JP4330321B2 - Retardation plate, manufacturing method thereof, and circularly polarizing plate using the same - Google Patents

Description

【００１８】
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。
【００１９】
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−
【００２０】
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−
【００２１】
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−ブチニレンなどが上げられる。
【００２２】
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。
【００２３】
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。
【００２４】
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。
【００２５】
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。
【００２６】
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。
【００２７】
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。
【００２８】
【化２】

【００２９】
【化３】

【００３０】
【化４】

【００３１】
【化５】

【００３２】
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。
【００３３】
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。
【００３４】
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。
【００３５】
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（ハイブリッド配向）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（ハイブリッド配向）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。
【００３６】
本発明の位相差板は、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。
【００３７】
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。
【００３８】
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。
【００３９】
【化６】

【００４０】
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。
【００４１】
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−
【００４２】
ＨｙＤの具体例を以下に示す。
【００４３】
【化７】

【００４４】
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。
【００４５】
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−
【００４６】
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。
【００４７】
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。
【００４８】
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
【００４９】
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媒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媒としては、有機溶媒が好ましく用いられる。有機溶媒の例には、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媒を併用してもよい。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。
【００５０】
［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。
【００５１】
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。
【００５２】
［光学異方性層の硬度］
本発明の位相差板は、透明支持体に近い側の光学異方性層よりも遠い側の光学異方性層の硬度が高いことを特徴とする。本明細書において「硬度」とは、連続荷重式引掻強度試験機を用いて試験した場合に、連続して層の剥離が開始し始める限界荷重の重さとして示される。透明支持体に遠い側の光学異方性層と近い側の光学異方性層との硬度の差は、双方の層について測定された前記限界荷重の差によって示される。支持体に遠い側の光学異方性層および近い側の光学異方性層それぞれについて、新東科学（株）製 連続荷重式 引掻強度試験機（ＴＹＰＥＨＥＩＤＯＮ１８）を用いて、ダイヤモンド製先端角９０°、先端曲率（Ｒ）＝０．０２５ｍｍの針により試験を実施した場合に、支持体に遠い側の光学異方性層と近い側の光学異方性層との限界荷重の差が５ｇ以上であるのが好ましく、１０ｇ以上であるのがより好ましい。５ｇより低い場合は膜剥がれ防止に対する効果が小さくなり、光学異方性層が剥がれ易くなる場合がある。上限は１００ｇ以下が好ましい。１００ｇを超えると逆に割れやすい、曲げ耐性が悪くなるなどの問題を生じる場合がある。特に好ましくは８０ｇ以下である。
【００５３】
また、本発明の位相差板は、光学異方性層を積層した状態での硬度が３０ｇ以上であるのが好ましい。即ち、本発明の位相差板について、前記引掻強度試験機により引掻試験を実施した場合に、積層した状態の光学異方性層が連続して剥離し始める限界荷重が、３０ｇ以上であるのが好ましい。より好ましくは４０ｇ以上である。積層した状態でも硬度が３０ｇより低い場合には傷が付きやすくなったり、巻き取ったロール内で接着故障が発生したりする場合がある。上限は１００ｇ以下が好ましい。１００ｇを超えると逆に割れやすい、曲げ耐性が悪くなるなどの問題を生じる場合がある。特にこのましくは８０ｇ以下である。
【００５４】
光学異方性層それぞれの硬度、および積層状態での硬度は、硬化させる（重合させる）際の雰囲気の温湿度および酸素濃度（あるいは窒素置換率）、紫外線の照射量、照射時の試料温度、液晶化合物の多官能化、重合開始剤の種類・量、ならびに増感剤の種類・量によって適宜調整することができる。
【００５５】
［位相差板の光学的性質］
本発明の位相差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２４０〜２９０ｎｍであることが好ましく、２５０〜２８０ｎｍであることがより好ましく、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１１０〜１４５ｎｍであることが好ましく、１２０〜１４０ｎｍであることがより好ましい。
【００５６】
レターデーション値とは、光学異方性層の法線方向から入射した光に対する面内のレターデーション値を意味する。具体的には、下記式により定義される値である。
レターデーション値（Ｒｅ）＝（ｎｘ−ｎｙ）×ｄ
式中、ｎｘおよびｎｙは光学異方性層の面内の主屈折率であり、そしてｄは光学異方性層の厚み（ｎｍ）である。
【００５７】
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。
【００５８】
［位相差板の構成］
図１は、棒状液晶性化合物を用いた場合の本発明の位相差板の代表的な構成を示す模式図である。図１に示すように、基本的な位相差板は、長尺状の透明支持体（Ｓ）および第１の光学異方性層（Ａ）に加えて、さらに第２の光学異方性層（Ｂ）を有する。第１の光学異方性層（Ａ）の位相差はπである。第２の光学異方性層（Ｂ）の位相差は、π／２である。透明支持体（Ｓ）の長手方向と第１の光学異方性層（Ａ）の遅相軸（ａ）とのなす角は３０°である。第２の光学異方性層（Ｂ）の遅相軸（ｂ）と第１の光学異方性層（Ａ）の遅相軸（ａ）との角度（γ）は６０゜である。図１に示す第１光学異方性層（Ａ）および第２光学異方性層（Ｂ）は、それぞれ棒状液晶性化合物（ｃ１およびｃ２）を含む。棒状液晶性化合物ｃ１およびｃ２は水平に配向している。棒状液晶性化合物の長軸方向が光学異方性層の遅相軸（ａおよびｂ）に相当する。
【００５９】
なお、図１では、便宜のため、透明支持体Ｓにより近い位置にあるのが光学異方性層Ａ（位相差がπ）で、その外側に位置するのが光学異方性層Ｂ（位相差がπ／２）である位相差板および円偏光板の構成を示したが、光学異方性層Ａと光学異方性層Ｂとの位置を入れ替えた構成であってもよいが、好ましくは、透明支持体Ｓにより近い位置に光学異方性層Ａ（位相差がπ）、その外側に光学異方性層Ｂ（位相差がπ／２）が位置する構成である。
図２においても同様である。
【００６０】
［円偏光板］
本発明の位相差板は、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、位相差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。
【００６１】
［円偏光板の構成］
図２は、棒状液晶性化合物を用いた場合の本発明の位相差板を用いた円偏光板の代表的な構成を示す模式図である。図２に示す円偏光板は、図１に示した透明支持体（Ｓ）、第１光学異方性層（Ａ）および第２光学異方性層（Ｂ）に加えて、さらに偏光膜（Ｐ）を有する。偏光膜の偏光透過軸（ｐ）は透明支持体（Ｓ）の長手方向（ｓ）のなす角は４５°であり、偏光透過軸と光学異方性層（Ａ）の遅相軸（ａ）のなす角は１５°であり、図１と同様に、光学異方性層（Ａ）の遅相軸（ａ）と光学異方性層（Ｂ）の遅相軸（ｂ）とのなす角は６０°である。図２に示す第１光学異方性層（Ａ）および第２光学異方性層（Ｂ）も、それぞれ棒状液晶性化合物（ｃ１およびｃ２）を含む。棒状液晶性化合物（ｃ１およびｃ２）は、それぞれ水平に配向している。棒状液晶性化合物（ｃ１およびｃ２）の長軸方向が、光学異方性層（ＡおよびＢ）の面内の遅相軸（ａおよびｂ）に相当する。
【００６２】
本発明の位相差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。本発明の位相差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。
【００６３】
本発明に用いられる４５°偏光板は、偏光の吸収軸すなわち延伸軸が長手方向に対して４５゜傾斜しており、この角度がＬＣＤにおける液晶セルに貼り合わせる際の偏光板の吸収軸と、液晶セル自身の縦または横方向とのなす角度に一致しているため、打ち抜き工程において斜めの打ち抜きは不要となる。しかも、前記斜め延伸方法によって作製された偏光板は切断が長手方向に沿って一直線であるため、打ち抜かず長手方向に沿ってスリットすることによっても製造可能であるため、生産性も格段に優れている。
【００６４】
前記斜め延伸方法によって製造された偏光膜は、そのままの形態で偏光板として本発明の位相差板に用いることもできるが、両面あるいは片面に保護フィルムを貼り付けた形態のものを偏光板として用いるのが好ましい。保護フィルムの種類は特に限定されず、セルロースアセテート、セルロースアセテートブチレート、セルロースプロピオネート等のセルロースエステル類、ポリカーボネート、ポリオレフィン、ポリスチレン、ポリエステル等を用いることができるが、保護フィルムのレターデーション値が一定値以上であると、偏光軸と保護フィルムの配向軸が斜めにずれているため、直線偏光が楕円偏光に変化し、好ましくない。このため保護フィルムのレターデーションは低いことが好ましい。例えば、６３２．８ｎｍにおいて１０ｎｍ以下が好ましく、５ｎｍ以下がさらに好ましい。このような低レターデーションを得るためには、保護フィルムとして使用するポリマーはセルローストリアセテートが特に好ましい。また、ゼオネックス、ゼオノア（共に日本ゼオン（株）製）、ＡＲＴＯＮ（ＪＳＲ（株）製）のようなポリオレフィン類も好ましく用いられる。その他、例えば特開平８−１１０４０２号公報あるいは特開平１１−２９３１１６号公報に記載されているような非複屈折性光学樹脂材料が挙げられる。
【００６５】
偏光膜と保護層との接着剤は特に限定されないが、ＰＶＡ系樹脂（アセトアセチル基、スルホン酸基、カルボキシル基、オキシアルキレン基等の変性ＰＶＡを含む）やホウ素化合物水溶液等が挙げられ、中でもＰＶＡ系樹脂が好ましい。接着剤層厚みは、乾燥後に０．０１〜１０μｍが好ましく、０．０５〜５μｍが特に好ましい。
【００６６】
本発明に用いる偏光板は、液晶表示装置のコントラストを高める観点から、透過率は高い方が好ましく、偏光度は高い方が好ましい。透過率は好ましくは５５０ｎｍで３０％以上が好ましく、４０％以上がさらに好ましい。偏光度は５５０ｎｍで９５．０％以上が好ましく、９９％以上がさらに好ましく、特に好ましくは９９．９％以上である。
【００６７】
偏光膜は、上記した様に、一般に両側に保護膜を有するが、本発明では、本発明の位相差板を偏光膜の片側の保護膜として機能させることができる。４５°偏光膜を用いて円偏光板を作製する場合、重ね合わせ方を変えることで容易に右および左円偏光板を作り分けることができる。
［円偏光板の構成］
図４に本発明の位相差板を用いた円偏光板の一態様の概略断面図を示す。
図４に示す円偏光板は、本発明の位相差版に４５°偏光膜Ｐおよび保護膜Ｇを積層した構成である。位相差板は、光学異方性層ＡおよびＢ（但し、図中には一層として示した）と、透明支持体Ｓとからなる。位相差板は、透明支持体Ｓの光学異方性層ＡおよびＢが設けられていない側の面を、４５°偏光膜Ｐに向けて積層されている。この構成において、前記位相差板は４５°偏光膜Ｐの保護膜としても機能する。図４中に、透明支持体Ｓの長手方向ｓと、光学異方性層ＡおよびＢの遅相軸ａおよびｂと、４５°偏光膜Ｐの透過軸ｐとの関係を併せて示す。
【００６８】
図４の円偏光板を表示装置に組み込む場合は、保護膜Ｐ側を表示面側にする（図中の矢印で示す方向が見る方向を示す）。図４の構成から得られる円偏光板は右円偏光である。図４中、矢印方向から入射した光は、偏光膜Ｐ、光学異方性層ＡおよびＢを順次通過することによって右円偏光となって出射する。
【００６９】
本発明の位相差版を用いた円偏光板の他の構成の概略断面図を図５に示す。図５に示す円偏光板は、図４に示す円偏光板の保護膜Ｇと位相差板の位置を代えた構成であり、図５中下方から、保護膜Ｇ、４５°偏光膜Ｐ、透明支持体Ｓおよび光学異方性層ＡおよびＢを積層した構成である。かかる構成の円偏光板では左円偏光が得られる。
この様に、４５°偏光膜に、保護層と位相差板を貼り合わせる場合に、上下を入れ替えて貼り合せるだけで右円偏光と左円偏光を製造することができる。
【００７０】
透明支持体とは別に保護膜を用いる場合は、保護膜として光学的等方性が高いセルロースエステルフィルム、特にトリアセチルセルロースフィルムを用いることが好ましい。
【００７１】
本発明の円偏光板は、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、広帯域λ／４板であるのが好ましい。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より好ましく、０．２２〜０．２８の範囲内であることがさらに好ましく、０．２３〜０．２７の範囲内であることが特に好ましく、０．２４〜０．２６の範囲内であることが最も好ましい。
【００７２】
【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。
［実施例１］
（位相差フィルムの作製）
厚さ８０μｍ、幅６８０ｍｍ、長さ５００ｍの光学的に等方性のトリアセチルセルロースフィルム（酢化度６０．９±０．２％、レターデーション値６．０ｎｍ）を透明支持体として用いた。この透明支持体の両面をケン化処理した後、下記組成の配向膜塗布液Ａ（ＮＨ４ＯＨでｐＨを４〜５に調整）を透明支持体の片面に連続的に塗布、乾燥し、厚さ１μｍの配向膜を形成した。次いで、透明支持体の長手方向に対し３０°の方向に連続的に配向膜上にラビング処理を実施した。
【００７３】
配向膜塗布液Ａ組成
下記の変性ポリビニルアルコール ４質量％
水 ７２．６質量％
メタノール ２３．３質量％
グルタールアルデヒド ０．２質量％
【００７４】
【化８】

【００７５】
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、さらに照射量として大気雰囲気下で６００ｍＪ／ｃｍ²紫外線照射して厚さ２．０μｍの光学的異方性層（Ａ）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。５５０ｎｍにおけるレターデーション値（Ｒｅ５５０）は２５０ｎｍであった。
光学異方性層（Ａ）用塗布液組成
本明細書中の棒状液晶性化合物（例示化合物 Ｉ−４） 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％
本明細書中の例示化合物（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％
【００７６】
増感剤 Ａ
【化９】

【００７７】
光重合開始剤 Ｂ
【化１０】

【００７８】
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°になるように連続的に光学的異方性層（Ａ）上にラビング処理を施した。
【００７９】
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ラビング処理後に巻き取らずに連続的に塗布、乾燥、および加熱（配向熟成）し、さらに窒素雰囲気下で照射量６００ｍＪ／ｃｍ²紫外線照射して厚さ１．０μｍの光学的異方性層（Ｂ）を形成し、位相差板（λ／４板）を作製した。５５０ｎｍにおける平均レターデーション値（Ｒｅ５５０）は１３１ｎｍであった。
光学異方性層（Ｂ）用塗布液組成
本発明の棒状液晶性化合物（例示化合物 Ｉ−４） ３８．４質量％
増感剤 Ａ ０．３８質量％
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％
【００８０】
配向制御剤 Ｃ
【化１１】

【００８１】
（偏光膜の調整）
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２の形態の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特開２００２−８６５５４号公報の図２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。
【００８２】
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。さらに３１０×２３３ｍｍサイズに裁断したところ、９１．５％の面積効率で辺に対し４５゜吸収軸が傾斜した偏光板を得ることができた。
【００８３】
（円偏光板の作製）
図５のように、上記で作製したヨウ素系偏光フィルム９１の片面上に先に作製した位相差板９６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９７を貼り合わせて、円偏光板９２を作製した。偏光板の作製においては、偏光膜と位相差板の長手方向が一致するように貼り合わせて、円偏光板を作製した。
【００８４】
（反射型液晶表示装置の作製）
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）の偏光板と位相差板を剥ぎとり、代わりに先に作製した円偏光板９２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、白表示、黒表示、そして中間調のいずれにおいても、傷や剥がれ起因のムラは観察されず、色味のないニュートラルグレーが表示されていることがわかった。
【００８５】
［参考例２］
実施例１において、光学的異方性層（Ａ）の重合時の照射量を１００ｍＪ／ｃｍ²とし、光学異方性層（Ｂ）の重合時の雰囲気を大気雰囲気とし、さらに照射量を１００ｍＪ／ｃｍ²とした以外は、実施例１と全く同様にして位相差板および引き続き円偏光板を作製し、該円偏光板を用いて、同様にして反射型液晶表示装置を作製した。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、白表示、黒表示、そして中間調のいずれにおいても、剥がれ起因のムラはないものの傷起因のムラが観察された。
【００８６】
［比較例１］
実施例１において、光学異方性層（Ａ）の重合時の雰囲気を窒素雰囲気とした以外は実施例１と全く同様にして位相差板および引き続き円偏光板を作製し、該円偏光板を用いて、同様にして反射型液晶表示装置を作製した。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、白表示、黒表示、そして中間調のいずれにおいても、傷起因のムラは無いものの剥がれ起因のムラが観察された。
【００８７】
［比較例２］
実施例１において、光学異方性層（Ａ）の重合時の雰囲気を窒素雰囲気とし、さらに光学異方性層（Ｂ）の重合時の雰囲気を大気雰囲気とするとともに、照射量を１００ｍＪ／ｃｍ²とした以外は、実施例１と全く同様にして位相差板および引き続き円偏光板を作製し、該円偏光板を用いて反射型液晶表示装置を作製した。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、白表示、黒表示、そして中間調のいずれにおいても、傷起因のムラおよび剥がれ起因のムラの両方が観察された。
【００８８】
［比較例３］
実施例１において、光学異方性層（Ｂ）の重合時に照射量を４００ｍＪ／ｃｍ²とした以外は実施例１と全く同様にして位相差板および引き続き円偏光板を作製し、該円偏光板を用いて反射型液晶表示装置を作製した。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、白表示、黒表示、そして中間調のいずれにおいても、傷起因のムラは無いものの剥がれ起因のムラが観察された。
【００８９】
実施例１及び比較例１〜４で作製した位相差板について、引っ掻き硬度を荷重針法で測定した結果、および作製した反射型液晶表示装置の観察結果を表１に示した。尚、引っ掻き硬度測定は新東科学（株）製 連続荷重式 引掻強度試験機（ＴＹＰＥ ＨＥＩＤＯＮ１８）を用いて、ダイヤモンド製先端角９０°、Ｒ＝０．０２５ｍｍの針を使用して実施し、連続して層の剥離が発生し始める荷重を限界荷重として測定した。
【００９０】
【表１】

【００９１】
表１に示す結果より、積層状態での限界荷重が大きく、下層より上層の硬度が高い方が、反射型液晶表示装置とした場合に膜剥がれ起因の表示ムラが少ないことがわかる。また。傷起因のムラについても上層の引っかき硬度が３５ｇ以上で発生が抑えられることがわかる。従って本発明の効果は明らかである。
【００９２】
【発明の効果】
本発明によれば、密着性に優れ、傷・剥がれが少なく、且つ安価に作製可能な位相差板およびその製造方法、ならびにそれを用いた円偏光板を提供することができる。
【図面の簡単な説明】
【図１】 本発明の位相差板の基本的な構成を示す模式図である。
【図２】 本発明の位相差板を用いた円偏光板の基本的な構成を示す模式図である。
【図３】 本発明の位相差板を用いた円偏光板の層構成の一例を示す概略断面図である。
【図４】 本発明の位相差板を用いた円偏光板の層構成の他の例を示す概略断面図である。
【図５】 実施例で作製した円偏光板の層構成を示す概略断面図である。
【符号の説明】
Ｓ 透明支持体
Ｇ 保護膜
Ｐ 偏光膜
Ａ 第１の光学異方性層
Ｂ 第２の光学異方性層
ｓ 透明支持体の長手方向
ａ 第１の光学異方性層の遅相軸
ｂ 第２の光学異方性層の遅相軸
ｐ 偏光膜の透過軸
ｃ１ 棒状液晶性化合物
ｃ２ 棒状液晶性化合物
９１ 実施例１で作製した偏光膜
９２ 実施例１の位相差板を用いた円偏光板
９６ 実施例１で作製した位相差板
９７ 防眩性反射防止フィルム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a retardation plate having an optically anisotropic layer composed of at least two liquid crystal compounds and a method for producing the same. The present invention also provides a retardation plate obtained by the above method, in particular, a λ / 4 plate used for at least a reflective liquid crystal display device, a transflective liquid crystal display device, an optical disk writing pickup, or an antireflection film. The present invention relates to an effective retardation plate and a circularly polarizing plate using the same.
[0002]
[Prior art]
The retardation plate targeted by the present invention, especially the λ / 4 plate, has a great many applications and has already been used in practice. Conventional techniques capable of achieving λ / 4 in a wide wavelength region include a method of laminating two polymer films having optical anisotropy (see, for example, Patent Documents 1 and 2), and an optical anisotropic including a liquid crystalline compound. There is a method of providing at least two layers (for example, see Patent Documents 3 to 6). However, in the method of laminating two polymer films having optical anisotropy, in order to adjust the optical orientation (optical axis and slow axis) of the two polymer films, two kinds of polymer films are provided in a predetermined manner. It is necessary to cut the angle and paste the resulting chips together. If a phase difference plate is manufactured by bonding chips, the process is complicated, the quality is likely to deteriorate due to axial misalignment, the yield decreases, the cost increases, and deterioration due to contamination is likely to occur. In addition, it is difficult for the polymer film to strictly adjust the retardation value required for the λ / 4 plate. On the other hand, the method of providing at least two optically anisotropic layers containing a liquid crystalline compound does not require cutting or bonding at an oblique angle with respect to the transport direction, and is long by applying continuously. A broadband λ / 4 plate can be provided in the form of. However, in order to handle continuously, considerable scratch resistance and interlayer adhesion are required, and until now, sufficient scratch resistance and adhesion have not been obtained, so there is a problem that scratches or film peeling occurs. there were. In particular, when the adhesiveness is low, there is a problem that it is difficult to reuse the cell because it cannot be peeled off again at the interface between the retardation plate and the cell after being once bonded to the liquid crystal cell.
[0003]
[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]
JP 2001-4837 A
[Patent Document 5]
JP 2001-21720 A
[Patent Document 6]
Japanese Patent Laid-Open No. 2001-91741
[0004]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problem, that is, an inexpensive phase difference plate having two or more optically anisotropic layers made of a liquid crystalline compound, excellent adhesion, and less scratching / peeling. And a manufacturing method thereof, and a circularly polarizing plate using the same.
[0005]
[Means for Solving the Problems]
The problems of the present invention have been solved by the following method. That is, it was achieved by the following retardation plates (1) and (2), the production method (3), and the circularly polarizing plate (4).
(1) The process of polymerizing and forming an optically anisotropic layer after applying a composition containing a liquid crystalline compound having a polymerizable group on the orientation-treated surface side of the orientation-treated transparent support is repeated at least twice. A retardation plate manufactured by the method, wherein the optical anisotropic layer on the side far from the transparent support is higher in hardness than the optical anisotropic layer on the side.
(2) The phase difference plate according to (1), wherein the scratch strength by the load needle method in the laminated state is 30 g or more when a diamond needle having a tip angle of 90 ° and a tip curvature of 0.025 mm is used.
(3) The process of forming an optically anisotropic layer by applying a composition containing a liquid crystalline compound having a polymerizable group on the orientation-treated surface side of the orientation-treated transparent support is repeated at least twice. A method for producing a retardation plate, wherein the hardness of the optically anisotropic layer far from the transparent support when the optically anisotropic layer is cured is greater than the hardness of the optically anisotropic layer closer to the transparent support. A method for producing a retardation plate, wherein the retardation plate is cured so as to be high.
(4) A circularly polarizing plate having at least the retardation plate according to (1) or (2) and a polarizing film.
[0006]
In the present specification, “substantially” for the angle means that the angle is within a range of a strict angle of less than ± 5 °. The error from the exact angle is preferably less than 4 °, more preferably less than 3 °. Further, the “slow axis” means a direction in which the refractive index is maximized.
In this specification, “substantially vertically oriented” does not mean only strictly vertical orientation, but includes orientation within an average angle (average inclination angle) of 50 ° to 90 °. The “substantially horizontally oriented” does not mean only a strict horizontal orientation, but includes an orientation having an average angle (average inclination angle) in the range of 0 ° to 40 °.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
[Method for producing retardation plate]
The phase difference plate of the present invention is a step of forming an optically anisotropic layer by applying a composition containing a liquid crystal compound having a polymerizable group on the orientation-treated surface side of the orientation-treated transparent support and then polymerizing the composition. Is repeated at least twice. An example of the production method of the present invention is to continuously move a long roll-shaped transparent support, and apply an alignment film on the transparent support,
(A) rubbing the surface of the support on which the alignment film is formed (preferably using at least one rubbing roller),
(B) applying a composition containing a liquid crystal compound on the rubbed surface;
(C) After heating the liquid crystal to take a predetermined alignment state,
(D) The composition applied in step (b) is polymerized (preferably polymerized and / or crosslinked by exposure to heat or actinic radiation in air or nitrogen atmosphere) to form an optically anisotropic layer. ,
(D) Steps (a) to (d) are repeated at least once, and finally
(E) winding up the support;
It is a manufacturing method including the above process.
[0008]
Hereinafter, each process and various materials used in each process will be described in more detail.
[Transparent support]
In the present invention, a transparent support is used. The transparent support means a support having a light transmittance of 80% or more. Further, the wavelength dispersion of the transparent support is preferably small, and specifically, the ratio of Re400 / Re700 is preferably less than 1.2. Further, the transparent support preferably has a small optical anisotropy. Specifically, the in-plane retardation (Re) is preferably 20 nm or less, and more preferably 10 nm or less.
[0009]
The transparent support is preferably a polymer film. Examples of the polymer include cellulose ester, polycarbonate, polysulfone, polyethersulfone, polyacrylate and polymethacrylate. Cellulose esters are preferred, acetyl cellulose is more preferred, and triacetyl cellulose is most preferred. In particular, when triacetyl cellulose is used, one having an acetylation degree of 60.25 to 61.50 is preferable. The polymer film is preferably formed by a solvent cast method.
[0010]
In this invention, it is preferable to apply | coat an optically anisotropic layer continuously using a long roll-shaped support body. After forming the optically anisotropic layer, it can be cut into the required size. The thickness of the transparent support is preferably 20 to 500 μm, and more preferably 40 to 200 μm. In addition, in order to improve the adhesion between the transparent support and the layer (adhesive layer, horizontal alignment film, vertical alignment film or optically anisotropic layer) provided thereon, surface treatment (eg, glow discharge treatment) is applied to the transparent support. , Corona discharge treatment, ultraviolet (UV) treatment, flame treatment, saponification treatment) may be carried out, or an adhesive layer (undercoat layer) may be provided on the transparent support. The surface treatment is preferably saponification treatment.
[0011]
[Alignment film]
In the present invention, a support having an alignment film on the surface is used. When the transparent support is in the form of a roll, it is preferable to form an alignment film on the surface of the support while continuously moving the transparent support. The alignment film has a function of bringing the liquid crystalline compound in the optically anisotropic layer into a desired alignment state. As the alignment film, an alignment film that generates an alignment function by rubbing 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 crystal compound parallel to the rubbing direction and horizontally, a polymer that does not reduce 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. In addition, in order to align the liquid crystal compound in a direction orthogonal to the rubbing direction and horizontally, a polyvinyl alcohol-based alignment film disclosed in Japanese Patent Application No. 2000-246279 or a polyamic acid-based alignment film disclosed in Japanese Patent Application No. 2000-64626 is used. It may be used.
The rubbing treatment can change the alignment direction of the liquid crystal compound with respect to the longitudinal direction of the support and the tilt angle of the liquid crystal compound with respect to the film plane by rubbing the surface of these polymer layers several times in a certain direction with paper or cloth.
[0012]
For the purpose of improving the adhesion with the liquid crystal compound layer formed above, the alignment film preferably has a polymerizable group. 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. It is more preferable to use an alignment film that forms a chemical bond with the liquid crystalline compound at the interface. 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.
[0013]
It is preferable to rub the surface of the alignment film formed on the surface of the transparent support or the optically anisotropic layer formed through the steps (a) to (d) (the step (d)).
[Rubbing]
The rubbing treatment can be performed at a predetermined arbitrary angle with respect to the conveying direction of the long roll-shaped support. The angle of the rubbing direction with respect to the transport direction is preferably rubbed in the same direction or an oblique direction with respect to the transport direction. The angle in the oblique direction is preferably in the range of −45 degrees to +45 degrees.
The rubbing treatment can be performed by any method, but it is preferably performed by at least one rubbing roll. For example, on a stage that transports a long film in the transport direction, a rubbing roll is arranged at an arbitrary angle with respect to the transport direction of the long film, and the rubbing roll is rotated while transporting the film in the transport direction. The alignment film surface of the transparent support can be rubbed. It is preferable to provide a mechanism that can freely adjust the angle formed by the rubbing roll and the moving direction of the stage. The rubbing roll refers to a roll having an appropriate rubbing cloth material attached to the surface.
[0014]
Next, a composition containing a liquid crystal compound is applied to the rubbed surface (step (b)), and heated to bring the liquid crystal in the composition into a predetermined alignment state (step (c)). ), Polymerized and / or crosslinked by exposure to heat or actinic radiation in an air or nitrogen atmosphere to form an optically anisotropic layer (step (d)).
[0015]
[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.
[0016]
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.
[0017]
[Chemical 1]

[0018]
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.
[0019]
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-
[0020]
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-
[0021]
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.
[0022]
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.
[0023]
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
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
Examples of liquid crystal compounds having a polymerizable group represented by formula (I) are shown below. The present invention is not limited to these.
[0028]
[Chemical formula 2]

[0029]
[Chemical 3]

[0030]
[Formula 4]

[0031]
[Chemical formula 5]

[0032]
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.
[0033]
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.
[0034]
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.
[0035]
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 changed so that the inclination angle gradually changes (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 oriented obliquely or may be changed so that the inclination angle gradually changes (hybrid orientation). Even in the case of oblique orientation or hybrid orientation, the average inclination angle is preferably 50 ° to 90 °.
[0036]
The retardation plate of the present invention 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.
[0037]
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%).
[0038]
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).
[0039]
[Chemical 6]

[0040]
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.
[0041]
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-
[0042]
Specific examples of HyD are shown below.
[0043]
[Chemical 7]

[0044]
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.
[0045]
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−
[0046]
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%.
[0047]
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.
[0048]
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-diisocyanatododecane
Isophorone diisocyanate
Glioquizal
[0049]
In the present invention, the optically anisotropic layer is formed by coating the rubbing surface with a coating solution prepared by dissolving the liquid crystalline compound, and optionally the modified polyvinyl alcohol, and the following polymerization initiator and other additives in a solvent. Is preferably formed. As the 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).
[0050]
[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).
[0051]
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.
[0052]
[Hardness of optically anisotropic layer]
The retardation plate of the present invention is characterized in that the optically anisotropic layer on the far side is higher in hardness than the optically anisotropic layer on the side close to the transparent support. In the present specification, “hardness” is shown as the weight of a critical load at which peeling of a layer starts to start continuously when tested using a continuous load type scratch strength tester. The difference in hardness between the optically anisotropic layer on the side farther from the transparent support and the optically anisotropic layer on the closer side is indicated by the difference in the critical load measured for both layers. For each of the optically anisotropic layer on the side far from the support and the optically anisotropic layer on the near side, a diamond tip angle of 90 using a continuous load type scratch strength tester (TYPEEIDON18) manufactured by Shinto Kagaku Co., Ltd. ° When the test was conducted with a needle having a tip curvature (R) of 0.025 mm, the difference in the critical load between the optically anisotropic layer far from the support and the optically anisotropic layer closer to the support was 5 g or more. It is preferable that it is 10 g or more. If it is lower than 5 g, the effect for preventing film peeling is reduced, and the optically anisotropic layer may be easily peeled off. The upper limit is preferably 100 g or less. On the other hand, if it exceeds 100 g, problems such as easy cracking and poor bending resistance may occur. Particularly preferably, it is 80 g or less.
[0053]
In addition, the retardation plate of the present invention preferably has a hardness of 30 g or more in a state where the optically anisotropic layer is laminated. That is, for the retardation plate of the present invention, when the scratch test is performed by the scratch strength tester, the limit load at which the laminated optically anisotropic layer starts to peel continuously is 30 g or more. Is preferred. More preferably, it is 40 g or more. Even in the laminated state, if the hardness is lower than 30 g, it may be easily damaged, or an adhesion failure may occur in the wound roll. The upper limit is preferably 100 g or less. On the other hand, if it exceeds 100 g, problems such as easy cracking and poor bending resistance may occur. In particular, this is preferably 80 g or less.
[0054]
The hardness of each optically anisotropic layer and the hardness in the laminated state are the temperature and humidity and oxygen concentration (or nitrogen substitution rate) of the atmosphere during curing (polymerization), the irradiation amount of ultraviolet rays, the sample temperature during irradiation, It can be appropriately adjusted depending on the polyfunctionalization of the liquid crystal compound, the type and amount of the polymerization initiator, and the type and amount of the sensitizer.
[0055]
[Optical properties of retardation plate]
It is preferable that the optically anisotropic layer constituting the retardation 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 290 nm. The other optically anisotropic layer (second optically anisotropic layer) preferably has a retardation value measured at a wavelength of 550 nm of 110 to 145 nm, preferably 120 to 280 nm. More preferably, it is 140 nm.
[0056]
The retardation value means an in-plane retardation value for light incident from the normal direction of the optically anisotropic layer. Specifically, it is a value defined by the following formula.
Retardation value (Re) = (nx−ny) × d
Where nx and ny are the in-plane main refractive indices of the optically anisotropic layer, and d is the thickness (nm) of the optically anisotropic layer.
[0057]
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.
[0058]
[Configuration of retardation plate]
FIG. 1 is a schematic diagram showing a typical configuration of the retardation plate of the present invention when a rod-like liquid crystalline compound is used. As shown in FIG. 1, in addition to the long transparent support (S) and the first optical anisotropic layer (A), the basic retardation plate further includes a second optical anisotropic layer. (B). The phase difference of the first optically anisotropic layer (A) is π. The retardation of the second optical anisotropic layer (B) is π / 2. The angle formed by the longitudinal direction of the transparent support (S) and the slow axis (a) of the first optically anisotropic layer (A) is 30 °. The angle (γ) between the slow axis (b) of the second optical anisotropic layer (B) and the slow axis (a) of the first optical anisotropic layer (A) is 60 °. The first optical anisotropic layer (A) and the second optical anisotropic layer (B) shown in FIG. 1 each contain a rod-like liquid crystalline compound (c1 and c2). The rod-like liquid crystal compounds c1 and c2 are horizontally aligned. The major axis direction of the rod-like liquid crystal compound corresponds to the slow axis (a and b) of the optically anisotropic layer.
[0059]
In FIG. 1, for convenience, the optically anisotropic layer A (having a phase difference of π) is located closer to the transparent support S, and the optically anisotropic layer B (positional phase) is located on the outer side thereof. Although the configuration of the retardation plate and the circularly polarizing plate having a phase difference of π / 2) is shown, a configuration in which the positions of the optically anisotropic layer A and the optically anisotropic layer B are interchanged may be preferable. Is a configuration in which the optically anisotropic layer A (having a phase difference of π) is located closer to the transparent support S, and the optically anisotropic layer B (having a phase difference of π / 2) is located outside thereof.
The same applies to FIG.
[0060]
[Circularly polarizing plate]
The retardation 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 retardation 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.
[0061]
[Configuration of Circular Polarizing Plate]
FIG. 2 is a schematic diagram showing a typical configuration of a circularly polarizing plate using the retardation plate of the present invention when a rod-like liquid crystal compound is used. In addition to the transparent support (S), the first optical anisotropic layer (A) and the second optical anisotropic layer (B) shown in FIG. P). The polarizing transmission axis (p) of the polarizing film has an angle formed by the longitudinal direction (s) of the transparent support (S) of 45 °, and the slow axis (a) of the polarizing transmission axis and the optically anisotropic layer (A). The angle between the slow axis (a) of the optically anisotropic layer (A) and the slow axis (b) of the optically anisotropic layer (B) is the same as in FIG. Is 60 °. The first optical anisotropic layer (A) and the second optical anisotropic layer (B) shown in FIG. 2 also contain rod-like liquid crystalline compounds (c1 and c2), respectively. The rod-like liquid crystal compounds (c1 and c2) are horizontally aligned. The major axis direction of the rod-like liquid crystal compounds (c1 and c2) corresponds to the in-plane slow axis (a and b) of the optically anisotropic layer (A and B).
[0062]
There is no restriction | limiting in particular about the polarizing film combined with the phase difference plate of this invention, The dye type polarizing film and polyene type polarizing film using an iodine type polarizing film, a dichroic dye can be used. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The polarizing film is preferably laminated so that the transmission axis of the polarizing film is 45 ° with respect to the longitudinal direction of the transparent support of the retardation 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.
[0063]
In the 45 ° polarizing plate used in the present invention, the absorption axis of polarized light, that is, the stretching axis is inclined by 45 ° with respect to the longitudinal direction, and this angle is the absorption axis of the polarizing plate when bonded to the liquid crystal cell in the LCD, Since the angle coincides with the vertical or horizontal direction of the liquid crystal cell itself, oblique punching is not necessary in the punching process. Moreover, since the polarizing plate produced by the oblique stretching method is straight along the longitudinal direction, and can be manufactured by slitting along the longitudinal direction without punching, the productivity is remarkably excellent. Yes.
[0064]
The polarizing film produced by the oblique stretching method can be used as it is for the retardation plate of the present invention as a polarizing plate, but a polarizing plate having a protective film attached on both sides or one side is used. Is preferred. The type of protective film is not particularly limited, and cellulose esters such as cellulose acetate, cellulose acetate butyrate, and cellulose propionate, polycarbonate, polyolefin, polystyrene, polyester, and the like can be used. If the value is above a certain value, the polarization axis and the orientation axis of the protective film are obliquely shifted, so that the linearly polarized light changes to elliptically polarized light, which is not preferable. For this reason, it is preferable that the retardation of a protective film is low. For example, at 632.8 nm, it is preferably 10 nm or less, and more preferably 5 nm or less. In order to obtain such low retardation, the polymer used as the protective film is particularly preferably cellulose triacetate. Polyolefins such as ZEONEX, ZEONOR (both manufactured by Nippon Zeon Co., Ltd.) and ARTON (manufactured by JSR Co., Ltd.) are also preferably used. Other examples include non-birefringent optical resin materials as described in JP-A-8-110402 or JP-A-11-293116.
[0065]
The adhesive between the polarizing film and the protective layer is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm, and particularly preferably 0.05 to 5 μm after drying.
[0066]
From the viewpoint of increasing the contrast of the liquid crystal display device, the polarizing plate used in the present invention preferably has a higher transmittance and a higher degree of polarization. The transmittance is preferably 30% or more at 550 nm, and more preferably 40% or more. The degree of polarization is preferably 95.0% or more at 550 nm, more preferably 99% or more, and particularly preferably 99.9% or more.
[0067]
As described above, the polarizing film generally has protective films on both sides, but in the present invention, the retardation plate of the present invention can function as a protective film on one side of the polarizing film. When a circularly polarizing plate is produced using a 45 ° polarizing film, the right and left circularly polarizing plates can be easily made separately by changing the way of superposition.
[Configuration of Circular Polarizing Plate]
FIG. 4 shows a schematic cross-sectional view of one embodiment of a circularly polarizing plate using the retardation plate of the present invention.
The circularly polarizing plate shown in FIG. 4 has a structure in which a 45 ° polarizing film P and a protective film G are laminated on the retardation plate of the present invention. The retardation plate is composed of optically anisotropic layers A and B (shown as one layer in the drawing) and a transparent support S. The phase difference plate is laminated so that the surface of the transparent support S on which the optically anisotropic layers A and B are not provided is directed to the 45 ° polarizing film P. In this configuration, the retardation plate also functions as a protective film for the 45 ° polarizing film P. FIG. 4 also shows the relationship among the longitudinal direction s of the transparent support S, the slow axes a and b of the optically anisotropic layers A and B, and the transmission axis p of the 45 ° polarizing film P.
[0068]
When the circularly polarizing plate of FIG. 4 is incorporated in a display device, the protective film P side is set to the display surface side (the direction indicated by the arrow in the figure indicates the viewing direction). The circularly polarizing plate obtained from the configuration of FIG. 4 is right circularly polarized light. In FIG. 4, the light incident from the direction of the arrow passes through the polarizing film P and the optically anisotropic layers A and B in sequence, and is emitted as right circularly polarized light.
[0069]
FIG. 5 shows a schematic cross-sectional view of another configuration of a circularly polarizing plate using the retardation plate of the present invention. The circularly polarizing plate shown in FIG. 5 has a configuration in which the positions of the protective film G and the retardation plate of the circularly polarizing plate shown in FIG. 4 are changed. From the lower side in FIG. The support S and the optically anisotropic layers A and B are laminated. With the circularly polarizing plate having such a configuration, left circularly polarized light is obtained.
As described above, when the protective layer and the retardation plate are bonded to the 45 ° polarizing film, the right circularly polarized light and the left circularly polarized light can be manufactured simply by switching the upper and lower layers.
[0070]
When a protective film is used separately from the transparent support, it is preferable to use a cellulose ester film having high optical isotropy, particularly a triacetyl cellulose film, as the protective film.
[0071]
The circularly polarizing plate of the present invention is a broadband λ / 4 plate in which retardation values / wavelength values measured at wavelengths of 450 nm, 550 nm, and 650 nm are all in the range of 0.2 to 0.3. preferable. The retardation value / wavelength value is more preferably in the range of 0.21 to 0.29, further preferably in the range of 0.22 to 0.28, and 0.23 to 0.27. Is particularly preferably within the range of 0.24 to 0.26.
[0072]
【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. .
[Example 1]
(Production of retardation film)
An optically isotropic triacetylcellulose film (acetylation degree 60.9 ± 0.2%, retardation value 6.0 nm) having a thickness of 80 μm, a width of 680 mm, and a length of 500 m was used as a transparent support. After saponifying both surfaces of this transparent support, an alignment film coating solution A (with pH adjusted to 4 to 5 with NH4OH) was continuously applied to one side of the transparent support and dried, and the thickness was 1 μm. An alignment film was formed. Next, a rubbing treatment was performed on the alignment film continuously in a direction of 30 ° with respect to the longitudinal direction of the transparent support.
[0073]
Alignment film coating solution A composition
4% by mass of the following modified polyvinyl alcohol
72.6% by mass of water
Methanol 23.3 mass%
Glutaraldehyde 0.2% by mass
[0074]
[Chemical 8]

[0075]
On the alignment film, a coating solution having the following composition is continuously applied using a bar coater, dried and heated (orientation aging), and the irradiation amount is 600 mJ / cm in an air atmosphere.²An optically anisotropic layer (A) having a thickness of 2.0 μm was formed by ultraviolet irradiation. The optically anisotropic layer had a slow axis in the direction of 30 ° with respect to the longitudinal direction of the transparent support. The retardation value (Re550) at 550 nm was 250 nm.
Coating liquid composition for optically anisotropic layer (A)
38.1% by mass of a rod-like liquid crystal compound (Exemplary Compound I-4) in the present specification
Sensitizer A 0.38% by mass
The following photopolymerization initiator B 1.14% by mass
Exemplary compound (PX-9) in the present specification 0.19% by mass
Glutaraldehyde 0.04% by mass
Methyl ethyl ketone 60.1% by mass
[0076]
Sensitizer A
[Chemical 9]

[0077]
Photopolymerization initiator B
[Chemical Formula 10]

[0078]
Optically continuously so that it 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 on the partially anisotropic layer (A).
[0079]
On the optically anisotropic layer (A) subjected to the rubbing treatment, a coating solution having the following composition is continuously applied, dried, and heated (orientated and matured) without being wound after the rubbing treatment using a bar coater. Furthermore, the irradiation amount is 600 mJ / cm in a nitrogen atmosphere.²An optically anisotropic layer (B) having a thickness of 1.0 μm was formed by irradiation with ultraviolet rays, and a retardation plate (λ / 4 plate) was produced. The average retardation value (Re550) at 550 nm was 131 nm.
Coating liquid composition for optically anisotropic layer (B)
Rod-shaped liquid crystalline compound of the present invention (Exemplary Compound I-4) 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%
[0080]
Orientation control agent C
Embedded image

[0081]
(Adjustment of polarizing film)
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 into the tenter stretching machine in the form of FIG. 2 of 2002-86554, stretched 5.3 times, bent the tenter with respect to the stretching direction as shown in FIG. It was kept constant and dried in an atmosphere at 80 ° C. while shrinking, and then 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.
[0082]
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%. Further, when the substrate was cut into a size of 310 × 233 mm, a polarizing plate with an absorption axis inclined by 45 ° with respect to the side with an area efficiency of 91.5% could be obtained.
[0083]
(Production of circularly polarizing plate)
As shown in FIG. 5, the retardation plate 96 prepared above is laminated on one side of the iodine polarizing film 91 prepared above, and the antiglare antireflection film 97 subjected to saponification treatment is pasted on the other side. In addition, a circularly polarizing plate 92 was produced. In the production of the polarizing plate, the polarizing film and the retardation plate were bonded so that the longitudinal directions thereof coincided to produce a circularly polarizing plate.
[0084]
(Production of reflective liquid crystal display device)
The polarizing plate and the retardation plate of a commercially available reflective liquid crystal display device (“Color Zaurus MI-310”; manufactured by Sharp Corporation) were peeled off, and the circularly polarizing plate 92 previously prepared was attached instead.
When the produced reflective liquid crystal display device was visually evaluated, no irregularities due to scratches or peeling were observed in any of white display, black display, and halftone, and neutral gray without color was displayed. I found out.
[0085]
[Reference example2]
In Example 1, the irradiation amount at the time of polymerization of the optically anisotropic layer (A) is 100 mJ / cm.²The atmosphere during polymerization of the optically anisotropic layer (B) is an air atmosphere, and the irradiation amount is 100 mJ / cm.²Except for the above, a retardation plate and a circularly polarizing plate were produced in the same manner as in Example 1, and a reflective liquid crystal display device was similarly produced using the circularly polarizing plate. When the produced reflective liquid crystal display device was visually evaluated, in any of white display, black display, and halftone, there was no unevenness due to peeling, but unevenness due to scratches was observed.
[0086]
[Comparative Example 1]
In Example 1, a retardation plate and a circularly polarizing plate were produced in the same manner as in Example 1 except that the atmosphere during polymerization of the optically anisotropic layer (A) was a nitrogen atmosphere. In the same manner, a reflective liquid crystal display device was produced. When the produced reflective liquid crystal display device was evaluated visually, in any of white display, black display, and halftone, there was no unevenness due to scratches, but unevenness due to peeling was observed.
[0087]
[Comparative Example 2]
In Example 1, the atmosphere at the time of polymerization of the optically anisotropic layer (A) is a nitrogen atmosphere, the atmosphere at the time of polymerization of the optically anisotropic layer (B) is an air atmosphere, and the irradiation amount is 100 mJ / cm.²A retardation plate and a circularly polarizing plate were produced in exactly the same manner as in Example 1, except that a reflective liquid crystal display device was produced using the circularly polarizing plate. When the produced reflective liquid crystal display device was evaluated by visual observation, both unevenness due to scratches and unevenness due to peeling were observed in any of white display, black display, and halftone.
[0088]
[Comparative Example 3]
In Example 1, the irradiation dose was 400 mJ / cm during the polymerization of the optically anisotropic layer (B).²A retardation plate and a circularly polarizing plate were produced in exactly the same manner as in Example 1, except that a reflective liquid crystal display device was produced using the circularly polarizing plate. When the produced reflective liquid crystal display device was evaluated visually, in any of white display, black display, and halftone, there was no unevenness due to scratches, but unevenness due to peeling was observed.
[0089]
Table 1 shows the results obtained by measuring the scratch hardness of the retardation plates produced in Example 1 and Comparative Examples 1 to 4 by the load needle method and the observation results of the produced reflective liquid crystal display device. In addition, the scratch hardness measurement was carried out using a continuous load type scratch strength tester (TYPE HEIDON18) manufactured by Shinto Kagaku Co., Ltd., using a diamond tip angle 90 °, R = 0.025 mm needle. The load at which delamination began to occur continuously was measured as the limit load.
[0090]
[Table 1]

[0091]
From the results shown in Table 1, it can be seen that when the limit load in the laminated state is larger and the hardness of the upper layer is higher than that of the lower layer, there is less display unevenness due to film peeling in the case of a reflective liquid crystal display device. Also. It can be seen that the occurrence of unevenness due to scratches is suppressed when the scratch hardness of the upper layer is 35 g or more. Therefore, the effect of the present invention is clear.
[0092]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it can provide the phase difference plate which is excellent in adhesiveness, there are few cracks and peeling, and can be manufactured cheaply, its manufacturing method, and a circularly-polarizing plate using the same.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a basic configuration of a retardation plate of the present invention.
FIG. 2 is a schematic diagram showing a basic configuration of a circularly polarizing plate using the retardation plate of the present invention.
FIG. 3 is a schematic cross-sectional view showing an example of a layer configuration of a circularly polarizing plate using the retardation plate of the present invention.
FIG. 4 is a schematic cross-sectional view showing another example of the layer structure of a circularly polarizing plate using the retardation plate of the present invention.
FIG. 5 is a schematic cross-sectional view showing a layer structure of a circularly polarizing plate produced in an example.
[Explanation of symbols]
S transparent support
G Protective film
P Polarizing film
A first optically anisotropic layer
B Second optically anisotropic layer
s Longitudinal direction of transparent support
a Slow axis of the first optically anisotropic layer
b Slow axis of the second optically anisotropic layer
p Transmission axis of polarizing film
c1 Rod-like liquid crystalline compound
c2 Rod-like liquid crystalline compound
91 Polarizing film produced in Example 1
92 Circularly Polarizing Plate Using Retardation Plate of Example 1
96 Phase difference plate produced in Example 1
97 Antiglare antireflection film

Claims (8)

The alignment treatment surface alignment treated transparent support, a step of forming an optically anisotropic layer is polymerized after application of the composition containing a liquid crystal compound and a photopolymerization initiator having a polymerizable group at least 2 An optically anisotropic layer on the side close to the transparent support formed by polymerizing the composition in an air atmosphere, and the composition in a nitrogen atmosphere. A transparent support formed by polymerization with a far-side optical anisotropic layer, the hardness of the far-side optical anisotropic layer closer to the transparent support being higher than the hardness of the near-side optical anisotropic layer Phase difference plate. Light of the composition used for forming the optically anisotropic layer on the side close to the transparent support is the content of the photopolymerization initiator of the composition used for forming the optically anisotropic layer on the side far from the transparent support. The retardation plate according to claim 1, wherein the retardation plate is more than the content of the polymerization initiator. The optically anisotropic layer on the side close to the transparent support contains a modified polyvinyl alcohol having a hydrocarbon group having 9 or less carbon atoms, the surface of which is subjected to rubbing treatment, and the optical on the side far from the transparent support The retardation plate according to claim 1, wherein an anisotropic layer is formed on the rubbing surface. The phase difference plate according to any one of claims 1 to 3, wherein a scratch strength by a load needle method in a laminated state is 30 g or more when a diamond needle having a tip angle of 90 ° and a tip curvature of 0.025 mm is used. . At least two steps of forming an optically anisotropic layer by applying a composition containing a liquid crystalline compound having a polymerizable group and a photopolymerization initiator to the orientation-treated surface side of the orientation-treated transparent support and then curing the composition. A method for producing a phase difference plate that is repeated several times, wherein the composition is polymerized in an air atmosphere to form an optically anisotropic layer on the side close to the transparent support, and the composition is polymerized in a nitrogen atmosphere. By forming the optically anisotropic layer far from the transparent support, the hardness of the optically anisotropic layer far from the transparent support is higher than the hardness of the optically anisotropic layer closer to the transparent support. characterized by high, method for producing a retardation plate. Light of the composition used for forming the optically anisotropic layer on the side close to the transparent support is the content of the photopolymerization initiator of the composition used for forming the optically anisotropic layer on the side far from the transparent support. The method according to claim 4, wherein the content of the polymerization initiator is larger than that of the polymerization initiator. The composition used for forming the optically anisotropic layer on the side close to the transparent support further contains a modified polyvinyl alcohol having a hydrocarbon group having 9 or less carbon atoms, and the surface of the optically anisotropic layer is 6. The method according to claim 4, wherein after the rubbing treatment, an optically anisotropic layer on the side far from the transparent support is formed on the rubbing treatment surface. The circularly-polarizing plate which has at least the phase difference plate of any one of Claims 1-4, and a polarizing film.

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