JP3846760B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

（式中、置換基Ｒ⁴ 及びＲ⁵ 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員環の飽和炭化水素の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。）で表わされる構造単位を含む導電性高分子組成物である。
【００１１】
さらに本発明は、好適には下記一般式（IV）、
【化８】

（式中、置換基Ｒ⁴ 及びＲ⁵ の範囲は、前記一般式（II）と同じである）で表される単量体のin-situ 重合の方法も提供するものである。
【００１２】
以下、本発明を詳細に説明する。本発明は、誘電体層上に少なくともナフチルアミンスルホン酸アニオンをドーパントとして含み、そのドーパントと電荷移動錯体を形成し得る前記一般式（II）で表される構造単位を含む該高分子の導電性重合体組成物を、固体電解質として具備した固体電解コンデンサ及びその製造方法に関する。
【００１５】
一般式（II）または一般式（IV）中のＲ⁴ 及びＲ⁵ の有用な置換基の例としては、メチル、エチル、プロピル、イソプロピル、ビニル、アリルが挙げられる。さらに、Ｒ⁴ 及びＲ⁵ 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（II）または一般式（IV）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員環の飽和炭化水素の環状構造を形成する置換基であり、例えば、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、Ｒ⁴ 及びＲ⁵ 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してもよく、例えば、１，２−ビニレン、１，２−プロペニレン、２，３−ブチレン２−エン、１，２−シクロヘキシレン、メチル−ｏ−フェニレン、１，２−ジメチル−ｏ−フェニレン、エチル−ｏ−フェニレンが挙げられる。
【００１６】
本発明のコンデンサ及びその製造方法において、使用される前記一般式 (III)で表される単量体のうち、例えばチオフェン（Ｒ¹ ＝Ｒ² ＝Ｈ、Ｘ＝Ｓ）やピロール（Ｒ¹ ＝Ｒ² ＝Ｈ、Ｘ＝ＮＨ）、または前記一般式（IV）で表されるチオフェン類のうち３，４−ジオキシエチレン−チオフェンの単量体は公知であり、これらの単量体を重合し得る酸化剤も多くは公知である。しかしながら、導電性組成物中にドーパントとしてナフチルアミンスルホン酸アニオンを含有する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かった。
【００１７】
本発明のコンデンサにおいて、低インピーダンス特性の優れたコンデンサを提供できる固体電解質においては、ナフチルアミンスルホン酸アニオンの含量は、導電性高分子の全繰り返し構造単位に対して少なくとも０．１〜５０モル％の範囲であり、好ましくは１〜３０モル％の範囲である。しかしながら、本発明の製造方法においては単量体の重合時に酸化剤を使用するために、前記導電性高分子組成物中に酸化剤の還元体アニオンを含有してもよく、その含量は、該組成物中０．１〜１５モル％の範囲であり、望ましくは０．１〜５モル％の範囲である。
【００１８】
通常、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）、耐久性等を改善するためには、前記固体電解質の形成方法が重要である。そのためには、固体電解質を密に充填形成して導電パスの均一性を改善することは重要であり、導電性組成物の構成が非常にコンデンサ特性に影響を与える。本発明においては、前記単量体をナフチルアミンスルホン酸アニオンの共存下で、酸化剤の作用によって化学酸化重合させて該固体電解質を製造する工程を、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容易に達成することができる。好ましい例の１つとして、酸化剤とナフチルアミンスルホン酸アニオンを含む溶液（溶液１）を陽極誘電体層に塗布または浸漬する工程と、前記単量体を溶解した溶液（溶液２）を前後して別々に塗布または浸漬する工程を含んでもよく、また溶液１及び溶液２の溶媒は同じでもよく、あるいは異なった溶媒系でもよい。
【００１９】
さらに前記化学酸化重合の繰り返し処理は、ハンダ耐熱性（熱安定性）の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の変動が大きく信頼性を悪くしていたが、本発明で示された導電性組成物の固体電解質を具備したコンデンサは、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２種以上のドーパントを有する重合体組成物が誘電体表面および細孔内部まで充填よく段階的に析出させることができるために、該重合体組成物の薄い膜質が何層にも重なった状態を作ることができる。これにより、該重合体が誘電体皮膜に対するダメージを生じない熱安定性に優れたコンデンサを提供することができる。
【００２０】
また、本発明で使用するナフチルアミンスルホン酸アニオンは、分子内に塩基性のアミノ基と電子吸引性のスルホン酸アニオンを有するzwitterion構造を取り得る化合物であるために、従来既知の分子アニオン（例えば、ＣｌＯ₄ ^-、ＢＦ₄ ^-、Ｃｌ^- 、ＳＯ₄ ^2- 等）とはドーパント能及び化学的性質が異なっている。その結果、コンデンサ素子を製作した時のコンデンサ性能に対して優れた効果を引き出すことができるものである。
【００２１】
本発明において使用するナフチルアミンスルホン酸化合物とは、ナフタレン環にアミノ基とスルホン酸基とが置換した化合物の総称であり、そのアニオンを供出できる化合物の具体例には、１−ナフチルアミン−４−スルホン酸、１−ナフチルアミン−５−スルホン酸、１−ナフチルアミン−６−スルホン酸、１−ナフチルアミン−７−スルホン酸、１−ナフチルアミン−８−スルホン酸、２−ナフチルアミン−１−スルホン酸、２−ナフチルアミン−５−スルホン酸、２−ナフチルアミン−６−スルホン酸、２−ナフチルアミン−７−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、またスルホン酸基が１つ以上置換された化合物でもよく、例えば１−ナフチルアミン−２，７−ジスルホン酸、１−ナフチルアミン−３，６−ジスルホン酸、１−ナフチルアミン−４，７−ジスルホン酸、２−ナフチルアミン−３，６−ジスルホン酸、２−ナフチルアミン−５，６−ジスルホン酸、２−ナフチルアミン−６，８−ジスルホン酸、１−ナフチルアミン−３，６，８−トリスルホン酸、１−ナフチルアミン−４，６，８−トリスルホン酸及びその各種塩化合物が有用に用いられる。
【００２２】
本発明で使用される酸化剤とは、ピロールやチオフェン類の化学酸化重合に対して適する酸化剤であり、例えば特開平２−１５６１１号記載の塩化鉄（III）、Ｆｅ（ＣｌＯ₄）₃や有機酸鉄（III）、無機酸鉄（III）、アルキル過硫酸塩、過硫酸アンモニウム、過酸化水素、Ｋ₂Ｃｒ₂Ｏ₇等が広範に使用できる。しかしながら、前記酸化剤の使用範囲は、詳細には単量体の化学構造と酸化剤および反応条件等の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単量体と酸化剤、反応条件の組合せが重要である。
【００２３】
本発明の固体電解コンデンサの製造方法においては、前記一般式（IV）で表されるチオフェン類の化学重合は、過硫酸塩の使用が特に好適であり、鉄 (III)塩系酸化剤の使用は鉄元素の残存が問題となり、コンデンサ特性に対して好ましくなかった。さらに、前記一般式（IV）の単量体に対して好適な過硫酸塩は、前記一般式 (III)のチオフェン（Ｒ¹ ＝Ｒ² ＝Ｈ、Ｘ＝Ｓ）には好適ではなく、詳細には酸化剤の使用制限が存在する。前記一般式（IV）で表され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は、過硫酸アンモニウム、過硫酸カリウムが挙げられる。
【００２４】
次に重合反応の好ましい条件を以下に示す。
本発明のコンデンサの製造方法において用いられる一般式 (III)または一般式（IV）の単量体濃度及び酸化剤、ナフチルアミンスルホン酸の各使用濃度は、化合物及びその置換基の種類や溶媒等との組合せによって異なるが、一般には１０^-4〜１０モル／リットルの範囲であり、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、それぞれ反応方法によって定められるもので特に限定できるものでないが、一般的には−７０℃〜２５０℃の温度範囲であり、望ましくは０℃〜１５０℃であり、さらに１５〜１００℃の温度範囲で行われることが好ましい。
【００２５】
前記本発明の製造方法において用いられる溶液の溶媒は、例えばテトラヒドロフラン（ＴＨＦ）やジオキサン、ジエチルエーテル等のエーテル類、あるいはアセトン、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やアセトニトリル、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、酢酸エチルや酢酸ブチル等のエステル類、クロロホルムや塩化メチレン等の非芳香族性の塩素系溶媒、ニトロメタンやニトロエタン、ニトロベンゼン等のニトロ化合物、あるいはメタノールやエタノール、プロパノール等のアルコール類、または蟻酸や酢酸、プロピオン酸等の有機酸または該有機酸の酸無水物（例、無水酢酸等）、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、ケトン類および／またはその混合系が望ましい。
【００２６】
このようにして製造された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。
【００２７】
本発明の一方の電極にはアルミニウムまたはチタン、タンタル、ニオブあるいはこれらを基質とする合金系（等弁作用を有する）の箔、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、比表面積を大きくする目的で公知な方法によってエッチング処理や化成処理されて金属箔上に該金属系酸化皮膜層を形成されたものが用いられる。
【００２８】
固体電解質の形成は、誘電体層上で形成する方法が好ましく、とりわけ本発明の耐熱性の優れた有機系導電体を細孔あるいは空隙構造を有する誘電体上に化学的に析出する方法が好ましい。さらに、半導体上に電気的接触をよくするために導電体層を設けることが好ましく、例えば、導電ペーストの固体、またはメッキや、金属蒸着、導電樹脂フィルムの形成等が行われる。
【００２９】
このように、本発明の製造方法から構成されるコンデンサは、例えば樹脂モールド、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により各種用途のコンデンサ製品とすることができる。
【００３０】
【実施例】
以下、実施例及び参考例をあげて本発明を詳しく説明する。
（実施例１）
規定の面積に加工したアルミニウム化成箔を１０ｗｔ％のアジピン酸アンモニウム水溶液で１３Ｖ化成して、誘電体を準備した。この誘電体表面に、過硫酸アンモニウム（以下、ＡＰＳと略する）２０ｗｔ％と１−ナフチルアミン−４−スルホン酸ナトリウム０．３ｗｔ％になるように調製した水溶液（溶液１）を含浸させ、次いで３，４−ジオキシエチレン−チオフェンを５ｇ溶解したイソプロパノール（以下ＩＰＡと略する）溶液（溶液２）に浸漬した。この基板を６０℃の環境下で１０分放置することで酸化重合を完成させ、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。重合体組成物中の硫酸イオン及び１−ナフチルアミン−４−スルホン酸イオンの含量は、先ず前記重合体組成物を水／ＩＰＡ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高分子の全繰り返し構造単位に対して１．７モル％、１−ナフチルアミン−４−スルホン酸イオン含量は、１４．４モル％であった。固体電解質層の電導度は、６５Ｓ／ｃｍであった。
【００３１】
次に、アルミ芯部をプラス側リード端子に溶接することによって陽極端子とし、高分子層にカーボンペーストと銀ペーストを付けてマイナス側リード端子に接続し陰極とした後、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。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１にまとめた。ここで、表１中のＣは容量を表し、ＤＦは損失角の正接値（ｔａｎδ）を意味する。いずれも１２０Ｈｚで測定したものである。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以上をショート（不良）品として表示し、これを除いてＬＣ値の平均を算出した。耐湿性能試験での結果を表２に示した。ここでＬＣ値は、１０μＡ以上をショート（不良）品として表示した以外は初期値と同様である。耐湿性能試験は、８５℃、８５ＲＨ％の高温高湿下で５００時間放置して行った。
【００３２】
（実施例２）
実施例１で使用した１−ナフチルアミン−４−スルホン酸ナトリウムを１−ナフチルアミン−２，７−ジスルホン酸ナトリウムに替えた以外は、実施例１の記載と同様であり、該コンデンサ素子を同じく評価した。結果を表１、表２に示した。但し、重合体組成物中の硫酸イオン及び１−ナフチルアミン−２，７−ジスルホン酸イオンの含量は、実施例１記載の方法で求め、硫酸イオン含量は１．６モル％、１−ナフチルアミン−２，７−ジスルホン酸イオン含量は、８．３モル％であった。固体電解質層の電導度は、８０Ｓ／ｃｍであった。
【００３３】
（実施例３）
実施例１で使用した１−ナフチルアミン−４−スルホン酸アンモニウムを１−ナフチルアミン−３，６，８−トリスルホン酸ナトリウムに替えた以外は、実施例１の記載と同様であり、該コンデンサ素子を同じく評価した。結果を表１、表２に示した。但し、重合体組成物中の硫酸イオン及び１−ナフチルアミン−３，６，８−トリスルホン酸イオンの含量は、実施例１記載の方法で求め、硫酸イオン含量は２．３モル％、１−ナフチルアミン−３，６，８−トリスルホン酸イオン含量は、０．６モル％であった。固体電解質層の電導度は、６５Ｓ／ｃｍであった。
【００３４】
（実施例４）
実施例１で使用したＡＰＳを過硫酸カリウムに、３，４−ジオキシエチレン−チオフェンをＮ−メチルピロールに替えた以外は、実施例１の記載と同じであり該コンデンサ素子を評価した。結果を表１、表２に示した。但し、重合体組成物中の硫酸イオン及び１−ナフチルアミン−４−スルホン酸イオンの含量は、実施例１記載の方法で求め、硫酸イオン含量は５．４モル％、１−ナフチルアミン−４−スルホン酸イオン含量は、１４モル％であった。固体電解質層の電導度は、１５Ｓ／ｃｍであった。
【００３５】
（実施例５）
実施例１で使用した導電性高分子組成物の製造方法を以下の方法に替えた以外は、実施例１の記載と同じであり該コンデンサ素子を評価した。結果を表１、表２に示した。実施例１記載と同じ方法と準備した誘電体表面に、２，３−ジクロロ−５，６−ジシアノベンゾキノン（以下、ＤＤＱと略する）１０ｗｔ％と１−ナフチルアミン−４−スルホン酸アンモニウム０．１ｗｔ％になるように調製したジオキサン溶液（溶液１）を含浸させ、次いでイソチアナフテンを５ｇ溶解したイソプロパノール（以下ＩＰＡと略する）溶液（溶液２）に浸漬した。この基板を８０℃の環境下で３０分放置することで酸化重合を完成させ、ジオキサン及び水で各々洗浄した。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。重合体組成物中の１−ナフチルアミン−４−スルホン酸イオンの含量は、前記重合体組成物を水／ＩＰＡ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、１−ナフチルアミン−４−スルホン酸イオン含量は導電性高分子の全繰り返し構造単位に対して３．６モル％であった。固体電解質層の電導度は、２５Ｓ／ｃｍであった。
【００３６】
（実施例６）
実施例１で使用したＡＰＳの替わりに硫酸鉄を１０ｗｔ％に調製した溶液に変更した以外は、実施例１の記載と同様であり、該コンデンサ素子を評価した。結果を表１、表２に示した。但し、重合体組成物中の硫酸イオン及び１−ナフチルアミン−４−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１５．６モル％、１−ナフチルアミン−４−スルホン酸イオン含量は、１７モル％であった。しかしながら、鉄元素が８重量％存在するために、コンデンサ特性は好ましくなかった。
【００３７】
（実施例７）
実施例１で使用したＡＰＳの替わりに塩化鉄を１０ｗｔ％とし、１−ナフチルアミン−４−スルホン酸ナトリウム０．１ｗｔ％に調製された溶液に変更した以外は、実施例１の記載と同様であり、該コンデンサ素子を評価した。結果を表１、表２に示した。但し、重合体組成物中の１−ナフチルアミン−４−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、３．０モル％であった。硫酸イオンが併用して含有されていないためにコンデンサ特性はあまり好ましくなかった。
【００３８】
（参考例１）
実施例１記載の３，４−ジオキシエチレン−チオフェンをチオフェンに替えた以外は実施例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、黒青色のポリチオフェン重合体は全く生成せず、チオフェンの重合がＡＰＳの作用では起こらなかった。すなわち、ＡＰＳによるチオフェン類の酸化重合は、３，４−ジオキシ基置換のチオフェン類に対して特に特異的に起こった。
【００３９】
【表１】

【００４０】
【表２】

【００４１】
【発明の効果】
固体電解質として用いた導電性高分子組成物中にドーパントとして、少なくともナフチルアミンスルホン酸アニオン及び酸化剤の還元体アニオンの両者を含み、その含量が導電性高分子の全繰り返し構造単位に対してナフチルアミンスルホン酸アニオンを０．１〜５０モル％の範囲で含有させることにより、低インピーダンスな固体電解コンデンサを提供することができる。さらに本発明は、導電性高分子として、特定構造の前記一般式（II）で表される構造単位を含む組成物において、特に顕著に低インピーダンスなコンデンサを提供するだけでなく、リフロー試験や耐湿試験においても優れた耐久性能を有する効果を見いだした。[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a low-impedance solid electrolytic capacitor and a method for producing the same, and in particular, a conductive polymer composition containing both a naphthylamine sulfonate anion and a reductant anion of an oxidizing agent as dopants in the solid electrolyte. The present invention relates to a method of manufacturing a solid electrolytic capacitor including the capacitor and the capacitor.
[0002]
[Prior art]
In a solid electrolytic capacitor, a dielectric oxide film layer is 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 a solid electrolyte) is used as an electrode facing the outside. And a conductor layer such as a conductive paste is further formed to manufacture a basic element of the capacitor. Next, the entire device is completely sealed with an epoxy resin or the like, and is widely used as a capacitor component in electric products.
[0003]
Among them, conventionally, for example, inorganic semiconductor materials such as manganese dioxide and lead dioxide, TCNQ complex salts, or intrinsic conductive polymers having an electric conductivity in the range of 10 ^{−3 to} 5 × 10 ³ S / cm have been used as solid electrolytes. (JP-A-1-169914), π-conjugated polyaniline (JP-A-61-239617), polypyrrole (JP-A-61-240625), polythiophene derivative (JP-A-2-15611), It is known to use polyisothianaphthene containing no dopant (Japanese Patent Laid-Open No. 62-118509), doped polyisothianaphthene (Japanese Patent Laid-Open No. 62-118511), and the like.
[0004]
As for the formation method of the solid electrolyte, the conventional method is to melt the solid electrolyte layer on the dielectric layer on the surface of the valve metal having a pore or void structure, or the conductive polymer solid on the dielectric layer. Methods for producing electrolytes are known. For example, when a polymer of a hetero five-membered cyclic compound such as pyrrole or thiophene is used, the anode foil is immersed in a lower alcohol / aqueous solution of the hetero five-membered cyclic compound, and then the oxidizing agent and the electrolyte are dissolved. A method of forming a conductive polymer by immersion in an aqueous solution and chemical polymerization (JP-A-5-177502), 3,4-dioxyethylene-thiophene monomer and oxidant, preferably in the form of a solution. For example, a method of forming an oxide coating layer of a metal foil by coating separately or together (JP-A-2-15611) is known.
[0005]
Oxidizing agents capable of chemically polymerizing a hetero five-membered cyclic compound such as thiophene include iron (III) chloride, Fe (ClO ₄ ) ₃ , organic acid iron (III), inorganic acid iron (III), alkyl persulfate, Ammonium persulfate (hereinafter abbreviated as APS), hydrogen peroxide, K ₂ Cr ₂ O _{7 and the} like are disclosed (Japanese Patent Laid-Open No. 2-15611).
[0006]
[Problems to be solved by the invention]
However, the solid electrolyte capacitor using manganese dioxide has the disadvantage that the oxide film layer is destroyed during the thermal decomposition of manganese nitrate, and the impedance characteristics are insufficient. The use of lead dioxide was not preferable due to environmental considerations. The solid electrolyte capacitor using the TCNQ complex salt is excellent in hot melt processability and conductivity, but has a problem in the heat resistance of the TCNQ complex salt itself, and the solder heat resistance is not reliable. In order to remedy these drawbacks, conductive polymers such as polypyrrole were applied to the solid electrolyte on the dielectric surface by electrolytic polymerization or chemical polymerization, but the film uniformity and solder heat resistance, Impedance characteristics etc. were not sufficient.
In this way, when manufacturing practical capacitor elements, the material composition of the solid electrolyte and its manufacturing method are established, the thermal stability of conductivity is improved, the uniformity of the film is improved, etc. It is a problem to manufacture a solid electrolytic capacitor excellent in capacity, high frequency characteristics, tan δ, leakage current, heat resistance (reflow property), durability, and the like.
[0007]
[Means for Solving the Problems]
In the solid electrolytic capacitor provided with the conductive polymer composition layer, as a result of intensive studies on the types and contents of anions having dopant ability in the solid electrolyte in order to achieve the above object, A small-sized, low-impedance, high-performance solid electrolytic capacitor and its production by containing at least a naphthylamine sulfonate anion as a dopant in the solid electrolyte comprising the composition formed on the dielectric oxide film on the surface of the metal anode foil Provide a method.
[0008]
That is, the present invention relates to a solid electrolytic capacitor comprising a dielectric layer having a fine structure made of a metal oxide on the surface of a valve action metal foil as an opposing electrode and one electrode, and a solid electrolyte formed on the dielectric layer. In the solid electrolyte, the solid electrolyte includes at least naphthylamine sulfonate anion as a dopant, and the content thereof is in the range of 0.1 to 50 mol% with respect to the total amount of all repeating structural units of the conductive polymer. .
[0009]
According to the present invention, as the polymer capable of expressing the capacitor performance more remarkably, the following general formula (II)
[0010]
[Chemical 6]

(In the formula, each of the substituents R ⁴ and R ⁵ is independently hydrogen, 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. Represents a substituent which is bonded to each other at an arbitrary position to form a cyclic structure of at least one 5- to 7-membered saturated hydrocarbon containing two oxygen elements described in the formula. Is a conductive polymer composition comprising a structural unit represented by a chemical structure such as a substituted vinylene group or a substituted o-phenylene group, where δ is in the range of 0 to 1. .
[0011]
Furthermore, the present invention preferably has the following general formula (IV),
[Chemical 8]

(In the formula, the ranges of the substituents R ⁴ and R ⁵ are the same as those in the general formula (II).) A method for in-situ polymerization of the monomer represented by the formula (II) is also provided.
[0012]
Hereinafter, the present invention will be described in detail. The present invention comprises at least naphthylamine sulfonic acid anion as a dopant on the dielectric layer, the conductive of the polymer containing the structural unit represented by the dopant and before obtained by forming a charge transfer complex following general formula (II) The present invention relates to a solid electrolytic capacitor comprising a conductive polymer composition as a solid electrolyte and a method for producing the same.
[0015]
Examples of useful substituents for R ⁴ and R ⁵ in general formula (II) or general formula (IV) include methyl, ethyl, propyl, isopropyl, vinyl and allyl. Further, R ⁴ and R ⁵ hydrocarbon groups having 1 to 6 carbon atoms are bonded to each other at an arbitrary position, and contain at least two oxygen elements described in the general formula (II) or the general formula (IV), A substituent that forms a cyclic structure of one or more 5- to 7-membered saturated hydrocarbons, and for example, 1,2-ethylene, 1,2-propylene, and 1,2-dimethyl-ethylene are preferable. In addition, R ⁴ and R ⁵ form a cyclic structure of an unsaturated hydrocarbon such as a substituted vinylene group or a substituted o-phenylene group by bonding the hydrocarbon group having 1 to 6 carbon atoms to each other at an arbitrary position. For example, 1,2-vinylene, 1,2-propenylene, 2,3-butylene 2-ene, 1,2-cyclohexylene, methyl-o-phenylene, 1,2-dimethyl-o-phenylene And ethyl-o-phenylene.
[0016]
Among the monomers represented by the general formula (III) used in the capacitor of the present invention and the method for producing the same, for example, thiophene (R ¹ = R ² = H, X = S) or pyrrole (R ¹ = R ² = H, X = NH), or 3,4-dioxyethylene-thiophene monomer among the thiophenes represented by the general formula (IV) is known, and these monomers are polymerized Many oxidizing agents that can be used are also known. However, a capacitor having a solid electrolyte containing a naphthylamine sulfonate anion as a dopant in a conductive composition has not been known so far.
[0017]
In the capacitor of the present invention, in the solid electrolyte capable of providing a capacitor having excellent low impedance characteristics, the content of the naphthylamine sulfonate anion is at least 0.1 to 50 mol% with respect to all repeating structural units of the conductive polymer. It is a range, Preferably it is the range of 1-30 mol%. However, in the production method of the present invention, since an oxidizing agent is used during the polymerization of the monomer, the conductive polymer composition may contain a reductant anion of the oxidizing agent, It is the range of 0.1-15 mol% in a composition, It is the range of 0.1-5 mol% desirably.
[0018]
Usually, in the method of manufacturing a capacitor, the method of forming the solid electrolyte is important in order to improve high capacity high frequency characteristics, tan δ, leakage current, heat resistance (reflow properties), durability, and the like. For this purpose, it is important to improve the uniformity of the conductive path by densely filling the solid electrolyte, and the configuration of the conductive composition greatly affects the capacitor characteristics. In the present invention, the step of producing the solid electrolyte by subjecting the monomer to chemical oxidative polymerization by the action of an oxidizing agent in the presence of a naphthylamine sulfonate anion is preferably performed once or more for one anode substrate. Can be easily achieved by repeating 3 to 20 times. As one of preferred examples, a step of applying or immersing a solution (solution 1) containing an oxidizing agent and a naphthylamine sulfonate anion on the anode dielectric layer, and a solution (solution 2) in which the monomer is dissolved are mixed. It may include a step of coating or dipping separately, and the solvent of Solution 1 and Solution 2 may be the same or different solvent systems.
[0019]
Furthermore, the chemical oxidative polymerization repeated treatment facilitates the production of a solid electrolyte having excellent solder heat resistance (thermal stability). Conventionally known capacitors using a solid electrolyte made of polypyrrole or the like have a large variation in capacitor characteristics at high temperature and high humidity, and have deteriorated reliability. However, the capacitor has a solid electrolyte of the conductive composition shown in the present invention. The capacitor thus obtained has excellent thermal stability and good stability in the doped state. This is because the polymer composition having two or more kinds of dopants can be deposited stepwise into the dielectric surface and inside the pores with good filling, so that the thin film quality of the polymer composition can be divided into many layers. Overlapping conditions can be created. Thereby, the capacitor | condenser excellent in the thermal stability which does not produce the damage with respect to a dielectric film can be provided.
[0020]
In addition, since the naphthylamine sulfonate anion used in the present invention is a compound that can take a zwitterion structure having a basic amino group and an electron-withdrawing sulfonate anion in the molecule, a conventionally known molecular anion (for example, ClO ₄ ⁻ , BF ₄ ⁻ , Cl ⁻ , SO ₄ ^2−, etc.) differ in dopant ability and chemical properties. As a result, it is possible to bring out an excellent effect on the capacitor performance when the capacitor element is manufactured.
[0021]
The naphthylamine sulfonic acid compound used in the present invention is a general term for compounds in which an amino group and a sulfonic acid group are substituted on the naphthalene ring. Specific examples of the compound capable of supplying an anion thereof include 1-naphthylamine-4-sulfone. Acid, 1-naphthylamine-5-sulfonic acid, 1-naphthylamine-6-sulfonic acid, 1-naphthylamine-7-sulfonic acid, 1-naphthylamine-8-sulfonic acid, 2-naphthylamine-1-sulfonic acid, 2-naphthylamine Examples include -5-sulfonic acid, 2-naphthylamine-6-sulfonic acid, 2-naphthylamine-7-sulfonic acid and its alkali metal salts, ammonium salts, and the like, and compounds in which one or more sulfonic acid groups are substituted may be used. For example, 1-naphthylamine-2,7-disulfonic acid, 1-naphthylamine-3 6-disulfonic acid, 1-naphthylamine-4,7-disulfonic acid, 2-naphthylamine-3,6-disulfonic acid, 2-naphthylamine-5,6-disulfonic acid, 2-naphthylamine-6,8-disulfonic acid, 1 -Naphthylamine-3,6,8-trisulfonic acid, 1-naphthylamine-4,6,8-trisulfonic acid and various salt compounds thereof are useful.
[0022]
The oxidizing agent used in the present invention is an oxidizing agent suitable for chemical oxidative polymerization of pyrrole and thiophenes. For example, iron (III) chloride, Fe (ClO ₄ ) ₃ described in JP-A-2-15611, Organic acid iron (III), inorganic acid iron (III), alkyl persulfate, ammonium persulfate, hydrogen peroxide, K ₂ Cr ₂ O _{7 and the} like can be widely used. However, the range of use of the oxidizing agent may be limited in particular by the chemical structure of the monomer , the oxidizing agent, and the reaction conditions. For example, the oxidation (polymerization) of thiophenes is based on the description of the Handbook of Conducting Polymers (Marcel Dekker, Inc., published in 1987, page 99, FIG. 5). (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, the combination of the monomer used, the oxidizing agent, and the reaction conditions is important.
[0023]
In the method for producing a solid electrolytic capacitor of the present invention, the chemical polymerization of the thiophenes represented by the general formula (IV) is particularly preferably performed using a persulfate, and using an iron (III) salt-based oxidizing agent. However, the remaining iron element was a problem, which was not preferable for the capacitor characteristics. Further, persulfate suitable for the monomer of the general formula (IV) is not suitable for the thiophene (R ¹ = R ² = H, X = S) of the general formula (III). There are restrictions on the use of oxidizing agents. Examples of the persulfate that can be particularly preferably used for the chemical polymerization of the thiophenes represented by the general formula (IV) include ammonium persulfate and potassium persulfate.
[0024]
Next, preferable conditions for the polymerization reaction are shown below.
The monomer concentration of the general formula (III) or the general formula (IV) used in the method for producing a capacitor of the present invention, and the concentration of each of the oxidizing agent and naphthylamine sulfonic acid are as follows: Generally, it is in the range of 10 ⁻⁴ to 10 mol / liter, and more preferably in the range of 10 ^{−3 to} 5 mol / liter. The reaction temperature is determined by the reaction method and is not particularly limited, but is generally in the temperature range of −70 ° C. to 250 ° C., preferably 0 ° C. to 150 ° C., and more preferably 15 to It is preferable to be performed in a temperature range of 100 ° C.
[0025]
Examples of the solvent of the solution used in the production method of the present invention include ethers such as tetrahydrofuran (THF), dioxane, and diethyl ether, ketones such as acetone and methyl ethyl ketone, dimethylformamide, acetonitrile, benzonitrile, and N-methylpyrrolidone. (NMP), aprotic polar solvents such as dimethyl sulfoxide (DMSO), esters such as ethyl acetate and butyl acetate, non-aromatic chlorine solvents such as chloroform and methylene chloride, nitro such as nitromethane, nitroethane, and nitrobenzene Use compounds, alcohols such as methanol, ethanol, and propanol, organic acids such as formic acid, acetic acid, and propionic acid, acid anhydrides of the organic acids (eg, acetic anhydride, etc.), water, or a mixed solvent thereof. But Kill. Preferably, water, alcohols, ketones and / or mixed systems thereof are desirable.
[0026]
The electrical conductivity of the solid electrolyte thus produced is in the range of 0.1 to 200 S / cm, but is preferably in the range of 1 to 100 S / cm, more preferably 10 to 100 S / cm under desirable conditions.
[0027]
One electrode of the present invention is made of a known material such as aluminum, titanium, tantalum, niobium or an alloy-based foil (having an isovalve action), a rod, or a sintered body containing these as a main component. used. The surface of these metal electrodes is used in which the metal-based oxide film layer is formed on the metal foil by etching or chemical conversion by a known method for the purpose of increasing the specific surface area.
[0028]
For the formation of the solid electrolyte, a method of forming on a dielectric layer is preferable, and in particular, a method of chemically depositing the organic conductor having excellent heat resistance of the present invention on a dielectric having a pore or a void structure is preferable. . Furthermore, it is preferable to provide a conductor layer on the semiconductor in order to improve electrical contact. For example, solid or plating of a conductive paste, metal deposition, formation of a conductive resin film, or the like is performed.
[0029]
Thus, the capacitor comprised from the manufacturing method of this invention can be used as a capacitor | condenser product of various uses by the exterior by resin mold, resin case, metal exterior case, resin dipping etc., for example.
[0030]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples and Reference Examples.
Example 1
The aluminum conversion foil processed to the specified area was subjected to 13V conversion with a 10 wt% aqueous solution of ammonium adipate to prepare a dielectric. This dielectric surface was impregnated with an aqueous solution (Solution 1) prepared so as to be 20 wt% ammonium persulfate (hereinafter abbreviated as APS) and 0.3 wt% sodium 1-naphthylamine-4-sulfonate, It was immersed in an isopropanol (hereinafter abbreviated as IPA) solution (solution 2) in which 5 g of 4-dioxyethylene-thiophene was dissolved. The substrate was allowed to stand for 10 minutes in an environment of 60 ° C. to complete the oxidation polymerization and washed with water. This polymerization reaction treatment and washing step were repeated 10 times each. The contents of sulfate ion and 1-naphthylamine-4-sulfonic acid ion in the polymer composition were obtained by first carefully extracting the polymer composition by hydrazine reduction in a water / IPA solvent, and obtaining by ion chromatography. However, the sulfate ion content was 1.7 mol% with respect to all repeating structural units of the conductive polymer, and the 1-naphthylamine-4-sulfonic acid ion content was 14.4 mol%. The conductivity of the solid electrolyte layer was 65 S / cm.
[0031]
Next, the aluminum core is welded to the positive lead terminal to make an anode terminal, carbon paste and silver paste are applied to the polymer layer, connected to the negative lead terminal to make the cathode, and finally sealed with epoxy resin. Then, a capacitor element was produced. Initial characteristics were measured after the capacitor element was aged at 125 ° C. for 2 hours. These results are summarized in Table 1. Here, C in Table 1 represents the capacity, and DF represents the tangent value (tan δ) of the loss angle. Both are measured at 120 Hz. The impedance indicates a value at the resonance frequency. LC (leakage current) was measured 1 minute after applying the rated voltage. Each measurement value is an average value of 30 samples, and for LC, 1 μA or more was displayed as a short (defective) product, and the average LC value was calculated by excluding this. The results of the moisture resistance performance test are shown in Table 2. Here, the LC value is the same as the initial value except that 10 μA or more is displayed as a short (defective) product. The moisture resistance performance test was performed by leaving it to stand at a high temperature and high humidity of 85 ° C. and 85 RH% for 500 hours.
[0032]
(Example 2)
The capacitor element was also evaluated in the same manner as in Example 1 except that sodium 1-naphthylamine-4-sulfonate used in Example 1 was replaced with sodium 1-naphthylamine-2,7-disulfonate. . The results are shown in Tables 1 and 2. However, the content of sulfate ion and 1-naphthylamine-2,7-disulfonate ion in the polymer composition was determined by the method described in Example 1, and the sulfate ion content was 1.6 mol%, 1-naphthylamine-2. , 7-disulfonic acid ion content was 8.3 mol%. The conductivity of the solid electrolyte layer was 80 S / cm.
[0033]
Example 3
Except that 1-naphthylamine-4-sulfonic acid ammonium used in Example 1 was replaced with sodium 1-naphthylamine-3,6,8-trisulfonate, the same as described in Example 1, the capacitor element was It was also evaluated. The results are shown in Tables 1 and 2. However, the content of sulfate ion and 1-naphthylamine-3,6,8-trisulfonate ion in the polymer composition was determined by the method described in Example 1, and the sulfate ion content was 2.3 mol%, 1- The naphthylamine-3,6,8-trisulfonic acid ion content was 0.6 mol%. The conductivity of the solid electrolyte layer was 65 S / cm.
[0034]
Example 4
The capacitor element was evaluated in the same manner as in Example 1 except that APS used in Example 1 was replaced with potassium persulfate and 3,4-dioxyethylene-thiophene was replaced with N-methylpyrrole. The results are shown in Tables 1 and 2. However, the content of sulfate ion and 1-naphthylamine-4-sulfonic acid ion in the polymer composition was determined by the method described in Example 1, and the sulfate ion content was 5.4 mol%, and 1-naphthylamine-4-sulfone. The acid ion content was 14 mol%. The conductivity of the solid electrolyte layer was 15 S / cm.
[0035]
(Example 5)
The capacitor element was evaluated in the same manner as in Example 1 except that the method for producing the conductive polymer composition used in Example 1 was changed to the following method. The results are shown in Tables 1 and 2. The same method as described in Example 1 and the prepared dielectric surface were coated with 10 wt% of 2,3-dichloro-5,6-dicyanobenzoquinone (hereinafter abbreviated as DDQ) and 0.1 wt of 1-naphthylamine-4-sulfonate. % Was impregnated with a dioxane solution (solution 1) prepared so as to be 5%, and then immersed in an isopropanol (hereinafter abbreviated as IPA) solution (solution 2) in which 5 g of isothianaphthene was dissolved. The substrate was allowed to stand for 30 minutes in an environment of 80 ° C. to complete the oxidation polymerization, and each was washed with dioxane and water. This polymerization reaction treatment and washing step were repeated 10 times each. The content of 1-naphthylamine-4-sulfonic acid ion in the polymer composition was obtained by carefully extracting the polymer composition by hydrazine reduction in a water / IPA solvent, and determining it by ion chromatography. The naphthylamine-4-sulfonic acid ion content was 3.6 mol% based on all repeating structural units of the conductive polymer. The conductivity of the solid electrolyte layer was 25 S / cm.
[0036]
(Example 6)
The capacitor element was evaluated in the same manner as in Example 1 except that the solution was changed to a solution prepared by adding 10 wt% of iron sulfate instead of APS used in Example 1. The results are shown in Tables 1 and 2. However, when the content of sulfate ion and 1-naphthylamine-4-sulfonic acid ion in the polymer composition was determined by the method described in Example 1, the sulfate ion content was 15.6 mol% and 1-naphthylamine-4 -The sulfonate ion content was 17 mol%. However, since the iron element is present at 8% by weight, the capacitor characteristics are not preferable.
[0037]
(Example 7)
The same as described in Example 1, except that 10% by weight of iron chloride was used instead of APS used in Example 1 and the solution was changed to 0.1% by weight of sodium 1-naphthylamine-4-sulfonate. The capacitor element was evaluated. The results are shown in Tables 1 and 2. However, when the content of 1-naphthylamine-4-sulfonic acid ion in the polymer composition was determined by the method described in Example 1, it was 3.0 mol%. Capacitor characteristics were not so favorable because sulfate ions were not contained in combination.
[0038]
(Reference Example 1)
A process for producing a capacitor element was performed under the same conditions as in Example 1 except that 3,4-dioxyethylene-thiophene described in Example 1 was replaced with thiophene. However, no black-blue polythiophene polymer was formed, and thiophene polymerization did not occur by the action of APS. That is, oxidative polymerization of thiophenes by APS occurred particularly specifically with respect to 3,4-dioxy group-substituted thiophenes.
[0039]
[Table 1]

[0040]
[Table 2]

[0041]
【The invention's effect】
The conductive polymer composition used as the solid electrolyte contains at least both a naphthylamine sulfonate anion and a reductant anion of an oxidizing agent as dopants, the content of which is naphthylamine sulfone with respect to all repeating structural units of the conductive polymer. By containing an acid anion in the range of 0.1 to 50 mol%, a low-impedance solid electrolytic capacitor can be provided. Furthermore, the present invention provides not only a particularly low-impedance capacitor in a composition containing a structural unit represented by the above general formula (II) having a specific structure as a conductive polymer. In the test, an effect having excellent durability performance was found.

Claims (4)

In a solid electrolytic capacitor provided with a conductive polymer composition layer by chemical oxidative polymerization, at least naphthylamine sulfonate anion and oxidation in the solid electrolyte made of the composition formed on the dielectric oxide film on the surface of the valve action metal anode foil in the solid electrolytic capacitor, characterized in that both the reductant anion of the agent comprises as a dopant, comprises in the range of 0.1 to 50 mol% naphthylamine sulfonic acid anion on all repeating structural units of the conductive polymer In the conductive polymer composition, the following general formula (II)

(In the formula, each of the substituents R ⁴ and R ⁵ is independently hydrogen, 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. Represents a substituent which is bonded to each other at an arbitrary position to form a cyclic structure of at least one 5- to 7-membered saturated hydrocarbon containing two oxygen elements described in the formula. Includes a chemical structure such as a substituted vinylene group or a substituted o-phenylene group, and δ is in the range of 0 to 1.) .    The naphthylamine sulfonate anion according to claim 1 is in a range of 0.1 to 50 mol% with respect to all repeating structural units of the conductive polymer, and the reductant anion of the oxidizing agent is all repeating of the conductive polymer. A solid electrolytic capacitor comprising 0.1 to 15 mol% with respect to a structural unit. 3. The method for producing a solid electrolytic capacitor according to claim 1 , wherein the following general formula (IV) is applied on the dielectric oxide film on the surface of the valve-acting metal anode foil.

(Wherein the ranges of the substituents R ⁴ and R ⁵ are the same as those in the general formula (II)), wherein the monomer is formed by chemical oxidative polymerization using an oxidizing agent, A method for producing a solid electrolytic capacitor, wherein the chemical oxidative polymerization reaction is performed in the presence of a naphthylamine sulfonate anion and an oxidizing agent . The method for producing a solid electrolytic capacitor according to claim 3 , wherein the oxidizing agent used for polymerization of the monomer is a persulfate.