【０００１】
【発明の属する技術分野】
この発明は、ＴＮ（ツイステッドネマティック）型の液晶表示素子に関する。
【０００２】
【従来の技術】
液晶表示素子としては、互いに対向する面にそれぞれ電極が形成された一対の基板間に、液晶分子を前記基板間において実質的に９０°のツイスト角でツイスト配向させた液晶層を設けてなる液晶セルと、前記液晶セルを挟んで配置された一対の偏光板とにより構成されたＴＮ型液晶表示素子が広く利用されている（特許文献１参照）。
【０００３】
【特許文献１】
特開平０６−２０２０６８号公報
【０００４】
【発明が解決しようとする課題】
前記ＴＮ型液晶表示素子の表示特性は、液晶の屈折率異方性Δｎと液晶層厚ｄとの積Δｎｄの値によって決まる。
【０００５】
しかし、従来のＴＮ型液晶表示素子は、明るい表示が得られるようにΔｎｄ値を設定したものは表示に帯色を生じ、また、帯色を生じないようにΔｎｄ値を設定したものは明るい表示が得られないという問題をもっている。
【０００６】
この発明は、明るく、しかも帯色の無い高品質の表示を得ることができるＴＮ型の液晶表示素子を提供することを目的としたものである。
【０００７】
【課題を解決するための手段】
この発明の液晶表示素子は、互いに対向する面にそれぞれ電極が形成された一対の基板間に、液晶分子を前記基板間において実質的に９０°のツイスト角でツイスト配向させ、液晶の屈折率異方性Δｎと液晶層厚ｄとの積Δｎｄの値を３５０〜５００ｎｍの範囲に設定した液晶層を設けてなる液晶セルと、前記液晶セルを挟んで配置された一対の偏光板と、前記一対の偏光板の少なくとも一方と前記液晶セルとの間に配置された実質的に６５０ｎｍまたは４００ｎｍのリタデーションを有する位相差板とを備え、前記位相差板の遅相軸と前記液晶セルの前記位相差板に隣接する基板の近傍の液晶分子配向方向とのずれ角を、実質的に５°に設定したことを特徴とする。
【０００８】
この液晶表示素子は上記のような構成であるため、明るく、しかも帯色の無い高品質の表示を得ることができる。
【０００９】
このように、この発明の液晶表示素子は、液晶分子を実質的に９０°のツイスト角でツイスト配向させ、Δｎｄの値を３５０〜５００ｎｍの範囲に設定した液晶層を有する液晶セルと、前記液晶セルを挟んで配置された一対の偏光板と、前記一対の偏光板の少なくとも一方と前記液晶セルとの間に配置された実質的に６５０ｎｍまたは４００ｎｍのリタデーションを有する位相差板とを備え、前記位相差板の遅相軸と前記液晶セルの前記位相差板に隣接する基板の近傍の液晶分子配向方向とのずれ角を実質的に５°に設定することにより、明るく、しかも帯色の無い高品質の表示を得ることができるようにしたものである。
【００１０】
この発明の液晶表示素子は、前記液晶層のΔｎｄを実質的に５００ｎｍに設定し、前記一対の偏光板の一方と前記液晶セルとの間に、実質的に６５０ｎｍのリタデーションを有する位相差板を、その遅相軸を前記液晶セルの前記位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらして配置した構成とするのが望ましい。
【００１１】
また、この発明の液晶表示素子は、前記液晶層のΔｎｄを実質的に４００ｎｍに設定し、前記一対の偏光板の一方と前記液晶セルとの間に、実質的に４００ｎｍのリタデーションを有する位相差板を、その遅相軸を前記液晶セルの前記位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらして配置した構成とするのが望ましい。
【００１２】
さらに、この発明の液晶表示素子は、前記液晶層のΔｎｄを実質的に４７０ｎｍに設定し、前記一対の偏光板の一方と前記液晶セルとの間に、実質的に６５０ｎｍのリタデーションを有する第１の位相差板を、その遅相軸を前記液晶セルの前記第１の位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記第１の位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらして配置し、他方の偏光板と前記液晶セルとの間に、実質的に４００ｎｍのリタデーションを有する第２の位相差板を、その遅相軸を前記液晶セルの前記第２の位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記第２の位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらして配置した構成とするのが望ましい。
【００１３】
【発明の実施の形態】
図１〜図４はこの発明の第１の実施例を示しており、図１及び図２は液晶表示素子の分解斜視図及び一部分の断面図である。
【００１４】
この液晶表示素子はＴＮ型のものであり、図１及び図２に示したように、液晶セル１と、前記液晶セル１を挟んでその前側と後側とに配置された一対の偏光板１１，１２と、前記一対の偏光板１１，１２の一方と前記液晶セル１との間に配置された位相差板１３とを備えている。
【００１５】
前記液晶セル１は、図２に示したように、互いに対向する面にそれぞれ透明な電極４，５が形成された一対の透明基板２，３間に、液晶分子を前記基板２，３間において実質的に９０°のツイスト角でツイスト配向させた液晶層１０を設けたものであり、その液晶の屈折率異方性Δｎと液晶層厚ｄとの積Δｎｄの値は３５０〜５００ｎｍの範囲に設定されている。
【００１６】
この液晶セル１は、例えばＴＦＴ（薄膜トランジスタ）をアクティブ素子とするアクティブマトリックス型のものであり、一対の基板２，３の対向面にそれぞれ形成された電極４，５のうち、一方の基板、例えば表示の観察側である前側（図において上側）の基板（以下、前基板と言う）１に形成された電極４は、基板１面の略全体にわたる一枚膜状の対向電極、他方の基板（以下、後基板と言う）３に形成された電極５は、行方向及び列方向にマトリックス状に配列する複数の画素電極である。
【００１７】
なお、図では省略しているが、前記後基板３の前基板２に対向する面には、前記複数の画素電極５にそれぞれ接続された複数のＴＦＴと、各行のＴＦＴにゲート信号を供給する複数のゲート配線と、各列のＴＦＴにデータ信号を供給する複数のデータ配線が設けられている。
【００１８】
また、この液晶セル１は、前記複数の画素電極５と対向電極４とが互いに対向する領域からなる複数の画素にそれぞれ対応する複数の色、例えば赤、緑、青の３色のカラーフィルタ６Ｒ，６Ｇ，６Ｂを備えており、このカラーフィルタ６Ｒ，６Ｇ，６Ｂは、前基板２の後基板３に対向する面に形成され、その上に前記対向電極４が形成されている。
【００１９】
そして、前記一対の基板２，３は、前記複数の画素の配列領域（表示エリア）を囲む枠状のシール材９（図１参照）を介して接合されており、これらの基板２，３間の前記シール材９により囲まれた領域に液晶層１０が設けられている。
【００２０】
前記液晶層１０の液晶分子は、前記一対の基板２，３の対向面にそれぞれ前記電極４，５を覆って形成された配向膜７，８により両基板２，３の近傍の配向方向を規定され、前記基板２，３間において実質的に９０°のツイスト角でツイスト配向している。
【００２１】
この実施例では、図１に示したように、前基板２の近傍の液晶分子を画面の横軸ｘに対し前側から見て左回りに実質的に４５°ずれた方向２ａに配向させ、後基板３の近傍の液晶分子を前記横軸ｘに対し前側から見て右回りに実質的に４５°ずれた方向３ａに配向させ、前記液晶層１０の液晶分子を、そのツイスト方向を破線矢印で示したように、後基板３から前基板２に向かい、前側から見て右回りに実質的に９０°のツイスト角でツイスト配向させている。
【００２２】
また、この実施例の液晶表示素子はノーマリーホワイトモードのものであり、前記液晶セル１を挟んでその前側と後側とに配置された一対の偏光板１１，１２は、それぞれの透過軸１１ａ，１２ａを実質的に互いに直交させるとともに、前側の偏光板１１の透過軸１１ａを前記液晶セル１の前基板２の近傍の液晶分子配向方向２ａと実質的に直交させるか或いは実質的に平行にし、後側の偏光板１２の透過軸１２ａを前記液晶セル１の後基板３の近傍の液晶分子配向方向３ａと実質的に直交させるか或いは実質的に平行にして配置されている。
【００２３】
なお、前記液晶セル１の液晶分子のツイスト角と、一対の偏光板１１，１２の透過軸１１ａ，１２ａの交差角は、いずれも９０°±１０°であり、好ましくは９０°±５°、より好ましくは９０°±３°である。
【００２４】
さらに、前記位相差板１３は、実質的に６５０ｎｍまたは４００ｎｍのリタデーションを有する位相差板であり、この位相差板１３は、前記一対の偏光板１１，１２の一方と前記液晶セル１との間に、前記位相差板１３の遅相軸１３ａと前記液晶セル１の前記位相差板１３に隣接する前基板の近傍の液晶分子配向方向２ａとのずれ角を実質的に５°に設定して配置されている。
【００２５】
この実施例では、前記液晶セル１の液晶層１０のΔｎｄを実質的に５００ｎｍに設定し、実質的に６５０ｎｍのリタデーションを有する位相差板１３を、前側の偏光板１１と前記液晶セル１との間に、前記位相差板１３の遅相軸１３ａを前記液晶セル１の前記位相差板１３に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記前基板２から後基板３に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらして配置している。
【００２６】
図３は、この実施例における前側から見た液晶セル１の前後の基板２，３の近傍の液晶分子配向方向２ａ，３ａ及び液晶分子のツイスト方向と位相差板１３の遅相軸１３ａの向きを示しており、この図では、前記位相差板１３の遅相軸１３ａを一点鎖線で示している。
【００２７】
なお、上述したように、前記液晶セル１の前基板２の近傍の液晶分子配向方向２ａは、画面の横軸ｘに対し前側から見て左回りに実質的に４５°ずれた方向であり、液晶分子は、後基板３から前基板２に向かい、前側から見て右回りにツイスト配向している。
【００２８】
そして、この実施例では、前記位相差板１３を前側の偏光板１１と液晶セル１との間に配置しているため、前記液晶セル１の前記位相差板１３に隣接する前基板２から他方の後基板３に向かう液晶分子のツイスト方向は、図に破線矢印で示した方向とは逆の左回り方向である。
【００２９】
そのため、この実施例では、前記位相差板１３を図１のように、その遅相軸１３ａを前記画面の横軸ｘに対し前側から見て左回りに実質的に５０°ずらして配置し、この位相差板１３の遅相軸１３ａを、前記液晶セル１の前記位相差板１３に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記前基板２から後基板３に向かう液晶分子のツイスト方向（図の破線矢印の向きとは逆のツイスト方向）と同方向に実質的に５°ずらしている。
【００３０】
なお、この実施例において、前記液晶セル１の液晶層１０のΔｎｄは、５００ｎｍ±１０ｎｍであり、好ましくは５００ｎｍ±５ｎｍである。また、前記位相差板１３のリタデーションは、６５０ｎｍ±１０ｎｍであり、好ましくは６５０ｎｍ±５ｎｍである。さらに、前記位相差板１３の遅相軸１３ａと前記液晶セル１の前記位相差板１３に隣接する前基板２の近傍の液晶分子配向方向２ａとのずれ角は、５°±２°であり、好ましくは５°±１°である。
【００３１】
この液晶表示素子は、上述したように、液晶分子を実質的に９０°のツイスト角でツイスト配向させ、Δｎｄの値を実質的に５００ｎｍに設定した液晶層１０を有する液晶セル１と、前記液晶セル１を挟んでその前側と後側とに配置された一対の偏光板１１，１２と、前側の偏光板１１と前記液晶セル１との間に配置された実質的に６５０ｎｍのリタデーションを有する位相差板１３とを備え、前記位相差板１３の遅相軸１３ａを、前記液晶セル１の前記位相差板１３に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記位相差板１３に隣接する前基板２から他方の後基板３に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらしたものであるため、明るく、しかも帯色の無い高品質の表示を得ることができる。
【００３２】
図４は、前記第１の実施例についてカラーフィルタを省略した試験素子を製作し、その波長―透過率特性を測定した結果を、前記位相差板１３を備えない比較例１，２の波長―透過率特性と比較して示している。
【００３３】
なお、前記比較例１，２はいずれも、カラーフィルタを備えないノーマリーホワイトモードのＴＮ型液晶表示素子であり、比較例１はΔｎｄを４７０ｎｍに設定したもの、比較例２はΔｎｄを４００ｎｍに設定したものである。
【００３４】
図４のように、Δｎｄを４７０ｎｍに設定した比較例１は、可視光帯域の中間付近（５５０ｎｍ付近）の波長光の透過率が高く、明るい表示が得られるが、人間の眼による感度が弱い青の波長域（４５０ｎｍ付近）の光の透過率が低いため、白表示が黄緑色に帯色する。
【００３５】
また、Δｎｄを４００ｎｍに設定した比較例２は、透過率が最大となる波長域が前記比較例１よりも青の波長側にシフトするため、白表示の帯色は改善されるが、可視光帯域の中間付近の波長光の透過率が低く、明るい表示が得られない。
【００３６】
それに対し、前記第１の実施例は、透過率が、青の波長域（４５０ｎｍ付近）から赤の波長域（６５０ｎｍ付近）にわたって高く、したがって、高輝度でしかも帯色の無い白表示が得られる。
【００３７】
そして、前記第１の実施例の液晶表示素子は、液晶セル１に、複数の画素にそれぞれ対応する赤、緑、青の３色のカラーフィルタ６Ｒ，６Ｇ，６Ｂを備えさせたものであり、これらの画素から色純度の良い赤、緑、青の光を出射させることができるため、明るく、しかも色相の良い高品質のカラー画像を表示することができる。
【００３８】
なお、前記第１の実施例では、前側の偏光板１１と液晶セル１との間に位相差板１３を配置しているが、前記位相差板１３は、後側の偏光板１２と液晶セル１との間に配置してもよく、その場合は、前記位相差板１３を、その遅相軸１３ａを前記液晶セル１の前記位相差板１３に隣接する後基板３の近傍の液晶分子配向方向３ａに対し、前記位相差板１３に隣接する後基板３から他方の前基板２に向かう液晶分子のツイスト方向（図の破線矢印の方向）と同方向に実質的に５°ずらして配置すればよい。
【００３９】
図５はこの発明の第２の実施例を示す液晶表示素子の分解斜視図であり、この液晶表示素子は、液晶セル１の液晶層のΔｎｄを実質的に４００ｎｍに設定し、前側の偏光板１１と前記液晶セル１との間に、実質的に４００ｎｍのリタデーションを有する位相差板１４を、その遅相軸１４ａを前記液晶セル１の前記位相差板１４に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記前基板２から後基板３に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらして配置したものである。
【００４０】
なお、この実施例の液晶表示素子は、液晶セル１の液晶層のΔｎｄと位相差板１４のリタデーション及びその遅相軸１４ａの向きが上述した第１の実施例と異なるが、他の構成は同じであるから、重複する説明は図に同符号を付して省略する。
【００４１】
図６は、この実施例における前側から見た液晶セル１の前後の基板２，３の近傍の液晶分子配向方向２ａ，３ａ及び液晶分子のツイスト方向と位相差板１４の遅相軸１４ａの向きを示しており、この図では、前記位相差板１４の遅相軸１４ａを二点鎖線で示している。
【００４２】
図６のように、この実施例では、前記位相差板１４を、その遅相軸１４ａを画面の横軸ｘに対し前側から見て左回りに実質的に４０°ずらして配置し（図５参照）、この位相差板１４の遅相軸１４ａを、前記液晶セル１の前記位相差板１４に隣接する前基板２の近傍の液晶分子配向方向（画面の横軸ｘに対し前側から見て左回りに実質的に４５°ずれた方向）２ａに対し、前記前基板２から後基板３に向かう液晶分子のツイスト方向（図の破線矢印の向きとは逆のツイスト方向）とは逆方向に実質的に５°ずらしている。
【００４３】
なお、この実施例において、前記液晶セル１の液晶層のΔｎｄは、４００ｎｍ±１０ｎｍであり、好ましくは４００ｎｍ±５ｎｍである。また、前記位相差板１４のリタデーションは、４００ｎｍ±１０ｎｍであり、好ましくは４００ｎｍ±５ｎｍである。さらに、前記位相差板１４の遅相軸１４ａと前記液晶セル１の前記位相差板１４に隣接する前基板２の近傍の液晶分子配向方向２ａとのずれ角は、５°±２°であり、好ましくは５°±１°である。
【００４４】
この液晶表示素子は、上述したように、液晶分子を実質的に９０°のツイスト角でツイスト配向させ、Δｎｄの値を実質的に４００ｎｍに設定した液晶層を有する液晶セル１と、前記液晶セル１を挟んでその前側と後側とに配置された一対の偏光板１１，１２と、前側の偏光板１１と前記液晶セル１との間に配置された実質的に４００ｎｍのリタデーションを有する位相差板１４とを備え、前記位相差板１４の遅相軸１４ａを、前記液晶セル１の前記位相差板１４に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記位相差板１４に隣接する前基板２から他方の後基板３に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらしたものであるため、明るく、しかも帯色の無い高品質の表示を得ることができる。
【００４５】
図７は、前記第２の実施例についてカラーフィルタを省略した試験素子を製作し、その波長―透過率特性を測定した結果を、上述した比較例１，２の波長―透過率特性と比較して示している。
【００４６】
図７のように、前記第２の実施例は、透過率が、可視光帯域の中間付近である緑の波長域（４５０ｎｍ付近）から青の波長域（４５０ｎｍ付近）にわたって高くしかも略一定で、また赤の波長域（６５０ｎｍ付近）においても充分に高く、高輝度でしかも帯色の無い白表示が得られる。
【００４７】
したがって、前記第２の実施例の液晶表示素子は、明るく、しかも色相の良い高品質のカラー画像を表示することができる。
【００４８】
なお、前記第２の実施例では、前側の偏光板１１と液晶セル１との間に位相差板１４を配置しているが、前記位相差板１４は、後側の偏光板１２と液晶セル１との間に配置してもよく、その場合は、前記位相差板１４を、その遅相軸１４ａを前記液晶セル１の前記位相差板１４に隣接する後基板３の近傍の液晶分子配向方向３ａに対し、前記位相差板１４に隣接する後基板３から他方の前基板２に向かう液晶分子のツイスト方向（図の破線矢印の方向）とは逆方向に実質的に５°ずらして配置すればよい。
【００４９】
図８はこの発明の第３の実施例を示す液晶表示素子の分解斜視図であり、この液晶表示素子は、液晶セル１の液晶層のΔｎｄを実質的に４７０ｎｍに設定し、前側の偏光板１１と前記液晶セル１との間に、実質的に６５０ｎｍのリタデーションを有する第１の位相差板（第１の実施例における位相差板）１３を、その遅相軸１３ａを前記液晶セル１の前記第１の位相差板１３に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記前基板２から後基板３に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらして配置し、後側の偏光板１２と前記液晶セル１との間に、実質的に４００ｎｍのリタデーションを有する第２の位相差板（第２の実施例における位相差板）１４を、その遅相軸１４ａを前記液晶セル１の前記第２の位相差板１４に隣接する後基板３の近傍の液晶分子配向方向３ａに対し、前記後基板３から前基板２に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらして配置したものである。
【００５０】
なお、この実施例において、前記液晶セル１は、その液晶層のΔｎｄの値が上述した第１の実施例と異なるが、他の構成は同じであり、また、前後の偏光板１１，１２の配置状態も第１の実施例と同じであるから、重複する説明は図に同符号を付して省略する。
【００５１】
図９は、この実施例における前側から見た液晶セル１の前後の基板２，３の近傍の液晶分子配向方向２ａ，３ａ及び液晶分子のツイスト方向と第１及び第２の位相差板１３，１４の遅相軸１３ａ，１４ａの向きを示しており、この図では、第１の位相差板１３の遅相軸１３ａを一点鎖線で示し、第２の位相差板１４の遅相軸１４ａを二点鎖線で示している。
【００５２】
図９のように、この実施例では、前記第１の位相差板１３を、その遅相軸１３ａを画面の横軸ｘに対し前側から見て左回りに実質的に５０°ずらして配置し（図８参照）、この第１の位相差板１３の遅相軸１３ａを、前記液晶セル１の前記第１の位相差板１３に隣接する前基板２の近傍の液晶分子配向方向（画面の横軸ｘに対し前側から見て左回りに実質的に４５°ずれた方向）２ａに対し、前記前基板２から後基板３に向かう液晶分子のツイスト方向（図の破線矢印の向きとは逆のツイスト方向）と同方向に実質的に５°ずらし、前記第２の位相差板１４を、その遅相軸１４ａを前記画面の横軸ｘに対し前側から見て右回りに実質的に４０°ずらして配置し（図８参照）、この第２の位相差板１４の遅相軸１４ａを、前記液晶セル１の前記第２の位相差板１４に隣接する後基板３の近傍の液晶分子配向方向（画面の横軸ｘに対し前側から見て右回りに実質的に４５°ずれた方向）３ａに対し、前記後基板３から前基板２に向かう液晶分子のツイスト方向（図の破線矢印の方向）とは逆方向に実質的に５°ずらしている。
【００５３】
なお、この実施例において、前記液晶セル１の液晶層のΔｎｄは、４７０ｎｍ±１０ｎｍであり、好ましくは５００ｎｍ±５ｎｍである。また、前記第１の位相差板１３のリタデーションは、６５０ｎｍ±１０ｎｍ、好ましくは６５０ｎｍ±５ｎｍであり、第２の位相差板１４のリタデーションは、４００ｎｍ±１０ｎｍ、好ましくは４００ｎｍ±５ｎｍである。さらに、前記第１の位相差板１３の遅相軸１３ａと前記液晶セル１の前記第１の位相差板１３に隣接する前基板２の近傍の液晶分子配向方向２ａとのずれ角は、５°±２°、好ましくは５°±１°であり、前記第２の位相差板１４の遅相軸１４ａと前記液晶セル１の前記第２の位相差板１４に隣接する後基板３の近傍の液晶分子配向方向３ａとのずれ角は、５°±２°、好ましくは５°±１°である。
【００５４】
この液晶表示素子は、上述したように、液晶分子を実質的に９０°のツイスト角でツイスト配向させ、Δｎｄの値を実質的に４７０ｎｍに設定した液晶層を有する液晶セル１と、前記液晶セル１を挟んでその前側と後側とに配置された一対の偏光板１１，１２と、前側の偏光板１１と前記液晶セル１との間に配置された実質的に６５０ｎｍのリタデーションを有する第１の位相差板１３と、後側の偏光板１２と前記液晶セル１との間に配置された実質的に４００ｎｍのリタデーションを有する第２の位相差板１４とを備え、前記第１の位相差板１３の遅相軸１３ａを、前記液晶セル１の前記第１の位相差板１３に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記第１の位相差板１３に隣接する前基板２から他方の後基板３に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらし、前記第２の位相差板１４の遅相軸１４ａを、前記液晶セル１の前記第２の位相差板１４に隣接する後基板３の近傍の液晶分子配向方向３ａに対し、前記前記第２の位相差板１４に隣接する後基板３から他方の前基板２に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらしたものであるため、明るく、しかも帯色の無い高品質の表示を得ることができる。
【００５５】
図１０は、前記第３の実施例についてカラーフィルタを省略した試験素子を製作し、その波長―透過率特性を測定した結果を、上述した比較例１，２の波長―透過率特性と比較して示している。
【００５６】
図１０のように、前記第３の実施例は、透過率が、青の波長域（４５０ｎｍ付近）から赤の波長域（６５０ｎｍ付近）にわたって高く、しかも略一定であり、したがって、上述した第１及び第２の実施例よりもさらに高輝度でしかも帯色の無い白表示が得られる。
【００５７】
したがって、前記第３の実施例の液晶表示素子は、さらに明るく、しかも、より色相の良い高品質のカラー画像を表示することができる。
【００５８】
なお、前記第３の実施例では、前側の偏光板１１と液晶セル１との間に実質的に６５０ｎｍのリタデーションを有する第１の位相差板１３を配置し、後側の偏光板１２と液晶セル１との間に実質的に４００ｎｍのリタデーションを有する第２の位相差板１４を配置しているが、それと反対に、前記第１の位相差板１３を後側の偏光板１２と液晶セル１との間に配置し、前記第２の位相差板１４を前側の偏光板１１と液晶セル１との間に配置してもよい。
【００５９】
その場合は、前記第１の位相差板１３を、その遅相軸１３ａを前記液晶セル１の前記第１の位相差板１３に隣接する後基板３の近傍の液晶分子配向方向３ａに対し、前記第１の位相差板１３に隣接する後基板３から他方の前基板２に向かう液晶分子のツイスト方向（図の破線矢印の方向）と同方向に実質的に５°ずらして配置し、前記第２の位相差板１４を、その遅相軸１４ａを前記液晶セル１の前記第２の位相差板１４に隣接する前基板２の近傍の液晶分子配向方向２ａに対し、前記第２の位相差板１４に隣接する前基板２から他方の後基板３に向かう液晶分子のツイスト方向とは逆方向（図の破線矢印の向きとは逆のツイスト方向）に実質的に５°ずらして配置すればよい。
【００６０】
また、この発明において、液晶セルの液晶層のΔｎｄと位相差板のリタデーションは、上述した第１〜第３の実施例の値に限らず、前記液晶層のΔｎｄの値が３５０〜５００ｎｍの範囲、位相差板のリタデーションが実質的に６５０ｎｍまたは４００ｎｍであればよく、その場合も、前記液晶セルの位相差板に隣接する基板の近傍の液晶分子配向方向と前記位相差板の遅相軸とのずれ角を実質的に５°にし、且つ、前記液晶層のΔｎｄ値と、位相差板のリタデーション値と、前記液晶分子配向方向に対する前記位相差板の遅相軸のずれ方向とを適正に設定することにより、明るく、しかも帯色の無い高品質の表示を得ることができる。
【００６１】
さらに、上記実施例の液晶表示素子、液晶セル１に、複数の画素にそれぞれ対応する赤、緑、青の３色のカラーフィルタ６Ｒ，６Ｇ，６Ｂを備えさせたものであるが、この発明は、カラーフィルタを備えないフィールドシーケンシャル液晶表示装置用の液晶表示素子や、白黒画像を表示する液晶表示素子にも適用することができる。
【００６２】
【発明の効果】
この発明の液晶表示素子は、液晶分子を実質的に９０°のツイスト角でツイスト配向させ、Δｎｄの値を３５０〜５００ｎｍの範囲に設定した液晶層を有する液晶セルと、前記液晶セルを挟んで配置された一対の偏光板と、前記一対の偏光板の少なくとも一方と前記液晶セルとの間に配置された実質的に６５０ｎｍまたは４００ｎｍのリタデーションを有する位相差板とを備え、前記位相差板の遅相軸と前記液晶セルの前記位相差板に隣接する基板の近傍の液晶分子配向方向とのずれ角を実質的に５°に設定したものであるため、明るく、しかも帯色の無い高品質の表示を得ることができる。
【００６３】
この発明の液晶表示素子は、前記液晶層のΔｎｄを実質的に５００ｎｍに設定し、前記一対の偏光板の一方と前記液晶セルとの間に、実質的に６５０ｎｍのリタデーションを有する位相差板を、その遅相軸を前記液晶セルの前記位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらして配置した構成とするのが望ましく、このような構成とすることにより、明るく、しかも帯色の無い高品質の表示を得ることができる。
【００６４】
また、この発明の液晶表示素子は、前記液晶層のΔｎｄを実質的に４００ｎｍに設定し、前記一対の偏光板の一方と前記液晶セルとの間に、実質的に４００ｎｍのリタデーションを有する位相差板を、その遅相軸を前記液晶セルの前記位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらして配置した構成とするのが望ましく、このような構成とすることにより、明るく、しかも帯色の無い高品質の表示を得ることができる。
【００６５】
さらに、この発明の液晶表示素子は、前記液晶層のΔｎｄを実質的に４７０ｎｍに設定し、前記一対の偏光板の一方と前記液晶セルとの間に、実質的に６５０ｎｍのリタデーションを有する第１の位相差板を、その遅相軸を前記液晶セルの前記第１の位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記第１の位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向と同方向に実質的に５°ずらして配置し、他方の偏光板と前記液晶セルとの間に、実質的に４００ｎｍのリタデーションを有する第２の位相差板を、その遅相軸を前記液晶セルの前記第２の位相差板に隣接する基板の近傍の液晶分子配向方向に対し、前記第２の位相差板に隣接する基板から他方の基板に向かう液晶分子のツイスト方向とは逆方向に実質的に５°ずらして配置した構成とするのが望ましく、このような構成とすることにより、さらに明るく、しかも、より帯色の無い高品質の表示を得ることができる。
【図面の簡単な説明】
【図１】この発明の第１の実施例を示す液晶表示素子の分解斜視図。
【図２】第１の実施例の液晶表示素子の一部分の断面図。
【図３】第１の実施例における液晶セルの前後の基板の近傍の液晶分子配向方向及び液晶分子のツイスト方向と位相差板の遅相軸の向きを示す図。
【図４】第１の実施例と比較例の波長―透過率特性図。
【図５】この発明の第２の実施例を示す液晶表示素子の分解斜視図。
【図６】第２の実施例における液晶セルの前後の基板の近傍の液晶分子配向方向及び液晶分子のツイスト方向と位相差板の遅相軸の向きを示す図。
【図７】第２の実施例と比較例の波長―透過率特性図。
【図８】この発明の第３の実施例を示す液晶表示素子の分解斜視図。
【図９】第３の実施例における液晶セルの前後の基板の近傍の液晶分子配向方向及び液晶分子のツイスト方向と位相差板の遅相軸の向きを示す図。
【図１０】第３の実施例と比較例の波長―透過率特性図。
【符号の説明】
１…液晶セル、２，３…基板、２ａ，３ａ…基板近傍の液晶分子配向方向、４，５…電極、６Ｒ，６Ｇ，６Ｂ…カラーフィルタ、７，８…配向膜、１０…液晶層、１１，１２…偏光板、１１ａ，１２ａ…透過軸、１３，１４…位相差板、１３ａ，１４ａ…遅相軸。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a TN (twisted nematic) liquid crystal display device.
[0002]
[Prior art]
A liquid crystal display element includes a liquid crystal layer provided between a pair of substrates having electrodes formed on surfaces facing each other and having a liquid crystal layer in which liquid crystal molecules are twisted substantially at a twist angle of 90 ° between the substrates. 2. Description of the Related Art A TN-type liquid crystal display device including a cell and a pair of polarizing plates sandwiching the liquid crystal cell is widely used (see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-06-202068
[0004]
[Problems to be solved by the invention]
The display characteristics of the TN type liquid crystal display element are determined by the value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal and the thickness d of the liquid crystal layer.
[0005]
However, in the conventional TN type liquid crystal display element, a display in which the .DELTA.nd value is set so as to obtain a bright display produces a band, and a display in which the .DELTA.nd value is set so as not to produce a band produces a bright display. Have a problem that they cannot be obtained.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide a TN type liquid crystal display device capable of obtaining a bright, high-quality display without banding.
[0007]
[Means for Solving the Problems]
According to the liquid crystal display device of the present invention, liquid crystal molecules are twisted at a twist angle of substantially 90 ° between a pair of substrates having electrodes formed on surfaces facing each other, and the refractive index of the liquid crystal is changed. A liquid crystal cell provided with a liquid crystal layer in which the value of the product Δnd of the anisotropy Δn and the liquid crystal layer thickness d is set in a range of 350 to 500 nm; a pair of polarizing plates disposed so as to sandwich the liquid crystal cell; A retardation plate having a retardation of substantially 650 nm or 400 nm disposed between at least one of the polarizing plates and the liquid crystal cell, wherein a slow axis of the retardation plate and the retardation of the liquid crystal cell are provided. The angle of deviation from the liquid crystal molecule alignment direction near the substrate adjacent to the plate is set to substantially 5 °.
[0008]
Since the liquid crystal display element has the above-described structure, it is possible to obtain a bright, high-quality display without banding.
[0009]
As described above, the liquid crystal display element of the present invention comprises a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twist-oriented substantially at a twist angle of 90 ° and the value of Δnd is set in a range of 350 to 500 nm. A pair of polarizing plates disposed with a cell interposed therebetween, and a retardation plate having a retardation of substantially 650 nm or 400 nm disposed between at least one of the pair of polarizing plates and the liquid crystal cell; By setting the shift angle between the slow axis of the phase difference plate and the liquid crystal molecule alignment direction near the substrate adjacent to the phase difference plate of the liquid crystal cell to substantially 5 °, it is bright and free of banding. High quality display can be obtained.
[0010]
In the liquid crystal display element of the present invention, a Δnd of the liquid crystal layer is set to substantially 500 nm, and a retardation plate having a retardation of substantially 650 nm is provided between one of the pair of polarizing plates and the liquid crystal cell. The slow axis of the liquid crystal cell in the same direction as the twist direction of the liquid crystal molecules from the substrate adjacent to the retardation plate to the other substrate with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the retardation plate of the liquid crystal cell. It is desirable to adopt a configuration in which they are arranged substantially 5 ° apart from each other.
[0011]
Further, in the liquid crystal display element of the present invention, Δnd of the liquid crystal layer is set to substantially 400 nm, and a phase difference having a retardation of substantially 400 nm between one of the pair of polarizing plates and the liquid crystal cell. The plate has its slow axis with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the phase difference plate of the liquid crystal cell, and the twist direction of the liquid crystal molecules from the substrate adjacent to the phase difference plate toward the other substrate. Are desirably arranged at substantially 5 ° in the opposite direction.
[0012]
Further, in the liquid crystal display element of the present invention, the liquid crystal layer has a Δnd of substantially 470 nm, and a first liquid crystal layer having a retardation of substantially 650 nm between one of the pair of polarizing plates and the liquid crystal cell. The retardation axis of the liquid crystal cell, with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the first retardation plate of the liquid crystal cell, from the substrate adjacent to the first retardation plate to the other. A second retardation plate having a retardation of substantially 400 nm is disposed between the other polarizing plate and the liquid crystal cell at a position substantially shifted by 5 ° in the same direction as the twist direction of the liquid crystal molecules toward the substrate. Liquid crystal molecules whose slow axis is directed from the substrate adjacent to the second retardation plate to the other substrate with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the second retardation plate of the liquid crystal cell. In the direction opposite to the twist direction It is desirable to adopt a configuration qualitatively shifted by 5 °.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 4 show a first embodiment of the present invention. FIGS. 1 and 2 are an exploded perspective view and a partial cross-sectional view of a liquid crystal display device.
[0014]
This liquid crystal display element is of a TN type, and as shown in FIGS. 1 and 2, a liquid crystal cell 1 and a pair of polarizing plates 11 arranged on the front and rear sides of the liquid crystal cell 1 therebetween. , 12 and a retardation plate 13 arranged between one of the pair of polarizing plates 11, 12 and the liquid crystal cell 1.
[0015]
As shown in FIG. 2, the liquid crystal cell 1 includes a pair of transparent substrates 2 and 3 having transparent electrodes 4 and 5 formed on opposing surfaces, respectively. A liquid crystal layer 10 that is twist-oriented substantially at a twist angle of 90 ° is provided. The value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d is in the range of 350 to 500 nm. Is set.
[0016]
The liquid crystal cell 1 is of an active matrix type using, for example, a TFT (thin film transistor) as an active element, and is one of electrodes 4, 5 formed on opposing surfaces of a pair of substrates 2, 3, for example, An electrode 4 formed on a substrate (hereinafter, referred to as a front substrate) 1 on a front side (upper side in the figure) which is a display observation side includes a single-film counter electrode covering substantially the entire surface of the substrate 1 and the other substrate ( The electrodes 5 formed on the rear substrate 3 are a plurality of pixel electrodes arranged in a matrix in the row direction and the column direction.
[0017]
Although not shown in the figure, on the surface of the rear substrate 3 facing the front substrate 2, a plurality of TFTs connected to the plurality of pixel electrodes 5 and a gate signal are supplied to the TFTs in each row. A plurality of gate wirings and a plurality of data wirings for supplying data signals to the TFTs in each column are provided.
[0018]
The liquid crystal cell 1 has a plurality of color filters 6R corresponding to a plurality of pixels formed of regions where the plurality of pixel electrodes 5 and the counter electrode 4 face each other, for example, three colors of red, green, and blue. , 6G, and 6B. The color filters 6R, 6G, and 6B are formed on the surface of the front substrate 2 facing the rear substrate 3, and the counter electrode 4 is formed thereon.
[0019]
The pair of substrates 2 and 3 are joined via a frame-shaped sealing material 9 (see FIG. 1) surrounding the array area (display area) of the plurality of pixels. A liquid crystal layer 10 is provided in a region surrounded by the sealing material 9.
[0020]
The alignment directions of the liquid crystal molecules of the liquid crystal layer 10 in the vicinity of the substrates 2 and 3 are defined by the alignment films 7 and 8 formed on the opposing surfaces of the pair of substrates 2 and 3 so as to cover the electrodes 4 and 5, respectively. The substrates 2 and 3 are twist-oriented at a twist angle of substantially 90 °.
[0021]
In this embodiment, as shown in FIG. 1, the liquid crystal molecules in the vicinity of the front substrate 2 are aligned in a direction 2a substantially 45 ° counterclockwise as viewed from the front with respect to the horizontal axis x of the screen. The liquid crystal molecules in the vicinity of the substrate 3 are oriented in a direction 3a substantially 45 ° clockwise shifted with respect to the horizontal axis x when viewed from the front, and the twist direction of the liquid crystal molecules of the liquid crystal layer 10 is indicated by a broken line arrow. As shown, the substrate is twisted from the rear substrate 3 to the front substrate 2 at a twist angle of substantially 90 ° clockwise when viewed from the front.
[0022]
The liquid crystal display element of this embodiment is of a normally white mode, and a pair of polarizing plates 11 and 12 disposed on the front and rear sides of the liquid crystal cell 1 have respective transmission axes 11a. , 12a are substantially perpendicular to each other, and the transmission axis 11a of the front polarizer 11 is substantially perpendicular to or substantially parallel to the liquid crystal molecule alignment direction 2a near the front substrate 2 of the liquid crystal cell 1. The transmission axis 12a of the rear polarizing plate 12 is arranged substantially orthogonal to or substantially parallel to the liquid crystal molecule orientation direction 3a near the rear substrate 3 of the liquid crystal cell 1.
[0023]
Note that the twist angle of the liquid crystal molecules of the liquid crystal cell 1 and the cross angle of the transmission axes 11a and 12a of the pair of polarizing plates 11 and 12 are both 90 ° ± 10 °, preferably 90 ° ± 5 °. More preferably, it is 90 ° ± 3 °.
[0024]
Further, the retardation plate 13 is a retardation plate having a retardation of substantially 650 nm or 400 nm, and the retardation plate 13 is provided between one of the pair of polarizing plates 11 and 12 and the liquid crystal cell 1. Then, the shift angle between the slow axis 13a of the retardation plate 13 and the liquid crystal molecule alignment direction 2a near the front substrate of the liquid crystal cell 1 adjacent to the retardation plate 13 is set to substantially 5 °. Are located.
[0025]
In this embodiment, Δnd of the liquid crystal layer 10 of the liquid crystal cell 1 is set to substantially 500 nm, and the retardation plate 13 having a retardation of substantially 650 nm is provided between the front polarizing plate 11 and the liquid crystal cell 1. In the meantime, the slow axis 13a of the retardation plate 13 is moved from the front substrate 2 to the rear substrate 3 with respect to the liquid crystal molecule alignment direction 2a near the front substrate 2 adjacent to the retardation plate 13 of the liquid crystal cell 1. The liquid crystal molecules are arranged at substantially the same direction as the twist direction of the liquid crystal molecules to be shifted by 5 °.
[0026]
FIG. 3 shows the liquid crystal molecule orientation directions 2a and 3a near the substrates 2 and 3 before and after the liquid crystal cell 1 and the twist direction of the liquid crystal molecules and the direction of the slow axis 13a of the phase difference plate 13 in this embodiment. In this figure, the slow axis 13a of the phase difference plate 13 is indicated by a one-dot chain line.
[0027]
As described above, the liquid crystal molecule orientation direction 2a in the vicinity of the front substrate 2 of the liquid crystal cell 1 is substantially 45 ° counterclockwise when viewed from the front with respect to the horizontal axis x of the screen, The liquid crystal molecules are twisted clockwise from the rear substrate 3 to the front substrate 2 when viewed from the front.
[0028]
In this embodiment, since the retardation plate 13 is disposed between the front polarizing plate 11 and the liquid crystal cell 1, the other end of the liquid crystal cell 1 is separated from the front substrate 2 adjacent to the retardation plate 13. The twist direction of the liquid crystal molecules toward the rear substrate 3 is a counterclockwise direction opposite to the direction indicated by the dashed arrow in the figure.
[0029]
Therefore, in this embodiment, as shown in FIG. 1, the retardation plate 13 is arranged such that its slow axis 13a is substantially 50 ° counterclockwise as viewed from the front with respect to the horizontal axis x of the screen, The liquid crystal flowing from the front substrate 2 to the rear substrate 3 with respect to the liquid crystal molecule orientation direction 2a near the front substrate 2 adjacent to the phase plate 13 of the liquid crystal cell 1 It is substantially shifted by 5 ° in the same direction as the twist direction of the molecule (the twist direction opposite to the direction of the dashed arrow in the figure).
[0030]
In this embodiment, Δnd of the liquid crystal layer 10 of the liquid crystal cell 1 is 500 nm ± 10 nm, preferably 500 nm ± 5 nm. The retardation of the retardation plate 13 is 650 nm ± 10 nm, preferably 650 nm ± 5 nm. Further, the shift angle between the slow axis 13a of the phase difference plate 13 and the liquid crystal molecule alignment direction 2a near the front substrate 2 of the liquid crystal cell 1 adjacent to the phase difference plate 13 is 5 ° ± 2 °. , Preferably 5 ° ± 1 °.
[0031]
As described above, this liquid crystal display element has a liquid crystal cell 1 having a liquid crystal layer 10 in which liquid crystal molecules are twist-oriented substantially at a twist angle of 90 ° and the value of Δnd is set to substantially 500 nm. A pair of polarizers 11 and 12 disposed on the front side and the rear side of the cell 1, and a position having a retardation of substantially 650 nm disposed between the front polarizer 11 and the liquid crystal cell 1. A retardation plate 13, wherein the retardation axis 13 a of the retardation plate 13 is set such that the retardation axis 13 a of the retardation plate 13 Since the liquid crystal molecules are substantially shifted by 5 ° in the same direction as the twist direction of the liquid crystal molecules from the front substrate 2 adjacent to the substrate 13 to the other rear substrate 3, it is possible to obtain a bright and high-quality display without banding. Can be.
[0032]
FIG. 4 shows the results of measuring a wavelength-transmittance characteristic of a test element in which the color filter was omitted from the first embodiment and measuring the wavelength-transmittance characteristics of Comparative Examples 1 and 2 without the retardation plate 13. It is shown in comparison with the transmittance characteristics.
[0033]
Each of Comparative Examples 1 and 2 is a normally white mode TN-type liquid crystal display device without a color filter. Comparative Example 1 sets Δnd to 470 nm, and Comparative Example 2 sets Δnd to 400 nm. It is set.
[0034]
As shown in FIG. 4, in Comparative Example 1 in which Δnd is set to 470 nm, the transmittance of light having a wavelength near the middle of the visible light band (around 550 nm) is high, and a bright display is obtained, but the sensitivity of the human eye is weak. Since the transmittance of light in the blue wavelength range (around 450 nm) is low, white display is colored yellow-green.
[0035]
In Comparative Example 2 in which Δnd was set to 400 nm, the wavelength range in which the transmittance became maximum shifted to the blue wavelength side as compared with Comparative Example 1, so that the band of white display was improved, but visible light was The transmittance of light having a wavelength near the center of the band is low, and a bright display cannot be obtained.
[0036]
On the other hand, in the first embodiment, the transmittance is high from the blue wavelength range (around 450 nm) to the red wavelength range (around 650 nm), so that white display with high luminance and no banding can be obtained. .
[0037]
The liquid crystal display element of the first embodiment has the liquid crystal cell 1 provided with three color filters 6R, 6G, 6B of red, green, and blue corresponding to a plurality of pixels, respectively. Since red, green, and blue light with good color purity can be emitted from these pixels, a bright, high-quality color image with good hue can be displayed.
[0038]
In the first embodiment, the retardation plate 13 is disposed between the front polarizing plate 11 and the liquid crystal cell 1, but the retardation plate 13 is connected to the rear polarizing plate 12 and the liquid crystal cell 1. In this case, the retardation plate 13 has a slow axis 13 a whose liquid crystal molecule alignment near the rear substrate 3 adjacent to the retardation plate 13 of the liquid crystal cell 1. With respect to the direction 3 a, the liquid crystal molecules are arranged at a position substantially shifted by 5 ° from the rear substrate 3 adjacent to the phase difference plate 13 in the same direction as the twist direction of the liquid crystal molecules from the rear substrate 3 toward the other front substrate 2 (the direction of the broken arrow in the drawing). Just fine.
[0039]
FIG. 5 is an exploded perspective view of a liquid crystal display device showing a second embodiment of the present invention. In this liquid crystal display device, the liquid crystal layer of the liquid crystal cell 1 has a Δnd of substantially 400 nm and a front polarizing plate. A retardation plate 14 having a retardation of substantially 400 nm is provided between the liquid crystal cell 11 and the liquid crystal cell 1 so that its slow axis 14a is located near the front substrate 2 adjacent to the retardation plate 14 of the liquid crystal cell 1. The liquid crystal molecules are arranged so as to be substantially 5 ° away from the liquid crystal molecule alignment direction 2 a in a direction opposite to the twist direction of the liquid crystal molecules from the front substrate 2 to the rear substrate 3.
[0040]
The liquid crystal display element of this embodiment is different from the first embodiment in the Δnd of the liquid crystal layer of the liquid crystal cell 1, the retardation of the retardation plate 14, and the direction of the slow axis 14a thereof, but other configurations are the same. Since they are the same, the same description is given to the drawings with the same reference numerals and their description is omitted.
[0041]
FIG. 6 shows the liquid crystal molecule alignment directions 2a and 3a near the substrates 2 and 3 before and after the liquid crystal cell 1 and the twist direction of the liquid crystal molecules and the direction of the slow axis 14a of the retardation plate 14 in this embodiment. In this figure, the slow axis 14a of the phase difference plate 14 is indicated by a two-dot chain line.
[0042]
As shown in FIG. 6, in this embodiment, the retardation plate 14 is arranged such that its slow axis 14a is shifted substantially 40 ° counterclockwise as viewed from the front with respect to the horizontal axis x of the screen (FIG. 5). ), The slow axis 14a of the retardation plate 14 is aligned with the liquid crystal molecule alignment direction near the front substrate 2 adjacent to the retardation plate 14 of the liquid crystal cell 1 (as viewed from the front with respect to the horizontal axis x of the screen). In the direction opposite to the twist direction of the liquid crystal molecules from the front substrate 2 toward the rear substrate 3 (the direction opposite to the direction of the dashed arrow in the figure) with respect to the counterclockwise direction 2a). Substantially 5 ° shifted.
[0043]
In this embodiment, Δnd of the liquid crystal layer of the liquid crystal cell 1 is 400 nm ± 10 nm, preferably 400 nm ± 5 nm. The retardation of the retardation plate 14 is 400 nm ± 10 nm, preferably 400 nm ± 5 nm. Further, the shift angle between the slow axis 14a of the phase difference plate 14 and the liquid crystal molecule alignment direction 2a near the front substrate 2 of the liquid crystal cell 1 adjacent to the phase difference plate 14 is 5 ° ± 2 °. , Preferably 5 ° ± 1 °.
[0044]
As described above, this liquid crystal display element has a liquid crystal cell 1 having a liquid crystal layer in which liquid crystal molecules are twisted at a twist angle of substantially 90 ° and the value of Δnd is set to substantially 400 nm. 1 and a pair of polarizers 11 and 12 disposed on the front side and the rear side of the liquid crystal cell 1 and a phase difference having a retardation of substantially 400 nm disposed between the front polarizer 11 and the liquid crystal cell 1. A retardation axis 14a of the retardation plate 14 with respect to a liquid crystal molecule alignment direction 2a near the front substrate 2 adjacent to the retardation plate 14 of the liquid crystal cell 1. The liquid crystal molecules are displaced substantially 5 ° in the direction opposite to the twist direction of liquid crystal molecules from the front substrate 2 adjacent to the other rear substrate 3 to obtain a bright, high-quality display without banding. Can be.
[0045]
FIG. 7 shows a result of fabricating a test device in which the color filter was omitted from the second embodiment and measuring the wavelength-transmittance characteristics thereof with the wavelength-transmittance characteristics of Comparative Examples 1 and 2 described above. Is shown.
[0046]
As shown in FIG. 7, in the second embodiment, the transmittance is high and substantially constant from the green wavelength range (around 450 nm), which is near the middle of the visible light band, to the blue wavelength range (around 450 nm). Also in the red wavelength range (around 650 nm), white display with high luminance and no banding can be obtained.
[0047]
Therefore, the liquid crystal display device of the second embodiment can display a high-quality color image that is bright and has good hue.
[0048]
In the second embodiment, the retardation plate 14 is disposed between the front polarizing plate 11 and the liquid crystal cell 1, but the retardation plate 14 is connected to the rear polarizing plate 12 and the liquid crystal cell 1. In this case, the retardation plate 14 may be arranged such that its slow axis 14a has a liquid crystal molecule alignment near the rear substrate 3 adjacent to the retardation plate 14 of the liquid crystal cell 1. The liquid crystal molecules are arranged at a position substantially shifted by 5 ° with respect to the direction 3a in a direction opposite to the twist direction of the liquid crystal molecules from the rear substrate 3 adjacent to the retardation plate 14 toward the other front substrate 2 (the direction of the broken arrow in the drawing). do it.
[0049]
FIG. 8 is an exploded perspective view of a liquid crystal display device according to a third embodiment of the present invention. In this liquid crystal display device, the liquid crystal layer of the liquid crystal cell 1 has Δnd substantially set to 470 nm, and the front polarizing plate is set. A first retardation plate (a retardation plate in the first embodiment) 13 having a retardation of substantially 650 nm is provided between the liquid crystal cell 1 and the liquid crystal cell 1. The liquid crystal molecule alignment direction 2a in the vicinity of the front substrate 2 adjacent to the first retardation plate 13 is shifted by substantially 5 ° in the same direction as the twist direction of the liquid crystal molecules from the front substrate 2 to the rear substrate 3. And a second retardation plate (retardation plate in the second embodiment) 14 having a retardation of substantially 400 nm is provided between the rear polarizing plate 12 and the liquid crystal cell 1. The phase axis 14a is set to the second phase of the liquid crystal cell 1. The liquid crystal molecules are arranged at a position substantially shifted by 5 ° in a direction opposite to the twist direction of the liquid crystal molecules from the rear substrate 3 toward the front substrate 2 with respect to the liquid crystal molecule alignment direction 3a near the rear substrate 3 adjacent to the difference plate 14. It is.
[0050]
In this embodiment, the liquid crystal cell 1 is different from the above-described first embodiment in the value of Δnd of the liquid crystal layer, but the other configuration is the same. Since the arrangement state is also the same as that of the first embodiment, the same explanation is given to the drawings by omitting the duplicated explanations.
[0051]
FIG. 9 shows the liquid crystal molecule orientation directions 2a and 3a near the substrates 2 and 3 before and after the liquid crystal cell 1 viewed from the front side in this embodiment and the twist directions of the liquid crystal molecules and the first and second retardation plates 13 and 14 shows the directions of the slow axes 13a, 14a. In this figure, the slow axis 13a of the first retardation plate 13 is indicated by a dashed line, and the slow axis 14a of the second retardation plate 14 is This is indicated by a two-dot chain line.
[0052]
As shown in FIG. 9, in this embodiment, the first retardation plate 13 is arranged such that its slow axis 13a is substantially 50 ° counterclockwise as viewed from the front with respect to the horizontal axis x of the screen. (Refer to FIG. 8), the slow axis 13a of the first retardation plate 13 is aligned with the liquid crystal molecule orientation direction near the front substrate 2 adjacent to the first retardation plate 13 of the liquid crystal cell 1 (in the screen). With respect to 2a, a twist direction of liquid crystal molecules from the front substrate 2 toward the rear substrate 3 (a direction deviated substantially 45 degrees counterclockwise as viewed from the front side with respect to the horizontal axis x) Of the second retardation plate 14 by substantially 5 ° in the same direction as the twist direction of FIG. 8 (see FIG. 8), and the slow axis 14a of the second retardation plate 14 is The liquid crystal molecule alignment direction 3a (direction substantially 45 ° clockwise as viewed from the front with respect to the horizontal axis x of the screen) near the rear substrate 3 adjacent to the retardation plate 14 of FIG. The liquid crystal molecules are displaced substantially by 5 ° in a direction opposite to the twist direction of the liquid crystal molecules from the liquid crystal molecules toward the front substrate 2 (the direction of the dashed arrow in the figure).
[0053]
In this embodiment, Δnd of the liquid crystal layer of the liquid crystal cell 1 is 470 nm ± 10 nm, preferably 500 nm ± 5 nm. Further, the retardation of the first retardation plate 13 is 650 nm ± 10 nm, preferably 650 nm ± 5 nm, and the retardation of the second retardation plate 14 is 400 nm ± 10 nm, preferably 400 nm ± 5 nm. Further, the shift angle between the slow axis 13a of the first retardation plate 13 and the liquid crystal molecule orientation direction 2a near the front substrate 2 of the liquid crystal cell 1 adjacent to the first retardation plate 13 is 5 °. ° ± 2 °, preferably 5 ° ± 1 °, in the vicinity of the slow axis 14a of the second retardation plate 14 and the rear substrate 3 adjacent to the second retardation plate 14 of the liquid crystal cell 1. Is 5 ° ± 2 °, and preferably 5 ° ± 1 °.
[0054]
As described above, this liquid crystal display element has a liquid crystal cell 1 having a liquid crystal layer in which liquid crystal molecules are twist-oriented substantially at a twist angle of 90 ° and the value of Δnd is set to substantially 470 nm. And a pair of polarizing plates 11 and 12 disposed on the front side and the rear side of the liquid crystal cell 1, and a first 650 nm retardation disposed between the front polarizing plate 11 and the liquid crystal cell 1. , And a second retardation plate 14 having a retardation of substantially 400 nm disposed between the rear polarizing plate 12 and the liquid crystal cell 1, wherein the first retardation The slow axis 13a of the plate 13 is adjacent to the first retardation plate 13 with respect to the liquid crystal molecule orientation direction 2a near the front substrate 2 adjacent to the first retardation plate 13 of the liquid crystal cell 1. From the front substrate 2 to the other rear substrate 3 The liquid crystal molecules are shifted by substantially 5 ° in the same direction as the twist direction, so that the slow axis 14a of the second retardation plate 14 is shifted from the rear substrate 3 adjacent to the second retardation plate 14 of the liquid crystal cell 1. Is substantially shifted by 5 ° in a direction opposite to the twist direction of the liquid crystal molecules from the rear substrate 3 adjacent to the second retardation plate 14 toward the other front substrate 2 with respect to the liquid crystal molecule orientation direction 3a near the second retardation plate 14. Therefore, a high-quality display that is bright and has no banding can be obtained.
[0055]
FIG. 10 shows a result of fabricating a test device in which the color filter was omitted from the third embodiment and measuring the wavelength-transmittance characteristics thereof with the wavelength-transmittance characteristics of Comparative Examples 1 and 2 described above. Is shown.
[0056]
As shown in FIG. 10, in the third embodiment, the transmittance is high from the blue wavelength range (around 450 nm) to the red wavelength range (around 650 nm) and is substantially constant. In addition, a white display having a higher luminance than the second embodiment and having no banding can be obtained.
[0057]
Therefore, the liquid crystal display device of the third embodiment can display a brighter and higher quality color image with better hue.
[0058]
In the third embodiment, the first retardation plate 13 having a retardation of substantially 650 nm is disposed between the front polarizing plate 11 and the liquid crystal cell 1, and the rear polarizing plate 12 and the liquid crystal cell 1 are disposed. A second retardation plate 14 having a retardation of substantially 400 nm is arranged between the first retardation plate 13 and the rear polarizing plate 12 and the liquid crystal cell. 1 and the second retardation plate 14 may be disposed between the front polarizer 11 and the liquid crystal cell 1.
[0059]
In this case, the first retardation plate 13 is set so that its slow axis 13a is oriented with respect to the liquid crystal molecule alignment direction 3a near the rear substrate 3 adjacent to the first retardation plate 13 of the liquid crystal cell 1. The liquid crystal molecules are arranged at a position substantially shifted by 5 ° in the same direction as the twist direction of the liquid crystal molecules from the rear substrate 3 adjacent to the first retardation plate 13 toward the other front substrate 2 (the direction of the dashed arrow in the drawing). The second retardation plate 14 has its slow axis 14a with respect to the liquid crystal molecule alignment direction 2a in the vicinity of the front substrate 2 adjacent to the second retardation plate 14 of the liquid crystal cell 1. The liquid crystal molecules are arranged at a position substantially shifted by 5 ° in a direction opposite to the twist direction of the liquid crystal molecules from the front substrate 2 adjacent to the phase difference plate 14 toward the other rear substrate 3 (the direction opposite to the direction of the dashed arrow in the drawing). Just fine.
[0060]
Further, in the present invention, the Δnd of the liquid crystal layer of the liquid crystal cell and the retardation of the retardation plate are not limited to the values of the above-described first to third embodiments. The retardation of the retardation plate may be substantially 650 nm or 400 nm. In this case, too, the liquid crystal molecule alignment direction near the substrate adjacent to the retardation plate of the liquid crystal cell and the slow axis of the retardation plate Is substantially 5 °, and the Δnd value of the liquid crystal layer, the retardation value of the phase difference plate, and the direction of the shift of the slow axis of the phase difference plate with respect to the liquid crystal molecule alignment direction are properly adjusted. By setting, it is possible to obtain a bright, high-quality display without banding.
[0061]
Further, the liquid crystal display element and the liquid crystal cell 1 of the above embodiment are provided with three color filters 6R, 6G and 6B of red, green and blue corresponding to a plurality of pixels, respectively. Also, the present invention can be applied to a liquid crystal display element for a field sequential liquid crystal display device having no color filter and a liquid crystal display element for displaying a black and white image.
[0062]
【The invention's effect】
The liquid crystal display element of the present invention has a liquid crystal cell having a liquid crystal layer in which liquid crystal molecules are twisted substantially at a twist angle of 90 ° and the value of Δnd is set in a range of 350 to 500 nm, and the liquid crystal cell is sandwiched between the liquid crystal cells. A pair of polarizing plates disposed, a retardation plate having a retardation of substantially 650 nm or 400 nm disposed between at least one of the pair of polarizing plates and the liquid crystal cell; Since the angle of deviation between the slow axis and the liquid crystal molecule alignment direction near the substrate adjacent to the retardation plate of the liquid crystal cell is set to substantially 5 °, it is bright and has high quality without banding. Can be obtained.
[0063]
In the liquid crystal display device of the present invention, Δnd of the liquid crystal layer is set to substantially 500 nm, and a retardation plate having a retardation of substantially 650 nm is provided between one of the pair of polarizing plates and the liquid crystal cell. The slow axis of the liquid crystal cell in the same direction as the twist direction of the liquid crystal molecules from the substrate adjacent to the retardation plate to the other substrate with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the retardation plate of the liquid crystal cell. It is desirable to adopt a configuration in which the display is substantially shifted by 5 ° from the center. With such a configuration, it is possible to obtain a bright, high-quality display without banding.
[0064]
Further, in the liquid crystal display device of the present invention, Δnd of the liquid crystal layer is set to substantially 400 nm, and a phase difference having a retardation of substantially 400 nm between one of the pair of polarizing plates and the liquid crystal cell. The plate has its slow axis with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the phase difference plate of the liquid crystal cell, and the twist direction of the liquid crystal molecules from the substrate adjacent to the phase difference plate toward the other substrate. Is desirably arranged so as to be substantially shifted by 5 ° in the reverse direction. With such a structure, a bright, high-quality display without banding can be obtained.
[0065]
Further, in the liquid crystal display element of the present invention, the liquid crystal layer has a Δnd of substantially 470 nm, and a first liquid crystal layer having a retardation of substantially 650 nm between one of the pair of polarizing plates and the liquid crystal cell. The retardation axis of the liquid crystal cell, with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the first retardation plate of the liquid crystal cell, from the substrate adjacent to the first retardation plate to the other. A second retardation plate having a retardation of substantially 400 nm is disposed between the other polarizing plate and the liquid crystal cell at a position substantially shifted by 5 ° in the same direction as the twist direction of the liquid crystal molecules toward the substrate. Liquid crystal molecules whose slow axis is directed from the substrate adjacent to the second retardation plate to the other substrate with respect to the liquid crystal molecule alignment direction near the substrate adjacent to the second retardation plate of the liquid crystal cell. In the direction opposite to the twist direction It is desirable to adopt a configuration qualitatively displaced by 5 °. With such a configuration, it is possible to obtain a brighter, high-quality display without banding.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a sectional view of a part of the liquid crystal display device of the first embodiment.
FIG. 3 is a diagram showing a liquid crystal molecule alignment direction, a twist direction of liquid crystal molecules, and a slow axis direction of a retardation plate in the vicinity of a substrate before and after a liquid crystal cell in a first embodiment.
FIG. 4 is a wavelength-transmittance characteristic diagram of the first embodiment and a comparative example.
FIG. 5 is an exploded perspective view of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 6 is a diagram showing a liquid crystal molecule orientation direction, a liquid crystal molecule twist direction, and a slow axis direction of a retardation plate in the vicinity of a substrate before and after a liquid crystal cell in a second embodiment.
FIG. 7 is a wavelength-transmittance characteristic diagram of the second embodiment and a comparative example.
FIG. 8 is an exploded perspective view of a liquid crystal display device according to a third embodiment of the present invention.
FIG. 9 is a diagram showing a liquid crystal molecule alignment direction, a liquid crystal molecule twist direction, and a slow axis direction of a retardation plate in the vicinity of a substrate before and after a liquid crystal cell in a third embodiment.
FIG. 10 is a wavelength-transmittance characteristic diagram of a third embodiment and a comparative example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal cell, 2,3 ... Substrate, 2a, 3a ... Liquid crystal molecule orientation direction near a substrate, 4,5 ... Electrode, 6R, 6G, 6B ... Color filter, 7,8 ... Alignment film, 10 ... Liquid crystal layer, 11, 12: polarizing plate, 11a, 12a: transmission axis, 13, 14: retardation plate, 13a, 14a: slow axis.
