JP2004029695A

JP2004029695A - Display device

Info

Publication number: JP2004029695A
Application number: JP2002301821A
Authority: JP
Inventors: Tetsushi Yoshida; 吉田　哲志; Ikuhiro Yamaguchi; 山口　郁博; Tetsuya Kusuno; 楠野　哲也; Yoshiaki Sawano; 澤野　義昭
Original assignee: Casio Computer Co Ltd
Current assignee: Casio Computer Co Ltd
Priority date: 2002-04-30
Filing date: 2002-10-16
Publication date: 2004-01-29

Abstract

【課題】二重像の無い良好な品質で、しかも充分な明るさの反射表示を行なうことができる表示装置を提供する。
【解決手段】入射光の透過と遮断を制御する液晶表示素子１の後側に、前側から入射した光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる第１の反射偏光板１１と、その後側に配置され、前記第１の偏光分離素子１１の後側への透過光及び反射光の少なくとも一部を反射する第２の反射偏光板１２とからなり、前記液晶表示素子１を透過して前側から入射し、前記第１の偏光分離素子１１を透過した光の少なくとも一部を前記第１と第２の反射偏光板１１，１２の間で多重反射させるとともに、その反射毎に反射光の一部を前記第１の反射偏光板１１を透過させて前側に出射する多重反射手段１０を配置した。
【選択図】　　図２An object of the present invention is to provide a display device capable of performing reflective display with good quality without double images and with sufficient brightness.
A liquid crystal display element (1) for controlling transmission and blocking of incident light reflects one of two different polarization components of light incident from a front side and controls the other polarization component on the rear side of the liquid crystal display element (1). A first reflective polarizing plate 11 that transmits light, and a second reflective polarizing plate 12 that is disposed on the rear side and reflects at least part of transmitted light and reflected light to the rear side of the first polarization separation element 11. At least a portion of the light transmitted through the liquid crystal display element 1 and incident from the front side and transmitted through the first polarization splitting element 11 between the first and second reflective polarizing plates 11 and 12. Multiple reflection means 10 is provided for performing multiple reflection and transmitting a part of the reflected light through the first reflective polarizing plate 11 to the front side for each reflection.
[Selection] Figure 2

Description

【０００１】
【発明の属する技術分野】
この発明は、反射表示を行なう表示装置に関する。
【０００２】
【従来の技術】
外部環境の光である外光を利用して反射表示を行なう反射型の表示装置は、従来、例えば液晶表示素子等のような入射光の透過と遮断を制御する表示素子と、この表示素子の表示の観察側とは反対側である後側に配置された反射膜とにより構成されている（特許文献１、２、３参照）。
【０００３】
この反射型表示装置は、表示の観察側である前側から入射した光を前記表示素子により遮断することにより暗表示を得、前側から入射して前記表示素子を透過した光を前記反射膜により反射し、その反射光を前記表示素子の前側に出射して明表示を得るものであり、その表示は、正面方向、つまり画面の法線付近の方向から観察される。
【０００４】
【特許文献１】
特開２０００−７５２８４号公報
【０００５】
【特許文献２】
特開平−９０６７８号公報
【０００６】
【特許文献３】
特開２００１−２９０４４５号公報
【０００７】
【発明が解決しようとする課題】
しかし、上記反射型の表示装置は、通常、画面の法線に対して斜めに傾いた方向（ほとんどの場合は、画面の法線に対して前記画面の上縁方向に傾いた方向）を最も明るい外光が入射する方向に向けて使用されるため、前記表示素子での入射光の遮断による暗表示の影が、前記表示素子の暗表示部からずれた位置にできる。
【０００８】
そのため、従来の反射型表示装置は、表示が二重像となって見えるという問題をもっている。
【０００９】
この発明は、二重像の無い良好な品質で、しかも充分な明るさの反射表示を行なうことができる表示装置を提供することを目的としたものである。
【００１０】
【課題を解決するための手段】
この発明の表示装置は、
入射光の透過と遮断を制御する表示素子と、
前記表示素子の表示の観察側とは反対側である後側に配置され、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記表示素子を透過して前側から入射した光の少なくとも一部を透過させ、後側から入射した光の一部を反射する第１の偏光分離素子と、前記第１の偏光分離素子の後側に配置され、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記第１の偏光分離素子の後側への透過光及び反射光の少なくとも一部を反射する第２の偏光分離素子とからなり、前記表示素子を透過して前側から入射し、前記第１の偏光分離素子を透過した光の少なくとも一部を前記第１と第２の偏光分離素子の間で多重反射させるとともに、その反射毎に反射光の一部を前記第１の偏光分離素子を透過させて前側に出射する多重反射手段と、
を備えたことを特徴とする。
【００１１】
すなわち、この表示装置は、表示の観察側である前側から入射した光を前記表示素子により遮断することにより暗表示を得、前側から入射して前記表示素子を透過した光を前記多重反射手段に入射させ、この多重反射手段の第１の偏光分離素子を透過した光の少なくとも一部を前記第１と第２の偏光分離素子の間で多重反射させ、その反射毎に反射光の一部を前記第１の偏光分離素子を透過させて前記多重反射手段の前側に出射し、その光を前記表示素子の前側に出射させて明表示を得るものである。
【００１２】
この表示装置によれば、前記多重反射手段が、その前側から入射した光を多重反射させ、その反射の度に反射光の一部を前側に出射するため、前記表示素子の前側から入射し、この表示素子を透過して前記多重反射手段に入射した光が、上述した多重反射により広がって前記多重反射手段の前側に出射する。
【００１３】
そのため、前側からの入射光が前記表示素子により遮断された部分からも前記多重反射手段による反射光が出射し、前記表示素子での入射光の遮断による暗表示の影が無くなり、二重像の無い良好な品質の表示が得られる。
【００１４】
しかも、この表示装置は、前記多重反射手段が、光吸収のない２つの偏光分離素子からなっているため、光の吸収による損失が無く、明表示の輝度を充分に高くし、充分な明るさの反射表示を行なうことができる。
【００１５】
このように、この発明の表示装置は、入射光の透過と遮断を制御する表示素子の後側に、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記表示素子を透過して前側から入射した光の少なくとも一部を透過させ、後側から入射した光の一部を反射する第１の偏光分離素子と、前記第１の偏光分離素子の後側に配置され、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記第１の偏光分離素子の後側への透過光及び反射光の少なくとも一部を反射する第２の偏光分離素子とからなり、前記表示素子を透過して前側から入射し、前記第１の偏光分離素子を透過した光の少なくとも一部を前記第１と第２の偏光分離素子の間で多重反射させるとともに、その反射毎に反射光の一部を前記第１の偏光分離素子を透過させて前側に出射する多重反射手段を配置することにより、二重像の無い良好な品質で、しかも充分な明るさの反射表示を行なうことができるようにしたものである。
【００１６】
また、この表示装置において、前記多重反射手段の第１と第２の偏光分離素子はそれぞれ、互いに直交する方向に透過軸と反射軸を有し、入射光の互いに直交する２つの直線偏光成分のうち、前記反射軸に平行な振動面をもった一方の偏光成分を反射し、前記透過軸に平行な振動面をもった他方の偏光成分を透過させる反射偏光素子であり、これらの反射偏光素子が、それぞれの透過軸を互いに斜めにずらして配置されているのが好ましい。
【００１７】
また、この表示装置において、前記多重反射手段は、前記第１と第２の偏光分離素子の間に、その一方の偏光分離素子から他方の偏光分離素子に向かう光と、前記他方の偏光分離素子から前記一方の偏光分離素子に向かう光の振動面の方向を変化させる第３の偏光分離素子をさらに配置した構成としてもよい。
【００１８】
さらに、前記多重反射手段は、前記第１と第２の偏光分離素子の間に、その一方の偏光分離素子から他方の偏光分離素子に向かう光と、前記他方の偏光分離素子から前記一方の偏光分離素子に向かう光の偏光状態を変化させる位相差板をさらに配置した構成としてもよい。
【００１９】
前記多重反射手段は、前記第２の偏光分離素子の裏側に配置され、前記第２の偏光分離素子の後側への透過光及び反射光を反射し、前記第１及び第２の偏光分離素子との間で多重反射を生じさせる反射膜をさらに備えているのが望ましい。
【００２０】
また、前記多重反射手段は、前記第１と第２の偏光分離素子の間に、前面及び後面からの入射光をそれぞれ透過させ、端面からの入射光を前記前面と後面の少なくとも一方から出射する導光板と、この導光板の前記端面に対向させて設けられた発光素子とからなる面光源をさらに配置した構成とするのが望ましい。
【００２１】
その場合は、前記面光源の導光板を、前記多重反射手段の第１と第２の一方の偏光分離素子から他方の偏光分離素子に向かう光と、前記他方の偏光分離素子から前記一方の偏光分離素子に向かう光の偏光状態を変化させる位相差板としてもよい。
【００２２】
【発明の実施の形態】
図１〜図３はこの発明の第１の実施例を示しており、図１は表示装置の分解斜視図、図２及び図３は前記表示装置の反射表示のときと透過表示のときの入射光の透過経路を示す模式図である。
【００２３】
この実施例の表示装置は、図１に示したように、入射光の透過と遮断を制御する表示素子１と、前記表示素子１の表示の観察側（図１において上側）とは反対側である後側に配置された多重反射手段１０とを備えている。
【００２４】
前記表示素子１は、例えば液晶表示素子であり、表示の観察側である前側の透明基板３と、この前側基板３に対向する後側の透明基板４とが枠状のシール材５を介して接合され、これらの基板３，４間の前記シール材５で囲まれた領域に、印加される電界に応じて透過光の偏光状態を制御する液晶層６（図２及び図３参照）が設けられた液晶セル２と、前記液晶セル２を挟んでその前後に配置された一対の偏光板７，８とからなっている。
【００２５】
なお、図では省略しているが、前記液晶セル２の前後の基板３，４の内面には、互いに対向する領域によりマトリックス状に配列する複数の画素を形成する透明電極が設けられ、その上に配向膜が設けられている。
【００２６】
この液晶セル２は、例えばＴＦＴ（薄膜トランジスタ）を能動素子とするアクティブマトリックス液晶セルであり、その一方の基板、例えば後側基板４の内面に、行方向及び列方向にマトリックス状に配列する複数の画素電極と、これらの画素電極にそれぞれ接続された複数のＴＦＴと、各行のＴＦＴにそれぞれゲート信号を供給する複数のゲート配線と、各列のＴＦＴにそれぞれデータ信号を供給する複数のデータ配線とが設けられ、他方の基板である前側基板３の内面に、前記複数の画素電極にそれぞれ対向させて交互に並べて形成された複数の色、例えば赤、緑、青の３色のカラーフィルタと、前記複数の画素電極に対向する一枚膜状の対向電極とが設けられている。
【００２７】
前記液晶表示素子１は、ＴＮ（ツイステッドネマティック）型のものであり、前記液晶セル２の液晶層６は、液晶分子が前後の基板３，４間において実質的に９０°のツイスト角でツイスト配向した誘電異方性が正のネマティック液晶からなっている。
【００２８】
図１において、矢印３ａは前記液晶セル２の前側基板３の近傍における液晶分子配向方向、矢印４ａは後側基板４の近傍における液晶分子配向方向を示しており、前側基板３の近傍における液晶分子配向方向３ａは、表示装置の画面の横軸ｘに対して一方の方向に実質的に４５°の方向、後側基板４の近傍における液晶分子配向方向４ａは、前記横軸ｘに対して他方の方向に実質的に４５°の方向にあり、前記液晶層６の液晶分子は、そのツイスト方向を図１に破線矢印で示したように、後側基板４から前側基板３に向かって実質的に９０°のツイスト角でツイスト配向している。
【００２９】
また、前記液晶セル２を挟んで配置された一対の偏光板７，８はそれぞれ、互いに直交する方向に透過軸７ａ，８ａと吸収軸（図示せず）を有し、入射光の互いに直交する２つの直線偏光成分のうち、前記吸収軸に平行な振動面をもった一方の偏光成分を吸収し、前記透過軸７ａ，８ａに平行な振動面をもった他方の偏光成分を透過させる吸収偏光板であり、前側の吸収偏光板７は、その透過軸７ａを前記液晶セル２の前側基板３の近傍における液晶分子配向方向３ａと実質的に直交または平行（図では直交）にして前記液晶セル２の前側基板３の外面に貼付けられ、後側の吸収偏光板８は、その透過軸８ａを前記前側の吸収偏光板７の透過軸７ａと実質的に直交させて前記液晶セル２の後側基板４の外面に貼付けられている。
【００３０】
一方、前記液晶表示素子１の後側に配置された多重反射手段１０は、前記液晶表示素子１の表示の観察側とは反対側である後側に配置された第１の偏光分離素子１１と、この第１の偏光分離素子１１の後側に配置された第２の偏光分離素子１２とを有し、さらに、前記第２の偏光分離素子１２の後側に反射膜１５が配置され、前記第１と第２の偏光分離素子１１，１２の間に面光源１６が配置された構成となっている。
【００３１】
前記第１と第２の偏光分離素子１１，１２はそれぞれ、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる偏光分離特性を有している。
【００３２】
前記第１と第２の偏光分離素子１１，１２は、例えば、入射光の互いに直交する２つの直線偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる反射偏光素子であり、この実施例では、互いに直交する方向に透過軸１１ａ，１２ａと反射軸１１ｂ，１２ｂを有し、入射光の互いに直交する２つの直線偏光成分のうち、前記反射軸１１ｂ，１２ｂに平行な振動面をもった一方の偏光成分を反射し、前記透過軸１１ａ，１２ａに平行な振動面をもった他方の偏光成分を透過させる反射偏光板を用いている。以下、前記第１の偏光分離素子１１を第１の反射偏光板と言い、前記第２の偏光分離素子１２を第２の反射偏光板と言う。
【００３３】
そして、前記液晶表示素子１の後側の第１の反射偏光板１１は、その透過軸１１ａを前記液晶表示素子１の後側の吸収偏光板８の透過軸８ａと実質的に平行にして配置され、この第１の反射偏光板１１の後側の第２の反射偏光板１２は、その透過軸１２ａを前記第１の反射偏光板１１の透過軸１１ａに対し、実質的に４５°の角度で斜めにずらして配置されている。
【００３４】
また、前記第１と第２の反射偏光板１１，１２の間に配置された面光源１６は、前面及び後面からの入射光をそれぞれ透過させ、端面からの入射光を前記前面と後面の少なくとも一方から出射する導光板１７と、この導光板１７の前記端面に対向させて設けられた発光素子１８とからなっている。
【００３５】
なお、この実施例で用いた面光源１６は、ＬＥＤ（発光ダイオード）からなる複数の前記発光素子１８を前記導光板１７の端面に対向させて配置したものであるが、前記導光板１７の端面に対向させて配置する発光素子は、直管状の冷陰極管等でもよい。
【００３６】
この面光源１６は、前記導光板１７の前面から入射した光を透過させてこの導光板１７の後面から出射し、前記導光板１７の後面から入射した光を透過させてこの導光板１７の前面から出射するとともに、前記発光素子１８から出射して前記導光板１７にその端面から入射した光を、この導光板１７の前面及び後面と外気（空気）との界面で全反射しながら導光板１７内を導いてその前面及び後面から出射するものであり、前記発光素子１８は、充分な明るさの外光が得られる環境下で表示装置を使用するときは消灯され、充分な明るさの外光が得られない環境下で表示装置を使用するときに点灯される。
【００３７】
この面光源１６は、前記導光板１７の前面を前側の第１の反射偏光板１１の後面に対向させ、前記導光板１７の後面を後側の第２の反射偏光板１２の前面に対向させるとともに、前記導光板１７の前後面と前記第１及び第２の反射偏光板１１，１２との間に空気層を設けて配置されており、前記反射膜１５は、前記第２の反射偏光板１２の後側に、その後面に近接させるか、あるいは貼付けて配置されている。
【００３８】
この表示装置は、充分な明るさの外光が得られる環境下では、表示の観察側である前側から入射した外光を利用する反射表示を行ない、充分な明るさの外光が得られないときに前記多重反射手段１０の面光源１６から照明光を出射させてその照明光を利用する透過表示を行なうものであり、その表示は、正面方向（画面の法線付近の方向）から観察される。
【００３９】
この実施例の表示装置は、図１に示したように、前記液晶表示素子１の前側の吸収偏光板７の透過軸７ａと後側の吸収偏光板８の透過軸８ａとを実質的に直交させたものであるため、外光を利用する反射表示も、また前記面光源１６からの照明光を利用する透過表示も、前記液晶セル２の液晶層６に電界を印加しない無電界時（液晶層６の液晶分子の配向状態が初期のツイスト配向であるとき）の表示が明表示である、いわゆるノーマリーホワイトモードの表示である。
【００４０】
図２は前記表示装置の反射表示のときの入射光の透過経路を示す模式図、図３は前記表示装置の透過表示のときの入射光の透過経路を示す模式図であり、図では、前記液晶表示素子１の液晶セル２の液晶層６の層厚を大きく誇張して示している。
【００４１】
まず、図２に示した反射表示のときの入射光の透過経路を説明する。図２（ａ）は前記液晶セル２の液晶層６に電界を印加しない無電界時（Ｖ＝０）の透過経路を示し、図２（ｂ）は前記液晶セル２の液晶層６に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加した電界印加時（Ｖ＞Ｖｔｈ）の透過経路を示している。
【００４２】
この反射表示のときは、図２（ａ），（ｂ）のように、前側から入射した外光（非偏光）の互いに直交する２つの直線偏光成分のうち、液晶表示素子１の前側の吸収偏光板７の吸収軸に平行な振動面をもった偏光成分が、この吸収偏光板７により吸収され、前記吸収偏光板７の透過軸７ａに平行な振動面をもった偏光成分が、この吸収偏光板７を透過し、前記吸収偏光板７の透過軸７ａに平行な直線偏光Ｓとなって液晶セル２にその前側から入射する。
【００４３】
前記液晶セル２にその前側から入射した直線偏光Ｓは、前記液晶セル２の電極間に印加される電界により変化する液晶分子の配向状態に応じた液晶層６の複屈折作用を受けてこの液晶セル２の後側に出射し、後側の吸収偏光板８により遮断されるか、あるいは前記後側の吸収偏光板８を透過して液晶表示素子１の後側に出射する。
【００４４】
すなわち、前記液晶セル２の電極間に電界を印加しない無電界時（Ｖ＝０）の液晶分子の配向状態は、実質的に９０°のツイスト角のツイスト配向であり、このときは、図２（ａ）に示したように、前側の吸収偏光板７を透過して液晶セル２に入射した直線偏光Ｓが、液晶層６の複屈折作用により実質的に９０°旋光し、後側の吸収偏光板８の透過軸８ａに平行な直線偏光Ｐとなって液晶セル２の後側に出射するため、この無電界時は、前記液晶セル２の後側に出射した前記直線偏光Ｐが前記後側の吸収偏光板８を透過して液晶表示素子１の後側に出射する。
【００４５】
前記液晶表示素子１の後側に出射した前記直線偏光Ｐは、前記多重反射手段１０にその前側から入射する。
【００４６】
この実施例では、前記多重反射手段１０の前側の偏光分離素子である第１の反射偏光板１１の透過軸１１ａを、前記液晶表示素子１の後側の吸収偏光板８の透過軸８ａと実質的に平行にしているため、前記液晶表示素子１の後側に出射して多重反射手段１０に入射した前記直線偏光Ｐは、そのほとんどが前記第１の反射偏光板１１を透過してその後側に出射する。
【００４７】
前記第１の反射偏光板１１の後側に出射した前記直線偏光Ｐは、面光源１６の導光板１７を透過して多重反射手段１０の後側の偏光分離素子である第２の反射偏光板１２に入射する。
【００４８】
そして、前記第２の反射偏光板１２の透過軸１２ａは、前記第１の反射偏光板１１の透過軸１１ａに対して斜めにずれているため、前記第１の反射偏光板１１を透過して第２の反射偏光板１２にその前側から入射した前記直線偏光Ｐの前記第２の反射偏光板１２の透過軸１２ａに平行な振動面をもった偏光成分が、この第２の反射偏光板１２を透過してその後側に出射し、前記第２の反射偏光板１２の反射軸１２ｂに平行な振動面をもった偏光成分が、この第２の反射偏光板１２により前側に反射される。
【００４９】
前記第２の反射偏光板１２を透過してその後側に出射した光、つまり、前記第２の反射偏光板１２の透過軸１２ａに平行な直線偏光Ｐａは、反射膜１５により反射され、前記第２の反射偏光板１２を再び透過し、さらに前記導光板１７を透過して前記第１の反射偏光板１１にその後側から再入射する。
【００５０】
一方、前記第２の反射偏光板１２にその前側から入射した前記直線偏光Ｐのうち、この第２の反射偏光板１２により反射された光、つまり、前記第２の反射偏光板１２の反射軸１２ｂに平行な直線偏光Ｓａは、前記導光板１７を透過して前記第１の反射偏光板１１にその後側から再入射する。
【００５１】
前記第１の反射偏光板１１にその後側から再入射した直線偏光Ｐａ，Ｓａは、いずれも、前記第１の反射偏光板１１の透過軸１１ａ及び反射軸１１ｂの両方に対して斜めにずれた振動面を有する直線偏光であるため、その直線偏光Ｐａ，Ｓａの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０の前側に出射する。
【００５２】
また、前記第１の反射偏光板１１にその後側から再入射した前記直線偏光Ｐａ，Ｓａの前記第１の反射偏光板１１の反射軸１１ｂに平行な振動面をもった偏光成分（第１の反射偏光板１１の反射軸１１ｂに平行な直線偏光）Ｓは、この第１の反射偏光板１１により後側に反射されて前記第２の反射偏光板１２に再び入射し、その光Ｓの前記第２の反射偏光板１２の透過軸１２ａに平行な振動面をもった偏光成分（第２の反射偏光板１２の透過軸１２ａに平行な直線偏光）Ｐａが、この第２の反射偏光板１２を透過してその後側に出射し、前記第２の反射偏光板１２の反射軸１２ａに平行な振動面をもった偏光成分（第２の反射偏光板１２の反射軸１２ｂに平行な直線偏光）Ｓａが、この第２の反射偏光板１２により反射される。
【００５３】
前記第２の反射偏光板１２を透過してその後側に出射した直線偏光Ｐａは、前記反射膜１５により再度反射され、前記第２の反射偏光板１２と前記導光板１７とを再び透過して前記第１の反射偏光板１１にその後側から再入射し、その光Ｐａの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０の前側に出射する。
【００５４】
また、前記第１の反射偏光板１１により後側に反射されて前記第２の反射偏光板１２に再び入射した前記直線偏光Ｓのうち、前記第２の反射偏光板１２により反射された光Ｓａは、前記第１の反射偏光板１１にその後側から再入射し、その光Ｓａの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０の前側に出射する。
【００５５】
なお、この実施例では、前記第１と第２の反射偏光板１１，１２の透過軸１１ａ，１２ａ実質的に４５°の角度で斜めにずらしているため、前側から第１の反射偏光板１１を透過して第２の反射偏光板１２に入射した直線偏光Ｐの略半分が前記第２の反射偏光板１２を透過してその後側に出射し、他の略半分が前記第２の反射偏光板１２により反射されるとともに、前記反射膜１５により反射され、前記第２の反射偏光板１２を再び透過して前記第１の反射偏光板１１にその後側から再入射した直線偏光Ｐａの略半分と、前記第２の反射偏光板１２により前側に反射されて前記第１の反射偏光板１１にその後側から再入射した直線偏光Ｓａの略半分がそれぞれ前記第１の反射偏光板１１を透過して多重反射手段１０の前側に出射し、前記直線偏光Ｐａ，Ｓａの他の略半分が前記第１の反射偏光板１１により後側に反射される。
【００５６】
すなわち、前記多重反射手段１０は、その前側から前記第１の反射偏光板１１を透過して入射し、前記第２の反射偏光板１２により反射された光の一部を前記第１の反射偏光板１１を透過させて前側に出射するとともに、他の光を前記第１と第２の反射偏光板１１，１２の間で１回または複数回多重反射させ、その反射毎に、前記第２の反射偏光板１２による反射光の一部を前記第１の偏光分離素子１１を透過させて前側に出射する。
【００５７】
さらに、この多重反射手段１０は、その前側から前記第１の反射偏光板１１を透過して入射した光のうち、前記第２の反射偏光板１２を透過してその後側に出射した光を反射膜１５により反射し、前記第２の反射偏光板１２を再び透過した光の一部を前記第１の反射偏光板１１を透過させて前側に出射するとともに、他の光を前記第１と第２の反射偏光板１１，１２の間で１回または複数回多重反射させ、その反射毎に、前記第２の反射偏光板１２による反射光の一部を前記第１の偏光分離素子１１を透過させて前側に出射する。
【００５８】
そのため、前記液晶表示素子１の前側から入射し、この液晶表示素子１を透過して前記多重反射手段１０に入射した光は、上述した第１と第２の反射偏光板１１，１２間での多重反射及び前記反射膜１５と第１及び第２の反射偏光板１１，１２との間での多重反射によりその光の入射部分から周囲に広がり、前記入射部分の周囲から前記第１の反射偏光板１１の透過軸１１ａに平行な直線偏光Ｐとなって前側に出射する。
【００５９】
前記多重反射手段１０の前側に出射した直線偏光Ｐは、前記液晶表示素子１の後側の吸収偏光板８を透過して液晶セル２にその後側から入射して液晶層６により実質的に９０°旋光され、前側の吸収偏光板７を透過して前記液晶表示素子１の前側に出射する。
【００６０】
したがって、無電界時（Ｖ＝０）は、前側から入射し、前記液晶表示素子１を透過してその後側の多重反射手段１０に入射した光が、多重反射手段１０により光束を広げて反射され、その反射光が前記液晶表示素子１を再び透過して前側に出射して、明表示（着色表示）になる。
【００６１】
一方、前記液晶セル２の電極間に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加した電界印加時（Ｖ＞Ｖｔｈ）は、図２（ｂ）に示したように、前側の吸収偏光板７を透過して液晶セル２に入射した直線偏光Ｓが、液晶層６の複屈折作用を受けずにその偏光状態のまま前記液晶セル２を透過して後側の吸収偏光板８に入射し、その光のほとんどが前記後側の吸収偏光板８により吸収される。
【００６２】
したがって、電界印加時は、前側から入射した光が液晶表示素子１により遮断されて暗表示（黒表示）になる。
【００６３】
なお、この表示装置の表示の明暗は、前記液晶セル２の液晶分子の配向状態に応じて変化するため、前記液晶セル２の電極間に印加する電界を制御することにより、前記明暗の階調を制御することができる。
【００６４】
すなわち、この表示装置は、表示の観察側である前側から入射した光を前記液晶表示素子１により遮断することにより暗表示を得、前側から入射して前記液晶表示素子１を透過した光を前記多重反射手段１０に入射させ、この多重反射手段１０の第１の反射偏光板１１を透過して第２の反射偏光板１２及び反射膜１５により反射され、前記第１の反射偏光板１１を透過して前記多重反射手段１０の前側に出射する光の一部を、前記第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と前記反射膜１５との間で多重反射させ、その反射毎に反射光の一部を前記第１の反射偏光板１１を透過させて前記多重反射手段１０の前側に出射し、その光を前記液晶表示素子１の前側に出射させて明表示を得るものである。
【００６５】
この表示装置によれば、前記多重反射手段１０が、その前側から入射した光を多重反射させ、その反射の度に反射光の一部を前側に出射するため、前記液晶表示素子１の前側から入射し、この液晶表示素子１を透過して前記多重反射手段１０に入射した光が、上述した多重反射により広がって前記多重反射手段の前側に出射する。
【００６６】
そのため、前側からの入射光が前記液晶表示素子１により遮断された部分からも前記多重反射手段１０による反射光が出射し、前記液晶表示素子１での入射光の遮断による暗表示の影が無くなり、二重像の無い良好な品質の表示が得られる。
【００６７】
すなわち、外光を利用する反射表示を行なう表示装置は、通常、画面の法線に対して斜めに傾いた方向を最も明るい外光が入射する方向に向けて使用されるため、表示素子の後側に反射膜を前記表示素子に直接対向させて配置した構成の従来の反射型表示装置では、前記表示素子での入射光の遮断による暗表示の影が、前記表示素子の暗表示部からずれた位置にでき、正面方向から観察される表示画像が二重像となって見える。
【００６８】
それに対し、この実施例の表示装置では、前側から入射し、液晶表示素子１を透過して前記多重反射手段１０に入射した光が、この多重反射手段１０での多重反射により、その光の入射部分よりも広い領域に広がって反射され、その光が前記暗表示の影となる領域からも出射するため、前記暗表示の影を実質的に消し、二重像の発生を防ぐことができる。
【００６９】
しかも、この表示装置は、前記多重反射手段１０が、光吸収のない２つの偏光分離素子（反射偏光板）１１，１２からなっているため、光の吸収による損失が無く、明表示の輝度を充分に高くし、充分な明るさの反射表示を行なうことができる。
【００７０】
さらに、この表示装置は、前側から入射して前記液晶表示素子１を透過した光を前記多重反射手段１０に入射させ、前記多重反射手段１０の多重反射により出射の範囲が広がった光を前記液晶表示素子１の前側に出射して明表示を得るものであるため、前記明表示の輝度を均一に且つ充分に高くすることができる。特に、前記液晶表示素子１がノーマリーホワイトモードである場合には、液晶表示素子１を透過して、前記多重反射手段１０に入射する光が多くなり、前記明表示がより明るく且つ均一になる。
【００７１】
なお、この表示装置において、前記多重反射手段１０の第１と第２の反射偏光板１１，１２の透過軸１１ａ，１２ａの交差角は、第２の反射偏光板１２または反射膜１５による１回の反射で多重反射手段１０の前側に出射する光（以下、一次出射光と言う）と、前記第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と前記反射膜１５との間での多重反射により広がって多重反射手段１０の前側に出射する光（以下、二次出射光と言う）との割合を定めるものであり、前記交差角が小さい角度のときは、前記一次出射光の割合が大きくなって表示がより明るくなり、前記交差角が大きいときは、広がった前記二次出射光の割合が大きくなって二重像を消す効果が高くなる。
【００７２】
この実施例では、上述したように、前記多重反射手段１０の第１と第２の反射偏光板１１，１２を、それぞれの透過軸１１ａ，１２ａを実質的に４５°の角度で斜めにずらして配置し、第２の反射偏光板１２または反射膜１５による１回の反射で多重反射手段１０の前側に出射する一次出射光と、第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と反射膜１５との間での多重反射により広がって多重反射手段１０の前側に出射する二次出射光とに略均等に配分している。
【００７３】
したがって、前記多重反射手段１０により多重反射される光の量を充分に確保し、二重像の発生をより効果的に防ぐとともに、前記多重反射手段１０から出射して前記液晶表示素子１に再入射する光の量も充分にし、前記明表示の輝度を充分高くすることができる。
【００７４】
次に、図３に示した透過表示のときの入射光の透過経路を説明する。図３（ａ）は前記液晶セル２の液晶層６に電界を印加しない無電界時（Ｖ＝０）の透過経路を示し、図３（ｂ）は前記液晶セル２の液晶層６に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加した電界印加時（Ｖ＞Ｖｔｈ）の透過経路を示している。
【００７５】
この透過表示は、前記多重反射手段１０の面光源１６の発光素子１８を点灯させて行なわれ、前記発光素子１８からの出射光（非偏光）は、図３（ａ），（ｂ）に示したように導光板１７にその端面から入射し、この導光板１７の前面及び後面とその外側の空気層との界面で全反射しながら導光板１７内を導かれ、前記導光板１７の前面及び後面から出射する。
【００７６】
なお、図では省略しているが、前記導光板１７の後面には、この導光板１７内をその後面に向かって進んできた光を、導光板１７の前後面の法線に対する角度が小さくなる方向に反射する複数の溝状凹部が導光板端面と平行に形成されており、したがって、前記導光板１７内を導かれてきた光の大部分は、前記導光板１７の前面から出射する。
【００７７】
ただし、前記導光板１７内を導かれる光の中には、導光板１７の後面と外気との界面を透過して後側に漏れる光もあるが、その漏れ光は、前記導光板１７の後側の第２の反射偏光板１２により反射されるか、あるいは前記第２の反射偏光板１２を透過して反射膜１５により反射され、前記導光板１７を透過してその前面から出射するため、前記発光素子１８からの出射光を、略１００％の出射率で前記導光板１７の前面から出射することができる。
【００７８】
前記導光板１７の前面から出射した照明光は、前記導光板１７の前側の第１の反射偏光板１１にその後側から入射し、その互いに直交する２つの直線偏光成分のうち、前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１２を透過して多重反射手段１０の前側に出射する。
【００７９】
また、前記第１の反射偏光板１１にその後側から入射した光のうち、前記第１の反射偏光板１１の反射軸１１ｂに平行な振動面をもった偏光成分（第１の反射偏光板１１の反射軸１１ｂに平行な直線偏光）光Ｓは、この第１の反射偏光板１１により後側に反射される。
【００８０】
前記第１の反射偏光板１１により後側に反射された直線偏光Ｓは、前記導光板１７を透過して第２の反射偏光板１２に前側から入射し、その光Ｓの前記第２の反射偏光板１２の反射軸１２ｂに平行な振動面をもった偏光成分（第２の反射偏光板１２の反射軸１２ｂに平行な直線偏光）Ｓａが、この第２の反射偏光板１２により反射され、前記導光板１７を再び透過して前記第１の反射偏光板１１にその後側から再入射する。
【００８１】
一方、前記第１の反射偏光板１１により後側に反射されて前記第２の反射偏光板１２にその前側から入射した前記直線偏光Ｓの前記第２の反射偏光板１２の透過軸１２ａに平行な振動面をもった偏光成分（第２の反射偏光板１２の透過軸１２ａに平行な直線偏光）Ｐａは、この第２の反射偏光板１２を透過して反射膜１５により反射され、前記第２の反射偏光板１２を再び透過し、さらに前記導光板１７を透過して前記第１の反射偏光板１１にその後側から再入射する。
【００８２】
前記第１の反射偏光板１１にその後側から再入射した前記光Ｐａ，Ｓａの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐは、この第１の反射偏光板１１を透過して多重反射手段１０の前側に出射する。
【００８３】
また、前記第１の反射偏光板１１にその後側から再入射した前記光Ｐａ，Ｓａの前記第１の反射偏光板１１の反射軸１１ｂに平行な振動面をもった偏光成分（第１の反射偏光板１１の反射軸１１ｂに平行な直線偏光）Ｓは、この第１の反射偏光板１１により後側に再反射され、上述した反射表示のときと同様に、第２の反射偏光板１２との間及び反射膜１５との間で多重反射され、その反射毎に、前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０の前側に出射する。
【００８４】
すなわち、前記多重反射手段１０は、面光源１６からの照明光を出射するときも、第２の反射偏光板１２または反射膜１５による１回の反射で出射する一次出射光と、第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と前記反射膜１５との間での多重反射により広がって出射する二次出射光とを、前記第１の反射偏光板１１の透過軸１１ａに平行な直線偏光Ｐとして前側に出射する。
【００８５】
このときも、この実施例では、前記多重反射手段１０の第１と第２の反射偏光板１１，１１の透過軸１１ａ，１２ａを実質的に４５°の角度で斜めにずらしているため、面光源１６からの照明光が、前記一次出射光と二次出射光とに略均等に配分される。
【００８６】
前記多重反射手段１０の前側に出射した直線偏光Ｐは、前記液晶表示素子１にその後側から入射する。
【００８７】
この実施例では、前記液晶表示素子１の後側の吸収偏光板８を、その透過軸８ａを前記多重反射手段１０の前側の偏光分離素子である第１の反射偏光板１１の透過軸１１ａと実質的に平行にしているため、前記多重反射手段１０の前側に出射した直線偏光Ｐは、そのほとんどが前記液晶表示素子１の後側の吸収偏光板８を透過して液晶セル２に入射する。
【００８８】
前記液晶表示素子１の後側の吸収偏光板８を透過して液晶セル２に入射する直線偏光Ｐは、前記面光源１６から照明光を出射させたときの前記この多重反射手段１０からの出射光であるため、充分に強度の高い光である。
【００８９】
すなわち、前記面光源１６から出射した非偏光の照明光を直接液晶表示素子１に入射させる場合は、その照明光の５０％以下の光、つまり液晶表示素子１の後側の吸収偏光板８を透過する直線偏光成分の光しか液晶セル２に入射させることができない。
【００９０】
それに対し、この実施例の表示装置では、前記多重反射手段１０が、第１と第２の反射偏光板１１，１２の間に配置された面光源１６から出射し、前記第２の反射偏光板１２または反射膜１５による１回の反射で前側に出射する直線偏光（一次出射光）Ｐと、前記面光源１６から出射し、前記第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と前記反射膜１５との間での多重反射により広がって出射する直線偏光（二次出射光）ｐとを出射するため、前記面光源１６からの照明光を、より多く、液晶表示素子１の後側の吸収偏光板８を透過する直線偏光Ｐとして前記液晶表示素子１に入射させ、高強度の直線偏光Ｐを液晶セル２に入射させることができる。
【００９１】
前記液晶セル２にその後側から入射した前記直線偏光Ｐは、前記液晶セル２の電極間に印加される電界により変化する液晶分子の配向状態に応じた液晶層６の複屈折作用を受けてこの液晶セル２の前側に出射する。
【００９２】
すなわち、前記液晶セル２の電極間に電界を印加しない無電界時（Ｖ＝０）の液晶分子の配向状態は、実質的に９０°のツイスト角のツイスト配向であり、このときは、図３（ａ）に示したように、前記液晶セル２にその後側から入射した直線偏光Ｐが、液晶層６の複屈折作用により実質的に９０°旋光し、前側の吸収偏光板７の透過軸７ａに平行な直線偏光Ｓとなって液晶セル２の前側に出射し、前記吸収偏光板７に入射する。
【００９３】
そのため、無電界時は、前記液晶セル２の前側に出射した直線偏光Ｐのほとんどが、前側の吸収偏光板７を透過して前側に出射し、明表示となる。この明表示は、前記液晶セル２にその後側から入射した直線偏光Ｐが上述したような高強度の光であるため、充分な明るさの表示である。
【００９４】
一方、前記液晶セル２の電極間に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加したときは、図３（ｂ）に示したように、前記液晶セル２にその後側から入射した直線偏光Ｐが、液晶層６の複屈折作用を受けること無く液晶セル２の前側に出射して前側の吸収偏光板７により吸収され、充分な暗さの暗表示になる。
【００９５】
上述したように、この表示装置は、入射光の透過と遮断を制御する液晶表示素子１の後側に、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記液晶表示素子１を透過して前側から入射した光の少なくとも一部を透過させ、後側から入射した光の一部を反射する第１の偏光分離素子１１と、前記第１の偏光分離素子１１の後側に配置され、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記第１の偏光分離素子１１の後側への透過光及び反射光の少なくとも一部を反射する第２の偏光分離素子１２とからなり、前記液晶表示素子１を透過して前側から入射し、前記第１の偏光分離素子１１を透過した光の少なくとも一部を前記第１と第２の偏光分離素子１１，１２の間で多重反射させるとともに、その反射毎に反射光の一部を前記第１の偏光分離素子１１を透過させて前側に出射する多重反射手段１０を配置したものであるため、二重像の無い良好な品質で、しかも充分な明るさの反射表示を行なうことができる。
【００９６】
そして、この実施例では、前記多重反射手段１０の第１と第２の偏光分離素子１１，１２をそれぞれ、互いに直交する方向に透過軸１１ａ，１２ａと反射軸１１ｂ，１２ｂを有し、入射光の互いに直交する２つの直線偏光成分のうち、前記反射軸１１ｂ，１２ｂに平行な振動面をもった一方の偏光成分を反射し、前記透過軸１１ａ，１２ａに平行な振動面をもった他方の偏光成分を透過させる反射偏光板とし、これらの反射偏光板１１，１２を、それぞれの透過軸１１ａ，１２ａを互いに斜めにずらして配置しているため、前記多重反射手段１０にその前側から入射し、前記第１の反射偏光板１１を透過した光を前記第２の反射偏光板１２により反射し、その一部の光を前記第１の反射偏光板１１を透過させて前記多重反射手段１０の前側に出射するとともに、他の光を前記第１と第２の反射偏光板１１，１２の間で多重反射させ、その反射毎に、前記第２の反射偏光板１２による反射光の一部を前記第１の偏光分離素子１１を透過させて前記多重反射手段１０の前側に出射することができる。
【００９７】
さらに、この実施例では、前記多重反射手段１０に、前記第２の反射偏光板１２の後側に配置された反射膜１５をさらに備えさせているため、この多重反射手段１０の前側から前記第１の反射偏光板１１を透過して入射した光のうち、前記第２の反射偏光板１２を透過してその後側に出射した光を前記反射膜１５により反射し、前記第２の反射偏光板１２を再び透過した光の一部を前記第１の反射偏光板１１を透過させて前側に出射するとともに、他の光を前記第１と第２の反射偏光板１１，１２の間で多重反射させ、その反射毎に、前記第２の反射偏光板１２による反射光の一部を前記第１の偏光分離素子１１を透過させて多重反射手段１０の前側に出射することができ、したがって、前記液晶表示素子１を透過して前記多重反射手段１０に入射した光の全てを上述した多重反射により広がらせて反射し、その光を前記液晶表示素子１の前側に出射させて、より明るい反射表示を得ることができる。
【００９８】
なお、上記実施例では、前記多重反射手段１０の第１と第２の反射偏光板１１，１２の透過軸１１ａ，１２ａを実質的に４５°の角度で斜めにずらし、前記第２の反射偏光板１２または反射膜１５による１回の反射で多重反射手段１０の前側に出射する一次出射光と、第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と反射膜１５との間での多重反射により広がって多重反射手段１０の前側に出射する二次出射光とに略均等に配分するようにしているが、前記第１と第２の反射偏光板１１，１２の透過軸１１ａ，１２ａのずれ角は、反射表示における充分な二重像の防止効果と、反射表示及び透過表示における明表示を充分に明るくできる範囲であればよい。
【００９９】
しかも、上記実施例の表示装置は、前記多重反射手段１０に、前記第１と第２の反射偏光板１１，１２の間に配置され、前面及び後面からの入射光をそれぞれ透過させ、端面からの入射光を前記前面と後面の少なくとも一方から出射する導光板１７と、この導光板１７の前記端面に対向させて設けられた発光素子１８とからなる面光源１６をさらに備えさせたものであるため、充分な明るさの外光が得られる環境下では外光を利用する反射表示を行ない、充分な明るさの外光が得られないときに、前記面光源１６から照明光を出射させてその照明光を利用する透過表示を行なうことができる。
【０１００】
図４〜図６はこの発明の第２の実施例を示しており、図４は表示装置の分解斜視図、図５及び図６は前記表示装置の反射表示のときと透過表示のときの入射光の透過経路を示す模式図である。
【０１０１】
この実施例の表示装置は、図４に示したように、入射光の透過と遮断を制御する液晶表示素子１の後側に、液晶表示素子１側の第１の反射偏光板１１と、その後側に配置された第２の反射偏光板１２と、さらにその後側に配置された反射膜１５と、前記第１の反射偏光板１１と第２の反射偏光板１２との間に配置された、第３の偏光分離素子１３及び面光源１６とからなる多重反射手段１０ａを配置したものである。
【０１０２】
なお、この実施例において、液晶表示素子１と多重反射手段１０ａの面光源１６は、上述した第１の実施例のものと同じであるから、その構成の説明は図に同符号を付して省略する。
【０１０３】
この実施例において、前記多重反射手段１０ａの第１と第２の反射偏光板１２，１３の間に配置された第３の偏光分離素子１３は、入射光の互いに直交する２つの直線偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる反射偏光素子であり、この実施例では、互いに直交する方向に透過軸１３ａと反射軸１３ｂを有し、入射光の互いに直交する２つの直線偏光成分のうち、前記反射軸１３ｂに平行な振動面をもった一方の偏光成分を反射し、前記透過軸１３ａに平行な振動面をもった他方の偏光成分を透過させる反射偏光板を用いている。以下、前記第３の偏光分離素子１３を第３の反射偏光板と言う。
【０１０４】
この第３の反射偏光板１３は、前記第１と第２の反射偏光板１１，１２の一方から他方に向かう直線偏光と、他方から一方に向かう直線偏光の振動面の方向を変化させるためのものであり、この実施例では、前記第３の反射偏光板１３を、液晶表示素子１側の第１の反射偏光板１１と面光源１６の導光板１７との間に配置している。
【０１０５】
前記多重反射手段１０ａの液晶表示素子１側の第１の反射偏光板１１は、上述した第１の実施例と同様に、その透過軸１１ａを前記液晶表示素子１の後側の吸収偏光板８の透過軸８ａと実質的に平行にして配置されており、反射膜１５側の第２の反射偏光板１２は、その透過軸１２ａを前記第１の反射偏光板１１の透過軸１１ａと実質的に平行にして配置され、前記第３の反射偏光板１３は、その透過軸１３ａを前記第１と第２の反射偏光板１１，１２の両方の透過軸１１ａ，１２ａに対して斜めにずらして配置されている。
【０１０６】
この実施例では、図４に示したように、前記第３の反射偏光板１３を、その透過軸１３ａを画面の横軸ｘに対して１５°±１０°の方向に向けて配置し、前記第３の反射偏光板１３の透過軸１３ａと前記第１及び第２の反射偏光板１１，１２の透過軸１１ａ，１２ａとのずれ角を３０°±１０°としている。
【０１０７】
なお、図４では、前記第３の反射偏光板１３の透過軸１３ａを、前記第１及び第２の反射偏光板１１，１２の透過軸１１ａ，１２ａに対して前側から見て右回り方向に３０°±１０°ずらしているが、前記第３の反射偏光板１３は、その透過軸１３ａを前記第１及び第２の反射偏光板１１，１２の透過軸１１ａ，１２ａに対して前側から見て左回り方向に３０°±１０°ずらして配置してもよい。
【０１０８】
この表示装置の反射表示のときの入射光の透過経路を説明すると、図５は反射表示のときの入射光の透過経路を示しており、図５（ａ）は無電界時（Ｖ＝０）の透過経路、図５（ｂ）は電界印加時（Ｖ＞Ｖｔｈ）の透過経路を示している。
【０１０９】
なお、この反射表示のときの前側から入射した光及び多重反射手段１０ａの前側に出射した光が液晶表示素子１を透過するときの偏光状態の変化は上述した第１の実施例と同じであるから、その説明は省略する。
【０１１０】
まず、前記液晶セル２の電極間に電界を印加しない無電界時（Ｖ＝０）の透過経路を説明すると、この無電界時は、前記液晶表示素子１の後側に出射した直線偏光Ｐが前記多重反射手段１０ａに入射し、そのほとんどが前記第１の反射偏光板１１を透過してその後側に出射する。
【０１１１】
前記第１の反射偏光板１１の後側に出射した前記直線偏光Ｐは、前記第１の反射偏光板１１の透過軸１１ａに対して透過軸１３ａが斜めにずれている第３の反射偏光板１３に入射し、その直線偏光Ｐの前記第３の反射偏光板１３の透過軸１３ａに平行な振動面をもった偏光成分（第３の反射偏光板１３の透過軸１３ａに平行な直線偏光）Ｐｂが、この第３の反射偏光板１３を透過してその後側に出射し、前記第３の反射偏光板１３の反射軸１３ｂに平行な振動面をもった偏光成分（第３の反射偏光板１３の反射軸１３ｂに平行な直線偏光）Ｓｂが、この第３の反射偏光板１３により反射される。
【０１１２】
前記第３の反射偏光板１３を透過してその後側に出射した直線偏光Ｐｂは、面光源１６の導光板１７を透過して、前記第３の反射偏光板１３の透過軸１３ａに対して透過軸１２ａが斜めにずれている第２の反射偏光板１２に入射し、その直線偏光Ｐｂの前記第２の反射偏光板１２の透過軸１２ａに平行な振動面をもった偏光成分（第２の反射偏光板１２の透過軸１２ａに平行な直線偏光）Ｐｃが、この第２の反射偏光板１２を透過してその後側に出射し、前記第２の反射偏光板１２の反射軸１２ｂに平行な振動面をもった偏光成分（第２の反射偏光板１２の反射軸１２ｂに平行な直線偏光）Ｓｃが、この第２の反射偏光板１２により反射される。
【０１１３】
前記第２の反射偏光板１２を透過してその後側に出射した直線偏光Ｐｃは、反射膜１５により反射され、前記第２の反射偏光板１２を再び透過し、さらに前記導光板１７を透過して前記第３の反射偏光板１３にその後側から再入射する。
【０１１４】
一方、前記第２の反射偏光板１２にその前側から入射した前記直線偏光Ｐｂのうち、この第２の反射偏光板１２により反射された直線偏光Ｓｃは、前記導光板１７を透過して前記第３の反射偏光板１３にその後側から再入射する。
【０１１５】
前記第３の反射偏光板１３にその後側から再入射した直線偏光Ｐｃ，Ｓｃは、いずれも、前記第３の反射偏光板１３の透過軸１３ａ及び反射軸１３ｂに対して斜めにずれた振動面を有する直線偏光であるため、その直線偏光Ｐｃ，Ｓｃの前記第３の反射偏光板１３の透過軸１３ａに平行な振動面をもった偏光成分（第３の反射偏光板１３の透過軸１３ａに平行な直線偏光）Ｐが、この第３の反射偏光板１３を透過して前記第１の反射偏光板１１にその後側から再入射する。
【０１１６】
また、前記第１の反射偏光板１１にその前側から入射してその後側に出射した前記直線偏光Ｐのうち、前記第３の反射偏光板１３により反射された直線偏光Ｓｂも、前記第１の反射偏光板１１にその後側から再入射する。
【０１１７】
前記第１の反射偏光板１１にその後側から再入射した前記直線偏光Ｓｂ，Ｐｃ，Ｓｃは、いずれも、前記第１の反射偏光板１１の透過軸１１ａ及び反射軸１１ｂに対して斜めにずれた振動面を有する直線偏光であるため、その直線偏光Ｓｂ，Ｐｃ，Ｓｃの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して前記多重反射手段１０ａの前側に出射する。
【０１１８】
また、前記第１の反射偏光板１１にその後側から再入射した前記直線偏光Ｓｂ，Ｐａ，Ｓａの前記第１の反射偏光板１１の反射軸１１ｂに平行な振動面をもった偏光成分（第１の反射偏光板１１の反射軸１１ｂに平行な直線偏光）Ｓは、この第１の反射偏光板１１により後側に反射され、上記と同様な経路で前記第３の反射偏光板１３と第２の反射偏光板１２とを透過して反射膜１５により反射されるか、あるいは前記第３の反射偏光板１３と第２の反射偏光板１２のいずれかで反射されて前記第１の反射偏光板１１にその後側から再び入射し、その光Ｐａの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０ａの前側に出射する。
【０１１９】
すなわち、前記多重反射手段１０ａは、第１と第２の反射偏光板１１，１２の間に配置された第３の反射偏光板１３により、前記第１の反射偏光板１１を透過して前記第２の反射偏光板１２に入射する光と、前記第２の反射偏光板１２または反射膜１５により反射されて前記第１の反射偏光板１１に入射する直線偏光の振動面の方向を変化させてそれぞれ第１と第２の反射偏光板１１，１２に入射させるようにしたものであり、前記第３及び第２の反射偏光板１３，１２と反射膜１５のいずれかによる１回の反射で多重反射手段１０ａの前側に出射する一次出射光と、前記第１、第２、第３の反射偏光板１１，１２，１３間及びこれらの反射偏光板１１，１２，１３と前記反射膜１５との間での多重反射により広がって多重反射手段１０ａの前側に出射する二次出射光とを、前記第１の反射偏光板１１の透過軸１１ａに平行な直線偏光Ｐとして前側に出射する。
【０１２０】
そして、無電界時（Ｖ＝０）は、前記多重反射手段１０ａの前側に出射した直線偏光Ｐが前記液晶表示素子１を透過してその前側に出射し、明表示になる。
【０１２１】
そのため、この表示装置によれば、上述した第１の表示装置と同様に、二重像の無い良好な品質で、しかも充分な明るさの反射表示を行なうことができる。
【０１２２】
一方、前記液晶セル２の電極間に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加した電界印加時（Ｖ＞Ｖｔｈ）は、図５（ｂ）に示したように、前側の吸収偏光板７を透過して液晶セル２に入射した直線偏光Ｓが、液晶層６の複屈折作用を受けずにその偏光状態のまま前記液晶セル２を透過して後側の吸収偏光板８に入射し、その光のほとんどが前記後側の吸収偏光板８により吸収されて暗表示になる。
【０１２３】
次に、この実施例の表示装置の透過表示のときの入射光の透過経路を説明すると、図６は透過表示のときの入射光の透過経路を示しており、図６（ａ）は無電界時（Ｖ＝０）の透過経路、図６（ｂ）は電界印加時（Ｖ＞Ｖｔｈ）の透過経路を示している。
【０１２４】
なお、この透過表示のときの面光源１６からの照明光の出射と、多重反射手段１０ａの前側に出射した光が液晶表示素子１を透過するときの偏光状態の変化は上述した第１の実施例と同じであるから、その説明は省略する。
【０１２５】
この透過表示のときは、図６（ａ），（ｂ）に示したように、前記面光源１６の導光板１７の前面から出射した照明光が、前記導光板１７の前側の第３の反射偏光板１３にその後側から入射し、その互いに直交する２つの直線偏光成分のうち、前記第３の反射偏光板１３の透過軸１３ａに平行な振動面をもった偏光成分（第３の反射偏光板１３の透過軸１３ａに平行な直線偏光）Ｐｂが、この第３の反射偏光板１３を透過して第１の反射偏光板１１に入射し、その直線偏光Ｐｂの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０ａの前側に出射する。
【０１２６】
一方、前記第３の反射偏光板１３を透過して前記第１の反射偏光板１１に入射した前記直線偏光Ｐｂの前記第１の反射偏光板１１の反射軸１１ｂに平行な振動面をもった偏光成分（第１の反射偏光板１１の反射軸１１ｂに平行な直線偏光）Ｓは、この第１の反射偏光板１１により後側に反射され、また、前記導光板１７の前面から出射して前記第３の反射偏光板１３にその後側から入射した光の前記第３の反射偏光板１３の反射軸１３ｂに平行な振動面をもった偏光成分（第３の反射偏光板１３の反射軸１３ｂに平行な直線偏光）Ｓｂは、この第３の反射偏光板１３により後側に反射される。
【０１２７】
前記第１の反射偏光板１１により後側に反射された直線偏光Ｓは、前記第３の反射偏光板１３にその前側から再入射し、その光の前記第３の反射偏光板１３の反射軸１３ｂに平行な振動面をもった偏光成分（第３の反射偏光板１３の反射軸１３ｂに平行な直線偏光）Ｓｂがこの第３の反射偏光板１３により前側に反射され、前記第３の反射偏光板１３の透過軸１３ａに平行な振動面をもった偏光成分（第３の反射偏光板１３の透過軸１３ａに平行な直線偏光）Ｐｂがこの第３の反射偏光板１３を透過してその後側に出射する。
【０１２８】
前記第３の反射偏光板１３を透過してその後側に出射した直線偏光Ｐｂと、前記第３の反射偏光板１３により後側に反射された直線偏光Ｓｂは、前記導光板１７を透過して第２の反射偏光板１２に入射し、その光Ｐｂ，Ｓｂの前記第２の反射偏光板１２の反射軸１２ｂに平行な振動面をもった偏光成分（第２の反射偏光板１２の反射軸１２ｂに平行な直線偏光）Ｓｃがこの第２の反射偏光板１２により反射され、前記第２の反射偏光板１２の透過軸１３ａに平行な振動面をもった偏光成分（第２の反射偏光板１２の透過軸１２ａに平行な直線偏光）Ｐｃがこの第２の反射偏光板１２を透過して反射膜１５により反射される。
【０１２９】
すなわち、前記多重反射手段１０ａは、面光源１６からの照明光を利用する透過表示のときも、第３及び第２の反射偏光板１３，１２と反射膜１５のいずれかによる１回の反射で出射する一次出射光と、前記第１、第２、第３の反射偏光板１１，１２，１３間及びこれらの反射偏光板１１，１２，１３と前記反射膜１５との間での多重反射により広がって出射する二次出射光とを、前記第１の反射偏光板１１の透過軸１１ａに平行な直線偏光Ｐとして前側に出射する。
【０１３０】
そして、前記液晶セル２の電極間に電界を印加しない無電界時（Ｖ＝０）は、図６（ａ）に示したように、前記多重反射手段１０ａの前側に出射した直線偏光Ｐが前記液晶表示素子１を透過してその前側に出射し、明表示になる。
【０１３１】
一方、前記液晶セル２の電極間に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加した電界印加時（Ｖ＞Ｖｔｈ）は、図６（ｂ）に示したように、前記多重反射手段１０ａの前側に出射した直線偏光Ｐが、前記液晶表示素子１の前側の吸収偏光板７により吸収され、暗表示（黒表示）になる。
【０１３２】
なお、この実施例のように、前記多重反射手段１０ａの第１と第２の反射偏光板１１，１２を、それぞれの透過軸１１ａ，１２ａを実質的に互いに平行にして配置する場合は、前記第３の反射偏光板１３を、上述したように、その透過軸１３ａを前記第１及び第２の反射偏光板１１，１２の透過軸１１ａ，１２ａに対して３０°±１０°、より好ましくは３０°ずらして配置するのが望ましく、このようにすることにより、この多重反射手段１０ａの前側に出射する光を、前記第３及び第２の反射偏光板１３，１２と反射膜１５のいずれかによる１回の反射で出射する一次出射光と、第１、第２、第３の反射偏光板１１，１２，１３間及びこれらの反射偏光板１１，１２，１３と反射膜１５との間での多重反射により広がって出射する二次出射光とに略均等に配分し、反射表示のときの二重像の発生をより効果的に防ぐとともに、反射表示及び透過表示における明表示をより明るくすることができる。
【０１３３】
なお、前記多重反射手段１０ａの第１と第２の反射偏光板１１，１２及び第３の反射偏光板１３の透過軸１１ａ，１２ａ，１３ａの向きは、上記実施例に限らず、反射表示における充分な二重像の防止効果が得られ、且つ、反射表示及び透過表示における明表示を充分に明るくできる範囲であればよい。
【０１３４】
また、上記実施例では、前記多重反射手段１０ａを、液晶表示素子１側の第１の反射偏光板１１と面光源１６との間に第３の反射偏光板１３を配置した構成としているが、前記第３の反射偏光板１３は、反射膜１５側の第２の反射偏光板１２と前記面光源１６との間に配置してもよい。
【０１３５】
図７〜図９はこの発明の第３の実施例を示しており、図７は表示装置の分解斜視図、図８及び図９は前記表示装置の反射表示のときと透過表示のときの入射光の透過経路を示す模式図である。
【０１３６】
この実施例の表示装置は、図７に示したように、入射光の透過と遮断を制御する液晶表示素子１との後側に、、液晶表示素子１側の第１の反射偏光板１１と、その後側に配置された第２反射偏光板１２と、さらにその後側に配置された反射膜１５と、前記第１の反射偏光板１１と第２の反射偏光板１２との間に配置された位相差板１４及び面光源１６とからなる多重反射手段１０ｂを配置したものである。
【０１３７】
なお、この実施例において、液晶表示素子１と多重反射手段１０ｂの面光源１６は、上述した第１の実施例のものと同じであるから、その構成の説明は図に同符号を付して省略する。
【０１３８】
この実施例において、前記多重反射手段１０ｂの第１と第２の反射偏光板１１，１２の間に配置された位相差板１４は、前記第１と第２の反射偏光板１１，１２の一方から他方に向かう光と、他方から一方に向かう光の偏光状態を変化させるためのものであり、この実施例では、前記位相差板１４を、液晶表示素子１側の第１の反射偏光板１１と面光源１６の導光板１７との間に配置している。
【０１３９】
前記位相差板１４は、例えば透過光の常光と異常光との間に１／４波長の位相差を与えるλ／４板であり、この実施例では、前記多重反射手段１０ｂの液晶表示素子１側の第１の反射偏光板１１を、上述した第１の実施例と同様に、その透過軸１１ａを前記液晶表示素子１の後側の吸収偏光板８の透過軸８ａと実質的に平行にして配置するとともに、反射膜１５側の第２の反射偏光板１２を、その透過軸１２ａを前記第１の反射偏光板１１の透過軸１１ａと実質的に平行にして配置し、前記λ／４板１４を、その遅相軸１４ａを前記第１と第２の反射偏光板１１，１２の両方の透過軸１１ａ，１２ａに対して実質的に４５°の角度で斜めにずらして配置している。
【０１４０】
この表示装置の反射表示のときの入射光の透過経路を説明すると、図８は反射表示のときの入射光の透過経路を示しており、図８（ａ）は無電界時（Ｖ＝０）の透過経路、図８（ｂ）は電界印加時（Ｖ＞Ｖｔｈ）の透過経路を示している。
【０１４１】
なお、この反射表示のときの前側から入射した光及び多重反射手段１０ｂの前側に出射した光が液晶表示素子１を透過するときの偏光状態の変化は上述した第１の実施例と同じであるから、その説明は省略する。
【０１４２】
まず、前記液晶セル２の電極間に電界を印加しない無電界時（Ｖ＝０）の透過経路を説明すると、この無電界時は、前記液晶表示素子１の後側に出射した直線偏光Ｐが前記多重反射手段１０ｂに入射し、そのほとんどが前記第１の反射偏光板１１を透過してその後側に出射する。
【０１４３】
前記第１の反射偏光板１１の後側に出射した前記直線偏光Ｐは、前記第１の反射偏光板１１の透過軸１１ａに対して遅相軸１４ａが実質的に４５の角度で斜めにずれているλ／４板１４に入射し、このλ／４板１４により１／４波長の位相差を与えられ、円偏光Ｃとなって前記λ／４板１４の後側に出射する。
【０１４４】
前記λ／４板１４の後側に出射した前記円偏光Ｃは、面光源１６の導光板１７を透過して、第２の反射偏光板１２に入射し、その円偏光Ｃの前記第２の反射偏光板１２の透過軸１２ａに平行な振動面をもった偏光成分（第２の反射偏光板１２の透過軸１２ａに平行な直線偏光）Ｐが、この第２の反射偏光板１２を透過してその後側に出射し、前記第２の反射偏光板１２の反射軸１２ｂに平行な振動面をもった偏光成分（第２の反射偏光板１２の反射軸１２ｂに平行な直線偏光）光Ｓが、この第２の反射偏光板１２により反射される。
【０１４５】
前記第２の反射偏光板１２を透過してその後側に出射した直線偏光Ｐは、反射膜１５により反射され、前記第２の反射偏光板１２を再び透過し、さらに前記導光板１７を透過して前記λ／４板１４にその後側から再入射する。
【０１４６】
一方、前記第２の反射偏光板１２にその前側から入射した前記円偏光Ｃのうち、この第２の反射偏光板１２により反射された直線偏光Ｓは、前記導光板１７を透過して前記λ／４板１４にその後側から再入射する。
【０１４７】
前記λ／４板１４にその後側から再入射した直線偏光Ｐ，Ｓは、前記λ／４板１４により再び円偏光Ｃとされて前記第１の反射偏光板１１にその後側から再入射し、その円偏光Ｃの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して前記多重反射手段１０ｂの前側に出射する。
【０１４８】
また、前記第１の反射偏光板１１にその後側から再入射した前記円偏光Ｃの前記第１の反射偏光板１１の反射軸１１ｂに平行な振動面をもった偏光成分（第１の反射偏光板１１の反射軸１１ｂに平行な直線偏光）Ｓは、この第１の反射偏光板１１により後側に反射され、前記λ／４板１４により再度円偏光Ｃとされて前記第２の反射偏光板１２に再び入射し、上記のような経路で、前記第２の反射偏光板１２を透過して反射膜１５により反射されるか、あるいは前記第２の反射偏光板１２により前側に反射される。
【０１４９】
そして、前記第２の反射偏光板１２を透過して反射膜１５により反射され、前記第２の反射偏光板１２を再び透過してその前側に出射した直線偏光Ｐと、前記第２の反射偏光板１２により前側に反射された直線偏光Ｓは、前記λ／４板１４により再び円偏光Ｃとされて前記第１の反射偏光板１１にその後側から再び入射し、その光Ｐａの前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０ｂの前側に出射する。
【０１５０】
すなわち、前記多重反射手段１０ｂは、第１と第２の反射偏光板１１，１２の間に配置されたλ／４板１４により、前記第１の反射偏光板１１を透過して前記第２の反射偏光板１２に入射する光と、前記第２の反射偏光板１２または反射膜１５により反射されて前記第１の反射偏光板１２に入射する光の偏光状態を変化させてそれぞれ第１と第２の反射偏光板１１，１２に入射させるようにしたものであり、前記第２の反射偏光板１２と反射膜１５のいずれかによる１回の反射で出射する一次出射光と、前記第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と前記反射膜１５との間での多重反射により広がって出射する二次出射光とを、前記第１の反射偏光板１１の透過軸１１ａに平行な直線偏光Ｐとして前側に出射する。
【０１５１】
そして、無電界時（Ｖ＝０）は、前記多重反射手段１０ｂの前側に出射した直線偏光Ｐが前記液晶表示素子１を透過してその前側に出射し、明表示になる。
【０１５２】
そのため、この表示装置によれば、上述した第１の表示装置と同様に、二重像の無い良好な品質で、しかも充分な明るさの反射表示を行なうことができる。
【０１５３】
一方、前記液晶セル２の電極間に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加した電界印加時（Ｖ＞Ｖｔｈ）は、図８（ｂ）に示したように、前側の吸収偏光板７を透過して液晶セル２に入射した直線偏光Ｓが、液晶層６の複屈折作用を受けずにその偏光状態のまま前記液晶セル２を透過して後側の吸収偏光板８に入射し、その光のほとんどが前記後側の吸収偏光板８により吸収されて暗表示（黒表示）になる。
【０１５４】
次に、この実施例の表示装置の透過表示のときの入射光の透過経路を説明すると、図９は透過表示のときの入射光の透過経路を示しており、図９（ａ）は無電界時（Ｖ＝０）の透過経路、図９（ｂ）は電界印加時（Ｖ＞Ｖｔｈ）の透過経路を示している。
【０１５５】
なお、この透過表示のときの面光源１６からの照明光の出射と、多重反射手段１０ｂの前側に出射した光が液晶表示素子１を透過するときの偏光状態の変化は上述した第１の実施例と同じであるから、その説明は省略する。
【０１５６】
この透過表示のときは、図９（ａ），（ｂ）に示したように、前記面光源１６の導光板１７の前面から出射した照明光が、前記導光板１７の前側のλ／４板１４を透過して第１の反射偏光板１１に入射し、その光のうち、前記第１の反射偏光板１１の透過軸１１ａに平行な振動面をもった偏光成分（第１の反射偏光板１１の透過軸１１ａに平行な直線偏光）Ｐが、この第１の反射偏光板１１を透過して多重反射手段１０ｂの前側に出射し、前記第１の反射偏光板１１の反射軸１１ｂに平行な振動面をもった偏光成分（第１の反射偏光板１１の反射軸１１ｂに平行な直線偏光）光Ｓが、この第１の反射偏光板１１により後側に反射される。
【０１５７】
前記第１の反射偏光板１１により後側に反射された直線偏光Ｓは、前記λ／４板１４により円偏光Ｃとされ、前記導光板１７を透過して第２の反射偏光板１２に入射し、その円偏光Ｃの前記第２の反射偏光板１２の反射軸１２ｂに平行な振動面をもった偏光成分（第２の反射偏光板１２の反射軸１２ｂに平行な直線偏光）Ｓｃがこの第２の反射偏光板１２により反射され、前記第２の反射偏光板１２の透過軸１２ａに平行な振動面をもった偏光成分（第２の反射偏光板１２の透過軸１２ａに平行な直線偏光）Ｐｃがこの第２の反射偏光板１２を透過して反射膜１５により反射される。
【０１５８】
すなわち、前記多重反射手段１０ｂは、面光源１６からの照明光を利用する透過表示のときも、第１と第２の反射偏光板１１，１２の一方のから他方に向かう直線偏光と、他方から一方に向かう直線偏光の偏光状態を変化させ、前記第２の反射偏光板１２と反射膜１５のいずれかによる１回の反射で出射する一次出射光と、前記第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と前記反射膜１５との間での多重反射により広がって出射する二次出射光とを、前記第１の反射偏光板１１の透過軸１１ａに平行な直線偏光Ｐとして前側に出射する。
【０１５９】
そして、前記液晶セル２の電極間に電界を印加しない無電界時（Ｖ＝０）は、図９（ａ）に示したように、前記多重反射手段１０ｂの前側に出射した直線偏光Ｐが前記液晶表示素子１を透過してその前側に出射し、明表示になる。
【０１６０】
一方、前記液晶セル２の電極間に液晶分子を基板３，４面に対して実質的に垂直に立上がり配向させる電界を印加した電界印加時（Ｖ＞Ｖｔｈ）は、図９（ｂ）に示したように、前記多重反射手段１０ｂの前側に出射した直線偏光Ｐが、前記液晶表示素子１の前側の吸収偏光板７により吸収され、暗表示（黒表示）になる。
【０１６１】
この実施例では、上記のように、前記多重反射手段１０ｂの第１と第２の反射偏光板１１，１２を、それぞれの透過軸１１ａ，１２ａを実質的に互いに平行にして配置し、その間に、位相差板として、透過光の常光と異常光との間に１／４波長の位相差を与えるλ／４板１４を配置しているため、この多重反射手段１０ｂの前側に出射する光を、前記第２の反射偏光板１１２と反射膜１５のいずれかによる１回の反射で出射する一次出射光と、第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と反射膜１５との間での多重反射により広がって出射する二次出射光とに略均等に配分し、反射表示のときの二重像の発生をより効果的に防ぐとともに、反射表示及び透過表示における明表示をより明るくすることができる。
【０１６２】
なお、前記多重反射手段１０ｂの第１と第２の反射偏光板１１，１２の透過軸１１ａ，１２ａの向きと、その間に配置する位相差板の位相差は、上記実施例に限らず、反射表示における充分な二重像の防止効果が得られ、且つ、反射表示及び透過表示における明表示を充分に明るくできる範囲であればよい。
【０１６３】
さらに、前記位相差板は、透過光に指向性をもたせるためのレンズシートを積層したものでもよく、このようなレンズシート積層位相差板を用いることにより、表示装置の前側に出射する光の正面輝度を高くし、より明るい明表示を得ることができる。
【０１６４】
また、上記実施例では、前記多重反射手段１０ｂを、液晶表示素子１側の第１の反射偏光板１２と面光源１６との間に位相差板（実施例ではλ／４板）１４を配置した構成としているが、前記位相差板１４は、反射膜１５側の第２の反射偏光板１２と前記面光源１６との間に配置してもよい。
【０１６５】
さらに、上記実施例では、前記多重反射手段１０ｂを、第１と第２の反射偏光板１１，１２の間に位相差板１４と面光源１６とを配置した構成としているが、前記面光源１６の導光板を位相差板としてもよい。
【０１６６】
図１０はこの発明の第４の実施例を示す表示装置の分解斜視図であり、この実施例は、液晶表示素子１の後側に、第１と第２の反射偏光板１２，１３と、これらの反射偏光板１２，１３の間に配置された位相差板からなる導光板１９と、その端面に端面に対向させて設けられた発光素子１８とからなる面光源１６ａとを備えた多重反射手段１０ｃを配置したものである。
【０１６７】
なお、この実施例では、前記面光源１６ａの導光板１９を、透過光の常光と異常光との間に１／４波長の位相差を与えるλ／４板とし、多重反射手段１０ｃの第１と第２の反射偏光板１１，１２を、それぞれの透過軸１１ａ，１２ａを実質的に互いに平行にして配置し、前記λ／４板からなる導光板１９を、その遅相軸１９ａを第１と第２の反射偏光板１１，１２の透過軸１１ａ，１２ａに対して実質的に４５°の角度で斜めにずらして配置している。
【０１６８】
この実施例の表示装置によれば、前記面光源１６ａの導光板１９を利用して、前記多重反射手段１０ｃの第１と第２の反射偏光板１１，１２の一方のから他方に向かう直線偏光と、他方から一方に向かう直線偏光の偏光状態を変化させ、前記第２の反射偏光板１２と反射膜１５のいずれかによる１回の反射で出射する一次出射光と、前記第１と第２の反射偏光板１１，１２間及びこれらの反射偏光板１１，１２と前記反射膜１５との間での多重反射により広がって出射する二次出射光とを、前記第１の反射偏光板１１の透過軸１１ａに平行な直線偏光Ｐとして前記多重反射手段１０ｃの前側に出射させることができる。
【０１６９】
なお、上述した第１〜第４の実施例の表示装置では、前記多重反射手段１０，１０ａ，１０ｂ，１０ｃに、第２の反射偏光板１２の後側に配置された反射膜１５を備えさせているが、前記反射膜１５を省略しても、二重像の発生を防止した明るい反射表示が得られる。
【０１７０】
また、上記第１〜第４の実施例では、前記多重反射手段１０，１０ａ，１０ｂ，１０ｃの第１と第２の偏光分離素子１１，１２及び第２の実施例の多重反射手段１０ａの第３の偏光分離素子１３を反射偏光板としているが、前記偏光分離素子は、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分の光を反射し、他方の偏光成分を透過させるものであれば、反射偏光板に限らない。
【０１７１】
図１１は他の偏光分離素子の分解側面図であり、この偏光分離素子２０は、入射光の右回りと左回りの２つの円偏光成分のうち、一方の円偏光成分を反射し、他方の円偏光成分を透過させる円偏光分離板（例えばコレステリック液晶フィルム）２１を挟んで、入射する直線偏光を円偏光にして前記円偏光分離板２１に入射させ、前記円偏光分離板２１から出射した円偏光を直線偏光にして出射する一対の位相差板２２，２３を積層したものである。
【０１７２】
なお、前記一対の位相差板２２，２３はそれぞれ、透過光の常光と異常光との間に１／４波長の位相差を与えるλ／４板であり、これらのλ／４板２２，２３は、それぞれの遅相軸を実質的に互いに直交させて配置されている。
【０１７３】
この偏光分離素子２０は、前記一対のλ／４板２２，２３の遅相軸に対して実質的に４５°ずれた互いに直交する２つの方向のうち、一方の方向、例えば図において上側のλ／４板２２の遅相軸に対し、上側（上側λ／４板２２の外面側）から見て右回りに４５°ずれた方向に透過軸をもち、それと直交する他方の方向（下側λ／４板２３の遅相軸に対し、上側から見て左回りに４５°ずれた方向）に反射軸をもっており、入射光の入射光の互いに直交する２つの直線偏光成分のうち、前記反射軸に平行な振動面をもった一方の直線偏光成分を反射し、前記透過軸に平行な振動面をもった他方の直線偏光成分を透過させる。
【０１７４】
すなわち、この偏光分離素子２０は、その一方の面側、例えば図において上側から入射した光のうち、前記反射軸に平行な直線偏光Ｓを、前記上側λ／４板２２により、光の進行方向（図において下方向）に向かって右回りの円偏光Ｒ１として前記円偏光分離板２１に入射させ、前記透過軸に平行な直線偏光Ｐを、前記上側λ／４板２２により、光の進行方向に向かって左回りの円偏光Ｒ２として前記円偏光分離板２１に入射させるとともに、他方の面側、つまり図において下側から入射した光のうち、前記反射軸に平行な直線偏光Ｓを、前記下側λ／４板２３により、光の進行方向（図において上方向）に向かって右回りの円偏光Ｒ１として前記円偏光分離板２１に入射させ、前記透過軸に平行な直線偏光Ｐを、前記下側λ／４板２３により、光の進行方向に向かって左回りの円偏光Ｒ２として前記円偏光分離板２１に入射させる。
【０１７５】
なお、図１１では便宜上、前記円偏光Ｒ１，Ｒ２の回転方向（矢印の向き）を、図において上側から見た方向に統一して示しているが、これらの円偏光Ｒ１，Ｒ２のうち、図において上側から下側に向かう円偏光Ｒ１，Ｒ２の進行方向に向かう方向から見た回転方向は図と同じ方向、図において下側から上側に向かう光の円偏光Ｒ１，Ｒ２の進行方向に向かう方向から見た回転方向は図とは逆の方向である。
【０１７６】
一方、円偏光分離板２１は、その一方と他方のいずれの面側から入射した光に対しても、その進行方向に向かって右回りの円偏光成分を反射し、左回りの円偏光成分を透過させる偏光分離特性を有している。
【０１７７】
そのため、図において上側から入射した光のうち、前記上側λ／４板２２により進行方向に向かって右回りの円偏光Ｒ１とされて前記円偏光分離板２１に入射した光が、この円偏光分離板２１により反射され、その反射光Ｒ１が前記上側λ／４板２２により前記反射軸に平行な直線偏光Ｓとされて上側に出射し、前記上側λ／４板２２により進行方向に向かって左回りの円偏光Ｒ２とされて前記円偏光分離板２１に入射した光が、この円偏光分離板２１を透過して下側λ／４板２３に入射し、この下側λ／４板２３により前記透過軸に平行な直線偏光Ｐとされて下側に出射する。
【０１７８】
また、図において下側から入射した光のうち、前記下側λ／４板２３により進行方向に向かって右回りの円偏光Ｒ１とされて前記円偏光分離板２１に入射した光が、この円偏光分離板２１により反射され、その反射光Ｒ１が前記下側λ／４板２３により前記反射軸に平行な直線偏光Ｓとされて下側に出射し、前記下側λ／４板２３により進行方向に向かって左回りの円偏光Ｒ２とされて前記円偏光分離板２１に入射した光が、この円偏光分離板２１を透過して上側λ／４板２２に入射し、この上側λ／４板２２により前記透過軸に平行な直線偏光Ｐとされて上側に出射する。
【０１７９】
このように、前記偏光分離素子２０は、入射光の互いに直交する２つの直線偏光成分のうち、前記反射軸に平行な振動面をもった一方の偏光成分を反射し、前記透過軸に平行な振動面をもった他方の偏光成分を透過させる偏光分離特性を有しており、したがって、上述した各実施例の多重反射手段１０，１０ａ，１０ｂ，１０ｃの反射偏光板１１，１２，１３を前記偏光分離素子２０に置き換えても、同様な効果を得ることができる。
【０１８０】
さらに、上記各実施例の表示装置は、ノーマリーホワイトモードのものであるが、この発明は、液晶表示素子１の前後の吸収偏光板７，８の透過軸７ａ，８ａを実質的に平行にし、液晶セル２の液晶層６に電界を印加しない無電界時の表示を暗表示としたノーマリーブラックモードの表示装置にも適用できるものであり、その場合も、前記多重反射手段１０，１０ａ，１０ｂ，１０ｃの液晶表示素子１側の第１の反射偏光板１１は、その透過軸１１ａを、前記液晶表示素子１の後側の吸収偏光板８の透過軸８ａと実質的に平行にして配置すればよい。
【０１８１】
また、上記各実施例の表示装置は、表示素子として、ＴＮ型の液晶表示素子１を備えたものであるが、前記表示素子は、ＴＮ型に限らず、ＳＴＮ型、非ツイストのホモジニアス配向型、ホメオトロピック配向型、横電界型、強誘電または反強誘電型、ＥＣＢ（複屈折効果）型等の液晶表示素子でもよく、さらに、入射光の透過と遮断を制御するものであれば、液晶表示素子以外の表示素子でもよい。
【０１８２】
さらに、上記各実施例の表示装置は、外光を利用する反射表示と、面光源からの照明光を利用する透過表示との両方の表示を行なうようにしたものであるが、この発明は、前記多重反射手段１０，１０ａ，１０ｂ，１０ｃから面光源１６，１６ａを省略した、反射表示専用の表示装置にも適用することができる。
【０１８３】
【発明の効果】
この発明の表示装置は、入射光の透過と遮断を制御する表示素子の後側に、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記表示素子を透過して前側から入射した光の少なくとも一部を透過させ、後側から入射した光の一部を反射する第１の偏光分離素子と、前記第１の偏光分離素子の後側に配置され、入射光の互いに異なる２つの偏光成分のうち、一方の偏光成分を反射し、他方の偏光成分を透過させる特性を有し、前記第１の偏光分離素子の後側への透過光及び反射光の少なくとも一部を反射する第２の偏光分離素子とからなり、前記表示素子を透過して前側から入射し、前記第１の偏光分離素子を透過した光の少なくとも一部を前記第１と第２の偏光分離素子の間で多重反射させるとともに、その反射毎に反射光の一部を前記第１の偏光分離素子を透過させて前側に出射する多重反射手段を配置したものであるため、二重像の無い良好な品質で、しかも充分な明るさの反射表示を行なうことができる。
【０１８４】
この表示装置において、前記多重反射手段の第１と第２の偏光分離素子はそれぞれ、互いに直交する方向に透過軸と反射軸を有し、入射光の互いに直交する２つの直線偏光成分のうち、前記反射軸に平行な振動面をもった一方の偏光成分を反射し、前記透過軸に平行な振動面をもった他方の偏光成分を透過させる反射偏光素子であり、これらの反射偏光素子が、それぞれの透過軸を互いに斜めにずらして配置されているのが好ましく、このようにすることにより、前記多重反射手段にその前側から入射し、前記第１の反射偏光板を透過した光を前記第２の反射偏光板により反射し、その一部の光を前記第１の反射偏光板を透過させて前記多重反射手段の前側に出射するとともに、他の光を前記第１と第２の反射偏光板の間で多重反射させ、その反射毎に、前記第２の反射偏光板による反射光の一部を前記第１の偏光分離素子を透過させて前記多重反射手段の前側に出射することができる。
【０１８５】
また、この表示装置において、前記多重反射手段は、前記第１と第２の偏光分離素子の間に、その一方の偏光分離素子から他方の偏光分離素子に向かう光と、前記他方の偏光分離素子から前記一方の偏光分離素子に向かう光の振動面の方向を変化させる第３の偏光分離素子をさらに配置した構成としてもよく、このようにすることにより、前記多重反射手段に入射した光を前記第１、第２、第３の反射偏光素子の間で多重反射することができる。
【０１８６】
さらに、前記多重反射手段は、前記第１と第２の偏光分離素子の間に、その一方の偏光分離素子から他方の偏光分離素子に向かう光と、前記他方の偏光分離素子から前記一方の偏光分離素子に向かう光の偏光状態を変化させる位相差板をさらに配置した構成としてもよく、このようにすることにより、前記多重反射手段に入射した光を前記第１と第２の反射偏光素子の間で多重反射することができる。
【０１８７】
また、この表示装置において、前記多重反射手段は、前記第２の偏光分離素子の裏側に配置され、前記第２の偏光分離素子の後側への透過光及び反射光を反射し、前記第１及び第２の偏光分離素子との間で多重反射を生じさせる反射膜をさらに備えているのが望ましく、前記多重反射手段をこのような構成とすることにより、前記表示素子を透過して前記多重反射手段に入射した光の全てを上述した多重反射により広がらせて反射し、その光を前記表示素子の前側に出射させて、より明るい反射表示を得ることができる。
【０１８８】
さらに、この表示装置において、前記多重反射手段は、前記第１と第２の偏光分離素子の間に、前面及び後面からの入射光をそれぞれ透過させ、端面からの入射光を前記前面と後面の少なくとも一方から出射する導光板と、この導光板の前記端面に対向させて設けられた発光素子とからなる面光源をさらに配置した構成とするのが望ましく、このような構成とすることにより、充分な明るさの外光が得られる環境下では、表示の観察側である前側から入射した外光を利用する反射表示を行ない、充分な明るさの外光が得られないときに前記多重反射手段の面光源から照明光を出射させてその照明光を利用する透過表示を行なうことができる。
【０１８９】
その場合は、前記面光源の導光板を、前記多重反射手段の第１と第２の一方の反射偏光素子から他方の反射偏光素子に向かう光と、前記他方の反射偏光素子から前記一方の反射偏光素子に向かう光の偏光状態を変化させる位相差板としてもよく、このようにすることにより、前記面光源の導光板を利用して、前記多重反射手段に入射した光を前記第１と第２の反射偏光素子の間で多重反射することができる。
【図面の簡単な説明】
【図１】この発明の第１の実施例を示す表示装置の分解斜視図。
【図２】第１の実施例の表示装置の反射表示のときの入射光の透過経路を示す模式図。
【図３】第１の実施例の表示装置の透過表示のときの入射光の透過経路を示す模式図。
【図４】この発明の第２の実施例を示す表示装置の分解斜視図。
【図５】第２の実施例の表示装置の反射表示のときの入射光の透過経路を示す模式図。
【図６】第２の実施例の表示装置の透過表示のときの入射光の透過経路を示す模式図。
【図７】この発明の第３の実施例を示す表示装置の分解斜視図。
【図８】第３の実施例の表示装置の反射表示のときの入射光の透過経路を示す模式図。
【図９】第３の実施例の表示装置の透過表示のときの入射光の透過経路を示す模式図。
【図１０】この発明の第４の実施例を示す表示装置の分解斜視図。
【図１１】他の偏光分離素子の分解側面図。
【符号の説明】
１…液晶表示素子
２…液晶セル
６…液晶層
７，８…吸収偏光板
７ａ，８ａ…透過軸
１０，１０ａ，１０ｂ，１０ｃ…多重反射手段
１１，１２，１３…反射偏光板（偏光分離素子）
１１ａ，１２ａ，１３ａ…透過軸
１１ｂ，１２ｂ，１３ｂ…反射軸
１４…位相差板（λ／４板）
１４ａ…遅相軸
１５…反射膜
１６，１６ａ…面光源
１７…導光板
１８…発光素子
１９…位相差板からなる導光板
１９ａ…遅相軸
２０…反射偏光素子（偏光分離素子）
２１…円偏光分離板
２２，２３…位相差板（λ／４板）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a display device that performs reflective display.
[0002]
[Prior art]
Conventionally, a reflective display device that performs reflection display using external light that is light of an external environment is a display device that controls transmission and blocking of incident light, such as a liquid crystal display device, and a display device of this type. It is constituted by a reflective film disposed on the rear side opposite to the display observation side (see Patent Documents 1, 2, and 3).
[0003]
This reflective display device obtains a dark display by blocking light incident from the front side, which is the display observation side, by the display element, and reflects light incident from the front side and transmitted through the display element by the reflective film. Then, the reflected light is emitted to the front side of the display element to obtain a bright display, and the display is observed from the front direction, that is, the direction near the normal to the screen.
[0004]
[Patent Document 1]
JP 2000-75284 A
[0005]
[Patent Document 2]
JP-A-90678
[0006]
[Patent Document 3]
JP 2001-290445 A
[0007]
[Problems to be solved by the invention]
However, the above-mentioned reflection type display device usually has the most inclined direction (in most cases, the direction inclined toward the upper edge of the screen with respect to the screen normal). Since it is used in the direction in which bright external light is incident, the shadow of the dark display due to the blocking of the incident light on the display element can be shifted from the dark display portion of the display element.
[0008]
Therefore, the conventional reflection type display device has a problem that a display is viewed as a double image.
[0009]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a display device capable of performing reflective display with good quality without double images and with sufficient brightness.
[0010]
[Means for Solving the Problems]
The display device of the present invention includes:
A display element for controlling transmission and blocking of incident light;
It is disposed on the rear side opposite to the display side of the display of the display element, and has a characteristic of reflecting one polarized component and transmitting the other polarized component among two different polarized components of incident light. A first polarization splitting element that transmits at least a part of the light incident from the front side through the display element and reflects a part of the light incident from the rear side; It is disposed on the rear side and has a property of reflecting one polarized light component and transmitting the other polarized light component of two different polarized light components of the incident light, and is provided on the rear side of the first polarization splitting element. A second polarization splitting element that reflects at least a part of the transmitted light and the reflected light, and transmits at least a part of the light that has passed through the display element, entered from the front side, and transmitted through the first polarization splitting element. Multiple reflection between the first and second polarization splitting elements Causes, and multiple reflection means emitted to the front part of the reflected light for each reflected by transmitting the first polarization separating element,
It is characterized by having.
[0011]
That is, the display device obtains a dark display by blocking light incident from the front side, which is the display observation side, by the display element, and transmits light incident from the front side and transmitted through the display element to the multiple reflection unit. At least a part of the light transmitted through the first polarization separation element of the multiple reflection means is multiple-reflected between the first and second polarization separation elements, and a part of the reflected light is reflected at each reflection. The light is transmitted through the first polarization splitting element and emitted to the front side of the multiple reflection means, and the light is emitted to the front side of the display element to obtain a bright display.
[0012]
According to this display device, the multiple reflection unit multiple-reflects the light incident from the front side, and emits a part of the reflected light to the front side at each reflection, so that the light enters from the front side of the display element, The light transmitted through the display element and incident on the multiple reflection means spreads out by the multiple reflection described above and exits to the front side of the multiple reflection means.
[0013]
Therefore, the reflected light by the multiple reflection unit is also emitted from the portion where the incident light from the front side is blocked by the display element, and the shadow of the dark display due to the blocking of the incident light on the display element is eliminated, and the double image is formed. No good quality display is obtained.
[0014]
In addition, in this display device, since the multiple reflection means is composed of two polarization separation elements having no light absorption, there is no loss due to light absorption, the brightness of bright display is sufficiently increased, and sufficient brightness is obtained. Can be reflected.
[0015]
As described above, the display device of the present invention reflects one of the two different polarization components of the incident light behind the display element that controls transmission and blocking of the incident light, and reflects the other polarization component. A first polarization splitting element having a property of transmitting components, transmitting at least a part of light incident from the front side through the display element, and reflecting a part of light incident from the rear side; The first polarized light is disposed on the rear side of the first polarized light separating element, and has a property of reflecting one polarized light component and transmitting the other polarized light component among two different polarized light components of the incident light, A second polarization separation element that reflects at least a part of the transmitted light and the reflected light to the rear side of the separation element, transmits through the display element, enters from the front side, and transmits through the first polarization separation element. The first and second polarized light at least a portion of the By providing multiple reflection between the separation elements and arranging multiple reflection means for transmitting a part of the reflected light through the first polarization separation element and emitting the reflected light to the front side for each reflection, a good image without double images is obtained. Thus, it is possible to perform reflective display with high quality and sufficient brightness.
[0016]
Further, in this display device, the first and second polarization separation elements of the multiple reflection means each have a transmission axis and a reflection axis in directions orthogonal to each other, and form two orthogonal polarization components of incident light orthogonal to each other. A reflection polarization element that reflects one polarization component having a vibration plane parallel to the reflection axis and transmits the other polarization component having a vibration plane parallel to the transmission axis; However, it is preferable that the respective transmission axes are arranged obliquely shifted from each other.
[0017]
Further, in this display device, the multiple reflection means may include, between the first and second polarization separation elements, light traveling from one polarization separation element to the other polarization separation element, and the other polarization separation element. A third polarization separation element for changing the direction of the vibration plane of light traveling from the first polarization separation element to the one polarization separation element may be further arranged.
[0018]
Further, the multi-reflecting means may include a light between the first and second polarization splitting elements, the light traveling from one polarization splitting element to the other polarization splitting element, and the one polarization splitting element from the other polarization splitting element. A configuration may be employed in which a retardation plate that changes the polarization state of light traveling toward the separation element is further disposed.
[0019]
The multiple reflection unit is disposed on the back side of the second polarization separation element, reflects the transmitted light and the reflected light to the rear side of the second polarization separation element, and reflects the first and second polarization separation elements. It is desirable to further include a reflective film that causes multiple reflection between the light emitting device and the light emitting device.
[0020]
Further, the multiple reflection means transmits incident light from the front surface and the rear surface between the first and second polarization separation elements, and emits incident light from the end surface from at least one of the front surface and the rear surface. It is preferable that a surface light source including a light guide plate and a light emitting element provided to face the end face of the light guide plate is further arranged.
[0021]
In this case, the light guide plate of the surface light source is provided with light traveling from one of the first and second polarization separation elements of the multiple reflection means to the other polarization separation element, and the one polarization light from the other polarization separation element. It may be a retardation plate that changes the polarization state of light traveling toward the separation element.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show a first embodiment of the present invention. FIG. 1 is an exploded perspective view of a display device, and FIGS. 2 and 3 show incident light in the display device in a reflective display and in a transmissive display. It is a schematic diagram which shows the transmission path of light.
[0023]
As shown in FIG. 1, the display device of this embodiment has a display element 1 for controlling transmission and blocking of incident light, and a display element 1 on the side opposite to the display observation side (upper side in FIG. 1). And a multiple reflection means 10 disposed on a certain rear side.
[0024]
The display element 1 is, for example, a liquid crystal display element. A front transparent substrate 3 which is a display observation side and a rear transparent substrate 4 opposed to the front substrate 3 are provided with a frame-shaped sealing material 5 therebetween. A liquid crystal layer 6 (see FIGS. 2 and 3) for controlling the polarization state of transmitted light in accordance with an applied electric field is provided in a region which is bonded and surrounded by the sealing material 5 between these substrates 3 and 4. And a pair of polarizing plates 7 and 8 disposed before and after the liquid crystal cell 2 with the liquid crystal cell 2 interposed therebetween.
[0025]
Although not shown in the drawing, on the inner surfaces of the substrates 3 and 4 before and after the liquid crystal cell 2, there are provided transparent electrodes for forming a plurality of pixels arranged in a matrix by opposing regions. Is provided with an alignment film.
[0026]
The liquid crystal cell 2 is, for example, an active matrix liquid crystal cell using a TFT (thin film transistor) as an active element. A plurality of liquid crystal cells 2 are arranged in a matrix in a row direction and a column direction on one substrate, for example, an inner surface of a rear substrate 4. A plurality of pixel electrodes, a plurality of TFTs respectively connected to the pixel electrodes, a plurality of gate lines for supplying gate signals to the TFTs in each row, and a plurality of data lines for supplying data signals to the TFTs in each column. A plurality of color filters, for example, three colors of red, green, and blue, which are alternately formed on the inner surface of the front substrate 3, which is the other substrate, in opposition to the plurality of pixel electrodes. A single film counter electrode facing the plurality of pixel electrodes is provided.
[0027]
The liquid crystal display element 1 is of a TN (twisted nematic) type. The liquid crystal layer 6 of the liquid crystal cell 2 has a liquid crystal molecule in a twist orientation of substantially 90 ° between the front and rear substrates 3 and 4 at a twist angle. Made of a nematic liquid crystal having a positive dielectric anisotropy.
[0028]
In FIG. 1, an arrow 3 a indicates a liquid crystal molecule alignment direction near the front substrate 3 of the liquid crystal cell 2, and an arrow 4 a indicates a liquid crystal molecule alignment direction near the rear substrate 4, and the liquid crystal molecules near the front substrate 3. The orientation direction 3a is substantially 45 ° in one direction with respect to the horizontal axis x of the screen of the display device, and the liquid crystal molecule orientation direction 4a in the vicinity of the rear substrate 4 is the other direction with respect to the horizontal axis x. And the liquid crystal molecules of the liquid crystal layer 6 have a twist direction substantially from the rear substrate 4 toward the front substrate 3 as indicated by the dashed arrow in FIG. At a twist angle of 90 °.
[0029]
The pair of polarizers 7 and 8 arranged with the liquid crystal cell 2 interposed therebetween have transmission axes 7a and 8a and absorption axes (not shown) in directions orthogonal to each other, and are orthogonal to each other of incident light. Absorption polarized light that absorbs one of the two linearly polarized light components having a vibration plane parallel to the absorption axis and transmits the other polarization component with a vibration plane parallel to the transmission axes 7a and 8a. The front absorption polarizing plate 7 has its transmission axis 7a substantially orthogonal or parallel (orthogonal in the figure) to the liquid crystal molecule orientation direction 3a near the front substrate 3 of the liquid crystal cell 2. The rear absorption polarizer 8 is attached to the outer surface of the front substrate 3 of the liquid crystal cell 2 and the transmission axis 8a of the rear absorption polarizer 8 is substantially orthogonal to the transmission axis 7a of the front absorption polarizer 7. It is attached to the outer surface of the substrate 4.
[0030]
On the other hand, the multiple reflection means 10 disposed on the rear side of the liquid crystal display element 1 includes a first polarization separation element 11 disposed on the rear side opposite to the display side of the liquid crystal display element 1 on the display side. A second polarization separation element 12 disposed on the rear side of the first polarization separation element 11, and a reflection film 15 disposed on the rear side of the second polarization separation element 12. The configuration is such that a surface light source 16 is disposed between the first and second polarization separation elements 11 and 12.
[0031]
The first and second polarization separation elements 11 and 12 each have a polarization separation characteristic of reflecting one of the two different polarization components of the incident light and transmitting the other. I have.
[0032]
The first and second polarization separation elements 11 and 12 are, for example, reflection polarization elements that reflect one polarized light component and transmit the other polarized light component among two linearly polarized light components of incident light that are orthogonal to each other. In this embodiment, there are transmission axes 11a and 12a and reflection axes 11b and 12b in directions orthogonal to each other, and of two linear polarization components of incident light orthogonal to each other, the components are parallel to the reflection axes 11b and 12b. A reflection polarizer is used which reflects one polarized component having a vibrating surface and transmits the other polarized component having a vibrating surface parallel to the transmission axes 11a and 12a. Hereinafter, the first polarization separation element 11 is referred to as a first reflection polarization plate, and the second polarization separation element 12 is referred to as a second reflection polarization plate.
[0033]
The first reflective polarizer 11 on the rear side of the liquid crystal display element 1 is disposed with its transmission axis 11a substantially parallel to the transmission axis 8a of the absorption polarizer 8 on the rear side of the liquid crystal display element 1. The second reflective polarizer 12 on the rear side of the first reflective polarizer 11 has a transmission axis 12a at an angle of substantially 45 ° with respect to the transmission axis 11a of the first reflective polarizer 11. It is arranged to be shifted at an angle.
[0034]
The surface light source 16 disposed between the first and second reflective polarizers 11 and 12 transmits the incident light from the front surface and the rear surface, and transmits the incident light from the end surface to at least the front and rear surfaces. The light guide plate 17 includes a light guide plate 17 that emits light from one side, and a light emitting element 18 provided to face the end face of the light guide plate 17.
[0035]
The surface light source 16 used in this embodiment has a plurality of light emitting elements 18 made of LEDs (light emitting diodes) arranged opposite to the end face of the light guide plate 17. The light emitting element arranged to face the device may be a straight tube cold cathode tube or the like.
[0036]
The surface light source 16 transmits light incident from the front surface of the light guide plate 17 and emits light from the rear surface of the light guide plate 17, transmits light incident from the rear surface of the light guide plate 17, and transmits the light incident on the rear surface of the light guide plate 17. And the light emitted from the light emitting element 18 and incident on the light guide plate 17 from the end face thereof is totally reflected at the interface between the front and rear surfaces of the light guide plate 17 and the outside air (air), while the light guide plate 17 is being reflected. The light-emitting element 18 is turned off when the display device is used in an environment in which external light with sufficient brightness is obtained, and the light-emitting element 18 is turned off. Lights when the display device is used in an environment where light cannot be obtained.
[0037]
In the surface light source 16, the front surface of the light guide plate 17 faces the rear surface of the first reflective polarizer 11 on the front side, and the rear surface of the light guide plate 17 faces the front surface of the second reflective polarizer 12 on the rear side. In addition, an air layer is provided between the front and rear surfaces of the light guide plate 17 and the first and second reflective polarizers 11 and 12, and the reflective film 15 is provided with the second reflective polarizer. At the rear side of 12, it is disposed close to or attached to the rear surface.
[0038]
In an environment where external light of sufficient brightness can be obtained, this display device performs reflection display using external light incident from the front side which is the display observation side, and external light of sufficient brightness cannot be obtained. Sometimes, the illuminating light is emitted from the surface light source 16 of the multiple reflection means 10 to perform transmissive display using the illuminating light, and the display is observed from the front direction (the direction near the normal to the screen). You.
[0039]
In the display device of this embodiment, as shown in FIG. 1, the transmission axis 7a of the absorption polarizer 7 on the front side of the liquid crystal display element 1 is substantially orthogonal to the transmission axis 8a of the absorption polarizer 8 on the rear side. Therefore, the reflective display using external light and the transmissive display using illumination light from the surface light source 16 can be used in the absence of an electric field (liquid crystal) without applying an electric field to the liquid crystal layer 6 of the liquid crystal cell 2. This is a so-called normally white mode display in which the display when the alignment state of the liquid crystal molecules in the layer 6 is the initial twist alignment) is a bright display.
[0040]
FIG. 2 is a schematic diagram showing a transmission path of incident light at the time of reflection display of the display device, and FIG. 3 is a schematic diagram showing a transmission path of incident light at the time of transmission display of the display device. The layer thickness of the liquid crystal layer 6 of the liquid crystal cell 2 of the liquid crystal display element 1 is greatly exaggerated.
[0041]
First, the transmission path of the incident light in the reflective display shown in FIG. 2 will be described. 2A shows a transmission path when no electric field is applied to the liquid crystal layer 6 of the liquid crystal cell 2 when no electric field is applied (V = 0). FIG. 2B shows liquid crystal molecules in the liquid crystal layer 6 of the liquid crystal cell 2. 4 shows a transmission path when an electric field is applied (V> Vth) in which an electric field is applied which causes the substrate to rise substantially perpendicularly to the surfaces of the substrates 3 and 4.
[0042]
In the case of this reflective display, as shown in FIGS. 2A and 2B, of the two linearly polarized light components orthogonal to each other of the external light (non-polarized light) incident from the front side, the absorption on the front side of the liquid crystal display element 1 is performed. The polarized light component having a vibration plane parallel to the absorption axis of the polarizing plate 7 is absorbed by the absorbing polarizing plate 7, and the polarized light component having a vibration plane parallel to the transmission axis 7a of the absorbing polarizing plate 7 is absorbed by the absorption component. The light passes through the polarizing plate 7 and becomes linearly polarized light S parallel to the transmission axis 7a of the absorbing polarizing plate 7 and enters the liquid crystal cell 2 from the front side.
[0043]
The linearly polarized light S incident on the liquid crystal cell 2 from the front side is subjected to a birefringence effect of the liquid crystal layer 6 according to the alignment state of the liquid crystal molecules which changes according to the electric field applied between the electrodes of the liquid crystal cell 2, and this liquid crystal is The light is emitted to the rear side of the cell 2 and cut off by the rear absorption polarizer 8, or transmitted through the rear absorption polarizer 8 and emitted to the rear side of the liquid crystal display element 1.
[0044]
That is, the alignment state of the liquid crystal molecules when no electric field is applied between the electrodes of the liquid crystal cell 2 when no electric field is applied (V = 0) is substantially a twist alignment with a twist angle of 90 °. As shown in (a), the linearly polarized light S that has passed through the front absorption polarizer 7 and entered the liquid crystal cell 2 is substantially rotated by 90 ° due to the birefringence of the liquid crystal layer 6, and absorbed by the rear side. In the absence of an electric field, the linearly polarized light P emitted to the rear side of the liquid crystal cell 2 is converted to the linearly polarized light P parallel to the transmission axis 8a of the polarizing plate 8 and emitted to the rear side. The light is transmitted through the absorption polarizer 8 on the side of the liquid crystal display device 1 and emitted to the rear side.
[0045]
The linearly polarized light P emitted to the rear side of the liquid crystal display element 1 enters the multiple reflection means 10 from the front side.
[0046]
In this embodiment, the transmission axis 11a of the first reflection polarizing plate 11, which is the polarization splitting element on the front side of the multiple reflection means 10, is substantially the same as the transmission axis 8a of the absorption polarizing plate 8 on the rear side of the liquid crystal display element 1. Most of the linearly polarized light P emitted from the rear side of the liquid crystal display element 1 and incident on the multiple reflection means 10 is transmitted through the first reflective polarizing plate 11 and is substantially parallel to the rear side. Out.
[0047]
The linearly polarized light P emitted to the rear side of the first reflection polarizing plate 11 passes through the light guide plate 17 of the surface light source 16 and is a second reflection polarizing plate which is a polarization separation element on the rear side of the multiple reflection unit 10. It is incident on 12.
[0048]
The transmission axis 12a of the second reflective polarizer 12 is obliquely shifted with respect to the transmission axis 11a of the first reflective polarizer 11, so that the transmission axis 12a of the second reflective polarizer 12 is transmitted through the first reflective polarizer 11. The polarization component of the linearly polarized light P incident on the second reflective polarizing plate 12 from the front side thereof and having a vibration plane parallel to the transmission axis 12a of the second reflective polarizer 12 is converted to the second reflective polarizer 12. Is transmitted to the rear side, and the polarized light component having a vibration plane parallel to the reflection axis 12b of the second reflective polarizing plate 12 is reflected forward by the second reflective polarizing plate 12.
[0049]
The light transmitted through the second reflective polarizer 12 and emitted to the rear side, that is, the linearly polarized light Pa parallel to the transmission axis 12a of the second reflective polarizer 12 is reflected by the reflective film 15, and The light passes through the second reflective polarizer 12 again, passes through the light guide plate 17, and re-enters the first reflective polarizer 11 from the rear side.
[0050]
On the other hand, of the linearly polarized light P incident on the second reflective polarizer 12 from the front side, the light reflected by the second reflective polarizer 12, that is, the reflection axis of the second reflective polarizer 12 The linearly polarized light Sa parallel to 12b passes through the light guide plate 17 and re-enters the first reflective polarizing plate 11 from the rear side.
[0051]
The linearly polarized lights Pa and Sa re-incident on the first reflective polarizer 11 from the rear side are both obliquely shifted with respect to both the transmission axis 11a and the reflective axis 11b of the first reflective polarizer 11. Since the linearly polarized light has a vibrating surface, the polarization component of the linearly polarized light Pa, Sa having a vibrating surface parallel to the transmission axis 11a of the first reflective polarizing plate 11 (the transmission axis of the first reflective polarizing plate 11). The linearly polarized light (P) parallel to the light 11a passes through the first reflective polarizing plate 11 and is emitted to the front side of the multiple reflection means 10.
[0052]
Further, a polarization component of the linearly polarized light Pa, Sa re-entering the first reflective polarizing plate 11 from the rear side having a vibration plane parallel to the reflection axis 11b of the first reflective polarizing plate 11 (first component). The linearly polarized light (S) parallel to the reflection axis 11b of the reflection polarizing plate 11 is reflected rearward by the first reflection polarizing plate 11 and re-enters the second reflection polarizing plate 12, and the light S The polarization component Pa (linearly polarized light parallel to the transmission axis 12a of the second reflective polarizer 12) having a vibration plane parallel to the transmission axis 12a of the second reflective polarizer 12 is , And is emitted to the rear side, and has a vibration component having a vibration plane parallel to the reflection axis 12a of the second reflection polarization plate 12 (linear polarization parallel to the reflection axis 12b of the second reflection polarization plate 12). Sa is reflected by the second reflective polarizer 12.
[0053]
The linearly polarized light Pa transmitted through the second reflective polarizing plate 12 and emitted to the rear side is reflected again by the reflective film 15 and transmitted again through the second reflective polarizing plate 12 and the light guide plate 17. A polarized component of the light Pa having a vibrating surface parallel to the transmission axis 11a of the first reflective polarizing plate 11 (the first reflective polarizing plate 11). The linearly polarized light (P) parallel to the transmission axis 11a passes through the first reflective polarizing plate 11 and is emitted to the front side of the multiple reflection means 10.
[0054]
Also, of the linearly polarized light S reflected back by the first reflective polarizer 11 and incident again on the second reflective polarizer 12, the light Sa reflected by the second reflective polarizer 12 is reflected. Is a polarized component (a first reflected polarized light) having a vibration plane parallel to the transmission axis 11a of the first reflective polarizing plate 11 of the light Sa which re-enters the first reflective polarizing plate 11 from behind. The linearly polarized light (P) P parallel to the transmission axis 11a of the plate 11 passes through the first reflective polarizing plate 11 and is emitted to the front side of the multiple reflection means 10.
[0055]
In this embodiment, since the transmission axes 11a and 12a of the first and second reflective polarizers 11 and 12 are obliquely shifted at an angle of substantially 45 °, the first reflective polarizer 11 is moved from the front side. , Approximately half of the linearly polarized light P incident on the second reflective polarizing plate 12 is transmitted through the second reflective polarizing plate 12 and emitted to the rear side, and the other approximately half is the second reflected polarized light. While being reflected by the plate 12, the reflected light is reflected by the reflective film 15, transmitted through the second reflective polarizing plate 12 again, and is substantially half of the linearly polarized light Pa that has reentered the first reflective polarizing plate 11 from the rear side. Approximately half of the linearly polarized light Sa that has been reflected forward by the second reflective polarizing plate 12 and re-entered the first reflective polarizing plate 11 from the rear side passes through the first reflective polarizing plate 11, respectively. Out to the front side of the multiple reflection means 10 and Light Pa, other about half of that Sa is reflected rearward by the first reflective polarizing plate 11.
[0056]
That is, the multiple reflection means 10 transmits a part of the light reflected by the second reflection polarizing plate 12 through the first reflection polarization plate 11 from the front side thereof, and reflects a part of the light reflected by the second reflection polarization plate 12. The light is transmitted through the plate 11 and emitted to the front side, and the other light is multiply reflected once or plural times between the first and second reflective polarizers 11 and 12. A part of the light reflected by the reflective polarizing plate 12 is transmitted through the first polarization separation element 11 and emitted to the front side.
[0057]
Further, the multiple reflection means 10 reflects the light transmitted through the second reflective polarizing plate 12 and emitted to the rear side of the light transmitted through the first reflective polarizing plate 11 and incident from the front side. A part of the light reflected by the film 15 and transmitted through the second reflective polarizer 12 again is transmitted through the first reflective polarizer 11 and emitted to the front side, and the other light is transmitted to the first and second polarizers 12. The light is reflected multiple times between the two reflective polarizers 11 and 12 one or more times, and for each reflection, a part of the light reflected by the second reflective polarizer 12 is transmitted through the first polarization separation element 11. Then, the light is emitted to the front side.
[0058]
Therefore, light incident from the front side of the liquid crystal display element 1 and transmitted through the liquid crystal display element 1 and incident on the multiple reflection means 10 is transmitted between the first and second reflective polarizers 11 and 12 described above. Due to multiple reflection and multiple reflection between the reflective film 15 and the first and second reflective polarizers 11 and 12, the light spreads from the incident portion to the periphery, and the first reflected polarized light from the periphery of the incident portion. The light becomes linearly polarized light P parallel to the transmission axis 11a of the plate 11, and is emitted to the front side.
[0059]
The linearly polarized light P emitted to the front side of the multiple reflection means 10 passes through the absorption polarizer 8 on the rear side of the liquid crystal display element 1 and is incident on the liquid crystal cell 2 from the rear side. The liquid crystal is rotated and transmitted through the absorption polarizer 7 on the front side, and is emitted to the front side of the liquid crystal display element 1.
[0060]
Therefore, when there is no electric field (V = 0), the light incident from the front side, transmitted through the liquid crystal display element 1, and incident on the multiple reflection means 10 on the rear side is reflected by the multiple reflection means 10 while expanding the light flux. Then, the reflected light passes through the liquid crystal display element 1 again and is emitted to the front side, and a bright display (colored display) is obtained.
[0061]
On the other hand, FIG. 2B shows an electric field applied (V> Vth) between the electrodes of the liquid crystal cell 2 when an electric field is applied which causes liquid crystal molecules to rise and align substantially perpendicular to the surfaces of the substrates 3 and 4. As described above, the linearly polarized light S transmitted through the front absorption polarizer 7 and incident on the liquid crystal cell 2 is transmitted through the liquid crystal cell 2 in the polarized state without being affected by the birefringence of the liquid crystal layer 6 and thereafter. The light enters the absorption polarizer 8 on the side, and most of the light is absorbed by the absorption polarizer 8 on the rear side.
[0062]
Therefore, when an electric field is applied, light incident from the front side is cut off by the liquid crystal display element 1 and dark display (black display) is performed.
[0063]
Since the brightness of the display of this display device changes according to the alignment state of the liquid crystal molecules of the liquid crystal cell 2, the electric field applied between the electrodes of the liquid crystal cell 2 is controlled to control the gradation of the light and dark. Can be controlled.
[0064]
That is, this display device obtains a dark display by blocking the light incident from the front side, which is the display observation side, by the liquid crystal display element 1 and obtains the light incident from the front side and transmitted through the liquid crystal display element 1. The light is incident on the multiple reflection means 10, passes through the first reflection polarization plate 11 of the multiple reflection means 10, is reflected by the second reflection polarization plate 12 and the reflection film 15, and passes through the first reflection polarization plate 11. Then, a part of the light emitted to the front side of the multiple reflection means 10 is transferred between the first and second reflection polarizing plates 11 and 12 and between these reflection polarizing plates 11 and 12 and the reflection film 15. Multiple reflection is performed, and for each reflection, a part of the reflected light is transmitted through the first reflection polarizing plate 11 and emitted to the front side of the multiple reflection means 10, and the light is emitted to the front side of the liquid crystal display element 1. To obtain a bright display.
[0065]
According to this display device, since the multiple reflection unit 10 multiple-reflects the light incident from the front side and emits a part of the reflected light to the front side at each reflection, the multiple reflection unit 10 starts from the front side of the liquid crystal display element 1. The light that enters, passes through the liquid crystal display element 1, and enters the multiple reflection unit 10 is spread by the multiple reflection described above and exits to the front side of the multiple reflection unit.
[0066]
Therefore, the reflected light by the multiple reflection means 10 is also emitted from the portion where the incident light from the front side is blocked by the liquid crystal display element 1, and the shadow of the dark display due to the blocking of the incident light on the liquid crystal display element 1 is eliminated. Thus, a display of good quality without double images can be obtained.
[0067]
That is, a display device that performs reflective display using external light is normally used with a direction inclined obliquely with respect to the screen normal directed to a direction in which the brightest external light is incident. In a conventional reflective display device having a configuration in which a reflective film is disposed directly facing the display element on the side, the shadow of dark display due to blocking of incident light on the display element is shifted from the dark display portion of the display element. And the display image viewed from the front direction appears as a double image.
[0068]
On the other hand, in the display device of this embodiment, the light incident from the front side, transmitted through the liquid crystal display element 1 and incident on the multiple reflection means 10 is incident on the multiple reflection means 10 due to multiple reflection. Since the light is spread and reflected in an area wider than the portion, and the light is also emitted from the area serving as the shadow of the dark display, the shadow of the dark display can be substantially eliminated, and the generation of a double image can be prevented.
[0069]
Moreover, in this display device, since the multiple reflection means 10 is composed of two polarization separating elements (reflection polarizing plates) 11 and 12 having no light absorption, there is no loss due to light absorption and the brightness of bright display can be reduced. A sufficiently high reflection display with sufficient brightness can be performed.
[0070]
Further, in this display device, light incident from the front side and transmitted through the liquid crystal display element 1 is made incident on the multiple reflection means 10, and light whose emission range is widened by the multiple reflection of the multiple reflection means 10 is transmitted to the liquid crystal. Since the light is emitted to the front side of the display element 1 to obtain a bright display, the brightness of the bright display can be made uniform and sufficiently high. In particular, when the liquid crystal display element 1 is in a normally white mode, the amount of light transmitted through the liquid crystal display element 1 and incident on the multiple reflection means 10 increases, and the bright display becomes brighter and more uniform. .
[0071]
In this display device, the crossing angle between the transmission axes 11a and 12a of the first and second reflective polarizers 11 and 12 of the multiple reflection means 10 is determined by the second reflective polarizer 12 or the reflective film 15 once. (Hereinafter referred to as “primary emission light”) that is emitted to the front side of the multiple reflection means 10 due to the reflection of light between the first and second reflective polarizers 11 and 12 and between these reflective polarizers 11 and 12 and the reflection. It determines the ratio of light (hereinafter referred to as secondary emission light) which spreads due to multiple reflection with the film 15 and is emitted to the front side of the multiple reflection means 10, and when the crossing angle is a small angle, When the ratio of the primary emission light increases, the display becomes brighter, and when the intersection angle is large, the ratio of the spread secondary emission light increases, and the effect of eliminating double images increases.
[0072]
In this embodiment, as described above, the first and second reflective polarizers 11 and 12 of the multiple reflection means 10 are obliquely shifted at an angle of substantially 45 ° with respect to the respective transmission axes 11a and 12a. The primary emission light which is disposed and emitted to the front side of the multiple reflection means 10 by one reflection by the second reflection polarizing plate 12 or the reflection film 15, and between the first and second reflection polarizing plates 11 and 12, and between these. The light is spread almost evenly by the multiple reflection between the reflective polarizers 11 and 12 and the reflective film 15 and is distributed almost equally to the secondary emission light emitted to the front side of the multiple reflection means 10.
[0073]
Therefore, the amount of light that is multiple-reflected by the multiple reflection means 10 is sufficiently ensured to prevent a double image from occurring more effectively, and the light is emitted from the multiple reflection means 10 and re-transmitted to the liquid crystal display element 1. The amount of incident light can be made sufficient, and the brightness of the bright display can be made sufficiently high.
[0074]
Next, the transmission path of the incident light in the transmissive display shown in FIG. 3 will be described. FIG. 3A shows a transmission path when no electric field is applied to the liquid crystal layer 6 of the liquid crystal cell 2 when no electric field is applied (V = 0). FIG. 3B shows liquid crystal molecules in the liquid crystal layer 6 of the liquid crystal cell 2. 4 shows a transmission path when an electric field is applied (V> Vth) in which an electric field is applied which causes the substrate to rise substantially perpendicularly to the surfaces of the substrates 3 and 4.
[0075]
This transmissive display is performed by turning on the light emitting element 18 of the surface light source 16 of the multiple reflection means 10. Light emitted from the light emitting element 18 (non-polarized light) is shown in FIGS. 3 (a) and 3 (b). As described above, the light enters the light guide plate 17 from its end surface, and is guided inside the light guide plate 17 while being totally reflected at the interface between the front and rear surfaces of the light guide plate 17 and the air layer outside the light guide plate 17. The light exits from the rear surface.
[0076]
Although not shown in the drawing, on the rear surface of the light guide plate 17, the angle of the light traveling toward the rear surface in the light guide plate 17 with respect to the normal to the front and rear surfaces of the light guide plate 17 becomes smaller. A plurality of groove-shaped concave portions reflecting in the direction are formed in parallel with the end surface of the light guide plate, so that most of the light guided in the light guide plate 17 exits from the front surface of the light guide plate 17.
[0077]
However, some of the light guided inside the light guide plate 17 may leak through the interface between the rear surface of the light guide plate 17 and the outside air and leak to the rear side. Reflected by the second reflective polarizing plate 12 on the side, or transmitted through the second reflective polarizing plate 12, reflected by the reflective film 15, transmitted through the light guide plate 17, and emitted from the front surface thereof. The light emitted from the light emitting element 18 can be emitted from the front surface of the light guide plate 17 at an emission rate of about 100%.
[0078]
The illumination light emitted from the front surface of the light guide plate 17 is incident on the first reflective polarizing plate 11 on the front side of the light guide plate 17 from the rear side, and the first linear polarization component of the two linearly polarized light components orthogonal to each other. A polarization component P (linearly polarized light parallel to the transmission axis 11a of the first reflection polarizing plate 11) having a vibration plane parallel to the transmission axis 11a of the reflection polarization plate 11 is transmitted through the first reflection polarization plate 12. Out of the multiple reflection means 10.
[0079]
Also, of the light incident on the first reflective polarizing plate 11 from behind, a polarized component having a vibration plane parallel to the reflection axis 11b of the first reflective polarizing plate 11 (the first reflective polarizing plate 11). The linearly polarized light S parallel to the reflection axis 11b is reflected to the rear side by the first reflection polarizing plate 11.
[0080]
The linearly polarized light S reflected rearward by the first reflective polarizing plate 11 passes through the light guide plate 17 and enters the second reflective polarizing plate 12 from the front side, where the second reflection of the light S is performed. A polarization component Sa (linearly polarized light parallel to the reflection axis 12b of the second reflection polarization plate 12) having a vibration plane parallel to the reflection axis 12b of the polarization plate 12 is reflected by the second reflection polarization plate 12, The light again passes through the light guide plate 17 and reenters the first reflective polarizing plate 11 from the rear side.
[0081]
On the other hand, the linearly polarized light S that is reflected rearward by the first reflective polarizer 11 and enters the second reflective polarizer 12 from its front side is parallel to the transmission axis 12a of the second reflective polarizer 12. The polarized component Pa having a vibrating surface (linearly polarized light parallel to the transmission axis 12a of the second reflective polarizer 12) Pa is transmitted through the second reflective polarizer 12, reflected by the reflective film 15, and reflected by the second reflective polarizer 12. The light passes through the second reflective polarizer 12 again, passes through the light guide plate 17, and re-enters the first reflective polarizer 11 from the rear side.
[0082]
A polarization component (a first reflection polarizing plate) of the light Pa, Sa that has re-entered the first reflection polarizing plate 11 from the rear side and has a vibration plane parallel to the transmission axis 11a of the first reflection polarizing plate 11. 11 (linearly polarized light parallel to the transmission axis 11 a) passes through the first reflective polarizing plate 11 and exits to the front side of the multiple reflection means 10.
[0083]
Further, a polarization component (first reflection) of the light Pa, Sa re-entering the first reflection polarizing plate 11 from the rear side, having a vibration plane parallel to the reflection axis 11b of the first reflection polarizing plate 11. The linearly polarized light (S) parallel to the reflection axis 11b of the polarizing plate 11 is re-reflected to the rear side by the first reflecting polarizing plate 11, and the second reflective polarizing plate 12 and And the reflection film 15, and for each reflection, a polarization component having a vibration plane parallel to the transmission axis 11 a of the first reflection polarizing plate 11 (the first reflection polarizing plate 11). The linearly polarized light (P) P parallel to the transmission axis 11a passes through the first reflective polarizing plate 11 and is emitted to the front side of the multiple reflection means 10.
[0084]
That is, the multiple reflection means 10 also emits the illumination light from the surface light source 16, the primary emission light emitted by one reflection by the second reflection polarizing plate 12 or the reflection film 15, And the secondary emission light that is spread and emitted by multiple reflection between the two reflective polarizers 11 and 12 and between the reflective polarizers 11 and 12 and the reflective film 15 is transmitted to the first reflective polarizer 11. Out to the front side as linearly polarized light P parallel to the transmission axis 11a.
[0085]
Also at this time, in this embodiment, the transmission axes 11a and 12a of the first and second reflection polarizers 11 and 11 of the multiple reflection means 10 are obliquely shifted at an angle of substantially 45 °. Illumination light from the light source 16 is substantially equally distributed between the primary emission light and the secondary emission light.
[0086]
The linearly polarized light P emitted to the front side of the multiple reflection means 10 enters the liquid crystal display element 1 from the rear side.
[0087]
In this embodiment, the transmission axis 8a of the absorption polarizing plate 8 on the rear side of the liquid crystal display element 1 is set to the transmission axis 11a of the first reflection polarization plate 11, which is the polarization separation element on the front side of the multiple reflection means 10. Since they are substantially parallel, most of the linearly polarized light P emitted to the front side of the multiple reflection means 10 passes through the absorption polarizer 8 on the rear side of the liquid crystal display element 1 and enters the liquid crystal cell 2. .
[0088]
The linearly polarized light P transmitted through the absorption polarizer 8 on the rear side of the liquid crystal display element 1 and incident on the liquid crystal cell 2 is emitted from the multiple reflection means 10 when the surface light source 16 emits illumination light. Since the light is emitted, the light has sufficiently high intensity.
[0089]
That is, when the non-polarized illumination light emitted from the surface light source 16 is directly incident on the liquid crystal display element 1, the light of 50% or less of the illumination light, that is, the absorption polarizer 8 on the rear side of the liquid crystal display element 1 Only light of the transmitted linearly polarized light component can enter the liquid crystal cell 2.
[0090]
On the other hand, in the display device of this embodiment, the multiple reflection means 10 emits light from the surface light source 16 disposed between the first and second reflection polarizing plates 11 and 12, and the second reflection polarizing plate 12 or a linearly polarized light (primary emission light) P emitted to the front side by one reflection by the reflection film 15, emitted from the surface light source 16, between the first and second reflection polarizing plates 11 and 12, and between them. In order to emit linearly polarized light (secondarily emitted light) p that is spread and emitted by multiple reflection between the reflective polarizing plates 11 and 12 and the reflective film 15, more illumination light from the surface light source 16 is used. The liquid crystal display device 1 can be made to enter the liquid crystal display device 1 as linearly polarized light P passing through the absorption polarizer 8 on the rear side, and the high intensity linearly polarized light P can be made to enter the liquid crystal cell 2.
[0091]
The linearly polarized light P incident on the liquid crystal cell 2 from the rear side is subjected to the birefringence effect of the liquid crystal layer 6 according to the alignment state of the liquid crystal molecules which changes according to the electric field applied between the electrodes of the liquid crystal cell 2. The light is emitted to the front side of the liquid crystal cell 2.
[0092]
That is, when no electric field is applied between the electrodes of the liquid crystal cell 2, the alignment state of the liquid crystal molecules when there is no electric field (V = 0) is substantially a twist alignment with a twist angle of 90 °. As shown in (a), the linearly polarized light P incident on the liquid crystal cell 2 from the rear side is rotated by substantially 90 ° due to the birefringence action of the liquid crystal layer 6, and the transmission axis 7a of the absorption polarizing plate 7 on the front side. As a result, the light is emitted as linearly polarized light S parallel to the light, and exits the front side of the liquid crystal cell 2 and enters the absorption polarizer 7.
[0093]
Therefore, when there is no electric field, most of the linearly polarized light P emitted to the front side of the liquid crystal cell 2 passes through the absorption polarizer 7 on the front side and is emitted to the front side, and a bright display is obtained. This bright display is a display with sufficient brightness because the linearly polarized light P incident on the liquid crystal cell 2 from behind is high intensity light as described above.
[0094]
On the other hand, when an electric field is applied between the electrodes of the liquid crystal cell 2 so as to rise and orient liquid crystal molecules substantially perpendicularly to the surfaces of the substrates 3 and 4, as shown in FIG. The linearly polarized light P incident on the liquid crystal layer 2 from the rear side is emitted to the front side of the liquid crystal cell 2 without being affected by the birefringence of the liquid crystal layer 6 and is absorbed by the absorption polarizer 7 on the front side. Become.
[0095]
As described above, this display device reflects one of the two different polarization components of the incident light on the rear side of the liquid crystal display element 1 that controls transmission and blocking of the incident light, and reflects the other polarization component on the other side. A first polarization splitting element having a property of transmitting a polarized light component, transmitting at least a part of light incident on the liquid crystal display element 1 from the front side, and reflecting a part of light incident on the rear side; 11 and is disposed on the rear side of the first polarization separation element 11, and has a characteristic of reflecting one polarized component and transmitting the other polarized component among two different polarized components of the incident light, A second polarization splitting element 12 that reflects at least a part of the transmitted light and the reflected light to the rear side of the first polarization splitting element 11, passes through the liquid crystal display element 1 and enters from the front side, Of light transmitted through the first polarization separation element 11 At least part of the reflected light is multiple-reflected between the first and second polarization splitting elements 11 and 12, and at each reflection, part of the reflected light is transmitted through the first polarization splitting element 11 to the front side. Since the multiple reflection means 10 for emitting light is disposed, it is possible to perform reflection display with good quality without double images and with sufficient brightness.
[0096]
In this embodiment, the first and second polarization separation elements 11 and 12 of the multiple reflection means 10 have transmission axes 11a and 12a and reflection axes 11b and 12b, respectively, in directions orthogonal to each other. Of the two linearly polarized light components orthogonal to each other, reflects one polarized light component having a vibration plane parallel to the reflection axes 11b and 12b, and the other has a vibration plane parallel to the transmission axes 11a and 12a. Since the reflection polarizing plates 11 and 12 are arranged so that their transmission axes 11a and 12a are obliquely shifted from each other, the reflection polarizing plates 11 and 12 enter the multiple reflection means 10 from the front side thereof. The light transmitted through the first reflective polarizer 11 is reflected by the second reflective polarizer 12, and a part of the light is transmitted through the first reflective polarizer 11, and On the front side And the other light is multiple-reflected between the first and second reflective polarizers 11 and 12, and for each reflection, a part of the light reflected by the second reflective polarizer 12 is The light can be transmitted through one polarization splitting element 11 and output to the front side of the multiple reflection means 10.
[0097]
Furthermore, in this embodiment, since the multiple reflection means 10 is further provided with a reflection film 15 disposed on the rear side of the second reflection polarizing plate 12, the multiple reflection means 10 is provided from the front side of the multiple reflection means 10. The light transmitted through the first reflective polarizing plate 11 and incident thereon and transmitted through the second reflective polarizing plate 12 and emitted to the rear side is reflected by the reflective film 15 and is reflected by the second reflective polarizing plate. A part of the light transmitted again through the first reflective polarizer 11 is transmitted through the first reflective polarizer 11 and emitted to the front side, and another light is multiply reflected between the first and second reflective polarizers 11 and 12. For each reflection, a part of the light reflected by the second reflective polarizer 12 can be transmitted through the first polarization splitting element 11 and emitted to the front side of the multiple reflection means 10, The multiple reflection means 10 transmitted through the liquid crystal display element 1 All of the incident light reflected by spreading the multiple reflection as described above, by emitting the light to the front side of the liquid crystal display device 1, it is possible to obtain a brighter reflective display.
[0098]
In the above embodiment, the transmission axes 11a and 12a of the first and second reflective polarizers 11 and 12 of the multiple reflection means 10 are obliquely shifted at an angle of substantially 45 °, and the second reflected polarized light is changed. The primary emission light emitted to the front side of the multiple reflection means 10 by one reflection by the plate 12 or the reflection film 15 and the reflection between the first and second reflection polarizing plates 11 and 12 and the reflection between these reflection polarizing plates 11 and 12. Although it is made to spread almost evenly to the secondary emission light which spreads by multiple reflection with the film 15 and is emitted to the front side of the multiple reflection means 10, the first and second reflective polarizers 11, The shift angle between the transmission axes 11a and 12a of the light source 12 may be in a range in which a sufficient double image prevention effect in the reflective display and the bright display in the reflective display and the transmissive display can be sufficiently brightened.
[0099]
In addition, the display device of the above embodiment is arranged between the first and second reflective polarizers 11 and 12 to allow the multiple reflection means 10 to transmit the incident light from the front surface and the rear surface, respectively. And a light source plate 16 for emitting light from at least one of the front surface and the rear surface, and a light emitting element 18 provided to face the end surface of the light guide plate 17. Therefore, in an environment where external light with sufficient brightness can be obtained, reflection display using external light is performed, and when external light with sufficient brightness cannot be obtained, illumination light is emitted from the surface light source 16. Transmission display using the illumination light can be performed.
[0100]
FIGS. 4 to 6 show a second embodiment of the present invention. FIG. 4 is an exploded perspective view of a display device, and FIGS. 5 and 6 show incident light in the display device in a reflective display and in a transmissive display. It is a schematic diagram which shows the transmission path of light.
[0101]
As shown in FIG. 4, the display device of this embodiment includes a first reflective polarizer 11 on the liquid crystal display element 1 side behind the liquid crystal display element 1 for controlling transmission and blocking of incident light, and thereafter, A second reflective polarizer 12 disposed on the side, a reflective film 15 further disposed on the rear side, and disposed between the first reflective polarizer 11 and the second reflective polarizer 12. A multiple reflection unit 10a including a third polarization separation element 13 and a surface light source 16 is arranged.
[0102]
In this embodiment, the liquid crystal display element 1 and the surface light source 16 of the multiple reflection means 10a are the same as those of the first embodiment described above. Omitted.
[0103]
In this embodiment, a third polarization separation element 13 disposed between the first and second reflection polarizers 12 and 13 of the multiple reflection means 10a is a component of two linear polarization components of incident light that are orthogonal to each other. Of these, a reflective polarizing element that reflects one polarized light component and transmits the other polarized light component. In this embodiment, the reflective polarizing element has a transmission axis 13a and a reflection axis 13b in directions orthogonal to each other, and is orthogonal to the incident light. A reflection polarizing plate that reflects one of the two linearly polarized light components having a vibration plane parallel to the reflection axis 13b and transmits the other polarization component with a vibration plane parallel to the transmission axis 13a. Is used. Hereinafter, the third polarized light separating element 13 is referred to as a third reflective polarizing plate.
[0104]
The third reflective polarizer 13 is used to change the direction of the vibrating plane between the linearly polarized light traveling from one of the first and second reflective polarizers 11 and 12 to the other and the linear polarized light traveling from the other to the one. In this embodiment, the third reflective polarizer 13 is disposed between the first reflective polarizer 11 on the liquid crystal display element 1 side and the light guide plate 17 of the surface light source 16.
[0105]
The first reflective polarizer 11 on the liquid crystal display element 1 side of the multiple reflection means 10a is connected to the transmission axis 11a by the absorption polarizer 8 on the rear side of the liquid crystal display element 1 in the same manner as in the first embodiment. And the second reflective polarizer 12 on the reflective film 15 side has its transmission axis 12a substantially equal to the transmission axis 11a of the first reflective polarizer 11. The third reflective polarizer 13 is arranged so that its transmission axis 13a is obliquely shifted with respect to both the transmission axes 11a and 12a of the first and second reflective polarizers 11 and 12. Are located.
[0106]
In this embodiment, as shown in FIG. 4, the third reflective polarizer 13 is disposed with its transmission axis 13a oriented in a direction of 15 ° ± 10 ° with respect to the horizontal axis x of the screen. The shift angle between the transmission axis 13a of the third reflective polarizing plate 13 and the transmission axes 11a and 12a of the first and second reflective polarizing plates 11 and 12 is set to 30 ° ± 10 °.
[0107]
In FIG. 4, the transmission axis 13a of the third reflective polarizer 13 is turned clockwise with respect to the transmission axes 11a and 12a of the first and second reflective polarizers 11 and 12 from the front. Although shifted by 30 ° ± 10 °, the third reflective polarizing plate 13 has its transmission axis 13a viewed from the front with respect to the transmission axes 11a and 12a of the first and second reflective polarizing plates 11 and 12. And may be shifted by 30 ° ± 10 ° counterclockwise.
[0108]
The transmission path of the incident light at the time of reflection display of this display device will be described. FIG. 5 shows the transmission path of the incident light at the time of reflection display, and FIG. 5 (a) shows the case of no electric field (V = 0). FIG. 5B shows a transmission path when an electric field is applied (V> Vth).
[0109]
The change of the polarization state when the light incident from the front side and the light emitted to the front side of the multiple reflection means 10a pass through the liquid crystal display element 1 in the reflective display is the same as that in the first embodiment. Therefore, the description is omitted.
[0110]
First, the transmission path in the absence of an electric field (V = 0) where no electric field is applied between the electrodes of the liquid crystal cell 2 will be described. In the absence of the electric field, the linearly polarized light P emitted to the rear side of the liquid crystal display element 1 is Most of the light is incident on the multiple reflection means 10a, and most of the light is transmitted through the first reflective polarizing plate 11 and emitted to the rear side.
[0111]
The linearly polarized light P emitted to the rear side of the first reflective polarizer 11 is a third reflective polarizer whose transmission axis 13a is obliquely shifted with respect to the transmission axis 11a of the first reflective polarizer 11. 13, a polarization component of the linearly polarized light P having a vibration plane parallel to the transmission axis 13a of the third reflection polarizing plate 13 (linearly polarized light parallel to the transmission axis 13a of the third reflection polarization plate 13). Pb passes through the third reflective polarizer 13 and exits to the rear side, and a polarization component having a vibration plane parallel to the reflection axis 13b of the third reflective polarizer 13 (third reflective polarizer) 13) is reflected by the third reflective polarizer 13.
[0112]
The linearly polarized light Pb transmitted through the third reflective polarizer 13 and emitted to the rear is transmitted through the light guide plate 17 of the surface light source 16 and transmitted through the transmission axis 13a of the third reflective polarizer 13. The polarization component (second component) of the linearly polarized light Pb having an oscillation plane parallel to the transmission axis 12a of the second reflective polarizing plate 12 is incident on the second reflective polarizing plate 12 whose axis 12a is obliquely shifted. The linearly polarized light Pc parallel to the transmission axis 12a of the reflective polarizer 12 passes through the second reflective polarizer 12 and is emitted to the rear side, and is parallel to the reflective axis 12b of the second reflective polarizer 12. A polarization component Sc having a vibration surface (linearly polarized light parallel to the reflection axis 12b of the second reflective polarizing plate 12) Sc is reflected by the second reflective polarizing plate 12.
[0113]
The linearly polarized light Pc transmitted through the second reflective polarizing plate 12 and emitted to the rear side is reflected by the reflective film 15, transmitted again through the second reflective polarizing plate 12, and further transmitted through the light guide plate 17. Then, the light enters the third reflective polarizing plate 13 again from the rear side.
[0114]
On the other hand, of the linearly polarized light Pb incident on the second reflective polarizing plate 12 from the front side, the linearly polarized light Sc reflected by the second reflective polarizing plate 12 passes through the light guide plate 17 and passes through the second linearly polarized light Sc. Then, the light re-enters the third reflective polarizing plate 13 from the rear side.
[0115]
The linearly polarized light Pc and Sc re-entering the third reflective polarizer 13 from the rear side are both vibrating surfaces that are obliquely shifted with respect to the transmission axis 13a and the reflective axis 13b of the third reflective polarizer 13. Therefore, a polarized light component having a vibration plane parallel to the transmission axis 13a of the third reflective polarizing plate 13 of the linearly polarized light Pc, Sc (the transmission axis 13a of the third reflective polarizing plate 13 The parallel linearly polarized light P transmits through the third reflective polarizer 13 and re-enters the first reflective polarizer 11 from the rear side.
[0116]
Also, of the linearly polarized light P incident on the first reflective polarizing plate 11 from the front side and emitted to the rear side, the linear polarized light Sb reflected by the third reflective polarizing plate 13 is also the first linearly polarized light Sb. The light re-enters the reflective polarizing plate 11 from the rear side.
[0117]
The linearly polarized light beams Sb, Pc and Sc re-entering the first reflective polarizing plate 11 from the rear side are all obliquely shifted with respect to the transmission axis 11a and the reflection axis 11b of the first reflective polarizing plate 11. Since the linearly polarized light has a vibrating plane, the polarization component of the linearly polarized light Sb, Pc, Sc having a vibrating plane parallel to the transmission axis 11a of the first reflective polarizing plate 11 (the first reflective polarizing plate 11). (A linearly polarized light parallel to the transmission axis 11a) passes through the first reflective polarizing plate 11 and is emitted to the front side of the multiple reflection means 10a.
[0118]
Also, the linearly polarized light components Sb, Pa, and Sa that have re-entered the first reflective polarizing plate 11 from the rear side have polarization components having a vibration plane parallel to the reflection axis 11b of the first reflective polarizing plate 11 (second component). The linearly polarized light (S) parallel to the reflection axis 11b of the first reflective polarizing plate 11 is reflected rearward by the first reflective polarizing plate 11, and is reflected by the third reflective polarizing plate 13 and the The first reflected polarized light is transmitted through the second reflective polarizing plate 12 and reflected by the reflective film 15, or is reflected by one of the third reflective polarizing plate 13 and the second reflective polarizing plate 12 and is reflected by the first reflected polarized light. The light Pa is again incident on the plate 11 from the rear side, and a polarization component of the light Pa having a vibration plane parallel to the transmission axis 11a of the first reflection polarization plate 11 (parallel to the transmission axis 11a of the first reflection polarization plate 11). Linearly polarized light) P is transmitted through the first Emitted to the front side of the reflecting means 10a.
[0119]
That is, the multiple reflection means 10a transmits through the first reflective polarizing plate 11 by the third reflective polarizing plate 13 disposed between the first and second reflective polarizing plates 11 and 12, and By changing the direction of the plane of vibration of the light incident on the second reflective polarizer 12 and the direction of the linearly polarized light reflected by the second reflective polarizer 12 or the reflective film 15 and incident on the first reflective polarizer 11. The first and second reflective polarizers 11 and 12 are made to be incident on the first and second reflective polarizers 13 and 12, respectively, and are multiplexed by one reflection by one of the third and second reflective polarizers 13 and 12 and the reflective film 15. The primary emission light emitted to the front side of the reflection means 10a and the first, second, and third reflection polarizing plates 11, 12, 13 and between these reflection polarizing plates 11, 12, 13 and the reflection film 15 The multiple reflection means 10a A secondary emission light emitted to the side to be emitted to the front side as linearly polarized light parallel P to the transmission axis 11a of the first reflective polarizing plate 11.
[0120]
When there is no electric field (V = 0), the linearly polarized light P emitted to the front side of the multiple reflection means 10a passes through the liquid crystal display element 1 and is emitted to the front side to provide a bright display.
[0121]
Therefore, according to this display device, similarly to the above-described first display device, it is possible to perform reflection display with good quality without double images and with sufficient brightness.
[0122]
On the other hand, FIG. 5B shows an electric field applied between the electrodes of the liquid crystal cell 2 (V> Vth) in which an electric field that causes liquid crystal molecules to rise and align substantially perpendicular to the surfaces of the substrates 3 and 4 is applied. As described above, the linearly polarized light S transmitted through the front absorption polarizer 7 and incident on the liquid crystal cell 2 is transmitted through the liquid crystal cell 2 in the polarized state without being affected by the birefringence of the liquid crystal layer 6 and thereafter. Most of the light is incident on the absorption polarizing plate 8 on the side, and is absorbed by the absorption polarizing plate 8 on the rear side, thereby displaying a dark image.
[0123]
Next, the transmission path of the incident light in the transmissive display of the display device of this embodiment will be described. FIG. 6 shows the transmissive path of the incident light in the transmissive display, and FIG. FIG. 6B shows the transmission path when the electric field is applied (V> Vth).
[0124]
The emission of the illumination light from the surface light source 16 in the transmissive display and the change in the polarization state when the light emitted to the front side of the multiple reflection means 10a passes through the liquid crystal display element 1 are described in the first embodiment. The description is omitted because it is the same as the example.
[0125]
In the case of this transmissive display, as shown in FIGS. 6A and 6B, the illumination light emitted from the front surface of the light guide plate 17 of the surface light source 16 is reflected by the third reflection on the front side of the light guide plate 17. The polarization component having the vibration plane parallel to the transmission axis 13a of the third reflection polarization plate 13 (third reflection polarization) among the two linear polarization components that enter the polarization plate 13 from the rear side and are orthogonal to each other. The linearly polarized light Pb parallel to the transmission axis 13a of the plate 13 is transmitted through the third reflective polarizing plate 13 and is incident on the first reflective polarizing plate 11, and the linearly polarized light Pb is reflected by the first reflective polarizing plate. The polarization component P (linearly polarized light parallel to the transmission axis 11a of the first reflection polarizing plate 11) P having a vibration plane parallel to the transmission axis 11a of the first transmission mirror 11 is transmitted through the first reflection polarizing plate 11 and multiple reflected. Light is emitted to the front side of the means 10a.
[0126]
On the other hand, the linearly polarized light Pb transmitted through the third reflective polarizer 13 and incident on the first reflective polarizer 11 has a vibration plane parallel to the reflection axis 11b of the first reflective polarizer 11. The polarization component (linearly polarized light parallel to the reflection axis 11 b of the first reflection polarizing plate 11) S is reflected by the first reflection polarization plate 11 to the rear side, and is emitted from the front surface of the light guide plate 17. A polarized light component having a vibration plane parallel to the reflection axis 13b of the third reflection polarizing plate 13 of the light incident on the third reflection polarization plate 13 from the rear side (the reflection axis 13b of the third reflection polarization plate 13). Is reflected by the third reflective polarizing plate 13 to the rear side.
[0127]
The linearly polarized light S reflected rearward by the first reflective polarizer 11 re-enters the third reflective polarizer 13 from the front, and the reflection axis of the light is reflected by the third reflective polarizer 13. The polarized light component Sb (linearly polarized light parallel to the reflection axis 13b of the third reflective polarizer 13) having a vibration plane parallel to the third reflective polarizer 13 is reflected forward by the third reflective polarizer 13 and the third reflection A polarization component Pb having a vibration plane parallel to the transmission axis 13a of the polarizing plate 13 (linearly polarized light parallel to the transmission axis 13a of the third reflecting polarizing plate 13) Pb passes through the third reflecting polarizing plate 13 and thereafter Out to the side.
[0128]
The linearly polarized light Pb transmitted through the third reflective polarizing plate 13 and emitted to the rear side and the linearly polarized light Sb reflected by the third reflective polarizing plate 13 on the rear side are transmitted through the light guide plate 17. A polarization component having a vibration plane parallel to the reflection axis 12b of the second reflection polarization plate 12 of the light Pb and Sb that is incident on the second reflection polarization plate 12 (the reflection axis of the second reflection polarization plate 12). A linearly polarized light Sc parallel to the second reflective polarizer 12 Sc is reflected by the second reflective polarizer 12, and has a polarization component (a second reflective polarizer) having a vibration plane parallel to the transmission axis 13 a of the second reflective polarizer 12. 12) (the linearly polarized light parallel to the transmission axis 12a) Pc passes through the second reflective polarizer 12 and is reflected by the reflective film 15.
[0129]
In other words, the multi-reflection means 10a can perform one reflection by any of the third and second reflective polarizers 13 and 12 and the reflective film 15 even in the transmissive display using the illumination light from the surface light source 16. The primary emission light to be emitted and multiple reflection between the first, second, and third reflective polarizers 11, 12, and 13 and between these reflective polarizers 11, 12, and 13 and the reflective film 15 are generated. The secondary emission light that spreads and exits is emitted to the front side as linearly polarized light P parallel to the transmission axis 11a of the first reflective polarizing plate 11.
[0130]
When no electric field is applied between the electrodes of the liquid crystal cell 2 (V = 0), as shown in FIG. 6A, the linearly polarized light P emitted to the front side of the multiple reflection means 10a is The light passes through the liquid crystal display element 1 and is emitted to the front side to provide a bright display.
[0131]
On the other hand, when an electric field (V> Vth) is applied between the electrodes of the liquid crystal cell 2 so that liquid crystal molecules rise and orient substantially perpendicular to the surfaces of the substrates 3 and 4, (V> Vth) is shown in FIG. As described above, the linearly polarized light P emitted to the front side of the multiple reflection means 10a is absorbed by the absorption polarizer 7 on the front side of the liquid crystal display element 1, and a dark display (black display) is obtained.
[0132]
In the case where the first and second reflective polarizers 11 and 12 of the multiple reflecting means 10a are arranged with their transmission axes 11a and 12a substantially parallel to each other as in this embodiment, As described above, the transmission axis 13a of the third reflective polarizing plate 13 is set at 30 ° ± 10 ° with respect to the transmission axes 11a and 12a of the first and second reflective polarizing plates 11 and 12, more preferably. It is desirable to displace the light by 30 °, so that the light emitted to the front side of the multiple reflection means 10a is transmitted to one of the third and second reflection polarizing plates 13 and 12 and the reflection film 15. And the primary emission light emitted by one reflection by the first and second reflection mirrors 11, 12, and 13, and between these reflection polarization plates 11, 12, 13 and the reflection film 15. Emission that spreads out due to multiple reflections of light Substantially uniformly distributed bets, while preventing the occurrence of a double image when the reflective display can be more effectively be brighter bright display in the reflective display and the transmissive display.
[0133]
The directions of the transmission axes 11a, 12a, and 13a of the first and second reflective polarizers 11 and 12 and the third reflective polarizer 13 of the multiple reflection means 10a are not limited to those in the above-described embodiment, but may be used in a reflective display. Any range may be used as long as a sufficient effect of preventing double images can be obtained and bright display in reflective display and transmissive display can be sufficiently brightened.
[0134]
Further, in the above embodiment, the multiple reflection means 10a has a configuration in which the third reflection polarizing plate 13 is disposed between the first reflection polarizing plate 11 and the surface light source 16 on the liquid crystal display element 1 side. The third reflective polarizer 13 may be disposed between the second reflective polarizer 12 on the reflective film 15 side and the surface light source 16.
[0135]
7 to 9 show a third embodiment of the present invention. FIG. 7 is an exploded perspective view of a display device, and FIGS. 8 and 9 show incident light in the display device in a reflective display and in a transmissive display. It is a schematic diagram which shows the transmission path of light.
[0136]
As shown in FIG. 7, the display device of this embodiment has a first reflective polarizing plate 11 on the liquid crystal display element 1 side behind a liquid crystal display element 1 for controlling transmission and blocking of incident light. , A second reflective polarizer 12 disposed on the rear side, a reflective film 15 further disposed on the rear side, and the first reflective polarizer 11 and the second reflective polarizer 12. A multiple reflection unit 10b including a phase difference plate 14 and a surface light source 16 is arranged.
[0137]
In this embodiment, since the liquid crystal display element 1 and the surface light source 16 of the multiple reflection means 10b are the same as those of the first embodiment described above, the description of the configuration is given the same reference numerals in the drawings. Omitted.
[0138]
In this embodiment, the phase difference plate 14 disposed between the first and second reflective polarizers 11 and 12 of the multiple reflection means 10b is one of the first and second reflective polarizers 11 and 12. In this embodiment, the phase difference plate 14 is used as the first reflection polarizing plate 11 on the liquid crystal display element 1 side. And the light guide plate 17 of the surface light source 16.
[0139]
The phase difference plate 14 is, for example, a λ / 4 plate that gives a phase difference of １／ wavelength between the ordinary light and the extraordinary light of the transmitted light. In this embodiment, the liquid crystal display element 1 of the multiple reflection unit 10b is used. The first reflection polarizing plate 11 on the side of the liquid crystal display element 1 is made substantially parallel to the transmission axis 8a of the absorption polarizing plate 8 on the rear side of the liquid crystal display element 1 in the same manner as in the first embodiment. The second reflective polarizer 12 on the reflective film 15 side is disposed with its transmission axis 12a substantially parallel to the transmission axis 11a of the first reflective polarizer 11, and the λ / 4 The plate 14 is arranged such that its slow axis 14a is obliquely shifted at an angle of substantially 45 ° with respect to the transmission axes 11a and 12a of both the first and second reflective polarizers 11 and 12. .
[0140]
The transmission path of the incident light at the time of reflection display of this display device will be described. FIG. 8 shows the transmission path of the incident light at the time of reflection display, and FIG. 8A shows the case of no electric field (V = 0). FIG. 8B shows a transmission path when an electric field is applied (V> Vth).
[0141]
The change in the polarization state when the light incident from the front side and the light emitted to the front side of the multiple reflection means 10b pass through the liquid crystal display element 1 in the reflective display is the same as that in the first embodiment. Therefore, the description is omitted.
[0142]
First, the transmission path in the absence of an electric field (V = 0) where no electric field is applied between the electrodes of the liquid crystal cell 2 will be described. In the absence of the electric field, the linearly polarized light P emitted to the rear side of the liquid crystal display element 1 is Most of the light is incident on the multiple reflection means 10b, and most of the light is transmitted through the first reflection polarizing plate 11 and emitted to the rear side.
[0143]
The linearly polarized light P emitted to the rear side of the first reflective polarizing plate 11 has a slow axis 14a obliquely shifted at an angle of substantially 45 with respect to the transmission axis 11a of the first reflective polarizing plate 11. Incident on the λ / 4 plate 14, the λ / 4 plate 14 gives a phase difference of １／ wavelength, and becomes a circularly polarized light C and exits to the rear side of the λ / 4 plate 14.
[0144]
The circularly polarized light C emitted to the rear side of the λ / 4 plate 14 passes through the light guide plate 17 of the surface light source 16 and enters the second reflective polarizing plate 12, where the second circularly polarized light C A polarized component (linearly polarized light parallel to the transmission axis 12a of the second reflective polarizing plate 12) P having a vibration plane parallel to the transmission axis 12a of the reflective polarizing plate 12 transmits through the second reflective polarizing plate 12. The polarized light component S (linearly polarized light parallel to the reflection axis 12b of the second reflection polarizing plate 12) having a vibration plane parallel to the reflection axis 12b of the second reflection polarization plate 12 The light is reflected by the second reflective polarizing plate 12.
[0145]
The linearly polarized light P transmitted through the second reflective polarizing plate 12 and emitted to the rear side is reflected by the reflective film 15, transmitted again through the second reflective polarizing plate 12, and further transmitted through the light guide plate 17. Then, it re-enters the λ / 4 plate 14 from the rear side.
[0146]
On the other hand, of the circularly polarized light C incident on the second reflective polarizer 12 from the front side, the linearly polarized light S reflected by the second reflective polarizer 12 is transmitted through the light guide plate 17 and passes through the λ. The light again enters the / 4 plate 14 from the rear side.
[0147]
The linearly polarized light beams P and S re-incident on the λ / 4 plate 14 from the rear side are again converted into circularly polarized light C by the λ / 4 plate 14 and re-incident on the first reflective polarizing plate 11 from the rear side. The polarization component P (linearly polarized light parallel to the transmission axis 11a of the first reflective polarizing plate 11) P having a vibration plane parallel to the transmission axis 11a of the first reflective polarizing plate 11 of the circularly polarized light C is generated by this second component. The reflected light passes through one reflection polarizing plate 11 and is emitted to the front side of the multiple reflection means 10b.
[0148]
Further, a polarization component of the circularly polarized light C having a vibration plane parallel to the reflection axis 11b of the first reflective polarizing plate 11 (the first reflected polarized light) is incident on the first reflective polarizing plate 11 again from the rear side. The linearly polarized light (S) parallel to the reflection axis 11b of the plate 11 is reflected to the rear side by the first reflection polarizing plate 11 and is again converted into circularly polarized light C by the λ / 4 plate 14 to form the second reflected polarization. The light again enters the plate 12 and is transmitted through the second reflective polarizer 12 and reflected by the reflective film 15 or reflected forward by the second reflective polarizer 12 along the path as described above. .
[0149]
Then, the linearly polarized light P transmitted through the second reflective polarizer 12 and reflected by the reflective film 15, transmitted again through the second reflective polarizer 12 and emitted to the front side thereof, and the second reflected polarized light P The linearly polarized light S reflected to the front side by the plate 12 is again converted into circularly polarized light C by the λ / 4 plate 14 and re-enters the first reflective polarizing plate 11 from the rear side, and the first light of the light Pa The polarization component P (linearly polarized light parallel to the transmission axis 11a of the first reflection polarizing plate 11) having a vibration plane parallel to the transmission axis 11a of the reflection polarization plate 11 is transmitted through the first reflection polarization plate 11. Then, the light is emitted to the front side of the multiple reflection means 10b.
[0150]
That is, the multiple reflection means 10b transmits through the first reflective polarizing plate 11 by the λ / 4 plate 14 disposed between the first and second reflective polarizing plates 11 and 12, and transmits the second reflected light. The polarization states of the light incident on the reflective polarizer 12 and the light reflected on the second reflective polarizer 12 or the reflective film 15 and incident on the first reflective polarizer 12 are changed to first and second light polarizers, respectively. The first outgoing light emitted by one reflection by either the second reflecting polarizing plate 12 or the reflecting film 15, the first outgoing light, The secondary emission light that is spread and emitted by the multiple reflection between the second reflective polarizers 11 and 12 and between the reflective polarizers 11 and 12 and the reflective film 15 is transmitted to the first reflective polarizer. Emitted to the front side as linearly polarized light P parallel to the transmission axis 11a of 11 That.
[0151]
When no electric field is applied (V = 0), the linearly polarized light P emitted to the front side of the multiple reflection means 10b passes through the liquid crystal display element 1 and is emitted to the front side, thereby providing a bright display.
[0152]
Therefore, according to this display device, similarly to the above-described first display device, it is possible to perform reflection display with good quality without double images and with sufficient brightness.
[0153]
On the other hand, when an electric field (V> Vth) is applied between the electrodes of the liquid crystal cell 2 so that liquid crystal molecules rise and orient substantially perpendicular to the surfaces of the substrates 3 and 4, (V> Vth) is shown in FIG. As described above, the linearly polarized light S transmitted through the front absorption polarizer 7 and incident on the liquid crystal cell 2 is transmitted through the liquid crystal cell 2 in the polarized state without being affected by the birefringence of the liquid crystal layer 6 and thereafter. Most of the light enters the absorption polarizer 8 on the side, and is absorbed by the absorption polarizer 8 on the rear side, so that a dark display (black display) is obtained.
[0154]
Next, the transmission path of the incident light in the transmissive display of the display device of this embodiment will be described. FIG. 9 shows the transmission path of the incident light in the transmissive display, and FIG. FIG. 9B shows a transmission path when the electric field is applied (V> Vth).
[0155]
The emission of the illumination light from the surface light source 16 during the transmissive display and the change in the polarization state when the light emitted to the front side of the multiple reflection means 10b passes through the liquid crystal display element 1 are described in the first embodiment. The description is omitted because it is the same as the example.
[0156]
In the case of this transmissive display, as shown in FIGS. 9A and 9B, the illumination light emitted from the front surface of the light guide plate 17 of the surface light source 16 is applied to the λ / 4 plate in front of the light guide plate 17. 14 and is incident on the first reflective polarizer 11, and out of the light, a polarized component having a vibration plane parallel to the transmission axis 11 a of the first reflective polarizer 11 (first reflective polarizer) 11) is transmitted through the first reflection polarizing plate 11 and is emitted to the front side of the multiple reflection means 10b, and is parallel to the reflection axis 11b of the first reflection polarizing plate 11. The polarized light component S (linearly polarized light parallel to the reflection axis 11b of the first reflective polarizing plate 11) having a vibrating surface is reflected to the rear side by the first reflective polarizing plate 11.
[0157]
The linearly polarized light S reflected rearward by the first reflective polarizing plate 11 is converted into circularly polarized light C by the λ / 4 plate 14, passes through the light guide plate 17, and enters the second reflective polarizing plate 12. The polarization component Sc (linearly polarized light parallel to the reflection axis 12b of the second reflection polarizing plate 12) having a vibration plane parallel to the reflection axis 12b of the second reflection polarization plate 12 is generated by the circularly polarized light C. A polarized component reflected by the second reflective polarizer 12 and having a vibration plane parallel to the transmission axis 12a of the second reflective polarizer 12 (linearly polarized light parallel to the transmission axis 12a of the second reflective polarizer 12). ) Pc is transmitted through the second reflective polarizer 12 and is reflected by the reflective film 15.
[0158]
In other words, the multi-reflecting means 10b is also capable of transmitting linearly polarized light from one of the first and second reflective polarizers 11 and 12 to the other, and performing transmissive display using illumination light from the surface light source 16, and Changing the polarization state of the linearly polarized light traveling toward one side, and outputting the primary emitted light by one reflection by either the second reflective polarizer 12 or the reflective film 15; and the first and second reflective polarizers The secondary emission light that is spread and emitted by the multiple reflection between the reflective polarizers 11 and 12 and between the reflective polarizers 11 and 12 and the reflective film 15 is transmitted to the transmission axis 11 a of the first reflective polarizer 11. The light is emitted to the front side as parallel linearly polarized light P.
[0159]
When no electric field is applied between the electrodes of the liquid crystal cell 2 (V = 0), as shown in FIG. 9A, the linearly polarized light P emitted to the front side of the The light passes through the liquid crystal display element 1 and is emitted to the front side to provide a bright display.
[0160]
On the other hand, when an electric field (V> Vth) is applied between the electrodes of the liquid crystal cell 2 so that the liquid crystal molecules rise and orient substantially perpendicular to the surfaces of the substrates 3 and 4, (V> Vth) is shown in FIG. As described above, the linearly polarized light P emitted to the front side of the multiple reflection means 10b is absorbed by the absorption polarizer 7 on the front side of the liquid crystal display element 1, and a dark display (black display) is obtained.
[0161]
In this embodiment, as described above, the first and second reflective polarizers 11 and 12 of the multiple reflection means 10b are arranged with their respective transmission axes 11a and 12a substantially parallel to each other, and between them. Since a λ / 4 plate 14 for providing a phase difference of １／ wavelength between the ordinary light and the extraordinary light is disposed as a phase difference plate, the light emitted to the front side of the multiple reflection means 10b is , The primary emission light emitted by one reflection by any one of the second reflective polarizing plate 112 and the reflective film 15, between the first and second reflective polarizers 11 and 12, and between these first and second reflective polarizers 11, 12. The light is distributed approximately evenly to the secondary emission light that is spread and emitted by the multiple reflection between the reflective film 12 and the reflection film 15 to more effectively prevent the occurrence of a double image at the time of the reflection display, and to perform the reflection display and the The bright display in the transmissive display can be made brighter.
[0162]
The directions of the transmission axes 11a and 12a of the first and second reflective polarizers 11 and 12 of the multiple reflection means 10b and the phase difference of the phase difference plate disposed therebetween are not limited to those in the above-described embodiment. Any range may be used as long as a sufficient effect of preventing double images in display can be obtained and bright display in reflective display and transmissive display can be sufficiently brightened.
[0163]
Further, the retardation plate may be formed by laminating a lens sheet for giving directivity to transmitted light, and by using such a lens sheet laminated retardation plate, a front surface of light emitted to the front side of the display device can be formed. Brightness can be increased and a brighter display can be obtained.
[0164]
In the above embodiment, the multiple reflection means 10b is provided by disposing a retardation plate (λ / 4 plate in the embodiment) 14 between the first reflective polarizing plate 12 and the surface light source 16 on the liquid crystal display element 1 side. However, the retardation plate 14 may be disposed between the second reflective polarizer 12 on the reflective film 15 side and the surface light source 16.
[0165]
Further, in the above embodiment, the multiple reflection means 10b has a configuration in which the phase difference plate 14 and the surface light source 16 are disposed between the first and second reflection polarizing plates 11 and 12, but the surface light source 16 May be used as the phase difference plate.
[0166]
FIG. 10 is an exploded perspective view of a display device showing a fourth embodiment of the present invention. In this embodiment, first and second reflective polarizers 12 and 13 are provided behind a liquid crystal display element 1. Multiple reflection provided with a light guide plate 19 composed of a retardation plate disposed between the reflective polarizers 12 and 13 and a surface light source 16a composed of a light emitting element 18 provided at the end face of the light guide element 18 facing the end face. The means 10c is arranged.
[0167]
In this embodiment, the light guide plate 19 of the surface light source 16a is a λ / 4 plate that gives a phase difference of 波長 wavelength between the ordinary light and the extraordinary light of the transmitted light, And the second reflective polarizers 11 and 12 are disposed with their transmission axes 11a and 12a substantially parallel to each other, and the light guide plate 19 made of the λ / 4 plate is connected to the slow axis 19a by the first axis. And the transmission axes 11a and 12a of the second reflection polarizing plates 11 and 12 are obliquely displaced at an angle of substantially 45 °.
[0168]
According to the display device of this embodiment, the linearly polarized light traveling from one of the first and second reflective polarizers 11 and 12 of the multiple reflection means 10c to the other is utilized by using the light guide plate 19 of the surface light source 16a. And the primary emission light that changes the polarization state of linearly polarized light traveling from one side to the other and is emitted by one reflection by either the second reflective polarizing plate 12 or the reflective film 15; Of the first reflective polarizer 11 and the secondary output light that is spread and emitted by multiple reflection between the reflective polarizers 11 and 12 and between the reflective polarizers 11 and 12 and the reflective film 15. The linearly polarized light P parallel to the transmission axis 11a can be emitted to the front side of the multiple reflection means 10c.
[0169]
In the display devices of the above-described first to fourth embodiments, the multiple reflection means 10, 10a, 10b, and 10c are provided with the reflection film 15 disposed on the rear side of the second reflection polarizing plate 12. However, even if the reflective film 15 is omitted, a bright reflective display in which generation of a double image is prevented can be obtained.
[0170]
In the first to fourth embodiments, the first and second polarization splitting elements 11 and 12 of the multiple reflection means 10, 10a, 10b and 10c and the second reflection means 10a of the second embodiment. 3 is a reflective polarizing plate, and the polarized light separating element reflects one polarized light component of the two different polarized light components of the incident light and transmits the other polarized light component. If it is, it is not limited to a reflective polarizing plate.
[0171]
FIG. 11 is an exploded side view of another polarization beam splitter. This polarization beam splitter 20 reflects one of the two clockwise circularly polarized light components of the incident light, and reflects the other circularly polarized light component. With a circularly polarized light separating plate (for example, a cholesteric liquid crystal film) 21 that transmits a circularly polarized light component interposed therebetween, the incident linearly polarized light is converted into circularly polarized light, and the circularly polarized light is emitted from the circularly polarized light separating plate 21. It is obtained by laminating a pair of retardation plates 22 and 23 that emit linearly polarized light.
[0172]
Each of the pair of phase difference plates 22 and 23 is a λ / 4 plate that provides a phase difference of １／ wavelength between the ordinary light and the extraordinary light of the transmitted light. Are arranged such that their respective slow axes are substantially orthogonal to each other.
[0173]
The polarized light separating element 20 has one of two directions orthogonal to each other, which is substantially 45 ° shifted from the slow axis of the pair of λ / 4 plates 22 and 23, for example, the upper λ in the drawing. The transmission axis has a direction shifted 45 ° clockwise with respect to the slow axis of the 板 plate 22 from the upper side (the outer surface side of the upper λ / 4 plate 22), and the other direction perpendicular thereto (the lower λ). (In a direction deviated by 45 ° counterclockwise as viewed from above with respect to the slow axis of the） plate 23), and of the two linearly polarized light components of the incident light, And reflects one linearly polarized light component having a vibration plane parallel to the transmission axis, and transmits the other linearly polarized light component having a vibration plane parallel to the transmission axis.
[0174]
That is, the polarization splitting element 20 converts the linearly polarized light S parallel to the reflection axis out of the light incident from one surface side, for example, the upper side in the drawing, into the light traveling direction by the upper λ / 4 plate 22. The light is made incident on the circularly polarized light separating plate 21 as clockwise circularly polarized light R1 (downward in the figure), and the linearly polarized light P parallel to the transmission axis is transmitted by the upper λ / 4 plate 22 in the traveling direction of light. While entering the circularly polarized light separating plate 21 as circularly polarized light R2 counterclockwise toward the other side, of the light incident from the other surface side, that is, from the lower side in the figure, the linearly polarized light S parallel to the reflection axis, The lower λ / 4 plate 23 causes the circularly polarized light separating plate 21 to enter the circularly polarized light separating plate 21 as clockwise circularly polarized light R1 in the light traveling direction (upward in the figure), and converts the linearly polarized light P parallel to the transmission axis into: By the lower λ / 4 plate 23 To be incident on the circularly polarized separated plate 21 in the traveling direction of light as a circularly polarized light R2 on the left around.
[0175]
In addition, in FIG. 11, for convenience, the rotation direction (the direction of the arrow) of the circularly polarized light R1 and R2 is shown in the same direction as viewed from above in the figure. In the figure, the rotation direction viewed from the direction toward the traveling direction of the circularly polarized light R1 and R2 from the upper side to the lower side is the same as that in the drawing, and the direction toward the traveling direction of the circularly polarized light R1 and R2 from the lower side to the upper side in the figure. The rotation direction viewed from the direction is opposite to the direction shown in the figure.
[0176]
On the other hand, the circularly polarized light separating plate 21 reflects the clockwise circularly polarized light component toward the traveling direction of the light incident from either one of the other surface or the other surface, and converts the clockwise circularly polarized light component toward the traveling direction. It has a polarization separation characteristic that allows transmission.
[0177]
Therefore, of the light incident from the upper side in the drawing, the light that has been converted into clockwise circularly polarized light R1 in the traveling direction by the upper λ / 4 plate 22 and incident on the circularly polarized light separating plate 21 is The reflected light R1 is reflected by the plate 21, the reflected light R1 is converted into linearly polarized light S parallel to the reflection axis by the upper λ / 4 plate 22, and emitted upward, and leftward in the traveling direction by the upper λ / 4 plate 22. The light that has been made into the surrounding circularly polarized light R2 and incident on the circularly polarized light separating plate 21 passes through the circularly polarized light separating plate 21 and is incident on the lower λ / 4 plate 23. The light is converted into linearly polarized light P parallel to the transmission axis and emitted downward.
[0178]
In the figure, of the light incident from the lower side, the light that has been converted into clockwise circularly polarized light R1 in the traveling direction by the lower λ / 4 plate 23 and incident on the circularly polarized light separating plate 21 is the circle. The reflected light R <b> 1 is reflected by the polarization separating plate 21, is converted into linearly polarized light S parallel to the reflection axis by the lower λ / 4 plate 23, is emitted downward, and travels by the lower λ / 4 plate 23. The light that has been made into the left-handed circularly polarized light R <b> 2 in the direction and entered the circularly polarized light separating plate 21 passes through the circularly polarized light separating plate 21 and is incident on the upper λ / 4 plate 22. The light is converted into linearly polarized light P parallel to the transmission axis by the plate 22 and emitted upward.
[0179]
As described above, the polarization separation element 20 reflects one of the two linearly polarized light components of the incident light orthogonal to each other, which has a vibration plane parallel to the reflection axis, and reflects the one polarized light parallel to the transmission axis. It has a polarization separation characteristic of transmitting the other polarization component having a vibrating surface. Therefore, the reflection polarizers 11, 12, and 13 of the multiple reflection means 10, 10a, 10b, and 10c of each of the above-described embodiments are used as described above. Similar effects can be obtained by replacing the polarization separation element 20.
[0180]
Further, the display device of each of the above embodiments is of a normally white mode. However, in the present invention, the transmission axes 7a and 8a of the absorbing polarizers 7 and 8 before and after the liquid crystal display element 1 are made substantially parallel. Also, the present invention can be applied to a normally black mode display device in which the display in the absence of an electric field without applying an electric field to the liquid crystal layer 6 of the liquid crystal cell 2 is a dark display. In this case, the multiple reflection means 10, 10a, The first reflective polarizer 11 on the liquid crystal display element 1 side of 10b and 10c is arranged with its transmission axis 11a substantially parallel to the transmission axis 8a of the absorption polarizer 8 on the rear side of the liquid crystal display element 1. do it.
[0181]
Further, the display device of each of the above embodiments includes the TN type liquid crystal display element 1 as a display element. However, the display element is not limited to the TN type, and may be an STN type or a non-twist homogeneous alignment type. , A homeotropic alignment type, a lateral electric field type, a ferroelectric or antiferroelectric type, an ECB (birefringence effect) type, etc., and a liquid crystal display device which controls transmission and blocking of incident light. A display element other than the display element may be used.
[0182]
Further, the display device of each of the above embodiments is configured to perform both a reflective display using external light and a transmissive display using illumination light from a surface light source. The present invention can also be applied to a display device dedicated to reflective display in which the surface light sources 16 and 16a are omitted from the multiple reflection means 10, 10a, 10b and 10c.
[0183]
【The invention's effect】
According to the display device of the present invention, one of two different polarization components of the incident light is reflected and the other polarization component is transmitted behind the display element that controls transmission and blocking of the incident light. A first polarization separation element having characteristics, transmitting at least a part of light incident from the front side through the display element, and reflecting a part of light incident from the rear side; It is arranged on the rear side of the separation element, and has a property of reflecting one polarization component and transmitting the other polarization component among two different polarization components of the incident light, and is provided after the first polarization separation element. A second polarized light separating element that reflects at least a part of the transmitted light and reflected light to the side, and transmits at least a part of the light that has passed through the display element, entered from the front side, and transmitted through the first polarized light separating element. Partly between the first and second polarization splitting elements In addition to the multiple reflection, the multiple reflection means for transmitting a part of the reflected light for each reflection through the first polarization separation element and emitting the reflected light to the front side is arranged, so that there is no double image and good quality. In addition, it is possible to perform reflective display with sufficient brightness.
[0184]
In this display device, the first and second polarization separation elements of the multiple reflection means each have a transmission axis and a reflection axis in directions orthogonal to each other, and among two linear polarization components orthogonal to each other of incident light, A reflection polarizing element that reflects one polarization component having a vibration plane parallel to the reflection axis and transmits the other polarization component having a vibration plane parallel to the transmission axis, and these reflection polarization elements are: It is preferable that the respective transmission axes are arranged obliquely shifted from each other. In this way, the light incident on the multiple reflection means from the front side and transmitted through the first reflective polarizing plate is transmitted to the first reflection polarizing plate. And a part of the light is transmitted through the first reflection polarizing plate and emitted to the front side of the multiple reflection means, and the other light is reflected by the first and second reflection polarization plates. Multiple reflections between the plates Every reflection, it is possible to the part of the light reflected by the second reflective polarizer is transmitted through the first polarization separating element is emitted to the front side of the multiple reflection means.
[0185]
Further, in this display device, the multiple reflection means may include, between the first and second polarization separation elements, light traveling from one polarization separation element to the other polarization separation element, and the other polarization separation element. And a third polarization separation element for changing the direction of the vibration plane of the light traveling toward the one polarization separation element may be further disposed. In this way, the light incident on the multiple reflection means can be reflected by the third polarization separation element. Multiple reflection can be performed between the first, second, and third reflective polarizing elements.
[0186]
Further, the multi-reflecting means may include a light between the first and second polarization splitting elements, the light traveling from one polarization splitting element to the other polarization splitting element, and the one polarization splitting element from the other polarization splitting element. A phase difference plate for changing the polarization state of the light traveling toward the separation element may be further arranged. In this way, the light incident on the multiple reflection means can be reflected by the first and second reflection polarization elements. Can be multiple reflected between.
[0187]
Further, in this display device, the multiple reflection means is disposed on the back side of the second polarization separation element, reflects the transmitted light and the reflected light to the rear side of the second polarization separation element, and And a reflection film for causing multiple reflection with the second polarization splitting element, and the multiple reflection means having such a configuration allows the multiple reflection means to transmit through the display element and to perform the multiple reflection. All of the light incident on the reflection means is diffused and reflected by the multiple reflection described above, and the light is emitted to the front side of the display element, whereby a brighter reflective display can be obtained.
[0188]
Further, in this display device, the multiple reflection unit transmits the incident light from the front surface and the rear surface between the first and second polarization splitting elements, and transmits the incident light from the end surface to the front and rear surfaces. It is desirable to further arrange a surface light source composed of a light guide plate that emits light from at least one side and a light emitting element that is provided to face the end face of the light guide plate. In an environment where external light with high brightness is obtained, reflection display is performed using external light incident from the front side, which is the display observation side, and when external light with sufficient brightness cannot be obtained, the multiple reflection means is used. The illumination light is emitted from the surface light source, and the transmissive display using the illumination light can be performed.
[0189]
In that case, the light guide plate of the surface light source may be provided with light directed from one of the first and second reflective polarizing elements of the multiple reflecting means to the other reflective polarizing element, and one of the reflective lights from the other reflective polarizing element. It may be a retardation plate that changes the polarization state of the light traveling toward the polarization element. In this manner, the light incident on the multiple reflection unit is transmitted to the first and second light sources using the light guide plate of the surface light source. Multiple reflection can occur between the two reflective polarizing elements.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a display device according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a transmission path of incident light in the reflective display of the display device of the first embodiment.
FIG. 3 is a schematic diagram showing a transmission path of incident light in the transmission display of the display device of the first embodiment.
FIG. 4 is an exploded perspective view of a display device according to a second embodiment of the present invention.
FIG. 5 is a schematic diagram showing a transmission path of incident light in the reflective display of the display device according to the second embodiment.
FIG. 6 is a schematic diagram showing a transmission path of incident light in the transmission display of the display device of the second embodiment.
FIG. 7 is an exploded perspective view of a display device showing a third embodiment of the present invention.
FIG. 8 is a schematic diagram showing a transmission path of incident light in the reflective display of the display device according to the third embodiment.
FIG. 9 is a schematic diagram showing a transmission path of incident light in the transmission display of the display device of the third embodiment.
FIG. 10 is an exploded perspective view of a display device showing a fourth embodiment of the present invention.
FIG. 11 is an exploded side view of another polarized light separating element.
[Explanation of symbols]
1: Liquid crystal display element
2: Liquid crystal cell
6. Liquid crystal layer
7, 8 ... absorption polarizer
7a, 8a ... transmission axis
10, 10a, 10b, 10c ... multiple reflection means
11, 12, 13 ... reflective polarizing plate (polarization separating element)
11a, 12a, 13a ... transmission axis
11b, 12b, 13b ... reflection axis
14 ... Phase plate (λ / 4 plate)
14a: slow axis
15 ... Reflection film
16, 16a: Surface light source
17 ... Light guide plate
18 Light-emitting element
19: Light guide plate composed of a phase difference plate
19a ... Slow axis
20: Reflection polarization element (polarization separation element)
21 ... Circularly polarized light separating plate
22, 23 ... Phase plate (λ / 4 plate)

Claims

A display element for controlling transmission and blocking of incident light;
It is disposed on the rear side opposite to the display side of the display of the display element, and has a characteristic of reflecting one polarized component and transmitting the other polarized component among two different polarized components of incident light. A first polarization splitting element that transmits at least a part of the light incident from the front side through the display element and reflects a part of the light incident from the rear side; It is disposed on the rear side and has a property of reflecting one polarized light component and transmitting the other polarized light component of two different polarized light components of the incident light, and is provided on the rear side of the first polarization splitting element. A second polarization splitting element that reflects at least a part of the transmitted light and the reflected light, and transmits at least a part of the light that has passed through the display element, entered from the front side, and transmitted through the first polarization splitting element. Multiple reflection between the first and second polarization splitting elements Causes, and multiple reflection means emitted to the front part of the reflected light for each reflected by transmitting the first polarization separating element,
A display device comprising:

Each of the first and second polarization splitting elements of the multiple reflection means has a transmission axis and a reflection axis in directions orthogonal to each other, and of two linear polarization components of the incident light orthogonal to each other, which are parallel to the reflection axis. A reflective polarizing element that reflects one polarized light component having a vibrating surface and transmits the other polarized light component having a vibrating surface parallel to the transmission axis. The display device according to claim 1, wherein the display device is disposed obliquely.

The multiple reflection means is disposed between the first and second polarization splitting elements, the polarized light traveling from one polarization splitting element to the other polarization splitting element, and the one polarization splitting element from the other polarization splitting element. The display device according to claim 1, further comprising a third polarization separation element that changes a direction of a vibration plane of polarized light traveling toward.

The multiple reflection means is disposed between the first and second polarization splitting elements, the polarized light traveling from one polarization splitting element to the other polarization splitting element, and the one polarization splitting element from the other polarization splitting element. The display device according to claim 1, further comprising a retardation plate that changes a polarization state of polarized light traveling toward.

The multi-reflection means is disposed on the rear side of the second polarization separation element, reflects the transmitted light and the reflected light to the rear side of the second polarization separation element, and includes the first and second polarization separation elements. The display device according to any one of claims 1 to 4, further comprising a reflective film that causes multiple reflection between the display device and the display device.

The multi-reflection means is disposed between the first and second polarization splitting elements, and transmits light incident from the front surface and the rear surface, respectively, and emits light incident from the end surface from at least one of the front surface and the rear surface. The display device according to claim 1, further comprising a surface light source comprising: a light emitting element provided to face the end surface of the light guide plate.

The light guide plate of the surface light source changes the polarization state of polarized light traveling from one of the first and second polarization splitting elements of the multiple reflection means to the other, and polarized light traveling from the other reflective polarizing element to the one reflective polarizing element. 7. The display device according to claim 6, wherein the display device comprises a retardation plate.