JP4212793B2 - Adhesive composition, flexible printed wiring board and coverlay film using the same - Google Patents

Description

（但し、式中Ｒは水素原子、アミノ基、エポキシ基、ヒドロキシ基もしくはカルボキシル基を含有する一価炭化水素基又はアルコキシ基を示し、Ｒ’は置換もしくは非置換の一価炭化水素基を示し、a、bは０．００１≦a≦１；１≦b≦２；１≦（a+b）≦３を満足する正数である。また一分子中のケイ素原子の数は２〜１，０００であり、一分子中のケイ素原子に直結した官能基Ｒの数は１以上である。）
Ｅ）反応性リン含有化合物 １０〜１００重量部、
Ｆ）硬化促進剤 １〜５０重量部。
更に、本撥明は上記接着剤組成物を介して電気絶縁性フィルムと離型紙を積層してなる高耐熱性、ハロゲンフリーの難燃性カバーレイフィルム及び上記接着剤組成物を介して電気絶縁性フィルムと金属箔とを接着してなる高耐熱性、ハロゲンフリーの難燃性フレキシブル印刷配線用基板を提供するものである。
【０００８】
【発明の実施の形態】
以下に本発明を更に詳細に説明する。
本発明におけるポリイミドシロキサンは、テトラカルボン酸二無水物と、シロキサン化合物の両末端をアミン化した化合物を含むジアミン化合物とを重合してポリアミド酸共重合体を得、次いで、このポリアミド酸共重合体を脱水閉環して得られる化合物であるが、製造方法はこれに限定されるものではない。具体的にはテトラカルボン酸二無水物としてはＤＳＤＡ（３，３’、４，４’−ジフェニルスルホンテトラカルボン酸二無水物）、ＢＰＤＡ（３，３’、４，４’−ビフェニルテトラカルボン酸二無水物）が、ジアミン化合物としては両末端をアミン変性したジメチルポリシロキサンが原料として用いられる。このジメチルポリシロキサンのシロキサン単位は１〜１００の範囲が必要で、好ましくは５〜２０である。シロキサン単位が１未満では、接着剤組成物の柔軟性が得られず、１００を超える場合には、得られるポリイミドシロキサンの耐熱性、難燃性が不十分となることが懸念される。更に、ＢＡＰＰ{２，２−ビス［４−(４−アミノフェノキシ）フェニル］プロパン}及び／またはＨＡＢ（３，３’−ジハイドロキシ−４，４’−ジアミノビフェニル）を加えて本発明におけるポリイミドシロキサンが得られる。
【０００９】
本発明におけるＡ）成分のポリイミドシロキサン化合物は、例えば、以下の具体的製造方法で得られる。テトラカルボン酸二無水物とジアミノポリシロキサンあるいはシロキサンを含有しないジアミン成分を有機溶媒中で混合し０〜７０℃、特に０〜３０℃の温度で１〜５０時間、特に３〜２０時間重合反応を行うことが好ましく、この条件でより効率的にポリアミド酸を得ることができる。次いで、このポリアミド酸を通常の方法で脱水閉環することにより、求めるポリイミドシロキサン化合物を得ることができるが、具体的には２００〜５００℃で１〜２４時間加熱することが好ましい。
【００１０】
上記反応に使用する溶媒としては、例えばジメチルスルホキシド等のスルホキシド系溶媒；Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジエチルホルムアミド等のホルムアミド系溶媒；Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジエチルアセトアミド等のアセトアミド系溶媒；Ｎ−メチル−２−ピロリドン、Ｎ−ビニル−2−ピロリドン等のピロリドン系溶媒；フェノール、o−クレゾール、m−クレゾール、p−クレゾール、キシレノール、ハロゲン化フェノール、カテコール等のフェノール系溶媒；ジエチレングリコール、ジメチルエーテル（ジグライム）、トリエチレングリコールジメチルエーテル（トリグライム）、テトラグライム等のジグライム系溶媒；あるいはヘキサメチルホスホホルムアミド、γ−ブチロラクトン等を挙げることが出来る。これら有機極性溶媒は一種類を単独で用いても、２種類以上を混合して用いてもよく、またキシレン、トルエン等の芳香族炭化水素系の有機極性溶媒を併用して用いることもできる。上記有機極性溶媒の使用量は特に限定されないが、重合反応により得られるポリアミド酸共重合体が有機極性溶媒中に５〜３０重量％、特に１０〜４０重量％溶解するようにジアミン化合物、テトラカルボン酸二無水物、有機極性溶媒の使用量を決定することが好ましい。
【００１１】
上記脱水閉環反応においては脱水剤及び触媒を用いる方法が好適である。この場合、脱水剤としては、例えば、脂肪族酸無水物、芳香族酸無水物、Ｎ，Ｎ≡ジアルキルカルボンイミド、低級脂肪酸ハロゲン化物、ハロゲン化低級脂肪酸ハロゲン化物、ハロゲン化低級脂肪酸無水物、アリルホスホン酸ジハロゲン化物、チオニルハロゲン化物等が挙げられ、これらは１種または２種以上を混合して使用することが出来る。脱水剤の使用量はポリアミド酸の繰り返し単位当たり約０．５〜１０モル量、特に２〜６モル量が好ましい。
また、上記脱水閉環反応において用いられる触媒としては、例えば、トリエチルアミン等の脂肪族第三級アミン、ジメチルアニリン等の芳香族第三級アミン、ピリジン、β−ピコリン、イソキノリン等の複素環式第三級アミン等が挙げられ、これらの１種又は２種以上を混合して使用することができる。触媒の使用量はポリアミド酸の繰り返し単位あたり約０．０１〜４モル量、特に０．１〜２モル量が好ましい。
【００１２】
本発明におけるＢ）成分のエポキシ樹脂は、１分子中にエポキシ基を２個以上有し、ハロゲン原子を含有しないものであればよく、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、フェノールノボラック型エポキシ樹脂等のグリシジルエーテル系エポキシ樹脂；ヘキサヒドロフタル酸グリシジルエステル、ダイマー酸グリシジルエステル等のグリシジルエステル系エポキシ樹脂；トリグリシジルイソシアヌレート、テトラグリシジルジアミノジフェニルメタン等のグリシジルアミン系エポキシ樹脂；エポキシ化ポリブタジエン、エポキシ化大豆油等の線状脂肪族エポキサイド系樹脂等が広く用いられる。以上のエポキシ樹脂の中でも耐熱性の向上という点からナフタレン、ジシクロペンタジエン等を骨格に含む多官能エポキシ樹脂が好ましい。また難燃性の点からは上記のエポキシ骨格にリン原子を含むリン含有エポキシ樹脂を併用することもできる。
上記のエポキシ樹脂を添加することにより、ポリイミドシロキサン化合物のみを含む接着剤では不十分であった接着性の向上、電気絶縁性フィルム上に塗布、半硬化させた後の金属箔、あるいは印刷回路との熱圧着性の向上を図ることができる。
エポキシ樹脂の配合量は、ポリイミドシロキサン１００重量部に対して１０〜３００重量部であればよく、好ましくは、１０重量部から２００重量部である。配合量が１０重量部未満では、接着性が低下する虞れがあり、３００重量部を超える場合には難燃性が不十分となる。
【００１３】
本発明におけるＣ）成分のフェノール樹脂としては以下のものが挙げられる。フェノールノボラック樹脂、クレゾールノボラック樹脂、フェノールとクレゾールの共重合体ノボラック樹脂あるいはトリスヒドロキシフェニルメタン型フェノール樹脂、ナフタレン型フェノール樹脂、シクロペンタジエン型フェノール樹脂、フェノールアラルキル樹脂等、公知のフェノール樹脂が広く用いられる。
フェノール樹脂の添加量はポリイミドシロキサン１００重量部に対し１０部〜３００重量部が好ましく、特に、好ましくは１０重量部〜２００重量部である。１０重量部未満では耐熱性、難燃性が低下し、３００重量部を超えると接着剤組成物の硬化が不十分になる虞れがある。
【００１４】
本発明におけるＤ）成分の芳香族重合体とオルガノポリシロキサンとを反応させることにより得られる共重合体としては、以下の化合物が例示される。まず、反応に使用される芳香族重合体としては、種々の化合物を使用でき、例えば、下記式（２）、（３）の構造のエポキシ樹脂やフェノール樹脂などが挙げられる。
【００１５】
【化１】

【００１６】
また、下記式（４）〜（６）の構造のアルケニル基含有エポキシ樹脂またはアルケニル基含有フェノール樹脂を用いることもできる。
【化２】

なお、上記式においてＲ⁴は水素原子又はメチル基、Ｒ⁵は水素原子又はメチル基、Ｒ⁶は水素原子又はグリシジル基であり、ｎは0又は自然数、好ましくは０〜５０の整数、特に好ましくは１〜２０の整数であり、ｍは０又は自然数、好ましくは０〜５０の整数、特に好ましくは０または１である。ｐ、ｑは自然数、好ましくは（ｐ+ｑ）が２〜５０、より好ましくは２〜２０の整数である。
【００１７】
一方、本発明におけるＤ）成分の他の原料であるオルガノポリシロキサンは下記組成式（1）で示されるものである。

（但し、式中Ｒは水素原子、アミノ基、エポキシ基、ヒドロキシ基もしくはカルボキシル基を含有する一価炭化水素基またはアルコキシ基を示し、Ｒ’は置換もしくは非置換の一価炭化水素基を示し、a、bは０．００１≦a≦１；１≦b≦２；１≦（a+b）≦３を満足する正数である。また一分子中のケイ素原子の数は２〜１，０００であり、一分子中のケイ素原子に直結した官能基Ｒの数は1以上である。）
【００１８】
前記Ｒの中のアミノ基含有一価炭化水素基としては、下記のものが挙げられる。
【化３】

【００１９】
前記Ｒの中のエポキシ基含有一価炭化水素基としては下記のものが挙げられる。
【化４】

【００２０】
前記Ｒの中のヒドロキシ基含有一価炭化水素基としては下記のものが挙げられる。
【化５】

【００２１】
前記Ｒの中のカルボキシル基含有一価炭化水素基としては一般式−Ｃ_xＨ_2xＣＯＯＨ（ｘ =０〜１０の整数）で示されるものが挙げられ、アルコキシ基としてはメトキシ基、エトシキ基、ｎ−プロポキシ基等の炭素数１〜４のアルコキシ基が挙げられる。
【００２２】
またＲ’の置換または非置換の一価炭化水素基としては炭素数１〜１０のものが好ましく、例えば，メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ter−ブチル基、ペンチル基、ネオペンチル基、へキシル基、シクロへキシル基、オクチル基、デシル基等のアルキル基；ビニル基、アリル基、プロペニル基、ブテニル基等のアルケニル基；フェニル基、トリル基等のアリール基；ベンジル基、フェニルエチル基等のアラルキル基；これらの基の炭素原子に結合する水素原子の一部又は全部が他の有機基（但しハロゲン原子を含まない）で置換された基などを挙げることができる。これらの中でも脂肪族不飽和結合を含まない基、例えばアルキル基、アリール基、アラルキル基が好ましく、特にメチル基、フェニル基が好ましい。更に、ａ、ｂは上述した値であるが、好ましくは０．０１≦ａ≦０．１；１．８≦ｂ≦２；１．８５≦（ａ+ｂ）≦２．１；ケイ素原子数は好ましくは１０〜４００、より好ましくは２０〜２１０である。
このようなオルガノポリシロキサンとしては例えば下記構造式（１４）、（１５）の化合物を挙げることができる。
【００２３】
【化６】

上記式（１４）、（１５）におけるＲ’は、式（１）におけるＲ’と同じ非置換または置換の一価炭化水素基、好ましくはメチル基またはフェニル基を示し、Ｘはアミノ基、エポキシ基、ヒドロキシ基またはカルボキシル基含有一価炭化水素基を示し、ｐは０〜１，０００、好ましくは８〜４００の整数、ｑは０〜２０、好ましく０〜５の整数を示す。
具体的には下記のジオルガノポリシロキサン（１６）〜（２１）を挙げることができる。
【００２４】
【化７】

【００２５】
上記オルガノポリシロキサンの分子量は特に限定されるものではないが１００〜７０，０００が好ましい。これはオルガノポリシロキサンの分子量が１００〜７０，０００であるものを使用して、得られた共重合体を接着剤構成成分に配合すると、マトリクス中に共重合体が相溶せず、かつ微細な海島構造を形成し、マトリクスの物性を保持したまま、オルガノポリシロキサン独自の柔軟性等の効果を同時に発揮できるためである。分子量が１００未満であると、マトリクス中に共重合体が相溶、海島構造が消滅し、接着剤硬化物の柔軟性が低下する。一方、分子量が７０，０００を超えると海島構造が大きくなってしまい、接着剤硬化物の耐熱性が低下する虞れがある。
【００２６】
芳香族重合体とオルガノポリシロキサンを反応させて、本発明におけるＤ）成分の共重合体を得る方法としては、公知の方法が使用できる。
具体的には、上記の芳香族共重合体とオルガノシロキサンをトルエン中で混合し、窒素雰囲気下、１００℃で１２時間加熱、反応、熟成させた後、トルエンを常圧で留去し、真空下、１５０℃で1時間ストリップを行い粗生成物を得る。これを少量のトルエンに溶解し、大量のヘキサン中で洗浄、精製した後、目的の共重合体を得ることができる。なお、合成方法に関しては上記の方法に限定されるものではない。また、この共重合体の配合量はポリイミドシロキサン１００重量部に対して１〜１００重量部が好ましく、より好ましくは、１０〜６０重量部である。１重量部未満の場合には接着剤硬化物の柔軟性が低下し、１００重量部を超える場合には耐熱性が低下する虞れがある。
【００２７】
本発明におけるＥ）成分の反応性リン含有化合物としては、リン原子を有し、且つ、反応性の基を合わせ持った化合物であればよく、具体的には三光（株）のＨＣＡ、９，１０−dihydoro−９−oxa−１０−phosphaphenanthrene−１０−oxide 、またＨＣＡ にハイドロキノンを付加させたＨＣＡ−ＨＱ 、大八化学（株）のＭＲ−２００（２−メタクリロイル−オキシエチルアシッドホスフェート）、ＭＲ−２６０ （ジフェニル−２≡メタクリロイル−オキシエチルホスフェート）等が挙げられる。
本発明におけるＥ）成分の反応性リン含有化合物としては、リンの含有量が６〜３０重量％の範囲にあるものが好ましい。これらの反応性リン含有化合物は接着剤の調合時、あるいは仮接着後のアフターベイクの過程で他の成分と反応する。これにより、従来の反応性のないリン系難燃剤に比べて同等の難燃効果を保持したまま、耐イオンマイグレーション性を始めとする電気特性を格段に向上させることができる。上記反応性リン含有化合物の配合量はポリイミドシロキサン１００重量部に対し１０〜１００重量部で、且つ、接着剤中での全リン原子の割合が０．５〜２．５重量％になるように配合することが好ましく、より好ましくは０．５〜２．０重量％である。全リン原子含有量が０．５重量％未満の場合には十分な難燃性が得られず、一方２．５重量％を超えると接着剤硬化物の耐熱性の低下をきたす虞れがある。
【００２８】
本発明におけるＦ)成分の硬化促進剤としては、有機リン化合物を用いることができ、具体的にはトリフェニルホスフィン、トリブチルホスフィン、トリ（ｐ−トルイル〕ホスフィン、トリ（ｐ−メトキシフェニル）ホスフィン、トリ（ｐ−エトキシフェニル〕ホスフィン、トリフェニルホスフィン・トリフェニルボレート、テトラフェニルホスホニウム・テトラフェニルボレート等のトリオルガノホスフィン類や四級ホスホニウム塩などが挙げられ、この中から単独あるいは2種類以上を混合して用いることができる。
また硬化促進剤としては、他に、種々のイミダゾール化合物も使用でき、例えば２−メチルイミダゾール、２−エチルイミダゾール、２−エチル−４−メチルイミダゾール、またこの化合物のエチルイソシアネート化合物、２−フェニルイミダゾール、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等が挙げられる。これらの中から単独または2種類以上を混合して用いることができる。
【００２９】
本発明における硬化促進剤としては、その他にも、トリエチレンアンモニウムトリフェニルボレート等の第三級アミンのテトラフェニルホウ素酸塩、ホウ弗化亜鉛、ホウ弗化錫、ホウ弗化ニッケル等のホウ弗化物、オクチル酸錫、オクチル酸亜鉛等のオクチル酸塩も挙げられ、これらは単独又は２種類以上併用して用いることができる。
以上の硬化促進剤の配合量はポリイミドシロキサン１００重量部に対して１〜５０重量部が好ましく、更に、より好ましくは５〜２０重量部である。硬化促進剤の添加量が１重量部未満では接着剤が十分に硬化せず、また、５０重量部を超えると接着剤組成物の保存安定性が低下する。
【００３０】
本発明の接着剤組成物においては諸特性を低下させない範囲で、その他の樹脂やフィラー等の添加剤を加えてもよい。例えば難燃助剤としての水酸化アルミニウム、水酸化マグネシウム、二酸化ケイ素、更に、窒素及びリンを含有する種々の化合物、例えばリン酸メラミンや各種のホスファゼン化合物等が挙げられる。これらの窒素及びリンの両成分を含む添加物は難燃助剤としても有効である。
本発明においてはエポキシ樹脂に用いられる公知の硬化剤を併用することも可能である。例えば脂肪族アミン系硬化剤、脂環族アミン系硬化剤、芳香族アミン系硬化剤、酸無水物系硬化剤、ジシアンジアミド、三弗化ホウ素アミン錯塩等が例示される。これらの硬化剤が本発明の課題としている金属イオンの耐マイグレーション性に与える影響も大きく、特に活性の高いアミンを使用すると耐マイグレーション性が低下するとから、芳香族アミン、例えば４，４’−ジアミノジフェニルスルホン、３，３’−ジアミノジフェニルスルホン、４，４’−ジアミノジフェニルメタン等を使用することが好ましく、これらは単独または2種以上併用して用いることもできる。
【００３１】
本発明の接着剤組成物に用いられる溶剤としては上述のポリイミドシロキサンの合成に用いられる有機極性溶媒が好適に用いられる。
本発明の接着剤組成物溶液の固形分濃度は１０〜４５重量％であればよく、好ましくは２０〜３５重量％である。固形分濃度が４５重量％を超えると、溶液粘度の上昇や固形分と溶剤との相溶性の低下により塗布性が悪くなり、作業性が低下し、１０重量％未満であると塗工むらが生じやすくなり、更には、脱溶剤量が多くなるため、環境面への悪影響や経済性の悪化等の問題を生じる。
本発明の接着剤組成物はポットミル、ボールミル、ホモジナイザ、スーパーミル等を用いて混合される。
【００３２】
本発明における電気絶縁性フィルムはポリイミドフィルム、ポリエステルフィルム、ポリバラン酸フィルム、ポリフェニレンサルファイドフィルム、アラミドフィルム等が例示され、中でもポリイミドフィルムが好ましい。フィルムの厚さは必要に応じて適宜の厚さのものを使用すればよいが、１０〜１２５μmが好ましい。また、これらのフィルムの片面もしくは両面に表面処理を行うことも可能であり、その表面処理としては低温プラズマ処理、コロナ放電処理、サンドブラスト処理等が挙げられる。
【００３３】
本発明における金属箔としては銅箔、アルミニウム箔、鉄箔等が例示され、特に銅箔を用いるものが好ましい。金属箔の厚さは必要に応じて適宜の厚さのものを使用すればよいが、５〜７０μmが好ましい。
【００３４】
次に、本発明のフレキシブル印刷配線用基板の製造方法について述べる。
まず、予め、調製された本発明の接着剤組成物に所定の溶剤を混合してなる接着剤溶液をリバースロールコータ、コンマコータ等を用いて電気絶縁性フィルムに塗布する。これをインラインドライヤに通し、８０℃〜１８０℃で２〜２０分間処理して接着剤の溶剤を除去、乾燥して半硬化状態とした後、加熱ロールでこの接着剤塗布面に金属箔を線圧２〜２００Ｎ／cm、温度６０〜１８０℃で熱圧着させる。得られた積層フィルムの接着剤を更に硬化させるために加熱してもよく、その加熱温度は８０〜２００℃、加熱時間は１〜２４時間である。
本発明における接着剤組成物の塗布膜の厚さは乾燥状態で５〜４５μmであればよく、好ましくは、５〜３０μmである。本発明のフレキシブル印刷配線用基板は電気絶縁性フィルムの片面または両面に、接着剤を介して金属箔を積層したものである。
【００３５】
一般に、カバーレイフィルムはフレキシブル印刷配線用基板上に回路を作製してなるフレキシブル配線板の回路を保護するために、これに積層一体化して用いるもので、半硬化状態の接着剤付き電気絶縁性フィルムと剥離紙とからなり、使用する際に剥離紙を剥がして、フレキシブル配線板の回路面に積層する。一般的にはカバーレイフィルムを積層一体化したものを総称してフレキシブル配線板ということもある。ここで、電気絶縁性フィルムは前記したものが使用可能である。また、使用可能な剥離紙には原紙の片面または両面にポリエチレンフィルム、４−メチル−１−ペンテン−α−オレフィン共重合体（以下ＴＰＸとする）フィルム、または、ポリプロピレンフィルムを貼りあわせたもの、原紙の片面あるいは両面にポリ塩化ビニリデンをコートしたもの、更に、これら剥離紙の片面あるいは両面にシリコーン離型剤を施したものなどがあり、孔加工時の条件により適宜使用することができる。
【００３６】
本発明のカバーレイフィルムは、本発明の接着剤組成物の有機溶剤溶液を電気絶縁性フィルムに乾燥状態で１０〜６０μmの厚さになるように塗布し、次いで、乾燥して溶剤を除去し、接着剤を半硬化状態とする。この場合、必要に応じて５０℃〜１８０℃の温度で、短時間加熱することができる。次いで、この半硬化状態の接着剤付き電気絶縁性フィルムを前記剥離紙と重ね合わせ、ロールラミネーター等により温度２０〜１８０℃、線圧２〜２００Ｎ／cmの条件下に積層し、ロール状に巻きとってカバーレイフィルムが製造される。
【００３７】
【実施例】
次に、本発明の実施例を挙げるが、本発明はこれらの実施例に限定されるものではない。なお、％濃度表示は全て重量％である。
［ポリイミドシロキサンの合成例１］
ＤＳＤＡ（３，３’、４，４’−ジフェニルスルホンテトラカルボン酸二無水物）３５８g（１モル）をＮ−メチル−２−ピロリドン７００g に溶解した後、α, ω−ビス(３−アミノプロピル）ポリジメチルシロキサン〔信越化学工業（株）製、商品名ＫＦ−８０１０、シロキサン単位９）１６８g（０．２モル）及びＮ−メチル−２−ピロリドン５０g を加え、均一に溶解させた後、窒素雰囲気下、２５℃で５時間重合した。次いで、ＢＰＡＡ{２，２−ビス［４−(４−アミノフェノキシ）フェニル］プロパン}２１３g (０．３モル）とＨＡＢ（３，３’−ジハイドロキシ−４，４’−ジアミノフェニル）１１４g (０．５モル）及びＮ−メチル−２−ピロリドン１，０００g を加えた後、反応温度２５℃で、更に、５時間重合反応させた後、２５０℃で３時間脱水閉環反応を行い、ポリイミドシロキサン溶液を得た（固形分濃度約３０％）。
【００３８】
［ポリイミドシロキサンの合成例2］
ＤＰＤＡ（３，３’、４，４’−ビフェニルテトラカルボン酸二無水物）２９４g（１モル）をＮ−メチル−２−ピロリドン７００g に溶解した後、α, ω−ビス(３−アミノプロピル）ポリジメチルシロキサン〔信越化学工業（株）製、ＫＦ−８０１０、シロキサン単位９）１６８g（０．２モル）及びＮ−メチル−２−ピロリドン５０g を加え均一に溶解させた後、窒素雰囲気下、２５℃で５時間重合した。次いでＢＡＰＰ{２，２−ビス［４−(４−アミノフェノキシ）フェニル］プロパン}２１３g (０．３モル）とＨＡＢ（３，３’−ジハイドロキシ−４，４’−ジアミノフェニル）１１４g (０．５モル）及びＮ−メチル−２−ピロリドン１，０００g を加えた後、反応温度２５℃で、更に、５時間重合反応させた後、２５０℃で３時間脱水閉環反応を行い、ポリイミドシロキサン溶液を得た（固形分濃度約３０％）。
【００３９】
［実施例1］
表１の実施例1の欄に示す接着剤組成を用い、溶剤としてＮ−メチル−２−ピロリドンを用いて固形分濃度が２５％の接着剤溶液を得た。次いで、厚さが２５μm、２００mm×２００mm のポリイミドフィルム・カプトン（東レ・デュポン社製商品名）にアプリケータで接着剤溶液を乾燥後の厚さが２０μmになるように塗布し、１８０℃、１０分間の加熱で接着剤を半硬化状態とし、接着剤付きポリイミドフィルムを得た。この接着剤付ポリイミドフィルムの接着剤塗布面に、厚さ３５μm、２００mm×２００mmの銅箔・ＢＨＮ（ジャパンエナジー社製圧延銅箔商品名）を重ね合わせ、温度１８０℃、線圧１００Ｎ／cmの条件下で加熱、圧着し、更に、１８０℃で１０時間加熱硬化させてフレキシブル印刷配線用基板を得た。このフレキシブル印刷配線用基板の特性を後記の方法で測定し、結果を表３に示した。
【００４０】
［実施例２〜４］
表１の実施例２〜４の各欄に示す接着剤処方を用いること以外は、実施例１と同様の方法でフレキシブル印刷配線用基板を作製した。これらのフレキシブル印刷配線用基板の特性の測定結果を表３に示した。
【００４１】
［実施例５］
表１の実施例５の欄に示す接着剤組成物を用い、溶剤のＮ−メチル−２−ピロリドンとともに撹拌混合し固形分濃度が２５％の接着剤溶液を得た。次いで、厚さ２５μm、２００×２００mmのポリイミドフィルム・カプトン（前出）にアプリケータで接着剤溶液を乾燥後の厚さが３０μmになるように塗布し、１８０℃、１０分間の加熱で接着剤を半硬化状態として、カバーレイフィルムを得た。このカバーレイフィルムの接着剤塗布面と２００mm×２００mmの銅箔、ＢＨＮ（前出）の光沢面を重ね合わせ温度１８０℃、圧力５ＭＰa、３０分の条件で加熱、圧着し評価用のサンプルとした。この積層板の特性を下記の方法で測定し結果を表３に示した。
【００４２】
［比較例１〜４］
表２の比較例１〜４の各欄に示す接着剤組成物を用いること以外は実施例１と同様の方法でフレキシブル印刷配線用基板を作製した。このフレキシブル印刷配線用基板の特性の測定結果を表３に示した。
【００４３】
［比較例５］
表２の比較例５の欄に示す接着剤組成物を用いること以外は実施例５と全く同様の方法でカバーレイフィルム及び評価用サンプルを作製した。このカバーレイフィルムの評価用サンプルの特性の測定結果を表３に示した。
【００４４】
【表１】

【００４５】
（接着剤の各組成として使用した原材料の出所）
ＨＰ４０３２：大日本インキ化学工業（株）製ナフタレン型二官能エポキシ樹脂商品名、エポキシ当量１５０、
ＨＰ７２００：大日本インキ化学工業（株）製ジシクロペンタジエン型エポキシ樹脂商品名、エポキシ当量２６０、
ＬＡ７０５４：大日本インキ化学工業（株）製トリアジン基含有フェノールノボラック樹脂商品名、水酸基当量１２５、
ＭＥＨ７８５１ＳＳ：明和化成（株）製フェノール樹脂商品名、水酸基当量１９９、
ＨＣＡ：三光（株）製反応性リン含有難燃剤、リン含有率約１５重量％、
ＣＰＨＯ−ＨＱ：日本化学工業（株）製反応性リン含有難燃剤、リン含有率約１１．６重量％、
ＤＤＳ：４，４’−ジアミノジフェニルスルホン商品名、
２Ｅ−４ＭＺ−ＣＮ：四国化成工業（株）製イミダゾール系硬化促進剤商品名、
ＴＰＰ：トリフェニルホスフィン商品名、
キスマ５：協和化学工業（株）製水酸化マグネシウム商品名、粒子径０．６〜１．０μm、
ＭＰＰ−Ａ：（株）三和ケミカル製リン酸メラミン商品名、リン含有量１５重量％。
【００４６】
実施例で、Ｄ）成分として使用した共重合体は下記式（２２）で示される。
【化８】

【００４７】
【表２】

ＰＸ−２００：大八化学工業（株）製リン系難燃剤、リン含有量９重量％
【００４８】
【表３】

【００４９】
各特性値の測定は下記の方法に従って行った。
（剥離強度）
ＪＩＳＣ６４８１ に準拠して、１mm 幅のサンプルを作製し、９０°方向に５０mm／分の速度で銅箔側に引き剥がしたときの接着力を測定した。
（半田耐熱性）
ＪＩＳＣ６４８１ に準拠して、サンプルを２５mm毎に切断しフロー半田上に３０秒間浮かべて膨れ、剥れ等を生じない最高温度を測定した。
（耐マイグレーション性試験）
線間が１００μm の櫛形パターンを作製し、温度１３０℃、湿度８５％、電圧１００Ｖで、２５０時間印加し、印加前後のサンプルを拡大鏡で観察し、線間に発生するマイグレーションの生成状態を検査し、下記の基準で評価した。
○：線間への析出物の形成なし、△：回路部分に析出物が僅かにみられるが線間を埋めることはない、×：線間全体にまたがって析出物が形成され熱劣化の跡が観られる。
【００５０】
（難燃性）
各例で得られたフレキシブル印刷用基板、銅箔を圧着したカバーレイフィルムについて、銅箔を化学処理し除去した（接着剤／ポリイミドフィルム）を用いてＵＬ９４難燃性規格に準拠して難燃性グレードを測定した。
（耐折性）
ＪＩＳＣ６４７１ に準拠し、実施例１〜４のフレキシブル印刷配線用基板に指定の回路を印刷した後、実施例５のカバーレイフィルムと組み合わせ１６０℃／５０kg／cm²、３０分でプレスしたものをサンプルとした（ロール方向、及びロールに垂直方向でサンプリングした）。同様に比較例１〜４で得られたフレキシブル印刷用基板と比較例５の カバーレイフィルムを組み合わせてサンプルとし、曲率半径０．３８mm、２５℃で下記基準で評価した。なお、表中のＭＤ、ＴＤは略語であり、それぞれロール方向（ＭＤ）及びロール方向に垂直な方向（ＴＤ）を意味する。
n=5における平均値が２００回以上を○、２００回未満を×とした。
【００５１】
（接着剤硬化物のガラス転移点測定法）
難燃性試験を行ったものと同じ構成(ポリイミドフィルム／接着剤層）のサンプルを用いて動的粘弾性測定を行い、得られたtanδの最大値を示す温度を接着剤硬化物のガラス転移点と定義した。
なお、実施例１の組成物についてＴg１６０℃の値を、また、実施例５の組成物についてＴg１２０℃の値を得た。一方、比較例１の組成物についてＴg９０℃の値を得た。
測定機器：レオメトリック・サイエンティフィック・エフ・イー（株）製粘弾性アナライザー、ＲＳＡ−II、
測定モード：引っ張り、
チャック間距離：３５mm、
測定温度：０〜３００℃、
昇温速度：２．５℃／分
摂動周波数：５ヘルツ、
サンプルサイズ：１０mm〔幅）×５０mm(長）。
【００５２】
【発明の効果】
本発明により諸特性のバランスがとれ、且つ、耐熱性、耐マイグレーション性に優れたハロゲンフリーの接着剤組成物が得られ、それを用いることで耐マイグレーション性に優れたハロゲンフリーのフレキシブル印刷用基板、カバーレイフィルムを得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an adhesive composition used for producing a flexible printed wiring board and the like, a coverlay film used for protecting the flexible printed wiring board, and a flexible printed wiring board.
[0002]
[Prior art]
A flexible printed wiring board is a circuit on a flexible printed wiring board in which an electrically insulating film and a metal foil are laminated and integrated via an adhesive, and further, via a semi-cured adhesive for circuit protection. A product obtained by peeling a release paper from a coverlay film obtained by laminating an electrically insulating film and a release paper is laminated and integrated therewith.
Properties required for these flexible printed wiring boards, flexible printed wiring boards, and coverlay films include high adhesion between the insulating film and the metal foil, heat resistance, solvent resistance, electrical characteristics, and dimensional stability. And various properties such as long-term heat resistance and flame retardancy. Recently, with increasing density and weight of circuit boards, flexible printed wiring boards have been made finer, more dense, and thinner. In addition to excellent adhesiveness, excellent heat resistance and excellent From the viewpoint of bending resistance and environmental problems, it is desired to make the material halogen-free without using brominated flame retardants.
[0003]
On the other hand, in recent years, IC mounting by the COF (chip-on-film) method is used for wiring of liquid crystal peripheral materials, and it has superior bending resistance and drilling processing compared to the conventional TAB (tape automatic bonding) method. The switch to the COF method is gradually progressing from the advantage that it becomes unnecessary. As a COF substrate material, high heat resistance is required when mounting an IC. Therefore, a two-layer film obtained by copper-plating a polyimide film having a glass transition point (Tg) of 200 ° C. or higher, or polyimide on a copper foil. A two-layer film (two-layer flexible printed wiring board) in which a solution is cast and a polyimide layer is formed has been used. However, these two-layer flexible printed wiring boards are in a state where the above demand cannot be satisfied because the yield at the time of manufacture is low and the manufacturing costs are high, and the conventional two-layer flexible printed wiring board is replaced. Therefore, there is a strong demand for a three-layer type high heat resistance (high glass transition point) flexible printed wiring board in which an electrically insulating film and a metal foil are bonded together with an adhesive that has been used. In addition, the cover layer film with high heat resistance (high glass transition point) corresponding to the substrate for three-layer flexible printed wiring is in a state where there is no material that can be used at present, and early commercialization is required. Yes.
[0004]
Conventionally, as an adhesive used for a flexible printed wiring board, various combinations of thermosetting resins and elastomer compounds have been used. For example, various adhesives such as an epoxy resin / polyester resin system, an epoxy resin / acrylonitrile-butadiene copolymer system, and an epoxy resin / acrylic resin system have been studied. In order to improve the heat resistance of these adhesives, the application of higher heat-resistant epoxy resins, butyral / phenolic resins, and reduction of elastomer components in epoxy resin / elastomer compound systems have been studied. (See JP-A-60-79080, JP-A-60-139770, JP-A-61-108679, JP-A-2001-15876), and thermoplastic silicone-modified polyimide system Adhesives or silicone-modified polyamideimide resins are also widely used (see JP 2000-226666, JP 2000-345035, and JP 2000-265149). Epoxy is used to compensate for the lack of flame retardancy and insufficient adhesion. It is common to add the resin, there is a possibility that the flame-retardant polyimide has the addition of the epoxy resin is impaired.
[0005]
On the other hand, the use of a highly heat-resistant material such as polyimide increases the hardness of the obtained adhesive cured product, and also reduces the flexibility of the film, which is the most important physical property for flexible printed wiring boards. It has occurred.
Since the two-layer flexible wiring board does not have a flammable adhesive layer such as an epoxy resin, it exhibits not only heat resistance but also flame retardancy without using a halogen compound as described below. On the other hand, conventionally, as a method of imparting flame retardancy to the three-layer flexible printed wiring board and the coverlay film, adding an epoxy resin containing bromine to the adhesive composition has been widely performed. However, non-halogenation of adhesives is strongly demanded in recent years with increasing interest in environmental problems.
Addition of a flame retardant containing phosphoric acid has been studied as a non-halogenation method for the adhesive, but this flame retardant has no effect unless added in a large amount. Further, the added phosphorus flame retardant Deterioration in electrical insulation between the formed circuits (particularly during moisture absorption) due to the occurrence of resinous protrusions (dendrites) between the formed conductors, and in the worst case, there is a gap between the conductors. At present, the short circuit due to the dendrite growth causes the inconvenience that the circuit is destroyed, and satisfactory characteristics are not obtained.
As described above, a highly heat-resistant and halogen-free flame-retardant three-layer flexible printed wiring board that can replace the two-layer flexible printed wiring board and a coverlay film corresponding thereto have not been developed at present.
[0006]
[Problems to be solved by the present invention]
The object of the present invention is to provide a new high-heat-resistant, halogen-free flame-retardant adhesive composition without impairing the excellent adhesiveness, flexibility, various electrical properties, etc., that the conventional adhesive compositions have. An object is to provide a flexible printed wiring board and a coverlay film using the adhesive.
[0007]
[Means for Solving the Problems]
That is, this invention solves the said subject, and consists of following A) -F), and is an adhesive composition characterized by the total phosphorus content being 0.5-2.5 weight%. .
A) 100 parts by weight of polyimide siloxane,
B) 10 to 300 parts by weight of epoxy resin,
C) 10 to 300 parts by weight of phenol resin,
D) 1 to 100 parts by weight of a copolymer obtained by reacting an aromatic polymer with an organopolysiloxane represented by the following composition formula (1),

(In the formula, R represents a hydrogen atom, amino group, epoxy group, hydroxy group or carboxyl group-containing monovalent hydrocarbon group or alkoxy group, and R ′ represents a substituted or unsubstituted monovalent hydrocarbon group. , A and b are positive numbers satisfying 0.001 ≦ a ≦ 1; 1 ≦ b ≦ 2; 1 ≦ (a + b) ≦ 3, and the number of silicon atoms in one molecule is 2 to 1, The number of functional groups R directly bonded to silicon atoms in one molecule is 1 or more.)
E) 10 to 100 parts by weight of a reactive phosphorus-containing compound,
F) Curing accelerator 1 to 50 parts by weight.
Furthermore, the present light repellent is a highly heat-resistant, halogen-free flame-retardant cover lay film formed by laminating an electrically insulating film and release paper via the adhesive composition, and electrically insulated via the adhesive composition. The present invention provides a highly heat-resistant and halogen-free flame-retardant flexible printed wiring board obtained by bonding a conductive film and a metal foil.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in further detail below.
The polyimidesiloxane in the present invention is obtained by polymerizing tetracarboxylic dianhydride and a diamine compound containing a compound obtained by aminating both ends of the siloxane compound to obtain a polyamic acid copolymer, and then the polyamic acid copolymer. However, the production method is not limited to this. Specifically, as tetracarboxylic dianhydride, DSDA (3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride), BPDA (3,3 ′, 4,4′-biphenyltetracarboxylic acid) As the diamine compound, dimethylpolysiloxane whose both ends are amine-modified is used as a raw material. The dimethyl unit of dimethylpolysiloxane needs to have a range of 1 to 100, preferably 5 to 20. When the siloxane unit is less than 1, the flexibility of the adhesive composition cannot be obtained, and when it exceeds 100, there is a concern that the heat resistance and flame retardancy of the resulting polyimide siloxane will be insufficient. Furthermore, BAPP {2,2-bis [4- (4-aminophenoxy) phenyl] propane} and / or HAB (3,3′-dihydroxy-4,4′-diaminobiphenyl) is added to the polyimide in the present invention. Siloxane is obtained.
[0009]
The polyimidesiloxane compound of component A) in the present invention can be obtained, for example, by the following specific production method. Tetracarboxylic dianhydride and diaminopolysiloxane or diamine-free siloxane component are mixed in an organic solvent and subjected to a polymerization reaction at a temperature of 0 to 70 ° C., particularly 0 to 30 ° C. for 1 to 50 hours, particularly 3 to 20 hours. Preferably, the polyamic acid can be obtained more efficiently under these conditions. Next, this polyamic acid can be dehydrated and cyclized by a usual method to obtain the desired polyimidesiloxane compound. Specifically, it is preferable to heat at 200 to 500 ° C. for 1 to 24 hours.
[0010]
Examples of the solvent used in the above reaction include sulfoxide solvents such as dimethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N, N-dimethylacetamide and N, N-diethylacetamide. Acetamide solvents such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone and the like; pyrrolidone solvents such as phenol, o-cresol, m-cresol, p-cresol, xylenol, halogenated phenol, catechol, etc. Phenol solvents; diglyme solvents such as diethylene glycol, dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetraglyme; or hexamethylphosphoformamide, γ-butyrolactone, etc. That. These organic polar solvents may be used singly or in combination of two or more, and may be used in combination with aromatic hydrocarbon organic polar solvents such as xylene and toluene. The amount of the organic polar solvent used is not particularly limited, but the diamine compound or tetracarboxylic acid is used so that the polyamic acid copolymer obtained by the polymerization reaction is dissolved in the organic polar solvent by 5 to 30% by weight, particularly 10 to 40% by weight. It is preferable to determine the amounts of acid dianhydride and organic polar solvent used.
[0011]
In the dehydration ring closure reaction, a method using a dehydrating agent and a catalyst is suitable. In this case, as the dehydrating agent, for example, aliphatic acid anhydride, aromatic acid anhydride, N, N≡dialkylcarbonimide, lower fatty acid halide, halogenated lower fatty acid halide, halogenated lower fatty acid anhydride, allyl Examples thereof include phosphonic acid dihalides and thionyl halides, and these can be used alone or in combination of two or more. The amount of the dehydrating agent used is preferably about 0.5 to 10 mol, particularly 2 to 6 mol, per repeating unit of polyamic acid.
Examples of the catalyst used in the dehydration ring closure reaction include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic tertiary amines such as pyridine, β-picoline, and isoquinoline. A primary amine etc. are mentioned, These 1 type (s) or 2 or more types can be mixed and used. The catalyst is preferably used in an amount of about 0.01 to 4 mol, particularly 0.1 to 2 mol, per repeating unit of polyamic acid.
[0012]
The epoxy resin of component B) in the present invention is not limited as long as it has two or more epoxy groups in one molecule and does not contain a halogen atom. Bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type Glycidyl ether type epoxy resins such as epoxy resins; glycidyl ester type epoxy resins such as glycidyl hexahydrophthalate and dimer acid glycidyl esters; glycidyl amine type epoxy resins such as triglycidyl isocyanurate and tetraglycidyl diaminodiphenylmethane; epoxidized polybutadiene, Linear aliphatic epoxide resins such as epoxidized soybean oil are widely used. Among the above epoxy resins, a polyfunctional epoxy resin containing naphthalene, dicyclopentadiene or the like in the skeleton is preferable from the viewpoint of improving heat resistance. From the viewpoint of flame retardancy, a phosphorus-containing epoxy resin containing a phosphorus atom in the above epoxy skeleton can be used in combination.
By adding the above epoxy resin, an adhesive containing only a polyimidesiloxane compound is not sufficient for improving adhesiveness, applied on an electrically insulating film, semi-cured metal foil, or printed circuit It is possible to improve the thermocompression bonding.
The compounding quantity of an epoxy resin should just be 10-300 weight part with respect to 100 weight part of polyimide siloxane, Preferably, it is 10 to 200 weight part. If the blending amount is less than 10 parts by weight, the adhesiveness may be lowered. If it exceeds 300 parts by weight, the flame retardancy becomes insufficient.
[0013]
The following are mentioned as a phenol resin of C) component in this invention. Known phenol resins such as phenol novolac resin, cresol novolak resin, phenol-cresol copolymer novolak resin or trishydroxyphenylmethane type phenol resin, naphthalene type phenol resin, cyclopentadiene type phenol resin, phenol aralkyl resin are widely used. .
The amount of the phenol resin added is preferably 10 to 300 parts by weight, particularly preferably 10 to 200 parts by weight, based on 100 parts by weight of the polyimidesiloxane. If the amount is less than 10 parts by weight, the heat resistance and flame retardancy are lowered. If the amount exceeds 300 parts by weight, the adhesive composition may be insufficiently cured.
[0014]
The following compounds are illustrated as a copolymer obtained by making the aromatic polymer of D) component and organopolysiloxane in this invention react. First, various compounds can be used as the aromatic polymer used in the reaction, and examples thereof include epoxy resins and phenol resins having the structures of the following formulas (2) and (3).
[0015]
[Chemical 1]

[0016]
Moreover, the alkenyl group containing epoxy resin or alkenyl group containing phenol resin of the structure of following formula (4)-(6) can also be used.
[Chemical formula 2]

In the above formula, R ^Four Is a hydrogen atom or a methyl group, R ^Five Is a hydrogen atom or a methyl group, R ⁶ Is a hydrogen atom or a glycidyl group, n is 0 or a natural number, preferably an integer of 0-50, particularly preferably an integer of 1-20, and m is 0 or a natural number, preferably 0-50, particularly preferably. Is 0 or 1. p and q are natural numbers, preferably (p + q) is an integer of 2 to 50, more preferably 2 to 20.
[0017]
On the other hand, organopolysiloxane which is another raw material of component D) in the present invention is represented by the following composition formula (1).

(In the formula, R represents a hydrogen atom, amino group, epoxy group, hydroxy group or carboxyl group-containing monovalent hydrocarbon group or alkoxy group, and R ′ represents a substituted or unsubstituted monovalent hydrocarbon group. , A and b are positive numbers satisfying 0.001 ≦ a ≦ 1; 1 ≦ b ≦ 2; 1 ≦ (a + b) ≦ 3, and the number of silicon atoms in one molecule is 2 to 1, The number of functional groups R directly bonded to silicon atoms in one molecule is 1 or more.)
[0018]
Examples of the amino group-containing monovalent hydrocarbon group in R include the following.
[Chemical 3]

[0019]
Examples of the epoxy group-containing monovalent hydrocarbon group in R include the following.
[Formula 4]

[0020]
Examples of the hydroxy group-containing monovalent hydrocarbon group in R include the following.
[Chemical formula 5]

[0021]
The carboxyl group-containing monovalent hydrocarbon group in R is represented by the general formula -C _x H _2x What is shown by COOH (x = integer of 0 to 10) is exemplified, and examples of the alkoxy group include C1-C4 alkoxy groups such as a methoxy group, an ethoxy group, and an n-propoxy group.
[0022]
The substituted or unsubstituted monovalent hydrocarbon group for R ′ is preferably one having 1 to 10 carbon atoms, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, ter-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, decyl group and other alkyl groups; vinyl group, allyl group, propenyl group, butenyl group and other alkenyl groups; phenyl group, tolyl Aryl groups such as groups; aralkyl groups such as benzyl groups and phenylethyl groups; some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with other organic groups (not including halogen atoms) Examples include groups. Among these, a group not containing an aliphatic unsaturated bond, for example, an alkyl group, an aryl group, and an aralkyl group are preferable, and a methyl group and a phenyl group are particularly preferable. Further, a and b are the values described above, but preferably 0.01 ≦ a ≦ 0.1; 1.8 ≦ b ≦ 2; 1.85 ≦ (a + b) ≦ 2.1; number of silicon atoms Is preferably 10 to 400, more preferably 20 to 210.
Examples of such organopolysiloxanes include compounds of the following structural formulas (14) and (15).
[0023]
[Chemical 6]

R ′ in the above formulas (14) and (15) represents the same unsubstituted or substituted monovalent hydrocarbon group as R ′ in formula (1), preferably a methyl group or a phenyl group, X is an amino group, epoxy Group, a hydroxy group or a carboxyl group-containing monovalent hydrocarbon group, p is an integer of 0 to 1,000, preferably 8 to 400, and q is an integer of 0 to 20, preferably 0 to 5.
Specific examples thereof include the following diorganopolysiloxanes (16) to (21).
[0024]
[Chemical 7]

[0025]
The molecular weight of the organopolysiloxane is not particularly limited, but is preferably 100 to 70,000. This is because when an organopolysiloxane having a molecular weight of 100 to 70,000 is used and the obtained copolymer is blended with an adhesive component, the copolymer is not compatible with the matrix and is fine. This is because a unique sea-island structure can be formed and the effects such as flexibility unique to organopolysiloxane can be exhibited at the same time while maintaining the physical properties of the matrix. When the molecular weight is less than 100, the copolymer is compatible in the matrix, the sea-island structure disappears, and the flexibility of the cured adhesive is lowered. On the other hand, when the molecular weight exceeds 70,000, the sea-island structure becomes large, and the heat resistance of the cured adhesive may be reduced.
[0026]
As a method for obtaining a copolymer of component D) in the present invention by reacting an aromatic polymer with an organopolysiloxane, a known method can be used.
Specifically, the above aromatic copolymer and organosiloxane are mixed in toluene, heated in a nitrogen atmosphere at 100 ° C. for 12 hours, reacted and aged, and then the toluene is distilled off at normal pressure. Then, stripping is performed at 150 ° C. for 1 hour to obtain a crude product. This is dissolved in a small amount of toluene, washed and purified in a large amount of hexane, and then the desired copolymer can be obtained. The synthesis method is not limited to the above method. Further, the amount of the copolymer blended is preferably 1 to 100 parts by weight, more preferably 10 to 60 parts by weight with respect to 100 parts by weight of the polyimidesiloxane. When the amount is less than 1 part by weight, the flexibility of the cured adhesive is lowered, and when it exceeds 100 parts by weight, the heat resistance may be lowered.
[0027]
The reactive phosphorus-containing compound of component E) in the present invention may be any compound having a phosphorus atom and a reactive group. Specifically, the HCA of Sanko Co., Ltd., 9, 10-dihydoro-9-oxa-10-phosphaphenanthrene-10-oxide, HCA-HQ obtained by adding hydroquinone to HCA, Daihachi Chemical Co., Ltd. MR-200 (2-methacryloyl-oxyethyl acid phosphate), MR -260 (diphenyl-2≡methacryloyl-oxyethyl phosphate) and the like.
As the reactive phosphorus-containing compound of component E) in the present invention, those having a phosphorus content in the range of 6 to 30% by weight are preferred. These reactive phosphorus-containing compounds react with other components during the preparation of the adhesive or after baking after temporary bonding. Thereby, the electrical characteristics including the ion migration resistance can be remarkably improved while maintaining the same flame retardant effect as compared with the conventional non-reactive phosphorus flame retardant. The compounding amount of the reactive phosphorus-containing compound is 10 to 100 parts by weight with respect to 100 parts by weight of the polyimidesiloxane, and the ratio of all phosphorus atoms in the adhesive is 0.5 to 2.5% by weight. It is preferable to mix | blend, More preferably, it is 0.5 to 2.0 weight%. If the total phosphorus atom content is less than 0.5% by weight, sufficient flame retardancy cannot be obtained, while if it exceeds 2.5% by weight, the heat resistance of the cured adhesive may be lowered. .
[0028]
As the curing accelerator of component F) in the present invention, an organic phosphorus compound can be used. Specifically, triphenylphosphine, tributylphosphine, tri (p-toluyl) phosphine, tri (p-methoxyphenyl) phosphine, Examples include triorganophosphines such as tri (p-ethoxyphenyl) phosphine, triphenylphosphine / triphenylborate, tetraphenylphosphonium / tetraphenylborate, and quaternary phosphonium salts. Can be used.
In addition, various imidazole compounds can be used as curing accelerators, such as 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, and ethylisocyanate compounds of this compound, 2-phenylimidazole. 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and the like. These can be used alone or in admixture of two or more.
[0029]
Other curing accelerators in the present invention include borofluorides such as tetraphenylborates of tertiary amines such as triethyleneammonium triphenylborate, zinc borofluoride, tin borofluoride and nickel borofluoride. Also included are octylates such as compounds, tin octylate and zinc octylate, and these can be used alone or in combination of two or more.
The blending amount of the curing accelerator is preferably 1 to 50 parts by weight, more preferably 5 to 20 parts by weight with respect to 100 parts by weight of the polyimidesiloxane. When the addition amount of the curing accelerator is less than 1 part by weight, the adhesive is not sufficiently cured, and when it exceeds 50 parts by weight, the storage stability of the adhesive composition is lowered.
[0030]
In the adhesive composition of this invention, you may add other additives, such as resin and a filler, in the range which does not reduce various characteristics. For example, aluminum hydroxide, magnesium hydroxide, silicon dioxide as a flame retardant aid, and various compounds containing nitrogen and phosphorus, such as melamine phosphate and various phosphazene compounds. These additives containing both nitrogen and phosphorus components are also effective as flame retardant aids.
In the present invention, known curing agents used for epoxy resins can be used in combination. Examples include aliphatic amine curing agents, alicyclic amine curing agents, aromatic amine curing agents, acid anhydride curing agents, dicyandiamide, and boron trifluoride amine complex salts. These curing agents also have a great influence on the migration resistance of metal ions, which is the subject of the present invention, and particularly when highly active amines are used, the migration resistance is reduced. Therefore, aromatic amines such as 4,4′-diamino are used. Diphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenylmethane, and the like are preferably used, and these can be used alone or in combination of two or more.
[0031]
As the solvent used in the adhesive composition of the present invention, an organic polar solvent used in the synthesis of the above-described polyimide siloxane is preferably used.
The solid content concentration of the adhesive composition solution of the present invention may be 10 to 45% by weight, and preferably 20 to 35% by weight. When the solid content concentration exceeds 45% by weight, the coating property deteriorates due to an increase in the viscosity of the solution and the compatibility between the solid content and the solvent, and the workability deteriorates. This is likely to occur, and further, the amount of solvent removal increases, which causes problems such as adverse environmental effects and economic deterioration.
The adhesive composition of the present invention is mixed using a pot mill, a ball mill, a homogenizer, a super mill or the like.
[0032]
Examples of the electrically insulating film in the present invention include a polyimide film, a polyester film, a polyvaleric acid film, a polyphenylene sulfide film, an aramid film, and the like, and a polyimide film is particularly preferable. A film having an appropriate thickness may be used as necessary, but is preferably 10 to 125 μm. Further, it is possible to perform surface treatment on one or both surfaces of these films, and examples of the surface treatment include low-temperature plasma treatment, corona discharge treatment, and sandblast treatment.
[0033]
Examples of the metal foil in the present invention include copper foil, aluminum foil, iron foil and the like, and those using copper foil are particularly preferable. Although what is necessary is just to use the thing of thickness appropriate for the thickness of metal foil as needed, 5-70 micrometers is preferable.
[0034]
Next, a method for manufacturing the flexible printed wiring board of the present invention will be described.
First, an adhesive solution prepared by mixing a predetermined solvent with the prepared adhesive composition of the present invention is applied to an electrically insulating film using a reverse roll coater, a comma coater, or the like. This is passed through an in-line dryer, treated at 80 ° C. to 180 ° C. for 2 to 20 minutes to remove the solvent of the adhesive, dried to a semi-cured state, and then a metal foil is drawn on the adhesive coated surface with a heating roll. Thermocompression bonding is performed at a pressure of 2 to 200 N / cm and a temperature of 60 to 180 ° C. In order to further harden the adhesive of the obtained laminated film, you may heat, the heating temperature is 80-200 degreeC, and heating time is 1 to 24 hours.
The thickness of the coating film of the adhesive composition in the present invention may be 5 to 45 μm in a dry state, preferably 5 to 30 μm. The flexible printed wiring board of the present invention is obtained by laminating a metal foil on one or both sides of an electrically insulating film with an adhesive.
[0035]
Generally, a coverlay film is used by laminating and integrating a flexible printed circuit board formed by forming a circuit on a flexible printed wiring board, and is electrically insulated with an adhesive in a semi-cured state. It consists of a film and release paper. When using, the release paper is peeled off and laminated on the circuit surface of the flexible wiring board. Generally, a cover wiring film laminated and integrated may be collectively referred to as a flexible wiring board. Here, the electrical insulating film described above can be used. In addition, the release paper that can be used is a laminate of a polyethylene film, a 4-methyl-1-pentene-α-olefin copolymer (hereinafter referred to as TPX) film, or a polypropylene film on one or both sides of the base paper, There are those in which polyvinylidene chloride is coated on one side or both sides of the base paper, and those in which a silicone release agent is applied on one side or both sides of these release papers, which can be used appropriately depending on the conditions during the hole processing.
[0036]
In the coverlay film of the present invention, the organic solvent solution of the adhesive composition of the present invention is applied to an electrically insulating film so as to have a thickness of 10 to 60 μm, and then dried to remove the solvent. The adhesive is brought into a semi-cured state. In this case, it can be heated for a short time at a temperature of 50 ° C. to 180 ° C. as necessary. Next, this semi-cured adhesive-attached electrically insulating film is superposed on the release paper, and laminated with a roll laminator or the like at a temperature of 20 to 180 ° C. and a linear pressure of 2 to 200 N / cm, and wound into a roll. A coverlay film is produced.
[0037]
【Example】
Next, although the Example of this invention is given, this invention is not limited to these Examples. The% concentration display is all weight%.
[Synthesis Example 1 of Polyimide Siloxane]
After dissolving 358 g (1 mol) of DSDA (3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride) in 700 g of N-methyl-2-pyrrolidone, α, ω-bis (3-aminopropyl) was dissolved. ) Polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KF-8010, siloxane unit 9) 168 g (0.2 mol) and N-methyl-2-pyrrolidone 50 g were added and dissolved uniformly. Polymerization was performed at 25 ° C. for 5 hours in an atmosphere. Subsequently, 213 g (0.3 mol) of BPAA {2,2-bis [4- (4-aminophenoxy) phenyl] propane} and 114 g of HAB (3,3'-dihydroxy-4,4'-diaminophenyl) ( 0.5 mol) and 1,000 g of N-methyl-2-pyrrolidone were added, followed by further polymerization for 5 hours at a reaction temperature of 25 ° C., followed by a dehydration ring-closing reaction at 250 ° C. for 3 hours. A solution was obtained (solid content concentration about 30%).
[0038]
[Polyimide siloxane synthesis example 2]
After 294 g (1 mol) of DPDA (3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride) was dissolved in 700 g of N-methyl-2-pyrrolidone, α, ω-bis (3-aminopropyl) After adding 168 g (0.2 mol) of polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., KF-8010, siloxane unit 9) and 50 g of N-methyl-2-pyrrolidone, the mixture was uniformly dissolved, and then added under nitrogen atmosphere. Polymerization was carried out at 5 ° C. for 5 hours. Next, 213 g (0.3 mol) of BAPP {2,2-bis [4- (4-aminophenoxy) phenyl] propane} and 114 g of HAB (3,3′-dihydroxy-4,4′-diaminophenyl) (0 0.5 mol) and 1,000 g of N-methyl-2-pyrrolidone were added, followed by further polymerization for 5 hours at a reaction temperature of 25 ° C, followed by a dehydration ring-closing reaction at 250 ° C for 3 hours to obtain a polyimidesiloxane solution. (Solid content concentration about 30%).
[0039]
[Example 1]
Using the adhesive composition shown in the column of Example 1 in Table 1, N-methyl-2-pyrrolidone was used as a solvent to obtain an adhesive solution having a solid content concentration of 25%. Next, the adhesive solution was applied to a polyimide film Kapton (trade name, manufactured by Toray DuPont Co., Ltd.) having a thickness of 25 μm and 200 mm × 200 mm with an applicator so that the thickness after drying was 20 μm. The adhesive was brought into a semi-cured state by heating for a minute to obtain a polyimide film with an adhesive. A 35 μm thick, 200 mm × 200 mm copper foil / BHN (trade name of rolled copper foil manufactured by Japan Energy Co., Ltd.) is superimposed on the adhesive-coated surface of this polyimide film with adhesive, and the temperature is 180 ° C. and the linear pressure is 100 N / cm. It was heated and pressure-bonded under the conditions, and further heat-cured at 180 ° C. for 10 hours to obtain a flexible printed wiring board. The characteristics of this flexible printed wiring board were measured by the method described later, and the results are shown in Table 3.
[0040]
[Examples 2 to 4]
A flexible printed wiring board was produced in the same manner as in Example 1 except that the adhesive formulation shown in each column of Examples 2 to 4 in Table 1 was used. Table 3 shows the measurement results of the characteristics of these flexible printed wiring boards.
[0041]
[Example 5]
The adhesive composition shown in the column of Example 5 in Table 1 was stirred and mixed with N-methyl-2-pyrrolidone as a solvent to obtain an adhesive solution having a solid content concentration of 25%. Next, an adhesive solution was applied to a 25 μm thick, 200 × 200 mm polyimide film Kapton (described above) with an applicator so that the thickness after drying was 30 μm, and the adhesive was heated at 180 ° C. for 10 minutes. Was made into a semi-cured state to obtain a coverlay film. The cover-lay film adhesive-coated surface, 200 mm × 200 mm copper foil, and BHN (previously) glossy surface were heated and pressed under the conditions of a temperature of 180 ° C. and a pressure of 5 MPa for 30 minutes to obtain a sample for evaluation. . The characteristics of this laminate were measured by the following method and the results are shown in Table 3.
[0042]
[Comparative Examples 1-4]
A flexible printed wiring board was produced in the same manner as in Example 1 except that the adhesive composition shown in each column of Comparative Examples 1 to 4 in Table 2 was used. The measurement results of the characteristics of the flexible printed wiring board are shown in Table 3.
[0043]
[Comparative Example 5]
A coverlay film and a sample for evaluation were produced in the same manner as in Example 5 except that the adhesive composition shown in the column of Comparative Example 5 in Table 2 was used. The measurement results of the characteristics of the coverlay film evaluation sample are shown in Table 3.
[0044]
[Table 1]

[0045]
(Source of raw materials used for each composition of adhesive)
HP4032: Dainippon Ink & Chemicals, Inc. Naphthalene type bifunctional epoxy resin trade name, epoxy equivalent 150,
HP7200: Dainippon Ink & Chemicals, Inc. dicyclopentadiene type epoxy resin trade name, epoxy equivalent 260,
LA7054: Dainippon Ink & Chemicals, Inc. Triazine group-containing phenol novolac resin trade name, hydroxyl equivalent 125
MEH7851SS: Meiwa Kasei Co., Ltd. product name of phenol resin, hydroxyl group equivalent 199,
HCA: Reactive phosphorus-containing flame retardant manufactured by Sanko Co., Ltd., phosphorus content of about 15% by weight,
CPHO-HQ: Reactive phosphorus-containing flame retardant manufactured by Nippon Chemical Industry Co., Ltd., phosphorus content of about 11.6% by weight,
DDS: 4,4′-diaminodiphenylsulfone trade name,
2E-4MZ-CN: Shikoku Kasei Kogyo Co., Ltd. imidazole curing accelerator trade name,
TPP: Triphenylphosphine trade name,
Kisuma 5: Kyowa Chemical Industry Co., Ltd. magnesium hydroxide trade name, particle size 0.6-1.0 μm,
MPP-A: Sanwa Chemical Co., Ltd. melamine phosphate trade name, phosphorus content 15% by weight.
[0046]
In the examples, the copolymer used as component D) is represented by the following formula (22).
[Chemical 8]

[0047]
[Table 2]

PX-200: Phosphoric flame retardant manufactured by Daihachi Chemical Industry Co., Ltd., phosphorus content 9% by weight
[0048]
[Table 3]

[0049]
Each characteristic value was measured according to the following method.
(Peel strength)
In accordance with JISC6481, a sample having a width of 1 mm was prepared, and the adhesive strength when peeled to the copper foil side at a speed of 50 mm / min in the 90 ° direction was measured.
(Solder heat resistance)
In accordance with JISC6481, a sample was cut every 25 mm, and the maximum temperature at which the sample floated on the flow solder for 30 seconds and did not swell and peel off was measured.
(Migration resistance test)
Create a comb-shaped pattern with a line spacing of 100 μm, apply it at a temperature of 130 ° C., a humidity of 85%, and a voltage of 100 V for 250 hours, observe the sample before and after application with a magnifier, and inspect the generation state of migration that occurs between the lines And evaluated according to the following criteria.
○: No formation of precipitates between the lines, Δ: Precipitates are slightly seen in the circuit portion, but the gaps between the lines are not filled, and X: Precipitates are formed over the entire lines, and traces of thermal deterioration Can be seen.
[0050]
(Flame retardance)
Flame retardant in accordance with UL94 flame retardant standard using flexible printed circuit board obtained in each example, cover lay film to which copper foil is pressure-bonded and copper foil is chemically treated and removed (adhesive / polyimide film) Sex grade was measured.
(Folding resistance)
In accordance with JISC6471, after a designated circuit is printed on the flexible printed wiring board of Examples 1 to 4, it is combined with the coverlay film of Example 5 at 160 ° C./50 kg / cm. ² Samples pressed in 30 minutes were used as samples (sampled in the roll direction and in the direction perpendicular to the roll). Similarly, the flexible printing substrate obtained in Comparative Examples 1 to 4 and the coverlay film of Comparative Example 5 were combined to prepare a sample, which was evaluated according to the following criteria at a curvature radius of 0.38 mm and 25 ° C. In the table, MD and TD are abbreviations, and mean a roll direction (MD) and a direction perpendicular to the roll direction (TD), respectively.
When the average value at n = 5, 200 times or more was marked with ◯, and less than 200 times was marked with ×.
[0051]
(Measurement method of glass transition point of cured adhesive)
Dynamic viscoelasticity measurement was performed using a sample with the same structure (polyimide film / adhesive layer) as the one subjected to the flame retardancy test, and the temperature at which the maximum value of the obtained tan δ was measured was the glass transition of the cured adhesive. Defined as a point.
A value of Tg of 160 ° C. was obtained for the composition of Example 1, and a value of Tg of 120 ° C. was obtained for the composition of Example 5. On the other hand, a value of Tg 90 ° C. was obtained for the composition of Comparative Example 1.
Measuring instrument: Rheometric Scientific F.E. viscoelasticity analyzer, RSA-II,
Measurement mode: Pull,
Distance between chucks: 35mm,
Measurement temperature: 0 to 300 ° C
Temperature increase rate: 2.5 ° C / min
Perturbation frequency: 5 Hz
Sample size: 10 mm (width) x 50 mm (length).
[0052]
【The invention's effect】
According to the present invention, a halogen-free adhesive composition having a balance of various properties and excellent in heat resistance and migration resistance can be obtained, and by using this, a halogen-free flexible printing substrate excellent in migration resistance can be obtained. A coverlay film can be obtained.

Claims (6)

An adhesive composition comprising the following A) to F), wherein the total phosphorus content is 0.5 to 2.5% by weight.
A) 100 parts by weight of polyimide siloxane,
B) 10 to 300 parts by weight of epoxy resin,
C) 10 to 300 parts by weight of phenol resin,
D) 1 to 100 parts by weight of a copolymer obtained by reacting an aromatic polymer with an organopolysiloxane represented by the following composition formula (1),

Wherein R represents a monovalent hydrocarbon group or alkoxy group containing a hydrogen atom, amino group, epoxy group, hydroxy group or carboxyl group, and R ′ represents a substituted or unsubstituted monovalent hydrocarbon group. A and b are positive numbers satisfying 0.001 ≦ a ≦ 1; 1 ≦ b ≦ 2; 1 ≦ (a + b) ≦ 3, and the number of silicon atoms in one molecule is 2 to 2. 1,000, and the number of functional groups R directly bonded to the silicon atom in one molecule is 1 or more.)
E) 10 to 100 parts by weight of a reactive phosphorus-containing compound,
F) Curing accelerator 1 to 50 parts by weight. A coverlay film obtained by laminating an electrical insulating film and release paper through the adhesive composition of claim 1. A flexible printed wiring board obtained by bonding an electrical insulating film and a metal foil through the adhesive composition of claim 1. Polyimide siloxane is used as acid dianhydride as DSDA (3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride) and / or BPDA (3,3 ′, 4,4′-biphenyltetracarboxylic acid). Dianhydride) is used as a diamine compound, and dimethylpolysiloxane modified with amine at both ends is used. In addition, BAPP {2,2-bis [4- (4-aminophenoxy) phenyl] propane} and / or HAB ( 3. The adhesive composition according to claim 1, which is obtained using 3,3′-dihydroxy-4,4′-diaminobiphenyl) as a raw material. A coverlay film obtained by laminating an electrical insulating film and a release paper through the adhesive composition according to claim 4. A flexible printed wiring board obtained by bonding an electrical insulating film and a metal foil through the adhesive composition of claim 4.