JP4095122B2 - Optical resin material and manufacturing method thereof - Google Patents

Description

【００３４】
［上記（Ｉ）〜（ＩＶ）式において、ｓは０〜５、ｔは０〜４、ｕは０〜１、ｓ＋ｔ＋ｕは１〜６、ｐ，ｑ，ｒはそれぞれ０〜５、ｐ＋ｑ＋ｒは１〜６、ＲはＦまたはＣＦ₃、Ｒ¹はＦまたはＣＦ₃、Ｒ²はＦまたはＣＦ₃、Ｘ¹はＦまたはＣｌ、Ｘ²はＦまたはＣｌ、Ｘ³はＦまたはＣｌである。］
含フッ素脂肪族環構造を有する重合体は、主鎖に環構造を有する重合体が好適であり、含フッ素脂肪族環構造を有する重合体の全重合単位に対して環構造を有する重合単位を２０モル％以上、好ましくは４０モル％以上含有するものが透明性、機械的特性等の面から好ましい。
【００３５】
物質（ｂ）は、含フッ素重合体（ａ）との比較において屈折率の差が０．００１以上である少なくとも１種類の物質で、含フッ素重合体（ａ）と同様な理由から実質的にＣ−Ｈ結合を有しないものである。物質（ｂ）は、含フッ素重合体（ａ）よりも高屈折率であっても低屈折率であってもよい。光ファイバー等においては通常は含フッ素重合体（ａ）よりも高屈折率の物質を用いる。
【００３６】
物質（ｂ）としては、低分子化合物、オリゴマー、ポリマーいずれであってもく、フッ素、塩素、臭素またはヨウ素のハロゲン原子、ベンゼン環等の芳香族環、エーテル結合等の結合基を含むものが好ましい。物質（ｂ）は、通常含フッ素重合体（ａ）のガラス転移温度を低下させる物質から選ばれ、また含フッ素重合体（ａ）との屈折率の差は０．００５以上であることが好ましい。
【００３７】
物質（ｂ）は、含フッ素重合体（ａ）との比較において、溶解性パラメータの差が７（ｃａｌ／ｃｍ³)^1/2以内であることが好ましい。ここで溶解性パラメータとは物質間の混合性の尺度となる特性値であり、溶解性パラメータをδ、物質の分子凝集エネルギーをＥ、分子容をＶとして、式δ＝（Ｅ／Ｖ）^1/2で表される。
【００３８】
低分子化合物としては、例えば炭素原子に結合した水素原子を含まないハロゲン化芳香族炭化水素がある。特に、ハロゲン原子としてフッ素原子のみを含むハロゲン化芳香族炭化水素やフッ素原子と他のハロゲン原子を含むハロゲン化芳香族炭化水素が、含フッ素重合体（ａ）との相溶性の面で好ましい。また、これらのハロゲン化芳香族炭化水素は、カルボニル基、シアノ基などの官能基を有していないことがより好ましい。
【００３９】
このようなハロゲン化芳香族炭化水素としては、例えば式Φｒ−Ｚｂ［Φｒは水素原子のすべてがフッ素原子に置換されたｂ価のフッ素化芳香環残基、Ｚはフッ素以外のハロゲン原子、−Ｒｆ、−ＣＯ−Ｒｆ、−Ｏ−Ｒｆ、あるいは−ＣＮ。ただし、Ｒｆはパーフルオロアルキル基、ポリフルオロパーハロアルキル基、または１価のΦｒ。ｂは０または１以上の整数。］で表される化合物がある。芳香環としてはベンゼン環やナフタレン環がある。Ｒｆであるパーフルオロアルキル基やポリフルオロパーハロアルキル基の炭素数は５以下が好ましい。フッ素以外のハロゲン原子としては、塩素原子や臭素原子が好ましい。
【００４０】
具体的な化合物としては例えば、１，３−ジブロモテトラフルオロベンゼン、１，４−ジブロモテトラフルオロベンゼン、２−ブロモテトラフルオロベンゾトリフルオライド、クロロペンタフルオロベンゼン、ブロモペンタフルオロベンゼン、ヨードペンタフルオロベンゼン、デカフルオロベンゾフェノン、パーフルオロアセトフェノン、パーフルオロビフェニル、クロロヘプタフルオロナフタレン、ブロモヘプタフルオロナフタレンなどがある。
【００４１】
オリゴマーやポリマーである物質（ｂ）としては、前記したような含フッ素重合体（ａ）を形成するモノマーの重合体からなり、含フッ素重合体（ａ）との比較において屈折率の差が０．００１以上であるオリゴマーやポリマーであってもよい。このモノマーとしては、含フッ素重合体（ａ）との比較において屈折率の差が０．００１以上であるオリゴマーやポリマーを形成するものから選ばれる。たとえば、屈折率の異なる２種の含フッ素重合体（ａ）を用い、一方の重合体（ａ）を物質（ｂ）として他の重合体（ａ）中に分布させることができる。
【００４２】
オリゴマーやポリマーである物質（ｂ）としては、前記（Ｉ）〜（Ｖ）の繰り返し単位を有するものの内、組み合される含フッ素重合体（ａ）とは異なる屈折率を有する含フッ素重合体（例えば、ハロゲン原子としてフッ素原子のみを含む含フッ素重合体とフッ素原子と塩素原子を含む含フッ素重合体との組み合せ、異なる種類や異なる割合の２以上のモノマーを重合して得られた２種の含フッ素重合体の組み合せなど）が好ましい。
【００４３】
また、上記のごとき主鎖に環構造を有する含フッ素重合体以外に、テトラフルオロエチレン、クロロトリフルオロエチレン、ジクロロジフルオロエチレン、ヘキサフルオロプロピレン、パーフルオロアルキルビニルエーテルなどの水素原子を含まないモノマーからなるオリゴマー、これらモノマー２種以上からなる共重合オリゴマーなども物質（ｂ）として使用できる。また、−ＣＦ₂ＣＦ（ＣＦ₃）Ｏ−や−（ＣＦ₂）_nＯ−（ｎは１〜３の整数）の構造単位を有するパーフルオロポリエーテルなども使用できる。これらオリゴマーの分子量は、非結晶性となる分子量範囲から選ばれ、数平均分子量３００〜１０，０００が好ましい。拡散のしやすさを考慮すると、数平均分子量３００〜５０００がさらに好ましい。
【００４４】
特に好ましい物質（ｂ）は、含フッ素重合体（ａ）特に主鎖に環構造を有する含フッ素重合体との相溶性が良好であることなどから、クロロトリフルオロエチレンオリゴマーである。相溶性が良好であることにより、含フッ素重合体（ａ）、特に主鎖に環構造を有する含フッ素重合体、とクロロトリフルオロエチレンオリゴマーとを２００〜３００℃で加熱溶融により容易に混合させることができる。又、含フッ素溶媒に溶解させて混合した後、溶媒を除去することにより両者を均一に混合させることができる。クロロトリフルオロエチレンオリゴマーの好ましい分子量は、数平均分子量５００〜１５００である。
【００４５】
本発明の光学樹脂材料は、含フッ素重合体（ａ）中に物質（ｂ）が特定の方向に沿って濃度勾配を有して分布しているために、その分布状況によっては光学樹脂材料全体のガラス転移温度が実質的に均一とならないことがある。この場合、含フッ素重合体（ａ）中に物質（ｃ）を分布させることにより、物質（ｂ）の濃度分布によって変化した光学樹脂材料のガラス転移温度を修正でき、光学樹脂材料全体のガラス転移温度を実質的に均一とできる。
【００４６】
通常物質（ｂ）と（ｃ）はいずれも、含フッ素重合体（ａ）のガラス転移温度を低下させる物質から選ばれる。含フッ素重合体（ａ）中で物質（ｂ）の濃度が低いためにガラス転移温度が高くなる領域は、物質（ｃ）を分布させ物質（ｂ）と（ｃ）を混在させることによりガラス転移温度を低下させることができる。また、含フッ素重合体（ａ）中で物質（ｂ）または物質（ｃ）のみが分布する領域がある場合には、これらの領域と物質（ｂ）と（ｃ）が混在する領域のガラス転移温度が実質的に均一となるように、物質（ｂ）と（ｃ）の種類や濃度を選択する。図１に含フッ素重合体（ａ）と物質（ｃ）の混合物のガラス転移温度（Ｔｇ）が混合物中の物質（ｃ）の濃度が高くなるに従い低下する関係を示す。
【００４７】
したがって、例えば含フッ素重合体（ａ）のガラス転移温度を低下させる度合いが同じである物質（ｂ）と（ｃ）を使用し、含フッ素重合体（ａ）全体に物質（ｂ）と（ｃ）が分布している場合、物質（ｂ）と（ｃ）の合計の濃度を含フッ素重合体（ａ）全体で等しくするように両物質を分布させれば光学樹脂材料全体のガラス転移温度を実質的に均一とできる。含フッ素重合体（ａ）のガラス転移温度を低下させる度合いが物質（ｂ）と（ｃ）で異なる場合には、含フッ素重合体（ａ）中の両物質の分布の度合を調節することにより光学樹脂材料全体のガラス転移温度を実質的に均一とできる。
【００４８】
なお、「含フッ素重合体（ａ）、物質（ｂ）および物質（ｃ）の混合物」、「含フッ素重合体（ａ）と物質（ｂ）の混合物」または「含フッ素重合体（ａ）と物質（ｃ）を混合物」は均一な混合物とすることにより、これらの混合物には一定のガラス転移温度が存在する。
【００４９】
上記の本発明製造法（２）において、ノズル中心部に供給する材料は通常含フッ素重合体（ａ）と物質（ｂ）の混合物からなり、外周部に供給する材料は通常含フッ素重合体（ａ）からなる。同様に本発明製造法（３）において、プリフォームのコア部に相当する部分の材料は通常含フッ素重合体（ａ）と物質（ｂ）の混合物からなり、プリフォームのクラッド部に相当する部分の材料は通常含フッ素重合体（ａ）からなる。
【００５０】
ノズル中心部に供給する材料のガラス転移温度と外周部に供給する材料のガラス転移温度を実質的に均一にするためには、外周部に供給する含フッ素重合体（ａ）中に含フッ素重合体（ａ）と相溶性のある物質（ｃ）を混合することが有効である。同様にプリフォームのコア部に相当する部分の材料のガラス転移温度とプリフォームのクラッド部に相当する部分の材料のガラス転移温度を実質的に均一にするためには、クラッド部に相当する部分の含フッ素重合体（ａ）中に含フッ素重合体（ａ）と相溶性のある物質（ｃ）を混合することが有効である。
【００５１】
本発明製造法（２）の好ましい例は、ノズル中心部に供給する材料を、含フッ素重合体（ａ）と物質（ｂ）の混合物または物質（ｂ）とし、ノズル外周部に供給する材料を、含フッ素重合体（ａ）と物質（ｃ）を溶融混合して得た均一な混合物とする、ノズル中心部と外周部の２層からなる押し出し溶融成形法である。この場合、含フッ素重合体（ａ）と物質（ｃ）の混合物の溶融液の中心部に、含フッ素重合体（ａ）と物質（ｂ）の混合物または物質（ｂ）を注入し、物質（ｂ）および物質（ｃ）を拡散させながら、または拡散させた後に成形する方法が好ましい。
【００５２】
光学樹脂材料全体のガラス転移温度が実質的に均一である光学樹脂材料を得るために、本発明製造法（２）においてノズル中心部に供給する材料のガラス転移温度とノズル外周部に供給する材料のガラス転移温度を予め実質的に均一にする。
【００５３】
本発明の光学樹脂材料が物質（ｃ）を含む場合、上記好ましい方法の様に光学樹脂材料の中心部から周辺部に向かって物質（ｂ）が拡散する状況においては、それと同時に周辺部から中心に向かって物質（ｃ）が拡散するため、光学樹脂材料全体として均一なガラス転移温度が保持される。すなわち、中心部から周辺部に向かって物質（ｂ）が拡散すると、通常ガラス転移温度は通常中心部から周辺部に向かって変化するが、この変化分を補う様に周辺部から中心に向かって物質（ｃ）が拡散されてくるため、本発明製造法（２）においてノズル中心部に供給する重合体のガラス転移温度とノズル外周部に供給する重合体のガラス転移温度を予め実質的に均一にしておけば、最終的に光学樹脂材料全体のガラス転移温度が実質的に均一である光学樹脂材料が得られる。
【００５４】
ノズル中心部に供給する材料あるいはノズル外周部に供給する材料は、１層のみならず多層に注入してもよい。成形方法には光ファイバーのプリフォーム等のごときロッド状母材を成形するために適する押出溶融成形、光ファイバーを成形するために適する溶融紡糸成形等がある。
【００５５】
本発明製造法（３）において、プリフォームにはある程度以上の屈折率分布を形成しておくことが好ましい。プリフォームにはある程度以上の屈折率分布を形成しておくことにより、プリフォームから屈折率分布型光ファイバーを製造する効率が向上する。本発明製造法（３）の好ましい例には、以下の（４）〜（６）の方法がある。
【００５６】
（４）回転ガラス管などの回転管を利用して中空状の含フッ素重合体（ａ）と物質（ｃ）の均一混合体からなり、プリフォームのクラッド部に相当する管（チューブ）を形成し、この管の内部に物質（ｂ）を均一に含む含フッ素重合体（ａ）からなり、プリフォームのコア部に相当するロッドを挿入した後、両者を熱融着させて一体化してプリフォームを製造する方法。
【００５７】
上記（４）の方法においては、熱融着時に物質（ｂ）および物質（ｃ）の拡散を起こしてもよく、またその後の線引き工程時に拡散を起こさせてもよい。また、プリフォームのクラッド部に相当する管の製造法としては他にも、アルミ管を心棒としてその回りに含フッ素重合体（ａ）と物質（ｃ）の均一混合体からなる管を形成し、後にそのアルミ管を酸で溶解除去する方法や、ガラス管を心棒として成形し、後にフッ化水素酸でガラス管を溶解除去する方法などがあるが、これらに限定されるものではない。
【００５８】
（５）含フッ素重合体（ａ）と物質（ｃ）の均一混合体からなり、上記（４）の方法と同様にして得た管を型として、その内面に物質（ｂ）を均一に含む含フッ素重合体（ａ）からなり、プリフォームのコア部に相当する少なくとも１つの層を回転成形により形成し、内外少なくとも２層の構成を有する円筒状ないし円柱状の成形物からなるプリフォームを製造する方法。
【００５９】
（６）上記（５）の方法で外層となる成形体を回転成形により成形すると共に、引き続き物質（ｂ）を均一に含む含フッ素重合体（ａ）からなる内層を回転成形により形成し、内外少なくとも２層の構成を有する円筒状ないし円柱状の成形物からなるプリフォームを製造する方法。
【００６０】
光学樹脂材料全体のガラス転移温度が実質的に均一である光学樹脂材料を得るために、本発明製造法（３）においてプリフォームのコア部に相当する部分の材料のガラス転移温度とプリフォームのクラッド部に相当する部分の材料のガラス転移温度を予め実質的に均一にする。
【００６１】
本発明の光学樹脂材料が物質（ｃ）を含む場合、例えば上記（４）の方法で光学樹脂材料の中心部から周辺部に向かって物質（ｂ）が拡散する状況において、それと同時に周辺部から中心に向かって物質（ｃ）が拡散するため、光学樹脂材料全体として均一なガラス転移温度が保持される。すなわち、中心部から周辺部に向かって物質（ｂ）が拡散すると、通常ガラス転移温度は通常中心部から周辺部に向かって変化するが、この変化分を補う様に周辺部から中心に向かって物質（ｃ）が拡散されてくるため、本発明製造法（３）においてプリフォームのコア部に相当する部分の材料のガラス転移温度とプリフォームのクラッド部に相当する部分の材料のガラス転移温度を予め実質的に均一にしておけば、最終的に光学樹脂材料全体のガラス転移温度が実質的に均一である光学樹脂材料が得られる。物質（ｃ）は、含フッ素重合体（ａ）と同様な理由から実質的にＣ−Ｈ結合を有しない物質であることが好ましい。また、上述の通り物質（ｂ）の分布により変化する光学樹脂材料のガラス転移温度を修正するものである。物質（ｃ）は、含フッ素重合体（ａ）よりも高屈折率であっても低屈折率であってもよい。通常、光ファイバー等においては物質（ｂ）の拡散による屈折率分布を阻害しないために、含フッ素重合体（ａ）よりも低屈折率、または含フッ素重合体（ａ）と同程度の屈折率を持つ物質を用いる。
【００６２】
物質（ｃ）の屈折率は、含フッ素重合体（ａ）および物質（ｂ）との関係において下記式 (1) (2) (3)または(4) を満足するものから選ばれる。
【００６３】
(1) 物質（ｃ）の屈折率≦含フッ素重合体（ａ）の屈折率＜物質（ｂ）の屈折率(2) 含フッ素重合体（ａ）の屈折率≦物質（ｃ）の屈折率＜物質（ｂ）の屈折率(3) 物質（ｃ）の屈折率≧含フッ素重合体（ａ）の屈折率＞物質（ｂ）の屈折率(4) 含フッ素重合体（ａ）の屈折率≧物質（ｃ）の屈折率＞物質（ｂ）の屈折率光ファイバー等においては、ファイバー中心部と外周部の屈折率の差が大きくとれ、光ファイバーを折り曲げた際の伝送損失を抑制できることから、上記 (1)〜(4) のうち、 (1)または(3) を満足するものが好ましい。
【００６４】
物質（ｃ）としては、前述の物質（ｂ）として挙げた低分子化合物、オリゴマーおよびポリマーから選ばれるものが好ましい。物質（ｃ）は、物質（ｂ）と同様に含フッ素重合体（ａ）との比較において、溶解性パラメータの差が７（ｃａｌ／ｃｍ³)^1/2以内であることが好ましい。
【００６５】
物質（ｃ）がオリゴマーの場合、その分子量は非結晶性となる分子量範囲から選ばれ、数平均分子量３００〜１０，０００が好ましい。これらの化合物は成形条件において拡散することが好ましく、ガラス転移温度を調整するのに十分な量を均一に混合するためには、含フッ素重合体（ａ）との相溶性を考慮すると、数平均分子量５００〜５０００がさらに好ましい。
【００６６】
特に好ましい物質（ｃ）は、含フッ素重合体（ａ）特に主鎖に環構造を有する含フッ素重合体との相溶性が良好であること等から、パーフルオロポリエーテルである。相溶性が良好であることにより、含フッ素重合体（ａ）、特に主鎖に環構造を有する含フッ素重合体、とパーフルオロポリエーテルとを２００〜３００℃で加熱溶融により容易に混合させることができる。又、含フッ素溶媒に溶解させて混合した後、溶媒を除去することにより両者を均一に混合させることができる。パーフルオロポリエーテルの好ましい分子量は、数平均分子量５００〜５０００である。
【００６７】
本発明の光学樹脂材料は屈折率分布型光ファイバーであることが最も好ましい。この光ファイバーにおいて、物質（ｂ）は含フッ素重合体（ａ）中に中心から周辺方向に沿って濃度勾配を有して分布している。好ましくは、物質（ｂ）が含フッ素重合体（ａ）よりも高屈折率の物質であり、この物質（ｂ）が光ファイバーの中心から周辺方向に沿って濃度が低下する濃度勾配を有して分布している光ファイバーである。ある場合には物質（ｂ）が含フッ素重合体（ａ）よりも低屈折率の物質であり、この物質が光ファイバーの周辺から中心方向に沿って濃度が低下する濃度勾配を有して分布している光ファイバーも有用である。前者の光ファイバーなどの光伝送体は通常物質（ｂ）を中心に配置し周辺方向に向かって拡散させることにより製造できる。後者の光ファイバーなどの光伝送体は物質（ｂ）を周辺から中心方向に拡散させることによって製造できる。
【００６８】
本発明の光学樹脂材料は光学樹脂材料全体のガラス転移温度が実質的に均一であることにより、製造後冷却する際に発生する熱膨張率差に伴うマイクロボイドの生成が抑制され、散乱損失が低く抑えられる。本発明においてガラス転移温度を実質的に均一にするとは、上記冷却時に発生する熱膨張率差に伴うマイクロボイドの生成が抑制されれば、ガラス転移温度が多少相違していてもよい意味である。マイクロボイドの生成を抑制するためには冷却速度が重要であり、冷却速度が速くなればなる程、ガラス転移温度をできるだけ均一に近づける必要がある。
【００６９】
また、物質（ｃ）による可塑化効果により、一定温度における溶融粘度が含フッ素重合体（ａ）単独の場合よりも低下するため、低温、短時間で物質（ｂ）の拡散が可能となり、従来と比較して生産性向上、あるいは成形に伴う素材の熱劣化の大幅な低減をもたらす等の効果がある。
【００７０】
本発明の光学樹脂材料である光伝送体は、波長７００〜１，６００ｎｍで、１００ｍの伝送損失が１００ｄｂ以下とすることができる。特に主鎖に脂肪族環構造を有する含フッ素重合体では同様な波長で、１００ｍの伝送損失が５０ｄｂ以下とすることができる。波長７００〜１，６００ｎｍという比較的長波長において、このような低レベルの伝送損失であることは極めて有利である。すなわち、石英光ファイバーと同じ波長を使えることにより、石英光ファイバーとの接続が容易であり、また波長７００〜１，６００ｎｍよりも短波長を使わざるをえない従来のプラスチック光ファイバーに比べ、安価な光源で済むという利点がある。本発明の光学樹脂材料製造において、樹脂の成形と屈折率分布の形成は同時であっても別々であってもよい。たとえば、紡糸や押し出し成形等により屈折率分布を形成すると同時に屈折率分布を形成して本発明光学樹脂材料を製造できる。また、紡糸や押し出し成形で樹脂の成形を行った後、屈折率分布を形成することができる。さらに、屈折率分布を有するプリフォーム（母材）を製造し、このプリフォームを成形（たとえば紡糸）して光ファイバー等の光学樹脂材料を製造できる。なお、前記のように本発明光学樹脂材料は、上記屈折率分布を有するプリフォームをも意味する。
【００７１】
【実施例】
「合成例１」
パーフルオロ（ブテニルビニルエーテル）［ＰＢＶＥ］の３５ｇ、イオン交換水の１５０ｇ、及び重合開始剤として（（ＣＨ₃)₂ＣＨＯＣＯＯ）₂の９０ｍｇを、内容積２００ｍｌの耐圧ガラス製オートクレーブに入れた。系内を３回窒素で置換した後、４０℃で２２時間懸濁重合を行った。その結果、数平均分子量約１．５×１０⁵の重合体（以下、重合体Ａという）を２８ｇ得た。
【００７２】
重合体Ａの固有粘度［η］は、パーフルオロ（２−ブチルテトラヒドロフラン）［ＰＢＴＨＦ］中３０℃で０．５０であった。重合体Ａのガラス転移点は１０８℃であり、室温ではタフで透明なガラス状の重合体であった。また１０％熱分解温度は４６５℃であり、溶解性パラメーターは５．３（ｃａｌ／ｃｍ³)^1/2であり、屈折率は１．３４であった。
【００７３】
「参考例１」
−ＣＦ₂ＣＦ（ＣＦ₃）Ｏ−、−（ＣＦ₂)Ｏ−および−（ＣＦ₂)₂Ｏ−の構造単位を有するパーフルオロポリエーテル（屈折率１．２９、数平均分子量１８００、以下ＰＦＰＥという）と重合体Ａをガラス管中に真空封管して、２５０℃で溶融混合させて混合重合体を得た。ＰＦＰＥの含有量を、５〜３０重量％まで５重量％刻みに混合比を変えたところ、３０重量％までは均一透明な混合重合体が得られることを確認した。これらの混合重合体に対して、アッベの屈折率計で屈折率を、ＤＳＣでガラス転移温度の測定を行った結果、屈折率は含有量と共に緩やかに低下し、ガラス転移温度はほぼ直線的に低下することを見い出した。図１に結果のグラフを示す。
【００７４】
「実施例１」
重合体ＡをＰＢＴＨＦ溶媒中で溶解し、これに屈折率１．５２であり重合体Ａとの溶解性パラメーターの差が３．２（ｃａｌ／ｃｍ³)^1/2である１，３−ジブロモテトラフルオロベンゼン（ＤＢＴＦＢ）を１２重量％量添加し混合溶液を得た。この溶液を脱溶媒し透明な混合重合体（以下、重合体Ｂという）を得た。この重合体Ｂのガラス転移温度は８２℃であった。
【００７５】
さらに重合体ＡにＰＦＰＥを１２重量％溶融混合した均一透明な混合重合体（以下、重合体Ｃという）を得た。この重合体Ｃのガラス転移温度は８２℃であった。その重合体Ｃを２５０℃で溶融させ、その中心に溶融液の重合体Ｂを注入しながら２５０℃で溶融紡糸することにより屈折率が中心部から周辺部に向かって徐々に低下する光ファイバーが得られた。
【００７６】
得られた光ファイバーの光伝送特性は、７８０ｎｍで１５０ｄＢ／ｋｍ、１５５０ｎｍで８０ｄＢ／ｋｍであり、可視光から近赤外光までの光を良好に伝達できる光ファイバーであることを確かめた。またこのファイバーを液体窒素で冷却して割断した面を走査型電子顕微鏡（ＳＥＭ）観察したところ、散乱の原因となる様なマイクロボイド等の不均一構造は一切観察されなかった。
【００７７】
「実施例２」
ＤＢＴＦＢを１２重量％用いる代わりに数平均分子量８００のクロロトリフルオロエチレン（ＣＴＦＥ）オリゴマーを１２重量％用いる以外実施例１と同様な方法で光ファイバーを得た。このオリゴマーの屈折率は１．４１であり、重合体Ａとの溶解性パラメーターの差は１．４（ｃａｌ／ｃｍ³)^1/2であった。得られた光ファイバーは屈折率が中心部から周辺部に向かって徐々に低下していた。
【００７８】
この光ファイバーの光伝送特性は、７８０ｎｍで１００ｄＢ／ｋｍ、１５５０ｎｍで６５ｄＢ／ｋｍであり、可視光から近赤外までの光を良好に伝達できる光ファイバーであることを確かめた。なお、重合体Ａに上記数平均分子量８００のクロロトリフルオロエチレン（ＣＴＦＥ）オリゴマーを１２重量％溶融混合した重合体は、均一透明な混合重合体でありこのガラス転移温度は８２℃であった。
「実施例３」
重合体Ａと１５重量％ＰＦＰＥをガラス管中に真空封管して２５０℃で溶融混合し、均一な混合重合体（以下、重合体Ｄという）を得た。この重合体Ｄのガラス転移温度は７６℃であった。この重合体Ｄを同心円状に２重構造を持つガラス管の一層目と、２層目の隙間に２５０℃で溶融させて溶かし落とした。これを冷却後、外側のガラス管は割り、中心のガラス管は中空管の内壁を傷つけないために、５０％のフッ化水素酸で溶解させて取り除いた。こうして外径１７ｍｍ、内径９ｍｍの重合体Ｄの中空管を得た。
【００７９】
さらに、重合体Ａと数平均分子量１０００のＣＴＦＥオリゴマー１５重量％をガラス管中に真空封管して、２５０℃で溶融混合し均一な混合重合体（以下、重合体Ｅという）の直径８ｍｍのロッドを得た。この重合体Ｅのガラス転移温度は７６℃であった。
【００８０】
こうして得られた重合体Ｄの中空管に、重合体Ｅのロッドを挿入し、中空管の外側に熱収縮チューブを装着した後、全体をガラス管中に真空封管して、２００℃にて重合体Ｄの中空管と重合体Ｅのロッドを熱融着させてプリフォーム（以下、プリフォームＦという）を得た。このプリフォームＦを２４０℃で溶融紡糸することにより屈折率が中心部から周辺部に向かって徐々に低下する光ファイバーが得られた。
【００８１】
得られた光ファイバーの光伝送特性は、７８０ｎｍで１００ｄＢ／ｋｍ、１５５０ｎｍで７０ｄＢ／ｋｍであり、可視光から近赤外光までの光を良好に伝達できる光ファイバーであることを確かめた。
【００８２】
「実施例４」
ＰＢＶＥ９０部とＣＴＦＥ１０部とを重合することにより数平均分子量約２×１０⁵の重合体（以下、重合体Ｇという）を得た。重合体Ｇのガラス転移温度は１００℃であった。重合体Ｇに数平均分子量１８００のＰＦＰＥを溶融均一混合してそのＰＦＰＥ含量が１２重量％となるような混合重合体（以下、重合体Ｈという）を得た。重合体Ｈのガラス転移温度は７５℃であった。
【００８３】
この重合体Ｈをガラス管中に真空封管した後、水平にセットした中空電気炉に挿入して、両端にベアリングを、一端にモーターを取り付けた。２０００ｒｐｍの回転数で水平に回転させながら、３００℃で加熱することにより、ガラス管内壁に重合体Ｈが均一に積層された。これを回転しながら徐々に冷却した後、外側のガラス管を取り除くことにより、重合体Ｈの中空管を得た。
【００８４】
この重合体Ｈの中空管中に実施例３と同様にして作成した重合体Ｅのロッドを挿入して、プリフォーム（以下、プリフォームＩという）を得た。このプリフォームＩを２１０℃で溶融紡糸することにより屈折率が中心部から周辺部に向かって徐々に低下する光ファイバーが得られた。
【００８５】
得られた光ファイバーの光伝送特性は、７８０ｎｍで１５０ｄＢ／ｋｍ、１５５０ｎｍで８０ｄＢ／ｋｍであり、可視光から近赤外光までの光を良好に伝達できる光ファイバーであることを確かめた。
【００８６】
「比較例１」
屈折率分布型プラスチック光ファイバーにおいて、ＰＭＭＡの光伝送損失は波長６５０ｎｍで約４００ｄＢ／ｋｍ、また波長７８０ｎｍ、１３００ｎｍ、１５５０ｎｍでは非常に伝送損失が大きく光伝送体としては実用性がないものであった。
【００８７】
又、段階屈折率型プラスチック光ファイバーにおいて、コアとクラッドが含フッ素樹脂光ファイバーは可視光から近赤外光までの光を伝送可能だが、その光伝送損失は約３００ｄＢ／ｋｍと報告されている。
【００８８】
これに比較して本発明による屈折率分布型透明フッ素樹脂光ファイバーは可視光から近赤外光までの光を極めて低損失に伝送することが可能である。
【００８９】
「比較例２」
ＰＦＰＥを加えない以外は「実施例１」と同様にしてつくったファイバーの場合には、中心部のガラス転移温度が８２℃であるのに対して、外周部のガラス転移温度は１０８℃となり、得られた光ファイバーの光伝送特性は、７８０ｎｍで４００ｄＢ／ｋｍ、１５５０ｎｍで２８０ｄＢ／ｋｍとなり、ＰＦＰＥを加えた場合の数倍以上の伝送損失増加をもたらした。また、このファイバーの割断面を走査型電子顕微鏡（ＳＥＭ）で観察したところ、ファイバー内に多くのマイクロボイドが発生していることが確認された。
【００９０】
【発明の効果】
本発明の光学樹脂材料は、非結晶性のフッ素樹脂を利用しかつマイクロボイド等の発生が抑制されているため、プラスチック光伝送体において紫外光から近赤外光までの光を極めて低損失に伝送することが可能になった。
【００９１】
特に屈折率分布型光ファイバーはファイバー径が大きいにもかかわらずフレキシブルで分岐・接続が容易であるため短距離光通信用に最適であるが、これまで実用可能な低損失の光ファイバーは提案されなかった。本発明は短距離光通信用に実用可能な低損失の光ファイバーを提供するものである。
【００９２】
又、本発明の光学樹脂材料は、自動車のエンジンルーム、ＯＡ機器、プラント、家電等での過酷な使用条件に耐える、耐熱性、耐薬品性、耐湿性、不燃性を備えるプラスチック光伝送体を提供するものである。更に、本発明の光学樹脂材料は、光ファイバーのみならず平板型やロッド型のレンズとしても利用可能である。その場合、中心部から周辺部への屈折率変化を低くするか高くするかにより、凸レンズ及び凹レンズとして機能させることができる。
【図面の簡単な説明】
【図１】重合体ＡとＰＦＰＥの均一透明混合物における、ＰＦＰＥ含有率と屈折率、及びガラス転移温度の相関を示す図。[0001]
BACKGROUND OF THE INVENTION
The present invention has a refractive index distribution type optical resin material (hereinafter sometimes abbreviated as an optical resin material) that has high transparency and heat resistance and has reduced microvoids, which has been difficult to realize with conventional optical resins. It relates to the manufacturing method.
[0002]
The optical resin material of the present invention itself may be an optical transmission body such as an optical fiber, or may be a base material of an optical transmission body such as an optical fiber preform.
[0003]
The optical transmission material, which is the optical resin material of the present invention, is an amorphous resin, so there is no light scattering, and the transparency is very high in a wide wavelength band from ultraviolet light to near infrared light. It can be effectively used for optical systems of wavelengths. In particular, the present invention provides an optical transmission body having a low loss at wavelengths of 1300 nm and 1550 nm, which are wavelengths used for a trunk silica fiber in the optical communication field.
[0004]
In addition, the optical transmission material that is the optical resin material of the present invention has heat resistance, chemical resistance, moisture resistance, and nonflammability that can withstand severe use conditions in an engine room of an automobile.
[0005]
The optical transmission material, which is the optical resin material of the present invention, is a refractive index distribution type optical fiber, rod lens, optical waveguide, optical splitter, optical multiplexer, optical demultiplexer, optical attenuator, optical switch, optical isolator, optical The present invention is useful as a wide variety of refractive index distribution type optical transmitters such as a transmitter module, an optical receiver module, a coupler, a deflector, and an optical integrated circuit. Here, the refractive index distribution means a region in which the refractive index continuously changes along a specific direction of the optical transmission body. For example, the refractive index distribution of the refractive index distribution type optical fiber is a radial direction from the center of the fiber. The refractive index is decreasing along a curve close to a parabola.
[0006]
When the optical resin material of the present invention is a base material of an optical transmission body, it can be spun by hot drawing or the like to produce an optical transmission body such as a gradient index optical fiber.
[0007]
[Prior art]
Conventionally known resins for refractive index distribution type plastic optical transmission bodies include optical resins typified by methyl methacrylate resins and tetrafluoroethylene resins and vinylidene fluoride resins described in WO94 / 04949. Has been. WO94 / 04949 proposes a method of manufacturing a refractive index distribution type plastic optical transmission body by a multilayer extrusion melt molding method of two or more layers.
[0008]
Many proposals have been made for stepped refractive index type plastic optical fibers in which the core is made of an optical resin such as methyl methacrylate resin, styrene resin, carbonate resin, norbornene resin, and the clad is made of a fluorine-containing polymer. JP-A-2-244007 also proposes using a fluorine-containing resin for the core and the clad.
[0009]
[Problems to be solved by the invention]
The present invention, which could not be achieved by an optical transmission body such as methyl methacrylate resin, carbonate resin, norbornene resin, required heat resistance, moisture resistance, and chemical resistance required for automobiles, office automation (OA) equipment, home appliances, etc. An object of the present invention is to provide a nonflammable optical resin material and a method for producing the same.
[0010]
In addition, the present invention makes it possible to use ultraviolet light (wavelength 200 nm to 400 nm) and near infrared light (wavelength 700 nm to 2500 nm) that could not be achieved by an optical transmission body such as methyl methacrylate resin, carbonate resin, norbornene resin, and a wider range. It is an object of the present invention to provide an optical resin material having a low optical transmission loss in the transmission region band and a manufacturing method thereof.
[0011]
In addition, it has been the cause of increased scattering loss in the conventional rod-in-tube molding method using materials with different glass transition temperatures between the core and cladding, and the multilayer extrusion melt molding method of two or more layers. An object of the present invention is to provide an optical resin material having a low optical transmission loss and a method for producing the same, in which microvoids resulting from a difference in thermal expansion coefficient between the center portion and the outer peripheral portion of the molded body during cooling are reduced.
[0012]
[Means for Solving the Problems]
As a result of intensive studies based on recognition of the above problems, the present inventor has imparted heat resistance, moisture resistance, chemical resistance, nonflammability, and C—H bond (wherein light absorption occurs in near infrared light) That is, in order to eliminate the carbon-hydrogen bond), it was found that a fluoropolymer substantially free of C—H bonds is optimal. This fluoropolymer has a C—F bond (that is, a carbon-fluorine bond) instead of a C—H bond.
[0013]
That is, when a substance is irradiated with light, light having a wavelength that causes stretching vibration of a bond between certain atoms or resonance vibration and bending vibration is preferentially absorbed. Until now, the polymer substances used in plastic optical fibers have been mainly compounds having C—H bonds. In the polymer substance based on this C—H bond, since hydrogen atoms are light and easily vibrate, basic absorption appears on the short wavelength side (3000 to 4000 nm) in the infrared region. Therefore, in the near-infrared to infrared region (600 to 1550 nm), which is the wavelength of the light source, the relatively low harmonic overtone absorption of this C—H stretching vibration appears rapidly, which causes a large absorption loss.
[0014]
Therefore, when hydrogen atoms are replaced with fluorine atoms, the wavelength of those overtone absorption peaks shifts to the longer wavelength side, and the amount of absorption in the near infrared region decreases. From the theoretical value, in the case of a methyl methacrylate resin having a C—H bond, the absorption loss of the C—H bond at a wavelength of 650 nm is estimated to be 105 dB / km, and at a wavelength of 1300 nm, it is more than 10,000 dB / km Become.
[0015]
On the other hand, a substance in which a hydrogen atom is replaced with a fluorine atom has substantially no loss due to absorption at a wavelength of 650 nm. It can be considered that there is no absorption loss. To that end, we propose to use compounds with C—F bonds.
[0016]
In addition, it is desirable to exclude functional groups such as a carboxyl group and a carbonyl group, which are factors that inhibit heat resistance, moisture resistance, chemical resistance, and nonflammability. In addition, if there is a carboxyl group, it absorbs near-infrared light, and if there is a carbonyl group, it absorbs ultraviolet light, it is desirable to exclude these groups. Further, in order to reduce transmission loss due to light scattering, it is important to use an amorphous polymer.
[0017]
Furthermore, in the case of a graded index optical fiber, multimode light propagates while being reflected at the interface between the core and the clad. As a result, mode dispersion occurs and the transmission band decreases. However, in the graded index optical fiber, mode dispersion hardly occurs and the transmission band increases.
[0018]
Furthermore, in order to suppress the generation of microvoids due to the difference in thermal expansion coefficient during cooling of the molded body, the entire optical resin material has a substantially uniform glass transition regardless of the central portion and the outer periphery thereof. We propose that having temperature is important.
[0019]
Therefore, an amorphous fluoropolymer having substantially no C—H bond as an optical resin material, particularly a fluoropolymer having a ring structure in the main chain, and a substance having a refractive index different from that of the polymer. The optical resin material having a gradient in a specific direction and the entire optical resin material has a substantially uniform glass transition temperature and a method for producing the same have been found. Clearly It came.
[0020]
[1] At least 1 in which the difference in refractive index is 0.001 or more in comparison between the amorphous fluoropolymer (a) having substantially no CH bond and the fluoropolymer (a). It consists of a substance (b) having substantially no CH bond, and the substance (b) is distributed in the fluoropolymer (a) with a concentration gradient along a specific direction. Refractive index distribution type optical resin material, Regardless of its center and outer periphery, An optical resin material, wherein the glass transition temperature of the entire optical resin material is substantially uniform.
[2] Substance (c) which has substantially no C—H bond in the fluoropolymer (a) and corrects the glass transition temperature of the optical resin material which varies depending on the distribution of the substance (b)
The optical resin material according to [1], in which is distributed.
[3] The optical resin material according to [1] or [2], wherein the fluoropolymer (a) is a fluoropolymer having a ring structure in the main chain.
[4] The optical resin material according to [1], [2] or [3], wherein the optical resin material is a preform for manufacturing a gradient index optical fiber or a gradient index optical fiber.
[5] At least 1 having a difference in refractive index of 0.001 or more in comparison between the amorphous fluoropolymer (a) having substantially no CH bond and the fluoropolymer (a). It consists of a substance (b) having substantially no CH bond, and the substance (b) is distributed in the fluoropolymer (a) with a concentration gradient along a specific direction. In manufacturing a refractive index distribution type optical resin material by a multi-layer extrusion melt molding method of two or more layers, the glass transition temperature of the material supplied to the nozzle central portion and the glass transition temperature of the material supplied to the outer peripheral portion are substantially By making it uniform Regardless of the center and outer periphery A method for producing an optical resin material, comprising: obtaining an optical resin material having a substantially uniform glass transition temperature of the entire optical resin material.
[0023]
As fluoropolymers, tetrafluoroethylene resin, perfluoro (ethylene-propylene) resin, perfluoroalkoxy resin, vinylidene fluoride resin, ethylene-tetrafluoroethylene resin, chlorotrifluoroethylene resin, etc. have been widely known. Yes. However, since these fluorine-containing resins have crystallinity, light scattering occurs, transparency is not good, and it is not preferable as a material for a plastic optical transmission body.
[0024]
On the other hand, an amorphous fluoropolymer is excellent in transparency because it does not scatter light by crystals. The fluoropolymer (a) in the present invention is not limited as long as it is an amorphous fluoropolymer having no C—H bond, but a fluoropolymer having a ring structure in the main chain is preferred. The fluorine-containing polymer having a ring structure in the main chain is preferably a fluorine-containing polymer having a fluorine-containing aliphatic ring structure, a fluorine-containing imide ring structure, a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure. Of the fluorine-containing polymers having a fluorine-containing aliphatic ring structure, those having a fluorine-containing aliphatic ether ring structure are more preferable.
[0025]
The fluorine-containing polymer having a fluorine-containing aliphatic ring structure is a fiber obtained by hot drawing or melt spinning, which will be described later, as compared with a fluorine-containing polymer having a fluorine-containing imide ring structure, a fluorine-containing triazine ring structure or a fluorine-containing aromatic ring structure. This is a more preferred polymer because the polymer molecules are difficult to be oriented during the conversion, and as a result, no light scattering occurs.
[0026]
The viscosity of the fluoropolymer (a) in the molten state is 10 at a melting temperature of 200 ° C. to 300 ° C. ^Three -10 ^Five Poise is preferred. If the melt viscosity is too high, melt spinning is not only difficult, but also the diffusion of the substance (b) necessary for forming the refractive index distribution hardly occurs and the refractive index distribution is difficult to form. Moreover, when melt viscosity is too low, a problem will arise practically. That is, when it is used as an optical transmission body in an electronic device or an automobile, it is softened by being exposed to a high temperature, and the light transmission performance is lowered.
[0027]
The number average molecular weight of the fluoropolymer (a) is preferably 10,000 to 5,000,000, more preferably 50,000 to 1,000,000. If the molecular weight is too small, heat resistance may be inhibited, and if it is too large, formation of an optical transmission body having a refractive index distribution becomes difficult, which is not preferable.
[0028]
The polymer having a fluorine-containing aliphatic ring structure is obtained by polymerizing a monomer having a fluorine-containing ring structure, or obtained by cyclopolymerizing a fluorine-containing monomer having at least two polymerizable double bonds. A polymer having a fluorinated aliphatic ring structure in the main chain is preferred.
[0029]
A polymer having a fluorine-containing aliphatic ring structure in the main chain obtained by polymerizing a monomer having a fluorine-containing aliphatic ring structure is known from JP-B 63-18964. That is, by homopolymerizing a monomer having a fluorine-containing aliphatic ring structure such as perfluoro (2,2-dimethyl-1,3-dioxole), this monomer is converted into tetrafluoroethylene, chlorotrifluoroethylene, perfluoro. By copolymerizing with a radical polymerizable monomer such as (methyl vinyl ether), a polymer having a fluorine-containing aliphatic ring structure in the main chain is obtained.
[0030]
Further, polymers having a fluorinated aliphatic ring structure in the main chain obtained by cyclopolymerizing a fluorinated monomer having at least two polymerizable double bonds are disclosed in JP-A-63-238111 and No. 63-238115 is known. That is, by cyclopolymerizing monomers such as perfluoro (allyl vinyl ether) and perfluoro (butenyl vinyl ether), or such monomers as tetrafluoroethylene, chlorotrifluoroethylene, perfluoro (methyl vinyl ether), etc. A polymer having a fluorine-containing aliphatic ring structure in the main chain is obtained by copolymerizing with the radical polymerizable monomer.
[0031]
In addition, a monomer having a fluorinated aliphatic ring structure such as perfluoro (2,2-dimethyl-1,3-dioxole) and at least two polymerizable properties such as perfluoro (allyl vinyl ether) and perfluoro (butenyl vinyl ether). A polymer having a fluorine-containing aliphatic ring structure in the main chain can also be obtained by copolymerizing with a fluorine-containing monomer having a double bond.
[0032]
Specific examples of the polymer having the above fluorinated aliphatic ring structure include a fluorinated polymer having a repeating unit selected from the following formulas (I) to (IV), or the following (I) to (IV): ) A fluoropolymer having a repeating unit selected from the formula and a repeating unit of the formula (V). In addition, in order to raise a refractive index, the fluorine atom in the polymer which has these fluorine-containing aliphatic ring structures may be partially substituted by the chlorine atom.
[0033]
[Chemical 1]

[0034]
[In the above formulas (I) to (IV), s is 0 to 5, t is 0 to 4, u is 0 to 1, s + t + u is 1 to 6, p, q, and r are 0 to 5, p + q + r is 1 respectively. ~ 6, R is F or CF _Three , R ¹ Is F or CF _Three , R ² Is F or CF _Three , X ¹ Is F or Cl, X ² Is F or Cl, X ^Three Is F or Cl. ]
The polymer having a fluorine-containing aliphatic ring structure is preferably a polymer having a ring structure in the main chain, and the polymer units having a ring structure with respect to all the polymer units of the polymer having a fluorine-containing aliphatic ring structure. What contains 20 mol% or more, preferably 40 mol% or more is preferable in terms of transparency, mechanical properties and the like.
[0035]
The substance (b) is at least one substance having a refractive index difference of 0.001 or more in comparison with the fluoropolymer (a), and is substantially the same for the same reason as the fluoropolymer (a). It does not have a C—H bond. The substance (b) may have a higher refractive index or a lower refractive index than the fluoropolymer (a). In an optical fiber or the like, a substance having a higher refractive index than that of the fluoropolymer (a) is usually used.
[0036]
The substance (b) may be any of a low molecular compound, an oligomer and a polymer, and includes a halogen atom of fluorine, chlorine, bromine or iodine, an aromatic ring such as a benzene ring, or a bonding group such as an ether bond. preferable. The substance (b) is usually selected from substances that lower the glass transition temperature of the fluoropolymer (a), and the difference in refractive index from the fluoropolymer (a) is preferably 0.005 or more. .
[0037]
In comparison with the fluoropolymer (a), the substance (b) has a solubility parameter difference of 7 (cal / cm ^Three ) ^1/2 Is preferably within. Here, the solubility parameter is a characteristic value that is a measure of the mixing property between substances, where the solubility parameter is δ, the molecular cohesive energy of the substance is E, the molecular volume is V, and the formula δ = (E / V) ^1/2 It is represented by
[0038]
Examples of the low molecular weight compound include halogenated aromatic hydrocarbons that do not contain a hydrogen atom bonded to a carbon atom. In particular, a halogenated aromatic hydrocarbon containing only a fluorine atom as a halogen atom or a halogenated aromatic hydrocarbon containing a fluorine atom and another halogen atom is preferable in terms of compatibility with the fluorine-containing polymer (a). Moreover, it is more preferable that these halogenated aromatic hydrocarbons do not have a functional group such as a carbonyl group or a cyano group.
[0039]
Examples of such a halogenated aromatic hydrocarbon include, for example, the formula Φr-Zb [Φr is a b-valent fluorinated aromatic ring residue in which all of the hydrogen atoms are substituted with fluorine atoms, Z is a halogen atom other than fluorine, − Rf, -CO-Rf, -O-Rf, or -CN. Rf is a perfluoroalkyl group, a polyfluoroperhaloalkyl group, or a monovalent Φr. b is 0 or an integer of 1 or more. There is a compound represented by Aromatic rings include benzene and naphthalene rings. The perfluoroalkyl group or polyfluoroperhaloalkyl group as Rf preferably has 5 or less carbon atoms. As a halogen atom other than fluorine, a chlorine atom or a bromine atom is preferable.
[0040]
Specific examples of the compound include 1,3-dibromotetrafluorobenzene, 1,4-dibromotetrafluorobenzene, 2-bromotetrafluorobenzotrifluoride, chloropentafluorobenzene, bromopentafluorobenzene, iodopentafluorobenzene, There are decafluorobenzophenone, perfluoroacetophenone, perfluorobiphenyl, chloroheptafluoronaphthalene, bromoheptafluoronaphthalene and the like.
[0041]
The substance (b) which is an oligomer or a polymer is composed of a polymer of a monomer that forms the fluoropolymer (a) as described above, and the difference in refractive index is 0 in comparison with the fluoropolymer (a). It may be an oligomer or polymer that is .001 or more. The monomer is selected from those that form an oligomer or polymer having a refractive index difference of 0.001 or more in comparison with the fluoropolymer (a). For example, two types of fluorine-containing polymers (a) having different refractive indexes can be used, and one polymer (a) can be distributed as a substance (b) in another polymer (a).
[0042]
As the substance (b) which is an oligomer or a polymer, a fluorine-containing polymer having a refractive index different from that of the combined fluorine-containing polymer (a) among those having the repeating units (I) to (V) (for example, , A combination of a fluorine-containing polymer containing only fluorine atoms as halogen atoms and a fluorine-containing polymer containing fluorine atoms and chlorine atoms, and two types of polymers obtained by polymerizing two or more monomers of different types or in different proportions. Combinations of fluoropolymers) are preferred.
[0043]
In addition to the fluorine-containing polymer having a ring structure in the main chain as described above, it comprises a monomer not containing a hydrogen atom such as tetrafluoroethylene, chlorotrifluoroethylene, dichlorodifluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether. Oligomers and copolymer oligomers composed of two or more of these monomers can also be used as the substance (b). -CF ₂ CF (CF _Three ) O- and-(CF ₂ ) _n A perfluoropolyether having a structural unit of O- (n is an integer of 1 to 3) can also be used. The molecular weight of these oligomers is selected from the molecular weight range that is amorphous, and the number average molecular weight is preferably from 300 to 10,000. Considering the ease of diffusion, the number average molecular weight is more preferably 300 to 5,000.
[0044]
A particularly preferred substance (b) is a chlorotrifluoroethylene oligomer because of its good compatibility with the fluoropolymer (a), particularly a fluoropolymer having a ring structure in the main chain. Due to the good compatibility, the fluoropolymer (a), in particular, the fluoropolymer having a ring structure in the main chain, and the chlorotrifluoroethylene oligomer are easily mixed by heating and melting at 200 to 300 ° C. be able to. Moreover, after dissolving and mixing in a fluorine-containing solvent, both can be mixed uniformly by removing a solvent. The preferred molecular weight of the chlorotrifluoroethylene oligomer is a number average molecular weight of 500-1500.
[0045]
In the optical resin material of the present invention, since the substance (b) is distributed in the fluorine-containing polymer (a) with a concentration gradient along a specific direction, the entire optical resin material depends on the distribution situation. The glass transition temperature may not be substantially uniform. In this case, by distributing the substance (c) in the fluoropolymer (a), the glass transition temperature of the optical resin material changed by the concentration distribution of the substance (b) can be corrected, and the glass transition of the entire optical resin material The temperature can be made substantially uniform.
[0046]
The normal substances (b) and (c) are both selected from substances that lower the glass transition temperature of the fluoropolymer (a). In the fluoropolymer (a), the region where the glass transition temperature is high due to the low concentration of the substance (b) is the glass transition by distributing the substance (c) and mixing the substances (b) and (c). The temperature can be lowered. In addition, when there is a region where only the substance (b) or the substance (c) is distributed in the fluoropolymer (a), the glass transition of these regions and the region where the substances (b) and (c) are mixed. The types and concentrations of the substances (b) and (c) are selected so that the temperatures are substantially uniform. FIG. 1 shows a relationship in which the glass transition temperature (Tg) of the mixture of the fluoropolymer (a) and the substance (c) decreases as the concentration of the substance (c) in the mixture increases.
[0047]
Therefore, for example, the substances (b) and (c) having the same degree of lowering the glass transition temperature of the fluoropolymer (a) are used, and the substances (b) and (c) are added to the entire fluoropolymer (a). ) Is distributed, if both substances are distributed so that the total concentration of the substances (b) and (c) is the same throughout the fluoropolymer (a), the glass transition temperature of the entire optical resin material can be reduced. It can be substantially uniform. When the degree of lowering the glass transition temperature of the fluoropolymer (a) is different between the substances (b) and (c), the degree of distribution of both substances in the fluoropolymer (a) is adjusted. The glass transition temperature of the entire optical resin material can be made substantially uniform.
[0048]
"Fluoropolymer (a), substance (b) and substance (c) mixture", "fluoropolymer (a) and substance (b) mixture" or "fluorine polymer (a)" By making the substance (c) a “mixture” a homogeneous mixture, these mixtures have a certain glass transition temperature.
[0049]
In the production method (2) of the present invention, the material supplied to the nozzle center is usually a mixture of the fluoropolymer (a) and the substance (b), and the material supplied to the outer periphery is usually a fluoropolymer ( a). Similarly, in the production method (3) of the present invention, the material corresponding to the core portion of the preform is usually composed of a mixture of the fluoropolymer (a) and the substance (b), and corresponds to the cladding portion of the preform. The material is usually composed of a fluoropolymer (a).
[0050]
In order to make the glass transition temperature of the material supplied to the central part of the nozzle and the glass transition temperature of the material supplied to the outer peripheral part substantially uniform, the fluorine-containing polymer (a) supplied to the outer peripheral part contains It is effective to mix a substance (c) that is compatible with the coalescence (a). Similarly, in order to make the glass transition temperature of the material corresponding to the core portion of the preform and the glass transition temperature of the material corresponding to the cladding portion of the preform substantially uniform, the portion corresponding to the cladding portion It is effective to mix a substance (c) having compatibility with the fluoropolymer (a) in the fluoropolymer (a).
[0051]
In a preferred example of the production method (2) of the present invention, the material supplied to the nozzle center is a mixture of the fluoropolymer (a) and the substance (b) or the substance (b), and the material supplied to the nozzle outer peripheral part is used. This is an extrusion melt molding method consisting of two layers of a nozzle center portion and an outer peripheral portion, which is a uniform mixture obtained by melt-mixing the fluoropolymer (a) and the substance (c). In this case, the mixture of the fluoropolymer (a) and the substance (b) or the substance (b) is injected into the center of the melt of the mixture of the fluoropolymer (a) and the substance (c), and the substance ( A method in which b) and the substance (c) are molded while being diffused or after being diffused is preferred.
[0052]
In order to obtain an optical resin material in which the glass transition temperature of the entire optical resin material is substantially uniform, the glass transition temperature of the material supplied to the nozzle central portion and the material supplied to the nozzle outer peripheral portion in the production method (2) of the present invention The glass transition temperature of is substantially uniform in advance.
[0053]
When the optical resin material of the present invention contains the substance (c), in the situation where the substance (b) diffuses from the central part of the optical resin material toward the peripheral part as in the above preferred method, at the same time, the central part from the peripheral part. Since the substance (c) diffuses toward the surface, a uniform glass transition temperature is maintained as the entire optical resin material. That is, when the substance (b) diffuses from the central part to the peripheral part, the glass transition temperature usually changes from the central part to the peripheral part, but from the peripheral part to the center so as to compensate for this change. Since the substance (c) is diffused, the glass transition temperature of the polymer supplied to the central part of the nozzle and the glass transition temperature of the polymer supplied to the outer peripheral part of the nozzle in the production method (2) of the present invention are substantially uniform in advance. If it is made, the optical resin material whose glass transition temperature of the whole optical resin material will be substantially uniform finally is obtained.
[0054]
The material supplied to the nozzle central part or the material supplied to the nozzle outer peripheral part may be injected not only into one layer but also into multiple layers. Examples of the molding method include extrusion melt molding suitable for molding a rod-shaped base material such as an optical fiber preform, and melt spinning molding suitable for molding an optical fiber.
[0055]
In the production method (3) of the present invention, it is preferable to form a refractive index distribution of a certain degree or more in the preform. By forming a refractive index distribution of a certain degree or more in the preform, the efficiency of manufacturing a refractive index distribution type optical fiber from the preform is improved. Preferred examples of the production method (3) of the present invention include the following methods (4) to (6).
[0056]
(4) Using a rotating tube such as a rotating glass tube, a tube (tube) corresponding to the clad portion of the preform is formed from a homogeneous mixture of the hollow fluoropolymer (a) and the substance (c). The rod is made of a fluoropolymer (a) that uniformly contains the substance (b) inside the tube, and after inserting a rod corresponding to the core portion of the preform, the two are heat-fused and integrated into a tube. A method of manufacturing a renovation.
[0057]
In the method (4), the materials (b) and (c) may be diffused during thermal fusion, or may be diffused during the subsequent drawing step. In addition, as a method of manufacturing a tube corresponding to the clad portion of the preform, an aluminum tube is used as a mandrel, and a tube made of a homogeneous mixture of the fluoropolymer (a) and the substance (c) is formed therearound. There are a method of dissolving and removing the aluminum tube with an acid later, a method of forming a glass tube as a mandrel, and a method of dissolving and removing the glass tube with hydrofluoric acid later, but are not limited thereto.
[0058]
(5) Consisting of a homogeneous mixture of the fluoropolymer (a) and the substance (c), the tube obtained in the same manner as in the method (4) above is used as a mold, and the substance (b) is uniformly contained on the inner surface thereof. A preform composed of a fluoropolymer (a), formed of a cylindrical or columnar molded article having at least one layer formed by rotational molding of at least one layer corresponding to the core of the preform, and having at least two layers inside and outside. How to manufacture.
[0059]
(6) The molded body as the outer layer is molded by rotational molding by the method of (5) above, and the inner layer composed of the fluoropolymer (a) containing the substance (b) uniformly is formed by rotational molding. A method for producing a preform comprising a cylindrical or columnar molded product having a constitution of at least two layers.
[0060]
In order to obtain an optical resin material in which the glass transition temperature of the entire optical resin material is substantially uniform, the glass transition temperature of the material corresponding to the core portion of the preform in the production method (3) of the present invention and the preform The glass transition temperature of the material corresponding to the clad portion is made substantially uniform in advance.
[0061]
When the optical resin material of the present invention includes the substance (c), for example, in the situation where the substance (b) diffuses from the central part of the optical resin material toward the peripheral part by the method of (4), at the same time, from the peripheral part. Since the substance (c) diffuses toward the center, a uniform glass transition temperature is maintained as the entire optical resin material. That is, when the substance (b) diffuses from the central part to the peripheral part, the glass transition temperature usually changes from the central part to the peripheral part, but from the peripheral part to the center so as to compensate for this change. Since the substance (c) is diffused, the glass transition temperature of the material corresponding to the core portion of the preform and the glass transition temperature of the material corresponding to the cladding portion of the preform in the production method (3) of the present invention. Is made substantially uniform in advance, finally, an optical resin material can be obtained in which the glass transition temperature of the entire optical resin material is substantially uniform. The substance (c) is preferably a substance that has substantially no C—H bond for the same reason as the fluoropolymer (a). Moreover, the glass transition temperature of the optical resin material which changes with the distribution of the substance (b) as described above is corrected. The substance (c) may have a higher refractive index or a lower refractive index than the fluoropolymer (a). Usually, in an optical fiber or the like, in order not to inhibit the refractive index distribution due to the diffusion of the substance (b), the refractive index is lower than that of the fluoropolymer (a), or the same refractive index as that of the fluoropolymer (a). Use the substance you have.
[0062]
The refractive index of the substance (c) is selected from those satisfying the following formula (1), (2), (3) or (4) in relation to the fluoropolymer (a) and the substance (b).
[0063]
(1) Refractive index of substance (c) ≦ refractive index of fluoropolymer (a) <refractive index of substance (b) (2) Refractive index of fluoropolymer (a) ≦ refractive index of substance (c) <Refractive index of substance (b) (3) Refractive index of substance (c) ≧ Refractive index of fluoropolymer (a)> Refractive index of substance (b) (4) Refractive index of fluoropolymer (a) ≧ Refractive index of substance (c)> Refractive index of substance (b) In the optical fiber or the like, the difference in refractive index between the center and the outer periphery of the fiber is large, and transmission loss when the optical fiber is bent can be suppressed. Among (1) to (4), those satisfying (1) or (3) are preferable.
[0064]
The substance (c) is preferably selected from the low molecular compounds, oligomers and polymers mentioned as the substance (b). The substance (c) has a solubility parameter difference of 7 (cal / cm) in comparison with the fluoropolymer (a) as in the substance (b). ^Three ) ^1/2 Is preferably within.
[0065]
When the substance (c) is an oligomer, its molecular weight is selected from a molecular weight range in which it is amorphous, and a number average molecular weight of 300 to 10,000 is preferable. These compounds are preferably diffused under molding conditions, and in order to uniformly mix an amount sufficient to adjust the glass transition temperature, the number average is taken into consideration for compatibility with the fluoropolymer (a). A molecular weight of 500 to 5000 is more preferable.
[0066]
A particularly preferred substance (c) is perfluoropolyether because of its good compatibility with the fluoropolymer (a), particularly the fluoropolymer having a ring structure in the main chain. Due to good compatibility, the fluoropolymer (a), in particular, the fluoropolymer having a ring structure in the main chain, and perfluoropolyether can be easily mixed by heating and melting at 200 to 300 ° C. Can do. Moreover, after dissolving and mixing in a fluorine-containing solvent, both can be mixed uniformly by removing a solvent. A preferred molecular weight of the perfluoropolyether is a number average molecular weight of 500 to 5,000.
[0067]
The optical resin material of the present invention is most preferably a gradient index optical fiber. In this optical fiber, the substance (b) is distributed in the fluoropolymer (a) with a concentration gradient from the center to the peripheral direction. Preferably, the substance (b) is a substance having a higher refractive index than that of the fluoropolymer (a), and the substance (b) has a concentration gradient in which the concentration decreases along the peripheral direction from the center of the optical fiber. It is a distributed optical fiber. In some cases, the substance (b) is a substance having a lower refractive index than that of the fluoropolymer (a), and this substance is distributed with a concentration gradient in which the concentration decreases from the periphery of the optical fiber along the central direction. The optical fiber is also useful. The former optical transmission body such as an optical fiber can be usually manufactured by arranging the substance (b) in the center and diffusing in the peripheral direction. The latter optical transmission body such as an optical fiber can be manufactured by diffusing the substance (b) from the periphery toward the center.
[0068]
In the optical resin material of the present invention, the glass transition temperature of the entire optical resin material is substantially uniform, so that the generation of microvoids due to the difference in thermal expansion coefficient that occurs when cooling after manufacturing is suppressed, and the scattering loss is reduced. It can be kept low. In the present invention, making the glass transition temperature substantially uniform means that the glass transition temperature may be somewhat different as long as the generation of microvoids due to the difference in thermal expansion coefficient generated during the cooling is suppressed. . In order to suppress the formation of microvoids, the cooling rate is important. The higher the cooling rate, the closer the glass transition temperature should be as uniform as possible.
[0069]
In addition, because of the plasticizing effect of the substance (c), the melt viscosity at a certain temperature is lower than that of the fluoropolymer (a) alone, so that the substance (b) can be diffused at a low temperature in a short time. Compared to the above, there are effects such as improvement in productivity or a significant reduction in thermal deterioration of the raw material accompanying molding.
[0070]
The optical transmission material which is the optical resin material of the present invention has a wavelength of 700 to 1,600 nm and a 100 m transmission loss of 100 db or less. In particular, in a fluoropolymer having an aliphatic ring structure in the main chain, the transmission loss at 100 m can be reduced to 50 db or less at the same wavelength. Such a low level of transmission loss is extremely advantageous at a relatively long wavelength of 700 to 1,600 nm. That is, by using the same wavelength as the quartz optical fiber, it is easy to connect to the quartz optical fiber, and it is an inexpensive light source compared to the conventional plastic optical fiber that has to use a wavelength shorter than 700 to 1,600 nm. There is an advantage of being able to finish In the production of the optical resin material of the present invention, the molding of the resin and the formation of the refractive index profile may be performed simultaneously or separately. For example, the optical resin material of the present invention can be produced by forming a refractive index distribution by spinning or extrusion molding and simultaneously forming the refractive index distribution. Further, the refractive index distribution can be formed after the resin is molded by spinning or extrusion molding. Furthermore, an optical resin material such as an optical fiber can be manufactured by manufacturing a preform (base material) having a refractive index distribution and molding (for example, spinning) the preform. As described above, the optical resin material of the present invention also means a preform having the above refractive index distribution.
[0071]
【Example】
“Synthesis Example 1”
35 g of perfluoro (butenyl vinyl ether) [PBVE], 150 g of ion-exchanged water, and ((CH _Three ) ₂ CHOCOO) ₂ Was put in a pressure-resistant glass autoclave having an internal volume of 200 ml. After the system was replaced with nitrogen three times, suspension polymerization was carried out at 40 ° C. for 22 hours. As a result, the number average molecular weight was about 1.5 × 10 ^Five 28 g of polymer (hereinafter referred to as polymer A) was obtained.
[0072]
The intrinsic viscosity [η] of the polymer A was 0.50 at 30 ° C. in perfluoro (2-butyltetrahydrofuran) [PBTHF]. The glass transition point of the polymer A was 108 ° C., and it was a tough and transparent glassy polymer at room temperature. The 10% thermal decomposition temperature is 465 ° C., and the solubility parameter is 5.3 (cal / cm ^Three ) ^1/2 And the refractive index was 1.34.
[0073]
"Reference Example 1"
-CF ₂ CF (CF _Three ) O-,-(CF ₂ ) O- and-(CF ₂ ) ₂ Perfluoropolyether having a structural unit of O- (refractive index 1.29, number average molecular weight 1800, hereinafter referred to as PFPE) and polymer A are vacuum sealed in a glass tube, and melt mixed at 250 ° C. and mixed. A polymer was obtained. When the mixing ratio was changed in increments of 5 wt% from 5 to 30 wt%, it was confirmed that a uniform transparent mixed polymer was obtained up to 30 wt%. For these mixed polymers, the refractive index was measured with an Abbe refractometer, and the glass transition temperature was measured with DSC. As a result, the refractive index gradually decreased with the content, and the glass transition temperature was almost linear. I found it to decline. The resulting graph is shown in FIG.
[0074]
"Example 1"
The polymer A was dissolved in a PBTHF solvent, and the refractive index was 1.52 and the difference in solubility parameter from the polymer A was 3.2 (cal / cm ^Three ) ^1/2 1,3-dibromotetrafluorobenzene (DBTFB) was added in an amount of 12% by weight to obtain a mixed solution. This solution was desolvated to obtain a transparent mixed polymer (hereinafter referred to as polymer B). The glass transition temperature of this polymer B was 82 ° C.
[0075]
Further, a uniformly transparent mixed polymer (hereinafter referred to as polymer C) obtained by melting and mixing PFPE with polymer 12% by weight was obtained. The glass transition temperature of this polymer C was 82 ° C. The polymer C is melted at 250 ° C., and melt spinning at 250 ° C. while injecting the polymer B as a melt into the center thereof, thereby obtaining an optical fiber whose refractive index gradually decreases from the central portion toward the peripheral portion. It was.
[0076]
The optical transmission characteristics of the obtained optical fiber were 150 dB / km at 780 nm and 80 dB / km at 1550 nm, and it was confirmed that the optical fiber can transmit light from visible light to near infrared light well. Further, when the fiber was cooled with liquid nitrogen and the cut surface was observed with a scanning electron microscope (SEM), no non-uniform structure such as microvoids that would cause scattering was observed.
[0077]
"Example 2"
An optical fiber was obtained in the same manner as in Example 1 except that 12% by weight of chlorotrifluoroethylene (CTFE) oligomer having a number average molecular weight of 800 was used instead of 12% by weight of DBTFB. The refractive index of this oligomer is 1.41, and the difference in solubility parameter from polymer A is 1.4 (cal / cm ^Three ) ^1/2 Met. The obtained optical fiber had a refractive index that gradually decreased from the center to the periphery.
[0078]
The optical transmission characteristics of this optical fiber were 100 dB / km at 780 nm and 65 dB / km at 1550 nm, and it was confirmed that the optical fiber can transmit light from visible light to near infrared well. The polymer obtained by melting and mixing 12% by weight of the chlorotrifluoroethylene (CTFE) oligomer having the number average molecular weight of 800 with the polymer A was a homogeneous transparent mixed polymer and had a glass transition temperature of 82 ° C.
"Example 3"
Polymer A and 15% by weight PFPE were vacuum sealed in a glass tube and melt-mixed at 250 ° C. to obtain a uniform mixed polymer (hereinafter referred to as polymer D). The glass transition temperature of this polymer D was 76 ° C. The polymer D was melted and melted off at 250 ° C. in the gap between the first layer and the second layer of the glass tube having a double structure concentrically. After cooling this, the outer glass tube was split, and the central glass tube was removed by dissolving with 50% hydrofluoric acid so as not to damage the inner wall of the hollow tube. Thus, a hollow tube of polymer D having an outer diameter of 17 mm and an inner diameter of 9 mm was obtained.
[0079]
Further, 15% by weight of the polymer A and a CTFE oligomer having a number average molecular weight of 1000 are vacuum sealed in a glass tube, melt-mixed at 250 ° C., and a uniform mixed polymer (hereinafter referred to as polymer E) having a diameter of 8 mm. I got a rod. The glass transition temperature of this polymer E was 76 ° C.
[0080]
After inserting the rod of polymer E into the hollow tube of polymer D obtained in this way and mounting the heat shrink tube on the outside of the hollow tube, the whole was vacuum-sealed in a glass tube, and 200 ° C. The preform D (hereinafter referred to as preform F) was obtained by heat-sealing the polymer D hollow tube and the polymer E rod. The preform F was melt-spun at 240 ° C. to obtain an optical fiber in which the refractive index gradually decreased from the central portion toward the peripheral portion.
[0081]
The optical transmission characteristics of the obtained optical fiber were 100 dB / km at 780 nm and 70 dB / km at 1550 nm, and it was confirmed that the optical fiber can transmit light from visible light to near infrared light well.
[0082]
Example 4
By polymerizing 90 parts of PBVE and 10 parts of CTFE, the number average molecular weight is about 2 × 10. ^Five Polymer (hereinafter referred to as polymer G). The glass transition temperature of the polymer G was 100 ° C. A PFPE having a number average molecular weight of 1800 was melted and uniformly mixed with the polymer G to obtain a mixed polymer having a PFPE content of 12% by weight (hereinafter referred to as polymer H). The glass transition temperature of the polymer H was 75 ° C.
[0083]
The polymer H was vacuum sealed in a glass tube, and then inserted into a horizontally set hollow electric furnace, and a bearing was attached to both ends and a motor was attached to one end. The polymer H was uniformly laminated | stacked on the inner wall of the glass tube by heating at 300 degreeC, rotating horizontally at the rotation speed of 2000 rpm. After gradually cooling this while rotating, the outer glass tube was removed to obtain a hollow tube of polymer H.
[0084]
A rod of polymer E prepared in the same manner as in Example 3 was inserted into the hollow tube of polymer H to obtain a preform (hereinafter referred to as preform I). The preform I was melt-spun at 210 ° C. to obtain an optical fiber in which the refractive index gradually decreased from the central portion toward the peripheral portion.
[0085]
The optical transmission characteristics of the obtained optical fiber were 150 dB / km at 780 nm and 80 dB / km at 1550 nm, and it was confirmed that the optical fiber can transmit light from visible light to near infrared light well.
[0086]
"Comparative Example 1"
In the refractive index distribution type plastic optical fiber, the optical transmission loss of PMMA is about 400 dB / km at a wavelength of 650 nm, and the transmission loss is very large at wavelengths of 780 nm, 1300 nm, and 1550 nm, making it impractical as an optical transmission body.
[0087]
Further, in a step-index plastic optical fiber, a fluororesin optical fiber with a core and a clad can transmit light from visible light to near infrared light, but its optical transmission loss is reported to be about 300 dB / km.
[0088]
In contrast, the gradient index transparent fluororesin optical fiber according to the present invention can transmit light from visible light to near infrared light with extremely low loss.
[0089]
"Comparative Example 2"
In the case of the fiber made in the same manner as in “Example 1” except that PFPE is not added, the glass transition temperature of the central portion is 82 ° C., whereas the glass transition temperature of the outer peripheral portion is 108 ° C. The optical transmission characteristics of the obtained optical fiber were 400 dB / km at 780 nm and 280 dB / km at 1550 nm, resulting in an increase in transmission loss several times or more when PFPE was added. Moreover, when the fractured surface of this fiber was observed with a scanning electron microscope (SEM), it was confirmed that many microvoids were generated in the fiber.
[0090]
【The invention's effect】
Since the optical resin material of the present invention uses an amorphous fluororesin and the occurrence of microvoids is suppressed, light from ultraviolet light to near infrared light is extremely low loss in a plastic optical transmission body. It became possible to transmit.
[0091]
In particular, the gradient index optical fiber is flexible and easy to branch and connect despite its large fiber diameter, making it ideal for short-distance optical communications. However, no practical low-loss optical fiber has been proposed so far. . The present invention provides a low-loss optical fiber that can be used for short-distance optical communication.
[0092]
In addition, the optical resin material of the present invention is a plastic optical transmission body having heat resistance, chemical resistance, moisture resistance, and nonflammability that can withstand severe use conditions in automobile engine rooms, OA equipment, plants, home appliances, etc. It is to provide. Furthermore, the optical resin material of the present invention can be used not only as an optical fiber but also as a flat plate or rod type lens. In that case, it can function as a convex lens and a concave lens depending on whether the refractive index change from the central part to the peripheral part is lowered or raised.
[Brief description of the drawings]
FIG. 1 is a graph showing a correlation between a PFPE content, a refractive index, and a glass transition temperature in a homogeneous transparent mixture of a polymer A and PFPE.

Claims (5)

Amorphous fluorinated polymer substantially free of C—H bonds (a)
And at least one substance (b) having substantially no CH bond having a difference in refractive index of 0.001 or more in comparison with the fluoropolymer (a). (A) a refractive index distribution type optical resin material in which the substance (b) is distributed with a concentration gradient along a specific direction, and the optical resin An optical resin material characterized in that the glass transition temperature of the entire material is substantially uniform. Substance (c) which has substantially no C—H bond in the fluoropolymer (a) and corrects the glass transition temperature of the optical resin material which varies depending on the distribution of the substance (b)
The optical resin material according to claim 1, wherein is distributed. The optical resin material according to claim 1 or 2, wherein the fluoropolymer (a) is a fluoropolymer having a ring structure in the main chain. The optical resin material according to claim 1, 2 or 3, wherein the optical resin material is a preform for manufacturing a gradient index optical fiber or a gradient index optical fiber. Amorphous fluorinated polymer substantially free of C—H bonds (a)
And at least one substance (b) having substantially no CH bond having a difference in refractive index of 0.001 or more in comparison with the fluoropolymer (a). In manufacturing a refractive index distribution type optical resin material in which a substance (b) is distributed with a concentration gradient along a specific direction in (a) by a multilayer extrusion melt molding method of two or more layers, a nozzle By making the glass transition temperature of the material supplied to the center and the glass transition temperature of the material supplied to the outer periphery substantially uniform, the glass transition temperature of the entire optical resin material can be increased regardless of the center and outer periphery. A method for producing an optical resin material, comprising: obtaining an optical resin material that is substantially uniform.

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