JP2004163450A - Substrate for liquid crystal element, liquid crystal element, and liquid crystal projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the contrast of a projected picture from lowering in the case the picture is projected onto a screen with a liquid crystal projector. <P>SOLUTION: Red light for illumination turns into linearly polarized light via a polarizing plate and is made incident on the rear surface side of a transmissive liquid crystal element 11R. The liquid crystal element 11R comprises a pair of substrates 31, 32 for the liquid crystal element placed opposite to each other and interposing a liquid crystal layer 30. A structural birefringent layer 38 made of an inorganic material is formed, being integrated with the glass substrate, on an inner surface 37 of a glass plate 37 constituting the substrate 32 for the liquid crystal element on the common electrode 39 side. The common electrode 39 and an alignment layer 40 are formed on the upper layer of the structural birefringent layer 38. The structural birefringent layer 38 compensates the phase difference of light emitted from the liquid crystal element 11R and turns the light emitted from the liquid crystal element 11R into linearly polarized light. <P>COPYRIGHT: (C)2004,JPO

Description

【００５８】
上記表１中ではガラス板の内面側または外面のいずれか一方に構造性複屈折層が設けられている場合を「片面」とし、ガラス板の内面側及び外面の両方に構造性複屈折層が設けられている場合を「両面」として、各液晶素子用基板３１，３２を分類し、それらの組み合わせをに組合Ｎｏ．１〜９を付して、製造コストの高低、ソリ調整の良否，光学補償性能の良否を示してある。「組合Ｎｏ．」に対応する液晶素子用基板３１，３２の実際の組み合わせは、次の表２に示すとおりである。
【００５９】
【表２】

【００６０】
表１のコストの欄は、数字が大きいほど製造コストが高いことを示している。また、ソリ調整は、「×」がソリ調整が不可能であることを表し、「△」，「○」「◎」の順に調整がより好ましく行えることを表している。光学補償性能は「△」が好ましい結果が得られ、「○」がより好ましい結果を得られることを表している。
【００６１】
プロジェクタ用の液晶素子は強い光を受けて温度が上昇するが、その際、液晶の熱膨張と複屈折率の温度依存によってコントラスト特性が変化する。このような状況で基板のソリが大きいとコントラストの表示面内での均一性が損なわれる。したがって、液晶プロジェクタ用の液晶素子用基板においては、基板のソリは重要な特性であり、その温度依存特性も含めて精密に制御できることが好ましい。
【００６２】
表１からわかるように、光学補償性能の点からは、各液晶素子用基板３１，３２に少なくとも１面ずつ構造性複屈折層を設けるのがよく、ソリ調整の観点からは少なくともいずれか一方のガラス板の両面に構造性複屈折層を設けるのが好ましく、より好ましくは各ガラス板３３，３７のそれぞれの両面に構造性複屈折層を設けるのがよいことがわかる。
【００６３】
なお、タイプＡ３，Ａ５の液晶素子用基板３１やタイプＢ３，Ｂ５の液晶素子用基板３２のように電極とガラス板（基板本体）との間に構造性複屈折層３８を形成した構成の場合では、誘電体、すなわち絶縁体で構成される構造成複屈折層３８を電極間の短絡防止用の絶縁層としても機能させることができるという利点がある。
【００６４】
しかし、その反面、電極を外部の回路と接続するために、ガラス板の表示領域外に構造性複屈折層を設けずに電極を露呈させたエリアを設ける必要がある。このようなパターニングは、フォトリソグラフィによって構造性複屈折層の一部を除去する手法や、露呈すべき電極の部分に構造性複屈折層を形成しないようにマスク蒸着する手法を用いることができるが、構造性複屈折層はエッチング性の異なる薄膜が多数積層しているという難点があり、またマスク蒸着では、液晶素子のデザイン毎に成膜工程が影響を受けるので工程管理が煩雑になるという欠点がある。さらに、画素電極と共通電極との間に構造性複屈折層を設けた場合には、その層の厚みにもよるが液晶層に印加される電圧が構造性複屈折層による容量分割で低下する点をも考慮しなくてはならない。
【００６５】
タイプＡ１，Ａ３，Ａ４，Ａ５の液晶素子用基板３１やタイプＢ１，Ｂ３，Ｂ４，Ｂ５の液晶素子用基板３２のように構造性複屈折層３８がガラス板の内面側に形成されている場合では、構造性複屈折層３８の各面が空気よりも屈折率が高い材料と接触するため、それらの境界面での光の反射率は空気と面を接する光学補償素子に比べて極めて低い。したがって、境界面の反射防止層を簡略化できたり、省略できるという利点がある。また、構造性複屈折層３３の傷つき等を防止できるという利点もある。
【００６６】
タイプＡ２，Ａ４，Ａ５の液晶素子用基板３１やタイプＢ２，Ｂ４，Ｂ５の液晶素子用基板３２のように構造性複屈折層３８がガラス板の外面に設けた場合には、構造性複屈折層３８の傷付きを防止するために、構造性複屈折層３８の上層に透明な保護層を設けるのも好ましい。
【００６７】
基板本体に構造性複屈折層を設けた構成では、液晶層を通過する光について、その液晶層を通過する角度と構造性複屈折層を通過する角度とを同じにできる。また、ポリマー材料等を用いて作成した位相差補償素子を液晶素子の内側に設けることは困難であるが、上記のような無機材料で作成された構造性複屈折層では可能である他、熱や紫外線等に対しても十分な耐久性を有する。
【００６８】
本発明の液晶素子は、図１０に示す例のようにマイクロレンズと組み合わせることができる。マイクロレンズアレイ５０は、液晶素子の入射面側に配されている。マイクロレンズアレイ５０には、画素毎にマイクロレンズ５０ａが形成されている。このマイクロレンズ５０ａは、イオン交換技術を用いてガラス板に連続した屈折率分布をつけることにより作成されている。もちろん、マイクロレンズとしては、ガラスや樹脂をレンズ形状に加工したものを用いてもよい。マイクロレンズ５０ａは、画素電極３５を画素ごとに区画している出射面側のガラス板３３に形成されたブラックマトリクス部（図示せず）によって画素単位での開口率が低下することを改善する。
【００６９】
マイクロレンズ５０ａを組み合わせることによって、偏光子となる偏光板で直線偏光とされた照明光は、マイクロレンズ５０ａで収斂光束とされ、ガラス板３７，構造性複屈折層３８，共通電極３９，配向膜４０を通って液晶層３０に達し、さらに配向膜３６，画素電極３５を通ってガラス板３３，検光子となる偏光板を透過して出射する。
【００７０】
構造性複屈折層３８は、液晶層３０を通過する光の角度によって位相の変調度が異なってくることを補償するためのものであるから、この例のように、マイクロレンズ５０ａによって入射してくる光に角度がつくような場合に特に有効となり、コントラストの向上や、マイクロレンズ５０ａの開口数を大きくした設計が可能となるという大きな利点がある。
【００７１】
上記の例では、構造性複屈折層３８を共通電極側のガラス板３７の内面３７ａに設けた液晶素子用基板３２であるが、例えば図１１に示すようにガラス板３７の外面３７ｂに設けたタイプの液晶素子用基板３２でもよい。また、この他に図５ないし図８に示される各種の層構造の液晶素子用基板３１，３２の組み合わせであってもよい。
【００７２】
本発明の無機材料で作成された構造性複屈折層は、反射型液晶素子にも適用が可能である。反射型液晶素子を用いた投影ユニットの一例を図１２に示す。光源１２からの放射光は、フィルタ１３を透過することにより紫外線及び赤外線がカットされた白色光となり、集光光学系５５を透過して赤色光だけを反射するダイクロイックミラー５６に入射する。反射された赤色光は、ミラー５７で反射して偏光膜５８ａが斜設された偏光ビームスプリッタ５８に入射する。偏光膜５８ａによりｓ偏光成分が直線偏光となって反射され、反射型の液晶素子６１Ｒに入射する。なお、ダイクロイックミラー５６を透過した緑色光と青色光のうち、緑色光はダイクロイックミラー６２で反射され偏光ビームスプリッタ６３に入射し、ダイクロイックミラー６２を透過した青色光は偏光ビームスプリッタ６４に入射する。
【００７３】
ここで用いられている反射型の液晶素子６１Ｒは、図１３に示すような構成になっている。図１３では、上記と実質的に同じ構成部材には同一の符号を付してその説明を省略する。また、構造性複屈折層３８が設けられた共通電極３９側の液晶素子用基板の層構造は最初の実施形態と同じである。
【００７４】
画素電極側の液晶素子用基板６５は、不透明なシリコン基板６６を基板本体としている。このシリコン基板６６には、電極間の印加電圧を制御する画素回路６７が画素毎に形成され、その画素回路６７にそれぞれ画素電極６８が接続されている。画素電極６８は、アルミや銀等の反射率の高い材料で作成された反射板となっており、液晶層３０を透過してきた光を反射する。シリコン基板６６と画素電極６８と間には層間絶縁層６９が形成され、画素電極６８と層間絶縁層６９を覆うように配向膜７１が形成されている。
【００７５】
偏光ビームスプリッタ５８で直線偏光とされた光は、液晶素子用基板３２を通って液晶層３０に入射し、配向膜７１を通って画素電極６８に入射する。そして、この画素電極６８で反射されて、配向膜７１，液晶層３０，液晶素子用基板３２を通って偏光ビームスプリッタ５８に入射する。液晶素子用基板３２を光が透過する際に、その光はガラス板３７に形成された構造性複屈折層３８を透過する。偏光ビームスプリッタ５８に再び入射した直線偏光光は、偏光膜５８ａに対してｐ偏光成分となっているから、偏光膜５８ａを透過して合成プリズム２４に入射する。なお、合成プリズム２４及び投影レンズ２５の機能は先の実施形態と全く同様である。
【００７６】
ここで用いられている構造性複屈折層３８には、液晶層３０に入射するときと出射するときとで光が２度通過することになるため、これを考慮して構造性複屈折層３８自体の複屈折による位相差を設計しておく必要がある。また、反射型の液晶素子をオフアクシスで使用する場合にも利用できる。
【００７７】
構造性複屈折層３８を画素電極側の液晶素子用基板６５に設けてもよい。図１４は、構造性複屈折層３８を画素電極側の液晶素子用基板６５に設けた例を示しており、シリコン基板６６側の画素電極６８と配向膜７１との間に構造性複屈折層３８が設けられている。また、図１３及び図１４に示される画素電極側の各タイプの液晶素子用基板６５を、図７及び図８に示されるタイプＢ０〜Ｂ５のガラス板と組み合わせることができる。もちろん、図１３に示される液晶素子用基板６５とタイプＢ０の液晶素子用基板３２との組み合わせは除かれる。
【００７８】
次の表３に上記の液晶素子用基板６５と、タイプＢ０〜Ｂ５の液晶素子用基板３２との組合せにおける製造コスト、ソリ調整の良否，光学補償性能の良否を表１と同様に示す。表３に示す「組合Ｎｏ．」の実際の組み合わせ表４に示すとおりであり、図１３に示される層構造の液晶素子用基板３２をタイプＣ０，図１４に示す層構造の液晶素子用基板６５をタイプＣ１としてある。
【００７９】
【表３】

【００８０】
【表４】

【００８１】
なお、本発明は、透過型の液晶素子の一方の面に反射板を配置することで反射型液晶素子とした構成にも利用できるのはいうまでもない。
【００８２】
本発明に用いられる構造性複屈折層は、図４に示すような多層薄膜の積層体だけでなく、無機材料で作成された様々な形態のものを利用することができる。先に説明し図４に示す薄膜積層体は、光学的な異方性が発現しない光学軸がガラス板の法線に合致した一軸性の負の複屈折層であり、ｃ−ｐｌａｔｅとして用いる例として挙げられているが、負の一軸性を有したものとしては図１５に示すように、透明な板状突起７７を格子状に配列した構造性複屈折層８０を用いることも可能である。なお、符号７６は、基板本体、すなわち共通電極側または画素電極側のガラス板，あるいは反射型ＬＣＤのシリコン基板である。
【００８３】
この構造性複屈折層８０の物理的構造を構成している板状突起７７の厚みｄ，高さｈ及び配列間隔は光の波長に対して充分に小さく、例えば光学膜厚がλ／１００〜λ／５、好ましくはλ／５０〜λ／５、実際的にはλ／３０〜λ／１０程度であればよく、光学異方性を示さない光学軸８０ａは図示の方向となる。液晶素子を構成する液晶素子用基板として組み込まれることによりａ−ｐｌａｔｅとして用いられる。そして、照明光軸または投影光軸と直交する面内で板状突起７７が一次元で配列されているため、その一次元配列の方向で空気層と板状突起７７による異なった屈折率が交互に分布するようになる。
【００８４】
また、図１６に示すように、基板本体７６上に透明な板状突起８１を傾斜して配列した構造性複屈折層８２も本発明の目的を達成するうえで有用である。この構造性複屈折層８２も負の一軸性複屈折体として作用し基板本体７６の面が照明光軸あるいは投影光軸と垂直になるように配置されるためｏ−ｐｌａｔｅとして用いられる。この構造性複屈折層８２も、照明光軸または投影光軸と直交する面内で屈折率の異なる部分が一次元配列となり、しかも異なる屈折率を与えるための物理的構造が照明光軸または投影光軸に対して傾斜することになる。
【００８５】
これらの構造性複屈折層８０，８２のもつ物理的な繰り返し構造パターンは、フォトリソグラフィにより作成することができる。なお、負の一軸性複屈折体としての作用を得るためには、それぞれの板状突起７７，８１の幅ｄに対する高さｈで表されるアスペクト比を充分に大きくしておく必要がある。このアスペクト比が充分に大きくない場合には、屈折率楕円体のｎ_ｘ ，ｎ_ｙ ，ｎ_ｚ が全て異なる２軸性複屈折体となる。さらにアスペクト比が小さくなると、極限的には正のａ−ｐｌａｔｅになる。
【００８６】
図１７に正のａ−ｐｌａｔｅの一例を示す。この構造性複屈折層８５は、基板本体７６の表面に透明な誘電体による突状８４を一定ピッチで格子状に配列することによって構成され、突条８４の幅Ｗ，高さｈ及び配列ピッチは先の例と同様に波長よりも充分に小さくしてある。光学軸８５ａは図示のように格子構造と平行となる。液晶素子に組み込まれる際には、上記構造が形成された基板本体７６の表面が照明光軸あるいは投影光軸に垂直になるように配置され、やはり照明光軸または投影光軸と直交する面内で屈折率が異なる部分が一次元配列となる。なお、位相差は突条８４の高さｈとその屈折率との積となる。高さｈが波長に対して大きくなると屈折率異方性が一軸からずれ、二軸となる。さらに大きくなると、負のｃ−ｐｌａｔｅに近づく。
【００８７】
また、基板本体７６の外面側に上記の構造性複屈折層８５を設ける場合に突条８４による格子構造が空気層に接していてもよいが、他の異なる屈折率をもった誘電体層で、突条８４の相互間を埋めるように全体的に覆ってもよい。また、基板本体７６の内面側に設ける場合にも同様に他の異なる屈折率をもった誘電体層で突条８４の相互間を埋めるようにしてもよい。
【００８８】
正のｃ−ｐｌａｔｅもまた本発明の構造性複屈折層として利用できる。正のｃ−ｐｌａｔｅは、図１８に示すように、基板本体７６の表面に透明な誘電体からなる多数の突起８６を垂直に林立させることで作成することができる。突起８６のサイズや配列ピッチは、これまで同様に、光の波長に比して充分に小さいものであればよい。基板本体７６の表面が照明光軸または投影光軸と直交するように配置されるため、図１５〜図１７に示す構造性複屈折層８０，８２，８５とは異なり、屈折率の異なる部分が照明光軸または投影光軸と直交する面内で二次元に分布するようになる。このような構造をもつ構造性複屈折層８７も、やはりフォトリソグラフィで作成が可能であり、その光学軸８７ａは基板本体７６の表面に垂直となる。また、基板本体７６の外面側に上記物理的構造部分を設ける場合では、先のものと同様空気層に接していてもよく、外面側，内面側のいずれの場合も屈折率が異なる別の誘電体層で全体的に覆う形態で使用することも可能である。
【００８９】
さらに、正のｏ−ｐｌａｔｅは図１９に示す形態で得ることができ、このような二次元の物理的構造の配列パターンをもつこれらの構造性複屈折層も本発明の目的のために効果的に用いることができる。図１９に示す構造性複屈折層９０は、基板７６の表面に透明な誘電体からなる突起９１を一定の傾斜角度で規則的に林立させたもので、フォトリソグラフィにより作成可能である。やはり、これらの構造のサイズや繰り返しピッチは光の波長よりも充分に小さくしておく必要があり、構造表面は空気層あるいは別の透明な誘電体層のいずれに接していてもよい。光学軸９０ａは、図示のように基板７６の表面に対して傾斜し、突起９１の傾斜方向と平行になる。
【００９０】
正のｏ−ｐｌａｔｅを作成するにあたっては、図２０に示すように、基板本体７６の表面に対し、斜め方向から一種類の誘電体を蒸着することによっても得られることが米国特許第５６３８１９７号公報明細書（前掲特許文献１）でも知られている。この方法によれば、光の波長に対して充分に小さい物理的構造を簡単に得ることができる。なお、同図中に示す斜線は、基板７６に斜め方向から成膜を行ったことを模式的に表すためのもので、それぞれ個別の薄膜層を表すものではない。この構造性複屈折層９３も、基板７６の表面が照明光軸または投影光軸と垂直になるように配置して用いられ、斜設した薄膜層９４がｏ−ｐｌａｔｅ複屈折体の光学異方性を示す。
【００９１】
複数の構造性複屈折層を組み合わせて使用する際に、異なった種類の構造性複屈折層を用いることも可能であり、より精密な位相差補償を行い、スクリーンに投影される画像のコントラストをより向上させることができる。また、本発明を適用し得る液晶素子の動作モードとしても、上述した透過型ＴＮ液晶モードのみならず、反射型ＴＮ液晶モードや公知のＥＣＢ（Ｅｌｅｃｔｒｉｃａｌｌｙ Ｃｏｎｔｒｏｌｌｅｄ Ｂｉｒｅｆｒｉｎｇｅｎｃｅ ）、ＶＡ（Ｖｅｒｔｉｃａｌ Ａｌｉｇｎｅｄ）、ＯＣＢ（Ｏｐｔｉｃａｌｌｙ Ｃｏｍｐｅｎｓａｔｏｒｙ Ｂｅｎｄ ）、ＦＬＣ（Ｆｅｒｒｏｅｌｅｃｔｒｉｃ Ｌｉｑｕｉｄ Ｃｒｙｓｔａｌ）などの各種の動作モードのものが挙げられ、さらにオフアクシス方式やマイクロレンズ方式などのように、ＲＧＢの各色光が液晶素子を異なった入射角度で通過するような光学系を採用したプロジェクタにも本発明は適用可能である。また、駆動方式についても、アクテイブマトリクス駆動方式に限らず各種の駆動方式に本発明は適用可能である。
【００９２】
さらに、薄膜層を積層した構造性複屈折層を作成するにあたっては、各層の膜厚は必ずしも等しくする必要はなく、また２種類の薄膜を交互に積層することにのみ限られない。例えば屈折率が異なる３種類以上の薄膜を適宜の順序，膜厚で積層してもよく、成膜工程の容易さ、各層の内部応力による歪みの吸収、屈折率の波長依存性などを考慮して適宜に設計することが可能である。また、構造性複屈折層は、屈折率が異なる２種類あるいはそれ以上の薄膜を積層した多層薄膜だけで構成する必要はなく、例えば図１５〜図２０に示されるような構造性複屈折体と多層薄膜とを組み合わせたものであってもよい。
【００９３】
【実施例】
［透過型液晶素子］
共通電極側の基板本体となる厚さ０．７ｍｍのガラス板に、ＳｉＯ_２ とＴｉＯ_２ を交互に各々膜厚１５ｎｍで４６層ずつ電子ビーム蒸着により積層して構造性複屈折層を形成した。この構造性複屈折層は、層の厚さが１．３８μｍで、波長５５０ｎｍの光に対して３１０ｎｍの負の複屈折を示した。次いで、その上に共通電極となるＩＴＯ膜をスパッタ法により１００ｎｍの膜厚で成膜した。さらにポリイミドの配向膜形成用樹脂膜を形成してラビングを施すことにより配向膜とし、共通電極側の液晶素子基板を作成した。一方、画素電極側の基板本体となる厚さ０．７ｍｍのガラス板上に画素電極アレイを作成したものにポリイミドの配向膜形成用樹脂膜を形成してラビングを施すことにより配向膜とし、画素電極側の液晶素子基板を作成した。
【００９４】
上記のように作成された各液晶素子基板を、互いにラビング方向が直交するように貼り合わせ、その間に正の誘電率のネマティック液晶を封入し、樹脂製マイクロレンズアレイを貼り合わせてＴＮ液晶素子を作成した。
【００９５】
このＴＮ液晶素子を用いたプロジェクタは、緑の光に対してコントラストが５５０：１を示し、構造性複屈折層を設けていないＴＮ液晶素子を用いたプロジェクタのコントラストの３５０：１に比べて改善効果が認められた。
【００９６】
［反射型液晶素子］
画素電極アレイが作成されたシリコン基板に垂直配向用ポリイミド配向膜を形成し、ラビングを施して画素電極側の液晶素子用基板を作成した。また、ガラス板に構造性複屈折層と共通電極となるＩＴＯ膜とを形成し、さらにＩＴＯ膜の上に垂直配向用ポリイミド配向膜を形成してラビングを施して共通電極側の液晶素子用基板を作成した。この共通電極側のガラス板，構造性複屈折層，ＩＴＯ膜の仕様は透過型液晶素子の共通電極側のものと同一である。
【００９７】
上記のように作成された各液晶素子基板を、互いにラビング方向が逆向きで平行となるように貼り合わせ、その間に負の誘電率のネマティック液晶を封入し、ＶＡ液晶素子を作成した。
【００９８】
このＶＡ液晶素子を用いたプロジェクタは、緑の光に対してコントラストが９００：１を示し、構造性複屈折層を設けていないＶＡ晶素子を用いたプロジェクタのコントラストの５００：１に比べて改善効果が認められた。
【００９９】
【発明の効果】
以上に述べたとおり、本発明によれば、無機材料で作成される構造性複屈折層を液晶素子を構成する液晶素子用基板の基板本体に形成して、位相差補償を行うようにしたから、耐久性に富み、しかもコスト負担も大きくすることなく、スクリーンに投影される画像のコントラストを向上させることができる。
【図面の簡単な説明】
【図１】リア方式の液晶プロジェクタの概略を示す外観図である。
【図２】透過型液晶素子を用いた投影ユニットの概略構成図である。
【図３】液晶素子の概略的な構造を示す概略断面図である。
【図４】構造性複屈折層の層構造を示す説明図である。
【図５】画素電極側の液晶素子用基板の構成例を示すものである。
【図６】画素電極側の液晶素子用基板の別の構成例を示すものである。
【図７】共通電極側の液晶素子用基板の構成例を示すものである。
【図８】共通電極側の液晶素子用基板の別の構成例を示すものである。
【図９】層間絶縁層を設けた画素電極側の液晶素子用基板を用いた液晶素子の例を示すものである。
【図１０】マイクロレンズを併用した例を示すものである。
【図１１】共通電極側の液晶素子用基板の外面に構造性複屈折層を設けた液晶素子にマイクロレンズを併用した例を示すものである。
【図１２】反射型液晶素子を用いた投影ユニットの概略構成図である。
【図１３】反射型液晶素子の構成例を示すものである。
【図１４】シリコン基板に構造性複屈折層を形成した例を示すものである。
【図１５】形状パターンを有する構造性複屈折体の一実施形態を示す概念図である。
【図１６】形状パターンを有する構造性複屈折体の他の実施形態を示す概念図である。
【図１７】形状パターンを有する構造性複屈折体の別の実施形態を示す概念図である。
【図１８】構造性複屈折体のさらに別の実施形態を示す概念図である。
【図１９】構造性複屈折体のさらに他の実施形態を示す概念図である。
【図２０】斜め方向からの成膜で作成された構造性複屈折体の概念図である。
【符号の説明】
３ スクリーン
５ 投影ユニット
１１Ｒ，１１Ｇ，１１Ｂ，６１Ｒ，６１Ｇ，６１Ｂ 液晶素子
１２ 光源
２６Ｒ，２６Ｇ，２６Ｂ 偏光板
２８Ｒ，２８Ｇ，２８Ｂ 偏光板
２４ 合成プリズム
２５ 投影レンズ
３０ 液晶
３１，３２，６５ 液晶素子用基板
３３，３７ ガラス板
３４，６７ 薄膜トランジスタ
３５，６８ 画素電極
３６，４０，７１ 配向膜
３８ 構造性複屈折層
３９ 共通電極
６６ シリコン基板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal element substrate, a liquid crystal element, and a liquid crystal projector.
[0002]
[Prior art]
[Patent Document 1]
US Pat. No. 5,638,197
[Patent Document 2]
JP 2002-14345 A
[Patent Document 3]
JP 2002-31782 A
[Patent Document 4]
JP 2002-131750 A
[Non-Patent Document 1]
Ebren JP and 5 others. “Birefringent Compensators for Normal White TN-LCDs”. SID Symposium Digest. SOCIETY FOR INFORMATION DISPLAY. 1994. p. 245-248
[0003]
A liquid crystal projector projects an image by projecting light modulated by a liquid crystal element onto a screen. There are a front system that projects an image from the front side of the screen and a rear system that projects an image from the back side of the screen. is there. In addition, the illumination method differs depending on whether the liquid crystal element used is a transmissive type or a reflective type. In any case, an image to be projected is displayed on the liquid crystal element, and illumination is given to the projection lens. Thus, an image is formed on the screen.
[0004]
Although liquid crystal elements of various operation modes can be used as the liquid crystal elements of the liquid crystal projector, a commonly used TN (Twisted Nematic) liquid crystal will be described. In TN liquid crystal, liquid crystal molecules constituting a liquid crystal layer between two substrates are maintained so that the major axis thereof is parallel to the substrate, and the major axis is gradually tilted in the thickness direction, so that the total angle is 90 °. It is twisted and used so that it is sandwiched between a pair of polarizing plates (one is a polarizer and the other is an analyzer). Then, depending on whether the liquid crystal element is used in normally white or normally black, either the crossed Nicols arrangement or the parallel Nicols arrangement is selected for the pair of polarizing plates.
[0005]
By the way, not only the TN liquid crystal but also the liquid crystal element generally has a drawback that the viewing angle is narrow. Taking a normally white TN liquid crystal as an example, in the state where no voltage is applied to the liquid crystal layer, the liquid crystal layer rotates the plane of polarization by 90 ° according to the twisted arrangement of liquid crystal molecules. Showing gender. Then, the linearly polarized light that has passed through the liquid crystal layer is emitted through the other polarizing plate arranged in a crossed Nicols state, and becomes a white state. When a voltage is applied to the liquid crystal layer, the twist of the liquid crystal molecules disappears, and the incident linearly polarized light is emitted as it is in the plane of polarization, so that the other polarizing plate is blocked from passing and becomes black.
[0006]
However, the liquid crystal also acts as a birefringent medium. In the case of the above-described TN liquid crystal, in the process of applying a voltage to the liquid crystal layer and losing its twisted alignment, optical rotation and birefringence are mixed, and birefringence dominates as the voltage application level increases. It ’s going to be. When the twist of the liquid crystal molecules disappears and the black state is obtained, the liquid crystal layer hardly exhibits birefringence with respect to the normal incident light, so that the linearly polarized light is transmitted as it is, but with respect to the oblique incident light. In other words, it exhibits birefringence, and light incident as linearly polarized light is modulated into elliptically polarized light. The elliptically polarized light generated in this way is partially transmitted through the polarizing plate on the output side, resulting in a decrease in the density of the black state. The tendency of the liquid crystal layer to be a birefringent medium gradually appears in the process of transition from the white state to the black state. The angle dependency of is inevitable. Such angle dependency of the degree of modulation is a phenomenon that is observed not only in TN liquid crystals but also in all liquid crystal elements.
[0007]
In order to improve the above drawbacks of the liquid crystal element, it is known to use a phase difference compensation element together in a direct-view type liquid crystal display device that directly observes an image displayed on the liquid crystal element. As a phase difference compensation element used for this purpose, “Fuji WV Film Wide View A” (trade name / hereinafter referred to as WV film) manufactured by Fuji Photo Film Co., Ltd. has already been put into practical use. Describes that, by using a structural birefringent body in which thin films are laminated as a phase difference compensation element, the contrast of a display image of a TN liquid crystal is not lowered even when the viewing angle is increased. Further, Patent Document 1 describes that a phase difference compensation element in which a multilayer thin film is vapor-deposited from an oblique direction with respect to a substrate is used, and the viewing angle of a liquid crystal display is widened by its optical anisotropy.
[0008]
These phase difference compensation elements are applied to direct-view type liquid crystal elements, but direct-view type liquid crystal elements are usually observed with an image almost facing the display screen from a position more than a clear viewing distance. It is often the usage form of. If the contrast is observed at the periphery of the display screen and the image is observed with a slight shift of the eye position, the image of that part can be observed almost normally. In addition, in the case of applications where a large number of people observe at the same time, the distance between the display screen and the observer becomes large, so the range of normal observation is limited, but the contrast of the display image is partially different. Hateful.
[0009]
In contrast, in a liquid crystal projector, image light modulated by a liquid crystal element is projected onto a screen by a projection lens, and the image light diffuses on the screen and becomes an observation target. Therefore, when the black level is to be displayed, if the contrast of the projected image itself decreases due to the fact that light that is incident on the liquid crystal layer and passes through the liquid crystal molecules obliquely is included, Even when observed from various positions, the reduction in contrast is not improved at all. In order to increase the contrast of the projected image as much as possible, it is only necessary to obtain a projected image without using a light beam emitted from the liquid crystal element at a large angle.To that end, it is necessary to lengthen the back focus of the projection lens, Liquid crystal projectors that require miniaturization are disadvantageous in achieving compactness. In order to solve these difficulties in principle, it is also effective to use the viewing angle expansion technology used in direct-view liquid crystal panels for the liquid crystal elements used in liquid crystal projectors. Can be improved.
[0010]
From such a background, Patent Documents 2 and 3 describe that a liquid crystal element for a liquid crystal projector is used in combination with a phase difference compensation element in the same manner as a direct-view liquid crystal element for the purpose of improving contrast. In the liquid crystal projector described in Patent Document 2, a phase difference compensation element for a TN liquid crystal that is made of an organic material such as the WV film described above is used. Patent Document 3 describes using a uniaxial birefringent crystal such as single crystal sapphire or quartz as a phase difference compensation element. Japanese Patent Application Laid-Open No. H10-228667 describes a discotic liquid crystal using an optical phase compensation plate. All of these phase difference compensation elements act as a birefringent material that exhibits optical anisotropy depending on the incident angle of light, and that the contrast of an image is lowered by a light beam emitted from the liquid crystal element at a large emission angle. It is preventing.
[0011]
[Problems to be solved by the invention]
However, in general, a retardation compensation element made of an organic material is likely to be faded when exposed to strong light including ultraviolet rays for a long time. In particular, when used in a liquid crystal projector, the brightness of the light source is increased and the degree of overheating is increased compared to a direct-view type liquid crystal monitor or the like for projecting an image on a screen. It tends to turn brown gradually over time. Therefore, there is a problem in terms of durability in applications that are used for a long time, such as home projection televisions, and it is difficult to put it to practical use. On the other hand, a phase difference compensation element using a birefringent material such as single crystal sapphire or crystal has no problem in durability, but the crystal itself such as sapphire or crystal is expensive, and the crystal cutting surface and thickness are increased. It must be managed with accuracy. In addition, adjustment when the phase difference compensation element is incorporated in the optical system is troublesome.
[0012]
Further, in some transmissive liquid crystal elements, a microlens is combined in order to improve a decrease in aperture ratio in units of pixels due to a black matrix section partitioned for each pixel on the substrate. However, when a microlens is combined, the angle of light changes before and after the microlens, so the desired effect of the phase difference compensation element may not be obtained, and the arrangement of the phase difference compensation element is limited. There was a problem of being.
[0013]
The present invention has been made in consideration of the above-mentioned background, and is excellent in durability for a long time use such as a home television, has a low manufacturing cost, and can be easily used in combination with a microlens. However, it is an object of the present invention to provide a liquid crystal element substrate, a liquid crystal element, and a liquid crystal projector capable of improving the contrast of the image itself.
[0014]
[Means for Solving the Problems]
In order to solve the above problem, the present invention provides a substrate for a liquid crystal element according to claim 1, wherein light transmitted through the liquid crystal layer is incident on at least one surface of the substrate body on which light transmitted through the liquid crystal layer is incident. A structural birefringent layer made of an inorganic material for compensating an optical retardation is formed.
[0015]
According to a second aspect of the present invention, the structural birefringent layer includes a multilayer thin film having at least a thin film made of a high refractive index material and a thin film made of a low refractive index material.
[0016]
In the substrate for a liquid crystal element according to claim 3, the structural birefringent layer is a multilayer thin film in which thin films made of a high refractive index material and thin films made of a low refractive index material are alternately laminated.
[0017]
In the substrate for a liquid crystal element according to claim 4, the structural birefringent layer is formed on the inner surface of the substrate body.
[0018]
In the liquid crystal element substrate according to claim 5, the structural birefringent layer is formed between the substrate body and the electrode.
[0019]
In the substrate for a liquid crystal element according to claim 6, the electrode of the substrate body on which the structural birefringent layer is provided is a counter electrode for the active matrix driving system.
[0020]
In the liquid crystal element substrate according to claim 7, the structural birefringent layer is formed on the outer surface of the substrate body.
[0021]
The substrate for a liquid crystal device according to claim 8 is a substrate in which a structural birefringent layer is formed on each of an inner surface and an outer surface of a substrate body.
[0022]
10. The liquid crystal device according to claim 9, wherein a structural birefringent layer made of an inorganic material is formed on at least one surface of a substrate main body on which light transmitted through the liquid crystal layer is incident, and the light transmitted through the liquid crystal layer. To compensate for the optical phase difference of
[0023]
In the liquid crystal element according to claim 10, the structural birefringent layer is a multilayer thin film in which thin films made of a high refractive index material and thin films made of a low refractive index material are alternately laminated.
[0024]
The liquid crystal projector according to claim 11, wherein the liquid crystal projector is made of an inorganic material on at least one surface of the substrate body on which light transmitted through the liquid crystal layer is incident, out of the pair of substrate bodies provided with the alignment film and the electrode. A structural birefringent layer is formed to compensate for an optical phase difference of light transmitted through the liquid crystal layer.
[0025]
In the liquid crystal projector according to claim 12, the structural birefringent layer is a multilayer thin film in which thin films made of a high refractive index material and thin films made of a low refractive index material are alternately laminated.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the appearance of a rear type liquid crystal projector. A diffusion transmission type screen 3 is provided on the front surface of the housing 2, and an image projected on the rear surface is observed from the front surface side. A projection unit 5 is incorporated inside the housing 2, and the projected image is reflected by the mirrors 6 and 7 and formed on the back surface of the screen 3. This liquid crystal projector incorporates a well-known circuit unit for reproducing video signals and audio signals in addition to a tuner circuit in the housing 2 and reproduces the video signals on a liquid crystal element incorporated as an image display means in the projection unit 5. By displaying images, it can be used as a large-screen television.
[0027]
FIG. 2 schematically shows the configuration of the projection unit 5. The projection unit 5 includes three transmissive liquid crystal elements 11R, 11G, and 11B, and can perform full-color image projection. Radiated light from the light source 12 passes through a filter 13 that cuts ultraviolet rays and infrared rays to become white light including red light, green light, and blue light, and is applied to the glass rod 14 according to the illumination optical axis from the light source to the liquid crystal element. Incident. The light incident surface of the glass rod 14 is located in the vicinity of the focal position of the ellipsoidal mirror used in the light source 12, and the light from the light source 12 efficiently enters the glass rod 14.
[0028]
A relay lens 15 is disposed opposite to the exit surface of the glass rod 14, and the white light from the glass rod 14 is incident on the mirror 17 as parallel light by the relay lens 15 and the subsequent collimating lens 16. The white light reflected by the mirror 17 is divided into two light beams by the dichroic mirror 18R that transmits only red light, and the transmitted red light is reflected by the mirror 19 to illuminate the liquid crystal element 11R from the back. Further, the green light and the blue light reflected by the dichroic mirror 18R are further divided into two light beams by the dichroic mirror 18G that reflects only the green light. The green light reflected by the dichroic mirror 18G illuminates the liquid crystal element 11G from the back side. The blue light transmitted through the dichroic mirror 18G is reflected by the mirrors 18B and 20, and illuminates the liquid crystal element 11B from the back.
[0029]
Each of the liquid crystal elements 11R, 11G, and 11B is composed of a TN liquid crystal, and a density pattern image of a red image, a green image, and a blue image constituting a full color image is displayed on each of the liquid crystal elements 11R, 11G, and 11B. A synthetic prism 24 is arranged so that the center is optically equidistant from these liquid crystal elements 11R, 11G, and 11B, and a projection lens 25 is provided facing the emission surface of the synthetic prism 24. The composite prism 24 has two dichroic surfaces 24a and 24b inside thereof, and receives the red light transmitted through the liquid crystal element 11R, the green light transmitted through the liquid crystal element 11G, and the blue light transmitted through the liquid crystal element 11B. The combined image is incident on the projection lens 25.
[0030]
A projection lens 25 is provided on the projection optical axis from the center of the emission surface of each of the liquid crystal elements 11R, 11G, and 11B to the center of the screen 3 through the center of the combining prism 24 and the projection lens 25. The projection lens 25 has its object-side focal plane coincident with the exit surfaces of the liquid crystal elements 11R, 11G, and 11B and its image-side focal plane coincides with the screen 3, so that the full color synthesized by the synthesizing prism 24 is used. The image is formed on the screen 3. The mirrors 6 and 7 shown in FIG. 1 are omitted in order to avoid complication of the drawing.
[0031]
Polarizing plates 26R, 26G, and 26B are provided on the illumination light incident surfaces of the liquid crystal elements 11R, 11G, and 11B, respectively. Further, polarizing plates 28R, 28G, and 28B are provided on the exit surface side of each liquid crystal element. The polarizing plates 26R, 26G, and 26B on the incident surface side and the polarizing plates 28R, 28G, and 28B on the outgoing surface side are arranged in a crossed Nicols arrangement. Acts as a photon. As will be described later in detail, the liquid crystal elements 11R, 11G, and 11B are provided with a structural birefringent layer on a substrate constituting the liquid crystal elements 11R, 11G, and 11B. The operation of the liquid crystal element provided for each color channel and the action of the polarizing plates provided on both sides of the liquid crystal element are substantially the same, although there are differences based on the respective color lights. Hereinafter, the red channel will be described as a representative.
[0032]
FIG. 3 schematically shows the structure of the liquid crystal element 11R. The liquid crystal element 11R is of a TFT (Thin Film Transistor) type and is driven by an active matrix. The liquid crystal element 11R is provided with a pair of liquid crystal element substrates 31 and 32 facing each other with the liquid crystal layer 30 interposed therebetween.
[0033]
The liquid crystal element substrate 31 includes a transparent glass plate 33 as a substrate body, a thin film transistor 34 formed on the inner surface 33 a on the liquid crystal layer 30 side, a transparent pixel electrode 35, and an alignment film 36. On the inner surface 33a of the glass plate 33, a thin film transistor 34 and a pixel electrode 35 are provided as a set, and a large number of these are provided in a matrix. One set of the thin film transistor 34 and the pixel electrode 35 is one pixel of a red image. Corresponding to. The alignment film 36 is formed on almost the entire surface so as to cover the thin film transistor 34 and the pixel electrode 35.
[0034]
The other liquid crystal element substrate 32 includes a transparent birefringent layer 38 and a transparent glass plate 37 on the substantially entire surface of a transparent glass plate 37 as a substrate body and an inner surface (surface on the liquid crystal layer side) 37a. A common electrode (counter electrode) 39 and an alignment film 40 are layered.
[0035]
The liquid crystal element substrate 31 is formed with a black matrix portion (not shown) that divides the pixel electrode portion 35 for each pixel to improve the reduction in contrast in pixel units.
[0036]
The liquid crystal element 11R has the same configuration as a conventional TFT liquid crystal element except that the structural birefringent layer 38 is provided. That is, the voltage applied to the liquid crystal layer 30 between the pixel electrode 35 and the common electrode 39 is controlled by the thin film transistor 34 to change the orientation posture of the liquid crystal layer 30 between the respective electrodes, thereby entering from the polarizing plate 26R. The shade of the pixel is expressed by controlling the amount of light emitted from the polarizing plate 28R.
[0037]
The red illumination light reflected by the mirror 19 becomes linearly polarized light by the polarizing plate 26R on the incident surface side and enters the liquid crystal element 11R. In the normally white mode, a signal voltage is applied between the pixel electrode 35 and the common electrode 39 in the TN liquid crystal used in the liquid crystal element 11R in order to display black in the image. At this time, the liquid crystal molecules contained in the liquid crystal layer 30 take various orientations. For this reason, even if the illumination light becomes a parallel light flux and enters the liquid crystal layer 30, the light emitted by the optical rotation and birefringence exhibited by the liquid crystal layer 30 is not completely linearly polarized, and is generally an elliptically polarized image. Light is emitted and sufficient black cannot be obtained. Even in the normally black mode, the black level does not become sufficiently black due to a slight inclination of the liquid crystal molecules.
[0038]
If the linear polarization of the image light that has passed through the liquid crystal layer 30 is preserved in a state in which black display is desired, the image light is blocked by the other polarizing plate 28R and becomes weak enough to enter the composite prism 24. To do. However, when light that passes through the liquid crystal molecules obliquely is included, the image light modulated by the liquid crystal layer 30 becomes elliptically polarized light having a slightly different optical phase from that of linearly polarized light. Sufficient black is not obtained.
[0039]
The structural birefringent layer 38 compensates for an optical phase difference by changing the polarization state of light incident on the structural birefringent layer 38 so that the component that the image light becomes elliptically polarized light is canceled by passing through the liquid crystal layer 30 as described above. . As a result, the image light emitted from the liquid crystal element 11R becomes linearly polarized image light and enters the polarizing plate 28R, thereby improving the contrast of the image.
[0040]
The structural birefringent layer 38 having such a function is preferably made of an inorganic material and includes a multilayer thin film having at least a thin film made of a high refractive index material and a thin film made of a low refractive index material. The structural birefringent layer 38 shown in FIG. 4 is formed as a multilayer film in which dielectric thin films L1 and L2 having different refractive indexes are alternately stacked on the inner surface 37a of the glass plate 37 of the liquid crystal element 11R. Then, the common electrode 39 is formed on the surface of the structural birefringent layer 38 configured as described above, and the alignment film 40 is further formed.
[0041]
The optical film thickness (product of geometric film thickness and refractive index) of each layer constituting the structural birefringent layer 38 is sufficiently smaller than the wavelength of light, preferably λ / 100 to λ / 5, more preferably λ / 50 to λ / 5, and practically λ / 30 to λ / 10 are appropriate. By this method, the structural birefringent layer 38 having uniaxial negative birefringence can be easily formed on the glass plate 37.
[0042]
As a material for a thin film layer having a high refractive index, TiO ₂ (N = 2.2-2.4), ZrO ₂ (N = 2.20) and other materials having a low refractive index such as SiO ₂ (N = 1.40-1.48) and MgF ₂ (N = 1.39), CaF ₂ (N = 1.30) or the like can be used. Further, for example, various materials listed below can be used for the high refractive index and low refractive index thin film layers constituting the structural birefringent layer 37 of the present invention. In addition, the numerical value shown in () represents the approximate value of the refractive index. CeO ₂ (2.45), SnO ₂ (2.30), Ta ₂ O ₅ (2.12), In ₂ O ₃ (2.00), ZrTiO ₄ (2.01), HfO ₂ (1.91), Al ₂ O ₃ (1.59-1.70), MgO (1.7), AlF ₃ , Diamond thin film, LaTiO _X , Samarium oxide and so on. As a combination of the high refractive index thin film layer material and the low refractive index thin film layer material, TiO ₂ / SiO ₂ Is preferable, but Ta ₂ O ₅ / Al ₂ O ₃ , HfO ₂ / SiO ₂ , MgO / MgF ₂ , ZrTiO ₄ / Al ₂ O ₃ , CeO ₂ / CaF ₂ , ZrO ₂ / SiO ₂ , ZrO ₂ / Al ₂ O ₃ And so on.
[0043]
Further, since it is necessary to avoid the phenomenon of light interference between the laminated thin films L1 and L2, it is preferable that each optical film thickness is thin. However, in order to obtain a necessary total film thickness, the number of film formation times Therefore, when designing a realistic film thickness configuration, the refractive index, film thickness ratio, and total film thickness of each layer are determined in consideration of the desired birefringence effect, and thin film interference is sufficient for coloring. In addition, it is necessary to pay attention to the selection of materials so that defects such as generation of cracks due to internal stress do not occur after film formation.
[0044]
In order to manufacture the structural birefringent layer 38 composed of a multilayer thin film, a vacuum vapor deposition method or a sputter film formation method can be effectively used. In order to alternately form two types of thin film layers, ie, a high refractive index thin film layer and a low refractive index thin film layer, each evaporation source can be shielded from the glass plate 37 to be deposited. Each of the shutters is provided as described above, and the shutters are alternately opened and closed, and two types of thin film layers are alternately stacked, or the glass plate 37 is held by a substrate holder that circulates at a constant speed. It is possible to take a technique such as alternately laminating two kinds of thin films by passing over each evaporation source in the process of circulating and moving. Thereby, when a multilayer thin film is obtained, the vacuum chamber only needs to be evacuated once, so that the production efficiency can be increased.
[0045]
The design procedure of the structural birefringent layer 38 using such a multilayer thin film is as follows. The birefringence Δn of the structural birefringent layer 37 is the ratio of the optical film thicknesses of two types of thin films having different refractive indices as described in “Optical Vol. 27 No. 1 (1998) p.12-17”. As the refractive index is different, the larger the value is obtained. The phase difference is given by the product “dΔn” of the birefringence Δn and the geometric total film thickness d of the structural birefringent layer 38. Therefore, in order to obtain a desired phase difference, a film thickness ratio is obtained such that the value of the birefringence Δn obtained from these materials is increased, and the required physical birefringence layer structure is obtained from the birefringence Δn. The total film thickness d is determined. Considering the suitability for manufacturing, provided that the product of the geometric film thickness and the number of layers of each thin film is the total film thickness d and that the geometric film thickness is in the optical film thickness range as described above. However, the number of layers may be selected.
[0046]
Dichroic mirrors, polarizing beam splitters, color synthesis prisms, antireflection films, etc. are known as devices that obtain unique optical effects by multilayer thin films in which dielectric thin films having different refractive indexes are laminated. Each of the individual thin film layers constituting the thin film is designed so that its optical film thickness is an integral multiple of λ / 4, and achieves the intended purpose by utilizing the light interference phenomenon. In this respect, the structural birefringent layer 38 described above has a specific birefringence index Δn determined by the optical film thickness of each thin film layer being thinner than λ / 4 and the ratio of the optical film thicknesses of the two types of thin films. From this, it can be seen that this is based on a completely different principle of action from the light interference phenomenon.
[0047]
The structural birefringent layer 38 compensates for the difference in the degree of phase modulation depending on the angle of light passing through the liquid crystal layer 30. For this reason, even if the angle of the light passing through the liquid crystal layer 30 is increased, it is possible to suppress a decrease in contrast, so that an optical system having a large numerical aperture can be used. Therefore, the size of the liquid crystal element can be reduced, a lens with a large aperture can be used to increase the light utilization efficiency, the optical path length can be shortened for compactness, and the entire optical system can be reduced to reduce the manufacturing cost. The selection range of the design factors such as can be widened.
[0048]
The structural birefringent layer 38 as described above is provided on the inner surface 37a of the glass plate 37 on the common electrode side, in addition to the outer surface (surface opposite to the liquid crystal layer) of the glass plate 37 on the common electrode side, It can be provided on the liquid crystal element substrate 31. The structural birefringent layer 38 may be provided between the alignment film and the electrode in addition to being provided on the surface of the glass plate, and the structural birefringent layer 38 may be provided on both surfaces of the glass plate. Further, various liquid crystal element substrates 31 and 32 provided with the structural birefringent layer 38 in various forms can be combined.
[0049]
FIGS. 5 to 7 show various examples of the layer structure of the liquid crystal element substrate, FIGS. 5 and 6 show examples of the liquid crystal element substrate layer structure on the pixel electrode side, and FIGS. Examples of the layer structure of the electrode side liquid crystal element substrate are shown. In addition, the same code | symbol is attached | subjected to the substantially same thing as what is shown by FIG. 3, and detailed description is abbreviate | omitted. For convenience, each liquid crystal element substrate will be described using the type names shown in the drawing.
[0050]
A liquid crystal element substrate 31 of type A0 shown in FIG. 5 (a) is the same as that shown in FIG. 3, and is combined with a liquid crystal element substrate 32 provided with a structural birefringent layer 38 without a structural birefringent layer. Used. In the liquid crystal element substrate 31 of type A1 shown in FIG. 5B, a structural birefringent layer 38 is provided on the inner surface 33a of the glass plate 33, and the thin film transistor 34 and the pixel electrode 35 are formed on the upper layer of the structural birefringent layer 38. Further, an alignment film 36 is provided on the upper layer. In the type A2 shown in FIG. 5C, the thin film transistor 34, the pixel electrode 35, and the alignment film 36 are formed on the inner surface 33a of the glass plate 33 and the structural birefringence is formed on the outer surface 33b of the glass plate 33 in the same manner as the type A0. The layer 38 is formed.
[0051]
A liquid crystal device substrate 31 of type A3 shown in FIG. 6A is obtained by forming a structural birefringent layer 37 between a pixel electrode 35 and an alignment film 36. In this type A3 example, a transparent planarizing layer (for example, Si0) is formed on the thin film transistor 34 and the pixel electrode 35 on the inner surface 33a. ₂ ) 41 is formed, the structural birefringent layer 38 is formed, and the alignment film 36 is formed on the structural birefringent layer 38. The type A4 liquid crystal element substrate 31 shown in FIG. 6B has a structural birefringent layer 38 formed on the inner surface 33a and the outer surface 33b of the glass plate 33 in the same manner as the type A1 shown in FIG. In addition, the structural birefringent layer 38 is formed on two surfaces by forming the structural birefringent layer 38. In the type A5 shown in FIG. 6C, the inner side layer structure is the same as that of the type A3, and the structural birefringent layer 38 is provided on the outer surface 33b of the glass plate 33 by providing two structural birefringent layers 38. It is a surface.
[0052]
The pixel electrodes 35 formed on the glass plate 33 need to be electrically insulated from each other. As described above, the structural birefringent layer 38 is a dielectric, that is, an electrical insulator. Therefore, even if the pixel electrodes 38 are formed in close contact with each other, the pixel electrodes 38 are not short-circuited.
[0053]
The type B0 liquid crystal element substrate 32 shown in FIG. 7A is not provided with a structural birefringent layer, and is combined with the liquid crystal element substrate 31 on the pixel electrode side provided with the structural birefringent layer. used. The type B1 liquid crystal element substrate 32 shown in FIG. 7B is the same as that shown in FIG. 3, and a structural birefringent layer 38 is provided on the inner surface 37a, and is common to the upper layer of the structural birefringent layer 38. The electrode 39 and the alignment film 40 are sequentially provided. In the type B2 liquid crystal element substrate 32 shown in FIG. 7C, the common electrode 39 and the alignment film 40 are formed on the inner surface 37a of the glass plate 37, and the structural birefringent layer 38 is formed on the outer surface 37b. Formed.
[0054]
A liquid crystal element substrate 32 of type B3 shown in FIG. 8A is obtained by forming a structural birefringent layer 38 between a common electrode 39 and an alignment film 40. This is because the structural birefringent layer 38 is formed after the common electrode 39 is formed on the inner surface 37 a of the glass plate 37, and the alignment film 40 is formed above the structural birefringent layer 38. In the type B4 shown in FIG. 8B, the structural birefringent layer 38, the common electrode 39, and the alignment film 40 are sequentially formed on the inner surface 37a of the glass plate 37 in the same manner as the type B1. The structural birefringent layer 38 is provided on the two surfaces by forming the structural birefringent layer 38 also on the outer surface 37b. In the type B5 shown in FIG. 8C, the common electrode 39, the structural birefringent layer 38, and the alignment film 40 are formed on the inner surface 37a as in the case of type B3, and the structural compound is also formed on the outer surface 37b of the glass plate 37. A refraction layer 38 is provided, and a structural birefringence layer 38 is provided on two surfaces.
[0055]
The liquid crystal element substrates 31 and 32 may be formed with other layers such as a structural birefringent layer, various electrodes, a thin film transistor, an alignment film, and the above-described black matrix portion. For example, as shown in FIG. 9, an interlayer insulating layer 42 may be provided between the thin film transistor 34 and the pixel electrode 35. Of course, a structural birefringent layer is provided on a liquid crystal element substrate having such an interlayer insulating layer 42. It may be formed.
[0056]
Table 1 shows the level of manufacturing cost, the quality of warp adjustment, and the quality of optical compensation performance in the combination of the liquid crystal element substrates 31 and 32 described above.
[0057]
[Table 1]

[0058]
In Table 1 above, the case where the structural birefringent layer is provided on either the inner surface side or the outer surface of the glass plate is referred to as “one side”, and the structural birefringent layer is provided on both the inner surface side and the outer surface of the glass plate. The case where the liquid crystal element is provided is classified as “both sides”, and the liquid crystal element substrates 31 and 32 are classified. Reference numerals 1 to 9 denote the manufacturing cost, the quality of the warp adjustment, and the quality of the optical compensation performance. The actual combinations of the liquid crystal element substrates 31 and 32 corresponding to “Combination No.” are as shown in Table 2 below.
[0059]
[Table 2]

[0060]
The cost column in Table 1 indicates that the larger the number, the higher the manufacturing cost. Also, in the warp adjustment, “x” indicates that the warp adjustment is impossible, and that the adjustment can be performed more preferably in the order of “Δ”, “◯”, “◎”. As for the optical compensation performance, “Δ” indicates that a preferable result is obtained, and “◯” indicates that a more preferable result is obtained.
[0061]
A liquid crystal element for a projector receives strong light and rises in temperature. At this time, contrast characteristics change depending on the thermal expansion of the liquid crystal and the temperature dependence of the birefringence. In such a situation, if the substrate warp is large, the uniformity of contrast within the display surface is impaired. Therefore, in a liquid crystal element substrate for a liquid crystal projector, the warpage of the substrate is an important characteristic, and it is preferable that it can be precisely controlled including its temperature dependent characteristics.
[0062]
As can be seen from Table 1, from the viewpoint of optical compensation performance, it is preferable to provide at least one structural birefringent layer on each of the liquid crystal element substrates 31 and 32. It can be seen that a structural birefringent layer is preferably provided on both sides of the glass plate, and more preferably, a structural birefringent layer is provided on both sides of each glass plate 33, 37.
[0063]
In the case of a structure in which a structural birefringent layer 38 is formed between an electrode and a glass plate (substrate body), such as a liquid crystal element substrate 31 of types A3 and A5 and a liquid crystal element substrate 32 of types B3 and B5. Then, there is an advantage that the structural birefringent layer 38 formed of a dielectric, that is, an insulator can also function as an insulating layer for preventing a short circuit between the electrodes.
[0064]
However, on the other hand, in order to connect the electrode to an external circuit, it is necessary to provide an area where the electrode is exposed without providing a structural birefringent layer outside the display region of the glass plate. For such patterning, a method of removing a part of the structural birefringent layer by photolithography or a method of mask vapor deposition so as not to form the structural birefringent layer on the electrode portion to be exposed can be used. In addition, the structural birefringent layer has a drawback that a large number of thin films with different etching properties are laminated, and the mask deposition has a drawback that the process control becomes complicated because the film forming process is affected for each liquid crystal element design. There is. Furthermore, when a structural birefringent layer is provided between the pixel electrode and the common electrode, the voltage applied to the liquid crystal layer is reduced by capacitive division by the structural birefringent layer, depending on the thickness of the layer. You must also consider the points.
[0065]
When the structural birefringent layer 38 is formed on the inner surface side of the glass plate as in the liquid crystal element substrate 31 of types A1, A3, A4 and A5 and the liquid crystal element substrate 32 of types B1, B3, B4 and B5 Then, since each surface of the structural birefringent layer 38 is in contact with a material having a refractive index higher than that of air, the reflectance of light at those boundary surfaces is extremely lower than that of an optical compensation element in contact with the air. Therefore, there is an advantage that the antireflection layer on the boundary surface can be simplified or omitted. Further, there is an advantage that the structural birefringent layer 33 can be prevented from being damaged.
[0066]
When the structural birefringent layer 38 is provided on the outer surface of the glass plate as in the liquid crystal element substrate 31 of type A2, A4, A5 and the liquid crystal element substrate 32 of type B2, B4, B5, the structural birefringence In order to prevent the layer 38 from being damaged, it is also preferable to provide a transparent protective layer above the structural birefringent layer 38.
[0067]
In the configuration in which the structural birefringent layer is provided on the substrate body, the angle of passing through the liquid crystal layer and the angle of passing through the structural birefringent layer can be the same for the light passing through the liquid crystal layer. In addition, it is difficult to provide a retardation compensation element made of a polymer material or the like inside a liquid crystal element. However, a structural birefringent layer made of an inorganic material as described above is possible, Sufficient durability against ultraviolet rays and ultraviolet rays.
[0068]
The liquid crystal element of the present invention can be combined with a microlens as in the example shown in FIG. The microlens array 50 is disposed on the incident surface side of the liquid crystal element. In the microlens array 50, a microlens 50a is formed for each pixel. The microlens 50a is created by providing a continuous refractive index distribution on a glass plate using an ion exchange technique. Of course, as the microlens, glass or resin processed into a lens shape may be used. The microlens 50a improves that the aperture ratio per pixel is lowered by a black matrix portion (not shown) formed on the glass plate 33 on the emission surface side that partitions the pixel electrode 35 for each pixel.
[0069]
By combining the microlens 50a, the illumination light that has been linearly polarized by the polarizing plate serving as a polarizer is converted into a convergent light beam by the microlens 50a, and the glass plate 37, the structural birefringent layer 38, the common electrode 39, and the alignment film. 40 passes through the liquid crystal layer 30, passes through the alignment film 36 and the pixel electrode 35, passes through the glass plate 33, and the polarizing plate serving as an analyzer, and exits.
[0070]
The structural birefringent layer 38 is used to compensate for the difference in phase modulation depending on the angle of light passing through the liquid crystal layer 30. Therefore, as shown in this example, the structural birefringent layer 38 is incident by the microlens 50a. This is particularly effective when the angle of the incoming light is such that there is a great advantage in that it is possible to improve the contrast and to design the microlens 50a with a large numerical aperture.
[0071]
In the above example, the structural birefringent layer 38 is the liquid crystal element substrate 32 provided on the inner surface 37a of the glass plate 37 on the common electrode side. For example, as shown in FIG. 11, it is provided on the outer surface 37b of the glass plate 37. A type liquid crystal element substrate 32 may also be used. In addition, a combination of liquid crystal element substrates 31 and 32 having various layer structures shown in FIGS. 5 to 8 may be used.
[0072]
The structural birefringent layer made of the inorganic material of the present invention can also be applied to a reflective liquid crystal element. An example of a projection unit using a reflective liquid crystal element is shown in FIG. The emitted light from the light source 12 passes through the filter 13 to become white light from which ultraviolet rays and infrared rays are cut, and enters the dichroic mirror 56 that passes through the condensing optical system 55 and reflects only red light. The reflected red light is reflected by the mirror 57 and enters the polarizing beam splitter 58 in which the polarizing film 58a is obliquely provided. The s-polarized component is reflected by the polarizing film 58a as linearly polarized light, and enters the reflective liquid crystal element 61R. Of the green light and blue light transmitted through the dichroic mirror 56, the green light is reflected by the dichroic mirror 62 and enters the polarization beam splitter 63, and the blue light transmitted through the dichroic mirror 62 enters the polarization beam splitter 64.
[0073]
The reflective liquid crystal element 61R used here is configured as shown in FIG. In FIG. 13, components that are substantially the same as those described above are assigned the same reference numerals, and descriptions thereof are omitted. The layer structure of the liquid crystal element substrate on the common electrode 39 side where the structural birefringent layer 38 is provided is the same as that of the first embodiment.
[0074]
The liquid crystal element substrate 65 on the pixel electrode side has an opaque silicon substrate 66 as a substrate body. On the silicon substrate 66, a pixel circuit 67 that controls an applied voltage between the electrodes is formed for each pixel, and a pixel electrode 68 is connected to the pixel circuit 67. The pixel electrode 68 is a reflecting plate made of a material having high reflectivity such as aluminum or silver, and reflects the light transmitted through the liquid crystal layer 30. An interlayer insulating layer 69 is formed between the silicon substrate 66 and the pixel electrode 68, and an alignment film 71 is formed so as to cover the pixel electrode 68 and the interlayer insulating layer 69.
[0075]
The light that has been linearly polarized by the polarizing beam splitter 58 enters the liquid crystal layer 30 through the liquid crystal element substrate 32, and enters the pixel electrode 68 through the alignment film 71. Then, the light is reflected by the pixel electrode 68 and enters the polarization beam splitter 58 through the alignment film 71, the liquid crystal layer 30, and the liquid crystal element substrate 32. When light passes through the liquid crystal element substrate 32, the light passes through the structural birefringent layer 38 formed on the glass plate 37. The linearly polarized light that has entered the polarization beam splitter 58 again is a p-polarized component with respect to the polarizing film 58 a, and thus passes through the polarizing film 58 a and enters the combining prism 24. The functions of the combining prism 24 and the projection lens 25 are exactly the same as in the previous embodiment.
[0076]
The structural birefringent layer 38 used here passes light twice when it enters and exits the liquid crystal layer 30, so that the structural birefringent layer 38 is taken into consideration. It is necessary to design the phase difference due to its own birefringence. It can also be used when a reflective liquid crystal element is used off-axis.
[0077]
The structural birefringent layer 38 may be provided on the liquid crystal element substrate 65 on the pixel electrode side. FIG. 14 shows an example in which the structural birefringent layer 38 is provided on the liquid crystal element substrate 65 on the pixel electrode side, and the structural birefringent layer is provided between the pixel electrode 68 on the silicon substrate 66 side and the alignment film 71. 38 is provided. Further, each type of liquid crystal element substrate 65 on the pixel electrode side shown in FIGS. 13 and 14 can be combined with the glass plates of types B0 to B5 shown in FIGS. Of course, the combination of the liquid crystal element substrate 65 and the type B0 liquid crystal element substrate 32 shown in FIG. 13 is excluded.
[0078]
The following Table 3 shows the manufacturing cost, the quality of warp adjustment, and the quality of optical compensation performance in the combination of the liquid crystal element substrate 65 and the type B0 to B5 liquid crystal element substrate 32 as in Table 1. The actual combination of “Union No.” shown in Table 3 is as shown in Table 4. The liquid crystal element substrate 32 having the layer structure shown in FIG. 13 is the type C0, and the liquid crystal element substrate 65 having the layer structure shown in FIG. Is type C1.
[0079]
[Table 3]

[0080]
[Table 4]

[0081]
Needless to say, the present invention can also be used in a configuration in which a reflective plate is provided on one surface of a transmissive liquid crystal element to obtain a reflective liquid crystal element.
[0082]
As the structural birefringent layer used in the present invention, not only a multilayer thin film laminate as shown in FIG. 4 but also various forms made of an inorganic material can be used. The thin film laminate described above and shown in FIG. 4 is an example in which an optical axis that does not exhibit optical anisotropy is a uniaxial negative birefringent layer that matches the normal line of the glass plate, and is used as a c-plate. As shown in FIG. 15, it is possible to use a structural birefringent layer 80 in which transparent plate-like protrusions 77 are arranged in a lattice pattern, as shown in FIG. Reference numeral 76 denotes a substrate body, that is, a glass plate on the common electrode side or the pixel electrode side, or a silicon substrate of a reflective LCD.
[0083]
The thickness d, height h, and arrangement interval of the plate-like protrusions 77 constituting the physical structure of the structural birefringent layer 80 are sufficiently small with respect to the wavelength of light. For example, the optical film thickness is λ / 100 to λ / 5, preferably λ / 50 to λ / 5, and practically about λ / 30 to λ / 10, and the optical axis 80a not exhibiting optical anisotropy is in the direction shown in the figure. By being incorporated as a liquid crystal element substrate constituting the liquid crystal element, it is used as an a-plate. Since the plate-like projections 77 are arranged one-dimensionally in a plane orthogonal to the illumination optical axis or the projection optical axis, different refractive indexes due to the air layer and the plate-like projections 77 alternate in the one-dimensional arrangement direction. To become distributed.
[0084]
Further, as shown in FIG. 16, a structural birefringent layer 82 in which transparent plate-like protrusions 81 are inclined and arranged on a substrate body 76 is also useful for achieving the object of the present invention. This structural birefringent layer 82 also functions as a negative uniaxial birefringent body and is used as an o-plate because the surface of the substrate body 76 is disposed so as to be perpendicular to the illumination optical axis or the projection optical axis. This structural birefringent layer 82 also has a one-dimensional array of portions having different refractive indexes in a plane orthogonal to the illumination optical axis or the projection optical axis, and the physical structure for providing different refractive indexes has an illumination optical axis or projection. It will be inclined with respect to the optical axis.
[0085]
The physical repetitive structure pattern of the structural birefringent layers 80 and 82 can be created by photolithography. In order to obtain an effect as a negative uniaxial birefringent body, it is necessary to sufficiently increase the aspect ratio represented by the height h with respect to the width d of each plate-like protrusion 77, 81. If this aspect ratio is not large enough, the refractive index ellipsoid n _x , N _y , N _z Are all different biaxial birefringent bodies. Further, when the aspect ratio becomes smaller, it becomes a positive a-plate in the limit.
[0086]
FIG. 17 shows an example of a positive a-plate. The structural birefringent layer 85 is configured by arranging protrusions 84 made of a transparent dielectric material on the surface of the substrate body 76 in a lattice pattern at a constant pitch, and the width W, height h, and arrangement pitch of the protrusions 84. Is sufficiently smaller than the wavelength as in the previous example. The optical axis 85a is parallel to the lattice structure as shown. When incorporated in a liquid crystal element, the surface of the substrate body 76 on which the above structure is formed is disposed so as to be perpendicular to the illumination optical axis or the projection optical axis, and also in a plane orthogonal to the illumination optical axis or the projection optical axis. The portions with different refractive indices become a one-dimensional array. The phase difference is the product of the height h of the protrusion 84 and its refractive index. When the height h increases with respect to the wavelength, the refractive index anisotropy deviates from one axis and becomes two axes. As it becomes larger, it approaches a negative c-plate.
[0087]
Further, when the structural birefringent layer 85 is provided on the outer surface side of the substrate body 76, the lattice structure by the protrusions 84 may be in contact with the air layer, but other dielectric layers having different refractive indexes may be used. In addition, it may be entirely covered so as to fill the gaps between the protrusions 84. Similarly, when provided on the inner surface side of the substrate body 76, the gaps between the protrusions 84 may be filled with other dielectric layers having different refractive indexes.
[0088]
Positive c-plate can also be used as the structural birefringent layer of the present invention. As shown in FIG. 18, the positive c-plate can be created by vertically growing a large number of protrusions 86 made of a transparent dielectric material on the surface of the substrate body 76. The size and the arrangement pitch of the protrusions 86 may be sufficiently small as compared with the wavelength of light as before. Since the surface of the substrate body 76 is arranged so as to be orthogonal to the illumination optical axis or the projection optical axis, unlike the structural birefringent layers 80, 82, 85 shown in FIGS. It is distributed two-dimensionally in a plane orthogonal to the illumination optical axis or the projection optical axis. The structural birefringent layer 87 having such a structure can also be formed by photolithography, and its optical axis 87a is perpendicular to the surface of the substrate body 76. Further, in the case where the physical structure portion is provided on the outer surface side of the substrate body 76, it may be in contact with the air layer as in the previous case, and another dielectric having a different refractive index on either the outer surface side or the inner surface side. It is also possible to use it in a form entirely covered with a body layer.
[0089]
Further, a positive o-plate can be obtained in the form shown in FIG. 19, and these structural birefringent layers having such a two-dimensional physical structure arrangement pattern are also effective for the purposes of the present invention. Can be used. The structural birefringent layer 90 shown in FIG. 19 is formed by regularly projecting protrusions 91 made of a transparent dielectric on the surface of the substrate 76 at a constant inclination angle, and can be formed by photolithography. Again, the size and repeat pitch of these structures must be sufficiently smaller than the wavelength of light, and the structure surface may be in contact with either the air layer or another transparent dielectric layer. The optical axis 90 a is inclined with respect to the surface of the substrate 76 as shown in the figure, and is parallel to the inclination direction of the protrusion 91.
[0090]
US Pat. No. 5,638,197 discloses that a positive o-plate can be obtained by depositing one kind of dielectric material in an oblique direction on the surface of the substrate body 76 as shown in FIG. It is also known in the specification (the aforementioned Patent Document 1). According to this method, a sufficiently small physical structure with respect to the wavelength of light can be easily obtained. The oblique lines shown in the figure are for schematically showing that the film is formed on the substrate 76 from the oblique direction, and do not represent individual thin film layers. This structural birefringent layer 93 is also used so that the surface of the substrate 76 is perpendicular to the illumination optical axis or the projection optical axis, and the obliquely disposed thin film layer 94 is an optical anisotropic of an o-plate birefringent body. Showing gender.
[0091]
When a plurality of structural birefringent layers are used in combination, it is possible to use different types of structural birefringent layers, and perform more precise phase difference compensation to reduce the contrast of the image projected on the screen. It can be improved further. In addition, the operation mode of the liquid crystal element to which the present invention can be applied includes not only the above-described transmissive TN liquid crystal mode, but also a reflective TN liquid crystal mode, known ECB (Electrically Controlled Birefringence), VA (Vertical Aligned), and OCB (OCB). Examples include various operation modes such as Optically Compensatory Bend (FLC) and FLC (Ferroelectric Liquid Crystal), and each color light of RGB passes through the liquid crystal elements at different incident angles as in the off-axis method and the microlens method. The present invention can also be applied to a projector that employs such an optical system. Also, the drive method is not limited to the active matrix drive method, and the present invention can be applied to various drive methods.
[0092]
Furthermore, when creating a structural birefringent layer in which thin film layers are laminated, the thicknesses of the layers do not necessarily have to be equal, and are not limited to alternately laminating two types of thin films. For example, three or more types of thin films with different refractive indexes may be stacked in an appropriate order and thickness, taking into consideration the ease of the film forming process, the absorption of strain due to internal stress of each layer, the wavelength dependency of the refractive index, etc. Can be designed appropriately. Further, the structural birefringent layer need not be composed of only a multilayer thin film in which two or more types of thin films having different refractive indexes are laminated. For example, the structural birefringent layer shown in FIGS. A combination with a multilayer thin film may also be used.
[0093]
【Example】
[Transmission type liquid crystal element]
To a glass plate with a thickness of 0.7 mm that becomes the substrate body on the common electrode side, ₂ And TiO ₂ 46 layers each having a film thickness of 15 nm were stacked by electron beam evaporation to form a structural birefringent layer. This structural birefringent layer had a thickness of 1.38 μm and exhibited a negative birefringence of 310 nm with respect to light having a wavelength of 550 nm. Next, an ITO film serving as a common electrode was formed thereon with a thickness of 100 nm by sputtering. Further, a resin film for forming an alignment film of polyimide was formed and rubbed to obtain an alignment film, thereby preparing a liquid crystal element substrate on the common electrode side. On the other hand, a pixel electrode array is formed on a glass plate having a thickness of 0.7 mm which is a substrate body on the pixel electrode side, and a polyimide alignment film forming resin film is formed and rubbed to obtain an alignment film. A liquid crystal element substrate on the electrode side was prepared.
[0094]
The liquid crystal element substrates prepared as described above are bonded so that the rubbing directions are orthogonal to each other, a nematic liquid crystal having a positive dielectric constant is sealed therebetween, and a resin microlens array is bonded to form a TN liquid crystal element. Created.
[0095]
The projector using the TN liquid crystal element shows a contrast of 550: 1 with respect to green light, which is improved compared to the contrast of the projector using the TN liquid crystal element without the structural birefringent layer, 350: 1. The effect was recognized.
[0096]
[Reflective liquid crystal element]
A vertical alignment polyimide alignment film was formed on the silicon substrate on which the pixel electrode array was formed, and rubbed to prepare a liquid crystal element substrate on the pixel electrode side. Further, a structural birefringent layer and an ITO film serving as a common electrode are formed on a glass plate, a polyimide alignment film for vertical alignment is further formed on the ITO film, and rubbing is performed thereon, thereby the liquid crystal element substrate on the common electrode side It was created. The specifications of the glass plate, the structural birefringent layer, and the ITO film on the common electrode side are the same as those on the common electrode side of the transmissive liquid crystal element.
[0097]
The liquid crystal element substrates prepared as described above were bonded to each other so that the rubbing directions were opposite and parallel to each other, and a nematic liquid crystal having a negative dielectric constant was sealed between them to prepare a VA liquid crystal element.
[0098]
The projector using the VA liquid crystal element has a contrast of 900: 1 with respect to green light, which is improved compared to the contrast of the projector using the VA crystal element without the structural birefringent layer, which is 500: 1. The effect was recognized.
[0099]
【The invention's effect】
As described above, according to the present invention, the structural birefringent layer made of an inorganic material is formed on the substrate body of the liquid crystal element substrate that constitutes the liquid crystal element, and phase difference compensation is performed. The contrast of the image projected on the screen can be improved without being expensive and increasing the cost.
[Brief description of the drawings]
FIG. 1 is an external view schematically showing a rear type liquid crystal projector.
FIG. 2 is a schematic configuration diagram of a projection unit using a transmissive liquid crystal element.
FIG. 3 is a schematic cross-sectional view showing a schematic structure of a liquid crystal element.
FIG. 4 is an explanatory diagram showing a layer structure of a structural birefringent layer.
FIG. 5 shows a configuration example of a liquid crystal element substrate on the pixel electrode side.
FIG. 6 shows another configuration example of the liquid crystal element substrate on the pixel electrode side.
FIG. 7 shows a configuration example of a liquid crystal element substrate on the common electrode side.
FIG. 8 shows another configuration example of the liquid crystal element substrate on the common electrode side.
FIG. 9 shows an example of a liquid crystal element using a liquid crystal element substrate on the pixel electrode side provided with an interlayer insulating layer.
FIG. 10 shows an example in which a microlens is used in combination.
FIG. 11 shows an example in which a microlens is used in combination with a liquid crystal element in which a structural birefringence layer is provided on the outer surface of a liquid crystal element substrate on the common electrode side.
FIG. 12 is a schematic configuration diagram of a projection unit using a reflective liquid crystal element.
FIG. 13 illustrates a configuration example of a reflective liquid crystal element.
FIG. 14 shows an example in which a structural birefringent layer is formed on a silicon substrate.
FIG. 15 is a conceptual diagram showing an embodiment of a structural birefringent body having a shape pattern.
FIG. 16 is a conceptual diagram showing another embodiment of a structural birefringent body having a shape pattern.
FIG. 17 is a conceptual diagram showing another embodiment of a structural birefringent body having a shape pattern.
FIG. 18 is a conceptual diagram showing still another embodiment of a structural birefringent body.
FIG. 19 is a conceptual diagram showing still another embodiment of a structural birefringent body.
FIG. 20 is a conceptual diagram of a structural birefringent body formed by film formation from an oblique direction.
[Explanation of symbols]
3 screens
5 Projection unit
11R, 11G, 11B, 61R, 61G, 61B Liquid crystal element
12 Light source
26R, 26G, 26B Polarizing plate
28R, 28G, 28B Polarizing plate
24 Synthetic prism
25 Projection lens
30 LCD
31, 32, 65 Liquid crystal element substrate
33, 37 glass plate
34,67 thin film transistor
35,68 pixel electrodes
36, 40, 71 Alignment film
38 Structural Birefringent Layer
39 Common electrode
66 Silicon substrate

Claims (12)

In the substrate for a liquid crystal element in which the alignment film and the electrode are formed on the inner surface of the substrate body,
A structural birefringent layer made of an inorganic material is formed on at least one surface of a substrate body on which light transmitted through the liquid crystal layer is incident to compensate for an optical phase difference of the light transmitted through the liquid crystal layer. A substrate for a liquid crystal element. 2. The substrate for a liquid crystal device according to claim 1, wherein the structural birefringent layer includes a multilayer thin film having at least a thin film made of a high refractive index material and a thin film made of a low refractive index material. 3. The substrate for a liquid crystal element according to claim 2, wherein the structural birefringent layer is a multilayer thin film in which thin films made of a high refractive index material and thin films made of a low refractive index material are alternately laminated. The liquid crystal element substrate according to claim 1, wherein the structural birefringent layer is formed on an inner surface of the substrate body. 5. The substrate for a liquid crystal element according to claim 4, wherein the structural birefringent layer is formed between the substrate body and the electrode. The liquid crystal element substrate according to claim 5, wherein the electrode is a counter electrode for an active matrix driving method. The liquid crystal element substrate according to claim 1, wherein the structural birefringent layer is formed on an outer surface of the substrate body. 4. The substrate for a liquid crystal element according to claim 1, wherein the structural birefringent layer is formed on each of an inner surface and an outer surface of the substrate body. 5. In a liquid crystal element having a pair of substrate bodies arranged opposite to each other, an alignment film and an electrode formed on each of the opposing inner surfaces of each substrate body, and a liquid crystal layer between the pair of substrate bodies,
A structural birefringent layer made of an inorganic material is formed on at least one surface of a substrate main body on which light transmitted through the liquid crystal layer is incident, and compensates for an optical phase difference of the light transmitted through the liquid crystal layer. A liquid crystal element characterized by that. 10. The liquid crystal device according to claim 9, wherein the structural birefringent layer is a multilayer thin film in which thin films made of a high refractive index material and thin films made of a low refractive index material are alternately laminated. Illumination from a light source on a liquid crystal element having a pair of substrate bodies arranged opposite to each other, alignment films and electrodes respectively formed on opposing inner surfaces of each substrate body, and a liquid crystal layer between the pair of substrate bodies In a liquid crystal projector that irradiates light and images image light modulated by a liquid crystal element on a screen by a projection optical system,
A structural birefringent layer made of an inorganic material is formed on at least one surface of a substrate main body on which light transmitted through the liquid crystal layer is incident, and compensates for an optical phase difference of the light transmitted through the liquid crystal layer. A liquid crystal projector characterized by that. 12. The liquid crystal projector according to claim 11, wherein the structural birefringent layer is a multilayer thin film in which thin films made of a high refractive index material and thin films made of a low refractive index material are alternately laminated.

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