JP3620751B2

JP3620751B2 - Anisotropic conductive film

Info

Publication number: JP3620751B2
Application number: JP28145395A
Authority: JP
Inventors: 道雄小林
Original assignee: Sumitomo Bakelite Co Ltd
Current assignee: Sumitomo Bakelite Co Ltd
Priority date: 1995-10-30
Filing date: 1995-10-30
Publication date: 2005-02-16
Anticipated expiration: 2015-10-30
Also published as: JPH09124771A

Description

【０００１】
【発明の属する技術分野】
本発明は、微細な回路同士の電気的接続、更に詳しくはＬＣＤ（液晶ディスプレイ）とフレキシブル回路基板やＴＡＢフィルムとの接続や、半導体ＩＣとＩＣ搭載回路基板のマイクロ接合に用いる異方導電フィルムに関するものである。
【０００２】
【従来の技術】
最近の電子機器の小型化、薄型化に伴い、微細な回路同士の接続、微小部品と微細回路の接続等の必要性が飛躍的に増大してきており、その接続方法として、異方性の導電性接着剤やフィルムが使用され始めている。（例えば、特開昭５９−１２０４３６、６０−１９１２２８、６１−２７４３９４、６１−２８７９７４、６２−２４４２４２、６３−１５３５３４、６３−３０５５９１、６４−８１８７８、平１−４６５４９、１−２５１７８各号公報等）。
更なる部品の微細化が進み、それに伴う異方性導電フィルムによる回路同士の接続作業において、位置ずれ等の理由によって一度接続した被接続部材を破損または損傷せずに剥離し再圧着すること（所謂“リペア”）が可能であることへの要求や、異方導電フィルムの熱硬化反応時の硬化収縮や種々の雰囲気中での樹脂自体の歪み応力に基づき、被着体が損傷（例えば、ＬＣＤに用いられるガラス基板のクラックや基板の反り）するという問題が生じてきている。これらの問題を解決するために、速硬化、長ライフ、耐湿性、更には低歪みの高信頼性熱硬化タイプの異方導電フィルムが強く要求されている。
【０００３】
【発明が解決しようとする課題】
本発明は、従来の熱硬化型では得られなかった、常温での貯蔵安定性に優れ、加熱加圧して硬化後、広範囲の温度領域（−４０℃〜１００℃）において優れた接着性を有し、しかも接合部に残る歪み（応力）が極めて小さく、更に温湿度サイクル試験のような厳しい処理後も接続抵抗の安定性が優れた熱硬化型異方導電フィルムを提供するものである。
【０００４】
【課題を解決するための手段】
本発明は、重合度が１５００〜２５００、アセチル化度が３モル％以下、ブチラール化度が６５モル％以上、フロー軟化点が２００℃以上の特性を有するポリビニルブチラール樹脂（Ａ）、エポキシ樹脂（Ｂ）、イミダゾール誘導体と式（１）で表わされるシリコーンエポキシ化合物との反応物（Ｃ）、及び高分子球状核材の表面に金属被覆を有する導電粒子（Ｄ）を必須成分とする異方導電フィルムである。
【０００５】
【化３】

（Ｒ_１、Ｒ_２は２価の炭素数１〜５の脂肪族基、又は炭素数６以上の芳香族から２個の水素を除いた残基を示し、互いに同じであっても異なっていてもよい）
【０００６】
【発明の実施の態様】
本発明に用いるポリビニルブチラール樹脂の重合度は１５００〜２５００であるが、重合度が１５００未満だと加熱、加圧時の樹脂流動性が大きく接着力が不十分となる。また、重合度が２５００を越えると樹脂の流動性が不足し、導電粒子が端子と接触できず導通性が得られない。
また、本発明に用いるポリビニルブチラール樹脂のアセチル化度は３モル％以下であるが、３モル％を越えると被着体（ＬＣＤガラス基板やＴＡＢフィルム）との相性が悪くなり接着力が不足し、ブチラール化度が６５モル％未満だと分子中のポリビニルアルコール及びポリ酢酸ビニルの含有割合が増加し接着力が不足する。
更に、ポリビニルブチラール樹脂のフロー軟化点は、２００℃以上であるが、２００℃未満だと加熱、加圧時の樹脂流動性が大きく気泡の抱き込みが大きくなり接着力が不足する。
【０００７】
本発明に用いるエポキシ樹脂は、１分子中に少なくとも２個以上のエポキシ基を有するものである。具体的には、ビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂、ビスフェノールＳ型エポキシ樹脂、フェノールノボラック型エポキシ樹脂、クレゾールノボラック型エポキシ樹脂等の他、分子中にナフタレン骨格を有するエポキシ樹脂としては、１，６−ビス−（２，３−エポキシプロポキシ）ナフタレン、または２，７−ジヒドロキシナフタレンとホルムアルデヒドとの縮合物をエピクドルヒドリンと反応した樹脂、２−ヒドロキシナフタレンと２，７−ジヒドロキシナフタレンとホルムアルデヒドとの縮合物をエピクドルヒドリンと反応した樹脂等が挙げられるが、これらのものに限定されるものではなく、また単独でも混合して用いても差し支えない。
【０００８】
本発明に用いるイミダゾール誘導体としては、２−メチルイミダゾール、２−エチルイミダゾール、２−ウンデシルイミダゾール、２−ヘプタジシルイミダゾール、２−フェニルイミダゾール、２−エチル−４−メチルイミダゾール、２−フェニル−４−メチルイミダゾール、２−フェニル−４−メチル−５−ヒドロキシメチルイミダゾール、２−フェニル−４，５−ジヒドロキシメチルイミダゾールが挙げられる。本発明に用いるシリコーンエポキシ化合物は、式（１）で示されるが、Ｒ₁、Ｒ₂としてはプロピレン基である、式（２）で示される構造のものが工業的入手の容易さから好ましい。本発明に用いるイミダゾール誘導体とシリコーンエポキシ化合物との反応物は、イミダゾール誘導体とシリコーンエポキシ化合物とを仕込モル比１．５〜２．５の割合で混合し、必要により溶剤を加えて１００℃以上の条件で１〜１００時間反応させて得られる。仕込モル比が２．５を越えると、イミダゾール誘導体が未反応成分として残るため、これを用いた場合樹脂組成物の保存性が低下する。また、１．５未満だとシリコーンエポキシ化合物が未反応成分として残り、硬化性が低下するため好ましくない。該反応物は、イミダゾール誘導体の種類や仕込モル比によって常温で固形または液状の状態であり、エポキシ樹脂の硬化剤として用いる。この反応物は単独で用いても良いが、更に保存性を向上するために、固形の場合には微粉化し、少量のイソシアネート化合物と反応させて表面処理を行い、液状の場合にはポリウレタン樹脂等でマイクロカプセル化して用いても良い。反応物は、エポキシ樹脂１００重量部に対して５〜２００重量部用いられる。５重量部未満だと硬化性、耐湿性、応力性において効果が少なく、また２００重量部を越えると保存性、接着強度が低下する。反応物以外の硬化剤としては、従来から用いられているエポキシ樹脂用硬化剤であれば良く、例えば、イミダゾール誘導体、アミン類、フェノール類酸無水物などを併用しても良い。
以上
【０００９】
本発明では、式（１）で示される低鎖長シロキサンユニットを含むエポキシ化合物を用いるため、低温及び高温時における接着力の低下が少なく、吸湿性も少なく、更に適度の可撓性を有するため応力も少なくなるため、吸湿処理後及びヒートサイクル処理後の劣化の少ない異方導電フィルムが得られる。
【００１０】
本発明で用いる高分子球状核材の表面に金属被覆を有する導電粒子は、高分子球状核材の表面にニッケル膜を有し、該ニッケル膜の更に外層に金膜を有する導電粒子であるが、導電粒子表面の金膜、ニッケル膜の皮膜の厚さは特に限定しないが、薄すぎると導電性が不安定になり、厚すぎると粒子変形が困難になったり凝集などが生じるため、金及びニッケル皮膜の厚さは０．０１〜１μｍが好ましい。また皮膜の形成方法では、この皮膜と中心核となる高分子球状核材との密着力、導通性などを考慮し、均一に形成されていることが良く、従来から用いられている無電解メッキなどが望ましい。
【００１１】
また、本発明に用いる高分子球状核材の表面に金属被覆を有する導電粒子の粒径は３〜１５μｍ、平均粒径は５〜１０μｍであることが好ましい。粒径が３μｍ未満および平均粒径が５μｍ未満だと、接続する回路表面の凹凸の大きさに近く、熱圧着時に回路厚みのバラツキを吸収できず、接続抵抗増やオープン不良の原因となる。また粒径が１５μｍを越え、かつ平均粒径１０μｍを越えると回路ピッチ（回路幅＋回路間隔）が０．１ｍｍ以下に適用した際に隣接回路間で粒子が接触し、隣接回路間での絶縁性が低下したり、ショートを起こす危険性がある。
これらの範囲内で接続する回路端子ピッチ、端子厚さバラツキ等により最適値を選択すればよい。例えば、異方導電フィルムの主要な用途である液晶ディスプレイパネルとフレキシブル回路基板（以下ＦＰＣ）との接続では、金属被覆を有する導電粒子の粒径は３〜１５μｍ程度で、かつ絶縁性接着剤に対する配合量は、０．５〜１０体積％が好ましい。
又、高分子球状核材の表面に金属被覆を有する導電粒子の圧縮破壊強度は１０〜１００ｋｇ／ｍｍ^２、圧縮弾性率は１００〜１０００ｋｇ／ｍｍ^２である。
圧縮破壊強度が１０ｋｇ／ｍｍ^２未満および圧縮弾性率が１００ｋｇ／ｍｍ^２未満であると電気的接続を得る前に粒子が破壊されてしまい接続できない。また圧縮破壊強度が１００ｋｇ／ｍｍ^２を越え、かつ圧縮弾性率が１０００ｋｇ／ｍｍ^２を越える場合には、端子と端子の接続に充分な面積を得るには過大な圧力をかけなくてはならなく被着体を破損する原因となる。
熱圧着後の金属被覆粒子をつぶれ具合が接続信頼性等の諸特性に影響を及ぼすため、圧縮破壊強度は１０〜１００ｋｇ／ｍｍ^２、圧縮弾性率は１００〜１０００ｋｇ／ｍｍ^２である必要がある。
【００１２】
高分子球状核材の組成は特に限定しないが、例えばエポキシ樹脂、ウレタン樹脂、メラミン樹脂、フェノール樹脂、アクリル樹脂、ポリエステル樹脂、スチレン樹脂、スチレン−ブタジエン共重合体等のポリマーが挙げられ、これらは単独でも混合して用いても差し支えない。
又金属被覆には、Ａｕ、Ｎｉ、Ａｇ、Ｃｕ、Ｚｎ、Ｓｎ、Ｉｎ、Ａｌ、Ｐｄ等が挙げられ、これらは組み合わせても良い。これらの高分子球状核材と金属被覆は、両者の密着力などを考慮して適切なものを選択すればよい。
【００１３】
本発明の異方導電フィルムは、（Ａ）〜（Ｄ）成分を適宜選択して、溶剤を使用して均一に溶解または分散させた後、離型処理をしたポリエステル系フィルムまたはフッ素系フィルム等に均一な厚みに流延して、熱処理で溶剤を揮散させることで得られる。
作業性や各種性能の向上を狙って、各種添加剤、例えば非反応性希釈剤、反応性希釈剤、揺変性付与剤、カップリング剤、増粘剤、無機充填材等を適宜添加しても差し支えない。
【００１３】
反応物の製造例１
２−ウンデシルイミダゾール（分子量２２２）４４．４ｇ（０．２モル）を１５０℃に加温し撹拌しながら、前記の式（２）のシリコーンエポキシ化合物（分子量３９２）３９．２ｇ（０．１モル）を徐々に添加し、１７０℃に昇温して３時間反応させ、褐色で粘稠な生成物を得た。この生成物を反応生成物（１）とする。
反応物の製造例２
２−ヘプタデシルイミダゾール（分子量３０６）６１．２ｇ（０．２モル）を１５０℃に加温し撹拌しながら、前記の式（２）のシリコーンエポキシ化合物３９．２ｇ（０．１モル）を徐々に添加し、１８０℃に昇温し５時間反応させ、褐色で粘稠な生成物を得た。この生成物を反応生成物（２）とする。
【００１４】
反応物の製造例３
２−ウンデシルイミダゾール４４．４ｇ（０．２モル）を１５０℃に加温し撹拌しながら、式（３）で表わされる長鎖シロキサンユニットを含有するエポキシ化合物（分子量６６０）６６ｇ（０．１モル）を徐々に添加し、１８０℃に昇温して１０時間反応させて褐色で粘稠な生成物を得た。この生成物を反応生成物（３）とする。
【００１５】
【化４】

【００１６】
反応物の製造例４
２−ウンデシルイミダゾール４４．４ｇ（０．２モル）を１２０℃に加温し撹拌しながら、式（４）で表わされるシロキサンユニットを含まないエポキシ化合物（分子量３４０）３４．０ｇ（０．１モル）を徐々に添加し更に１２０℃で５時間反応させて赤色で固形の生成物を得た。この生成物を２０メッシュ程度に微粉砕したものを反応生成物（４）とする。
【００１７】
【化５】

【００１８】
反応物の製造例５
２−ウンデシルイミダゾールを６６．６ｇ（０．３モル）を用いる以外は、製造例１と同様に反応して反応生成物（５）を得た。
反応物の製造例６
２−ウンデシルイミダゾールを２２．２ｇ（０．１モル）を用いる以外は、製造例１と同様に反応して反応生成物（６）を得た。
【００１９】
以下本発明を実施例で具体的に説明する。
実施例１
反応性エラストマーとして、重合度１７００、アセチル化度３モル％以下、ブチラール化度６５モル％以上、フロー軟化点が２２５℃のポリビニルブチラール樹脂２５重量部をトルエン／酢酸エチル＝５：１（重量比）混合溶液に１０重量％となるように溶解した溶液、高分子量ビスフェノールＡ型エポキシ樹脂（エポキシ当量４０００）２５重量部をトルエン／酢酸ブチル＝３：１混合溶液に５０重量％となるように溶解した溶液、低分子量ビスフェノールＡ型エポキシ樹脂（エポキシ当量２００）４０重量部、反応生成物（１）４０重量部を速やかに撹拌混合し、これにポリスチレン球状核材にＮｉ／Ａｕメッキした導電粒子（平均粒径５μｍ）を４重量部添加し均一に分散し、更にトルエンを添加し、４−フッ化エチレン−パーフルオロアルキルビニルエーテル共重合体フィルム上に流延・乾燥し厚みが２５μｍの異方導電フィルムを得た。
この異方導電フィルムについて保存性、接着力及び接続抵抗値の各種処理後の評価を実施した結果を表１に示す。
保存性は、フィルムを室温（２３℃）で３０日間、又は４０℃で７日間放置後、ＴＡＢとＩＴＯガラスを接続した場合の接続抵抗値が、初期の接続抵抗値に対して２０％以上上昇しておれば×＜２０％未満の上昇であれば○とした。
接着力は、被着体として銅箔／ポリイミド＝３５／７５μｍに０．４μｍの錫メッキを施したＴＡＢ（ピッチ０．１０ｍｍ、端子数２００本）とシート抵抗値３０Ωのインジウム／錫酸化物導電皮膜を全面に形成した厚さ１．１ｍｍのＩＴＯガラスを用いて、両者を２ｍｍ幅の異方導電フィルムを３０ｋｇ／ｃｍ^２の圧力で、１８０℃で３０秒間圧着したサンプルを９０°剥離試験によって評価した。
接続抵抗値は上記のサンプルを用いて、２００端子の端子間の接続抵抗値を測定して平均値を算出した。
【００２０】
実施例２〜６
表１の配合に従い、実施例１と同一の方法で異方導電フィルムを調整し、実施例１と同一の試験を行った。評価結果を表１に示す。
比較例１、２
反応性エラストマーとして、比較例１では、重合度３００、アセチル化度が３モル％を越え、ブチラール化度６３±３モル％、フロー軟化点１１５℃のポリビニルブチラール樹脂を、比較例２では重合度１０００、アセチル化度３モル％以下、ブチラール化度７０モル％、フロー軟化点１６０℃のポリビニルブチラール樹脂を用いた以外は、実施例１と同様にして異方導電フィルムを得た。評価結果を表２に示す。
比較例３〜６
反応生成物（３）〜（６）を用いる以外は、実施例１と同じ方法で異方導電フィルムを調製した。評価結果を表２に示す。
【００２１】
【表１】

【００２２】
【表２】

【００２３】
【発明の効果】
本発明によれば、０．０５ｍｍピッチ以下の微細なマイクロ接合に使用可能であり、かつ接着力に優れ、信頼性の高い異方導電フィルムを得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anisotropic conductive film used for electrical connection between fine circuits, more particularly connection between an LCD (liquid crystal display) and a flexible circuit board or TAB film, or micro-joining between a semiconductor IC and an IC-mounted circuit board. Is.
[0002]
[Prior art]
With the recent miniaturization and thinning of electronic devices, the need for connections between minute circuits and connections between minute parts and minute circuits has increased dramatically. Adhesives and films are beginning to be used. (For example, JP-A-59-120436, 60-191228, 61-274394, 61-287974, 62-244242, 63-153534, 63-305591, 64-81878, Hei 1-446549, 1-225178, etc. ).
With further miniaturization of parts, in connection work between circuits using anisotropic conductive film, the connected member once separated due to misalignment or the like is peeled off without being damaged or damaged and re-pressed ( The so-called “repair”) is possible, the shrinkage of the anisotropic conductive film during the thermosetting reaction, and the distortion stress of the resin itself in various atmospheres. There has been a problem that the glass substrate used in the LCD is cracked or warped. In order to solve these problems, there is a strong demand for a highly reliable thermosetting anisotropic conductive film with fast curing, long life, moisture resistance, and low distortion.
[0003]
[Problems to be solved by the invention]
The present invention has excellent storage stability at room temperature, which could not be obtained with a conventional thermosetting type, and has excellent adhesiveness in a wide temperature range (−40 ° C. to 100 ° C.) after curing by heating and pressing. In addition, the present invention provides a thermosetting anisotropic conductive film in which distortion (stress) remaining in the joint is extremely small and the stability of connection resistance is excellent even after severe processing such as a temperature and humidity cycle test.
[0004]
[Means for Solving the Problems]
The present invention relates to a polyvinyl butyral resin (A) having an polymerization degree of 1500 to 2500, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 200 ° C. or more. B), an anisotropic conductive material containing, as an essential component, a reaction product (C) of an imidazole derivative and a silicone epoxy compound represented by the formula (1), and conductive particles (D) having a metal coating on the surface of a polymer spherical core material It is a film.
[0005]
[Chemical 3]

(R ₁ and R ₂ represent a divalent aliphatic group having 1 to 5 carbon atoms, or a residue obtained by removing two hydrogen atoms from an aromatic group having 6 or more carbon atoms. Also good)
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
The degree of polymerization of the polyvinyl butyral resin used in the present invention is 1500 to 2500, but if the degree of polymerization is less than 1500, the resin fluidity at the time of heating and pressurization is large and the adhesive strength is insufficient. On the other hand, if the polymerization degree exceeds 2500, the fluidity of the resin is insufficient, and the conductive particles cannot be brought into contact with the terminals, so that the conductivity cannot be obtained.
Further, the degree of acetylation of the polyvinyl butyral resin used in the present invention is 3 mol% or less. However, if it exceeds 3 mol%, the compatibility with the adherend (LCD glass substrate or TAB film) is deteriorated and the adhesive strength is insufficient. When the degree of butyralization is less than 65 mol%, the content ratio of polyvinyl alcohol and polyvinyl acetate in the molecule increases, resulting in insufficient adhesion.
Furthermore, the flow softening point of the polyvinyl butyral resin is 200 ° C. or higher, but if it is lower than 200 ° C., the resin fluidity at the time of heating and pressurization is large, and the entrapment of bubbles becomes large and the adhesive strength is insufficient.
[0007]
The epoxy resin used in the present invention has at least two epoxy groups in one molecule. Specifically, in addition to bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, etc., as an epoxy resin having a naphthalene skeleton in the molecule, 1,6-bis- (2,3-epoxypropoxy) naphthalene or a resin obtained by reacting a condensation product of 2,7-dihydroxynaphthalene and formaldehyde with epicudolhydrin, 2-hydroxynaphthalene and 2,7-dihydroxy Examples thereof include resins obtained by reacting a condensate of naphthalene and formaldehyde with epicudolhydrin, but are not limited to these, and may be used alone or in combination.
[0008]
Examples of the imidazole derivatives used in the present invention include 2 -methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadicylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl- 4-methyl imidazole, 2-phenyl-4-methyl-5-hydroxymethyl imidazole, 2-phenyl-4,5-dihydroxy methyl imidazole. The silicone epoxy compound used in the present invention is represented by the formula (1), but R ₁ and R ₂ are preferably propylene groups, and those having a structure represented by the formula (2) are preferable from the viewpoint of industrial availability. The reaction product of an imidazole derivative and a silicone epoxy compound used in the present invention is a mixture of an imidazole derivative and a silicone epoxy compound in a charge molar ratio of 1.5 to 2.5, and if necessary, a solvent is added to at least 100 ° C. It is obtained by reacting for 1 to 100 hours under conditions. When the charged molar ratio exceeds 2.5, the imidazole derivative remains as an unreacted component, and when this is used, the storage stability of the resin composition is lowered. On the other hand, if it is less than 1.5, the silicone epoxy compound remains as an unreacted component, and the curability is lowered. The reaction product is in a solid or liquid state at room temperature depending on the type of imidazole derivative and the charged molar ratio, and is used as a curing agent for the epoxy resin. This reaction product may be used alone, but in order to further improve the storage stability, it is finely pulverized in the case of a solid, subjected to a surface treatment by reacting with a small amount of an isocyanate compound, and in the case of a liquid, a polyurethane resin or the like. And may be used after microencapsulation. The reaction product is used in an amount of 5 to 200 parts by weight based on 100 parts by weight of the epoxy resin. If it is less than 5 parts by weight, the effect on curability, moisture resistance and stress is small, and if it exceeds 200 parts by weight, storage stability and adhesive strength are lowered. As the curing agent other than the reactant, any conventional epoxy resin curing agent may be used. For example, an imidazole derivative, an amine, a phenolic acid anhydride, or the like may be used in combination.
[0009]
In the present invention, since an epoxy compound containing a low-chain-length siloxane unit represented by the formula (1) is used, there is little decrease in adhesion at low and high temperatures, low hygroscopicity, and moderate flexibility. Since stress is also reduced, an anisotropic conductive film with little deterioration after moisture absorption treatment and heat cycle treatment is obtained.
[0010]
The conductive particles having a metal coating on the surface of the polymer spherical core material used in the present invention are conductive particles having a nickel film on the surface of the polymer spherical core material and a gold film on the outer layer of the nickel film. The thickness of the gold film or nickel film on the surface of the conductive particles is not particularly limited. However, if the thickness is too thin, the conductivity becomes unstable, and if the thickness is too thick, the deformation of the particles becomes difficult or aggregation occurs. The thickness of the nickel film is preferably 0.01 to 1 μm. Also, in the method of forming the film, it is preferable that the film is uniformly formed in consideration of the adhesion, conductivity, etc. between the film and the polymer spherical core material serving as the central core. Etc. are desirable.
[0011]
Moreover, it is preferable that the particle diameter of the electrically conductive particle which has a metal coating on the surface of the polymeric spherical nucleus material used for this invention is 3-15 micrometers, and an average particle diameter is 5-10 micrometers. If the particle size is less than 3 μm and the average particle size is less than 5 μm, the size of the circuit surface to be connected is close to the size of the concavities and convexities, and variations in circuit thickness cannot be absorbed during thermocompression bonding, resulting in increased connection resistance and open defects. In addition, when the particle size exceeds 15 μm and the average particle size exceeds 10 μm, when the circuit pitch (circuit width + circuit interval) is applied to 0.1 mm or less, the particles come into contact with each other and insulation between adjacent circuits There is a risk of loss of performance or short circuit.
What is necessary is just to select an optimal value by the circuit terminal pitch, terminal thickness dispersion | variation, etc. which are connected within these ranges. For example, in the connection between a liquid crystal display panel and a flexible circuit board (hereinafter referred to as FPC), which is the main application of anisotropic conductive film, the particle size of the conductive particles having a metal coating is about 3 to 15 μm, and for the insulating adhesive The blending amount is preferably 0.5 to 10% by volume.
Further, compressive fracture strength of the conductive particles with a metal coating on the surface of the polymer spherical nuclear material 10 to 100 kg / mm ^2, compression modulus is 100 to 1000 / mm ^2.
When the compression fracture strength is less than 10 kg / mm ² and the compression modulus is less than 100 kg / mm ² , the particles are broken before electrical connection is obtained, and connection cannot be made. If the compressive fracture strength exceeds 100 kg / mm ² and the compression modulus exceeds 1000 kg / mm ² , excessive pressure must be applied to obtain a sufficient area for connection between terminals. This may cause damage to the adherend.
For degree collapsed metal coated particles after thermal bonding affects the various properties such as connection reliability, compressive fracture strength is 10 to 100 kg / mm ^2, compression modulus should be 100 to 1000 / mm ² .
[0012]
The composition of the polymeric spherical core material is not particularly limited, and examples thereof include polymers such as epoxy resins, urethane resins, melamine resins, phenol resins, acrylic resins, polyester resins, styrene resins, styrene-butadiene copolymers, and the like. They can be used alone or in combination.
Examples of the metal coating include Au, Ni, Ag, Cu, Zn, Sn, In, Al, and Pd, and these may be combined. An appropriate polymer spherical core material and metal coating may be selected in consideration of the adhesion between them.
[0013]
The anisotropic conductive film of the present invention is a polyester-based film or a fluorine-based film that has been subjected to a release treatment after appropriately selecting components (A) to (D) and uniformly dissolving or dispersing them using a solvent. It is obtained by casting to a uniform thickness and volatilizing the solvent by heat treatment.
Various additives such as non-reactive diluents, reactive diluents, thixotropic agents, coupling agents, thickeners, inorganic fillers, etc. may be added as appropriate for the purpose of improving workability and various performances. There is no problem.
[0013]
Production Example 1 of Reactant
While heating and stirring 44.4 g (0.2 mol) of 2-undecylimidazole (molecular weight 222) at 150 ° C., 39.2 g (0.1) of the silicone epoxy compound of formula (2) (molecular weight 392) Mol) was gradually added, the temperature was raised to 170 ° C., and the mixture was reacted for 3 hours to obtain a brown and viscous product. This product is designated as reaction product (1).
Production Example 2 of Reactant
While heating 61.2 g (0.2 mol) of 2-heptadecylimidazole (molecular weight 306) to 150 ° C. and stirring, 39.2 g (0.1 mol) of the silicone epoxy compound of the above formula (2) was gradually added. The mixture was heated to 180 ° C. and reacted for 5 hours to obtain a brown and viscous product. This product is designated as reaction product (2).
[0014]
Production Example 3 of Reactant
While heating and stirring 44.4 g (0.2 mol) of 2-undecylimidazole at 150 ° C., 66 g of epoxy compound (molecular weight 660) containing a long-chain siloxane unit represented by the formula (3) (0.1%) Mol) was gradually added, the temperature was raised to 180 ° C., and the mixture was reacted for 10 hours to obtain a brown and viscous product. This product is designated as reaction product (3).
[0015]
[Formula 4]

[0016]
Production Example 4 of Reactant
While heating and stirring 44.4 g (0.2 mol) of 2-undecylimidazole at 120 ° C., 34.0 g (0.1 wt.) Of an epoxy compound (molecular weight 340) represented by the formula (4) is not contained. Mol) was gradually added and further reacted at 120 ° C. for 5 hours to obtain a red solid product. A product obtained by pulverizing this product to about 20 mesh is defined as a reaction product (4).
[0017]
[Chemical formula 5]

[0018]
Production Example 5 of Reactant
A reaction product (5) was obtained by reacting in the same manner as in Production Example 1 except that 66.6 g (0.3 mol) of 2-undecylimidazole was used.
Production Example 6 of Reactant
A reaction product (6) was obtained by reacting in the same manner as in Production Example 1 except that 22.2 g (0.1 mol) of 2-undecylimidazole was used.
[0019]
Hereinafter, the present invention will be described in detail by way of examples.
Example 1
As a reactive elastomer, 25 parts by weight of a polyvinyl butyral resin having a polymerization degree of 1700, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 225 ° C. was toluene / ethyl acetate = 5: 1 (weight ratio). ) A solution dissolved in a mixed solution to 10% by weight, 25 parts by weight of a high molecular weight bisphenol A type epoxy resin (epoxy equivalent 4000) dissolved in a toluene / butyl acetate = 3: 1 mixed solution to 50% by weight. The obtained solution, 40 parts by weight of a low molecular weight bisphenol A type epoxy resin (epoxy equivalent 200) and 40 parts by weight of the reaction product (1) are rapidly stirred and mixed, and conductive particles (Ni / Au plated on a polystyrene spherical core material) 4 parts by weight of an average particle size of 5 μm) is added and dispersed uniformly, and further toluene is added to form 4-fluoroethylene-perfluoride. Thickness cast and dried on a vinyl ether copolymer film on to obtain a anisotropic conductive film of 25 [mu] m.
Table 1 shows the results of evaluating the anisotropic conductive film after various treatments of storage stability, adhesive strength, and connection resistance value.
With regard to storage stability, the connection resistance when TAB and ITO glass are connected after leaving the film at room temperature (23 ° C.) for 30 days or at 40 ° C. for 7 days is 20% or more higher than the initial connection resistance value. If it was an increase of less than x <20%, it was rated as ○.
Adhesive strength is TAB (pitch 0.10 mm, number of terminals 200) with copper foil / polyimide = 35/75 μm plated with 0.4 μm tin, and indium / tin oxide conductive sheet resistance 30Ω. Using an ITO glass with a thickness of 1.1 mm with a coating formed on the entire surface, a sample obtained by pressure bonding an anisotropic conductive film with a width of 2 mm at a pressure of 30 kg / cm ² for 30 seconds at 180 ° C. by a 90 ° peel test evaluated.
For the connection resistance value, the average value was calculated by measuring the connection resistance value between 200 terminals using the above sample.
[0020]
Examples 2-6
According to the composition of Table 1, an anisotropic conductive film was prepared by the same method as in Example 1, and the same test as in Example 1 was performed. The evaluation results are shown in Table 1.
Comparative Examples 1 and 2
As the reactive elastomer, in Comparative Example 1, a polymerization degree of 300, a degree of acetylation exceeding 3 mol%, a butyralization degree of 63 ± 3 mol% and a flow softening point of 115 ° C., a polyvinyl butyral resin, and in Comparative Example 2 a polymerization degree. An anisotropic conductive film was obtained in the same manner as in Example 1 except that a polyvinyl butyral resin having a degree of acetylation of 3 mol% or less, a degree of butyralization of 70 mol%, and a flow softening point of 160 ° C. was used. The evaluation results are shown in Table 2.
Comparative Examples 3-6
An anisotropic conductive film was prepared in the same manner as in Example 1 except that the reaction products (3) to (6) were used. The evaluation results are shown in Table 2.
[0021]
[Table 1]

[0022]
[Table 2]

[0023]
【The invention's effect】
According to the present invention, it is possible to obtain an anisotropic conductive film that can be used for micro-joining with a pitch of 0.05 mm or less, has excellent adhesion, and has high reliability.

Claims

Polyvinyl butyral resin (A), epoxy resin (B), imidazole having a polymerization degree of 1500 to 2500, an acetylation degree of 3 mol% or less, a butyralization degree of 65 mol% or more, and a flow softening point of 200 ° C. or more. The reaction product (C) of the derivative and the silicone epoxy compound represented by the formula (1), and conductive particles having a metal coating on the surface of the polymer spherical core material are essential components, and the imidazole derivative and the formula (1) The anisotropic conductive film characterized by the reaction molar ratio of the silicone epoxy compound being 1.5-2.5 .

(R ₁ and R ₂ represent a divalent aliphatic group having 1 to 5 carbon atoms, or a residue obtained by removing two hydrogen atoms from an aromatic group having 6 or more carbon atoms. Also good)

The anisotropic conductive film of the silicone epoxy compound represented by the formula (1) is, according to claim 1 Symbol placement is the following formula (2).

The particle size of the conductive particles with a metal coating on the surface of the polymer spherical nucleus material 3 to 15 [mu] m, the anisotropic conductive film having an average particle size of 5~10μm claim 1 or claim 2 Symbol placement.