JP4505774B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

（式中、Ｒ^１及びＲ^２は、各々独立に水素または炭素数１〜６の直鎖状もしくは分岐状の飽和もしくは不飽和の炭化水素基、もしくは炭素数１〜６の直鎖状もしくは分岐状の飽和または不飽和のアルコキシ基、水酸基、ハロゲン原子、ニトロ基、シアノ基、トリハロメチル基、フェニル基及び置換フェニル基等から選ばれるいずれかの一価基を表わす。また、Ｒ^１及びＲ^２が互いに任意の位置で結合して、少なくとも１つ以上の５〜７員環の飽和もしくは不飽和の環状構造を形成する二価鎖を少なくとも１つ以上形成してもよい。Ｘはヘテロ原子を表わしＳ、Ｏ、Ｓｅ、ＴｅまたはＮＲ^３である。Ｒ^３はＨ、炭素数１〜６の直鎖状もしくは分岐状の飽和もしくは不飽和の炭化水素基、フェニル基、もしくは炭素数１〜６の直鎖状もしくは分岐状の飽和または不飽和のアルコキシ基を表わす。上記のＲ^１、Ｒ^２及びＲ^３のアルキル基、アルコキシ基の鎖中には、カルボニル結合、エーテル結合、エステル結合、アミド結合、イミノ結合を任意に含有してもよい。ただし、δは０〜１の範囲である。）で示される構造単位を含むπ電子共役重合体である。
さらに好ましくは一般式（２）

（式中、Ｒ^４及びＲ^５は、各々独立に水素または炭素数１〜６の直鎖状もしくは分岐状の飽和もしくは不飽和の炭化水素基、もしくは炭素数１〜６の炭化水素基が互いに任意の位置で結合して、式中記載の２つの酸素元素を含む少なくとも１つ以上の５乃至７員環の複素環状構造を形成する置換基を表わす。また前記環状構造を形成する範囲には、置換ビニレン基または置換Ｏ−フェニレン基等の化学構造が含まれる。δは０〜１の範囲である。）で示される構造単位を含むπ電子共役重合体である。
前記一般式（１）において、置換基Ｒ^１、Ｒ^２及びＲ^３が表わす炭素数１〜６の直鎖状もしくは分岐状の飽和もしくは不飽和の炭化水素基の例としては、メチル基、エチル基、ビニル基、プロピル基、アリル基、イソプロピル基、ブチル基、１−ブテニル基が挙げられる。また、炭素数１〜６の直鎖状もしくは分岐状の飽和または不飽和のアルコキシ基の例としては、メトキシ基、エトキシ基、プロポキシ基、イソプロポキシ基、ブトキシ基が挙げられる。
さらに前記炭化水素基やアルコキシ基以外置換基の例としては、ニトロ基、シアノ基、フェニル基及び置換フェニル（Ｃｌ、Ｂｒ、Ｆ等のハロゲン原子置換フェニル）基が挙げられる。前記Ｒ^１、Ｒ^２のアルキル基、アルコキシ基の鎖中には、カルボニル結合、エーテル結合、エステル結合、アミド結合、イミノ結合を任意に含有してもよく、特に有用な例としてはメトキシエトキシ基、メトキシエトキシエトキシ基が挙げられる。
また、Ｒ^１及びＲ^２が、互いに任意の位置で結合して少なくとも１つ以上の５〜７員環の飽和もしくは不飽和の環状構造を形成する二価鎖を少なくとも１つ以上形成する一般式（１）の例としては、３，４−プロピレン構造［一般式（３）］、３，４−ブチレン構造［一般式（４）］、３，４−（２’−ブテニレン）構造［一般式（５）］、３，４−ブタジエニレン構造［一般式（６）］、ナフト［２，３−ｃ］縮合構造［一般式（７）］などが挙げられる。

ここで、Ｘはヘテロ原子を表わし、例としては、Ｓ、Ｏ、Ｓｅ、ＴｅまたはＮＲ^３である。ＸがＳである前記３，４−ブタジエニレン構造（一般式（６））は、一般式（１）の繰り返し構造単位では別名イソチアナフテニレン構造と呼ばれる。さらに、ナフト［２，３−ｃ］縮合構造（一般式（７））は、一般式（１）の場合はナフト［２，３−ｃ］チエニレン構造と呼ばれる。式中、δは繰り返し構造単位当りの荷電数を表わし、０〜１の範囲の値である。
一般式（２）中のＲ^４及びＲ^５の例としては、メチル基、エチル基、プロピル基、イソプロピル基、ビニル基、アリル基が挙げられる。さらに、Ｒ^４及びＲ^５の炭素数１〜６の炭化水素基が互いに任意の位置で結合して、前記一般式（２）中記載の２つの酸素元素を含む、少なくとも１つ以上の５乃至７員環の複素環状構造を形成する置換基としては、１，２−エチレン、１，２−プロピレン、１，２−ジメチル−エチレンが好ましい。
また、Ｒ^４及びＲ^５は、前記、炭素数１〜６の炭化水素基が互いに任意の位置で結合して、置換ビニレン基または置換Ｏ−フェニレン基等の不飽和炭化水素の環状構造を形成する具体例としては、１，２−エチレン［一般式（８）］、１，２−シクロヘキシレン［一般式（９）］、１，２−ジメチル−ｏ−フェニレン［一般式（１０）］が挙げられる。

本発明の固体電解コンデンサ及びその製造方法において使用されるモノマー化合物のうち、例えばチオフェン、ピロールや３，４−エチレンジオキシチオフェンのモノマー化合物は公知であり、これらのモノマー化合物を重合し得る酸化剤も多くは公知である。
しかしながら、上記導電性重合体組成物中にゴム状弾性体を使用した固体電解質を具備したコンデンサはこれまで知られていない。
本発明においては固体電解質を構成しているゴム状弾性体は導電性重合体中に溶解しているかまたはマトリックスとしての導電性重合体中に分散していると考えられる。
本発明の固体電解コンデンサの固体電解質を構成している前記π共役系導電性重合体に対するゴム状弾性体の配合量は、０．０１〜２５質量％、好ましくは０．１〜１０質量％である。ゴム状弾性体を含む固体電解質を具備した電解コンデンサは、特に低インピーダンス特性に優れ、火花電圧試験に耐久性があり、また外的応力に緩和性のある耐熱性固体電解コンデンサとなる。
ゴム状弾性体の配合量が０．０１質量％に満たない時は、ゴム状弾性体を配合した効果がまったく期待できない。また配合量が２５質量％を超える時は固体電解質の導電性が低下する。特にゴム状弾性体が多くなりマトリックスが逆転すると導電性は急激に低下するので配合量は２５質量％以下にすることが必要である。したがって固体電解質の組成物全質量に対して０．０１〜２５質量％の範囲、好ましくは０．１〜１０質量％の範囲である時には低インピーダンス特性に優れたコンデンサを提供できる。
通常、固体電解コンデンサの製造方法において、高容量の高周波特性並びにｔａｎδ、漏洩電流、耐熱性（リフロー性）、インピーダンス特性、耐久性等を改善するためには、前記固体電解質の製造（形成）方法が重要である。そのためには固体電解質を構成する導電性重合体のπ電子共役構造、ゴム状弾性体との組み合わせによる導電性重合体組成物の構成、導電性重合体組成物層を微細な表面構造の誘電体層上に密に充填形成して導電パスの均一性を向上させることが重要であり、そのうちでも特に導電性重合体組成物の構成が非常にコンデンサ特性に影響を与える。
本発明の固体電解質の製造方法においては、前記π電子共役構造を有する重合体を形成する際に、モノマー及び／または酸化剤を含む溶液にゴム状弾性体を添加することにより上記溶液の付着量が増加し、必要含浸回数を減少することができる特徴がある。また、ゴム状弾性体を添加することで、導電性重合体組成物に応力緩和性を提供することができるためエージングや封止等による外的圧力に対し、弾力性が上がる。その結果、初期特性の漏洩電流の低下、高温、高湿下に長時間放置した際の容量、損失等の劣化が小さくなる等の特徴があらわれる。
具体的な例としては、モノマー化合物を含む溶液にゴム状弾性体の溶液または分散液を混合し、これを弁作用金属陽極箔の微細孔を有する誘電体皮膜上に被覆し、モノマーを酸化剤の作用によって酸化的重合を起こさせ、生じた該重合体組成物を固体電解質として誘電体表面上に形成させる。そして、前記工程を１つの陽極基板に対して１回以上、好ましくは３〜２０回繰り返すことによって緻密な固体電解質層を容易に形成することができる。
例えば、好ましい製造工程の一つとして浸漬法を代表にして説明する。前記重合反応にあっては誘電体皮膜を形成した弁作用金属陽極箔を、酸化剤を含む溶液（溶液１）に浸漬する工程とモノマー化合物及びゴム状弾性体を含む溶液（溶液２）に浸漬する工程を含むものである。浸漬工程の順序としては前記溶液１に浸漬した後で前記溶液２に浸漬する工程で行ってもよく、また逆順に前記弁作用金属陽極箔を前記溶液２に浸漬した後で前記溶液１に浸漬する工程で行ってもよい。
あるいは別の実施形態として、該陽極箔を、酸化剤とゴム状弾性体を含む溶液（溶液３）に浸漬する工程とモノマー化合物を含む溶液（溶液４）に浸漬する工程を含むものであってもよい。この場合には前記溶液３に浸漬した後で前記溶液４に浸漬する工程で行うか、または逆順に該陽極箔を前記溶液４に浸漬した後で前記溶液３に浸漬する工程を含んだ製造方法を採用してもよい。前記溶液１乃至溶液４はそれぞれ懸濁状態のものでもよい。
さらには、前記浸漬工程を塗布法、吹きつけ法あるいは流延法など、陽極箔上において上記の重合反応を進行可能な被覆法に代えることもできる。
溶液１乃至４の溶媒は必要に応じて同じ溶媒でもよく、あるいは異なった溶媒系でもよく、溶媒の種類に応じて溶液１と溶液２の間あるいは溶液３と溶液４の被覆工程の間に乾燥工程を入れてもよい。
前記導電性重合体皮膜（固体電解質）を形成しコンデンサ素子とした後は、これを有機溶媒洗浄または水洗により洗浄する工程を加えてもよい。洗浄用有機溶媒には好ましくは溶液１乃至４で使用した溶媒で行うのが簡便で好ましいが、単にモノマー化合物やドーパント能を有するアニオンを保持する化合物を溶解する溶媒であれば何でもよい。
さらに前記酸化的重合の繰り返し処理により固体電解質層を厚くする時は、ハンダ耐熱性（熱安定性）に優れた固体電解質の生成を容易にする。従来既知のポリピロール等からなる固体電解質を用いたコンデンサでは、高温、高湿度でのコンデンサ特性が大きく変動し信頼性を悪くしていたが、本発明の導電性重合体組成物からなる固体電解質を使用した固体電解コンデンサは熱安定性に優れ、かつドープ状態の安定性がよい。
これは、前記ゴム状弾性体を配合した導電性重合体組成物は誘電体表面のみならずその細孔内部まで充填性よく段階的に析出させることができること及び該重合体組成物の薄い膜質を作ることができるためであり、特にそれが何層にも重なった状態を形成した時に上記特性が強く発揮され、該重合体が誘電体皮膜に対するダメージを与えず、熱安定性に優れ、ゴム弾性体の柔軟性により外的ダメージから誘電体皮膜及び導電性重合体皮膜を保護するため、この固体電解質を使用したコンデンサはその性能を十分に享受できる。
本発明において使用できるゴム状弾性体としては、弾性ゴム又はゴム類似物質の特異な弾性を有するもので、外力によってひずみを受けるとそのひずみをもとに戻そうとする性質を有するものである。具体例として一般的なゴム（天然ゴム、ウレタンゴム、エチレン・プロピレン共重合体、エチレン・プロピレン・ジエン共重合体、スチレン−ブタジエンゴム、ブチルゴム、イソプレンゴム、シリコンゴム、フッ素系ゴムなどの合成ゴム）や熱可塑性エラストマー（スチレン系、オレフィン系、ウレタン系、１，２−ポリブタジエン系、塩ビ系など）を用いることができる。
フッ素系ゴムは分子中にフッ素原子を含む合成ゴムの総称で、特殊ゴムとして用いられ、汎用ゴムとは区別されている。含フッ素アクリレートの重合体、フッ化ビニリデン系共重合体、四フッ化エチレン−パーフルオロメチルビニルエーテル共重合体、含フッ素ホスファゼン系、含フッ素シリコーン系などがある。種類により性質が異なるが市販のゴムの中では抜群の耐熱性を有する。また、耐薬品性、耐候性などにも優れている。シリコンゴムは主鎖がシロキサン結合で構成され側鎖にメチル基、フェニル基等の置換基を持った線状重合体が相互に橋かけしたゴム状弾性体であり、耐熱性、電気絶縁性が良好である。導電性重合体の重合反応に対しては、好ましくは有機溶媒中に溶解できるもの、例えばポリエステルウレタン、ポリエーテルウレタン、フッ化ビニリデン−ヘキサプロピレン共重合体などが挙げられることができる。この時に使用する有機溶剤としては、エチルメチルケトン、アセトンなどのケトン系、酢酸イソプロピルなどの酢酸エステル系、ジオキサン、ＴＨＦなどのエーテル系、メタノールなどのアルコール系が望ましい。また有機溶媒に不溶性のゴムである時は、モノマーまたは酸化剤を含む溶液の溶媒と同じ溶媒またはこれに混合可能な溶媒の分散液を使用すればよい。
固体電解質が耐熱性を特に必要とする時は、耐熱性の高いフッ素系ゴム、シリコンゴムなどを使用する。
本発明で使用される酸化剤としては、ピロールやチオフェン類の酸化重合に対して適する公知の酸化剤であればよく、例えば特開平２−１５６１１号公報（米国特許第４９１０６４５号）記載の塩化鉄（ＩＩＩ）、Ｆｅ（ＣｌＯ_４）_３、有機酸鉄（ＩＩＩ）、無機酸鉄（ＩＩＩ）、アルキル過硫酸塩、過硫酸塩、過酸化水素、Ｋ_２Ｃｒ_２Ｏ_７等が広範に使用できる。
前記有機酸鉄（ＩＩＩ）の有機酸の例としては、メタンスルホン酸やドデシルベンゼンスルホン酸のような炭素数１〜２０のアルカンスルホン酸や脂肪族カルボン酸が挙げられる。しかしながら、前記酸化剤の使用範囲はすべての組み合わせが可能ということではなく、モノマー化合物の化学構造において酸化剤及び反応条件等に制限を受けることがある。
例えば、チオフェン類の酸化（重合）は、Ｈａｎｄｂｏｏｋ ｏｆ Ｃｏｎｄｕｃｔｉｎｇ Ｐｏｌｙｍｅｒｓ誌（Ｍａｒｃｅｌ Ｄｅｋｋｅｒ，Ｉｎｃ．社発行、１９８７年、９９頁、図５参照）の説明によると、置換基の種類により酸化電位（重合の起こり易さを示す１つの尺度）が大きくかわり、重合反応を左右する（酸化電位は約１．８〜約２．７Ｖの範囲に広範に広がっている）。従って具体的には使用するモノマー化合物と酸化剤には特定の組み合わせが必要であることが知られている。本発明ではこの制限の範囲内においてコンデンサ特性を改良できる製法上の組み合わせを見出し、前記課題の解決を行った。
本発明の導電性重合体では、必要に応じて共存させるドーパント能を有するアニオンとして前記酸化剤から産生される酸化剤アニオン（酸化剤の還元体）を対イオンに持つ電解質化合物または他のアニオン系電解質を使用することができる。具体的には、塩素イオン、ＣｌＯ_４イオン、炭素数１〜１２の脂肪族有機カルボン酸アニオン、硫酸アニオン、リン酸アニオン、炭素数１〜１２の脂肪族有機リン酸アニオン、ほう酸アニオンが挙げられる。またＮＯ^＋，ＮＯ_２ ^＋塩（例えば、ＮＯＢＦ_４、ＮＯＰＦ_６、ＮＯＳｂＦ_６、ＮＯＡｓＦ_６、ＮＯＣＨ_３ＳＯ_３、ＮＯ_２ＢＦ_４、ＮＯ_２ＰＦ_６、ＮＯ_２ＣＨ_３ＳＯ_３等）の電子受容体ドーパントを使用してもよい。
また、従来既知の分子アニオン（例えば、ＣｌＯ_４ ⁻、ＢＦ_４ ⁻等）とはドーパント能力（電荷移動錯体の安定性、導電性等）及び化学的性質が異なり、また従来既知の前記分子アニオン（ＣｌＯ_４ ⁻、ＢＦ_４ ⁻等）単独で使用する系に比べて優位な効果を示す。すなわち、複数のコンデンサ素子を製作した時のコンデンサ性能で比較した場合、特に優れた効果を引き出すことができる化合物として、本発明では、芳香族系化合物（スルホキノン、アントラセンモノスルホン酸、置換ナフタレンモノスルホン酸、置換ベンゼンスルホン酸）あるいは複素環式スルホン酸を用いてもよい。
本発明において使用するスルホキノンとは、分子内に一つ以上のスルホン酸基とキノン構造を有する化合物の総称であり、ドーパントとしてそのスルホン酸アニオンの形態で有効に働く化学構造であればよい。例えば、スルホキノンの基本骨格を例示すると、ｐ−ベンゾキノン、ｏ−ベンゾキノン、１，２−ナフトキノン、１，４−ナフトキノン、２，６−ナフトキノン、９，１０−アントラキノン（以下、単にアントラキノンと略す。）、１，４−アントラキノン、１，２−アントラキノン、１，４−クリセンキノン、５，６−クリセンキノン、６，１２−クリセンキノン、アセナフトキノン、アセナフテンキノン、カンホルキノン、２，３−ボルナンジオン、９，１０−フエナントレンキノン、２，７−ピレンキノン等を挙げることができる。
さらにまた、前記スルホキノンにおけるスルホン酸基は、前記キノン化合物の水素が一つ以上、スルホン酸基で置換された芳香族スルホン酸構造、もしくはＣ１〜１２の飽和または不飽和炭化水素基の２価基を介するスルホアルキレン基で置換された脂肪族スルホン酸構造を含むものである。さらに、前記スルホキノンの水素が一つ以上、Ｃ１〜１２、好ましくはＣ１〜６の飽和または不飽和アルキル基、あるいは同アルコキシ基、またはＦ、Ｃｌ、Ｂｒから選ばれる置換基で置換された化学構造であってもよい。
中でも、本発明において使用するスルホキノンとしてはアントラキノン、１，４−ナフトキノン、２，６−ナフトキノンの骨格を有するスルホキノンが好ましく使用される。例えばアントラキノン類の場合、アントラキノン−１−スルホン酸、アントラキノン−２−スルホン酸、アントラキノン−１，５−ジスルホン酸、アントラキノン−１，４−ジスルホン酸、アントラキノン−１，３−ジスルホン酸、アントラキノン−１，６−ジスルホン酸、アントラキノン−１，７−ジスルホン酸、アントラキノン−１，８−ジスルホン酸、アントラキノン−２，６−ジスルホン酸、アントラキノン−２，３−ジスルホン酸、アントラキノン−２，７−ジスルホン酸、アントラキノン−１，４，５−トリスルホン酸、アントラキノン−２，３，６，７−テトラスルホン酸、これらのアルカリ金属塩、及びこれらのアンモニウム塩等が使用できる。
１，４−ナフトキノン類の場合は、１，４−ナフトキノン−５−スルホン酸、１，４−ナフトキノン−６−スルホン酸、１，４−ナフトキノン−５，７−ジスルホン酸、１，４−ナフトキノン−５，８−ジスルホン酸、これらのアルカリ金属塩、及びこれらのアンモニウム塩等が使用できる。
２，６−ナフトキノン類の場合は、２，６−ナフトキノン−１−スルホン酸、２，６−ナフトキノン−３−スルホン酸、２，６−ナフトキノン−４−スルホン酸、２，６−ナフトキノン−３，７−ジスルホン酸、２，６−ナフトキノン−４，８−ジスルホン酸、これらのアルカリ金属塩、及びこれらのアンモニウム塩等が使用できる。
また、前記スルホキノンとしては、工業的な染料として知られている、例えばアントラキノンアイリスＲ、アントラキノンバイオレットＲＮ−３ＲＮがあり、これらも同様に有用なスルホキノン系ドーパントとして前記塩の形態で使用できる。
本発明において使用するスルホキノンは、化合物によってはモノマー化合物の重合反応に関与して、１つの酸化的脱水素化剤として働き、その結果スルホキノンは還元されてキノン構造体のプロトン付加体、すなわちハイドロキノン構造、またはキンヒドロンのまま、ドーパントとして固体電解質内に含有されてもよい。
本発明において使用するアントラセンモノスルホン酸は、一つのスルホン酸基がアントラセン骨格に置換したアントラセンモノスルホン酸化合物の総称であり、好ましい化合物としては、無置換のアントラセンスルホン酸やアントラセンスルホン酸のアントラセン環の水素がＣ１〜１２、好ましくは１〜６の直鎖状もしくは分岐状の飽和もしくは不飽和の炭化水素基またはアルコキシ基で一つ以上置換された置換化合物が挙げられる。
前記無置換のアントラセンモノスルホン酸アニオンを供出する化合物の具体例としてはアントラセン−１−スルホン酸、アントラセン−２−スルホン酸、アントラセン−９−スルホン酸及びそのアルカリ金属塩、アンモニウム塩等が挙げられる。また、上記アントラセン環の水素がさらに置換されたアントラセンモノスルホン酸置換化合物の置換基の具体例としては、メチル、エチル、プロピル、イソプロピル、ブチル、イソブチル、ｔ−ブチル、ペンチル、ヘキシル、オクチル、デシル、ドデシル等のアルキル基や、ビニル、アリル、３−ブテニル、５−ヘキセニル等の不飽和基、及びメトキシ、エトキシ、プロピルオキシ、ブトキシ、ペントキシ、ヘキシルオキシ、オクチルオキシ、デシルオキシ、ドデシルオキシ等が挙げられる。
本発明において使用する置換ナフタレンモノスルホン酸は、一つのスルホン酸基がナフタレン骨格に置換したナフタレンモノスルホン酸化合物及びアルコキシ置換ナフタレンモノスルホン酸化合物の総称であり、好ましい化合物としては、ナフタレンモノスルホン酸のナフタレン環の水素が炭素数１乃至１２、好ましくは１乃至６の直鎖状または分岐状の飽和もしくは不飽和のアルコキシ基で少なくとも一つ以上置換されてもよい化合物である。
前記置換ナフタレンモノスルホン酸アニオンを供出する化合物の具体例としては、ナフタレン−１−スルホン酸、ナフタレン−２−スルホン酸及びそのアルカリ金属塩、アンモニウム塩、有機第４級アンモニウム塩等の化合物骨格を有し、これにナフタレン環の水素がアルコキシ基で１つ以上置換されていてもよい化学構造を有するものが挙げられる。
本発明において使用する置換ベンゼンスルホン酸は、１つ以上のスルホン酸基がベンゼン骨格に置換したベンゼンスルホン酸及びアルキル置換ベンゼンスルホン酸の総称であり、好ましい化合物としては、無置換のベンゼンスルホン酸やベンゼンスルホン酸のベンゼン環の水素がＣ１〜２０、好ましくは１〜１２の直鎖状もしくは分岐状の飽和もしくは不飽和の炭化水素基で１つ以上置換された化合物が挙げられる。
本発明において使用できる複素環式スルホン酸アニオンとしては、一つ以上のスルホン酸基が複素環に直接またはアルキレン基を介して間接的に置換した化学構造を有する複素環式スルホン酸化合物のアニオンの総称であり、好ましい複素環化合物の骨格としては、モルホリン、ピペリジン、ピペラジン、イミダゾール、フラン、１，４−ジオキサン、ベンズイミダゾール、ベンゾチアゾリルチオ、ベンズイソオキサゾール、ベンゾトリアゾール、ベンゾフラン骨格が挙げられる。
前記複素環式スルホン酸アニオンを供出する化合物の具体例としては、２−イミダゾールスルホン酸、４−モルホリンプロパンスルホン酸、フラン−３−スルホン酸、２−ベンズイミダゾールスルホン酸、２−ベンズイミダゾールプロパンスルホン酸、４−メチル−１−ピペラジンメタンスルホン酸、２，３−ベンゾフラン−３−スルホン酸及びそれら化合物のナトリウム塩等のアルカリ金属塩、アンモニウム塩または第４級アンモニウム塩が挙げられる。
これらの中でも好ましいのは、芳香族系スルホン酸化合物（ドデシルベンゼンスルホン酸ナトリウム、ナフタレンスルホン酸ナトリウム、アントラキノン−２−スルホン酸ナトリウム、アントラキノン−２，６−ジスルホン酸アンモニウム、１，４−ナフトキノン−２−スルホン酸ナトリウム、３−メチル−２−アントラキノリルメタンスルホン酸ナトリウム、アントラセン−１−スルホン酸ナトリウム、アントラセン−２−スルホン酸ナトリウム、９，１０−ジメトキシアントラセン−２−スルホン酸テトラブチルアンモニウム塩、９，１０−ジヘキシルアントラセン−２−スルホン酸テトラブチルアンモニウム塩、２−プロピルオキシナフタレン−６−スルホン酸ナトリウム、２−プロピルオキシナフタレン−６−スルホン酸テトラブチルアンモニウム塩、２−メトキシナフタレン−６−スルホン酸ナトリウム、２，３−ジメトキシナフタレン−６−スルホン酸テトラブチルアンモニウム塩等）、複素環式スルホン酸（４−モルホリンプロパンスルホン酸ナトリウム、２−ベンズイミダゾールプロパンスルホン酸ナトリウム、４−メチル−１−ピペラジンスタンスルホン酸ナトリウム、２，３−ベンゾフラン−３−スルホン酸ナトリウム等）である。
本発明において固体電解質を形成するための、チオフェン及びピロール類モノマー化合物の化学重合においては、酸化剤として過硫酸塩の使用が特に好適である。チオフェン類の化学重合に特に好適に使用できる過硫酸塩としては、過硫酸アンモニウム、過硫酸カリウムが挙げられる。これに対し鉄（ＩＩＩ）塩系酸化剤の使用は、導電性重合体組成物中に鉄（元素）の残存が避けられず、コンデンサ特性に対して好ましくない。
しかし、上記のモノマー化合物に対して好適な過硫酸塩は、チオフェンモノマーには好適ではないというように、モノマーの種類によっては酸化剤として使用できない制限が存在する。
次に導電性重合体組成物層形成（重合反応）の好ましい条件について説明する。
重合反応に用いられるモノマー化合物、酸化剤、ドーパント、ゴム状弾性体のそれぞれの使用濃度は、モノマー、酸化剤、ドーパント及びゴム状弾性体の種類（置換基の種類も含む）や溶媒等との組合せによって異なるが、一般にはモノマー濃度として１×１０^−４〜１０モル／リットルの範囲であり、１×１０^−３〜５モル／リットルの範囲がさらに好ましい。
また、反応温度は、反応組成物の種類、反応方法等によって変わるので特に限定できるものでないが、一般的には−７０℃〜２５０℃の温度範囲、望ましくは−２０℃〜１５０℃であり、さらに０℃〜１００℃の温度範囲で行うことが好ましい。
前記重合反応において用いられる溶液または重合後の洗浄用溶媒としては、例えばテトラヒドロフラン（ＴＨＦ）、ジオキサン、ジエチルエーテル等のエーテル類；アセトン、メチルエチルケトン等のケトン類；ジメチルホルムアミド、アセトニトリル、ベンゾニトリル、Ｎ−メチルピロリドン（ＮＭＰ）、ジメチルスルホキシド（ＤＭＳＯ）等の非プロトン性極性溶媒；酢酸エチル、酢酸ブチル、酢酸イソプロピル等のエステル類；クロロホルム、塩化メチレン等の非芳香族系塩素化炭化水素溶媒；ニトロメタン、ニトロエタン、ニトロベンゼン等のニトロ化合物；メタノール、エタノール、プロパノール等のアルコール類；蟻酸、酢酸、プロピオン酸等の有機酸；該有機酸の酸無水物（例、無水酢酸等）及び水あるいはこれらの混合溶媒を用いることができる。好ましくは、水、アルコール類、ケトン類、酢酸エステル類及び／またはそれらの混合系が望ましい。
このようにして製造される固体電解質の電導度は、０．１〜２００Ｓ／ｃｍの範囲であるが、望ましい条件では１〜１００Ｓ／ｃｍ、さらに好ましくは１０〜１００Ｓ／ｃｍの範囲である。
図１を参照して本発明の固体電解コンデンサの構成の概要を示す。
接続用端子７に結合した細孔２が全面に設けられた一方の電極（陽極）１には、アルミニウム、チタン、タンタル、ニオブあるいはこれらを基質とする合金系等の弁作用を有する金属箔、棒あるいはこれらを主成分とする焼結体等の公知な材料が使用される。これらの金属電極表面は、誘電体層の形成と比表面積を大きくする目的で公知の方法によってエッチング処理や化成処理され、金属箔上に該金属系酸化皮膜層３を形成したものが用いられる。
固体電解質（導電性重合体組成物）４の形成は、弁作用金属電極箔の誘電体層上でモノマー化合物を重合する方法によることが好ましく、とりわけ該固体電解質においてはゴム状弾性体を含むことにより耐熱性、耐衝撃性の優れた導電性重合体組成物を上記誘電体皮膜細孔あるいは空隙構造を有する誘電体層上に化学的に析出する方法が好ましい。
このように形成した導電性重合体組成物層上にさらに電気的接触をよくするために他の導電体層５が設けられる。導電体層は、例えば導電ペースト層またはメッキ、金属蒸着、導電樹脂フィルム等により形成することができる。
このように、本発明の製造方法により製造される固体電解コンデンサは、更に上記導電体層の上を樹脂モールドするとか、樹脂ケース、金属製の外装ケース、樹脂ディッピング等による外装６を設け、これに接続用端子７を設けることにより各種の用途に適した固体電解コンデンサ製品とすることができる。
（ＩＩ）金属粉末含有導電体層にゴム状弾性体を含む場合
金属粉末含有導電体層にゴム状弾性体を含有させる場合には、金属粉末からなる導電性充填材及びゴム状弾性体をバインダーの主成分とする金属粉末含有導電性ペーストを使用する。
ゴム状弾性体としては、一般的なゴム（天然ゴム、ウレタンゴム、エチレン・プロピレン共重合体、エチレン・プロピレン・ジエン共重合体、スチレン−ブタジエンゴム、ブチルゴム、イソプレンゴム、シリコン系ゴム、フッ素系ゴムなどの合成ゴム）や熱可塑性エラストマー（スチレン系、オレフィン系、ウレタン系、１，２−ポリブタジエン系、塩ビ系など）を用いることができる。
これらの中でも耐熱性に優れたフッ素系ゴム、シリコン系ゴムが好ましく、特にフッ素系ゴムが好ましい。
フッ素系ゴムは分子中にフッ素原子を含む合成ゴムの総称で、特殊ゴムとして用いられ、汎用ゴムとは区別されている。含フッ素アクリレートの重合体、フッ化ビニリデン系共重合体、四フッ化エチレン−パーフルオロメチルビニルエーテル共重合体、含フッ素ホスファゼン系、含フッ素シリコーン系などがある。種類により性質が異なるが市販のゴムの中では抜群の耐熱性を有する。また、耐薬品性、耐候性などにも優れている。
導電性ペーストの溶剤としては、通常の導電性ペーストに使用する溶媒を同じもので良く、例えばＮ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルアセトアミド、ジメチルホルムアミド、酢酸ブチルなどの溶媒を単独または混合して使用する。導電性ペーストに配合する溶媒量は、導電性ペーストの使用目的に応じた粘度となるように配合することが必要であるが、通常はペーストの固形分に対して等量ないし十倍の量を使用する。
導電性ペーストに用いられる導電性充填材としては、銀粉の他、金、銅等の金属粉末、カーボン粉末なども用いられるが、銀粉が好ましく、銀粉を充填材全体の８０質量％以上含むものが特に好ましい。粉末の粒度は平均粒径で１〜１０μｍが好ましい。平均粒径が１μｍ未満では嵩密度が小さく、ペーストの体積が大きくなり、導電体層の形成に不利である。また平均粒径が１０μｍを超えると粗すぎて、陰極リード端子との接続不良が起こり易い。
以下、好ましいバインダーであるフッ素系ゴムを使用する場合について説明する。
好ましいバインダーはフッ素系ゴムが好ましくはバインダーの８０〜１００質量％がフッ素系ゴムからなるものである。残りの成分としては従来の樹脂等を混合することができる。フッ素系ゴムはゴム弾性を有するもので歪を受けるとその歪を元に戻そうとする性質があり、歪が戻らないフッ素系樹脂とは区別される。フッ素系ゴムとしては、例えば公知のフッ化ビニリデン系共重合体ゴム、６−フッ化プロピレン系共重合体ゴム、４−フッ化エチレン系共重合体ゴム、含フッ素アクリレートゴム、含フッ素シリコーンゴム等を用いることができる。これらのゴムは未加硫のものでガラス転移点（Ｔｇ）が室温より低い点でもフッ素樹脂と区別される。
上記の導電性充填材とバインダーの混合割合は導電性充填材５０〜９５質量％、バインダー５〜５０質量％が好ましい。導電性充填材が５０質量％より少ないと導電性が低下し、また９５質量％より多いとバインダー（５質量％未満）の結合力が低下し、導電体層の形成が難しくなる。
以上の導電性充填材とバインダーの混合物（固形分）にペーストとしての適度な粘性を付与するために、通常有機溶媒を添加する。有機溶媒としては、好ましくはフッ素系ゴムが溶解するものである。溶媒としては、酢酸ブチル、酢酸アミル、酢酸プロピルなどを用いることができる。有機溶媒の量は固形分１００質量部に対し、一般的には４０〜１００質量部が適する。
次に、本発明のゴム弾性体を含有する導電性ペーストを用いた固体電解コンデンサについて説明する。
本発明の固体電解コンデンサの一例を図２に示す。
図２において、１はアルミニウム、タンタル等の弁作用金属箔（陽極）で、その表面に電解陽極酸化等で誘電体酸化皮膜３、細孔２が形成されている。陽極１には陽極リード端子７ａが溶接等により接合される。４は酸化皮膜３上に形成されている固体電解質層（陰極）である。固体電解質層は無機半導体化合物も用いることができるが、本発明の導電性ペーストを用いた場合、固体電解質は特に導電性重合体が適する。
導電性重合体については、前記（Ｉ）の固体電解質層にゴム状弾性体を含む場合の項で詳しく説明したが、ポリ（３，４−エチレンジオキシチオフェン）、ポリピロール、ポリアニリンなどを用いることができ、ポリピロールやポリ（３，４−エチレンジオキシチオフェン）が好ましい。これにドーパントとしてアントラキノンスルホン酸、アルキルアントラキノンスルホン酸、アルコキシアントラキノンスルホン酸、アントラセンスルホン酸、アルキルアントラセンスルホン酸、アルコキシアントラセンスルホン酸、ナフタレンスルホン酸、アルキルナフタレンスルホン酸、アルコキシナフタレンスルホン酸、ベンゼンスルホン酸、アルキルベンゼンスルホン酸、アルコキシベンゼンスルホン酸のアニオンを含有させる。前記有機スルホン酸アニオンのスルホン酸置換基は、その骨格化合物に任意な結合可能な位置に結合された化学構造であればよく、またアルキル基またはアルコキシ基を有する前記化合物は、炭素数１〜１０を有するアルキル基またはアルコキシ基がその骨格化合物に任意な結合可能な位置に結合された化学構造を有する。
導電性重合体の形成方法は、上記重合体を形成するモノマーの酸化剤（重合開始剤）による化学重合、あるいは電解重合、これらの併用など公知の方法が用いられる。例えば酸化皮膜層をモノマー溶液に浸漬し、次いで酸化剤溶液に浸漬し、加温して化学重合させ、この操作を複数回繰り返す。この繰り返し重合により導電性重合体層は多層積層構造となり、外装樹脂により封止する際の耐熱応力性に優れたものとなる。
また、固体電解質層として、前記したゴム状弾性体を含む導電性重合体組成物からなるものも好ましく用いられる。
導電性ペーストとしてフッ素系ゴムバインダーを使用することによる作用効果は次の通りである。導電性重合体層は多層積層構造をもち耐熱応力性に優れるが、これにエポキシ樹脂等の熱収縮の大きいバインダーを使用した導電性ペーストを塗布すると、導電性重合体の表層へ侵入する。このペーストは加熱時の応力発生が大きく、導電性重合体層の多層形状が影響を受ける。フッ素系ゴムバインダーを用いた場合には、導電性重合体表層に侵入したペーストの熱応力発生は小さく、生成された導電性重合体層形状を保持する。これによりコンデンサの耐熱性がより良好なものとなる。
化学重合の際の酸化剤としては過硫酸アンモニウム、有機スルホン酸鉄（ＩＩＩ）、塩化鉄（ＩＩＩ）などの無機酸鉄、Ｆｅ（ＣｌＯ_４）_３、有機酸鉄（ＩＩＩ）、過硫酸塩、アルキル過硫酸塩、過酸化水素、Ｋ_２Ｃｒ_２Ｏ_７などが用いられる。
固体電解質層４の表面に導電体層５が形成される。導電体層５は固体電解質層と密着接合し、陰極として作用すると同時に陰極リード端子７ｂを接合するための接着剤となるものである。導電体層５の厚さは一般的には１０〜５０μｍ程度である。
導電体層５は上記した本発明の導電性ペーストのみでも形成することは可能であるが、好ましくは次項で詳しく説明するように導電性重合体層４の上にカーボンペーストにより形成された層を設け、その上に本発明の導電性ペーストにより形成された層を設ける。カーボンペーストは黒鉛粉末にバインダーの樹脂及び溶媒を加えた公知のカーボンペーストが使用できるが、好ましくはバインダーの樹脂としてフッ素系ゴムを用いる。カーボンペースト層の厚さは１〜２μｍ程度でよい。
導電体層５の外表面に陰極リード端子７ｂを接合する。そして陰極リード端子７ｂと陽極リード端子７ａの露出部を残して絶縁性樹脂６により封止する。絶縁性樹脂には主としてエポキシ樹脂が用いられる。封止は例えばトランスファモールドにより行うことができる。
（ＩＩＩ）導電性カーボン層にゴム状弾性体を含む場合
導電性カーボン層は、導電性材料、バインダー及び溶媒を主成分とする導電性カーボンペーストを用いて形成される。前記導電性材料は８０質量％以上が人造黒鉛粉からなることが好ましい。人造黒鉛粉としては、好ましくは固定炭素分９７質量％以上、平均粒子径が１〜１３μｍ、アスペクト比が１０以下であって、粒子径３２μｍ以上の粒子が１２質量％以下のものが用いられる。
鱗片状、あるいは葉片状の天然黒鉛はアスペクト比が常に１０以上であるため、本発明で使用する導電性材料とは異なる。人造黒鉛のアスペクト比が高いほど導電性カーボンペーストとしての充填性が低下しペーストの抵抗性を高めるため、人造黒鉛粉のアスペクト比は１０以下が必要である。このような人造黒鉛は天然黒鉛やカーボンブラックに比較して純度が高く、充填率を高くすることができ、熱による劣化も小さい特性を有している。
また該黒鉛粉の固定炭素分も同様にペーストの抵抗性に影響があり、人造黒鉛粉の固定炭素分が高いほど抵抗性を低くすることができる。したがって本発明の目的を達成するためには固定炭素分が９７質量％以上の人造黒鉛粉を使用することが必要である。ここで、固定炭素分とは炭素含量の目安となる値で、ＪＩＳ法（ＪＩＳＫ２４２５）、炭素協会法、ＡＳＴＭ法、ＢＳ法がある。
該黒鉛粉の平均粒子径は、導電性カーボンペーストの均一な塗布性を得るためには１〜１３μｍの範囲が好ましい。人造黒鉛粉を使用しても平均粒子径が１３μｍを超える粉末を使用すると均一なペースト層が得られない場合があり、固体電解コンデンサに使用した時はコンデンサ特性におけるｔａｎδ、等価直列抵抗（ＥＳＲ）などが悪化する。また、平均粒子径がこの範囲内にあっても、粗い粒子を含有する時も均一な塗布を妨害するが、粒子径３２μｍ以上の粒子の含有量を１２質量％以下とした時にはこのような問題は生じない。
本発明の導電性カーボンペーストの導電性材料として、上記した人造黒鉛粉を少なくとも８０質量％以上含む材料を使用することが必要である。天然黒鉛、カーボンブラックなどを併用して上記人造黒鉛粉が８０質量％未満となる時は、得られる導電性カーボンペーストとして十分な電導度を確保できない。人造黒鉛粉の使用は、好ましくは９５質量％以上、さらに好ましくは１００質量％である。導電性材料の残りの部分は、銀、金、銅などの金属粉、カーボンブラック、天然黒鉛、その他の粉末状導電性物質である。
本発明の固体電解コンデンサは人造黒鉛粉を８０質量％以上含む導電性材料、バインダー及び溶媒を主たる成分とする導電性カーボンペーストを使用するものである。人造黒鉛粉としては上記したような固定炭素分、平均粒子径、アスペクト比等の限定がなくても使用可能であるが、好ましくは上記のように限定した人造黒鉛粉を使用したペーストである。
導電性カーボンペーストのバインダーとしては、ゴム弾性を有するもの（以下ゴム弾性体ともいう。）で歪みを受けるとその歪みを元に戻そうとする性質のある材料であり、好ましくはさらに実施形態において溶剤に膨潤又は懸濁可能な材料であり、またコンデンサ製造時のリフロー処理に対して優れた耐熱性を有するゴム弾性体が使用される。具体例として、前記特性を有する材料としては、イソプレンゴム、ブタジエンゴム、スチレン／ブタジエンゴム、ニトリルゴム、ブチルゴム、エチレン／プロピレン共重合体（ＥＰＭ、ＥＰＤＭ等）、アクリルゴム、多硫化系ゴム、フッ素系ポリマー、シリコーンゴム、他の熱可塑性エラストマー等が挙げられる。その中で好ましくはＥＰＭ、ＥＰＤＭ、フッ素系ポリマーが使用される。フッ素系ポリマーは、フッ素元素を含むポリマーであれば特に制限はない。これらのゴム性ポリマーは一般に導電性カーボンペーストに使用されているエポキシ樹脂に比べて弾性率、吸水性が低く、接着部の応力の緩和に効果があるものである。
前記フッ素系ポリマーとしては、ポリテトラフロロエチレン、ポリ（クロロトリフロロエチレン）、フッ化ビニリデン（ＶＤＦ）とヘキサフロロプロピレン（ＨＦＰ）の二元共重合体、テトラフルオロエチレンを含む共重合体、テトラフルオロエチレン−プロピレン共重合体、ポリフッ化ビニリデン、ポリフッ化ビニル、含フッ素アクリレートゴム、含フッ素シリコーンゴム等を挙げることができる。
導電性カーボンペースト中の導電性材料とバインダー樹脂の配合比は、全固形分質量あたり導電性材料が３０〜９９質量％、好ましくは５０〜９０質量％、バインダー樹脂が１〜７０質量％である。導電性材料が３０質量％より少ないと導電性カーボンペーストの導電性が低くなり過ぎ、また９９質量％を越えると導電性カーボンペーストの接着性や応力緩和能が失われる。
導電性カーボンペーストに使用する溶媒としては、通常の導電性カーボンペーストに使用する溶媒を同じもので良く、例えばＮ−メチル−２−ピロリドン、Ｎ，Ｎ−ジメチルアセトアミド、ジメチルホルムアミド、酢酸ブチルなどの溶媒を単独または混合して使用する。導電性カーボンペーストに配合する溶媒量は、導電性カーボンペーストの使用目的に応じた粘度となるように配合することが必要であるが、通常はペーストの固形分に対して等量ないし十倍の量を使用する。
本発明の導電性カーボンペーストを使用して固体電解コンデンサを作製する場合、陽極としては、弁作用を有するアルミニウム、タンタル、ニオブ、チタン、ジルコニウムなどの単体金属またはこれらの合金の金属箔のエッチングしたもの、あるいは微粉焼結体など表面積を大きくしたものであればいずれも使用できる。
この金属表面に化成処理などにより誘電体層を形成し、その外側に固体の半導電体層（好ましくは、前述の導電性重合体からなる固体電解質層）を設け、更にその外側に本発明の導電性カーボンペースト層を形成し、その上に金属含有導電体層、好ましくは前記したゴム状弾性体を含む金属含有導電体層を形成し、リード線を接続して固体電解コンデンサとする。
本発明に係る導電性カーボンペーストを使用した固体電解コンデンサは、耐熱性が高く、ＥＳＲ（等価直列抵抗）、インピーダンスが低く、またインピーダンスの熱劣化が小さく、更に耐湿性が優れた性能を有するものである。
発明を実施するための最良の形態
以下、実施例、比較例及び参考例をあげて本発明を具体的に説明するが、本発明は下記の記載により何等限定されるものではない。
実施例１
規定の面積に加工したアルミニウム化成箔を１０質量％のアジピン酸アンモニウム水溶液で１３Ｖの化成電圧にて化成し、箔表面に誘電体層を形成させた。このアルミニウム化成箔（基板）を、３，４−エチレンジオキシチオフェン５ｇを溶解した１．２モル／リットルのエチルメチルケトン溶液にポリエステルウレタンゴム０．０５ｇを溶解させた溶液（溶液４）に浸漬し、次いで過硫酸アンモニウム（以下、ＡＰＳと略する。）：２０質量％及び２−アントラキノンスルホン酸ナトリウム（東京化成社製）：０．１２５質量％に調製した水溶液（溶液３）に浸漬した。
この基板を取り出して６０℃の環境下で１０分放置することで酸化的重合を完成させ、該基板を水で洗浄した。この重合反応処理及び洗浄工程をそれぞれ１０回繰り返した。導電性重合体層は電子顕微鏡写真により層状構造を形成していることが確認された。
導電性重合体組成物中の硫酸イオン及び２−アントラキノンスルホン酸イオンの含量は、先ず該重合処理した基板を水／イソプロピルアルコール溶媒中でヒドラジン還元して注意深く抽出し、イオンクロマトグラフィー法で求めたところ、硫酸イオン含量は導電性重合体組成物中の重合体の全繰り返し構造単位当り１．５モル％、２−アントラキノンスルホン酸イオン含量は、１４．０モル％であった。さらに、この基板の付着質量増加は、添加しないものに比べて１５％の質量増加を示した。固体電解質層の電導度は７３Ｓ／ｃｍであった。
次に、ポリ−３，４−エチレンジオキシチオフェン重合体組成物を蓄積させたアルミニウム箔基板を、１０質量％アジピン酸アンモニウム水溶液中で処理して、火花電圧について調べた。試験は、素子特性を比較する上で、素子数を増やして行った（以下の実施例も同じ。）。すなわち、５０℃環境下、電流密度１０ｍＡ／ｃｍ^２の条件でｎ＝５回行ない表１の結果を得た。
次いで、固体電解コンデンサは陽極からの集電は基板のアルミニウム芯部をプラス側リード端子に溶接することによって行ない、また陰極からの集電は、カーボンペーストと銀ペーストを介してマイナス側リード端子に接続し、最後にエポキシ樹脂で封止してコンデンサ素子を作製した。このようにして得たコンデンサ素子を１２５℃で２時間エージングした後に初期特性を測定した。これらの結果を表２にまとめた。
ここで、表中初期特性のＣは容量を表わし、ＤＦは損失角の正接（ｔａｎδ）を意味する。いずれも１２０Ｈｚで測定したものである。Ｚ（インピーダンス）は、共振周波数での値を示した。ＬＣ（漏れ電流）は、定格電圧を印加して１分後に測定した。各測定値は、試料数が３０個の平均値であり、ＬＣについては１μＡ以上を不良品に、また１０μＡ以上をショート品として表示し、これを除いてＬＣ値の平均を算出した。
比較例１
実施例１においてポリエステルウレタンゴムを添加しないこと以外は実施例１の記載と同様に処理して得たコンデンサ素子を実施例１と同様に評価した。結果を表１及び表２に示す。
なお、重合体組成物中の硫酸イオン及び２−アントラキノンスルホン酸イオンの含量は、実施例１記載の方法で求めたところ、硫酸イオン含量は１．６モル％、２−アントラキノンスルホン酸イオン含量は、１３．５モル％であった。固体電解質層の電導度は、７０Ｓ／ｃｍであった。
実施例２
実施例１で酸化重合の回数を１０回から７回にした以外は、実施例１の記載と同様に処理して得たコンデンサ素子を実施例１と同様に評価した。結果を表１及び表２に示す。
なお重合体組成物中の硫酸イオン及び２−アントラキノンスルホン酸イオンの含量は、実施例１記載の方法で求めたところ、硫酸イオン含量は１．２モル％、２−アントラキノンスルホン酸イオン含量は、１３．０モル％であった。付着質量はポリエステルウレタンゴムを入れない１０回含浸とほぼ同程度であった。固体電解質層の電導度は、７０Ｓ／ｃｍであった。
実施例３
実施例１で使用したポリエステルウレタンゴムの代わりにテトラフロロエチレン−プロピレン共重合体の同濃度のアセトン溶液を用いた以外は、実施例１の記載と同様に処理して得たコンデンサ素子を実施例１と同様に評価した。結果を表１及び表２に示す。
なお、重合体組成物中の硫酸イオン及び２−アントラキノンスルホン酸イオンの含量は、実施例１記載の方法で求めたところ、硫酸イオン含量は１．８モル％、２−アントラキノンスルホン酸イオン含量は、１５．８モル％であった。基板における質量増加は２５％であった。固体電解質層の電導度は、６５Ｓ／ｃｍであった。
実施例４
実施例１で使用した２−アントラキノンスルホン酸ナトリウムの代わりにドデシルベンゼンスルホン酸ナトリウムの同濃度溶液を用いた以外は、実施例１の記載と同様に処理して得たコンデンサ素子を実施例１と同様に評価した。結果を表１及び表２に示す。
なお、重合体組成物中の硫酸イオン及びドデシルベンゼンスルホン酸イオンの含量は、実施例１記載の方法で求めたところ、硫酸イオン含量は１．３モル％、ドデシルベンゼンスルホン酸イオン含量は、１４．５モル％であった。基板における質量増加は２０％であった。固体電解質層の電導度は、６７Ｓ／ｃｍであった。
実施例５
実施例１で使用したポリエステルウレタンゴムの代わりにフッ化ビニリデン−ヘキサプロピレン共重合体の同濃度のアセトン溶液を用いた以外は、実施例１の記載と同様に処理して得たコンデンサ素子を実施例１と同様に評価した。結果を表１及び表２に示す。
なお、重合体組成物中の硫酸イオン及び２−アントラキノンスルホン酸イオンの含量は、実施例１記載の方法で求めたところ、硫酸イオン含量は１．４モル％、２−アントラキノンスルホン酸イオン含量は、１４．２モル％であった。基板における質量増加は２４％であった。固体電解質層の電導度は、７３Ｓ／ｃｍであった。酸素フラスコ燃焼法とイオンクロマトグラフィー法を併用して、フッ素含量を求めたところ、０．５質量％になり、従ってフッ素ゴムは重合体組成物中約１質量％相当含有されている。
実施例６
実施例１で使用した３，４−エチレンジオキシチオフェンの代わりにピロールの同濃度溶液を用い、酸化的重合温度を５℃にした以外は、実施例１の記載と同様に処理して得たコンデンサ素子を実施例１と同様に評価した。結果を表１及び表２に示す。
なお重合体組成物中の硫酸イオン及び２−アントラキノンスルホン酸イオンの含量は、実施例１記載の方法で求めたところ、硫酸イオン含量は１．７モル％、２−アントラキノンスルホン酸イオン含量は、１５．９モル％であった。基板における質量増加は２１％であった。固体電解質層の電導度は、８０Ｓ／ｃｍであった。
参考例１
実施例１記載の３，４−エチレンジオキシチオフェンを４−メチルチオフェンに代えた以外は実施例１記載の条件と同じにして、コンデンサ素子を作製する処理を行った。しかし、黒青色のポリ−４−メチルチオフェン重合体は全く生成せず、４−メチルチオフェンの重合がＡＰＳの作用では起こらなかった。

実施例１〜６において、コンデンサ素子の初期特性を測定した後、高温高湿下に５００時間暴露し、再度１２０Ｈｚでの容量と損失係数を測定した。結果を表３に示す。また、比較例１として、ポリエステルウレタンゴムを添加しない以外は実施例１と同条件でコンデンサ素子の同様な測定を行った。結果を表３に示す。表３から明らかなように、実施例１によるコンデンサ素子は、寿命加速試験後の特性と初期特性の差が比較例１に比べ著しく小さい優れた効果が得られる。
以上のように本実施例によれば、外的応力に緩和性のある、寿命特性の優れた高性能のコンデンサを実現させることができる。

実施例７：導電性ペーストの調製
導電性充填材として平均粒径５．５μｍの銀粉を用い、バインダーにはフッ素系ゴムとしてバイトンゴム（フッ化ビニリデン−４フッ化エチレン−６フッ化プロピレン共重合体）を用いた。そして銀粉８５質量％とバイトンゴム粉末１５質量％を混合し、ペーストの固形分とした。これに溶媒として酢酸ブチルを加え、混練して固形分６０質量％の粘稠な銀ペーストを得た。
実施例８：固体電解コンデンサの作製
エッチング処理後陽極酸化したアルミニウム化成箔を３ｍｍ幅にスリットしたものを長さ１０ｍｍずつ切り取り、それぞれ１３Ｖの化成電圧にて切口部の未化成部を化成し、アルミニウム箔全面に誘電体酸化皮膜を形成した。この化成箔の長さ方向の約５０％の部分を３，４−ジオキシエチレンチオフェンの１モル／リットル濃度のエチルアルコール溶液に浸漬し、次いで酸化剤（重合開始剤）として過硫酸アンモニウムの１．５モル／リットル及びドーパントとしてナフタレン−２−スルホン酸ナトリウム０．１２モル／リットル濃度の水溶液に浸漬し、４０℃に保持して重合した。この重合操作を２０回繰り返して行ない、箔の酸化皮膜上にポリ（３，４−エチレンジオキシチオフェン）からなる導電性重合体層を形成した。２０回の繰り返し重合により、導電性重合体層は図２の電子顕微鏡の拡大写真（５０００倍）のように層状構造となった（図２において、上部が層状構造の導電性重合体層である。）。この導電性重合体層を有する部分をカーボンペーストに浸漬し、１００℃、３０分間熱処理した。カーボンペースト層は平均粒径３μｍの黒鉛粉末６０質量％と実施例１のフッ素系ゴム４０質量％を混合し、ペーストの固形分とした。これに溶媒として酢酸ブチルを加え、混練して固形分１６質量％の粘稠なカーボンペーストとしたものを用いた。
次にこのカーボンペーストにより形成された層の部分を実施例７の銀ペースト中に浸漬し、導電体層を形成して一単位のコンデンサ素子とした。この単位コンデンサ素子を導電性重合体のついていない側のアルミニウム箔部分を切断し、これらを４枚重ねて同じ銀ペーストを用いて接合し、リードフレーム（銅合金）に接合し、１００℃、３時間乾燥させた。その後、導電性重合体のついていないアルミニウム箔部分をリードフレーム（銅合金）に溶接した。最後にこれらのフレームの一端部を露出させて、エポキシ樹脂（住友ベークライト社製ＥＭＥ−７３２０Ａ）を用い、トランスファモールドにより封止してチップ型のコンデンサとした。このコンデンサの特性を表４に示す。
比較例２
実施例８において、銀ペーストのバインダーをエポキシ樹脂（油化シェルエポキシ（株）製エピコート８２８型）に変えた他は実施例８と同様にしてチップ型の固体電解コンデンサを作製した。その特性を表４に示す。

表４中、ＥＳＲ（１００ＫＨｚでの等価直列抵抗）は試料３０個の平均値、リフロー不良率、耐湿不良率は以下の方法により測定した試料３０個中の不良品数を表わす。
リフロー不良率：
リフロー炉（２３０℃、３０秒）に通した後、定格電圧（１３Ｖ）を印加し、１分後の漏れ電流値を測定する。１２μＡ未満を合格（良品）、１２μＡ以上を不良品とした。
耐湿不良率：
温度６０℃／湿度９０％雰囲気中にコンデンサを放置した。１０００時間後これを取り出し定格電圧を印加し１分後の漏れ電流値を測定する。１２μＡ未満を合格（良品）、１２μＡ以上を不良品とした。
実施例９
導電性材料としてアスペクト比が３〜１．５、平均粒子径が３μｍ、粒子径が３２μｍ以上である粒子が２質量％以下、固定炭素分が９９質量％である人造黒鉛粉末（昭和電工（株）製：ＵＦＧ−５）１００質量部に、バインダー樹脂としてエチレン／プロピレン／ジエンターポリマー（ＥＰＤＭ）の酢酸ブチル懸濁液（懸濁液中のＥＰＤＭ７質量％）を該樹脂固形分が人造黒鉛粉末１００質量部に対して８０質量％となるように投入して、これを２４時間撹拌して導電性カーボンペーストを作製した。
次に、３ｍｍ×１０ｍｍに切り出したアルミニウム化成箔を、端から４ｍｍと５ｍｍの部分に区切るように、両面に渡って幅１ｍｍのポリイミドテープを貼り付けて前記３ｍｍ×４ｍｍの部分を、１０質量％のアジピン酸アンモニウム水溶液中、１３Ｖの電圧を印加して化成した。これにより、前記領域に誘電体酸化皮膜を形成した。さらにアルミニウム箔の前記３ｍｍ×４ｍｍの部分を、３，４−ジオキシエチレン−チオフェン２０質量％を含むイソプロパノール溶液（溶液１）に浸漬した後引き上げ、室温下で風乾させ、続いて前記誘電体酸化皮膜を形成した部分を、過硫酸アンモニウム（ＡＰＳ）３０質量％とアントラキノン−２−スルホン酸ナトリウム１質量％を含む水溶液（溶液２）に浸漬した後、引き上げ６０℃の雰囲気に１０分放置することで酸化重合を行った。これを再び前記溶液１に浸漬し、さらに前記と同様な処理を行った。溶液１に浸漬してから酸化重合を行うまでの操作を２５回繰り返した後、５０℃の温水で１０分洗浄を行い、１００℃で３０分乾燥を行うことにより導電性重合体層（固体電解質層）を形成した。
かくして、得られた導電性重合体層を形成したアルミニウム箔の断面を走査電子顕微鏡写真（２，０００倍）で調べたところ、導電性重合体層が金属アルミニウム上の誘電体（アルミナ）の微細孔内の表面に層状構造をなして覆い尽くしており、また層状導電性重合体層間に空間部が存在することが確認された。ここで、微細孔構造の外部表面に形成された導電性重合体層の厚さは約５μｍであり、層構造を形成する１層当りの厚さは約０．１〜０．３μｍの範囲であった。
次に前記アルミニウム箔の導電性重合体層を形成した部分に、前記方法で作製した導電性カーボンペーストを塗布した後、１００℃、３０分間熱処理を行い、前記導電性重合体上にカーボンペーストによる導電層を形成した。次に、銀ペーストを付けて陰極リード端子を接続し、また導電性重合体層の形成されていない部分には陽極リード端子を溶接により接続した素子をエポキシ樹脂で封止した後、１２５℃で定格電圧を印加して２時間エージングを行い、合計３０個のコンデンサを完成させた。
これら３０個のコンデンサ素子について、等価直列抵抗（ＥＳＲ）を通常の方法で測定し、リフロー処理をした。次いでリフロー後のＥＳＲを再度測定し、リフロー前後のＥＳＲの変化を見積もった。次に、コンデンサ素子全量に対して後述の耐湿不良率の試験をそれぞれ行った。結果を表５にまとめた。
実施例１０
実施例９記載のＥＰＤＭ・酢酸ブチル懸濁液をフッ素系ポリマー（フッ化ビニリデン−ヘキサフルオロプロピレン−テトラフルオロ共重合体）・酢酸ブチル懸濁液に、またＥＰＤＭ固形分が人造黒鉛粉末１００質量部に対して８０質量部使用した条件を、フッ素系ポリマー固形分が人造黒鉛粉末１００質量部に対して７０質量％に代えた以外は、実施例９記載の方法に準じて合計３０個のコンデンサ素子を完成させ、実施例９の記載と同様なコンデンサの特性評価を行った。結果を表５に併せてまとめた。
比較例３
導電性材料として、実施例９記載の人造黒鉛粉末を、平均粒子径４μｍ、粒子径が３２μｍ以上の粒子が２質量％以下、固定炭素分が９８．５質量％であり、アスペクト比が明らかに１０以上の鱗片状天然黒鉛に代え、またバインダーとしてＥＰＤＭをエポキシ樹脂に替えた以外は、実施例９と同様にして合計３０個のコンデンサを完成させ、コンデンサの特性評価を行った。結果を表５に併せてまとめた。
比較例４
導電性材料として、実施例１０記載の人造黒鉛粉末を、平均粒子径４μｍ、粒子径が３２μｍ以上の粒子が２質量％以下、固定炭素分が９８．５質量％であり、アスペクト比が明らかに１０以上の鱗片状天然黒鉛に代えた以外は、実施例１０と同様にして合計３０個のコンデンサを完成させ、コンデンサの特性評価を行った。結果を表５に併せてまとめた。
前記実施例９〜１０及び比較例３〜４において、実施した各種評価試験は下記の測定方法、条件で行った。
［測定方法］
１．リフロー不良率
作製した３０個の固体電解コンデンサをピーク温度２３０℃のリフロー炉に３０秒通した後、定格電圧（６．３Ｖ）を印加し、１分後の漏れ電流を測定した。判定として３μＡ未満を合格品とした。
２．耐湿不良率
温度６０℃、湿度９０％の雰囲気中にリフロー試験で合格した固体電解コンデンサ全数を放置し、１０００時間後これを取り出し、定格電圧（６．３Ｖ）を印加し、１分後の漏れ電流値を測定する。判定として１２μＡ未満を合格品とした。

産業上の利用可能性
本発明は、固体電解質層及び金属粉末を含む導電体層、または導電性カーボン層およびその層上に設けた金属粉末を含む導電体層からなる少なくとも一つの層にゴム状弾性体を含む固体電解コンデンサ、その製造方法、その固体電解コンデンサに使用される固体電解質、固体電解質の製造方法、固体電解コンデンサ用導電性ペースト、及び固体電解コンデンサ用導電性カーボンペーストを提供したものである。
本発明の固体電解コンデンサは、固体電解質を形成する導電性重合体組成物中にゴム弾性体が含むことにより、含浸回数を大幅に少なくでき、生産性の向上に繋がり、小型でより低インピーダンスで、より高性能であり、外的応力に緩和性のある固体電解コンデンサ及びその製造方法を提供することができる。
また、固体電解質に特定のポリヘテロ５員環式化合物、特に導電性ポリチオフェンをπ電子共役重合体として使用することによって、耐電圧特性（火花電圧試験）、高周波特性、ｔａｎδ、インピーダンス特性、漏洩電流、耐熱性（リフロー性）等が大幅に向上する効果が得られる。
特に、前記導電性重合体組成物中には、１つのゴム状弾性体の含量がπ電子共役構造構造を有する重合体の繰り返し単位に対して、０．０１〜２５質量％の範囲であり、更に硫酸イオン含量が０．１〜１０モル％の範囲で含まれていることによって、より高性能なコンデンサ特性を有する固体電解コンデンサとすることができる。
本発明の固体電解コンデンサは、導電体層（金属粉末を含む導電体層、または導電性カーボン層及びその層上に設けた金属粉末を含む導電体層）にゴム状弾性体を含む場合には、以下の効果が得られる。
（１）本発明の導電性ペーストはバインダーがフッ素系ゴムで弾性率が低く、かつ耐熱性、耐湿性に優れる。
（２）この導電性ペーストを導電体層に用いた固体電解コンデンサはリフロー等で発生する熱応力が小さく、導電体層界面での剥れが起らない。
（３）そのためリフロー前後のＥＳＲの変化が小さく、またリフロー不良、耐湿不良が発生しないなどの効果を有する。
さらに、本発明の固体電解コンデンサは、導電性カーボン層をゴム状弾性体、特にフッ素系ゴム状弾性体を使用することにより、耐湿性（撥水性）に優れ、さらに導電性カーボン層に特定の導電性材料（人造黒鉛粉）を使用することにより、充填密度を高くすることが可能で導電性、耐熱性に優れる。
このため、これを導電性カーボンペーストとして使用した固体電解コンデンサは、ＥＳＲ（１００ＫＨｚでの等価直列抵抗）が低くリフロー前後のＥＳＲ変化が小さく、耐湿不良率が低い格別な効果を奏する。
【図面の簡単な説明】
第１図は、本発明の固体電解コンデンサの一例を示す断面図である。
第２図は、本発明の固体電解コンデンサの他の一例を示す断面図である。
第３図は、本発明における導電性重合体層の電子顕微鏡写真である（倍率：５０００倍）。
図中、１は弁作用金属、２は細孔、３は誘電体皮膜、４は固体電解質層、５は導電体層、６は外装体、７は接続用端子、７ａは陽極端子、７ｂは陰極端子である。Relationship with related applications
No. 60 / 135,846 filed May 24, 1999, US application 60/135 filed July 21, 1999, in accordance with the provisions of US law 111 (b). No. 144,817 and U.S. Application No. 60 / 162,235 filed October 29, 1999, which are alleged by 119 (e) (i) This is an application based on the provision of a).
Technical field
In the present invention, at least one of a solid electrolyte layer and a conductor layer (a conductor layer including a metal powder, or a conductor layer including a conductive carbon layer and a layer including a metal powder thereon) has rubber-like elasticity. The present invention relates to a solid electrolytic capacitor including a body and a method for manufacturing the same. More specifically, the present invention relates to a solid electrolytic capacitor that can be reduced in size, increased in capacity, reduced in impedance, and excellent in external stress relaxation characteristics, productivity, heat resistance, moisture resistance, and the like, and a method for manufacturing the same.
The present invention also relates to a solid electrolyte for a solid electrolytic capacitor, a metal powder-containing conductive paste, and a conductive carbon paste.
Background art
In a solid electrolytic capacitor, a dielectric oxide film layer is generally formed on an anode substrate made of an etched metal foil having a large specific surface area, and a solid semiconductive layer (hereinafter referred to as “solid”) is formed as an electrode facing the outside. An electrolyte layer "), and a conductor layer including a metal powder or a conductive carbon layer and a layer including a metal powder thereon is preferably formed on the outer surface. The basic element of the capacitor is manufactured by connecting to the lead wire. Next, it is widely used in electrical products as a capacitor component in which the entire element is completely sealed with an epoxy resin or the like.
In recent years, in order to meet demands for digitization of electrical equipment and higher speeds of personal computers, these solid electrolytic capacitors have been required to be small and large-capacity capacitors and low-impedance capacitors in a high-frequency region.
In order to meet these demands as solid electrolytic capacitors, various proposals have been made for solid electrolytes, conductors, and the like.
Conventionally, as the solid electrolyte, for example, an inorganic semiconductor material such as manganese dioxide or lead dioxide, or a TCNQ complex salt as an organic semiconductor material, or an electric conductivity of 10^-3~ 5x10³Intrinsic conductive polymers in the range of S / cm (Japanese Patent Laid-Open No. 1-169914, US Pat. No. 4,803,596), π-conjugated polyaniline (Japanese Patent Laid-Open No. 61-239617), polypyrrole (Japanese Patent Laid-Open No. 61-61) -240625), polythiophene derivatives (Japanese Patent Laid-Open No. 2-15611, US Pat. No. 4,910,645), polyisothianaphthene (Japanese Patent Laid-Open No. 62-118511) and the like. The use of this is also known.
Capacitors using manganese dioxide as a solid electrolyte not only have the disadvantage that the dielectric oxide film layer of the anode foil once formed is destroyed when manganese nitrate is pyrolyzed to form manganese dioxide, but also impedance. The characteristics are also insufficient.
When using lead dioxide, further environmental considerations are necessary.
Capacitors using TCNQ complex salt as a solid electrolyte are excellent in heat-melt processability and conductivity, but there are problems with the heat resistance of TCNQ complex salt itself, and the reliability of heat resistance (solder heat resistance) during solder bonding Is said to be bad.
On the other hand, a capacitor using a conductive polymer as a solid electrolyte has no risk of breaking the dielectric film and has high impedance characteristics. On the other hand, it lacks heat resistance, thermal shock resistance, and earthquake resistance.
As a method for forming a solid electrolyte using a conductive polymer, for example, a conductive polymer (solid electrolyte) as described above is melted on a dielectric layer on the surface of a valve metal having a fine void structure to make it conductive. A method for forming a polymer layer or a method for depositing the conductive polymer on a dielectric layer is known.
Specifically, for example, when a polymer of a hetero five-membered cyclic compound such as pyrrole or thiophene is used as the solid electrolyte, the anode foil on which the dielectric film is formed is used as a lower alcohol of the hetero five-membered cyclic compound monomer and / or A method of forming a conductive polymer layer having a required film thickness by immersing it in an aqueous solution and then taking it out, then immersing it in an aqueous solution in which an oxidizing agent and an electrolyte are dissolved to chemically polymerize the monomer, and repeating this process. No. 5-175082), 3,4-ethylenedioxythiophene monomer and an oxidizing agent, preferably in the form of a solution, separately or together on the oxide film layer of the metal foil by coating the conductive polymer layer. (Japanese Patent Application Laid-Open No. 2-15611 (US Pat. No. 4,910,645) and Japanese Patent Application Laid-Open No. 10-32145 (EP-A 820076). ), And the like are known.
In these prior arts, for example, iron (III) chloride, Fe (ClO) are used as oxidizing agents when chemically polymerizing a hetero five-membered cyclic compound such as thiophene.₄)₃Or organic acid iron (III), inorganic acid iron (III), alkyl persulfate, ammonium persulfate (hereinafter sometimes abbreviated as APS), hydrogen peroxide, K₂Cr₂O₇(Japanese Patent Laid-Open No. 2-15611, US Pat. No. 4,910,645), cupric compounds, silver compounds, etc. (Japanese Patent Laid-Open No. 10-32145, European Patent Application Publication No. 820076) are known.
Recently, powdered polyaniline is used as a conductive raw material, and rubber and / or thermoplastic resin is used as a raw material for matrix, and polyaniline powder is dispersed and compounded in this to make a mechanically strong and flexible polyaniline composite. A method for producing a polyaniline composite (Japanese Patent Laid-Open No. 64-69666) is disclosed.
Further, a conductive polymer layer in which a composite film is formed from a polyaniline solution containing 1 to 25% by weight of a polymer binder on the metal oxide of the capacitor electrode, and an anion is added to the polyaniline is further formed thereon. A method for manufacturing a capacitor (Japanese Patent Laid-Open No. 5-3138) is disclosed.
In the above method, in order to form a conductive polymer layer on an oxide film that is an insulator, it is necessary to previously form a thin conductive layer by chemical polymerization. Furthermore, there are the following problems when applied to individual capacitors.
First, in the case of electrolytic polymerization, in a polymer having poor flexibility, increasing the viscosity leads to a decrease in capacity appearance. This is because an aluminum foil obtained by etching the surface is impregnated with an oxidant solution into an aluminum foil with a dielectric formed on the surface and dried to form a highly viscous oxidant film on the surface of the porous body. The entrance of the micropores existing on the surface of the porous body is blocked. Further, this is because the polymer is formed on the surface from the contact with the monomer, the polymer is not formed inside the pores, and the capacity appearance rate is lowered.
Secondly, in the case of chemical polymerization, since the amount of polymer to be polymerized at one time is small, it is necessary to impregnate a certain number of times, and there is a demand for an advantageous method in productivity.
Third, the dielectric film and the solid electrolyte must have good adhesion, and if they are bad, there will be problems with product deterioration and uniformity in production, resulting in reduced production yields and durability in use. Problems arise.
In order to remedy these drawbacks, the above method uses a conductive polymer such as polypyrrole as a solid electrolyte of a solid electrolytic capacitor by an electrolytic polymerization method or a chemical polymerization method. The uniformity of the conductive polymer film, the solder heat resistance when used as an electrolytic capacitor, the impedance characteristics, etc. cannot be said to be sufficient.
On the other hand, as the conductor layer used for joining the cathode lead terminal and the solid electrolyte layer, a conductive paste having a conductive filler and a synthetic resin as a binder is usually used. As the conductive filler, metal powder such as gold, silver, copper, or carbon powder is generally used, and silver powder is widely used from the viewpoint of cost and performance. Epoxy resin, phenol resin, and the like are usually used as the synthetic resin for the binder, but other polyamides, polyimide resins, fluorine resins (JP-A-5-152171) and acrylic resins (JP-A-7-233298). Etc. are also known.
In addition, the conductive paste is generally used as an adhesive between the silicone chip and the lead frame, that is, as a die bonding material. As a conductive paste for die bonding material, a paste containing a fluorine-containing polymer as a binder resin has been proposed (Japanese Patent Laid-Open No. 2-5304). The conductive paste for die bonding is required to have high conductivity, high heat resistance, low shrinkage stress generated during die bonding, and low water absorption after die bonding. Further, at the time of heat bonding, the conductive paste needs to have a performance of reducing stress generated between the silicon chip and the lead frame.
However, silver paste using a general synthetic resin as a binder has a high elastic modulus and is likely to generate high stress due to reflow, etc., which causes an increase in leakage current and causes thermal degradation of impedance due to peeling at the paste interface. It becomes. And since this kind of paste has a high water absorption rate, it tends to cause performance deterioration under high temperature and high humidity.
There is a silver paste using a fluororesin as a binder, but the elastic modulus is high as described above, and a high stress is generated due to reflow or the like, causing a defect.
Silver, which is widely used as a conductive material, is excellent in terms of cost and performance. However, in order to cause migration, depending on the conductive paste of the solid electrolytic capacitor, a conductive carbon paste must be applied first. In addition, conductive silver paste is often used.
There are many proposals for the conductive material, binder, and solvent of the conductive carbon paste. For example, as a conductive material, natural graphite (10-20 μm flaky graphite) and carbon black (Japanese Patent Laid-Open No. 9-31402), carbon particles with protrusions (Japanese Patent Laid-Open No. 5-7078), conductive material and binder In combination, carbon black of 20 μm or less and synthetic resin (Japanese Patent Laid-Open No. 4-181607), flaky graphite powder and fine graphite powder (aspect ratio of 10 or more, average particle diameter of 10 μm or less) and epoxy resin (Japanese Patent Laid-Open No. 262822), graphite and fluorine-containing polymer, for example, PTFE fine particles (Japanese Patent Laid-Open No. 61-69853), and a combination of a conductive material and a solvent include carbon powder and glycidyl ether (Japanese Patent Laid-Open No. 4-177802). There are many other synthetic resins as binders such as polyethylene, epoxy resin, and phenol resin. It has been proposed.
However, the conductive carbon paste using natural graphite has the disadvantage that the natural graphite is scaly, has poor filling properties, has a low conductivity due to many impurities, and has few irregularities on the surface after coating. Peeling easily occurs, and also has a drawback of easily causing thermal deterioration of impedance.
Since the conductive carbon paste using carbon black has extremely small powder particles, the filling property cannot be increased, and it is difficult to increase the conductivity as in the case of natural graphite. These natural graphite and carbon black-based conductive carbon pastes also have a problem that a dispersion treatment is required at the time of producing the paste.
The use of epoxy resin as a binder is advantageous in that it is low in cost and easy to handle, but it has high rigidity and reduces stress generated between the chip and the lead frame during heating during reflow as the chip size increases. There are problems such as low relaxation ability against water, high water absorption, and moisture resistance deterioration.
Object of the invention
An object of the present invention is to provide a solid electrolytic capacitor excellent in small size, light weight, high capacity, high frequency characteristics, tan δ, leakage current, heat resistance (reflow property), thermal shock resistance, durability, and the like. In particular, an object of the present invention is to provide a heat-resistant solid electrolytic capacitor that is excellent in low impedance characteristics, durable in a spark voltage test, and relaxed in external stress.
Another object of the present invention is to use a conductive paste for a solid electrolytic capacitor that has low thermal stress during reflow, little thermal degradation of impedance due to peeling at the paste layer interface, etc., and excellent moisture resistance. The object is to provide a solid electrolytic capacitor.
Another object of the present invention is a conductive carbon paste that can be used for die bonding or a solid electrolytic capacitor. The conductive paste has a high packing density of a conductive material and a high conductivity. Conductive carbon paste capable of reducing stress due to difference in thermal expansion coefficient between materials, reducing water absorption and improving product moisture resistance, and solid electrolysis using the conductive carbon paste It is to provide a capacitor.
Summary of the Invention
The present invention includes at least one of the following solid electrolyte layer, a conductor layer containing metal powder, and a conductive carbon layer formed between the solid electrolyte layer and the conductor layer containing metal powder as required. The present invention relates to a solid electrolytic capacitor including a rubber-like elastic body, a manufacturing method thereof, a solid electrolyte used for the solid electrolytic capacitor, a metal powder-containing conductive paste, and a conductive carbon paste.
1) In a solid electrolytic capacitor in which a solid electrolyte layer and a conductor layer made of a conductive polymer are formed on a dielectric film formed on a valve action metal, at least one of the solid electrolyte layer and the conductor layer. A solid electrolytic capacitor comprising a rubbery elastic body in one layer.
2) The solid electrolytic capacitor as described in 1 above, wherein the conductor layer comprises a conductor layer containing metal powder or a conductive carbon layer and a conductor layer containing metal powder provided on the conductive carbon layer.
3) The solid electrolytic capacitor as described in 1 or 2 above, wherein the solid electrolyte layer contains a rubber-like elastic body.
4) The solid electrolytic capacitor as described in 2 above, wherein the conductive carbon layer contains a rubber-like elastic body.
5) The solid electrolytic capacitor as described in 2 above, wherein the metal powder-containing conductor layer contains a rubber-like elastic body.
6) The solid electrolytic capacitor as described in 2 above, wherein the solid electrolyte layer and the conductive carbon layer contain a rubber-like elastic body.
7) The solid electrolytic capacitor as described in 2 above, wherein the solid electrolyte layer and the metal powder-containing conductor layer include a rubber-like elastic body.
8) The solid electrolytic capacitor as described in 2 above, wherein the conductive carbon layer and the metal powder-containing conductor layer include a rubber-like elastic body.
9) The solid electrolytic capacitor as described in 2 above, wherein the solid electrolyte layer, the conductive carbon layer, and the metal powder-containing conductor layer include a rubber-like elastic body.
10) The solid electrolytic capacitor as described in any one of 1 to 9 above, wherein the solid electrolyte of the solid electrolytic capacitor has a film-like or layered structure.
11) The solid according to 1, 3, 6, 7 or 9, wherein the solid electrolyte layer comprises a film-like or layer-like conductive polymer composition containing a rubber-like elastic body in the range of 0.01 to 25% by mass. Electrolytic capacitor.
12) The solid electrolytic capacitor as described in 11 above, wherein the rubber-like elastic body is at least one of natural rubber and synthetic rubber.
13) The solid electrolytic capacitor as described in 11 or 12 above, wherein the rubber-like elastic body is a fluorine-based rubber.
14) The solid electrolytic capacitor as described in 11 above, wherein the conductive polymer is a polymer containing at least one divalent repeating unit of pyrrole, thiophene, aniline or a derivative thereof.
15) The solid electrolytic capacitor as described in 2, 5, 7, 8 or 9, wherein the metal powder-containing conductor layer contains a conductive filler made of metal powder and fluorine rubber as a main component of the binder.
16) The solid electrolytic capacitor as described in 15 above, wherein 80% by mass or more of the binder is fluororubber.
17) The solid electrolytic capacitor as described in 15 above, wherein 80% by mass or more of the conductive filler is silver powder.
18) The solid electrolytic capacitor as described in 15 or 17 above, wherein the conductive filler has an average particle size of 1 μm or more and 10 μm or less.
19) The solid electrolytic capacitor as described in 15, 17 or 18, wherein the conductive filler is 50 to 95% by mass and the binder is 5 to 50% by mass.
20) The solid electrolytic capacitor as described in 15 above, wherein the metal powder-containing conductor layer is a layer formed of a conductive paste containing a conductive filler, a binder and an organic solvent.
21) Capacitor elements having a dielectric oxide film, a solid electrolyte layer, and a conductor layer formed on the surface of an anode body made of a valve metal were sealed with an insulating resin, leaving exposed portions of the anode lead terminal and the cathode lead terminal. A solid electrolytic capacitor, wherein the solid electrolyte layer is a conductive polymer layer, and the conductive layer is the metal powder-containing conductive layer described in 15 or 20 above.
22) In the above-mentioned 21, wherein the conductor layer is a layer composed of a conductive carbon layer on a conductive polymer layer and the metal powder-containing conductor layer according to any one of 15 to 20 laminated on the layer. The solid electrolytic capacitor as described.
23) The solid electrolytic capacitor as described in 21 or 22 above, wherein the conductive polymer layer is poly (3,4-ethylenedioxythiophene).
24) The conductive carbon layer is a layer formed using a conductive carbon paste whose main components are a conductive material, a binder, and a solvent, and 80% by mass or more of the conductive material is artificial graphite, The artificial graphite has a fixed carbon content of 97% by mass or more, an average particle diameter of 1 to 13 μm, an aspect ratio of 10 or less, and particles having a particle diameter of 32 μm or more are 12% by mass or less. The solid electrolytic capacitor as described.
25) The solid electrolytic capacitor as described in 24 above, wherein a material having rubber elasticity that can swell or suspend in a solvent is used as a binder.
26) Rubber elastic material that can swell or suspend in a solvent is isoprene rubber, butadiene rubber, styrene / butadiene rubber, nitrile rubber, butyl rubber, ethylene / propylene copolymer, acrylic rubber, polysulfide rubber, fluorine-based material 26. The solid electrolytic capacitor as described in 25 above, which is at least one material selected from the group consisting of a polymer, a silicone rubber, and a thermoplastic elastomer.
27) The solid electrolytic capacitor as described in 24 above, wherein the conductive material is 30 to 99% by mass and the binder is 1 to 70% by mass of the solid content in the conductive carbon paste.
28) In a method for producing a solid electrolytic capacitor in which a solid electrolyte layer and a conductor layer are formed on a dielectric film formed on a valve action metal, the valve action metal having a dielectric film formed on the surface thereof, Dielectric material in which at least one of the monomer solution and the oxidant solution of the conductive polymer is alternately coated once or a plurality of times using the monomer solution and the oxidant solution of the conductive polymer containing a rubber-like elastic body. A method for producing a solid electrolytic capacitor, comprising forming a film or layer of a conductive polymer composition on a film.
29) The method for producing a solid electrolytic capacitor as described in 28 above, wherein the conductive polymer composition contains 0.01 to 25% by mass of a rubber-like elastic body.
30) The method for producing a solid electrolytic capacitor as described in 28 or 29 above, wherein the rubber-like elastic body is a fluorine-based rubber.
31) In a method for producing a solid electrolytic capacitor formed by forming a solid electrolyte layer made of a conductive polymer and a conductive layer on a dielectric film formed on a valve action metal, a conductive material is formed on the solid electrolyte. A method for producing a solid electrolytic capacitor, comprising forming a conductor layer using a conductive paste containing a rubber-elastic binder and a solvent.
32) The solid electrolytic capacitor as described in 31 above, wherein the conductor layer is a metal powder-containing conductor layer formed using a conductive paste comprising a conductive filler made of metal powder, a rubber elastic binder and a solvent. Manufacturing method.
33) The method according to 31 above, wherein the conductive layer is formed using a conductive carbon paste including a conductive material, a rubber-elastic binder and a solvent, and then a conductive layer including a metal powder is formed. Manufacturing method for solid electrolytic capacitor.
34) After a conductive carbon layer is formed using a conductive carbon paste containing a conductive material, a rubber elastic binder and a solvent, the conductive layer is made of a metal powder, a conductive filler, and a rubber elastic binder. 32. The method for producing a solid electrolytic capacitor as described in 31 above, wherein the metal powder-containing conductor layer is formed using a conductive paste containing a solvent.
35) The solid electrolyte layer is formed on the dielectric film by using the conductive polymer monomer solution and the oxidant solution containing a rubber-like elastic body in at least one of the conductive polymer monomer solution and the oxidant solution. 35. The method for producing a solid electrolytic capacitor as described in any one of 31 to 34, wherein the coating is alternately repeated once or a plurality of times to form a film of the conductive polymer composition.
36) The method for producing a solid electrolytic capacitor as described in any one of 31 to 35 above, wherein the solid electrolyte has a film-like or layered structure.
37) The solid electrolyte according to 36 above, wherein the solid electrolyte having a layered structure has a film-like or layered structure layer or a thickness per layer of about 0.1 to 0.3 μm. Capacitor manufacturing method.
38) A solid electrolyte in which a conductive polymer composition containing a rubber-like elastic body in a range of 0.01 to 25% by mass is formed into a film or a layer.
39) The solid electrolyte as described in 38 above, wherein the rubber-like elastic body is at least one of natural rubber and synthetic rubber.
40) The solid electrolyte as described in 38 or 39 above, wherein the rubber-like elastic body is a fluorine-based rubber.
41) The solid electrolyte as described in 38 above, wherein the conductive polymer is a polymer containing at least one divalent repeating unit of pyrrole, thiophene, aniline or a derivative thereof.
42) The above conductive material containing a rubber-like elastic body in at least one of a monomer solution and an oxidizer solution of a conductive polymer for an object that requires formation of a solid electrolyte made of a conductive polymer composition on the surface. A method for producing an object having a solid electrolyte in which a conductive polymer composition is formed into a film or a layer, wherein the coating is alternately repeated one or more times with a polymer monomer solution and an oxidant solution.
43) The method for producing an object having a solid electrolyte as described in 42 above, wherein the coating means is any one of dipping, coating, spraying or casting.
44) The method for producing an object having a solid electrolyte as described in 42 above, wherein the rubber-like elastic body is added to a solution containing a monomer and / or an oxidizing agent of a conductive polymer in the form of a solution or dispersion.
45) A conductive paste for a solid electrolytic capacitor containing a conductive filler made of metal powder and fluorine rubber as a main component of the binder.
46) The conductive paste as described in 45 above, wherein 80% by mass or more of the binder is a fluorinated rubber.
47) The conductive paste as described in 45 above, wherein 80% by mass or more of the conductive filler is silver powder.
48) The conductive paste as described in 45 or 47 above, wherein the conductive filler has an average particle size of 1 μm or more and 10 μm or less.
49) The conductive paste according to 45, 47 or 48, wherein the conductive filler is 50 to 95% by mass and the binder is 5 to 50% by mass.
50) The conductive paste according to any one of 45 to 49, which contains an organic solvent.
51) In a conductive carbon paste for a solid electrolytic capacitor mainly comprising a conductive carbon material, a binder and a solvent, 80% by mass or more of the conductive carbon material is artificial graphite, and the artificial graphite has a fixed carbon content of 97. A conductive carbon paste for a solid electrolytic capacitor having a mass% or more, an average particle diameter of 1 to 13 μm, an aspect ratio of 10 or less, and a particle diameter of 32 μm or more of 12 mass% or less.
52) The conductive carbon paste for a solid electrolytic capacitor as described in 51 above, wherein a material having rubber elasticity that can swell or suspend in a solvent is used as a binder.
53) Rubber elastic material that can swell or suspend in a solvent is isoprene rubber, butadiene rubber, styrene / butadiene rubber, nitrile rubber, butyl rubber, ethylene / propylene copolymer, acrylic rubber, polysulfide rubber, fluorine-based material 53. The conductive carbon paste for a solid electrolytic capacitor as described in 52 above, which is at least one material selected from the group consisting of a polymer, a silicone rubber, and a thermoplastic elastomer.
54) The conductive carbon paste for a solid electrolytic capacitor as described in any one of 51 to 53, wherein the conductive material is 30 to 99% by mass and the binder is 1 to 70% by mass of the solid content in the conductive carbon paste. .
Detailed Description of the Invention
The solid electrolytic capacitor of the present invention comprises a dielectric layer formed on a valve action metal, a conductive layer containing a solid electrolyte layer and a metal powder, or a conductive layer containing the solid electrolyte layer and the metal powder as required. A conductive carbon layer is formed therebetween, and a rubber-like elastic body is included in at least one of the solid electrolyte layer, the conductive layer containing metal powder, and the conductive carbon layer.
Hereinafter, (I) When the solid electrolyte layer includes a rubber-like elastic body, (II) When the metal powder-containing conductor layer includes a rubber-like elastic body, (III) When the conductive carbon layer includes a rubber-like elastic body Although the present invention will be described in detail, the present invention may include a case where a rubber-like elastic body is included in any two of the solid electrolyte layer, the conductor layer including the metal powder, and the conductive carbon layer and all three layers. Is included.
(I) When the solid electrolyte layer contains a rubber-like elastic body
When the rubber-like elastic body is contained in the solid electrolyte layer, the solid electrolyte layer may be formed from a film-like or layer-like conductive polymer composition containing the rubber-like elastic body in the range of 0.01 to 25% by mass. preferable.
By including at least one selected from rubber-like elastic bodies in the conductive polymer composition, even if the number of coatings is reduced, the conductive layer having a heat resistance having a necessary thickness can be formed on the dielectric layer. A coalescence composition layer (charge transfer complex) can be formed. The solid electrolyte formed by adding the properties of the rubber-like elastic body can retain stress relaxation properties. As a result, a high-performance solid electrolyte and a solid electrolytic capacitor excellent in low impedance characteristics and durable in spark voltage tests and the like can be obtained.
The conductive polymer in the conductive polymer composition suitable for the capacitor of the present invention is a polymer having a π-electron conjugated structure in the polymer main chain, and has a polymerization degree of 2 or more and 1000 or less, preferably 5 or more and 500 or less. Specific examples include polyhetero 5-membered cyclic polymers, polyaniline, polyparaphenylene, polyparaphenylene vinylene, polythienylene vinylene and substituted derivatives thereof. Moreover, the copolymer which copolymerized using the monomer which produces | generates the said polymer at least 2 or more types may be sufficient.
The polyhetero 5-membered cyclic polymer used as a preferred specific example is represented by the general formula (1)

(Wherein R¹And R²Each independently represents hydrogen or a linear or branched saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, or a linear or branched saturated or unsaturated alkoxy group having 1 to 6 carbon atoms. Represents a monovalent group selected from a hydroxyl group, a halogen atom, a nitro group, a cyano group, a trihalomethyl group, a phenyl group and a substituted phenyl group. R¹And R²May be bonded to each other at any position to form at least one or more divalent chains that form at least one or more 5- to 7-membered saturated or unsaturated cyclic structures. X represents a heteroatom, and S, O, Se, Te or NR³It is. R³H represents a linear or branched saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, a phenyl group, or a linear or branched saturated or unsaturated alkoxy group having 1 to 6 carbon atoms. Represent. R above¹, R²And R³The chain of the alkyl group or alkoxy group may optionally contain a carbonyl bond, an ether bond, an ester bond, an amide bond, or an imino bond. However, (delta) is the range of 0-1. And a π-electron conjugated polymer containing a structural unit represented by
More preferably, the general formula (2)

(Wherein R⁴And R⁵Each independently represents hydrogen or a linear or branched saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms, or a hydrocarbon group having 1 to 6 carbon atoms bonded to each other at an arbitrary position. It represents a substituent which forms at least one 5- to 7-membered heterocyclic structure containing two oxygen elements described in the middle. Further, the range for forming the cyclic structure includes a chemical structure such as a substituted vinylene group or a substituted O-phenylene group. δ is in the range of 0-1. And a π-electron conjugated polymer containing a structural unit represented by
In the general formula (1), the substituent R¹, R²And R³Examples of the linear or branched saturated or unsaturated hydrocarbon group having 1 to 6 carbon atoms represented by are methyl group, ethyl group, vinyl group, propyl group, allyl group, isopropyl group, butyl group, 1 -A butenyl group is mentioned. Examples of the linear or branched, saturated or unsaturated alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, and a butoxy group.
Furthermore, examples of the substituent other than the hydrocarbon group and the alkoxy group include a nitro group, a cyano group, a phenyl group, and a substituted phenyl (halogen atom-substituted phenyl such as Cl, Br, and F) group. R¹, R²In the chain of the alkyl group and alkoxy group, a carbonyl bond, an ether bond, an ester bond, an amide bond, and an imino bond may optionally be contained. Particularly useful examples include a methoxyethoxy group and a methoxyethoxyethoxy group. Can be mentioned.
R¹And R²Is an example of the general formula (1) in which at least one divalent chain that forms at least one or more 5- to 7-membered saturated or unsaturated cyclic structures bonded to each other at any position is formed. 3,4-propylene structure [general formula (3)], 3,4-butylene structure [general formula (4)], 3,4- (2′-butenylene) structure [general formula (5)], 3, 4-butadienylene structure [general formula (6)], naphtho [2,3-c] condensed structure [general formula (7)], and the like.

Here, X represents a hetero atom, for example, S, O, Se, Te or NR³It is. The 3,4-butadienylene structure (general formula (6)) in which X is S is also referred to as an isothianaphthenylene structure in the repeating structural unit of the general formula (1). Furthermore, the naphtho [2,3-c] condensed structure (general formula (7)) is called a naphtho [2,3-c] thienylene structure in the case of general formula (1). In the formula, δ represents the number of charges per repeating structural unit, and is a value in the range of 0-1.
R in general formula (2)⁴And R⁵Examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a vinyl group, and an allyl group. In addition, R⁴And R⁵At least one 5- to 7-membered heterocyclic structure containing the two oxygen elements described in the general formula (2), wherein the hydrocarbon groups having 1 to 6 carbon atoms are bonded to each other at an arbitrary position As the substituent for forming 1, 2,2-ethylene, 1,2-propylene, and 1,2-dimethyl-ethylene are preferable.
R⁴And R⁵As specific examples of the above-mentioned hydrocarbon group having 1 to 6 carbon atoms bonded to each other at an arbitrary position to form a cyclic structure of an unsaturated hydrocarbon such as a substituted vinylene group or a substituted O-phenylene group, , 2-ethylene [general formula (8)], 1,2-cyclohexylene [general formula (9)], 1,2-dimethyl-o-phenylene [general formula (10)].

Among the monomer compounds used in the solid electrolytic capacitor and the method for producing the same of the present invention, for example, thiophene, pyrrole and 3,4-ethylenedioxythiophene monomer compounds are known, and an oxidizing agent capable of polymerizing these monomer compounds. Are well known.
However, a capacitor including a solid electrolyte using a rubber-like elastic body in the conductive polymer composition has not been known so far.
In the present invention, it is considered that the rubber-like elastic body constituting the solid electrolyte is dissolved in the conductive polymer or dispersed in the conductive polymer as a matrix.
The compounding amount of the rubber-like elastic body with respect to the π-conjugated conductive polymer constituting the solid electrolyte of the solid electrolytic capacitor of the present invention is 0.01 to 25% by mass, preferably 0.1 to 10% by mass. is there. An electrolytic capacitor provided with a solid electrolyte containing a rubber-like elastic body is a heat-resistant solid electrolytic capacitor that is particularly excellent in low impedance characteristics, durable in a spark voltage test, and relaxed to external stress.
When the blending amount of the rubber-like elastic body is less than 0.01% by mass, the effect of blending the rubber-like elastic body cannot be expected at all. On the other hand, when the blending amount exceeds 25% by mass, the conductivity of the solid electrolyte is lowered. In particular, when the amount of rubber-like elastic material increases and the matrix is reversed, the conductivity is rapidly lowered, so the blending amount must be 25% by mass or less. Therefore, when the content is in the range of 0.01 to 25% by mass, preferably in the range of 0.1 to 10% by mass with respect to the total mass of the solid electrolyte composition, a capacitor having excellent low impedance characteristics can be provided.
Usually, in the method for producing a solid electrolytic capacitor, in order to improve the high-capacity high-frequency characteristics, tan δ, leakage current, heat resistance (reflow properties), impedance characteristics, durability, etc., the method for producing (forming) the solid electrolyte is important. To that end, a π-electron conjugated structure of a conductive polymer constituting a solid electrolyte, a composition of a conductive polymer composition in combination with a rubbery elastic body, a conductive polymer composition layer having a fine surface structure dielectric It is important to improve the uniformity of the conductive path by densely filling the layer, and among them, the configuration of the conductive polymer composition particularly affects the capacitor characteristics.
In the method for producing a solid electrolyte of the present invention, when the polymer having the π-electron conjugated structure is formed, an adhesion amount of the solution is obtained by adding a rubbery elastic body to a solution containing a monomer and / or an oxidizing agent. There is a feature that the number of impregnations can be decreased and the required number of impregnations can be decreased. In addition, by adding a rubber-like elastic body, it is possible to provide stress relaxation to the conductive polymer composition, so that the elasticity increases against external pressure due to aging, sealing, or the like. As a result, characteristics such as a decrease in leakage current of initial characteristics and a decrease in capacity and loss when left at high temperature and high humidity for a long time appear.
As a specific example, a solution or dispersion of a rubber-like elastic body is mixed with a solution containing a monomer compound, and this is coated on a dielectric film having fine pores of a valve action metal anode foil, and the monomer is an oxidizing agent. Oxidative polymerization is caused by this action, and the resulting polymer composition is formed on the dielectric surface as a solid electrolyte. A dense solid electrolyte layer can be easily formed by repeating the above process once or more, preferably 3 to 20 times, for one anode substrate.
For example, the dipping method will be described as a representative one of preferable manufacturing steps. In the polymerization reaction, the step of immersing the valve action metal anode foil on which the dielectric film is formed in the solution containing the oxidizing agent (solution 1) and the solution containing the monomer compound and the rubber-like elastic body (solution 2) The process to perform is included. The immersion process may be performed in the process of immersing in the solution 2 after immersing in the solution 1, or immersing in the solution 1 after immersing the valve metal anode foil in the solution 2 in reverse order. You may carry out at the process to.
Alternatively, as another embodiment, the method includes a step of immersing the anode foil in a solution (solution 3) containing an oxidizing agent and a rubber-like elastic body and a step of immersing the anode foil in a solution (solution 4) containing a monomer compound. Also good. In this case, the manufacturing method includes the step of immersing in the solution 4 after immersing in the solution 3 or the step of immersing the anode foil in the solution 4 after immersing the anode foil in the reverse order. May be adopted. The solutions 1 to 4 may be in suspension.
Furthermore, the dipping step may be replaced with a coating method such as a coating method, a spraying method, or a casting method that can proceed the above polymerization reaction on the anode foil.
The solvents of the solutions 1 to 4 may be the same solvent or different solvent systems as required, and are dried between the solutions 1 and 2 or between the coating steps of the solutions 3 and 4 depending on the type of the solvent. A process may be included.
After forming the conductive polymer film (solid electrolyte) to form a capacitor element, a step of washing it with an organic solvent or water may be added. The organic solvent for washing is preferably a solvent used in the solutions 1 to 4 for convenience and convenience, but any solvent can be used as long as it can dissolve the monomer compound or the compound having an anion having a dopant ability.
Furthermore, when the thickness of the solid electrolyte layer is increased by repeating the oxidative polymerization, the production of a solid electrolyte having excellent solder heat resistance (thermal stability) is facilitated. In a capacitor using a solid electrolyte made of polypyrrole or the like that has been known in the past, the capacitor characteristics at high temperature and high humidity have greatly fluctuated and deteriorated in reliability, but the solid electrolyte made of the conductive polymer composition of the present invention has been deteriorated. The solid electrolytic capacitor used has excellent thermal stability and good dope stability.
This is because the conductive polymer composition blended with the rubber-like elastic body can be deposited not only on the dielectric surface but also in the pores in a stepwise manner with good filling properties and the thin film quality of the polymer composition. This is because, especially when it is formed in a state where it is layered, the above properties are exerted strongly, the polymer does not damage the dielectric film, has excellent thermal stability, and rubber elasticity Since the dielectric film and the conductive polymer film are protected from external damage by the flexibility of the body, the capacitor using this solid electrolyte can fully enjoy its performance.
The rubber-like elastic body that can be used in the present invention has a specific elasticity of elastic rubber or a rubber-like substance, and has a property of returning to the original strain when it is strained by an external force. Specific examples include general rubber (natural rubber, urethane rubber, ethylene / propylene copolymer, ethylene / propylene / diene copolymer, styrene-butadiene rubber, butyl rubber, isoprene rubber, silicone rubber, fluorine rubber, etc. ) And thermoplastic elastomers (styrene, olefin, urethane, 1,2-polybutadiene, vinyl chloride, etc.) can be used.
Fluorine-based rubber is a general term for synthetic rubbers containing fluorine atoms in the molecule, and is used as a special rubber, and is distinguished from general-purpose rubber. Examples include fluorine-containing acrylate polymers, vinylidene fluoride copolymers, tetrafluoroethylene-perfluoromethyl vinyl ether copolymers, fluorine-containing phosphazene systems, and fluorine-containing silicone systems. Although the properties differ depending on the type, it has outstanding heat resistance among commercially available rubbers. It also has excellent chemical resistance and weather resistance. Silicone rubber is a rubbery elastic body in which the main chain is composed of siloxane bonds and linear polymers with substituents such as methyl and phenyl groups in the side chain are cross-linked with each other, and it has heat resistance and electrical insulation. It is good. For the polymerization reaction of the conductive polymer, those that can be preferably dissolved in an organic solvent, such as polyester urethane, polyether urethane, vinylidene fluoride-hexapropylene copolymer, and the like can be mentioned. The organic solvent used at this time is preferably a ketone type such as ethyl methyl ketone or acetone, an acetate type such as isopropyl acetate, an ether type such as dioxane or THF, or an alcohol type such as methanol. When the rubber is insoluble in the organic solvent, the same solvent as the solvent containing the monomer or the oxidizing agent or a dispersion of a solvent that can be mixed with the solvent may be used.
When the solid electrolyte particularly requires heat resistance, fluorine-based rubber, silicon rubber or the like having high heat resistance is used.
The oxidizing agent used in the present invention may be any known oxidizing agent suitable for oxidative polymerization of pyrrole or thiophenes. For example, iron chloride described in JP-A-2-15611 (US Pat. No. 4,910,645). (III), Fe (ClO₄)₃, Organic acid iron (III), inorganic acid iron (III), alkyl persulfate, persulfate, hydrogen peroxide, K₂Cr₂O₇Etc. can be used widely.
Examples of the organic acid of the organic acid iron (III) include alkanesulfonic acid having 1 to 20 carbon atoms and aliphatic carboxylic acid such as methanesulfonic acid and dodecylbenzenesulfonic acid. However, the range of use of the oxidizing agent is not limited to all combinations, and the chemical structure of the monomer compound may be limited by the oxidizing agent and reaction conditions.
For example, according to the description of Handbook of Conducting Polymers (published by Marcel Dekker, Inc., 1987, page 99, FIG. 5), the oxidation (polymerization) of thiophenes depends on the type of substituent. (One measure of the likelihood of occurrence) varies greatly and influences the polymerization reaction (the oxidation potential broadly ranges from about 1.8 to about 2.7 V). Therefore, specifically, it is known that a specific combination is required for the monomer compound and the oxidizing agent to be used. In the present invention, a combination on the manufacturing method capable of improving the capacitor characteristics within the range of this limitation has been found, and the above problems have been solved.
In the conductive polymer of the present invention, an electrolyte compound having an oxidant anion (reduced form of the oxidant) produced from the oxidant as an anion having a dopant ability to coexist if necessary, or other anion system An electrolyte can be used. Specifically, chlorine ions, ClO₄Examples thereof include an ion, an aliphatic organic carboxylate anion having 1 to 12 carbon atoms, a sulfate anion, a phosphate anion, an aliphatic organic phosphate anion having 1 to 12 carbon atoms, and a borate anion. NO⁺, NO₂ ⁺Salt (eg NOBF)₄, NOPF₆, NOSbF₆, NOAsF₆, NOCH₃SO₃, NO₂BF₄, NO₂PF₆, NO₂CH₃SO₃And the like) may be used.
In addition, conventionally known molecular anions (for example, ClO).₄ ⁻, BF₄ ⁻Etc.) are different in dopant ability (stability of the charge transfer complex, conductivity, etc.) and chemical properties, and the above-mentioned molecular anion (ClO₄ ⁻, BF₄ ⁻Etc.) Superior effect compared to the system used alone. That is, when compared with the capacitor performance when a plurality of capacitor elements are manufactured, in the present invention, an aromatic compound (sulfoquinone, anthracene monosulfonic acid, substituted naphthalene monosulfone) is used as a compound that can bring out a particularly excellent effect. Acid, substituted benzenesulfonic acid) or heterocyclic sulfonic acid may be used.
The sulfoquinone used in the present invention is a general term for compounds having one or more sulfonic acid groups and a quinone structure in the molecule, and may be any chemical structure that works effectively as a dopant in the form of its sulfonate anion. For example, the basic skeleton of sulfoquinone is exemplified by p-benzoquinone, o-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 2,6-naphthoquinone, and 9,10-anthraquinone (hereinafter simply referred to as anthraquinone). 1,4-anthraquinone, 1,2-anthraquinone, 1,4-chrysenequinone, 5,6-chrysenequinone, 6,12-chrysenequinone, acenaphthoquinone, acenaphthenequinone, camphorquinone, 2,3-bornanedione, 9,10- Examples thereof include phenanthrenequinone and 2,7-pyrenequinone.
Furthermore, the sulfonic acid group in the sulfoquinone is an aromatic sulfonic acid structure in which one or more hydrogen of the quinone compound is substituted with a sulfonic acid group, or a divalent group of a C1-12 saturated or unsaturated hydrocarbon group. It contains an aliphatic sulfonic acid structure substituted with a sulfoalkylene group via. Further, the chemical structure in which one or more hydrogen of the sulfoquinone is substituted with a substituent selected from C1-12, preferably C1-6 saturated or unsaturated alkyl group, the same alkoxy group, or F, Cl, Br. It may be.
Among these, as the sulfoquinone used in the present invention, a sulfoquinone having a skeleton of anthraquinone, 1,4-naphthoquinone or 2,6-naphthoquinone is preferably used. For example, in the case of anthraquinones, anthraquinone-1-sulfonic acid, anthraquinone-2-sulfonic acid, anthraquinone-1,5-disulfonic acid, anthraquinone-1,4-disulfonic acid, anthraquinone-1,3-disulfonic acid, anthraquinone-1 , 6-disulfonic acid, anthraquinone-1,7-disulfonic acid, anthraquinone-1,8-disulfonic acid, anthraquinone-2,6-disulfonic acid, anthraquinone-2,3-disulfonic acid, anthraquinone-2,7-disulfonic acid Anthraquinone-1,4,5-trisulfonic acid, anthraquinone-2,3,6,7-tetrasulfonic acid, alkali metal salts thereof, ammonium salts thereof and the like can be used.
In the case of 1,4-naphthoquinones, 1,4-naphthoquinone-5-sulfonic acid, 1,4-naphthoquinone-6-sulfonic acid, 1,4-naphthoquinone-5,7-disulfonic acid, 1,4-naphthoquinone -5,8-disulfonic acid, alkali metal salts thereof, ammonium salts thereof and the like can be used.
In the case of 2,6-naphthoquinones, 2,6-naphthoquinone-1-sulfonic acid, 2,6-naphthoquinone-3-sulfonic acid, 2,6-naphthoquinone-4-sulfonic acid, 2,6-naphthoquinone-3 , 7-disulfonic acid, 2,6-naphthoquinone-4,8-disulfonic acid, alkali metal salts thereof, ammonium salts thereof and the like can be used.
Examples of the sulfoquinone include anthraquinone iris R and anthraquinone violet RN-3RN, which are known as industrial dyes, and these can also be used in the form of the salt as a useful sulfoquinone dopant.
The sulfoquinone used in the present invention is involved in the polymerization reaction of the monomer compound depending on the compound, and acts as one oxidative dehydrogenating agent. As a result, the sulfoquinone is reduced to form a proton adduct of a quinone structure, that is, a hydroquinone structure. Alternatively, the quinhydrone may be contained in the solid electrolyte as a dopant.
Anthracene monosulfonic acid used in the present invention is a general term for anthracene monosulfonic acid compounds in which one sulfonic acid group is substituted on an anthracene skeleton. Preferred compounds include unsubstituted anthracene sulfonic acid and anthracene ring of anthracene sulfonic acid. And a substituted compound in which one or more hydrogen atoms are substituted with one or more C1-12, preferably 1-6 linear or branched, saturated or unsaturated hydrocarbon groups or alkoxy groups.
Specific examples of the compound that provides the unsubstituted anthracene monosulfonate anion include anthracene-1-sulfonic acid, anthracene-2-sulfonic acid, anthracene-9-sulfonic acid, and alkali metal salts and ammonium salts thereof. . Specific examples of the substituent of the anthracene monosulfonic acid substituted compound in which hydrogen of the anthracene ring is further substituted include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, hexyl, octyl, and decyl. , Alkyl groups such as dodecyl, unsaturated groups such as vinyl, allyl, 3-butenyl, 5-hexenyl, and methoxy, ethoxy, propyloxy, butoxy, pentoxy, hexyloxy, octyloxy, decyloxy, dodecyloxy, etc. It is done.
The substituted naphthalene monosulfonic acid used in the present invention is a general term for a naphthalene monosulfonic acid compound in which one sulfonic acid group is substituted on the naphthalene skeleton and an alkoxy-substituted naphthalene monosulfonic acid compound. Preferred compounds include naphthalene monosulfonic acid. In this compound, hydrogen in the naphthalene ring may be substituted with at least one linear or branched saturated or unsaturated alkoxy group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms.
Specific examples of the compound that provides the substituted naphthalene monosulfonate anion include compound skeletons such as naphthalene-1-sulfonic acid, naphthalene-2-sulfonic acid and alkali metal salts, ammonium salts, and organic quaternary ammonium salts. And having a chemical structure in which one or more hydrogen atoms of the naphthalene ring may be substituted with an alkoxy group.
The substituted benzenesulfonic acid used in the present invention is a general term for benzenesulfonic acid and alkyl-substituted benzenesulfonic acid in which one or more sulfonic acid groups are substituted on the benzene skeleton. Preferred compounds include unsubstituted benzenesulfonic acid and Examples thereof include compounds in which one or more hydrogen atoms in the benzene ring of benzenesulfonic acid are substituted with C1-20, preferably 1-12, straight or branched saturated or unsaturated hydrocarbon groups.
The heterocyclic sulfonate anion that can be used in the present invention is an anion of a heterocyclic sulfonate compound having a chemical structure in which one or more sulfonic acid groups are substituted directly on the heterocyclic ring or indirectly through an alkylene group. Generic and preferred heterocyclic compound skeletons include morpholine, piperidine, piperazine, imidazole, furan, 1,4-dioxane, benzimidazole, benzothiazolylthio, benzisoxazole, benzotriazole, and benzofuran skeleton.
Specific examples of the compound that provides the heterocyclic sulfonic acid anion include 2-imidazolesulfonic acid, 4-morpholinepropanesulfonic acid, furan-3-sulfonic acid, 2-benzimidazolesulfonic acid, and 2-benzimidazolepropanesulfone. Examples include acids, 4-methyl-1-piperazine methanesulfonic acid, 2,3-benzofuran-3-sulfonic acid, and alkali metal salts such as sodium salts of these compounds, ammonium salts, or quaternary ammonium salts.
Among these, aromatic sulfonic acid compounds (sodium dodecylbenzenesulfonate, sodium naphthalenesulfonate, sodium anthraquinone-2-sulfonate, ammonium anthraquinone-2,6-disulfonate, 1,4-naphthoquinone-2 are preferable. -Sodium sulfonate, sodium 3-methyl-2-anthraquinolylmethanesulfonate, sodium anthracene-1-sulfonate, sodium anthracene-2-sulfonate, 9,10-dimethoxyanthracene-2-sulfonic acid tetrabutylammonium salt 9,10-dihexylanthracene-2-sulfonic acid tetrabutylammonium salt, 2-propyloxynaphthalene-6-sulfonic acid sodium salt, 2-propyloxynaphthalene-6-sulfonic acid tetrabutyric acid Ammonium salt, sodium 2-methoxynaphthalene-6-sulfonate, 2,3-dimethoxynaphthalene-6-sulfonic acid tetrabutylammonium salt, etc., heterocyclic sulfonic acid (sodium 4-morpholinepropane sulfonate, 2-benzimidazole) Sodium propanesulfonate, sodium 4-methyl-1-piperazine stannate, sodium 2,3-benzofuran-3-sulfonate, etc.).
In chemical polymerization of thiophene and pyrrole monomer compounds for forming a solid electrolyte in the present invention, it is particularly preferable to use a persulfate as an oxidizing agent. Examples of persulfate that can be particularly preferably used for chemical polymerization of thiophenes include ammonium persulfate and potassium persulfate. On the other hand, the use of an iron (III) salt-based oxidant is unavoidable for the capacitor characteristics because iron (element) remains in the conductive polymer composition.
However, persulfates suitable for the above monomer compounds are not suitable for thiophene monomers, and there are limitations that cannot be used as oxidizing agents depending on the type of monomer.
Next, preferable conditions for forming the conductive polymer composition layer (polymerization reaction) will be described.
The concentration of each monomer compound, oxidant, dopant and rubber-like elastic body used in the polymerization reaction is different from that of the monomer, oxidant, dopant and rubber-like elastic body (including the types of substituents) and solvents. Although it depends on the combination, in general, the monomer concentration is 1 × 10^-410 × 10 mol / liter, 1 × 10^-3The range of ˜5 mol / liter is more preferred.
The reaction temperature is not particularly limited because it varies depending on the type of reaction composition, reaction method, etc., but is generally in the temperature range of −70 ° C. to 250 ° C., preferably −20 ° C. to 150 ° C., Furthermore, it is preferable to carry out in a temperature range of 0 ° C to 100 ° C.
Examples of the solution used in the polymerization reaction or the washing solvent after polymerization include ethers such as tetrahydrofuran (THF), dioxane, and diethyl ether; ketones such as acetone and methyl ethyl ketone; dimethylformamide, acetonitrile, benzonitrile, N- Aprotic polar solvents such as methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO); esters such as ethyl acetate, butyl acetate and isopropyl acetate; non-aromatic chlorinated hydrocarbon solvents such as chloroform and methylene chloride; nitromethane, Nitro compounds such as nitroethane and nitrobenzene; alcohols such as methanol, ethanol and propanol; organic acids such as formic acid, acetic acid and propionic acid; acid anhydrides of these organic acids (eg, acetic anhydride, etc.) and water or mixed solvents thereof It can be used. Preferably, water, alcohols, ketones, acetate esters and / or mixed systems thereof are desirable.
The conductivity of the solid electrolyte thus produced is in the range of 0.1 to 200 S / cm, but is preferably 1 to 100 S / cm, and more preferably 10 to 100 S / cm, under desirable conditions.
The outline of the configuration of the solid electrolytic capacitor of the present invention will be described with reference to FIG.
One electrode (anode) 1 provided with pores 2 coupled to the connection terminal 7 on the entire surface is made of a metal foil having a valve action such as aluminum, titanium, tantalum, niobium or an alloy system using these as a substrate, A known material such as a rod or a sintered body containing these as a main component is used. The surface of these metal electrodes is subjected to etching treatment or chemical conversion treatment by a known method for the purpose of forming a dielectric layer and increasing the specific surface area, and the metal oxide film layer 3 formed on a metal foil is used.
The formation of the solid electrolyte (conductive polymer composition) 4 is preferably by a method of polymerizing a monomer compound on the dielectric layer of the valve action metal electrode foil, and in particular, the solid electrolyte contains a rubber-like elastic body. A method of chemically depositing a conductive polymer composition having excellent heat resistance and impact resistance on the dielectric layer having the dielectric film pores or void structure is preferred.
Another conductive layer 5 is provided on the conductive polymer composition layer thus formed in order to further improve electrical contact. The conductor layer can be formed by, for example, a conductive paste layer or plating, metal vapor deposition, a conductive resin film, or the like.
Thus, the solid electrolytic capacitor manufactured by the manufacturing method of the present invention is further provided with a resin mold on the conductor layer, a resin case, a metal outer case, an outer case 6 made of resin dipping, etc. By providing the connection terminal 7 in the solid electrolytic capacitor product suitable for various applications.
(II) When the metal powder-containing conductor layer contains a rubbery elastic body
When a rubber-like elastic body is contained in the metal powder-containing conductor layer, a conductive filler made of metal powder and a metal powder-containing conductive paste containing a rubber-like elastic body as a main component of a binder are used.
Rubber-like elastic materials include general rubber (natural rubber, urethane rubber, ethylene / propylene copolymer, ethylene / propylene / diene copolymer, styrene-butadiene rubber, butyl rubber, isoprene rubber, silicone rubber, fluorine-based rubber). Synthetic rubbers such as rubber) and thermoplastic elastomers (styrene, olefin, urethane, 1,2-polybutadiene, vinyl chloride, etc.) can be used.
Among these, fluorine rubber and silicon rubber excellent in heat resistance are preferable, and fluorine rubber is particularly preferable.
Fluorine-based rubber is a general term for synthetic rubbers containing fluorine atoms in the molecule, and is used as a special rubber, and is distinguished from general-purpose rubber. Examples include fluorine-containing acrylate polymers, vinylidene fluoride copolymers, tetrafluoroethylene-perfluoromethyl vinyl ether copolymers, fluorine-containing phosphazene systems, and fluorine-containing silicone systems. Although the properties differ depending on the type, it has outstanding heat resistance among commercially available rubbers. It also has excellent chemical resistance and weather resistance.
As the solvent for the conductive paste, the same solvents as those used for ordinary conductive pastes may be used. For example, solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylformamide, and butyl acetate may be used alone or in combination. Use by mixing. The amount of the solvent to be blended in the conductive paste needs to be blended so as to have a viscosity corresponding to the purpose of use of the conductive paste. Usually, the amount is equivalent to ten times the solid content of the paste. use.
As the conductive filler used in the conductive paste, metal powder such as gold and copper, carbon powder, and the like are used in addition to silver powder, but silver powder is preferable, and silver powder contains 80% by mass or more of the entire filler. Particularly preferred. The average particle size of the powder is preferably 1 to 10 μm. If the average particle size is less than 1 μm, the bulk density is small, the paste volume is large, and this is disadvantageous for the formation of the conductor layer. On the other hand, if the average particle size exceeds 10 μm, it is too coarse and poor connection with the cathode lead terminal is likely to occur.
Hereinafter, the case of using a fluorine-based rubber which is a preferable binder will be described.
A preferred binder is a fluorine-based rubber, preferably 80 to 100% by mass of the binder is a fluorine-based rubber. A conventional resin or the like can be mixed as the remaining components. Fluorine-based rubber has rubber elasticity and has a property of returning to its original strain when subjected to strain, and is distinguished from fluorine-based resin that does not return strain. Examples of the fluorine rubber include known vinylidene fluoride copolymer rubber, 6-fluoropropylene copolymer rubber, 4-fluoroethylene copolymer rubber, fluorine-containing acrylate rubber, fluorine-containing silicone rubber, and the like. Can be used. These rubbers are unvulcanized and are also distinguished from fluororesins in that their glass transition point (Tg) is lower than room temperature.
The mixing ratio of the conductive filler and the binder is preferably 50 to 95% by mass of the conductive filler and 5 to 50% by mass of the binder. When the amount of the conductive filler is less than 50% by mass, the conductivity is lowered, and when it is more than 95% by mass, the binding force of the binder (less than 5% by mass) is lowered, and the formation of the conductor layer becomes difficult.
In order to impart a suitable viscosity as a paste to the mixture (solid content) of the above conductive filler and binder, an organic solvent is usually added. The organic solvent is preferably a solvent in which a fluorinated rubber is dissolved. As the solvent, butyl acetate, amyl acetate, propyl acetate or the like can be used. The amount of the organic solvent is generally 40 to 100 parts by mass with respect to 100 parts by mass of the solid content.
Next, a solid electrolytic capacitor using a conductive paste containing the rubber elastic body of the present invention will be described.
An example of the solid electrolytic capacitor of the present invention is shown in FIG.
In FIG. 2, 1 is a valve action metal foil (anode) such as aluminum or tantalum, on which a dielectric oxide film 3 and pores 2 are formed by electrolytic anodic oxidation or the like. An anode lead terminal 7a is joined to the anode 1 by welding or the like. Reference numeral 4 denotes a solid electrolyte layer (cathode) formed on the oxide film 3. An inorganic semiconductor compound can also be used for the solid electrolyte layer, but when the conductive paste of the present invention is used, a conductive polymer is particularly suitable for the solid electrolyte.
The conductive polymer has been described in detail in the section (I) when the solid electrolyte layer includes a rubber-like elastic body, but poly (3,4-ethylenedioxythiophene), polypyrrole, polyaniline, etc. should be used. Polypyrrole and poly (3,4-ethylenedioxythiophene) are preferable. As an dopant, anthraquinonesulfonic acid, alkylanthraquinonesulfonic acid, alkoxyanthraquinonesulfonic acid, anthracenesulfonic acid, alkylanthracenesulfonic acid, alkoxyanthracenesulfonic acid, naphthalenesulfonic acid, alkylnaphthalenesulfonic acid, alkoxynaphthalenesulfonic acid, benzenesulfonic acid, Anions of alkylbenzene sulfonic acid and alkoxybenzene sulfonic acid are contained. The sulfonic acid substituent of the organic sulfonate anion may have a chemical structure bonded to any position where it can be bonded to the skeleton compound, and the compound having an alkyl group or an alkoxy group has 1 to 10 carbon atoms. And a chemical structure in which an alkyl group or an alkoxy group having a bond is bonded to an arbitrary bondable position to the skeleton compound.
As a method for forming the conductive polymer, a known method such as chemical polymerization using an oxidizing agent (polymerization initiator) of the monomer forming the polymer, electrolytic polymerization, or a combination thereof may be used. For example, the oxide film layer is immersed in a monomer solution, then immersed in an oxidant solution, heated and chemically polymerized, and this operation is repeated a plurality of times. By this repeated polymerization, the conductive polymer layer has a multilayer laminated structure, and has excellent heat stress resistance when sealed with an exterior resin.
Moreover, what consists of a conductive polymer composition containing an above described rubber-like elastic body as a solid electrolyte layer is also used preferably.
The effect by using a fluorine-type rubber binder as an electrically conductive paste is as follows. The conductive polymer layer has a multilayer laminated structure and is excellent in heat stress resistance. However, when a conductive paste using a binder having a large thermal shrinkage such as an epoxy resin is applied to the conductive polymer layer, the conductive polymer layer penetrates into the surface layer of the conductive polymer. This paste generates a large amount of stress during heating, and the multilayer shape of the conductive polymer layer is affected. When a fluorine rubber binder is used, the thermal stress generation of the paste that has entered the surface of the conductive polymer is small, and the generated conductive polymer layer shape is maintained. Thereby, the heat resistance of the capacitor becomes better.
As the oxidizing agent for chemical polymerization, ammonium persulfate, organic iron sulfonate (III), inorganic acid iron such as iron (III) chloride, Fe (ClO₄)₃, Organic acid iron (III), persulfate, alkyl persulfate, hydrogen peroxide, K₂Cr₂O₇Etc. are used.
A conductor layer 5 is formed on the surface of the solid electrolyte layer 4. The conductor layer 5 is in close contact with the solid electrolyte layer and acts as a cathode and simultaneously serves as an adhesive for joining the cathode lead terminal 7b. The thickness of the conductor layer 5 is generally about 10 to 50 μm.
The conductor layer 5 can be formed only with the above-described conductive paste of the present invention, but preferably a layer formed of a carbon paste on the conductive polymer layer 4 as described in detail in the next section. And a layer formed of the conductive paste of the present invention is provided thereon. As the carbon paste, a known carbon paste in which a binder resin and a solvent are added to graphite powder can be used. Preferably, fluorine-based rubber is used as the binder resin. The thickness of the carbon paste layer may be about 1 to 2 μm.
A cathode lead terminal 7 b is joined to the outer surface of the conductor layer 5. Then, the exposed portions of the cathode lead terminal 7b and the anode lead terminal 7a are left and sealed with the insulating resin 6. An epoxy resin is mainly used as the insulating resin. Sealing can be performed by, for example, transfer molding.
(III) When the conductive carbon layer contains a rubber-like elastic body
The conductive carbon layer is formed using a conductive carbon paste mainly composed of a conductive material, a binder, and a solvent. It is preferable that 80% by mass or more of the conductive material is made of artificial graphite powder. As the artificial graphite powder, those having a fixed carbon content of 97% by mass or more, an average particle diameter of 1 to 13 μm, an aspect ratio of 10 or less, and particles having a particle diameter of 32 μm or more are 12% by mass or less are used.
Scale-like or leaf-like natural graphite always has an aspect ratio of 10 or more, and is different from the conductive material used in the present invention. The higher the aspect ratio of the artificial graphite, the lower the filling property as the conductive carbon paste and the higher the resistance of the paste. Therefore, the aspect ratio of the artificial graphite powder needs to be 10 or less. Such artificial graphite has a higher purity than natural graphite and carbon black, can have a high filling rate, and has a characteristic that deterioration due to heat is small.
Similarly, the fixed carbon content of the graphite powder also affects the resistance of the paste, and the higher the fixed carbon content of the artificial graphite powder, the lower the resistance. Therefore, in order to achieve the object of the present invention, it is necessary to use artificial graphite powder having a fixed carbon content of 97% by mass or more. Here, the fixed carbon content is a value serving as a standard for the carbon content, and includes a JIS method (JIS K2425), a carbon association method, an ASTM method, and a BS method.
The average particle diameter of the graphite powder is preferably in the range of 1 to 13 μm in order to obtain uniform coating properties of the conductive carbon paste. Even if artificial graphite powder is used, if a powder with an average particle diameter exceeding 13 μm is used, a uniform paste layer may not be obtained. When used for a solid electrolytic capacitor, tan δ in capacitor characteristics, equivalent series resistance (ESR) Etc. get worse. Further, even if the average particle size is within this range, even when coarse particles are contained, uniform coating is hindered. However, when the content of particles having a particle size of 32 μm or more is set to 12% by mass or less, such a problem is caused. Does not occur.
As the conductive material of the conductive carbon paste of the present invention, it is necessary to use a material containing at least 80% by mass or more of the above artificial graphite powder. When natural graphite and carbon black are used in combination and the artificial graphite powder is less than 80% by mass, sufficient conductivity cannot be ensured as the conductive carbon paste obtained. The use of artificial graphite powder is preferably 95% by mass or more, and more preferably 100% by mass. The remaining portion of the conductive material is metal powder such as silver, gold, copper, carbon black, natural graphite, and other powdered conductive substances.
The solid electrolytic capacitor of the present invention uses a conductive carbon paste containing a conductive material containing 80% by mass or more of artificial graphite powder, a binder and a solvent as main components. The artificial graphite powder can be used without limitation of the fixed carbon content, the average particle diameter, the aspect ratio and the like as described above, but is preferably a paste using the artificial graphite powder limited as described above.
The binder of the conductive carbon paste is a material having rubber elasticity (hereinafter also referred to as a rubber elastic body), and is a material having a property of returning the distortion to the original, preferably in the embodiment. A rubber elastic body that is a material that can swell or suspend in a solvent and that has excellent heat resistance against reflow treatment during capacitor manufacture is used. As specific examples, materials having the above characteristics include isoprene rubber, butadiene rubber, styrene / butadiene rubber, nitrile rubber, butyl rubber, ethylene / propylene copolymer (EPM, EPDM, etc.), acrylic rubber, polysulfide rubber, fluorine And polymer polymers, silicone rubbers, other thermoplastic elastomers, and the like. Among them, EPM, EPDM and fluorine-based polymers are preferably used. The fluorine-based polymer is not particularly limited as long as it contains a fluorine element. These rubber polymers are generally lower in elastic modulus and water absorption than epoxy resins used in conductive carbon paste, and are effective in relieving stress at the bonded portion.
Examples of the fluoropolymer include polytetrafluoroethylene, poly (chlorotrifluoroethylene), a binary copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), a copolymer containing tetrafluoroethylene, tetra Fluoroethylene-propylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, fluorine-containing acrylate rubber, fluorine-containing silicone rubber and the like can be mentioned.
The compounding ratio of the conductive material and the binder resin in the conductive carbon paste is 30 to 99% by mass, preferably 50 to 90% by mass, and 1 to 70% by mass of the binder resin per total solid mass. . When the amount of the conductive material is less than 30% by mass, the conductivity of the conductive carbon paste becomes too low, and when it exceeds 99% by mass, the adhesion and stress relaxation ability of the conductive carbon paste are lost.
As the solvent used for the conductive carbon paste, the same solvent as that used for the normal conductive carbon paste may be used. For example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, dimethylformamide, butyl acetate, etc. Solvents are used alone or in combination. The amount of solvent blended in the conductive carbon paste needs to be blended so as to have a viscosity corresponding to the purpose of use of the conductive carbon paste, but is usually equivalent to ten times the solid content of the paste. Use quantity.
When producing a solid electrolytic capacitor using the conductive carbon paste of the present invention, as an anode, a single metal such as aluminum, tantalum, niobium, titanium, zirconium having a valve action or a metal foil of an alloy thereof is etched. Any one having a large surface area, such as a sintered product or a fine powder sintered body, can be used.
A dielectric layer is formed on the surface of the metal by chemical conversion treatment, a solid semiconductive layer (preferably, a solid electrolyte layer made of the above-mentioned conductive polymer) is provided on the outer side, and the outer side of the present invention is further provided on the outer side. A conductive carbon paste layer is formed, a metal-containing conductor layer, preferably a metal-containing conductor layer containing the rubber-like elastic body described above, is formed, and lead wires are connected to form a solid electrolytic capacitor.
The solid electrolytic capacitor using the conductive carbon paste according to the present invention has high heat resistance, low ESR (equivalent series resistance), low impedance, low thermal degradation of impedance, and excellent performance in moisture resistance. It is.
BEST MODE FOR CARRYING OUT THE INVENTION
EXAMPLES Hereinafter, although an Example, a comparative example, and a reference example are given and this invention is demonstrated concretely, this invention is not limited at all by the following description.
Example 1
The aluminum conversion foil processed to a specified area was formed with a 10% by mass aqueous solution of ammonium adipate at a conversion voltage of 13 V to form a dielectric layer on the foil surface. This aluminum conversion foil (substrate) was immersed in a solution (solution 4) in which 0.05 g of polyester urethane rubber was dissolved in a 1.2 mol / liter ethyl methyl ketone solution in which 5 g of 3,4-ethylenedioxythiophene was dissolved. Then, it was immersed in an aqueous solution (solution 3) prepared to 20% by mass ammonium persulfate (hereinafter abbreviated as APS) and sodium 2-anthraquinonesulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.): 0.125% by mass.
The substrate was taken out and allowed to stand at 60 ° C. for 10 minutes to complete oxidative polymerization, and the substrate was washed with water. This polymerization reaction treatment and washing step were repeated 10 times each. It was confirmed from the electron micrograph that the conductive polymer layer formed a layered structure.
The contents of sulfate ion and 2-anthraquinone sulfonate ion in the conductive polymer composition were obtained by first carefully extracting the polymerized substrate by hydrazine reduction in a water / isopropyl alcohol solvent, and obtaining by ion chromatography. However, the sulfate ion content was 1.5 mol% per all repeating structural units of the polymer in the conductive polymer composition, and the 2-anthraquinone sulfonate ion content was 14.0 mol%. Furthermore, the increase in the adhesion mass of this substrate showed a 15% increase in mass compared to the case where it was not added. The conductivity of the solid electrolyte layer was 73 S / cm.
Next, the aluminum foil substrate on which the poly-3,4-ethylenedioxythiophene polymer composition was accumulated was treated in a 10% by mass ammonium adipate aqueous solution, and the spark voltage was examined. The test was carried out by increasing the number of elements when comparing element characteristics (the same applies to the following examples). That is, in a 50 ° C. environment, the current density is 10 mA / cm.²Under the conditions, n = 5 times and the result of Table 1 was obtained.
Next, the solid electrolytic capacitor collects current from the anode by welding the aluminum core of the substrate to the positive lead terminal, and collects current from the cathode to the negative lead terminal via carbon paste and silver paste. The capacitor element was produced by connecting and finally sealing with epoxy resin. The capacitor element thus obtained was aged at 125 ° C. for 2 hours, and then the initial characteristics were measured. These results are summarized in Table 2.
Here, C of the initial characteristic in the table represents the capacity, and DF represents the tangent (tan δ) of the loss angle. Both are measured at 120 Hz. Z (impedance) represents a value at the resonance frequency. LC (leakage current) was measured 1 minute after applying the rated voltage. Each measured value is an average value of 30 samples, and for LC, 1 μA or more is displayed as a defective product and 10 μA or more is displayed as a short product, and the average LC value is calculated by excluding this.
Comparative Example 1
The capacitor element obtained by the same treatment as in Example 1 except that no polyester urethane rubber was added in Example 1 was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.
In addition, when the content of sulfate ion and 2-anthraquinone sulfonate ion in the polymer composition was determined by the method described in Example 1, the sulfate ion content was 1.6 mol%, and the 2-anthraquinone sulfonate ion content was It was 13.5 mol%. The conductivity of the solid electrolyte layer was 70 S / cm.
Example 2
A capacitor element obtained by the same treatment as in Example 1 was evaluated in the same manner as in Example 1 except that the number of times of oxidative polymerization in Example 1 was changed from 10 to 7. The results are shown in Tables 1 and 2.
In addition, when the content of sulfate ion and 2-anthraquinone sulfonate ion in the polymer composition was determined by the method described in Example 1, the sulfate ion content was 1.2 mol%, and the 2-anthraquinone sulfonate ion content was It was 13.0 mol%. The adhesion mass was almost the same as 10 impregnations without adding polyester urethane rubber. The conductivity of the solid electrolyte layer was 70 S / cm.
Example 3
A capacitor element obtained by treating in the same manner as described in Example 1 except that an acetone solution having the same concentration of tetrafluoroethylene-propylene copolymer was used instead of the polyester urethane rubber used in Example 1. Evaluation was performed in the same manner as in 1. The results are shown in Tables 1 and 2.
In addition, when the content of sulfate ion and 2-anthraquinone sulfonate ion in the polymer composition was determined by the method described in Example 1, the sulfate ion content was 1.8 mol%, and the 2-anthraquinone sulfonate ion content was 15.8 mol%. The increase in mass on the substrate was 25%. The conductivity of the solid electrolyte layer was 65 S / cm.
Example 4
A capacitor element obtained by treating in the same manner as described in Example 1, except that the same concentration solution of sodium dodecylbenzenesulfonate was used instead of sodium 2-anthraquinonesulfonate used in Example 1, and Evaluation was performed in the same manner. The results are shown in Tables 1 and 2.
The sulfate ion content and dodecylbenzene sulfonate ion content in the polymer composition were determined by the method described in Example 1. As a result, the sulfate ion content was 1.3 mol%, and the dodecylbenzene sulfonate ion content was 14%. It was 5 mol%. The increase in mass on the substrate was 20%. The conductivity of the solid electrolyte layer was 67 S / cm.
Example 5
A capacitor element obtained by treating in the same manner as described in Example 1 except that an acetone solution of the same concentration of vinylidene fluoride-hexapropylene copolymer was used instead of the polyester urethane rubber used in Example 1. Evaluation was performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.
In addition, when the content of sulfate ion and 2-anthraquinone sulfonate ion in the polymer composition was determined by the method described in Example 1, the sulfate ion content was 1.4 mol%, and the 2-anthraquinone sulfonate ion content was 14.2 mol%. The increase in mass on the substrate was 24%. The conductivity of the solid electrolyte layer was 73 S / cm. When the fluorine content was determined by using both the oxygen flask combustion method and the ion chromatography method, it was 0.5% by mass. Therefore, the fluororubber was contained in an amount equivalent to about 1% by mass in the polymer composition.
Example 6
It was obtained by treating in the same manner as described in Example 1 except that the same concentration solution of pyrrole was used instead of 3,4-ethylenedioxythiophene used in Example 1 and the oxidative polymerization temperature was 5 ° C. The capacitor element was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.
In addition, when the content of sulfate ion and 2-anthraquinone sulfonate ion in the polymer composition was determined by the method described in Example 1, the sulfate ion content was 1.7 mol%, and the 2-anthraquinone sulfonate ion content was It was 15.9 mol%. The increase in mass on the substrate was 21%. The conductivity of the solid electrolyte layer was 80 S / cm.
Reference example 1
A process for producing a capacitor element was performed under the same conditions as those described in Example 1, except that 3,4-ethylenedioxythiophene described in Example 1 was replaced with 4-methylthiophene. However, a black-blue poly-4-methylthiophene polymer was not formed at all, and the polymerization of 4-methylthiophene did not occur by the action of APS.

In Examples 1 to 6, after measuring the initial characteristics of the capacitor element, it was exposed to high temperature and high humidity for 500 hours, and the capacity and loss factor at 120 Hz were measured again. The results are shown in Table 3. Further, as Comparative Example 1, the same measurement of the capacitor element was performed under the same conditions as in Example 1 except that the polyester urethane rubber was not added. The results are shown in Table 3. As is apparent from Table 3, the capacitor element according to Example 1 has an excellent effect that the difference between the characteristic after the life acceleration test and the initial characteristic is significantly smaller than that of Comparative Example 1.
As described above, according to the present embodiment, it is possible to realize a high-performance capacitor having a relaxation property with respect to external stress and having excellent life characteristics.

Example 7: Preparation of conductive paste
Silver powder having an average particle size of 5.5 μm was used as the conductive filler, and Viton rubber (vinylidene fluoride-4 fluoroethylene-6 fluoropropylene copolymer) was used as the fluorine-based rubber for the binder. Then, 85% by mass of silver powder and 15% by mass of Viton rubber powder were mixed to obtain a solid content of the paste. To this was added butyl acetate as a solvent and kneaded to obtain a viscous silver paste having a solid content of 60% by mass.
Example 8: Production of a solid electrolytic capacitor
Anodized aluminum formed foil that has been anodized after etching is cut to a length of 10 mm, and an unformed portion of the cut portion is formed at a forming voltage of 13 V, and a dielectric oxide film is formed on the entire surface of the aluminum foil. did. About 50% of the length of the chemical conversion foil is immersed in a 1 mol / liter ethyl alcohol solution of 3,4-dioxyethylenethiophene, and then 1.1 of ammonium persulfate is used as an oxidizing agent (polymerization initiator). The polymer was immersed in an aqueous solution having a concentration of 5 mol / liter and sodium naphthalene-2-sulfonate as a dopant at a concentration of 0.12 mol / liter, and was maintained at 40 ° C. for polymerization. This polymerization operation was repeated 20 times to form a conductive polymer layer made of poly (3,4-ethylenedioxythiophene) on the oxide film of the foil. By repeating the polymerization 20 times, the conductive polymer layer became a layered structure as shown in the enlarged photograph (5000 magnification) of the electron microscope in FIG. 2 (in FIG. 2, the upper part is a conductive polymer layer having a layered structure). .) The part having the conductive polymer layer was immersed in a carbon paste and heat-treated at 100 ° C. for 30 minutes. The carbon paste layer was prepared by mixing 60% by mass of graphite powder having an average particle size of 3 μm and 40% by mass of the fluorine rubber of Example 1 to obtain a solid content of the paste. To this was added butyl acetate as a solvent and kneaded to obtain a viscous carbon paste having a solid content of 16% by mass.
Next, the portion of the layer formed of this carbon paste was immersed in the silver paste of Example 7 to form a conductor layer to form a unit capacitor element. The unit capacitor element is cut at the aluminum foil portion on the side not having the conductive polymer, and four of them are stacked and bonded using the same silver paste, and bonded to a lead frame (copper alloy) at 100 ° C., 3 ° C. Let dry for hours. Thereafter, the aluminum foil portion without the conductive polymer was welded to a lead frame (copper alloy). Finally, one end portions of these frames were exposed, and an epoxy resin (EME-7320A manufactured by Sumitomo Bakelite Co., Ltd.) was used and sealed by transfer molding to obtain a chip-type capacitor. Table 4 shows the characteristics of this capacitor.
Comparative Example 2
A chip-type solid electrolytic capacitor was produced in the same manner as in Example 8, except that the silver paste binder was changed to an epoxy resin (Epicoat 828 type manufactured by Yuka Shell Epoxy Co., Ltd.). The characteristics are shown in Table 4.

In Table 4, ESR (equivalent series resistance at 100 KHz) represents the average value of 30 samples, the reflow failure rate, and the moisture resistance failure rate represent the number of defective products in 30 samples measured by the following method.
Reflow defect rate:
After passing through a reflow furnace (230 ° C., 30 seconds), a rated voltage (13 V) is applied, and a leakage current value after 1 minute is measured. Less than 12 μA was accepted (good product), and 12 μA or more was judged defective.
Moisture resistance rate:
The capacitor was left in an atmosphere of temperature 60 ° C./humidity 90%. After 1000 hours, this is taken out, a rated voltage is applied, and the leakage current value after 1 minute is measured. Less than 12 μA was accepted (good product), and 12 μA or more was judged defective.
Example 9
Artificial graphite powder having an aspect ratio of 3 to 1.5, an average particle diameter of 3 μm, a particle diameter of 32 μm or more as a conductive material, 2% by mass or less, and a fixed carbon content of 99% by mass (Showa Denko K.K. ) Product: UFG-5) In 100 parts by mass, a butyl acetate suspension of ethylene / propylene / diene terpolymer (EPDM) as a binder resin (7% by mass of EPDM in the suspension) is solid graphite powder. The conductive carbon paste was prepared by adding 80% by mass with respect to 100 parts by mass and stirring the mixture for 24 hours.
Next, a 1 mm wide polyimide tape was applied to both sides of the aluminum conversion foil cut out to 3 mm × 10 mm so as to be divided into 4 mm and 5 mm portions from the end, and the 3 mm × 4 mm portion was 10% by mass. In an aqueous solution of ammonium adipate, a voltage of 13 V was applied for formation. Thereby, a dielectric oxide film was formed in the region. Further, the 3 mm × 4 mm portion of the aluminum foil was dipped in an isopropanol solution (solution 1) containing 3,4-dioxyethylene-thiophene 20% by mass, pulled up, air-dried at room temperature, and then the dielectric oxidation. By immersing the film-formed part in an aqueous solution (solution 2) containing 30% by mass of ammonium persulfate (APS) and 1% by mass of sodium anthraquinone-2-sulfonate, and then leaving it in an atmosphere of 60 ° C. for 10 minutes. Oxidative polymerization was performed. This was again immersed in the solution 1 and further subjected to the same treatment as described above. The operation from immersion in solution 1 to oxidative polymerization was repeated 25 times, followed by washing with warm water at 50 ° C. for 10 minutes and drying at 100 ° C. for 30 minutes to form a conductive polymer layer (solid electrolyte Layer).
Thus, when the cross section of the obtained aluminum foil on which the conductive polymer layer was formed was examined with a scanning electron micrograph (2,000 times), the conductive polymer layer was a fine dielectric (alumina) on metal aluminum. It was confirmed that the surface in the hole was covered with a layered structure, and that a space portion was present between the layered conductive polymer layers. Here, the thickness of the conductive polymer layer formed on the outer surface of the microporous structure is about 5 μm, and the thickness per layer forming the layer structure is in the range of about 0.1 to 0.3 μm. there were.
Next, after applying the conductive carbon paste prepared by the above method to the portion of the aluminum foil where the conductive polymer layer is formed, heat treatment is performed at 100 ° C. for 30 minutes, and the conductive polymer is coated on the conductive polymer with the carbon paste. A conductive layer was formed. Next, a silver paste is applied to connect the cathode lead terminal, and the element where the anode lead terminal is connected to the portion where the conductive polymer layer is not formed is sealed with an epoxy resin, and then at 125 ° C. The rated voltage was applied and aging was performed for 2 hours to complete a total of 30 capacitors.
About these 30 capacitor | condenser elements, the equivalent series resistance (ESR) was measured by the normal method, and the reflow process was carried out. Next, ESR after reflow was measured again, and the change in ESR before and after reflow was estimated. Next, the moisture resistance defect rate test described later was performed on the total amount of capacitor elements. The results are summarized in Table 5.
Example 10
The EPDM / butyl acetate suspension described in Example 9 was changed to a fluoropolymer (vinylidene fluoride-hexafluoropropylene-tetrafluoro copolymer) / butyl acetate suspension, and the EPDM solid content was 100 parts by mass of artificial graphite powder. A total of 30 capacitor elements in accordance with the method described in Example 9 except that the conditions of using 80 parts by mass with respect to 100 parts by mass of the fluorine-based polymer solid were changed to 100% by mass with respect to the artificial graphite powder. The capacitor was evaluated for characteristics similar to those described in Example 9. The results are summarized in Table 5.
Comparative Example 3
As the conductive material, the artificial graphite powder described in Example 9 has an average particle size of 4 μm, particles having a particle size of 32 μm or more are 2% by mass or less, fixed carbon content is 98.5% by mass, and the aspect ratio is clear. A total of 30 capacitors were completed and the characteristics of the capacitors were evaluated in the same manner as in Example 9, except that 10 or more scaly natural graphite was used and EPDM was replaced with an epoxy resin as a binder. The results are summarized in Table 5.
Comparative Example 4
As the conductive material, the artificial graphite powder described in Example 10 has an average particle diameter of 4 μm, particles having a particle diameter of 32 μm or more are 2 mass% or less, fixed carbon content is 98.5 mass%, and the aspect ratio is clear. A total of 30 capacitors were completed in the same manner as in Example 10 except that 10 or more scaly natural graphite was used, and the characteristics of the capacitors were evaluated. The results are summarized in Table 5.
In Examples 9 to 10 and Comparative Examples 3 to 4, the various evaluation tests performed were performed under the following measuring methods and conditions.
[Measuring method]
1. Reflow defect rate
The 30 prepared solid electrolytic capacitors were passed through a reflow furnace having a peak temperature of 230 ° C. for 30 seconds, then a rated voltage (6.3 V) was applied, and a leakage current after 1 minute was measured. As a judgment, less than 3 μA was regarded as an acceptable product.
2. Moisture resistance rate
Leave all the solid electrolytic capacitors that passed the reflow test in an atmosphere of temperature 60 ° C and humidity 90%, take them out after 1000 hours, apply the rated voltage (6.3V), and determine the leakage current value after 1 minute. taking measurement. As a judgment, less than 12 μA was regarded as an acceptable product.

Industrial applicability
The present invention relates to a solid electrolyte comprising a rubber-like elastic body in at least one layer comprising a solid electrolyte layer and a conductor layer containing metal powder, or a conductive carbon layer and a conductor layer containing metal powder provided on the conductive carbon layer. A capacitor, a manufacturing method thereof, a solid electrolyte used in the solid electrolytic capacitor, a manufacturing method of the solid electrolyte, a conductive paste for a solid electrolytic capacitor, and a conductive carbon paste for a solid electrolytic capacitor are provided.
The solid electrolytic capacitor of the present invention includes a rubber elastic body in the conductive polymer composition forming the solid electrolyte, so that the number of impregnations can be greatly reduced, leading to an improvement in productivity, small size and lower impedance. Therefore, it is possible to provide a solid electrolytic capacitor having higher performance and relaxing to external stress, and a method for manufacturing the same.
In addition, by using a specific polyhetero 5-membered cyclic compound, particularly conductive polythiophene, as a π-electron conjugated polymer in the solid electrolyte, withstand voltage characteristics (spark voltage test), high frequency characteristics, tan δ, impedance characteristics, leakage current, The effect of greatly improving heat resistance (reflow properties) and the like can be obtained.
In particular, in the conductive polymer composition, the content of one rubber-like elastic body is in the range of 0.01 to 25% by mass with respect to the repeating unit of the polymer having a π-electron conjugated structure structure, Furthermore, when the sulfate ion content is contained in the range of 0.1 to 10 mol%, a solid electrolytic capacitor having higher performance capacitor characteristics can be obtained.
When the solid electrolytic capacitor of the present invention includes a rubber-like elastic body in a conductive layer (a conductive layer including a metal powder or a conductive carbon layer and a conductive layer including a metal powder provided on the conductive layer). The following effects can be obtained.
(1) In the conductive paste of the present invention, the binder is fluorine rubber, the elastic modulus is low, and the heat resistance and moisture resistance are excellent.
(2) The solid electrolytic capacitor using the conductive paste for the conductor layer has a small thermal stress generated by reflow or the like, and does not peel at the interface of the conductor layer.
(3) Therefore, there is an effect that a change in ESR before and after reflow is small, and that reflow failure and moisture resistance failure do not occur.
Furthermore, the solid electrolytic capacitor of the present invention is excellent in moisture resistance (water repellency) by using a rubber-like elastic body, particularly a fluorine-based rubber-like elastic body, as the conductive carbon layer. By using a conductive material (artificial graphite powder), the packing density can be increased and the conductivity and heat resistance are excellent.
For this reason, a solid electrolytic capacitor using this as a conductive carbon paste has an exceptional effect of low ESR (equivalent series resistance at 100 KHz), small ESR change before and after reflow, and low moisture resistance rate.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of the solid electrolytic capacitor of the present invention.
FIG. 2 is a cross-sectional view showing another example of the solid electrolytic capacitor of the present invention.
FIG. 3 is an electron micrograph of the conductive polymer layer in the present invention (magnification: 5000 times).
In the figure, 1 is a valve metal, 2 is a pore, 3 is a dielectric film, 4 is a solid electrolyte layer, 5 is a conductor layer, 6 is an exterior body, 7 is a connection terminal, 7a is an anode terminal, and 7b is Cathode terminal.

Claims (41)

In a solid electrolytic capacitor formed by forming a solid electrolyte layer made of a conductive polymer and a conductive layer on a dielectric film formed on a valve action metal, at least one of the solid electrolyte layer and the conductive layer rubber-like elastic material only contains a solid electrolytic capacitor, wherein the solid electrolyte layer is a membrane-like or a conductive polymer composition layer containing a fluorine-based rubber.   The solid electrolytic capacitor according to claim 1, wherein the conductor layer includes a conductor layer containing metal powder, or a conductive carbon layer and a conductor layer containing metal powder provided on the conductive carbon layer.   The solid electrolytic capacitor according to claim 2, wherein the conductive carbon layer includes a rubber-like elastic body.   The solid electrolytic capacitor according to claim 2, wherein the metal powder-containing conductor layer includes a rubber-like elastic body.   The solid electrolytic capacitor according to claim 2, wherein the conductive carbon layer and the metal powder-containing conductor layer include a rubber-like elastic body. The solid electrolytic capacitor according to any one of claims 1 to 5, wherein the solid electrolyte layer is made of a film-like or layer-like conductive polymer composition containing fluorine rubber in a range of 0.01 to 25% by mass. Conductive polymer, pyrrole, thiophene, aniline or a solid electrolytic capacitor according to any one of claims 1 to 6 is a polymer comprising at least one repeating unit of the divalent radical derivatives thereof. The solid electrolytic capacitor according to any one of claims 2 to 5, wherein the metal powder-containing conductor layer includes a conductive filler made of metal powder and fluorine rubber as a main component of the binder. The solid electrolytic capacitor according to claim 8 , wherein 80% by mass or more of the binder is a fluorine-based rubber. The solid electrolytic capacitor according to claim 8 or 9 , wherein 80% by mass or more of the conductive filler is silver powder. The solid electrolytic capacitor according to claim 8, wherein the conductive filler has an average particle size of 1 μm or more and 10 μm or less. The solid electrolytic capacitor according to claim 8 , wherein the conductive filler is 50 to 95 mass% and the binder is 5 to 50 mass%. The solid electrolytic capacitor according to claim 8 , wherein the metal powder-containing conductor layer is a layer formed of a conductive paste containing a conductive filler, a binder, and an organic solvent. Solid electrolysis in which a capacitor element with a dielectric oxide film, solid electrolyte layer, and conductor layer formed on the surface of an anode body made of a valve metal is sealed with an insulating resin leaving the exposed portions of the anode lead terminal and cathode lead terminal. The capacitor is characterized in that the solid electrolyte layer is a conductive polymer layer containing a fluorine-based rubber , and the conductor layer is the metal powder-containing conductor layer according to any one of claims 8 to 13. Solid electrolytic capacitor. Conductor layer, conductive carbon layer on the conductive polymer layer and to claim 14 is a layer formed of a metal powder-containing conductor layer according to any one of claims 8 to 13 is laminated over the layer The solid electrolytic capacitor described. The solid electrolytic capacitor according to claim 14 or 15 , wherein the conductive polymer layer is poly (3,4-ethylenedioxythiophene). The conductive carbon layer is a layer formed using a conductive carbon paste mainly composed of a conductive material, a binder, and a solvent, and 80% by mass or more of the conductive material is artificial graphite, and the artificial carbon The solid electrolysis according to any one of claims 2 to 5 and 15, wherein graphite has a fixed carbon content of 97 mass% or more, an average particle size of 1 to 13 µm, an aspect ratio of 10 or less, and a particle size of 32 µm or more of 12 mass% or less. Capacitor. The solid electrolytic capacitor according to claim 17 , wherein a material having rubber elasticity that can swell or suspend in a solvent is used as a binder. Rubber elastic materials that can swell or suspend in a solvent are isoprene rubber, butadiene rubber, styrene / butadiene rubber, nitrile rubber, butyl rubber, ethylene / propylene copolymer, acrylic rubber, polysulfide rubber, fluoropolymer, The solid electrolytic capacitor according to claim 18 , which is at least one material selected from the group consisting of silicone rubber and thermoplastic elastomer. The solid electrolytic capacitor according to any one of claims 17 to 19 , wherein the conductive material is 30 to 99% by mass and the binder is 1 to 70% by mass of the solid content in the conductive carbon paste. In a method of manufacturing a solid electrolytic capacitor in which a solid electrolyte layer and a conductor layer are formed on a dielectric film formed on a valve action metal, the valve action metal having a dielectric film formed on the surface is made conductive. Coating is repeated one or more times alternately using the conductive polymer monomer solution and the oxidant solution containing fluororubber as a rubbery elastic body in at least one of the polymer monomer solution and the oxidant solution. And forming a film or layer of the conductive polymer composition on the dielectric film. The method for producing a solid electrolytic capacitor according to claim 21 , wherein the conductive polymer composition contains 0.01 to 25 % by mass of a rubber-like elastic body. On the dielectric film formed on the valve action metal, a conductive polymer composition containing a fluorine-based rubber made of a conductive polymer forms a solid electrolyte layer and a conductor layer that are formed in a film shape or a layer shape. A method for producing a solid electrolytic capacitor comprising: forming a conductor layer on a solid electrolyte by using a conductive paste containing a conductive material, a rubber elastic binder and a solvent. Method. 24. The solid electrolytic capacitor according to claim 23 , wherein the conductor layer is a metal powder-containing conductor layer formed using a conductive paste comprising a conductive filler made of metal powder, a binder having rubber elasticity, and a solvent. Production method. 24. The conductor layer according to claim 23 , wherein the conductor layer is formed using a conductive carbon paste containing a conductive material, a rubber-elastic binder and a solvent, and then a conductor layer containing metal powder is formed. A method for producing a solid electrolytic capacitor. After the conductive layer is formed using a conductive carbon paste containing a conductive material, a rubber elastic binder and solvent, a conductive filler made of metal powder, a rubber elastic binder and solvent The method for producing a solid electrolytic capacitor according to claim 23 , wherein the metal powder-containing conductor layer is formed using a conductive paste containing The conductive polymer monomer solution and the oxidant solution, wherein the solid electrolyte layer contains a fluorine-based rubber as a rubber-like elastic body in at least one of the conductive polymer monomer solution and the oxidant solution on the dielectric film. 27. The method for producing a solid electrolytic capacitor according to any one of claims 23 to 26 , wherein the coating is alternately repeated once or a plurality of times to form a film of the conductive polymer composition. 28. The solid according to claim 23 , wherein the solid electrolyte having a layered structure has a thickness of about 0.1 to 0.3 [mu] m per film or layer-structured layer or layer. Manufacturing method of electrolytic capacitor. A solid electrolyte comprising a conductive polymer composition containing a fluorine-based rubber as a rubber-like elastic body in a range of 0.01 to 25% by mass in the form of a film or a layer. 30. The solid electrolyte according to claim 29 , wherein the conductive polymer is a polymer containing at least one divalent repeating unit of pyrrole, thiophene, aniline or a derivative thereof. Fluorine rubber as a rubbery elastic material is contained in at least one of a monomer solution and an oxidizer solution of a conductive polymer for an object that requires formation of a solid electrolyte composed of a conductive polymer composition on the surface. An object having a solid electrolyte in which a conductive polymer composition is formed in a film shape or a layer shape, wherein the conductive polymer composition is repeatedly coated one or more times with the monomer solution and the oxidant solution of the conductive polymer. Production method. 32. The method for producing an object having a solid electrolyte according to claim 31 , wherein the covering means is any one of dipping, coating, spraying or casting. 32. The method for producing an object having a solid electrolyte according to claim 31 , wherein the rubber-like elastic body is added to the solution containing the monomer and / or the oxidizing agent of the conductive polymer in a dissolved or dispersed form. Metal powders observed containing a fluorine-based rubber as a main component of the conductive filler and a binder consisting of a solid electrolytic capacitor conductive paste more than 80 wt% of the binder is a fluorine-based rubber. The conductive paste according to claim 34 , wherein 80% by mass or more of the conductive filler is silver powder. 36. The conductive paste according to claim 34 or 35 , wherein the conductive filler has an average particle size of 1 to 10 [mu] m. The conductive paste according to claim 34 , 35 or 36 , wherein the conductive filler is 50 to 95% by mass and the binder is 5 to 50% by mass. The conductive paste according to any one of claims 34 to 37 containing an organic solvent. In the conductive carbon paste for a solid electrolytic capacitor mainly comprising a conductive carbon material, a binder having a rubber elasticity that can swell or suspend in a solvent, and a solvent, the conductive carbon material is 80% by mass or more. Is artificial graphite, and the artificial graphite has a fixed carbon content of 97% by mass or more, an average particle diameter of 1 to 13 μm, an aspect ratio of 10 or less, and particles having a particle diameter of 32 μm or more are 12% by mass or less. Carbon paste. Rubber elastic materials that can swell or suspend in a solvent are isoprene rubber, butadiene rubber, styrene / butadiene rubber, nitrile rubber, butyl rubber, ethylene / propylene copolymer, acrylic rubber, polysulfide rubber, fluoropolymer, 40. The conductive carbon paste for a solid electrolytic capacitor according to claim 39 , wherein the conductive carbon paste is at least one material selected from the group consisting of silicone rubber and thermoplastic elastomer. 41. The conductive carbon paste for a solid electrolytic capacitor according to claim 39 or 40 , wherein the conductive material is 30 to 99% by mass and the binder is 1 to 70% by mass of the solid content in the conductive carbon paste.

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