JPWO2002046811A1 - Plastic optical fiber - Google Patents

Abstract

A step index type plastic optical fiber having a large numerical aperture (NA), low transmission loss over a wide wavelength range, and low bending loss. The material of the core and the clad is made of an amorphous fluorine resin having substantially no hydrogen atoms, and the material of the core is made of an amorphous fluorine resin having a higher refractive index than before, and / or A step index type plastic optical fiber in which the difference in refractive index between the two materials is increased by employing an amorphous fluororesin having a lower refractive index than the conventional one.

Description

また本発明は、コアが実質的に水素原子を有しない含フッ素重合体から構成される非晶質フッ素樹脂（Ａ）、または高屈折率化剤を含む該非晶質フッ素樹脂（Ａ）からなり、クラッドが実質的に水素原子を有しない含フッ素重合体から構成される非晶質フッ素樹脂（Ｂ）、または実質的に水素原子を有しない含フッ素可塑剤を含む該非晶質フッ素樹脂（Ｂ）からなり、開口数（ＮＡ）が０．４１５以上であることを特徴とする、ＳＩ型光ファイバ、である。
また本発明は、ペルフルオロ（２−ペンチル−１，３−ジオキソール）、これを単量体として重合した繰り返し単位を有する含フッ素重合体、および該重合体を用いたことを特徴とする、光学部材である。
発明を実施するための最良の形態
本発明における非晶質フッ素樹脂は、１種のみのまたは混合された２種以上の、非晶質となる特定の含フッ素重合体から構成され、他の構成成分として該含フッ素重合体以外に少量の添加剤を含んでいてもよい。さらに、非晶質フッ素樹脂は、それが全体として非晶質であるかぎり、少量の結晶性含フッ素重合体（単独では結晶質となる含フッ素重合体）を含んでいてもよい。
特定の含フッ素重合体はまた実質的に水素原子を有しない重合体である。非晶質となる特定の含フッ素重合体以外の他の重合体が併用される場合はその他の重合体も実質的に水素原子を有しない重合体である。すなわち、本発明における非晶質フッ素樹脂を構成する重合体は、実質的に水素原子を有しない重合体から構成される。以下特に言及しないかぎり、非晶質フッ素樹脂を構成する重合体とは実質的に水素原子を有しないものを意味する。なお、以下「重合体」とは、特に「単独重合体」、「共重合体」と言及しないかぎり、単独重合体であっても共重合体であってもよい。
ＳＩ型光ファイバは、コアとそれよりも相対的に低屈折率のクラッドからなる。コアとクラッドの屈折率差が大きいほど開口数（ＮＡ）が大きくなる。非晶質フッ素樹脂は本来低屈折率の樹脂であり、これをコアの材料として使用するとそれに比較してさらに低屈折率でなくてはならないクラッドの材料の選択の巾が小さく屈折率差を大きくすることは困難であった。本発明は、クラッドの材料としてコアと同じ範疇の非晶質フッ素樹脂を使用し、かつ従来に比較してコアとクラッドの屈折率差を大きくするとともに、各材料の光学的物性や機械的物性を高めることを目的とする。
本発明の１つは、コアの材料として屈折率を高める効果のある塩素原子を有する含フッ素重合体から構成される非晶質フッ素樹脂を使用してコアの屈折率を高め、クラッドとの屈折率差を大きくするものである。この塩素原子は重合体の側鎖に結合した塩素原子でなくてはならず、塩素原子が主鎖の炭素原子に結合していると、単量体の重合性が悪くなり重合体として安定な物性の得られる高分子量体が得られない、または結晶性が高くなり散乱損失が増加する等の問題がある。
なお、本発明において、非晶質フッ素樹脂を構成する含フッ素重合体の主鎖は、炭素原子のみの連鎖からなり、その主鎖は重合性二重結合を構成する２個の炭素原子の連鎖から形成される。また、重合性二重結合を２個有する単量体（以下含フッ素ジエン類ともいう）の環化重合で得られる重合体においては２個の重合性二重結合を構成する４個の炭素原子の連鎖から主鎖が形成される。したがって、側鎖に塩素原子を有するとは、これら重合性二重結合を構成する炭素原子に直接結合した塩素原子を有さず、他の炭素原子に結合している塩素原子を有することを意味する。
本発明はまた、コアの材料として高屈折率化剤を含む非晶質フッ素樹脂を使用することによりコアの屈折率を高め、クラッドとの屈折率差を大きくするものである。この高屈折率化剤は配合される非晶質フッ素樹脂を構成する含フッ素重合体よりも高屈折率の化合物であり、それが配合された非晶質フッ素樹脂の屈折率はそれが配合されていない非晶質フッ素樹脂よりも高い屈折率を有する。通常非晶質フッ素樹脂の屈折率は高屈折率化剤の配合量に従って高くなる。高屈折率化剤としては特に実質的に水素原子を有しない含フッ素芳香族化合物が好ましい。
さらに本発明は、クラッドの非晶質フッ素樹脂を構成する含フッ素重合体として従来より屈折率の低い含フッ素重合体を用いてコアとの屈折率差を大きくするものである。クラッドの非晶質フッ素樹脂を構成する含フッ素重合体としてペルフルオロ（２，２−ジメチル−１，３−ジオキソール）（下式（５）、以下ＰＤＤという）の重合体が知られているが、この発明ではそれよりもさらに屈折率の低い含フッ素重合体を使用する。

これらコアとクラッドの屈折率差を大きくする手段は２以上を組み合わせることもできる。例えば、塩素原子を有する含フッ素重合体と高屈折率化剤を組み合わせてコアとする、さらにこのコアとより低屈折率の含フッ素重合体からなるクラッドを組み合わせる、高屈折率化剤を含む非晶質フッ素樹脂からなるコアとより低屈折率の含フッ素重合体からなるクラッドを組み合わせる、等である。
さらに本発明ではクラッドを含フッ素可塑剤を含む非晶質フッ素樹脂とすることができる。クラッドの材料である低屈折率の含フッ素重合体は通常剛性が高く脆いことより可塑剤を配合して柔軟性を高めることが好ましい。クラッドを柔軟性の高い材料で構成することにより、ＳＩ型光ファイバを曲げたとき等にクラック等の発生を抑制しうる。この可塑剤としては含フッ素重合体との親和性を高めるうえでフッ素化合物であることが必要であり、しかも実質的に水素原子を有しないことが好ましい。この含フッ素可塑剤がフッ素含有量の高い化合物である場合はクラッドの屈折率を低める効果もある。
本発明においてコアとクラッドの屈折率差を大きくすること、すなわち開口数（ＮＡ）を大きくすることは、ＳＩ型光ファイバを曲げたときに伝送損失の増大を抑制する、センサに使用した場合、広い範囲から集光できるため、センサ感度が向上する、等の効果が得られ好ましい。
本発明ＳＩ型光ファイバが充分大きな開口数を達成するためにはコアの非晶質フッ素樹脂とクラッドの非晶質含フッ素樹脂との屈折率差は０．０２０以上であることが必要である。この屈折率差が大きいほど高い大きい開口数が得られる。この屈折率差としては、好ましくは０．０３０以上であり、より好ましくは０．０４０以上であり、さらに好ましくは０．０４５以上であり、特に好ましくは０．０５０以上であり、最も好ましくは０．０６０以上である。屈折率差の上限は特にはないが通常０．２である。
この屈折率差に基づき、本発明ＳＩ型光ファイバの開口数としては、０．２８０以上が好ましい。より好ましくは０．３２５以上であり、さらに好ましくは０．３６４以上であり、特に好ましくは０．３８０以上であり、最も好ましくは０．４１５以上である。開口数の上限は特にはないが通常０．７５である。
上記屈折率差を大きくするためには、従来に比較してより高屈折率のコア材料を使用する方法、従来に比較してより低屈折率のクラッド材料を使用する方法、従来に比較してより高屈折率のコア材料と従来に比較してより低屈折率のクラッド材料とを組み合わせる方法があり、本発明におけるコアの非晶質フッ素樹脂とクラッドの非晶質フッ素樹脂はこれら方法のいずれにも適用できる。
本発明におけるコアの非晶質フッ素樹脂とクラッドの非晶質フッ素樹脂は、屈折率が相違する点を除き、同じ範疇の非晶質フッ素樹脂である。両者を区別するために、以下コアの非晶質フッ素樹脂を非晶質フッ素樹脂（Ａ）といい、クラッドの非晶質フッ素樹脂を非晶質フッ素樹脂（Ｂ）という。
これら非晶質フッ素樹脂を構成する含フッ素重合体は、実質的に水素原子を有しないものであり、炭素−水素結合を有しない重合体である。非晶質フッ素樹脂が実質的に水素原子を有しない含フッ素重合体から構成されることにより、近赤外領域での伝送損失が低減され、可視光から近赤外光までの光を良好に伝達できるＳＩ型光ファイバが得られる。またフッ素樹脂が非晶質であることは、ＳＩ型光ファイバの特に短波長領域における散乱損失を減少させる。
また非晶質フッ素樹脂は含フッ素重合体のみからなっていてもよく、光伝送性能や機械的性能等を実質的に阻害しないかぎり添加剤を含んでいてもよい。添加剤としては、可塑剤、屈折率調整剤、各種安定剤、架橋剤等が挙げられる。これらは、光伝送性能を実質的に阻害しないために、または性能を向上させるために、含フッ素重合体と親和性の高いフッ素化合物であることが好ましい。特にコアの非晶質フッ素樹脂（Ａ）に屈折率調整剤として高屈折率化剤を含ませることはＳＩ型光ファイバのＮＡを大きくするうえで好ましい。またクラッドの非晶質フッ素樹脂（Ｂ）に可塑剤を含ませることは光ファイバに柔軟性を持たせるうえで好ましい。
本発明における非晶質フッ素樹脂を構成する含フッ素重合体としては、含フッ素ジエン類が環化重合した繰り返し単位を有する重合体（以下環化重合体ともいう）および含フッ素ジオキソール類が重合した繰り返し単位を有する重合体（以下ジオキソール系重合体ともいう）が好ましい。環化重合体は含フッ素ジエン類の２種以上の共重合体であってもよく、含フッ素ジエン類と他の共重合性単量体との共重合体であってもよい。他の共重合性単量体としては重合性モノエン類が適当である。ジオキソール系重合体も含フッ素ジオキソール類２種以上の共重合体であってもよく、含フッ素ジオキソール類と他の共重合性単量体との共重合体であってもよい。さらに非晶質フッ素樹脂を構成する含フッ素重合体としては含フッ素ジエン類と含フッ素ジオキソール類の共重合体であってもよい。
上記含フッ素重合体の中でジオキソール系重合体は環化重合体に比較して特に屈折率が低くなる傾向があることより、クラッドの非晶質フッ素樹脂（Ｂ）を構成する含フッ素重合体としてはジオキソール系重合体が好ましく、コアの非晶質フッ素樹脂（Ａ）を構成する含フッ素重合体としては環化重合体が好ましい。含フッ素ジエン類と含フッ素ジオキソール類の共重合体の場合、組み合わされる他の非晶質フッ素樹脂との屈折率の相違によりコアにもクラッドにも使用しうるが、通常はクラッドの材料として適当である。
上記重合体は後記の単量体を用いてバルク重合、溶液重合、懸濁重合、乳化重合等公知のいずれの方法を使用しても得られる。重合には通常ラジカル発生剤が重合開始剤として用いられる。重合後に重合体末端の不安定性基を除去するために得られた重合体をフッ素化する等の後処理を行うこともできる。
上記含フッ素重合体の溶融状態における粘度は、溶融温度２００〜３００℃において１×１０^２〜１×１０^５Ｐａ・ｓが好ましい。溶融粘度が高すぎると溶融紡糸が困難になる。また、溶融粘度が低すぎても実用上好ましくない。すなわち、電子機器や自動車等での光伝送体として用いられる場合に高温で軟化し、ＳＩ型光ファイバとしての伝送性能が劣化する。
また上記含フッ素重合体の数平均分子量Ｍ_ｎは１×１０^４〜５×１０^６が好ましく、５×１０^４〜１×１０^６がより好ましい。分子量が小さすぎると耐熱性が悪くなることがあり、大きすぎると溶融粘度が高くなり成形が困難となり好ましくない。
非晶質フッ素樹脂を構成する含フッ素重合体のうち環化重合体としては下記式（１）で表される単量体（以下単量体（ａ）という）が環化重合した繰り返し単位を有する重合体が好ましい。

ただし、ｍは０〜５の整数、Ｒ^１、Ｒ^２、Ｒ^３およびＲ^４はそれぞれ独立に炭素数１〜９のペルフルオロアルキル基、塩素原子またはフッ素原子、を表す。ｍが２以上の場合、複数のＲ^３（Ｒ^４も同じ）は互いに異なっていてもよい。ｍとしては特に０〜３の整数が好ましい。
Ｒ^１、Ｒ^２、Ｒ^３およびＲ^４としては、多くとも３個がペルフルオロアルキル基または塩素原子であり他がフッ素原子であることが好ましい。特に、ペルフルオロアルキル基または塩素原子を有する単量体（ａ）としては、Ｒ^１とＲ^２の少なくとも一方がペルフルオロアルキル基または塩素原子であり、他は全てフッ素原子である化合物が好ましい。また、ペルフルオロアルキル基としては炭素数１〜２のペルフルオロアルキル基が好ましい。
単量体（ａ）が環化重合した繰り返し単位は通常下記式（１ａ）または（１ｂ）の構造を有する。

単量体（ａ）のうち塩素原子を有しない単量体（以下単量体（ａ−２）という）としては、例えば以下の単量体が挙げられる。これらの単量体の合成方法は、特開平１−１３１２１５号公報、特開平４−３４６９５７号公報等に開示されている。
ペルフルオロ（３−オキサ−１，５−ヘキサジエン）（ＣＦ_２＝ＣＦ−ＣＦ_２−Ｏ−ＣＦ＝ＣＦ_２）、ペルフルオロ（３−オキサ−１，６−ヘプタジエン）（ＣＦ_２＝ＣＦ−ＣＦ_２−ＣＦ_２−Ｏ−ＣＦ＝ＣＦ_２）（以下ＢＶＥという）、ペルフルオロ（３−オキサ−４−メチル−１，６−ヘプタジエン）（ＣＦ_２＝ＣＦ−ＣＦ_２−ＣＦ（ＣＦ_３）−Ｏ−ＣＦ＝ＣＦ_２）（以下ＢＶＥ−４Ｍという）、ペルフルオロ（３−オキサ−４，４−ジメチル−１，６−ヘプタジエン）（ＣＦ_２＝ＣＦ−ＣＦ_２−Ｃ（ＣＦ_３）_２−Ｏ−ＣＦ＝ＣＦ_２）、ペルフルオロ（３−オキサ−５−メチル−１，６−ヘプタジエン）（ＣＦ_２＝ＣＦ−ＣＦ（ＣＦ_３）−ＣＦ_２−Ｏ−ＣＦ＝ＣＦ_２）。
単量体（ａ）のうち塩素原子を有する単量体（以下単量体（ａ−１）という）としては、例えば以下の単量体が挙げられる。
４−クロロ−ペルフルオロ（３−オキサ−１，５−ヘキサジエン）（ＣＦ_２＝ＣＦ−ＣＣｌＦ−Ｏ−ＣＦ＝ＣＦ_２）、４−クロロ−ペルフルオロ（３−オキサ−１，６−ヘプタジエン）（ＣＦ_２＝ＣＦ−ＣＦ_２−ＣＣｌＦ−Ｏ−ＣＦ＝ＣＦ_２）（以下ＢＶＥ−４ＣＬという）、４，４−ジクロロ−ペルフルオロ（３−オキサ−１，６−ヘプタジエン）（ＣＦ_２＝ＣＦ−ＣＦ_２−ＣＣｌ_２−Ｏ−ＣＦ＝ＣＦ_２）（以下ＢＶＥ−４ＤＣＬという）、５−クロロ−ペルフルオロ（３−オキサ−１，６−ヘプタジエン）（ＣＦ_２＝ＣＦ−ＣＣｌＦ−ＣＦ_２−Ｏ−ＣＦ＝ＣＦ_２）。
環化重合体は単量体（ａ）の２種以上の共重合体であってもよく、単量体（ａ）と他の共重合性単量体との共重合体であってもよい。すなわち、環化重合体は、単量体（ａ）が環化重合した繰り返し単位以外に他の共重合性単量体が重合した繰り返し単位を含んでいてもよい。他の共重合性単量体としてはモノエン類が好ましく、このモノエン類は実質的に水素原子を有せず、塩素原子を有する場合は重合性二重結合を構成する炭素原子に直接結合する塩素原子を有しない化合物である。
具体的には例えば、後述式（２）で表される単量体である単量体（ｃ）、後述式（４）で表される単量体である単量体（ｂ）、テトラフルオロエチレン（以下ＴＦＥという）等のペルフルオロオレフィン類、ペルフルオロ（３−オキサ−１−ヘキセン）（ＣＦ_３−ＣＦ_２−ＣＦ_２−Ｏ−ＣＦ＝ＣＦ_２）等のペルフルオロ（アルキルビニルエーテル）類、ペルフルオロ（２−メチレン−４−メチル−１，３−ジオキソラン）（下式（６）、以下ＭＭＤという）等のペルフルオロ（メチレンジオキソラン）類等がある。

単量体（ｂ）との共重合体を除き、環化重合体中の全繰り返し単位に対する単量体（ａ）が環化重合した繰り返し単位の割合は２０〜１００モル％が適当であり、４０〜１００モル％が好ましく、特に５０〜１００モル％が好ましい。この割合が少なすぎると光学物性や機械的物性の良好な重合体が得られ難い。単量体（ｂ）との共重合体の場合は単量体（ａ）が環化重合した繰り返し単位の割合は特に限定されない。
下記式（２）で表される単量体（以下単量体（ｃ）という）は側鎖に塩素原子を有する環化重合体を製造するために好ましい単量体である。この単量体は重合性二重結合から遠い位置に塩素原子を２個有することより、この単量体（ｃ）と単量体（ａ）とを共重合して得られる環化重合体は屈折率が高くかつ物性の良好な環化重合体となる。

ただし、ｎは０〜５の整数、Ｒ^５、Ｒ^６、Ｒ^７およびＲ^８はそれぞれ独立に炭素数１〜９のペルフルオロアルキル基、塩素原子またはフッ素原子、を表す。ｎが２以上の場合複数のＲ^７（Ｒ^８も同じ）は互いに異なっていてもよい。ｎは０〜３の整数が好ましく、Ｒ^５、Ｒ^６、Ｒ^７およびＲ^８はすべてフッ素原子であることが好ましい。また、ペルフルオロアルキル基を有する場合はＲ^５とＲ^６のいずれか一方または両方のみがペルフルオロアルキル基で他はすべてフッ素原子であることが好ましい。また、ペルフルオロアルキル基としては炭素数１〜２のペルフルオロアルキル基が好ましい。
単量体（ｃ）の具体例としては、例えば、６，７−ジクロロ−ペルフルオロ（３−オキサ−１−ヘプテン）（ＣＣｌＦ_２−ＣＣｌＦ−ＣＦ_２−ＣＦ_２−Ｏ−ＣＦ＝ＣＦ_２）（以下２ＣＬＢＶＥという）等が挙げられる。単量体（ｃ）の合成方法は特開平１−１３１２１５号公報等に開示されている。
ジオキソール系重合体は含フッ素ジオキソール類の１種以上の重合体または含フッ素ジオキソール類と他の共重合性単量体との共重合体である。含フッ素ジオキソール類としては下記式（３）で表される単量体（以下単量体（ｂ）という）が好ましい。

ただし、Ｒ^１１およびＲ^１２はそれぞれ独立に炭素数１〜９のペルフルオロアルキル基またはフッ素原子を表す。Ｒ^１１およびＲ^１２のうち少なくとも一方はペルフルオロアルキル基であることが好ましい。また、ペルフルオロアルキル基の炭素数は１〜６がより好ましい。
ジオキソール系重合体は単量体（ｂ）の１種以上の重合体であってもよいが、通常は他の共重合性単量体との共重合体が好ましい。すなわち、ジオキソール系重合体は、単量体（ｂ）が重合した繰り返し単位以外に他の共重合性単量体が重合した繰り返し単位を含んでいることが好ましい。他の共重合性単量体としてはモノエン類や環化重合しうるジエン類が好ましく、これらは実質的に水素原子を有しない単量体であり、また塩素原子を有しないことが好ましい。具体的には例えば、前記単量体（ａ）、ＴＦＥ等のペルフルオロオレフィン類、ペルフルオロ（３−オキサ−１−ヘキセン）（ＣＦ_３−ＣＦ_２−ＣＦ_２−Ｏ−ＣＦ＝ＣＦ_２）等のペルフルオロ（アルキルビニルエーテル）類、ＭＭＤ等のペルフルオロ（メチレンジオキソラン）類等がある。他の単量体としては特にＴＦＥが好ましい。
単量体（ａ）との共重合体を除き、ジオキソール系重合体中の全繰り返し単位に対する単量体（ｂ）が重合した繰り返し単位の割合は２０〜９５モル％が適当であり、３０〜９０モル％が好ましく、特に３５〜８５モル％が好ましい。この割合が少なすぎても多すぎても光学物性や機械的物性の良好な重合体が得られ難い。
単量体（ａ）と単量体（ｂ）の共重合体の場合は、得られる含フッ素重合体を非晶質フッ素樹脂（Ａ）の構成成分とするか非晶質フッ素樹脂（Ｂ）の構成成分とするかによって（すなわち、高屈折率の含フッ素重合体と低屈折率含フッ素重合体のいずれに用いるかによって）、その共重合割合が選択される。高屈折率含フッ素重合体の場合は単量体（ａ）が環化重合した繰り返し単位の割合の高い重合体とし、低屈折率の含フッ素重合体の場合は単量体（ｂ）が重合した繰り返し単位の割合が高い重合体とする。前者の場合、単量体（ｂ）が重合した繰り返し単位の割合は０モル％超〜４０モル％が好ましく、特に１〜３０モル％が好ましい。後者の場合、単量体（ｂ）が重合した繰り返し単位の割合は３０モル％〜１００モル％未満が好ましく、特に４０〜９５モル％が好ましい。
ジオキソール系重合体のうち、下記式（４）で表される単量体（以下単量体（ｂ−１）という）が重合した繰り返し単位を有する含フッ素重合体はより低い屈折率を有する。すなわち、ＰＤＤが重合した繰り返し単位を有する重合体とＰＤＤが重合した繰り返し単位の代わりに単量体（ｂ−１）が重合した繰り返し単位を有する以外は同じ重合体とを比較すると、後者はより低い屈折率を有する。

ただし、Ｒ^１３は炭素数２〜９のペルフルオロアルキル基、Ｒ^１４は炭素数９以下のペルフルオロアルキル基またはフッ素原子を表す。Ｒ^１３は炭素数２〜６のペルフルオロアルキル基が好ましく、Ｒ^１４は炭素数１〜６のペルフルオロアルキル基またはフッ素原子が好ましい。
単量体（ｂ−１）の具体例としては、以下のもの等が挙げられる。
ペルフルオロ（２−エチル−１，３−ジオキソール）（下記式（７）でｋが１のもの）、
ペルフルオロ（２−プロピル−１，３−ジオキソール）（下記式（７）でｋが２のもの）、
ペルフルオロ（２−ペンチル−１，３−ジオキソール）（下記式（７）でｋが４のもの）、
ペルフルオロ（２−エチル−２−メチル−１，３−ジオキソール）（下記式（８）でｊが１のもの）、
ペルフルオロ（２−メチル−２−プロピル−１，３−ジオキソール）（下記式（８）でｊが２のもの）、
ペルフルオロ（２−メチル−２−ペンチル−１，３−ジオキソール）（下記式（８）でｊが４のもの）。

単量体（ｂ−１）以外の単量体（ｂ）の例としては、ＰＤＤ、ペルフルオロ（２−メチル−１，３−ジオキソール）等が挙げられる。
単量体（ｂ）のうち、ＰＤＤは米国特許第３８６５８４５号明細書に合成法が開示されている。また、その共重合体は米国特許第３９７８０３０号明細書に合成法が開示されている。他の単量体（ｂ）は特開平２−１１７６７２号公報、特開平５−１９４６５５号公報等に合成法が開示されている。
コアの非晶質フッ素樹脂（Ａ）は高屈折率化剤を含むことが好ましい。高屈折率化剤は非晶質フッ素樹脂（Ａ）を構成する含フッ素重合体より高屈折率であり、かつその含フッ素重合体に対して高い親和性を有する必要がある。高い親和性を有するとは含フッ素重合体に充分に溶解して不溶解物がなくかつミクロな相分離構造が生じるおそれのないことをいう。そのような不溶解物やミクロ相分離構造が存在するとその部分が光散乱の要因となる。したがって、高屈折率化剤としてはコアの含フッ素重合体にその飽和溶解度量以下配合され、しかもその量でコアの非晶質フッ素樹脂（Ａ）を充分高屈折率化しうる化合物が使用される。
高い親和性を有するために高屈折率化剤は比較的低分子量のフッ素化合物が好ましい。また、高屈折率であるために、塩素原子、芳香核、金属成分等を有することが好ましい。特に塩素原子および／または芳香核を有する化合物が好ましい。さらに、高屈折率化剤は含フッ素重合体と同様に実質的に水素原子を有しない化合物が好ましい。これにより高屈折率化剤を含む非晶質フッ素樹脂の近赤外領域での伝送損失低減が維持される。これらの理由により、高屈折率化剤としては、実質的に水素原子を有しない、かつ、塩素原子および／または芳香核を有する比較的低分子量のフッ素化合物であることが好ましい。
高屈折率化剤の分子量は２０００以下が好ましく、オリゴマー等の重合体ではその平均分子量が２０００以下が好ましい。例えば、塩素原子を有するフッ素化合物、含フッ素芳香族化合物、含フッ素縮合多環式化合物、金属キレート化合物等が挙げられる。好ましい高屈折率化剤は、実質的に水素原子を有せず、塩素原子を有するフッ素化合物、および、実質的に水素原子を有しない含フッ素芳香族化合物である。さらに好ましくは実質的に水素原子を有しない含フッ素芳香族化合物であり、そのうちでも１分子中のベンゼン核の数が３〜５のペルフルオロ芳香族化合物が特に好ましい。またこれら高屈折率化剤は単独でもまたは２種以上を混合しても使用できる。
含フッ素縮合多環式化合物としては、ペルフルオロアントラセン、ペルフルオロフルオレン、ペルフルオロフェナレン、ペルフルオロフェナントレン等が挙げあれる。
金属キレート化合物としては、ペルフルオロ（テトラフェニルスズ）等が挙げられる。
塩素原子を有するフッ素化合物の例としては、クロロペンタフルオロベンゼン、クロロ−ペルフルオロナフタレン、平均分子量２０００以下のクロロトリフルオロエチレンオリゴマーが挙げられる。クロロトリフルオロエチレンオリゴマーは市販されている平均分子量が２０００以下のものを使用しうるし、蒸留によって平均分子量２０００以下の留分を集めることでも得られる。
含フッ素芳香族化合物としては、ペルフルオロ（トリフェニルホスフィン）、ペルフルオロベンゾフェノン、ペルフルオロビフェニル、ペルフルオロテルフェニル、ペルフルオロ（ジフェニルスルフィド）、ペルフルオロ（２，４，６−トリフェニル−１，３，５−トリアジン）、ペルフルオロ（１，３，５−トリフェニルベンゼン）（以下ＴＰＢという）等が挙げられる。なかでもペルフルオロ（２，４，６−トリフェニル−１，３，５−トリアジン）またはＴＰＢが好ましく、含フッ素重合体との親和性が高いことよりＴＰＢが特に好ましい。
高屈折率化剤を含む非晶質フッ素樹脂（Ａ）において、非晶質含フッ素樹脂（Ａ）中の高屈折率化剤の割合は、非晶質含フッ素樹脂（Ａ）が所望の屈折率に達する量以上でかつ高屈折率化剤の含フッ素重合体に対する溶解度量以下であるかぎり、特に限定されない。通常は非晶質含フッ素樹脂（Ａ）中に３０質量％以下含みうる。好ましい含有量は１〜２０質量％であり、特に５〜２０質量％の高屈折率化剤を含むことが好ましい。
クラッドの非晶質フッ素樹脂（Ｂ）は実質的に水素原子を有しない含フッ素可塑剤を含むことが好ましい。含フッ素可塑剤はクラッドの非晶質フッ素樹脂を柔軟化してＳＩ型光ファイバの加工性を改良し、また太径のファイバにおいてはさらにクラックが発生し難くなる等の特徴を付与する。加えて、フッ素含有量の高い含フッ素可塑剤の配合は、クラッドの非晶質フッ素樹脂の屈折率をさらに低下させる効果もある。
含フッ素可塑剤としてはペルフルオロポリエーテル類等が好ましい。ペルフルオロポリエーテル類としては、例えばペルフルオロ（ポリオキシアルキレンアルキルエーテル）がある。ペルフルオロポリエーテル類の具体例としては、クライトックス（商品名、デュポン社製）、デムナム（商品名、ダイキン工業社製）、フォンブリン（商品名、アウジモント社製）等が挙げられる。成形時や使用時に揮発し難い等の観点から、その平均分子量は１０００以上のものが好ましい。また分子量の上限は特に制限されないが、クラッドの含フッ素重合体との相溶性の観点から、２００００以下が好ましい。
含フッ素可塑剤を含む非晶質フッ素樹脂（Ｂ）において、非晶質含フッ素樹脂（Ｂ）中の含フッ素可塑剤の割合は、非晶質含フッ素樹脂（Ｂ）が所望の可塑化効果を達成する量でかつ含フッ素可塑剤の含フッ素重合体に対する溶解度量以下であるかぎり、特に限定されない。通常は非晶質含フッ素樹脂（Ｂ）中に５０質量％以下含みうる。好ましい含有量は１〜４０質量％、特に５〜４０質量％の含フッ素可塑剤を含むことが好ましい。
非晶質フッ素樹脂（Ａ）は前記のように環化重合体から構成されることが好ましい。この非晶質フッ素樹脂（Ａ）を構成する環化重合体自身の屈折率は１．３３０以上、特に１．３３５以上であることが好ましい。環化重合体自身の屈折率の上限は特にはないが、通常は１．４５である。
環化重合体自身の屈折率が充分高い場合には高屈折率化剤を含ませることなく環化重合体のみで非晶質フッ素樹脂（Ａ）を構成しうる。環化重合体自身の屈折率が充分高くない場合や非晶質フッ素樹脂（Ｂ）の屈折率が比較的高く環化重合体との間の屈折率差が大きくない場合は高屈折率化剤を含む非晶質フッ素樹脂（Ａ）を用いることが好ましい。高屈折率化剤を含んでもよい非晶質フッ素樹脂（Ａ）の屈折率は１．３４０以上が好ましく、１．３４５以上がより好ましく、１．３５０以上がさらに好ましく、１．３５５以上が最も好ましい。非晶質フッ素樹脂（Ａ）の屈折率の上限は特にはないが、通常は１．５である。
本発明において、実質的に水素原子を有しないかつ側鎖に塩素原子を有する含フッ素重合体から構成される非晶質フッ素樹脂（Ａ−１）は、前記非晶質フッ素樹脂（Ａ）のうち側鎖に塩素原子を有する含フッ素重合体から構成される。非晶質フッ素樹脂（Ａ）は環化重合体が好ましいことより、非晶質フッ素樹脂（Ａ−１）もまた環化重合体が好ましい。この側鎖に塩素原子を有する含フッ素重合体自身の屈折率は１．３４５以上、特に１．３５０以上であることが好ましい。また、非晶質フッ素樹脂（Ａ−１）の屈折率は同様に１．３４５以上、特に１．３５０以上であることが好ましい。
非晶質フッ素樹脂（Ａ−１）を構成する、側鎖に塩素原子を有する含フッ素重合体としては、単量体（ａ−１）の環化重合した繰り返し単位を含む重合体（下記単量体（ａ−２）が環化重合した繰り返し単位を有していてもよい）、および、重合性二重結合を構成する炭素原子に直接結合する塩素原子を有せずかつ他の炭素原子に塩素原子を有する共重合性単量体（特にそのような塩素原子を含有するモノエン類）が重合した繰り返し単位と単量体（ａ）が環化重合した繰り返し単位とを含む重合体、が好ましい。塩素原子含有の共重合性単量体としては、特に単量体（ｃ）が好ましい。なお、単量体（ａ）のうち塩素原子を有しない単量体を以下単量体（ａ−２）という。
特に好ましい側鎖に塩素原子を有する含フッ素重合体は、単量体（ａ−１）が環化重合した繰り返し単位を有する重合体（ただし、単量体（ａ−２）が環化重合した繰り返し単位を有しない重合体）、単量体（ａ−１）が環化重合した繰り返し単位と単量体（ａ−２）が環化重合した繰り返し単位とを有する重合体、および、単量体（ａ）が環化重合した繰り返し単位と単量体（ｃ）が重合した繰り返し単位とを有する重合体、である。
非晶質フッ素樹脂（Ａ−１）は、塩素原子を有する含フッ素重合体から構成されることより、高屈折率化剤を含まなくても充分高い屈折率を有する。しかし場合によっては、高屈折率化剤を含んでいてもよい。非晶質フッ素樹脂（Ａ）は、非晶質フッ素樹脂（Ａ−１）をその範疇として含むが、特に塩素原子を有しない含フッ素重合体から構成される場合には高屈折率化剤を含むことが好ましい。非晶質フッ素樹脂（Ａ）が塩素原子を有しない含フッ素重合体から構成される場合であっても、クラッドとして組み合わされる非晶質フッ素樹脂（Ｂ）との間の屈折率差が大きい場合には高屈折率化剤を含む必要はない。
非晶質フッ素樹脂（Ｂ）は前記のようにジオキソール系重合体から構成されることが好ましい。非晶質フッ素樹脂（Ｂ）を構成するジオキソール系重合体と非晶質フッ素樹脂（Ａ）との間の屈折率差が大きいかぎりジオキソール系重合体の屈折率は特に限定されないが、非晶質フッ素樹脂（Ｂ）を構成するジオキソール系重合体自身の屈折率は１．３３０未満、特に１．３１０未満であることが好ましい。非晶質フッ素樹脂（Ａ）との間でより高い屈折率差を達成するためにはジオキソール系重合体自身の屈折率は１．３００未満、特に１．２９６未満であることがさらに好ましい。ジオキソール系重合体自身の屈折率の下限は特にはないが通常は１．２９０である。ジオキソール系重合体に限定されないが、屈折率１．３００未満の含フッ素重合体から構成される非晶質フッ素樹脂を以下非晶質フッ素樹脂（Ｂ−２）という。
前記のように単量体（ｂ−１）が重合した繰り返し単位を有する含フッ素重合体は単量体（ｂ−１）以外の単量体（ｂ）が重合した繰り返し単位を有する含フッ素重合体よりも低屈折率である。この単量体（ｂ−１）が重合した繰り返し単位を有する含フッ素重合体から構成される非晶質フッ素樹脂（Ｂ）を以下非晶質フッ素樹脂（Ｂ−３）という。また、単量体（ｂ−１）が重合した繰り返し単位を有する含フッ素重合体のうちでさらに好ましい重合体は屈折率が１．３００未満、特に１．２９６未満の含フッ素重合体である。
したがって、非晶質フッ素樹脂（Ｂ−２）および非晶質フッ素樹脂（Ｂ−３）を構成する含フッ素重合体としては、単量体（ｂ−１）が重合した繰り返し単位を有しかつ屈折率が１．３００未満の含フッ素重合体が好ましい。特に好ましいこの含フッ素重合体は、単量体（ｂ−１）とＴＦＥとの共重合モル比が９９〜２０／１〜８０の範囲の共重合体である。
含フッ素可塑剤を含んでいてもよい非晶質フッ素樹脂（Ｂ）の屈折率は１．３３０未満が好ましく、特に１．３１０未満が好ましい。特に好ましい非晶質フッ素樹脂（Ｂ）の屈折率は１．３００未満であり、最も好ましくは１．２９６未満である。非晶質フッ素樹脂（Ｂ）の屈折率の下限は特にはないが通常は１．２８５である。
本発明のＳＩ型光ファイバは公知のＳＩ型光ファイバを製造する方法で製造できる。例えば前記特許第２８２１９３５号公報記載の方法で製造できる。また、特開平８−５８４８号公報や特開平１１−１６７０３０号公報等に記載されている屈折率分布型プラスチック光ファイバの製造法を応用して本発明のＳＩ型光ファイバを製造することもできる。例えばＳＩ型光ファイバ製造用プリフォーム（以下単にプリフォームという）を製造し、プリフォームから紡糸してＳＩ型光ファイバとする方法、または押出機で多色紡糸する方法に準じてＳＩ型光ファイバを製造する方法等が挙げられる。
本発明のＳＩ型光ファイバはフッ素原子の撥水撥油効果により水の吸収による伝送損失の増加がなく、耐溶剤性も高い。また可視領域から近赤外領域までの広い波長範囲にわたって伝送損失が少ない光ファイバとなる。
また本発明のＳＩ型光ファイバはコアとクラッドの屈折率差を充分大きくできることよりその開口数（ＮＡ）を０．４１５以上にもすることができる。大きな開口数を備えたＳＩ型光ファイバは、広い角度から光を入射できる、すなわちセンサとして広い角度からの信号が検出できる、光源−ファイバ間の結合効率が高くできる、すなわち高効率で光源のエネルギーを入力・伝送できる、伝送時の曲げ損失が小さく抑えられる、等の特徴がある。
本発明のＳＩ型光ファイバは、さらに被覆をして光ファイバコードや光ファイバケーブル、または束ねてバンドル光ファイバケーブル等の形で使用できる。
本発明のＳＩ型光ファイバは、波長６００〜１６００ｎｍで、１００ｍの伝送損失が５ｄｂ以下（すなわち５０ｄＢ／ｋｍ以下）とすることができる。波長６００〜１６００ｎｍという広い波長領域において、このような低レベルの伝送損失であることはきわめて有利である。すなわち、石英光ファイバと同じ波長を使えることにより、石英光ファイバとの接続が容易であり、また波長６００〜１６００ｎｍ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に比べ、安価な光源ですむ利点がある。
一方、プラスチック光ファイバはファイバ径が太く光源・受光素子との接続またはファイバ同士の接続が容易なことから安価な短距離通信システムの構築への期待が高まっている。本発明のＳＩ型光ファイバは耐熱性が飛躍的に向上しているので、熱的な安定性が高く、室温以上の高温に長期間さらされた場合においても、伝送損失の低下を防止できる。
（実施例）
次に、本発明を実施例によって具体的に説明するが、本発明はこれらに限定されない。部は質量部を表す。例１〜３は含フッ素ジオキソール類を合成した単量体合成例である。例４〜２７は非晶質フッ素樹脂を構成する含フッ素重合体を製造するための重合体製造例である。例２８〜４１はＳＩ型光ファイバを製造するための非晶質フッ素樹脂製造例である。例４２〜５８はＳＩ型光ファイバの作成例である。
［単量体合成例］
（例１）ペルフルオロ（２−メチル−２−プロピル−１，３−ジオキソール）（以下ＰＭＰＲＯＤという）の合成。
２Ｌガラス製４口フラスコに、６０％発煙硫酸１．５ｋｇを入れ、滴下ロートを用いてＣＦ_３（ＣＦ_２）_５Ｉを４４６ｇ滴下した。６５℃に保って２４時間撹拌を続けた。反応終了後、冷却すると２相に分離したので、上層だけを集めて蒸留を行い、無色透明なＣＦ_３（ＣＦ_２）_４ＣＯＦを１９０ｇ（収率６０％）得た。
次に、２Ｌポリプロピレン製ビーカーに１Ｌのエタノールと数滴のフェノールフタレインを入れ、マグネチックスターラで撹拌しながらＣＦ_３（ＣＦ_２）_４ＣＯＦを１９０ｇ滴下した。その溶液に、１０％水酸化ナトリウムのエタノール溶液を液が中性になるまで滴下した。得られた反応溶液からエバポレータを用いてエタノールを除去し、得られた固体を真空乾燥機に移し、１００℃で１８時間真空乾燥を行った。次に、真空乾燥後の固体を５Ｌガラス製フラスコに移し、そのフラスコをドライアイストラップを通して真空ポンプを用いた減圧下で、油浴中で２５０〜２７０℃を保ちながら２４時間加熱を続けた。ドライアイストラップに捕集された液体を蒸留することにより、ＣＦ_３ＣＦ_２ＣＦ_２ＣＦ＝ＣＦ_２を１１３ｇ（収率７５％）得た。
次に、２Ｌガラス製４口フラスコに１５％次亜塩素酸ナトリウム水溶液１０００ｇとトリオクチルメチルアンモニウムクロリド８ｇを入れ、よく撹拌しながら内温が１０〜１５℃になるまで冷却した。そこへＣＦ_３ＣＦ_２ＣＦ_２ＣＦ＝ＣＦ_２を１１３ｇ、内温を２０〜３０℃に保つように滴下した。その後、ガスクロマトグラフで反応を追跡しながら、原料であるＣＦ_３ＣＦ_２ＣＦ_２ＣＦ＝ＣＦ_２がほぼ消費されるまで反応させた。２相分離により下層の生成物を抜き出し、残存次亜塩素酸ナトリウムを除くためイオン交換水で３回洗浄を行った。さらに粗生成物を蒸留することにより純粋な含フッ素エポキシド（ペルフルオロ（１，２−エポキシペンタン））を８３ｇ（収率７０％）得た。
次に、２００ｍＬガラス製４口フラスコに塩化アルミニウム３ｇを入れ、トリクロロフルオロメタン１０ｇを加えて活性化を行った。そこへ上記で合成した含フッ素エポキシド８３ｇをよく撹拌しながら内温を２０〜３０℃に保つように滴下した。その後、ガスクロマトグラフで反応を追跡しながら反応温度２０〜４０℃で原料がほぼ消費されるまで反応させた。続いてろ過により粗生成物を単離し、蒸留することにより純粋なＣＦ_３ＣＦ_２ＣＦ_２ＣＯＣＦ_３を７６ｇ（収率９２％）得た。
次に、３００ｍＬガラス製４口フラスコ中に２−クロロエタノールを２５ｇ入れ、撹拌しながら７６ｇのＣＦ_３ＣＦ_２ＣＦ_２ＣＯＣＦ_３を室温にて滴下した。得られた反応粗液を、別の１Ｌガラス製フラスコ中に入れた５００ｇの２０％水酸化ナトリウム水溶液中に激しく撹拌させながら滴下した。この反応液を３回水洗し、蒸留することにより、目的のジオキソラン化合物（４，４，５，５−テトラヒドロ−ペルフルオロ（２−メチル−２−プロピル−１，３−ジオキソラン））を７７ｇ（収率８７％）得た。
次に、撹拌機、ドライアイス還流コンデンサ、塩素ガス吹き込み管、熱電対温度計を備えた５００ｍＬガラス製４口フラスコに上記ジオキソラン化合物７７ｇを入れ、５℃にて塩素ガス導入を始めた。反応初期は反応が激しいため塩素の導入はゆっくりと行った。徐々に昇温させ最後は７８℃で反応を続け、塩素の消費が行われなくなった時点で反応終了とした。得られたテトラクロロジオキソラン化合物（４，４，５，５−テトラクロロ−ペルフルオロ（２−メチル−２−プロピル−１，３−ジオキソラン））１００ｇ（収率８９％）を、精製せずにそのまま次の反応に用いた。
次に、撹拌機、還流コンデンサ、熱電対温度計を備えた５００ｍＬガラス製３口フラスコに、三フッ化アンチモン５０ｇ、五塩化アンチモン５ｇ、溶媒としてペルフルオロ（２−ブチルテトラヒドロフラン）（以下ＰＢＴＨＦという）を５０ｍＬ入れ、室温にて上記テトラクロロジオキソラン化合物１００ｇを加え、２４時間還流を続けた。この条件下では目的とするビシナル位の２個の塩素がフッ素置換された化合物のみが選択的に得られた。室温まで冷却させた後、上澄み液のみをデカンテーションで集め、減圧蒸留を行うことで、目的とするジクロロジオキソラン化合物（４，５−ジクロロ−ペルフルオロ（２−メチル−２−プロピル−１，３−ジオキソラン））を７８ｇ（収率８５％）得た。
次に、撹拌機、還流コンデンサ、滴下ロート、熱電対温度計を備えた１Ｌガラス製４口フラスコに、マグネシウム粉末１５ｇ、ヨウ素１ｇ、塩化第二水銀０．５ｇ、テトラヒドロフラン３５０ｍＬを入れ、マントルヒーターを用いて加熱した。還流が始まったら加熱を止め、上記ジクロロジオキソラン化合物を７８ｇゆっくり滴下した。激しく発熱するため必要に応じて反応装置を冷却した。滴下終了後、反応容器を減圧にして液体窒素トラップにてテトラヒドロフランおよび生成物を捕集した。捕集物を冷水に注ぎ込み、下層のフルオロカーボン相を分液し、減圧蒸留によって純度９９．５％の目的とするＰＭＰＲＯＤ（前記式（８）でｊが２のもの）を２５ｇ（収率４０％）得た。これを以下の重合に用いた。
（例２）ペルフルオロ（２−メチル−２−ペンチル−１，３−ジオキソール）（以下ＰＭＰＥＮＤという）の合成。
２Ｌガラス製４口フラスコに、６０％発煙硫酸１．５ｋｇを入れ、滴下ロートを用いてＣＦ_３（ＣＦ_２）_７Ｉを５４６ｇ滴下した。６５℃に保って２０時間撹拌を続けた。反応終了後、冷却すると２相に分離したので、上層だけを集めて蒸留を行い、無色透明なＣＦ_３（ＣＦ_２）_６ＣＯＦを２７０ｇ（収率６５％）得た。
次に、２Ｌポリプロピレン製ビーカーに１Ｌのエタノールとフェノールフタレインを数滴入れ、マグネチックスターラで撹拌しながらＣＦ_３（ＣＦ_２）_６ＣＯＦを２７０ｇ滴下した。その溶液に、１０％水酸化ナトリウムのエタノール溶液を液が中性になるまで滴下した。得られた反応溶液からエバポレータを用いてエタノールを除去し、得られた固体を真空乾燥機に移し、１００℃で１５時間真空乾燥を行った。次に、真空乾燥後の固体を５Ｌガラス製フラスコに移し、そのフラスコをドライアイストラップを通して真空ポンプを用いた減圧下で、油浴中で２６０〜２８０℃を保ちながら２４時間加熱を続けた。ドライアイストラップに捕集された液体を蒸留することにより、ＣＦ_３（ＣＦ_２）_４ＣＦ＝ＣＦ_２を１８０ｇ（収率７９％）得た。
次に、２Ｌガラス製４口フラスコに１５％次亜塩素酸ナトリウム水溶液１０００ｇとトリオクチルメチルアンモニウムクロリド１０ｇを入れ、よく撹拌しながら内温が１０〜１５℃になるまで冷却した。そこへＣＦ_３（ＣＦ_２）_４ＣＦ＝ＣＦ_２を１８０ｇ、内温を２０〜３０℃に保つように滴下した。その後、ガスクロマトグラフで反応を追跡しながら原料であるＣＦ_３（ＣＦ_２）_４ＣＦ＝ＣＦ_２がほぼ消費されるまで反応させた。２相分離により下層の生成物を抜き出し、残存次亜塩素酸ナトリウムを除くためイオン交換水で３回洗浄を行った。さらに粗生成物を蒸留することにより純粋な含フッ素エポキシド（ペルフルオロ（１，２−エポキシヘプタン））を１２２ｇ（収率６５％）得た。
次に、２００ｍＬガラス製４口フラスコに塩化アルミニウム３ｇを入れ、トリクロロフルオロメタン１０ｇを加えて活性化を行った。そこへ上記で合成した含フッ素エポキシド１２０ｇをよく撹拌しながら内温を２０〜３０℃に保つように滴下した。その後、ガスクロマトグラフで反応を追跡しながら反応温度２０〜４０℃で原料がほぼ消費されるまで反応させた。続いてろ過により粗生成物を単離し、蒸留することにより純粋なＣＦ_３（ＣＦ_２）_４ＣＯＣＦ_３を１０８ｇ（収率９０％）得た。
次に、３００ｍＬガラス製４口フラスコ中に２３ｇの２−クロロエタノールを入れ、撹拌しながら１０８ｇのＣＦ_３（ＣＦ_２）_４ＣＯＣＦ_３を室温にて滴下した。得られた反応粗液を、別の１Ｌガラス製フラスコ中に入れた５００ｇの２０％水酸化ナトリウム水溶液中に激しく撹拌させながら滴下した。この反応液を分液ロートを用いて３回水洗し、蒸留することにより、目的のジオキソラン化合物（４，４，５，５−テトラヒドロ−ペルフルオロ（２−メチル−２−ペンチル−１，３−ジオキソラン））を１０３ｇ（収率８５％）得た。
次に、撹拌機、ドライアイス還流コンデンサ、塩素ガス吹き込み管、熱電対温度計を備えた５００ｍＬガラス製４口フラスコに上記ジオキソラン化合物１０３ｇを入れ、５℃にて塩素ガス導入を始めた。反応初期は反応が激しいため塩素の導入はゆっくりと行った。徐々に昇温させ最後は８０℃で反応を続け、塩素の消費が行われなくなった時点で反応終了とした。得られたテトラクロロジオキソラン化合物（４，４，５，５−テトラクロロ−ペルフルオロ（２−メチル−２−ペンチル−１，３−ジオキソラン））１２１ｇ（収率８８％）を、精製せずにそのまま次の反応に用いた。
次に、撹拌機、還流コンデンサ、熱電対温度計を備えた５００ｍＬガラス製３口フラスコに、三フッ化アンチモン５０ｇ、五塩化アンチモン５ｇ、溶媒としてＰＢＴＨＦ５０ｍＬを入れ、室温にて上記テトラクロロジオキソラン化合物１２１ｇを加え、３２時間還流を続けた。この条件下では目的とするビシナル位の２個の塩素がフッ素置換された化合物のみが選択的に得られた。室温まで冷却させた後、上澄み液のみをデカンテーションで集め、減圧蒸留を行うことで、目的とするジクロロジオキソラン化合物（４，５−ジクロロ−ペルフルオロ（２−メチル−２−ペンチル−１，３−ジオキソラン））９９ｇ（収率８７％）を得た。
次に、撹拌機、還流コンデンサ、滴下ロート、熱電対温度計を備えた１Ｌガラス製４口フラスコに、マグネシウム粉末１３ｇ、ヨウ素２ｇ、塩化第二水銀０．５ｇ、テトラヒドロフラン３５０ｍＬを入れ、マントルヒーターを用いて加熱した。還流が始まったら加熱を止め、上記ジクロロジオキソラン化合物９９ｇをゆっくり滴下した。激しく発熱するため必要に応じて反応装置を冷却した。滴下終了後、反応容器を減圧にして液体窒素トラップにてテトラヒドロフランおよび生成物を捕集した。捕集物を冷水に注ぎ込み、下層のフルオロカーボン相を分液し、減圧蒸留によって純度９９．２％の目的とするＰＭＰＥＮＤ（前記式（８）でｊが４のもの）の３４ｇ（収率４１％）を得た。これを以下の重合に用いた。
（例３）ペルフルオロ（２−ペンチル−１，３−ジオキソール）（以下ＰＰＤという）の合成。
２Ｌガラス製４口フラスコに、６０％発煙硫酸１．５ｋｇを入れ、滴下ロートを用いてＣＦ_３（ＣＦ_２）_５Ｉの４４６ｇを滴下していった。６５℃に保って１８時間撹拌を続けた。反応終了後、冷却すると２相に分離したので、上層だけを集めて蒸留を行い、無色透明なＣＦ_３（ＣＦ_２）_４ＣＯＦを２００ｇ（収率６３％）得た。
次に、１Ｌポリプロピレン製ビーカーに５１ｇの２−クロロエタノールを入れ、ＣＦ_３（ＣＦ_２）_４ＣＯＦの２００ｇを滴下して、さらにピリジン５０ｇを加えた後、水洗し、蒸留することにより、ＣＦ_３（ＣＦ_２）_４ＣＯＯＣＨ_２ＣＨ_２Ｃｌを１９０ｇ（収率８０％）得た。
次に１Ｌガラス製４口フラスコにジメチルスルホキシド５００ｍＬと水素化ナトリウム（６０％鉱油中分散）７．３ｇを入れたところに、撹拌しながら、上記で合成した１９０ｇのＣＦ_３（ＣＦ_２）_４ＣＯＯＣＨ_２ＣＨ_２Ｃｌを２０℃以下を保つように加えた。そのまま３０℃以下を保って一晩撹拌を続けた。減圧蒸留することにより、目的とするジオキソラン化合物（２，４，４，５，５−ペンタヒドロ−ペルフルオロ（２−ペンチル−１，３−ジオキソラン））８６ｇ（収率５０％）を得た。
次に、撹拌機、ドライアイス還流コンデンサ、塩素ガス吹き込み管、熱電対温度計を備えた５００ｍＬガラス製４口フラスコに上記ジオキソラン化合物８６ｇを入れ、２℃にて塩素ガス導入を始めた。反応初期は反応が激しいため塩素の導入はゆっくりと行った。徐々に昇温させ最後は８２℃で反応を続け、塩素の消費が行われなくなった時点で反応終了とした。得られたペンタクロロジオキソラン化合物（２，４，４，５，５−ペンタクロロ−ペルフルオロ（２−ペンチル−１，３−ジオキソラン））９５ｇ（収率７４％）を、精製せずにそのまま次の反応に用いた。
次に、撹拌機、還流コンデンサ、熱電対温度計を備えた５００ｍＬガラス製３口フラスコに、三フッ化アンチモン５０ｇ、五塩化アンチモン５ｇ、溶媒としてＰＢＴＨＦ５０ｍＬを入れ、室温にて上記ペンタクロロジオキソラン化合物９５ｇを加え、２４時間還流を続けた。この条件下では２位の塩素、および、ビシナル位の２個の塩素がフッ素置換された化合物のみが選択的に得られた。室温まで冷却させた後、上澄み液のみをデカンテーションで集め、減圧蒸留を行うことで、目的とするジクロロジオキソラン化合物（４，５−ジクロロ−ペルフルオロ（２−ペンチル−１，３−ジオキソラン））７３ｇ（収率８５％）を得た。
次に、撹拌機、還流コンデンサ、滴下ロート、熱電対温度計を備えた１Ｌガラス製４口フラスコに、マグネシウム粉末１５ｇ、ヨウ素１ｇ、塩化第二水銀０．５ｇ、テトラヒドロフラン３５０ｍＬを入れ、マントルヒーターを用いて加熱した。還流が始まったら加熱を止め、上記ジクロロジオキソラン化合物７３ｇをゆっくり滴下した。激しく発熱するため必要に応じて反応装置を冷却した。滴下終了後、反応容器を減圧にして液体窒素トラップにてテトラヒドロフランおよび生成物を捕集した。捕集物を冷水に注ぎ込み、下層のフルオロカーボン相を分液し、減圧蒸留によって純度９９．７％の目的とするＰＰＤ（下記式（９））を２２ｇ（収率３５％）得た。これを以下の重合に用いた。

^１９Ｆ−ＮＭＲ（ＣＤＣｌ_３，ＣＦＣｌ_３基準）δｐｐｍ；−７０．１（１Ｆ），−８０．９（３Ｆ），−１２１．８〜−１２６．０（９Ｆ），−１５７．９（１Ｆ）。
［重合体製造例］
以下の例４〜２８において、含フッ素重合体または非晶質フッ素樹脂のガラス転移温度Ｔ_ｇは示差走査熱分析（ＪＩＳ−Ｋ７１２１に準拠）を用いて測定した。屈折率はアッベ屈折率計を用いて測定した。分子量はジクロロペンタフルオロプロパン溶媒（以下Ｒ２２５という）を使用したゲルパーミエーションクロマトグラフ法（ＧＰＣ）による、ポリメチルメタクリレート換算の数平均分子量Ｍ_ｎとして測定した。固有粘度［η］（単位ｄｌ／ｇ）はＰＢＴＨＦ（ただし例７で得た重合体Ｐ−４についてはＲ２２５）に溶解して３０℃にて測定した。
以下の重合体製造例において重合体のフッ素化処理は、原則として重合体をフッ素／窒素混合ガス（フッ素ガス濃度２０体積％）雰囲気中にて２５０℃で５時間処理することにより行った（条件を変えた場合は明記）。
（例４）重合体Ｐ−１（ＢＶＥ重合体）
５Ｌガラス製フラスコにＢＶＥを７５０ｇ、イオン交換水（以下水ともいう）を４ｋｇ、メタノールを２６０ｇ、およびジイソプロピルペルオキシジカーボネートを３．７ｇ入れた。系内を窒素で置換した後、４０℃で２２時間懸濁重合を行い、Ｍ_ｎが約５×１０^４の重合体を６９０ｇ得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１という）を得た。重合体Ｐ−１の［η］は０．２５、Ｔ_ｇは１０８℃、屈折率は１．３４２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。
（例５）重合体Ｐ−２（ＢＶＥ−４Ｍ重合体）
ガラスアンプル中にＢＶＥ−４Ｍを２ｇとジイソプロピルペルオキシジカーボネートを６．２ｍｇ入れ、液体窒素中で凍結、真空脱気後封管した。４０℃で２０時間オーブン中で加熱後、固化した内容物を取り出して、２００℃で１時間乾燥した。得られた重合体の収率は９９％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−２という）を得た。重合体Ｐ−２の［η］は０．４４、Ｍ_ｎは１３１５００、屈折率は１．３３、Ｔ_ｇは１２４℃であった。重合体Ｐ−２の引張特性は、引張弾性率１４３０ＭＰａ、降伏応力３６ＭＰａ、破断伸度４．２％であり、回転式溶融粘弾性測定装置による２３０℃におけるゼロシェア粘度は８９０００Ｐａ・ｓであった。
（例６）重合体Ｐ−３（ＢＶＥ／ＢＶＥ−４Ｍ共重合体）
２００ｍＬのオートクレーブに水を８０ｇ、ＢＶＥ−４Ｍを１５ｇ、ＢＶＥを１５ｇ、ペルフルオロベンゾイルペルオキシドを７５ｍｇ、メタノールを２．４ｇ入れた。そのオートクレーブを窒素置換した後、オートクレーブの内温が７０℃になるまで加熱し２０時間重合を行った。得られた重合体を水、メタノールで洗浄した後、２００℃で１時間乾燥した。得られた重合体の収率は８５％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−３という）を得た。重合体Ｐ−３の［η］は０．３５、屈折率は１．３３６、Ｔ_ｇは１１６℃であった。
（例７）重合体Ｐ−４（ＢＶＥ−４ＣＬ重合体）
ガラスアンプル中にＢＶＥ−４ＣＬを５ｇとジイソプロピルペルオキシジカーボネートを１２．５ｍｇ入れ、液体窒素中で凍結、真空脱気後封管した。４０℃で２０時間オーブン中で加熱後、固化した内容物を取り出して、２００℃で１時間乾燥した。得られた重合体の収率は８０％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−４という）を得た。重合体Ｐ−４の［η］は０．２０、Ｍ_ｎは１２１５００、屈折率は１．３７２、Ｔ_ｇは１２６℃であった。重合体Ｐ−４の引張特性は、引張弾性率１７００ＭＰａ、降伏応力５０ＭＰａ、降伏伸度３．８％であった。
（例８）重合体Ｐ−５（ＢＶＥ／ＢＶＥ−４ＣＬ共重合体）
２００ｍＬのオートクレーブに水を８０ｇ、ＢＶＥ−４ＣＬを２０ｇ、ＢＶＥを１５ｇ、ペルフルオロベンゾイルペルオキシドを８０ｍｇ、メタノールを２．０ｇ入れた。そのオートクレーブを窒素置換した後、オートクレーブの内温が７０℃になるまで加熱し２４時間重合を行った。得られた重合体を水、メタノールで洗浄した後、２００℃で１時間乾燥した。得られた重合体の収率は８０％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−５という）を得た。重合体Ｐ−５の［η］は０．３０、屈折率は１．３６、Ｔ_ｇは１２０℃であった。
（例９）重合体Ｐ−６（ＢＶＥ−４ＤＣＬ重合体）
１００ｍＬのステンレス鋼製オートクレーブにトリクロロトリフルオロエタンを５０ｇ、ＢＶＥ−４ＤＣＬを３０ｇおよびジイソプロピルペルオキシジカーボネートを０．１ｇを入れた。そのオートクレーブを５０℃で３日間加熱、撹拌した後、オートクレーブを開放し、メタノールで洗浄した。得られたポリマーを取り出し、溶媒および残存モノマーを減圧下留去することによって無色透明の重合体２９ｇが得られた。得られた重合体の収率は９６％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−６という）を得た。重合体Ｐ−６のＭ_ｎは１２３０００、屈折率は１．４１、Ｔ_ｇは１６８℃であった。重合体Ｐ−６の引張特性は、引張弾性率１６９０ＭＰａ、降伏応力５０ＭＰａ、降伏伸度３．６％であった。
（例１０）重合体Ｐ−７（ＢＶＥ／ＢＶＥ−４ＤＣＬ共重合体）
２００ｍＬのオートクレーブに水を８０ｇ、ＢＶＥ−４ＤＣＬを２２ｇ、ＢＶＥを１５ｇ、ペルフルオロベンゾイルペルオキシドを７５ｍｇ、メタノールを２．０ｇ入れた。そのオートクレーブを窒素置換した後、オートクレーブの内温が７０℃になるまで加熱し２８時間重合を行った。得られた重合体を水、メタノールで洗浄した後、２００℃で２時間乾燥した。得られた重合体の収率は８０％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−７という）を得た。重合体Ｐ−７の［η］は０．２８、屈折率は１．３８、Ｔ_ｇは１４５℃であった。
（例１１）重合体Ｐ−８（ＢＶＥ／２ＣＬＢＶＥ共重合体）
２００ｍＬのオートクレーブに水を８０ｇ、２ＣＬＢＶＥを１２ｇ、ＢＶＥを１５ｇ、ペルフルオロベンゾイルペルオキシドを７５ｍｇ、メタノールを１．０ｇ入れた。そのオートクレーブを窒素置換した後、オートクレーブの内温が７５℃になるまで加熱し４０時間重合を行った。得られた重合体を水、メタノールで洗浄した後、２００℃で２時間乾燥した。得られた重合体の収率は７０％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−８という）を得た。重合体Ｐ−８の［η］は０．２５、屈折率は１．３５、Ｔ_ｇは９８℃であった。
（例１２）重合体Ｐ−９（ＰＤＤ／ＴＦＥ共重合体）
ＰＤＤとＴＦＥを質量比８０：２０で、ＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１６０℃でＭ_ｎが約１．７×１０^５の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−９という）を得た。重合体Ｐ−９は無色透明であり、屈折率は１．３０５であった。
（例１３）重合体Ｐ−１０（ＰＭＰＲＯＤ／ＴＦＥ共重合体）
ＰＭＰＲＯＤとＴＦＥを質量比８５：１５で、ＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが２００℃でＭ_ｎが約１．５×１０^５の重合体を得た。この重合体をフッ素化処理（ただし、処理時間は７時間）することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１０という）を得た。重合体Ｐ−１０は無色透明であり、屈折率は１．２９８であった。
（例１４）重合体Ｐ−１１（ＰＭＰＥＮＤ／ＴＦＥ共重合体）
ＰＭＰＥＮＤとＴＦＥを質量比８５：１５で、ＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１９０℃でＭ_ｎが約１．３×１０^５の重合体を得た。この重合体をフッ素化処理（ただし、処理時間は６時間）することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１１という）を得た。重合体Ｐ−１１は無色透明であり、屈折率は１．２９５であった。
（例１５）重合体Ｐ−１２（ＰＤＤ／ＢＶＥ−４Ｍ共重合体）
ＰＤＤとＢＶＥ−４Ｍを質量比５０：５０で、ＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１７０℃で［η］が０．３４の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１２という）を得た。重合体Ｐ−１２は無色透明であり、屈折率は１．３２０であった。
（例１６）重合体Ｐ−１３（ＰＭＰＲＯＤ／ＢＶＥ−４Ｍ共重合体）
ＰＭＰＲＯＤとＢＶＥ−４Ｍを質量比４５：５５でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１６０℃で［η］が０．３２の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１３という）を得た。重合体Ｐ−１３は無色透明であり、屈折率は１．３１８であった。
（例１７）重合体Ｐ−１４（ＰＭＰＥＮＤ／ＢＶＥ−４Ｍ共重合体）
ＰＭＰＥＮＤとＢＶＥ−４Ｍを質量比５０：５０でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１６２℃で［η］が０．３７の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１４という）を得た。重合体Ｐ−１４は無色透明であり、屈折率は１．３１９であった。
（例１８）重合体Ｐ−１５（ＰＰＤ／ＢＶＥ−４Ｍ共重合体）
ＰＰＤとＢＶＥ−４Ｍを質量比５５：４５でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１６０℃で［η］が０．３３の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１５という）を得た。重合体Ｐ−１５は無色透明であり、屈折率は１．３１０であった。
（例１９）重合体Ｐ−１６（ＰＤＤ／ＰＨＶＥ共重合体）
ＰＤＤとペルフルオロ（３，６−ジオキサ−４−メチル−１−ノネン）（ＣＦ_２＝ＣＦ−Ｏ−ＣＦ（ＣＦ_３）−ＣＦ_２−Ｏ−ＣＦ_２−ＣＦ_２−ＣＦ_３）（以下ＰＨＶＥという）を質量比８５：１５でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１８２℃で［η］が０．３８の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１６という）を得た。重合体Ｐ−１６は無色透明であり、屈折率は１．３００であった。
（例２０）重合体Ｐ−１７（ＰＭＰＲＯＤ／ＢＶＥ共重合体）
ＰＭＰＲＯＤとＢＶＥを質量比５０：５０でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１４５℃で［η］が０．３０の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１７という）を得た。重合体Ｐ−１７は無色透明であり、屈折率は１．３２１であった。
（例２１）重合体Ｐ−１８（ＰＭＰＥＮＤ／ＢＶＥ共重合体）
ＰＭＰＥＮＤとＢＶＥを質量比５０：５０でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１５０℃で［η］が０．３２の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１８という）を得た。重合体Ｐ−１８は無色透明であり、屈折率は１．３２０であった。
（例２２）重合体Ｐ−１９（ＰＰＤ／ＢＶＥ共重合体）
ＰＰＤとＢＶＥを質量比５０：５０でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１４８℃で［η］が０．３５の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−１９という）を得た。重合体Ｐ−１９は無色透明であり、屈折率は１．３２２であった。
（例２３）重合体Ｐ−２０（ＰＤＤ／ＭＭＤ共重合体）
ＰＤＤとＭＭＤを質量比６５：３５でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１７０℃で［η］が０．３０の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−２０という）を得た。重合体Ｐ−２０は無色透明であり、屈折率は１．３２５であった。
（例２４）重合体Ｐ−２１（ＰＭＰＲＯＤ／ＭＭＤ共重合体）
ＰＭＰＲＯＤとＭＭＤを質量比６５：３５でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１６８℃で［η］が０．３１の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−２１という）を得た。重合体Ｐ−２１は無色透明であり、屈折率は１．３２４であった。
（例２５）重合体Ｐ−２２（ＰＭＰＥＮＤ／ＭＭＤ共重合体）
ＰＭＰＥＮＤとＭＭＤを質量比６０：４０でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１４２℃で［η］が０．３８の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−２２という）を得た。重合体Ｐ−２２は無色透明であり、屈折率は１．３２７であった。
（例２６）重合体Ｐ−２３（ＰＰＤ／ＭＭＤ共重合体）
ＰＰＤとＭＭＤを質量比６５：３５でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１６２℃で［η］が０．２９の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−２３という）を得た。重合体Ｐ−２３は無色透明であり、屈折率は１．３２５であった。
（例２７）重合体Ｐ−２４（ＰＰＤ／ＴＦＥ共重合体）
ＰＰＤとＴＦＥを質量比８５：１５でＰＢＴＨＦを溶媒として用いてラジカル重合し、Ｔ_ｇが１６２℃で［η］が０．３５の重合体を得た。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−２４という）を得た。重合体Ｐ−２４は無色透明であり、屈折率は１．３０７であった。
（例２８）重合体Ｐ−２５（ＰＰＤ重合体）
ガラスアンプル中にＰＰＤを５ｇ、塩化スルフリルを６．０ｍｇ、ジイソプロピルペルオキシジカーボネートを５．０ｍｇ入れ、液体窒素中で凍結、真空脱気後封管した。４０℃で３時間オーブン中で加熱後、固化した内容物を取り出して、２００℃で１時間乾燥した。得られた重合体の収率は９７％であった。この重合体をフッ素化処理することにより光透過性および熱安定性の良好な重合体（以下重合体Ｐ−２５という）を得た。重合体Ｐ−４の［η］は０．８７、Ｍ_ｎは１０５０００、屈折率は１．３２０、Ｔ_ｇは１０５℃であった。重合体Ｐ−４の引張特性は、引張弾性率５００ＭＰａ、破断伸度６３％であった。
［非晶質フッ素樹脂製造例］
（例２９〜４２）樹脂Ｒ−１〜樹脂Ｒ−１４
重合体Ｐ−１およびＴＰＢを混合し（両者の合計に対し後者を７．４質量％含む）、２５０℃で溶融混合して均一な混合物を製造した。以下、この混合物を樹脂Ｒ−１という。樹脂Ｒ−１の屈折率は１．３５７、Ｔ_ｇは９０℃であった。
上記と同様に重合体と添加剤を溶融混合して均一な混合物を製造した。得られた混合物を樹脂Ｒ−２〜樹脂Ｒ−１５と名付け、樹脂Ｒ−１を含め表１にその組成、屈折率、Ｔ_ｇ（℃）を示す。表１中「添加剤量」は混合物中の添加剤の割合（質量％）を表す。使用した添加剤は以下のとおり。
ＣＦＥ：平均分子量２０００のクロロトリフルオロエチレンオリゴマー。
ＰＰＥ：平均分子量４０００のペルフルオロポリエーテル（商品名「フォンブリンＺ０３」アウジモント社製）。

［ファイバ作成例］
以下のＳＩ型光ファイバを作成した例において、得られたＳＩ型光ファイバの開口数（ＮＡ）の測定は、ファーフィールドパターン法（ＪＩＳ−Ｃ６８６２に準拠）により測定した。また、伝送損失は波長５００〜１６００ｎｍにおける伝送損失をカットバック法で測定した。ファイバの作成は以下の２方法で行った。
プリフォーム法：クラッドとなる重合体（または樹脂）を２５０℃で溶融成形して円筒管を製造し、またコアとなる重合体（または樹脂）を２５０℃で溶融成形して円筒管の内径よりもわずかに小さい外径を有する円柱体を製造する。円筒管の中空部に円筒体を挿入して２３０℃に加熱して両者を合体させることによりプリフォームを製造し、このプリフォームを２５０℃で溶融紡糸することによりＳＩ型光ファイバを得る。
２層押出紡糸法：押出機を用いて、コアとなる重合体（または樹脂）を中心部に、および、クラッドとなる重合体（または樹脂）を外周部に配置し、２５０℃で同心円状に押出紡糸することによりＳＩ型光ファイバを得る。
（例４４）
プリフォーム法によりコアが重合体Ｐ−１、クラッドが重合体Ｐ−１０であり、外径が１０００μｍ、コア径が９８０μｍのＳＩ型光ファイバを得た。得られたＳＩ型光ファイバの伝送損失を測定した結果を図１に示す。図１に示されるように、このＳＩ型光ファイバの伝送損失は６５０ｎｍで６２ｄＢ／ｋｍ、８５０ｎｍで２０ｄＢ／ｋｍ、１３００ｎｍで２２ｄＢ／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であった。また、ＮＡは０．３４であった。このＳＩ型光ファイバを７０℃のオーブン中に５０００時間保存した後、伝送損失を再測定する耐熱試験を実施したところ変化は見られず、耐熱性は良好であった。
（例４５〜５４）
例４４と同様にプリフォーム法でＳＩ型光ファイバを作成した。得られたＳＩ型光ファイバのコアとクラッドの材料の種類、外径とコア径、伝送損失、ＮＡを表２に示す。また、例４４と同一の条件で耐熱試験を行ったところいずれのＳＩ型光ファイバも伝送損失は変化せず、耐熱性は良好であった。

（例５７）
２層押出紡糸法によりクラッドが樹脂Ｒ−１２、コアが重合体Ｐ−１であり、外径が１０００μｍ、コア径が９００μｍのＳＩ型光ファイバを得た。このＳＩ型光ファイバの光伝送損失は、６５０ｎｍで１４６ｄＢ／ｋｍ、８５０ｎｍで８５ｄＢ／ｋｍ、１３００ｎｍで７１ｄＢ／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であった。また、ＮＡは０．３５であった。この光ファイバを８０℃のオーブン中に３０００時間保存した後、伝送損失を再測定する耐熱試験を実施したところ変化は見られず、耐熱性は良好であった。
（例５８〜７０）
例４４と同様にプリフォーム法でＳＩ型光ファイバを作成した。得られたＳＩ型光ファイバのコアとクラッドの材料の種類、外径とコア径、伝送損失、ＮＡを表３に示す。また、例４４と同一の条件で耐熱試験を行ったところいずれのＳＩ型光ファイバも伝送損失は変化せず、耐熱性は良好であった。

（例７１〜８０）
例４４と同様にプリフォーム法でＳＩ型光ファイバを作成した。得られたＳＩ型光ファイバのコアとクラッドの材料の種類、外径とコア径、伝送損失、ＮＡを表４に示す。また、例４４と同一の条件で耐熱試験を行ったところいずれのＳＩ型光ファイバも伝送損失は変化せず、耐熱性は良好であった。

（例８１）
２層押出紡糸法によりコアが樹脂Ｒ−８、クラッドが樹脂Ｒ−１２であり、外径が１０００μｍ、コア径が９５０μｍのＳＩ型光ファイバを得た。このＳＩ型光ファイバの光伝送損失は、６５０ｎｍで１４６ｄＢ／ｋｍ、８５０ｎｍで８５ｄＢ／ｋｍ、１３００ｎｍで７１ｄＢ／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であった。また、ＮＡは０．５８であった。また、例５７と同一の条件で耐熱試験を行ったところ伝送損失は変化せず、耐熱性は良好であった。
産業上の利用の可能性
本発明のＳＩ型光ファイバは、光透過性能を落とすことなくコアとクラッドの屈折率差を大きくして開口数を大きくできる。これにより、曲げ時の伝送損失を増大させず、さらにセンサ等に使用した場合には広い範囲から集光できるためセンサ感度が向上する。また、波長６００〜１６００ｎｍという広い波長領域にわたって、低レベルの伝送損失を与えうる。すなわち、石英光ファイバと同じ波長を使えることにより、石英光ファイバとの接続が容易であり、また波長６００〜１６００ｎｍ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に比べ、安価な光源ですむ利点がある。
一方、本発明のＳＩ型光ファイバは通常のプラスチック光ファイバと同様にファイバ径が太く光源・受光素子との接続またはファイバ同士の接続が容易なことから安価な短距離通信システムを構築しうる。さらに、本発明のＳＩ型光ファイバは通常のプラスチック光ファイバに比較して耐熱性が飛躍的に向上しているので、熱的な安定性が高く、室温以上の高温に長期間さらされた場合においても、伝送損失の低下を防止できる。また、クラッドに柔軟性を持たせうることより、クラックを起こし難いファイバが得られる。
【図面の簡単な説明】
図１は例４３のＳＩ型光ファイバの伝送損失（波長５００〜１６００ｎｍ）を示すグラフである。Technical field
The present invention relates to a step index type plastic optical fiber (hereinafter, referred to as an SI type optical fiber), and more particularly, to an SI type optical fiber which can transmit a wide range of light from a visible to a near infrared region and has a large numerical aperture.
Background art
Conventional optical fibers are mainly made of quartz, but plastic optical fibers have been developed and put to practical use in order to overcome poor workability and weakness against bending. An ordinary plastic optical fiber has, as basic constituent units, a core made of a transparent resin such as polymethyl methacrylate and polycarbonate, and a clad made of a resin such as a fluoropolymer having a smaller refractive index and having a lower refractive index.
However, these resin materials have overtone absorption of stretching vibration based on carbon-hydrogen bonds present in the polymer, and have a large transmission loss in the near infrared region. To solve this problem, studies have been made to reduce transmission loss in the near infrared region by introducing a fluorine atom instead of a hydrogen atom to eliminate carbon-hydrogen bonds. For example, Japanese Patent No. 2821935 describes an SI type optical fiber using a perfluoropolymer for the core and cladding materials.
A conventional plastic optical fiber using a perfluoropolymer for the core and the clad has a problem that the numerical aperture (NA) is small because the refractive index difference between the core and the clad is small. The present invention solves this problem, and provides a plastic optical fiber suitable for use in optical communication media such as various sensors for industrial use and medical use, which can receive light in a wide range with a small loss at bending. With the goal.
Disclosure of the invention
The present invention provides an amorphous fluororesin (A-1) in which a core has substantially no hydrogen atom and is composed of a fluorine-containing polymer having a chlorine atom in a side chain, and a clad substantially has a hydrogen atom. An SI type optical fiber, comprising an amorphous fluororesin (B) composed of a fluoropolymer having no, and having a refractive index difference between the core and the clad of 0.020 or more.
Further, in the present invention, the core comprises an amorphous fluororesin (A) composed of a fluorine-containing polymer substantially containing no hydrogen atom and containing a high refractive index agent, and the cladding is substantially composed of a hydrogen atom. An SI type optical fiber, comprising an amorphous fluororesin (B) composed of a fluoropolymer having no, and having a refractive index difference between the core and the clad of 0.020 or more.
Further, the present invention provides an amorphous fluororesin (A) whose core is composed of a fluorinated polymer having substantially no hydrogen atoms, or an amorphous fluororesin (A) containing a high refractive index agent. The cladding is made of an amorphous fluororesin (B-2) composed of a fluoropolymer having a refractive index of less than 1.300 and having substantially no hydrogen atoms, and the refractive index difference between the core and the cladding is 0.020. An SI type optical fiber characterized by the above.
Further, the present invention provides an amorphous fluororesin (A) or a high-refractive-index resin in which the core is composed of a fluoropolymer having a repeating unit in which the monomer (a) is represented by the following formula (1) and the monomer (a) is cyclopolymerized. The cladding is composed of a fluorine-containing polymer having a repeating unit in which a monomer (b-1) represented by the following formula (4) is polymerized. It is made of an amorphous fluororesin (B-3) or an amorphous fluororesin (B-3) containing a fluorine-containing plasticizer having substantially no hydrogen atom, and has a refractive index difference of 0.020 or more between a core and a clad. An SI type optical fiber, characterized in that:
Here, m is an integer of 0 to 5, R ¹ , R ² , R ³ And R ⁴ Is independently a perfluoroalkyl group having 1 to 9 carbon atoms, a chlorine atom or a fluorine atom, ^Thirteen Is a perfluoroalkyl group having 2 to 9 carbon atoms, R ¹⁴ Represents a perfluoroalkyl group having 1 to 9 carbon atoms or a fluorine atom.

Further, the present invention provides an amorphous fluororesin (A) whose core is composed of a fluorinated polymer having substantially no hydrogen atoms, or an amorphous fluororesin (A) containing a high refractive index agent. An amorphous fluororesin (B) whose cladding is composed of a fluoropolymer substantially having no hydrogen atoms, or an amorphous fluororesin (B) containing a fluoroplastic plasticizer having substantially no hydrogen atoms. ), Wherein the numerical aperture (NA) is 0.415 or more.
Further, the present invention provides perfluoro (2-pentyl-1,3-dioxole), a fluorine-containing polymer having a repeating unit obtained by polymerizing perfluoro (2-pentyl-1,3-dioxole), and an optical member using the polymer. It is.
BEST MODE FOR CARRYING OUT THE INVENTION
The amorphous fluororesin in the present invention is composed of only one kind or two or more kinds of mixed specific fluorine-containing polymers to be amorphous, and other constituents other than the fluorine-containing polymer. It may contain small amounts of additives. Further, the amorphous fluororesin may contain a small amount of a crystalline fluoropolymer (a fluoropolymer which becomes crystalline alone) as long as it is amorphous as a whole.
Certain fluoropolymers are also polymers having substantially no hydrogen atoms. When a polymer other than the specific fluorine-containing polymer which becomes amorphous is used in combination, the other polymer is a polymer having substantially no hydrogen atom. That is, the polymer constituting the amorphous fluororesin in the present invention is composed of a polymer having substantially no hydrogen atom. Unless otherwise specified, the polymer constituting the amorphous fluororesin means a polymer having substantially no hydrogen atoms. Hereinafter, the “polymer” may be a homopolymer or a copolymer unless otherwise specifically referred to as a “homopolymer” or a “copolymer”.
The SI type optical fiber includes a core and a clad having a relatively lower refractive index than the core. The larger the difference in refractive index between the core and the clad, the larger the numerical aperture (NA). Amorphous fluororesin is originally a resin with a low refractive index, and when it is used as a material for the core, the range of choice of cladding materials that must have a lower refractive index is smaller than that of the resin, and the refractive index difference is larger. It was difficult to do. The present invention uses an amorphous fluororesin in the same category as the core as the material of the clad, and increases the difference in the refractive index between the core and the clad as compared with the conventional one. The purpose is to increase.
One aspect of the present invention is to increase the refractive index of the core by using an amorphous fluororesin composed of a fluorine-containing polymer having a chlorine atom which has the effect of increasing the refractive index as a material of the core, and to increase the refractive index of the core. This is to increase the rate difference. This chlorine atom must be a chlorine atom bonded to the side chain of the polymer, and if the chlorine atom is bonded to a carbon atom of the main chain, the polymerizability of the monomer becomes poor and the polymer becomes stable. There are problems such as the inability to obtain a high molecular weight substance having the physical properties, or the increase in crystallinity and the increase in scattering loss.
In the present invention, the main chain of the fluorinated polymer constituting the amorphous fluororesin comprises a chain of only carbon atoms, and the main chain is a chain of two carbon atoms constituting a polymerizable double bond. Formed from Further, in a polymer obtained by cyclopolymerization of a monomer having two polymerizable double bonds (hereinafter also referred to as fluorine-containing dienes), four carbon atoms constituting two polymerizable double bonds are used. The main chain is formed from the chain of Therefore, having a chlorine atom in the side chain means having a chlorine atom bonded to another carbon atom without having a chlorine atom directly bonded to a carbon atom constituting these polymerizable double bonds. I do.
The present invention also increases the refractive index of the core by using an amorphous fluororesin containing a high refractive index agent as the material of the core, thereby increasing the refractive index difference from the cladding. This high-refractive-index agent is a compound having a higher refractive index than the fluorine-containing polymer constituting the amorphous fluororesin to be compounded, and the refractive index of the amorphous fluororesin in which it is compounded is It has a higher refractive index than non-crystalline amorphous resin. Usually, the refractive index of the amorphous fluororesin increases with the amount of the high refractive index agent. As the high refractive index agent, a fluorine-containing aromatic compound having substantially no hydrogen atom is particularly preferable.
Further, in the present invention, the refractive index difference from the core is increased by using a fluorine-containing polymer having a lower refractive index than the conventional one as the fluorine-containing polymer constituting the amorphous fluorine resin of the clad. A polymer of perfluoro (2,2-dimethyl-1,3-dioxole) (formula (5) below, hereinafter referred to as PDD) is known as a fluorine-containing polymer constituting the cladding amorphous fluororesin. In the present invention, a fluoropolymer having a lower refractive index is used.

These means for increasing the refractive index difference between the core and the clad may be used in combination of two or more. For example, a fluorine-containing polymer having a chlorine atom and a high-refractive-index agent are combined to form a core, and this core is combined with a clad made of a lower-refractive-index fluoropolymer to form a core. And a combination of a core made of a crystalline fluororesin and a clad made of a fluoropolymer having a lower refractive index.
Further, in the present invention, the clad can be made of an amorphous fluororesin containing a fluoroplasticizer. The fluoropolymer having a low refractive index, which is a material of the clad, usually has high rigidity and is brittle, so that it is preferable to increase flexibility by adding a plasticizer. By forming the clad with a highly flexible material, it is possible to suppress the occurrence of cracks and the like when bending the SI optical fiber. The plasticizer needs to be a fluorine compound in order to increase the affinity with the fluoropolymer, and preferably has substantially no hydrogen atom. When the fluorine-containing plasticizer is a compound having a high fluorine content, it also has the effect of lowering the refractive index of the clad.
In the present invention, increasing the refractive index difference between the core and the clad, that is, increasing the numerical aperture (NA), suppresses an increase in transmission loss when the SI optical fiber is bent. Since light can be collected from a wide range, effects such as improvement in sensor sensitivity are obtained, which is preferable.
In order for the SI optical fiber of the present invention to achieve a sufficiently large numerical aperture, the refractive index difference between the amorphous fluororesin of the core and the amorphous fluororesin of the clad needs to be 0.020 or more. . The larger the difference in refractive index, the higher the numerical aperture. The refractive index difference is preferably 0.030 or more, more preferably 0.040 or more, further preferably 0.045 or more, particularly preferably 0.050 or more, and most preferably 0 or more. 0.060 or more. The upper limit of the refractive index difference is not particularly limited, but is usually 0.2.
Based on this refractive index difference, the numerical aperture of the SI type optical fiber of the present invention is preferably 0.280 or more. It is more preferably at least 0.325, even more preferably at least 0.364, particularly preferably at least 0.380, most preferably at least 0.415. The upper limit of the numerical aperture is not particularly limited, but is usually 0.75.
In order to increase the refractive index difference, a method using a core material having a higher refractive index as compared with the conventional method, a method using a clad material having a lower refractive index as compared with the conventional method, There is a method of combining a core material having a higher refractive index and a clad material having a lower refractive index as compared with the conventional one, and the amorphous fluororesin of the core and the amorphous fluororesin of the clad in the present invention are any of these methods. Also applicable to
The amorphous fluororesin of the core and the amorphous fluororesin of the clad in the present invention are amorphous fluororesins in the same category except that the refractive index is different. In order to distinguish them, the amorphous fluororesin of the core is hereinafter referred to as amorphous fluororesin (A), and the amorphous fluororesin of the clad is referred to as amorphous fluororesin (B).
The fluorine-containing polymer constituting these amorphous fluorine-containing resins has substantially no hydrogen atom and is a polymer having no carbon-hydrogen bond. Since the amorphous fluororesin is composed of a fluorinated polymer having substantially no hydrogen atoms, transmission loss in the near infrared region is reduced, and light from visible light to near infrared light is favorably transmitted. An SI optical fiber that can be transmitted is obtained. In addition, the fact that the fluororesin is amorphous reduces the scattering loss of the SI optical fiber, particularly in the short wavelength region.
Further, the amorphous fluororesin may be composed of only a fluoropolymer, and may contain an additive as long as the optical transmission performance, the mechanical performance and the like are not substantially impaired. Examples of the additive include a plasticizer, a refractive index adjuster, various stabilizers, and a crosslinking agent. These are preferably fluorine compounds having a high affinity for the fluoropolymer in order not to substantially impair the optical transmission performance or to improve the performance. In particular, it is preferable to include a high refractive index agent as a refractive index adjusting agent in the amorphous fluororesin (A) of the core in order to increase the NA of the SI optical fiber. It is preferable to include a plasticizer in the amorphous fluorine resin (B) of the clad in order to impart flexibility to the optical fiber.
As the fluorinated polymer constituting the amorphous fluororesin in the present invention, a polymer having a repeating unit in which a fluorinated diene is cyclopolymerized (hereinafter also referred to as a cyclized polymer) and a fluorinated dioxol polymerized A polymer having a repeating unit (hereinafter also referred to as a dioxole polymer) is preferred. The cyclized polymer may be a copolymer of two or more fluorine-containing dienes, or a copolymer of a fluorine-containing diene and another copolymerizable monomer. As other copolymerizable monomers, polymerizable monoenes are suitable. The dioxol-based polymer may be a copolymer of two or more kinds of fluorinated dioxols, or may be a copolymer of fluorinated dioxols and another copolymerizable monomer. Further, as the fluorine-containing polymer constituting the amorphous fluorine resin, a copolymer of a fluorine-containing diene and a fluorine-containing dioxole may be used.
Among the above-mentioned fluoropolymers, dioxole-based polymers tend to have a particularly low refractive index as compared with cyclized polymers, so that the fluoropolymer constituting the amorphous fluororesin (B) of the clad is used. Is preferably a dioxol-based polymer, and the fluorinated polymer constituting the core amorphous fluororesin (A) is preferably a cyclized polymer. In the case of a copolymer of a fluorinated diene and a fluorinated dioxol, the copolymer can be used for both the core and the clad due to the difference in the refractive index from other amorphous fluororesins to be combined, but is usually suitable as a material for the clad. It is.
The polymer can be obtained by using any of the known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization using the monomers described below. In the polymerization, a radical generator is usually used as a polymerization initiator. After the polymerization, a post-treatment such as fluorination of the obtained polymer to remove the unstable group at the terminal of the polymer can also be performed.
The viscosity of the above fluoropolymer in the molten state is 1 × 10 at a melting temperature of 200 to 300 ° C. ² ~ 1 × 10 ⁵ Pa · s is preferred. If the melt viscosity is too high, melt spinning becomes difficult. Further, if the melt viscosity is too low, it is not practically preferable. That is, when used as an optical transmission body in an electronic device or an automobile, it is softened at a high temperature, and the transmission performance as an SI optical fiber is deteriorated.
Further, the number average molecular weight M of the above fluoropolymer is M _n Is 1 × 10 ⁴ ~ 5 × 10 ⁶ Is preferably 5 × 10 ⁴ ~ 1 × 10 ⁶ Is more preferred. If the molecular weight is too small, the heat resistance may be deteriorated, and if it is too large, the melt viscosity becomes high and molding becomes difficult, which is not preferable.
As the cyclized polymer among the fluorinated polymers constituting the amorphous fluororesin, a repeating unit obtained by cyclized polymerization of a monomer represented by the following formula (1) (hereinafter referred to as monomer (a)): Is preferred.

Here, m is an integer of 0 to 5, R ¹ , R ² , R ³ And R ⁴ Each independently represents a perfluoroalkyl group having 1 to 9 carbon atoms, a chlorine atom or a fluorine atom. When m is 2 or more, a plurality of R ³ (R ⁴ May also be different from each other. m is particularly preferably an integer of 0 to 3.
R ¹ , R ² , R ³ And R ⁴ It is preferable that at most three are perfluoroalkyl groups or chlorine atoms and the others are fluorine atoms. In particular, the monomer (a) having a perfluoroalkyl group or a chlorine atom includes R ¹ And R ² Are preferably perfluoroalkyl groups or chlorine atoms, and the others are all fluorine atoms. Moreover, as a perfluoroalkyl group, a C1-C2 perfluoroalkyl group is preferable.
The repeating unit obtained by subjecting the monomer (a) to cyclopolymerization usually has a structure represented by the following formula (1a) or (1b).

Examples of the monomer (a) having no chlorine atom (hereinafter, referred to as monomer (a-2)) include the following monomers. Methods for synthesizing these monomers are disclosed in JP-A-1-131215, JP-A-4-346957, and the like.
Perfluoro (3-oxa-1,5-hexadiene) (CF ₂ = CF-CF ₂ -O-CF = CF ₂ ), Perfluoro (3-oxa-1,6-heptadiene) (CF ₂ = CF-CF ₂ -CF ₂ -O-CF = CF ₂ ) (Hereinafter referred to as BVE), perfluoro (3-oxa-4-methyl-1,6-heptadiene) (CF ₂ = CF-CF ₂ −CF (CF ₃ ) -O-CF = CF ₂ ) (Hereinafter referred to as BVE-4M), perfluoro (3-oxa-4,4-dimethyl-1,6-heptadiene) (CF ₂ = CF-CF ₂ −C (CF ₃ ) ₂ -O-CF = CF ₂ ), Perfluoro (3-oxa-5-methyl-1,6-heptadiene) (CF ₂ = CF-CF (CF ₃ ) -CF ₂ -O-CF = CF ₂ ).
Examples of the monomer having a chlorine atom among the monomers (a) (hereinafter referred to as monomer (a-1)) include the following monomers.
4-chloro-perfluoro (3-oxa-1,5-hexadiene) (CF ₂ = CF-CCIF-O-CF = CF ₂ ), 4-chloro-perfluoro (3-oxa-1,6-heptadiene) (CF ₂ = CF-CF ₂ -CCIF-O-CF = CF ₂ ) (Hereinafter referred to as BVE-4CL), 4,4-dichloro-perfluoro (3-oxa-1,6-heptadiene) (CF ₂ = CF-CF ₂ -CCl ₂ -O-CF = CF ₂ ) (Hereinafter referred to as BVE-4DCL), 5-chloro-perfluoro (3-oxa-1,6-heptadiene) (CF ₂ = CF-CCIF-CF ₂ -O-CF = CF ₂ ).
The cyclized polymer may be a copolymer of two or more types of the monomer (a), or may be a copolymer of the monomer (a) and another copolymerizable monomer. . That is, the cyclized polymer may include a repeating unit in which another copolymerizable monomer is polymerized in addition to the repeating unit in which the monomer (a) is cyclopolymerized. As the other copolymerizable monomer, monoenes are preferable, and these monoenes have substantially no hydrogen atom and, when having a chlorine atom, chlorine directly bonded to a carbon atom constituting a polymerizable double bond. It is a compound having no atom.
Specifically, for example, a monomer (c) which is a monomer represented by the following formula (2), a monomer (b) which is a monomer represented by the following formula (4), tetrafluoro Perfluoroolefins such as ethylene (hereinafter referred to as TFE), perfluoro (3-oxa-1-hexene) (CF ₃ -CF ₂ -CF ₂ -O-CF = CF ₂ )), And perfluoro (methylene dioxolanes) such as perfluoro (2-methylene-4-methyl-1,3-dioxolane) (the following formula (6), hereinafter referred to as MMD).

Except for the copolymer with the monomer (b), the proportion of the repeating unit in which the monomer (a) is cyclopolymerized with respect to all the repeating units in the cyclized polymer is suitably 20 to 100 mol%, It is preferably from 40 to 100 mol%, particularly preferably from 50 to 100 mol%. If this ratio is too small, it is difficult to obtain a polymer having good optical and mechanical properties. In the case of a copolymer with the monomer (b), the ratio of the repeating unit in which the monomer (a) is cyclopolymerized is not particularly limited.
The monomer represented by the following formula (2) (hereinafter referred to as monomer (c)) is a preferred monomer for producing a cyclized polymer having a chlorine atom in a side chain. Since this monomer has two chlorine atoms far from the polymerizable double bond, the cyclized polymer obtained by copolymerizing the monomer (c) and the monomer (a) is A cyclized polymer having a high refractive index and good physical properties is obtained.

Where n is an integer of 0 to 5, R ⁵ , R ⁶ , R ⁷ And R ⁸ Each independently represents a perfluoroalkyl group having 1 to 9 carbon atoms, a chlorine atom or a fluorine atom. When n is 2 or more, a plurality of R ⁷ (R ⁸ May also be different from each other. n is preferably an integer of 0 to 3; ⁵ , R ⁶ , R ⁷ And R ⁸ Are preferably all fluorine atoms. Further, when the compound has a perfluoroalkyl group, R ⁵ And R ⁶ It is preferable that only one or both of them are perfluoroalkyl groups and the others are all fluorine atoms. Moreover, as a perfluoroalkyl group, a C1-C2 perfluoroalkyl group is preferable.
Specific examples of the monomer (c) include, for example, 6,7-dichloro-perfluoro (3-oxa-1-heptene) (CCIF ₂ -CCIF-CF ₂ -CF ₂ -O-CF = CF ₂ ) (Hereinafter referred to as 2CLBVE). A method for synthesizing the monomer (c) is disclosed in, for example, JP-A-1-131215.
The dioxol-based polymer is one or more polymers of fluorinated dioxols or a copolymer of fluorinated dioxols and another copolymerizable monomer. As the fluorinated dioxole, a monomer represented by the following formula (3) (hereinafter, referred to as monomer (b)) is preferable.

Where R ¹¹ And R ¹² Each independently represents a perfluoroalkyl group having 1 to 9 carbon atoms or a fluorine atom. R ¹¹ And R ¹² Preferably, at least one of them is a perfluoroalkyl group. Further, the number of carbon atoms of the perfluoroalkyl group is more preferably 1 to 6.
The dioxol-based polymer may be one or more polymers of the monomer (b), but usually a copolymer with another copolymerizable monomer is preferred. That is, the dioxole-based polymer preferably contains a repeating unit in which another copolymerizable monomer is polymerized in addition to the repeating unit in which the monomer (b) is polymerized. As other copolymerizable monomers, monoenes and cycloene-polymerizable dienes are preferable, and these are monomers having substantially no hydrogen atom, and preferably have no chlorine atom. Specifically, for example, the monomer (a), perfluoroolefins such as TFE, perfluoro (3-oxa-1-hexene) (CF ₃ -CF ₂ -CF ₂ -O-CF = CF ₂ ) And perfluoro (methylenedioxolanes) such as MMD. TFE is particularly preferred as the other monomer.
Except for the copolymer with the monomer (a), the proportion of the repeating unit in which the monomer (b) is polymerized to all the repeating units in the dioxole-based polymer is suitably from 20 to 95 mol%, and from 30 to 95 mol%. 90 mol% is preferable, and particularly preferably 35 to 85 mol%. If the ratio is too small or too large, it is difficult to obtain a polymer having good optical and mechanical properties.
In the case of a copolymer of the monomer (a) and the monomer (b), the obtained fluoropolymer is used as a component of the amorphous fluororesin (A) or the amorphous fluororesin (B) (Ie, depending on whether it is used for a fluoropolymer having a high refractive index or a fluoropolymer having a low refractive index), the copolymerization ratio thereof is selected. In the case of a high-refractive-index fluoropolymer, the monomer (a) is a polymer having a high ratio of repeating units obtained by cyclopolymerization. A polymer having a high proportion of the repeating unit. In the former case, the ratio of the repeating unit in which the monomer (b) is polymerized is preferably more than 0 mol% to 40 mol%, and particularly preferably 1 to 30 mol%. In the latter case, the proportion of the repeating unit in which the monomer (b) is polymerized is preferably 30 mol% to less than 100 mol%, and particularly preferably 40 mol% to 95 mol%.
Among the dioxol-based polymers, a fluorine-containing polymer having a repeating unit obtained by polymerizing a monomer represented by the following formula (4) (hereinafter, referred to as a monomer (b-1)) has a lower refractive index. That is, when comparing a polymer having a repeating unit in which PDD is polymerized and the same polymer except having a repeating unit in which monomer (b-1) is polymerized instead of the repeating unit in which PDD is polymerized, the latter is more It has a low refractive index.

Where R ^Thirteen Is a perfluoroalkyl group having 2 to 9 carbon atoms, R ¹⁴ Represents a perfluoroalkyl group having 9 or less carbon atoms or a fluorine atom. R ^Thirteen Is preferably a perfluoroalkyl group having 2 to 6 carbon atoms; ¹⁴ Is preferably a perfluoroalkyl group having 1 to 6 carbon atoms or a fluorine atom.
Specific examples of the monomer (b-1) include the following.
Perfluoro (2-ethyl-1,3-dioxole) (wherein k is 1 in the following formula (7)),
Perfluoro (2-propyl-1,3-dioxole) (wherein k is 2 in the following formula (7)),
Perfluoro (2-pentyl-1,3-dioxole) (wherein k is 4 in the following formula (7)),
Perfluoro (2-ethyl-2-methyl-1,3-dioxole) (in the following formula (8), j is 1),
Perfluoro (2-methyl-2-propyl-1,3-dioxole) (in the following formula (8), j is 2),
Perfluoro (2-methyl-2-pentyl-1,3-dioxole) (in the following formula (8), j is 4).

Examples of the monomer (b) other than the monomer (b-1) include PDD, perfluoro (2-methyl-1,3-dioxole) and the like.
Among monomers (b), a method for synthesizing PDD is disclosed in US Pat. No. 3,865,845. The synthesis method of the copolymer is disclosed in US Pat. No. 3,978,030. The synthesis method of the other monomer (b) is disclosed in JP-A-2-117672, JP-A-5-194655 and the like.
The core amorphous fluororesin (A) preferably contains a high refractive index agent. The high refractive index agent needs to have a higher refractive index than the fluoropolymer constituting the amorphous fluororesin (A) and have a higher affinity for the fluoropolymer. Having high affinity means that the compound is sufficiently dissolved in the fluoropolymer, there is no insoluble matter, and there is no possibility of generating a micro phase separation structure. If such an insoluble matter or a microphase-separated structure is present, the portion causes light scattering. Therefore, as the high refractive index agent, a compound which is blended with the core fluoropolymer in an amount not more than its saturation solubility and which can sufficiently increase the refractive index of the amorphous fluororesin (A) in the core is used. .
In order to have a high affinity, the high refractive index agent is preferably a fluorine compound having a relatively low molecular weight. Further, it preferably has a chlorine atom, an aromatic nucleus, a metal component, and the like because of a high refractive index. Particularly, a compound having a chlorine atom and / or an aromatic nucleus is preferable. Further, the high refractive index agent is preferably a compound having substantially no hydrogen atom as in the case of the fluoropolymer. Thereby, the transmission loss reduction in the near infrared region of the amorphous fluororesin containing the high refractive index agent is maintained. For these reasons, it is preferable that the high refractive index agent is a relatively low molecular weight fluorine compound having substantially no hydrogen atom and having a chlorine atom and / or an aromatic nucleus.
The molecular weight of the high refractive index agent is preferably 2000 or less, and the average molecular weight of polymers such as oligomers is preferably 2000 or less. Examples thereof include a fluorine compound having a chlorine atom, a fluorine-containing aromatic compound, a fluorine-containing condensed polycyclic compound, and a metal chelate compound. Preferred high-refractive-index agents are a fluorine compound having substantially no hydrogen atom and having a chlorine atom, and a fluorine-containing aromatic compound having substantially no hydrogen atom. More preferably, it is a fluorine-containing aromatic compound having substantially no hydrogen atom, and among them, a perfluoroaromatic compound having 3 to 5 benzene nuclei in one molecule is particularly preferable. These high refractive index agents can be used alone or in combination of two or more.
Examples of the fluorinated condensed polycyclic compound include perfluoroanthracene, perfluorofluorene, perfluorophenalene, perfluorophenanthrene and the like.
Examples of the metal chelate compound include perfluoro (tetraphenyltin).
Examples of the fluorine compound having a chlorine atom include chloropentafluorobenzene, chloro-perfluoronaphthalene, and a chlorotrifluoroethylene oligomer having an average molecular weight of 2000 or less. As the chlorotrifluoroethylene oligomer, a commercially available one having an average molecular weight of 2000 or less can be used, or it can be obtained by collecting a fraction having an average molecular weight of 2000 or less by distillation.
Examples of the fluorinated aromatic compound include perfluoro (triphenylphosphine), perfluorobenzophenone, perfluorobiphenyl, perfluoroterphenyl, perfluoro (diphenylsulfide), and perfluoro (2,4,6-triphenyl-1,3,5-triazine). And perfluoro (1,3,5-triphenylbenzene) (hereinafter referred to as TPB). Among them, perfluoro (2,4,6-triphenyl-1,3,5-triazine) or TPB is preferable, and TPB is particularly preferable because of its high affinity with the fluoropolymer.
In the amorphous fluororesin (A) containing the high refractive index agent, the ratio of the high refractive index agent in the amorphous fluororesin (A) is such that the amorphous fluororesin (A) has a desired refractive index. The amount is not particularly limited as long as it is not less than the amount to reach the refractive index and not more than the solubility of the high refractive index agent in the fluoropolymer. Usually, it may be contained in an amount of 30% by mass or less in the amorphous fluorine-containing resin (A). The preferred content is 1 to 20% by mass, and particularly preferably 5 to 20% by mass of a high refractive index agent.
The amorphous fluororesin (B) of the clad preferably contains a fluorine-containing plasticizer having substantially no hydrogen atoms. The fluorine-containing plasticizer softens the cladding amorphous fluororesin to improve the workability of the SI optical fiber, and imparts a feature such that cracks hardly occur in a large diameter fiber. In addition, the addition of a fluorine-containing plasticizer having a high fluorine content has an effect of further lowering the refractive index of the amorphous fluorine resin of the clad.
As the fluorinated plasticizer, perfluoropolyethers and the like are preferable. Examples of perfluoropolyethers include perfluoro (polyoxyalkylene alkyl ether). Specific examples of perfluoropolyethers include Krytox (trade name, manufactured by Dupont), Demnum (trade name, manufactured by Daikin Industries, Ltd.), Fomblin (trade name, manufactured by Audimont) and the like. The average molecular weight is preferably 1,000 or more from the viewpoint that it is difficult to volatilize during molding or use. The upper limit of the molecular weight is not particularly limited, but is preferably 20,000 or less from the viewpoint of compatibility with the fluoropolymer of the clad.
In the amorphous fluorine-containing resin (B) containing a fluorine-containing plasticizer, the proportion of the fluorine-containing plasticizer in the amorphous fluorine-containing resin (B) is such that the amorphous fluorine-containing resin (B) has a desired plasticizing effect. The amount is not particularly limited as long as the amount is attained and the solubility of the fluorinated plasticizer in the fluorinated polymer is not more than the amount. Usually, it can be contained in an amount of 50% by mass or less in the amorphous fluorine-containing resin (B). The preferable content is 1 to 40% by mass, particularly preferably 5 to 40% by mass of a fluorine-containing plasticizer.
The amorphous fluororesin (A) is preferably composed of a cyclized polymer as described above. The refractive index of the cyclized polymer itself constituting the amorphous fluororesin (A) is preferably 1.330 or more, particularly preferably 1.335 or more. The upper limit of the refractive index of the cyclized polymer itself is not particularly limited, but is usually 1.45.
When the refractive index of the cyclized polymer itself is sufficiently high, the amorphous fluorinated resin (A) can be constituted only by the cyclized polymer without including a high refractive index agent. When the refractive index of the cyclized polymer itself is not sufficiently high, or when the refractive index of the amorphous fluororesin (B) is relatively high and the refractive index difference with the cyclized polymer is not large, a high refractive index agent It is preferable to use an amorphous fluororesin (A) containing The refractive index of the amorphous fluororesin (A) which may contain a high refractive index agent is preferably 1.340 or more, more preferably 1.345 or more, still more preferably 1.350 or more, and most preferably 1.355 or more. preferable. The upper limit of the refractive index of the amorphous fluororesin (A) is not particularly limited, but is usually 1.5.
In the present invention, the amorphous fluororesin (A-1) composed of a fluoropolymer having substantially no hydrogen atom and having a chlorine atom in a side chain is the same as the amorphous fluororesin (A). Of these, it is composed of a fluoropolymer having a chlorine atom in the side chain. Since the amorphous fluororesin (A) is preferably a cyclized polymer, the amorphous fluororesin (A-1) is also preferably a cyclized polymer. The refractive index of the fluoropolymer having a chlorine atom in the side chain itself is preferably 1.345 or more, particularly preferably 1.350 or more. Similarly, the refractive index of the amorphous fluororesin (A-1) is preferably 1.345 or more, particularly preferably 1.350 or more.
Examples of the fluorine-containing polymer constituting the amorphous fluororesin (A-1), which has a chlorine atom in a side chain, include a polymer containing a repeating unit obtained by cyclic polymerization of the monomer (a-1) (the following unit). Monomer (a-2) may have a cyclically polymerized repeating unit), and another carbon atom having no chlorine atom directly bonded to a carbon atom constituting the polymerizable double bond A polymer containing a repeating unit obtained by polymerizing a copolymerizable monomer having a chlorine atom (particularly, a monoene containing such a chlorine atom) and a repeating unit obtained by subjecting the monomer (a) to cyclopolymerization; preferable. As the chlorine atom-containing copolymerizable monomer, the monomer (c) is particularly preferred. In addition, the monomer which does not have a chlorine atom among the monomers (a) is hereafter called a monomer (a-2).
Particularly preferred fluorine-containing polymer having a chlorine atom in the side chain is a polymer having a repeating unit in which monomer (a-1) is cyclopolymerized (provided that monomer (a-2) has undergone cyclopolymerization). A polymer having no repeating unit), a polymer having a repeating unit in which the monomer (a-1) is cyclopolymerized and a repeating unit in which the monomer (a-2) is cyclopolymerized, and a monomer It is a polymer having a repeating unit in which the body (a) is cyclopolymerized and a repeating unit in which the monomer (c) is polymerized.
Since the amorphous fluororesin (A-1) is composed of a fluorine-containing polymer having a chlorine atom, it has a sufficiently high refractive index without containing a high refractive index agent. However, in some cases, a high refractive index agent may be included. The amorphous fluororesin (A) includes the amorphous fluororesin (A-1) as a category thereof. In particular, when the amorphous fluororesin (A-1) is composed of a fluorine-containing polymer having no chlorine atom, a high refractive index agent is used. It is preferred to include. Even when the amorphous fluororesin (A) is composed of a fluorine-containing polymer having no chlorine atom, the refractive index difference between the amorphous fluororesin and the amorphous fluororesin (B) combined as a clad is large. Need not include a high refractive index agent.
The amorphous fluororesin (B) is preferably composed of a dioxol-based polymer as described above. The refractive index of the dioxol-based polymer is not particularly limited as long as the refractive index difference between the dioxol-based polymer constituting the amorphous fluororesin (B) and the amorphous fluororesin (A) is large. The refractive index of the dioxol-based polymer itself constituting the fluororesin (B) is preferably less than 1.330, particularly preferably less than 1.310. In order to achieve a higher refractive index difference from the amorphous fluororesin (A), it is more preferable that the dioxole-based polymer itself has a refractive index of less than 1.300, particularly less than 1.296. The lower limit of the refractive index of the dioxole polymer itself is not particularly limited, but is usually 1.290. Although not limited to the dioxol-based polymer, an amorphous fluororesin composed of a fluoropolymer having a refractive index of less than 1.300 is hereinafter referred to as an amorphous fluororesin (B-2).
As described above, the fluorine-containing polymer having a repeating unit in which the monomer (b-1) is polymerized is a fluorine-containing polymer having a repeating unit in which the monomer (b) other than the monomer (b-1) is polymerized. It has a lower refractive index than the union. The amorphous fluororesin (B) composed of a fluoropolymer having a repeating unit in which the monomer (b-1) is polymerized is hereinafter referred to as an amorphous fluororesin (B-3). Further, among the fluorinated polymers having a repeating unit in which the monomer (b-1) is polymerized, a more preferred polymer is a fluorinated polymer having a refractive index of less than 1.300, particularly less than 1.296.
Therefore, the fluoropolymer constituting the amorphous fluororesin (B-2) and the amorphous fluororesin (B-3) has a repeating unit in which the monomer (b-1) is polymerized, and A fluoropolymer having a refractive index of less than 1.300 is preferred. This particularly preferred fluoropolymer is a copolymer having a copolymerization molar ratio of the monomer (b-1) and TFE in the range of 99 to 20/1 to 80.
The refractive index of the amorphous fluororesin (B) which may contain a fluorine-containing plasticizer is preferably less than 1.330, particularly preferably less than 1.310. Particularly preferred refractive index of the amorphous fluororesin (B) is less than 1.300, most preferably less than 1.296. The lower limit of the refractive index of the amorphous fluororesin (B) is not particularly limited, but is usually 1.285.
The SI optical fiber of the present invention can be manufactured by a known method for manufacturing an SI optical fiber. For example, it can be manufactured by the method described in Japanese Patent No. 2821935. Further, the SI optical fiber of the present invention can be manufactured by applying the method for manufacturing a refractive index distribution type plastic optical fiber described in JP-A-8-5848 and JP-A-11-167030. . For example, a SI preform for producing an SI type optical fiber (hereinafter simply referred to as a preform) is manufactured and spun from the preform into an SI type optical fiber, or an SI type optical fiber according to a method of multicolor spinning with an extruder. And the like.
The SI optical fiber of the present invention does not increase transmission loss due to water absorption due to the water / oil repellency of fluorine atoms, and has high solvent resistance. Further, the optical fiber has a small transmission loss over a wide wavelength range from the visible region to the near infrared region.
In addition, the SI type optical fiber of the present invention can have a numerical aperture (NA) of 0.415 or more because the refractive index difference between the core and the clad can be made sufficiently large. An SI type optical fiber having a large numerical aperture can input light from a wide angle, that is, can detect a signal from a wide angle as a sensor, and can increase the coupling efficiency between the light source and the fiber. Can be input and transmitted, and the bending loss at the time of transmission can be kept small.
The SI type optical fiber of the present invention can be used in the form of an optical fiber cord or an optical fiber cable after being further coated, or a bundled optical fiber cable or the like.
In the SI optical fiber of the present invention, the transmission loss at 100 m can be set to 5 db or less (i.e., 50 dB / km or less) at a wavelength of 600 to 1600 nm. It is extremely advantageous to have such a low level of transmission loss in a wide wavelength range of 600 to 1600 nm. That is, since the same wavelength as the quartz optical fiber can be used, the connection with the quartz optical fiber is easy, and the light source is inexpensive as compared with the conventional plastic optical fiber which has to use a wavelength shorter than 600 to 1600 nm. There are advantages.
On the other hand, since plastic optical fibers have a large fiber diameter and are easy to connect to a light source / light receiving element or to connect fibers to each other, expectations for construction of an inexpensive short-distance communication system are increasing. Since the SI type optical fiber of the present invention has remarkably improved heat resistance, it has high thermal stability and can prevent a reduction in transmission loss even when exposed to a high temperature above room temperature for a long time.
(Example)
Next, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto. Parts represent parts by mass. Examples 1 to 3 are examples of monomer synthesis in which fluorinated dioxols were synthesized. Examples 4 to 27 are polymer production examples for producing a fluorine-containing polymer constituting an amorphous fluororesin. Examples 28 to 41 are examples of producing an amorphous fluororesin for producing an SI optical fiber. Examples 42 to 58 are examples of producing an SI type optical fiber.
[Example of monomer synthesis]
(Example 1) Synthesis of perfluoro (2-methyl-2-propyl-1,3-dioxole) (hereinafter referred to as PMPROD).
1.5 kg of 60% fuming sulfuric acid is put into a 2 L glass four-necked flask, and CF is added using a dropping funnel. ₃ (CF ₂ ) ₅ 446 g of I was added dropwise. Stirring was maintained at 65 ° C. for 24 hours. After the completion of the reaction, the mixture was cooled and separated into two phases. Therefore, only the upper layer was collected and distilled to obtain a colorless and transparent CF. ₃ (CF ₂ ) ₄ 190 g (60% yield) of COF was obtained.
Next, 1 L of ethanol and a few drops of phenolphthalein were placed in a 2 L polypropylene beaker, and CF was stirred with a magnetic stirrer. ₃ (CF ₂ ) ₄ 190 g of COF was added dropwise. An ethanol solution of 10% sodium hydroxide was added dropwise to the solution until the solution became neutral. Ethanol was removed from the obtained reaction solution using an evaporator, and the obtained solid was transferred to a vacuum drier and vacuum-dried at 100 ° C. for 18 hours. Next, the solid after vacuum drying was transferred to a 5-L glass flask, and the flask was heated through a dry ice trap under reduced pressure using a vacuum pump in an oil bath at 250 to 270 ° C. for 24 hours. By distilling the liquid collected in the dry ice trap, CF ₃ CF ₂ CF ₂ CF = CF ₂ Was obtained (113%, yield: 75%).
Next, 1000 g of a 15% aqueous solution of sodium hypochlorite and 8 g of trioctylmethylammonium chloride were placed in a 2 L glass four-necked flask, and the mixture was cooled to an internal temperature of 10 to 15 ° C. with good stirring. There CF ₃ CF ₂ CF ₂ CF = CF ₂ Was added dropwise to keep the internal temperature at 20 to 30 ° C. Then, while tracking the reaction by gas chromatography, the raw material CF ₃ CF ₂ CF ₂ CF = CF ₂ Until almost consumed. The lower layer product was extracted by two-phase separation, and washed three times with ion-exchanged water to remove residual sodium hypochlorite. Further, by distilling the crude product, 83 g (yield 70%) of pure fluorine-containing epoxide (perfluoro (1,2-epoxypentane)) was obtained.
Next, 3 g of aluminum chloride was placed in a 200 mL glass four-necked flask, and activated by adding 10 g of trichlorofluoromethane. To this, 83 g of the fluorinated epoxide synthesized above was added dropwise while stirring well so as to keep the internal temperature at 20 to 30 ° C. Thereafter, the reaction was carried out at a reaction temperature of 20 to 40 ° C. until the starting material was almost consumed, while following the reaction with a gas chromatograph. The crude product is subsequently isolated by filtration and distilled to obtain pure CF. ₃ CF ₂ CF ₂ COCF ₃ Was obtained (yield 92%).
Next, 25 g of 2-chloroethanol was placed in a 300 mL glass four-necked flask, and 76 g of CF was stirred. ₃ CF ₂ CF ₂ COCF ₃ Was added dropwise at room temperature. The obtained reaction crude liquid was added dropwise to 500 g of a 20% aqueous sodium hydroxide solution in another 1 L glass flask with vigorous stirring. The reaction solution was washed with water three times and distilled to obtain 77 g (yield) of the desired dioxolane compound (4,4,5,5-tetrahydro-perfluoro (2-methyl-2-propyl-1,3-dioxolane)). 87%).
Next, 77 g of the dioxolane compound was placed in a 500 mL glass four-necked flask equipped with a stirrer, a dry ice reflux condenser, a chlorine gas injection tube, and a thermocouple thermometer, and introduction of chlorine gas was started at 5 ° C. At the beginning of the reaction, the introduction of chlorine was carried out slowly because the reaction was intense. The temperature was gradually raised, and the reaction was continued at 78 ° C. at the end, and the reaction was terminated when chlorine was no longer consumed. 100 g (89% yield) of the obtained tetrachlorodioxolane compound (4,4,5,5-tetrachloro-perfluoro (2-methyl-2-propyl-1,3-dioxolane)) was directly used without purification. Used for the next reaction.
Next, 50 g of antimony trifluoride, 5 g of antimony pentachloride, and perfluoro (2-butyltetrahydrofuran) (hereinafter referred to as PBTHF) as a solvent were placed in a 500 mL glass three-necked flask equipped with a stirrer, a reflux condenser, and a thermocouple thermometer. 50 mL was added, 100 g of the above tetrachlorodioxolane compound was added at room temperature, and the mixture was refluxed for 24 hours. Under these conditions, only the desired compound in which two chlorine atoms at the vicinal position were substituted with fluorine was selectively obtained. After cooling to room temperature, only the supernatant was collected by decantation and distilled under reduced pressure to obtain the desired dichlorodioxolane compound (4,5-dichloro-perfluoro (2-methyl-2-propyl-1,3- Dioxolane)) (78 g, yield 85%).
Next, 15 g of magnesium powder, 1 g of iodine, 0.5 g of mercuric chloride, and 350 mL of tetrahydrofuran were placed in a 1-L glass four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermocouple thermometer. And heated. When the reflux started, the heating was stopped and 78 g of the above dichlorodioxolane compound was slowly dropped. The reactor was cooled as needed due to vigorous heat generation. After the completion of the dropwise addition, the pressure in the reaction vessel was reduced, and tetrahydrofuran and the product were collected by a liquid nitrogen trap. The collected matter was poured into cold water, the lower fluorocarbon phase was separated, and 25 g (40% yield) of the target PMPROD having a purity of 99.5% (j is 2 in the above formula (8)) was obtained by distillation under reduced pressure. )Obtained. This was used for the following polymerization.
Example 2 Synthesis of perfluoro (2-methyl-2-pentyl-1,3-dioxole) (hereinafter referred to as PMPEND).
1.5 kg of 60% fuming sulfuric acid is put into a 2 L glass four-necked flask, and CF is added using a dropping funnel. ₃ (CF ₂ ) ₇ 546 g of I was added dropwise. Stirring was maintained at 65 ° C. for 20 hours. After the completion of the reaction, the mixture was cooled and separated into two phases. Therefore, only the upper layer was collected and distilled to obtain a colorless and transparent CF. ₃ (CF ₂ ) ₆ 270 g (65% yield) of COF was obtained.
Next, a few drops of 1 L of ethanol and phenolphthalein are placed in a 2 L polypropylene beaker, and CF is stirred with a magnetic stirrer. ₃ (CF ₂ ) ₆ 270 g of COF was added dropwise. An ethanol solution of 10% sodium hydroxide was added dropwise to the solution until the solution became neutral. Ethanol was removed from the obtained reaction solution using an evaporator, and the obtained solid was transferred to a vacuum dryer and vacuum-dried at 100 ° C. for 15 hours. Next, the solid after vacuum drying was transferred to a 5 L glass flask, and the flask was heated through a dry ice trap under reduced pressure using a vacuum pump and kept in an oil bath at 260 to 280 ° C. for 24 hours. By distilling the liquid collected in the dry ice trap, CF ₃ (CF ₂ ) ₄ CF = CF ₂ 180g (79% yield) was obtained.
Next, 1000 g of a 15% aqueous solution of sodium hypochlorite and 10 g of trioctylmethylammonium chloride were placed in a 2 L glass four-necked flask, and the mixture was cooled to an internal temperature of 10 to 15 ° C. with good stirring. There CF ₃ (CF ₂ ) ₄ CF = CF ₂ Was added dropwise to keep the internal temperature at 20 to 30 ° C. Then, while tracking the reaction by gas chromatography, the raw material CF ₃ (CF ₂ ) ₄ CF = CF ₂ Until almost consumed. The lower layer product was extracted by two-phase separation, and washed three times with ion-exchanged water to remove residual sodium hypochlorite. The crude product was further distilled to obtain 122 g of pure fluorinated epoxide (perfluoro (1,2-epoxyheptane)) (65% yield).
Next, 3 g of aluminum chloride was placed in a 200 mL glass four-necked flask, and activated by adding 10 g of trichlorofluoromethane. Thereto, 120 g of the fluorinated epoxide synthesized above was added dropwise while stirring well so as to keep the internal temperature at 20 to 30 ° C. Thereafter, the reaction was carried out at a reaction temperature of 20 to 40 ° C. until the starting material was almost consumed, while following the reaction with a gas chromatograph. The crude product is subsequently isolated by filtration and distilled to obtain pure CF. ₃ (CF ₂ ) ₄ COCF ₃ Was obtained (90% of yield).
Next, 23 g of 2-chloroethanol was placed in a 300 mL four-neck glass flask, and 108 g of CF was stirred while stirring. ₃ (CF ₂ ) ₄ COCF ₃ Was added dropwise at room temperature. The obtained reaction crude liquid was added dropwise to 500 g of a 20% aqueous sodium hydroxide solution in another 1 L glass flask with vigorous stirring. The reaction solution is washed three times with a separating funnel and distilled to obtain the desired dioxolane compound (4,4,5,5-tetrahydro-perfluoro (2-methyl-2-pentyl-1,3-dioxolane). )) Was obtained in an amount of 103 g (yield: 85%).
Next, 103 g of the above dioxolane compound was placed in a 500 mL glass four-necked flask equipped with a stirrer, a dry ice reflux condenser, a chlorine gas injection tube, and a thermocouple thermometer, and introduction of chlorine gas was started at 5 ° C. At the beginning of the reaction, the introduction of chlorine was carried out slowly because the reaction was intense. The temperature was gradually raised, and the reaction was continued at 80 ° C. at the end, and the reaction was terminated when chlorine was not consumed any more. 121 g (88% yield) of the obtained tetrachlorodioxolane compound (4,4,5,5-tetrachloro-perfluoro (2-methyl-2-pentyl-1,3-dioxolane)) was directly used without purification. Used for the next reaction.
Next, 50 g of antimony trifluoride, 5 g of antimony pentachloride, and 50 mL of PBTHF as a solvent were placed in a 500 mL glass three-necked flask equipped with a stirrer, a reflux condenser, and a thermocouple thermometer. Was added and reflux continued for 32 hours. Under these conditions, only the desired compound in which two chlorine atoms at the vicinal position were substituted with fluorine was selectively obtained. After cooling to room temperature, only the supernatant was collected by decantation and distilled under reduced pressure to obtain the desired dichlorodioxolane compound (4,5-dichloro-perfluoro (2-methyl-2-pentyl-1,3- Dioxolane)) 99 g (87% yield).
Next, 13 g of magnesium powder, 2 g of iodine, 0.5 g of mercuric chloride, and 350 mL of tetrahydrofuran were placed in a 1-L glass four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermocouple thermometer. And heated. When the reflux started, the heating was stopped and 99 g of the dichlorodioxolane compound was slowly dropped. The reactor was cooled as needed due to vigorous heat generation. After the completion of the dropwise addition, the pressure in the reaction vessel was reduced, and tetrahydrofuran and the product were collected by a liquid nitrogen trap. The collected matter was poured into cold water, the lower fluorocarbon phase was separated, and 34 g (41% yield) of the target PMPEND having a purity of 99.2% (j is 4 in the above formula (8)) was obtained by distillation under reduced pressure. ) Got. This was used for the following polymerization.
Example 3 Synthesis of perfluoro (2-pentyl-1,3-dioxole) (hereinafter referred to as PPD).
1.5 kg of 60% fuming sulfuric acid is put into a 2 L glass four-necked flask, and CF is added using a dropping funnel. ₃ (CF ₂ ) ₅ 446 g of I was added dropwise. Stirring was maintained at 65 ° C. for 18 hours. After the completion of the reaction, the mixture was cooled and separated into two phases. Therefore, only the upper layer was collected and distilled to obtain a colorless and transparent CF. ₃ (CF ₂ ) ₄ 200 g (63% yield) of COF was obtained.
Next, 51 g of 2-chloroethanol was placed in a 1 L polypropylene beaker, and CF ₃ (CF ₂ ) ₄ After dropping 200 g of COF and further adding 50 g of pyridine, the mixture was washed with water and distilled to obtain CF. ₃ (CF ₂ ) ₄ COOCH ₂ CH ₂ 190 g (80% yield) of Cl was obtained.
Next, into a 1 L glass four-necked flask, 500 mL of dimethyl sulfoxide and 7.3 g of sodium hydride (60% dispersion in mineral oil) were placed, and while stirring, 190 g of CF synthesized above was stirred. ₃ (CF ₂ ) ₄ COOCH ₂ CH ₂ Cl was added to keep the temperature below 20 ° C. Stirring was continued overnight while keeping the temperature at 30 ° C. or lower. By distillation under reduced pressure, 86 g (yield: 50%) of the target dioxolane compound (2,4,4,5,5-pentahydro-perfluoro (2-pentyl-1,3-dioxolane)) was obtained.
Next, 86 g of the above dioxolane compound was placed in a 500 mL glass four-necked flask equipped with a stirrer, a dry ice reflux condenser, a chlorine gas injection tube, and a thermocouple thermometer, and introduction of chlorine gas was started at 2 ° C. At the beginning of the reaction, the introduction of chlorine was carried out slowly because the reaction was intense. The temperature was gradually raised, and the reaction was continued at 82 ° C. at the end, and the reaction was terminated when the chlorine was no longer consumed. 95 g (yield 74%) of the obtained pentachlorodioxolane compound (2,4,4,5,5-pentachloro-perfluoro (2-pentyl-1,3-dioxolane)) was directly used in the next reaction without purification. It was used for.
Next, 50 g of antimony trifluoride, 5 g of antimony pentachloride, and 50 mL of PBTHF as a solvent were placed in a 500 mL glass three-necked flask equipped with a stirrer, a reflux condenser, and a thermocouple thermometer. Was added and reflux was continued for 24 hours. Under these conditions, only compounds in which the chlorine at the 2-position and the two chlorines at the vicinal position were substituted with fluorine were selectively obtained. After cooling to room temperature, only the supernatant was collected by decantation and distilled under reduced pressure to obtain 73 g of the desired dichlorodioxolane compound (4,5-dichloro-perfluoro (2-pentyl-1,3-dioxolane)). (85% yield).
Next, 15 g of magnesium powder, 1 g of iodine, 0.5 g of mercuric chloride, and 350 mL of tetrahydrofuran were placed in a 1-L glass four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermocouple thermometer. And heated. When the reflux started, the heating was stopped and 73 g of the dichlorodioxolane compound was slowly dropped. The reactor was cooled as needed due to vigorous heat generation. After the completion of the dropwise addition, the pressure in the reaction vessel was reduced, and tetrahydrofuran and the product were collected by a liquid nitrogen trap. The collected matter was poured into cold water, the lower fluorocarbon phase was separated, and 22 g (yield 35%) of the target PPD (the following formula (9)) having a purity of 99.7% was obtained by distillation under reduced pressure. This was used for the following polymerization.

¹⁹ F-NMR (CDCl ₃ , CFCl ₃ (Reference) δ ppm; -70.1 (1F), -80.9 (3F), -121.8 to -126.0 (9F), -157.9 (1F).
[Example of polymer production]
In the following Examples 4 to 28, the glass transition temperature T of the fluoropolymer or the amorphous fluororesin _g Was measured using differential scanning calorimetry (based on JIS-K7121). The refractive index was measured using an Abbe refractometer. The molecular weight was determined by gel permeation chromatography (GPC) using a dichloropentafluoropropane solvent (hereinafter referred to as R225), as a number average molecular weight M in terms of polymethyl methacrylate. _n Was measured. The intrinsic viscosity [η] (unit: dl / g) was measured at 30 ° C. by dissolving in PBTHF (R225 for the polymer P-4 obtained in Example 7).
In the following polymer production examples, the fluorination treatment of the polymer was performed by treating the polymer in a fluorine / nitrogen mixed gas (fluorine gas concentration: 20% by volume) atmosphere at 250 ° C. for 5 hours in principle (conditions). If you change it, specify).
(Example 4) Polymer P-1 (BVE polymer)
In a 5 L glass flask, 750 g of BVE, 4 kg of ion-exchanged water (hereinafter also referred to as water), 260 g of methanol, and 3.7 g of diisopropyl peroxydicarbonate were placed. After purging the system with nitrogen, suspension polymerization was carried out at 40 ° C. for 22 hours. _n Is about 5 × 10 ⁴ 690 g of a polymer was obtained. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-1) was obtained. [Η] of the polymer P-1 is 0.25, T _g Was 108 ° C. and the refractive index was 1.342. At room temperature, the polymer was a tough and transparent glassy polymer.
(Example 5) Polymer P-2 (BVE-4M polymer)
A glass ampoule was charged with 2 g of BVE-4M and 6.2 mg of diisopropyl peroxydicarbonate, frozen in liquid nitrogen, degassed under vacuum, and sealed. After heating in an oven at 40 ° C. for 20 hours, the solidified contents were taken out and dried at 200 ° C. for 1 hour. The yield of the obtained polymer was 99%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-2) was obtained. [Η] of the polymer P-2 was 0.44, M _n Is 131500, refractive index is 1.33, T _g Was 124 ° C. The tensile properties of the polymer P-2 were a tensile modulus of elasticity of 1430 MPa, a yield stress of 36 MPa, and an elongation at break of 4.2%.
(Example 6) Polymer P-3 (BVE / BVE-4M copolymer)
80 g of water, 15 g of BVE-4M, 15 g of BVE, 75 mg of perfluorobenzoyl peroxide, and 2.4 g of methanol were placed in a 200 mL autoclave. After the autoclave was purged with nitrogen, the autoclave was heated to an internal temperature of 70 ° C. and polymerized for 20 hours. The obtained polymer was washed with water and methanol, and then dried at 200 ° C. for 1 hour. The yield of the obtained polymer was 85%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-3) was obtained. [Η] of the polymer P-3 was 0.35, the refractive index was 1.336, and T _g Was 116 ° C.
(Example 7) Polymer P-4 (BVE-4CL polymer)
5 g of BVE-4CL and 12.5 mg of diisopropyl peroxydicarbonate were put in a glass ampule, frozen in liquid nitrogen, degassed under vacuum, and sealed. After heating in an oven at 40 ° C. for 20 hours, the solidified contents were taken out and dried at 200 ° C. for 1 hour. The yield of the obtained polymer was 80%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and heat stability (hereinafter referred to as polymer P-4) was obtained. [Η] of polymer P-4 is 0.20, M _n Is 121500, refractive index is 1.372, T _g Was 126 ° C. The tensile properties of the polymer P-4 were a tensile modulus of elasticity of 1700 MPa, a yield stress of 50 MPa, and a yield elongation of 3.8%.
(Example 8) Polymer P-5 (BVE / BVE-4CL copolymer)
80 g of water, 20 g of BVE-4CL, 15 g of BVE, 80 mg of perfluorobenzoyl peroxide, and 2.0 g of methanol were placed in a 200 mL autoclave. After the autoclave was replaced with nitrogen, the autoclave was heated until the internal temperature reached 70 ° C., and polymerization was performed for 24 hours. The obtained polymer was washed with water and methanol, and then dried at 200 ° C. for 1 hour. The yield of the obtained polymer was 80%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-5) was obtained. [Η] of the polymer P-5 is 0.30, the refractive index is 1.36, and T _g Was 120 ° C.
(Example 9) Polymer P-6 (BVE-4DCL polymer)
A 100 mL stainless steel autoclave was charged with 50 g of trichlorotrifluoroethane, 30 g of BVE-4DCL, and 0.1 g of diisopropyl peroxydicarbonate. After heating and stirring the autoclave at 50 ° C. for 3 days, the autoclave was opened and washed with methanol. The obtained polymer was taken out, and the solvent and the residual monomer were distilled off under reduced pressure to obtain 29 g of a colorless and transparent polymer. The yield of the obtained polymer was 96%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-6) was obtained. M of polymer P-6 _n Is 123,000, refractive index is 1.41, T _g Was 168 ° C. The tensile properties of the polymer P-6 were a tensile modulus of 1690 MPa, a yield stress of 50 MPa, and a yield elongation of 3.6%.
(Example 10) Polymer P-7 (BVE / BVE-4DCL copolymer)
A 200 mL autoclave was charged with 80 g of water, 22 g of BVE-4DCL, 15 g of BVE, 75 mg of perfluorobenzoyl peroxide, and 2.0 g of methanol. After the autoclave was purged with nitrogen, the autoclave was heated until the internal temperature reached 70 ° C., and polymerization was performed for 28 hours. The obtained polymer was washed with water and methanol, and then dried at 200 ° C. for 2 hours. The yield of the obtained polymer was 80%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-7) was obtained. [Η] of the polymer P-7 was 0.28, the refractive index was 1.38, and T _g Was 145 ° C.
(Example 11) Polymer P-8 (BVE / 2CLBVE copolymer)
A 200 mL autoclave was charged with 80 g of water, 12 g of 2CLBVE, 15 g of BVE, 75 mg of perfluorobenzoyl peroxide, and 1.0 g of methanol. After the autoclave was replaced with nitrogen, the autoclave was heated until the internal temperature reached 75 ° C., and polymerization was performed for 40 hours. The obtained polymer was washed with water and methanol, and then dried at 200 ° C. for 2 hours. The yield of the obtained polymer was 70%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-8) was obtained. [Η] of the polymer P-8 was 0.25, the refractive index was 1.35, and T _g Was 98 ° C.
(Example 12) Polymer P-9 (PDD / TFE copolymer)
Radical polymerization of PDD and TFE at a mass ratio of 80:20 using PBTHF as a solvent is carried out. _g At 160 ° C _n Is about 1.7 × 10 ⁵ Was obtained. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-9) was obtained. Polymer P-9 was colorless and transparent, and had a refractive index of 1.305.
(Example 13) Polymer P-10 (PMPROD / TFE copolymer)
Radical polymerization of PMPROD and TFE at a mass ratio of 85:15 using PBTHF as a solvent, _g At 200 ° C _n Is about 1.5 × 10 ⁵ Was obtained. By subjecting this polymer to a fluorination treatment (the treatment time was 7 hours), a polymer having good light transmittance and heat stability (hereinafter referred to as polymer P-10) was obtained. The polymer P-10 was colorless and transparent, and had a refractive index of 1.298.
(Example 14) Polymer P-11 (PMPEND / TFE copolymer)
Radical polymerization of PMPEND and TFE at a mass ratio of 85:15 using PBTHF as a solvent was carried out. _g At 190 ° C _n Is about 1.3 × 10 ⁵ Was obtained. By subjecting this polymer to a fluorination treatment (the treatment time was 6 hours), a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-11) was obtained. Polymer P-11 was colorless and transparent, and had a refractive index of 1.295.
(Example 15) Polymer P-12 (PDD / BVE-4M copolymer)
Radical polymerization of PDD and BVE-4M at a mass ratio of 50:50 using PBTHF as a solvent is carried out. _g At 170 ° C. to give a polymer with [η] of 0.34. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-12) was obtained. Polymer P-12 was colorless and transparent, and had a refractive index of 1.320.
(Example 16) Polymer P-13 (PMPROD / BVE-4M copolymer)
Radical polymerization of PMPROD and BVE-4M at a mass ratio of 45:55 using PBTHF as a solvent was carried out. _g At 160 ° C. to give a polymer with [η] of 0.32. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-13) was obtained. Polymer P-13 was colorless and transparent, and had a refractive index of 1.318.
(Example 17) Polymer P-14 (PMPEND / BVE-4M copolymer)
Radical polymerization of PMPEND and BVE-4M at a mass ratio of 50:50 using PBTHF as a solvent, _g At 162 ° C. to give a polymer with [η] of 0.37. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-14) was obtained. Polymer P-14 was colorless and transparent, and had a refractive index of 1.319.
(Example 18) Polymer P-15 (PPD / BVE-4M copolymer)
Radical polymerization of PPD and BVE-4M at a mass ratio of 55:45 using PBTHF as a solvent was carried out. _g At 160 ° C. to obtain a polymer having an [η] of 0.33. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-15) was obtained. Polymer P-15 was colorless and transparent, and had a refractive index of 1.310.
(Example 19) Polymer P-16 (PDD / PHVE copolymer)
PDD and perfluoro (3,6-dioxa-4-methyl-1-nonene) (CF ₂ = CF-O-CF (CF ₃ ) -CF ₂ -O-CF ₂ -CF ₂ -CF ₃ ) (Hereinafter referred to as PHVE) in a mass ratio of 85:15 by radical polymerization using PBTHF as a solvent, _g At 182 ° C. to give a polymer with [η] of 0.38. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-16) was obtained. Polymer P-16 was colorless and transparent, and had a refractive index of 1.300.
(Example 20) Polymer P-17 (PMPROD / BVE copolymer)
Radical polymerization of PMPROD and BVE at a mass ratio of 50:50 using PBTHF as a solvent _g At 145 ° C. to give a polymer with [η] of 0.30. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-17) was obtained. Polymer P-17 was colorless and transparent, and had a refractive index of 1.321.
(Example 21) Polymer P-18 (PMPEND / BVE copolymer)
PMPEND and BVE are radically polymerized at a mass ratio of 50:50 using PBTHF as a solvent. _g At 150 ° C. to give a polymer with [η] of 0.32. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-18) was obtained. Polymer P-18 was colorless and transparent, and had a refractive index of 1.320.
(Example 22) Polymer P-19 (PPD / BVE copolymer)
Radical polymerization of PPD and BVE at a mass ratio of 50:50 using PBTHF as a solvent, _g At 148 ° C. to give a polymer having an [η] of 0.35. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-19) was obtained. Polymer P-19 was colorless and transparent, and had a refractive index of 1.322.
(Example 23) Polymer P-20 (PDD / MMD copolymer)
Radical polymerization of PDD and MMD at a mass ratio of 65:35 using PBTHF as a solvent _g At 170 ° C. to obtain a polymer having an [η] of 0.30. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-20) was obtained. Polymer P-20 was colorless and transparent, and had a refractive index of 1.325.
(Example 24) Polymer P-21 (PMPROD / MMD copolymer)
Radical polymerization of PMPROD and MMD at a mass ratio of 65:35 using PBTHF as a solvent _g At 168 ° C. to give a polymer with [η] of 0.31. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-21) was obtained. Polymer P-21 was colorless and transparent, and had a refractive index of 1.324.
(Example 25) Polymer P-22 (PMPEND / MMD copolymer)
PMPEND and MMD are radically polymerized at a mass ratio of 60:40 using PBTHF as a solvent. _g At 142 ° C. to give a polymer with [η] of 0.38. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-22) was obtained. Polymer P-22 was colorless and transparent, and had a refractive index of 1.327.
(Example 26) Polymer P-23 (PPD / MMD copolymer)
Radical polymerization of PPD and MMD at a mass ratio of 65:35 using PBTHF as a solvent _g At 162 ° C. to give a polymer with [η] of 0.29. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-23) was obtained. Polymer P-23 was colorless and transparent, and had a refractive index of 1.325.
(Example 27) Polymer P-24 (PPD / TFE copolymer)
Radical polymerization of PPD and TFE at a mass ratio of 85:15 using PBTHF as a solvent, _g At 162 ° C. to give a polymer with [η] of 0.35. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-24) was obtained. Polymer P-24 was colorless and transparent, and had a refractive index of 1.307.
(Example 28) Polymer P-25 (PPD polymer)
5 g of PPD, 6.0 mg of sulfuryl chloride, and 5.0 mg of diisopropyl peroxydicarbonate were placed in a glass ampule, frozen in liquid nitrogen, vacuum-degassed, and sealed. After heating in an oven at 40 ° C. for 3 hours, the solidified contents were taken out and dried at 200 ° C. for 1 hour. The yield of the obtained polymer was 97%. By subjecting this polymer to a fluorination treatment, a polymer having good light transmittance and thermal stability (hereinafter referred to as polymer P-25) was obtained. [Η] of the polymer P-4 was 0.87, M _n Is 105000, refractive index is 1.320, T _g Was 105 ° C. The tensile properties of the polymer P-4 were a tensile modulus of elasticity of 500 MPa and an elongation at break of 63%.
[Amorphous fluororesin production example]
(Examples 29 to 42) Resins R-1 to R-14
Polymer P-1 and TPB were mixed (the latter was contained in an amount of 7.4% by mass with respect to the total of both) and melt-mixed at 250 ° C. to produce a uniform mixture. Hereinafter, this mixture is referred to as resin R-1. Resin R-1 has a refractive index of 1.357, T _g Was 90 ° C.
In the same manner as described above, the polymer and the additive were melt-mixed to produce a uniform mixture. The resulting mixtures were designated as Resin R-2 to Resin R-15, and the composition, refractive index, T _g (° C.). "Amount of additive" in Table 1 represents the ratio (% by mass) of the additive in the mixture. The additives used are as follows.
CFE: chlorotrifluoroethylene oligomer having an average molecular weight of 2000.
PPE: perfluoropolyether having an average molecular weight of 4000 (trade name “Fomblin Z03” manufactured by Ausimont).

[Example of fiber creation]
In the following examples in which the SI optical fiber was prepared, the numerical aperture (NA) of the obtained SI optical fiber was measured by the far field pattern method (based on JIS-C6862). The transmission loss was measured by measuring the transmission loss at a wavelength of 500 to 1600 nm by a cutback method. The fiber was prepared by the following two methods.
Preform method: A polymer (or resin) to be a clad is melt-molded at 250 ° C. to produce a cylindrical tube, and a polymer (or resin) to be a core is melt-molded at 250 ° C. It also produces cylinders with slightly smaller outer diameters. A preform is manufactured by inserting the cylindrical body into the hollow portion of the cylindrical tube and heating the mixture to 230 ° C. to combine them, and the preform is melt-spun at 250 ° C. to obtain an SI type optical fiber.
Two-layer extrusion spinning method: Using an extruder, a polymer (or resin) serving as a core is disposed at the center and a polymer (or resin) serving as a clad is disposed at an outer periphery, and concentrically at 250 ° C. An SI optical fiber is obtained by extrusion spinning.
(Example 44)
By the preform method, an SI type optical fiber having a core of polymer P-1 and a clad of polymer P-10, an outer diameter of 1000 μm, and a core diameter of 980 μm was obtained. FIG. 1 shows the result of measuring the transmission loss of the obtained SI optical fiber. As shown in FIG. 1, the transmission loss of this SI type optical fiber is 62 dB / km at 650 nm, 20 dB / km at 850 nm, and 22 dB / km at 1300 nm. It was an optical fiber that could transmit. NA was 0.34. After storing this SI type optical fiber in an oven at 70 ° C. for 5000 hours, a heat resistance test for re-measuring the transmission loss was carried out, and no change was observed, and the heat resistance was good.
(Examples 45 to 54)
In the same manner as in Example 44, an SI type optical fiber was prepared by the preform method. Table 2 shows the types of core and cladding materials, outer diameter and core diameter, transmission loss, and NA of the obtained SI optical fiber. Further, when a heat resistance test was performed under the same conditions as in Example 44, the transmission loss did not change for any of the SI type optical fibers, and the heat resistance was good.

(Example 57)
According to the two-layer extrusion spinning method, an SI optical fiber having a clad of resin R-12, a core of polymer P-1, an outer diameter of 1000 μm, and a core diameter of 900 μm was obtained. The optical transmission loss of this SI type optical fiber is 146 dB / km at 650 nm, 85 dB / km at 850 nm, and 71 dB / km at 1300 nm. Was. NA was 0.35. After storing this optical fiber in an oven at 80 ° C. for 3000 hours, a heat resistance test for re-measuring the transmission loss was performed, and no change was observed, and the heat resistance was good.
(Examples 58 to 70)
In the same manner as in Example 44, an SI type optical fiber was prepared by the preform method. Table 3 shows the types of core and cladding materials, outer diameter and core diameter, transmission loss, and NA of the obtained SI optical fiber. Further, when a heat resistance test was performed under the same conditions as in Example 44, the transmission loss did not change for any of the SI type optical fibers, and the heat resistance was good.

(Examples 71 to 80)
In the same manner as in Example 44, an SI type optical fiber was prepared by the preform method. Table 4 shows the types of core and cladding materials, outer diameter and core diameter, transmission loss, and NA of the obtained SI optical fiber. Further, when a heat resistance test was performed under the same conditions as in Example 44, the transmission loss did not change for any of the SI type optical fibers, and the heat resistance was good.

(Example 81)
An SI optical fiber having a core of resin R-8 and a clad of resin R-12, an outer diameter of 1000 μm, and a core diameter of 950 μm was obtained by a two-layer extrusion spinning method. The optical transmission loss of this SI type optical fiber is 146 dB / km at 650 nm, 85 dB / km at 850 nm, and 71 dB / km at 1300 nm. Was. NA was 0.58. A heat resistance test was performed under the same conditions as in Example 57. As a result, the transmission loss did not change, and the heat resistance was good.
Industrial potential
The SI optical fiber of the present invention can increase the numerical aperture by increasing the refractive index difference between the core and the cladding without deteriorating the light transmission performance. Thereby, the transmission loss at the time of bending is not increased, and when used in a sensor or the like, the light can be collected from a wide range, so that the sensor sensitivity is improved. In addition, a low level transmission loss can be provided over a wide wavelength range of 600 to 1600 nm. That is, since the same wavelength as the quartz optical fiber can be used, the connection with the quartz optical fiber is easy, and the light source is inexpensive as compared with the conventional plastic optical fiber which has to use a wavelength shorter than 600 to 1600 nm. There are advantages.
On the other hand, since the SI optical fiber of the present invention has a large fiber diameter and is easy to connect to a light source and a light receiving element or to connect fibers to each other similarly to an ordinary plastic optical fiber, an inexpensive short distance communication system can be constructed. Furthermore, since the SI type optical fiber of the present invention has a remarkably improved heat resistance as compared with a normal plastic optical fiber, it has a high thermal stability and can be exposed to a high temperature above room temperature for a long time. Also, it is possible to prevent a reduction in transmission loss. In addition, since the cladding can have flexibility, a fiber that is less likely to crack can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the transmission loss (wavelength 500 to 1600 nm) of the SI type optical fiber of Example 43.

Claims (21)

The core is made of an amorphous fluororesin (A-1) composed of a fluoropolymer having substantially no hydrogen atoms and having a chlorine atom in a side chain, and the clad is substantially free of hydrogen atoms. A step index type plastic optical fiber comprising an amorphous fluororesin (B) composed of a fluoropolymer and having a refractive index difference between a core and a clad of 0.020 or more. The fluorine-containing polymer constituting the amorphous fluororesin (A-1) is a polymer having a repeating unit represented by the following formula (1) and having a cyclic unit of a monomer (a-1) having a chlorine atom. Having a repeating unit in which a monomer (a) represented by the following formula (1) is cyclopolymerized and a repeating unit in which a monomer (c) represented by the following formula (2) is polymerized: The step index type plastic optical fiber according to claim 1, which is a polymer.
However, m and n are each independently an integer of 0 to 5, and R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a C 1 to C 9 perfluoroalkyl Represents a group, a chlorine atom or a fluorine atom.

The fluorinated polymer constituting the amorphous fluororesin (B) is a polymer having a repeating unit in which a monomer (b) represented by the following formula (3) is polymerized. The described step index type plastic optical fiber.
Here, R ¹¹ and R ¹² each independently represent a C 1-9 perfluoroalkyl group or a fluorine atom.

4. The step index type plastic optical fiber according to claim 1, wherein the amorphous fluorine resin (B) contains a fluorine-containing plasticizer having substantially no hydrogen atom. The core comprises an amorphous fluororesin (A) comprising a high refractive index agent and comprising a fluorine-containing polymer substantially having no hydrogen atoms, and the cladding has substantially no hydrogen atoms. A step index type plastic optical fiber comprising an amorphous fluororesin (B) composed of a polymer and having a refractive index difference between a core and a clad of 0.020 or more. The fluorine-containing polymer constituting the amorphous fluororesin (A) is a polymer having a repeating unit obtained by cyclopolymerizing a monomer (a) represented by the following formula (1): The described step index type plastic optical fiber.
Here, m represents an integer of 0 to 5, and R ¹ , R ² , R ³ and R ⁴ each independently represent a C 1-9 perfluoroalkyl group, a chlorine atom or a fluorine atom.

The step index type plastic optical fiber according to claim 5 or 6, wherein the high refractive index agent is a fluorine-containing aromatic compound having substantially no hydrogen atom. The fluorine-containing polymer constituting the amorphous fluororesin (B) is a polymer having a repeating unit in which a monomer (b) represented by the following formula (3) is polymerized. 8. The step index type plastic optical fiber according to 7.
Here, R ¹¹ and R ¹² each independently represent a C 1-9 perfluoroalkyl group or a fluorine atom.

9. The step index type plastic optical fiber according to claim 5, wherein the amorphous fluororesin (B) contains a fluorine-containing plasticizer having substantially no hydrogen atoms. The core is composed of an amorphous fluororesin (A) composed of a fluoropolymer substantially having no hydrogen atom, or the amorphous fluororesin (A) containing a high refractive index agent, and the cladding is substantially formed. Made of an amorphous fluororesin (B-2) composed of a fluorine-containing polymer having no hydrogen atom and having a refractive index of less than 1.300, wherein the refractive index difference between the core and the clad is 0.020 or more. Characterized by a step index type plastic optical fiber. The fluoropolymer constituting the amorphous fluororesin (A) is a polymer represented by the following formula (1) and having a repeating unit in which the monomer (a) is cyclopolymerized. Step index type plastic optical fiber.
Here, m represents an integer of 0 to 5, and R ¹ , R ² , R ³ and R ⁴ each independently represent a C 1-9 perfluoroalkyl group, a chlorine atom or a fluorine atom.

The step index type plastic optical fiber according to claim 10 or 11, wherein the high refractive index agent is a fluorine-containing aromatic compound having substantially no hydrogen atom. The fluoropolymer constituting the amorphous fluororesin (B-2) has a repeating unit in which a monomer (b-1) represented by the following formula (4) is polymerized, and has a refractive index of 1. The step index type plastic optical fiber according to claim 10, 11 or 12, which is less than 300 fluoropolymers.
Here, R ¹³ represents a perfluoroalkyl group having 2 to 9 carbon atoms, and R ¹⁴ represents a perfluoroalkyl group having 1 to 9 carbon atoms or a fluorine atom.

14. The step index type plastic optical fiber according to claim 10, wherein the amorphous fluororesin (B-2) contains a fluorine-containing plasticizer having substantially no hydrogen atom. The core contains an amorphous fluororesin (A) composed of a fluoropolymer having a repeating unit in which the monomer (a) is represented by the following formula (1) and the monomer (a) is cyclopolymerized, or contains a high refractive index agent. An amorphous fluororesin comprising the amorphous fluororesin (A), wherein the cladding is composed of a fluoropolymer having a repeating unit in which a monomer (b-1) represented by the following formula (4) is polymerized: (B-3) or the amorphous fluorine-containing resin (B-3) containing a fluorine-containing plasticizer having substantially no hydrogen atom, wherein a difference in refractive index between the core and the clad is 0.020 or more. A step index type plastic optical fiber.
However, m is an integer of 0 to 5, R ¹ , R ² , R ³ and R ⁴ are each independently a C 1-9 perfluoroalkyl group, a chlorine atom or a fluorine atom, and R ¹³ is a C 2-9 carbon atom. A perfluoroalkyl group, R ¹⁴ represents a C 1-9 perfluoroalkyl group or a fluorine atom.

The core is composed of an amorphous fluororesin (A) composed of a fluoropolymer substantially having no hydrogen atom, or the amorphous fluororesin (A) containing a high refractive index agent, and the cladding is substantially formed. An amorphous fluororesin (B) composed of a fluorine-containing polymer having no hydrogen atom or an amorphous fluororesin (B) containing a fluorine-containing plasticizer substantially having no hydrogen atom A step index type plastic optical fiber having a number (NA) of 0.415 or more. Perfluoro (2-pentyl-1,3-dioxole). A fluorine-containing polymer having a repeating unit in which perfluoro (2-pentyl-1,3-dioxole) is polymerized as a monomer. An optical member, wherein a fluoropolymer having a repeating unit in which perfluoro (2-pentyl-1,3-dioxole) is polymerized is used as a monomer. The optical member according to claim 19, wherein the optical member is a plastic optical fiber. 21. The optical member according to claim 20, wherein a fluoropolymer having a repeating unit in which perfluoro (2-pentyl-1,3-dioxole) is polymerized as a monomer is used as a core or a clad of the plastic optical fiber.

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