JP4019968B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

【００１２】
本発明の請求項２に記載の発明は、請求項１に記載の発明において、導電性高分子を形成するモノマー１ｍｏｌに対し、（化１）で示される化合物のドープ量が０．０５〜０．５ｍｏｌである構成としたものであり、これにより、請求項１に記載の発明により得られる作用に加え、固体電解コンデンサとしてさらに優れたＥＳＲおよびインピーダンス特性を可能にすることができるという作用を有する。
【００１３】
なお、導電性高分子を形成するモノマー１ｍｏｌに対し、（化１）で示される化合物のドープ量が０．０５ｍｏｌ未満の場合には得られる導電性高分子の電導度が低いためにＥＳＲ特性が低下し、また（化１）で示される化合物のドープ量が０．５ｍｏｌを超える場合には余剰のドーパントが立体障害となり、導電性高分子主鎖の規則性が低下してＥＳＲ特性の低下を招くために好ましくない。
【００１４】
本発明の請求項３に記載の発明は、請求項１に記載の発明において、導電性高分子層を形成するモノマーがピロール、チオフェン、フラン、アニリンあるいはそれらの誘導体の少なくとも一つ以上から選ばれる構成としたものであり、これにより、高い導電性が得られ、高周波領域でのインピーダンス特性の優れた固体電解コンデンサが得られるという作用を有する。
【００１５】
本発明の請求項４に記載の発明は、請求項１に記載の発明において、導電性高分子層の一部にフェノール誘導体が添加された構成としたものであり、これにより、フェノール誘導体が高分子骨格の秩序性を高める効果を有しているために、より高温条件下でも安定な固体電解コンデンサが得られるという作用を有する。
【００１６】
本発明の請求項５に記載の発明は、請求項４に記載の発明において、フェノール誘導体がニトロフェノール、シアノフェノール、ヒドロキシ安息香酸、ヒドロキシフェノールの少なくとも一つ以上から選ばれる構成としたものであり、これにより、請求項４に記載の発明により得られる作用に加え、さらに高温および高湿下における特性の優れた固体電解コンデンサが得られるという作用を有する。
【００１７】
なお、ここで用いられるフェノール誘導体としては、ｏ−ニトロフェノール、ｍ−ニトロフェノール、ｐ−ニトロフェノール、ｏ−シアノフェノール、ｍ−シアノフェノール、ｐ−シアノフェノール、ｏ−ヒドロキシ安息香酸、ｍ−ヒドロキシ安息香酸、ｐ−ヒドロキシ安息香酸、ｏ−ヒドロキシフェノール、ｍ−ヒドロキシフェノール、ｐ−ヒドロキシフェノールが挙げられる。
【００１８】
本発明の請求項６に記載の発明は、請求項１に記載の発明において、導電性高分子層の一部に硫酸がドープされた構成としたものであり、これにより、硫酸はドーパントとして導電性高分子内に取り込まれていると考えられるために、このような分子構造的に立体障害の小さな化合物が取り込まれると、形成される高分子の充填率が変化することにより、高い容量引き出し率を有する固体電解コンデンサを作製することが可能になるという作用を有する。
【００１９】
本発明の請求項７に記載の発明は、重合性モノマーおよび（化１）で示される化合物を少なくとも含む重合液を用いて導電性高分子層を形成させるようにした固体電解コンデンサの製造方法というものであり、この方法により、水を主溶媒として用いることで、特に電解重合時に化成を行うと、（化１）で示されるドーパントの優れた化成性により、さらに漏れ電流特性及び高湿下のＥＳＲおよび静電容量特性に優れた固体電解コンデンサが得られるという作用を有する。
【００２０】
【化４】

【００２１】
本発明の請求項８に記載の発明は、請求項７に記載の発明において、重合性モノマーがピロール、チオフェン、アニリンあるいはそれらの誘導体の少なくとも一つから選ばれるものであるという製造方法であり、この方法により、請求項７に記載の発明により得られる作用に加え、上記重合性モノマーを用いることでより高い導電性が得られ、高周波領域でのインピーダンス特性の優れた固体電解コンデンサが得られるという作用を有する。
【００２２】
本発明の請求項９に記載の発明は、請求項７に記載の発明において、重合液にフェノール誘導体、硫酸、アルコール類の少なくとも一つを添加したという製造方法であり、この方法により、優れた容量引き出し効率が得られ、かつ安定な膜質を有する導電性高分子を形成させることが可能になるという作用を有する。
【００２３】
本発明の請求項１０に記載の発明は、請求項９に記載の発明において、フェノール誘導体がニトロフェノール、シアノフェノール、ヒドロキシ安息香酸、ヒドロキシフェノールの少なくとも一つ以上から選ばれ、かつ重合液中の濃度を０．００１〜０．１Ｍとしたという製造方法であり、この方法により、請求項９に記載の発明により得られる作用に加え、フェノール誘導体が高分子骨格の秩序性を高めるため、さらに高温および高湿下におけるＥＳＲおよび静電容量特性に優れた固体電解質層を形成させることが可能になるという作用を有する。
【００２４】
なお、フェノール誘導体の重合液中の濃度が０．０１Ｍ未満の場合には形成される高分子の秩序性が低いために耐熱特性が低下し、また、フェノール誘導体の重合液中の濃度が０．１Ｍを超える場合には重合速度が速くなり、エッジ部分に重合電流が集中し、それにより高分子層の厚さが不均一となってコンデンサ素子積層時のストレスにより漏れ電流特性が低下するために好ましくない。
【００２５】
本発明の請求項１１に記載の発明は、請求項９に記載の発明において、硫酸の重合液中での濃度を０．０１〜１ｗｔ％としたという製造方法であり、これにより、請求項９に記載の発明により得られる作用に加え、硫酸がドープされることで形成される高分子の充填度が変化し、さらに優れた容量引き出し効率を示す固体電解質を形成させることが可能になるという作用を有する。
【００２６】
なお、硫酸の重合液中での濃度が０．０１ｗｔ％未満の場合には容量引き出し率に対する効果が充分ではなく、一方、硫酸の重合液中での濃度が１ｗｔ％を超える場合には高湿度下においてドープされた硫酸が溶出し、高湿度下におけるＥＳＲおよび静電容量特性が著しく低下するために好ましくない。
【００２７】
本発明の請求項１２に記載の発明は、請求項９に記載の発明において、アルコール類の炭素数が１〜４であり、かつ重合液中の濃度を０．５〜２０ｗｔ％としたという製造方法であり、これにより、請求項９に記載の発明により得られる作用に加え、重合液中にアルコールなどの有機溶剤を添加することで、特にエッジ部分における重合反応の反応性を抑制し、形成される導電性高分子の表面形状を改善することが可能になるという作用を有する。
【００２８】
なお、ここで用いられる有機溶剤としては、メチルアルコール、エチルアルコール、ｎ−プロピルアルコール、２−プロピルアルコール、ｎ−ブチルアルコール、２−ブチルアルコール、３−ブチルアルコール、ｔｅｒｔ−ブチルアルコール、アセトニトリル、アセトン、テトラヒドロフラン、エチレングリコール、γ−ブチルラクトン、ジメチルホルムアミド、ジメチルスルホキシドが挙げられる。
【００２９】
また、アルコール類の重合液中の濃度が０．５ｗｔ％未満の場合にはエッジ部分に重合電流が集中し、それにより高分子層の厚さが不均一となるためコンデンサ素子積層時のストレスにより漏れ電流特性が低下し、また、アルコール類の重合液中の濃度が２０ｗｔ％を超える場合には重合速度が低下するために重合時間が長くなり、生産性が急激に悪化するために好ましくない。
【００３０】
本発明の請求項１３に記載の発明は、請求項７に記載の発明において、導電性高分子の形成を電解重合により行うようにした製造方法であり、これにより、請求項７に記載の発明により得られる作用に加え、電解重合を行うことで立体秩序性の高い導電性高分子が形成され、それにより均一な重合膜厚を有し、かつ電気電導度の高い固体電解質を形成させることが可能になるという作用を有する。
【００３１】
本発明の請求項１４に記載の発明は、請求項１３に記載の発明において、電解重合時の電圧を１〜３Ｖで行うようにしたという製造方法であり、これにより、請求項１３に記載の発明により得られる作用に加え、電圧により反応性を制御することができるので高い容量引き出し特性を示す固体電解質を形成することが可能になるという作用を有する。
【００３２】
なお、電解重合時の電圧が１Ｖ未満の場合には重合時間が長くなり、また電圧が３Ｖを超える場合には水の電気分解などの副反応の比率が上がるために初期のＥＳＲ、静電容量などのコンデンサ特性が低下するために好ましくない。
【００３３】
【発明の実施の形態】
以下に本発明の具体的な実施の形態について説明するが、本発明はこれらに限定されるものではない。
【００３４】
（実施例１）
図１は本発明の一実施の形態による固体電解コンデンサの構成を示す断面図であり、まず陽極としてリードをつけた３ｍｍ×４ｍｍのアルミニウムエッチド箔１を使用した。これに３％アジピン酸アンモニウム水溶液を用いて印加電圧１２Ｖ、水溶液温度７０℃で６０分間陽極酸化を行うことにより、アルミニウムエッチド箔１の表面に誘電体酸化皮膜２を形成した。その後、硝酸マンガン３０％水溶液に浸漬して引き上げて自然乾燥させた後、３００℃で１０分間の熱分解処理を行うことにより固体電解質層３の一部となるマンガン酸化物層を形成した。
【００３５】
次に、エチレンジオキシチオフェンモノマー０．５ｍｏｌ／Ｌと（化１）で示されるドーパント化合物である３−スルホ−１．８−ナフタル酸を濃度０．１ｍｏｌ／Ｌと主溶媒である水を加えて調製した固体電解質形成用の重合液を作製し、この重合液中で重合開始用電極をアルミニウムエッチド箔１の表面に近接させ、重合液温度２５℃、重合電圧２Ｖで電解重合を行って固体電解質層３を形成した。この固体電解質層３における（化１）で示されるドーパント化合物である３−スルホ−１．８−ナフタル酸のドープ量は、導電性高分子を形成するモノマー１ｍｏｌに対して０．３ｍｏｌであった。
【００３６】
【化５】

【００３７】
その後、陰極引き出し層としてカーボンを塗布、乾燥することによって得られるカーボン層４、および銀ペーストを塗布乾燥することによって得られる銀層５を形成し、カーボン層４と銀層５を併せて陰極引き出し部とした。その後、図示しないエポキシ樹脂を用いて外装することにより、定格が６．３Ｖ、１０μＦの固体電解コンデンサを１０個完成させた。
【００３８】
（実施例２）
上記実施例１において、誘電体酸化皮膜２形成後、水溶性ポリアニリン５％溶液に浸漬して２００℃１０分間の加熱処理を行うことによって固体電解質層３の一部となる導電性層を形成した。次に、ピロールモノマー０．５ｍｏｌ／Ｌと（化１）で示されるドーパント化合物である３−スルホ−１．８−ナフタル酸を濃度０．１ｍｏｌ／Ｌと主溶媒である水を加えて調製した固体電解質形成用の重合液を作製し、重合液温度２５℃、重合電圧２Ｖで電解重合を行って固体電解質層３を形成した以外は上記実施例１と同様に固体電解コンデンサを作製した。
【００３９】
（実施例３）
上記実施例１において、固体電解質層３の一部となるマンガン酸化物層を形成した後、エチレンジオキシチオフェンモノマー０．５ｍｏｌ／Ｌと（化１）で示されるドーパント化合物である３−スルホ−１．８−ナフタル酸を濃度０．１ｍｏｌ／Ｌと溶媒であるエタノールを加えて調製した固体電解質形成用の重合液を作製し、この重合液中で重合開始用電極を素子表面に近接させ、重合液温度２５℃、重合電圧２Ｖで電解重合を行って固体電解質層３を形成した以外は上記実施例１と同様に固体電解コンデンサを作製した。
【００４０】
（実施例４）
上記実施例１において、固体電解質層３を（化１）で示されるドーパント化合物である３−スルホ−１．８−ナフタル酸とバインダ成分を含むポリエチレンジオキシチオフェンのスルホン酸溶液１．０％とスルホン化ポリアニリン１．０％の水−アルコール混合溶液中にコンデンサ素子を浸漬して引き上げた後、１５０℃で５分間の乾燥処理を行い、ポリエチレンジオキシチオフェンのスルフォネートの層を形成し、続いて、複素環式モノマーであるエチレンジオキシチオフェン０．５ｍｏｌ／Ｌと酸化剤であるｐ−トルエンスルホン酸第二鉄１ｍｏｌ／Ｌと重合溶剤であるｎ−ブタノール２ｍｏｌ／Ｌを含む溶液に浸漬して引き上げた後、８５℃で６０分間放置することにより化学重合性導電性高分子であるポリエチレンジオキシチオフェンの固体電解質層３を形成した以外は上記実施例１と同様に固体電解コンデンサを作製した。
【００４１】
（比較例１）
上記実施例１と同様の方法で陽極となるアルミニウムエッチド箔１の外表面に誘電体酸化皮膜２を形成した後、熱処理を行うことによって固体電解質層３の一部となる導電性のプレコート層を形成した。この後、ピロールモノマー０．５ｍｏｌ／Ｌとブチルナフタレンスルホン酸ナトリウム０．１ｍｏｌ／Ｌと主溶媒である水を加えて調整した固体電解質形成用の重合液を作製し、この重合液中で重合開始用電極を素子表面に近接させ、液温度２５℃、重合電圧２Ｖで電解重合を行って固体電解質層３を形成した。その後、実施例１と同様の方法でカーボン層４と銀層５を形成し、カーボン層４と銀層５からなる陰極引き出し部を形成してから外装を施し、１０個の固体電解コンデンサを完成させた。
【００４２】
（実施例５）
タンタル粉末をタンタルリード線の一部が表出するように埋設した状態で成形した後、焼結して、厚み１．４ｍｍ、幅３．０ｍｍ、長さ３．８ｍｍの陽極体を得た。この陽極体の表面にリン酸水溶液を用いて化成電圧２０Ｖで化成して誘電体酸化皮膜を形成した。
【００４３】
次に、この陽極体をエチレングリコール水溶液に複素環式モノマーであるピロールと（化１）で示されるドーパント化合物である４−スルホ−１．８−ナフタル酸を含んだ重合溶液に５分間浸漬して引き上げ、直ちにエチレングリコール水溶液に酸化剤である硫酸鉄（III）を含む酸化剤溶液に１０分間浸漬して引き上げた後、この陽極体を洗浄して修復化成し、乾燥（１００℃）を行った。この一連の操作を１０回繰り返して導電性高分子の固体電解質層を形成した。
【００４４】
次に、この固体電解質層の表面に２ｗｔ％のカーボン粒子と２ｗｔ％のピロガロールを含み、アンモニアを添加してｐＨ１０に調製した水溶液を含浸させ、１５０℃で乾燥してカーボン層を形成した。その後、銀ペーストの導電体層を形成してコンデンサ素子を得た。
【００４５】
次に、タンタルリード線と陽極端子を接続し、また、コンデンサ素子の陰極層に導電性接着剤を介して陰極端子を接続して、この陽極端子と陰極端子の一部が露呈するように外装樹脂で被覆形成して固体電解コンデンサを作製した（Ｄサイズ：７．３×４．３×２．８ｍｍ）。
【００４６】
（比較例２）
上記実施例５において、誘電体酸化皮膜を形成した後、陽極体をエチレングリコール水溶液に複素環式モノマーであるピロールとブチルナフタレンスルホン酸ナトリウムを含んだ重合溶液に５分間浸漬して引き上げた以外は実施例５と同様に固体電解コンデンサを作製した（Ｄサイズ：７．３×４．３×２．８ｍｍ）。
【００４７】
上記実施例１〜５と比較例１および２の固体電解コンデンサの初期値と耐湿負荷（６０℃、９０％、６．３Ｖ ５００時間）試験後のＥＳＲ特性を（表１）に示す。なお、ＥＳＲ特性は１００ｋＨｚで測定した。
【００４８】
【表１】

【００４９】
（表１）から明らかなように、実施例１〜４と比較例１の比較から、ドーパントとしてブチルナフタレンスルホン酸ナトリウムを用いると耐湿負荷試験でのＥＳＲ特性が著しく悪化することが分かり、（化１）で示されるドーパント化合物のアルミニウムに対する高い化成性を表わしているものである。また、実施例１と２から、固体電解質の一部となる導電性層を水溶性ポリアニリン層としても、同等のＥＳＲ特性が得られることが分かる。また、実施例１と３の比較により、重合溶液の溶媒をエタノールにすると耐湿負荷試験でのＥＳＲ特性が実施例１と比べて低下する傾向が見られ、主溶媒として水を用いることが効果的であることが分かる。
【００５０】
さらに、実施例４から重合プロセスを酸化剤を用いた化学重合とした場合、実施例１と同等のＥＳＲ特性を得ることはできず、電解重合により得られる固体電解コンデンサの特性の方がより優れていることが分かる。また、実施例１と比較例１および実施例５と比較例２の比較により、ブチルナフタレンスルホン酸ナトリウムのような崇高いドーパントを用いると緻密な導電性高分子層を形成させるのが困難なため、初期の静電容量特性が著しく悪化することが分かる。
【００５１】
（実施例６）
（化１）で示されるドーパント化合物の添加量を変えることにより、導電性高分子を形成するモノマー１ｍｏｌに対する（化１）で示されるドーパント化合物の含有量が０．０１、０．０５、０．１、０．５、０．７ｍｏｌと変化させた以外は実施例２と同様に固体電解コンデンサ１０個を作製した。
【００５２】
この固体電解コンデンサの初期値のＥＳＲ特性を図２に示す。なお、ＥＳＲ特性は１００ｋＨｚで測定した。
【００５３】
図２から明らかなように、導電性高分子を形成するモノマー１ｍｏｌに対する（化１）で示されるドーパント化合物の含有量が０．０５〜０．５ｍｏｌの固体電解コンデンサはＥＳＲ特性が優れており、添加量が０．０５ｍｏｌ未満および０．５ｍｏｌを超える場合にはＥＳＲ特性が悪化する傾向が見られる。従って、（化１）で示されるドーパント化合物を用いることでコンデンサとしてさらに優れたＥＳＲおよびインピーダンス特性を可能にするには、導電性高分子層における（化１）で示されるドーパント化合物の含有量が、導電性高分子を形成するモノマー１ｍｏｌに対して０．０５〜０．５ｍｏｌとなるように調製することが好ましい。
【００５４】
（実施例７）
実施例１に示した固体電解質形成用の重合液にパラニトロフェノールを０．００１、０．００５、０．０１、０．０５、０．１、０．２Ｍ添加することにより、導電性高分子層の一部にパラニトロフェノールが添加された以外は実施例１と同様に固体電解コンデンサ１０個を作製した。
【００５５】
この固体電解コンデンサの初期値と高温無負荷（１２５℃ １０００時間）試験後のＥＳＲ特性を図３に示す。なお、ＥＳＲ特性は１００ｋＨｚで測定した。
【００５６】
図３から明らかなように、パラニトロフェノール添加量が０．０１〜０．１Ｍの固体電解コンデンサはＥＳＲ特性が優れており、０．０１Ｍ未満および０．１Ｍを超える場合にはＥＳＲ特性が悪化する傾向が見られる。従って、パラニトロフェノールが高分子骨格の秩序性を高め、高温条件下でも安定な固体電解コンデンサを得るためには、パラニトロフェノール添加量を０．０１〜０．１Ｍの範囲にするのが好ましい。
【００５７】
また、添加剤としてパラニトロフェノールの代わりにパラシアノフェノール、パラヒドロキシ安息香酸、パラヒドロキシフェノールを添加しても同様の効果が得られることを確認した。
【００５８】
（実施例８）
実施例１に示した固体電解質形成用の重合液に硫酸を０．００５、０．０１、０．１、１、１．５、２ｗｔ％添加することにより、導電性高分子層の一部に硫酸がドープされた以外は実施例１と同様に固体電解コンデンサ１０個を作製した。
【００５９】
この固体電解コンデンサの初期値の静電容量特性と耐湿負荷（６０℃、９０％、６．３Ｖ ５００時間）試験後のＥＳＲ特性を図４に示す。なお、静電容量特性は１２０ｋＨｚ、またＥＳＲ特性は１００ｋＨｚで測定した。
【００６０】
図４から明らかなように、硫酸添加量が０．０１〜１ｗｔ％の固体電解コンデンサは静電容量および高湿下における特性が優れており、０．０１ｗｔ％未満では静電容量が低く、１ｗｔ％を超えるものでは耐湿試験におけるＥＳＲ特性が悪化する傾向が見られる。従って、硫酸が形成される高分子の充填率を変化させて高い容量引き出し率を示し、かつ優れた耐湿特性を有する固体電解コンデンサを得るためには、硫酸添加量を０．０１〜１ｗｔ％の範囲にするのが好ましい。
【００６１】
（実施例９）
実施例１に示した固体電解質形成用の重合液に２−プロパノールを０．１、０．５、１、１０、２０、３０ｗｔ％添加した以外は実施例１と同様に固体電解コンデンサ１０個を作製した。
【００６２】
この固体電解コンデンサの初期値の漏れ電流特性（６．３Ｖ、１分値）を図５に示す。
【００６３】
図５から明らかなように、２−プロパノール添加量が０．５〜２０ｗｔ％の固体電解コンデンサは漏れ電流特性が優れているが、０．５ｗｔ％未満では漏れ電流特性が悪化する傾向が見られる。また、２−プロパノール添加量が２０ｗｔ％を超える場合には重合性が悪くなって重合時間が長くなる。従って、重合液中にアルコールなどの有機溶剤を添加することで重合反応の反応性を抑制し、エッジ部分への電流の集中を防ぎ、形成される導電性高分子の表面形状を改善することで漏れ電流特性に優れた固体電解コンデンサを得るためには、２−プロパノール添加量を０．５〜２０ｗｔ％の範囲にするのが好ましい。
【００６４】
また、有機溶剤として２−プロパノールの代わりにメチルアルコール、エチルアルコール、ｎ−プロピルアルコール、２−プロピルアルコール、ｎ−ブチルアルコール、２−ブチルアルコール、３−ブチルアルコール、ｔｅｒｔ−ブチルアルコール、アセトニトリル、アセトン、テトラヒドロフラン、エチレングリコール、γ−ブチルラクトン、ジメチルホルムアミド、ジメチルスルホキシドを添加しても同様の効果が得られることを確認した。
【００６５】
（実施例１０）
実施例１に示した電解重合の重合電圧を０．５、１、２、３、５Ｖにした以外は実施例１と同様に固体電解コンデンサ１０個を作製した。
【００６６】
この固体電解コンデンサの初期値のＥＳＲ特性を図６に示す。なお、ＥＳＲ特性は１００ｋＨｚで測定した。
【００６７】
図６から明らかなように、重合電圧が１〜３Ｖの固体電解コンデンサはＥＳＲ特性が優れており、１Ｖ未満では重合が速やかに進行せず、また３Ｖを超える場合には緻密な高分子が形成されずにＥＳＲ特性が悪化する傾向が見られる。従って、重合電圧により反応を制御し、優れたＥＳＲ特性を有する固体電解コンデンサを得るためには、重合電圧を１〜３Ｖの範囲にするのが好ましい。
【００６８】
なお、実施の形態１では陽極として弁作用金属のアルミニウムおよびタンタルを使用した固体電解コンデンサについてのみ述べたが、本発明はこれらに限定されるものではなく、外表面に酸化皮膜を有する弁作用金属であるニオブ、チタン等の他の物質でも同様の効果が得られるものである。
【００６９】
【発明の効果】
以上のように本発明は、弁作用金属からなる陽極体の表面に誘電体酸化皮膜、導電性高分子層、陰極層が順次積層形成された固体電解コンデンサにおいて、上記導電性高分子層が少なくとも（化１）で示される化合物がドープされた構成としたことにより、ナフタル酸のように分子内にカルボン酸を有するドーパントは化成性に優れているため、特に漏れ電流特性および高温高湿の環境下における特性に優れた固体電解コンデンサを得ることができるという格別の効果を奏するものである。
【図面の簡単な説明】
【図１】本発明の一実施の形態による固体電解コンデンサの構成を示す断面図
【図２】同ドーパント化合物の含有量とＥＳＲ特性の関係を示す特性図
【図３】同パラニトロフェノールの重合液中への添加量とＥＳＲ特性変化の関係を示す特性図
【図４】同硫酸の重合液中への添加量と初期の静電容量特性の関係を示す特性図
【図５】同２−プロパノールの重合液中への添加量と初期の漏れ電流特性を表す特性図
【図６】同電解重合電圧による初期の静電容量特性の関係を示す特性図
【符号の説明】
１ アルミニウムエッチド箔
２ 誘電体酸化皮膜
３ 固体電解質層
４ カーボン層
５ 銀層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solid electrolytic capacitor used in various electronic devices and a method for manufacturing the same.
[0002]
[Prior art]
With the recent digitization of electronic devices, there is an increasing demand for capacitors used in these devices that have a low impedance in the high frequency region and have a small size and a large capacity. Conventionally, as a capacitor used for such a high frequency region, a plastic film capacitor, a mica capacitor, a multilayer ceramic capacitor, or the like is used. In addition, there are aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. In the above aluminum dry electrolytic capacitors, the element is formed by winding an etched positive / cathode aluminum foil with a separator interposed therebetween. It is formed and impregnated with a liquid electrolyte.
[0003]
In addition, in an aluminum or tantalum solid electrolytic capacitor, the electrolyte is solidified in order to improve the characteristics of the above-mentioned aluminum dry capacitor. To form this solid electrolyte, an anode body is immersed in a manganese nitrate solution, and this is heated to 250 to 350 ° C. A manganese oxide layer is formed by thermal decomposition in front and rear high-temperature furnaces. In the case of this capacitor, the electrolyte is solid, so there are no drawbacks such as electrolyte outflow at high temperature, capacity reduction due to dry-up, and functional degradation caused by solidification in a low temperature range, and better frequency characteristics and temperature characteristics than liquid electrolytes Is shown.
[0004]
In recent years, solid electrolytic capacitors in which a polymerizable monomer such as pyrrole or thiophene is polymerized to form a conductive polymer for the purpose of increasing the conductivity of the solid electrolyte have been put to practical use.
[0005]
As prior art document information related to the invention of this application, for example, Non-Patent Document 1 is known.
[0006]
[Non-Patent Document 1]
A. Shimada et al., Electrochemistry, 69, No. 2 (2001)
[0007]
[Problems to be solved by the invention]
As a method for forming a solid electrolyte of a solid electrolytic capacitor using a conductive polymer as the solid electrolyte, a precoat layer made of a conductive material such as manganese oxide or a conductive polymer is formed on the surface of a dielectric oxide film of a valve action metal. After the formation, the conductive polymer is formed by immersing it in a polymerization solution containing an oxidant, or by electropolymerization to form a solid electrolyte of the conductive polymer by supplying power from outside in a polymerization solution containing a polymerizable monomer and a dopant. Chemical polymerization to form a solid electrolyte is known.
[0008]
However, the solid electrolytic capacitor obtained by the above method generally uses mainly a sulfonic acid compound or a phosphoric acid compound as a dopant. However, due to its acidic strength, the dopant is not particularly effective in a high humidity environment. When dedoped, the dielectric oxide film of the valve action metal is eroded or has a problem that the reliability is lowered by lowering the chemical conversion property. The characteristics of ESR and capacitance by this dedoping In order to suppress deterioration, it has been proposed to use an aromatic sulfone compound having an alkyl group as a dopant, but in that case, there is also a problem that the capacity drawing rate is lowered.
[0009]
An object of the present invention is to solve such a conventional problem, and to provide a solid electrolytic capacitor excellent in ESR and leakage current characteristics under high temperature and high humidity and having a high capacity drawing rate, and a method for manufacturing the same. To do.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the invention according to claim 1 of the present invention is a solid electrolytic in which a dielectric oxide film, a conductive polymer layer, and a cathode layer are sequentially laminated on the surface of an anode body made of a valve metal. In the capacitor, the conductive polymer layer is configured to be doped with at least a compound represented by (Chemical Formula 1), thereby obtaining a solid electrolytic capacitor having excellent characteristics even at high temperature and high humidity. It has the effect that it becomes possible. This is because a dopant having a carboxylic acid in the molecule like naphthalic acid is excellent in chemical conversion, and thus a solid electrolytic capacitor excellent in leakage current characteristics and ESR characteristics in a high temperature and high humidity environment can be obtained. Furthermore, a dopant having a small steric hindrance such as the compound represented by (Chemical Formula 1) can form a dense conductive polymer layer, and a solid electrolytic capacitor having excellent initial capacitance characteristics can be obtained. It is considered to be obtained.
[0011]
[Chemical 3]

[0012]
The invention according to claim 2 of the present invention is the invention according to claim 1, wherein the doping amount of the compound represented by (Chemical Formula 1) is 0.05 to 0 with respect to 1 mol of the monomer forming the conductive polymer. In addition to the action obtained by the invention according to claim 1, this has the action of enabling even more excellent ESR and impedance characteristics as a solid electrolytic capacitor. .
[0013]
In addition, when the doping amount of the compound represented by (Chemical Formula 1) is less than 0.05 mol with respect to 1 mol of the monomer that forms the conductive polymer, the conductivity of the obtained conductive polymer is low, and thus the ESR characteristic is low. When the doping amount of the compound represented by (Chemical Formula 1) exceeds 0.5 mol, excess dopant becomes steric hindrance, the regularity of the conductive polymer main chain is lowered, and the ESR characteristic is lowered. It is not preferable to invite.
[0014]
The invention according to claim 3 of the present invention is the invention according to claim 1, wherein the monomer forming the conductive polymer layer is selected from at least one of pyrrole, thiophene, furan, aniline, and derivatives thereof. This has the effect of obtaining a solid electrolytic capacitor having high conductivity and excellent impedance characteristics in a high frequency region.
[0015]
The invention according to claim 4 of the present invention is the invention according to claim 1, wherein a phenol derivative is added to a part of the conductive polymer layer. Since it has the effect of increasing the order of the molecular skeleton, it has the effect that a stable solid electrolytic capacitor can be obtained even under higher temperature conditions.
[0016]
The invention according to claim 5 of the present invention is the invention according to claim 4, wherein the phenol derivative is selected from at least one of nitrophenol, cyanophenol, hydroxybenzoic acid, and hydroxyphenol. Thus, in addition to the action obtained by the invention according to claim 4, it has the action that a solid electrolytic capacitor excellent in characteristics at high temperature and high humidity can be obtained.
[0017]
In addition, as a phenol derivative used here, o-nitrophenol, m-nitrophenol, p-nitrophenol, o-cyanophenol, m-cyanophenol, p-cyanophenol, o-hydroxybenzoic acid, m-hydroxy Examples include benzoic acid, p-hydroxybenzoic acid, o-hydroxyphenol, m-hydroxyphenol, and p-hydroxyphenol.
[0018]
The invention according to claim 6 of the present invention is the structure according to claim 1, wherein a part of the conductive polymer layer is doped with sulfuric acid, whereby sulfuric acid is conductive as a dopant. Since a polymer with a small steric hindrance in terms of its molecular structure is incorporated, the packing rate of the formed polymer changes, resulting in a high capacity extraction rate. It has the effect | action that it becomes possible to produce the solid electrolytic capacitor which has this.
[0019]
The invention according to claim 7 of the present invention is a method for producing a solid electrolytic capacitor in which a conductive polymer layer is formed using a polymerization liquid containing at least a polymerizable monomer and a compound represented by (Chemical Formula 1). In this method, when water is used as a main solvent, particularly when chemical conversion is performed at the time of electrolytic polymerization, the excellent chemical conversion property of the dopant represented by (Chemical Formula 1) further improves leakage current characteristics and high humidity. A solid electrolytic capacitor having excellent ESR and capacitance characteristics can be obtained.
[0020]
[Formula 4]

[0021]
The invention according to claim 8 of the present invention is the production method according to the invention according to claim 7, wherein the polymerizable monomer is selected from at least one of pyrrole, thiophene, aniline or derivatives thereof, According to this method, in addition to the action obtained by the invention according to claim 7, higher conductivity can be obtained by using the polymerizable monomer, and a solid electrolytic capacitor having excellent impedance characteristics in a high frequency region can be obtained. Has an effect.
[0022]
The invention according to claim 9 of the present invention is a manufacturing method in which at least one of a phenol derivative, sulfuric acid, and alcohols is added to the polymerization solution in the invention according to claim 7, and this method is excellent. Capacitance extraction efficiency can be obtained, and a conductive polymer having a stable film quality can be formed.
[0023]
The invention according to claim 10 of the present invention is the invention according to claim 9, wherein the phenol derivative is selected from at least one of nitrophenol, cyanophenol, hydroxybenzoic acid and hydroxyphenol, and in the polymerization solution. This is a production method in which the concentration is 0.001 to 0.1 M. By this method, in addition to the action obtained by the invention according to claim 9, the phenol derivative increases the order of the polymer skeleton. In addition, it has an effect that a solid electrolyte layer excellent in ESR and capacitance characteristics under high humidity can be formed.
[0024]
When the concentration of the phenol derivative in the polymerization solution is less than 0.01M, the heat resistance is lowered due to the low order of the polymer formed, and the concentration of the phenol derivative in the polymerization solution is less than 0. If it exceeds 1M, the polymerization rate will increase, and the polymerization current will concentrate at the edge, which will cause the polymer layer thickness to become non-uniform and the leakage current characteristics to deteriorate due to stress during capacitor element lamination. It is not preferable.
[0025]
The invention described in claim 11 of the present invention is the manufacturing method according to the invention described in claim 9, wherein the concentration of sulfuric acid in the polymerization solution is 0.01 to 1 wt%. In addition to the action obtained by the invention described in 1., the filling degree of the polymer formed by doping with sulfuric acid changes, and it becomes possible to form a solid electrolyte exhibiting further excellent capacity drawing efficiency Have
[0026]
When the concentration of sulfuric acid in the polymerization solution is less than 0.01 wt%, the effect on the capacity drawing rate is not sufficient, while when the concentration of sulfuric acid in the polymerization solution exceeds 1 wt%, the humidity is high. The doped sulfuric acid elutes below, and the ESR and capacitance characteristics under high humidity are remarkably deteriorated.
[0027]
The invention according to claim 12 of the present invention is the production according to the invention according to claim 9, wherein the alcohol has 1 to 4 carbon atoms and the concentration in the polymerization solution is 0.5 to 20 wt%. In this way, in addition to the action obtained by the invention according to claim 9, by adding an organic solvent such as alcohol in the polymerization solution, the reactivity of the polymerization reaction particularly at the edge portion is suppressed and formed. The surface shape of the conductive polymer to be improved can be improved.
[0028]
In addition, as an organic solvent used here, methyl alcohol, ethyl alcohol, n-propyl alcohol, 2-propyl alcohol, n-butyl alcohol, 2-butyl alcohol, 3-butyl alcohol, tert-butyl alcohol, acetonitrile, acetone , Tetrahydrofuran, ethylene glycol, γ-butyllactone, dimethylformamide, and dimethyl sulfoxide.
[0029]
In addition, when the concentration of alcohol in the polymerization solution is less than 0.5 wt%, the polymerization current concentrates on the edge portion, thereby making the thickness of the polymer layer non-uniform. When the leakage current characteristic is lowered and the concentration of the alcohol in the polymerization solution exceeds 20 wt%, the polymerization rate is lowered, the polymerization time is prolonged, and the productivity is rapidly deteriorated, which is not preferable.
[0030]
The invention described in claim 13 of the present invention is the manufacturing method according to the invention described in claim 7, wherein the conductive polymer is formed by electrolytic polymerization. In addition to the action obtained by the above, it is possible to form a conductive polymer with high stereoordering by performing electrolytic polymerization, thereby forming a solid electrolyte having a uniform polymerization film thickness and high electrical conductivity. It has the effect of becoming possible.
[0031]
The invention described in claim 14 of the present invention is the manufacturing method according to the invention described in claim 13, wherein the voltage at the time of electrolytic polymerization is 1 to 3 V. In addition to the effects obtained by the invention, the reactivity can be controlled by the voltage, so that it is possible to form a solid electrolyte exhibiting high capacity drawing characteristics.
[0032]
When the voltage at the time of electrolytic polymerization is less than 1V, the polymerization time becomes longer, and when the voltage exceeds 3V, the ratio of side reactions such as water electrolysis increases, so that the initial ESR and capacitance are increased. It is not preferable because the capacitor characteristics such as
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of the present invention will be described, but the present invention is not limited thereto.
[0034]
Example 1
FIG. 1 is a sectional view showing the structure of a solid electrolytic capacitor according to an embodiment of the present invention. First, a 3 mm × 4 mm aluminum etched foil 1 with a lead attached as an anode was used. A dielectric oxide film 2 was formed on the surface of the aluminum etched foil 1 by performing anodic oxidation using an aqueous 3% ammonium adipate solution at an applied voltage of 12 V and an aqueous solution temperature of 70 ° C. for 60 minutes. Then, after dipping in a 30% aqueous solution of manganese nitrate and pulling it up to dry naturally, a manganese oxide layer that becomes a part of the solid electrolyte layer 3 was formed by performing a thermal decomposition treatment at 300 ° C. for 10 minutes.
[0035]
Next, 0.5 mol / L of ethylenedioxythiophene monomer and 3-sulfo-1.8-naphthalic acid which is a dopant compound represented by (Chemical Formula 1) were added at a concentration of 0.1 mol / L and water as a main solvent. A polymerization solution for forming a solid electrolyte prepared in this manner is prepared, and an electrode for initiating polymerization is brought close to the surface of the aluminum etched foil 1 in this polymerization solution, and electrolytic polymerization is performed at a polymerization solution temperature of 25 ° C. and a polymerization voltage of 2 V. A solid electrolyte layer 3 was formed. In this solid electrolyte layer 3, the doping amount of 3-sulfo-1.8-naphthalic acid, which is a dopant compound represented by (Chemical Formula 1), was 0.3 mol with respect to 1 mol of the monomer forming the conductive polymer. .
[0036]
[Chemical formula 5]

[0037]
Thereafter, a carbon layer 4 obtained by applying and drying carbon as a cathode lead layer, and a silver layer 5 obtained by applying and drying silver paste are formed, and the carbon layer 4 and the silver layer 5 are combined to form a cathode lead. The part. Then, 10 solid electrolytic capacitors having a rating of 6.3 V and 10 μF were completed by packaging with an epoxy resin (not shown).
[0038]
(Example 2)
In Example 1 above, after the dielectric oxide film 2 was formed, a conductive layer that was a part of the solid electrolyte layer 3 was formed by dipping in a 5% water-soluble polyaniline solution and performing a heat treatment at 200 ° C. for 10 minutes. . Next, pyrrole monomer 0.5 mol / L and 3-sulfo-1.8-naphthalic acid as a dopant compound represented by (Chemical Formula 1) were prepared by adding 0.1 mol / L concentration and water as a main solvent. A solid electrolytic capacitor was prepared in the same manner as in Example 1 except that a polymerization liquid for forming a solid electrolyte was prepared, and electrolytic polymerization was performed at a polymerization liquid temperature of 25 ° C. and a polymerization voltage of 2 V to form the solid electrolyte layer 3.
[0039]
(Example 3)
In Example 1 above, after forming a manganese oxide layer to be a part of the solid electrolyte layer 3, 3-sulfo- which is a dopant compound represented by 0.5 mol / L of ethylenedioxythiophene monomer and (Chemical Formula 1) A solid electrolyte forming polymerization solution prepared by adding 1.8-naphthalic acid at a concentration of 0.1 mol / L and ethanol as a solvent was prepared, and in this polymerization solution, a polymerization initiation electrode was brought close to the element surface, A solid electrolytic capacitor was produced in the same manner as in Example 1 except that the solid electrolyte layer 3 was formed by performing electrolytic polymerization at a polymerization solution temperature of 25 ° C. and a polymerization voltage of 2 V.
[0040]
(Example 4)
In Example 1 above, the solid electrolyte layer 3 was treated with a 1.0% sulfonic acid solution of polyethylenedioxythiophene containing 3-sulfo-1.8-naphthalic acid, which is a dopant compound represented by (Chemical Formula 1), and a binder component; The capacitor element was dipped in a 1.0% water-alcohol mixed solution of sulfonated polyaniline and pulled up, followed by drying at 150 ° C. for 5 minutes to form a polyethylene dioxythiophene sulfonate layer, And dipping in a solution containing 0.5 mol / L of ethylenedioxythiophene as a heterocyclic monomer, 1 mol / L of p-toluenesulfonic acid ferric acid as an oxidizing agent and 2 mol / L of n-butanol as a polymerization solvent. After being pulled up, it is allowed to stand at 85 ° C. for 60 minutes, so that polyethylenedioxythiophene, which is a chemically polymerizable conductive polymer, is used. Except that the formation of the solid electrolyte layer 3 was formed a solid electrolytic capacitor in the same manner as in Example 1.
[0041]
(Comparative Example 1)
A conductive precoat layer that becomes a part of the solid electrolyte layer 3 by forming a dielectric oxide film 2 on the outer surface of the aluminum etched foil 1 serving as an anode in the same manner as in Example 1 and then performing a heat treatment. Formed. Thereafter, a polymer solution for forming a solid electrolyte prepared by adding pyrrole monomer 0.5 mol / L, sodium butylnaphthalenesulfonate 0.1 mol / L and water as a main solvent was prepared, and polymerization was started in this polymer solution. A solid electrolyte layer 3 was formed by bringing the electrode for use close to the element surface and performing electropolymerization at a liquid temperature of 25 ° C. and a polymerization voltage of 2 V. Thereafter, a carbon layer 4 and a silver layer 5 are formed in the same manner as in Example 1, and a cathode lead portion composed of the carbon layer 4 and the silver layer 5 is formed, and then the exterior is applied to complete 10 solid electrolytic capacitors. I let you.
[0042]
(Example 5)
The tantalum powder was molded in a state where a part of the tantalum lead wire was exposed, and then sintered to obtain an anode body having a thickness of 1.4 mm, a width of 3.0 mm, and a length of 3.8 mm. A dielectric oxide film was formed on the surface of the anode body using a phosphoric acid aqueous solution at a formation voltage of 20V.
[0043]
Next, this anode body was immersed in an ethylene glycol aqueous solution for 5 minutes in a polymerization solution containing pyrrole as a heterocyclic monomer and 4-sulfo-1.8-naphthalic acid as a dopant compound represented by (Chemical Formula 1). Immediately after being pulled up by immersing in an oxidizer solution containing iron (III) sulfate as an oxidizer in an ethylene glycol aqueous solution for 10 minutes, this anode body is washed and repaired and dried (100 ° C.). It was. This series of operations was repeated 10 times to form a conductive polymer solid electrolyte layer.
[0044]
Next, the surface of this solid electrolyte layer was impregnated with an aqueous solution containing 2 wt% carbon particles and 2 wt% pyrogallol, adjusted to pH 10 by adding ammonia, and dried at 150 ° C. to form a carbon layer. Thereafter, a conductive layer of silver paste was formed to obtain a capacitor element.
[0045]
Next, the tantalum lead wire and the anode terminal are connected, and the cathode terminal is connected to the cathode layer of the capacitor element via a conductive adhesive so that the anode terminal and a part of the cathode terminal are exposed. A solid electrolytic capacitor was produced by coating with resin (D size: 7.3 × 4.3 × 2.8 mm).
[0046]
(Comparative Example 2)
In Example 5 above, after the dielectric oxide film was formed, the anode body was pulled up by being immersed in an ethylene glycol aqueous solution for 5 minutes in a polymerization solution containing pyrrole as a heterocyclic monomer and sodium butylnaphthalenesulfonate. A solid electrolytic capacitor was produced in the same manner as in Example 5 (D size: 7.3 × 4.3 × 2.8 mm).
[0047]
The initial values of the solid electrolytic capacitors of Examples 1 to 5 and Comparative Examples 1 and 2 and the ESR characteristics after the moisture resistance load test (60 ° C., 90%, 6.3 V, 500 hours) are shown in Table 1. The ESR characteristic was measured at 100 kHz.
[0048]
[Table 1]

[0049]
As is clear from Table 1, the comparison between Examples 1 to 4 and Comparative Example 1 shows that the use of sodium butyl naphthalenesulfonate as a dopant significantly deteriorates the ESR characteristics in the moisture resistance load test. This shows the high chemical conversion properties of the dopant compound represented by 1) with respect to aluminum. Further, from Examples 1 and 2, it can be seen that the same ESR characteristics can be obtained even when the conductive layer that is part of the solid electrolyte is a water-soluble polyaniline layer. In addition, by comparing Examples 1 and 3, when the solvent of the polymerization solution is ethanol, the ESR characteristic in the moisture resistance load test tends to be lower than that of Example 1, and it is effective to use water as the main solvent. It turns out that it is.
[0050]
Furthermore, when the polymerization process is chemical polymerization using an oxidizing agent from Example 4, ESR characteristics equivalent to Example 1 cannot be obtained, and the characteristics of the solid electrolytic capacitor obtained by electrolytic polymerization are better. I understand that Moreover, it is difficult to form a dense conductive polymer layer when a subtle dopant such as sodium butylnaphthalene sulfonate is used in comparison between Example 1 and Comparative Example 1 and Example 5 and Comparative Example 2. It can be seen that the initial capacitance characteristics are significantly deteriorated.
[0051]
(Example 6)
By changing the addition amount of the dopant compound represented by (Chemical Formula 1), the content of the dopant compound represented by (Chemical Formula 1) with respect to 1 mol of the monomer forming the conductive polymer is 0.01, 0.05,. Ten solid electrolytic capacitors were produced in the same manner as in Example 2 except that the amount was changed to 1, 0.5, and 0.7 mol.
[0052]
FIG. 2 shows the initial ESR characteristics of the solid electrolytic capacitor. The ESR characteristic was measured at 100 kHz.
[0053]
As is clear from FIG. 2, the solid electrolytic capacitor in which the content of the dopant compound represented by (Chemical Formula 1) with respect to 1 mol of the monomer forming the conductive polymer is 0.05 to 0.5 mol has excellent ESR characteristics, When the addition amount is less than 0.05 mol and exceeds 0.5 mol, the ESR characteristics tend to deteriorate. Therefore, in order to enable further excellent ESR and impedance characteristics as a capacitor by using the dopant compound represented by (Chemical Formula 1), the content of the dopant compound represented by (Chemical Formula 1) in the conductive polymer layer is It is preferable to prepare such that the amount is 0.05 to 0.5 mol with respect to 1 mol of the monomer forming the conductive polymer.
[0054]
(Example 7)
By adding 0.001, 0.005, 0.01, 0.05, 0.1, 0.2M of paranitrophenol to the polymerization liquid for forming a solid electrolyte shown in Example 1, a conductive polymer Ten solid electrolytic capacitors were produced in the same manner as in Example 1 except that paranitrophenol was added to a part of the layer.
[0055]
FIG. 3 shows the initial value of this solid electrolytic capacitor and the ESR characteristics after a high temperature no load (125 ° C., 1000 hours) test. The ESR characteristic was measured at 100 kHz.
[0056]
As is apparent from FIG. 3, the solid electrolytic capacitor with 0.01 to 0.1M of paranitrophenol added has excellent ESR characteristics, and when it is less than 0.01M and exceeds 0.1M, the ESR characteristics deteriorate. The tendency to do is seen. Therefore, in order to increase the order of the polymer skeleton by paranitrophenol and to obtain a solid electrolytic capacitor that is stable even under high temperature conditions, the amount of paranitrophenol added is preferably in the range of 0.01 to 0.1M. .
[0057]
Further, it was confirmed that the same effect can be obtained by adding paracyanophenol, parahydroxybenzoic acid, and parahydroxyphenol instead of paranitrophenol as an additive.
[0058]
(Example 8)
By adding 0.005, 0.01, 0.1, 1, 1.5, 2 wt% of sulfuric acid to the solid electrolyte forming polymerization solution shown in Example 1, a part of the conductive polymer layer was added. Ten solid electrolytic capacitors were produced in the same manner as in Example 1 except that sulfuric acid was doped.
[0059]
FIG. 4 shows the initial capacitance characteristics and the ESR characteristics after the moisture resistance load test (60 ° C., 90%, 6.3 V, 500 hours) of this solid electrolytic capacitor. The capacitance characteristics were measured at 120 kHz, and the ESR characteristics were measured at 100 kHz.
[0060]
As is apparent from FIG. 4, the solid electrolytic capacitor having an addition amount of sulfuric acid of 0.01 to 1 wt% is excellent in the capacitance and characteristics under high humidity. When the content exceeds 100%, the ESR characteristics in the moisture resistance test tend to deteriorate. Therefore, in order to obtain a solid electrolytic capacitor having a high capacity drawing rate by changing the polymer filling rate in which sulfuric acid is formed and having excellent moisture resistance characteristics, the amount of sulfuric acid added is 0.01 to 1 wt%. The range is preferable.
[0061]
Example 9
Ten solid electrolytic capacitors were prepared in the same manner as in Example 1 except that 0.1, 0.5, 1, 10, 20, and 30 wt% of 2-propanol was added to the polymerization liquid for forming the solid electrolyte shown in Example 1. Produced.
[0062]
FIG. 5 shows the initial leakage current characteristics (6.3 V, 1 minute value) of the solid electrolytic capacitor.
[0063]
As is clear from FIG. 5, the solid electrolytic capacitor having a 2-propanol addition amount of 0.5 to 20 wt% has excellent leakage current characteristics, but if it is less than 0.5 wt%, the leakage current characteristics tend to deteriorate. . On the other hand, if the amount of 2-propanol added exceeds 20 wt%, the polymerizability becomes worse and the polymerization time becomes longer. Therefore, by adding an organic solvent such as alcohol to the polymerization solution, the reactivity of the polymerization reaction is suppressed, current concentration on the edge portion is prevented, and the surface shape of the formed conductive polymer is improved. In order to obtain a solid electrolytic capacitor having excellent leakage current characteristics, the amount of 2-propanol added is preferably in the range of 0.5 to 20 wt%.
[0064]
Further, instead of 2-propanol as an organic solvent, methyl alcohol, ethyl alcohol, n-propyl alcohol, 2-propyl alcohol, n-butyl alcohol, 2-butyl alcohol, 3-butyl alcohol, tert-butyl alcohol, acetonitrile, acetone It was confirmed that the same effect was obtained even when tetrahydrofuran, ethylene glycol, γ-butyl lactone, dimethylformamide, or dimethyl sulfoxide was added.
[0065]
(Example 10)
Ten solid electrolytic capacitors were produced in the same manner as in Example 1 except that the polymerization voltage of the electrolytic polymerization shown in Example 1 was changed to 0.5, 1, 2, 3, 5V.
[0066]
FIG. 6 shows the initial ESR characteristics of the solid electrolytic capacitor. The ESR characteristic was measured at 100 kHz.
[0067]
As is apparent from FIG. 6, the solid electrolytic capacitor having a polymerization voltage of 1 to 3V has excellent ESR characteristics, and when it is less than 1V, the polymerization does not proceed rapidly, and when it exceeds 3V, a dense polymer is formed. However, ESR characteristics tend to deteriorate. Therefore, in order to control the reaction by the polymerization voltage and obtain a solid electrolytic capacitor having excellent ESR characteristics, the polymerization voltage is preferably in the range of 1 to 3V.
[0068]
Although only a solid electrolytic capacitor using valve action metals aluminum and tantalum as the anode has been described in the first embodiment, the present invention is not limited to these, and the valve action metal having an oxide film on the outer surface. The same effect can be obtained with other materials such as niobium and titanium.
[0069]
【The invention's effect】
As described above, the present invention provides a solid electrolytic capacitor in which a dielectric oxide film, a conductive polymer layer, and a cathode layer are sequentially laminated on the surface of an anode body made of a valve action metal. Since the compound represented by (Chemical Formula 1) is doped, a dopant having a carboxylic acid in the molecule such as naphthalic acid is excellent in chemical conversion, and therefore, particularly in an environment with leakage current characteristics and high temperature and high humidity. The solid electrolytic capacitor excellent in the following characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a solid electrolytic capacitor according to an embodiment of the present invention.
FIG. 2 is a characteristic diagram showing the relationship between the content of the dopant compound and the ESR characteristic.
FIG. 3 is a characteristic diagram showing the relationship between the amount of paranitrophenol added to the polymerization solution and the change in ESR characteristics.
FIG. 4 is a characteristic diagram showing the relationship between the amount of sulfuric acid added to the polymerization solution and the initial capacitance characteristics.
FIG. 5 is a characteristic diagram showing the amount of 2-propanol added to the polymerization liquid and the initial leakage current characteristics.
FIG. 6 is a characteristic diagram showing the relationship of the initial capacitance characteristics with the same electropolymerization voltage.
[Explanation of symbols]
1 Aluminum etched foil
2 Dielectric oxide film
3 Solid electrolyte layer
4 Carbon layer
5 Silver layer

Claims (14)

In a solid electrolytic capacitor in which a dielectric oxide film, a conductive polymer layer, and a cathode layer are sequentially laminated on the surface of an anode body made of a valve metal, the conductive polymer layer is a compound represented by at least (Chemical Formula 1) Is a solid electrolytic capacitor that is doped.

The solid electrolytic capacitor according to claim 1, wherein the amount of the compound represented by (Chemical Formula 1) is 0.05 to 0.5 mol with respect to 1 mol of the monomer forming the conductive polymer layer. 2. The solid electrolytic capacitor according to claim 1, wherein the monomer forming the conductive polymer layer is selected from at least one of pyrrole, thiophene, furan, aniline, and derivatives thereof. The solid electrolytic capacitor according to claim 1, wherein a phenol derivative is added to a part of the conductive polymer layer. The solid electrolytic capacitor according to claim 4, wherein the phenol derivative is selected from at least one of nitrophenol, cyanophenol, hydroxybenzoic acid, and hydroxyphenol. The solid electrolytic capacitor according to claim 1, wherein a part of the conductive polymer layer is doped with sulfuric acid. A method for producing a solid electrolytic capacitor, wherein a conductive polymer layer is formed using a polymerization solution containing a polymerizable monomer and water containing at least a compound represented by (Chemical Formula 1) as a main solvent.

The method for producing a solid electrolytic capacitor according to claim 7, wherein the polymerizable monomer is selected from at least one of pyrrole, thiophene, aniline, and derivatives thereof. The method for producing a solid electrolytic capacitor according to claim 7, wherein at least one of a phenol derivative, sulfuric acid, and alcohols is added to the polymerization solution. The solid electrolytic capacitor according to claim 9, wherein the phenol derivative is selected from at least one of nitrophenol, cyanophenol, hydroxybenzoic acid, and hydroxyphenol, and the concentration in the polymerization solution is 0.001 to 0.1M. Production method. The method for producing a solid electrolytic capacitor according to claim 9, wherein the concentration of sulfuric acid in the polymerization solution is 0.01 to 1 wt%. The method for producing a solid electrolytic capacitor according to claim 9, wherein the alcohol has 1 to 4 carbon atoms and the concentration in the polymerization solution is 0.5 to 20 wt%. The method for producing a solid electrolytic capacitor according to claim 7, wherein the conductive polymer is formed by electrolytic polymerization. The method for producing a solid electrolytic capacitor according to claim 13, wherein the voltage during electrolytic polymerization is 1 to 3 V.

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