JP3785480B2 - Paste-like conductive resin composition and method for forming sintered body thereof - Google Patents

Description

但し、一般式［Ｉ］において、Ｒ_１〜Ｒ_５ は、それぞれ独立に、水素原子又は炭素数Ｃ_１〜Ｃ_１２のアルキル基であり、Ｒ_６は、水酸基、炭素数Ｃ_１〜Ｃ_１２のアルコキシ基及び炭素数Ｃ_１〜Ｃ_１２のアルキル基より選ばれた少なくとも１種類の基である。また、少なくとも１個のチオール基（−ＳＨ）と２級水酸基を有していることが特徴である。
【００３９】
これを重合開始剤及び反応制御剤とするこの塊状重合法においては、実質的に無溶剤型で反応を進捗させることができ、上述した反応性の高いモノマーであっても、反応を暴走させることなく重合反応を進捗できる。その結果、分子量分布の狭い低重合体を安定に塊状重合させることができる。
【００４０】
そこで、一般式［Ｉ］で表される化合物として、例えば、チオグリセロール、１−メルカプト−２，３−プロパンジオール、２−メルカプト−３−ブタノール、２−メルカプト−３，４−ブタンジオール、１−メルカプト−２，３−ブタンジオール、１−メルカプト−２−ブタノール、２−メルカプト−３，４，４’−ブタントリオール、１−メルカプト−３，４−ブタンジオール、１−メルカプト−３，４，４’−ブタントリオール等を挙げることができる。本発明においては、これらの化合物のうち、塊状重合用の触媒として、チオグリセロールが特に好適に用いられる。
【００４１】
また、次式［II］で表される有機金属化合物（メタロセン化合物）とチオール類からなる塊状重合用触媒を用いて重合性不飽和化合物を重合させる塊状重合方法に準拠させることでも適宜好適に調製することができる。
【００４２】
【化２】

だだし、上記式［II］において、Ｍは、周期律表４Ａ属、４Ｂ属、５Ａ属、５Ｂの金属、クロム、ルテニウムおよびパラジウムよりなる群から選ばれる金属である。具体的にはＭは、チタン、ジルコニウム、クロム、ルテニウム、バナジウム、パラジウム、錫などである。
また、式［II］において、Ｒ１およびＲ２は、それぞれ独立に、
置換基を有することもある脂肪族炭化水素基、
置換基を有することもある脂環族炭化水素基、
置換基を有することもある芳香族炭化水素基、
置換基を有することもあるケイ素含有基よりなる群から選ばれる少なくとも一種の基、水素原子または単結合のいずれかである。
さらに、Ｒ１およびＲ２が共同して該２個の５員環を結合していてもよく、また、複数の隣接するＲ１またはＲ２は、共同して環状構造を形成していてもよい。
また、式［II］において、ａおよびｂは、それぞれ独立に、１〜４の整数であり、Ｘは塩素、臭素、ヨウ素などのハロゲン原子または水素原子の少なくとも一部がハロゲン原子で置換されていることもある炭化水素基であり、ｎは０または金属Ｍの価数−２の整数である。
【００４３】
そこで、式［II］で表される有機金属化合物としては、例えば、ジシクロペンタジエン−Ｔｉ−ジクロライド、ジシクロペンタジエン−Ｔｉ−ビスフェニル、ジシクロペンタジエン−Ｔｉ−ビス−２，３，４，５，６−ペンタフルオロフェニ−１−イル、ジシクロペンタジエン−Ｔｉ−ビス−２，３，５，６−テトラフルオロフェニ−１−イル、ジシクロペンタジエン−Ｔｉ−ビス−２，５，６−トリフルオロフェニ−１−イル、ジシクロペンタジエン−Ｔｉ−ビス−２，６−ジフルオロフェニ−１−イル等のチタノセン化合物；ジシクロペンタジエン−Ｚｒ−ジクロライド、ジシクロペンタジエン−Ｚｒ−ビスフェニル、ジシクロペンタジエン−Ｚｒ−ビス−２，３，４，５，６−ペンタフルオロフェニ−１−イル等のジルコノセン化合物；ジシクロペンタジエル−Ｖ−クロライド、ビスペンタメチルシクロペンタジエニル−Ｖ−クロライド等を挙げることができる。これらの有機金属化合物は単独又は２種以上を組合わせて使用することができる。
【００４４】
この有機金属化合物は、触媒量として、重合性不飽和化合物１００重量部に対して、通常、１〜０．００１重量部、好ましくは、０．０１〜０．００５重量部の量で好適に使用される。
また、チオール類としては、エチルメルカプタン、ブチルメルカプタン、ヘキシルメルカプタン等のアルキルチオール類、ヘニルメルカプタン、ベンジルメルカプタン、β−メルカプトプロピオン酸、３−メルカプトプロピル−トリメトキシシラン、チオフェーニル等を挙げることができる。この触媒において、有機金属化合物が反応全体に活性化触媒的に作用し、チオール類は重合開始作用があり、チオール類の使用量は、分子量、重合率に影響を与える。
従って、有機金属化合物とチオール類とは、通常、１００：１〜１：５００００の範囲のモル比で使用される。また、重合速度や重合度を調整する目的で、ジスフィド化合物、トリスルフィド化合物、テトラスルフィド化合物を使用することができる。
【００４５】
本発明においては、既に上述した（メタ）アクリル系重合体としては、好ましくは、重量平均分子量Ｍｗが５００〜１００００、更に好ましくは、１０００〜７０００の範囲にある低重合体を適宜好適に使用することができる。
このＭｗが下限値未満では、重合硬化させた塗布ペースト層の形体賦形性が低下し、また、機能性無機粉体に十分な結着性が発現されない。一方、このＭｗが上限値を超えると樹脂粘度が高くなり、ペースト粘度を上げるため、モノマー成分を増やしたり、粉体濃度を下げたり等の調整を要して経済的に不利になることから好ましくない。
【００４６】
また、本発明においては、この低重合体のガラス転移温度（Ｔｇ）は、好ましくは、−８０〜５０℃の範囲にあることが好適である。このＴｇがこの範囲から外れると、すなわち、Ｔｇが５０℃を超えると重合硬化後の塗膜の可撓性が悪く、また、ビヒクルの粘度が高くなり、スクリーン塗工時の刷毛切れ性、塗工性を低下させる傾向にある。一方、Ｔｇが−８０℃より低い場合、重合硬化後の塗膜の形体賦形性が悪く、また、焼成時のフィラー保持性を低下させる等の理由から好ましくない。
【００４７】
また、本発明においては、この低重合体の酸価が、好ましくは、６０〜１８０の範囲にあることが好適である。
すなわち、本発明においては、既に公知のペースト用バインダー樹脂であって、側鎖にカルボキシル基と不飽和基を有するアクリル系共重合体の低重合体の傾向とは異なり、そのペースト状組成物の経時的な粘度上昇によって、塗布性が損なわれることがない。
特に、本発明においては、用いる導電性無機粉体の表面濡れ性等にも影響されるが、その酸価が上述した範囲から外れると、本発明の導電性樹脂ペースト中の導電性無機粉体に対して、分散剤としての効果を損なう傾向から好ましくない。
【００４８】
また、本発明において、ラジカル反応をする重合性不飽和基を複数個（２〜６個）有する重合性多官能モノマーとして、例えば、エチレングリコールジ（メタ）アクリレート、ジエチレングリコールジ（メタ）アクリレート、テトラエチレングリコールジ（メタ）アクリレート、プロピレングリコールジ（メタ）アクリレート、ポリプロピレングリコールジ（メタ）アクリレート、ブチレングリコールジ（メタ）アクリレート、ネオペンチルグリコールジ（メタ）アクリレート、１，６−ヘキサグリコールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、グリセリンジ（メタ）アクリレート、ペンタエリスリトールジ（メタ）アクリレート、ペンタエリスリトールトリ（メタ）アクリレート、ジペンタエリススリトールペンタ（メタ）アクリレート、２，２−ビス（４−（メタ）アクリロキシジエトキシフェニル）プロパン、２，２−ビス（４−（メタ）アクリロキシポリエトキシフェニル）プロパン、２−ヒドロキシ−２−メチル−１−フェニル−プロパン−１−オン、２，４，６−トリメチルベンゾイルジフェニル−フォスフィンオキサイド、２−ベンジル−２−ジメチルアミノ−１−（４−モルフォリノフェニル）−ブタノン−１、２−ヒドロキシ−３−（メタ）アクリロイルオキシプロピル（メタ）アクリレート、エチレングリコールジグリシジルエーテルジ（メタ）アクリレート、ジエチレングリコールジグリシジルエーテルジ（メタ）アクリレート、フタル酸ジグリシジルエステルジ（メタ）アクリレート、グリセリントリアクリレート、グリセリンポリグリシジルエーテルポリ（メタ）アクリレート等に代表される多官能アクリレートや、これらに対応するメタアクリレートモノマーが挙げることができる。
【００４９】
特に、ＵＶ硬化型である場合に、光重合開始剤として、ベンゾフェノン、ο−ベンゾイル安息香酸メチル、４，４−ビス（ジメチルアミン）ベンゾフェノン、４，４−ビス（ジエチルアミン）ベンゾフェノン、α−アミノアセトヘノン、４，４−ジクロロベンゾフェノン、４−ベンゾイル−４−メチルジフェニルケトン、ジべンジルケトン、フロオレノン、２，２−ジエトキシアセトフェノン、２，２−ジメトキシ−２−フェニルアセトヘノン、２−ヒドロキシ−２−メチル−１−フェニル−プロパン−１−オン、２−ヒドロキシ−２−メチルプロピオフェノン、チオキサントン、２−メチルチオキサントン、２−クロロチオキサントン、ベンジルジメチルケタール、ベンジルメトキシエチルアセタール、ベンゾインメチルエーテル、ベンゾインブチルエーテル、２，４，６−トリメチルベンゾイルジフェニル−フォスフィンオキサイド、２−ベンジル−２−ジメチルアミノ−１−（４−モルフォリノフェニル）−ブタノン−１、トアントラキノン、２−ｔｅｒｔ−ブチルアントラキノン、２−アミルアントラキノン、β−クロロアントラキノン、アントロン、ベンズアントロン、メチレンアントロン、４−アジドベンジルアセトフェノン、２，６−ビス（ρ−アジドベンジリデン）シクロヘキサン、２，６−ビス（ρ−アジドベンジリデン）−４−メチルシクロヘキサノン、２−フェニル−１，２−ブタジオン−２−（ο−メトキシカルボニル）オキシム、ベンゾチアゾールジスルフィド等を挙げることができ、これらの光重合開始剤の１種又は２種以上を組合わせて使用することができる。
これらの光重合開始剤は、（Ｂ）の１００重量部に対して、０．０５〜５重量部を添加することができる。
添加量が下限値よりも少ないと導電性樹脂ペーストの光硬化性が低く好ましくなく、また、上限値を超えて添加させると可視光でも硬化してポットライフを短くし、焼成後、残査を残す傾向があり好ましくない。
【００５０】
また、必要に応じて、ラジカル反応を誘起させる光重合開始剤に併用させて、光重合開始助剤を用いて、光重合開始反応を促進させ、重合硬化を効率的にすることができる。このような光重合開始助剤として、例えば、トリエチレンテトラミン、トリエタノールアミン、メチルジエタノールアミン、トリイソプロパノールアミン、ｎ−ブチルアミン、ジメチルチオキサントン、イソプロピルチオキサントン、Ｎ−メチルジエタノールアミン、４−ジメチルアミノ安息香酸エチル等の脂肪族、芳香族アミンを挙げることができる。
これらの光開始助剤は、光重合開始剤１重量部に対して、０．１〜５重量部の範囲で添加できる。
また、このように導電性樹脂ペーストの有機ビヒクルを感光性樹脂組成物にすることで、レジスト塗布層としてパターン形成をすることができるので、適宜ホトレジスト法による所定のパターン形成をすることができる。
【００５１】
また、必要に応じて、このビヒクルに他の添加剤として、可塑剤、分散剤、増粘剤、沈降防止剤、消泡剤、レベリング剤又は熱重合禁止剤等を適宜に添加することができる。
例えば、ペーストの流動性を向上させる目的で添加される可塑剤としては、 ジエチルフタレート、ジブチルフタレート、ブチルベンジルフタレート、ジベンジルフタレーチ、ポリアルキレングリコール、トリエチレングリコールジアセテート、ポリエチレンオコシド等が挙げられ、特に、光硬化性感度及び熱分解・揮発性を損ねない範囲において添加することができる。
【００５２】
＜導電性焼結体の形成方法＞
各種のエレクトロニクス製品及びその周辺機器として、例えば、基板上に形成されたセラミックコンデンサ素子、圧電体素子、焦電体素子、半導体デバイス等のエレクトロニクス部品には、内部電極、回路パターン、外部電極端子等の導電性部材が組み込まれている。
その形成方法は、例えば、ＣＶＤ・焼結法、スパッタ法、又は導電性ペーストを塗布・焼結法等によって形成することができる。
【００５３】
既に上述した如く、本発明による無溶剤型のバインダー樹脂組成物（ビヒクル）に、導電性金属及び／又はその導電性合金の無機粉体を混練させることで容易にペースト状になり、既に上述した塗布性、賦形性及び焼結性等に優れる本発明による導電性樹脂ペーストを調製することができる。
このように得られた導電性樹脂ペーストをアルミナ等のセラミック基板上又は各種のセラミックグリーンシートの基材上に塗布することができる。その塗布法としては、スクリーン印刷法、バーコーター法、 ロールコーター法、スリットダイコーター法、ドクターブレードコーター法、感光性樹脂ペースト法（ホトレジスト形成法）が挙げられ、適宜好適に使用することができる。
【００５４】
また、このようなペーストを塗布させる用途例としては、例えば、アルミナ、窒化アルミナ等のセラミック基板や、コージェライト、ムライト、ステアタイト、ガラス成分を主成分とした低温焼成用基板のセラミックグリーンシート上に内層又は外層導電体として、又は、タンタルコンデンサー、ペロブスカイト型複合酸化物粒子の強誘電体層を用いた積層セラミックコンデンサー、積層圧電セラミック素子、積層セラミック（ＬＣ）フィルター等の外部電極として適宜塗布させて焼結形成することができる。
【００５５】
また、上述したセラミック基板上又はセラミックグリーンシート等の基材上に塗布される導電性ペーストは、絶縁体層、誘電体層、絶縁体層−誘電体層等上に積層形成されるか、又は絶縁体層−導電層−絶縁体層、絶縁体層−誘電体層−導電体層−絶縁体層、絶縁体層−誘電体層−導電体層−誘電体層等のように層間導電材として形成されることになる。
【００５６】
また、本発明のように、ペースト状樹脂組成物が、感光性樹脂組成物である場合には、これらの塗布法に係わって、好ましくは、レジスト形成法（フォトリソグラフィー）で、塗布・パターン露光させて、現像−キュア−プレー焼成−焼結させて回路パターンとして導電性焼結層を形成させることができる。
【００５７】
焼成用導電性樹脂ペーストの導電材としては、金、銀、白金、パラジウム、銀−パラジウム合金、ニッケル、アルミニウム、アルミニウム−Ｓｉ、アルミニウム−銅−Ｓｉ、銅、銅−銀合金、チタニウム、チタニウム−Ｓｉ、タングステン、タングステン−Ｓｉ、モリブデン、モリブデン−Ｓｉ、ＩＴＯ等が挙げられる。また、必要に応じて、導電性粉体の基板に対する密着性の向上又は通常、焼結させる６００〜１１００℃の温度領域における、焼結性、焼結温度の低下、熱膨張率等の改良・改善等から、必要に応じて、導電性樹脂ペーストにガラスフリットを混ぜることができる。
【００５８】
このガラスフリットとしては、好ましくは、アルカリ金属や、アルカリ土類金属を実質的に含まれない系であることから、例えば、酸化ビスマス、酸化珪素、酸化ホウ素、酸化亜鉛、酸化ジルコニウム等を主成分とする、ＺｎＯ−Ｂ_２Ｏ_３−ＳｉＯ_２系、ＰｂＯ−Ｂ_２Ｏ_３−ＳｉＯ_２系、ＰｂＯ−Ｂ_２Ｏ_３−ＳｉＯ_２−Ａｌ_２Ｏ_３系、ＰｂＯ−ＺｎＯ−Ｂ_２Ｏ_３−ＳｉＯ_２系等を挙げることができる。
本発明においては、導電性粉体１００重量部に対して、ガラスフリット０．１〜１０重量部を含有させることができる。
【００５９】
また、必要に応じて、このような低融点ガラスの誘電性粉体に係わって、アルミナ、窒化アルミニウム、ムライト、コージエライト、結晶化ガラス等の低誘電率の粉体や、チタン酸バリウム、チタン酸ストロンチウム、チタン酸鉛、チタン酸ジルコン酸鉛、チタン酸ネオジウム等の高誘電率粉体や、その他の窒化珪素、炭化珪素のセラミックス粉体や、他の高融点ガラス等の単独又は２種以上を組合わせてフィラーとして添加することができる。
【００６０】
【実施例】
以下に、本発明を更に実施例によって説明するが、本発明はこれらにいささかも限定されるものではない。
【００６１】
（参考例１）
導電性樹脂ペーストのバインダー樹脂組成物（ビヒクル）の構成成分である（Ａ）（メタ）アクリル系重合体の低重合体を調製する。
撹拌装置、窒素導入管、温度計及び還流冷却管を備えたフラスコに、２−エチルヘキシルメタクリレート１００重量部を仕込みフラスコ内に窒素ガスを導入しながらフラスコ内の内容物を８０℃に加熱した。
次いで、十分に窒素ガス置換したチオグリセロール７重量部を撹拌下のフラスコ内に添加した。その後、撹拌中のフラスコ内の内容物の温度が８０℃に維持できるように、冷却及び加温を２時間行った。その後続けて、撹拌中のフラスコ内の内容物の温度が９５℃に維持できるように、冷却及び加温を行いながら、更に重合反応を６時間行い、次いで、アゾビスイソブチロニトリル０．１６重量部を添加し、更に２時間９５℃にて重合を行った。
【００６２】
上記のようにして合計で８時間の反応後、反応物の温度を室温に戻し、反応物にハイドロキノンを０．０５重量部添加して反応物（ａ−１）を得た。
得られた重合反応物（ａ−１）の単量体残存率をガスクロマトグラフィーを用いて測定した結果、その重合率が９９．４％であった。
また、そのゲルパーミエーションクロマトグラフィー（ＧＰＣ）により測定した分子量は、Ｍｗ＝３８００、Ｍｎ＝１７００であり、分散指数＝２．１であり、２３℃における粘度が３３０（Ｐａ・ｓ）である（メタ）アクリル系重合体の低重合体であった。
【００６３】
（参考例２）
参考例１において、モノマーとしてＭＭＡ（メチルメタクリレート）を使用し、添加するチオグリセロールを２４重量部とした以外は参考例１と同様にして重合させて反応物（ａ−２）を得た。
得られた重合反応物（ａ−２）の単量体残存率をガスクロマトグラフィーを用いて測定した結果、重合率が９８．８％であった。
また、そのＧＰＣにより測定した分子量は、Ｍｗ＝１１００、Ｍｎ＝７９０であり、分散指数＝１．３９であり、２３℃における粘度が２．３（Ｐａ・ｓ）であるメチルメタクリル系重合体の低重合体であった。
【００６４】
（参考例３）
参考例１において、チオグリセロールの添加量を３．９重量部とした以外には、参考例１と同様にして重合させて反応物（ａ−３）を得た。
得られた重合反応物（ａ−３）の単量体残存率をガスクロマトグラフィーを用いて測定した結果、重合率が９９．８％であった。
また、そのＧＰＣにより測定した分子量は、Ｍｗ＝７４００、Ｍｎ＝４３００であり、分散指数＝１．６９であり、２３℃における粘度は、９９０（Ｐａ・ｓ）であるメチルメタクリル系重合体の低重合体であった。
【００６５】
実施例１
２００ｍｌビーカーに、参考例１で得られた（メタ）アクリル系重合体の低重合体（ａ−１）の５０重量部と、重合性多官能モノマーであるエチレングリコールジメタクリレートの５０重量部とを採り、十分均一になるまで、攪拌混合を行い本発明に用いるアクリル系のバインダー樹脂組成物（ビヒクル）の（ｂ−１）を得た。得られた、ビヒクル（ｂ−１）の粘度は、２３℃で０．０８（Ｐａ・ｓ）であった。
【００６６】
（熱重合性ペースト及びその硬化）
次いで、平均粒子径３．２μｍの銅粉末５０重量部に、上記ビヒクル（ｂ−１）１０重量部と、ラジカル開始剤として１，１，３，３−テトラメチルブチルパーオキシ−２−エチルヘキサノール０．４重量部と、禁止剤としてハイドロキノン０．０４重量部とをロールミルで十分に混練させて、銅粉体のペースト状導電性樹脂組成物（ｃ−１）を調製した。得られたそのペースト（ｃ−１）の粘度は、６．８（Ｐａ・ｓ）であった。
【００６７】
次いで、上記ペースト（ｃ−１）をアルミナ基板上にバーコーターにて、膜厚５０μｍに成るように塗布し、窒素雰囲気下で、１２０で５分間加熱重合硬化を行った。得られた塗膜厚みは４８μｍと殆ど体積減少もなく、表面のひび割れ等も見られなかった。しかも、その加熱重合硬化に際して、塗布層は流れ崩れることなく良好な形体賦形性を付与させることができた。
【００６８】
（ＵＶ重合性ペースト及びその硬化）
平均粒子径３．２μｍの銅粉末５０重量部に、上記ビヒクル（ｂ−１）１０重量部と、（ガラス粉末として、酸化亜鉛８２重量％、酸化ホウ素８重量％、酸化珪素１０重量％の組成比のガラスフリット粉体８重量部に）、上記ビヒクル（ｂ−１）１０重量部と、ＵＶラジカル開始剤としてイルガノックスＩ−３６９ ０．３重量部と、禁止剤としてハイドロキノン０．０１重量部とを混練させて、銅粉体のペースト状導電性樹脂組成物（ｄ−１）を調製した。得られたそのペースト（ｄ−１）の粘度は、８．７（Ｐａ・ｓｅｃ）であった。
【００６９】
次いで、上記ペースト（ｄ−１）をアルミナ基板上にバーコーターにて、膜厚５０μｍになるように塗布し、窒素雰囲気下で、光源として高圧水銀灯を用い、照射強度２１４ｍＷ／ｃｍ^２、積算光量１９３０ｍＪ／ｃｍ^２になるよう、塗膜表面から、ＵＶ露光を行った。
得られた塗膜厚みは４９μｍと殆ど体積減少もなく、表面のひび割れ等も見られず、しかも、そのＵＶ重合硬化に際して、塗布層は流れ崩れることなく良好な形体賦形性を付与させることができた。
【００７０】
（プレー焼成及び焼結）
次いで、基板上にペーストｃ−１及びｄ−１を塗布・熱及びＵＶ重合硬化させた上記の試験体のｃ−１及びｄ−１を窒素雰囲気下の常温から３５０℃まで２０分間で昇温させ、３５０℃で２０分間、加熱処理を行った。その結果、各試験体の塗布層中のビヒクルの有機樹脂分を完全に熱分解・揮散除去させることができた。
すなわち、加熱処理を通しての目視観察では、塗布層上には、残渣や煤などが見られず、また、その表面及びサンドペーパを掛けて削りとられた表面のそれぞれを、MEKを湿らせたガーゼで拭いたが、ガーゼ上には汚れ成分が付着しなかった。
【００７１】
次いで、上記したプレー焼成で有機樹脂分を除去した試験体のｃ−１及びｄ−１を、窒素雰囲気下で、９００℃で３０分間保持させて塗布層の銅粉体を焼結させた。その結果、目視的に焼結層に剥離、亀裂等の異常がなく、良好な銅金属光沢を有していた。
【００７２】
実施例２
２００ｍｌビーカーに、参考例２で得られたメチルメタアクリル系重合体の低重合体（ａ−２）の６５重量部と、エチレングリコールジメタクリレート３５重量部とを採り、十分均一になるまで攪拌混合させて本発明に用いるアクリル系のバインダー樹脂組成物（ビヒクル）の（ｂ−２）を得た。得られた、ビヒクル（ｂ−２）の粘度は、２３℃で０．０３７（Ｐａ・ｓ）であった。
【００７３】
（熱重合性ペースト及びその硬化）
次いで、平均粒子径３．２μｍの銅粉末５０重量部に、上記ビヒクル（ｂ−２）７重量部に、実施例１において、ラジカル開始剤を０．２重量部とした以外は、実施例１と同様にしてロールミルで十分に混練させて、銅粉体のペースト状導電性樹脂組成物（ｃ−２）を調製した。得られたそのペースト（ｃ−２）の粘度は、７．２（Ｐａ・ｓ）であった。
【００７４】
次いで、上記ペースト（ｃ−２）をアルミナ基板上にバーコーターにて、膜厚５０μｍに成るように塗布し、窒素雰囲気下で、１２０℃で５分間加熱重合を行った。得られた塗膜厚みは４８μｍと殆ど体積減少もなく、表面のひび割れ等も見られなく、しかも、その熱重合硬化に際して、塗布層は流れ崩れることなく良好な形体賦形性を付与させることができた。
【００７５】
（ＵＶ重合性ペースト及びその硬化）
平均粒子径３．２μｍの銅粉末５０重量部に、上記ビヒクル（ｂ−２）７重量部に、実施例１と同様にしてＵＶ重合性の銅粉体のペースト状導電性樹脂組成物（ｄ−２）を調製した。得られたそのペースト（ｄ−２）の粘度は、７．２（Ｐａ・ｓ）であった。
次いで、得られたＵＶ硬化性のペースト（ｄ−２）を実施例１と同様にしてアルミナ基板上にバーコーターにて、膜厚５０μｍに成るように塗布し、窒素雰囲気下で、実施例１と同様の条件で、ＵＶ露光を行い塗布ペースト層を重合硬化させた。得られた塗膜厚みは４８μｍと殆ど体積減少もなく、表面のひび割れ等も見られず、しかも、そのＵＶ重合硬化に際して、塗布層は流れ崩れることなく良好な形体賦形性を付与させることができた。
【００７６】
（プレー焼成及び焼結）
次いで、アルミナ基板上にペーストｃ−２及びｄ−２を塗布・熱及びＵＶ重合硬化させた上記試験体のｃ−２及びｄ−２を実施例１と同様の条件でプレー焼成させて、各試験体の塗布層中の有機ビヒクルを除去するための加熱処理（プレー焼成）を行った。その結果、実施例１の試験体と同様に、各試験体の塗布層中のビヒクルの有機樹脂分を完全に熱分解・揮散除去させることができた。
【００７７】
すなわち、実施例１の試験体と同様に、加熱処理を通しての目視観察では、塗布層上には、残渣や煤などが見られず、また、その表面及びサンドペーパを掛けて削りとられた表面のそれぞれを、MEKを湿らせたガーゼで拭いたが、ガーゼ上には汚れ成分が付着しなかった。
また、上記したプレー焼成で有機樹脂分を除去した試験体のｃ−２及びｄ−２を実施例１の試験体と同様に焼結させた。その結果、目視的に焼結層に剥離、亀裂等の異常がなく、良好な銅金属光沢を有する焼結層が得られた。
【００７８】
実施例３
２００ｍｌビーカーに、参考例３で得られたメチルメタアクリル系重合体の低重合体（ａ−３）の７０重量部と、エチレングリコールジメタクリレート３０重量部とを採り、十分均一になるまで攪拌混合させて本発明に用いるアクリル系のバインダー樹脂組成物（ビヒクル）の（ｂ−３）を得た。得られた、ビヒクル（ｂ−３）の粘度は、２３℃で７．８（Ｐａ・ｓ）であった。
【００７９】
（熱重合性ペースト及びその硬化）
このビヒクル（ｂ−３）１５重量部に、実施例１において、ラジカル開始剤を０．４５重量部とした以外は、実施例１と同様にして銅粉体のペースト状導電性樹脂組成物（ｃ−３）を調製した。得られたそのペースト（ｃ−３）の粘度は、７．２（Ｐａ・ｓ）であった。
【００８０】
次いで、上記ペースト（ｃ−３）をアルミナ基板上にバーコーターにて、膜厚５０μｍに成るように塗布し、窒素雰囲気下で、１２０℃で５分間加熱重合を行った。得られた塗膜厚みは４９μｍと殆ど体積減少もなく、表面のひび割れ等も見られなく、しかも、その熱重合硬化に際して、塗布層は流れ崩れることなく良好な形体賦形性を付与させることができた。
【００８１】
（ＵＶ重合性ペースト及びその硬化）
このビヒクル（ｂ−３）１５重量部に、実施例１において、ラジカル開始剤を０．４５重量部とした以外は、実施例１と同様にして銅粉体のペースト状導電性樹脂組成物（ｃ−３）を調製した。得られたそのペースト（ｃ−３）の粘度は、７．５（Ｐａ・ｓ）であった。
次いで、得られたＵＶ硬化性のペースト（ｄ−３）を実施例１と同様にしてアルミナ基板上にバーコーターにて、膜厚５０μｍに成るように塗布し、窒素雰囲気下で、実施例１と同様の条件で、ＵＶ露光を行い塗布ペースト層を重合硬化させた。得られた塗膜厚みは４９μｍと殆ど体積減少もなく、表面のひび割れ等も見られず、しかも、そのＵＶ重合硬化に際して、塗布層は流れ崩れることなく良好な形体賦形性を付与させることができた。
【００８２】
（プレー焼成及び焼結）
次いで、ガラス基板上にペーストｃ−３及びｄ−３を塗布・熱及びＵＶ重合硬化させた上記試験体のｃ−３及びｄ−３を実施例１と同様の条件でプレー焼成させて、各試験体の塗布層中の有機ビヒクルを除去するための加熱処理（プレー焼成）を行った。その結果、実施例１の試験体と同様に、各試験体の塗布層中のビヒクルの有機樹脂分を完全に熱分解・揮散除去させることができ、同様に、加熱処理を通しての目視観察や、塗布素中のMEKを湿らせたガーゼでの拭いで、残査、コーキング質が確認されなかった。また、上記したプレー焼成で有機樹脂分を除去した試験体のｃ−３及びｄ−３を実施例１の試験体と同様に焼結させた。その結果、目視的に焼結層に剥離、亀裂等の異常がなく、良好な銅金属光沢を有する焼結層が得られた。
【００８３】
実施例４
実施例１で得られたビヒクル（ｂ−１）１０重量部に、平均粒径２μｍのガラスフリット７重量部と、平均粒子径３．２μｍの銅粉末４５重量部とした以外は実施例１のペースト（ｄ−１）と同様にして、ＺｎＯ−Ｂ_２Ｏ_３−ＳｉＯ_２系、のガラスフリット入りのＵＶ重合性の銅粉体のペースト状導電性樹脂組成物を調製し、アルミナ基板上にバーコーターにて、膜厚３０μｍに成るように塗布し、窒素雰囲気下で、実施例１と同様の条件で、ＵＶ露光を行い塗布ペースト層を重合硬化（キュア）させた。
次いで、キュアさせたこの塗布ペースト上に、実施例１で同様に調製したＵＶ重合性の銅粉体のペースト状導電性樹脂組成物（ｄ−２）を、バーコーターにて、膜厚５０μｍに成るように塗布し、窒素雰囲気下で、実施例１と同様の条件で、ＵＶ露光を行い塗布ペースト層を重合硬化させて、導電性ペーストの積層体を形成させた。
【００８４】
（積層体のプレー焼成及び焼結）
次いで、この基板上の積層体を窒素雰囲気下の常温から３５０℃まで３０分間で昇温させ、３５０℃で３０分間、加熱処理を行った。その結果、目視的に積層塗布層に剥離、亀裂等を発生させることなく積層塗布層中のビヒクルの有機樹脂分を完全に熱分解・揮散除去させることができた。
次いで、窒素雰囲気下の８７０℃で４０分間保持させて焼結したとこら目視的に焼結層に剥離、亀裂等の異常がなく、良好な金属銅光沢を有していた。
【００８５】
比較例１
比較例１においては、実施例２において用いたＭｗ１１００のメチルメタクリル系重合体の低重合体（ａ−２）に代えて、Ｍｗ５００未満のものを用いてビヒクルを調製した。その結果、ビヒクルはしゃぶしゃぶ状で、塗布性が著しく低下し、しかも、溶剤性、塗布後のキュアを最適にさせるため、重合性多官能モノマーをビヒクル成分として組合わせることができず、その結果、ペーストの賦形性を著しく低下させた。
【００８６】
比較例２
比較例２においては、実施例３において用いたＭｗ７４００のメチルメタクリル系重合体の低重合体（ａ−３）に代えて、Ｍｗ１００００を超えるＭｗ１１０００のものを用いてビヒクルを調製した。その結果、塗布後のペースト層をキュアさせて、塗布ペースト層に形体賦形性を発揮させる多官能モノマーを組合わせ配合量も増加させることになり、ビヒクルコストを経済的に不利にさせるだけでなく、塗布性、粉体の充填量を低下させることになり、そのために溶剤を添加さた溶剤型ビヒクルとなる。
【００８７】
【発明の効果】
以上から、本発明によれば、導電性樹脂ペーストにおいて、そのバインダー樹脂組成物（ビヒクル）が、Ｍｗが５００〜１００００程度の低重合体の（メタ）アクリル系重合体と、熱硬化又はＵＶ硬化性の低分子量の重合性多官能モノマーとを含有する流動粘性体として形成されている。
これによって、このビヒクルは、無溶剤であるが、溶剤性を兼ね備えた塗布性に優れ、また、塗布後の塗布層を重合硬化されて、導電性無機粉体に賦形性を賦与させ、しかも、低温度で容易に熱分解除去されることから、塗布層は、気泡孔や、亀裂や、撓みや、収縮等の発生が防止されて、良好な焼結性を発揮させる導電性樹脂ペーストを提供することができる。
【００８８】
また、従来法の溶剤型のビヒクルに比較して、ペースト中の導電性無機粉体の充填量を高められることから、塗布層のプレー焼成及び焼結時の熱収縮等を低減させることができ、寸法安定性に優れた導電性焼結体を形成することができる。
【００８９】
また、従来法ペーストとは異なり、有機ビヒクルを除去させるプレー焼成を不活性雰囲気下で行えることから、特に、銅等の耐酸化性の低い導電性金属及び／又はその合金粉体の導電性、燒結性及び基板との密着性等を低下させない。
【００９０】
しかも、無溶剤型であることから、ペースト調製時、その塗布・プレー焼成時における揮発、分解飛散する有機揮発成分を低下させられることから、作業環境及び地球環境保全の立場から、環境汚染を低減できる導電性樹脂ペーストを提供できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a paste-like resin composition for a conductive sintered body, and more specifically, there is no paste-like conductive resin composition for a conductive sintered body to be applied and sintered on a ceramic substrate or the like. The present invention relates to a paste-type resin composition for a conductive sintered body which is a solvent type and has excellent coatability, shape shaping, and sinterability, and a method for forming a conductive sintered body formed using the paste-like resin composition.
[0002]
[Prior art]
In recent years, with the increase in functionality, performance, size, and thickness of electronic equipment, semiconductor devices that play the core role are various electronic products, mechanical devices used in various manufacturing processes, or automobiles, airplanes, and ships. In air conditioners, rice cookers, VTRs, etc., they are incorporated into a memory such as a computer (microcomputer) as a wide variety of IC chips in logic and analog.
[0003]
Along with the rapid progress in the information society in recent years, DSPs (digital signal processors) are used for telephones, audio, DVDs, servers, etc., and CCDs (solid-state image sensors) are used for VTRs, digital cameras, and gastrocameras. , Artificial satellites, electrophotographic image forming devices such as printers, facsimiles, copiers, etc., flash memory for mobile phones, electronic notebooks, IC cards, etc., and modem ICs for information communication , Internet and so on.
[0004]
Thus, in an IC chip and a peripheral device using the IC chip, a conductive member is used as an electrode material or a circuit pattern. Examples of the forming method include a CVD / sintering method, a sputtering method, a coating / sintering method of a conductive paste, and the like. That is, these conductive members are laminated or formed on an insulating layer, a dielectric layer, an insulating layer-dielectric layer, etc. on a substrate such as a ceramic substrate such as alumina or a ceramic green sheet. Formed as an interlayer conductive material such as body layer-conductive layer-insulator layer, insulator layer-dielectric layer-conductor layer-insulator layer, insulator layer-dielectric layer-conductor layer-dielectric layer, etc. Has been.
[0005]
Therefore, conventionally, examples of the conductive material of the conductive paste for firing include silver, gold, platinum, silver-palladium, nickel, copper, copper-silver alloy, tungsten, molybdenum, and the like, for example, JP-A-6-295614. The gazette states that the conductive material is Ag. _x Cu _1-x A conductive paste for firing is described in which a copper alloy is used and a vehicle is made of an acrylic resin such as polybutyl methacrylate and a solvent such as terpenol.
[0006]
Japanese Patent Laid-Open No. 5-212833 discloses that a conductive material is a metal such as copper or an alloy thereof, and a polymer such as methyl methacrylate having a molecular weight of 100,000 or more and a polymerizable polymer such as methacrylic acid. A photopolymerizable conductive paste composed of a functional monomer and a solvent such as ethylene glycol monoethyl ether is described.
[0007]
JP-A-5-206600 discloses that a conductive material is a metal or alloy such as copper, a vehicle is a polymer such as methyl methacrylate having a molecular weight of 1000 or more, and a polymerizable polyfunctional monomer such as methacrylic acid. And a laminate for forming a conductor pattern in which a photopolymerizable conductive paste made of a solvent such as ethylene glycol monoethyl ether is laminated on a ceramic green sheet that can be fired at 1000 ° C. or lower.
[0008]
Furthermore, Japanese Patent Application Laid-Open No. 9-282941 discloses a multilayer ceramic electronic component in which an internal electrode, a through hole or a via hole is formed by screen printing or filling a ceramic paste sheet with a conductive paste.
[0009]
[Problems to be solved by the invention]
In the situation as described above, various electronic products and peripheral devices thereof, for example, ceramic capacitors formed on a substrate, piezoelectric / pyroelectric elements, semiconductor devices and other electronic products include internal electrodes, Conductive members such as circuit patterns and external electrode terminals are incorporated.
[0010]
Such a conductive material is usually used for patterning as a thin film layer on an insulating layer or dielectric layer on a substrate by a CVD method, a sputtering method, etc. After applying or embedding a conductive paste on the surface of a substrate such as a sheet, drying and curing, and then removing the solvent, binder resin, etc. by burning off under a thermal history, sintering and conductive sintering The layer is formed as a single layer or a laminate.
In other words, screen printing, dip coating, spin coating, and the like are used for patterning circuits and electrodes on ceramic substrates and chip parts using conductive paste. In addition, shape shaping is important.
[0011]
In addition, as the conductive metal material, a paste of noble metal powder such as gold, platinum, palladium, silver or the like is conventionally used from the viewpoint of oxidation resistance at the time of sintering formation. It is difficult to use for high-frequency circuits, high-density circuits, and high-density mounting due to migration between conductor circuits, solder erosion, and the like.
Conventionally, copper metal powder, which is low in cost and particularly low in resistance, is basically inferior in oxidation resistance, and thus has many unsolved problems in handling properties and the like. Yes. In view of this, for example, JP-A-6-295614 proposes a conductive paste using a copper alloy powder in which a titanium component is coated on the surface of copper particles in order to improve oxidation resistance during firing. .
[0012]
Usually, in order to sinter such a conductive paste, it is generally sintered in a temperature range of 500 to 1100 ° C. in an inert atmosphere such as nitrogen. Further, when sintering in this inert atmosphere, the organic vehicle is sufficiently burned off in an oxygen atmosphere in a temperature range of 200 to 550 ° C., which is a temperature raising process before the sintering. In particular, when the conductive metal powder has low oxidation resistance such as aluminum, silver, and copper, the organic vehicle is usually removed while strictly controlling the oxygen concentration in the atmosphere.
Therefore, upon such removal, the applied conductive paste layer is exposed to an oxidizing atmosphere, resulting in deterioration in properties such as deterioration in conductivity, and deterioration in sinterability and adhesion of the sintered film to the substrate. Tend to come.
[0013]
Further, as already described above, the conventional conductive paste contains a solvent as a dispersion medium for the conductive metal powder and the binder resin. In addition, the selection of the solvent type is an important additive from the viewpoint of exerting good coating properties to the paste, and the conductive paste for coating prepared by the conventional method contains a large amount of solvent. It is the actual situation.
[0014]
Therefore, when sintering a paste layer applied on a substrate or the like, or a paste layer applied on a ceramic green sheet, etc., under the heat history before sintering such as drying, polymerization hardening (curing), pre-firing etc. In this case, the organic vehicle such as a solvent and a binder resin must be completely removed.
As long as a solvent is used as in the conventional method, in this treatment step, there is a tendency to cause bubble holes, cracks, deflection, peeling, shrinkage, etc. in the coating layer. Therefore, in order to prevent such troubles, if necessary, coating-play baking is performed in a number of times to form a coating layer having a predetermined thickness.
[0015]
In addition, the paste by the conventional method using a solvent as described above has a remarkable working environment due to organic components such as a solvent that volatilizes and decomposes and scatters at the time of preparing the paste and pre-firing before sintering the coating paste layer. It is not preferable from the viewpoint of occupational safety and health because it is contaminated. In addition, from the standpoint of global environmental conservation in recent years, scattering of organic substances such as solvents pollutes the global environment and also causes global warming. Therefore, in the industry, when manufacturing a product, switching from a solvent type to a solventless type has become an extremely important issue.
[0016]
Therefore, the solvents conventionally used in such fields have many boiling points in the range of 80 to 260 ° C., for example, n-methylpyrrolidone, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, butyl Examples include high-boiling polyhydric alcohol derivatives such as carbitol acetate and ethylene glycol monoethyl ether acetate, high-boiling aromatic compounds such as ethyl cellosolve and xylene, methyl lactate, ethyl lactate, ketones, and terpenes.
[0017]
From the above, the object of the present invention is to replace the paste-like conductive resin composition containing the conductive metal and / or conductive alloy powder with the solvent-type paste of the conventional method. However, it has applicability and shape shaping before sintering. In addition, paste-like conductive resin that can be applied thicker than conventional methods, and can be processed in an inert atmosphere such as nitrogen, after the paste layer is cured, pre-fired and sintered. It is to provide a composition.
[0018]
Another object of the present invention is to provide a method for forming a conductive sintered body that is formed on an alumina ceramic substrate or the like using such a paste-like conductive resin composition.
[0019]
[Means for Solving the Problems]
As a result of intensive investigations in view of the above-mentioned problems, the present inventors have prepared a paste-like resin composition from a conductive metal powder and an organic vehicle, and the vehicle component in the paste-formed body after application has been baked. Focusing on organic vehicles that can be easily pyrolyzed, volatilized and scattered and removed in a nitrogen atmosphere at 200 to 550 ° C. prior to sintering, baked in an oxygen atmosphere like conventional binder resins (organic vehicles) The present inventors have found a method capable of completely removing the organic vehicle without performing skipping, and have reached the present invention.
[0020]
According to the present invention, the paste-like resin composition is a solventless type, but does not impair applicability on the substrate, and the organic vehicle including the curing treatment before sintering can be performed under a thermal history. Through the pre-firing to be removed, it is possible to maintain the shape forming property of the coating paste layer, and the firing treatment through the sintering treatment at a further elevated temperature after the pre-firing is performed under an inert atmosphere such as nitrogen. A paste-like conductive resin composition for a conductive sintered body (hereinafter simply referred to as a conductive resin paste) is provided.
[0021]
Further, according to the present invention, in the pre-baking after the application of the conductive resin paste, the formed coating layer or formwork casting product has pinholes such as bubble holes, cracks, deflection, or Provided is a solvent-free conductive resin paste characterized by not causing shrinkage or the like.
That is, conductive metal powder and / or alloy powder thereof Conductive inorganic powder A binder resin composition according to the present invention comprising Or organic vehicle resin component) ,
(A) A (meth) acrylic resin having a weight average molecular weight Mw of 500 to 10,000 and a glass transition temperature (Tg) of −80 to 50 ° C. Low A polymer, and (B) a molecular weight of 100 to 5000 and 2 to 6 polymerizable unsaturated groups. Low molecular weight thermosetting or UV curable Polymerizable polyfunctional monomer Is a viscous resin component having a viscosity (at 23 ° C.) in the range of 10 to 900 parts by mass of 0.01 to 10 Pa · s. It is characterized by that.
In this binder resin composition (organic vehicle), (C) at least one conductive inorganic powder having an average particle size of 0.1 to 20 μm is added. In the range of 100 to 9000 parts by mass This is a conductive resin paste to be contained.
[0022]
Thereby, unlike the conventional paste-like resin composition, the organic vehicle containing (A) and (B) is a (meth) acrylic polymer (A) which is the main component of the vehicle. Low polymer having a specific Mw or this low polymer For 100 parts by mass (B) Thermosetting or UV curable Polymerizable polyfunctional monomer In the range of 10 to 900 parts by mass In combination, this organic vehicle according to the present invention is a solvent-free type, but is a fluid viscous material that also has solvent properties, and has good wettability with conductive metal and / or alloy powder thereof. Have.
[0023]
In addition, the conductive resin paste containing conductive metal powder or the like in this organic vehicle is excellent in coatability and is combined with the low molecular weight polymerizable polyfunctional monomer (B). Since it can be polymerized and cured (cured) with heat or UV after application, excellent formability can be imparted to the applied paste layer after application.
[0024]
In addition, the vehicle in which the paste layer applied after curing is formed does not contain any solvent unlike the conventional vehicle. And since the binder resin component consists of the low polymer mentioned above, after hardening, it is not necessary to burn off a binder resin component (vehicle component) under an oxygen atmosphere conventionally. Because it is easily pyrolyzed and scattered under a low temperature thermal history in an inert atmosphere such as nitrogen, the caulking that tends to occur under the thermal history of a conventional vehicle in the coating paste layer Do not leave carbonaceous matter due to etc.
[0025]
Moreover, according to this invention, (A) weight average molecular weight Mw is 500-10000, and the glass transition temperature (Tg) is in the range of -80-50 degreeC (meth) acrylic type. Low A polymer and (B) a molecular weight of 100-5000 Low molecular weight And having 2 to 6 polymerizable unsaturated groups Thermosetting or UV curable Contains photopolymerizable polyfunctional monomer and polymerization initiator And in the range of 10 to 900 parts by weight of (B) with respect to 100 parts by weight of (A). A resin composition having a viscosity (23 ° C.) of 0.01 to 10 Pa · s is prepared. In this resin composition, (C) a conductive metal having an average particle diameter in the range of 0.1 to 20 μm and / or an alloy powder thereof is kneaded. Solventless A conductive resin paste is used. Next, after applying this paste on a substrate or the like, the applied layer is polymerized and cured (cured). Next, in an inert atmosphere, in the pre-sintering temperature range before sintering, the vehicle resin component in the applied paste layer is thermally decomposed and volatilized to be scattered and removed, and then further heated. The present invention relates to a method for forming a conductive sintered body characterized by sintering.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a paste-like conductive resin composition (hereinafter simply referred to as a conductive resin paste) containing a conductive sintered body or a conductive metal powder for forming a layer thereof according to the present invention will be further described. explain.
[0027]
Therefore, as already described above, the conductive resin paste according to the present invention has a binder resin composition (or organic vehicle) for forming the paste, which is a solvent-free type, and a (meth) acrylic low polymer, And a polymerizable polyfunctional monomer having 2 to 6 polymerizable unsaturated groups. This organic vehicle in the present invention is This This polymerizable polyfunctional monomer is a resin composition in the range of 10 to 900 parts by weight with respect to 100 parts by weight of the specific low polymer.
[0028]
In the present invention, when the content of the polymerizable polyfunctional monomer is less than 10 parts by weight of the lower limit value described above, the shape of the applied paste layer is sufficiently retained even when the paste layer is polymerized and cured after application. The shape forming property of the applied paste is reduced. On the other hand, even if the upper limit value of 900 parts by weight is exceeded, the resin component content is increased more than necessary, and the unnecessarily shaped property corresponding to the increased amount is not exhibited. It only becomes.
[0029]
Further, the viscosity of the vehicle resin composition at 23 ° C. is in the range of 0.01 to 10 Pa · s, preferably 0.05 to 8 Pa · s. If this viscosity is less than the lower limit, it depends on the surface wettability of the inorganic powder to be filled, but a stable paste cannot be obtained, and the applicability or formability is reduced. In addition to significantly reducing the filling amount of the inorganic powder, the applicability of the paste is significantly reduced.
[0030]
In the present invention, as already described above, the vehicle for forming the paste is , The solvent-free type conductive resin paste formed is excellent in coating property and shape shaping property, and further has a temperature lower than that of a conventional vehicle through drying, pre-firing, and sintering. In the temperature range of ˜550 ° C., preferably 350 ° C. to 500 ° C., and under an inert atmosphere, the vehicle component is characterized by being almost completely thermally decomposed and volatilized and scattered and removed.
[0031]
Further, in the present invention, the polymerizable polyfunctional monomer having 2 to 6 polymerizable unsaturated groups, which is a resin component of the vehicle, is a photopolymerizable monomer such as UV. Any of these can be suitably used, but it is preferable to use a photopolymerizable polyfunctional monomer such as UV rather than a thermopolymerizable polyfunctional monomer in terms of pot life of the conductive resin paste. To preferred.
[0032]
That is, because it is UV polymerizable, the pot life of the conductive resin paste according to the present invention does not increase with time even if a photopolymerization initiator is contained in the vehicle in advance. Will not be damaged.
However, when this polymerizable polyfunctional monomer is a thermopolymerizable monomer, if the thermal polymerization initiator is brought into contact with the thermopolymerizable monomer in advance over time, the viscosity of the vehicle increases. After the initiator is dissolved in a (meth) acrylic low polymer containing conductive inorganic powder, a heat-polymerizable monomer is mixed with the paste immediately before application to obtain the conductivity according to the present invention. It can be used as a resin paste.
[0033]
In the conductive resin paste using the vehicle according to the present invention, various conductive metals and / or alloy powders thereof described later have an average particle size of 0. 10 per 100 parts by weight of the low polymer. 1-20 micrometers conductive inorganic powder can be contained in the range of 100-9000 parts by weight, preferably 500-6000 parts by weight.
Therefore, the conductive inorganic powder that can be filled in the above-described range in the organic vehicle according to the present invention in the above-described viscosity range is within a range in which the obtained conductive resin paste does not impair the above-described applicability and formability. The filling amount is preferably as high as possible.
[0034]
Such a filling amount is particularly the wettability with the vehicle of the conductive metal and / or alloy powder (depending on the oil absorption amount of the powder itself), and the fine filling of the powder. From the viewpoint, the particle size and particle size distribution, and the particle shape such as spherical shape, needle shape, and irregular shape are greatly affected.
Therefore, although it cannot be generally specified, from the viewpoint of making the powder particles in the paste into a finely packed state, the particle shape is preferably approximately spherical, satisfies the above average particle diameter, and has an appropriate particle size distribution. The conductive inorganic powder is preferable.
[0035]
Therefore, as described above, as the (meth) acrylic polymer constituting the binder resin composition according to the present invention, a low polymer of a polymerizable monomer described below can be appropriately used.
[0036]
In the present invention, as the polymerizable monomer for such a low polymer, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, sec -Butyl acrylate, sec-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, n- Examples thereof include sil acrylate, n-decyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. In the present invention, at least one of these monomers can be used as appropriate. .
[0037]
In order to prepare the low polymer used in the present invention from these monomers, for example, it is suitably suitable by conforming to the bulk polymerization method described in JP-A No. 2000-128911, which has already been applied for a patent by the present inventors. Can be prepared.
That is, a compound having at least one thiol group and secondary hydroxyl group represented by the following general formula [I] is used as a bulk polymerization catalyst for the polymerizable unsaturated compound of the (meth) acrylic monomer described above. It is.
[0038]
[Chemical 1]

However, in the general formula [I], R ₁ ~ R ₅ Each independently represents a hydrogen atom or a carbon number C ₁ ~ C ₁₂ An alkyl group of R ₆ Is a hydroxyl group, carbon number C ₁ ~ C ₁₂ Alkoxy group and carbon number C ₁ ~ C ₁₂ And at least one group selected from the alkyl groups. In addition, it is characterized by having at least one thiol group (—SH) and a secondary hydroxyl group.
[0039]
In this bulk polymerization method using this as a polymerization initiator and a reaction control agent, the reaction can be progressed substantially in a solvent-free manner, and the reaction can run away even with the above-mentioned highly reactive monomer. The polymerization reaction can proceed without any problems. As a result, a low polymer having a narrow molecular weight distribution can be stably bulk polymerized.
[0040]
Therefore, examples of the compound represented by the general formula [I] include thioglycerol, 1-mercapto-2,3-propanediol, 2-mercapto-3-butanol, 2-mercapto-3,4-butanediol, 1 -Mercapto-2,3-butanediol, 1-mercapto-2-butanol, 2-mercapto-3,4,4'-butanetriol, 1-mercapto-3,4-butanediol, 1-mercapto-3,4 , 4′-butanetriol and the like. In the present invention, among these compounds, thioglycerol is particularly preferably used as a catalyst for bulk polymerization.
[0041]
Further, it can be suitably suitably prepared by conforming to a bulk polymerization method in which a polymerizable unsaturated compound is polymerized using a bulk polymerization catalyst composed of an organometallic compound (metallocene compound) represented by the following formula [II] and thiols. can do.
[0042]
[Chemical 2]

However, in the above formula [II], M is a metal selected from the group consisting of metals of Periodic Tables 4A, 4B, 5A, 5B, chromium, ruthenium and palladium. Specifically, M is titanium, zirconium, chromium, ruthenium, vanadium, palladium, tin or the like.
In the formula [II], R1 and R2 are each independently
An aliphatic hydrocarbon group which may have a substituent,
An alicyclic hydrocarbon group which may have a substituent,
An aromatic hydrocarbon group which may have a substituent,
It is at least one group selected from the group consisting of silicon-containing groups which may have a substituent, either a hydrogen atom or a single bond.
Further, R1 and R2 may jointly bind the two 5-membered rings, and a plurality of adjacent R1 or R2 may jointly form a cyclic structure.
In Formula [II], a and b are each independently an integer of 1 to 4, and X is a halogen atom such as chlorine, bromine or iodine, or at least a part of the hydrogen atom is substituted with a halogen atom. And n is an integer of 0 or the valence-2 of the metal M.
[0043]
Accordingly, examples of the organometallic compound represented by the formula [II] include dicyclopentadiene-Ti-dichloride, dicyclopentadiene-Ti-bisphenyl, dicyclopentadiene-Ti-bis-2,3,4,5. , 6-pentafluorophen-1-yl, dicyclopentadiene-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, dicyclopentadiene-Ti-bis-2,5,6-tri Titanocene compounds such as fluorophen-1-yl and dicyclopentadiene-Ti-bis-2,6-difluorophen-1-yl; dicyclopentadiene-Zr-dichloride, dicyclopentadiene-Zr-bisphenyl, dicyclopentadiene -Zr-bis-2,3,4,5,6-pentafluorophen-1-yl and other zirconocene compounds Dicyclopentadiene El -V- chloride, and bis pentamethylcyclopentadienyl -V- chloride and the like. These organometallic compounds can be used alone or in combination of two or more.
[0044]
This organometallic compound is suitably used in an amount of usually 1 to 0.001 parts by weight, preferably 0.01 to 0.005 parts by weight, based on 100 parts by weight of the polymerizable unsaturated compound, as a catalyst amount. Is done.
Examples of the thiols include alkyl thiols such as ethyl mercaptan, butyl mercaptan, and hexyl mercaptan, hexyl mercaptan, benzyl mercaptan, β-mercaptopropionic acid, 3-mercaptopropyl-trimethoxysilane, and thiophenyl. In this catalyst, the organometallic compound acts as an activation catalyst on the entire reaction, and thiols have a polymerization initiating action, and the amount of thiols used affects the molecular weight and the polymerization rate.
Therefore, the organometallic compound and the thiols are usually used at a molar ratio in the range of 100: 1 to 1: 50000. Moreover, a disulfide compound, a trisulfide compound, and a tetrasulfide compound can be used for the purpose of adjusting the polymerization rate and the degree of polymerization.
[0045]
In the present invention, as the above-mentioned (meth) acrylic polymer, a low polymer having a weight average molecular weight Mw of 500 to 10,000, more preferably 1000 to 7000 is preferably used as appropriate. be able to.
When this Mw is less than the lower limit, the formability of the polymerized and cured coating paste layer is lowered, and sufficient binding properties are not exhibited in the functional inorganic powder. On the other hand, if this Mw exceeds the upper limit value, the resin viscosity increases, and the paste viscosity is increased. Therefore, it is economically disadvantageous because adjustments such as increasing the monomer component or lowering the powder concentration are disadvantageous, which is preferable. Absent.
[0046]
In the present invention, the glass transition temperature (Tg) of the low polymer is preferably in the range of −80 to 50 ° C. When this Tg is out of this range, that is, when Tg exceeds 50 ° C., the flexibility of the coating film after polymerization and curing is poor, the viscosity of the vehicle becomes high, the brushing property at the time of screen coating, It tends to reduce workability. On the other hand, when Tg is lower than −80 ° C., the shape forming property of the coating film after polymerization and curing is poor, and it is not preferable because the filler retention during firing is lowered.
[0047]
In the present invention, the acid value of the low polymer is preferably in the range of 60 to 180.
That is, in the present invention, it is a known binder resin for pastes, and unlike the tendency of low-polymers of acrylic copolymers having a carboxyl group and an unsaturated group in the side chain, The applicability is not impaired by the increase in viscosity over time.
In particular, in the present invention, although affected by the surface wettability and the like of the conductive inorganic powder used, if the acid value deviates from the above range, the conductive inorganic powder in the conductive resin paste of the present invention. On the other hand, it is not preferable from the tendency to impair the effect as a dispersant.
[0048]
In the present invention, examples of the polymerizable polyfunctional monomer having a plurality (2 to 6) of polymerizable unsaturated groups that undergo radical reaction include, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetra Ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexaglycol di (meth) ) Acrylate, trimethylolpropane tri (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaeryth Tall penta (meth) acrylate, 2,2-bis (4- (meth) acryloxydiethoxyphenyl) propane, 2,2-bis (4- (meth) acryloxypolyethoxyphenyl) propane, 2-hydroxy-2 -Methyl-1-phenyl-propan-1-one, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, 2-hydroxy-3- (meth) acryloyloxypropyl (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, diglycidyl phthalate di (meth) acrylate, glycerin Triacrylate And polyfunctional acrylates typified by glycerol polyglycidyl ether poly (meth) acrylate, can methacrylate monomers corresponding to these exemplified.
[0049]
In particular, in the case of the UV curable type, as a photopolymerization initiator, benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone, α-aminoacetate Henone, 4,4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzylketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy 2-methyl-1-phenyl-propan-1-one, 2-hydroxy-2-methylpropiophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, benzyldimethyl ketal, benzylmethoxyethyl acetal, benzoin methyl ether , Benzoy Butyl ether, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, toanthraquinone, 2-tert-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, methyleneanthrone, 4-azidobenzylacetophenone, 2,6-bis (ρ-azidobenzylidene) cyclohexane, 2,6-bis (ρ-azidobenzylidene) -4 -Methylcyclohexanone, 2-phenyl-1,2-butadion-2- (ο-methoxycarbonyl) oxime, benzothiazole disulfide, etc. can be mentioned, and one or more of these photopolymerization initiators are combined Can be used Kill.
These photoinitiators can add 0.05-5 weight part with respect to 100 weight part of (B).
If the addition amount is less than the lower limit, the photocuring property of the conductive resin paste is low, which is not preferable.If the addition amount exceeds the upper limit, it is cured even by visible light to shorten the pot life, and after firing, the residue is removed. It tends to remain, which is not preferable.
[0050]
In addition, if necessary, it can be used in combination with a photopolymerization initiator that induces a radical reaction, and a photopolymerization initiation assistant can be used to promote the photopolymerization initiation reaction, whereby the polymerization and curing can be made efficient. Examples of such photopolymerization initiation assistants include triethylenetetramine, triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, dimethylthioxanthone, isopropylthioxanthone, N-methyldiethanolamine, ethyl 4-dimethylaminobenzoate, and the like. And aliphatic and aromatic amines.
These photoinitiators can be added in the range of 0.1 to 5 parts by weight with respect to 1 part by weight of the photopolymerization initiator.
In addition, by using the organic resin of the conductive resin paste as the photosensitive resin composition in this way, a pattern can be formed as a resist coating layer, so that a predetermined pattern can be appropriately formed by a photoresist method.
[0051]
Further, as necessary, a plasticizer, a dispersant, a thickener, an antisettling agent, an antifoaming agent, a leveling agent, a thermal polymerization inhibitor, or the like can be appropriately added to the vehicle as necessary. .
For example, as a plasticizer added for the purpose of improving the fluidity of the paste, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, dibenzyl phthalate, polyalkylene glycol, triethylene glycol diacetate, polyethylene octoside and the like can be mentioned. In particular, it can be added within a range that does not impair the photocurable sensitivity and thermal decomposition / volatility.
[0052]
<Method for forming conductive sintered body>
Various electronic products and peripheral devices such as ceramic capacitors, piezoelectric elements, pyroelectric elements, semiconductor devices and other electronic components formed on substrates include internal electrodes, circuit patterns, external electrode terminals, etc. The conductive member is incorporated.
As the formation method, for example, a CVD / sintering method, a sputtering method, or a conductive paste can be formed by a coating / sintering method or the like.
[0053]
As already described above, the solvent-free binder resin composition (vehicle) according to the present invention is easily paste-like by kneading an inorganic powder of a conductive metal and / or a conductive alloy thereof. It is possible to prepare a conductive resin paste according to the present invention that is excellent in applicability, formability, sinterability, and the like.
The conductive resin paste thus obtained can be applied on a ceramic substrate such as alumina or on various ceramic green sheet substrates. Examples of the coating method include a screen printing method, a bar coater method, a roll coater method, a slit die coater method, a doctor blade coater method, and a photosensitive resin paste method (photoresist formation method), which can be suitably used. .
[0054]
Examples of applications for applying such paste include ceramic substrates such as alumina and alumina nitride, and ceramic green sheets for low-temperature firing substrates mainly composed of cordierite, mullite, steatite, and glass components. As an inner layer or outer layer conductor, or as an external electrode for a tantalum capacitor, a multilayer ceramic capacitor using a ferroelectric layer of perovskite-type composite oxide particles, a multilayer piezoelectric ceramic element, a multilayer ceramic (LC) filter, etc. Can be formed by sintering.
[0055]
In addition, the conductive paste applied on the above-described ceramic substrate or ceramic green sheet or the like is laminated on an insulator layer, a dielectric layer, an insulator layer-dielectric layer, or the like, or Insulator layer-conductive layer-insulator layer, insulator layer-dielectric layer-conductor layer-insulator layer, insulator layer-dielectric layer-conductor layer-dielectric layer, etc. Will be formed.
[0056]
In addition, when the paste-like resin composition is a photosensitive resin composition as in the present invention, it is related to these coating methods, and preferably, a resist forming method (photolithography) is used for coating and pattern exposure. The conductive sintered layer can be formed as a circuit pattern by developing-curing-pre-firing-sintering.
[0057]
As the conductive material of the conductive resin paste for firing, gold, silver, platinum, palladium, silver-palladium alloy, nickel, aluminum, aluminum-Si, aluminum-copper-Si, copper, copper-silver alloy, titanium, titanium- Examples thereof include Si, tungsten, tungsten-Si, molybdenum, molybdenum-Si, and ITO. Further, if necessary, improvement in adhesion of the conductive powder to the substrate or improvement in sinterability, decrease in sintering temperature, coefficient of thermal expansion, etc. in a temperature range of 600 to 1100 ° C., which is usually sintered, From improvement etc., glass frit can be mixed with the conductive resin paste as required.
[0058]
The glass frit is preferably a system that does not substantially contain an alkali metal or an alkaline earth metal. Therefore, for example, bismuth oxide, silicon oxide, boron oxide, zinc oxide, zirconium oxide and the like are the main components. ZnO-B ₂ O ₃ -SiO ₂ System, PbO-B ₂ O ₃ -SiO ₂ System, PbO-B ₂ O ₃ -SiO ₂ -Al ₂ O ₃ System, PbO-ZnO-B ₂ O ₃ -SiO ₂ And the like.
In this invention, 0.1-10 weight part of glass frit can be contained with respect to 100 weight part of electroconductive powder.
[0059]
In addition, if necessary, in connection with such low melting point glass dielectric powder, low dielectric constant powder such as alumina, aluminum nitride, mullite, cordierite, crystallized glass, barium titanate, titanate High dielectric constant powder such as strontium, lead titanate, lead zirconate titanate, neodymium titanate, other silicon nitride, silicon carbide ceramic powder, other high melting point glass, etc. They can be combined and added as fillers.
[0060]
【Example】
EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.
[0061]
(Reference Example 1)
A low polymer (A) (meth) acrylic polymer, which is a constituent component of the binder resin composition (vehicle) of the conductive resin paste, is prepared.
A flask equipped with a stirrer, a nitrogen introduction tube, a thermometer, and a reflux condenser was charged with 100 parts by weight of 2-ethylhexyl methacrylate, and the contents in the flask were heated to 80 ° C. while introducing nitrogen gas into the flask.
Subsequently, 7 parts by weight of thioglycerol sufficiently purged with nitrogen gas was added to the stirred flask. Then, cooling and warming were performed for 2 hours so that the temperature of the content in the stirring flask could be maintained at 80 degreeC. Subsequently, the polymerization reaction was further carried out for 6 hours while cooling and warming so that the temperature of the contents in the flask under stirring could be maintained at 95 ° C., and then 0.16 of azobisisobutyronitrile. A part by weight was added, and polymerization was further performed at 95 ° C. for 2 hours.
[0062]
After the reaction for 8 hours in total as described above, the temperature of the reaction product was returned to room temperature, and 0.05 parts by weight of hydroquinone was added to the reaction product to obtain a reaction product (a-1).
As a result of measuring the monomer residual ratio of the obtained polymerization reaction product (a-1) using gas chromatography, the polymerization ratio was 99.4%.
Moreover, the molecular weight measured by the gel permeation chromatography (GPC) is Mw = 3800, Mn = 1700, dispersion index = 2.1, and the viscosity at 23 ° C. is 330 (Pa · s) ( It was a low polymer of a (meth) acrylic polymer.
[0063]
(Reference Example 2)
In Reference Example 1, polymerization was carried out in the same manner as in Reference Example 1 except that MMA (methyl methacrylate) was used as a monomer and thioglycerol to be added was changed to 24 parts by weight to obtain a reaction product (a-2).
As a result of measuring the monomer residual rate of the obtained polymerization reaction product (a-2) using gas chromatography, the polymerization rate was 98.8%.
The molecular weight measured by GPC is Mw = 1100, Mn = 790, dispersion index = 1.39, and a viscosity of 2.3 (Pa · s) at 23 ° C. is 2.3 (Pa · s). It was a low polymer.
[0064]
(Reference Example 3)
A reaction product (a-3) was obtained by polymerization in the same manner as in Reference Example 1 except that the amount of thioglycerol added was 3.9 parts by weight in Reference Example 1.
As a result of measuring the monomer residual ratio of the obtained polymerization reaction product (a-3) using gas chromatography, the polymerization ratio was 99.8%.
The molecular weight measured by GPC is Mw = 7400, Mn = 4300, dispersion index = 1.69, and the viscosity at 23 ° C. is 990 (Pa · s). It was a polymer.
[0065]
Example 1
In a 200 ml beaker, 50 parts by weight of the (meth) acrylic polymer low polymer (a-1) obtained in Reference Example 1 and 50 parts by weight of ethylene glycol dimethacrylate, which is a polymerizable polyfunctional monomer, were added. The mixture was stirred and mixed until sufficiently uniform to obtain (b-1) of the acrylic binder resin composition (vehicle) used in the present invention. The resulting vehicle (b-1) had a viscosity of 0.08 (Pa · s) at 23 ° C.
[0066]
(Thermopolymerizable paste and its curing)
Next, 50 parts by weight of copper powder having an average particle diameter of 3.2 μm, 10 parts by weight of the vehicle (b-1), and 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanol as a radical initiator 0.4 parts by weight and 0.04 parts by weight of hydroquinone as an inhibitor were sufficiently kneaded by a roll mill to prepare a copper-powder paste conductive resin composition (c-1). The viscosity of the obtained paste (c-1) was 6.8 (Pa · s).
[0067]
Next, the paste (c-1) was applied on an alumina substrate with a bar coater so as to have a film thickness of 50 μm, and was subjected to heat polymerization curing at 120 for 5 minutes in a nitrogen atmosphere. The thickness of the obtained coating film was 48 μm with almost no volume reduction, and no cracks on the surface were observed. In addition, during the heat polymerization and curing, the coating layer was able to impart good shape-forming properties without breaking the flow.
[0068]
(UV polymerizable paste and its curing)
50 parts by weight of copper powder having an average particle size of 3.2 μm, 10 parts by weight of the vehicle (b-1), and (as glass powder, zinc oxide 82% by weight, boron oxide 8% by weight, silicon oxide 10% by weight) Ratio of glass frit powder (to 8 parts by weight), 10 parts by weight of the vehicle (b-1), 0.3 parts by weight of Irganox I-369 as a UV radical initiator, and 0.01 parts by weight of hydroquinone as an inhibitor Were kneaded to prepare a paste conductive resin composition (d-1) of copper powder. The viscosity of the obtained paste (d-1) was 8.7 (Pa · sec).
[0069]
Next, the paste (d-1) was applied to an alumina substrate with a bar coater so as to have a film thickness of 50 μm, and a nitrogen atmosphere was used and a high pressure mercury lamp was used as a light source, and the irradiation intensity was 214 mW / cm. ² , Integrated light quantity 1930mJ / cm ² Then, UV exposure was performed from the coating film surface.
The obtained coating thickness is 49 μm with almost no volume reduction, no cracks are observed on the surface, and the coating layer can be imparted with good shape shaping without flow breakage during the UV polymerization curing. did it.
[0070]
(Play firing and sintering)
Next, the temperature of c-1 and d-1 of the above-mentioned test specimens obtained by applying paste c-1 and d-1 on the substrate, applying heat and UV polymerization and curing, from room temperature in a nitrogen atmosphere to 350 ° C in 20 minutes. And heat treatment was performed at 350 ° C. for 20 minutes. As a result, the organic resin content of the vehicle in the coating layer of each test specimen could be completely pyrolyzed and volatilized.
That is, in the visual observation through the heat treatment, no residue or wrinkles are seen on the coating layer, and each of the surface and the surface scraped by sandpaper is gauze moistened with MEK. Although wiped, no dirt component adhered to the gauze.
[0071]
Next, c-1 and d-1 of the test body from which the organic resin component was removed by the above-described pre-bake were held at 900 ° C. for 30 minutes in a nitrogen atmosphere to sinter the copper powder of the coating layer. As a result, the sintered layer was visually free from abnormalities such as peeling and cracking, and had a good copper metal luster.
[0072]
Example 2
In a 200 ml beaker, 65 parts by weight of the low polymer (a-2) of methyl methacrylic polymer obtained in Reference Example 2 and 35 parts by weight of ethylene glycol dimethacrylate were taken and stirred and mixed until sufficiently uniform. (B-2) of an acrylic binder resin composition (vehicle) used in the present invention was obtained. The viscosity of the obtained vehicle (b-2) was 0.037 (Pa · s) at 23 ° C.
[0073]
(Thermopolymerizable paste and its curing)
Next, Example 1 except that 50 parts by weight of copper powder having an average particle size of 3.2 μm, 7 parts by weight of the vehicle (b-2), and 0.2 parts by weight of the radical initiator in Example 1 were used. In the same manner as above, the mixture was sufficiently kneaded with a roll mill to prepare a copper-powder paste conductive resin composition (c-2). The viscosity of the obtained paste (c-2) was 7.2 (Pa · s).
[0074]
Next, the paste (c-2) was applied onto an alumina substrate with a bar coater so as to have a film thickness of 50 μm, and subjected to heat polymerization at 120 ° C. for 5 minutes in a nitrogen atmosphere. The obtained coating thickness is 48 μm with almost no volume reduction, surface cracks and the like are not seen, and the coating layer can impart good shape shapeability without breaking the flow during the thermal polymerization curing. did it.
[0075]
(UV polymerizable paste and its curing)
Paste conductive resin composition of UV polymerizable copper powder (d) in the same manner as in Example 1 in 50 parts by weight of copper powder having an average particle size of 3.2 μm, 7 parts by weight of the vehicle (b-2). -2) was prepared. The viscosity of the obtained paste (d-2) was 7.2 (Pa · s).
Next, the obtained UV curable paste (d-2) was applied onto an alumina substrate with a bar coater in the same manner as in Example 1 so as to have a film thickness of 50 μm, and Example 1 was performed in a nitrogen atmosphere. Under the same conditions, UV exposure was performed to polymerize and cure the coated paste layer. The obtained coating film thickness is 48 μm with almost no volume reduction, no cracks on the surface, etc., and in addition, during the UV polymerization curing, the coating layer can impart good shape shapeability without flow disruption. did it.
[0076]
(Play firing and sintering)
Next, the specimens c-2 and d-2 of the above-mentioned test specimens obtained by applying paste c-2 and d-2 on an alumina substrate, heat and UV polymerization and curing were pre-fired under the same conditions as in Example 1, Heat treatment (pre-firing) was performed to remove the organic vehicle in the coating layer of the test specimen. As a result, like the test body of Example 1, the organic resin content of the vehicle in the coating layer of each test body could be completely pyrolyzed and removed by evaporation.
[0077]
That is, as in the test sample of Example 1, in the visual observation through the heat treatment, no residue or wrinkles are seen on the coating layer, and the surface and the surface scraped by sandpaper are removed. Each was wiped with gauze moistened with MEK, but no soil components adhered to the gauze.
Moreover, c-2 and d-2 of the test body from which the organic resin component was removed by the above-mentioned pre-bake were sintered in the same manner as the test body of Example 1. As a result, a sintered layer having a good copper metal luster with no abnormalities such as peeling and cracking in the sintered layer was obtained.
[0078]
Example 3
In a 200 ml beaker, 70 parts by weight of the low polymer (a-3) of the methylmethacrylic polymer obtained in Reference Example 3 and 30 parts by weight of ethylene glycol dimethacrylate are mixed with stirring until sufficiently uniform. (B-3) of an acrylic binder resin composition (vehicle) used in the present invention was obtained. The resulting vehicle (b-3) had a viscosity of 7.8 (Pa · s) at 23 ° C.
[0079]
(Thermopolymerizable paste and its curing)
The paste conductive resin composition of copper powder (Example 1) except that the radical initiator was changed to 0.45 parts by weight in Example 1 to 15 parts by weight of this vehicle (b-3). c-3) was prepared. The viscosity of the obtained paste (c-3) was 7.2 (Pa · s).
[0080]
Next, the paste (c-3) was applied onto an alumina substrate with a bar coater so as to have a film thickness of 50 μm, and heat polymerization was performed at 120 ° C. for 5 minutes in a nitrogen atmosphere. The obtained coating thickness is 49 μm, with almost no volume reduction, no cracks on the surface, etc., and upon thermal polymerization curing, the coating layer can impart good shape shaping without flow disruption. did it.
[0081]
(UV polymerizable paste and its curing)
The paste conductive resin composition of copper powder (Example 1) except that the radical initiator was changed to 0.45 parts by weight in Example 1 to 15 parts by weight of this vehicle (b-3). c-3) was prepared. The viscosity of the obtained paste (c-3) was 7.5 (Pa · s).
Next, the obtained UV curable paste (d-3) was applied onto an alumina substrate with a bar coater in the same manner as in Example 1 so as to have a film thickness of 50 μm, and Example 1 was performed in a nitrogen atmosphere. Under the same conditions, UV exposure was performed to polymerize and cure the coated paste layer. The obtained coating thickness is 49 μm with almost no volume reduction, no cracks are observed on the surface, and the coating layer can be imparted with good shape shaping without flow breakage during the UV polymerization curing. did it.
[0082]
(Play firing and sintering)
Next, the specimens c-3 and d-3 of the above-mentioned test specimens obtained by applying paste c-3 and d-3 on a glass substrate, heating and UV polymerization curing were pre-fired under the same conditions as in Example 1, Heat treatment (pre-firing) was performed to remove the organic vehicle in the coating layer of the test specimen. As a result, similar to the test body of Example 1, the organic resin content of the vehicle in the coating layer of each test body can be completely pyrolyzed and volatilized and removed, and similarly, visual observation through heat treatment, The residue and caulking quality were not confirmed by wiping with gauze moistened with MEK in the coating element. Moreover, c-3 and d-3 of the test body from which the organic resin component was removed by the above-mentioned pre-bake were sintered in the same manner as the test body of Example 1. As a result, a sintered layer having a good copper metal luster with no abnormalities such as peeling and cracking in the sintered layer was obtained.
[0083]
Example 4
Example 1 except that 10 parts by weight of the vehicle (b-1) obtained in Example 1 was replaced with 7 parts by weight of glass frit having an average particle diameter of 2 μm and 45 parts by weight of copper powder having an average particle diameter of 3.2 μm. In the same manner as in paste (d-1), ZnO-B ₂ O ₃ -SiO ₂ A paste-like conductive resin composition of UV polymerizable copper powder containing glass frit is prepared, applied to an alumina substrate with a bar coater so as to have a film thickness of 30 μm, and under a nitrogen atmosphere, Under the same conditions as in Example 1, UV exposure was performed to cure and cure the applied paste layer.
Next, on the cured coating paste, the paste-like conductive resin composition (d-2) of the UV polymerizable copper powder prepared in the same manner as in Example 1 was applied to a film thickness of 50 μm with a bar coater. The coating paste layer was polymerized and cured by UV exposure under the same conditions as in Example 1 under a nitrogen atmosphere to form a conductive paste laminate.
[0084]
(Play firing and sintering of laminate)
Next, the laminate on this substrate was heated from room temperature in a nitrogen atmosphere to 350 ° C. over 30 minutes, and heat treatment was performed at 350 ° C. for 30 minutes. As a result, it was possible to completely thermally decompose and volatilize the organic resin content of the vehicle in the laminated coating layer without visually peeling or cracking the laminated coating layer.
Next, when sintered by holding at 870 ° C. for 40 minutes under a nitrogen atmosphere, the sintered layer was visually free from abnormalities such as peeling and cracking, and had a good metallic copper luster.
[0085]
Comparative Example 1
In Comparative Example 1, instead of the low polymer (a-2) of methyl methacrylic polymer having Mw 1100 used in Example 2, a vehicle having a Mw of less than 500 was prepared. As a result, the vehicle is shabu-shabu, the coating property is remarkably lowered, and the solvent property and the curing after coating are optimized, so that the polymerizable polyfunctional monomer cannot be combined as a vehicle component. The formability of the paste was significantly reduced.
[0086]
Comparative Example 2
In Comparative Example 2, instead of the Mw7400 methyl methacrylic polymer low polymer (a-3) used in Example 3, a vehicle having an Mw of 11000 exceeding Mw10000 was prepared. As a result, the paste layer after application is cured, and the compounding amount of the polyfunctional monomer that exerts shape shaping on the application paste layer is also increased, which only makes the vehicle cost economically disadvantageous. Therefore, the coating property and the filling amount of the powder are lowered, so that a solvent-type vehicle to which a solvent is added is obtained.
[0087]
【The invention's effect】
From the above, according to the present invention, in the conductive resin paste, the binder resin composition (vehicle) is a low polymer (meth) acrylic polymer having a Mw of about 500 to 10,000, and thermosetting or UV curing. It is formed as a fluid viscous material containing a polymerizable low molecular weight polymerizable polyfunctional monomer.
As a result, this vehicle is solvent-free but has excellent coating properties with solvent properties, and the coating layer after coating is polymerized and cured to impart shapeability to the conductive inorganic powder. Since it is easily pyrolyzed and removed at low temperatures, the coating layer is made of a conductive resin paste that exhibits good sinterability by preventing the occurrence of bubble holes, cracks, bending, shrinkage, etc. Can be provided.
[0088]
In addition, the amount of conductive inorganic powder in the paste can be increased compared to conventional solvent-type vehicles, so that heat shrinkage during pre-firing and sintering of the coating layer can be reduced. A conductive sintered body having excellent dimensional stability can be formed.
[0089]
In addition, unlike conventional pastes, since pre-baking to remove the organic vehicle can be performed in an inert atmosphere, in particular, the conductivity of a conductive metal with low oxidation resistance such as copper and / or its alloy powder, Does not degrade the sinterability and adhesion to the substrate.
[0090]
In addition, since it is solvent-free, it can reduce the organic volatile components that volatilize and decompose and scatter during paste preparation, coating and pre-baking, and reduce environmental pollution from the standpoint of protecting the work environment and the global environment. A conductive resin paste can be provided.

Claims (6)

In a solvent-free paste-like resin composition containing conductive inorganic powder used to form a conductive sintered body,
(A) a (meth) acrylic low polymer having a weight average molecular weight Mw of 500 to 10,000 and a glass transition temperature (Tg) of −80 to 50 ° C. and (B) a low molecular weight of 100 to 5000, A thermosetting or UV curable polymerizable polyfunctional monomer having 2 to 6 polymerizable unsaturated groups;
(C) The paste-like resin composition containing at least one conductive metal having an average particle diameter of 0.1 to 20 μm and / or a conductive inorganic powder of an alloy powder thereof,
The organic vehicle resin component having a viscosity (23 ° C.) of 0.01 to 10 Pa · s contained in the range of 10 to 900 parts by weight of (B) with respect to 100 parts by weight of (A),
A paste-like conductive resin composition comprising 100 to 9000 parts by weight of the conductive inorganic powder (C) and excellent in coating property, shaping property and sintering property.   The conductive inorganic powder comprises at least one metal powder selected from the group consisting of gold, silver, platinum, palladium, aluminum, copper, nickel, tungsten, molybdenum, and titanium and / or at least two elements thereof. The paste-like conductive resin composition according to claim 1, which is an alloy powder.   The paste-like conductive resin composition according to claim 1 or 2, wherein the conductive inorganic powder is a combination of any of the conductive inorganic powders according to claim 2 and glass frit. object. The glass frit is made of Bi ₂ O ₃ —BO ₂ —SiO ₂ , BO ₂ —SiO ₂ —Al ₂ O ₃ —Li ₂ O, PbO—BO ₂ —SiO ₂ , PbO—ZnO—BO ₂ —SiO. The paste-like conductive resin composition according to claim 3, wherein the paste-like conductive resin composition is at least one glass powder selected from a group of _two systems. In a method of forming a conductive sintered body using a paste-like resin composition containing a conductive inorganic powder,
(A) a (meth) acrylic low polymer having a weight average molecular weight Mw of 500 to 10,000 and a glass transition temperature (Tg) in the range of −80 to 50 ° C .;
(B) a low molecular weight product having a molecular weight of 100 to 5,000 , containing a thermosetting or UV curable photopolymerizable polyfunctional monomer having 2 to 6 polymerizable unsaturated groups, and a UV polymerization initiator And the viscosity (23 degreeC) which contains in the range of 10-900 weight part of said (B) with respect to 100 weight part of said (A) is 0.01-10 Pa.s vehicle resin composition Prepare
The vehicle resin composition contains (C) a conductive metal having an average particle diameter in the range of 0.1 to 20 μm and / or a conductive inorganic powder of an alloy powder thereof, and is a solvent-free paste. A resin composition;
Next, the solvent-free paste-like resin composition after coating is UV-cured and cured under UV irradiation,
Next, the vehicle resin composition in the paste layer applied under a thermal history of 250 to 550 ° C. under an inert atmosphere is volatilized and thermally decomposed to be removed and sintered at a further elevated temperature. A method for forming an electrically conductive sintered body. In a method of forming a conductive sintered body using a paste-like resin composition containing a conductive inorganic powder,
A (meth) acrylic low polymer having a weight average molecular weight Mw of 500 to 10,000 and a glass transition temperature (Tg) in the range of −80 to 50 ° C. with the addition of a thermal polymerization initiator (A),
(B) molecular weight of the low molecular weight of 100 to 5000, a thermosetting or UV curable polymerizable polyfunctional monomer polymerizable unsaturated group having 2 to 6, an average particle diameter (C) 0. 10 to 900 parts by weight of (B) with respect to 100 parts by weight of (A) above , containing conductive metal in the range of 1 to 20 μm and / or conductive inorganic powder of alloy powder thereof. The organic vehicle resin component having a viscosity (23 ° C.) in the range of 0.01 to 10 Pa · s contains 100 to 9000 parts by weight of the conductive inorganic powder (C), and is a solvent-free paste. A resin composition;
Next, the solvent-free paste-like resin composition after coating is thermally polymerized and cured under heating at a temperature of 80 to 180 ° C.,
Next, under an inert atmosphere, the vehicle resin composition in the coating paste layer is volatilized and thermally decomposed under a thermal history at a temperature of 250 to 550 ° C. to be scattered and removed, and further sintered at a higher temperature. A method for forming a conductive sintered body.