〜５番目までの山の高さの平均と深い方から１〜５番目までの谷の深さの平均との間隔をもってＳＲｚとする。
【００６２】
（５）フイルムの表面粗さ（Ｒａ）
中心線平均粗さ（Ｒａ）としてＪＩＳ Ｂ０６０１で定義される値であり、本発明では（株）小坂研究所の触針式表面粗さ計（SURFCORDER SE-30C ）を用いて測定する。測定条件等は次の通りである。
（ａ）触針先端半径：２μｍ
（ｂ）測定圧力 ：３０ｍｇ
（ｃ）カットオフ ：０．２５ｍｍ
（ｄ）測定長 ：２．５ｍｍ
（ｅ）データのまとめ方：同一試料について６回繰り返し測定し最も大きい値を１つ除き、残りの５つのデータの平均値で表示する。
【００６３】
（６）カレンダー削れ性
ベースフイルムの走行面の削れ性を３段のミニスーパーカレンダーを使用して評価する。カレンダーはナイロンロールとスチールロールの３段カレンダーであり、処理温度は８０℃、フイルムにかかる線圧は２００ｋｇ／ｃｍ、フイルムスピードは１００ｍ／分で走行させる。走行フイルムを全長４０００ｍ走行させた時点でのカレンダーのトップローラーに附着する汚れでベースフイルムの削れ性を評価する。
【００６４】
＜５段階判定＞
１級：ナイロンロールの汚れが全くなし
２級：ナイロンロールの汚れがほとんどなし
３級：ナイロンロールの汚れが少しあるが、からぶきで簡単にとれる
４級：ナイロンロールの汚れがからぶきでとれにくく、アセトン等の溶媒でふきとれる
５級：ナイロンロールがひどく汚れ、溶媒でもなかなかとれにくい。
【００６５】
（７）ブレード削れ性
温度２０℃、湿度６０％の環境で、幅１／２インチに裁断したフイルムにブレード（米国ＧＫＩ製工業用カミソリ試験機用ブレード）の刃先を垂直にあて、更に２ｍｍ押し込んで接触させて毎分１００ｍの速さ、入口テンションＴ₁ ＝５０ｇで走行（摩擦）させる。フイルムが１００ｍ走行した後の、ブレードに付着した削れ粉量を評価する。
＜判定＞
◎：ブレード刃先に付着する削れ粉付着幅が０．５ｍｍ未満
○：ブレード刃先に付着する削れ粉付着幅が０．５ｍｍ以上２．０ｍｍ未満
△：ブレード刃先に付着する削れ粉付着幅が１．０ｍｍ以上２．０ｍｍ未満
×：ブレード刃先に付着する削れ粉付着幅が２．０ｍｍ以上。
【００６６】
（８）高速走行スクラッチ性、削れ性
図１に示した装置を用いて下記のようにして測定する。
【００６７】
図１中、１は巻出しリール、２はテンションコントローラー、３、５、６、８、９および１１はフリーローラー、４はテンション検出機（入口）、７は固定棒、１０はテンション検出機（出口）、１２はガイドローラー、１３は巻取りリールをそれぞれ示す。
【００６８】
温度２０℃、湿度６０％の環境で、巾１／２インチに裁断したフイルムを７の固定棒に角度θ＝６０°で接触させて、毎分３００ｍの速さで、入口張力が５０ｇとなるようにして２００ｍ走行させる。走行後に固定棒上７に付着した削れ粉および走行後フイルムのスクラッチを評価する。
【００６９】
このとき固定棒として、
ＳＵＳ３０４製で表面を十分に仕上げた６φのテープガイド（表面粗さＲａ＝０．０１５μｍ）を使った場合をＡ法、
ＳＵＳ焼結板を円柱形に曲げた表面仕上げが不充分な６φのテープガイド（表面粗さＲａ＝０．１５μｍ）を使った場合をＢ法、
カーボンブラック含有ポリアセタールの６φのテープガイドを使った場合をＣ法
とする。
【００７０】
＜削れ粉判定＞
◎：削れ粉が全く見られない
○：うっすらと削れ粉が見られる
△：削れ粉の存在が一見して判る
×：削れ粉がひどく付着している
＜スクラッチ判定＞
◎：スクラッチが全く見られない
○：１〜５本のスクラッチが見られる
△：６〜１５本のスクラッチが見られる
×：１６本以上のスクラッチが見られる
【００７１】
（９）低速繰り返し走行摩擦係数（μｋ）、スクラッチ性
図１に示した装置を用いて下記のようにして測定する。
温度２０℃、湿度６０％の環境で、磁気テープの非磁性面を７の固定棒に角度θ＝（１５２／１８０）πラジアン（１５２°）で接触させて毎分２００ｃｍの速さで移動（摩擦）させる。入口テンションＴ₁ が５０ｇとなるようにテンションコントローラー２を調整した時の出口テンション（Ｔ₂ ：ｇ）をフイルムが５０往復走行したのちに出口テンション検出機で検出し、次式で走行摩擦係数μｋを算出する。
【００７２】
【数１９】

【００７３】
走行摩擦係数（μｋ）が０．２５以上であると、ＶＴＲ中で繰り返し走行させた場合、走行が不安定となるため、この値以上のものを走行耐久性不良と判定する。
このとき固定棒として、
ＳＵＳ３０４製で表面を十分に仕上げた６φのテープガイド（表面粗さＲａ＝０．０１５μｍ）を使った場合をＡ法、
ＳＵＳ焼結板を円柱形に曲げた表面仕上げが不充分な６φのテープガイド（表面粗さＲａ＝０．１５μｍ）を使った場合をＢ法、
カーボンブラック含有ポリアセタールの６φのテープガイドを使った場合をＣ法
とする。
【００７４】
また、スクラッチ性は走行後テープの非磁性面スクラッチについて、下記基準により判定する。
＜スクラッチ判定＞
◎：スクラッチが全く見られない
○：１〜５本のスクラッチが見られる
△：６〜１５本のスクラッチが見られる
×：１６本以上のスクラッチが見られる
【００７５】
なお、磁気テープの製造法は次のとおり行なう。
γ―Ｆｅ₂ Ｏ₃ １００重量部（以下、単に「部」と記す）と下記の組成物をボールミルで１２時間混練分散する。

を添加してなお１０〜３０分混練する。更に、トリイソシアネート化合物の２５％酢酸エチル溶液７部を加え、１時間高速剪断分散して磁性塗布液を調整する。
【００７６】
得られる塗布液をポリエステルフイルムＡ１層の表面に乾燥膜厚が３．５μｍとなるように塗布する。次いで直流磁場中で配向処理した後、１００℃で乾燥する。乾燥後、カレンダリング処理を施して１／２インチ幅にスリットして、磁気テープを得る。
【００７７】
（１０）巻き取り性指数
図１に示した装置において、固定棒７を経由しないように幅１／２インチのフイルムを通し、温度２０℃、湿度６０％の環境において、２００ｍ／分の速度で２００ｍ走行させ、巻き取りリール１３で巻き取られる直前の位置でＣＣＤカメラにより端面位置を検出する。
【００７８】
この端面位置の変動量を時間軸に対する波形として表し、その波形について下記式により巻き取り性指数として算出する。
【００７９】
【数２０】

【００８０】
ここでｌ：測定時間（秒）
ｘ：端面変動量（μｍ）
である。
【００８１】
（１１）巻き取り性
図１に示した装置において、固定棒７を経由しないように前述の方法で製造した磁気テープを通し、４００ｍ／分の速度で５００ｍ走行させ、巻き取りリール側での巻き取りの可否及び巻き取られた磁気テープのロール形状にて評価する。
＜判定＞
○：巻き取られたロールでの端面ずれが１ｍｍ以内
△：巻き取られたロールでの端面ずれが１ｍｍを超える
×：巻き取り不可
【００８２】
（１２）電磁変換特性
ＶＨＳ方式ＶＴＲ（日本ビクター（株）製ＢＲ６４００）を改造し、４ＭＨｚの正弦波をアンプを通して記録再生ヘッドに入力し、磁気テープに記録した後再生し、その再生信号をスペクトラムアナライザーに入力する。キャリア信号４ＭＨｚから０．１ＭＨｚ離れたところに生ずるノイズを測定し、キャリアとノイズの比（Ｃ／Ｎ）をｄＢ単位で表わす。この方法を用いて前述の磁気テープを測定し、比較例１で得られたものを基準（±０ｄＢ）として、この磁気テープとの差をもって電磁変換特性とする。
【００８３】
【実施例】
以下、実施例をあげて本発明をさらに説明する。
【００８４】
［実施例１〜８、比較例１〜８］
ジメチルテレフタレートとエチレングリコールとを、エステル交換触媒として酢酸マンガンを、重合触媒として三酸化アンチモンを、安定剤として亜燐酸を、更に滑剤として表１、２のポリエステルＡ１、Ａ２層に示す添加粒子を添加して、常法により重合し、固有粘度（オルソクロロフェノール、３５℃）０．５６の、ポリエステルＡ１、Ａ２層用に用いるポリエチレンテレフタレートを得た。
【００８５】
また、ポリエステルＢ層用としては、粒子を添加させずに上記と同様の方法で、ポリエチレンテレフタレートを得た。
【００８６】
これらポリエチレンテレフタレートのペレットを１７０℃で３時間乾燥後２台の押出機ホッパーに供給し、溶融温度２８０〜３００℃で溶融し、マルチマニホールド型共押出ダイを用いてＢ層の両面にＡ１、Ａ２層を積層させ、表面仕上げ０．３ｓ程度、表面温度２０℃の回転冷却ドラム上に押出し、厚み２００μｍの未延伸積層フイルムを得た。ここで、ドラム面側をＡ₁ 層、反ドラム面側をＡ₂ 層とした。
【００８７】
このようにして得られた未延伸積層フイルムを７５℃に予熱し、更に低速、高速のロール間で１５ｍｍ上方より８００℃の表面温度のＩＲヒーター３本にて加熱して３．２倍に延伸し、急冷し、続いてステンターに供給し、１２０℃にて横方向に４．３倍に延伸した。得られた二軸配向フイルムを２０５℃の温度で５秒間熱固定し、厚み１４μｍの熱固定二軸配向積層ポリエステルフイルムを得た。
各層の厚みについては、２台の押出機の吐出量を変えること及び流路の幅を変えることにより調整した。また、各層の厚みについては、蛍光Ｘ線法、及びフイルムを薄片に切り出し、透過型電子顕微鏡にて境界面を捜す方法を併用して求めた。
【００８８】
［比較例９］
表２中の粒子を含有したポリエチレンテレフタレートを使用し、通常の単層のダイで押出す以外は実施例と同様の方法で単層の二軸配向ポリエステルフイルムを得た。
【００８９】
このようにして得られたフイルムの特性を表３、４に示す。表３、４から明らかなように本発明によるものは、優れた電磁変換特性を示しつつ巻き取り性及び削れ性に優れ、更に各種テープガイドに対するスクラッチ性、削れ性、走行耐久性にも優れた極めて総合的に優れた特性を示している。
【００９０】
【表１】

【００９１】
【表２】

【００９２】
【表３】

【００９３】
【表４】

【００９４】
【発明の効果】
本発明の二軸配向積層ポリエステルフイルムは高速デュプリケータ用磁気テープのベースフイルムとして要求される巻き取り性、ベース面の平坦性、耐削れ性及び電磁変換特性に優れており、また粗悪なカセットハーフ、ガイドピン等に対する耐削れ性、走行耐久性にも優れ、更に安価な製造コストで製造し得る、磁気記録媒体用として極めて優れたトータルパフォーマンスを有している。
【図面の簡単な説明】
【図１】走行摩擦係数測定装置の概略図である。
【符号の説明】
１ 巻出しリール
２ テンションコントローラー
３，５，６，８，９，１１ フリーローラー
４ テンション検出器（入口）
７ 固定棒
１０ テンション検出器（出口）
１２ ガイドローラー
１３ 巻取りリール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biaxially oriented laminated polyester film for magnetic recording media, and more particularly, for high-speed duplicators that are excellent in winding properties, abrasion resistance, running durability, electromagnetic conversion characteristics, and can be manufactured at low manufacturing costs. The present invention relates to a biaxially oriented laminated polyester film for magnetic recording media useful as a base film for magnetic recording media.
[0002]
[Prior art]
Biaxially oriented polyester films represented by polyethylene terephthalate films are widely used as base films for magnetic recording media such as magnetic tapes because of their excellent physical and chemical properties.
[0003]
Among the applications of magnetic tape, in recent years, there has been a large increase in the production of tapes prerecorded with software such as movies. Conventionally, a method of duplicating from a master VTR to thousands of VTRs at a high speed has been adopted. In this method, a magnetic master tape on which software is recorded is superposed on an unrecorded magnetic tape, and a magnetic field and temperature are applied to transfer the recording. In this case, the duplicating speed is very high, and the required characteristics of the magnetic tape are changing accordingly. Also, the required characteristics of the base film for the high-speed duplicator are emerging. For example, the winding property when wound at high speed, the close contact with the master tape, the flattening of the surface to improve the electromagnetic conversion characteristics, and the improvement of the scraping property with the guide roll that contacts when duplicating. Etc.
[0004]
Conventionally, in the base film of a magnetic recording medium, inactive particles having a large particle size are added to improve the squeezing property in order to improve the winding property. However, if a large amount of such inert particles having a large particle size is contained, the magnetic layer surface may be pushed up by protrusions, or the protrusions due to the large particle size inert particles may be transferred to the magnetic layer surface when rolled up. As a result, the surface properties of the magnetic layer of the magnetic tape are remarkably deteriorated. In addition, there is a problem in that large-sized inert particles are scraped by contact with a guide roll, generate white powder, and cause dropout.
[0005]
In addition, recently, the use of cassette halves, guide pins, or plastic guide pins with rough surfaces has been used to reduce costs, and the environment for wear resistance and running durability of magnetic tape has become severe. It is strongly desired more than before.
[0006]
[Problems to be solved by the invention]
The present inventor has proposed new characteristics required as a base film for the magnetic tape for the high-speed duplicator described above, namely, improvement in winding property at high speed, flatness of the base surface, wear resistance, etc. As a result of intensive studies to solve the problem of how to achieve improvement in abrasion resistance and durability that can also be applied to guide pins, etc., a laminated polyester film with a three-layer structure was used as the base film. The biaxially oriented laminated polyester film with excellent total performance can be obtained by solving the above-mentioned problems by making the thickness of the outermost layer and the surface properties of the front and back surfaces within a specific range and can be produced at a low production cost. And reached the present invention.
[0007]
[Means for Solving the Problems]
That is, the present invention is a biaxially oriented laminated polyester film in which polyester A1 layers and A2 layers containing inert particles are laminated on both sides of the polyester B layer, and is contained in the polyester A1 layer and A2 layer. The type and content of the inert particles are the same, and the thickness T of the polyester A1 layer and the A2 layer _A1 (Μm), T _A2 (Μm) satisfies the following formulas (1) and (2), and the ratio between the three-dimensional ten-point average roughness SRz (nm) and the three-dimensional center plane average roughness SRa (nm) of these surfaces (SRz / SRa) satisfies the following formulas (3) to (5): a biaxially oriented laminated polyester film for magnetic recording media.
[0008]
[Formula 6]
1.0 (μm) ≦ T _A1 + T _A2 ≦ 4.0 (μm) (1)
[0009]
[Expression 7]
0.5 (μm) ≦ T _A2 -T _A1 ≦ 1.5 (μm) (2)
[0010]
[Equation 8]
30 ≦ (SRz / SRa) _A1 ≦ 60 (3)
[0011]
[Equation 9]
20 ≦ (SRz / SRa) _A2 ≦ 45 (4)
[0012]
[Expression 10]
(SRz / SRa) _A1 > (SRz / SRa) _A2 ... (5)
[0013]
Where T _A1 : Polyester A1 layer thickness (μm)
T _A2 : Polyester A2 layer thickness (μm)
SRz: Three-dimensional ten-point average roughness of the polyester A layer surface (nm)
SRa: Three-dimensional center plane average roughness of the polyester A layer surface (nm)
(SRz / SRa) _A1 : SRz / SRa on the surface of the polyester A1 layer
(SRz / SRa) _A2 : SRz / SRa on the surface of the polyester A2 layer
It is.
[0014]
The polyester in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. This polyester is substantially linear and has film-forming properties, particularly film-forming properties by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. it can. Examples of the alicyclic glycol include aliphatic groups such as polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, and cyclohexanedimethanol. A diol etc. can be mentioned.
[0015]
In the present invention, the polyester is preferably composed mainly of alkylene terephthalate and / or alkylene naphthalate.
[0016]
Among these polyesters, particularly polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% or more of the total dicarboxylic acid component is terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, A copolymer in which 80 mol% or more is ethylene glycol is preferred. In this case, 20 mol% or less of the total acid component can be the aromatic dicarboxylic acid other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Acid: An alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid can be used. Further, 20 mol% or less of the total glycol component may be the glycol other than ethylene glycol, and an aromatic diol such as hydroquinone, resorcin, 2,2-bis (4-hydroxyphenyl) propane, An aliphatic diol having an aromatic ring such as 4-dihydroxydimethylenebenzene; a polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can also be used.
[0017]
The polyester in the present invention includes, for example, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid and an aliphatic oxyacid such as ω-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. Those which are copolymerized or bonded in an amount of 20 mol% or less based on the total amount of the above are included.
[0018]
Furthermore, the polyester in the present invention has an amount in a substantially linear range, for example, an amount of 2 mol% or less based on the total acid component, and a trifunctional or higher polycarboxylic acid or polyhydroxy compound such as trimellitic acid, A copolymer of pentaerythritol and the like is also included.
[0019]
The polyester is known per se and can be produced by a method known per se.
[0020]
The biaxially oriented laminated polyester film of the present invention has a three-layer structure in which a polyester A1 layer and an A2 layer are laminated on both sides of a polyester B layer, and the above polyester can be used as the polyester of each layer. The polymers of the A1, A2 and B layers may be the same or different, but are preferably the same.
[0021]
The polyester A1 layer and the A2 layer are made of polyester containing inert particles, but the type and content of the inert particles need to be the same. If the types and contents of the inert particles contained in the A1 layer and the A2 layer are different, separate extruders are required, which increases the production cost, and thus the object of the present invention cannot be achieved.
[0022]
The polyester A1 layer and A2 layer need to have different thicknesses. By changing the thickness of each, even if it is the same inert particle and content, different surface properties can be formed, and the specific surface properties of the present invention can be controlled.
[0023]
Polyester A1 layer thickness T _A1 (Μm) and polyester A2 layer thickness T _A2 (Μm) needs to satisfy the following formulas (1) and (2).
[0024]
[Expression 11]
1.0 (μm) ≦ T _A1 + T _A2 ≦ 4.0 (μm) (1)
[0025]
[Expression 12]
0.5 (μm) ≦ T _A2 -T _A1 ≦ 1.5 (μm) (2)
[0026]
In the above formula (1), (T _A1 + T _A2 If the value of) is less than 1.0 (μm), the film surface becomes too flat, and the winding property deteriorates. On the other hand, (T _A1 + T _A2 When the value of) exceeds 4.0 (μm), the ratio of the surface layer thickness to the total thickness increases, so even if the recovered polymer is used for the polyester B layer forming the intermediate layer (core layer), the cost reduction is achieved. The effect is reduced, and even if the polyester A1 layer and the A2 layer have different thicknesses, the difference in surface properties is reduced, making it difficult to control the specific surface properties of the present invention. (T _A1 + T _A2 ) Is preferably in the range of 1.2 to 3.5 (μm), more preferably in the range of 1.5 to 3.0 (μm).
[0027]
In the above formula (2), (T _A2 -T _A1 When the value of) is 0.5 (μm), the difference in surface properties between the surface of the polyester A1 layer and the surface of the polyester A2 layer is small, so that it is difficult to control the specific surface properties of the present invention. On the other hand, (T _A2 -T _A1 When the value of) exceeds 1.5 (μm), the difference in surface properties between the surface of the polyether A1 layer and the surface of the polyester A2 layer becomes too large, and the winding property deteriorates. (T _A2 -T _A1 ) Is preferably in the range of 0.5 to 1.0 (μm).
[0028]
Furthermore, the biaxially oriented laminated polyester film of the present invention has a ratio (SRz / SRa) between the three-dimensional ten-point average roughness SRz and the three-dimensional center plane average roughness SRa of the surface of each of the polyester A1 layer and the A2 layer represented by the following formula: It is necessary to satisfy (3), (4), and (5).
[0029]
[Formula 13]
30 ≦ (SRz / SRa) _A1 ≦ 60 (3)
[0030]
[Expression 14]
20 ≦ (SRz / SRa) _A2 ≦ 45 (4)
[0031]
[Expression 15]
(SRz / SRa) _A1 > (SRz / SRa) _A2 ... (5)
[0032]
Here, SRz: SRa, (SRz / SRa) _A1 And (SRz / SRa) _A2 Are the same as defined above.
[0033]
In the above formula (3), (SRz / SRa) _A1 When the value of is less than 30, the effect of improving the winding property is insufficient. On the other hand, (SRz / SRa) _A1 If the value exceeds 60, the surface becomes too flat and the slipperiness is poor, and the winding property deteriorates. (SRz / SRa) _A1 The value of is preferably in the range of 35 to 55, and more preferably in the range of 40 to 50.
[0034]
In the above formula (4), (SRz / SRa) _A2 If the value of is less than 20, the effect of improving the winding property is insufficient. On the other hand, (SRz / SRa) _A2 If the value exceeds 45, the surface becomes too flat, the slipperiness is poor, the winding property is deteriorated, and the abrasion resistance and running durability are also deteriorated. (SRz / SRa) _A2 The value of is preferably in the range of 25 to 40, more preferably in the range of 30 to 40.
[0035]
Furthermore, as in the above equation (5), (SRz / SRa) _A1 Is (SRz / SRa) _A2 Although it is necessary to be a larger value, if this cannot be satisfied, improvement in electromagnetic conversion characteristics, running durability, and improvement in winding property cannot be satisfied at the same time.
[0036]
In the biaxially oriented laminated polyester film of the present invention, the center line average roughness Ra of the surface of the polyester A1 layer _A1 Is the centerline average roughness Ra of the surface of the polyester A2 layer is 5 to 15 nm _A2 Is in the range of 10-25 nm and Ra _A1 And Ra _A2 The difference ΔRa is preferably in the range of 2 to 10 nm. Ra _A1 , Ra _A2 And ΔRa satisfying the above range is preferable because it is easy to satisfy further improvements in electromagnetic conversion characteristics, running durability, and winding properties at the same time.
[0037]
The polyester A1 layer and the A2 layer of the biaxially oriented laminated polyester film of the present invention have 0.001 to 0.03% by weight of average cross-linked polymer particles a having an average particle diameter da of 0.8 to 1.6 μm, respectively. 0.1 to 0.8% by weight of inert particles b having a particle size db of 0.4 to 0.8 μm, an average particle size dc of 0.01 to 0.3 μm, and a Mohs hardness of 7 or more It is preferable to contain 0.05 to 1.0% by weight of inert inorganic particles C, whereby the surface property of the film surface can be easily within the above range, and the electromagnetic conversion characteristics are improved and the abrasion resistance is reduced. The effect of satisfying the improvement of the performance, running durability, and winding property at the same time is particularly great.
[0038]
The crosslinked polymer a is preferably at least one selected from crosslinked silicone resin particles and crosslinked polystyrene particles. This is because the affinity for polyester is high, and since the particles are soft, the impact applied to the projections is easily absorbed, and the projections are difficult to fall off at high speed.
[0039]
The crosslinked polymer particles a have an apparent Young's modulus of 10 to 100 kgf / mm. ² Is preferable, more preferably 10 to 50 kgf / mm ² It is.
[0040]
The inert particles b are not particularly limited. For example, (1) silicon dioxide (including hydrate, silica sand, quartz, etc.); (2) alumina in various crystal forms; (3) SiO ₂ Silicates containing at least 30% by weight (eg amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), warm asbestos, zircon, fly ash, etc.); (4) Mg Oxides of Zn, Zn, Zr, and Ti; (5) sulfates of Ca and Ba; (6) phosphates of Li, Ba, and Ca (including monohydrogen and dihydrogen salts): (7) Benzoates of Li, Na, and K; (8) terephthalates of Ca, Ba, Zn, and Mn; (9) Mg, Ca, Ba, Zn, Cd, Pd, Sr, Mn, Fe, Co, (10) Ba and Pb chromate; (11) Carbonic acid (eg, carbon black, graphite, etc.): (12) Glass (eg, glass powder, glass beads, etc.); (13) Ca And carbonate of Mg; (14) fluorite; (1 ) ZnS and the like preferably. Of these, calcium carbonate is preferred.
[0041]
The inert inorganic particles C having a Mohs hardness of 7 or more are preferably agglomerated particles made of aluminum oxide (alumina) and a spinel oxide, and have an average agglomeration rate in the range of 2-20. When the average degree of aggregation is within this range, the effect of improving scratch resistance is great.
[0042]
Furthermore, when the inert inorganic particles C are aggregated particles made of aluminum oxide (alumina), it is preferable that the crystal form is a θ-type crystal because the effect of improving scratch resistance is greater. In addition, when the inert inorganic particles C are aggregated particles made of spinel oxide, MgAl ₂ O _Four It is preferable because the effect of improving scratch resistance is greater.
[0043]
In the biaxially oriented laminated polyester film of the present invention, the polyester B layer may not contain inert particles, but inactive particles having an average particle size of 0.4 μm or more in the B layer, for example, the above-mentioned cross-linking Polymer particles a, inert particles b, etc. are contained in this content (C _B ) In a proportion satisfying the following formula is preferable because waste film produced in the production process of the polyester film can be recovered and used in the B layer.
[0044]
[Expression 16]

[0045]
[However, C _A Is the content (% by weight) of inert particles having an average particle size of 0.4 μm or more in the polyester A1 layer and the A2 layer,
C _B Is the content (% by weight) of inert particles having an average particle size of 0.4 μm or more in the polyester B layer,
d _A Is the total thickness (μm) of the polyester film A1 layer and A2 layer,
d _B Is the thickness of the polyester film B layer (μm),
R is a numerical value of 0.3 to 0.07
It is. ]
[0046]
In the above formula, if R (value) exceeds 0.7 or less than 0.3, the average particle size of the polyester B layer when the recovered film is used is the content of inert particles of 0.4 μm or more. The fluctuation becomes large, and as a result, the roughness of the surface of the polyester A1 layer and the A2 layer also becomes large. A preferable R (value) is 0.4 to 0.6. Even if the small particle size inert particles having an average particle size of less than 0.4 μm are contained in the polyester B layer, the influence on the surfaces of the polyester A1 layer and the A2 layer is small.
[0047]
The biaxially oriented laminated polyester film of the present invention preferably has a winding property index of 100 or less at a winding speed of 200 m / min. When the rollability index is 100 or less, the effect of improving the windability is remarkable when used as a base film for a high-speed duplicator. On the other hand, if the rollability index is larger than 100, it is preferable that the film roll end surface becomes uneven when wound at a high speed, and the roll shape is deteriorated when it is severed. Absent. The winding property index at a winding speed of 200 m / min is more preferably 85 or less, and particularly preferably 70 or less.
[0048]
Furthermore, the biaxially oriented laminated polyester film of the present invention preferably has a total film thickness of 5 to 25 μm, and more preferably 10 to 20 μm.
[0049]
The Young's modulus in the machine direction of the film is 400 kg / mm ² Above, further 450kg / mm ² The above is preferable. The lateral Young's modulus is 500 kg / mm. ² More than that, 600kg / mm ² The above is preferable. It is preferable that the Young's modulus in the vertical and horizontal directions is in the above-mentioned range since it can sufficiently cope with the thinning of the tape for a long time.
[0050]
The biaxially oriented laminated polyester film of the present invention is used by providing a magnetic layer on the surface of the polyester A1 layer in the production of a magnetic recording medium. By doing so, it is possible to manufacture a magnetic recording medium that simultaneously satisfies excellent electromagnetic conversion characteristics, abrasion resistance, running durability, and winding property.
[0051]
The biaxially oriented laminated polyester film of the present invention can basically be obtained by a method conventionally known or accumulated in the art. For example, it can be obtained by first producing a laminated unstretched film and then biaxially orienting the film. This unstretched laminated film can be produced by a conventional method for producing a laminated film. For example, a method of laminating a film layer (polyester A1, A2 layer) that forms the surface and a film layer (polyester B layer) that forms the core layer in a molten state or a cooled and solidified state can be used. More specifically, for example, it can be produced by a method such as coextrusion or extrusion lamination.
[0052]
The unstretched film laminated by the above-described method can be made into a biaxially oriented film according to the production method of the biaxially oriented film accumulated conventionally. For example, the laminated unstretched film is uniaxially (longitudinal or transverse) 2.5 to 8.0 times at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester). Stretching at a magnification, and then in the direction perpendicular to the stretching direction (when the first stage stretching is the longitudinal direction, the second stage stretching is the transverse direction) at a temperature of Tg (° C.) to (Tg + 70) ° C. at 2.5 It can be manufactured by stretching at a magnification of ˜8.0 times. In this case, the area stretch ratio is preferably 9 to 32 times, more preferably 12 to 28 times. The stretching means may be simultaneous biaxial stretching or sequential biaxial stretching. Furthermore, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° C. to Tm (° C.). For example, a laminated polyethylene terephthalate film is preferably heat-set at 190 to 230 ° C. The heat setting time is, for example, 1 to 60 seconds.
[0053]
The biaxially oriented laminated polyester film of the present invention is a laminated polyester film having a three-layer structure in which the polyester A1 layer and the A2 layer are laminated on both sides of the polyester B layer, and the thickness and surface property of both outermost layers are in a specific range. It has excellent performance in terms of windability, base surface flatness, abrasion resistance, and electromagnetic conversion characteristics required as a base film for magnetic recording media for duplicators. It is extremely excellent in total performance that can be manufactured, and is particularly useful as a base film for a magnetic recording medium.
[0054]
Various physical property values and characteristics in the present invention are measured and defined as follows.
[0055]
(1) Average particle diameter (DP)
Measured with a CP-50 Centrifugal Particle Size Analyzer manufactured by Shimadzu Corporation. The particle size corresponding to 50 mass percent is read from the integrated curve of the particles of each particle size calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is used as the average particle size (Book “Particle Size Measurement”). Technology ", published by Nikkan Kogyo Shimbun, 1975, pages 242-247).
[0056]
(2) Apparent Young's modulus of particles
A diamond indenter is lowered at a constant load speed (29 mgf / second) using an ultra-small compression tester MCTM-201 manufactured by Shimadzu Corporation, and an external force is applied to one particle. Then, the apparent Young's modulus Y is obtained from the load P (kgf) when the particles are broken, the displacement Z (mm) of the indenter when the particles are broken, and the particle diameter d (mm) of the particles according to the following formula: The same operation is performed 10 times, and the average value of 10 times is used as the apparent Young's modulus of the particles.
[0057]
[Expression 17]
Y = 2.8P / πdZ
[0058]
(3) Average aggregation degree of particles
When the film containing the particles is cut into thin sections having a thickness of 100 nm in the cross-sectional direction, and the particles are observed at a magnification of about 100,000 times using a transmission electron microscope (for example, JEM-1200EX manufactured by JEOL), no more particles are obtained. The smallest particles that cannot be divided (primary particles) can be observed. From this observation photograph, for 100 particles, in particular for aggregated particles (secondary particles), the number of primary particles is counted, and the value obtained by dividing the sum of primary particles by the number of particles measured is the average aggregation degree. .
[0059]
(4) Three-dimensional center plane average roughness (SRa), three-dimensional ten-point average roughness (SRz)
Using a three-dimensional roughness measuring machine (SE-3CK manufactured by Kosaka Laboratory), needle diameter 2μmR, needle pressure 30mg, measurement length 1mm, sampling pitch 2μm, cut-off 0.25mm, longitudinal magnification 20,000 times, horizontal A three-dimensional surface profile of the film surface is imaged under conditions of a direction magnification ratio of 200 times and a scanning number of 100. From the profile obtained, the area S on the center plane _M This part is extracted, the orthogonal coordinate axis, the X axis, and the Y axis are placed on the central plane of the extracted part, the axis orthogonal to the central plane is the Z axis, and the value given by the following equation is SRa.
[0060]
[Formula 18]

[0061]
Regarding SRz, the average of the heights of the first to fifth peaks and the valleys of the first to fifth peaks from the deepest of the planes parallel to the average line of the portion extracted from the profile by the reference area. SRz is defined as an interval from the average depth.
[0062]
(5) Film surface roughness (Ra)
The center line average roughness (Ra) is a value defined by JIS B0601, and in the present invention, it is measured using a stylus type surface roughness meter (SURFCORDER SE-30C) of Kosaka Laboratory. The measurement conditions are as follows.
(A) Stylus tip radius: 2 μm
(B) Measurement pressure: 30 mg
(C) Cutoff: 0.25mm
(D) Measurement length: 2.5 mm
(E) How to summarize the data: Repeat the measurement six times for the same sample, remove one of the largest values, and display the average value of the remaining five data.
[0063]
(6) Calendar sharpness
Evaluate the wear resistance of the running surface of the base film using a three-stage mini super calendar. The calender is a three-stage calender of nylon roll and steel roll, which is run at a processing temperature of 80 ° C., a linear pressure applied to the film of 200 kg / cm, and a film speed of 100 m / min. The wear resistance of the base film is evaluated by the dirt attached to the top roller of the calendar when the running film runs for a total length of 4000 m.
[0064]
<5-level judgment>
First grade: Nylon roll is completely free of dirt
Second grade: Nylon roll is almost free of dirt
3rd grade: Nylon roll is slightly dirty, but can be easily removed by brushing
Grade 4: Nylon roll stains are difficult to remove by wiping, and can be wiped off with a solvent such as acetone.
Grade 5: Nylon rolls are very dirty and difficult to remove even with solvents.
[0065]
(7) Blade sharpness
Put the blade (blade for an industrial razor testing machine manufactured by US GKI) vertically on a film cut to 1/2 inch width in an environment of temperature 20 ° C and humidity 60%, and push it further 2 mm to make contact every minute 100m speed, entrance tension T ₁ Travel (friction) at 50 g. The amount of shavings adhering to the blade after the film has traveled 100 m is evaluated.
<Judgment>
A: Debris adhesion width adhering to the blade edge is less than 0.5 mm
◯: The shaving powder adhesion width adhering to the blade edge is 0.5 mm or more and less than 2.0 mm
Δ: The shaving powder adhesion width adhering to the blade edge is 1.0 mm or more and less than 2.0 mm
X: The shaving powder adhesion width adhering to the blade edge is 2.0 mm or more.
[0066]
(8) High-speed running scratching and scraping
Measurement is performed as follows using the apparatus shown in FIG.
[0067]
In FIG. 1, 1 is an unwinding reel, 2 is a tension controller, 3, 5, 6, 8, 9 and 11 are free rollers, 4 is a tension detector (inlet), 7 is a fixing rod, 10 is a tension detector ( (Exit), 12 is a guide roller, and 13 is a take-up reel.
[0068]
In an environment with a temperature of 20 ° C. and a humidity of 60%, a film cut to ½ inch in width is brought into contact with a fixing rod of 7 at an angle θ = 60 °, and the inlet tension is 50 g at a speed of 300 m / min. In this way, the vehicle travels 200 m. Evaluate the scraps of the shavings adhering to the fixed rod 7 after running and the film after running.
[0069]
At this time,
A method in which a 6φ tape guide (surface roughness Ra = 0.015 μm) made of SUS304 and having a sufficiently finished surface is used.
Method B when using a 6φ tape guide (surface roughness Ra = 0.15 μm) with an insufficient surface finish obtained by bending a SUS sintered plate into a cylindrical shape,
C method when using 6φ tape guide of polyacetal containing carbon black
And
[0070]
<Shaving powder judgment>
A: No shaving powder is seen
○: Slightly scraped powder can be seen
Δ: The presence of shavings can be seen at a glance
X: The shaving powder is adhering badly
<Scratch determination>
A: No scratches are seen
○: 1 to 5 scratches are seen
Δ: 6 to 15 scratches are seen
X: 16 or more scratches are seen
[0071]
(9) Low speed repeated friction coefficient (μk), scratch property
Measurement is performed as follows using the apparatus shown in FIG.
In an environment where the temperature is 20 ° C. and the humidity is 60%, the nonmagnetic surface of the magnetic tape is brought into contact with the fixing rod 7 at an angle θ = (152/180) π radians (152 °) and moved at a speed of 200 cm per minute ( Friction). Inlet tension T ₁ The outlet tension (T) when the tension controller 2 is adjusted so as to be 50 g ₂ G) is detected by the exit tension detector after the film has traveled 50 times, and the running friction coefficient μk is calculated by the following equation.
[0072]
[Equation 19]

[0073]
If the running friction coefficient (μk) is 0.25 or more, when running repeatedly in the VTR, running becomes unstable.
At this time,
A method in which a 6φ tape guide (surface roughness Ra = 0.015 μm) made of SUS304 and having a sufficiently finished surface is used.
Method B when using a 6φ tape guide (surface roughness Ra = 0.15 μm) with an insufficient surface finish obtained by bending a SUS sintered plate into a cylindrical shape,
C method when using 6φ tape guide of polyacetal containing carbon black
And
[0074]
Further, the scratch property is determined by the following criteria for the non-magnetic surface scratch of the tape after running.
<Scratch determination>
A: No scratches are seen
○: 1 to 5 scratches are seen
Δ: 6 to 15 scratches are seen
X: 16 or more scratches are seen
[0075]
The magnetic tape is manufactured as follows.
γ-Fe ₂ O _Three 100 parts by weight (hereinafter simply referred to as “parts”) and the following composition are kneaded and dispersed in a ball mill for 12 hours.

And kneaded for 10 to 30 minutes. Further, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound is added, and the magnetic coating solution is prepared by high-speed shear dispersion for 1 hour.
[0076]
The resulting coating solution is applied to the surface of the polyester film A1 layer so that the dry film thickness is 3.5 μm. Next, the film is subjected to orientation treatment in a DC magnetic field and then dried at 100 ° C. After drying, a calendering process is performed and slit into a 1/2 inch width to obtain a magnetic tape.
[0077]
(10) Windability index
In the apparatus shown in FIG. 1, a film having a width of 1/2 inch is passed so as not to pass through the fixing rod 7, and is run for 200 m at a speed of 200 m / min in an environment of temperature 20 ° C. and humidity 60%. The position of the end face is detected by the CCD camera at the position immediately before being wound in step 13.
[0078]
The fluctuation amount of the end face position is expressed as a waveform with respect to the time axis, and the waveform is calculated as a winding property index by the following formula.
[0079]
[Expression 20]

[0080]
Where l: measurement time (seconds)
x: End face variation (μm)
It is.
[0081]
(11) Windability
In the apparatus shown in FIG. 1, the magnetic tape manufactured by the above-described method is passed so as not to go through the fixing rod 7, and it is run for 500 m at a speed of 400 m / min. Evaluation is made on the roll shape of the magnetic tape.
<Judgment>
○: End face deviation of the wound roll is within 1 mm
Δ: End face deviation of the wound roll exceeds 1 mm
×: Unwinding
[0082]
(12) Electromagnetic conversion characteristics
A VHS VTR (BR6400 manufactured by Victor Co., Ltd.) is modified, a 4 MHz sine wave is input to a recording / reproducing head through an amplifier, recorded on a magnetic tape, reproduced, and the reproduced signal is inputted to a spectrum analyzer. The noise generated at a frequency 0.1 MHz away from the carrier signal 4 MHz is measured, and the carrier to noise ratio (C / N) is expressed in dB. Using this method, the magnetic tape described above is measured, and the magnetic tape obtained as a reference (± 0 dB) is used as the reference (± 0 dB) to obtain the electromagnetic conversion characteristic.
[0083]
【Example】
Hereinafter, the present invention will be further described with reference to examples.
[0084]
[Examples 1-8, Comparative Examples 1-8]
Add dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and additive particles shown in the polyester A1 and A2 layers of Tables 1 and 2 as a lubricant. Then, polymerization was carried out by a conventional method to obtain polyethylene terephthalate used for the polyester A1 and A2 layers having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.56.
[0085]
For the polyester B layer, polyethylene terephthalate was obtained by the same method as above without adding particles.
[0086]
These polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours and then supplied to two extruder hoppers, melted at a melting temperature of 280 to 300 ° C. The layers were laminated and extruded onto a rotary cooling drum having a surface finish of about 0.3 s and a surface temperature of 20 ° C. to obtain an unstretched laminated film having a thickness of 200 μm. Here, the drum side is A ₁ Layer, anti-drum surface side A ₂ Layered.
[0087]
The unstretched laminated film thus obtained is preheated to 75 ° C., and further heated by three IR heaters having a surface temperature of 800 ° C. from 15 mm above between low-speed and high-speed rolls and stretched 3.2 times. Then, it was rapidly cooled and then supplied to a stenter, and stretched 4.3 times in the transverse direction at 120 ° C. The obtained biaxially oriented film was heat-fixed at a temperature of 205 ° C. for 5 seconds to obtain a heat-fixed biaxially oriented laminated polyester film having a thickness of 14 μm.
About the thickness of each layer, it adjusted by changing the discharge amount of two extruders, and changing the width | variety of a flow path. In addition, the thickness of each layer was determined by using both a fluorescent X-ray method and a method of cutting a film into thin pieces and searching for a boundary surface with a transmission electron microscope.
[0088]
[Comparative Example 9]
A single-layer biaxially oriented polyester film was obtained in the same manner as in Example except that polyethylene terephthalate containing the particles in Table 2 was used and extruded with a normal single-layer die.
[0089]
The properties of the film thus obtained are shown in Tables 3 and 4. As apparent from Tables 3 and 4, the present invention exhibits excellent electromagnetic conversion characteristics while being excellent in winding properties and scraping properties, and also excellent in scratch properties, scraping properties and running durability against various tape guides. It shows extremely excellent characteristics.
[0090]
[Table 1]

[0091]
[Table 2]

[0092]
[Table 3]

[0093]
[Table 4]

[0094]
【The invention's effect】
The biaxially oriented laminated polyester film of the present invention has excellent winding properties, flatness of the base surface, abrasion resistance and electromagnetic conversion characteristics required as a base film of a magnetic tape for a high-speed duplicator, and a poor cassette half, It has excellent total performance as a magnetic recording medium that is excellent in wear resistance and running durability against guide pins and can be manufactured at a lower manufacturing cost.
[Brief description of the drawings]
FIG. 1 is a schematic view of a running friction coefficient measuring device.
[Explanation of symbols]
1 Unwinding reel
2 Tension controller
3, 5, 6, 8, 9, 11 Free roller
4 Tension detector (inlet)
7 Fixed rod
10 Tension detector (exit)
12 Guide roller
13 Take-up reel

Claims (7)

A biaxially oriented laminated polyester film in which polyester A1 layers and A2 layers containing inert particles are laminated on both sides of the polyester B layer, and the kind of inert particles contained in the polyester A1 layer and A2 layer And the thicknesses T _A1 (μm) and T _A2 (μm) of the polyester A1 layer and A2 layer satisfy the following formulas (1) and (2), and The ratio (SRz / SRa) between the point average roughness SRz (nm) and the three-dimensional center plane average roughness SRa (nm) satisfies the following formulas (3) to (5). Axial oriented laminated polyester film.

Here, T _A1 : Polyester A1 layer thickness (μm)
T _A2 : Polyester A2 layer thickness (μm)
SRz: Three-dimensional ten-point average roughness of the polyester A layer surface (nm)
SRa: Three-dimensional center plane average roughness of the polyester A layer surface (nm)
(SRz / SRa) _A1 : SRz / SRa of polyester A1 layer surface
(SRz / SRa) _A2 : SRz / SRa on the surface of the polyester A2 layer
It is. The polyester A1 layer and the A2 layer have 0.001 to 0.03% by weight of the crosslinked polymer particles a having an average particle diameter da of 0.8 to 1.6 μm and an average particle diameter db of 0.4 to 0.8 μm, respectively. 0.1 to 0.8% by weight of inert particles b, and 0.05 to 1 of inert inorganic particles C having an average particle diameter dc of 0.01 to 0.3 μm and a Mohs hardness of 7 or more. The biaxially oriented laminated polyester film for magnetic recording media according to claim 1, containing 0.0 wt%. 3. The biaxial magnetic recording medium according to claim ² , wherein the crosslinked polymer particles a are at least one selected from crosslinked silicone resin particles and crosslinked polystyrene particles, and the apparent Young's modulus of the particles is 10 to 100 kgf / mm ^2. Oriented laminated polyester film. The biaxially oriented laminate for a magnetic recording medium according to claim 2, wherein the inert inorganic particles C are at least one aggregated particle selected from aluminum oxide particles and spinel-type oxide particles, and the average aggregation degree thereof is 2 to 20. Polyester film. The center line average roughness Ra _{A1 of the} polyester A1 layer surface is 5 to 15 nm, the center line average roughness Ra _{A2 of} the polyester A2 layer surface is 10 to 25 nm, and the difference (ΔRa) between Ra _A1 and Ra _A2 is 2 The biaxially oriented laminated polyester film for magnetic recording media according to claim 1 or 2, wherein the thickness is 10 nm. The biaxially oriented laminated polyester film for magnetic recording media according to claim 1 or 2, wherein the total thickness of the laminated film is 5 to 25 µm. The biaxially oriented laminated polyester film for a magnetic recording medium according to claim 1, wherein the winding property index at a winding speed of 200 m / min is 100 or less.

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