JP4138276B2 - Light guide plate and flat illumination device - Google Patents

Light guide plate and flat illumination device Download PDF

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JP4138276B2
JP4138276B2 JP2001221659A JP2001221659A JP4138276B2 JP 4138276 B2 JP4138276 B2 JP 4138276B2 JP 2001221659 A JP2001221659 A JP 2001221659A JP 2001221659 A JP2001221659 A JP 2001221659A JP 4138276 B2 JP4138276 B2 JP 4138276B2
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light
surface portion
incident
guide plate
light source
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JP2003035824A (en
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カリル カランタル
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日本ライツ株式会社
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Abstract

PROBLEM TO BE SOLVED: To maintain a necessary angle of field and to obtain uniform and light luminance. SOLUTION: A light guide plate 2 has an arcuately cut incidence part 8 in a corner 7 and a reverse-surface part 5 is provided with a projected or recessed ridge 9 which totally reflects the light from a light source 3 almost to a surface part 4 concentrically with the cut arcuate shape of the incidence part 8 and has a tilted surface 9a in the direction of the incidence part 8. The arcuate (radial) light from the light source 3 is guided in the light guide plate 2 from the incidence part 8 conforming with the arcuate shape and in similar fashion the incident light which travels arcuately is totally reflected almost to the surface part 4 by the tilted surface 9a tilting in the direction of the incident part 8, of the projected or recessed ridge 9 provided in the reverse- surface part 5 and concentrically with the accurate shape and emitted from the surface part 4; and a fine optical control element 13 which is provided at the surface part 4 and refracts the projection light, a polarizing sheet 11 in a prism shape of 60 to 80 deg. in vertical angle which is provided radially at a position corresponding to the ridge 9, etc., are used.

Description

【０００１】
【発明の属する技術分野】
本発明は、液晶表示装置等に用いる導光板および平面照明装置に関するものであり、導光板の少なくとも１つの隅を円弧状に欠切した入射部を有し、この欠切した円弧形状と同心に光源からの光を略表面部方向に全反射する入射部方向に傾斜面を持つ凸状や凹状の稜を裏面部に設け、輝度の高い出射光が得られ、さらに偏光シートや拡散シートを用いることで出射光をコントロールして目的とする視野角が得られ、明るく均一な光を得ることを目的とする導光板および平面照明装置に関する。
【０００２】
【従来の技術】
従来の導光板および平面照明装置は、液晶表示装置の大きさに無関係に輝度を上げるために、単に表面部や裏面部に設けた溝や凸や凹の形状のドット等の数量を入射端面部から反入射端面部方向に進むに従い増加させて、表面部からの出射光を均一にする様にする方法が知られている。
【０００３】
また、従来の光源がＬＥＤ等の点光源を用いた平面照明装置では、導光板の側面にＬＥＤを複数並べ、これらＬＥＤに対向する位置の導光板の側面部にプリズム等の凸や凹の形状を設け、導光板の隅部分的まで光線が達するようにしている。
【０００４】
【発明が解決しようとする課題】
従来の導光板および平面照明装置は、液晶表示装置の大きさに無関係に輝度を上げるために、単に表面部や裏面部に設けた溝や凸や凹の形状のドット等の数量を入射端面部から反入射端面部方向に進むに従い増加させて、表面部からの出射光を均一にする様にする方法なので、輝度的には溝や凸形状および凹形状を入射端面部から反入射端面部方向に進むに従い増加させることによって、導光板に対して輝度量を得ることはできる。しかし、側面側方向等に光のコーンの広がりを得ることができない課題がある。
【０００５】
また、従来の光源がＬＥＤ等の点光源を用いた平面照明装置では、導光板の側面にＬＥＤを複数並べ、これらＬＥＤに対向する位置の導光板の側面部にプリズム等の凸や凹の形状を設ける方法なので、プリズムによって全体としては両側面方向に光が進む。しかし、光源が点光源であるため、個々の光源からの左右方向に進む光線が左右方向で重なり合ってしまう部分が存在してしまい、全体として部分的な明暗が発生してしまう課題がある。
【０００６】
この発明は、このような課題を解決するためなされたもので、その目的は導光板の隅に円弧状に欠切した入射部を有し、裏面部に入射部の欠切した円弧形状と同心に光源からの光を略表面部方向に全反射する入射部方向に傾斜面を持つ凸状や凹状の稜を設け、光源からの円弧状（放射状）に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状（放射状）に進んだ入射光を裏面部に入射部方向に持つ傾斜面を入射部の円弧形状と同心位置に凸状や凹状の稜を設けて略表面部方向に全反射させて表面部から出射し、この出射光を表面部に設けた光を屈折させる微細な光制御素子や導光板に設けた稜に対応した位置に放射状に設けた頂角が６０〜８０度のプリズム形状をなした偏光シート等を用いることによって、必要視野角を維持し、均一で明るい輝度を得ることができる導光板および平面照明装置を提供することにある。
【０００７】
【課題を解決するための手段】
上記課題を解決するため請求項１に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う偏光シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したことを特徴とする。
【０００８】
請求項１に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う偏光シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射して表面部から導光板に沿ったように出射した光線を表面部から最短距離で完全に光偏光シートの凸状や凹状の稜に導き、光偏光シートによって略垂直方向に偏光して平面照明装置から出射することができる。
【０００９】
また、請求項２に係る導光板は、傾斜面を裏面部の仮想水平面と成す角度が０．０１度〜１０度の範囲であることを特徴とする。
【００１０】
請求項２に係る導光板は、傾斜面を裏面部の仮想水平面と成す角度が０．０１度〜１０度の範囲であるので、導光板内に存在する光線の大部分を仮想水平面と成す小さい角度の傾斜面により表面部方向に全反射することができる。
【００１１】
さらに、請求項３に係る導光板は、傾斜面を曲線または円弧状であることを特徴とする。
【００１２】
請求項３に係る導光板は、傾斜面を曲線または円弧状であるので、曲線または円弧状が内側にへこんだ稜の面に場合には、光を拡散し、また、曲線または円弧状が外側に膨らんだ稜の面の場合には、曲率と一致する場所では光を集光し、それ以上遠ざかると光を拡散するように出射光の出射角等可変することができる。
【００１３】
また、請求項４に係る導光板は、稜を連続または非連続に欠切した円弧形状と同心に設けることを特徴とする。
【００１４】
請求項４に係る導光板は、稜を連続または非連続に欠切した円弧形状と同心に設けるので、表面部や裏面部から出射光を稜に沿って全域に出射することができるばかりでなく、目的とする位置に部分的に出射することもできる。
【００１５】
さらに、請求項５に係る導光板は、稜を頂角が８０度〜１７９度の範囲であることを特徴とする。
【００１６】
請求項５に係る導光板は、稜を頂角が８０度〜１７９度の範囲であるので、導光板に於ける稜の角度変化に伴い稜の相互間の間隔を調整することができるとともに光源から離れるにしたがって稜の相互間のピッチを短く設定することもでき、さらに凸状または凹状の稜の高さまたは深さを設定することができる。
【００１７】
また、請求項６に係る導光板は、稜を頂角が平坦に欠切したことを特徴とする。
【００１８】
請求項６に係る導光板は、稜を頂角が平坦に欠切したので、例えば表面部のみに平坦に欠切させた稜を設け、裏面部の近傍に反射体を備えた場合には、表面部で全反射した光が裏面部方向に進み、裏面部から外部に出射した光線が反射体で反射して再度導光板に入射した光線は、表面部の稜の斜面では反射や屈折を行うが、本請求項に於ける平坦部では略ストレートに表面部から出射することができる。
【００１９】
さらに、請求項７に係る平面照明装置は、円弧状または放射状に出射する光源と、当該光源からの光を出射する表面部または裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部から入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を設け、光源からの光を傾斜面によって略表面部方向に全反射する導光板と、表面部を覆う偏光シートとを具備することを特徴とする。
【００２０】
請求項７に係る平面照明装置は、円弧状または放射状に出射する光源と、当該光源からの光を出射する表面部または裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部から入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を設け、光源からの光を傾斜面によって略表面部方向に全反射する導光板と、表面部を覆う偏光シートとを具備するので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射して表面部から導光板に沿ったように出射した光線を表面部から最短距離で完全に光偏光シートの凸状や凹状の稜に導き、光偏光シートによって略垂直方向に偏光して平面照明装置から出射することができる。
【００２１】
また、請求項２に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有するとともに表面部に光を屈折させる微細な光制御素子を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う拡散シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したことを特徴とする。
【００２２】
請求項２に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有するとともに表面部に光を屈折させる微細な光制御素子を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う拡散シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射して表面部方向に進んだ光線を表面部に設けた微細な光制御素子により表面部より出射し、この光線を拡散シートによって、拡散した光を出射することができる。
【００２３】
さらにまた、請求項３に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜連続または非連続に複数を設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う拡散シートまたは偏光シートと、
表面部および入射部以外の部分を覆う反射シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したことを特徴とする。
【００２４】
請求項３に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜連続または非連続に複数を設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う拡散シートまたは偏光シートと、
表面部および入射部以外の部分を覆う反射シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射したり、裏面部より少量の光やエネルギの低い光等を反射シートにより、隅無く再度導光板に戻して、表面部方向に進んだ光線を表面部に設けた微細な光制御素子により表面部より出射し、この光線を拡散シートによって、拡散した光を出射させたり、または表面部から導光板に沿ったように出射した光線を表面部から最短距離で完全に光偏光シートの凸状や凹状の稜に導き、光偏光シートによって略垂直方向に偏光して平面照明装置から出射することができる。
【００２５】
またさらに、請求項４に係る平面照明装置は、偏光シートを導光板に放射状に設けた稜に対応した位置に頂角が６０度〜８０度のプリズム形状を有することを特徴とする。
【００２６】
請求項４に係る平面照明装置は、偏光シートを導光板に放射状に設けた稜に対応した位置に頂角が６０度〜８０度のプリズム形状を有するので、導光板から導光板に沿ったように出射した光線を略垂直な上方に偏光することができるとともに目的に合わせて稜の相互間のピッチや稜の高さまたは深さを設定することができる。
【００２７】
【発明の実施の形態】
以下、本発明の実施の形態を添付図面に基づき説明する。
なお、本発明は、円弧状に欠切した入射部を導光板の隅に設けるとともに裏面部に入射部の欠切した円弧形状と同心位置に入射部方向に傾斜面を持つ凸状や凹状の稜を設け、光源からの円弧状（放射状）に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状（放射状）に進んだ入射光を傾斜面で全反射して略表面部から出射し、この出射光を表面部に設けた微細な光制御素子で屈折させたり、導光板の上部に備えた頂角が６０〜８０度のプリズム形状をなすとともに導光板に設けた稜と同様な放射状の偏光シート等を用いることによって、必要視野角を維持しながら均一で明るい輝度を得ることができる導光板および平面照明装置を提供することにある。
【００２８】
図１は本発明に係る平面照明装置の概略構成を示す分解斜視図、図２は本発明に係る導光板の裏面部に設けた稜の平面図、図３は図２の導光板の入射部と入射部から同心の稜の法線と直角方向７とを結ぶ線２ｃの導光板の部分断面図、図４は図３において導光板の表面部に光制御素子を設けた部分断面図、図５（ａ），（ｂ）、図６および図７は本発明に係る導光板に設けられる稜の他の構成例を示す部分拡大図、図８は本発明に係る平面照明装置の光偏光シートの平面図、図９は図８の光偏光シートの部分断面図、図１０は本発明に係る平面照明装置の光線の軌跡を示す図である。
【００２９】
図１の平面照明装置１は、導光板２、光源３、拡散シートまたは光偏光シート１１、反射体１５を備えて概略構成される。
【００３０】
光源３は、半導体発光素子であって、例えばＬＥＤやレーザ等からなる。この光源３としては、単色光やＲＧＢ（赤色、緑色、青色）からなる白色や蛍光材料を用いて波長変換することによって白色光にしたものも用いられる。
【００３１】
なお、本例では、導光板２の二つの側面部６が交差する隅７の一つに設けられる構成について説明するが、例えば対象位置の端部に複数の入射部８を持つ場合には、各入射部８に異なる発光色の光源３を用いて導光板２全体から白色の光を出射しても良い。
【００３２】
反射体１５は、熱可塑性樹脂に例えば酸化チタンのような白色材料を混入したシートや熱可塑性樹脂のシートにアルミニウム等の金属蒸着を施したり、金属箔を積層した物やシート状金属からなる。この反射体１５は、入射部８と表面部４以外の部分を覆い、光源３からの光が導光板２によって表面部４に出射した以外の光を反射または乱反射し、再び導光板２に入射させて光源３からの光を全て表面部４から出射するようにする。
【００３３】
導光板２は、屈折率が１．４〜１．７程度の透明なアクリル樹脂（ＰＭＭＡ）やポリカーボネート（ＰＣ）等で形成される。導光板２は、側面部６と、光の出射目的である表面部４と、その反対側に位置する裏面部５および光源３からの光を導く入射部８とを有する。
【００３４】
表面部４は、最終的な平面照明装置１の必要とする目的である視野角や輝度等の選択により鏡面とするか、または表面に光制御素子１３が設けられる。
【００３５】
図４に示すように、光制御素子１３は、微細（例えば５μｍ〜１００μｍ程度）な円弧形状、楕円、多角柱および多角錐等からなる凹形状または凸形状を成している。この光制御素子１３は、裏面部５から表面部４に向かう光線を屈折させる。また、光制御素子１３が特に微細な場合には、この光制御素子１３内で全反射等を行い、全体としては散乱光のような振る舞いをする。
【００３６】
また、光制御素子１３は、目的とする角度や輝度分布をコントロールするためにグラデーションを施してもよい。これにより、裏面部４からの色々の角度での視野角を持った光線を導光板２から出射する光に対して最適な視野角の分布や輝度の分布をコントロールすることができる。
【００３７】
入射部８は、導光板２の二つの側面部６が交差する隅７のうちの少なくとも１つを点光源３の放射光と同等な円弧状に欠切して形成される。図１の例では、導光板２の手前側の隅が円弧状に欠切されて入射部８が形成されている。
【００３９】
裏面部５には、導光板２の一端部（一隅部）に設けた入射部８の欠切した円弧形状と同心に入射部８方向に傾斜面９ａを持つ稜９が設けてられている。
【００４０】
更に説明すると、裏面部５には、図２や図３に示すように、入射部８である裏面部５の一端部位置と同心に凸状の稜９ｃや凹状の稜９ｄを有している。そして、一端部位置である入射部８を中心に同心を描くように凸状の稜９ｃ（奇数）および凹状の稜９ｄ（偶数）とが連続に形成され、複数の凸状の稜ライン９ｃｎおよび複数の凹状の稜ライン９ｄｎを形成している。
【００４１】
なお、図示しないが、裏面部５には、飛び飛びに凸状の稜９ｃを設け、二つの凸状の稜９ｃとの間を平面としてもよい。また、裏面部５に飛び飛びに凹状の稜９ｄを設けたり、凸状の稜９ｃや凹状の稜９ｄとの間を平面にすることも可能である。
【００４２】
図３に示すように、凸状の稜９ｃや凹状の稜９ｄは、傾斜面９ａや傾斜面９ｂを備えている。特に、傾斜面９ａは、常に光源３からの光が表面部４方向に全反射するように入射部８方向（図３の入射部８に対して右上がり方向）に傾きを持っている。
【００４３】
以上の構成により、光源３から入射して稜９ｃおよび稜９ｄに達した光線は、放射出射光の光源３から同距離にあるので、これらに対する任意の距離に於いて光エネルギが等しく出射される。
【００４４】
図３は図２に於ける入射部８と同心の稜９の法線と直角方向の隅７とを結ぶ線２ｃの断面の一部を示している。この図３に示すように、入射部８から放射状に裏面部５に設けた凸状の稜９ｃおよび凹状の稜９ｄは三角形状をしている。本例では、凸状の稜９ｃの角度θ１を８０度〜１７９度の範囲、凹状の稜９ｄの角度θ２を８０度〜１７９度の範囲としている。また、裏面部５の仮想水平面５１と成す角度θ３を０．０１度〜１０度の範囲としている。
【００４５】
なお、図３の例では、凸状の稜９ｃおよび凹状の稜９ｄの傾斜面９ａと傾斜面９ｂとが等しい形状としたが、本発明の目的とするように光源３からの光が表面部４方向に全反射するように常に傾斜面９ａが入射部８方向に傾きを持てば良い。従って、二等辺三角形でなくても良く、例えば傾斜面９ａのみを持ち、傾斜面９ｂを垂直にした直角三角形の形状でも良い。
【００４６】
以上のように各角度θ１，θ２およびθ３を設定することにより、図３に示すように、導光板２の一端部位置の入射部８から導光板２に光線が入射されると、導光板２内に存在する光は、導光板２に使用する材料によって屈折角が所定の範囲内になる。例えば導光板２の材料をポリカーボネート（ＰＣ）樹脂とした場合、ポリカーボネート樹脂の屈折率ｎ＝１．５９であるので、空気層から導光板２に光線Ｌ０が入射されると、導光板２内に存在する光は、０≦｜α｜≦ｓｉｎ-1（１／ｎ）（但し、ｎは空気層とし屈折率ｎ＝１）の式より、略屈折角α＝±３８．９７１３°の範囲内にある。
【００４７】
また、屈折角α＝±３８．９７１３°の範囲内で導光板２内に入射した光は、導光板２と空気層（屈折率ｎ＝１）との境界面では、ｓｉｎγ＝（１／ｎ）の式により臨界角を表わすことができる。例えば一般の導光板２に使用されている樹脂材料であるポリカーボネート樹脂の屈折率はｎ＝１．５９程度であるので、臨界角γはγ＝３８．９７°程度になる。なお、導光板２の材料としてアクリル樹脂（ＰＭＭＡ）材を用いた場合には、アクリル樹脂の屈折率ｎがｎ＝１．４９程度であり、屈折角αはα＝４２．３８°程度となるので、臨界角γもγ＝４２．３８°程度となる。
【００４８】
よって、表面部４が鏡面の場合、図３に示すように、最大屈折角αで表面部５や裏面部６方向に進んだ光線Ｌ１の中で表面部４方向に進んだ光線Ｌ１は、臨界角γより大きいので、表面部４で光線Ｌ１１として全反射する。この光線Ｌ１１は、裏面部５方向に向かい、仮想水平面５１と角度θ３でなす傾斜面９ｂに到達する。そして、ここでも傾斜面９ｂの垂線と成す角（入射角）が臨界角γよりも大きいため、光線Ｌ１１が傾斜面９ｂで光線Ｌ１２として全反射する。そして、光線Ｌ１２は、入射部８の反対側方向に進む。なお、ここでは図示しないが、光線Ｌ１２は、入射部８の反対側の側面部６の近傍に設けた反射体等により再度導光板２内に戻される。
【００４９】
また、図示はしないが、最大屈折角αで表面部５や裏面部６方向に進んだ光線Ｌ１が直接および表面部４で全反射し、この光線が仮想水平面５１と角度θ３でなす傾斜面９ａに向かった場合には、傾斜面９ａの垂線と成す角（入射角）が臨界角γよりも小さくなる。このため、上記表面部４で全反射した光線は、臨界角γを破り、屈折して裏面部５から出射する。このときの出射光は、エネルギが小さく直接的に導光板２の輝度に対する影響は少ないが、本例では全ての光を利用するため、図１に示す反射体１５により再度導光板２に戻して最終的には表面部４から出射させている。
【００５０】
さらに、屈折角αがやや小さい場合、図３に示すように、傾斜面９ａに到達した光線Ｌ２は、傾斜面９ａの垂線と成す角（入射角）が臨界角γよりも大きい。このため、光線Ｌ２が傾斜面９ａで光線Ｌ２１として全反射する。この全反射した光線Ｌ２１は表面部４方向に進む。そして、表面部４に達した光線Ｌ２１は、垂線と成す角（入射角）が臨界角γよりも小さいので、臨界角γを破り、屈折して表面部４より光線Ｌ２２として出射される。この光線Ｌ２２は、表面部４からある程度の角度で表面部４に沿ったように出射する。
【００５１】
また、図３に示すように、例えば光線Ｌ３のような屈折角αが小さな光線の場合には、傾斜面９ａの垂線と成す角（入射角）が臨界角γよりも大きい。このため、光線Ｌ３が傾斜面９ａで光線Ｌ３１として全反射する。この全反射した光線Ｌ３１は、表面部４に達するが、表面部４の垂線と成す角（入射角）が臨界角γよりも大きいので、光線Ｌ３０として再度裏面部５方向に進む。
【００５２】
以上の説明は導光板２の表面部４が鏡面の場合である。これに対し、図４に示すように、表面部４に光制御素子１３が設けられている場合には、光線Ｌ３のような屈折角αが小さな光線でも、傾斜面９ａで全反射をした光線Ｌ３１は表面部４に達する。しかし、表面部４に設けた光制御素子１３によって、この光制御素子１３に進んだ光線Ｌ３１での光制御素子１３の法線と直角に成す角（入射角）が臨界角γより小さい。このため、光線Ｌ３１は臨界角γを破り、屈折して光線Ｌ３０’として表面部４からある程度の角度で出射する。なお、光制御素子１３が無い時は全反射する。
【００５３】
また、同様に、図３で表面部４に沿ったように出射した光線Ｌ２２（図４中の破線）も表面部４に達した光線Ｌ２１は、表面部４に設けた光制御素子１３によって、この光制御素子１３に進んだ光線Ｌ３０での光制御素子１３の法線と直角に成す角（入射角）が臨界角γより小さい。このため、Ｌ２１は臨界角γを破り、屈折して光線Ｌ２２’として表面部４から光制御素子１３が無い時（Ｌ２２）よりも表面部４と成す角度が大きな角度で出射する。
【００５４】
このように、本例では、入射部８から放射状に表面部５に設けた凸状の稜９ｃおよび凹状の稜９ｄの法線と直角方向の断面の三角形状の角度範囲に於いて、表面部４から出射する光線の大部分は、裏面部５に設けた凸状の稜９ｃの傾斜面９ｂで全反射した光線となる。
【００５５】
なお、導光板２の中に存在する（略屈折角α＝±３８．９７１３°の範囲内）光線のうち、屈折角αが小さいほど光のエネルギが大きく、このエネルギが大きい光線は直接出射する光線でなく、一度凸状の稜９ｃの傾斜面９ａで全反射した光線が主なものである。すなわち、表面部４から出射する光線の大部分は、裏面部５に設けた凸状の稜９ｃの傾斜面９ａで全反射した光のエネルギが大きな光線である。
【００５６】
また、これら出射光は、表面部４側に傾いたように出射する。従って、図示しないフィルム状の拡散シートや図１に於けるフィルム状の光偏光シート１１および反射体１５等を用いず、例えば導光板２を上下逆に用いて表面部４から下方向に出射させることにより、反射型液晶パネルに光を投射し、反射型液晶パネルからの反射光を導光板２を透過させるようなフロントライトに用いることができる。
【００５７】
さらに、光源３から離れるにしたがって凸状の稜９ｃや凹状の稜９ｄ等の相互間のピッチを変化させたり、凸状の稜９ｃの稜の高さや凹状の稜９ｄの深さを設定することによって、傾斜面９ａに達する光線量を変化させることで出射光量を変えることができる。
【００５８】
また、図５（ａ）に示すように、導光板２の裏面部５に凸状の稜９ｃや凹状の稜９ｄを連続に形成した場合、光源３から入射して稜９ｃおよび稜９ｄに達した光線は放射出射光の光源３から同距離にあり、これらに対応する任意の距離の稜全ての光エネルギが等しく出射される。
【００５９】
さらに、図５（ｂ）に示すように、導光板２の裏面部５に凸状の稜９ｃや凹状の稜９ｄを非連続に形成した場合、凸状の稜９ｃや凹状の稜９ｄの間に平坦な鏡面９０を有し、光源３から入射し稜９ｃおよび稜９ｄに達した光線は放射出射光の光源３から同距離にあるが、これらに対応する任意の距離にある稜のみ光エネルギが等しく出射される。これにより、表面部５からの出射光を目的とする位置に部分的に出射することができる。
【００６０】
また、図６に示すように、導光板２の裏面部５に形成される稜は、三角形状の稜部を平坦に欠切した平坦部９１および平坦部９２を設けたものであってもよい。さらに、図示しないが、例えば表面部４の稜９ｃや稜９ｄに平坦に欠切させた平坦部９１や平坦部９２を設け、裏面部５の近傍に反射体を備えた構成とすることができる。この場合には、表面部４で全反射した光が直接裏面部５方向に進んだ光を裏面部５から外部に出射する。そして、この出射した光線が反射体１５で反射し、再度導光板２に入射した光線は、表面部４の稜９ｃや稜９ｄの傾斜面９ａや傾斜面９ｂでは反射や屈折を行うが、平坦部９１や平坦部９２では概略ストレートに表面部４から出射することができる。
【００６１】
さらに、図７に示すように、導光板２の裏面部５の三角形状の稜の隣り合った傾斜面９ａや傾斜面９ｂを曲線または円弧状にしてもよい。図７では、曲線または円弧状が内側にへこんだ稜の傾斜面９ａおよび傾斜面９ｂを示している。これにより、導光板２内に存在した光は、このへこんだ凹状の稜の傾斜面９ｂに達すると、この傾斜面９ｂの法線に対して出射角が直線の稜よりも大きくなり、外側寄りに拡散した状態となる。
【００６２】
また、図示しないが、曲線または円弧状が外側に膨らんだ稜の面の場合、導光板２内に存在した光は、この膨らんだ凸状の稜の傾斜面９ａや傾斜面９ｂに達すると、この面の法線に対して出射角が直線の稜よりも小さくなり、内側寄り状態となり、曲率と一致する場所では光を集光し、それ以上遠ざかると光を拡散する。そして、導光板２の三角形状の稜の隣り合った傾斜面９ａや傾斜面９ｂを曲線または円弧状にした場合には、出射光の出射角等を可変することができる。
【００６３】
なお、ここでの凸状の稜９ｃおよび凹状の稜９ｄの傾斜面９ａや傾斜面９ｂが等しい形状としたが、本発明の目的とする表面部４に出射するため、光源３からの光を表面部４方向に全反射する入射部８方向に傾斜面９ａを有すれば良い。従って、二等辺三角形でなくとも良く、例えば傾斜面９ａのみを持ち、傾斜面９ｂを垂直にした直角三角形の形状でも良い。
【００６４】
さらに、導光板２の上部にフィルム状の拡散シートを用いれば、導光板２の表面部４から任意の方向や特定の方向に出射した光線を拡散することができる。その際、平面照明装置１からの出射光としては、広い視野角を得ることができるとともに本発明の導光板２により高輝度の出射光を得ることができる。
【００６５】
ところで、導光板２の上部に配設される部材としては、拡散シートの他、図８および図９に示す光偏光シート１１を用いることができる。
【００６６】
光偏光シート１１は、アクリル樹脂（ＰＭＭＡ）やポリカーボネート（ＰＣ）等の透明樹脂からフィルム状に成形される。光偏光シート１１は、導光板２に対応させた形状を有し、図９に示すように、断面が三角形状をし、凸状の稜１０ａや凹状の稜１０ｂからなる。光偏光シート１１は、導光板２と同様に、導光板２の使用法により、図示しないが飛び飛びに凸状の稜１０ａを設けたり、飛び飛びに凹状の稜１０ｂを設けたり、凸状の稜１０ａや凹状の稜１０ｂとの間を平面にすることも可能である。
【００６７】
また、光偏光シート１１は、図９に示すように、凸状の稜１０ａの角度θ５や凹状の稜１０ｂの角度θ６を６０度〜８０度の範囲としている。また、光偏光シート１１は、表面部１２と平行な仮想水平面１１ａと成す角度θ７を２０度〜６０度の範囲としている。
【００６８】
さらに、光偏光シート１１は、導光板２と対応させるために、光源３が導光板２の入射部８から放射状に片面に、ここでは表面部１２の裏側に設けた凸状の稜１０ａおよび凹状の稜１０ｂを導光板２の入射部８と同等の１１ｂと同心の稜の法線と直角方向の１１ｄとを結ぶ線１１ｃｂに図９の断面の三角形状を設ける。
【００６９】
また、光偏光シート１１は、導光板２と同様に凸状の稜１０ａがライン１０ａ１および凹状の稜１０ｂがライン１０ｂ１のように放射状に設けられ、凸状の稜１０ａをライン１０ａ１，１０ａ２（奇数）とし、凹状の稜１０ｂをライン１０ｂ１，１０ｂ２（偶数）として、凸状および凹状の稜が交互または連続に（ライン１０ａｎや１０ｂｎ）形成されている。
【００７０】
なお、ここでの凸状稜１０ａおよび凹状稜１０ｂの辺１２ａと辺１２ｂとが等しい形状としたが、導光板２の表面部４からの出射光に合わせた形状とすればよく、二等辺三角形でなくても良い。
【００７１】
図１０は本発明に係る平面照明装置１の導光板２と光偏光シート１１の一部拡大側面図である。図１０における平面照明装置１は、光偏光シート１１を導光板２の上部に備えている。光偏光シート１１は、凸状稜１０ａが導光板２に設けた凸状の稜９ｃに対向するように導光板２の表面部４側に向けて配置される。そして、導光板２の一端部である隅７に形成された入射部８に対面して光源３が配置される。
【００７２】
ここでは、導光板２や光偏光シート１１についての説明は先に説明したことと重複するので、その説明については省略し、光の軌跡等の説明を行う。
【００７３】
図１０において、傾斜面９ａに到達した光線Ｌ２は、傾斜面９ａの垂線と成す角（入射角）が臨界角γよりも大きい。このため、光線Ｌ２は、傾斜面９ａで光線Ｌ２１として全反射する。この全反射した光線Ｌ２１は表面部４方向に進む。表面部４に達した光線Ｌ２１は、垂線と成す角（入射角）が臨界角γよりも小さいので、臨界角γを破り、屈折して光線Ｌ２２として導光板２の表面部４から出射する。この光線Ｌ２２は、光偏光シート１１の凸状の稜１０ａの辺１２ｂに到達する。そして、ここでも導光板２と光偏光シート１１との材質が同じ（ポリカーボネート（ＰＣ））であり、空気層から空気よりも屈折率の大きい光偏光シート１１の辺１２ｂに対する光線Ｌ２２は、辺１２ｂで屈折して光偏光シート１１内に光線Ｌ２３となって進む。
【００７４】
さらに、光線Ｌ２３は、光偏光シート１１内の辺１２ａに到達し、ここでの入射角が臨界角γ＝３８．９７°よりも大きい。このため、光線Ｌ２３は、辺１２ａで光線Ｌ２４として全反射する。この全反射した光線Ｌ２４は、光偏光シート１１の表面部１２方向に進む。
【００７５】
そして、光線Ｌ２４は、光偏光シート１１の表面部１２での入射角が臨界角γ＝３８．９７°よりも小さいので、表面部１２から略垂直に光線Ｌ２５を出射する。
【００７６】
このように、光偏光シート１１は、導光板２からの低く導光板２に沿ったような光線を、全反射を利用して光偏光シート１１に対して略垂直方向に光を出射することができる。
【００７７】
また、例えば光線Ｌ３の場合には、傾斜面９ａの垂線と成す角（入射角）が臨界角γよりも大きい。このため、光線Ｌ３は、傾斜面９ａで光線Ｌ３１として全反射する。この全反射した光線Ｌ３１は、表面部４に設けた光制御素子１３に達し、光制御素子１３の法線と直角に成す角（入射角）が臨界角γより小さい。このため、光線Ｌ３１は、臨界角γを破り、屈折して光線Ｌ３０’として出射される。そして、光線Ｌ３０’は、光偏光シート１１内に光線Ｌ３２となって進む。
【００７８】
さらに、光線Ｌ３２は、光偏光シート１１内の辺１２ａに到達する。ここでの光線Ｌ３２の入射角は、臨界角γ＝３８．９７°よりも大きい。このため、光線Ｌ３２は、辺１２ａで光線Ｌ３３として全反射する。この全反射した光線Ｌ３３は、光偏光シート１１の表面部１２方向に進む。
【００７９】
光線Ｌ３３は、光偏光シート１１の表面部１２での入射角が臨界角γ＝３８．９７°よりも小さい。このため、光線Ｌ３３は、表面部１２から略垂直に光線Ｌ３４として出射する。
【００８０】
ところで、図１０の構成において、光偏光シート１１の上部に拡散シートを用いるようにしてもよい。この場合、光偏光シート１１からの高輝度の光線が拡散シートにより拡散される。これにより、導光板２の表面部４から任意の方向や特定の方向に出射した光線を拡散し、平面照明装置１からの出射光としては、高輝度で視野角の広い出射光を得ることができる。
【００８１】
以上説明したように、本発明の平面照明装置１によれば、導光板２の裏面部５に光源３の放射光に略等しい円弧形状に欠切した入射部８を設けるとともに常に光源３からの光を表面部４方向に全反射させる入射部８方向に傾斜面９ａを持つ稜９ｃまたは稜９ｄを入射部８と同心に設け、表面部４に設けた微細な光制御素子や光偏光シートによって輝度の高い光線を出射させることができる。さらに、拡散シートにより出射光を拡散して視野の広い出射光を平面照明装置１から出射することができる。
【００８２】
また、本発明の導光板２および拡散シートや光偏光シート１１等を備えた平面照明装置１は、少ない点光源３でも、光源３の位置する所から導光板２の表面部４に放射状に稜をもたせ、どこでも一定の光エネルギを与え、導光板２内に入射した光線の中でも光のエネルギの大きな光線を導光板２から任意の角度で出射することができる。そして、この光線を光偏光シート１１で略垂直方向に偏光したり、拡散シートで拡散することにより、平面照明装置１として、視野角の広い高輝度の出射光を得ることができる。
【００８３】
このように、本発明の導光板および平面照明装置は、導光板の隅に円弧状に欠切した入射部を設けるとともに裏面部に入射部の欠切した円弧形状と同心位置に入射部方向に傾斜面を持つ凸状や凹状の稜を設け、光源からの円弧状（放射状）に出射した光を円弧状に一致した円弧形状の入射部から導光板内に取り込み、同様に円弧状（放射状）に進んだ入射光を傾斜面で全反射して略表面部から出射し、この出射光を表面部に設けた微細な光制御素子で屈折させたり、導光板の上部に備えた頂角が６０〜８０度のプリズム形状をなすとともに導光板に設けた稜と同様な放射状の偏光シート等を用いることにより、必要視野角を維持しながら均一で明るい輝度を得ることができる。
【００８４】
【発明の効果】
以上のように、請求項１に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う偏光シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射して表面部から導光板に沿ったように出射した光線を表面部から最短距離で完全に光偏光シートの凸状や凹状の稜に導き、光偏光シートによって略垂直方向に偏光して平面照明装置から出射することができる。これにより、液晶表示装置等に用いた場合には明るく斑が無く適度の視野角を得ることができる。
【００８５】
また、請求項２に係る導光板は、傾斜面を裏面部の仮想水平面と成す角度が０．０１度〜１０度の範囲であるので、導光板内に存在する光線の大部分を仮想水平面と成す小さい角度の傾斜面により表面部方向に全反射することができる。これにより、光源からのエネルギの高い光線を表面部に進ませ、表面部に設けた微細な光制御素子や表面部近傍に備えた光偏光シート等により出射することができる。
【００８６】
さらに、請求項３に係る導光板は、傾斜面を曲線または円弧状であるので、曲線または円弧状が内側にへこんだ稜の面に場合には、光を拡散し、また、曲線または円弧状が外側に膨らんだ稜の面の場合には、曲率と一致する場所では光を集光し、それ以上遠ざかると光を拡散するように出射光の出射角等可変することができ、目的に合った設計をすることができる。
【００８７】
また、請求項４に係る導光板は、稜を連続または非連続に欠切した円弧形状と同心に設けるので、表面部や裏面部から出射光を稜に沿って全域に出射することができるばかりでなく、目的とする位置に部分的に出射することもできる。これにより、視野角のコントロールや輝度のコントロール等を行うことができる。
【００８８】
さらに、請求項５に係る導光板は、稜を頂角が８０度〜１７９度の範囲であるので、導光板に於ける稜の角度変化に伴い稜の相互間の間隔を調整することができるとともに光源から離れるにしたがって稜の相互間のピッチを短く設定することもできる。さらに、凸状または凹状の稜の高さまたは深さを設定することができるので、光源から離れるほど稜の相互間のピッチを短くしたり、凸状の稜の高さを高く、または凹状の稜の深さを深くすることによって、光源からの光強度の減衰分を出射量でコントロールすることにより均一な出射光を得ることができる。
【００８９】
また、請求項６に係る導光板は、稜を頂角が平坦に欠切したので、例えば表面部のみに平坦に欠切させた稜を設け、裏面部の近傍に反射体を備えた場合には、表面部で全反射した光が裏面部方向に進み、裏面部から外部に出射した光線が反射体で反射して再度導光板に入射した光線は、表面部の稜の斜面では反射や屈折を行うが、本請求項に於ける平坦部では略ストレートに表面部から出射することができる。これにより、例えばフロントライトの様な使用法に於いて直進光を導光板の上部から観測することができる。
【００９０】
さらに、請求項７に係る平面照明装置は、円弧状または放射状に出射する光源と、当該光源からの光を出射する表面部または裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部から入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を設け、光源からの光を傾斜面によって略表面部方向に全反射する導光板と、表面部を覆う偏光シートとを具備するので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射して表面部から導光板に沿ったように出射した光線を表面部から最短距離で完全に光偏光シートの凸状や凹状の稜に導き、光偏光シートによって略垂直方向に偏光して平面照明装置から出射することができる。これにより、液晶表示装置等に用いた場合には明るく斑が無く適度の視野角を得ることができる。
【００９１】
また、請求項２に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有するとともに表面部に光を屈折させる微細な光制御素子を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う拡散シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射して表面部方向に進んだ光線を表面部に設けた微細な光制御素子により表面部より出射し、この光線を拡散シートによって、拡散した光を出射することができる。これにより、導光板の大きさに左右されずに明るく光源の輝度に対応した輝度分布を得ることができ、且つ視野角の広い出射光を得ることができる。
【００９２】
さらに、請求項３に係る平面照明装置は、円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、表面部の反対側に位置する裏面部と、これら表面部と裏面部とに直角に交わる側面部と、この二つの側面部が交差する隅の少なくとも１つを光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、裏面部に入射部の欠切した円弧形状と同心に円弧状または放射状に広がりを持って入射部方向に傾斜面を持つ凸状または／および凹状の稜連続または非連続に複数を設け、光源からの円弧状または放射状の光を傾斜面によって略表面部方向に全反射する導光板と、
表面部を覆う拡散シートまたは偏光シートと、
表面部および入射部以外の部分を覆う反射シートとを具備し、
光源の互いに隣合う２つの側面が交差する端部位置と導光板の円弧状に欠切した入射部とが対向する位置で入射部の欠切部分内に光源を配置したので、光源からの円弧状に出射した光を円弧状に一致した入射部から導光板内に取り込み、同様に円弧状に伝播した入射光を裏面部に設けた円弧形状と同心な凸状や凹状の稜の入射部方向に持つ傾斜面によって、同心領域のどこでも均一に全反射したり、裏面部より少量の光やエネルギの低い光等を反射シートにより、隅無く再度導光板に戻して、表面部方向に進んだ光線を表面部に設けた微細な光制御素子により表面部より出射し、この光線を拡散シートによって、拡散した光を出射させたり、または表面部から導光板に沿ったように出射した光線を表面部から最短距離で完全に光偏光シートの凸状や凹状の稜に導き、光偏光シートによって略垂直方向に偏光して平面照明装置から出射することができる。これにより、導光板の大きさに左右されずに明るく光源の輝度に対応した輝度分布を得ることができ、且つ視野角の広い出射光を得ることができる。
【００９３】
また、請求項４に係る平面照明装置は、偏光シートを導光板に放射状に設けた稜に対応した位置に頂角が６０度〜８０度のプリズム形状を有するので、導光板から導光板に沿ったように出射した光線を略垂直な上方に偏光することができるとともに目的に合わせて稜の相互間のピッチや稜の高さまたは深さを設定することができる。そして、本平面照明装置に対して略垂直な光を出射し、導光板からの出射光を取り込む光量をコントロールすることにより、出射光分布を均一にすることができる。
【図面の簡単な説明】
【図１】本発明に係る平面照明装置の略斜視構成図
【図２】本発明に係る導光板の裏面部に設けた稜の平面図
【図３】図２の導光板の部分断面図
【図４】図３における導光板の表面部に光制御素子を設けた導光板の部分断面図
【図５】（ａ），（ｂ）本発明に係る導光板に設けられる稜の他の構成例を示す部分拡大図
【図６】本発明に係る導光板に設けられる稜の他の構成例を示す部分拡大図
【図７】本発明に係る導光板に設けられる稜の他の構成例を示す部分拡大図
【図８】本発明に係る平面照明装置の光偏光シートの平面図
【図９】図８の光偏光シートの部分断面図
【図１０】本発明に係る平面照明装置の導光板と光偏光シートの一部拡大側面図であり、光線の軌跡を示す図
【符号の説明】
１…平面照明装置、２…導光板、２ｃ，１１ｃ…線、３…光源、４，１２…表面部、５…裏面部、６…側面部、７…隅、８…入射部、９…稜、９ａ，９ｂ…傾斜面、９ｃ…凸稜、９ｄ…凹稜、９ｃｎ…凸稜ライン、９ｄｎ…凹稜ライン、１５…反射体、１３…微細光制御素子、１１…光偏光シート、ｎ…屈折率、５１，６１，１０ａ，１０ａ１，１０ａ２，１０ａｎ…凸状稜、５２，６２，１０ｂ，１０ｂ１，１０ｂ２，１０ｂｎ…凹状稜、５１…仮想水平線、１１ｄ…光源と同心の法線の垂直方向の点、９１，９２…平坦部、９ａ１，９ｂ１…曲面稜、１２ａ，１２ｂ…辺、α…屈折角、θ１，θ５…凸状稜の角度、θ２，θ６…凹状稜の角度、θ３，θ７…仮想水平線と成す角度、γ…臨界角、Ｌ０，Ｌ１，Ｌ２，Ｌ２１，Ｌ３，Ｌ２２，Ｌ２２’，Ｌ３１，Ｌ３０’，Ｌ１２，Ｌ３０，Ｌ１１，Ｌ３２，Ｌ３３，Ｌ３４，Ｌ２３，Ｌ２４，Ｌ２５…光線。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light guide plate and a flat illumination device used for a liquid crystal display device or the like, and has an incident portion in which at least one corner of the light guide plate is cut out in an arc shape, and is concentric with the cut out arc shape. A convex or concave ridge with an inclined surface in the direction of the incident portion that totally reflects light from the light source substantially in the direction of the front surface portion is provided on the back surface portion to obtain a high-luminance outgoing light, and a polarizing sheet or a diffusion sheet is used. The present invention relates to a light guide plate and a flat illumination device that are intended to obtain light and uniform light by controlling emitted light to obtain a desired viewing angle.
[0002]
[Prior art]
Conventional light guide plates and flat lighting devices simply increase the number of grooves, convex or concave dots, etc. provided on the front and back surfaces to increase the luminance regardless of the size of the liquid crystal display device. A method is known in which the light emitted from the surface portion is made uniform by increasing in the direction toward the non-incident end face portion.
[0003]
Further, in a conventional flat illumination device using a point light source such as an LED, a plurality of LEDs are arranged on the side surface of the light guide plate, and a convex or concave shape such as a prism is formed on the side surface portion of the light guide plate at a position facing these LEDs. The light beam reaches the corner part of the light guide plate.
[0004]
[Problems to be solved by the invention]
Conventional light guide plates and flat lighting devices simply increase the number of grooves, convex or concave dots, etc. provided on the front and back surfaces to increase the luminance regardless of the size of the liquid crystal display device. Since the light emitted from the surface is made uniform as it goes from the incident end surface toward the non-incident end surface, the groove, convex shape, and concave shape from the incident end surface toward the anti-incident end surface The luminance amount can be obtained with respect to the light guide plate by increasing it as proceeding to. However, there is a problem that the spread of the cone of light cannot be obtained in the side surface direction or the like.
[0005]
Further, in a conventional flat illumination device using a point light source such as an LED, a plurality of LEDs are arranged on the side surface of the light guide plate, and a convex or concave shape such as a prism is formed on the side surface portion of the light guide plate at a position facing these LEDs. The light travels in the direction of both sides as a whole by the prism. However, since the light source is a point light source, there is a portion where light beams traveling in the left-right direction from the individual light sources overlap in the left-right direction, and there is a problem that partial brightness occurs as a whole.
[0006]
The present invention has been made to solve such a problem, and the object thereof is to have an incident part cut out in an arc shape at the corner of the light guide plate, and to be concentric with the arc shape in which the incident part is cut out on the back surface part. A convex or concave ridge with an inclined surface in the direction of the incident part that totally reflects light from the light source substantially in the direction of the surface part is provided, and the light emitted in a circular arc shape (radial) from the light source coincides with the circular arc shape. A convex or concave ridge is provided concentrically with the arc shape of the incident portion on the back surface of the incident light that enters the light guide plate from the same portion and has an incident light that advances in a circular arc shape (radially) in the direction of the incident portion. The light is emitted from the surface part after being totally reflected in the direction of the surface part, and the emitted light is radially provided at positions corresponding to the ridges provided on the light control plate or the light guide plate that refracts the light provided on the surface part. By using a polarizing sheet having a prism shape with an angle of 60 to 80 degrees, Maintaining the corners, it is to provide a light guide plate and a plane illumination device capable of obtaining a uniform and bright luminance.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, a flat illumination device according to claim 1 is provided. ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and the arc shape or radial light is incident from the entire incident portion and proceeds while spreading radially. To correspond to light, a convex or / and concave ridge having an arcuate or radial extension concentrically with the arc shape with the incident portion cut off on the back surface and having an inclined surface in the direction of the incident portion is continuous or non-contiguous. A plurality of light guide plates that are continuously provided, and that totally reflects the arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A polarizing sheet covering the surface portion,
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. It is characterized by that.
[0008]
The flat illumination device according to claim 1 ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and the arc shape or radial light is incident from the entire incident portion and proceeds while spreading radially. To correspond to light, a convex or / and concave ridge having an arcuate or radial extension concentrically with the arc shape with the incident portion cut off on the back surface and having an inclined surface in the direction of the incident portion is continuous or non-contiguous. A plurality of light guide plates that are continuously provided, and that totally reflects the arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A polarizing sheet covering the surface portion,
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. Therefore, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion coincident with the circular arc shape, and similarly, the incident light propagated in the circular arc shape has a convex shape concentric with the circular arc shape provided on the back surface portion. Due to the inclined surface of the concave ridge in the direction of the incident part, the light beam emitted from the surface part along the light guide plate is totally totally reflected anywhere in the concentric region, and is completely projected at the shortest distance from the surface part. Can be guided to a ridge having a shape or a concave shape, and can be polarized in a substantially vertical direction by the light polarizing sheet and emitted from the flat illumination device.
[0009]
The light guide plate according to claim 2 is characterized in that an angle between the inclined surface and the virtual horizontal surface of the back surface portion is in the range of 0.01 degrees to 10 degrees.
[0010]
Since the angle which makes an inclined surface and the virtual horizontal surface of a back surface part is the range which is 0.01 degree-10 degree | times, the light guide plate which concerns on Claim 2 is small which comprises most virtual rays which exist in a light guide plate with a virtual horizontal surface. Total reflection in the direction of the surface portion can be achieved by the inclined surface of the angle.
[0011]
Furthermore, the light guide plate according to claim 3 is characterized in that the inclined surface is curved or arcuate.
[0012]
The light guide plate according to claim 3 has a curved surface or an arc shape on the inclined surface, and therefore diffuses light when the curved surface or the arc shape is indented on the inside, or the curved surface or the arc shape is on the outside. In the case of a ridge surface that swells, light can be collected at a location that matches the curvature, and the outgoing angle of the outgoing light can be varied to diffuse the light further away.
[0013]
The light guide plate according to a fourth aspect is characterized in that the light guide plate is provided concentrically with an arc shape in which a ridge is continuously or discontinuously cut.
[0014]
Since the light guide plate according to claim 4 is provided concentrically with the circular arc shape in which the ridges are cut continuously or discontinuously, not only can the emitted light be emitted from the front surface portion and the back surface portion along the ridge to the entire area. In addition, it can be partially emitted to a target position.
[0015]
Furthermore, the light guide plate according to claim 5 is characterized in that the apex angle of the ridge is in the range of 80 degrees to 179 degrees.
[0016]
In the light guide plate according to claim 5, since the apex angle of the ridge is in the range of 80 degrees to 179 degrees, the distance between the ridges can be adjusted with the change in the angle of the ridge in the light guide plate, and the light source The pitch between the ridges can be set shorter as the distance from the object increases, and the height or depth of the convex or concave ridge can be set.
[0017]
Further, the light guide plate according to claim 6 is characterized in that the ridge is notched so that the apex angle is flat.
[0018]
In the light guide plate according to claim 6, since the apex of the ridge is cut out flat, for example, a ridge cut out flat only on the front surface portion is provided, and when a reflector is provided in the vicinity of the back surface portion, The light totally reflected at the front surface proceeds in the direction of the back surface, and the light beam emitted from the back surface portion to the outside is reflected by the reflector and reenters the light guide plate, and is reflected or refracted on the slope of the ridge of the surface portion. However, in the flat part in this claim, it can radiate | emit from a surface part substantially straight.
[0019]
Furthermore, the flat illumination device according to claim 7 includes a light source that emits in an arc shape or a radial shape, a front surface portion or a back surface portion that emits light from the light source, and a side surface portion that intersects the front surface portion and the back surface portion at a right angle. And at least one of the corners where the two side surfaces intersect has an incident portion cut out in an arc shape that matches the light emitted in an arc shape or a radial shape. In order to correspond to the light that enters from the incident part and travels while spreading radially, Arc or radial concentric with the arc shape with the incident part cut off on the back With expanse A convex or / and concave ridge with an inclined surface in the direction of the incident part The light from the light source is totally reflected by the inclined surface toward the surface portion. A light guide plate and a polarizing sheet covering the surface portion are provided.
[0020]
The flat illumination device according to claim 7 is a light source that emits in an arc shape or a radial shape, a front surface portion or a back surface portion that emits light from the light source, and a side surface portion that intersects the front surface portion and the back surface portion at a right angle, At least one of the corners where the two side surfaces intersect has an incident portion cut out in an arc shape that matches the light emitted in an arc shape or a radial shape. In order to correspond to the light that enters from the incident part and travels while spreading radially, Arc or radial concentric with the arc shape with the incident part cut off on the back With expanse A convex or / and concave ridge with an inclined surface in the direction of the incident part The light from the light source is totally reflected by the inclined surface toward the surface portion. Since the light guide plate and the polarizing sheet covering the surface portion are provided, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion coincident with the circular arc shape, and similarly the incident light propagated in the circular arc shape is received. Convex and concave ridges concentric with the circular arc shape provided on the back surface, and the light rays emitted from the surface portion along the light guide plate are totally reflected anywhere in the concentric region by the inclined surface. The light polarizing sheet can be completely guided to the convex or concave ridge of the light polarizing sheet at the shortest distance from the surface portion, and can be polarized in a substantially vertical direction by the light polarizing sheet and emitted from the flat illumination device.
[0021]
A flat illumination device according to claim 2 ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in a circular arc shape or a radial shape, and has a fine light control element that refracts light on the surface portion. Inclined in the direction of the incident part with an arc or radial extension concentrically with the arc shape with the incident part cut off on the back surface so as to correspond to the light that travels while spreading in an arc or radial direction. A plurality of convex or / and concave ridges having a surface continuously or discontinuously, and a light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A diffusion sheet covering the surface portion,
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. It is characterized by that.
[0022]
The flat illumination device according to claim 2 ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in a circular arc shape or a radial shape, and has a fine light control element that refracts light on the surface portion. Inclined in the direction of the incident part with an arc or radial extension concentrically with the arc shape with the incident part cut off on the back surface so as to correspond to the light that travels while spreading in an arc or radial direction. A plurality of convex or / and concave ridges having a surface continuously or discontinuously, and a light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A diffusion sheet covering the surface portion,
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. Therefore, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion coincident with the circular arc shape, and similarly, the incident light propagated in the circular arc shape has a convex shape concentric with the circular arc shape provided on the back surface portion. A light beam that has been totally reflected anywhere in the concentric region and proceeded in the direction of the surface portion by the inclined surface in the direction of the incident portion of the concave ridge is emitted from the surface portion by a fine light control element provided on the surface portion. The diffused light can be emitted by the diffusion sheet.
[0023]
Furthermore, a flat illumination device according to claim 3 is provided. ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and the arc shape or radial light is incident from the entire incident portion and proceeds while spreading radially. Convex or / and concave ridges that are concentric with the arc shape with the incident part cut off on the back side and concentric with the light, and that have an inclined surface in the direction of the incident part. A light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A diffusion sheet or a polarizing sheet covering the surface,
A reflection sheet covering a portion other than the surface portion and the incident portion;
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. It is characterized by that.
[0024]
The flat illumination device according to claim 3 ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and the arc shape or radial light is incident from the entire incident portion and proceeds while spreading radially. Convex or / and concave ridges that are concentric with the arc shape with the incident part cut off on the back side and concentric with the light, and that have an inclined surface in the direction of the incident part. A light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A diffusion sheet or a polarizing sheet covering the surface,
A reflection sheet covering a portion other than the surface portion and the incident portion;
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. Therefore, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion that coincides with the circular arc shape, and similarly, the incident light propagated in the circular arc shape has a convex shape concentric with the circular arc shape provided on the back surface portion. By the inclined surface having the concave ridge in the incident part direction, it is totally totally reflected anywhere in the concentric region, or a small amount of light or light with lower energy than the back part is returned to the light guide plate again without a corner by the reflection sheet, A light beam traveling in the direction of the surface portion is emitted from the surface portion by a fine light control element provided on the surface portion, and this light beam is emitted from the surface portion by the diffusion sheet or from the surface portion along the light guide plate. The light beam emitted from the surface can be completely guided to the convex or concave ridge of the light polarizing sheet at the shortest distance from the surface portion, and can be polarized in a substantially vertical direction by the light polarizing sheet and emitted from the flat illumination device.
[0025]
Still further, the flat illumination device according to claim 4 has a prism shape with an apex angle of 60 degrees to 80 degrees at a position corresponding to a ridge provided with the polarizing sheet radially on the light guide plate. Yes It is characterized by doing.
[0026]
According to a fourth aspect of the present invention, there is provided a planar illumination device having a prism shape with an apex angle of 60 degrees to 80 degrees at a position corresponding to a ridge provided with a polarizing sheet radially on a light guide plate. Yes Therefore, the light beam emitted from the light guide plate along the light guide plate can be polarized vertically upward, and the pitch between the ridges and the height or depth of the ridges can be set according to the purpose. Can do.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The present invention provides a convex or concave shape in which an incident portion cut in an arc shape is provided at the corner of the light guide plate and an inclined surface in the direction of the incident portion is concentric with the arc shape in which the incident portion is cut off on the back surface portion. A ridge is provided, and light emitted in a circular arc shape (radial) from the light source is taken into the light guide plate from the incident portion coincident with the circular arc shape. Similarly, the incident light that has progressed in the circular arc shape (radial) is totally reflected on the inclined surface. The light is emitted from the substantially surface portion, and the emitted light is refracted by a fine light control element provided on the surface portion, or a prism shape with an apex angle of 60 to 80 degrees provided on the upper portion of the light guide plate is formed. An object of the present invention is to provide a light guide plate and a flat illumination device capable of obtaining uniform and bright luminance while maintaining a necessary viewing angle by using a radial polarizing sheet or the like similar to the provided ridge.
[0028]
FIG. 1 is an exploded perspective view showing a schematic configuration of a flat illumination device according to the present invention, FIG. 2 is a plan view of a ridge provided on the back surface portion of the light guide plate according to the present invention, and FIG. 3 is an incident portion of the light guide plate in FIG. FIG. 4 is a partial cross-sectional view of the light guide plate taken along line 2c connecting the normal line of the concentric ridge from the incident portion and the perpendicular direction 7, and FIG. 4 is a partial cross-sectional view of FIG. 5 (a), (b), FIG. 6 and FIG. 7 are partial enlarged views showing other examples of the ridges provided on the light guide plate according to the present invention, and FIG. 8 is a light polarizing sheet of the flat illumination device according to the present invention. FIG. 9 is a partial cross-sectional view of the light polarizing sheet of FIG. 8, and FIG. 10 is a view showing the locus of light rays of the flat illumination device according to the present invention.
[0029]
The flat illumination device 1 of FIG. 1 includes a light guide plate 2, a light source 3, a diffusion sheet or light polarizing sheet 11, and a reflector 15.
[0030]
The light source 3 is a semiconductor light emitting element, and is composed of, for example, an LED or a laser. As the light source 3, a monochromatic light, a white color composed of RGB (red, green, blue), or a white color light converted by wavelength conversion using a fluorescent material is also used.
[0031]
In addition, in this example, although the structure provided in one of the corners 7 where the two side surface parts 6 of the light guide plate 2 intersect with each other, for example, when having a plurality of incident parts 8 at the end of the target position, White light may be emitted from the entire light guide plate 2 by using light sources 3 of different emission colors for each incident portion 8.
[0032]
The reflector 15 is made of a sheet obtained by depositing metal such as aluminum on a sheet in which a white material such as titanium oxide is mixed in a thermoplastic resin or a sheet of a thermoplastic resin, or by laminating metal foil. The reflector 15 covers portions other than the incident portion 8 and the surface portion 4, reflects or irregularly reflects light other than light emitted from the light source 3 to the surface portion 4 by the light guide plate 2, and enters the light guide plate 2 again. Thus, all the light from the light source 3 is emitted from the surface portion 4.
[0033]
The light guide plate 2 is formed of a transparent acrylic resin (PMMA) or polycarbonate (PC) having a refractive index of about 1.4 to 1.7. The light guide plate 2 includes a side surface portion 6, a front surface portion 4 for light emission, and a back surface portion 5 located on the opposite side and an incident portion 8 that guides light from the light source 3.
[0034]
The surface portion 4 is made into a mirror surface by selecting a viewing angle, luminance, or the like, which is a purpose required of the final flat illumination device 1, or a light control element 13 is provided on the surface.
[0035]
As shown in FIG. 4, the light control element 13 has a concave shape or a convex shape including a fine arc shape (for example, about 5 μm to 100 μm), an ellipse, a polygonal column, a polygonal pyramid, and the like. The light control element 13 refracts light rays from the back surface portion 5 toward the front surface portion 4. In addition, when the light control element 13 is particularly fine, total reflection or the like is performed in the light control element 13 and the whole behaves like scattered light.
[0036]
Further, the light control element 13 may perform gradation in order to control a target angle and luminance distribution. As a result, it is possible to control the distribution of the viewing angle and the luminance distribution that are optimal for the light emitted from the light guide plate 2 by the light beams having various viewing angles from the back surface portion 4.
[0037]
The incident portion 8 is formed by cutting out at least one of the corners 7 where the two side surface portions 6 of the light guide plate 2 intersect in an arc shape equivalent to the emitted light of the point light source 3. In the example of FIG. 1, the incident portion 8 is formed by cutting away the front corner of the light guide plate 2 in an arc shape.
[0039]
The back surface portion 5 is provided with a ridge 9 having an inclined surface 9a in the direction of the incident portion 8 concentrically with the arc shape of the incident portion 8 provided at one end portion (one corner portion) of the light guide plate 2.
[0040]
More specifically, the back surface portion 5 has a convex ridge 9c and a concave ridge 9d concentric with one end position of the back surface portion 5 as the incident portion 8, as shown in FIGS. . A convex ridge 9c (odd number) and a concave ridge 9d (even number) are continuously formed so as to be concentric about the incident part 8 as one end position, and a plurality of convex ridge lines 9cn and A plurality of concave ridge lines 9dn are formed.
[0041]
In addition, although not shown in figure, the back surface part 5 is good also as providing the convex ridge 9c in a jump, and making between the two convex ridges 9c into a plane. Further, it is also possible to provide a concave ridge 9d so as to jump on the back surface portion 5, or to make a plane between the convex ridge 9c and the concave ridge 9d.
[0042]
As shown in FIG. 3, the convex ridge 9c and the concave ridge 9d include an inclined surface 9a and an inclined surface 9b. In particular, the inclined surface 9a is inclined in the direction of the incident portion 8 (in the upward direction with respect to the incident portion 8 in FIG. 3) so that the light from the light source 3 is always totally reflected in the direction of the surface portion 4.
[0043]
With the above configuration, the light rays that have entered from the light source 3 and reached the ridges 9c and 9d are at the same distance from the light source 3 of the emitted light, so that the light energy is emitted equally at any distance with respect to them. .
[0044]
FIG. 3 shows a part of a cross section of a line 2c that connects a normal line of the ridge 9 concentric with the incident portion 8 and the corner 7 in the perpendicular direction in FIG. As shown in FIG. 3, convex ridges 9c and concave ridges 9d provided on the back surface portion 5 radially from the incident portion 8 have a triangular shape. In this example, the angle θ1 of the convex ridge 9c is in the range of 80 to 179 degrees, and the angle θ2 of the concave ridge 9d is in the range of 80 to 179 degrees. Moreover, the angle θ3 formed with the virtual horizontal surface 51 of the back surface portion 5 is set to a range of 0.01 degrees to 10 degrees.
[0045]
In the example of FIG. 3, the inclined surface 9 a and the inclined surface 9 b of the convex ridge 9 c and the concave ridge 9 d have the same shape, but the light from the light source 3 is the surface portion for the purpose of the present invention. It is sufficient that the inclined surface 9a always has an inclination in the direction of the incident portion 8 so as to be totally reflected in the four directions. Therefore, it does not have to be an isosceles triangle, and for example, it may be a right triangle having only the inclined surface 9a and the inclined surface 9b being vertical.
[0046]
By setting the angles θ1, θ2, and θ3 as described above, when a light beam is incident on the light guide plate 2 from the incident portion 8 at one end portion position of the light guide plate 2, as shown in FIG. The light present inside has a refraction angle within a predetermined range depending on the material used for the light guide plate 2. For example, when the material of the light guide plate 2 is polycarbonate (PC) resin, the refractive index n of the polycarbonate resin is 1.59. Therefore, when the light beam L0 enters the light guide plate 2 from the air layer, The existing light is 0 ≦ | α | ≦ sin -1 From the formula of (1 / n) (where n is an air layer and refractive index n = 1), the angle of refraction is approximately in the range of α = ± 38.997 °.
[0047]
Further, the light incident on the light guide plate 2 within the range of the refraction angle α = ± 38.997 ° is sin γ = (1 / n at the boundary surface between the light guide plate 2 and the air layer (refractive index n = 1). ) Can be used to express the critical angle. For example, since the refractive index of polycarbonate resin which is a resin material used for the general light guide plate 2 is about n = 1.59, the critical angle γ is about γ = 38.97 °. When an acrylic resin (PMMA) material is used as the material of the light guide plate 2, the refractive index n of the acrylic resin is about n = 1.49, and the refraction angle α is about α = 42.38 °. Therefore, the critical angle γ is also about γ = 42.38 °.
[0048]
Therefore, when the front surface portion 4 is a mirror surface, as shown in FIG. 3, the light beam L1 traveling in the direction of the front surface portion 4 among the light beams L1 traveling in the direction of the front surface portion 5 and the back surface portion 6 at the maximum refraction angle α is critical. Since it is larger than the angle γ, it is totally reflected as the light ray L11 at the surface portion 4. The light ray L11 travels in the direction of the back surface 5 and reaches the inclined surface 9b formed by the virtual horizontal surface 51 and the angle θ3. Also here, since the angle (incident angle) formed with the perpendicular to the inclined surface 9b is larger than the critical angle γ, the light ray L11 is totally reflected as the light ray L12 on the inclined surface 9b. Then, the light beam L12 travels in the direction opposite to the incident portion 8. Although not shown here, the light beam L12 is returned again into the light guide plate 2 by a reflector or the like provided in the vicinity of the side surface portion 6 on the opposite side of the incident portion 8.
[0049]
Although not shown, the light ray L1 traveling in the direction of the front surface portion 5 and the rear surface portion 6 at the maximum refraction angle α is directly and totally reflected by the front surface portion 4, and the inclined surface 9a formed by this light ray and the virtual horizontal plane 51 at an angle θ3. When the angle is toward, the angle (incident angle) formed with the perpendicular of the inclined surface 9a is smaller than the critical angle γ. For this reason, the light beam totally reflected by the front surface portion 4 breaks the critical angle γ and is refracted and emitted from the back surface portion 5. The emitted light at this time is small in energy and has little influence on the luminance of the light guide plate 2 directly. In this example, since all the light is used, it is returned again to the light guide plate 2 by the reflector 15 shown in FIG. Finally, the light is emitted from the surface portion 4.
[0050]
Further, when the refraction angle α is slightly small, as shown in FIG. 3, the light ray L2 reaching the inclined surface 9a has an angle (incident angle) formed with a perpendicular to the inclined surface 9a larger than the critical angle γ. For this reason, the light ray L2 is totally reflected as the light ray L21 on the inclined surface 9a. The totally reflected light beam L21 travels in the direction of the surface portion 4. Then, the light ray L21 that has reached the surface portion 4 has an angle (incident angle) formed with a perpendicular line that is smaller than the critical angle γ. The light beam L22 is emitted from the surface portion 4 along the surface portion 4 at a certain angle.
[0051]
Further, as shown in FIG. 3, in the case of a light beam having a small refraction angle α such as the light beam L3, the angle (incident angle) formed with the perpendicular of the inclined surface 9a is larger than the critical angle γ. For this reason, the light ray L3 is totally reflected as the light ray L31 on the inclined surface 9a. The totally reflected light beam L31 reaches the front surface portion 4, but since the angle (incident angle) formed with the perpendicular of the front surface portion 4 is larger than the critical angle γ, the light beam L31 travels again toward the back surface portion 5 as the light beam L30.
[0052]
The above description is a case where the surface portion 4 of the light guide plate 2 is a mirror surface. On the other hand, as shown in FIG. 4, when the light control element 13 is provided on the surface portion 4, even a light beam having a small refraction angle α such as the light beam L <b> 3 is totally reflected by the inclined surface 9 a. L31 reaches the surface portion 4. However, the light control element 13 provided on the surface portion 4 has an angle (incident angle) perpendicular to the normal of the light control element 13 at the light beam L31 traveling to the light control element 13 is smaller than the critical angle γ. For this reason, the light ray L31 breaks the critical angle γ and is refracted to be emitted as a light ray L30 ′ from the surface portion 4 at a certain angle. When there is no light control element 13, total reflection is performed.
[0053]
Similarly, the light beam L22 emitted along the surface portion 4 in FIG. 3 (broken line in FIG. 4) also reaches the surface portion 4, and the light beam L21 that reaches the surface portion 4 is caused by the light control element 13 provided on the surface portion 4. The angle (incident angle) formed at right angles to the normal line of the light control element 13 at the light beam L30 traveling to the light control element 13 is smaller than the critical angle γ. For this reason, L21 breaks the critical angle γ, and refracts to be emitted as a light ray L22 ′ from the surface portion 4 at a larger angle with the surface portion 4 than when there is no light control element 13 (L22).
[0054]
As described above, in this example, the surface portion is in a triangular angle range in a cross section perpendicular to the normal line of the convex ridge 9c and the concave ridge 9d provided radially on the surface portion 5 from the incident portion 8. Most of the light rays emitted from 4 are totally reflected by the inclined surface 9 b of the convex ridge 9 c provided on the back surface portion 5.
[0055]
Of the light rays existing in the light guide plate 2 (substantially within the range of refraction angle α = ± 38.997 °), the smaller the refraction angle α, the greater the energy of the light, and the light rays having a greater energy are emitted directly. The main rays are not rays but once totally reflected by the inclined surface 9a of the convex ridge 9c. That is, most of the light rays emitted from the front surface portion 4 are light rays having a large energy of light totally reflected by the inclined surface 9 a of the convex ridge 9 c provided on the back surface portion 5.
[0056]
Further, these emitted lights are emitted so as to be inclined toward the surface portion 4 side. Accordingly, without using a film-like diffusion sheet (not shown) or the film-like light polarizing sheet 11 and the reflector 15 shown in FIG. 1, for example, the light guide plate 2 is used upside down to emit light downward from the surface portion 4. Thus, the light can be projected onto the reflective liquid crystal panel, and the reflected light from the reflective liquid crystal panel can be used for a front light that transmits the light guide plate 2.
[0057]
Further, as the distance from the light source 3 increases, the pitch between the convex ridge 9c and the concave ridge 9d is changed, or the height of the convex ridge 9c and the depth of the concave ridge 9d are set. Thus, the amount of emitted light can be changed by changing the amount of light reaching the inclined surface 9a.
[0058]
Further, as shown in FIG. 5A, when the convex ridge 9c and the concave ridge 9d are continuously formed on the back surface portion 5 of the light guide plate 2, the light enters the light source 3 and reaches the ridge 9c and the ridge 9d. The emitted light rays are at the same distance from the light source 3 of the emitted radiation light, and the optical energy of all the ridges at arbitrary distances corresponding thereto is emitted equally.
[0059]
Further, as shown in FIG. 5B, when the convex ridge 9c and the concave ridge 9d are formed discontinuously on the back surface portion 5 of the light guide plate 2, the gap between the convex ridge 9c and the concave ridge 9d is formed. The light beam that has entered the light source 3 and reaches the ridges 9c and 9d is at the same distance from the light source 3 of the emitted radiation, but only the ridges at any distance corresponding to these light energy. Are equally emitted. Thereby, the emitted light from the surface part 5 can be partially emitted to the target position.
[0060]
As shown in FIG. 6, the ridge formed on the back surface portion 5 of the light guide plate 2 may be provided with a flat portion 91 and a flat portion 92 in which a triangular ridge portion is cut flat. . Further, although not shown, for example, a flat portion 91 or a flat portion 92 that is flatly cut out on the ridge 9c or ridge 9d of the front surface portion 4 may be provided, and a reflector may be provided in the vicinity of the back surface portion 5. . In this case, the light totally reflected by the front surface portion 4 directly travels in the direction of the back surface portion 5 is emitted from the back surface portion 5 to the outside. The emitted light beam is reflected by the reflector 15 and incident again on the light guide plate 2. The light beam is reflected and refracted on the inclined surface 9a and inclined surface 9b of the ridge 9c and ridge 9d of the surface portion 4, but is flat. In the part 91 and the flat part 92, it can radiate | emit from the surface part 4 substantially straight.
[0061]
Furthermore, as shown in FIG. 7, the inclined surfaces 9 a and 9 b adjacent to the triangular ridges of the back surface portion 5 of the light guide plate 2 may be curved or arcuate. In FIG. 7, the inclined surface 9a and the inclined surface 9b of the edge where the curve or circular arc shape was dented inward are shown. As a result, when the light existing in the light guide plate 2 reaches the inclined surface 9b of the concave concave ridge, the emission angle becomes larger than the straight ridge with respect to the normal line of the inclined surface 9b, and the outer side is closer. It will be in the state diffused.
[0062]
Although not shown, in the case of a curved or arcuate ridge surface that bulges outward, the light present in the light guide plate 2 reaches the sloping surface 9a or sloping surface 9b of the bulging convex ridge. With respect to the normal of this surface, the emission angle is smaller than the straight edge, and the light is inward, condensing the light at a location that matches the curvature, and diffusing the light further away. And when the inclined surface 9a and the inclined surface 9b which adjoin the triangular edge of the light-guide plate 2 are made into the curve or circular arc shape, the emission angle etc. of emitted light can be varied.
[0063]
In addition, although the inclined surface 9a and the inclined surface 9b of the convex ridge 9c and the concave ridge 9d here have the same shape, the light from the light source 3 is emitted to the surface portion 4 which is the object of the present invention. It suffices to have the inclined surface 9a in the direction of the incident portion 8 that totally reflects in the direction of the surface portion 4. Therefore, it does not have to be an isosceles triangle, and for example, it may be a right triangle having only the inclined surface 9a and the inclined surface 9b being vertical.
[0064]
Furthermore, if a film-like diffusion sheet is used in the upper part of the light guide plate 2, light rays emitted from the surface portion 4 of the light guide plate 2 in an arbitrary direction or a specific direction can be diffused. At that time, as the emitted light from the flat illumination device 1, a wide viewing angle can be obtained, and high-intensity emitted light can be obtained by the light guide plate 2 of the present invention.
[0065]
By the way, as a member arrange | positioned at the upper part of the light-guide plate 2, the light polarizing sheet 11 shown to FIG. 8 and FIG. 9 other than a diffusion sheet can be used.
[0066]
The light polarizing sheet 11 is formed into a film from a transparent resin such as acrylic resin (PMMA) or polycarbonate (PC). The light polarizing sheet 11 has a shape corresponding to the light guide plate 2 and has a triangular cross section as shown in FIG. 9 and is composed of a convex ridge 10a and a concave ridge 10b. As with the light guide plate 2, the light polarizing sheet 11 is provided with a convex ridge 10a, a concave ridge 10b, or a convex ridge 10a. It is also possible to make a flat surface with the concave ridge 10b.
[0067]
Further, as shown in FIG. 9, the light polarizing sheet 11 has an angle θ5 of the convex ridge 10a and an angle θ6 of the concave ridge 10b in the range of 60 to 80 degrees. The light polarizing sheet 11 has an angle θ7 formed with a virtual horizontal plane 11a parallel to the surface portion 12 in a range of 20 degrees to 60 degrees.
[0068]
Furthermore, the light polarizing sheet 11 has a convex ridge 10 a and a concave shape provided on the back side of the front surface portion 12, here the light source 3 radiates from the incident portion 8 of the light guide plate 2 in order to correspond to the light guide plate 2. 9b is provided on a line 11cb that connects 11b equivalent to the incident portion 8 of the light guide plate 2 to the normal line of the concentric ridge and 11d in the perpendicular direction.
[0069]
Similarly to the light guide plate 2, the light polarizing sheet 11 is provided such that the convex ridges 10 a are radially provided as lines 10 a 1 and the concave ridges 10 b are formed as lines 10 b 1, and the convex ridges 10 a are line 10 a 1, 10 a 2 (odd numbers). ), And concave ridges 10b are lines 10b1 and 10b2 (even numbers), and convex and concave ridges are alternately or continuously formed (lines 10an and 10bn).
[0070]
Here, the side 12a and the side 12b of the convex ridge 10a and the concave ridge 10b have the same shape, but the shape may match the light emitted from the surface portion 4 of the light guide plate 2, and isosceles triangles. Not necessarily.
[0071]
FIG. 10 is a partially enlarged side view of the light guide plate 2 and the light polarizing sheet 11 of the flat illumination device 1 according to the present invention. The flat illumination device 1 in FIG. 10 includes a light polarizing sheet 11 on the light guide plate 2. The light polarizing sheet 11 is arranged toward the surface portion 4 side of the light guide plate 2 so that the convex ridge 10 a faces the convex ridge 9 c provided on the light guide plate 2. And the light source 3 is arrange | positioned facing the incident part 8 formed in the corner 7 which is the one end part of the light-guide plate 2. FIG.
[0072]
Here, the description of the light guide plate 2 and the light polarizing sheet 11 is the same as that described above, so the description thereof will be omitted, and the locus of light will be described.
[0073]
In FIG. 10, the light ray L2 that has reached the inclined surface 9a has an angle (incident angle) formed with the perpendicular of the inclined surface 9a larger than the critical angle γ. For this reason, the light ray L2 is totally reflected as the light ray L21 on the inclined surface 9a. The totally reflected light beam L21 travels in the direction of the surface portion 4. The light beam L21 that has reached the surface portion 4 has an angle (incident angle) formed with a perpendicular line that is smaller than the critical angle γ. The light beam L22 reaches the side 12b of the convex ridge 10a of the light polarizing sheet 11. Also here, the light guide plate 2 and the light polarizing sheet 11 are made of the same material (polycarbonate (PC)), and the light beam L22 from the air layer to the side 12b of the light polarizing sheet 11 having a refractive index larger than air is the side 12b. The light is refracted and travels into the light polarizing sheet 11 as a light beam L23.
[0074]
Furthermore, the light ray L23 reaches the side 12a in the light polarizing sheet 11, and the incident angle here is larger than the critical angle γ = 38.97 °. For this reason, the light ray L23 is totally reflected as the light ray L24 on the side 12a. The totally reflected light beam L24 travels in the direction of the surface portion 12 of the light polarizing sheet 11.
[0075]
And since the incident angle in the surface part 12 of the light polarizing sheet 11 is smaller than critical angle (gamma) = 38.97 degrees, the light ray L24 radiate | emits the light ray L25 from the surface part 12 substantially perpendicularly.
[0076]
As described above, the light polarizing sheet 11 can emit light from the light guide plate 2 that is low along the light guide plate 2 in a direction substantially perpendicular to the light polarizing sheet 11 using total reflection. it can.
[0077]
For example, in the case of the light ray L3, the angle (incident angle) formed with the perpendicular of the inclined surface 9a is larger than the critical angle γ. For this reason, the light ray L3 is totally reflected as the light ray L31 on the inclined surface 9a. The totally reflected light beam L31 reaches the light control element 13 provided on the surface portion 4, and an angle (incident angle) perpendicular to the normal line of the light control element 13 is smaller than the critical angle γ. For this reason, the light ray L31 breaks the critical angle γ and is refracted to be emitted as a light ray L30 ′. Then, the light beam L30 ′ travels as a light beam L32 in the light polarizing sheet 11.
[0078]
Further, the light beam L32 reaches the side 12a in the light polarizing sheet 11. The incident angle of the light beam L32 here is larger than the critical angle γ = 38.97 °. For this reason, the light ray L32 is totally reflected as the light ray L33 on the side 12a. The totally reflected light beam L33 travels in the direction of the surface portion 12 of the light polarizing sheet 11.
[0079]
The incident angle of the light beam L33 at the surface portion 12 of the light polarizing sheet 11 is smaller than the critical angle γ = 38.97 °. For this reason, the light ray L33 is emitted from the surface portion 12 as a light ray L34 substantially perpendicularly.
[0080]
In the configuration of FIG. 10, a diffusion sheet may be used above the light polarizing sheet 11. In this case, the high-intensity light beam from the light polarizing sheet 11 is diffused by the diffusion sheet. Thereby, the light beam emitted from the surface portion 4 of the light guide plate 2 in an arbitrary direction or a specific direction is diffused, and as the emitted light from the flat illumination device 1, the emitted light having a high luminance and a wide viewing angle can be obtained. it can.
[0081]
As described above, according to the flat illumination device 1 of the present invention, the rear surface portion 5 of the light guide plate 2 is provided with the incident portion 8 cut out in an arc shape substantially equal to the radiated light of the light source 3 and always from the light source 3. A ridge 9c or ridge 9d having an inclined surface 9a in the direction of the incident portion 8 that totally reflects light in the direction of the surface portion 4 is provided concentrically with the incident portion 8, and is provided by a fine light control element or light polarizing sheet provided on the surface portion 4. A light beam with high luminance can be emitted. Furthermore, the emitted light can be diffused by the diffusion sheet, and the emitted light having a wide field of view can be emitted from the flat illumination device 1.
[0082]
Further, the flat illumination device 1 including the light guide plate 2 and the diffusion sheet or the light polarizing sheet 11 according to the present invention has a radial ridge from the position of the light source 3 to the surface portion 4 of the light guide plate 2 even with few point light sources 3. Therefore, a constant light energy can be given everywhere, and a light beam having a large light energy can be emitted from the light guide plate 2 at an arbitrary angle. Then, by polarizing this light beam in the substantially vertical direction with the light polarizing sheet 11 or diffusing with the diffusion sheet, it is possible to obtain high-luminance outgoing light with a wide viewing angle as the flat illumination device 1.
[0083]
As described above, the light guide plate and the flat illumination device of the present invention are provided with the incident part cut out in an arc shape at the corner of the light guide plate and in the incident part direction concentric with the arc shape of the cut off incident part on the back surface part. A convex or concave ridge with an inclined surface is provided, and the light emitted in a circular arc shape (radial) from the light source is taken into the light guide plate from the arc-shaped incident portion that coincides with the circular arc shape. Similarly, the circular arc shape (radial) The incident light that has traveled to is totally reflected by the inclined surface and emitted from the substantially surface portion, and the emitted light is refracted by a fine light control element provided on the surface portion, or the apex angle provided on the upper portion of the light guide plate is 60. By using a radial polarizing sheet similar to the ridge provided on the light guide plate and having a prism shape of ˜80 degrees, uniform and bright luminance can be obtained while maintaining the required viewing angle.
[0084]
【The invention's effect】
As described above, the flat illumination device according to claim 1 is ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and the arc shape or radial light is incident from the entire incident portion and proceeds while spreading radially. To correspond to light, a convex or / and concave ridge having an arcuate or radial extension concentrically with the arc shape with the incident portion cut off on the back surface and having an inclined surface in the direction of the incident portion is continuous or non-contiguous. A plurality of light guide plates that are continuously provided, and that totally reflects the arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A polarizing sheet covering the surface portion,
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. Therefore, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion coincident with the circular arc shape, and similarly, the incident light propagated in the circular arc shape has a convex shape concentric with the circular arc shape provided on the back surface portion. Due to the inclined surface of the concave ridge in the direction of the incident part, the light beam emitted from the surface part along the light guide plate is totally totally reflected anywhere in the concentric region, and is completely projected at the shortest distance from the surface part. Can be guided to a ridge having a shape or a concave shape, and can be polarized in a substantially vertical direction by the light polarizing sheet and emitted from the flat illumination device. As a result, when used in a liquid crystal display device or the like, an appropriate viewing angle can be obtained with no bright spots.
[0085]
Moreover, since the angle which makes an inclined surface and the virtual horizontal surface of a back surface part is the range which is 0.01 degree-10 degree | times, the light guide plate which concerns on Claim 2 makes most light rays which exist in a light guide plate a virtual horizontal surface. It can be totally reflected in the direction of the surface portion by the small inclined surface formed. Thereby, the light beam with high energy from a light source can be advanced to a surface part, and can be radiate | emitted by the light polarizing sheet with which the fine light-control element provided in the surface part, the surface part vicinity, etc. were provided.
[0086]
Furthermore, since the light guide plate according to claim 3 has an inclined surface that is curved or arcuate, it diffuses light when the curved surface or arcuate shape is indented on the inside, or is curved or arcuate. In the case of a ridged surface that bulges outward, the light can be condensed at a location that matches the curvature, and the output angle of the emitted light can be varied so that the light is diffused further away from it. Can be designed.
[0087]
In addition, since the light guide plate according to the fourth aspect is provided concentrically with the circular arc shape in which the ridges are cut out continuously or discontinuously, the emitted light can be emitted from the front surface portion or the back surface portion along the ridge to the entire area. In addition, the light can be partially emitted to a target position. Thereby, viewing angle control, brightness control, and the like can be performed.
[0088]
Furthermore, since the light guide plate according to claim 5 has an apex angle in the range of 80 degrees to 179 degrees, the distance between the ridges can be adjusted as the ridge angle changes in the light guide plate. At the same time, the pitch between the edges can be set shorter as the distance from the light source increases. In addition, the height or depth of convex or concave ridges can be set, so the distance between the ridges decreases as the distance from the light source decreases, the height of the convex ridges increases, or the height of the concave ridges increases. By increasing the depth of the ridge, uniform emission light can be obtained by controlling the attenuation of the light intensity from the light source by the emission amount.
[0089]
Moreover, since the light guide plate according to claim 6 has the ridges cut out flatly at the apex angle, for example, when a ridge cut out flatly only on the front surface portion is provided and a reflector is provided in the vicinity of the back surface portion, The light totally reflected on the front surface travels in the direction of the back surface, and the light beam emitted from the back surface portion is reflected by the reflector and incident on the light guide plate again. However, in the flat part in this claim, it can radiate | emit from a surface part substantially straight. Thereby, for example, in a usage such as a front light, straight light can be observed from the upper part of the light guide plate.
[0090]
Furthermore, the flat illumination device according to claim 7 includes a light source that emits in an arc shape or a radial shape, a front surface portion or a back surface portion that emits light from the light source, and a side surface portion that intersects the front surface portion and the back surface portion at a right angle. And at least one of the corners where the two side surfaces intersect has an incident portion cut out in an arc shape that matches the light emitted in an arc shape or a radial shape. In order to correspond to the light that enters from the incident part and travels while spreading radially, Arc or radial concentric with the arc shape with the incident part cut off on the back With expanse A convex or / and concave ridge with an inclined surface in the direction of the incident part The light from the light source is totally reflected by the inclined surface toward the surface portion. Since the light guide plate and the polarizing sheet covering the surface portion are provided, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion coincident with the circular arc shape, and similarly the incident light propagated in the circular arc shape is received. Convex and concave ridges concentric with the circular arc shape provided on the back surface, and the light rays emitted from the surface portion along the light guide plate are totally reflected anywhere in the concentric region by the inclined surface. The light polarizing sheet can be completely guided to the convex or concave ridge of the light polarizing sheet at the shortest distance from the surface portion, and can be polarized in a substantially vertical direction by the light polarizing sheet and emitted from the flat illumination device. As a result, when used in a liquid crystal display device or the like, an appropriate viewing angle can be obtained with no bright spots.
[0091]
A flat illumination device according to claim 2 ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in a circular arc shape or a radial shape, and has a fine light control element that refracts light on the surface portion. Inclined in the direction of the incident part with an arc or radial extension concentrically with the arc shape with the incident part cut off on the back surface so as to correspond to the light that travels while spreading in an arc or radial direction. A plurality of convex or / and concave ridges having a surface continuously or discontinuously, and a light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A diffusion sheet covering the surface portion,
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. Therefore, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion coincident with the circular arc shape, and similarly, the incident light propagated in the circular arc shape has a convex shape concentric with the circular arc shape provided on the back surface portion. A light beam that has been totally reflected anywhere in the concentric region and proceeded in the direction of the surface portion by the inclined surface in the direction of the incident portion of the concave ridge is emitted from the surface portion by a fine light control element provided on the surface portion. The diffused light can be emitted by the diffusion sheet. Thereby, it is possible to obtain a bright luminance distribution corresponding to the luminance of the light source regardless of the size of the light guide plate, and to obtain outgoing light having a wide viewing angle.
[0092]
Furthermore, the flat illumination device according to claim 3 ,Circle Arc or radial the light Exit Rectangular A light source;
A front surface portion that emits light from the light source, a back surface portion located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and at least a corner where the two side surface portions intersect One has an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and the arc shape or radial light is incident from the entire incident portion and proceeds while spreading radially. Convex or / and concave ridges that are concentric with the arc shape with the incident part cut off on the back side and concentric with the light, and that have an inclined surface in the direction of the incident part. A light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A diffusion sheet or a polarizing sheet covering the surface,
A reflection sheet covering a portion other than the surface portion and the incident portion;
The position where the end position where two adjacent side surfaces of the light source intersect each other and the incident section cut out in an arc shape of the light guide plate face each other To place the light source in the notched part of the incident part. Therefore, the light emitted in a circular arc shape from the light source is taken into the light guide plate from the incident portion that coincides with the circular arc shape, and similarly, the incident light propagated in the circular arc shape has a convex shape concentric with the circular arc shape provided on the back surface portion. By the inclined surface having the concave ridge in the incident part direction, it is totally totally reflected anywhere in the concentric region, or a small amount of light or light with lower energy than the back part is returned to the light guide plate again without a corner by the reflection sheet, A light beam traveling in the direction of the surface portion is emitted from the surface portion by a fine light control element provided on the surface portion, and this light beam is emitted from the surface portion by the diffusion sheet or from the surface portion along the light guide plate. The light beam emitted from the surface can be completely guided to the convex or concave ridge of the light polarizing sheet at the shortest distance from the surface portion, and can be polarized in a substantially vertical direction by the light polarizing sheet and emitted from the flat illumination device. Thereby, it is possible to obtain a bright luminance distribution corresponding to the luminance of the light source regardless of the size of the light guide plate, and to obtain outgoing light having a wide viewing angle.
[0093]
According to a fourth aspect of the present invention, there is provided a flat illumination device having a prism shape with an apex angle of 60 degrees to 80 degrees at a position corresponding to a ridge provided with a polarizing sheet radially on a light guide plate. Yes Therefore, the light beam emitted from the light guide plate along the light guide plate can be polarized vertically upward, and the pitch between the ridges and the height or depth of the ridges can be set according to the purpose. Can do. The emitted light distribution can be made uniform by emitting light substantially perpendicular to the flat illumination device and controlling the amount of light taken in from the light guide plate.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a flat illumination device according to the present invention.
FIG. 2 is a plan view of a ridge provided on the back surface of the light guide plate according to the present invention.
3 is a partial cross-sectional view of the light guide plate of FIG. 2;
4 is a partial cross-sectional view of a light guide plate in which a light control element is provided on the surface portion of the light guide plate in FIG. 3;
FIGS. 5A and 5B are partially enlarged views showing other configuration examples of ridges provided in the light guide plate according to the present invention. FIGS.
FIG. 6 is a partially enlarged view showing another configuration example of the ridge provided in the light guide plate according to the present invention.
FIG. 7 is a partially enlarged view showing another configuration example of the ridge provided in the light guide plate according to the present invention.
FIG. 8 is a plan view of a light polarizing sheet of the flat illumination device according to the present invention.
9 is a partial cross-sectional view of the light polarizing sheet of FIG.
FIG. 10 is a partially enlarged side view of the light guide plate and the light polarizing sheet of the flat illumination device according to the present invention, and shows a locus of light rays.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Plane illumination apparatus, 2 ... Light guide plate, 2c, 11c ... Line, 3 ... Light source, 4,12 ... Front surface part, 5 ... Back surface part, 6 ... Side surface part, 7 ... Corner, 8 ... Incident part, 9 ... Ridge , 9a, 9b ... inclined surface, 9c ... convex ridge, 9d ... concave ridge, 9cn ... convex ridge line, 9dn ... concave ridge line, 15 ... reflector, 13 ... fine light control element, 11 ... light polarizing sheet, n ... Refractive index, 51, 61, 10a, 10a1, 10a2, 10an ... convex ridge, 52, 62, 10b, 10b1, 10b2, 10bn ... concave ridge, 51 ... virtual horizontal line, 11d ... vertical direction of the normal line concentric with the light source , 91, 92 ... flat part, 9a1, 9b1 ... curved edge, 12a, 12b ... side, α ... refraction angle, θ1, θ5 ... convex ridge angle, θ2, θ6 ... concave ridge angle, θ3, θ7 ... An angle formed with a virtual horizon, γ ... Critical angle, L0, L1, L2, L21, L3, L22, L2 2 ′, L31, L30 ′, L12, L30, L11, L32, L33, L34, L23, L24, L25.

Claims (4)

円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、前記表面部の反対側に位置する裏面部と、これら前記表面部と前記裏面部とに直角に交わる側面部と、この二つの前記側面部が交差する隅の少なくとも１つを前記光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、前記入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、前記裏面部に前記入射部の前記欠切した円弧形状と同心に前記円弧状または放射状に広がりを持って前記入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、前記光源からの円弧状または放射状の光を前記傾斜面によって略前記表面部方向に全反射する導光板と、
前記表面部を覆う偏光シートとを具備し、
前記光源の互いに隣合う２つの側面が交差する端部位置と前記導光板の前記円弧状に欠切した入射部とが対向する位置で前記入射部の欠切部分内に前記光源を配置したことを特徴とする平面照明装置。 A rectangular light source for emitting light into circularly arcuate or radial,
A front surface portion that emits light from the light source, a back surface portion that is located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and the two side surface portions intersect. Having an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and entering the arc shape or radial light from the whole of the incident portion, A convex surface having an inclined surface in the direction of the incident portion with the arc or radial extent concentric with the notched arc shape of the incident portion on the back surface portion so as to correspond to light traveling while spreading radially. A plurality of continuous or non-continuous ridges, and / or a light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A polarizing sheet covering the surface portion,
The light source is arranged in a notched portion of the incident portion at a position where an end position where two adjacent side surfaces of the light source intersect each other and an incident portion notched in the arc shape of the light guide plate are opposed to each other . A flat illumination device characterized by that. 円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、前記表面部の反対側に位置する裏面部と、これら前記表面部と前記裏面部とに直角に交わる側面部と、この二つの前記側面部が交差する隅の少なくとも１つを前記光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有するとともに前記表面部に光を屈折させる微細な光制御素子を有し、前記入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、前記裏面部に前記入射部の前記欠切した円弧形状と同心に前記円弧状または放射状に広がりを持って前記入射部方向に傾斜面を持つ凸状または／および凹状の稜を連続または非連続に複数設け、前記光源からの円弧状または放射状の光を前記傾斜面によって略前記表面部方向に全反射する導光板と、
前記表面部を覆う拡散シートとを具備し、
前記光源の互いに隣合う２つの側面が交差する端部位置と前記導光板の前記円弧状に欠切した入射部とが対向する位置で前記入射部の欠切部分内に前記光源を配置したことを特徴とする平面照明装置。 A rectangular light source for emitting light into circularly arcuate or radial,
A front surface portion that emits light from the light source, a back surface portion that is located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and the two side surface portions intersect. And having a fine light control element that refracts light on the surface portion and has an incident portion cut out in an arc shape that coincides with light emitted radially or radially from the light source, The circular arc or radial light is incident from the entire incident portion, and the circular arc or concentricity with the notched circular arc shape of the incident portion on the back surface portion so as to correspond to the light traveling while spreading radially. A plurality of convex or / and concave ridges having a radially extending surface and an inclined surface in the direction of the incident portion are provided continuously or discontinuously, and the arc-shaped or radial light from the light source is approximately formed on the surface by the inclined surface. Direction A light guide plate is totally reflected,
A diffusion sheet covering the surface portion,
The light source is arranged in a notched portion of the incident portion at a position where an end position where two adjacent side surfaces of the light source intersect each other and an incident portion notched in the arc shape of the light guide plate are opposed to each other . A flat illumination device characterized by that. 円弧状または放射状に光を出射する矩形状の光源と、
当該光源からの光を出射する表面部と、前記表面部の反対側に位置する裏面部と、これら前記表面部と前記裏面部とに直角に交わる側面部と、この二つの前記側面部が交差する隅の少なくとも１つを前記光源からの円弧状または放射状に出射した光に一致した円弧状に欠切した入射部を有し、前記入射部の全体から円弧状または放射状の光を入射し、放射状に広がりながら進行する光に対応するように、前記裏面部に前記入射部の前記欠切した円弧形状と同心に前記円弧状または放射状に広がりを持って前記入射部方向に傾斜面を持つ凸状または／および凹状の稜連続または非連続に複数を設け、前記光源からの円弧状または放射状の光を前記傾斜面によって略前記表面部方向に全反射する導光板と、
前記表面部を覆う拡散シートまたは偏光シートと、
前記表面部および前記入射部以外の部分を覆う反射シートとを具備し、
前記光源の互いに隣合う２つの側面が交差する端部位置と前記導光板の前記円弧状に欠切した入射部とが対向する位置で前記入射部の欠切部分内に前記光源を配置したことを特徴とする平面照明装置。 A rectangular light source for emitting light into circularly arcuate or radial,
A front surface portion that emits light from the light source, a back surface portion that is located on the opposite side of the front surface portion, a side surface portion that intersects the front surface portion and the back surface portion at a right angle, and the two side surface portions intersect. Having an incident part cut out in an arc shape that coincides with the light emitted from the light source in an arc shape or a radial shape, and entering the arc shape or radial light from the whole of the incident portion, A convex surface having an inclined surface in the direction of the incident portion with the arc or radial extent concentric with the notched arc shape of the incident portion on the back surface portion so as to correspond to light traveling while spreading radially. A plurality of continuous or non-continuous ridges or / and concave ridges, and a light guide plate that totally reflects arc-shaped or radial light from the light source substantially in the direction of the surface portion by the inclined surface;
A diffusion sheet or a polarizing sheet covering the surface portion;
A reflection sheet covering a portion other than the surface portion and the incident portion;
The light source is arranged in a notched portion of the incident portion at a position where an end position where two adjacent side surfaces of the light source intersect each other and an incident portion notched in the arc shape of the light guide plate are opposed to each other . A flat illumination device characterized by that. 前記偏光シートは、前記導光板に放射状に設けた前記稜に対応した位置に頂角が６０度〜８０度のプリズム形状を有することを特徴とする請求項１または請求項３記載の平面照明装置。The polarizing sheet, flat illumination according to claim 1 or claim 3, wherein the apex angle at a position corresponding to the edge provided radially on the light guide plate, characterized in that have a 60 to 80 degrees of prism-shaped apparatus.
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