JP2004286961A - Optical element, light deflecting element, and image display device - Google Patents

Abstract

A liquid crystal including a liquid crystal composed of a chiral smectic C phase having a homeotropic alignment is provided between a pair of transparent substrates 2 so as to improve a wavefront aberration and obtain a sharp image. Layer 5 is filled. A plurality of line electrodes 6 are provided on at least one of the pair of substrates 2 so as to be spaced apart in the width direction of the substrate 2. The dielectric layer 4 is provided between the liquid crystal layer 5 and the line electrode 6. The filler 3 is filled between the line electrodes 6 to reduce the diffraction of the line electrodes 6. The thickness of the line electrodes 6 d, the refractive index at a wavelength of 546nm and _{n el,} a refractive index of the filler 3 is taken as _{n fl, "| (n el} -n fl) · d | <0.11 ( μm) ”.
[Selection] Fig. 9

Description

また、電界方向を反転させた時、液晶分子８は図３においてＸ軸を中心とした線対称の配置（第２の配向状態）を取り、偏光方向がＺ軸方向である直線偏光の進行方向は、図３（ａ）中のｂ´に示す通りとなる。
【００７９】
従って、この直線偏光に対して液晶層５に作用させる電界方向を制御することで、ｂとｂ´との２位置、即ち、２Ｓ分の光偏向が可能となる。
【００８０】
液晶層５の材料の代表的物性値（ｎｏ＝１．６，ｎｅ＝１．８）に対して得られる光偏向量について，光偏向量Ｓを計算した結果を図４に示す。図４に明らかなように、θ＝４５°付近が最も光偏向量が大きい。仮に、液晶分子８のチルト角θが２２．５°のとき、２Ｓ＝５（μｍ）の偏向量を得るためには、ここに示される通り、液晶の厚みを３２μｍ厚に設定すれば良い。また、ホメオトロピック配向強誘電液晶において、約７００Ｖ／ｃｍの電界に対して，０．１ｍｓの応答速度が報告されており（Ｏｚａｋｉ他、Ｊ．Ｊ．Ａｐｐｌ．Ｐｈｙｓｉｃｓ、Ｖｏｌ．３０、Ｎｏ．９Ｂ、ｐｐ２３６６−２３６８（１９９１）を参照）、サブｍｓオーダの十分高速な応答速度が得られる。
【００８１】
また、キラルスメクチックＣ相よりなる液晶においては、チルト角θは温度Ｔにより変化し、相転移点をＴｃとすると、θ∝（Ｔ−Ｔｃ）^βなる関係がある。βは材料により異なるが、０．５程度の値をとる。この特性を利用した温度制御で光偏向量を制御することも可能である。
【００８２】
例えば、仮にチルト角θとして上記の２２．５°を設定し、これに対応する温度をＴ_{θ＝２２．５°}とすれば、Ｔ＞Ｔ_{θ＝２２．５°}では，θ≦２２．５°であり、Ｔ≦Ｔ_{θ＝２２．５°}ではθ＞２２．５°であるため、温度によりチルト角θを制御でき、これによって光偏向量を制御できることとなる。また、位置制御に関しては、電界による微調を同様に行うことができ、温度、電界あるいはその両者の組合せにより適切な光偏向を達成できる。
【００８３】
以上は、電界強度がＥｓ以上で螺旋構造が解けてチルト角θが光学軸の傾斜角に等しい場合について説明したが、電界強度がＥｓ以下の場合には、上記θを液晶分子８の方向を平均化した光学軸の傾斜角として扱えば良い。
【００８４】
図５は、電界発生用の印加電圧とそれにともなう光偏向量の変化を示すグラフである。印加電圧は一般的には矩形波状である。図１及び図２の光偏向素子１の構成において、この電圧印加により液晶層５の内部に所定方向（±Ｙ方向）の電界が発生する。電圧の切替え直後に液晶分子８の回転が発生し、液晶物性や発生電界により決まる時間（光偏向方向切替時間）後、光偏向量が一定となる。この偏向方向は電圧値を保持する間は変化しない（光偏向方向保持時間）。
【００８５】
次に、本光偏向素子１のさらに詳細な構成や、その作用効果について説明する。
【００８６】
図６は、本実施の形態の光偏向素子１におけるライン電極６周辺の断面構造を説明するための模式図である。図６において、基板２上の隣接するライン電極６間には、透明な充填材３が充填されている。また、液晶層５と基板２上のライン電極６との間には誘電体層４が設けられている。なお、液晶層５と対向する側の基板２、ライン電極６等は図示を省略している。
【００８７】
また、ライン電極６として透明材料を用いることで、光利用効率を高め信号品質を向上させることができる。この場合、透明なライン電極６としては、酸化スズ（ＳｎＯ_２）、酸化インジウム（Ｉｎ_２Ｏ_３）、酸化インジウム・スズ（ＩＴＯ）、酸化亜鉛（ＺｎＯ）、酸化亜鉛・アンチモン（ＺｎＯ・Ｓｂ２０５）、酸化スズ・アンチモン（ＡＴＯ）などを用いることができる。
【００８８】
これらを形成する場合、ライン電極６の形状の開口マスクを重ねた状態で、スパッタリング法、蒸着法、イオンプレーティング法などの方法で直接基板２上に所定形状の膜を成長させる方法や、塗布法、浸漬法、ゾルゲル法などで基板全面に成膜させた後、所定のマスキングを施した上で、塩酸系エッチャントなどによりウェットエッチングさせ、あるいはドライエッチングする方法がある。
【００８９】
中でも、酸化亜鉛・アンチモン及び酸化スズ・アンチモンよりなるライン電極６の材料は、透明性に優れ、表面抵抗値も液晶に印加する電界を発生する上で問題のない値に制御でき、さらに、屈折率も従来多く使用されていた酸化インジウム・スズ（屈折率１．８〜２．０）に比較して小さく制御できるため、透明充填材との屈折率差を低くでき有用である。
【００９０】
これらのライン電極６を基板２上に形成する場合、回折を低減するため、隣接するライン電極６の電極幅を異なる値に設定したり、隣接する３本のライン電極６において形成される２つのライン電極６間の距離（ライン電極の中心線間距離）を異なる値に設定したり、隣接するライン電極６の電極厚を異なる値に設定したり、電極６の断面形状に曲線を持たせたりすることが有効である。ライン電極６の電極幅やライン電極間距離としては、光路内のライン電極６の形成面に周期構造が発生しないように、ランダマイズするのが好ましい。ただし、その構造によって、液晶層５に印加される電界が局所的に変動しない範囲に設定する必要がある。
【００９１】
具体的構造を、図７を参照して説明する。図７は、基板２、ライン電極６などの正面図（部分図）である。図７において、ライン電極６に番号（（ｉ−１）〜（ｉ＋３））をつけ、各ライン電極の幅をＷ、電極間距離をＤとした場合、
Ｗ_ｉ≠Ｗ_ｉ＋１，Ｗ_ｉ＋１≠Ｗ_ｉ＋２，Ｄ_{ｉ／ （ ｉ＋１ ）}≠Ｄ_{（ ｉ＋１ ） ／ （ ｉ＋２ ）}
を満たすように設定する。
【００９２】
図８は、基板２及びライン電極６の側面図（部分図）である。ライン電極６の電極厚は、図８に示すように、
ｔ_ｉ≠ｔ_ｉ＋１
とする。
【００９３】
透明な充填材３は、無機系であれば、酸化チタン（ＴｉＯ_ｘ）、窒化チタン（ＴｉＮ_ｘ）、酸化ジルコニア（ＺｒＯ_ｘ）、窒化ジルコニア（ＺｒＮ_ｘ）、酸化アルミニウム（ＡｌＯ_ｘ）、酸化シリコン（ＳｉＯ_ｘ）、ホウ素添加酸化シリコン（ＳｉＢＯ_ｘ）、ホウ素添加窒化シリコン（ＳｉＢＮ_ｘ）、炭化シリコン（ＳｉＣ）、硫化亜鉛（ＺｎＳ）、酸化シリコン−硫化亜鉛（ＳｉＯ_ｘ−ＺｎＳ）、炭化シリコン−硫化亜鉛（ＳｉＣ−ＺｎＳ）などを用いることができる。これらは、スパッタリング法、蒸着法、イオンプレーティング法、塗布法、浸漬法、ゾルゲル法などで、基板２の全面にライン電極６の膜厚以上に成膜させた後、ＣＭＰ（化学機械的研磨）により平坦化するのが望ましい。
【００９４】
透明な充填材３として有機系材料を用いる場合、光硬化又は熱硬化型樹脂が利用可能である。これらは、プレポリマー状態で基板２上にスピンコート、ディッピング、バーコートなどの塗布法や、スクリーン印刷、グラビア印刷、フレキソ印刷等の印刷法で形成可能である。基板２上の隣接するライン電極６間に充填するため、あらかじめ離型可能な平滑面と基板２とを光硬化又は熱硬化型樹脂を介して圧接し、硬化処理後、平滑面を剥離してもよい。
【００９５】
本実施の形態において、透明な充填材３はライン電極６の回折を低減させる目的で設けられるため、その屈折率はライン電極６の屈折率に極力近いことが望ましい。後述の実施例で示す通り、本出願人が検討したところ、該ライン電極６の厚みをｄ、屈折率（波長５４６ｎｍでの値、以下同様）をｎ_ｆｌとしたとき、
“｜（ｎ_ｅｌ−ｎ_ｆｌ）・ｄ｜”が、０．１１μｍ未満、さらに望ましくは０．０７μｍ未満のときに優れた光学特性を示した。
【００９６】
特に、透明な一対の基板２と、基板２間に充填されたホメオトロピック配向をなすキラルスメクチックＣ相よりなる液晶層５と、少なくとも一方の基板２上の光路を含む領域に配置された複数本のライン電極６と、基板２上の隣接するライン電極６間に充填された透明な充填材３と、を備え、ライン電極群の隣接する各ライン電極６に対して段階的に異なる電圧値を設定することで光を偏向させる光偏向素子１において、上記屈折率の関係を満たすことで、所定偏向位置と異なる位置に形成される回折光のビームスポットを抑えることができ有用である。
【００９７】
図９は、光偏向素子１の別の構成例におけるライン電極６周辺の断面構造を説明するための模式図である。図９において、前述の図９の構成の光偏向素子１と異なるのは、まず、液晶層５と基板２上のライン電極６との間に誘電体層４設けられている点である。なお、図９の例においても、液晶層５と対向する側の基板２、ライン電極６等は図示を省略している。この構成においても、透明な充填材３には前述の無機系あるいは有機系材料を用いることが可能である。特に有機系材料の場合、上記離型可能な平滑面に変え誘電体層４をそのまま使用してもよい。当然ながらこの場合は剥離の必要はない。また、有機材料を用いて誘電体層４と透明な充填材３を一体に成形することも可能である。この場合、上述の離型可能な平滑面を利用し、誘電体層４の厚みと透明充電材３の厚みの和に相当するギャップをあらかじめ確保した状態で、ライン電極６側の基板表面と平滑面を対向させ、硬化前のプレポリマーを充填させた後硬化させればよい。
【００９８】
有機材料によって透明な充填材３を形成し、誘電体層４を設けない場合、又は、誘電体層４が有機材料によって構成される場合、その液晶層５側表面に溶剤によって変質しないハードコートを形成するのが望ましい。特に、液晶層５を配向させるための配向膜として、溶剤に溶解しているタイプの物を用いる場合は、その形成時に溶剤が上記誘電体層４や透明な充填材３を変質させる恐れがあるため、ハードコートを形成するのは極めて有用である。
【００９９】
ハードコート層は溶剤に汚染されない無機材料が好ましく、酸化チタン（ＴｉＯ_ｘ）、窒化チタン（ＴｉＮ_ｘ）、酸化ジルコニア（ＺｒＯ_ｘ）、窒化ジルコニア（ＺｒＮ_ｘ）、酸化アルミニウム（ＡｌＯ_ｘ）、酸化シリコン（ＳｉＯ_ｘ）、ホウ素添加酸化シリコン（ＳｉＢＯ_ｘ）、ホウ素添加窒化シリコン（ＳｉＢＮ_ｘ）、炭化シリコン（ＳｉＣ）、硫化亜鉛（ＺｎＳ）、酸化シリコン−硫化亜鉛（ＳｉＯ_ｘ−ＺｎＳ）、炭化シリコン−硫化亜鉛（ＳｉＣ−ＺｎＳ）などを用いることができる。特に液晶の屈折率と近い酸化シリコン（ＳｉＯ_２）が界面反射を低減する上で優れている。
【０１００】
誘電体層４の機能は、液晶層５に印加する電界の局所的な変動を抑制することであり、光学的には、内部吸収、界面反射、回折等極力発生しないよう構成するのが望ましい。特に、界面反射については反射光がノイズ光となり結像性能を劣化させるので小さく抑える必要がある。誘電体層４としては、透明で電気的に絶縁性を有し、耐候性が高く、しかも複屈折性の小さいものが望ましく、無機材料であればガラス、有機材料であればポリカーボネート、アクリルなどを好適に用いることができる。特にガラスは複屈折がなく、変形が少ないことから有用である。
【０１０１】
後述の実施例で示す通り、本発明者が検討したところ、誘電体層４の屈折率をｎ_ｄｅとするとき、
｜ｎ_ｅｌ−ｎ_ｄｅ｜＜０．５６
さらに望ましくは、
｜ｎ_ｅｌ−ｎ_ｄｅ｜＜０．４６
であるときに、反射光によるコントラスト劣化が小さく、好適であることが確認できた。
【０１０２】
特に、透明な一対の基板２と、基板２間に充填されたホメオトロピック配向をなすキラルスメクチックＣ相よりなる液晶層５と、少なくとも一方の基板２上の光路を含む領域に配置された複数本のライン電極６と、基板２上の隣接するライン電極６間に充填された透明な充填材３と、を備え、ライン電極群の隣接する各ライン電極６に対して段階的に異なる電圧値を設定することで光を偏向させるようにした光偏向素子１において、これをピクセルシフト技術に応用した場合、光利用効率改善、コントラスト改善が図れて有用である。
【０１０３】
図１０は、光偏向素子１を用いた画像表示装置の概要を示す概念図である。図１０において、符号１１は、照明用の光源であり、白色あるいは任意の色の光を高速にＯＮ、ＯＦＦできるものであるならば、いかなる種類や型の光源であっても利用することができる。たとえば、ＬＥＤランプやレーザ光源、あるいは、白色のランプ光源などを２次元アレイ状に配列して、かかる光源に対して高速動作するシャッタを組合せたものなどを照明用の光源として用いることができる。
【０１０４】
符号１２は、光源から出た光を均一に画像表示素子１３に照射させるための照明装置であり、拡散板１２ａ、コンデンサレンズ１２ｂなどから構成される。
【０１０５】
符号１３は、照明装置１２から入射した均一の照明光を、画像フィールドを時間的に更に細分割した複数個の画像サブフィールドごとに、画像情報に基づいて空間光変調して、画像光として出射する画像表示素子である。画像表示素子１３としては、透過型液晶ライトバルブ、反射型液晶ライトバルブ、ＤＭＤ素子などを用いることができる。
【０１０６】
符号１４は、前記画像サブフィールドごとに、画像表示素子１３から出射される画像光の光路を偏向して、偏向画像光として出射する光偏向素子である。該光偏向素子１４により、画像サブフィールドごとの光路の偏向量に応じて、スクリーン１６上に投射される画像表示位置がずらされる状態となる画像パターンを表示させることが可能となり、画像表示素子３の実際の画素数を見かけ上増倍した画素数として、画像表示させることができる。
【０１０７】
符号１５は、画像表示素子１３に表示された画像パターンを観察するための光学部材であり、符号５は投射レンズ、符号６はスクリーンである。さらに、符号１７は光源１１を駆動するための光源駆動手段であり、符号１８は画像表示素子１３を駆動するための表示駆動回路であり、符号１９は光偏向素子１を駆動するための光偏向駆動回路である。また、符号２０は、光源駆動回路１７、表示駆動回路１８、光偏向駆動回路１９などを含め画像表示装置の全体を制御するための画像表示制御回路である。
【０１０８】
次に、図１０に示す画像表示装置の基本的な動作について説明する。光源駆動回路１７で制御されて光源１１から放射された光は、拡散板１２ａにより均一化された照明光となり、コンデンサレンズ１２ｂにより、光源駆動回路１７と同期して動作する表示駆動回路１８により制御されている画像表示素子１３をクリティカルに照明する。ここでは、画像表示素子１３の例として、透過型液晶パネル、すなわち、透過型液晶ライトバルブを用いている。透過型液晶ライトバルブからなる画像表示素子１３により空間光変調された照明光は、画像光として光偏向素子１に入射され、光偏向素子１から出射された出射光は、偏向画像光として、投射レンズ１５で拡大された後、スクリーン１６に投射される。すなわち、透過型液晶ライトバルブからなる画像表示素子１３の画像光の出射側に配置されている光偏向素子１によって、画像光は、光偏向駆動回路１９からの駆動信号に応じて、画素の配列方向に任意の距離だけシフト（偏向）された偏向画像光として出射されて、投射レンズ１５を介して、スクリーン１６上に投射される。
【０１０９】
なお、図１０においては、透過型液晶ライトバルブからなる画像表示素子１３の直後に、光偏向素子１を配置しているが、光偏向素子１の配置位置はかかる場合に限定されるものではなく、スクリーン１６の直前などに配置することとしても良い。ただし、スクリーン１６付近に配置する場合、光偏向素子１を形成する光偏向素子の大きさや、更には、光偏向素子を形成する透明電極の配設ピッチなどを、光偏向素子１の配置位置における画面サイズや画素サイズに応じて設定することが必要になる。
【０１１０】
しかし、いかなる配置位置に光偏向素子１４を配置する場合であっても、前記偏向画像光の光路のシフト（偏向）量は、画素ピッチの整数分の１であることが望ましい。すなわち、画素の配列方向に対して２倍の画素増倍を行なう場合は、偏向画像光の光路のシフト量は、画素ピッチの１／２とし、配列方向に対して３倍の画素増倍を行なう場合は、画素ピッチの１／３とすることが望ましい。また、光偏向素子４の構成によって、偏向画像光の光路のシフト量が画素ピッチよりも大きくなる場合には、光路のシフト量を画素ピッチの（整数倍＋整数分の１）の距離に設定してもよい。
【０１１１】
この光偏向素子１を画素配列方向の縦横２次元に用いることにより、例えば２倍の画像増倍を行なう光偏向素子を２枚用いることにより、見かけ上の画素４倍の効果が得られ、使用した透過型液晶ライトバルブの解像度以上の高精細な画像を表示することができる。また、光偏向素子１の構成によってシフト量が大きくなる場合には、シフト量を画素ピッチの（整数倍＋整数分の１）の距離に設定しても良い。いずれの場合も、画素のシフト位置に対応したサブフィールドの画像信号で透過型液晶ライトバルブである画像表示素子１３を駆動する。
【０１１２】
なお、図１０では、単板の透過型液晶ライトバルブと単色ＬＥＤランプを用いた単色の画像表示装置を示したが、３原色の光源１１と、照明装置１２と、３枚の画像表示素子１３とを用いて、３原色の画像を混合してフルカラー画像を表示させることもできる。また、単板の画像表示素子１３を時間順次に三原色光で照明するフィールドシーケンシャル方式でもフルカラー画像を表示することができる。この場合、三色の光源１１からの光路をクロスプリズムで混合して照明しても良いし、白色ランプ光源１１と回転カラーフィルターの組合せで、時間順次の三原色光を生成してもよい。
【０１１３】
【実施例】
本発明の一実施例について説明する。
【０１１４】
以下では、前述の図９を参照して説明した光偏向素子１を作成し、さまざまな条件で検証している。
【０１１５】
［実施例１］
大きさ３０ｍｍ×４０ｍｍ、厚さ３ｍｍのガラス製の基板２の中央領域表面に０．１ｍｍピッチ、０．０１ｍｍ幅、０．２μｍ厚の酸化インジウム・スズ（ＩＴＯ）よりなる１００本のライン電極６を、高周波マグネトロンスパッタリング法により形成した。そのピッチと幅は、フォトリソ工程により、あらかじめレジスト材料でライン電極６の形成部以外をカバリングし、成膜後、レジストをリフトオフすることで所定値を得た。このＩＴＯの屈折率をエリプソメータにより測定したところ、波長５４６ｎｍにおいて２．００であった（以後の屈折率測定値もすべて同波長による）。その後、レジストを洗浄除去した後、市販のＵＶ硬化樹脂を基板上に滴下し、１５０μｍ厚の誘電体（硼珪酸ガラス）をその上から重ね、加圧した状態で紫外線露光し、樹脂を硬化させた。このＵＶ硬化樹脂と硼珪酸ガラスの屈折率は、それぞれ１．６３、１．４７であった。この誘電体の表面に、ＩＰＡ（イソプロピルアルコール）に溶解したポリアミック酸を塗布して焼結させることで、ポリイミドよりなる垂直配向膜を形成した。これを基板２とし、同条件で作製した２枚の基板２を、ＩＴＯを半ピッチずらした状態で重ね、空セルを形成した。なお両基板２のギャップを調整するためのスペーサは、基板２の端部に配置し、この部分を接着剤で固定した。基板２を約９０度に加熱した状態で、二枚の基板２間に強誘電性液晶（チッソ製ＣＳ１０２９）を毛管法にて注入した。冷却後の液晶層５は透明であり、コノスコープ像観察から基板に垂直に配向していることが確認できた。
【０１１６】
図１１に示すように、この液晶サンプル２１に、レーザ光源２２により波長６３３ｎｍのＨｅ−Ｎｅレーザを照射した。レーザはビームエキスパンダ２３で電極６の形成部（１０ｍｍ幅）近傍まで広げて照射した。透過した光はコリメートレンズ２４で集光させた。集光面２５上には、０次光のビームスポットが形成され、近傍にかすかに回折光が発生していたものの、利用可能なレベルであった。
【０１１７】
本サンプル２１を図１０に示す画像表示装置の光偏向素子１の位置に挿入し、画像表示素子１３に対して、縦方向に１画素幅からなる白黒の周期的な線を形成させた。この周期的な線の数本分をＣＣＤカメラで撮影して、その画像をコンピュータに採り込み、画像処理ソフトウエアで幅方向の輝度分布を計算した。輝度の最高値Ｉｍａｘ（白部）と最低値Ｉｍｉｎ（黒部）を用いて、以下の式によりコントラストＣを低量化した。
【０１１８】
Ｃ_{ｓａｍｐｌｅ}＝（Ｉｍａｘ−Ｉｍｉｎ）／（Ｉｍａｘ＋Ｉｍｉｎ）
このサンプル２１に使用しているガラス基板２と同じ屈折率で、サンプル全体２１の厚さとほぼ等しい厚さのガラス基板を用意し、同様にコントラストＣ_{ｒｅｆｅｒｅｎｃｅ}を測定・計算した。両者の比Ｃ_{ｓａｍｐｌｅ}／Ｃ_{ｒｅｆｅｒｅｎｃｅ}（コントラスト比）は７５％であり、多重反射や回折による画像劣化は少ないことが判明した。そして、
（ｎ_ｅｌ−ｎ_ｆｌ）・ｄ
を計算したところ、０．０７４であった。
【０１１９】
［比較例１］
実施例１の比較例として、実施例１のＵＶ硬化樹脂に代えて屈折率１．４２のＵＶ硬化樹脂を用い、その他は実施例１と同様の条件で、サンプルの作製、その評価を実施した。これによると、数次の回折光がはっきり現れ、コントラスト比は５０％であり、良好な特性ではなかった。そして、
（ｎ_ｅｌ−ｎ_ｆｌ）・ｄ
を計算したところ、０．１１６であった。
【０１２０】
［比較例２］
実施例１の別の比較例として、実施例１のＵＶ硬化樹脂に代えて屈折率１．５２のＵＶ硬化樹脂を用い、その他は実施例１と同様の条件で、サンプル２１作製、その評価を実施した。その結果、数次の回折光がわずかに現れ、コントラスト比は６５％であった。光学特性としては、実施例１と比較例１の中間のものであるが使用可能なレベルであった。そして、
（ｎ_ｅｌ−ｎ_ｆｌ）・ｄ
を計算したところ、０．０９６であった。
【０１２１】
［実施例２］
大きさ３０ｍｍ×４０ｍｍ、厚さ３ｍｍのガラス製の基板２の中央領域表面に０．１ｍｍピッチ、０．０１ｍｍ幅、０．２μｍ厚の酸化亜鉛・アンチモン（ＺｎＯ−Ｓｂ２０５）よりなる１００本のライン電極６を形成した。酸化亜鉛・アンチモン微粒子をアルコール溶剤に分散させ、これを基板２にスピンコーティングした。その後、これを２００℃で加熱し固着させた。電極６のピッチと幅は、フォトリソ工程によりレジスト材料でライン電極形成部以外をカバリングした後、酸化亜鉛・アンチモンをドライエッチングした。そして、この酸化亜鉛・アンチモンの屈折率をエリプソメータにより測定したところ、波長５４６ｎｍにおいて１．６０であった。その後のデバイス化及び評価の工程を、比較例２と同様に実施した。すなわち、Ｈｅ−Ｎｅレーザを照射したところ、回折はまったく発生していなかった。コントラスト比は８０％であった。比較例２に比べて光学特性が向上していた。
【０１２２】
［実施例３］
実施例１，２、比較例１，２のサンプル構成で、ライン電極６、透明な充填材３の種類、厚みを変化させて、サンプル２１を作製し、上記回折とコントラストにかかる光学特性を評価した。
【０１２３】
結果を表１に示す。表１中、光学特性で、○は一次回折光が全く確認できないか、コントラスト比が７０％以上のものである。 △のものは、一次回折光がわずかに確認できるか、コントラスト比が７０％以下６０％以上のものである。×は、一次回折光がはっきり認識できるか、コントラスト比が６０％以下のものである。実施例１に示す条件は表中△で示される。
【０１２４】
【表１】

【０１２５】
この表から、光学特性は、透明ライン電極群の厚みｄ、屈折率ｎ_ｅｌ、および透明充填材の屈折率をｎ_ｆｌに依存し、
｜（ｎ_ｅｌ−ｎ_ｆｌ）・ｄ｜＜０．１１（μｍ）
を満たす場合に有用であることが判明した。
【０１２６】
また透明な充填材３の材料や厚みを選択する上で、ライン電極６の材料として酸化亜鉛・アンチモンが一般的な透明な充填材３の屈折率に近く、有用であることが判明した。酸化亜鉛・アンチモンに代えて、酸化スズ・アンチモンにて構成した場合も同様の結果が得られた。
【０１２７】
［実施例４］
比較例２と同様のサンプル２１の構成で、誘電体層４の種類を変化させてサンプル２１を作製し、上記と同様にコントラストにかかる光学特性を評価した。
【０１２８】
ライン電極材料の屈折率ｎ_ｅｌと誘電体層屈折率ｎ_ｄｅとの関係を表２に示す。２種の屈折率の異なる酸化インジウム・スズは酸化インジウムと酸化スズの配合比を変化させ得た。ここでの光学特性判定は、実施例１に示すコントラスト比に基づいて実施した。
【０１２９】
【表２】

【０１３０】
本実施例から、
｜ｎ_ｅｌ―ｎ_ｄｅ｜＜０．５６
さらに望ましくは、
｜ｎ_ｅｌ―ｎ_ｄｅ｜≦０．４６
であるときに、反射光によるコントラスト劣化が小さく、望ましいことが確認できた。
【０１３１】
また、ライン電極６の材料の屈折率として、基板２の材料や誘電体層４の材料の材料選択幅を広く持つ意味から、２．１０以下が望ましいといえる。
【０１３２】
［実施例５］
比較例２のＵＶ硬化樹脂に代えて、市販の２液性の熱硬化樹脂（屈折率１．５２）を使用した。硬化は，熱硬化樹脂を基板２上に塗布し、１５０μｍ厚の誘電体（硼珪酸ガラス）をその上から重ね、加圧した状態で一昼夜放置して硬化させた。その後，比較例２と同様にデバイス化し、光学特性を評価したところ、比較例２に示すＵＶ硬化樹脂と同程度の性能であり、使用可能な品質が得られた。
【０１３３】
［実施例６］
比較例２で形成したライン電極６を有する基板２に対して、３０ｍｍ長の短冊状マイラーフィルム（厚み１５０μｍ）を基板２の短辺側両端に配置し、その内部にポリカーボネート系のＵＶ硬化樹脂を滴下した。これは平滑なテフロン樹脂（テフロンは登録商標である（以下同様））で、その上から加圧し、ＵＶ照射することで硬化させた。テフロンを外して厚みを測定したところ、ほぼ１５０μｍの樹脂層（誘電体層４）が得られた。硬化後の樹脂層の屈折率は１．５８であった。その後ＳｉＯ_２膜をスパッタリング法で０．２μｍ形成した後、比較例２と同様にデバイス化し、光学特性を評価したところ、比較例２に示すＵＶ硬化樹脂よりも回折が少なく、コントラスト比に優れた特性が得られた。
【０１３４】
なお，ＳｉＯ_２を形成せずにＩＰＡ溶液を塗布したところ、樹脂よりなる誘電体層４の表面が劣化した。従って，無機透明材料よりなるハードコート層が有用であることが確認された。
【０１３５】
［実施例７］
実施例２と同様の方法で、酸化亜鉛・アンチモンよりなるライン電極６を形成した。その後、スパッタリング法でＳｉＯ_２膜を基板全面に２０００Å形成し、ＣＭＰによりこのＳｉＯ_２膜表面を研磨、平坦化した。ＳｉＯ_２膜の屈折率は１．４７であった。これに配向膜を形成し，以後の工程を実施例１と同様に行った。そして、光学特性を評価したところ、回折のないコントラスト比に優れた特性が得られた。
【０１３６】
［実施例８］
比較例２におけるライン電極６のパターン（０．１ｍｍピッチ、０．０１ｍｍ幅）に代え、表３に示すパターンを形成した。表３において、数値が範囲で示されている部分は、乱数によって各寸法を求めていった。その他の条件は比較例２と同様にデバイス化し、評価を行った。表３中に示すとおり、光学特性は比較例２に比較して性能が向上した。これは、比較例２でわずかに観察された１次回折光が、低減又は消滅したためである。従って、隣接するライン電極６の電極幅を異なる値に設定し、あるいは、隣接する３本のライン電極６において形成される２つの電極間距離（ライン電極６の中心線間距離）を異なる値に設定することの効果が確認できた。
【０１３７】
【表３】

【０１３８】
［実施例９］
大きさ３０ｍｍ×４０ｍｍ、厚さ３ｍｍのガラス製の基板２の全面に酸化インジウム・スズ（ＩＴＯ）を高周波マグネトロンスパッタリング法により形成した。一方、フォトリソ工程用の露光マスクとして、ＩＴＯ以外の部分を光が完全透過し、ＩＴＯ部分は、隣接するライン電極６毎に透過率が異なるものを用意した。ポジ型レジストを、上記ＩＴＯを全面に形成した基板２に塗布し、前記の露光マスクをＩＴＯ面に密着させ露光した。露光条件として、洗浄時に、ＩＴＯ以外の部分のレジストが完全に除去され、ＩＴＯ部分のレジストが、透過率に依存した厚みで残存するようにした。この状態でドライエッチングを行い、ライン電極６を形成した。各電極６は前記レジスト厚に依存し、その膜厚が変化している。この膜厚は０．１５μｍ〜０．２μｍとなるようにエッチング条件を設定した。その他の条件は、比較例２と同様にしてデバイス化し、その評価を行った。表１〜３中に示すとおり、光学特性は比較例２に比較して性能が向上した。これは、比較例２でわずかに観察された１次回折光が低減したためである。従って、隣接するライン電極６の電極厚を異なる値に設定することの効果が確認できた。
【０１３９】
［実施例１０］
比較例２の光偏向素子１の各ライン電極６を、異方性導電ペーストを介在させ、対応する金属線を有するフレキシブル基板と接続した。金属線の逆側には図１に示す抵抗回路７ａを接続し、抵抗回路７ａに電圧を印加することで、各ライン電極６に電位勾配が発生するようにした。このときの電位勾配は１００Ｖ／ｍｍとなるように電圧を選んだ。この電圧を印加しながら、図１０の装置を用いて画像表示を行った。この場合、電圧の方向を切り替えることで、画像表示素子１３の半ピッチ分の光路シフトがなされることを確認した。この場合の画像表示のフレーム周波数は６０Ｈｚとした。この時、サブフィールド時間は８．３ｍｓに相当する。
【０１４０】
表１に示す各サンプル２１に同様の実装を施し、画像表示装置内に装填し、ピクセルシフト画像を形成した。表１〜３中、○がついているサンプルではコントラストに優れた画像が得られた。一方、×がついているサンプル２１ではコントラストが低く画像品質が低下していた。
【０１４１】
このように、本発明の光学素子を用いることで、極めて良好な画像が得られる事を確認した。
【０１４２】
【発明の効果】
請求項１〜５に記載の発明は、電極が周期構造を持つ場合に光の回折が生じ、本来の結像位置とは異なる位置に結像することを防止して、波面収差を改善し、シャープな結像を得ることができる。
【０１４３】
請求項６に記載の発明は、請求項３〜５のいずれかの一に記載の発明において、一般に使用されている基板や誘電体層の材料との屈折率差が大きくなって、界面反射量が増加し、回折光量が増加することを防止して、波面収差を改善し、シャープな結像を得ることができる。
【０１４４】
請求項７に記載の発明は、請求項３〜６のいずれかの一に記載の発明において、透明性に優れ、表面抵抗値も液晶に印加する電界を発生する上で問題のない値に制御でき、屈折率も従来一般的に使用されていた酸化インジウム・スズに比較して小さく制御できるため、波面収差を改善し、シャープな結像を得ることができる。
【０１４５】
請求項８に記載の発明は、請求項３〜７のいずれかの一に記載の発明において、光硬化型樹脂を透明充填材として用いた場合、樹脂充填から硬化まで短時間に行えるので製造時間を短縮でき、熱硬化型樹脂を透明充填材として用いた場合、光硬化型樹脂を用いる場合に比べ光による劣化が発生しないため、通常白色照明下で製造作業が行えて作業性に優れる。また、いずれの樹脂においても十分な光透過性を確保でき、良好な光学特性が得られる。
【０１４６】
請求項９に記載の発明は、請求項４に記載の発明において、所望の厚みに制御でき、また、請求項８の充填材を介して電極を有する基板と貼り合せた後、光学研磨を行うことで、きわめて平滑性に優れた表面を得ることができ、かつ光の回折、散乱等を抑えることが可能となる。
【０１４７】
請求項１０に記載の発明は、請求項４又は９に記載の発明において、製造工程を短縮でき、請求項９の構造に比べて界面を減らすことができるため、光学性能の劣化を低減できる。
【０１４８】
請求項１１に記載の発明は、請求項４，９又は１０に記載の発明において、液晶の配向膜を形成する際に用いられる溶剤によって、光硬化又は熱硬化型樹脂よりなる誘電体層が変質することを防ぎ、誘電体層の変質による光学劣化を防止できる。
【０１４９】
請求項１２に記載の発明は、請求項３，４〜７，９のいずれかの一に記載の発明において、請求項８の充填材に比べて、組成による屈折率の選択自由度が大きく、電極との屈折率差を小さくすることができる。
【０１５０】
請求項１３に記載の発明は、請求項３，４〜７，９，１２のいずれかの一に記載の発明において、透過率が高く、組成により屈折率を調整できるため、電極との屈折率差を小さくできる。また、請求項７の電極に用いた場合、液晶層、電極、充填材がほぼ等しい屈折率に設定できるため、波面収差を改善し、シャープな結像を得ることができる。
【０１５１】
請求項１４に記載の発明は、請求項３〜１３のいずれかの一に記載の発明において、所定の方向とは異なる方向に進行するノイズ光を低減し、電極の配列に起因する光の回折が低減できる。
【０１５２】
請求項１５に記載の発明は、請求項１４に記載の発明において、所定の方向とは異なる方向に進行するノイズ光を低減し、電極の配列に起因する光の回折が低減できる。
【０１５３】
請求項１６に記載の発明は、請求項３〜１５のいずれかの一に記載の発明において、所定の方向とは異なる方向に進行するノイズ光を低減し、電極の配列に起因する光の回折が低減できる。
【０１５４】
請求項１７に記載の発明は、コントラスト、光利用効率を改善し、より高精細画像を得ることができる画像表示装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態である光偏向素子の全体構成の説明図である。
【図２】光偏向素子の液晶分子配向状態を模式的に示した説明図である。
【図３】光偏向素子の液晶分子配向状態を模式的に示した説明図である。
【図４】光偏向素子の液晶配向角と光軸シフト量との関係を示すグラフである。
【図５】光偏向素子の電圧と光偏向量の時間変化を示すグラフである。
【図６】光偏向素子におけるライン電極の周辺の断面構造を説明するための模式図である。
【図７】基板、ライン電極などの正面図である。
【図８】基板及びライン電極の側面図である。
【図９】光偏向素子の別の構成例におけるライン電極の周辺の断面構造を説明するための模式図である。
【図１０】本発明の一実施の形態である画像表示装置の概要を示す概念図である。
【図１１】本発明の一実施例を説明する説明図である。
【符号の説明】
１ 光学素子、光偏向素子
２ 基板
３ 充填層
４ 誘電体層
５ 液晶層
６ 電極
１３ 画像表示素子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical element using a liquid crystal, an optical deflecting element, and an image display device including the optical deflecting element.
[0002]
[Prior art]
Conventionally, various proposals have been made for an optical element which is a light deflecting element using a liquid crystal material (see Patent Documents 1 to 3).
[0003]
In addition, various proposals have been made for pixel shift elements (see Patent Documents 4 to 7).
[0004]
[Patent Document 1]
JP-A-6-18940
[Patent Document 2]
JP-A-9-133904
[Patent Document 3]
JP-A-10-221703
[Patent Document 4]
Japanese Patent No. 2939826
[Patent Document 5]
JP-A-5-313116
[Patent Document 6]
JP-A-6-324320
[Patent Document 7]
JP-A-10-133135
[0005]
[Problems to be solved by the invention]
Regarding the technology related to the optical deflecting element, Patent Document 1 proposes a light beam shifter including an artificial birefringent plate for the purpose of reducing light loss of an optical space switch. In detail, two wedge-shaped transparent substrates are arranged in opposite directions, a light beam shifter having a liquid crystal layer sandwiched between the transparent substrates, and a light in which the light beam shifter is connected to a rear surface of a matrix-type deflection control element. A beam shifter has been proposed. In addition, two wedge-shaped transparent substrates are arranged in opposite directions, and a matrix drive can be performed between the transparent substrates, and a light beam shifter that sandwiches a liquid crystal layer that shifts an incident light beam by half a cell is used. There has been proposed a light beam shifter in which a half cell is shifted and connected in multiple stages.
[0006]
Patent Document 2 proposes an optical deflection switch that can obtain large deflection, has high deflection efficiency, and can arbitrarily set a deflection angle and a deflection distance. Specifically, two transparent substrates are arranged facing each other at a predetermined interval, the surfaces facing each other are subjected to a vertical alignment treatment, a ferroelectric liquid crystal of a smectic A phase is sealed between the transparent substrates, and the transparent substrate is sealed. The liquid crystal device is provided with a driving device that vertically aligns the electrodes with each other so that an AC electric field can be applied in parallel with the smectic layer, and that applies an AC electric field to the electrode pairs. That is, the refraction angle and the direction of displacement of the polarized light incident on the liquid crystal layer can be changed by the birefringence caused by the tilt of the liquid crystal molecules using the electroclinical effect of the ferroelectric liquid crystal of the smectic A phase.
[0007]
In the technique of Patent Document 1, since a nematic liquid crystal is used as a liquid crystal material, it is difficult to increase the response speed to sub-millisecond, and it cannot be used for applications that require high-speed switching. Further, the technique of Patent Document 2 proposes switching by an electroclinical effect using a smectic A-phase ferroelectric liquid crystal. However, the electroclinic effect has a high temperature dependence and a stable shift cannot be expected.
[0008]
Therefore, in Patent Document 3, a first window having an optically transparent common electrode, a second window having a large number of transparent conductive electrodes in the form of parallel stripes electrically bundled, a first window and a second window are described. An optical element comprising a liquid crystal molecular layer provided in the middle of the window, wherein the optical device is positioned such that an optical beam is incident on the first window and is reflected or transmitted by the second window, and further includes a control signal To the electrodes outside of each cell individually to generate a voltage gradient of linear information along the junction electrode and through the cell area, thereby providing a linear or non-linear portion of the electro-optical properties of the LC. An apparatus for wavefront modulating an optical beam, characterized in that the liquid crystal layer is configured to cause a local change in refractive index, has been proposed. Also, in claim 4, by addressing the active area with a voltage from within the linear portion of the LC electro-optical properties of the CL layer at a predetermined tilt angle between 0 and 3 degrees, the transmitted or reflected optical wavefront is An apparatus is proposed which is used to deflect an optical beam by generating a phase characteristic with a blaze effect.
[0009]
According to the technique of Patent Document 3, since a nematic liquid crystal is also used as the liquid crystal, it is not suitable for applications requiring high-speed response, as in Patent Document 1. Further, Patent Document 3 describes a transparent conductive electrode having a parallel stripe shape. However, in this structure, there is a possibility that local fluctuation of an electric field described as a problem of the present invention occurs, It is difficult to obtain a uniform light deflection amount.
[0010]
Next, with respect to the technology relating to the pixel shift element, Japanese Patent Application Laid-Open No. H11-163873 discloses an optical path from the display element to the screen in a projection display device that enlarges and projects an image displayed on the display element onto a screen by a projection optical system. Means for shifting a projected image comprising at least one optical element capable of rotating the polarization direction of transmitted light and at least one transparent element having a birefringence effect in the middle of the display, and an aperture ratio of the display element And a means for effectively reducing the number of pixels and projecting the projection area of each pixel of the display element discretely on the screen.
[0011]
In this patent document 4, at least one or more optical element (referred to as optical rotation element) capable of rotating the polarization direction and at least one or more transparent element having a birefringence effect (referred to as birefringent element) are provided. The pixel shift is performed by the projection image shift means (pixel shift means). However, the problem is that since the optical rotation element and the birefringent element are used in combination, the light amount loss is large and the pixel shift amount depends on the wavelength of light. Fluctuating and the resolution is likely to decrease, optical noise such as ghost due to leaked light is likely to be generated at a position outside the pixel shift where an image is not originally formed due to mismatch of optical characteristics between the optical rotation element and the birefringent element. Cost is high. In particular, as described above for the birefringent element, KH₂PO₄(KDP), NH₄H₂PO₄(ADP), LiNbO₃, LiTaO₃This is remarkable when a material having a large first-order electro-optic effect (Pockels effect) such as GaAs, GaAs, and CdTe is used.
[0012]
Further, in the projector disclosed in Patent Document 5, the control circuit samples the image to be displayed originally stored in the image storage circuit in a checkered pattern to the pixel selection circuit and sequentially displays the sampled image on the spatial light modulator. By projecting the image, the control circuit controls the panel swing mechanism corresponding to this display to move the adjacent pixel pitch distance of the spatial light modulator by an integral number, so that the image to be displayed originally can be time-shifted. It is made to reproduce by a typical synthesis. This makes it possible to display an image at a resolution of an integral multiple of the pixels of the spatial light modulator, and to configure a projector at low cost using a spatial light modulator with coarse pixels and a simple optical system.
[0013]
However, Patent Document 5 describes a pixel shift method in which the image display element itself is swung at a high speed by a distance smaller than the pixel pitch. In this method, since the optical system is fixed, various types of aberrations are generated. Although the occurrence is small, it is necessary to translate the image display element itself accurately and at high speed, so that the accuracy and durability of the movable part are required, and vibration and sound become problems.
[0014]
Furthermore, according to the technology disclosed in Patent Document 6, the resolution of a display image is apparently improved without increasing the number of pixels of an image display device such as an LCD, in the vertical and horizontal directions. Each of the plurality of pixels emits light in accordance with the display pixel pattern, so that an image display device on which an image is displayed and an observer or a screen are provided with an optical member for changing an optical path for each field. Further, a display pixel pattern whose display position is shifted in accordance with the change of the optical path is displayed on the image display device for each field. Here, the portion having a different refractive index is alternately displayed in the optical path between the image display device and an observer or a screen for each field of image information, whereby the optical path is changed. It is.
[0015]
In the technique of Patent Document 6, as a means for changing an optical path, a combination mechanism of an electro-optical element and a birefringent material, a lens shift mechanism, a variangle prism, a rotating mirror, a rotating glass, and the like are described. In addition to the method using a combination of birefringent elements, a method has been proposed in which an optical element such as a lens, a reflection plate, or a birefringence plate is displaced (translated or tilted) by a voice coil, a piezoelectric element, or the like to switch an optical path. However, in this method, the structure is complicated and the cost is high because the optical element is driven.
[0016]
Further, according to the technology of Patent Document 7, a light beam deflecting device that eliminates the need for a rotating mechanical element, achieves overall miniaturization, achieves high accuracy and high resolution, and is less susceptible to external vibrations is proposed. Have been. Specifically, a translucent piezoelectric element disposed on the traveling path of the light beam, a transparent electrode provided on the surface of the piezoelectric element, a light beam incident surface A and a light beam exit surface B of the piezoelectric element. Voltage applying means for applying a voltage to the piezoelectric element via an electrode in order to deflect the optical axis of the light beam by changing the optical path length between them.
[0017]
In this technology, a method has been proposed in which a light-transmitting piezoelectric element is sandwiched between transparent electrodes and the optical path is shifted by changing the thickness by applying a voltage, but a relatively large transparent piezoelectric element is required, There are the same problems as in the case of Patent Document 6 described above, such as an increase in device cost.
[0018]
To summarize the problems of the prior art described above, the problem in the conventional pixel shift element is that
1. High cost due to complicated configuration, large equipment, loss of light, optical noise such as ghost, or reduced resolution
2. Problems with positioning accuracy, durability, vibration and sound, especially in the case of a structure with movable parts
3. Response speed in nematic liquid crystal etc.
It is.
[0019]
Therefore, in order to solve these problems, the present applicant has proposed a plurality of electrode line groups arranged substantially parallel to a desired optical path shift direction in a region including an optical path on a substrate for applying an electric field. Has been proposed (see Japanese Patent Application No. 2001-287907).
[0020]
However, for example, in such an optical deflecting element, detailed structures and physical properties of electrodes and dielectrics necessary for solving the above-mentioned problems have not been known.
[0021]
SUMMARY OF THE INVENTION It is an object of the present invention to improve a wavefront aberration in an optical element and a light deflecting element so that a sharp image can be obtained.
[0022]
[Means for Solving the Problems]
The invention according to claim 1 is provided such that a pair of transparent substrates, a liquid crystal layer filled between the substrates, and at least one of the pair of substrates are arranged at intervals in a width direction of the substrates. A plurality of electrodes, and a filler filled between the electrodes to reduce diffraction of the electrodes, wherein the thickness of the electrodes is d, and the refractive index at a wavelength of 546 nm is n._elAnd the refractive index of the filler is n_flAnd when
| (N_el-N_fl) · D | <0.11 (μm)
Which is an optical element.
[0023]
Therefore, when the electrode has a periodic structure, light diffraction occurs, preventing image formation at a position different from the original image formation position, improving wavefront aberration, and obtaining a sharp image. . When this optical element is used in an image display device that incorporates a pixel shift technology, the MTF (Modulation Transfer Function) on the screen can be improved, and when applied to an optical memory, the beam shape on the medium can be improved. It is possible to improve the pit shape at the time of recording and the S / N at the time of reading, and it is possible to improve the S / N even when applied to an optical switch.
[0024]
The invention according to claim 2 is the optical element according to claim 1, further comprising a dielectric layer provided between the liquid crystal layer and the electrode, wherein the dielectric has a refractive index of n._deAnd when
| N_{e l}-N_de| <0.56
It is.
[0025]
Therefore, by setting the dielectric layer that suppresses local fluctuation of the electric field applied to the liquid crystal under such conditions, diffraction occurs when the electrode has a periodic structure, and the electrode is located at a position different from the original imaging position. Image formation is prevented, wavefront aberration is improved, and a sharp image can be obtained.
[0026]
The invention according to claim 3 includes a pair of transparent substrates, a liquid crystal layer including a liquid crystal composed of a chiral smectic C phase having homeotropic alignment filled between the substrates, and at least one of the pair of substrates. A plurality of electrodes arranged side by side in the plate width direction of the substrate, a filler filled between the electrodes to reduce diffraction of the electrodes, and a step between the electrodes adjacent to each of the electrodes. Voltage applying means for deflecting light by applying voltages of different magnitudes, wherein the thickness of the electrode is d, and the refractive index at a wavelength of 546 nm is n._elAnd the refractive index of the filler is n_flAnd when
| (N_el-N_fl) · D | <0.11 (μm)
Which is a light deflection element.
[0027]
Therefore, when the electrode has a periodic structure, diffraction occurs, preventing image formation at a position different from the original image formation position, improving wavefront aberration, and obtaining a sharp image.
[0028]
According to a fourth aspect of the present invention, in the light deflecting element according to the third aspect, a dielectric layer provided between the liquid crystal layer and the electrode is further provided.
[0029]
Therefore, local fluctuation of the electric field applied to the liquid crystal layer can be suppressed.
[0030]
According to a fifth aspect of the present invention, in the optical deflecting element according to the fourth aspect, the refractive index of the dielectric is n._deAnd when
| N_{e l}-N_de| <0.56
It is.
[0031]
Therefore, by setting the dielectric layer that suppresses local fluctuation of the electric field applied to the liquid crystal under such conditions, diffraction occurs when the electrode has a periodic structure, and the electrode is located at a position different from the original imaging position. Image formation is prevented, wavefront aberration is improved, and a sharp image can be obtained.
[0032]
According to a sixth aspect of the present invention, in the light deflecting element according to any one of the third to fifth aspects, the electrode has a refractive index n._elBut,
1.5 <n_{e l}<2.0
It is.
[0033]
Therefore, the difference in the refractive index between the material of the substrate and the dielectric layer that is generally used increases, the amount of interfacial reflection increases, the amount of diffracted light is prevented from increasing, the wavefront aberration is improved, and the sharpness is improved. An image can be obtained.
[0034]
According to a seventh aspect of the present invention, in the optical deflection element according to any one of the third to sixth aspects, the electrode includes zinc oxide / antimony or tin / antimony oxide.
[0035]
Therefore, it is excellent in transparency, the surface resistance can be controlled to a value that does not cause problems in generating an electric field applied to the liquid crystal, and the refractive index is controlled to be smaller than that of indium tin oxide, which has been commonly used in the past. Therefore, the wavefront aberration can be improved and a sharp image can be obtained.
[0036]
According to an eighth aspect of the present invention, in the light deflecting element according to any one of the third to seventh aspects, the filler is a light-curing or thermosetting resin.
[0037]
Therefore, when the photo-curable resin is used as the transparent filler, the manufacturing time can be shortened because the resin filling to curing can be performed in a short time, and when the thermosetting resin is used as the transparent filler, the photo-curable resin is used. Since the deterioration due to light does not occur as compared with the case, the manufacturing operation can be performed under normal white illumination, and the workability is excellent. In addition, sufficient light transmittance can be ensured for any of the resins, and good optical characteristics can be obtained.
[0038]
According to a ninth aspect of the present invention, in the optical deflecting element according to the fourth aspect, the dielectric layer is a glass material.
[0039]
Therefore, it can be controlled to a desired thickness, and after bonding to a substrate having electrodes through the filler of claim 8, by performing optical polishing, a surface with extremely excellent smoothness can be obtained, In addition, it becomes possible to suppress light diffraction, scattering, and the like.
[0040]
According to a tenth aspect of the present invention, in the optical deflecting element according to the fourth or ninth aspect, the dielectric layer is a photo-curing or thermosetting resin and also serves as the filler.
[0041]
Therefore, the manufacturing process can be shortened, and the number of interfaces can be reduced as compared with the structure of the ninth aspect, so that deterioration of optical performance can be reduced.
[0042]
According to an eleventh aspect of the present invention, in the optical deflecting element according to the fourth, ninth or tenth aspect, the dielectric layer has a hard coat layer made of a transparent inorganic material formed on a surface of the liquid crystal side. I have.
[0043]
Therefore, it is possible to prevent the solvent used for forming the liquid crystal alignment film from deteriorating the dielectric layer made of the photo-curable or thermosetting resin, and to prevent optical deterioration due to the degraded dielectric layer.
[0044]
According to a twelfth aspect of the present invention, in the light deflecting element according to any one of the third to fourth and ninth aspects, the filler is made of a transparent inorganic material.
[0045]
Therefore, as compared with the filler of claim 8, the degree of freedom in selecting the refractive index depending on the composition is large, and the difference in the refractive index from the electrode can be reduced.
[0046]
According to a thirteenth aspect, in the optical deflecting element according to any one of the third to fourth, ninth and twelfth aspects, the filler is made of silicon oxide.
[0047]
Therefore, the transmittance is high and the refractive index can be adjusted by the composition, so that the difference in refractive index from the electrode can be reduced. Further, when the liquid crystal layer, the electrode, and the filler are set to have substantially the same refractive index when used for the electrode of claim 7, the wavefront aberration can be improved and a sharp image can be obtained.
[0048]
According to a fourteenth aspect of the present invention, in the optical deflecting element according to any one of the third to thirteenth aspects, the electrode widths of the plurality of electrodes are not uniform.
[0049]
Therefore, noise light traveling in a direction different from the predetermined direction can be reduced, and light diffraction due to the arrangement of the electrodes can be reduced.
[0050]
According to a fifteenth aspect of the present invention, in the optical deflecting element according to the fourteenth aspect, the distance between the center lines of two electrodes formed by three adjacent electrodes is set to a different value. .
[0051]
Therefore, noise light traveling in a direction different from the predetermined direction can be reduced, and light diffraction due to the arrangement of the electrodes can be reduced.
[0052]
According to a sixteenth aspect of the present invention, in the optical deflecting element according to any one of the third to fifteenth aspects, the plurality of electrodes have uneven electrode thicknesses.
[0053]
Therefore, noise light traveling in a direction different from the predetermined direction can be reduced, and light diffraction due to the arrangement of the electrodes can be reduced.
[0054]
An image display device according to claim 17, wherein the image field is spatially modulated on the basis of image information and emitted as image light for each of a plurality of image subfields obtained by further subdividing an image field temporally. In synchronism with the image display element, the optical path of image light incident from each pixel of the image display element driven for each image subfield is deflected to multiply the apparent number of pixels of the image display element. An image display device comprising: the light deflecting element according to any one of claims 3 to 16 for displaying the image.
[0055]
Therefore, it is possible to provide an image display device capable of improving contrast and light use efficiency and obtaining a higher definition image.
[0056]
BEST MODE FOR CARRYING OUT THE INVENTION
[Definition]
Hereinafter, main terms used in the present specification will be described.
[0057]
(1) Optical deflection element
The “light deflecting element” means that the optical path of light is deflected by an external electric signal, that is, the outgoing light is shifted in parallel with respect to the incident light, rotated at a certain angle, or both. Means an optical element capable of switching the optical path. In this description, the magnitude of the shift with respect to the light deflection due to the parallel shift is referred to as “shift amount”, and the amount of rotation as to the light deflection due to rotation is referred to as “rotation angle”. The “optical deflecting device” means a device that includes such an optical deflecting element and deflects the optical path of light.
[0058]
(2) Light deflection switching time
The light deflection direction switching time is the time required for switching the optical path, and is the time corresponding to the liquid crystal switching time.
[0059]
(3) Subfield
Usually, in an image display device such as a liquid crystal projector, images are sequentially rewritten and displayed at a certain cycle. The image per sheet is called a field. In the present invention, the pixels are doubled and displayed by performing the optical path shift in a time-division manner as described above, and the image displayed in a time-division manner is called a subfield. Therefore, for example, when the number of divisions is 2, that is, when the optical path shift is switched at two positions, an image of one field is formed by two subfields.
[0060]
At the time of subfield switching, it is a time during which the optical path is shifted, and at the time of subfield display, it is a time during which the optical path shift is completed and one subfield is displayed.
[0061]
(4) Pixel shift element
"Pixel shift element" refers to an image display element in which a plurality of pixels capable of controlling light at least according to image information are two-dimensionally arranged, a light source for illuminating the image display element, and an image pattern displayed on the image display element. An optical member for observation, and a light deflecting unit for deflecting an optical path between the image display element and the optical member for each of a plurality of subfields obtained by temporally dividing the image field, This means a light deflecting unit in an image display device that displays an image pattern in which the display position is shifted in accordance with the deflection of the optical path, thereby increasing the apparent number of pixels of the image display element and displaying the image. Therefore, basically, it can be said that the light deflecting element or the light deflecting device defined above can be applied as the light deflecting means.
[0062]
[Embodiment of the invention]
An embodiment of the present invention will be described.
[0063]
First, the basic configuration and operation of the light deflection element 1 according to the present embodiment will be described.
[0064]
FIG. 1 is an explanatory diagram of the entire configuration of the light deflection element 1. The light deflecting element 1 of FIG. 1 implements the optical element and the light deflecting element of the present invention. First, a pair of transparent substrates 2 are provided so as to face each other. It is preferable to form an alignment film (not shown in FIG. 1) on the inner surface of at least one of the substrates 2 in order to properly align the liquid crystal layer 5. A liquid crystal layer 5 composed of a ferroelectric liquid crystal composed of a chiral smectic C phase is filled between the alignment film and the other substrate 2.
[0065]
A plurality of line electrodes 6 serving as electric field applying means for applying an electric field to the liquid crystal layer 5 corresponding to a desired light deflection direction to the liquid crystal panel having the pair of substrates 2 and the liquid crystal layer 5. Are connected to a power supply 7 which is a voltage control means. Each line electrode 6 is provided outside the optical path, is connected to each resistance end of the resistor 7a arranged in series, and is configured so that a potential gradient is generated between adjacent transparent electrodes 6 and an electric field is applied. ing.
[0066]
Next, the liquid crystal layer 5 will be described. "Smectic liquid crystal" is a liquid crystal molecule in which the major axis directions of the liquid crystal molecules are arranged in layers. With respect to such a liquid crystal, a liquid crystal in which the normal direction of the layer (the layer normal direction) coincides with the major axis direction of the liquid crystal molecules is referred to as “smectic A phase”, and a liquid crystal in which the normal direction is not coincident is referred to as “ "Chiral smectic C phase".
[0067]
A ferroelectric liquid crystal composed of a chiral smectic C phase generally has a so-called helical structure in which the direction of liquid crystal molecules is helically rotated for each layer without an external electric field acting. The liquid crystal molecules face each other in each layer. Since the liquid crystal composed of these chiral smectic C phases has an asymmetric carbon in the molecular structure and is spontaneously polarized, the liquid crystal molecules are rearranged in a direction determined by the spontaneous polarization Ps and the external electric field E. And the optical properties are controlled. In the following, the light deflecting element 1 will be described by taking a ferroelectric liquid crystal as an example of the liquid crystal layer 5, but the present invention is not limited to this, and the same applies to the case of an antiferroelectric liquid crystal. Can be.
[0068]
The structure of a ferroelectric liquid crystal composed of a chiral smectic C phase includes a main chain, a spacer, a skeleton, a bonding portion, a chiral portion, and the like. As the main chain structure, polyacrylate, polymethacrylate, polysiloxane, polyoxyethylene and the like can be used. The spacer is for linking a skeleton, a bonding portion, and a chiral portion responsible for molecular rotation to the main chain, and a methylene chain having an appropriate length is selected. Further, a —COO— bond or the like is selected as a bonding portion that bonds the chiral portion and a rigid skeleton such as a biphenyl structure.
[0069]
In the optical deflecting element 1 of the present embodiment, the rotation axis of the molecular helical rotation of the ferroelectric liquid crystal layer 5 composed of a chiral smectic C phase is oriented perpendicular to the surface of the substrate 2 by the alignment film. Eggplant A well-known technique can be applied as an alignment method for such homeotropic alignment. That is, (1) shear stress method, (2) magnetic field orientation method, (3) temperature gradient method, (4) SiO oblique deposition method, (5) photo-alignment method, etc. Takezo, Fukuda, "Structure and physical properties of ferroelectric liquid crystal", Corona, p. 235).
[0070]
In the present light deflecting element 1, the chiral smectic C phase has an extremely high-speed response compared to the nematic liquid crystal, and switching in sub-ms is possible. In addition, the direction of the liquid crystal molecules is uniquely determined with respect to the direction of the electric field, and since the direction of the director is fixed at a certain electric field intensity or higher, the smectic A phase using the electroclinical effect that takes a director angle proportional to the electric field intensity is used. The control of the director direction is easier and easier to handle than liquid crystal.
[0071]
In addition, the liquid crystal layer 5 composed of a chiral smectic C phase forming a homeotopic alignment has a lower liquid crystal molecule operation than the liquid crystal layer 2 having a homogeneous alignment (a state in which liquid crystal molecules are aligned parallel to the substrate surface). This is advantageous in that it is difficult to receive a regulating force from the light source, that the light deflection direction can be easily controlled by adjusting the direction of the external electric field, and that the required electric field is low. In addition, when the liquid crystal molecules are homogeneously aligned, the liquid crystal molecules strongly depend not only on the electric field direction but also on the substrate surface, so that a higher positional accuracy is required for the installation of the light deflecting element. Conversely, in the case of the homeotopic alignment as in the present embodiment, the setting margin of the light deflection element 1 with respect to the light deflection increases. In order to take advantage of these features, the helical axis does not need to be strictly oriented perpendicular to the substrate surface, but may be inclined to some extent. For example, even if a part of the side surface forming the helical structure is perpendicular to the substrate 2 and the helical axis itself is inclined from the normal direction of the substrate, the liquid crystal molecules are not affected by the restricting force from the substrate 2. It is only necessary to be able to turn in one direction.
[0072]
Next, the basic operation principle of the light deflecting element 1 will be described with reference to FIGS. FIG. 2 schematically shows a liquid crystal molecule alignment state in the configuration shown in FIG. In FIG. 2, the line electrode 6 is provided on a substrate (not shown) on both sides of the light deflecting element 1. The line electrode 6 may be formed on only one side of the substrate. In order to apply an electric field in the direction, it is desirable to form them on both sides.
[0073]
The incident light to the light deflecting element 1 is linearly polarized light, and its polarization direction is up and down as shown by the arrow in FIG. 2 (hereinafter, similarly, the polarization direction is incident by up and down or left and right arrows). The line electrodes 6 are arranged to face each other such that the direction of the electric field is orthogonal to the polarization direction, and different voltage values are set stepwise with respect to each adjacent line electrode of the line electrode group. Note that it is preferable to provide an electromagnetic shield so that the leakage electric field from the electrode 6 does not adversely affect devices around the light deflection element 1. The liquid crystal molecules 8 can take a helical alignment direction depending on the direction of the applied electric field as described above. FIG. 2 shows a possible alignment state in a cone shape.
[0074]
FIG. 3 shows an XZ section in the liquid crystal layer 5 when the XYZ orthogonal coordinate system is taken as shown in FIG. As shown in FIG. 3, if the electric field of the liquid crystal molecules 8 is sufficiently large, the liquid crystal molecules 8 take either the first alignment state or the second alignment state (see FIG. 3B) depending on the direction of the electric field. Distribute. θ is the tilt angle of the liquid crystal molecules 8 from the liquid crystal rotation axis, and is hereinafter simply referred to as “tilt angle”. Assuming that the spontaneous polarization Ps of the liquid crystal layer 5 is positive and the electric field E is applied in the positive Y-axis direction (upward on the paper surface), the liquid crystal molecules 8 have a liquid crystal rotation axis substantially in the direction perpendicular to the substrate. This corresponds to the first orientation direction shown in b).
[0075]
Assuming that the refractive index in the major axis direction of the liquid crystal layer 5 is ne and the refractive index in the minor axis direction is no, linearly polarized light having a polarization direction in the Y-axis direction is selected as the incident light, and the incident light proceeds in the X-axis positive direction. At this time, the light receives the refractive index no as ordinary light in the liquid crystal layer 5 and travels straight, and travels in the direction a in FIG. That is, the light is not deflected.
[0076]
On the other hand, when linearly polarized light whose polarization direction is the Z-axis direction is incident, the refractive index in the incident direction can be obtained from both the direction of the liquid crystal molecules and the refractive indices no and ne. More specifically, it is obtained from the relationship with the direction of light passing through the center of the ellipsoid in the refractive index ellipsoid having the refractive indices no and ne as main axes, but the details are omitted here. The light is deflected according to the refractive indices no and ne and the direction of the liquid crystal molecules 8 (tilt angle θ), and shifts in the direction shown in b (in the case of the first alignment state) in FIG.
[0077]
Assuming that the thickness (gap) of the liquid crystal layer 5 is d, the shift amount S is represented by the following equation 1 (see, for example, "Crystal Optics", Japan Society of Applied Physics, Optical Society, p. 198).
[0078]

When the direction of the electric field is reversed, the liquid crystal molecules 8 assume a line-symmetric arrangement (the second alignment state) centered on the X-axis in FIG. 3, and the traveling direction of the linearly polarized light whose polarization direction is the Z-axis direction. Is as shown by b 'in FIG. 3 (a).
[0079]
Therefore, by controlling the direction of the electric field applied to the liquid crystal layer 5 with respect to the linearly polarized light, light deflection at two positions b and b ', that is, 2S can be performed.
[0080]
FIG. 4 shows the result of calculating the light deflection amount S with respect to the light deflection amount obtained for the typical physical property values (no = 1.6, ne = 1.8) of the material of the liquid crystal layer 5. As is clear from FIG. 4, the light deflection amount is largest near θ = 45 °. If the tilt angle θ of the liquid crystal molecules 8 is 22.5 °, in order to obtain a deflection amount of 2S = 5 (μm), the thickness of the liquid crystal may be set to 32 μm as shown here. A response time of 0.1 ms has been reported for a homeotropically aligned ferroelectric liquid crystal with respect to an electric field of about 700 V / cm (Ozaki et al., JJ Appl. Physics, Vol. 30, No. 9B). Pp2366-2368 (1991)), and a sufficiently high response speed on the order of sub-ms is obtained.
[0081]
In a liquid crystal composed of a chiral smectic C phase, the tilt angle θ changes depending on the temperature T. When the phase transition point is Tc, θ∝ (T−Tc)^βThere is a relationship. β varies depending on the material, but takes a value of about 0.5. It is also possible to control the amount of light deflection by temperature control utilizing this characteristic.
[0082]
For example, the above-mentioned 22.5 ° is temporarily set as the tilt angle θ, and the temperature corresponding to this is set to T_{θ = 22.5 °}Then T> T_{θ = 22.5 °}, Θ ≦ 22.5 ° and T ≦ T_{θ = 22.5 °}Since θ> 22.5 °, the tilt angle θ can be controlled by the temperature, whereby the amount of light deflection can be controlled. As for the position control, fine adjustment by the electric field can be similarly performed, and appropriate light deflection can be achieved by the temperature, the electric field, or a combination of both.
[0083]
In the above description, the case where the helical structure is melted and the tilt angle θ is equal to the inclination angle of the optical axis when the electric field strength is Es or more is described. What is necessary is just to treat as the inclination angle of the optical axis averaged.
[0084]
FIG. 5 is a graph showing an applied voltage for generating an electric field and a change in the amount of light deflection accompanying the applied voltage. The applied voltage is generally rectangular. In the configuration of the light deflecting element 1 in FIGS. 1 and 2, an electric field in a predetermined direction (± Y direction) is generated inside the liquid crystal layer 5 by applying the voltage. The rotation of the liquid crystal molecules 8 occurs immediately after the switching of the voltage, and after a time (light deflection direction switching time) determined by the liquid crystal properties and the generated electric field, the light deflection amount becomes constant. This deflection direction does not change while the voltage value is held (light deflection direction holding time).
[0085]
Next, a more detailed configuration of the present light deflecting element 1 and its operational effects will be described.
[0086]
FIG. 6 is a schematic diagram for explaining a cross-sectional structure around the line electrode 6 in the optical deflection element 1 according to the present embodiment. In FIG. 6, a transparent filler 3 is filled between adjacent line electrodes 6 on the substrate 2. Further, a dielectric layer 4 is provided between the liquid crystal layer 5 and the line electrode 6 on the substrate 2. The illustration of the substrate 2, the line electrode 6, and the like on the side facing the liquid crystal layer 5 is omitted.
[0087]
Further, by using a transparent material for the line electrode 6, the light use efficiency can be increased and the signal quality can be improved. In this case, tin oxide (SnO) is used as the transparent line electrode 6.₂), Indium oxide (In)₂O₃), Indium tin oxide (ITO), zinc oxide (ZnO), zinc oxide / antimony (ZnO · Sb205), tin oxide / antimony (ATO), and the like.
[0088]
When these are formed, a method of directly growing a film of a predetermined shape on the substrate 2 by a method such as a sputtering method, a vapor deposition method, or an ion plating method in a state where an opening mask having the shape of the line electrode 6 is overlaid, There is a method in which a film is formed on the entire surface of the substrate by a method such as an immersion method, a sol-gel method, and then a predetermined masking is performed, followed by wet etching with a hydrochloric acid-based etchant or the like or dry etching.
[0089]
Above all, the material of the line electrode 6 made of zinc oxide / antimony and tin oxide / antimony has excellent transparency, and the surface resistance can be controlled to a value that does not cause a problem in generating an electric field applied to the liquid crystal. The refractive index can be controlled to be smaller than that of indium tin oxide (refractive index: 1.8 to 2.0), which has been widely used in the past, so that the refractive index difference from the transparent filler can be reduced, which is useful.
[0090]
When these line electrodes 6 are formed on the substrate 2, in order to reduce diffraction, the electrode widths of the adjacent line electrodes 6 are set to different values, or two line electrodes 6 formed by three adjacent line electrodes 6 are used. The distance between the line electrodes 6 (distance between the center lines of the line electrodes) may be set to different values, the electrode thickness of the adjacent line electrodes 6 may be set to different values, or the cross-sectional shape of the electrodes 6 may have a curve. It is effective to do. The electrode width of the line electrodes 6 and the distance between the line electrodes are preferably randomized so that a periodic structure is not generated on the formation surface of the line electrodes 6 in the optical path. However, depending on the structure, it is necessary to set the electric field applied to the liquid crystal layer 5 to a range in which the electric field does not locally change.
[0091]
The specific structure will be described with reference to FIG. FIG. 7 is a front view (partial view) of the substrate 2, the line electrode 6, and the like. In FIG. 7, when the line electrodes 6 are numbered ((i-1) to (i + 3)), the width of each line electrode is W, and the distance between the electrodes is D,
W_i≠ W_{i + 1}, W_{i + 1}≠ W_{i + 2}, D_{i / ( i + 1 )}≠ D_{( i + 1 ) / ( i + 2 )}
Set to satisfy.
[0092]
FIG. 8 is a side view (partial view) of the substrate 2 and the line electrode 6. The electrode thickness of the line electrode 6 is, as shown in FIG.
t_i≠ t_{i + 1}
And
[0093]
If the transparent filler 3 is an inorganic material, titanium oxide (TiO 2)_x), Titanium nitride (TiN)_x), Zirconia oxide (ZrO)_x), Zirconia nitride (ZrN_x), Aluminum oxide (AlO)_x), Silicon oxide (SiO_x), Boron-doped silicon oxide (SiBO)_x), Boron-doped silicon nitride (SiBN)_x), Silicon carbide (SiC), zinc sulfide (ZnS), silicon oxide-zinc sulfide (SiO_x-ZnS), silicon carbide-zinc sulfide (SiC-ZnS), or the like can be used. These are formed by a sputtering method, a vapor deposition method, an ion plating method, a coating method, an immersion method, a sol-gel method, etc., on the entire surface of the substrate 2 to a thickness equal to or greater than the film thickness of the line electrode 6, and then by CMP (chemical mechanical polishing). ) Is desirable.
[0094]
When an organic material is used as the transparent filler 3, a photo-curing or thermosetting resin can be used. These can be formed on the substrate 2 in a prepolymer state by a coating method such as spin coating, dipping, or bar coating, or a printing method such as screen printing, gravure printing, or flexographic printing. In order to fill the space between the adjacent line electrodes 6 on the substrate 2, the smooth surface that can be separated from the substrate 2 is press-contacted with the substrate 2 via a light-curing or thermosetting resin in advance, and after the curing process, the smooth surface is peeled off. Is also good.
[0095]
In the present embodiment, since the transparent filler 3 is provided for the purpose of reducing the diffraction of the line electrode 6, its refractive index is preferably as close as possible to the refractive index of the line electrode 6. As will be shown in Examples described later, the present applicant has studied and found that the thickness of the line electrode 6 is d, and the refractive index (the value at a wavelength of 546 nm, hereinafter the same) is n._flAnd when
"| (N_el-N_fl) · D | ″ was less than 0.11 μm, more preferably less than 0.07 μm, showing excellent optical properties.
[0096]
In particular, a pair of transparent substrates 2, a liquid crystal layer 5 composed of a chiral smectic C phase having a homeotropic alignment filled between the substrates 2, and a plurality of liquid crystal layers arranged in a region including an optical path on at least one of the substrates 2. And a transparent filler 3 filled between adjacent line electrodes 6 on the substrate 2, and different voltage values are applied stepwise to each adjacent line electrode 6 in the line electrode group. In the light deflecting element 1 that deflects light by setting, by satisfying the above-described relationship of the refractive index, the beam spot of the diffracted light formed at a position different from the predetermined deflection position can be suppressed, which is useful.
[0097]
FIG. 9 is a schematic diagram for explaining a cross-sectional structure around the line electrode 6 in another configuration example of the light deflection element 1. 9 differs from the light deflecting element 1 having the configuration shown in FIG. 9 in that the dielectric layer 4 is provided between the liquid crystal layer 5 and the line electrode 6 on the substrate 2. Note that, also in the example of FIG. 9, the illustration of the substrate 2, the line electrode 6, and the like on the side facing the liquid crystal layer 5 is omitted. Also in this configuration, the above-mentioned inorganic or organic material can be used for the transparent filler 3. In particular, in the case of an organic material, the dielectric layer 4 may be used as it is, instead of the above-mentioned releasable smooth surface. Of course, in this case, there is no need for peeling. It is also possible to integrally mold the dielectric layer 4 and the transparent filler 3 using an organic material. In this case, using the above-mentioned smooth surface that can be separated, a gap corresponding to the sum of the thickness of the dielectric layer 4 and the thickness of the transparent charging material 3 is secured in advance, and the surface of the substrate on the line electrode 6 side is smoothed. The surfaces may be opposed to each other, and the prepolymer before curing may be filled and then cured.
[0098]
In the case where the transparent filler 3 is formed of an organic material and the dielectric layer 4 is not provided, or in the case where the dielectric layer 4 is formed of an organic material, a hard coat which is not deteriorated by a solvent is provided on the surface of the liquid crystal layer 5. It is desirable to form. In particular, when an alignment film for aligning the liquid crystal layer 5 is of a type dissolved in a solvent, the solvent may deteriorate the dielectric layer 4 and the transparent filler 3 during the formation. Therefore, it is extremely useful to form a hard coat.
[0099]
The hard coat layer is preferably made of an inorganic material that is not contaminated by a solvent._x), Titanium nitride (TiN)_x), Zirconia oxide (ZrO)_x), Zirconia nitride (ZrN_x), Aluminum oxide (AlO)_x), Silicon oxide (SiO_x), Boron-doped silicon oxide (SiBO)_x), Boron-doped silicon nitride (SiBN)_x), Silicon carbide (SiC), zinc sulfide (ZnS), silicon oxide-zinc sulfide (SiO_x-ZnS), silicon carbide-zinc sulfide (SiC-ZnS), or the like can be used. In particular, silicon oxide (SiO₂) Is excellent in reducing interfacial reflection.
[0100]
The function of the dielectric layer 4 is to suppress local fluctuations of an electric field applied to the liquid crystal layer 5, and it is desirable to optically configure such that internal absorption, interface reflection, diffraction, and the like are not generated as much as possible. In particular, it is necessary to suppress the interface reflection because the reflected light becomes noise light and deteriorates the imaging performance. The dielectric layer 4 is desirably transparent, electrically insulating, has high weather resistance, and has low birefringence. For an inorganic material, glass, and for an organic material, polycarbonate, acrylic, or the like is used. It can be suitably used. In particular, glass is useful because it has no birefringence and little deformation.
[0101]
As will be described in the examples below, the present inventor has studied and found that the refractive index of the dielectric layer 4 is n_deWhen
| N_el-N_de| <0.56
More preferably,
| N_el-N_de| <0.46
When, the contrast deterioration due to the reflected light was small, and it was confirmed that it was suitable.
[0102]
In particular, a pair of transparent substrates 2, a liquid crystal layer 5 composed of a chiral smectic C phase having a homeotropic alignment filled between the substrates 2, and a plurality of liquid crystal layers arranged in a region including an optical path on at least one of the substrates 2. And a transparent filler 3 filled between adjacent line electrodes 6 on the substrate 2, and different voltage values are applied stepwise to each adjacent line electrode 6 in the line electrode group. When this is applied to a pixel shift technique in the light deflecting element 1 which deflects light by setting, it is useful to improve light use efficiency and contrast.
[0103]
FIG. 10 is a conceptual diagram showing an outline of an image display device using the light deflecting element 1. In FIG. 10, reference numeral 11 denotes a light source for illumination, and any type or type of light source can be used as long as it can turn on or off white or any color light at high speed. . For example, an LED lamp, a laser light source, a white lamp light source, or the like is arranged in a two-dimensional array, and a combination of such a light source and a shutter that operates at a high speed can be used as a light source for illumination.
[0104]
Reference numeral 12 denotes an illumination device for uniformly irradiating the light emitted from the light source to the image display element 13, and includes a diffusion plate 12a, a condenser lens 12b, and the like.
[0105]
Reference numeral 13 denotes uniform illumination light incident from the illumination device 12, which is spatially modulated based on image information for each of a plurality of image subfields obtained by further subdividing an image field temporally, and emitted as image light. Image display device. As the image display element 13, a transmission type liquid crystal light valve, a reflection type liquid crystal light valve, a DMD element, or the like can be used.
[0106]
Reference numeral 14 denotes an optical deflecting element that deflects the optical path of the image light emitted from the image display element 13 for each image subfield and emits it as deflected image light. The light deflecting element 14 can display an image pattern in which the image display position projected on the screen 16 is shifted according to the amount of deflection of the optical path for each image subfield. Can be displayed as an apparently multiplied number of pixels.
[0107]
Reference numeral 15 denotes an optical member for observing an image pattern displayed on the image display element 13, reference numeral 5 denotes a projection lens, and reference numeral 6 denotes a screen. Further, reference numeral 17 denotes a light source driving unit for driving the light source 11, reference numeral 18 denotes a display driving circuit for driving the image display element 13, and reference numeral 19 denotes an optical deflecting device for driving the optical deflecting element 1. It is a drive circuit. Reference numeral 20 denotes an image display control circuit for controlling the entire image display device including the light source drive circuit 17, the display drive circuit 18, the light deflection drive circuit 19, and the like.
[0108]
Next, a basic operation of the image display device shown in FIG. 10 will be described. Light emitted from the light source 11 controlled by the light source driving circuit 17 becomes illumination light uniformed by the diffusion plate 12a, and is controlled by the display driving circuit 18 operating in synchronization with the light source driving circuit 17 by the condenser lens 12b. Critically illuminates the image display element 13 that is being used. Here, as an example of the image display element 13, a transmissive liquid crystal panel, that is, a transmissive liquid crystal light valve is used. The illumination light spatially modulated by the image display element 13 composed of a transmissive liquid crystal light valve enters the light deflecting element 1 as image light, and the light emitted from the light deflecting element 1 is projected as deflected image light. After being enlarged by the lens 15, it is projected on the screen 16. That is, by the light deflecting element 1 arranged on the emission side of the image light of the image display element 13 composed of a transmission type liquid crystal light valve, the image light is arranged in accordance with the driving signal from the light deflecting driving circuit 19 in the pixel arrangement. The light is emitted as deflected image light shifted (deflected) by an arbitrary distance in the direction, and is projected onto a screen 16 via a projection lens 15.
[0109]
In FIG. 10, the light deflecting element 1 is disposed immediately after the image display element 13 formed of a transmissive liquid crystal light valve. However, the position of the light deflecting element 1 is not limited to this. , Just before the screen 16 or the like. However, when the light deflecting element 1 is arranged near the screen 16, the size of the light deflecting element forming the light deflecting element 1, and further, the arrangement pitch of the transparent electrodes forming the light deflecting element 1, etc. It is necessary to set according to the screen size and the pixel size.
[0110]
However, no matter where the light deflecting element 14 is arranged, the amount of shift (deflection) of the optical path of the deflected image light is desirably 1 / integer of the pixel pitch. That is, when the pixel multiplication is performed twice in the pixel arrangement direction, the shift amount of the optical path of the deflected image light is set to 画素 of the pixel pitch, and the pixel multiplication is performed three times in the arrangement direction. If so, it is desirable to set it to 1/3 of the pixel pitch. Further, when the shift amount of the optical path of the deflected image light is larger than the pixel pitch due to the configuration of the light deflecting element 4, the shift amount of the optical path is set to a distance of (integer multiple + 1 / integer) of the pixel pitch. May be.
[0111]
By using the light deflecting element 1 two-dimensionally in the vertical and horizontal directions in the pixel array direction, for example, by using two light deflecting elements for performing a double image multiplication, an apparent effect of four times the number of pixels can be obtained. It is possible to display a high-definition image higher than the resolution of the transmission type liquid crystal light valve. When the shift amount is increased by the configuration of the light deflecting element 1, the shift amount may be set to a distance of (integer multiple + 1 / integer) of the pixel pitch. In any case, the image display element 13 which is a transmissive liquid crystal light valve is driven by the image signal of the subfield corresponding to the shift position of the pixel.
[0112]
Although FIG. 10 shows a single-color image display device using a single-plate transmission-type liquid crystal light valve and a single-color LED lamp, a three-primary-color light source 11, a lighting device 12, and three image display elements 13 are provided. The full color image can be displayed by mixing the three primary color images. Also, a full-color image can be displayed by a field sequential method in which the single-plate image display element 13 is sequentially illuminated with three primary colors of light. In this case, the light paths from the three color light sources 11 may be mixed and illuminated by a cross prism, or time-sequential three primary color lights may be generated by a combination of the white lamp light source 11 and a rotating color filter.
[0113]
【Example】
An embodiment of the present invention will be described.
[0114]
Hereinafter, the light deflecting element 1 described with reference to FIG. 9 described above is created and verified under various conditions.
[0115]
[Example 1]
100 line electrodes 6 made of indium tin oxide (ITO) having a pitch of 0.1 mm, a width of 0.01 mm, and a thickness of 0.2 μm are formed on the surface of a central region of a glass substrate 2 having a size of 30 mm × 40 mm and a thickness of 3 mm. Was formed by a high frequency magnetron sputtering method. The pitch and width were obtained in a photolithography step by covering the area other than the area where the line electrode 6 was formed with a resist material in advance, forming the film, and lifting off the resist. The refractive index of this ITO was measured by an ellipsometer and found to be 2.00 at a wavelength of 546 nm (all subsequent refractive index measurements were at the same wavelength). Thereafter, after the resist is washed and removed, a commercially available UV-curable resin is dropped on the substrate, a dielectric (borosilicate glass) having a thickness of 150 μm is overlaid thereon, and the resin is cured by UV exposure under pressure. Was. The refractive indices of this UV curable resin and borosilicate glass were 1.63 and 1.47, respectively. A vertical alignment film made of polyimide was formed on the surface of the dielectric by applying a polyamic acid dissolved in IPA (isopropyl alcohol) and sintering. This was used as a substrate 2, and two substrates 2 manufactured under the same conditions were stacked with ITO shifted by a half pitch to form an empty cell. The spacer for adjusting the gap between the two substrates 2 was arranged at the end of the substrate 2 and this portion was fixed with an adhesive. While the substrate 2 was heated to about 90 degrees, a ferroelectric liquid crystal (CS1029 manufactured by Chisso) was injected between the two substrates 2 by a capillary method. After cooling, the liquid crystal layer 5 was transparent, and it was confirmed from observation with a conoscopic image that the liquid crystal layer 5 was oriented perpendicular to the substrate.
[0116]
As shown in FIG. 11, the liquid crystal sample 21 was irradiated with a He-Ne laser having a wavelength of 633 nm by a laser light source 22. The laser was irradiated by the beam expander 23 so as to extend to the vicinity of the formation portion (10 mm width) of the electrode 6. The transmitted light was collected by the collimator lens 24. A beam spot of zero-order light was formed on the light-collecting surface 25, and although diffracted light was slightly generated in the vicinity, it was at a usable level.
[0117]
The sample 21 was inserted at the position of the light deflecting element 1 of the image display device shown in FIG. 10, and a black-and-white periodic line having a width of one pixel was formed on the image display element 13 in the vertical direction. Several periodic lines were photographed with a CCD camera, the images were taken into a computer, and the luminance distribution in the width direction was calculated by image processing software. Using the maximum value Imax (white part) and the minimum value Imin (black part) of the luminance, the contrast C was reduced by the following equation.
[0118]
C_sample= (Imax-Imin) / (Imax + Imin)
A glass substrate having the same refractive index as that of the glass substrate 2 used for the sample 21 and having a thickness substantially equal to the thickness of the entire sample 21 was prepared._referenceWas measured and calculated. Ratio C of both_sample/ C_reference(Contrast ratio) was 75%, and it was found that image deterioration due to multiple reflection and diffraction was small. And
(N_el-N_fl) ・ D
Was 0.074.
[0119]
[Comparative Example 1]
As a comparative example of Example 1, a sample was prepared and evaluated under the same conditions as in Example 1 except that a UV-curable resin having a refractive index of 1.42 was used instead of the UV-curable resin of Example 1. . According to this, several orders of diffracted light clearly appeared, and the contrast ratio was 50%, which was not a good characteristic. And
(N_el-N_fl) ・ D
Was 0.116.
[0120]
[Comparative Example 2]
As another comparative example of Example 1, a sample 21 was prepared and evaluated under the same conditions as in Example 1 except that a UV-curable resin having a refractive index of 1.52 was used instead of the UV-curable resin of Example 1. Carried out. As a result, several orders of diffracted light appeared slightly, and the contrast ratio was 65%. The optical characteristics were intermediate between Example 1 and Comparative Example 1, but at a usable level. And
(N_el-N_fl) ・ D
Was 0.096.
[0121]
[Example 2]
100 lines of zinc oxide / antimony (ZnO-Sb205) having a pitch of 0.1 mm, a width of 0.01 mm, and a thickness of 0.2 μm are formed on the surface of a central region of a glass substrate 2 having a size of 30 mm × 40 mm and a thickness of 3 mm. The electrode 6 was formed. Zinc oxide / antimony fine particles were dispersed in an alcohol solvent, and this was spin-coated on the substrate 2. Thereafter, this was heated at 200 ° C. and fixed. The pitch and width of the electrode 6 were determined by covering the area other than the line electrode forming portion with a resist material by a photolithography process, and then dry-etching zinc oxide / antimony. The refractive index of the zinc oxide / antimony measured by an ellipsometer was 1.60 at a wavelength of 546 nm. The subsequent steps of device fabrication and evaluation were performed in the same manner as in Comparative Example 2. That is, upon irradiation with a He-Ne laser, no diffraction occurred. The contrast ratio was 80%. The optical characteristics were improved as compared with Comparative Example 2.
[0122]
[Example 3]
With the sample configurations of Examples 1 and 2 and Comparative Examples 1 and 2, the type and thickness of the line electrode 6 and the transparent filler 3 were changed to prepare a sample 21, and the optical characteristics related to the above diffraction and contrast were evaluated. did.
[0123]
Table 1 shows the results. In Table 1, in the optical characteristics, ○ indicates that no first-order diffracted light can be confirmed at all or the contrast ratio is 70% or more. The symbol Δ indicates that the first-order diffracted light can be slightly confirmed or the contrast ratio is 70% or less and 60% or more. X indicates that the first-order diffracted light can be clearly recognized or the contrast ratio is 60% or less. The conditions shown in Example 1 are indicated by △ in the table.
[0124]
[Table 1]

[0125]
From this table, the optical characteristics are as follows: transparent line electrode group thickness d, refractive index n_el, And the refractive index of the transparent filler is n_flDepends on
| (N_el-N_fl) · D | <0.11 (μm)
It has been found useful when satisfying.
[0126]
In selecting the material and thickness of the transparent filler 3, it has been found that zinc oxide / antimony is useful as the material of the line electrode 6 because it is close to the refractive index of general transparent filler 3. Similar results were obtained when tin oxide / antimony was used instead of zinc oxide / antimony.
[0127]
[Example 4]
Sample 21 was manufactured with the same configuration of sample 21 as in Comparative Example 2 except that the type of dielectric layer 4 was changed, and the optical characteristics related to contrast were evaluated in the same manner as described above.
[0128]
Refractive index n of line electrode material_elAnd the refractive index n of the dielectric layer_deIs shown in Table 2. Two kinds of indium tin oxide having different refractive indexes could change the mixing ratio of indium oxide and tin oxide. Here, the optical characteristic determination was performed based on the contrast ratio shown in Example 1.
[0129]
[Table 2]

[0130]
From this example,
| N_el-N_de| <0.56
More preferably,
| N_el-N_de| ≦ 0.46
When, the contrast deterioration due to the reflected light was small and it was confirmed that it was desirable.
[0131]
Further, it can be said that the refractive index of the material of the line electrode 6 is preferably 2.10 or less from the viewpoint that the material selection of the material of the substrate 2 and the material of the dielectric layer 4 is wide.
[0132]
[Example 5]
A commercially available two-part thermosetting resin (refractive index 1.52) was used in place of the UV curable resin of Comparative Example 2. For curing, a thermosetting resin was applied on the substrate 2 and a dielectric (borosilicate glass) having a thickness of 150 μm was overlaid on the substrate 2 and left for 24 hours under pressure to cure. Thereafter, a device was formed in the same manner as in Comparative Example 2, and the optical characteristics were evaluated. As a result, the performance was comparable to that of the UV curable resin shown in Comparative Example 2, and usable quality was obtained.
[0133]
[Example 6]
With respect to the substrate 2 having the line electrode 6 formed in Comparative Example 2, a strip-shaped Mylar film (thickness: 150 μm) having a length of 30 mm was arranged at both short side ends of the substrate 2, and a polycarbonate-based UV-curable resin was placed inside thereof. It was dropped. This is a smooth Teflon resin (Teflon is a registered trademark (the same applies hereinafter)), and is pressurized from above and cured by UV irradiation. When the thickness was measured with Teflon removed, a resin layer (dielectric layer 4) of approximately 150 μm was obtained. The cured resin layer had a refractive index of 1.58. Then SiO₂After the film was formed to a thickness of 0.2 μm by a sputtering method, it was formed into a device in the same manner as in Comparative Example 2, and the optical characteristics were evaluated. Was done.
[0134]
In addition, SiO₂When the IPA solution was applied without forming the layer, the surface of the dielectric layer 4 made of resin was deteriorated. Therefore, it was confirmed that a hard coat layer made of an inorganic transparent material was useful.
[0135]
[Example 7]
In the same manner as in Example 2, a line electrode 6 made of zinc oxide / antimony was formed. After that, the sputtering method₂A film is formed on the entire surface of the substrate by 2000 mm, and the SiO₂The film surface was polished and flattened. SiO₂The refractive index of the film was 1.47. An alignment film was formed thereon, and the subsequent steps were performed in the same manner as in Example 1. When the optical characteristics were evaluated, characteristics excellent in a contrast ratio without diffraction were obtained.
[0136]
Example 8
The patterns shown in Table 3 were formed in place of the pattern (0.1 mm pitch, 0.01 mm width) of the line electrode 6 in Comparative Example 2. In Table 3, in the part where the numerical values are shown in the range, the respective dimensions were obtained by random numbers. Other conditions were converted to devices in the same manner as in Comparative Example 2, and evaluation was performed. As shown in Table 3, the optical properties were improved as compared with Comparative Example 2. This is because the first-order diffracted light slightly observed in Comparative Example 2 was reduced or disappeared. Therefore, the electrode widths of the adjacent line electrodes 6 are set to different values, or the distance between two electrodes formed between the three adjacent line electrodes 6 (the distance between the center lines of the line electrodes 6) is set to a different value. The effect of setting was confirmed.
[0137]
[Table 3]

[0138]
[Example 9]
Indium tin oxide (ITO) was formed on the entire surface of a glass substrate 2 having a size of 30 mm × 40 mm and a thickness of 3 mm by a high-frequency magnetron sputtering method. On the other hand, as an exposure mask for the photolithography process, a mask was used in which light was completely transmitted through portions other than the ITO and the transmittance of the ITO portion was different for each adjacent line electrode 6. A positive resist was applied to the substrate 2 on which the above-mentioned ITO was formed on the entire surface, and the above-mentioned exposure mask was brought into close contact with the ITO surface and exposed. Exposure conditions were such that during cleaning, the resist in portions other than ITO was completely removed, and the resist in the ITO portion remained with a thickness dependent on the transmittance. Dry etching was performed in this state to form a line electrode 6. Each electrode 6 depends on the resist thickness, and the film thickness changes. The etching conditions were set so that this film thickness was 0.15 μm to 0.2 μm. Other conditions were made into a device in the same manner as in Comparative Example 2, and the device was evaluated. As shown in Tables 1 to 3, the optical properties were improved as compared with Comparative Example 2. This is because the first-order diffracted light slightly observed in Comparative Example 2 was reduced. Therefore, the effect of setting the electrode thickness of the adjacent line electrode 6 to a different value was confirmed.
[0139]
[Example 10]
Each line electrode 6 of the light deflecting element 1 of Comparative Example 2 was connected to a flexible substrate having a corresponding metal wire via an anisotropic conductive paste. The resistor circuit 7a shown in FIG. 1 is connected to the opposite side of the metal wire, and a voltage gradient is generated at each line electrode 6 by applying a voltage to the resistor circuit 7a. The voltage was selected such that the potential gradient at this time was 100 V / mm. While applying this voltage, an image was displayed using the apparatus shown in FIG. In this case, it was confirmed that by switching the direction of the voltage, the optical path was shifted by a half pitch of the image display element 13. In this case, the frame frequency of the image display was set to 60 Hz. At this time, the subfield time corresponds to 8.3 ms.
[0140]
Each sample 21 shown in Table 1 was mounted in the same manner, loaded into an image display device, and a pixel-shifted image was formed. In Tables 1 to 3, in the samples marked with “○”, images excellent in contrast were obtained. On the other hand, in the sample 21 marked with x, the contrast was low and the image quality was low.
[0141]
Thus, it was confirmed that an extremely good image could be obtained by using the optical element of the present invention.
[0142]
【The invention's effect】
The invention according to claims 1 to 5 improves the wavefront aberration by preventing light diffraction from occurring when the electrode has a periodic structure and preventing an image from being formed at a position different from the original image formation position, A sharp image can be obtained.
[0143]
According to a sixth aspect of the present invention, in the invention of any one of the third to fifth aspects, the difference in refractive index between the material of the substrate and the dielectric layer that is generally used increases, and the amount of interface reflection increases. Increases and the amount of diffracted light is prevented from increasing, the wavefront aberration is improved, and a sharp image can be obtained.
[0144]
The invention according to claim 7 is the invention according to any one of claims 3 to 6, wherein the transparency is excellent and the surface resistance is controlled to a value that does not cause a problem in generating an electric field applied to the liquid crystal. Since the refractive index can be controlled to be smaller than that of indium tin oxide which has been generally used conventionally, the wavefront aberration can be improved and a sharp image can be obtained.
[0145]
In the invention according to claim 8, in the invention according to any one of claims 3 to 7, when a photocurable resin is used as the transparent filler, the process from resin filling to curing can be performed in a short time, so that the production time is shortened. When the thermosetting resin is used as the transparent filler, deterioration due to light does not occur as compared with the case where the photocurable resin is used, so that the manufacturing operation can be usually performed under white illumination and the workability is excellent. In addition, sufficient light transmittance can be ensured for any of the resins, and good optical characteristics can be obtained.
[0146]
According to a ninth aspect of the present invention, in the fourth aspect of the present invention, the thickness can be controlled to a desired value, and optical bonding is performed after bonding to a substrate having electrodes through the filler of the eighth aspect. This makes it possible to obtain a surface with extremely excellent smoothness and to suppress diffraction, scattering, and the like of light.
[0147]
According to the tenth aspect of the present invention, in the invention of the fourth or ninth aspect, the manufacturing process can be shortened and the number of interfaces can be reduced as compared with the structure of the ninth aspect, so that deterioration of optical performance can be reduced.
[0148]
According to an eleventh aspect of the present invention, in the invention of the fourth, ninth or tenth aspect, the dielectric layer made of a photocurable or thermosetting resin is altered by a solvent used for forming an alignment film of liquid crystal. And optical deterioration due to deterioration of the dielectric layer can be prevented.
[0149]
According to a twelfth aspect of the present invention, in the invention according to any one of the third, fourth to seventh, and ninth aspects, the degree of freedom in selecting the refractive index depending on the composition is greater than that of the filler of the eighth aspect, The difference in refractive index from the electrode can be reduced.
[0150]
According to a thirteenth aspect of the present invention, in the invention according to any one of the third, fourth to seventh, ninth, and twelfth aspects, the transmittance is high and the refractive index can be adjusted by the composition. The difference can be reduced. Further, when the liquid crystal layer, the electrode, and the filler are set to have substantially the same refractive index when used for the electrode of claim 7, the wavefront aberration can be improved and a sharp image can be obtained.
[0151]
According to a fourteenth aspect of the present invention, in the invention according to any one of the third to thirteenth aspects, noise light traveling in a direction different from a predetermined direction is reduced, and light diffraction caused by the arrangement of the electrodes is reduced. Can be reduced.
[0152]
According to a fifteenth aspect, in the fourteenth aspect, noise light traveling in a direction different from the predetermined direction can be reduced, and light diffraction caused by the arrangement of the electrodes can be reduced.
[0153]
According to a sixteenth aspect of the present invention, in the invention according to any one of the third to fifteenth aspects, noise light traveling in a direction different from the predetermined direction is reduced, and light diffraction caused by the arrangement of the electrodes is reduced. Can be reduced.
[0154]
The invention according to claim 17 can provide an image display device that can improve contrast and light use efficiency and can obtain a higher definition image.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an overall configuration of a light deflection element according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram schematically showing a liquid crystal molecule alignment state of a light deflection element.
FIG. 3 is an explanatory diagram schematically showing a liquid crystal molecule alignment state of the light deflecting element.
FIG. 4 is a graph showing a relationship between a liquid crystal alignment angle of an optical deflection element and an optical axis shift amount.
FIG. 5 is a graph showing a time change of a voltage of the light deflection element and a light deflection amount.
FIG. 6 is a schematic diagram for explaining a cross-sectional structure around a line electrode in the light deflection element.
FIG. 7 is a front view of a substrate, a line electrode, and the like.
FIG. 8 is a side view of a substrate and a line electrode.
FIG. 9 is a schematic diagram for explaining a cross-sectional structure around a line electrode in another configuration example of the light deflection element.
FIG. 10 is a conceptual diagram illustrating an outline of an image display device according to an embodiment of the present invention.
FIG. 11 is an explanatory diagram illustrating an embodiment of the present invention.
[Explanation of symbols]
1 optical element, light deflection element
2 Substrate
3 packed bed
4 Dielectric layer
5 Liquid crystal layer
6 electrodes
13 Image display device

Claims (17)

A pair of transparent substrates,
A liquid crystal layer filled between the substrates,
A plurality of electrodes provided at least one of the pair of substrates arranged at intervals in the width direction of the substrate,
A filler filled between the electrodes to reduce diffraction of the electrodes,
With
The thickness of the electrode d, the refractive index at a wavelength of 546nm and _{n el,} a refractive index of the filling material is taken as _{n fl,
| (N el -n fl) ·} d | <0.11 (μm)
An optical element. Further comprising a dielectric layer provided between the liquid crystal layer and the electrode,
When the refractive index of this dielectric is n _de ,
_{| N e l -n de | <} 0.56
The optical element according to claim 1, wherein A pair of transparent substrates,
A liquid crystal layer containing a liquid crystal composed of a chiral smectic C phase having homeotropic alignment and filled between the substrates;
A plurality of electrodes provided at least one of the pair of substrates arranged at intervals in the width direction of the substrate,
A filler filled between the electrodes to reduce diffraction of the electrodes,
Voltage applying means for deflecting light by applying a voltage of different magnitude in a stepwise manner between adjacent electrodes for each electrode,
With
The thickness of the electrode d, the refractive index at a wavelength of 546nm and _{n el,} a refractive index of the filling material is taken as _{n fl,
| (N el -n fl) ·} d | <0.11 (μm)
An optical deflection element. The light deflecting element according to claim 3, further comprising a dielectric layer provided between the liquid crystal layer and the electrode. When the refractive index of the dielectric is n _de ,
_{| N e l -n de | <} 0.56
The light deflecting element according to claim 4, wherein The electrode has a refractive index n _el of:
1.5 _<n e l _<2.0
The optical deflection element according to claim 3, wherein: The light deflecting element according to any one of claims 3 to 6, wherein the electrode comprises zinc oxide / antimony or tin oxide / antimony. The light deflecting element according to claim 3, wherein the filler is a light-curing or thermosetting resin. The light deflecting element according to claim 4, wherein the dielectric layer is a glass material. The light deflecting element according to claim 4, wherein the dielectric layer is a light-curable or thermosetting resin and also serves as the filler. The light deflecting device according to claim 4, 9 or 10, wherein the dielectric layer has a hard coat layer made of a transparent inorganic material formed on a surface on the liquid crystal side. The light deflecting element according to any one of claims 3, 4 to 7, and 9, wherein the filler is made of a transparent inorganic material. The light deflecting element according to claim 3, wherein the filler is made of silicon oxide. 14. The light deflecting element according to claim 3, wherein the electrode widths of the plurality of electrodes are not uniform. 15. The light deflecting element according to claim 14, wherein the plurality of electrodes are set such that a distance between center lines of two electrodes formed by three adjacent electrodes is different. The light deflecting element according to claim 3, wherein the plurality of electrodes have irregular electrode thicknesses. An image display device that spatially modulates illumination light for each of a plurality of image subfields obtained by further subdividing an image field temporally based on image information and emits the image light as image light,
In synchronism with this image display element, the optical path of image light coming from each pixel of the image display element driven for each image subfield is deflected to multiply the apparent number of pixels of the image display element. The light deflecting element according to any one of claims 3 to 16, wherein
An image display device comprising:

Images