JP4228703B2 - Method for producing retardation film - Google Patents

Description

【００４８】
（式中、ａは０または正の整数を、ｂ及びｃはそれぞれ正の整数を、Ｒ¹、Ｒ²、Ｒ³、Ｒ⁴はそれぞれ独立に水素原子、炭化水素残基、フェニル基または極性基を表す。）で示される構成単位を有する高分子を挙げることができる。ここで、極性基としてはニトリル基等が挙げられる。
【００４９】
セルロースエステルとしては、セルロースジアセテート、セルローストリアセテート、セルロースアセテートプロピオネート、セルロースアセテートブチレート、またはセルロースアセテートプロピオネートブチレート等が挙げられる。中でも本発明に用いられるセルロースエステルは、炭素数２〜４のアシル基の置換度が２．４〜３．０であることが好ましく、更に２．６〜２．９であることが好ましい。炭素数２〜３のアシル基の置換度がこの範囲にあることにより所望のレタデーション特性を得るのが容易となる。置換度が低過ぎると、位相差フィルムとしての耐湿熱性に劣る場合があり、置換度が大き過ぎると波長分散特性が負の特性となったり、十分なレタデーションが得られなくなる場合がある。
【００５０】
本発明に用いられるセルロースエステルの原料のセルロースとしては、特に限定はないが、綿花リンター、木材パルプ、ケナフ等を挙げることができる。またそれらから得られたセルロースエステルはそれぞれ任意の割合で混合使用することができる。
【００５１】
本発明のセルロースエステルは、セルロース原料をアシル化剤が酸無水物（無水酢酸、無水プロピオン酸、無水酪酸等）である場合には、酢酸のような有機酸やメチレンクロライド等の有機溶媒を用い、硫酸のようなプロトン性触媒を用いて反応させる。アシル化剤が酸クロライド（ＣＨ₃ＣＯＣｌ、Ｃ₂Ｈ₅ＣＯＣｌ、Ｃ₃Ｈ₇ＣＯＣｌ等）の場合には、触媒としてアミンのような塩基性化合物を用いて反応が行われる。具体的には特開平１０−４５８０４号公報に記載の方法で合成することができる。セルロースエステルはアシル基がセルロース分子の水酸基に反応する。セルロース分子はグルコースユニットが多数連結したものからなっており、グルコースユニットに３個の水酸基がある。この３個の水酸基にアシル基が誘導された数を置換度という。例えば、セルローストリアセテートはグルコースユニットの３個の水酸基全てにアセチル基が結合しており置換度３である。
【００５２】
アシル基の置換度の測定方法はＡＳＴＭ−Ｄ８１７−９６に準じて測定することができる。
【００５３】
本発明のセルロースエステルの数平均分子量は、６００００〜３０００００が得られるフィルムの機械的強度が強く好ましい。更に７００００〜２５００００が好ましい。
【００５４】
本発明では、セルロースエステルがセルロースとカルボン酸とのエステルからなるセルロースアシレートであって、カルボン酸が芳香族カルボン酸であるセルロースエステルも好ましく用いられる。
【００５５】
芳香族カルボン酸が有する芳香族環は、芳香族性炭化水素環、芳香族性複素環またはそれらの縮合環である。芳香族性炭化水素環または芳香族性炭化水素環と芳香族性複素環との縮合環が好ましく、芳香族性炭化水素環がさらに好ましい。芳香族性炭化水素環の例には、ベンゼン環、インデン環、ナフタレン環、アズレン環、フルオレン環、フェナントレン環、アントラセン環、アセナフチレン環、ビフェニレン環、ナフタセン環及びピレン環が含まれる。ベンゼン環、ナフタレン環及びアントラセン環が好ましく、ベンゼン環及びナフタレン環がさらに好ましく、ベンゼン環が最も好ましい。言い換えると、芳香族カルボン酸としては安息香酸が最も好ましい。芳香族性炭化水素環と芳香族性複素環との縮合環の例には、ベンゾトリアゾール環、キノリン環、イソキノリン環、クロメン環、フタラジン環及びインドール環が含まれる。芳香族性炭化水素環に脂肪族性炭化水素環が縮合していてもよい。そのような縮合環の例には、インダン環が含まれる。芳香族性炭化水素環に非芳香族性複素環が縮合していてもよい。そのような縮合環の例には、クロマン環及びインドリン環が含まれる。
【００５６】
芳香族カルボン酸は置換基を有することが好ましい。芳香族カルボン酸が安息香酸である場合、置換基の少なくとも一つが安息香酸のメタ位またはパラ位に結合していることが特に好ましい。また、安息香酸のオルト位は無置換であることが好ましい。置換基の数は１〜５個であることが好ましく、１〜４個であることがより好ましく、１〜３個であることがさらに好ましく、１個または２個であることが最も好ましい。
【００５７】
芳香族カルボン酸の置換基には、ハロゲン原子、シアノ、ヒドロキシル、ニトロ、シリル、シリルオキシ、カルバモイル、カルバモイルオキシ、スルファモイル、スルファモイルアミノ、ホスフィノ、ホスフィニル、ホスホノ、ホスフィニルオキシ、ホスホノオキシ、ホスフィニルアミノ、ホスホノアミノ、脂肪族基、芳香族基、複素環基、−Ｏ−Ｒ、−Ｓ−Ｒ、−ＣＯ−Ｒ、−Ｏ−ＣＯ−Ｒ、−ＣＯ−ＮＨ−Ｒ、−ＣＯ−Ｎ（−Ｒ）₂、−Ｏ−ＣＯ−ＮＨ−Ｒ、−Ｏ−ＣＯ−Ｎ（−Ｒ）₂、−ＣＯ−Ｏ−Ｒ、−Ｏ−ＣＯ−Ｏ−Ｒ、−ＮＨ−Ｒ、−Ｎ（−Ｒ）₂、−ＮＨ−ＣＯ−Ｒ、−ＮＨ−ＣＯ−ＮＨ−Ｒ、−ＮＨ−ＣＯ−Ｎ（−Ｒ）₂、−ＮＨ−ＣＯ−Ｏ−Ｒ、−ＳＯ₂−ＮＨ−Ｒ、−ＳＯ₂−Ｎ（−Ｒ）₂、−ＮＨ−ＳＯ₂−ＮＨ−Ｒ、−ＮＨ−ＳＯ₂−Ｎ（−Ｒ）₂、−ＮＨ−ＳＯ₂−Ｒ、−ＳＯ−Ｒ、−ＳＯ₂−Ｒ、−Ｎ（−ＣＯ−Ｒ）₂、−ＰＨ−Ｒ、−Ｐ（−Ｒ）₂、−ＰＨ−Ｏ−Ｒ、−Ｐ（−Ｒ）−Ｏ−Ｒ、−Ｐ（−Ｏ−Ｒ）₂、−ＰＨ（＝Ｏ）−Ｒ、−Ｐ（＝Ｏ）（−Ｒ）₂、−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−Ｏ−ＰＨ（＝Ｏ）−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｒ）₂、−Ｏ−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−ＮＨ−ＰＨ（＝Ｏ）−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｒ）₂、−ＮＨ−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−ＳｉＨ₂−Ｒ、−ＳｉＨ（−Ｒ）₂、−Ｓｉ（−Ｒ）₃、−Ｏ−ＳｉＨ₂−Ｒ、−Ｏ−ＳｉＨ（−Ｒ）₂及び−Ｏ−Ｓｉ（−Ｒ）₃が含まれる。
【００５８】
上記Ｒは、脂肪族基、芳香族基または複素環基である。同一の基に含まれる複数のＲは互いに異なっていてもよい。上記脂肪族基は、アルキル基、置換アルキル基、アルケニル基、置換アルケニル基、アルキニル基または置換アルキニル基を意味する。アルキル基は、環状構造または分岐構造を有していてもよい。アルキル基の炭素原子数は１〜３０であることが好ましい。アルキル基の例には、メチル、エチル、ｎ−プロピル、イソプロピル、ｔ−ブチル、ｎ−オクチル、エイコシル、２−エチルヘキシル、シクロヘキシル、シクロペンチル、４−ｎ−ドデシルシクロヘキシル、ビシクロ［１，２，２］へプタン−２−イル及びビシクロ［２，２，２］オクタン−３−イルが含まれる。置換アルキル基のアルキル部分は上記アルキル基と同様である。
【００５９】
置換アルキル基の置換基の例には、ハロゲン原子、シアノ、ヒドロキシル、ニトロ、シリル、シリルオキシ、カルバモイル、カルバモイルオキシ、スルファモイル、スルファモイルアミノ、ホスフィノ、ホスフィニル、ホスホノ、ホスフィニルオキシ、ホスホノオキシ、ホスフィニルアミノ、ホスホノアミノ、芳香族基、複素環基、−Ｏ−Ｒ、−Ｓ−Ｒ、−ＣＯ−Ｒ、−Ｏ−ＣＯ−Ｒ、−ＣＯ−ＮＨ−Ｒ、−ＣＯ−Ｎ（−Ｒ）₂、−Ｏ−ＣＯ−ＮＨ−Ｒ、−Ｏ−ＣＯ−Ｎ（−Ｒ）₂、−ＣＯ−Ｏ−Ｒ、−Ｏ−ＣＯ−Ｏ−Ｒ、−ＮＨ−Ｒ、−Ｎ（−Ｒ）₂、−ＮＨ−ＣＯ−Ｒ、−ＮＨ−ＣＯ−ＮＨ−Ｒ、−ＮＨ−ＣＯ−Ｎ（−Ｒ）₂、−ＮＨ−ＣＯ−Ｏ−Ｒ、−ＳＯ₂−ＮＨ−Ｒ、−ＳＯ₂−Ｎ（−Ｒ）₂、−ＮＨ−ＳＯ₂−ＮＨ−Ｒ、−ＮＨ−ＳＯ₂−Ｎ（−Ｒ）₂、−ＮＨ−ＳＯ₂−Ｒ、−ＳＯ−Ｒ、−ＳＯ₂−Ｒ、−Ｎ（−ＣＯ−Ｒ）₂、−ＰＨ−Ｒ、−Ｐ（−Ｒ）₂、−ＰＨ−Ｏ−Ｒ、−Ｐ（−Ｒ）−Ｏ−Ｒ、−Ｐ（−Ｏ−Ｒ）₂、−ＰＨ（＝Ｏ）−Ｒ、−Ｐ（＝Ｏ）（−Ｒ）₂、−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−Ｏ−ＰＨ（＝Ｏ）−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｒ）₂、−Ｏ−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−ＮＨ−ＰＨ（＝Ｏ）−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｒ）₂、−ＮＨ−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−ＳｉＨ₂−Ｒ、−ＳｉＨ（−Ｒ）₂、−Ｓｉ（−Ｒ）₃、−Ｏ−ＳｉＨ₂−Ｒ、−Ｏ−ＳｉＨ（−Ｒ）₂及び−Ｏ−Ｓｉ（−Ｒ）₃が含まれる。
【００６０】
上記Ｒは脂肪族基、芳香族基または複素環基である。同一の基に含まれる複数のＲは互いに異なっていてもよい。置換アルキル基の例には、２−クロロエチル及び２−シアノエチルが含まれる。アルケニル基は、環状構造または分岐構造を有していてもよい。アルケニル基の炭素原子数は２〜３０であることが好ましい。アルケニル基の例には、ビニル、アリル、プレニル、ゲラニル、オレイル、２−シクロペンテン−１−イル、２−シクロヘキセン−１−イル、ビシクロ［１，２，２］へプト−２−エン−１−イル及びビシクロ［２，２，２］オクト−２−エン−４−イルが含まれる。置換アルケニル基のアルケニル部分は、上記アルケニル基と同様である。置換アルケニル基の置換基は置換アルキル基の置換基と同様である。アルキニル基は環状構造または分岐構造を有していてもよい。アルキニル基の炭素原子数は２〜３０であることが好ましい。アルキニル基の例にはエチニル及びプロパルギルが含まれる。置換アルキニル基のアルキニル部分は上記アルキニル基と同様である。置換アルキニル基の置換基は置換アルキル基の置換基と同様である。置換アルキニル基の例にはトリメチルシリルエチニルが含まれる。
【００６１】
前記芳香族基はアリール基または置換アリール基を意味する。アリール基の炭素原子数は６〜３０であることが好ましい。アリール基の例にはフェニル及びナフチルが含まれる。置換アリール基のアリール部分は上記アリール基と同様である。
【００６２】
置換アリール基の置換基の例には、ハロゲン原子、シアノ、ヒドロキシル、ニトロ、シリル、シリルオキシ、カルバモイル、カルバモイルオキシ、スルファモイル、スルファモイルアミノ、ホスフィノ、ホスフィニル、ホスホノ、ホスフィニルオキシ、ホスホノオキシ、ホスフィニルアミノ、ホスホノアミノ、脂肪族基、芳香族基、複素環基、−Ｏ−Ｒ、−Ｓ−Ｒ、−ＣＯ−Ｒ、−Ｏ−ＣＯ−Ｒ、−ＣＯ−ＮＨ−Ｒ、−ＣＯ−Ｎ（−Ｒ）₂ −Ｏ−ＣＯ−ＮＨ−Ｒ、−Ｏ−ＣＯ−Ｎ（−Ｒ）₂ −ＣＯ−Ｏ−Ｒ、−Ｏ−ＣＯ−Ｏ−Ｒ、−ＮＨ−Ｒ、−Ｎ（−Ｒ）₂ −ＮＨ−ＣＯ−Ｒ、−ＮＨ−ＣＯ−ＮＨ−Ｒ、−ＮＨ−ＣＯ−Ｎ（−Ｒ）₂−ＮＨ−ＣＯ−Ｏ−Ｒ、−ＳＯ₂ＮＨ−Ｒ、−ＳＯ₂Ｎ（−Ｒ）₂−ＮＨ−ＳＯ₂ＮＨ−Ｒ、−ＮＨ−ＳＯ₂Ｎ（−Ｒ）₂−ＮＨ−ＳＯ₂Ｒ、−ＳＯ−Ｒ、−ＳＯＲ、−Ｎ（−ＣＯ−Ｒ）₂−ＰＨ−Ｒ、−Ｐ（−Ｒ）₂−ＰＨ−Ｏ−Ｒ、−Ｐ（−Ｒ）−Ｏ−Ｒ、−Ｐ（−Ｏ−Ｒ）₂ＰＨ（＝Ｏ）−Ｒ、−Ｐ（＝Ｏ）（−Ｒ）₂、−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−Ｏ−ＰＨ（＝Ｏ）−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｒ）₂、−Ｏ−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−Ｏ−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−ＮＨ−ＰＨ（＝Ｏ）−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｒ）、−ＮＨ−ＰＨ（＝Ｏ）−Ｏ−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｒ）−Ｏ−Ｒ、−ＮＨ−Ｐ（＝Ｏ）（−Ｏ−Ｒ）₂、−ＳｉＨ₂−Ｒ、−ＳｉＨ（−Ｒ）₂、−Ｓｉ（−Ｒ）₃、−Ｏ−ＳｉＨ₂−Ｒ、−Ｏ−ＳｉＨ（−Ｒ）₂及び−Ｏ−Ｓｉ（−Ｒ）₃が含まれる。
【００６３】
上記Ｒは、脂肪族基、芳香族基または複素環基である。同一の基に含まれる複数のＲは互いに異なっていてもよい。置換アリール基の例には、ｐ−トリル、ｍ−クロロフェニル及びｏ−ヘキサデカノイルアミノフェニルが含まれる。前記複素環基には、無置換複素環基及び置換複素環基が含まれる。複素環基は、芳香族性を有していてもよい。複素環基の複素環は、５員環または６員環であることが好ましい。複素環基の炭素原子数は３〜３０であることが好ましい。置換複素環基の置換基は、置換アリール基の置換基と同様である。複素環基の例には、２−フリル、２−チエニル、２−ピリミジニル及び２−ベンゾチアゾリルが含まれる。
【００６４】
芳香族カルボン酸の置換基としては、ハロゲン原子、シアノ、アルキル基、アルコキシ基、アリール基、アリールオキシ基、アシル基、カルボンアミド基、スルホンアミド基、ウレイド基、アラルキル基、ニトロ、アルコキシカルボニル基、アリールオキシカルボニル基、アラルキルオキシカルボニル基、カルバモイル基、スルファモイル基、アシルオキシ基、アルケニル基、アルキニル基、アルキルスルホニル基、アリールスルホニル基、アルキルオキシスルホニル基、アリールオキシスルホニル基、アルキルスルホニルオキシ基及びアリールオキシスルホニル基が好ましく、ハロゲン原子、シアノ、アルキル基、アルコキシ基、アリール基、アリールオキシ基、アシル基、カルボンアミド基、スルホンアミド基及びウレイド基がより好ましく、ハロゲン原子、シアノ、アルキル基、アルコキシ基、アリールオキシ基、アシル基及びカルボンアミド基がさらに好ましく、ハロゲン原子、シアノ、アルキル基、アルコキシ基及びアリールオキシ基がさらにまた好ましく、ハロゲン原子、アルキル基及びアルコキシ基が最も好ましい。
【００６５】
上記ハロゲン原子には、フッ素原子、塩素原子、臭素原子及びヨウ素原子が含まれる。上記アルキル基は、環状構造あるいは分岐を有していてもよい。アルキル基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがより好ましく、１〜６であることがさらに好ましく、１〜４であることが最も好ましい。アルキル基の例には、メチル、エチル、プロピル、イソプロピル、ブチル、ｔ−ブチル、ヘキシル、シクロヘキシル、オクチル及び２−エチルヘキシルが含まれる。上記アルコキシ基は、環状構造あるいは分岐を有していてもよい。アルコキシ基の炭素原子数は、１〜２０であることが好ましく、１〜１２であることがより好ましく、１〜６であることがさらに好ましく、１〜４であることが最も好ましい。アルコキシ基は、さらに別のアルコキシ基で置換されていてもよい。アルコキシ基の例には、メトキシ、エトキシ、２−メトキシエトキシ、２−メトキシ−２−エトキシエトキシ、ブチルオキシ、ヘキシルオキシ及びオクチルオキシが含まれる。
【００６６】
上記アリール基の炭素原子数は６〜２０であることが好ましく、６〜１２であることがさらに好ましい。アリール基の例にはフェニル及びナフチルが含まれる。上記アリールオキシ基の炭素原子数は６〜２０であることが好ましく、６〜１２であることがさらに好ましい。アリールオキシ基の例にはフェノキシ及びナフトキシが含まれる。上記アシル基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。アシル基の例にはホルミル、アセチル及びベンゾイルが含まれる。上記カルボンアミド基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。カルボンアミド基の例にはアセトアミド及びベンズアミドが含まれる。上記スルホンアミド基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。スルホンアミド基の例にはメタンスルホンアミド、ベンゼンスルホンアミド及びｐ−トルエンスルホンアミドが含まれる。上記ウレイド基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。ウレイド基の例には（無置換）ウレイドが含まれる。
【００６７】
記アラルキル基の炭素原子数は７〜２０であることが好ましく、７〜１２であることがさらに好ましい。アラルキル基の例にはベンジル、フェネチル及びナフチルメチルが含まれる。上記アルコキシカルボニル基の炭素原子数は１〜２０であることが好ましく、２〜１２であることがさらに好ましい。アルコキシカルボニル基の例にはメトキシカルボニルが含まれる。上記アリールオキシカルボニル基の炭素原子数は７〜２０であることが好ましく、７〜１２であることがさらに好ましい。アリールオキシカルボニル基の例にはフェノキシカルボニルが含まれる。上記アラルキルオキシカルボニル基の炭素原子数は８〜２０であることが好ましく、８〜１２であることがさらに好ましい。アラルキルオキシカルボニル基の例にはベンジルオキシカルボニルが含まれる。上記カルバモイル基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。カルバモイル基の例には（無置換）カルバモイル及びＮ−メチルカルバモイルが含まれる。上記スルファモイル基の炭素原子数は２０以下であることが好ましく、１２以下であるこおがさらに好ましい。スルファモイル基の例には（無置換）スルファモイル及びＮ−メチルスルファモイルが含まれる。上記アシルオキシ基の炭素原子数は１〜２０であることが好ましく、２〜１２であることがさらに好ましい。アシルオキシ基の例にはアセトキシ及びベンゾイルオキシが含まれる。
【００６８】
上記アルケニル基の炭素原子数は２〜２０であることが好ましく、２〜１２であることがさらに好ましい。アルケニル基の例にはビニル、アリル及びイソプロペニルが含まれる。上記アルキニル基の炭素原子数は２〜２０であることが好ましく、２〜１２であることがさらに好ましい。アルキニル基の例にはエチニルが含まれる。上記アルキルスルホニル基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。上記アリールスルホニル基の炭素原子数は６〜２０であることが好ましく、６〜１２であることがさらに好ましい。上記アルキルオキシスルホニル基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。上記アリールオキシスルホニル基の炭素原子数は６〜２０であることが好ましく、６〜１２であることがさらに好ましい。上記アルキルスルホニルオキシ基の炭素原子数は１〜２０であることが好ましく、１〜１２であることがさらに好ましい。上記アリールオキシスルホニル基の炭素原子数は６〜２０であることが好ましく、６〜１２であることがさらに好ましい。
【００６９】
セルロースを構成するグルコース単位が有する３個の水酸基のうち、上記芳香族カルボン酸とエステル結合している水酸基の数の平均（アシル基の置換度）は１．０〜３．０であることが好ましく、２．０〜３．０であることがさらに好ましい。２種類以上の芳香族カルボン酸を用いて、セルロースの混合カルボン酸エステルを形成してもよい。芳香族カルボン酸と、脂肪族カルボン酸（例、酢酸、プロピオン酸、酪酸）との混合エステルを形成してもよい。ただし、脂肪族カルボン酸との混合エステルを形成する場合も、芳香族カルボン酸の置換度が、上記の定義のように１．０〜３．０であることが好ましく、２．０〜３．０であることがさらに好ましい。
【００７０】
セルロースアシレートは、セルロースと芳香族カルボン酸クロライドまたは芳香族カルボン酸無水物との反応により製造することができる。セルロースと芳香族カルボン酸無水物との反応により製造することが好ましい。芳香族カルボン酸無水物は、芳香族カルボン酸とハロゲン化カルボン酸（例、トリフルオロ酢酸）との混合酸無水物であることが特に好ましい。混合酸無水物は、芳香族カルボン酸とハロゲン化カルボン酸無水物との反応により合成することができる。セルロースと芳香族カルボン酸無水物（または混合酸無水物）との反応については、各種文献（例えば、Ｊｏｕｒｎａｌ ｏｆ Ａｐｐｌｉｅｄ Ｐｏｌｙｍｅｒ Ｓｃｉｅｎｃｅ，Ｖｏｌ．２９，３９８１−３９９０（１９８４））に記載がある。セルロースアシレートの原料となるセルロースは、一般に綿花リンターまたは木材パルプである。綿花リンターと木材パルプとを混合して使用してもよい。セルロースアシレートの合成反応では、反応溶媒としてハロゲン化炭化水素（例、ジクロロメタン）が好ましく用いられる。セルロースアシレートの粘度平均重合度は１５０〜７００であることがが好ましく、２５０〜５５０であることがさらに好ましい。粘度平均重合度は、オストワルド粘度計で測定することができる。
【００７１】
合成方法の具体的な方法は、特開２００２−２４１５１２号公報に詳しく記載されている。
【００７２】
本発明の有機溶媒は、ポリマーの溶解性に優れ、乾燥負荷が少ない等溶液流延製膜法に適したものであれば制限はなく、例えば、塩素系有機溶媒としては、塩化メチレン（沸点３９．８℃）が挙げられる。非塩素系有機溶媒としては、酢酸メチル（沸点５６．９℃）、酢酸エチル（沸点７７．１℃）、アセトン（沸点５６．１℃）、テトラヒドロフラン（沸点６６℃）、１，３−ジオキソラン（沸点７４℃）、１，４−ジオキサン（沸点１０１．１℃）、シクロヘキサノン（沸点１５５．６℃）、ギ酸エチル（沸点５３℃）、２，２，２−トリフルオロエタノール（沸点７３．６℃）、２，２，３，３−テトラフルオロ−１−プロパノール（沸点１０９℃）、１，１，１，３，３，３−ヘキサフルオロ−２−メチル−２−プロパノール（沸点６０℃）、１，１，１，３，３，３−ヘキサフルオロ−２−プロパノール（沸点５８℃）、ニトロエタン（沸点１０１．２℃）等を挙げることができる。ポリマーがセルロースエステルの場合では、特に塩化メチレン、酢酸メチル、酢酸エチル、アセトンを好ましく使用し得る。特に酢酸メチルを有機溶剤中に５０質量％以上含有させることにより、支持体から剥離したウェブの強度が高くなり延伸時の破断頻度が減少できるので好ましい。
【００７３】
本発明に係るポリマー溶液には、上記有機溶媒の他に、炭素原子数１〜４のアルコールを１〜４０質量％含有させることが好ましい。これらはドープを流延用支持体に流延後溶媒が蒸発し始めアルコールの比率が多くなるとウェブ（流延膜）がゲル化し、ウェブを丈夫にできるのでテンターで延伸する場合の破断を防止するのに有効であるばかりでなく、ウェブ中のレタデーション上昇剤等がウェブ中を自由に移動することを防止でき、レタデーションや遅相軸角度のむらを抑制するのに有効である。炭素原子数１〜４のアルコールとしては、メタノール、エタノール、ｎ−プロパノール、ｉｓｏ−プロパノール、ｎ−ブタノール、ｓｅｃ−ブタノール、ｔｅｒｔ−ブタノールを挙げることができる。これらのうちドープの安定性、沸点も比較的低く、乾燥性もよく、かつ毒性がないこと等からエタノールが最も好ましい。
【００７４】
ドープ中のポリマー濃度は１５〜３５質量％、ドープ粘度は１０〜７０Ｐａ・ｓの範囲に調製されることが良好なフィルム面品質を得る上で好ましい。
【００７５】
本発明のドープに可塑剤を配合することにより、フィルムの脆弱性が改善されて強靱性が向上されるので、テンターで延伸した際の破断を防止するのに有効であり好ましい。可塑剤としては、従来公知のポリマーとの相溶性がある化合物から適宜選択できる。ポリマーがセルロースエステルの場合は特にリン酸エステルやカルボン酸エステルが好ましく用いられる。リン酸エステルとしては、例えばトリフェニルホスフェート、トリクレジルホスフェート、フェニルジフェニルホスフェート等を挙げることができる。カルボン酸エステルとしては、フタル酸エステル及びクエン酸エステル等、フタル酸エステルとしては、例えばジメチルフタレート、ジエチルホスフェート、ジオクチルフタレート及びジエチルヘキシルフタレート等、またクエン酸エステルとしてはクエン酸アセチルトリエチル及びクエン酸アセチルトリブチルを挙げることができる。またその他、オレイン酸ブチル、リシノール酸メチルアセチル、セバチン酸ジブチル、トリアセチン等も挙げられる。アルキルフタリルアルキルグリコレートもこの目的で好ましく用いられる。アルキルフタリルアルキルグリコレートのアルキルは炭素原子数１〜８のアルキル基である。アルキルフタリルアルキルグリコレートとしてはメチルフタリルメチルグリコレート、エチルフタリルエチルグリコレート、プロピルフタリルプロピルグリコレート、ブチルフタリルブチルグリコレート、オクチルフタリルオクチルグリコレート、メチルフタリルエチルグリコレート、エチルフタリルメチルグリコレート、エチルフタリルプロピルグリコレート、プロピルフタリルエチルグリコレート、メチルフタリルプロピルグリコレート、メチルフタリルブチルグリコレート、エチルフタリルブチルグリコレート、ブチルフタリルメチルグリコレート、ブチルフタリルエチルグリコレート、プロピルフタリルブチルグリコレート、ブチルフタリルプロピルグリコレート、メチルフタリルオクチルグリコレート、エチルフタリルオクチルグリコレート、オクチルフタリルメチルグリコレート、オクチルフタリルエチルグリコレート等を挙げることができ、メチルフタリルメチルグリコレート、エチルフタリルエチルグリコレート、プロピルフタリルプロピルグリコレート、ブチルフタリルブチルグリコレート、オクチルフタリルオクチルグリコレートが好ましく、特にエチルフタリルエチルグリコレートが好ましく用いられる。またこれらアルキルフタリルアルキルグリコレートを２種以上混合して使用してもよい。
【００７６】
これらの化合物の添加量は目的の効果の発現及びフィルムからのブリードアウト抑制等の観点から、ポリマーに対して１〜３０質量％が好ましい。
【００７７】
本発明の位相差フィルムには、レタデーションを調整するためにレタデーション上昇剤を含有させることが好ましい。
【００７８】
レタデーション上昇剤は、ポリマーに対して、０．０１〜２０質量％含有させることが好ましく、０．１〜１０質量％の範囲で使用することがより好ましく、０．２〜５質量％の範囲で使用することがさらに好ましく、０．５〜２質量％の範囲で使用することが最も好ましい。２種類以上のレタデーション上昇剤を併用してもよい。レタデーション上昇剤は２５０〜４００ｎｍの波長領域に最大吸収を有することが好ましい。レタデーション上昇剤は可視領域に実質的に吸収を有していないことが好ましい。
【００７９】
また、レタデーション上昇剤としては少なくとも二つの芳香族環を有する化合物を用いることが好ましい。本明細書において、「芳香族環」は、芳香族炭化水素環に加えて芳香族性ヘテロ環を含む。芳香族炭化水素環は、６員環（すなわち、ベンゼン環）であることが特に好ましい。芳香族性ヘテロ環は一般に不飽和ヘテロ環である。芳香族性ヘテロ環は、５員環、６員環または７員環であることが好ましく、５員環または６員環であることがさらに好ましい。芳香族性ヘテロ環は一般に最多の二重結合を有する。ヘテロ原子としては、窒素原子、酸素原子及び硫黄原子が好ましく、窒素原子が特に好ましい。芳香族性ヘテロ環の例には、フラン環、チオフェン環、ピロール環、オキサゾール環、イソオキサゾール環、チアゾール環、イソチアゾール環、イミダゾール環、ピラゾール環、フラザン環、トリアゾール環、ピラン環、ピリジン環、ピリダジン環、ピリミジン環、ピラジン環及び１，３，５−トリアジン環が含まれる。芳香族環としては、ベンゼン環、フラン環、チオフェン環、ピロール環、オキサゾール環、チアゾール環、イミダゾール環、トリアゾール環、ピリジン環、ピリミジン環、ピラジン環及び１，３，５−トリアジン環が好ましい。
【００８０】
レタデーション上昇剤が有する芳香族環の数は２〜２０であることが好ましく、２〜１２であることがより好ましく、２〜８であることがさらに好ましく、２〜６であることが最も好ましい。二つの芳香族環の結合関係は、（ａ）縮合環を形成する場合、（ｂ）単結合で直結する場合及び（ｃ）連結基を介して結合する場合に分類できる（芳香族環のため、スピロ結合は形成できない）。結合関係は、（ａ）〜（ｃ）のいずれでもよい。
【００８１】
（ａ）の縮合環（二つ以上の芳香族環の縮合環）の例には、インデン環、ナフタレン環、アズレン環、フルオレン環、フェナントレン環、アントラセン環、アセナフチレン環、ビフェニレン環、ナフタセン環、ピレン環、インドール環、イソインドール環、ベンゾフラン環、ベンゾチオフェン環、インドリジン環、ベンゾオキサゾール環、ベンゾチアゾール環、ベンゾイミダゾール環、ベンゾトリアゾール環、プリン環、インダゾール環、クロメン環、キノリン環、イソキノリン環、キノリジン環、キナゾリン環、シンノリン環、キノキサリン環、フタラジン環、プテリジン環、カルバゾール環、アクリジン環、フェナントリジン環、キサンテン環、フェナジン環、フェノチアジン環、フェノキサチイン環、フェノキサジン環及びチアントレン環が含まれる。ナフタレン環、アズレン環、インドール環、ベンゾオキサゾール環、ベンゾチアゾール環、ベンゾイミダゾール環、ベンゾトリアゾール環及びキノリン環が好ましい。
【００８２】
（ｂ）の単結合は、二つの芳香族環の炭素原子間の結合であることが好ましい。２以上の単結合で二つの芳香族環を結合して、二つの芳香族環の間に脂肪族環または非芳香族性複素環を形成してもよい。
【００８３】
（ｃ）の連結基も、二つの芳香族環の炭素原子と結合することが好ましい。連結基は、アルキレン基、アルケニレン基、アルキニレン基、−ＣＯ−、−Ｏ−、−ＮＨ−、−Ｓ−またはそれらの組み合わせであることが好ましい。組み合わせからなる連結基の例を以下に示す。なお、以下の連結基の例の左右の関係は、逆になってもよい。
【００８４】
ｃ１：−ＣＯ−Ｏ−
ｃ２：−ＣＯ−ＮＨ−
ｃ３：−アルキレン−Ｏ−
ｃ４：−ＮＨ−ＣＯ−ＮＨ−
ｃ５：−ＮＨ−ＣＯ−Ｏ−
ｃ６：−Ｏ−ＣＯ−Ｏ−
ｃ７：−Ｏ−アルキレン−Ｏ−
ｃ８：−ＣＯ−アルケニレン−
ｃ９：−ＣＯ−アルケニレン−ＮＨ−
ｃ１０：−ＣＯ−アルケニレン−Ｏ−
ｃ１１：−アルキレン−ＣＯ−Ｏ−アルキレン−Ｏ−ＣＯ−アルキレン−
ｃ１２：−Ｏ−アルキレン−ＣＯ−Ｏ−アルキレン−Ｏ−ＣＯ−アルキレン−Ｏ−
ｃ１３：−Ｏ−ＣＯ−アルキレン−ＣＯ−Ｏ−
ｃ１４：−ＮＨ−ＣＯ−アルケニレン−
ｃ１５：−Ｏ−ＣＯ−アルケニレン−
芳香族環及び連結基は、置換基を有していてもよい。置換基の例には、ハロゲン原子（Ｆ、Ｃｌ、Ｂｒ、Ｉ）、ヒドロキシル、カルボキシル、シアノ、アミノ、ニトロ、スルホ、カルバモイル、スルファモイル、ウレイド、アルキル基、アルケニル基、アルキニル基、脂肪族アシル基、脂肪族アシルオキシ基、アルコキシ基、アルコキシカルボニル基、アルコキシカルボニルアミノ基、アルキルチオ基、アルキルスルホニル基、脂肪族アミド基、脂肪族スルホンアミド基、脂肪族置換アミノ基、脂肪族置換カルバモイル基、脂肪族置換スルファモイル基、脂肪族置換ウレイド基及び非芳香族性複素環基が含まれる。
【００８５】
アルキル基の炭素原子数は、１〜８であることが好ましい。環状アルキル基よりも鎖状アルキル基の方が好ましく、直鎖状アルキル基が特に好ましい。アルキル基は、さらに置換基（例、ヒドロキシ、カルボキシ、アルコキシ基、アルキル置換アミノ基）を有していてもよい。アルキル基の（置換アルキル基を含む）例には、メチル、エチル、ｎ−ブチル、ｎ−ヘキシル、２−ヒドロキシエチル、４−カルボキシブチル、２−メトキシエチル及び２−ジエチルアミノエチルが含まれる。アルケニル基の炭素原子数は２〜８であることが好ましい。環状アルケニル基よりも鎖状アルケニル基の方が好ましく、直鎖状アルケニル基が特に好ましい。アルケニル基は、さらに置換基を有していてもよい。アルケニル基の例には、ビニル、アリル及び１−ヘキセニルが含まれる。アルキニル基の炭素原子数は、２〜８であることが好ましい。環状アルキケニル基よりも鎖状アルキニル基の方が好ましく、直鎖状アルキニル基が特に好ましい。アルキニル基は、さらに置換基を有していてもよい。アルキニル基の例には、エチニル、１−ブチニル及び１−ヘキシニルが含まれる。
【００８６】
脂肪族アシル基の炭素原子数は１〜１０であることが好ましい。脂肪族アシル基の例には、アセチル、プロパノイル及びブタノイルが含まれる。脂肪族アシルオキシ基の炭素原子数は、１〜１０であることが好ましい。脂肪族アシルオキシ基の例には、アセトキシが含まれる。アルコキシ基の炭素原子数は、１〜８であることが好ましい。アルコキシ基は、さらに置換基（例、アルコキシ基）を有していてもよい。アルコキシ基の（置換アルコキシ基を含む）例には、メトキシ、エトキシ、ブトキシ及びメトキシエトキシが含まれる。アルコキシカルボニル基の炭素原子数は、２〜１０であることが好ましい。アルコキシカルボニル基の例には、メトキシカルボニル及びエトキシカルボニルが含まれる。アルコキシカルボニルアミノ基の炭素原子数は、２〜１０であることが好ましい。アルコキシカルボニルアミノ基の例には、メトキシカルボニルアミノ及びエトキシカルボニルアミノが含まれる。
【００８７】
これらの化合物は、溶液の調製の際に、ポリマーや溶媒と共に添加してもよいし、溶液調製中や調製後に添加してもよい。
【００８８】
本発明では、流延用支持体上にドープを流延してウェブとし、支持体上の剥離位置における温度を１０〜４０℃、好ましくは１５〜３０℃とし、かつ剥離位置におけるウェブの残留溶媒量を３０〜１２０質量％とした時点でウェブを剥離することが好ましい。ウェブの剥離時の残留溶媒量をこの範囲にするには、流延後の流延用支持体の表面温度を制御し、ウェブからの有機溶媒の蒸発を効率的に行えるように上記温度範囲にする方法が好ましく用いることができる。支持体温度を制御するには、伝熱効率のよい伝熱方法を使用するのがよい。例えば、液体による裏面伝熱方法が好ましい。ベルト（支持体）マシンにおいて、移送するベルトが下側に来た所の温度制御には、緩やかな風でベルト温度を調節することができる。支持体の温度は、加熱手段を分割することによって、部分的に支持体温度を変えることができ、流延用支持体の流延位置、乾燥部、剥離位置等異なる温度とすることができる。
【００８９】
本発明の位相差フィルムの製造方法では、上記の溶液流延製膜の剥離工程〜乾燥工程の間、または、乾燥工程の途中で前述したように延伸を行う点に特徴がある。
【００９０】
ウェブ両端部の把持部分は通常、フィルムが変形しており製品として使用できないので切除されて、原料として再利用される。切除される幅は狭いほど収率がよくなるので好ましい。通常、１０〜１００ｍｍの範囲であり、より好ましくは１０〜５０ｍｍの範囲である。
【００９１】
以上のようにして得られた位相差フィルムは、フィルムの遅相軸方向（フィルム面内での屈折率の最大方向）が、巻き取り方向に対して２０〜７０度であることが好ましく、更に４０〜５０度の範囲にあることが好ましく、４５度±０．５度であることが最も好ましい。
【００９２】
本発明のポリマーフィルムがＶＡモード、ＴＮモード等の液晶セルを用いた液晶表示装置に用いられる位相差フィルムの場合は、面内レタデーションを２０〜７０ｎｍ、厚み方向レタデーションを７０〜４００ｎｍの範囲とすることにより、視野角拡大効果が得られるので好ましい。レタデーションのばらつきは±５ｎｍ以内であることが好ましく、更に±３ｎｍ以内であることが好ましい。
【００９３】
本発明の位相差フィルムを四分の一波長板や二分の一波長板として用いる場合は、面内レタデーションを１００〜３５０ｎｍとし、フィルム面内の遅相軸方向の屈折率をｎｘ、面内の遅相軸に直交する方向の屈折率をｎｙ、厚み方向の屈折率をｎｚとしたときの（ｎｘ−ｎｚ）／（ｎｘ−ｎｙ）の値を１〜２の範囲とすることが好ましい。
【００９４】
本発明の位相差フィルムは、偏光フィルムの少なくとも片面に貼り合わせることにより偏光板とすることができる。
【００９５】
偏光フィルムは従来から公知のものを用いることができ、例えば、ポリビニルアルコールフィルムの如きの親水性ポリマーフィルムを、沃素のような二色性染料で処理して延伸したものである。偏光フィルムは、それ単体では十分耐久性がないので、一般にはその両面に保護フィルムとしてセルローストリアセテートフィルムを接着してある。
【００９６】
偏光板をなすには、この保護フィルム付の偏光フィルムと貼り合わせてもよいし、保護フィルムを兼ねて直接偏光フィルムと貼り合わせてもよい。貼り合わせる方法は特に限定はないが、水溶性ポリマーの水溶液からなる接着剤により行うことができる。この水溶性ポリマー接着剤は完全鹸化型のポリビニルアルコール水溶液が好ましく用いられる。
【００９７】
本発明の位相差フィルムには、更に液晶性化合物から形成された光学異方性層を設けることができる。光学異方性層は、円盤状または棒状の液晶化合物の溶液を配向膜上に塗設することで得られる。
【００９８】
このようにして得られた偏光板は、液晶表示装置に有効に用いられる。
液晶表示装置は、液晶セル及びその両側に配置された２枚の偏光板からなり、液晶セルは、２枚の電極基板の間に液晶を担持している。本発明に係る偏光板は、液晶セルの一方の面に液晶セル側に本発明の位相差フィルムがくるように配置するか、液晶セルの両面に同様に配置することで視野角拡大効果が得られる。
【００９９】
【実施例】
以下、実施例を挙げて本発明を詳細に説明するが、本発明の態様はこれに限定されるものではない。
【０１００】
実施例中の各測定及び評価は以下の方法で行った。
（フィルムの面内方向のレタデーションＲｏ値、厚み方向のレタデーションＲｔ値及び遅相軸の角度θ）
フィルムの幅方向に等間隔で１０点測定用サンプルを切り出し、下記の方法で面内方向のレタデーションＲｏ値、厚み方向のレタデーションＲｔ値及び遅相軸の角度θを求めた。
【０１０１】
自動複屈折率計ＫＯＢＲＡ−２１ＡＤＨ（王子計測機器（株）製）を用いて２３℃、５５％ＲＨの雰囲気下で５９０ｎｍの波長において３次元屈折率測定を行い、遅相軸の縦方向とのなす角度及び遅相軸方向の屈折率ｎｘ、遅相軸方向の屈折率ｎｙ、厚み方向の屈折率ｎｚを求める。Ｒｏ値及びＲｔ値を下記式から算出した。なお、屈折率の演算に必要な平均屈折率の値は、アッベ屈折率計を用いてフィルムサンプルの縦、横、厚み方向それぞれの屈折率を測定し、その平均値を用いた。式中ｄはフィルムの厚み（ｎｍ）である。
【０１０２】
Ｒｔ＝（（ｎｘ＋ｎｙ）／２−ｎｚ）×ｄ
Ｒｏ＝（ｎｘ−ｎｙ）×ｄ
（フィルムの透明性）
フィルムの透明性はフィルムのヘーズにより評価した。フィルムの幅方向に１０点等間隔で測定用サンプルを切り出し、ＪＩＳ Ｋ７１０５−１９８１に準じて測定した。
【０１０３】
実施例１
セルローストリアセテート ８９質量部
トリフェニルフォスフェート ７．３９質量部
ビフェニルジフェニルフォスフェート ３．６０質量部
シリカ ０．０１質量部
塩化メチレン ２６７質量部
エタノール ２６質量部
以上を加圧密閉容器に投入して攪拌しながら溶解しドープを調製した。このドープを支持体上に流延し、ウェブ中の残留溶媒が８０質量％となった時点で支持体から剥離した。このフィルムをロール搬送させながら残留溶媒量が３５質量％になるまで乾燥し、次いで図１のテンターに導入し、１００℃、溶媒蒸気濃度が９０％の雰囲気下で１．４倍に延伸した後、１．２倍まで収縮させ、以降幅を一定に保ち、１２０℃、溶媒蒸気濃度が２質量％の雰囲気下で乾燥した後、ウェブを把持具から解放した。左右のテンター把持具の搬送速度差は０．０５％未満であった。ここで｜Ｌ１−Ｌ２｜は１．１ｍ、Ｗは１．１ｍであり、｜Ｌ１−Ｌ２｜＝Ｗの関係にあった。テンター出口におけるシワ等は観察されず、テンター出口におけるウェブ中の残留溶媒量は１０質量％であった。さらにロール搬送させながら１１５℃で乾燥させ、両端部の把持部分をスリットし膜厚８０μｍのフィルムを得た。最終的に得られたフィルム中の残留溶媒量は０．２質量％であった。得られたフィルムの面内のレタデーションＲｏ、厚み方向のレタデーションＲｔ、遅相軸のフィルム長手方向とのなす角度及びヘーズを測定した。その結果を表１、２に示した。
【０１０４】
比較例１
セルローストリアセテート ８９質量部
トリフェニルフォスフェート ７．３９質量部
ビフェニルジフェニルフォスフェート ３．６０質量部
シリカ ０．０１質量部
塩化メチレン ２６７質量部
エタノール ２６質量部
以上を加圧密閉容器に投入して攪拌しながら溶解しドープを調製した。このドープを支持体上に流延し、ウェブ中の残留溶媒が８０質量％となった時点で支持体から剥離した。このフィルムをロール搬送させながら残留溶媒量が３５質量％になるまで乾燥し、次いで図１のテンターに導入し、１００℃、溶媒蒸気濃度が２０％の雰囲気下で１．４倍に延伸した後、１．２倍まで収縮させ、以降幅を一定に保ち、１２０℃、溶媒蒸気濃度５％の雰囲気下で乾燥した後、ウェブを把持具から解放した。左右のテンター把持具の搬送速度差は０．０５％未満であった。ここで｜Ｌ１−Ｌ２｜は１．１ｍ、Ｗは１．１ｍであり、｜Ｌ１−Ｌ２｜＝Ｗの関係にあった。テンター出口におけるシワ等は観察されず、テンター出口におけるウェブ中の残留溶媒量は８質量％であった。さらにロール搬送させながら１１０℃で乾燥させ、両端部の把持部分をスリットして膜厚８０μｍのフィルムを得た。最終的に得られたフィルム中の残留溶媒量は０．２質量％であった。得られたフィルムの面内のレタデーションＲｏ、厚み方向のレタデーションＲｔ、遅相軸のフィルム長手方向とのなす角度及びヘーズを測定した。その結果を表１、２に示した。
【０１０５】
実施例２
セルローストリアセテート ８３．４質量部
トリフェニルフォスフェート ６．６７質量部
ビフェニルジフェニルフォスフェート ３．３３質量部
シリカ ０．０１質量部
下記のレタデーション上昇剤 ６．５９質量部
塩化メチレン ２６７質量部
エタノール ２６質量部
以上を加圧密閉容器に投入し攪拌しながら溶解しドープを調製した。このドープを支持体上に流延し、ウェブ中の残留溶媒が８０質量％となった時点で支持体から剥離した。このフィルムをロール搬送させながら残留溶媒量が３５質量％になるまで乾燥し、次いで図１のテンターに導入し、１００℃、溶媒蒸気濃度が５０％の雰囲気下で１．４倍に延伸した後、１．２倍まで収縮させ、以降幅を一定に保ち、１２０℃、溶媒蒸気濃度が２％の雰囲気下で乾燥した後、ウェブを把持具から解放した。左右のテンター把持具の搬送速度差は、０．０５％未満であった。ここで｜Ｌ１−Ｌ２｜は１．１ｍ、Ｗは１．１ｍであり、｜Ｌ１−Ｌ２｜＝Ｗの関係にあった。テンター出口におけるシワ等は観察されず、テンター出口におけるウェブ中の残留溶媒量は１０質量％であった。さらにロール搬送させながら１１５℃で乾燥させ、両端部の把持部分をスリットし４０μｍのフィルムを得た。最終的に得られたフィルム中の残留溶媒量は０．２質量％であった。得られたフィルムの面内のレタデーションＲｏ、厚み方向のレタデーションＲｔ、遅相軸のフィルム長手方向とのなす角度及びヘーズを測定した。その結果を表１、２に示した。
【０１０６】
【化２】

【０１０７】
実施例３
ＡＲＴＯＮ（ジェー・エス・アール社製） ７７質量部
塩化メチレン ２１質量部
エタノール ２質量部
以上を加圧密閉容器に投入し攪拌しながら溶解しドープを調製した。このドープを支持体上に流延し、ウェブ中の残留溶媒が３０質量％となった時点で支持体から剥離した。このフィルムをロール搬送させながら残留溶媒量が１５質量％になるまで乾燥し、次いで図１のテンターに導入し、１５０℃、溶媒蒸気濃度が５０％の雰囲気下で１．４倍に延伸した後、１．２倍まで収縮させ、以降幅を一定に保ち、１４０℃、溶媒蒸気濃度が２％の雰囲気下で乾燥した後、ウェブを把持具から解放した。左右のテンター把持具の搬送速度差は０．０５％未満であった。ここで｜Ｌ１−Ｌ２｜は１．１ｍ、Ｗは１．１ｍであり、｜Ｌ１−Ｌ２｜＝Ｗの関係にあった。テンター出口におけるシワ等は観察されず、テンター出口におけるウェブ中の残留溶媒量は５質量％であった。さらにロール搬送させながら１１５℃で乾燥させ、両端部の把持部分をスリットし膜厚８０μｍのフィルムを得た。最終的に得られたフィルム中の残留溶媒量は０．２質量％であった。得られたフィルムの面内のレタデーションＲｏ、厚み方向のレタデーションＲｔ、遅相軸のフィルム長手方向とのなす角度及びヘーズを測定した。その結果を表１、２に示した。
【０１０８】
実施例４
ビスフェノールＡからなるポリカーボネート（ポリスチレン換算での数平均分子量が約７００００） ７７質量部
塩化メチレン ２３質量部
以上を加圧密閉容器に投入し攪拌しながら溶解しドープを調製した。このドープを支持体上に流延し、ウェブ中の残留溶媒が３０質量％となった時点で支持体から剥離した。このフィルムをロール搬送させながら残留溶媒量が１０質量％になるまで乾燥し、次いで図１のテンターに導入し、１２０℃、溶媒蒸気濃度５０％の雰囲気下で２．５倍に延伸した後、２．０倍まで収縮させ、以降幅を一定に保ち、１３０℃、溶媒蒸気濃度が２％の雰囲気下で乾燥した後、ウェブを把持具から解放した。左右のテンター把持具の搬送速度差は、０．０５％未満であった。ここで｜Ｌ１−Ｌ２｜は１．８３ｍ、Ｗは１．８３ｍであり、｜Ｌ１−Ｌ２｜＝Ｗの関係にあった。テンター出口におけるシワ等は観察されず、テンター出口におけるウェブ中の残留溶媒量は５質量％であった。さらにロール搬送させながら１１５℃で乾燥させ、両端部の把持部分をスリットし膜厚４０μｍのフィルムを得た。最終的に得られたフィルム中の残留溶媒量は０．１質量％であった。得られたフィルムの面内のレタデーションＲｏ、厚み方向のレタデーションＲｔ、遅相軸のフィルム長手方向とのなす角度及びヘーズを測定した。その結果を表１、２に示した。
【０１０９】
実施例５
ｐ−クロロ安息香酸１２．５質量部、無水トリフルオロ酢酸１６．８質量部を容器に入れ５０℃で３０分間撹拌混合した。次いでセルロース４．１質量部、塩化メチレン１０６質量部を加えて５時間加熱還流した。反応終了後、反応液を室温まで冷却した後、さらにメタノール５００質量部を撹拌しながら徐々に投入し、反応物を沈殿処理した。得られた固形分を濾別、乾燥し、置換度２．９、粘度平均重合度３００のセルロースのクロロ安息香酸エステルを得た。
【０１１０】
上記セルロースのクロロ安息香酸エステル ８３．４質量部
トリフェニルフォスフェート ６．６７質量部
ビフェニルジフェニルフォスフェート ３．３３質量部
シリカ ０．０１質量部
前記レタデーション上昇剤 ６．５９質量部
塩化メチレン ２６７質量部
エタノール ２６質量部
以上を加圧密閉容器に投入し攪拌しながら溶解しドープを調製した。このドープを支持体上に流延し、ウェブ中の残留溶媒が６０質量％となった時点で支持体から剥離した。このフィルムをロール搬送させながら残留溶媒量が３０質量％になるまで乾燥し、次いで図１のテンターに導入し、１００℃、溶媒蒸気濃度が５０％の雰囲気下で１．４倍に延伸した後、１．２倍まで収縮させ、以降幅を一定に保ち、１２０℃、溶媒蒸気濃度が２％の雰囲気下で乾燥した後、ウェブを把持具から解放した。左右のテンター把持具の搬送速度差は、０．０５％未満であった。ここで｜Ｌ１−Ｌ２｜は１．１ｍ、Ｗは１．１ｍであり、｜Ｌ１−Ｌ２｜＝Ｗの関係にあった。テンター出口におけるシワ等は観察されず、テンター出口におけるウェブ中の残留溶媒量は８質量％であった。さらにロール搬送させながら１１５℃で乾燥させ、両端部の把持部分をスリットし６０μｍのフィルムを得た。最終的に得られたフィルム中の残留溶媒量は０．２質量％であった。得られたフィルムの面内のレタデーションＲｏ、厚み方向のレタデーションＲｔ、遅相軸のフィルム長手方向とのなす角度及びヘーズを測定した。その結果を表１、２に示した。
【０１１１】
【表１】

【０１１２】
【表２】

【０１１３】
【発明の効果】
本発明により、位相差フィルム打ち抜き工程における収率が高く、均一なレタデーション特性及び良好な透明性を有する位相差フィルムの製造方法を提供することができる。これにより、優れた表示品位の液晶表示装置が安価に提供される。
【図面の簡単な説明】
【図１】本発明の延伸装置の一例を示す概略平面図である。
【図２】本発明で用いる延伸工程の雰囲気中の溶媒濃度を調整する方法の一例を示す説明図である。
【符号の説明】
１１ ウェブ導入方向
１２ 次工程へのウェブ搬送方向
１３ ウェブを導入する工程
１４ ウェブを延伸する工程
１５ 延伸ウェブを次工程へ送る工程
Ａ１、Ｂ１ 把持開始点
Ｂｘ、Ａｙ 把持解除点
Ａｙ−Ａｘ 左右のウェブ把持手段の行程差
Ｗ 二つの解除点の距離
１６ ウェブ把持手段の軌跡
１７ ウェブ把持手段の軌跡
２１ ウェブ
２２ オーブン
２３ 緩衝ゾーン
２４ ノズル
２５ 送風ファン
２６ 加熱ヒーター
２７ フィルター
２８ 除湿装置
２９ 排気ファン
３０ 凝縮装置
３１ 不活性ガス供給装置
３２〜３６ ダンパー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a retardation film.
[0002]
[Prior art]
A liquid crystal display device has features such as being effective in space saving and low power consumption compared to a CRT, and is widely used in monitors and the like. In general, a liquid crystal display device has a pair of polarizing plates arranged on the front side and the back side of a liquid crystal cell, and the retardation film is composed of a polarizing plate and a liquid crystal for the purpose of optical compensation such as coloring prevention and viewing angle expansion. It is the structure arrange | positioned between cells.
[0003]
The retardation film is required to set the slow axis at various angles with respect to the transmission axis of the polarizing plate. The retardation film is usually produced by uniaxially stretching an unstretched polymer film in the longitudinal direction or the transverse direction, and its slow axis is in the longitudinal direction or the transverse direction. Therefore, in the step of punching the retardation film from the roll-shaped retardation film, the periphery is punched and cut so that the slow axis is at a predetermined inclination angle with respect to the side according to the size of the liquid crystal cell. As a result, scrap material was generated at the end of the roll, and a decrease in yield was inevitable.
[0004]
In order to solve this problem, it is considered that the slow axis direction of the retardation film should be oriented in an oblique direction with an angle from the longitudinal direction. From this point of view, the roll-shaped cellulose ester film is stretched in a direction substantially 45 degrees with respect to the longitudinal direction, so that the angle between the longitudinal direction and the slow axis is substantially 45 degrees. A method for manufacturing a quarter-wave plate has been proposed (see, for example, Patent Document 1). Specifically, it can be achieved by stretching a polymer film whose thickness in the width direction has been changed in advance by a tenter in which the speeds of the grip portions at both ends are different. However, in this method, a film having a film thickness deviation in the film width direction is originally stretched, and further, the film is stretched unbalanced not only in the lateral direction but also in the longitudinal direction. It was difficult. That is, the dispersion of retardation of the obtained retardation film was large.
[0005]
Also, when stretching while applying tension while holding both ends of the continuously supplied polymer film, the difference in trajectory from the holding start point to the holding release point at both ends of the film at a volatile content rate of 5% or more. A method is disclosed in which the absolute value of and the distance between the holding release points at both ends are in a fixed relationship. (For example, refer to Patent Document 2). In this method, since it is not necessary to change the speed of the holders at both ends, it is not necessary to add a film thickness deviation to the film before stretching, and further, unbalanced stretching is not performed in the longitudinal direction, so the above problems are overcome. I thought it was possible. However, even if it is stretched by this method, the dispersion of retardation of the obtained retardation film is practically insufficient, and further, when the stretching ratio becomes high as in the case of producing a quarter-wave plate, etc. When the film is stretched, there is a problem that the film becomes cloudy, transparency is deteriorated, and breakage frequently occurs.
[0006]
Further, when stretching the film while holding both ends of the polymer film by holding means, the volatile content of the stretched part is 1.3 times the volatile content of the part contacting the holding means. A stretching method for increasing the size has been proposed. (For example, refer to Patent Document 3). According to this method, it is said that breakage during stretching can be reduced even during oblique stretching. However, in this method, the film in the vicinity of the holding means is not stretched, and if the volatile content is changed, the stretch ratio is changed and uniform stretching is difficult, and the transparency deterioration due to cloudiness of the highly stretched film is improved. The actual situation was not.
[0007]
[Patent Document 1]
JP 2002-22944 A
[0008]
[Patent Document 2]
JP 2002-86554 A
[0009]
[Patent Document 3]
JP 2002-127245 A
[0010]
[Problems to be solved by the invention]
The objective of this invention is providing the manufacturing method of the retardation film which has a high yield in a retardation film punching process, has a uniform retardation characteristic, and favorable transparency.
[0011]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitution.
[0012]
1. After peeling a web prepared by casting a dope containing a polymer and an organic solvent on a support from the support, while holding both ends of the web with a gripping tool, the advancing direction and slow axis direction of the web Is stretched so as to be inclined by 20 to 70 degrees, the gripping means trajectory L1 from the substantial gripping start point to the substantial gripping release point at one end of the web and the substantial other end of the web The trajectory L2 of the gripping means from the grip start point to the substantial grip release point and the distance W between the two substantial grip release points satisfy the formula (1), and the residual solvent amount in the web is 5 In the method for producing a retardation film in which the amount of the residual solvent is reduced while being contracted after being stretched in the presence of a mass% or more state, between the substantial grip start point of the web and the substantial grip release point. In the atmosphere of the web. Method for producing a retardation film density is characterized in that it comprises a step of at least 50% of the saturated vapor concentration.
[0013]
2. 2. The method for producing a retardation film as described in 1 above, wherein a difference in travel speed in the longitudinal direction of the gripping means at both ends of the web is less than 1%.
[0014]
3. 3. The method for producing a retardation film as described in 1 or 2 above, wherein the polymer is a cellulose ester or a norbornene polymer.
[0015]
4). 4. The method for producing a retardation film as described in 3 above, wherein the polymer is a cellulose ester.
[0016]
5. 5. The method for producing a retardation film as described in 4 above, wherein the cellulose ester is cellulose acylate composed of an ester of cellulose and carboxylic acid, and the carboxylic acid is an aromatic carboxylic acid.
[0017]
6). 5. The method for producing a retardation film as described in 4 above, wherein the acyl group of the cellulose ester is an acyl group having 2 to 4 carbon atoms, and the degree of substitution is 2.6 to 2.9.
[0018]
7). The method for producing a retardation film as described in 4 above, wherein the cellulose ester contains 0.1 to 10% by mass of a retardation increasing agent.
[0019]
The present invention will be described in detail below.
As a result of intensive studies on the reason why uniform retardation characteristics cannot be obtained in the lateral width by the oblique stretching method described in JP-A-2002-86554, the present inventors have found the following. That is, in a normal tenter, the film heating means has a structure in which a plurality of nozzles are arranged in parallel in the horizontal direction, and heating is performed by blowing hot air from the nozzles onto the film surface. In the case of normal transverse stretching, the stretching point is perpendicular to the traveling direction (transverse direction), and the film being stretched is heated uniformly in the width direction, but in the oblique stretching, the stretching point is relative to the traveling direction. Therefore, it was thought that this was due to the fact that the thermal history in the width direction of the film at the stretching point at a certain point in time was not uniform. In particular, when a polymer film (web) peeled off from a support is cast in a solution using a dope in which a polymer is dissolved in an organic solvent and stretched obliquely, the difference in heat history becomes uneven and drying is uniform. Stretching is extremely difficult.
[0020]
In addition, about the problem that the film becomes cloudy and the transparency deteriorates due to stretching, when the surface of the film dries and a skin layer is generated, the subsequent stretching causes fine cracks on the film surface. There was found.
[0021]
The present invention has been completed by continuously studying a stretching method in which drying unevenness hardly occurs even when the heat history is different, and a skin layer is not generated on the film surface.
[0022]
A method of obliquely stretching in the method for producing a retardation film of the present invention will be described. FIG. 1 is a plan view of a tenter preferably used in the present invention, a step 13 for introducing a raw dry web peeled from a support in 11 directions, a stretching step 14 for expanding gripping tools at both ends in a width direction, and The process 15 which sends a stretched film to the following process is included. The web is introduced continuously in 11 directions. The grip start point of the present invention is the point at which both ends of the web are gripped for the first time, that is, A1 and a straight line drawn substantially perpendicularly to the center line of the introduction side web from A1 intersect the trajectory 16 of the gripping means on the opposite side. This is indicated by two points B1. With this point as the starting point, if the gripping means at both ends are transported at substantially constant speed, A1 moves to A2, A3,... An every unit time, and B1 similarly to B2, B3,. Moving. That is, the straight line connecting points An and Bn through which the gripping means serving as a reference passes at the same point is the extending direction at that time.
[0023]
By using such a stretching method, An is gradually delayed with respect to Bn as shown in FIG. 1, so that the stretching direction is gradually inclined from the width direction. The substantial grip release point of the present invention is a point where both ends of the web or one of the ends is released from the gripper, that is, substantially perpendicular to the Bx point and the center line of the web sent from Bx to the next process. The drawn straight line is defined by two points Ay that intersect the trajectory 17 of the gripping means on the opposite side. The final angle in the stretching direction of the film includes the stroke difference Ay−Ax (ie, | L1−L2 |) of the right and left gripping means at the grip release point and the distance W between the two grip release points (the distance between Bx and Ay). It is determined by the ratio. Therefore, the inclination angle θ formed by the stretching direction with respect to the transport direction to the next process is tan θ = W / (Ay−Ax), that is, an angle satisfying tan θ = W / | L1-L2 |. Here, “substantially orthogonal” means 90 ± 0.5 °.
[0024]
The inclination angle of the orientation axis in the obtained stretched film is controlled by the ratio of the exit width W of the stretching process 14 for expanding the gripping tool at both ends in the width direction and the stroke difference | L1-L2 | Can be adjusted. For polarizing plates and retardation films, films that are often oriented at 45 ° to the longitudinal direction are required. In this case, in order to obtain an orientation angle close to 45 °, it is preferable to satisfy the following formula (1),
Formula (1) 0.9W <| L1-L2 | <1.1W
More preferably, it is preferable to satisfy | fill following formula (2).
[0025]
Formula (2) 0.97W <| L1-L2 | <1.03W
If there is a difference in the traveling speed between the left and right webs at the exit of the stretching process, wrinkles are generated at the exit of the stretching process. Therefore, it is preferable that the transport speed difference between the left and right web gripping means is substantially the same. The speed difference is preferably 1% or less, more preferably less than 0.5%, and most preferably less than 0.05%. The speed described here is the length of the trajectory traveled by the left and right gripping means per minute.
[0026]
In addition, as the left and right stroke difference occurs, the web may wrinkle. From this point, it is preferable to reduce the amount of residual solvent while shrinking after stretching in a state where the amount of residual solvent in the web is 5% by mass or more.
[0027]
In the present invention, if the amount of residual solvent in the web during stretching is too small, there is a risk that the film cannot be stretched and breaks. On the other hand, if it is too large, a large stretching ratio is required to obtain the desired retardation, and the apparatus becomes large Therefore, the preferable range of the residual solvent amount is preferably 10 to 90% when the polymer is a cellulose ester.
[0028]
The amount of residual solvent can be expressed by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web, and N is the mass after drying the web at 110 ° C. for 3 hours.
[0029]
In the present invention, the stretching temperature is not particularly limited, but if the temperature is too high, the plasticizer in the web may be scattered, and if it is too low, uniform retardation may not be obtained or the film may become cloudy. Therefore, the range of 70 to 160 ° C. is preferable.
[0030]
In the present invention, the draw ratio can be appropriately adjusted so as to obtain a desired retardation, but is preferably 1.05 to 2.0 times from the viewpoint of the uniformity of retardation of the obtained retardation film.
[0031]
The present invention is characterized in that the concentration of the organic solvent in the atmosphere through which the web passes between the grip start point and the grip release point in the stretching step is 50% or more of the saturated vapor concentration at the ambient temperature. . The step of maintaining this range is preferably the entire range of the width direction stretching step 14 in FIG. 1, and more preferably the entire stretching step. When the concentration of the organic solvent in the atmosphere is within this range, the drying rate of the solvent from the web becomes moderate, and the variation in the amount of residual solvent in the web during stretching can be suppressed to a range that can be substantially ignored. Furthermore, by stretching in such an atmosphere, the formation of a skin layer on the web surface can be suppressed, so that retardation variation and white turbidity of the obtained retardation film can be suppressed. The method for setting the organic solvent concentration in the atmosphere within the above range is not particularly limited. For example, as shown in FIG. 2, the atmosphere in the stretching process is circulated by a circulation fan, The solvent concentration in the atmosphere can be adjusted by adjusting and taking in the amount of fresh air from the fresh air supply pipe. The air conditioning system preferably includes a heater for temperature control, an aggregator that removes volatile components in the circulating air, a recovery device that recovers the solvent, an inert gas supply device, and the like as necessary. If the concentration of the organic solvent in the atmosphere is too high, problems such as condensation may occur, and therefore the range of 50 to 90% of the saturated vapor concentration is more preferable.
[0032]
The solution casting film forming method according to the present invention will be described.
In the present invention, a solution obtained by dissolving a polymer in an organic solvent is referred to as a dope.
[0033]
First, (1) dissolution step: a step in which a dope is formed by dissolving in an organic solvent mainly containing a good solvent for a polymer while stirring in a dissolution vessel. There are various dissolution methods such as a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, a method performed using a cooling dissolution method, and a method performed at high pressure. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next process with a pump.
[0034]
A plasticizer, an antioxidant, a dye, and the like may be added to the dope. These compounds may be added together with the polymer or solvent during the preparation of the solution, or may be added during or after the preparation of the solution. For a liquid crystal screen display device, it is preferable to add a plasticizer, an antioxidant, an ultraviolet ray inhibitor or the like that imparts heat and humidity resistance.
[0035]
As the antioxidant, a hindered phenol compound is preferably used, and 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl). -4-hydroxyphenyl) propionate] and triethyleneglycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] are preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose ester.
[0036]
As an ultraviolet absorber, from the viewpoint of preventing the deterioration of polarizers and liquid crystals, it has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, it has little absorption of visible light having a wavelength of 400 nm or more Is preferred. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Of these, benzotriazole compounds are preferred because they have less unnecessary coloration on cellulose esters. The content of the ultraviolet absorber is 0.01 to 5%, particularly 0.5 to 3% by mass ratio. In addition, heat stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina, and alkaline earth metal salts such as calcium and magnesium may be added. . Furthermore, an antistatic agent, a flame retardant, a lubricant, an oil agent, etc. may be added.
[0037]
(2) Casting step: The dope is fed to a pressure die through a pressurized metering gear pump, and an endless metal belt for infinite transfer or a support for casting a rotating metal drum at the casting position (hereinafter simply referred to as “casting”). This is a step of casting a dope from a pressure die onto a support. The surface of the casting support is a mirror surface. Other casting methods include a doctor blade method in which the film thickness of the cast dope film is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll, but the slit shape of the die part is prepared. A pressure die capable of making the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the dope amount may be divided and stacked. Moreover, it is good also as a laminated structure of a composition from which each layer differs by co-casting.
[0038]
(3) Solvent evaporation step: The web can be peeled from the support by heating the web (referred to as the dope film after casting the dope on the casting support). This is a step of evaporating the solvent until. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. The drying efficiency is good and preferable. A method of combining them is also preferable.
[0039]
(4) Peeling step: This is a step of peeling the web in which the solvent has evaporated on the support at the peeling position. The peeled web is sent to the next process. If the residual solvent amount of the web at the time of peeling is too large, peeling is difficult, or conversely, if it is peeled off after sufficiently drying on the support, a part of the web is peeled off.
[0040]
As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the amount of residual solvent is as large as possible), there is a gel casting method (gel casting) in which even a large amount of residual solvent can be removed. For example, a poor solvent for the polymer is added to the dope, and the dope is cast and then gelled, and the temperature of the support is lowered to gel. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, it is possible to speed up the peeling and increase the film forming speed. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be damaged, or slippage and vertical stripes due to peeling tension will tend to occur, and the amount of residual solvent will be reduced in consideration of economic speed and quality. I can decide.
[0041]
(5) Drying step: a step of drying the web using a drying device that alternately conveys the web through rolls arranged in a staggered manner and / or a tenter device that clips and conveys both ends of the web with a clip. Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying a microwave instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from a residual solvent of about 8% by mass or less. Throughout, the drying temperature is usually 40 to 250 ° C, preferably 70 to 180 ° C. The drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.
[0042]
(6) Winding step: The step of winding the web as a film after the residual solvent amount becomes 2% by mass or less. By setting the residual solvent amount to 0.4% by mass or less, a film having good dimensional stability can be obtained. As a winding method, a generally used method may be used, and there are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.
[0043]
Although the film thickness of the retardation film varies depending on the purpose of use, the finished film is usually preferably 20 to 200 μm, more preferably 30 to 120 μm, and particularly preferably 35 to 100 μm. If it is too thin, the film may be weak and handleability may be poor. If it is too thick, the display device becomes thick, and for example, portability may be impaired. To adjust the film thickness, it is necessary to control the dope concentration, the pumping amount of the pump, the slit gap of the die base, the extrusion pressure of the die, the speed of the casting support, etc. so as to obtain the desired thickness. Good. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.
[0044]
In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. However, it goes without saying that the danger of the explosion limit of the evaporating solvent in a dry atmosphere must always be taken into account.
[0045]
The polymer used in the present invention is not particularly limited as long as it can be used for solution casting film formation, and examples thereof include cellulose ester, polyolefin, polysulfone, polycarbonate, polymethyl methacrylate, polyester, and polyvinyl alcohol. In particular, it is preferable to use a polymer having a small photoelastic coefficient because retardation unevenness due to thermal strain can be suppressed, and cellulose esters and polyolefins are preferably used. Most preferred is cellulose ester.
[0046]
As the polyolefin, a cyclic olefin polymer is preferable, and a norbornene polymer is particularly preferable because of excellent heat resistance. Examples of norbornene polymers include the following general formula (1)
[0047]
[Chemical 1]

[0048]
(Wherein, a is 0 or a positive integer, b and c are each a positive integer, R ¹ , R ² , R ^Three , R ^Four Each independently represents a hydrogen atom, a hydrocarbon residue, a phenyl group or a polar group. And a polymer having a structural unit represented by Here, a nitrile group etc. are mentioned as a polar group.
[0049]
Examples of the cellulose ester include cellulose diacetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. Among them, the cellulose ester used in the present invention preferably has a substitution degree of an acyl group having 2 to 4 carbon atoms of 2.4 to 3.0, and more preferably 2.6 to 2.9. When the degree of substitution of the acyl group having 2 to 3 carbon atoms is within this range, it becomes easy to obtain desired retardation characteristics. If the degree of substitution is too low, the heat-and-moisture resistance as a retardation film may be inferior, and if the degree of substitution is too large, the wavelength dispersion characteristic may be negative or sufficient retardation may not be obtained.
[0050]
The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.
[0051]
In the cellulose ester of the present invention, when the acylating agent for the cellulose raw material is an acid anhydride (such as acetic anhydride, propionic anhydride, butyric anhydride), an organic solvent such as acetic acid or an organic solvent such as methylene chloride is used. The reaction is carried out using a protic catalyst such as sulfuric acid. The acylating agent is acid chloride (CH _Three COCl, C ₂ H _Five COCl, C _Three H ₇ In the case of COCl or the like, the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized by the method described in JP-A-10-45804. In the cellulose ester, the acyl group reacts with the hydroxyl group of the cellulose molecule. Cellulose molecules are composed of many glucose units linked together, and the glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution. For example, cellulose triacetate has a substitution degree of 3 with acetyl groups bonded to all three hydroxyl groups of the glucose unit.
[0052]
The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.
[0053]
The number average molecular weight of the cellulose ester of the present invention is preferred because the mechanical strength of the film from which 60000 to 300000 is obtained is strong. Furthermore, 70000-250,000 are preferable.
[0054]
In the present invention, a cellulose ester in which the cellulose ester is an ester of cellulose and carboxylic acid and the carboxylic acid is an aromatic carboxylic acid is also preferably used.
[0055]
The aromatic ring of the aromatic carboxylic acid is an aromatic hydrocarbon ring, an aromatic heterocyclic ring or a condensed ring thereof. An aromatic hydrocarbon ring or a condensed ring of an aromatic hydrocarbon ring and an aromatic heterocycle is preferable, and an aromatic hydrocarbon ring is more preferable. Examples of the aromatic hydrocarbon ring include benzene ring, indene ring, naphthalene ring, azulene ring, fluorene ring, phenanthrene ring, anthracene ring, acenaphthylene ring, biphenylene ring, naphthacene ring and pyrene ring. A benzene ring, a naphthalene ring and an anthracene ring are preferable, a benzene ring and a naphthalene ring are more preferable, and a benzene ring is most preferable. In other words, benzoic acid is most preferable as the aromatic carboxylic acid. Examples of the condensed ring of an aromatic hydrocarbon ring and an aromatic heterocyclic ring include a benzotriazole ring, a quinoline ring, an isoquinoline ring, a chromene ring, a phthalazine ring, and an indole ring. An aliphatic hydrocarbon ring may be condensed with an aromatic hydrocarbon ring. Examples of such fused rings include indane rings. A non-aromatic heterocycle may be condensed with an aromatic hydrocarbon ring. Examples of such fused rings include chroman and indoline rings.
[0056]
The aromatic carboxylic acid preferably has a substituent. When the aromatic carboxylic acid is benzoic acid, it is particularly preferred that at least one of the substituents is bonded to the meta position or para position of benzoic acid. The ortho position of benzoic acid is preferably unsubstituted. The number of substituents is preferably 1 to 5, more preferably 1 to 4, more preferably 1 to 3, and most preferably 1 or 2.
[0057]
Aromatic carboxylic acid substituents include halogen atoms, cyano, hydroxyl, nitro, silyl, silyloxy, carbamoyl, carbamoyloxy, sulfamoyl, sulfamoylamino, phosphino, phosphinyl, phosphono, phosphinyloxy, phosphonooxy, phosphini Ruamino, phosphonoamino, aliphatic group, aromatic group, heterocyclic group, —O—R, —S—R, —CO—R, —O—CO—R, —CO—NH—R, —CO—N (-R) ₂ , -O-CO-NH-R, -O-CO-N (-R) ₂ , —CO—O—R, —O—CO—O—R, —NH—R, —N (—R) ₂ , -NH-CO-R, -NH-CO-NH-R, -NH-CO-N (-R) ₂ , -NH-CO-O-R, -SO ₂ -NH-R, -SO ₂ -N (-R) ₂ , -NH-SO ₂ -NH-R, -NH-SO ₂ -N (-R) ₂ , -NH-SO ₂ -R, -SO-R, -SO ₂ -R, -N (-CO-R) ₂ , -PH-R, -P (-R) ₂ , -PH-O-R, -P (-R) -O-R, -P (-O-R) ₂ , -PH (= O) -R, -P (= O) (-R) ₂ , -PH (= O) -O-R, -P (= O) (-R) -O-R, -P (= O) (-O-R) ₂ , -O-PH (= O) -R, -O-P (= O) (-R) ₂ , -O-PH (= O) -O-R, -O-P (= O) (-R) -O-R, -O-P (= O) (-O-R) ₂ , -NH-PH (= O) -R, -NH-P (= O) (-R) ₂ , —NH—PH (═O) —O—R, —NH—P (═O) (— R) —O—R, —NH—P (═O) (— O—R) ₂ , -SiH ₂ -R, -SiH (-R) ₂ , -Si (-R) _Three , -O-SiH ₂ -R, -O-SiH (-R) ₂ And -O-Si (-R) _Three Is included.
[0058]
R is an aliphatic group, an aromatic group or a heterocyclic group. A plurality of R contained in the same group may be different from each other. The aliphatic group means an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group or a substituted alkynyl group. The alkyl group may have a cyclic structure or a branched structure. The alkyl group preferably has 1 to 30 carbon atoms. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl, 2-ethylhexyl, cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl, bicyclo [1,2,2]. Heptan-2-yl and bicyclo [2,2,2] octane-3-yl are included. The alkyl part of the substituted alkyl group is the same as the above alkyl group.
[0059]
Examples of the substituent of the substituted alkyl group include halogen atom, cyano, hydroxyl, nitro, silyl, silyloxy, carbamoyl, carbamoyloxy, sulfamoyl, sulfamoylamino, phosphino, phosphinyl, phosphono, phosphinyloxy, phosphonooxy, phos Finylamino, phosphonoamino, aromatic group, heterocyclic group, —O—R, —S—R, —CO—R, —O—CO—R, —CO—NH—R, —CO—N (—R ) ₂ , -O-CO-NH-R, -O-CO-N (-R) ₂ , —CO—O—R, —O—CO—O—R, —NH—R, —N (—R) ₂ , -NH-CO-R, -NH-CO-NH-R, -NH-CO-N (-R) ₂ , -NH-CO-O-R, -SO ₂ -NH-R, -SO ₂ -N (-R) ₂ , -NH-SO ₂ -NH-R, -NH-SO ₂ -N (-R) ₂ , -NH-SO ₂ -R, -SO-R, -SO ₂ -R, -N (-CO-R) ₂ , -PH-R, -P (-R) ₂ , -PH-O-R, -P (-R) -O-R, -P (-O-R) ₂ , -PH (= O) -R, -P (= O) (-R) ₂ , -PH (= O) -O-R, -P (= O) (-R) -O-R, -P (= O) (-O-R) ₂ , -O-PH (= O) -R, -O-P (= O) (-R) ₂ , -O-PH (= O) -O-R, -O-P (= O) (-R) -O-R, -O-P (= O) (-O-R) ₂ , -NH-PH (= O) -R, -NH-P (= O) (-R) ₂ , —NH—PH (═O) —O—R, —NH—P (═O) (— R) —O—R, —NH—P (═O) (— O—R) ₂ , -SiH ₂ -R, -SiH (-R) ₂ , -Si (-R) _Three , -O-SiH ₂ -R, -O-SiH (-R) ₂ And -O-Si (-R) _Three Is included.
[0060]
R is an aliphatic group, an aromatic group or a heterocyclic group. A plurality of R contained in the same group may be different from each other. Examples of the substituted alkyl group include 2-chloroethyl and 2-cyanoethyl. The alkenyl group may have a cyclic structure or a branched structure. The alkenyl group preferably has 2 to 30 carbon atoms. Examples of alkenyl groups include vinyl, allyl, prenyl, geranyl, oleyl, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl, bicyclo [1,2,2] hept-2-ene-1- Yl and bicyclo [2,2,2] oct-2-en-4-yl. The alkenyl part of the substituted alkenyl group is the same as the above alkenyl group. The substituent of the substituted alkenyl group is the same as the substituent of the substituted alkyl group. The alkynyl group may have a cyclic structure or a branched structure. The alkynyl group preferably has 2 to 30 carbon atoms. Examples of alkynyl groups include ethynyl and propargyl. The alkynyl part of the substituted alkynyl group is the same as the above alkynyl group. The substituent of the substituted alkynyl group is the same as the substituent of the substituted alkyl group. Examples of substituted alkynyl groups include trimethylsilylethynyl.
[0061]
The aromatic group means an aryl group or a substituted aryl group. The aryl group preferably has 6 to 30 carbon atoms. Examples of the aryl group include phenyl and naphthyl. The aryl part of the substituted aryl group is the same as the above aryl group.
[0062]
Examples of substituents for substituted aryl groups include halogen atoms, cyano, hydroxyl, nitro, silyl, silyloxy, carbamoyl, carbamoyloxy, sulfamoyl, sulfamoylamino, phosphino, phosphinyl, phosphono, phosphinyloxy, phosphonooxy, phosphineoxy Finylamino, phosphonoamino, aliphatic group, aromatic group, heterocyclic group, —O—R, —S—R, —CO—R, —O—CO—R, —CO—NH—R, —CO— N (-R) ₂ -O-CO-NH-R, -O-CO-N (-R) ₂ -CO-O-R, -O-CO-O-R, -NH-R, -N (-R) ₂ -NH-CO-R, -NH-CO-NH-R, -NH-CO-N (-R) ₂ —NH—CO—O—R, —SO ₂ NH-R, -SO ₂ N (-R) ₂ -NH-SO ₂ NH-R, -NH-SO ₂ N (-R) ₂ -NH-SO ₂ R, —SO—R, —SOR, —N (—CO—R) ₂ -PH-R, -P (-R) ₂ -PH-O-R, -P (-R) -O-R, -P (-O-R) ₂ PH (= O) -R, -P (= O) (-R) ₂ , -PH (= O) -O-R, -P (= O) (-R) -O-R, -P (= O) (-O-R) ₂ , -O-PH (= O) -R, -O-P (= O) (-R) ₂ , -O-PH (= O) -O-R, -O-P (= O) (-R) -O-R, -O-P (= O) (-O-R) ₂ , -NH-PH (= O) -R, -NH-P (= O) (-R), -NH-PH (= O) -O-R, -NH-P (= O) (-R) —O—R, —NH—P (═O) (— O—R) ₂ , -SiH ₂ -R, -SiH (-R) ₂ , -Si (-R) _Three , -O-SiH ₂ -R, -O-SiH (-R) ₂ And -O-Si (-R) _Three Is included.
[0063]
R is an aliphatic group, an aromatic group or a heterocyclic group. A plurality of R contained in the same group may be different from each other. Examples of substituted aryl groups include p-tolyl, m-chlorophenyl and o-hexadecanoylaminophenyl. The heterocyclic group includes an unsubstituted heterocyclic group and a substituted heterocyclic group. The heterocyclic group may have aromaticity. The heterocyclic ring of the heterocyclic group is preferably a 5-membered ring or a 6-membered ring. The number of carbon atoms in the heterocyclic group is preferably 3-30. The substituent of the substituted heterocyclic group is the same as the substituent of the substituted aryl group. Examples of the heterocyclic group include 2-furyl, 2-thienyl, 2-pyrimidinyl and 2-benzothiazolyl.
[0064]
As substituents of aromatic carboxylic acids, halogen atoms, cyano, alkyl groups, alkoxy groups, aryl groups, aryloxy groups, acyl groups, carbonamido groups, sulfonamido groups, ureido groups, aralkyl groups, nitro, alkoxycarbonyl groups , Aryloxycarbonyl group, aralkyloxycarbonyl group, carbamoyl group, sulfamoyl group, acyloxy group, alkenyl group, alkynyl group, alkylsulfonyl group, arylsulfonyl group, alkyloxysulfonyl group, aryloxysulfonyl group, alkylsulfonyloxy group and aryl An oxysulfonyl group is preferred, and a halogen atom, cyano, alkyl group, alkoxy group, aryl group, aryloxy group, acyl group, carbonamido group, sulfonamido group and ureido group are more preferred. More preferably a halogen atom, cyano, alkyl group, alkoxy group, aryloxy group, acyl group and carbonamido group, still more preferably a halogen atom, cyano, alkyl group, alkoxy group and aryloxy group, halogen atom, alkyl group Most preferred are groups and alkoxy groups.
[0065]
The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. The alkyl group may have a cyclic structure or a branch. The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 12, further preferably 1 to 6, and most preferably 1 to 4. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl. The alkoxy group may have a cyclic structure or a branch. The number of carbon atoms in the alkoxy group is preferably 1-20, more preferably 1-12, still more preferably 1-6, and most preferably 1-4. The alkoxy group may be further substituted with another alkoxy group. Examples of the alkoxy group include methoxy, ethoxy, 2-methoxyethoxy, 2-methoxy-2-ethoxyethoxy, butyloxy, hexyloxy and octyloxy.
[0066]
The aryl group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. Examples of the aryl group include phenyl and naphthyl. The aryloxy group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. Examples of the aryloxy group include phenoxy and naphthoxy. The acyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of acyl groups include formyl, acetyl and benzoyl. The carbonamide group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of the carbonamido group include acetamide and benzamide. The number of carbon atoms of the sulfonamide group is preferably 1-20, and more preferably 1-12. Examples of the sulfonamide group include methanesulfonamide, benzenesulfonamide and p-toluenesulfonamide. The ureido group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of ureido groups include (unsubstituted) ureido.
[0067]
The number of carbon atoms in the aralkyl group is preferably 7-20, and more preferably 7-12. Examples of aralkyl groups include benzyl, phenethyl and naphthylmethyl. The alkoxycarbonyl group preferably has 1 to 20 carbon atoms, more preferably 2 to 12 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl. The aryloxycarbonyl group preferably has 7 to 20 carbon atoms, and more preferably 7 to 12 carbon atoms. Examples of the aryloxycarbonyl group include phenoxycarbonyl. The aralkyloxycarbonyl group preferably has 8 to 20 carbon atoms, and more preferably 8 to 12 carbon atoms. Examples of the aralkyloxycarbonyl group include benzyloxycarbonyl. The carbamoyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of the carbamoyl group include (unsubstituted) carbamoyl and N-methylcarbamoyl. The sulfamoyl group preferably has 20 or less carbon atoms, more preferably 12 or less. Examples of sulfamoyl groups include (unsubstituted) sulfamoyl and N-methylsulfamoyl. The acyloxy group preferably has 1 to 20 carbon atoms, more preferably 2 to 12 carbon atoms. Examples of the acyloxy group include acetoxy and benzoyloxy.
[0068]
The alkenyl group has preferably 2 to 20 carbon atoms, and more preferably 2 to 12 carbon atoms. Examples of alkenyl groups include vinyl, allyl and isopropenyl. The alkynyl group preferably has 2 to 20 carbon atoms, and more preferably 2 to 12 carbon atoms. Examples of alkynyl groups include ethynyl. The alkylsulfonyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. The arylsulfonyl group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. The alkyloxysulfonyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. The aryloxysulfonyl group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. The alkylsulfonyloxy group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. The aryloxysulfonyl group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms.
[0069]
Among the three hydroxyl groups of the glucose unit constituting cellulose, the average number of hydroxyl groups ester-bonded to the aromatic carboxylic acid (acyl group substitution degree) is 1.0 to 3.0. Preferably, it is 2.0-3.0. A mixed carboxylic acid ester of cellulose may be formed using two or more kinds of aromatic carboxylic acids. A mixed ester of an aromatic carboxylic acid and an aliphatic carboxylic acid (eg, acetic acid, propionic acid, butyric acid) may be formed. However, also when forming mixed ester with aliphatic carboxylic acid, it is preferable that the substitution degree of aromatic carboxylic acid is 1.0-3.0 like said definition, and 2.0-3. More preferably, it is 0.
[0070]
Cellulose acylate can be produced by reacting cellulose with an aromatic carboxylic acid chloride or an aromatic carboxylic acid anhydride. It is preferable to produce by reacting cellulose with an aromatic carboxylic acid anhydride. The aromatic carboxylic acid anhydride is particularly preferably a mixed acid anhydride of an aromatic carboxylic acid and a halogenated carboxylic acid (eg, trifluoroacetic acid). The mixed acid anhydride can be synthesized by a reaction between an aromatic carboxylic acid and a halogenated carboxylic acid anhydride. About reaction of a cellulose and an aromatic carboxylic acid anhydride (or mixed acid anhydride), various literature (For example, Journal of Applied Polymer Science, Vol. 29, 3981-3990 (1984)) has description. Cellulose as a raw material for cellulose acylate is generally cotton linter or wood pulp. Cotton linter and wood pulp may be mixed and used. In the synthesis reaction of cellulose acylate, a halogenated hydrocarbon (eg, dichloromethane) is preferably used as a reaction solvent. The cellulose acylate preferably has a viscosity average degree of polymerization of 150 to 700, and more preferably 250 to 550. The viscosity average degree of polymerization can be measured with an Ostwald viscometer.
[0071]
A specific synthesis method is described in detail in JP-A No. 2002-241512.
[0072]
The organic solvent of the present invention is not limited as long as it is suitable for a solution casting film forming method such as excellent polymer solubility and low drying load. For example, as a chlorinated organic solvent, methylene chloride (boiling point 39 .8 ° C.). Non-chlorine organic solvents include methyl acetate (boiling point 56.9 ° C), ethyl acetate (boiling point 77.1 ° C), acetone (boiling point 56.1 ° C), tetrahydrofuran (boiling point 66 ° C), 1,3-dioxolane ( Boiling point 74 ° C), 1,4-dioxane (boiling point 101.1 ° C), cyclohexanone (boiling point 155.6 ° C), ethyl formate (boiling point 53 ° C), 2,2,2-trifluoroethanol (boiling point 73.6 ° C) ), 2,2,3,3-tetrafluoro-1-propanol (boiling point 109 ° C.), 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol (boiling point 60 ° C.), Examples thereof include 1,1,1,3,3,3-hexafluoro-2-propanol (boiling point 58 ° C.), nitroethane (boiling point 101.2 ° C.), and the like. When the polymer is a cellulose ester, methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used. In particular, it is preferable to contain 50% by mass or more of methyl acetate in an organic solvent because the strength of the web peeled from the support is increased and the breaking frequency during stretching can be reduced.
[0073]
The polymer solution according to the present invention preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent. After casting the dope on the casting support, the solvent begins to evaporate and the alcohol ratio increases and the web (casting film) gels, making the web strong and preventing breakage when stretching with a tenter. In addition to being effective, the retardation increasing agent in the web can be prevented from freely moving in the web, and this is effective in suppressing retardation and unevenness of the slow axis angle. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is most preferable because of stability of the dope, relatively low boiling point, good drying property, and no toxicity.
[0074]
The polymer concentration in the dope is preferably adjusted in the range of 15 to 35% by mass and the dope viscosity in the range of 10 to 70 Pa · s for obtaining good film surface quality.
[0075]
By blending a plasticizer with the dope of the present invention, the brittleness of the film is improved and the toughness is improved, which is effective and preferable for preventing breakage when stretched with a tenter. As a plasticizer, it can select suitably from the compound compatible with a conventionally well-known polymer. In particular, when the polymer is a cellulose ester, a phosphate ester or a carboxylic acid ester is preferably used. Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like. Examples of carboxylic acid esters include phthalic acid esters and citric acid esters; phthalic acid esters such as dimethyl phthalate, diethyl phosphate, dioctyl phthalate and diethyl hexyl phthalate; and citrate esters such as acetyl triethyl citrate and acetyl citrate. Mention may be made of tributyl. Other examples include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and triacetin. Alkylphthalylalkyl glycolates are also preferably used for this purpose. The alkyl in the alkylphthalylalkyl glycolate is an alkyl group having 1 to 8 carbon atoms. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl glycolate, Ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl Phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl Collate, octyl phthalyl methyl glycolate, octyl phthalyl ethyl glycolate and the like can be mentioned, such as methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, Octyl phthalyl octyl glycolate is preferable, and ethyl phthalyl ethyl glycolate is particularly preferably used. These alkyl phthalyl alkyl glycolates may be used in combination of two or more.
[0076]
The addition amount of these compounds is preferably 1 to 30% by mass with respect to the polymer from the viewpoints of achieving the desired effect and suppressing bleeding out from the film.
[0077]
The retardation film of the present invention preferably contains a retardation increasing agent in order to adjust the retardation.
[0078]
The retardation increasing agent is preferably contained in an amount of 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and more preferably 0.2 to 5% by mass with respect to the polymer. It is more preferable to use, and it is most preferable to use in the range of 0.5 to 2% by mass. Two or more types of retardation increasing agents may be used in combination. The retardation increasing agent preferably has a maximum absorption in a wavelength region of 250 to 400 nm. It is preferable that the retardation increasing agent has substantially no absorption in the visible region.
[0079]
Further, it is preferable to use a compound having at least two aromatic rings as the retardation increasing agent. In the present specification, the “aromatic ring” includes an aromatic heterocycle in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable.
[0080]
The number of aromatic rings contained in the retardation increasing agent is preferably 2 to 20, more preferably 2 to 12, further preferably 2 to 8, and most preferably 2 to 6. The bonding relationship between two aromatic rings can be classified into (a) when forming a condensed ring, (b) when directly connecting with a single bond, and (c) when connecting via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).
[0081]
Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiantole Ring is included. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.
[0082]
The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded by two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.
[0083]
The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
[0084]
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-
The aromatic ring and the linking group may have a substituent. Examples of the substituent include halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic Substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups are included.
[0085]
It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl. The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of alkenyl groups include vinyl, allyl and 1-hexenyl. The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.
[0086]
The aliphatic acyl group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl. The number of carbon atoms in the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include acetoxy. The number of carbon atoms of the alkoxy group is preferably 1-8. The alkoxy group may further have a substituent (eg, alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy. The number of carbon atoms of the alkoxycarbonyl group is preferably 2-10. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl. The number of carbon atoms of the alkoxycarbonylamino group is preferably 2-10. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.
[0087]
These compounds may be added together with the polymer or solvent during the preparation of the solution, or may be added during or after the preparation of the solution.
[0088]
In the present invention, the dope is cast on a casting support to form a web, the temperature at the peeling position on the support is 10 to 40 ° C., preferably 15 to 30 ° C., and the residual solvent of the web at the peeling position It is preferable to peel the web when the amount is 30 to 120% by mass. In order to keep the residual solvent amount at the time of peeling of the web within this range, the surface temperature of the casting support after casting is controlled so that the organic solvent can be efficiently evaporated from the web. Can be preferably used. In order to control the support temperature, it is preferable to use a heat transfer method with good heat transfer efficiency. For example, a back surface heat transfer method using a liquid is preferable. In the belt (supporting body) machine, the belt temperature can be adjusted with a gentle wind to control the temperature at which the belt to be transferred comes to the lower side. The temperature of the support can be partially changed by dividing the heating means, and can be set to different temperatures such as a casting position, a drying part, and a peeling position of the casting support.
[0089]
The method for producing a retardation film of the present invention is characterized in that the film is stretched as described above during the solution casting film peeling step to the drying step or during the drying step.
[0090]
The grip portions at both ends of the web are usually cut out and reused as raw materials because the film is deformed and cannot be used as a product. A narrower width is preferable because the yield is improved. Usually, it is the range of 10-100 mm, More preferably, it is the range of 10-50 mm.
[0091]
In the retardation film obtained as described above, the slow axis direction of the film (the maximum direction of the refractive index in the film plane) is preferably 20 to 70 degrees with respect to the winding direction. It is preferably in the range of 40 to 50 degrees, and most preferably 45 degrees ± 0.5 degrees.
[0092]
In the case where the polymer film of the present invention is a retardation film used in a liquid crystal display device using a VA mode, TN mode or the like liquid crystal cell, the in-plane retardation is in the range of 20 to 70 nm and the thickness direction retardation is in the range of 70 to 400 nm. This is preferable because a viewing angle expansion effect can be obtained. The variation in retardation is preferably within ± 5 nm, and more preferably within ± 3 nm.
[0093]
When the retardation film of the present invention is used as a quarter-wave plate or a half-wave plate, the in-plane retardation is 100 to 350 nm, the refractive index in the slow axis direction in the film plane is nx, The value of (nx−nz) / (nx−ny) is preferably in the range of 1 to 2, where ny is the refractive index in the direction perpendicular to the slow axis and nz is the refractive index in the thickness direction.
[0094]
The retardation film of the present invention can be made into a polarizing plate by bonding to at least one side of a polarizing film.
[0095]
A conventionally known polarizing film can be used. For example, a hydrophilic polymer film such as a polyvinyl alcohol film is treated with a dichroic dye such as iodine and stretched. Since the polarizing film itself is not sufficiently durable, a cellulose triacetate film is generally adhered to both sides as a protective film.
[0096]
In order to form a polarizing plate, it may be bonded to the polarizing film with the protective film, or may be directly bonded to the polarizing film also serving as the protective film. The method of bonding is not particularly limited, but can be performed with an adhesive composed of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution.
[0097]
The retardation film of the present invention can be further provided with an optically anisotropic layer formed from a liquid crystalline compound. The optically anisotropic layer can be obtained by coating a disk-like or rod-like liquid crystal compound solution on the alignment film.
[0098]
The polarizing plate thus obtained is effectively used for a liquid crystal display device.
The liquid crystal display device includes a liquid crystal cell and two polarizing plates arranged on both sides of the liquid crystal cell, and the liquid crystal cell carries a liquid crystal between two electrode substrates. The polarizing plate according to the present invention is arranged so that the retardation film of the present invention is placed on one side of the liquid crystal cell on the side of the liquid crystal cell, or similarly disposed on both sides of the liquid crystal cell, thereby obtaining a viewing angle expansion effect. It is done.
[0099]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this.
[0100]
Each measurement and evaluation in an Example was performed with the following method.
(Retardation Ro value in the in-plane direction of the film, retardation Rt value in the thickness direction, and angle θ of the slow axis)
Samples for 10-point measurement were cut out at equal intervals in the width direction of the film, and the retardation Ro value in the in-plane direction, the retardation Rt value in the thickness direction, and the angle θ of the slow axis were determined by the following methods.
[0101]
Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), a three-dimensional refractive index measurement is performed at a wavelength of 590 nm under an atmosphere of 23 ° C. and 55% RH. The angle formed and the refractive index nx in the slow axis direction, the refractive index ny in the slow axis direction, and the refractive index nz in the thickness direction are obtained. The Ro value and Rt value were calculated from the following formulas. In addition, the value of the average refractive index required for calculating the refractive index was obtained by measuring the refractive index in the vertical, horizontal, and thickness directions of the film sample using an Abbe refractometer, and using the average value. In the formula, d is the thickness (nm) of the film.
[0102]
Rt = ((nx + ny) / 2−nz) × d
Ro = (nx−ny) × d
(Transparency of film)
The transparency of the film was evaluated by the haze of the film. Samples for measurement were cut out at equal intervals of 10 points in the width direction of the film and measured according to JIS K7105-1981.
[0103]
Example 1
Cellulose triacetate 89 parts by mass
7.39 parts by mass of triphenyl phosphate
Biphenyl diphenyl phosphate 3.60 parts by mass
Silica 0.01 parts by mass
267 parts by mass of methylene chloride
26 parts by mass of ethanol
The above was put into a pressure sealed container and dissolved while stirring to prepare a dope. The dope was cast on a support, and was peeled from the support when the residual solvent in the web reached 80% by mass. This film was dried while being rolled until the residual solvent amount was 35% by mass, then introduced into the tenter of FIG. 1, and stretched 1.4 times in an atmosphere of 100 ° C. and 90% solvent vapor concentration. Then, after shrinking to 1.2 times, keeping the width constant, and drying in an atmosphere of 120 ° C. and a solvent vapor concentration of 2 mass%, the web was released from the gripper. The difference in transport speed between the left and right tenter grippers was less than 0.05%. Here, | L1-L2 | is 1.1 m, W is 1.1 m, and | L1-L2 | = W. No wrinkles or the like were observed at the tenter outlet, and the amount of residual solvent in the web at the tenter outlet was 10% by mass. Furthermore, it was made to dry at 115 degreeC, making it roll convey, the holding part of both ends was slit, and the film with a film thickness of 80 micrometers was obtained. The amount of residual solvent in the finally obtained film was 0.2% by mass. The in-plane retardation Ro of the obtained film, the retardation Rt in the thickness direction, and the angle and haze formed by the slow axis and the longitudinal direction of the film were measured. The results are shown in Tables 1 and 2.
[0104]
Comparative Example 1
Cellulose triacetate 89 parts by mass
7.39 parts by mass of triphenyl phosphate
Biphenyl diphenyl phosphate 3.60 parts by mass
Silica 0.01 parts by mass
267 parts by mass of methylene chloride
26 parts by mass of ethanol
The above was put into a pressure sealed container and dissolved while stirring to prepare a dope. The dope was cast on a support, and was peeled from the support when the residual solvent in the web reached 80% by mass. The film was dried while being conveyed until the residual solvent amount became 35% by mass, then introduced into the tenter of FIG. 1 and stretched 1.4 times in an atmosphere of 100 ° C. and a solvent vapor concentration of 20%. Then, after shrinking to 1.2 times, keeping the width constant, and drying in an atmosphere of 120 ° C. and a solvent vapor concentration of 5%, the web was released from the gripper. The difference in transport speed between the left and right tenter grippers was less than 0.05%. Here, | L1-L2 | is 1.1 m, W is 1.1 m, and | L1-L2 | = W. Wrinkles and the like at the tenter outlet were not observed, and the amount of residual solvent in the web at the tenter outlet was 8% by mass. Furthermore, it was made to dry at 110 degreeC, making it roll convey, and the holding part of both ends was slit, and the film with a film thickness of 80 micrometers was obtained. The amount of residual solvent in the finally obtained film was 0.2% by mass. The in-plane retardation Ro of the obtained film, the retardation Rt in the thickness direction, and the angle and haze formed by the slow axis and the longitudinal direction of the film were measured. The results are shown in Tables 1 and 2.
[0105]
Example 2
Cellulose triacetate 83.4 parts by mass
6.67 parts by mass of triphenyl phosphate
Biphenyl diphenyl phosphate 3.33 parts by mass
Silica 0.01 parts by mass
The following retardation increasing agent 6.59 parts by mass
267 parts by mass of methylene chloride
26 parts by mass of ethanol
The above was put into a pressure sealed container and dissolved while stirring to prepare a dope. The dope was cast on a support, and was peeled from the support when the residual solvent in the web reached 80% by mass. The film was dried while being conveyed until the residual solvent amount became 35% by mass, then introduced into the tenter of FIG. 1 and stretched 1.4 times in an atmosphere of 100 ° C. and a solvent vapor concentration of 50%. Then, after shrinking to 1.2 times, keeping the width constant, and drying in an atmosphere of 120 ° C. and a solvent vapor concentration of 2%, the web was released from the gripper. The difference in transport speed between the left and right tenter grippers was less than 0.05%. Here, | L1-L2 | is 1.1 m, W is 1.1 m, and | L1-L2 | = W. No wrinkles or the like were observed at the tenter outlet, and the amount of residual solvent in the web at the tenter outlet was 10% by mass. Further, the film was dried at 115 ° C. while being conveyed by rolls, and the gripping portions at both ends were slit to obtain a 40 μm film. The amount of residual solvent in the finally obtained film was 0.2% by mass. The in-plane retardation Ro of the obtained film, the retardation Rt in the thickness direction, and the angle and haze formed by the slow axis and the longitudinal direction of the film were measured. The results are shown in Tables 1 and 2.
[0106]
[Chemical formula 2]

[0107]
Example 3
ARTON (manufactured by JSR) 77 parts by mass
21 parts by mass of methylene chloride
2 parts by mass of ethanol
The above was put into a pressure sealed container and dissolved while stirring to prepare a dope. This dope was cast on a support, and was peeled from the support when the residual solvent in the web reached 30% by mass. This film is dried while being conveyed until the residual solvent amount becomes 15% by mass, and then introduced into the tenter of FIG. 1 and stretched 1.4 times in an atmosphere at 150 ° C. and a solvent vapor concentration of 50%. After shrinking to 1.2 times, keeping the width constant, and drying in an atmosphere of 140 ° C. and a solvent vapor concentration of 2%, the web was released from the gripper. The difference in transport speed between the left and right tenter grippers was less than 0.05%. Here, | L1-L2 | is 1.1 m, W is 1.1 m, and | L1-L2 | = W. Wrinkles and the like at the tenter outlet were not observed, and the amount of residual solvent in the web at the tenter outlet was 5% by mass. Furthermore, it was made to dry at 115 degreeC, making it roll convey, the holding part of both ends was slit, and the film with a film thickness of 80 micrometers was obtained. The amount of residual solvent in the finally obtained film was 0.2% by mass. The in-plane retardation Ro of the obtained film, the retardation Rt in the thickness direction, and the angle and haze formed by the slow axis and the longitudinal direction of the film were measured. The results are shown in Tables 1 and 2.
[0108]
Example 4
77 parts by mass of polycarbonate composed of bisphenol A (number average molecular weight in terms of polystyrene is about 70,000)
23 parts by mass of methylene chloride
The above was put into a pressure sealed container and dissolved while stirring to prepare a dope. This dope was cast on a support, and was peeled from the support when the residual solvent in the web reached 30% by mass. This film was dried while being conveyed until the residual solvent amount reached 10% by mass, then introduced into the tenter of FIG. 1, and stretched 2.5 times under an atmosphere of 120 ° C. and a solvent vapor concentration of 50%. After shrinking to 2.0 times, the width was kept constant thereafter, drying was performed in an atmosphere at 130 ° C. and a solvent vapor concentration of 2%, and then the web was released from the gripping tool. The difference in transport speed between the left and right tenter grippers was less than 0.05%. Here, | L1-L2 | was 1.83 m, W was 1.83 m, and the relationship was | L1-L2 | = W. Wrinkles and the like at the tenter outlet were not observed, and the amount of residual solvent in the web at the tenter outlet was 5% by mass. Furthermore, it was made to dry at 115 degreeC, making it roll convey, the holding part of both ends was slit, and the film with a film thickness of 40 micrometers was obtained. The amount of residual solvent in the finally obtained film was 0.1% by mass. The in-plane retardation Ro of the obtained film, the retardation Rt in the thickness direction, and the angle and haze formed by the slow axis and the longitudinal direction of the film were measured. The results are shown in Tables 1 and 2.
[0109]
Example 5
12.5 parts by mass of p-chlorobenzoic acid and 16.8 parts by mass of trifluoroacetic anhydride were placed in a container and mixed with stirring at 50 ° C. for 30 minutes. Next, 4.1 parts by mass of cellulose and 106 parts by mass of methylene chloride were added and heated to reflux for 5 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and 500 parts by mass of methanol was gradually added while stirring to precipitate the reaction product. The obtained solid content was separated by filtration and dried to obtain a chlorobenzoic acid ester of cellulose having a substitution degree of 2.9 and a viscosity average polymerization degree of 300.
[0110]
83.4 parts by mass of chlorobenzoic acid ester of cellulose
6.67 parts by mass of triphenyl phosphate
Biphenyl diphenyl phosphate 3.33 parts by mass
Silica 0.01 parts by mass
6. Retardation increasing agent 6.59 parts by mass
267 parts by mass of methylene chloride
26 parts by mass of ethanol
The above was put into a pressure sealed container and dissolved while stirring to prepare a dope. This dope was cast on a support, and was peeled from the support when the residual solvent in the web reached 60% by mass. The film is dried while being conveyed until the residual solvent amount reaches 30% by mass, and then introduced into the tenter of FIG. 1 and stretched 1.4 times in an atmosphere of 100 ° C. and a solvent vapor concentration of 50%. Then, after shrinking to 1.2 times, keeping the width constant, and drying in an atmosphere of 120 ° C. and a solvent vapor concentration of 2%, the web was released from the gripper. The difference in transport speed between the left and right tenter grippers was less than 0.05%. Here, | L1-L2 | is 1.1 m, W is 1.1 m, and | L1-L2 | = W. Wrinkles and the like at the tenter outlet were not observed, and the amount of residual solvent in the web at the tenter outlet was 8% by mass. Furthermore, it was made to dry at 115 degreeC, making it roll convey, and the holding part of both ends was slit, and the film of 60 micrometers was obtained. The amount of residual solvent in the finally obtained film was 0.2% by mass. The in-plane retardation Ro of the obtained film, the retardation Rt in the thickness direction, and the angle and haze formed by the slow axis and the longitudinal direction of the film were measured. The results are shown in Tables 1 and 2.
[0111]
[Table 1]

[0112]
[Table 2]

[0113]
【The invention's effect】
According to the present invention, it is possible to provide a method for producing a retardation film having a high yield in the retardation film punching step, uniform retardation characteristics, and good transparency. Thereby, an excellent display quality liquid crystal display device is provided at low cost.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing an example of a stretching apparatus of the present invention.
FIG. 2 is an explanatory view showing an example of a method for adjusting the solvent concentration in the atmosphere of the stretching step used in the present invention.
[Explanation of symbols]
11 Web introduction direction
12 Web transport direction to the next process
13 Web introduction process
14 Stretching web
15 Step to send stretched web to next step
A1, B1 Grasping start point
Bx, Ay Grasp release point
Ay-Ax Stroke difference between left and right web gripping means
W Distance between two release points
16 Trajectory of web gripping means
17 Trajectory of web gripping means
21 Web
22 Oven
23 Buffer zone
24 nozzles
25 Fan
26 Heating heater
27 Filter
28 Dehumidifier
29 Exhaust fan
30 Condenser
31 Inert gas supply device
32-36 damper

Claims (7)

After peeling a web prepared by casting a dope containing a polymer and an organic solvent on a support from the support, while holding both ends of the web with a gripping tool, the advancing direction and slow axis direction of the web Is stretched so as to be inclined by 20 to 70 degrees, the gripping means trajectory L1 from the substantial gripping start point to the substantial gripping release point at one end of the web and the substantial other end of the web The trajectory L2 of the gripping means from the grip start point to the substantial grip release point and the distance W between the two substantial grip release points satisfy the following formula (1), and the residual solvent amount in the web is 5 In the method for producing a retardation film in which the amount of the residual solvent is reduced while being contracted after being stretched in the presence of a mass% or more state, between the substantial grip start point of the web and the substantial grip release point. In the atmosphere of the web. Method for producing a retardation film density is characterized in that it comprises a step of at least 50% of the saturated vapor concentration.
Formula (1) 0.9W <| L2-L1 | <1.1W 2. The method for producing a retardation film according to claim 1, wherein a difference in traveling speed in the longitudinal direction of the gripping means at both ends of the web is less than 1%. The method for producing a retardation film according to claim 1, wherein the polymer is a cellulose ester or a norbornene-based polymer. The method for producing a retardation film according to claim 3, wherein the polymer is a cellulose ester. The method for producing a retardation film according to claim 4, wherein the cellulose ester is a cellulose acylate composed of an ester of cellulose and a carboxylic acid, and the carboxylic acid is an aromatic carboxylic acid. The method for producing a retardation film according to claim 4, wherein the acyl group of the cellulose ester is an acyl group having 2 to 4 carbon atoms, and the substitution degree is 2.6 to 2.9. The method for producing a retardation film according to claim 4, wherein the cellulose ester contains 0.1 to 10% by mass of a retardation increasing agent.

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