JP4266528B2 - Laminated polyester film - Google Patents

Description

【００６４】
〔ここで、ｆは体積形状係数、Ｖは粒子の体積（μｍ³）、Ｄは粒子の平均粒径（μｍ）である。〕
【００６５】
なお、体積形状係数（ｆ）がπ／６である粒子の形状は、球（真球）である。すなわち、体積形状係数（ｆ）が０．４〜π／６のものは、実質的に球ないしは真球、ラグビーボールのような楕円球を含むものであり、不活性粒子Ｃとして好ましい。体積形状係数（ｆ）が０．１未満の粒子、例えば薄片状の粒子では、走行耐久性が低下してしまうので好ましくない。
【００６６】
前記不活性粒子Ｃの含有量は、皮膜層Ｃ（塗液の固形分）に対し、０．５〜３０重量％、好ましくは２〜２０重量％、さらに好ましくは３〜１０重量％である。この含有量が０．５重量％未満であると、フィルムの滑り性向上が不充分であることがあり、一方３０重量％を超えると、磁気記録媒体の電磁変換特性が不良となることがあるため好ましくない。
【００６７】
本発明における積層ポリエステルフィルムは、ポリエステル層Ａの表面（ポリエステル層Ｂと接しない側の表面）（皮膜層Ｃを設ける場合は皮膜層Ｃの表面）の表面粗さ（ＷＲａＡ）が０．１〜４ｎｍであることが好ましい。さらに好ましくは０．２〜３．５ｎｍ、特に好ましくは０．３〜３．０ｎｍ、就中０．４〜２．５ｎｍである。このＷＲａＡが０．１ｎｍ未満であると、滑り性が悪くフィルムの製造が極めて困難であり、一方ＷＲａＡが４ｎｍを超えると、電磁変換特性が悪化するので好ましくない。
【００６８】
この表面粗さ（ＷＲａＡ）は、皮膜層Ｃに含有させる不活性粒子Ｃの粒径と量、および／またはポリエステル層Ａに含有させる不活性粒子Ａの粒径と量によって調整することができる。
【００６９】
本発明における積層ポリエステルフィルムの全厚みは、通常２μｍ以上８μｍ未満、好ましくは２．5〜７．５μｍである。ポリエステル層Ａとポリエステル層Ｂの厚み構成は、好ましくは層Ｂの厚みが積層フィルムの全厚みの１／５０〜１／２、さらに好ましくは１／３０〜１／３、特に好ましくは１／２０〜１／４である。皮膜層Ｃの厚みは、通常１〜１００ｎｍ、好ましくは２〜５０ｎｍ、さらに好ましくは３〜１０ｎｍ、特に好ましくは３〜８ｎｍである。
【００７０】
本発明における積層ポリエステルフィルムは、従来から知られている、または当業界に蓄積されている方法に準じて製造することができる。そのうち、ポリエステル層Ａとポリエステル層Ｂとの積層構造は、共押出し法により製造するのが好ましく、皮膜層Ｃの積層は塗布法により行うのが好ましい。
【００７１】
例えば、二軸配向ポリエステルフィルムで説明すると、押出し口金内または口金以前（一般に、前者はマルチマニホールド方式、後者はフィードブロック方式と呼ぶ）で（部分ケン化）エステルワックス及び不活性粒子Ｂを微分散、含有させたポリエステルＢと、必要に応じて不活性粒子Ａを含有するポリエステルＡとを、それぞれ高精度ろ過したのち、溶融状態にて積層複合し、上記好適な厚み比の積層構造となし、次いで口金より融点（Ｔｍ）〜（Ｔｍ＋７０）℃の温度でフィルム状に共押出ししたのち、４０〜９０℃の冷却ロールで急冷固化し、未延伸積層フィルムを得る。その後、該未延伸積層フィルムを常法に従い、一軸方向（縦方向または横方向）に（Ｔｇ−１０）〜（Ｔｇ＋７０）℃の温度（ただし、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、好ましくは３．０〜７．５倍の倍率で延伸し、次いで上記延伸方向とは直角方向（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、好ましくは３．０〜７．５倍の倍率で延伸する。さらに、必要に応じて、縦方向および／または横方向に再度延伸してもよい。すなわち、２段、３段、４段あるいは多段の延伸を行うとよい。全延伸倍率としては、通常９倍以上、好ましくは１０〜３５倍、さらに好ましくは１２〜３０倍である。
【００７２】
さらに、前記二軸配向フィルムは（Ｔｇ＋７０）〜（Ｔｍ−１０）℃の温度、例えば、ポリエチレンテレフタレートフィルムの場合、１８０〜２５０℃で熱固定結晶化することによって、優れた寸法安定性が付与される。その際、熱固定時間は１〜６０秒が好ましい。
【００７３】
なお、積層ポリエステルフィルムの製造に際し、ポリエステルＡ、Ｂに所望により上記不活性粒子以外の添加剤、例えば安定剤、着色剤、溶融ポリマーの固有抵抗調整剤などを添加含有させることができる。
【００７４】
本発明におけるポリエステル層Ａへの皮膜層Ｃの積層は、水性塗液を塗布する方法で行うのが好ましい。
【００７５】
塗布は最終延伸処理を施す以前のポリエステル層Ａの表面に行い、塗布後にはフィルムを少なくとも一軸方向に延伸するのが好ましい。この延伸の前ないし途中で皮膜は乾燥される。その中で、塗布は、未延伸積層フィルムまたは縦（一軸）延伸積層フィルム、特に縦（一軸）延伸積層フィルムに行うのが好ましい。塗布方法としては特に限定されないが、例えばロールコート法、ダイコート法などが挙げられる。
【００７６】
前記塗液、特に水性塗液の固形分濃度は、０．２〜８重量％、さらに０．３〜６重量％、特に０．５〜４重量％であることが好ましい。そして、水性塗液には、本発明の効果を妨げない範囲で、他の成分、例えば他の界面活性剤、安定剤、分散剤、紫外線吸収剤、増粘剤などを添加することができる。
【００７７】
本発明においては、磁気記録媒体としてのヘッドタッチ、走行耐久性をはじめとする各種性能を向上させ、同時に薄膜化を達成するには、積層フィルムのヤング率を、縦方向および横方向でそれぞれ、通常４５００Ｎ／ｍｍ²以上および６０００Ｎ／ｍｍ²以上、好ましくは４８００Ｎ／ｍｍ²以上および６８００Ｎ／ｍｍ²以上、さらに好ましくは５５００Ｎ／ｍｍ²以上および８０００Ｎ／ｍｍ²以上、特に好ましくは５５００Ｎ／ｍｍ²以上および１０，０００Ｎ／ｍｍ²以上とする。
【００７８】
また、ポリエステル層Ａ、Ｂの結晶化度は、ポリエステルがポリエチレンテレフタレートの場合は３０〜５０％、ポリエチレン−２，６−ナフタレートの場合は２８〜３８％であることが望ましい。いずれも下限を下回ると、熱収縮率が大きくなるし、一方上限を上回るとフィルムの耐摩耗性が悪化し、ロールやガイドピン表面と摺動した場合に白粉が生じやすくなる。
【００７９】
本発明によれば、ポリエステル層Ａの片面にポリエステル層Ｂが積層されてなる積層ポリエステルフィルム、および該ポリエステル層Ａの表面（ポリエステル層Ｂと接していない表面）に皮膜層Ｃが積層されている積層ポリエステルフィルムのそれぞれをベースフィルムとする磁気記録媒体が同様に提供される。
【００８０】
本発明の積層ポリエステルフィルムから磁気記録媒体を製造する実施態様は、下記のとおりである。
【００８１】
本発明の積層ポリエステルフィルムは、ポリエステル層Ａ、好ましくは皮膜層Ｃの表面に、真空蒸着、スパッタリング、イオンプレーティング等の方法により、鉄、コバルト、ニッケル、クロムまたはこれらを主成分とする合金もしくは酸化物よりなる強磁性金属薄膜層（磁性層）を形成した磁気記録媒体のベースフイルムとして特に有用である。金属薄膜層の厚さは１００〜３００ｎｍであるものが好ましい。
【００８２】
また本発明の積層ポリエステルフイルムは更に強磁性金属薄膜層の表面に、目的、用途、必要に応じてダイアモンドライクカーボン（ＤＬＣ）などの保護層、含フッ素カルボン酸系潤滑層を順次設け、さらに必要により、ポリエステル層Ｂの磁性層とは反対側の表面に、公知の方法でバックコート層を設けることにより、特に短波長領域での出力、Ｓ／Ｎ、Ｃ／Ｎなどの電磁変換特性に優れ、ドロップアウト、エラーレートの少ない高密度記録用蒸着型磁気記録媒体として使用することが好ましい。この蒸着型磁気記録媒体は、アナログ信号記録用Ｈｉ８、ディジタル信号記録用ディジタルビデオカセットレコーダー（ＤＶＣ）、データ８ミリ、ＤＤＳＩＶ用磁気テープ媒体として極めて有用であり、特にデジタルビデオテープ用途に使用すると優れた結果を得ることができ、好適である。またデータストレージテープ用途にしても優れた結果を得ることができ、好適である。
【００８３】
また、本発明の積層ポリエステルフィルムは、ポリエステル層Ａ、好ましくは皮膜層Ｃの表面に、鉄または鉄を主成分とする針状微細磁性粉（メタル粉）をポリ塩化ビニル、塩化ビニル・酢酸ビニル共重合体などのバインダーに均一に分散し、磁性層厚みが１μｍ以下、好ましくは０．１〜１μｍとなるように塗布し、さらに必要により、ポリエステル層Ｂの磁性層とは反対側の表面に、公知の方法でバックコート層を設けることにより、特に短波長領域での出力、Ｓ／Ｎ、Ｃ／Ｎなどの電磁変換特性に優れ、ドロップアウト、エラーレートの少ない高密度記録用メタル塗布型磁気記録媒体とすることができる。また、必要に応じてポリエステル層Ａまたは皮膜層Ｃの表面に、上記メタル粉含有磁性層の下地層として微細な酸化チタン粒子などを含有する非磁性層を磁性層と同様の有機バインダー中に分散し、塗設することもできる。このメタル塗布型磁気記録媒体は、アナログ信号記録用８ミリビデオ、Ｈｉ８、βカムＳＰ、Ｗ−ＶＨＳ、ディジタル信号記録用ディジタルビデオカセットレコーダー（ＤＶＣ）、データ８ミリ、ＤＤＳＩＶ、ディジタルβカム、Ｄ２、Ｄ３、ＳＸなど用磁気テープ媒体として極めて有用である。
【００８４】
さらに、本発明の積層ポリエステルフィルムは、ポリエステル層Ａ、好ましくは皮膜層Ｃの表面に、酸化鉄または酸化クロムなどの針状微細磁性粉、またはバリウムフェライトなどの板状微細磁性粉をポリ塩化ビニル、塩化ビニル・酢酸ビニル共重合体などのバインダーに均一に分散し、磁性層厚みが１μｍ以下、好ましくは０．１〜１μｍとなるように塗布し、さらに必要により、ポリエステル層Ｂの磁性層とは反対側の表面に、公知の方法でバックコート層を設けることにより、特に短波長領域での出力、Ｓ／Ｎ、Ｃ／Ｎ等の電磁変換特性に優れ、ドロップアウト、エラーレートの少ない高密度記録用酸化物塗布型磁気記録媒体とすることができる。また、必要に応じて、ポリエステル層Ａまたは皮膜層Ｃの表面に、上記酸化物粉末含有磁性層の下地層として微細な酸化チタン粒子などを含有する非磁性層を磁性層と同様の有機バインダー中に分散し、塗設することもできる。この酸化物塗布型磁気記録媒体は、ディジタル信号記録用データストリーマー用ＱＩＣなどの高密度記録用酸化物塗布型磁気記録媒体として有用である。
【００８５】
本発明における磁気記録媒体は、上述のように、磁性層形成面の反対面に、固体微粒子及び結合剤からなり、必要に応じて各種添加剤を加えた溶液を塗布することにより形成されるバックコート層を設けてもよいが、この固体微粒子、結合剤、添加剤は公知のものを使用でき、特に限定されない。該バックコート層の厚さは０．３〜１．５μｍであることが好ましい。
【００８６】
上述のＷ−ＶＨＳはアナログのＨＤＴＶ信号記録用ＶＴＲであり、またＤＶＣはディジタルのＨＤＴＶ信号記録用として適用可能なものである。それゆえ、本発明の積層ポリエステルフィルムは、これらＨＤＴＶ対応ＶＴＲ用磁気記録媒体に極めて有用なベースフィルムと言うことができる。
【００８７】
【実施例】
以下、実施例を挙げて本発明をさらに具体的に説明するが、本発明はこれら実施例により限定されるものではない。なお、実施例および比較例における「部」および「％」は、特に断らない限り重量部および重量％である。また、本発明における物性値および特性は、それぞれ下記の方法で測定し、かつ定義されるものである。
【００８８】
（１）固有粘度
オルソクロロフェノール溶媒中３５℃で測定した値から求める。
【００８９】
（２）末端カルボキシル基濃度（ｅｑ／１０⁶ｇ）
A.Conixの方法に準じて測定した。（Makromol.Chem.26,226（1958））
【００９０】
（３）粒子の平均粒径（Ｉ）（平均粒径：６０ｎｍ以上）
株式会社島津製作所製「ＣＰ−５０型セントリヒューグル 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「等価球直径」を読み取り、この値を上記平均粒径（ｎｍ）とする（「粒度測定技術」日刊工業新聞社発行、１９７５年、頁２４２〜２４７）。
【００９１】
（４）粒子の平均粒径（II）（平均粒径：６０ｎｍ未満）
小突起を形成する平均粒径６０ｎｍ未満の粒子は、光散乱法を用いて測定する。すなわち、ニコンプインストゥルメント株式会社（Nicomp Instruments Inc.）製の商品名「NICOMP MODEL 270 SUBMICRON PARTICLE SIZER」により求められる全粒子の５０％の点にある粒子の「等価球直径」をもって、平均粒径（ｎｍ）とする。
【００９２】
（５）体積形状係数（ｆ）
走査型電子顕微鏡により、用いたサイズに応じた倍率にて各粒子の写真を撮影し、画像解析処理装置ルーゼックス５００（日本レギュレーター社製）を用い、投影面最大径を粒子の平均粒径（Ｄ）（μｍ）として求め、また粒子の体積（Ｖ）（μｍ³）を算出し、下記式（II）により計算する。
【００９３】
【数２】

【００９４】
（６）ポリエステル層Ａ、Ｂの厚み、およびフィルム全体の厚み
フィルム全体の厚みはマイクロメーターにてランダムに１０点測定し、その平均値を用いる。ポリエステル層Ａ、Ｂの層厚については、薄いポリエステル層の層厚みを下記に述べる方法にて測定し、厚いポリエステル層の層厚みは、全厚みより皮膜層および薄いポリエステル層の層厚を引き算して求める。すなわち、二次イオン質量分析装置（SIMS）を用いて、被覆層を除いた表層から深さ５，０００ｎｍの範囲のフィルム中の粒子の内最も高濃度の粒子に起因する金属元素（Ｍ⁺）とポリエステルの炭化水素（Ｃ⁺）の濃度比（Ｍ⁺／Ｃ⁺）を粒子濃度とし、表面から深さ５，０００ｎｍまで厚さ方向の分析を行う。表層では表面という界面のために粒子濃度は低く、表面から遠ざかるにつれて粒子濃度は高くなる。本発明の場合、粒子濃度は一旦安定値１になったのち、上昇して安定値２になる場合と、単調に減少する場合とがある。この分布曲線をもとに、前者の場合は、（安定値１＋安定値２）／２の粒子濃度を与える深さをもって、また後者の場合は粒子濃度が安定値１の１／２になる深さ（この深さは安定値１を与える深さよりも深い）をもって、薄いポリエステル層の厚み（μｍ）とする。
測定条件は、以下のとおりである。
【００９５】
（ａ）測定装置
二次イオン質量分析装置（SIMS）；パーキン・エルマー株式会社
（PERKIN ELMER INC.）製、「6300」
（ｂ）測定条件
一次イオン種：Ｏ²⁺
一次イオン加速電圧：１２ＫＶ
一次イオン電流：２００ｎＡ
ラスター領域：４００μｍ□
分析領域：ゲート３０％
測定真空度：６．０×１０^-9Torr
E−GUNN：０．５ＫＶ−３．０Ａ
【００９６】
なお、表層から５，０００ｎｍの範囲に最も多く存在する粒子がシリコーン樹脂以外の有機高分子粒子の場合はSIMSでは測定が難しいので、表面からエッチングしながらFT−IR（フーリエトランスフォーム赤外分光法）、粒子によってはＸＰＳ（Ｘ線光電分光法）などで上記同様の濃度分布曲線を測定し、層厚（μｍ）を求める。
【００９７】
（７）皮膜層Ｃの厚み
フィルムの小片をエポキシ樹脂にて固定成形し、ミクロトームにて約６００オングストロームの厚みの超薄切片（フィルムの流れ方向に平行に切断する）を作成した。この試料を透過型電子顕微鏡（株式会社日立製作所製：H−800型）にて観察し、皮膜層Ｃの境界面を探して皮膜層の厚み（ｎｍ）を求める。
【００９８】
（８）表面粗さ
▲１▼ ＷＲａ
WYKO株式会社製の非接触三次元粗さ計、商品名「TOPO−3D」を用いて、測定倍率４０倍、測定面積２４２μｍ×２３９μｍ（０．０５８ｍｍ²）の条件にて測定を行い、表面粗さのプロフィル（オリジナルデータ）を得た。上記粗さ計内蔵ソフトによる表面解析により、下式によって定義される中心面平均粗さ（ＷＲａ）を得る。
【００９９】
【数３】

【０１００】
また、Ｚjkは、測定方向（２４２μｍ）、それと直行する方向（２３９μｍ）を、それぞれＭ分割、Ｎ分割したときの各方向のｊ番目、ｋ番目の位置における三次元粗さチャート上の高さである。
【０１０１】
▲２▼ 十点平均粗さＷＲｚ
▲１▼と同じ測定器を用い、同じ条件で測定して得られたデーターから、同粗さ計内臓のソフトによる表面解析により、ピーク（Ｈｐ）の高い方から５点と谷（Ｈｖ）の低い方から５点をとった平均値を求めＷＲｚとする。
【０１０２】
【数４】

【０１０３】
（９）ヤング率
東洋ボールドウィン株式会社製の引っ張り試験機、商品名「テンシロン」を用いて、温度２０℃、湿度５０％に調節された室内において、長さ３００ｍｍ、幅１２．７ｍｍの試料フィルムを１０％／分のひずみ速度で引っ張り、引っ張り応力−ひずみ曲線の初めの直線部分を用いて下記式（Ｖ）によって計算する。
【０１０４】
【数５】

【０１０５】
ここで、Ｅはヤング率、Δσは直線上の２点間の元の平均断面積による応力差、Δεは同じ２点間のひずみ差である。
【０１０６】
（１０）巻き取り性
スリット時の巻き取り条件を最適化したのち、幅６００ｍｍ×１２，０００ｍのサイズで、３０ロールを速度１００ｍ／分でスリットし、スリット後のフィルム表面に、ブツ状、突起やシワのないロールを良品として、以下の基準にて巻き取り性を評価する。
◎：良品ロールの本数２８本以上
○：良品ロールの本数２５〜２７本
×：良品ロールの本数２４本以下
【０１０７】
（１１）異物析出性（１５０℃、３０分保持）
フィルムを１５０℃に設定したオーブン中に３０分間放置し、その後ポリエステル層Ｂ側の表面をＡｌ蒸着して、この表面を微分干渉顕微鏡で９５０倍で観察する。ポリエステル中の粒子による突起以外の、表面に付着した異物の数をカウントし、１ｍｍ²あたりの数に換算する。
【０１０８】
（１２）磁気テープの製造および特性（電磁変換特性）評価
積層ポリエステルフィルムの皮膜層Ｃの表面に、真空蒸着法により、コバルト１００％の強磁性薄膜を０．２μｍの厚みになるように２層（各層厚約０．１μｍ）形成する。形成した強磁性薄膜の表面にダイヤモンドライクカーボン（DLC）膜、さらに含フッ素カルボン酸系潤滑層を順次設け、さらにポリエステル層Ａの表面に、公知の方法でバックコート層を設ける。その後、８ｍｍ幅にスリットし、市販の８ｍｍビデオカセットにローディングした。次いで、下記の市販の機器を用いてテープの特性（Ｃ／Ｎ）を測定する。
【０１０９】
（ａ）使用機器
８ｍｍビデオテープレコーダー、ソニー株式会社製、商品名「EDV−6000」
株式会社シバソク製、ノイズメーター
（ｂ）測定方法
記録波長０．５μｍ（周波数約７．４ＭＨｚ）の信号を記録し、その再生信号の６．４ＭＨｚと７．４ＭＨｚの値の比をそのテープのＣ／Ｎとし、市販８ｍｍビデオ用蒸着テープのＣ／Ｎを０ｄＢとし、相対値で評価する。
【０１１０】
［実施例１］
ジメチルテレフタレート１００部とエチレングリコール７０部の混合物に、エステル交換触媒として酢酸マンガン・4水塩０．０２５部を添加し、内温を１５０℃から徐々に上げながらエステル交換反応を行った。エステル交換反応が９５％となった時点で、安定剤として亜リン酸を０．０１部添加し、充分撹拌した後、エチレングリコール２．５部中で無水トリメリット酸０．８部とテトラブチルチタネート０．６５部を反応せしめた液（チタン含有率は１１重量％）０．０１４部を添加した。さらに滑剤（不活性粒子Ａ）として平均粒径６０ｎｍの球状シリカ（体積形状係数０．５）を０．０３％（ポリマーに対し）添加して充分撹拌した後、次いで反応生成物を重合反応器に移し、高温真空下（最終内温２９５℃）にて重縮合を行い、固有粘度０．６０のポリエステルＡ用のポリエチレンテレフタレート（樹脂Ａ１）を得た。
【０１１１】
さらに、上記と同様の方法で、エステル交換反応を行い、エステル交換反応が９５％となった時点で、安定剤として亜リン酸を０．０１部添加し、充分撹拌した後、三酸化アンチモン０．０３部添加した。系内に混入した水を充分留出させた後、滑剤（不活性粒子Ｂ）として、平均粒径３００ｎｍのシリコーン粒子および平均粒径１００ｎｍのθ型アルミナを、樹脂中にそれぞれ０．０５％および０．２％添加して充分撹拌した後、次いで反応生成物を重合反応器に移し、高温真空下（最終内温２９５℃）にて重縮合を行い、固有粘度０．７０のポリエチレンテレフタレートを得た。この際、本ポリマー中のアンチモン残存量は２５０ｐｐｍであった。
【０１１２】
得られたポリエチレンテレフタレート９９．７％に、炭素数が８個以上の脂肪族モノカルボン酸および多価アルコールからなる（部分ケン化）エステルワックスとしてソルビタントリステアレート（融点５５℃）の粉末０．１５％をまぶし、ベント付き二軸ルーダーにて練り込み、固有粘度０．６９のポリエステル層Ｂ用のポリエチレンテレフタレート（樹脂Ｂ１）を得た。
【０１１３】
得られた樹脂Ａ１、樹脂Ｂ１を、それぞれ１７０℃で３時間乾燥後、２台の押し出し機に供給し、溶融温度２８０〜３００℃にて溶融し、平均目開き１１μｍの鋼線フィルターで高精度ろ過したのち、マルチマニホールド型共押出しダイを用いて、ポリエステル層Ａの片面にポリエステル層Ｂを積層させ、急冷して厚さ８９μｍの未延伸積層ポリエステルフィルムを得た。
【０１１４】
得られた未延伸フィルムを予熱し、さらに低速・高速のロール間でフィルム温度１００℃にて３．３倍に延伸し、急冷して縦延伸フィルムを得た。次いで縦延伸フィルムのＡ層側に下記に示す組成（固形分換算）の水性塗液（全固形分濃度１．０％）をキスコート法により塗布した。
【０１１５】

【０１１６】
続いてステンターに供給し、１１０℃にて横方向に４．２倍に延伸した。得られた二軸延伸フィルムを、２２０℃の熱風で４秒間熱固定し、全厚み６．４μｍで、ポリエステル層Ｂの厚み１．０μｍの積層二軸配向ポリエステルフィルムを得た。このフィルムのポリエステル層Ａ、Ｂの厚みについては、２台の押し出し機の吐出量により調整した。このフィルムの皮膜層Ｃ側の表面から測定した表面粗さＷＲａは、１．７ｎｍ、このフィルムのヤング率は縦方向５０００Ｎ／ｍｍ²、横方向７０００Ｎ／ｍｍ²であった。この積層フィルムのその他の特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１１７】
［実施例２］
ポリエステル層Ａに粒子を含有させないようにし（樹脂Ａ２）、ポリエステル層Ｂに含有させる不活性粒子Ｂの種類、平均粒径、添加量を表１に示すとおり変更した（樹脂Ｂ２）以外は、実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性、およびそのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１１８】
［実施例３］
ポリエステル層Ａを形成する原料樹脂Ａ（樹脂Ａ３）およびポリエステル層Ｂを形成する原料樹脂Ｂ（樹脂Ｂ３）の固有粘度を０．６７とする以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムの特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１１９】
［実施例４］
ポリエステル層Ａおよびポリエステル層Ｂにおけるジメチルテレフタレートの代わりに２，６−ナフタレンジカルボン酸ジメチルを同モル量使用した以外は、実施例１と同様にしてポリエステル層Ａ、Ｂ用のポリエチレン−２，６−ナフタレート（ＰＥＮ）（樹脂Ａ３、Ｂ３）を得た。固有粘度は樹脂Ａ３は０．６０、樹脂Ｂ３は０．６７であった。
【０１２０】
この樹脂Ａ３、Ｂ４を、それぞれ１７０℃で６時間乾燥後、実施例１と同様にして、各層厚みを調整し、厚さ８９μｍの未延伸積層熱可塑性樹脂フィルムを得た。
【０１２１】
得られた未延伸フィルムを予熱し、さらに低速・高速のロール間でフィルム温度１３５℃にて３．６倍に延伸し、急冷して縦延伸フィルムを得た。次いで縦延伸フィルムのＡ層側に、不活性粒子Ｃをコアシェルフィラー（コア；架橋ポリスチレン、シェル；ポリメチルメタクリレート）（平均粒径；３０ｎｍ、体積形状係数０．４５）ジェイエスアール株式会社製、「SX 8721」に変更した以外は実施例１と同じ組成の水性塗液（全固形分濃度１．０％）を実施例１と同様に塗布した。
【０１２２】
続いてステンターに供給し、１５５℃にて横方向に５．７倍に延伸した。得られた二軸延伸フィルムを、２００℃の熱風で４秒間熱固定し、全厚み４．４μｍ、熱可塑性樹脂層Ｂの厚み０．６μｍの積層二軸配向ポリエステルフィルムを得た。このフィルムの熱可塑性樹脂層Ａ、Ｂの厚みについては、２台の押し出し機の吐出量により調整した。このフィルムの塗膜層Ｃ側の表面から測定した表面粗さＷＲａは、１．２ｎｍ、このフィルムのヤング率は縦方向５５００Ｎ／ｍｍ²、横方向１０，５００Ｎ／ｍｍ²であった。この積層フィルムのその他の特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１２３】
［比較例１］
ポリエステル層Ｂを形成する原料樹脂Ｂの固有粘度を０．５３とする以外は実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムは、フイルム走行時のポリエステル層Ｂから不活性粒子Ｂが脱落する頻度が増加し、反対面への転写も多数起こったり、析出オリゴマーが反対面（蒸着面）に多数転写したため、磁気テープにした際、十分な電磁変換特性を得ることができなかった。その他の特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１２４】
［比較例２，３］
ポリエステル層Ｂに含有させる不活性粒子Ｂの種類、平均粒径、添加量を表１に示すようにした以外は、実施例１と同様にして積層ポリエステルフィルムを得た。得られたフィルムは、Ｂ層からブリードアウトしたオリゴマーが反対面へ転写することは問題なく良好であったが、比較例２の場合、Ｂ層側の突起の反対面への形状転写の程度が強く、磁気テープにした際、十分な電磁変換特性を得ることができなかった。比較例３の場合はＢ層が平坦すぎて良好な巻取り性が得られなかった。その他の特性、およびこのフィルムを用いた強磁性薄膜蒸着型磁気テープの特性を表１に示す。
【０１２５】
【表１】

【０１２６】
表１から明らかなように、本発明による積層ポリエステルフィルムは、片面が非常に平坦で、反対面からのオリゴマーの転写も少なく、優れた電磁変換特性を示すとともに、巻き取り性が極めて良好である。一方、本発明の要件を満たさないものは、これらの特性を同時に満足できない。
【０１２７】
【発明の効果】
本発明によれば、耐ブロッキング性、平坦性、巻き取り性、加工適性に優れ、特に金属蒸着薄膜型磁気記録媒体としたときに電磁変換特性に優れた積層ポリエステルフィルムを得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laminated polyester film, and more particularly, a magnetic recording medium excellent in electromagnetic conversion characteristics and running durability, particularly a ferromagnetic metal thin film type magnetic recording medium for recording / reproducing digital signals, such as a digital video cassette tape, data storage. The present invention relates to a laminated polyester film useful as a base film such as a tape.
[0002]
[Prior art]
In recent years, the progress of high-density recording of magnetic recording media has been remarkable. For example, a ferromagnetic metal thin film type magnetic recording in which a ferromagnetic metal thin film is formed on a nonmagnetic support by a physical deposition method such as vacuum deposition or sputtering or a plating method. The development and practical application of media are underway. Specifically, a Co vapor-deposited tape (Japanese Patent Laid-Open No. 54-147010) and a perpendicular magnetic recording medium made of a Co—Cr alloy (Japanese Patent Laid-Open No. 52-134706) are known.
[0003]
Conventional coating type magnetic recording media (magnetic recording media in which magnetic powder is mixed in an organic polymer binder and coated on a nonmagnetic support) have a magnetic layer thickness of about 2 μm or more and a recording density of Low and long recording wavelength. On the other hand, the metal thin film (magnetic layer) in the ferromagnetic metal thin film type magnetic recording medium has a very thin thickness of 0.2 μm or less.
[0004]
For this reason, the extent to which the surface state of the nonmagnetic support (base film) affects the surface properties of the magnetic recording layer is much greater for metal thin films. That is, in the case of a ferromagnetic metal thin film type magnetic recording medium, the surface state of the nonmagnetic support appears as it is as the surface irregularities of the metal thin film, which causes noise in recording / reproducing signals. Therefore, it is desirable that the surface of the nonmagnetic support is as smooth as possible.
[0005]
On the other hand, it is preferable that the film is excellent in slipperiness from the viewpoint of handling such as film formation of the non-magnetic support, conveyance in the processing step, winding and unwinding. If the film surface is too smooth, the slipperiness between the film and the film deteriorates, and the surface is liable to be damaged, resulting in a decrease in product yield and an increase in manufacturing cost. Therefore, from the viewpoint of manufacturing cost, the surface of the nonmagnetic support is preferably as rough as possible.
[0006]
In the case of a metal thin film type magnetic recording medium, in order to improve the adhesion between the metal thin film and the base film, a process called ion bombardment treatment that activates the surface of the base film with ions before forming the metal thin film. To do. Then, when forming a metal thin film, the back surface of the film is cooled so that heat at a considerably high temperature is applied to the film surface and the base film is not melted and physical properties such as mechanical properties are not deteriorated. For this backside cooling, a method of winding a base film around a drum-shaped cooling body is usually employed. At this time, both ends of the base film are masked so that a metal thin film is not formed on the drum surface.
[0007]
Therefore, at both ends of the film roll that has passed the above-described deposition process, the portions where the metal thin film was not formed by this masking are continuously present in the longitudinal direction while being surface activated by ion bombardment treatment. To do. And in the state wound up in roll shape, this part will contact with an opposite surface side with high force, and it will become easy to cause blocking. When manufacturing a metal thin film type magnetic recording medium, after depositing a metal thin film, a back coat layer and, if necessary, a top coat layer are provided. If the blocking occurs in these processing steps, There arises a problem that the film is likely to be cut or wrinkled, and the yield is greatly reduced. In order to prevent such blocking, the surface of the nonmagnetic support is preferably rough.
[0008]
Thus, the surface of the nonmagnetic support is required to be smooth from the viewpoint of electromagnetic conversion characteristics, and on the other hand, it is required to be rough from the viewpoint of handling properties, manufacturing cost, and blocking prevention.
[0009]
In order to satisfy the conflicting requirements as described above, a laminated film (for example, Japanese Patent Publication No. 1-26338), which has two layers and the surface of the other layer is rougher than the surface of one layer, has been proposed. However, this laminated film has an electromagnetic effect when it is used as a magnetic recording medium due to the effect of transferring protrusions with a rough surface layer onto the surface of the flat surface layer or pushing up the flat surface layer by large particles added to the rough surface layer. There is a problem that the conversion characteristics deteriorate.
[0010]
In addition, as a measure to prevent the surface smoothness from being reduced by catalyst residues (fine particles) inside the base film, a germanium compound is used as a polymerization catalyst as a raw material for the smooth surface layer, and a polyester containing a specific amount of germanium and phosphorus is used. A laminated film (for example, JP-A-12-15695) has been proposed. However, even in this laminated film, foreign matter bleed-outs such as protrusions dropping off from the surface of the rough surface layer or oligomers occur during film production or in the metal thin film processing step described above, and these foreign matters are smoothed on the smooth surface layer in each production process. Have the problem of deteriorating sex.
[0011]
[Problems to be solved by the invention]
An object of the present invention is a laminated polyester film that eliminates the disadvantages of the prior art, is excellent in blocking resistance, flatness, processability, and exhibits excellent electromagnetic conversion characteristics when used as a metal-deposited thin film magnetic recording medium. Is to provide.
[0012]
[Means for Solving the Problems]
  The object of the present invention is according to the present invention:It contains substantially no particles or contains 0.001 to 0.2% by weight of inert particles A having an average particle size of 30 to 400 nm.Polyester layer A and polymer laminated on one side of the layer A have an intrinsic viscosity of 0.55 or more and a terminal carboxyl group concentration of 36 eq / 10.⁶g and the average particle diameter is 50 to 1000 nm, andWhen the layer A contains inert particles AA polyester layer B containing 0.001 to 1% by weight of inert particles B larger than the average particle diameter of the inert particles A contained in the layer A;The ten-point average roughness (WRzB) of the polyester layer B surface is 50 to 200 nm.This is achieved by a laminated polyester film.
[0013]
  In the present invention, as a preferred embodiment, the inert particles B are at least one particle selected from the group consisting of a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, aluminum oxide, titanium dioxide, silicon dioxide, kaolin, and clay. The polyester layer B contains (partially saponified) ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol.,The surface roughness (WRaA) of the surface of the polyester layer A is 0.1 to 4 nm.,The coating layer C is laminated on the surface of the polyester layer A. The coating layer C contains 0.5 to 30% by weight of inert particles C having an average particle size of 10 to 50 nm and a volume shape factor of 0.1 to π / 6. Content, film thickness of 2 μm or more and less than 8 μm, polyester of layer A or layer B is polyethylene terephthalate or polyethylene-2,6-naphthalate, polyester layer A or coating layer C It includes that the surface is a surface on which a magnetic layer is provided, and that the magnetic layer is a ferromagnetic metal thin film layer.
[0014]
The present invention also includes a magnetic recording medium having the laminated polyester film as a support.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The laminated polyester film of the present invention is a laminated film in which a polyester layer B is laminated on one side of a polyester layer A.
[0016]
Examples of the polyesters A and B forming the polyester layer A and the layer B include aliphatic polyesters and aromatic polyesters, and aromatic polyesters are particularly preferable. Polyesters A and B may be the same type or different types.
[0017]
Examples of the aromatic polyester include polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalate (polyethylene-2,6-naphthalenedicarboxylate). Etc. can be illustrated. Of these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable.
[0018]
These polyesters may be homopolyesters or copolyesters. In the case of a copolyester, for example, as a copolymerization component of polyethylene terephthalate or polyethylene-2,6-naphthalate, diethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, polyethylene glycol, 1,4-cyclohexanedi Other diol components such as methanol and p-xylylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid (in the case of polyethylene-2,6-naphthalate), 2,6-naphthalenedicarboxylic acid ( However, in the case of polyethylene terephthalate), other dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, oxycarboxylic acid components such as p-oxyethoxybenzoic acid, and the like. The amount of these copolymer components is preferably 20 mol% or less, more preferably 10 mol% or less, as long as the effects of the present invention are not impaired.
[0019]
Furthermore, trifunctional or more polyfunctional compounds such as trimellitic acid, pyromellitic acid and pentaerythritol can be copolymerized. In this case, the copolymer is preferably copolymerized in an amount that is substantially linear, for example, 2 mol% or less.
[0020]
The copolymer component in the case of polyester other than polyethylene terephthalate and polyethylene-2,6-naphthalate may be considered in the same manner as described above.
[0021]
The polyester further contains additives such as pigments, dyes, antioxidants, antistatic agents, light stabilizers, light-shielding agents (for example, carbon black, titanium oxide, etc.) as long as the effects of the present invention are not impaired. Can be contained as required.
[0022]
In the laminated polyester film of the present invention, the polyester layer A and the layer B are preferably made of the same polyester, but may be made of different polyesters. For example, a laminated film in which both layer A and layer B are made of polyethylene terephthalate or polyethylene-2,6-naphthalate is preferable, but layer A (or layer B) is polyethylene terephthalate, and layer B (or layer A) is polyethylene-2, A laminated film made of 6-naphthalate may be used.
[0023]
The polyester A forming the polyester layer A can be produced by a conventionally known method. For example, polyethylene terephthalate can be produced by a method in which terephthalic acid and ethylene glycol are esterified, or dimethyl terephthalate and ethylene glycol are transesterified, and then the reaction product is polycondensed.
[0024]
The polyester obtained by the above method (melt polymerization) can be made into a polymer having a higher degree of polymerization by a solid phase polymerization method (solid phase polymerization) as necessary.
[0025]
A known catalyst can be used in this polymerization, and the transesterification catalyst in the melt polymerization is preferably manganese, calcium, magnesium, titanium oxide, chloride, carbonate, carboxylate, etc. Preferable examples include manganese acetate, calcium acetate, magnesium acetate, and titanium acetate.
[0026]
Examples of the polycondensation catalyst include antimony compounds, titanium compounds, and germanium compounds.
[0027]
Preferred examples of the antimony compound include antimony trioxide, antimony pentoxide, and antimony acetate.
[0028]
Preferred examples of the titanium compound include organic titanium compounds, such as those described in JP-A-5-298670. More specifically, titanium alcoholate, organic acid salt, reaction product of tetraalkyl titanate and aromatic polyvalent carboxylic acid or anhydride, etc. can be exemplified, and preferred examples include titanium tetrabutoxide, titanium isopropoxide, titanium oxalate. , Titanium acetate, titanium benzoate, trimellitic acid titanium, a reaction product of tetrabutyl titanate and trimellitic anhydride, and the like.
[0029]
Examples of the germanium compound include those described in Japanese Patent No. 2792068. More specifically, (a) amorphous germanium oxide, (b) crystalline germanium, (c) a solution of germanium oxide dissolved in glycol in the presence of an alkali metal, an alkaline earth metal or a compound thereof, and (d) Examples thereof include a solution of germanium oxide in a solution prepared by dissolving germanium oxide in water, adding glycol thereto and distilling off water.
[0030]
In addition, it is preferable that the polyester A contains a phosphorus compound that is conventionally added in the production process of polyester in order to maintain thermal stability. Although this phosphorus compound is not particularly limited, orthophosphoric acid, phosphorous acid, trimethyl phosphate, triethyl phosphate, and tri-n-butyl phosphate are preferable.
[0031]
The intrinsic viscosity of the polymer in the polyester layer A is preferably 0.45 or more. More preferably, it is 0.47 or more, Most preferably, it is 0.50 or more. When the intrinsic viscosity of the polymer in the polyester layer A is less than 0.45, it is not preferable because bleedout of oligomers or the like occurs in the film winding process.
[0032]
As a method for increasing the intrinsic viscosity of the polymer in the polyester layer A to 0.45 or more, a method of increasing the intrinsic viscosity of the raw material polymer, or milder melt extrusion conditions (adopting extrusion conditions that suppress polymer degradation as much as possible) Etc. are used.
[0033]
The polyester layer A in the present invention may contain substantially no particles or may contain inert particles A. When the polyester layer A does not substantially contain particles, excellent electromagnetic conversion characteristics can be obtained when a magnetic recording medium is used. However, if particles in a range that does not adversely affect the electromagnetic conversion characteristics are included, the running durability is improved. Can be achieved. Specifically, it is preferable to contain 0.001 to 0.2% by weight of inert particles A having a volume shape factor of 0.1 to π / 6 and an average particle size of 30 to 400 nm with respect to the polyester layer A.
[0034]
Preferred inert particles A include, for example, (1) heat-resistant polymer particles (for example, crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, crosslinked polyester, etc. Particles), (2) metal oxides (eg, aluminum oxide, titanium dioxide, silicon dioxide (silica), magnesium oxide, zinc oxide, zirconium oxide, etc.), (3) metal carbonates (eg, magnesium carbonate, Calcium carbonate, etc.), (4) metal sulfates (eg, calcium sulfate, barium sulfate, etc.), (5) carbon (eg, carbon black, graphite, diamond, etc.), and (6) clay minerals (eg, kaolin, 1 such as clay and bentonite) They include the fine particles made from the above. Among these, crosslinked silicone resin particles, crosslinked polystyrene resin particles, melamine-formaldehyde resin particles, polyamideimide resin particles, other aluminum oxide (alumina), titanium dioxide, silicon dioxide, zirconium oxide, synthetic calcium carbonate, barium sulfate, diamond, Alternatively, fine particles made of kaolin are preferred. More preferred are fine particles made of crosslinked silicone resin particles, crosslinked polystyrene resin particles, and other aluminum oxide (alumina), titanium dioxide, silicon dioxide, or calcium carbonate. These may be used alone or in combination of two or more.
[0035]
When two or more kinds of particles having different average particle diameters are used as the inert particles A, examples of the second and third particles (fine particles) having a small average particle diameter include colloidal silica, α, γ, δ, θ, and the like. Fine particles such as alumina having the following crystal form can be preferably used. Of the particle types exemplified as the inert particles A having the average particle diameter dA, fine particles having a small average particle diameter can also be used as the second and third particles (fine particles).
[0036]
As for the shape of the inert particles A, the volume shape factor (f) described later is preferably 0.1 to π / 6, more preferably 0.2 to π / 6, and particularly preferably 0.4 to π / 6. The average particle diameter dA of the inert particles A is preferably 30 to 400 nm, more preferably 40 to 200 nm, and particularly preferably 50 to 100 nm. If the average particle diameter dA is less than 30 nm, the slipperiness of the film may be insufficiently improved. On the other hand, if it exceeds 400 nm, the electromagnetic conversion characteristics of the magnetic recording medium may be deteriorated.
[0037]
The content when the inert particles A are contained in the polyester A is preferably 0.001 to 0.2% by weight, more preferably 0.01 to 0.1% by weight, particularly preferably the polyester layer A. Is 0.02 to 0.06% by weight. If this amount is less than 0.001% by weight, the slipperiness of the film may be insufficiently improved. On the other hand, if it exceeds 0.2% by weight, the electromagnetic conversion characteristics of the magnetic recording medium may be poor. This is not preferable.
[0038]
The polyester B which forms the polyester layer B in the present invention can be produced by a conventionally known method like the polyester A. In that case, a known catalyst can be used, and it is preferable to use the same catalyst as that of polyester A. Further, like the polyester A, it is preferable to contain a phosphorus compound.
[0039]
The polyester layer B needs to have a polymer intrinsic viscosity of 0.55 or more. Preferably it is 0.57 or more, Most preferably, it is 0.60 or more. Therefore, it is necessary to determine the intrinsic viscosity of the raw material polymer used for forming the polyester layer B in consideration of the rate of polymer deterioration during film formation (a reduction amount of the intrinsic viscosity). When the intrinsic viscosity of the polymer in the polyester layer B is less than 0.55, bleeding out of oligomers and dropping off of protrusions become severe, and troubles such as transfer to the opposite surface and loss of smoothness are likely to occur. In addition, it is preferable that the intrinsic viscosity of the polymer in the polyester layer A is 0.45 or more from the point of the physical characteristics (for example, Young's modulus etc.) of a film as mentioned above.
[0040]
As a method for increasing the intrinsic viscosity of the polymer in the polyester layer B to 0.55 or more, a method for increasing the intrinsic viscosity of the raw material polymer, a mild melt extrusion condition (adopting an extrusion condition that suppresses polymer degradation as much as possible) ) Etc. are used.
[0041]
Further, the polyester layer B in the present invention has a polymer terminal carboxyl group concentration of 36 eq / 10.⁶g or more. This terminal carboxyl group concentration is preferably 60 eq / 10.⁶g or less. More preferably 38 to 60 eq / 10⁶g, particularly preferably 40 to 55 eq / 10.⁶g. The terminal carboxyl group concentration is 36 eq / 10.⁶If it is less than g, the affinity for the inactive particles B is inferior, the inactive particles B drop off during film production or in the metal thin film forming process, and the smoothness of the surface is reduced by transferring to the opposite surface. This is not preferable. On the other hand, the terminal carboxyl group concentration is 60 eq / 10.⁶If it exceeds g, the affinity for the inert particles B is further improved, but the thermal stability of the layer B during the deposition of the metal thin film becomes poor, the surface flatness is impaired, and the strength required for the product Cannot be obtained, which is not preferable.
[0042]
The terminal carboxyl group concentration of the polymer in the polyester layer B is 36 eq / 10.⁶A conventionally known method is used to make the amount g or more. For example, a method of melting and holding the polymer after completion of polycondensation, polycondensation under conditions where the terminal carboxyl group concentration is higher than usual, etc. can be exemplified.
[0043]
The polyester layer B in the present invention needs to contain inert particles B having an average particle size larger than that of the inert particles A contained in the polyester layer A. When the average particle diameter of the inert particles B is smaller than that of the inert particles A, problems such as blocking in the film manufacturing process and the metal thin film forming process occur. The average particle diameter (dB) of the inert particles B is 50 to 1,000 nm, preferably 100 to 800 nm, more preferably 150 to 700 nm, and particularly preferably 200 to 600 nm. The content of the inert particles B is 0.001 to 1% by weight, preferably 0.005 to 0.8% by weight, more preferably 0.01 to 0.6% by weight, based on the polyester layer B. Particularly preferred is 0.01 to 0.2% by weight.
[0044]
Preferred inert particles B include the same type of particles as the inert particles A. These particles may be used alone or in combination of two or more. From the viewpoint of resistance to dropping from the polyester layer B, the affinity can be further improved by reaction with the terminal carboxyl group of the polyester layer B. Particles in which many hydroxyl groups are present on the particle surface are preferable, and contain at least one particle selected from a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, aluminum oxide, titanium dioxide, silicon dioxide (silica), kaolin, and clay. It is particularly preferred.
[0045]
When the average particle diameter of the inert particles B is less than 50 nm or the content is less than 0.001% by weight, the winding property and blocking resistance of the film are poor. On the other hand, when the average particle size exceeds 1,000 nm or the content exceeds 1% by weight, the shape transfer of the protrusions on the opposite surface (the surface of the polyester layer A) or the protrusions from below the layer A The electromagnetic conversion characteristics are deteriorated by pushing up.
[0046]
In addition to the inert particles B, the polyester layer B may contain second and third particles (fine particles) having an average particle size smaller than that of the inert particles B. The average particle diameter of the fine particles is preferably 5 to 450 nm, more preferably 10 to 400 nm, and particularly preferably 30 to 350 nm. Further, the content of the second and third particles (fine particles) is preferably 0.005 to 1% by weight, more preferably 0.01 to 0.7% by weight, particularly preferably based on the polyester layer B. 0.02 to 0.5% by weight.
[0047]
The polyester layer B in the present invention preferably further contains 0.001 to 1% by weight of an ester wax (partially saponified) composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol. Here, (partially saponified) ester wax includes ester wax and partially saponified ester wax.
[0048]
The aliphatic monocarboxylic acid has 8 or more carbon atoms, preferably 8 to 34 carbon atoms. If the number of carbon atoms is less than 8, the resulting ester product has insufficient heat resistance, and the aliphatic monocarboxylic acid is easily decomposed under heating conditions when dispersed in polyester. Is appropriate.
[0049]
Examples of aliphatic monocarboxylic acids having 8 or more carbon atoms include pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid , Pehenic acid, lignoceric acid, serotic acid, montanic acid, melissic acid, hentriacontanoic acid, petroceric acid, oleic acid, erucic acid, linoleic acid, and mixtures containing these.
[0050]
The alcohol component of the (partially saponified) ester wax is a polyhydric alcohol having two or more hydroxyl groups. Furthermore, it is preferable that it is a polyhydric alcohol which has 3 or more of hydroxyl groups from a heat resistant viewpoint. When monoalcohol is used, the heat resistance of the produced (partially saponified) ester wax is insufficient.
[0051]
Examples of the polyhydric alcohol having two hydroxyl groups include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, Preferred examples include 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, triethylene glycol, polyethylene glycol and the like. Preferable examples of the polyhydric alcohol having 3 or more hydroxyl groups include glycerin, erythritol, trait, pentaerythlit, arabit, xylit, tarit, sorbit, mannitol and the like.
[0052]
Examples of the ester wax obtained from the aliphatic monocarboxylic acid and the polyhydric alcohol include monoesters, diesters, triesters and the like, depending on the number of hydroxyl groups of the polyhydric alcohol. Among these, from the viewpoint of heat resistance, a diester is preferable to a monoester, and a triester is preferable to a diester. Specific examples of preferred ester waxes include sorbitan tristearate, pentaerythritol triphenate, glycerin tripalmitate, polyoxyethylene distearate and the like.
[0053]
The partially saponified ester wax composed of an aliphatic monocarboxylic acid and a polyhydric alcohol is obtained by partially esterifying a polyhydric alcohol with a higher fatty acid having 8 or more carbon atoms and then saponifying with a metal hydroxide having a valence of 2 or more. Can be obtained. Specific examples include wax E, wax OP, wax O, wax OM, and wax FL (all trade names manufactured by Hoechst Co., Ltd.) obtained by saponifying montanic acid diol ester with calcium hydroxide. Such (partially saponified) ester wax may be used alone or in combination of two or more.
[0054]
The amount of the (partially saponified) ester wax added to the layer B is 0.001 to 1% by weight, preferably 0.003 to 0.5% by weight, more preferably 0.005 to 0.5% by weight, Particularly preferred is 0.01 to 0.3% by weight. When the content of this (partially saponified) ester wax is less than 0.001% by weight, the winding property is not sufficiently improved, and the effect of improving blocking cannot be obtained. On the other hand, when the content exceeds 1% by weight, a large amount of the wax component bleed out on the surface of the layer B is transferred to the opposite surface that comes into contact with the film when it is wound up on a roll in the film production process, or particles and polyester In the process of depositing a metal thin film layer from the void generated at the interface of the metal, many oligomers are bleed out and transferred to the opposite surface, which prevents, for example, adhesion between the metal deposition layer and the base film or causes dropout. Cause the negative effects.
[0055]
The ten-point average roughness (WRzB) of the polyester layer B is 30 to 300 nm, preferably 40 to 250 nm, and particularly preferably 50 to 200 nm. When this WRzB is 30 nm or less, the handleability of the laminated film is poor, sufficient productivity cannot be increased, and the blocking improvement effect is insufficient. On the other hand, if the thickness exceeds 300 nm, the shape transfer of the protrusions to the surface on the side where the opposite magnetic layer is provided (the surface of the polyester layer A) becomes large, and electromagnetic conversion characteristics may be impaired, which is not preferable.
[0056]
The laminated polyester film of the present invention has a coating layer C on the surface on which the magnetic layer is provided, that is, on the surface of the polyester layer A (the surface not in contact with the polyester layer B) in order to improve various properties when used as a magnetic tape. Is preferably provided.
[0057]
The coating layer C preferably contains 0.5 to 30% by weight of inert particles C having an average particle size of 10 to 50 nm and a volume shape factor of 0.1 to π / 6.
[0058]
Preferred examples of the resin forming the coating layer C include water-based polyester resins, water-based acrylic resins, water-based polyurethane resins, and the like, and water-based polyester resins are particularly preferable.
[0059]
As this aqueous polyester resin, the acid component is, for example, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid, dodecane. From one or more polycarboxylic acids such as dicarboxylic acid, succinic acid, sodium 5-sulfoisophthalate, potassium 2-sulfoterephthalate, trimellitic acid, trimesic acid, trimellitic acid monopotassium salt, p-hydroxybenzoic acid For example, ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, p-xylylene glycol, dimethylolpropane, and bisphenol A. Echile Mainly comprising a polyester resin from one or more polyhydroxy compounds such as oxide adducts are preferably used. Also, a graft polymer or block copolymer in which an acrylic polymer chain is bonded to a polyester chain, or a specific physical configuration (IPN (interpenetrating polymer network) type, core-shell type, etc.) in the form of microscopic particles of two types of polymers It may be an acrylic-modified polyester resin formed. As this aqueous polyester resin, a type that dissolves, emulsifies and finely disperses in water can be freely used, but a type that emulsifies and finely disperses in water is preferable. Moreover, since these impart hydrophilicity, for example, a sulfonate group, a carboxylate group, or a polyether unit may be introduced into the molecule.
[0060]
The inert particles C contained in the coating layer C are not particularly limited, but those having a relatively low specific gravity that are difficult to settle in the coating liquid are preferable. For example, from cross-linked silicone resin, acrylic resin, polystyrene, melamine-formaldehyde resin, aromatic polyamide resin, polyamideimide resin, cross-linked polyester, organic particles made of wholly aromatic polyester, silicon dioxide (silica), calcium carbonate, etc. Preferred are inorganic particles. Among these, cross-linked silicone resin particles, acrylic resin particles, silica particles, and core-shell type organic particles (core: cross-linked polystyrene, shell: polymethyl methacrylate particles, etc.) are preferable.
[0061]
The average particle diameter dC of the inert particles C is 10 to 50 nm, preferably 12 to 45 nm, and more preferably 15 to 40 nm. If the average particle size is less than 10 nm, the slipperiness of the film may be insufficiently improved. On the other hand, if it exceeds 50 nm, the electromagnetic conversion characteristics of the magnetic recording medium may be deteriorated.
[0062]
The shape of the inert particles C is such that the volume shape factor (f) represented by the following formula (I) is 0.1 to π / 6, preferably 0.2 to π / 6, more preferably 0.4 to π. / 6.
[0063]
[Expression 1]

[0064]
[Where f is the volume shape factor and V is the volume of the particles (μm^Three), D is the average particle size (μm) of the particles. ]
[0065]
The shape of the particles having a volume shape factor (f) of π / 6 is a sphere (true sphere). That is, those having a volume shape factor (f) of 0.4 to π / 6 substantially include spheres, true spheres, and elliptical spheres such as rugby balls, and are preferable as the inert particles C. Particles having a volume shape factor (f) of less than 0.1, such as flaky particles, are not preferred because running durability is reduced.
[0066]
The content of the inert particles C is 0.5 to 30% by weight, preferably 2 to 20% by weight, and more preferably 3 to 10% by weight with respect to the coating layer C (solid content of the coating liquid). If the content is less than 0.5% by weight, the slipperiness of the film may be insufficiently improved. On the other hand, if it exceeds 30% by weight, the electromagnetic conversion characteristics of the magnetic recording medium may be deteriorated. Therefore, it is not preferable.
[0067]
In the laminated polyester film of the present invention, the surface roughness (WRaA) of the surface of the polyester layer A (surface on the side not in contact with the polyester layer B) (surface of the coating layer C when the coating layer C is provided) is 0.1 to 0.1. 4 nm is preferable. More preferably, it is 0.2-3.5 nm, Most preferably, it is 0.3-3.0 nm, Especially 0.4-2.5 nm. If this WRaA is less than 0.1 nm, the slipperiness is poor and the production of the film is extremely difficult. On the other hand, if WRaA exceeds 4 nm, the electromagnetic conversion characteristics deteriorate, such being undesirable.
[0068]
This surface roughness (WRaA) can be adjusted by the particle size and amount of the inert particles C contained in the coating layer C and / or the particle size and amount of the inert particles A contained in the polyester layer A.
[0069]
The total thickness of the laminated polyester film in the present invention is usually 2 μm or more and less than 8 μm, preferably 2.5 to 7.5 μm. The thickness constitution of the polyester layer A and the polyester layer B is preferably such that the thickness of the layer B is 1/50 to 1/2 of the total thickness of the laminated film, more preferably 1/30 to 1/3, particularly preferably 1/20. ~ 1/4. The thickness of the coating layer C is usually 1 to 100 nm, preferably 2 to 50 nm, more preferably 3 to 10 nm, and particularly preferably 3 to 8 nm.
[0070]
The laminated polyester film in the present invention can be produced according to methods conventionally known or accumulated in the industry. Among them, the laminated structure of the polyester layer A and the polyester layer B is preferably manufactured by a coextrusion method, and the coating layer C is preferably laminated by a coating method.
[0071]
For example, in the case of a biaxially oriented polyester film, the ester wax and the inert particles B are finely dispersed in the extrusion die or before the die (generally, the former is called a multi-manifold method and the latter is called a feed block method). The polyester B contained, and the polyester A containing the inert particles A as necessary, after high-accuracy filtration, respectively, are laminated and composited in a molten state, and there is a laminated structure with the above preferred thickness ratio, Next, the film is coextruded from the die at a melting point (Tm) to (Tm + 70) ° C., and then rapidly cooled and solidified with a cooling roll at 40 to 90 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is uniaxially (longitudinal or transverse) uniaxially (longitudinal or transverse) at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of the polyester). The film is stretched at a magnification of 8.0 times, preferably at a magnification of 3.0 to 7.5 times, and then in a direction perpendicular to the stretching direction (when the first-stage stretching is the longitudinal direction, the second-stage stretching is transverse The film is stretched at a temperature of (Tg) to (Tg + 70) ° C. at a magnification of 2.5 to 8.0 times, preferably at a magnification of 3.0 to 7.5 times. Furthermore, you may extend | stretch again in the vertical direction and / or a horizontal direction as needed. That is, it is good to perform 2 steps | paragraphs, 3 steps | paragraphs, 4 steps | paragraphs, or multistage extending | stretching. The total draw ratio is usually 9 times or more, preferably 10 to 35 times, and more preferably 12 to 30 times.
[0072]
Further, the biaxially oriented film is imparted with excellent dimensional stability by heat-set crystallization at a temperature of (Tg + 70) to (Tm-10) ° C., for example, 180 to 250 ° C. in the case of a polyethylene terephthalate film. The At that time, the heat setting time is preferably 1 to 60 seconds.
[0073]
In the production of the laminated polyester film, additives other than the above-mentioned inert particles, for example, a stabilizer, a colorant, a specific resistance adjusting agent for a molten polymer, and the like can be added to the polyesters A and B as required.
[0074]
The film layer C is preferably laminated on the polyester layer A in the present invention by a method of applying an aqueous coating liquid.
[0075]
The coating is preferably performed on the surface of the polyester layer A before the final stretching treatment, and after coating, the film is preferably stretched at least in a uniaxial direction. The film is dried before or during the stretching. Among them, the coating is preferably performed on an unstretched laminated film or a longitudinal (uniaxial) stretched laminated film, particularly a longitudinal (uniaxial) stretched laminated film. Although it does not specifically limit as a coating method, For example, a roll coat method, a die coat method, etc. are mentioned.
[0076]
The solid concentration of the coating liquid, particularly the aqueous coating liquid, is preferably 0.2 to 8% by weight, more preferably 0.3 to 6% by weight, and particularly preferably 0.5 to 4% by weight. In addition, other components such as other surfactants, stabilizers, dispersants, ultraviolet absorbers, thickeners and the like can be added to the aqueous coating liquid as long as the effects of the present invention are not hindered.
[0077]
In the present invention, in order to improve various performances including head touch as a magnetic recording medium, running durability, and at the same time to achieve a thin film, the Young's modulus of the laminated film is set in the vertical and horizontal directions, respectively. Usually 4500 N / mm²Above and 6000 N / mm²Or more, preferably 4800 N / mm²Above and 6800 N / mm²Or more, more preferably 5500 N / mm²Above and 8000 N / mm²Above, particularly preferably 5500 N / mm²Above and 10,000 N / mm²That's it.
[0078]
The degree of crystallinity of the polyester layers A and B is desirably 30 to 50% when the polyester is polyethylene terephthalate and 28 to 38% when the polyester is polyethylene-2,6-naphthalate. If both are below the lower limit, the thermal shrinkage rate is increased, while if the upper limit is exceeded, the abrasion resistance of the film is deteriorated, and white powder is liable to be produced when sliding with the roll or guide pin surface.
[0079]
According to the present invention, the polyester layer B is laminated on one side of the polyester layer A, and the coating layer C is laminated on the surface of the polyester layer A (the surface not in contact with the polyester layer B). A magnetic recording medium having each of the laminated polyester films as a base film is also provided.
[0080]
An embodiment for producing a magnetic recording medium from the laminated polyester film of the present invention is as follows.
[0081]
The laminated polyester film of the present invention is formed on the surface of the polyester layer A, preferably the coating layer C, by a method such as vacuum deposition, sputtering, ion plating, or the like. It is particularly useful as a base film of a magnetic recording medium on which a ferromagnetic metal thin film layer (magnetic layer) made of an oxide is formed. The metal thin film layer preferably has a thickness of 100 to 300 nm.
[0082]
Further, the laminated polyester film of the present invention is further provided with a protective layer such as diamond-like carbon (DLC) and a fluorine-containing carboxylic acid-based lubricating layer in order on the surface of the ferromagnetic metal thin film layer according to the purpose, application, and necessity. By providing a back coat layer on the surface of the polyester layer B opposite to the magnetic layer by a known method, the output in the short wavelength region, particularly the electromagnetic conversion characteristics such as S / N and C / N are excellent. It is preferably used as a vapor deposition type magnetic recording medium for high density recording with a low dropout and error rate. This vapor deposition type magnetic recording medium is extremely useful as a magnetic tape medium for Hi8 for analog signal recording, digital video cassette recorder (DVC) for digital signal recording, data 8 mm, DDSIV, and particularly excellent when used for digital video tape. It is possible to obtain the results. Further, excellent results can be obtained even for data storage tape applications, which is preferable.
[0083]
In addition, the laminated polyester film of the present invention is made of polyvinyl chloride, vinyl chloride / vinyl acetate on the surface of the polyester layer A, preferably the coating layer C, with iron or iron-like fine magnetic powder (metal powder) mainly composed of iron. Uniformly dispersed in a binder such as a copolymer and coated so that the thickness of the magnetic layer is 1 μm or less, preferably 0.1 to 1 μm, and if necessary, on the surface of the polyester layer B opposite to the magnetic layer By providing a backcoat layer by a known method, it is excellent in electromagnetic conversion characteristics such as output in the short wavelength region, S / N, C / N, etc., and has low dropout and error rate. It can be a magnetic recording medium. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like as an underlayer of the metal powder-containing magnetic layer is dispersed in the same organic binder as the magnetic layer on the surface of the polyester layer A or the coating layer C. It can also be applied. This metal-coated magnetic recording medium includes 8 mm video for recording analog signals, Hi8, β cam SP, W-VHS, digital video cassette recorder (DVC) for recording digital signals, 8 mm data, DDSIV, digital β cam, D2 , D3, SX, etc. are very useful as magnetic tape media.
[0084]
Furthermore, the laminated polyester film of the present invention is made of polyvinyl chloride containing acicular fine magnetic powder such as iron oxide or chromium oxide or plate-like fine magnetic powder such as barium ferrite on the surface of the polyester layer A, preferably the coating layer C. , Uniformly dispersed in a binder such as vinyl chloride / vinyl acetate copolymer, and coated so that the magnetic layer thickness is 1 μm or less, preferably 0.1 to 1 μm. By providing a backcoat layer on the opposite surface using a known method, the output in the short wavelength region, S / N, C / N and other electromagnetic conversion characteristics are excellent, and dropout and error rate are high. An oxide-coated magnetic recording medium for density recording can be obtained. If necessary, a nonmagnetic layer containing fine titanium oxide particles or the like as an underlayer of the oxide powder-containing magnetic layer may be provided on the surface of the polyester layer A or the coating layer C in the same organic binder as the magnetic layer. It can also be dispersed and coated. This oxide-coated magnetic recording medium is useful as an oxide-coated magnetic recording medium for high-density recording, such as a QIC for data streamers for digital signal recording.
[0085]
As described above, the magnetic recording medium of the present invention is formed by applying a solution composed of solid fine particles and a binder to which the various additives are added as necessary on the opposite surface of the magnetic layer forming surface. Although a coat layer may be provided, known solid fine particles, binders, and additives can be used and are not particularly limited. The back coat layer preferably has a thickness of 0.3 to 1.5 μm.
[0086]
The W-VHS is an analog HDTV signal recording VTR, and the DVC is applicable for digital HDTV signal recording. Therefore, it can be said that the laminated polyester film of the present invention is a very useful base film for these HDTV compatible VTR magnetic recording media.
[0087]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these Examples. In the examples and comparative examples, “parts” and “%” are parts by weight and% by weight unless otherwise specified. The physical property values and characteristics in the present invention are each measured and defined by the following methods.
[0088]
(1) Intrinsic viscosity
It is determined from the value measured at 35 ° C. in an orthochlorophenol solvent.
[0089]
(2) Terminal carboxyl group concentration (eq / 10⁶g)
Measured according to A. Conix method. (Makromol. Chem. 26, 226 (1958))
[0090]
(3) Average particle diameter (I) (average particle diameter: 60 nm or more)
Measured using a “CP-50 Centrifugal Particle Size Analyzer” manufactured by Shimadzu Corporation. A particle diameter “equivalent sphere diameter” corresponding to 50 mass percent is read from an integrated curve of particles of each particle diameter calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is calculated as the average particle diameter (nm). ("Particle size measurement technology", published by Nikkan Kogyo Shimbun, 1975, pages 242-247).
[0091]
(4) Average particle diameter (II) (average particle diameter: less than 60 nm)
Particles having an average particle diameter of less than 60 nm that form small protrusions are measured using a light scattering method. That is, the average particle diameter is equal to the “equivalent sphere diameter” of the particles at 50% of the total particles determined by the product name “NICOMP MODEL 270 SUBMICRON PARTICLE SIZER” manufactured by Nicomp Instruments Inc. The diameter (nm).
[0092]
(5) Volume shape factor (f)
A photograph of each particle was taken with a scanning electron microscope at a magnification according to the size used, and an image analysis processor Luzex 500 (manufactured by Nippon Regulator Co., Ltd.) was used to determine the maximum projection surface diameter as the average particle diameter (D ) (Μm) and particle volume (V) (μm^Three) And calculated by the following formula (II).
[0093]
[Expression 2]

[0094]
(6) Thickness of polyester layers A and B, and thickness of the entire film
The thickness of the entire film is measured at 10 points randomly with a micrometer, and the average value is used. Regarding the layer thickness of the polyester layers A and B, the layer thickness of the thin polyester layer is measured by the method described below, and the layer thickness of the thick polyester layer is subtracted from the total thickness of the coating layer and the thin polyester layer. Ask. That is, using a secondary ion mass spectrometer (SIMS), a metal element (M) caused by the highest concentration of particles in a film having a depth of 5,000 nm from the surface layer excluding the coating layer.⁺) And polyester hydrocarbons (C⁺) Concentration ratio (M⁺/ C⁺) Is the particle concentration, and analysis in the thickness direction is performed from the surface to a depth of 5,000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the present invention, the particle concentration may once rise to a stable value 1 and then rise to a stable value 2 or may monotonously decrease. Based on this distribution curve, the former has a depth that gives a particle concentration of (stable value 1 + stable value 2) / 2, and the latter has a depth at which the particle concentration is ½ of the stable value 1. The thickness (μm) of the thin polyester layer is defined as the depth (this depth is deeper than the depth that provides the stable value 1).
The measurement conditions are as follows.
[0095]
(A) Measuring device
Secondary ion mass spectrometer (SIMS); Perkin Elmer Co., Ltd.
(PERKIN ELMER INC.), "6300"
(B) Measurement conditions
Primary ion species: O²⁺
Primary ion acceleration voltage: 12KV
Primary ion current: 200 nA
Raster area: 400 μm
Analysis area: 30% gate
Measuring vacuum: 6.0 × 10^-9Torr
E-GUNN: 0.5KV-3.0A
[0096]
In addition, when the most abundant particles in the range of 5,000 nm from the surface layer are organic polymer particles other than silicone resin, it is difficult to measure by SIMS, so FT-IR (Fourier transform infrared spectroscopy while etching from the surface) ) Depending on the particle, a concentration distribution curve similar to the above is measured by XPS (X-ray photoelectric spectroscopy) or the like to determine the layer thickness (μm).
[0097]
(7) Film layer C thickness
A small piece of film was fixed and molded with an epoxy resin, and an ultrathin section (cut parallel to the film flow direction) having a thickness of about 600 angstroms was prepared with a microtome. This sample is observed with a transmission electron microscope (manufactured by Hitachi, Ltd .: Model H-800), the boundary surface of the coating layer C is searched, and the thickness (nm) of the coating layer is obtained.
[0098]
(8) Surface roughness
▲ 1 ▼ WRa
Using a non-contact three-dimensional roughness meter manufactured by WYKO Co., Ltd., trade name “TOPO-3D”, measurement magnification is 40 times, measurement area is 242 μm × 239 μm (0.058 mm)²) To obtain a surface roughness profile (original data). The center plane average roughness (WRa) defined by the following equation is obtained by surface analysis using the above-described roughness meter built-in software.
[0099]
[Equation 3]

[0100]
Zjk is the height on the three-dimensional roughness chart at the j-th and k-th positions in each direction when the measurement direction (242 μm) and the direction orthogonal to it (239 μm) are divided into M and N, respectively. is there.
[0101]
(2) Ten-point average roughness WRz
From the data obtained by measuring under the same conditions using the same measuring instrument as in (1), surface analysis using the software built in the same roughness meter, 5 points from the highest peak (Hp) and valley (Hv) An average value obtained by taking 5 points from the lower side is obtained and set as WRz.
[0102]
[Expression 4]

[0103]
(9) Young's modulus
Using a tensile tester manufactured by Toyo Baldwin Co., Ltd., trade name “Tensilon”, a sample film having a length of 300 mm and a width of 12.7 mm is 10% / min in a room adjusted to a temperature of 20 ° C. and a humidity of 50%. It pulls with a strain rate and calculates by the following formula (V) using the first linear part of the tensile stress-strain curve.
[0104]
[Equation 5]

[0105]
Here, E is the Young's modulus, Δσ is the stress difference due to the original average cross-sectional area between two points on the straight line, and Δε is the strain difference between the same two points.
[0106]
(10) Windability
After optimizing the winding conditions at the time of slitting, 30 rolls are slit at a speed of 100 m / min with a width of 600 mm × 12,000 m, and a roll without bumps, protrusions or wrinkles is formed on the film surface after the slit. As a good product, the winding property is evaluated according to the following criteria.
A: 28 or more non-defective rolls
○: Number of non-defective rolls 25 to 27
×: Number of non-defective rolls 24 or less
[0107]
(11) Precipitation of foreign matter (held at 150 ° C. for 30 minutes)
The film is left in an oven set at 150 ° C. for 30 minutes, and then the surface on the polyester layer B side is evaporated with Al, and this surface is observed with a differential interference microscope at 950 times. Count the number of foreign substances attached to the surface other than the protrusions due to particles in the polyester, and 1 mm²Convert to per number.
[0108]
(12) Manufacture of magnetic tape and evaluation of characteristics (electromagnetic conversion characteristics)
On the surface of the coating layer C of the laminated polyester film, two layers (each layer thickness of about 0.1 μm) of a ferromagnetic thin film of 100% cobalt are formed to a thickness of 0.2 μm by vacuum deposition. A diamond-like carbon (DLC) film and a fluorine-containing carboxylic acid-based lubricating layer are sequentially provided on the surface of the formed ferromagnetic thin film, and a backcoat layer is provided on the surface of the polyester layer A by a known method. Then, it was slit to 8 mm width and loaded onto a commercially available 8 mm video cassette. Subsequently, the characteristic (C / N) of a tape is measured using the following commercially available apparatus.
[0109]
(A) Equipment used
8mm video tape recorder, manufactured by Sony Corporation, trade name “EDV-6000”
Noise meter manufactured by Shibasoku Co., Ltd.
(B) Measuring method
A signal with a recording wavelength of 0.5 μm (frequency of about 7.4 MHz) is recorded, and the ratio of the 6.4 MHz and 7.4 MHz values of the reproduced signal is defined as the C / N of the tape, and the C of the 8 mm video vapor-deposited tape for video is commercially available. / N is set to 0 dB, and evaluation is performed with a relative value.
[0110]
[Example 1]
To a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol, 0.025 part of manganese acetate tetrahydrate was added as a transesterification catalyst, and the ester exchange reaction was carried out while gradually raising the internal temperature from 150 ° C. When the transesterification reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and after sufficient stirring, 0.8 part of trimellitic anhydride and tetrabutyl in 2.5 parts of ethylene glycol A liquid obtained by reacting 0.65 part of titanate (titanium content: 11% by weight) was added in an amount of 0.014 part. Furthermore, 0.03% of spherical silica (volume shape factor 0.5) having an average particle diameter of 60 nm was added as a lubricant (inert particles A) and sufficiently stirred, and then the reaction product was polymerized into a polymerization reactor. And polycondensation was performed under high temperature vacuum (final internal temperature 295 ° C.) to obtain polyethylene terephthalate (resin A1) for polyester A having an intrinsic viscosity of 0.60.
[0111]
Further, a transesterification reaction was carried out in the same manner as described above. When the transesterification reaction reached 95%, 0.01 part of phosphorous acid was added as a stabilizer, and after sufficient stirring, antimony trioxide was added. 0.03 part was added. After sufficiently distilling water mixed in the system, silicone particles having an average particle diameter of 300 nm and θ-type alumina having an average particle diameter of 100 nm were added as 0.05% and After adding 0.2% and stirring sufficiently, the reaction product is then transferred to a polymerization reactor and subjected to polycondensation under high temperature vacuum (final internal temperature 295 ° C.) to obtain polyethylene terephthalate having an intrinsic viscosity of 0.70. It was. At this time, the remaining amount of antimony in this polymer was 250 ppm.
[0112]
A powder of sorbitan tristearate (melting point 55 ° C.) as an ester wax (partially saponified) composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol was added to 99.7% of the obtained polyethylene terephthalate. 15% was coated and kneaded with a vented biaxial ruder to obtain polyethylene terephthalate (resin B1) for polyester layer B having an intrinsic viscosity of 0.69.
[0113]
The obtained resin A1 and resin B1 were each dried at 170 ° C. for 3 hours, then supplied to two extruders, melted at a melting temperature of 280 to 300 ° C., and highly accurate with a steel wire filter having an average opening of 11 μm. After filtration, the polyester layer B was laminated on one side of the polyester layer A using a multi-manifold type coextrusion die and quenched to obtain an unstretched laminated polyester film having a thickness of 89 μm.
[0114]
The obtained unstretched film was preheated, stretched 3.3 times at a film temperature of 100 ° C. between low-speed and high-speed rolls, and rapidly cooled to obtain a longitudinally stretched film. Next, an aqueous coating solution (total solid concentration: 1.0%) having the following composition (in terms of solid content) was applied to the A layer side of the longitudinally stretched film by a kiss coating method.
[0115]

[0116]
Then, it supplied to the stenter and extended | stretched 4.2 times in the horizontal direction at 110 degreeC. The obtained biaxially stretched film was heat-fixed with hot air of 220 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a total thickness of 6.4 μm and a polyester layer B thickness of 1.0 μm. The thicknesses of the polyester layers A and B of this film were adjusted by the discharge amounts of two extruders. The surface roughness WRa measured from the surface on the film layer C side of this film is 1.7 nm, and the Young's modulus of this film is 5000 N / mm in the longitudinal direction.², Horizontal direction 7000N / mm²Met. Table 1 shows the other characteristics of the laminated film and the characteristics of the ferromagnetic thin film deposition type magnetic tape using the film.
[0117]
[Example 2]
Implementation was performed except that the polyester layer A did not contain particles (resin A2), and the type, average particle size, and addition amount of the inert particles B contained in the polyester layer B were changed as shown in Table 1 (resin B2). A laminated polyester film was obtained in the same manner as in Example 1. Table 1 shows the characteristics of the obtained film and the characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using the film.
[0118]
[Example 3]
A laminated polyester film is obtained in the same manner as in Example 1 except that the intrinsic viscosity of the raw material resin A (resin A3) forming the polyester layer A and the raw material resin B (resin B3) forming the polyester layer B is 0.67. It was. Table 1 shows the characteristics of the obtained film and the characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using the film.
[0119]
[Example 4]
Polyethylene-2,6- for polyester layers A and B in the same manner as in Example 1 except that the same molar amount of dimethyl 2,6-naphthalenedicarboxylate was used instead of dimethyl terephthalate in polyester layer A and polyester layer B. Naphthalate (PEN) (resins A3 and B3) was obtained. Intrinsic viscosities were 0.60 for resin A3 and 0.67 for resin B3.
[0120]
After the resins A3 and B4 were dried at 170 ° C. for 6 hours, the thickness of each layer was adjusted in the same manner as in Example 1 to obtain an unstretched laminated thermoplastic resin film having a thickness of 89 μm.
[0121]
The obtained unstretched film was preheated, stretched 3.6 times at a film temperature of 135 ° C. between low-speed and high-speed rolls, and rapidly cooled to obtain a longitudinally stretched film. Next, on the A layer side of the longitudinally stretched film, the inert particles C are core-shell filler (core: crosslinked polystyrene, shell: polymethyl methacrylate) (average particle size: 30 nm, volume shape factor 0.45) manufactured by JSR Corporation, “ An aqueous coating liquid having the same composition as in Example 1 (total solid content concentration: 1.0%) was applied in the same manner as in Example 1 except that it was changed to “SX 8721”.
[0122]
Then, it supplied to the stenter and extended | stretched 5.7 times in the horizontal direction at 155 degreeC. The obtained biaxially stretched film was heat-fixed with hot air at 200 ° C. for 4 seconds to obtain a laminated biaxially oriented polyester film having a total thickness of 4.4 μm and a thermoplastic resin layer B thickness of 0.6 μm. About the thickness of the thermoplastic resin layers A and B of this film, it adjusted with the discharge amount of two extruders. The surface roughness WRa measured from the surface on the coating layer C side of this film is 1.2 nm, and the Young's modulus of this film is 5500 N / mm in the longitudinal direction.², Lateral direction 10,500 N / mm²Met. Table 1 shows the other characteristics of the laminated film and the characteristics of the ferromagnetic thin film deposition type magnetic tape using the film.
[0123]
[Comparative Example 1]
A laminated polyester film was obtained in the same manner as in Example 1 except that the intrinsic viscosity of the raw material resin B forming the polyester layer B was 0.53. In the obtained film, the frequency of the inactive particles B dropping off from the polyester layer B during film running increased, and many transfers to the opposite surface occurred, or many precipitated oligomers transferred to the opposite surface (deposition surface). When magnetic tape was used, sufficient electromagnetic conversion characteristics could not be obtained. Table 1 shows other characteristics and characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using this film.
[0124]
[Comparative Examples 2 and 3]
A laminated polyester film was obtained in the same manner as in Example 1 except that the type, average particle diameter, and addition amount of the inert particles B contained in the polyester layer B were as shown in Table 1. In the obtained film, the oligomer bleeded out from the B layer was satisfactory and transferred to the opposite surface, but in the case of Comparative Example 2, the degree of shape transfer to the opposite surface of the protrusion on the B layer side was Strongly, when it was made into a magnetic tape, sufficient electromagnetic conversion characteristics could not be obtained. In the case of Comparative Example 3, the B layer was too flat to obtain good winding properties. Table 1 shows other characteristics and characteristics of the ferromagnetic thin film vapor deposition type magnetic tape using this film.
[0125]
[Table 1]

[0126]
As is clear from Table 1, the laminated polyester film according to the present invention is very flat on one side, has little oligomer transfer from the opposite side, exhibits excellent electromagnetic conversion characteristics, and has very good winding properties. . On the other hand, those not satisfying the requirements of the present invention cannot satisfy these characteristics at the same time.
[0127]
【The invention's effect】
According to the present invention, it is possible to obtain a laminated polyester film that is excellent in blocking resistance, flatness, winding property and processability, and particularly excellent in electromagnetic conversion characteristics when used as a metal-deposited thin film type magnetic recording medium.

Claims (12)

Polyester layer A containing 0.001 to 0.2% by weight of inert particles A having an average particle size of 30 to 400 nm, which is substantially free of particles, and the intrinsic viscosity of the polymer laminated on one side of the layer A Is 0.55 or more, the terminal carboxyl group concentration is 36 eq / 10 ⁶ g or more, the average particle diameter is 50 to 1000 nm, and the layer A contains the inert particles A, it is not included in the layer A. Ri Na more the average particle diameter greater than inert particles B of the active particles a and the polyester layer B containing 0.001 wt%, the ten-point average roughness of the polyester layer B surface (WRzB) is 50~200nm der Laminated polyester film.   The laminated polyester film according to claim 1, wherein the inert particles B are at least one particle selected from the group consisting of a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, aluminum oxide, titanium dioxide, silicon dioxide, kaolin and clay. .   The laminated polyester film according to claim 1, wherein the polyester layer B contains (partially saponified) ester wax composed of an aliphatic monocarboxylic acid having 8 or more carbon atoms and a polyhydric alcohol.   The laminated polyester film according to claim 1, wherein the surface roughness (WRaA) of the surface of the polyester layer A is 0.1 to 4 nm.   The laminated polyester film according to claim 1, wherein a film layer C is laminated on the surface of the polyester layer A. The laminated polyester film according to claim 5 , wherein the coating layer C contains 0.5 to 30% by weight of inert particles C having an average particle size of 10 to 50 nm and a volume shape factor of 0.1 to π / 6. The laminated polyester film according to any one of claims 1 to 6 , wherein the film has a thickness of 2 µm or more and less than 8 µm. The polyester of layer A or layer B is polyethylene terephthalate, The laminated polyester film according to any one of claims 1 to 7 . The laminated polyester film according to any one of claims 1 to 7 , wherein the polyester of layer A or layer B is polyethylene-2,6-naphthalate.   The laminated polyester film according to any one of claims 1 to 12, wherein the surface of the polyester layer A or the coating layer C is a surface on which a magnetic layer is provided. The laminated polyester film according to claim 10 , wherein the magnetic layer is a ferromagnetic metal thin film layer. A magnetic recording medium using the laminated polyester film according to claim 10 or 11 as a support.