JP2004126434A - Lighting device, projection-type display device, and liquid crystal element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control outgoing light quantity for a wide range with less light loss in a lighting device, a projection-type display device having the lighting device, and a liquid crystal element suitable as a light quantity adjustment of the lighting device. <P>SOLUTION: The liquid crystal element 5 which has a liquid crystal macromolecule composite layer where macromolecules 152 oriented in one direction are dispersed in a state where they are separated in liquid crystals 151 between a pair of substrates, and in which the liquid crystals 151 and the macromolecules 152 are oriented in a direction where they are almost aligned or a direction different from each other in accordance with presence/no presence of an electric field applied to the liquid crystal macromolecule composite layer is arranged between a polarized light conversion means 4d aligning the a polarizing direction of illumination light in one direction, and light modulation devices 22-24. The polarizing direction of light which is made incident on the liquid crystal element 5 from the polarized light conversion means 4d is aligned in an orientation direction of the macromolecules 152 of the liquid crystal element 5. <P>COPYRIGHT: (C)2004,JPO

Description

【００２２】
【化２】

【００２３】
【表１】

【００２４】
【表２】

【００２５】
【表３】

【００２６】
【表４】

【００２７】
なお、上述のモノマーは、後述の配向膜１０２，２０２により基板１００，２００間で平行配向した状態で重合，硬化されており、外部電界によって配向状態が変化することはない。
【００２８】
配向膜１０２，２０２は、例えばその配向方向が基板１００と基板２００とでアンチパラレルとなるように配向処理が施されており、液晶１５１及び液晶１５１中に添加された上述のモノマーを基板１００，２００間でホモジニアス配向させるようになっている。また、配向膜１０２，２０２は、液晶１５１のプレチルト角が例えば３°以下となるように配向処理されることが好ましい。このように液晶のプレチルト角を小さくすることで、電界の作用により液晶が高分子の配向方向と異なる方向に配向する際に、各液晶分子の立ち上がり方向がランダムとなり、液晶素子の散乱性を高めることができる。特に、プレチルト角を３°以下とすることで、プレチルト角による立ち上がりの方向性より電界による立ち上がりの方向性が支配的となり立ち上がりの方向性がランダムとなるため良好な散乱特性が得られる。
【００２９】
このように液晶１５１及びモノマーを配向させる手段としては、一般にポリイミド膜をラビングする方法が用いられるが、イミド結合は光や熱等により分解され易いことが知られており、特に液晶素子を光束密度が２〜１０ｌｍ／ｍｍ２程度の強度の強い光が照射される投射型表示装置等に搭載する場合に素子の信頼性を損なう虞がある。このため、本実施形態では、一酸化珪素等の無機膜を蒸着装置により基板１００，２００上に斜方蒸着したものを配向膜１０２，２０２として用いている。
【００３０】
図２は蒸着装置３００の概略構成を示しており、蒸着装置３００は蒸着室３０８中に一酸化珪素等の蒸着部材を充填された蒸着源３０２が備えられ、この蒸着源３０２の上方に仕切り部３０３を介して基板設置部３０７が設けられている。
この基板設置部３０７は基板１００（又は基板２００）の取り付け角度を蒸着源３０２からの蒸発流の流出方向に対して斜めに設置できるようになっている。また、仕切り部３０３には開口部３０３ａが形成されており、蒸着源３０２からの蒸発流が基板１００（又は基板２００）に向けて流出できるようになっている。
【００３１】
上述の液晶素子は、例えば以下のように製造される。
まず、ガラス等からなる二枚の透明な基板１００，２００の表面にスパッタリング等によりＩＴＯ等からなる透明電極１０１，２０１を形成し、続いて、図２に示した蒸着装置３００を用いて透明電極１０１，２０１上に２０ｎｍ程度の膜厚の配向膜１０２，２０２を形成する。この際、まず、基板設置部３０７により基板１００，２００の法線方向を鉛直方向に対して例えば６０°傾けて設置し、真空ポンプ３１０により蒸着室３０８を真空にする。そして、図示しないヒータにより蒸着源３０２を加熱して蒸着部材を蒸発させ、蒸発流を開口部３０３ａを介して基板１００，２００に向けて流出させる。この際、ヒータの温度や開口部３０３ａに設けられた図示しないシャッタの開閉量を調節することで、蒸着速度や蒸着量或いは得られる配向膜１０２，２０２の配向性等を制御することができる。また、基板の設置角度を制御することによって、配向膜によって付与されるプレチルト角を制御することができる。
【００３２】
このように無機物を基板面に対して斜め方向から蒸着した場合、基板１０１，２０１上には、蒸着方向を長軸方向とする無機の柱状構造物が形成される。この柱状構造物は蒸着条件によってその密度を変化させることができ、例えば上記構造物を基板上に疎に形成した場合には、この無機膜近傍の液晶分子やモノマーはその長軸方向が上記構造物の長軸方向に沿うように配向する。また、上記構造物を基板上に密に形成した場合には、無機膜近傍の液晶分子等は構造物の長軸方向に垂直な方向に配向する。
【００３３】
次に、基板１００，２００を、透明電極１０１，２０１が対向するように封止材（図示略）を介して貼り合わせる。この際、各基板１００，２００の配向方向は、上記二枚の基板１００，２００を組み合わせたときに互いにアンチパラレルとなるようにする。また、散乱強度を十分確保するために基板間隔（セル厚）を例えば７．５μｍ程度とする。
【００３４】
次に、上述の高分子前駆体を液晶１５１中に添加した液晶組成物を、基板１００，２００と封止材とにより形成された空間内に充填する。そして、基板表面から紫外線等を照射して高分子前駆体を重合，硬化させ、液晶１５１と高分子１５２とを相分離して、液晶高分子複合層１５０を形成する。
以上により、液晶素子が製造される。
【００３５】
本実施形態の液晶素子は、上述のように構成されているため、電圧無印加状態では、液晶１５１及び高分子１５２の実効的な屈折率が略一致し、液晶素子に入射した光は液晶１５１と高分子１５２との界面で散乱されることなく透過する。この結果、液晶素子は良好な透明状態となる。
【００３６】
一方、透明電極１０１，２０１間に電圧を印加すると、高分子１５２の配向は固定されたまま、液晶１５１のみ基板１００，２００に対して略垂直に配向する。しかし、高分子界面に存在する液晶分子は高分子１５２とのアンカリングにより電界により配向方向を変えない。よって液晶１５１には異なる方向の液晶分子が存在することになり、液晶の屈折率異方性に起因した大きな屈折率差が生じる。このような液晶素子に、高分子１５２の配向方向と平行な偏光軸を持った直線偏光が入射すると、入射光は液晶１５１中で強く散乱される。この際、液晶１５１のプレチルト角が小さいため、電圧印加によって液晶分子が立ち上がるときに各液晶分子の立ち上がり方向がランダムになり、又、高分子１５２の影響で液晶分子の立ち上がり角に一定の幅を生じるため、散乱強度はより大きくなる。また、高分子１５２は液晶１５１中に細かいブロックとして均一に分散されているため、このような散乱は略基板全面に亘って観察される。この結果、液晶素子は上述の直線偏光に対して良好な散乱状態となる。
【００３７】
したがって、本発明によれば、配向膜１０２，２０２によってモノマーを配向させた状態で重合を行なっているため、得られた高分子１５２は、各分子の配向方向が一方向に揃った状態で液晶１５１中に分散されることになる。このため、高分子１５２が無秩序に配向したものに比べて高分子界面付近での液晶１５１の配向乱れが少なくなり、電圧無印加時（即ち、液晶１５１と高分子１５２との実効的な屈折率を一致させた状態）における液晶素子の透明性が高まる。また、配向膜１０２，２０２により電圧無印加時の液晶１５１の配向状態を規定できるため、電圧印加時（即ち、液晶１５１中に屈折率分布を持たせた状態）における散乱強度を更に高めることができる。これにより、光利用効率が高くコントラストの高い液晶素子が得られる。
【００３８】
また、液晶のプレチルト角を小さくしているため、電圧印加により液晶を高分子１５２と異なる方向に配向させる場合に、各液晶分子の立ち上がり方向がランダムになり、素子の散乱性を更に高めることができる。
さらに、本構成では、配向膜１０１，２０１にポリイミドを用いていないため、耐光性や耐熱性に優れた液晶素子を得ることができる。
【００３９】
［照明装置及び投射型表示装置］
次に、本発明の電子機器の一例としての投射型表示装置について説明する。
図３は、本発明の一実施形態に係る投射型表示装置の全体構成を示す模式図であり、図４は、その駆動回路の機能的な構成を示すブロック図である。
【００４０】
図３に示すように、本実施形態の投射型表示装置は、Ｒ（赤）、Ｇ（緑）、Ｂ（青）の異なる色毎に透過型液晶ライトバルブ（光変調装置）２２〜２４を備えた３板式の投射型カラー液晶表示装置であり、光源２，フライアイレンズ（インテグレータ）３，４，偏光変換装置（偏光変換手段）４ｄ，調光素子５を有する照明装置１と、ダイクロイックミラー１３，１４，反射ミラー１５〜１７，レンズ１８〜２０，液晶ライトバルブ２２〜２４，クロスダイクロイックプリズム２５，投射レンズ２６を有する投射光学系３０とを備えて構成されている。
【００４１】
光源２は高圧水銀ランプ或いはメタルハライドランプ等のランプ７とランプ７の光を反射するリフレクタ８とから構成されている。また、光源光の照度分布を被照明領域である液晶ライトバルブ２２，２３，２４において均一化させるための均一照明手段として、光源２側から第１フライアイレンズ３、第２フライアイレンズ４が順次設置されている。各フライアイレンズ３，４は、複数（本実施形態では例えば６×８個）のレンズ９，１０から構成されている。そして、光源２から射出された光は、フライアイレンズ３，４によって被照明領域である液晶ライトバルブにおいて照度分布を均一化されて出射されるようになっている。
【００４２】
偏光変換装置４ｄは、均一照明手段側に設けられた偏光ビームスプリッタアレイ（ＰＢＳアレイ）と、ＰＢＳアレイによって反射された偏光の偏光方向を変換する１／２波長板アレイとから構成され、光源光の光強度を損なうことなく光の偏光方向を一方向に揃えるようになっている。
【００４３】
調光素子５は、上述した高分子分散型の液晶素子からなり、後述の調光素子ドライバからの駆動信号により透過率を変更され、光量調整した光源光を投射光学系３０に出力するようになっている。また、この調光素子５は、高分子１５２の配向方向が、偏光変換装置４ｄから入射される偏光の偏光方向及び液晶ライトバルブ２２〜２４の光源２側の偏光板の透過軸方向と略一致するように配置されており、光の変調幅を最大限大きくできるようになっている。
【００４４】
このような照明装置１では、電圧無印加時には、調光素子５は上述のように高い透過率を示すため、偏光変換装置４ｄによって偏光方向を一方向に揃えられた光源光Ｌｉｎは光損失を殆ど受けることなくライトバルブ２２（〜２４）側に出射される（図５（ａ）参照）。一方、電圧印加時には、液晶分子の配向変化が、入射光Ｌｉｎの偏光方向及び入射光の伝播方向を含む平面内で生じるため、入射光Ｌｉｎの感じる屈折率変化は最も大きくなる。このため、光源光Ｌｉｎは強く散乱され、ライトバルブ２２（〜２４）に入射される光の光量は最も少なくなる（図５（ｂ）参照）。
【００４５】
したがって、本照明装置１によれば、調光を行なわない場合（即ち、電圧無印加時）に、偏光変換装置４ｄから入射された照明光の光損失を極力低減できるとともに、照明光を調光してライトバルブ側に出射する場合（即ち、電圧印加時）に、出射光量を最大限広い範囲で調節できる。
【００４６】
ダイクロイックミラー１３，１４は、例えばガラス表面に誘電体多層膜を積層したもので、所定の色光を選択的に反射し、それ以外の波長の光を透過するようになっている。すなわち、青色光・緑色光反射のダイクロイックミラー１３は、光源２からの光束のうちの赤色光ＬＲを透過させるとともに、青色光ＬＢと緑色光ＬＧとを反射するようになっている。また、緑色光反射のダイクロイックミラー１４は、ダイクロイックミラー１３で反射された青色光ＬＢと緑色光ＬＧの内、青色光ＬＢを透過し緑色光ＬＧを反射するようになっている。
【００４７】
これにより、照明装置１から入射された光の内、赤色光ＬＲはダイクロイックミラー１３を透過した後、反射ミラー１７で反射され、赤色光用ライトバルブ２２に入射される。緑色光ＬＧはダイクロイックミラー１４に反射されて緑色光用ライトバルブ２３に入射される。青色光ＬＢはダイクロイックミラー１４を透過した後、リレーレンズ１８、反射ミラー１５、リレーレンズ１９、反射ミラー１６、リレーレンズ２０からなるリレー系２１を経て、青色光用ライトバルブ２４に入射されるようになっている。
【００４８】
ライトバルブ２２〜２４は、例えばアクティブマトリクス型の透過型液晶装置として構成され、各ライトバルブ２２〜２４で変調された色光ＬＲ，ＬＧ，ＬＢは、クロスダイクロイックプリズム２５に入射されるようになっている。
クロスダイクロイックプリズム２５は、直角プリズムが貼り合わされた構造となっており、その内面に赤色光ＬＲを反射するミラー面と青色光ＬＢを反射するミラー面とが十字状に形成されている。そして、三つの色光ＬＲ，ＬＧ，ＬＢがこれらのミラー面によって合成されてカラー画像を表わす光が形成された後、投射レンズ２６によりスクリーン２７上に拡大投射されるようになっている。
【００４９】
次に、本実施形態の投射型液晶表示装置の駆動方法について説明する。
本実施形態の投射型表示装置では、映像信号に基づいて調光素子５を駆動することで照明装置１の光出力を制御するようになっており、デジタル信号処理ブロックであるＤＳＰ（１）〜ＤＳＰ（２）や、映像信号をＡＤ変換或いはＤＡ変換するためのＡＤコンバータ３１，ＤＡコンバータ３７等の回路を備えている。
【００５０】
本実施形態では、図４に示すように、アナログ信号として入力された映像信号がＡＤコンバータ３１を経て第１のデジタル信号処理回路であるＤＳＰ（１）３２（制御信号決定手段）に入力される。そして、このＤＳＰ（１）により、映像信号から調光素子５に印加する電圧値、即ち、調光素子５の透過率を決める明るさ制御信号が決定され、ＤＳＰ（２）３３に入力される。そして、このＤＳＰ（２）３３により、明るさ制御信号に基づいて調光素子ドライバ３４が制御され、最終的に、この調光素子ドライバ３４により調光素子５が駆動される。
一方、ＤＳＰ（１）３２に入力された映像信号は、ＤＡコンバータ３７により再びアナログ信号に変換された後、パネルドライバ３８に入力され、パネルドライバ３８から各ライトバルブ２２〜２４に各色毎の映像信号が供給される。
【００５１】
したがって、本発明の投射型表示装置によれば、光源２と投射光学系３０との間に高コントラストな調光素子５を配置して出力光を調整しているため、光源２の光出力強度が一定のままでも投射光学系３０に対して所望の光量の光を出力することができる。これにより、投射表示装置のダイナミックレンジを拡大でき、映像表現力に優れた投射表示装置を実現することができる。
【００５２】
［第２実施形態］
次に、図６を用いて本発明の第２実施形態に係る液晶素子について説明する。
本液晶素子は、図６に示すように、内面側に透明電極１０１′，２０１′の形成された基板１００，２００により液晶高分子複合層１５０が挟持された構成となっている。
【００５３】
基板表面の透明電極１０１′，２０１′には直接ラビング処理が施されており、ラビングにより生じた細かい傷により、基板に接する液晶分子やモノマーをラビング方向に沿って配向させるようになっている。また、このように透明電極１０１′，２０１′を直接ラビング処理した場合、基板に対し垂直方向へ立ち上がる物質の存在がないため、液晶１５１にプレチルト角を殆ど付与しない構造とすることができる。そして、これらの基板１００，２００は、ラビング方向が互いにアンチパラレルとなるように貼り合わされ、液晶１５１及び液晶１５１中に添加されたモノマーを基板１００，２００間でホモジニアス配向させるようになっている。
【００５４】
上述の液晶素子は、例えば以下のように製造される。
まず、ガラス等からなる二枚の透明な基板１００，２００の表面にスパッタリング等によりＩＴＯ等からなる透明電極１０１′，２０１′を形成し、続いて、この透明電極１０１′，２０１′上を一方向にラビングする。
【００５５】
次に、基板１００，２００を、透明電極１０１′，２０１′が対向するように封止材（図示略）を介して貼り合わせる。この際、各基板１００，２００の配向方向（ラビング方向）は、上記二枚の基板１００，２００を組み合わせたときに互いにアンチパラレルとなるようにする。また、散乱強度を十分確保するために基板間隔（セル厚）を例えば７．５μｍ程度とする。
【００５６】
次に、上述した液晶組成物を基板１００，２００と封止材とにより形成された空間内に充填した後、高分子前駆体を重合，硬化させ、液晶１５１と高分子１５２とを相分離して液晶高分子複合層１５０を形成する。
そして、これ以外は上記第１実施形態と同様であるため、その説明を省略する。
【００５７】
したがって、本構成でも、光利用効率が高くコントラストの大きい液晶素子を得ることができる。また、配向膜を用いていないため、液晶素子を安価に製造することができる。
【００５８】
［第３実施形態］
次に、図７を用いて本発明の第３実施形態に係る液晶素子について説明する。
なお、図７（ａ），図７（ｂ）はいずれも本液晶素子の断面構造を示す図であり、図７（ｂ）は図７（ａ）のＡ矢視図である。
【００５９】
本液晶素子は、図７（ｂ）に示すように、内面側に透明電極１０１′′，２０１′′の形成された基板１００′′，２００′′により液晶高分子複合層１５０が挟持された構成となっている。
【００６０】
基板１００′′，２００′′の内面側には、それぞれ所定幅の複数の溝１１０，２１０が一定間隔でストライプ状に形成されており、透明電極１０１′′，２０１′′の表面には、これらの溝１１０，２１０に対応してストライプ状の溝１１１，２１１が形成されている。このように透明電極１０１′′，２０１′′の表面に溝構造を形成した場合、溝１１１，２１１付近の液晶分子やモノマーは溝１１１，２１１の延在方向に沿って略揃って配向する一方、液晶１５１にはプレチルトが全く生じない構造となる。そして、これらの基板１００′′，２００′′は、溝１１０，２１０の延在方向が互いに平行となるように貼り合わされ、液晶１５１及び液晶１５１中に添加されたモノマーを基板１００′′，２００′′間でホモジニアス配向させるようになっている。
【００６１】
上述の液晶素子は、例えば以下のように製造される。
まず、ガラス等からなる二枚の透明な基板１００′′，２００′′の表面に、例えば幅０．５μｍ，深さ０．２μｍの溝を０．５μｍ間隔でストライプ状に複数形成し、その上にＩＴＯ等からなる透明電極１０１′，２０１′をスパッタリング等により形成する。
【００６２】
次に、基板１００′′，２００′′を、透明電極１０１′′，２０１′′が対向するように封止材（図示略）を介して貼り合わせる。この際、各基板１００′′，２００′′の配向方向（溝１１０，２１０の延在方向）は、上記二枚の基板１００′′，２００′′を組み合わせたときに互いに平行となるようにする。また、散乱強度を十分確保するために基板間隔（セル厚）を例えば７．５μｍ程度とする。
次に、上述した液晶組成物を基板１００′′，２００′′と封止材とにより形成された空間内に充填した後、液晶組成物中の高分子前駆体を重合，硬化させ、液晶１５１と高分子１５２とを相分離して液晶高分子複合層１５０を形成する。そして、これ以外は上記第１実施形態と同様であるため、その説明を省略する。
【００６３】
したがって、本構成でも、光利用効率が高くコントラストの大きい液晶素子を得ることができる。また、配向膜を用いていないため、信頼性の高い液晶素子を製造することができる。さらに、本構成では、液晶１５１にプレチルトが全く生じないため、散乱性を更に高めることができる。
【００６４】
なお、本発明は上述の実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で種々変形して実施することができる。
例えば、均一照明手段に関しては上記実施の形態のようなフライアイレンズ３、４に限ることなく、適宜変更が可能で、ロッドレンズ等のロッド状導光体を用いることもできる。また、光変調素子として透過型液晶ライトバルブ２２〜２４を用いた例を挙げたが、反射型液晶ライトバルブやＤＭＤ（Ｄｉｇｉｔａｌ　Ｍｉｒｒｏｒ　Ｄｅｖｉｃｅ）を適用することも可能である。
【００６５】
さらに、上記実施形態では、調光素子５によって、液晶ライトバルブ２２〜２４の被照明領域全面を照明する光量を調節する場合について説明したが、調光素子５の調光領域を複数に分割して、各分割された領域毎に透過光量を調節するようにしてもよい。この場合、例えば調光素子５をセグメント型の液晶素子、或いは、パッシブマトリクス型の液晶素子として構成する。
【００６６】
【実施例】
本発明者らは、本発明の効果を実証するために、本発明に係る投射型表示装置を実際に作製し、その照度の電圧依存性について調べた。その結果について以下、報告する。
【００６７】
本実施例で用いる液晶素子は、上記第２実施形態に示した構成を基本とし、液晶として塩素系液晶であるＴＬ２１５（商品名、メルク社製）を用い、この液晶中にジメタクリレートモノマー（表４のモノマー２６参照）を５ｗｔ％添加して液晶混合材料を作成した。
【００６８】
次に、ＩＴＯ付きガラス基板の表面をラビングし、ラビング方向がアンチパラレルとなるように貼り合わせて空セルを作製した。なお、セル厚は７．５μｍとした。続いて、この空セルに上述の液晶混合材料を真空注入し、紫外線を２０ｍＷ／ｃｍ２で３分間照射した。これにより、モノマーを光重合して高分子と液晶とを相分離させ、ホモジニアス配向したＰＤＬＣセルを作製した。
【００６９】
そして、このように作製したＰＤＬＣセルを用いて上記第１実施形態で説明した投射表示装置を作製した。すなわち、セルを図８中のＰ１の位置に配置し、偏光変換装置から入射される光の偏光方向とセルの高分子の配向方向とを一致させた。そして、投射光学系からスクリーン上に出射される光の照度Ｌをセルの印加電圧Ｖに対してプロットした（図９中のＬ１（Ａ）参照）。また、比較のため、上述のセルを図８中のＰ２で示す位置に配置し、同様の測定を行なった（図９中のＬ２（Ａ）参照）。なお、Ｐ１はＰＢＳと投射光学系との間の位置（即ち、インテグレータの外側となる位置）を示し、Ｐ２は一対のフライアイレンズからなるインテグレータの内側となる位置を示している。
【００７０】
その結果、印加電圧ＶＯＰが０Ｖ〜６Ｖの範囲では、照度ＬはＬ１（Ａ），Ｌ２（Ａ）共１７ｌｘ程度で略一定であり、印加電圧ＶＯＰが６Ｖを超えると照度Ｌは大きく下がり始めた。そして、印加電圧ＶＯＰが１５Ｖ以降になると照度Ｌは略一定値に収束し、Ｌ１（Ａ）では２ｌｘ程度となり、Ｌ２（Ａ）では１０ｌｘ程度となった。これは、液晶の配向方向と入射光の偏光方向とを一致させることにより大きな散乱が得られることを示している。そして、本実施例では、このように光学系を配置することで、照明装置の光量をコントラスト８以上の範囲で調光でき、実用上殆ど問題のないレベルの特性が得られた。
【００７１】
また、本実施例では、更に比較のため、セルの高分子の配向方向を９０°回転して（即ち、高分子の配向方向とＰＢＳからの入射光の偏光方向とを直交させて）配置し、同様の測定を行なった。なお、図９中のＬ１（Ｂ），Ｌ２（Ｂ）はそれぞれセルをＰ１，Ｐ２の位置に配置した時の特性を示している。
この結果、Ｌ２（Ｂ）ではＬ２（Ａ）と略同じ特性が得られる一方、Ｌ１（Ｂ）では照度Ｌは印加電圧ＶＯＰに対して略一定の値となった。これは、液晶分子の配向変化が、入射光の偏光方向と直交する平面内でのみ生じたことを示しており、基板上を単にラビングするのみでも良好な配向状態が得られることがわかる。
【図面の簡単な説明】
【図１】本発明の第１実施形態に係る液晶素子の構成を示す断面図である。
【図２】同、液晶素子の配向膜の蒸着装置を示す模式的断面図である。
【図３】同、投射型表示装置の構成を示す模式図である。
【図４】同、投射型表示装置の駆動回路構成を示すブロック図である。
【図５】同、投射型表示装置の作用を説明するための模式図である。
【図６】本発明の第２実施形態に係る液晶素子の構成を示す断面図である。
【図７】本発明の第３実施形態に係る液晶素子の構成を示す断面図である。
【図８】本発明の実施例に係る投射型表示装置の光学配置を示す図である。
【図９】同、投射型表示装置の散乱特性を示す図である。
【符号の説明】
１　照明装置、　５　調光素子（液晶素子）、５ｄ　偏光変換装置（偏光変換手段）、２２〜２４　ライトバルブ（光変調装置）、１００，２００　基板、１０１，２０１　透明電極、１０２，２０２　配向膜（無機膜）、１１１，２１１
溝（溝構造）、１５０　液晶高分子複合層、１５１　液晶、１５２　高分子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lighting device, a projection display device provided with the lighting device, and a liquid crystal element suitable for adjusting a light amount of the lighting device.
[0002]
[Prior art]
2. Description of the Related Art In recent years, the development of information equipment has been remarkable, and the demand for a thin display device with high resolution, low power consumption and high power consumption has been increased, and research and development have been promoted. Among them, a liquid crystal display device is expected to be a display device that can electrically control the arrangement of liquid crystal molecules and change optical characteristics, and can meet the above needs. As one form of such a liquid crystal display device, there is known a projection type liquid crystal display device (liquid crystal projector) that modulates light emitted from a lighting device with a liquid crystal light valve and then enlarges and projects the light on a screen.
[0003]
The projection type liquid crystal display device uses a liquid crystal light valve as light modulating means, and the projection type display device includes a digital mirror device (hereinafter abbreviated as DMD) in addition to the liquid crystal light valve. Light modulators have also been put to practical use. However, the conventional projection display device has the following problems.
(1) Sufficient contrast cannot be obtained due to light leakage or stray light generated by various optical elements constituting the optical system. That is, the range of displayable brightness (dynamic range) is narrow, and the image quality is inferior to that of an existing video monitor using a cathode ray tube (CRT).
(2) Even if an attempt is made to improve the quality of an image by various kinds of image signal processing, a sufficient effect cannot be exhibited because the dynamic range is fixed.
[0004]
As a solution to such a problem of the projection type display device, that is, as a method of expanding the dynamic range, it is conceivable to change the amount of light incident on the light modulation means (light valve) according to the video signal. At this time, since it is extremely difficult to control the light output of the light source itself such as a high-pressure mercury lamp, a method of arranging a dimming element capable of adjusting the amount of transmitted light between the light source and the light valve has been proposed. It has been proposed (for example, Patent Document 1). As such a light control element, a polymer dispersion type liquid crystal element (PDLC) which does not require a polarizing plate and has high light use efficiency can be suitably used.
[0005]
[Patent Document 1]
JP-A-9-116840
[Problems to be solved by the invention]
[0006]
However, conventional polymer-dispersed liquid crystal devices have disordered polymer orientation, so that even when the effective refractive indices of the liquid crystal and the polymer are matched, sufficient transparent display cannot be obtained, resulting in dimming. The light loss when not performing was large. In addition, since the orientation of the liquid crystal dispersed in the polymer becomes disordered, the difference between the average refractive index of the liquid crystal and the refractive index of the polymer becomes small, and even if the orientation between the liquid crystal and the polymer is made different, it is sufficient. A good scattering state cannot be obtained. For this reason, the contrast of the liquid crystal element was low, so that light control could not be performed sufficiently.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an illumination device capable of adjusting the amount of emitted light in a wide range with a small light loss, a projection display device including the illumination device, and a light amount adjustment of the illumination device. It is an object of the present invention to provide a liquid crystal element having high scattering intensity suitable for use.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an illuminating device of the present invention is an illuminating device for illuminating a light valve, comprising: a polarization conversion unit for aligning a polarization direction of illumination light in one direction; A liquid crystal polymer composite layer dispersed in a state of being phase-separated between a pair of substrates, and in a direction in which the liquid crystal and the polymer are substantially aligned according to the presence or absence of an electric field applied to the liquid crystal polymer composite layer Or a liquid crystal element oriented in different directions, wherein the liquid crystal element is provided between the polarization conversion means and the light modulation device, and the polarization direction of light incident on the liquid crystal element from the polarization conversion means is changed. It is characterized by being arranged in a direction substantially aligned with the orientation direction of the polymer.
[0009]
In this configuration, since the polymer of the liquid crystal element is aligned in one direction, the refractive index between the liquid crystal and the polymer is controlled by controlling the alignment of the liquid crystal, compared to a polymer in which the polymer is randomly aligned. Can be increased together with the transmittance of the liquid crystal element when the values are substantially equal to each other, and the scattering intensity of the liquid crystal element when the refractive indexes of the liquid crystal and the polymer are different. Therefore, light loss can be reduced when dimming is not performed, and the amount of emitted light can be adjusted over a wide range when dimming is performed. In addition, since the orientation direction of the polymer is substantially aligned with the polarization direction of the incident light, the orientation change of the liquid crystal molecules occurs in a plane including the polarization direction of the incident light and the propagation direction of the incident light, and the refraction felt by the incident light. The rate change is greatest. Thereby, the scattering of the element can be further enhanced.
[0010]
The electrode surface of at least one of the pair of substrates is rubbed so that the liquid crystal and the polymer near the surface of the one substrate are aligned substantially in the rubbing direction when no electric field is applied. It may be.
According to this configuration, since the alignment film made of polyimide is not used for at least one substrate of the liquid crystal element, the light resistance of the liquid crystal element is improved. For this reason, a highly reliable lighting device with little deterioration due to light can be obtained.
[0011]
In addition, an inorganic film is obliquely deposited on at least one substrate surface of the pair of substrates, and the liquid crystal and the polymer in the vicinity of the surface of the one substrate in a direction in which the inorganic film is formed when no electric field is applied. You may make it align substantially substantially.
When an inorganic substance is obliquely deposited on a substrate, an inorganic columnar structure is formed on the substrate with the deposition direction as a long axis direction, and liquid crystal molecules or polymer precursors are formed along the inorganic film forming direction. Are oriented. Note that the direction in which the inorganic film is formed refers to the major axis direction of the columnar structure or a direction perpendicular to the major axis direction. As described above, even with this configuration, since an alignment film made of polyimide is not used, a highly reliable lighting device with little deterioration due to light can be obtained.
[0012]
Furthermore, a groove structure is formed on the surface of at least one of the pair of substrates, and when no electric field is applied, the liquid crystal and the polymer near the surface of the one substrate substantially extend in the extending direction of the groove structure. Orientation may be aligned.
Even with this configuration, since an alignment film made of polyimide is not used, a highly reliable lighting device with little deterioration due to light can be obtained.
[0013]
According to another aspect of the invention, a projection display device includes the above-described lighting device.
According to this configuration, since an illumination device capable of adjusting the amount of emitted light in a wide range is provided, for example, information based on a video signal, a method based on a projection magnification, and external information such as a state of brightness in a use environment are used. By adjusting the amount of illumination light based on this, it is possible to obtain a display with a wide dynamic range and excellent image expressiveness.
[0014]
Further, the liquid crystal element of the present invention includes a liquid crystal polymer composite layer in which liquid crystal and a polymer are dispersed in a direction substantially aligned with each other, and a pair of substrates sandwiching the liquid crystal polymer composite layer. An alignment treatment is performed on the surface of the substrate to reduce the pretilt of the liquid crystal to 3 ° or less, and the liquid crystal and the polymer are substantially aligned according to the presence or absence of an electric field applied to the liquid crystal polymer composite layer. Orienting in different directions.
According to this configuration, both the transparency and the scattering property of the liquid crystal element can be increased as compared with the case where the polymer is randomly oriented, and a liquid crystal element with high contrast can be obtained.
In addition, since the pretilt angle of the liquid crystal is small, when the liquid crystal is oriented in a direction different from the orientation direction of the polymer by the action of the electric field, the rising direction of each liquid crystal molecule becomes random, and the scattering property of the liquid crystal element can be further improved. it can. In particular, by setting the pretilt angle to 3 ° or less, the directionality of the rising by the electric field becomes more dominant than the directionality of the rising by the pretilt angle, and the directionality of the rising becomes random, so that good scattering characteristics can be obtained.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
[Liquid crystal element]
Hereinafter, the liquid crystal device according to the first embodiment of the present invention will be described with reference to FIGS. In all of the following drawings, the thickness of each component, the ratio of dimensions, and the like are appropriately changed in order to make the drawings easy to see.
[0016]
As shown in FIG. 1, the liquid crystal element of the present invention is configured such that a liquid crystal polymer composite layer 150 is sandwiched between transparent substrates 100 and 200 made of glass or the like disposed to face each other. On the two substrates 100 and 200, transparent electrodes 101 and 201 made of a transparent conductive material such as ITO (indium tin oxide) are formed on the inner surface side (the liquid crystal polymer composite layer 150 side), respectively. Orientation films 102 and 202 are formed on the transparent electrodes 101 and 202, respectively.
[0017]
The liquid crystal polymer composite layer 150 is composed of a liquid crystal composition in which a particulate polymer 152 is dispersed in a liquid crystal 151 in a state of phase separation.
[0018]
The liquid crystal 151 is made of, for example, a nematic liquid crystal having a positive dielectric anisotropy, and is made of a material having a large refractive index anisotropy (Δn). From the viewpoint of reliability, the liquid crystal 151 preferably has a side chain such as an alkyl group, an alkoxy group, a fluorine group, or a chlorine group in a benzene skeleton, a cyclohexane skeleton, or an alkylene skeleton. It is desirable that the structure does not include a bonding group.
[0019]
The polymer 152 is obtained by polymerizing a polymer precursor (monomer) in the liquid crystal 151 in a liquid crystal phase state by, for example, ultraviolet light or the like. The polymer 152 is compatible with the liquid crystal 151 in the monomer state, and is polymerized when polymerized. 151 is used. In addition, a material having high liquid crystallinity is used for the above-described monomer so that the polymer 152 obtained by the polymerization becomes fine blocks and is uniformly dispersed in the liquid crystal 151.
[0020]
Note that the liquid crystallinity of a substance (for example, a monomer or a polymer) refers to the stability of the substance in a liquid crystal state, and the magnitude of the liquid crystallinity is determined by the molecular structure of the substance. Generally, a substance having a rod-shaped molecular structure has a higher liquid crystallinity. For example, a material having a molecular structure represented by the following general formulas (1) and (2) is preferably used. More specifically, those shown in Tables 1 to 4 below are used.
[0021]
Embedded image

[0022]
Embedded image

[0023]
[Table 1]

[0024]
[Table 2]

[0025]
[Table 3]

[0026]
[Table 4]

[0027]
The above-mentioned monomer is polymerized and cured in a state where it is parallel-aligned between the substrates 100 and 200 by the later-described alignment films 102 and 202, and the alignment state does not change due to an external electric field.
[0028]
For example, the alignment films 102 and 202 are subjected to an alignment process so that their alignment directions are anti-parallel between the substrate 100 and the substrate 200, and the liquid crystal 151 and the above-described monomer added to the liquid crystal 151 are coated on the substrate 100, 202. The alignment is performed homogeneously between 200 positions. Further, it is preferable that the alignment films 102 and 202 are subjected to alignment processing so that the pretilt angle of the liquid crystal 151 is, for example, 3 ° or less. By thus reducing the pretilt angle of the liquid crystal, the rising direction of each liquid crystal molecule becomes random when the liquid crystal is aligned in a direction different from the alignment direction of the polymer by the action of an electric field, thereby increasing the scattering of the liquid crystal element. be able to. In particular, by setting the pretilt angle to 3 ° or less, the rising direction due to the electric field becomes more dominant than the rising direction due to the pretilt angle, and the rising direction becomes random, so that good scattering characteristics can be obtained.
[0029]
As a means for aligning the liquid crystal 151 and the monomer, a method of rubbing a polyimide film is generally used. However, it is known that an imide bond is easily decomposed by light, heat, or the like. When mounted on a projection display device or the like to which strong light of about 2 to 10 lm / mm2 is applied, the reliability of the element may be impaired. For this reason, in the present embodiment, the alignment films 102 and 202 are obtained by obliquely depositing an inorganic film such as silicon monoxide on the substrates 100 and 200 using a deposition apparatus.
[0030]
FIG. 2 shows a schematic configuration of the vapor deposition apparatus 300. The vapor deposition apparatus 300 includes a vapor deposition source 302 filled with a vapor deposition member such as silicon monoxide in a vapor deposition chamber 308, and a partition section above the vapor deposition source 302. A substrate setting unit 307 is provided via 303.
The substrate setting section 307 can set the mounting angle of the substrate 100 (or the substrate 200) obliquely to the outflow direction of the evaporation flow from the evaporation source 302. An opening 303a is formed in the partition 303 so that the evaporation flow from the evaporation source 302 can flow toward the substrate 100 (or the substrate 200).
[0031]
The above-described liquid crystal element is manufactured, for example, as follows.
First, transparent electrodes 101 and 201 made of ITO or the like are formed on the surfaces of two transparent substrates 100 and 200 made of glass or the like by sputtering or the like, and then the transparent electrodes 101 and 201 are formed using the vapor deposition apparatus 300 shown in FIG. Alignment films 102 and 202 having a thickness of about 20 nm are formed on 101 and 201. At this time, first, the normal direction of the substrates 100 and 200 is set to be inclined by, for example, 60 ° with respect to the vertical direction by the substrate setting unit 307, and the vapor deposition chamber 308 is evacuated by the vacuum pump 310. Then, the evaporation source 302 is heated by a heater (not shown) to evaporate the evaporation member, and the evaporation flow is caused to flow toward the substrates 100 and 200 through the opening 303a. At this time, by adjusting the temperature of the heater and the opening / closing amount of a shutter (not shown) provided in the opening 303a, the vapor deposition rate and the vapor deposition amount, or the orientation of the obtained alignment films 102 and 202 can be controlled. Further, by controlling the installation angle of the substrate, the pretilt angle given by the alignment film can be controlled.
[0032]
When the inorganic substance is deposited obliquely with respect to the substrate surface in this manner, an inorganic columnar structure having the deposition direction as the major axis direction is formed on the substrates 101 and 201. The density of the columnar structure can be changed depending on the vapor deposition conditions. For example, when the above structure is sparsely formed on a substrate, the liquid crystal molecules and monomers near the inorganic film have the major axis direction of the above structure. It is oriented along the long axis direction of the object. When the above structure is densely formed on a substrate, liquid crystal molecules and the like near the inorganic film are oriented in a direction perpendicular to the major axis direction of the structure.
[0033]
Next, the substrates 100 and 200 are bonded via a sealing material (not shown) such that the transparent electrodes 101 and 201 face each other. At this time, the orientation directions of the substrates 100 and 200 are set to be anti-parallel to each other when the two substrates 100 and 200 are combined. In addition, in order to secure sufficient scattering intensity, the distance between the substrates (cell thickness) is set to, for example, about 7.5 μm.
[0034]
Next, a liquid crystal composition obtained by adding the above-described polymer precursor to the liquid crystal 151 is filled in a space formed by the substrates 100 and 200 and the sealing material. Then, the polymer precursor is polymerized and cured by irradiating ultraviolet rays or the like from the substrate surface, and the liquid crystal 151 and the polymer 152 are phase-separated to form the liquid crystal polymer composite layer 150.
Thus, a liquid crystal element is manufactured.
[0035]
Since the liquid crystal element of the present embodiment is configured as described above, the effective refractive indexes of the liquid crystal 151 and the polymer 152 substantially match when no voltage is applied, and light incident on the liquid crystal element At the interface between the polymer and the polymer 152 without being scattered. As a result, the liquid crystal element is in a good transparent state.
[0036]
On the other hand, when a voltage is applied between the transparent electrodes 101 and 201, only the liquid crystal 151 is oriented substantially perpendicular to the substrates 100 and 200 while the orientation of the polymer 152 is fixed. However, the liquid crystal molecules existing at the polymer interface do not change the alignment direction due to the electric field due to anchoring with the polymer 152. Therefore, the liquid crystal 151 has liquid crystal molecules in different directions, and a large refractive index difference is generated due to the refractive index anisotropy of the liquid crystal. When linearly polarized light having a polarization axis parallel to the orientation direction of the polymer 152 enters such a liquid crystal element, the incident light is strongly scattered in the liquid crystal 151. At this time, since the pretilt angle of the liquid crystal 151 is small, the rising direction of each liquid crystal molecule becomes random when the liquid crystal molecule rises by applying a voltage, and a certain width is given to the rising angle of the liquid crystal molecule under the influence of the polymer 152. As a result, the scattering intensity is higher. In addition, since the polymer 152 is uniformly dispersed as fine blocks in the liquid crystal 151, such scattering is observed over substantially the entire surface of the substrate. As a result, the liquid crystal element is in a good scattering state with respect to the linearly polarized light.
[0037]
Therefore, according to the present invention, since the polymerization is performed in a state where the monomers are oriented by the orientation films 102 and 202, the obtained polymer 152 has a liquid crystal state in which the orientation directions of the respective molecules are aligned in one direction. 151 will be distributed. For this reason, the disorder of the alignment of the liquid crystal 151 near the polymer interface is reduced as compared with the case where the polymer 152 is randomly aligned, and the effective refractive index between the liquid crystal 151 and the polymer 152 when no voltage is applied (ie, the effective refractive index between the liquid crystal 151 and the polymer 152). (In a state where coincides with each other), the transparency of the liquid crystal element is increased. Further, since the alignment state of the liquid crystal 151 when no voltage is applied can be defined by the alignment films 102 and 202, it is possible to further increase the scattering intensity when a voltage is applied (that is, a state where the liquid crystal 151 has a refractive index distribution). it can. Thereby, a liquid crystal element having high light use efficiency and high contrast can be obtained.
[0038]
In addition, since the pretilt angle of the liquid crystal is reduced, when the liquid crystal is oriented in a direction different from that of the polymer 152 by applying a voltage, the rising direction of each liquid crystal molecule becomes random, and the scattering of the element can be further improved. it can.
Further, in this configuration, since no polyimide is used for the alignment films 101 and 201, a liquid crystal element having excellent light resistance and heat resistance can be obtained.
[0039]
[Lighting device and projection display device]
Next, a projection display device as an example of the electronic apparatus of the invention will be described.
FIG. 3 is a schematic diagram illustrating an overall configuration of a projection display device according to an embodiment of the present invention, and FIG. 4 is a block diagram illustrating a functional configuration of a driving circuit thereof.
[0040]
As shown in FIG. 3, the projection type display device of the present embodiment includes transmission type liquid crystal light valves (light modulation devices) 22 to 24 for different colors of R (red), G (green), and B (blue). A three-plate projection color liquid crystal display device provided with a light source 2, a fly-eye lens (integrator) 3, 4, a polarization conversion device (polarization conversion means) 4d, a lighting device 1 having a dimming element 5, and a dichroic mirror 13, 14, a reflection mirror 15 to 17, a lens 18 to 20, a liquid crystal light valve 22 to 24, a cross dichroic prism 25, and a projection optical system 30 having a projection lens 26.
[0041]
The light source 2 includes a lamp 7 such as a high-pressure mercury lamp or a metal halide lamp, and a reflector 8 that reflects light from the lamp 7. Further, as uniform illumination means for equalizing the illuminance distribution of the light source light in the liquid crystal light valves 22, 23, and 24, which are the illuminated areas, a first fly-eye lens 3 and a second fly-eye lens 4 from the light source 2 side. It is installed sequentially. Each fly-eye lens 3, 4 is composed of a plurality of (for example, 6 × 8) lenses 9, 10 in the present embodiment. The light emitted from the light source 2 is emitted by the fly-eye lenses 3 and 4 with the illuminance distribution being made uniform in the liquid crystal light valve which is the illuminated area.
[0042]
The polarization conversion device 4d includes a polarization beam splitter array (PBS array) provided on the uniform illumination means side, and a half-wave plate array for converting the polarization direction of polarized light reflected by the PBS array. The light polarization direction is aligned in one direction without impairing the light intensity of the light.
[0043]
The light control element 5 is formed of the above-described polymer dispersion type liquid crystal element, the transmittance of which is changed by a drive signal from a light control element driver to be described later, and the light amount adjusted light source light is output to the projection optical system 30. Has become. In the light modulating element 5, the orientation direction of the polymer 152 substantially coincides with the polarization direction of the polarized light incident from the polarization conversion device 4d and the transmission axis direction of the polarizing plate on the light source 2 side of the liquid crystal light valves 22 to 24. The modulation width of light can be maximized.
[0044]
In such a lighting device 1, when no voltage is applied, the dimming element 5 exhibits a high transmittance as described above, so that the light source light Lin whose polarization direction has been aligned in one direction by the polarization conversion device 4d causes light loss. The light is emitted to the light valve 22 (to 24) side with almost no reception (see FIG. 5A). On the other hand, when a voltage is applied, the change in the orientation of the liquid crystal molecules occurs in a plane including the polarization direction of the incident light Lin and the propagation direction of the incident light, so that the change in the refractive index felt by the incident light Lin is the largest. For this reason, the light source light Lin is strongly scattered, and the amount of light incident on the light valves 22 (to 24) is minimized (see FIG. 5B).
[0045]
Therefore, according to the present illumination device 1, when dimming is not performed (that is, when no voltage is applied), the optical loss of the illumination light incident from the polarization conversion device 4d can be reduced as much as possible, and the illumination light is dimmed. When the light is emitted to the light valve side (that is, when a voltage is applied), the amount of emitted light can be adjusted in a widest range.
[0046]
The dichroic mirrors 13 and 14 are formed by laminating a dielectric multilayer film on a glass surface, for example, and selectively reflect light of a predetermined color and transmit light of other wavelengths. That is, the dichroic mirror 13 that reflects blue light and green light transmits the red light LR of the light flux from the light source 2 and reflects the blue light LB and the green light LG. The green light reflecting dichroic mirror 14 transmits the blue light LB and reflects the green light LG among the blue light LB and the green light LG reflected by the dichroic mirror 13.
[0047]
Thereby, the red light LR of the light incident from the illumination device 1 passes through the dichroic mirror 13, is reflected by the reflection mirror 17, and is incident on the light valve 22 for red light. The green light LG is reflected by the dichroic mirror 14 and enters the green light valve 23. After passing through the dichroic mirror 14, the blue light LB passes through a relay system 21 including a relay lens 18, a reflection mirror 15, a relay lens 19, a reflection mirror 16, and a relay lens 20, and is incident on a blue light valve 24. It has become.
[0048]
The light valves 22 to 24 are configured as, for example, active matrix type transmissive liquid crystal devices, and the color lights LR, LG, and LB modulated by the light valves 22 to 24 are incident on the cross dichroic prism 25. I have.
The cross dichroic prism 25 has a structure in which right angle prisms are bonded, and a mirror surface that reflects the red light LR and a mirror surface that reflects the blue light LB are formed in a cross shape on the inner surface. Then, after the three color lights LR, LG, LB are combined by these mirror surfaces to form light representing a color image, the light is enlarged and projected on the screen 27 by the projection lens 26.
[0049]
Next, a driving method of the projection type liquid crystal display device of the present embodiment will be described.
In the projection display device of the present embodiment, the light output of the illumination device 1 is controlled by driving the light control element 5 based on the video signal, and the DSP (1) to digital signal processing blocks are used. A circuit such as a DSP (2), an AD converter 31 for performing AD conversion or DA conversion of a video signal, a DA converter 37, and the like are provided.
[0050]
In the present embodiment, as shown in FIG. 4, a video signal input as an analog signal is input to a DSP (1) 32 (control signal determining means) as a first digital signal processing circuit via an AD converter 31. . A voltage value to be applied to the light control element 5 from the video signal, that is, a brightness control signal for determining the transmittance of the light control element 5 is determined by the DSP (1), and is input to the DSP (2) 33. . The DSP (2) 33 controls the dimming element driver 34 based on the brightness control signal, and finally the dimming element 5 is driven by the dimming element driver 34.
On the other hand, the video signal input to the DSP (1) 32 is again converted into an analog signal by the DA converter 37, and then input to the panel driver 38, and the video signal for each color is transmitted from the panel driver 38 to each of the light valves 22 to 24. A signal is provided.
[0051]
Therefore, according to the projection type display device of the present invention, the light output intensity is adjusted by arranging the high-contrast dimming element 5 between the light source 2 and the projection optical system 30 to adjust the output light intensity. It is possible to output a desired amount of light to the projection optical system 30 even if is kept constant. As a result, the dynamic range of the projection display device can be expanded, and a projection display device with excellent image expression power can be realized.
[0052]
[Second embodiment]
Next, a liquid crystal device according to a second embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 6, the present liquid crystal element has a configuration in which a liquid crystal polymer composite layer 150 is sandwiched between substrates 100 and 200 having transparent electrodes 101 ′ and 201 ′ formed on the inner surface side.
[0053]
The transparent electrodes 101 'and 201' on the surface of the substrate are directly subjected to rubbing treatment, and liquid crystal molecules and monomers in contact with the substrate are aligned along the rubbing direction by fine scratches generated by the rubbing. Further, when the transparent electrodes 101 ′ and 201 ′ are directly rubbed as described above, there is no substance that rises in the vertical direction with respect to the substrate, so that a structure in which a pretilt angle is hardly given to the liquid crystal 151 can be provided. The substrates 100 and 200 are bonded together so that the rubbing directions are antiparallel to each other, and the liquid crystal 151 and the monomer added to the liquid crystal 151 are homogeneously aligned between the substrates 100 and 200.
[0054]
The above-described liquid crystal element is manufactured, for example, as follows.
First, transparent electrodes 101 'and 201' made of ITO or the like are formed on the surfaces of two transparent substrates 100 and 200 made of glass or the like by sputtering or the like. Rub in the direction.
[0055]
Next, the substrates 100 and 200 are bonded via a sealing material (not shown) such that the transparent electrodes 101 'and 201' face each other. At this time, the orientation direction (rubbing direction) of each of the substrates 100 and 200 is set to be antiparallel to each other when the two substrates 100 and 200 are combined. In addition, in order to secure sufficient scattering intensity, the distance between the substrates (cell thickness) is set to, for example, about 7.5 μm.
[0056]
Next, after filling the above-mentioned liquid crystal composition into the space formed by the substrates 100 and 200 and the sealing material, the polymer precursor is polymerized and cured, and the liquid crystal 151 and the polymer 152 are phase-separated. Thus, a liquid crystal polymer composite layer 150 is formed.
The rest is the same as the first embodiment, and the description is omitted.
[0057]
Therefore, even with this configuration, a liquid crystal element having high light use efficiency and high contrast can be obtained. Further, since no alignment film is used, a liquid crystal element can be manufactured at low cost.
[0058]
[Third embodiment]
Next, a liquid crystal device according to a third embodiment of the present invention will be described with reference to FIG.
7 (a) and 7 (b) are views each showing a cross-sectional structure of the present liquid crystal element, and FIG. 7 (b) is a view taken in the direction of arrow A in FIG. 7 (a).
[0059]
In the present liquid crystal element, as shown in FIG. 7B, a liquid crystal polymer composite layer 150 is sandwiched between substrates 100 "and 200" on which transparent electrodes 101 "and 201" are formed on the inner surface side. It has a configuration.
[0060]
A plurality of grooves 110, 210 each having a predetermined width are formed in a stripe shape at regular intervals on the inner surface side of the substrates 100 '', 200 '', and the surfaces of the transparent electrodes 101 '', 201 '' are Stripe-shaped grooves 111 and 211 are formed corresponding to these grooves 110 and 210. When the groove structure is formed on the surfaces of the transparent electrodes 101 ″ and 201 ″ in this manner, the liquid crystal molecules and monomers near the grooves 111 and 211 are aligned substantially uniformly along the extending direction of the grooves 111 and 211. Thus, the liquid crystal 151 has a structure in which no pretilt is generated. These substrates 100 "and 200" are bonded so that the extending directions of the grooves 110 and 210 are parallel to each other, and the liquid crystal 151 and the monomer added to the liquid crystal 151 are coated with the substrates 100 "and 200". The alignment is performed homogeneously between "" and "".
[0061]
The above-described liquid crystal element is manufactured, for example, as follows.
First, a plurality of grooves having a width of 0.5 μm and a depth of 0.2 μm, for example, are formed in stripes at intervals of 0.5 μm on the surfaces of two transparent substrates 100 ″ and 200 ″ made of glass or the like. Transparent electrodes 101 'and 201' made of ITO or the like are formed thereon by sputtering or the like.
[0062]
Next, the substrates 100 "and 200" are bonded together via a sealing material (not shown) such that the transparent electrodes 101 "and 201" face each other. At this time, the orientation direction (extending direction of the grooves 110 and 210) of the substrates 100 "and 200" is parallel to each other when the two substrates 100 "and 200" are combined. I do. In addition, in order to secure sufficient scattering intensity, the distance between the substrates (cell thickness) is set to, for example, about 7.5 μm.
Next, after filling the above-mentioned liquid crystal composition into the space formed by the substrates 100 ″ and 200 ″ and the encapsulant, the polymer precursor in the liquid crystal composition is polymerized and cured to form the liquid crystal 151. And the polymer 152 are phase-separated to form the liquid crystal polymer composite layer 150. The rest is the same as the first embodiment, and the description is omitted.
[0063]
Therefore, even with this configuration, a liquid crystal element having high light use efficiency and high contrast can be obtained. Further, since an alignment film is not used, a highly reliable liquid crystal element can be manufactured. Further, in the present configuration, since no pretilt occurs in the liquid crystal 151, the scattering property can be further improved.
[0064]
Note that the present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the spirit of the present invention.
For example, the uniform illuminating means is not limited to the fly-eye lenses 3 and 4 as in the above embodiment, but can be appropriately changed, and a rod-shaped light guide such as a rod lens can be used. In addition, an example in which the transmission type liquid crystal light valves 22 to 24 are used as the light modulation elements has been described, but a reflection type liquid crystal light valve or a DMD (Digital Mirror Device) can be applied.
[0065]
Further, in the above-described embodiment, the case has been described where the amount of light for illuminating the entire illuminated area of the liquid crystal light valves 22 to 24 is adjusted by the dimming element 5, but the dimming area of the dimming element 5 is divided into a plurality. Thus, the amount of transmitted light may be adjusted for each divided area. In this case, for example, the light control element 5 is configured as a segment type liquid crystal element or a passive matrix type liquid crystal element.
[0066]
【Example】
The present inventors have actually manufactured a projection type display device according to the present invention and examined the voltage dependency of the illuminance to demonstrate the effect of the present invention. The results are reported below.
[0067]
The liquid crystal element used in this example is based on the configuration described in the second embodiment, and uses TL215 (trade name, manufactured by Merck) which is a chlorine-based liquid crystal as a liquid crystal. 4 monomer 26) was added at 5 wt% to prepare a liquid crystal mixed material.
[0068]
Next, the surface of the glass substrate with ITO was rubbed and bonded so that the rubbing direction was anti-parallel to produce an empty cell. The cell thickness was 7.5 μm. Subsequently, the above-mentioned liquid crystal mixed material was vacuum-injected into the empty cell and irradiated with ultraviolet rays at 20 mW / cm 2 for 3 minutes. As a result, the monomer was photopolymerized, and the polymer and the liquid crystal were phase-separated to produce a homogeneously aligned PDLC cell.
[0069]
The projection display device described in the first embodiment was manufactured using the PDLC cell manufactured as described above. That is, the cell was arranged at the position P1 in FIG. 8, and the polarization direction of the light incident from the polarization converter and the orientation direction of the polymer of the cell were matched. Then, the illuminance L of the light emitted from the projection optical system onto the screen was plotted against the voltage V applied to the cell (see L1 (A) in FIG. 9). For comparison, the above-mentioned cell was arranged at the position indicated by P2 in FIG. 8 and the same measurement was performed (see L2 (A) in FIG. 9). Note that P1 indicates a position between the PBS and the projection optical system (that is, a position outside the integrator), and P2 indicates a position inside the integrator including a pair of fly-eye lenses.
[0070]
As a result, when the applied voltage VOP is in the range of 0V to 6V, the illuminance L is approximately constant at about 17 lx for both L1 (A) and L2 (A), and when the applied voltage VOP exceeds 6V, the illuminance L starts to decrease significantly. . When the applied voltage VOP became 15 V or more, the illuminance L converged to a substantially constant value, and was about 2 lx in L1 (A) and about 10 lx in L2 (A). This indicates that large scattering can be obtained by matching the orientation direction of the liquid crystal with the polarization direction of the incident light. In this embodiment, by arranging the optical system in this manner, the light amount of the illumination device can be adjusted in a range of a contrast of 8 or more, and a level of a characteristic having practically no problem is obtained.
[0071]
In this example, for further comparison, the alignment direction of the polymer in the cell was rotated by 90 ° (that is, the alignment direction of the polymer and the polarization direction of the incident light from the PBS were orthogonalized). The same measurement was performed. Note that L1 (B) and L2 (B) in FIG. 9 show the characteristics when the cells are arranged at the positions P1 and P2, respectively.
As a result, in L2 (B), substantially the same characteristics as L2 (A) were obtained, while in L1 (B), the illuminance L was substantially constant with respect to the applied voltage VOP. This indicates that the alignment change of the liquid crystal molecules occurred only in a plane perpendicular to the polarization direction of the incident light, and it can be seen that a favorable alignment state can be obtained by simply rubbing the substrate.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a liquid crystal element according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing an apparatus for depositing an alignment film of a liquid crystal element.
FIG. 3 is a schematic diagram showing a configuration of the projection display device.
FIG. 4 is a block diagram showing a drive circuit configuration of the projection display device.
FIG. 5 is a schematic diagram for explaining the operation of the projection display device.
FIG. 6 is a cross-sectional view illustrating a configuration of a liquid crystal element according to a second embodiment of the present invention.
FIG. 7 is a cross-sectional view illustrating a configuration of a liquid crystal element according to a third embodiment of the present invention.
FIG. 8 is a diagram showing an optical arrangement of a projection display device according to an embodiment of the present invention.
FIG. 9 is a diagram showing a scattering characteristic of the projection display device.
[Explanation of symbols]
Reference Signs List 1 lighting device, 5 dimming element (liquid crystal element), 5d polarization conversion device (polarization conversion means), 22 to 24 light valve (light modulation device), 100, 200 substrate, 101, 201 transparent electrode, 102, 202 alignment film (Inorganic film), 111, 211
Groove (groove structure), 150 liquid crystal polymer composite layer, 151 liquid crystal, 152 polymer

Claims (6)

An illumination device for illuminating a light modulation device,
Polarization conversion means for aligning the polarization direction of the illumination light in one direction,
Having a liquid crystal polymer composite layer in which a polymer oriented in one direction is dispersed in a liquid crystal in a state of phase separation between a pair of substrates, depending on the presence or absence of an electric field applied to the liquid crystal polymer composite layer, Comprising a liquid crystal element in which the liquid crystal and the polymer are aligned in a direction substantially aligned or in different directions,
The liquid crystal element is provided between the polarization conversion unit and the light modulation device, and is arranged in a direction in which a polarization direction of light incident on the liquid crystal element from the polarization conversion unit is substantially aligned with an alignment direction of the polymer. A lighting device, characterized in that: Rubbing is performed on the electrode surface of at least one of the pair of substrates,
The lighting device according to claim 1, wherein the liquid crystal and the polymer near the surface of the one substrate are aligned substantially in the direction of the rubbing when no electric field is applied. An inorganic film is obliquely deposited on the surface of at least one of the pair of substrates,
The lighting device according to claim 1, wherein the liquid crystal and the polymer near the surface of the one substrate are aligned substantially in the same direction as the inorganic film when no electric field is applied. A groove structure is formed on the surface of at least one of the pair of substrates,
The lighting device according to claim 1, wherein the liquid crystal and the polymer near the surface of the one substrate are aligned substantially in the direction in which the groove structure extends when no electric field is applied. A projection display device comprising the lighting device according to claim 1. A liquid crystal polymer composite layer in which the liquid crystal and the polymer are dispersed in a phase separated state,
A pair of substrates sandwiching the liquid crystal polymer composite layer,
Out of the pair of substrates, at least one of the substrates is subjected to an alignment process to reduce the pretilt of the liquid crystal to 3 ° or less,
A liquid crystal element characterized in that the liquid crystal and the polymer are aligned in a direction in which the liquid crystal and the polymer are substantially aligned or in different directions depending on the presence or absence of an electric field applied to the liquid crystal polymer composite layer.

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