JP3728409B2 - Liquid crystal display device - Google Patents

Description

表１は、ツイスト角を４５°に設定した液晶表示装置３０において、液晶層３２の厚さｄを様々に変化させた場合の、各々の液晶表示装置の動作特性および視角特性の、２５°Ｃにおける評価結果を示す。ただし、表１には、配向膜３１ａ，３１ｂとして日産化学製の垂直配向材ＲＮ７８３を使い、偏光板３４Ａ，３４Ｂとして日東電工製のＧ１２２０ＤＵ偏光板あるいは住友化学製のＳＫ−１８３２ＡＰ７偏光板を使った場合の結果を示す。また、表１の液晶表示装置では、図４５に示した位相差補償フィルム３３Ａ，３３Ｂは省略してあるが、偏光板の保護フィルムがある程度のリターデーション補償作用を行う。例えば、前記Ｇ１２２０ＤＵ偏光板に付随する保護フィルムは大きさが４４ｎｍの負のリターデーションを示し、また前記ＳＫー１８３２ＡＰ７偏光板に付随する保護フィルムは大きさが５０ｎｍの負のリターデーションを示す。また、液晶層３２にはカイラル材は一切添加していない。
【００６１】
表１を参照するに、液晶層３２の厚さｄが減少するに伴って立ち上がり時間Ｔｏｎおよび立ち下がり時間Ｔｏｆｆ が減少し、液晶表示装置の応答速度が改善されることがわかる。また、前記液晶層の厚さｄが減少するに伴って、コントラスト比１０以上を与える視角範囲が増大する。ただし、先にも説明したように、液晶層の厚さが減少すると輝度が低下するため、先に説明したように、液晶層３２の厚さは、リタデーションΔｎ・ｄが約８０〜約４００ｎｍの範囲に納まるように設定する必要がある。
【００６２】
図４６（Ａ），（Ｂ）は、図４５の構成の液晶表示装置において、セル厚ｄを３μｍ、ツイスト角を４５°とした場合の視角特性を示す。ただし、図４６の例ではカイラル材は添加しておらず、また液晶には前記ＭＪ９４１２９６を、偏光板にはＧ１２２０ＤＵを使っている。ただし、図４６（Ａ），（Ｂ）の結果は、偏光板３４Ａ，３４Ｂが位相差補償フィルム３３Ｂ，３４Ｂを兼用した場合についてのものである。
【００６３】
図４６（Ａ）中、コントラスト比が１０以上の領域を白色で示すが、白色の領域は非常に広く、非常に広い視角特性が得られていることがわかる。また、図４６（Ｂ）よりわかるように、かかる液晶表示装置では、正面方向において２０００近いコントラスト比か得られる。
【００６４】
図４７（Ａ），（Ｂ）は、図４５の液晶表示装置において、市販の位相差補償フィルム（住友化学製ＶＡＣ０）を位相差補償フィルム３３Ａ，３３Ｂとして使った場合の視角特性を示す。ただし、液晶パネルは、２４１ｎｍのリタデーション値Δｎ・ｄを有するため、偏光板３４Ａ，３４Ｂおよび位相差補償フィルム３３Ａ，３３Ｂの合計リタデーション値Ｒ’の大きさを、前記２４１ｎｍに近い２１８ｎｍに設定している。
【００６５】
図４７（Ａ）よりわかるように、この場合コントラスト比が１０を越える視野角領域は、図４６（Ａ）の場合よりもさらに拡大し、またパネル正面方向のコントラスト比も、図４７（Ｂ）に示すように４０００に達することがわかる。
【００６６】
先に、図４０〜４４に関連して、プレチルト角が７５°以下になると、ＶＡモード液晶表示装置では、視角特性が従来のＴＮモード液晶表示装置程度に劣化することを説明したが、図４５のような、液晶層３２の上下に位相差補償フィルム３４Ａ，３４Ｂを有する構成では、プレチルト角が７５°においても、図４８に示すように、コントラスト比１０（ＣＲ＝１０）を与える領域は広くなり、液晶表示装置として満足できる視角特性が得られる。ただし、図４８は、液晶層３２の厚さが３μｍ、ツイスト角が４５°，プレチルト角が７５°の場合についてのものである。
［実施例２］
次に、本発明の第２実施例による液晶表示装置について説明する。
【００６７】
本実施例では、図４５の構成を有する液晶表示装置において、液晶として、先のＭＪ９４１２９６の代わりに同じメルク社製のＭＸ９５７８５（Δｎ＝０．０８１３，Δε＝−４．６）を使う。その他の構成は図４５の装置と同じであるため、装置の構成についての説明は省略する。
【００６８】
図４９は、液晶層３２のセル厚ｄを３μｍとした場合の本実施例による液晶表示装置の立ち上がり特性を、ツイスト角を０°，４５°および９０°とした場合について示す。この例では、液晶層３２中にカイラル材は添加していない。図４９よりわかるように、立ち上がり時間ＴＯＮは、ツイスト角が０°の場合を除き、印加電圧が４〜８Ｖの範囲で１０ｍｓ前後であり、液晶表示装置は非常に優れた立ち上がり特性を有することがわかる。これに対し、ＴＮモードの液晶表示装置では、立ち上がり時間ＴＯＮは一般に２０ｍｓ以上である。
【００６９】
図５０は、セル厚ｄを同じく３μｍとした場合の本実施例による液晶表示装置の立ち下がり特性を、ツイスト角を０°，４５°および９０°とした場合について示す。この例でも、液晶層３２中にカイラル材は添加していない。図５０よりわかるように、立ち下がり時間ＴＯＦＦ は、いずれのツイスト角においても、５ｍｓ前後であり、液晶表示装置は非常に優れた立ち下がり特性を有することがわかる。これに対し、ＴＮモードの液晶表示装置では、立ち下がり時間ＴＯＦＦは一般に４０ｍｓ以上である。
【００７０】
【表２】

表２は、本実施例による液晶表示装置において、偏光板３４Ａ，３４Ｂおよび位相差補償フィルム３３Ａ，３３Ｂが形成する負のリタデーションＲ’の合計値を変化させた場合の視角特性、特にコントラスト比１０を与える視角範囲および１１階調反転角度の変化を示す。１１階調反転角度とは、液晶パネルの正面方向に１１階調により中間調を行った場合に、かかる中間調を構成する階調の輝度が互いに反転して見えるような極角方向を表す。このような階調反転が生じると表示がつぶれて見にくくなる。このため、階調反転角度は、広い程好ましい。ただし、本実施例では液晶層３２のリタデーションΔｎ・ｄは正で、２４６ｎｍの値を有する。表２は、位相差補償フィルム３３Ａ，３３Ｂおよび偏光板３４Ａ，３４Ｂが形成するリタデーションＲ’の合計値を液晶層３２のリタデーションΔｎ・ｄに近く設定することにより、９０°，−９０°，１８０°の方位角において、視野角が拡大することがわかる。
【００７１】
【表３】

表３は、本実施例において、ツイスト角を変化させた場合の視角特性および１１階調反転角度の変化を示す。表３の結果は、ツイスト角による視角依存性は実質的に存在しないことを示す。ただし、表３の結果は、位相差補償フィルム３３Ａ，３３Ｂは設けず、偏光板３４Ａ，３４Ｂの位相差補償作用（Ｒ’＝８８ｎｍ）のみが存在する場合についてのものである。
［実施例３］
図５１は、本発明の第３実施例による液晶表示装置４０の構成を示す。ただし、図５１中、先に説明した部分には同一の参照符号を付し、説明を省略する。
【００７２】
図５１を参照するに、液晶表示装置４０は図４５に説明した液晶表示装置３０と類似した構成を有するが、図４５の負リタデーションを有するの位相差補償フィルム３３Ｂの代わりに、正のリタデーションを有する第１の位相差補償フィルム（３３Ｂ）１ と負のリタデーションを有する第２の位相差補償フィルム（３３Ｂ）２ とを、前記正の位相差補償フィルム（３３Ｂ）１ を液晶パネル３１の近傍に、また負の位相差補償フィルム（３３Ｂ）２ をその外側に配設する点で異なっている。位相差補償フィルム（３３Ｂ）２ は液晶パネル３１の主面に垂直な光軸を有するのに対し、位相差補償フィルム（３３Ｂ）１ は液晶パネル３１の主面に平行な光軸を有する。
【００７３】
図５２は、図５１の液晶表示装置４０において、液晶層３２の厚さｄを３．５μｍ、ツイスト角を４５°とした場合の、様々な極角に対する黒表示状態（非駆動時）の透過率を示す。ただし、図５２においては、正の位相差補償フィルム（３３Ｂ）１ のリタデーションを１００ｎｍとし、その光軸角θを様々に変化させている。光軸角θは、図５１に示したように、ツイスト中心軸に対して位相差補償フィルム（３３Ｂ）１ の光軸がなす角度として定義される。その際、負の位相差補償フィルム（３３Ｂ）２ のリタデーション値は前記液晶パネル３１のリタデーションΔｎ・ｄに略等しく設定してあり、また図示した透過率は９０°方位角方向についてのものである。
【００７４】
図５２を参照するに、いずれの極角においても、光軸角θが約４５°の場合に、黒表示状態の透過率が最小になることがわかる。このように、黒表示の透過率をあらゆる視角について最小化することにより、視角特性の向上を実現することができる。図５２では、極角が０°および２０°の場合に、約１３５°の光軸角においても黒表示状態の透過率が最小になるが、この場合は極角が４０°以上において透過率が大きくなるため、望ましい視角特性の改善はもたらされない。
【００７５】
図５３は、図５１の液晶表示装置４０において、正の位相差補償フィルム（３３Ｂ）１ のリタデーションを変化させた場合の黒表示状態の透過率を様々な極角について示す。ただし、図５３の場合にも、方位角は９０°としてある。
【００７６】
図５３を参照するに、正の位相差補償フィルム（３３Ｂ）１ のリタデーション値を２０〜６０ｎｍの範囲に設定することにより、黒表示状態における透過率を、あらゆる極角について最小化することができる。この場合、透過率は０．００２を下回る。
【００７７】
図５４は、さらに図５１の液晶表示装置４０において、下側偏光板３４Ａと液晶パネル３１との間にも、負のリタデーションを有する別の負の位相差補償フィルムを配設し、前記別の負の位相差補償フィルムと前記位相差補償フィルム（３３Ｂ）２ の合計のリタデーション値を前記液晶パネル３１のリタデーション値に略等しく設定した場合における、黒表示状態の透過率を、前記正の位相差補償フィルム（３３Ｂ）１ のリタデーション値の関数として示す。
【００７８】
図５４よりわかるように、かかる構成により、黒表示状態における透過率の極角依存性は実質的に消滅し、位相差補償フィルム（３３Ｂ）１ のリタデーションが５０〜６０ｎｍの範囲にある場合に透過率が最小になる。かかる位相差補償フィルム（３３Ｂ）１ が有効であるためには、位相差補償フィルム（３３Ｂ）１ のリタデーション値を約１００ｎｍ以下に設定する必要がある。
【００７９】
図５５は、図５１の液晶表示装置４０において、前記位相差補償フィルム（３３Ｂ）１ のリタデーション値を３０ｎｍに固定し、位相差補償フィルム（３３Ｂ）２ のリタデーション値Ｒ’を変化させた場合の黒表示状態における透過率を示す。ただし、先の場合と同様に、透過率は９０°方位角方向へのもので、極角の値を様々に変化させている。
【００８０】
図５５よりわかるように、透過率が最小となるのは、位相差補償フィルム（３３Ｂ）２ が形成する負のリタデーションＲ’の値が約２５０ｎｍの場合であるが、この最適値は、液晶層３２のリタデーションΔｎ・ｄの値よりも多少小さい。先にも説明したように、正の位相差補償フィルム（３３Ｂ）１ を設けない場合には、位相差補償フィルム（３３Ｂ）１ の最適リタデーション値は、液晶層３２のリタデーション値Δｎ・ｄと等しい。すなわち、前記負の位相差補償フィルム（３３Ｂ）２ に加えて正の位相差補償フィルム（３３Ｂ）１ を使う場合、負の位相差補償フィルム（３３Ｂ）２ の最適値は、液晶層３２のリタデーション値Δｎ・ｄよりも多少小さく設定する必要がある。いずれにせよ、負の位相差補償フィルムの合計リタデーション値Ｒ’は、位相差補償フィルム（３２Ｂ）２のみを使う場合でも、またさらに別の負の位相差補償フィルムを使う場合でも、液晶層３２のリタデーション値Δｎ・ｄの２倍以下に設定する必要がある。
【００８１】
図５６は、図５１の液晶表示装置４０の視角特性を示す。負の位相差補償フィルムだけを使った場合の対応する視角特性を示す図１７の結果と比較すると、コントラスト比が１０以上の領域の面積が拡大していることがわかる。
［実施例４］
図５７は、本発明の第４実施例による液晶表示装置５０の構成を示す。ただし、図５７中先に説明した部分には対応する参照符号を付し、説明を省略する。
【００８２】
図５７を参照するに、液晶表示装置５０は図５１の液晶表示装置４０と同様な構成を有するが、前記位相差補償フィルム（３３Ｂ）１ ，（３３Ｂ）２ と同様な位相差補償フィルム（３３Ａ）１ および（３３Ａ）２ を偏光板３４Ａと液晶パネル３１との間にも設ける。その際、正のリタデーションを有する位相差補償フィルム（３３Ａ）１ を液晶パネル３２に近い側に、負のリタデーションを有する位相差補償フィルム（３３Ａ）２ を液晶パネル３２から遠い側に設けることにより、液晶パネル３２の上側の構成と下側の構成が対称的になり、図５８に示すように視角特性がさらに向上する。
［実施例５］
図５９は、本発明の第５実施例による液晶表示装置６０の構成を示す。ただし、図５９中先に説明した部分には対応する参照符号を付し、説明を省略する。
【００８３】
図５９を参照するに、本実施例においては、先に説明した液晶表示装置４０において、正の位相差補償フィルム（３３Ｂ）１ と負の位相差補償フィルム（３３Ｂ）２ とを設ける代わりに、単一の２軸性位相差補償フィルム３３Ｂ’を液晶パネル３１と偏光板３４Ｂとの間に挿入する。
【００８４】
位相差補償フィルム３３Ｂ’は光学的２軸性を有し、ｘ，ｙ，ｚの各方向への屈折率ｎＸ ，ｎｙ ，ｎｚ について、ｎＸ ＞ｎｙ ＞ｎｚ あるいはｎｙ ＞ｎＸ ＞ｎｚ が成立する。かかる２軸性位相差補償フィルムは公知であり、例えば特開昭５９−１８９３２５に記載されているものを使ってもよい。
【００８５】
かかる２軸性位相差補償フィルムが形成するリタデーションは、面内方向について式｜ｎＸ −ｎｙ ｜・ｄにより与えられ、また液晶パネル３２に垂直な方向（厚さ方向）に式（ｎＸ ＋ｎｙ ）２＋ｎｚ で与えられる。本実施例では、面内のリタデーション値を１２０ｎｍ以下、厚さ方向のリタデーションを液晶層３２のリタデーションΔｎ・ｄに等しく設定することにより、最適な結果が得られる。ただし、図５９の例では、位相差補償フィルム３３Ｂ’は、その面内遅相軸が偏光板３４Ｂの吸収軸に略平行になるように配設される。面内遅相軸は、ｎＸ＞ｎｙ ＞ｎｚ の関係が成立する場合にはｘ軸に、またｎｙ ＞ｎＸ ＞ｎｚ が成立する場合にはｙ軸に一致する。
［実施例６］
図６０は、本発明の第６実施例によるアクティブマトリクス駆動方式の液晶表示装置７０の構成を示す。
【００８６】
本実施例においては、図５７の構成において、ガラス基板３１Ａまたは３１Ｂ上に、液晶パネル中に画成された画素に対応して複数の透明画素電極（３１ａ’）ＰＩＸＥＬ と、これを駆動するＴＦＴ（３１ａ’）ＴＦＴ とが形成される。すなわち、前記透明画素電極（３１ａ’）ＰＩＸＥＬ とＴＦＴ（３１ａ’）ＴＦＴ とは、図４５の電極３１ａ’あるいは３１ｂ’に対応する。また、前記基板３１Ａまたは３１Ｂ上には、マトリクス配列されたＴＦＴに駆動信号を供給するデータバスＤＡＴＡとこれを活性化するアドレスバスＡＤＤＲとが延在する。
【００８７】
図６１は、液晶表示装置７０の視角特性を、液晶としてメルクジャパン社ＭＪ９５７８５を使い、液晶層の厚さを３μｍとした場合について示す。この場合、液晶分子のツイスト角は４５°、液晶層３２のリタデーションΔｎ・ｄは２４１ｎｍとしてあり、分子配向膜３１ａ，３１ｂ（図４５参照）として日産化学性ＲＮ７８３を使っている。図６１よりわかるように、非常に広い視角範囲を有するアクティブマトリクス駆動液晶表示装置が得られる。
［実施例７］
以上に説明した各実施例においては、図６２（Ａ）〜（Ｃ）に示すように、各々の画素で液晶の分子配向が一様な、いわゆる単一ドメイン分子配向構成を使っていた。ただし、図６２（Ａ）は液晶表示装置の一画素分の領域の平面図、図６２（Ｂ）は、図６２（Ａ）中の線Ａ−Ｂに沿った断面図、図６２（Ｃ）は図６２（Ｂ）の液晶表示装置に二つの異なった方向から入射光ＸおよびＹを入射させた場合の構成を示し、図中先に説明した部分には同一の参照符号を付してある。また、図６２（Ａ）において、実線の矢印は、上側基板３１Ｂに担持された分子配向膜３１ｂのラビング方向を、また点線の矢印は、下側基板３１Ａに担持された分子配向膜３１ａのラビング方向を示す。分子配向膜３１ｂのラビング方向と分子配向膜３１ａのラビング方向とはα１ の角度で交差するが、液晶分子のツイスト角を４５°に設定する場合には、前記角度α１ は４５°の角度に設定する。
【００８８】
図６２（Ｃ）よりわかるように、このような単一ドメイン分子配向構成を有する液晶表示装置においては、その駆動状態において、入射光Ｘの方向から見た分子配向と入射光Ｙの方向から見た分子配向とが異なるため、実質的な視角特性の低下が避けられない。
【００８９】
これに対し、図６３（Ａ）〜（Ｃ）は本発明の第７実施例による液晶表示装置の構成を示す。ただし、先に説明した部分には同一の参照符号を付し、説明を省略する。
【００９０】
図６３（Ａ）〜（Ｃ）の構成では、図６３（Ｂ）に示すように、各々の画素において、紫外線改質分子配向膜３１ａ’，３１ｂ’を、それぞれ分子配向膜３１ａ，３１ｂの一部を覆うように形成する。かかる紫外線改質分子配向膜は、例えば分子配向膜３１ａ，３１ｂのラビングの後、別の分子配向膜をその上に堆積し、これに紫外線を照射して分子配向を変化させた後、各画素においてその一部だけを残すようにパターニングすることにより形成すればよい。
【００９１】
その際、図６３（Ｂ）の断面図に示すように、図６３（Ａ）の平面図の紙面下側の領域に前記改質分子配向膜３１ａ’を形成し、また紙面上側の領域に前記改質分子配向膜３１ｂ’を形成することにより、図６３（Ｃ）に示すように入射光ＸおよびＹを異なった方向から入射させた場合に、前記いずれの方向においても光が感受する液晶分子配向が、液晶表示装置の駆動状態において同等になり、液晶表示装置の視角特性がさらに改善される。
【００９２】
図６４（Ａ）〜（Ｃ）は本実施例の一変形例を示す。
【００９３】
図６４（Ａ）を参照するに、本実施例においては、紙面上側の領域と紙面下側の領域においてラビング方向を変化させてあり、その結果図６４（Ｂ）の断面図に示すように、分子配向が各画素中において右側領域と左側領域（図６４（Ａ）の上側領域と下側領域に対応）で異なる。その結果、図６４（Ｃ）に示すように、入射光ＸおよびＹを二つの異なった方向から入射させた場合、それそれの方向において液晶分子の配向は図６３（Ｃ）の場合と同様に等価になり、液晶表示装置の視角特性が向上する。
【００９４】
図６５は、図６４の構成の液晶表示装置において、角度α１ ，α２ をいずれも４５°、液晶層３２の厚さｄを３μｍとした場合の視角特性を示す。ただし、液晶表示装置は図６５において、液晶層３２として前記メルクジャパン社のＭＪ９５７８５を使い、カイラル材は添加していない。すなわち、液晶層３２は、この場合リタデーションΔｎ・ｄとして２８７ｎｍの値を有し、ツイスト角は４５°に設定される。また、図５７に示す正および負の位相差補償フィルムを、正の位相差補償フィルム（３３Ａ）１ ，（３３Ａ）１ の合計リタデーション値Ｒが２５ｎｍ、負の位相差補償フィルム（３３Ｂ）２ ，の合計リタデーション値Ｒ’が１６０ｎｍになるように設けている。
【００９５】
図６５を参照するに、液晶表示装置をこのように構成することにより、コントラスト比が１０を下回る領域は非常に限定されており、非常にすぐれた視角特性が得られることがわかる。
【００９６】
図６６は、同じ構成の液晶表示装置の視角特性のシミュレーションの結果であるが、これによれば、液晶表示装置は各部材の最適化により、さらに優れた視角特性を実現可能であることがわかる。
【００９７】
図６７は、前記第１〜第７の各実施例で記載した液晶表示装置を使って構成した直視型液晶表示装置１００の構成を示す。
【００９８】
図６７を参照するに、直視型液晶表示装置１００は、前記液晶表示装置１０〜７０のいずれであってもよいＶＡモード液晶表示装置１０１と、その背後に配設された面光源１０３とより構成される。液晶表示装置１０１には、複数の画素領域１０２が画成され、前記面光源１０３から放射されるバックライトを光学的に変調する。一方、面光源１０３は、蛍光管等の線光源を含む光源部１０３と、前記線光源から放射された光を拡散させ、前記液晶表示装置１０１の全面を、２次元的に照明する光拡散部１０４とよりなる。
【００９９】
先に各実施例で説明した本発明によるＶＡモード液晶表示装置は、特に広い視角特性を与えるため、図６７に示したような構成の直視型液晶表示装置に特に適している。
［実施例８］
先に、図３５，３６において、本発明によるＶＡモード液晶表示装置では、液晶層中にカイラル材は添加しない方が好ましいことを説明した。しかし、これは本発明ではカイラル材を添加できない、あるいはすべきではないということではない。実際、液晶層中における液晶分子のカイラルピッチをカイラル材により、適当な範囲で規制することにより、表示の明るさ、コントラスト比および応答速度を最適に保持したまま、表示の着色を最小化することが可能になる。
【０１００】
以下、かかるカイラル材を使った本発明の第８実施例について説明する。
【０１０１】
図６８は、図５１の構成の液晶表示装置４０において、液晶層３２としてメルクジャパン社製ＭＸ９４１２９６（Δｎ＝０．０８２，Δε＝−４．６）を使い、偏光板３４Ａ，３４Ｂには日東電工製Ｇ１２２０ＤＵを、さらに正の位相差補償フィルム（３３Ｂ）１ として屈折率ｎｘ ＝１．５０１，ｎｙ ＝ｎｚ ＝１．５の複屈折フィルムを、また負の位相差補償フィルム（３３Ｂ）２ として屈折率ｎｘ ＝ｎｙ ＝１．５０１，ｎｚ ＝１．５の複屈折フィルムを使った場合において、液晶層３２に添加したカイラル材のピッチｐを様々に変化させた場合の視角特性の変化を示す。ただし、液晶層３２の厚さｄは３．２５μｍに固定し、また液晶分子のツイスト角は４５°としている。ただし、図６８中、「順カイラル」方向は、カイラル材のツイスト方向が液晶分子のツイスト方向に一致する場合を、また「逆カイラル」方向は、カイラル材のツイスト方向が液晶分子のツイスト方向と逆方向である場合を示す。
【０１０２】
図６８を参照するに、前記ｄ／ｐ比の絶対値｜ｄ／ｐ｜が０．３７５（＝Ψ／１２０°；Ψはツイスト角で、今の場合４５°）以内であれば、５０°を超える視野角が確保できることがわかる。ただし、上記絶対値表示において、カイラルピッチｐは、順カイラル方向を＋、逆カイラル方向を−として表現している。
【０１０３】
図６９〜７６は、先に説明した図２７〜３１と同様な図であり、前記図５１の液晶表示装置４０において、カイラル材を添加することにより、ｄ／ｐ比を様々に変化させた場合の着色特性を示す。ただし、液晶層の厚さｄは３．２５μｍに設定している。このうち、図６９はカイラル材を添加しない場合で、図２８におおよそ対応するのに対し、図７０はｄ／ｐ比を順カイラル方向に０．０３２５とした場合を、また図７１はｄ／ｐ比を順カイラル方向に０．１３とした場合を、図７２はｄ／ｐ比を順カイラル方向に０．３２５とした場合を、さらに図７３はｄ／ｐ比を順カイラル方向に０．６５とした場合を示す。これに対し、図７４は、ｄ／ｐ比を逆カイラル方向に０．０３２５とした場合を、図７５はｄ／ｐ比を逆カイラル方向に０．１３とした場合を、さらに図７６はｄ／ｐ比を逆カイラル方向に０．３２５に設定した場合を示す。
【０１０４】
図６９〜７６を参照するに、液晶表示装置の着色は、カイラル材により、カイラルピッチを順カイラル方向に規制することにより減少させることができるのがわかる。これに対し、逆カイラル方向へのカイラルピッチの規制は着色特性を劣化させる。図６８の視野角特性を考えると、厚さｄが３．２５μｍの液晶層では、ｄ／ｐ比の絶対値｜ｄ／ｐ｜をΨ／１２０°以内に設定するのが好ましいことが結論される。
【０１０５】
図７７は、｜ｄ／ｐ｜を約Ψ／３６０°に固定し、セル厚ｄとツイスト角Ψとを様々に変化させた場合の表示特性の評価を示す。
【０１０６】
図７７を参照するに、評価は４段階で行い、良い方から悪い方に順に、◎，○，△，×で表示した。先の実施例でも説明したように、セル厚ｄおよびリタデーションΔｎ・ｄが小さすぎると応答特性は速くなるが透過率が低くなってしまう問題が生じる。これに対し、セル厚ｄを大きくすると着色が激しくなっていまう。またツイスト角Ψを大きくしすぎると、応答時間が長くなってしまう。結論として、液晶層のリタデーションΔｎ・ｄが図７７に実線で示した領域、すなわち式
Ψ／５４９≦Δｎ・ｄ≦（２２５＋Ψ）／５４９
で与えられる範囲内にあれば、特に式
（９０＋Ψ）／５４９≦Δｎ・ｄ≦（１８０＋Ψ）／５４９
で与えられる範囲内にあれば、優れた表示特性が得られることがわかる。ただし、上の式において、ツイスト角Ψの単位は度（°）としている。
【０１０７】
図７８，７９は、図５７の液晶表示装置５０において、位相差補償フィルム（３３Ａ）１ を除去し、液晶分子のツイスト角Ψを４５°、液晶層３２のセル厚ｄを４μｍ、位相差補償フィルム（３３Ａ）２ ，（３３Ｂ）２ による負の合計リタデーション値Ｒ’を３００ｎｍ、位相差補償フィルム（３３Ｂ）１ による正のリタデーション値Ｒを２５ｎｍとした場合に、さらにｄ／ｐ比が０．１２５となるように液晶層３２中にカイラル材を添加した場合の視角特性と着色特性とをそれぞれ示す。
【０１０８】
通常のＴＮ型液晶表示装置の視角特性と着色特性を示す図８０，８１と比較するに、本実施例による液晶表示装置は、視野角および着色共、従来のＴＮ型液晶表示装置のものに対して大きく改善されていることがわかる。
【０１０９】
以上、本発明を好ましい実施例について説明したが、本発明は上記の実施例に限定されるものではなく、特許請求の範囲に記載した要旨内において様々な変形・変更が可能である。
【０１１０】
【発明の効果】
請求項１記載の本発明によれば、垂直配向構成の液晶表示装置において、前記液晶層のリタデーションΔｎ・ｄが、Δｎ・ｄ≦０．４ｎｍの範囲において、前記液晶分子の前記液晶層中におけるツイスト角をΨとして、式
（９０＋Ψ）／５４９≦Δｎ・ｄ≦（１８０＋Ψ）／５４９
で表される範囲に入るように、また前記液晶層のセル厚が５μｍ未満であり、前記ツイスト角Ψが、０＜Ψ＜９０°の関係を満たすように、液晶分子のツイスト角を最適に制御することにより、明るく、応答速度が速く、さらに着色の少ない液晶表示装置を得ることができる。
【図面の簡単な説明】
【図１】本発明による液晶表示装置の基本的構成を説明する図である。
【図２】図１の液晶表示装置のコントラスト比と、液晶パネルに対するポラライザ，アナライザの方位との関係を説明する図である。
【図３】図１の液晶表示装置の動的特性を示す図である。
【図４】図１の液晶表示装置において、さらに位相差補償板を設けた構成を示す図である。
【図５】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を０．４５とした場合の視角特性を示す図である。
【図６】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を０．６とした場合の視角特性を示す図である。
【図７】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を０．７５とした場合の視角特性を示す図である。
【図８】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を０．８２とした場合の視角特性を示す図である。
【図９】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を０．９０とした場合の視角特性を示す図である。
【図１０】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を０．９７とした場合の視角特性を示す図である。
【図１１】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を１．０５とした場合の視角特性を示す図である。
【図１２】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を１．１２とした場合の視角特性を示す図である。
【図１３】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を１．２０とした場合の視角特性を示す図である。
【図１４】図４の液晶表示装置において、液晶パネルのリターデーション値に対する位相差補償板の合計リターデーション値の比の値を１．３４とした場合の視角特性を示す図である。
【図１５】図４の液晶表示装置において、液晶層の厚さを１μｍ、液晶層のリタデーション値を８２ｎｍとした場合の視角特性を示す図である。
【図１６】図４の液晶表示装置において、液晶層の厚さを２μｍ、液晶層のリタデーション値を１６４ｎｍとした場合の視角特性を示す図である。
【図１７】図４の液晶表示装置において、液晶層の厚さを３μｍ、液晶層のリタデーション値を２４６ｎｍとした場合の視角特性を示す図である。
【図１８】図４の液晶表示装置において、液晶層の厚さを４μｍ、液晶層のリタデーション値を３２８ｎｍとした場合の視角特性を示す図である。
【図１９】図４の液晶表示装置において、液晶層の厚さを５μｍ、液晶層のリタデーション値を４１０ｎｍとした場合の視角特性を示す図である。
【図２０】図４の液晶表示装置において、液晶層の厚さを６μｍ、液晶層のリタデーション値を４９２ｎｍとした場合の視角特性を示す図である。
【図２１】図４の液晶表示装置において、液晶層の厚さを１μｍとした場合の透過率特性を示す図である。
【図２２】図４の液晶表示装置において、液晶層の厚さを２μｍとした場合の透過率特性を示す図である。
【図２３】図４の液晶表示装置において、液晶層の厚さを３μｍとした場合の透過率特性を示す図である。
【図２４】図４の液晶表示装置において、液晶層の厚さを４μｍとした場合の透過率特性を示す図である。
【図２５】図４の液晶表示装置において、液晶層の厚さを５μｍとした場合の透過率特性を示す図である。
【図２６】図４の液晶表示装置において、液晶層の厚さを６μｍとした場合の透過率特性を示す図である。
【図２７】図４の液晶表示装置において、液晶層の厚さを１μｍとした場合の着色特性を示す図である。
【図２８】図４の液晶表示装置において、液晶層の厚さを３μｍとした場合の着色特性を示す図である。
【図２９】図４の液晶表示装置において、液晶層の厚さを４μｍとした場合の着色特性を示す図である。
【図３０】図４の液晶表示装置において、液晶層の厚さを５μｍとした場合の着色特性を示す図である。
【図３１】図４の液晶表示装置において、液晶層の厚さを６μｍとした場合の着色特性を示す図である。
【図３２】図４の液晶表示装置において、液晶層の厚さを３μｍ、ツイスト角を０°とした場合の視角特性を示す図である。
【図３３】図４の液晶表示装置において、液晶層の厚さを３μｍ、ツイスト角を９０°とした場合の視角特性を示す図である。
【図３４】図４の液晶表示装置において、液晶層の厚さを３μｍ、ツイスト角を１８０°とした場合の視角特性を示す図である。
【図３５】（Ａ），（Ｂ）は、図４の液晶表示装置において、カイラル材を含んだ液晶層中の分子配向を、それぞれ非駆動状態および駆動状態について示す図である。
【図３６】（Ａ），（Ｂ）は、図４の液晶表示装置において、カイラル材を含まない液晶層中の分子配向を、それぞれ非駆動状態および駆動状態について示す図である。
【図３７】図４の液晶表示装置において、液晶層中にカイラル材を添加した場合の視角特性を示す図である。
【図３８】図４の液晶表示装置において、液晶層中にカイラル材を添加した場合の透過率特性を示す図である。
【図３９】図４の液晶表示装置において、液晶層中にカイラル材を添加しない場合の透過率特性を示す図である。
【図４０】図４の液晶表示装置において、プレチルト角を９０°に設定した場合の視角特性を示す図である。
【図４１】図４の液晶表示装置において、プレチルト角を８５°に設定した場合の視角特性を示す図である。
【図４２】図４の液晶表示装置において、プレチルト角を８０°に設定した場合の視角特性を示す図である。
【図４３】図４の液晶表示装置において、プレチルト角を７５°に設定した場合の視角特性を示す図である。
【図４４】標準的なＴＮモード液晶表示装置の視角特性を示す図である。
【図４５】本発明の第１実施例による液晶表示装置の構成を示す図である。
【図４６】図４５の液晶表示装置の視角特性を示す図である。
【図４７】図４５の液晶表示装置において、位相差補償板を設けた場合の視角特性を示す図である。
【図４８】図４５の液晶表示装置において、プレチルト角を７５°とし、液晶パネルの上下に位相差補償フィルムを配設した場合の視角特性を示す図である。
【図４９】本発明の第２実施例による液晶表示装置の立ち上がり特性を示す図である。
【図５０】本発明の第２実施例による液晶表示装置の立ち下がり特性を示す図である。
【図５１】本発明の第３実施例による液晶表示装置の構成を示す図である。
【図５２】図５１の液晶表示装置における黒表示状態の透過率を示す図である。
【図５３】図５１の液晶表示装置における黒表示状態の透過率を示す別の図である。
【図５４】図５１の液晶表示装置における黒表示状態の透過率を示す別の図である。
【図５５】図５１の液晶表示装置における黒表示状態の透過率を示す別の図である。
【図５６】図５１の液晶表示装置の視角特性を示す図である。
【図５７】本発明の第４実施例による液晶表示装置の構成を示す図である。
【図５８】図５７の液晶表示装置の視角特性を示す図である。
【図５９】本発明の第５実施例による液晶表示装置の構成を示す図である。
【図６０】本発明の第６実施例による液晶表示装置の構成を示す図である。
【図６１】図６０の液晶表示装置の視角特性を示す図である。
【図６２】単一ドメイン構成を有する本発明による液晶表示装置の構成を示す図である。
【図６３】分割配向構成を有する本発明の第７実施例による液晶表示装置の構成を示す図である。
【図６４】図６３の液晶表示装置の一変形例を示す図である。
【図６５】図６４の液晶表示装置の視角特性を示す図である。
【図６６】図６４の液晶表示装置の視角特性のシミュレーション結果を示す図である。
【図６７】本発明による垂直配向液晶表示装置を使った直視型液晶表示装置の構成を示す図である。
【図６８】本発明の第８実施例による、カイラル材を添加した場合の垂直配向液晶表示装置の視角特性を示す図である。
【図６９】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その一）である。
【図７０】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その二）である。
【図７１】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その三）である。
【図７２】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その四）である。
【図７３】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その五）である。
【図７４】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その六）である。
【図７５】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その七）である。
【図７６】カイラル材を添加した場合の垂直配向液晶表示装置の着色特性を示す色度図（その八）である。
【図７７】
好ましいツイスト角とセル厚の組み合わせを示す図である。
【図７８】
第８実施例の一変形例による液晶表示装置の視角特性を示す図である。
【図７９】
図７８の液晶表示装置の着色特性を示す色度図である。
【図８０】
従来のＴＮ型液晶表示装置の視角特性を示す図である。
【図８１】
図８０の従来のＴＮ型液晶表示装置の着色特性を示す色度図である。
【符号の説明】
１０，２０，３０，４０，５０，６０，７０ 液晶表示装置
１１，３１ 液晶パネル
１１Ａ，１１Ｂ，３１Ａ，３１Ｂ ガラス基板
１２，３２ 液晶層
１３Ａ，１３Ｂ，３３Ａ，３３Ｂ 偏光板
１４Ａ，１４Ｂ，３４Ａ，３４Ｂ，（３４Ａ）１ ，（３４Ｂ）１ ，（３４Ａ）２ ，（３２Ｂ）２ 位相差補償フィルム
３１ａ，３１ｂ 分子配向膜
３１ａ’，３１ｂ’ （３１ａ’）ＰＩＸＥＬ 電極
（３１ａ’）ＴＦＴ ＴＦＴ
３１ｃ スペーサ
１００ 直視型液晶表示装置
１０１ 垂直配向液晶表示装置
１０２ 画素
１０３ 面光源
１０４ 光源部
１０６ 線光源[0001]
BACKGROUND OF THE INVENTION
The present invention generally relates to a liquid crystal display device, and in particular, a liquid crystal operating in a so-called VA (Vertical Aligned) mode in which a liquid crystal having negative dielectric anisotropy is aligned in a direction substantially perpendicular to the panel surface of the liquid crystal display device. The present invention relates to a display device.
[0002]
[Prior art]
Liquid crystal display devices are widely used as display devices for various information processing apparatuses such as computers. Since the liquid crystal display device is small and consumes little power, it is often used especially for portable information processing devices. However, application to fixed information processing devices such as a so-called desktop type is also being studied.
[0003]
By the way, in the conventional liquid crystal display device, a so-called TN (twisted nematic) mode type in which p-type liquid crystal having positive dielectric anisotropy is horizontally aligned between the substrates of the liquid crystal display devices facing each other is mainly used. I have been. The TN mode liquid crystal display device is characterized in that the alignment direction of liquid crystal molecules adjacent to one substrate is twisted by 90 ° with respect to the alignment direction of liquid crystal molecules adjacent to the other substrate.
[0004]
In such a TN mode liquid crystal display device, various liquid crystals have already been developed and inexpensive manufacturing techniques have been established, but it is difficult to achieve high contrast. As a result, in such a TN mode liquid crystal display device in general, The liquid crystal molecules constituting the liquid crystal panel are configured to perform white display in a non-driving state in which no electric field is applied, and to perform black display in a driving state in which an electric field is applied to the liquid crystal molecules (that is, normally white mode). . In a conventional TN mode liquid crystal display device, liquid crystal molecules are aligned parallel to the surface of the liquid crystal panel in the non-driven state, and the alignment direction of the liquid crystal molecules changes substantially perpendicular to the liquid crystal panel in the driven state. The liquid crystal molecules adjacent to the substrate surface of the liquid crystal panel maintain the horizontal alignment even in the driving state, and light passes through the liquid crystal panel to some extent even in the driving state due to the birefringence formed by the liquid crystal molecules having the horizontal alignment. It is because it ends up. In such a TN mode liquid crystal display device, even if an attempt is made to display the background in black (that is, normally black mode), as a result of dispersion at a wavelength (wavelength dispersion), the background black is actually completely black. Therefore, there arises a problem that light leaks or is colored. The black display in this case is worse than in the normally white mode. Under such circumstances, white is used as the background color in the conventional TN mode liquid crystal display device.
[0005]
[Problems to be solved by the invention]
On the other hand, in a VA mode liquid crystal display device in which a liquid crystal layer having negative dielectric anisotropy is sealed so as to be vertically aligned or vertically inclined between a pair of substrates constituting a liquid crystal panel, in a non-driven state Since the liquid crystal molecules have an orientation substantially perpendicular to the substrate surface, the light passes through the liquid crystal layer with almost no change in the polarization plane, and as a result, the polarizing plates are arranged above and below the substrate, thereby Almost complete black display is possible in the driving state. In other words, such a VA mode liquid crystal display device can easily realize a very high contrast, which is impossible with a TN mode liquid crystal display device. In a driving state in which a driving electric field is applied to the liquid crystal molecules, the liquid crystal molecules are aligned parallel to the panel surface in the liquid crystal panel and rotate the polarization plane of the incident light beam. However, in the driving state of the VA mode liquid crystal display device, the horizontally aligned liquid crystal molecules exhibit a 90 ° twist between one substrate and the other substrate. By doing so, the polarization plane of the light passing through the liquid crystal layer rotates.
[0006]
The VA mode itself has been known for a long time. For example, D. de Rossi et al. Have already reported the properties of liquid crystals exhibiting negative dielectric anisotropy (J. Appl. Phys. 49 (3), March 1978).
[0007]
On the other hand, VA-mode liquid crystal display devices have been considered to be inferior in display quality, such as response time, viewing angle characteristics, and voltage holding ratio, even though the contrast ratio is superior to TN-mode liquid crystal display devices. There has not been much research and development effort towards the future. In particular, it was believed that it was difficult to realize an active matrix liquid crystal panel using thin film transistors (TFTs).
[0008]
On the other hand, a VA mode liquid crystal display device can provide a contrast exceeding that of a conventional CRT, so that it can be applied to a desktop display device. However, such a desktop liquid crystal display device has a large area. In addition to the high response speed, a particularly wide viewing angle is required.
[0009]
In a VA mode liquid crystal display device, in Japanese Patent Application Laid-Open No. 62-180326, a liquid crystal having a negative dielectric anisotropy is aligned between a pair of glass substrates and the molecular orientation of the liquid crystal is inactive when no driving voltage is applied. A configuration in which the liquid is sealed so as to be perpendicular or hybrid to the surface is known. In this known configuration, the liquid crystal molecules are aligned with a twist angle of 90 ° substantially parallel to the substrate surface when a driving voltage is applied. In this known example, the polarizer and the analyzer are arranged so that the absorption axes are orthogonal to each other so as to sandwich the pair of substrates.
[0010]
Japanese Patent Laid-Open No. 3-5721 discloses a VA mode liquid crystal display device in which a liquid crystal having negative dielectric anisotropy is sealed between a pair of substrates, and the retardation Δn · d of the liquid crystal layer is 0.6 μm to 0.9 μm. A configuration is disclosed in which a birefringent medium is disposed on both sides of a liquid crystal panel having such a configuration so that the optical axis angles are orthogonal to each other. In this known configuration, further, a polarizer and an analyzer are arranged outside the respective birefringent media in a crossed Nicol state and at an angle of 45 ° with respect to the optical axis angle of the birefringent medium. .
[0011]
Japanese Patent Application Laid-Open No. 5-53134 describes a photoconductive liquid crystal light valve having a photoconductive layer and a liquid crystal layer. In this known example, a liquid crystal having a negative dielectric anisotropy is used as the liquid crystal constituting the liquid crystal layer. Is used to set the molecular orientation of the liquid crystal molecules to be substantially perpendicular to the electrode in the non-driven state. Further, this known example describes a feature that the retardation Δn · d of the liquid crystal layer having the negative dielectric anisotropy is set to 0.3 μm or more.
[0012]
Further, Japanese Patent Laid-Open No. 5-113561 discloses a VA mode liquid crystal display device in which liquid crystal molecules are sealed between a pair of substrates so as to be aligned perpendicular to the substrate surface, and is adjacent to the substrate and perpendicular to the substrate surface. An optical compensator having negative optical activity with the optical axis as the optical axis, a first quarter-wave plate having an optical axis in a plane parallel to the substrate surface and having positive optical activity, and the first A second quarter-wave plate having an optical axis parallel to the optical axis of one quarter-wave plate and having negative optical activity, and a polarizer in a crossed Nicol state on both sides of the configuration. And the structure which arrange | positioned the analyzer is disclosed.
[0013]
However, although any of these configurations can achieve substantially higher contrast than conventional TN type or STN type liquid crystal display devices, the response speed, viewing angle, luminance, and low coloration required for desktop type display devices are achieved. There is nothing that can realize sex.
[0014]
SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to provide a new and useful VA mode liquid crystal display device that solves the above-mentioned problems.
[0015]
A more specific object of the present invention is to provide a VA mode liquid crystal display device optimized for response speed, viewing angle and contrast.
[0016]
[Means for Solving the Problems]
The present invention solves the above problems.
First and second substrates that are substantially parallel and opposite each other; first electrode means formed on a first major surface of the first substrate facing the second substrate; A second electrode means formed on a second main surface of the second substrate facing the first substrate; on the first main surface of the first substrate; A first molecular orientation film covering the electrode means; a second molecular orientation film covering the second electrode means on the second main surface of the second substrate; and the first and second In a liquid crystal display device comprising a liquid crystal layer made of liquid crystal molecules having negative dielectric anisotropy enclosed between substrates,
The retardation Δn · d of the liquid crystal layer is expressed by a formula where the twist angle of the liquid crystal molecules in the liquid crystal layer is Ψ.
(90 + Ψ) / 549 ≦ Δn · d ≦ (180 + Ψ) / 549
In the range represented by
The retardation Δn · d is,
Δn · d ≦ 0.4μm
In the range of
The liquid crystal layer has a cell thickness of less than 5 μm;
The twist angle Ψ is solved by a liquid crystal display device characterized by satisfying a relationship of 0 <Ψ <90 °.
[0017]
Hereinafter, the principle of the present invention will be described.
[0018]
The operation of the liquid crystal display device according to the present invention will be described below.
[0019]
FIG. 1 is a diagram showing a basic configuration of a liquid crystal display device 10 according to the present invention.
[0020]
Referring to FIG. 1, a liquid crystal display device 10 includes a liquid crystal panel composed of a pair of glass substrates 11A and 11B facing each other and a liquid crystal layer 12 sealed therebetween, and below the liquid crystal panel. A first polarizing plate (polarizer) 13A having an absorption axis in the direction indicated by an arrow 13a is disposed above, and a second polarizing plate (analyzer) 13B having an absorption axis in the direction indicated by an arrow 3b is disposed above. The
[0021]
The liquid crystal constituting the liquid crystal layer 12 is an n-type liquid crystal having negative dielectric anisotropy, and liquid crystal molecules in the vicinity of the lower substrate 11A in a non-driven state of the liquid crystal panel in which no electric field is applied between the substrates 11A and 11B. 12a is oriented substantially perpendicular to the substrate 11A. Similarly, the liquid crystal molecules 12b in the vicinity of the upper substrate 11B are aligned substantially perpendicular to the substrate 11B. In other words, the liquid crystal display device 10 constitutes a liquid crystal display device that operates in a so-called VA mode.
[0022]
In the configuration example of FIG. 1, the lower substrate 11A carries a first alignment film (not shown) rubbed on the upper main surface in a direction offset by about 22.5 ° counterclockwise from its longitudinal direction. The director indicating the alignment direction of the liquid crystal molecules points to a direction inclined at an angle of about 87 ° from the rubbing direction of the first alignment film with respect to the liquid crystal molecules 12a. Similarly, the lower substrate 11B carries a second alignment film (not shown) rubbed in a direction offset by about 22.5 ° in the clockwise direction from the longitudinal direction on the lower main surface, and the liquid crystal molecules The director indicating the alignment direction points the direction of the liquid crystal molecules 12b inclined at an angle of about 87 ° downward from the rubbing direction of the second alignment film. That is, in the liquid crystal layer 12, the liquid crystal molecules form a 45 ° twist angle between the upper and lower substrates 11A and 11B. However, when the liquid crystal panel is formed from the substrates 11A and 11B as shown in FIG. 1, the substrates 11A and 11B are combined so that the rubbing directions face each other at an angle of 45 °.
[0023]
A polarizer 13A having an absorption axis 13a is disposed below the liquid crystal panel composed of the substrates 11A and 11B, and polarizes light incident from below in a direction perpendicular to the absorption axis 13a. Similarly, an analyzer 13B having an absorption axis 13b is disposed on the upper side of the liquid crystal panel, and polarizes light passing through the liquid crystal panel in a direction orthogonal to the absorption axis 13b. Therefore, when the polarizer 13A and the analyzer 13B are arranged so that the absorption axes 13a and 13b are orthogonal to each other, if the light polarized by the polarizer 13A passes through the liquid crystal panel without changing the polarization plane, the light is analyzed. It is blocked by 13B and a black display is obtained.
[0024]
A transparent electrode (not shown) is formed on the outside of the substrate 13A and the inside of each alignment film of the substrate 13B. However, in a non-driving state in which a driving voltage is not applied to the electrodes, the liquid crystal molecules in the liquid crystal layer 12 are Like the liquid crystal molecules 12a or 12b, the light is aligned substantially perpendicular to the substrate surface, and as a result, the polarization state of light passing through the liquid crystal panel hardly changes. That is, the liquid crystal display device 10 realizes an ideal black display in a non-driven state. On the other hand, in the driving state, the liquid crystal molecules are inclined substantially parallel to the substrate surface, and the light passing through the liquid crystal panel changes the polarization state by the inclined liquid crystal molecules. In other words, in the liquid crystal display device 10, white display is obtained in the driving state.
[0025]
FIG. 2A shows the contrast ratio of the liquid crystal display device 10 when the angles φ and θ of the absorption axes 13a and 13b of the polarizer 13A and the analyzer 13B are variously changed. However, the angles φ and θ are defined as shown in the plan view of FIG. 2B, and the contrast ratio is a comparison between a non-driving state (driving voltage 0 V) and a state in which a driving voltage of 5 V is applied. . In the example of FIG. 2A, the liquid crystal constituting the liquid crystal layer 12 is one having Δn = 0.0813, Δε = −4.6 (for example, a liquid crystal product available as a trade name MJ95785 from Merck Japan). As the polarizing plates 13A and 13B, commercially available products such as G1220DU manufactured by Nitto Denko were used. The thickness of the liquid crystal cell, that is, the thickness d of the liquid crystal layer 12 is set to 3.5 μm. However, Δn = ne−n0, and ne and no are the refractive indices of extraordinary light and normal light in the liquid crystal, respectively. Δε represents dielectric anisotropy.
[0026]
First, referring to FIG. 2B, this figure shows the twist angle of the liquid crystal molecules in the liquid crystal display device 10, the angle φ formed by the polarizer absorption axis 13a with respect to the twist center line, and the analyzer absorption axis with respect to the twist center line. An angle θ formed by 13b is shown. However, in the plan view of FIG. 2B, in order to clearly show the twist angle and the center line thereof, unlike the display of FIG. 1, the liquid crystal display device 10 is inverted by 180 ° in the direction of the upper substrate 11B. The direction is the same as the direction of the lower substrate 11A.
[0027]
Referring to FIG. 2A, the contrast ratio of the liquid crystal display device 10 is maximized when the polarizer 13A and the analyzer 13B are in a crossed Nicols state, that is, in a state where the absorption axis 13a and the absorption axis 13b are orthogonal, particularly φ = It can be seen that the contrast is maximized when the angle formed by the polarizer absorption axis 13a with respect to 45 °, that is, the twist center line corresponding to the straight line connecting 0 ° -180 ° in FIG. . In such a crossed Nicols state, the angle formed by the analyzer absorption axis 13b with reference to the twist centerline is 135 °. It is clear that the same maximum contrast can be obtained even when the angles φ and θ are set to −45 ° and −135 ° in FIG. 2B, respectively. In this case, in FIG. 1, the angle formed with respect to the twist center line of the absorption shaft 13a is 135 °, and the angle formed with respect to the twist center line of the absorption shaft 13b is 45 °.
[0028]
As can be seen from FIG. 2 (A), in the liquid crystal display device 10 according to the present invention, a contrast ratio exceeding 700 can be obtained at any setting of φ and θ, but this result is only a contrast ratio of about 100 at most. This shows the superiority of the VA liquid crystal display device over the usual twisted nematic (TN) liquid crystal display device that cannot be obtained.
[0029]
3A to 3D are diagrams illustrating the operating characteristics of the liquid crystal display device 10 of FIG. However, the liquid crystal and the polarizing plate are as described above.
[0030]
3A is a waveform diagram showing the waveform of the voltage pulse applied to the liquid crystal display device 10, and FIG. 3B is a liquid crystal display generated in response to the voltage pulse of FIG. 3A. The change in the transmittance of the device 10 is indicated by a solid line and a broken line, respectively, when no chiral material is added to the liquid crystal layer 12 and when the chiral material is added. However, the result of FIG. 3B is for the liquid crystal cell with the thickness d set to 3.5 μm, and the twist angle of the liquid crystal molecules is 45 ° as described above. In the illustrated example, the pitch p of the chiral material is set so that the ratio d / p to the thickness d of the liquid crystal layer 12 is 0.25. As can be seen from FIG. 3B, when no chiral material is added, the liquid crystal display device 10 exhibits a substantially constant high light transmittance corresponding to the applied voltage pulse. It can be seen that when the chiral material is added, the transmittance of the liquid crystal display device 10 decreases with time. In other words, in the VA mode liquid crystal display device 10, the addition of a chiral material generally used in the TN mode liquid crystal display device results in undesirable deterioration of dynamic response characteristics.
[0031]
FIG. 3C shows a dynamic transmittance characteristic when the twist angle of liquid crystal molecules is changed in the range of 0 ° to 90 ° in the liquid crystal display device 10 in which the thickness d of the liquid crystal cell is 3.5 μm. Shows changes. As can be seen from FIG. 3C, the dynamic transmittance characteristic accompanying the input pulse in FIG. 3A is hardly affected by the twist angle of the liquid crystal molecules. The twist angle is controlled by controlling the rubbing direction of the molecular alignment film on the substrates 11A and 11B.
[0032]
FIG. 3D shows a change in dynamic transmittance characteristics when the thickness d of the liquid crystal cell is changed in the range of 4.5 μm to 2.5 μm. As can be seen from FIG. 3 (D), the transmittance accompanying the input pulse in FIG. 3 (A) decreases as the cell thickness d decreases, but the index indicating the response speed, that is, the transmittance is 0% when ON. The time TON until the saturation value (transmittance = 100%) reaches 90%, and the OFF time TOFF until the transmittance decreases to 10% from the saturation value decreases when the cell thickness decreases. Therefore, it can be seen that the response speed increases. In particular, when the cell thickness d is set to 2.5 μm or less, the dynamic transmittance characteristic curve rises and falls very steeply. FIG. 4 shows a phase difference compensation in one of the liquid crystal panels 11 formed of the substrates 11A and 11B and the liquid crystal layer 12 enclosed therebetween in order to further improve the viewing angle characteristics of the liquid crystal display device 10 of FIG. 1 shows a liquid crystal display device 20 having a structure in which a film 14A is inserted.
[0033]
Referring to FIG. 4, the retardation compensation film 14A has a negative retardation Δn · d1 in the z direction (Δn = ny−nz = nx−nz; nx, ny, nz are the principal axes x, y of the refractive index ellipsoid, respectively. , Z-direction refractive index, d1 is the thickness of the retardation film), and are respectively disposed between the liquid crystal panel 11 and the polarizer 13A to compensate for the birefringence of light passing through the liquid crystal panel 11.
[0034]
5 to 14 show the viewing angle characteristics of the liquid crystal display device 20 provided with the retardation compensation film 14A when the magnitude of the retardation R ′ of the film 14A is changed variously. However, in FIGS. 5 to 11, the angle values in the circumferential direction of 0.0 °, 90.0 °, 180.0 °, and 270.0 ° are azimuth angles, and concentric circles are 0 ° in the front direction of the panel. The measured viewing angles are shown at 20 ° intervals. Accordingly, in the drawing, the outermost concentric circle represents a viewing angle of 80.0 °. Each contour line represents an iso-contrast line having a contrast ratio CR of 500.0, 200.0, 100.0, 50.0 and 10.0. In any of the cases of FIGS. 4 to 6, the viewing angle characteristic is the same as that in the previous case when the driving voltage pulse of 0V / 5V shown in FIG. 5 to 14, the birefringence Δn of the liquid crystal panel 11 is 0.0804, the cell thickness d is 3 μm, the twist angle of the liquid crystal molecules is 45 °, and the pretilt angle is 89 °. In this case, the retardation Δn · d of the liquid crystal panel 11 is 241 nm.
[0035]
In the example of FIG. 5, the retardation R ′ is 108 nm and the ratio R ′ / Δn · d to the retardation value 241 nm of the liquid crystal panel is 0.45, whereas in the example of FIG. 6, the retardation R ′ is 144 nm. The ratio R ′ / Δn · d is 0.6. Further, in the example of FIG. 7, the retardation R ′ is 180 nm and the ratio R ′ / Δn · d is 0.75, and in the example of FIG. 8, the retardation R ′ is 198 nm and the ratio R ′ / Δn · d is 0. 9, the retardation R ′ is 216 nm and the ratio R ′ / Δn · d is 0.90. In the example of FIG. 10, the retardation R ′ is 234 nm and the ratio R ′ / Δn · d. In the example of FIG. 11, the total retardation R ′ is 252 nm and the ratio R ′ / Δn · d is 1.05. In the example of FIG. 12, the retardation R ′ is 270 nm and the ratio R ′. / Δn · d is 1.12. In the example of FIG. 13, the retardation R ′ is 288 nm and the ratio R ′ / Δn · d is 1.20. Further, in the example of FIG. 14, the retardation R ′ is 324 nm. Ratio R ′ / Δn · d Is 1.34.
[0036]
5 to 14, the liquid crystal display device 20 is particularly excellent when the ratio R ′ / Δn · d is in the vicinity of 1 (0.97 to 1.05) as shown in FIG. 9 or FIG. It can be seen that the viewing angle characteristic is exhibited. In other words, the results shown in FIGS. 5 to 14 indicate that the viewing angle characteristics of the liquid crystal display device 20 are obtained by disposing the retardation compensation film 14 </ b> A adjacent to the liquid crystal panel 11 and having a retardation value substantially equal to the retardation value of the liquid crystal panel. Shows significant improvement.
[0037]
The above-described results also hold when the phase difference compensation film 14B different from the phase difference compensation film 14A is disposed above the liquid crystal panel 11 in the configuration of FIG. However, in this case, the retardation R ′ is the total value of the retardation compensation film 14A and the retardation compensation film 14B.
[0038]
15 to 20, in the configuration of FIG. 4, the total retardation R ′ of the phase difference compensation films 14 </ b> A and / or 14 </ b> B is substantially matched with the retardation Δn · d of the liquid crystal panel 11, and the liquid crystal layer 12 in the liquid crystal panel 11 The viewing angle characteristic when the thickness d is changed is shown. However, in FIGS. 15 to 20, contour lines represented by CR = 10 indicate viewing angles at which a contrast ratio of 10 can be obtained.
[0039]
As can be seen from FIGS. 15 to 20, when the thickness d is 1 μm, and therefore the retardation Δn · d of the liquid crystal panel 11 is 82 nm or less, the viewing angle characteristic is clearly deteriorated, and the thickness d is 5 μm. When the retardation Δn · d of the panel 11 is 410 nm or more, the viewing angle characteristic is deteriorated again. From this, it can be seen that in the liquid crystal display device 20 of FIG. 4, the retardation of the liquid crystal panel 11 is preferably set to about 80 nm or more, more preferably 82 nm or more, and about 400 nm or less, more preferably 410 nm or less.
[0040]
21 to 26 show the transmissivity in the front direction of the liquid crystal display device 20 of FIG. 4 when the thickness d of the liquid crystal layer 12 is changed in various colors (B = blue, G = green, R = blue). However, the transmittance was measured while changing the applied voltage from 0V to 6V.
[0041]
As can be seen from FIGS. 21 to 26, when the thickness d of the liquid crystal layer is 1 μm (Δn · d = 82 nm) or less, the transmittance is very low in any color even when a driving voltage of 6 V is applied. (FIG. 21).
[0042]
On the other hand, when the thickness d of the liquid crystal layer is increased to 1 μm or more, the transmittance of each of the three primary colors when driving the liquid crystal display device is greatly increased. In particular, as shown in FIGS. When the thickness d of 12 is 4 to 5 μm, substantially the same transmittance is realized for each of the colors R, G, and B by setting the magnitude of the drive voltage pulse to about 4V.
[0043]
On the other hand, when the thickness of the liquid crystal layer d is further increased and is set to 6 μm or more as shown in FIG. 26, the drive voltage at which substantially the same transmittance is obtained for each of R, G, and B is slightly higher than 3V. In this case, the range of the drive voltage in which the transmittances for the respective colors R, G, and B are substantially equal is narrower than that in FIG. 24 or 25. In other words, in the configuration of FIG. 26, there is a problem that the white display is colored by a slight change in the drive voltage. However, in a liquid crystal display device that is actually mass-produced, it is difficult to strictly control the driving voltage.
Also from this, in the liquid crystal display device of FIG. 4, the thickness d of the liquid crystal layer 12 is preferably 1 μm or more and 6 μm or less. Accordingly, the retardation of the liquid crystal layer 12 is preferably about 80 nm or more and about 400 nm or less.
[0044]
27 to 30 show the color change observed for each azimuth angle when the polar angle is changed from + 80 ° to −80 ° in the liquid crystal display device of FIG. 27 to 30 are graphs in which the observed color change is plotted in the CIE (1931) standard color system. 27 to 30, a thick solid line indicates a case where the azimuth angle is 0 °, a thin solid line indicates a case where the azimuth angle is 45 °, and a broken line indicates a case where the azimuth angle is 90 °.
[0045]
First, referring to FIG. 27, when the thickness d of the liquid crystal layer 12 is 1 μm, and thus the retardation Δn · d of the liquid crystal panel 11 is 82 nm, it is observed whether the polar angle or the azimuth angle changes. The color change is slight. However, as shown in FIG. 28, when the thickness d of the liquid crystal layer 12 is 3 μm (Δn · d = 246 nm), the color change becomes slightly large. However, in the case of FIG. 28, the azimuth angle dependency of the color change is not yet observed.
[0046]
On the other hand, in the case of FIG. 29 in which the thickness d of the liquid crystal layer 12 is 4 μm (Δn · d = 328 nm), the color change caused by the liquid crystal display device 20 is further increased and the azimuth angle is 90 °. Different color changes are observed depending on the case and 0 ° or 45 °. Further, when the thickness d of the liquid crystal layer 12 is set to 5 μm (Δn · d = 410 nm) as shown in FIG. 30, or the thickness d is set to 6 μm (Δn · d = 492 nm) as shown in FIG. When set, the observed color change is very large.
[0047]
27 to 31, when the VA mode liquid crystal display device is applied to a full color liquid crystal display device that requires a wide viewing angle, the retardation Δn · d of the liquid crystal layer 12 is about 300 nm or less, for example, FIG. It is shown that it is preferable to set it to about 280 nm, which is between
[0048]
Further, the inventor of the present invention, in the liquid crystal display device 20 of FIG. 4, influences the twist angle formed by the liquid crystal molecules between the upper surface and the lower surface of the liquid crystal layer 12 on the viewing angle characteristics. The thickness d was set to 3 μm and examined.
[0049]
32 to 34 show viewing angle characteristics when the twist angles are 0 °, 90 °, and 180 °, respectively. As can be seen from FIGS. 32 to 34, a substantial change in the viewing angle characteristic due to the twist angle is hardly seen.
[0050]
In the above-described experiment described with reference to FIG. 4 and subsequent figures, the addition of a chiral material generally performed in a normal TN mode liquid crystal display device is not performed on the liquid crystal layer 12 constituting the liquid crystal display device 20. Not. The inventor of the present invention further examined the influence of the addition of the chiral material on the viewing angle characteristics in the VA mode liquid crystal display device.
[0051]
In the VA mode liquid crystal display device, in the non-driving state in which no driving voltage is applied, the liquid crystal molecules are substantially vertically aligned as schematically shown in FIG. However, in the driving state in which the liquid crystal molecules shown in FIG. 35B are horizontally aligned, it is considered that some effect due to the restriction of the chiral pitch by the chiral material appears. In the state of FIG. 35B, the liquid crystal molecules are twisted by the chiral material in the thickness direction of the liquid crystal layer at a uniform twist angle determined by the chiral pitch p of the chiral material and the thickness d of the liquid crystal layer. On the other hand, when no chiral material is added, as shown in FIG. 36A, the liquid crystal molecules in the non-driven state have the same orientation as in FIG. In this case, since there is no restriction of the chiral pitch by the chiral material, the twist of the liquid crystal molecules becomes non-uniform. That is, as shown in FIG. 35B, although the twist of the liquid crystal molecules occurs in the vicinity of the molecular alignment films respectively supported on the upper and lower substrates, the region in the upper central portion in the thickness direction of the liquid crystal layer 12 (FIG. 36). In the region C) in (B), almost no twist of liquid crystal molecules occurs.
[0052]
FIG. 37 shows the case where the thickness d of the liquid crystal layer 12 is 3 μm and the twist angle of the liquid crystal molecules is 90 ° in the liquid crystal display device 20 of FIG. The viewing angle characteristic in the case of .25 is shown. The viewing angle characteristics of FIG. 37 are compared with FIG. 33, which shows the viewing angle characteristics when no chiral material is added in the liquid crystal display device having the same configuration, and it can be seen that the region where the contrast ratio is 10 or more is reduced. In other words, it is concluded that in the VA mode liquid crystal display device, it is preferable not to add a chiral material from the viewpoint of viewing angle characteristics.
[0053]
38 and 39, similarly, the brightness of each color of R, G, and B in the front direction of the liquid crystal panel of the liquid crystal display device 20 when the thickness d of the liquid crystal layer 12 is 3 μm and the twist angle of the liquid crystal molecules is 90 °. Show properties. However, FIG. 38 shows a case where a chiral material is added, and FIG. 39 shows a case where a chiral material is not added. Obviously, the addition of the chiral material decreases the luminance of the liquid crystal display device. When a chiral material is added, as shown in FIG. 35 (B) in the driving state, a uniform twist of liquid crystal molecules occurs, whereas when no chiral material is added, FIG. 356 (B). As shown in FIG. 5, in the driving state of the liquid crystal display device, a region C in which liquid crystal molecules are not twisted is formed. In this region C, it is considered that the light beam efficiently changes the plane of polarization. In other words, it is concluded that in the VA mode liquid crystal display device, it is preferable not to add a chiral material also from the viewpoint of luminance characteristics.
[0054]
The inventor of the present invention further examined the change in viewing angle characteristics by changing the pretilt angle of the liquid crystal molecules in the liquid crystal display device 20 of FIG. The results are shown in FIGS. However, FIG. 40 shows the case where the pretilt angle is set to 89.99 °, FIG. 41 shows the case where the pretilt angle is set to 85 °, FIG. 42 shows the case where the pretilt angle is set to 80 °, and FIG. The case where the pretilt angle is set to 75 ° is shown. Further, FIG. 44 shows viewing angle characteristics of a standard TN mode liquid crystal display device.
[0055]
40 to 44, the widest viewing angle is realized in the case of FIG. 40 in which the pretilt angle is substantially 90 °, while the viewing angle also decreases as the pretilt angle decreases. When the pretilt angle shown in FIG. 43 is 75 °, the viewing angle is equivalent to that of the standard TN mode liquid crystal display device shown in FIG.
[0056]
For this reason, in the VA mode liquid crystal display device, the pretilt angle of the liquid crystal molecules is preferably set to 75 ° or more, preferably 87 ° or more, more preferably 89 ° or more.
[0057]
DETAILED DESCRIPTION OF THE INVENTION
[Example 1]
FIG. 45 is a cross-sectional view showing the configuration of the liquid crystal display device 30 according to the first embodiment of the present invention.
[0058]
Referring to FIG. 45, a transparent electrode 31a ′ made of ITO and a glass substrate 31A carrying an alignment film 31a subjected to rubbing treatment, and an ITO electrode 31b ′ and an alignment film 31b subjected to similar rubbing treatment are carried. The glass substrate 31B is aligned in such a way that the alignment films 31a and 31b face each other using the polymer sphere 31C as a spacer, and sealed with a sealing material (not shown) to form a liquid crystal panel. Further, in the liquid crystal panel, in the space defined by the alignment films 31a and 31b, a liquid crystal having negative dielectric anisotropy, for example, liquid crystal MJ941296 manufactured by Merck Japan (Δn = 0.0804, Δε = -4) is sealed by a vacuum injection method to form a liquid crystal layer 32. In such a configuration, the thickness of the liquid crystal layer 32, that is, the cell thickness d is determined by the diameter of the polymer spacer sphere 31C.
[0059]
Further, retardation compensation films 33A and 33B are disposed on the upper and lower sides of the liquid crystal panel thus formed, respectively, a polarizer 34A is provided below the retardation compensation film 33A, and a retardation compensation film 33B is provided. On the upper side, an analyzer 34B is formed in an orientation with reference to the twist center line as shown in FIG. 1 or FIG. That is, the liquid crystal display device of FIG. 45 corresponds to the case where the second retardation compensation film 14B is provided in the configuration of FIG.
[0060]
[Table 1]

Table 1 shows 25 ° C. of the operating characteristics and viewing angle characteristics of each liquid crystal display device when the thickness d of the liquid crystal layer 32 is variously changed in the liquid crystal display device 30 in which the twist angle is set to 45 °. The evaluation result in is shown. However, in Table 1, a vertical alignment material RN783 manufactured by Nissan Chemical is used as the alignment films 31a and 31b, and a G1220DU polarizing plate manufactured by Nitto Denko or a SK-1832AP7 polarizing plate manufactured by Sumitomo Chemical is used as the polarizing plates 34A and 34B. The result of the case is shown. Further, in the liquid crystal display device of Table 1, the retardation compensation films 33A and 33B shown in FIG. 45 are omitted, but the protective film of the polarizing plate performs some retardation compensation action. For example, the protective film associated with the G1220DU polarizing plate exhibits a negative retardation with a size of 44 nm, and the protective film associated with the SK-1832AP7 polarizing plate exhibits a negative retardation with a size of 50 nm. Further, no chiral material is added to the liquid crystal layer 32.
[0061]
Referring to Table 1, it can be seen that the rise time Ton and the fall time Toff decrease as the thickness d of the liquid crystal layer 32 decreases, and the response speed of the liquid crystal display device is improved. Further, as the thickness d of the liquid crystal layer decreases, the viewing angle range that gives a contrast ratio of 10 or more increases. However, as described above, when the thickness of the liquid crystal layer decreases, the luminance decreases. Therefore, as described above, the thickness of the liquid crystal layer 32 has a retardation Δn · d of about 80 to about 400 nm. It is necessary to set to fit within the range.
[0062]
46A and 46B show viewing angle characteristics when the cell thickness d is 3 μm and the twist angle is 45 ° in the liquid crystal display device having the configuration shown in FIG. However, in the example of FIG. 46, the chiral material is not added, the above-mentioned MJ941296 is used for the liquid crystal, and G1220DU is used for the polarizing plate. However, the results of FIGS. 46A and 46B are for the case where the polarizing plates 34A and 34B also serve as the retardation compensation films 33B and 34B.
[0063]
In FIG. 46A, a region having a contrast ratio of 10 or more is shown in white, but it can be seen that the white region is very wide and a very wide viewing angle characteristic is obtained. In addition, as can be seen from FIG. 46B, such a liquid crystal display device can obtain a contrast ratio close to 2000 in the front direction.
[0064]
47A and 47B show viewing angle characteristics when a commercially available retardation compensation film (VAC0 manufactured by Sumitomo Chemical Co., Ltd.) is used as the retardation compensation films 33A and 33B in the liquid crystal display device of FIG. However, since the liquid crystal panel has a retardation value Δn · d of 241 nm, the size of the total retardation value R ′ of the polarizing plates 34A and 34B and the retardation compensation films 33A and 33B is set to 218 nm, which is close to 241 nm. Yes.
[0065]
As can be seen from FIG. 47 (A), the viewing angle region where the contrast ratio exceeds 10 in this case is further enlarged than in the case of FIG. 46 (A), and the contrast ratio in the panel front direction is also shown in FIG. 47 (B). As shown in FIG.
[0066]
Previously, in connection with FIGS. 40 to 44, it has been described that when the pretilt angle is 75 ° or less, the viewing angle characteristics deteriorate in the VA mode liquid crystal display device to the same level as the conventional TN mode liquid crystal display device. In the configuration having the retardation compensation films 34A and 34B above and below the liquid crystal layer 32, as shown in FIG. 48, the region giving the contrast ratio 10 (CR = 10) is wide even when the pretilt angle is 75 °. Thus, a viewing angle characteristic satisfactory as a liquid crystal display device can be obtained. However, FIG. 48 is for the case where the thickness of the liquid crystal layer 32 is 3 μm, the twist angle is 45 °, and the pretilt angle is 75 °.
[Example 2]
Next, a liquid crystal display device according to a second embodiment of the present invention will be described.
[0067]
In the present embodiment, in the liquid crystal display device having the configuration of FIG. 45, MX95785 (Δn = 0.0813, Δε = −4.6) manufactured by Merck Co., Ltd. is used as the liquid crystal instead of the previous MJ941296. Since the other configuration is the same as that of the apparatus of FIG. 45, the description of the configuration of the apparatus is omitted.
[0068]
FIG. 49 shows the rising characteristics of the liquid crystal display device according to this example when the cell thickness d of the liquid crystal layer 32 is 3 μm, when the twist angles are 0 °, 45 °, and 90 °. In this example, no chiral material is added to the liquid crystal layer 32. As can be seen from FIG. 49, the rise time TON is around 10 ms when the applied voltage is in the range of 4 to 8 V, except for the case where the twist angle is 0 °, and the liquid crystal display device has very good rise characteristics. Understand. On the other hand, in the TN mode liquid crystal display device, the rise time TON is generally 20 ms or more.
[0069]
FIG. 50 shows the falling characteristics of the liquid crystal display device according to this example when the cell thickness d is also 3 μm when the twist angles are 0 °, 45 ° and 90 °. Also in this example, no chiral material is added to the liquid crystal layer 32. As can be seen from FIG. 50, the fall time TOFF is about 5 ms at any twist angle, and it can be seen that the liquid crystal display device has a very good fall characteristic. On the other hand, in the TN mode liquid crystal display device, the fall time TOFF is generally 40 ms or more.
[0070]
[Table 2]

Table 2 shows the viewing angle characteristics when the total value of the negative retardation R ′ formed by the polarizing plates 34A and 34B and the retardation compensation films 33A and 33B is changed in the liquid crystal display device according to the present embodiment, particularly the contrast ratio of 10. Changes in the viewing angle range and 11 gradation inversion angles. The eleventh gradation inversion angle represents a polar angle direction in which when the halftone is performed with eleven gradations in the front direction of the liquid crystal panel, the luminances of the gradations constituting the halftone appear to be reversed with respect to each other. When such gradation inversion occurs, the display is crushed and difficult to see. For this reason, the gradation inversion angle is preferably as wide as possible. However, in this embodiment, the retardation Δn · d of the liquid crystal layer 32 is positive and has a value of 246 nm. Table 2 shows that the total value of the retardation R ′ formed by the retardation compensation films 33A and 33B and the polarizing plates 34A and 34B is set close to the retardation Δn · d of the liquid crystal layer 32, so that 90 °, −90 °, 180 It can be seen that the viewing angle increases at an azimuth angle of °.
[0071]
[Table 3]

Table 3 shows changes in viewing angle characteristics and 11 gradation inversion angles when the twist angle is changed in the present embodiment. The results in Table 3 indicate that viewing angle dependence by the twist angle is substantially absent. However, the results in Table 3 are for the case where the retardation compensation films 33A and 33B are not provided and only the retardation compensation action (R ′ = 88 nm) of the polarizing plates 34A and 34B exists.
[Example 3]
FIG. 51 shows a configuration of a liquid crystal display device 40 according to the third embodiment of the present invention. However, in FIG. 51, the same reference numerals are given to the parts described above, and the description thereof is omitted.
[0072]
Referring to FIG. 51, the liquid crystal display device 40 has a configuration similar to that of the liquid crystal display device 30 described in FIG. 45, but instead of the retardation compensation film 33B having the negative retardation of FIG. 45, a positive retardation is provided. A first retardation compensation film (33B) 1 having a second retardation compensation film (33B) 2 having a negative retardation, and the positive retardation compensation film (33B) 1 in the vicinity of the liquid crystal panel 31. Further, the difference is that the negative retardation compensation film (33B) 2 is disposed outside thereof. The retardation compensation film (33B) 2 has an optical axis perpendicular to the main surface of the liquid crystal panel 31, whereas the retardation compensation film (33B) 1 has an optical axis parallel to the main surface of the liquid crystal panel 31.
[0073]
FIG. 52 shows the transmission in the black display state (when not driven) with respect to various polar angles in the liquid crystal display device 40 of FIG. 51 when the thickness d of the liquid crystal layer 32 is 3.5 μm and the twist angle is 45 °. Indicates the rate. However, in FIG. 52, the retardation of the positive retardation compensation film (33B) 1 is set to 100 nm, and its optical axis angle θ is variously changed. As shown in FIG. 51, the optical axis angle θ is defined as an angle formed by the optical axis of the retardation compensation film (33B) 1 with respect to the twist center axis. At that time, the retardation value of the negative retardation compensation film (33B) 2 is set to be substantially equal to the retardation Δn · d of the liquid crystal panel 31, and the illustrated transmittance is for the 90 ° azimuth direction. .
[0074]
Referring to FIG. 52, it can be seen that at any polar angle, the transmittance in the black display state is minimized when the optical axis angle θ is about 45 °. As described above, the viewing angle characteristics can be improved by minimizing the transmittance of black display for all viewing angles. In FIG. 52, when the polar angle is 0 ° and 20 °, the transmittance in the black display state is minimized even at the optical axis angle of about 135 °. In this case, the transmittance is obtained when the polar angle is 40 ° or more. As a result, the desired viewing angle characteristics are not improved.
[0075]
FIG. 53 shows the transmittance in the black display state for various polar angles when the retardation of the positive retardation compensation film (33B) 1 is changed in the liquid crystal display device 40 of FIG. However, also in the case of FIG. 53, the azimuth angle is 90 °.
[0076]
Referring to FIG. 53, by setting the retardation value of the positive retardation compensation film (33B) 1 in the range of 20 to 60 nm, the transmittance in the black display state can be minimized for all polar angles. . In this case, the transmittance is below 0.002.
[0077]
In FIG. 54, in the liquid crystal display device 40 of FIG. 51, another negative retardation compensation film having a negative retardation is disposed between the lower polarizing plate 34A and the liquid crystal panel 31. When the total retardation value of the negative retardation compensation film and the retardation compensation film (33B) 2 is set to be approximately equal to the retardation value of the liquid crystal panel 31, the transmittance in the black display state is the positive retardation. It shows as a function of the retardation value of compensation film (33B) 1.
[0078]
As can be seen from FIG. 54, this configuration substantially eliminates the polar angle dependency of the transmittance in the black display state, and transmits when the retardation of the retardation compensation film (33B) 1 is in the range of 50 to 60 nm. The rate is minimized. In order for such retardation compensation film (33B) 1 to be effective, the retardation value of retardation compensation film (33B) 1 needs to be set to about 100 nm or less.
[0079]
FIG. 55 shows a case where, in the liquid crystal display device 40 of FIG. 51, the retardation value of the retardation compensation film (33B) 1 is fixed to 30 nm and the retardation value R ′ of the retardation compensation film (33B) 2 is changed. The transmittance in the black display state is shown. However, as in the previous case, the transmittance is in the 90 ° azimuth direction, and the polar angle value is variously changed.
[0080]
As can be seen from FIG. 55, the transmittance is minimized when the value of the negative retardation R ′ formed by the retardation compensation film (33B) 2 is about 250 nm. It is slightly smaller than the retardation Δn · d of 32. As described above, when the positive retardation compensation film (33B) 1 is not provided, the optimum retardation value of the retardation compensation film (33B) 1 is equal to the retardation value Δn · d of the liquid crystal layer 32. . That is, when the positive retardation compensation film (33B) 1 is used in addition to the negative retardation compensation film (33B) 2, the optimum value of the negative retardation compensation film (33B) 2 is the retardation of the liquid crystal layer 32. It is necessary to set it slightly smaller than the value Δn · d. In any case, the total retardation value R ′ of the negative retardation compensation film is equal to the liquid crystal layer 32 even when only the retardation compensation film (32B) 2 is used or when another negative retardation compensation film is used. It is necessary to set the retardation value Δn · d to 2 times or less.
[0081]
FIG. 56 shows viewing angle characteristics of the liquid crystal display device 40 of FIG. When compared with the result of FIG. 17 showing the corresponding viewing angle characteristics when only the negative retardation compensation film is used, it can be seen that the area of the region having the contrast ratio of 10 or more is enlarged.
[Example 4]
FIG. 57 shows a configuration of a liquid crystal display device 50 according to the fourth embodiment of the present invention. However, the parts described above in FIG. 57 are denoted by the corresponding reference numerals, and the description thereof is omitted.
[0082]
Referring to FIG. 57, the liquid crystal display device 50 has the same configuration as the liquid crystal display device 40 of FIG. 51, but the same retardation compensation film (33A) as the retardation compensation films (33B) 1 and (33B) 2. ) 1 and (33A) 2 are also provided between the polarizing plate 34A and the liquid crystal panel 31. At that time, by providing the retardation compensation film (33A) 1 having a positive retardation on the side close to the liquid crystal panel 32 and the retardation compensation film (33A) 2 having a negative retardation on the side far from the liquid crystal panel 32, The configuration on the upper side and the configuration on the lower side of the liquid crystal panel 32 become symmetrical, and the viewing angle characteristics are further improved as shown in FIG.
[Example 5]
FIG. 59 shows a configuration of a liquid crystal display device 60 according to the fifth embodiment of the present invention. However, the parts described above in FIG. 59 are denoted by the corresponding reference numerals, and the description thereof is omitted.
[0083]
Referring to FIG. 59, in this embodiment, in the liquid crystal display device 40 described above, instead of providing the positive retardation compensation film (33B) 1 and the negative retardation compensation film (33B) 2, A single biaxial retardation compensation film 33B ′ is inserted between the liquid crystal panel 31 and the polarizing plate 34B.
[0084]
The retardation compensation film 33B 'has optical biaxiality, and nX> ny> nz or ny> nx> nz holds for the refractive indexes nx, ny, nz in the x, y, z directions. Such biaxial retardation compensation films are known, and for example, those described in JP-A-59-189325 may be used.
[0085]
The retardation formed by such a biaxial retardation compensation film is given by the expression | nX −ny | · d in the in-plane direction, and the expression (nX + ny) 2 + nz in the direction perpendicular to the liquid crystal panel 32 (thickness direction). Given in. In this embodiment, an optimum result can be obtained by setting the in-plane retardation value to 120 nm or less and the retardation in the thickness direction equal to the retardation Δn · d of the liquid crystal layer 32. However, in the example of FIG. 59, the retardation compensation film 33B 'is disposed so that its in-plane slow axis is substantially parallel to the absorption axis of the polarizing plate 34B. The in-plane slow axis coincides with the x-axis when the relationship of nX> ny> nz is established, and coincides with the y-axis when ny> nX> nz is established.
[Example 6]
FIG. 60 shows a configuration of an active matrix liquid crystal display device 70 according to a sixth embodiment of the present invention.
[0086]
In the present embodiment, in the configuration of FIG. 57, a plurality of transparent pixel electrodes (31a ′) PIXEL corresponding to the pixels defined in the liquid crystal panel on the glass substrate 31A or 31B, and TFTs for driving the transparent pixel electrodes (31a ′) (31a ′) TFTs are formed. That is, the transparent pixel electrode (31a ') PIXEL and the TFT (31a') TFT correspond to the electrode 31a 'or 31b' in FIG. On the substrate 31A or 31B, a data bus DATA for supplying a drive signal to the TFTs arranged in a matrix and an address bus ADDR for activating the data bus extend.
[0087]
FIG. 61 shows the viewing angle characteristics of the liquid crystal display device 70 when Merck Japan MJ95785 is used as the liquid crystal and the thickness of the liquid crystal layer is 3 μm. In this case, the twist angle of the liquid crystal molecules is 45 °, the retardation Δn · d of the liquid crystal layer 32 is 241 nm, and Nissan Chemical RN783 is used as the molecular alignment films 31a and 31b (see FIG. 45). As can be seen from FIG. 61, an active matrix driving liquid crystal display device having a very wide viewing angle range can be obtained.
[Example 7]
In each of the embodiments described above, as shown in FIGS. 62A to 62C, a so-called single domain molecular alignment configuration in which the liquid crystal molecular alignment is uniform in each pixel is used. 62A is a plan view of a region for one pixel of the liquid crystal display device, FIG. 62B is a cross-sectional view taken along line AB in FIG. 62A, and FIG. FIG. 62B shows a configuration in which incident light X and Y are incident on the liquid crystal display device of FIG. 62B from two different directions, and the same reference numerals are given to the portions described earlier in the figure. . In FIG. 62A, the solid arrow indicates the rubbing direction of the molecular alignment film 31b supported on the upper substrate 31B, and the dotted arrow indicates the rubbing of the molecular alignment film 31a supported on the lower substrate 31A. Indicates direction. The rubbing direction of the molecular alignment film 31b and the rubbing direction of the molecular alignment film 31a intersect at an angle α1, but when the twist angle of the liquid crystal molecules is set to 45 °, the angle α1 is set to an angle of 45 °. To do.
[0088]
As can be seen from FIG. 62 (C), in the liquid crystal display device having such a single domain molecular alignment structure, the molecular alignment viewed from the direction of the incident light X and the direction of the incident light Y in the driving state. Since the molecular orientation is different, a substantial reduction in viewing angle characteristics is inevitable.
[0089]
On the other hand, FIGS. 63A to 63C show the configuration of the liquid crystal display device according to the seventh embodiment of the present invention. However, the parts described above are denoted by the same reference numerals, and description thereof is omitted.
[0090]
In the configurations of FIGS. 63A to 63C, as shown in FIG. 63B, in each pixel, the ultraviolet modified molecular alignment films 31a ′ and 31b ′ are formed as one of the molecular alignment films 31a and 31b, respectively. It is formed so as to cover the part. For example, after the rubbing of the molecular alignment films 31a and 31b, another molecular alignment film is deposited thereon and irradiated with ultraviolet rays to change the molecular alignment. In this case, patterning may be performed so as to leave only a part thereof.
[0091]
At that time, as shown in the cross-sectional view of FIG. 63 (B), the modified molecular alignment film 31a ′ is formed in the lower area of the drawing in the plan view of FIG. By forming the modified molecular alignment film 31b ′, when incident light X and Y are incident from different directions as shown in FIG. 63 (C), the liquid crystal molecules sense light in either direction. The orientation becomes equivalent in the driving state of the liquid crystal display device, and the viewing angle characteristics of the liquid crystal display device are further improved.
[0092]
FIGS. 64A to 64C show a modification of this embodiment.
[0093]
Referring to FIG. 64 (A), in this embodiment, the rubbing direction is changed in the upper area and the lower area in the drawing, and as a result, as shown in the sectional view of FIG. 64 (B), In each pixel, the molecular orientation is different between the right region and the left region (corresponding to the upper region and the lower region in FIG. 64A). As a result, as shown in FIG. 64C, when incident light X and Y are incident from two different directions, the orientation of the liquid crystal molecules in each direction is the same as in the case of FIG. 63C. The viewing angle characteristics of the liquid crystal display device are improved.
[0094]
FIG. 65 shows viewing angle characteristics when the angles α1 and α2 are both 45 ° and the thickness d of the liquid crystal layer 32 is 3 μm in the liquid crystal display device having the configuration of FIG. However, in FIG. 65, the liquid crystal display device uses MJ95785 of Merck Japan as the liquid crystal layer 32, and no chiral material is added. That is, in this case, the liquid crystal layer 32 has a value of 287 nm as the retardation Δn · d, and the twist angle is set to 45 °. 57, the positive retardation compensation films (33A) 1 and (33A) 1 have a total retardation value R of 25 nm and a negative retardation compensation film (33B) 2. The total retardation value R ′ is set to 160 nm.
[0095]
Referring to FIG. 65, it can be seen that by configuring the liquid crystal display device in this way, the region where the contrast ratio is less than 10 is very limited, and a very good viewing angle characteristic can be obtained.
[0096]
FIG. 66 shows the result of the simulation of the viewing angle characteristics of the liquid crystal display device having the same configuration. According to this, it can be seen that the liquid crystal display device can realize further excellent viewing angle characteristics by optimizing each member. .
[0097]
FIG. 67 shows the configuration of a direct-view type liquid crystal display device 100 configured using the liquid crystal display devices described in the first to seventh embodiments.
[0098]
Referring to FIG. 67, the direct-view liquid crystal display device 100 includes a VA mode liquid crystal display device 101 that may be any of the liquid crystal display devices 10 to 70, and a surface light source 103 disposed behind the VA mode liquid crystal display device 101. Is done. A plurality of pixel regions 102 are defined in the liquid crystal display device 101, and the backlight emitted from the surface light source 103 is optically modulated. On the other hand, the surface light source 103 includes a light source unit 103 including a line light source such as a fluorescent tube, and a light diffusion unit that diffuses light emitted from the line light source and illuminates the entire surface of the liquid crystal display device 101 two-dimensionally. 104.
[0099]
The VA mode liquid crystal display device according to the present invention described above in each embodiment is particularly suitable for a direct-view type liquid crystal display device having a configuration as shown in FIG.
[Example 8]
Previously, in FIGS. 35 and 36, it has been described that it is preferable not to add a chiral material to the liquid crystal layer in the VA mode liquid crystal display device according to the present invention. However, this does not mean that the present invention cannot or should not add chiral material. In fact, by controlling the chiral pitch of the liquid crystal molecules in the liquid crystal layer with a chiral material within an appropriate range, the display brightness, contrast ratio, and response speed are kept optimal while minimizing display coloration. Is possible.
[0100]
Hereinafter, an eighth embodiment of the present invention using such a chiral material will be described.
[0101]
FIG. 68 shows a case where MX941296 (Δn = 0.082, Δε = −4.6) manufactured by Merck Japan is used as the liquid crystal layer 32 in the liquid crystal display device 40 having the configuration shown in FIG. G1220DU manufactured by G1220DU is further refracted as a positive retardation compensation film (33B) 1 as a birefringence film having a refractive index nx = 1.501, ny = nz = 1.5, and as a negative retardation compensation film (33B) 2. When the birefringent film having the ratios nx = ny = 1.501 and nz = 1.5 is used, the change in the viewing angle characteristics when the pitch p of the chiral material added to the liquid crystal layer 32 is variously changed is shown. However, the thickness d of the liquid crystal layer 32 is fixed to 3.25 μm, and the twist angle of the liquid crystal molecules is 45 °. However, in FIG. 68, the “forward chiral” direction refers to the case where the twist direction of the chiral material coincides with the twist direction of the liquid crystal molecules, and the “reverse chiral” direction refers to the twist direction of the chiral material as the twist direction of the liquid crystal molecules. The case in the reverse direction is shown.
[0102]
Referring to FIG. 68, if the absolute value | d / p | of the d / p ratio is within 0.375 (= ψ / 120 °; ψ is a twist angle, in this case 45 °), 50 ° It can be seen that a viewing angle exceeding can be secured. However, in the absolute value display, the chiral pitch p is expressed as + for the forward chiral direction and-for the reverse chiral direction.
[0103]
69 to 76 are the same as FIGS. 27 to 31 described above, and in the liquid crystal display device 40 of FIG. 51, the d / p ratio is changed variously by adding a chiral material. The coloring characteristics of are shown. However, the thickness d of the liquid crystal layer is set to 3.25 μm. Of these, FIG. 69 shows the case where no chiral material is added and roughly corresponds to FIG. 28, whereas FIG. 70 shows the case where the d / p ratio is 0.0325 in the forward chiral direction, and FIG. FIG. 72 shows the case where the p / ratio is 0.13 in the forward chiral direction, FIG. 72 shows the case where the d / p ratio is 0.325 in the forward chiral direction, and FIG. The case of 65 is shown. On the other hand, FIG. 74 shows the case where the d / p ratio is 0.0325 in the reverse chiral direction, FIG. 75 shows the case where the d / p ratio is 0.13 in the reverse chiral direction, and FIG. The case where the / p ratio is set to 0.325 in the reverse chiral direction is shown.
[0104]
69 to 76, it can be seen that the coloration of the liquid crystal display device can be reduced by controlling the chiral pitch in the forward chiral direction with a chiral material. On the other hand, the restriction of the chiral pitch in the reverse chiral direction deteriorates the coloring characteristics. Considering the viewing angle characteristics of FIG. 68, it is concluded that in a liquid crystal layer having a thickness d of 3.25 μm, it is preferable to set the absolute value | d / p | of the d / p ratio within Ψ / 120 °. The
[0105]
FIG. 77 shows evaluation of display characteristics when | d / p | is fixed to about Ψ / 360 ° and the cell thickness d and the twist angle Ψ are changed variously.
[0106]
Referring to FIG. 77, the evaluation was performed in four stages and displayed in the order of ◎, ○, △, × from the better to the worse. As described in the previous embodiment, if the cell thickness d and the retardation Δn · d are too small, the response characteristic becomes fast but the transmittance is lowered. On the other hand, when the cell thickness d is increased, coloring becomes intense. If the twist angle Ψ is too large, the response time becomes long. In conclusion, the retardation Δn · d of the liquid crystal layer is the region indicated by the solid line in FIG.
Ψ / 549 ≦ Δn · d ≦ (225 + Ψ) / 549
If it is within the range given byEspecially formula
(90 + Ψ) / 549 ≦ Δn · d ≦ (180 + Ψ) / 549
If it is within the range given byIt can be seen that excellent display characteristics can be obtained. However, in the above equation, the unit of the twist angle Ψ is degrees (°).
[0107]
FIGS. 78 and 79 show that the retardation compensation film (33A) 1 is removed from the liquid crystal display device 50 of FIG. 57, the twist angle Ψ of the liquid crystal molecules is 45 °, the cell thickness d of the liquid crystal layer 32 is 4 μm, and the retardation compensation. When the negative total retardation value R ′ by the films (33A) 2 and (33B) 2 is 300 nm and the positive retardation value R by the retardation compensation film (33B) 1 is 25 nm, the d / p ratio is further reduced to 0. Viewing angle characteristics and coloring characteristics when a chiral material is added to the liquid crystal layer 32 so as to be 125 are shown.
[0108]
Compared with FIGS. 80 and 81 showing the viewing angle characteristics and coloring characteristics of a normal TN type liquid crystal display device, the liquid crystal display device according to this example is different from that of the conventional TN type liquid crystal display device in both viewing angle and coloring. It can be seen that there is a significant improvement.
[0109]
As mentioned above, although this invention was demonstrated about the preferable Example, this invention is not limited to said Example, A various deformation | transformation and change are possible within the summary described in the claim.
[0110]
【The invention's effect】
According to the first aspect of the present invention, in the vertically aligned liquid crystal display device, the retardation Δn · d of the liquid crystal layer is:In the range of Δn · d ≦ 0.4 nm,The twist angle of the liquid crystal molecules in the liquid crystal layer is Ψ, and the formula
(90 + Ψ) / 549 ≦ Δn · d ≦ (180 + Ψ) / 549
The twist angle of the liquid crystal molecules is optimized so that the cell thickness of the liquid crystal layer is less than 5 μm and the twist angle Ψ satisfies the relationship 0 <Ψ <90 °. By controlling, it is possible to obtain a liquid crystal display device that is bright, has a high response speed, and is less colored.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a basic configuration of a liquid crystal display device according to the present invention.
FIG. 2 is a diagram for explaining the relationship between the contrast ratio of the liquid crystal display device of FIG. 1 and the orientation of the polarizer and analyzer with respect to the liquid crystal panel.
FIG. 3 is a diagram showing dynamic characteristics of the liquid crystal display device of FIG. 1;
4 is a diagram showing a configuration in which a phase difference compensation plate is further provided in the liquid crystal display device of FIG. 1. FIG.
5 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel in the liquid crystal display device of FIG. 4 is set to 0.45. FIG.
6 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel in the liquid crystal display device of FIG. 4 is 0.6.
7 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel is 0.75 in the liquid crystal display device of FIG.
8 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel in the liquid crystal display device of FIG. 4 is 0.82.
9 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel is 0.90 in the liquid crystal display device of FIG.
10 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel is 0.97 in the liquid crystal display device of FIG.
11 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel is 1.05 in the liquid crystal display device of FIG.
12 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel is 1.12 in the liquid crystal display device of FIG.
13 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel is 1.20 in the liquid crystal display device of FIG.
14 is a diagram showing viewing angle characteristics when the ratio of the total retardation value of the retardation compensation plate to the retardation value of the liquid crystal panel is 1.34 in the liquid crystal display device of FIG.
15 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 1 μm and the retardation value of the liquid crystal layer is 82 nm in the liquid crystal display device of FIG. 4;
16 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 2 μm and the retardation value of the liquid crystal layer is 164 nm in the liquid crystal display device of FIG. 4;
17 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 3 μm and the retardation value of the liquid crystal layer is 246 nm in the liquid crystal display device of FIG. 4;
18 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 4 μm and the retardation value of the liquid crystal layer is 328 nm in the liquid crystal display device of FIG. 4;
19 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 5 μm and the retardation value of the liquid crystal layer is 410 nm in the liquid crystal display device of FIG. 4;
20 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 6 μm and the retardation value of the liquid crystal layer is 492 nm in the liquid crystal display device of FIG. 4;
FIG. 21 is a diagram showing transmittance characteristics when the thickness of the liquid crystal layer is 1 μm in the liquid crystal display device of FIG. 4;
22 is a diagram showing transmittance characteristics when the thickness of the liquid crystal layer is 2 μm in the liquid crystal display device of FIG. 4;
23 is a diagram showing transmittance characteristics when the thickness of the liquid crystal layer is 3 μm in the liquid crystal display device of FIG. 4;
24 is a diagram showing transmittance characteristics when the thickness of the liquid crystal layer is 4 μm in the liquid crystal display device of FIG. 4;
25 is a diagram showing transmittance characteristics when the thickness of the liquid crystal layer is 5 μm in the liquid crystal display device of FIG. 4;
26 is a diagram showing the transmittance characteristics when the thickness of the liquid crystal layer is 6 μm in the liquid crystal display device of FIG. 4;
27 is a diagram showing coloring characteristics when the thickness of the liquid crystal layer is 1 μm in the liquid crystal display device of FIG. 4;
28 is a diagram illustrating coloring characteristics when the thickness of the liquid crystal layer is 3 μm in the liquid crystal display device of FIG. 4;
29 is a diagram showing coloring characteristics when the thickness of the liquid crystal layer is 4 μm in the liquid crystal display device of FIG. 4;
30 is a diagram showing coloring characteristics when the thickness of the liquid crystal layer is 5 μm in the liquid crystal display device of FIG. 4;
31 is a diagram showing coloring characteristics when the thickness of the liquid crystal layer is 6 μm in the liquid crystal display device of FIG. 4;
32 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 3 μm and the twist angle is 0 ° in the liquid crystal display device of FIG. 4;
33 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 3 μm and the twist angle is 90 ° in the liquid crystal display device of FIG. 4;
34 is a diagram showing viewing angle characteristics when the thickness of the liquid crystal layer is 3 μm and the twist angle is 180 ° in the liquid crystal display device of FIG. 4;
FIGS. 35A and 35B are diagrams showing molecular orientation in a liquid crystal layer containing a chiral material in a non-driving state and a driving state, respectively, in the liquid crystal display device of FIG.
36A and 36B are diagrams showing the molecular orientation in the liquid crystal layer not including the chiral material in the non-driving state and the driving state, respectively, in the liquid crystal display device of FIG.
FIG. 37 is a view showing viewing angle characteristics when a chiral material is added to the liquid crystal layer in the liquid crystal display device of FIG. 4;
38 is a diagram showing transmittance characteristics when a chiral material is added to the liquid crystal layer in the liquid crystal display device of FIG. 4;
FIG. 39 is a diagram showing transmittance characteristics when no chiral material is added in the liquid crystal layer in the liquid crystal display device of FIG. 4;
40 is a diagram showing viewing angle characteristics when the pretilt angle is set to 90 ° in the liquid crystal display device of FIG. 4; FIG.
41 is a diagram showing viewing angle characteristics when the pretilt angle is set to 85 ° in the liquid crystal display device of FIG. 4; FIG.
42 is a diagram showing viewing angle characteristics when the pretilt angle is set to 80 ° in the liquid crystal display device of FIG. 4; FIG.
43 is a diagram showing viewing angle characteristics when the pretilt angle is set to 75 ° in the liquid crystal display device of FIG. 4. FIG.
FIG. 44 is a diagram showing viewing angle characteristics of a standard TN mode liquid crystal display device.
FIG. 45 is a diagram showing a configuration of a liquid crystal display device according to a first embodiment of the present invention.
46 is a diagram showing viewing angle characteristics of the liquid crystal display device of FIG. 45. FIG.
47 is a diagram showing viewing angle characteristics when a phase difference compensation plate is provided in the liquid crystal display device of FIG. 45. FIG.
FIG. 48 is a diagram showing viewing angle characteristics when the pretilt angle is 75 ° and retardation compensation films are provided above and below the liquid crystal panel in the liquid crystal display device of FIG.
FIG. 49 is a diagram illustrating rising characteristics of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 50 is a diagram illustrating falling characteristics of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 51 is a diagram showing a configuration of a liquid crystal display device according to a third embodiment of the present invention.
52 is a diagram showing the transmittance in the black display state in the liquid crystal display device of FIG. 51. FIG.
FIG. 53 is another diagram showing the transmittance in the black display state in the liquid crystal display device of FIG. 51;
54 is another diagram showing the transmittance in the black display state in the liquid crystal display device of FIG. 51. FIG.
FIG. 55 is another diagram showing the transmittance in the black display state in the liquid crystal display device of FIG. 51.
FIG. 56 is a diagram showing viewing angle characteristics of the liquid crystal display device of FIG.
FIG. 57 is a diagram showing a configuration of a liquid crystal display device according to a fourth embodiment of the present invention.
58 is a view showing viewing angle characteristics of the liquid crystal display device of FIG. 57. FIG.
FIG. 59 is a diagram showing a configuration of a liquid crystal display device according to a fifth embodiment of the present invention.
FIG. 60 is a diagram showing a configuration of a liquid crystal display device according to a sixth embodiment of the present invention.
61 is a diagram showing viewing angle characteristics of the liquid crystal display device of FIG. 60. FIG.
FIG. 62 is a diagram showing a configuration of a liquid crystal display device according to the present invention having a single domain configuration.
FIG. 63 is a view showing a configuration of a liquid crystal display device according to a seventh embodiment of the present invention having a divided alignment configuration.
64 is a diagram showing a modification of the liquid crystal display device of FIG. 63. FIG.
65 is a view showing viewing angle characteristics of the liquid crystal display device of FIG. 64;
66 is a diagram showing a simulation result of viewing angle characteristics of the liquid crystal display device of FIG. 64. FIG.
FIG. 67 is a diagram showing a configuration of a direct view liquid crystal display device using a vertical alignment liquid crystal display device according to the present invention.
FIG. 68 is a view showing viewing angle characteristics of a vertically aligned liquid crystal display device when a chiral material is added according to an eighth embodiment of the present invention.
FIG. 69 is a chromaticity diagram (part 1) showing a coloring characteristic of a vertical alignment liquid crystal display device when a chiral material is added.
FIG. 70 is a chromaticity diagram (part 2) showing the coloring characteristics of the vertical alignment liquid crystal display device when a chiral material is added.
FIG. 71 is a chromaticity diagram (part 3) showing the coloring characteristics of the vertical alignment liquid crystal display device when a chiral material is added;
FIG. 72 is a chromaticity diagram (part 4) showing the coloring characteristics of the vertical alignment liquid crystal display device when a chiral material is added;
FIG. 73 is a chromaticity diagram (No. 5) showing the coloring characteristic of the vertical alignment liquid crystal display device when a chiral material is added.
FIG. 74 is a chromaticity diagram (No. 6) showing the coloring characteristics of the vertical alignment liquid crystal display device when a chiral material is added.
FIG. 75 is a chromaticity diagram (part 7) showing the coloring characteristics of the vertical alignment liquid crystal display device when a chiral material is added.
FIG. 76 is a chromaticity diagram (No. 8) showing the coloring characteristics of the vertical alignment liquid crystal display device when a chiral material is added.
FIG. 77
It is a figure which shows the combination of preferable twist angle and cell thickness.
FIG. 78
It is a figure which shows the viewing angle characteristic of the liquid crystal display device by the modification of 8th Example.
FIG. 79
FIG. 79 is a chromaticity diagram illustrating coloring characteristics of the liquid crystal display device of FIG. 78.
FIG. 80
It is a figure which shows the viewing angle characteristic of the conventional TN type | mold liquid crystal display device.
FIG. 81
FIG. 81 is a chromaticity diagram showing coloring characteristics of the conventional TN liquid crystal display device of FIG.
[Explanation of symbols]
10, 20, 30, 40, 50, 60, 70 Liquid crystal display device
11, 31 LCD panel
11A, 11B, 31A, 31B Glass substrate
12, 32 liquid crystal layer
13A, 13B, 33A, 33B Polarizing plate
14A, 14B, 34A, 34B, (34A) 1, (34B) 1, (34A) 2, (32B) 2 retardation compensation film
31a, 31b molecular alignment film
31a ', 31b' (31a ') PIXEL electrode
(31a ') TFT TFT
31c spacer
100 Direct-view liquid crystal display device
101 Vertical alignment liquid crystal display device
102 pixels
103 Surface light source
104 Light source
106 line light source

Claims (1)

First and second substrates that are substantially parallel and opposite each other; first electrode means formed on a first major surface of the first substrate facing the second substrate; A second electrode means formed on a second main surface of the second substrate facing the first substrate; on the first main surface of the first substrate; A first molecular alignment film covering the electrode means; a second molecular alignment film covering the second electrode means on the second main surface of the second substrate; and the first and second films In a liquid crystal display device including a liquid crystal layer made of liquid crystal molecules having negative dielectric anisotropy enclosed between substrates,
The retardation Δn · d of the liquid crystal layer is expressed by the formula where the twist angle of the liquid crystal molecules in the liquid crystal layer is Ψ.
(90 + Ψ) / 549 ≦ Δn · d ≦ (180 + Ψ) / 549
In the range represented by
The retardation Δn · d is :
Δn · d ≦ 0.4μm
In the range of
The liquid crystal layer has a cell thickness of less than 5 μm;
The liquid crystal display device, wherein the twist angle Ψ satisfies a relationship of 0 <Ψ <90 °.

Images