JP2004151160A

JP2004151160A - Manufacturing method of optical waveguide

Info

Publication number: JP2004151160A
Application number: JP2002313421A
Authority: JP
Inventors: Tatsuya Yamashita; 達弥山下; Shuri Kawasaki; 朱里河崎; Manabu Kagami; 学各務; Hiroshi Ito; 伊藤　　博; Yukitoshi Inui; 幸利伊縫; Kuniyoshi Kondo; 国芳近藤
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: 2002-10-28
Filing date: 2002-10-28
Publication date: 2004-05-27

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide having an optical path formed with a low refractive index part on the surface, by photosetting very slowly and selectively through light leakage. <P>SOLUTION: In a transparent container 1, there is filled a mixed solution 2 consisting of a first photosetting resin with a low refractive index and a second photosetting resin with a high refractive index which are each different in the hardening mechanism. Into this mixed solution 2, using an optical fiber 3, a light beam having a wavelength λ<SB>1</SB>is supplied that hardens the first photosetting resin but not the second. As a result, it is possible to harden the first photosetting resin in a fashion taking in the second photosetting resin. This is because hardening raises a refractive index, causing a self-condensing phenomenon to form an optical path part 4. The optical path part 4 generates light leakage around, thereby forming an outer peripheral part 5. Subsequently, the entire unhardened resin is hardened. The outer peripheral part 5 having a high ratio of the first photosetting resin hardenable becomes smaller in the refractive index than the optical path part 4, thereby serving as a clad. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は簡便・安価な光伝送路の製造方法並びにその製法に好適な材料の組成に関する。本発明の光導波路の製造方法は、光ファイバー通信分野における安価で低損失な光インターコネクション、光分波器あるいは合波器等の光導波路部品の製造に応用可能である。
【０００２】
【従来の技術】
光硬化性樹脂溶液にビーム状の所定波長光を導入し、自己集光現象を利用して、光導波路デバイスを形成する技術が注目されている。例えば、本願共同出願人による下記特許文献１、２に記載された光導波路の製造方法がある。また、本願出願人以外の出願人によるものとしては下記特許文献３、４に記載された技術が知られている。
【０００３】
【特許文献１】
特開２０００−３４７０４３号公報
【特許文献２】
特開２００２−１６９０３８号公報
【特許文献３】
特開２００２− ３１７３３号公報
【特許文献４】
特開２００２−２５８０９５号公報
【０００４】
この製造方法によると、まず、高屈折率の光硬化性樹脂と低屈折率の光硬化性樹脂の混合溶液を所定の容器に充たす。次に、光ファイバーの先端を混合溶液に浸け、当該高屈折率の光硬化性樹脂のみを硬化させる特定波長帯の光を光ファイバーにて導入する。すると、光ファイバーの先端から出射する光によって当該光ファイバー先端から当該光ファイバーのコア径と同程度の径を有する高屈折率の硬化物を自己集光現象を利用して徐々に形成できる。この後、溶液内に残った高屈折率及び低屈折率の光硬化性樹脂の混合溶液を両樹脂が共に光硬化するよう所定波長帯の光を全体に照射する。こうして、先に形成した屈折率の高い硬化物の周囲に低屈折率の硬化物を形成することにより、ステップ状の屈折率分布を持った光導波路を作成する技術である。
【０００５】
【発明が解決しようとする課題】
特許文献１、２に開示された技術では、屈折率の分布は基本的にステップ状の段階的なものとなる。ここで、コア（高屈折率部分）とクラッド（低屈折率部分）の屈折率差を大きくしようとすると、コア形成の時間を長くして、高屈折率材料のみを選択的に重合させる必要があり、生産性が向上しない。この点は特許文献３、４においても同様と言える。
【０００６】
本発明者らは、光硬化性樹脂の組み合わせを逆にし、低屈折率の光硬化性樹脂のみを硬化させる特定波長帯の光を光ファイバーにて導入したところ、高屈折率の光硬化性樹脂を取り込んだ状態で低屈折率の光硬化性樹脂を光照射の形状に応じたパターンに重合硬化させることによって光学的に透明な光路部分（コア）を形成できることを見出した。尚、取り込まれた高屈折率の光硬化性樹脂はこの状態では硬化していない。次に、引き続いて低屈折率材料のみを硬化させる特定波長帯の光を光伝送路部分に一定時間以上照射継続すると、光伝送路部分からの漏洩または散乱による光成分によって光路部分の表面に低屈折率の光硬化性樹脂のみが選択的に重合し、光伝送路部分よりも屈折率の低い重合硬化物の層（擬似クラッド層）が形成される。尚、やはりこの状態では光路部分の表面に屈折率の高い光硬化性樹脂が取り込まれたとしても当該屈折率の高い光硬化性樹脂は硬化していない。その後、溶液内に残った高屈折率及び低屈折率の光硬化性樹脂の混合溶液を両樹脂が光硬化する特定波長帯の光を照射することによって、先に形成した屈折率の低い硬化物層の周囲に高屈折率の硬化物（基体部）が形成され、光照射方向の直交断面内に、高屈折率部分（基体部）に保持された低屈折率部分に被覆された高屈折率部分となる屈折率分布を形成できることを見出した。
【０００７】
即ち、本発明はこの知見に基づき、漏光にて極めて遅い、選択的な光硬化を行うことで、低屈折率部分を表面に形成した光路を有する光導波路の製造方法を提供するものである。
【０００８】
【課題を解決するための手段】
請求項１に記載の手段は、光伝送を担うものであって、周囲に漏光を発する光学部材の表面に、当該光学部材の外周の屈折率よりも低い硬化後屈折率を有する光硬化性樹脂を、漏光により硬化付着させることを特徴とする、外周をより低い屈折率を有する光硬化性樹脂硬化物で被覆された光導波路の製造方法である。
【０００９】
また、請求項２に記載の手段は、請求項１に記載の手段に加えて、光硬化性樹脂硬化物は硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液を硬化させて成るものであって、漏光は第１の光硬化性樹脂を硬化させるが第２の光硬化性樹脂を硬化させないものであり、漏光による第１の光硬化性樹脂を硬化させたのち第１の光硬化性樹脂及び第２の光硬化性樹脂を共に硬化させる工程を更に含み、光硬化性樹脂硬化物の屈折率は、光学部材の表面から遠ざかる少なくとも一部において、屈折率が単調減少することを特徴とする。
【００１０】
また、請求項３に記載の手段は、硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液を用い、第１の光硬化性樹脂を硬化させるが第２の光硬化性樹脂を硬化させない第１の光照射により、第２の光硬化性樹脂を取り込む形で第１の光硬化性樹脂を硬化させ、光学的に透明な光路部分を形成する第１の光硬化工程と、光路部分を形成した後、第１の光硬化性樹脂を硬化させるが第２の光硬化性樹脂を硬化させない第２の光照射を第１の光照射と同様に照射して、光路部分の表面に第１の光硬化樹脂を硬化させる第２の光硬化工程と、第１の光硬化性樹脂と第２の光硬化性樹脂の両方を硬化させる第３の光照射により、光路部分に取り込まれた第２の光硬化性樹脂、並びに、未硬化の残余の混合溶液全体を硬化させる第３の光硬化工程とから成り、屈折率の高い光路部分と、その表面の低屈折率部分とを有する光導波路を製造する方法である。ここで、第２の光照射を第１の光照射と同様に照射するとは、強度のことを言うのではなく、その照射方向、照射形状が同様であることを意味し、第２の光照射が第１の光照射と波長が異なるときは照射光の波長を切り換え、波長が同一であるときは照射方向、照射形状については継続することを意味する。この際、第１の光照射と第２の光照射の光強度については任意とする。このことは本願の他の請求項においても同様である。
【００１１】
また、請求項４に記載の手段は、請求項３に記載の手段で硬化した部分を未硬化溶液から取り出して別途硬化させるものである。即ち、硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液を用い、第１の光硬化性樹脂を硬化させるが第２の光硬化性樹脂を硬化させない第１の光照射により、第２の光硬化性樹脂を取り込む形で第１の光硬化性樹脂を硬化させ、光学的に透明な光路部分を形成する第１の光硬化工程と、光路部分を形成した後、第１の光硬化性樹脂を硬化させるが第２の光硬化性樹脂を硬化させない第２の光照射を第１の光照射と同様に照射して、光路部分の表面に第１の光硬化樹脂を硬化させる第２の光硬化工程と、第２の光硬化性樹脂を取り込んだ形で硬化した第１の光硬化樹脂からなる光路部分及び表面部分を取り出し、第１の光硬化性樹脂と第２の光硬化性樹脂の両方を硬化させる第３の光照射により、光路部分に取り込まれた第２の光硬化性樹脂、並びに、未硬化の残余の第１の光硬化性樹脂を硬化させる第３の光硬化工程とから成り、屈折率の高い光路部分と、その表面の低屈折率部分とを有する光導波路を製造する方法である。
【００１２】
また、請求項５に記載の手段は、請求項３又は請求項４に記載の光導波路を製造する方法において、第１の光照射と第２の光照射を同時に行い、前記光路部分を形成しながら、前記光路部分の側面に前記第１の光硬化性樹脂を硬化させることを特徴とする。更に、請求項６に記載の手段は、請求項３乃至請求項５に記載の光導波路を製造する方法において、第１及び第２の光照射は、光ファイバにより供給されることを特徴とする。
【００１３】
【作用及び発明の効果】
光導波路の作製には、例えばステップイッデックス型光ファイバ様の光導波路であればコア部とその周囲のクラッド部を構成する必要がある。請求項１に記載の発明では、光学材料によりコア部のみを形成したのち、当該コア部の外周の屈折率よりも、硬化後の屈折率が低い光硬化性樹脂を用い、当該光学材料の漏光を用いて極めて薄いクラッド部を表面に有する光導波路を作製することが可能となる（請求項１）。
【００１４】
この時、当該周囲の光硬化性樹脂を、硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液とし、漏光は第１の光硬化性樹脂を硬化させるが第２の光硬化性樹脂を硬化させないものとすると、当該漏光により、第１の光硬化性樹脂は未硬化の第２の光硬化性樹脂を取り込んだ形で硬化することとなる。この時、当該溶液の粘度に依存するが、光学材料からなるコア部の外周直近では混合溶液の組成に近く、そこから遠ざかるにつれて第１の光硬化性樹脂の体積割合が多くなることとなる。このような状態で第１の光硬化性樹脂及び第２の光硬化性樹脂を共に硬化させると、もとの光学材料からなるコア部の外周に、屈折率分布が単調減少するような構造を形成することが可能となる（請求項２）。ここで例えば、もとの光学材料からなるコア部も中心付近から外周にかけて屈折率分布が単調減少するような構造であれば、コアとクラッドとの２段に屈折率が単調減少する光導波路を形成することができる。
【００１５】
硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液を用い、第１の光硬化性樹脂を硬化させるが第２の光硬化性樹脂を硬化させない第１の光照射を行うと、第２の光硬化性樹脂を取り込む形で第１の光硬化性樹脂を硬化させることが可能である。この時の光照射は第１の光硬化性樹脂硬化物から第２の光硬化性樹脂が散逸しないよう、強度を強くする必要がある。また、硬化すると屈折率が上昇するので、これにより自己集光現象が生じて光路部分が形成されることとなる。ここで形成される光学的に透明な光路部分は、第１の光硬化性樹脂硬化物と未硬化の第２の光硬化性樹脂の混合状態であるので、光伝送方向の周囲に漏光を発するようになる。そこでこのような漏光、即ち第１の光照射と同様に第２の光照射を行って光伝送方向の周囲に生じる漏光により光路部分外周の第１の光硬化性樹脂を硬化させると、当該漏光は光路部分を形成した際の光照射よりも弱いので、第１の光硬化性樹脂硬化物に取り込まれる第２の光硬化性樹脂が少ないように、即ち、第１の光硬化性樹脂硬化物から第２の光硬化性樹脂が散逸しやすいようにすることができる。すると、少なくとも光路部分の第１の光硬化性樹脂硬化物の体積割合よりも第１の光硬化性樹脂硬化物の体積割合の高い周囲部分を形成することが可能となる。こののち、全体の未硬化樹脂を硬化させれば、光路部分及びその外周の、第１の光硬化性樹脂硬化物に取り込まれた未硬化の第２の光硬化性樹脂をも硬化できる。すると、光路部分の少なくとも中心部分はもとの混合溶液の硬化物の混合比となり、光路部分の外周部はもとの混合溶液の硬化物の混合比よりも第１の光硬化性樹脂硬化物の割合が高くなり、更にその外周は混合溶液の硬化物の混合比で光硬化性樹脂硬化物が形成される。このとき第１の光硬化性樹脂の屈折率が第２の光硬化性樹脂の屈折率よりも低いのであるから、第１の光硬化性樹脂硬化物の割合が高い外周部は屈折率が光路部分より小さくなり、クラッドとして働くこととなる。このようにして、光導波路を容易に形成することができる（請求項３）。尚、本発明においては光路部分の中心から、外周部の最も屈折率の低い部分にかけて、屈折率が連続的に減少していくもの、段階的に減少するもの、それらいずれをも排除するものではない。本明細書では屈折率が連続的に減少していく場合にも「コア、クラッド」の表現をあえて用いる。
【００１６】
クラッドの第１の光硬化性樹脂硬化物を形成したのちに、外周部（クラッド）と光路部分（コア）を混合溶液から取り出し、未硬化の第２の光硬化性樹脂を硬化させれば、「コア、クラッド」のみからなる光導波路を容易に形成することができる（請求項４）。第１の光照射と第２の光照射は同時に行っても良い（請求項５）。これは実質的に第１の光照射が、請求項３、４で言う第１の光硬化工程と第２の光硬化工程が同時進行的に行われるものを言い、第１の光照射と第２の光照射が実質的に例えば１つの波長の光照射で同時に行われる場合を含む。
【００１７】
自己集光現象を生じさせるための光照射の形状が、光路部分を決定するのであるので、軸状の光照射を行えば軸状の光路部分が自己集光現象により容易に形成される。よって、光ファイバにより第１及び第２の光照射を行うと、軸状の光路部分（コア）を容易に形成することができる（請求項６）。ここで「軸状」とは完全な円柱状を言うものではなく、一部にテーパを有する様なものであっても良く、ミラーを置いて屈曲部を設けるような場合も本願発明に包含される。
【００１８】
【発明の実施の形態】
以下、本発明の具体的な実施例について説明する。
【００１９】
〔第１実施例〕
ビスフェノールＡグリシジルエーテル（旭電化工業、商品名「アデカオプトマーＫＲＭ−２４０５」、屈折率１．５７３）５０部、ＥＯ変性トリメチロールプロパントリアクリレート（サートマー社製、商品名ＳＲ−４５４、屈折率１．４７１）５０部、ラジカル重合開始剤としてビス（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（チバスペシャリティ・ケミカルズ社製、商品名「ＩＲＵＧＡＣＵＲＥ８１９」λｒ＝４６０ｎｍ）１．０部、カチオン重合開始剤としてプロピレンカーボネート溶媒に希釈したビス（ｐ−ｔ−ブチルフェニル）スルホニウム及びトリアリールスルホニウムのヘキサフルオロリン酸塩（ユニオンカーバイド社製、商品名「ＵＶＩ−６９９０」）３．０部を混合し、光硬化性樹脂の混合溶液を作製した。この混合溶液の硬化前の屈折率は１．５２１であり、紫外線照射により、ラジカル重合性材料、カチオン重合性材料を共に硬化させたときの全体の屈折率は１．５５１であった。
【００２０】
透明容器１に上記混合溶液２を充たし、プラスチック光ファイバ３（三菱レイヨン製、商品名「エスカメガ」、コア径０．９８ｍｍ、クラッド径１．０ｍｍ、開口数０．３）の片側の先端を浸漬した（図１の（ａ））。このプラスチック光ファイバ３の他端からレーザー光（波長λ_１＝４８８ｎｍ）を入射し、浸漬したプラスチック光ファイバ３の先端から透明容器１中の光硬化性樹脂の混合溶液２に出射し、自己形成法にて光硬化性樹脂を軸状に硬化させた。この時、ＥＯ変性トリメチロールプロパントリアクリレートはラジカル重合するが、ビスフェノールＡグリシジルエーテルはカチオン重合しない。５２秒で長さ１８ｍｍのコア４が形成されたのが観察されたが、以下に述べる通りこれはビスフェノールＡグリシジルエーテルを取り込んだ形でＥＯ変性トリメチロールプロパントリアクリレートがラジカル重合したものである。こののちもレーザー光（波長λ_１＝４８８ｎｍ）の照射を継続したところ、軸状のコア４から硬化していない光硬化性樹脂溶液の混合溶液に向けて散乱光が観察された（図１の（ｂ））。レーザー光（波長λ_１＝４８８ｎｍ）の照射を５分行ったのち、透明容器１の周囲から高圧水銀ランプにより紫外線ＵＶを一様に照射して、透明容器１中のビスフェノールＡグリシジルエーテルとＥＯ変性トリメチロールプロパントリアクリレートを全て硬化させ、軸状のコア部４を有する光導波路とした。
【００２１】
このようにして軸状のコア部を有する光導波路を長さ１５ｍｍに切断し、波長６５０ｎｍのレーザー光に対する挿入損失を測定したところ、２．２５ｄＢであった。カットバック法により波長６５０ｎｍのレーザー光に対する伝送損失と接続損失を測定したところ、各々１．４４ｄＢ／ｃｍ、０．１５ｄＢであった。二光束干渉顕微鏡により屈折率分布を測定したところ、光導波路の長さ方向に垂直な方向に屈折率分布が見られ、軸状のコア部を覆うように低屈折率部分が膜状に形成されていることが観察され、それらの屈折率の差は最大０．０１５７であった。透明容器中の屈折率は、当該最も屈折率の低い膜状部分５を谷として、軸状のコア部４の屈折率と透明容器中のその他の部分２’の屈折率は、上記ラジカル重合性材料、カチオン重合性材料を共に硬化させたときの全体の屈折率である１．５５１にほぼ等しいものであった。また、コア部４の屈折率は中心部から外周に向かって連続的に減少するものであった。この屈折率の概略を図２に示す。
【００２２】
〔検証実験１〕
実施例１で用いた光硬化性樹脂の混合溶液を透明ガラス製毛細管（内径１．０ｍｍ、肉厚０．２ｍｍ、長さ２４ｍｍ、屈折率１．４７２）に注入した。この透明ガラス製毛細管の一端に実施例１で用いたプラスチック光ファイバの先端を挿入して固定した。こうしてプラスチック光ファイバの他端からレーザー光（波長４８８ｎｍ）を入射して光の伝搬状況を観察した。プラスチック光ファイバの出射光は、屈折率１．４７２の透明ガラス製毛細管をクラッドとして、硬化前屈折率１．５２１の光硬化性樹脂の混合溶液を伝搬すると同時に、毛細管側方へも散乱することが確認された。この散乱光は光硬化性樹脂の混合溶液が、屈折率の大きく異なるモノマーを含むために、大きな屈折率揺らぎを有することにより発生するものと考えられる。
【００２３】
〔検証実験２〕
透明容器中に、ＥＯ変性トリメチロールプロパントリアクリレート（上記）とラジカル重合開始剤としてビス（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（上記）の混合液を充たした。ＥＯ変性トリメチロールプロパントリアクリレート１００部に対しラジカル重合開始剤を１部の混合比とした。ここに、検証実験１と同様にプラスチック光ファイバの先端を挿入し、実施例１で用いた光硬化性樹脂の混合溶液を注入した透明ガラス製毛細管を浸漬した。こうしてプラスチック光ファイバの他端からレーザー光（波長４８８ｎｍ）を照射パワー３０ｍＷで５分間入射させた。こののち、光硬化性樹脂の混合溶液を注入した透明ガラス製毛細管を引き上げ、透明ガラス製毛細管外壁の未硬化の混合液を有機溶媒にて除去した。電子顕微鏡で透明ガラス製毛細管外壁を観察したところ、膜厚２０μｍ程度の高分子重合体が付着していることが確認された。これは、透明容器中のＥＯ変性トリメチロールプロパントリアクリレートが、光硬化性樹脂の混合溶液を注入した透明ガラス製毛細管から側方に漏れだした散乱光により硬化したことを意味する。
【００２４】
〔検証実験３〕
透明容器１中に、実施例１で用いた光硬化性樹脂の混合溶液２を充たした。ここに、検証実験１と同様にプラスチック光ファイバ３の先端を挿入し、実施例１で用いた光硬化性樹脂の混合溶液２を注入した透明ガラス製毛細管１０を浸漬した（図３の（ａ））。こうしてプラスチック光ファイバの他端からレーザー光（波長λ_１＝４８８ｎｍ）を入射させ、所定時間の照射ののち（図３の（ｂ）、（ｃ））、透明容器の周囲から紫外線ＵＶを照射して、全ての未反応の樹脂を硬化させた（図３の（ｄ））。レーザー光（波長４８８ｎｍ）の照射パワーと照射時間を変化させて入射させたものにつき、各々二光束干渉顕微鏡により、透明ガラス製毛細管１０外壁から側方（毛細管の長さ方向に対して垂直方向）に向けての屈折率分布を測定した。その結果を図４、図５、図６に示す。
【００２５】
図４は、照射パワーを３０ｍＷ、照射時間を１分としたときの屈折率分布である。毛細管１０からの距離０μｍと、２０μｍ以上では屈折率は１．５５１で、光硬化性樹脂の混合溶液２がそのまま硬化した状態であることが理解できる。一方、毛細管１０からの距離２０μｍ以下では、８μｍにて屈折率が最小値１．５３８となる屈折率の谷部が形成されている。これはこの位置において、低屈折率のＥＯ変性トリメチロールプロパントリアクリレートの硬化物の濃度が高いことを意味している。
【００２６】
図５は照射パワーを３０ｍＷで固定し、照射時間を変化させた場合の屈折率の差の最大値を示したものである。また、図６は照射時間を５分に固定し、照射パワーを変化させた場合の屈折率の差の最大値を示したものである。図５、６から、照射パワーが大きいほど、また、照射時間が長いほど最大屈折率差が大きいことが理解できる。
【００２７】
さらに、図７は、照射パワーを５０ｍＷ、照射時間を２０分として、屈折率差の導波路の長さ方向の分布を示したものである。照射パワーと照射時間を２０分とし調整することで、屈折率差の長さ方向での変化を小さくできることがわかる。このように、本発明は光学部品の製造方法として有効であることがわかった。
【００２８】
検証実験１乃至３は、透明ガラス製毛細管を用いて行ったものであるが、実施例１においても、原理的には検証実験３と同様の現象により低屈折率部分が形成されたものと考えられる。また、検証実験１乃至３は、透明ガラス製毛細管に高屈折率の光硬化性樹脂の混合溶液を充たしたもので実験をおこなったが、例えば検証実験２で、側方に散乱光を生じる高屈折率の光学部品を低屈折率の光硬化性樹脂に浸漬させて、散乱光にて低屈折率の光硬化性樹脂皮膜を形成することも本願発明に包含される。尚、検証実験２は本発明の請求項１の実施例に、検証実験３は本発明の請求項２の実施例に相当するものである。
【００２９】
〔第２実施例〕
第１実施例と同様に、透明容器１に第１実施例で用いた混合溶液２を充たし、プラスチック光ファイバ３の片側の先端を浸漬した。このプラスチック光ファイバ３の他端からレーザー光（波長λ_１＝４８８ｎｍ）を入射し、浸漬したプラスチック光ファイバ３の先端から透明容器１中の光硬化性樹脂の混合溶液２に出射し、自己形成法にて光硬化性樹脂を軸状に硬化させた。こののち、レーザー光を切り換えて（波長λ_２＝４５８ｎｍ）、同様に照射したところ、軸状のコア４から硬化していない光硬化性樹脂溶液の混合溶液に向けて散乱光が観察された。こののち透明容器１の周囲から高圧水銀ランプにより紫外線ＵＶを一様に照射して、透明容器１中の混合溶液２を全て硬化させ、軸状のコア部４を有する光導波路とした。この光導波路の特性は、伝送損失が１．８ｄＢ／ｃｍ、接続損失が０．１３ｄＢ／ｃｍ（いずれも波長６５０ｎｍの光に対する値）、最大屈折率差が０．０１６４であった。
【００３０】
〔第３実施例〕
２枚の透明ガラス板を用意し、間隙を１５０μｍとして重ね合わせるようにして周囲を固着し、当該間隙に第１実施例で用いた混合溶液２を充たした。これを水平におき、一方のガラス板表面に直線上の明暗パターンを有するフォトマスクを形成した。明部、即ちフォトマスクの形成されていない部分は幅２００μｍとした。こうして当該明部に対してレーザー光（波長λ_１＝４８８ｎｍ）を１５秒間、一様に照射した。次にマスクを外してガラス板を通して混合溶液２全体にレーザー光を走査して、混合溶液２を硬化させた。二光束干渉顕微鏡により屈折率分布を測定したところ、ガラス面とマスク明部の長手方向に平行方向に、幅２００μｍのストライプ状の高屈折率部分の両側に若干の屈折率の低下した、幅約１５μｍのストライプ状の低屈折率部分が形成されていることが確認された。当該２つの低屈折率部分は、いずれもその両側が高屈折率部分であり、屈折率分布はなめらかな谷を２箇所形成するものであった。当該低屈折率部分の最低屈折率と高屈折率部分の屈折率との差は０．００４であった。一方、各部分において、ガラス面に垂直方向には屈折率の変化が無かった。ガラス板として混合溶液の硬化物（高屈折率部分）よりも屈折率の小さいものを用いると、幅２００μｍの高屈折率部分は、２枚のガラス板と両脇の低屈折率硬化物部分を有し、光導波路として用いることができる。この場合は、高屈折率部分を形成する際の光照射方向（ガラス面に垂直）と、形成した光導波路の光伝送方向（ガラス面に平行で、マスク明部の長手方向）が異なる方向となっているが、第１、第２実施例と同様に、好適な位置に低屈折率硬化物部分が形成されたことが確認された。即ち、やはり本実施例においても散乱光が生じ、低屈折率の硬化物がより多い部分が形成されたことが確認された。この方法によれば光ファイバを用いることなく、任意幅の光路を形成することが可能となる。
【００３１】
〔検証実験４〕
本発明による「コア形成」の中途の状態を確認するため、次のような検証実験を行った。即ち、第１実施例と同様に、透明容器１に第１実施例で用いた混合溶液２を充たし、プラスチック光ファイバ３の片側の先端を浸漬した。このプラスチック光ファイバ３の他端からレーザー光（波長λ_１＝４８８ｎｍ）を入射し、浸漬したプラスチック光ファイバ３の先端から透明容器１中の光硬化性樹脂の混合溶液２に出射し、自己形成法にて光硬化性樹脂の硬化を開始させて３０秒で当該光照射を停止し、直ぐに透明容器１の周囲から高圧水銀ランプにより紫外線ＵＶを一様に照射して、透明容器１中の混合溶液２を全て硬化させた。すると、光ファイバ３の先端から波長λ_１の入射方向に１０ｍｍの位置においては、もはや低屈折率部分は見当たらなかった。一方、光ファイバ３の先端から波長λ_１の入射方向に２ｍｍの位置においては、低屈折率部分が既に形成されており、最大屈折率差は約０．００２であった。即ち、当該２ｍｍの位置では既に、コアと、不十分ながらクラッド部が形成され始めていることが確認された。このように、本発明においては、高屈折率部分であるコアの形成中に、低屈折率分であるクラッドの形成が実質的には開始していることが確認された。
【図面の簡単な説明】
【図１】第１実施例の実施工程を示す工程図。
【図２】第１実施例にて形成された光導波路の光伝送方向に垂直な断面における屈折率分布。
【図３】検証実験３の実施工程を示す工程図。
【図４】検証実験３にて形成された、毛細管外部の毛細管長さ方向に垂直な断面における屈折率分布。
【図５】照射パワーを固定し、照射時間を変化させた場合の屈折率の差の最大値を示したグラフ図。
【図６】照射時間を固定し、照射パワーを変化させた場合の屈折率の差の最大値を示したグラフ図。
【図７】屈折率差の導波路の長さ方向の分布を示したグラフ図。
【符号の説明】
１透明容器
１０透明ガラス毛細管
２混合溶液
２’ 混合溶液の硬化物
３光ファイバ
４コア部
５クラッド部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a simple and inexpensive method for manufacturing an optical transmission line and a composition of a material suitable for the method. INDUSTRIAL APPLICABILITY The method of manufacturing an optical waveguide according to the present invention is applicable to the manufacture of optical waveguide components such as inexpensive and low-loss optical interconnections, optical demultiplexers and multiplexers in the field of optical fiber communication.
[0002]
[Prior art]
A technique of forming an optical waveguide device by introducing a beam of light having a predetermined wavelength into a photocurable resin solution and utilizing a self-condensing phenomenon has attracted attention. For example, there is a method of manufacturing an optical waveguide described in Patent Literatures 1 and 2 by the present applicant. In addition, techniques described in Patent Literatures 3 and 4 are known as applicants other than the present applicant.
[0003]
[Patent Document 1]
JP 2000-347043 A
[Patent Document 2]
JP-A-2002-169038
[Patent Document 3]
JP-A-2002-31733
[Patent Document 4]
JP-A-2002-258095
[0004]
According to this manufacturing method, first, a mixed solution of a high-refractive-index photocurable resin and a low-refractive-index photocurable resin is filled in a predetermined container. Next, the tip of the optical fiber is immersed in the mixed solution, and light in a specific wavelength band for curing only the high-refractive-index photocurable resin is introduced through the optical fiber. Then, by the light emitted from the tip of the optical fiber, a cured product having a high refractive index having a diameter substantially equal to the core diameter of the optical fiber can be gradually formed from the tip of the optical fiber by utilizing the self-focusing phenomenon. Thereafter, the mixed solution of the high-refractive-index and low-refractive-index photocurable resins remaining in the solution is entirely irradiated with light in a predetermined wavelength band so that both resins are photocured. This is a technique for forming an optical waveguide having a step-like refractive index distribution by forming a cured product having a low refractive index around the previously formed cured product having a high refractive index.
[0005]
[Problems to be solved by the invention]
In the techniques disclosed in Patent Literatures 1 and 2, the refractive index distribution basically has a step-like stepwise shape. Here, in order to increase the refractive index difference between the core (high-refractive-index portion) and the clad (low-refractive-index portion), it is necessary to lengthen the core formation time and selectively polymerize only the high-refractive-index material. Yes, productivity does not improve. The same can be said for Patent Documents 3 and 4.
[0006]
The present inventors have reversed the combination of the photocurable resin and introduced light of a specific wavelength band for curing only the low-refractive-index photocurable resin through an optical fiber. It has been found that an optically transparent optical path portion (core) can be formed by polymerizing and curing a low-refractive-index photocurable resin into a pattern corresponding to the shape of light irradiation in the loaded state. Note that the incorporated high-refractive-index photocurable resin is not cured in this state. Next, when light of a specific wavelength band that continuously cures only the low refractive index material is continuously applied to the optical transmission path for a certain period of time or more, the light component due to leakage or scattering from the optical transmission path causes a low surface of the optical path. Only the photocurable resin having a refractive index selectively polymerizes, and a layer of a polymer cured product (pseudo-cladding layer) having a lower refractive index than the light transmission path portion is formed. In this state, even if the photocurable resin having a high refractive index is taken into the surface of the optical path portion, the photocurable resin having a high refractive index is not cured. Thereafter, the mixed solution of the high-refractive index and the low-refractive index photocurable resin remaining in the solution is irradiated with light in a specific wavelength band where both resins are photocured, thereby forming a cured product having a low refractive index formed earlier. A cured product (base portion) having a high refractive index is formed around the layer, and a high refractive index coated on a low refractive index portion held by the high refractive index portion (base portion) in a cross section orthogonal to the light irradiation direction. It has been found that a partial refractive index distribution can be formed.
[0007]
That is, based on this finding, the present invention provides a method for manufacturing an optical waveguide having an optical path having a low refractive index portion formed on its surface by performing selective photocuring, which is extremely slow due to light leakage.
[0008]
[Means for Solving the Problems]
The means according to claim 1, which is responsible for light transmission, and has a photocurable resin having a post-curing refractive index lower than the refractive index of the outer periphery of the optical member on the surface of the optical member that emits light to the periphery. And curing and adhering the resin by light leakage, and a method of manufacturing an optical waveguide having an outer periphery coated with a cured photocurable resin having a lower refractive index.
[0009]
According to a second aspect of the present invention, in addition to the first aspect, the photocurable resin cured product has a low refractive index first photocurable resin and a high refractive index first photocurable resin having different curing mechanisms. Wherein the light leakage cures the first light-curable resin but does not cure the second light-curable resin. Further comprising a step of curing both the first photocurable resin and the second photocurable resin after curing the photocurable resin, and the refractive index of the cured photocurable resin is determined from the surface of the optical member. The refractive index is monotonously reduced in at least a part of the distance.
[0010]
The means according to claim 3 uses a mixed solution of a first photocurable resin having a low refractive index and a second photocurable resin having a high refractive index having different curing mechanisms, and the first photocurable resin is used. The first light-curing resin is cured by taking in the second light-curing resin by irradiating the first light that cures the resin but does not cure the second light-curing resin. A first light-curing step for forming a portion, and a second light irradiation for curing the first light-curable resin but not the second light-curable resin after forming the optical path portion with the first light Irradiation is performed in the same manner as the irradiation to cure the first photocurable resin on the surface of the optical path portion, and to cure both the first photocurable resin and the second photocurable resin. The second light-curable resin taken into the light path by the third light irradiation, and the entire uncured remaining mixed solution And a third light-curing step of curing, a high light path portion refractive index, a method of manufacturing an optical waveguide having a low refractive index portion of the surface. Here, irradiating the second light irradiation in the same manner as the first light irradiation does not mean intensity but means that the irradiation direction and the irradiation shape are the same. When the wavelength is different from that of the first light irradiation, the wavelength of the irradiation light is switched, and when the wavelength is the same, the irradiation direction and the irradiation shape are continued. At this time, the light intensity of the first light irradiation and the second light irradiation is arbitrary. This applies to other claims of the present application.
[0011]
According to a fourth aspect of the present invention, a portion cured by the third aspect is taken out of the uncured solution and separately cured. That is, the first photocurable resin is cured using a mixed solution of the first photocurable resin having a low refractive index and the second photocurable resin having a high refractive index, which have different curing mechanisms, but the second light is cured. First light curing for curing the first photocurable resin by taking in the second photocurable resin by the first light irradiation that does not cure the curable resin, and forming an optically transparent optical path portion Forming a light path portion, and then irradiating a second light irradiation that cures the first photocurable resin but does not cure the second light curable resin in the same manner as the first light irradiation, A second photo-curing step of curing the first photo-curable resin on the surface of the portion, and taking out an optical path portion and a surface portion made of the first photo-curable resin cured in a form incorporating the second photo-curable resin A third light irradiation for curing both the first photocurable resin and the second photocurable resin, A third photo-curing step of curing the second photo-curable resin taken into the portion, and the remaining uncured first photo-curable resin, and an optical path portion having a high refractive index; And a method of manufacturing an optical waveguide having a low refractive index portion.
[0012]
According to a fifth aspect of the present invention, in the method for manufacturing an optical waveguide according to the third or fourth aspect, the first light irradiation and the second light irradiation are simultaneously performed to form the optical path portion. The first light-curable resin is cured on the side surface of the optical path portion. Furthermore, a means according to claim 6 is the method for manufacturing an optical waveguide according to claims 3 to 5, wherein the first and second light irradiations are supplied by an optical fiber. .
[0013]
[Action and effect of the invention]
For manufacturing an optical waveguide, for example, in the case of an optical waveguide such as a step-index type optical fiber, it is necessary to configure a core portion and a clad portion around the core portion. According to the first aspect of the present invention, after forming only the core portion with the optical material, a light-curing resin having a lower refractive index after curing than the refractive index of the outer periphery of the core portion is used, and light leakage of the optical material is performed. It is possible to fabricate an optical waveguide having an extremely thin clad portion on the surface by using (1).
[0014]
At this time, the surrounding photocurable resin is a mixed solution of a first photocurable resin having a low refractive index and a second photocurable resin having a high refractive index having different curing mechanisms, and light leakage is caused by the first light. Assuming that the curable resin is cured but the second photocurable resin is not cured, the light leakage cures the first photocurable resin in a form incorporating the uncured second photocurable resin. It will be. At this time, although depending on the viscosity of the solution, the composition of the mixed solution is close to the outer periphery of the core portion made of the optical material, and the volume ratio of the first photocurable resin increases as the distance from the mixture increases. When the first photocurable resin and the second photocurable resin are cured together in such a state, a structure in which the refractive index distribution monotonously decreases around the core portion made of the original optical material. It can be formed (claim 2). Here, for example, if the core portion made of the original optical material also has a structure in which the refractive index distribution monotonically decreases from the vicinity of the center to the outer periphery, an optical waveguide in which the refractive index monotonically decreases in two stages of the core and the clad is used. Can be formed.
[0015]
The first photocurable resin is cured using a mixed solution of the first photocurable resin having a low refractive index and the second photocurable resin having a high refractive index, which have different curing mechanisms, but the second photocurable resin is cured. When the first light irradiation that does not cure the resin is performed, the first light-curable resin can be cured in a form in which the second light-curable resin is incorporated. At this time, it is necessary to increase the intensity of the light irradiation so that the second photocurable resin does not dissipate from the first photocurable resin cured product. Further, when cured, the refractive index increases, which causes a self-condensing phenomenon to form an optical path portion. Since the optically transparent optical path portion formed here is a mixed state of the first cured photo-curable resin and the uncured second photo-curable resin, it emits light around the light transmission direction. Become like Accordingly, such light leakage, that is, the second light irradiation similar to the first light irradiation is performed to cure the first photocurable resin around the optical path portion by the light leakage generated around the light transmission direction. Is weaker than the light irradiation at the time of forming the optical path portion, so that the second photocurable resin taken in the first photocurable resin cured product is small, that is, the first photocurable resin cured product Therefore, the second photocurable resin can be easily dissipated. Then, it is possible to form a peripheral portion in which the volume ratio of the first cured photocurable resin is higher than the volume ratio of the first cured photocurable resin at least in the optical path portion. After that, if the entire uncured resin is cured, the uncured second photocurable resin taken into the first cured photocurable resin at the optical path portion and its outer periphery can also be cured. Then, at least the central portion of the optical path portion has the mixing ratio of the cured product of the original mixed solution, and the outer peripheral portion of the optical path portion has the first cured photocurable resin composition higher than the mixing ratio of the cured product of the original mixed solution. , And a photocurable resin cured product is formed on the outer periphery at the mixing ratio of the cured product of the mixed solution. At this time, since the refractive index of the first photo-curable resin is lower than the refractive index of the second photo-curable resin, the outer peripheral portion where the ratio of the first cured photo-curable resin is high has a refractive index of the optical path. It becomes smaller than the part and acts as a cladding. Thus, the optical waveguide can be easily formed (claim 3). In the present invention, the refractive index continuously decreases from the center of the optical path portion to the lowest refractive index portion of the outer peripheral portion, the refractive index decreases gradually, and neither of them is excluded. Absent. In the present specification, the expression “core, clad” is also used when the refractive index continuously decreases.
[0016]
After forming the first photocurable resin cured product of the clad, the outer peripheral portion (clad) and the optical path portion (core) are taken out from the mixed solution, and the uncured second photocurable resin is cured. An optical waveguide consisting only of “core, clad” can be easily formed (claim 4). The first light irradiation and the second light irradiation may be performed simultaneously (claim 5). This means that the first light irradiation is performed substantially simultaneously with the first light curing step and the second light curing step described in claims 3 and 4, and the first light irradiation and the second light curing step are performed simultaneously. This includes the case where the two light irradiations are performed substantially simultaneously by, for example, light irradiation of one wavelength.
[0017]
Since the shape of the light irradiation for causing the self-focusing phenomenon determines the optical path portion, if the axial light irradiation is performed, the axial light path portion is easily formed by the self-focusing phenomenon. Therefore, when the first and second light irradiations are performed by the optical fiber, the axial optical path portion (core) can be easily formed (claim 6). Here, the term "axial" does not mean a perfect columnar shape, but may be a shape having a taper in part, and a case where a mirror is provided to form a bent portion is also included in the present invention. You.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific examples of the present invention will be described.
[0019]
[First embodiment]
50 parts of bisphenol A glycidyl ether (Asahi Denka Kogyo, trade name "ADEKA OPTOMER KRM-2405", refractive index 1.573), EO-modified trimethylolpropane triacrylate (manufactured by Sartomer, trade name SR-454, refractive index 1) .471) 50 parts, as a radical polymerization initiator, 1.0 part of bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (trade name “IRUGACURE 819”, manufactured by Ciba Specialty Chemicals, λr = 460 nm), cationic polymerization As an initiator, 3.0 parts of hexafluorophosphate of bis (pt-butylphenyl) sulfonium and triarylsulfonium (trade name “UVI-6990” manufactured by Union Carbide) diluted in a propylene carbonate solvent were mixed. , Photo-curable resin mixed solution It was produced. The refractive index of the mixed solution before curing was 1.521, and the total refractive index when both the radical polymerizable material and the cationic polymerizable material were cured by ultraviolet irradiation was 1.551.
[0020]
A transparent container 1 is filled with the mixed solution 2 and one end of a plastic optical fiber 3 (manufactured by Mitsubishi Rayon, trade name "Eskamega", core diameter 0.98 mm, clad diameter 1.0 mm, numerical aperture 0.3) is immersed in one end. (FIG. 1A). From the other end of the plastic optical fiber 3, laser light (wavelength λ ₁ = 488 nm), and emitted from the tip of the immersed plastic optical fiber 3 to the mixed solution 2 of the photocurable resin in the transparent container 1, and the photocurable resin was axially cured by a self-forming method. At this time, EO-modified trimethylolpropane triacrylate undergoes radical polymerization, but bisphenol A glycidyl ether does not undergo cationic polymerization. It was observed that a core 4 having a length of 18 mm was formed in 52 seconds, but as described below, this was a radical polymerization of EO-modified trimethylolpropane triacrylate in a form incorporating bisphenol A glycidyl ether. The laser light (wavelength λ) ₁ (488 nm), scattered light was observed from the axial core 4 toward the uncured mixed solution of the photocurable resin solution (FIG. 1B). Laser light (wavelength λ ₁ = 488 nm) for 5 minutes, and then uniformly irradiate ultraviolet light UV from around the transparent container 1 with a high-pressure mercury lamp to remove bisphenol A glycidyl ether and EO-modified trimethylolpropane triacrylate in the transparent container 1. All were cured to obtain an optical waveguide having an axial core portion 4.
[0021]
The optical waveguide having the axial core portion was cut into a length of 15 mm in this way, and the insertion loss with respect to a laser beam having a wavelength of 650 nm was measured and found to be 2.25 dB. When the transmission loss and the connection loss with respect to the laser light having a wavelength of 650 nm were measured by the cutback method, they were 1.44 dB / cm and 0.15 dB, respectively. When the refractive index distribution was measured with a two-beam interference microscope, the refractive index distribution was observed in the direction perpendicular to the length direction of the optical waveguide, and the low refractive index portion was formed in a film shape so as to cover the axial core. And the difference between the refractive indices was 0.0157 at the maximum. The refractive index in the transparent container is defined as the valley of the film-shaped portion 5 having the lowest refractive index, and the refractive index of the axial core portion 4 and the refractive index of the other portion 2 ′ in the transparent container are the same as those of the radical polymerizable polymer. The refractive index was approximately equal to 1.551 which is the total refractive index when both the material and the cationically polymerizable material were cured. Further, the refractive index of the core portion 4 was continuously reduced from the center to the outer periphery. FIG. 2 schematically shows the refractive index.
[0022]
[Verification experiment 1]
The mixed solution of the photocurable resin used in Example 1 was injected into a transparent glass capillary tube (inner diameter 1.0 mm, wall thickness 0.2 mm, length 24 mm, refractive index 1.472). The tip of the plastic optical fiber used in Example 1 was inserted and fixed to one end of the transparent glass capillary. In this way, laser light (wavelength 488 nm) was incident from the other end of the plastic optical fiber, and the light propagation state was observed. The light emitted from the plastic optical fiber propagates through a mixed solution of a photocurable resin having a refractive index of 1.521 before curing, using a transparent glass capillary having a refractive index of 1.472 as a cladding, and simultaneously scatters to the side of the capillary. Was confirmed. This scattered light is considered to be generated when the mixed solution of the photocurable resin has a large fluctuation in the refractive index because the mixed solution contains a monomer having a significantly different refractive index.
[0023]
[Verification experiment 2]
A transparent container was filled with a mixture of EO-modified trimethylolpropane triacrylate (described above) and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (described above) as a radical polymerization initiator. The mixing ratio of the radical polymerization initiator was 1 part with respect to 100 parts of the EO-modified trimethylolpropane triacrylate. Here, the tip of the plastic optical fiber was inserted as in the verification experiment 1, and the transparent glass capillary into which the mixed solution of the photocurable resin used in Example 1 was injected was immersed. Thus, a laser beam (wavelength: 488 nm) was irradiated from the other end of the plastic optical fiber at an irradiation power of 30 mW for 5 minutes. Thereafter, the transparent glass capillary into which the mixed solution of the photocurable resin was injected was pulled up, and the uncured mixed solution on the outer wall of the transparent glass capillary was removed with an organic solvent. When the outer wall of the transparent glass capillary was observed with an electron microscope, it was confirmed that a high-molecular polymer having a thickness of about 20 μm had adhered. This means that the EO-modified trimethylolpropane triacrylate in the transparent container was cured by scattered light leaking laterally from the transparent glass capillary into which the mixed solution of the photocurable resin was injected.
[0024]
[Verification experiment 3]
A mixed solution 2 of the photocurable resin used in Example 1 was filled in a transparent container 1. Here, the tip of the plastic optical fiber 3 was inserted as in the verification experiment 1, and the transparent glass capillary tube 10 into which the mixed solution 2 of the photocurable resin used in Example 1 was injected was immersed ((a in FIG. 3) )). Thus, the laser light (wavelength λ) ₁ = 488 nm), and after irradiation for a predetermined time (FIGS. 3B and 3C), UV light was irradiated from around the transparent container to cure all unreacted resins (FIG. 3). 3 (d)). The laser beam (wavelength: 488 nm) was irradiated at different irradiation powers and irradiation times, and each was irradiated laterally (perpendicular to the longitudinal direction of the capillary) from the outer wall of the transparent glass capillary 10 by a two-beam interference microscope. The refractive index distribution toward was measured. The results are shown in FIG. 4, FIG. 5, and FIG.
[0025]
FIG. 4 shows the refractive index distribution when the irradiation power is 30 mW and the irradiation time is 1 minute. At a distance of 0 μm from the capillary 10 and at a distance of 20 μm or more, the refractive index is 1.551, and it can be understood that the mixed solution 2 of the photocurable resin is cured as it is. On the other hand, at a distance of 20 μm or less from the capillary 10, a valley of the refractive index at which the refractive index has a minimum value of 1.538 at 8 μm is formed. This means that at this position, the concentration of the cured product of the low refractive index EO-modified trimethylolpropane triacrylate is high.
[0026]
FIG. 5 shows the maximum value of the difference in refractive index when the irradiation power is fixed at 30 mW and the irradiation time is changed. FIG. 6 shows the maximum value of the difference in the refractive index when the irradiation time is fixed to 5 minutes and the irradiation power is changed. 5 and 6, it can be understood that the larger the irradiation power and the longer the irradiation time, the larger the maximum refractive index difference.
[0027]
Further, FIG. 7 shows the distribution of the refractive index difference in the length direction of the waveguide when the irradiation power is 50 mW and the irradiation time is 20 minutes. It can be seen that by adjusting the irradiation power and the irradiation time to 20 minutes, the change in the refractive index difference in the length direction can be reduced. Thus, the present invention was found to be effective as a method for manufacturing an optical component.
[0028]
The verification experiments 1 to 3 were performed using a transparent glass capillary tube. In Example 1, it is considered that the low refractive index portion was formed by the same phenomenon as the verification experiment 3 in principle. Can be In the verification experiments 1 to 3, experiments were conducted using a transparent glass capillary tube filled with a mixed solution of a high-refractive-index photocurable resin. The present invention also includes immersing an optical component having a refractive index in a photocurable resin having a low refractive index to form a photocurable resin film having a low refractive index with scattered light. Verification experiment 2 corresponds to the embodiment of claim 1 of the present invention, and verification experiment 3 corresponds to the embodiment of claim 2 of the present invention.
[0029]
[Second embodiment]
In the same manner as in the first embodiment, the mixed solution 2 used in the first embodiment was filled in the transparent container 1, and one end of the plastic optical fiber 3 was immersed. From the other end of the plastic optical fiber 3, laser light (wavelength λ ₁ = 488 nm), and emitted from the tip of the immersed plastic optical fiber 3 to the mixed solution 2 of the photocurable resin in the transparent container 1, and the photocurable resin was axially cured by a self-forming method. After that, the laser light is switched (wavelength λ ₂ = 458 nm), similarly, scattered light was observed from the axial core 4 toward the uncured mixed solution of the photocurable resin solution. Thereafter, ultraviolet light UV was uniformly irradiated from the periphery of the transparent container 1 by a high-pressure mercury lamp, and the mixed solution 2 in the transparent container 1 was entirely cured to obtain an optical waveguide having an axial core 4. As the characteristics of this optical waveguide, the transmission loss was 1.8 dB / cm, the connection loss was 0.13 dB / cm (all values for light having a wavelength of 650 nm), and the maximum refractive index difference was 0.0164.
[0030]
[Third embodiment]
Two transparent glass plates were prepared, the gap was set to 150 μm, and the periphery was fixed so as to overlap each other, and the gap was filled with the mixed solution 2 used in the first example. This was placed horizontally, and a photomask having a linear light / dark pattern was formed on one glass plate surface. The bright portion, that is, the portion where the photomask was not formed, had a width of 200 μm. Thus, a laser beam (wavelength λ) ₁ = 488 nm) for 15 seconds. Next, the mask was removed and the mixed solution 2 was cured by scanning the entire mixed solution 2 with a laser beam through a glass plate. When the refractive index distribution was measured with a two-beam interference microscope, the refractive index was slightly reduced on both sides of a 200 μm-wide stripe-like high refractive index portion in a direction parallel to the glass surface and the longitudinal direction of the bright portion of the mask. It was confirmed that a 15 μm stripe-shaped low refractive index portion was formed. Both of the two low refractive index portions were high refractive index portions on both sides, and the refractive index distribution formed two smooth valleys. The difference between the lowest refractive index of the low refractive index portion and the refractive index of the high refractive index portion was 0.004. On the other hand, in each part, there was no change in the refractive index in the direction perpendicular to the glass surface. When a glass plate having a smaller refractive index than the cured product of the mixed solution (high refractive index portion) is used, a high refractive index portion having a width of 200 μm is formed by two glass plates and low refractive index cured portions on both sides. And can be used as an optical waveguide. In this case, the light irradiation direction (perpendicular to the glass surface) when forming the high refractive index portion is different from the light transmission direction (parallel to the glass surface and the longitudinal direction of the bright portion of the mask) of the formed optical waveguide. However, as in the first and second examples, it was confirmed that a low refractive index cured material portion was formed at a suitable position. That is, it was confirmed that scattered light was generated also in this example, and a portion having more cured material having a low refractive index was formed. According to this method, an optical path having an arbitrary width can be formed without using an optical fiber.
[0031]
[Verification experiment 4]
The following verification experiment was performed to confirm the halfway state of “core formation” according to the present invention. That is, similarly to the first example, the transparent container 1 was filled with the mixed solution 2 used in the first example, and one end of the plastic optical fiber 3 was immersed. From the other end of the plastic optical fiber 3, laser light (wavelength λ ₁ = 488 nm), emitted from the tip of the immersed plastic optical fiber 3 to the mixed solution 2 of the photocurable resin in the transparent container 1, and started curing of the photocurable resin by a self-forming method for 30 seconds. Then, the light irradiation was stopped, and immediately, UV light was uniformly irradiated from the periphery of the transparent container 1 with a high-pressure mercury lamp to cure the entire mixed solution 2 in the transparent container 1. Then, the wavelength λ from the tip of the optical fiber 3 ₁ No low refractive index portion was found anymore at a position of 10 mm in the direction of incidence. On the other hand, the wavelength λ ₁ At the position of 2 mm in the incident direction, a low refractive index portion was already formed, and the maximum refractive index difference was about 0.002. That is, it was confirmed that the core and the cladding part, though insufficient, were already formed at the position of 2 mm. Thus, in the present invention, it was confirmed that the formation of the clad having the low refractive index substantially started during the formation of the core which was the high refractive index portion.
[Brief description of the drawings]
FIG. 1 is a process chart showing an implementation process of a first embodiment.
FIG. 2 shows a refractive index distribution in a cross section perpendicular to the light transmission direction of the optical waveguide formed in the first embodiment.
FIG. 3 is a process diagram showing an implementation process of a verification experiment 3.
FIG. 4 shows a refractive index distribution in a cross section perpendicular to the capillary length direction outside the capillary formed in verification experiment 3.
FIG. 5 is a graph showing the maximum value of the difference in refractive index when the irradiation power is fixed and the irradiation time is changed.
FIG. 6 is a graph showing the maximum difference in refractive index when the irradiation time is fixed and the irradiation power is changed.
FIG. 7 is a graph showing the distribution of the refractive index difference in the length direction of the waveguide.
[Explanation of symbols]
1 transparent container
10 Transparent glass capillary
2 Mixed solution
2 'Cured product of mixed solution
3 Optical fiber
4 core part
5 Cladding part

Claims

光伝送を担うものであって、周囲に漏光を発する光学部材の表面に、当該光学部材の外周の屈折率よりも低い硬化後屈折率を有する光硬化性樹脂を、前記漏光により硬化付着させることを特徴とする、外周をより低い屈折率を有する光硬化性樹脂硬化物で被覆された光導波路の製造方法。A light-curing resin that is responsible for light transmission and has a post-curing refractive index that is lower than the refractive index of the outer periphery of the optical member on the surface of the optical member that emits light leakage around the surface of the optical member. A method for producing an optical waveguide having an outer periphery covered with a cured photocurable resin having a lower refractive index.

前記光硬化性樹脂硬化物は硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液を硬化させて成るものであって、
前記漏光は前記第１の光硬化性樹脂を硬化させるが前記第２の光硬化性樹脂を硬化させないものであり、
前記漏光による前記第１の光硬化性樹脂を硬化させたのち前記第１の光硬化性樹脂及び前記第２の光硬化性樹脂を共に硬化させる工程を更に含み、
前記光硬化性樹脂硬化物の屈折率は、前記光学部材の表面から遠ざかる少なくとも一部において、屈折率が単調減少することを特徴とする請求項１に記載の光導波路の製造方法。The cured photo-curable resin is obtained by curing a mixed solution of a first photo-curable resin having a low refractive index and a second photo-curable resin having a high refractive index having different curing mechanisms,
The light leakage cures the first photocurable resin but does not cure the second photocurable resin,
After curing the first photocurable resin due to the light leakage, further comprising a step of curing the first photocurable resin and the second photocurable resin together,
The method of manufacturing an optical waveguide according to claim 1, wherein the refractive index of the cured photocurable resin decreases monotonously at least in a part away from the surface of the optical member.

硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液を用い、
前記第１の光硬化性樹脂を硬化させるが前記第２の光硬化性樹脂を硬化させない第１の光照射により、前記第２の光硬化性樹脂を取り込む形で前記第１の光硬化性樹脂を硬化させ、光学的に透明な光路部分を形成する第１の光硬化工程と、前記光路部分を形成した後、前記第１の光硬化性樹脂を硬化させるが前記第２の光硬化性樹脂を硬化させない第２の光照射を、前記第１の光照射と同様に照射して前記光路部分の表面に前記第１の光硬化樹脂を硬化させる第２の光硬化工程と、
前記第１の光硬化性樹脂と前記第２の光硬化性樹脂の両方を硬化させる第３の光照射により、前記光路部分に取り込まれた前記第２の光硬化性樹脂、並びに、未硬化の残余の混合溶液全体を硬化させる第３の光硬化工程とから成り、
屈折率の高い光路部分と、その表面の低屈折率部分とを有する光導波路を製造する方法。Using a mixed solution of a first photocurable resin having a low refractive index and a second photocurable resin having a high refractive index having different curing mechanisms,
A first light-curing resin that cures the first light-curable resin but does not cure the second light-curable resin, thereby taking in the second light-curable resin. A first light-curing step of curing the first light-curable resin to form an optically transparent optical path portion, and curing the first light-curable resin after forming the optical path portion, but the second light-curable resin A second light curing step of irradiating a second light irradiation not curing the same as the first light irradiation to cure the first light curable resin on the surface of the optical path portion;
By the third light irradiation for curing both the first light-curable resin and the second light-curable resin, the second light-curable resin taken in the optical path portion, and an uncured resin A third photo-curing step of curing the entire remaining mixed solution,
A method for producing an optical waveguide having an optical path portion having a high refractive index and a low refractive index portion on the surface thereof.

硬化機構の異なる低屈折率の第１の光硬化性樹脂と高屈折率の第２の光硬化性樹脂の混合溶液を用い、
前記第１の光硬化性樹脂を硬化させるが前記第２の光硬化性樹脂を硬化させない第１の光照射により、前記第２の光硬化性樹脂を取り込む形で前記第１の光硬化性樹脂を硬化させ、光学的に透明な光路部分を形成する第１の光硬化工程と、前記光路部分を形成した後、前記第１の光硬化性樹脂を硬化させるが前記第２の光硬化性樹脂を硬化させない第２の光照射を、前記第１の光照射と同様に照射して前記光路部分の表面に前記第１の光硬化樹脂を硬化させる第２の光硬化工程と、
前記第２の光硬化性樹脂を取り込んだ形で硬化した前記第１の光硬化樹脂からなる光路部分及び表面部分を前記混合溶液から取り出し、前記第１の光硬化性樹脂と前記第２の光硬化性樹脂の両方を硬化させる第３の光照射により、前記光路部分に取り込まれた前記第２の光硬化性樹脂、並びに、未硬化の残余の前記第１の光硬化性樹脂を硬化させる第３の光硬化工程とから成り、
屈折率の高い光路部分と、その表面の低屈折率部分とを有する光導波路を製造する方法。Using a mixed solution of a first photocurable resin having a low refractive index and a second photocurable resin having a high refractive index having different curing mechanisms,
A first light-curing resin that cures the first light-curable resin but does not cure the second light-curable resin, thereby taking in the second light-curable resin. A first light-curing step of curing the first light-curable resin to form an optically transparent optical path portion, and curing the first light-curable resin after forming the optical path portion, but the second light-curable resin A second light curing step of irradiating a second light irradiation not curing the same as the first light irradiation to cure the first light curable resin on the surface of the optical path portion;
An optical path portion and a surface portion made of the first photocurable resin cured in a form in which the second photocurable resin is taken in are taken out of the mixed solution, and the first photocurable resin and the second light are taken out. By the third light irradiation for curing both of the curable resins, the second light-curable resin taken into the optical path portion, and the remaining uncured first light-curable resin are cured. 3 light curing process,
A method for producing an optical waveguide having an optical path portion having a high refractive index and a low refractive index portion on the surface thereof.

前記第１の光照射と第２の光照射を同時に行い、前記光路部分を形成しながら、前記光路部分の側面に前記第１の光硬化性樹脂を硬化させることを特徴とする請求項３又は請求項４に記載の光導波路を製造する方法。4. The method according to claim 3, wherein the first light irradiation and the second light irradiation are performed simultaneously, and the first photocurable resin is cured on a side surface of the optical path portion while forming the optical path portion. 5. A method for manufacturing the optical waveguide according to claim 4.

前記第１の光照射は、光ファイバにより供給されることを特徴とする請求項３乃至請求項５のいずれか１項に記載の光導波路を製造する方法。The method for manufacturing an optical waveguide according to claim 3, wherein the first light irradiation is provided by an optical fiber.