JP4321911B2

JP4321911B2 - Thermosetting adhesive and its adhesive sheets

Info

Publication number: JP4321911B2
Application number: JP13445699A
Authority: JP
Inventors: 和人細川; 後藤　　陽一郎; 正裕大浦
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 1999-05-14
Filing date: 1999-05-14
Publication date: 2009-08-26
Anticipated expiration: 2019-05-14
Also published as: TW546360B; JP2000319612A

Description

【０００１】
【発明の属する技術分野】
本発明は、電子部品の固定用途などに用いられる熱硬化型接着剤と、そのシ―ト状やテ―プ状などの接着シ―ト類とに関する。
【０００２】
【従来の技術】
近年、電子部品の固定用途などに、種々の接合材料が使用されている。この種の用途では、強接着性に加え、電子部品を基板に実装するときのハンダリフロ―に耐える高耐熱性が必要である。また、接着時の濡れ性を確保するため、通常、熱プレスで接着処理しているが、生産性の向上、熱接着時の部品の損傷の低減などの理由により、低圧、短時間の接着条件が求められている。
【０００３】
この要望に対し、加熱処理により硬化する熱硬化型接着剤が提案されている。熱硬化性接着剤は、ガラス転移温度が室温以上のため、室温では粘着性がなく、熱プレスでの接着時に気泡の抱き込みなどがなく、良好に接着処理でき、耐熱性にもすぐれている。しかし、この熱硬化性接着剤は、未反応の低分子量分を多く含み、これが熱プレス時に流動して被着体に対する濡れを良くし、短時間接着を可能とする反面、その後の硬化反応時の収縮にて応力が残留し、長期の連続高温使用下で容易に剥離する問題があつた。また、この硬化収縮を回避するため、あらかじめ部分的に反応させる（Ｂステ―ジ化する）手法も考えられているが、この場合、プレス接着処理に長時間を要し、短時間処理に適さない。
【０００４】
また、粘着テ―プなどでは、粘着剤のガラス転移温度が−５０℃以下のため、常温で粘着性を有しており、なんの予備操作もなしに目的物に貼り付けでき、この貼り付けでただちに接着強度を発現できる。また、一般に未反応物を含んでいないため、常温保存が可能であり、特性の経時変化が少ないなどの利点がある。しかし、この種の粘着テ―プは、粘着性のために、熱プレス時に気泡の抱き込みなどが生じやすく、１００℃以上の高温になると、抱き込んだ気泡の膨張により剥離や発泡などが起こる問題がある。しかも、接着強度や耐熱性が、熱硬化型接着剤に比べて、かなり劣るという問題もある。
【０００５】
【発明が解決しようとする課題】
本発明は、このような事情に照らし、常温で粘着性が低く、プレス接着時に気泡の抱き込みなどを生じず、低圧、短時間とくに数秒以内の加熱処理で強固に接着処理でき、高温での連続使用下でも接着力の大きな低下などの不都合がなく、ハンダリフロ―に耐える高耐熱性を発揮する、信頼性にすぐれた熱硬化型接着剤とその接着シ―ト類を提供することを目的としている。
【０００６】
【課題を解決するための手段】
本発明者らは、上記目的に対する鋭意検討の過程において、まず、アクリル系重合体の合成に際し、粘着シ―ト類の作製に一般に用いられているアルキル基の炭素数が平均２〜１４個の（メタ）アクリル酸アルキルエステルを主成分とし、これに粘着性をなくすためにポリマ―のガラス転移温度が高くなる単量体を加えて共重合させ、これにエポキシ樹脂などを加えた系で検討したところ、粘着性の低い接着シ―ト類の作製はできるが、接着性、耐熱性ともに満足できるものは得られなかつた。また、（メタ）アクリル酸アルキルエステルとして、ポリマ―のガラス転移温度が−３０℃以上となるようなアルキル基を持つた単量体を用い、上記同様に接着シ―ト類の作製を試みたが、非常にもろい接着シ―ト類となり、可撓性、柔軟性の点で満足できるものは得られなかつた。
【０００７】
本発明者らは、上記の知見を踏まえて、さらに検討した結果、ホモポリマ―のガラス転移温度が−３０℃以上となる特定の分子構造を持つ（メタ）アクリル酸エステルを使用し、これにエポキシ樹脂と架橋結合を起こさせるための官能基を持つモノエチレン性不飽和単量体を加えて共重合させ、得られる非粘着性重合物にさらに低圧、短時間のプレス接着を実現するための特定の流動性付与成分と、耐熱性向上成分としてのエポキシ樹脂を加えたものによれば、可撓性、柔軟性に富むシ―ト状物などを形成でき、このものは、常温での粘着性が低く、プレス接着時に気泡の抱き込みなどを生じず、低圧、短時間とくに数秒以内の加熱処理で強固に接着処理できるとともに、高温での連続使用下においても硬化収縮による残留応力に起因した接着力の大きな低下などがみられず、またハンダリフロ―に耐える高耐熱性を発揮する、信頼性に非常にすぐれた熱硬化型接着剤とその接着シ―ト類が得られることを知り、本発明を完成するに至つた。
【０００８】
すなわち、本発明は、ａ）つぎの式（１）；

（式中、Ｒ¹は水素原子またはメチル基、Ｒ²はメチレン基、エチレン基またはプロピレン基、ｎ＝１〜３の整数、φはフエニル基、モノアルキル置換フエニル基またはジアルキル置換フエニル基である）
で表される、ホモポリマ―のガラス転移温度（以下、Ｔｇという）が−３０℃以上である（メタ）アクリル酸エステル７０〜９９重量％と、これと共重合可能でエポキシ樹脂と反応する官能基を持つモノエチレン性不飽和単量体３０〜１重量％とからなる単量体混合物の非粘着性重合物１００重量部に、ｂ）軟化点が８０〜２００℃である流動性付与樹脂３〜３０重量部と、ｃ）エポキシ樹脂５〜３０重量部とを含ませてなり、かつ上記ｃ成分のエポキシ樹脂の硬化剤を実質的に含まないことを特徴とする熱硬化型接着剤（請求項１）に係るものであり、とくに、上記ａ成分の非粘着性重合物が紫外線などの放射線の照射による重合物である上記構成の熱硬化型接着剤（請求項２）に係るものである。また、本発明は、基材の片面または両面に上記構成の熱硬化型接着剤からなる層を有することを特徴とする接着シ―ト類（請求項３）に係るものである。
【０００９】
【発明の実施の形態】
本発明における単量体混合物は、式（１）で表される（メタ）アクリル酸エステルと、これと共重合可能でエポキシ樹脂と反応する官能基を持つモノエチレン性不飽和単量体との混合物である。前者の（メタ）アクリル酸エステルは、その３０重量％までを、アクリル系粘着剤の改質用単量体として知られる酢酸ビニル、スチレン、アクリロニトリルなどのエポキシ樹脂と反応する官能基を持たないビニル系単量体に置換してもよいが、共重合物のＴｇが低下して粘着性を示すことのないように、各単量体の種類に応じてその置換量が決められる。
【００１０】
式（１）で表される（メタ）アクリル酸エステルは、ホモポリマ―のＴｇが−３０℃以上、好ましくは−１０℃以上となるものであり、代表的なものとして、フエノキシエチル（メタ）アクリレ―ト、フエノキシプロピル（メタ）アクリレ―ト、ノニルフエノキシエチル（メタ）アクリレ―ト、ノニルフエノキシプロピル（メタ）アクリレ―トなどがある。また、フエノ―ル、クレゾ―ルノニルフエノ―ルなどのエチレンオキシド付加物、プロピレンオキシド付加物など（付加モル数３まで）と（メタ）アクリル酸とのエステルなども好ましく用いられる。これらのエステルは、１種または２種以上用いられる。
【００１１】
上記エステルと共重合可能でエポキシ樹脂と反応する官能基を持つモノエチレン性不飽和単量体は、上記エステルとの共重合により生成する非粘着性重合物とエポキシ樹脂との間で架橋結合を起こさせ、これにより耐熱性や接着性を改善、改質する目的で用いられる。このような単量体には、エポキシ樹脂と反応する官能基としてカルボキシル基を持つカルボキシル基含有単量体、同官能基として水酸基を持つ水酸基含有単量体がある。カルボキシル基含有単量体にはアクリル酸、メタクリル酸、カプロラクトン変性アクリレ―トなどがあり、水酸基含有単量体には２−ヒドロキシ−３−フエノキシプロピルアクリレ―トなどがある。これらは、必要により１種または２種以上用いられる。なお、エポキシ樹脂と反応する官能基としてアミノ基を持つアミノ基含有単量体は、エポキシ樹脂との反応性が強すぎて、貯蔵安定性が低下するため、好ましくない。
【００１２】
単量体混合物において、式（１）で表される（メタ）アクリル酸エステルと、これと共重合可能でエポキシ樹脂と反応する官能基を持つモノエチレン性不飽和単量体との使用割合としては、前者の（メタ）アクリル酸エステルが７０〜９９重量％、好ましくは８５〜９５重量％で、後者の共重合可能なモノエチレン性不飽和単量体が３０〜１重量％、好ましくは１５〜５重量％となるようにするのがよい。このような使用割合とすることにより、熱硬化型接着剤としての耐熱性や接着性などのバランスをうまくとることができる。
【００１３】
本発明では、上記の単量体混合物を重合させて、ａ成分である非粘着性重合物を得る。重合は、溶液重合法、乳化重合法、塊状重合法など適宜の重合方式を採用できるが、紫外線や電子線などの放射線の照射による塊状重合法が好ましい。これによれば、有機溶剤の残存による電子部品の腐食、高温での気化膨張による膨れ、剥がれ、ずれ、乳化剤のブリ―ドによる汚染、接着不良、耐湿性低下などの心配がなく、また比較的弱い強度の紫外線などを照射することで重合物の分子量を高くでき、高い架橋度と大きな凝集力を有する耐熱性にとくにすぐれた非粘着性重合物が得られる。重合には、重合触媒として、熱重合開始剤や光重合開始剤が用いられ、また過硫酸カリウム、過硫酸アンモニウム、過酸化水素などや、これらと還元剤とからなるレドツクス系開始剤なども使用できる。
【００１４】
本発明の熱硬化型接着剤は、上記のようにして得られるａ成分である非粘着性重合物とともに、ｂ成分である軟化点が８０〜２００℃である流動性付与樹脂とｃ成分であるエポキシ樹脂を必須成分としたものである。これらｂ成分およびｃ成分は、非粘着性重合物を得たのちに配合してもよいし、得る前の単量体混合物中に配合してもよい。とくに、単量体混合物の重合を紫外線などの放射線の照射により行う場合は、単量体混合物中に上記ｂ成分およびｃ成分を混合した状態で紫外線などの放射線を照射して重合させるのが望ましい。
【００１５】
ｂ成分としての流動性付与樹脂は、軟化点（または融点）が８０〜２００℃、好ましくは１００〜２００℃、より好ましくは１２０〜１５０℃のものであり、ロジン系、テルペン系、合成石油系、フエノ―ル系、キシレン系など、一般に、粘着付与樹脂として知られる各種の樹脂をいずれも使用できる。このような流動性付与樹脂を配合することにより、熱硬化型接着剤に適度の流動性が付与されて低圧、短時間とくに数秒以内の加熱処理て強固に接着させることができる。この流動性付与樹脂の軟化点が８０℃より低いと、低圧、短時間の接着には有利であるが、耐熱性が不十分となり、２００℃を超えると、プレス接着時に流動性付与成分として機能しなくなり、短時間での接着が困難となる。
【００１６】
このような流動性付与樹脂の使用量としては、非粘着性重合物１００重量部あたり、３〜３０重量部の範囲内、好ましくは５〜１５重量部の範囲内で、その種類や非粘着性重合物の種類に応じて、適宜決められる。上記の使用量が３重量部より少ないと、プレス接着時に流動性付与成分として機能しなくなり、低圧、短時間での接着が困難となり、３０重量部よりも多くなると、低圧、短時間での接着には有利であるが、耐熱性が不十分となる。
【００１７】
ｃ成分としてのエポキシ樹脂は、分子内に２個以上のエポキシ基を含有する化合物であり、たとえば、ビスフエノ―ルエポキシ樹脂、脂肪族系エポキシ樹脂、フエノリツクエポキシ樹脂、ハロゲン化ビスフエノ―ルエポキシ樹脂などを挙げることができ、これらの中から、その１種または２種以上が用いられる。なお、単量体混合物中にエポキシ樹脂を混合した状態で放射線重合する場合は、分子内に放射線重合基を持たないエポキシ樹脂が用いられる。
【００１８】
このようなエポキシ樹脂の使用量としては、非粘着性重合物１００重量部あたり、５〜３０重量部の範囲内、好ましくは５〜２０重量部の範囲内で、その種類や非粘着性重合物の種類に応じて、適宜決められる。上記の使用量が５重量部より少ないと、非粘着性重合物とエポキシ樹脂との架橋反応が十分に進行しないため、耐熱性が不十分となる。また、上記の使用量が３０重量部より多くなると、高温での連続使用において、接着剤硬化物の過剰な架橋に起因して、接着強度の低下が起こりやすくなり、信頼性を損なう結果となる。
【００１９】
本発明の熱硬化型接着剤には、接着剤としての保持特性を向上させるため、交叉結合剤として、イソシアネ―ト系化合物、エポキシ系化合物などの公知の架橋剤や、光重合を行う場合などには、トリメチロ―ルプロパントリ（メタ）アクリレ―ト、ペンタエリスリト―ルテトラ（メタ）アクリレ―ト、１，２−エチレングリコ―ルジ（メタ）アクリレ―ト、１，６−ヘキサンジオ―ルジ（メタ）アクリレ―トなどの多官能（メタ）アクリレ―トを含有させるのが望ましい。
【００２０】
上記の架橋剤や多官能（メタ）アクリレ―トからなる交叉結合剤の使用量は、単量体混合物１００重量部に対し、通常０．０５〜５重量部、好ましくは０．１〜３重量部の範囲とするのがよい。多官能（メタ）アクリレ―トを用いる場合、上記範囲内で２官能の場合は多く、３官能やそれ以上の多官能の場合は少なくするのがよい。上記使用量が少なすぎると、重合後の架橋度を十分に高くできず、保持特性の低下を招きやすく、逆に多すぎると、熱硬化型接着剤の弾性率が極端に高くなり、接着不良などの接着性の低下を引き起こしやすい。
【００２１】
本発明の熱硬化型接着剤には、任意成分として、可塑剤、軟化剤、充填剤、顔料、染料、老化防止剤などの従来公知の各種の添加剤を、接着剤の諸特性を低下させない程度に添加することができる。しかし、任意成分のひとつとして、エポキシ樹脂の硬化剤として知られるイミダゾ―ル、ジシアンジアミド、ポリアミンなどの一般の硬化剤を添加することはできない。ただし、これら硬化剤が存在しても、エポキシ樹脂との硬化反応が加熱処理を施す前に実質的に進行せず、貯蔵安定性を大きく損なうおそれのないときは、その限りではない。本発明において“実質的に含まない”とは、このような意味である。
【００２２】
本発明の熱硬化型接着シ―ト類は、基材の片面または両面に、上記のａ〜ｃ三成分を必須とした熱硬化型接着剤からなる層を設けて、シ―ト状やテ―プ状などの形態としたものである。上記の層は、あらかじめ適宜の重合法でａ成分である非粘着性重合物を得、これにｂ成分の流動性付与樹脂、ｃ成分のエポキシ樹脂および架橋剤などを加えて熱硬化型接着剤を調製し、これを基材上に塗工し、必要に応じ加熱などにより架橋処理する方式で形成できる。また、より好ましくは、重合前の単量体混合物またはその部分重合物にｂ成分の流動性付与樹脂、ｃ成分のエポキシ樹脂および多官能（メタ）アクリレ―トなどを加えた放射線重合性組成物を調製し、これを基材上に塗工し紫外線などの放射線を照射して重合させ、ａ成分である非粘着性重合物の合成と同時に層形成するのがよい。この方法によれば、接着剤の耐熱性により好結果を得ることができる。
【００２３】
基材としては、ポリエステルフイルムなどの合成樹脂フイルムや繊維基材などの非剥離性基材のほか、剥離紙などの剥離性基材を使用できる。剥離性基材の場合、この上に形成した熱硬化型接着剤からなる層を最終的に非剥離性基材の上に転写してもよい。本発明の接着シ―ト類には、基材としてこのような非剥離性基材を用いたものと剥離性基材を用いたものとの両方が含まれる。
【００２４】
本発明の熱硬化型接着シ―ト類は、上記した特定の非粘着性重合物に耐熱性を低下させない程度の少量の流動性付与樹脂と上記重合物と架橋反応させる少量のエポキシ樹脂を含ませたことにより、常温での粘着性が低くて、プレス接着時に気泡の抱き込みなどを生じず、低圧、短時間とくに数秒以内の加熱処理で強固な接着性を発現でき、しかも８０℃以上の高温での連続使用下においても硬化収縮による残留応力に起因した接着力の大きな低下や剥離などの不都合がなく、かつハンダリフロ―に耐える高耐熱性を発揮し、また加熱処理を施す前の状態では架橋反応などがほとんど進行せず、貯蔵安定性の面でもすぐれている。このため、電子部品の固定用途などとして、また耐熱フイルムや金属板などの接合材料として、その他上記特徴を生かした幅広い用途に使用できる。
【００２５】
【実施例】
つぎに、本発明の実施例を記載して、より具体的に説明する。なお、以下において、部とあるのは重量部を意味するものとする。
【００２６】
実施例１
冷却管、窒素導入管、温度計、撹拌機を備えた反応容器に、酢酸エチル２１０部を溶媒として、フエノキシエチルアクリレ―ト（ホモポリマ―のＴｇ：−１０℃）９５部、アクリル酸５部、過酸化ベンゾイル０．３部を入れ、窒素気流中で重合処理して、固形分が約３０重量％の非粘着性重合物の溶液を得た。この溶液に、その固形分１００部あたり、フエノ―ル樹脂〔三井東圧化学（株）製の商品名「ＸＬ−２２５Ｌ」、軟化点：８５℃〕５部、エポキシ樹脂（油化シエルエポキシ社製の商品名「エピコ―ト８２８」）１５部、多官能イソシアネ―ト系架橋剤１部を、均一に混合して、熱硬化型接着剤溶液を調製した。つぎに、この熱硬化型接着剤溶液を剥離性基材上に塗布し、１３０℃で５分間乾燥処理して、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００２７】
実施例２
四つ口フラスコに、フエノキシエチルアクリレ―ト９０部、アクリロイルモルフオリン５部、アクリル酸５部、２，２−ジメトキシ−２−フエニルアセトフエノン０．０５部を投入し、窒素雰囲気下紫外線を照射して部分的に光重合させ、粘度が約３０ポイズのシロツプを得た。この部分重合したシロツプ１００部に、フエノ―ル樹脂〔三井東圧化学（株）製の商品名「ＸＬ−２２５Ｌ」、軟化点：８５℃〕５部、エポキシ樹脂（油化シエルエポキシ社製の商品名「エピコ―ト８２８」）１５部、交叉結合剤としての１，６−ヘキサンジオ―ルジアクリレ―ト０．３部を、均一に混合し、光重合性組成物を調製した。つぎに、この光重合性組成物を剥離性基材上に塗布し、９００mj／cm²の紫外線を照射して光重合させ、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００２８】
実施例３
フエノキシエチルアクリレ―ト９０部の代わりに、クレゾ―ルのエチレンオキシド付加物（付加モル数１）とアクリル酸とのエステル（ホモポリマ―のＴｇ：−２０℃）９０部を使用した以外は、実施例２と同様にして、光重合性組成物を調製し、これを用いて、実施例２と同様にして、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００２９】
実施例４
四つ口フラスコに、ノニルフエノ―ルのエチレンオキシド付加物（付加モル数１）とアクリル酸とのエステル（ホモポリマ―のＴｇ：−２５℃）９５部、２−ヒドロキシ−３−フエノキシプロピルアクリレ―ト５部、２，２−ジメトキシ−２−フエニルアセトフエノン０．０５部を投入し、窒素雰囲気下で紫外線を照射して部分的に光重合させ、粘度が約３０ポイズのシロツプを得た。この部分重合したシロツプ１００部に、テルペンフエノ―ル樹脂（住友デユレス社製の商品名「スミライトレジンＰＲ−１２６０３」、軟化点：１３３℃）１０部、エポキシ樹脂（油化シエルエポキシ社製の商品名「エピコ―ト８１５」）１０部、交叉結合剤としてのトリメチロ―ルプロパントリアクリレ―ト０．２部を、均一に混合して、光重合性組成物を調製した。つぎに、この光重合性組成物を剥離性基材上に塗布し、９００mj／cm²の紫外線を照射して光重合させ、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００３０】
比較例１
冷却管、窒素導入管、温度計、撹拌機を備えた反応容器に、酢酸エチル２１０部を溶媒として、ブチルアクリレ―ト（ホモポリマ―のＴｇ＜−３０℃）６０部、アクリロニトリル３５部、アクリル酸５部、過酸化ベンゾイル０．３部を入れ窒素気流中で重合処理して、固形分が約３０重量％の重合物の溶液を得た。この溶液に、その固形分１００部あたり、フエノ―ル樹脂〔三井東圧化学（株）製の商品名「ＸＬ−２２５Ｌ」、軟化点：８５℃〕５部、エポキシ樹脂（油化シエルエポキシ社製の商品名「エピコ―ト８２８」）１５部、多官能イソシアネ―ト系架橋剤１部を、均一に混合して、熱硬化型接着剤溶液を調製した。つぎに、この熱硬化型接着剤溶液を剥離性基材上に塗布し、１３０℃で５分間乾燥処理して、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００３１】
比較例２
四つ口フラスコに、イソオクチルアクリレ―ト（ホモポリマ―のＴｇ＜−３０℃）８０部、アクリル酸２０部、２，２−ジメトキシ−２−フエニルアセトフエノン０．０５部を投入し、窒素雰囲気下紫外線を照射して部分的に光重合させ、粘度が約３０ポイズのシロツプを得た。この部分重合したシロツプ１００部に、フエノ―ル樹脂〔三井東圧化学（株）製の商品名「ＸＬ−２２５Ｌ」、軟化点：８５℃）５部、エポキシ樹脂（油化シエルエポキシ社製の商品名「エピコ―ト８２８」）１０部、交叉結合剤としての１，６−ヘキサンジオ―ルジアクリレ―ト０．３部を均一に混合して、光重合性組成物を調製した。つぎに、この光重合性組成物を剥離性基材上に塗布し、９００mj／cm²の紫外線を照射して光重合させ、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００３２】
比較例３
四つ口フラスコに、エチルアクリレ―ト（ホモポリマ―のＴｇ＜−３０℃）８０部、アクリロイルモルフオリン１５部、アクリル酸５部、２，２−ジメトキシ−２−フエニルアセトフエノン０．０５部を投入し、窒素雰囲気下紫外線を照射して部分的に光重合させ、粘度が約３０ポイズのシロツプを得た。この部分重合したシロツプ１００部に、フエノ―ル樹脂〔三井東圧化学（株）製の商品名「ＸＬ−２２５Ｌ」、軟化点：８５℃〕５部、エポキシ樹脂（油化シエルエポキシ社製の商品名「エピコ―ト８１５」）１０部、交叉結合剤としての１，６−ヘキサンジオ―ルジアクリレ―ト０．３部を均一に混合して、光重合性組成物を調製した。つぎに、この光重合性組成物を剥離性基材上に塗布し、９００mj／cm²の紫外線を照射して光重合させ、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００３３】
比較例４
フエノ―ル樹脂〔三井東圧化学（株）製の商品名「ＸＬ−２２５Ｌ」、軟化点：８５℃）５部を使用しなかつた以外は、実施例２と同様にして、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００３４】
比較例５
四つ口フラスコに、フエノキシエチルアクリレ―ト１００部、２，２−ジメトキシ−２−フエニルアセトフエノン０．０５部を投入し、窒素雰囲気下紫外線を照射して部分的に光重合させ、粘度が約３０ポイズのシロツプを得た。この部分重合したシロツプ１００部に、テルペンフエノ―ル樹脂（住友デユレス社製の商品名「スミライトレジンＰＲ−１２６０３」、軟化点：１３３℃）１０部、エポキシ樹脂（油化シエルエポキシ社製の商品名「エピコ―ト８２８」）５０部、変性ポリアミン（エポキシ樹脂の硬化剤、エ―・シ―・ア―ル社製の商品名「ＡＣＲハ―ドナ―Ｘ−３６１５」）７部、交叉結合剤としての１，６−ヘキサンジオ―ルジアクリレ―ト０．３部を、均一に混合して、光重合性組成物を調製した。つぎに、この光重合性組成物を剥離性基材上に塗布し、９００mj／cm²の紫外線を照射して光重合させ、厚さが１００μｍの熱硬化型接着剤層を形成し、接着シ―トを作製した。
【００３５】
上記の実施例１〜４および比較例１〜５の各接着シ―トについて、下記の方法により、プレス接着後の外観、接着力およびハンダ耐熱性を調べた。これらの結果は、表１に示されるとおりであつた。
【００３６】
＜プレス接着後の外観＞
３０mm角に切断した接着シ―トを、常温でラミネ―タ（圧力：５kg／cm²、速度：２ｍ／分）によりＳＵＳ３０４に貼り合わせ、これを厚さが７５μｍのポリイミドフイルムにプレス機（温度１５０℃、時間１秒、圧力５kg／cm²）で貼り合わせた。そのときの貼り合わせ面の状態を目視にて観察し、○：気泡の抱き込みや未接着部分がほとんどみられない、×：気泡の抱き込みや未接着部分が明らかにみられる、と評価した。
【００３７】
＜接着力＞
幅１０mm、長さ５０mmに切断した接着シ―トを、厚さが７５μｍのポリイミドフイルムにラミネ―タ（温度：１００℃、圧力：５kg／cm²、速度：２ｍ／分）により貼り合わせ、これをＳＵＳ３０４にプレス機（温度：１５０℃、時間：１秒、圧力：５kg／cm²）で貼り合わせた。このサンプルを、１５０℃で１時間の加熱処理により硬化させたのち、初期（常温で３０分放置後）および高温放置後（１００℃で１００時間放置後）に、引張り速度５０mm／分の条件で、９０°方向に引張り、その中心値を９０°剥離接着強度として、接着力を求めた。
【００３８】
＜ハンダ耐熱性＞
幅１０mm、長さ５０mmに切断した接着シ―トを、厚さが７５μｍのポリイミドフイルムにラミネ―タ（温度：１００℃、圧力：５kg／cm²、速度：２ｍ／分）により貼り合わせ、これを３０mm角のＳＵＳ３０４にプレス機（温度：１５０℃、時間：１秒、圧力：５kg／cm²）で貼り合わせた。このサンプルを１５０℃で１時間の加熱処理により硬化させたのち、ＳＵＳ３０４面を上にして、２４０℃に溶融したハンダ浴に浮かせた状態で６０秒間処理した。処理後のシ―トの貼り合わせ状態を目視により観察し、○：接着剤の発泡や接着異常（浮き、しわ、剥がれ、ずれ）がほとんどみられない、×：上記発泡や接着異常が明らかにみられる、と評価した。
【００３９】

【００４０】
上記の表１の結果から明らかなように、本発明の実施例１〜４の各接着シ―トは、プレス接着時に気泡の抱き込みや接着不良がみられず、大きな接着力を示しており、また高温連続放置後においても上記接着力の低下が少なく、ハンダ耐熱性もすぐれていることがわかる。これに対し、比較例１〜３の各接着シ―トは、（メタ）アクリル酸アルキルエステルを主成分とし、これと高いＴｇを付与する単量体とを共重合させることにより、重合物の粘着性が低くなり、プレス接着時に気泡の抱き込みや接着不良を引き起こすことはないが、接着力に乏しくなり、ましてやハンダ耐熱性を満足させることはできない。
【００４１】
また、比較例４の粘着シ―トは、流動性付与樹脂を含ませなかつたため、プレス接着時に未接触部分が残り、それが機転となつてハンダ耐熱時の浮きの原因となり、ハンダ耐熱性を満足させることができない。さらに、比較例５の粘着シ―トは、エポキシ樹脂を過剰に含ませるとともに、このエポキシ樹脂の硬化剤を含ませたため、高温連続放置後に硬化が徐々に進行して架橋密度が密になりすぎ、接着力が大幅な低下して、使用に供し得なくなる。
【００４２】
【発明の効果】
以上のように、本発明においては、ホモポリマ―のＴｇが−３０℃以上となる特定の分子構造を持つ（メタ）アクリル酸エステルと、エポキシ樹脂と反応する官能基を持つモノエチレン性不飽和単量体とを共重合させてなる非粘着性重合物を使用し、これに特定の軟化点を有する流動性付与樹脂およびエポキシ樹脂を含ませる構成としたことにより、常温で粘着性が低くて、プレス接着時に気泡の抱き込みなどを生じず、低圧、短時間とくに数秒以内の加熱処理で強固に接着処理できるとともに、高温での連続使用下でも硬化収縮などでの残留応力に起因した接着力の大きな低下などがみられず、しかもハンダリフロ―に耐える高耐熱性を発揮する、また貯蔵安定性も満足する、信頼性に非常にすぐれた熱硬化型接着剤とその接着シ―ト類を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermosetting adhesive used for fixing electronic parts and the like, and an adhesive sheet such as a sheet or tape.
[0002]
[Prior art]
In recent years, various bonding materials have been used for fixing electronic parts. In this type of application, in addition to strong adhesion, high heat resistance is required to withstand solder reflow when electronic components are mounted on a substrate. Also, in order to ensure wettability during bonding, bonding is usually performed with a hot press, but due to reasons such as improved productivity and reduced damage to parts during thermal bonding, bonding conditions under low pressure and short time Is required.
[0003]
In response to this demand, a thermosetting adhesive that is cured by heat treatment has been proposed. Thermosetting adhesives have a glass transition temperature above room temperature, so there is no stickiness at room temperature, there is no air bubble embedding at the time of bonding with a hot press, they can be well bonded, and they have excellent heat resistance. . However, this thermosetting adhesive contains a large amount of unreacted low molecular weight, which flows during hot pressing to improve the wetness to the adherend and enables adhesion for a short time, but at the time of subsequent curing reaction There was a problem that stress remained due to shrinkage of the film and easily peeled off under long-term continuous high-temperature use. In order to avoid this curing shrinkage, a method of partially reacting (B stage) in advance is also considered, but in this case, it takes a long time for the press bonding process and is suitable for a short time process. Absent.
[0004]
In adhesive tapes, etc., the glass transition temperature of the adhesive is -50 ° C or lower, so it has adhesiveness at room temperature and can be applied to the target without any preliminary operation. The adhesive strength can be immediately expressed. In addition, since it generally does not contain unreacted substances, it can be stored at room temperature, and there are advantages such as little change in characteristics over time. However, since this type of adhesive tape is sticky, it tends to cause entrapment of bubbles at the time of hot pressing. When the temperature is higher than 100 ° C, exfoliation or foaming occurs due to expansion of the encapsulated bubbles. There's a problem. In addition, there is a problem that the adhesive strength and heat resistance are considerably inferior to those of thermosetting adhesives.
[0005]
[Problems to be solved by the invention]
In light of such circumstances, the present invention has low adhesiveness at room temperature, does not cause bubble embedding at the time of press bonding, and can be firmly bonded by low-temperature, short-time heating treatment, particularly within a few seconds, at high temperatures. The purpose is to provide a highly reliable thermosetting adhesive and its adhesive sheets that exhibit high heat resistance that can withstand solder reflow, without inconveniences such as a significant decrease in adhesive strength even under continuous use. Yes.
[0006]
[Means for Solving the Problems]
In the process of earnestly examining the above object, the present inventors first have an average of 2 to 14 carbon atoms of an alkyl group generally used for preparing an adhesive sheet in the synthesis of an acrylic polymer. Considering a system in which (meth) acrylic acid alkyl ester is the main component, a monomer that increases the glass transition temperature of the polymer is added and copolymerized, and an epoxy resin is added to this to eliminate stickiness. As a result, it was possible to produce adhesive sheets with low tackiness, but no satisfactory one was obtained in terms of both adhesiveness and heat resistance. In addition, as a (meth) acrylic acid alkyl ester, a monomer having an alkyl group with a polymer glass transition temperature of −30 ° C. or higher was used, and an adhesive sheet was prepared in the same manner as described above. However, it became extremely brittle adhesive sheets, and no satisfactory one was obtained in terms of flexibility and flexibility.
[0007]
As a result of further investigation based on the above findings, the present inventors used (meth) acrylic acid ester having a specific molecular structure in which the glass transition temperature of the homopolymer is -30 ° C. or higher, and epoxy resin was used for this. Specific to realize press adhesion at a lower pressure and in a shorter time to the resulting non-adhesive polymer by adding and copolymerizing a monoethylenically unsaturated monomer with a functional group to cause crosslinking with the resin With the addition of a fluidity-imparting component and an epoxy resin as a heat resistance improving component, it is possible to form a sheet-like material with high flexibility and flexibility. It is low, does not cause bubble embedding during press bonding, can be firmly bonded by low-temperature, short-time heating, especially within a few seconds, and can be bonded due to residual stress due to curing shrinkage even under continuous use at high temperatures. Knowing that a highly reliable thermosetting adhesive and its adhesive sheet exhibiting high heat resistance that can withstand solder reflow are obtained, and there is no significant decrease in strength, etc. Has been completed.
[0008]
That is, the present invention provides: a) the following formula (1);

Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a methylene group, an ethylene group or a propylene group, n is an integer of 1 to 3, φ is a phenyl group, a monoalkyl-substituted phenyl group or a dialkyl-substituted phenyl group. )
Represented by the formula (70) to 99% by weight of a (meth) acrylic acid ester having a glass transition temperature (hereinafter referred to as Tg) of −30 ° C. or higher, and a functional group that can be copolymerized therewith and react with an epoxy resin. 100 parts by weight of a non-adhesive polymer of a monomer mixture consisting of 30 to 1% by weight of a monoethylenically unsaturated monomer having b) a fluidity imparting resin 3 having a softening point of 80 to 200 ° C. A thermosetting adhesive comprising 30 parts by weight and c) 5 to 30 parts by weight of an epoxy resin, and substantially free of a curing agent for the epoxy resin of the component c (claim) 1), and in particular, relates to the thermosetting adhesive having the above-described structure, in which the non-tacky polymer of component a is a polymer obtained by irradiation with radiation such as ultraviolet rays. The present invention also relates to an adhesive sheet (Claim 3) characterized by having a layer made of the thermosetting adhesive having the above-described structure on one or both sides of a base material.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The monomer mixture in the present invention comprises a (meth) acrylic acid ester represented by the formula (1) and a monoethylenically unsaturated monomer that has a functional group that can be copolymerized therewith and react with an epoxy resin. It is a mixture. The former (meth) acrylic acid ester has up to 30% by weight of vinyl having no functional group that reacts with epoxy resins such as vinyl acetate, styrene and acrylonitrile, which are known as monomers for modifying acrylic adhesives. Although it may be substituted with a monomer, the amount of substitution is determined according to the type of each monomer so that the Tg of the copolymer does not decrease and does not exhibit tackiness.
[0010]
The (meth) acrylic acid ester represented by the formula (1) has a homopolymer Tg of −30 ° C. or higher, preferably −10 ° C. or higher, and is typically phenoxyethyl (meth) acrylate. , Phenoxypropyl (meth) acrylate, nonylphenoxyethyl (meth) acrylate, nonylphenoxypropyl (meth) acrylate, and the like. Further, ethylene oxide adducts such as phenol and cresol nonylphenol, propylene oxide adducts (up to 3 addition moles) and esters of (meth) acrylic acid are also preferably used. These esters are used alone or in combination of two or more.
[0011]
Monoethylenically unsaturated monomers that can be copolymerized with the ester and have a functional group that reacts with the epoxy resin are cross-linked between the non-adhesive polymer formed by copolymerization with the ester and the epoxy resin. This is used for the purpose of improving and improving heat resistance and adhesion. Such monomers include a carboxyl group-containing monomer having a carboxyl group as a functional group that reacts with an epoxy resin, and a hydroxyl group-containing monomer having a hydroxyl group as the functional group. Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, and caprolactone-modified acrylate, and examples of the hydroxyl group-containing monomer include 2-hydroxy-3-phenoxypropyl acrylate. These may be used alone or in combination of two or more. An amino group-containing monomer having an amino group as a functional group that reacts with the epoxy resin is not preferable because the reactivity with the epoxy resin is too strong and the storage stability is lowered.
[0012]
In the monomer mixture, the use ratio of the (meth) acrylic acid ester represented by the formula (1) and the monoethylenically unsaturated monomer copolymerizable therewith and having a functional group that reacts with the epoxy resin The former (meth) acrylic acid ester is 70 to 99% by weight, preferably 85 to 95% by weight, and the latter copolymerizable monoethylenically unsaturated monomer is 30 to 1% by weight, preferably 15%. It is good to make it -5 weight%. By setting it as such a use ratio, the balance of heat resistance, adhesiveness, etc. as a thermosetting adhesive can be taken well.
[0013]
In the present invention, the monomer mixture is polymerized to obtain a non-adhesive polymer as component a. For the polymerization, an appropriate polymerization method such as a solution polymerization method, an emulsion polymerization method or a bulk polymerization method can be adopted, but a bulk polymerization method by irradiation with radiation such as ultraviolet rays or electron beams is preferred. According to this, there is no concern about corrosion of electronic components due to remaining organic solvent, swelling, peeling, slippage due to vaporization and expansion at high temperature, contamination due to emulsifier blades, poor adhesion, reduced moisture resistance, etc. By irradiating with weak UV light, the molecular weight of the polymer can be increased, and a non-adhesive polymer with excellent heat resistance having a high degree of crosslinking and a large cohesion can be obtained. In the polymerization, a thermal polymerization initiator or a photopolymerization initiator is used as a polymerization catalyst, and potassium persulfate, ammonium persulfate, hydrogen peroxide, or a redox initiator composed of these and a reducing agent can also be used. .
[0014]
The thermosetting adhesive of the present invention is a fluidity-imparting resin having a softening point of 80 to 200 ° C. and a c component, together with a non-tacky polymer that is the a component obtained as described above. An epoxy resin is an essential component. These b component and c component may be blended after obtaining the non-adhesive polymer, or may be blended in the monomer mixture before being obtained. In particular, when the polymerization of the monomer mixture is performed by irradiation with radiation such as ultraviolet rays, it is desirable to perform polymerization by irradiating the monomer mixture with radiation such as ultraviolet rays in a state where the b component and the c component are mixed. .
[0015]
The fluidity imparting resin as component b has a softening point (or melting point) of 80 to 200 ° C., preferably 100 to 200 ° C., more preferably 120 to 150 ° C., and is a rosin, terpene, or synthetic petroleum type. Any of various resins generally known as tackifying resins such as phenolic and xylene-based resins can be used. By blending such a fluidity-imparting resin, the thermosetting adhesive is imparted with an appropriate fluidity, and can be firmly bonded by heat treatment within a low pressure for a short time, particularly within a few seconds. When the softening point of the fluidity-imparting resin is lower than 80 ° C., it is advantageous for low-pressure and short-time adhesion, but the heat resistance becomes insufficient, and when it exceeds 200 ° C., it functions as a fluidity-imparting component during press adhesion. Therefore, adhesion in a short time becomes difficult.
[0016]
The amount of the fluidity-imparting resin used is 3 to 30 parts by weight, preferably 5 to 15 parts by weight per 100 parts by weight of the non-adhesive polymer. It is determined as appropriate according to the type of polymer. If the amount used is less than 3 parts by weight, it will not function as a fluidity-imparting component during press bonding, making it difficult to bond at a low pressure in a short time, and if it exceeds 30 parts by weight, bonding at a low pressure in a short time However, the heat resistance is insufficient.
[0017]
The epoxy resin as the component c is a compound containing two or more epoxy groups in the molecule, such as bisphenol epoxy resin, aliphatic epoxy resin, phenolic epoxy resin, halogenated bisphenol epoxy resin, etc. Among these, one or more of them are used. In addition, when carrying out radiation polymerization in the state which mixed the epoxy resin in the monomer mixture, the epoxy resin which does not have a radiation polymerization group in a molecule | numerator is used.
[0018]
The amount of the epoxy resin used is within the range of 5 to 30 parts by weight, preferably within the range of 5 to 20 parts by weight per 100 parts by weight of the non-adhesive polymer. It is determined as appropriate according to the type. When the amount used is less than 5 parts by weight, the cross-linking reaction between the non-adhesive polymer and the epoxy resin does not proceed sufficiently, so that the heat resistance becomes insufficient. Further, when the amount used is more than 30 parts by weight, the adhesive strength is likely to be lowered due to excessive crosslinking of the cured adhesive in continuous use at a high temperature, resulting in loss of reliability. .
[0019]
In the thermosetting adhesive of the present invention, a known crosslinking agent such as an isocyanate compound or an epoxy compound or a photopolymerization is used as a cross-linking agent in order to improve retention characteristics as an adhesive. For example, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, 1,2-ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) It is desirable to include polyfunctional (meth) acrylates such as acrylate.
[0020]
The amount of the crosslinking agent comprising the above-mentioned crosslinking agent or polyfunctional (meth) acrylate is usually 0.05 to 5 parts by weight, preferably 0.1 to 3 parts by weight per 100 parts by weight of the monomer mixture. It is better to be in the range of parts. In the case of using a polyfunctional (meth) acrylate, it is preferable that the number of difunctionals is large within the above range, and that the number of trifunctional or higher functionals is small. If the amount used is too small, the degree of cross-linking after polymerization cannot be sufficiently increased, and the retention characteristics are liable to decrease. Conversely, if the amount is too large, the elastic modulus of the thermosetting adhesive becomes extremely high, resulting in poor adhesion. It tends to cause a decrease in adhesion.
[0021]
In the thermosetting adhesive of the present invention, conventionally known various additives such as plasticizers, softeners, fillers, pigments, dyes, and anti-aging agents are added as optional components, and the various properties of the adhesive are not deteriorated. Can be added to the extent. However, a general curing agent such as imidazole, dicyandiamide, or polyamine known as a curing agent for epoxy resins cannot be added as an optional component. However, the presence of these curing agents is not limited to the case where the curing reaction with the epoxy resin does not substantially proceed before the heat treatment and there is no risk of greatly impairing the storage stability. In the present invention, “substantially free” has such a meaning.
[0022]
The thermosetting adhesive sheets of the present invention are provided with a layer made of a thermosetting adhesive essentially comprising the above-mentioned three components a to c on one or both sides of a base material, so -It is in the form of a cup. The above layer is obtained in advance by a suitable polymerization method to obtain a non-tacky polymer as component a, and to this, a fluidity imparting resin of component b, an epoxy resin of component c, a crosslinking agent, etc. are added to form a thermosetting adhesive Can be formed by coating it on a substrate and, if necessary, crosslinking treatment by heating or the like. More preferably, the radiation-polymerizable composition obtained by adding a fluidity-providing resin of component b, an epoxy resin of component c, and a polyfunctional (meth) acrylate to a monomer mixture before polymerization or a partial polymer thereof. It is preferable to form a layer simultaneously with the synthesis of the non-adhesive polymer as the component a by coating the substrate on a substrate and irradiating it with radiation such as ultraviolet rays to polymerize it. According to this method, good results can be obtained due to the heat resistance of the adhesive.
[0023]
As the base material, in addition to a non-peelable base material such as a synthetic resin film such as a polyester film and a fiber base material, a peelable base material such as a release paper can be used. In the case of a peelable substrate, the layer made of the thermosetting adhesive formed thereon may be finally transferred onto the non-peelable substrate. The adhesive sheets of the present invention include both those using such a non-peelable substrate as a substrate and those using a peelable substrate.
[0024]
The thermosetting adhesive sheets of the present invention include a small amount of fluidity imparting resin that does not decrease the heat resistance of the specific non-tacky polymer and a small amount of epoxy resin that undergoes a crosslinking reaction with the polymer. As a result, it has low adhesiveness at room temperature, does not cause bubble embedding during press bonding, and can exhibit strong adhesiveness at low pressure for a short time, especially within a few seconds, and more than 80 ° C. Even under continuous use at high temperatures, there is no inconvenience such as a large drop in adhesion due to residual stress due to curing shrinkage and peeling, high heat resistance to withstand solder reflow, and in the state before heat treatment Crosslinking reaction hardly progresses and is excellent in storage stability. For this reason, it can be used for a wide range of applications utilizing the above characteristics, such as for fixing electronic parts and as a joining material for heat-resistant films and metal plates.
[0025]
【Example】
Next, examples of the present invention will be described in more detail. In the following, “parts” means parts by weight.
[0026]
Example 1
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer, 210 parts of ethyl acetate as a solvent, 95 parts of phenoxyethyl acrylate (homopolymer Tg: −10 ° C.), acrylic acid 5 parts and 0.3 part of benzoyl peroxide were added and polymerized in a nitrogen stream to obtain a non-adhesive polymer solution having a solid content of about 30% by weight. To this solution, 5 parts of phenol resin (trade name “XL-225L” manufactured by Mitsui Toatsu Chemical Co., Ltd., softening point: 85 ° C.) per 100 parts of the solid content, epoxy resin (Oka Shell Shell Epoxy Co., Ltd.) A product name "Epicoat 828") and 15 parts of a polyfunctional isocyanate-based cross-linking agent were uniformly mixed to prepare a thermosetting adhesive solution. Next, this thermosetting adhesive solution is applied onto a peelable substrate and dried at 130 ° C. for 5 minutes to form a thermosetting adhesive layer having a thickness of 100 μm. Produced.
[0027]
Example 2
In a four-necked flask, 90 parts of phenoxyethyl acrylate, 5 parts of acryloylmorpholine, 5 parts of acrylic acid, 0.05 part of 2,2-dimethoxy-2-phenylacetophenone are added, and nitrogen is added. Irradiation with ultraviolet rays in the atmosphere caused partial photopolymerization to obtain a syrup having a viscosity of about 30 poise. To 100 parts of this partially polymerized syrup, 5 parts of phenolic resin (trade name “XL-225L” manufactured by Mitsui Toatsu Chemical Co., Ltd., softening point: 85 ° C.), epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) A product name "Epicoat 828") and 15 parts of 1,6-hexanediol diacrylate as a cross-linking agent were uniformly mixed to prepare a photopolymerizable composition. Next, this photopolymerizable composition is applied onto a peelable substrate and photopolymerized by irradiating with 900 mj / cm ² of ultraviolet rays to form a thermosetting adhesive layer having a thickness of 100 μm. -Prepared
[0028]
Example 3
Instead of using 90 parts of phenoxyethyl acrylate, 90 parts of an ester of cresol with an ethylene oxide adduct (addition mole number 1) and acrylic acid (Tg of homopolymer: -20 ° C.) was used. A photopolymerizable composition was prepared in the same manner as in Example 2, and a thermosetting adhesive layer having a thickness of 100 μm was formed in the same manner as in Example 2 to form an adhesive sheet. Was made.
[0029]
Example 4
In a four-necked flask, 95 parts of an ester of ethylene oxide adduct of nonylphenol (addition mole number 1) and acrylic acid (Tg of homopolymer: −25 ° C.), 2-hydroxy-3-phenoxypropyl acrylate -5 parts, 0.05 parts of 2,2-dimethoxy-2-phenylacetophenone, charged with ultraviolet light in a nitrogen atmosphere and partially photopolymerized to form a syrup having a viscosity of about 30 poise Obtained. To 100 parts of the partially polymerized syrup, 10 parts of terpene phenol resin (trade name “Sumilite Resin PR-12603” manufactured by Sumitomo Deyures Co., Ltd., softening point: 133 ° C.), epoxy resin (commercial product manufactured by Yuka Shell Epoxy Co., Ltd.) A photopolymerizable composition was prepared by uniformly mixing 10 parts of name "Epicoat 815") and 0.2 parts of trimethylolpropane triacrylate as a cross-linking agent. Next, this photopolymerizable composition is applied onto a peelable substrate and photopolymerized by irradiating with 900 mj / cm ² of ultraviolet rays to form a thermosetting adhesive layer having a thickness of 100 μm. -Prepared
[0030]
Comparative Example 1
In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirrer, 210 parts of ethyl acetate and 60 parts of butyl acrylate (homopolymer Tg <-30 ° C.), 35 parts of acrylonitrile, acrylic acid 5 And 0.3 part of benzoyl peroxide were added and polymerized in a nitrogen stream to obtain a polymer solution having a solid content of about 30% by weight. To this solution, 5 parts of phenol resin (trade name “XL-225L” manufactured by Mitsui Toatsu Chemical Co., Ltd., softening point: 85 ° C.) per 100 parts of the solid content, epoxy resin (Oka Shell Shell Epoxy Co., Ltd.) A product name "Epicoat 828") and 15 parts of a polyfunctional isocyanate-based cross-linking agent were uniformly mixed to prepare a thermosetting adhesive solution. Next, this thermosetting adhesive solution is applied onto a peelable substrate and dried at 130 ° C. for 5 minutes to form a thermosetting adhesive layer having a thickness of 100 μm. Produced.
[0031]
Comparative Example 2
In a four-necked flask, 80 parts of isooctyl acrylate (homopolymer Tg <-30 ° C.), 20 parts of acrylic acid, and 0.05 part of 2,2-dimethoxy-2-phenylacetophenone are added. The film was partially photopolymerized by irradiation with ultraviolet rays in a nitrogen atmosphere to obtain a syrup having a viscosity of about 30 poise. To 100 parts of this partially polymerized syrup, 5 parts of a phenol resin (trade name “XL-225L” manufactured by Mitsui Toatsu Chemical Co., Ltd., softening point: 85 ° C.), epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) A photopolymerizable composition was prepared by uniformly mixing 10 parts of a trade name “Epicoat 828”) and 0.3 part of 1,6-hexanediol diacrylate as a cross-linking agent. Next, this photopolymerizable composition is applied onto a peelable substrate and photopolymerized by irradiating with 900 mj / cm ² of ultraviolet rays to form a thermosetting adhesive layer having a thickness of 100 μm. -Prepared
[0032]
Comparative Example 3
In a four-necked flask, 80 parts of ethyl acrylate (Tg <-30 ° C. of homopolymer), 15 parts of acryloylmorpholine, 5 parts of acrylic acid, 0.05 part of 2,2-dimethoxy-2-phenylacetophenone And partially photopolymerized by irradiating ultraviolet rays under a nitrogen atmosphere to obtain a syrup having a viscosity of about 30 poise. To 100 parts of this partially polymerized syrup, 5 parts of phenolic resin (trade name “XL-225L” manufactured by Mitsui Toatsu Chemical Co., Ltd., softening point: 85 ° C.), epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd.) A photopolymerizable composition was prepared by uniformly mixing 10 parts of a trade name "Epicoat 815") and 0.3 part of 1,6-hexanediol diacrylate as a cross-linking agent. Next, this photopolymerizable composition is applied onto a peelable substrate and photopolymerized by irradiating with 900 mj / cm ² of ultraviolet rays to form a thermosetting adhesive layer having a thickness of 100 μm. -Prepared
[0033]
Comparative Example 4
A thickness of 100 μm was obtained in the same manner as in Example 2 except that 5 parts of a phenol resin (trade name “XL-225L” manufactured by Mitsui Toatsu Chemical Co., Ltd., softening point: 85 ° C.) was not used. A thermosetting adhesive layer was formed to produce an adhesive sheet.
[0034]
Comparative Example 5
A four-necked flask was charged with 100 parts of phenoxyethyl acrylate and 0.05 part of 2,2-dimethoxy-2-phenylacetophenone, and irradiated with ultraviolet light in a nitrogen atmosphere to partially light. Polymerization was performed to obtain a syrup having a viscosity of about 30 poise. To 100 parts of the partially polymerized syrup, 10 parts of terpene phenol resin (trade name “Sumilite Resin PR-12603” manufactured by Sumitomo Deyures Co., Ltd., softening point: 133 ° C.), epoxy resin (commercial product manufactured by Yuka Shell Epoxy Co., Ltd.) Name "Epicoat 828") 50 parts, modified polyamine (epoxy resin curing agent, product name "ACR Hardener X-3615" manufactured by ASC All), cross-linked A photopolymerizable composition was prepared by uniformly mixing 0.3 part of 1,6-hexanediol diacrylate as an agent. Next, this photopolymerizable composition is applied onto a peelable substrate and photopolymerized by irradiating with 900 mj / cm ² of ultraviolet rays to form a thermosetting adhesive layer having a thickness of 100 μm. -Prepared
[0035]
About each adhesion sheet of said Examples 1-4 and Comparative Examples 1-5, the external appearance after press adhesion | attachment and solder heat resistance were investigated with the following method. These results were as shown in Table 1.
[0036]
<Appearance after press bonding>
The adhesive sheet cut into 30 mm squares was bonded to SUS304 with a laminator (pressure: 5 kg / cm ² , speed: 2 m / min) at room temperature, and this was applied to a 75 μm-thick polyimide film with a press (temperature). Bonding was performed at 150 ° C., time 1 second, pressure 5 kg / cm ² ). The state of the bonded surface at that time was visually observed, and it was evaluated that ○: almost no inclusion of bubbles or unbonded parts were observed, and x: inclusion of bubbles or unbonded parts were clearly seen. .
[0037]
<Adhesive strength>
An adhesive sheet cut to a width of 10 mm and a length of 50 mm is bonded to a polyimide film having a thickness of 75 μm by a laminator (temperature: 100 ° C., pressure: 5 kg / cm ² , speed: 2 m / min). Was bonded to SUS304 with a press (temperature: 150 ° C., time: 1 second, pressure: 5 kg / cm ² ). This sample was cured by heat treatment at 150 ° C. for 1 hour, and then initially (after standing at room temperature for 30 minutes) and after being left at high temperature (after leaving at 100 ° C. for 100 hours) at a pulling speed of 50 mm / min. The adhesive strength was determined by pulling in the 90 ° direction and setting the center value as 90 ° peel adhesive strength.
[0038]
<Solder heat resistance>
An adhesive sheet cut to a width of 10 mm and a length of 50 mm is bonded to a polyimide film having a thickness of 75 μm by a laminator (temperature: 100 ° C., pressure: 5 kg / cm ² , speed: 2 m / min). Was bonded to a 30 mm square SUS304 with a press (temperature: 150 ° C., time: 1 second, pressure: 5 kg / cm ² ). The sample was cured by heat treatment at 150 ° C. for 1 hour, and then treated for 60 seconds with the SUS304 surface facing up and floating in a solder bath melted at 240 ° C. The pasted state of the sheet after processing was visually observed. ○: Foaming or adhesion abnormality (floating, wrinkle, peeling, deviation) of the adhesive was hardly observed. X: The above foaming or adhesion abnormality was obvious. It was evaluated that it was seen.
[0039]

[0040]
As is apparent from the results in Table 1 above, each of the adhesive sheets of Examples 1 to 4 of the present invention shows a large adhesive force without any inclusion of bubbles or poor adhesion during press bonding. In addition, it can be seen that the adhesive force is hardly lowered even after continuous standing at a high temperature and the solder heat resistance is excellent. In contrast, each of the adhesive sheets of Comparative Examples 1 to 3 is mainly composed of (meth) acrylic acid alkyl ester, and this is copolymerized with a monomer that imparts a high Tg. The adhesiveness is low and does not cause bubble embedding or poor adhesion at the time of press bonding, but the adhesive strength is poor, and even soldering heat resistance cannot be satisfied.
[0041]
In addition, since the adhesive sheet of Comparative Example 4 did not contain a fluidity-imparting resin, a non-contact portion remained at the time of press bonding, which became a cause of floating during solder heat resistance, and improved solder heat resistance. I can't be satisfied. Furthermore, since the adhesive sheet of Comparative Example 5 contained an excessive amount of epoxy resin and a curing agent for this epoxy resin, curing gradually progressed after standing at a high temperature and the crosslinking density became too dense. , Adhesive strength is greatly reduced and cannot be used.
[0042]
【The invention's effect】
As described above, in the present invention, a monoethylenically unsaturated monomer having a specific molecular structure with a homopolymer Tg of −30 ° C. or more and a functional group that reacts with an epoxy resin. By using a non-adhesive polymer obtained by copolymerization with a monomer, and having a composition including a fluidity-imparting resin and an epoxy resin having a specific softening point, the adhesiveness is low at room temperature, It does not cause bubble embedding during press bonding, and can be firmly bonded by low-temperature, short-time heat treatment, especially within a few seconds, and it also has adhesive strength due to residual stress due to curing shrinkage even under continuous use at high temperatures. A highly reliable thermosetting adhesive and its adhesive sheets that exhibit high heat resistance that can withstand solder reflow and that also satisfy storage stability, with no major deterioration. It can be provided.

Claims

a) The following formula (1);

Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a methylene group, an ethylene group or a propylene group, n is an integer of 1 to 3, φ is a phenyl group, a monoalkyl-substituted phenyl group or a dialkyl-substituted phenyl group. )
A homopolymer having a glass transition temperature of −30 ° C. or higher and a (meth) acrylic acid ester of 70 to 99% by weight, a monoethylenic copolymer having a functional group capable of copolymerizing with it and reacting with an epoxy resin. 100 parts by weight of a non-adhesive polymer of a monomer mixture consisting of 30 to 1% by weight of a saturated monomer, b) 3 to 30 parts by weight of a fluidity imparting resin having a softening point of 80 to 200 ° C., and c A thermosetting adhesive comprising 5 to 30 parts by weight of an epoxy resin and substantially free of the curing agent for the epoxy resin as the component c.

The thermosetting adhesive according to claim 1, wherein the non-tacky polymer of component a is a polymer obtained by irradiation with radiation such as ultraviolet rays.

An adhesive sheet comprising a layer made of the thermosetting adhesive according to claim 1 or 2 on one side or both sides of a substrate.