JP4142981B2 - UV-curable epoxy resin composition and process for producing the same - Google Patents

Description

（ａ２）脂環式エポキシ樹脂。
（Ｂ）光重合開始剤。
（Ｃ）レーザー回折散乱式粒度分布測定装置を用いて測定された平均粒径が０．３〜０．５μｍの範囲で、かつレーザー回折散乱式粒度分布測定装置を用いて測定された粒径５μｍ以上のものを含有しない球状シリカ粉末。
【０００９】
また、本発明は、上記（Ａ）〜（Ｃ）を含有する紫外線硬化型エポキシ樹脂組成物の製法であって、予め上記球状シリカ粉末（Ｃ）を上記脂環式エポキシ樹脂（ａ２）に分散させた後、この分散物と上記式（１）で表されるエポキシ樹脂（ａ１）および光重合開始剤（Ｂ）を含む残りの成分を配合し混合する紫外線硬化型エポキシ樹脂組成物の製法を第２の要旨とする。
【００１０】
すなわち、本発明者らは、高温高湿条件下でも優れた接着性を有し、しかも線膨張係数が低く寸法安定性に優れた紫外線硬化型のエポキシ樹脂組成物を得るために鋭意検討を重ねた。その結果、エポキシ樹脂（Ａ）として、上記式（１）で表されるエポキシ樹脂（ａ１）および脂環式エポキシ樹脂（ａ２）の２つのエポキシ樹脂を併用するとともに、上記特定の平均粒径を有し、かつ特定の粒径以上の粒子を含有しない球状シリカ粉末（Ｃ）を用いると、式（１）で表されるエポキシ樹脂（ａ１）の屈折率が１．４７以下であることから、エポキシ樹脂成分全体の屈折率を下げ、シリカ粉末の屈折率に近づけることが可能となる。そのため、シリカ粉末を含有していながら光硬化性が良好となる。しかも、上記球状シリカ粉末（Ｃ）が均一分散され、光も通し易く紫外線硬化性も良好で、低線膨張係数化が実現して優れた寸法安定性が得られるようになり上記のような所期の目的が達成されることを突き止めた。そして、このようなエポキシ樹脂組成物としては、予め上記特定の球状シリカ粉末（Ｃ）を脂環式エポキシ樹脂（ａ２）に分散させた後、これに残りの成分を配合し混合することにより、上記特定の球状シリカ粉末（Ｃ）がエポキシ樹脂組成物中に均一に分散されたものが得られることを見出し本発明に到達した。
【００１１】
【発明の実施の形態】
つぎに、本発明の実施の形態について詳しく説明する。
【００１２】
本発明の紫外線硬化型エポキシ樹脂組成物は、特定のエポキシ樹脂（ａ１）および脂環式エポキシ樹脂（ａ２）を含有するエポキシ樹脂（Ａ）と、光重合開始剤（Ｂ）と、特定の球状シリカ粉末（Ｃ）とを用いることにより得られる。
【００１３】
上記特定のエポキシ樹脂（ａ１）は、下記の式（１）で表されるものであり、非グリシジルエーテル型であり、エーテル結合を持たないため、エポキシ樹脂の高反応性を付与する。上記式（１）で表されるエポキシ樹脂（ａ１）は、例えば、つぎのようにして製造される。すなわち、オレフィンを、例えば、過酸化安息香酸等の有機過酸化物により酸化することで製造することができる。
【００１４】
【化４】

【００１５】
そして、上記式（１）で表されるエポキシ樹脂（ａ１）の含有量は、エポキシ樹脂（Ａ）全体中１５〜７０重量％を占めるように設定することが好ましい。特に好ましくは３０〜４０重量％である。すなわち、１５重量％未満では、光硬化性の低下や粘度の上昇が発生し易く、逆に７０重量％を超えると、光硬化性が悪くなり、作業性が著しく低下する傾向がみられるからである。
【００１６】
さらに、上記ａ１とともに用いられる脂環式エポキシ樹脂（ａ２）としては、特に限定するものではないが、反応性が高く透明なものを用いることが好ましく、しかも、低粘度であることが好ましい。また、反応性の点から、２官能以上であることが好ましく、波長５００〜１７００ｎｍでの光透過率が厚み１００ｍｍで９０％以上であることが好ましい。粘度は、５Ｐａ・ｓ（室温）以下であると、球状シリカ粉末混合後の取り扱い性の点から好ましい。具体的には、水添ビスフェノールＡ型エポキシ樹脂、３，４−エポキシシクロヘキシルメチル−３，４−エポキシシクロヘキサンカルボキシレート、３，４−エポキシシクロヘキシルエチル−３，４−エポキシシクロヘキサンカルボキシレート等が、透明性、粘性、反応性の観点から好ましい。これらは単独でもしくは２種以上併せて用いられる。なかでも、３，４−エポキシシクロヘキシルメチル−３，４−エポキシシクロヘキサンカルボキシレートで低粘度であり特に好ましく用いられる。
【００１７】
本発明において、エポキシ樹脂（Ａ）としては、上記式（１）で表されるエポキシ樹脂（ａ１）および脂環式エポキシ樹脂（ａ２）を必須成分とし、これに従来公知のエポキシ樹脂を用いてもよい。具体的には、汎用のビスフェノール型エポキシ樹脂、水添ビスフェノール型エポキシ樹脂、ノボラック型エポキシ樹脂、グリシジルエーテル型エポキシ樹脂、グリシジルエステル型エポキシ樹脂等を用いることができる。なお、上記従来公知のエポキシ樹脂を用いる場合、その使用量は、エポキシ樹脂（Ａ）全体中の３０重量％以下に設定することが好ましい。
【００１８】
上記エポキシ樹脂（Ａ）とともに用いられる光重合開始剤（Ｂ）としては、特に限定するものではなく、芳香族ジアゾニウム塩、芳香族スルホニウム塩、芳香族ヨードニウム塩、芳香族スルホキソニウム塩、メタロセン化合物あるいは鉄アレーン系化合物等を用いることができる。その中でも、光硬化性の観点から、芳香族スルホニウム塩が好ましく、特に芳香族スルホニウム・ヘキサフロロホスホニウム化合物、芳香族スルホニウム・ヘキサフロロアンチモネート化合物、またはその両者の併用が、硬化性、接着性等の観点から好ましい。さらに、上記光重合開始剤（Ｂ）とともに、光増感剤や酸増殖剤等も必要に応じて添加することができる。
【００１９】
上記光重合開始剤（Ｂ）の含有量は、上記エポキシ樹脂（Ａ）および後述の特定の球状シリカ粉末（Ｃ）の合計量１００重量部（以下「部」と略す）に対して１〜１５部に設定することが好ましく、特に好ましくは２〜１０部である。
【００２０】
上記エポキシ樹脂（Ａ）および光重合開始剤（Ｂ）とともに用いられる特定の球状シリカ粉末（Ｃ）は、一般に略球状を有するシリカ粉末であれば特に限定するものではないが、真球度の高いものを用いることがより好ましい。そして、本発明においては、球状シリカ粉末（Ｃ）は、平均粒径０．３〜０．５μｍの範囲で、かつ粒径５μｍ以上のものを含有しないものである。上記範囲の平均粒径を有し、しかも粒径５μｍ以上の大きな粒径の粒子を含まない球状シリカ粉末を用いることにより、紫外線硬化性の低下と粘度の上昇が軽減されるのである。なお、上記平均粒径の測定は、例えば、レーザー回折散乱式粒度分布測定装置を用いて測定することができる。上記粒径５μｍ以上の球状シリカ粒子を含有しないものを得るための、粒径５μｍ以上の球状シリカ粒子の分別・除去方法としては、例えば、篩や遠心分離等により除去する方法があげられる。また、合成シリカであれば、ｐＨの調整により２次凝集を発生させないようにして取り扱うことにより、粒径と分布を精密に制御することが可能である。そして、粒径を制御して合成した後、表面処理によって凝集を防ぐ方法も、粒径５μｍ以上の粒子を発生させない方法として有効である。
【００２１】
上記特定の球状シリカ粉末（Ｃ）の含有量は、上記エポキシ樹脂（Ａ）および球状シリカ粉末（Ｃ）の合計量中５０〜８０重量％の範囲に設定することが好ましい。すなわち、特定の球状シリカ粉末（Ｃ）の含有量が５０重量％未満では、エポキシ樹脂組成物硬化体の線膨張係数が充分に下げられず、良好な寸法安定性が得られ難く、８０重量％を超えると、エポキシ樹脂組成物が非常に高粘度となり作業性が低下するばかりでなく、光硬化性の低下をも引き起こす傾向がみられるからである。
【００２２】
また、本発明の紫外線硬化型エポキシ樹脂組成物には、上記（Ａ）〜（Ｃ）以外に、接着性を高めるためにシラン系あるいはチタン系のカップリング剤、合成ゴムやシリコーン化合物等の可撓性付与剤等の化合物、さらに酸化防止剤、消泡剤等の他の添加剤を必要に応じて適宜に配合することができる。
【００２３】
本発明の紫外線硬化型エポキシ樹脂組成物は、例えば、前記式（１）で表されるエポキシ樹脂（ａ１）および脂環式エポキシ樹脂（ａ２）と、光重合開始剤（Ｂ）、特定の球状シリカ粉末（Ｃ）さらに必要に応じて他の添加剤を用いて、つぎのようにして作製される。まず、予め、上記特定の球状シリカ粉末（Ｃ）を上記脂環式エポキシ樹脂（ａ２）に配合して分散させる。ついで、この分散物に、残りの配合成分を所定の割合で配合し溶融混合した後、室温に冷却することにより作製される。
【００２４】
上記特定の球状シリカ粉末（Ｃ）を上記脂環式エポキシ樹脂（ａ２）に配合して分散させる予備混合における条件としては、温度２５〜１００℃が好ましく、５０〜７０℃の範囲が特に好ましい。また、凝集を防ぐために、溶剤を加えて分散させた後に脱溶媒してもよい。また、上記分散物に残りの配合成分を配合して溶融混合する際の溶融条件としては、温度２５〜１００℃が好ましく、５０〜７０℃の範囲が特に好ましい。
【００２５】
このように、予め球状シリカ粉末（Ｃ）を脂環式エポキシ樹脂（ａ２）に配合して分散させることにより、球状シリカ粉末（Ｃ）のエポキシ樹脂組成物全体における均一分散が図られ、さらには球状シリカ粉末（Ｃ）の粒子とエポキシ樹脂との界面において濡れ性が向上して粘度の上昇が軽減できるようになる。また、上記濡れ性の一層の向上を図る目的で、先に述べたシランカップリング剤等のカップリング剤により球状シリカ粉末（Ｃ）の表面処理を行うことが好ましい。
【００２６】
そして、本発明の紫外線硬化型エポキシ樹脂組成物の粘度は、接着剤としての使用時における作業性等を考慮して、２５℃で１〜１００Ｐａ・ｓ程度であることが好ましい。
【００２７】
このようにして得られる紫外線硬化型エポキシ樹脂組成物は、例えば、ＵＶランプ等により紫外線を照射した後、所定の温度でのポストキュアを行うことにより硬化させることができる。
【００２８】
つぎに、実施例について比較例と併せて説明する。
【００２９】
まず、下記に示す各成分を準備した。
【００３０】
〔エポキシ樹脂１〕
下記の式（ａ）で表されるエポキシ樹脂
【化５】

【００３１】
〔エポキシ樹脂２〕
下記の式（ｂ）で表されるエポキシ樹脂
【化６】

【００３２】
〔エポキシ樹脂３〕
下記の式（ｃ）で表される脂環式エポキシ樹脂（ダイセル化学社製、セロキサイド２０２１Ｐ：３，４−エポキシシクロヘキシルメチル−３，４−エポキシシクロヘキサンカルボキシレート）
【化７】

【００３３】
〔球状シリカ粉末Ａ〕
平均粒径０．３μｍで粒径５μｍ以上の粒子を含まない球状シリカ粉末（アドマテックス社製、ＳＥ１０５０）
【００３４】
〔球状シリカ粉末Ｂ〕
平均粒径０．５μｍで粒径５μｍ以上の粒子を含まない球状シリカ粉末（アドマテックス社製、ＳＥ２０５０）
【００３５】
〔球状シリカ粉末Ｃ〕
平均粒径１．５μｍで粒径５μｍ以上の粒子を３重量％含有する球状シリカ粉末（アドマテックス社製、ＳＯ−Ｅ５）
【００３６】
〔光重合開始剤〕
スルホニウム・ヘキサフロロアンチモン系重合開始剤（旭電化社製、ＳＰ−１７０）
【００３７】
〔酸化防止剤〕
ＨＣＡ（三光化学社製）
【００３８】
〔カップリング剤〕
γ−グリシドキシプロピルトリメトキシシラン
【００３９】
【実施例１〜６、比較例１〜３】
まず、下記の表１〜表２に示す割合で、予め球状シリカ粉末をエポキシ樹脂２（脂環式エポキシ樹脂）に配合して分散させた（条件：５０℃×３０分）。ついで、この分散物に、同表に示す割合で残りの配合成分を配合し溶融混合（条件：５０℃×３０分）した後、室温に冷却することにより紫外線硬化型エポキシ樹脂組成物を作製した。なお、比較例１，２は球状シリカ粉末を配合しないため、予備分散を行わず、下記の表２に示す各成分を同表に示す割合で配合し混合した。
【００４０】
【表１】

【００４１】
【表２】

【００４２】
このようにして得られた実施例および比較例の各紫外線硬化型エポキシ樹脂組成物を用いて、２５℃でのエポキシ樹脂組成物の粘度、線膨張係数、硬化後の初期接着強度・耐湿接着強度、耐湿試験、吸水率を下記の方法に従ってそれぞれ測定・評価した。これらの結果を後記の表３〜表４に併せて示す。
【００４３】
〔エポキシ樹脂組成物の粘度〕
Ｅ型粘度計を用いて２５℃での粘度を測定した。
【００４４】
〔線膨張係数〕
５００ＷのＵＶランプ（高圧水銀ランプ）を用いて７２０ｍＪ／ｃｍ² にて光照射した後、１００℃で１時間のポストキュアを行うことにより、厚み１００μｍのフィルムを作製した。そして、このフィルムを用い、ＴＭＡ（測定機器：リガク社製のThermoplus 8210 、測定温度：３０〜２５０℃）により引張モードにて測定した。そして、３５℃での線膨張係数の数値を読み取った。
【００４５】
〔初期接着強度・耐湿接着強度〕
まず、柱状の石英ガラス板（縦３．３ｍｍ×横３．３ｍｍ×厚み５ｍｍ）に、紫外線硬化型エポキシ樹脂組成物を接着剤として塗布した後、石英ガラス板（縦２０ｍｍ×横３５ｍｍ×厚み２ｍｍ）に圧着して貼り合わせ、つぎの硬化条件で接着剤を硬化させることにより接着片を作製した。すなわち、上記硬化は、上記と同様、５００ＷのＵＶランプ（高圧水銀ランプ）を用いて７２０ｍＪ／ｃｍ² にて光照射した後、１００℃で１時間のポストキュアを行うことにより硬化させた。
【００４６】
そして、初期接着強度は、上記接着片を用い、２５℃にてプッシュプルゲージを用いて、剪断の接着強度を測定した。
【００４７】
また、耐湿接着強度は、上記接着片を、ＰＣＴ条件下（１２１℃×２０２．６ｋＰａ）に２４時間放置して吸湿させた後、２５℃にてプッシュプルゲージを用いて、剪断の接着強度を測定した。
【００４８】
〔耐湿試験〕
３０ｍｍ×２０ｍｍ×厚み２ｍｍの石英ガラス板を２枚準備し、両石英ガラス板を紫外線硬化型エポキシ樹脂組成物を用いて貼り合わせ、厚み１００μｍとなるよう硬化させた。ついで、これをＰＣＴ条件下（１２１℃×２０２．６ｋＰａ）に２４時間放置して吸湿させた後、石英ガラス板の剥離状況の有無を目視により観察した。上記硬化条件は、上記初期接着強度における試料の作製と同様に設定した。
【００４９】
〔吸水率〕
紫外線硬化型エポキシ樹脂組成物を用い、５００ＷのＵＶランプ（高圧水銀ランプ）を用いて７２０ｍＪ／ｃｍ² にて光照射した後、１００℃で１時間のポストキュアを行うことにより、厚み１００μｍのフィルムを作製した。そして、このフィルムを用い、２５℃で水中に２４時間浸漬させ、その初期重量からの重量変化から吸水率を求めた。
【００５０】
【表３】

【００５１】
【表４】

【００５２】
上記結果から、実施例品は、シリカ粉末が含有されているにもかかわらず充分硬化し、初期接着強度はもちろん耐湿接着強度においても高い数値が得られ、耐湿試験における剥離の発生も見られなかった。しかも、吸水率も低く、さらに線膨張係数も低く低線膨張化が図られている。
【００５３】
これに対して、球状シリカ粉末を用いない比較例１，２品は、吸水率が高く、そして耐湿接着強度も低く、しかも耐湿試験において剥離が発生し、線膨張係数も６０ｐｐｍを超えて高いものであった。また、平均粒径が０．５μｍを超え、粒径５μｍ以上の粒子を含有する球状シリカ粉末を用いた比較例３品では、紫外線が樹脂組成物の内部に到達しにくいため、硬化性が悪く、その結果、耐湿接着強度が低く、耐湿試験において剥離が発生した。
【００５４】
【発明の効果】
以上のように、本発明は、前記式（１）で表されるエポキシ樹脂（ａ１）および脂環式エポキシ樹脂（ａ２）を含有するエポキシ樹脂（Ａ）とともに、前記特定の球状シリカ粉末（Ｃ）を用いた紫外線硬化型エポキシ樹脂組成物である。このため、紫外線が樹脂組成物の内部に到達し易く、光硬化性が良好であり、かつ高温高湿雰囲気下での吸水性が低く、初期および吸湿後の耐湿接着強度も高く優れた実用性を備えている。しかも、上記特定の球状シリカ粉末（Ｃ）を含有するため、低線膨張係数で優れた寸法安定性を備えている。そして、このような本発明の紫外線硬化型エポキシ樹脂組成物は、予め上記特定の球状シリカ粉末（Ｃ）を上記脂環式エポキシ樹脂（ａ２）に分散させた後、これに残りの成分を配合し混合することにより製造され、このような製造工程を経由することにより、上記特定の球状シリカ粉末（Ｃ）が樹脂組成物中に均一に分散される。したがって、本発明の紫外線硬化型エポキシ樹脂組成物を、光通信系における光導波路やＶグルーヴ等の精密光部品の接着およびファイバーアレイの接着用途、またレンズ等の小型部品の固定用等に適用すると、長期信頼性に優れた接着結合部が実現する。
【００５５】
そして、上記ａ１の含有量を、エポキシ樹脂（Ａ）全体の１５〜７０重量％の範囲に設定すると、耐湿接着性および流動性に一層優れるようになる。
【００５６】
また、上記特定の球状シリカ粉末（Ｃ）の含有量を、上記エポキシ樹脂（Ａ）および特定の球状シリカ粉末（Ｃ）の合計量中５０〜８０重量％の範囲に設定すると、低線膨張係数化が図られ寸法安定性に一層優れるようになり、しかも作業性に関してもより良好なものが得られるようになる。
【００５７】
さらに、上記ａ２である脂環式エポキシ樹脂として、３，４−エポキシシクロヘキシルメチル−３，４−エポキシシクロヘキサンカルボキシレートを用いると、良好な透明性および反応性とともに低粘度であり、一層好ましいものとなる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultraviolet curable transparent liquid epoxy resin composition having excellent adhesive strength, low outgas generation (gas that volatilizes under high temperature conditions), low hygroscopicity and high dimensional stability, and a method for producing the same. Adhesive suitable for fixing optical parts and lenses such as ball lenses, sealing optical device packages, and fixing optical fibers to V-groove substrates, that is, it does not deteriorate even under severe temperature and humidity conditions The present invention relates to an ultraviolet curable epoxy resin composition which is an adhesive useful for fixing optical elements and optical components having adhesiveness, and a method for producing the same.
[0002]
[Prior art]
In recent years, a method using an adhesive has been used in the assembly of precision optical fiber connector parts. Since this assembly requires fixing accuracy on the order of microns, an adhesive material having a low coefficient of linear expansion and excellent dimensional stability with small molding shrinkage has been desired. In addition, from the viewpoint of excellent adhesion to quartz glass and optical fibers and long-term reliability, it has been demanded to maintain excellent adhesion even when placed in a high temperature and high humidity environment. And since an optical component dislikes a thermal stress, many photocurable adhesives, such as ultraviolet curing, are used. In particular, a resin having a high dimensional stability has been demanded because optical axis misalignment occurs in fixing fibers and cover glasses and fixing lenses in the assembly of a fiber array.
[0003]
For example, a conventional cationic polymerization type photo-curing adhesive using an epoxy resin is relatively excellent in adhesiveness, but in terms of adhesiveness to quartz glass and optical fibers, especially when used under high temperature and high humidity. The adhesive strength was greatly reduced, which was not satisfactory. In addition, radical polymerization type photo-curing adhesives using acrylic resins generally have high adhesion strength but high dimensional stability and heat resistance due to large cure shrinkage and low glass transition temperature. Was not satisfactory.
[0004]
On the other hand, a technique of reducing the linear expansion coefficient of a cured resin obtained by adding an inorganic filler is widely used. As an example of the ultraviolet curable resin composition containing the inorganic filler, there has been proposed a resin composition containing, as an essential component, an inorganic filler composed of a plate-like inorganic filler and a scale-like inorganic filler together with an epoxy compound. (See Patent Document 1).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-191745
[Problems to be solved by the invention]
However, when the particle size of the inorganic filler added becomes finer and becomes sub-micron units, the surface area is significantly increased and the interaction is strengthened, so that it cannot be uniformly dispersed or thickened. Therefore, it is known that it becomes difficult to add a large amount of an inorganic filler because it cannot be handled as a liquid resin. Further, it is known that if a large amount of an inorganic filler is added, it is difficult for light to pass through and ultraviolet curing becomes difficult. As described above, the conventional ultraviolet curable epoxy resin composition containing an inorganic filler does not provide sufficient properties as various optical adhesives, and is still not satisfactory. .
[0007]
The present invention has been made in view of such circumstances, and has an optical element and an optical component fixing made of a resin composition having a stable adhesive force even under high temperature and high humidity conditions, and having a low linear expansion coefficient and high dimensional stability. It is an object of the present invention to provide an ultraviolet curable epoxy resin composition used for an adhesive and the like and a method for producing the same.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has as its first gist an ultraviolet curable epoxy resin composition containing the following (A) to (C).
(A) An epoxy resin containing the following (a1) and (a2).
(A1) An epoxy resin represented by the following formula (1).
[Chemical 3]

(A2) Alicyclic epoxy resin.
(B) Photopolymerization initiator.
(C) The average particle size measured using a laser diffraction / scattering particle size distribution measuring device is in the range of 0.3 to 0.5 μm, and the particle size is 5 μm measured using the laser diffraction / scattering particle size distribution measuring device. containing no spherical silica powder more than.
[0009]
Moreover, this invention is a manufacturing method of the ultraviolet curable epoxy resin composition containing said (A)-(C), Comprising: The said spherical silica powder (C) is disperse | distributed to the said alicyclic epoxy resin (a2) previously. Then, the dispersion, the epoxy resin (a1) represented by the above formula (1), and the remaining components including the photopolymerization initiator (B) are blended and mixed to prepare a method for producing an ultraviolet curable epoxy resin composition. This is the second gist.
[0010]
That is, the present inventors have made extensive studies in order to obtain an ultraviolet curable epoxy resin composition having excellent adhesiveness even under high temperature and high humidity conditions, and having a low linear expansion coefficient and excellent dimensional stability. It was. As a result, as the epoxy resin (A), the two epoxy resins of the epoxy resin (a1) and the alicyclic epoxy resin (a2) represented by the above formula (1) are used in combination, and the specific average particle size is When using a spherical silica powder (C) that does not contain particles having a specific particle size or more, the refractive index of the epoxy resin (a1) represented by the formula (1) is 1.47 or less, It becomes possible to lower the refractive index of the entire epoxy resin component and to approach the refractive index of the silica powder. Therefore, the photocurability is improved while containing the silica powder. In addition, the spherical silica powder (C) is uniformly dispersed, easily transmits light, has good ultraviolet curability, achieves a low coefficient of linear expansion, and provides excellent dimensional stability. I found out that the purpose of the period was achieved. And as such an epoxy resin composition, after previously dispersing the above-mentioned specific spherical silica powder (C) in the alicyclic epoxy resin (a2), by mixing and mixing the remaining components therein, The inventors have found that the specific spherical silica powder (C) is uniformly dispersed in the epoxy resin composition, and have reached the present invention.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail.
[0012]
The ultraviolet curable epoxy resin composition of the present invention comprises an epoxy resin (A) containing a specific epoxy resin (a1) and an alicyclic epoxy resin (a2), a photopolymerization initiator (B), and a specific spherical shape. It is obtained by using silica powder (C).
[0013]
The specific epoxy resin (a1) is represented by the following formula (1), is a non-glycidyl ether type, and does not have an ether bond, thereby imparting high reactivity of the epoxy resin. The epoxy resin (a1) represented by the above formula (1) is produced, for example, as follows. That is, it can be produced by oxidizing an olefin with an organic peroxide such as peroxybenzoic acid.
[0014]
[Formula 4]

[0015]
And it is preferable to set so that content of the epoxy resin (a1) represented by the said Formula (1) may occupy 15 to 70 weight% in the whole epoxy resin (A). Especially preferably, it is 30 to 40 weight%. That is, if it is less than 15% by weight, a decrease in photocurability and an increase in viscosity are likely to occur. On the other hand, if it exceeds 70% by weight, the photocurability deteriorates and workability tends to be remarkably reduced. is there.
[0016]
Furthermore, the alicyclic epoxy resin (a2) used together with the a1 is not particularly limited, but it is preferable to use a highly reactive and transparent material, and it is preferable that the viscosity is low. Moreover, it is preferable that it is bifunctional or more from a reactive point, and it is preferable that the light transmittance in wavelength 500-1700nm is 90% or more by thickness 100mm. The viscosity is preferably 5 Pa · s (room temperature) or less from the viewpoint of handleability after mixing the spherical silica powder. Specifically, hydrogenated bisphenol A type epoxy resin, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxycyclohexylethyl-3,4-epoxycyclohexanecarboxylate, etc. are transparent. From the viewpoint of property, viscosity, and reactivity. These may be used alone or in combination of two or more. Of these, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate is particularly preferred because of its low viscosity.
[0017]
In the present invention, as the epoxy resin (A), the epoxy resin (a1) represented by the above formula (1) and the alicyclic epoxy resin (a2) are essential components, and a conventionally known epoxy resin is used for this. Also good. Specifically, general-purpose bisphenol type epoxy resins, hydrogenated bisphenol type epoxy resins, novolac type epoxy resins, glycidyl ether type epoxy resins, glycidyl ester type epoxy resins and the like can be used. In addition, when using the said conventionally well-known epoxy resin, it is preferable to set the usage-amount to 30 weight% or less in the whole epoxy resin (A).
[0018]
The photopolymerization initiator (B) used together with the epoxy resin (A) is not particularly limited, and is an aromatic diazonium salt, aromatic sulfonium salt, aromatic iodonium salt, aromatic sulfoxonium salt, metallocene compound. Alternatively, an iron arene compound or the like can be used. Among these, from the viewpoint of photocurability, aromatic sulfonium salts are preferable, especially aromatic sulfonium / hexafluorophosphonium compounds, aromatic sulfonium / hexafluoroantimonate compounds, or a combination of both, curability, adhesiveness, etc. From the viewpoint of Furthermore, a photosensitizer, an acid proliferating agent, etc. can be added with the said photoinitiator (B) as needed.
[0019]
Content of the said photoinitiator (B) is 1-15 with respect to 100 weight part (henceforth "part") of the total amount of the said epoxy resin (A) and the specific spherical silica powder (C) mentioned later. It is preferable to set it in parts, and particularly preferably 2 to 10 parts.
[0020]
The specific spherical silica powder (C) used together with the epoxy resin (A) and the photopolymerization initiator (B) is not particularly limited as long as it is generally a silica powder having a substantially spherical shape, but has a high sphericity. It is more preferable to use one. Then, in the present invention, spherical silica powder (C) is in the range of an average particle diameter of 0.3 to 0.5 [mu] m, and those that do not have free more than a particle size 5 [mu] m. By using a spherical silica powder having an average particle size in the above range and not containing particles having a large particle size of 5 μm or more, a decrease in ultraviolet curable property and an increase in viscosity are reduced. In addition, the measurement of the said average particle diameter can be measured using a laser diffraction scattering type particle size distribution measuring apparatus, for example. For obtaining those without containing the particle size 5μm or more spherical silica particles, the separation and removal method of the particle size 5μm or more spherical silica particles, for example, a method of removing by sieving or centrifugation and the like. In the case of synthetic silica, the particle size and distribution can be precisely controlled by handling so as not to generate secondary aggregation by adjusting pH. A method of preventing aggregation by controlling the particle size and then performing surface treatment is also effective as a method for preventing generation of particles having a particle size of 5 μm or more.
[0021]
The content of the specific spherical silica powder (C) is preferably set in the range of 50 to 80% by weight in the total amount of the epoxy resin (A) and the spherical silica powder (C). That is, when the content of the specific spherical silica powder (C) is less than 50% by weight, the linear expansion coefficient of the cured epoxy resin composition cannot be sufficiently lowered, and it is difficult to obtain good dimensional stability. This is because the epoxy resin composition has a very high viscosity, and not only the workability is lowered but also the photocurability tends to be lowered.
[0022]
In addition to the above (A) to (C), the ultraviolet curable epoxy resin composition of the present invention may include a silane-based or titanium-based coupling agent, a synthetic rubber, a silicone compound, or the like in order to improve adhesiveness. A compound such as a flexibility imparting agent and other additives such as an antioxidant and an antifoaming agent can be appropriately blended as necessary.
[0023]
The ultraviolet curable epoxy resin composition of the present invention includes, for example, the epoxy resin (a1) and alicyclic epoxy resin (a2) represented by the formula (1), a photopolymerization initiator (B), and a specific spherical shape. Silica powder (C) is produced as follows using other additives as required. First, the specific spherical silica powder (C) is blended and dispersed in the alicyclic epoxy resin (a2) in advance. Then, the remaining blending components are blended in this dispersion in a predetermined ratio, melt-mixed, and then cooled to room temperature.
[0024]
As conditions in the preliminary mixing in which the specific spherical silica powder (C) is blended and dispersed in the alicyclic epoxy resin (a2), a temperature of 25 to 100 ° C is preferable, and a range of 50 to 70 ° C is particularly preferable. In addition, in order to prevent aggregation, the solvent may be removed after the solvent is added and dispersed. Moreover, as a melting condition at the time of mix | blending the remaining compounding component and melt-mixing with the said dispersion, the temperature of 25-100 degreeC is preferable and the range of 50-70 degreeC is especially preferable.
[0025]
Thus, the spherical silica powder (C) is preliminarily blended and dispersed in the alicyclic epoxy resin (a2), whereby the spherical silica powder (C) can be uniformly dispersed in the entire epoxy resin composition, The wettability is improved at the interface between the spherical silica powder (C) particles and the epoxy resin, and the increase in viscosity can be reduced. Further, for the purpose of further improving the wettability, it is preferable to perform the surface treatment of the spherical silica powder (C) with the coupling agent such as the silane coupling agent described above.
[0026]
The viscosity of the ultraviolet curable epoxy resin composition of the present invention is preferably about 1 to 100 Pa · s at 25 ° C. in consideration of workability during use as an adhesive.
[0027]
The ultraviolet curable epoxy resin composition thus obtained can be cured by, for example, irradiating ultraviolet rays with a UV lamp or the like and then performing post-curing at a predetermined temperature.
[0028]
Next, examples will be described together with comparative examples.
[0029]
First, each component shown below was prepared.
[0030]
[Epoxy resin 1]
Epoxy resin represented by the following formula (a)

[0031]
[Epoxy resin 2]
Epoxy resin represented by the following formula (b)

[0032]
[Epoxy resin 3]
Cycloaliphatic epoxy resin represented by the following formula (c) (Dacel Chemical Co., Celoxide 2021P: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate)
[Chemical 7]

[0033]
[Spherical silica powder A]
Spherical silica powder with an average particle size of 0.3 μm and no particles having a particle size of 5 μm or more (manufactured by ADMATEX, SE1050)
[0034]
[Spherical silica powder B]
Spherical silica powder with an average particle size of 0.5 μm and no particles with a particle size of 5 μm or more (SE2050, manufactured by Admatechs)
[0035]
[Spherical silica powder C]
Spherical silica powder containing 3% by weight of particles having an average particle size of 1.5 μm and a particle size of 5 μm or more (manufactured by Admatechs, SO-E5)
[0036]
(Photopolymerization initiator)
Sulfonium hexafluoroantimony polymerization initiator (Asahi Denka Co., SP-170)
[0037]
〔Antioxidant〕
HCA (manufactured by Sanko Chemical Co., Ltd.)
[0038]
[Coupling agent]
γ-Glycidoxypropyltrimethoxysilane
Examples 1-6, Comparative Examples 1-3
First, spherical silica powder was previously blended and dispersed in epoxy resin 2 (alicyclic epoxy resin) at the ratios shown in Tables 1 and 2 below (condition: 50 ° C. × 30 minutes). Next, the remaining blended components were blended into this dispersion in the proportions shown in the table, melt mixed (conditions: 50 ° C. × 30 minutes), and then cooled to room temperature to prepare an ultraviolet curable epoxy resin composition. . In Comparative Examples 1 and 2, since spherical silica powder was not blended, preliminary dispersion was not performed, and the components shown in Table 2 below were blended and mixed in the proportions shown in the same table.
[0040]
[Table 1]

[0041]
[Table 2]

[0042]
Using the ultraviolet curable epoxy resin compositions of Examples and Comparative Examples thus obtained, the viscosity of the epoxy resin composition at 25 ° C., the linear expansion coefficient, the initial adhesive strength after curing and the moisture resistant adhesive strength The moisture resistance test and water absorption were measured and evaluated according to the following methods. These results are shown in Tables 3 to 4 below.
[0043]
[Viscosity of epoxy resin composition]
The viscosity at 25 ° C. was measured using an E-type viscometer.
[0044]
[Linear expansion coefficient]
After irradiation at 720 mJ / cm ² using a 500W UV lamp (high pressure mercury lamp), and then post-cured for 1 hour at 100 ° C., to form a film having a thickness of 100 [mu] m. And using this film, it measured in the tension mode by TMA (Measuring instrument: Thermoplus 8210 manufactured by Rigaku Corporation, measurement temperature: 30 to 250 ° C.). And the numerical value of the linear expansion coefficient in 35 degreeC was read.
[0045]
[Initial adhesive strength / moisture resistant adhesive strength]
First, an ultraviolet curable epoxy resin composition was applied as an adhesive to a columnar quartz glass plate (length 3.3 mm × width 3.3 mm × thickness 5 mm), and then a quartz glass plate (length 20 mm × width 35 mm × thickness 2 mm). ) And bonded together, and the adhesive was cured under the following curing conditions to produce an adhesive piece. That is, in the same manner as described above, the curing was performed by irradiating light at 720 mJ / cm ² using a 500 W UV lamp (high pressure mercury lamp), followed by curing at 100 ° C. for 1 hour.
[0046]
And the initial adhesive strength measured the adhesive strength of shear using the said adhesive piece and using the push pull gauge at 25 degreeC.
[0047]
Further, the moisture-resistant adhesive strength is determined by allowing the above-mentioned adhesive piece to stand for 24 hours under PCT conditions (121 ° C. × 202.6 kPa) to absorb moisture and then using a push-pull gauge at 25 ° C. It was measured.
[0048]
[Moisture resistance test]
Two quartz glass plates of 30 mm × 20 mm × 2 mm thickness were prepared, and both quartz glass plates were bonded together using an ultraviolet curable epoxy resin composition and cured to a thickness of 100 μm. Next, this was allowed to stand for 24 hours under PCT conditions (121 ° C. × 202.6 kPa) to absorb moisture, and then the presence or absence of the peeling state of the quartz glass plate was visually observed. The curing conditions were set in the same manner as the preparation of the sample at the initial adhesive strength.
[0049]
[Water absorption rate]
A film having a thickness of 100 μm is obtained by using a UV curable epoxy resin composition, irradiating light at 720 mJ / cm ² using a 500 W UV lamp (high pressure mercury lamp), and post-curing at 100 ° C. for 1 hour. Was made. The film was then immersed in water at 25 ° C. for 24 hours, and the water absorption was determined from the change in weight from the initial weight.
[0050]
[Table 3]

[0051]
[Table 4]

[0052]
From the above results, the example products were sufficiently cured despite containing silica powder, and high values were obtained not only in the initial adhesive strength but also in the moisture-resistant adhesive strength, and no occurrence of peeling in the moisture resistance test was observed. It was. In addition, the water absorption rate is low, the coefficient of linear expansion is also low, and low linear expansion is achieved.
[0053]
In contrast, Comparative Examples 1 and 2 that do not use spherical silica powder have high water absorption, low moisture-resistant adhesive strength, peeling in the moisture resistance test, and high linear expansion coefficient exceeding 60 ppm. Met. Moreover, in the comparative example 3 product using the spherical silica powder containing particles having an average particle size of more than 0.5 μm and a particle size of 5 μm or more, the ultraviolet rays hardly reach the inside of the resin composition, so the curability is poor. As a result, the moisture-resistant adhesive strength was low, and peeling occurred in the moisture resistance test.
[0054]
【The invention's effect】
As described above, the present invention includes the specific spherical silica powder (C) together with the epoxy resin (A) containing the epoxy resin (a1) represented by the formula (1) and the alicyclic epoxy resin (a2). Is an ultraviolet curable epoxy resin composition. For this reason, UV rays easily reach the inside of the resin composition, have good photocurability, have low water absorption in a high-temperature and high-humidity atmosphere, have high initial and post-moisture moisture-resistant adhesive strength, and excellent practicality It has. And since it contains the said specific spherical silica powder (C), it has the dimensional stability excellent in the low linear expansion coefficient. Such an ultraviolet curable epoxy resin composition of the present invention is obtained by dispersing the specific spherical silica powder (C) in the alicyclic epoxy resin (a2) in advance and then adding the remaining components thereto. The specific spherical silica powder (C) is uniformly dispersed in the resin composition by going through such a production process. Therefore, when the ultraviolet curable epoxy resin composition of the present invention is applied to the bonding of precision optical components such as optical waveguides and V grooves in optical communication systems, the bonding of fiber arrays, and the fixing of small components such as lenses. This realizes an adhesive joint with excellent long-term reliability.
[0055]
And when content of said a1 is set to the range of 15 to 70 weight% of the whole epoxy resin (A), it will become further excellent in moisture-proof adhesiveness and fluidity | liquidity.
[0056]
Further, when the content of the specific spherical silica powder (C) is set in a range of 50 to 80% by weight in the total amount of the epoxy resin (A) and the specific spherical silica powder (C), a low linear expansion coefficient is obtained. Thus, the dimensional stability is further improved, and the operability is improved.
[0057]
Furthermore, when 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate is used as the alicyclic epoxy resin which is a2, the viscosity is low with good transparency and reactivity, and is more preferable. Become.

Claims (5)

An ultraviolet curable epoxy resin composition comprising the following (A) to (C):
(A) An epoxy resin containing the following (a1) and (a2).
(A1) An epoxy resin represented by the following formula (1).

(A2) Alicyclic epoxy resin.
(B) Photopolymerization initiator.
(C) The average particle size measured using a laser diffraction / scattering particle size distribution measuring device is in the range of 0.3 to 0.5 μm, and the particle size is 5 μm measured using the laser diffraction / scattering particle size distribution measuring device. containing no spherical silica powder more than.   The ultraviolet curable epoxy according to claim 1, wherein the content of the epoxy resin (a1) represented by the formula (1) is set in a range of 15 to 70% by weight of the whole epoxy resin (A). Resin composition.   The ultraviolet curable type according to claim 1 or 2, wherein the content of the spherical silica powder (C) is set in the range of 50 to 80% by weight in the total amount of the epoxy resin (A) and the spherical silica powder (C). Epoxy resin composition.   The ultraviolet curable epoxy resin composition according to any one of claims 1 to 3, wherein the alicyclic epoxy resin (a2) is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. A process for preparing an ultraviolet-curable epoxy resin composition containing (A) ~ (C) below according to any one of claims 1 to 4, lower spherical silica powder (C) in advance under Symbol after dispersing the serial alicyclic epoxy resin (a2), the remaining ingredients including the epoxy resin (a1) and a photopolymerization initiator (B) represented by the formula (1) of the dispersion and the lower Stories A method for producing an ultraviolet curable epoxy resin composition, comprising mixing and mixing.
(A) An epoxy resin containing the following (a1) and (a2).
(A1) An epoxy resin represented by the following formula (1).

(A2) Alicyclic epoxy resin.
(B) Photopolymerization initiator.
(C) The average particle size measured using a laser diffraction / scattering particle size distribution measuring device is in the range of 0.3 to 0.5 μm, and the particle size is 5 μm measured using the laser diffraction / scattering particle size distribution measuring device. containing no spherical silica powder more than.