JP2004062023A - Liquid crystal display element and phase difference film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element of a vertical orientation mode, having a wide visual field angle by using a phase difference film, having a particular wavelength dispersion, and a phase difference film that can realize a wide visual field angle of a vertical orientation mode. <P>SOLUTION: A phase difference film, having certain specified phase difference wavelength dispersion, is arranged between a liquid crystal cell and polarization films one piece each. By this, making wide visual field angle of a liquid crystal display element, having a structure in a state with the liquid crystal molecular major axis without voltage impressed, is oriented in almost the vertical direction with respect to a panel surface is realized. <P>COPYRIGHT: (C)2004,JPO

Description

（式中のＫ_ＳＵＭ（５５０）は波長５５０ｎｍにおける位相差フィルム二枚の厚み方向位相差値の和、Ｋ_ＬＣ（５５０）は波長５５０ｎｍにおける液晶セルの厚み方向位相差値であり、Ｋ_ＯＴＨ（５５０）は一対の偏光フィルム間における位相差フィルムと液晶セル以外の厚み方向位相差値の和である。）
４．　位相差フィルムの光弾性定数が７０×１０^−１２Ｐａ^−１以下である上記１〜３記載の液晶表示素子。
５．　位相差フィルムの吸水率１重量％以下である上記１〜４に記載の液晶表示素子。
６．　位相差フィルムが下記式（Ａ）
【００１３】
【化７】

【００１４】
（上記式（Ａ）においてＲ_１〜Ｒ_８はそれぞれ独立に水素原子、ハロゲン原子および炭素数１〜６の炭化水素基から選ばれる少なくとも一種の基であり、Ｘは下記式（Ｘ）
【００１５】
【化８】

【００１６】
であり、Ｒ_９およびＲ_１０はそれぞれ独立して水素原子、ハロゲン原子または炭素数１〜３のアルキル基である。）
で示される繰り返し単位および下記式（Ｂ）
【００１７】
【化９】

【００１８】
（上記式（Ｂ）においてＲ_１１〜Ｒ_１８はそれぞれ独立に水素原子、ハロゲン原子および炭素数１〜２２の炭化水素基から選ばれる少なくとも一種の基であり、Ｙは下記式群（Ｙ）
【００１９】
【化１０】

【００２０】
であり、ここでＲ_１９〜Ｒ_２１、Ｒ_２３及びＲ_２４はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基から選ばれる少なくとも１種の基であり、Ｒ_２２及びＲ_２５はそれぞれ独立に炭素数１〜２０の炭化水素基から選ばれる少なくとも１種の基であり、Ａｒ_１〜Ａｒ_３はそれぞれ独立に炭素数６〜１０のアリール基から選ばれる少なくとも１種の基である。）
で示される繰り返し単位からなり、上記式（Ａ）で表される繰り返し単位が全体の８０〜３０ｍｏｌ％を占めるポリカーボネート共重合体および／またはブレンド体からなる上記１〜５の記載の液晶表示素子。
７．位相差フィルムが下記式（Ｃ）
【００２１】
【化１１】

【００２２】
（上記式（Ｃ）においてＲ_２６〜Ｒ_２７はそれぞれ独立に水素原子またはメチル基から選ばれる。）で示される繰り返し単位が全体の３０〜６０ｍｏｌ％と、下記式（Ｄ）
【００２３】
【化１２】

【００２４】
（上記式（Ｄ）においてＲ_２８〜Ｒ_２９はそれぞれ独立に水素原子またはメチル基から選ばれる。）で示される繰り返し単位が全体の７０〜４０ｍｏｌ％を占めるポリカーボネート共重合体および／またはブレンド体からなる上記１〜６記載の液晶表示素子。
８．　上記１〜７記載の位相差フィルム。
【００２５】
本発明でいう、垂直配向モードの液晶セルとは、少なくとも一方が透明である電極付き基板が向かい合うように一定の距離をおいて配置されており、この隙間に挟持された液晶分子長軸が電圧無印加状態において基板に略垂直な方向に配向した構造を有するものである。略垂直な方向に配向とは基板と表示画素部における液晶分子長軸とのなす角度の平均値が略垂直であることであり、一般には８０°以上であり、よりこの好ましくは８５°以上であり、さらに好ましくは８７°以上である。また、特開２００１−２３５７５０号公報に記載されているような電圧無印加時においても表示画素部以外では液晶が基板に対して並行配向しているようなものであっても良い。なお、ここで基板とは、ガラス、高分子フィルム等のプラスチックが挙げられる。
【００２６】
垂直配向モードの液晶セルにおいて、平行基板間に液晶を垂直配向させただけでは電圧印加状態に液晶がさまざまな方位角方向に傾き、配向の不連続な部分、いわゆるディスクリネーションがランダムに生じ均一表示が得られないという現象がある。このディスクリネーションに関しては様々な研究が行われており、ＳＩＤ９８ＤＩＧＥＳＴ，（１９９８）ｐ．１０８１「Ａ　Ｗｉｄｅ　Ｖｉｅｗｉｎｇ　Ａｎｇｌｅ　Ｐｏｌｙｍｅｒ　Ｓｔａｂｉｌｉｚｅｄ　Ｈｏｍｅｏｔｒｏｐｉｃ　Ａｌｉｇｎｅｄ　ＬＣＤ」やＤｉｓｐｌａｙ９９Ｌａｔｅ　ｎｅｗｓｐａｐｅｒｓ，（１９９９）ｐ．３１「Ａ　Ｗｉｄｅ　Ｖｉｅｗｉｎｇ　Ａｎｇｌｅ　Ｂａｃｋ　Ｓｉｄｅ　Ｅｘｐｏｓｕｒｅ　ＭＶＡ　ＴＦＴ　ＬＣＤ　ｗｉｔｈ　Ｎｏｖｅｌ　Ｓｔｒｕｃｔｕｒｅ　ａｎｄ　Ｐｒｏｃｅｓｓ」に記載されているように基板に突起体を形成すること、あるいは特開平７−１９９１９０号公報に記載されているように画素電極に窓部を設けることにより電圧印加時の液晶分子の傾く方向を制御しているものがある。さらに、シャープ技報第８０号２００１年８月ｐ．１１「Ｃｏｎｔｉｎｕｏｕｓ　Ｐｉｎｗｈｅｅｌ　Ａｌｉｇｎｍｅｎｔ　（ＣＰＡ）　モードを用いたＡＳＶ−ＬＣＤの開発」に記載されているように、液晶にカイラル材を加えることにより電圧印加時に液晶がねじれながら倒れるようになっているリバースＴＮ方式もある。このように垂直配向モードの液晶セルの電圧印加状態における液晶の配向状態は様々な形態をとるものがあるが、本発明は電圧印加状態の液晶配向状態によって制限されるものではない。
【００２７】
また、液晶の屈折率異方性と液晶を挟持している基板間距離との積で表される、波長５５０ｎｍにおける液晶セルの厚み方向位相差値は、通常−４５０〜−２５０ｎｍ程度となるように設定される。
【００２８】
本発明の（透過型の）液晶表示素子では、このような液晶セルの上下にその透過軸が略直交するような角度で一対の偏光フィルムが配置される。
【００２９】
本発明によれば、驚くべきことに、液晶セルと偏光フィルムの間に、特定の位相差波長分散を有する位相差フィルムを、その遅相軸が隣接する当該偏光フィルムの透過軸と平行あるいは直交するように一枚ずつ配置することにより、垂直配向モードの液晶表示素子の視野角が格段に向上する。図１には本発明の液晶表示素子の一例を示した。図１では、かかる位相差フィルムが、偏光フィルム（ＨＬＣ２−５６１８）と液晶セルの間に配置され、かつ該位相差フィルムの遅相軸は、隣接する該偏光フィルムの透過軸と平行になっている。液晶セルの上下に配置された一対の該位相差フィルムの波長分散値、面内位相差値、厚み方向位相差値は等しいことが望ましい。もちろん、本発明には、位相差フィルムの遅相軸が隣接する該偏光フィルムの透過軸と直交する場合も含まれるし、一対の位相差フィルムの波長分散値、面内位相差値、厚み方向位相差値が等しくなくてもよい。なお後述するが、偏光フィルムには通常保護フィルムが付されており、位相差フィルムはかかる保護フィルムを介して偏光フィルムと隣接してもよい。さらには、位相差フィルムと偏光フィルムとの隣接は通常粘着剤を介する場合が多いので、そのような粘着剤からなる粘着層があってもよい。
【００３０】
ここで、かかる特定の位相差波長分散を有する位相差フィルムとは、下記式（１）および（２）
１．０２５＜Ｒ（４５０）／Ｒ（５５０）＜１．０７０　　　（１）
１．０２５＜Ｋ（４５０）／Ｋ（５５０）＜１．０７０　　　（２）
の少なくとも一方を満足する。ここで、式中のＲ（４５０）、Ｒ（５５０）はそれぞれ波長４５０ｎｍ、５５０ｎｍにおける位相差フィルムの面内位相差値であり、下記式（３）によって表される。また、Ｋ（４５０）、Ｋ（５５０）はそれぞれ波長４５０ｎｍ、５５０ｎｍにおける厚み方向位相差値であり、下記式（４）によって表される。
【００３１】
Ｒ＝（ｎ_ｘ−ｎ_ｙ）×ｄ　　　　　　　　　　　（３）
Ｋ＝｛（ｎ_ｘ＋ｎ_ｙ）／２−ｎ_ｚ｝×ｄ　　　　（４）
式中のｎ_ｘ、ｎ_ｙ、ｎ_ｚは三次元屈折率であり、それぞれ位相差フィルムの面内ｘ軸、ｙ軸、およびｘ軸とｙ軸に垂直なｚ軸方向の屈折率である。また、ｄは位相差フィルムの厚みである。
【００３２】
上記位相差フィルムはより好ましくは下記式（８）および／または（９）を満たすことである。
【００３３】
１．０３＜Ｒ（４５０）／Ｒ（５５０）＜１．０６　　　（８）
１．０３＜Ｋ（４５０）／Ｋ（５５０）＜１．０６　　　（９）
また、位相差フィルムの波長５５０ｎｍにおける面内位相差値は１０〜１００ｎｍであり厚み方向位相差値は５０〜２００ｎｍであることが好ましく、より好ましくは面内位相差値１５〜６５ｎｍであり厚み方向位相差値８０〜１８０ｎｍであることである。また、偏光フィルム間に存在する光学異方層の厚み方向位相差値の和は−１５０ｎｍ〜１５０ｎｍであることが好ましく、より好ましくは−１００ｎｍ〜１００ｎｍである。なお、ここでいう光学異方層とは、液晶セルと二枚の位相差フィルム以外に例として偏光フィルムの保護膜（通常はトリアセチルセルロース（以下「ＴＡＣ」）が挙げられる。通常ＴＡＣフィルムは面配向しており、５０ｎｍ程度の厚み方向位相差値を有している。
【００３４】
上記の位相差フィルムは垂直配向モードの液晶表示素子の視野角補償に最適であり、これを用いることにより本発明の液晶表示素子は優れた視野角特性を有することが可能となる。
【００３５】
また、位相差フィルムはそのハンドリング性および安定性の点から光弾性定数が７０×１０^−１２Ｐａ^−１以下で吸水率が０．１重量％以下であることが好ましい。
【００３６】
【発明の実施の形態】
本発明の液晶表示素子は、電圧無印加状態において液晶分子長軸がパネル面に対して略垂直な方向に配向した構造を有する液晶セルと、該液晶セルの上下に相互の透過軸が直交するように配置された一対の偏光フィルムと、該液晶セルと該偏光フィルムとの間に位相差フィルムがそれぞれ一枚ずつ具備されてなり、かつ該位相差フィルムの遅相軸が該位相差フィルムと隣接する偏光フィルムの透過軸に平行あるいは直交するように配置されてなる液晶表示素子であって、該位相差フィルムが上記式（１）および／または（２）を満たすことを特徴とする液晶表示素子である。
【００３７】
上記特性を満足する位相差フィルムの具体的な材料について以下に説明する。
【００３８】
例えば、位相差フィルムが高分子配向フィルムからなる場合、光弾性定数は７０×１０^−１２Ｐａ^−１以下、好ましくは６０×１０^−１２Ｐａ^−１以下であることが好ましい。７０×１０^−１２Ｐａ^−１を越えると、位相差フィルムを貼り合わせる際の張力によって位相差が発現したり、他の材料との寸法安定性のミスマッチから生じる応力によって位相差が発現したりすることにより表示斑の問題が発生する場合がある。また、ガラス転移点温度が１２０℃以上、好ましくは１４０℃以上、より好ましくは１６０℃以上、さらに好ましくは１８０℃以上であることが好ましい。１２０℃未満では、表示素子の使用条件にもよるが、配向緩和などの問題が発生する場合がある。また、吸水率は１重量％以下であることが好ましい。高分子材料の吸水率が１重量％未満では位相差フィルムとして実用する上で光学特性変化や寸法変化などの問題がある場合があり、フィルム材料はフィルム吸水率が１重量％以下、好ましくは０．５重量％以下の条件を満たすように選択することが良い。
【００３９】
本発明に用いられる位相差フィルムは、２種類以上ブレンドした高分子組成物（ブレンド体とよぶことがある）からなるものでも共重合体からなるものでもよい。
【００４０】
かかる高分子配向フィルムを構成する高分子材料は特に限定されず、耐熱性に優れ、光学性能が良好で、溶液製膜ができる材料、例えばポリアリレート、ポリエステル、ポリカーボネート、ポリオレフィン、ポリエーテル、ポリスルフィン系共重合体、ポリスルホン、ポリエーテルスルホンなどの熱可塑性ポリマーが好適である。この熱可塑性ポリマーを用いた場合、異なる位相差波長分散を有する高分子のブレンド体、あるいは異なる位相差波長分散を有するモノマー単位からなる共重合体により目的とする位相差フィルムを得ることができる。また、正の屈折率異方性を有する高分子と負の屈折率異方性を有する高分子とからなるブレンド体、正の屈折率異方性を有する高分子のモノマー単位と負の屈折率異方性を有する高分子のモノマー単位とからなる共重合体がより好適である。それらは２種類以上組み合わせてもよく、また１種類以上のブレンド高分子と１種類以上の共重合体とを組み合わせて用いてもよい。
【００４１】
高分子組成物であれば、光学的に透明である必要があることから相溶ブレンドまたは、各々の高分子の屈折率が略等しいことが好ましい。ブレンド高分子の具体的な組み合わせとしては、例えば負の光学異方性を有する高分子としてポリ（メチルメタクリレート）と、正の光学異方性を有する高分子としてポリ（ビニリデンフロライド）、ポリ（エチレンオキサイド）及びポリ（ビニリデンフロライド−コ−トリフルオロエチレン）からなる群から選ばれる少なくとも１種のポリマーとの組み合わせ、正の光学異方性を有する高分子としてポリ（フェニレンオキサイド）と負の光学異方性を有する高分子としてポリスチレン、ポリ（スチレン−コ−ラウロイルマレイミド）、ポリ（スチレン−コ−シクロヘキシルマレイミド）及びポリ（スチレン−コ−フェニルマレイミド）からなる群から選ばれる少なくとも１種のポリマーとの組み合わせ、負の光学異方性を有するポリ（スチレン−コ−マレイン酸無水物）と正の光学異方性を有するポリカーボネートとの組み合わせ、正の光学異方性を有するポリ（アクリロニトリル−コ−ブタジエン）と負の光学異方性を有するポリ（アクリロニトリル−コ−スチレン）との組み合わせ、正の光学異方性を有するポリカーボネートと負の光学異方性を有するポリカーボネートとの組み合わせを好適に挙げることができるが、これらに限定されるものではない。特に透明性の観点から、ポリスチレンとポリ（２，６−ジメチル−１，４−フェニレンオキサイド）等のポリ（フェニレンオキサイド）とを組み合わせたブレンドポリマー、正の光学異方性を有するポリカーボネートと負の光学異方性を有するポリカーボネートとを組み合わせたブレンド体が好ましい。
【００４２】
また、共重合体としては例えばポリ（ブタジエン−コ−ポリスチレン）、ポリ（エチレン−コ−ポリスチレン）、ポリ（アクリロニトリル−コ−ブタジエン）、ポリ（アクリロニトリル−コ−ブタジエン−コ−スチレン）、ポリカーボネート共重合体、ポリエステル共重合体、ポリエステルカーボネート共重合体、ポリアリレート共重合体等を用いることが出来る。特に、フルオレン骨格を有するセグメントは負の光学異方性となり得るため、フルオレン骨格を有するポリカーボネート共重合体、ポリエステル共重合体、ポリエステルカーボネート共重合体、ポリアリレート共重合体等はより好ましく用いられる。
【００４３】
上記高分子材料は、２種類以上の共重合体のブレンド体でもよく、１種以上の共重合体と上記ブレンド体または他のポリマーとからなるブレンド体であってもよく、２種類以上のブレンド体または共重合体または他のポリマーのブレンド体でもよい。
【００４４】
ビスフェノール類とホスゲンあるいは炭酸ジフェニルなどの炭酸エステル形成性化合物と反応させて製造されるポリカーボネート共重合体は透明性、耐熱性、生産性に優れており特に好ましく用いることが出来る。ポリカーボネート共重合体としては、フルオレン骨格を有する構造を含む共重合体であることが好ましく、具体的には下記式（Ａ）
【００４５】
【化１３】

【００４６】
で示される繰り返し単位２０〜７０ｍｏｌ％と下記式（Ｂ）
【００４７】
【化１４】

【００４８】
で示される繰り返し単位８０〜３０ｍｏｌ％からなるポリカーボネート共重合体、または高分子組成物またはこれらの混合物である。
【００４９】
上記式（Ａ）において、Ｒ_１〜Ｒ_８はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜６の炭化水素基から選ばれる。かかる炭素数１〜６の炭化水素基としては、メチル基、エチル基、イソプロピル基、シクロヘキシル基等のアルキル基、フェニル基等のアリール基が挙げられる。この中で、水素原子、メチル基が好ましい。
【００５０】
Ｘは下記式（Ｘ）
【００５１】
【化１５】

【００５２】
であり、Ｒ_９およびＲ_１０はそれぞれ独立して水素原子、ハロゲン原子または炭素数１〜３のアルキル基である。ハロゲン原子、炭素数１〜３のアルキル基としては上記したものと同じものをあげることができる。
【００５３】
上記式（Ｂ）において、Ｒ_１１〜Ｒ_１８はそれぞれ独立に水素原子、ハロン原子及び炭素数１〜２２の炭化水素基から選ばれる。かかる炭素数１〜２２の炭化水素基としては、メチル基、エチル基、イソプロピル基、シクロヘキシル基等の炭素数１〜９のアルキル基、フェニル基、ビフェニル基、ターフェニル基等のアリール基が挙げられる。この中で、水素原子、メチル基が好ましい。
【００５４】
Ｙは下記式群
【００５５】
【化１６】

【００５６】
であり、Ｒ_１９〜Ｒ_２１、Ｒ_２３及びＲ_２４はそれぞれ独立に水素原子、ハロゲン原子及び炭素数１〜２２の炭化水素基から選ばれる少なくとも１種の基である。かかる炭化水素基については、上記したものと同じものを挙げることができる。Ｒ_２２及びＲ_２５はそれぞれ独立に炭素数１〜２０の炭化水素基から選ばれ、かかる炭化水素基については、上記したものと同じものを挙げることができる。Ａｒ_１〜Ａｒ_３としてはフェニル基、ナフチル基等の炭素数６〜１０のアリール基を挙げられる。
【００５７】
上記ポリカーボネートとしては、好ましくは下記式（Ｃ）
【００５８】
【化１７】

【００５９】
で示される繰り返し単位３０〜６０ｍｏｌ％と、下記式（Ｄ）
【００６０】
【化１８】

【００６１】
で示される繰り返し単位７０〜４０ｍｏｌ％からなるポリカーボネート共重合体および／またはブレンド体である、
さらに好ましくは上記式（Ｃ）で示される繰り返し単位４５〜５５ｍｏｌ％と上記式（Ｄ）で示される繰り返し単位５５〜４５ｍｏｌ％からなるポリカーボネート共重合体および／またはブレンド体である。
【００６２】
上記式（Ｃ）においてＲ_２６〜Ｒ_２７はそれぞれ独立に水素原子またはメチル基であり、取り扱い性の点から好ましくはメチル基である。
【００６３】
上記式（Ｄ）においてＲ_２８〜Ｒ_２９はそれぞれ独立に水素原子またはメチル基であり、経済性、フィルム特性等から水素原子が好ましい。
【００６４】
本発明における位相差フィルムは、上記したフルオレン骨格を有するポリカーボネートを用いたものが好ましい。このフルオレン骨格を有するポリカーボネートとしては、例えば上記式（Ａ）で表わされる繰り返し単位と上記式（Ｂ）で表わされる繰り返し単位とからなる異なる組成比のポリカーボネート共重合体のブレンド体がよく、上記式（Ａ）の含有率はポリカーボネート全体の２０〜７０ｍｏｌ％が好ましく、より好ましくは３０〜６０ｍｏｌ％であり、さらに好ましくは４０〜５５ｍｏｌ％である。
【００６５】
上記共重合体は、上記式（Ａ）および（Ｂ）で表わされる繰り返し単位をそれぞれ２種類以上組み合わせたものでもよく、ブレンド体の場合も、上記繰り返し単位はそれぞれ２種類以上組み合わせてもよい。
【００６６】
ここで上記モル比は共重合体、ブレンド体に関わらず、高分子配向フィルムを構成するポリカーボネートバルク全体で、例えば核磁気共鳴（ＮＭＲ）装置により求めることができる。
【００６７】
上記した共重合体および／またはブレンド体は公知の方法によって製造し得る。ポリカーボネートはジヒドロキシ化合物とホスゲンとの重縮合による方法、溶融重縮合法等が好適に用いられる。ブレンド体の場合は、相溶性ブレンドが好ましいが、完全に相溶しなくても成分間の屈折率を合わせれば成分間の光散乱を抑え、透明性を向上させることが可能である。
【００６８】
上記ポリカーボネートの極限粘度は０．３〜２．０ｄｌ／ｇであることが好ましい。０．３未満では脆くなり機械的強度が保てないといった問題があり、２．０を超えると溶液粘度が上がりすぎるため溶液製膜においてダイラインの発生等の問題や、重合終了時の精製が困難になるといった問題がある。
【００６９】
位相差フィルムは透明であることが好ましく、ヘーズ値は３％以下、全光線透過率は８５％以上であることが好ましい。
【００７０】
かかる位相差フィルム中には、さらに、フェニルサリチル酸、２−ヒドロキシベンゾフェノン、トリフェニルフォスフェート等の紫外線吸収剤や、色味を変えるためのブルーイング剤、酸化防止剤等が含有されていてもよい。
【００７１】
本発明の位相差フィルムは上記ポリカーボネートなどの未延伸フィルムに延伸等を行い、高分子鎖を配向させた高分子配向フィルムからなるものである。かかるフィルムの製造方法としては、公知の溶融押し出し法、溶液キャスト法等が用いられるが、膜厚むら、外観等の観点から溶液キャスト法がより好ましく用いられる。溶液キャスト法における溶剤としては、メチレンクロライド、ジオキソラン等が好適に用いられる。
【００７２】
延伸法としては、例えば、フィルム流れ方向に速度差のついたクリップにてフィルムを幅方向に広げる同時二軸延伸法、フィルム幅方向をピンあるいはクリップにより把持し、把持した部分のフィルム流れ方向速度差を利用する縦一軸延伸方法、把持した部分を幅方向に広げる横一軸延伸法等があり、またこれらの延伸方法やロール速度差を利用するロール縦一軸延伸方法等を組み合わせた逐次二軸延伸法等が挙げられる。
【００７３】
位相差フィルムを得るための連続延伸法の例をいくつか挙げたが、本発明の位相差フィルムの延伸方法はこれらに限定されるものではなく、生産性の観点から連続延伸が好ましいが、連続延伸である必要はない。
【００７４】
上述したような延伸方法に代表される公知の技術にて延伸する際、フィルム中には延伸性を向上させる目的で、公知の可塑剤であるジメチルフタレート、ジエチルフタレート、ジブチルフタレート等のフタル酸エステル、トリブチルフォスフェート等のりん酸エステル、脂肪族二塩基エステル、グリセリン誘導体、グリコール誘導体等が含有してもよい。延伸時には、先述のフィルム製膜時に用いた有機溶剤をフィルム中に残留させ延伸しても良い。この有機溶剤の量としてはポリマー固形分対比１〜２０重量％であることが好ましい。
【００７５】
また、上記可塑剤や液晶等の添加剤は、本発明の位相差フィルムの位相差波長分散を変化させ得るが、添加量は、ポリマー固形分対比１０重量％以下が好ましく、３重量％以下がより好ましい。
【００７６】
位相差フィルムの膜厚としては、１μｍから３００μｍであることが好ましい。なお、本発明では位相差フィルムと表現しているが、共通して「フィルム」といい、あるいは「シート」といわれるいずれのものも含む意味である。
【００７７】
先述したように、位相差フィルムの位相差波長分散を特定の値にするためには、高分子配向フィルムを構成する高分子の化学構造が重要であり、位相差波長分散はかなりの部分がその化学構造で決まるが、製膜条件、添加剤、延伸条件、ブレンド状態、分子量等によっても変動することに留意されるべきである。
【００７８】
本発明において用いられる偏光フィルムは、公知のヨウ素や二色性色素等をポリビニールアルコール等のポリマー（バインダーポリマーともいう）中に分散し、延伸等により少なくともヨウ素等を配向固定したフィルム、主鎖型または側鎖型のポリアセチレンを延伸したフィルム等、公知の偏光フィルムを用いることが可能である。ポリビニールアルコールをバインダーポリマーとして用いたフィルムでは通常、該保護フィルムとしてセルロースアセテートフィルム等が積層されていることが多いので、偏光フィルムはこのような保護フィルムを積層して用いることもできるし、また該保護フィルムを用いずに本発明の位相差フィルムを該保護フィルムの代わりを兼ねさせても良い。
【００７９】
用いる偏光フィルムの厚さとしては、上記のようなバインダーポリマーを用いたタイプであれば、通常３０〜３００μｍである。また、液晶性で二色性の材料をコーテイングにより配向固定させたものであれば、厚みは０．０１〜３０μｍ程度である。
【００８０】
本発明の液晶表示素子は、位相差フィルム、液晶パネル基板、偏光フィルムを組み合わせて用いる。位相差フィルム、液晶パネル基板、偏光フィルムは密着していることが好ましく、密着させるためには公知の粘着剤や接着剤を用いることができる。
【００８１】
また、本発明の液晶表示素子には、上記の位相差フィルム、液晶パネル基板、偏光フィルム等の部材間にてプリズムシート、拡散フィルムなどの各種光学フィルムを用いても良い。
【００８２】
本発明の液晶表示素子は主として液晶ディスプレイ、液晶プロジェクタなどの液晶表示素子として用いられるが、広視野角を必要とする垂直配向モードの液晶表示素子全てに用いることができる。
【００８３】
また、位相差フィルムの面内位相差と厚み方向位相差の好ましい値は液晶の厚み方向位相差値、液晶および位相差フィルムの平均屈折率ｎにより若干変化するが、目的に応じて最適化される。
【００８４】
【実施例】
以下に実施例を挙げて本発明をより詳細に説明するが、本発明はこれらに限定されるものではない。
【００８５】
（評価法）
本明細書中に記載の材料特性値等は以下の評価法によって得られたものである。
【００８６】
（１）面内位相差値、厚み方向位相差値の測定
面内位相差Ｒ値および厚み方向位相差Ｋ値は、分光エリプソメータ『Ｍ１５０』（日本分光（株）製）により測定した。面内位相差値は入射光線とフィルム表面が直交する状態で測定した。また、厚み方向位相差値は入射光線とフィルム表面の角度を変えることにより、各角度での位相差値を測定し、公知の屈折率楕円体の式でカーブフィッチングすることにより三次元屈折率であるｎ_ｘ、ｎ_ｙ、ｎ_ｚを求めた。なお、その際、別のパラメータとして平均屈折率ｎが必要になるが、これはアッベ屈折計（（株）アタゴ社製の『アッベ屈折計２−Ｔ』）により測定した。
【００８７】
（２）吸水率の測定
乾燥させたフィルムの状態で膜厚を　１３０±５０μｍとした以外は、ＪＩＳＫ　７２０９記載の『プラスチックの吸水率及び沸騰吸水率試験方法』に準拠して測定した。試験片の大きさは５０ｍｍ正方形で、水温２５℃、２４時間サンプルを浸水させた後、重量変化を測定した。単位は重量％である。
【００８８】
（３）高分子のガラス転移点温度（Ｔｇ）の測定
『ＤＳＣ２９２０　Ｍｏｄｕｌａｔｅｄ　ＤＳＣ』（ＴＡ　Ｉｎｓｔｒｕｍｅｎｔｓ社製）により測定した。フィルム成形後ではなく、樹脂重合後、フレークスまたはチップの状態で測定した。
【００８９】
（４）フィルム膜厚測定
アンリツ社製の電子マイクロで測定した。
【００９０】
（５）高分子共重合比の測定
『ＪＮＭ−ａｌｐｈａ６００』（日本電子社製）のプロトンＮＭＲにより測定した。特にビスフェノールＡ（ＢＰＡ）とビスクレゾールフルオレン（ＢＣＦ）の共重合体の場合には、溶媒として重ベンゼンを用い、それぞれのメチル基のプロトン強度比から算出した。
【００９１】
また、以下の実施例、比較例で用いたポリカーボネートのモノマー構造を以下に示す。
【００９２】
【化１９】

【００９３】
［実施例１］
攪拌機、温度計および環流冷却器を備えた反応槽に水酸化ナトリウム水溶液およびイオン交換水を仕込み、これに上記構造を有するモノマー（Ｅ）、（Ｆ）を５０：５０のモル比で溶解させ、少量のハイドロサルフィトを加えた。次にこれに塩化メチレンを加え、２０℃でホスゲンを約６０分かけて吹き込んだ。さらに、ｐ−ｔｅｒｔ−ブチフェノールを加えて乳化させた後、トリエチルアミンを加えて３０℃で約３時間攪拌して反応を終了させた。反応終了後有機相を分取し、塩化メチレンを蒸発させてポリカーボネート共重合体を得た。得られた共重合体の組成比はモノマー仕込み量比とほぼ同等であった。
【００９４】
この共重合体を塩化メチレンに溶解させ、固形分濃度１８重量％のドープ溶液を作製した。このドープ溶液からキャストフィルムを作製し、２１５℃にて１．４倍に縦一軸延伸した後、２１５℃にて１．６倍に横一軸延伸することにより表１に示すような特性の位相差フィルムを得た。
【００９５】
次に、表２に示すような特性を持つＶＡ液晶セルを作製し、市販のヨウ素系偏光板である（株）サンリッツ製『ＨＬＣ２−５６１８』と上記位相差フィルムを図１に示す構成となるように粘着剤を用いて積層させた。この偏光板には、保護層としてＴＡＣフィルムが液晶セル側に具備されているが、該ＴＡＣフィルムの面内位相差値は２ｎｍであり、厚み方向位相差値は４８ｎｍであった。
【００９６】
このパネルを斜め方向のあらゆる角度から見てもほとんど光漏れはなく、漏れている光についても着色が無いものであった。
【００９７】
【表１】

【００９８】
【表２】

【００９９】
［比較例１］
ＪＳＲ（株）製ＡＲＴＯＮを塩化メチレンに溶解させ、固形分濃度１８重量％のドープ溶液を作製した。このドープ溶液からキャストフィルムを作製し、１７５℃にて１．４倍に縦一軸延伸した後、１７５℃にて１．６倍に横一軸延伸することにより表１に示すような特性の位相差フィルムを得た。
【０１００】
次に、実施例１と同様、表２に示すような特性を持つＶＡ液晶セルを作製し、市販のヨウ素系偏光板である（株）サンリッツ製『ＨＬＣ２−５６１８』と上記位相差フィルムを実施例１と同様、図１に示す構成となるように粘着剤を用いて積層させた。この偏光板の保護層として用いられているＴＡＣフィルムの面内位相差値は２ｎｍであり、厚み方向位相差値は４８ｎｍであった。
【０１０１】
このパネルを斜め方向から見たところ、特に４５°方位において光漏れが顕著であり、漏れている光についても着色が確認できた。
【０１０２】
［比較例２］
帝人化成（株）製Ｃ１４００を塩化メチレンに溶解させ、固形分濃度１８重量％のドープ溶液を作製した。このドープ溶液からキャストフィルムを作製し、１６５℃にて１．１倍に縦一軸延伸した後、１６５℃にて１．２倍に横一軸延伸することにより表１に示すような特性の位相差フィルムを得た。
【０１０３】
次に、実施例１と同様、表２に示すような特性を持つＶＡ液晶セルを作製し、市販のヨウ素系偏光板である（株）サンリッツ製『ＨＬＣ２−５６１８』と上記位相差フィルムを実施例１と同様、図１に示す構成となるように粘着剤を用いて積層させた。この偏光板の保護層として用いられているＴＡＣフィルムの面内位相差値は２ｎｍであり、厚み方向位相差値は４８ｎｍであった。
【０１０４】
このパネルを斜め方向から見たところ、特に４５°方位において光漏れが顕著であり、漏れている光についても着色が確認できた。
【０１０５】
［比較例３］
ＪＳＲ（株）製ＡＲＴＯＮを塩化メチレンに溶解させ、固形分濃度１８重量％のドープ溶液を作製した。このドープ溶液からキャストフィルムを作製し、１７５℃にて１．３倍に縦一軸延伸した後、１７５℃にて１．５倍に横一軸延伸することにより表１に示すような特性の位相差フィルムを得た。
【０１０６】
次に、実施例１と同様、表２に示すような特性を持つＶＡ液晶セルを作製し、市販のヨウ素系偏光板である（株）サンリッツ製『ＨＬＣ２−５６１８』と上記位相差フィルムを実施例１と同様、図１に示す構成となるように粘着剤を用いて積層させた。この偏光板の保護層として用いられているＴＡＣフィルムの面内位相差値は２ｎｍであり、厚み方向位相差値は４８ｎｍであった。
【０１０７】
このパネルを斜め方向から見てもほとんど光漏れはなかったが、４５°方位において若干の光漏れが確認でき、特に短波長の光漏れが顕著であった。
【０１０８】
［比較例４］
帝人化成（株）製Ｃ１４００を塩化メチレンに溶解させ、固形分濃度１８重量％のドープ溶液を作製した。このドープ溶液からキャストフィルムを作製し、１６５℃にて１．１倍に縦一軸延伸した後、１６８℃にて１．２倍に横一軸延伸することにより表１に示すような特性の位相差フィルムを得た。
【０１０９】
次に、実施例１と同様、表２に示すような特性を持つＶＡ液晶セルを作製し、市販のヨウ素系偏光板である（株）サンリッツ製『ＨＬＣ２−５６１８』と上記位相差フィルムを実施例１と同様、図１に示す構成となるように粘着剤を用いて積層させた。この偏光板の保護層として用いられているＴＡＣフィルムの面内位相差値は２ｎｍであり、厚み方向位相差値は４８ｎｍであった。
【０１１０】
このパネルを斜め方向から見てもほとんど光漏れはなかったが、４５°方位において若干の光漏れが確認でき、特に短波長の光漏れが顕著であった。
【０１１１】
【発明の効果】
以上説明したように、ある特定の位相差波長分散を有する位相差フィルムを液晶セルと偏光フィルムとの間にそれぞれ１枚ずつ配置することにより、電圧無印加状態の液晶分子長軸がパネル面に対して略垂直な方向に配向した構造を有する液晶表示素子の広視野角化を実現することが可能となる。
【図面の簡単な説明】
【図１】実施例１のＶＡ液晶パネルの構成を表す模式図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device, and in particular, to a liquid crystal display device of a vertical alignment mode having a structure in which a long axis of liquid crystal molecules is aligned in a direction substantially perpendicular to a panel surface in a state where no voltage is applied, and a phase difference used therein. About the film.
[0002]
[Prior art]
Liquid crystal display devices have been widely used from small devices such as watches and calculators to large devices such as monitors and televisions. In such a liquid crystal display element, a TN (Twisted Nematic) mode using liquid crystal molecules having a positive dielectric anisotropy has been mainly used. When no voltage is applied to the TN mode liquid crystal display element, the alignment direction of liquid crystal molecules adjacent to one substrate is twisted by about 90 ° with respect to the alignment direction of liquid crystal molecules adjacent to the other substrate.
[0003]
Various developments have been made on TN mode liquid crystal display elements, but in order to achieve good black display and high contrast, voltage is applied, that is, the long axis of the liquid crystal molecules is oriented in a direction substantially perpendicular to the panel surface. It is necessary to display black while performing. However, in the TN mode, even when a voltage is applied, the liquid crystal molecules adjacent to the liquid crystal panel substrate maintain the horizontal alignment, so that the polarization state of light changes due to the birefringence of the liquid crystal molecules, and complete black display can be performed. Therefore, it is difficult to realize high contrast.
[0004]
On the other hand, in a liquid crystal display element of a vertical alignment mode, that is, a so-called VA (Vertical Aligned) mode, the liquid crystal molecule major axis is substantially perpendicular to the panel surface in a state where no voltage is applied between a pair of substrates constituting the liquid crystal panel. Oriented. In the vertical alignment mode, since the liquid crystal molecules adjacent to the liquid crystal panel substrate are also aligned substantially perpendicular to the panel surface, the polarization state hardly changes when light passes through the liquid crystal layer. That is, when there is a liquid crystal cell in the vertical alignment mode with no voltage applied between the orthogonally arranged polarizing films, almost perfect black display, which is better than in the TN mode, is possible.
[0005]
[Problems to be solved by the invention]
However, the VA mode liquid crystal display element has almost perfect black display at the front, but in order to obtain a wide viewing angle, it is necessary to use one or more retardation films like the TN mode liquid crystal display element. . As described in JP-A-11-95208, JP-A-2000-131693, etc., a single uniaxial film and / or a biaxial film is used for the viewing angle compensation of a VA mode liquid crystal display element. Although it is known to be used as described above, although the total light transmittance when the liquid crystal display element for displaying black is viewed obliquely can be reduced, there is a problem that the wavelength dependence of transmitted light is large and black is colored. .
[0006]
The present invention has been made in view of the above-described problems, and in particular, a liquid crystal display element of a vertical alignment mode in which coloring of transmitted light is reduced when a black display of the liquid crystal display element is viewed obliquely. It is an object of the present invention to provide a retardation film having the above wavelength dispersion and to provide a retardation film realizing this.
[0007]
In other words, an object of the present invention is to provide a vertical alignment mode liquid crystal display device having a wide viewing angle by using a retardation film having a specific wavelength dispersion, and realize a wide viewing angle in the vertical alignment mode. To provide a retardation film that can be used.
[0008]
[Means for Solving the Problems]
The present inventors use a retardation film having a specific retardation wavelength dispersion in a specific arrangement between a liquid crystal cell and a polarizing film to increase the viewing angle of a liquid crystal display element in a vertical alignment mode. And realized the present invention.
[0009]
That is, the present invention is as follows.
1. A liquid crystal cell having a structure in which the major axis of the liquid crystal molecules is oriented in a direction substantially perpendicular to the panel surface in the absence of a voltage, and a pair of polarized lights arranged above and below the liquid crystal cell so that their transmission axes are orthogonal to each other. A liquid crystal display device comprising a film, and a retardation film provided one by one between the liquid crystal cell and the polarizing film, wherein a slow axis of the retardation film is adjacent to the retardation film. A liquid crystal display device arranged so as to be parallel or orthogonal to the transmission axis of the polarizing film to be formed, and wherein the retardation film satisfies the following formulas (1) and / or (2).
[0010]
1.025 <R (450) / R (550) <1.070 (1)
1.025 <K (450) / K (550) <1.070 (2)
(R (450) and R (550) in the formulas are in-plane retardation values of the retardation film at wavelengths of 450 nm and 550 nm, respectively, and are represented by the following formula (3). (550) is a retardation value in the thickness direction at wavelengths of 450 nm and 550 nm, respectively, and is represented by the following equation (4).
[0011]
_{R = (n x -n y)} × d (3)
K = {( _nx + _ny ) / 2- _nz } xd (4)
In the formula, _nx , _ny , and _nz are three-dimensional refractive indices, and are the refractive indices in the x-axis, the y-axis, and the z-axis direction perpendicular to the x-axis and the y-axis in the plane of the retardation film, respectively. D is the thickness of the retardation film. )
2. 2. The liquid crystal display device according to the above item 1, wherein the retardation film satisfies the following formulas (5) and (6).
[0012]
10 nm <R (550) <100 nm (5)
50 nm <K (550) <200 nm (6)
3. 3. The liquid crystal display device according to any one of the above items 1 to 2, wherein the retardation film satisfies the following formula (7).

( _Where K _SUM (550) is the sum of the thickness direction retardation values of two retardation films at a wavelength of 550 nm, K _LC (550) is the thickness direction retardation value of the liquid crystal cell at a wavelength of 550 nm, and K _OTH ( 550) is the sum of the retardation values in the thickness direction of the pair of polarizing films other than the retardation film and the liquid crystal cell.)
4. ^4. The liquid crystal display device according to any one of the above 1 to 3, wherein the photoelastic constant of the retardation film is 70 × 10 ⁻¹² Pa ⁻¹ or less.
5. 5. The liquid crystal display device according to any one of the above items 1 to 4, wherein the water absorption of the retardation film is 1% by weight or less.
6. The retardation film has the following formula (A)
[0013]
Embedded image

[0014]
(In the above formula (A), R _{1 to} R ₈ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms, and X is the following formula (X)
[0015]
Embedded image

[0016]
Wherein R ₉ and R ₁₀ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms. )
And a repeating unit represented by the following formula (B):
[0017]
Embedded image

[0018]
(In the formula (B), R _{11 to} R ₁₈ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms, and Y is a group represented by the following formula group (Y)
[0019]
Embedded image

[0020]
, And the wherein _R 19 _{to R 21, R 23} and _{R 24} is at least one group each independently a hydrogen atom, selected from a halogen atom and a hydrocarbon group having 1 to 22 carbon _{atoms, R 22} and R ₂₅ is at least one group independently selected from hydrocarbon groups having 1 to 20 carbon atoms, and Ar _{1 to} Ar ₃ are each at least one group independently selected from aryl groups having 6 to 10 carbon atoms. It is. )
6. The liquid crystal display device according to any one of the above items 1 to 5, comprising a repeating unit represented by the formula (A), wherein the repeating unit represented by the formula (A) accounts for 80 to 30 mol% of the entirety of the polycarbonate copolymer and / or blend.
7. The retardation film has the following formula (C)
[0021]
Embedded image

[0022]
(In the above formula (C), R _{26 to} R ₂₇ are each independently selected from a hydrogen atom or a methyl group.) The repeating unit represented by 30 to 60 mol% of the following formula (D)
[0023]
Embedded image

[0024]
(In the above formula (D), each of R _{28 to} R ₂₉ is independently selected from a hydrogen atom or a methyl group.) From the polycarbonate copolymer and / or blend in which the repeating unit represented by 70 to 40 mol% accounts for 70 to 40 mol% of the whole 7. The liquid crystal display element according to any one of the above 1 to 6.
8. The retardation film according to any one of the above 1 to 7.
[0025]
In the present invention, the liquid crystal cell of the vertical alignment mode is arranged at a fixed distance so that substrates with electrodes, at least one of which is transparent, are opposed to each other. It has a structure oriented in a direction substantially perpendicular to the substrate when no voltage is applied. The orientation in a substantially perpendicular direction means that the average value of the angle between the substrate and the long axis of the liquid crystal molecules in the display pixel portion is substantially perpendicular, and is generally 80 ° or more, and more preferably 85 ° or more. And more preferably at least 87 °. In addition, even when no voltage is applied as described in JP-A-2001-235750, liquid crystals may be aligned in parallel with the substrate except for the display pixel portion. Here, examples of the substrate include plastics such as glass and a polymer film.
[0026]
In a vertical alignment mode liquid crystal cell, simply aligning the liquid crystal vertically between the parallel substrates causes the liquid crystal to tilt in various azimuthal directions when voltage is applied, causing discontinuous alignment, or so-called disclination, to occur uniformly. There is a phenomenon that display cannot be obtained. Various studies have been conducted on this disclination, and SID98DIGEST, (1998) p. 1081 "A Wide Viewing Angle Polymer Stabilized Homeotropic Aligned LCD" and Display99 Late newspapers, (1999) p. 31 "A Wide Viewing Angle Back Side Exposure MVA TFT LCD with Novel Structure and Process", or a pixel as described in JP-A-7-199190. In some cases, the direction of tilt of liquid crystal molecules when a voltage is applied is controlled by providing a window in the electrode. Further, Sharp Technical Report No. 80, August 2001, p. As described in 11 “Development of ASV-LCD Using Continuous Pinwheel Alignment (CPA) Mode”, by adding a chiral material to the liquid crystal, the liquid crystal is twisted and collapses when twisted when a voltage is applied. There is also. As described above, the alignment state of the liquid crystal in the voltage application state of the liquid crystal cell in the vertical alignment mode may take various forms, but the present invention is not limited by the liquid crystal alignment state in the voltage application state.
[0027]
The retardation value in the thickness direction of the liquid crystal cell at a wavelength of 550 nm, which is represented by the product of the refractive index anisotropy of the liquid crystal and the distance between the substrates sandwiching the liquid crystal, is usually about -450 to -250 nm. Is set to
[0028]
In the (transmissive) liquid crystal display device of the present invention, a pair of polarizing films are disposed above and below such a liquid crystal cell at an angle such that the transmission axes thereof are substantially perpendicular to each other.
[0029]
According to the present invention, surprisingly, a retardation film having a specific retardation wavelength dispersion is provided between a liquid crystal cell and a polarizing film, and the slow axis thereof is parallel or orthogonal to the transmission axis of the adjacent polarizing film. In this case, the viewing angle of the liquid crystal display device in the vertical alignment mode is significantly improved. FIG. 1 shows an example of the liquid crystal display device of the present invention. In FIG. 1, such a retardation film is disposed between a polarizing film (HLC2-5618) and a liquid crystal cell, and the slow axis of the retardation film is parallel to the transmission axis of the adjacent polarizing film. I have. It is desirable that the wavelength dispersion value, the in-plane retardation value, and the thickness direction retardation value of a pair of the retardation films disposed above and below the liquid crystal cell are equal. Of course, the present invention includes the case where the slow axis of the retardation film is orthogonal to the transmission axis of the adjacent polarizing film, and the wavelength dispersion value, in-plane retardation value, and thickness direction of a pair of retardation films. The phase difference values need not be equal. As described later, the polarizing film is usually provided with a protective film, and the retardation film may be adjacent to the polarizing film via the protective film. Furthermore, since the adjoining of the retardation film and the polarizing film is usually through an adhesive, there may be an adhesive layer made of such an adhesive.
[0030]
Here, the retardation film having the specific retardation wavelength dispersion is defined by the following formulas (1) and (2).
1.025 <R (450) / R (550) <1.070 (1)
1.025 <K (450) / K (550) <1.070 (2)
Satisfy at least one of the following. Here, R (450) and R (550) in the equations are in-plane retardation values of the retardation film at wavelengths of 450 nm and 550 nm, respectively, and are represented by the following equation (3). K (450) and K (550) are thickness-direction retardation values at wavelengths of 450 nm and 550 nm, respectively, and are represented by the following equation (4).
[0031]
_{R = (n x -n y)} × d (3)
K = {( _nx + _ny ) / 2- _nz } xd (4)
In the formula, _nx , _ny , and _nz are three-dimensional refractive indexes, which are the in-plane x-axis, the y-axis, and the refractive index in the z-axis direction perpendicular to the x-axis and the y-axis of the retardation film, respectively. D is the thickness of the retardation film.
[0032]
The retardation film more preferably satisfies the following formulas (8) and / or (9).
[0033]
1.03 <R (450) / R (550) <1.06 (8)
1.03 <K (450) / K (550) <1.06 (9)
Further, the in-plane retardation value at a wavelength of 550 nm of the retardation film is preferably from 10 to 100 nm, and the retardation value in the thickness direction is preferably from 50 to 200 nm, more preferably from 15 to 65 nm in the thickness direction. The phase difference value is 80 to 180 nm. The sum of retardation values in the thickness direction of the optically anisotropic layer existing between the polarizing films is preferably from -150 nm to 150 nm, more preferably from -100 nm to 100 nm. In addition, the optically anisotropic layer here includes, for example, a protective film of a polarizing film (usually triacetyl cellulose (hereinafter, “TAC”) in addition to the liquid crystal cell and the two retardation films. It is plane-oriented and has a retardation value in the thickness direction of about 50 nm.
[0034]
The above retardation film is most suitable for compensating a viewing angle of a liquid crystal display device in a vertical alignment mode. By using the retardation film, the liquid crystal display device of the present invention can have excellent viewing angle characteristics.
[0035]
The retardation film preferably has a photoelastic constant of 70 × 10 ⁻¹² Pa ⁻¹ or less and a water absorption of 0.1% by weight or less from the viewpoint of handling properties and stability.
[0036]
BEST MODE FOR CARRYING OUT THE INVENTION
The liquid crystal display element of the present invention has a structure in which the major axis of liquid crystal molecules is oriented in a direction substantially perpendicular to the panel surface in a state where no voltage is applied, and the transmission axes of the liquid crystal cell are perpendicular to each other above and below the liquid crystal cell. A pair of polarizing films arranged as described above, a retardation film is provided between the liquid crystal cell and the polarizing film one by one, and the slow axis of the retardation film is the retardation film. A liquid crystal display device arranged so as to be parallel or orthogonal to the transmission axis of an adjacent polarizing film, wherein the retardation film satisfies the above formula (1) and / or (2). Element.
[0037]
Specific materials of the retardation film satisfying the above characteristics will be described below.
[0038]
For example, when the retardation film is made of a polymer oriented film, the photoelastic constant is preferably 70 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 60 × 10 ⁻¹² Pa ⁻¹ or less. If it exceeds 70 × 10 ⁻¹² Pa ⁻¹ , a phase difference is generated due to a tension at the time of bonding the phase difference film, or a phase difference is generated due to a stress generated from a dimensional stability mismatch with another material. This may cause a problem of display unevenness. Further, the glass transition temperature is preferably 120 ° C. or higher, preferably 140 ° C. or higher, more preferably 160 ° C. or higher, and further preferably 180 ° C. or higher. If the temperature is lower than 120 ° C., depending on the use conditions of the display element, a problem such as relaxation of orientation may occur. Further, the water absorption is preferably 1% by weight or less. If the water absorption of the polymer material is less than 1% by weight, there may be a problem such as a change in optical characteristics and a change in dimensions in practical use as a retardation film, and the film material has a water absorption of 1% by weight or less, preferably 0%. It is preferable to select such that the condition of not more than 0.5% by weight is satisfied.
[0039]
The retardation film used in the present invention may be composed of a polymer composition in which two or more kinds are blended (sometimes referred to as a blend) or may be composed of a copolymer.
[0040]
The polymer material constituting such a polymer oriented film is not particularly limited, and is a material having excellent heat resistance, good optical performance, and capable of forming a solution, such as polyarylate, polyester, polycarbonate, polyolefin, polyether, and polysulfine. Thermoplastic polymers such as copolymers, polysulfones and polyethersulfones are preferred. When this thermoplastic polymer is used, a desired retardation film can be obtained from a blend of polymers having different retardation wavelength dispersions or a copolymer of monomer units having different retardation wavelength dispersions. Also, a blend composed of a polymer having a positive refractive index anisotropy and a polymer having a negative refractive index anisotropy, a monomer unit of the polymer having a positive refractive index anisotropy and a negative refractive index A copolymer composed of a monomer unit of a polymer having anisotropy is more preferable. They may be used in combination of two or more kinds, or one or more kinds of blended polymers and one or more kinds of copolymers may be used in combination.
[0041]
In the case of a polymer composition, since it is necessary to be optically transparent, it is preferable that the compatible blend or the refractive index of each polymer is substantially equal. As a specific combination of the blended polymers, for example, a polymer having negative optical anisotropy is poly (methyl methacrylate), and a polymer having positive optical anisotropy is poly (vinylidene fluoride) or poly (vinylidene fluoride). A combination of at least one polymer selected from the group consisting of ethylene oxide) and poly (vinylidene fluoride-co-trifluoroethylene), and poly (phenylene oxide) as a polymer having positive optical anisotropy; At least one selected from the group consisting of polystyrene, poly (styrene-co-lauroylmaleimide), poly (styrene-co-cyclohexylmaleimide) and poly (styrene-co-phenylmaleimide) as the polymer having optical anisotropy Combination with polymer, poly (styrene) having negative optical anisotropy (Poly (acrylonitrile-co-butadiene)) and a poly (acrylonitrile-co-butadiene) having a positive optical anisotropy and a poly (acrylonitrile-co-butadiene) having a positive optical anisotropy. (Acrylonitrile-co-styrene), and a combination of a polycarbonate having a positive optical anisotropy and a polycarbonate having a negative optical anisotropy, but the present invention is not limited thereto. In particular, from the viewpoint of transparency, a blend polymer obtained by combining polystyrene and a poly (phenylene oxide) such as poly (2,6-dimethyl-1,4-phenylene oxide), a polycarbonate having a positive optical anisotropy and a negative polymer A blend in which a polycarbonate having optical anisotropy is combined is preferable.
[0042]
Examples of the copolymer include poly (butadiene-co-polystyrene), poly (ethylene-co-polystyrene), poly (acrylonitrile-co-butadiene), poly (acrylonitrile-co-butadiene-co-styrene) and polycarbonate copolymer. Polymers, polyester copolymers, polyester carbonate copolymers, polyarylate copolymers and the like can be used. In particular, since a segment having a fluorene skeleton can have negative optical anisotropy, a polycarbonate copolymer, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer, or the like having a fluorene skeleton is more preferably used.
[0043]
The polymer material may be a blend of two or more copolymers, or may be a blend of one or more copolymers and the blend or another polymer, or may be a blend of two or more copolymers. It may be a polymer or a copolymer or a blend of other polymers.
[0044]
A polycarbonate copolymer produced by reacting a bisphenol with a phosgene or a carbonate-forming compound such as diphenyl carbonate has excellent transparency, heat resistance, and productivity, and can be particularly preferably used. The polycarbonate copolymer is preferably a copolymer containing a structure having a fluorene skeleton, and specifically, the following formula (A)
[0045]
Embedded image

[0046]
20 to 70 mol% of the repeating unit represented by the following formula (B)
[0047]
Embedded image

[0048]
Or a polymer composition comprising 80 to 30 mol% of repeating units, or a polymer composition or a mixture thereof.
[0049]
In the above formula (A), R _{1 to} R ₈ are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms. Examples of the hydrocarbon group having 1 to 6 carbon atoms include an alkyl group such as a methyl group, an ethyl group, an isopropyl group and a cyclohexyl group, and an aryl group such as a phenyl group. Of these, a hydrogen atom and a methyl group are preferred.
[0050]
X is the following formula (X)
[0051]
Embedded image

[0052]
Wherein R ₉ and R ₁₀ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the halogen atom and the alkyl group having 1 to 3 carbon atoms include the same as those described above.
[0053]
In the above formula (B), R _{11 to} R ₁₈ are each independently selected from a hydrogen atom, a halon atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group having 1 to 22 carbon atoms include an alkyl group having 1 to 9 carbon atoms such as a methyl group, an ethyl group, an isopropyl group and a cyclohexyl group, and an aryl group such as a phenyl group, a biphenyl group and a terphenyl group. Can be Of these, a hydrogen atom and a methyl group are preferred.
[0054]
Y is the following formula group:
Embedded image

[0056]
Wherein R _{19 to} R ₂₁ , R ₂₃ and R ₂₄ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group include the same as those described above. R ₂₂ and R ₂₅ are each independently selected from hydrocarbon groups having 1 to 20 carbon atoms, and examples of such hydrocarbon groups include the same as those described above. Ar _{1 to} Ar ₃ include aryl groups having 6 to 10 carbon atoms such as a phenyl group and a naphthyl group.
[0057]
The above polycarbonate is preferably represented by the following formula (C):
[0058]
Embedded image

[0059]
And a repeating unit represented by the following formula (D):
[0060]
Embedded image

[0061]
Is a polycarbonate copolymer and / or blend comprising 70 to 40 mol% of repeating units represented by
More preferably, it is a polycarbonate copolymer and / or blend comprising 45 to 55 mol% of the repeating unit represented by the formula (C) and 55 to 45 mol% of the repeating unit represented by the formula (D).
[0062]
In the above formula (C), R _{26 to} R ₂₇ are each independently a hydrogen atom or a methyl group, and preferably a methyl group from the viewpoint of handleability.
[0063]
In the above formula (D), R _{28 to} R ₂₉ are each independently a hydrogen atom or a methyl group, and a hydrogen atom is preferable in terms of economy, film characteristics, and the like.
[0064]
The retardation film in the invention is preferably one using the above-mentioned polycarbonate having a fluorene skeleton. As the polycarbonate having a fluorene skeleton, for example, a blend of polycarbonate copolymers having different composition ratios composed of a repeating unit represented by the above formula (A) and a repeating unit represented by the above formula (B) is preferable. The content of (A) is preferably from 20 to 70 mol%, more preferably from 30 to 60 mol%, even more preferably from 40 to 55 mol% of the entire polycarbonate.
[0065]
The copolymer may be a combination of two or more kinds of the repeating units represented by the above formulas (A) and (B), and in the case of a blend, two or more kinds of the above repeating units may be combined.
[0066]
Here, the molar ratio can be determined by, for example, a nuclear magnetic resonance (NMR) apparatus for the entire polycarbonate bulk constituting the polymer oriented film regardless of the copolymer or the blend.
[0067]
The above-mentioned copolymer and / or blend can be produced by a known method. As the polycarbonate, a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method, and the like are suitably used. In the case of a blend, a compatible blend is preferred, but even if they are not completely compatible, light scattering between the components can be suppressed and transparency can be improved by adjusting the refractive index between the components.
[0068]
The intrinsic viscosity of the polycarbonate is preferably 0.3 to 2.0 dl / g. If it is less than 0.3, there is a problem that it becomes brittle and mechanical strength cannot be maintained. If it exceeds 2.0, the solution viscosity becomes too high, so that problems such as generation of die lines in solution film formation and purification at the end of polymerization are difficult. Problem.
[0069]
The retardation film is preferably transparent, the haze value is preferably 3% or less, and the total light transmittance is preferably 85% or more.
[0070]
Such a retardation film may further contain an ultraviolet absorber such as phenylsalicylic acid, 2-hydroxybenzophenone, and triphenyl phosphate, a bluing agent for changing color, and an antioxidant. .
[0071]
The retardation film of the present invention comprises a polymer oriented film obtained by stretching a non-stretched film of the above polycarbonate or the like and orienting the polymer chains. As a method for producing such a film, a known melt extrusion method, a solution casting method, or the like is used, and a solution casting method is more preferably used from the viewpoints of uneven film thickness and appearance. As the solvent in the solution casting method, methylene chloride, dioxolane and the like are preferably used.
[0072]
As the stretching method, for example, a simultaneous biaxial stretching method in which the film is spread in the width direction with a clip having a speed difference in the film flow direction, the film width direction is gripped by a pin or a clip, and the film flow direction speed of the gripped portion is There is a longitudinal uniaxial stretching method using the difference, a horizontal uniaxial stretching method in which the gripped part is widened in the width direction, and a sequential biaxial stretching combining these stretching methods and a roll longitudinal uniaxial stretching method using a roll speed difference. And the like.
[0073]
Although several examples of the continuous stretching method for obtaining the retardation film have been given, the stretching method of the retardation film of the present invention is not limited thereto, and continuous stretching is preferable from the viewpoint of productivity. It does not need to be stretched.
[0074]
When stretched by a known technique represented by the above-described stretching method, phthalate esters such as dimethyl phthalate, diethyl phthalate, and dibutyl phthalate, which are known plasticizers, are used in the film for the purpose of improving stretchability. , A phosphate ester such as tributyl phosphate, an aliphatic dibasic ester, a glycerin derivative, a glycol derivative and the like. At the time of stretching, the organic solvent used at the time of forming the film may be left in the film and stretched. The amount of the organic solvent is preferably 1 to 20% by weight based on the solid content of the polymer.
[0075]
Further, the above-mentioned additives such as the plasticizer and the liquid crystal can change the retardation wavelength dispersion of the retardation film of the present invention, but the addition amount is preferably 10% by weight or less, and more preferably 3% by weight or less based on the polymer solid content. More preferred.
[0076]
The thickness of the retardation film is preferably from 1 μm to 300 μm. In the present invention, the term “retardation film” is used, but the meaning is commonly referred to as “film” or “sheet”.
[0077]
As described above, in order to set the retardation wavelength dispersion of the retardation film to a specific value, the chemical structure of the polymer constituting the polymer oriented film is important, and a considerable part of the retardation wavelength dispersion is that. It should be noted that although it depends on the chemical structure, it also varies depending on film forming conditions, additives, stretching conditions, blending conditions, molecular weight, and the like.
[0078]
The polarizing film used in the present invention is a film in which a known iodine or dichroic dye or the like is dispersed in a polymer such as polyvinyl alcohol (also referred to as a binder polymer), and at least iodine or the like is oriented and fixed by stretching or the like. It is possible to use a known polarizing film such as a stretched type or side chain type polyacetylene film. In a film using polyvinyl alcohol as a binder polymer, usually, a cellulose acetate film or the like is often laminated as the protective film, so that the polarizing film can be used by laminating such a protective film, or The retardation film of the present invention may be used instead of the protective film without using the protective film.
[0079]
The thickness of the polarizing film to be used is usually 30 to 300 μm if it is a type using the above binder polymer. In addition, if a liquid crystal dichroic material is fixed in alignment by coating, the thickness is about 0.01 to 30 μm.
[0080]
The liquid crystal display device of the present invention uses a combination of a retardation film, a liquid crystal panel substrate, and a polarizing film. It is preferable that the retardation film, the liquid crystal panel substrate, and the polarizing film are in close contact, and a known adhesive or adhesive can be used for close contact.
[0081]
Further, in the liquid crystal display element of the present invention, various optical films such as a prism sheet and a diffusion film may be used between members such as the above-mentioned retardation film, liquid crystal panel substrate and polarizing film.
[0082]
The liquid crystal display device of the present invention is mainly used as a liquid crystal display device such as a liquid crystal display and a liquid crystal projector, but can be used for all liquid crystal display devices of a vertical alignment mode requiring a wide viewing angle.
[0083]
The preferred values of the in-plane retardation and the retardation in the thickness direction of the retardation film slightly vary depending on the retardation value in the thickness direction of the liquid crystal and the average refractive index n of the liquid crystal and the retardation film. You.
[0084]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.
[0085]
(Evaluation method)
The material property values and the like described in this specification were obtained by the following evaluation methods.
[0086]
(1) Measurement of in-plane retardation value and thickness direction retardation value In-plane retardation R value and thickness direction retardation K value were measured with a spectroscopic ellipsometer “M150” (manufactured by JASCO Corporation). The in-plane retardation value was measured in a state where the incident light beam was orthogonal to the film surface. The thickness direction retardation value is obtained by measuring the phase difference value at each angle by changing the angle between the incident light beam and the film surface, and performing curve fitting with a known refractive index ellipsoidal equation to obtain a three-dimensional refractive index. _{n x,} n y is to obtain the _{n z.} In this case, an average refractive index n is required as another parameter, which was measured by an Abbe refractometer (“Abe refractometer 2-T” manufactured by Atago Co., Ltd.).
[0087]
(2) Measurement of water absorption The measurement was carried out in accordance with JIS K 7209, "Testing Method of Water Absorption and Boiling Water Absorption" of JIS K7209, except that the thickness of the dried film was changed to 130 ± 50 μm. The size of the test piece was a 50 mm square, and the sample was immersed in water at 25 ° C. for 24 hours, and the weight change was measured. The unit is% by weight.
[0088]
(3) Measurement of Glass Transition Temperature (Tg) of Polymer The polymer was measured by "DSC2920 Modulated DSC" (manufactured by TA Instruments). The measurement was made not in the state of film formation but in the state of flakes or chips after resin polymerization.
[0089]
(4) Film thickness measurement The film thickness was measured with an electronic micro manufactured by Anritsu Corporation.
[0090]
(5) Measurement of Polymer Copolymerization Ratio It was measured by proton NMR of "JNM-alpha600" (manufactured by JEOL Ltd.). In particular, in the case of a copolymer of bisphenol A (BPA) and biscresol fluorene (BCF), heavy benzene was used as a solvent, and calculation was performed from the proton intensity ratio of each methyl group.
[0091]
The monomer structures of the polycarbonates used in the following Examples and Comparative Examples are shown below.
[0092]
Embedded image

[0093]
[Example 1]
An aqueous sodium hydroxide solution and ion-exchanged water are charged into a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser, and the monomers (E) and (F) having the above structure are dissolved therein at a molar ratio of 50:50. A small amount of hydrosulfite was added. Next, methylene chloride was added thereto, and phosgene was blown at 20 ° C. for about 60 minutes. Furthermore, after adding p-tert-butyphenol and emulsifying, triethylamine was added and the mixture was stirred at 30 ° C. for about 3 hours to complete the reaction. After completion of the reaction, the organic phase was separated and methylene chloride was evaporated to obtain a polycarbonate copolymer. The composition ratio of the obtained copolymer was almost equal to the monomer charge ratio.
[0094]
This copolymer was dissolved in methylene chloride to prepare a dope solution having a solid content of 18% by weight. A cast film was prepared from this dope solution, stretched longitudinally uniaxially by a factor of 1.4 at 215 ° C., and then stretched uniaxially by a factor of 1.6 at 215 ° C. to obtain a retardation having properties as shown in Table 1. A film was obtained.
[0095]
Next, a VA liquid crystal cell having the characteristics shown in Table 2 was prepared, and the commercially available iodine-based polarizing plate “HLC2-5618” manufactured by Sanritz Co., Ltd. and the above retardation film were configured as shown in FIG. Was laminated using an adhesive as described above. This polarizing plate was provided with a TAC film as a protective layer on the liquid crystal cell side. The TAC film had an in-plane retardation value of 2 nm and a thickness direction retardation value of 48 nm.
[0096]
There was almost no light leakage when the panel was viewed from all angles in the oblique direction, and there was no coloring of the leaked light.
[0097]
[Table 1]

[0098]
[Table 2]

[0099]
[Comparative Example 1]
ARTON manufactured by JSR Corporation was dissolved in methylene chloride to prepare a dope solution having a solid content of 18% by weight. A cast film was prepared from this dope solution, and then stretched uniaxially by a factor of 1.4 at 175 ° C., and then stretched uniaxially by a factor of 1.6 at 175 ° C. to obtain a retardation having properties as shown in Table 1. A film was obtained.
[0100]
Next, in the same manner as in Example 1, a VA liquid crystal cell having the characteristics shown in Table 2 was prepared, and the commercially available iodine-based polarizing plate “HLC2-5618” manufactured by Sanritz Co., Ltd. and the above retardation film were implemented. As in Example 1, they were laminated using an adhesive so as to have the configuration shown in FIG. The in-plane retardation value of the TAC film used as a protective layer of the polarizing plate was 2 nm, and the thickness direction retardation value was 48 nm.
[0101]
When this panel was viewed from an oblique direction, light leakage was remarkable especially in the 45 ° azimuth, and coloring was confirmed even for the leaked light.
[0102]
[Comparative Example 2]
C1400 manufactured by Teijin Chemicals Ltd. was dissolved in methylene chloride to prepare a dope solution having a solid content of 18% by weight. A cast film was prepared from this dope solution, and then stretched uniaxially at 165 ° C by 1.1 times and then uniaxially stretched at 165 ° C by 1.2 times to obtain a retardation having properties as shown in Table 1. A film was obtained.
[0103]
Next, in the same manner as in Example 1, a VA liquid crystal cell having the characteristics shown in Table 2 was prepared, and the commercially available iodine-based polarizing plate “HLC2-5618” manufactured by Sanritz Co., Ltd. and the above retardation film were implemented. As in Example 1, they were laminated using an adhesive so as to have the configuration shown in FIG. The in-plane retardation value of the TAC film used as a protective layer of the polarizing plate was 2 nm, and the thickness direction retardation value was 48 nm.
[0104]
When this panel was viewed from an oblique direction, light leakage was remarkable especially in the 45 ° azimuth, and coloring was confirmed even for the leaked light.
[0105]
[Comparative Example 3]
ARTON manufactured by JSR Corporation was dissolved in methylene chloride to prepare a dope solution having a solid content of 18% by weight. A cast film was prepared from this dope solution, stretched uniaxially by a factor of 1.3 at 175 ° C., and then uniaxially stretched by a factor of 1.5 at 175 ° C. to obtain a retardation having properties as shown in Table 1. A film was obtained.
[0106]
Next, in the same manner as in Example 1, a VA liquid crystal cell having the characteristics shown in Table 2 was prepared, and the commercially available iodine-based polarizing plate “HLC2-5618” manufactured by Sanritz Co., Ltd. and the above retardation film were implemented. As in Example 1, they were laminated using an adhesive so as to have the configuration shown in FIG. The in-plane retardation value of the TAC film used as a protective layer of the polarizing plate was 2 nm, and the thickness direction retardation value was 48 nm.
[0107]
Although there was almost no light leakage when this panel was viewed from an oblique direction, slight light leakage was confirmed in the 45 ° azimuth, and light leakage of a short wavelength was particularly remarkable.
[0108]
[Comparative Example 4]
C1400 manufactured by Teijin Chemicals Ltd. was dissolved in methylene chloride to prepare a dope solution having a solid content of 18% by weight. A cast film was prepared from this dope solution, stretched uniaxially at 165 ° C by 1.1 times and then uniaxially stretched at 168 ° C by 1.2 times to obtain a retardation having properties as shown in Table 1. A film was obtained.
[0109]
Next, in the same manner as in Example 1, a VA liquid crystal cell having the characteristics shown in Table 2 was prepared, and the commercially available iodine-based polarizing plate “HLC2-5618” manufactured by Sanritz Co., Ltd. and the above retardation film were implemented. As in Example 1, they were laminated using an adhesive so as to have the configuration shown in FIG. The in-plane retardation value of the TAC film used as a protective layer of the polarizing plate was 2 nm, and the thickness direction retardation value was 48 nm.
[0110]
Although there was almost no light leakage when this panel was viewed from an oblique direction, slight light leakage was confirmed in the 45 ° azimuth, and light leakage of a short wavelength was particularly remarkable.
[0111]
【The invention's effect】
As described above, by arranging one retardation film having a specific retardation wavelength dispersion between the liquid crystal cell and the polarizing film, the long axis of the liquid crystal molecule in a state where no voltage is applied is on the panel surface. It is possible to realize a wide viewing angle of a liquid crystal display element having a structure oriented in a direction substantially perpendicular to the liquid crystal display element.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration of a VA liquid crystal panel according to a first embodiment.

Claims (8)

A liquid crystal cell having a structure in which the major axis of the liquid crystal molecules is oriented in a direction substantially perpendicular to the panel surface in the absence of a voltage, and a pair of polarized lights arranged above and below the liquid crystal cell so that their transmission axes are orthogonal to each other. A liquid crystal display device comprising a film, and a retardation film provided one by one between the liquid crystal cell and the polarizing film, wherein the slow axis of the retardation film is adjacent to the retardation film. A liquid crystal display device arranged so as to be parallel or orthogonal to the transmission axis of the polarizing film to be formed, and wherein the retardation film satisfies the following formulas (1) and / or (2).
1.025 <R (450) / R (550) <1.070 (1)
1.025 <K (450) / K (550) <1.070 (2)
(R (450) and R (550) in the formulas are in-plane retardation values of the retardation film at wavelengths of 450 nm and 550 nm, respectively, and are represented by the following formula (3), and K (450) and K (550) Are retardation values in the thickness direction at wavelengths of 450 nm and 550 nm, respectively, and are represented by the following equation (4).
_{R = (n x -n y)} × d (3)
K = {( _nx + _ny ) / 2- _nz } xd (4)
In the formula, _nx , _ny , and _nz are three-dimensional refractive indices, and are the refractive indices in the x-axis, the y-axis, and the z-axis direction perpendicular to the x-axis and the y-axis in the retardation film plane, respectively. d is the thickness of the retardation film. ) The liquid crystal display device according to claim 1, wherein the retardation film further satisfies the following formulas (5) and (6).
10 nm <R (550) <100 nm (5)
50 nm <K (550) <200 nm (6) The liquid crystal display device according to claim 1, wherein the retardation film further satisfies the following formula (7).

( _Where K _SUM (550) is the sum of the thickness direction retardation values of the two retardation films at a wavelength of 550 nm, K _LC (550) is the thickness direction retardation value of the liquid crystal cell at a wavelength of 550 nm, and K _OTH ( 550) is the sum of the retardation values in the thickness direction of the pair of polarizing films other than the retardation film and the liquid crystal cell.) The liquid crystal display device according to any one of claims 1 to 3, wherein a photoelastic constant of the retardation film is 70 ^10-12 Pa- ¹ or less. The liquid crystal display device according to any one of claims 1 to 4, wherein the water absorption of the retardation film is 1% by weight or less. The retardation film has the following formula (A)

(In the above formula (A), R _{1 to} R ₈ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms, and X is the following formula (X)

Wherein R ₉ and R ₁₀ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms. )
And a repeating unit represented by the following formula (B):

(In the formula (B), R _{11 to} R ₁₈ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms, and Y is a group represented by the following formula group (Y)

, And the wherein _R 19 _{to R 21, R 23} and _{R 24} is at least one group each independently a hydrogen atom, selected from a halogen atom and a hydrocarbon group having 1 to 22 carbon _{atoms, R 22} and R ₂₅ is at least one group independently selected from hydrocarbon groups having 1 to 20 carbon atoms, and Ar _{1 to} Ar ₃ are each at least one group independently selected from aryl groups having 6 to 10 carbon atoms. It is. )
The repeating unit represented by the formula (A), wherein the repeating unit represented by the formula (A) comprises a polycarbonate copolymer and / or a blend occupying 80 to 30 mol% of the whole. Liquid crystal display device. The retardation film has the following formula (C)

(In the above formula (C), R _{26 to} R ₂₇ are each independently selected from a hydrogen atom or a methyl group.) The repeating unit represented by 30 to 60 mol% of the following formula (D)

(In the above formula (D), each of R _{28 to} R ₂₉ is independently selected from a hydrogen atom or a methyl group.) From the polycarbonate copolymer and / or blend in which the repeating unit represented by 70 to 40 mol% accounts for 70 to 40 mol% of the whole The liquid crystal display device according to claim 1. The retardation film according to claim 1.

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