JP4335562B2 - λ / 4 plate - Google Patents

Description

【００３９】
前記式（Ｉ）中、Ｌ¹およびＬ⁴はそれぞれ独立に二価の連結基である。Ｌ¹およびＬ⁴はそれぞれ独立に、−Ｏ−、−Ｓ−、−ＣＯ−、−ＮＲ²−、二価の鎖状基、二価の環状基およびそれらの組み合わせからなる群より選ばれる二価の連結基であることが好ましい。上記Ｒ²は炭素原子数が１〜７のアルキル基または水素原子である。
【００４０】
組み合わせからなる二価の連結基の例を以下に示す。ここで、左側がＱ（Ｑ¹またはＱ²）に、右側がＣｙ（Ｃｙ¹またはＣｙ³）に結合する。
Ｌ−１：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−
Ｌ−２：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−
Ｌ−３：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−Ｏ−
Ｌ−４：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−二価の環状基−
Ｌ−５：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−二価の環状基−ＣＯ−Ｏ−
Ｌ−６：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−二価の環状基−Ｏ−ＣＯ−
Ｌ−７：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−二価の環状基−二価の鎖状基−
Ｌ−８：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−二価の環状基−二価の鎖状基−ＣＯ−Ｏ−
Ｌ−９：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−二価の環状基−二価の鎖状基−Ｏ−ＣＯ−
【００４１】
Ｌ−１０：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−二価の環状基−
Ｌ−１１：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−二価の環状基−ＣＯ−Ｏ−
Ｌ−１２：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−二価の環状基−Ｏ−ＣＯ−
Ｌ−１３：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−二価の環状基−二価の鎖状基−
Ｌ−１４：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−二価の環状基−二価の鎖状基−ＣＯ−Ｏ−
Ｌ−１５：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−二価の環状基−二価の鎖状基−Ｏ−ＣＯ−
Ｌ−１６：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−Ｏ−二価の環状基−
Ｌ−１７：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−Ｏ−二価の環状基−ＣＯ−Ｏ−
Ｌ−１８：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−Ｏ−二価の環状基−Ｏ−ＣＯ−
Ｌ−１９：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−Ｏ−二価の環状基−二価の鎖状基−
Ｌ−２０：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−Ｏ−二価の環状基−二価の鎖状基−ＣＯ−Ｏ−
Ｌ−２１：−ＣＯ−Ｏ−二価の鎖状基−Ｏ−ＣＯ−Ｏ−二価の環状基−二価の鎖状基−Ｏ−ＣＯ−
【００４２】
前記式中、二価の鎖状基は、アルキレン基、置換アルキレン基、アルケニレン基、置換アルケニレン基、アルキニレン基または置換アルキニレン基を意味する。アルキレン基、置換アルキレン基、アルケニレン基、置換アルケニレン基が好ましく、アルキレン基およびアルケニレン基がさらに好ましい。
アルキレン基は、分岐を有していてもよい。アルキレン基の炭素数は１〜１２であることが好ましく、２〜１０であることがさらに好ましく、２〜８であることがもっとも好ましい。
置換アルキレン基のアルキレン部分は、上記アルキレン基と同様である。置換基の例としてはハロゲン原子が含まれる。
アルケニレン基は、分岐を有していてもよい。アルケニレン基の炭素数は２〜１２であることが好ましく、２〜１０であることがさらに好ましく、２〜８であることがもっとも好ましい。
置換アルキレン基のアルキレン部分は、上記アルキレン基と同様である。置換基の例としてはハロゲン原子が含まれる。
アルキニレン基は、分岐を有していてもよい。アルキニレン基の炭素数は２〜１２であることが好ましく、２〜１０であることがさらに好ましく、２〜８であることがもっとも好ましい。
置換アルキニレン基のアルキニレン部分は、上記アルキニレン基と同様である。置換基の例としてはハロゲン原子が含まれる。
二価の鎖状基の具体例としては、エチレン、トリメチレン、プロピレン、ブタメチレン、１−メチル−ブタメチレン、ペンタメチレン、ヘキサメチレン、オクタメチレン、２−ブテニレン、２−ブチニレンなどが挙げられる。
【００４３】
二価の環状基の定義および例は、後述するＣｙ¹、Ｃｙ²およびＣｙ³の定義および例と同様である。
Ｒ²は、炭素原子数１から４のアルキル基または水素原子であることが好ましく、メチル基、エチル基または水素原子であることがさらに好ましく、水素原子であることがもっとも好ましい。
【００４４】
Ｌ²またはＬ³はそれぞれ独立に単結合または二価の連結基である。Ｌ²およびＬ³はそれぞれ独立に、−Ｏ−、−Ｓ−、−ＣＯ−、−ＮＲ₂−、二価の鎖状基、二価の環状基およびそれらの組み合わせからなる群より選ばれる二価の連結基または単結合であることが好ましい。上記Ｒ²は炭素原子数が１〜７のアルキル基または水素原子であり、炭素原子数１から４のアルキル基または水素原子であることが好ましく、メチル基、エチル基または水素原子であることがさらに好ましく、水素原子であることがもっとも好ましい。二価の鎖状基、および二価の環状基についてはＬ¹およびＬ⁴の定義と同義である。
【００４５】
式（Ｉ）において、ｎは０、１または２である。ｎが２の場合、二つのＬ³は同じであっても異なっていてもよく、２つのＣｙ²も同じであっても異なっていてもよい。ｎは１または２であることが好ましく、１であることがさらに好ましい。
【００４６】
式（Ｉ）において、Ｃｙ¹、Ｃｙ²およびＣｙ³は、それぞれ独立に、二価の環状基である。
環状基に含まれる環は、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く、６員環であることが最も好ましい。環状基に含まれる環は、縮合環であってもよい。ただし、縮合環よりも単環であることがより好ましい。環状基に含まれる環は、芳香族環、脂肪族環、および複素環のいずれでもよい。芳香族環の例には、ベンゼン環およびナフタレン環が含まれる。脂肪族環の例には、シクロヘキサン環が含まれる。複素環の例には、ピリジン環およびピリミジン環が含まれる。ベンゼン環を有する環状基としては、１，４−フェニレンが好ましい。ナフタレン環を有する環状基としては、ナフタレン−１，５−ジイルおよびナフタレン−２，６−ジイルが好ましい。シクロヘキサン環を有する環状基としては１，４−シクロへキシレンであることが好ましい。ピリジン環を有する環状基としてはピリジン−２，５−ジイルが好ましい。ピリミジン環を有する環状基としては、ピリミジン−２，５−ジイルが好ましい。
【００４７】
環状基は、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、シアノ基、ニトロ基、炭素原子数が１〜５のアルキル基、炭素原子数が１〜５のハロゲン置換アルキル基、炭素原子数が１〜５のアルコキシ基、炭素原子数が１〜５のアルキルチオ基、炭素原子数が２〜６のアシルオキシ基、炭素原子数が２〜６のアルコキシカルボニル基、カルバモイル基、炭素原子数が２〜６のアルキル置換カルバモイル基および炭素原子数が２〜６のアシルアミノ基が含まれる。
【００４８】
以下に、式（Ｉ）で表される重合性基を有する液晶化合物の例を示す。本発明はこれらに限定されるものではない。
【００４９】
【化２】

【００５０】
【化３】

【００５１】
【化４】

【００５２】
【化５】

【００５３】
本発明の液晶性化合物として、円盤状液晶性化合物も好ましく用いることができる。円盤状液晶性化合物は、ポリマーフィルム面に対して実質的に垂直（５０〜９０度の範囲の平均傾斜角）に配向させることが好ましい。円盤状液晶性化合物は、様々な文献（Ｃ．Ｄｅｓｔｒａｄｅ ｅｔ ａｌ．，Ｍｏｌ．Ｃｒｙｓｒ．Ｌｉｑ．Ｃｒｙｓｔ．，ｖｏｌ．７１，ｐａｇｅ １１１（１９８１）；日本化学会編、季刊化学総説、Ｎｏ．２２、液晶の化学、第５章、第１０章第２節（１９９４）；Ｂ．Ｋｏｈｎｅ ｅｔ ａｌ．，Ａｎｇｅｗ．Ｃｈｅｍ．Ｓｏｃ．Ｃｈｅｍ．Ｃｏｍｍ．，ｐａｇｅ １７９４（１９８５）；Ｊ．Ｚｈａｎｇ ｅｔ ａｌ．，Ｊ．Ａｍ．Ｃｈｅｍ．Ｓｏｃ．，ｖｏｌ．１１６，ｐａｇｅ ２６５５（１９９４））に記載されている。円盤状液晶性化合物の重合については、特開平８−２７２８４号公報に記載がある。
【００５４】
円盤状液晶性化合物は、重合により固定可能なように、重合性基を有するのが好ましい。例えば、円盤状液晶性化合物の円盤状コアに、置換基として重合性基を結合させた構造が考えられるが、但し、円盤状コアに重合性基を直結させると、重合反応において配向状態を保つことが困難になる。そこで、円盤状コアと重合性基との間に連結基を有する構造が好ましい。即ち、重合性基を有する円盤状液晶性化合物は、下記式（III）で表わされる化合物が好ましい。
式（III）
Ｄ（−Ｌ−Ｐ）_n
式中、Ｄは円盤状コアであり、Ｌは二価の連結基であり、Ｐは重合性基であり、ｎは４〜１２の整数である。
【００５５】
前記式（III）中の円盤状コア（Ｄ）、二価の連結基（Ｌ）および重合性基（Ｐ）の好ましい具体例は、それぞれ、特開２００１−４８３７号公報に記載の（Ｄ１）〜（Ｄ１５）、（Ｌ１）〜（Ｌ２５）、（Ｐ１）〜（Ｐ１８）であり、同公報に記載の内容を好ましく用いることができる。
【００５６】
これらの液晶性化合物は、光学異方性層中では、実質的に均一に配向していることが好ましく、実質的に均一に配向している状態で固定されていることがさらに好ましく、重合反応により液晶性分子が固定されていることが最も好ましい。
重合性基を有する棒状液晶性化合物の場合は、実質的に水平（ホモジニアス）配向に固定化することが好ましい。実質的に水平とは、棒状液晶性化合物の長軸方向と光学異方性層の面との平均角度（平均傾斜角）が０°〜４０°の範囲内であることを意味する。棒状液晶性化合物を斜め配向させてもよいし、傾斜角が徐々に変化するように（ハイビリッド配向）させてもよい。斜め配向またはハイブリッド配向の場合でも、平均傾斜角は０°〜４０°であることが好ましい。
重合性基を有する円盤状液晶性化合物の場合は、実質的に垂直配向させることが好ましい。実質的に垂直とは、円盤状液晶性化合物の円盤面と光学異方性層の面との平均角度（平均傾斜角）が５０°〜９０°の範囲内であることを意味する。円盤状液晶性化合物を斜め配向させてもよいし、傾斜角が徐々に変化するように（ハイビリッド配向）させてもよい。斜め配向またはハイブリッド配向の場合でも、平均傾斜角は５０°〜９０°であることが好ましい。
【００５７】
前記態様のλ／４板は、２層以上の光学異方性層を有する。光学異方性層間に配向膜を形成してもよいし、光学異方性層を、その上に形成する光学異方性層の配向膜として機能させることもできる。光学異方性層を、その上に形成する光学異方性層の配向膜として機能させる場合は、液晶性化合物とともに、炭素原子数が９以下の炭化水素基を有する変性ポリビニルアルコールを含有する組成物を用いて光学異方性層を形成し、さらに引き続き、該光学異方性層の表面にラビングを行って、上層の光学異方異方性層を形成するのが好ましい。
【００５８】
液晶性化合物とともに用いる、前記炭素原子数が９以下の炭化水素基を有する変性ポリビニルアルコールについて説明する。
好ましい変性ポリビニルアルコールとしては、下記式（ＰＸ）で表されるものである。
（ＰＸ）−（ＶＡｌ）_x−（ＨｙＤ）_y−（ＶＡｃ）_z−
式中、ＶＡｌは、ビニルアルコールの繰り返し単位であり、ＨｙＤは炭素原子数が９以下の炭化水素基を有する繰り返し単位であり、ＶＡｃは酢酸ビニル繰り返し単位であり、ｘは２０〜９５質量％（好ましくは２５〜９０質量％）であり、ｙは２〜９８質量％（好ましくは１０〜８０質量％）であり、ｚは０〜３０質量％（好ましくは２〜２０質量％）である。
【００５９】
ＨｙＤに含まれる炭化水素基は、脂肪族基、芳香族基またはそれらの組み合わせである。脂肪族基は、環状、分岐状あるいは直鎖状のいずれでもよい。脂肪族基は、アルキル基（シクロアルキル基であってもよい）またはアルケニル基（シクロアルケニル基であってもよい）であることが好ましい。前記炭化水素基は置換基を有していてもよい。前記炭化水素基の炭素原子数は１〜９であり、１〜８が好ましい。ＨｙＤの好ましい例は、下記式（ＨｙＤ−Ｉ）および（ＨｙＤ−ＩＩ）で表される。
【００６０】
【化６】

【００６１】
式中、Ｌ¹は、−Ｏ−、−ＣＯ−、−ＳＯ₂−、−ＮＨ−、アルキレン基、アリーレン基およびそれらの組み合わせから選ばれる二価の連結基であり、Ｌ²は単結合、または−Ｏ−、−ＣＯ−、−ＳＯ₂−、−ＮＨ−、アルキレン基、アリーレン基およびそれらの組み合わせから選ばれる二価の連結基であり、Ｒ¹およびＲ²は、それぞれ炭素原子数が９以下の炭化水素基である。上記の組み合わせにより形成される二価の連結基の例を以下に示す。
【００６２】
Ｌ１：−Ｏ−ＣＯ−
Ｌ２：−Ｏ−ＣＯ−アルキレン基−Ｏ−
Ｌ３：−Ｏ−ＣＯ−アルキレン基−ＣＯ−ＮＨ−
Ｌ４：−Ｏ−ＣＯ−アルキレン基−ＮＨ−ＳＯ₂−アリーレン基−Ｏ−
Ｌ５：−アリーレン基−ＮＨ−ＣＯ−
Ｌ６：−アリーレン基−ＣＯ−Ｏ−
Ｌ７：−アリーレン基−ＣＯ−ＮＨ−
Ｌ８：−アリーレン基−Ｏ−
Ｌ９：−Ｏ−ＣＯ−ＮＨ−アリーレン基−ＮＨ−ＣＯ−
【００６３】
ＨｙＤの具体例を以下に示す。
【００６４】
【化７】

【００６５】
前記変性ポリビニルアルコールの重合度は、２００〜５０００であることが好ましく、３００〜３０００であることが好ましい。ポリマーの分子量は、９０００〜２０００００であることが好ましく、１３０００〜１３００００であることがさらに好ましい。二種類以上のポリマーを併用してもよい。
【００６６】
以下に好ましい変性ポリビニルアルコールの具体例を示すが、本発明はこれらに限定されるものではない。
ＰＸ−１：−（ＶＡｌ）₂₁−（ＨｙＤ−１３）₇₇−（ＶＡｃ）₂−
ＰＸ−２：−（ＶＡｌ）₁₄−（ＨｙＤ−１３）₈₄−（ＶＡｃ）₂−
ＰＸ−３：−（ＶＡｌ）₂₁−（ＨｙＤ−１６）₇₇−（ＶＡｃ）₂−
ＰＸ−４：−（ＶＡｌ）₃₄−（ＨｙＤ−１５）₆₄−（ＶＡｃ）₂−
ＰＸ−５：−（ＶＡｌ）₂₉−（ＨｙＤ−１２）₆₉−（ＶＡｃ）₂−
ＰＸ−６：−（ＶＡｌ）₄₆−（ＨｙＤ−１４）₅₂−（ＶＡｃ）₂−
ＰＸ−７：−（ＶＡｌ）₂₁−（ＨｙＤ−２）₇₇−（ＶＡｃ）₂−
ＰＸ−８：−（ＶＡｌ）₁₇−（ＨｙＤ−８）₈₅−（ＶＡｃ）₂−
ＰＸ−９：−（ＶＡｌ）₂₁−（ＨｙＤ−１３）₇₇−（ＶＡｃ）₂−
ＰＸ−10：−（ＶＡｌ）₄₆−（ＨｙＤ−９）₅₂−（ＶＡｃ）₂−
【００６７】
上記変性ポリビニルアルコールの添加量は、該制御剤の添加する液晶性化合物に対し０．０５質量％〜１０質量％添加することが好ましい。より好ましくは０．１質量〜５質量％である。
【００６８】
上記変性ポリビニルアルコールは縮合剤と併用してもよい。縮合剤としてはイソシアネート基またはホルミル基を末端に有する化合物が好ましい。以下に具体的な化合物を挙げるが、これらに限定されるものではない。
【００６９】
ポリ（１，４−ブタンジオール）、イソホロンジイソシアネートターミネーテッド
ポリ（１，４−ブタンジオール）、トリレン２，４−ジイソシアネートターミネーテッド
ポリ（エチレンアジペート）、トリレン２，４−ジイソシアネートターミネーテッド
ポリ（プロピレングリコール）、トリレン２，４−ジイソシアネートターミネーテッド、
１，６−ジイソシアナートヘキサン
１，８−ジイソシアナートオクタン
１，１２−ジイソシアナートドデカン
イソホロンジイソシアナート
グリオキザール
【００７０】
本発明において、光学異方性層は、前記液晶性化合物、所望により、前記変性ポリビニルアルコール、および下記の重合開始剤や他の添加剤を溶剤に溶解させた塗布液を、ラビング表面に塗布して形成するのが好ましい。塗布液の調製に使用する溶剤としては、有機溶剤が好ましく用いられる。有機溶剤の例には、アミド（例、Ｎ，Ｎ−ジメチルホルムアミド）、スルホキシド（例、ジメチルスルホキシド）、ヘテロ環化合物（例、ピリジン）、炭化水素（例、ベンゼン、ヘキサン）、アルキルハライド（例、クロロホルム、ジクロロメタン）、エステル（例、酢酸メチル、酢酸ブチル）、ケトン（例、アセトン、メチルエチルケトン）、エーテル（例、テトラヒドロフラン、１，２−ジメトキシエタン）が含まれる。アルキルハライドおよびケトンが好ましい。二種類以上の有機溶剤を併用してもよい。塗布液の塗布は、公知の方法（例、押し出しコーティング法、ダイレクトグラビアコーティング法、リバースグラビアコーティング法、ダイコーティング法）により実施できる。
【００７１】
［液晶性化合物の配向状態の固定化］
配向させた液晶性化合物は、配向状態を維持して固定することが好ましい。固定化は、液晶性化合物に導入した重合性基の重合反応により実施するのが好ましい。重合反応には、熱重合開始剤を用いる熱重合反応と光重合開始剤を用いる光重合反応とが含まれるが、光重合反応がより好ましい。光重合開始剤の例には、α−カルボニル化合物（米国特許２３６７６６１号明細書、同２３６７６７０号明細書の各明細書記載）、アシロインエーテル（米国特許２４４８８２８号明細書記載）、α−炭化水素置換芳香族アシロイン化合物（米国特許２７２２５１２号明細書記載）、多核キノン化合物（米国特許３０４６１２７号、同２９５１７５８号の各明細書記載）、トリアリールイミダゾールダイマーとｐ−アミノフェニルケトンとの組み合わせ（米国特許３５４９３６７号明細書記載）、アクリジンおよびフェナジン化合物（特開昭６０−１０５６６７号公報、米国特許４２３９８５０号明細書記載）およびオキサジアゾール化合物（米国特許４２１２９７０号明細書記載）が含まれる。
【００７２】
光重合開始剤の使用量は、塗布液の固形分の０．０１〜２０質量％であることが好ましく、０．５〜５質量％であることがさらに好ましい。液晶性化合物の重合のための光照射は、紫外線を用いることが好ましい。照射エネルギーは、２０ｍＪ／ｃｍ²〜５０Ｊ／ｃｍ²であることが好ましく、１００〜８００ｍＪ／ｃｍ²であることがさらに好ましい。光重合反応を促進するため、加熱条件下で光照射を実施してもよい。また、光照射する際の雰囲気中の酸素濃度を窒素置換等によって下げる事も反応促進に効果がある。光学異方性層の厚さは、０．１〜１０μｍであることが好ましく、０．５〜５μｍであることがさらに好ましい。
【００７３】
［λ／４板の光学的性質］
本発明のλ／４板を構成している光学異方性層は、特定の波長において、実質的にπまたはπ／２の位相差を達成していることが好ましい。特定波長（λ）において位相差πを達成するためには、特定波長（λ）において測定した偏光子のレターデーション値をλ／２に調整すればよく、特定波長（λ）において位相差π／２を達成するためには、特定波長（λ）において測定した偏光子のレターデーション値をλ／４に調整すればよい。ただし、可視領域のほぼ中間の波長である５５０ｎｍにおいて、一方が位相差πおよび他方がπ／２を達成していることが好ましい。例えば、２層の光学異方性層からなる態様では、一方の光学異方性層（第１光学異方性層）は、波長５５０ｎｍで測定したレターデーション値が２４０〜３００ｎｍが好ましく、２４０〜２９０ｎｍがより好ましく、２５０〜２８０ｎｍがさらに好ましく、もう一方の光学異方性層（第２光学異方性層）は、波長５５０ｎｍで測定したレターデーション値が８０〜１７０ｎｍが好ましく、１１０〜１４５ｎｍがより好ましく、１２０〜１４０ｎｍがさらに好ましい。前者が支持体に近い層で、後者が支持体に遠い方の層であるのが好ましい。
【００７４】
前記第１および第２の光学異方性層の厚さは、各々の層が所望のレターデーションを示す範囲で任意に決定することができる。例えば、同一の棒状液晶化合物を水平配向させて、前記第１および第２の光学異方性層を各々形成する場合は、位相差がπである光学異方性層の厚みを、位相差がπ／２の光学異方性の厚みの倍にするのが好ましい。それぞれの光学異方性層の厚みの好ましい範囲は、用いる液晶性化合物の種類によって異なるが、一般的には、０．１〜１０μｍであり、０．２〜０．８μｍがより好ましく、０．５〜５μｍがさらに好ましい。また、双方の光学異方性層において、液晶性化合物が支持体の面内に平行に配向した態様では、１層目の配向方向と２層目の配向方向が異なっているのが好ましい。［１５］ 前記光学異方性層の支持体に近い層の５５０ｎｍにおけるＲｅ値が２４０〜３００ｎｍであり、支持体に遠い方の層の５５０ｎｍにおけるＲｅ値が８０〜１７０ｎｍである［１３］または［１４］に記載のλ／４板。
【００７５】
本発明のλ／４板および該λ／４板と偏光板とから構成される広帯域λ／４板とは、具体的には、波長４５０ｎｍ、５５０ｎｍおよび６５０ｎｍで測定したレターデーション値／波長の値が、いずれも０．２〜０．３の範囲内であることを意味する。レターデーション値／波長の値は、０．２１〜０．２９の範囲内であることが好ましく、０．２２〜０．２８の範囲内であることがより好ましく、０．２３〜０．２７の範囲内であることがさらに好ましく、０．２３〜０．２６の範囲内であることが最も好ましい。
【００７６】
［円偏光板］
本発明のλ／４板は、反射型液晶表示装置において使用されるλ／４板、光ディスクの書き込み用のピックアップに使用されるλ／４板、あるいは反射防止膜として利用されるλ／４板として、特に有利に用いることができる。λ／４板は、一般に偏光膜と組み合わせた円偏光板として使用される。よって、λ／４板と偏光膜とを組み合わせた円偏光板として構成しておくと、容易に反射型液晶表示装置のような用途とする装置に組み込むことができる。偏光膜には、ヨウ素系偏光膜、二色性染料を用いる染料系偏光膜やポリエン系偏光膜がある。ヨウ素系偏光膜および染料系偏光膜は、一般にポリビニルアルコール系フィルムを用いて製造する。
【００７７】
本発明のλ／４板と組み合わせる偏光膜については、特に制限はなく、ヨウ素系偏光膜、二色性染料を用いる染料系偏光膜やポリエン系偏光膜を用いることができる。ヨウ素系偏光膜および染料系偏光膜は、一般にポリビニルアルコール系フィルムを用いて製造する。本発明のλ／４板の透明支持体の長手方向に対して、偏光膜の透過軸を４５°となるように積層するのが好ましい。長手方向に対して実質的に４５°方向に偏光の透過軸を有する偏光膜（以下４５°偏光膜と称する）を用いれば、積層の際の角度調整が不要になり、本発明の円偏光板を容易に作製できる。延伸フィルムからなる偏光膜の透過軸は、延伸方向と実質的に一致するので、フィルムを長手方向に対して４５°の方向に延伸処理することで、４５°偏光膜を作製することができる。このような実質的に４５°方向に偏光の透過軸を有する偏光膜（以下４５°偏光膜と称する）は、特開２００２−８６５５４号公報に記載の斜め延伸方法により作製することができ、第０００９欄〜第００４５欄の記載の条件、使用可能な装置の構成等を参考に作製することができる。
【００７８】
【実施例】
以下に実施例を挙げて本発明をさらに具体的に説明する。以下の実施例に示す材料、試薬、物質量とその割合、操作等は本発明の主旨から逸脱しない限り適宜変更することができる従って本発明の範囲は以下の具体例に制限されるものではない。
【００７９】
（セルロースアシレートのアシル基の種類および置換度）
ＡＳＴＭ Ｄ８１７に従って算出した。
（透明支持体のＲｅおよびＲｔｈ測定）
透明支持体の正面レターデーション（Ｒｅ）は自動複屈折計（ＫＯＢＲＡ−２１ＡＤＨ／ＰＲ：王子計測器（株）製）を用いて、サンプルフィルム表面に対し垂直方向から測定した。なお、特に記載の無い場合、サンプル２５℃６０％Ｒ．Ｈ．の環境で２時間保持した後、同様の環境において波長５４８．３ｎｍで測定したレターデーション値を意味する。
透明支持体の厚み方向のレターデーション（Ｒｔｈ）は自動複屈折計（ＫＯＢＲＡ−２１ＡＤＨ／ＰＲ：王子計測器（株）製）を用い、フィルム面に対し垂直方向、４０度、−４０度傾斜した方向から波長５４８．３ｎｍでレターデーションを測定し、求めた３つの値からＲｔｈを計算した。
【００８０】
（レターデーション値のばらつき）
レターデーションのばらつきはサンプルから任意の１０箇所を選択して測定した値から求めた。
（円偏光板に含まれるλ／４板の波長分散測定）
λ／４板の波長分散測定は自動複屈折計（ＫＯＢＲＡ−２１ＡＤＨ／ＰＲ：王子計測機器（株）製）を用いて測定した。円偏光板に加工したサンプルを２５℃６０％Ｒ．Ｈ．で１日放置した後、波長４７８ｎｍ、５４８ｎｍ、５８９ｎｍ、６３０ｎｍ、７４７ｎｍでＲｅを測定した。得られた５つの値をコーシーの式に最小二乗法を用いてフィッテイングし、得られたパラメータから４５０ｎｍ、５５０ｎｍ、６５０ｎｍの値を計算して求めた。
【００８１】
（セルロースアシレートフィルムの作製）
表１に記載の素材および条件で溶液（ドープ）を調製した。なお、溶解方法は「通常法」および「冷却溶解法」を用いた。通常法では、２５℃の環境下で溶剤を攪拌しながら、セルロースアシレートを徐々に添加した。さらに紫外線吸収剤等の添加物を加え、ドープを得た。「冷却溶解法」では２５℃の環境下で溶剤を攪拌しながら、セルロースアシレートを徐々に添加し、さらに添加剤を加えて２時間放置して膨潤させた。得られた膨潤混合物をゆっくり攪拌しながら、−８℃／分で−３０℃まで冷却し、その後攪拌を止めてさらに−７０℃まで冷却し、６時間放置した。その後、＋８℃／分で昇温し、ゲル化がある程度進んだところで攪拌を開始した。５０℃まで加温しドープを得た。
得られたドープを、絶対ろ過精度０．０１ｍｍの濾紙（東洋濾紙（株）製、＃６３）でろ過し、さらに絶対ろ過精度０．００２５ｍｍの濾紙（ポール社製、ＦＨ０２５）にてろ過した。
得られた濾過済みドープを公知の流延機（特許文献８）を用いて流延し、セルロースアシレートフィルムを得た。フィルムの膜厚はギーサー部のクリアランスで調整し所望のフィルムを得た。乾燥温度は１２０℃であり、得られたフィルムの残留溶剤量は０．２質量部以下であった。
得られたフィルムについて、ＲｅおよびＲｔｈの値を測定した結果を表２に示す。
【００８２】
【表１】

【００８３】
＊１）アシル基：Ｐｒ＝プロピオニル基を示す。
＊２）溶剤：ＭＡ＝酢酸メチル、ＭＣ＝メチレンクロリド、ＡＴ＝アセトン、ＭＯＬ＝メタノール、ＥＯＬ＝エタノール、ＢＯＬ＝ｎ−ブタノールを示す。
＊３）添加剤：ＴＰＰ＝トリフェニルホスフェート、ＢＤＰ＝ビフェニルジフェニルホスフェートを示す。
【００８４】
【表２】

【００８５】
（λ／４板の作製）
得られた透明支持体の両面をけん化処理した後、下記組成の配向膜塗布液を透明支持体の片面に塗布し、１００℃で乾燥させた。配向膜の膜厚は１μｍであった。次に光学異方性層の遅相軸の方向が透明支持体の長手方向に対して３０°の方向になるようにラビング処理を実施した。

【００８６】
変性ポリビニルアルコール
【化８】

【００８７】
配向膜の上に、下記の組成の塗布液をバーコーターを用いて連続的に塗布、乾燥、および加熱（配向熟成）し、さらに紫外線照射して厚さ２．１μｍの光学的異方性層を形成した。光学的異方性層は透明支持体の長手方向に対して３０°の方向に遅相軸を有していた。
光学異方性層（Ａ）用塗布液組成
棒状液晶性化合物（例示化合物Ｉ−２） ３８．１質量％
下記の増感剤Ａ ０．３８質量％
下記の光重合開始剤Ｂ １．１４質量％
例示化合物（ＰＸ−９） ０．１９質量％
グルタールアルデヒド ０．０４質量％
メチルエチルケトン ６０．１質量％
【００８８】
増感剤Ａ
【化９】

【００８９】
光重合開始剤Ｂ
【化１０】

【００９０】
上記で作製した光学的異方性層（Ａ）の遅相軸に対し−６０°であり、かつ光学異方性層（Ａ）の長手方向に対し−３０°になるように、光学異方性層（Ａ）塗布後にラビング処理を施した。
【００９１】
ラビング処理した光学的異方性層（Ａ）の上に、下記の組成の塗布液を、バーコーターを用いて塗布、乾燥、および加熱（配向熟成）し、さらに紫外線照射して厚さ１．０μｍの光学的異方性層（Ｂ）を形成し、λ／４板を作製した。
光学異方性層（Ｂ）用塗布液組成
棒状液晶性化合物（例示化合物Ｉ−２） ３８．４質量％
上記増感剤Ａ ０．３８質量％
上記光重合開始剤Ｂ １．１５質量％
配向制御剤Ｃ ０．０６質量％
メチルエチルケトン ６０．０質量％
【００９２】
配向制御剤Ｃ
【化１１】

【００９３】
（偏光板の作製）
ＰＶＡフィルムをヨウ素２．０ｇ／Ｌ、ヨウ化カリウム４．０ｇ／Ｌの水溶液に２５℃にて２４０秒浸漬し、さらにホウ酸１０ｇ／Ｌの水溶液に２５℃にて６０秒浸漬後、特開２００２−８６５５４号公報の図１のごときテンター延伸機に導入し、５．３倍に延伸し、テンターを延伸方向に対し図１の如く屈曲させ、以降幅を一定に保ち、収縮させながら８０℃雰囲気で乾燥させた後テンターから離脱した。延伸開始前のＰＶＡフィルムの含水率は３１％で、乾燥後の含水率は１．５％であった。
左右のテンタークリップの搬送速度差は、０．０５％未満であり、導入されるフィルムの中心線と次工程に送られるフィルムの中心線のなす角は、４６゜であった。ここで｜Ｌ１−Ｌ２｜は０．７ｍ、Ｗは０．７ｍであり、｜Ｌ１−Ｌ２｜＝Ｗの関係にあった。テンター出口における実質延伸方向Ａｘ−Ｃｘは、次工程へ送られるフィルムの中心線２２に対し４５゜傾斜していた。テンター出口におけるシワ、フィルム変形は観察されなかった。
【００９４】
さらに、ＰＶＡ（（株）クラレ製ＰＶＡ−１１７Ｈ）３％水溶液を接着剤としてケン化処理した富士写真フイルム（株）製フジタック（セルローストリアセテート、レターデーション値３．０ｎｍ）と貼り合わせ、さらに８０℃で乾燥して有効幅６５０ｍｍの偏光板を得た。
得られた偏光板の吸収軸方向は、長手方向に対し４５゜傾斜していた。この偏光板の５５０ｎｍにおける透過率は４３．７％、偏光度は９９．９７％であった。次に、上記で作製したヨウ素系偏光フィルムの片面上に、上記で作製したλ／４板を積層し、もう一方の面上にケン化処理した防眩性反射防止フィルムを貼り合わせて、円偏光板を作製した。
円偏光板に貼り合わせたλ／４板の波長分散を測定し、Ｒｅ（λ）／λの値を求めた結果、
Ｒｅ（４５０）／４５０＝０．２６、
Ｒｅ（５５０）／５５０＝０．２７、
Ｒｅ（６５０）／６５０＝０．２５、
であり、可視領域の広い範囲で広帯域性を有していることが分かった。
【００９５】
（反射型液晶表示素子の作製）
市販の反射型液晶表示装置（カラーザウルス ＭＩ−３１０、シャープ（株）製）の偏光板とλ／４板を剥ぎとり、代わりに上記で作製したそれぞれを取り付けた。
作製した反射型液晶表示装置について、目視で評価したところ、実施例では白表示、黒表示、そして中間調のいずれにおいても、着色やムラがなく、ニュートラルグレーが表示されていることがわかった。一方、比較例では着色ムラがあった。
次に、測定機（ＥＺｃｏｎｔｒａｓｔ１６０Ｄ、Ｅｌｄｉｍ社製）を用いて反射輝度のコントラスト比を測定した。実施例では正面からのコントラスト比は１０であり、コントラスト比３の視野角は上下左右１２０°以上であり、実質的に十分な特性を示した。一方、比較例ではコントラスト比３の視野角が方向によっては８０°以下であり、視野角特性が不十分であった。
【００９６】
（環境試験）
上記で作製した反射型液晶表示素子を、−３０℃の冷凍庫、８０℃のドライボックス、４０℃９５％Ｒ．Ｈ．の温湿度可変装置、２５℃１０％Ｒ．Ｈ．および２５℃８０％Ｒ．Ｈ．の恒温恒湿室で１ヶ月保持した。目視で処理前の素子と比較した結果、比較例のλ／４板を用いた反射型液晶表示素子では着色の変化が起こっていたのに対して、実施例のλ／４板を用いた反射型液晶表示素子では変化が見られなかった。
【００９７】
【発明の効果】
本発明によれば、レターデーションと膜厚が所定の範囲にあるセルロースアシレートフィルムからなる透明支持体を用いることにより、反射型液晶表示素子や半透過型液晶表示素子、およびＥＬ素子などの表示素子に好適に用いることができるλ／４板を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a λ / 4 plate having a transparent support made of a cellulose acylate film, and particularly to a λ / 4 plate having the transparent support and two or more optically anisotropic layers made of a liquid crystalline compound. . The present invention also relates to a λ / 4 plate preferably used for a reflection type liquid crystal display element, a projection type projector, an optical pickup element, an antireflection film and a circularly polarizing plate.
[0002]
[Prior art]
The λ / 4 plate has a great many applications and has already been used for applications of a reflective liquid crystal display element and a transflective liquid crystal display element. It is known that the λ / 4 plate used for such a display element needs to have the function of the λ / 4 plate over the entire wavelength range of visible light. However, most of the conventional λ / 4 plates achieve λ / 4 retardation at a specific wavelength.
[0003]
As a technique for realizing λ / 4 retardation in a wide wavelength region, a method of laminating two polymer films having optical anisotropy (for example, Patent Documents 1 and 2), an optical anisotropy containing a liquid crystalline compound A method of laminating at least two layers (for example, Patent Documents 3 and 4), a method of stretching a polymer to which a copolymer or an additive has been added, and realizing a single polymer film (for example, Patent Documents 5 and 6). Are known. However, since the method of laminating two polymer films needs to adjust the direction of the optical axis, it is necessary to cut out the polymer film at a predetermined angle and bond them together. For this reason, there is a problem that the processing is complicated and the quality is likely to be deteriorated due to the axis deviation, the yield is reduced, and the cost is increased. In addition, the method realized with one copolymer film has a limitation in adjustment of wavelength dispersion, and there is a problem that coloring occurs when used in a liquid crystal display device and contrast is lowered.
On the other hand, the method of providing at least two optically anisotropic layers containing a liquid crystalline compound can easily provide a broadband λ / 4 plate with a thinner film thickness than the method of laminating two polymer films. There are advantages. However, each time a layer made of a liquid crystal compound is laminated, it is necessary to provide an alignment film layer that regulates the alignment of the liquid crystal compound, which causes a problem in manufacturing cost.
[0004]
In general, it is known that a polymer film used as a support for an optical film is preferably a polymer film having a high transmittance and a small in-plane retardation so that light transmission and polarization are not affected. .
However, even though the conventional transparent support has “small retardation in the film surface”, the range thereof is various and sometimes has a retardation of several tens of nm. There was also in-plane variation in phase difference. As for the retardation in the thickness direction, the preferable range is almost always described in a wide range of several hundred nm (for example, Patent Document 7), and the variation is not specified. Therefore, it has been found that when a conventional support is used for the λ / 4 plate, there is a problem that display unevenness, partial coloring, and a viewing angle are narrowed.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-68816
[Patent Document 2]
JP-A-10-90521
[Patent Document 3]
JP 2000-206331 A
[Patent Document 4]
Japanese Patent Laid-Open No. 2001-91741
[Patent Document 5]
WO00 / 26705
[Patent Document 6]
WO00 / 65384 Publication
[Patent Document 7]
JP 2001-129927 A
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a λ / 4 plate having excellent display quality. Another object of the present invention is to provide a λ / 4 plate that can be used for a circularly polarizing plate that contributes to improving the display quality of a liquid crystal display device.
[0007]
[Means for Solving the Problems]
The object of the present invention has been achieved by the following [1] to [19].
[1] A λ / 4 plate having a transparent support composed of a cellulose acylate film, and the cellulose acylate film satisfies the following conditions (A) to (D).
(A) Re value represented by following formula (1) is 0 nm or more and 20 nm or less
(B) Rth value represented by the following formula (2) is 0 nm or more and 100 nm or less
(C) Re and Rth values are within ± 3 nm of the average value
(D) Thickness is 40 μm or more and 100 μm or less
Expression (1) Re value = (nx−ny) × d
Formula (2) Rth value = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the plane of the transparent support, ny is the refractive index in the direction perpendicular to nx in the plane of the transparent support, and nz is the refractive index in the thickness direction of the transparent support) , D represents the thickness of the transparent support.)
[0008]
[2] The cellulose acylate film has an acyl substitution degree of 2.7 or more and 3.0 or less, an acetyl group substitution degree of 2.7 or more and 3 or less, and an acyl having 3 to 22 carbon atoms. [Lambda] / 4 board as described in [1] formed by casting film-forming the solution of the density | concentration of 20-30 mass% which melt | dissolved the cellulose acylate whose group substitution degree is 0-0.4.
[3] The λ / 4 plate according to [2], wherein the degree of acyl substitution at the 6-position of the cellulose acylate is 0.90 or more and 1.00 or less.
[4] Temperature is −30 ° C. to 80 ° C., relative humidity is 10% R.D. H. ~ 80% R.D. H. The λ / 4 plate according to any one of [1] to [3], wherein the Re value after being left in an environment of the range of 500 hours is within ± 10% of the Re value before processing.
[5] The λ / 4 plate according to any one of [1] to [4], having a transparent support composed of the cellulose acylate film and at least two optically anisotropic layers composed of a liquid crystalline compound on one side thereof. .
[0009]
[6] Any one of [1] to [5], wherein the support composed of the cellulose acylate film is formed by casting a solution obtained by dissolving cellulose acylate in a substantially non-chlorinated solvent. The λ / 4 plate as described.
[7] The λ according to any one of [1] to [6], wherein the support composed of the cellulose acylate film is a film formed by casting two or more layers simultaneously by a co-casting method. / 4 plate.
[8] The λ / 4 according to any one of [1] to [7], wherein the support composed of the cellulose acylate film is a cellulose acylate film having an acetyl substitution degree of 2.75 to 2.91. Board.
[9] The support according to any one of [1] to [8], wherein the support composed of the cellulose acylate film contains a plasticizer or an ultraviolet absorber in a range of 1 to 20 parts by mass with respect to the mass of the cellulose acylate. Λ / 4 plate.
[10] The support composed of the cellulose acylate film includes fine particles having an average particle diameter of 0.1 μm to 1 μm in a range of 0.005 to 0.2 parts by mass with respect to the mass of the cellulose acylate. The λ / 4 plate according to any one of [9].
[11] The cellulose acylate film according to any one of [1] to [10], wherein the cellulose acylate film has an Re value of 0 nm to 10 nm, an Rth value of 0 nm to 20 nm, and a thickness of 60 μm to 80 μm. Λ / 4 plate.
[0010]
[12] Temperature is −30 ° C. to 80 ° C., relative humidity is 10% R.D. H. ~ 80% R.D. H. The λ / 4 plate according to any one of [1] to [11], wherein the Re value after being left in an environment of the range of 500 hours is within ± 10% of the Re value before processing.
[13] A λ / 4 plate having at least two optically anisotropic layers made of a liquid crystal compound on one side thereof, and a transparent support made of the cellulose acylate film.
[14] λ / 4 according to [13], wherein the liquid crystalline compound of the optically anisotropic layer is aligned in parallel in the plane of the support, and the alignment direction of the first layer is different from the alignment direction of the second layer. Board.
[15] The Re value at 550 nm of the layer close to the support of the optically anisotropic layer is 240 to 300 nm, and the Re value at 550 nm of the layer far from the support is 80 to 170 nm [13] or [ 14].
[16] The λ / 4 plate according to any one of [13] to [15], wherein the liquid crystalline compound of at least one optically anisotropic layer is a photopolymerizable rod-like liquid crystal.
[0011]
[17] A circularly polarizing plate having the λ / 4 plate according to any one of [1] to [16] and a polarizing plate.
[18] A circularly polarizing plate in which a transparent protective film, a polarizer, and the λ / 4 plate according to any one of [1] to [16] are laminated in this order.
[19] A liquid crystal display layer device using the circularly polarizing plate according to [17] or [18].
[0012]
The Re value and Rth value of the present invention mean values at a wavelength of 548.3 nm unless otherwise specified.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[Transparent support]
The λ / 4 plate of the present invention has a transparent support made of a cellulose acylate film. The cellulose acylate film satisfies the following conditions (A) to (D).
(A) Re value represented by following formula (1) is 0 nm or more and 20 nm or less
(B) Rth value represented by the following formula (2) is 0 nm or more and 100 nm or less
(C) Re and Rth values are within ± 3 nm of the average value
(D) Thickness is 40 μm or more and 100 μm or less
Expression (1) Re value = (nx−ny) × d
Formula (2) Rth value = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the plane of the transparent support, ny is the refractive index in the direction perpendicular to nx in the plane of the transparent support, and nz is the refractive index in the thickness direction of the transparent support) , D represents the thickness of the transparent support.)
[0014]
The Re value of the cellulose acylate film is preferably 0 nm or more and 10 nm or less. The Rth value is preferably 0 nm or more and 50 nm or less, and more preferably 0 nm or more and 20 nm or less. Moreover, it is preferable that the thickness of the said cellulose acylate film is 60 micrometers or more and 80 micrometers or less.
[0015]
In the present invention, a cellulose acylate film is used as the transparent support. By adjusting the type and substitution degree of the acyl group of cellulose acylate and / or adjusting various conditions of the film production method, a transparent support satisfying the above relational expression can be produced.
[0016]
Although there is no restriction | limiting in particular about the kind of the substituted acyl group of a cellulose acylate, It is preferable to use the cellulose acylate substituted by any 1 type or 2 types or more of C2-C22 acyl groups. Among them, cellulose acylate substituted with at least one selected from an acetyl group (2 carbon atoms), a propionyl group (3 carbon atoms), and a butyryl group (4 carbon atoms) is preferable. A cellulose acylate substituted with a group and a propionyl group or a butyryl group is preferred.
[0017]
On the other hand, if the total acyl substitution degree of cellulose acylate is too low, Re is likely to be larger than a desired value due to the conveying tension when a film is produced by casting, and in-plane variation is likely to occur. From this viewpoint, it is preferable to use a cellulose acylate having a total acyl substitution degree of 2.7 to 3.0. Among them, cellulose acylate having an acetyl group substitution degree of 2.7 or more and 3.0 or less and a C 3-22 acyl group substitution degree of 0 or more and 0.4 or less is particularly preferable.
Further, the substitution degree of the acyl group at the 6-position also affects variations in Re and Rth. It is preferable to use cellulose acylate having a substitution degree of the acyl group at the 6-position of 0.9 or more because variations in Re and Rth can be reduced.
[0018]
The raw material for cellulose acylate used in the present invention is not particularly limited, and can be selected from widely known raw materials. Various known methods can also be used for the synthesis of cellulose acylate. For example, the method described in Mita et al., Wood Chemistry, 180-190 (Kyoritsu Shuppan, 1968) can be used. it can.
[0019]
The cellulose acylate film used as the transparent support is preferably produced by a solvent cast method, more preferably produced using a dope prepared by dissolving cellulose acylate in a solvent. The organic solvent used for the preparation of the dope is not particularly limited, but a mixture of a chlorinated solvent, alcohols, ketones and esters is preferably used. These esters and ketones may have a cyclic structure and may have two or more types of functional groups. Examples of esters include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate and the like. Of these, methyl acetate is particularly preferred. Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone and the like. Of these, acetone, cyclopentanone, and cyclohexanone are particularly preferable.
Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, and the like. Of these, methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol are particularly preferable.
[0020]
By the way, from the viewpoint of the global environment and the working environment, the organic solvent is preferably one that does not substantially contain a chlorinated solvent. “Substantially free” means that the proportion of the chlorinated solvent in the organic solvent is less than 10 mass%, preferably less than 5 mass%, more preferably less than 3 mass%. Further, it is preferable that no chlorine-based solvent such as methylene chloride is detected from the produced cellulose acylate film.
[0021]
From the viewpoint of reducing variations in Re and Rth of the film to be produced, the concentration of cellulose acylate in the solution is preferably 20% by mass to 30% by mass, and more preferably 20 to 26% by mass.
[0022]
In order to prepare the cellulose acylate solution, the cellulose acylate is added while stirring the solvent in the tank at room temperature, and the cellulose acylate is first swollen with the solvent. The swelling time is required to be 10 minutes or longer, and insoluble matters remain if the swelling time is less than 10 minutes. Moreover, in order to fully swell cellulose acylate, the temperature of the solvent is preferably 0 to 40 ° C. If the temperature is below 0 ° C., the swelling rate tends to decrease and insoluble matter tends to remain. If the temperature exceeds 40 ° C., the swelling rapidly occurs, so the central portion does not swell sufficiently.
[0023]
After the swelling step, cellulose acylate is dissolved in a solvent. For the dissolution, either a cooling dissolution method, a high temperature dissolution method, or both can be used. As a specific method relating to the cooling dissolution method and the high temperature dissolution method, for example, a known method described in JIII Journal of Technical Disclosure 2001-1745 can be used.
[0024]
Further, in order to facilitate dissolution of cellulose acylate in a solvent, the cellulose acylate may be dissolved at a low concentration and then concentrated to an optimum concentration using a concentration means.
Prior to casting, the prepared solution is preferably filtered off foreign matters such as undissolved matter, dust, and impurities using an appropriate filter medium such as a wire mesh, paper, or flannel. A method is not specifically limited, For example, the well-known method as described in invention association public technical bulletin 2001-1745 grade | etc., Can be utilized. Moreover, various additives according to a use can be added to a cellulose acylate solution in each preparation process. These additives include plasticizers, UV inhibitors and degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines), and release agents. , Fine particles and the like. When adding a plasticizer or a ultraviolet absorber, it is preferable that it is the range of 1-20 mass parts with respect to the mass of a cellulose acylate. Moreover, when adding microparticles | fine-particles, it is preferable to use microparticles | fine-particles with an average particle diameter of 0.1 micrometer-1 micrometer, and adding in 0.005-0.2 mass part with respect to the mass of a cellulose acylate. preferable.
[0025]
As a method and equipment for producing a film using a cellulose acylate solution, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. An example is shown below.
First, a dope (cellulose acylate solution) prepared from a dissolution tank (pot) is temporarily stored in a stock tank, and bubbles contained in the dope are defoamed for final preparation. The dope is sent from the dope discharge port to the pressurizing die through a pressurizing quantitative gear pump capable of feeding the dope with high accuracy by the number of rotations, for example, and the dope is run endlessly from the die (slit) of the pressurizing die Cast uniformly on the metal support. The raw dry dope film (also referred to as a web) is peeled off from the metal support at the peeling point where the metal support has almost gone around. Both ends of the obtained web are sandwiched between clips, transported by a tenter while maintaining the width, dried, and then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group drying apparatus can be variously changed according to the purpose. In the solution casting film forming method used for silver halide photographic light-sensitive materials and functional protective films for electronic displays, in addition to the solution casting film forming apparatus, an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. In many cases, a coating apparatus is added to the surface treatment of the film, and the apparatus for producing the support of the present invention can also be used.
[0026]
In order to reduce the variation in the film thickness of the cellulose film and reduce the variation in the retardation, the cellulose acylate solution can be used as a single layer or a plurality of cellulose layers on a smooth band or drum as a metal support. The acylate liquid may be co-cast. For example, when casting a plurality of cellulose acylate solutions, a film is formed while casting and laminating a solution containing cellulose acylate from a plurality of casting ports provided at intervals in the traveling direction of the metal support. For example, a method described in JP-A-11-198285 can be applied.
[0027]
Moreover, the method of forming into a film by casting a cellulose acylate solution from two casting openings may be used. Alternatively, a cellulose acylate film casting method may be used in which a flow of a high-viscosity cellulose acylate solution is wrapped with a low-viscosity cellulose acylate solution and the high- and low-viscosity cellulose acylate solutions are simultaneously extruded. By performing such co-casting, as described above, since the smoothing in the drying of the surface proceeds, a significant improvement in the surface shape can be expected. In the case of co-casting, the thickness of each layer is not particularly limited, but the outer layer is preferably thinner than the inner layer. In this case, the thickness of the outer layer is preferably 1 to 30 μm, particularly preferably 1 to 20 μm. Here, the outer layer refers to a surface that is not a band surface (drum surface) in the case of two layers, and layers on both surface sides of the completed film in the case of three or more layers. The inner layer refers to a band surface (drum surface) in the case of two layers, and a layer located inside the outer layer in the case of three or more layers.
[0028]
Furthermore, when the cellulose acylate solution is cast, a solution containing other materials is cast at the same time, and a functional layer (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer). Etc.) can also be produced.
[0029]
Drying of the dope on the metal support is preferably performed at 30 to 250 ° C, more preferably 40 to 180 ° C.
[0030]
The thickness of the cellulose acylate film produced by the above method (after drying) is 40 to 100 μm, preferably 40 to 80 μm, and more preferably 60 to 80 μm. The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap of the die base, the extrusion pressure from the die, the metal support speed, and the like so as to obtain a desired thickness.
[0031]
Here, depending on the case, the surface treatment of the cellulose acylate film can improve the adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the back layer). Depending on the application, it is preferable to provide an antistatic layer on at least one layer of the cellulose acylate film or a hydrophilic binder layer for adhering to the polarizer.
[0032]
The transparent support used in the present invention has a temperature of −30 ° C. to 80 ° C. and a relative humidity of 10% R.D. H. ~ 80% R.D. H. The Re value after standing for 500 hours in an environment of the above range is preferably within ± 10%, more preferably within ± 3% relative to the Re value before treatment. When the Re value fluctuation before and after the treatment is within the above range, it is possible to reduce the optical characteristics of the transparent support depending on the environment. As a result, the optical characteristics of the λ / 4 plate can be changed depending on the environment. The fluctuation can be reduced. By adjusting the conditions of the casting method, a film having the above characteristics can be produced.
[0033]
One aspect of the λ / 4 plate of the present invention is a λ / 4 plate having two or more optically anisotropic layers containing a liquid crystalline compound on one surface thereof, and a transparent support made of the cellulose acylate film. It is. Hereinafter, a manufacturing method of the λ / 4 plate of this embodiment and various materials used for the manufacturing will be described.
[Alignment film]
In order to form an optically anisotropic layer made of a liquid crystal compound, an alignment film for aligning the liquid crystal compound is used. As the alignment film, an alignment film that generates an alignment function by a rubbing treatment of an organic compound (preferably a polymer) is used. The type of polymer forming the alignment film is determined according to the alignment (particularly the average tilt angle) of the liquid crystal compound.
In order to align the liquid crystalline compound horizontally, a polymer that does not decrease the surface energy of the alignment film (ordinary alignment polymer) is used. Polymers preferably used during the rubbing treatment include polyvinyl alcohol, polyimide derivatives and nylon.
[0034]
The alignment film also preferably has a polymerizable group for the purpose of improving the adhesion between the liquid crystalline compound layer and the transparent support. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. More preferably, an alignment film that forms a chemical bond with the liquid crystal compound at the interface is used, and such an alignment film is described in JP-A-9-152509.
The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 3 μm.
[0035]
[Rubbing]
In the rubbing treatment, the tilt angle of the liquid crystalline compound with respect to the film plane can be changed by rubbing the surface of these polymer layers several times in a certain direction with paper or cloth.
The rubbing treatment can be performed at a predetermined arbitrary angle with respect to the MD direction (slow axis direction) of the support. The angle of the rubbing direction with respect to the MD direction is preferably rubbed in the same to the oblique direction with respect to the MD direction. The angle in the oblique direction is preferably in the range of −50 degrees to +50 degrees. The rubbing treatment can be performed by an arbitrary method. For example, a rubbing roll is arranged at an arbitrary angle with respect to the MD direction of the long film on a stage that conveys the long film in the MD direction. The rubbing roll is rotated while being conveyed in the MD direction to rub the film surface. The angle formed by the rubbing roll and the moving direction of the stage is a mechanism that can be freely adjusted, and an appropriate rubbing cloth material is stuck on the surface of the rubbing roll.
As will be described later, the rubbing treatment direction and treatment method are the same as those described above in the embodiment in which the lower optical anisotropic layer functions as the alignment film of the upper optical anisotropic layer.
[0036]
[Optically anisotropic layer made of liquid crystalline compound]
As the liquid crystalline compound used in the present invention, a rod-like liquid crystalline compound or a discotic liquid crystalline compound is preferable, and a rod-like liquid crystalline compound having a polymerizable group or a discotic liquid crystalline compound having a polymerizable group. More preferred.
Examples of rod-like liquid crystalline compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. In addition to the above low-molecular liquid crystalline molecules, high-molecular liquid crystalline molecules can also be used. The rod-like liquid crystalline compound having a low molecular polymerizable group that is particularly preferably used is a rod-like liquid crystalline compound of the following formula (I).
Formula (I)
Q¹-L¹-Cy¹-L²-(Cy²-L^Three)_n-Cy^Three-L^Four-Q²
Where Q¹And Q²Each independently represents a polymerizable group, L¹And L^FourAre each independently a divalent linking group, L²And L^ThreeAre each independently a single bond or a divalent linking group, and Cy¹, Cy²And Cy^ThreeAre each independently a divalent cyclic group, and n is 0, 1 or 2.
[0037]
The polymerizable rod-like liquid crystal compound will be further described below.
Where Q¹And Q²Are each independently a polymerizable group. The polymerization reaction of the polymerizable group is preferably addition polymerization (including ring-opening polymerization) or condensation polymerization. In other words, the polymerizable group is preferably a functional group capable of addition polymerization reaction or condensation polymerization reaction. Examples of polymerizable groups are shown below.
[0038]
[Chemical 1]

[0039]
In the formula (I), L¹And L^FourAre each independently a divalent linking group. L¹And L^FourAre each independently -O-, -S-, -CO-, -NR²It is preferably a divalent linking group selected from the group consisting of-, a divalent chain group, a divalent cyclic group, and combinations thereof. R above²Is an alkyl group having 1 to 7 carbon atoms or a hydrogen atom.
[0040]
The example of the bivalent coupling group which consists of a combination is shown below. Here, the left side is Q (Q¹Or Q²), The right side is Cy (Cy¹Or Cy^Three).
L-1: —CO—O—divalent chain group —O—
L-2: -CO-O-divalent chain group -O-CO-
L-3: —CO—O—divalent chain group —O—CO—O—
L-4: -CO-O-divalent chain group -O-divalent cyclic group-
L-5: -CO-O-divalent chain group -O-divalent cyclic group -CO-O-
L-6: -CO-O-divalent chain group -O-divalent cyclic group -O-CO-
L-7: -CO-O-divalent chain group-O-divalent cyclic group-divalent chain group-
L-8: -CO-O-divalent chain group -O-divalent cyclic group -divalent chain group -CO-O-
L-9: -CO-O-divalent chain group -O-divalent cyclic group -divalent chain group -O-CO-
[0041]
L-10: —CO—O—divalent chain group—O—CO—divalent cyclic group—
L-11: -CO-O-divalent chain group -O-CO-divalent cyclic group -CO-O-
L-12: -CO-O-divalent chain group -O-CO-divalent cyclic group -O-CO-
L-13: —CO—O—Divalent chain group—O—CO—Divalent cyclic group—Divalent chain group—
L-14: -CO-O-divalent chain group -O-CO-divalent cyclic group -divalent chain group -CO-O-
L-15: -CO-O-divalent chain group-O-CO-divalent cyclic group-divalent chain group-O-CO-
L-16: —CO—O—divalent chain group—O—CO—O—divalent cyclic group—
L-17: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -CO-O-
L-18: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -O-CO-
L-19: —CO—O—Divalent chain group—O—CO—O—Divalent cyclic group—Divalent chain group—
L-20: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -divalent chain group -CO-O-
L-21: -CO-O-divalent chain group -O-CO-O-divalent cyclic group -divalent chain group -O-CO-
[0042]
In the above formula, the divalent chain group means an alkylene group, a substituted alkylene group, an alkenylene group, a substituted alkenylene group, an alkynylene group or a substituted alkynylene group. An alkylene group, a substituted alkylene group, an alkenylene group and a substituted alkenylene group are preferred, and an alkylene group and an alkenylene group are more preferred.
The alkylene group may have a branch. The alkylene group preferably has 1 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkylene part of the substituted alkylene group is the same as the above alkylene group. Examples of the substituent include a halogen atom.
The alkenylene group may have a branch. The alkenylene group preferably has 2 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkylene part of the substituted alkylene group is the same as the above alkylene group. Examples of the substituent include a halogen atom.
The alkynylene group may have a branch. The alkynylene group preferably has 2 to 12 carbon atoms, more preferably 2 to 10 carbon atoms, and most preferably 2 to 8 carbon atoms.
The alkynylene part of the substituted alkynylene group is the same as the above alkynylene group. Examples of the substituent include a halogen atom.
Specific examples of the divalent chain group include ethylene, trimethylene, propylene, butamethylene, 1-methyl-butamethylene, pentamethylene, hexamethylene, octamethylene, 2-butenylene, 2-butynylene and the like.
[0043]
The definition and examples of the divalent cyclic group are described later in Cy.¹, Cy²And Cy^ThreeDefinitions and examples are the same.
R²Is preferably an alkyl group having 1 to 4 carbon atoms or a hydrogen atom, more preferably a methyl group, an ethyl group or a hydrogen atom, and most preferably a hydrogen atom.
[0044]
L²Or L^ThreeAre each independently a single bond or a divalent linking group. L²And L^ThreeAre each independently -O-, -S-, -CO-, -NR₂It is preferably a divalent linking group or a single bond selected from the group consisting of-, a divalent chain group, a divalent cyclic group, and combinations thereof. R above²Is an alkyl group having 1 to 7 carbon atoms or a hydrogen atom, preferably an alkyl group having 1 to 4 carbon atoms or a hydrogen atom, more preferably a methyl group, an ethyl group or a hydrogen atom, Most preferably, it is a hydrogen atom. L for a divalent chain group and a divalent cyclic group¹And L^FourIt is synonymous with the definition of
[0045]
In the formula (I), n is 0, 1 or 2. If n is 2, then two L^ThreeMay be the same or different and the two Cy²May be the same or different. n is preferably 1 or 2, and more preferably 1.
[0046]
In formula (I), Cy¹, Cy²And Cy^ThreeAre each independently a divalent cyclic group.
The ring contained in the cyclic group is preferably a 5-membered ring, a 6-membered ring, or a 7-membered ring, more preferably a 5-membered ring or a 6-membered ring, and most preferably a 6-membered ring. The ring contained in the cyclic group may be a condensed ring. However, it is more preferably a monocycle than a condensed ring. The ring contained in the cyclic group may be any of an aromatic ring, an aliphatic ring, and a heterocyclic ring. Examples of the aromatic ring include a benzene ring and a naphthalene ring. Examples of the aliphatic ring include a cyclohexane ring. Examples of the heterocyclic ring include a pyridine ring and a pyrimidine ring. As the cyclic group having a benzene ring, 1,4-phenylene is preferable. As the cyclic group having a naphthalene ring, naphthalene-1,5-diyl and naphthalene-2,6-diyl are preferable. The cyclic group having a cyclohexane ring is preferably 1,4-cyclohexylene. As the cyclic group having a pyridine ring, pyridine-2,5-diyl is preferable. The cyclic group having a pyrimidine ring is preferably pyrimidine-2,5-diyl.
[0047]
The cyclic group may have a substituent. Examples of the substituent include a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 5 carbon atoms, a halogen-substituted alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. , An alkylthio group having 1 to 5 carbon atoms, an acyloxy group having 2 to 6 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, a carbamoyl group, and an alkyl-substituted carbamoyl group having 2 to 6 carbon atoms And an acylamino group having 2 to 6 carbon atoms.
[0048]
Examples of liquid crystal compounds having a polymerizable group represented by formula (I) are shown below. The present invention is not limited to these.
[0049]
[Chemical formula 2]

[0050]
[Chemical 3]

[0051]
[Formula 4]

[0052]
[Chemical formula 5]

[0053]
As the liquid crystalline compound of the present invention, a discotic liquid crystalline compound can also be preferably used. The discotic liquid crystalline compound is preferably oriented substantially perpendicularly to the polymer film surface (average inclination angle in the range of 50 to 90 degrees). The discotic liquid crystalline compounds are disclosed in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by the Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am.Chem.Soc., Vol.116, page 2655 (1994)). The polymerization of the discotic liquid crystalline compound is described in JP-A-8-27284.
[0054]
The discotic liquid crystalline compound preferably has a polymerizable group so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to a disk-shaped core of a disk-shaped liquid crystalline compound can be considered. However, when a polymerizable group is directly bonded to the disk-shaped core, the alignment state is maintained in the polymerization reaction. It becomes difficult. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula (III).
Formula (III)
D (-LP)_n
In the formula, D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12.
[0055]
Preferred specific examples of the discotic core (D), the divalent linking group (L), and the polymerizable group (P) in the formula (III) are (D1) described in JP-A No. 2001-4837, respectively. To (D15), (L1) to (L25), and (P1) to (P18), and the contents described in the publication can be preferably used.
[0056]
These liquid crystalline compounds are preferably substantially uniformly oriented in the optically anisotropic layer, more preferably fixed in a substantially uniformly oriented state. Most preferably, the liquid crystal molecules are fixed by the above.
In the case of a rod-like liquid crystal compound having a polymerizable group, it is preferably fixed in a substantially horizontal (homogeneous) orientation. Substantially horizontal means that the average angle (average inclination angle) between the major axis direction of the rod-like liquid crystal compound and the surface of the optically anisotropic layer is in the range of 0 ° to 40 °. The rod-like liquid crystalline compound may be oriented obliquely, or may be caused to change gradually (hybrid orientation). Even in the case of oblique alignment or hybrid alignment, the average inclination angle is preferably 0 ° to 40 °.
In the case of a discotic liquid crystalline compound having a polymerizable group, it is preferable to substantially align vertically. Substantially perpendicular means that the average angle (average tilt angle) between the disc surface of the discotic liquid crystalline compound and the surface of the optically anisotropic layer is in the range of 50 ° to 90 °. The discotic liquid crystalline compound may be obliquely aligned or may be gradually changed (hybrid alignment). Even in the case of oblique orientation or hybrid orientation, the average inclination angle is preferably 50 ° to 90 °.
[0057]
The λ / 4 plate of the above aspect has two or more optically anisotropic layers. An alignment film may be formed between the optically anisotropic layers, or the optically anisotropic layer may function as an alignment film for the optically anisotropic layer formed thereon. When the optically anisotropic layer functions as an alignment film for the optically anisotropic layer formed thereon, a composition containing a modified polyvinyl alcohol having a hydrocarbon group having 9 or less carbon atoms together with a liquid crystalline compound It is preferable that an optically anisotropic layer is formed using a material, and subsequently, the surface of the optically anisotropic layer is rubbed to form an upper optically anisotropic layer.
[0058]
The modified polyvinyl alcohol having a hydrocarbon group having 9 or less carbon atoms used together with the liquid crystal compound will be described.
A preferable modified polyvinyl alcohol is represented by the following formula (PX).
(PX)-(VAl)_x-(HyD)_y-(VAc)_z−
In the formula, VAl is a repeating unit of vinyl alcohol, HyD is a repeating unit having a hydrocarbon group having 9 or less carbon atoms, VAc is a vinyl acetate repeating unit, and x is 20 to 95% by mass ( Preferably it is 25-90 mass%), y is 2-98 mass% (preferably 10-80 mass%), and z is 0-30 mass% (preferably 2-20 mass%).
[0059]
The hydrocarbon group contained in HyD is an aliphatic group, an aromatic group, or a combination thereof. The aliphatic group may be cyclic, branched or linear. The aliphatic group is preferably an alkyl group (which may be a cycloalkyl group) or an alkenyl group (which may be a cycloalkenyl group). The hydrocarbon group may have a substituent. The hydrocarbon group has 1 to 9 carbon atoms, and preferably 1 to 8 carbon atoms. Preferred examples of HyD are represented by the following formulas (HyD-I) and (HyD-II).
[0060]
[Chemical 6]

[0061]
Where L¹Are —O—, —CO—, and —SO.₂A divalent linking group selected from-, -NH-, an alkylene group, an arylene group, and combinations thereof;²Is a single bond, or -O-, -CO-, -SO₂A divalent linking group selected from-, -NH-, an alkylene group, an arylene group, and combinations thereof;¹And R²Are hydrocarbon groups each having 9 or less carbon atoms. Examples of divalent linking groups formed by the above combinations are shown below.
[0062]
L1: -O-CO-
L2: -O-CO-alkylene group -O-
L3: -O-CO-alkylene group -CO-NH-
L4: -O-CO-alkylene group -NH-SO₂-Arylene group-O-
L5: -Arylene group -NH-CO-
L6: -Arylene group -CO-O-
L7: -Arylene group -CO-NH-
L8: -Arylene group -O-
L9: -O-CO-NH-arylene group -NH-CO-
[0063]
Specific examples of HyD are shown below.
[0064]
[Chemical 7]

[0065]
The degree of polymerization of the modified polyvinyl alcohol is preferably 200 to 5000, and preferably 300 to 3000. The molecular weight of the polymer is preferably 9000 to 200000, and more preferably 13000 to 130,000. Two or more kinds of polymers may be used in combination.
[0066]
Specific examples of preferable modified polyvinyl alcohol are shown below, but the present invention is not limited thereto.
PX-1 :-( VAl)_{twenty one}-(HyD-13)₇₇-(VAc)₂−
PX-2 :-( VAl)₁₄-(HyD-13)₈₄-(VAc)₂−
PX-3 :-( VAl)_{twenty one}-(HyD-16)₇₇-(VAc)₂−
PX-4 :-( VAl)₃₄-(HyD-15)₆₄-(VAc)₂−
PX-5 :-( VAl)₂₉-(HyD-12)₆₉-(VAc)₂−
PX-6 :-( VAl)₄₆-(HyD-14)₅₂-(VAc)₂−
PX-7 :-( VAl)_{twenty one}-(HyD-2)₇₇-(VAc)₂−
PX-8 :-( VAl)₁₇-(HyD-8)₈₅-(VAc)₂−
PX-9 :-( VAl)_{twenty one}-(HyD-13)₇₇-(VAc)₂−
PX-10 :-( VAl)₄₆-(HyD-9)₅₂-(VAc)₂−
[0067]
The amount of the modified polyvinyl alcohol added is preferably 0.05% by mass to 10% by mass with respect to the liquid crystalline compound added by the control agent. More preferably, it is 0.1 mass-5 mass%.
[0068]
The modified polyvinyl alcohol may be used in combination with a condensing agent. As the condensing agent, a compound having an isocyanate group or a formyl group at the terminal is preferable. Specific compounds are listed below, but are not limited thereto.
[0069]
Poly (1,4-butanediol), isophorone diisocyanate terminated
Poly (1,4-butanediol), tolylene 2,4-diisocyanate terminated
Poly (ethylene adipate), tolylene 2,4-diisocyanate terminated
Poly (propylene glycol), tolylene 2,4-diisocyanate terminated,
1,6-diisocyanatohexane
1,8-diisocyanate octane
1,12-diisocyanate dodecane
Isophorone diisocyanate
Glioquizal
[0070]
In the present invention, the optically anisotropic layer is formed by coating the rubbing surface with a coating solution in which the liquid crystalline compound, and optionally the modified polyvinyl alcohol, and the following polymerization initiator and other additives are dissolved in a solvent. Is preferably formed. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
[0071]
[Fixation of alignment state of liquid crystalline compounds]
The aligned liquid crystalline compound is preferably fixed while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is more preferable. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbons. Substituted aromatic acyloin compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US patent) 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970).
[0072]
The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. Irradiation energy is 20mJ / cm²~ 50J / cm²It is preferably 100 to 800 mJ / cm.²More preferably. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. In addition, reducing the oxygen concentration in the atmosphere during light irradiation by nitrogen substitution or the like is also effective for promoting the reaction. The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.
[0073]
[Optical properties of λ / 4 plate]
It is preferable that the optically anisotropic layer constituting the λ / 4 plate of the present invention substantially achieves a phase difference of π or π / 2 at a specific wavelength. In order to achieve the phase difference π at the specific wavelength (λ), the retardation value of the polarizer measured at the specific wavelength (λ) may be adjusted to λ / 2, and the phase difference π / In order to achieve 2, the retardation value of the polarizer measured at a specific wavelength (λ) may be adjusted to λ / 4. However, it is preferable that at 550 nm, which is a wavelength approximately in the middle of the visible region, one achieves the phase difference π and the other achieves π / 2. For example, in an embodiment composed of two optically anisotropic layers, one of the optically anisotropic layers (first optically anisotropic layer) preferably has a retardation value measured at a wavelength of 550 nm of 240 to 300 nm. 290 nm is more preferable, 250 to 280 nm is more preferable, and the other optically anisotropic layer (second optically anisotropic layer) has a retardation value measured at a wavelength of 550 nm of preferably 80 to 170 nm, and more preferably 110 to 145 nm. More preferably, 120-140 nm is further more preferable. It is preferable that the former is a layer close to the support and the latter is a layer farther from the support.
[0074]
The thicknesses of the first and second optically anisotropic layers can be arbitrarily determined as long as each layer exhibits a desired retardation. For example, when the first and second optically anisotropic layers are formed by horizontally aligning the same rod-like liquid crystal compound, the thickness of the optically anisotropic layer having a phase difference of π is set as the phase difference. It is preferable to double the thickness of the optical anisotropy of π / 2. Although the preferable range of the thickness of each optically anisotropic layer varies depending on the type of liquid crystal compound used, it is generally 0.1 to 10 μm, more preferably 0.2 to 0.8 μm, 5-5 micrometers is further more preferable. In both optically anisotropic layers, in the embodiment in which the liquid crystalline compound is aligned in parallel in the plane of the support, it is preferable that the alignment direction of the first layer is different from the alignment direction of the second layer. [15] The Re value at 550 nm of the layer close to the support of the optically anisotropic layer is 240 to 300 nm, and the Re value at 550 nm of the layer far from the support is 80 to 170 nm [13] or [ 14].
[0075]
Specifically, the λ / 4 plate of the present invention and the broadband λ / 4 plate composed of the λ / 4 plate and the polarizing plate are specifically retardation values / wavelength values measured at wavelengths of 450 nm, 550 nm and 650 nm. Means that both are within the range of 0.2 to 0.3. The retardation value / wavelength value is preferably in the range of 0.21 to 0.29, more preferably in the range of 0.22 to 0.28, and 0.23 to 0.27. More preferably, it is within the range, and most preferably within the range of 0.23 to 0.26.
[0076]
[Circularly polarizing plate]
The λ / 4 plate of the present invention is a λ / 4 plate used in a reflective liquid crystal display device, a λ / 4 plate used for a pickup for writing on an optical disk, or a λ / 4 plate used as an antireflection film. Can be used particularly advantageously. The λ / 4 plate is generally used as a circularly polarizing plate combined with a polarizing film. Therefore, if it is configured as a circularly polarizing plate in which a λ / 4 plate and a polarizing film are combined, it can be easily incorporated into a device for use such as a reflective liquid crystal display device. Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film.
[0077]
The polarizing film to be combined with the λ / 4 plate of the present invention is not particularly limited, and an iodine polarizing film, a dye polarizing film using a dichroic dye, or a polyene polarizing film can be used. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. It is preferable to laminate so that the transmission axis of the polarizing film is 45 ° with respect to the longitudinal direction of the transparent support of the λ / 4 plate of the present invention. If a polarizing film having a transmission axis of polarized light substantially in the direction of 45 ° with respect to the longitudinal direction (hereinafter referred to as 45 ° polarizing film) is used, the angle adjustment at the time of lamination becomes unnecessary, and the circularly polarizing plate of the present invention Can be easily produced. Since the transmission axis of the polarizing film made of a stretched film substantially coincides with the stretching direction, a 45 ° polarizing film can be produced by stretching the film in a direction of 45 ° with respect to the longitudinal direction. Such a polarizing film having a polarization transmission axis substantially in the 45 ° direction (hereinafter referred to as a 45 ° polarizing film) can be produced by the oblique stretching method described in JP-A-2002-86554. It can be produced with reference to the conditions described in columns 0009 to 0045, the configuration of the usable apparatus, and the like.
[0078]
【Example】
The present invention will be described more specifically with reference to the following examples. The materials, reagents, amounts and ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples. .
[0079]
(Type of acyl group and substitution degree of cellulose acylate)
Calculated according to ASTM D817.
(Re and Rth measurement of transparent support)
The front retardation (Re) of the transparent support was measured from the direction perpendicular to the sample film surface using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments). Unless otherwise specified, sample 25 ° C. 60% R.D. H. The retardation value measured at a wavelength of 548.3 nm in the same environment after being held for 2 hours in this environment.
The retardation (Rth) in the thickness direction of the transparent support was inclined at 40 ° and −40 ° in the vertical direction with respect to the film surface using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments). The retardation was measured at a wavelength of 548.3 nm from the direction, and Rth was calculated from the obtained three values.
[0080]
(Retardation value variation)
The variation in retardation was determined from values measured by selecting 10 arbitrary locations from the sample.
(Measurement of wavelength dispersion of λ / 4 plate included in circularly polarizing plate)
The wavelength dispersion of the λ / 4 plate was measured using an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments). A sample processed into a circularly polarizing plate was subjected to 25 ° C. and 60% R.D. H. Then, Re was measured at wavelengths of 478 nm, 548 nm, 589 nm, 630 nm, and 747 nm. The obtained five values were fitted to the Cauchy equation using the least square method, and values of 450 nm, 550 nm, and 650 nm were calculated from the obtained parameters.
[0081]
(Preparation of cellulose acylate film)
A solution (dope) was prepared using the materials and conditions described in Table 1. As the dissolution method, “normal method” and “cooling dissolution method” were used. In the usual method, cellulose acylate was gradually added while stirring the solvent in an environment at 25 ° C. Furthermore, additives such as an ultraviolet absorber were added to obtain a dope. In the “cooling dissolution method”, cellulose acylate was gradually added while stirring the solvent in an environment of 25 ° C., and an additive was further added and allowed to stand for 2 hours to swell. The obtained swollen mixture was cooled to −30 ° C. at −8 ° C./min with slow stirring, and then the stirring was stopped and further cooled to −70 ° C. and left for 6 hours. Thereafter, the temperature was raised at + 8 ° C./min, and stirring was started when gelation progressed to some extent. The dope was obtained by heating to 50 ° C.
The obtained dope was filtered with a filter paper having an absolute filtration accuracy of 0.01 mm (manufactured by Toyo Filter Paper Co., Ltd., # 63), and further filtered with a filter paper having an absolute filtration accuracy of 0.0025 mm (manufactured by Pall, FH025).
The obtained filtered dope was cast using a known casting machine (Patent Document 8) to obtain a cellulose acylate film. The film thickness was adjusted by the clearance of the Giesser section to obtain the desired film. The drying temperature was 120 ° C., and the amount of residual solvent in the obtained film was 0.2 parts by mass or less.
Table 2 shows the results of measuring the Re and Rth values of the obtained film.
[0082]
[Table 1]

[0083]
* 1) Acyl group: Pr = propionyl group.
* 2) Solvent: MA = methyl acetate, MC = methylene chloride, AT = acetone, MOL = methanol, EOL = ethanol, BOL = n-butanol.
* 3) Additive: TPP = triphenyl phosphate, BDP = biphenyl diphenyl phosphate.
[0084]
[Table 2]

[0085]
(Production of λ / 4 plate)
After saponifying both surfaces of the obtained transparent support, an alignment film coating solution having the following composition was applied to one side of the transparent support and dried at 100 ° C. The thickness of the alignment film was 1 μm. Next, rubbing treatment was performed so that the slow axis direction of the optically anisotropic layer was 30 ° with respect to the longitudinal direction of the transparent support.

[0086]
Modified polyvinyl alcohol
[Chemical 8]

[0087]
On the alignment film, a coating solution having the following composition is continuously applied using a bar coater, dried and heated (alignment aging), and further irradiated with ultraviolet rays to give an optically anisotropic layer having a thickness of 2.1 μm. Formed. The optically anisotropic layer had a slow axis in the direction of 30 ° with respect to the longitudinal direction of the transparent support.
Coating liquid composition for optically anisotropic layer (A)
Rod-shaped liquid crystalline compound (Exemplary Compound I-2) 38.1% by mass
Sensitizer A 0.38% by mass
The following photoinitiator B 1.14 mass%
Exemplary compound (PX-9) 0.19 mass%
Glutaraldehyde 0.04% by mass
Methyl ethyl ketone 60.1% by mass
[0088]
Sensitizer A
[Chemical 9]

[0089]
Photoinitiator B
[Chemical Formula 10]

[0090]
The optical anisotropy is −60 ° with respect to the slow axis of the optically anisotropic layer (A) prepared above and −30 ° with respect to the longitudinal direction of the optically anisotropic layer (A). A rubbing treatment was performed after the application of the adhesive layer (A).
[0091]
On the optically anisotropic layer (A) subjected to the rubbing treatment, a coating solution having the following composition was applied, dried and heated (orientation aging) using a bar coater, and further irradiated with ultraviolet rays to obtain a thickness of 1. A 0 μm optically anisotropic layer (B) was formed to produce a λ / 4 plate.
Coating liquid composition for optically anisotropic layer (B)
Rod-shaped liquid crystalline compound (Exemplary Compound I-2) 38.4% by mass
Sensitizer A 0.38% by mass
Photopolymerization initiator B 1.15% by mass
Orientation control agent C 0.06% by mass
Methyl ethyl ketone 60.0 mass%
[0092]
Orientation control agent C
Embedded image

[0093]
(Preparation of polarizing plate)
The PVA film was immersed in an aqueous solution of 2.0 g / L of iodine and 4.0 g / L of potassium iodide at 25 ° C. for 240 seconds, and further immersed in an aqueous solution of boric acid 10 g / L for 60 seconds at 25 ° C. Introduced in a tenter stretching machine as shown in FIG. 1 of 2002-86554, stretched 5.3 times, bent the tenter as shown in FIG. 1 with respect to the stretching direction, and thereafter kept the width constant and contracted at 80 ° C. After drying in the atmosphere, it was detached from the tenter. The moisture content of the PVA film before starting stretching was 31%, and the moisture content after drying was 1.5%.
The difference in transport speed between the left and right tenter clips was less than 0.05%, and the angle between the center line of the introduced film and the center line of the film sent to the next process was 46 °. Here, | L1-L2 | is 0.7 m, W is 0.7 m, and | L1-L2 | = W. The substantial stretching direction Ax-Cx at the tenter outlet was inclined by 45 ° with respect to the center line 22 of the film sent to the next process. Wrinkles and film deformation at the tenter exit were not observed.
[0094]
Furthermore, it was bonded to Fuji Photo Film Co., Ltd. Fujitac (cellulose triacetate, retardation value 3.0 nm), which was saponified with an aqueous solution of PVA (Pura-117H, Kuraray Co., Ltd.) 3%, and further 80 ° C. And dried to obtain a polarizing plate having an effective width of 650 mm.
The absorption axis direction of the obtained polarizing plate was inclined 45 ° with respect to the longitudinal direction. The polarizing plate had a transmittance at 550 nm of 43.7% and a polarization degree of 99.97%. Next, the above-prepared λ / 4 plate is laminated on one side of the iodine-based polarizing film produced above, and a saponification-treated antiglare antireflection film is laminated on the other side, A polarizing plate was produced.
As a result of measuring the wavelength dispersion of the λ / 4 plate bonded to the circularly polarizing plate and determining the value of Re (λ) / λ,
Re (450) /450=0.26,
Re (550) /550=0.27,
Re (650) /650=0.25,
It was found that it has a broadband property in a wide range of the visible region.
[0095]
(Production of reflective liquid crystal display device)
A polarizing plate and a λ / 4 plate of a commercially available reflective liquid crystal display device (Color Zaurus MI-310, manufactured by Sharp Corporation) were peeled off, and each of the above-prepared products was attached instead.
When the produced reflection type liquid crystal display device was visually evaluated, it was found that neutral gray was displayed without coloring or unevenness in any of white display, black display, and halftone in the examples. On the other hand, in the comparative example, there was uneven coloring.
Next, the contrast ratio of the reflected luminance was measured using a measuring machine (EZcontrast 160D, manufactured by Eldim). In the example, the contrast ratio from the front is 10, and the viewing angle of the contrast ratio 3 is 120 ° or more in the vertical and horizontal directions, showing substantially sufficient characteristics. On the other hand, in the comparative example, the viewing angle with a contrast ratio of 3 was 80 ° or less depending on the direction, and the viewing angle characteristics were insufficient.
[0096]
(Environmental testing)
The reflection type liquid crystal display device produced above was subjected to a −30 ° C. freezer, an 80 ° C. dry box, 40 ° C. and 95% R.D. H. Temperature and humidity variable device, 25 ° C., 10% R.V. H. And 25 ° C. 80% R.V. H. For one month. As a result of visual comparison with the element before treatment, the reflective liquid crystal display element using the λ / 4 plate of the comparative example had a change in coloring, whereas the reflection using the λ / 4 plate of the example was used. No change was observed in the liquid crystal display device.
[0097]
【The invention's effect】
According to the present invention, by using a transparent support composed of a cellulose acylate film having a retardation and a film thickness in a predetermined range, a display such as a reflective liquid crystal display element, a transflective liquid crystal display element, and an EL element is displayed. A λ / 4 plate that can be suitably used for an element can be provided.

Claims (7)

A λ / 4 plate having a transparent support made of a cellulose acylate film, the cellulose acylate film satisfying the following conditions (A) to (D) :
(A) Re value represented by the following formula (1) is 0 nm or more and 20 nm or less (B) Rth value represented by the following formula (2) is 0 nm or more and 100 nm or less (C) The variation of the Re value and the Rth value is an average Within ± 3 nm of value (D) Thickness is 40 μm or more and 100 μm or less Formula (1) Re value = (nx−ny) × d
Formula (2) Rth value = {(nx + ny) / 2−nz} × d
(Where nx is the refractive index in the slow axis direction in the plane of the transparent support, ny is the refractive index in the direction perpendicular to nx in the plane of the transparent support, and nz is the refractive index in the thickness direction of the transparent support) , D represents the thickness of the transparent support.)
One side of the transparent support has at least two optically anisotropic layers made of a composition containing a liquid crystalline compound, and at least one optically anisotropic layer has a hydrocarbon group having 9 or less carbon atoms. A λ / 4 plate containing the modified polyvinyl alcohol. 2. The λ / 4 plate according to claim 1, wherein the surface of the optically anisotropic layer containing the modified polyvinyl alcohol is rubbed and has another optically anisotropic layer on the rubbed surface. The λ / 4 plate according to claim 1 or 2, wherein the modified polyvinyl alcohol is a compound represented by the following general formula (PX):
Formula (PX)
      (PX)-(VAl) _x -(HyD) _y -(VAc) _z −
  In the formula, VAl is a repeating unit of vinyl alcohol, HyD is a repeating unit having a hydrocarbon group having 9 or less carbon atoms, VAc is a vinyl acetate repeating unit, and x is 20 to 95% by mass. Yes, y is 2 to 98% by mass, and z is 0 to 30% by mass. The optically anisotropic layer containing the modified polyvinyl alcohol contains the modified polyvinyl alcohol in an amount of 0.05 to 10% by mass with respect to the liquid crystalline compound. 4 plates. The λ / 4 plate according to any one of claims 1 to 4, wherein the liquid crystal compound is a rod-like liquid crystal compound or a discotic liquid crystal compound. The cellulose acylate film has a total acyl substitution degree of 2.7 or more and 3.0 or less, an acetyl group substitution degree of 2.7 or more and 3 or less, and substitution of an acyl group having 3 to 22 carbon atoms. The λ / according to any one of claims 1 to 5, wherein a film having a concentration of 20 to 30% by mass in which a cellulose acylate having a degree of 0 to 0.4 is dissolved in a solvent is cast. 4 plates. The λ / 4 plate according to claim 6 , wherein the acyl substitution degree at the 6-position of the cellulose acylate is 0.90 or more and 1.00 or less.