JP2004047278A

JP2004047278A - Lighting device

Info

Publication number: JP2004047278A
Application number: JP2002203431A
Authority: JP
Inventors: Ichiro Fujishiro; 藤代　一朗; Hideo Maeda; 前田　英男; Hiroshi Omori; 大森　宏
Original assignee: Minolta Co Ltd
Current assignee: Minolta Co Ltd
Priority date: 2002-07-12
Filing date: 2002-07-12
Publication date: 2004-02-12

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device equipped with a light source and light guide element which illuminates an object for illumination from an appropriate direction with a high utilization rate of light to the illumination. <P>SOLUTION: The light guide element (10) has prism-shaped protruded parts (13) repeatedly formed on a top face (11) and makes light incident inside from a light source emit from the underside as an illumination light (La) by reflecting at a surface (14) of the protruded part while making the incident light propagate by a total reflection at an upper surface and a lower surface (12).A reflecting member (30) is arranged in opposition to the upper surface of the light guide element, and a reflecting part (31) is arranged corresponding with the protruded part (13) at the reflecting member reflecting light transmitting the surface (14) to have it entered into the light guide element again, so that light reflected at each reflecting part is made to emit from the lower surface of the light guide element. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、対向する２つの表面で全反射して光を導きながら、一方の表面より出射させる導光素子を備える照明装置に関する。
【０００２】
【従来の技術】
携帯電話、携帯情報端末、ノート型パーソナルコンピュータ等の普及に伴い、薄型の映像表示装置が望まれており、これを満たす表示素子として、照明光を変調して映像を表す光とする液晶表示器が多用されている。液晶表示器は、照明光を透過させつつ変調する透過型と、照明光を反射しつつ変調する反射型に大別される。透過型液晶表示器の照明にはバックライト照明装置が用いられ、反射型液晶表示器の照明にはフロントライト照明装置が用いられる。
【０００３】
いずれの照明装置も、広い範囲を均一に照明するために、照明光を発する光源と、光源からの光を内部を進行させながら少しずつ液晶表示器側の表面より出射させる面状導光素子とで構成するのが一般的である。面状導光素子は、繰り返し設けられたプリズム状の凸部を一方の表面に有し、全反射によって光を凸部の繰り返しの方向に進行させながら、凸部の一部の表面で光を反射して進路を大きく変えて出射させる。液晶表示器には照明光の入射角の範囲に制約があり、出射光を生じさせる凸部の表面は、出射した光が適正な角度で液晶表示器に入射するように、傾斜を設定される。
【０００４】
光源としては棒状の冷陰極管が用いられてきたが、電力消費の低減と軽量化のために発光ダイオードを用い、線状導光素子と組み合わせることが行われている。線状導光素子は面状導光素子と同様に構成され、面状導光素子の端面に対向して配置されて、発光ダイオードからの光を面状導光素子に与える。
【０００５】
面状導光素子と線状導光素子のいずれにおいても、出射光を生じさせる凸部の表面は、光の進路を大きく変えるために、光の入射角が小さくなるように設定する必要がある。このため、光を所定の方向に反射することができるものの、透過してしまう光も存在する。この透過光は１０〜２０％に達し、光の利用効率の大きな低下を招いている。
【０００６】
出射光を生じさせる凸部の表面を透過した光を、導光素子に再入射させるために、反射部材を設けることが提案されている。このような照明装置を備えた映像表示装置の例を図１０に示す。この映像表示装置は、線状導光素子９１、面状導光素子９２、反射部材９３、発光ダイオード９４、および反射型液晶表示器９５より成る。
【０００７】
面状導光素子９２は、断面が三角形のプリズム状の凸部が繰り返し形成された上面を有し、下面を液晶表示器９５の前面に向けて配置されている。図には現れていないが、線状導光素子９１も、断面が三角形のプリズム状の凸部が繰り返し形成された上面を有する。線状導光素子９１は、下面を面状導光素子９２の端面に向けて配置されており、発光ダイオード９４は、線状導光素子９１の端面に向けて配置されている。
【０００８】
線状導光素子９１は、端面より入射した発光ダイオード９４からの光を、各凸部の発光ダイオード９４に近い方の表面と下面で全反射して内部を進行させながら、各凸部の発光ダイオード９４から遠い方の表面で反射して下面より出射させる。面状導光素子９２も同様に、端面より入射した線状導光素子９１からの光を、各凸部の線状導光素子９１に近い方の表面と下面で全反射して内部を進行させながら、各凸部の線状導光素子９１から遠い方の表面で反射して下面より出射させる。
【０００９】
反射部材９３は、コの字状の断面を有し、線状導光素子９１の上面および両側面を覆うように配置されている。線状導光素子９１の出射光を生じさせる表面を透過した光は、反射部材９３によって反射されて線状導光素子９１に再入射し、これにより、光の損失が抑えられる。
【００１０】
面状導光素子９２においても、出射光を生じさせる凸部の表面を透過する光が存在するが、反射型液晶表示器９５からの映像光を観察者に導く必要があるため、面状導光素子９２の上面に対向して反射部材を備えることはできない。ただし、液晶表示器が透過型の場合は、面状導光素子の下面を液晶表示器の後面に向けて配置し、凸部が設けられている上面に対向して平板状の反射部材を備えることが行われている。
【００１１】
このように、出射光を生じさせる表面を透過した光を、反射部材によって導光素子に再入射させるようにすると、照明への光の利用効率が高まると期待される。
【００１２】
【発明が解決しようとする課題】
従来の反射部材の光を反射する部位は、光を正反射する反射面、または、光を散乱させる拡散反射面であり、また、導光素子の凸部の繰り返しの方向に平行な一様な面である。光を反射する部位が単なる反射面の場合、その反射光は導光素子の上面を透過した時と同じ角度で導光素子に向かう。反射部材への光の入射角は大きく、しかも広がりがあるため、反射光は、導光素子に再入射するものの、下面に対して臨界角未満かつ臨界角に近い角度となるものを多く含む。この様子を図１１に示す。このような光Ｌｂは、本来の照明光Ｌａと同様に下面を透過して出射するが、照明光Ｌａとは大きな角度差を有することになる。
【００１３】
このような事態が線状導光素子で生じると、光Ｌｂは面状導光素子に入射してもその側面を透過して出射することになり、照明には利用されない。また、同様の事態が面状導光素子で生じると、光Ｌｂは液晶表示器に対する入射角が許容範囲を超えてしまい、適正に変調されなくなるか、不適正な方向に出射することになる。これは、光の利用効率に向上をもたらさないばかりか、提供する映像の品位を著しく低下させる結果となる。
【００１４】
反射部材の光を反射する部位が拡散反射面の場合、導光素子の凸部の配列方向については本来の照明光Ｌａとの角度差が大きい光Ｌｂは減少する。しかし、逆に、導光素子の幅方向（凸部の繰り返しの方向に垂直な方向）について本来の照明光との角度差が大きい光が生じることになる。このような事態が線状導光素子で生じると、その光は面状導光素子の上面や下面への入射角が臨界角よりも小さくなり、全反射されずに上面や下面を透過してしまう。これは、光の損失を招く上、照明に不均一さを生じさせて、映像の品位を低下させる。また、同様の事態が面状導光素子で生じると、側面を透過して失われる光が増すことになる。
【００１５】
本発明は、このような問題点に鑑みてなされたもので、照明への光の利用効率が高く、照明対象物を適正な方向から照明することが可能な照明装置を提供することを目的とする。
【００１６】
【課題を解決するための手段】
上記目的を達成するために、本発明では、上面または下面にプリズム状の凸部が繰り返し設けられ、内部に入射した光を上面と下面で全反射して凸部の繰り返しの方向に進行させながら、一部ずつ下面を透過させて出射させる導光素子と、導光素子の上面に対向して配置され、上面を透過した光を反射して導光素子に再入射させる反射部材とを備え、導光素子の下面から出射した光を照明用の光とする照明装置において、反射部材が導光素子の凸部に対応して繰り返し設けられた反射部を有し、反射部材の各反射部が、導光素子の凸部の繰り返しの方向に対して傾斜した反射面を有する構成とする。
【００１７】
この照明装置は、導光素子の上面を透過した光を反射して導光素子に再入射させる反射部材を備えるが、反射部材は、光を一様に反射するのではなく、導光素子の凸部に対応して繰り返し設けられた反射部ごとに個別に反射する。各反射部は、導光素子の凸部の繰り返しの方向に対して傾斜した反射面を有しており、反射後の光の導光素子の上面や下面に対する角度を、上面透過時よりも小さくすることができる。これにより、導光素子の上面を透過した光を、導光素子の下面から照明光としての方向に出射させることができて、光の利用効率が高まり、また、照明対象物を適正な方向から照明することが可能になる。
【００１８】
導光素子の凸部は、上面に設けてもよいし、下面に設けてもよい。上面に凸部を設ける場合は、その一部の表面で下面に向けて反射した光を、そのまま照明光とすることができる。凸部の表面を透過して反射部材によって反射された光も照明光となる。また、下面に凸部を設ける場合は、その一部の表面で上面に向けて反射した光を、反射部材で反射して照明光とすることができる。なお、導光素子は、幅を大きくすれば面状導光素子となり、幅を小さくすれば線状導光素子となる。
【００１９】
ここで、反射部材の各反射部が２つ以上の平面の反射面を有するようにするとよい。各反射部に集光機能をもたせることが可能になり、照明光の角度範囲（発散の度合い）を小さくすることができる。また、反射部の形状設定も容易である。
【００２０】
反射部材の各反射部が凹曲面の反射面を有するようにしてもよい。各反射部に精度の高い集光機能をもたせることが可能になり、照明光の角度範囲を一層小さくすることができる。
【００２１】
導光素子の凸部が上面に設けられている構成では、各凸部が、凸部の繰り返しの方向に対して８０゜以上かつ１００゜以下の角度を成す表面を有するようにするとよい。このような角度の表面は光を透過させ易く、照明光の大部分は反射部材によって反射された光となる。したがって、照明光を所望の方向に向けることが容易になり、また、上述のよう反射部に集光機能をもたせておくと、その機能が十分発揮されて、照明光を所望の方向に向けることが一層容易になる。
【００２２】
前記目的を達成するために、本発明ではまた、上面または下面にプリズム状の凸部が繰り返し設けられ、内部に入射した光を上面と下面で全反射して凸部の繰り返しの方向に進行させながら、一部ずつ下面を透過させて出射させる導光素子を備え、導光素子の下面から出射した光を照明用の光とする照明装置において、導光素子の凸部に対応して繰り返し設けられた集光部を有する集光部材を、導光素子の下面に対向して備え、集光部材の各集光部が、導光素子の下面から出射した光の発散の度合いを、少なくとも導光素子の凸部の繰り返しの方向について、小さくする構成とする。
【００２３】
この照明装置では、導光素子から出射した照明光の角度範囲を狭くして、照明対象物を適正な方向から照明することが可能である。導光素子に入射する光の発散の度合いが導光素子の幅の方向について小さいときは、凸部の繰り返しの方向についてのみ、発散の度合いを小さくするように集光部を設定すればよい。また、導光素子に入射する光の発散の度合いが導光素子の幅の方向について大きいときは、凸部の繰り返しの方向と幅方向の双方について発散の度合いを小さくするように、集光部を設定するのが好ましい。
【００２４】
【発明の実施の形態】
以下、本発明のいくつかの実施形態について図面を参照しながら説明する。第１の実施形態の照明装置１の光学構成を図１に示す。照明装置１は、線状導光素子１０、面状導光素子２０、反射部材３０、および光源である発光ダイオード４０より成る。
【００２５】
線状導光素子１０は、巨視的に見て互いに平行な上面と下面を有し、下面を面状導光素子２０の端面に向けて配置されている。面状導光素子２０も、巨視的に見て互いに平行な上面と下面を有する。線状導光素子１０の上面には、断面が三角形のプリズム状の凸部１３が繰り返し形成されており、面状導光素子２０の上面にも、断面が三角形のプリズム状の凸部２３が繰り返し形成されている。線状導光素子１０と面状導光素子２０は、幅に大きな差異があるのみで、同様の構成である。これらは、ガラス、樹脂等の透明な光学材料で作製されている。
【００２６】
発光ダイオード４０は、線状導光素子１０の端面に向けて配置されている。照明装置１は、使用に際し、面状導光素子２０の下面を照明対象物に向けて配置される。
【００２７】
線状導光素子１０は、端面より入射した発光ダイオード４０からの光を、各凸部の発光ダイオード４０に近い方の表面と下面で全反射して、矢印Ａで示すように内部を進行させながら、各凸部の発光ダイオード４０から遠い方の表面で反射して下面より出射させる。面状導光素子２０も同様に、端面より入射した線状導光素子１０からの光を、各凸部の線状導光素子１０に近い方の表面と下面で全反射して、矢印Ｂで示すように内部を進行させながら、各凸部の線状導光素子１０から遠い方の表面で反射して、矢印Ｃで示すように下面より出射させる。
【００２８】
反射部材３０は、線状導光素子１０と同程度の幅を有し、線状導光素子１０の上面に沿って配置されている。線状導光素子１０および反射部材３０の拡大縦断面を図２に示す。線状導光素子１０の上面１１に設けられている凸部１３のうち、発光ダイオード４０から遠い方の表面（光の進行方向に沿って下降する表面）１４が下面１２を透過して出射する光を生じさせる表面であり、発光ダイオード４０に近い方の表面（光の進行方向に沿って上昇する表面）１５が、下面１２と共に全反射によって光を進行させる表面である。
【００２９】
反射部材３０は２つの表面３１、３２から成る組を複数有しており、これらの組は、線状導光素子１０の凸部１３の繰り返し方向に、凸部１３の繰り返しと同じピッチで設けられている。表面３１は反射面とされており、凸部１３の表面１５の上方に位置している。また、表面３１は、線状導光素子１０の凸部１３の繰り返し方向に対して傾斜しており、凸部１３の表面１４を透過した光を反射して、線状導光素子１０に再入射させる反射部を成す。なお、表面３２は、表面３１を繰り返し形成するために副次的に生じたもので、光の反射には関与しない。
【００３０】
反射部を成す表面３１は、凹曲面であり、より具体的には、線状導光素子１０に垂直な方向（上面１１と下面１２を結ぶ方向）に軸を有し、凸部１３の表面１４上に焦点を有する放物面である。したがって、凸部１３の配列方向に対して成す角は、部位によって異なる。
【００３１】
発光ダイオード４０が発する光は発散光であり、凸部１３の表面１４を透過した光の角度には広がりがある。表面１４を透過した光のうち凸部１３の繰り返しの方向に対する角度が小さいものは、表面３１のうち凸部１３の繰り返しの方向に対する角度が大きい部位に入射する。また、表面１４を透過した光のうち凸部１３の繰り返しの方向に対する角度が大きいものは、表面３１のうち凸部１３の繰り返しの方向に対する角度が小さい部位に入射する。いずれの光も、表面３１によって反射された後は、略同じ方向に進む。つまり、表面３１は集光機能を有し、反射光を平行光に近づける。
【００３２】
表面３１による反射光は凸部１３の表面１５に入射する。表面３１からの反射光の進行方向は、放物面である表面３１の曲率の設定次第で調節可能である。ここでは、反射光が線状導光素子１０の下面から垂直に出射するように、表面１５を透過する際の屈折を考慮して、表面３１の曲率を設定している。
【００３３】
凸部１３の表面１４で反射された光の角度にも広がりがあるが、表面１４の傾斜は、反射後の光の中心の光線が下面に対して垂直になるように設定している。したがって、反射部材３０の表面３１で反射された光は、線状導光素子１０の凸部１３の表面１４で反射された光と同様に、照明光Ｌａを成す。しかも、表面３１で反射された光の角度範囲は表面１４で反射された光の角度範囲よりも小さい。
【００３４】
このような構成の線状導光素子１０と反射部材３０とを有する照明装置１においては、発光ダイオード４０が発した光を損失少なく面状導光素子２０に与えることができる。また、その光は、面状導光素子２０の幅方向についての角度範囲が小さく、面状導光素子２０の両側面を透過して失われることがない。したがって、光の利用効率が高い。
【００３５】
反射部材３０は、樹脂の成形、金属のプレス加工等によって作製することができる。樹脂成形で作製する場合、表面３１にアルミニウム等の金属を蒸着しておき、金属加工で作成する場合、表面３１を鏡面仕上げしておく。
【００３６】
以下、他の実施形態について説明するが、各実施形態は第１の実施形態の照明装置１と同様の照明装置であるので、重複する説明は省略して、相違点を述べる。
【００３７】
第２の実施形態の照明装置２の線状導光素子１０および反射部材３０の拡大縦断面を図３に示す。本実施形態の照明装置２の反射部材３０は、上記照明装置１の放物面の表面３１を、線状導光素子１０の凸部１３の繰り返し方向に対する傾斜が異なる３つの平面３１ａ、３１ｂ、３１ｃで近似したものである。このように反射部が平面のみを有するようにすると、集光機能は低下するものの、樹脂成形で反射部材３０を作製する場合に、金型の形成が容易になる。
【００３８】
線状導光素子１０のプリズム状の凸部１３は、断面が台形であり、表面１４、１５に加えて表面１６を有する。この表面１６は隣の凸部１３の表面１４の下部を透過した光を再入射させる。表面１６から再入射した光の一部は、表面１４によって反射されて下面１２より出射して照明光となり、残りは下面１２によって全反射されて内部をさらに進行する。線状導光素子１０内を進行する光は、途中で照明光として出射するため減少していくが、このように表面１６を加えて、表面１４を透過した光の一部が内部をさらに進行し得るようにしたことで、光量の減少が抑えられ、発光ダイオード４０から遠い部位においても照明光を面状導光素子２０に与えることが可能になる。
【００３９】
第３の実施形態の照明装置３の線状導光素子１０および反射部材３０の縦断面を図４に示す。これは、凸部１３の繰り返しの方向について、線状導光素子１０および反射部材３０を対称にするとともに、線状導光素子１０の２つの端面それぞれに、発光ダイオード４０を配置したものである。このようにすると、高輝度の照明が可能となり、また、均一度の高い照明ができる。
【００４０】
線状導光素子１０および反射部材３０の拡大縦断面を図５に示す。反射部材３０の反射部は、第１の実施形態の照明装置１と同様に放物面である。線状導光素子１０の凸部１３の表面１４が凸部１３の繰り返しの方向に対して成す角βは、９０゜に設定されている。このように設定すると、表面１４によって反射される光はごく僅かになり、照明光Ｌａを成す光はほとんど全て、表面１４を透過して反射部材３０の表面３１によって反射された光となる。前述のように、表面３１で反射された光の角度範囲は、表面１４で反射された光の角度範囲よりも小さいから、本実施形態では第１の実施形態よりも、面状導光素子２０に与える光の角度範囲をさらに小さくすることができる。
【００４１】
表面１４が凸部１３の繰り返しの方向に対して成す角βは、厳密に９０゜である必要はなく、８０〜１００゜の範囲内であればよい。この角度範囲であれば、表面１４に入射する光はほとんど全て表面１４を透過する。
【００４２】
第４の実施形態の照明装置４の線状導光素子１０および反射部材３０の縦断面を図６に示す。本実施形態の照明装置４は、第１の実施形態の照明装置１を修飾して、線状導光素子１０の下面１２を上面１１に対して傾斜した平面としたものである。下面１２は発光ダイオード３０から遠い部位ほど上面１１に接近する。
【００４３】
線状導光素子１０に入射する光には、凸部１１の繰り返し方向に対して平行なものやきわめて平行に近いものも含まれる。このような光は、上面１１と下面１２が平行であれば、上面１１や下面１２に入射することなく、直接下流側の端面に達することになる。
【００４４】
本実施形態のように、下面１２を光の進行方向に沿って上昇する傾斜面とすることにより、上面１１と下面１２が平行な場合の光の平均の光路１７が下面１２と交差するようにすることができて、凸部１３の繰り返しの方向に対して平行に近い光を照明に有効に利用することが可能になる。しかも、上面１１と下面１２が平行な場合の光の平均の光路１７が下面１２と交差する位置を、線状導光素子１０の両端面の中央付近とすることができるため、発光ダイオード４０の主光線のように平均の光路１７に近い光を、途中での出射により光量が減少することになる発光ダイオード４０から遠い部位で出射させることが可能であり、均一な照明が容易になる。
【００４５】
第５の実施形態の照明装置５の線状導光素子１０および反射部材３０の拡大縦断面を図７に示す。本実施形態の照明装置５は、線状導光素子１０の凸部１３を上面１１ではなく下面１２に設けたものである。反射部材３０は上面１１に対向して配置されている。凸部１３のうち、発光ダイオード４０に近い方の表面（光の進行方向に沿って下降する表面）１５は、上面１１と共に全反射によって光を進行させる。一方、発光ダイオード４０から遠い方の表面（光の進行方向に沿って上昇する表面）１４は、反射により上面１１を透過する光を生じさせる。表面１４によって反射され上面１１を透過した光は、反射部材３０によって反射され、線状導光素子１０に再入射して下面１２より出射する照明光となる。
【００４６】
反射部材３０の各反射部を成す表面３１は、第１の実施形態の照明装置１と同様に、線状導光素子１０に垂直な方向に軸を有する放物面である。ただし、表面３１は、幅が繰り返しピッチに等しく、繰り返しの方向について対称である。また、その焦点は凸部１３の表面１４の中央に位置する。照明装置１で存在していた表面３２は、照明装置５では存在しない。
【００４７】
線状導光素子１０の凸部１３の表面１４で反射された光は、反射部材３０の表面３１で反射されることにより、略平行光となり、線状導光素子１０の上面１１に略垂直に入射する。この光は上面１１を透過し、さらに下面１２を透過して、照明光として出射する。下面１１を透過する際には、表面１４を透過するものと表面１５を透過するものが生じて、光の角度範囲は少し広がるが、それでも、面状導光素子２０に入射する光の角度範囲は狭く、面状導光素子２０の側面を透過して失われる光は生じない。
【００４８】
第６の実施形態の照明装置６の線状導光素子１０およびその周辺の拡大縦断面を図８に示す。本実施形態の照明装置６は、線状導光素子１０の下面１２に対向して、集光部材５０を備えている。集光部材５０の上面５１には、複数の凸面５３が設けられている。凸面５３は、線状導光素子１０の凸部１３の繰り返しの方向に、凸部１３の繰り返しと同じピッチで設けられている。各凸面５３は、凸部１３の繰り返しの方向にのみ曲率（パワー）を有しており、シリンドリカルレンズとして機能し、凸部１３の表面１４で反射され下面１２より出射した光を、集光して略平行光とする集光部を成す。
【００４９】
上面５１に凸面５３を設けることに代えて、下面５２に凸面５３を設けてもよい。また、凸面５３が線状導光素子１０の幅方向にもパワーを有するようにしてもよい。発光ダイオード４０からの光の発散の度合いが大きいときは、面状導光素子２０の上面や下面への入射角が小さい光が存在することになり、そのような光は面状導光素子２０で全反射されなくなるおそれがあるが、凸面５３に線状導光素子１０の幅方向のパワーをもたせることで、面状導光素子２０で確実に全反射することができるようになる。
【００５０】
なお、本実施形態の照明装置６は反射部材３０を備えていないが、反射部材３０と集光部材５０とを併用してもかまわない。反射部材３０の集光機能と集光部材５０の集光機能とによって、下面１２から出射した光を平行光に近づければよい。
【００５１】
バックライト照明装置とする場合は、反射部材を面状導光素子２０に対しても備えることができる。その１例である第７の実施形態の照明装置７の光学構成を図９に示す。照明装置７は、第１の実施形態の照明装置１に、反射部材６０を加えたものである。反射部材６０は、幅が異なるのみで線状導光素子１０に対する反射部材３０と同様に構成されており、面状導光素子２０の上面に対向して配置されている。
【００５２】
このように、線状導光素子１０、面状導光素子２０のそれぞれに対して反射部材３０、６０を備えると、照明への光の利用効率が大きく向上し、また、照明対象物に対する照明光の入射角の範囲を小さくすることができる。例えば、透過型液晶表示器を照明する場合、明るく、しかも品位の高い映像を提供することが可能になる。
【００５３】
フロントライト照明装置とするときは、反射部材３０のような反射部材を面状導光素子２０に対して備えることはできない。この場合は、第６の実施形態の集光部材５０と同様の集光部材を、面状導光素子２０に対して備えるとよい。
【００５４】
【発明の効果】
上面または下面にプリズム状の凸部が繰り返し設けられ、内部に入射した光を上面と下面で全反射して凸部の繰り返しの方向に進行させながら、一部ずつ下面を透過させて出射させる導光素子と、導光素子の上面に対向して配置され、上面を透過した光を反射して導光素子に再入射させる反射部材とを備え、導光素子の下面から出射した光を照明用の光とする照明装置において、本発明のように、反射部材が導光素子の凸部に対応して繰り返し設けられた反射部を有し、反射部材の各反射部が、導光素子の凸部の繰り返しの方向に対して傾斜した反射面を有するようにすると、反射部材による反射後の光の導光素子の上面や下面に対する角度を、上面透過時よりも小さくすることができて、導光素子の上面を透過した光を、導光素子の下面から照明光としての方向に出射させることが可能になる。したがって、光の利用効率が高まり、照明対象物を適正な方向から照明することができる。
【００５５】
反射部材の各反射部が２つ以上の平面の反射面を有するようにすると、各反射部に集光機能をもたせることが可能になり、照明光の発散の度合いを小さくすることができる。また、反射部の形状設定も容易である。
【００５６】
反射部材の各反射部が凹曲面の反射面を有するようにすると、各反射部に精度の高い集光機能をもたせることが可能になり、照明光の角度範囲を一層小さくすることができる。
【００５７】
導光素子の凸部が上面に設けられている構成で、各凸部が、凸部の繰り返しの方向に対して８０゜以上かつ１００゜以下の角度を成す表面を有するようにすると、素子内を進行する光がその表面を透過し易くなり、照明光の大部分を反射部材によって反射された光とすることができる。したがって、照明光を所望の方向に向けることが容易になり、反射部に集光機能をもたせておくと、その機能が十分発揮されて、照明光を所望の方向に向けることが一層容易になる。
【００５８】
上面または下面にプリズム状の凸部が繰り返し設けられ、内部に入射した光を上面と下面で全反射して凸部の繰り返しの方向に進行させながら、一部ずつ下面を透過させて出射させる導光素子を備え、導光素子の下面から出射した光を照明用の光とする照明装置において、本発明のように、導光素子の凸部に対応して繰り返し設けられた集光部を有する集光部材を、導光素子の下面に対向して備え、集光部材の各集光部が、導光素子の下面から出射した光の発散の度合いを、少なくとも導光素子の凸部の繰り返しの方向について、小さくするようにすると、照明対象物への照明光の入射角の範囲を狭くすることができて、照明対象物を適正な方向から照明することが可能である。
【００５９】
導光素子の凸部の繰り返しの方向についてのみ発散の度合いを小さくするように集光部を設定すれば、集光部材の作製が容易であり、導光素子の幅方向についても発散の度合いを小さくするように集光部を設定すれば、導光素子に入射する光の発散の度合いが導光素子の幅の方向について大きいときでも、照明対象物を適正な方向から照明することができる。
【図面の簡単な説明】
【図１】第１の実施形態の照明装置の光学構成を示す斜視図。
【図２】第１の実施形態の照明装置が備える線状導光素子および反射部材の拡大縦断面図。
【図３】第２の実施形態の照明装置が備える線状導光素子および反射部材の拡大縦断面図。
【図４】第３の実施形態の照明装置が備える線状導光素子および反射部材の縦断面図。
【図５】第３の実施形態の照明装置が備える線状導光素子および反射部材の拡大縦断面図。
【図６】第４の実施形態の照明装置が備える線状導光素子および反射部材の縦断面図。
【図７】第５の実施形態の照明装置が備える線状導光素子および反射部材の拡大縦断面図。
【図８】第６の実施形態の照明装置が備える線状導光素子および集光部材の拡大縦断面図。
【図９】第７の実施形態の照明装置の光学構成を示す斜視図。
【図１０】従来の照明装置の光学構成を示す斜視図。
【図１１】従来の照明装置が備える線状導光素子および反射部材の拡大縦断面図。
【符号の説明】
１〜７　照明装置
１０　　　線状導光素子
１１　　　上面
１２　　　下面
１３　　　凸部
１４、１５、１６　凸部表面
２０　　　面状導光素子
２３　　　凸部
３０　　　反射部材
３１　　　反射面（反射部）
３１ａ、３１ｂ、３１ｃ　反射面（反射部）
３２　　　表面
４０　　　発光ダイオード
５０　　　集光部材
５１　　　上面
５２　　　下面
５３　　　凸面（集光部）
６０　　　反射部材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lighting device including a light guide element that emits light from one surface while guiding light by total reflection on two opposing surfaces.
[0002]
[Prior art]
With the spread of mobile phones, personal digital assistants, notebook personal computers, and the like, a thin image display device is desired. As a display element that satisfies this, a liquid crystal display device that modulates illumination light to emit light representing an image. Is often used. Liquid crystal displays are roughly classified into a transmission type, which modulates while transmitting illumination light, and a reflection type, which modulates while reflecting illumination light. A backlight illumination device is used for illumination of the transmissive liquid crystal display, and a front light illumination device is used for illumination of the reflection type liquid crystal display.
[0003]
In order to uniformly illuminate a wide range, any of the illumination devices includes a light source that emits illumination light, and a planar light guide element that emits the light from the light source little by little from the surface on the liquid crystal display side while traveling inside. In general, it is composed of The planar light-guiding element has a prism-shaped convex portion provided repeatedly on one surface, and transmits light in a part of the surface of the convex portion while advancing light in the direction of repetition of the convex portion by total reflection. The light is reflected to change the course and is emitted. The liquid crystal display has a limitation on the range of the incident angle of the illumination light, and the surface of the convex portion that generates the emitted light is set to be inclined such that the emitted light enters the liquid crystal display at an appropriate angle. .
[0004]
Although a rod-shaped cold cathode tube has been used as a light source, a light emitting diode is used in combination with a linear light guide element for reducing power consumption and weight. The linear light guide element is configured in the same manner as the planar light guide element, is arranged to face the end face of the planar light guide element, and supplies light from the light emitting diode to the planar light guide element.
[0005]
In any of the planar light guide element and the linear light guide element, the surface of the convex portion that generates the emitted light needs to be set so that the incident angle of the light is small in order to largely change the course of the light. . For this reason, although light can be reflected in a predetermined direction, some light is transmitted. This transmitted light reaches 10 to 20%, causing a significant decrease in light use efficiency.
[0006]
It has been proposed to provide a reflecting member in order to re-enter the light transmitted through the surface of the projection that generates the emitted light to the light guide element. FIG. 10 shows an example of a video display device provided with such a lighting device. This image display device includes a linear light guide element 91, a planar light guide element 92, a reflection member 93, a light emitting diode 94, and a reflection type liquid crystal display 95.
[0007]
The planar light guide element 92 has an upper surface in which prism-shaped convex portions having a triangular cross section are repeatedly formed, and the lower surface is disposed with the lower surface facing the front surface of the liquid crystal display 95. Although not shown in the drawing, the linear light guide element 91 also has an upper surface in which prism-shaped protrusions having a triangular cross section are repeatedly formed. The linear light guide element 91 is arranged with the lower surface facing the end face of the planar light guide element 92, and the light emitting diode 94 is arranged toward the end face of the linear light guide element 91.
[0008]
The linear light guide element 91 totally reflects the light from the light emitting diode 94 incident from the end surface on the surface and the lower surface of the convex portion closer to the light emitting diode 94 and travels inside the light emitting device. The light is reflected by the surface farther from the diode 94 and emitted from the lower surface. Similarly, the planar light guide element 92 totally reflects the light from the linear light guide element 91 incident from the end face on the surface and the lower surface of the convex portion closer to the linear light guide element 91 and travels inside. Then, the light is reflected by the surface of each convex portion farther from the linear light guide element 91 and emitted from the lower surface.
[0009]
The reflecting member 93 has a U-shaped cross section, and is arranged so as to cover the upper surface and both side surfaces of the linear light guide element 91. The light transmitted through the surface of the linear light guide element 91 that emits the emitted light is reflected by the reflecting member 93 and re-enters the linear light guide element 91, thereby suppressing light loss.
[0010]
In the planar light guide element 92 as well, there is light that passes through the surface of the convex portion that generates emitted light. However, since it is necessary to guide image light from the reflective liquid crystal display 95 to an observer, the planar light The reflection member cannot be provided facing the upper surface of the optical element 92. However, when the liquid crystal display is a transmissive type, the lower surface of the planar light guide element is arranged facing the rear surface of the liquid crystal display, and a flat reflecting member is provided facing the upper surface where the convex portion is provided. That is being done.
[0011]
As described above, when the light transmitted through the surface that generates the outgoing light is made to re-enter the light guide element by the reflecting member, it is expected that the efficiency of use of the light for illumination is improved.
[0012]
[Problems to be solved by the invention]
The portion of the conventional reflecting member that reflects light is a reflecting surface that specularly reflects light, or a diffusing reflecting surface that scatters light, and a uniform surface parallel to the direction of repetition of the convex portion of the light guide element. Plane. If the portion that reflects light is simply a reflection surface, the reflected light is directed to the light guide element at the same angle as when transmitted through the upper surface of the light guide element. Since the angle of incidence of light on the reflecting member is large and wide, the reflected light includes many light rays which are incident again on the light guide element but have an angle smaller than the critical angle and close to the critical angle with respect to the lower surface. This is shown in FIG. Such light Lb is transmitted through the lower surface and emitted like the original illumination light La, but has a large angle difference from the illumination light La.
[0013]
If such a situation occurs in the linear light guide element, even if the light Lb enters the planar light guide element, the light Lb is transmitted through the side surface and emitted, and is not used for illumination. Further, when the same situation occurs in the planar light guide element, the light Lb has an incident angle with respect to the liquid crystal display exceeding an allowable range, and is not properly modulated or emitted in an inappropriate direction. This not only does not improve the light use efficiency, but also significantly reduces the quality of the provided image.
[0014]
When the portion of the reflecting member that reflects light is a diffuse reflection surface, the light Lb having a large angle difference from the original illumination light La decreases in the arrangement direction of the projections of the light guide element. However, conversely, light having a large angle difference from the original illumination light in the width direction of the light guide element (the direction perpendicular to the direction in which the convex portions are repeated) is generated. When such a situation occurs in the linear light guide element, the light is incident on the upper and lower faces of the planar light guide element at a smaller angle than the critical angle, and is transmitted through the upper and lower faces without being totally reflected. I will. This leads to loss of light and non-uniformity of illumination, thereby deteriorating image quality. Further, when the same situation occurs in the planar light guide element, the amount of light transmitted through the side surface and lost increases.
[0015]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a lighting device that has a high use efficiency of light for lighting and can illuminate an illumination target from an appropriate direction. I do.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a prism-shaped convex portion is repeatedly provided on the upper surface or the lower surface, and light incident inside is totally reflected by the upper surface and the lower surface and travels in the direction of repetition of the convex portion. A light guide element that transmits and emits the lower surface part by part, and a reflecting member that is arranged to face the upper surface of the light guide element and reflects light transmitted through the upper surface and re-enters the light guide element, In an illumination device in which light emitted from the lower surface of the light guide element is used as illumination light, the reflection member has a reflection portion repeatedly provided corresponding to the convex portion of the light guide element, and each reflection portion of the reflection member is The light guide element has a reflective surface inclined with respect to the direction in which the convex portions are repeated.
[0017]
This illumination device includes a reflecting member that reflects light transmitted through the upper surface of the light guide element and causes the light to be incident again on the light guide element. The light is individually reflected for each of the reflection portions repeatedly provided corresponding to the projections. Each reflecting portion has a reflecting surface inclined with respect to the direction of repetition of the convex portion of the light guide element, and the angle of the reflected light with respect to the upper and lower surfaces of the light guide element is smaller than that at the time of transmission through the upper surface. can do. Thereby, the light transmitted through the upper surface of the light guide element can be emitted from the lower surface of the light guide element in the direction as illumination light, and the light use efficiency is increased, and the object to be illuminated from an appropriate direction is improved. It becomes possible to illuminate.
[0018]
The projection of the light guide element may be provided on the upper surface or on the lower surface. When a convex portion is provided on the upper surface, light reflected toward the lower surface on a part of the surface can be used as illumination light as it is. Light transmitted through the surface of the projection and reflected by the reflection member is also illumination light. When a convex portion is provided on the lower surface, light reflected toward the upper surface on a part of the surface can be reflected by a reflective member to be used as illumination light. The light guide element becomes a planar light guide element when the width is increased, and becomes a linear light guide element when the width is reduced.
[0019]
Here, it is preferable that each reflecting portion of the reflecting member has two or more flat reflecting surfaces. Each reflecting portion can be provided with a light collecting function, and the angle range (degree of divergence) of the illumination light can be reduced. In addition, the shape of the reflecting portion can be easily set.
[0020]
Each reflecting portion of the reflecting member may have a concave curved reflecting surface. Each reflecting section can be provided with a highly accurate light collecting function, and the angle range of illumination light can be further reduced.
[0021]
In a configuration in which the projections of the light guide element are provided on the upper surface, each projection may have a surface that forms an angle of 80 ° or more and 100 ° or less with respect to the direction in which the projections are repeated. The surface having such an angle easily transmits light, and most of the illumination light is light reflected by the reflecting member. Therefore, it is easy to direct the illumination light in a desired direction, and if the reflecting portion is provided with a light collecting function as described above, the function is sufficiently exhibited, and the illumination light is directed in a desired direction. Becomes easier.
[0022]
In order to achieve the above object, in the present invention, a prism-shaped convex portion is repeatedly provided on the upper surface or the lower surface, and light incident on the inside is totally reflected by the upper surface and the lower surface and travels in the direction of repetition of the convex portion. A light guide element that transmits light through the lower surface of the light guide element and emits light from the lower surface of the light guide element, and the light emitted from the lower surface of the light guide element is used as illumination light. A light-collecting member having a light-collecting portion is provided to face the lower surface of the light-guiding element, and each light-collecting portion of the light-gathering member guides at least the degree of divergence of light emitted from the lower surface of the light-guiding element. The configuration is such that the direction of repetition of the convex portion of the optical element is reduced.
[0023]
In this illumination device, it is possible to illuminate the illumination target from an appropriate direction by narrowing the angle range of the illumination light emitted from the light guide element. When the degree of divergence of light incident on the light guide element is small in the direction of the width of the light guide element, the condensing section may be set so as to reduce the degree of divergence only in the direction in which the convex portions are repeated. Further, when the degree of divergence of the light incident on the light guide element is large in the width direction of the light guide element, the condensing unit is configured to reduce the degree of divergence in both the repetition direction of the convex part and the width direction. Is preferably set.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, some embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an optical configuration of the illumination device 1 according to the first embodiment. The lighting device 1 includes a linear light guide element 10, a planar light guide element 20, a reflecting member 30, and a light emitting diode 40 as a light source.
[0025]
The linear light guide element 10 has an upper surface and a lower surface that are parallel to each other when viewed macroscopically, and is disposed with the lower surface facing the end surface of the planar light guide element 20. The planar light guide element 20 also has an upper surface and a lower surface that are macroscopically parallel to each other. On the upper surface of the linear light guide element 10, prism-shaped protrusions 13 having a triangular cross section are repeatedly formed. On the upper surface of the planar light guide element 20, a prism-shaped protrusion 23 having a triangular cross section is formed. It is formed repeatedly. The linear light guide element 10 and the planar light guide element 20 have the same configuration except for a large difference in width. These are made of transparent optical materials such as glass and resin.
[0026]
The light emitting diode 40 is arranged toward the end face of the linear light guide element 10. In use, the illumination device 1 is arranged with the lower surface of the planar light guide element 20 facing the object to be illuminated.
[0027]
The linear light guide element 10 totally reflects the light from the light emitting diode 40 incident from the end surface on the surface and the lower surface of each convex portion closer to the light emitting diode 40, and proceeds inside as shown by the arrow A. While being reflected, the light is reflected from the surface of the convex portion farther from the light emitting diode 40 and emitted from the lower surface. Similarly, the planar light-guiding element 20 totally reflects the light from the linear light-guiding element 10 incident from the end face on the surface and the lower surface of each convex portion closer to the linear light-guiding element 10, and the arrow B The light is reflected on the surface of the convex portion farther from the linear light guide element 10 and is emitted from the lower surface as shown by the arrow C while traveling inside as shown by.
[0028]
The reflecting member 30 has the same width as the linear light guide element 10 and is arranged along the upper surface of the linear light guide element 10. FIG. 2 shows an enlarged vertical cross section of the linear light guide element 10 and the reflection member 30. Of the protrusions 13 provided on the upper surface 11 of the linear light guide element 10, the surface 14 (the surface descending along the light traveling direction) 14 farther from the light emitting diode 40 transmits through the lower surface 12 and emits. The surface that generates light and is closer to the light emitting diode 40 (the surface that rises in the light traveling direction) 15 is the surface that propagates the light by total reflection together with the lower surface 12.
[0029]
The reflecting member 30 has a plurality of sets each including two surfaces 31 and 32, and these sets are provided in the repetition direction of the protrusions 13 of the linear light guide element 10 at the same pitch as the repetition of the protrusions 13. Have been. The surface 31 is a reflection surface, and is located above the surface 15 of the projection 13. In addition, the surface 31 is inclined with respect to the repetition direction of the convex portions 13 of the linear light guide element 10, and reflects the light transmitted through the surface 14 of the convex portions 13, and retransmits the light to the linear light guide element 10. It forms a reflecting part to be incident. It should be noted that the surface 32 is formed as a by-product due to the repeated formation of the surface 31 and does not contribute to light reflection.
[0030]
The surface 31 forming the reflecting portion is a concave curved surface, more specifically, has an axis in a direction perpendicular to the linear light guide element 10 (a direction connecting the upper surface 11 and the lower surface 12), and the surface of the convex portion 13. 14 is a paraboloid with a focal point on 14. Therefore, the angle formed with respect to the arrangement direction of the protrusions 13 differs depending on the part.
[0031]
The light emitted from the light emitting diode 40 is divergent light, and the angle of the light transmitted through the surface 14 of the projection 13 has a spread. The light transmitted through the surface 14 having a small angle with respect to the repetition direction of the convex portion 13 is incident on a portion of the surface 31 where the angle with respect to the repetition direction of the convex portion 13 is large. Further, of the light transmitted through the surface 14, the light having a large angle with respect to the repetition direction of the projection 13 is incident on a portion of the surface 31 where the angle with respect to the repetition direction of the projection 13 is small. After any light is reflected by the surface 31, it travels in substantially the same direction. That is, the surface 31 has a light collecting function, and makes the reflected light closer to the parallel light.
[0032]
The light reflected by the surface 31 is incident on the surface 15 of the projection 13. The traveling direction of the reflected light from the surface 31 can be adjusted by setting the curvature of the surface 31 which is a paraboloid. Here, the curvature of the surface 31 is set in consideration of refraction when transmitting through the surface 15 so that the reflected light is emitted perpendicularly from the lower surface of the linear light guide element 10.
[0033]
Although the angle of the light reflected by the surface 14 of the convex portion 13 has a spread, the inclination of the surface 14 is set so that the central ray of the reflected light is perpendicular to the lower surface. Therefore, the light reflected on the surface 31 of the reflection member 30 forms the illumination light La, similarly to the light reflected on the surface 14 of the projection 13 of the linear light guide element 10. Moreover, the angle range of the light reflected by the surface 31 is smaller than the angle range of the light reflected by the surface 14.
[0034]
In the lighting device 1 having the linear light guide element 10 and the reflection member 30 having such a configuration, the light emitted from the light emitting diode 40 can be given to the planar light guide element 20 with little loss. In addition, the light has a small angle range in the width direction of the planar light guide element 20, and does not pass through both side surfaces of the planar light guide element 20 and is not lost. Therefore, light use efficiency is high.
[0035]
The reflection member 30 can be manufactured by molding a resin, pressing a metal, or the like. In the case of manufacturing by resin molding, a metal such as aluminum is vapor-deposited on the surface 31, and in the case of forming by metal working, the surface 31 is mirror-finished.
[0036]
Hereinafter, other embodiments will be described. However, since each embodiment is a lighting device similar to the lighting device 1 of the first embodiment, a duplicate description will be omitted and different points will be described.
[0037]
FIG. 3 shows an enlarged vertical cross section of the linear light guide element 10 and the reflection member 30 of the illumination device 2 according to the second embodiment. The reflecting member 30 of the illumination device 2 according to the present embodiment includes three flat surfaces 31 a, 31 b, which are different from each other in the inclination of the parabolic surface 31 of the illumination device 1 with respect to the repetition direction of the projection 13 of the linear light guide element 10. 31c. When the reflecting portion has only a flat surface as described above, the light collecting function is reduced, but when the reflecting member 30 is manufactured by resin molding, the formation of the mold is facilitated.
[0038]
The prism-shaped convex portion 13 of the linear light guide element 10 has a trapezoidal cross section, and has a surface 16 in addition to the surfaces 14 and 15. The surface 16 re-enters the light transmitted through the lower part of the surface 14 of the adjacent protrusion 13. A part of the light re-entered from the surface 16 is reflected by the surface 14 and emerges from the lower surface 12 to become illumination light, and the rest is totally reflected by the lower surface 12 and travels further inside. The light traveling in the linear light guide element 10 is reduced as it is emitted as illumination light on the way, but as described above, the surface 16 is added, and a part of the light transmitted through the surface 14 travels further inside. By doing so, a decrease in the amount of light is suppressed, and illumination light can be provided to the planar light guide element 20 even at a portion far from the light emitting diode 40.
[0039]
FIG. 4 shows a vertical cross section of the linear light guide element 10 and the reflection member 30 of the illumination device 3 according to the third embodiment. This is one in which the linear light guide element 10 and the reflection member 30 are symmetrical with respect to the direction of repetition of the convex portions 13, and the light emitting diodes 40 are arranged on each of two end faces of the linear light guide element 10. . In this manner, illumination with high luminance can be achieved, and illumination with high uniformity can be achieved.
[0040]
FIG. 5 shows an enlarged longitudinal section of the linear light guide element 10 and the reflection member 30. The reflecting portion of the reflecting member 30 is a paraboloid like the lighting device 1 of the first embodiment. The angle β formed by the surface 14 of the projection 13 of the linear light guide element 10 with respect to the direction in which the projection 13 is repeated is set to 90 °. With this setting, the light reflected by the surface 14 becomes very small, and almost all the light constituting the illumination light La is transmitted through the surface 14 and reflected by the surface 31 of the reflecting member 30. As described above, the angle range of the light reflected by the surface 31 is smaller than the angle range of the light reflected by the surface 14, and therefore, in the present embodiment, the planar light guide element 20 is smaller than in the first embodiment. Can be further narrowed.
[0041]
The angle β formed by the surface 14 with respect to the repetition direction of the projections 13 does not need to be strictly 90 °, but may be in the range of 80 to 100 °. In this angle range, almost all light incident on the surface 14 passes through the surface 14.
[0042]
FIG. 6 shows a vertical cross section of the linear light guide element 10 and the reflection member 30 of the illumination device 4 according to the fourth embodiment. The illumination device 4 according to the present embodiment is obtained by modifying the illumination device 1 according to the first embodiment so that the lower surface 12 of the linear light guide element 10 is a plane inclined with respect to the upper surface 11. The lower surface 12 is closer to the upper surface 11 as the portion is farther from the light emitting diode 30.
[0043]
The light incident on the linear light guide element 10 includes a light parallel to the repetition direction of the convex portion 11 and a light very parallel to the repetition direction. If the upper surface 11 and the lower surface 12 are parallel to each other, such light directly reaches the downstream end surface without being incident on the upper surface 11 or the lower surface 12.
[0044]
As in the present embodiment, by forming the lower surface 12 as an inclined surface that rises along the traveling direction of light, the average optical path 17 of light when the upper surface 11 and the lower surface 12 are parallel is intersected with the lower surface 12. This makes it possible to effectively use light that is nearly parallel to the direction in which the protrusions 13 are repeated for illumination. Moreover, the position where the average optical path 17 of light when the upper surface 11 and the lower surface 12 are parallel to each other intersects the lower surface 12 can be set near the center of both end surfaces of the linear light guide element 10. Light close to the average light path 17 such as a principal ray can be emitted from a portion far from the light emitting diode 40 whose light quantity decreases due to emission on the way, and uniform illumination is facilitated.
[0045]
FIG. 7 shows an enlarged vertical cross section of the linear light guide element 10 and the reflection member 30 of the illumination device 5 according to the fifth embodiment. In the illumination device 5 of the present embodiment, the projection 13 of the linear light guide element 10 is provided on the lower surface 12 instead of the upper surface 11. The reflection member 30 is arranged to face the upper surface 11. The surface 15 (the surface descending along the light traveling direction) 15 of the convex portion 13 that is closer to the light emitting diode 40 causes the light to travel by total reflection together with the upper surface 11. On the other hand, the surface 14 (the surface rising along the light traveling direction) farther from the light emitting diode 40 generates light that passes through the upper surface 11 by reflection. The light reflected by the surface 14 and transmitted through the upper surface 11 is reflected by the reflecting member 30, re-enters the linear light guide element 10, and becomes illumination light emitted from the lower surface 12.
[0046]
The surface 31 forming each reflecting portion of the reflecting member 30 is a paraboloid having an axis in a direction perpendicular to the linear light guide element 10, as in the lighting device 1 of the first embodiment. However, the surface 31 has a width equal to the repetition pitch and is symmetric about the repetition direction. The focal point is located at the center of the surface 14 of the projection 13. The surface 32 that was present in the lighting device 1 does not exist in the lighting device 5.
[0047]
The light reflected on the surface 14 of the projection 13 of the linear light guide element 10 becomes substantially parallel light by being reflected on the surface 31 of the reflection member 30, and is substantially perpendicular to the upper surface 11 of the linear light guide element 10. Incident on. This light transmits through the upper surface 11 and further transmits through the lower surface 12, and is emitted as illumination light. When the light passes through the lower surface 11, the light passing through the surface 14 and the light passing through the surface 15 are generated, and the angle range of the light is slightly widened. Is small, and no light is lost when transmitted through the side surface of the planar light guide element 20.
[0048]
FIG. 8 shows an enlarged vertical cross section of the linear light guide element 10 and its periphery of the illumination device 6 of the sixth embodiment. The illumination device 6 of the present embodiment includes a light condensing member 50 facing the lower surface 12 of the linear light guide element 10. A plurality of convex surfaces 53 are provided on the upper surface 51 of the light collecting member 50. The convex surfaces 53 are provided at the same pitch as the repetition of the convex portions 13 in the direction in which the convex portions 13 of the linear light guide element 10 are repeated. Each convex surface 53 has a curvature (power) only in the repetition direction of the convex portion 13, functions as a cylindrical lens, and collects light reflected by the surface 14 of the convex portion 13 and emitted from the lower surface 12. To form a light condensing unit that makes the light substantially parallel.
[0049]
Instead of providing the convex surface 53 on the upper surface 51, a convex surface 53 may be provided on the lower surface 52. Further, the convex surface 53 may have power also in the width direction of the linear light guide element 10. When the degree of divergence of the light from the light emitting diode 40 is large, light having a small incident angle on the upper surface or the lower surface of the planar light guide element 20 exists, and such light is transmitted to the planar light guide element 20. However, the total reflection can be reliably performed by the planar light guide element 20 by giving the convex surface 53 the power in the width direction of the linear light guide element 10.
[0050]
Although the lighting device 6 of the present embodiment does not include the reflection member 30, the reflection member 30 and the light collection member 50 may be used in combination. The light emitted from the lower surface 12 may be made closer to parallel light by the light collecting function of the reflecting member 30 and the light collecting function of the light collecting member 50.
[0051]
In the case of a backlight illumination device, a reflecting member can be provided for the planar light guide element 20. FIG. 9 shows an optical configuration of an illumination device 7 according to a seventh embodiment, which is one example of the illumination device. The lighting device 7 is obtained by adding a reflecting member 60 to the lighting device 1 of the first embodiment. The reflection member 60 has the same configuration as the reflection member 30 for the linear light guide element 10 except for the width, and is arranged to face the upper surface of the planar light guide element 20.
[0052]
As described above, when the reflecting members 30 and 60 are provided for the linear light guide element 10 and the planar light guide element 20, respectively, the efficiency of use of light for illumination is greatly improved, and the illumination of the illumination target is improved. The range of the incident angle of light can be reduced. For example, when illuminating a transmissive liquid crystal display, a bright and high-quality image can be provided.
[0053]
When a front light illuminating device is used, a reflecting member such as the reflecting member 30 cannot be provided for the planar light guide element 20. In this case, a light collecting member similar to the light collecting member 50 of the sixth embodiment may be provided for the planar light guide element 20.
[0054]
【The invention's effect】
A prism-shaped convex portion is repeatedly provided on the upper surface or the lower surface, and light incident inside is totally reflected by the upper surface and the lower surface and travels in the direction of repetition of the convex portion, and is transmitted through the lower surface partly and emitted. An optical element, and a reflecting member disposed opposite to the upper surface of the light guide element to reflect the light transmitted through the upper surface and re-enter the light guide element, and emit light emitted from the lower surface of the light guide element for illumination. In the lighting device of the present invention, as in the present invention, the reflection member has a reflection portion repeatedly provided corresponding to the projection of the light guide element, and each reflection portion of the reflection member has a projection of the light guide element. If the reflecting surface is inclined with respect to the repetition direction of the portion, the angle of the light reflected by the reflecting member with respect to the upper surface and the lower surface of the light guide element can be made smaller than when the light is transmitted through the upper surface. The light transmitted through the upper surface of the optical element is It is possible to emit in the direction of the illumination light. Therefore, the light use efficiency is enhanced, and the illumination target can be illuminated from an appropriate direction.
[0055]
When each reflecting portion of the reflecting member has two or more flat reflecting surfaces, each reflecting portion can have a light collecting function, and the degree of divergence of illumination light can be reduced. In addition, the shape of the reflecting portion can be easily set.
[0056]
When each reflecting portion of the reflecting member has a concave curved reflecting surface, each reflecting portion can be provided with a highly accurate light collecting function, and the angle range of illumination light can be further reduced.
[0057]
When the projections of the light guide element are provided on the upper surface, and each projection has a surface that forms an angle of 80 ° or more and 100 ° or less with respect to the direction in which the projections are repeated, Light that travels through the surface easily passes through the surface, and most of the illumination light can be light reflected by the reflecting member. Therefore, it is easy to direct the illumination light in a desired direction, and if the reflection portion is provided with a light collecting function, the function is sufficiently exhibited, and it is easier to direct the illumination light in a desired direction. .
[0058]
A prism-shaped convex portion is repeatedly provided on the upper surface or the lower surface, and light incident inside is totally reflected by the upper surface and the lower surface and travels in the direction of repetition of the convex portion, and is transmitted through the lower surface partly and emitted. An illumination device comprising an optical element and using light emitted from the lower surface of the light guide element as illumination light, as in the present invention, having a light collecting section repeatedly provided corresponding to the convex portion of the light guide element. A light-collecting member is provided facing the lower surface of the light guide element, and each light-collecting portion of the light-collector member determines the degree of divergence of light emitted from the lower surface of the light guide element by repeating at least the convex portions of the light guide element. When the direction is reduced, the range of the incident angle of the illumination light to the illumination target can be narrowed, and the illumination target can be illuminated from an appropriate direction.
[0059]
If the light-collecting portion is set so as to reduce the degree of divergence only in the direction of repetition of the convex portion of the light guide element, it is easy to manufacture the light-collecting member, and the degree of divergence is also reduced in the width direction of the light guide element. If the condensing portion is set to be small, the illuminating object can be illuminated from an appropriate direction even when the degree of divergence of light incident on the light guide element is large in the width direction of the light guide element.
[Brief description of the drawings]
FIG. 1 is an exemplary perspective view showing an optical configuration of a lighting device according to a first embodiment;
FIG. 2 is an enlarged vertical cross-sectional view of a linear light guide element and a reflection member included in the illumination device of the first embodiment.
FIG. 3 is an enlarged vertical cross-sectional view of a linear light guide element and a reflection member included in a lighting device according to a second embodiment.
FIG. 4 is a vertical cross-sectional view of a linear light guide element and a reflection member included in a lighting device according to a third embodiment.
FIG. 5 is an enlarged vertical cross-sectional view of a linear light guide element and a reflection member included in a lighting device according to a third embodiment.
FIG. 6 is a longitudinal sectional view of a linear light guide element and a reflection member included in a lighting device according to a fourth embodiment.
FIG. 7 is an enlarged longitudinal sectional view of a linear light guide element and a reflection member included in a lighting device according to a fifth embodiment.
FIG. 8 is an enlarged vertical cross-sectional view of a linear light guide element and a light condensing member included in a lighting device according to a sixth embodiment.
FIG. 9 is a perspective view showing an optical configuration of a lighting device according to a seventh embodiment.
FIG. 10 is a perspective view showing an optical configuration of a conventional lighting device.
FIG. 11 is an enlarged longitudinal sectional view of a linear light guide element and a reflection member provided in a conventional lighting device.
[Explanation of symbols]
1-7 Lighting device
10 Linear light guide element
11 Top
12 Lower surface
13 convex part
14, 15, 16 Convex surface
20 Planar light guide element
23 convex
30 Reflective member
31 Reflective surface (reflective part)
31a, 31b, 31c Reflective surface (reflective part)
32 surface
40 light emitting diode
50 Condensing member
51 Top
52 bottom
53 convex surface (light condensing part)
60 Reflective member

Claims

A prism-shaped convex portion is repeatedly provided on the upper surface or the lower surface, and light incident inside is totally reflected by the upper surface and the lower surface and travels in the direction of repetition of the convex portion, and a part of the light is transmitted through the lower surface and emitted. An optical element, and a reflecting member disposed opposite to the upper surface of the light guide element, for reflecting light transmitted through the upper surface and re-entering the light guide element, and emitting light emitted from the lower surface of the light guide element for illumination. In a lighting device with light of
The reflection member has a reflection portion repeatedly provided corresponding to the convex portion of the light guide element,
An illumination device, wherein each reflecting portion of the reflecting member has a reflecting surface inclined with respect to a direction in which the convex portion of the light guide element is repeated.

The lighting device according to claim 1, wherein each reflecting portion of the reflecting member has two or more flat reflecting surfaces.

The lighting device according to claim 1, wherein each reflecting portion of the reflecting member has a concave curved reflecting surface.

The projection of the light guide element is provided on the upper surface, and each projection has a surface forming an angle of 80 ° or more and 100 ° or less with respect to the direction of repetition of the projection. The lighting device according to any one of claims 1 to 3.

A prism-shaped convex portion is repeatedly provided on the upper surface or the lower surface, and light incident inside is totally reflected by the upper surface and the lower surface and travels in the direction of repetition of the convex portion, and a part of the light is transmitted through the lower surface and emitted. An illumination device comprising an optical element and using light emitted from the lower surface of the light guide element as light for illumination,
A light-collecting member having a light-collecting portion repeatedly provided corresponding to the convex portion of the light-guiding element is provided facing the lower surface of the light-guiding element,
An illumination device, wherein each light condensing portion of the light converging member reduces the degree of divergence of light emitted from the lower surface of the light guide element at least in a direction in which the convex portion of the light guide element is repeated.