JP3710722B2 - Reflective liquid crystal display - Google Patents

Description

【００４１】
の式を満たすものであり、上記円偏光手段は、光学位相差補償板を用いたものであり、上記光学位相差補償板は、液晶層への入射光が円偏光になる条件から、液晶層に電圧が印加された状態で生じる残留位相差をキャンセルする分だけ変更された条件に設定して暗状態とすることを特徴としている。
【００４２】
また、本願発明のさらに他の反射型液晶表示装置は、少なくとも光反射手段を有する第１の基板と光透過性を有する第２の基板とに挟持された液晶層と、自然光から左右廻りいずれかの概ね円偏光を可視波長領域全域において選択的に透過する円偏光手段とを備え、前記円偏光手段に自然光が入射した場合に、概ね円偏光を出射する面が前記液晶層側に設置されるとともに、入射された概ね円偏光は、 白表示を行う場合に、前記第１の基板の面上で、前記自然光のそれぞれの波長に対し任意の方向の直線偏光となるものであると共に、前記液晶は、配向されたネマティック液晶からなり、かつ、正の誘電異方性を有し、前記液晶層の液晶の複屈折率差Δｎと液晶層厚ｄとの積Δｎｄ、および、液晶層ツイスト角φｔｗの値が、
【００４３】
【数４】

【００４４】
の式を満たすものであり、前記円偏光手段は、第１の光学位相差補償板と、基板法線方向のリタデーションが２００ｎｍ以上３６０ｎｍ以下に設定された第２の光学位相差補償板と、直線偏光板とからなり、かつ、前記直線偏光板の透過軸又は吸収軸と前記第１の光学位相差補償板の遅相軸とのなす角度をθ１として前記直線偏光板の透過軸又は吸収軸と前記第２の光学位相差補償板の遅相軸とのなす角度をθ２としたとき｜２×θ２−θ１｜の値が３５度以上５５度以下であり、上記第１の光学位相差補償板の遅相軸の方位が、液晶層の厚さ方向の両端面の中央における液晶配向方向と平行であり、前記第１の光学位相差補償板の基板法線方向のリタデーションが、可視波長領域全域において四分の１波長だけの位相差を与えることのできる１００ｎｍ以上１８０ｎｍ以下のリタデーションより、１０ｎｍから５０ｎｍ小さいリタデーションに設定されていることを特徴としている。
【００４５】
また、本願発明のさらに他の反射型液晶表示装置は、少なくとも光反射手段を有する第１の基板と光透過性を有する第２の基板とに挟持された液晶層と、自然光から左右廻りいずれかの概ね円偏光を可視波長領域全域において選択的に透過する円偏光手段とを備え、前記円偏光手段に自然光が入射した場合に、概ね円偏光を出射する面が前記液晶層側に設置されるとともに、入射された概ね円偏光は、 白表示を行う場合に、前記第１の基板の面上で、前記自然光のそれぞれの波長に対し任意の方向の直線偏光となるものであると共に、前記液晶は、配向されたネマティック液晶からなり、かつ、正の誘電異方性を有し、前記液晶層の液晶の複屈折率差Δｎと液晶層厚ｄとの積Δｎｄ、および、液晶層ツイスト角φｔｗの値が、
【００４６】
【数４】

【００４７】
の式を満たすものであり、前記円偏光手段は、第１の光学位相差補償板と、基板法線方向のリタデーションが２００ｎｍ以上３６０ｎｍ以下に設定された第２の光学位相差補償板と、直線偏光板とからなり、かつ、前記直線偏光板の透過軸又は吸収軸と前記第１の光学位相差補償板の遅相軸とのなす角度をθ１として前記直線偏光板の透過軸又は吸収軸と前記第２の光学位相差補償板の遅相軸とのなす角度をθ２としたとき｜２×θ２−θ１｜の値が３５度以上５５度以下であり、上記第１の光学位相差補償板の遅相軸の方位が、液晶層の厚さ方向の両端面の中央における液晶配向方向と直交し、前記第１の光学位相差補償板の基板法線方向のリタデーションが、可視波長領域全域において四分の１波長だけの位相差を与えることのできる１００ｎｍ以上１８０ｎｍ以下のリタデーションより、１０ｎｍから５０ｎｍ大きいリタデーションに設定されていることを特徴としている。
【００４８】
【発明の実施の形態】
以下、実施の形態および実施例により、本発明をさらに詳細に説明するが、本発明はこれらにより何ら限定されるものではない。
【００４９】
〔発明の第１の実施の形態〕
以下に、本発明の実施の一形態について、図面を参照して説明する。
【００５０】
図１は、本発明による実施形態の反射型液晶表示装置の概略構成を示す要部断面図である。図１に示すように、この反射型液晶表示装置は、配向処理された配向膜２の形成された基板４と、同様に配向処理された配向膜３の形成された基板５とによって、正の誘電異方性を有するツイストされたねじれネマティック液晶が挟持されてなる液晶層１を備える。そして、下部の基板５上には、光反射膜７が配置されており、その光反射膜７の反射面は反射光の偏光性を保存する程度に滑らかな凹凸形状とすることが好ましい。さらに、その滑らかな凹凸形状は、光反射膜７の反射面で、方向によって異なる凹凸周期のものが好ましい。
【００５１】
上部の基板４には透明電極６が形成され、下部の基板５上の光反射膜７が導電性材料により形成され電極の機能も果たし、これら透明電極６と光反射膜７とによって液晶層１に電圧が印加される。このように構成された電極対への電圧印加手段として、アクティブ素子等が用いられてもよいが、特には限定しない。なお、光反射膜７が電極として機能しないものを用いた場合には、基板５側に別途電極を設ければ良い。
【００５２】
そして、このように基板４，５及び液晶層１から構成される液晶駆動セルの基板４側の表示面上には、自然光から左右廻りいずれかの円偏光を選択的に透過する円偏光手段１００が備えられている。本実施形態においてこの円偏光手段１００は、基板４側の表示面上にこの順に積層配置された、光学位相差補償板８、光学位相差補償板９、及び偏光板１０から構成される。
【００５３】
以下、光学位相差補償板８、光学位相差補償板９、及び偏光板１０の各光学素子の光学特性とその作用について説明する。
【００５４】
本実施形態の反射型液晶表示装置は、液晶層１に偏光板１０を通して外光等の照明光が入射され、照明光が入射された偏光板１０側から観察されるものである。この偏光板１０によって特定の方位の直線偏光成分のみが選択的に透過され、その入射直線偏光は光学位相差補償板９と光学位相差補償板８とによって偏光状態が変更される。
【００５５】
ここで、光学位相差補償板８の基板法線方向のリタデーションが１００ｎｍ以上１８０ｎｍ以下であり、光学位相差補償板９の基板法線方向のリタデーションが２００ｎｍ以上３６０ｎｍ以下であり、かつ、偏光板１０の透過軸又は吸収軸と光学位相差補償板８の遅相軸とのなす角度をθ１として偏光板１０の透過軸又は吸収軸と第２の光学位相差補償板９の遅相軸とのなす角度をθ２としたとき｜２×θ２−θ１｜の値が３５度以上５５度以下とすると、光学位相差補償板８を通過した後の入射光は概ね円偏光になる。このとき、左右のどちらの円偏光になるかはこれらの３つの光学素子（光学位相差補償板８，光学位相差補償板９，偏光板１０）の配置に依存する。
【００５６】
このことについて、一例として図２に示すように配置した場合について、より詳細に説明する。ただし、この例では、反射型液晶表示装置の入射光の方位から観察したものである。図２に示すように、偏光板１０の透過軸を１１、光学位相差補償板８の遅相軸を１３、光学位相差補償板９の遅相軸を１２とし、偏光板１０の透過軸１１と光学位相差補償板８の遅相軸１３とのなす角度をθ１、偏光板１０の透過軸１１と光学位相差補償板９の遅相軸１２とのなす角度をθ２とし、それぞれが、θ１＝７５°、θ２＝１５°になるように配置すると、液晶表示装置に入射した光は偏光板１０と光学位相差補償板９および光学位相差補償板８を通過して、入射光は概ね右回り円偏光に近い偏光になる。
【００５７】
そして、液晶層１に入射された入射光は、印加された電圧に対応して配列した液晶層１の捩じれた複屈折媒体（液晶）による偏光変換作用にしたがって偏光状態を変化させて反射板に到達する。このとき、光反射膜７上での偏光状態は液晶分子の配向によって異なる状態に実現される。
【００５８】
まず、暗状態について説明する。電圧印加時に液晶分子の配向状態が電圧印加方向に並び、装置の法線方向に進む光に対して偏光変換作用を持たない場合には、円偏光になった入射光は偏光の変化を伴わずに光反射膜７に到達するので、暗状態が実現される。この暗状態を可視波長領域全域で成立させることができれば、黒表示が実現されることになる。
【００５９】
これに近い偏光状態を、実質的に可視波長領域で準備するために、本願発明者らは次のような条件が必要であることを見出した。すなわち、光学位相差補償板８は、主たる可視波長である４００ｎｍから７００ｎｍの光に対して四分の１波長だけの位相差を与えることのできる位相差、つまり波長５５０ｎｍの光に対するリタデーションで１００ｎｍから１８０ｎｍの特性とする。そして、光学位相差補償板９は、同様の範囲の可視波長に対して二分の１波長だけの位相差を与えることのできる位相差、つまり波長５５０ｎｍの光に対するリタデーションで２００ｎｍから３６０ｎｍの特性とする。
【００６０】
そして、図２に示す偏光板１０と光学位相差補償板８，９の配置では、前述のとおり、θ１＝７５°、θ２＝１５°としたので、｜２×θ２−θ１｜＝４５°なので、下式の条件を満たす。
【００６１】
３５°≦｜２×θ２−θ１｜≦５５°…（１）
この条件を満たす範囲でθ１、θ２の各値を変更可能であることは言うまでもないが、その具体的な値は、用いる光学位相差補償板８，９の２枚の複屈折の波長分散の組み合わせによって決定するのが望ましい。また、式（１）の角度設定によると、｜２×θ２−θ１｜の値の範囲が２０度あるが、この範囲でどの値を取るのが良いかは、さらに、液晶層１に電圧を印加した場合の液晶層１の偏光変換作用に依存している。すなわち、光学位相差補償板８，９と液晶層１の複屈折を含めて、光反射膜７上で円偏光になるように設定するのが望ましい。このとき、十分に電圧を印加した状態の液晶層１の偏光変換作用は、液晶層１の作製精度に大きくは依存しないため、液晶層１の作製・製造が容易である。
【００６２】
次に、明状態の作用について説明する。前述の式（１）のように設定された光学位相差補償板８，９によって、概ね円偏光になっている入射光を光反射膜７上で直線偏光にすることによって明状態が実現されるが、このときの直線偏光の光電界の振動方位は、光反射膜７平面内で任意である。つまり、可視波長の光が、波長によって異なる方位の直線偏光になっていても、あるいはすべて同じ方位の直線偏光になっていても、同様に明るい明状態が実現される。
【００６３】
これにより、上記明状態を実現するために概ね円偏光にした液晶層１への入射光を、可視波長範囲で任意の方位の直線偏光にするような液晶層１の光学的作用を実現することが肝要である。
【００６４】
液晶層１が作製及び製造の容易な上記の電気的駆動を考慮すると、暗状態が電圧印加状態により実現されるので、明状態は、電圧の印加されていない状態にて実現するか、もしくは、電圧によって液晶分子の配向状態が変化しているが暗状態とは大きく異なる配向の状態で実現することが必要である。
【００６５】
鋭意検討を重ねた結果、本願発明者らは、明状態の作用を実用上十分な範囲、つまり、可視波長域での十分な明度が確保でき、かつ、容易かつ高歩留まりに製造可能な液晶表示装置に適する液晶組成物の開発が可能な範囲を見出した。
【００６６】
その具体的条件は、液晶層１のねじれネマティック液晶のツイスト角が４５度以上１００度以下とすることである。そして、その液晶の複屈折率差Δｎと液晶層１の厚さｄとの積のΔｎｄ値で１５０ｎｍ以上３５０ｎｍ以下の範囲とすることである。
【００６７】
ここで、より好ましくは、ツイスト角は６０度以上１００度以下、かつ、液晶層１の液晶の複屈折率差Δｎと液晶層１の厚さｄとの積のΔｎｄ値が２５０ｎｍ以上３００ｎｍ以下の範囲であり、さらに好ましくは、ツイスト角は６５度以上９０度以下、かつ、液晶層１の液晶の複屈折率差Δｎと液晶層１の厚さｄとの積のΔｎｄ値が２５０ｎｍ以上３００ｎｍ以下の範囲である。このさらに好ましい範囲の条件は、たとえば液晶層１の厚みを４．５μｍに設定する液晶表示装置の作製条件を用いても、液晶層１のΔｎは０．０６６７程度の実用的な液晶材料によって実現可能であり、高い実用性の液晶表示装置が製造できる。
【００６８】
以下、本実施の形態に係る具体的な実施例を以下に示す。
【００６９】
〔実施例１〕
まずは、実施例１として、液晶層の光学的な作用を考慮した具体的な設計を行うために、本願発明者らが、計算によって液晶層の設定を検討した経緯を説明する。まず、液晶層の設定の最適化にあたり、式（２）に示す評価関数を用いて液晶層の設定を検討した。
【００７０】
【数１】

【００７１】
ここで、ｓ₃ は、偏光状態を指定するストークスパラメータであり、液晶層を一度だけ透過する光の、反射面上の偏光状態に関するストークスパラメータである。なお、ストークスパラメータは、ここでは規格化されたものを用いている。
【００７２】
偏光状態が記述できる完全偏光は、光の強度を規格化した場合、３つの成分を有するストークスパラメータで偏光状態が記述でき、互いに４５度振動面の異なった直線偏光を表すｓ₁ およびｓ₂ と、円偏光成分を表すｓ₃ によって指定される。ｓ₁ ，ｓ₂ ，ｓ₃ は、−１以上１以下の値を取り、特にｓ₃ は、円偏光の場合には±１、直線偏光の場合には０、楕円偏光の場合にはこれらの中間の値を取る。
【００７３】
即ち、評価関数ｆは、ｓ₃ を二乗することにより偏光の回転方向に関係なく、反射面上での偏光状態によって、円偏光になる場合はｆ＝０、楕円偏光になる場合は０＜ｆ＜１、直線偏光になる場合はｆ＝１に分類できる。
【００７４】
本願発明者らは、１枚の偏光板と鏡面反射を示す反射面によって挟まれた任意の複屈折媒体に偏光板側から光が入射した場合、反射板上でｆ＝０（円偏光）の時には、反射した光は、入射時に通過した偏光板によってすべて吸収され、ｆ＝１の場合には、該偏光板によって吸収されることなく通過できることを、解析的な検討によって確認している。評価関数ｆがこの中間の値をとる場合には、反射光の一部は偏光板によって吸収され、残りの反射光は偏光板を透過し、中間の反射率の表示となる。
【００７５】
さらに、上記の評価関数ｆが、このような１枚の偏光板を用いて反射板で入射光を反射させる反射型液晶表示装置の反射率に比例し、１枚偏光板方式の反射率が評価できることを見出している。従って、この評価関数ｆによって、明表示において良好な明るさが得られるかどうかと、良好な暗状態が得られるかどうかとを共に評価することが可能である。
【００７６】
このように、評価関数ｆによって、表示性能が予測可能であることから、１枚偏光板方式の最も良好な性能が期待できる液晶表示方式を鋭意検討した。次にその具体的な手法について説明する。
【００７７】
まず、液晶表示装置を作製するに当たり、量産性に関する考察を行った。特に、液晶表示装置の光学特性を決定する液晶層厚の保持精度が、量産性に大きな影響を与えるため、これに関して考察を行った。
【００７８】
この液晶層厚の保持方法としては、液晶層を挟持する基板の間に一定の粒径で作製された球状スペーサーを設ける方法が最も精度と実用性のバランスが優れている。しかし、この方法によっても、量産工程において高い精度を要求することは量産コストの上昇を招く。このことから、液晶層厚の精度が必要でない方法を検討することが産業上重要である。
【００７９】
また、作製された液晶表示装置の表示品位に関しては、人の視覚の特徴を考慮することが重要である。即ち、人の視覚は、実際に眼球の網膜を刺激する光の強度と認知される明度とは比例関係にはなく、非線型特性を有していることが知られている。つまり、表示装置の光強度の一定量の変動に対しても、同時に網膜に加わっている刺激の強弱によって小さな明度の変動のように感じられたり（背景が強い刺激の場合）、大きな明度の変調に感じられたり（背景が弱い刺激の場合）する。このような視覚の非線型特性を考慮すると、反射率のムラが同程度であっても、それが明表示に生じる場合に比較して、暗表示に生じる場合のほうが、表示品位の低下が大きい。
【００８０】
このことから、反射率のむらが大きい状態と小さい状態が存在する場合には、反射率のむらが小さい状態を暗表示に割り当て、反射率のむらが大きい状態を明表示に割り当てることが、良好な表示品位の液晶表示素子を作製する点から望ましい。
【００８１】
さらに、液晶層に十分に電圧を印加して偏光変換作用が消失した場合のほうが、液晶層厚のむらが偏光変換作用の大きな変動になり難い。
【００８２】
以上の３点を考慮し、電圧が充分に加えられた配向状態を暗表示に割り当てることによって、良好な表示が得られることが考察される。つまり、液晶に電圧が印加されていない状態を明表示に設定し、電圧を印加した場合を暗表示に設定すること、いわゆるノーマリーホワイト表示が望ましい。
【００８３】
次に、この設定を実現する光学位相差補償板の設定と液晶層部分の設定に関して、評価関数ｆに基づいて説明する。
【００８４】
まず、液晶層に十分に電圧が印加された場合に関しては、液晶層には偏光変換作用が無い。光学位相差補償板に必要な特性は、そのような液晶層を通過して反射板上に到達した反射板上で、円偏光にする特性である。ここに、円偏光の回転方向は、どちらであってもよい。
【００８５】
光学位相差補償板に関する前述の設定によって、広い波長帯域でこの特性を実現可能である。このとき、液晶の偏光変換作用が消失しているため、評価関数ｆは０となり、良好な暗状態になる。
【００８６】
一方、液晶層に電圧が印加されない場合において、十分な反射明度が得られる条件を検討するためには、このような円偏光を生じる光学位相差補償板の設定において、この評価関数ｆを評価する必要がある。本願発明者らは、液晶層に電圧が印加されない状態で、液晶層が一様にツイストした配向に対して評価関数ｆを求めた。その結果、液晶に円偏光が入射した場合には、評価関数ｆは、式（３）となることが、Jones Matrix 法によってｓ₃ を解析的に計算することによって明らかとなった。
【００８７】
【数２】

【００８８】
図３に、視感度が最も高い波長（λ＝５５０ｎｍ）での評価関数ｆの値を、液晶層の設計パラメータであるΔｎｄとツイスト角に関して、等値線図にして示す。なお、ツイスト角Φtwに関して、ｆが偶関数であることから、ツイスト角は正の値についてのみｆを記載しているが、実際の液晶配向の捩じれ方向が左右どちらであっても良いことは言うまでもない。
【００８９】
図３は、単一波長（５５０ｎｍ）での値であるが、可視波長である３８０ｎｍから７８０ｎｍの波長に関しても、同様の方法で評価できる。すなわち、５５０ｎｍ以外の波長の入射光に対しては、評価関数ｆの変数のうちΔｎとλのみが変更されることを考慮すればよい。
【００９０】
このように波長によって視覚の感度が異なる効果を考慮して、視感度と標準的な照明光源を仮定してｆとの重なり積分をとることにより、さらに精密な最適化が可能になる。つまり、前述の式（３）に、視感度曲線（ＣＩＥ１９３１等色関数のｙ_BAR （λ））およびＤ６５標準光源のスペクトル密度Ｓ_D65(λ) を用いて、式（４）と定義することが有効である。
【００９１】
【数３】

【００９２】
ここに、ｆ（λ) は、式（３）によって計算されるが、波長λに依存した値を持つことを明示している。
【００９３】
このように定義されたｆvis を、図３と同様にΔｎｄおよびツイスト角に対して計算したものが、図４である。ここで、Δｎの波長分散を考慮した計算をしており、縦軸のΔｎｄは、５５０ｎｍの波長の光における値である。
【００９４】
さらに、式（２）による評価関数ｆが表示の反射率に比例した値を示すため、式（４）の等色関数ｙ_BAR （λ）をＣＩＥ１９３１に同様に規定されているｘ_BAR （λ）、ｚ_BAR （λ）に変更することによって、色度の計算が可能になる。これより、Ｄ６５光源での色度（ｘ，ｙ）を図４と同様のパラメータに対して計算を行った。この結果をｘ、ｙそれぞれ図５、図６に示す。
【００９５】
以上のような検討によって、十分な視感反射率（ｆvis が０．７以上）で、白表示における良好な色相（ｘが０．２７以上０．３５以下で、かつｙが０．２８以上０．３６以下）の条件を設定し、これに適うΔｎｄとツイスト色の範囲を求めた。この結果を図７に示す。図７より、良好なホワイトバランスと反射率が得られる領域は、ツイスト角が０度より大きく１００度以下の領域であることが分かる。また、この良好な領域は、液晶の屈折率差Δｎと液晶層厚ｄとの積であるΔｎｄの下限が８５ｎｍ以上であることが分かる。また、この良好な領域は、Δｎｄの上限が３１５ｎｍ以下であることが分かる。
【００９６】
以上のように、十分な明度と色相を得るために必要な液晶層のパラメータの範囲が定まるが、液晶層の設定には、更に、液晶材料と液晶層厚の設定による制限も存在する。このため、図７の斜線に示した範囲のすべてが実用的とは限らない。また、この範囲から若干外れた範囲であっても良好な条件が存在する。この点に関して、更に詳細に説明する。
【００９７】
液晶材料の光学的な物性値であるΔｎと、液晶材料の使用可能な温度範囲には、一定の相関があることが知られている。すなわち、実用に付される液晶材料は、一般に複数の化合物のブレンドによって必要な特性に調整されるが、この際のブレンド比率を変更してΔｎを小さくすると、ネマティック相の得られる温度範囲が狭くなる。このような場合、液晶表示装置の使用温度範囲や、保存温度範囲を著しく狭める困難がある。つまり、ネマティック相が安定して得られる温度範囲の観点から、液晶材料Δｎには、下限が存在する。このような理由により、室温におけるΔｎは、必要な温度範囲等に依存するものの、概ね0.０５以上、望ましくは0.０６５以上の値が要求される。
【００９８】
また、液晶層の層厚は、液晶表示装置の作製工程の異物等に起因する不良発生率の問題や、液晶を駆動するための素子の作製段差、用いる基板の平面度等から制限がある。さらに、本願発明の一部の構成に用いる場合には、液晶層に近接して配置される凹凸拡散反射板の凹凸形状の点からも制限がある。
【００９９】
液晶層の層厚としては、透過型液晶表示装置の場合には、概ね５μｍ前後の値が用いられており、生産技術が確立している。しかし、液晶層の層厚をこれよりも著しく小さくすることは、多大な困難を伴い、実用性に乏しい。これにより、液晶層厚は、概ね３μｍ以上、望ましくは４μｍ以上にて作製することが有用である。
【０１００】
以上の観点から、液晶の屈折率差Δｎと液晶層厚ｄの積であるΔｎｄの下限を１５０ｎｍ、望ましくは、２６０ｎｍ以上にすることが有用である。
【０１０１】
さらに、実際の液晶表示装置の駆動状態の液晶においては、閾値特性を示す液晶の閾値付近以上の電圧を印加して駆動することが多い。このとき、閾値程度の印加電圧において、液晶は全く電圧が印加されていない状態から若干傾斜しており、この若干傾斜した状態での基板法線方向の屈折率差が、実際の表示に表れる。
【０１０２】
このことから、液晶材料によってきまるΔｎは、この傾斜した液晶に関する実効的なΔｎよりも１０％程度大きな値を取りうる。なお、液晶の閾値以下での表示も可能であるため、このΔｎｄの値の変更をΔｎｄの下限には適用しないのが適当である。
【０１０３】
以上のように、実際の液晶層の設定を用いた具体的な計算を行い、１枚偏光板方式の反射型液晶表示装置においては、Δｎｄを１５０ｎｍからΔｎｄの上限を３５０ｎｍに、液晶のツイスト角を４５度から１００度に設定することが有効であることを見出した。
【０１０４】
〔実施例２〕
実施例２では、前述の図１に示した構造を有する反射型液晶表示装置を、表１に記載のパラメータにて作製し、５つのサンプル♯２ａ〜♯２ｆを得た。
【０１０５】
【表１】

【０１０６】
各サンプルの表示結果の概略を表２に示す。
【０１０７】
【表２】

【０１０８】
なお、Ｖｔｈは、各サンプルにおける液晶層１の配向変化が見られる閾値電圧であり、異なるΔｎｄに設定されるために、異なった値をとっている。
【０１０９】
以上に示したように、パラメータが本発明の反射型液晶表示装置の範囲に入るサンプル♯２ａ，♯２ｂにおいては、実際に使用する電圧であるＶｔｈから３．０×Ｖｔｈにおいて、白表示から黒表示へと表示が変化した。これに対し、パラメータが本発明の反射型液晶表示装置の範囲に入らないサンプル♯２ｃ〜♯２ｆにおいては、表示が暗かったり（サンプル♯２ｃ，♯２ｆ）、表示に着色が見られた（サンプル♯２ｄ，♯２ｅ）。
【０１１０】
表２に示した表示の概略は、偏光板１０と光学位相差補償板８，９の相対角度（θ１、θ２）を変更せずに、液晶配向との方向の設定θ３を変更しただけでは、サンプル♯２ａ〜♯２ｆに見られるような大きな特性変動は観察されず、むしろ液晶層１部分の設定に依存していることを確認している。
【０１１１】
また、液晶に対して逆周りの円偏光が入射するような設定（つまり、θ１とθ２に共通に９０度を加える、あるいは、θ１とθ２を共に符号を逆転させる）、同じ方向の円偏光が得られる別の設定（つまり、θ１とθ２ともに、符号を反転し９０度を加える）のような組合わせのすべてにおいて、表２と同様な表示となった。
【０１１２】
以上のように、液晶層１の液晶の複屈折率差と液晶層厚との積が１５０ｎｍ以上３５０ｎｍ以下であり、かつ、該液晶層のツイスト角が４５度から１００度の範囲であるように液晶層１を設定することにより、良好な表示が実現し、その範囲に限定されることが示された。
【０１１３】
さらに好ましい表示が得られるような条件を検討し、最適化を行った例を、次の実施例３、実施例４に示す。
【０１１４】
〔実施例３〕
実施例３として、ねじれネマティック液晶のツイスト角を９０度に設定した液晶層に、リタデーションが１３５ｎｍと２７０ｎｍの光学位相差補償板をそれぞれ１枚用いた例を示す。
【０１１５】
実施例３では、前述の図１に示した構造を有する反射型液晶表示装置を作製した。基板５上の光反射膜７は、アルミニウムを用い、光反射性電極とした。また、液晶駆動セルは、液晶導入後に液晶層１の厚さが４．２μｍになるよう調整された９０度にツイストされた液晶層１とし、導入した液晶材料は通常のＴＦＴ透過型液晶ディスプレイに使用されている液晶と同様の液晶物性（誘電異方性、弾性、粘性、ネマティック温度範囲、電圧保持特性）を有していて、Δｎだけが０．０６５に調整されたものを用いた。ここで、液晶層１の厚さと液晶の複屈折率差との積を２７３ｎｍになるように設定した。
【０１１６】
本実施例の偏光板１０、光学位相差補償板８、及び光学位相差補償板９の配置は、図８に示すように設定した。なお、図８において、１１は偏光板１０の透過軸方位、１２は光学位相差補償板９の遅相軸方位、１３は光学位相差補償板８の遅相軸方位、１４は基板４上に形成された配向膜２に接触する即ち配向膜２近傍の液晶分子の配向の方位、１５は基板５上に形成された配向膜３に接触する即ち配向膜３近傍の液晶分子の配向の方位をそれぞれ示し、この図は液晶表示装置の入射光の方位から観察したものである。
【０１１７】
そして、これらの配置関係は、図８に示すように、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、基板４上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１とのなす角度θ３を３０°としたものである。
【０１１８】
光学位相差補償板８と光学位相差補償板９とは、ともにポリビニールアルコール製の延伸フィルムからなり、光学位相差補償板８は波長５５０ｎｍの面法線方向の透過光に対して１３０ｎｍから１４０ｎｍに制御された位相差を持ち、光学位相差補償板９は同様の光に対して２６５ｎｍから２７５ｎｍに制御された位相差を持つ。
【０１１９】
これらの光学位相差補償板８，９の配置は、作製後の液晶表示装置の正面方位に対する光学特性を良好にする配置であるが、液晶層１と共に傾斜方位からの観察による特性を考慮して設計変更も可能である。例えば、図８に示す本実施例の設定角条件を成立させつつ、傾斜方位への通過光に対する光学位相補償板８，９の位相差を変化させる設計としては、光学位相差補償板８，９のうちの少なくとも１枚を二軸性の光学位相差補償板に変更することで可能である。また、前述の式（１）の範囲内で角度設定を変更できることは言うまでもない。
【０１２０】
そして、偏光板１０としては、誘電体多層膜によるＡＲ層を有する単体内部透過率が４５％の偏光板を用いた。
【０１２１】
以上のような構成の反射型液晶表示装置の反射率の電圧依存性を示すグラフを図９に示す。この反射率の測定には、図１０に示すように、本実施例の反射型液晶表示装置に電圧を印加して駆動させた状態で、照明光源装置からの光をハーフミラーを介して基板４側から入射させ、基板５上の光反射膜からの反射光を光検出器にて検出したものである。そして、図９において、反射率１００％は、光学位相差補償板を用いずに、被測定装置と同様の偏光板のみを用いた以外は本実施例と同じ液晶表示装置において、液晶未注入の状態での反射率である。また、反射率は、視感輝度率（Ｙ値）を用いた。
【０１２２】
図９に示す測定結果から、１Ｖ程度以下の低い駆動電圧で、高い反射率が得られたことがわかる。
【０１２３】
〔実施例４〕
実施例４として、ねじれネマティック液晶のツイスト角を７０度に設定した液晶層に、リタデーションが１３５ｎｍと２７０ｎｍの光学位相差補償板をそれぞれ１枚用いた例を示す。
【０１２４】
実施例４では、前述の図１に示した構造を有する反射型液晶表示装置を作製した。基板５上の光反射膜７は、アルミニウムを用い、光反射性電極とした。又、液晶駆動セルは、液晶導入後に液晶層１の厚さが４．５μｍ（サンプル♯４ａ）及び４．２μｍ（サンプル♯４ｂ）になるよう調整された７０度にツイストされた液晶層１とし、導入した液晶材料は通常のＴＦＴ透過型液晶ディスプレイに使用されている液晶と同様の液晶物性（誘電異方性、弾性、ネマティック温度範囲、電圧保持特性）を有していて、Δｎだけが０．０６に調整されたものを用いた。ここで、液晶層１の厚さと液晶の複屈折率差との積を２７０ｎｍ（サンプル♯４ａ）及び２５０ｎｍ（サンプル♯４ｂ）になるように設定した。
【０１２５】
本実施例の偏光板の１０、光学位相差補償板８、および光学位相差補償板９の配置は、図１１に示すように設定した。なお、図１１において、１１は偏光板の透過軸方位、１２は光学位相差補償板９の遅相軸方位、１３は光学位相差補償板８の遅相軸方位、１４は基板４上に形成された配向膜２に接触する即ち配向膜２近傍の液晶分子の配向の方位、１５は基板５上に形成された配向膜３に接触する即ち配向膜３近傍の液晶分子の配向の方位をそれぞれ示し、この図は液晶表示装置の入射光の方位から観察したものである。
【０１２６】
そして、これらの配置関係は、図１１に示すように、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、基板４上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１となす角度θ３を４５°としたものである。
【０１２７】
光学位相差補償板８と光学位相差補償板９とは、ともにポリビニールアルコール製の延伸フィルムからなり、光学位相差補償板８は波長５５０ｎｍの面法線方向の透過光に対して１３０ｎｍから１４０ｎｍに制御された位相差を持ち、光学位相差補償板９は同様の光に対して２６５ｎｍから２７５ｎｍに制御された位相差を持つ。
【０１２８】
これらの光学位相差補償板８、９の配置は、作製後の液晶表示装置の正面方位に対する光学特性を良好にする配置であるが、液晶層１とともに傾斜方位からの観察による特性を考慮して設計変更も可能である。例えば、図１１に示す本実施例の設定角条件を成立させつつ、傾斜方位への透過光に対する光学位相差補償板８、９の位相差を変化させる設計としては、光学位相差補償板８、９のうち少なくとも１枚を二軸性の光学位相差補償板に変更することで可能である。又、前述の式（１）の範囲内で角度設定を変更できることは言うまでもない。
【０１２９】
そして、偏光板１０としては、誘電体多層膜によるＡＲ層を有する単体内部透過率が４５％の偏光板を用いた。
【０１３０】
以上のような構成の反射型液晶表示装置の反射率の電圧依存性は、前述の図９に示すグラフと同じであった。この結果より、１Ｖ程度以下の低い駆動電圧で、高い反射率が得られたことがわかる。なお、この反射率も、上記実施例３と同様に図１０に示す測定光学系の配置にて測定されたもので、１００％は上記実施例３と同様に設定した。
【０１３１】
また、偏光板１０の透過軸と上基板４近傍の液晶の配向方向のなす角θ３の各角度におけるコントラスト、白の色付、黒の色付を表３に示す。
【０１３２】
【表３】

【０１３３】
この結果からθ３は２０度以上７０度以下又は１１０度以上１５０度以下に設定することにより表示品位の高い反射型液晶表示装置を実現できることを確認した。
【０１３４】
〔実施例５〕
実施例５として、ねじれネマティック液晶のツイスト角を７０度に設定した液晶層に、リタデーションが１３５ｎｍと２７０ｎｍの光学位相差補償板をそれぞれ１枚用いた例を示す。
【０１３５】
実施例５では、前述の図１に示した構造を有する反射型液晶表示装置を作製した。基板５上の光反射膜７は、アルミニウムを用い、光反射性電極とした。また、液晶駆動セルは、液晶導入後に液晶層１の厚さが４．５μｍになるよう調整された７０度にツイストされた液晶層１とし、導入した液晶材料は通常のＴＦＴ透過型液晶ディスプレイに使用されている液晶と同様の液晶物性（誘電異方性、弾性、粘性、温度特性、電圧保持特性）を有していて、Δｎだけが０．０６６７に調整されたものを用いた。ここで、液晶層１の厚さと液晶の複屈折率差との積を３００ｎｍになるように設定した。
【０１３６】
本実施例の偏光板１０、光学位相差補償板８、及び光学位相差補償板９の配置は、図１２（ａ），（ｂ）に示すように、２種類の設定をして、２種類のサンプルを作製した。なお、図１２（ａ），（ｂ）において、前述の図８と同様に、１１は偏光板１０の透過軸方位、１２は光学位相差補償板９の遅相軸方位、１３は光学位相差補償板８の遅相軸方位、１４は基板４上に形成された配向膜２に接触する即ち配向膜２近傍の液晶分子の配向の方位、１５は基板５上に形成された配向膜３に接触する即ち配向膜３近傍の液晶分子の配向の方位をそれぞれ示し、この図は液晶表示装置の入射光の方位から観察したものである。
【０１３７】
そして、一つのサンプルでの配置関係は、図１２（ａ）に示すように、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、基板４上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１とのなす角度θ３を４０°としたものであり、このサンプルをサンプル♯５ａとする。
【０１３８】
他方のサンプルでの配置関係は、図１２（ｂ）に示すように、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、基板４上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１とのなす角度θ３を１３０°としたものであり、このサンプルをサンプル♯５ｂとする。すなわち、サンプル♯５ａとサンプル♯５ｂとは、θ３が異なり、θ１及びθ２は同じである。
【０１３９】
なお、これらのサンプル♯５ａ，♯５ｂは、上記実施例３と同様に、光学位相差補償板８，９がともにポリビニールアルコール製の延伸フィルムからなり、光学位相差補償板８が波長５５０ｎｍの面法線方向の透過光に対して１３０ｎｍから１４０ｎｍに制御された位相差を持ち、光学位相差補償板９が同様の光に対して２６５ｎｍから２７５ｎｍに制御された位相差を持つものである。また、偏光板１０には、誘電体多層膜によるＡＲ層を有する単体内部透過率が４５％の偏光板を用いた。
【０１４０】
以上のような構成の反射型液晶表示装置（サンプル♯５ａ，♯５ｂ）の反射率の電圧依存性を示すグラフを図１３に示す。図１３において、曲線１３−１はサンブル♯５ａの測定結果、曲線１３−２はサンプル♯５ｂの測定結果をそれぞれ示す。なお、この反射率は、上記実施例３と同様に図１０に示す測定光学系の配置にて測定されたもので、１００％は上記実施例３と同様に設定した。図１３に示す測定結果から、１．５Ｖ程度以下の低い駆動電圧で、高い反射率が得られたことがわかり、中でも曲線１３−１で示されるサンプル♯５ａの方が高い反射率が得られた。
【０１４１】
また、以上のような実施例５の反射型液晶表示装置（サンプル♯５ａ，♯５ｂ）及び前述の実施例３の反射型液晶表示装置について、電圧反射率特性を調べた結果を表４に示す。
【０１４２】
【表４】

【０１４３】
表４から、いずれにおいても十分な明状態の反射率と、コントラスト比が実現されたことがわかり、目視観察においても良好な反射型液晶表示装置であった。
【０１４４】
なお、表４において、コントラスト比は、明状態の反射率を暗状態の反射率で除して定義したものである。ここで、明状態の印加電圧は、各実施例毎に最も反射率の高い電圧を用い、暗状態は、印加電圧を３Ｖに設定した。
【０１４５】
〔実施例６〕
実施例６として、前述の実施例４と同じ条件で作製された反射型液晶表示装置において、光学位相差補償板８と光学位相差補償板９の波長４５０ｎｍの光に対する屈折率異方性Δｎ（４５０）及び波長６５０ｎｍの光に対する屈折率異方性Δｎ（６５０）と波長５５０ｎｍの光に対する屈折率異方性Δｎ（５５０）の比であるΔｎ（４５０）／Δｎ（５５０）、Δｎ（６５０）／Δｎ（５５０）が、それぞれΔｎ（４５０）／Δｎ（５５０）とΔｎ（６５０）／Δｎ（５５０）の組合せが（１，１）、（１．００３，０．９９３）、（１．００７，０．９８７）、（１．０１，０．９８）、（１．０３，０．９６）、（１．０６，０．９５）、（１．１，０．９３）のときの光学特性を測定した。測定結果を表５に示す。
【０１４６】
【表５】

【０１４７】
この結果から１≦Δｎ（４５０）／Δｎ（５５０）≦１．０６、０．９５≦Δｎ（６５０）／Δｎ（５５０）≦１の関係を満たすように設定することにより表示品位の高い反射型液晶表示装置を実現することができ、さらに１≦Δｎ（４５０）／Δｎ（５５０）≦１．００７、０．９８７≦Δｎ（６５０）／Δｎ（５５０）≦１の関係を満たすように設定することによりさらに表示品位の高い反射型液晶表示装置を実現できることを確認した。
【０１４８】
〔実施例７〕
実施例７として、前述の実施例４と同じ条件で作製された反射型液晶表示装置において、図１４に示す観察方位と表示面の法線とを含む平面内の方位１６と前記第２の基板近傍の液晶分子の方向１４とのなす角θ４の各角度における明るさ、コントラスト、色付き及び総合評価を行った。評価結果を図１５に示す。この結果からθ４が０度以上３０度以下又は１８０度以上２１０度以下に設定することにより、明るさ、コントラスト、無彩色軸からの色差にほぼ優れた表示品位の高い反射型液晶表示装置を実現できることを確認した。
【０１４９】
〔実施例８〕
実施例８では、アクティブマトリクス方式による駆動方式により、滑らかな凹凸を有する光反射膜を用いた例について説明する。
【０１５０】
図１６は、本実施例の反射型液晶表示装置の構成を示す要部断面図である。図１６に示すように、この反射型液晶表示装置１６は、第１の基板５と透明なガラスからなる第２の基板４を備え、第１の基板５上にアクティブ素子としてＴＦＴ素子１７が各画素に形成されている。ＴＦＴ素子１７や駆動用配線（図示せず）上には層間絶縁膜１８が形成され、ＴＦＴ素子１７のドレイン端子（図示せず）と光反射性画素電極１９とはコンタクトホールを介して電気的に接続される。光反射性画素電極１９上には、配向膜３が１００ｎｍの厚さで形成されている。
【０１５１】
ここで、光反射性画素電極１９は、たとえばアルミニウム、ニッケル、クロム、銀や、それを用いた合金などの導電性の金属材料が使用でき、光の反射性を有するものである。そして、光反射性画素電極１９の形状は、コンタクトホールの部分を除くと滑らかな凹凸を有しており、金属反射面が鏡面になることを防止しているものである。
【０１５２】
次に、その形成方法についてさらに詳細に説明する。
【０１５３】
上記のＴＦＴ素子１７および駆動用配線（図示せず）を形成した基板５表面に、感光性樹脂材料からなる大突起２０および小突起２１をそれぞれ多数形成した。これら大突起２０および小突起２１は、底部直径Ｄ１，Ｄ２（図１６参照）の円形のパターンをフォトリソグラフィーの技術によって多数形成したものである。このＤ１，Ｄ２は、それぞれ例えば５μｍと３μｍに設定されている。また、これらの間隔Ｄ３は少なくとも２μｍ以上に設定されている。また、これらの突起の高さは、感光性樹脂材料の形成時の膜厚により制御でき、本実施例では１．５μｍとし、その後の露光工程、焼成工程によって、なだらかな突起に形成した。
【０１５４】
これに次いで、上記突起２０，２１を被覆し、これら突起２０，２１の間の平坦部を埋めるべく、同様の感光性樹脂材料で平滑化膜２２を形成した。このようにして、平滑化膜２２の表面は、突起２０，２１の影響を受けて、滑らかな曲面状に形成され、目的の形状が得られた。なお、上記コンタクトホール部には、突起および平滑化膜２２のどちらも形成されないように作製している。
【０１５５】
以上のような構造のＴＦＴ素子基板２３を作製することにより、光反射性画素電極１９が反射板を兼務して液晶層１の近くに配置されて視差を生じることなく、しかも、液晶層１を通過し光反射性画素電極１９によって反射される光がＴＦＴ素子１７や素子駆動用配線（図示しない）部分のために損なわれることのない、いわゆる開口率の高い明るい反射型液晶表示装置のＴＦＴ素子基板２３を実現した。
【０１５６】
一方、上記ＴＦＴ素子基板２３とともに用いる他方の基板には、反射方式に合わせて、高明度化されたカラーフィルタ２４を配置した。このカラーフィルタ２４には、各画素間に色の混合を防止し、画素電極間の電圧未印加部や電界乱れに伴う暗表示での反射光のもれを防止するブラックマトリクス２５を配している。
【０１５７】
このブラックマトリクス２５は、ここに入射する光がすでに概ね円偏光になっており、ブラックマトリクス２５による反射光は出射時に再度光学位相差補償板の作用を受け偏光板に吸収されるので、低コストの金属膜等を用いてもブラックマトリクス２５が反射光を生じて視認性を悪化させることはなかった。なお、さらに、ブラックマトリクス２５に低反射処理を行うとより高コントラストな表示に好適であることは言うまでもない。
【０１５８】
このカラーフィルタ２４上に、透明電極６としてＩＴＯ(Indium Tin Oxide)をスパッタリングによってマスクデポして、１４０ｎｍ厚の所望のパターンを有するＴＦＴ素子駆動用の光反射性画素電極１９の対向電極６を形成した。そして、その上に配向膜２を形成し、カラーフィルタ基板２６とした。
【０１５９】
なお、透明電極６が１４０ｎｍ厚以外の厚さであっても、入射光が透明電極６の膜厚の干渉効果で液晶層１に到達することなく反射する光は、光学位相差補償板８，９と偏光板１０によって吸収されるので、暗状態には影響なく、視認性を損なわない。
【０１６０】
また、このときに用いられたカラーフィルタ２４は、偏光板を利用した高コントラスト表示モードに適した明度になるように適正に設計され、ブラックマトリクス２５の開口率が９０％の場合に、カラーフィルタ基板２６の透過率がＹ値で５０％であった。
【０１６１】
このように準備されたＴＦＴ素子基板２３とカラーフィルタ基板２６とに、ラビング法によって配向処理を施し、液晶層１の厚さを保持するためのプラスティックスペーサー（図示せず）の散布、周縁部のシール配置工程をへて対向配置し、位置合わせのうえ加圧下にて硬化させて封止し、液晶注入用液晶セルを準構した。そして、液晶層１には、誘電異方性Δεが正である液晶材料を真空注入法にて導入した。以後、液晶表示装置の方位の表現は、装置に正対する観察者の上下左右方向を時計の文字盤の向きで、上方位を１２時方位として記載する。
【０１６２】
上記カラーフィルタ基板２６の液晶層１と反対側には、ポリビニールアルコール製の延伸フィルムからなる光学位相補償板８及び光学位相差補償板９とが設けられ、さらにその上には、偏光板１０が配置されている。
【０１６３】
本実施例の、円偏光板１００を構成する偏光板１０、光学位相差補償板８、及び光学位相差補償板９の配置は、図１７に示すように設定した。なお、図１７において、１１は偏光板１０の透過軸方位、１２は光学位相差補償板９の遅相軸方位、１３は光学位相差補償板８の遅相軸方位、１４はカラーフィルタ基板２６上に形成された配向膜２に接触する即ち配向膜２近傍の液晶分子の配向の方位、１５はＴＦＴ素子基板２３上に形成された配向膜３に接触する即ち配向膜３近傍の液晶分子の配向の方位をそれぞれ示すものである。ここで、カラーフィルタ基板２６上の配向膜２の配向処理方位１４は装置の３時方位になるように作製している。
【０１６４】
そして、これらの配置関係は、図１７に示すように、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、カラーフィルタ基板２６上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１との成す角度θ３を１３０°としたものである。
【０１６５】
また、液晶層１は液晶材料導入後に４．０〜５．０μｍの層厚になるよう調整された液晶層を用い、液晶はΔｎが０．０６６７のものを用い、液晶層厚と複屈折率差の積を概ね３００ｎｍになるように設定した。液晶層１の層厚は、光反射性画素電極１９の凹凸のため、位置によって異なる値をもつ。
【０１６６】
さらに、このようにして作製された液晶表示パネルの周囲に駆動用回路を実装し、反射型液晶表示装置とした。
【０１６７】
本実施例の反射型液晶表示装置では、光反射性画素電極１９が液晶層１の近くに配置されているので、視差がなく、良好な高解像度表示が実現された。反射光は、光反射性画素電極１９に付与した凹凸形状により、観察者の顔が写り込むことがなく、良好な白表示を実現できた。さらに、散乱性を有するものが液晶表示装置の前面に配置されないので、良好な暗状態を示し、それらのため、高コントラスト比の表示となった。
【０１６８】
また、高明度のカラーフィルタ２４を使用したので、偏光板を利用した表示であっても十分な明度が確保でき、暗状態の反射率が低く、この暗状態に選択された色要素による反射光が明状態に選択された色要素の反射光とともに観察されて色純度が悪化することが無い。これにより、高明度のカラーフィルタ２４で彩度が低いにもかかわらず、カラーフィルタ２４の色再現範囲を損なうことのない良好な色再現性であった。
【０１６９】
また、各画素に印加される電圧が暗状態と明状態との中間状態に設定されることによって、中間調の再現にも問題無く、したがって、カラーフィルタ２４の各色の中間色彩の表現にも問題無かった。また、実際の駆動においても応答速度は動画再現に問題無いことを確認した。
【０１７０】
以上のように、多階調表示可能で、動画表示の可能な、良好な色再現範囲を確保した反射型液晶表示装置が実用的な作製法により実現できた。
【０１７１】
〔実施例９〕
実施例９として、面内に異方性を有するような凹凸形状の光反射膜を作製することによって明度の向上を図り、さらにその明度の高い方位に液晶層の傾斜視角の良好な方位を向けた例について説明する。
【０１７２】
実施例９では、実施例８で作製した反射型液晶表示装置の光反射性画素電極１９の凹凸形状を、異なるパターンで作製し、凹凸形状を反射性電極の形成された平面内の方位によって異なるものを作製した。
【０１７３】
本実施例においては、上記条件を満たすパターンのものとして、図１８の要部拡大平面図に示すように、凹凸形状は円形ではなく楕円形で、方向性を有するものを作製した。この凹凸形状の光反射膜のみの光反射板の反射特性を、図１９に示すような測定系の配置で測定した。つまり、図１９に示すように、照明光を３０°傾斜方位から入射させ、光反射板面の法線方位に向かう反射光強度を、その光源を回転させ反射の異方性を測定した。
【０１７４】
その結果は図２０に示すようなものになり、特定の方位からの光を効率よく液晶表示装置正面に向けていることが確認された。ただし、液晶材料の屈折率が空気とは大きく異なっていることを考慮し、測定に際しては光反射板面に屈折率１．５１６のインマージョンオイル（マッチングオイル）を滴下し、その上から透明なガラス板を貼付して測定した。また、測定値は、１００％がＭｇＯの標準拡散板（標準白色板）を同様に測定した場合の値になるよう、換算して得られたものである。図２０において、曲線２０−１は本実施例の異方性拡散性反射板の測定換算値であり、曲線２０−２は実施例８で用いたものと同様の拡散性反射板の同様の測定換算値である。
【０１７５】
この結果、図２０に示すように、本実施例の凹凸形状の平均周期が反射板面内で変化しているような方向性の反射板による曲線２０−１では、照明光の入射方位φの変化に伴って、反射明度（反射光強度）が大きく変化している。これに対して、凹凸形状に異方性がない反射板（実施例８）による曲線２０−２では、その照明光の入射方位φの変化に伴う反射明度（反射光強度）の変化がそれほど大きくない。
【０１７６】
これらのことから、本願発明者らは、反射明度を高めるためには、本実施例にて用いた反射板のように、平均凹凸周期が反射板面内の方位によって変化するような方向性（異方性）が有力な手段となることを見い出したものである。さらに、図２０においてφ＝９０°，２７０°の方位が凹凸形状の平均周期の短い方位であり、このように、平均周期の短い方位からの照明光の反射明度が高いことが確認されたことになる。
【０１７７】
このような特徴を有する光反射板を備えたＴＦＴ素子基板２３と、実施例８と同様に作製されたカラーフィルタ基板２６とに、実施例８と同様の配向膜２，３を形成し配向処理を行って（ツイスト角７０°）、４種類のサンプルを作製した。
【０１７８】
これらのサンプルでは偏光板１０、光学位相差補償板８、及び光学位相差補償板９の配置が異なり、それらの配置は図２１（ａ）〜（ｄ）に示すようなものである。なお、図２１（ａ）〜（ｄ）において、前述の図１７と同様に、１１は偏光板１０の透過軸方位、１２は光学位相差補償板９の遅相軸方位、１３は光学位相差補償板８の遅相軸方位、１４はカラーフィルタ基板２６上に形成された配向膜２に接触する即ち配向膜２近傍の液晶分子の配向の方位、１５はＴＦＴ素子基板２３上に形成された配向膜３に接触する即ち配向膜３近傍の液晶分子の配向の方位をそれぞれ示し、この図は液晶表示装置の入射光の方位から観察したものである。
【０１７９】
すなわち、図２１（ａ）に示すサンプルでの配置関係は、偏光板１０の透過軸方位１１と光学位相差補償板８と遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、カラーフィルタ基板２６上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１とのなす角度θ３を１３０°としたものであり、このサンプルをサンプル♯９ａとする（上記実施例８と同様のもの）。なお、カラーフィルタ基板２６上の液晶分子の配向方向１４を３時方向に平行としている。
【０１８０】
また、図２１（ｂ）に示すサンプルでの配置関係は、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、カラーフィルタ基板２６上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１とのなす角度θ３を１３０°としたものであり、このサンプルをサンプル♯９ｂとする。なお、カラーフィルタ基板２６上の液晶分子の配向方向１４を１２時方向に平行としている。
【０１８１】
また、図２１（ｃ）に示すサンプルでの配置関係は、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、カラーフィルタ基板２６上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１とのなす角度θ３を４０°としたものであり、このサンプルをサンプル♯９ｃとする。なお、カラーフィルタ基板２６上の液晶分子の配向方向１４を３時方向に平行としている。
【０１８２】
また、図２１（ｄ）に示すサンプルでの配置関係は、偏光板１０の透過軸方位１１と光学位相差補償板８の遅相軸方位１３とのなす角度θ１を７５°、偏光板１０の透過軸方位１１と光学位相差補償板９の遅相軸方位１２とのなす角度θ２を１５°、カラーフィルタ基板２６上の液晶分子の配向方向１４と偏光板１０の透過軸方位１１とのなす角度θ３を４０°としたものであり、このサンプルをサンプル♯９ｄとする。なお、カラーフィルタ基板２６上の液晶分子の配向方向１４を１２時方向に平行としている。
【０１８３】
なお、これらのサンプルは、光反射板作製の凹凸形状パターン作製工程以外は上記実施例８と同様に作製されたものである。
【０１８４】
このような凹凸形状の光反射板を持つ各サンプルの反射型液晶表示装置を、目視観察したところ、各サンプル♯９ａ〜♯９ｄにおいて、上記実施例８のものよりさらに正面方向から観察すると明度の高い表示が実現され、異方性凹凸の明度向上効果が発現した。このとき、反射明度が高いのは、１２時方位と６時方位から照明光が入射した場合であった。さらに、正面方位から照明し、傾斜方位からの観察においても、同様に１２時方位と、６時方位で明度が高かった。
【０１８５】
さらに、これらのサンプルの液晶表示装置に正面方位から照明光を入射させ、正面より４５度傾斜したさまざまな方位から観察したところ、サンプル♯９ａとサンプル♯９ｄは、反射明度が高い傾斜方位である６時方位および１２時方位で良好な表示となり、さらにこれらの方位において良好なコントラストの表示が実現し、明度の高い観察方位からは特に傾斜に伴う表示変化は感じられなかった。一方、サンプル♯９ｂとサンプル♯９ｃは、明度の高い方位である６時方位及び１２時方位の表示にコントラスト比の悪化が観察された。
【０１８６】
これは、液晶表示変調層（液晶層１）のもっとも視認性の優れた視野角方位は、異なるθ３の値に対して異なっていることを示している。また、この視認性の良好な方位を上記の光反射板の異方性凹凸形状の明度の高い方位に一致させたサンプル♯９ａ及びサンプル♯９ｄによって、本発明の偏光板と光学位相差補償板と液晶変調層（液晶層）の高いコントラスト比を生かした高品位表示が可能になった。
【０１８７】
なお、本発明の液晶表示装置の主たる使用環境にあわせて本実施例で用いた光反射板の異方性凹凸形状の方位を他の方位に設定することも可能であり、かつ、その場合には液晶配向と偏光板および光学位相差補償板の設定角を同様に高明度な方位に傾斜視野角特性の良好な方位に向けることが同様の効果をもたらすことは言うまでもない。
【０１８８】
〔実施例１０〕
次に、実施例１０として、本発明の反射型液晶表示装置の主な利用分野である携帯機器における情報入力手段としてのタッチパネルを用いたタッチパネル一体型反射型液晶表示装置の実施例について説明する。
【０１８９】
まず、本実施例で用いたタッチパネルの概略構成を、その要部断面図である図２２に示す。図２２に示すように、このタッチパネル３１は、押圧位置検出用の透明電極３０が形成された支持基板２８と、押圧位置検出用の透明電極２９が形成された可動基板２７とが、空隙を介して、透明電極２９，３０が対向するようにして配置されて構成される平面状感圧素子である。なお、可動基板２７および支持基板２８ともに複屈折を持たないものを用いた。
【０１９０】
本実施例の概略構造を図２３の要部断面図に示す。図２３に示すように、本実施例のタッチパネル一体型反射型液晶表示装置は、タッチパネル３１の可動基板２７上に、光学位相差補償板８、光学位相差補償板９、偏光板１０を貼付し、これが上記実施例８の偏光板１０及び光学位相差補償板８，９の貼付されていないものと同様の構造の液晶駆動セルの表示面側に配置されたものである。
【０１９１】
このとき、液晶層１の配向方位と偏光板１０及び光学位相差補償板８，９の配置は前述の図１７に示したと同様のもの（実施例８）であり、また、タッチパネル以外の構成は同様である。なお、タッチパネルの支持基板２８と反射型液晶表示装置のカラーフィルタ基板２６の間隙を一定に保つことによって押圧力伝達防止効果を持たせるべく、空隙３２を設け、押圧力緩衝部材を用いることなく軽量にタッチパネルヘの押圧力がカラーフィルタ基板２６に伝わらないよう構成した。
【０１９２】
また、比較例として、図２４の要部断面図に示すような構造のタッチパネル一体型反射型液晶表示装置を作製した。すなわち、比較例の構造は、上記実施例８の構造のものの偏光板１０の上部に、図２２に示したタッチパネル３１を配置したものである。したがって、本実施例と比較例とにおいて異なる点は、タッチパネル３１の配置位置だけである。
【０１９３】
次に、これら本案施例と比較例との比較を行った。まず、比較例のものでは、タッチパネルでの反射光成分が直接観察されて大きく視認性を劣化させた。この反射光は、押圧位置検出用透明電極２９，３０に挟持された空隙によるものだけではなく、タッチパネル支持基板２８と偏光板１０に挟持された空隙によっても生じていた。
【０１９４】
これに対して、本実施例のものでは、比較例で発生したような反射光成分はまったく観察されず、タッチパネルを用いない場合（実施例８）と同様に、非常に良好な表示を示した。そして、本実施例のものでは、比較例のように、タッチパネルの押圧位置検出用透明電極２９，３０に挟持された空隙によるものも観察されなかった。
【０１９５】
さらに、押圧力伝達防止用空隙３２とタッチパネル支持基板２８との界面、タッチパネル支持基板２８と液晶表示装置のカラーフィルタ基板２６との界面による反射も観察されなかった。したがって、実施例１０によれば、押圧力緩衝部材が不要で軽量で、かつ、表示装置が入力装置の反射防止手段によるところの円偏光状態を有効に表示に利用できる、入力装置（タッチパネル）一体型反射型液晶表示装置が実現できた。
【０１９６】
また、詳細は示さないが、タッチパネル３１の可動基板２７を省略し、光学位相差補償板８の液晶層１側に透明電極２９を直接配置して、より簡便かつ軽量な構成が可能であった。
【０１９７】
〔発明の第２の実施の形態〕
以下に、本発明の実施の他の形態ついて、図面を参照して説明する。
【０１９８】
尚、説明の便宜上、前記実施の形態にて示した部材と同一の機能を有する部材には、同一の符号を付記し、その説明を省略する。
【０１９９】
これまでは、液晶層に電圧を十分に印加した場合に関しては、液晶層に偏光変換作用がなく、このような近似の下に良好な特性が得られた例を記載したが、さらに、液晶に印加される電圧が有限の電圧にとどまることを考慮して、詳細な最適化を行うことが有効である。
【０２００】
つまり、前述の図１を参照して説明すると、液晶に印加される電圧の最大値において黒表示を実現するが、このときの液晶は、全く基板法線方向に向いているのではなく、液晶の配向には基板４，５に平行な成分が残る効果を考慮する。これを考慮した暗表示の条件は、これまでと同様に、液晶に実用上の最大電圧を印加した状態において、偏光板１０から入射した光が、光学位相差補償板８，９と液晶層１を共に通過した段階で円偏光になることである。
【０２０１】
このとき液晶層１には、実用上の最大電圧が印加されているため、ほぼ偏光変換作用が生じない状態になってはいるものの、液晶配向の基板に平行な成分にしたがって若干の偏光変換作用（以後、残留位相差と称する）が残っており、これに合わせて、光学位相差補償板８，９をこれまでの条件から若干変更することによって、実用上の最大電圧で良好な暗表示が実現する。
【０２０２】
一方、このようにして良好な暗表示を実現するように最適化された光学位相差補償板８，９と液晶層１の配向を用いて良好な明表示を得る条件は、同様に、反射板３面上での偏光状態が直線偏光であることであるが、それを実現する液晶層１の設計パラメータは、これまでの液晶の残留複屈折が無視できる程度に十分な電圧が印加可能であった場合に準じている。
【０２０３】
つまり、液晶の残留位相差に合わせて若干の変更を受けた光学位相差補償板８，９を用いた場合、液晶層１の設定は、変更以前の液晶層１の設定から大きくずれることはなく、これまでの設定に基づく探索が可能である。
【０２０４】
図２５に、本実施形態の反射型液晶表示装置の概略構成を示す。図２５に示すように、この反射型液晶表示装置は、前述した実施の形態１の反射型液晶表示装置において、円偏光板１００における光学位相差補償板８と基板４との間に、液晶層１の残留位相差をキャンセルするために第３の光学位相差補償板１０１が配設されている構成である。図２６に、この反射型液晶表示装置における３枚の光学位相差補償板８，９，１０１の配置の一例を示す。
【０２０５】
液晶層１の残留位相差は、液晶層１の設定が本願発明に示したツイスト角の設定の中心付近であるツイスト角７０度付近では、液晶層１の基板４，５の中央の液晶配向方向に平行な遅相軸の複屈折成分が残留する。これをキャンセルするには、この液晶配向と直交した方位に遅相軸を有する光学位相差補償板を第３の光学位相差補償板１０１として配置するのが適している。そのリタデーションの量は、液晶に印加される最大電圧に依存するものの、概ね１０から５０ｎｍ前後にすることで、液晶層１の残留位相差をキャンセルできる。
【０２０６】
続いて、図２５の反射型液晶表示装置に対し、視野角の改善を図り、良好な表示を実現する方法をさらに検討する。
【０２０７】
図２５の反射型液晶表示装置では、実際に駆動される電圧の最大値において良好な暗表示を実現し、これによって良好な表示が得られる方法においては、液晶層１に十分な電圧が印加された状態での液晶の残留複屈折を補償することが有効である。
【０２０８】
このため、液晶層１の残留複屈折を良好にキャンセルできるような観察角度範囲を拡大することにより、視野角の拡大が可能である。これを実現するためには、液晶の配向の立体配置を考慮した光学位相差補償板の使用が有効である。
【０２０９】
図２７に、液晶層１の実駆動状態における立体配向の概略を示す。なお、この図２７は、図２５の反射型液晶表示装置における液晶配向を実際より忠実にしたものである。この状態において、液晶層１を表示面法線方向に通過する光に対しては、通常の平面内に遅相軸方位を有する一軸性の光学位相差補償板で残留複屈折のキャンセルが可能になるが、液晶層１を傾斜して通過する光に関しては、さらに液晶層１の配向の傾斜を考慮した光学位相差補償板の使用が有効である。
【０２１０】
まず、液晶が概ね基板４，５に垂直に配向していることから、液晶層１の屈折率は、基板法線方向の電界に対する成分が大きくなっている。これをキャンセルするには、第３の光学位相差補償板１０１の層厚方向の電界に対する屈折率が小さいような特性を有する光学位相差補償板が有効であり、光学位相差補償板１０１を光学的に１軸性で膜厚方向の電界に対する屈折率が膜面方向よりも小さい光学位相差補償板にすることでこれが実現される。さらに、前述の液晶層の層面内方向の残留位相差をキャンセルさせるべく、光学的に２軸性の屈折率楕円体となっていてもよい。
【０２１１】
また、さらに厳密には、液晶配向が基板４，５に完全には垂直でない点を考慮することが有効である。特に、反射型液晶表示装置に拡散性反射膜や、表示面に対して反射膜が傾斜して配置される場合、より一般的に、光の方位が表示面に関して正反射方向とは異なる方向に変更するような作用を有する反射面を用いた場合には、液晶層１を通過して光反射膜７に達するまでの光路と、光反射膜７から液晶層１を通過する出射時の光路それぞれに対して液晶の残留複屈折をキャンセルさせることが良好な視野角の実現には有効である。
【０２１２】
図２８によって、さらに詳細に説明する。図２８に記載したように、反射型液晶表示装置の正面方向の観察者に対して周囲の照明光Ａが用いられる場合から、照明光Ｂが主に用いられる場合に照明環境が変化する場合を考える。
【０２１３】
このとき、観察者と液晶表示装置の位置が固定されているにもかかわらず、周囲の照明光の変化によって、暗表示の明度や色相が変化してしまう。これは、液晶層１を通過する光路の方向によって、液晶の残留複屈折のキャンセルの程度が変化するためであり、これを防止することによって、更に良好な表示を実現できる。
【０２１４】
〔実施例１１〕
実施例１１として、前述の図２５に示した構成の反射型液晶表示装置を、表６に記載のパラメータにて作製し、２つのサンプル♯１１ａ，♯１１ｂを得た。
【０２１５】
【表６】

【０２１６】
各サンプル♯１１ａ，♯１１ｂの電圧反射率曲線を図２９に記載する。比較のため、実施例３の反射型液晶表示装置の電圧反射率曲線を記載している。
【０２１７】
これから、本実施例のサンプル♯１１ａにおいては、明表示の反射率が若干低下するものの、良好な暗表示が実現していることが分かる。また、サンプル♯１１ｂにおいては、明度の低下もなく、良好な暗表示が実現している。
【０２１８】
ここで、さらに、光学位相差補償板の使用枚数を削減することによって、さらに低コストなこれらの構成例と同様の液晶表示装置を作製することを目的に、光学位相差補償板１０１と光学位相差補償板８の２枚の作用を光学位相差補償板１枚で実現するための検討を行った。
【０２１９】
このとき、２枚の光学位相差補償板が遅相軸を平行に配置して積層されている場合には、それぞれのリタデーションの和のリタデーションを有する１枚の光学位相差補償板によって代替が可能であり、また、２枚の光学位相差補償板が遅相軸を直交に配置して積層されている場合には、それぞれのリタデーションの差のリタデーションを有する１枚の光学位相差補償板によって代替が可能であることを利用した。
【０２２０】
つまり、本実施例のサンプル♯１１ｂにおける光学位相差補償板８と光学位相差補償板１０１は、近接して積層配置され、かつ遅相軸方位が直交して配置されているため、これら２枚の差のリタデーションを有する光学位相差補償板１枚で代替が可能である。つまり、光学位相差補償板８のリタデーションの変更によって、サンプル♯１１ａ，♯１１ｂ等と同様の効果が発現する。
【０２２１】
この効果を確かめるため、さらにサンプル♯１１ｃ，♯１１ｄを作製した。これらの各サンプル♯１１ｃ，♯１１ｄは、前述の実施の形態１の図１と同様の断面構造を有している。各サンプル♯１１ｃ，♯１１ｄにおける光学位相差補償板８，９の配置を、表７に示す。
【０２２２】
【表７】

【０２２３】
各サンプル♯１１ｃ，♯１１ｄにおける電圧反射率曲線は、図２９に示したサンプル♯１１ｂと同様であった。
【０２２４】
これにより、液晶に印加される実用上の最大電圧において、液晶の残留位相差をキャンセルするための第３の光学位相差補償板を追加することによってより良好な特性が実現できることが示された。さらに、２枚の光学位相差補償板を用いる場合にも、リタデーションの調整によって、同様の効果が実現可能であることを確認した。つまり、実施の駆動を考慮した光学位相差補償板の追加や調整を行うことで、より良好な黒表示が実現できることを確認した。
【０２２５】
〔実施例１２〕
実施例１２では、液晶層１の残留複屈折をより多くの方位に関してキャンセル可能となるよう、第３の光学位相差補償板１０１として、光学的に１軸性の傾斜した光軸を有する光学位相差補償板を配置し、図３０に示す構成の反射型液晶表示装置を実現し、これをサンプル♯１２ａとした。また、第３の光学位相差補償板１０１として、２軸性光学位相差補償板を用いた、図３１に示す構成の反射型液晶表示装置を実現し、これをサンプル♯１２ｂとした。
【０２２６】
この例では、光学位相差補償板１０１の屈折率楕円体が基板に対して傾斜していない。
【０２２７】
ここで、図示していないが、光の拡散性を有するように、光反射膜７として、図１６の反射型液晶表示装置と同様の凹凸金属反射板を用いている。
【０２２８】
また、サンプル♯１２ｃとして、光学位相差補償板１０１に正の一軸性の光学位相差補償板を用いた以外は、サンプル♯１２ａ，♯１２ｂと同じ構成を有する反射型液晶表示装置を作製した。
【０２２９】
各サンプル♯１２ａ〜♯１２ｃの光学素子の配置を表８に示す。
【０２３０】
【表８】

【０２３１】
また、各サンプル♯１２ａ〜♯１２ｃの視野角の評価結果を表９に記載する。
【０２３２】
【表９】

【０２３３】
サンプル♯１２ａに用いた光学位相差補償板１０１は、延伸方法の工夫によって屈折率楕円体が傾斜したように作製され、正面方向に透過する光線に対するリタデーションが３０ｎｍ程度になるように作製されている。
【０２３４】
図３０に記載のように、このフィルムは、電界のｚ成分に対する屈折率のみが他のｘおよびｙ成分に対する屈折率よりも小さい負の一軸性を示し、かつ、このｚ方向が平面状フィルムの光学位相差補償板１０１の面の法線方向から傾斜している。このｚ方位が実用上の最大電圧における液晶配向の方位に近くなるように配置され、光学位相差補償板１０１の正面方向の光に対しては、ｘ方向が遅相軸として作用する。
【０２３５】
この光学位相差補償板１０１は、光学機能層の厚みをｄ₁₀₁ とし、図３０記載のｘ、ｙ、ｚ方向の屈折率をそれぞれｎ_x,ｎ_y,ｎ_z として、（ｎ_y −ｎ_z ）ｄ₁₀₁ ＝（ｎ_x −ｎ_z ）ｄ₁₀₁ ＝３００ｎｍであった。
【０２３６】
さらに、液晶層１の立体配向を精密にキャンセルするべく、ネマティック液晶性配向や、ディスコティック液晶性配向を固定化した高分子フィルムを用いてもよいことは言うまでもない。
【０２３７】
サンプル♯１２ｂに用いた光学位相差補償板１０１は、延伸方法の工夫によって2 軸性の屈折率楕円体となるように作製されている。正面方向に透過する光軸に対するリタデーションが３０ｎｍ程度になるように作製されている。
【０２３８】
図３１に記載のように、このフィルムは、電界の各成分に対する屈折率は、大きいものからｘ成分、ｙ成分、ｚ成分となる。また、（ｎ_x −ｎ_y ）ｄ₁₀₁ ＝３０ｎｍ、（ｎ_y −ｎ_z ）ｄ₁₀₁ ＝３００ｎｍであった。
【０２３９】
表９に示したように、明表示はどれも白表示であったが、暗表示は、良好なものから、サンプル♯１２ａ，♯１２ｂ，♯１２ｃとなった。また、全体の評価は、良好なものから、サンプル♯１２ａ，♯１２ｂ，♯１２ｃの順になっていた。これは、白表示においても特性が変動しているが、視覚的な差がないためである。これに対して、黒表示においては、視覚的な差が大きく、全体の評価に影響したためである。
【０２４０】
以上のように、液晶の立体配向を考慮した光学位相差補償板の工夫によって、良好な視野角の液晶表示装置が実現できることを確認した。さらに、光学位相差補償板８および９を２軸性にすることで、より良好な暗状態が実現することを確認している。
【０２４１】
なお、本実施例においても、実施例１１のように、低コスト化のために、光学位相差補償板８と光学位相差補償板１０１の機能を併せもつ位相差フィルムが利用可能であることは言うまでもない。
【０２４２】
以上で説明したように、本発明の反射型液晶表示装置によれば、光反射膜等の光反射板の反射面を液晶層側に設置することができ、良好な暗状態を実現できる。よって、視差のない高コントラストの高精細で動画表示可能な反射型液晶表示装置が実現できる。
【０２４３】
また、本発明のタッチパネル一体型反射型液晶表示装置によれば、上記本発明の反射型液晶表示装置にタッチパネルを付加する場合に、偏光板と２枚の光学位相差補償板と組み合わせたタッチパネルを配置することにより、表示特性に悪影響を及ぼす反射光の発生を防止し、高品位のタッチパネル一体型反射型液晶表示装置が実現できる。
【０２４４】
【発明の効果】
以上説明したように、本発明の反射型液晶表示装置によれば、光反射膜等の光反射板の反射面を液晶層側に設置することができ、良好な暗状態を実現できる。よって、視差のない、高コントラストの高精細で動画表示可能な反射型液晶表示装置が実現できる。
【０２４５】
また、本発明の反射型液晶表示装置に高明度に調整されたカラーフィルタを用いれば、良好な色再現性を有した表示品位の高いカラー表示反射型液晶表示装置を実現することができる。
【０２４６】
さらに、本発明の反射型液晶表示装置によれば、上記円偏光手段として、液晶層への入射光が円偏光になる条件から、液晶層に電圧が印加された状態で生じる残留位相差をキャンセルする分だけ変更された光学位相差補償板を用いたので、液晶層に電圧が印加された状態で生じる残留位相差をキャンセルでき、液晶層に電圧が印加された状態で良好な暗表示を実現できる。
【図面の簡単な説明】
【図１】 図１は、本発明による一実施形態の反射型液晶表示装置の概略構造を示す要部断面図である。
【図２】 図２は、一実施形態の偏光板と２枚の光学位相差補償板との配置の設定方位を示す図である。
【図３】 図３は、実施例１の反射型液晶表示装置における反射率を予測するための評価関数の５５０ｎｍの単色光における数値を等値線図に図示した計算結果グラフである。
【図４】 図４は、実施例１の反射型液晶表示装置における反射率を予測するための評価関数の視感度を考慮した数値を等値線図に図示した計算結果グラフである。
【図５】 図５は、実施例１の反射型液晶表示装置における反射率を予測するための評価関数とＤ６５標準光源スペクトルによって計算されるＣＩＥ１９３１色度座標のｘを等値線図に図示した計算結果グラフである。
【図６】 図６は、実施例１の反射型液晶表示装置における反射率を予測するための評価関数とＤ６５標準光源スペクトルによって計算されるＣＩＥ１９３１色度座標のｙを等値線図に図示した計算結果グラフである。
【図７】 図７は、図４、図５、図６によって良好なホワイトバランスと明度がともに得られる領域を示す図である。
【図８】 図８は、実施例３の反射型液晶表示装置の偏光板と２枚の光学位相差補償板との配置の設定方位を示す図である。
【図９】 図９は、実施例３の反射型液晶表示装置の反射率の電圧依存性の測定値を示す図である。
【図１０】 図１０は、実施例３の反射型液晶表示装置の反射率の電圧依存性を測定した測定光学系を示す配置概念図である。
【図１１】 図１１は、実施例４の反射型液晶表示装置の偏光板と２枚の光学位相差補償板との配置の設定方位を示す図である。
【図１２】 図１２（ａ) 、図１２ (ｂ）はそれぞれ実施例５の反射型液晶表示装置のサンプル♯５ａ，♯５ｂについて、偏光板配置方向と２枚の光学位相差補償板の配置方向と液晶層の液晶配向との設定方位を示す図である。
【図１３】 図１３は、実施例５の反射型液晶表示装置の反射率の電圧依存性の測定値を示す図である。
【図１４】 図１４は、実施例７の上基板近傍の液晶の配向方向と観察方位を含む平面との配置の設定方位を示す図である。
【図１５】 図１５は、実施例７の反射型液晶表示装置をθ４の値を変化させて目視観察した結果を示す表である。
【図１６】 図１６は、実施例８の反射型液晶表示装置の概略構造を示す要部断面図である。
【図１７】 図１７は、実施例８の反射型液晶表示装置の偏光板配置方向と２枚の光学位相差補償板の配置方向と液晶層の液晶配向との設定方位を示す図である。
【図１８】 図１８は、実施例９の反射型液晶表示装置に用いた光反射板の凹凸形状を示す部分拡大平面図である。
【図１９】 図１９は、実施例９の反射性電極（光反射板）の反射特性の測定光学系の測定方位を示す概念図である。
【図２０】 図２０は、図１９の測定系による実施例９の反射性電極（光反射板）の反射特性の測定値を示す図である。
【図２１】 図２１（ａ）ないし図２１（ｄ）はそれぞれ実施例９の反射型液晶表示装置のサンプル♯９ａ，♯９ｂ，♯９ｃ，♯９ｄについて、偏光板配置方向と２枚の光学位相差補償板の配置方向と液晶層の液晶配向との設定方位を示す図である。
【図２２】 図２２は、実施例１０のタッチパネル一体型反射型液晶表示装置に用いたタッチパネルの概略構造を示す要部断面図である。
【図２３】 図２３は、実施例１０のタッチパネル一体型反射型液晶表示装置の概略構造を示す要部断面図である。
【図２４】 図２４は、比較例のタッチパネル一体型反射型液晶表示装置の概略構造を示す要部断面図である。
【図２５】 図２５は、本発明による他の実施形態の反射型液晶表示装置の概略構造を示す要部断面図である。
【図２６】 図２６は、他の実施形態の偏光板と２枚の光学位相差補償板との配置の設定方位を示す図である。
【図２７】 図２７は、反射型液晶表示装置の液晶層の配向の電圧による違いを示す説明図である。
【図２８】 図２８は、反射型液晶表示装置の液晶層の配向の方向と照明方向の関係によって視野角が変化する様子を示す説明図である。
【図２９】 図２９は、実施例１１の反射型液晶表示装置の反射率の電圧依存性の測定値を示す図である。
【図３０】 図３０は、実施例１２のサンプル♯１２ａの構造を示す要部断面図である。
【図３１】 図３１は、実施例１２のサンプル♯１２ｂの構造を示す要部断面図である。
【符号の説明】
１ 液晶層
２，３ 配向膜
４，５ 基板
６ 透明電極
７ 光反射膜
８ 光学位相差補償板
９ 光学位相差補償板
１０ 偏光板
１１ 偏光板の透過軸方位
１２ 光学位相差補償板９の遅相軸方位
１３ 光学位相差補償板８の遅相軸方位
１４ カラーフィルタ上に形成された配向膜近傍の液晶分子の配向の方位
１５ ＴＦＴ素子基板上に形成された配向膜近傍の液晶分子の配向の方位
１６ 反射型液晶表示装置
１９ 光反射性画素電極
２３ ＴＦＴ素子基板
２６ カラーフィルタ基板[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a reflective liquid crystal display device that is used in office automation (OA) devices such as word processors and notebook personal computers, various video devices, game devices, and the like and does not require a direct-view backlight. .
[0002]
[Prior art]
  At present, liquid crystal display devices having features such as thinness and light weight are practically used as color displays. Among the color liquid crystal display devices, a particularly widely used one is a transmissive liquid crystal display device using a light source as a background, and its applications are expanding in various fields due to the above-described features.
[0003]
  On the other hand, in comparison with the transmissive liquid crystal display device, the reflective liquid crystal display device does not require a backlight for display, so that the power of the light source can be reduced and the space and weight of the backlight can be saved. It has the characteristics.
[0004]
  In other words, the reflective liquid crystal display device can achieve a reduction in power consumption and is suitable for a device that is lightweight and thin. As an example, if the device operating time is made the same, not only the space and weight of the backlight can be saved, but also the power consumption is small, so it is possible to use a small battery and make it even smaller Weight reduction is possible. Alternatively, if the devices are made to have the same size or weight, a dramatic increase in operation time can be expected by using a large battery.
[0005]
  In terms of display contrast characteristics, a CRT or the like, which is a light emitting display device, shows a significant decrease in contrast ratio outdoors in the daytime, or a transmissive liquid crystal display device that has been subjected to a low reflection treatment is also subjected to direct sunlight. Similarly, when the ambient light such as lower light is much stronger than the display light, a significant reduction in the contrast ratio cannot be avoided.
[0006]
  On the other hand, the reflective liquid crystal display device can obtain display light proportional to the amount of ambient light, and is particularly suitable for outdoor use such as portable information terminal devices, digital cameras, and portable video cameras.
[0007]
  In spite of having such very promising application fields, sufficient contrast ratio, reflectivity, multicolored color, high-definition display, and support for video, etc. are insufficient, so that it is practical enough A reflective color liquid crystal display device having the above has not been obtained.
[0008]
  Hereinafter, the reflective liquid crystal display device will be described in more detail. A conventional twisted nematic (TN) type liquid crystal element uses two linearly polarizing plates (hereinafter simply referred to as “polarizing plates”), and is excellent in contrast ratio and its viewing angle dependency. The rate is low. In addition, since the distance between the liquid crystal modulation layer and the light reflection layer is separated by the thickness of the substrate or the like, parallax is generated due to the deviation of the optical path between the incident light and the reflected light. For this reason, in particular, in a configuration used for a normal transmissive liquid crystal display in which a color filter having different pixels for each color element is combined in one liquid crystal modulation layer, the light traveling direction is inclined from the substrate normal direction. The color element through which ambient light passes when incident is different from the color element through which the light passes after reflection. In such a case, problems such as moire occur, and it is not suitable for a color high-resolution and high-definition display device.
[0009]
  For these reasons, the reflective color display using this display mode has not been put into practical use.
[0010]
  On the other hand, guest host type liquid crystal elements (hereinafter abbreviated as GH) in which a dye is added to a liquid crystal without using a polarizing plate or by using only one sheet have been developed. And a high contrast ratio cannot be obtained because the dichroic ratio of the dye is low.
[0011]
  Among these, in particular, the lack of contrast greatly reduces the color purity in color display using a color filter, so it must be combined with a color filter having a high color purity. For this reason, there is a problem that the brightness is lowered due to the color filter having a high color purity, and the advantage of the high brightness of the present system due to the absence of the polarizing plate is impaired.
[0012]
  Against this background, a liquid crystal display element of a type using a single polarizing plate (hereinafter referred to as a single polarizing plate method) that can be expected to display with high resolution and high contrast has been developed.
[0013]
  As an example, a reflective TN (45 ° twist type) type liquid crystal display device using one polarizing plate and a quarter wavelength plate is disclosed in Japanese Patent Laid-Open No. 55-48733.
[0014]
  In this liquid crystal display device, by using a liquid crystal layer twisted by 45 ° and controlling the applied electric field, the plane of polarization of incident linearly polarized light differs from the state parallel to the optical axis of the quarter-wave plate by 45 °. Black and white display is performed by realizing two states. This liquid crystal cell is composed of a polarizer, a 45 ° twist liquid crystal cell, a quarter-wave plate, and a reflector from the light incident side.
[0015]
  Further, USP 4,701,028 (Clerc et al.) Discloses a reflective vertical alignment type liquid crystal display device in which one polarizing plate, a quarter wavelength plate and a vertical alignment liquid crystal cell are combined.
[0016]
  The inventors of the present application have applied for a reflective parallel alignment method in which one polarizing plate, a parallel alignment liquid crystal cell, and an optical phase difference compensator are combined (see JP-A-6-167708).
[0017]
  This reflection type liquid crystal display device includes a liquid crystal cell composed of homogeneous (parallel) liquid crystal layers, a reflector (located inside the liquid crystal cell below the liquid crystal layer), a polarizing plate (located above the liquid crystal cell), It comprises a single optical phase difference compensation plate (arranged between the liquid crystal cell and the polarizing plate). In this display mode, the optical path is combined with the incident optical path and the outgoing optical path, and passes through the polarizing plate twice and the transparent electrode, which cannot avoid absorption on the glass substrate (upper substrate) of the liquid crystal cell, only twice. Therefore, a high reflectance can be obtained with the configuration of the reflective liquid crystal display device.
[0018]
  Japanese Patent Application Laid-Open No. 2-236523 discloses a configuration in which a twisted nematic liquid crystal layer is disposed between a reflector (disposed on the inner surface of a liquid crystal cell) and one polarizing plate.
[0019]
  Furthermore, a fourth Asian Symposium on Information Display (Chung-Kuang Wei et al., Proceedings of The Fourth Asian Symposium on Information Display, 1997, p25, hereinafter abbreviated as ASID97) is made of a nematic liquid crystal twisted 90 degrees as a reflector ( And a configuration arranged between a quarter-wave plate and a polarizing plate realizing a wide band.
[0020]
  Japanese Patent Application Laid-Open No. 4-116515 discloses a liquid crystal display device that uses circularly polarized light for display. As a technique for obtaining circularly polarized light in a wide band, Pancharatnam has found that Proc. Ind. Acad. Sci. Vol. XLI, No4. SecA, p130, 1955 use a plurality of optical phase difference compensators.
[0021]
  The display principle of the single polarizing plate system as described in JP-A-6-167708, JP-A-2-236523, ASID97, and JP-A-4-116515 will be described.
[0022]
  The polarizing plate disposed on the incident side has a function of allowing only one direction of the linear components of polarized light of incident light and outgoing light to pass therethrough and absorbing the other direction. The incident light that has passed through the polarizing plate changes its polarization state by an optical phase difference compensation plate such as a λ / 4 plate (in the case of JP-A-6-167708, ASID97) or as it is (in JP-A-2-2). In the case of No. 236523, when the light is incident on the liquid crystal layer and passes through the liquid crystal layer, the polarization state further changes and reaches the reflector.
[0023]
  Furthermore, the light that has reached the reflecting plate passes through the liquid crystal layer, the λ / 4 plate, etc. while the polarization state changes in the reverse order to that of the incident light. The ratio determines the reflectivity of the entire liquid crystal layer. That is, it is brightest when the polarization state immediately before passing through the polarizing plate at the time of emission is linearly polarized light in the transmission direction of the polarizing plate, and darkest if it is linearly polarized light in the absorption direction of the polarizing plate.
[0024]
  Necessary and sufficient conditions for realizing these states with respect to light incident and emitted perpendicularly to the liquid crystal display device are linearly polarized light in an arbitrary direction with respect to the bright state. In addition, it is known that, for a dark state, it becomes right or left circularly polarized light on the reflector.
[0025]
  On the other hand, in a portable information device, in addition to a conventionally used keyboard, a touch panel is an effective input means. In particular, in languages that require input from the keyboard, such as Japanese input, the touch panel is not directly used as a pointing device, but as a pointing device, as information processing capabilities become more advanced and software develops. It has become common to use it as an input device such as an input.
[0026]
  In the case of such an input form, an input device is placed on the front surface of the display device. However, since the reflection type liquid crystal display device uses reflected light for display, the means for low reflection processing of the touch panel must not impair the display of the reflection type liquid crystal display device installed below. For example, Japanese Patent Laid-Open No. 5-127822 discloses that a low-reflection process is performed by overlapping a quarter-wave plate and a polarizing plate on a touch panel.
[0027]
[Problems to be solved by the invention]
  However, in the liquid crystal display device described in Japanese Patent Laid-Open No. 55-48733 among the above prior arts, it is necessary to provide a quarter-wave plate between the liquid crystal layer and the reflecting plate. It is difficult to form a reflective film on the inside of the film, which is not suitable for high resolution and high definition display.
[0028]
  Further, the vertical alignment type liquid crystal display device described in USP 4,701,028 has the following problems. First, vertical alignment, in particular tilted vertical alignment, is extremely difficult to control, and in order to realize such control, the configuration becomes complicated and is not suitable for mass production. In addition, the vertical alignment has a drawback that the response speed is slow.
[0029]
  Further, in the reflection type parallel alignment method, coloring occurred due to wavelength dispersion between the liquid crystal cell and the optical retardation compensator. As described above, in the conventional configuration, there is a problem that coloring is easily generated in the dark state, and black and white cannot be realized.
[0030]
  Further, in the configurations of the above-mentioned Japanese Patent Laid-Open Nos. 2-236523 and 4-116515, the reflectance in the bright state is higher than the configuration using two polarizing plates, but the wavelength dependence of the transmittance in the dark state. A good black display is not realized.
[0031]
  In the display mode disclosed in the ASID 97, black-and-white display is possible. However, there is no disclosure about the configuration of a quarter-wave plate manufactured in a wide band in this document.
[0032]
  In addition, according to the report by Pancharatnam, it is necessary to use three optical phase difference compensators in order to obtain good circularly polarized light, which is not practical. Further, a detailed study has not yet been made when this is combined with a liquid crystal display device.
[0033]
  On the other hand, even if the touch panel integrated reflection type liquid crystal display device achieves a practical performance as a reflection type liquid crystal display device, there is a problem that the visibility is extremely deteriorated when the touch panel is arranged.
[0034]
  That is, the light from a light source (for example, a ceiling light) that causes the reflected light of the touch panel to be reduced when the touch panel is arranged in a transmissive liquid crystal display device or other light emitting display devices is removed. In the reflective display device, the same light source causes reflection of the touch panel and serves as the display light source of the display device, as compared with the above that can be easily solved by changing the direction. It cannot be measured properly. For this reason, the solution to the reduction in visibility is the key to realizing a portable information device with practical low power consumption as well as a display device.
[0035]
  Moreover, although the structure of the touch panel shown by Unexamined-Japanese-Patent No. 5-127822 has an effect which prevents reflection by the effect | action of a 1/4 wavelength plate, a normal 1/4 wavelength plate is used for the specific wavelength of visible region. On the other hand, the antireflection function is excellent, but a decrease in antireflection ability is inevitable at wavelengths around that wavelength. Further, the brightness of the display is determined depending on how much the polarization state of the display device installed in the lower part includes the transmitted light component of the circular polarizer obtained by the combination of the quarter wavelength plate and the polarizing plate.
[0036]
  That is, when a display device having substantially no polarization characteristics at the bottom (for example, a white tailor-type guest-host liquid crystal display device in which a dye is mixed in a 360-degree twisted liquid crystal) is used, the reflection efficiency is as follows. Depending on the transmittance, the maximum is ½ when the touch panel is not used. As another example, the same applies to the case where the lower display device uses linearly polarized light for display (for example, a TN type or STN type liquid crystal display device in which a polarizing plate is further provided between the touch panel and the liquid crystal cell). The maximum efficiency is ½ when the touch panel is not used. Furthermore, in this example, since the phase difference of the quarter wavelength plate depends on the wavelength of light, the color tone changes due to the arrangement in which this is sandwiched between polarizing plates. In any case, the brightness is insufficient, and it is not suitable as a combination with a reflection type liquid crystal display device having no brightness improvement means such as background light.
[0037]
  For these reasons, it is necessary to further improve the antireflection function of the touch panel described in JP-A-5-127822. Further, in this publication, external light incident on such a touch panel is applied to the reflective liquid crystal display device. A preferred configuration for use is not disclosed.
[0038]
  SUMMARY OF THE INVENTION An object of the present invention is to provide a reflective liquid crystal display device capable of solving a problem of a single polarizing plate type reflective liquid crystal display device capable of high-resolution display and having a high contrast ratio and easy to see and capable of color display. There is to do.
[0039]
[Means for Solving the Problems]
  The reflective liquid crystal display device of the present invention comprises a liquid crystal layer sandwiched between at least a first substrate having light reflecting means and a second substrate having light transmission, and substantially circularly polarized light that is either left or right from natural light. A circularly polarizing means that selectively transmits in the entire visible wavelength region, and when natural light is incident on the circularly polarizing means, a surface that emits circularly polarized light is disposed on the liquid crystal layer side and is incident on the liquid crystal layer side. In general, circularly polarized light is linearly polarized light in an arbitrary direction with respect to each wavelength of the natural light on the surface of the first substrate when white display is performed, and the liquid crystal is aligned. The liquid crystal layer has a positive dielectric anisotropy and has a liquid crystal layer birefringence difference Δn and a liquid crystal layer thickness d of a product Δnd, and a liquid crystal layer twist angle φtw.
[0040]
[Expression 4]

[0041]
The circularly polarizing means uses an optical retardation compensator, and the optical retardation compensator has a liquid crystal layer from the condition that light incident on the liquid crystal layer becomes circularly polarized. It is characterized in that the dark phase is set by setting the condition changed by the amount that cancels the residual phase difference that occurs in the state where the voltage is applied.
[0042]
  Further, another reflection type liquid crystal display device of the present invention includes a liquid crystal layer sandwiched between at least a first substrate having a light reflecting means and a second substrate having a light transmission property, and either left or right from natural light. And circularly polarized light that selectively transmits substantially circularly polarized light in the entire visible wavelength region, and a surface that emits circularly polarized light when natural light is incident on the circularly polarized light is disposed on the liquid crystal layer side. In addition, the incident substantially circularly polarized light is linearly polarized light in an arbitrary direction with respect to each wavelength of the natural light on the surface of the first substrate when performing white display, and the liquid crystal Is made of oriented nematic liquid crystal and has a positive dielectric anisotropy, the product Δnd of the liquid crystal layer birefringence difference Δn and the liquid crystal layer thickness d, and the liquid crystal layer twist angle φtw. Value of
[0043]
[Expression 4]

[0044]
The circular polarization means includes a first optical phase difference compensation plate, a second optical phase difference compensation plate whose retardation in the substrate normal direction is set to 200 nm or more and 360 nm or less, a straight line A polarizing plate, and the transmission axis or absorption axis of the linear polarizing plate is defined as θ1 as an angle formed between the transmission axis or absorption axis of the linear polarizing plate and the slow axis of the first optical retardation compensator. When the angle formed with the slow axis of the second optical phase difference compensation plate is θ2, the value of | 2 × θ2−θ1 | is not less than 35 degrees and not more than 55 degrees, and the first optical phase difference compensation plate The slow axis direction of the liquid crystal layer is parallel to the liquid crystal alignment direction at the center of both end faces in the thickness direction of the liquid crystal layer, and the retardation in the substrate normal direction of the first optical retardation compensation plate is the entire visible wavelength region. 1 can give a phase difference of only a quarter wavelength in The retardation is set to be 10 nm to 50 nm smaller than the retardation of 00 nm to 180 nm.
[0045]
  Further, another reflection type liquid crystal display device of the present invention includes a liquid crystal layer sandwiched between at least a first substrate having a light reflecting means and a second substrate having a light transmission property, and either left or right from natural light. And circularly polarized light that selectively transmits substantially circularly polarized light in the entire visible wavelength region, and a surface that emits circularly polarized light when natural light is incident on the circularly polarized light is disposed on the liquid crystal layer side. In addition, the incident substantially circularly polarized light is linearly polarized light in an arbitrary direction with respect to each wavelength of the natural light on the surface of the first substrate when performing white display, and the liquid crystal Is made of oriented nematic liquid crystal and has a positive dielectric anisotropy, the product Δnd of the liquid crystal layer birefringence difference Δn and the liquid crystal layer thickness d, and the liquid crystal layer twist angle φtw. Value of
[0046]
[Expression 4]

[0047]
The circular polarization means includes a first optical phase difference compensation plate, a second optical phase difference compensation plate whose retardation in the substrate normal direction is set to 200 nm or more and 360 nm or less, a straight line A polarizing plate, and the transmission axis or absorption axis of the linear polarizing plate is defined as θ1 as an angle formed between the transmission axis or absorption axis of the linear polarizing plate and the slow axis of the first optical retardation compensator. When the angle formed with the slow axis of the second optical phase difference compensation plate is θ2, the value of | 2 × θ2−θ1 | is not less than 35 degrees and not more than 55 degrees, and the first optical phase difference compensation plate The direction of the slow axis of the liquid crystal layer is perpendicular to the liquid crystal alignment direction at the center of both end faces in the thickness direction of the liquid crystal layer, and the retardation in the substrate normal direction of the first optical retardation compensator is in the entire visible wavelength region. 100 that can give a phase difference of only a quarter wavelength It is characterized in that the retardation is set to be 10 nm to 50 nm larger than the retardation of nm to 180 nm.
[0048]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described in more detail with reference to embodiments and examples, but the present invention is not limited thereto.
[0049]
  First Embodiment of the Invention
  Embodiments of the present invention will be described below with reference to the drawings.
[0050]
  FIG. 1 is a cross-sectional view showing the schematic structure of a reflective liquid crystal display device according to an embodiment of the present invention. As shown in FIG. 1, this reflective liquid crystal display device is positive by a substrate 4 on which an alignment film 2 having been subjected to an alignment process is formed and a substrate 5 on which an alignment film 3 having been subjected to an alignment process is formed. A liquid crystal layer 1 is provided in which twisted twisted nematic liquid crystal having dielectric anisotropy is sandwiched. A light reflecting film 7 is disposed on the lower substrate 5, and the reflecting surface of the light reflecting film 7 is preferably smooth and uneven so as to preserve the polarization of the reflected light. Further, it is preferable that the smooth uneven shape is a reflection surface of the light reflecting film 7 and has an uneven period that varies depending on the direction.
[0051]
  A transparent electrode 6 is formed on the upper substrate 4, and a light reflecting film 7 on the lower substrate 5 is formed of a conductive material and also functions as an electrode. The transparent electrode 6 and the light reflecting film 7 form the liquid crystal layer 1. A voltage is applied to. An active element or the like may be used as a means for applying a voltage to the electrode pair configured as described above, but is not particularly limited. When the light reflecting film 7 that does not function as an electrode is used, a separate electrode may be provided on the substrate 5 side.
[0052]
  Then, on the display surface on the substrate 4 side of the liquid crystal driving cell composed of the substrates 4 and 5 and the liquid crystal layer 1 in this way, circularly polarized light means 100 that selectively transmits any circularly polarized light from the natural light to the left and right. Is provided. In the present embodiment, the circularly polarizing means 100 includes an optical phase difference compensation plate 8, an optical phase difference compensation plate 9, and a polarizing plate 10 that are stacked in this order on the display surface on the substrate 4 side.
[0053]
  Hereinafter, the optical characteristics and functions of the optical elements of the optical phase difference compensation plate 8, the optical phase difference compensation plate 9, and the polarizing plate 10 will be described.
[0054]
  In the reflective liquid crystal display device of this embodiment, illumination light such as external light is incident on the liquid crystal layer 1 through the polarizing plate 10 and is observed from the polarizing plate 10 side where the illumination light is incident. Only the linearly polarized light component in a specific direction is selectively transmitted by the polarizing plate 10, and the polarization state of the incident linearly polarized light is changed by the optical phase difference compensating plate 9 and the optical phase difference compensating plate 8.
[0055]
  Here, the retardation in the substrate normal direction of the optical retardation compensation plate 8 is 100 nm or more and 180 nm or less, the retardation in the substrate normal direction of the optical retardation compensation plate 9 is 200 nm or more and 360 nm or less, and the polarizing plate 10 The angle formed between the transmission axis or absorption axis of the optical axis and the slow axis of the optical retardation compensation plate 8 is θ1, and the transmission axis or absorption axis of the polarizing plate 10 and the slow axis of the second optical retardation compensation plate 9 are formed. If the value of | 2 × θ2−θ1 | is 35 ° or more and 55 ° or less when the angle is θ2, the incident light after passing through the optical phase difference compensation plate 8 is substantially circularly polarized. At this time, which of the circularly polarized light is left and right depends on the arrangement of these three optical elements (the optical phase difference compensation plate 8, the optical phase difference compensation plate 9, and the polarizing plate 10).
[0056]
  This will be described in more detail with respect to an arrangement as shown in FIG. 2 as an example. However, in this example, it is observed from the direction of incident light of the reflective liquid crystal display device. As shown in FIG. 2, the transmission axis of the polarizing plate 10 is 11, the slow axis of the optical retardation compensation plate 8 is 13, the slow retardation of the optical retardation compensation plate 9 is 12, and the transmission axis 11 of the polarizing plate 10 is. And the slow axis 13 of the optical retardation compensation plate 8 is θ1, and the angle between the transmission axis 11 of the polarizing plate 10 and the slow axis 12 of the optical retardation compensation plate 9 is θ2, = 75 ° and θ2 = 15 °, the light incident on the liquid crystal display device passes through the polarizing plate 10, the optical phase difference compensation plate 9 and the optical phase difference compensation plate 8, and the incident light is almost right. It becomes polarized light that is close to circularly polarized light.
[0057]
  The incident light incident on the liquid crystal layer 1 changes its polarization state according to the polarization conversion action by the twisted birefringence medium (liquid crystal) of the liquid crystal layer 1 arranged in accordance with the applied voltage, and is applied to the reflector. To reach. At this time, the polarization state on the light reflection film 7 is realized in a different state depending on the orientation of the liquid crystal molecules.
[0058]
  First, the dark state will be described. If the alignment state of the liquid crystal molecules is aligned in the voltage application direction when voltage is applied and does not have a polarization conversion effect on the light traveling in the normal direction of the device, the incident light that is circularly polarized does not change in polarization. Therefore, the dark state is realized. If this dark state can be established over the entire visible wavelength region, black display is realized.
[0059]
  In order to prepare a polarization state close to this in the visible wavelength region, the present inventors have found that the following conditions are necessary. That is, the optical phase difference compensation plate 8 is a retardation that can give a phase difference of only a quarter wavelength to light having a main visible wavelength of 400 nm to 700 nm, that is, retardation from 100 nm to light having a wavelength of 550 nm. The characteristic is 180 nm. The optical phase difference compensation plate 9 has a phase difference that can give a phase difference of a half wavelength with respect to a visible wavelength in the same range, that is, a retardation of 200 nm to 360 nm with respect to light having a wavelength of 550 nm. .
[0060]
  In the arrangement of the polarizing plate 10 and the optical phase difference compensation plates 8 and 9 shown in FIG. 2, since θ1 = 75 ° and θ2 = 15 ° as described above, | 2 × θ2−θ1 | = 45 °. The condition of the following formula is satisfied.
[0061]
  35 ° ≦ | 2 × θ2−θ1 | ≦ 55 ° (1)
  It goes without saying that each value of θ1 and θ2 can be changed within the range satisfying this condition, but the specific value is a combination of the two birefringent wavelength dispersions of the optical retardation compensation plates 8 and 9 to be used. It is desirable to determine by. Further, according to the angle setting of the equation (1), the range of the value of | 2 × θ2−θ1 | is 20 degrees. The value that should be taken within this range is further determined by applying a voltage to the liquid crystal layer 1. It depends on the polarization conversion action of the liquid crystal layer 1 when applied. That is, it is desirable to set so as to be circularly polarized on the light reflection film 7 including the birefringence of the optical phase difference compensation plates 8 and 9 and the liquid crystal layer 1. At this time, the polarization conversion action of the liquid crystal layer 1 in a state where a sufficient voltage is applied does not greatly depend on the production accuracy of the liquid crystal layer 1, so that the production and production of the liquid crystal layer 1 are easy.
[0062]
  Next, the operation in the bright state will be described. A bright state is realized by making incident light, which is substantially circularly polarized, into linearly polarized light on the light reflecting film 7 by the optical phase difference compensating plates 8 and 9 set as in the above-described equation (1). However, the vibration direction of the optical field of linearly polarized light at this time is arbitrary in the plane of the light reflecting film 7. That is, a bright bright state is similarly realized even if light of visible wavelength is linearly polarized light with different orientations depending on the wavelength, or linearly polarized light with all the same orientations.
[0063]
  As a result, the optical action of the liquid crystal layer 1 is realized so that the light incident on the liquid crystal layer 1 that is substantially circularly polarized in order to realize the above-described bright state is converted into linearly polarized light in an arbitrary direction in the visible wavelength range. Is essential.
[0064]
  Considering the above-described electrical drive that the liquid crystal layer 1 is easy to manufacture and manufacture, the dark state is realized by the voltage application state, so the bright state is realized in the state where no voltage is applied, or Although the alignment state of the liquid crystal molecules changes depending on the voltage, it is necessary to realize the alignment state that is significantly different from the dark state.
[0065]
  As a result of intensive investigations, the inventors of the present application have realized a liquid crystal display capable of ensuring a sufficient brightness in the visible wavelength range, that is, sufficient brightness in the visible wavelength range, and capable of being manufactured easily and at a high yield. We have found a range in which liquid crystal compositions suitable for devices can be developed.
[0066]
  The specific condition is that the twist angle of the twisted nematic liquid crystal of the liquid crystal layer 1 is 45 degrees or more and 100 degrees or less. In addition, the Δnd value of the product of the birefringence difference Δn of the liquid crystal and the thickness d of the liquid crystal layer 1 is in the range of 150 nm to 350 nm.
[0067]
  More preferably, the twist angle is not less than 60 degrees and not more than 100 degrees, and the Δnd value of the product of the liquid crystal birefringence difference Δn of the liquid crystal layer 1 and the thickness d of the liquid crystal layer 1 is not less than 250 nm and not more than 300 nm. More preferably, the twist angle is 65 degrees or more and 90 degrees or less, and the Δnd value of the product of the birefringence difference Δn of the liquid crystal of the liquid crystal layer 1 and the thickness d of the liquid crystal layer 1 is 250 nm or more and 300 nm or less. Range. The condition of this more preferable range is realized by a practical liquid crystal material in which Δn of the liquid crystal layer 1 is about 0.0667 even if, for example, the manufacturing condition of the liquid crystal display device in which the thickness of the liquid crystal layer 1 is set to 4.5 μm is used. It is possible to manufacture a highly practical liquid crystal display device.
[0068]
  Hereinafter, specific examples according to the present embodiment will be described.
[0069]
  [Example 1]
  First, as Example 1, a description will be given of how the present inventors examined the setting of the liquid crystal layer by calculation in order to perform a specific design in consideration of the optical action of the liquid crystal layer. First, in optimizing the setting of the liquid crystal layer, the setting of the liquid crystal layer was examined using the evaluation function shown in Expression (2).
[0070]
[Expression 1]

[0071]
  Where s_ThreeIs a Stokes parameter that specifies the polarization state, and is a Stokes parameter related to the polarization state on the reflection surface of light that passes through the liquid crystal layer only once. The Stokes parameters used here are standardized ones.
[0072]
  Perfectly polarized light that can describe the polarization state can be described by Stokes parameters having three components when the intensity of light is normalized, and represents linearly polarized light having different vibration planes of 45 degrees from each other.₁And s₂And s representing a circularly polarized light component_ThreeSpecified by. s₁, S₂, S_ThreeTakes a value between -1 and 1, in particular s._ThreeTakes a value of ± 1 for circularly polarized light, 0 for linearly polarized light, and an intermediate value for elliptically polarized light.
[0073]
  That is, the evaluation function f is s_ThreeIs squared, f = 0 for circular polarization, 0 <f <1 for elliptical polarization, and 0 <f <1 for linear polarization, regardless of the direction of polarization rotation. It can be classified as f = 1.
[0074]
  The inventors of the present application have f = 0 (circularly polarized light) on the reflector when light is incident on an arbitrary birefringent medium sandwiched between one polarizing plate and a reflecting surface exhibiting specular reflection. In some cases, it is confirmed by analytical examination that the reflected light is all absorbed by the polarizing plate that has passed at the time of incidence, and can pass without being absorbed by the polarizing plate when f = 1. When the evaluation function f takes this intermediate value, a part of the reflected light is absorbed by the polarizing plate, and the remaining reflected light is transmitted through the polarizing plate, thereby displaying an intermediate reflectance.
[0075]
  Further, the above evaluation function f is proportional to the reflectance of a reflective liquid crystal display device in which incident light is reflected by a reflector using such a single polarizing plate, and the reflectance of the single polarizing plate system is evaluated. I find out what I can do. Therefore, it is possible to evaluate whether or not a good brightness can be obtained in bright display and whether or not a good dark state can be obtained by this evaluation function f.
[0076]
  As described above, since the display performance can be predicted by the evaluation function f, a liquid crystal display method that can expect the best performance of the single-polarizing plate method has been intensively studied. Next, the specific method will be described.
[0077]
  First, in producing a liquid crystal display device, mass productivity was considered. In particular, since the holding accuracy of the liquid crystal layer thickness that determines the optical characteristics of the liquid crystal display device has a large influence on the mass productivity, this has been considered.
[0078]
  As a method for maintaining the thickness of the liquid crystal layer, a method in which a spherical spacer made with a certain particle size is provided between the substrates sandwiching the liquid crystal layer has the best balance between accuracy and practicality. However, even with this method, requiring high accuracy in the mass production process leads to an increase in the mass production cost. Therefore, it is industrially important to examine a method that does not require the accuracy of the liquid crystal layer thickness.
[0079]
  In addition, regarding the display quality of the manufactured liquid crystal display device, it is important to consider human visual characteristics. That is, it is known that human vision has a non-linear characteristic, and the intensity of light that actually stimulates the retina of the eyeball is not proportional to the perceived brightness. In other words, even for a certain amount of light intensity fluctuation of the display device, it may be felt as a small lightness fluctuation due to the intensity of the stimulus applied to the retina at the same time (in the case of a stimulus with a strong background) or a large lightness modulation. (If the background is a weak stimulus). Considering such non-linear characteristics of vision, even if the unevenness of the reflectance is the same, the deterioration in display quality is larger when it occurs in dark display than when it occurs in bright display. .
[0080]
  Therefore, when there is a state with large or small reflectance unevenness, it is possible to assign a state with small reflectance unevenness to dark display and to assign a state with large reflectance unevenness to bright display. This is desirable from the viewpoint of manufacturing a liquid crystal display element.
[0081]
  Furthermore, when a sufficient voltage is applied to the liquid crystal layer and the polarization conversion action disappears, the unevenness of the liquid crystal layer thickness is less likely to cause a large fluctuation in the polarization conversion action.
[0082]
  Considering the above three points, it is considered that a good display can be obtained by assigning an alignment state in which a voltage is sufficiently applied to a dark display. That is, it is desirable to set a state where no voltage is applied to the liquid crystal to a bright display and to set a case where a voltage is applied to a dark display, so-called normally white display.
[0083]
  Next, the setting of the optical phase difference compensation plate and the setting of the liquid crystal layer portion for realizing this setting will be described based on the evaluation function f.
[0084]
  First, when a sufficient voltage is applied to the liquid crystal layer, the liquid crystal layer has no polarization conversion effect. The characteristic required for the optical retardation compensator is a characteristic of circularly polarized light on the reflector that has passed through the liquid crystal layer and reached the reflector. Here, the rotation direction of the circularly polarized light may be either.
[0085]
  This characteristic can be realized in a wide wavelength band by the above-described setting for the optical phase difference compensator. At this time, since the polarization conversion action of the liquid crystal has disappeared, the evaluation function f becomes 0, and a good dark state is obtained.
[0086]
  On the other hand, in order to study the conditions for obtaining sufficient reflection brightness when no voltage is applied to the liquid crystal layer, the evaluation function f is evaluated in the setting of the optical phase difference compensator that generates such circularly polarized light. There is a need. The inventors of the present application obtained an evaluation function f for the alignment in which the liquid crystal layer is twisted uniformly in the state where no voltage is applied to the liquid crystal layer. As a result, when circularly polarized light is incident on the liquid crystal, the evaluation function f can be expressed by Equation (3) according to the Jones Matrix method._ThreeIt became clear by calculating it analytically.
[0087]
[Expression 2]

[0088]
  FIG. 3 shows the value of the evaluation function f at the wavelength with the highest visibility (λ = 550 nm) as an isoline diagram with respect to Δnd and the twist angle, which are design parameters of the liquid crystal layer. As for the twist angle Φtw, since f is an even function, f is described only for a positive value of the twist angle, but it goes without saying that the twist direction of the actual liquid crystal alignment may be left or right. Yes.
[0089]
  Although FIG. 3 shows values at a single wavelength (550 nm), the visible wavelength 380 nm to 780 nm can also be evaluated by the same method. That is, for incident light having a wavelength other than 550 nm, it is only necessary to consider that only Δn and λ among the variables of the evaluation function f are changed.
[0090]
  In this way, by taking into account the effect that the visual sensitivity varies depending on the wavelength, and assuming the visual sensitivity and the standard illumination light source and taking the overlap integral with f, a more precise optimization is possible. In other words, the visibility curve (CIE1931 color matching function y_BAR(Λ)) and D65 standard light source spectral density S_D65It is effective to define (4) using (λ).
[0091]
[Equation 3]

[0092]
  Here, f (λ) is calculated by the equation (3), but clearly shows that it has a value depending on the wavelength λ.
[0093]
  FIG. 4 shows the fvis defined as described above calculated with respect to Δnd and the twist angle as in FIG. Here, calculation is performed in consideration of chromatic dispersion of Δn, and Δnd on the vertical axis is a value in light having a wavelength of 550 nm.
[0094]
  Further, since the evaluation function f according to the expression (2) indicates a value proportional to the reflectance of the display, the color matching function y of the expression (4)_BAR(Λ) is similarly defined in CIE1931 x_BAR(Λ), z_BARBy changing to (λ), the chromaticity can be calculated. From this, the chromaticity (x, y) with the D65 light source was calculated for the same parameters as in FIG. The results are shown in FIGS. 5 and 6, respectively.
[0095]
  As a result of the above studies, a satisfactory hue (x is 0.27 or more and 0.35 or less, and y is 0.28 or more and 0) with sufficient luminous reflectance (fvis is 0.7 or more) and white display. .36 or less) was set, and Δnd and twist color range suitable for this were determined. The result is shown in FIG. From FIG. 7, it can be seen that the region where a good white balance and reflectivity can be obtained is a region where the twist angle is greater than 0 degree and less than 100 degrees. In addition, in this favorable region, it can be seen that the lower limit of Δnd, which is the product of the refractive index difference Δn of the liquid crystal and the liquid crystal layer thickness d, is 85 nm or more. In addition, in this favorable region, it can be seen that the upper limit of Δnd is 315 nm or less.
[0096]
  As described above, the range of parameters of the liquid crystal layer necessary for obtaining sufficient brightness and hue is determined. However, the setting of the liquid crystal layer is further limited by the setting of the liquid crystal material and the liquid crystal layer thickness. For this reason, the entire range shown by the oblique lines in FIG. 7 is not practical. Moreover, even in a range slightly deviating from this range, there are good conditions. This point will be described in more detail.
[0097]
  It is known that there is a certain correlation between Δn, which is an optical property value of a liquid crystal material, and a usable temperature range of the liquid crystal material. In other words, liquid crystal materials that are put to practical use are generally adjusted to the required characteristics by blending a plurality of compounds. However, if Δn is decreased by changing the blend ratio at this time, the temperature range in which the nematic phase can be obtained becomes narrow. Become. In such a case, there is a difficulty in remarkably narrowing the operating temperature range and storage temperature range of the liquid crystal display device. That is, there is a lower limit in the liquid crystal material Δn from the viewpoint of a temperature range in which a nematic phase can be stably obtained. For these reasons, Δn at room temperature depends on the required temperature range and the like, but generally requires a value of 0.05 or more, preferably 0.065 or more.
[0098]
  In addition, the thickness of the liquid crystal layer is limited by a problem of a defect occurrence rate caused by foreign matters or the like in a manufacturing process of a liquid crystal display device, a manufacturing step of an element for driving a liquid crystal, flatness of a substrate to be used, and the like. Furthermore, when it is used for a part of the configuration of the present invention, there is a limitation also from the point of the concavo-convex shape of the concavo-convex diffusing reflector disposed close to the liquid crystal layer.
[0099]
  As the thickness of the liquid crystal layer, in the case of a transmissive liquid crystal display device, a value of about 5 μm is generally used, and production technology has been established. However, it is very difficult to make the thickness of the liquid crystal layer significantly smaller than this, and the practicality is poor. Thus, it is useful to make the liquid crystal layer thickness approximately 3 μm or more, preferably 4 μm or more.
[0100]
  From the above viewpoint, it is useful to set the lower limit of Δnd, which is the product of the refractive index difference Δn of the liquid crystal and the liquid crystal layer thickness d, to 150 nm, preferably 260 nm or more.
[0101]
  Furthermore, the liquid crystal in the actual driving state of the liquid crystal display device is often driven by applying a voltage near the threshold value of the liquid crystal exhibiting threshold characteristics. At this time, at an applied voltage of about the threshold value, the liquid crystal is slightly tilted from the state where no voltage is applied, and the refractive index difference in the substrate normal direction in this slightly tilted state appears in the actual display.
[0102]
  From this, Δn determined by the liquid crystal material can take a value about 10% larger than the effective Δn for the tilted liquid crystal. In addition, since display below the threshold value of the liquid crystal is also possible, it is appropriate not to apply this change in the value of Δnd to the lower limit of Δnd.
[0103]
  As described above, the specific calculation using the actual setting of the liquid crystal layer is performed, and in the single-polarization-type reflective liquid crystal display device, the upper limit of Δnd is changed from 150 nm to 350 nm, and the twist angle of the liquid crystal It was found that it is effective to set the angle from 45 degrees to 100 degrees.
[0104]
  [Example 2]
  In Example 2, a reflective liquid crystal display device having the structure shown in FIG. 1 was manufactured with the parameters shown in Table 1, and five samples # 2a to # 2f were obtained.
[0105]
[Table 1]

[0106]
  An outline of the display result of each sample is shown in Table 2.
[0107]
[Table 2]

[0108]
  Vth is a threshold voltage at which the orientation change of the liquid crystal layer 1 is observed in each sample, and has a different value because it is set to a different Δnd.
[0109]
  As described above, in samples # 2a and # 2b whose parameters fall within the range of the reflective liquid crystal display device of the present invention, white display is changed to black at a voltage Vth to 3.0 × Vth that is actually used. The display has changed to display. On the other hand, in samples # 2c to # 2f whose parameters do not fall within the range of the reflective liquid crystal display device of the present invention, the display is dark (samples # 2c and # 2f), and the display is colored (samples). # 2d, # 2e).
[0110]
  The outline of the display shown in Table 2 can be obtained by changing the setting θ3 of the direction with the liquid crystal alignment without changing the relative angles (θ1, θ2) between the polarizing plate 10 and the optical retardation compensation plates 8, 9. It has been confirmed that the large characteristic variation as seen in samples # 2a to # 2f is not observed, but rather depends on the setting of the liquid crystal layer 1 portion.
[0111]
  In addition, when the circularly polarized light in the reverse direction is incident on the liquid crystal (that is, 90 degrees is commonly added to θ1 and θ2, or both the signs of θ1 and θ2 are reversed), In all combinations such as another setting obtained (that is, both θ1 and θ2 are inverted and 90 degrees are added), the display is the same as in Table 2.
[0112]
  As described above, the product of the birefringence difference of the liquid crystal of the liquid crystal layer 1 and the thickness of the liquid crystal layer is 150 nm or more and 350 nm or less, and the twist angle of the liquid crystal layer is in the range of 45 degrees to 100 degrees. It was shown that by setting the liquid crystal layer 1, good display was realized and the range was limited.
[0113]
  The following Example 3 and Example 4 show examples in which the conditions under which a more preferable display can be obtained are examined and optimized.
[0114]
  Example 3
  As Example 3, an example in which one optical retardation compensator having retardations of 135 nm and 270 nm is used for the liquid crystal layer in which the twist angle of the twisted nematic liquid crystal is set to 90 degrees is shown.
[0115]
  In Example 3, a reflective liquid crystal display device having the structure shown in FIG. 1 was manufactured. The light reflecting film 7 on the substrate 5 was made of aluminum and used as a light reflecting electrode. Further, the liquid crystal driving cell is the liquid crystal layer 1 twisted at 90 degrees adjusted so that the thickness of the liquid crystal layer 1 becomes 4.2 μm after the liquid crystal is introduced, and the introduced liquid crystal material is used in a normal TFT transmission type liquid crystal display. A liquid crystal having the same liquid crystal physical properties (dielectric anisotropy, elasticity, viscosity, nematic temperature range, voltage holding characteristic) as the liquid crystal used, and only Δn adjusted to 0.065 was used. Here, the product of the thickness of the liquid crystal layer 1 and the birefringence difference of the liquid crystal was set to be 273 nm.
[0116]
  The arrangement of the polarizing plate 10, the optical phase difference compensation plate 8, and the optical phase difference compensation plate 9 of this example was set as shown in FIG. In FIG. 8, 11 is the transmission axis orientation of the polarizing plate 10, 12 is the slow axis orientation of the optical retardation compensation plate 9, 13 is the slow axis orientation of the optical retardation compensation plate 8, and 14 is on the substrate 4. The orientation direction of the liquid crystal molecules in contact with the formed alignment film 2, that is, the orientation direction of liquid crystal molecules in the vicinity of the alignment film 2, 15 is the orientation direction of liquid crystal molecules in contact with the alignment film 3 formed on the substrate 5. Each figure is shown, and is observed from the direction of incident light of the liquid crystal display device.
[0117]
  As shown in FIG. 8, these arrangement relationships are such that the angle θ1 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical retardation compensation plate 8 is 75 °, and the transmission of the polarizing plate 10 is performed. An angle θ2 formed by the axis direction 11 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and an angle θ3 formed by the alignment direction 14 of the liquid crystal molecules on the substrate 4 and the transmission axis direction 11 of the polarizing plate 10 30 °.
[0118]
  The optical retardation compensation plate 8 and the optical retardation compensation plate 9 are both made of a stretched film made of polyvinyl alcohol, and the optical retardation compensation plate 8 is 130 nm to 140 nm with respect to transmitted light in the surface normal direction with a wavelength of 550 nm. The optical phase difference compensation plate 9 has a phase difference controlled from 265 nm to 275 nm with respect to similar light.
[0119]
  The arrangement of these optical phase difference compensation plates 8 and 9 is an arrangement that improves the optical characteristics with respect to the front direction of the liquid crystal display device after fabrication. Design changes are also possible. For example, as a design for changing the phase difference of the optical phase compensation plates 8 and 9 with respect to the light passing through the tilt direction while satisfying the set angle condition of the present embodiment shown in FIG. 8, the optical phase difference compensation plates 8 and 9 are used. It is possible to change at least one of them to a biaxial optical phase difference compensator. Needless to say, the angle setting can be changed within the range of the above-described equation (1).
[0120]
  As the polarizing plate 10, a polarizing plate having an AR layer made of a dielectric multilayer film and having a single internal transmittance of 45% was used.
[0121]
  FIG. 9 is a graph showing the voltage dependence of the reflectance of the reflective liquid crystal display device configured as described above. As shown in FIG. 10, the reflectance is measured by applying light from the illumination light source device through the half mirror while driving the reflective liquid crystal display device of this embodiment by applying a voltage. The incident light is incident from the side, and the reflected light from the light reflecting film on the substrate 5 is detected by the photodetector. In FIG. 9, the reflectance is 100% in the same liquid crystal display device as in this example except that only the polarizing plate similar to the device under measurement is used without using the optical phase difference compensation plate. It is the reflectance in the state. Moreover, the luminous brightness factor (Y value) was used for the reflectance.
[0122]
  From the measurement results shown in FIG. 9, it can be seen that a high reflectance was obtained with a low driving voltage of about 1 V or less.
[0123]
  Example 4
  Example 4 shows an example in which one optical retardation compensator having a retardation of 135 nm and 270 nm is used for the liquid crystal layer in which the twist angle of the twisted nematic liquid crystal is set to 70 degrees.
[0124]
  In Example 4, a reflective liquid crystal display device having the structure shown in FIG. 1 was prepared. The light reflecting film 7 on the substrate 5 was made of aluminum and used as a light reflecting electrode. The liquid crystal driving cell is a liquid crystal layer 1 twisted at 70 degrees and adjusted so that the thickness of the liquid crystal layer 1 becomes 4.5 μm (sample # 4a) and 4.2 μm (sample # 4b) after the liquid crystal is introduced. The introduced liquid crystal material has the same liquid crystal properties (dielectric anisotropy, elasticity, nematic temperature range, voltage holding characteristic) as the liquid crystal used in the normal TFT transmission type liquid crystal display, and only Δn is 0. The one adjusted to 0.06 was used. Here, the product of the thickness of the liquid crystal layer 1 and the birefringence difference of the liquid crystal was set to be 270 nm (sample # 4a) and 250 nm (sample # 4b).
[0125]
  The arrangement of the polarizing plate 10, the optical phase difference compensation plate 8, and the optical phase difference compensation plate 9 of this example was set as shown in FIG. In FIG. 11, 11 is the transmission axis direction of the polarizing plate, 12 is the slow axis direction of the optical retardation compensation plate 9, 13 is the slow axis orientation of the optical retardation compensation plate 8, and 14 is formed on the substrate 4. The orientation direction of the liquid crystal molecules in contact with the oriented film 2, that is, the orientation direction of liquid crystal molecules in the vicinity of the orientation film 2, 15 is the orientation direction of the liquid crystal molecules in contact with the orientation film 3 formed on the substrate 5, ie This figure is observed from the direction of the incident light of the liquid crystal display device.
[0126]
  As shown in FIG. 11, these arrangement relationships are such that the angle θ1 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical retardation compensation plate 8 is 75 °, and the transmission of the polarizing plate 10 An angle θ2 formed by the axis direction 11 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and an angle θ3 formed by the alignment direction 14 of the liquid crystal molecules on the substrate 4 and the transmission axis direction 11 of the polarizing plate 10 is 45. °.
[0127]
  The optical retardation compensation plate 8 and the optical retardation compensation plate 9 are both made of a stretched film made of polyvinyl alcohol, and the optical retardation compensation plate 8 is 130 nm to 140 nm with respect to transmitted light in the surface normal direction with a wavelength of 550 nm. The optical phase difference compensation plate 9 has a phase difference controlled from 265 nm to 275 nm with respect to similar light.
[0128]
  The arrangement of these optical retardation compensation plates 8 and 9 is an arrangement that improves the optical characteristics with respect to the front direction of the liquid crystal display device after fabrication. However, in consideration of the characteristics observed from the tilt direction together with the liquid crystal layer 1. Design changes are also possible. For example, as a design for changing the phase difference of the optical phase difference compensation plates 8 and 9 with respect to the transmitted light in the tilt direction while satisfying the set angle condition of the present embodiment shown in FIG. It is possible to change at least one of the nine to a biaxial optical retardation compensator. Needless to say, the angle setting can be changed within the range of the aforementioned equation (1).
[0129]
  As the polarizing plate 10, a polarizing plate having an AR layer made of a dielectric multilayer film and having a single internal transmittance of 45% was used.
[0130]
  The voltage dependency of the reflectance of the reflective liquid crystal display device having the above configuration is the same as that of the graph shown in FIG. From this result, it can be seen that a high reflectance was obtained with a low driving voltage of about 1 V or less. This reflectance was also measured by the arrangement of the measurement optical system shown in FIG. 10 in the same manner as in Example 3, and 100% was set in the same manner as in Example 3.
[0131]
  Table 3 shows the contrast, white coloring, and black coloring at each angle θ3 formed by the transmission axis of the polarizing plate 10 and the alignment direction of the liquid crystal near the upper substrate 4.
[0132]
[Table 3]

[0133]
  From this result, it was confirmed that a reflective liquid crystal display device with high display quality can be realized by setting θ3 to 20 ° to 70 ° or 110 ° to 150 °.
[0134]
  Example 5
  Example 5 shows an example in which one optical retardation compensator having a retardation of 135 nm and 270 nm is used for the liquid crystal layer in which the twist angle of the twisted nematic liquid crystal is set to 70 degrees.
[0135]
  In Example 5, a reflective liquid crystal display device having the structure shown in FIG. 1 was produced. The light reflecting film 7 on the substrate 5 was made of aluminum and used as a light reflecting electrode. Further, the liquid crystal driving cell is the liquid crystal layer 1 twisted at 70 degrees adjusted so that the thickness of the liquid crystal layer 1 becomes 4.5 μm after the liquid crystal is introduced, and the introduced liquid crystal material is an ordinary TFT transmissive liquid crystal display. The liquid crystal used had liquid crystal properties (dielectric anisotropy, elasticity, viscosity, temperature characteristics, voltage holding characteristics) similar to the liquid crystal used, and only Δn was adjusted to 0.0667. Here, the product of the thickness of the liquid crystal layer 1 and the birefringence difference of the liquid crystal was set to be 300 nm.
[0136]
  As shown in FIGS. 12A and 12B, the arrangement of the polarizing plate 10, the optical phase difference compensation plate 8, and the optical phase difference compensation plate 9 of the present embodiment is set to two types and two types are arranged. A sample of was prepared. 12A and 12B, similarly to FIG. 8 described above, 11 is the transmission axis direction of the polarizing plate 10, 12 is the slow axis direction of the optical retardation compensator 9, and 13 is the optical phase difference. The slow axis direction of the compensation plate 8, 14 is in contact with the alignment film 2 formed on the substrate 4, that is, the alignment direction of liquid crystal molecules in the vicinity of the alignment film 2, and 15 is the alignment film 3 formed on the substrate 5. The orientation directions of the liquid crystal molecules in contact with each other, that is, in the vicinity of the alignment film 3 are shown, and this figure is observed from the orientation of incident light of the liquid crystal display device.
[0137]
  As shown in FIG. 12A, the arrangement relationship of one sample is that the angle θ1 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical phase difference compensation plate 8 is 75 °. The angle θ2 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, the alignment direction 14 of the liquid crystal molecules on the substrate 4 and the transmission axis direction 11 of the polarizing plate 10. Is set to 40 °, and this sample is designated as sample # 5a.
[0138]
  As shown in FIG. 12B, the arrangement relationship in the other sample is that the angle θ1 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical retardation compensation plate 8 is 75 °, The angle θ2 formed by the transmission axis direction 11 of the plate 10 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and the alignment direction 14 of the liquid crystal molecules on the substrate 4 and the transmission axis direction 11 of the polarizing plate 10 The formed angle θ3 is 130 °, and this sample is designated as sample # 5b. That is, sample # 5a and sample # 5b have different θ3, and θ1 and θ2 are the same.
[0139]
  In these samples # 5a and # 5b, as in Example 3, the optical retardation compensation plates 8 and 9 are both made of a stretched film made of polyvinyl alcohol, and the optical retardation compensation plate 8 has a wavelength of 550 nm. The transmitted light in the surface normal direction has a phase difference controlled from 130 nm to 140 nm, and the optical phase difference compensator 9 has a phase difference controlled from 265 nm to 275 nm for similar light. Further, as the polarizing plate 10, a polarizing plate having an AR layer made of a dielectric multilayer film and having a single internal transmittance of 45% was used.
[0140]
  FIG. 13 is a graph showing the voltage dependency of the reflectance of the reflective liquid crystal display device (samples # 5a and # 5b) having the above-described configuration. In FIG. 13, curve 13-1 shows the measurement result of sample # 5a, and curve 13-2 shows the measurement result of sample # 5b. This reflectance was measured with the arrangement of the measurement optical system shown in FIG. 10 as in Example 3, and 100% was set in the same manner as in Example 3. From the measurement results shown in FIG. 13, it can be seen that a high reflectance was obtained with a low driving voltage of about 1.5 V or less, and in particular, the sample # 5a indicated by the curve 13-1 has a higher reflectance. It was.
[0141]
  Table 4 shows the results of examining the voltage reflectivity characteristics of the reflective liquid crystal display device (samples # 5a and # 5b) of Example 5 and the reflective liquid crystal display device of Example 3 described above. .
[0142]
[Table 4]

[0143]
  From Table 4, it can be seen that the reflectance and contrast ratio in a sufficiently bright state were realized in all cases, and the reflection type liquid crystal display device was good even in visual observation.
[0144]
  In Table 4, the contrast ratio is defined by dividing the reflectance in the bright state by the reflectance in the dark state. Here, as the applied voltage in the bright state, a voltage having the highest reflectance was used for each example, and in the dark state, the applied voltage was set to 3V.
[0145]
  Example 6
  As Example 6, in the reflection type liquid crystal display device manufactured under the same conditions as in Example 4 described above, the refractive index anisotropy Δn (for light with a wavelength of 450 nm of the optical retardation compensation plate 8 and the optical retardation compensation plate 9) 450) and the refractive index anisotropy Δn (650) for light having a wavelength of 650 nm and the refractive index anisotropy Δn (550) for light having a wavelength of 550 nm, Δn (450) / Δn (550), Δn (650) / Δn (550) is the combination of Δn (450) / Δn (550) and Δn (650) / Δn (550), respectively (1, 1), (1.003, 0.993), (1.007) , 0.987), (1.01, 0.98), (1.03, 0.96), (1.06, 0.95), and (1.1, 0.93). Was measured. Table 5 shows the measurement results.
[0146]
[Table 5]

[0147]
  From this result, the reflective type with high display quality is set by satisfying the relationship of 1 ≦ Δn (450) / Δn (550) ≦ 1.06, 0.95 ≦ Δn (650) / Δn (550) ≦ 1. A liquid crystal display device can be realized, and further, 1 ≦ Δn (450) / Δn (550) ≦ 1.007 and 0.987 ≦ Δn (650) / Δn (550) ≦ 1 are set to satisfy the relationship. It was confirmed that a reflective liquid crystal display device with higher display quality could be realized.
[0148]
  Example 7
  As Example 7, in the reflective liquid crystal display device manufactured under the same conditions as in Example 4 above, the orientation 16 in the plane including the observation orientation and the normal of the display surface shown in FIG. 14 and the second substrate The brightness, contrast, coloring, and comprehensive evaluation at each angle θ4 formed by the direction 14 of the liquid crystal molecules in the vicinity were performed. The evaluation results are shown in FIG. From this result, by setting θ4 to 0 degrees or more and 30 degrees or less, or 180 degrees or more and 210 degrees or less, a reflective liquid crystal display device with high display quality that is almost excellent in brightness, contrast, and color difference from the achromatic axis is realized. I confirmed that I can do it.
[0149]
  Example 8
  In Example 8, an example in which a light reflecting film having smooth irregularities is used by an active matrix driving method will be described.
[0150]
  FIG. 16 is a cross-sectional view of the main part showing the configuration of the reflective liquid crystal display device of this example. As shown in FIG. 16, the reflective liquid crystal display device 16 includes a first substrate 5 and a second substrate 4 made of transparent glass, and TFT elements 17 are provided as active elements on the first substrate 5. It is formed in a pixel. An interlayer insulating film 18 is formed on the TFT element 17 and driving wiring (not shown), and the drain terminal (not shown) of the TFT element 17 and the light reflective pixel electrode 19 are electrically connected via a contact hole. Connected to. On the light-reflective pixel electrode 19, the alignment film 3 is formed with a thickness of 100 nm.
[0151]
  Here, the light-reflective pixel electrode 19 can be made of a conductive metal material such as aluminum, nickel, chromium, silver, or an alloy using the same, and has light reflectivity. The shape of the light-reflective pixel electrode 19 has smooth irregularities except for the contact hole portion, and prevents the metal reflecting surface from becoming a mirror surface.
[0152]
  Next, the formation method will be described in more detail.
[0153]
  A large number of large protrusions 20 and small protrusions 21 made of a photosensitive resin material were formed on the surface of the substrate 5 on which the TFT element 17 and the driving wiring (not shown) were formed. The large protrusions 20 and the small protrusions 21 are formed by forming a large number of circular patterns having bottom diameters D1 and D2 (see FIG. 16) by photolithography. These D1 and D2 are set to 5 μm and 3 μm, for example. Further, the distance D3 is set to at least 2 μm. The height of these protrusions can be controlled by the film thickness at the time of forming the photosensitive resin material. In this embodiment, the height is set to 1.5 μm, and the protrusions are formed into gentle protrusions by the subsequent exposure process and baking process.
[0154]
  Next, the smoothing film 22 was formed of the same photosensitive resin material so as to cover the protrusions 20 and 21 and fill the flat portion between the protrusions 20 and 21. In this way, the surface of the smoothing film 22 was formed into a smooth curved surface under the influence of the protrusions 20 and 21, and the desired shape was obtained. In the contact hole portion, neither the protrusion nor the smoothing film 22 is formed.
[0155]
  By manufacturing the TFT element substrate 23 having the above-described structure, the light-reflective pixel electrode 19 also serves as a reflector and is disposed near the liquid crystal layer 1 without causing parallax. The TFT element of a bright reflective liquid crystal display device with a high so-called aperture ratio in which the light that passes through and is reflected by the light-reflective pixel electrode 19 is not impaired by the TFT element 17 and the element driving wiring (not shown) part. A substrate 23 was realized.
[0156]
  On the other hand, on the other substrate used together with the TFT element substrate 23, a color filter 24 with high brightness was arranged in accordance with the reflection method. The color filter 24 is provided with a black matrix 25 for preventing color mixture between pixels and preventing leakage of reflected light in a dark display due to a voltage non-applied portion between pixel electrodes and electric field disturbance. Yes.
[0157]
  In the black matrix 25, the light incident thereon is already substantially circularly polarized, and the reflected light from the black matrix 25 is absorbed by the polarizing plate again upon receiving the action of the optical phase difference compensation plate when emitted. Even when the metal film or the like was used, the black matrix 25 did not cause reflected light to deteriorate visibility. Furthermore, it goes without saying that a low-reflection treatment on the black matrix 25 is suitable for display with higher contrast.
[0158]
  On this color filter 24, ITO (Indium Tin Oxide) was mask deposited as a transparent electrode 6 by sputtering to form a counter electrode 6 of a light-reflective pixel electrode 19 for driving a TFT element having a desired pattern of 140 nm thickness. . Then, the alignment film 2 was formed thereon to obtain a color filter substrate 26.
[0159]
  Even when the transparent electrode 6 has a thickness other than 140 nm, the incident light reflects without reaching the liquid crystal layer 1 due to the interference effect of the film thickness of the transparent electrode 6. 9 and the polarizing plate 10, the dark state is not affected and the visibility is not impaired.
[0160]
  Further, the color filter 24 used at this time is appropriately designed so as to have brightness suitable for a high contrast display mode using a polarizing plate, and the color filter 24 is used when the aperture ratio of the black matrix 25 is 90%. The transmittance of the substrate 26 was 50% in terms of Y value.
[0161]
  The TFT element substrate 23 and the color filter substrate 26 thus prepared are subjected to an alignment process by a rubbing method, a plastic spacer (not shown) for maintaining the thickness of the liquid crystal layer 1 is dispersed, A seal placement step was arranged opposite to each other, aligned, cured under pressure, and sealed to prepare a liquid crystal cell for liquid crystal injection. A liquid crystal material having a positive dielectric anisotropy Δε was introduced into the liquid crystal layer 1 by a vacuum injection method. Hereinafter, in the expression of the orientation of the liquid crystal display device, the observer's up / down / left / right direction facing the device is described as the clock face direction, and the upper direction is described as the 12 o'clock orientation.
[0162]
  On the opposite side of the color filter substrate 26 from the liquid crystal layer 1, an optical phase compensation plate 8 and an optical phase difference compensation plate 9 made of a stretched film made of polyvinyl alcohol are provided. Is arranged.
[0163]
  The arrangement of the polarizing plate 10, the optical retardation compensator 8, and the optical retardation compensator 9 constituting the circularly polarizing plate 100 in this example was set as shown in FIG. In FIG. 17, 11 is the transmission axis orientation of the polarizing plate 10, 12 is the slow axis orientation of the optical retardation compensation plate 9, 13 is the slow axis orientation of the optical retardation compensation plate 8, and 14 is the color filter substrate 26. The orientation direction of the liquid crystal molecules in contact with the alignment film 2 formed thereon, that is, the orientation direction of the liquid crystal molecules in the vicinity of the alignment film 2, 15 is in contact with the alignment film 3 formed on the TFT element substrate 23, that is, the liquid crystal molecules in the vicinity of the alignment film 3. Each orientation direction is shown. Here, the alignment processing direction 14 of the alignment film 2 on the color filter substrate 26 is fabricated to be the 3 o'clock direction of the apparatus.
[0164]
  As shown in FIG. 17, these arrangement relationships are such that the angle θ1 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical retardation compensation plate 8 is 75 °, and the transmission of the polarizing plate 10 The angle θ2 formed by the axis direction 11 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and the angle formed by the alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 and the transmission axis direction 11 of the polarizing plate 10. θ3 is set to 130 °.
[0165]
  The liquid crystal layer 1 is a liquid crystal layer adjusted to have a layer thickness of 4.0 to 5.0 μm after the introduction of the liquid crystal material, and the liquid crystal having a Δn of 0.0667 is used. The product of the difference was set to approximately 300 nm. The layer thickness of the liquid crystal layer 1 has different values depending on the position because of the unevenness of the light-reflective pixel electrode 19.
[0166]
  Further, a driving circuit is mounted around the liquid crystal display panel thus manufactured, thereby obtaining a reflective liquid crystal display device.
[0167]
  In the reflective liquid crystal display device of this example, the light-reflective pixel electrode 19 is disposed near the liquid crystal layer 1, so that there is no parallax and a good high-resolution display is realized. Reflected light was able to realize good white display without the appearance of the observer's face due to the uneven shape imparted to the light-reflective pixel electrode 19. Furthermore, since the thing which has a scattering property is not arrange | positioned in the front surface of a liquid crystal display device, the favorable dark state was shown and it became the display of high contrast ratio for them.
[0168]
  In addition, since the color filter 24 having high brightness is used, sufficient brightness can be secured even in the display using the polarizing plate, the reflectance in the dark state is low, and the reflected light from the color element selected in the dark state. Is observed together with the reflected light of the color element selected in the bright state, and the color purity is not deteriorated. As a result, despite the low saturation of the color filter 24 with high brightness, the color reproduction range of the color filter 24 was not impaired, and good color reproducibility was obtained.
[0169]
  In addition, since the voltage applied to each pixel is set to an intermediate state between the dark state and the light state, there is no problem in reproducing halftones, and therefore, there is also a problem in expressing intermediate colors of the respective colors of the color filter 24. There was no. Moreover, it was confirmed that the response speed has no problem in reproducing the moving image even in actual driving.
[0170]
  As described above, a reflective liquid crystal display device capable of displaying multiple gradations and displaying a moving image and having a satisfactory color reproduction range can be realized by a practical manufacturing method.
[0171]
  Example 9
  As Example 9, the brightness is improved by producing a light-reflecting film having an uneven shape with in-plane anisotropy, and the liquid crystal layer has a favorable orientation with a tilted viewing angle in the high brightness direction. An example will be described.
[0172]
  In Example 9, the uneven shape of the light-reflective pixel electrode 19 of the reflective liquid crystal display device manufactured in Example 8 is formed in a different pattern, and the uneven shape varies depending on the orientation in the plane where the reflective electrode is formed. Things were made.
[0173]
  In the present example, as shown in the enlarged plan view of the main part in FIG. 18, as the pattern satisfying the above conditions, the uneven shape was not a circle but an ellipse and a directional pattern was produced. The reflection characteristics of the light reflecting plate having only the uneven light reflecting film were measured by the arrangement of the measuring system as shown in FIG. That is, as shown in FIG. 19, illumination light was incident from a 30 ° tilt azimuth, and the reflected light intensity toward the normal direction of the light reflector plate was rotated to measure the anisotropy of reflection.
[0174]
  The result was as shown in FIG. 20, and it was confirmed that the light from a specific direction was efficiently directed to the front of the liquid crystal display device. However, in consideration of the fact that the refractive index of the liquid crystal material is significantly different from that of air, in the measurement, an immersion oil (matching oil) having a refractive index of 1.516 is dropped on the surface of the light reflecting plate, and transparent from above. Measurement was performed with a glass plate attached. The measured values were obtained by conversion so that 100% would be the value when the MgO standard diffusion plate (standard white plate) was measured in the same manner. In FIG. 20, a curve 20-1 is a measurement conversion value of the anisotropic diffusive reflector of the present example, and a curve 20-2 is a similar measurement of the diffusive reflector similar to that used in Example 8. It is a converted value.
[0175]
  As a result, as shown in FIG. 20, in the curve 20-1 due to the directional reflecting plate in which the average period of the concavo-convex shape of the present embodiment changes within the reflecting plate surface, the incident direction φ of the illumination light is With the change, the reflected lightness (reflected light intensity) changes greatly. On the other hand, in the curve 20-2 by the reflecting plate (Example 8) having no anisotropy in the concavo-convex shape, the change in reflected brightness (reflected light intensity) accompanying the change in the incident direction φ of the illumination light is so large. Absent.
[0176]
  From these facts, in order to increase the reflection brightness, the inventors of the present application, as in the reflector used in the present embodiment, the directionality (average concavo-convex period changes depending on the orientation in the reflector surface ( It has been found that anisotropy is an effective means. Furthermore, in FIG. 20, the azimuths of φ = 90 ° and 270 ° are azimuths with a short average period of the concavo-convex shape, and thus it was confirmed that the reflected light intensity of illumination light from the azimuth with a short average period was high. become.
[0177]
  The alignment films 2 and 3 similar to those in the eighth embodiment are formed on the TFT element substrate 23 having the light reflecting plate having the above characteristics and the color filter substrate 26 manufactured in the same manner as in the eighth embodiment. (Twist angle 70 °) to prepare four types of samples.
[0178]
  In these samples, the arrangement of the polarizing plate 10, the optical phase difference compensation plate 8, and the optical phase difference compensation plate 9 is different, and the arrangement is as shown in FIGS. 21 (a) to 21 (d). 21A to 21D, similarly to FIG. 17 described above, 11 is the transmission axis orientation of the polarizing plate 10, 12 is the slow axis orientation of the optical retardation compensation plate 9, and 13 is the optical phase difference. The slow axis direction of the compensation plate 8, 14 is in contact with the alignment film 2 formed on the color filter substrate 26, that is, the alignment direction of liquid crystal molecules in the vicinity of the alignment film 2, and 15 is formed on the TFT element substrate 23. The orientation directions of the liquid crystal molecules in contact with the orientation film 3, that is, in the vicinity of the orientation film 3, are shown, and this figure is observed from the orientation of incident light of the liquid crystal display device.
[0179]
  That is, the arrangement relationship in the sample shown in FIG. 21A is that the angle θ1 formed between the transmission axis direction 11 of the polarizing plate 10, the optical phase difference compensation plate 8 and the slow axis direction 13 is 75 °, The angle θ2 formed by the transmission axis direction 11 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and the alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 and the transmission axis direction 11 of the polarizing plate 10 are formed. The angle θ3 is set to 130 °, and this sample is designated as sample # 9a (the same as in Example 8 above). The alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 is parallel to the 3 o'clock direction.
[0180]
  In addition, the arrangement relationship in the sample shown in FIG. 21B is that the angle θ1 formed between the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical retardation compensation plate 8 is 75 °, The angle θ2 formed by the transmission axis direction 11 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and the alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 and the transmission axis direction 11 of the polarizing plate 10 are formed. The angle θ3 is set to 130 °, and this sample is designated as sample # 9b. The alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 is parallel to the 12 o'clock direction.
[0181]
  In addition, the arrangement relationship in the sample shown in FIG. 21C is that the angle θ1 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical retardation compensation plate 8 is 75 °, The angle θ2 formed by the transmission axis direction 11 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and the alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 and the transmission axis direction 11 of the polarizing plate 10 are formed. The angle θ3 is 40 °, and this sample is designated as sample # 9c. The alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 is parallel to the 3 o'clock direction.
[0182]
  In addition, the arrangement relationship in the sample shown in FIG. 21D is that the angle θ1 formed by the transmission axis direction 11 of the polarizing plate 10 and the slow axis direction 13 of the optical retardation compensation plate 8 is 75 °, The angle θ2 formed by the transmission axis direction 11 and the slow axis direction 12 of the optical retardation compensation plate 9 is 15 °, and the alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 and the transmission axis direction 11 of the polarizing plate 10 are formed. The angle θ3 is 40 °, and this sample is designated as sample # 9d. The alignment direction 14 of the liquid crystal molecules on the color filter substrate 26 is parallel to the 12 o'clock direction.
[0183]
  In addition, these samples were produced similarly to the said Example 8 except the uneven | corrugated shaped pattern preparation process of light reflection board preparation.
[0184]
  When the reflection type liquid crystal display device of each sample having such an uneven light reflecting plate was visually observed, the brightness of each sample # 9a to # 9d was observed when observed from the front direction further than that of Example 8 above. High display was realized and the effect of improving the brightness of the anisotropic unevenness was exhibited. At this time, the reflected brightness was high when the illumination light was incident from the 12 o'clock direction and the 6 o'clock direction. Further, the illumination from the front azimuth and the observation from the tilt azimuth were similarly high in brightness at 12 o'clock and 6 o'clock.
[0185]
  Further, when illumination light is incident on the liquid crystal display devices of these samples from the front direction and observed from various directions inclined by 45 degrees from the front, sample # 9a and sample # 9d are inclined directions with high reflected brightness. Good display was obtained in the 6 o'clock direction and the 12 o'clock direction. Further, display of good contrast was realized in these directions, and no change in display due to inclination was particularly felt from the observation direction with high brightness. On the other hand, in sample # 9b and sample # 9c, deterioration of the contrast ratio was observed in the display of the 6 o'clock azimuth and 12 o'clock azimuth, which are directions with high brightness.
[0186]
  This indicates that the viewing angle azimuth with the highest visibility of the liquid crystal display modulation layer (liquid crystal layer 1) is different for different values of θ3. Further, the polarizing plate and the optical phase difference compensating plate of the present invention are obtained by using the sample # 9a and the sample # 9d in which the azimuth having good visibility coincides with the high azimuth direction of the anisotropic uneven shape of the light reflecting plate. And high-definition display using the high contrast ratio of the liquid crystal modulation layer (liquid crystal layer).
[0187]
  It is possible to set the orientation of the anisotropic uneven shape of the light reflector used in this embodiment to another orientation according to the main use environment of the liquid crystal display device of the present invention, and in that case Needless to say, directing the liquid crystal alignment and the set angles of the polarizing plate and the optical retardation compensator to the same direction with high brightness and the favorable direction of tilted viewing angle characteristics brings about the same effect.
[0188]
  Example 10
  Next, as a tenth embodiment, an embodiment of a reflective liquid crystal display device integrated with a touch panel using a touch panel as information input means in a portable device, which is a main field of application of the reflective liquid crystal display device of the present invention, will be described.
[0189]
  First, the schematic configuration of the touch panel used in this example is shown in FIG. As shown in FIG. 22, the touch panel 31 includes a support substrate 28 on which a transparent electrode 30 for detecting a pressed position is formed and a movable substrate 27 on which a transparent electrode 29 for detecting a pressed position is formed via a gap. Thus, the planar pressure sensitive element is configured such that the transparent electrodes 29 and 30 are arranged to face each other. Note that the movable substrate 27 and the support substrate 28 used were not birefringent.
[0190]
  A schematic structure of the present embodiment is shown in a cross-sectional view of the main part in FIG. As shown in FIG. 23, in the touch panel integrated reflection type liquid crystal display device of this embodiment, an optical phase difference compensation plate 8, an optical phase difference compensation plate 9, and a polarizing plate 10 are pasted on a movable substrate 27 of the touch panel 31. This is disposed on the display surface side of the liquid crystal driving cell having the same structure as that of the polarizing plate 10 and the optical retardation compensation plates 8 and 9 of Example 8 not attached.
[0191]
  At this time, the orientation direction of the liquid crystal layer 1 and the arrangement of the polarizing plate 10 and the optical retardation compensation plates 8 and 9 are the same as those shown in FIG. 17 (Example 8). It is the same. It should be noted that a gap 32 is provided to keep the gap between the support substrate 28 of the touch panel and the color filter substrate 26 of the reflection type liquid crystal display device constant, thereby providing a pressing force transmission effect, and the weight is reduced without using a pressing force buffer member. In addition, the pressing force applied to the touch panel is not transmitted to the color filter substrate 26.
[0192]
  Further, as a comparative example, a touch panel integrated reflection type liquid crystal display device having a structure as shown in the cross-sectional view of the main part in FIG. 24 was produced. That is, the structure of the comparative example is one in which the touch panel 31 shown in FIG. Therefore, the only difference between the present embodiment and the comparative example is the arrangement position of the touch panel 31.
[0193]
  Next, comparison was made between these examples and comparative examples. First, in the comparative example, the reflected light component on the touch panel was directly observed and the visibility was greatly deteriorated. The reflected light is generated not only by the gap sandwiched between the pressing position detecting transparent electrodes 29 and 30 but also by the gap sandwiched between the touch panel support substrate 28 and the polarizing plate 10.
[0194]
  On the other hand, the reflected light component generated in the comparative example was not observed at all in the present example, and a very good display was shown as in the case where the touch panel was not used (Example 8). . And in the present Example, the thing by the space | gap clamped by the transparent electrodes 29 and 30 for the press position detection of a touch panel was not observed like the comparative example.
[0195]
  Further, no reflection was observed at the interface between the pressing force transmission preventing gap 32 and the touch panel support substrate 28, or at the interface between the touch panel support substrate 28 and the color filter substrate 26 of the liquid crystal display device. Therefore, according to the tenth embodiment, an input device (touch panel) that does not require a pressing force buffer member, is lightweight, and that the display device can effectively use the circular polarization state by the antireflection means of the input device for display. A body-type reflective liquid crystal display device was realized.
[0196]
  Although not shown in detail, the movable substrate 27 of the touch panel 31 is omitted, and the transparent electrode 29 is directly disposed on the liquid crystal layer 1 side of the optical phase difference compensation plate 8 to enable a simpler and lighter configuration. .
[0197]
  [Second Embodiment of the Invention]
  Other embodiments of the present invention will be described below with reference to the drawings.
[0198]
  For convenience of explanation, members having the same functions as the members shown in the above embodiment are given the same reference numerals, and explanation thereof is omitted.
[0199]
  So far, regarding the case where a sufficient voltage is applied to the liquid crystal layer, examples have been described in which the liquid crystal layer has no polarization conversion action and good characteristics are obtained under such approximation. In consideration of the fact that the applied voltage remains at a finite voltage, it is effective to perform detailed optimization.
[0200]
  That is, with reference to FIG. 1, the black display is realized at the maximum value of the voltage applied to the liquid crystal, but the liquid crystal at this time is not oriented in the normal direction of the substrate at all. Considering the effect that the components parallel to the substrates 4 and 5 remain in this orientation. The dark display conditions taking this into consideration are the same as before, in the state where the practical maximum voltage is applied to the liquid crystal, the light incident from the polarizing plate 10 is the optical phase difference compensation plates 8 and 9 and the liquid crystal layer 1. It becomes circularly polarized light when it passes through both.
[0201]
  At this time, since the practical maximum voltage is applied to the liquid crystal layer 1, the polarization conversion action is not substantially generated, but a slight polarization conversion action according to the component parallel to the liquid crystal alignment substrate. (Hereinafter referred to as residual phase difference) remains, and in accordance with this, the optical phase difference compensators 8 and 9 are slightly changed from the previous conditions, so that a good dark display can be obtained at a practical maximum voltage. Realize.
[0202]
  On the other hand, the conditions for obtaining a good bright display by using the alignment of the optical phase difference compensation plates 8 and 9 and the liquid crystal layer 1 optimized to realize a good dark display in this manner are the same as the reflector. The polarization state on the three planes is linearly polarized light. The design parameter of the liquid crystal layer 1 that realizes this is that a voltage sufficient to neglect the residual birefringence of the liquid crystal so far can be applied. It is based on the case.
[0203]
  That is, when the optical retardation compensation plates 8 and 9 that have undergone a slight change according to the residual phase difference of the liquid crystal are used, the setting of the liquid crystal layer 1 does not deviate significantly from the setting of the liquid crystal layer 1 before the change. The search based on the setting so far is possible.
[0204]
  FIG. 25 shows a schematic configuration of the reflective liquid crystal display device of the present embodiment. As shown in FIG. 25, this reflection type liquid crystal display device is the same as the reflection type liquid crystal display device of the first embodiment described above, but the liquid crystal layer between the optical retardation compensation plate 8 and the substrate 4 in the circularly polarizing plate 100. In order to cancel the residual phase difference of 1, a third optical phase difference compensation plate 101 is provided. FIG. 26 shows an example of the arrangement of the three optical phase difference compensators 8, 9, 101 in this reflection type liquid crystal display device.
[0205]
  The residual phase difference of the liquid crystal layer 1 is such that the liquid crystal layer 1 is set at the center of the substrates 4 and 5 of the liquid crystal layer 1 when the twist angle is around 70 degrees, which is the center of the twist angle setting shown in the present invention. The birefringence component of the slow axis parallel to In order to cancel this, it is suitable to dispose an optical retardation compensation plate having a slow axis in an orientation orthogonal to the liquid crystal orientation as the third optical retardation compensation plate 101. Although the amount of retardation depends on the maximum voltage applied to the liquid crystal, the residual phase difference of the liquid crystal layer 1 can be canceled by setting the retardation to approximately 10 to 50 nm.
[0206]
  Next, a method for improving the viewing angle and realizing a good display for the reflective liquid crystal display device of FIG. 25 will be further examined.
[0207]
  In the reflection type liquid crystal display device of FIG. 25, a satisfactory dark display is realized at the maximum value of the actually driven voltage, and in this method, a satisfactory display is obtained, and a sufficient voltage is applied to the liquid crystal layer 1. It is effective to compensate for the residual birefringence of the liquid crystal in such a state.
[0208]
  For this reason, it is possible to expand the viewing angle by expanding the observation angle range that can satisfactorily cancel the residual birefringence of the liquid crystal layer 1. In order to realize this, it is effective to use an optical retardation compensator in consideration of the three-dimensional arrangement of liquid crystal alignment.
[0209]
  In FIG. 27, the outline of the three-dimensional orientation in the actual drive state of the liquid crystal layer 1 is shown. FIG. 27 shows the liquid crystal alignment in the reflective liquid crystal display device of FIG. In this state, for the light passing through the liquid crystal layer 1 in the normal direction of the display surface, the residual birefringence can be canceled by a uniaxial optical phase difference compensator having a slow axis orientation in a normal plane. However, for light passing through the liquid crystal layer 1 with an inclination, it is effective to use an optical retardation compensator in consideration of the inclination of the alignment of the liquid crystal layer 1.
[0210]
  First, since the liquid crystal is aligned substantially perpendicular to the substrates 4 and 5, the refractive index of the liquid crystal layer 1 has a large component with respect to the electric field in the normal direction of the substrate. In order to cancel this, an optical retardation compensation plate having such a characteristic that the refractive index with respect to the electric field in the layer thickness direction of the third optical retardation compensation plate 101 is small is effective. In particular, this is realized by using an optical retardation compensator that is uniaxial and has a refractive index with respect to the electric field in the film thickness direction smaller than that in the film surface direction. Furthermore, in order to cancel the residual phase difference in the in-plane direction of the liquid crystal layer, an optically biaxial refractive index ellipsoid may be used.
[0211]
  More strictly, it is effective to consider that the liquid crystal alignment is not completely perpendicular to the substrates 4 and 5. In particular, when the reflective liquid crystal display device is provided with a diffusive reflective film or a reflective film that is inclined with respect to the display surface, the direction of light is more generally different from the regular reflection direction with respect to the display surface. In the case of using a reflecting surface having such a function as to change, an optical path from the light reflecting film 7 to the light reflecting film 7 through the liquid crystal layer 1 and an optical path at the time of emission passing through the liquid crystal layer 1 from the light reflecting film 7 respectively. On the other hand, canceling the residual birefringence of the liquid crystal is effective for realizing a good viewing angle.
[0212]
  This will be described in more detail with reference to FIG. As shown in FIG. 28, the case where the illumination environment changes from the case where the surrounding illumination light A is used to the observer in the front direction of the reflective liquid crystal display device to the case where the illumination light B is mainly used. Think.
[0213]
  At this time, although the positions of the observer and the liquid crystal display device are fixed, the brightness and hue of the dark display change due to the change of the surrounding illumination light. This is because the degree of cancellation of the residual birefringence of the liquid crystal changes depending on the direction of the optical path passing through the liquid crystal layer 1. By preventing this, a better display can be realized.
[0214]
  Example 11
  As Example 11, the reflection type liquid crystal display device having the structure shown in FIG. 25 was manufactured with the parameters shown in Table 6, and two samples # 11a and # 11b were obtained.
[0215]
[Table 6]

[0216]
  FIG. 29 shows voltage reflectance curves of the samples # 11a and # 11b. For comparison, the voltage reflectance curve of the reflective liquid crystal display device of Example 3 is shown.
[0217]
  From this, it can be seen that sample # 11a of the present embodiment realizes good dark display although the reflectance of bright display is slightly reduced. In sample # 11b, good dark display is realized without a decrease in brightness.
[0218]
  Here, the optical phase difference compensation plate 101 and the optical position are further reduced for the purpose of manufacturing a liquid crystal display device similar to these structural examples at lower cost by reducing the number of optical phase difference compensation plates used. A study was carried out to realize the operation of the two retardation compensators 8 with one optical retardation compensator.
[0219]
  At this time, when two optical retardation compensators are stacked with their slow axes arranged in parallel, they can be replaced by a single optical retardation compensator having the retardation of the sum of the respective retardations. In the case where two optical phase difference compensators are stacked with the slow axes arranged orthogonally, they are replaced by one optical phase difference compensator having a retardation difference of each retardation. Utilized that is possible.
[0220]
  In other words, the optical phase difference compensation plate 8 and the optical phase difference compensation plate 101 in the sample # 11b of the present embodiment are laminated close to each other and the slow axis directions are perpendicular to each other. A single optical phase difference compensation plate having a retardation difference can be substituted. That is, by changing the retardation of the optical phase difference compensating plate 8, the same effect as the samples # 11a, # 11b, etc. is exhibited.
[0221]
  In order to confirm this effect, samples # 11c and # 11d were further produced. Each of these samples # 11c and # 11d has the same cross-sectional structure as FIG. 1 of the first embodiment. Table 7 shows the arrangement of the optical phase difference compensating plates 8 and 9 in the samples # 11c and # 11d.
[0222]
[Table 7]

[0223]
  The voltage reflectivity curves in the samples # 11c and # 11d were the same as the sample # 11b shown in FIG.
[0224]
  As a result, it was shown that better characteristics can be realized by adding a third optical phase difference compensator for canceling the residual phase difference of the liquid crystal at the practical maximum voltage applied to the liquid crystal. Furthermore, when using two optical phase difference compensation plates, it was confirmed that the same effect could be realized by adjusting the retardation. That is, it was confirmed that better black display can be realized by adding or adjusting an optical phase difference compensation plate in consideration of the actual driving.
[0225]
  Example 12
  In Example 12, the third optical phase difference compensator 101 has an optical position having an optical axis that is optically uniaxially inclined so that the residual birefringence of the liquid crystal layer 1 can be canceled with respect to more directions. A phase difference compensator is arranged to realize a reflection type liquid crystal display device having the configuration shown in FIG. 30, and this is designated as sample # 12a. In addition, a reflective liquid crystal display device having the configuration shown in FIG. 31 using a biaxial optical phase difference compensation plate as the third optical phase difference compensation plate 101 is realized, and this is designated as sample # 12b.
[0226]
  In this example, the refractive index ellipsoid of the optical retardation compensation plate 101 is not inclined with respect to the substrate.
[0227]
  Here, although not shown in the drawing, a concavo-convex metal reflector similar to the reflective liquid crystal display device of FIG. 16 is used as the light reflecting film 7 so as to have light diffusibility.
[0228]
  Further, as sample # 12c, a reflective liquid crystal display device having the same configuration as samples # 12a and # 12b was manufactured except that a positive uniaxial optical phase difference compensation plate was used for optical phase difference compensation plate 101.
[0229]
  Table 8 shows the arrangement of the optical elements of the samples # 12a to # 12c.
[0230]
[Table 8]

[0231]
  Table 9 shows the evaluation results of the viewing angles of the samples # 12a to # 12c.
[0232]
[Table 9]

[0233]
  The optical retardation compensation plate 101 used for the sample # 12a is manufactured so that the refractive index ellipsoid is inclined by devising the stretching method, and is manufactured so that the retardation with respect to the light beam transmitted in the front direction is about 30 nm. .
[0234]
  As shown in FIG. 30, this film exhibits negative uniaxiality in which only the refractive index for the z component of the electric field is smaller than the refractive index for the other x and y components, and the z direction is that of the planar film. Inclined from the normal direction of the surface of the optical retardation compensation plate 101. The z direction is arranged so as to be close to the orientation of the liquid crystal alignment at the practical maximum voltage, and the x direction acts as a slow axis for the light in the front direction of the optical retardation compensation plate 101.
[0235]
  This optical phase difference compensation plate 101 has an optical functional layer thickness d.₁₀₁And the refractive indexes in the x, y, and z directions shown in FIG._x,n_y,n_z(N_y-N_z  ) D₁₀₁= (N_x-N_z ) D₁₀₁= 300 nm.
[0236]
  Furthermore, it goes without saying that a nematic liquid crystal alignment or a polymer film in which the discotic liquid crystal alignment is fixed may be used in order to precisely cancel the three-dimensional alignment of the liquid crystal layer 1.
[0237]
  The optical retardation compensator 101 used for sample # 12b is manufactured to be a biaxial refractive index ellipsoid by devising a stretching method. It is fabricated so that the retardation with respect to the optical axis transmitting in the front direction is about 30 nm.
[0238]
  As shown in FIG. 31, this film has an x component, a y component, and a z component in descending order of the refractive index for each component of the electric field. Also, (n_x-N_y) D₁₀₁= 30 nm, (n_y-N_z) D₁₀₁= 300 nm.
[0239]
  As shown in Table 9, all of the bright displays were white displays, but the dark displays were from good ones to samples # 12a, # 12b, and # 12c. In addition, the overall evaluation was in the order of samples # 12a, # 12b, and # 12c from the best. This is because the characteristics change even in white display, but there is no visual difference. On the other hand, the black display has a large visual difference, which affects the overall evaluation.
[0240]
  As described above, it has been confirmed that a liquid crystal display device having a favorable viewing angle can be realized by devising an optical retardation compensator in consideration of the three-dimensional alignment of liquid crystal. Furthermore, it has been confirmed that a better dark state is realized by making the optical phase difference compensating plates 8 and 9 biaxial.
[0241]
  In this embodiment, as in the case of Example 11, a retardation film having both functions of the optical retardation compensation plate 8 and the optical retardation compensation plate 101 can be used for cost reduction. Needless to say.
[0242]
  As described above, according to the reflective liquid crystal display device of the present invention, the reflecting surface of a light reflecting plate such as a light reflecting film can be installed on the liquid crystal layer side, and a good dark state can be realized. Therefore, a reflective liquid crystal display device capable of displaying a high-contrast, high-definition video without parallax can be realized.
[0243]
  In addition, according to the reflective liquid crystal display device integrated with a touch panel of the present invention, when a touch panel is added to the reflective liquid crystal display device of the present invention, a touch panel combined with a polarizing plate and two optical phase difference compensation plates is provided. By disposing, it is possible to prevent the generation of reflected light that adversely affects the display characteristics, and to realize a high-quality touch panel integrated reflective liquid crystal display device.
[0244]
【The invention's effect】
  As described above, according to the reflective liquid crystal display device of the present invention, the reflecting surface of the light reflecting plate such as a light reflecting film can be installed on the liquid crystal layer side, and a good dark state can be realized. Therefore, a reflective liquid crystal display device capable of displaying a high-contrast, high-definition video without parallax can be realized.
[0245]
  If a color filter adjusted to high brightness is used in the reflective liquid crystal display device of the present invention, a color display reflective liquid crystal display device having good color reproducibility and high display quality can be realized.
[0246]
  Furthermore, according to the reflection type liquid crystal display device of the present invention, the circularly polarizing means cancels the residual phase difference that occurs when a voltage is applied to the liquid crystal layer from the condition that the incident light to the liquid crystal layer becomes circularly polarized light. Because the optical phase difference compensation plate changed by the amount used is used, the residual phase difference that occurs when a voltage is applied to the liquid crystal layer can be canceled, and a good dark display can be achieved when a voltage is applied to the liquid crystal layer. it can.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic structure of a reflective liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating setting orientations of an arrangement of a polarizing plate and two optical phase difference compensators according to an embodiment.
FIG. 3 is a calculation result graph illustrating numerical values in monochromatic light of 550 nm of an evaluation function for predicting reflectance in the reflective liquid crystal display device of Example 1 in an isoline diagram.
FIG. 4 is a calculation result graph showing numerical values in consideration of the visibility of an evaluation function for predicting the reflectance in the reflective liquid crystal display device of Example 1 in an isoline diagram.
FIG. 5 is an isoline diagram illustrating an evaluation function for predicting the reflectance in the reflective liquid crystal display device of Example 1 and x of CIE1931 chromaticity coordinates calculated from a D65 standard light source spectrum. It is a calculation result graph.
6 is an isoline diagram showing an evaluation function for predicting the reflectance in the reflective liquid crystal display device of Example 1 and y of CIE1931 chromaticity coordinates calculated from a D65 standard light source spectrum. FIG. It is a calculation result graph.
FIG. 7 is a diagram illustrating a region where both good white balance and lightness can be obtained according to FIGS. 4, 5, and 6.
FIG. 8 is a diagram illustrating a setting azimuth of an arrangement of a polarizing plate and two optical phase difference compensators in the reflective liquid crystal display device of Example 3.
FIG. 9 is a graph showing measured values of the voltage dependence of the reflectance of the reflective liquid crystal display device of Example 3.
FIG. 10 is an arrangement conceptual diagram showing a measurement optical system in which the voltage dependence of the reflectance of the reflective liquid crystal display device of Example 3 is measured.
FIG. 11 is a diagram illustrating a setting azimuth of an arrangement of a polarizing plate and two optical retardation compensators in a reflective liquid crystal display device of Example 4.
FIGS. 12 (a) and 12 (b) show the arrangement direction of the polarizing plate and the arrangement of two optical phase difference compensators for samples # 5a and # 5b of the reflective liquid crystal display device of Example 5, respectively. It is a figure which shows the setting azimuth | direction of the direction and the liquid crystal orientation of a liquid-crystal layer.
FIG. 13 is a graph showing measured values of the voltage dependence of the reflectance of the reflective liquid crystal display device of Example 5.
FIG. 14 is a diagram illustrating a set orientation of an alignment direction of a liquid crystal in the vicinity of the upper substrate of Example 7 and a plane including an observation orientation.
FIG. 15 is a table showing the results of visual observation of the reflective liquid crystal display device of Example 7 while changing the value of θ4.
FIG. 16 is a cross-sectional view of a principal part showing a schematic structure of a reflective liquid crystal display device of Example 8.
FIG. 17 is a diagram illustrating setting orientations of a polarizing plate arrangement direction, an arrangement direction of two optical retardation compensation plates, and a liquid crystal alignment of a liquid crystal layer in a reflective liquid crystal display device of Example 8.
FIG. 18 is a partially enlarged plan view showing the uneven shape of the light reflecting plate used in the reflective liquid crystal display device of Example 9.
FIG. 19 is a conceptual diagram showing the measurement direction of the measurement optical system for the reflection characteristics of the reflective electrode (light reflection plate) of Example 9.
20 is a diagram showing measured values of the reflection characteristics of the reflective electrode (light reflecting plate) of Example 9 by the measurement system of FIG.
FIGS. 21 (a) to 21 (d) show the polarizing plate arrangement direction and two optical sheets for samples # 9a, # 9b, # 9c, and # 9d of the reflective liquid crystal display device of Example 9, respectively. It is a figure which shows the setting direction of the arrangement direction of a phase difference compensating plate, and the liquid crystal orientation of a liquid crystal layer.
FIG. 22 is a cross-sectional view of a principal part showing a schematic structure of a touch panel used in the reflective liquid crystal display device with an integrated touch panel of Example 10.
FIG. 23 is a cross-sectional view of a principal part showing a schematic structure of a touch-panel-integrated reflective liquid crystal display device of Example 10.
FIG. 24 is a cross-sectional view of a principal part showing a schematic structure of a touch panel integrated reflective liquid crystal display device of a comparative example.
FIG. 25 is a cross-sectional view of a principal part showing a schematic structure of a reflective liquid crystal display device according to another embodiment of the present invention.
FIG. 26 is a diagram illustrating a setting azimuth of an arrangement of a polarizing plate and two optical phase difference compensation plates according to another embodiment.
FIG. 27 is an explanatory diagram showing the difference in the orientation of the liquid crystal layer in the reflective liquid crystal display device depending on the voltage.
FIG. 28 is an explanatory diagram showing how the viewing angle changes depending on the relationship between the orientation direction of the liquid crystal layer and the illumination direction of the reflective liquid crystal display device.
FIG. 29 is a graph showing measured values of the voltage dependency of the reflectance of the reflective liquid crystal display device of Example 11.
30 is a main-portion cross-sectional view showing the structure of Sample # 12a of Example 12. FIG.
FIG. 31 is a main-portion cross-sectional view showing the structure of sample # 12b of Example 12.
[Explanation of symbols]
    1 Liquid crystal layer
    2,3 alignment film
    4,5 substrate
    6 Transparent electrodes
    7 Light reflecting film
    8 Optical phase difference compensator
    9 Optical retardation compensation plate
  10 Polarizing plate
  11 Transmission axis direction of polarizing plate
  12 Slow axis orientation of optical phase difference compensation plate 9
  13 Slow axis orientation of optical phase difference compensation plate 8
  14 Orientation of alignment of liquid crystal molecules in the vicinity of alignment film formed on color filter
  15 Orientation direction of liquid crystal molecules in the vicinity of the alignment film formed on the TFT element substrate
  16 reflective liquid crystal display
  19 Light reflective pixel electrode
  23 TFT element substrate
  26 Color filter substrate

Claims (3)

A liquid crystal layer sandwiched between at least a first substrate having a light reflecting means and a second substrate having a light transmitting property, and selectively transmits substantially circularly polarized light in a visible wavelength range from the natural light to the left or right. A circularly polarizing means, and when natural light is incident on the circularly polarizing means, a surface that emits circularly polarized light is installed on the liquid crystal layer side, and the substantially circularly polarized light that is incident is When white display is performed, on the surface of the first substrate, the light is linearly polarized in an arbitrary direction with respect to each wavelength of the natural light,
The liquid crystal is composed of oriented nematic liquid crystal and has positive dielectric anisotropy,
The product Δnd of the liquid crystal layer birefringence difference Δn and the liquid crystal layer thickness d, and the value of the liquid crystal layer twist angle φtw are:

Which satisfies the equation
The circularly polarizing means uses an optical phase difference compensation plate,
The optical retardation compensator is darkened by setting a condition changed from the condition that incident light to the liquid crystal layer becomes circularly polarized to cancel the residual phase difference that occurs when a voltage is applied to the liquid crystal layer. A reflective liquid crystal display device characterized by being in a state. A liquid crystal layer sandwiched between at least a first substrate having a light reflecting means and a second substrate having a light transmitting property, and selectively transmits substantially circularly polarized light in a visible wavelength range from the natural light to the left or right. A circularly polarizing means, and when natural light is incident on the circularly polarizing means, a surface that emits circularly polarized light is installed on the liquid crystal layer side, and the substantially circularly polarized light that is incident is When white display is performed, on the surface of the first substrate, the light is linearly polarized in an arbitrary direction with respect to each wavelength of the natural light,
The liquid crystal is composed of oriented nematic liquid crystal and has positive dielectric anisotropy,
The product Δnd of the liquid crystal layer birefringence difference Δn and the liquid crystal layer thickness d, and the value of the liquid crystal layer twist angle φtw are:

Which satisfies the equation
The circularly polarizing means comprises a first optical phase difference compensation plate, a second optical phase difference compensation plate whose retardation in the substrate normal direction is set to 200 nm or more and 360 nm or less, and a linear polarizing plate, and An angle formed between the transmission axis or absorption axis of the linearly polarizing plate and the slow axis of the first optical phase difference compensating plate is θ1, and the transmission axis or absorption axis of the linearly polarizing plate and the second optical phase difference compensation are set as θ1. When the angle between the slow axis of the plate and θ2 is θ2, the value of | 2 × θ2−θ1 | is 35 degrees or more and 55 degrees or less,
The orientation of the slow axis of the first optical retardation compensator is parallel to the liquid crystal alignment direction at the center of both end faces in the thickness direction of the liquid crystal layer,
The retardation in the substrate normal direction of the first optical retardation compensator is 10 nm to 50 nm smaller than the retardation of 100 nm or more and 180 nm or less capable of giving a phase difference of only a quarter wavelength in the entire visible wavelength region. A reflective liquid crystal display device characterized in that it is set as described above. A liquid crystal layer sandwiched between at least a first substrate having a light reflecting means and a second substrate having a light transmitting property, and selectively transmits substantially circularly polarized light in a visible wavelength range from the natural light to the left or right. A circularly polarizing means, and when natural light is incident on the circularly polarizing means, a surface that emits circularly polarized light is installed on the liquid crystal layer side, and the substantially circularly polarized light that is incident is When white display is performed, on the surface of the first substrate, the light is linearly polarized in an arbitrary direction with respect to each wavelength of the natural light,
The liquid crystal is composed of oriented nematic liquid crystal and has positive dielectric anisotropy,
The product Δnd of the liquid crystal layer birefringence difference Δn and the liquid crystal layer thickness d, and the value of the liquid crystal layer twist angle φtw are:

Which satisfies the equation
The circularly polarizing means comprises a first optical phase difference compensation plate, a second optical phase difference compensation plate whose retardation in the substrate normal direction is set to 200 nm or more and 360 nm or less, and a linear polarizing plate, and The angle formed between the transmission axis or absorption axis of the linearly polarizing plate and the slow axis of the first optical phase difference compensating plate is θ1, and the transmission axis or absorption axis of the linearly polarizing plate and the second optical phase difference compensation. When the angle between the slow axis of the plate and θ2 is θ2, the value of | 2 × θ2−θ1 | is 35 degrees or more and 55 degrees or less,
The direction of the slow axis of the first optical retardation compensator is orthogonal to the liquid crystal alignment direction at the center of both end faces in the thickness direction of the liquid crystal layer,
Retardation in the normal direction of the substrate of the first optical retardation compensation plate is 10 nm to 50 nm larger than the retardation of 100 nm or more and 180 nm or less that can give a phase difference of only a quarter wavelength in the entire visible wavelength region. A reflective liquid crystal display device characterized in that it is set as described above.

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