JP3542905B2 - Biaxially oriented polyester film - Google Patents

Description

【００２３】
ここで、Ｒは前記と同じ。
【００２４】
前記シリコーン樹脂微粒子は従来から知られている製造方法、例えばオルガノトリアルコキシシランを加水分解、縮合する方法（例えば特公昭４０―１４９１７号あるいは特公平２―２２７６７号等）やメチルトリクロロシランを出発原料とするポリメチルシルセスキオキサン微粒子の製造方法（例えばベルギ国特許５７２４１２号）などがに準じて製造することができる。もっとも、本発明においては後述する条件を満足すれば、製造方法を限定するものではなく、如何なる方法で製造されたシリコーン樹脂微粒子を用いても構わない。
【００２５】
前記式［化１〜３］や構造式［化４］におけるＲは炭素数１〜６のアルキル基およびフェニル基から選ばれる少くとも一種である。該アルキル基としては、例えばメチル基、エチル基、プロピル基、ブチル基、ペンチル基、ヘキシル基等を挙げることができる。これらは一種以上であることができる。Ｒが複数の基である、例えばメチル基とエチル基であるとき、メチルトリメトキシシランとエチルトリメトキシシランの混合物を出発原料として製造することで得ることができる。もっとも、製造コストや合成方法の容易さなどを考慮すると、Ｒがメチル基のシリコーン樹脂（ポリメチルシルセスキオキサン）微粒子が好ましい。
【００２６】
前記シリコーン樹脂微粒子Ａは好ましくはその形状が実質的に球状、特に好ましくは真球状であると、滑り性付与に効果的である。
【００２７】
本発明においては、かかるシリコーン樹脂微粒子Ａは、界面活性剤の存在下で重合されていることが好ましい。この方法により、例えばフィルムにした場合、粗大突起の少ない良好な品質を得ることができる。
【００２８】
界面活性剤としては、例えば、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレンソルビタンアルキルエステル、アルキルベンゼンスルホン酸塩等が挙げられ、中でもポリオキシエチレンアルキルフェニルエーテル、アルキルベンゼンスルホン酸塩がシリコーン樹脂微粒子を重合する際に好ましく用いられる。ポリオキシエチレンアルキルフェニルエーテルとしてはノニルフェノールのエチレンオキシド付加物が、アルキルベンゼンスルホン酸塩としてはドデシルベンゼンスルホン酸ナトリウム等が好ましい具体例として挙げられる。
【００２９】
本発明においては、かかるシリコーン樹脂微粒子Ａをシランカップリング剤で表面処理して用いると耐削れ性が更に向上するので好ましい。
【００３０】
シランカップリング剤としては、不飽和結合を有するビニルトリエトキシシラン、ビニルトリクロルシラン、ビニルトリス（β―メトキシエトキシ）シランなど、アミノ系シランのＮ―β（アミノエチル）γ―アミノプロピルメチルジメトキシシラン、Ｎ―β（アミノエチル）γ―アミノプロピルトリメトキシシラン、γ―アミノプロピルトリメトキシシラン、γ―アミノプロピルトリエトキシシラン、Ｎ―フェニル―γ―アミノプロピルトリメトキシシランなど、エポキシ系シランのβ（３，４―エポキシシクロヘキシル）エチルトリメトキシシラン、γ―グリシドキシプロピルトリメトキシシラン、γ―グリシドキシプロピルメチルジエトキシシラン、γ―グリシドキシプロピルトリエトキシシランなど、メタクリレート系シランのγ―メタクリロキシプロピルメチルジメトキシシラン、γ―メタクリロキシプロピルトリメトキシシラン、γ―メタクリロキシプロピルメチルジエトキシシラン、γ―メタクリロキシプロピルトリエトキシシランなど、更にはγ―メルカプトプロピルトリメトキシシラン、γ―クロロプロピルトリメトキシシランなどが例示される。これらの中、エポキシ系シランカップリング剤が取り扱い易さ、ポリエステルへ添加したときの色の付き難さや耐削れ性の効果が大きいことなどから好ましい。
【００３１】
また、シランカップリング剤による表面処理は合成直後のシリコーン樹脂微粒子スラリー（水スラリー又は有機溶媒スラリー）を濾過又は遠心分離機などで処理してシリコーン樹脂微粒子を分離した後、乾燥前にシランカップリング剤を分散させた水又は有機溶媒で再度スラリー化し、加熱処理後再度微粒子を分離し、次いで分離微粒子を乾燥し、シランカップリング剤の種類によっては更に熱処理を施す方法が実用的で好ましいが、一旦乾燥されたシリコーン樹脂微粒子を同様の方法で再度スラリー化処理しても良い。
【００３２】
以下、シリコーン樹脂微粒子の製造例を示す。
撹拌翼付きの１０リットルのガラス容器に０．０６重量％の水酸化ナトリウムを含む水溶液７０００ｇを張込み、上層へノニルフェノールのエチレンオキシド付加物０．０１％を含む１０００ｇのメチルトリメトキシシランを静かに注入し、２層を形成したのち、１０〜１５℃でわずかに回転させながら２時間界面反応させ、球状粒子を生成させる。その後、系内の温度を７０℃として約１時間熟成させ、冷却後、減圧濾過機で濾過し、水分率約４０％のシリコーン樹脂微粒子のケーク状物を得る。次に別のガラス容器に、シランカップリング剤としてγ―グリシドキシプロピルトリメトキシシランを２重量％分散させた水溶液４０００ｇを張込み、そこへ先の反応で得られたケーク状物を全量加えスラリー化し、内温７０℃、撹拌下３時間かけて表面処理を行い、冷却後、減圧濾過機で濾過処理し、ケーク状物を得る。続いて、このケーク状物を純水６００ｇに全量加えて再度スラリー化し、常温で１時間撹拌し、その後再度減圧濾過機にて濾過処理することにより、余分の乳化剤およびシランカップリング剤が除去された水分率約４０％のケーク状物を得ることができる。最後に、このケーク状物を、１００℃で１５ｔｏｒｒにて１０時間減圧処理し、凝集粒子の少ないシリコーン樹脂微粒子粉末約４００ｇを得る。
【００３３】
得られる該微粒子は粒子形状は真球状であり、更に先に示した遠心沈降法で求めた粒度分布は狭いものである。
【００３４】
本発明において好ましく用いられるシランカップリング剤で表面処理されたシリコーン樹脂微粒子Ａが白粉などの発生を防止し、耐削れ性を向上させるメカニズムは、一つはシリコーン樹脂微粒子Ａ中の、たとえば出発原料成分や、原料の一つであるオルガノトリアルコキシシランの加水分解物などの未反応物、あるいはシリコーン樹脂中の末端シラノール基などがシランカップリング剤と化学的に結合することにより安定化することで、未処理の状態で発生していたこれらの物質のフィルム表面への偏折あるいは逃散などの作用を防止すること、更には、粒子へのシランカップリング剤の吸着により、もともとポリエステルとの親和性に劣ると見られるシリコーン樹脂微粒子の親和性が向上し、削れによる微粒子の脱落や、微粒子周辺のポリエステルの削れ粉などの白粉の発生が押さえられるためではないかと思われる。
【００３５】
本発明におけるシリコーン樹脂微粒子Ａの平均粒径は０．８〜２．０μｍであり、好ましくは０．８〜１．６μｍである。この平均粒径が０．８μｍ未満では滑り性や巻き取り性の向上効果が小さく、一方２．０μｍを超えると磁気記録媒体用途においては、耐削れ性の悪化やフィルム表面粗面化による電磁変換特性の悪化が起こり、また、コンデンサー用途においてはスペースファクターの増大や絶縁欠陥の増加が起こるため好ましくない。
【００３６】
また、本発明におけるシリコーン樹脂微粒子Ａは、粒子の見掛けのヤング率が１０〜１００ｋｇ／ｍｍ²であるものが好ましく、更に好ましくは１０〜５０ｋｇ／ｍｍ²である。見掛けのヤング率が１０ｋｇ／ｍｍ²未満であると、フィルム中に粒子を添加した場合、延伸時の応力に耐え切れず粒子が変形してしまい、滑り性や巻き取り性付与に必要な高い突起が形成しにくくなる。他方見掛けのヤング率が１００ｋｇ／ｍｍ²を超えると、粒子が硬くなりすぎて耐衝撃性が悪くなり、粒子が脱落しやすくなるため、耐削れ性の悪化や、コンデンサーとしたときの絶縁破壊電圧の低下が起こる。
【００３７】
本発明におけるシリコーン樹脂微粒子Ａの含有量は０．０００１〜０．０３重量％、好ましくは０．０００１〜０．０２重量％、更に好ましくは０．０００１〜０．０１重量％である。この含有量が少なすぎると削り性、巻き取り性が悪化し、一方含有量が多すぎるとフィルム表面が粗くなり、磁気記録媒体用途における電磁変換特性の悪化や、耐削れ性の悪化が起こり、またコンデンサー用途におけるスペースファクターの増大や絶縁破壊電圧の低下が起こるので好ましくない。
【００３８】
本発明において、ポリエステル中に含有させる不活性微粒子Ｂは、前記シリコーン樹脂微粒子Ａの平均粒径よりも小さな平均粒径を有する粒子である必要がある。不活性微粒子Ｂの平均粒径がシリコーン樹脂微粒子Ａの平均粒径に対して、同等以上であると、シリコーン樹脂微粒子Ａを含有する効果が低減し、耐削れ性が悪化する。
【００３９】
この不活性微粒子Ｂの平均粒径は、０．１〜１．２μｍの範囲、より好ましくは０．１〜０．８μｍの範囲であると、滑り性、耐削れ性に対する向上効果が大きいので好ましい。
【００４０】
不活性微粒子Ｂの種類としては、シリコーン樹脂微粒子Ａと同じ種類のものでも使用できるが、シリコーン樹脂微粒子ａとは異なる機能を付与できるという点で、シリコーン樹脂微粒子Ａとは異なる種類の粒子であることが好ましい。
【００４１】
不活性微粒子Ｂの種類としては、例えば（１）二酸化ケイ素（水和物、ケイ砂、石英等を含む）；（２）各種結晶形態のアルミナ；（３）ＳｉＯ₂分を３０重量％以上含有するケイ酸塩（例えば非晶質あるいは結晶質の粘土鉱物、アルミノシリケート（焼成物や水和物を含む）、温石綿、ジルコン、フライアッシュ等）；（４）Ｍｇ、Ｚｎ、Ｚｒ、及びＴｉの酸化物；（５）Ｃａ、及びＢａの硫酸塩；（６）Ｌｉ、Ｂａ、及びＣａのリン酸塩（１水素塩や２水素塩を含む）：（７）Ｌｉ、Ｎａ、及びＫの安息香酸塩；（８）Ｃａ、Ｂａ、Ｚｎ、及びＭｎのテレフタル酸塩；（９）Ｍｇ、Ｃａ、Ｂａ、Ｚｎ、Ｃｄ、Ｐｂ、Ｓｒ、Ｍｎ、Ｆｅ、Ｃｏ、及びＮｉのチタン酸塩；（１０）Ｂａ、及びＰｂのクロム酸塩；（１１）炭素（例えばカーボンブラック、グラファイト等）；（１２）ガラス（例えばガラス粉、ガラスビーズ等）；（１３）Ｃａ、及びＭｇの炭酸塩；（１４）ホタル石；（１５）スピネル型酸化物等が挙げられるが、良好な滑り性、耐削れ性が得られるという点で炭酸カルシウム、球状シリカであることが好ましい。
【００４２】
本発明において、不活性微粒子Ｂの含有量は０．０５〜１．０重量％である必要がある。この含有量が０．０５重量％未満では滑り性が悪化し、一方１．０重量％を超えると耐削れ性が悪化する。この含有量は、好ましくは０．１〜０．６重量%であり、さらに好ましくは０．２〜０．４重量%である。
【００４３】
本発明の二軸配向ポリエステルフィルムはフィルム表面の中心線平均粗さＲａが０．０１〜０．１μｍであることが好ましい。この中心線平均粗さＲａが０．０１μｍ未満では、表面が平坦すぎるため、滑り性、巻き取り性に対する改善効果が小さく、他方０．１μｍより大きいと、磁気記録媒体用途においては耐削れ性、電磁変換特性の悪化が、コンデンサー用途においてはスペースファクターの増大、絶縁破壊電圧の低下が起こりやすくなる。更に本発明の二軸配向ポリエステルフィルムを磁気記録媒体用ベースフィルムとして使用する場合、この中心線平均粗さＲａが０．０１〜０．０２５μｍの範囲であると、電磁変換特性の改善効果が大きく、高密度磁気記録媒体としての使用にも耐えるのでより一層好ましい。
【００４４】
本発明の二軸配向ポリエステルフィルムはフィルム表面の三次元十点平均粗さＳＲｚが０．２５〜１．２μｍであることが好ましい。この三次元十点平均粗さＳＲｚが０．２５μｍ未満では滑り性、巻き取り性に対する改善効果が小さく、他方１．２μｍより大きいと磁気記録媒体用途においては耐削れ性、電磁変換特性の悪化が、コンデンサー用途においては、スペースファクターの増大、絶縁破壊電圧の低下が起こりやすくなる。
【００４５】
更に、本発明の二軸配向ポリエステルフィルムを磁気記録媒体のベースフィルムとして使用する場合、この三次元十点平均粗さＳＲｚが０．２５〜０．８μｍの範囲であると、ドロップアウトの低減効果、電磁変換特性の改善効果が大きく、高密度磁気記録媒体用としての使用にも耐え得るので、より一層好ましい。
【００４６】
また、本発明の二軸配向ポリエステルフィルムは、磁気記録媒体用として使用する場合、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、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、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。
【００４７】
本発明の二軸配向ポリエステルフィルムをコンデンサー用として使用する場合、そのスペースファクターが３〜２３％であることが好ましい。
【００４８】
スペースファクターとは、試料フィルム１００ｃｍ²の重量ｗ（ｇ）と、密度ｄ（ｃｍ³／ｇ）から求めた重量法厚みをｔ₁（μｍ）、１００ｃｍ角の試料フィルムを１０枚重ね、マイクロメーターを用いて求めた試料フィルム１枚分の厚みをｔ₂（μｍ）としたとき、下記式より算出される値である。
【００４９】
【数１】
スペースファクターＦ（％）＝１００−ｔ₁／ｔ₂×１００
【００５０】
このスペースファクターが３％未満では、フィルムの滑り性、作業性（ハンドリング性）が不充分であり、一方２３％を超えると、体積当りのコンデンサー容量が低くコンデンサーの小型容量化に不適であるため好ましくない。
【００５１】
また、本発明の二軸配向ポリエステルフィルムをコンデンサー用として使用する場合、電気絶縁材料であるという観点から絶縁破壊電圧（ＢＤＶ）は２００Ｖ／μｍ以上であることが好ましい。
【００５２】
更に、本発明の二軸配向ポリエステルフィルムをコンデンサー用として使用する場合、フィルムのＣＲ値（絶縁抵抗）は１０００ΩＦ以上であることが好ましい。ＣＲ値が１０００ΩＦ未満では、フィルムの絶縁抵抗が不足し、電気絶縁材料として不適となることがある。
【００５３】
本発明の二軸配向ポリエステルフィルムは、その厚みが０．５〜２５μｍの範囲であると、磁気記録媒体用途からコンデンサー用途まで幅広く使用し得るので好ましいが、コンデンサー用として用いる場合、厚みがより好ましくは０．５〜１０μｍ、特に好ましくは０．５〜５μｍであると、コンデンサーとしたときの小型化が図りやすいのでより一層好ましい。
【００５４】
本発明の二軸配向ポリエステルフィルムは、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、先ず未延伸フィルムを製造し、次いで該フィルムを二軸配向させることで得ることができる。未延伸フィルムは、例えば、融点（Ｔｍ：℃）〜（Ｔｍ＋７０）℃の温度でポリエステルをフィルム状に溶融押出し、急冷固化して固有粘度０．３５〜０．９ｄｌ／ｇの未延伸フィルムとして得ることができる。
【００５５】
この未延伸フィルムは、更に従来から蓄積された二軸配向フィルムの製造法に準じて、二軸配向フィルムとすることができる。例えば、未延伸フィルムを一軸方向（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２．５〜７．０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２．５〜７．０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１２〜３２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良い。更に、二軸配向フィルムは、（Ｔｇ＋７０）℃〜Ｔｍ（℃）の温度で熱固定することができる。例えばポリエチレンテレフタレートフィルムについては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。
【００５６】
本発明の二軸配向ポリエステルフィルムは特定のシリコーン樹脂微粒子とシリコーン樹脂微粒子より小さな平均粒径を有する他の不活性粒子を組み合わせて含有することで、各粒子の優れた特性による効果が相乗的に発現されるため、粗大突起が極めて少なく、滑り性、巻き取り性、耐削れ性に特に優れ、磁気記録媒体用及びコンデンサー用として極めて有用な二軸配向ポリエステルフィルムである。
【００５７】
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測定されたものであり、かつ定義される。
【００５８】
（１）粒子の平均粒径
（ｉ）粒体から平均粒径を求める場合
島津製作所製ＣＰ―５０型セントリフュグル パーティクル サイズ アナライザー（Centrifugal Particle Size Analyzer）を用いて得られる遠心沈降曲線を基に算出した粒径とその粒径を有する粒子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（単行本「粒度測定技術」日刊工業新聞社発行、１９７５年、頁２４２〜２４７参照）。
【００５９】
（ii）フィルム中の粒子の場合
試料フィルム小片を走査型電子顕微鏡用試料台に固定し、日本電子（株）製スパッターリング装置（ＪＦＣ―１１００型イオンエッチング装置）を用いてフィルム表面に下記条件にてイオンエッチング処理を施す。条件は、ベルジャー内に試料を設置し、約１０^-3Ｔｏｒｒの真空状態まで真空度を上げ、電圧０．２５ｋＶ、電流１２．５ｍＡにて約１０分間イオンエッチングを実施する。更に同装置にて、フィルム表面に金スパッターを施し、走査型電子顕微鏡にて５０，０００〜１０，０００倍で観察し、日本レギュレーター（株）製ルーゼックス５００にて少なくとも１００個の粒子の等価球径分布を求め、その重量積算５０％の点より算出する。
【００６０】
（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。
【００６１】
【数２】
Ｙ＝２．８Ｐ／πｄＺ
【００６２】
（３）フィルムの表面粗さ（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】
（４）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４２μｍ、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本の条件にてフィ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。
【００６４】
（５）カレンダー削れ性
ベースフィ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℃、フィルムにかかる線圧は２００ｋｇ／ｃｍ、フィルムスピードは１００ｍ／分で走行させる。走行フィルムを全長４０００ｍ走行させた時点で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ィルムの削れ性を評価する。
＜５段階判定＞
１級：ナイロンロールの汚れ全くなし
２級：ナイロンロールの汚れほとんどなし
３級：ナイロンロールの汚れ少しあるが、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】
（６）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ィルムにブレード（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。フィルムが１００ｍ走行した後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１．０ｍｍ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】
（７）高速走行削れ性
図１に示した装置を用いて下記のようにして測定する。
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。
【００６７】
温度２０℃、湿度６０％の環境で、巾１／２インチに裁断したフィルムを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に付着した削れ粉を評価する。
【００６８】
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。
＜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
【００６９】
（８）低速繰り返し走行摩擦係数（μｋ）
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）をフィルムが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。
【００７０】
【数３】

【００７１】
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。
【００７２】
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。
【００７３】
なお、磁気テープの製造法は次のとおり行なう。
γ―Ｆｅ₂Ｏ₃１００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。
ポリエステルウレタン １２部
塩化ビニル―酢酸ビニル―
無水マレイン酸共重合体 １０部
α―アルミナ ５部
カーボンブラック １部
酢酸ブチル ７０部
メチルエチルケトン ３５部
シクロヘキサノン １００部
分散後更に
脂肪酸：オレイン酸 １部
脂肪酸：パルミチン酸 １部
脂肪酸エステル（アミルステアレート） １部
を添加してから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製する。
【００７４】
得られる塗布液をポリエステルフィルム上に乾燥膜厚が２．５μｍとなるように塗布する。
【００７５】
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。
【００７６】
（９）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インチのフィルムを通し、温度２０℃、湿度６０％の環境において、入口テンションＴ₁が５０ｇとなるように調整し、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。
【００７７】
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。
【００７８】
【数４】

【００７９】
ここでｔ：測定時間（秒）
ｘ：端面変動量（μｍ）
である。
【００８０】
（１０）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、入口テンションＴ₁が６０ｇとなるように調整して、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
【００８１】
（１１）粗大突起数
フィルム表面にアルミニウムを蒸着し、二光束干渉顕微鏡を用いて観察し、測定波長０．５４μｍで３次以上の干渉縞を示す突起を粗大突起とし、測定面積５ｃｍ²中の粗大突起数を１ｃｍ²当たりの数に換算する。この測定を５回行ない、その平均値を粗大突起数として評価する。
【００８２】
（１２）ドロップアウト
磁気テープ（１／２インチ巾）を市販のドロップアウトカウンター（例えばシバソクＶＨ０１ＢＺ型）にて５μｓｅｃ×１０ｄＢのドロップアウトをカウントし、１分間のカウント数を算出する。
【００８３】
（１３）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５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。
【００８４】
（１４）スペースファクター（Ｆ）
試料１００ｃｍ²のフィルム重量ｗ（ｇ）と、密度ｄ（ｃｍ³／ｇ）から求めた重量法厚みをｔ₁（μｍ）、１０ｃｍ角の試料フィルムを１０枚重ね、マイクロメーターを用いて求めた試料フィルム１枚分の厚みをｔ₂（μｍ）としたとき、下記式より算出する。
【００８５】
【数５】
スペースファクターＦ（％）＝１００−ｔ₁／ｔ₂×１００
【００８６】
（１５）絶縁破壊電圧（ＢＤＶ）
ＪＩＳ Ｃ ２３１８に示す方法に従って測定し、ｎ＝１００の平均値を絶縁破壊電圧（ＢＤＶ）とする。
【００８７】
（１６）ＣＲ値
試料フィルムを、２３℃、５０％ＲＨ、１６時間の条件で状態調節した後、２３℃、５０％ＲＨの雰囲気下で、ＪＩＳ Ｃ ２３１９に示す方法に従って測定する。
【００８８】
（１７）摩擦係数
ＡＳＴＭ Ｄ１８９４に従い測定する。
【００８９】
（１８）巻姿（２）
試料フィルムを、幅５００ｍｍ、長さ５０００ｍ巻き取った時の巻姿を観察して下記の基準で評価する。
○：巻姿がきれいで、表面のしわ、巻きずれ等が肉眼で確認できないもの。
×：巻姿が不良で、表面にしわ、巻きずれ等が肉眼で確認できるもの。
【００９０】
【実施例】
以下、実施例をあげて本発明をさらに説明する。
【００９１】
［実施例１〜４、比較例１３、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に示す添加粒子を表１に示す添加量で添加して、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のポリエチレンテレフタレートを得た。
【００９２】
このポリエチレンテレフタレートのペレットを１７０℃、３時間乾燥後押出機ホッパーに供給し、溶融温度２８０〜３００℃で溶融し、この溶融ポリマーを１ｍｍのスリット状ダイを通して表面仕上げ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の未延伸フィルムを得た。
【００９３】
このようにして得られた未延伸フィルムを７５℃にて予熱し、更に低速、高速のロール間で１５ｍｍ上方より６００℃の表面温度のＩＲヒーター３本にて加熱して３．５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４．５倍に延伸した。得られた二軸配向フィルムを２０５℃の温度で５秒間熱固定し、厚み１４μｍの熱固定二軸配向ポリエステルフィルムを得た。
【００９４】
得られたフィルムの磁気記録媒体用ベースフィルムとしての特性を表２に示す。
【００９５】
【表１】

【００９６】
【表２】

【００９７】
［実施例６〜７、比較例９〜１２］
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３に示す添加粒子を表３に示す添加量で添加して、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のポリエチレンテレフタレートを得た。
【００９８】
このポリエチレンテレフタレートのペレットを１７０℃、３時間乾燥後押出機ホッパーに供給し、溶融温度２８０〜３００℃で溶融し、この溶融ポリマーを１ｍｍのスリット状ダイを通して表面仕上げ０．３ｓ程度、表面温度２０℃の回転冷却ドラム上に押出し、比較例１０は厚み２０μｍの、それ以外は厚み３５μｍの未延伸フィルムを得た。
【００９９】
このようにして得られた未延伸フィルムを７５℃にて予熱し、更に低速、高速のロール間で１５ｍｍ上方より６００℃の表面温度のＩＲヒーター１本にて加熱して３．６倍に延伸し、急冷し、続いてステンターに供給し、１０５℃にて横方向に４．０倍に延伸した。得られた二軸配向フィルムを２０５℃の温度で５秒間熱固定し、比較例１０は厚み１．５μｍの、それ以外は厚み２．５μｍの熱固定二軸配向ポリエステルフィルムを得た。得られたフィルムのコンデンサー用ベースフィルムとしての特性を表４に示す。
【０１００】
本発明によるものは、表２から明らかなように粗大突起が極めて少なく、ドロップアウト、電磁変換特性に優れ、かつ滑り性、巻き取り性、耐削れ性にも優れ、磁気記録媒体用として優れた特性を示している。また、表４から明らかなように、各コンデンサー特性に優れ、かつ滑り性、巻き取り性にも優れ、コンデンサー用としても優れた特性を示している。
【０１０１】
【表３】

【０１０２】
【表４】

【０１０３】
【発明の効果】
本発明の二軸配向ポリエステルフィルムは粗大突起が極めて少なく、良好な滑り性、巻き取り性、耐削れ性を有し、特に電磁記録媒体用及びコンデンサー用のベースフィルムとして適した特性を持ち合わせたものである。
【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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a biaxially oriented polyester film, and more particularly, to a biaxially oriented polyester film which has very few coarse protrusions, is excellent in slipperiness, windability, and abrasion resistance, and is particularly useful for magnetic recording media and capacitors.
[0002]
[Prior art]
BACKGROUND ART Biaxially oriented polyester films represented by polyethylene terephthalate films have been used for various applications, particularly for magnetic recording media and capacitors, because of their excellent physical and chemical properties.
[0003]
In a biaxially oriented polyester film, its slipperiness and abrasion resistance are major factors that affect the workability of the film manufacturing process and processing process, and further, the product quality. If these are insufficient, for example, when a magnetic layer is applied to the surface of a biaxially oriented polyester film and used as a magnetic tape, friction and wear between the coating roll and the film surface are severe, and wrinkles and scratches on the film surface are likely to occur. Also, when used for VTRs and data cartridges, friction occurs between many guides, reproducing heads, etc. during pulling out, winding up and other operations from cassettes, etc., causing scratches, distortion, and base film. The generation of white powder due to surface shaving or the like often causes dropout.
[0004]
Many studies have been made on these problems, and among them, the method of adding silicone resin fine particles (for example, Japanese Patent Application Laid-Open No. 62-172131) has a large improvement effect, and is expected to develop as a technology in the future.
[0005]
However, even in such a method, a high-speed processing for improving productivity such as a magnetic layer coating or a calendering step in a recent video tape manufacturing process, a high-speed dubbing of a soft tape, and a repetitive running / rewinding are also mentioned. Problems such as an increase in the amount of white powder generated under severe conditions have been newly pointed out.
[0006]
In addition, the conventional silicone resin fine particles include coarse particles and aggregated particles. For example, when used for a base film that requires higher electromagnetic conversion characteristics, coarse protrusions called fly specs are generated and dropouts occur. Therefore, improvement was desired.
[0007]
On the other hand, in capacitor applications, with the recent demand for miniaturization of electric or electronic circuits, quality requirements for capacitors have been reduced in size and capacity, and the thin film, which is the base dielectric material, must also be formed. Is being promoted. In a film capacitor, the reason why a film as a dielectric is made thinner is that (a) the capacitance of the capacitor is proportional to the area of the dielectric electrode of the dielectric material, and (b) it is inversely proportional to the film thickness. Since the capacitance per unit volume of the dielectric and the dielectric material is inversely proportional to the square of the film thickness and proportional to the dielectric constant, as long as a dielectric material having the same dielectric constant is used, the capacitor can be reduced in size or increased in capacitance. This is because it is indispensable to reduce the film thickness in order to achieve this.
[0008]
Although there is a need to make such a film thinner, simply reducing the thickness of a conventional stretched film has the following problems. For example, as the film becomes thinner, there is a problem that workability in the process of depositing an electrode on the film or in the process of slitting, winding the element, and the like deteriorates.
[0009]
This workability relates to the slipperiness of the film, and in order to improve the slipperiness, a method of giving minute irregularities to the film surface of a thermoplastic resin film is generally known. Examples of such a method include adding inert particles during or after polymerization of a thermoplastic polymer that is a raw material of a film (external particle addition method), or a part of a catalyst or the like used at the time of polymerization of a thermoplastic polymer. Alternatively, a technique of precipitating the whole in a polymer in a reaction step (internal particle precipitation method) is known.
[0010]
However, in the method for producing an ultra-thin film, when the polymer added with the same concentration of inert fine particles is thinned, the number of inert fine particles per unit area decreases, and the distance between the fine particles on the film surface increases, There is a tendency that the film surface is flattened and slipperiness is reduced. Therefore, in order to compensate for the decrease in slipperiness due to thinning, it is necessary to increase the concentration of added inert fine particles or increase the particle size as the film thickness becomes thinner.
[0011]
In this case, due to poor affinity between the inert fine particles and the thermoplastic polymer, particularly during melt extrusion or drawing with a high draft ratio, voids frequently occur around the interface, that is, around the inert fine particles, As a result of the generation of voids, not only the mechanical properties (e.g., breaking strength, elongation at break) of the obtained film are remarkably reduced and the breakdown voltage is lowered, but also the film is liable to be broken when producing the film. As a result, there have been problems that the productivity is lowered and the stability of the manufacturing conditions is lacking.
[0012]
[Problems to be solved by the invention]
The present inventors have intensively studied to solve such a problem, and as a result, when a specific silicone resin fine particle and other inert particles are combined and contained in a polyester film, the above problem can be solved, and The present inventors have found that a biaxially oriented polyester film suitable for a capacitor can be obtained, and have reached the present invention.
[0013]
[Means for Solving the Problems]
That is, according to the present invention, the silicone resin fine particles A having an average particle size of 0.8 to 2.0 μm, of which 80% by weight or more is composed of a bonding unit represented by the following formula, is 0.0001 to0.02% by weightContainsSilicone resin fine particles A are polymerized in the presence of a surfactant, wherein the surfactant is polyoxyethylene alkylphenyl ether and / or sodium dodecylbenzenesulfonate,And inert fine particles B having an average particle size smaller than the silicone resin fine particles A.0.1-0.6It is a biaxially oriented polyester film characterized by containing by weight.
[0014]
Embedded image
RSiO_3/2
(Here, R is at least one selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group.)
[0015]
The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film-forming properties, especially film-forming properties by melt molding. Examples of the aromatic dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, biphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid And the like. Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, and 1,4-cyclohexanedimethanol. And alicyclic diols as described above.
[0016]
In the present invention, polyesters containing alkylene terephthalate and / or alkylene naphthalate as a main component are preferably used.
[0017]
Among such polyesters, in particular, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, terephthalic acid and / or 2,6-naphthalenedicarboxylic acid account for at least 80 mol% of all dicarboxylic acid components, and all glycol components Is preferably a copolymer in which 80 mol% or more of ethylene glycol is ethylene glycol. At this time, 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. Acids and alicyclic dicarboxylic acids such as cyclohexane-1,4-dicarboxylic acid can be used. In addition, 20 mol% or less of the total glycol component can be the above-mentioned glycol other than ethylene glycol. For example, aromatic diols such as hydroquinone, resorcin, 2,2-bis (4-hydroxyphenyl) propane, Aliphatic diols having an aromatic ring such as 4-dihydroxydimethylbenzene, and polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol can also be used.
[0018]
In the polyester of the present invention, for example, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid or an aliphatic oxyacid such as ω-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. And those which are copolymerized or bonded in an amount of 20 mol% or less based on the total amount.
[0019]
The silicone resin fine particles A contained in the polyester in the present invention have the following formula:
[0020]
Embedded image
RSiO_3/2
(Here, R is at least one selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group.)
Are particles of a silicone resin having a bonding unit of 80% by weight or more.
[0021]
The bonding unit has the following structural formula.
[0022]
Embedded image

[0023]
Here, R is the same as above.
[0024]
The silicone resin fine particles can be prepared by a conventionally known production method, for example, a method of hydrolyzing and condensing an organotrialkoxysilane (for example, Japanese Patent Publication No. 40-917 or Japanese Patent Publication No. 2-22767) or a starting material such as methyltrichlorosilane. (Eg, Belgian Patent No. 572412) according to the method for producing polymethylsilsesquioxane fine particles described below. However, in the present invention, the production method is not limited as long as the following conditions are satisfied, and silicone resin fine particles produced by any method may be used.
[0025]
R in the formulas [Chemical Formulas 1 to 3] and the structural formula [Chemical Formula 4] is at least one kind selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. These can be one or more. When R is a plurality of groups, for example, a methyl group and an ethyl group, it can be obtained by producing a mixture of methyltrimethoxysilane and ethyltrimethoxysilane as a starting material. However, in consideration of the production cost and the ease of the synthesis method, silicone resin (polymethylsilsesquioxane) fine particles in which R is a methyl group are preferable.
[0026]
Preferably, the silicone resin fine particles A have a substantially spherical shape, particularly preferably a true spherical shape, so as to be effective in imparting slipperiness.
[0027]
In the present invention, such silicone resin fine particles A are preferably polymerized in the presence of a surfactant. By this method, for example, when a film is formed, good quality with few coarse protrusions can be obtained.
[0028]
Examples of the surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene sorbitan alkyl ester, and alkyl benzene sulfonate. It is preferably used when polymerizing silicone resin fine particles. Preferred specific examples of the polyoxyethylene alkylphenyl ether include an ethylene oxide adduct of nonylphenol, and examples of the alkylbenzenesulfonate include sodium dodecylbenzenesulfonate.
[0029]
In the present invention, it is preferable to use the silicone resin fine particles A after being surface-treated with a silane coupling agent, since the abrasion resistance is further improved.
[0030]
Examples of the silane coupling agent include N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane of an amino silane such as vinyltriethoxysilane, vinyltrichlorosilane, and vinyltris (β-methoxyethoxy) silane having an unsaturated bond; N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, etc. 3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, etc. Methacrylic Xypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, etc., and further γ-mercaptopropyltrimethoxysilane, γ-chloropropyltri Methoxysilane and the like are exemplified. Of these, epoxy silane coupling agents are preferred because they are easy to handle, hardly colored when added to polyester, and have a great effect on abrasion resistance.
[0031]
The surface treatment with a silane coupling agent is performed by filtering or centrifuging a silicone resin fine particle slurry (water slurry or organic solvent slurry) immediately after synthesis to separate the silicone resin fine particles and then drying the silane coupling before drying. The slurry is again slurried with water or an organic solvent in which the agent is dispersed, the fine particles are separated again after the heat treatment, then the separated fine particles are dried, and depending on the type of the silane coupling agent, a method of further performing a heat treatment is practical and preferable. The once dried silicone resin fine particles may be re-slurried by the same method.
[0032]
Hereinafter, production examples of silicone resin fine particles will be described.
7000 g of an aqueous solution containing 0.06% by weight of sodium hydroxide is placed in a 10-liter glass container equipped with a stirring blade, and 1,000 g of methyltrimethoxysilane containing 0.01% of ethylene oxide adduct of nonylphenol is gently poured into the upper layer. Then, after forming two layers, an interfacial reaction is performed for 2 hours while slightly rotating at 10 to 15 ° C. to generate spherical particles. Thereafter, the system is aged at an internal temperature of 70 ° C. for about 1 hour, cooled, and filtered with a reduced pressure filter to obtain a cake of silicone resin fine particles having a moisture content of about 40%. Next, 4000 g of an aqueous solution in which 2% by weight of γ-glycidoxypropyltrimethoxysilane was dispersed as a silane coupling agent was poured into another glass container, and the entire cake obtained by the previous reaction was added thereto. The slurry is slurried, subjected to a surface treatment over 3 hours with stirring at an internal temperature of 70 ° C., cooled, and then filtered with a reduced pressure filter to obtain a cake. Subsequently, the entire cake-like substance was added to 600 g of pure water to form a slurry again, stirred at room temperature for 1 hour, and then filtered again with a reduced pressure filter to remove excess emulsifier and silane coupling agent. A cake having a moisture content of about 40% can be obtained. Finally, the cake-like substance is subjected to a reduced pressure treatment at 100 ° C. and 15 torr for 10 hours to obtain about 400 g of silicone resin fine particle powder having few aggregated particles.
[0033]
The obtained fine particles have a true spherical shape, and the particle size distribution obtained by the centrifugal sedimentation method described above is narrow.
[0034]
The mechanism by which the silicone resin fine particles A surface-treated with the silane coupling agent preferably used in the present invention prevents the generation of white powder and the like and improves the abrasion resistance is based on one of the mechanisms in the silicone resin fine particles A, such as the starting material. The components and unreacted substances such as the hydrolyzate of organotrialkoxysilane, which is one of the raw materials, or the terminal silanol groups in the silicone resin are stabilized by being chemically bonded to the silane coupling agent. Prevents the action of these substances, which have occurred in the untreated state, such as folding or escape to the film surface, and furthermore, by adsorbing the silane coupling agent to the particles, the affinity with the polyester originally. The affinity of the fine particles of silicone resin, which is considered to be inferior, is improved. White powder generation, such as abrasion dust of the ester is thought whether not to be pressing.
[0035]
The average particle size of the silicone resin fine particles A in the present invention is 0.8 to 2.0 μm, preferably 0.8 to 1.6 μm. When the average particle size is less than 0.8 μm, the effect of improving the slipperiness and the winding property is small. On the other hand, when the average particle size is more than 2.0 μm, the electromagnetic conversion due to the deterioration of the abrasion resistance and the roughening of the film surface in magnetic recording medium applications. Deterioration of characteristics occurs, and it is not preferable for use in capacitors because a space factor and insulation defects increase.
[0036]
Further, the silicone resin fine particles A in the present invention have an apparent Young's modulus of the particles of 10 to 100 kg / mm.^TwoAnd more preferably 10 to 50 kg / mm^TwoIt is. Apparent Young's modulus is 10kg / mm^TwoWhen the particle size is less than the above, when the particles are added to the film, the particles cannot withstand the stress at the time of stretching, and the particles are deformed, so that it is difficult to form high projections necessary for imparting the slipperiness and the winding property. On the other hand, the apparent Young's modulus is 100 kg / mm^TwoIf it exceeds, the particles become too hard and the impact resistance deteriorates, and the particles easily fall off, resulting in deterioration of the abrasion resistance and a decrease in the dielectric breakdown voltage of a capacitor.
[0037]
The content of the silicone resin fine particles A in the present invention is 0.0001 to 0.03% by weight, preferably 0.0001 to 0.02% by weight, and more preferably 0.0001 to 0.01% by weight. If the content is too small, the shaving property and the winding property are deteriorated, while if the content is too large, the film surface is roughened, the electromagnetic conversion characteristics in magnetic recording medium applications are deteriorated, and the abrasion resistance is deteriorated, Further, it is not preferable because an increase in a space factor and a decrease in a dielectric breakdown voltage occur in a capacitor application.
[0038]
In the present invention, the inert fine particles B contained in the polyester need to be particles having an average particle diameter smaller than the average particle diameter of the silicone resin fine particles A. When the average particle size of the inert fine particles B is equal to or larger than the average particle size of the silicone resin fine particles A, the effect of containing the silicone resin fine particles A is reduced, and the abrasion resistance is deteriorated.
[0039]
The average particle size of the inert fine particles B is preferably in the range of 0.1 to 1.2 μm, more preferably in the range of 0.1 to 0.8 μm, because the effect of improving the slipperiness and the abrasion resistance is large. .
[0040]
As the type of the inert fine particles B, the same type as the silicone resin fine particles A can be used, but they are different from the silicone resin fine particles A in that a function different from that of the silicone resin fine particles a can be imparted. Is preferred.
[0041]
Examples of the type of the inert fine particles B include (1) silicon dioxide (including hydrate, silica sand, quartz, etc.); (2) alumina in various crystal forms;_Two(For example, amorphous or crystalline clay minerals, aluminosilicates (including calcined products and hydrates), hot asbestos, zircon, fly ash, etc.) containing 30% by weight or more; (4) Mg (5) Sulfates of Ca and Ba; (6) Phosphates of Li, Ba and Ca (including mono- and di-hydrogen salts): (7) Benzoates of Li, Na, and K; (8) terephthalates of Ca, Ba, Zn, and Mn; (9) Mg, Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co, (10) Chromates of Ba and Pb; (11) Carbon (eg, carbon black, graphite, etc.); (12) Glass (eg, glass powder, glass beads, etc.); (13) Ca (14) fluorite; (1 ) While spinel-type oxides, and the like, satisfactory lubricity, calcium carbonate in terms of chipping resistance can be obtained, it is preferable that spherical silica.
[0042]
In the present invention, the content of the inert fine particles B needs to be 0.05 to 1.0% by weight. If the content is less than 0.05% by weight, the slipperiness deteriorates, while if it exceeds 1.0% by weight, the abrasion resistance deteriorates. This content is preferably from 0.1 to 0.6% by weight, more preferably from 0.2 to 0.4% by weight.
[0043]
The biaxially oriented polyester film of the present invention preferably has a center line average roughness Ra of the film surface of 0.01 to 0.1 μm. When the center line average roughness Ra is less than 0.01 μm, the surface is too flat, and the effect of improving the slipperiness and winding property is small. On the other hand, when the center line average roughness Ra is more than 0.1 μm, the abrasion resistance in magnetic recording medium applications is poor. Deterioration of the electromagnetic conversion characteristics tends to increase the space factor and decrease the dielectric breakdown voltage in capacitor applications. Further, when the biaxially oriented polyester film of the present invention is used as a base film for a magnetic recording medium, when the center line average roughness Ra is in the range of 0.01 to 0.025 μm, the effect of improving the electromagnetic conversion characteristics is large. It is even more preferable because it withstands use as a high-density magnetic recording medium.
[0044]
The biaxially oriented polyester film of the present invention preferably has a three-dimensional ten-point average roughness SRz of the film surface of 0.25 to 1.2 μm. When the three-dimensional ten-point average roughness SRz is less than 0.25 μm, the effect of improving slipperiness and winding property is small. On the other hand, when the three-dimensional ten-point average roughness SRz is more than 1.2 μm, abrasion resistance and electromagnetic conversion characteristics deteriorate in magnetic recording media. In a capacitor application, an increase in space factor and a decrease in dielectric breakdown voltage are likely to occur.
[0045]
Further, when the biaxially oriented polyester film of the present invention is used as a base film of a magnetic recording medium, when the three-dimensional ten-point average roughness SRz is in the range of 0.25 to 0.8 μm, the effect of reducing dropout is reduced. This is more preferable because the effect of improving the electromagnetic conversion characteristics is large and can be used for high-density magnetic recording media.
[0046]
When the biaxially oriented polyester film of the present invention is used for a magnetic recording medium, it preferably has a winding index of 100 or less at a winding speed of 200 m / min. A winding property index of 100 or less is preferable because the effect of improving the winding property is remarkable. On the other hand, when the winding index is larger than 100, the winding shape is deteriorated due to irregular end faces when the film is wound at high speed. The winding property index at a winding speed of 200 m / min is more preferably 85 or less, and particularly preferably 70 or less.
[0047]
When the biaxially oriented polyester film of the present invention is used for a capacitor, the space factor is preferably 3 to 23%.
[0048]
The space factor is a sample film 100cm^TwoWeight w (g) and density d (cm^Three/ G) is the gravimetric thickness obtained from t₁(Μm), 10 sample films of 100 cm square are stacked, and the thickness of one sample film determined using a micrometer is represented by t._Two(Μm) is a value calculated from the following equation.
[0049]
(Equation 1)
Space factor F (%) = 100-t₁/ T_Two× 100
[0050]
If the space factor is less than 3%, the slipperiness and workability (handling properties) of the film are insufficient, while if it exceeds 23%, the capacitor capacity per volume is low, which is not suitable for reducing the size of the capacitor. Not preferred.
[0051]
When the biaxially oriented polyester film of the present invention is used for a capacitor, the dielectric breakdown voltage (BDV) is preferably 200 V / μm or more from the viewpoint of being an electrically insulating material.
[0052]
Further, when the biaxially oriented polyester film of the present invention is used for a capacitor, the CR value (insulation resistance) of the film is preferably 1000ΩF or more. If the CR value is less than 1000 ΩF, the insulation resistance of the film becomes insufficient, and the film may be unsuitable as an electrical insulating material.
[0053]
The biaxially oriented polyester film of the present invention has a thickness in the range of 0.5 to 25 μm, and is preferably used because it can be widely used from a magnetic recording medium to a capacitor, but when used for a capacitor, the thickness is more preferable. Is preferably from 0.5 to 10 μm, particularly preferably from 0.5 to 5 μm, because it is easy to reduce the size of the capacitor.
[0054]
The biaxially oriented polyester film of the present invention can be obtained basically by a conventionally known method or a method accumulated in the art. For example, it can be obtained by first producing an unstretched film and then biaxially orienting the film. The unstretched film is, for example, melt-extruded into a film at a temperature of melting point (Tm: ° C) to (Tm + 70) ° C and solidified by quenching to obtain an unstretched film having an intrinsic viscosity of 0.35 to 0.9 dl / g. be able to.
[0055]
This unstretched film can be further made into a biaxially oriented film in accordance with a conventionally accumulated method for producing a biaxially oriented film. For example, the unstretched film is stretched in a uniaxial direction (longitudinal direction or transverse direction) at a temperature of (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of polyester) and a magnification of 2.5 to 7.0 times. At a temperature of Tg (° C.) to (Tg + 70) ° C. in a direction perpendicular to the above stretching direction (when the first-stage stretching is a longitudinal direction, the second-stage stretching is a transverse direction). It can be manufactured by stretching at a magnification of 7.0 times. In this case, the area stretching ratio is preferably 9 to 32 times, more preferably 12 to 32 times. The stretching means may be either simultaneous biaxial stretching or sequential biaxial stretching. Further, the biaxially oriented film can be heat-set at a temperature of (Tg + 70) ° C. to Tm (° C.). For example, a polyethylene terephthalate film is preferably heat-set at 190 to 230 ° C. The heat setting time is, for example, 1 to 60 seconds.
[0056]
The biaxially oriented polyester film of the present invention contains a combination of specific silicone resin fine particles and other inert particles having an average particle diameter smaller than that of the silicone resin fine particles, so that the effect of the excellent properties of each particle is synergistic. Since it is developed, it is a biaxially oriented polyester film having extremely few coarse protrusions, and particularly excellent in slipperiness, winding property and abrasion resistance, and extremely useful for magnetic recording media and capacitors.
[0057]
The various physical properties and properties in the present invention are measured and defined as follows.
[0058]
(1) Average particle size
(I) When calculating the average particle size from the granules
From the integrated curve of the particle size calculated based on the centrifugal sedimentation curve obtained using a Shimadzu CP-50 Centrifugal Particle Size Analyzer (Centrifugal Particle Size Analyzer) and the abundance of particles having the particle size, 50 mass The particle size corresponding to the percentage is read, and this value is defined as the above average particle size (see the book "Particle Size Measurement Technique", Nikkan Kogyo Shimbun, 1975, pp. 242 to 247).
[0059]
(Ii) In the case of particles in a film
A small piece of the sample film is fixed on a sample stage for a scanning electron microscope, and the film surface is subjected to ion etching under the following conditions using a sputtering device (JFC-1100 type ion etching device) manufactured by JEOL Ltd. The conditions are as follows.^-3The degree of vacuum is raised to a vacuum of Torr, and ion etching is performed at a voltage of 0.25 kV and a current of 12.5 mA for about 10 minutes. Further, the film surface was subjected to gold sputtering with the same apparatus, observed at a magnification of 50,000 to 10,000 with a scanning electron microscope, and an equivalent sphere of at least 100 particles was obtained with Luzex 500 manufactured by Nippon Regulator Co., Ltd. The diameter distribution is obtained and calculated from the point of 50% of the weight integration.
[0060]
(2) Apparent Young's modulus of particles
The diamond indenter is lowered at a constant load speed (29 mgf / sec) using an ultra-small compression tester MCTM-201 manufactured by Shimadzu Corporation to apply an external force 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 size d (mm) of the particles according to the following equation. The same operation is performed ten times, and the average value of the ten times is defined as the apparent Young's modulus of the particles.
[0061]
(Equation 2)
Y = 2.8P / πdZ
[0062]
(3) Surface roughness of film (Ra)
The center line average roughness (Ra) is a value defined in JIS B0601. In the present invention, it is measured using a stylus type surface roughness meter (SURFCORDER SE-30C) of Kosaka Laboratory Co., Ltd. The measurement conditions and the like are as follows.
(A) Stylus tip radius: 2 μm
(B) Measurement pressure: 30 mg
(C) Cutoff: 0.25 mm
(D) Measurement length: 2.5 mm
(E) How to summarize data: The same sample is repeatedly measured six times, the largest value is removed, and the average value of the remaining five data is displayed.
[0063]
(4) Three-dimensional ten-point average roughness (SRz)
Using a three-dimensional roughness measuring machine (SE-3CK manufactured by Kosaka Laboratory), needle diameter 2 μmR, needle pressure 30 mg, measurement length 1 mm, sampling pitch 42 μm, cutoff 0.25 mm, vertical magnification 20,000 times, horizontal The three-dimensional surface profile of the film surface is imaged under the conditions of a magnification of 200 times in the direction and 100 scanning lines. The average of the heights of the first to fifth peaks and the depths of the first to fifth valleys from the deepest plane in the plane parallel to the average line of the portion extracted by the reference area from the obtained profile Is defined as SRz.
[0064]
(5) Calendar shaving
The wearability of the running surface of the base film is evaluated using a three-stage mini super calendar. The calender is a three-stage calender of a nylon roll and a steel roll. The processing temperature is 80 ° C., the linear pressure applied to the film is 200 kg / cm, and the film speed is 100 m / min. When the running film has traveled a total length of 4000 m, the dirt attached to the top roller of the calender is used to evaluate the sharpness of the base film.
<5-stage judgment>
Grade 1: No dirt on the nylon roll
Grade 2: Almost no dirt on nylon rolls
Grade 3: Nylon roll is a little dirty, but can be easily removed by dusting
Grade 4: Nylon roll dirt is difficult to remove by dusting 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]
(6) Blade sharpness
At a temperature of 20 ° C. and a humidity of 60%, the edge of a blade (a blade for an industrial razor testing machine manufactured by US GKI) is vertically applied to a film cut to a width of イ ン チ inch, and further pressed in by 2 mm to make contact with the film every minute. The vehicle is run (frictional) at a speed of 100 m and an inlet tension T1 of 50 g. After the film has traveled 100 m, the amount of shavings attached to the blade is evaluated.
<Judgment>
◎: The width of the shaving powder adhering to the blade tip is less than 0.5 mm
：: the width of the shaving powder adhering to the blade tip is 0.5 mm or more and less than 1.0 mm
Δ: The width of the shaving powder adhering to the blade tip is 1.0 mm or more and less than 2.0 mm.
C: The width of the shaving powder adhering to the blade tip is 2.0 mm or more.
[0066]
(7) Sharpness at high speed running
The measurement is performed as follows using the apparatus shown in FIG.
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 (entrance), 7 is a fixed rod, and 10 is a tension detector ( Exit), 12 indicates a guide roller, and 13 indicates a take-up reel.
[0067]
At a temperature of 20 ° C. and a humidity of 60%, a film cut to a width of 1/2 inch is brought into contact with a fixing rod 7 at an angle θ = 60 °, and at a speed of 300 m / min, the inlet tension becomes 50 g. In this way, the vehicle travels 200 m. The shavings adhering to the fixed bar 7 after traveling are evaluated.
[0068]
At this time,
The method A is the case where a 6φ tape guide (surface roughness Ra = 0.015 μm) made of SUS304 and having a sufficiently finished surface is used.
The B method is used when a SUS sintered plate is bent into a cylindrical shape and a 6φ tape guide (surface roughness Ra = 0.15 μm) with insufficient surface finish is used.
Method C using carbon black containing polyacetal 6φ tape guide
And
<Determination of shavings>
◎: No shavings are seen
○: Slightly shaved powder is seen
△: The presence of shavings can be seen at a glance
×: The shavings are badly attached
[0069]
(8) Friction coefficient at low speed repetition (μk)
The measurement is performed as follows using the apparatus shown in FIG.
In an environment of a temperature of 20 ° C. and a humidity of 60%, the non-magnetic surface of the magnetic tape is brought into contact with the fixing rod 7 at an angle θ = (152/180) π radian (152 °) and moved at a speed of 200 cm per minute ( Friction). Inlet tension T₁Outlet tension (T) when the tension controller 2 is adjusted so that the_Two: G) is detected by an exit tension detector after the film has traveled 50 times and the running friction coefficient μk is calculated by the following equation.
[0070]
(Equation 3)

[0071]
If the running friction coefficient (μk) is 0.25 or more, the running becomes unstable when repeatedly running in a VTR.
[0072]
At this time,
The method A is the case where a 6φ tape guide (surface roughness Ra = 0.015 μm) made of SUS304 and having a sufficiently finished surface is used.
The B method is used when a SUS sintered plate is bent into a cylindrical shape and a 6φ tape guide (surface roughness Ra = 0.15 μm) with insufficient surface finish is used.
Method C using carbon black containing polyacetal 6φ tape guide
And
[0073]
The magnetic tape is manufactured as follows.
γ-Fe_TwoO_Three100 parts by weight (hereinafter simply referred to as "parts") and the following composition are kneaded and dispersed in a ball mill for 12 hours.
12 parts polyester urethane
Vinyl chloride-vinyl acetate-
Maleic anhydride copolymer 10 parts
α-alumina 5 parts
1 part of carbon black
70 parts of butyl acetate
Methyl ethyl ketone 35 parts
Cyclohexanone 100 parts
After dispersion
Fatty acid: Oleic acid 1 part
Fatty acid: Palmitic acid 1 part
1 part fatty acid ester (amyl stearate)
And kneading for 10 to 30 minutes. Further, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound is added, and the mixture is sheared at high speed for 1 hour to prepare a magnetic coating solution.
[0074]
The obtained coating solution is applied on a polyester film so that the dry film thickness becomes 2.5 μm.
[0075]
Next, after performing an orientation treatment in a DC magnetic field, the resultant is dried at 100 ° C. After drying, it is subjected to a calendering treatment and slit to a width of 1/2 inch to obtain a magnetic tape.
[0076]
(9) Winding index
In the apparatus shown in FIG. 1, a film having a width of イ ン チ inch is passed without passing through the fixing rod 7, and the entrance tension T is set in an environment of a temperature of 20 ° C. and a humidity of 60%.₁Is adjusted to 50 g, the vehicle is run for 200 m at a speed of 200 m / min, and the end face position is detected by the CCD camera at a position immediately before being wound by the winding reel 13.
[0077]
The amount of change in the end face position is represented as a waveform with respect to the time axis, and the waveform is calculated as a winding index by the following equation.
[0078]
(Equation 4)

[0079]
Where t: measurement time (seconds)
x: end face variation (μm)
It is.
[0080]
(10) Rewindability
In the apparatus shown in FIG. 1, the magnetic tape manufactured by the above-described method is passed through the magnetic tape so as not to pass through the fixing rod 7, and the entrance tension T₁Is adjusted to 60 g, and the tape is run for 500 m at a speed of 400 m / min, and evaluation is made based on the possibility of winding on the winding reel side and the roll shape of the wound magnetic tape.
<Judgment>
：: The end face deviation of the wound roll is within 1 mm.
Δ: End face deviation of the wound roll exceeds 1 mm
×: winding is not possible
[0081]
(11) Number of coarse projections
Aluminum was vapor-deposited on the film surface, observed using a two-beam interference microscope, and projections showing tertiary or higher order interference fringes at a measurement wavelength of 0.54 μm were defined as coarse projections, and the measurement area was 5 cm.^TwoThe number of coarse projections inside is 1cm^TwoConvert to the number per hit. This measurement is performed five times, and the average value is evaluated as the number of coarse projections.
[0082]
(12) Dropout
The magnetic tape (1/2 inch width) is counted with a commercially available dropout counter (for example, Shibasoku VH01BZ type) to determine the dropout of 5 μsec × 10 dB, and the number of counts per minute is calculated.
[0083]
(13) Electromagnetic conversion characteristics
A VHS VTR (BR6400 manufactured by Victor Company of Japan, Ltd.) is modified, and a sine wave of 4 MHz is input to a recording / reproducing head through an amplifier, recorded on a magnetic tape, reproduced, and a reproduced signal is input to a spectrum analyzer. Noise generated at a distance of 0.1 MHz from the carrier signal 4 MHz is measured, and the ratio of carrier to noise (C / N) is expressed in dB. The magnetic tape described above was measured using this method, and the difference from this magnetic tape was used as the electromagnetic conversion characteristic with the magnetic tape obtained in Comparative Example 5 as a reference (± 0 dB).
[0084]
(14) Space factor (F)
Sample 100cm^TwoFilm weight w (g) and density d (cm^Three/ G) is the gravimetric thickness obtained from t₁(Μm) Ten sample films of 10 cm square are stacked, and the thickness of one sample film determined using a micrometer is represented by t._Two(Μm), it is calculated by the following equation.
[0085]
(Equation 5)
Space factor F (%) = 100-t₁/ T_Two× 100
[0086]
(15) Breakdown voltage (BDV)
It is measured according to the method shown in JIS C 2318, and the average value of n = 100 is defined as the breakdown voltage (BDV).
[0087]
(16) CR value
After conditioning the sample film under the conditions of 23 ° C. and 50% RH for 16 hours, the sample film is measured in an atmosphere of 23 ° C. and 50% RH according to the method shown in JIS C2319.
[0088]
(17) Friction coefficient
Measure according to ASTM D1894.
[0089]
(18) Volume (2)
The sample film was wound up to a width of 500 mm and a length of 5000 m, and the roll was observed and evaluated according to the following criteria.
：: The wound shape is beautiful, and wrinkles on the surface, winding deviation, etc. cannot be confirmed with the naked eye.
X: The winding shape is poor, and wrinkles and winding deviations on the surface can be visually confirmed.
[0090]
【Example】
Hereinafter, the present invention will be further described with reference to examples.
[0091]
[Examples 1 to4, Comparative Example 13, Comparative Examples 1 to 8]
Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and additional particles shown in Table 1 as lubricants in the amounts shown in Table 1 were added. Then, polymerization was carried out by a conventional method to obtain polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.56.
[0092]
The polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours and then supplied to an extruder hopper and melted at a melting temperature of 280 to 300 ° C., and the melted polymer was passed through a 1 mm slit die for surface finishing of about 0.3 s and surface temperature of 20 mm. It extruded on the rotating cooling drum of ° C, and obtained the 200-micrometer-thick unstretched film.
[0093]
The unstretched film thus obtained is preheated at 75 ° C., and is further stretched 3.5 times by heating with three IR heaters having a surface temperature of 600 ° C. from 15 mm above between low-speed and high-speed rolls. Then, the mixture was quenched, subsequently supplied to a stenter, and stretched 4.5 times in the transverse direction at 120 ° C. The obtained biaxially oriented film was heat set at a temperature of 205 ° C. for 5 seconds to obtain a heat fixed biaxially oriented polyester film having a thickness of 14 μm.
[0094]
Table 2 shows the properties of the obtained film as a base film for a magnetic recording medium.
[0095]
[Table 1]

[0096]
[Table 2]

[0097]
[Examples 6 and 7, Comparative Examples 9 and 12]
Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and additional particles shown in Table 3 as lubricants in the amounts shown in Table 3 were added. Then, polymerization was carried out by a conventional method to obtain polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.56.
[0098]
The polyethylene terephthalate pellets were dried at 170 ° C. for 3 hours and then supplied to an extruder hopper and melted at a melting temperature of 280 to 300 ° C., and the melted polymer was passed through a 1 mm slit die for surface finishing of about 0.3 s and surface temperature of 20 mm. It extruded on the rotary cooling drum of ° C, and the unstretched film of Comparative Example 10 having a thickness of 20 µm and the other thickness of 35 µm was obtained.
[0099]
The unstretched film thus obtained is preheated at 75 ° C., further heated by a single IR heater having a surface temperature of 600 ° C. from 15 mm above between low-speed and high-speed rolls and stretched 3.6 times. Then, the mixture was quenched, then supplied to a stenter, and stretched 4.0 times in the transverse direction at 105 ° C. The obtained biaxially oriented film was heat-set at a temperature of 205 ° C. for 5 seconds to obtain a heat-set biaxially oriented polyester film having a thickness of 1.5 μm in Comparative Example 10 and 2.5 μm in other cases. Table 4 shows the properties of the obtained film as a base film for a capacitor.
[0100]
According to the present invention, as is apparent from Table 2, there are very few coarse projections, excellent dropout, excellent electromagnetic conversion characteristics, and excellent slipperiness, take-up properties, and abrasion resistance, and are excellent for magnetic recording media. The characteristics are shown. Further, as is clear from Table 4, each capacitor has excellent characteristics, and also has excellent sliding properties and winding properties, and also has excellent characteristics for capacitors.
[0101]
[Table 3]

[0102]
[Table 4]

[0103]
【The invention's effect】
The biaxially oriented polyester film of the present invention has very few coarse projections, has good slipperiness, rewindability, and abrasion resistance, and has characteristics particularly suitable as base films for electromagnetic recording media and capacitors. It is.
[Brief description of the drawings]
FIG. 1 is a schematic diagram 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 (entrance)
7 fixed rod
10 tension detector (exit)
12 Guide roller
13 Take-up reel

Claims (21)

The average particle diameter is the 0.8～2.0Myuemu, the silicone resin fine particles A whose 80 wt% or more consisting of binding units represented by the following formula contained 0.0001 to 0.02 wt%, the silicone resin fine particles A Are polymerized in the presence of a surfactant, wherein the surfactant is polyoxyethylene alkylphenyl ether and / or sodium dodecylbenzenesulfonate, and the average particle size is smaller than the silicone resin fine particles A. A biaxially oriented polyester film comprising 0.1 to 0.6 % by weight of inert fine particles B having a diameter.

(Here, R is at least one selected from an alkyl group having 1 to 6 carbon atoms and a phenyl group.) The biaxially oriented polyester film of claim 1 Symbol mounting surface of the silicone resin fine particles A have been treated with a silane coupling agent. The biaxially oriented polyester film according to claim 2 , wherein the silane coupling agent is a silane coupling agent having an epoxy group. The biaxially oriented polyester film of claim 1 the apparent Young's modulus of the silicone resin fine particles A is 10 to 100 kg / mm ^2. The biaxially oriented polyester film according to claim 1, wherein the average particle size of the silicone resin fine particles A is 0.8 to 1.6 µm. The biaxially oriented polyester film according to claim 1, wherein the inert fine particles B are at least one selected from calcium carbonate particles and spherical silica particles. The biaxially oriented polyester film according to claim 1, wherein the inert fine particles B have an average particle size of 0.1 to 1.2 m. The biaxially oriented polyester film according to claim 8, wherein the inert fine particles B have an average particle size of 0.1 to 0.8 m. The biaxially oriented polyester film according to claim 1, wherein the center line average roughness Ra of the film surface is 0.01 to 0.1 µm. The biaxially oriented polyester film according to claim 1, wherein the three-dimensional ten-point average roughness SRz of the film surface is 0.25 to 1.2 m. The biaxially oriented polyester film according to claim 1, wherein the film has a thickness of 0.5 to 25 µm. The biaxially oriented polyester film according to claim 1, wherein the polyester is polyethylene terephthalate. The biaxially oriented polyester film according to claim 1, wherein the polyester is polyethylene-2,6-naphthalate. The biaxially oriented polyester film according to claim 1, which is used for a base film of a magnetic recording medium. The biaxially oriented polyester film of claim 1 or 14 center line average roughness Ra of the film surface is 0.01～0.025Myuemu. The biaxially oriented polyester film of claim 1 or 14 three dimensional ten point average roughness SRz of a film surface is 0.25～0.8Myuemu. The biaxially oriented polyester film according to claim 1, which is used for an insulating film of a capacitor. The biaxially oriented polyester film according to claim 17 , wherein the film has a space factor of 3 to 23%. The biaxially oriented polyester film according to claim 17 , wherein a dielectric breakdown voltage of the film is 200 V / μm or more. The biaxially oriented polyester film according to claim 17 , wherein the CR value of the film is 10,000 ΩF or more. The biaxially oriented polyester film according to claim 17 , wherein the film has a thickness of 0.5 to 5 µm.

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