JP4321026B2 - Polyester film for capacitors - Google Patents

Description

（上記式中、Ａｒは、炭素６〜４２個の炭素原子を有する芳香族基であり、Ｒは、６〜３０個の炭素原子を有する２価の芳香族基、２〜３０個の炭素原子を有する脂肪族基および４〜３０個の炭素原子を有する脂環族基からなる群から選択された２価の有機基である。）
上記一般式中のＡｒとしては、例えば、次に示される芳香族基を挙げることができる。
【００３０】
【化２】

【００３１】
【化３】

また、上記一般式中のＲとしては、例えば、次に示される芳香族基、脂肪族基または脂環族基を挙げることができる。
【００３２】
【化４】

【００３３】
【化５】

これらの芳香族基等は、本発明の効果を阻害しない範囲内で、１種あるいは２種以上一緒にポリマー鎖中に存在してもよい。
【００３４】
本発明で用いられるポリイミドとしては、ポリエステルとの溶融成形性や取り扱い性などの点から、好ましい例として、例えば、下記一般式で示されるように、ポリイミド構成成分にエーテル結合を含有する構造単位のポリエーテルイミドを挙げることができる。
【００３５】
【化６】

（ただし上記式中、Ｒ１とＲ２は、２〜３０個の炭素原子を有する２価の芳香族または脂肪族基、脂環族基からなる群から選択された２価の有機基である。）
上記一般式のＲ１およびＲ２としては、例えば、下記式群に示される芳香族基等を挙げることができる。
【００３６】
【化７】

本発明において、ポリエーテルイミドとしては、ポリエステルとの相溶性と溶融成形性等の観点から、下記式で示される構造単位を有する、２，２−ビス［４−（２，３−ジカルボキシフェノキシ）フェニル］プロパン二無水物とｍ−フェニレンジアミン、またはｐ−フェニレンジアミンとの縮合物が特に好ましい。
【００３７】
【化８】

本発明では、ガラス転移温度が好ましくは３５０℃以下、より好ましくは２５０℃以下のポリエーテルイミドを用いると、本発明の効果が得やすい。
【００３８】
上記ポリイミドは、次のような方法によって製造することができる。例えば、上記一般式中のＡｒを誘導することができる原料であるテトラカルボン酸および／またはその酸無水物と、上記一般式中のＲを誘導することができる原料である脂肪族一級ジアミンおよび／または芳香族一級ジアミンよりなる群から選ばれる一種もしくは二種以上の化合物を脱水縮合することにより得られ、具体的には、ポリアミド酸を得て、次いで、加熱閉環する方法を例示することができる。または、酸無水物とピリジン、カルボジイミドなどの化学閉環剤を用いて化学閉環する方法、上記テトラカルボン酸無水物と上記Ｒを誘導することのできるジイソシアネートとを加熱して脱炭酸を行って重合する方法などを例示することができる。
【００３９】
上記方法で用いられるテトラカルボン酸としては、例えば、ピロメリット酸、１, ２, ３, ４―ベンゼンテトラカルボン酸、３, ３', ４, ４'―ビフェニルテトラカルボン酸、２, ２', ３, ３'―ビフェニルテトラカルボン酸、３, ３', ４, ４'―ベンゾフェノンテトラカルボン酸、２, ２', ３, ３'―ベンゾフェノンテトラカルボン酸、ビス（２, ３―ジカルボキシフェニル）メタン、ビス（３, ４―ジカルボキシフェニル）メタン、１, １' ―ビス（２, ３―ジカルボキシフェニル）エタン、２, ２'―ビス（３, ４―ジカルボキシフェニル）プロパン、２, ２'―ビス（２, ３―ジカルボキシフェニル）プロパン、ビス（３, ４―ジカルボキシフェニル）エーテル、ビス（２, ３―ジカルボキシフェニル）エーテル、ビス（３, ４―ジカルボキシフェニル）スルホン、ビス（２, ３―ジカルボキシフェニル）スルホン、２, ３, ６, ７―ナフタレンテトラカルボン酸、１, ４, ５, ８―ナフタレンテトラカルボン酸、１, ２, ５, ６―ナフタレンテトラカルボン酸、２, ２'―ビス[（２, ３―ジカルボキシフェノキシ）フェニル]プロパン等および／またはその酸無水物等が用いられる。
【００４０】
またジアミンとしては、例えば、ベンジジン、ジアミノジフェニルメタン、ジアミノジフェニルエタン、ジアミノジフェニルプロパン、ジアミノジフェニルブタン、ジアミノジフェニルエーテル、ジアミノジフェニルスルホン、ジアミノジフェニルベンゾフェノン、ｏ, ｍ, ｐ―フェニレンジアミン、トリレンジアミン、キシレンジアミン等およびこれらの例示した芳香族一級ジアミンの炭化水素基を構造単位に有する芳香族一級ジアミン等や、エチレンジアミン、１，２−プロパンジアミン、１，３−プロパンジアミン、２，２−ジメチル−１，３−プロパンジアミン、１，６−ヘキサメチレンジアミン、１，８−オクタメチレンジアミン、１，９−ノナメチレンジアミン、１，１０−デカメチレンジアミン、１，１１−ウンデカメチレンジアミン、１，１２−ドデカメチレンジアミン、２，２，４−トリメチルヘキサメチレンジアミン、２，４，４−トリメチルヘキサメチレンジアミン、１，３−シクロヘキサンジアミン、１，４−シクロヘキサンジアミン、１，４−シクロヘキサンジメチルアミン、２−メチル−１，３−シクロヘキサンジアミン、イソホロンジアミン等およびこれらの例示した脂肪族および脂環族一級ジアミンの炭化水素基を構造単位に有する脂肪族および脂環族一級ジアミン等を例示することができる。
【００４１】
ポリエステルとポリイミドを相溶させる場合、ポリイミドをポリエステルに添加する時期は、特に限定されないが、ポリエステルの重合前、例えば、エステル化反応前に添加してもよいし、重合後に溶融押出前に添加してもよい。
【００４２】
本発明では、長期耐熱性と高温時の耐電圧を向上する観点から、ポリエステルフィルム中におけるポリイミドの含有量は５〜５０重量％であることが重要である。ポリイミドの含有量が５重量％より少なくなるとコンデンサー用ポリエステルフィルムの長期耐熱性、高温時の耐電圧が低下する。一方、ポリイミドの含有量が５０重量％を超えると製膜性が低下し、フィルム破れの頻度が増加する。上記の観点から、ポリイミドの含有量は、好ましくは８〜４０重量％であり、さらに好ましくは１０〜３５重量％である。
【００４３】
本発明の効果を得る上で、ポリエステルとポリイミドのみからなるフィルムは、好適なフィルムである。また、本発明の効果を損なわない範囲で、その他のポリマーや添加剤を含むことができる。
【００４４】
また、本発明のコンデンサー用ポリエステルフィルムの長手方向と幅方向の少なくとも一方向の温度１５０℃、３０分における熱収縮率は、特に限定されないが、コンデンサーに用いた場合の成形性、使用環境での変形などによる劣化の観点から、０．１〜３％であることが好ましい。１５０℃熱収縮率のより好ましい範囲は０．３〜２％、最も好ましい範囲は０．５〜１．５％である。
【００４５】
本発明のコンデンサー用ポリエステルフィルムの厚さは、特に限定されないが、１〜１５μｍの範囲が好ましい。フィルム厚さがこの範囲内であると、コンデンサーの小型化、フィルムの製膜性の観点から、好ましく用いられる。フィルムのより好ましい範囲は、１．２〜１０μｍ、最も好ましくは１．５〜６μｍである。
【００４６】
本発明のコンデンサーは、本発明のコンデンサー用ポリエステルフィルムを用いて公知の方法で製造することができる。導電体は、金属を箔状にした金属箔またはコンデンサー用ポリエステルに金属を真空蒸着、スパッタリング法等の方法で形成した金属薄膜のいずれかで合っても良い。また、コンデンサーを作製する場合には、本発明のフィルムのみでなく、多種フィルム（例えば、ポリオレフィンフィルム、フッ素フィルムなど）と重ねて使用することも可能である。導電体を構成する金属としては、アルミニウム、亜鉛、錫、チタン、ニッケル、或いはそれらの合金などが挙げられるが、もちろんこれに限定されるものではない。
【００４７】
本発明のコンデンサー用ポリエステルフィルムは、溶融押出製膜、溶液キャスト製膜などの公知の製膜法によりフィルムに成形され、実用に供される。無配向であっても、一軸や二軸に配向したフィルムであっても良いが、二軸配向フィルムとすることがより好ましい。
【００４８】
次いで、ポリエステルとして、ポリエチレンテレフタレート（ＰＥＴ）を用いた場合を例示して、本発明のコンデンサー用ポリエステルフィルムの好ましい製造法について説明するが、本発明は、かかる製造法に限定されるものではない。
【００４９】
まず、テレフタル酸を主成分とするカルボン酸またはそのアルキルエステルとエチレングリコールを主成分とするグリコールを、カルシウム、マグネシウム、リチウムあるいはマンガン元素などの金属触媒化合物の存在下、１３０〜２６０℃でエステル化あるいはエステル交換反応を行なう。その後、アンチモン、ゲルマニウムあるいはチタン元素からなる触媒化合物およびリン化合物を添加して、高真空下、温度２２０〜３００℃で重縮合反応させる。上記リン化合物の種類としては、亜リン酸、リン酸、リン酸トリエステル、ホスホン酸あるいはホスホネート等が挙げられるが、特に限定されず、またこれらのリン化合物を二種以上併用しても良い。
【００５０】
上記触媒化合物の添加量は、特に限定しないが、カルシウム、マグネシウム、リチウムあるいはマンガン等の触媒金属化合物とリン化合物の比が、下記の式を満足するように含むことが、本発明の目的を達成する上で好ましい。
０．３≦（Ｍ／Ｐ）≦１．８
（ここで、Ｍは、フィルム中のカルシウム、マグネシウム、リチウムあるいはマンガン等の触媒金属元素の全モル数であり、Ｐはフィルム中のリン元素のモル数である。）
また、エステル化あるいはエステル交換から重縮合の任意の段階で必要に応じて酸化防止剤、熱安定剤、滑剤、紫外線吸収剤、核生成剤、表面突起形成用無機および有機粒子を添加する。
【００５１】
その後、１８０℃で３時間以上真空乾燥する。その後、これらを押出機に投入し、２７０〜３２０℃にて溶融押出し、フィルター内を通過させた後、Ｔダイよりシート状に吐出し、このシート状物を表面温度２０〜７０℃の冷却ドラム上に密着させて冷却固化し、実質的に無配向状態の未延伸ポリエステルフィルムを得る。
【００５２】
また、本発明のコンデンサー用ポリエステルフィルムを積層フィルムとして得る場合、未延伸ポリエステルフィルムまでの製造方法は、次のような工程で製造されるが、一例でありこれに制約されることはない。まず、少なくとも２台以上の押出機を用いた溶融押出により口金から吐出し、溶融ポリマーを冷却固化させてシート状に成形する積層ポリエステルフィルムの製造方法において、１台はポリエステルとポリイミドを押出機に供給し、２７０〜３２０℃にて溶融させ、少なくとも１台は同様にポリエステルとポリイミドを押出機に供給し、２７０〜３２０℃にて溶融させ、その溶融体をパイプ内あるいは口金内で合流させて口金から吐出し、このシート状物を表面温度２０〜７０℃の冷却ドラム上に密着させて冷却固化し、実質的に無配向状態の未延伸ポリエステルフィルムを得る。
【００５３】
次に、この未延伸ポリエステルフィルムを二軸延伸して配向せしめる。延伸の方法としては、逐次二軸延伸または同時二軸延伸法を用いることができる。二軸延伸の条件は特に限定されないが、フィルムの長手方向および幅方向に一段階もしくは二段階以上の多段階で４．０〜６．０の倍率で延伸することが好ましい。延伸温度は、９０〜１８０℃の範囲であれば良く、未延伸ポリエステルフィルムのガラス転移温度（Ｔｇ）〜（Ｔｇ＋４０）℃の範囲で長手方向及び幅方向に二軸延伸を行なうことがより好ましい。さらに必要に応じて再延伸を行なっても良い。また、延伸後の熱処理は、温度１７５℃〜２２０℃の範囲であれば良く、好ましくは１９０〜２１５℃で１〜３０秒間熱処理し、その後８０〜１２０℃で急冷却処理を施すことが好ましい。さらに、熱処理時あるいは／または熱処理後フィルムを急冷却する段階で幅方向に１〜９％の弛緩処理を加えることが、本発明のコンデンサー用ポリエステルフィルムを得る上で有効である。
【００５４】
次に、上記のようにして得られた本発明のコンデンサー用ポリエステルフィルムを用いて、本発明にかかる耐熱性に優れたフィルムコンデンサーの製造方法について説明する。
【００５５】
上記の如くして得られたコンデンサー用フィルムを誘電体とし、金属箔または金属薄膜を導電体として、耐熱性コンデンサー用金属化フィルムを作製し、これを平板または円筒状に巻き回してコンデンサー素子を作るが、金属薄膜を導電体とした金属化フィルムを用いた方が、本発明の効果が得られ易い。この場合、金属薄膜形成法としては、周知の蒸着法やスパッタリング法等を用いることができ、特に誘電体フィルム厚みが１．３〜８μｍ、蒸着膜厚が５０〜２００オングストローム、あるいは金属膜の表面抵抗値が０．５〜５Ω／ｃｍの蒸着金属化フィルムを用いてコンデンサーにすることが、本発明の効果を得る上で好ましい。
【００５６】
次いで、このようにして得られたコンデンサー素子を、常法に従って、プレス、端面封止およびリード線取り付け、必要に応じて電圧処理、熱処理等を行なってコンデンサーとする。ここで、素子作製時のプレスは、部分損傷による荷電寿命低下を抑制する観点から、温度を１２０〜１８０℃、プレス圧を２０〜１００ｋｇ／ｃｍ²の条件下で、１〜３０分処理することが好ましい。より好ましいプレス条件は、１２０〜１６０℃、プレス圧２０〜６０ｋｇ／ｃｍ²、処理時間１〜８分である。
【００５７】
本発明では、上記耐熱性コンデンサー用フィルムに公知のコロナ放電処理を施しても良く、また、接着性、ヒートシール性、耐湿性、滑性および表面平滑性等を付与する目的で多種ポリマーを積層した構成や、有機または／および無機組成物で被覆した構成で使用しても良い。また、本発明のコンデンサーに絶縁油等を含浸させて、いわゆる油浸コンデンサーとして用いても良い。
【００５８】
［物性の測定方法ならびに効果の評価方法］
本発明における特性値の測定方法ならびに効果の評価方法は次のとおりである。
【００５９】
（１）ポリエステル及びポリイミドの含有量
ポリエステル及びポリイミドの両者を溶解する適切な溶媒（例えば、ＨＦＩＰ／重クロロホルム）に溶解し、１Ｈ核のＮＭＲスペクトルを測定する。得られたスペクトルで、ポリエステルとポリイミドに特有の吸収（例えば、ＰＥＴであればテレフタル酸の芳香族プロトン、ＰＥＩであればビスフェノールAの芳香族のプロトン）のピーク面積強度を求め、その比率とプロトン数よりブレンドのモル比を算出する。さらにポリマーの単位ユニットに相当する式量より重量比を算出する。測定条件は、例えば、以下のような条件であるが、ポリエステルとポリイミドの種類によって異なるため、この限りではない。
【００６０】
装置 ：BRUKER DRX-500（ブルカー社）
溶媒 ：ＨＦＩＰ／重クロロホルム
観測周波数 ：４９９．８MHz
基準 ：TMS（0ppm）
測定温度 ：３０℃
観測幅 ：１０KHz
データ点 ：６４K
acquisiton time ：４．９５２秒
pulse delay time ：３．０４８秒
積算回数 ：２５６回
また、必要に応じて、顕微ＦＴ−ＩＲ法（フーリエ変換顕微赤外分光法）で組成分析を行ってもよい。その場合、ポリエステルのカルボニル基に起因するピークと、ポリエステル以外の物質に起因するピークの比から求めた。なお、ピーク高さ比を重量比に換算するために、あらかじめ重量比既知のサンプルで検量線を作成してポリエステルとそれ以外の物質の合計量に対するポリエステル比率を求めた。これと、粒子含有量より熱可塑性樹脂比率を求めた。また、必要に応じてＸ線マイクロアナライザーを併用した。
【００６１】
（２）ガラス転移温度（Ｔｇ）
下記装置及び条件でフィルム試料について比熱測定を行い、ＪＩＳ Ｋ７１２１に従って決定した。
【００６２】
装置 ：ＴＡ Ｉｎｓｔｒｕｍｅｎｔ社製温度変調ＤＳＣ
測定条件：
加熱温度 ：２７０〜５７０Ｋ（ＲＣＳ冷却法）
温度校正 ：高純度インジウム及びスズの融点
温度変調振幅 ：±１Ｋ
温度変調周期 ：６０秒
昇温ステップ ：５Ｋ
試料重量 ：５ｍｇ
試料容器 ：アルミニウム製開放型容器（２２ｍｇ）
参照容器 ：アルミニウム製開放型容器（１８ｍｇ）。
【００６３】
（３）フィルムの熱収縮応力
フィルムサンプルを幅４ｍｍ、測定長２０ｍｍ、荷重１．５ｇ重／４ｍｍ幅とし、セイコーインスツルメンツ（株）製熱分析装置ＴＭＡ／ＳＳ６０００を用い、一定測定長条件で３０℃より１０℃／分の昇温速度で２６０℃まで測定した。得られた曲線から１５０℃での熱収縮応力を求めた。
【００６４】
（４）積層厚み比
フィルムサンプルを任意に１０箇所を選び断面方向に切り出し、電子顕微鏡で倍率２０００倍で写真撮影を行い、フィルムの厚さ、フィルム基層部の厚さ、フィルム積層部の厚さを測定し、その比を算出した。これを１０枚の写真について行い、その平均値で表した。
【００６５】
（５）表面粗さ（Ｒａ）と最大粗さ（Ｒｔ）
（株）小坂研究所製高精度薄膜段差計ＥＴ−１０を用いて測定し、ＪＩＳ Ｂ０６０１に従って中心線平均表面粗さ（Ｒａ、Ｒｔ）を求めた。触針先端半径０．５μｍ、針圧５ｍｇ、測定長１ｍｍ、カットオフ０．０８ｍｍとした。
【００６６】
（６）製膜性
逐次二軸延伸製膜機を用いた製膜に伴う製膜性を観察して次の基準で判定した。
◎：フィルム破れが皆無である場合
○：フィルム破れが極まれに生じる場合
△：フィルム破れが時々生じる場合
×：フィルム破れが頻発する場合
（７）フィルムコンデンサー特性
［コンデンサーの作製］
フィルムの片面に表面抵抗値が２Ω／ｃｍとなるようにアルミニウムを真空蒸着した。その際、長手方向に走るマージン部を有するストライブ状に蒸着する（蒸着部の幅５８ｍｍ、マージン部の幅２ｍｍの繰り返し）。次に、各蒸着部の中央と各マージン部の中央に刃を入れてスリットし、左もしくは右に１ｍｍのマージンを有する全幅３０ｍｍのテープ状巻取リールとした。得られたリールの左マージンおよび右マージンのものを各１枚づつ重ね合わせて巻回し、静電容量２．２μＦのコンデンサー素子とし、外装として別の１２μｍのＰＥＴフィルムを外周に３周巻き付けた。このコンデンサー素子を１３０℃、３０ｋｇ／ｃｍ²の温度、圧力で５分間プレスした。この両端面にメタリコンを溶射して外部電極とし、メタリコンにリード線を溶接した。このコンデンサーに直流１５０Ｖ／μｍ（フィルム厚み換算）の電圧で３０秒間の荷電処理を１回行い、さらに２本のリード線に印加する電極の正負を逆転させてもう１回行なう。作製したコンデンサーの静電容量が±１０％以内であること、絶縁抵抗が１００００ＭΩ以上であることを確認し、この規格外を選別した。さらに、このコンデンサー素子を樹脂ケースに入れ、周囲をサンユレック社製エポキシ樹脂（ＥＸ−２６５）を注入した後１００℃×２時間の条件でエポキシ樹脂を硬化させることによりコンデンサー素子を得た。
【００６７】
［長期耐熱性試験］
５個のコンデンサーについて、予めコンデンサー容量の測定を行い、この値をＣ_Sとする。次に、温度１５０℃、電圧５０Ｖ／μｍ（ＤＣ）の条件下でオーブン中に置き、５００時間経過後のコンデンサー容量をＣ_Eとして、下記式で求められる値をコンデンサーの容量変化によって評価する。
ΔＣ／Ｃ＝（Ｃ_S−Ｃ_E）／Ｃ_S
［１５０℃絶縁破壊電圧］
コンデンサーを１５０℃のオーブン中で６０分間放置した後、電圧を１００Ｖ／秒の昇圧速度でＤＣ電圧を印加し、コンデンサーが絶縁破壊し、１０ｍＡ以上の電流が流れた時点の電圧を絶縁破壊電圧とした。本発明では、３０個のコンデンサーの絶縁破壊電圧値の平均値を示す。なおコンデンサーの容量が大きく、充電電流のみで１０ｍＡ以上の電流が流れる場合は、該電流値を充電電流と絶縁破壊電流を分離できる適切な値に設定する。
【００６８】
［高温絶縁抵抗］
１２５℃に調節されたオーブン中でＤＣ１００Ｖの電圧を印可し、１分間経過時の値を絶縁抵抗計によって測定した。
【００６９】
【実施例】
次に、本発明を実施例に基づいて説明する。
【００７０】
（参考例１）
ジメチルテレフタレート１００重量部とエチレングリコール６０重量部の混合物に、エステル交換反応触媒として酢酸カルシウムを添加し、加熱昇温してメタノールを留出させてエステル交換反応を行った。次いで、該エステル交換反応生成物に、重合触媒として三酸化アンチモン、熱安定剤としてリン酸を加え重縮合反応槽に移行した。次いで、加熱昇温しながら反応系を徐々に減圧し、２９０℃減圧下で内部を攪拌しメタノールを留出させながら重合し、固有粘度０．６２相当まで重合度が上がった時点で吐出し、Ｍ／Ｐ＝１．１６のポリエチレンテレフタレート（ＰＥＴ）を得た。得られた固有粘度０．６２のＰＥＴ（平均径２．５μｍの凝集シリカ０．１重量％含有）のペレットを１８０℃で３時間真空乾燥した後に供給し、押出機から溶融押出し、表面温度２５℃のキャストドラムに静電荷を印可させながら密着冷却固化し、未延伸フィルムを作製した。この未延伸フィルムを、加熱された複数のロール群からなる縦延伸機を用い、ロールの周速差を利用して、１００℃の温度でフィルムの縦方向に４．５倍の倍率で延伸した。その後、このフィルムの両端部をクリップで把持して、テンターに導き、延伸温度１０５℃、延伸倍率３．５倍でフィルムの幅方向に延伸を行い、引き続いて２００℃の温度で３秒間熱処理を行った後、１００℃にコントロールされた冷却ゾーンで横方向に４％弛緩処理を行って室温まで冷却した後、フィルムエッジを除去し、厚さ６μｍのコンデンサー用ポリエステルフィルムを得た。得られたコンデンサー用ポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。
【００７１】
【表１】

また、上記のコンデンサー用ポリエステルフィルムを用いて、上述のとおりコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に示す。得られたコンデンサーは、長期耐熱性試験後の容量変化に優れ、かつ、高温絶縁破壊電圧や高温絶縁抵抗にも優れたコンデンサーであった。
【００７２】
【表２】

（参考例２）
ポリエチレンテレフタレート（ＰＥＴ）の替わりに、公知の方法によって得られたポリエチレン−２，６−ナフタレート（ＰＥＮ）を用いたこと以外は、参考例１と同様にしてポリエステルフィルムを得た。得られたポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。また、得られたポリエステルフィルムを用いてコンデンサー素子を作成し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に示す。得られたコンデンサーは、長期耐熱性試験後の容量変化に優れ、かつ、高温絶縁破壊電圧や高温絶縁抵抗にも優れたコンデンサーであった。
【００７３】
（参考例３）
参考例１と同様にして得た、固有粘度０．６２のＰＥＴ（５０重量％）と、１５０℃で５時間熱風乾燥を行ったポリエーテルイミド（絶対重量平均分子量３０，０００、日本ジーイープラスチックス（株）製、“ウルテム”（登録商標）１０１０）（５０重量％）をドライブレンドし、同方向回転型二軸混練押出機（東芝機械（株）製ＴＥＭ−３５Ｂ）を用いて溶融混練し、ポリエーテルイミドを５０重量％含有したブレンドチップを作製した。溶融混練は、３１０℃、平均滞留時間３．５分、ベント真空度０．５ｍｍＨｇの条件で実施した。押出機を用い、２８５℃に加熱された押出機に固有粘度０．６２のポリエチレンテレフタレート（ＰＥＴ）のペレット（平均径２．５μｍの凝集シリカ０．１重量％含有）（８０重量％）と上記ブレンドチップ（２０重量％）を１８０℃で３時間真空乾燥した後に供給し、押出機から溶融押出し、表面温度２５℃のキャストドラムに静電荷を印可させながら密着冷却固化し、未延伸フィルムを作製した。この未延伸フィルムを、加熱された複数のロール群からなる縦延伸機を用い、ロールの周速差を利用して、１１０℃の温度でフィルムの縦方向に４．５倍の倍率で延伸した。その後、このフィルムの両端部をクリップで把持して、テンターに導き、延伸温度１１５℃、延伸倍率３．５倍でフィルムの幅方向に延伸を行い、引き続いて２００℃の温度で３秒間熱処理を行った後、１００℃にコントロールされた冷却ゾーンで横方向に４％弛緩処理を行って室温まで冷却した後、フィｒムエッジを除去し、厚さ６μｍのポリエステルフィルムを得た。得られたポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、長期耐熱性試験後の容量変化に優れ、かつ、高温絶縁破壊電圧や高温絶縁抵抗にも優れたコンデンサーであった。
【００７４】
（参考例４）
ポリエーテルイミドの含有量を変更し、参考例３と同様にしてポリエステルフィルムを得た。得られたフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、長期耐熱性試験後の容量変化に優れ、かつ、高温絶縁破壊電圧や高温絶縁抵抗にも優れたコンデンサーであった。
【００７５】
（実施例１）
参考例１と同様にして得た、固有粘度０．６２のＰＥＴ（５０重量％）と、１５０℃で５時間熱風乾燥を行ったポリエーテルイミド（絶対重量平均分子量３０，０００、日本ジーイープラスチックス（株）製、“ウルテム”（登録商標）１０１０）（５０重量％）をドライブレンドし、同方向回転型二軸混練押出機（東芝機械（株）製ＴＥＭ−３５Ｂ）を用いて溶融混練し、ポリエーテルイミドを５０重量％含有したブレンドチップを作製した。溶融混練は、３１０℃、平均滞留時間３．５分、ベント真空度０．５ｍｍＨｇの条件で実施した。押出機２台を用い、２８５℃に加熱された押出機Ａには固有粘度０．６２のポリエチレンテレフタレート（ＰＥＴ）のペレット（８０重量％）と上記ブレンドチップ（ｂ）（２０重量％）を１８０℃で３時間真空乾燥した後に供給し、同じく２８５℃に加熱された押出機Ｂには固有粘度０．６２のＰＥＴ（平均径２．５μｍの凝集シリカ０．１重量％含有）のペレット（８０重量％）と上記ブレンドチップ（ｂ）（２０重量％）を１８０℃で３時間真空乾燥した後に供給し、押出機Ａからのポリマーが主層、押出機Ｂからのポリマーが最外層になるように３層積層するべくＴダイ中で合流させ（積層比Ｂ／Ａ／Ｂ＝３／１０／３）、表面温度２５℃のキャストドラムに静電荷を印可させながら密着冷却固化し、積層未延伸フィルムを作製した。このようにして得られた未延伸フィルムを、加熱された複数のロール群からなる縦延伸機を用い、ロールの周速差を利用して、１１０℃の温度でフィルムの縦方向に４．５倍の倍率で延伸した。その後、このフィルムの両端部をクリップで把持して、テンターに導き、延伸温度１１５℃、延伸倍率３．５倍でフィルムの幅方向に延伸を行い、引き続いて２００℃の温度で３秒間熱処理を行った後、１００℃にコントロールされた冷却ゾーンで横方向に４％弛緩処理を行って室温まで冷却した後、フィルムエッジを除去し、厚さ６μｍの積層ポリエステルフィルムを得た。得られた積層ポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、長期耐熱性試験後の容量変化に優れ、かつ、高温絶縁破壊電圧や高温絶縁抵抗にも優れたコンデンサーであった。
【００７６】
（実施例２）
基層部（Ａ層）と積層部（Ｂ層）の積層厚み比を表１に示す値にしたこと以外は、実施例１と同様にしてポリエステルフィルムを得た。得られたポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、長期耐熱性試験後の容量変化に優れ、かつ、高温絶縁破壊電圧や高温絶縁抵抗にも優れたコンデンサーであった。
【００７７】
（比較例１）
フィルムの縦方向の延伸倍率を３．０倍にしたこと以外は、参考例１と同様にしてポリエステルフィルムを得た。得られたポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、ガラス転移温度が本発明の規定の範囲外であった為、長期耐熱性試験後の容量変化、高温絶縁破壊電圧や高温絶縁抵抗も劣るコンデンサーしか得られなかった。
【００７８】
（比較例２）
フィルムの幅方向に延伸を行い、引き続いて１７０℃の温度で３秒間熱処理を行った以外は参考例１と同様にポリエステルフィルムを得た。得られたポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。
【００７９】
また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、１５０℃での熱収縮応力が本発明の規定の範囲外であった為、長期耐熱性試験後の容量変化、高温絶縁破壊電圧や高温絶縁抵抗も劣るコンデンサーしか得られなかった。
【００８０】
（比較例３）
フィルムの幅方向に延伸を行い、引き続いて２４５℃の温度で３秒間熱処理を行ったこと以外は、参考例１と同様にしてポリエステルフィルムを得た。得られたポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、１５０℃での熱収縮応力が本発明の規定の範囲外であった為、長期耐熱性試験後の容量変化、高温絶縁破壊電圧や高温絶縁抵抗も劣るコンデンサーしか得られなかった。
【００８１】
（比較例４）
ポリエーテルイミドの含有量を変更し、参考例３と同様にポリエステルフィルムを得た。得られたポリエステルフィルムのＴｇ、熱収縮応力、ｔ／ｄ、表面粗さ、最大粗さおよび製膜性を表１に示す。Ｔｇが本発明の規定の範囲外であった為、製膜時に破れが頻繁に発生した。また、本発明のコンデンサー用ポリエステルフィルムを用いてコンデンサー素子を作製し、その後エポキシ樹脂で外装した後、コンデンサーの特性評価を行った。結果を表２に併せて示す。得られたコンデンサーは、１５０℃での熱収縮応力が本発明の規定の範囲外であった為、長期耐熱性試験後の容量変化、高温絶縁破壊電圧や高温絶縁抵抗も劣るコンデンサーしか得られなかった。
【００８２】
【発明の効果】
本発明によれば、優れた耐熱性と電気特性（耐電圧）を有し、生産性の点でも優れたコンデンサー用ポリエステルフィルムが得られる。本発明のコンデンサー用ポリエステルフィルムは、フィルムコンデンサーとして使用した場合に、長期耐熱性、高温下での耐電圧に優れたフィルムコンデンサーが得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film for capacitors. Specifically, the present invention relates to a polyester film for capacitors that is excellent in long-term heat resistance and electrical characteristics and is suitable for productivity.
[0002]
[Prior art]
Conventionally, a capacitor in which a polyester film is used as a dielectric layer and a metal vapor deposition layer is formed on the surface thereof as an electrode has been widely used so far. In recent years, there has also been a technical disclosure of blending a different polyester or polycarbonate with a polyester as a main component for the purpose of increasing the use temperature as a condenser to increase the use temperature range to the high temperature side. For example, a capacitor film excellent in heat resistance using a film made of a blend of various polyesters is disclosed (see Patent Document 1). Separately, for the purpose of improving the heat resistance of a film capacitor, a biaxially oriented polyester film in which a polyimide is contained in a polyester is disclosed (see Patent Document 2).
[0003]
[Patent Document 1]
Japanese Patent Publication No. 7-21070
[0004]
[Patent Document 2]
JP 2001-319825 A
[0005]
[Problems to be solved by the invention]
However, in recent years, capacitors used in electric / electronic circuits and the like have a tendency to require further heat resistance. Conventional polyester films have a low withstand voltage at high temperatures and cause dielectric breakdown. There was a problem that the progress of the disappearance of oxidation was accelerated and the capacity decrease with time became large. In addition, the film made of a blend of polyesters shown in the above-mentioned prior art shows an improvement in heat resistance, but the crystallinity is lowered due to the transesterification reaction and the dimensional stability is lowered. There was a problem of lacking.
[0006]
The present invention provides a polyester film for a capacitor that improves the disadvantages of the conventional polyester film for capacitors, has excellent heat resistance and electrical characteristics (withstand voltage), and is excellent in productivity. It is intended to do.
[0007]
[Means for Solving the Problems]
  The present invention has been found by intensive studies to solve the above problems, the polyester film for capacitors of the present invention,It is a polyester film containing 5 to 50 wt% of polyimide, and the polyester film is a laminated film in which a laminated part (B layer) is provided on at least one outermost layer of a base layer part (A layer). The relationship between the average particle diameter d of the inert particles contained in the B layer) and the thickness t of the laminated portion (B layer) is 0.05 ≦ (t / d) ≦ 10, and the base layer portion (A layer) ) And the layered portion (B layer) have a thickness ratio of 10: 0.5 to 5,A polyester film for capacitors having a glass transition temperature of 100 ° C. or more and less than 150 ° C. and a heat shrinkage stress at 150 ° C. in the longitudinal direction of 1500 kPa or more and less than 3500 kPa is used as a gist.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the polyester film for capacitors of the present invention will be described in detail.
[0009]
The polyester constituting the condenser polyester film of the present invention is composed of an acid component such as an aromatic dicarboxylic acid, an alicyclic dicarboxylic acid or an aliphatic dicarboxylic acid, or a diol component.
[0010]
Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid. Acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and the like can be used. Among them, terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid can be preferably used. . As the alicyclic dicarboxylic acid component, for example, cyclohexane dicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. These acid components may be used alone or in combination of two or more.
[0011]
Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2′-bis (4 '-Β-hydroxyethoxyphenyl) propane and the like can be used. Among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be used, and particularly preferably. Use ethylene glycol, etc. Can do. These diol components may be used alone or in combination of two or more.
[0012]
The polyester may be copolymerized with a monofunctional compound such as lauryl alcohol or phenyl isocyanate, trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, 2,4-dioxybenzoic acid, etc. Trifunctional compounds and the like may be copolymerized within a range in which the polymer is substantially linear without excessive branching or crosslinking.
[0013]
In addition to the acid component and the diol component, aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid, m-hydroxybenzoic acid or 2,6-hydroxynaphthoic acid, p-aminophenol, p-aminobenzoic acid, etc. If the amount is small enough not to impair the effects of the invention, it can be further copolymerized.
[0014]
The polyester used in the present invention is composed of a polyester mainly composed of ethylene terephthalate and / or ethylene-2,6-naphthalenedicarboxylate units and their modified products from the viewpoints of mechanical strength, productivity, and handleability. It is preferably at least one selected from the group consisting of
[0015]
The polyester used in the present invention can be produced by a conventionally known production method. For example, in the case of polyethylene terephthalate, terephthalic acid and ethylene glycol are reacted directly to remove water and esterify, then the direct ester method in which polycondensation is performed under reduced pressure, dimethyl terephthalate and ethylene glycol are reacted to react methyl alcohol. For example, a transesterification method in which polycondensation is performed under reduced pressure after removal and transesterification is included.
[0016]
As a transesterification catalyst in the transesterification method, a carboxylic acid metal salt compound of a metal element such as manganese, zinc, cobalt, magnesium or calcium and a carboxylic acid such as acetic acid is used, and a germanium compound as a catalyst for the polycondensation reaction Antimony compounds or titanium compounds are used. Moreover, in order to reduce the activity of the transesterification reaction, a phosphorus compound such as phosphoric acid or trimethyl phosphate can be added after the ester reaction is completed. In the case of the direct esterification method, a germanium compound, an antimony compound, a titanium compound, or the like is used as a polycondensation catalyst.
[0017]
The polyester film for capacitors of the present invention has a glass transition temperature of 100 ° C. or more and less than 150 ° C. from the viewpoint of improving long-term heat resistance. More preferably, the glass transition temperature is 103 ° C. or higher and lower than 145 ° C., more preferably 105 ° C. or higher and lower than 140 ° C. When the glass transition start temperature is less than 100 ° C., there is a problem that dielectric loss at 100 ° C. or more is large and dielectric breakdown occurs at a high temperature. On the other hand, if the glass transition temperature exceeds 150 ° C., the film is torn frequently and cannot be stably produced.
[0018]
The glass transition temperature of the polyester can be controlled by the mixing ratio of the polyester used, the film forming conditions, and at least two kinds of polyesters having different glass transition temperatures.
[0019]
  The polyester film for capacitors of the present invention has a heat shrinkage stress at 150 ° C. in the longitudinal direction of the polyester film in the range of 1500 kPa or more and less than 3500 kPa from the viewpoint of improving the withstand voltage at high temperatures. More preferably, the heat shrinkage stress is 1700 kPa or more and less than 3300 kPa, and more preferably 1900 kPa or more and less than 3000 kPa. When the heat shrinkage stress is less than 1500 kPa, the capacitorElementaryThere is a problem that the shrinkage force at the time of hot pressing in the child manufacturing process is insufficient, the gap between the element layers becomes wide, the dielectric loss increases, and dielectric breakdown occurs at a high temperature. On the other hand, if the heat shrinkage stress in the longitudinal direction is greater than 3500 kPa, heat loss and wrinkles are likely to occur during metal deposition, resulting in poor productivity.
[0020]
The heat shrinkage stress in the longitudinal direction can be controlled by the stretching ratio, stretching temperature and heat setting temperature of the film in the longitudinal direction.
[0021]
  The polyester film for capacitors of the present invention is a laminated polyester film from the viewpoint of increasing the withstand voltage at high temperatures and narrowing the gap between capacitor element layers.ForI can. A suitable laminated polyester film is formed by providing a laminated part (B layer) made of polyester on at least one outermost layer of a base part (A layer) made of polyester, and is contained in the laminated part (B layer). The relationship between the average particle diameter d of the inert particles and the thickness t of the laminated part (B layer) is 0.05 ≦ (t / d) ≦ 10GoodPreferably 0.08 ≦ (t / d) ≦ 8YesMore preferably, 0.1 ≦ (t / d) ≦ 6. When the above relationship t / d is smaller than 0.05, the film becomes less stretchable and easily broken when the film is formed.TheFurther, when the above relationship t / d is larger than 10, the withstand voltage at high temperature is low, and the gap between the capacitor element layers is wide.The
[0022]
  Moreover, the lamination thickness ratio of the base layer part (A layer) and the laminated part (B layer) made of polyester of the laminated polyester film suitable for the present invention is as follows.In the case of laminated part (B layer) / base layer part (A layer) / laminated part (B layer),0.5 to 5/10 / 0.5 to 5TheIf the lamination thickness ratio is in this range, the particle surface with uniform height is formed on the film surface by the inert particles, and the properties such as winding property, stability of the deposited film and withstand voltage when used as a capacitor element are obtained. improves. Lamination thickness ratioFavorA preferable range is 0.8 to 4/10 / 0.8 to 4, and a most preferable range is 1 to 3/10/1 to 3.
[0023]
In addition, it is preferable that the lamination part (B layer) contains inactive particles having an average particle diameter of 0.1 to 2.5 μm. When the inert particles are in this range, characteristics such as winding property, stability of the deposited film, and withstand voltage when used as a capacitor element are improved. The more preferable average particle diameter of the inert particles is 0.3 to 2.2 μm, and the most preferable range is 0.5 to 2.0 μm.
[0024]
As the inert particles, inorganic particles such as silicon dioxide, titanium dioxide, zirconium dioxide, calcium carbonate, alumina, talc or kaolin are generally used. Further, inert aggregated particles obtained by aggregating these inert particles may be used, and organic particles of a high heat resistant polymer such as styrene, silicone, polymethylmethacrylate, or polyamideimide may be used.
[0025]
The average surface roughness (Ra) of the polyester film for capacitors of the present invention is preferably 5 nm or more and 150 nm or less, and the maximum roughness (Rt) is preferably 50 nm or more and 1.2 μm or less. When the average surface roughness (Ra) and the maximum roughness (Rt) are within the above ranges, particle projections having a uniform height are formed on the film surface, and the winding property, the stability of the deposited film, the capacitor Characteristics such as withstand voltage when used as an element are improved. A more preferable range of the average surface roughness (Ra) is 15 nm to 130 nm, and a more preferable range is 25 nm to 100 nm. A more preferable range of the maximum roughness (Rt) is 150 nm or more and 1.0 μm or less, and a more preferable range is 250 nm or more and 800 nm or less.
[0026]
  In the present invention, from the viewpoint of improving the withstand voltage at high temperatures and long-term heat resistance, the polyester film contains polyetherimide.Is a thing. The polyimide used in the present invention is a polymer containing a cyclic imide group as a repeating unit, and is preferably a polymer having melt moldability. Suitable polymers include, for example, US Pat. No. 4,141,927 and Patent No. No. 2622678, Japanese Patent No. 2609912, Japanese Patent No. 2606914, Japanese Patent No. 2596565, Japanese Patent No. 2596656, Japanese Patent No. 2598478, and other polyetherimides, Japanese Patent No. 2598536, Japanese Patent No. 2599171 JP-A-9-48852, Japanese Patent No. 2565556, Japanese Patent No. 2564636, Japanese Patent No. 2564737, Japanese Patent No. 2563548, Japanese Patent No. 2563547, Japanese Patent No. 2558341, Japanese Patent No. 2558339 Preliminary described in Patent No. 2834580 Patent Publication.
[0027]
As long as the effect of the present invention is not impaired, the main chain of polyimide contains structural units other than cyclic imide, for example, aromatic, aliphatic, alicyclic, alicyclic ester units, oxycarbonyl units, and the like. Of course, you may have.
[0028]
The polyimide suitably used in the present invention is a polyimide represented by the following general formula.
[0029]
[Chemical 1]

(In the above formula, Ar is an aromatic group having 6 to 42 carbon atoms, R is a divalent aromatic group having 6 to 30 carbon atoms, and 2 to 30 carbon atoms. And a divalent organic group selected from the group consisting of an alicyclic group having 4 to 30 carbon atoms.)
Examples of Ar in the above general formula include the following aromatic groups.
[0030]
[Chemical formula 2]

[0031]
[Chemical 3]

Moreover, as R in the said general formula, the aromatic group, aliphatic group, or alicyclic group shown next can be mentioned, for example.
[0032]
[Formula 4]

[0033]
[Chemical formula 5]

These aromatic groups and the like may be present alone or in combination of two or more in the polymer chain as long as the effects of the present invention are not impaired.
[0034]
As a polyimide used in the present invention, from the viewpoint of melt moldability with polyester and handleability, as a preferable example, for example, as shown by the following general formula, a structural unit containing an ether bond in a polyimide constituent component Mention may be made of polyetherimide.
[0035]
[Chemical 6]

(In the above formula, R1 and R2 are divalent organic groups selected from the group consisting of divalent aromatic or aliphatic groups having 2 to 30 carbon atoms, and alicyclic groups.)
As R1 and R2 of the said general formula, the aromatic group shown by the following formula group etc. can be mentioned, for example.
[0036]
[Chemical 7]

In the present invention, the polyetherimide is 2,2-bis [4- (2,3-dicarboxyphenoxy) having a structural unit represented by the following formula from the viewpoint of compatibility with polyester and melt moldability. The condensate of phenyl) propane dianhydride and m-phenylenediamine or p-phenylenediamine is particularly preferred.
[0037]
[Chemical 8]

In the present invention, when a polyetherimide having a glass transition temperature of preferably 350 ° C. or lower, more preferably 250 ° C. or lower is used, the effects of the present invention are easily obtained.
[0038]
The polyimide can be produced by the following method. For example, tetracarboxylic acid and / or an acid anhydride that is a raw material capable of deriving Ar in the above general formula, and an aliphatic primary diamine that is a raw material capable of deriving R in the above general formula and / or Or, it can be obtained by dehydrating and condensing one or more compounds selected from the group consisting of aromatic primary diamines. Specifically, a method of obtaining polyamic acid and then ring-closing by heating can be exemplified. . Alternatively, a method of chemically ring-closing using an acid anhydride and a chemical ring-closing agent such as pyridine or carbodiimide, polymerization is performed by heating the tetracarboxylic acid anhydride and the diisocyanate capable of deriving R to perform decarboxylation. A method etc. can be illustrated.
[0039]
Examples of the tetracarboxylic acid used in the above method include pyromellitic acid, 1, 2, 3, 4-benzenetetracarboxylic acid, 3, 3 ′, 4, 4′-biphenyltetracarboxylic acid, 2, 2 ′, 3,3′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 2,2 ′, 3,3′-benzophenonetetracarboxylic acid, bis (2,3-dicarboxyphenyl) Methane, bis (3,4-dicarboxyphenyl) methane, 1,1′-bis (2,3-dicarboxyphenyl) ethane, 2,2′-bis (3,4-dicarboxyphenyl) propane, 2, 2′-bis (2,3-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) ether, bis (2,3-dicarboxyphenyl) ether, bis (3,4-dicarbo) Xylphenyl) sulfone, bis (2,3-dicarboxyphenyl) sulfone, 2, 3, 6, 7-naphthalene tetracarboxylic acid, 1, 4, 5, 8-naphthalene tetracarboxylic acid, 1, 2, 5, 6- Naphthalenetetracarboxylic acid, 2,2′-bis [(2,3-dicarboxyphenoxy) phenyl] propane, and / or an acid anhydride thereof are used.
[0040]
Examples of the diamine include benzidine, diaminodiphenylmethane, diaminodiphenylethane, diaminodiphenylpropane, diaminodiphenylbutane, diaminodiphenyl ether, diaminodiphenylsulfone, diaminodiphenylbenzophenone, o, m, p-phenylenediamine, tolylenediamine, xylenediamine. And aromatic primary diamines having a hydrocarbon group of the aromatic primary diamine exemplified above as structural units, ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 2,2-dimethyl-1, and the like. 3-propanediamine, 1,6-hexamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 1,10-decamethylenediamine, 1,11-undecamethylene Amine, 1,12-dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,4- Cycloaliphatic dimethylamine, 2-methyl-1,3-cyclohexanediamine, isophorone diamine, etc., and aliphatic and alicyclic primary diamines having the hydrocarbon groups of these exemplified aliphatic and alicyclic primary diamines as structural units. It can be illustrated.
[0041]
When the polyester and the polyimide are compatible, the timing of adding the polyimide to the polyester is not particularly limited, but may be added before the polymerization of the polyester, for example, before the esterification reaction, or after the polymerization and before the melt extrusion. May be.
[0042]
  In the present invention, from the viewpoint of improving long-term heat resistance and withstand voltage at high temperatures, the content of polyimide in the polyester film is 5 to 50% by weight.is important. If the polyimide content is less than 5% by weight, the long-term heat resistance and withstand voltage at high temperatures of the polyester film for capacitors will decrease.TheOn the other hand, when the polyimide content exceeds 50% by weight, the film forming property is loweredShiThe frequency of film tearing increasesTheFrom the above viewpoint, the polyimide content isGood8-40% by weightAndMore preferably, it is 10 to 35% by weight.
[0043]
In obtaining the effects of the present invention, a film composed only of polyester and polyimide is a suitable film. Moreover, in the range which does not impair the effect of this invention, another polymer and an additive can be included.
[0044]
In addition, the thermal shrinkage rate at 30 ° C. for 30 minutes at a temperature of 150 ° C. in at least one direction in the longitudinal direction and the width direction of the polyester film for a capacitor of the present invention is not particularly limited. From the viewpoint of deterioration due to deformation or the like, it is preferably 0.1 to 3%. A more preferable range of 150 ° C. heat shrinkage is 0.3 to 2%, and a most preferable range is 0.5 to 1.5%.
[0045]
The thickness of the polyester film for capacitors of the present invention is not particularly limited, but is preferably in the range of 1 to 15 μm. When the film thickness is within this range, it is preferably used from the viewpoint of miniaturization of the capacitor and film-forming property of the film. A more preferable range of the film is 1.2 to 10 μm, most preferably 1.5 to 6 μm.
[0046]
The capacitor of the present invention can be produced by a known method using the polyester film for capacitors of the present invention. The conductor may be a metal foil made of a metal foil or a metal thin film formed by vacuum deposition, sputtering or the like on a polyester for capacitors. Moreover, when producing a capacitor | condenser, it is also possible to use not only the film of this invention but a multi-layered film (for example, polyolefin film, a fluorine film, etc.) and to use it. Examples of the metal constituting the conductor include aluminum, zinc, tin, titanium, nickel, and alloys thereof, but the present invention is not limited to this.
[0047]
The polyester film for capacitors of the present invention is formed into a film by a known film formation method such as melt extrusion film formation or solution cast film formation, and is provided for practical use. Although it may be non-oriented or a film uniaxially or biaxially oriented, it is more preferably a biaxially oriented film.
[0048]
Next, a case where polyethylene terephthalate (PET) is used as the polyester will be exemplified to describe a preferred method for producing the polyester film for capacitors of the present invention. However, the present invention is not limited to such a production method.
[0049]
First, carboxylic acid or its alkyl ester containing terephthalic acid as a main component and glycol containing ethylene glycol as its main component are esterified at 130 to 260 ° C. in the presence of a metal catalyst compound such as calcium, magnesium, lithium or manganese element. Or transesterification is performed. Thereafter, a catalyst compound composed of antimony, germanium or titanium element and a phosphorus compound are added, and a polycondensation reaction is performed at a temperature of 220 to 300 ° C. under a high vacuum. Examples of the phosphorus compound include phosphorous acid, phosphoric acid, phosphoric acid triester, phosphonic acid, and phosphonate, but are not particularly limited, and two or more of these phosphorus compounds may be used in combination.
[0050]
The amount of the catalyst compound added is not particularly limited, but the object of the present invention is achieved by including the ratio of the catalyst metal compound such as calcium, magnesium, lithium or manganese to the phosphorus compound so as to satisfy the following formula: This is preferable.
0.3 ≦ (M / P) ≦ 1.8
(Here, M is the total number of moles of catalytic metal elements such as calcium, magnesium, lithium or manganese in the film, and P is the number of moles of phosphorus element in the film.)
Further, an antioxidant, a heat stabilizer, a lubricant, an ultraviolet absorber, a nucleating agent, and inorganic and organic particles for forming surface protrusions are added as needed at any stage from esterification or transesterification to polycondensation.
[0051]
Then, it vacuum-drys at 180 degreeC for 3 hours or more. Thereafter, these are put into an extruder, melt extruded at 270 to 320 ° C., passed through a filter, and then discharged into a sheet form from a T die, and this sheet-like product is cooled to a surface temperature of 20 to 70 ° C. It adheres to the top and is cooled and solidified to obtain a substantially non-oriented unstretched polyester film.
[0052]
  Moreover, when obtaining the polyester film for capacitors of the present invention as a laminated film, the production method up to the unstretched polyester film is produced in the following steps, but is an example and is not limited thereto. First, a laminated polyester that is discharged from a die by melt extrusion using at least two or more extruders, and the molten polymer is cooled and solidified to form a sheet.the filmIn one production method, one unit supplies polyester and polyimide to an extruder and melts at 270 to 320 ° C., and at least one unit similarly supplies polyester and polyimide to the extruder and melts at 270 to 320 ° C. The melt is merged in the pipe or in the base and discharged from the base, and the sheet-like material is brought into close contact with a cooling drum having a surface temperature of 20 to 70 ° C. to be cooled and solidified. An unstretched polyester film is obtained.
[0053]
Next, this unstretched polyester film is oriented by biaxial stretching. As the stretching method, sequential biaxial stretching or simultaneous biaxial stretching can be used. The conditions for biaxial stretching are not particularly limited, but it is preferable to stretch the film in the longitudinal direction and the width direction of the film at a magnification of 4.0 to 6.0 in one or more stages. The stretching temperature may be in the range of 90 to 180 ° C, and it is more preferable to perform biaxial stretching in the longitudinal direction and the width direction in the range of glass transition temperature (Tg) to (Tg + 40) ° C of the unstretched polyester film. Furthermore, you may redraw as needed. The heat treatment after stretching may be performed at a temperature in the range of 175 ° C. to 220 ° C., preferably heat treatment at 190 to 215 ° C. for 1 to 30 seconds, and then a rapid cooling treatment at 80 to 120 ° C. is preferably performed. Furthermore, it is effective to obtain a 1-9% relaxation treatment in the width direction at the stage of rapid cooling of the film during heat treatment and / or after heat treatment, in order to obtain the polyester film for capacitors of the present invention.
[0054]
Next, the manufacturing method of the film capacitor | condenser excellent in the heat resistance concerning this invention using the polyester film for condensers of this invention obtained as mentioned above is demonstrated.
[0055]
A capacitor film obtained as described above is used as a dielectric, and a metal foil or a metal thin film is used as a conductor to produce a metallized film for a heat-resistant capacitor. The effect of the present invention is more easily obtained when using a metallized film having a metal thin film as a conductor. In this case, as the metal thin film forming method, a well-known vapor deposition method, sputtering method, or the like can be used. In particular, the dielectric film thickness is 1.3 to 8 μm, the vapor deposition film thickness is 50 to 200 angstroms, or the surface of the metal film. In order to obtain the effect of the present invention, it is preferable to use a vapor-deposited metallized film having a resistance value of 0.5 to 5 Ω / cm as a capacitor.
[0056]
Subsequently, the capacitor element obtained in this manner is subjected to pressing, end face sealing and lead wire attachment, and voltage treatment, heat treatment, etc., if necessary, to obtain a capacitor. Here, the press at the time of device fabrication is performed at a temperature of 120 to 180 ° C. and a press pressure of 20 to 100 kg / cm from the viewpoint of suppressing a decrease in charge life due to partial damage.²It is preferable to process for 1 to 30 minutes under these conditions. More preferable pressing conditions are 120 to 160 ° C., pressing pressure 20 to 60 kg / cm.²The processing time is 1 to 8 minutes.
[0057]
In the present invention, the film for heat-resistant capacitors may be subjected to a known corona discharge treatment, and various polymers are laminated for the purpose of imparting adhesiveness, heat sealability, moisture resistance, lubricity and surface smoothness. You may use in the structure covered with organic or / and an inorganic composition. Further, the capacitor of the present invention may be impregnated with insulating oil or the like and used as a so-called oil-immersed capacitor.
[0058]
[Methods for measuring physical properties and methods for evaluating effects]
The characteristic value measurement method and the effect evaluation method in the present invention are as follows.
[0059]
(1) Content of polyester and polyimide
Dissolve both polyester and polyimide in a suitable solvent (eg HFIP / deuterated chloroform) and measure the NMR spectrum of the 1H nucleus. In the obtained spectrum, the peak area intensity of absorption peculiar to polyester and polyimide (for example, the aromatic proton of terephthalic acid for PET, the aromatic proton of bisphenol A for PEI) is determined, and the ratio and proton The molar ratio of the blend is calculated from the number. Further, the weight ratio is calculated from the formula amount corresponding to the unit unit of the polymer. The measurement conditions are, for example, the following conditions, but are not limited to this because they differ depending on the type of polyester and polyimide.
[0060]
Equipment: BRUKER DRX-500 (Bruker)
Solvent: HFIP / deuterated chloroform
Observation frequency: 499.8MHz
Standard: TMS (0ppm)
Measurement temperature: 30 ° C
Observation width: 10KHz
Data point: 64K
acquisiton time: 4.952 seconds
pulse delay time: 3.048 seconds
Integration count: 256 times
Moreover, you may perform a composition analysis by microscopic FT-IR method (Fourier transform microinfrared spectroscopy) as needed. In that case, it calculated | required from ratio of the peak resulting from the carbonyl group of polyester, and the peak resulting from substances other than polyester. In order to convert the peak height ratio to the weight ratio, a calibration curve was prepared in advance from a sample with a known weight ratio, and the ratio of polyester to the total amount of polyester and other substances was determined. The thermoplastic resin ratio was determined from this and the particle content. Moreover, the X-ray microanalyzer was used together as needed.
[0061]
(2) Glass transition temperature (Tg)
Specific heat measurement was performed on the film sample with the following apparatus and conditions, and the film sample was determined according to JIS K7121.
[0062]
Apparatus: Temperature modulation DSC manufactured by TA Instrument
Measurement condition:
Heating temperature: 270-570K (RCS cooling method)
Temperature calibration: Melting point of high purity indium and tin
Temperature modulation amplitude: ± 1K
Temperature modulation period: 60 seconds
Temperature rising step: 5K
Sample weight: 5mg
Sample container: Aluminum open container (22 mg)
Reference container: Aluminum open container (18 mg).
[0063]
(3) Thermal shrinkage stress of film
The film sample is 4 mm wide, 20 mm measuring length, 1.5 g weight / 4 mm wide, and using a thermal analyzer TMA / SS6000 manufactured by Seiko Instruments Inc., the temperature is increased from 30 ° C. to 10 ° C./min under constant measuring length conditions. Measured to 260 ° C. at a rate. The heat shrinkage stress at 150 ° C. was determined from the obtained curve.
[0064]
(4) Lamination thickness ratio
Select 10 film samples arbitrarily, cut out in the cross-sectional direction, take a picture with an electron microscope at a magnification of 2000 times, measure the thickness of the film, the thickness of the film base layer, the thickness of the film lamination part, the ratio Was calculated. This was performed for 10 photographs and expressed as an average value.
[0065]
(5) Surface roughness (Ra) and maximum roughness (Rt)
Measurement was performed using a high precision thin film level gauge ET-10 manufactured by Kosaka Laboratory Ltd., and centerline average surface roughness (Ra, Rt) was determined according to JIS B0601. The radius of the stylus tip was 0.5 μm, the needle pressure was 5 mg, the measurement length was 1 mm, and the cutoff was 0.08 mm.
[0066]
(6) Film forming property
The film forming properties associated with film formation using a sequential biaxial stretching film forming machine were observed and judged according to the following criteria.
A: When there is no film breakage
○: When film tearing occurs rarely
Δ: When film breaks occur occasionally
×: When film tears occur frequently
(7) Film capacitor characteristics
[Production of capacitors]
Aluminum was vacuum-deposited on one side of the film so that the surface resistance value was 2 Ω / cm. At this time, vapor deposition is performed in a stripe shape having a margin portion running in the longitudinal direction (repetition of a vapor deposition portion width of 58 mm and a margin portion width of 2 mm). Next, a blade was inserted into the center of each vapor deposition section and the center of each margin section and slitted to obtain a tape-shaped take-up reel having a total width of 30 mm having a margin of 1 mm on the left or right. The obtained reels having the left margin and the right margin were overlapped and wound one by one to form a capacitor element having a capacitance of 2.2 μF, and another 12 μm PET film was wound around the outer periphery three times. This capacitor element is 130 ° C. and 30 kg / cm.²Was pressed at a temperature and pressure of 5 minutes. Metallicon was sprayed on both end faces to form external electrodes, and lead wires were welded to the metallicon. This capacitor is charged once for 30 seconds at a voltage of DC 150 V / μm (in terms of film thickness), and is again performed by reversing the polarity of the electrodes applied to the two lead wires. After confirming that the capacitance of the produced capacitor was within ± 10% and that the insulation resistance was 10000 MΩ or more, this standard was selected. Furthermore, this capacitor element was put in a resin case, and after injecting an epoxy resin (EX-265) manufactured by Sanyu Rec Co., Ltd., the epoxy resin was cured under conditions of 100 ° C. × 2 hours to obtain a capacitor element.
[0067]
[Long-term heat resistance test]
For the five capacitors, the capacitor capacity is measured in advance, and this value is calculated as C_SAnd Next, it is placed in an oven under conditions of a temperature of 150 ° C. and a voltage of 50 V / μm (DC), and the capacitor capacity after 500 hours has passed._EThen, the value obtained by the following formula is evaluated by the change in the capacitance of the capacitor.
ΔC / C = (C_S-C_E) / C_S
[150 ° C breakdown voltage]
After the capacitor is left in an oven at 150 ° C. for 60 minutes, a DC voltage is applied at a voltage increase rate of 100 V / sec, the capacitor breaks down, and the voltage when a current of 10 mA or more flows is defined as a breakdown voltage. did. In this invention, the average value of the dielectric breakdown voltage value of 30 capacitors is shown. When the capacity of the capacitor is large and a current of 10 mA or more flows only with the charging current, the current value is set to an appropriate value that can separate the charging current and the breakdown current.
[0068]
[High temperature insulation resistance]
A voltage of DC 100 V was applied in an oven adjusted to 125 ° C., and the value after 1 minute was measured with an insulation resistance meter.
[0069]
【Example】
Next, this invention is demonstrated based on an Example.
[0070]
(referenceExample 1)
  Calcium acetate was added as a transesterification reaction catalyst to a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, and heated to increase the temperature to distill methanol to conduct transesterification. Subsequently, the transesterification product was added with antimony trioxide as a polymerization catalyst and phosphoric acid as a heat stabilizer, and transferred to a polycondensation reaction tank. Next, the reaction system is gradually depressurized while heating and heating, polymerized while distilling methanol by stirring the inside at 290 ° C. under reduced pressure, and discharged when the degree of polymerization increased to an intrinsic viscosity of 0.62. Polyethylene terephthalate (PET) with M / P = 1.16 was obtained. The obtained pellets of inherent viscosity 0.62 (containing 0.1% by weight of agglomerated silica having an average diameter of 2.5 μm) were vacuum-dried at 180 ° C. for 3 hours and then fed, melt-extruded from an extruder, and surface temperature 25 While applying an electrostatic charge to a cast drum at 0 ° C., the film was closely cooled and solidified to produce an unstretched film. This unstretched film was stretched at a magnification of 4.5 times in the longitudinal direction of the film at a temperature of 100 ° C. using a difference in peripheral speed of the roll using a longitudinal stretching machine composed of a plurality of heated roll groups. . Thereafter, both ends of the film are gripped with clips and guided to a tenter, stretched in the width direction of the film at a stretching temperature of 105 ° C. and a stretching ratio of 3.5 times, and subsequently heat treated at a temperature of 200 ° C. for 3 seconds. Thereafter, the film was subjected to a 4% relaxation treatment in the transverse direction in a cooling zone controlled at 100 ° C. and cooled to room temperature, and then the film edge was removed to obtain a polyester film for capacitors having a thickness of 6 μm. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film for capacitors.
[0071]
[Table 1]

  Also,the aboveUsing the polyester film for capacitors, a capacitor element was prepared as described above, and then packaged with an epoxy resin, and then the characteristics of the capacitor were evaluated. The results are shown in Table 2. The obtained capacitor was a capacitor excellent in capacity change after a long-term heat resistance test and excellent in high-temperature dielectric breakdown voltage and high-temperature insulation resistance.
[0072]
[Table 2]

(referenceExample 2)
  Except for using polyethylene-2,6-naphthalate (PEN) obtained by a known method instead of polyethylene terephthalate (PET),referenceA polyester film was obtained in the same manner as in Example 1. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film. In addition, a capacitor element was prepared using the obtained polyester film, and then packaged with an epoxy resin, and then the characteristics of the capacitor were evaluated. The results are shown in Table 2. The obtained capacitor was a capacitor excellent in capacity change after a long-term heat resistance test and excellent in high-temperature dielectric breakdown voltage and high-temperature insulation resistance.
[0073]
(referenceExample 3)
  referencePET (50 wt%) having an intrinsic viscosity of 0.62 obtained in the same manner as in Example 1 and polyetherimide (absolute weight average molecular weight 30,000, Nippon Gee Plastics ( “Ultem” (registered trademark) 1010) (50% by weight) manufactured by Kyushu Co., Ltd. is dry blended and melt-kneaded using a co-rotating twin-screw kneading extruder (TEM-35B manufactured by Toshiba Machine Co., Ltd.) A blend chip containing 50% by weight of polyetherimide was prepared. Melt kneading was performed under the conditions of 310 ° C., average residence time of 3.5 minutes, and vent vacuum of 0.5 mmHg. Using an extruder, pellets of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.62 (containing 0.1% by weight of agglomerated silica having an average diameter of 2.5 μm) (80% by weight) and an extruder heated to 285 ° C. and the above Blend chips (20% by weight) are vacuum-dried at 180 ° C for 3 hours, then supplied, melt-extruded from an extruder, solidified by cooling and solidifying while applying an electrostatic charge to a cast drum with a surface temperature of 25 ° C, and producing an unstretched film did. This unstretched film was stretched at a magnification of 4.5 times in the longitudinal direction of the film at a temperature of 110 ° C. using a difference in peripheral speed of the roll using a longitudinal stretching machine composed of a plurality of heated roll groups. . Thereafter, both ends of the film are gripped with a clip, guided to a tenter, stretched in the width direction of the film at a stretching temperature of 115 ° C. and a stretching ratio of 3.5 times, and subsequently heat treated at a temperature of 200 ° C. for 3 seconds. Thereafter, the film was subjected to a 4% relaxation treatment in the transverse direction in a cooling zone controlled at 100 ° C. and cooled to room temperature, and then the film edge was removed to obtain a polyester film having a thickness of 6 μm. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film. Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. The obtained capacitor was a capacitor excellent in capacity change after a long-term heat resistance test and excellent in high-temperature dielectric breakdown voltage and high-temperature insulation resistance.
[0074]
(referenceExample 4)
  Change the content of polyetherimide,referenceA polyester film was obtained in the same manner as in Example 3. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained film. Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. The obtained capacitor was a capacitor excellent in capacity change after a long-term heat resistance test and excellent in high-temperature dielectric breakdown voltage and high-temperature insulation resistance.
[0075]
(Example1)
  referencePET (50 wt%) having an intrinsic viscosity of 0.62 obtained in the same manner as in Example 1 and polyetherimide (absolute weight average molecular weight 30,000, Nippon Gee Plastics ( “Ultem” (registered trademark) 1010) (50% by weight) manufactured by Kyushu Co., Ltd. is dry blended and melt-kneaded using a co-rotating twin-screw kneading extruder (TEM-35B manufactured by Toshiba Machine Co., Ltd.) A blend chip containing 50% by weight of polyetherimide was prepared. Melt kneading was performed under the conditions of 310 ° C., average residence time of 3.5 minutes, and vent vacuum of 0.5 mmHg. Two extruders were used, and the extruder A heated to 285 ° C. was filled with polyethylene terephthalate (PET) pellets (80% by weight) having an intrinsic viscosity of 0.62 and the blended chip (b) (20% by weight) of 180%. Extruder B, which was supplied after being dried in vacuum at 3 ° C. for 3 hours and also heated to 285 ° C., was fed pellets of PET (containing 0.1% by weight of agglomerated silica having an average diameter of 2.5 μm) of 0.62 Wt%) and the above blended chip (b) (20 wt%) after being vacuum-dried at 180 ° C. for 3 hours, and supplied so that the polymer from Extruder A is the main layer and the polymer from Extruder B is the outermost layer In order to laminate three layers in a T-die (lamination ratio B / A / B = 3/10/3), solidify, cool and solidify while applying an electrostatic charge to a cast drum with a surface temperature of 25 ° C., unstretched Made the filmThe unstretched film thus obtained was used in a longitudinal direction of the film at a temperature of 110 ° C. at a temperature of 110 ° C. using a longitudinal stretching machine composed of a plurality of heated roll groups and utilizing the peripheral speed difference of the rolls. The film was stretched at a double magnification. Thereafter, both ends of the film are gripped with a clip, guided to a tenter, stretched in the width direction of the film at a stretching temperature of 115 ° C. and a stretching ratio of 3.5 times, and subsequently heat treated at a temperature of 200 ° C. for 3 seconds. Thereafter, the film was subjected to a 4% relaxation treatment in the transverse direction in a cooling zone controlled at 100 ° C. and cooled to room temperature, and then the film edge was removed to obtain a laminated polyester film having a thickness of 6 μm. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained laminated polyester film. Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. The obtained capacitor was a capacitor excellent in capacity change after a long-term heat resistance test and excellent in high-temperature dielectric breakdown voltage and high-temperature insulation resistance.
[0076]
(Example2)
  Example except that the lamination thickness ratio of the base layer part (A layer) and the lamination part (B layer) was set to the values shown in Table 1.1In the same manner, a polyester film was obtained. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film. Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. The obtained capacitor was a capacitor excellent in capacity change after a long-term heat resistance test and excellent in high-temperature dielectric breakdown voltage and high-temperature insulation resistance.
[0077]
(Comparative Example 1)
  Other than having made the draw ratio in the machine direction of the film 3.0 times,referenceA polyester film was obtained in the same manner as in Example 1. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film. Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. Since the obtained capacitor had a glass transition temperature outside the specified range of the present invention, only a capacitor having a poor capacity change, high temperature breakdown voltage and high temperature insulation resistance after a long-term heat resistance test was obtained.
[0078]
(Comparative Example 2)
  Except for stretching in the width direction of the film, followed by heat treatment at 170 ° C. for 3 seconds.referenceA polyester film was obtained in the same manner as in Example 1. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film.
[0079]
Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. Since the obtained capacitor had a heat shrinkage stress at 150 ° C. outside the specified range of the present invention, only a capacitor with inferior capacity change, high temperature breakdown voltage and high temperature insulation resistance after a long-term heat resistance test was obtained. It was.
[0080]
(Comparative Example 3)
  Except for stretching in the width direction of the film, followed by heat treatment at 245 ° C. for 3 seconds,referenceA polyester film was obtained in the same manner as in Example 1. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film. Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. Since the obtained capacitor had a heat shrinkage stress at 150 ° C. outside the specified range of the present invention, only a capacitor having a poor capacity change, high temperature breakdown voltage and high temperature insulation resistance after a long-term heat resistance test can be obtained. It was.
[0081]
(Comparative Example 4)
  Change the content of polyetherimide,referenceA polyester film was obtained in the same manner as in Example 3. Table 1 shows Tg, heat shrinkage stress, t / d, surface roughness, maximum roughness and film forming property of the obtained polyester film. Since Tg was outside the specified range of the present invention, tearing frequently occurred during film formation. Moreover, the capacitor | condenser element was produced using the polyester film for capacitor | condensers of this invention, and the exterior was covered with the epoxy resin after that, and the characteristic evaluation of the capacitor | condenser was performed. The results are also shown in Table 2. Since the obtained capacitor had a heat shrinkage stress at 150 ° C. outside the specified range of the present invention, only a capacitor with inferior capacity change, high temperature breakdown voltage and high temperature insulation resistance after a long-term heat resistance test was obtained. It was.
[0082]
【The invention's effect】
According to the present invention, a polyester film for a capacitor having excellent heat resistance and electrical characteristics (withstand voltage) and excellent in productivity can be obtained. When the polyester film for capacitors of the present invention is used as a film capacitor, a film capacitor excellent in long-term heat resistance and withstand voltage at high temperatures can be obtained.

Claims (5)

It is a polyester film containing 5 to 50 wt% of polyimide, and the polyester film is a laminated film in which a laminated part (B layer) is provided on at least one outermost layer of a base layer part (A layer). The relationship between the average particle diameter d of the inert particles contained in the B layer) and the thickness t of the laminated portion (B layer) is 0.05 ≦ (t / d) ≦ 10, and the base layer portion (A layer) ) And the laminated portion (B layer) is 10: 0.5 to 5, the glass transition temperature of the polyester film is 100 ° C. or higher and lower than 150 ° C., and heat shrinkage at 150 ° C. in the longitudinal direction. A polyester film for capacitors, wherein the stress is 1500 kPa or more and less than 3500 kPa. The average surface roughness (Ra) is at 5nm or 150nm or less, a polyester film for capacitor according to claim 1 Symbol placement, wherein the maximum roughness (Rt) is 50nm or more 1.2μm or less. The polyester film for a capacitor according to claim 1 or 2 , wherein the polyester is polyethylene terephthalate, polyethylene-2,6-naphthalate, a copolymer or a modified product thereof. The polyester film for a capacitor according to any one of claims 1 to 3, wherein the polyimide is a polyetherimide. The capacitor | condenser formed using the polyester film for capacitors in any one of Claims 1-4 .