JP4056314B2 - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device having wide viewing angle characteristics and high alignment stability and exhibiting high display quality. <P>SOLUTION: The liquid crystal display device is provided with first and second substrates, a vertical alignment type liquid crystal layer interposed between them; a pair of polarizing plates placed opposite to each other via the first and second substrates and arranged so as to make respective axes of polarization almost perpendicularly intersect each other, and a plurality of pixel regions. The first substrate has alignment controlling structures, in each region of a plurality of the pixel regions, exhibiting alignment controllability to form a plurality of liquid crystal domains, in each of which a radially inclined alignment state takes place in a voltage applied state, in the liquid crystal layer. Furthermore, the second substrate has projecting parts protruding to the liquid crystal layer side on a region corresponding to at least one liquid crystal domain out of a plurality of the liquid crystal domains. A sectional profile of the projecting part along the substrate surface of the second substrate is essentially constituted only of edges almost parallel to and edges almost vertical to the axis of polarization of one out of a pair of the polarizing plates. <P>COPYRIGHT: (C)2004,JPO

Description

表１および図１４（ｃ）から分かるように、ピッチｐが約２５μｍ以上のときにはポジ型（図１４（ａ））パターンの方が中実部１４ｂの面積比率が高くなり、約２５μｍよりも短くなるとネガ型（図１４（ｂ））の方が中実部１４ｂの面積比率が大きくなる。従って、表示輝度および配向の安定性の観点から、ピッチｐが約２５μｍを境にして、採用すべきパターンが変わる。例えば、幅７５μｍの絵素電極１４の幅方向に、３個以下の単位格子を設ける場合には、図１４（ａ）に示したポジ型パターンが好ましく、４個以上の単位格子を設ける場合には、図１４（ｂ）に示したネガ型パターンが好ましい。例示したパターン以外の場合においても、中実部１４ｂの面積比率が大きくなるように、ポジ型またはネガ型の何れかを選択すればよい。
【０１２２】
単位格子の数は、以下のようにして求められる。絵素電極１４の幅（横または縦）に対して、１つまたは２以上の整数個の単位格子が配置されるように、単位格子のサイズを計算し、それぞれの単位格子サイズについて中実部面積比率を計算し、中実部面積比率が最大となる単位格子サイズを選ぶ。但し、ポジ型パターンの場合には単位中実部１４ｂ’の直径が１５μｍ未満、ネガ型パターンの場合には開口部１４ａの直径が１５μｍ未満になると、斜め電界による配向規制力が低下し、安定した放射状傾斜配向が得られ難くなる。なお、これら直径の下限値は、液晶層３０の厚さが約３μｍの場合であり、液晶層３０の厚さがこれよりも薄いと、単位中実部１４ｂ’および開口部１４ａの直径は、上記の下限値よりもさらに小さくとも安定な放射状傾斜配向が得られ、液晶層３０の厚さがこれよりも厚い場合に安定な放射状傾斜配向を得るために必要な、単位中実部１４ｂ’および開口部１４ａの直径の下限値は、上記の下限値よりも大きくなる。
【０１２３】
なお、後述するように、開口部１４ａの内側に凸部（図３８参照）を形成することによって、放射状傾斜配向の安定性を高めることができる。上述の条件は、いずれも、凸部を形成していない場合についてである。
【０１２４】
上述した液晶表示装置１００の構成は、絵素電極１４が開口部１４ａを有する電極であること以外は、公知の垂直配向型液晶表示装置と同じ構成を採用することができ、公知の製造方法で製造することができる。
【０１２５】
なお、典型的には、負の誘電異方性を有する液晶分子を垂直配向させるために、絵素電極１４および対向電極２２の液晶層３０側表面には垂直配向層（不図示）が形成されている。
【０１２６】
液晶材料としては、負の誘電異方性を有するネマチック液晶材料が用いられる。また、負の誘電異方性を有するネマチック液晶材料に２色性色素添加することによって、ゲスト−ホストモードの液晶表示装置を得ることもできる。ゲスト−ホストモードの液晶表示装置は、偏光板を必要としない。
【０１２７】
（凸部）
次に、凸部の具体的な構造と作用を説明する。これまでの説明にそって、配向規制構造がＴＦＴ基板に設けられ、凸部が対向基板に設けられている場合について説明する。本発明による液晶表示装置は、液晶分子を基板面に対して垂直配向させるための構成（例えば一対の基板の液晶層側に設けられた垂直配向膜）に加え、上述したような液晶分子を放射状傾斜配向させるための配向規制構造と、後述するように配向規制構造と協同的に液晶分子を放射状傾斜配向させる（放射状傾斜配向状態を安定化させる）ための凸部とを有している。
【０１２８】
図１５（ａ）および（ｂ）を参照しながら、対向基板２００ｂに設けられた凸部２８Ａの構造とその作用とを説明する。図１５（ａ）は、液晶層３０側に突き出た凸部２８Ａを有する対向基板２００ｂを模式的に示す断面図であり、図１５（ｂ）は、凸部２８Ａを模式的に示す上面図である。上述の液晶表示装置と実質的に同じ構成要素には共通の参照符号を付して、その説明をここでは省略する。
【０１２９】
凸部２８Ａは、図１５（ａ）および（ｂ）に示したように、その側面２８ｓが凸面化された略正四角錐状であり、対向基板２００ｂの基板面に対して傾斜した側面２８ｓと、略正方形状の底面とを有している。凸部２８Ａは、ここでは、対向電極２２上に形成されている。凸部２８Ａは、図１５（ｂ）に示したように、略正方形状の底面の辺が、クロスニコル状態に配置された一対の偏光板（ＴＦＴ基板１００ａおよび対向基板２００ｂの外側に設けられている）の偏光軸（図１５（ｂ）中に矢印ＰＡで示している。）に略平行または略垂直となるように配置されている。言い換えると、凸部２８Ａの断面形状（対向基板２００ｂの基板面に沿った断面形状）は、一対の偏光板の一方の偏光軸に略平行な辺および略直交する辺のみから実質的に構成された形状である。
【０１３０】
凸部２８Ａの表面は、垂直配向性を有しており（典型的には、凸部２８Ａを覆うように垂直配向膜（不図示）が形成されている。）、図１５（ａ）に示したように、液晶分子３０ａは、傾斜側面２８ｓのアンカリング効果によって、これらに対してほぼ垂直に配向する。凸部２８Ａの対向基板２００ｂの基板面に沿った断面形状は、略正方形であるので、凸部２８Ａの周辺の液晶分子３０ａは、凸部２８Ａを中心に放射状に傾斜配向する。
【０１３１】
つまり、凸部２８Ａは、その表面（垂直配向性を有する）の形状効果によって、液晶分子３０ａを放射状に傾斜配向させるように作用する。凸部２８Ａによる液晶分子の傾斜方向は、配向規制構造によって絵素電極１４の単位中実部１４ｂ’（例えば図１参照）に対応する領域に形成される液晶ドメインの放射状傾斜配向の配向方向と整合する。凸部２８Ａは、電圧の印加無印加に関わらず、配向規制力を発現するので、全ての表示階調において安定した放射状傾斜配向が得られ、応力に対する耐性にも優れている。
【０１３２】
凸部２８Ａを形成する材料に特に制限はないが、樹脂などの誘電体材料を用いて容易に形成することができる。また、熱によって変形する樹脂材料を用いると、パターニングの後の熱処理によって、図１５（ａ）に示したような、なだらかな丘上の断面形状を有する凸部２８Ａを容易に形成できるので好ましい。図示したように、頂点を有するなだらかな形状（基板面の法線に沿った断面形状）を有する凸部２８Ａや図１６（ａ）および（ｂ）に示すような略正四角錐状の形状を有する凸部２８Ｂは、放射状傾斜配向の中心位置を固定する効果に優れている。勿論、凸部は、頂面を有していてもよく、例えば、略四角錐台状であってもよい。
【０１３３】
上述した、配向規制構造および凸部２８Ａを備える液晶表示装置２００を図１７（ａ）および（ｂ）に示す。図１７（ａ）は上面図であり、図１７（ｂ）は、図１７（ａ）中の１７Ｂ−１７Ｂ’線に沿った断面図に相当する。
【０１３４】
液晶表示装置２００は、配向規制構造を構成する開口部１４ａを有する絵素電極１４を有するＴＦＴ基板１００ａと、液晶層３０側に突き出た凸部２８Ａを有する対向基板２００ｂとを有している。なお、配向規制構造は、ここで例示する構成に限られず、前述した種々の構成を適宜用いることができる。また、液晶表示装置２００は、一対の基板１００ａおよび２００ｂを介して互いに対向し、偏光軸（図１７（ａ）中に矢印ＰＡで示す。）が互いに略直交するように配置された一対の偏光板７０ａおよび７０ｂを備えており、ノーマリブラックモードで表示を行う液晶表示装置である。
【０１３５】
液晶表示装置２００の対向基板２００ｂに設けられている凸部２８Ａは、絵素電極１４の中実部１４ｂに対向する領域に設けられており、より具体的には、中実部１４ｂに対向する領域の中央付近に設けられている。
【０１３６】
このように配置することによって、液晶層３０に電圧を印加した状態、すなわち、絵素電極１４と対向電極２２との間に電圧を印加した状態において、配向規制構造によって形成される放射状傾斜配向の方向と、凸部２８Ａによって形成される放射状傾斜配向の方向が整合し、放射状傾斜配向が安定化する。この様子を図１８（ａ）〜（ｃ）に模式的に示している。図１８（ａ）は電圧無印加時を示し、図１８（ｂ）は電圧印加後に配向が変化し始めた状態（ＯＮ初期状態）を示し、図１８（ｃ）は電圧印加中の定常状態を模式的に示している。
【０１３７】
凸部２８Ａによる配向規制力は、図１８（ａ）に示したように、電圧無印加状態においても、近傍の液晶分子３０ａに作用し、放射状傾斜配向を形成する。
【０１３８】
電圧を印加し始めると、図１８（ｂ）に示したような等電位線ＥＱで示される電界が発生し（配向規制構造による）、開口部１４ａおよび中実部１４ｂに対応する領域に液晶分子３０ａが放射状傾斜配向した液晶ドメインが形成され、図１８（ｃ）に示したような定常状態に達する。このとき、中実部１４ｂに対応する領域に形成される液晶ドメイン内の液晶分子３０ａの傾斜方向は、対応する領域に設けられた凸部２８Ａの配向規制力による液晶分子３０ａの傾斜方向と一致する。
【０１３９】
定常状態にある液晶表示装置２００に応力が印加されると、液晶層３０の放射状傾斜配向は一旦崩れるが、応力が取り除かれると、配向規制構造および凸部２８Ａによる配向規制力が液晶分子３０ａに作用しているので、放射状傾斜配向状態に復帰する。従って、応力による残像の発生が抑制される。
【０１４０】
凸部２８Ａによる配向規制力は、配向規制構造によって形成される放射状傾斜配向の安定化および中心軸位置を固定する効果を有せばいいので、それほど強い配向規制力は必要ない。例えば、直径が約３０μｍ〜約５０μｍの単位中実部１４ｂ’に対して、それぞれ直径が約１５μｍで高さ（厚さ）が約１μｍの凸部２８Ａを形成すれば、十分な配向規制力が得られる。
【０１４１】
また、液晶表示装置２００が備える凸部２８Ａの断面形状（対向基板２００ｂの基板面に沿った断面形状）は、図１５（ｂ）および図１７（ａ）に示したように、一対の偏光板７０ａおよび７０ｂの一方の偏光軸に対して略平行な辺および略垂直な辺のみで実質的に構成された形状である。つまり、凸部２８Ａの断面形状を構成する辺は、偏光板７０ａおよび７０ｂの偏光軸に略平行であるか、または略直交している。従って、電圧無印加時に凸部２８Ａの配向規制力を受けて放射状傾斜配向する液晶分子３０ａは、図１７（ａ）に示したように、偏光板７０ａおよび７０ｂの偏光軸に対して略平行または略垂直な方位角方向に配向する。そのため、凸部２８Ａ近傍の液晶分子（凸部の側面による配向規制力により基板面法線に対して傾斜する液晶分子）３０ａは、液晶層３０に入射する光に対してほとんど位相差を与えない。そのため、黒表示時の光漏れの発生が抑制され、その結果、コントラスト比の高い表示が実現される。
【０１４２】
比較例として、断面形状が略円形である凸部１０２８を備えた液晶表示装置１０００における、凸部１０２８近傍の液晶分子３０ａの配向の様子を図１９に示す。液晶表示装置１０００においても、凸部１０２８の近傍の液晶分子３０ａは、凸部１０２８の側面に垂直に配向し、基板面法線方向に対して傾斜して配向しているが、凸部１０２８の断面形状が略円形であるため、この傾斜配向する液晶分子３０ａは、図１９に示したように全方位角方向に対して同等の確率で配向する。従って、偏光板の偏光軸に対して傾斜した方位角方向に配向している液晶分子３０ａの存在確率が比較的高く、このような液晶分子３０ａは、液晶層３０を通過する光に対して位相差を与えるので、図１９中に楕円で囲んだ領域ＬＬにおいて光漏れが発生し、そのため、コントラスト比が低下してしまう。凸部１０２８の外周を小さくすることによって、凸部１０２８の配向規制力により放射状傾斜配向する液晶分子３０ａの存在確率を低くし、そのことによって光漏れを抑制することもできるが、その場合には、当然ながら、配向規制力を発現する凸部１０２８の側面の面積が小さくなるので、液晶ドメインに対する配向規制力が低下し、放射状傾斜配向の中心固定効果が低下してしまう。
【０１４３】
これに対して、本発明の液晶表示装置２００においては、図２０に示すように、電圧無印加時に放射状傾斜配向する液晶分子３０ａのうち、偏光板７０ａおよび７０ｂの偏光軸にほぼ平行またはほぼ垂直な方位角方向に配向する液晶分子３０ａの割合が高い。図２０に示したように、凸部２８Ａの角部近傍（図２０中の楕円で囲まれた領域）においては偏光軸に対して傾斜した液晶分子３０ａが存在することもあるが、その存在確率は、凸部の断面形状が略円形である場合に比べて遙かに小さく、光漏れの程度は遙かに軽微である。そのため、本発明によると、凸部による配向規制効果を低下させることなく、高コントラスト比の表示を行うことができる。つまり、高い耐応力性と、高い表示品位を有する液晶表示装置が提供される。
【０１４４】
上述したように、本発明による液晶表示装置２００においては、凸部２８Ａの断面形状が、一対の偏光板７０ａおよび７０ｂの一方の偏光軸に対して略平行な辺および略直交する辺のみで実質的に構成された形状であるので、コントラスト比の低下が抑制・防止され、そのため、高品位の表示を行うことができる。
【０１４５】
凸部の断面形状は、偏光軸に略平行な辺および略直交する辺のみで実質的に構成された形状であればよく、図１５（ｂ）に示した略正方形や、略長方形などの略矩形としてもよいし、略十字型としてもよい。また、凸部の断面形状は、視野角依存性を低減する観点からは、高い回転対称性を有することが好ましく、このような観点からは略長方形よりも略正方形の方が好ましい。
【０１４６】
なお、製造プロセスの制約上、図１５（ｂ）などに示したように、凸部の角部が丸く形成されてしまい、凸部の断面形状が厳密には偏光軸に略平行な辺および略直交する辺のみでは構成されないこともあるが、偏光軸に略平行な辺および略直交する辺のみで実質的に構成されていれば、十分高品位の表示を行うことができる。例えば、断面形状を構成する辺の長さの合計（外周）に対して、偏光軸に略平行な辺および略直交する辺の長さが占める割合が５０％以上であれば、偏光軸に略平行な辺および略直交する辺のみで実質的に構成されているといえる。
【０１４７】
図２１（ａ）および（ｂ）に、配向規制構造および凸部を備える他の液晶表示装置２００Ａを示す。図２１（ａ）は、基板法線方向から見た上面図であり、図２１（ｂ）は図２１（ａ）中の２１Ｂ−２１Ｂ’線に沿った断面図に相当する。液晶表示装置２００Ａは、スペーサとしても機能する凸部２８Ｃを備えている点において液晶表示装置２００と異なる。
【０１４８】
図２１（ａ）および（ｂ）に示したように、液晶表示装置２００Ａにおいては、凸部２８Ｃは、ＴＦＴ基板１００ａと対向基板３００ｂとの間にこれらの間隔を保持するように（つまりＴＦＴ基板１００ａおよび対向基板３００ｂの両方に接するように）設けられており、液晶層３０の厚さを規定するスペーサとしても機能する。
【０１４９】
液晶表示装置２００Ａにおいても、図２２（ａ）〜（ｃ）に模式的に示すように、液晶層３０に電圧を印加した状態、すなわち、絵素電極１４と対向電極２２との間に電圧を印加した状態において、配向規制構造によって形成される放射状傾斜配向の方向と、凸部２８Ｃによって形成される放射状傾斜配向の方向が整合するので、放射状傾斜配向が安定化する。
【０１５０】
また、液晶表示装置２００Ａは、絵素電極１４の中実部１４ｂ’に対向する領域の中央付近に設けられた凸部２８Ｃによって液晶層３０の厚さが規定されている。従って、このような構成を採用すると、液晶層３０の厚さを規定するスペーサを別途に設ける必要がなく、製造プロセスを簡略化することができる利点がある。
【０１５１】
ここでは、凸部２８Ｃは、図２１（ａ）および（ｂ）に示したように略正四角錐台状であり、凸部２８Ｃの断面形状は、略正方形である。さらに、凸部２８Ｃは、略正方形の断面形状を構成する辺が、クロスニコル状態に配置された一対の偏光板の偏光軸（図２１（ａ）中に矢印ＰＡで示している。）に略平行または略垂直になるように配置されている。すなわち、凸部２８Ｃの断面形状は、偏光板の偏光軸に略平行な辺および略直交する辺のみで実質的に構成された形状である。従って、液晶表示装置２００Ａにおいても、黒表示時の光漏れの発生が抑制され、その結果、コントラスト比の低下が抑制・防止される。
【０１５２】
上述した光漏れを抑制する効果は、図１７（ｂ）などに示したように凸部２８Ａの高さが低く、凸部２８Ａがスペーサとしては機能しない構成においてよりも、図２１（ｂ）に示したように凸部２８Ｃの高さが高く、凸部２８Ｃがスペーサとしても機能する構成においての方が高い。つまり、本発明は、凸部がスペーサとしても機能する構成において特に好適に用いられる。凸部の高さが高いと、配向規制力を発現する側面の面積も大きいので、凸部の配向規制力を受けて電圧無印加時に放射状傾斜配向する液晶分子の存在確率も高いからである。勿論、凸部の外周を小さくすることによっても、放射状傾斜配向する液晶分子の存在確率を低くすることはできるが、その場合には、液晶ドメインに対する配向規制力が低下するので、放射状傾斜配向の中心固定効果が低下してしまう。また、スペーサとして機能するには凸部は所定の高さに形成されている必要があり、外周が小さな凸部は、外周が大きな凸部に比べて、所定の高さに形成する場合にプロセス上の困難さを伴うことが多い。
【０１５３】
本願発明者は、図２１（ａ）および（ｂ）に示したように略正四角錐台状の凸部２８Ｃを備えた液晶表示装置２００Ａと、図２３（ａ）および（ｂ）に示すように略円錐台状の凸部１１２８を備えた比較例としての液晶表示装置１１００を実際に試作して検討した。その結果、比較例の液晶表示装置１１００のコントラスト比が約３００であったのに対して、本発明による液晶表示装置２００Ａのコントラスト比は約４５０であり、コントラスト比が大幅に向上していることが確認された。
【０１５４】
図２１（ｂ）に示したようなスペーサとしても機能する凸部２８Ｃの側面２８ｓは、基板２１の基板面に対して９０°未満のテーパ角θで傾斜していることが好ましい。側面２８ｓが基板面に対して９０°未満の角度で傾斜していると、凸部２８Ｃの側面２８ｓは、液晶層３０の液晶分子３０ａに対して、斜め電界による配向規制方向と同じ方向の配向規制力を有することになり、放射状傾斜配向を安定させるように作用する。勿論、側面２８ｓが基板面に対して９０°以上の角度で傾斜していてもよいが、放射状傾斜配向を安定化させる観点からは、側面２８ｓのテーパ角θが９０°を大きく超えないことが好ましく、９０°未満であることがさらに好ましい。テーパ角θが９０°を超える場合であっても、９０°に近ければ（９０°を大きく超えなければ）、凸部２８Ｃの傾斜側面２８ｓ近傍の液晶分子３０ａは、基板面に対してほぼ水平な方向に傾斜しているので、若干の捩れを発生させるだけで、エッジ部の液晶分子３０ａの傾斜方向と整合をとりながら放射状傾斜配向する。ただし、図２４に示す凸部２８Ｄのように、側面２８ｓが９０°を大きく超えて傾斜していると、側面２８ｓは、液晶層３０の液晶分子３０ａに対して、斜め電界による配向規制方向と逆方向の配向規制力を有することになるので、放射状傾斜配向が不安定となることがある。
【０１５５】
また、スペーサとして機能する凸部の側面は、図２５に示すように曲面であってもよい。図２５に示した凸部２８Ｅにおいては、側面２８ｓの基板面に対するテーパ角が液晶層３０の厚さ方向に沿って変化するが、液晶層３０の厚さ方向のどこの位置においても側面２８ｓの傾斜角は９０°未満であるため、このような凸部２８Ｅも放射状傾斜配向を安定させる凸部として好適に用いることができる。
【０１５６】
なお、上述したように上下の基板（ＴＦＴ基板および対向基板）に接し、液晶層３０の厚さを規定するスペーサとしても機能する凸部は、液晶表示装置の製造プロセスにおいては、上下のいずれの基板に形成されてもよい。いずれの基板に形成されていても、上下の基板が貼り合わされると、凸部は両方の基板に接し、スペーサとして機能するとともに、液晶ドメインの放射状傾斜配向を安定化させる。
【０１５７】
上述の説明では、図１９および図２３に示した液晶表示装置１０００および１１００において光漏れが発生してコントラスト比が低下することを述べたが、本願発明者が凸部の断面形状と表示品位との関係について詳細な検討を行ったところ、凸部の断面形状が略円形であると、以下の２つの問題も発生することがわかった。
【０１５８】
１つは、正面方向（表示面法線方向）から観察したときの階調輝度特性と斜め方向（表示面法線から傾斜した方向）から観察したときの階調輝度特性との差が大きく、違和感のある表示となってしまうという問題である。
【０１５９】
この問題は、以下の理由によって発生する。凸部の断面形状が略円形であると、液晶ドメイン内の液晶分子の配向方位の指向性が低く、液晶ドメイン内の液晶分子は、電圧印加時には全ての方位角方向に沿ってほぼ等しい確率で傾斜配向する。そのため、液晶ドメイン内の液晶分子のうち、特定の方位に配向する液晶分子が、斜め方向から観察したときの表示特性に悪影響を与える。例えば、一対の偏光板のうちの一方の偏光軸に沿って視角を倒したとき、この偏光軸に沿った方位に配向する液晶分子は表示に寄与しないものの、他方の偏光軸に沿った方位に配向する液晶分子は斜め方向から観察したときの表示特性に影響を与える。具体的には、一方の偏光軸に沿って視角を倒したとき、他方の偏光軸に沿った方位に配向する液晶分子は、中間調表示に対応した電圧で透過率が最大となるような電圧−透過率特性を示す。そのため、斜め方向から観察したときの階調輝度特性は、中間調での階調つぶれや白階調での階調反転を示す。
【０１６０】
また、もう１つは、凸部の断面形状が略円形であると、十分に速い応答速度が得られないために、電圧印加直後の透過率の過渡的な増大が残像として視認されるという問題である。
【０１６１】
この問題は、以下の理由によって発生する。液晶層を構成する液晶材料にカイラル剤が添加されている場合、液晶層の液晶分子は、電圧が印加された直後には図５（ａ）に示したような単純な放射状傾斜配向をとるが、配向安定時（定常状態）においては、図５（ｂ）および（ｃ）に示したような渦巻き状の放射状傾斜配向をとる。この配向状態の変化に伴って、消光領域（偏光板の偏光軸に沿って液晶分子が配向しているために位相差を与えない領域）の面積が典型的には増加するので、電圧印加直後に比べて、定常状態においては透過率が低くなる。つまり、電圧印加直後に過渡的に透過率が高くなる。このように過渡的に透過率が極大値を有するので、応答速度が十分に速くない場合には残像が視認されてしまう。
【０１６２】
上述した２つの問題の発生は、凸部の断面形状（基板面に沿った断面形状）を略十字形とすることによって抑制・防止される。
【０１６３】
図２６に、断面形状が略十字形の凸部２８Ｆを備えた液晶表示装置３００を示す。図２６に示したように、液晶表示装置３００は、対向基板上に断面形状が略十字形の凸部２８Ｆを有している。凸部２８Ｆは、絵素電極１４が有する複数の単位中実部１４ｂ’のそれぞれに対応して設けられており、互いに略直交する２つの方向に沿って延びる略十字形の断面形状を有している。十字の延びる方向は、偏光板の偏光軸（図２６中に矢印ＰＡで示している。）と一致しており、凸部２８Ｆの断面形状は、偏光板の偏光軸に略平行な辺および略直交する辺のみで構成された形状である。
【０１６４】
液晶表示装置３００においても、凸部２８Ｆの断面形状が偏光軸に略平行な辺および略直交する辺のみで構成されているので、液晶表示装置２００と同様に、黒表示時の光漏れの発生が抑制され、コントラスト比の低下が抑制・防止される。
【０１６５】
さらに、液晶表示装置３００では、凸部２８Ｆの断面形状が略十字形であるので、液晶分子の配向方位に指向性をもたせることができる。すなわち、全ての方位角方向のそれぞれに沿って配向する液晶分子の存在確率に指向性をもたせることができる。具体的には、凸部２８Ｆの断面形状が略十字形であると、電圧印加時には、十字の延びる方向（偏光軸と一致）に対して４５°傾斜した方向に配向する液晶分子の存在確率が高く、十字の延びる方向に沿って配向する液晶分子の存在確率が低い。言い換えると、配向指向性を偏光軸に対して４５°傾斜した方向に偏らせている。そのため、斜め方向の表示特性に悪影響を与える、特定の方位に配向する液晶分子（例えば偏光軸に沿って配向する液晶分子）の存在確率を低くすることができ、そのことによって、正面方向と斜め方向との階調輝度特性の差を少なくし、違和感のない自然な表示を実現することができる。
【０１６６】
この効果を検証するために、図２７（ａ）、（ｂ）、（ｃ）および（ｄ）に示す凸部と単位中実部との組み合わせについて、視野角特性を評価した。図２７（ａ）は、略円形の凸部１０２８と略円形の単位中実部１４ｂ’との組み合わせを示し、図２７（ｂ）は、略円形の凸部１０２８と樽形（角部が円弧状の略正方形）の単位中実部１４ｂ’との組み合わせを示す。また、図２７（ｃ）は、略十字形の凸部２８Ｆと略円形の単位中実部１４ｂ’との組み合わせを示し、図２７（ｄ）は、略十字形の凸部２８Ｆと樽形の単位中実部１４ｂ’との組み合わせを示す。なお、図中では、単位中実部１４ｂ’の相互に接続する役割を果たしている部分（四方に延びる枝部）を省略している。
【０１６７】
図２７（ａ）、（ｂ）、（ｃ）および（ｄ）に示した組み合わせについての視野角特性の評価結果を図２８、図２９、図３０および図３１にそれぞれ示す。図２８、図２９、図３０および図３１は、横軸に最大階調電圧（ここでは６．４Ｖ）で規格化した印加電圧（Ｖ／Ｖｍａｘと表記する）を示し、縦軸に最大階調電圧での透過率で規格化した各視角方向の輝度（Ｌ／Ｌ（Ｖｍａｘ）と表記する。）を示すグラフである。図中、上、右上、右、右下、下、左下、左、左上で示す視角方向は、極角（正面方向からの傾斜角度）が６０°であり、方位角（表示面を時計の文字盤に見立てたときに１２時方向を０度として定義される表示面内の角度）がそれぞれ０°、４５°、９０°、１３５°、１８０°、２２５°、２７０°、３１５°である。これらのグラフにおいては、各視角方向の階調輝度特性が、直線であらわされる正面方向の階調輝度特性に近いほど、より違和感の少ない表示が得られるといえる。
【０１６８】
図２７（ａ）および（ｂ）に示したように略円形の凸部１０２８を用いた場合には、図２８および図２９に示したように、正面から観察したときの階調輝度特性と、斜め方向から観察したときの階調輝度特性との差が大きく、斜め方向の階調輝度特性において中間調での階調つぶれや白階調での階調反転がみられる。
【０１６９】
これに対して、図２７（ｃ）および（ｄ）に示したように略十字形の凸部２８Ｆを用いた場合には、図３０および図３１に示したように、正面から観察したときの階調輝度特性と、斜め方向から観察したときの階調輝度特性との差が小さく、斜め方向の階調輝度特性において中間調での階調つぶれや白階調での階調反転が抑制されている。従って、違和感のない表示が実現される。
【０１７０】
参考までに、図２８、図２９、図３０および図３１に示した視野角特性の評価結果を、より一般的な電圧−輝度特性を示すグラフとして図３２、図３３、図３４および図３５に示す。図３２、図３３、図３４および図３５は、横軸に印加電圧（Ｖ）を示し、縦軸に最大階調電圧での透過率で規格化した各視角方向の輝度（Ｌ／Ｌ（Ｖｍａｘ））を示すグラフである。
【０１７１】
図３２および図３３と、図３４および図３５とを比較すると、凸部の断面形状を略十字形とすることで、斜め方向から観察したときの表示特性と正面方向から観察したときの表示特性との差が小さくなっており、そのことによって違和感のない表示が得られていることがわかる。
【０１７２】
また、断面形状が略十字形の凸部２８Ｆは、断面形状が略円形で同程度の面積を占める凸部に比べ、液晶分子に対して配向規制力を及ぼす傾斜側面の面積が大きく、また、液晶ドメイン内のより広範な範囲に亘って配向規制力を及ぼすことができる。従って、液晶分子に対してより大きな配向規制力を効果的に及ぼすことができる。そのため、断面形状が略十字形の凸部２８Ｆを備えた液晶表示装置３００においては、電圧を印加した際の応答速度が向上し、液晶層３０の液晶分子３０ａはより短い時間で定常状態に達する。その結果、残像の発生が抑制された表示が実現される。
【０１７３】
図２７（ａ）に示した略円形の凸部１０２８および略円形の単位中実部１４ｂ’の組み合わせと、図２７（ｃ）に示した略十字形の凸部２８Ｆおよび略円形の単位中実部１４ｂ’の組み合わせについての応答速度特性を図３６に示す。また、図２７（ｂ）に示した略円形の凸部１０２８および樽形の単位中実部１４ｂ’の組み合わせと、図２７（ｄ）に示した略十字形の凸部２８Ｆおよび樽形の単位中実部１４ｂ’の組み合わせについての応答速度特性を図３７に示す。図３６および図３７は、横軸に電圧印加後の時間（ｍｓ）を示し、縦軸に配向安定時の透過輝度にたいする輝度比（％）を示すグラフである。
【０１７４】
凸部の断面形状が略円形である場合には、図３６および図３７中に○を付した実線で示したように、電圧印加後に過渡的に透過率が高くなり、残像が発生する。これに対して、凸部の断面形状が略十字形である場合には、図３６および図３７中に＋を付した実線で示したように、透過率が過渡的に極大値を持つことがなく、残像が発生しない。
【０１７５】
上述したように、凸部の断面形状を略十字形とすることによって、違和感がなく、かつ、残像の発生が抑制された高品位の表示が実現される。
【０１７６】
なお、ここまでは、凸部として、偏光軸に略平行な辺および略直交する辺のみから実質的に構成された断面形状の凸部のみを備える構成を示したが、このような断面形状の凸部と、断面形状がこのような形状ではない凸部とが同一基板上に混在する構成としてもよい。例えば、表示に悪影響を与える不要な電界が発生しやすい領域（バスライン近傍など）に、配向規制力を向上する観点から断面形状が略十字形の凸部を設け、他の領域には断面形状が略円形の凸部を設けてもよい。勿論、断面形状が略矩形の凸部と、断面形状が略円形の凸部とが混在する構成としてもよい。
【０１７７】
（他の実施形態）
以下、配向規制構造の改変例について説明する。これまでの説明にそって、配向規制構造がＴＦＴ基板に設けられ、凸部が対向基板に設けられている場合について説明するが、説明の簡単さのために、対向基板に設けられている凸部の図示および説明を省略する。また、一対の基板の外側に設けられる一対の偏光板についても図示を省略する。
【０１７８】
図３８（ａ）および（ｂ）を参照しながら、本発明による配向規制構造を備える他の液晶表示装置４００の１つの絵素領域の構造を説明する。また、以下の図面においては、液晶表示装置１００の構成要素と実質的に同じ機能を有する構成要素を同じ参照符号で示し、その説明を省略する。図３８（ａ）は基板法線方向から見た上面図であり、図３８（ｂ）は図３８（ａ）中の３８Ｂ−３８Ｂ’線に沿った断面図に相当する。図３８（ｂ）は、液晶層に電圧を印加していない状態を示している。
【０１７９】
図３８（ａ）および（ｂ）に示したように、液晶表示装置４００は、ＴＦＴ基板４００ａが、絵素電極１４の開口部１４ａの内側に凸部４０を有する点において、図１（ａ）および（ｂ）に示した液晶表示装置１００と異なっている。凸部４０の表面には、垂直配向膜（不図示）が設けられている。
【０１８０】
凸部４０の基板１１の面内方向の断面形状は、図３８（ａ）に示したように、開口部１４ａの形状と同じであり、ここでは略星形である。但し、隣接する凸部４０は互いに繋がっており、単位中実部１４ｂ’を略円形に完全に包囲するように形成されている。この凸部４０の基板１１に垂直な面内方向の断面形状は、図３８（ｂ）に示したように台形である。すなわち、基板面に平行な頂面４０ｔと基板面に対してテーパ角θ（＜９０°）で傾斜した側面４０ｓとを有している。凸部４０を覆うように垂直配向膜（不図示）が形成されているので、凸部４０の側面４０ｓは、液晶層３０の液晶分子３０ａに対して、斜め電界による配向規制方向と同じ方向の配向規制力を有することになり、放射状傾斜配向を安定化させるように作用する。
【０１８１】
この凸部４０の作用を図３９（ａ）〜（ｄ）、および図４０（ａ）および（ｂ）を参照しながら説明する。
【０１８２】
まず、図３９（ａ）〜（ｄ）を参照しながら、液晶分子３０ａの配向と垂直配向性を有する表面の形状との関係を説明する。
【０１８３】
図３９（ａ）に示したように、水平な表面上の液晶分子３０ａは、垂直配向性を有する表面（典型的には、垂直配向膜の表面）の配向規制力によって、表面に対して垂直に配向する。このように垂直配向状態にある液晶分子３０ａに液晶分子３０ａの軸方位に対して垂直な等電位線ＥＱで表される電界が印加されると、液晶分子３０ａには時計回りまたは反時計回り方向に傾斜させるトルクが等しい確率で作用する。従って、互いに対向する平行平板型配置の電極間にある液晶層３０内には、時計回り方向のトルクを受ける液晶分子３０ａと、反時計回りに方向のトルクを受ける液晶分子３０ａとが混在する。その結果、液晶層３０に印加された電圧に応じた配向状態への変化がスムーズに起こらないことがある。
【０１８４】
図３９（ｂ）に示したように、傾斜した表面に対して垂直に配向している液晶分子３０ａに対して、水平な等電位線ＥＱで表される電界が印加されると、液晶分子３０ａは、等電位線ＥＱと平行になるための傾斜量が少ない方向（図示の例では時計回り）に傾斜する。また、水平な表面に対して垂直に配向している液晶分子３０ａは、図３９（ｃ）に示したように、傾斜した表面に対して垂直に配向している液晶分子３０ａと配向が連続となるように（整合するように）、傾斜した表面上に位置する液晶分子３０ａと同じ方向（時計回り）に傾斜する。
【０１８５】
図３９（ｄ）に示したように、断面が台形の連続した凹凸状の表面に対しては、それぞれの傾斜した表面上の液晶分子３０ａによって規制される配向方向と整合するように、頂面および底面上の液晶分子３０ａが配向する。
【０１８６】
液晶表示装置４００は、このような表面の形状（凸部）による配向規制力の方向と、斜め電界による配向規制方向とを一致させることによって、放射状傾斜配向を安定化させる。
【０１８７】
図４０（ａ）および（ｂ）は、それぞれ図３８（ｂ）に示した液晶層３０に電圧を印加した状態を示しており、図４０（ａ）は、液晶層３０に印加された電圧に応じて、液晶分子３０ａの配向が変化し始めた状態（ＯＮ初期状態）を模式的に示しており、図４０（ｂ）は、印加された電圧に応じて変化した液晶分子３０ａの配向が定常状態に達した状態を模式的に示している。図４０（ａ）および（ｂ）中の曲線ＥＱは等電位線ＥＱを示す。
【０１８８】
絵素電極１４と対向電極２２とが同電位のとき（液晶層３０に電圧が印加されていない状態）には、図３８（ｂ）に示したように、絵素領域内の液晶分子３０ａは、両基板１１および２１の表面に対して垂直に配向している。このとき、凸部４０の側面４０ｓの垂直配向膜（不図示）に接する液晶分子３０ａは、側面４０ｓに対して垂直に配向し、側面４０ｓの近傍の液晶分子３０ａは、周辺の液晶分子３０ａとの相互作用（弾性体として性質）によって、図示したように、傾斜した配向をとる。
【０１８９】
液晶層３０に電圧を印加すると、図４０（ａ）に示した等電位線ＥＱで表される電位勾配が形成される。この等電位線ＥＱは、絵素電極１４の中実部１４ｂと対向電極２２との間に位置する液晶層３０内では、中実部１４ｂおよび対向電極２２の表面に対して平行であり、絵素電極１４の開口部１４ａに対応する領域で落ち込み、開口部１４ａのエッジ部（開口部１４ａの境界（外延）を含む開口部１４ａの内側周辺）ＥＧ上の液晶層３０内には、傾斜した等電位線ＥＱで表される斜め電界が形成される。
【０１９０】
この斜め電界によって、上述したように、エッジ部ＥＧ上の液晶分子３０ａは、図４０（ａ）中に矢印で示したように、図中の右側エッジ部ＥＧでは時計回り方向に、図中の左側エッジ部ＥＧでは反時計回り方向に、それぞれ傾斜（回転）し、等電位線ＥＱに平行に配向する。この斜め電界による配向規制方向は、それぞれのエッジ部ＥＧに位置する側面４０ｓによる配向規制方向と同じである。
【０１９１】
上述したように、傾斜した等電位線ＥＱ上に位置する液晶分子３０ａから始まる配向の変化が進み、定常状態に達すると、図４０（ｂ）に模式的に示した配向状態となる。開口部１４ａの中央付近、すなわち、凸部４０の頂面４０ｔの中央付近に位置する液晶分子３０ａは、開口部１４ａの互いに対向する両側のエッジ部ＥＧの液晶分子３０ａの配向の影響をほぼ同等に受けるので、等電位線ＥＱに対して垂直な配向状態を保ち、開口部１４ａ（凸部４０の頂面４０ｔ）の中央から離れた領域の液晶分子３０ａは、それぞれ近い方のエッジ部ＥＧの液晶分子３０ａの配向の影響を受けて傾斜し、開口部１４ａ（凸部４０の頂面４０ｔ）の中心ＳＡに関して対称な傾斜配向を形成する。また、開口部１４ａおよび凸部４０によって実質的に包囲された単位中実部１４ｂ’に対応する領域においても、単位中実部１４ｂ’の中心ＳＡに関して対称な傾斜配向を形成する。
【０１９２】
このように、液晶表示装置４００においても、液晶表示装置１００と同様に、放射状傾斜配向を有する液晶ドメインが開口部１４ａおよび単位中実部１４ｂ’に対応して形成される。凸部４０は単位中実部１４ｂ’を略円形に完全に包囲するように形成されているので、液晶ドメインは凸部４０で包囲された略円形の領域に対応して形成される。さらに、開口部１４ａの内側に設けられた凸部４０の側面は、開口部１４ａのエッジ部ＥＧ付近の液晶分子３０ａを、斜め電界による配向方向と同じ方向に傾斜させるように作用するので、放射状傾斜配向を安定化させる。
【０１９３】
斜め電界の配向規制力は、当然のことながら、電圧印加時にしか作用せず、その強さは電界の強さ（印加電圧の大きさ）に依存する。したがって、電界強度が弱い（すなわち、印加電圧が低い）と、斜め電界による配向規制力は弱く、液晶パネルに応力が加わると、液晶材料の流動によって放射状傾斜配向が崩れることがある。一旦、放射状傾斜配向が崩れると、十分に強い配向規制力を発揮する斜め電界を生成するだけの電圧が印加されないと、放射状傾斜配向は復元されない。これに対し、凸部４０の側面４０ｓによる配向規制力は、印加電圧に関係なく作用し、配向膜のアンカリング効果として知られているように、非常に強い。従って、液晶材料の流動が生じて、一旦放射状傾斜配向が崩れても、凸部４０の側面４０ｓの近傍の液晶分子３０ａは放射状傾斜配向のときと同じ配向方向を維持している。従って、液晶材料の流動が止まりさえすれば、放射状傾斜配向が容易に復元される。
【０１９４】
この様に、液晶表示装置４００は、応力に対して強いという特徴を有している。従って、液晶表示装置４００は、応力が印加されやすい、携帯して使用される機会の多いＰＣやＰＤＡに好適に用いられる。
【０１９５】
なお、凸部４０を透明性の高い誘電体を用いて形成すると、開口部１４ａに対応して形成される液晶ドメインの表示への寄与率が向上するという利点が得られる。一方、凸部４０を不透明な誘電体を用いて形成すると、凸部４０の側面３４０ｓによって傾斜配向している液晶分子３０ａのリタデーションに起因する光漏れを防止できるという利点が得られる。いずれを採用するかは、液晶表示装置の用途などに応じて決めればよい。いずれの場合にも、感光性樹脂を用いると、開口部１４ａに対応してパターニングする工程を簡略化できる利点がある。
【０１９６】
また、ここでは断面形状が略星形の凸部４０を例示したが、凸部４０の断面形状は勿論これに限定されない。凸部４０の断面形状（ＴＦＴ基板１００の基板面に沿った断面形状）が、偏光板の偏光軸に対して略平行な辺および略直交する辺のみで実質的に構成された形状であると、対向基板側の凸部２８Ａなどについて図１９および図２０を参照しながら説明したのと同様に、光漏れの発生が抑制・防止されるので、コントラスト比の低下が抑制・防止され、高品位の表示を行うことができる。
【０１９７】
上述したように、液晶表示装置４００は、絵素電極１４の開口部１４ａの内側に凸部４０を有し、凸部４０の側面４０ｓは、液晶層３０の液晶分子３０ａに対して、斜め電界による配向規制方向と同じ方向の配向規制力を有する。側面４０ｓが斜め電界による配向規制方向と同じ方向の配向規制力を有するための好ましい条件を図４１（ａ）〜（ｃ）を参照しながら説明する。
【０１９８】
図４１（ａ）〜（ｃ）は、それぞれ液晶表示装置４００Ａ、４００Ｂおよび４００Ｃの断面図を模式的に示し、図４０（ａ）に対応する。液晶表示装置４００Ａ、４００Ｂおよび４００Ｃは、いずれも開口部４０の内側に凸部を有するが、１つの構造体としての凸部４０全体と開口部４０との配置関係が液晶表示装置４００と異なっている。
【０１９９】
上述した液晶表示装置４００においては、図４０（ａ）に示したように、構造体としての凸部４０の全体が開口部４０ａの内側に形成されており、且つ、凸部４０の底面は開口部４０ａよりも小さい。図４１（ａ）に示した液晶表示装置４００Ａにおいては、凸部４０Ａの底面は開口部１４ａと一致しており、図４１（ｂ）に示した液晶表示装置４００Ｂにおいては、凸部４０Ｂは開口部１４ａよりも大きい底面を有し、開口部１４ａの周辺の中実部（導電膜）１４ｂを覆うように形成されている。これらの凸部４０、４０Ａおよび４０Ｂのいずれの側面４０ｓ上にも中実部１４ｂが形成されていない。その結果、それぞれの図に示したように、等電位線ＥＱは、中実部１４ｂ上ではほぼ平坦で、そのまま開口部１４ａで落ち込む。従って、液晶表示装置４００Ａおよび４００Ｂの凸部４０Ａおよび４０Ｂの側面４０ｓは、上述した液晶表示装置４００の凸部４０と同様に、斜め電界による配向規制力と同じ方向の配向規制力を発揮し、放射状傾斜配向を安定化する。
【０２００】
これに対し、図４１（ｃ）に示した液晶表示装置４００Ｃの凸部４０Ｃの底面は開口部１４ａよりも大きく、開口部１４ａの周辺の中実部１４ｂは凸部４０Ｃの側面４０ｓ上に形成されている。この側面４０ｓ上に形成された中実部１４ｂの影響で、等電位線ＥＱに山が形成される。等電位線ＥＱの山は、開口部１４ａで落ち込む等電位線ＥＱと反対の傾きを有しており、これは、液晶分子３０ａを放射状傾斜配向させる斜め電界とは逆向きの斜め電界を生成していることを示している。従って、側面４０ｓが斜め電界による配向規制方向と同じ方向の配向規制力を有するためには、側面４０ｓ上に中実部（導電膜）１４ｂが形成されていないことが好ましい。
【０２０１】
次に、図４２を参照しながら、図３８（ａ）に示した凸部４０の４２Ａ−４２Ａ’線に沿った断面構造を説明する。
【０２０２】
上述したように、図３８（ａ）に示した凸部４０は、単位中実部１４ｂ’を略円形に完全に包囲するように形成されているので、隣接する単位中実部１４ｂ’の相互に接続する役割を果たしている部分（円形部から四方に延びる枝部）は、図４２に示したように、凸部４０上に形成される。従って、絵素電極１４の中実部１４ｂを形成する導電膜を堆積する工程において、凸部４０上で断線が生じたり、あるいは、製造プロセスの後工程で剥離が生じる危険性が高い。
【０２０３】
そこで、図４３（ａ）および（ｂ）に示す液晶表示装置４００Ｄのように、開口部１４ａ内に、それぞれ独立した凸部４０Ｄが完全に含まれるように形成すると、中実部１４ｂを形成する導電膜は、基板１１の平坦な表面に形成されるので断線や剥離が起こる危険性が無くなる。なお、凸部４０Ｄは、単位中実部１４ｂ’を略円形に完全に包囲するようには形成されていないが、単位中実部１４ｂ’に対応した略円形の液晶ドメインが形成され、先の例と同様に、その放射状傾斜配向は安定化される。
【０２０４】
開口部１４ａ内に凸部４０を形成することによって、放射状傾斜配向を安定化させる効果は、例示したパターンの開口部１４ａに限られず、先に説明した全てのパターンの開口部１４ａに対して同様に適用でき、同様の効果を得ることができる。なお、凸部４０による応力に対する配向安定化効果を十分に発揮させるためには、凸部４０のパターン（基板法線方向から見たときにパターン）は、できるだけ広い領域の液晶層３０を包囲する形状であることが好ましい。従って、例えば、円形の開口部１４ａを有するネガ型パターンよりも、円形の単位中実部１４ｂ’を有するポジ型パターンの方が、凸部４０による配向安定化効果が大きい。
【０２０５】
対向基板側の凸部を設けずに、凸部４０によって、液晶パネルに応力が印加されても応力による残像が視認されない程度に十分な配向規制力を得るためには、凸部４０の高さは、液晶層３０の厚さが約３μｍの場合、約０．５μｍ〜約２μｍの範囲にあることが好ましい。一般に、凸部４０の高さは、液晶層３０の厚さの約１／６〜約２／３の範囲内にあることが好ましい。しかしながら、凸部４０の側面の配向規制力によって配向が規制される液晶分子は電圧に対して応答し難い（電圧によるリタデーションの変化が小さい）ので、表示のコントラスト比を低下させる要因となる。従って、凸部４０の大きさ、高さや数は、表示品位を低下させないように設定することが好ましい。
【０２０６】
上述した一対の電極のうちの一方に開口部を設けた電極構造では、開口部に対応する領域の液晶層に十分な電圧が印加されず、十分なリタデーション変化が得られないために、光の利用効率が低下するという問題が発生することがある。そこで、開口部を設けた電極（上層電極）の液晶層とは反対側に誘電体層を設け、この誘電体層を介して電極の開口部の少なくとも一部に対向するさらなる電極（下層電極）を設ける（２層構造電極）ことによって、開口部に対応する液晶層に十分な電圧を印加することができ、光の利用効率や応答特性を向上することができる。
【０２０７】
図４４に、下層電極１２と、上層電極１４と、これらの間に設けられた誘電体層１３とを有する絵素電極（２層構造電極）１５を備える液晶表示装置５００の一絵素領域の断面構造を模式的に示す。絵素電極１５の上層電極１４は、上述した絵素電極１４と実質的に等価で、上述した種々の形状、配置の開口部および中実部を有する。以下では、２層構造を有する絵素電極１５の機能を説明する。
【０２０８】
液晶表示装置５００の絵素電極１５は、複数の開口部１４ａ（１４ａ１および１４ａ２を含む）を有する。図４４（ａ）は、電圧が印加されていない液晶層３０内の液晶分子３０ａの配向状態（ＯＦＦ状態）を模式的に示している。図４４（ｂ）は、液晶層３０に印加された電圧に応じて、液晶分子３０ａの配向が変化し始めた状態（ＯＮ初期状態）を模式的に示している。図４４（ｃ）は、印加された電圧に応じて変化した液晶分子３０ａの配向が定常状態に達した状態を模式的に示している。なお、図４４では、開口部１４ａ１および１４ａ２に誘電体層１３を介して対向するように設けられた下層電極１２は、開口部１４ａ１および１４ａ２のそれぞれと重なり、且つ、開口部１４ａ１および１４ａ２との間の領域（上層電極１４が存在する領域）にも存在するように形成された例を示したが、下層電極１２の配置はこれに限られず、開口部１４ａ１および１４ａ２のそれぞれに対して、下層電極１２の面積＝開口部１４ａの面積、または、下層電極１２の面積＜開口部１４ａの面積としてもよい。すなわち、下層電極１２は、誘電体層１３を介して開口部１４ａの少なくとも一部と対向するように設けられていればよい。但し、下層電極１２が開口部１４ａ内に形成された構成においては、基板１１の法線方向から見た平面内に、下層電極１２および上層電極１４のいずれもが存在しない領域（隙間領域）が存在し、この隙間領域に対向する領域の液晶層３０に十分な電圧が印加されないことがあるので、液晶層３０の配向を安定化するように、この隙間領域の幅を十分に狭くすることが好ましく、典型的には、約４μｍを越えないことが好ましい。また、誘電体層１３を介して上層電極１４の導電層が存在する領域と対向する位置に形成された下層電極１２は、液晶層３０に印加される電界に実質的に影響しないので、特にパターニングする必要はないが、パターニングしてもよい。
【０２０９】
図４４（ａ）に示したように、絵素電極１５と対向電極２２が同電位のとき（液晶層３０に電圧が印加されていない状態）には、絵素領域内の液晶分子３０ａは、両基板１１および２１の表面に対して垂直に配向している。ここでは、簡単のために、絵素電極１５の上層電極１４と下層電極１２の電位は互いに等しいとする。
【０２１０】
液晶層３０に電圧を印加すると、図４４（ｂ）に示した等電位線ＥＱで表される電位勾配が形成される。絵素電極１５の上層電極１４と対向電極２２との間に位置する液晶層３０内には、上層電極１４および対向電極２２の表面に対して平行な等電位線ＥＱで表される、均一な電位勾配が形成される。上層電極１４の開口部１４ａ１および１４ａ２の上に位置する液晶層３０には、下層電極１２と対向電極２２との電位差に応じた電位勾配が形成される。このとき、液晶層３０内に形成される電位勾配が、誘電体層１３による電圧降下の影響を受けるので、液晶層３０内に形成される等電位線ＥＱは、開口部１４ａ１および１４ａ２に対応する領域で落ち込む（等電位線ＥＱに複数の「谷」が形成される）。誘電体層１３を介して開口部１４ａ１および１４ａ２に対向する領域に下層電極１２が形成されているので、開口部１４ａ１および１４ａ２のそれぞれの中央付近上に位置する液晶層３０内にも、上層電極１４および対向電極２２の面に対して平行な等電位線ＥＱで表される電位勾配が形成される（等電位線ＥＱの「谷の底」）。開口部１４ａ１および１４ａ２のエッジ部（開口部の境界（外延）を含む開口部の内側周辺）ＥＧ上の液晶層３０内には、傾斜した等電位線ＥＱで表される斜め電界が形成される。
【０２１１】
図４４（ｂ）と図２（ａ）との比較から明らかなように、液晶表示装置５００は下層電極１２を有するので、開口部１４ａに対応する領域に形成される液晶ドメインの液晶分子にも十分な大きさの電界を作用させることができる。
【０２１２】
負の誘電異方性を有する液晶分子３０ａには、液晶分子３０ａの軸方位を等電位線ＥＱに対して平行に配向させようとするトルクが作用する。従って、エッジ部ＥＧ上の液晶分子３０ａは、図４４（ｂ）中に矢印で示したように、図中の右側エッジ部ＥＧでは時計回り方向に、図中の左側エッジ部ＥＧでは反時計回り方向に、それぞれ傾斜（回転）し、等電位線ＥＱに平行に配向する。
【０２１３】
図４４（ｂ）に示したように、液晶表示装置５００の開口部１４ａ１および１４ａ２のエッジ部ＥＧにおいて、液晶分子３０ａの軸方位に対して傾斜した等電位線ＥＱで表される電界（斜め電界）が発生すると、図３（ｂ）に示したように、液晶分子３０ａは、等電位線ＥＱと平行になるための傾斜量が少ない方向（図示の例では反時計回り）に傾斜する。また、液晶分子３０ａの軸方位に対して垂直方向の等電位線ＥＱで表される電界が発生する領域に位置する液晶分子３０ａは、図３（ｃ）に示したように、傾斜した等電位線ＥＱ上に位置する液晶分子３０ａと配向が連続となるように（整合するように）、傾斜した等電位線ＥＱ上に位置する液晶分子３０ａと同じ方向に傾斜する。
【０２１４】
上述したように、傾斜した等電位線ＥＱ上に位置する液晶分子３０ａから始まる配向の変化が進み、定常状態に達すると、図４４（ｃ）に模式的に示したように、開口部１４ａ１および１４ａ２のそれぞれの中心ＳＡに関して対称な傾斜配向（放射状傾斜配向）を形成する。また、隣接する２つの開口部１４ａ１および１４ａ２との間に位置する上層電極１４の領域上の液晶分子３０ａも、開口部１４ａ１および１４ａ２のエッジ部の液晶分子３０ａと配向が連続となるように（整合するように）、傾斜配向する。開口部１４ａ１および１４ａ２のエッジの中央に位置する部分上の液晶分子３０ａは、それぞれのエッジ部の液晶分子３０ａの影響を同程度に受けるので、開口部１４ａ１および１４ａ２の中央部に位置する液晶分子３０ａと同様に、垂直配向状態を維持する。その結果、隣接する２つの開口部１４ａ１と１４ａ２との間に上層電極１４上の液晶層も放射状傾斜配向状態となる。但し、開口部１４ａ１および１４ａ２内の液晶層の放射状傾斜配向と開口部１４ａ１と１４ａ２との間の液晶層の放射状傾斜方向とでは、液晶分子の傾斜方向が異なる。図４４（ｃ）に示した、それぞれの放射状傾斜配向している領域の中央に位置する液晶分子３０ａ付近の配向に注目すると、開口部１４ａ１およｂ１４ａ２内では、対向電極に向かって広がるコーンを形成するように液晶分子３０ａが傾斜しているのに対し、開口部間では、上層電極１４に向かって広がるコーンを形成するように液晶分子３０が傾斜している。なお、いずれの放射状傾斜配向もエッジ部の液晶分子３０ａの傾斜配向と整合するように形成されているので、２つの放射状傾斜配向は互いに連続している。
【０２１５】
上述したように、液晶層３０に電圧を印加すると、上層電極１４に設けた複数の開口部１４ａ１および１４ａ２それぞれのエッジ部ＥＧ上の液晶分子３０ａから傾斜し始め、その後周辺領域の液晶分子３０ａがエッジ部ＥＧ上の液晶分子３０ａの傾斜配向と整合するように傾斜することによって、放射状傾斜配向が形成される。従って、１つの絵素領域内に形成する開口部１４ａの数が多いほど、電界に応答して最初に傾斜し始める液晶分子３０ａの数が多くなるので、絵素領域全体に亘って放射状傾斜配向が形成されるのに要する時間が短くなる。すなわち、絵素領域毎に絵素電極１５に形成する開口部１４ａの数を増やすことによって、液晶表示装置の応答速度を改善することができる。また、絵素電極１５を上層電極１４と下層電極１２とを有する２層構造電極とすることによって、開口部１４ａに対応する領域の液晶分子にも十分な電界を作用させることができるので、液晶表示装置の応答特性が向上する。
【０２１６】
絵素電極１５の上層電極１４と下層電極１２との間に設けられた誘電体層１３が、上層電極１４の開口部１４ａ内に穴（孔）または凹部を有する構成としてもよい。すなわち、２層構造の絵素電極１５は、上層電極１４の開口部１４ａ内に位置する誘電体層１３の全部が除去された（穴が形成された）構造または一部が除去された（凹部が形成された）構造を有してもよい。
【０２１７】
まず、図４５を参照しながら、誘電体層１３に穴が形成された絵素電極１４を備える液晶表示装置６００の構造と動作を説明する。以下では、簡単さのために、上層電極１４に形成された１つの開口部１４ａに対して説明する。
【０２１８】
液晶表示装置６００は、絵素電極１５の上層電極１４が開口部１４ａを有するとともに、下層電極１２と上層電極１４との間に設けられている誘電体層１３が、上層電極１４が有する開口部１４ａに対応して形成された開口部１３ａを有している開口部１３ａ内に下層電極１２が露出されている。誘電体層１３の開口部１３の側壁は、一般にテーパ状に形成されている。液晶表示装置６００は、誘電体層１３が開口部１３ａを有していることを除いて、液晶表示装置５００と実質的に同じ構造を有しており、２層構造の絵素電極１５は、実質的に液晶表示装置５００の絵素電極１５と同じように作用し、電圧印加時に液晶層３０に放射状傾斜配向状態をとる液晶ドメインを形成する。
【０２１９】
液晶表示装置６００の動作を図４５（ａ）〜（ｃ）を参照しながら説明する。図４５（ａ）〜（ｃ）は、液晶表示装置１００についての図１（ａ）〜（ｃ）にそれぞれ対応する。
【０２２０】
図４５（ａ）に示したように、電圧無印加時（ＯＦＦ状態）には、絵素領域内の液晶分子３０ａは、両基板１１および２１の表面に対して垂直に配向している。ここでは、簡単さのために、開口部１３ａの側壁による配向規制力は無視して説明する。
【０２２１】
液晶層３０に電圧を印加すると、図４５（ｂ）に示した等電位線ＥＱで表される電位勾配が形成される。等電位線ＥＱが上層電極１４の開口部１４ａに対応する領域でが落ち込んでいる（「谷」が形成されている。）ことから分かるように、液晶表示装置６００の液晶層３０にも図４５（ｂ）に示した電位勾配と同様に、傾斜電界が形成されている。しかしながら、絵素電極１５の誘電体層１３が、上層電極１４の開口部１４ａに対応する領域に開口部１３ａを有するので、開口部１４ａ内（開口部１３ａ内）に対応する領域の液晶層３０に印加される電圧は、下層電極１２と対向電極２２との電位差そのものであり、誘電体層１３による電圧降下（容量分割）が発生しない。すなわち、上層電極１４と対向電極２２との間に図示した７本の等電位線ＥＱは、液晶層３０全体に亘って７本であり（図４４（ｂ）では、５本の等電位線ＥＱのうちの１本が誘電体層１３中に侵入しているのに対し）、絵素領域全体に亘って一定の電圧が印加される。
【０２２２】
このように、誘電体層１３に開口部１３ａを形成することによって、開口部１３ａに対応する液晶層３０にも、その他の領域に対応する液晶層３０と同じ電圧を印加することできる。しかしながら、電圧が印加される液晶層３０の厚さが絵素領域内の場所によって異なるので、電圧印加時のリタデーションの変化が場所によって異なり、その程度が著しく大きいと、表示品位が低下するという問題が発生する。
【０２２３】
図４５に示した構成においては、上層電極（開口部１４ａ以外の中実部）１４上の液晶層３０の厚さｄ１と、開口部１４ａ（および穴１３ａ）内に位置する下層電極１２上の液晶層３０の厚さｄ２とは、誘電体層１３の厚さ分だけ異なる。厚さｄ１の液晶層３０と厚さｄ２の液晶層３０とを同じ電圧範囲で駆動すると、液晶層３０の配向変化に伴うリタデーションの変化量は、それぞれの液晶層３０の厚さの影響を受けて互いに異なる。印加電圧と液晶層３０のリタデーション量との関係が場所によって著しく異なると、表示品位を重視した設計においては透過率が犠牲になり、透過率を重視すると白表示の色温度がシフトし表示品位が犠牲になるという問題が発生する。したがって、液晶表示装置６００を透過型液晶表示装置として用いる場合には、誘電体層１３の厚さは薄い方が良い。
【０２２４】
次に、絵素電極の誘電体層が凹部を有する液晶表示装置７００の一絵素領域の断面構造を図４６に示す。
【０２２５】
液晶表示装置７００の絵素電極１５を構成する誘電体層１３は、上層電極１４の開口部１４ａに対応する凹部１３ｂを有している。その他の構造は、図４５に示した液晶表示装置６００と実質的に同じ構造を有している。
【０２２６】
液晶表示装置７００においては、絵素電極１５が有する上層電極１４の開口部１４ａ内に位置する誘電体層１３は完全に除去されていないので、開口部１４ａ内に位置する液晶層３０の厚さｄ３は、液晶表示装置７００における開口部１４ａ内に位置する液晶層３０の厚さｄ２よりも、凹部１３ｂ内の誘電体層１３の厚さ分だけ薄い。また、開口部１４ａ内に位置する液晶層３０に印加される電圧は、凹部１３ｂ内の誘電体層１３による電圧降下（容量分割）を受けるので、上層電極（開口部１４ａを除く領域）１４上の液晶層３０に印加される電圧よりも低くなる。したがって、凹部１３ｂ内の誘電体層１３の厚さを調整することによって、液晶層３０の厚さの違いに起因するリタデーション量の違いと、液晶層３０に印加される電圧の場所による違い（開口部１４ａ内の液晶層に印加される電圧の低下量）との関係を制御し、印加電圧とリタデーションとの関係が絵素領域内の場所に依存しないようにすることができる。より厳密には、液晶層の複屈折率、液晶層の厚さ、誘電体層の誘電率および誘電体層の厚さ、誘電体層の凹部の厚さ（凹部の深さ）を調整することによって、印加電圧とリタデーションとの関係を絵素領域内の場所で均一にすることができ、高品位な表示が可能となる。特に、表面が平坦な誘電体層を有する透過型表示装置と比較し、上層電極１４の開口部１４ａに対応する領域の液晶層３０に印加される電圧の低下による透過率の減少（光の利用効率の低下）が抑制される利点がある。
【０２２７】
上述の説明は、絵素電極１５を構成する上層電極１４と下層電極１２とに同じ電圧を供給した場合について説明したが、下層電極１２と上層電極１４とに異なる電圧を印加する構成とすれば、表示むらの無い表示が可能な液晶表示装置の構成のバリエーションを増やすことができる。例えば、上層電極１４の開口部１４ａ内に誘電体層１３を有する構成においては、上層電極１４に印加する電圧よりも、誘電体層１３による電圧降下分だけ高い電圧を下層電極１２に印加することによって、液晶層３０に印加される電圧が絵素領域内の場所によって異なることを防止することができる。
【０２２８】
２層構造の絵素電極１５を有する液晶表示装置は、透過型や反射型だけでなく、透過反射両用型の液晶表示装置（例えば、特開平１１−１０１９９２号公報参照）を構成することができる。
【０２２９】
透過反射両用型液晶表示装置（以下、「両用型液晶表示装置」と略す）は、絵素領域内に、透過モードで表示を行う透過領域Ｔと、反射モードで表示を行う反射領域Ｒとを有する液晶表示装置を指す（図４４（ａ）参照）。透過領域Ｔおよび反射領域Ｒは、典型的には、透明電極および反射電極によって規定される。反射電極に代えて、反射層と透明電極との組み合わせた構造によって、反射領域を規定することもできる。
【０２３０】
この両用型液晶表示装置は、反射モードと透過モードとを切り替えて表示すること、または同時に両方の表示モードで表示することもできる。したがって、例えば、周囲光が明るい環境下では反射モードの表示を、暗い環境では透過モードの表示を実現することができる。また、両方のモードの表示を同時に行うと、透過モードの液晶表示装置を周囲光が明るい環境下（蛍光灯の光や太陽光が直接特定の角度で表示面に入射する状態）で使用したときに見られるコントラスト比の低下を抑制することができる。このように、透過型液晶表示装置の欠点を補うことができる。なお、透過領域Ｔと反射領域Ｒとの面積の比率は、液晶表示装置の用途に応じて適宜設定され得る。また、専ら透過型として用いる液晶表示装置においては、反射モードでの表示ができない程度にまで反射領域の面積比率を小さくしても、上述した透過型液晶表示装置の欠点を補うことができる。
【０２３１】
図４４（ａ）に示したように、例えば、液晶表示装置５００の上層電極１４を反射電極とし、下層電極１２を透明電極とすることによって、両用型液晶表示装置を得ることができる。両用型液晶表示装置は、この例に限られず、上述した液晶表示装置において、上層電極１４および下層電極１２の内のいずれか一方を透明導電層とし、他方を反射導電層とすることによって得られる。但し、反射モードと透過モードの表示の電圧−透過率特性を互いに整合させるためには、反射領域Ｒの液晶層３０の厚さ（例えば図４５（ａ）のｄ１）が、透過領域Ｔの液晶層３０の厚さ（例えば図４５（ａ）のｄ２）の約半分となるように構成することが好ましい。勿論、液晶層の厚さを調整する代わりに、上層電極１４に印加する電圧と、下層電極１２に印加する電圧とを調整してもよい。
【０２３２】
図４７（ａ）、（ｂ）および（ｃ）に、配向規制構造および凸部を備える液晶表示装置の一例を示す。図４７（ａ）、（ｂ）および（ｃ）は、配向規制構造および凸部を備える液晶表示装置８００を模式的に示す断面図である。図４７（ａ）は電圧無印加時を示し、図４７（ｂ）は電圧印加後に配向が変化し始めた状態（ＯＮ初期状態）を示し、図４７（ｃ）は電圧印加中の定常状態を模式的に示している。
【０２３３】
液晶表示装置８００は、絵素電極１４の開口部１４ａの内側に、図４０に示した凸部４０を備えている。また、絵素電極１４の中実部１４ｂに対向する領域の中央付近に、図１５に示した凸部２８Ａを備えている。
【０２３４】
液晶表示装置８００においては、ＴＦＴ基板４００ａの電極構造による配向規制力に加えて、凸部４０の側面４０ｓによる配向規制力と、凸部２８Ａの表面による配向規制力とによって、放射状傾斜配向が安定化される。上述した凸部４０および凸部２８Ａの形状効果による配向規制力は、印加電圧に関係なく放射状傾斜配向状態を安定させるので、液晶表示装置８００は、良好な耐応力性を備えている。
【０２３５】
なお、上述した全ての液晶表示装置に、必要に応じて、位相差補償素子（典型的には位相差板）を設けてもよい。
【０２３６】
【発明の効果】
本発明によると、放射状傾斜配向を有する液晶ドメインが安定に、高い連続性を有するように形成されるので、従来の広視角特性を有する液晶表示装置の表示品位をさらに向上することができる。また、配向規制構造と凸部とによって放射状傾斜配向を安定化させ、さらに、放射状傾斜配向の中心軸の位置を固定することもできるので、液晶パネルに応力が印加された場合に残像が発生することが抑制される。さらに、凸部の基板面に沿った断面形状が、クロスニコル状態に配置された一対の偏光板の偏光軸に略平行な辺および略直交する辺のみから実質的に構成された形状であるので、黒表示時の光漏れの発生が抑制・防止され、高コントラスト比の表示が実現される。
【図面の簡単な説明】
【図１】本発明による第１配向規制構造を備える液晶表示装置１００の一つの絵素領域の構造を模式的に示す図であり、（ａ）は上面図、（ｂ）は（ａ）中の１Ｂ−１Ｂ’線に沿った断面図である。
【図２】液晶表示装置１００の液晶層３０に電圧を印加した状態を示す図であり、（ａ）は、配向が変化し始めた状態（ＯＮ初期状態）を模式的に示し、（ｂ）は、定常状態を模式的に示している。
【図３】（ａ）〜（ｄ）は、電気力線と液晶分子の配向の関係を模式的に示す図である。
【図４】（ａ）〜（ｃ）は、液晶表示装置１００における、基板法線方向から見た液晶分子の配向状態を模式的に示す図である。
【図５】（ａ）〜（ｃ）は、液晶分子の放射状傾斜配向の例を模式的に示す図である。
【図６】（ａ）および（ｂ）は、本発明による液晶表示装置に用いられる他の絵素電極を模式的に示す上面図である。
【図７】（ａ）および（ｂ）は、本発明による液晶表示装置に用いられるさらに他の絵素電極を模式的に示す上面図である。
【図８】（ａ）および（ｂ）は、本発明による液晶表示装置に用いられるさらに他の絵素電極を模式的に示す上面図である。
【図９】（ａ）および（ｂ）は、本発明による液晶表示装置に用いられるさらに他の絵素電極を模式的に示す上面図である。
【図１０】（ａ）および（ｂ）は、本発明による液晶表示装置に用いられる絵素電極の単位中実部の角部を模式的に示す上面図である。
【図１１】（ａ）は、図８（ｂ）に示す絵素電極を備えた液晶表示装置および図９（ｂ）に示す絵素電極を備えた液晶表示装置において、偏光板の偏光軸の角度に対する透過率の変化を示すグラフであり、（ｂ）は、０度に対応する偏光軸の配置を模式的に示す図である。
【図１２】本発明による液晶表示装置に用いられるさらに他の絵素電極を模式的に示す上面図である。
【図１３】（ａ）および（ｂ）は、本発明による液晶表示装置に用いられるさらに他の絵素電極を模式的に示す上面図である。
【図１４】（ａ）は、図１（ａ）に示したパターンの単位格子を模式的に示す図であり、（ｂ）は、図１２に示したパターンの単位格子を模式的に示す図であり、（ｃ）はピッチｐと中実部面積比率との関係を示すグラフである。
【図１５】（ａ）は、凸部２８Ａを有する対向基板２００ｂを模式的に示す断面図であり、（ｂ）は、凸部２８Ａを模式的に示す上面図である。
【図１６】（ａ）は、凸部２８Ｂを有する対向基板２００ｂを模式的に示す断面図であり、（ｂ）は、凸部２８Ｂを模式的に示す上面図である。
【図１７】配向規制構造および凸部２８Ａを備える液晶表示装置２００を模式的に示す図であり、（ａ）は上面図であり、（ｂ）は（ａ）中の１７Ｂ−１７Ｂ’線に沿った断面図である。
【図１８】液晶表示装置２００の一絵素領域の断面構造を模式的に示す図であり、（ａ）は電圧無印加状態を示し、（ｂ）は配向が変化し始めた状態（ＯＮ初期状態）を示し、（ｃ）は定常状態を示している。
【図１９】断面形状が略円形である凸部１０２８を備えた比較例としての液晶表示装置１０００における、凸部１０２８近傍の液晶分子の配向の様子を模式的に示す図である。
【図２０】凸部２８Ａを備えた液晶表示装置２００における、凸部２８Ａ近傍の液晶分子の配向の様子を模式的に示す図である。
【図２１】配向規制構造および凸部２８Ｃを備える液晶表示装置２００Ａを模式的に示す図であり、（ａ）は上面図であり、（ｂ）は（ａ）中の２１Ｂ−２１Ｂ’線に沿った断面図である。
【図２２】液晶表示装置２００Ａの一絵素領域の断面構造を模式的に示す図であり、（ａ）は電圧無印加状態を示し、（ｂ）は配向が変化し始めた状態（ＯＮ初期状態）を示し、（ｃ）は定常状態を示している。
【図２３】配向規制構造および凸部１１２８を備える比較例としての液晶表示装置１１００を模式的に示す図であり、（ａ）は上面図であり、（ｂ）は（ａ）中の２３Ｂ−２３Ｂ’線に沿った断面図である。
【図２４】基板面に対する傾斜角が９０°を大きく超える側面を有する凸部２８Ｄを模式的に示す断面図である。
【図２５】スペーサとしても機能する凸部の改変例である凸部２８Ｅを模式的に示す断面図である。
【図２６】断面形状が略十字形の凸部２８Ｆを備えた、本発明による液晶表示装置３００を模式的に示す上面図である。
【図２７】（ａ）、（ｂ）、（ｃ）および（ｄ）は、凸部と単位中実部との組み合わせの例を示す上面図である。
【図２８】図２７（ａ）に示した略円形の凸部と略円形の単位中実部との組み合わせを用いたときの視野角特性の評価結果を示すグラフである。
【図２９】図２７（ｂ）に示した略円形の凸部と樽形の単位中実部との組み合わせを用いたときの視野角特性の評価結果を示すグラフである。
【図３０】図２７（ｃ）に示した略十字形の凸部と略円形の単位中実部との組み合わせを用いたときの視野角特性の評価結果を示すグラフである。
【図３１】図２７（ｄ）に示した略十字形の凸部と樽形の単位中実部との組み合わせを用いたときの視野角特性の評価結果を示すグラフである。
【図３２】図２７（ａ）に示した略円形の凸部と略円形の単位中実部との組み合わせを用いたときの電圧−輝度特性を示すグラフである。
【図３３】図２７（ｂ）に示した略円形の凸部と樽形の単位中実部との組み合わせを用いたときの電圧−輝度特性を示すグラフである。
【図３４】図２７（ｃ）に示した略十字形の凸部と略円形の単位中実部との組み合わせを用いたときの電圧−輝度特性を示すグラフである。
【図３５】図２７（ｄ）に示した略十字形の凸部と樽形の単位中実部との組み合わせを用いたときの電圧−輝度特性を示すグラフである。
【図３６】図２７（ａ）に示した略円形の凸部および略円形の単位中実部の組み合わせと、図２７（ｃ）に示した略十字形の凸部および略円形の単位中実部の組み合わせを用いたときの応答速度特性を示すグラフである。
【図３７】図２７（ｂ）に示した略円形の凸部および樽形の単位中実部の組み合わせと、図２７（ｄ）に示した略十字形の凸部および樽形の単位中実部の組み合わせについての応答速度特性を示すグラフである。
【図３８】本発明による配向規制構造を備える液晶表示装置４００の一つの絵素領域の構造を模式的に示す図であり、（ａ）は上面図、（ｂ）は（ａ）中の３８Ｂ−３８Ｂ’線に沿った断面図である。
【図３９】（ａ）〜（ｄ）は、液晶分子３０ａの配向と垂直配向性を有する表面の形状との関係を説明するための模式図である。
【図４０】液晶表示装置４００の液晶層３０に電圧を印加した状態を示す図であり、（ａ）は、配向が変化し始めた状態（ＯＮ初期状態）を模式的に示し、（ｂ）は、定常状態を模式的に示している。
【図４１】（ａ）〜（ｃ）は、開口部と凸部との配置関係が異なる、液晶表示装置４００Ａ、４００Ｂおよび４００Ｃの模式的な断面図である。
【図４２】液晶表示装置４００の断面構造を模式的に示す図であり、図３８（ａ）中の４２Ａ−４２Ａ’線に沿った断面図である。
【図４３】液晶表示装置４００Ｄの一つの絵素領域の構造を模式的に示す図であり、（ａ）は上面図、（ｂ）は（ａ）中の４３Ｂ−４３Ｂ’線に沿った断面図である。
【図４４】２層構造電極を備える液晶表示装置５００の一絵素領域の断面構造を模式的に示す図であり、（ａ）は電圧無印加状態を示し、（ｂ）は配向が変化し始めた状態（ＯＮ初期状態）を示し、（ｃ）は定常状態を示している。
【図４５】２層構造電極を備える他の液晶表示装置４００の一絵素領域の断面構造を模式的に示す図であり、（ａ）は電圧無印加状態を示し、（ｂ）は配向が変化し始めた状態（ＯＮ初期状態）を示し、（ｃ）は定常状態を示している。
【図４６】２層構造電極を備える他の液晶表示装置７００の一絵素領域の断面構造を模式的に示す図である。
【図４７】配向規制構造および凸部を備えるさらに他の液晶表示装置８００の一絵素領域の断面構造を模式的に示す図であり、（ａ）は電圧無印加状態を示し、（ｂ）は配向が変化し始めた状態（ＯＮ初期状態）を示し、（ｃ）は定常状態を示している。
【符号の説明】
１１、２１ 透明絶縁性基板
１２ 下層電極
１３ 誘電体層
１４、１４Ａ、１４Ｂ、１４Ｃ、１４Ｄ、１４Ｅ、１４Ｆ 絵素電極
１４Ｇ、１４Ｈ、１４Ｉ 絵素電極
１４ａ、１４ａ１、１４ａ２ 開口部
１４ｂ 中実部（導電膜）
１４ｂ’ 単位中実部
１５ 絵素電極（２層構造電極）
２２ 対向電極
２８Ａ、２８Ｂ、２８Ｃ、２８Ｄ、２８Ｅ 凸部
２８ｓ 凸部の側面
３０ 液晶層
３０ａ 液晶分子
４０、４０Ａ、４０Ｂ、４０Ｃ、４０Ｄ 凸部
４０ｓ 凸部の側面
４０ｔ 凸部の頂面
１００、１００’、１００’’ 液晶表示装置
２００、２００Ａ、３００、４００、５００ 液晶表示装置
６００、７００、８００ 液晶表示装置
１００ａ ＴＦＴ基板
１００ｂ 対向基板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a wide viewing angle characteristic and performing high-quality display.
[0002]
[Prior art]
In recent years, a thin and light liquid crystal display device has been used as a display device used for a display of a personal computer or a display unit of a portable information terminal device. However, the conventional twisted nematic type (TN type) and super twisted nematic type (STN type) liquid crystal display devices have a drawback that the viewing angle is narrow, and various technical developments have been made to solve this. ing.
[0003]
As a typical technique for improving the viewing angle characteristics of a TN type or STN type liquid crystal display device, there is a method of adding an optical compensation plate. As another method, there is a lateral electric field method in which an electric field in a horizontal direction is applied to the liquid crystal layer with respect to the surface of the substrate. This horizontal electric field type liquid crystal display device has recently been mass-produced and has attracted attention. As another technique, there is DAP (deformation of vertical aligned phase) using a nematic liquid crystal material having negative dielectric anisotropy as a liquid crystal material and using a vertical alignment film as an alignment film. This is one of voltage controlled birefringence (ECB) method, and the transmittance is controlled by utilizing the birefringence of liquid crystal molecules.
[0004]
[Problems to be solved by the invention]
However, although the horizontal electric field method is one of the effective methods for widening the viewing angle, the production margin is significantly narrower in the manufacturing process compared to the normal TN type, so that stable production is difficult. is there. This is because unevenness in the gap between the substrates and deviation in the transmission axis (polarization axis) direction of the polarizing plate with respect to the alignment axis of the liquid crystal molecules greatly affect the display brightness and contrast ratio. In order to achieve stable production, further technological development is necessary.
[0005]
In addition, in order to perform uniform display without display unevenness in a DAP liquid crystal display device, it is necessary to perform alignment control. As a method for controlling the alignment, there is a method of performing an alignment treatment by rubbing the surface of the alignment film. However, when the rubbing treatment is performed on the vertical alignment film, rubbing streaks are likely to occur in the display image, which is not suitable for mass production.
[0006]
On the other hand, as a method for controlling the alignment without rubbing, a method has been devised in which an oblique electric field is generated by forming slits (openings) in the electrodes and the alignment direction of liquid crystal molecules is controlled by the oblique electric field. (For example, JP-A-6-301036 and JP-A-2000-47217). However, as a result of examination by the inventors of the present application, in the method disclosed in the above publication, the alignment state of the region of the liquid crystal layer corresponding to the opening of the electrode is not defined, and the alignment continuity of the liquid crystal molecules is sufficient. Instead, it is difficult to obtain a stable orientation state over the entire picture element, resulting in a rough display.
[0007]
Therefore, the inventor forms a predetermined electrode structure including an opening and a solid part on one of a pair of electrodes facing each other through the liquid crystal layer together with others, and is generated at the edge of the opening. A method has been proposed in which a plurality of liquid crystal domains having a radially inclined orientation are formed in these openings and solid portions by an oblique electric field (AM-LCD'01, p101-p102). When this method is used, the liquid crystal domain having the radial tilt alignment is formed stably and has high continuity, so that viewing angle characteristics and display quality can be improved.
[0008]
However, with the widespread use of liquid crystal display devices, the required characteristics for liquid crystal display devices have become increasingly severe, and higher alignment stability is required depending on the application of the liquid crystal display device. For example, in a liquid crystal display device used in a situation where stress can be applied to the liquid crystal panel, alignment disorder of the liquid crystal layer due to the application of stress may be visually recognized as an afterimage phenomenon, so that not only the wide viewing angle characteristics There is a need for a liquid crystal display device that has higher alignment stability and suppresses deterioration in display quality due to stress.
[0009]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a liquid crystal display device having a wide viewing angle characteristic, high alignment stability, and high display quality.
[0010]
[Means for Solving the Problems]
A liquid crystal display device according to the present invention includes a first substrate, a second substrate, a vertical alignment type liquid crystal layer provided between the first substrate and the second substrate, and the first and second substrates. A first electrode provided on the liquid crystal layer side of the first substrate, and a second electrode provided on the second substrate. A plurality of pixel regions each defined by a second electrode facing the first electrode through the liquid crystal layer, and the first substrate is in each of the plurality of pixel regions. , Each of the plurality of liquid crystal domains having an alignment regulating structure that expresses an alignment regulating force so as to form a plurality of liquid crystal domains each having a radially inclined alignment state in a voltage application state in the liquid crystal layer. Corresponding to at least one liquid crystal domain A convex portion projecting toward the liquid crystal layer in a region, and a cross-sectional shape of the convex portion along the substrate surface of the second substrate has a side substantially parallel to one polarization axis of the pair of polarizing plates and The shape is substantially constituted only by a side substantially orthogonal to the one polarization axis, and thereby the above object is achieved.
[0011]
The cross-sectional shape along the substrate surface of the second substrate of the convex portion may be substantially rectangular, and the cross-sectional shape of the convex portion along the substrate surface of the second substrate is substantially square. It is good.
[0012]
The cross-sectional shape of the convex portion along the substrate surface of the second substrate may be a substantially cross shape.
[0013]
It is preferable that the convex portion exhibits an alignment regulating force that causes the liquid crystal molecules in the at least one liquid crystal domain to be radially inclined and aligned.
[0014]
The convex portion is preferably provided in a region corresponding to the vicinity of the center of the at least one liquid crystal domain.
[0015]
In the at least one liquid crystal domain, it is preferable that the alignment regulating direction by the convex portion is aligned with the direction of the radially inclined alignment by the alignment regulating structure.
[0016]
The convex portion may also function as a spacer that defines the thickness of the liquid crystal layer.
[0017]
The convex portion preferably has a side surface forming an angle of less than 90 ° with the substrate surface of the second substrate.
[0018]
The first electrode has a plurality of unit solid parts, and the orientation regulating structure is configured by the plurality of unit solid parts, and a voltage is applied between the first electrode and the second electrode. In some cases, the plurality of liquid crystal domains may be formed in a region corresponding to the plurality of unit solid portions by generating an oblique electric field around the plurality of unit solid portions.
[0019]
Each of the plurality of unit solid portions preferably has rotational symmetry. The plurality of unit solid parts are preferably arranged so as to have rotational symmetry within the pixel region.
[0020]
Each of the plurality of unit solid portions may have a shape in which corner portions are sharpened.
[0021]
The first electrode has at least one opening and a solid part, and the orientation regulating structure is configured by the at least one opening and the solid part of the first electrode, and the first electrode When a voltage is applied between the second electrode and the second electrode, an oblique electric field is generated at an edge of the at least one opening of the first electrode, whereby the at least one opening and the solid part are generated. The plurality of liquid crystal domains may be formed in the corresponding region.
[0022]
The first substrate includes a dielectric layer provided on a side of the first electrode opposite to the liquid crystal layer, and at least a part of the at least one opening of the first electrode through the dielectric layer. It is good also as a structure which further has the 3rd electrode which opposes.
[0023]
The at least one opening includes a plurality of openings having substantially the same shape and the same size, and at least a part of the plurality of openings is arranged to have rotational symmetry. It is preferable to form a unit cell. Moreover, it is preferable that each shape of the at least some of the plurality of openings has rotational symmetry.
[0024]
The convex portion may be provided only in a region corresponding to a liquid crystal domain formed in a region corresponding to the solid portion of the first electrode among the plurality of liquid crystal domains.
[0025]
Alternatively, the liquid crystal display device according to the present invention includes a first substrate, a second substrate, a vertically aligned liquid crystal layer provided between the first substrate and the second substrate, and the first and second substrates. A first electrode provided on the liquid crystal layer side of the first substrate; and a second substrate, each having a pair of polarizing plates opposed to each other through the substrate and having polarization axes substantially orthogonal to each other A plurality of pixel regions each defined by a second electrode opposed to the first electrode through the liquid crystal layer, and the first substrate includes a plurality of pixel regions. An alignment regulating structure that expresses an alignment regulating force so as to form a plurality of liquid crystal domains each having a radially inclined alignment state in a voltage applied state in the liquid crystal layer; A small number of the plurality of liquid crystal domains. A spacer provided in a region corresponding to at least one liquid crystal domain, wherein the spacer expresses an alignment regulating force that causes the liquid crystal molecules in the at least one liquid crystal domain to be radially inclined and aligned; The cross-sectional shape along the substrate surface of the first and second substrates is a shape substantially composed of only a side substantially parallel to one polarization axis of the pair of polarizing plates and a side substantially perpendicular to the one polarization axis. This achieves the above object.
[0026]
The cross-sectional shape of the spacer along the substrate surfaces of the first and second substrates may be substantially rectangular, and the cross-sectional shape of the spacer along the substrate surfaces of the first and second substrates is approximately It is good also as a structure which is a square.
[0027]
Moreover, the cross-sectional shape along the substrate surface of the said 1st and 2nd board | substrate of the said spacer may be a substantially cross shape.
[0028]
Alternatively, the liquid crystal display device according to the present invention includes a first substrate, a second substrate, a vertically aligned liquid crystal layer provided between the first substrate and the second substrate, and the first and second substrates. A first electrode provided on the liquid crystal layer side of the first substrate; and a second substrate, each having a pair of polarizing plates opposed to each other through the substrate and having polarization axes substantially orthogonal to each other And a plurality of pixel regions each defined by a second electrode facing the first electrode through the liquid crystal layer, wherein the first electrode is provided in each of the plurality of pixel regions. A plurality of unit solid portions each surrounded by at least a part of the plurality of openings, and the second substrate includes the plurality of unit solids. And a region corresponding to at least one unit solid part among the plurality of openings. And having a convex portion protruding toward the liquid crystal layer, the cross-sectional shape of the convex portion along the substrate surface of the second substrate is a side substantially parallel to one polarization axis of the pair of polarizing plates and The shape is substantially composed only of a side substantially orthogonal to one polarization axis, and the above object is achieved thereby.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
First, basic functions of each component included in the liquid crystal display device of the present invention will be described.
[0030]
In the liquid crystal display device of the present invention, one of the pair of substrates arranged so as to sandwich the vertical alignment type liquid crystal layer is radially inclined in each pixel region in a voltage application state. An alignment regulating structure that expresses an alignment regulating force so as to form a plurality of liquid crystal domains that take a state (also referred to as axially symmetric orientation), and the other substrate has at least one liquid crystal domain of the plurality of liquid crystal domains In the region corresponding to the above, a projection protruding to the liquid crystal layer side. The convex portion expresses an alignment regulating force that causes the liquid crystal molecules in the liquid crystal domain to be radially inclined and aligned. Therefore, at least in the voltage application state, the alignment regulating force due to the alignment regulating structure provided on one substrate and the convex portion provided on the other substrate acts on the liquid crystal molecules, so that the configuration having only the alignment regulating structure is used. The radial tilt alignment of the liquid crystal domain formed in the liquid crystal layer is stabilized. Further, in the liquid crystal display device of the present invention, the cross-sectional shape along the substrate surface of the convex portion provided on the other substrate is arranged in a crossed Nicol state (arranged so that the slow axes are substantially orthogonal to each other). It is a shape that is substantially constituted only by sides substantially parallel to and substantially orthogonal to one polarization axis of the polarizing plate. Therefore, the liquid crystal molecules that are radially inclined and aligned by the alignment regulating force of the convex portion are aligned in the azimuth direction substantially parallel or substantially perpendicular to the polarization axis of the polarizing plate, and thus light leakage during black display is suppressed. The Therefore, display with a high contrast ratio is realized.
[0031]
The preferred alignment regulating structure of the liquid crystal display device of the present invention is constituted by one electrode structure of a pair of electrodes for applying a voltage to the liquid crystal layer in the pixel region. One electrode has a plurality of unit solid portions, and when a voltage is applied between the pair of electrodes, an oblique electric field is generated around the plurality of unit solid portions, thereby generating a plurality of unit solid portions. A plurality of liquid crystal domains are formed in a region corresponding to the part. In other words, when a voltage is applied between a pair of electrodes, the outer shape of one electrode is defined so that a slant electric field is generated around one electrode and a plurality of liquid crystal domains having a radial tilt alignment are formed. Yes.
[0032]
A portion where the conductive film exists in the electrode is referred to as a solid portion, and a portion that generates an electric field forming one liquid crystal domain in the solid portion is referred to as a “unit solid portion”. The solid part is typically formed from a continuous conductive film.
[0033]
Each shape of the plurality of unit solid portions is preferably configured to have rotational symmetry. When the shape of the unit solid part has rotational symmetry, the radial tilt orientation of the liquid crystal domain to be formed also becomes orientation having rotational symmetry, that is, axial symmetry, and the viewing angle characteristics are improved.
[0034]
According to another preferred alignment regulating structure of the liquid crystal display device of the present invention, one of a pair of electrodes for applying a voltage to the liquid crystal layer in the pixel region has at least one opening (a conductive film exists in the electrode). This is an electrode structure having a solid portion (a portion other than the opening in the electrode, a portion where the conductive film exists). The solid part typically includes the unit solid part described above. By providing an opening in one electrode, unit solid parts (for example, four) arranged in a two-dimensional manner can be formed by one picture element region, so that an opening is formed in the electrode. Instead, by defining the outer shape of the electrode to a predetermined shape, more liquid crystal domains can be formed than when the unit solid part (for example, two) is formed.
[0035]
As will be described later, the opening can be formed so that a liquid crystal domain having a radially inclined orientation is formed also in a region corresponding to the opening of the electrode, but it is not always necessary to do so. If a liquid crystal domain having a radial tilt alignment corresponding to the solid part (unit solid part) is formed, the liquid crystal domain formed corresponding to the opening does not have a radial tilt alignment in the pixel region. Since the continuity of the alignment of the liquid crystal molecules can be obtained, the radial tilt alignment of the liquid crystal domain formed corresponding to the solid part is stable. In particular, when the area of the opening is small, the contribution to the display is small. Therefore, even if a liquid crystal domain having a radially inclined alignment is not formed in a region corresponding to the opening, the display quality does not deteriorate.
[0036]
The liquid crystal layer is in a vertical alignment state when no voltage is applied, and in the voltage application state, a plurality of liquid crystal domains having a radially inclined alignment state are formed by an oblique electric field generated at the edge of the opening of the electrode. . The vertical alignment type liquid crystal layer is a liquid crystal layer in which liquid crystal molecules are aligned substantially perpendicular to the substrate surface in the absence of applied voltage, and is typically made of a liquid crystal material having negative dielectric anisotropy, The alignment is regulated by vertical alignment films provided on both sides thereof.
[0037]
When a voltage is applied to the pair of electrodes, an oblique electric field is generated in the vertically aligned liquid crystal, and a liquid crystal domain formed by the oblique electric field is formed in a region corresponding to the opening and the solid part of the electrode. Display is performed by changing the alignment state of these liquid crystal domains in accordance with the voltage. Since each liquid crystal domain has a radial tilt alignment (axisymmetric alignment), the viewing angle dependency of display quality is small and a wide viewing angle characteristic is obtained.
[0038]
Furthermore, since the liquid crystal domain formed in the opening and the liquid crystal domain formed in the solid part are formed by an oblique electric field generated at the edge of the opening, they are alternately formed adjacent to each other, In addition, the alignment of liquid crystal molecules between adjacent liquid crystal domains is essentially continuous. Therefore, a disclination line is not generated between the liquid crystal domain formed in the opening and the liquid crystal domain formed in the solid portion, thereby preventing deterioration in display quality and stability of alignment of liquid crystal molecules. Is also expensive.
[0039]
Adopting the above electrode structure, the liquid crystal molecules take a radial tilt alignment not only in the region corresponding to the solid part of the electrode but also in the region corresponding to the opening, so compared with the conventional liquid crystal display device described above, Liquid crystal molecules have high alignment continuity, a stable alignment state is realized, and uniform display without roughness can be obtained. In particular, in order to achieve good response characteristics (fast response speed), it is necessary to apply an oblique electric field for controlling the alignment of liquid crystal molecules to many liquid crystal molecules, and for that purpose, openings (edge portions) are required. It is necessary to form a lot. In the liquid crystal display device of the present invention, since a liquid crystal domain having a stable radial tilt alignment is formed corresponding to the opening, even if many openings are formed to improve response characteristics, the display quality associated therewith is improved. Can be suppressed (occurrence of roughness).
[0040]
By forming at least one unit cell in which at least some of the plurality of openings have substantially the same shape and the same size and are arranged to have rotational symmetry Since the plurality of liquid crystal domains can be arranged with high symmetry using the unit cell as a unit, the viewing angle dependency of display quality can be improved. Furthermore, by dividing the entire picture element region into unit cells, the alignment of the liquid crystal layer can be stabilized over the entire picture element region. For example, the openings are arranged so that the centers of the openings form a square lattice. When one picture element region is divided by an opaque component such as an auxiliary capacitance wiring, for example, a unit grid may be arranged for each region contributing to display.
[0041]
The radial shape of the liquid crystal domain formed in the openings by making each of the openings (typically openings forming the unit cell) of the plurality of openings into a shape having rotational symmetry. The stability of the tilted orientation can be improved. For example, the shape of each opening (the shape when viewed from the substrate normal direction) is a circle or a regular polygon (for example, a square). In addition, it is good also as shapes, such as a shape (for example, ellipse) which does not have rotational symmetry, according to the shape (aspect ratio) etc. of a picture element. In addition, since the shape of the solid part region (“unit solid part”) substantially surrounded by the opening has rotational symmetry, the radial tilt alignment of the liquid crystal domain formed in the solid part can be stabilized. Can increase the sex. For example, when the openings are arranged in a square lattice shape, the shape of the openings may be a substantially star shape or a cross shape, and the shape of the solid portion may be a shape such as a substantially circular shape or a substantially square shape. Of course, both the opening and the solid part substantially surrounded by the opening may be substantially square.
[0042]
In order to stabilize the radial tilt alignment of the liquid crystal domain formed in the opening of the electrode, the liquid crystal domain formed in the opening is preferably substantially circular. In other words, the shape of the opening may be designed so that the liquid crystal domain formed in the opening is substantially circular.
[0043]
Of course, in order to stabilize the radial tilt alignment of the liquid crystal domain formed in the solid portion of the electrode, the solid portion region substantially surrounded by the opening is preferably substantially circular. One liquid crystal domain formed in a solid part formed of a continuous conductive film is formed corresponding to a solid part region (unit solid part) substantially surrounded by a plurality of openings. Is done. Therefore, the shape and arrangement of the openings may be determined so that the shape of the solid portion region (unit solid portion) is substantially circular.
[0044]
In any of the cases described above, in each of the pixel regions, the total area of the openings formed in the electrodes is preferably smaller than the area of the solid part. The larger the area of the solid part, the larger the area of the liquid crystal layer that is directly affected by the electric field generated by the electrode (defined in the plane when viewed from the normal direction of the substrate). The optical characteristics (for example, the transmittance) with respect to the voltage are improved.
[0045]
Whether to adopt a configuration in which the opening is substantially circular or a configuration in which the unit solid portion is substantially circular is preferably determined depending on which configuration can increase the area of the solid portion. Which configuration is preferred is appropriately selected depending on the pitch of the picture elements. Typically, when the pitch exceeds about 25 μm, the opening is preferably formed so that the solid part is substantially circular, and when it is about 25 μm or less, the opening is preferably substantially circular. .
[0046]
In the electrode structure in which the opening is provided in one of the pair of electrodes described above, a sufficient voltage is not applied to the liquid crystal layer in a region corresponding to the opening, and a sufficient retardation change cannot be obtained. There may be a problem that the utilization efficiency is lowered. Therefore, a dielectric layer is provided on the side opposite to the liquid crystal layer of the electrode provided with the opening, and an additional electrode facing at least a part of the opening of the electrode is provided via this dielectric layer (two-layer structure electrode) Thus, a sufficient voltage can be applied to the liquid crystal layer corresponding to the opening, and light utilization efficiency and response characteristics can be improved.
[0047]
If the electrode structure (that is, the alignment regulating structure) is only provided on one substrate, when the radial tilt alignment is disturbed by applying a stress to the liquid crystal layer, the disordered alignment state is maintained by the electric field effect and is visually recognized as an afterimage phenomenon. However, the liquid crystal display device of the present invention has a protrusion protruding to the liquid crystal layer side on the other substrate in addition to the alignment regulating structure, and at least in a voltage applied state, the one substrate has Since the alignment regulating force due to the provided alignment regulating structure and the convex portion provided on the other substrate acts on the liquid crystal molecules in the liquid crystal domain, the radial tilt alignment of the liquid crystal domain is more than the configuration having only the alignment regulating structure. It is stabilized and the deterioration of display quality due to stress is suppressed. Since the convex portion exhibits the alignment regulating force even in the state where no voltage is applied, the alignment can be stabilized regardless of the magnitude of the applied voltage.
[0048]
In the liquid crystal display device of the present invention, the cross-sectional shape along the substrate surface of the convex portion provided on the other substrate is a pair arranged in a crossed Nicol state (arranged so that the slow axes are substantially orthogonal to each other). The shape of the polarizing plate is substantially constituted only by sides substantially parallel to and substantially orthogonal to one polarization axis. Therefore, the liquid crystal molecules that are radially inclined (orientated in the direction inclined with respect to the normal to the substrate surface) by the alignment regulating force of the convex portion are aligned in an azimuth angle direction that is substantially parallel or substantially perpendicular to the polarization axis of the polarizing plate Therefore, the liquid crystal molecules in the vicinity of the convex portions hardly give a phase difference to the light incident on the liquid crystal layer. Therefore, the occurrence of light leakage during black display is suppressed, and as a result, display with a high contrast ratio is realized. On the other hand, for example, if the cross-sectional shape of the convex portion is substantially circular, the liquid crystal molecules that are radially inclined and aligned by the alignment regulating force of the convex portion are aligned with an equal probability in all azimuth directions. Therefore, the existence probability of the liquid crystal molecules aligned in the azimuth direction inclined with respect to the polarization axis of the polarizing plate is relatively high in the vicinity of the convex portion. Liquid crystal molecules aligned in the azimuthal direction inclined with respect to the polarization axis give a phase difference to the light passing through the liquid crystal layer, causing light leakage during black display and reducing the contrast ratio. There is.
[0049]
By providing the convex portion in a region corresponding to the vicinity of the center of the liquid crystal domain having the radial tilt alignment formed by the alignment control structure, the position of the central axis of the radial tilt alignment can be fixed. Resistance to stress is effectively improved.
[0050]
When the alignment regulating direction by the convex portion is set so as to match the direction of the radial inclined alignment by the alignment regulating structure (for example, the electrode structure described above), the continuity and stability of the alignment are increased, and the display quality and response characteristics are improved. .
[0051]
Further, if the alignment regulating force due to the convex portion extends only to the liquid crystal molecules in the liquid crystal domain having the radial tilt alignment formed by the alignment regulating structure, the radial tilt alignment of the liquid crystal domain can be stabilized. In particular, when the convex portion is provided in a region corresponding to the vicinity of the center of the liquid crystal domain, an effect of fixing the position of the central axis of the radial tilt alignment can be obtained. A convex part only needs to express the orientation control force weaker than the orientation control force by an orientation control structure.
[0052]
If the above-described electrode structure having an opening is adopted as the alignment regulating structure, the liquid crystal domain is formed in both the opening and the solid part, but with respect to the liquid crystal domain formed corresponding to the solid part. Only a convex portion may be provided.
[0053]
At this time, it is preferable to provide convex portions corresponding to all solid portions, but depending on the electrode structure (number and arrangement of openings), it is practical to provide only a portion of the solid portions. Orientation stability may be obtained in some cases. This is because the radial tilt alignment formed in the liquid crystal layer of the liquid crystal display device of the present invention is essentially continuous.
[0054]
Further, in order to further improve the resistance to stress, the liquid crystal molecules of the liquid crystal layer are further provided with a convex portion having a side surface having an alignment regulating force in the same direction as the alignment regulating direction by the oblique electric field described above. You may provide inside a part. The cross-sectional shape of the convex portion in the in-plane direction of the substrate is the same as the shape of the opening, and it is preferable to have rotational symmetry similar to the shape of the opening described above. However, since the liquid crystal molecules whose alignment is regulated by the alignment regulating force on the side surfaces of the convex portions are difficult to respond to the voltage (the change in retardation due to the voltage is small), this causes a reduction in the contrast ratio of the display. Therefore, it is preferable to set the size, height, and number of the convex portions so as not to deteriorate the display quality.
[0055]
Among the electrode structures functioning as the alignment regulating structure of the liquid crystal display device according to the present invention, the electrode having the opening described above is, for example, a switching element in an active matrix liquid crystal display device including a switching element such as a TFT for each pixel region. The other electrode is at least one counter electrode opposed to the plurality of pixel electrodes. In this way, stable radial tilt alignment can be realized by providing an opening only in one of the pair of electrodes provided to face each other with the liquid crystal layer interposed therebetween. That is, in a known manufacturing method, when patterning a conductive film into the shape of a pixel electrode, the alignment control structure can be obtained simply by modifying the photomask so that openings having a desired shape are formed in a desired arrangement. Can be manufactured. Of course, a plurality of openings may be formed in the counter electrode. Moreover, the two-layer structure electrode mentioned above can also be manufactured by a well-known method.
[0056]
Moreover, the convex part with which the liquid crystal display device by this invention is provided can also be manufactured by a well-known method.
[0057]
Hereinafter, embodiments of the liquid crystal display device according to the present invention will be described with reference to the drawings.
[0058]
(Orientation control structure)
First, an electrode structure, which is a preferred alignment regulating structure of the liquid crystal display device of the present invention, and its operation will be described.
[0059]
Since the liquid crystal display device according to the present invention has excellent display characteristics, it is preferably used for an active matrix liquid crystal display device. Hereinafter, an embodiment of the present invention will be described for an active matrix liquid crystal display device using a thin film transistor (TFT). The present invention is not limited to this, and can be applied to an active matrix liquid crystal display device or a simple matrix liquid crystal display device using MIM. In the following, embodiments of the present invention will be described by taking a transmissive liquid crystal display device as an example. However, the present invention is not limited to this, and the present invention is not limited to this. Can be applied.
[0060]
In the present specification, an area of the liquid crystal display device corresponding to “picture element” which is the minimum unit of display is referred to as “picture element area”. In the color liquid crystal display device, “picture elements” of R, G, and B correspond to one “pixel”. In an active matrix liquid crystal display device, a picture element region is defined by a picture element electrode and a counter electrode facing the picture element electrode. In the simple matrix liquid crystal display device, each region where a column electrode provided in a stripe shape and a row electrode provided orthogonal to the column electrode intersect with each other defines a pixel region. Strictly speaking, in the configuration in which the black matrix is provided, the region corresponding to the opening of the black matrix corresponds to the pixel region in the region to which the voltage is applied according to the state to be displayed. .
[0061]
With reference to FIGS. 1A and 1B, the structure of one picture element region of a liquid crystal display device 100 having an alignment regulating structure according to the present invention will be described. In the following, a color filter and a black matrix are omitted for the sake of simplicity. In the following drawings, components having substantially the same functions as the components of the liquid crystal display device 100 are denoted by the same reference numerals, and description thereof is omitted. FIG. 1A is a top view seen from the substrate normal direction, and FIG. 1B corresponds to a cross-sectional view taken along line 1B-1B ′ in FIG. FIG. 1B shows a state where no voltage is applied to the liquid crystal layer.
[0062]
The liquid crystal display device 100 is provided between an active matrix substrate (hereinafter referred to as “TFT substrate”) 100a, a counter substrate (also referred to as “color filter substrate”) 100b, and the TFT substrate 100a and the counter substrate 100b. And a liquid crystal layer 30. The liquid crystal molecules 30a of the liquid crystal layer 30 have negative dielectric anisotropy, and a vertical alignment film (not shown) as a vertical alignment layer provided on the surface of the TFT substrate 100a and the counter substrate 100b on the liquid crystal layer 30 side. Thus, when no voltage is applied to the liquid crystal layer 30, as shown in FIG. 1B, the liquid crystal layer 30 is aligned perpendicular to the surface of the vertical alignment film. At this time, the liquid crystal layer 30 is said to be in a vertically aligned state. However, the liquid crystal molecules 30a of the liquid crystal layer 30 in the vertical alignment state may be slightly inclined from the normal line of the surface of the vertical alignment film (substrate surface) depending on the type of the vertical alignment film and the type of the liquid crystal material. In general, a state in which liquid crystal molecular axes (also referred to as “axis orientation”) are aligned at an angle of about 85 ° or more with respect to the surface of the vertical alignment film is called a vertical alignment state.
[0063]
The TFT substrate 100a of the liquid crystal display device 100 includes a transparent substrate (for example, a glass substrate) 11 and pixel electrodes 14 formed on the surface thereof. The counter substrate 100b includes a transparent substrate (for example, a glass substrate) 21 and a counter electrode 22 formed on the surface thereof. The alignment state of the liquid crystal layer 30 for each pixel region changes according to the voltage applied to the pixel electrode 14 and the counter electrode 22 arranged so as to face each other via the liquid crystal layer 30. Display is performed using a phenomenon in which the polarization state and amount of light transmitted through the liquid crystal layer 30 change in accordance with the change in the alignment state of the liquid crystal layer 30.
[0064]
The pixel electrode 14 included in the liquid crystal display device 100 has a plurality of openings 14a and solid portions 14b. The opening 14a indicates a portion of the pixel electrode 14 formed from a conductive film (for example, an ITO film) from which the conductive film is removed, and the solid portion 14b indicates a portion where the conductive film exists (other than the opening 14a). Part). A plurality of openings 14a are formed for each pixel electrode, but the solid part 14b is basically formed of a single continuous conductive film.
[0065]
The plurality of openings 14a are arranged so that the centers thereof form a square lattice, and are substantially surrounded by the four openings 14a whose centers are located on the four lattice points forming one unit lattice. The solid part (referred to as “unit solid part”) 16b ′ has a substantially circular shape. Each of the openings 14a has a substantially star shape having four quarter arc sides (edges) and a four-fold rotation axis at the center thereof. In order to stabilize the alignment over the entire pixel region, it is preferable to form a unit cell up to the end of the pixel electrode 14. Therefore, as shown in the figure, the end of the pixel electrode 14 is about one half of the opening 14a (area corresponding to the side) and about one fourth of the opening 14a (area corresponding to the corner). It is preferable that it is patterned into a corresponding shape. Note that a square (set of square lattices) indicated by a solid line in FIG. 1A indicates a region (outer shape) corresponding to a conventional pixel electrode formed from a single conductive layer.
[0066]
The opening 14a located at the center of the picture element region has substantially the same shape and the same size. The unit solid portion 14b ′ located in the unit lattice formed by the openings 14a is substantially circular, and has substantially the same shape and the same size. The unit solid portions 14b ′ adjacent to each other are connected to each other, and constitute a solid portion 14b that substantially functions as a single conductive film.
[0067]
When a voltage is applied between the pixel electrode 14 and the counter electrode 22 having the above-described configuration, a plurality of liquid crystal domains each having a radial tilt alignment are formed by an oblique electric field generated at the edge portion of the opening 14a. It is formed. One liquid crystal domain is formed in each of regions corresponding to the respective openings 14a and regions corresponding to the solid portions 14b ′ in the unit cell.
[0068]
Here, a configuration having a plurality of openings 14a in one picture element region is illustrated, but a plurality of liquid crystal domains can be formed in one picture element area by providing only one opening. For example, when attention is paid to a square region composed of four units divided by broken lines shown in FIG. 1A and this is regarded as one pixel electrode, this pixel electrode has one opening portion. 14 a and four unit solid portions 14 b ′ arranged in the periphery thereof, but when a voltage is applied, five liquid crystal domains having a radial tilt alignment are formed.
[0069]
Furthermore, a plurality of liquid crystal domains can be formed in one picture element region without forming the opening 14a. For example, when attention is paid to two units adjacent to each other and this is considered as one picture element electrode, this picture element electrode is composed of two unit solid parts 14b 'and does not have an opening part 14a. At the time of application, two liquid crystal domains having a radially inclined alignment are formed. As described above, if the pixel electrode has at least a unit solid part that forms a plurality of liquid crystal domains having a radially inclined orientation when a voltage is applied (in other words, it has such an outer shape). In other words, since the continuity of the alignment of the liquid crystal molecules in the pixel region can be obtained, the radial tilt alignment of the liquid crystal domain formed corresponding to the unit solid portion 14b ′ is stable.
[0070]
Here, the square pixel electrode 14 is illustrated, but the shape of the pixel electrode 14 is not limited thereto. Since the general shape of the pixel electrode 14 is approximated to a rectangle (including a square and a rectangle), the openings 14a can be regularly arranged in a square lattice shape. Even if the pixel electrode 14 has a shape other than a rectangle, the openings 14a are formed regularly (for example, in a square lattice shape as illustrated) so that the liquid crystal domains are formed in all regions within the pixel region. If it arrange | positions, the effect of this invention can be acquired.
[0071]
The mechanism by which liquid crystal domains are formed by the above-described oblique electric field will be described with reference to FIGS. 2 (a) and 2 (b). 2A and 2B show a state in which a voltage is applied to the liquid crystal layer 30 shown in FIG. 1B, respectively. FIG. 2A shows the voltage applied to the liquid crystal layer 30. Accordingly, a state in which the orientation of the liquid crystal molecules 30a starts to change (ON initial state) is schematically shown, and FIG. 2B shows that the orientation of the liquid crystal molecules 30a changed according to the applied voltage is steady. The state which reached the state is shown typically. A curve EQ in FIGS. 2A and 2B shows an equipotential line EQ.
[0072]
When the pixel electrode 14 and the counter electrode 22 are at the same potential (a state in which no voltage is applied to the liquid crystal layer 30), as shown in FIG. 1A, the liquid crystal molecules 30a in the pixel region are , Oriented perpendicular to the surfaces of both substrates 11 and 21.
[0073]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by an equipotential line EQ (perpendicular to the electric force lines) EQ shown in FIG. This equipotential line EQ is parallel to the surface of the solid portion 14b and the counter electrode 22 in the liquid crystal layer 30 located between the solid portion 14b of the picture element electrode 14 and the counter electrode 22, and It falls in a region corresponding to the opening 14a of the elementary electrode 14 and is inclined in the liquid crystal layer 30 on the edge portion of the opening 14a (the inner periphery of the opening 14a including the boundary (extended) of the opening 14a). An oblique electric field represented by an equipotential line EQ is formed.
[0074]
A torque is applied to the liquid crystal molecules 30a having negative dielectric anisotropy so as to align the axial direction of the liquid crystal molecules 30a in parallel to the equipotential lines EQ (perpendicular to the lines of electric force). Accordingly, the liquid crystal molecules 30a on the edge portion EG are rotated clockwise in the right edge portion EG in the drawing and counterclockwise in the left edge portion EG in the drawing, as indicated by an arrow in FIG. Each direction is inclined (rotated) and oriented parallel to the equipotential line EQ.
[0075]
Here, the change in the alignment of the liquid crystal molecules 30a will be described in detail with reference to FIG.
[0076]
When an electric field is generated in the liquid crystal layer 30, a torque is applied to the liquid crystal molecules 30a having negative dielectric anisotropy so as to align the axial direction parallel to the equipotential line EQ. As shown in FIG. 3A, when an electric field represented by an equipotential line EQ perpendicular to the axial direction of the liquid crystal molecules 30a is generated, the liquid crystal molecules 30a are tilted clockwise or counterclockwise. Acts with equal probability of torque. Accordingly, in the liquid crystal layer 30 between the electrodes of the parallel plate type arrangement facing each other, the liquid crystal molecules 30a receiving the torque in the clockwise direction and the liquid crystal molecules 30a receiving the torque in the counterclockwise direction are mixed. As a result, the transition to the alignment state according to the voltage applied to the liquid crystal layer 30 may not occur smoothly.
[0077]
As shown in FIG. 2A, the electric field (diagonal) represented by an equipotential line EQ inclined with respect to the axial direction of the liquid crystal molecules 30a at the edge portion EG of the opening 14a of the liquid crystal display device 100 according to the present invention. When an electric field is generated, as shown in FIG. 3B, the liquid crystal molecules 30a are tilted in a direction with a small amount of tilt (counterclockwise in the illustrated example) to be parallel to the equipotential line EQ. Further, as shown in FIG. 3C, the liquid crystal molecules 30a located in the region where the electric field expressed by the equipotential line EQ perpendicular to the axis direction of the liquid crystal molecules 30a is inclined are equipotential. The liquid crystal molecules 30a positioned on the line EQ are tilted in the same direction as the liquid crystal molecules 30a positioned on the tilted equipotential line EQ so that the alignment is continuous (matched) with the liquid crystal molecules 30a. As shown in FIG. 3D, when an electric field that forms a continuous concavo-convex shape of the equipotential lines EQ is applied, the alignment is regulated by the liquid crystal molecules 30a positioned on the inclined equipotential lines EQ. The liquid crystal molecules 30a positioned on the flat equipotential lines EQ are aligned so as to match the direction. Note that “located on the equipotential line EQ” means “located within the electric field represented by the equipotential line EQ”.
[0078]
As described above, when the change in alignment starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses and reaches a steady state, the alignment state schematically shown in FIG. The liquid crystal molecules 30a located in the vicinity of the center of the opening 14a are almost equally affected by the orientation of the liquid crystal molecules 30a at the opposite edge portions EG of the opening 14a, and are therefore perpendicular to the equipotential line EQ. The liquid crystal molecules 30a in the region that maintains the alignment state and is away from the center of the opening 14a are inclined by the influence of the alignment of the liquid crystal molecules 30a in the closer edge portion EG, and are symmetric with respect to the center SA of the opening 14a. A tilted orientation is formed. This alignment state is a state in which the axial orientation of the liquid crystal molecules 30a is radially aligned with respect to the center of the opening 14a when viewed from the direction perpendicular to the display surface of the liquid crystal display device 100 (the direction perpendicular to the surfaces of the substrates 11 and 21). (Not shown). Therefore, in this specification, such an alignment state is referred to as “radially inclined alignment”. In addition, a region of the liquid crystal layer having a radially inclined alignment with respect to one center is referred to as a liquid crystal domain.
[0079]
Also in the region corresponding to the unit solid portion 14b ′ substantially surrounded by the opening 14a, a liquid crystal domain in which the liquid crystal molecules 30a have a radial tilt alignment is formed. The liquid crystal molecules 30a in the region corresponding to the unit solid portion 14b ′ are affected by the alignment of the liquid crystal molecules 30a in the edge portion EG of the opening 14a, and the center SA (the opening 14a is formed by the unit solid portion 14b ′). A symmetric radial orientation with respect to the center of the unit cell.
[0080]
The radial tilt alignment in the liquid crystal domain formed in the unit solid portion 14b ′ and the radial tilt alignment formed in the opening 14a are continuous, and both are aligned with the alignment of the liquid crystal molecules 30a in the edge portion EG of the opening 14a. Oriented to do. The liquid crystal molecules 30a in the liquid crystal domain formed in the opening 14a are aligned in a cone shape with the upper side (substrate 100b side) open, and the liquid crystal molecules 30a in the liquid crystal domain formed in the unit solid portion 14b ′ are The side (substrate 100a side) is oriented in an open cone. Thus, since the radial tilt alignment formed in the liquid crystal domain formed in the opening 14a and the liquid crystal domain formed in the unit solid portion 14b ′ is continuous with each other, the disclination line ( (Alignment defect) is not formed, so that the display quality is not deteriorated due to the occurrence of the disclination line.
[0081]
In order to improve the viewing angle dependence of the display quality of the liquid crystal display device in all directions, the existence probability of the liquid crystal molecules aligned along each of all the azimuth directions in each pixel region has rotational symmetry. Preferably, it has an axial symmetry. That is, it is preferable that the liquid crystal domains formed over the entire picture element region are arranged so as to have rotational symmetry and further axial symmetry. However, it is not always necessary to have rotational symmetry over the entire pixel region, and liquid crystal domains arranged to have rotational symmetry (or axial symmetry) (for example, a plurality of pixels arranged in a square lattice pattern). The liquid crystal layer in the picture element region may be formed as an aggregate of liquid crystal domains. Accordingly, the arrangement of the plurality of openings 14a formed in the picture element region is not necessarily required to have rotational symmetry over the entire picture element region, and is arranged so as to have rotational symmetry (or axial symmetry). What is necessary is just to represent as an aggregate | assembly of the opening part (for example, the several opening part arranged in the shape of a square lattice). Of course, the arrangement of the unit solid portion 14b ′ substantially surrounded by the plurality of openings 14a is the same. In addition, since the shape of each liquid crystal domain also preferably has rotational symmetry or axial symmetry, the shape of each opening 14a and unit solid portion 14b ′ also has rotational symmetry or axial symmetry. Is preferred.
[0082]
Note that a sufficient voltage is not applied to the liquid crystal layer 30 near the center of the opening 14a, and the liquid crystal layer 30 near the center of the opening 14a may not contribute to display. That is, even if the radial tilt alignment of the liquid crystal layer 30 near the center of the opening 14a is somewhat disturbed (for example, even if the central axis is shifted from the center of the opening 14a), the display quality may not be deteriorated. Accordingly, it is only necessary that the liquid crystal domains formed corresponding to at least the unit solid portion 14b ′ have rotational symmetry and further axial symmetry.
[0083]
As described with reference to FIGS. 2A and 2B, the pixel electrode 14 of the liquid crystal display device 100 according to the present invention has a plurality of openings 14a, and the liquid crystal layer 30 in the pixel region. An electric field represented by an equipotential line EQ having an inclined region is formed therein. The liquid crystal molecules 30a having negative dielectric anisotropy in the liquid crystal layer 30 in the vertical alignment state when no voltage is applied change the alignment direction by using the alignment change of the liquid crystal molecules 30a located on the inclined equipotential line EQ as a trigger. Then, a liquid crystal domain having a stable radial tilt alignment is formed in the opening 14a and the solid portion 14b. Display is performed by changing the orientation of the liquid crystal molecules in the liquid crystal domain in accordance with the voltage applied to the liquid crystal layer.
[0084]
The shape (shape seen from the substrate normal direction) of the opening 14a of the pixel electrode 14 of the liquid crystal display device 100 and the arrangement thereof will be described.
[0085]
The display characteristics of the liquid crystal display device show azimuth dependency due to the alignment state (optical anisotropy) of the liquid crystal molecules. In order to reduce the azimuth angle dependency of the display characteristics, it is preferable that the liquid crystal molecules are aligned with the same probability with respect to all azimuth angles. Further, it is more preferable that the liquid crystal molecules in each picture element region are aligned with the same probability with respect to all azimuth angles. Accordingly, the opening 14a preferably has a shape that forms a liquid crystal domain so that the liquid crystal molecules 30a in each pixel region are aligned with an equal probability with respect to all azimuth angles. . Specifically, the shape of the opening 14a preferably has rotational symmetry (preferably symmetry of two or more rotation axes) with each center (normal direction) as an axis of symmetry, The openings 14a are preferably arranged so as to have rotational symmetry. The shape of the unit solid portion 14b ′ substantially surrounded by these openings is also preferably rotationally symmetric, and the unit solid portion 14b is also preferably arranged to have rotational symmetry. .
[0086]
However, the openings 14a and the unit solid portions 14b are not necessarily arranged so as to have rotational symmetry over the entire picture element region. For example, as shown in FIG. If the picture element region is configured by combining them with a minimum unit of symmetry having a rotation axis), the liquid crystal molecules have a substantially equal probability for all azimuth angles over the whole picture element region. Can be oriented.
[0087]
The alignment state of the liquid crystal molecules 30a when the substantially star-shaped openings 14a having rotational symmetry and the substantially circular unit solid portions 14b shown in FIG. 1A are arranged in a square lattice is shown in FIG. A description will be given with reference to FIG.
[0088]
4A to 4C schematically show the alignment states of the liquid crystal molecules 30a viewed from the substrate normal direction. 4 (b) and (c) and the like showing the alignment state of the liquid crystal molecules 30a viewed from the normal direction of the substrate, the end of the liquid crystal molecules 30a drawn in an ellipse is shown in black. It is shown that the liquid crystal molecules 30a are inclined so that the end is closer to the substrate side on which the pixel electrode 14 having the opening 14a is provided than the other end. The same applies to the following drawings. Here, one unit cell (formed by four openings 14a) in the picture element region shown in FIG. 1A will be described. The cross sections along the diagonal lines in FIGS. 4A to 4C correspond to FIGS. 1B, 2A, and 2B, respectively, and are described with reference to these drawings together. To do.
[0089]
When the pixel electrode 14 and the counter electrode 22 are at the same potential, that is, when no voltage is applied to the liquid crystal layer 30, a vertical alignment layer (on the liquid crystal layer 30 side surfaces of the TFT substrate 100a and the counter substrate 100b) As shown in FIG. 4A, the liquid crystal molecules 30a whose alignment direction is regulated by an unillustrated state take a vertical alignment state.
[0090]
When an electric field is applied to the liquid crystal layer 30 and an electric field represented by the equipotential line EQ shown in FIG. 2A is generated, the liquid crystal molecules 30a having negative dielectric anisotropy have an axial orientation of equipotential. Torque that is parallel to the line EQ is generated. As described with reference to FIGS. 3A and 3B, the liquid crystal molecules 30a under the electric field represented by the equipotential line EQ perpendicular to the molecular axis of the liquid crystal molecules 30a are tilted. Since the (rotating) direction is not uniquely determined (FIG. 3 (a)), the orientation change (tilt or rotation) does not easily occur, whereas it is tilted with respect to the molecular axis of the liquid crystal molecules 30a. In the liquid crystal molecules 30a placed under the potential line EQ, the tilt (rotation) direction is uniquely determined, so that the change in orientation easily occurs. Accordingly, as shown in FIG. 4B, the liquid crystal molecules 30a start to tilt from the edge portion of the opening 14a where the molecular axis of the liquid crystal molecules 30a is tilted with respect to the equipotential line EQ. Then, as described with reference to FIG. 3C, the surrounding liquid crystal molecules 30a are also tilted so as to be aligned with the alignment of the tilted liquid crystal molecules 30a at the edge of the opening 14a. ), The axial orientation of the liquid crystal molecules 30a is stabilized (radial tilt alignment).
[0091]
As described above, when the opening 14a has a rotationally symmetric shape, the liquid crystal molecules 30a in the picture element region are liquid crystal molecules 30a from the edge of the opening 14a toward the center of the opening 14a when a voltage is applied. Therefore, the liquid crystal molecules 30a in the vicinity of the center of the opening 14a in which the alignment regulating force of the liquid crystal molecules 30a from the edge portion is balanced maintain a state of being aligned perpendicular to the substrate surface, and the liquid crystal molecules 30a around the liquid crystal molecules 30a A state is obtained in which the liquid crystal molecules 30a are continuously inclined radially about the liquid crystal molecules 30a near the center of the opening 14a.
[0092]
Further, liquid crystal molecules 30a in a region corresponding to the substantially circular unit solid portion 14b ′ surrounded by the four substantially star-shaped openings 14a arranged in a square lattice are also generated at the edge of the opening 14a. The liquid crystal molecules 30a are tilted so as to be aligned with the alignment of the tilted electric field. The liquid crystal molecules 30a in the vicinity of the center of the unit solid portion 14b ′ in which the alignment regulating force of the liquid crystal molecules 30a from the edge portion is balanced maintain a state of being aligned perpendicular to the substrate surface, and the surrounding liquid crystal molecules 30a are in the unit. A state is obtained in which the liquid crystal molecules 30a are continuously inclined radially about the liquid crystal molecules 30a near the center of the real part 14b ′.
[0093]
As described above, when the liquid crystal domains in which the liquid crystal molecules 30a have a radially inclined orientation are arranged in a square lattice pattern over the entire pixel region, the existence probabilities of the liquid crystal molecules 30a in the respective axial directions have rotational symmetry. As a result, high-quality display without roughness can be realized in all viewing angle directions. In order to reduce the viewing angle dependency of a liquid crystal domain having a radial tilt alignment, it is preferable that the liquid crystal domain has high rotational symmetry (two or more rotation axes are preferable, and four or more rotation axes are more preferable). In addition, in order to reduce the viewing angle dependency of the entire picture element region, a plurality of liquid crystal domains formed in the picture element region have high rotational symmetry (preferably a 2-fold rotation axis or more, and further a 4-fold rotation axis or more. It is preferable to constitute an array (for example, a square lattice) represented by a combination of units (for example, a unit cell) having (preferably).
[0094]
Note that the radial tilt alignment of the liquid crystal molecules 30a is counterclockwise or clockwise as shown in FIGS. 5B and 5C rather than the simple radial tilt alignment as shown in FIG. A spiral radial gradient orientation is more stable. In this spiral alignment, the alignment direction of the liquid crystal molecules 30a does not change spirally along the thickness direction of the liquid crystal layer 30 as in the normal twist alignment, but the alignment direction of the liquid crystal molecules 30a is seen in a minute region. And hardly changes along the thickness direction of the liquid crystal layer 30. That is, the cross-section at any position in the thickness direction of the liquid crystal layer 30 (the cross-section in a plane parallel to the layer surface) is in the same alignment state as FIG. 5B or 5C, and the thickness of the liquid crystal layer 30 Almost no twist deformation along the vertical direction occurs. However, a certain amount of twist deformation occurs in the entire liquid crystal domain.
[0095]
When a material in which a chiral agent is added to a nematic liquid crystal material having negative dielectric anisotropy is used, the liquid crystal molecules 30a center around the opening 14a and the unit solid portion 14b ′ when a voltage is applied, as shown in FIG. And take the counterclockwise or clockwise spiral gradient orientation shown in (c). Whether it is clockwise or counterclockwise depends on the type of chiral agent used. Therefore, when the voltage is applied, the liquid crystal layer 30 in the opening 14a is spirally inclined and oriented, so that the radially inclined liquid crystal molecules 30a are wound around the liquid crystal molecules 30a standing perpendicular to the substrate surface. Since the direction can be made constant in all liquid crystal domains, uniform display without roughness can be achieved. Furthermore, since the direction of winding around the liquid crystal molecules 30a standing perpendicular to the substrate surface is determined, the response speed when a voltage is applied to the liquid crystal layer 30 is also improved.
[0096]
When the chiral agent is added, the orientation of the liquid crystal molecules 30a changes spirally along the thickness direction of the liquid crystal layer 30 as in a normal twist orientation. In the alignment state in which the alignment of the liquid crystal molecules 30a does not change spirally along the thickness direction of the liquid crystal layer 30, the liquid crystal molecules 30a aligned in a direction perpendicular or parallel to the polarization axis of the polarizing plate are incident light. Therefore, the incident light passing through the region having such an alignment state does not contribute to the transmittance. On the other hand, in the alignment state in which the alignment of the liquid crystal molecules 30a changes spirally along the thickness direction of the liquid crystal layer 30, the liquid crystal molecules 30a aligned in the direction perpendicular or parallel to the polarization axis of the polarizing plate are also included. In addition to giving a phase difference to the incident light, the optical rotation of the light can be used. Accordingly, the incident light passing through the region having such an orientation also contributes to the transmittance, so that a liquid crystal display device capable of bright display can be obtained.
[0097]
FIG. 1A shows an example in which the opening 14a has a substantially star shape, the unit solid portion 14b ′ has a substantially circular shape, and these are arranged in a square lattice shape. The shape of the unit solid portion 14b ′ and the arrangement thereof are not limited to the above example.
[0098]
FIGS. 6A and 6B are top views of pixel electrodes 14A and 14B having openings 14a and unit solid portions 14b ′ having different shapes, respectively.
[0099]
The openings 14a and unit solid portions 14b ′ of the pixel electrodes 14A and 14B shown in FIGS. 6A and 6B are respectively the openings 14a of the pixel electrodes shown in FIG. The real part 14b 'has a slightly distorted shape. The openings 14a and unit solid portions 14b ′ of the pixel electrodes 14A and 14B have a 2-fold rotation axis (no 4-fold rotation axis), and are regularly arranged to form a rectangular unit cell. ing. Each of the openings 14a has a distorted star shape, and each of the unit solid portions 14b ′ has a substantially elliptical shape (distorted circle). Even when the pixel electrodes 14A and 14B are used, a liquid crystal display device having high display quality and excellent viewing angle characteristics can be obtained.
[0100]
Further, pixel electrodes 14C and 14D as shown in FIGS. 7A and 7B can be used.
[0101]
The pixel electrodes 14C and 14D have substantially cross-shaped openings 14a arranged in a square lattice so that the unit solid portion 14b ′ is substantially square. Of course, these may be distorted to form a rectangular unit cell. Thus, even when the unit solid portions 14b ′ of a substantially rectangular shape (a rectangle includes a square and a rectangle) are regularly arranged, a liquid crystal display device with high display quality and excellent viewing angle characteristics can be obtained. .
[0102]
However, the shape of the opening 14a and / or the unit solid portion 14b ′ is preferably a circle or an ellipse rather than a rectangle because the radial inclined orientation can be stabilized. This is presumably because the side of the opening 14a changes continuously (smoothly), and the orientation direction of the liquid crystal molecules 30a also changes continuously (smoothly).
[0103]
From the viewpoint of the continuity of the alignment direction of the liquid crystal molecules 30a described above, the pixel electrodes 14E and 14F shown in FIGS. 8A and 8B are also conceivable. A picture element electrode 14E shown in FIG. 8A is a modification of the picture element electrode 14 shown in FIG. 1A, and has an opening 14a composed of only four arcs. The pixel electrode 14F shown in FIG. 8B is a modification of the pixel electrode 14D shown in FIG. 7B, and the unit solid portion 14b ′ side of the opening 14a is formed by an arc. . Each of the openings 14a and unit solid portions 14b ′ of the pixel electrodes 14E and 14F has a four-fold rotation axis and is arranged in a square lattice pattern (having a four-turn rotation axis). 6 (a) and 6 (b), the shape of the unit solid portion 14b ′ of the opening 14a is distorted into a shape having a two-fold rotation axis, and a rectangular lattice (two-fold rotation axis). May be formed.
[0104]
Further, from the viewpoint of response speed, pixel electrodes 14G and 14H as shown in FIGS. 9A and 9B may be used. The pixel electrode 14G shown in FIG. 9A is a modification of the pixel electrode 14C having the substantially square unit solid portion 14b ′ shown in FIG. 7A, and is a unit of the pixel electrode 14G. The shape of the solid part 14b ′ is a distorted square shape with sharpened corners. Further, the shape of the unit solid portion 14b ′ of the pixel electrode 14H shown in FIG. 9B is a substantially star shape having eight sides (edges) and a four-fold rotation axis at the center thereof. Yes, each of the four corners is sharpened. The sharpening of the corner means that the corner is constituted by an angle or a curve of less than 90 °.
[0105]
In a liquid crystal display device in which the alignment of the liquid crystal molecules 30a is controlled by an oblique electric field generated at the edge portion of the opening 14a, when a voltage is applied to the liquid crystal layer 30, first, the liquid crystal molecules 30a on the edge portion are inclined. Thereafter, the liquid crystal molecules 30a in the peripheral region are tilted to form a radially tilted alignment. Therefore, the response speed may be slower than a liquid crystal display device in a display mode in which the liquid crystal molecules on the pixel electrode are simultaneously tilted when a voltage is applied to the liquid crystal layer.
[0106]
As shown in FIGS. 9A and 9B, when the unit solid portion 14b ′ has a shape with a sharpened corner, more edge portions that generate an oblique electric field are formed. Therefore, an oblique electric field can be applied to more liquid crystal molecules 30a. Accordingly, the number of liquid crystal molecules 30a that start to tilt first in response to an electric field is increased, and the time required to form a radial tilt alignment over the entire pixel region is shortened, so that a voltage is applied to the liquid crystal layer 30. The response speed is improved.
[0107]
For example, in the liquid crystal display device in which the length of one side of the unit solid portion 14b ′ is about 40 μm, the shape of the unit solid portion 14b ′ is the distorted square shape shown in FIG. When the angle θa formed by the sides constituting the corner portion is less than 90 ° as shown in a), the unit solid portion 14b ′ has a substantially square shape as shown in FIG. As shown in (b), the response speed when a voltage is applied to the liquid crystal layer 30 can be shortened by about 60%, compared with the case where the angle θa formed by the sides constituting the corner is 90 °. Of course, the response speed can be shortened in the same manner even if the unit solid portion 14b ′ has a substantially star shape as shown in FIG. 9B.
[0108]
Further, when the shape of the unit solid portion 14b ′ is a shape with sharpened corners, the unit solid portion 14b ′ is along a specific azimuth direction as compared with the case where the shape of the unit solid portion 14b ′ is substantially circular or substantially rectangular. Thus, the existence probability of the liquid crystal molecules 30a aligned can be increased (or decreased). That is, a high directivity can be provided by the existence probability of the liquid crystal molecules 30a aligned along all the azimuthal directions. Therefore, in a liquid crystal display device having a polarizing plate and a mode in which linearly polarized light is incident on the liquid crystal layer 30, when the corner of the unit solid portion 14b ′ is sharpened, the direction is perpendicular or parallel to the polarizing axis of the polarizing plate. The existence probability of the liquid crystal molecules 30a aligned in the direction, that is, the liquid crystal molecules 30a that do not give a phase difference to the incident light can be further reduced. Therefore, the light transmittance can be improved and a brighter display can be realized.
[0109]
A liquid crystal display device including the pixel electrode 14F shown in FIG. 8B having a substantially square unit solid portion 14b ′, and FIG. 9B having a substantially star-shaped unit solid portion 14b ′. FIG. 11A shows the transmittance when the angle of the polarization axis of the polarizing plate is changed in the liquid crystal display device including the pixel electrode 14H shown in FIG. A solid line 51 in FIG. 11A indicates the transmittance when a voltage is applied to the liquid crystal display device including the pixel electrode 14F illustrated in FIG. 8B, and a broken line 52 indicates the transmittance in FIG. 9B. The transmissivity at the time of voltage application of the liquid crystal display device provided with the picture element electrode 14H is shown. In FIG. 11A, as shown in FIG. 11B, the polarizing axis of the polarizing plate on the viewer side (indicated by the solid line arrow 61) corresponds to the vertical direction of the display surface (the vertical direction of the paper). ), And the angle when the polarization axis on the back side (indicated by the dashed arrow 62) is in the horizontal direction of the display surface (corresponding to the horizontal direction of the paper surface) is zero. The angle when rotated counterclockwise is positive, and the angle when rotated clockwise is negative.
[0110]
As shown in FIG. 11 (a), the maximum value of the transmittance (broken line 52) of the liquid crystal display device including the pixel electrode 14H with sharp corners of the unit solid portion 14b ′ is substantially square. Is larger than the maximum value of the transmittance (solid line 51) of the liquid crystal display device including the pixel electrode 14F having the unit solid portion 14 ′. Thus, when the corner portion of the unit solid portion 14b ′ is sharpened, the transmittance can be improved, and a brighter display can be performed.
[0111]
As described above, when the corner of the unit solid portion 14b ′ is sharpened, the response speed can be improved and the transmittance can be improved, but the stability of the radial gradient orientation may be deteriorated. . For example, as compared with the case where the shape of the unit solid portion 14b ′ is substantially circular, when the corner is sharpened, the side of the opening 14a has a shape of the unit solid portion 14b ′ having a substantially circular shape. Since it does not change as smoothly as in some cases, the continuity of the change in the alignment direction of the liquid crystal molecules 30a is poor. For this reason, the stability of the radially inclined alignment may be deteriorated, but practically sufficient alignment stability can be obtained by combining convex portions described later.
[0112]
6, 7, 8, and 9 exemplify the configuration having a plurality of openings 14 a in one picture element region, but as described with reference to FIG. 1, one opening is provided. Thus, it is possible to form a plurality of liquid crystal domains in one picture element region, and it is also possible to form a plurality of liquid crystal domains in one picture element region without forming the opening 14a. Further, it is not always necessary to form a liquid crystal domain having a radially inclined alignment in a region corresponding to the opening 14a of the pixel electrode, and the radial inclined alignment corresponding to the solid portion 14b (unit solid portion 14b ′). If the liquid crystal domain to be taken is formed, the continuity of the alignment of the liquid crystal molecules in the pixel region can be obtained even if the liquid crystal domain formed corresponding to the opening 14a does not take a radial tilt alignment. The radial tilt alignment of the liquid crystal domain formed corresponding to 14b is stable. In particular, as shown in FIGS. 7A and 7B, when the area of the opening 14a is small, the contribution to the display is small, and therefore, there is a liquid crystal domain having a radial tilt alignment in a region corresponding to the opening. Even if it is not formed, the deterioration of display quality is not a problem.
[0113]
In the above-described example, the substantially star-shaped or substantially cross-shaped opening 14a is formed, and the shape of the unit solid portion 14b ′ is approximately circular, approximately elliptical, approximately square (rectangular), and approximately rectangular with rounded corners. Explained the configuration. On the other hand, the relationship between the opening 14a and the unit solid portion 14b ′ may be negative / positive inverted. For example, FIG. 12 shows a pixel electrode 14I having a pattern in which the opening 14a and the unit solid portion 14b of the pixel electrode 14 shown in FIG. In this manner, the pixel electrode 14I having a negative-positive inverted pattern has substantially the same function as the pixel electrode 14 shown in FIG. If both the opening 14a and the unit solid portion 14b ′ are substantially square like the pixel electrodes 14J and 14K shown in FIGS. 13A and 13B, respectively, negative / positive inversion may be performed. Some of them have the same pattern as the original pattern.
[0114]
Even when the pattern shown in FIG. 1A is negative-positive-inverted like the pattern shown in FIG. 12, the unit solid part 14b ′ having rotational symmetry at the edge part of the pixel electrode 14 is provided. It is preferable to form a part (about one-half or about one-fourth) of the opening 14a so that is formed. By adopting such a pattern, the effect of the oblique electric field can be obtained at the edge portion of the pixel region similarly to the central portion of the pixel region, and a stable radial tilt orientation can be obtained over the entire pixel region. Can be realized.
[0115]
Next, the pixel electrode 14 shown in FIG. 12 having a pattern obtained by negative-positive reversal of the pattern of the pixel electrode 14 of FIG. 1A, the opening 14a of the pixel electrode 14 and the unit solid portion 14b ′. 14I is taken as an example to explain which negative-positive pattern should be adopted.
[0116]
Regardless of the negative-positive pattern, the length of the side of the opening 14a is the same for both patterns. Therefore, there is no difference between these patterns in the function of generating an oblique electric field. However, the area ratio of the unit solid portion 14b ′ (ratio to the total area of the pixel electrode 14) may be different between the two. That is, the area of the solid portion 16 (the portion where the conductive film actually exists) that generates an electric field acting on the liquid crystal molecules of the liquid crystal layer may be different.
[0117]
Since the voltage applied to the liquid crystal domain formed in the opening 14a is lower than the voltage applied to the liquid crystal domain formed in the solid part 14b, for example, when a normally black mode display is performed, the opening The liquid crystal domain formed in the portion 14a becomes dark. That is, as the area ratio of the opening 14a increases, the display luminance tends to decrease. Therefore, it is preferable that the area ratio of the solid portion 14b is high.
[0118]
Whether the area ratio of the solid portion 14b is higher in the pattern of FIG. 1A or the pattern of FIG. 12 depends on the pitch (size) of the unit cell.
[0119]
14A shows a unit cell having the pattern shown in FIG. 1A, and FIG. 14B shows a unit cell having the pattern shown in FIG. 9 (provided that the opening 14a is the center). Is shown. In FIG. 14B, the portion (branch portion extending in four directions from the circular portion) that plays the role of connecting the unit solid portions 14b ′ in FIG. 12 to each other is omitted. Let p be the length (pitch) of one side of the square unit cell, and s be the length of the gap (space on one side) between the opening 14a or unit solid portion 14b 'and the unit cell.
[0120]
Various pixel electrodes 14 having different values of the pitch p and the one-side space s were formed, and the stability of the radial tilt alignment was examined. As a result, first, an oblique electric field necessary for obtaining a radially inclined orientation is generated using the pixel electrode 14 having the pattern shown in FIG. 14A (hereinafter referred to as “positive pattern”). For this purpose, it has been found that the space s on one side is required to be about 2.75 μm or more. On the other hand, for the pixel electrode 14 having the pattern shown in FIG. 14B (hereinafter referred to as a “negative pattern”), a one-side space s is formed in order to generate an oblique electric field for obtaining a radially inclined alignment. It was found that about 2.25 μm or more is necessary. The space ratio of the solid portion 14b when the value of the pitch p was changed was examined using the one-side space s as the lower limit value. The results are shown in Table 1 and FIG.
[0121]

As can be seen from Table 1 and FIG. 14 (c), when the pitch p is about 25 μm or more, the positive type (FIG. 14 (a)) pattern has a higher area ratio of the solid portion 14b and is shorter than about 25 μm. In this case, the area ratio of the solid portion 14b is larger in the negative type (FIG. 14B). Therefore, from the viewpoint of display brightness and orientation stability, the pattern to be adopted changes with the pitch p of about 25 μm as a boundary. For example, when three or less unit cells are provided in the width direction of the pixel electrode 14 having a width of 75 μm, the positive pattern shown in FIG. 14A is preferable, and when four or more unit cells are provided. Is preferably the negative pattern shown in FIG. In cases other than the illustrated pattern, either a positive type or a negative type may be selected so that the area ratio of the solid portion 14b is increased.
[0122]
The number of unit cells is obtained as follows. The size of the unit cell is calculated so that one or two or more integer unit cells are arranged with respect to the width (horizontal or vertical) of the picture element electrode 14, and the solid part is obtained for each unit cell size. Calculate the area ratio and select the unit cell size that maximizes the solid area ratio. However, when the diameter of the unit solid portion 14b ′ is less than 15 μm in the case of a positive pattern, and when the diameter of the opening 14a is less than 15 μm in the case of a negative pattern, the alignment regulating force due to the oblique electric field is reduced and stable. It is difficult to obtain a radially inclined orientation. The lower limit of these diameters is when the thickness of the liquid crystal layer 30 is about 3 μm. When the thickness of the liquid crystal layer 30 is thinner than this, the diameters of the unit solid portion 14b ′ and the opening 14a are A stable radial tilt alignment can be obtained even if it is smaller than the above lower limit, and the unit solid portion 14b ′ and the solid solid tilt alignment 14b ′ necessary for obtaining a stable radial tilt alignment when the thickness of the liquid crystal layer 30 is thicker than this. The lower limit value of the diameter of the opening 14a is larger than the above lower limit value.
[0123]
As will be described later, by forming a convex portion (see FIG. 38) inside the opening portion 14a, the stability of the radial inclined alignment can be enhanced. All of the above-mentioned conditions are for the case where no protrusion is formed.
[0124]
The configuration of the liquid crystal display device 100 described above can adopt the same configuration as a known vertical alignment type liquid crystal display device, except that the pixel electrode 14 is an electrode having an opening 14a, and is a known manufacturing method. Can be manufactured.
[0125]
Typically, a vertical alignment layer (not shown) is formed on the surface of the pixel electrode 14 and the counter electrode 22 on the liquid crystal layer 30 side in order to vertically align liquid crystal molecules having negative dielectric anisotropy. ing.
[0126]
As the liquid crystal material, a nematic liquid crystal material having negative dielectric anisotropy is used. A guest-host mode liquid crystal display device can also be obtained by adding a dichroic dye to a nematic liquid crystal material having negative dielectric anisotropy. The guest-host mode liquid crystal display device does not require a polarizing plate.
[0127]
(Convex)
Next, a specific structure and operation of the convex portion will be described. In accordance with the above description, a case where the alignment regulating structure is provided on the TFT substrate and the convex portion is provided on the counter substrate will be described. The liquid crystal display device according to the present invention has a configuration for vertically aligning liquid crystal molecules with respect to the substrate surface (for example, a vertical alignment film provided on the liquid crystal layer side of a pair of substrates), in addition to the liquid crystal molecules as described above radially. It has an alignment regulating structure for tilting alignment, and a convex part for radially tilting alignment of liquid crystal molecules (stabilizing the radial tilt alignment state) in cooperation with the alignment regulating structure as will be described later.
[0128]
With reference to FIGS. 15A and 15B, the structure and operation of the convex portion 28A provided on the counter substrate 200b will be described. FIG. 15A is a cross-sectional view schematically showing a counter substrate 200b having a convex portion 28A protruding toward the liquid crystal layer 30, and FIG. 15B is a top view schematically showing the convex portion 28A. is there. Components that are substantially the same as those of the above-described liquid crystal display device are denoted by common reference numerals, and description thereof is omitted here.
[0129]
As shown in FIGS. 15A and 15B, the convex portion 28A has a substantially regular pyramid shape in which the side surface 28s is convex, and the side surface 28s is inclined with respect to the substrate surface of the counter substrate 200b. And a substantially square bottom surface. Here, the convex portion 28 </ b> A is formed on the counter electrode 22. As shown in FIG. 15B, the convex portion 28A is provided on the outside of a pair of polarizing plates (TFT substrate 100a and counter substrate 200b) in which the sides of the substantially square bottom surface are arranged in a crossed Nicol state. Are arranged so as to be substantially parallel to or substantially perpendicular to the polarization axis (indicated by an arrow PA in FIG. 15B). In other words, the cross-sectional shape of the convex portion 28A (the cross-sectional shape along the substrate surface of the counter substrate 200b) is substantially composed of only a side substantially parallel to one polarization axis and a side substantially orthogonal to the pair of polarizing plates. Shape.
[0130]
The surface of the convex portion 28A has vertical alignment (typically, a vertical alignment film (not shown) is formed so as to cover the convex portion 28A), and is shown in FIG. As described above, the liquid crystal molecules 30a are aligned substantially perpendicularly to the inclined side surfaces 28s due to the anchoring effect. Since the cross-sectional shape of the convex portion 28A along the substrate surface of the counter substrate 200b is substantially square, the liquid crystal molecules 30a around the convex portion 28A are radially inclined and oriented around the convex portion 28A.
[0131]
That is, the convex portion 28A acts to radially incline the liquid crystal molecules 30a by the shape effect of the surface (having vertical alignment). The inclination direction of the liquid crystal molecules by the convex portion 28A is the alignment direction of the radial inclination alignment of the liquid crystal domain formed in the region corresponding to the unit solid portion 14b ′ (for example, see FIG. 1) of the pixel electrode 14 by the alignment regulating structure. Align. Since the convex portion 28A exhibits an alignment regulating force regardless of whether a voltage is applied or not, a stable radial gradient alignment is obtained in all display gradations and is excellent in resistance to stress.
[0132]
Although there is no restriction | limiting in particular in the material which forms 28 A of convex parts, It can form easily using dielectric materials, such as resin. In addition, it is preferable to use a resin material that is deformed by heat because a convex portion 28A having a gentle cross-sectional shape as shown in FIG. 15A can be easily formed by heat treatment after patterning. As shown in the figure, the convex portion 28A has a gentle shape having a vertex (a cross-sectional shape along the normal line of the substrate surface) and a substantially regular quadrangular pyramid shape as shown in FIGS. 16 (a) and 16 (b). The convex portion 28B is excellent in the effect of fixing the center position of the radial inclined orientation. Of course, the convex portion may have a top surface, and may be, for example, a substantially square frustum shape.
[0133]
FIGS. 17A and 17B show the liquid crystal display device 200 including the alignment regulating structure and the convex portion 28A described above. FIG. 17A is a top view, and FIG. 17B corresponds to a cross-sectional view taken along line 17B-17B ′ in FIG.
[0134]
The liquid crystal display device 200 includes a TFT substrate 100a having a picture element electrode 14 having an opening 14a constituting an alignment regulating structure, and a counter substrate 200b having a convex portion 28A protruding toward the liquid crystal layer 30 side. The alignment regulating structure is not limited to the configuration exemplified here, and the various configurations described above can be used as appropriate. In addition, the liquid crystal display device 200 is opposed to each other via the pair of substrates 100a and 200b, and a pair of polarizations arranged such that the polarization axes (indicated by arrows PA in FIG. 17A) are substantially orthogonal to each other. The liquid crystal display device includes plates 70a and 70b and performs display in a normally black mode.
[0135]
The convex portion 28A provided on the counter substrate 200b of the liquid crystal display device 200 is provided in a region facing the solid portion 14b of the pixel electrode 14, and more specifically, faces the solid portion 14b. It is provided near the center of the area.
[0136]
By arranging in this way, in a state where a voltage is applied to the liquid crystal layer 30, that is, in a state where a voltage is applied between the pixel electrode 14 and the counter electrode 22, the radial inclined alignment formed by the alignment regulating structure is achieved. The direction and the direction of the radial inclined orientation formed by the convex portions 28A are matched, and the radial inclined orientation is stabilized. This is schematically shown in FIGS. 18 (a) to 18 (c). FIG. 18A shows a state in which no voltage is applied, FIG. 18B shows a state in which the orientation starts to change after voltage application (ON initial state), and FIG. 18C shows a steady state during voltage application. This is shown schematically.
[0137]
As shown in FIG. 18A, the alignment regulating force by the convex portion 28A acts on the liquid crystal molecules 30a in the vicinity even when no voltage is applied, thereby forming a radially inclined alignment.
[0138]
When the voltage starts to be applied, an electric field indicated by an equipotential line EQ as shown in FIG. 18B is generated (according to the alignment regulation structure), and liquid crystal molecules are formed in regions corresponding to the opening 14a and the solid portion 14b. A liquid crystal domain in which 30a is radially inclined is formed and reaches a steady state as shown in FIG. At this time, the tilt direction of the liquid crystal molecules 30a in the liquid crystal domain formed in the region corresponding to the solid portion 14b coincides with the tilt direction of the liquid crystal molecules 30a due to the alignment regulating force of the convex portion 28A provided in the corresponding region. To do.
[0139]
When a stress is applied to the liquid crystal display device 200 in a steady state, the radial tilt alignment of the liquid crystal layer 30 is temporarily lost, but when the stress is removed, the alignment regulating force due to the alignment regulating structure and the convex portion 28A is applied to the liquid crystal molecules 30a. Since it is acting, it returns to the radially inclined alignment state. Therefore, the occurrence of afterimages due to stress is suppressed.
[0140]
The orientation regulating force by the convex portion 28A only needs to have the effect of stabilizing the radial tilt alignment formed by the orientation regulating structure and fixing the center axis position, so that the orientation regulating force is not so strong. For example, if the convex portion 28A having a diameter of about 15 μm and a height (thickness) of about 1 μm is formed for the unit solid portion 14b ′ having a diameter of about 30 μm to about 50 μm, sufficient alignment regulating force can be obtained. can get.
[0141]
Further, the cross-sectional shape of the convex portion 28A included in the liquid crystal display device 200 (the cross-sectional shape along the substrate surface of the counter substrate 200b) is a pair of polarizing plates as shown in FIGS. 15B and 17A. It is a shape substantially constituted only by sides substantially parallel and substantially perpendicular to one of the polarization axes 70a and 70b. That is, the sides constituting the cross-sectional shape of the convex portion 28A are substantially parallel to or substantially orthogonal to the polarization axes of the polarizing plates 70a and 70b. Accordingly, the liquid crystal molecules 30a that undergo the alignment regulation force of the convex portion 28A when no voltage is applied and that are radially inclined and aligned are substantially parallel to the polarization axes of the polarizing plates 70a and 70b, as shown in FIG. Oriented in a substantially vertical azimuth direction. Therefore, the liquid crystal molecules (liquid crystal molecules inclined with respect to the normal to the substrate surface due to the alignment regulating force by the side surfaces of the convex portions) 30 a in the vicinity of the convex portions 28 </ b> A give little phase difference to the light incident on the liquid crystal layer 30. . Therefore, the occurrence of light leakage during black display is suppressed, and as a result, display with a high contrast ratio is realized.
[0142]
As a comparative example, FIG. 19 shows the orientation of the liquid crystal molecules 30a in the vicinity of the convex portion 1028 in the liquid crystal display device 1000 including the convex portion 1028 having a substantially circular cross-sectional shape. Also in the liquid crystal display device 1000, the liquid crystal molecules 30a in the vicinity of the convex portion 1028 are aligned perpendicular to the side surface of the convex portion 1028 and are inclined with respect to the normal direction of the substrate surface. Since the cross-sectional shape is substantially circular, the inclined liquid crystal molecules 30a are aligned with the same probability with respect to the omnidirectional direction as shown in FIG. Therefore, the existence probability of the liquid crystal molecules 30a oriented in the azimuth direction inclined with respect to the polarization axis of the polarizing plate is relatively high, and such liquid crystal molecules 30a are positioned relative to the light passing through the liquid crystal layer 30. Since a phase difference is given, light leakage occurs in a region LL surrounded by an ellipse in FIG. 19, and the contrast ratio decreases. By reducing the outer periphery of the convex portion 1028, the existence probability of the liquid crystal molecules 30a that are radially inclined and aligned by the alignment regulating force of the convex portion 1028 can be lowered, thereby suppressing light leakage. Of course, since the area of the side surface of the convex portion 1028 that expresses the alignment regulating force is reduced, the alignment regulating force for the liquid crystal domain is lowered, and the center fixing effect of the radial tilt alignment is lowered.
[0143]
On the other hand, in the liquid crystal display device 200 of the present invention, as shown in FIG. 20, among the liquid crystal molecules 30a that are radially inclined and aligned when no voltage is applied, the polarization axes of the polarizing plates 70a and 70b are substantially parallel or substantially perpendicular. The ratio of the liquid crystal molecules 30a that are aligned in the azimuthal direction is high. As shown in FIG. 20, liquid crystal molecules 30a tilted with respect to the polarization axis may exist in the vicinity of the corners of the convex portion 28A (region surrounded by an ellipse in FIG. 20). Is much smaller than the case where the cross-sectional shape of the convex portion is substantially circular, and the degree of light leakage is much lighter. Therefore, according to the present invention, it is possible to perform display with a high contrast ratio without reducing the alignment regulation effect by the convex portions. That is, a liquid crystal display device having high stress resistance and high display quality is provided.
[0144]
As described above, in the liquid crystal display device 200 according to the present invention, the cross-sectional shape of the convex portion 28A is substantially only on a side substantially parallel to and substantially orthogonal to one polarization axis of the pair of polarizing plates 70a and 70b. Since the shape is configured in a general manner, a decrease in contrast ratio is suppressed / prevented, so that high-quality display can be performed.
[0145]
The cross-sectional shape of the convex portion may be a shape substantially constituted only by a side substantially parallel to the polarization axis and a side substantially orthogonal, and is substantially a square, a substantially rectangle, or the like shown in FIG. It may be a rectangle or a substantially cross shape. Moreover, it is preferable that the cross-sectional shape of the convex portion has high rotational symmetry from the viewpoint of reducing the viewing angle dependency, and from this viewpoint, a substantially square shape is more preferable than a substantially rectangular shape.
[0146]
Note that due to restrictions on the manufacturing process, as shown in FIG. 15B and the like, the corners of the protrusions are rounded, and the cross-sectional shape of the protrusions is strictly parallel to the side substantially parallel to the polarization axis and the approximately Although it may not be configured only by the orthogonal sides, a sufficiently high-quality display can be performed if it is substantially configured only by sides substantially parallel to the polarization axis and substantially orthogonal sides. For example, if the ratio of the length of the side substantially parallel to the polarization axis and the length of the side substantially orthogonal to the total length (periphery) of the sides constituting the cross-sectional shape is 50% or more, the polarization axis is substantially It can be said that it is substantially composed of only parallel sides and substantially orthogonal sides.
[0147]
FIGS. 21A and 21B show another liquid crystal display device 200 </ b> A having an alignment regulating structure and a convex portion. FIG. 21A is a top view seen from the substrate normal direction, and FIG. 21B corresponds to a cross-sectional view taken along line 21B-21B ′ in FIG. The liquid crystal display device 200A is different from the liquid crystal display device 200 in that it includes a convex portion 28C that also functions as a spacer.
[0148]
As shown in FIGS. 21A and 21B, in the liquid crystal display device 200A, the convex portion 28C keeps the gap between the TFT substrate 100a and the counter substrate 300b (that is, the TFT substrate). 100a and the counter substrate 300b) and also functions as a spacer that defines the thickness of the liquid crystal layer 30.
[0149]
Also in the liquid crystal display device 200A, as schematically shown in FIGS. 22A to 22C, a voltage is applied to the liquid crystal layer 30, that is, a voltage is applied between the pixel electrode 14 and the counter electrode 22. In the applied state, the direction of the radial tilt alignment formed by the alignment regulating structure matches the direction of the radial tilt alignment formed by the convex portion 28C, so that the radial tilt alignment is stabilized.
[0150]
In the liquid crystal display device 200A, the thickness of the liquid crystal layer 30 is defined by a convex portion 28C provided near the center of the region facing the solid portion 14b ′ of the pixel electrode 14. Therefore, when such a configuration is adopted, there is no need to separately provide a spacer for defining the thickness of the liquid crystal layer 30, and there is an advantage that the manufacturing process can be simplified.
[0151]
Here, the convex portion 28C has a substantially regular quadrangular pyramid shape as shown in FIGS. 21A and 21B, and the cross-sectional shape of the convex portion 28C is substantially square. Further, the convex portion 28C has a substantially square cross-sectional shape, and a side of the polarizing plate of the pair of polarizing plates arranged in a crossed Nicols state (indicated by an arrow PA in FIG. 21A). It arrange | positions so that it may become parallel or substantially perpendicular | vertical. That is, the cross-sectional shape of the convex portion 28 </ b> C is a shape that is substantially constituted only by sides that are substantially parallel to and substantially perpendicular to the polarization axis of the polarizing plate. Therefore, also in the liquid crystal display device 200A, the occurrence of light leakage at the time of black display is suppressed, and as a result, a decrease in contrast ratio is suppressed / prevented.
[0152]
The effect of suppressing the light leakage described above is shown in FIG. 21B than in the configuration in which the convex portion 28A is low as shown in FIG. 17B and the convex portion 28A does not function as a spacer. As shown, the height of the convex portion 28C is high, and the convex portion 28C is higher in the configuration that also functions as a spacer. That is, the present invention is particularly preferably used in a configuration in which the convex portion also functions as a spacer. This is because, when the height of the convex portion is high, the area of the side surface that exerts the alignment regulating force is large, and therefore, the existence probability of the liquid crystal molecules that undergo radial tilt alignment when no voltage is applied in response to the alignment regulating force of the convex portion is high. Of course, by reducing the outer circumference of the convex portion, the existence probability of the liquid crystal molecules that are radially inclined and aligned can be lowered. However, in that case, the alignment regulating force for the liquid crystal domain is reduced, so The center fixing effect is reduced. In addition, the convex portion needs to be formed at a predetermined height in order to function as a spacer, and a convex portion with a small outer periphery is a process when forming a predetermined height compared to a convex portion with a large outer periphery. Often accompanied by above difficulties.
[0153]
The inventor of the present application, as shown in FIGS. 21 (a) and 21 (b), has a liquid crystal display device 200A provided with a convex portion 28C having a substantially regular quadrangular pyramid shape, and as shown in FIGS. 23 (a) and 23 (b). A liquid crystal display device 1100 as a comparative example having a substantially frustoconical convex portion 1128 was actually prototyped and examined. As a result, the contrast ratio of the liquid crystal display device 1100 of the comparative example is about 300, whereas the contrast ratio of the liquid crystal display device 200A according to the present invention is about 450, and the contrast ratio is greatly improved. Was confirmed.
[0154]
The side surface 28s of the convex portion 28C that also functions as a spacer as shown in FIG. 21B is preferably inclined at a taper angle θ of less than 90 ° with respect to the substrate surface of the substrate 21. When the side surface 28s is inclined at an angle of less than 90 ° with respect to the substrate surface, the side surface 28s of the convex portion 28C is aligned in the same direction as the alignment regulating direction by the oblique electric field with respect to the liquid crystal molecules 30a of the liquid crystal layer 30. It has a regulating force and acts to stabilize the radial tilt orientation. Of course, the side surface 28s may be inclined at an angle of 90 ° or more with respect to the substrate surface. However, from the viewpoint of stabilizing the radial inclined orientation, the taper angle θ of the side surface 28s may not greatly exceed 90 °. The angle is preferably less than 90 °. Even when the taper angle θ exceeds 90 °, if it is close to 90 ° (not greatly exceeding 90 °), the liquid crystal molecules 30a in the vicinity of the inclined side surface 28s of the convex portion 28C are substantially horizontal to the substrate surface. Since it is tilted in such a direction, it can be aligned in a radial gradient while aligning with the tilt direction of the liquid crystal molecules 30a in the edge portion by only generating a slight twist. However, when the side surface 28s is inclined more than 90 ° as in the convex portion 28D shown in FIG. 24, the side surface 28s is aligned with the alignment regulating direction by the oblique electric field with respect to the liquid crystal molecules 30a of the liquid crystal layer 30. Since it has an alignment regulating force in the reverse direction, the radial tilt alignment may become unstable.
[0155]
Further, the side surface of the convex portion functioning as a spacer may be a curved surface as shown in FIG. In the convex portion 28E shown in FIG. 25, the taper angle of the side surface 28s with respect to the substrate surface changes along the thickness direction of the liquid crystal layer 30, but at any position in the thickness direction of the liquid crystal layer 30, the side surface 28s Since the inclination angle is less than 90 °, such a protrusion 28E can also be suitably used as a protrusion that stabilizes the radial inclination alignment.
[0156]
Note that, as described above, the convex portion that is in contact with the upper and lower substrates (TFT substrate and counter substrate) and also functions as a spacer that defines the thickness of the liquid crystal layer 30 is either upper or lower in the manufacturing process of the liquid crystal display device. It may be formed on a substrate. Regardless of which substrate is formed, when the upper and lower substrates are bonded to each other, the convex portion comes into contact with both substrates, functions as a spacer, and stabilizes the radial tilt alignment of the liquid crystal domain.
[0157]
In the above description, the liquid crystal display devices 1000 and 1100 shown in FIGS. 19 and 23 described that light leakage occurs and the contrast ratio is lowered. As a result of detailed examination of the relationship, it was found that the following two problems also occur when the cross-sectional shape of the convex portion is substantially circular.
[0158]
One is a large difference between the gradation luminance characteristics when observed from the front direction (display surface normal direction) and the gradation luminance characteristics when observed from the oblique direction (direction inclined from the display surface normal line). This is a problem that the display becomes uncomfortable.
[0159]
This problem occurs for the following reasons. If the cross-sectional shape of the convex portion is substantially circular, the directivity of the orientation direction of the liquid crystal molecules in the liquid crystal domain is low, and the liquid crystal molecules in the liquid crystal domain have almost equal probability along all azimuth directions when a voltage is applied. Tilt orientation. Therefore, among the liquid crystal molecules in the liquid crystal domain, the liquid crystal molecules aligned in a specific direction adversely affect the display characteristics when observed from an oblique direction. For example, when the viewing angle is tilted along one polarization axis of a pair of polarizing plates, liquid crystal molecules oriented in the direction along the polarization axis do not contribute to display, but in the direction along the other polarization axis. The aligned liquid crystal molecules affect display characteristics when observed from an oblique direction. Specifically, when the viewing angle is tilted along one polarization axis, the liquid crystal molecules aligned in the direction along the other polarization axis have a voltage that maximizes the transmittance at a voltage corresponding to halftone display. -Shows the transmittance characteristics; Therefore, the gradation luminance characteristics when observed from an oblique direction indicate gradation collapse in a halftone and gradation inversion in a white gradation.
[0160]
Another problem is that if the cross-sectional shape of the convex portion is substantially circular, a sufficiently high response speed cannot be obtained, so that a transient increase in transmittance immediately after voltage application is visually recognized as an afterimage. It is.
[0161]
This problem occurs for the following reasons. When a chiral agent is added to the liquid crystal material constituting the liquid crystal layer, the liquid crystal molecules in the liquid crystal layer take a simple radial tilt alignment as shown in FIG. 5A immediately after voltage is applied. When the alignment is stable (steady state), a spiral radial inclined alignment as shown in FIGS. 5B and 5C is taken. As the alignment state changes, the area of the quenching region (the region that does not give a phase difference because the liquid crystal molecules are aligned along the polarization axis of the polarizing plate) typically increases, so immediately after voltage application In contrast, the transmittance is lower in the steady state. That is, the transmittance increases transiently immediately after voltage application. As described above, since the transmittance has a maximum value transiently, an afterimage is visually recognized when the response speed is not sufficiently high.
[0162]
Occurrence of the two problems described above can be suppressed / prevented by making the cross-sectional shape of the convex portion (cross-sectional shape along the substrate surface) substantially cross-shaped.
[0163]
FIG. 26 shows a liquid crystal display device 300 provided with a convex portion 28F having a substantially cross-shaped cross section. As shown in FIG. 26, the liquid crystal display device 300 has a convex portion 28F having a substantially cross-shaped cross section on the counter substrate. The convex portion 28F is provided corresponding to each of the plurality of unit solid portions 14b ′ of the pixel electrode 14, and has a substantially cross-shaped cross-sectional shape extending along two directions substantially orthogonal to each other. ing. The extending direction of the cross coincides with the polarization axis of the polarizing plate (indicated by an arrow PA in FIG. 26), and the cross-sectional shape of the convex portion 28F is substantially parallel to the polarizing axis of the polarizing plate, It is a shape composed only of orthogonal sides.
[0164]
Also in the liquid crystal display device 300, since the cross-sectional shape of the convex portion 28F is configured only by a side substantially parallel to the polarization axis and a side substantially perpendicular to the polarization axis, similarly to the liquid crystal display device 200, light leakage occurs during black display. Is suppressed, and a decrease in contrast ratio is suppressed / prevented.
[0165]
Furthermore, in the liquid crystal display device 300, since the cross-sectional shape of the convex portion 28F is a substantially cross shape, the orientation direction of the liquid crystal molecules can be given directivity. That is, directivity can be given to the existence probability of the liquid crystal molecules aligned along each of all azimuth directions. Specifically, if the cross-sectional shape of the convex portion 28F is substantially cross-shaped, the presence probability of liquid crystal molecules aligned in a direction inclined by 45 ° with respect to the direction in which the cross extends (coincident with the polarization axis) is applied when a voltage is applied. High and the existence probability of the liquid crystal molecules aligned along the direction in which the cross extends is low. In other words, the orientation directivity is biased in a direction inclined by 45 ° with respect to the polarization axis. Therefore, it is possible to reduce the existence probability of liquid crystal molecules oriented in a specific direction (for example, liquid crystal molecules oriented along the polarization axis) that adversely affect the display characteristics in the oblique direction. The difference in gradation luminance characteristics from the direction can be reduced, and a natural display with no sense of incongruity can be realized.
[0166]
In order to verify this effect, viewing angle characteristics were evaluated for the combinations of convex portions and unit solid portions shown in FIGS. 27 (a), (b), (c) and (d). FIG. 27A shows a combination of a substantially circular convex portion 1028 and a substantially circular unit solid portion 14b ′, and FIG. 27B shows a substantially circular convex portion 1028 and a barrel shape (the corners are circular). A combination with a unit solid portion 14b 'of an arcuate substantially square shape) is shown. FIG. 27C shows a combination of a substantially cross-shaped convex portion 28F and a substantially circular unit solid portion 14b ′, and FIG. 27D shows a substantially cross-shaped convex portion 28F and a barrel-shaped portion. A combination with the unit solid part 14b ′ is shown. In addition, in the figure, the part (branch part extended in four directions) which plays the role which connects unit solid part 14b 'mutually is abbreviate | omitted.
[0167]
Evaluation results of viewing angle characteristics for the combinations shown in FIGS. 27A, 27B, 27C, and 27D are shown in FIGS. 28, 29, 30, and 31, respectively. 28, 29, 30 and 31, the horizontal axis indicates the applied voltage (indicated as V / Vmax) normalized by the maximum gradation voltage (here, 6.4 V), and the vertical axis indicates the maximum gradation. It is a graph which shows the brightness | luminance (it describes with L / L (Vmax)) of each visual angle direction normalized with the transmittance | permeability in a voltage. In the figure, the viewing angle direction indicated by the upper, upper right, right, lower right, lower, lower left, left, and upper left is a polar angle (tilt angle from the front direction) of 60 °, and the azimuth angle (the display surface is the letter of the clock) The angles within the display surface defined as the 12 o'clock direction being 0 degrees when viewed on the board are 0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, and 315 °, respectively. In these graphs, it can be said that as the gradation luminance characteristics in each viewing angle direction are closer to the gradation luminance characteristics in the front direction represented by a straight line, a display with less discomfort can be obtained.
[0168]
When the substantially circular convex portion 1028 is used as shown in FIGS. 27 (a) and 27 (b), as shown in FIGS. 28 and 29, gradation luminance characteristics when observed from the front, There is a large difference from the gradation luminance characteristics when observed from an oblique direction, and gradation gradation in the halftone and gradation inversion in the white gradation are observed in the gradation luminance characteristics in the oblique direction.
[0169]
On the other hand, when the substantially cross-shaped convex portion 28F is used as shown in FIGS. 27C and 27D, as shown in FIGS. The difference between the gradation luminance characteristic and the gradation luminance characteristic when observed from an oblique direction is small, and the gradation gradation characteristic in the oblique direction suppresses gradation collapse in halftones and gradation inversion in white gradation. ing. Therefore, display without a sense of incongruity is realized.
[0170]
For reference, the evaluation results of the viewing angle characteristics shown in FIGS. 28, 29, 30 and 31 are shown in FIGS. 32, 33, 34 and 35 as graphs showing more general voltage-luminance characteristics. Show. 32, 33, 34, and 35, the horizontal axis indicates the applied voltage (V), and the vertical axis indicates the luminance (L / L (Vmax) in each viewing angle direction normalized by the transmittance at the maximum gradation voltage. )).
[0171]
32 and 33 are compared with FIG. 34 and FIG. 35, the cross-sectional shape of the convex portion is substantially cross-shaped so that the display characteristics when observed from an oblique direction and the display characteristics when observed from a front direction. It can be seen that a display with no sense of incongruity is obtained.
[0172]
Further, the convex portion 28F having a substantially cross-shaped cross section has a larger area of the inclined side surface that exerts an alignment regulating force on the liquid crystal molecules than a convex portion having a substantially circular cross-sectional shape and occupying the same area. The alignment control force can be exerted over a wider range within the liquid crystal domain. Therefore, it is possible to effectively exert a larger alignment regulating force on the liquid crystal molecules. Therefore, in the liquid crystal display device 300 including the convex portion 28F having a substantially cross-shaped cross section, the response speed when a voltage is applied is improved, and the liquid crystal molecules 30a of the liquid crystal layer 30 reach a steady state in a shorter time. . As a result, display in which the occurrence of afterimages is suppressed is realized.
[0173]
The combination of the substantially circular convex portion 1028 and the substantially circular unit solid portion 14b ′ shown in FIG. 27A, and the substantially cross-shaped convex portion 28F and the substantially circular unit solid portion shown in FIG. FIG. 36 shows the response speed characteristics for the combination of the parts 14b ′. The combination of the substantially circular convex portion 1028 and the barrel-shaped unit solid portion 14b ′ shown in FIG. 27B and the substantially cross-shaped convex portion 28F and the barrel-shaped unit shown in FIG. FIG. 37 shows the response speed characteristics for the combination of the solid part 14b ′. FIG. 36 and FIG. 37 are graphs in which the horizontal axis represents time (ms) after voltage application, and the vertical axis represents the luminance ratio (%) to the transmission luminance when the orientation is stable.
[0174]
When the cross-sectional shape of the convex portion is substantially circular, as shown by the solid line with a circle in FIGS. 36 and 37, the transmittance becomes transiently high after voltage application, and an afterimage is generated. On the other hand, when the cross-sectional shape of the convex portion is a substantially cross shape, the transmittance may have a transient maximum value as shown by the solid line with + in FIGS. There is no afterimage.
[0175]
As described above, by making the cross-sectional shape of the convex portion substantially cross-shaped, a high-quality display with no sense of incongruity and suppression of the occurrence of afterimages is realized.
[0176]
Heretofore, as the convex portion, the configuration including only the convex portion having a cross-sectional shape substantially composed only of a side substantially parallel to the polarization axis and a side substantially orthogonal to the polarization axis has been shown. It is good also as a structure where a convex part and the convex part whose cross-sectional shape is not such a shape are mixed on the same board | substrate. For example, in a region where an unnecessary electric field that adversely affects display is likely to occur (such as in the vicinity of a bus line), a convex portion having a substantially cross-shaped cross-section is provided from the viewpoint of improving the alignment control force, and the cross-sectional shape is provided in other regions. However, a substantially circular convex portion may be provided. Of course, it is good also as a structure where the convex part whose cross-sectional shape is substantially rectangular, and the convex part whose cross-sectional shape is substantially circular are mixed.
[0177]
(Other embodiments)
Hereinafter, modified examples of the alignment regulation structure will be described. In accordance with the description so far, the case where the alignment regulating structure is provided on the TFT substrate and the convex portion is provided on the counter substrate will be described. However, for the sake of simplicity of explanation, the convexity provided on the counter substrate is described. The illustration and description of the part are omitted. The illustration of the pair of polarizing plates provided outside the pair of substrates is also omitted.
[0178]
The structure of one picture element region of another liquid crystal display device 400 having an alignment regulating structure according to the present invention will be described with reference to FIGS. In the following drawings, components having substantially the same functions as the components of the liquid crystal display device 100 are denoted by the same reference numerals, and description thereof is omitted. FIG. 38A is a top view seen from the substrate normal direction, and FIG. 38B corresponds to a cross-sectional view taken along line 38B-38B ′ in FIG. FIG. 38B shows a state where no voltage is applied to the liquid crystal layer.
[0179]
As shown in FIGS. 38A and 38B, the liquid crystal display device 400 is different from the TFT substrate 400a in that the projection 40 is provided inside the opening 14a of the pixel electrode 14 as shown in FIG. And different from the liquid crystal display device 100 shown in FIG. A vertical alignment film (not shown) is provided on the surface of the convex portion 40.
[0180]
The cross-sectional shape of the convex portion 40 in the in-plane direction of the substrate 11 is the same as the shape of the opening 14a, as shown in FIG. However, the adjacent convex portions 40 are connected to each other, and are formed so as to completely surround the unit solid portion 14b ′ in a substantially circular shape. The cross-sectional shape of the convex portion 40 in the in-plane direction perpendicular to the substrate 11 is a trapezoid as shown in FIG. That is, it has a top surface 40t parallel to the substrate surface and a side surface 40s inclined at a taper angle θ (<90 °) with respect to the substrate surface. Since a vertical alignment film (not shown) is formed so as to cover the convex portion 40, the side surface 40 s of the convex portion 40 is in the same direction as the alignment regulating direction by the oblique electric field with respect to the liquid crystal molecules 30 a of the liquid crystal layer 30. It will have an orientation regulating force and will act to stabilize the radial tilt orientation.
[0181]
The operation of the convex portion 40 will be described with reference to FIGS. 39 (a) to 39 (d) and FIGS. 40 (a) and 40 (b).
[0182]
First, the relationship between the alignment of the liquid crystal molecules 30a and the shape of the surface having vertical alignment will be described with reference to FIGS. 39 (a) to 39 (d).
[0183]
As shown in FIG. 39A, the liquid crystal molecules 30a on the horizontal surface are perpendicular to the surface due to the alignment regulating force of the surface having vertical alignment (typically, the surface of the vertical alignment film). Oriented to When an electric field represented by an equipotential line EQ perpendicular to the axial direction of the liquid crystal molecules 30a is applied to the liquid crystal molecules 30a in the vertical alignment state in this way, the liquid crystal molecules 30a are rotated clockwise or counterclockwise. The torque to be tilted is applied with the same probability. Accordingly, in the liquid crystal layer 30 between the electrodes of the parallel plate type arrangement facing each other, the liquid crystal molecules 30a receiving the torque in the clockwise direction and the liquid crystal molecules 30a receiving the torque in the counterclockwise direction are mixed. As a result, the transition to the alignment state according to the voltage applied to the liquid crystal layer 30 may not occur smoothly.
[0184]
As shown in FIG. 39 (b), when an electric field represented by a horizontal equipotential line EQ is applied to the liquid crystal molecules 30a aligned perpendicular to the inclined surface, the liquid crystal molecules 30a. Is inclined in a direction (clockwise in the illustrated example) with a small amount of inclination for being parallel to the equipotential line EQ. Further, as shown in FIG. 39C, the liquid crystal molecules 30a aligned perpendicular to the horizontal surface are continuously aligned with the liquid crystal molecules 30a aligned perpendicular to the inclined surface. In such a manner (so as to be aligned), the liquid crystal molecules 30a located on the inclined surface are inclined in the same direction (clockwise).
[0185]
As shown in FIG. 39 (d), with respect to a continuous uneven surface having a trapezoidal cross section, the top surface is aligned with the alignment direction regulated by the liquid crystal molecules 30a on each inclined surface. And the liquid crystal molecules 30a on the bottom surface are aligned.
[0186]
The liquid crystal display device 400 stabilizes the radial tilt alignment by matching the direction of the alignment regulating force due to such a surface shape (convex portion) and the alignment regulating direction due to the oblique electric field.
[0187]
FIGS. 40A and 40B show a state in which a voltage is applied to the liquid crystal layer 30 shown in FIG. 38B, respectively. FIG. 40A shows the voltage applied to the liquid crystal layer 30. Accordingly, the state in which the orientation of the liquid crystal molecules 30a starts to change (ON initial state) is schematically shown, and FIG. 40B shows that the orientation of the liquid crystal molecules 30a changed according to the applied voltage is steady. The state which reached the state is shown typically. Curves EQ in FIGS. 40A and 40B show equipotential lines EQ.
[0188]
When the pixel electrode 14 and the counter electrode 22 are at the same potential (a state where no voltage is applied to the liquid crystal layer 30), as shown in FIG. 38B, the liquid crystal molecules 30a in the pixel region are , Oriented perpendicular to the surfaces of both substrates 11 and 21. At this time, the liquid crystal molecules 30a in contact with the vertical alignment film (not shown) on the side surface 40s of the protrusion 40 are aligned perpendicular to the side surface 40s, and the liquid crystal molecules 30a in the vicinity of the side surface 40s are aligned with the peripheral liquid crystal molecules 30a. As shown in the figure, the slanted orientation is obtained by the interaction (the property as an elastic body).
[0189]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by the equipotential line EQ shown in FIG. This equipotential line EQ is parallel to the surface of the solid portion 14b and the counter electrode 22 in the liquid crystal layer 30 located between the solid portion 14b of the picture element electrode 14 and the counter electrode 22, and It falls in a region corresponding to the opening 14a of the elementary electrode 14 and is inclined in the liquid crystal layer 30 on the edge portion of the opening 14a (the inner periphery of the opening 14a including the boundary (extended) of the opening 14a). An oblique electric field represented by an equipotential line EQ is formed.
[0190]
Due to this oblique electric field, as described above, the liquid crystal molecules 30a on the edge portion EG are rotated in the clockwise direction in the right edge portion EG in the drawing, as indicated by the arrows in FIG. The left edge portion EG is tilted (rotated) in the counterclockwise direction and oriented parallel to the equipotential line EQ. The orientation regulating direction by the oblique electric field is the same as the orientation regulating direction by the side surface 40s located at each edge portion EG.
[0191]
As described above, when the change in alignment starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses and reaches a steady state, the alignment state schematically shown in FIG. The liquid crystal molecules 30a located in the vicinity of the center of the opening 14a, that is, in the vicinity of the center of the top surface 40t of the convex portion 40, are substantially equal in the influence of the alignment of the liquid crystal molecules 30a on the opposite edge portions EG of the opening 14a. Therefore, the liquid crystal molecules 30a in the region away from the center of the opening 14a (the top surface 40t of the convex portion 40) are kept perpendicular to the equipotential line EQ, and the liquid crystal molecules 30a in the regions near the edge portion EG. The liquid crystal molecules 30a are tilted under the influence of the orientation of the liquid crystal molecules 30a, and form a symmetric tilt orientation with respect to the center SA of the opening 14a (the top surface 40t of the convex portion 40). Further, in the region corresponding to the unit solid portion 14b ′ substantially surrounded by the opening 14a and the convex portion 40, a symmetric inclined orientation is formed with respect to the center SA of the unit solid portion 14b ′.
[0192]
As described above, also in the liquid crystal display device 400, similarly to the liquid crystal display device 100, liquid crystal domains having a radially inclined alignment are formed corresponding to the openings 14a and the unit solid portions 14b ′. Since the convex portion 40 is formed so as to completely surround the unit solid portion 14 b ′ in a substantially circular shape, the liquid crystal domain is formed corresponding to the substantially circular region surrounded by the convex portion 40. Further, the side surface of the convex portion 40 provided inside the opening portion 14a acts to tilt the liquid crystal molecules 30a in the vicinity of the edge portion EG of the opening portion 14a in the same direction as the alignment direction by the oblique electric field. Stabilize the tilted orientation.
[0193]
Obviously, the alignment regulating force of the oblique electric field acts only when a voltage is applied, and its strength depends on the strength of the electric field (the magnitude of the applied voltage). Therefore, when the electric field strength is weak (that is, the applied voltage is low), the alignment regulating force due to the oblique electric field is weak, and when a stress is applied to the liquid crystal panel, the radial tilt alignment may collapse due to the flow of the liquid crystal material. Once the radial tilt alignment is broken, the radial tilt alignment is not restored unless a voltage sufficient to generate an oblique electric field that exhibits a sufficiently strong alignment regulating force is applied. On the other hand, the alignment regulating force by the side surface 40s of the convex portion 40 acts regardless of the applied voltage and is very strong as known as the anchoring effect of the alignment film. Therefore, even if the flow of the liquid crystal material occurs and the radial tilt alignment once collapses, the liquid crystal molecules 30a in the vicinity of the side surface 40s of the convex portion 40 maintain the same alignment direction as that in the radial tilt alignment. Therefore, as long as the liquid crystal material stops flowing, the radial tilt alignment can be easily restored.
[0194]
Thus, the liquid crystal display device 400 has a characteristic that it is strong against stress. Therefore, the liquid crystal display device 400 is preferably used for a PC or PDA that is easily applied with stress and frequently used in a portable manner.
[0195]
In addition, when the convex part 40 is formed using a highly transparent dielectric material, the advantage that the contribution rate to the display of the liquid crystal domain formed corresponding to the opening part 14a is improved. On the other hand, when the convex portion 40 is formed using an opaque dielectric, there is an advantage that light leakage due to retardation of the liquid crystal molecules 30a that are inclined and aligned by the side surface 340s of the convex portion 40 can be prevented. Which is adopted may be determined according to the use of the liquid crystal display device. In any case, the use of the photosensitive resin has an advantage that the patterning process corresponding to the opening 14a can be simplified.
[0196]
Moreover, although the cross-sectional shape illustrated the convex part 40 of the substantially star shape here, the cross-sectional shape of the convex part 40 is not limited to this of course. The cross-sectional shape of the convex portion 40 (the cross-sectional shape along the substrate surface of the TFT substrate 100) is a shape substantially constituted only by sides substantially parallel to and substantially perpendicular to the polarization axis of the polarizing plate. In the same manner as described with reference to FIGS. 19 and 20 for the convex portion 28A on the opposite substrate side, the occurrence of light leakage is suppressed / prevented, so that the reduction in contrast ratio is suppressed / prevented, resulting in high quality. Can be displayed.
[0197]
As described above, the liquid crystal display device 400 has the convex portion 40 inside the opening portion 14 a of the pixel electrode 14, and the side surface 40 s of the convex portion 40 has an oblique electric field with respect to the liquid crystal molecules 30 a of the liquid crystal layer 30. It has an orientation regulating force in the same direction as the orientation regulating direction by. A preferable condition for the side surface 40s to have the alignment regulating force in the same direction as the alignment regulating direction by the oblique electric field will be described with reference to FIGS.
[0198]
41A to 41C schematically show cross-sectional views of the liquid crystal display devices 400A, 400B, and 400C, respectively, and correspond to FIG. The liquid crystal display devices 400A, 400B, and 400C all have a convex portion inside the opening 40, but the arrangement relationship between the entire convex portion 40 as one structure and the opening 40 is different from the liquid crystal display device 400. Yes.
[0199]
In the liquid crystal display device 400 described above, as shown in FIG. 40A, the entire convex portion 40 as a structure is formed inside the opening 40a, and the bottom surface of the convex portion 40 is open. It is smaller than the part 40a. In the liquid crystal display device 400A shown in FIG. 41A, the bottom surface of the convex portion 40A coincides with the opening portion 14a. In the liquid crystal display device 400B shown in FIG. The bottom surface is larger than the portion 14a and is formed so as to cover the solid portion (conductive film) 14b around the opening 14a. The solid portion 14b is not formed on any side surface 40s of the convex portions 40, 40A and 40B. As a result, as shown in each figure, the equipotential line EQ is substantially flat on the solid portion 14b and falls at the opening 14a as it is. Accordingly, the side surfaces 40s of the convex portions 40A and 40B of the liquid crystal display devices 400A and 400B exhibit the same alignment regulating force in the same direction as the alignment regulating force due to the oblique electric field, similar to the convex portion 40 of the liquid crystal display device 400 described above. Stabilize the radial tilt orientation.
[0200]
On the other hand, the bottom surface of the protrusion 40C of the liquid crystal display device 400C shown in FIG. 41C is larger than the opening 14a, and the solid part 14b around the opening 14a is formed on the side surface 40s of the protrusion 40C. Has been. Due to the influence of the solid portion 14b formed on the side surface 40s, a peak is formed in the equipotential line EQ. The peak of the equipotential line EQ has a slope opposite to that of the equipotential line EQ that falls at the opening 14a, and this generates an oblique electric field that is opposite to the oblique electric field that causes the liquid crystal molecules 30a to be radially inclined and oriented. It shows that. Therefore, in order for the side surface 40s to have an alignment control force in the same direction as the alignment control direction by the oblique electric field, it is preferable that the solid part (conductive film) 14b is not formed on the side surface 40s.
[0201]
Next, a cross-sectional structure taken along line 42A-42A ′ of the convex portion 40 shown in FIG. 38A will be described with reference to FIG.
[0202]
As described above, the convex portion 40 shown in FIG. 38 (a) is formed so as to completely surround the unit solid portion 14b ′ in a substantially circular shape. As shown in FIG. 42, the portion (branch portion extending in all directions from the circular portion) that plays the role of connecting to is formed on the convex portion 40. Therefore, in the step of depositing the conductive film that forms the solid portion 14b of the pixel electrode 14, there is a high risk of disconnection on the convex portion 40 or peeling in the subsequent step of the manufacturing process.
[0203]
Therefore, as in the liquid crystal display device 400D shown in FIGS. 43 (a) and 43 (b), the solid portion 14b is formed when the openings 14a are completely included in the openings 14a. Since the conductive film is formed on the flat surface of the substrate 11, there is no risk of disconnection or peeling. The convex portion 40D is not formed so as to completely surround the unit solid portion 14b ′ in a substantially circular shape, but a substantially circular liquid crystal domain corresponding to the unit solid portion 14b ′ is formed. Similar to the example, its radial tilt orientation is stabilized.
[0204]
The effect of stabilizing the radial inclined orientation by forming the convex portion 40 in the opening 14a is not limited to the opening 14a of the pattern illustrated, but is the same for the openings 14a of all the patterns described above. The same effect can be obtained. In order to sufficiently exhibit the effect of stabilizing the alignment with respect to the stress caused by the convex portion 40, the pattern of the convex portion 40 (pattern when viewed from the normal direction of the substrate) surrounds the liquid crystal layer 30 in as wide a region as possible. The shape is preferred. Therefore, for example, the positive pattern having the circular unit solid portion 14b ′ has a larger alignment stabilization effect by the convex portion 40 than the negative pattern having the circular opening 14a.
[0205]
In order to obtain a sufficient alignment regulating force so that an afterimage due to stress is not visually recognized even when stress is applied to the liquid crystal panel without providing the convex portion on the counter substrate side, the height of the convex portion 40 is obtained. Is preferably in the range of about 0.5 μm to about 2 μm when the thickness of the liquid crystal layer 30 is about 3 μm. In general, the height of the protrusion 40 is preferably in the range of about 1/6 to about 2/3 of the thickness of the liquid crystal layer 30. However, since the liquid crystal molecules whose orientation is regulated by the orientation regulating force on the side surface of the convex portion 40 are difficult to respond to the voltage (the change in retardation due to the voltage is small), this causes a reduction in the contrast ratio of the display. Therefore, it is preferable to set the size, height, and number of the convex portions 40 so as not to deteriorate the display quality.
[0206]
In the electrode structure in which the opening is provided in one of the pair of electrodes described above, a sufficient voltage is not applied to the liquid crystal layer in a region corresponding to the opening, and a sufficient retardation change cannot be obtained. There may be a problem that the utilization efficiency is lowered. Therefore, a dielectric layer is provided on the side opposite to the liquid crystal layer of the electrode provided with the opening (upper layer electrode), and an additional electrode (lower layer electrode) facing at least a part of the opening of the electrode through this dielectric layer By providing (a two-layer structure electrode), a sufficient voltage can be applied to the liquid crystal layer corresponding to the opening, and the light utilization efficiency and response characteristics can be improved.
[0207]
FIG. 44 shows a pixel region of a liquid crystal display device 500 including a pixel electrode (two-layer structure electrode) 15 having a lower layer electrode 12, an upper layer electrode 14, and a dielectric layer 13 provided therebetween. A cross-sectional structure is schematically shown. The upper electrode 14 of the picture element electrode 15 is substantially equivalent to the picture element electrode 14 described above, and has openings and solid parts of the various shapes and arrangements described above. Hereinafter, the function of the pixel electrode 15 having a two-layer structure will be described.
[0208]
The pixel electrode 15 of the liquid crystal display device 500 has a plurality of openings 14a (including 14a1 and 14a2). FIG. 44A schematically shows the alignment state (OFF state) of the liquid crystal molecules 30a in the liquid crystal layer 30 to which no voltage is applied. FIG. 44B schematically shows a state where the alignment of the liquid crystal molecules 30a starts to change according to the voltage applied to the liquid crystal layer 30 (ON initial state). FIG. 44C schematically shows a state in which the alignment of the liquid crystal molecules 30a changed according to the applied voltage has reached a steady state. In FIG. 44, the lower layer electrode 12 provided so as to face the openings 14a1 and 14a2 with the dielectric layer 13 therebetween overlaps with the openings 14a1 and 14a2, respectively, and the openings 14a1 and 14a2. Although an example in which it is formed so as to exist also in the region between them (the region where the upper layer electrode 14 exists) is shown, the arrangement of the lower layer electrode 12 is not limited to this, and the lower layer electrode 12 is arranged with respect to each of the openings 14a1 and 14a2. The area of the electrode 12 may be equal to the area of the opening 14a or the area of the lower layer electrode 12 <the area of the opening 14a. That is, the lower layer electrode 12 may be provided so as to face at least a part of the opening 14a with the dielectric layer 13 in between. However, in the configuration in which the lower layer electrode 12 is formed in the opening 14 a, there is a region (gap region) where neither the lower layer electrode 12 nor the upper layer electrode 14 exists in the plane viewed from the normal direction of the substrate 11. Since a sufficient voltage may not be applied to the liquid crystal layer 30 in the region opposite to the gap region, the width of the gap region may be sufficiently narrowed to stabilize the alignment of the liquid crystal layer 30. Preferably, it is typically preferred not to exceed about 4 μm. In addition, the lower layer electrode 12 formed at a position facing the region where the conductive layer of the upper layer electrode 14 exists through the dielectric layer 13 does not substantially affect the electric field applied to the liquid crystal layer 30, so that it is particularly patterned. However, patterning may be performed.
[0209]
As shown in FIG. 44A, when the pixel electrode 15 and the counter electrode 22 are at the same potential (a state where no voltage is applied to the liquid crystal layer 30), the liquid crystal molecules 30a in the pixel region are It is oriented perpendicular to the surfaces of both substrates 11 and 21. Here, for the sake of simplicity, it is assumed that the upper electrode 14 and the lower electrode 12 of the pixel electrode 15 have the same potential.
[0210]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by the equipotential line EQ shown in FIG. 44 (b) is formed. In the liquid crystal layer 30 positioned between the upper layer electrode 14 and the counter electrode 22 of the pixel electrode 15, a uniform potential represented by an equipotential line EQ parallel to the surfaces of the upper layer electrode 14 and the counter electrode 22 is obtained. A potential gradient is formed. In the liquid crystal layer 30 located above the openings 14a1 and 14a2 of the upper layer electrode 14, a potential gradient corresponding to the potential difference between the lower layer electrode 12 and the counter electrode 22 is formed. At this time, since the potential gradient formed in the liquid crystal layer 30 is affected by the voltage drop due to the dielectric layer 13, the equipotential lines EQ formed in the liquid crystal layer 30 correspond to the openings 14a1 and 14a2. It falls in the region (a plurality of “valleys” are formed in the equipotential line EQ). Since the lower layer electrode 12 is formed in a region facing the openings 14a1 and 14a2 via the dielectric layer 13, the upper layer electrode is also formed in the liquid crystal layer 30 located near the center of each of the openings 14a1 and 14a2. 14 and a potential gradient represented by an equipotential line EQ parallel to the surface of the counter electrode 22 is formed (“bottom of the valley” of the equipotential line EQ). An oblique electric field represented by an inclined equipotential line EQ is formed in the liquid crystal layer 30 on the edge portion of the opening portions 14a1 and 14a2 (the inner periphery of the opening portion including the boundary (outward extension) of the opening portion) EG. .
[0211]
As is clear from a comparison between FIG. 44B and FIG. 2A, the liquid crystal display device 500 includes the lower layer electrode 12, so that the liquid crystal molecules in the liquid crystal domain formed in the region corresponding to the opening 14a are also included. A sufficiently large electric field can be applied.
[0212]
A torque that attempts to align the axial direction of the liquid crystal molecules 30a in parallel with the equipotential line EQ acts on the liquid crystal molecules 30a having negative dielectric anisotropy. Accordingly, the liquid crystal molecules 30a on the edge portion EG are rotated clockwise in the right edge portion EG in the drawing and counterclockwise in the left edge portion EG in the drawing, as indicated by arrows in FIG. 44 (b). Each direction is inclined (rotated) and oriented parallel to the equipotential line EQ.
[0213]
As shown in FIG. 44 (b), an electric field (an oblique electric field) represented by an equipotential line EQ inclined with respect to the axial direction of the liquid crystal molecules 30a at the edge portions EG of the openings 14a1 and 14a2 of the liquid crystal display device 500. 3), the liquid crystal molecules 30a are tilted in a direction (in the illustrated example, counterclockwise) with a small amount of tilt to be parallel to the equipotential line EQ. Further, as shown in FIG. 3C, the liquid crystal molecules 30a located in the region where the electric field expressed by the equipotential line EQ perpendicular to the axis direction of the liquid crystal molecules 30a is inclined are equipotential. The liquid crystal molecules 30a positioned on the line EQ are tilted in the same direction as the liquid crystal molecules 30a positioned on the tilted equipotential line EQ so that the alignment is continuous (matched) with the liquid crystal molecules 30a.
[0214]
As described above, when the change in orientation starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses and reaches a steady state, as schematically shown in FIG. 44 (c), the openings 14a1 and A symmetrical tilt orientation (radial tilt orientation) is formed with respect to each center SA of 14a2. Further, the liquid crystal molecules 30a on the region of the upper electrode 14 located between the two adjacent openings 14a1 and 14a2 are also aligned with the liquid crystal molecules 30a at the edges of the openings 14a1 and 14a2 ( Tilted to align). Since the liquid crystal molecules 30a on the portions located at the centers of the edges of the openings 14a1 and 14a2 are affected to the same extent by the liquid crystal molecules 30a at the respective edges, the liquid crystal molecules located at the center of the openings 14a1 and 14a2 As in 30a, the vertical alignment state is maintained. As a result, the liquid crystal layer on the upper electrode 14 is also in a radially inclined alignment state between the two adjacent openings 14a1 and 14a2. However, the tilt direction of the liquid crystal molecules is different between the radial tilt alignment of the liquid crystal layer in the openings 14a1 and 14a2 and the radial tilt direction of the liquid crystal layer between the openings 14a1 and 14a2. When attention is paid to the alignment in the vicinity of the liquid crystal molecules 30a located at the center of each radially inclined alignment region shown in FIG. 44 (c), cones extending toward the counter electrode are formed in the openings 14a1 and b14a2. While the liquid crystal molecules 30a are inclined so as to form, the liquid crystal molecules 30 are inclined so as to form a cone extending toward the upper electrode 14 between the openings. In addition, since any radial inclination alignment is formed so that it may correspond with the inclination alignment of the liquid crystal molecule 30a of an edge part, two radial inclination alignment is mutually continuous.
[0215]
As described above, when a voltage is applied to the liquid crystal layer 30, the liquid crystal molecules 30 a in the peripheral region start to tilt from the liquid crystal molecules 30 a on the edge portions EG of the openings 14 a 1 and 14 a 2 provided in the upper electrode 14. By tilting so as to match the tilt alignment of the liquid crystal molecules 30a on the edge portion EG, a radial tilt alignment is formed. Therefore, as the number of openings 14a formed in one picture element region increases, the number of liquid crystal molecules 30a that start to tilt first in response to an electric field increases. Therefore, the radial tilt alignment over the entire picture element region. The time required to form is shortened. That is, the response speed of the liquid crystal display device can be improved by increasing the number of openings 14a formed in the pixel electrode 15 for each pixel region. In addition, since the pixel electrode 15 is a two-layer structure electrode having the upper layer electrode 14 and the lower layer electrode 12, a sufficient electric field can be applied to the liquid crystal molecules in the region corresponding to the opening 14a. The response characteristic of the display device is improved.
[0216]
The dielectric layer 13 provided between the upper electrode 14 and the lower electrode 12 of the pixel electrode 15 may have a hole (hole) or a recess in the opening 14 a of the upper electrode 14. That is, the pixel electrode 15 having a two-layer structure has a structure in which the entire dielectric layer 13 located in the opening 14a of the upper layer electrode 14 is removed (a hole is formed) or a part thereof is removed (recessed portion). May be formed).
[0217]
First, with reference to FIG. 45, the structure and operation of a liquid crystal display device 600 including a picture element electrode 14 in which holes are formed in a dielectric layer 13 will be described. Hereinafter, for the sake of simplicity, one opening 14a formed in the upper layer electrode 14 will be described.
[0218]
In the liquid crystal display device 600, the upper electrode 14 of the pixel electrode 15 has the opening 14a, and the dielectric layer 13 provided between the lower electrode 12 and the upper electrode 14 has the opening of the upper electrode 14. The lower layer electrode 12 is exposed in the opening 13a having the opening 13a formed corresponding to 14a. The side wall of the opening 13 of the dielectric layer 13 is generally formed in a tapered shape. The liquid crystal display device 600 has substantially the same structure as the liquid crystal display device 500 except that the dielectric layer 13 has an opening 13a. The pixel electrode 15 having a two-layer structure includes: The liquid crystal domain that operates in substantially the same manner as the pixel electrode 15 of the liquid crystal display device 500 and takes a radially inclined alignment state in the liquid crystal layer 30 when a voltage is applied is formed.
[0219]
The operation of the liquid crystal display device 600 will be described with reference to FIGS. 45A to 45C correspond to FIGS. 1A to 1C for the liquid crystal display device 100, respectively.
[0220]
As shown in FIG. 45A, when no voltage is applied (OFF state), the liquid crystal molecules 30a in the pixel region are aligned perpendicular to the surfaces of both the substrates 11 and 21. Here, for the sake of simplicity, the description will be made ignoring the alignment regulating force due to the side wall of the opening 13a.
[0221]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by the equipotential line EQ shown in FIG. 45 (b) is formed. As can be seen from the fact that the equipotential line EQ falls in a region corresponding to the opening 14a of the upper layer electrode 14 (a “valley” is formed), the liquid crystal layer 30 of the liquid crystal display device 600 is also shown in FIG. Similar to the potential gradient shown in (b), a gradient electric field is formed. However, since the dielectric layer 13 of the pixel electrode 15 has the opening 13a in a region corresponding to the opening 14a of the upper electrode 14, the liquid crystal layer 30 in a region corresponding to the inside of the opening 14a (inside the opening 13a). The voltage applied to is the potential difference itself between the lower layer electrode 12 and the counter electrode 22, and no voltage drop (capacitance division) due to the dielectric layer 13 occurs. That is, the seven equipotential lines EQ shown between the upper layer electrode 14 and the counter electrode 22 are seven over the entire liquid crystal layer 30 (in FIG. 44B, five equipotential lines EQ are shown). A constant voltage is applied over the entire picture element region, whereas one of them penetrates into the dielectric layer 13).
[0222]
Thus, by forming the opening 13a in the dielectric layer 13, the same voltage as that of the liquid crystal layer 30 corresponding to other regions can be applied to the liquid crystal layer 30 corresponding to the opening 13a. However, since the thickness of the liquid crystal layer 30 to which a voltage is applied varies depending on the location in the picture element region, the change in retardation upon application of the voltage varies depending on the location, and if the degree is extremely large, the display quality deteriorates. Occurs.
[0223]
In the configuration shown in FIG. 45, the thickness d1 of the liquid crystal layer 30 on the upper layer electrode (solid portion other than the opening 14a) 14 and the lower layer electrode 12 located in the opening 14a (and the hole 13a). The thickness d2 of the liquid crystal layer 30 differs from the thickness d2 of the dielectric layer 13. When the liquid crystal layer 30 having the thickness d1 and the liquid crystal layer 30 having the thickness d2 are driven in the same voltage range, the amount of change in retardation accompanying the change in orientation of the liquid crystal layer 30 is affected by the thickness of each liquid crystal layer 30. Different from each other. If the relationship between the applied voltage and the amount of retardation of the liquid crystal layer 30 varies significantly depending on the location, the transmittance is sacrificed in the design that emphasizes display quality, and if the transmittance is emphasized, the color temperature of white display shifts and the display quality is improved. The problem of sacrificing arises. Therefore, when the liquid crystal display device 600 is used as a transmissive liquid crystal display device, the dielectric layer 13 is preferably thin.
[0224]
Next, FIG. 46 shows a cross-sectional structure of one picture element region of the liquid crystal display device 700 in which the dielectric layer of the picture element electrode has a recess.
[0225]
The dielectric layer 13 constituting the picture element electrode 15 of the liquid crystal display device 700 has a recess 13 b corresponding to the opening 14 a of the upper layer electrode 14. Other structures are substantially the same as those of the liquid crystal display device 600 shown in FIG.
[0226]
In the liquid crystal display device 700, the dielectric layer 13 located in the opening 14a of the upper electrode 14 of the picture element electrode 15 is not completely removed, so the thickness of the liquid crystal layer 30 located in the opening 14a is not removed. d3 is thinner than the thickness d2 of the liquid crystal layer 30 located in the opening 14a in the liquid crystal display device 700 by the thickness of the dielectric layer 13 in the recess 13b. Further, the voltage applied to the liquid crystal layer 30 located in the opening 14a is subjected to a voltage drop (capacitance division) due to the dielectric layer 13 in the recess 13b, so that the voltage on the upper layer electrode (region excluding the opening 14a) 14 is increased. The voltage applied to the liquid crystal layer 30 is lower. Therefore, by adjusting the thickness of the dielectric layer 13 in the recess 13b, a difference in retardation due to a difference in thickness of the liquid crystal layer 30 and a difference depending on the location of the voltage applied to the liquid crystal layer 30 (opening) And the relationship between the applied voltage and the retardation can be made independent of the location in the pixel region. More precisely, the birefringence of the liquid crystal layer, the thickness of the liquid crystal layer, the dielectric constant of the dielectric layer and the thickness of the dielectric layer, and the thickness of the concave portion of the dielectric layer (the depth of the concave portion) are adjusted. As a result, the relationship between the applied voltage and the retardation can be made uniform at a location in the picture element region, and high-quality display can be achieved. In particular, as compared with a transmissive display device having a dielectric layer having a flat surface, the transmittance is reduced (utilization of light) due to a decrease in voltage applied to the liquid crystal layer 30 in a region corresponding to the opening 14a of the upper electrode 14. (Efficiency reduction) is suppressed.
[0227]
In the above description, the case where the same voltage is supplied to the upper layer electrode 14 and the lower layer electrode 12 constituting the picture element electrode 15 has been described. However, if different voltages are applied to the lower layer electrode 12 and the upper layer electrode 14, Thus, variations in the configuration of the liquid crystal display device capable of display without display unevenness can be increased. For example, in the configuration having the dielectric layer 13 in the opening 14 a of the upper layer electrode 14, a voltage higher than the voltage applied to the upper layer electrode 14 by the voltage drop due to the dielectric layer 13 is applied to the lower layer electrode 12. Therefore, it is possible to prevent the voltage applied to the liquid crystal layer 30 from being different depending on the location in the pixel region.
[0228]
The liquid crystal display device having the two-layered picture element electrode 15 can constitute not only a transmission type and a reflection type but also a transmission / reflection type liquid crystal display device (see, for example, JP-A-11-101992). .
[0229]
The transflective liquid crystal display device (hereinafter abbreviated as “bipolar liquid crystal display device”) includes, in a pixel area, a transmissive region T for displaying in the transmissive mode and a reflective region R for displaying in the reflective mode. The liquid crystal display device is referred to (see FIG. 44A). The transmissive region T and the reflective region R are typically defined by a transparent electrode and a reflective electrode. Instead of the reflective electrode, the reflective region can be defined by a structure in which the reflective layer and the transparent electrode are combined.
[0230]
This dual-use liquid crystal display device can display by switching between the reflection mode and the transmission mode, or can simultaneously display in both display modes. Therefore, for example, it is possible to realize a reflection mode display in an environment where the ambient light is bright, and a transmission mode display in a dark environment. In addition, when both modes are displayed at the same time, the transmissive mode LCD device is used in an environment where the ambient light is bright (fluorescent light or sunlight is directly incident on the display surface at a specific angle). In the contrast ratio can be suppressed. In this way, the drawbacks of the transmissive liquid crystal display device can be compensated. The area ratio between the transmissive region T and the reflective region R can be set as appropriate according to the application of the liquid crystal display device. Further, in a liquid crystal display device used exclusively as a transmission type, the above-described drawbacks of the transmission type liquid crystal display device can be compensated even if the area ratio of the reflection region is reduced to such an extent that display in the reflection mode is not possible.
[0231]
As shown in FIG. 44A, for example, by using the upper electrode 14 of the liquid crystal display device 500 as a reflective electrode and the lower electrode 12 as a transparent electrode, a dual-use liquid crystal display device can be obtained. The dual-use liquid crystal display device is not limited to this example, and in the above-described liquid crystal display device, one of the upper layer electrode 14 and the lower layer electrode 12 is a transparent conductive layer, and the other is a reflective conductive layer. . However, in order to match the voltage-transmittance characteristics of the display in the reflection mode and the transmission mode with each other, the thickness of the liquid crystal layer 30 in the reflection region R (for example, d1 in FIG. The layer 30 is preferably configured to be approximately half the thickness of the layer 30 (for example, d2 in FIG. 45A). Of course, instead of adjusting the thickness of the liquid crystal layer, the voltage applied to the upper layer electrode 14 and the voltage applied to the lower layer electrode 12 may be adjusted.
[0232]
47A, 47B, and 47C show an example of a liquid crystal display device that includes an alignment regulating structure and a convex portion. 47 (a), (b), and (c) are cross-sectional views schematically showing a liquid crystal display device 800 having an alignment regulating structure and convex portions. FIG. 47A shows a state in which no voltage is applied, FIG. 47B shows a state in which the orientation starts to change after voltage application (ON initial state), and FIG. 47C shows a steady state during voltage application. This is shown schematically.
[0233]
The liquid crystal display device 800 includes the convex portion 40 shown in FIG. 40 inside the opening portion 14 a of the pixel electrode 14. Further, a convex portion 28A shown in FIG. 15 is provided in the vicinity of the center of the region facing the solid portion 14b of the pixel electrode 14.
[0234]
In the liquid crystal display device 800, in addition to the alignment regulating force due to the electrode structure of the TFT substrate 400a, the radial tilt alignment is stabilized by the alignment regulating force due to the side surface 40s of the convex portion 40 and the alignment regulating force due to the surface of the convex portion 28A. It becomes. Since the alignment regulating force due to the shape effect of the convex portions 40 and the convex portions 28A described above stabilizes the radially inclined alignment state regardless of the applied voltage, the liquid crystal display device 800 has good stress resistance.
[0235]
Note that a phase difference compensation element (typically, a phase difference plate) may be provided in all the liquid crystal display devices described above as necessary.
[0236]
【The invention's effect】
According to the present invention, since the liquid crystal domains having the radial tilt alignment are formed stably and have high continuity, the display quality of the conventional liquid crystal display device having wide viewing angle characteristics can be further improved. Further, the radial tilt alignment can be stabilized by the alignment regulating structure and the convex portion, and further, the position of the central axis of the radial tilt alignment can be fixed, so an afterimage occurs when stress is applied to the liquid crystal panel. It is suppressed. Furthermore, the cross-sectional shape along the substrate surface of the convex portion is a shape that is substantially composed only of sides substantially parallel to and substantially perpendicular to the polarization axis of the pair of polarizing plates arranged in a crossed Nicols state. The occurrence of light leakage during black display is suppressed / prevented, and display with a high contrast ratio is realized.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams schematically showing a structure of one picture element region of a liquid crystal display device 100 having a first alignment regulating structure according to the present invention, wherein FIG. 1A is a top view and FIG. It is sectional drawing along line 1B-1B '.
2A and 2B are diagrams illustrating a state in which a voltage is applied to the liquid crystal layer 30 of the liquid crystal display device 100. FIG. 2A schematically illustrates a state in which the orientation starts to change (ON initial state). Schematically shows a steady state.
FIGS. 3A to 3D are diagrams schematically showing the relationship between the lines of electric force and the orientation of liquid crystal molecules. FIGS.
4A to 4C are diagrams schematically illustrating alignment states of liquid crystal molecules viewed from the normal direction of the substrate in the liquid crystal display device 100. FIG.
FIGS. 5A to 5C are diagrams schematically showing an example of radial tilt alignment of liquid crystal molecules. FIG.
6 (a) and 6 (b) are top views schematically showing other picture element electrodes used in the liquid crystal display device according to the present invention.
FIGS. 7A and 7B are top views schematically showing still other pixel electrodes used in the liquid crystal display device according to the present invention. FIGS.
FIGS. 8A and 8B are top views schematically showing still other pixel electrodes used in the liquid crystal display device according to the present invention. FIGS.
FIGS. 9A and 9B are top views schematically showing still other pixel electrodes used in the liquid crystal display device according to the present invention. FIGS.
FIGS. 10A and 10B are top views schematically showing corner portions of unit solid parts of pixel electrodes used in the liquid crystal display device according to the present invention. FIGS.
11A is a liquid crystal display device having a picture element electrode shown in FIG. 8B and a liquid crystal display device having a picture element electrode shown in FIG. 9B; It is a graph which shows the change of the transmittance | permeability with respect to an angle, (b) is a figure which shows typically arrangement | positioning of the polarization axis corresponding to 0 degree | times.
FIG. 12 is a top view schematically showing still another picture element electrode used in the liquid crystal display device according to the present invention.
FIGS. 13A and 13B are top views schematically showing still other pixel electrodes used in the liquid crystal display device according to the present invention. FIGS.
14A is a diagram schematically showing a unit cell of the pattern shown in FIG. 1A, and FIG. 14B is a diagram schematically showing a unit cell of the pattern shown in FIG. (C) is a graph showing the relationship between the pitch p and the solid part area ratio.
15A is a cross-sectional view schematically showing a counter substrate 200b having a convex portion 28A, and FIG. 15B is a top view schematically showing the convex portion 28A.
16A is a cross-sectional view schematically showing a counter substrate 200b having a convex portion 28B, and FIG. 16B is a top view schematically showing the convex portion 28B.
FIGS. 17A and 17B are diagrams schematically showing a liquid crystal display device 200 including an alignment regulating structure and a convex portion 28A, where FIG. 17A is a top view and FIG. 17B is a line 17B-17B ′ in FIG. FIG.
18A and 18B are diagrams schematically showing a cross-sectional structure of one picture element region of the liquid crystal display device 200, where FIG. 18A shows a state in which no voltage is applied, and FIG. 18B shows a state in which the orientation starts to change (ON initial state). (C) shows a steady state.
FIG. 19 is a diagram schematically showing the state of alignment of liquid crystal molecules in the vicinity of a convex portion 1028 in a liquid crystal display device 1000 as a comparative example provided with a convex portion 1028 having a substantially circular cross-sectional shape.
FIG. 20 is a diagram schematically showing a state of alignment of liquid crystal molecules in the vicinity of the convex portion 28A in the liquid crystal display device 200 provided with the convex portion 28A.
FIGS. 21A and 21B are diagrams schematically illustrating a liquid crystal display device 200A including an alignment regulating structure and a convex portion 28C, where FIG. 21A is a top view and FIG. 21B is a line 21B-21B ′ in FIG. FIG.
22A and 22B are diagrams schematically showing a cross-sectional structure of one picture element region of the liquid crystal display device 200A, in which FIG. 22A shows a state in which no voltage is applied, and FIG. 22B shows a state in which the orientation starts to change (ON initial state). (C) shows a steady state.
FIGS. 23A and 23B are diagrams schematically showing a liquid crystal display device 1100 as a comparative example provided with an alignment regulating structure and a convex portion 1128, wherein FIG. 23A is a top view and FIG. 23B is a view of 23B- in FIG. It is sectional drawing along a 23B 'line.
FIG. 24 is a cross-sectional view schematically showing a convex portion 28D having a side surface whose inclination angle with respect to the substrate surface greatly exceeds 90 °.
FIG. 25 is a cross-sectional view schematically showing a protrusion 28E, which is a modified example of the protrusion that also functions as a spacer.
FIG. 26 is a top view schematically showing a liquid crystal display device 300 according to the present invention having a convex portion 28F having a substantially cross-shaped cross section.
FIGS. 27A, 27B, 27C and 27D are top views showing examples of combinations of convex portions and unit solid portions. FIGS.
FIG. 28 is a graph showing an evaluation result of viewing angle characteristics when a combination of the substantially circular convex portion and the substantially circular unit solid portion shown in FIG. 27A is used.
FIG. 29 is a graph showing an evaluation result of viewing angle characteristics when a combination of the substantially circular convex portion and the barrel-shaped unit solid portion shown in FIG. 27B is used.
30 is a graph showing the evaluation results of viewing angle characteristics when a combination of the substantially cross-shaped convex portion and the substantially circular unit solid portion shown in FIG. 27C is used.
FIG. 31 is a graph showing an evaluation result of viewing angle characteristics when a combination of the substantially cross-shaped convex portion and the barrel-shaped unit solid portion shown in FIG. 27D is used.
FIG. 32 is a graph showing voltage-luminance characteristics when using the combination of the substantially circular convex portion and the substantially circular unit solid portion shown in FIG.
FIG. 33 is a graph showing voltage-luminance characteristics when a combination of the substantially circular convex portion and the barrel-shaped unit solid portion shown in FIG. 27B is used.
FIG. 34 is a graph showing voltage-luminance characteristics when a combination of the substantially cross-shaped convex portion and the substantially circular unit solid portion shown in FIG. 27C is used.
FIG. 35 is a graph showing voltage-luminance characteristics when the combination of the substantially cross-shaped convex portion and the barrel-shaped unit solid portion shown in FIG. 27 (d) is used.
36 is a combination of the substantially circular convex portion and the substantially circular unit solid portion shown in FIG. 27 (a), and the substantially cross-shaped convex portion and the substantially circular unit solid portion shown in FIG. 27 (c). It is a graph which shows the response speed characteristic when using the combination of parts.
37 is a combination of a substantially circular convex portion and a barrel-shaped unit solid portion shown in FIG. 27 (b), and a substantially cross-shaped convex portion and a barrel-shaped unit solid portion shown in FIG. 27 (d). It is a graph which shows the response speed characteristic about the combination of a part.
38 is a diagram schematically showing the structure of one picture element region of a liquid crystal display device 400 having an alignment regulating structure according to the present invention, where (a) is a top view and (b) is 38B in (a). It is sectional drawing along the -38B 'line.
FIGS. 39A to 39D are schematic views for explaining the relationship between the alignment of the liquid crystal molecules 30a and the shape of the surface having vertical alignment properties. FIGS.
40 is a diagram showing a state in which a voltage is applied to the liquid crystal layer 30 of the liquid crystal display device 400, and (a) schematically shows a state in which the orientation starts to change (ON initial state), and FIG. Shows a steady state schematically.
FIGS. 41A to 41C are schematic cross-sectional views of liquid crystal display devices 400A, 400B, and 400C in which the positional relationship between the opening and the protrusion is different.
42 is a diagram schematically showing a cross-sectional structure of the liquid crystal display device 400, and is a cross-sectional view taken along line 42A-42A ′ in FIG.
43 is a diagram schematically showing the structure of one picture element region of the liquid crystal display device 400D, in which (a) is a top view and (b) is a cross section taken along line 43B-43B ′ in FIG. FIG.
44A and 44B are diagrams schematically showing a cross-sectional structure of one picture element region of a liquid crystal display device 500 including a two-layer structure electrode, where FIG. 44A shows a state in which no voltage is applied, and FIG. 44B shows a change in orientation. The state which started (ON initial state) is shown, and (c) shows the steady state.
FIG. 45 is a diagram schematically showing a cross-sectional structure of one picture element region of another liquid crystal display device 400 having a two-layer structure electrode, where (a) shows a state in which no voltage is applied, and (b) shows an orientation. The state which started changing (ON initial state) is shown, and (c) shows the steady state.
FIG. 46 is a diagram schematically showing a cross-sectional structure of one picture element region of another liquid crystal display device 700 including a two-layer structure electrode.
47 is a diagram schematically showing a cross-sectional structure of one picture element region of still another liquid crystal display device 800 having an alignment regulating structure and a convex portion, where (a) shows a state in which no voltage is applied, and (b) Indicates a state where the orientation starts to change (ON initial state), and (c) indicates a steady state.
[Explanation of symbols]
11, 21 Transparent insulating substrate
12 Lower layer electrode
13 Dielectric layer
14, 14A, 14B, 14C, 14D, 14E, 14F
14G, 14H, 14I Pixel electrodes
14a, 14a1, 14a2 opening
14b Solid part (conductive film)
14b 'Unit solid part
15 Pixel electrode (two-layer electrode)
22 Counter electrode
28A, 28B, 28C, 28D, 28E Convex part
28s Side of convex part
30 Liquid crystal layer
30a Liquid crystal molecules
40, 40A, 40B, 40C, 40D Convex part
40s Side of convex part
40t Top surface of convex part
100, 100 ', 100 "liquid crystal display device
200, 200A, 300, 400, 500 Liquid crystal display device
600, 700, 800 Liquid crystal display device
100a TFT substrate
100b Counter substrate

Claims (15)

A first substrate, a second substrate, a vertical alignment type liquid crystal layer provided between the first substrate and the second substrate, and opposite to each other via the first and second substrates, and a polarization axis And a pair of polarizing plates arranged so as to be substantially orthogonal to each other,
A plurality of electrodes each defined by a first electrode provided on the liquid crystal layer side of the first substrate and a second electrode provided on the second substrate and facing the first electrode through the liquid crystal layer. With a pixel area of
The first substrate has an alignment regulation force that exerts an alignment regulating force in each of the plurality of picture element regions so as to form a plurality of liquid crystal domains each having a radially inclined alignment state when a voltage is applied in the liquid crystal layer. Has a structure,
The second substrate has a convex portion protruding toward the liquid crystal layer in a region corresponding to at least one liquid crystal domain of the plurality of liquid crystal domains, and is along a substrate surface of the second substrate of the convex portion. The cross-sectional shape is a liquid crystal display device that is substantially composed of only a side substantially parallel to one polarization axis of the pair of polarizing plates and a side substantially perpendicular to the one polarization axis. The liquid crystal display device according to claim 1, wherein a cross-sectional shape of the convex portion along the substrate surface of the second substrate is substantially rectangular. The liquid crystal display device according to claim 2, wherein a cross-sectional shape of the convex portion along the substrate surface of the second substrate is substantially square. The liquid crystal display device according to claim 1, wherein a cross-sectional shape of the convex portion along the substrate surface of the second substrate is a substantially cross shape. 5. The liquid crystal display device according to claim 1, wherein the convex portion exhibits an alignment regulating force that causes the liquid crystal molecules in the at least one liquid crystal domain to be radially inclined and aligned. The liquid crystal display device according to claim 1, wherein the convex portion is provided in a region corresponding to a vicinity of a center of the at least one liquid crystal domain. 7. The liquid crystal display device according to claim 1, wherein in the at least one liquid crystal domain, an alignment regulation direction by the convex portion is aligned with a radial tilt alignment direction by the alignment regulation structure. The liquid crystal display device according to claim 1, wherein the convex portion also functions as a spacer that defines a thickness of the liquid crystal layer. The liquid crystal display device according to claim 1, wherein the convex portion has a side surface that forms an angle of less than 90 ° with the substrate surface of the second substrate. The first electrode has a plurality of unit solid portions, and the orientation regulating structure is configured by the plurality of unit solid portions, and a voltage is applied between the first electrode and the second electrode. In some cases, the plurality of liquid crystal domains are formed in a region corresponding to the plurality of unit solid portions by generating an oblique electric field around the plurality of unit solid portions. A liquid crystal display device according to claim 1. The first electrode has at least one opening and a solid part;
The orientation regulating structure is constituted by the at least one opening and a solid part of the first electrode, and when the voltage is applied between the first electrode and the second electrode, the first electrode The plurality of liquid crystal domains are formed in a region corresponding to the at least one opening and the solid part by generating an oblique electric field at an edge portion of the at least one opening. The liquid crystal display device according to any one of the above. A first substrate, a second substrate, a vertical alignment type liquid crystal layer provided between the first substrate and the second substrate, and opposite to each other via the first and second substrates, and a polarization axis And a pair of polarizing plates arranged so as to be substantially orthogonal to each other,
A plurality of electrodes each defined by a first electrode provided on the liquid crystal layer side of the first substrate and a second electrode provided on the second substrate and facing the first electrode through the liquid crystal layer. With a pixel area of
The first substrate has an alignment regulation force that exerts an alignment regulating force in each of the plurality of picture element regions so as to form a plurality of liquid crystal domains each having a radially inclined alignment state when a voltage is applied in the liquid crystal layer. Has a structure,
In each of the plurality of picture element regions, a spacer provided in a region corresponding to at least one liquid crystal domain of the plurality of liquid crystal domains,
The spacer exhibits an alignment regulating force that causes the liquid crystal molecules in the at least one liquid crystal domain to be radially inclined and aligned, and a cross-sectional shape of the spacer along the substrate surface of the first and second substrates is the pair of polarized light A liquid crystal display device having a shape substantially composed only of a side substantially parallel to one polarization axis of the plate and a side substantially perpendicular to the one polarization axis. The liquid crystal display device according to claim 12, wherein a cross-sectional shape of the spacer along the substrate surfaces of the first and second substrates is substantially rectangular. The liquid crystal display device according to claim 13, wherein a cross-sectional shape of the spacer along the substrate surfaces of the first and second substrates is substantially square. The liquid crystal display device according to claim 12, wherein a cross-sectional shape of the spacer along the substrate surfaces of the first and second substrates is a substantially cross shape.

Images