JP4011283B2

JP4011283B2 - Manufacturing method of optical transmission line

Info

Publication number: JP4011283B2
Application number: JP2000365223A
Authority: JP
Inventors: 学各務; 達弥山下; 伊藤　　博; 一夫岡本; 幸利伊縫
Original assignee: Toyoda Gosei Co Ltd; Toyota Central R&D Labs Inc
Current assignee: Toyoda Gosei Co Ltd; Toyota Central R&D Labs Inc
Priority date: 2000-11-30
Filing date: 2000-11-30
Publication date: 2007-11-21
Anticipated expiration: 2020-11-30
Also published as: JP2002169038A

Description

【０００１】
【発明の属する技術分野】
本発明は、光硬化性樹脂によりコアとクラッドから成る光伝送路を形成する光伝送路の製造方法に関する。本発明は、光ファイバに接続される光モジュールの製造に特に有用である。
【０００２】
【従来の技術】
従来、光硬化性樹脂を利用して光ファイバ先端に光伝送路を形成する技術として、例えば特開平４−１６５３１１号公報記載の技術が知られている。これは光ファイバの一端をフッ素系モノマーから成る光硬化成樹脂液に漬け、紫外線領域の短波長レーザーを光ファイバから樹脂液に照射することで光伝送路が形成されるものである。
【０００３】
【発明が解決しようとする課題】
しかし、上述の従来例では、コアのみしか形成できず、また、形成された光伝送路には未硬化のモノマーが付着しているため洗浄プロセスが必要であり、また、上述公報第１図乃至第３図にあるように形成されるコアも瓢箪様となって円筒形には制御できないという問題があった。
【０００４】
本発明者らは鋭意努力を重ね、２種類の光硬化性樹脂を用いることで有用な光伝送路を形成することを見出し、本願を完成させた。
【０００５】
即ち、本発明の目的は、２種類の光硬化性樹脂を用いることで有用な光伝送路を形成するための、好条件を備えた光伝送路の製造方法を提供することである。
【０００６】
【課題を解決するための手段】
上記の課題を解決するため、請求項１に記載の手段は、第１の光重合開始剤と該第１の光重合開始剤により第１の重合型により重合する第１のモノマー又はオリゴマーとから成る第１の光硬化性樹脂と、第２の光重合開始剤と該第２の光重合開始剤により第１の重合型とは異なる第２の重合型により重合する第２のモノマー又はオリゴマーとから成る第２の光硬化性樹脂とを混合する混合工程と、第１の光重合開始剤を活性化させるが第２の光重合開始剤を活性化させない第１の光照射により、第１の光硬化性樹脂を硬化させて光伝送路のコア部分を形成するコア形成工程と、第１の光重合開始剤と第２の光重合開始剤とをいずれも活性化させる第２の光照射により、第１の光硬化性樹脂と第２の光硬化性樹脂を各々硬化させて光伝送路のクラッド部分を形成するクラッド形成工程とから成り、第１の光照射と第２の光照射においては同じ波長の光照射を行い、第１の光照射は、第１の光硬化性樹脂がほぼ完全に硬化するのに必要な最小露光量より大きな露光量であり、第２の光硬化性樹脂がほぼ全く硬化しない最大露光量より小さな露光量にて行うことを特徴とする。
【０００７】
第１の光硬化性樹脂を硬化させてコア部分と成し、第１の光硬化性樹脂と第２の光硬化性樹脂を各々硬化させてクラッド部分と成すので、硬化後の第１の光硬化性樹脂は硬化後の第２の光硬化性樹脂よりも屈折率が高い必要がある。また、クラッド形成工程においては第１の光硬化性樹脂と第２の光硬化性樹脂は各々硬化するのであり、共重合するのではない。ただし、コア形成後、第２の光照射で２つの光硬化性樹脂が共に硬化し、且つ、硬化した混合樹脂の屈折率がより低ければクラッドとして機能することになる。
【０００８】
【０００９】
ここで、第１の光照射においては、第１の光硬化性樹脂がほぼ完全に硬化するのに必要な最小露光量とはコア形成に充分な硬化の程度を意味し、第２の光硬化性樹脂がほぼ全く硬化しない最大露光量とは、クラッド形成工程で形成されるクラッドの屈折率よりも十分高い屈折率のコアが形成される、即ちコアの屈折率を大きく下げない程度であれば、第２の光硬化性樹脂がコア部に微量含まれていても良いものとする。ただし、第１の光照射において、２つの光硬化性樹脂が共重合を行わないようにする必要がある。
【００１０】
また、請求項２に記載の手段によれば、第１の重合型と第２の重合型は、一方がラジカル重合によるものであり、もう一方がカチオン重合によるものであることを特徴とする。
【００１１】
【００１２】
また、請求項３に記載の手段は、第１の光重合開始剤が、２光子吸収を経て活性化することを特徴とする。
請求項４に記載の手段は、第１の光重合開始剤と該第１の光重合開始剤により第１の重合型により重合する第１のモノマー又はオリゴマーとから成る第１の光硬化性樹脂と、第２の光重合開始剤と該第２の光重合開始剤により第１の重合型とは異なる第２の重合型により重合する第２のモノマー又はオリゴマーとから成る第２の光硬化性樹脂とを混合する混合工程と、第１の光重合開始剤を活性化させるが第２の光重合開始剤を活性化させない第１の光照射により、第１の光硬化性樹脂を硬化させて光伝送路のコア部分を形成するコア形成工程と、第１の光重合開始剤と第２の光重合開始剤とをいずれも活性化させる第２の光照射により、第１の光硬化性樹脂と第２の光硬化性樹脂を各々硬化させて光伝送路のクラッド部分を形成するクラッド形成工程とから成り、第１の重合型と第２の重合型は、一方がラジカル重合によるものであり、もう一方がカチオン重合によるものであり、第１の光照射は、第１の光重合開始剤が活性化するのに必要な最長波長より短い波長であり、第２の光重合開始剤が活性化するのに必要な最長波長より長い波長にて行うものであって第１の光重合開始剤が、２光子吸収を経て活性化することを特徴とする。
第１又は第２の光重合開始剤が活性化するのに必要な最長波長とは、実質的にコア部として形成されるような硬化が起こる程度に必要なものをいう。
【００１３】
【作用及び発明の効果】
２種類の光硬化性樹脂を混合し、屈折率の高いほうのみ光照射により硬化させてコアを形成し、その後２種類の光硬化性樹脂を同時に硬化させればクラッドを形成することができる。これを可能とするためには、コアを形成する光照射が、第１の光重合開始剤が活性化するのに必要な最長波長より短い波長であり、第２の光重合開始剤が活性化するのに必要な最長波長より長い波長にて行えば良い（請求項４）。これにより、例えば反射ミラー、ハーフミラー等及び発光若しくは受光素子を組み合わせた光モジュールを容易に構成することができる。
【００１４】
また、第１の光照射と第２の光照射においては同じ波長の光照射を行うものとし、コアを形成する第１の光照射が、第１の光硬化性樹脂がほぼ完全に硬化するのに必要な最小露光量より大きな露光量であり、第２の光硬化性樹脂がほぼ全く硬化しない最大露光量より小さな露光量にて行うことでも良い（請求項１）。これにより、やはり反射ミラー、ハーフミラー等及び発光若しくは受光素子を組み合わせた光モジュールを容易に構成することができる。
【００１５】
２種類の光硬化性樹脂として、ラジカル重合により硬化するものと、カチオン重合により硬化するものとを組み合わせれば、第１の光照射工程において共重合を起こさない２種類の光硬化性樹脂を容易に組み合わせることができる（請求項２、４）。ラジカル重合により硬化する光硬化性樹脂としては、例えばアクリロイル基又はメタクリロイル基を有するモノマー或いはオリゴマー、感光性ポリイミド又はスチレン、ジビニルベンゼン若しくは不飽和ポリエステルなどを、光重合開始剤と組み合わせたものを用いることができる。また、カチオン重合により硬化する光硬化性樹脂としては、例えばエポキシ環、オキセタン環ほか環状エーテルを有する化合物、環状ラクトン化合物、環状アセタール化合物、ビニルエーテル化合物等のモノマー或いはオリゴマーを、光重合開始剤と組み合わせたものを用いることができる。
【００１６】
ラジカル重合のための光重合開始剤としては、ベンジルジメチルケタール系化合物、α−ヒドロキシケトン系化合物、α−アミノケトン系化合物、ビスアシルホスフィンオキシド系化合物、メタロセン系化合物その他の任意の光ラジカル重合開始剤を用いることができる。
【００１７】
カチオン重合のための光重合開始剤としては、トリアリールスルホニウム塩系化合物、ジアリールヨードニウム塩系化合物、メタロセン系化合物その他の任意の光カチオン重合開始剤を用いることができる。
【００１８】
光照射によりコア部を形成する際、コア部を長尺化するためにはコア部の光損失が重要となる。コア部が長さＬ(単位cm)形成された際、照度Ｉ₀(単位mW/cm²)の硬化光がコア部根元から成長端まで供給されるとき、硬化前の第１の光硬化性樹脂の光損失をα(単位dB/cm)とすると、成長端における照度Ｉ(単位mW/cm²)は次の式で求めることができる。
【数１】

【００１９】
波長λ_Wで長さＬ(cm)以上のコアを時間ｓ(単位は秒)で形成するためには、波長依存性のある最小露光量σ_A(λ_W)(単位はmJ/cm²)との間で次の式を充たす必要がある。
【数２】

【００２０】
ここから、光硬化性樹脂の硬化前の光損失αの上限が次の式で求められる。
【数３】

【００２１】
【００２２】
コアを形成するための第１の光重合開始剤が２光子吸収を経て活性化するならば、より長波長の硬化光を用いることができ、第２の光重合開始剤による重合をさせないようにすることが容易となる（請求項３、４）。
【００２３】
【発明の実施の形態】
本発明の光伝送路の製造方法に用いることのできる、光重合開始剤とモノマー又はオリゴマーは例えば以下のものが好適である。
【００２４】
光ラジカル重合を行うモノマーとしては、（メタ）アクリル酸エステル、（メタ）アクリル酸アミドが好ましい。具体的には（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸シクロヘキシル、（メタ）アクリル酸２−ブトキシエチル等の１官能性（メタ）アクリル酸エステル（モノ（メタ）アクリレート）を用いることができる。また、エチレングリコール、ネオペンチルグリコール、１，６−ヘキサンジオール等のジオールと２等量の（メタ）アクリル酸とのエステル（ジ（メタ）アクリレート）を用いることができる。同様に、アルコール性水酸基を複数有する有機化合物と（メタ）アクリル酸とのエステル（トリ、テトラ、…（メタ）アクリレート）を用いることができる。尚、これらのモノマーにおいて、（メタ）アクリロイル基及びその他の有機骨格のメチル水素、メチレン水素、メチン水素の一部をハロゲンで置換したものでも良い。
【００２５】
光ラジカル重合を行うオリゴマー（マクロモノマー）としては、末端又は分岐に（メタ）アクリロイル基を有するウレタン系オリゴマー、ポリエーテル系オリゴマー、エポキシ系オリゴマー、ポリエステル系オリゴマーなどが好ましい。尚、これらのオリゴマーにおいて、（メタ）アクリロイル基及びその他の有機骨格のメチル水素、メチレン水素、メチン水素の一部をハロゲンで置換したものでも良い。
【００２６】
光ラジカル重合開始剤としては、ベンジルジメチルケタール系化合物としては２，２−ジメトキシ−２−フェニルアセトフェノン、α−ヒドロキシケトン系化合物としては２−ヒドロキシ−２−メチル−フェニルプロパン−１−オン、（１−ヒドロキシシクロヘキシル）−フェニルケトン、α−アミノケトン系化合物としては２−ベンジル−２−ジメチルアミノ−１−（４−モルホリノフェニル）−ブタン−１−オン、２−メチル−１−（４−（メチルチオ）フェニル）−２−モルホリノプロパン−１−オン、ビスアシルホスフィンオキシド系化合物としてはビス（２，６−ジメトキシベンゾイル）−２，４，４−トリメチル−ペンチルホスフィンオキシド、ビス（２，４，６−トリメチルベンゾイル）−フェニルホスフィンオキシド、メタロセン系化合物としてはビス（η−シクロペンタジエニル）−ビス（２，６−ジフルオロ−３−（Ｎ−ピロイル）フェニル）チタンなどを用いることができる。これらを複数種類用いても良い。
【００２７】
光カチオン重合を行うモノマー或いはオリゴマーとしては、エポキシ環、オキセタン環ほか環状エーテルを有する化合物、環状ラクトン化合物、環状アセタール化合物、ビニルエーテル化合物等のモノマー或いはオリゴマーを用いることができる。
【００２８】
光カチオン重合開始剤としては、４，４’−ビス（ジ（２−ヒドロキシエトキシ）フェニルスルホニオ）フェニルスルフィド二ヘキサフルオロアンチモン酸、η−シクロペンタジエニル−η−クメン鉄（１＋）−ヘキサフルオロリン酸（１−）などを用いることができる。
【００２９】
上記述の光ラジカル重合開始剤又は光カチオン重合開始剤に、光増感剤を加えても良い。以上のような組み合わせにより、本発明に用いる光硬化性液状樹脂組成物とすることができる。また、本発明は、光アニオン重合性の重合開始剤とモノマー又はオリゴマーの組み合わせを排除するものではない。また、チオール・エン付加による重合を用いても良い。また、本発明と同様にして、コア部分の形成は光照射により行い、クラッド部分の形成は光照射以外の方法で行うことも可能である。
【００３０】
〔第１実施例〕
図１に本発明の具体的な第１の実施例に係る光伝送路の製造方法を示す。光ファイバ１、２つの異なる重合型により光重合する光硬化性樹脂２１、２２の混合液（光硬化性液状樹脂組成物）２、透明容器３を用意した。２つの異なる重合型により光重合する光硬化性樹脂２１、２２としては、光ラジカル重合を行うLoctite社製の品番358(以下、単に樹脂Ａという)と光カチオン重合を行うダイキン社製の品番UV-2100(以下、単に樹脂Ｂという)を用いた。
【００３１】
図１の（ａ）のように、樹脂Ａ２１及び樹脂Ｂ２２を混合（混合比７：３）して混合液２を調製し、透明容器３に充填した。次に光ファイバ１の先端面１２を混合液２に浸し、波長λ_W＝488nmの光を光ファイバ１に供給した。すると、図１の（ｂ）のように、光ファイバ１の先端面１２から略円錐台状の硬化した樹脂２１１が形成され、その後径が一定の略円柱状となって硬化部分２１１が成長した（図１の（ｃ））。硬化部分２１１が約23mmの長さになったところで波長λ_W＝488nmの光の供給を止め、透明容器３の全周から波長λ_C＝385nmの光（図で４）を照射し、透明容器３に残っていた混合液２を全て硬化させた（図１の（ｄ））。
【００３２】
硬化部分２１１と、透明容器３内のそれ以外の硬化部分２３の屈折率は、波長385nmに対し1.511と1.499と測定された。硬化部分２１１の屈折率は樹脂Ａの硬化後屈折率に等しく、硬化部分２３の屈折率は樹脂Ａ、樹脂Ｂの各々の硬化後屈折率の中間に位置する。よって、λ_W＝488nmの光照射により混合溶液２のうち樹脂Ａのみ硬化させて屈折率の高い略円柱状の部分の長いコアを形成し、λ_C＝385nmの光照射により樹脂Ａ、樹脂Ｂの各々を硬化させて屈折率の低いクラッドを形成することにより、光伝送路１０を形成することができた。
【００３３】
この実験結果は、次のように説明できる。図２は樹脂Ａと樹脂Ｂの硬化前の吸光度（光損失、単位dB/cm）の波長特性を示したものである。λ_W＝488nmにおいて、樹脂Ａと樹脂Ｂの吸収特性が大きく異なる。これは２種の光硬化性樹脂の光重合開始剤の活性化のための波長が異なることを意味する。このように、共重合しない、且つ硬化のための光重合開始剤の活性化波長が異なる２種の光硬化性樹脂を用いることで、硬化後屈折率の高い側の光硬化性樹脂の光重合開始剤の活性化波長が、硬化後屈折率の低い側の光硬化性樹脂の光重合開始剤の活性化波長より長いならば、それら２つの波長の間の波長により硬化後屈折率の高い側の光硬化性樹脂のみを硬化させることでコアのみを形成することができる。その後、クラッドとなるべき２種の光硬化性樹脂のいずれをも硬化させることで光伝送路を形成することができる。
【００３４】
〔第２実施例〕
本実施例は第１実施例と同様にして、露光量を異にしてコアとクラッドをそれぞれ形成して光伝送路を形成した。図１の（ａ）のように、樹脂Ａ２１及び樹脂Ｂ２２を混合して混合液（光硬化性液状樹脂組成物）２を調製し、透明容器３に充填した。次に光ファイバ１の先端面１２を混合液２に浸し、波長λ_W＝385nmの光を先端面１２において30mJ/cm²の露光量（図で１３）となるよう、光ファイバ１に供給した。すると、図１の（ｂ）のように、光ファイバ１の先端面１２から略円錐台状の硬化した樹脂２１１が形成され、その後径が一定の略円柱状となって硬化部分２１１が成長した（図１の（ｃ））。硬化部分２１１が約23mmの長さになった（露光量が30mJ/cm²）ところで光供給を止め、透明容器３の全周から波長λ_W＝385nmの光を60mJ/cm²の露光量（図で４）で照射し、透明容器３に残っていた混合液２を全て硬化させた（図１の（ｄ））。
【００３５】
硬化部分２１１と、透明容器３内のそれ以外の硬化部分２３の屈折率は、やはり波長385nmに対し1.511と1.499と測定された。硬化部分２１１の屈折率は樹脂Ａの硬化後屈折率に等しく、硬化部分２３の屈折率は樹脂Ａ、樹脂Ｂの各々の硬化後屈折率の中間に位置する。よって、λ_W＝385nm、30mJ/cm²の露光量の光照射により混合溶液２のうち樹脂Ａのみ硬化させて屈折率の高い略円柱状の部分の長いコアを形成し、λ_W＝385nm、60mJ/cm²の露光量の光照射により樹脂Ａ、樹脂Ｂの各々を硬化させて屈折率の低いクラッドを形成することにより、光伝送路１０を形成することができた。
【００３６】
この実験結果は、次のように説明できる。図３は樹脂Ａと樹脂Ｂを各々別にλ_W＝385nmの光を照射して、露光量と硬化による屈折率変化を調べたものである。樹脂Ａは露光量30mJ/cm²でほぼ屈折率が上昇しきってしまう（硬化が十分起こる）が、樹脂Ｂは露光量60mJ/cm²まで屈折率がほとんど上昇しない。これは、各々の光重合開始剤の感度（又は光重合開始剤と光増感剤との相互作用による感度）が異なるためである。このように、共重合しない、且つ硬化のための露光量が異なる２種の光硬化性樹脂を用いることで、硬化後屈折率の高い側の光硬化性樹脂が完全に硬化するための最小露光量が、硬化後屈折率の引い側の光硬化性樹脂が硬化しない最大露光量よりも小さいならば、それら２つの露光量の間の露光量により硬化後屈折率の高い側の光硬化性樹脂のみを硬化させることでコアのみを形成することができる。その後、クラッドとなるべき２種の光硬化性樹脂のいずれをも硬化させることで光伝送路を形成することができる。
【００３７】
上記実施例では２つの樹脂Ａ、Ｂを用いたが、本発明は共重合しない２つの光硬化性樹脂の任意の組み合わせから適宜コア形成樹脂（１方のみ）とクラッド形成樹脂（２種の混合物）となる組み合わせを選択した光硬化性液状樹脂組成物を用いることができる。この光硬化性液状樹脂組成物の２つの樹脂の、硬化波長又は硬化に必要な露光量の差を利用して、光硬化性液状樹脂組成物のうちのコア形成樹脂のみを硬化させてコア部を形成したのち、残部を硬化させてクラッドを形成する。このとき、共重合しない２つの光硬化性樹脂の重合型は光ラジカル重合と光カチオン重合に限定されない。
【図面の簡単な説明】
【図１】本発明の具体的な実施例に係る光伝送路の製造方法を示した工程図。
【図２】本発明の第１の実施例に係る光伝送路の製造方法の原理を説明するための吸光度の波長特性図。
【図３】本発明の第２の実施例に係る光伝送路の製造方法の原理を説明するための露光量による屈折率の変化図。
【符号の説明】
１光ファイバ
１０光伝送路（コアとクラッドを含めたデバイス）
１２光ファイバの混合液に浸された端面
１３光ファイバの端面からの照射光
２共重合しない２つの光硬化性樹脂の混合液（光硬化性液状樹脂組成物）
２１樹脂Ａ
２１１樹脂Ａが硬化して形成されるコア部分
２２樹脂Ｂ
２３樹脂Ａと樹脂Ｂがそれぞれ硬化して形成されるクラッド部分
３透明容器
４第２の光照射
λ_W第１の光照射の際の波長[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing an optical transmission line that forms an optical transmission line composed of a core and a clad with a photocurable resin. The present invention is particularly useful for manufacturing an optical module connected to an optical fiber.
[0002]
[Prior art]
Conventionally, as a technique for forming an optical transmission line at the tip of an optical fiber using a photocurable resin, for example, a technique described in Japanese Patent Laid-Open No. 4-165311 is known. In this method, one end of an optical fiber is immersed in a photo-curing resin solution made of a fluorine-based monomer, and an optical transmission path is formed by irradiating the resin solution with a short wavelength laser in the ultraviolet region.
[0003]
[Problems to be solved by the invention]
However, in the above-described conventional example, only the core can be formed, and an uncured monomer is attached to the formed optical transmission line, so that a cleaning process is necessary. The core formed as shown in FIG. 3 also has a problem that it cannot be controlled into a cylindrical shape due to the saddle shape.
[0004]
The present inventors have made intensive efforts and found that a useful optical transmission line can be formed by using two types of photo-curing resins, thereby completing the present application.
[0005]
That is, an object of the present invention is to provide a method of manufacturing an optical transmission line with favorable conditions for forming a useful optical transmission line by using two types of photocurable resins.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the means according to claim 1 includes: a first photopolymerization initiator; and a first monomer or oligomer that is polymerized in a first polymerization type by the first photopolymerization initiator. A first photocurable resin, a second photopolymerization initiator, and a second monomer or oligomer polymerized by a second polymerization type different from the first polymerization type by the second photopolymerization initiator. A mixing step of mixing a second photocurable resin comprising: a first photoirradiation that activates the first photopolymerization initiator but does not activate the second photopolymerization initiator; By a core formation step of curing the photocurable resin to form the core portion of the optical transmission line, and by the second light irradiation that activates both the first photopolymerization initiator and the second photopolymerization initiator. , the first photo-curable resin and the second photo-curable resin each cured optical transmission line click Consists of a cladding formation step of forming a head portion, a first light irradiation and in the second light irradiation is performed with light irradiation of the same wavelength, the first light irradiation, the first photo-curable resin is approximately The exposure dose is larger than the minimum exposure dose required for complete curing, and is smaller than the maximum exposure dose at which the second photo-curable resin is hardly cured .
[0007]
Since the first photocurable resin is cured to form the core portion, and the first photocurable resin and the second photocurable resin are respectively cured to form the cladding portion, the first light after curing The curable resin needs to have a higher refractive index than the second photocurable resin after curing. Further, in the clad formation step, the first photocurable resin and the second photocurable resin are cured, and are not copolymerized. However, if the two photo-curing resins are cured together by the second light irradiation after the core is formed and the refractive index of the cured mixed resin is lower, it functions as a cladding .
[0008]
[0009]
Here, in the first light irradiation, the minimum exposure amount necessary for almost completely curing the first photocurable resin means a degree of curing sufficient for core formation, and the second photocuring. The maximum exposure amount at which the resin does not harden at all is as long as a core having a refractive index sufficiently higher than the refractive index of the clad formed in the clad forming step is formed, that is, the refractive index of the core is not greatly reduced. The second photocurable resin may be contained in a trace amount in the core part. However, in the first light irradiation, it is necessary to prevent the two photocurable resins from copolymerizing.
[0010]
Further, according to the means described in claim 2 , one of the first polymerization type and the second polymerization type is based on radical polymerization, and the other is based on cationic polymerization.
[0011]
[0012]
The means described in claim 3 is characterized in that the first photopolymerization initiator is activated through two-photon absorption.
The means according to claim 4 comprises: a first photocurable resin comprising a first photopolymerization initiator and a first monomer or oligomer that is polymerized by the first photopolymerization initiator in a first polymerization type. And a second photocuring property comprising a second photopolymerization initiator and a second monomer or oligomer polymerized by the second photopolymerization initiator in a second polymerization type different from the first polymerization type. The first photocurable resin is cured by a mixing step of mixing the resin and the first light irradiation that activates the first photopolymerization initiator but does not activate the second photopolymerization initiator. The first photocurable resin is formed by a core forming step for forming a core portion of the optical transmission line, and a second light irradiation that activates both the first photopolymerization initiator and the second photopolymerization initiator. And a second photo-curing resin are cured to form a clad portion of the optical transmission line. The first polymerization type and the second polymerization type are ones based on radical polymerization, the other is based on cationic polymerization, and the first light irradiation is the first photopolymerization. The first photopolymerization is performed at a wavelength shorter than the longest wavelength necessary for activation of the initiator and longer than the longest wavelength necessary for activation of the second photopolymerization initiator. It is characterized in that the initiator is activated via two-photon absorption.
The longest wavelength necessary for the activation of the first or second photopolymerization initiator refers to that which is necessary to such an extent that curing is substantially formed as a core portion.
[0013]
[Operation and effect of the invention]
If two types of photocurable resins are mixed, only the one having a higher refractive index is cured by light irradiation to form a core, and then the two types of photocurable resins are simultaneously cured, thereby forming a clad. In order to enable this, the light irradiation for forming the core is shorter than the longest wavelength necessary for the first photopolymerization initiator to be activated, and the second photopolymerization initiator is activated. up may be performed than at longer wavelengths the wavelength needed to (claim 4). Thereby, for example, an optical module in which a reflection mirror, a half mirror, and the like and a light emitting or light receiving element are combined can be easily configured.
[0014]
Further, the first light irradiation and in the second light irradiation and performs light irradiation of the same wavelength, the first light irradiation, the first photo-curable resin is cured substantially completely to form a core in a larger exposure amount than the minimum exposure required, also be that performed at maximum exposure smaller amount of exposure second photo-curable resin is not substantially completely cured (claim 1). Thereby, an optical module in which a reflection mirror, a half mirror, and the like and a light emitting or receiving element are combined can be easily configured.
[0015]
If two types of photo-curable resins are combined with one that is cured by radical polymerization and one that is cured by cationic polymerization, two types of photo-curable resins that do not cause copolymerization in the first light irradiation step can be easily obtained. ( Claims 2 and 4 ). As a photocurable resin that is cured by radical polymerization, for example, a monomer or oligomer having an acryloyl group or a methacryloyl group, a photosensitive polyimide, or a combination of styrene, divinylbenzene, or an unsaturated polyester with a photopolymerization initiator is used. Can do. In addition, as a photocurable resin that is cured by cationic polymerization, for example, a monomer or oligomer such as an epoxy ring, an oxetane ring or a compound having a cyclic ether, a cyclic lactone compound, a cyclic acetal compound, or a vinyl ether compound is combined with a photopolymerization initiator. Can be used.
[0016]
As photopolymerization initiators for radical polymerization, benzyldimethyl ketal compounds, α-hydroxy ketone compounds, α-amino ketone compounds, bisacylphosphine oxide compounds, metallocene compounds and other arbitrary photo radical polymerization initiators Can be used.
[0017]
As a photopolymerization initiator for cationic polymerization, a triarylsulfonium salt compound, a diaryl iodonium salt compound, a metallocene compound, and other arbitrary photocation polymerization initiators can be used.
[0018]
When forming a core part by light irradiation, in order to lengthen a core part, the optical loss of a core part becomes important. When the core portion is formed with a length L (unit cm), when the curing light having an illuminance I ₀ (unit mW / cm ² ) is supplied from the root of the core portion to the growth end, the first photocurability before curing If the optical loss of the resin is α (unit dB / cm), the illuminance I (unit mW / cm ² ) at the growth edge can be obtained by the following equation.
[Expression 1]

[0019]
In order to form a core having a wavelength λ _W and a length L (cm) or more in a time s (unit: second), a wavelength-dependent minimum exposure amount σ _A (λ _W ) (unit: mJ / cm ² ) It is necessary to satisfy the following formula between
[Expression 2]

[0020]
From this, the upper limit of the light loss α before curing of the photocurable resin is determined by the following equation.
[Equation 3]

[0021]
[0022]
If the first photopolymerization initiator for forming the core is activated through two-photon absorption, longer wavelength curing light can be used, and polymerization by the second photopolymerization initiator is not allowed to occur. (Claims 3 and 4) .
[0023]
DETAILED DESCRIPTION OF THE INVENTION
As the photopolymerization initiator and the monomer or oligomer that can be used in the method for producing an optical transmission line of the present invention, for example, the following are suitable.
[0024]
As a monomer which performs radical photopolymerization, (meth) acrylic acid ester and (meth) acrylic acid amide are preferable. Specifically, monofunctional (meth) acrylic acid esters (mono (meth) acrylates) such as 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and 2-butoxyethyl (meth) acrylate are used. Can do. Further, an ester (di (meth) acrylate) of diol such as ethylene glycol, neopentyl glycol, 1,6-hexanediol and 2 equivalents of (meth) acrylic acid can be used. Similarly, an ester (tri, tetra,... (Meth) acrylate) of an organic compound having a plurality of alcoholic hydroxyl groups and (meth) acrylic acid can be used. In these monomers, a part of methyl hydrogen, methylene hydrogen and methine hydrogen in the (meth) acryloyl group and other organic skeletons may be substituted with halogen.
[0025]
As the oligomer (macromonomer) for performing radical photopolymerization, a urethane-based oligomer, a polyether-based oligomer, an epoxy-based oligomer, a polyester-based oligomer having a (meth) acryloyl group at the terminal or branch is preferable. In these oligomers, a part of methyl hydrogen, methylene hydrogen, and methine hydrogen in the (meth) acryloyl group and other organic skeletons may be substituted with halogen.
[0026]
As a radical photopolymerization initiator, 2,2-dimethoxy-2-phenylacetophenone as a benzyldimethyl ketal compound, 2-hydroxy-2-methyl-phenylpropan-1-one as an α-hydroxyketone compound, ( 1-hydroxycyclohexyl) -phenyl ketone and α-aminoketone compounds include 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- (4- ( Methylthio) phenyl) -2-morpholinopropan-1-one, and bisacylphosphine oxide compounds include bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, bis (2,4,4) 6-Trimethylbenzoyl) -phenylphosphine oxide, metallo As the senic compound, bis (η-cyclopentadienyl) -bis (2,6-difluoro-3- (N-pyroyl) phenyl) titanium or the like can be used. A plurality of these may be used.
[0027]
As the monomer or oligomer for performing cationic photopolymerization, monomers or oligomers such as an epoxy ring, an oxetane ring, a compound having a cyclic ether, a cyclic lactone compound, a cyclic acetal compound, and a vinyl ether compound can be used.
[0028]
As the photocationic polymerization initiator, 4,4′-bis (di (2-hydroxyethoxy) phenylsulfonio) phenyl sulfide dihexafluoroantimonic acid, η-cyclopentadienyl-η-cumene iron (1 +)-hexa Fluorophosphoric acid (1-) or the like can be used.
[0029]
A photosensitizer may be added to the above-mentioned photo radical polymerization initiator or photo cationic polymerization initiator. By the combination as described above, the photocurable liquid resin composition used in the present invention can be obtained. Further, the present invention does not exclude a combination of a photoanion polymerizable polymerization initiator and a monomer or oligomer. Further, polymerization by thiol-ene addition may be used. Similarly to the present invention, the core portion can be formed by light irradiation, and the clad portion can be formed by a method other than light irradiation.
[0030]
[First embodiment]
FIG. 1 shows a method of manufacturing an optical transmission line according to a specific first embodiment of the present invention. An optical fiber 1, a liquid mixture (photocurable liquid resin composition) 2 of a

photocurable resin

21, 22 photopolymerized by two different polymerization types, and a transparent container 3 were prepared. The photocurable resins 21 and 22 that are photopolymerized by two different polymerization types include a product number 358 manufactured by Loctite (hereinafter simply referred to as “resin A”) that performs photoradical polymerization and a product number UV manufactured by Daikin that performs photocationic polymerization. -2100 (hereinafter simply referred to as Resin B) was used.
[0031]
As shown in FIG. 1A, the resin A21 and the resin B22 were mixed (mixing ratio 7: 3) to prepare a mixed solution 2 and filled in the transparent container 3. Next, the tip surface 12 of the optical fiber 1 was immersed in the liquid mixture 2, and light having a wavelength λ _W = 488 nm was supplied to the optical fiber 1. Then, as shown in FIG. 1B, a substantially truncated cone-shaped cured resin 211 is formed from the end face 12 of the optical fiber 1, and then the cured portion 211 grows in a substantially cylindrical shape with a constant diameter. ((C) of FIG. 1). When the cured portion 211 has a length of about 23 mm, the supply of light of wavelength λ _W = 488 nm is stopped, and light of wavelength λ _C = 385 nm (4 in the figure) is irradiated from the entire circumference of the transparent container 3, All the mixed liquid 2 remaining in 3 was cured ((d) in FIG. 1).
[0032]
The refractive indexes of the cured part 211 and the other cured part 23 in the transparent container 3 were measured as 1.511 and 1.499 with respect to a wavelength of 385 nm. The refractive index of the cured portion 211 is equal to the refractive index after curing of the resin A, and the refractive index of the cured portion 23 is located between the refractive indexes after curing of the resin A and the resin B. Therefore, only the resin A in the mixed solution 2 is cured by light irradiation with λ _W = 488 nm to form a long core having a substantially cylindrical portion having a high refractive index, and the resin A and the resin B are irradiated with light irradiation with λ _C = 385 nm. Each of these was cured to form a clad having a low refractive index, whereby the optical transmission line 10 could be formed.
[0033]
The result of this experiment can be explained as follows. FIG. 2 shows the wavelength characteristics of the absorbance (light loss, unit dB / cm) of the resin A and the resin B before curing. At λ _W = 488 nm, the absorption characteristics of Resin A and Resin B are greatly different. This means that the wavelengths for the activation of the photopolymerization initiators of the two types of photocurable resins are different. As described above, by using two types of photocurable resins that are not copolymerized and have different activation wavelengths of photopolymerization initiators for curing, photopolymerization of the photocurable resin having a higher refractive index after curing is performed. If the activation wavelength of the initiator is longer than the activation wavelength of the photopolymerization initiator of the photocurable resin on the side having the lower refractive index after curing, the side having the higher refractive index after curing due to the wavelength between these two wavelengths Only the core can be formed by curing only the photo-curable resin. Thereafter, the optical transmission path can be formed by curing both of the two types of photo-curing resins to be the cladding.
[0034]
[Second Embodiment]
In this example, similarly to the first example, the optical transmission line was formed by forming the core and the clad respectively with different exposure amounts. As shown in FIG. 1A, resin A21 and resin B22 were mixed to prepare a mixed liquid (photocurable liquid resin composition) 2 and filled in a transparent container 3. Next, the tip surface 12 of the optical fiber 1 was immersed in the liquid mixture 2, and light having a wavelength λ _W = 385 nm was supplied to the optical fiber 1 so that the exposure amount (13 in the figure) was 30 mJ / cm ^{2 on} the tip surface 12. . Then, as shown in FIG. 1B, a substantially truncated cone-shaped cured resin 211 is formed from the end face 12 of the optical fiber 1, and then the cured portion 211 grows in a substantially cylindrical shape with a constant diameter. ((C) of FIG. 1). When the cured portion 211 has a length of about 23 mm (exposure amount is 30 mJ / cm ² ), the light supply is stopped and light with a wavelength λ _W = 385 nm from the entire circumference of the transparent container 3 is exposed to 60 mJ / cm ² ( Irradiation was performed at 4) in the figure, and all of the mixed liquid 2 remaining in the transparent container 3 was cured ((d) in FIG. 1).
[0035]
The refractive indexes of the cured part 211 and the other cured part 23 in the transparent container 3 were also measured as 1.511 and 1.499 for the wavelength of 385 nm. The refractive index of the cured portion 211 is equal to the refractive index after curing of the resin A, and the refractive index of the cured portion 23 is located between the refractive indexes after curing of the resin A and the resin B. Accordingly, only a resin A in the mixed solution 2 is cured by light irradiation with an exposure amount of λ _W = 385 nm and an exposure amount of 30 mJ / cm ² to form a long core having a substantially cylindrical portion having a high refractive index, and λ _W = 385 nm, The optical transmission line 10 could be formed by curing the resin A and the resin B by light irradiation with an exposure amount of 60 mJ / cm ² to form a clad having a low refractive index.
[0036]
The result of this experiment can be explained as follows. FIG. 3 shows the refractive index change due to the exposure amount and curing by irradiating the resin A and the resin B separately with light of λ _W = 385 nm. The refractive index of resin A almost increases at an exposure dose of 30 mJ / cm ² (curing occurs sufficiently), but the refractive index of resin B hardly increases up to an exposure dose of 60 mJ / cm ² . This is because the sensitivity of each photopolymerization initiator (or the sensitivity due to the interaction between the photopolymerization initiator and the photosensitizer) is different. Thus, by using two types of photo-curing resins that are not copolymerized and have different exposure amounts for curing, the minimum exposure for completely curing the photo-curing resin on the side having a higher refractive index after curing. If the amount is smaller than the maximum exposure amount at which the photocurable resin on the side where the refractive index is reduced after curing is not cured, the photocurable resin on the side where the post-curing refractive index is higher due to the exposure amount between the two exposure amounts. Only the core can be formed by curing only. Thereafter, the optical transmission path can be formed by curing both of the two types of photo-curing resins to be the cladding.
[0037]
In the above embodiment, two resins A and B are used, but the present invention appropriately selects a core-forming resin (only one) and a clad-forming resin (a mixture of two kinds) from any combination of two photo-curable resins that are not copolymerized. The photocurable liquid resin composition which selected the combination used to become) can be used. Utilizing the difference between the curing wavelength or the exposure amount necessary for curing of the two resins of the photocurable liquid resin composition, only the core-forming resin of the photocurable liquid resin composition is cured to form the core portion. After forming, the remainder is cured to form a clad. At this time, the polymerization types of the two photocurable resins that are not copolymerized are not limited to photoradical polymerization and photocationic polymerization.
[Brief description of the drawings]
FIG. 1 is a process diagram showing a method for manufacturing an optical transmission line according to a specific embodiment of the present invention.
FIG. 2 is an absorbance wavelength characteristic diagram for explaining the principle of the optical transmission line manufacturing method according to the first embodiment of the present invention.
FIG. 3 is a change diagram of a refractive index according to an exposure amount for explaining the principle of a method of manufacturing an optical transmission line according to a second embodiment of the present invention.
[Explanation of symbols]
1 Optical fiber 10 Optical transmission line (device including core and clad)
12 End face immersed in mixed liquid of optical fiber 13 Irradiation light from end face of optical fiber 2 Mixed liquid of two photo-curable resins not copolymerized (photo-curable liquid resin composition)
21 Resin A
211 Core portion formed by curing resin A 22 Resin B
23 Clad portion formed by curing resin A and resin B, respectively 3 Transparent container 4 Second light irradiation λ _W Wavelength at the time of first light irradiation

Claims

A first photopolymerization initiator comprising a first photopolymerization initiator and a first monomer or oligomer that is polymerized in a first polymerization type by the first photopolymerization initiator, and a second photopolymerization initiator And a second photocurable resin comprising a second monomer or oligomer polymerized by a second polymerization type different from the first polymerization type by the second photopolymerization initiator; ,
The first photo-polymerization initiator is activated but the second photo-polymerization initiator is not activated, and the first photo-curing resin is cured by the first light irradiation, so that the core portion of the optical transmission path Forming a core; and
By the second light irradiation that activates both the first photopolymerization initiator and the second photopolymerization initiator, the first photocurable resin and the second photocurable resin are respectively A clad forming step of curing and forming a clad portion of the optical transmission line,
In the first light irradiation and the second light irradiation, light irradiation with the same wavelength is performed,
The first light irradiation is an exposure amount larger than a minimum exposure amount necessary for the first photo-curing resin to be almost completely cured, and the second photo-curing resin is hardly cured at all. A method for manufacturing an optical transmission line, wherein the exposure is performed with an exposure amount smaller than the exposure amount.

2. The method of manufacturing an optical transmission line according to claim 1 , wherein one of the first polymerization type and the second polymerization type is based on radical polymerization and the other is based on cationic polymerization. .

The method for manufacturing an optical transmission line according to claim 1 or 2 , wherein the first photopolymerization initiator is activated through two-photon absorption.

A first photopolymerization initiator comprising a first photopolymerization initiator and a first monomer or oligomer that is polymerized in a first polymerization type by the first photopolymerization initiator, and a second photopolymerization initiator And a second photocurable resin comprising a second monomer or oligomer polymerized by a second polymerization type different from the first polymerization type by the second photopolymerization initiator; ,
The first photo-polymerization initiator is activated but the second photo-polymerization initiator is not activated, and the first photo-curing resin is cured by the first light irradiation, so that the core portion of the optical transmission path Forming a core; and
By the second light irradiation that activates both the first photopolymerization initiator and the second photopolymerization initiator, the first photocurable resin and the second photocurable resin are respectively A clad forming step of curing and forming a clad portion of the optical transmission line,
One of the first polymerization type and the second polymerization type is based on radical polymerization, and the other is based on cationic polymerization.
The first light irradiation has a wavelength shorter than the longest wavelength necessary for the first photopolymerization initiator to be activated, and the longest wavelength necessary for the second photopolymerization initiator to be activated. A method for producing an optical transmission line , which is performed at a longer wavelength and the first photopolymerization initiator is activated through two-photon absorption .