JP4192553B2

JP4192553B2 - Surface light source

Info

Publication number: JP4192553B2
Application number: JP2002309631A
Authority: JP
Inventors: 鈴木　　剛; 英裕森田
Original assignee: Casio Computer Co Ltd
Current assignee: Casio Computer Co Ltd
Priority date: 2002-10-24
Filing date: 2002-10-24
Publication date: 2008-12-10
Anticipated expiration: 2022-10-24
Also published as: JP2004146191A

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source which can emit light of sufficient intensity by uniform intensity distribution from all regions of the emitting face of a light guide plate with a small number of illuminant elements. SOLUTION: This surface light source comprises a light guide plate 2 in which one end side forms an incident end face 3 of two plate faces forms an outgoing face 4, and the other plate face forms a reflecting face 5 which emits light from the outgoing face 4 by the internal reflection of the incident light entered from an incident end-face 3, and a light guide member 7 in which one side face forms a slender outgoing face 9, one end-face crossing the slender outgoing face 9 forms an incident end-face 8, and the other side face facing the slender outgoing face 9 forms a reflecting face 10 which, by internally reflecting the incident light entered from the incident end face 8, emits light from the slender outgoing face 9 and which is arranged by having the slender outgoing face 9 face the incident end face 3 of the light-guide plate 2. Furthermore, the surface light source comprises a phase difference plate 12 which is arranged between the incident end face 3 of the lightguide plate 2 and slender outgoing face 9 of the lightguide member, and rotates at an angle of substantially 90 degrees the polarization face of a rectilinearly polarized component of the light from slender outgoing face 8 of the lightguide member 7, and a solid illuminant element 14 which is arranged facing the incident end face 8 of the lightguide member 7. COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
この発明は、表示装置の照明用光源等に利用される面光源に関する。
【０００２】
【従来の技術】
液晶表示装置等の表示装置の照明用光源として、少なくとも一方の端面を光が入射される入射端面とし、前記入射端面から入射した光を導いて前後面の一方の出射面から出射する導光板と、この導光板の前記入射端面に対向させて発光素子とからなる面光源が用いられている。
【０００３】
この種の面光源には、前記発光素子として前記導光板の入射端面の全長にわたる長さの直管状冷陰極管を用い、この冷陰極管を前記導光板の入射端面と平行に配置したもの（特許文献１、２参照）、或いは、前記発光素子として消費電力が少なく、しかも寿命が半永久的であるＬＥＤ（発光ダイオード）等からなる固体発光素子を用い、この固体発光素子を１つまたは複数、前記導光板の入射端面に対向させて配置したもの（特許文献３参照）が知られている。
【０００４】
【特許文献１】
特開平１０−７８５８１号公報
【０００５】
【特許文献２】
特開平１０−３１９３９３号公報
【０００６】
【特許文献３】
特開平１０−１６３５２７号公報
【０００７】
【発明が解決しようとする課題】
しかし、１つまたは複数の固体発光素子を導光板の入射端面に対向させて配置した従来の面光源は、前記固体発光素子から出射して前記導光板にその入射端面から入射する光が、前記固体発光素子を中心として放射状に広がる光であるため、前記導光板の入射端面から入射した光が導光板の全域に均等に行き渡らず、そのために、前記導光板の出射面から均一な強度分布の光を出射させることができない。
【０００８】
この面光源において、前記固体発光素子の数を多くし、この発光素子を前記導光板の入射端面に沿わせて密な間隔で配置すれば、前記導光板にその入射端面の略全域から光を入射させ、前記導光板の出射面から均一な強度分布の光を出射することができるが、前記固体発光素子数を多くしたのでは、コスト高になるとともに、消費電力が増大してしまう。
【０００９】
この発明は、固体発光素子を備えた面光源として、少ない発光素子数で、導光板の出射面の全域から均一な強度分布でしかも充分な強度の光を出射することができるもの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】
この発明の面光源は、透明板の少なくとも一つの端面が光を入射させる入射端面を形成し、前記透明板の２つの板面の一方が前記透明板内を導かれた光を出射する出射面を形成し、他方の板面が前記入射端面から入射した光の、その入射光と反射光とを含む入射面に対して垂直な方向に振動する直線偏光成分を前記入射面と平行な面内で振動する直線偏光成分より強く内面反射して前記出射面から出射させる反射面を形成する導光板と、細長透明材の一つの側面が光を出射する細長出射面を形成し、前記細長透明材の前記細長出射面と交差する２つの端面の少なくとも一方が光を入射させる入射端面を形成し、前記細長出射面と対峙する他の側面が前記入射端面から入射した光の、その入射光と反射光とを含む入射面に対して垂直な方向に振動する直線偏光成分を前記入射面と平行な面内で振動する直線偏光成分より強く内面反射して前記細長出射面から出射させる反射面を形成してなり、前記細長出射面を前記導光板の入射端面に対向させて配置された導光部材と、前記導光板の入射端面と前記導光部材の細長出射面との間に配置され、前記導光部材の細長出射面から出射した光の直線偏光成分の偏光面を実質的に９０度回転させて前記導光板の入射端面に入射させる位相差板と、前記導光部材の入射端面に対向させて配置された固体発光素子と、を備えたことを特徴とする。
【００１１】
すなわち、この面光源は、前記固体発光素子からの出射光を前記導光部材にその入射端面から入射させ、その光を前記導光部材の細長出射面とは反対側（細長出射面と対峙する側面）の反射面により内面反射して前記導光部材の細長出射面の全域から前記導光板の入射端面に向けて出射させることにより、前記導光板にその入射端面の全域から均一な強度分布の光を入射させ、その光を前記導光板の反射面により内面反射して前記導光板の出射面の全域から出射させるようにしたものであり、この面光源によれば、少ない発光素子数で、前記導光板の出射面の全域から均一な強度分布でしかも充分な強度の光を出射することができる。
【００１２】
しかも、この面光源は、前記導光部材の細長出射面から出射した光を、前記導光板の入射端面と前記導光部材の細長出射面との間に配置された位相差板により、その光の直線偏光成分の偏光面を実質的に９０度回転させて前記導光板の入射端面に入射させるようにしているため、前記導光部材にその入射端面から入射してこの導光部材の他側面の反射面により内面反射され、前記導光部材の細長出射面から出射して前記導光板にその入射端面から入射した光のうちの高強度の直線偏光成分を、前記導光板の反射面により高い反射強度で内面反射させ、この導光板の出射面から充分な強度の光を出射させることができる。
【００１３】
このように、この発明の面光源は、少なくとも一つの端面が入射端面を形成し、２つの板面の一方が出射面を、他方の板面が前記入射端面から入射した光の、その入射光と反射光とを含む入射面に対して垂直な方向に振動する直線偏光成分を前記入射面と平行な面内で振動する直線偏光成分より強く内面反射して前記出射面から出射させる反射面を形成する導光板と、一つの側面が細長出射面を形成し、前記細長出射面と交差する２つの端面の少なくとも一方が入射端面を、前記細長出射面と対峙する他の側面が前記入射端面から入射した光の、その入射光と反射光とを含む入射面に対して垂直な方向に振動する直線偏光成分を前記入射面と平行な面内で振動する直線偏光成分より強く内面反射して前記細長出射面から出射させる反射面を形成してなり、前記細長出射面を前記導光板の入射端面に対向させて配置された導光部材と、前記導光板の入射端面と前記導光部材の細長出射面との間に配置され、前記導光部材の細長出射面から出射した光の直線偏光成分の偏光面を実質的に９０度回転させて前記導光板の入射端面に入射させる位相差板と、前記導光部材の入射端面に対向させて配置された固体発光素子とを備えることにより、少ない発光素子数で、導光板の出射面の全域から均一な強度分布でしかも充分な強度の光を出射することができるようにしたものである。
【００１４】
この発明の面光源において、前記導光部材の反射面は、前記導光部材の入射端面から入射した光を前記導光部材の細長出射面の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部からなっているのが好ましい。
【００１５】
さらに、前記導光板の反射面は、前記導光板の入射端面から入射した光を前記導光板の出射面の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部からなっているのが好ましい。
またさらに、前記位相差板は、透過光の常光と異常光との間に１／２波長の位相差を与えるλ／２位相差板からなっていることが好ましい。
【００１６】
【発明の実施の形態】
図１及び図２はこの発明の第１の実施例を示しており、図１（ａ）及び（ｂ）は面光源の平面図及び側面図、図２は前記面光源の導光部材と位相差板と導光板からの出射光の直線偏光成分を示す模式図である。
【００１７】
この実施例の面光源１は、図１に示したように、導光板２と、この導光板２の側方に配置された導光部材７と、前記導光板２と導光部材７との間に配置された位相差板１２と、前記導光部材７の側方に配置された１つの発光素子１４とを備えている。
【００１８】
前記導光板２は、アクリル系樹脂板等の透明板からなっており、その一つの端面が光が入射される入射端面３を形成し、前記透明板の２つの板面の一方が前記透明板に導かれた光を出射する平坦な出射面４を、他方の板面が前記入射端面３から入射した光を内面反射して前記出射面４から出射させる反射面５を形成している。
【００１９】
この導光板２の反射面５は、前記導光板２の他方の板面の全域に密に並べて互いに平行に形成され、前記導光板２の入射端面３から入射した光を前記出射面４の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部６からなっている。
【００２０】
前記複数のプリズム部６は、前記導光板２の入射端面３と平行で、且つ前記導光板２の全幅にわたる長さを有する断面形状が台形状の細長プリズム部であり、これらのプリズム部６の両側面のうち、前記入射端面３側の側面は、出射面４に対して略垂直な急角度面に形成され、他方の側面は、導光板２の反射面５の外面側に向かって入射端面３の方向に前記出射面４に対し３０〜６０度（好ましくは略４５度）の角度で傾いた傾斜面に形成されており、これらの側面（急角度面と傾斜面）の間の頂面部は、出射面４と平行な平坦面に形成されている。
【００２１】
なお、図では前記複数のプリズム部６を大きく誇張して示しているが、これらのプリズム部６は、１０〜１００μｍ程度の極く小さいピッチで形成されている。
【００２２】
すなわち、前記導光板２は、その入射端面３から入射した光を導いて出射面４から出射するものであり、この導光板２に前記入射端面３から入射した光は、図１（ｂ）に矢線で示したように、導光板２内を直進するか、あるいは前記出射面４で外気（空気）との界面での全反射により内面反射されて前記反射面５の複数の細長プリズム部６のいずれかの傾斜面に入射し、その傾斜面で外気との界面での全反射により出射面４の法線に対する角度が小さくなる方向に向けて内面反射され、前記出射面４から出射する。
【００２３】
一方、前記導光板２の側方に配置された導光部材７は、前記導光板２の入射端面３に対応する長さを有する角棒状の細長透明材（例えばアクリル系樹脂材）からなっており、その一つの側面が光を出射する細長出射面９を形成し、前記細長透明材の前記細長出射面９と交差する２つの端面の一方が光が入射される入射端面８を、前記細長出射面９と対峙する他の側面が前記入射端面８から入射した光を内面反射して前記細長出射面９から出射させる反射面１０を形成している。
【００２４】
この導光部材７の他側面の反射面１０は、前記他側面の全域に密に並べて互いに平行に形成され、前記導光部材７の入射端面８から入射した光を前記導光部材７の一側面の細長出射面９の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部１１からなっている。
【００２５】
前記複数のプリズム部１１は、前記導光部材７の入射端面８と平行で、且つ前記導光部材７の他側面の全幅にわたる長さを有する断面形状が三角形状の細長プリズム部であり、これらのプリズム部１１の両側面のうち、前記入射端面８側の側面は、前記細長出射面９に対して略垂直な急角度面に形成され、他方の側面は、前記細長出射面９の外面側に向かって入射端面８の方向に前記細長出射面９に対し３０〜６０度（好ましくは略４５度）の角度で傾いた傾斜面に形成されている。
【００２６】
なお、図では前記複数のプリズム部１１を大きく誇張して示しているが、これらのプリズム部１１は、１０〜１００μｍ程度の極く小さいピッチで形成されている。
【００２７】
すなわち、前記導光部材７は、その入射端面８から入射した光を導いて一側面の細長出射面９から出射するものであり、この導光部材７に前記入射端面８から入射した光は、図１（ａ）に矢線で示したように、導光部材７内を直進するか、あるいは前記細長出射面９で外気との界面での全反射により内面反射されて前記反射面１０の複数の細長プリズム部１１のいずれかの傾斜面に入射し、その傾斜面で外気との界面での全反射により前記細長出射面９の法線に対する角度が小さくなる方向に向けて内面反射され、前記細長出射面９の全域から均一な強度分布で出射する。
【００２８】
そして、この導光部材７は、その細長出射面９を前記導光板２の入射端面３に対向させるとともに、前記導光部材７の細長出射面９と前記導光板２の入射端面３とを互いに平行にして配置されている。
【００２９】
なお、この実施例では、前記導光部材７の反射面１０の後側に、前記反射面１０を透過して導光部材７の後側に漏れた光を前記導光部材７に戻すためのリフレクタ１３を配置している。
【００３０】
また、前記導光板２と導光部材７との間に配置された位相差板１２は、透過光の常光と異常光との間に１／２波長の位相差を与えるλ／２位相差板であり、前記導光部材７の細長出射面９から出射した光の直線偏光成分の偏光面を、実質的に９０度回転させて前記導光板２の入射端面３に入射させる。
【００３１】
このλ／２位相差板１２は、前記導光板２の入射端面３及び前記導光部材７の細長出射面９の全域に対応する細長形状を有しており、前記導光板２の入射端面３と前記導光部材７の細長出射面９との間に、一方の面を前記導光板２の入射端面３に透明な粘着剤により貼付けられ、他方の面を前記導光部材７の細長出射面９に透明な粘着剤により貼付けられて配置されている。
【００３２】
また、前記導光部材７の入射端面８に対向させて配置された発光素子１４は、ＬＥＤ（発光ダイオード）等からなる白色光を出射する固体発光素子であり、例えば、赤色ＬＥＤと緑色ＬＥＤと青色ＬＥＤとを透明樹脂によりモールドし、これらのＬＥＤが発する赤、緑、青の光を混色させた白色光を出射するものである。
【００３３】
この面光源１は、前記固体発光素子１４からの出射光を前記導光部材７にその入射端面８から入射させ、その光を前記導光部材７の細長出射面９とは反対側の反射面１０により内面反射して前記導光部材７の細長出射面９の全域から均一な強度分布で前記導光板２の入射端面３に向けて出射させることにより、前記導光板２にその入射端面３の全域から均一な強度分布の光を入射させ、その光を前記導光板２の反射面５により内面反射して前記導光板２の出射面４の全域から出射させるようにしたものであり、この面光源１によれば、少ない発光素子数で、前記導光板２の出射面４の全域から均一な強度分布の光を出射することができる。
【００３４】
しかも、この面光源１は、前記導光部材７の細長出射面９から出射した光を、前記導光板２の入射端面３と前記導光部材７の細長出射面９との間に配置されたλ／２位相差板１２により、その光の直線偏光成分の偏光面を実質的に９０度回転させて前記導光板２の入射端面３に入射させるようにしているため、前記導光部材７にその入射端面８から入射してこの導光部材７の他側面の反射面１０により内面反射され、前記導光部材７の細長出射面９から出射して前記導光板２にその入射端面３から入射した光のうちの高強度の直線偏光成分を、前記導光板２の反射面５により高い反射強度で内面反射させ、この導光板２の出射面４から充分な強度の光を出射させることができる。
【００３５】
すなわち、前記導光板２は、上述したように、その入射端面３から入射し、導光板２内を直進するか、あるいは出射面４により内面反射されて反射面５に入射した光を、この反射面５により内面反射して出射面４から出射させるが、前記反射面５による反射強度は、その光に含まれる直線偏光成分によって異なるため、前記反射面１０への入射光線とその反射光線とを含む入射面に垂直な方向に振動する直線偏光成分（以下、Ｓ波と言う）が、前記入射面内で振動する直線偏光成分（以下、Ｐ波と言う）よりも高い強度で内面反射される。
【００３６】
また、前記導光部材７は、上述したように、その入射端面８から入射し、導光部材７内を直進するか、あるいは一側面の細長出射面９により内面反射されて他側面の反射面１０に入射した光を、この反射面１０により内面反射して前記細長出射面９から出射させるが、前記反射面１０による反射強度もその光に含まれる直線偏光成分によって異なり、前記反射面１０への入射光線とその反射光線とを含む入射面に垂直な方向に振動する直線偏光成分のＳ波が、前記入射面内で振動する直線偏光成分のＰ波よりも高い強度で内面反射される。
【００３７】
そのため、前記導光部材７の細長出射面９から出射する光は、前記Ｐ波の偏光成分よりもＳ波の偏光成分の強度が高い。
【００３８】
そして、前記導光板２の反射面５と前記導光部材７の反射面１０とは互いに９０度で交差する位置に配置されているため、前記導光部材７の細長出射面９から出射した光をそのまま前記導光板２に入射させた場合は、その光のうち、前記導光部材７の反射面１０で反射した反射強度の低いＰ波が、前記導光板２の反射面５に対して反射強度が高いＳ波として入射し、前記導光部材７の反射面１０で反射した反射強度の高いＳ波が、前記導光板２の反射面５に対して反射強度が低いＰ波として入射するため、前記導光板２の出射面４から出射する光の強度が低い。
【００３９】
それに対し、前記面光源１では、前記導光板２の入射端面３と前記導光部材７の細長出射面９との間にλ／２位相差板１２を配置しているため、図２に示したように、前記導光部材７の細長出射面９から出射したＳ波Ｓ１及びＰ波Ｐ１が前記λ／２位相差板１２により偏光面を９０度回転されて前記導光板２にその入射端面３から入射する。
【００４０】
そのため、前記導光部材７の細長出射面９から出射した光のうち、強度の高いＳ波Ｓ１が、前記導光板２の反射面５に、この反射面５による反射強度が高いＳ波Ｓ２となって入射し、強度の低いＰ波は、前記導光板２の反射面５に、この反射面５による反射強度が低いＰ波となって入射する。
【００４１】
したがって、この面光源１によれば、前記導光部材７の細長出射面９から出射した光の強度の高い偏光成分の光を、前記導光板２２の反射面２５により、高い反射強度で内面反射させることができ、そのために、前記導光板２２の出射面４から充分な強度の光を出射させることができる。
【００４２】
このように、前記面光源１は、透明板の一端面が光が入射される入射端面３を形成し、前記透明板の２つの板面の一方が前記透明板内を導かれた光を出射する出射面４を、他方の板面が前記入射端面３から入射した光を内面反射して前記出射面４から出射させる反射面５を形成する導光板と、細長透明材の一側面が光を出射する細長出射面９を形成し、前記細長透明材の前記細長出射面９と交差する２つの端面の一方が光が入射される入射端面８を、前記細長出射面９と対峙する他側面が前記入射端面８から入射した光を内面反射して前記細長出射面９から出射させる反射面１０を形成してなり、前記細長出射面９を前記導光板２の入射端面３に対向させて配置された導光部材７と、前記導光板２の入射端面３と前記導光部材７の細長出射面９との間に配置され、前記導光部材７の細長出射面９から出射した光の直線偏光成分の偏光面を実質的に９０度回転させて前記導光板２の入射端面３に入射させる位相差板１２と、前記導光部材７の入射端面８に対向させて配置された固体発光素子１４とを備えたものであるため、少ない発光素子数で、導光板２の出射面４の全域から均一な強度分布でしかも充分な強度の光を出射することができる。
【００４３】
この実施例の面光源１は、発光素子として、ＬＥＤ等からなる１つの固体発光素子１４を備えたものであるため、コストを低減するとともに、消費電極も少なくすることができる。
【００４４】
また、前記固体発光素子１４は、その駆動電圧を制御することにより発光強度を変化させることができるため、前記導光板２の出射面４から出射する光の強度を任意に調整することができる。
【００４５】
しかも、前記面光源１は、前記導光部材７の他側面の反射面１０を、前記導光部材７の入射端面８から入射した光を前記導光部材７の細長出射面９の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部１１により形成しているため、この導光部材７の細長出射面９から出射した光を、前記導光板２にその入射端面３に垂直な方向の付近から入射させ、その光を前記導光板２の全域に均等に行き渡らせて、前記導光板２の出射面４の全域から、より強度分布が均一な光を出射することができる。
【００４６】
さらに、前記面光源１は、前記導光板２の後面の反射面５を、前記導光板２の入射端面３から入射した光を前記導光板２の出射面４の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部６により形成しているため、前記導光板２の出射面４から、正面輝度（導光板２の出射面４の法線付近の方向に出射する光の輝度）の高い光を出射することができる。
【００４７】
前記面光源１は、例えば液晶表示装置の照明用光源に利用される。図３は前記面光源１を備えた液晶表示装置の一例を示す分解斜視図であり、この液晶表示装置は、透過型液晶表示素子２０の後側に、前記液晶表示素子２０をその後側から照明するためのバックライトとして、前記面光源１を配置したものである。
【００４８】
前記透過型液晶表示素子２０は、その内部構造は図示しないが、表示の観察面側である前側の透明基板２２と、この前側基板２２に対向する後側の透明基板２３とが枠状のシール材２４を介して接合され、これらの基板２２，２３間に液晶層が設けられるとともに、それぞれの基板２２，２３の前記液晶層に対向する内面に、互いに対向する領域により複数の画素を形成する透明電極が設けられた液晶セル２１と、この液晶セル２１をはさんでその前後に配置された一対の偏光板２５，２６とからなっている。
【００４９】
なお、この液晶表示素子２０は、ノーマリーホワイトモードのＴＮ（ツイステッドネマティック）型液晶表示素子であり、前記液晶セル２１の液晶層の液晶分子は、前後の基板２２，２３間において実質的に９０度のツイスト角でツイスト配向している。
【００５０】
また、前記一対の偏光板２５，２６はそれぞれ、互いに直交する方向に透過軸２５ａ，２６ａと吸収軸（図示せず）をもった吸収偏光板であり、これらの偏光板２５，２６は、それぞれの透過軸２５ａ，２６ａを実質的に直交させて配置されている。
【００５１】
そして、前記面光源１は、その導光板２の出射面４を前記液晶表示素子２０の後面（後側偏光板２６の外面）に対向させるとともに、前記導光板２の出射面４から出射する光のうち、強度の高いＳ波Ｓ２の偏光面に平行な方向、つまり導光板２の反射面５の複数の細長プリズム部６の長さ方向を、前記液晶表示素子２０の後側偏光板２６の透過軸２６ａと実質的に平行にして配置されている。
【００５２】
この液晶表示装置は、前記面光源１からの光を前記液晶表示素子２０にその後面から入射させて表示するものであり、前記面光源１の導光板２の出射面４から出射した光は、前記液晶表示素子２０の後側偏光板２６によりその吸収軸に平行な振動面をもった偏光成分を吸収され、前記後側偏光板２６の透過軸２６ａに平行な直線偏光とされて液晶セル２１に入射する。
【００５３】
なお、前記面光源１の導光板２の出射面４から出射する光は、前記導光板２の反射面５の複数の細長プリズム部６の長さ方向に平行な偏光面をもったＳ波Ｓ２の偏光強度が高く、それと直交するＰ波Ｐ２の偏光強度が弱い光であるが、この液晶表示装置では、前記面光源１を、前記導光板２の出射面４から出射する光のうち、強度の高いＳ波Ｓ２の偏光面に平行な方向を前記液晶表示素子２０の後側偏光板２６の透過軸２６ａと実質的に平行にして配置しているため、前記面光源１の導光板２の出射面４から出射した光の強度の高いＳ波Ｓ２を、前記液晶表示素子２０の後側偏光板２６を透過させて液晶セル２１に入射させることができる。
【００５４】
そして、前記液晶セル２１に入射した光は、その両基板２２，２３の電極間に印加される電界に応じた液晶層の複屈折作用を受けて液晶セル２１の前側に出射するため、前記液晶セル２１液晶層に印加される電界を制御し、前記液晶層を透過した光を前側偏光板２５の吸収軸に平行な偏光面をもった直線偏光とすることにより、その直線偏光を前記前側偏光板２５で吸収させる暗表示が行なわれ、前記液晶層を透過した光を前記前側偏光板２５の透過軸２５ａに平行な偏光面をもった直線偏光とすることにより、その直線偏光を前記前側偏光板２５を透過させて前側に出射して明表示が行なわれる。
【００５５】
この液晶表示装置は、上述したように導光板２の出射面４の全域から均一な強度分布でしかも充分な強度の光を出射する面光源１をバックライトとし、この面光源１を、その導光板２の出射面４から出射する光のうち、強度の高いＳ波Ｓ２の振動面に平行な方向を前記液晶表示素子２０の後側偏光板２６の透過軸２６ａと実質的に平行にして配置したものであるため、前記液晶表示素子２０に、明るく、しかも輝度むらの無い高品質の画像を表示することができる。
【００５６】
また、前記面光源１は、上述したように、固体発光素子１４の駆動電圧を制御することにより導光板２の出射面４から出射する光の強度を任意に調整することができるため、前記液晶表示装置の表示輝度を、外部環境の明るさに応じた最適輝度にすることができる。
【００５７】
なお、上記液晶表示装置は、前記面光源１からの光を利用する透過表示を行なうものであるが、例えば、前記面光源１の導光板２の後側に反射板を配置するか、あるいは前記液晶表示素子２０の後側偏光板２６を、互いに直交する方向に透過軸と反射軸をもち、入射光の互いに直交する２つの直線偏光成分のうち、前記透過軸に平行な偏光成分を透過させ、前記反射軸に平行な偏光成分を反射する反射偏光板に置き換えることにより、前記面光源１からの光を利用する透過表示と、表示の観察側である前側から入射する外光（外部環境の光）利用する反射表示との両方の表示を行なわせることができる。
【００５８】
また、上記液晶表示装置は、前記面光源１をバックライトとしたものであるが、前記面光源１は、反射表示を行なう反射型液晶表示素子を備えた液晶表示装置のフロントライトとして用いることもでき、その場合は、前記面光源１を、その導光板２の出射面４を前記反射型液晶表示素子の前面（前側偏光板の外面）に対向させるとともに、前記導光板２の出射面４から出射する光のうち、強度の高いＳ波Ｓ２の偏光面に平行な方向（導光板２の反射面５の複数の細長プリズム部６の長さ方向）を、前記反射型液晶表示素子の前側偏光板の透過軸と実質的に平行にして配置すればよい。
【００５９】
なお、上記実施例の面光源１は、導光部材７の他側面の反射面１０を、前記導光部材７の入射端面８から入射した光を前記導光部材７の一側面の細長出射面９の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部１１により形成したものであるが、前記導光部材７の他側面の反射面は、例えば、導光部材７の入射端面８側から他端側に向かって前記細長出射面９に近くなる方向に傾いた連続した傾斜面としてもよい。
【００６０】
また、上記実施例の面光源１は、前記導光板２の反射面５を、前記導光板２の入射端面３から入射した光を前記導光板２の出射面４の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部６により形成したものであるが、前記導光板２の反射面５は、例えば、導光板２の入射端面３側から他端側に向かって出射面４に近くなる方向に傾いた連続した傾斜面としてもよい。
【００６１】
さらに、上記実施例の面光源１は、前記導光部材７の入射端面８に対向させて１つの固体発光素子１４を配置したものであるが、前記導光部材７の入射端面８の面積が前記固体発光素子１４よりも大きい場合は、前記導光部材７の入射端面８に対向させて複数の固体発光素子１４を配置してもよい。
【００６２】
また、上記実施例の面光源１は、導光板２の一端面を入射端面３に形成し、その入射端面３に対向させて一端面が入射端面８に形成された導光部材７を配置するとともに、この導光部材７の入射端面８に対向させて固体発光素子１４を配置したものであるが、前記導光部材７の両端面をそれぞれ入射端面８に形成し、その両方の入射端面８にそれぞれ対向させて固体発光素子１４を配置してもよく、また、前記導光板２の両端面をそれぞれ入射端面３に形成し、その両方の入射端面３にそれぞれ対向させてλ／２位相差板１２と導光部材７とを配置するとともに、これらの導光部材７の入射端面８にそれぞれ対向させて固体発光素子１４を配置してもよい。
【００６３】
図４はこの発明の第２の実施例を示しており、（ａ）は面光源の平面図、（ｂ）は前記面光源の側面図である。
【００６４】
この実施例の面光源１ａは、導光部材７の両端面をそれぞれ入射端面８に形成し、その両方の入射端面８にそれぞれ対向させて固体発光素子１４を配置したものであり、この実施例では、前記導光部材７の他側面の反射面１０を、前記導光部材７の入射端面８と平行で、且つ前記導光部材７の他側面の全幅にわたる長さを有するとともに、両側面がそれぞれ導光部材７の細長出射面９に対して３０〜６０度（好ましくは略４５度）の角度で傾いた傾斜面に形成された断面形状が三角形状の複数の細長プリズム部１１ａにより形成し、前記導光部材７の両方の入射端面８から入射した光をそれぞれ、前記複数のプリズム部１１ａにより前記細長出射面９の法線に対する角度が小さくなる方向に向けて内面反射するようにしている。
【００６５】
この面光源１ａによれば、前記導光部材７の両端面をそれぞれ入射端面８に形成し、その両方の入射端面８にそれぞれ対向させて固体発光素子１４を配置しているため、その両方の固体発光素子１４から同じ強度の光を出射させることにより、前記導光部材７の細長出射面９の全域からより均一な強度分布の光を導光板２の入射端面３に向けて出射させ、前記導光板２にその入射端面３の全域から均一な強度分布の光を入射させることができる。
【００６６】
また、この面光源１ａによれば、前記導光部材７の両方の入射端面８にそれぞれ対向させて配置された２つの固体発光素子１４の一方を点灯させ、他方を消灯させたり、両方の固体発光素子１４の発光強度をそれぞれ制御することにより、前記導光板２にその入射端面３から入射させる光の強度を広範囲に変化させ、前記導光板２の出射面４から出射する光の強度をより広い強度範囲で調整することができる。
【００６７】
図５はこの発明の第３の実施例を示しており、（ａ）は面光源の平面図、（ｂ）は前記面光源の側面図である。
【００６８】
この実施例の面光源１ｂは、導光板２の両端面をそれぞれ入射端面３に形成し、その両方の入射端面３にそれぞれ対向させてλ／２位相差板１２と導光部材７を配置するとともに、これらの導光部材７の入射端面８にそれぞれ対向させて固体発光素子１４を配置したものであり、この実施例では、前記導光板２の反射面５を、前記導光板２の入射端面３と平行で、且つ前記導光板２の全幅にわたる長さを有するとともに、両側面がそれぞれ導光板２の出射面４に対して３０〜６０度（好ましくは略４５度）の角度で傾いた傾斜面に形成された断面形状が三角形状の複数の細長プリズム部６ａにより形成し、前記導光板２の両方の入射端面３から入射した光をそれぞれ、前記複数のプリズム部６ａにより出射面４の法線に対する角度が小さくなる方向に向けて内面反射するようにしている。
【００６９】
なお、この面光源１ｂは、前記導光板２の両方の入射端面３にそれぞれ対向させて配置した導光部材７の両端面をそれぞれ入射端面８に形成し、これらの導光部材７の両方の入射端面８にそれぞれ対向させて固体発光素子１４を配置したものであり、前記導光部材７の他側面の反射面１０は、図４に示した第２の実施例と同じ複数の細長プリズム部１１ａにより形成されている。
【００７０】
この面光源１ｂによれば、前記導光部材７の両端面をそれぞれ入射端面８に形成し、その両方の入射端面８にそれぞれ対向させてλ／２位相差板１２と導光部材７を配置するとともに、これらの導光部材７の入射端面８にそれぞれ対向させて固体発光素子１４を配置しているため、両方の導光部材７の入射端面８に対向する固体発光素子１４からそれぞれ同じ強度の光を出射させ、前記両方の導光部材７の細長出射面９からの出射光を前記導光板２にその両方の入射端面３から入射させることにより、前記導光板２の出射面４の全域からさらに均一な強度分布の光を入射させることができる。
【００７１】
また、この面光源１ａによれば、前記両方の導光部材７の入射端面８にそれぞれ対向させて配置された各固体発光素子１４の点灯及び消灯や、それぞれの固体発光素子１４の発光強度を制御することにより、前記導光板２にその両方の入射端面３から入射させる光の強度を広範囲に変化させ、前記導光板２の出射面４から出射する光の強度をさらに広い強度範囲で調整することができる。
【００７２】
なお、上述した各実施例の面光源１，１ａ，１ｂは、液晶表示装置に限らず、光の透過を制御して画像を表示する表示素子を備えた表示装置の照明光源や、表示装置以外の照明光源にも広く使用することができる。
【００７３】
【発明の効果】
この発明の面光源は、透明板の少なくとも一つの端面が光を入射させる入射端面を形成し、前記透明板の２つの板面の一方が前記透明板内を導かれた光を出射する出射面を形成し、他方の板面が前記入射端面から入射した光の、その入射光と反射光とを含む入射面に対して垂直な方向に振動する直線偏光成分を前記入射面と平行な面内で振動する直線偏光成分より強く内面反射して前記出射面から出射させる反射面を形成する導光板と、細長透明材の一つの側面が光を出射する細長出射面を形成し、前記細長透明材の前記細長出射面と交差する２つの端面の少なくとも一方が光を入射させる入射端面を形成し、前記細長出射面と対峙する他の側面が前記入射端面から入射した光の、その入射光と反射光とを含む入射面に対して垂直な方向に振動する直線偏光成分を前記入射面と平行な面内で振動する直線偏光成分より強く内面反射して前記細長出射面から出射させる反射面を形成してなり、前記細長出射面を前記導光板の入射端面に対向させて配置された導光部材と、前記導光板の入射端面と前記導光部材の細長出射面との間に配置され、前記導光部材の細長出射面から出射した光の直線偏光成分の偏光面を実質的に９０度回転させて前記導光板の入射端面に入射させる位相差板と、前記導光部材の入射端面に対向させて配置された固体発光素子とを備えたものであるため、少ない発光素子数で、導光板の出射面の全域から均一な強度分布でしかも充分な強度の光を出射することができる。
【００７４】
この発明の面光源において、前記導光部材の反射面は、前記導光部材の入射端面から入射した光を前記導光部材の細長出射面の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部からなっているのが好ましく、このようにすることにより、前記導光部材の細長出射面から出射した光を、前記導光板にその入射端面に垂直な方向の付近から入射させ、その光を前記導光板の全域に均等に行き渡らせて、前記導光板の出射面の全域から、より強度分布が均一な光を出射することができる。
【００７５】
さらに、前記導光板の反射面は、前記導光板の入射端面から入射した光を前記導光板の出射面の法線に対する角度が小さくなる方向に向けて内面反射する複数のプリズム部からなっているのが好ましく、このようにすることにより、前記導光板の出射面から、正面輝度の高い光を出射することができる。
また、さらに、位相差板は、透過光の常光と異常光との間に１／２波長の位相差を与えるλ／２位相差板からなることが好ましく、このようにすることにより、前記導光部材から出射した光の直線偏光成分の偏光面を確実に９０度回転させて前記導光板の入射端面に入射させることができる。
【図面の簡単な説明】
【図１】この発明の第１の実施例を示す面光源の平面図及び側面図。
【図２】前記面光源の導光部材と位相差板と導光板からの出射光の直線偏光成分を示す模式図。
【図３】前記面光源を備えた液晶表示装置の一例を示す分解斜視図。
【図４】この発明の第２の実施例を示す面光源の平面図及び側面図。
【図５】この発明の第３の実施例を示す面光源の平面図及び側面図。
【符号の説明】
１，１ａ，１ｂ…面光源
２…導光板
３…入射端面
４…出射面
５…反射面
６，６ａ…プリズム部
７…導光部材
８…入射端面
９…細長出射面
１０…反射面
１１，１１ａ…プリズム部
１２…位相差板
１４…固体発光素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface light source used as a light source for illumination of a display device.
[0002]
[Prior art]
As a light source for illumination of a display device such as a liquid crystal display device, at least one end surface is an incident end surface on which light is incident, and a light guide plate that guides light incident from the incident end surface and emits the light from one output surface of the front and rear surfaces A surface light source composed of a light emitting element is used to face the incident end face of the light guide plate.
[0003]
In this type of surface light source, a straight tubular cold cathode tube having a length over the entire length of the incident end face of the light guide plate is used as the light emitting element, and the cold cathode tube is arranged in parallel with the incident end face of the light guide plate ( Patent Documents 1 and 2), or a solid-state light-emitting element such as an LED (light-emitting diode) having low power consumption and a semi-permanent lifetime as the light-emitting element, and one or a plurality of the solid-state light-emitting elements, There is known one (see Patent Document 3) which is disposed so as to face the incident end face of the light guide plate.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-78581
[0005]
[Patent Document 2]
JP 10-319393 A
[0006]
[Patent Document 3]
Japanese Patent Laid-Open No. 10-163527
[0007]
[Problems to be solved by the invention]
However, in the conventional surface light source in which one or a plurality of solid light emitting elements are arranged to face the incident end face of the light guide plate, the light emitted from the solid light emitting element and incident on the light guide plate from the incident end face is Since the light spreads radially around the solid-state light emitting element, the light incident from the incident end face of the light guide plate does not spread evenly over the entire area of the light guide plate, and therefore has a uniform intensity distribution from the exit surface of the light guide plate. The light cannot be emitted.
[0008]
In this surface light source, if the number of the solid-state light emitting elements is increased and the light emitting elements are arranged at a close interval along the incident end face of the light guide plate, light is emitted from the substantially entire area of the incident end face to the light guide plate. Incident light can be emitted from the light exit surface of the light guide plate. However, increasing the number of the solid light emitting elements increases the cost and power consumption.
[0009]
The present invention provides a surface light source having a solid light-emitting element that can emit light having a uniform intensity distribution and a sufficient intensity from the entire emission surface of the light guide plate with a small number of light-emitting elements. It is aimed at.
[0010]
[Means for Solving the Problems]
 In the surface light source of the present invention, at least one end surface of the transparent plate is light.Make incidentAn exit end surface is formed, and one of the two plate surfaces of the transparent plate emits light guided through the transparent plate.FormingThe light incident on the other plate surface from the incident end surfaceThe linearly polarized light component oscillating in a direction perpendicular to the incident surface including the incident light and the reflected light is stronger than the linearly polarized light component oscillating in a plane parallel to the incident surface.A light guide plate that reflects the inner surface to form a reflecting surface that emits from the emitting surface, and one side surface of the elongated transparent material forms an elongated emitting surface that emits light, and intersects the elongated emitting surface of the elongated transparent material. At least one of the two end faces is lightMake incidentThe incident end faceFormingThe other side surface facing the elongated outgoing surface is incident from the incident end surface.The linearly polarized light component oscillating in a direction perpendicular to the incident surface including the incident light and the reflected light is stronger than the linearly polarized light component oscillating in a plane parallel to the incident surface.A light-reflecting surface formed by reflecting the inner surface to be emitted from the elongated light exit surface, the light guide member disposed with the elongated light exit surface facing the incident end surface of the light guide plate, the incident end surface of the light guide plate, and the It is disposed between the elongated light exit surface of the light guide member and is incident on the incident end surface of the light guide plate by substantially rotating the polarization plane of the linearly polarized light component of the light emitted from the elongated light exit surface of the light guide member by 90 degrees. And a solid-state light emitting element arranged to face the incident end face of the light guide member.
[0011]
That is, the surface light source causes the light emitted from the solid-state light emitting element to enter the light guide member from the incident end surface thereof, and the light is opposite to the elongated light emitting surface of the light guide member (opposite the elongated light emitting surface). The inner surface of the light guide member is reflected from the entire surface of the elongated light exit surface toward the incident end surface of the light guide plate, and the light guide plate has a uniform intensity distribution from the entire area of the incident end surface. Light is incident, the light is internally reflected by the reflecting surface of the light guide plate and emitted from the entire area of the light exiting surface of the light guide plate, and according to this surface light source, with a small number of light emitting elements, A light having a uniform intensity distribution and a sufficient intensity can be emitted from the entire emission surface of the light guide plate.
[0012]
In addition, the surface light source emits light emitted from the elongated emission surface of the light guide member by a phase difference plate disposed between the incident end surface of the light guide plate and the elongated emission surface of the light guide member. The plane of polarization of the linearly polarized light component is rotated substantially 90 degrees so as to be incident on the incident end surface of the light guide plate, so that it enters the light guide member from the incident end surface and the other side surface of the light guide member. Of the light that is reflected from the inner surface of the light guide member and is emitted from the elongated light emitting surface of the light guide member and incident on the light guide plate from its incident end surface. It is possible to reflect the inner surface with the reflection intensity, and to emit light having a sufficient intensity from the emission surface of the light guide plate.
[0013]
 As described above, in the surface light source of the present invention, at least one end surface forms an incident end surface, one of the two plate surfaces is an exit surface, and the other plate surface is incident from the incident end surface.The linearly polarized light component oscillating in a direction perpendicular to the incident surface including the incident light and the reflected light is stronger than the linearly polarized light component oscillating in a plane parallel to the incident surface.A light guide plate that reflects the inner surface to form a reflecting surface that is emitted from the emitting surface, and one side surface forms an elongated emitting surface, and at least one of two end surfaces intersecting the elongated emitting surface is an incident end surface. Light incident from the incident end surface on the other side facing the exit surfaceThe linearly polarized light component oscillating in a direction perpendicular to the incident surface including the incident light and the reflected light is stronger than the linearly polarized light component oscillating in a plane parallel to the incident surface.A light-reflecting surface formed by reflecting the inner surface to be emitted from the elongated light exit surface, the light guide member disposed with the elongated light exit surface facing the incident end surface of the light guide plate, the incident end surface of the light guide plate, and the It is disposed between the elongated light exit surface of the light guide member and is incident on the incident end surface of the light guide plate by substantially rotating the polarization plane of the linearly polarized light component of the light emitted from the elongated light exit surface of the light guide member by 90 degrees. And a solid-state light emitting element disposed so as to face the incident end face of the light guide member, and with a small number of light emitting elements, a uniform intensity distribution from the entire area of the light exiting surface of the light guide plate is sufficient. It is designed to emit light with a sufficient intensity.
[0014]
In the surface light source of the present invention, the reflection surface of the light guide member reflects the light incident from the incident end surface of the light guide member toward the direction in which the angle with respect to the normal of the elongated light emission surface of the light guide member decreases. It is preferable that a plurality of prism portions are formed.
[0015]
 Furthermore, the reflection surface of the light guide plate is composed of a plurality of prism portions that internally reflect light incident from the incident end surface of the light guide plate in a direction in which the angle with respect to the normal of the emission surface of the light guide plate decreases. Is preferred.
 Furthermore, it is preferable that the retardation plate is a λ / 2 retardation plate that gives a half-wave phase difference between ordinary light and extraordinary light of transmitted light.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1 and 2 show a first embodiment of the present invention. FIGS. 1A and 1B are a plan view and a side view of a surface light source, and FIG. It is a schematic diagram which shows the linearly polarized light component of the emitted light from a phase difference plate and a light-guide plate.
[0017]
As shown in FIG. 1, the surface light source 1 of this embodiment includes a light guide plate 2, a light guide member 7 disposed on the side of the light guide plate 2, and the light guide plate 2 and the light guide member 7. The phase difference plate 12 disposed therebetween and one light emitting element 14 disposed on the side of the light guide member 7 are provided.
[0018]
The light guide plate 2 is made of a transparent plate such as an acrylic resin plate, one end surface of which forms an incident end surface 3 on which light is incident, and one of the two plate surfaces of the transparent plate is the transparent plate. The flat emission surface 4 that emits the light guided to 1 is formed on the other surface, and the reflection surface 5 is formed such that the other plate surface reflects the light incident from the incident end surface 3 to the inner surface and emits the light from the emission surface 4.
[0019]
The reflection surface 5 of the light guide plate 2 is formed in close proximity to and parallel to the entire area of the other plate surface of the light guide plate 2, and light incident from the incident end surface 3 of the light guide plate 2 is used as a method of the emission surface 4. It consists of a plurality of prism portions 6 that are internally reflected toward the direction in which the angle with respect to the line decreases.
[0020]
The plurality of prism portions 6 are elongated prism portions having a trapezoidal cross-sectional shape parallel to the incident end surface 3 of the light guide plate 2 and having a length extending over the entire width of the light guide plate 2. Of the two side surfaces, the side surface on the incident end surface 3 side is formed as an acute angle surface substantially perpendicular to the exit surface 4, and the other side surface is the incident end surface toward the outer surface side of the reflecting surface 5 of the light guide plate 2. 3 is formed on an inclined surface inclined at an angle of 30 to 60 degrees (preferably approximately 45 degrees) with respect to the emission surface 4 in the direction 3, and the top surface portion between these side surfaces (steep angle surface and inclined surface) Is formed on a flat surface parallel to the emission surface 4.
[0021]
In the drawing, the plurality of prism portions 6 are greatly exaggerated, but these prism portions 6 are formed at a very small pitch of about 10 to 100 μm.
[0022]
That is, the light guide plate 2 guides the light incident from the incident end face 3 and emits the light from the output face 4, and the light incident on the light guide plate 2 from the incident end face 3 is shown in FIG. As indicated by the arrow lines, the plurality of elongated prism portions 6 of the reflecting surface 5 travel straight in the light guide plate 2 or are internally reflected by total reflection at the interface with the outside air (air) on the exit surface 4. The light is incident on one of the inclined surfaces, and is internally reflected toward the direction in which the angle with respect to the normal of the exit surface 4 becomes smaller due to total reflection at the interface with the outside air, and exits from the exit surface 4.
[0023]
On the other hand, the light guide member 7 disposed on the side of the light guide plate 2 is formed of a rectangular bar-like elongated transparent material (for example, an acrylic resin material) having a length corresponding to the incident end surface 3 of the light guide plate 2. One of the side surfaces forms an elongated exit surface 9 that emits light, and one of the two end surfaces intersecting the elongated exit surface 9 of the elongated transparent material defines the incident end surface 8 on which light is incident. The other side surface facing the emission surface 9 forms a reflection surface 10 that internally reflects the light incident from the incident end surface 8 and emits the light from the elongated emission surface 9.
[0024]
The reflecting surface 10 on the other side surface of the light guide member 7 is formed closely in parallel with each other over the entire other side surface so that light incident from the incident end surface 8 of the light guide member 7 is transmitted to one of the light guide members 7. It consists of a plurality of prism portions 11 that are internally reflected toward the direction in which the angle with respect to the normal of the elongated outgoing surface 9 on the side surface becomes smaller.
[0025]
The plurality of prism portions 11 are elongated prism portions having a triangular cross-section that is parallel to the incident end face 8 of the light guide member 7 and has a length extending over the entire width of the other side surface of the light guide member 7. Of the both side surfaces of the prism portion 11, the side surface on the incident end surface 8 side is formed as an acute angle surface substantially perpendicular to the elongated exit surface 9, and the other side surface is the outer surface side of the elongated exit surface 9. In the direction of the incident end face 8, the inclined outgoing face 9 is inclined at an angle of 30 to 60 degrees (preferably approximately 45 degrees).
[0026]
In the drawing, the plurality of prism portions 11 are greatly exaggerated, but these prism portions 11 are formed at a very small pitch of about 10 to 100 μm.
[0027]
That is, the light guide member 7 guides the light incident from the incident end face 8 and emits the light from the elongated outgoing face 9 on one side, and the light incident on the light guide member 7 from the incident end face 8 is As indicated by the arrow in FIG. 1 (a), the light guide member 7 travels straight inside or is internally reflected by total reflection at the interface with the outside air at the elongated light exit surface 9, and a plurality of the reflective surfaces 10 are reflected. Is incident on one of the inclined surfaces of the elongated prism portion 11 and is internally reflected toward the direction in which the angle with respect to the normal of the elongated emission surface 9 is reduced by total reflection at the interface with the outside air at the inclined surface, The light is emitted from the entire elongated outgoing surface 9 with a uniform intensity distribution.
[0028]
The light guide member 7 has the elongated light exit surface 9 opposed to the incident end surface 3 of the light guide plate 2, and the elongated light exit surface 9 of the light guide member 7 and the incident end surface 3 of the light guide plate 2 are mutually connected. They are arranged in parallel.
[0029]
In this embodiment, light that has passed through the reflection surface 10 and leaked to the rear side of the light guide member 7 is returned to the light guide member 7 on the rear side of the reflection surface 10 of the light guide member 7. A reflector 13 is arranged.
[0030]
The phase difference plate 12 disposed between the light guide plate 2 and the light guide member 7 is a λ / 2 phase difference plate that gives a half-wave phase difference between ordinary light and abnormal light of transmitted light. The polarization plane of the linearly polarized light component of the light emitted from the elongated light exit surface 9 of the light guide member 7 is substantially rotated by 90 degrees and is incident on the incident end face 3 of the light guide plate 2.
[0031]
The λ / 2 phase difference plate 12 has an elongated shape corresponding to the entire area of the incident end surface 3 of the light guide plate 2 and the elongated output surface 9 of the light guide member 7, and the incident end surface 3 of the light guide plate 2. One surface is affixed to the incident end surface 3 of the light guide plate 2 with a transparent adhesive, and the other surface is the elongated output surface of the light guide member 7. 9 is affixed with a transparent adhesive.
[0032]
The light-emitting element 14 disposed facing the incident end face 8 of the light guide member 7 is a solid-state light-emitting element that emits white light, such as an LED (light-emitting diode), and includes, for example, a red LED and a green LED. A blue LED is molded with a transparent resin, and white light in which red, green, and blue light emitted from these LEDs are mixed is emitted.
[0033]
The surface light source 1 causes the light emitted from the solid-state light emitting element 14 to enter the light guide member 7 from its incident end face 8, and the light is reflected on the opposite side of the elongated light emission surface 9 of the light guide member 7. 10 is reflected from the entire surface of the elongated light exit surface 9 of the light guide member 7 toward the incident end surface 3 of the light guide plate 2 with a uniform intensity distribution. Light having a uniform intensity distribution is incident from the entire area, and the light is internally reflected by the reflecting surface 5 of the light guide plate 2 and is emitted from the entire area of the output surface 4 of the light guide plate 2. According to the light source 1, light having a uniform intensity distribution can be emitted from the entire area of the emission surface 4 of the light guide plate 2 with a small number of light emitting elements.
[0034]
In addition, the surface light source 1 is configured such that the light emitted from the elongated emission surface 9 of the light guide member 7 is disposed between the incident end surface 3 of the light guide plate 2 and the elongated emission surface 9 of the light guide member 7. The λ / 2 phase difference plate 12 rotates the polarization plane of the linearly polarized light component of the light by substantially 90 degrees so as to be incident on the incident end face 3 of the light guide plate 2. The light is incident from the incident end surface 8 and is internally reflected by the reflecting surface 10 on the other side of the light guide member 7, and is emitted from the elongated light emitting surface 9 of the light guide member 7 and incident on the light guide plate 2 from the incident end surface 3. The high-intensity linearly polarized light component of the obtained light can be internally reflected with high reflection intensity by the reflection surface 5 of the light guide plate 2, and light with sufficient intensity can be emitted from the emission surface 4 of the light guide plate 2. .
[0035]
That is, as described above, the light guide plate 2 is incident on the incident end surface 3 and travels straight in the light guide plate 2 or is reflected by the light exit surface 4 and incident on the reflection surface 5. Although the light is reflected from the inner surface by the surface 5 and is emitted from the emitting surface 4, the reflection intensity by the reflecting surface 5 varies depending on the linearly polarized light component contained in the light. The linearly polarized light component (hereinafter referred to as “S wave”) that vibrates in the direction perpendicular to the incident surface is internally reflected with higher intensity than the linearly polarized light component (hereinafter referred to as “P wave”) that vibrates in the incident surface. .
[0036]
Further, as described above, the light guide member 7 is incident from the incident end face 8 and travels straight in the light guide member 7 or is internally reflected by one elongated outgoing surface 9 and reflected on the other side. The light incident on 10 is internally reflected by the reflecting surface 10 and is emitted from the elongated emitting surface 9, and the reflection intensity by the reflecting surface 10 varies depending on the linearly polarized light component contained in the light, and is reflected on the reflecting surface 10. The S-wave of the linearly polarized component that oscillates in the direction perpendicular to the incident surface including the incident light and the reflected light thereof is internally reflected with higher intensity than the P-wave of the linearly polarized component that oscillates in the incident surface.
[0037]
Therefore, the light emitted from the elongated light exit surface 9 of the light guide member 7 has a higher intensity of the polarization component of the S wave than the polarization component of the P wave.
[0038]
And since the reflective surface 5 of the light guide plate 2 and the reflective surface 10 of the light guide member 7 are arranged at positions that intersect each other at 90 degrees, the light emitted from the elongated light exit surface 9 of the light guide member 7 Is incident on the light guide plate 2 as it is, the P wave having a low reflection intensity reflected by the reflection surface 10 of the light guide member 7 out of the light is reflected on the reflection surface 5 of the light guide plate 2. A high-intensity S-wave incident as a high-intensity S-wave and reflected by the reflective surface 10 of the light guide member 7 is incident on the reflective surface 5 of the light-guide plate 2 as a low-reflection P-wave. The intensity of light emitted from the emission surface 4 of the light guide plate 2 is low.
[0039]
On the other hand, in the surface light source 1, a λ / 2 phase difference plate 12 is disposed between the incident end surface 3 of the light guide plate 2 and the elongated light exit surface 9 of the light guide member 7. As described above, the S wave S1 and the P wave P1 emitted from the elongated emission surface 9 of the light guide member 7 are rotated by 90 degrees on the polarization plane by the λ / 2 phase difference plate 12, and are incident on the light guide plate 2 at its incident end face. 3 is incident.
[0040]
For this reason, among the light emitted from the elongated emission surface 9 of the light guide member 7, the high-intensity S wave S 1 is reflected on the reflection surface 5 of the light guide plate 2 with the S wave S 2 having high reflection intensity by the reflection surface 5. The P wave having a low intensity is incident on the reflection surface 5 of the light guide plate 2 as a P wave having a low reflection intensity by the reflection surface 5.
[0041]
Therefore, according to the surface light source 1, light having a high polarization intensity of light emitted from the elongated light exit surface 9 of the light guide member 7 is reflected by the reflective surface 25 of the light guide plate 22 with high reflection intensity. Therefore, light with sufficient intensity can be emitted from the emission surface 4 of the light guide plate 22.
[0042]
Thus, in the surface light source 1, one end surface of the transparent plate forms an incident end surface 3 on which light is incident, and one of the two plate surfaces of the transparent plate emits light guided in the transparent plate. A light guide plate that forms a reflective surface 5 for reflecting the light incident from the incident end surface 3 on the other plate surface and emitting the light from the light emitting surface 4, and one side surface of the elongated transparent material transmits light. An elongated outgoing surface 9 is formed, and one of two end faces intersecting with the elongated outgoing surface 9 of the elongated transparent material has an incident end surface 8 on which light is incident, and the other side surface facing the elongated outgoing surface 9 A reflection surface 10 for reflecting the light incident from the incident end face 8 on the inner surface to be emitted from the elongated outgoing face 9 is formed, and the elongated outgoing face 9 is arranged to face the incident end face 3 of the light guide plate 2. The light guide member 7, the incident end face 3 of the light guide plate 2, and the elongated outgoing surface of the light guide member 7 The phase difference between the first and second light-guiding members 7 is incident on the incident end surface 3 of the light guide plate 2 by rotating the polarization plane of the linearly polarized light component of the light emitted from the elongated light exit surface 9 of the light guide member 7 substantially 90 degrees. Since the plate 12 and the solid light emitting element 14 disposed to face the incident end face 8 of the light guide member 7 are provided, the number of light emitting elements is small and uniform from the entire area of the light exit surface 4 of the light guide plate 2. Light with sufficient intensity distribution and sufficient intensity can be emitted.
[0043]
Since the surface light source 1 of this embodiment includes one solid-state light-emitting element 14 made of an LED or the like as a light-emitting element, the cost can be reduced and the number of consumed electrodes can be reduced.
[0044]
Further, since the solid-state light emitting element 14 can change the light emission intensity by controlling the driving voltage, the intensity of light emitted from the light emission surface 4 of the light guide plate 2 can be arbitrarily adjusted.
[0045]
In addition, the surface light source 1 is configured such that the light incident from the incident end surface 8 of the light guide member 7 is reflected on the reflective surface 10 on the other side of the light guide member 7 with respect to the normal line of the elongated light exit surface 9 of the light guide member 7. Since it is formed by a plurality of prism portions 11 that are internally reflected toward the direction in which the angle decreases, the light emitted from the elongated emission surface 9 of the light guide member 7 is perpendicular to the incident end surface 3 of the light guide plate 2. It is possible to emit light with a more uniform intensity distribution from the entire area of the emission surface 4 of the light guide plate 2 by allowing the light to enter from the vicinity of the appropriate direction and evenly spread the light over the entire area of the light guide plate 2.
[0046]
Further, the surface light source 1 is configured such that the angle of the light incident from the incident end surface 3 of the light guide plate 2 with respect to the normal surface of the output surface 4 of the light guide plate 2 is reduced. Is formed by a plurality of prism portions 6 that are internally reflected toward the light source, so that the front luminance (the luminance of light emitted in the direction near the normal line of the emission surface 4 of the light guide plate 2) from the emission surface 4 of the light guide plate 2. ) High light can be emitted.
[0047]
The surface light source 1 is used, for example, as an illumination light source for a liquid crystal display device. FIG. 3 is an exploded perspective view showing an example of a liquid crystal display device provided with the surface light source 1. This liquid crystal display device illuminates the liquid crystal display element 20 from the rear side and the liquid crystal display element 20 from the rear side. The surface light source 1 is disposed as a backlight for this purpose.
[0048]
Although the internal structure of the transmissive liquid crystal display element 20 is not shown, a transparent substrate 22 on the front side, which is the display observation surface side, and a transparent substrate 23 on the rear side facing the front substrate 22 are frame-shaped seals. A liquid crystal layer is provided between the substrates 22 and 23, and a plurality of pixels are formed on the inner surfaces of the substrates 22 and 23 facing the liquid crystal layer by regions facing each other. It comprises a liquid crystal cell 21 provided with a transparent electrode, and a pair of polarizing plates 25 and 26 disposed before and after the liquid crystal cell 21.
[0049]
The liquid crystal display element 20 is a normally white mode TN (twisted nematic) liquid crystal display element, and the liquid crystal molecules of the liquid crystal layer of the liquid crystal cell 21 are substantially 90 between the front and rear substrates 22 and 23. Twist orientation with a twist angle of degrees.
[0050]
The pair of polarizing plates 25 and 26 are absorption polarizing plates having transmission axes 25a and 26a and absorption axes (not shown) in directions orthogonal to each other, and these polarizing plates 25 and 26 are respectively The transmission axes 25a and 26a are arranged substantially orthogonal to each other.
[0051]
The surface light source 1 makes the emission surface 4 of the light guide plate 2 face the rear surface of the liquid crystal display element 20 (the outer surface of the rear polarizing plate 26), and the light emitted from the emission surface 4 of the light guide plate 2. Among them, the direction parallel to the polarization plane of the high-intensity S wave S2, that is, the length direction of the plurality of elongated prism portions 6 on the reflection surface 5 of the light guide plate 2, is indicated by the rear polarizing plate 26 of the liquid crystal display element 20. It is disposed substantially parallel to the transmission axis 26a.
[0052]
This liquid crystal display device displays light by making the light from the surface light source 1 incident on the liquid crystal display element 20 from its rear surface, and the light emitted from the emission surface 4 of the light guide plate 2 of the surface light source 1 is: A polarized light component having a vibration plane parallel to the absorption axis is absorbed by the rear polarizing plate 26 of the liquid crystal display element 20, and is converted into linearly polarized light parallel to the transmission axis 26 a of the rear polarizing plate 26. Is incident on.
[0053]
The light emitted from the emission surface 4 of the light guide plate 2 of the surface light source 1 has an S wave S2 having a polarization plane parallel to the length direction of the plurality of elongated prism portions 6 of the reflection surface 5 of the light guide plate 2. In this liquid crystal display device, the intensity of the light emitted from the light exit surface 4 of the light guide plate 2 is reduced by the liquid crystal display device. Since the direction parallel to the polarization plane of the high S wave S2 is arranged substantially parallel to the transmission axis 26a of the rear polarizing plate 26 of the liquid crystal display element 20, the light guide plate 2 of the surface light source 1 is arranged. The S wave S 2 having a high intensity of light emitted from the emission surface 4 can be transmitted through the rear polarizing plate 26 of the liquid crystal display element 20 and incident on the liquid crystal cell 21.
[0054]
The light incident on the liquid crystal cell 21 is emitted to the front side of the liquid crystal cell 21 due to the birefringence action of the liquid crystal layer according to the electric field applied between the electrodes of the substrates 22 and 23. The electric field applied to the liquid crystal layer of the cell 21 is controlled, and the light transmitted through the liquid crystal layer is converted into linearly polarized light having a polarization plane parallel to the absorption axis of the front polarizing plate 25, thereby converting the linearly polarized light into the front polarized light. Dark display to be absorbed by the plate 25 is performed, and the light transmitted through the liquid crystal layer is converted into linearly polarized light having a polarization plane parallel to the transmission axis 25a of the front polarizing plate 25, thereby converting the linearly polarized light into the front polarized light. The light is transmitted through the plate 25 and emitted to the front side to perform bright display.
[0055]
In this liquid crystal display device, as described above, the surface light source 1 that emits light having a uniform intensity distribution and sufficient intensity from the entire area of the emission surface 4 of the light guide plate 2 is used as a backlight. Of the light emitted from the emission surface 4 of the optical plate 2, the direction parallel to the vibration surface of the high-intensity S wave S2 is arranged substantially parallel to the transmission axis 26a of the rear polarizing plate 26 of the liquid crystal display element 20. Therefore, a high-quality image that is bright and free from uneven luminance can be displayed on the liquid crystal display element 20.
[0056]
In addition, as described above, the surface light source 1 can arbitrarily adjust the intensity of light emitted from the emission surface 4 of the light guide plate 2 by controlling the driving voltage of the solid state light emitting device 14, so that the liquid crystal The display brightness of the display device can be set to the optimum brightness according to the brightness of the external environment.
[0057]
The liquid crystal display device performs transmissive display using light from the surface light source 1. For example, a reflector is disposed behind the light guide plate 2 of the surface light source 1, or The rear polarizing plate 26 of the liquid crystal display element 20 has a transmission axis and a reflection axis in directions orthogonal to each other, and transmits a polarization component parallel to the transmission axis among two linearly polarized light components orthogonal to each other of incident light. By replacing the polarized light component parallel to the reflection axis with a reflective polarizing plate that reflects light, transmissive display using light from the surface light source 1 and external light incident from the front side that is the viewing side of the display (external environment) It is possible to display both the light and the reflective display used.
[0058]
The liquid crystal display device uses the surface light source 1 as a backlight, but the surface light source 1 may be used as a front light of a liquid crystal display device including a reflective liquid crystal display element that performs reflective display. In this case, the surface light source 1 is arranged so that the light emission surface 4 of the light guide plate 2 faces the front surface of the reflective liquid crystal display element (the outer surface of the front polarizing plate) and from the light emission surface 4 of the light guide plate 2. Of the emitted light, the direction parallel to the polarization plane of the high-intensity S wave S2 (the length direction of the plurality of elongated prism portions 6 of the reflection surface 5 of the light guide plate 2) is defined as the front polarization of the reflective liquid crystal display element. What is necessary is just to arrange | position substantially parallel to the transmission axis of a board.
[0059]
In addition, the surface light source 1 of the said Example is the elongate output surface of one side of the said light guide member 7 in the reflective surface 10 of the other side of the light guide member 7, and the light which injected from the incident end surface 8 of the said light guide member 7 9 is formed by a plurality of prism portions 11 that are internally reflected in a direction in which the angle with respect to the normal line 9 is reduced. The reflective surface on the other side of the light guide member 7 is, for example, incident on the light guide member 7. It is good also as a continuous inclined surface inclined in the direction close | similar to the said elongate output surface 9 toward the other end side from the end surface 8 side.
[0060]
In the surface light source 1 of the above embodiment, the angle of the light incident on the reflecting surface 5 of the light guide plate 2 from the incident end surface 3 of the light guide plate 2 with respect to the normal line of the light exit surface 4 of the light guide plate 2 is reduced. The reflecting surface 5 of the light guide plate 2 is, for example, the exit surface 4 from the incident end surface 3 side to the other end side of the light guide plate 2. It is good also as a continuous inclined surface inclined in the direction which becomes near.
[0061]
Further, in the surface light source 1 of the above embodiment, one solid light emitting element 14 is disposed so as to face the incident end face 8 of the light guide member 7, but the area of the incident end face 8 of the light guide member 7 is small. When it is larger than the solid light emitting element 14, a plurality of solid light emitting elements 14 may be arranged facing the incident end face 8 of the light guide member 7.
[0062]
Moreover, the surface light source 1 of the said Example forms the light guide member 7 in which the one end surface of the light-guide plate 2 was formed in the incident end surface 3, and the one end surface was formed in the incident end surface 8 facing the incident end surface 3. In addition, the solid light emitting element 14 is disposed so as to face the incident end face 8 of the light guide member 7. Both end faces of the light guide member 7 are formed on the incident end face 8, and both incident end faces 8 thereof are formed. The solid light-emitting elements 14 may be disposed so as to face each other, and both end faces of the light guide plate 2 are formed on the incident end faces 3, respectively, and both incident end faces 3 are respectively opposed to each other by a λ / 2 phase difference. While arrange | positioning the board 12 and the light guide member 7, you may arrange | position the solid light emitting element 14 so as to oppose the entrance end surface 8 of these light guide members 7, respectively.
[0063]
4A and 4B show a second embodiment of the present invention, in which FIG. 4A is a plan view of a surface light source, and FIG. 4B is a side view of the surface light source.
[0064]
In the surface light source 1a of this embodiment, both end faces of the light guide member 7 are formed on the incident end faces 8, and the solid light emitting elements 14 are arranged so as to face both the incident end faces 8, respectively. Then, the reflective surface 10 on the other side of the light guide member 7 is parallel to the incident end surface 8 of the light guide member 7 and has a length over the entire width of the other side of the light guide member 7, and both side surfaces are Each of the light guide members 7 is formed by a plurality of elongated prism portions 11a having a triangular cross-sectional shape formed on an inclined surface inclined at an angle of 30 to 60 degrees (preferably approximately 45 degrees) with respect to the elongated emission surface 9 of the light guide member 7. The light incident from both incident end faces 8 of the light guide member 7 is internally reflected by the plurality of prism portions 11a toward the direction in which the angle with respect to the normal line of the elongated outgoing surface 9 becomes smaller. .
[0065]
According to this surface light source 1a, both end faces of the light guide member 7 are formed on the incident end faces 8, and the solid light emitting elements 14 are arranged so as to face both the incident end faces 8, respectively. By emitting light having the same intensity from the solid light emitting element 14, light having a more uniform intensity distribution is emitted toward the incident end face 3 of the light guide plate 2 from the entire elongated output surface 9 of the light guide member 7. Light having a uniform intensity distribution can be incident on the light guide plate 2 from the entire area of the incident end face 3 thereof.
[0066]
Further, according to the surface light source 1a, one of the two solid-state light emitting elements 14 disposed to face both incident end faces 8 of the light guide member 7 is turned on and the other is turned off, or both solids are turned on. By controlling the light emission intensity of each light emitting element 14, the intensity of light incident on the light guide plate 2 from its incident end face 3 is changed over a wide range, and the intensity of light emitted from the light exit surface 4 of the light guide plate 2 is further increased. It can be adjusted over a wide intensity range.
[0067]
FIG. 5 shows a third embodiment of the present invention, in which (a) is a plan view of a surface light source, and (b) is a side view of the surface light source.
[0068]
In the surface light source 1 b of this embodiment, both end surfaces of the light guide plate 2 are formed on the incident end surface 3, and the λ / 2 phase difference plate 12 and the light guide member 7 are disposed so as to face both the incident end surfaces 3. In addition, a solid light emitting element 14 is disposed so as to face the incident end face 8 of each of the light guide members 7. In this embodiment, the reflecting surface 5 of the light guide plate 2 is used as the incident end face of the light guide plate 2. 3 and has a length extending over the entire width of the light guide plate 2, and both side surfaces are inclined at an angle of 30 to 60 degrees (preferably about 45 degrees) with respect to the exit surface 4 of the light guide plate 2. The cross-sectional shape formed on the surface is formed by a plurality of elongated prism portions 6a having a triangular shape, and light incident from both incident end surfaces 3 of the light guide plate 2 is applied to the exit surface 4 by the plurality of prism portions 6a. The angle to the line is small It is to be internally reflected toward the direction.
[0069]
In addition, this surface light source 1b forms both end surfaces of the light guide member 7 disposed so as to face both the incident end surfaces 3 of the light guide plate 2 on the incident end surface 8, respectively. The solid light emitting elements 14 are arranged so as to face the incident end faces 8, respectively, and the reflecting surface 10 on the other side of the light guide member 7 has the same plurality of elongated prism portions as in the second embodiment shown in FIG. 11a.
[0070]
According to the surface light source 1b, both end faces of the light guide member 7 are formed on the incident end face 8, and the λ / 2 phase difference plate 12 and the light guide member 7 are arranged so as to face both the incident end faces 8, respectively. In addition, since the solid light emitting elements 14 are arranged so as to face the incident end faces 8 of these light guide members 7, respectively, the solid light emitting elements 14 opposed to the incident end faces 8 of both light guide members 7 have the same strength. Of the light guide plate 2 and the light emitted from the elongated light exit surface 9 of both the light guide members 7 is incident on the light guide plate 2 from both the incident end surfaces 3 thereof, so that the entire area of the light exit surface 4 of the light guide plate 2 is obtained. Thus, light having a more uniform intensity distribution can be made incident.
[0071]
Moreover, according to this surface light source 1a, the lighting and extinguishing of each solid light emitting element 14 arranged facing the incident end faces 8 of both the light guide members 7 and the light emission intensity of each solid light emitting element 14 are set. By controlling, the intensity of light incident on the light guide plate 2 from both incident end faces 3 is changed in a wide range, and the intensity of light emitted from the exit surface 4 of the light guide plate 2 is adjusted in a wider intensity range. be able to.
[0072]
The surface light sources 1, 1a, 1b of the above-described embodiments are not limited to liquid crystal display devices, but are other than illumination light sources for display devices including display elements that control light transmission and display images, and display devices. It can also be widely used as an illumination light source.
[0073]
【The invention's effect】
 In the surface light source of the present invention, at least one end surface of the transparent plate is light.Make incidentAn exit end surface is formed, and one of the two plate surfaces of the transparent plate emits light guided through the transparent plate.FormingThe light incident on the other plate surface from the incident end surfaceThe linearly polarized light component oscillating in a direction perpendicular to the incident surface including the incident light and the reflected light is stronger than the linearly polarized light component oscillating in a plane parallel to the incident surface.A light guide plate that reflects the inner surface to form a reflecting surface that emits from the emitting surface, and one side surface of the elongated transparent material forms an elongated emitting surface that emits light, and intersects the elongated emitting surface of the elongated transparent material. At least one of the two end faces is lightMake incidentThe incident end faceFormingThe other side surface facing the elongated outgoing surface is incident from the incident end surface.The linearly polarized light component oscillating in a direction perpendicular to the incident surface including the incident light and the reflected light is stronger than the linearly polarized light component oscillating in a plane parallel to the incident surface.A light-reflecting surface formed by reflecting the inner surface to be emitted from the elongated light exit surface, the light guide member disposed with the elongated light exit surface facing the incident end surface of the light guide plate, the incident end surface of the light guide plate, and the It is disposed between the elongated light exit surface of the light guide member and is incident on the incident end surface of the light guide plate by substantially rotating the polarization plane of the linearly polarized light component of the light emitted from the elongated light exit surface of the light guide member by 90 degrees. And a solid-state light-emitting element disposed to face the incident end face of the light guide member, so that a uniform intensity distribution can be obtained from the entire exit surface of the light guide plate with a small number of light-emitting elements. In addition, a sufficiently strong light can be emitted.
[0074]
In the surface light source of the present invention, the reflection surface of the light guide member reflects the light incident from the incident end surface of the light guide member toward the direction in which the angle with respect to the normal of the elongated light emission surface of the light guide member decreases. It is preferable that the light is emitted from the elongated light emitting surface of the light guide member to enter the light guide plate from the vicinity of the direction perpendicular to the incident end surface. The light can be evenly distributed over the entire area of the light guide plate, and light having a more uniform intensity distribution can be emitted from the entire area of the light exit surface of the light guide plate.
[0075]
 Furthermore, the reflection surface of the light guide plate is composed of a plurality of prism portions that internally reflect light incident from the incident end surface of the light guide plate in a direction in which the angle with respect to the normal of the emission surface of the light guide plate decreases. It is preferable that light with high front luminance can be emitted from the emission surface of the light guide plate.
 Further, it is preferable that the retardation plate is a λ / 2 retardation plate that gives a half-wave phase difference between ordinary light and extraordinary light of the transmitted light. The polarization plane of the linearly polarized light component of the light emitted from the optical member can be reliably rotated by 90 degrees and incident on the incident end face of the light guide plate.
[Brief description of the drawings]
FIG. 1 is a plan view and a side view of a surface light source showing a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a linearly polarized light component of light emitted from a light guide member, a phase difference plate, and a light guide plate of the surface light source.
FIG. 3 is an exploded perspective view illustrating an example of a liquid crystal display device including the surface light source.
FIG. 4 is a plan view and a side view of a surface light source showing a second embodiment of the present invention.
FIGS. 5A and 5B are a plan view and a side view of a surface light source showing a third embodiment of the invention. FIGS.
[Explanation of symbols]
1, 1a, 1b ... surface light source
2 Light guide plate
3 ... Incident end face
4 ... Outgoing surface
5 ... Reflection surface
6, 6a ... Prism part
7. Light guide member
8 ... Incident end face
9: Elongate exit surface
10 ... Reflection surface
11, 11a ... Prism section
12 ... retardation plate
14 ... Solid state light emitting device

Claims

At least one end surface of the transparent plate forms an incident end surface on which light is incident , one of the two plate surfaces of the transparent plate forms an output surface for emitting the light guided in the transparent plate, and the other plate From the linearly polarized light component that oscillates in the direction perpendicular to the incident surface including the incident light and the reflected light, the linearly polarized light component that oscillates in the plane parallel to the incident surface. A light guide plate that strongly reflects the inner surface to form a reflecting surface that is emitted from the emitting surface;
One side surface of the elongated transparent material forms an elongated emission surface that emits light, and at least one of two end surfaces intersecting the elongated emission surface of the elongated transparent material forms an incident end surface that allows light to enter, In the plane parallel to the incident surface, a linearly polarized light component that oscillates in a direction perpendicular to the incident surface including the incident light and the reflected light of the light incident on the other end surface facing the exit surface from the incident end surface. A light guide member arranged to form a reflecting surface that reflects the inner surface more strongly than the linearly polarized light component oscillating at and emits from the elongated exit surface, and the elongated exit surface is disposed to face the incident end surface of the light guide plate;
The light guide plate is disposed between the incident end surface of the light guide plate and the elongated light exit surface of the light guide member, and the polarization plane of the linearly polarized light component emitted from the elongated light exit surface of the light guide member is substantially rotated by 90 degrees. A phase difference plate incident on an incident end face of the light guide plate;
A solid-state light-emitting element disposed to face the incident end face of the light guide member;
A surface light source comprising:

The reflection surface of the light guide member includes a plurality of prism portions that internally reflect light incident from the incident end surface of the light guide member toward a direction in which an angle with respect to the normal line of the elongated light emission surface of the light guide member decreases. The surface light source according to claim 1.

The reflection surface of the light guide plate includes a plurality of prism portions that internally reflect light incident from the incident end surface of the light guide plate toward a direction in which an angle with respect to a normal line of the output surface of the light guide plate is reduced. The surface light source according to claim 1 or 2.

3. The surface light source according to claim 1, wherein the phase difference plate is a λ / 2 phase difference plate that gives a half-wave phase difference between ordinary light and extraordinary light of transmitted light. .