JP3657708B2

JP3657708B2 - Liquid crystal electro-optical device

Info

Publication number: JP3657708B2
Application number: JP24835096A
Authority: JP
Inventors: ますみ岡本; 雅人庄子; 康晴田中; 正仁石川; 暢子福岡; 利博二ノ宮; 毅大山; 典弘吉田; 仁羽藤
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 1995-10-06
Filing date: 1996-09-19
Publication date: 2005-06-08
Anticipated expiration: 2016-09-19
Also published as: JPH09160022A

Description

【０００１】
【発明の属する技術分野】
本発明は液晶電気光学装置に係わり、特に高速応答の液晶電気光学装置に関する。
【０００２】
【従来の技術】
高速応答が得られる液晶電気光学装置として、ＯＣＢモードが注目を集めている。
【０００３】
ＯＣＢの基本構成を図２を用いて説明する。
【０００４】
ＯＣＢモードは、一主面に電極５１ａ、５２ａが形成された２枚の基板５１、５２を主面が対向するように配置し、２枚の基板間に液晶層５３が挟持された液晶セル５０と、液晶セル５０を狭持するように配置された２枚の偏光板６０と、偏光板６０と液晶セル５０間に配置された光学異方素子７０とを有している。
【０００５】
前記液晶層５３は、図２（ａ）に示すように、液晶層５３の液晶分子のうち前記２枚の基板の一方の基板５１に接する複数の液晶分子５３ａからなる第１の液晶層領域Ａと、液晶層の液晶分子のうち２枚の基板の他方の基板５２に接する複数の液晶分子５３ｂからなる第２の液晶層領域Ｂと、液晶層５３の液晶分子のうち第１の液晶層領域Ａと第２の液晶層領域Ｂとに挟まれた複数の液晶分子からなる第３の液晶層領域Ｃとからなる。電極に印加する電圧値を変えることにより、この液晶層の液晶分子は、図２（ａ）、（ｂ）、（ｃ）に示すような配列状態をとる。
【０００６】
ＯＣＢモードの液晶層は、２枚の基板の配向方向が等しく、電圧無印加状態では図２（ａ）に示すようにスプレイ配列状態をとり、電極に電圧を印加すると図２（ｂ）に示すような第３の液晶層領域Ｃの一部の液晶分子５３c1が基板の法線方向とほぼ平行に配列しているベンド配列状態をとり、更に電圧を印加すると図２（ｃ）に示すような第３の液晶層領域Ｃの液晶分子５３c2、５３c3が基板の法線方向とほぼ平行に配列している状態をとる。ＯＣＢモ−ドは、この図２（ｂ）（ｃ）の状態における各々の印加電圧間で表示を行い、電圧を制御することにより液晶層における位相差を変化させて表示する複屈折効果型の液晶表示モードであり、その応答速度は、ＯＣＢモードに関する文献によれば、数ｍｓという必要かつ十分な値が得られることが報告されている。
【０００７】
この表示モードの表示時の液晶分子配列は、液晶の上半分、下半分が常時ほぼ対称な形状となっていることが特徴である。したがって、液晶分子が並ぶ面（図２の紙面方向）に平行となるような視角（観察角度）の範囲であれば、液晶の上半分、下半分がほぼ対称な形状となり、この場合の液晶層の屈折率楕円体は球になり、この範囲であれば視角依存性がほとんど無くなり、広い視野角が得られる。
【０００８】
しかし、液晶が並ぶ面に対して平行でない視角に対しては、液晶層の屈折率楕円体が球にはならず観察角度により屈折率楕円体が変形してしまい視角依存を生じる。
【０００９】
この様な視野角の問題を解決する方法として、厚さ方向の屈折率を最適化した二軸の光軸を有する光学異方素子を附加することが報告されている（宮下ら、Eurodisplay '93, pp149-152）。
【００１０】
また、ＯＣＢモードで良好な黒表示を得るには、高電圧側で黒とするノーマリーホワイトモード表示が好ましい。これは、電圧を印加し液晶分子が図２（ｃ）に示すように第３の液晶層領域Ｃの液晶分子５３ｃがほぼ基板の法線方向に対して平行となる、すなわち液晶分子がほぼ立ち上がった状態を黒表示に用いるものであり、この状態では液晶層の位相差が比較的小さな値であるので、偏光板を直交して得られる黒の均一性が良い。
【００１１】
【発明が解決しようとする課題】
上述したように、広視角かつ高速応答を得るにはＯＣＢモードのＬＣＤが挙げられ、良好な黒表示を得るのにはノーマリホワイトモード表示が好ましい。そして視角を補償するには液晶層の屈折率楕円体を補償して球となるような光学異方素子を選定することが重要となる。
【００１２】
本発明は、ノーマリホワイトモード表示のＯＣＢモード及びその類似のモードに最適な光学異方素子を持つ液晶電気光学装置を提供することを目的とする。なお、ＯＣＢモードと類似のモードとは、液晶層５３が、図２（ｂ）に示すような第３の液晶層領域Ｃの一部の液晶分子５３c1が基板の法線方向とほぼ平行に配列している配列状態を持ち、この配列状態の液晶層に更に電圧をかけて図２（ｃ）に示すような第３の液晶層領域Ｃの液晶分子５３c2、５３c3が基板の法線方向とほぼ平行に配列している状態を持つ液晶電気光学装置をいう。例えば、ＯＣＢモードと同一の配向処理を施した液晶セルにカイラル能を持たせた液晶を入れると、電圧無印加時にはユニフォーム配列で１８０°ツイストの配列が得られる。このような配列に対し、大きな電圧を印加すると前述のベンド配列が容易に得られる。
【００１３】
【課題を解決するための手段】
本発明の液晶電気光学装置は、
ベンド配向を呈することが可能な液晶層を有する液晶セルと、前記液晶セルの視角依存性を低減させる少なくとも一つの光学異方素子と、を備えた液晶電気光学装置において、
前記光学異方素子は、
Ｚ＝（ｎｄｘ−ｎｄｚ）／（ｎｄｘ−ｎｄｙ）としたとき、７≦Ｚ≦１０（ｎｄｘ，ｎｄｙ，ｎｄｚは、前記液晶セルと前記光学異方素子をほぼ平行に配置したときの前記液晶セルの法線方向における前記光学異方素子の厚み（単位：μｍ）と前記光学異方素子との屈折率の積の総和のｘ，ｙ，ｚ方向の屈折率を表す。ｎｄｘ，ｎｄｙは前記光学異方素子の厚み方向とほぼ垂直である面の面内方向における前記光学異方素子の屈折率成分を表し、ｎｄｘ，ｎｄｙは互いに垂直である。ｎｄｚは、前記光学異方素子の厚み方向の前記光学異方素子の屈折率成分を表す。）を満たし、前記光学異方素子の光軸が前記液晶セルの面内方向か法線方向の少なくとも一方にねじれていることを特徴とする液晶電気光学装置を提供するものである。
【００１４】
すなわち、この液晶電気光学装置のベンド配向液晶セルの液晶層は、液晶層の液晶分子のうち２枚の基板の一方の基板に接する複数の液晶分子からなる第１の液晶層領域と、液晶層の液晶分子のうち前記２枚の基板の他方の基板に接する複数の液晶分子からなる第２の液晶層領域と、液晶層の液晶分子のうち第１の液晶層領域と第２の液晶層領域とに挟まれた複数の液晶分子からなる第３の液晶層領域とからなる。電極への第１の電圧印加時では、液晶層は第３の液晶層領域の複数の液晶分子のうちの一部の液晶分子の傾きが基板の法線方向と略平行に配列し、電極への第２の電圧印加時では、液晶層は前記第３の液晶層領域の前記複数の液晶分子はその傾きが前記基板の法線方向と略平行に配列されている。
【００１５】
そして、光学異方素子は、基板の法線方向に対して傾いた方向における、前記第２の電圧印加時の液晶層の、前記２枚の基板に狭持された液晶層の厚さ方向成分の光学異方性を補償することを特徴とする。すなわち、本発明のＯＣＢモード及びＯＣＢモードに類似したモードにおいては、第２の電圧印加時では基板付近の液晶分子を除く液晶分子は基板の法線方向に対してほぼ平行であるため、基板の法線方向、すなわち、液晶層の厚さ方向の光学異方性成分に屈折率異方性が非常に大きくなる。本発明では、、光学異方素子を配置して、基板の法線方向に対して傾いた方向における、このような液晶層の厚さ方向成分の液晶層の光学異方性を補償する。
【００１６】
本発明の液晶層の配列状態をＯＣＢモードに類似したモードの液晶電気光学装置を例にあげて図１を用いて説明する。
【００１７】
図１（ａ）に示すように、液晶層１３は複数の液晶分子からなり、この液晶層１３は、２枚の基板の一方の基板、すなわち電極１１ａを持つ基板１１に接する複数の液晶分子１３ａからなる第１の液晶層領域Ａと、２枚の基板の他方であり電極１２ａを持つ基板１２に接する複数の液晶分子１３ｂからなる第２の液晶層領域Ｂと、第１の液晶層領域と第２の液晶層領域とに挟まれた複数の液晶分子１３ｃからなる第３の液晶層領域Ｃとからなる。そして、図１（ａ）は電圧を電極への電圧無印加時の液晶分子の配列を示し、図１（ｂ）は電極への第１の電圧印加状態を示し、図１（ｃ）は電極への第２の電圧印加状態を示す。
【００１８】
図１（ａ）に示すように、電極に接続された電圧駆動源４０から電極１１ａ、１２ａへの電圧無印加時では、第３の液晶層領域Ｃの複数の液晶分子１３ｃは互いに略平行で、かつ一方の基板から他方の基板に向かって前記基板の面内方向でねじれて配列している。
【００１９】
図１（ｂ）に示すように、電極１１ａ、１２ａへの第１の電圧印加時では、第３の液晶層領域Ｃの複数の液晶分子のうち層中央の一部の液晶分子１３c1の傾きが基板の法線方向と略平行に配列している。この第１の電圧印加時とは、閾値電圧以上で液晶分子が基板の法線方向と略平行、すなわち液晶分子が立ち上がり始めた液晶セルの位相差の印加電圧による変化が急激である状態より更に、液晶への印加電圧を大きくした時である。
【００２０】
次に、図１（ｃ）に示すように、電極１１ａ、１２ａへの第２の電圧印加時では、第３の液晶層領域の電極に接する側の複数の液晶分子１３c2、１３c3の傾きが基板の法線方向と略平行に配列している。この第２の電圧印加時は、第１の電圧印加時よりも更に電圧をかけた状態であり、このとき第３の液晶層領域の液晶分子１３c2、１３c3が前記基板の法線方向とほぼ平行に配列している状態、すなわち液晶が立ち上がった状態となる。
【００２１】
このようなＯＣＢモードに類似のモード及びＯＣＢモードでは、図１（ｂ）、（ｃ）に示すような配列状態では、２枚の基板１１、１２間に液晶層１３を狭持した液晶層厚み方向で液晶層の上半分と下半分は液晶層の中央付近を境にほぼ対称のベンド配列となっている。このため、図４に示すように液晶分子が厚み方向に並ぶ平面４０に対してほぼ平行となるような視角（観察角度）の範囲であれば、液晶の上半分、下半分がほぼ対称な形状となり、この場合の液晶層の光学異方性を表す屈折率楕円体は球になり、この範囲であれば視角依存性がほとんど無くなり、広い視野角が得られる。一方、図４に示す平面４０に対して平行でない視角に対しては、液晶層の屈折率楕円体が球にはならず観察角度により屈折率楕円体が変形してしまい視角依存を生じる。
【００２２】
本発明はこのような液晶層の光学異方性を補償することにより、より広い視角を得ることができるものである。
【００２３】
すなわち、本発明の液晶電気光学装置は、下記の屈折率楕円係数Ｚ値をもつ２軸の光軸を有する負の光学異方性を持つ光学異方素子を有する。
【００２４】
Ｚ＝（ｎｄx −ｎｄz ）／（ｎｄx −ｎｄy ）としたとき、７≦Ｚ≦１０
ここに、ｎｄx ，ｎｄy ，ｎｄz は、基板と光学異方素子をほぼ平行に配置したときの前記基板の法線方向における前記光学異方素子の厚み（単位：μｍ）と前記光学異方素子との屈折率の積の総和のｘ，ｙ，ｚ方向の屈折率成分を表す。ｎｄx ，ｎｄy は、前記光学異方素子の厚み方向とほぼ垂直である面の面内方向における前記光学異方素子の屈折率成分を表し、ｎｄx ，ｎｄy は互いに垂直である。ｎｄz は、前記光学異方素子の厚み方向の前記光学異方素子の屈折率成分を表す。
【００２５】
液晶セルの液晶層が図４に示した配向の場合、これ等価な屈折率楕円体は図５に示すように
ｎzLC ＞ｎxLC ＞ｎyLC
で、図５の楕円体ＲＬの各断面であるｘｚ面、ｙｚ面、ｘｙ面から明らかなように、例えると「ラグビーボール」がｙ方向に圧縮された形状になる。
【００２６】
これを補償する光学異方素子の屈折率楕円体ＲＣは図６に示すように、図５と逆に「ラグビーボール」の長軸方向ｚを他の２軸よりも圧縮し、かつ他の２軸のうちｙ方向を長くした形状にするのが望ましい。
【００２７】
この屈折率楕円体を屈折率の式に表すと、
Ｚ＝（ｎxC−ｎzC）／（ｎxC−ｎyC）
ここに、ｎzC ＜ｎxC １２＜ｎyCである。
【００２８】
ここで、ｎz の大きさは、図１の液晶層１３の基板に接する領域Ａ、Ｂの液晶分子１３ａ、１３ｂの傾き、すなわちプレチルト角に依存する。
【００２９】
均一表示を得るには、プレチルト角と液晶層の厚みが均一であることが望まれるが、均一にし得るプレチルト角は高くなるに従い製作が難しく、高々８度が限界である。したがってＺ値はプレチルト角により変化し、実現可能なプレチルト角の範囲では、
７≦Ｚ≦１０
となる。
【００３０】
このような光学異方素子を配置した液晶電気光学装置は、ＯＣＢモード及びそれと類似のモードのノーマリーホワイト表示に適している。これにより、基板の法線方向に対して傾いた方向における、このような液晶層の厚さ方向成分の液晶層の光学異方性を補償して、視角をより広くすることができる。この範囲内であれば、視角が広く、反転領域の非常に少ない、優れた表示性能が得られる。Ｚの値が、７未満になると、反転領域が広くなり、コントラスト比が良好な範囲も狭くなる。また、１０より大きくなると、再度反転領域が増加する。
【００３１】
更に、本発明では、Ｚの値が、
８≦Ｚ≦１０
であることがより好ましい。
【００３２】
本発明では、ＯＣＢ及びこれと類似した表示モードＯＣＢ及びこれと類似した表示モードは、より広い視野角を得るために先に述べた条件の光学異方素子を使用する。更に、本発明では、光学異方素子のリタデーションと液晶セルのリタデーションの関係を特定の条件に設定することにより、駆動電圧を実用範囲内にし、かつ、明るい表示ができることを見出した。
【００３３】
ＯＣＢ及びこれと類似した表示モードは、全て複屈折モードであり、その液晶セルの透過率Ｔは、次式で表される。
【００３４】
Ｔ＝ｓｉｎ²（Ｒ／πλ）−−−（１）
（１）式は直交ニコルで、光軸は透過率軸と４５°の時の透過率を表す。Ｒは偏光板間に存在する光学異方体のリタデーション値であり、λは光源波長である。
【００３５】
光学異方素子の光軸の向きは、液晶セルのラビング軸の向きに対して垂直である。この様な配置の場合、総リタデーション値は、液晶セルのリタデーションＲLCと光学異方素子のリタデーションＲfxy のそれぞれのリタデーション値の差となり、式（１）中のパラメータＲは、
Ｒ＝ＲLC−Ｒfxy −−−（２）
となる。
【００３６】
したがって、（２）式から、液晶セルの透過率は、液晶セルのリタデーションと光学異方素子の面内方向のリタデーションの差により決まる。すなわち、光学異方素子の面内方向のリタデーションは、ディスプレイの明るさに影響する。
【００３７】
液晶セルのリタデーションは液晶層に印加される電圧によって変化する。液晶セルの電圧が変化し、液晶セルのリタデーションと光学異方素子の面内方向のリタデーションが等しくなったとき、総リタデーションは零となり、黒の表示が得られる。
【００３８】
すなわち、光学異方素子の面内方向リタデーションは、黒表示が得られる電圧値に影響する。そこで、光学異方素子の面内方向リタデーションと光学異方素子の面内方向リタデーションの比、すなわちリタデーション比Ｍとして次の様にＭを定義し、これらの影響を調べた。
【００３９】
Ｍ＝ＲLC／Ｒfxy ＝ΔｎLC×ｄLC／（ｎｄx −ｎｄy ）−−（３）
ここで、ΔｎLCは液晶の屈折率差、ｄLCは液晶層の厚みである。
【００４０】
図１１に、リタデーション比Ｍに対する電気光学特性への依存性を示す。Ｍの値が７．５以下になると、透過率が低下するため、コントラスト比が下がり、表示品位が劣化する。又、Ｍが１８以上になると、透過率が上がり表示品位は良くなるが、黒表示電圧が１０Ｖ以上と高くなり過ぎ、消費電力の増加や高電圧印加のための特殊な高耐圧集積回路が必要となり実用的でない。したがって、良好な明るさと実用的な黒表示電圧を達成できるリタデーション比Ｍは、
７．５＜Ｍ＜１８
である。
【００４１】
また、本発明の液晶電気光学装置は、光学異方素子が、
０．０２２≦ｎｄx −ｎｄy ≦０．６６７
０．１５＜ｎｄx −ｎｄz ＜６．７
とするのが好ましい。これにより、液晶層の△ｎLC・ｄLCの値が０．３μｍ以上５μｍ以下とした時に最適な光学異方素子を有する液晶電気光学装置を得ることができる。
【００４２】
また、本発明の液晶電気光学装置は、２枚の偏光板の内、１枚を反射板とすることができる。
【００４３】
この場合、光が装置を２度通過するので、（ｎｄx −ｎｄy ）の下限値は０．０１１となる。
【００４４】
また、本発明の液晶電気光学装置は、第１の電圧印加時を液晶電気光学装置の表示のオン時とすると、第１の電圧印加時では液晶層の配列状態が第３の液晶層領域Ｃの複数の液晶分子のうち一部の液晶分子９ａの傾きが基板の法線方向と略平行に配列しているため、高速応答の表示を得ることができる。
【００４５】
また、本発明の液晶電気光学装置は、第１の電圧印加時と第２の電圧印加時の間で表示を行うことを特徴とする。これにより高速応答の表示を得ることができる。
【００４６】
また、本発明の液晶光学素子は、第１の電圧印加時における第３の液晶層領域の前記基板の法線方向と略平行に配列した液晶分子を中心にして、２枚の基板間に挟持された液晶層の厚さ方向に、２枚の各々の基板に向かって段階的に液晶分子の傾きが変化していることを特徴とする。
【００４７】
また、本発明の液晶光学素子は、第１の電圧印加時の液晶層の厚さ方向における第３の液晶層領域の中央部の液晶分子の傾きが基板の法線方向と略平行に配列していることを特徴とする。
【００４８】
また、本発明の液晶電気光学装置は２枚の偏光板は各々の光学軸が直交するように配置されることを特徴とする。このように設定し、かつ上記のように屈折率楕円係数Ｚ、リタデーション比Ｍの値を設定することにより、第２の電圧印加時で良好な黒表示を得ることができる。
【００４９】
２枚の偏光板が直交する時と平行な時とを比較した場合、どちらでも表示可能であるが、良好なコントラスト比を得るためには良い黒を得るすなわち透過率が低いことが必要となるので、偏光板が直交状態であることがより好ましい。これは、偏光板が平行状態で黒の場合は、波長分散の影響が出るためである。偏光板が平行状態では、コントラスト比は低下すると考えられるが、透過率を高くしやすい。
【００５０】
偏光板の光学軸を、前記２枚の基板の各々の配向処理方向のなす角を２等分する２等分線から４５°傾いた方向に設定することを特徴とする。これは、２枚の偏光板を直交に配置した時でも平行に配置した時でも、このように設定することにより最大透過率を得ることができる。
【００５１】
以上の液晶電気光学装置に適用できる具体的なＯＣＢモードおよびＯＣＢモードに類似のモードの液晶層の配列状態を以下に示す。なお、２枚の偏光板のうち１枚を反射板とした場合にも適用できる。この場合、液晶セルに入射した光は液晶層厚の２倍の距離を通過することとなるので、透過型に比べ液晶層厚を約半分にでき、応答速度の更なる改善が期待できる。
【００５２】
本発明の液晶電気光学装置は、２枚の基板の一方の基板から他方の基板に向かって配列する液晶層の液晶分子は、電圧無印加時にスプレイ配列していることを特徴とする。すなわち、ＯＣＢモードに適用することができる。
【００５３】
さらに、本発明の液晶電気光学装置の一態様は、２枚の基板の一方の基板から他方の基板に向かって配列する液晶層の液晶分子の前記基板内の面内方向のねじれ能θ0 が、θ0 ＝０°である。
【００５４】
ここに、ねじれ能とは、液晶自体が持つ自発的なねじれ角を示し、一般にねじれ能はコレステリック液晶組成物の混合濃度により制御できる。
【００５５】
さらに、本発明の液晶電気光学装置の他の態様は、２枚の一方の基板から他方の基板に向かって配列する液晶層の液晶分子の基板内の面内方向のねじれ能θ0 が、θ0 ＞０°であることを特徴とする。このようにねじれ能θ0 をθ0 ＞０°にすることにより、電圧無印加時のスプレイ配向状態から第１の電圧印加時の第３の液晶層領域の１部の複数の液晶分子の傾きが基板の法線方向と略平行に配列している状態への移動時間がθ0 ＝０°であるときと比べ、格段に早くすることができる。
【００５６】
さらに、本発明の液晶電気光学装置の他の態様は、２枚の基板の一方の基板から他方の基板に向かって配列する液晶層の液晶分子の基板内の面内方向のねじれ能θ0 が、θ0 ＝９０°で、かつプレチルト角が２枚の基板で異なることを特徴とする。θ0 ＝９０°のとき、プレチルト角が２枚の基板で異ならせることにより、表示を可能とする。
【００５７】
さらに、本発明の液晶電気光学装置の他の態様は、２枚の基板の一方の基板から他方の基板に向かって配列する液晶層の液晶分子の基板内の面内方向のねじれ能θが、θ＝１８０°であることを特徴とする。バックフロー効果を考えた場合、ねじれ能が１８０°及びその前後である１７５°〜１８５°であることが最も望ましい。ここで、バックフロ−効果について説明する。例えば電圧がかかっている時の中央近傍のやや立ち上がった液晶分子は、電圧を切ることにより基板付近の寝ている状態の液晶分子に引き戻される。しかし、中央付近の立ち上がった部分の液晶分子は、中央近傍の液晶分子によって寝た状態になるのを妨げられ、戻りが遅くなる。これをバックフロー効果という。ベンド配列の場合、このバックフロー効果は無くなるが、液晶が１８０°ねじれた状態を除いたねじれ状態が生じた場合、このバックフロー効果が発生する。
【００５８】
また、本発明の液晶電気光学装置は、電極への電圧無印加時では、前記第３の液晶層領域の複数の液晶分子は互いに略平行で、かつ一方の基板から他方の基板に向かって基板の面内方向でねじれて配列することを特徴とする。すなわち、ＯＣＢモードと類似のモードであり、この場合でも本発明は適用可能である。この場合、ＯＣＢモードと同様に表示領域にて高速応答が可能となる。
【００５９】
さらに、ＯＣＢモードと類似のモードとしては、本発明の液晶電気光学装置は、２枚の基板の一方の基板から他方の基板に向かって配列する液晶層の液晶分子の基板内の面内方向のねじれ角θが、略９０°または略２７０°であり、かつ液晶層のプレチルト角が前記２枚の基板で異なることを特徴とする。この場合、ねじれ角θが、９０°または２７０°の場合、液晶層の中央付近の液晶分子が立ち上がった状態の領域では、二枚の基板表面での液晶分子のプレチルト角が等しい場合、液晶層の上半分と下半分での位相差の大きさが等しくなり、しかもその方向が互いにほぼ９０度となっている。この為セル全体としての位相差はセルの上半分と下半分が互いに補償する関係となる。このため、印加電圧を更に増加させて液晶分子を駆動しても光学応答を変化させることができない。これに対し、プレチルト角を２枚の基板間で異ならせることにより、セルの上半分と下半分とで配列が異なるために位相差が生じ、２枚の基板間でプレチルト角が等しいセルの飽和電圧を印加したときでも明の表示ができる。したがって、さらに、電圧を印加することで、暗の表示が得られ、高速表示が可能になる。このようなセル全体としての位相差がセルの上半分と下半分が互いに補償する関係となるねじれ角９０°または２７０°の場合、そしてこのような関係となる傾向の強いねじれ角９０°を除く８５°〜９５°、ねじれ角２７０°を除く２６５°〜２７５°の場合に、２枚の基板のプレチルト角の大きさを変えることは有効である。
【００６０】
また、本発明の液晶電気光学装置の他の態様は、液晶層が、第１の電圧印加時は電圧が無印加であることを特徴とする。すなわち、電圧無印加時に第３の液晶層領域の１部の複数の液晶分子の傾きが基板の法線方向と略平行に配列している状態となっているものであり、ＯＣＢモードと類似のモードであり、この場合でも本発明は適用可能である。
【００６１】
本発明の液晶電気光学装置に用いる光学異方素子について、以下に示す。
【００６２】
光学異方素子は２軸の光軸からなる少なくとも１枚の位相差板であることを特徴とする。
【００６３】
また、１枚のみで本発明のＺの範囲が実現できない場合の光学異方素子の一態様は、１軸の光軸からなる２枚以上の位相差板の組み合わせからなり、少なくとも２枚の位相差板の光軸が異なることを特徴とする。
【００６４】
また、一軸の光学異方素子の組み合わせでＺの値の範囲が実現できない場合は、光学異方素子の一態様は、１軸の光軸からなる少なくとも１枚の位相差板と、２軸の光軸からなる少なくとも１枚の位相差板とからなることを特徴とする。
【００６５】
また、光学異方素子の他の態様は、基板と光学異方素子をほぼ平行に配置したときの基板の法線方向に光学異方性が負である少なくとも１枚の位相差板とからなることを特徴とする。
【００６６】
また、液晶セルのねじれの光学効果をより良く補償したい場合には、光学異方素子の他の態様は、光学異方素子の光軸のねじれは、基板の面内方向または、基板の法線方向または基板の面内方向と法線方向の両方の方向にねじれていることを特徴とする。
【００６７】
この様な光学異方素子は液晶層のねじれを補償する、または、液晶層の基板の法線方向成分の光学異方性を補償する。
【００６８】
以上のように、本発明では、光学異方素子は、１軸または２軸の光軸をもつ位相差板、負の位相差板を単独あるいは組み合わせることにより、光学異方素子として２軸の光軸をもつようにすれば良い。例えば、１軸の光軸を有する位相差板を２枚以上組み合わせる場合であれば、少なくとも２枚の位相差板の光軸が一致しないように配置して、光学異方素子として２軸の光軸を持つようにする必要がある。
【００６９】
また、液晶層の液晶分子の基板の面内方向または、基板の法線方向または基板の面内方向と法線方向の両方によるねじれを補償するように、光学異方素子の光軸にねじれを持たせることにより、液晶層のねじれによる光学的影響を補償することができる。この場合、液晶層は、部分的あるいはほぼ全体的に、一方の基板から他方の基板に向かって連続的にあるいは段階的に液晶分子が、基板の面内方向あるいは法線方向あるいはその両方の方向でねじれている場合を含む。
【００７０】
また、液晶層の基板の法線方向成分に負である位相差板と光学特性上同等となるように、光学異方素子の光軸にねじれを持たせることにより、液晶層の基板の方線方向成分の光学異方性を補償することができる。この場合、光軸のねじれ角の大きい、例えば、光学異方素子の光軸を基板の面内方向にねじった光軸により実現できる。
【００７１】
位相差板の材質としては、ポリカーボネート、ポリアリレートなど、また、光学異方素子として光軸にねじれをもたせるために、コレステリック液晶ポリマー、ディスコティック液晶ポリマーなどの位相差板を用いることができるが、上記の特性が得られるものであれば、これら材料に限定されない。
【００７２】
【発明の実施の形態】
以下本発明の液晶電気光学装置の実施例を、液晶層の液晶分子が電圧無印加時に液晶分子同志がほぼ平行に配列しており、２枚の基板の一方の基板から他方の基板に向かって配列する前記液晶層の液晶分子の基板内の面内方向のねじれ角θは、θ＝１８０°である場合を例に挙げて詳細に説明する。
【００７３】
（実施例１）
図３及び図４に示すように、本実施例の液晶電気光学装置１は、液晶セル１０、この液晶セル１０を挟む２枚の偏光板２０および液晶セルと一方の偏光板で挟まれた光学異方素子３０と、電圧駆動源４０とからなる。
【００７４】
液晶セル１０は一主面に電極１１ａが形成された第１の基板１１と、一主面に電極１２ａが形成された第２の基板１２を電極が対向するように配置し、２枚の基板１１、１２間に液晶層１３を挟持している。この装置はノーマリホワイト表示の液晶電気光学装置である。光学異方素子３０は、液晶層１３の光学異方性を補償している。
【００７５】
図１に示すように、液晶層１３は複数の液晶分子からなり、この液晶層１３は、２枚の基板の一方の基板１１に接する複数の液晶分子１３ａからなる第１の液晶層領域Ａと、２枚の基板の他方の基板１２に接する複数の液晶分子１３ｂからなる第２の液晶層領域Ｂと、第１の液晶層領域と第２の液晶層領域とに挟まれた複数の液晶分子１３ｃからなる第３の液晶層領域Ｃとからなる。そして、図１（ａ）は電圧を電極への電圧無印加時の液晶分子の配列を示し、図１（ｂ）は電極への第１の電圧印加状態を示し、図１（ｃ）は電極への第２の電圧印加状態を示す。
【００７６】
図１（ａ）に示すように、電圧駆動源４０から電極１１ａ、１２ａへの電圧無印加時では、第３の液晶層領域Ｃの複数の液晶分子１３ｃは互いに略平行で、かつ一方の基板から他方の基板に向かって前記基板の面内方向でねじれて配列している。
【００７７】
図１（ｂ）に示すように、電極への第１の電圧印加時では、第３の液晶層領域Ｃの複数の液晶分子のうち一部の液晶分子１３c1の傾きが基板の法線方向と略平行に配列している。この第１の電圧印加時とは、閾値電圧以上で液晶分子が基板の法線方向と略平行、すなわち液晶分子が立ち上がり始めた液晶セルの位相差の印加電圧による変化が急激である状態より更に、液晶への印加電圧を更に大きくした時である。
【００７８】
図１（ｃ）に示すように、電極への第２の電圧印加時では、第３の液晶層領域の複数の液晶分子１３c1、１３c2、１３c3の傾きが基板の法線方向と略平行に配列している。この第２の電圧印加時は、第１の電圧印加時よりも更に電圧をかけた状態であり、このとき第３の液晶層領域の液晶分子１３ｃが前記基板の法線方向とほぼ平行に配列している状態、すなわち液晶が立ち上がった状態となる。
【００７９】
この液晶層１３を２枚の基板にて狭持した液晶セル１０を図３に示している。図に示すように、液晶セル１０は、ガラス基板の一主面に電極１２ａが形成されたアレイ基板１２とガラス基板の一主面上に電極１１ａが形成された対向基板１１の２枚の基板を主面が対向するように配置し、２枚の基板間にネマティック液晶層１３が挟持されてなる。
【００８０】
図３に示すようにアレイ基板１２は、ガラス基板上にマトリクス状に複数の信号線（図示せず）および複数の走査線（図示せず）が配設され、これらの交点に対応してポリシリコンのＴＦＴ１２ｂとこのＴＦＴに接続して形成された画素電極１２ａが形成されており、これらの上に配向膜１２ｃが形成されている。一方、対向基板１１は、ガラス基板上に前記アレイ基板１１の各画素電極１２ａに対応して赤、緑、青の三原色からなるカラーフィルタ１１ｂと、これら各色のカラーフルタを区画するように形成されたブラックマトリクス１１ｃが形成され、これらの上にＩＴＯ電極１１ａ、配向膜１１ｄが順次形成されている。
【００８１】
次に、製造方法および表示方法について説明する。
【００８２】
ガラス基板上にポリシリコンＴＦＴ３と走査線（図示せず）であるゲート線、信号線（図示せず）、画素電極１２ａを形成した、画素数が縦４８０、横６４０×３画素のアレイ基板１２を形成した。
【００８３】
次に、ガラス基板上にアレイ基板１２の各画素電極に対応して赤、緑、青の三原色からなるカラーフィルタ１１ｂと、これら各色のカラーフルタを区画するように形成されたブラックマトリクス１１ｃとを形成し、この上にＩＴＯ電極１１ａを形成して対向基板１１を形成した。これら２枚のアレイ基板１２、対向基板１１上に各々配向膜１２ｃ、１１ｄとしてとしてポリイミド（SE-5211 、（株）日産化学社製。プレチルト角約５゜）を８０ｎｍの厚さに塗布・形成した。ここで、画素ピッチは縦０．３３ｍｍ、横０．１１ｍｍである。続いて前記配向膜を、走査線に平行かつ、２枚の基板１１、１２上の各々の電極１１ａ、１２ａが対向するように配置したときに、２枚の基板のラビング方向ＲＡが互いに平行になるような方向にラビングした。
【００８４】
次に、アレイ基板１２上にスペーサ（図示せず）として直径７．１μｍの球状微粒子（ミクロパールＳＰ、（株）積水ファインケミカル製）を一方の基板の主面に８０個／ｍｍ²の密度で散布した。もう一方の対向基板１１の有効表示領域の周辺部をエポキシ樹脂の接着剤（XN-21 、三井東圧化学株式会社製）を、液晶注入のための開口部を除いてスクリーン印刷法によって塗布した。その後、アレイ基板１２と対向基板１１を前記配向膜どうしを対向させた状態で重ね合わせ、加圧しながら加熱して接着し、セルギャップが７．１μｍの液晶セル１０を作製した。
【００８５】
そしてこの液晶セルに液晶組成物１３としてネマティック液晶組成物（ZLI-1132、E.Merck 社製。Δｎ＝0.14）にカイラル剤（S811、E.Merck 社製）を添加したものを真空注入法により注入し、注入後液晶の注入口を紫外線硬化樹脂（UV-1000 、（株）ソニーケミカル製）にて封止した。この時、カイラル剤の濃度は、液晶のらせんピッチが約３５μm となるように調整した。この液晶セルのカラーフィルタ１１ｂが形成された対向基板１１側に、光学異方素子３０として、ポリカーボネート製の光学異方素子である位相差板を、位相差板の屈折率が大きい方向をラビング方向に直交するように配置した。
【００８６】
光学異方素子３０の楕円係数Ｚは，
Ｚ＝（ｎｄx −ｎｄz ）／（ｎｄx −ｎｄy ）
としたとき、Ｚ＝９になるようにした。
【００８７】
ここに、ｎｄx ，ｎｄy ，ｎｄz は、前記基板と前記光学異方素子をほぼ平行に配置したときの前記基板の法線方向における前記光学異方素子の厚み（単位：μｍ）と前記光学異方素子との屈折率の積の総和を表す。ｎｄx ，ｎｄy は、前記光学異方素子の厚み方向とほぼ垂直である面の面内方向における前記光学異方素子の屈折率成分を表し、ｎｄx ，ｎｄy は互いに垂直である。ｎｄz は、前記光学異方素子の厚み方向の前記光学異方素子の屈折率成分を表す。
【００８８】
さらに偏光板２０（G1220DU 、（株）日東電工製）を、光学軸がラビング方向に対して４５゜でかつ２枚の偏光板の光学軸が互いに直交するように貼り付けた。位相差板には、フィルムをｘ軸方向に延伸した後、ｙ軸方向に延伸して２軸とした位相差板の面内方向の位相差の値が１００ｎｍ（ｎｄx とｎｄy との差が０．１）である位相差板を用い、第２の電圧印加状態の時の前記液晶セルの位相差を補償するように配置、すなわち２枚の偏光板の光学軸が互いに直交し、かつ位相差板の屈折率が大きい方向をラビング方向に直交するように配置した。そして、この光学異方素子はリタデーション比をＭとしたとき、
Ｍ＝ΔｎLC・ｄLC／（ｎｄx −ｎｄy ）
から、Ｍ＝１０になるようにした。
【００８９】
前記液晶層の厚みをｄLC（単位：μｍ）、前記液晶層の屈折率異方性をΔｎLCとする。
【００９０】
得られた液晶電気光学装置は、電極への電圧無印加時では、第３の液晶層領域Ｃの複数の液晶分子は互いに略平行で、かつ一方の基板から他方の基板に向かって前記基板の面内方向で１８０°ねじれて配列している。
【００９１】
第１の電圧印加時では、第３の液晶層領域Ｃの複数の液晶分子のうち第３の液晶層領域Ｃの中央部の液晶分子１３c1の傾きが基板の法線方向と略平行に配列し、液晶分子１３c1を中心にして、２枚の基板間に挟持された液晶層１３の厚さ方向に、液晶分子１３c2、１３c3のように、２枚の各々の基板１１、１２に向かって段階的に液晶分子の傾きが変化している。
【００９２】
第２の電圧印加時では、第３の液晶層領域の複数の液晶分子１３ｃの傾きが基板の法線方向と略平行に配列している。
【００９３】
この第１の電圧印加時と前記第２の電圧印加時の間で電圧駆動源４０によりオン、オフ駆動して表示を行った。本実施例の場合、セルの実効的な位相差がおおよそ０．２６μｍとなる電圧を駆動電圧の最小値として使用した。第１の電圧印加を２．４Ｖ、第２の電圧印加を６．５Ｖとして表示を行った。
【００９４】
その結果、図９に示すように、駆動電圧に対して透過率が単調に減少する電気光学特性が得られ、正面でのコントラスト比は１００以上が得られ、視角も広かった。応答速度は階調間での差はほとんど無く、約５ｍｓと高速であり、動きのある画像を表示しても輪郭がぼやけることなど無く良好な表示が得られた。なお、図７〜図１０は等コントラストを表す図であり、円の中心を基板の法線方向を観察方向の基準とした時の観察方向によるコントラストを表し、斜線部分は反転領域を示す。図７〜図１０において、円の中心から外側に向かって同心円状に円が大きくなるにしたがって、基板の方線方向と観察方向とのなす角度が大きくなり、円の中心と円上のある任意の点を結んだ線の方向（アジマス）が基板の面内方向における観察方向を表す。
【００９５】
図中、曲線（５０）がコントラスト比（５０）、この曲線（５０）で囲まれた領域がコントラスト比５０以上、曲線（１０）で囲まれた領域がコントラスト比５０〜１０、曲線（１）で囲まれた領域がコントラスト比１〜１０である。
【００９６】
（実施例２）
実施例１における位相差板のＺの値を７として、実施例１と同一の部材と条件でＴＦＴ−ＬＣＤを作製した。この結果を図８に示す。こうして得られたＬＣＤは視角を振っても良好な表示が得られた。
【００９７】
（比較例１）
実施例１における位相差板のＺの値を１（１軸位相差板１枚使用）として、実施例１と同一の部材と条件でＴＦＴ−ＬＣＤを作製した。この結果を図７に示す。こうして得られたＬＣＤは視角を振ったときに反転領域が非常に広く、また、コントラストの低下も著しかった。
【００９８】
（比較例２）
実施例１における位相差板のＺの値を１２（１軸位相差板１枚使用）として、実施例１と同一の部材と条件でＴＦＴ−ＬＣＤを作製した。この結果を図１０に示す。こうして得られたＬＣＤは視角を振ったときに反転領域が非常に広く、また、コントラストの低下も著しかった。
【００９９】
以上のように、Ｚの値を７≦Ｚ≦１０、さらに好ましくは８≦Ｚ≦１０となるような光学異方素子を用いることにより、視角依存性の少ない液晶光学素子を得ることができる。
【０１００】
また、ここでは、液晶層の液晶分子が電圧無印加時に液晶分子同志がほぼ平行に配列しており、２枚の基板の一方の基板から他方の基板に向かって配列する前記液晶層の液晶分子の基板内の面内方向のねじれ角θは、θ＝１８０°である場合を例に挙げて説明したが、ノーマリホワイトモード表示のＯＣＢモード及びその類似のモードにも適用でき、同様の効果を得ることができる。
【０１０１】
また、△ｎLC・ｄLCを１．０として、Ｍの値を変化させた場合の印加電圧（横軸）と透過率（縦軸）との関係を図１１に示す。
【０１０２】
（実施例３）
実施例１における光学異方素子を、位相差板の面内方向における位相差の値が４００ｎｍの１軸位相差板と、位相差板の面内方向における位相差の値が５００ｎｍの１軸位相差板の２枚を、光軸が直交するように重ね合わせ、Ｚ＝９，Ｍ＝１０となるように光学異方素子を作製した以外は、実施例１と同一の部材と条件でＴＦＴ−ＬＣＤを作製した。こうして得られたＬＣＤは視角は視角特性が改善されていた。
【０１０３】
（実施例４）
実施例１における光学異方素子を、位相差板の面内方向における位相差の値が１００ｎｍの１軸位相差板１枚と負の位相差板（ｎｄx ，ｎｄy ＞ｎｄz ）を組み合わせて、光学異方素子としてＺ値が９となるように作製した以外は、実施例１と同一の部材と条件でＴＦＴ−ＬＣＤを作製した。こうして得られたＬＣＤは視角は視角特性が改善されていた。
【０１０４】
（比較例３）
実施例１におけるスペーサの直径を５．３μｍとし、セルギャップを５．３μｍとした以外は、実施例１と同様Ｚの値が９の光学異方素子を用い、同一の部材と条件でＭ＝７．４のＴＦＴ−ＬＣＤを作製した。こうして得られたＬＣＤは透過率が低く、表示品位が損なわれがちであった。
【０１０５】
（比較例４）
実施例１におけるスペーサの直径を１３μｍとし、セルギャップを１３μｍとした以外は、実施例１と同一の部材と条件でＭ＝１８．２のＴＦＴ−ＬＣＤを作製した。こうして得られたＬＣＤは最大電圧を６Ｖまでしかかけれれなかった（これ以上の電圧ではＴＦＴ素子が破壊されるため）ため、十分に黒くすることができず、表示品位が損なわれがちであった。
【０１０６】
以上のように、本発明の光学異方素子は、２軸の光軸を有する位相差板を１枚以上用いる、１軸の光軸を有する位相差板を２枚以上用いる、２軸あるいは１軸の光軸を有する位相差板と負の位相差板を併用することなどで得られる。また、Ｍの値を７．５＜Ｍ＜１８とすることにより表示品位の良い液晶光学素子を得ることができる。
【０１０７】
（実施例５）
実施例１における偏光板のうち１枚を反射板にかえ、スペーサの直径を３．６μｍとし、セルギャップを３．６μｍとし、位相差板の面内方向における位相差の値が５０ｎｍである２軸の位相差板を用いた以外は、実施例１と同一の部材と条件でＺ＝９、Ｍ＝１０のＴＦＴ−ＬＣＤを作製した。こうして得られたＬＣＤを駆動したところ、視角特性が良好で、明るい表示が得られた。
【０１０８】
（実施例６）
実施例１における光学異方素子を、ねじれ位相差板２枚を組み合わせて作製した。具体的には、コレステリック液晶ポリマーからなる基板の面内方向に光軸のねじれ角が１０°で面内方向の位相差が１００ｎｍの位相差板１枚と、基板の面内方向に光軸のねじれ角が６５０°で面内方向の位相差が零の位相差板１枚の２枚を組み合わせて作製した。この光学異方素子は、全体には光軸のねじれが基板の面内方向に６６０°ねじれている。
【０１０９】
このように、光学異方素子の光軸にねじれを与えたことにより、高コントラストが得られ、また、光軸のねじれ角が６５０°の位相差板を用いることにより、光学特性上負の位相差板を有したものと同じ効果を得、視角特性が良好となった。
【０１１０】
（実施例７）
実施例１における光学異方素子をねじれ位相差板１枚と、負の位相差板１枚とを組み合わせて作製した。すなわち、、コレステリック液晶ポリマーからなる基板の方向に光軸のねじれ角が１０°の位相差板１枚と、基板と光学異方素子をほぼ平行に配置したときの基板の法線方向に光学異方性が負である負の位相差板を組み合わして、光学異方素子全体でＺ＝９となるように光学異方素子を作製した。
【０１１１】
このように、光学異方素子の光軸にねじれを与えたことにより、高コントラストが得られ、負の位相差板であることから、視角特性が良好となった。
【０１１２】
（実施例８）
実施例１における光学異方素子を、２軸のねじれのない位相差板１枚とねじれ位相差板１枚を組み合わせて作製した。すなわち、コレステリック液晶ポリマーからなるねじれ位相差板１枚と２軸位相差板との組み合わせで、光学異方素子全体でＺ＝９となるように光学異方素子を作製した。これにより、視角特性が良好となった。
【０１１３】
以上の実施例で説明した本発明の液晶電気光学装置は、パソコン、ワープロ等に用いる液晶表示素子やビデオプロジェクタのライトバルブ、３Ｄ−ＴＶに使用するメガネに用いる高速液晶シャッタ等に広く応用することができる。
【０１１４】
【発明の効果】
本発明の液晶電気光学装置は、ＯＣＢモードまたは類似のモードの液晶セルに組み合わせる光学異方素子が２軸、かつ負の光学異方性を有し、楕円係数Ｚを７以上１０以下に設定したものであるから、上記モードのノーマリーホワイト表示に適した視角特性の良好な液晶電気光学装置を得ることができる。
【図面の簡単な説明】
【図１】本発明の一実施例を説明するもので、（ａ）は液晶セルの電圧無印加時の液晶分子の配列状態を示す断面図、（ｂ）は液晶セルの第１の電圧印加時の液晶分子の配列状態を示す断面図、（ｃ）は液晶セルの第２の電圧印加時の液晶分子の配列状態を示す断面図、
【図２】従来のＯＣＢモードの液晶電気光学装置の液晶セルを説明するもので、（ａ）は液晶セルの電圧無印加時の液晶分子の配列状態を示す断面図、（ｂ）は液晶セルの第１の電圧無印加時の液晶分子の配列状態を示す縦断面図、（ｃ）は液晶セルの第２の電圧無印加時の液晶分子の配列状態を示す縦断面図、
【図３】本発明の一実施例である液晶電気光学装置の断面図、
【図４】本発明の一実施例の動作を説明する略斜視図。
【図５】本発明に用いる液晶セルの屈折率楕円体を説明する図、
【図６】本発明に用いる光学異方素子の屈折率楕円体を説明する図、
【図７】比較例１の液晶電気光学装置の視角特性を示す図、
【図８】本発明の実施例２の液晶電気光学装置の視角特性を示す図、
【図９】本発明の実施例１の液晶電気光学装置の視角特性を示す図、
【図１０】比較例２の液晶電気光学装置の視角特性を示す図、
【図１１】リタデーションＭの値をパラメータとする印加電圧−透過率曲線図。
【符号の説明】
１…液晶電気光学装置
１０…液晶セル
１１…基板
１１ａ…電極
１２…基板
１２ａ…電極
１３…液晶層
１３ａ…第１の液晶層領域Ａの液晶分子
１３ｂ…第２の液晶層領域Ｂの液晶分子
１３ｂ…第３の液晶層領域Ｃの液晶分子
２０…偏光板
３０…光学異方素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal electro-optical device, and more particularly, to a high-speed response liquid crystal electro-optical device.
[0002]
[Prior art]
The OCB mode is attracting attention as a liquid crystal electro-optical device capable of obtaining a high-speed response.
[0003]
The basic configuration of OCB will be described with reference to FIG.
[0004]
In the OCB mode, a liquid crystal cell 50 in which two substrates 51 and 52 having electrodes 51a and 52a formed on one main surface are arranged so that the main surfaces face each other and a liquid crystal layer 53 is sandwiched between the two substrates. And two polarizing plates 60 arranged so as to sandwich the liquid crystal cell 50, and an optical anisotropic element 70 arranged between the polarizing plate 60 and the liquid crystal cell 50.
[0005]
As shown in FIG. 2A, the liquid crystal layer 53 includes a first liquid crystal layer region A composed of a plurality of liquid crystal molecules 53a in contact with one substrate 51 of the two substrates among the liquid crystal molecules of the liquid crystal layer 53. A second liquid crystal layer region B composed of a plurality of liquid crystal molecules 53b in contact with the other substrate 52 of the two substrates among the liquid crystal molecules of the liquid crystal layer, and a first liquid crystal layer region of the liquid crystal molecules of the liquid crystal layer 53 A third liquid crystal layer region C composed of a plurality of liquid crystal molecules sandwiched between A and the second liquid crystal layer region B. By changing the voltage value applied to the electrodes, the liquid crystal molecules in the liquid crystal layer are arranged as shown in FIGS. 2 (a), 2 (b), and 2 (c).
[0006]
In the OCB mode liquid crystal layer, the orientation directions of the two substrates are the same, and when no voltage is applied, the splay alignment state is taken as shown in FIG. When the liquid crystal molecules 53c1 in the third liquid crystal layer region C are in a bend alignment state in which the liquid crystal molecules 53c1 are aligned substantially in parallel with the normal direction of the substrate and a voltage is further applied, as shown in FIG. The liquid crystal molecules 53c2 and 53c3 in the third liquid crystal layer region C are arranged in substantially parallel to the normal direction of the substrate. The OCB mode is a birefringence effect type that displays between the applied voltages in the states shown in FIGS. 2B and 2C, and changes the phase difference in the liquid crystal layer by controlling the voltage. According to the literature concerning the OCB mode, it is reported that a necessary and sufficient value of several ms can be obtained for the response speed of the liquid crystal display mode.
[0007]
The liquid crystal molecular arrangement during display in this display mode is characterized in that the upper half and the lower half of the liquid crystal are always substantially symmetrical. Therefore, when the viewing angle (observation angle) is in a range parallel to the plane in which the liquid crystal molecules are arranged (in the direction of the paper in FIG. 2), the upper half and the lower half of the liquid crystal have substantially symmetrical shapes. The refractive index ellipsoid becomes a sphere, and within this range, there is almost no viewing angle dependency, and a wide viewing angle can be obtained.
[0008]
However, for a viewing angle that is not parallel to the plane in which the liquid crystal is arranged, the refractive index ellipsoid of the liquid crystal layer does not become a sphere, and the refractive index ellipsoid is deformed depending on the observation angle, resulting in viewing angle dependence.
[0009]
As a method for solving such a viewing angle problem, it has been reported that an optical anisotropic element having a biaxial optical axis with an optimized refractive index in the thickness direction is added (Miyashita et al., Eurodisplay '93). , pp149-152).
[0010]
In order to obtain a good black display in the OCB mode, a normally white mode display in which black is used on the high voltage side is preferable. This is because when the voltage is applied, the liquid crystal molecules 53c in the third liquid crystal layer region C are substantially parallel to the normal direction of the substrate as shown in FIG. This state is used for black display. In this state, the phase difference of the liquid crystal layer is a relatively small value, so that the uniformity of black obtained by orthogonally polarizing plates is good.
[0011]
[Problems to be solved by the invention]
As described above, an OCB mode LCD is used to obtain a wide viewing angle and a high-speed response, and a normally white mode display is preferable to obtain a good black display. In order to compensate the viewing angle, it is important to select an optical anisotropic element that compensates for the refractive index ellipsoid of the liquid crystal layer to form a sphere.
[0012]
It is an object of the present invention to provide a liquid crystal electro-optical device having an optically anisotropic element that is optimal for the OCB mode of normally white mode display and similar modes. Note that a mode similar to the OCB mode is a mode in which the liquid crystal layer 53 has a part of the liquid crystal molecules 53c1 in the third liquid crystal layer region C as shown in FIG. 2B arranged substantially parallel to the normal direction of the substrate. The liquid crystal molecules 53c2 and 53c3 in the third liquid crystal layer region C as shown in FIG. 2C are almost aligned with the normal direction of the substrate. A liquid crystal electro-optical device having a state of being arranged in parallel. For example, when a liquid crystal cell having a chiral function is inserted into a liquid crystal cell that has been subjected to the same alignment treatment as that in the OCB mode, a 180 ° twist arrangement is obtained in a uniform arrangement when no voltage is applied. When a large voltage is applied to such an arrangement, the aforementioned bend arrangement can be easily obtained.
[0013]
[Means for Solving the Problems]
The liquid crystal electro-optical device of the present invention is
In a liquid crystal electro-optical device comprising: a liquid crystal cell having a liquid crystal layer capable of exhibiting bend alignment; and at least one optical anisotropic element that reduces the viewing angle dependency of the liquid crystal cell.
The optical anisotropic element is:
When Z = (ndx−ndz) / (ndx−ndy), 7 ≦ Z ≦ 10 (ndx, ndy, ndz is the liquid crystal cell when the liquid crystal cell and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index in the x, y, and z directions of the sum of the product of the thickness (unit: μm) of the optical anisotropic element and the refractive index of the optical anisotropic element, ndx and ndy. The refractive index component of the optical anisotropic element in the in-plane direction of the plane that is substantially perpendicular to the thickness direction of the anisotropic element, ndx and ndy are perpendicular to each other, and ndz is the thickness direction of the optical anisotropic element. Represents the refractive index component of the optical anisotropic element). The optical axis of the optical anisotropic element is twisted in at least one of the in-plane direction and the normal direction of the liquid crystal cell. The liquid crystal electro-optical device is provided.
[0014]
That is, the liquid crystal layer of the bend alignment liquid crystal cell of the liquid crystal electro-optical device includes a first liquid crystal layer region composed of a plurality of liquid crystal molecules in contact with one of the two substrates among the liquid crystal molecules of the liquid crystal layer, and the liquid crystal layer A second liquid crystal layer region composed of a plurality of liquid crystal molecules in contact with the other substrate of the two substrates, and a first liquid crystal layer region and a second liquid crystal layer region among the liquid crystal molecules of the liquid crystal layer And a third liquid crystal layer region composed of a plurality of liquid crystal molecules sandwiched between them. When the first voltage is applied to the electrode, the liquid crystal layer is arranged such that the inclination of a part of the plurality of liquid crystal molecules in the third liquid crystal layer region is arranged substantially parallel to the normal direction of the substrate. When the second voltage is applied, the inclination of the plurality of liquid crystal molecules in the third liquid crystal layer region of the liquid crystal layer is arranged substantially parallel to the normal direction of the substrate.
[0015]
The optical anisotropic element is a component in the thickness direction of the liquid crystal layer sandwiched between the two substrates of the liquid crystal layer when the second voltage is applied in a direction inclined with respect to the normal direction of the substrate. The optical anisotropy is compensated for. That is, in the OCB mode and the mode similar to the OCB mode of the present invention, the liquid crystal molecules except for the liquid crystal molecules near the substrate are substantially parallel to the normal direction of the substrate when the second voltage is applied. The refractive index anisotropy becomes very large in the optically anisotropic component in the normal direction, that is, in the thickness direction of the liquid crystal layer. In the present invention, an optical anisotropic element is arranged to compensate for the optical anisotropy of the liquid crystal layer in the thickness direction component of the liquid crystal layer in the direction inclined with respect to the normal direction of the substrate.
[0016]
The alignment state of the liquid crystal layer of the present invention will be described with reference to FIG. 1 by taking a liquid crystal electro-optical device having a mode similar to the OCB mode as an example.
[0017]
As shown in FIG. 1A, the liquid crystal layer 13 is composed of a plurality of liquid crystal molecules, and the liquid crystal layer 13 is a plurality of liquid crystal molecules 13a in contact with one of the two substrates, that is, the substrate 11 having the electrode 11a. A first liquid crystal layer region A comprising: a second liquid crystal layer region B comprising a plurality of liquid crystal molecules 13b in contact with the substrate 12 having the electrode 12a which is the other of the two substrates; and a first liquid crystal layer region, The third liquid crystal layer region C is composed of a plurality of liquid crystal molecules 13c sandwiched between the second liquid crystal layer region. 1A shows the arrangement of liquid crystal molecules when no voltage is applied to the electrodes, FIG. 1B shows a first voltage application state to the electrodes, and FIG. 1C shows the electrodes. The 2nd voltage application state to is shown.
[0018]
As shown in FIG. 1A, when no voltage is applied from the voltage driving source 40 connected to the electrodes to the electrodes 11a and 12a, the plurality of liquid crystal molecules 13c in the third liquid crystal layer region C are substantially parallel to each other. And twisted in the in-plane direction of the substrate from one substrate to the other substrate.
[0019]
As shown in FIG. 1B, when a first voltage is applied to the electrodes 11a and 12a, the inclination of some of the liquid crystal molecules 13c1 at the center of the plurality of liquid crystal molecules in the third liquid crystal layer region C is inclined. They are arranged substantially parallel to the normal direction of the substrate. When the first voltage is applied, the liquid crystal molecules are substantially parallel to the normal direction of the substrate when the voltage is equal to or higher than the threshold voltage. This is when the voltage applied to the liquid crystal is increased.
[0020]
Next, as shown in FIG. 1C, when the second voltage is applied to the electrodes 11a and 12a, the inclination of the plurality of liquid crystal molecules 13c2 and 13c3 on the side in contact with the electrode in the third liquid crystal layer region is the substrate. Are arranged substantially in parallel with the normal direction. When the second voltage is applied, a voltage is applied more than when the first voltage is applied. At this time, the liquid crystal molecules 13c2 and 13c3 in the third liquid crystal layer region are substantially parallel to the normal direction of the substrate. In other words, the liquid crystal is standing up.
[0021]
In a mode similar to the OCB mode and the OCB mode, the thickness of the liquid crystal layer in which the liquid crystal layer 13 is sandwiched between the two substrates 11 and 12 in the arrangement state shown in FIGS. In the direction, the upper half and the lower half of the liquid crystal layer have a substantially symmetrical bend arrangement around the center of the liquid crystal layer. For this reason, as shown in FIG. 4, when the viewing angle (observation angle) is such that the liquid crystal molecules are substantially parallel to the plane 40 arranged in the thickness direction, the upper and lower halves of the liquid crystal are substantially symmetrical. In this case, the refractive index ellipsoid representing the optical anisotropy of the liquid crystal layer is a sphere, and within this range, there is almost no viewing angle dependency, and a wide viewing angle can be obtained. On the other hand, for a viewing angle that is not parallel to the plane 40 shown in FIG. 4, the refractive index ellipsoid of the liquid crystal layer does not become a sphere, and the refractive index ellipsoid is deformed depending on the observation angle, resulting in viewing angle dependence.
[0022]
The present invention can obtain a wider viewing angle by compensating for the optical anisotropy of the liquid crystal layer.
[0023]
That is, the liquid crystal electro-optical device of the present invention includes an optical anisotropic element having negative optical anisotropy having a biaxial optical axis having the following refractive index elliptic coefficient Z value.
[0024]
When Z = (ndx−ndz) / (ndx−ndy), 7 ≦ Z ≦ 10
Here, ndx, ndy, ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the substrate and the optical anisotropic element when the substrate and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index component in the x, y, and z directions of the sum of the refractive index products. ndx and ndy represent refractive index components of the optical anisotropic element in the in-plane direction of the plane that is substantially perpendicular to the thickness direction of the optical anisotropic element, and ndx and ndy are perpendicular to each other. ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element.
[0025]
When the liquid crystal layer of the liquid crystal cell has the orientation shown in FIG. 4, the equivalent refractive index ellipsoid is as shown in FIG.
nzLC>nxLC> nyLC
Thus, as is apparent from the xz plane, yz plane, and xy plane, which are cross sections of the ellipsoid RL in FIG. 5, for example, the “rugby ball” has a shape compressed in the y direction.
[0026]
As shown in FIG. 6, the refractive index ellipsoid RC of the optical anisotropic element that compensates for this compresses the long axis direction z of the “rugby ball” more than the other two axes contrary to FIG. It is desirable that the y direction of the shaft is elongated.
[0027]
When this refractive index ellipsoid is expressed in the formula of refractive index,
Z = (nxC-nzC) / (nxC-nyC)
Here, nzC <nxC 12 <nyC.
[0028]
Here, the magnitude of nz depends on the tilt of the liquid crystal molecules 13a and 13b in the regions A and B in contact with the substrate of the liquid crystal layer 13 in FIG. 1, that is, the pretilt angle.
[0029]
In order to obtain a uniform display, it is desired that the pretilt angle and the thickness of the liquid crystal layer are uniform. However, as the pretilt angle that can be made uniform increases, the manufacture becomes difficult, and the maximum is 8 degrees. Therefore, the Z value varies depending on the pretilt angle, and in the range of pretilt angles that can be realized,
7 ≦ Z ≦ 10
It becomes.
[0030]
A liquid crystal electro-optical device in which such an optical anisotropic element is arranged is suitable for OCB mode and normally white display in a similar mode. This makes it possible to compensate for the optical anisotropy of the liquid crystal layer as a component in the thickness direction of the liquid crystal layer in a direction inclined with respect to the normal direction of the substrate, and to widen the viewing angle. Within this range, excellent display performance can be obtained with a wide viewing angle and a very small inversion area. When the value of Z is less than 7, the inversion region is widened, and the range with a good contrast ratio is also narrowed. Moreover, when it becomes larger than 10, the inversion area increases again.
[0031]
Furthermore, in the present invention, the value of Z is
8 ≦ Z ≦ 10
It is more preferable that
[0032]
In the present invention, the OCB and the similar display mode OCB and the similar display mode use the optical anisotropic element having the above-described conditions in order to obtain a wider viewing angle. Furthermore, in the present invention, it has been found that by setting the relationship between the retardation of the optical anisotropic element and the retardation of the liquid crystal cell to a specific condition, the drive voltage is within the practical range and a bright display can be achieved.
[0033]
OCB and display modes similar to this are all birefringence modes, and the transmittance T of the liquid crystal cell is expressed by the following equation.
[0034]
T = sin ² (R / πλ) --- (1)
Equation (1) is crossed Nicols, and the optical axis represents the transmittance at 45 ° with respect to the transmittance axis. R is a retardation value of an optical anisotropic body existing between polarizing plates, and λ is a light source wavelength.
[0035]
The direction of the optical axis of the optical anisotropic element is perpendicular to the direction of the rubbing axis of the liquid crystal cell. In such an arrangement, the total retardation value is the difference between the retardation value RLC of the liquid crystal cell and the retardation value Rfxy of the optical anisotropic element, and the parameter R in the equation (1) is
R = RLC-Rfxy --- (2)
It becomes.
[0036]
Therefore, from the formula (2), the transmittance of the liquid crystal cell is determined by the difference between the retardation of the liquid crystal cell and the in-plane retardation of the optical anisotropic element. That is, the in-plane retardation of the optical anisotropic element affects the brightness of the display.
[0037]
The retardation of the liquid crystal cell varies depending on the voltage applied to the liquid crystal layer. When the voltage of the liquid crystal cell changes and the retardation of the liquid crystal cell and the retardation in the in-plane direction of the optical anisotropic element become equal, the total retardation becomes zero and a black display is obtained.
[0038]
That is, the in-plane retardation of the optical anisotropic element affects the voltage value at which black display is obtained. Therefore, M was defined as the ratio of the in-plane direction retardation of the optical anisotropic element and the in-plane direction retardation of the optical anisotropic element, that is, the retardation ratio M as follows, and the influences thereof were examined.
[0039]
M = RLC / Rfxy = ΔnLC × dLC / (ndx−ndy) −− (3)
Here, ΔnLC is the refractive index difference of the liquid crystal, and dLC is the thickness of the liquid crystal layer.
[0040]
FIG. 11 shows the dependence of the retardation ratio M on the electro-optical characteristics. When the value of M is 7.5 or less, the transmittance decreases, so the contrast ratio decreases and the display quality deteriorates. When M is 18 or more, the transmittance is increased and the display quality is improved. However, the black display voltage is excessively high, such as 10 V or more, and a special high voltage integrated circuit for increasing power consumption and applying a high voltage is required. It is not practical. Therefore, the retardation ratio M that can achieve good brightness and practical black display voltage is:
7.5 <M <18
It is.
[0041]
In the liquid crystal electro-optical device of the present invention, the optical anisotropic element is
0.022 ≦ ndx−ndy ≦ 0.667
0.15 <ndx-ndz <6.7
Is preferable. As a result, a liquid crystal electro-optical device having an optimal optical anisotropic element can be obtained when the value of ΔnLC · dLC of the liquid crystal layer is 0.3 μm or more and 5 μm or less.
[0042]
In the liquid crystal electro-optical device of the present invention, one of the two polarizing plates can be a reflecting plate.
[0043]
In this case, since the light passes through the device twice, the lower limit value of (ndx−ndy) is 0.011.
[0044]
In the liquid crystal electro-optical device according to the present invention, when the first voltage is applied when the display of the liquid crystal electro-optical device is turned on, the liquid crystal layer is arranged in the third liquid crystal layer region C when the first voltage is applied. Since the inclination of some liquid crystal molecules 9a among the plurality of liquid crystal molecules is arranged substantially parallel to the normal direction of the substrate, a high-speed response display can be obtained.
[0045]
The liquid crystal electro-optical device of the present invention is characterized in that display is performed between the time of applying the first voltage and the time of applying the second voltage. Thereby, a display of a high-speed response can be obtained.
[0046]
Further, the liquid crystal optical element of the present invention is sandwiched between two substrates around a liquid crystal molecule arranged substantially parallel to the normal direction of the substrate in the third liquid crystal layer region when the first voltage is applied. In the thickness direction of the liquid crystal layer, the inclination of the liquid crystal molecules changes stepwise toward each of the two substrates.
[0047]
In the liquid crystal optical element of the present invention, the tilt of the liquid crystal molecules at the center of the third liquid crystal layer region in the thickness direction of the liquid crystal layer when the first voltage is applied is arranged substantially parallel to the normal direction of the substrate. It is characterized by.
[0048]
The liquid crystal electro-optical device of the present invention is characterized in that the two polarizing plates are arranged so that their optical axes are orthogonal to each other. By setting in this way and setting the values of the refractive index elliptic coefficient Z and the retardation ratio M as described above, a good black display can be obtained when the second voltage is applied.
[0049]
When the two polarizing plates are compared with each other when they are orthogonal to each other, they can be displayed either, but in order to obtain a good contrast ratio, it is necessary to obtain good black, that is, low transmittance. Therefore, it is more preferable that the polarizing plate is in an orthogonal state. This is because when the polarizing plate is in a parallel state and black, the influence of wavelength dispersion appears. When the polarizing plates are in a parallel state, the contrast ratio is considered to decrease, but the transmittance is easily increased.
[0050]
The optical axis of the polarizing plate is set in a direction inclined by 45 ° from a bisector that bisects an angle formed by the alignment processing directions of the two substrates. The maximum transmittance can be obtained by setting in this way whether the two polarizing plates are arranged orthogonally or in parallel.
[0051]
The specific OCB mode applicable to the above liquid crystal electro-optical device and the arrangement state of the liquid crystal layer in a mode similar to the OCB mode are shown below. Note that the present invention can also be applied when one of the two polarizing plates is a reflector. In this case, since the light incident on the liquid crystal cell passes through a distance twice as large as the liquid crystal layer thickness, the liquid crystal layer thickness can be reduced to about half compared to the transmission type, and further improvement in response speed can be expected.
[0052]
The liquid crystal electro-optical device of the present invention is characterized in that the liquid crystal molecules of the liquid crystal layer aligned from one substrate to the other substrate of the two substrates are splay aligned when no voltage is applied. That is, it can be applied to the OCB mode.
[0053]
Furthermore, in one aspect of the liquid crystal electro-optical device of the present invention, the twisting ability θ0 in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates toward the other substrate is θ0 = 0 °.
[0054]
Here, the twisting ability indicates a spontaneous twisting angle of the liquid crystal itself, and in general, the twisting ability can be controlled by the mixing concentration of the cholesteric liquid crystal composition.
[0055]
Furthermore, in another aspect of the liquid crystal electro-optical device of the present invention, the twisting ability θ 0 in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one of the two substrates toward the other substrate is θ 0> It is 0 degree. Thus, by setting the twisting ability θ0 to θ0> 0 °, the inclination of the plurality of liquid crystal molecules in one part of the third liquid crystal layer region when the first voltage is applied is changed from the splay alignment state when no voltage is applied to the substrate. Compared with the case in which θ0 = 0 °, the movement time to the state of being arranged substantially parallel to the normal direction can be made much faster.
[0056]
Furthermore, in another aspect of the liquid crystal electro-optical device of the present invention, the twisting ability θ0 in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates toward the other substrate is θ0 = 90 °, and the pretilt angle is different between the two substrates. When θ0 = 90 °, display can be performed by making the pretilt angles different between the two substrates.
[0057]
Furthermore, in another aspect of the liquid crystal electro-optical device of the present invention, the twisting ability θ in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates toward the other substrate is It is characterized by θ = 180 °. In consideration of the backflow effect, it is most desirable that the twisting ability is 180 ° and 175 ° to 185 ° before and after that. Here, the backflow effect will be described. For example, liquid crystal molecules that have risen slightly in the vicinity of the center when voltage is applied are pulled back to liquid crystal molecules in a sleeping state near the substrate by turning off the voltage. However, the liquid crystal molecules in the rising portion near the center are prevented from sleeping by the liquid crystal molecules near the center, and the return is delayed. This is called a backflow effect. In the case of a bend arrangement, this backflow effect disappears, but this backflow effect occurs when a twisted state other than a state where the liquid crystal is twisted 180 ° occurs.
[0058]
In the liquid crystal electro-optical device according to the present invention, when no voltage is applied to the electrodes, the plurality of liquid crystal molecules in the third liquid crystal layer region are substantially parallel to each other and from one substrate toward the other substrate. It is characterized by being twisted in the in-plane direction. That is, it is a mode similar to the OCB mode, and the present invention is applicable even in this case. In this case, high-speed response is possible in the display area as in the OCB mode.
[0059]
Further, as a mode similar to the OCB mode, the liquid crystal electro-optical device of the present invention is arranged in the in-plane direction of the liquid crystal molecules of the liquid crystal layer arranged from one substrate of the two substrates toward the other substrate. The twist angle θ is approximately 90 ° or approximately 270 °, and the pretilt angle of the liquid crystal layer is different between the two substrates. In this case, when the twist angle θ is 90 ° or 270 °, in the region where the liquid crystal molecules in the vicinity of the center of the liquid crystal layer rise, when the pretilt angles of the liquid crystal molecules on the two substrate surfaces are equal, the liquid crystal layer The magnitudes of the phase differences in the upper half and the lower half are equal, and the directions are almost 90 degrees. For this reason, the phase difference of the entire cell has a relationship in which the upper half and the lower half of the cell compensate each other. For this reason, even if the applied voltage is further increased to drive the liquid crystal molecules, the optical response cannot be changed. On the other hand, by making the pretilt angle different between the two substrates, a phase difference occurs due to the arrangement difference between the upper half and the lower half of the cell, and saturation of the cells with the same pretilt angle between the two substrates is caused. Even when a voltage is applied, a bright display is possible. Therefore, by applying a voltage further, a dark display can be obtained and a high-speed display can be achieved. When the phase difference of the cell as a whole is a twist angle of 90 ° or 270 ° in which the upper half and the lower half of the cell compensate each other, and excluding the twist angle of 90 ° that tends to be in such a relationship In the case of 85 ° to 95 ° and 265 ° to 275 ° excluding the twist angle of 270 °, it is effective to change the size of the pretilt angle of the two substrates.
[0060]
According to another aspect of the liquid crystal electro-optical device of the present invention, the liquid crystal layer is characterized in that no voltage is applied when the first voltage is applied. That is, when no voltage is applied, the inclination of the plurality of liquid crystal molecules in a part of the third liquid crystal layer region is arranged in substantially parallel to the normal direction of the substrate, which is similar to the OCB mode. Mode, and even in this case, the present invention is applicable.
[0061]
The optical anisotropic element used in the liquid crystal electro-optical device of the present invention is shown below.
[0062]
The optical anisotropic element is at least one phase difference plate having two optical axes.
[0063]
One aspect of the optical anisotropic element when the Z range of the present invention cannot be realized with only one sheet is composed of a combination of two or more retardation plates composed of a uniaxial optical axis. The optical axis of the phase difference plate is different.
[0064]
Further, when the range of the Z value cannot be realized by a combination of uniaxial optical anisotropic elements, one aspect of the optical anisotropic element includes at least one retardation plate composed of a uniaxial optical axis and a biaxial optical axis. It consists of at least 1 phase difference plate which consists of an optical axis, It is characterized by the above-mentioned.
[0065]
Another aspect of the optical anisotropic element includes at least one retardation plate having negative optical anisotropy in the normal direction of the substrate when the substrate and the optical anisotropic element are arranged substantially in parallel. It is characterized by that.
[0066]
In addition, when it is desired to better compensate for the optical effect of the twist of the liquid crystal cell, another aspect of the optical anisotropic element is that the twist of the optical axis of the optical anisotropic element is the in-plane direction of the substrate or the normal line of the substrate. It is characterized by being twisted in the direction or both the in-plane direction and the normal direction of the substrate.
[0067]
Such an optical anisotropic element compensates for the twist of the liquid crystal layer or compensates for the optical anisotropy of the component in the normal direction of the substrate of the liquid crystal layer.
[0068]
As described above, in the present invention, the optical anisotropic element is a biaxial light as an optical anisotropic element by combining a retardation plate having a uniaxial or biaxial optical axis and a negative retardation plate alone or in combination. It only has to have an axis. For example, in the case of combining two or more retardation plates having a single optical axis, the optical axes of at least two retardation plates are arranged so that they do not coincide with each other, and biaxial light is used as an optical anisotropic element. It is necessary to have an axis.
[0069]
In addition, the optical axis of the optical anisotropic element is twisted so as to compensate for the twist in the in-plane direction of the liquid crystal molecules of the liquid crystal layer, the normal direction of the substrate, or both the in-plane direction and the normal direction of the substrate. By providing it, it is possible to compensate for the optical influence due to the twist of the liquid crystal layer. In this case, the liquid crystal layer is partially or almost entirely, the liquid crystal molecules are continuously or stepwise from one substrate to the other substrate, and the in-plane direction and / or normal direction of the substrate. Including the case of twisting.
[0070]
In addition, the optical axis of the optical anisotropic element is twisted so that the optical axis of the optical anisotropic element is equivalent to that of a phase difference plate that is negative in the component in the normal direction of the substrate of the liquid crystal layer. The optical anisotropy of the direction component can be compensated. In this case, it can be realized by an optical axis having a large twist angle of the optical axis, for example, the optical axis of the optical anisotropic element twisted in the in-plane direction of the substrate.
[0071]
As the material of the phase difference plate, polycarbonate, polyarylate, etc., and a phase difference plate such as a cholesteric liquid crystal polymer or a discotic liquid crystal polymer can be used to twist the optical axis as an optical anisotropic element. The material is not limited to these materials as long as the above characteristics can be obtained.
[0072]
DETAILED DESCRIPTION OF THE INVENTION
In the following embodiments of the liquid crystal electro-optical device according to the present invention, the liquid crystal molecules of the liquid crystal layer are aligned in parallel when no voltage is applied, and the two substrates are directed from one substrate to the other. The twist angle θ in the in-plane direction of the liquid crystal molecules of the liquid crystal layer to be aligned in the in-plane direction will be described in detail by taking as an example a case where θ = 180 °.
[0073]
(Example 1)
As shown in FIGS. 3 and 4, the liquid crystal electro-optical device 1 of this embodiment includes a liquid crystal cell 10, two polarizing plates 20 sandwiching the liquid crystal cell 10, and an optical device sandwiched between the liquid crystal cell and one polarizing plate. It consists of an anisotropic element 30 and a voltage drive source 40.
[0074]
In the liquid crystal cell 10, a first substrate 11 having an electrode 11a formed on one main surface and a second substrate 12 having an electrode 12a formed on one main surface are disposed so that the electrodes face each other. A liquid crystal layer 13 is sandwiched between 11 and 12. This device is a normally white display liquid crystal electro-optical device. The optical anisotropic element 30 compensates for the optical anisotropy of the liquid crystal layer 13.
[0075]
As shown in FIG. 1, the liquid crystal layer 13 includes a plurality of liquid crystal molecules, and the liquid crystal layer 13 includes a first liquid crystal layer region A including a plurality of liquid crystal molecules 13a in contact with one substrate 11 of two substrates. A plurality of liquid crystal molecules sandwiched between a second liquid crystal layer region B composed of a plurality of liquid crystal molecules 13b in contact with the other substrate 12 of the two substrates, and the first liquid crystal layer region and the second liquid crystal layer region. And a third liquid crystal layer region C made of 13c. 1A shows the arrangement of liquid crystal molecules when no voltage is applied to the electrodes, FIG. 1B shows a first voltage application state to the electrodes, and FIG. 1C shows the electrodes. The 2nd voltage application state to is shown.
[0076]
As shown in FIG. 1A, when no voltage is applied from the voltage driving source 40 to the electrodes 11a and 12a, the plurality of liquid crystal molecules 13c in the third liquid crystal layer region C are substantially parallel to each other and on one substrate. And twisted in the in-plane direction of the substrate toward the other substrate.
[0077]
As shown in FIG. 1B, when a first voltage is applied to the electrode, the inclination of some of the liquid crystal molecules 13c1 among the plurality of liquid crystal molecules in the third liquid crystal layer region C is in the normal direction of the substrate. They are arranged almost in parallel. When the first voltage is applied, the liquid crystal molecules are substantially parallel to the normal direction of the substrate when the voltage is equal to or higher than the threshold voltage. This is when the voltage applied to the liquid crystal is further increased.
[0078]
As shown in FIG. 1C, when a second voltage is applied to the electrodes, the inclinations of the plurality of liquid crystal molecules 13c1, 13c2, 13c3 in the third liquid crystal layer region are arranged substantially parallel to the normal direction of the substrate. doing. When the second voltage is applied, the voltage is further applied than when the first voltage is applied. At this time, the liquid crystal molecules 13c in the third liquid crystal layer region are arranged substantially parallel to the normal direction of the substrate. In other words, the liquid crystal stands up.
[0079]
A liquid crystal cell 10 in which the liquid crystal layer 13 is held between two substrates is shown in FIG. As shown in the figure, the liquid crystal cell 10 includes two substrates, an array substrate 12 having an electrode 12a formed on one main surface of a glass substrate and a counter substrate 11 having an electrode 11a formed on one main surface of the glass substrate. And the nematic liquid crystal layer 13 is sandwiched between two substrates.
[0080]
As shown in FIG. 3, the array substrate 12 has a plurality of signal lines (not shown) and a plurality of scanning lines (not shown) arranged in a matrix on a glass substrate. A silicon TFT 12b and a pixel electrode 12a formed in connection with the TFT are formed, and an alignment film 12c is formed thereon. On the other hand, the counter substrate 11 is formed on a glass substrate so as to partition a color filter 11b composed of three primary colors of red, green, and blue corresponding to each pixel electrode 12a of the array substrate 11 and a color filter of each color. A black matrix 11c is formed, and an ITO electrode 11a and an alignment film 11d are sequentially formed thereon.
[0081]
Next, a manufacturing method and a display method will be described.
[0082]
An array substrate 12 having a vertical number of 480 pixels and a horizontal size of 640 × 3 pixels, on which a polysilicon TFT 3, gate lines as signal lines (not shown), signal lines (not shown), and pixel electrodes 12 a are formed on a glass substrate. Formed.
[0083]
Next, a color filter 11b composed of the three primary colors red, green, and blue corresponding to each pixel electrode of the array substrate 12 on the glass substrate, and a black matrix 11c formed so as to partition the color filters of these colors are provided. The counter substrate 11 was formed by forming the ITO electrode 11a thereon. Polyimide (SE-5211, manufactured by Nissan Chemical Industries, Ltd., pretilt angle of about 5 °) is applied and formed as an alignment film 12c and 11d on the two array substrates 12 and the counter substrate 11, respectively. did. Here, the pixel pitch is 0.33 mm in length and 0.11 mm in width. Subsequently, when the alignment film is arranged in parallel to the scanning line and the electrodes 11a and 12a on the two substrates 11 and 12 face each other, the rubbing directions RA of the two substrates are parallel to each other. Rubbing was done in such a direction.
[0084]
Next, spherical fine particles (Micropearl SP, manufactured by Sekisui Fine Chemical Co., Ltd.) having a diameter of 7.1 μm as spacers (not shown) are placed on the array substrate 12 at 80 / mm on the main surface of one substrate. ² Sprayed at a density of. The periphery of the effective display area of the other counter substrate 11 was coated with an epoxy resin adhesive (XN-21, manufactured by Mitsui Toatsu Chemical Co., Ltd.) by screen printing except for the opening for liquid crystal injection. . Thereafter, the array substrate 12 and the counter substrate 11 were superposed with the alignment films facing each other, and heated and bonded with pressure to produce a liquid crystal cell 10 having a cell gap of 7.1 μm.
[0085]
A liquid crystal composition obtained by adding a nematic liquid crystal composition (ZLI-1132, manufactured by E. Merck, Δn = 0.14) to the liquid crystal cell 13 and a chiral agent (S811, manufactured by E. Merck) by vacuum injection. After injection, the liquid crystal injection port was sealed with an ultraviolet curable resin (UV-1000, manufactured by Sony Chemicals Corporation). At this time, the concentration of the chiral agent was adjusted so that the helical pitch of the liquid crystal was about 35 μm. On the counter substrate 11 side where the color filter 11b of the liquid crystal cell is formed, as the optical anisotropic element 30, a retardation plate which is an optical anisotropic element made of polycarbonate is rubbed in the direction in which the refractive index of the retardation plate is large. It was arranged so as to be orthogonal to.
[0086]
The elliptic coefficient Z of the optical anisotropic element 30 is
Z = (ndx-ndz) / (ndx-ndy)
Z = 9.
[0087]
Here, ndx, ndy, and ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the substrate and the optical anisotropic when the substrate and the optical anisotropic element are arranged substantially in parallel. This represents the total sum of the refractive index products with the element. ndx and ndy represent refractive index components of the optical anisotropic element in the in-plane direction of the plane that is substantially perpendicular to the thickness direction of the optical anisotropic element, and ndx and ndy are perpendicular to each other. ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element.
[0088]
Further, a polarizing plate 20 (G1220DU, manufactured by Nitto Denko Corporation) was attached so that the optical axis was 45 ° with respect to the rubbing direction and the optical axes of the two polarizing plates were orthogonal to each other. The retardation plate has an in-plane retardation value of 100 nm (the difference between ndx and ndy is 0) after the film is stretched in the x-axis direction and then stretched in the y-axis direction to be biaxial. .1) is used to compensate for the phase difference of the liquid crystal cell when the second voltage is applied, that is, the optical axes of the two polarizing plates are orthogonal to each other and the phase difference The direction in which the refractive index of the plate is large was arranged so as to be orthogonal to the rubbing direction. And this optical anisotropic element has a retardation ratio of M,
M = ΔnLC · dLC / (ndx−ndy)
Therefore, M = 10.
[0089]
The thickness of the liquid crystal layer is dLC (unit: μm), and the refractive index anisotropy of the liquid crystal layer is ΔnLC.
[0090]
In the obtained liquid crystal electro-optical device, when no voltage is applied to the electrodes, the plurality of liquid crystal molecules in the third liquid crystal layer region C are substantially parallel to each other and from one substrate toward the other substrate. They are twisted 180 ° in the in-plane direction.
[0091]
When the first voltage is applied, the inclination of the liquid crystal molecules 13c1 at the center of the third liquid crystal layer region C among the plurality of liquid crystal molecules in the third liquid crystal layer region C is arranged substantially parallel to the normal direction of the substrate. In the thickness direction of the liquid crystal layer 13 sandwiched between the two substrates with the liquid crystal molecule 13c1 as the center, stepwise toward the two substrates 11, 12 like the liquid crystal molecules 13c2, 13c3. The tilt of the liquid crystal molecules changes.
[0092]
When the second voltage is applied, the inclinations of the plurality of liquid crystal molecules 13c in the third liquid crystal layer region are arranged substantially parallel to the normal direction of the substrate.
[0093]
The display was performed by being driven on and off by the voltage driving source 40 between the time of applying the first voltage and the time of applying the second voltage. In this example, a voltage at which the effective phase difference of the cell is approximately 0.26 μm is used as the minimum value of the drive voltage. The display was performed by setting the first voltage application to 2.4V and the second voltage application to 6.5V.
[0094]
As a result, as shown in FIG. 9, an electro-optical characteristic in which the transmittance monotonously decreased with respect to the driving voltage was obtained, the contrast ratio at the front was 100 or more, and the viewing angle was wide. The response speed has almost no difference between gradations and is as fast as about 5 ms. Even when a moving image is displayed, a good display can be obtained without blurring the outline. 7 to 10 are diagrams showing equi-contrast. The center of the circle represents the contrast in the observation direction when the normal direction of the substrate is used as a reference for the observation direction, and the hatched portion represents the inversion region. 7-10, as the circle increases concentrically from the center of the circle to the outside, the angle formed between the direction of the substrate and the observation direction increases, and the center of the circle and any arbitrary position on the circle. The direction of the line connecting the points (azimuth) represents the observation direction in the in-plane direction of the substrate.
[0095]
In the figure, a curve (50) is a contrast ratio (50), a region surrounded by the curve (50) is a contrast ratio of 50 or more, a region surrounded by the curve (10) is a contrast ratio of 50 to 10, and the curve (1). The region surrounded by is a contrast ratio of 1-10.
[0096]
(Example 2)
A TFT-LCD was manufactured under the same members and conditions as in Example 1, with the Z value of the retardation plate in Example 1 set to 7. The result is shown in FIG. The LCD thus obtained gave a good display even when the viewing angle was changed.
[0097]
(Comparative Example 1)
A TFT-LCD was produced under the same members and conditions as in Example 1, with the Z value of the retardation plate in Example 1 being 1 (one uniaxial retardation plate was used). The result is shown in FIG. The LCD thus obtained had a very wide inversion area when the viewing angle was swung, and the contrast was greatly reduced.
[0098]
(Comparative Example 2)
A TFT-LCD was manufactured under the same members and conditions as in Example 1, with the Z value of the retardation plate in Example 1 being 12 (one uniaxial retardation plate was used). The result is shown in FIG. The LCD thus obtained had a very wide inversion area when the viewing angle was swung, and the contrast was greatly reduced.
[0099]
As described above, a liquid crystal optical element having little viewing angle dependency can be obtained by using an optical anisotropic element having a Z value of 7 ≦ Z ≦ 10, more preferably 8 ≦ Z ≦ 10.
[0100]
Further, here, the liquid crystal molecules of the liquid crystal layer are aligned in parallel when no voltage is applied, and the liquid crystal molecules of the liquid crystal layer are aligned from one substrate of the two substrates toward the other substrate. The twist angle θ in the in-plane direction of the substrate is described as an example where θ = 180 °. However, the present invention can be applied to the OCB mode of the normally white mode display and similar modes, and the same effect. Can be obtained.
[0101]
FIG. 11 shows the relationship between the applied voltage (horizontal axis) and the transmittance (vertical axis) when ΔnLC · dLC is 1.0 and the value of M is changed.
[0102]
(Example 3)
The optical anisotropic element in Example 1 is obtained by using a uniaxial retardation plate having a retardation value of 400 nm in the in-plane direction of the retardation plate and a uniaxial position having a retardation value of 500 nm in the in-plane direction of the retardation plate. The TFT- is fabricated under the same members and conditions as in Example 1 except that two retardation plates are stacked so that the optical axes are orthogonal to each other, and an optical anisotropic element is manufactured so that Z = 9 and M = 10. An LCD was produced. The LCD thus obtained had improved viewing angle characteristics.
[0103]
(Example 4)
The optical anisotropic element in Example 1 is combined with a single uniaxial retardation plate having a retardation value of 100 nm in the in-plane direction of the retardation plate and a negative retardation plate (ndx, ndy> ndz). A TFT-LCD was fabricated using the same members and conditions as in Example 1 except that the anisotropic element was fabricated so that the Z value was 9. The LCD thus obtained had improved viewing angle characteristics.
[0104]
(Comparative Example 3)
Except for the spacer diameter in Example 1 being 5.3 μm and the cell gap being 5.3 μm, as in Example 1, an optical anisotropic element having a Z value of 9 was used, and M = A TFT-LCD of 7.4 was produced. The LCD thus obtained had a low transmittance and the display quality was liable to be impaired.
[0105]
(Comparative Example 4)
A TFT-LCD with M = 18.2 was fabricated under the same members and conditions as in Example 1 except that the spacer diameter in Example 1 was 13 μm and the cell gap was 13 μm. The LCD thus obtained could only apply a maximum voltage of up to 6V (because the TFT element was destroyed at a voltage higher than this), it could not be made sufficiently black and the display quality was liable to be impaired. .
[0106]
As described above, the optical anisotropic element of the present invention uses one or more phase difference plates having two optical axes and uses two or more phase difference plates having one optical axis. It can be obtained by using a phase difference plate having an optical axis and a negative phase difference plate in combination. Further, when the value of M is set to 7.5 <M <18, a liquid crystal optical element having a good display quality can be obtained.
[0107]
(Example 5)
One of the polarizing plates in Example 1 is replaced with a reflector, the spacer diameter is 3.6 μm, the cell gap is 3.6 μm, and the retardation value in the in-plane direction of the retardation plate is 50 nm 2 A TFT-LCD with Z = 9 and M = 10 was manufactured using the same members and conditions as in Example 1 except that an axial retardation plate was used. When the LCD thus obtained was driven, the viewing angle characteristics were good and a bright display was obtained.
[0108]
(Example 6)
The optical anisotropic element in Example 1 was produced by combining two twisted phase difference plates. Specifically, one retardation plate having an optical axis twist angle of 10 ° in the in-plane direction of the substrate made of cholesteric liquid crystal polymer and a phase difference in the in-plane direction of 100 nm, and the optical axis in the in-plane direction of the substrate. It was produced by combining two retardation plates having a twist angle of 650 ° and a phase difference in the in-plane direction of zero. In this optically anisotropic element, the entire optical axis is twisted 660 ° in the in-plane direction of the substrate.
[0109]
As described above, by imparting a twist to the optical axis of the optical anisotropic element, a high contrast can be obtained, and by using a phase difference plate having a twist angle of the optical axis of 650 °, the optical characteristics are negative. The same effect as that having the phase difference plate was obtained, and the viewing angle characteristics were good.
[0110]
(Example 7)
The optical anisotropic element in Example 1 was manufactured by combining one twisted phase difference plate and one negative phase difference plate. That is, an optical anisotropy is formed in the normal direction of the substrate when one retardation plate having an optical axis twist angle of 10 ° in the direction of the substrate made of cholesteric liquid crystal polymer and the substrate and the optically anisotropic element are arranged substantially in parallel. An optically anisotropic element was manufactured by combining negative retardation plates having negative polarities so that Z = 9 in the entire optically anisotropic element.
[0111]
Thus, by giving a twist to the optical axis of the optical anisotropic element, a high contrast was obtained, and the viewing angle characteristics were improved because it was a negative retardation plate.
[0112]
(Example 8)
The optical anisotropic element in Example 1 was produced by combining one biaxial twisted phase difference plate and one twisted phase difference plate. That is, an optical anisotropic element was manufactured by combining one twisted phase difference plate made of a cholesteric liquid crystal polymer and a biaxial phase difference plate so that Z = 9 in the entire optical anisotropic element. Thereby, the viewing angle characteristics were improved.
[0113]
The liquid crystal electro-optical device of the present invention described in the above embodiments can be widely applied to liquid crystal display elements used in personal computers, word processors, etc., light valves for video projectors, and high-speed liquid crystal shutters used for glasses used in 3D-TV. Can do.
[0114]
【The invention's effect】
In the liquid crystal electro-optical device of the present invention, the optical anisotropic element combined with the liquid crystal cell of the OCB mode or similar mode has biaxial and negative optical anisotropy, and the elliptic coefficient Z is set to 7 or more and 10 or less. Therefore, it is possible to obtain a liquid crystal electro-optical device with good viewing angle characteristics suitable for normally white display in the above mode.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams illustrating an embodiment of the present invention, in which FIG. 1A is a cross-sectional view showing an alignment state of liquid crystal molecules when no voltage is applied to a liquid crystal cell, and FIG. 1B is a first voltage application of a liquid crystal cell; Sectional drawing which shows the arrangement state of the liquid crystal molecule at the time, (c) is a sectional view showing the arrangement state of the liquid crystal molecule when the second voltage is applied to the liquid crystal cell,
FIGS. 2A and 2B illustrate a liquid crystal cell of a conventional OCB mode liquid crystal electro-optical device. FIG. 2A is a cross-sectional view showing an alignment state of liquid crystal molecules when no voltage is applied to the liquid crystal cell, and FIG. A vertical cross-sectional view showing the alignment state of liquid crystal molecules when no first voltage is applied, (c) is a vertical cross-sectional view showing the alignment state of liquid crystal molecules when no second voltage is applied to the liquid crystal cell,
FIG. 3 is a cross-sectional view of a liquid crystal electro-optical device that is an embodiment of the present invention;
FIG. 4 is a schematic perspective view for explaining the operation of an embodiment of the present invention.
FIG. 5 is a diagram for explaining a refractive index ellipsoid of a liquid crystal cell used in the present invention;
FIG. 6 is a diagram for explaining a refractive index ellipsoid of an optical anisotropic element used in the present invention;
7 is a view showing viewing angle characteristics of the liquid crystal electro-optical device of Comparative Example 1. FIG.
FIG. 8 is a view showing viewing angle characteristics of a liquid crystal electro-optical device according to Example 2 of the invention;
FIG. 9 is a view showing viewing angle characteristics of the liquid crystal electro-optical device according to the first embodiment of the invention;
FIG. 10 is a view showing viewing angle characteristics of the liquid crystal electro-optical device of Comparative Example 2;
FIG. 11 is an applied voltage-transmittance curve diagram using the value of retardation M as a parameter.
[Explanation of symbols]
1. Liquid crystal electro-optical device
10 ... Liquid crystal cell
11 ... Board
11a ... Electrode
12 ... Board
12a ... Electrode
13 ... Liquid crystal layer
13a ... Liquid crystal molecules in the first liquid crystal layer region A
13b ... Liquid crystal molecules in the second liquid crystal layer region B
13b ... Liquid crystal molecules in the third liquid crystal layer region C
20 ... Polarizing plate
30. Optical anisotropic element

Claims

In a liquid crystal electro-optical device comprising: a liquid crystal cell having a liquid crystal layer capable of exhibiting bend alignment; and at least one optical anisotropic element that reduces the viewing angle dependency of the liquid crystal cell.
The optical anisotropic element has 7 ≦ Z ≦ 10 when Z = (ndx−ndz) / (ndx−ndy).
(Ndx, ndy, and ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the liquid crystal cell and the optical anisotropy when the liquid crystal cell and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index in the x, y, and z directions of the sum of the refractive index products with the element, where ndx and ndy are the optical anisotropic elements in the in-plane direction of the plane substantially perpendicular to the thickness direction of the optical anisotropic element. Ndx and ndy are perpendicular to each other, and ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element).
A liquid crystal electro-optical device, wherein an optical axis of the optical anisotropic element is twisted in at least one of an in-plane direction and a normal direction of the liquid crystal cell.

In a liquid crystal electro-optical device comprising: a liquid crystal cell having a liquid crystal layer capable of exhibiting bend alignment; and at least one optical anisotropic element that reduces the viewing angle dependency of the liquid crystal cell.
The optical anisotropic element has 7 ≦ Z ≦ 10 when Z = (ndx−ndz) / (ndx−ndy).
(Ndx, ndy, and ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the liquid crystal cell and the optical anisotropy when the liquid crystal cell and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index in the x, y, and z directions of the sum of the refractive index products with the element, where ndx and ndy are the optical anisotropic elements in the in-plane direction of the plane substantially perpendicular to the thickness direction of the optical anisotropic element. Ndx and ndy are perpendicular to each other, and ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element).
Liquid crystal molecules of the liquid crystal layer have a twist in the liquid crystal cell, and the optical anisotropic element has an optical axis twisted so as to compensate a viewing angle due to the twist of the liquid crystal molecules. apparatus.

In a liquid crystal electro-optical device having a liquid crystal cell having a liquid crystal layer capable of exhibiting bend alignment, and at least one optical anisotropic element for reducing the viewing angle dependency of the liquid crystal cell,
  The retardation ratio M in the in-plane direction of the optical anisotropic element
  M = ΔnLC · dLC / (ndx−ndy)
  When
7.5 <M <18
(Ndx, ndy are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the liquid crystal cell and the optical anisotropic element when the liquid crystal cell and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index in the x and y directions of the sum of the refractive index products, and the x and y directions are in-plane directions of the optical anisotropic element and are perpendicular to each other. : Μm) is dLC, and the difference between the refractive indexes orthogonal to each other in the in-plane direction when no electric field is applied to the liquid crystal layer is ΔnLC).
A liquid crystal electro-optical device, wherein an optical axis of the optical anisotropic element is twisted in at least one of an in-plane direction and a normal direction of the liquid crystal cell.

In a liquid crystal electro-optical device having a liquid crystal cell having a liquid crystal layer capable of exhibiting bend alignment, and at least one optical anisotropic element for reducing the viewing angle dependency of the liquid crystal cell,
  The retardation ratio M in the in-plane direction of the optical anisotropic element
  M = ΔnLC · dLC / (ndx−ndy)
  When
7.5 <M <18
(Ndx, ndy are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the liquid crystal cell and the optical anisotropic element when the liquid crystal cell and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index in the x and y directions of the sum of the refractive index products, and the x and y directions are in-plane directions of the optical anisotropic element and are perpendicular to each other. : Μm) is dLC, and the difference between the refractive indexes orthogonal to each other in the in-plane direction when no electric field is applied to the liquid crystal layer is ΔnLC).
Liquid crystal molecules of the liquid crystal layer have a twist in the liquid crystal cell, and the optical anisotropic element has an optical axis twisted so as to compensate a viewing angle due to the twist of the liquid crystal molecules. apparatus.

In a liquid crystal electro-optical device having a liquid crystal cell having a liquid crystal layer capable of exhibiting bend alignment, and at least one optical anisotropic element for reducing the viewing angle dependency of the liquid crystal cell,
  When the optical anisotropic element is Z = (ndx−ndz) / (ndx−ndy),
7 ≦ Z ≦ 10,
  and,
  When the retardation ratio M in the in-plane direction of the optical anisotropic element is M = ΔnLC · dLC / (ndx−ndy), 7.5 <M <18
(Ndx, ndy, and ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the liquid crystal cell and the optical anisotropy when the liquid crystal cell and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index in the x, y, and z directions of the sum of the refractive index products with the element, where ndx and ndy are the optical anisotropic elements in the in-plane direction of the plane substantially perpendicular to the thickness direction of the optical anisotropic element. Ndx and ndy are perpendicular to each other, ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element, and the thickness of the liquid crystal layer (unit: μm) is dLC, and the difference between the refractive indexes orthogonal to each other in the in-plane direction when no electric field is applied to the liquid crystal layer is ΔnLC).
A liquid crystal electro-optical device, wherein an optical axis of the optical anisotropic element is twisted in at least one of an in-plane direction and a normal direction of the liquid crystal cell.

In a liquid crystal electro-optical device having a liquid crystal cell having a liquid crystal layer capable of exhibiting bend alignment, and at least one optical anisotropic element for reducing the viewing angle dependency of the liquid crystal cell,
  When the optical anisotropic element is Z = (ndx−ndz) / (ndx−ndy),
7 ≦ Z ≦ 10,
  and,
  When the retardation ratio M in the in-plane direction of the optical anisotropic element is M = ΔnLC · dLC / (ndx−ndy), 7.5 <M <18
(Ndx, ndy, and ndz are the thickness (unit: μm) of the optical anisotropic element in the normal direction of the liquid crystal cell and the optical anisotropy when the liquid crystal cell and the optical anisotropic element are arranged substantially in parallel. Represents the refractive index in the x, y, and z directions of the sum of the refractive index products with the element, where ndx and ndy are the optical anisotropic elements in the in-plane direction of the plane substantially perpendicular to the thickness direction of the optical anisotropic element. Ndx and ndy are perpendicular to each other, ndz represents the refractive index component of the optical anisotropic element in the thickness direction of the optical anisotropic element, and the thickness of the liquid crystal layer (unit: μm) is dLC, and the difference between the refractive indexes orthogonal to each other in the in-plane direction when no electric field is applied to the liquid crystal layer is ΔnLC).
Liquid crystal molecules of the liquid crystal layer have a twist in the liquid crystal cell, and the optical anisotropic element has an optical axis twisted so as to compensate a viewing angle due to the twist of the liquid crystal molecules. apparatus.

The liquid crystal electro-optical device according to claim 1, wherein the optically anisotropic element is made of any one of polycarbonate, polyarylate, cholesteric liquid crystal polymer, and discotic liquid crystal polymer.