JP2004046076A - Optical deflecting element and surface light source unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source unit which has a superior field angle characteristic and image quality without spoiling a high-luminance characteristic with superior light use efficiency of a primary light source. <P>SOLUTION: This optical deflecting element has an incidence surface on which light is incident and a projection surface which is positioned on the opposite side to it and projects the incident light, and a plurality of prism arrays consisting of two prism surfaces are arrayed on the incidence surface almost in parallel to each other; and at least one prism surface of the prism arrays consists of at least two planes differing in tilt angle, a plane which is closer to the projection surface has a larger tilt angle, and the difference between the tilt angle of the plane closest to the projection surface and the plane farthest from the projection surface is ≤15°. <P>COPYRIGHT: (C)2004,JPO

Description

さらに、導光体３としては、その光出射率が０．５〜５％の範囲にあるものが好ましく、より好ましくは１〜３％の範囲である。これは、光出射率が０．５％より小さくなると導光体３から出射する光量が少なくなり十分な輝度が得られなくなる傾向にあり、光出射率が５％より大きくなると光源１近傍で多量の光が出射して、光出射面３３内でのＸ方向における光の減衰が著しくなり、光出射面３３での輝度の均斉度が低下する傾向にあるためである。このように導光体３の光出射率を０．５〜５％とすることにより、光出射面から出射する光の出射光光度分布（ＸＺ面内）におけるピーク光の角度（ピーク角度）が光出射面の法線に対し５０〜９０度の範囲にあり、出射光光度分布（ＸＺ面内）の半値全幅が１０〜４０度であるような指向性の高い出射特性の光を導光体３から出射させることができ、その出射方向を光偏向素子４で効率的に偏向させることができ、高い輝度を有する面光源素子を提供することができる。
【００２０】
本発明において、導光体３からの光出射率は次のように定義される。光出射面３３の光入射面３１側の端縁での出射光の光強度（Ｉ_０　）と光入射面３１側の端縁から距離Ｌの位置での出射光強度（Ｉ）との関係は、導光体３の厚さ（Ｚ方向寸法）をｔとすると、次の（３）式のような関係を満足する。
【００２１】
【数２】

ここで、定数Ａが光出射率であり、光出射面３３における光入射面３１と直交するＸ方向での単位長さ（導光体厚さｔに相当する長さ）当たりの導光体３から光が出射する割合（％）である。この光出射率Ａは、縦軸に光出射面２３からの出射光の光強度の対数と横軸に（Ｌ／ｔ）をプロットすることで、その勾配から求めることができる。
【００２２】
また、指向性光出射機能部が付与されていない他の主面には、導光体３からの出射光の光源１と平行な面（ＹＺ面）での指向性を制御するために、光入射面３１に対して略垂直の方向（Ｘ方向）に延びる多数のレンズ列を配列したレンズ面を形成することが好ましい。図１に示した実施形態においては、光出射面３３に粗面を形成し、裏面３４に光入射面３１に対して略垂直方向（Ｘ方向）に延びる多数のレンズ列の配列からなるレンズ面を形成している。本発明においては、図１に示した形態とは逆に、光出射面３３にレンズ面を形成し、裏面３４を粗面とするものであってもよい。
【００２３】
図１に示したように、導光体３の裏面３４あるいは光出射面３３にレンズ列を形成する場合、そのレンズ列としては略Ｘ方向に延びたプリズム列、レンチキュラーレンズ列、Ｖ字状溝等が挙げられるが、ＹＺ方向の断面の形状が略三角形状のプリズム列とすることが好ましい。
【００２４】
本発明において、導光体３に形成されるレンズ列としてプリズム列を形成する場合には、その頂角を７０〜１５０度の範囲とすることが好ましい。これは、頂角をこの範囲とすることによって導光体３からの出射光を十分集光さることができ、面光源素子としての輝度の十分な向上を図ることができるためである。すなわち、プリズム頂角をこの範囲内とすることによって、出射光光度分布（ＸＺ面内）におけるピーク光を含みＸＺ面に垂直な面において出射光光度分布の半値全幅が３５〜６５度である集光された出射光を出射させることができ、面光源素子としての輝度を向上させることができる。なお、プリズム列を光出射面３３に形成する場合には、頂角は８０〜１００度の範囲とすることが好ましく、プリズム列を裏面３４に形成する場合には、頂角は７０〜８０度または１００〜１５０度の範囲とすることが好ましい。
【００２５】
なお、本発明では、上記のような光出射面３３またはその裏面３４に光出射機能部を形成する代わりにあるいはこれと併用して、導光体内部に光拡散性微粒子を混入分散することで指向性光出射機能を付与したものでもよい。また、導光体３としては、図１に示したような断面形状に限定されるものではなく、くさび状、船型状等の種々の断面形状のものが使用できる。
【００２６】
図２は、光偏向素子４のプリズム列の形状の説明図であり、光偏向素子４は主表面の一方を入光面４１とし他方の面を出光面４２とする。入光面４１には多数のプリズム列が略並列に配列され、各プリズム列は光源側に位置する第１のプリズム面４４と光源から遠い側に位置する第２のプリズム面４５の２つのプリズム面から構成されている。図２に示した実施形態においては、第１のプリズム面４４が平面であり、第２のプリズム面４５が３つの傾斜角の異なる平面４６〜４８から構成され、出光面に近い平面ほど傾斜角が大きくなっている。また、平面４６〜４８のうち、最も出光面に近い平面４８と最も出光面から遠い平面４６との傾斜角の差が１５度以下となっている。なお、本発明において、平面の傾斜角とはプリズム列形成平面４３に対する各平面の傾斜角度をいう。
【００２７】
本発明の光偏向素子４は、第２のプリズム面４５を傾斜角の異なる少なくとも２つの平面より構成し、これら平面の傾斜角が出光面に近いほど大きくなり、最も出光面に近い平面と最も出光面から遠い平面との傾斜角の差を１５度以下とすることにより、極めて高い集光効果を発揮させることができ、光源装置として極めて高い輝度を得ることができる。この最も出光面に近い平面と最も出光面から遠い平面との傾斜角の差は、好ましくは０．５〜１０度の範囲であり、より好ましくは１〜７度の範囲である。なお、傾斜角の異なる平面を３つ以上形成する場合には、この傾斜角の差は上記範囲とすることが好ましいが、特にこの範囲に限定されるものではない。また、第２のプリズム面４５をこのような構造にすることにより、所望の集光性を有する偏向素子を容易に設計することもできるとともに、一定の光学特性を有する光偏向素子を安定して製造することもできる。
【００２８】
次に、本発明の光偏向素子のプリズム面の形状について説明する。図３〜１４は、２つのプリズム面がともに平面であり、プリズム頂角が６５．４度である従来の光偏向素子により導光体からの出射光光度分布（ＸＺ面内）のピーク角度が２０度である光が、導光体の光入射面および光出射面の両方の面に対して垂直な平面において、どのような出射光輝度分布（ＸＺ面内）で光偏向素子から出射するかを示したものである。図３〜１２は、第１プリズム面より入射した入射光が第２のプリズム面によって全反射され出光面４２から出射される状態を、第２プリズム面をｘ方向に１０個のエリアに均等に分割し、それぞれのエリアからの出射光輝度分布（ＸＺ面内）を示したものである。１０個のエリアは、プリズム頂部に近い方から順にＰａｒｔ１、Ｐａｒｔ２、・・・Ｐａｒｔ１０とした。第２プリズム面で全反射され出射する全体の光の出射光輝度分布（ＸＺ面内）においては、図１３に示すように、そのピ−ク光は法線方向に出射され、２２度の半値全幅を有している。
【００２９】
しかし、これらをＰａｒｔ１〜Ｐａｒｔ１０の各エリアにおける出射光輝度分布（ＸＺ面内）を見ると、そのピーク角度は、Ｐａｒｔ１およびＰａｒｔ２では約−９度（負の角度値は法線方向を０度として光源方向に傾いた場合を示す。）付近に出射し、Ｐａｒｔ３〜Ｐａｒｔ７では０度方向（法線方向）にピ−ク光がシフトし、さらにＰａｒｔ８〜Ｐａｒｔ１０ではピ−ク光は順に正の角度方向にシフトしているのがわかる。最も出光面４２に近いエリア（Ｐａｒｔ１０）で全反射され出射するピーク角度は７度であり、第２のプリズム面（Ｐａｒｔ１〜Ｐａｒｔ１０の間）ではピーク角度に１６度の広がりがある。また、各エリアからのピ−ク光の強度は、Ｐａｒｔ１からＰａｒｔ１０へと徐々に小さくなっている。
【００３０】
このように、一つの平面からなるプリズム面で全反射され出射した光は、プリズム面の全反射するエリアに依存してかなり広い範囲で分散していることがわかる。この各エリアからの出射光輝度分布（ＸＺ面内）におけるピ−ク光を、各エリアのプリズム面の傾斜角をそれぞれ調整し、すべてのエリアでピーク角度を略同方向に出射させることによって、大部分の出射光を特定方向に集中して出射させることが可能となる。このとき、各エリアにおけるプリズム面の傾斜角は、Ｐａｒｔ１からＰａｒｔ１０の順に、すなわち出光面４２に近いエリアのプリズム面ほど傾斜角を大きくするようにする。このように、各エリアのプリズム面の傾斜角を図１４に示したように調整することで、プリズム面全体で全反射される出射光を一定の方向に集光させることができ、より指向性が高く、ピ−ク強度の大きな光を出射することができる。
【００３１】
プリズム面を分割した各エリアの設定は、少なくとも２つのエリアを設定すればよいが、このエリア数（傾斜角の異なる平面の数）が少なすぎると、光偏向素子による集光性が低下し、輝度向上効果が損なわれる傾向にあるため、３つ以上とすることが好ましく、より好ましくは５つ以上、さらに好ましくは６つ以上である。なお、エリア数を２つにする場合には、集光特性の低下をある程度抑止できるためには、２つの平面の傾斜角の差を１５度以下とすることが必要であり、好ましくは０．５〜１０度の範囲、より好ましくは１〜７度の範囲である。エリア数が３つ以上の場合であっても、出光面に最も近い平面の傾斜角と出光面から最も遠い平面の傾斜角の差を１５度以下とすることが集光特性の点から好ましく、より好ましくは０．５〜１０度、さらに好ましくは１〜７度の範囲である。
【００３２】
一方、このエリア数を多くすと、プリズム面で全面にわたってピーク角度を細かく調整することができるため、全体としての集中度を高めることができるが、傾斜角の異なる平面を細かく形成しなければならず、光偏向素子のプリズム面を形成するための金型切削用のバイトの設計や製造が複雑となるとともに、一定の光学特性を有する光偏向素子を安定して得ることも難しくなる。このため、プリズム面に形成するエリア数は２０以下とすることが好ましく、より好ましくは１２以下である。このプリズム面の分割は均等に分割することが好ましいが、必ずしも均等に分割する必要はなく、所望のプリズム面全体の出射光輝度分布（ＸＺ面内）に応じて調整することができる。また、異なる傾斜角を有する各平面の幅（プリズム列断面における各平面部分の長さ）は、プリズム列のピッチに対して４〜４７％の範囲とすることが好ましく、より好ましくは６〜３０％、さらに好ましくは７〜２０％の範囲である。
【００３３】
本発明においては、例えば、図１５および図１６に示したように、上記のような異なる傾斜角を有する平面の少なくとも１つを凸曲面とすることもでき、全ての平面を凸曲面としてもよい。図１５では、第２のプリズム面４５を、４つのエリアに分割し、３つの平面４９〜５１と１つの凸曲面５２から構成している。図１６では、第２のプリズム面４５を２つのエリアに分割し、形状の異なる２つの凸曲面５３、５４から構成している。図中、５５、５６は、２つの曲面５３、５４の形状を決定する非球面形状である。また、第２のプリズム面４５を分割した各エリアの境界を通るような曲面で構成することもでき、この場合、輝度の大幅な低下を招かない範囲であれば曲面は各アリアの境界から多少ずれてもよい。例えば、曲面の通過位置（プリズム頂部からの距離）のプリズム列のピッチに対する割合のエリアの境界の割合に対するずれが４％以下であればよく、より好ましくは２％以下、さらに好ましくは１％以下の範囲である。なお、本発明において、凸曲面における傾斜角は、１つの凸曲面の全ての位置における傾斜角を平均したものをいう。このように、プリズム面を異なる傾斜角の複数の凸曲面で構成した場合には、異なる傾斜角の平面により構成する場合と比較して、エリア数は少なくすることができ、２〜１０のエリア数とすることができ、好ましくは２〜８の範囲である。しかし、エリア数が少なすぎると所望の出射光輝度分布（ＸＺ面内）を調整するための各凸曲面の設計が困難となるため、エリア数は３〜８の範囲とすることがより好ましい。
【００３４】
また、凸曲面の形状は、そのＸＺ方向の断面形状が球面あるいは非球面とすることができる。さらに、複数の凸曲面によりプリズム面を構成する場合には、各凸曲面の形状が異なることが好ましく、球面形状の凸曲面と非球面形状の凸曲面とを組み合わせることもできるが、少なくとも１つの凸曲面を非球面形状とすることが好ましい。複数の凸曲面を球面形状とする場合には、各凸曲面でその曲率を変えたものであってもよい。非球面形状としては、楕円形状の一部、放物線形状の一部等が挙げられる。
【００３５】
さらに、凸曲面は、その曲率半径（ｒ）をプリズム列のピッチ（Ｐ）との比（ｒ／Ｐ）が２〜５０の範囲とすることが好ましく、より好ましくは５〜３０、さらに好ましくは７〜１０の範囲である。このｒ／Ｐが２未満であったり、５０を超えると、十分な集光特性を発揮できなくなり、輝度が低下する傾向にある。
【００３６】
このような傾斜角の異なる平面および凸曲面は、各平面および凸曲面で全反射した光が出光面から出射した際の出射光輝度分布（ＸＺ面内）におけるピーク角度が略一定の角度になるように設計されるが、この各ピーク角度は必ずしも略一定の角度となるようにする必要はなく、全てのピーク角度が１５度以内の範囲内となるような範囲で設計することができ、好ましくは１０度以下、より好ましくは７度以下、さらに好ましくは５度以下の範囲である。
【００３７】
また、このような構成によるプリズム列においては、図３〜１２に示したように、Ｐａｒｔ１〜Ｐａｒｔ５のエリアで全反射され出光面から出射した光の出射光輝度分布（ＸＺ面内）における強度は、プリズム面全体で全反射され出光面から出射した光の出射光輝度分布（ＸＺ面内）における強度の７５％以上を占めることになるため、これらエリアで全反射され出射される出射光を所望の方向へ集光させることが特に重要となる。このため、プリズム列のプリズム頂部からの高さをｈ、プリズム列全体の高さをＨとした場合に、少なくともｈ／Ｈが６０％以下となる高さｈの領域に傾斜角の異なる平面あるいは凸曲面を少なくとも２つ形成することが好ましく、３つ以上形成することがより好ましい。高さｈの領域は、より好ましくはｈ／Ｈが５０％以下となる領域であり、さらに好ましくは４０％以下となる領域である。なお、高さｈの領域が小さくなりすぎると十分な集光特性が得られなくなる傾向になるとともに、金型の製造が複雑になることから、ｈ／Ｈは２０％以上であることが好ましい。この場合の高さｈの領域におけるエリア数は、３〜８の範囲とすることが好ましく、より好ましくは３〜６、さらに好ましくは３〜４の範囲である。
【００３８】
また、プリズム面が傾斜角の異なる複数の平面あるいは凸曲面より構成されるとき、十分な集光特性を確保するためには、プリズム列の頂部と低部とを結ぶ仮想平面Ｑ（図２、１５、１６）と複数の平面あるいは凸曲面（実際のプリズム面）との最大距離ｄがプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）で０．４〜５％とすることが好ましい。これは、ｄ／Ｐが０．４％未満あるいは５％を超えると、集光特性が低下する傾向にあり、十分な輝度向上を図れなくなる傾向にあるためであり、より好ましくは０．４〜３％の範囲であり、さらに好ましくは０．７〜２．２％の範囲である。
【００３９】
本発明において、プリズム列の頂角は集光特性や光の利用効率を考えると、３５〜８０度とすることが好ましく、より好ましくは３５〜７０度の範囲であり、さらに好ましくは４０〜７０度の範囲である。また、プリズム頂角の法線に対する左右の振り分け角（２つのプリズム面の法線に対する傾斜角度）α、βは、同一でも異なってもよいが、略法線方向（法線方向を０度とした場合のＸＺ面内における±１０度の範囲をいう。）の輝度を効率よく高めようとする場合には、異なった角度に設定することが好ましい。この場合、光源側に位置する振り分け角αを４０度以下、βを２５〜５０度の範囲とすることが好ましい。この頂角の振り分け角α、βは、その差がわずかにある場合が光利用効率が高くなり輝度をより向上させることができるため、振り分け角αを２５〜４０度、振り分け角βを２５〜４５度の範囲とし、振り分け角αとβの差の絶対値（Ｉα−βＩ）を０．５〜１０度とすることが好ましく、より好ましくは１〜１０度、さらに好ましくは１〜８度の範囲である。なお、出射光輝度分布（ＸＺ面内）におけるピ−ク光を略法線方向以外とする場合は、プリズム頂角の振り分け角α、βを調整することによって、所望の方向にピーク光を有する出射光輝度分布（ＸＺ面内）を得ることができる。
【００４０】
また、振り分け角αを２０度以下とすることによっても光利用効率を高くでき輝度をより向上させることができる。この振り分け角αを小さくするほど光利用効率を高くすることができるが、振り分け角αを小さくしすぎるとプリズム列の頂角が小さくなる傾向にありプリズムシートの製造が困難となるため、振り分け角αは３〜１５度の範囲とすることが好ましく、より好ましくは５〜１０度の範囲である。この場合、出射光輝度分布（ＸＺ面内）におけるピ−ク光を法線方向から±２度の範囲とし法線輝度を向上させるためには、振り分け角βを３５〜４０度の範囲とすればよい。
【００４１】
このように振り分け角αを２０度以下とする場合には、プリズム列の断面形状においてプリズム頂部と谷部を結んだ２つの直線の長さの比（光源に近い側の直線の長さＬ１に対する光源から遠い側の直線の長さＬ２の比Ｌ２／Ｌ１）を１．１倍以上とすることが好ましい。これは、Ｌ２／Ｌ１を１．１倍以上とすることにより光源に近い側のプリズム面から入射した光を光源から遠い側のプリズム面で効率よく受光することができ、光利用効率を高くでき輝度をより向上させることができるためであり、より好ましくは１．１５倍以上であり、さらに好ましくは１．１７倍以上である。一方、Ｌ２／Ｌ１を大きくしすぎるとプリズム列の頂角が小さくなる傾向にありプリズムシートの製造が困難となるため、１．３倍以下とすることが好ましく、より好ましくは１．２５倍以下、さらに好ましくは１．２倍以下である。また、プリズム列のピッチＰに対する光源から遠い側の直線の長さＬ２の比（Ｌ２／Ｐ）を１．２５倍以上とすることが同様の理由から好ましく、より好ましくは１．３倍以上であり、さらに好ましくは１．４倍以上である。一方、このＬ２／Ｐを大きくしすぎるとプリズム列の頂角が小さくなる傾向にありプリズムシートの製造が困難となるため、１．８倍以下とすることが好ましく、より好ましくは１．６倍以下、さらに好ましくは１．５倍以下である。
【００４２】
また、本発明の光偏向素子は、図１７、１８に例示すように隣接するプリズム列の間にプリズム列の傾斜角よりも傾斜角の小さい凸形状や平面（光透過領域）を形成してもよい。このような光透過領域を形成することにより、液晶パネル側から入射した外光をこの部分から光源装置内に導入することができ、導光体の裏面に配置された反射シ−ト５により反射し、再び液晶パネル側に出射することにより、外光も有効に利用することができる。このとき、反射シート５により反射した外光の均一性を維持するため、反射シートに微弱な拡散性を付与したり、光偏向素子の出光面に光拡散層を形成したり、光偏向素子の出光面に光拡散シ−トを載置することが好ましい。また、外光の利用効率を高めると、バックライトとしての光の利用効率が低下するため、使用形態等を考慮して光透過領域の割合を決めることが必要である。例えば、光透過領域の幅は、プリズム列のピッチの２０〜５０％の範囲とすることが好ましく、より好ましくは２０〜４０％の範囲である。光透過領域としては、図１７に示したような平面形状５９、図１８に示したような曲面形状６０や多角形状等が挙げられる。中でも、光透過領域を多角形状や曲面とすることにより、外光の反射を制御することができるため好ましい。
【００４３】
本発明の光偏向素子においては、光を集光させて出射させる際に導光体からの出射光光度分布が強く反映されるため、光偏向素子の出光面からの出射光輝度分布（ＸＺ面内）は法線方向前後の角度において非対称な分布になる傾向がある。特に、第２プリズム面４５を１つの曲面で構成した場合には、導光体の光入射面側の出射光輝度分布（ＸＺ面内）が急激に低下し、法線方向から観察した場合に有効視野角範囲内において非対称性が強く視認される。本発明においては、プリズム面を傾斜角の異なる複数の平面あるいは凸曲面より構成することで、上記のような出射光輝度分布（ＸＺ面内）の非対称性を緩和することができる。すなわち、出射光輝度分布（ＸＺ面内）の非対称性は、図１９に示すように、光偏向素子から出射した出射光輝度分布（ＸＺ面内）のピーク角度と輝度がピーク光の輝度（ピーク輝度）の１／２となる角度の差の絶対値（広がり幅）Δθ_ａとΔθ_ｂの差（｜Δθ_ａ−Δθ_ｂ｜）により定義することができる。従って、この｜Δθ_ａ−Δθ_ｂ｜が９度以下となるように、プリズム面を構成する平面あるいは凸曲面の傾斜角を調整することにより、出射光輝度分布（ＸＺ面内）の非対称性を緩和することができる。この｜Δθ_ａ−Δθ_ｂ｜は、より好ましくは６度以下、さらい好ましくは４度以下の範囲である。｜Δθ_ａ−Δθ_ｂ｜を９度以下とすることにより視認性はほぼ良好となり、４度以下とすることにより非対称性に起因する不快さはほとんど感じなくなる。
【００４４】
さらに、本発明の光偏向素子４においては、図２０に示したように、第１のプリズム面４４の平面が、プリズム列パターン形成の際に発生するそり等による形状の変化（プリズム列の頂部と底部を結ぶ平面からの変位）が起こる場合がある。しかし、このような平面の変位が大きい場合には、光偏向素子４の光学特性に影響を及ぼすことになり、微小な変位に抑えることが好ましい。すなわち、プリズム列の頂部と底部を結ぶ平面からのプリズム面の変位がプリズム列のピッチＰに対する前記平面との最大距離Ｓの割合（Ｓ／Ｐ）で０．００８以下であることが好ましく、さらに好ましくは０．００６５以下、より好ましくは０．００５以下の範囲である。このような略平面の変形は、プリズム列パターンを形成する際の重合収縮などの影響に主として起因するため、あらかじめ重合収縮による変形の程度を定量化しておき、それを相殺するように金型のプリズム列の形状を設計しておくことが好ましい。
【００４５】
本発明において、上記のような凸曲面形状部４６を有するプリズム面は、少なくとも一次光源１から遠い側の面（第２のプリズム面４５）に形成することが好ましい。これによれば、導光体３の端面３２にも一次光源を配置する場合の光偏向素子４から出射する光の出射光輝度分布（ＸＺ面内）における分布を十分に小さくすることができる。凸曲面形状部４６を有するプリズム面は、例えば、導光体３を伝搬する光が光入射面３１と反対側の端面３２で反射して戻ってくる割合が比較的高い場合、導光体３の対向する２つの端面にそれぞれ一次光源１を配置する場合には、一次光源１に近い側のプリズム面（第１のプリズム面４４）も同様の形状とすることがより好ましい。一方、導光体３を伝搬する光が光入射面３１と反対側の端面３２で反射して戻ってくる割合が比較的低い場合には、一次光源１に近い側のプリズム面を略平面としてもよい。また、本発明の光偏向素子４は、そのプリズム列の頂部のどちらかが略平面より構成されるのが好ましい。プリズム列形成のための成形用型部材の形状転写面形状のより正確な形成が可能になり、導光体３に光偏向素子４を載置した際のスティッキング現象の発生を抑止することができる。
【００４６】
このように、導光体３の光出射面３３上に上記のような光偏向素子４を、そのプリズム列形成面が入光面側となるように載置することによって、導光体３の光出射面３３から出射する指向性出射光の出射光光度分布（ＸＺ面内）をより狭くすることができ、光源装置としての高輝度化、狭視野化を図ることができる。このような光偏向素子４からの出射光の出射光輝度分布（ＸＺ面内）の半値全幅は、５〜２５度の範囲であることが好ましく、より好ましくは１０〜２０度の範囲であり、さらに好ましくは１２〜１８度の範囲である。これは、この出射光輝度分布（ＸＺ面内）の半値全幅を５度以上とすることによって極端な狭視野化による画像等の見づらさをなくすことができ、２５度以下とすることによって高輝度化と狭視野化を図ることができるためである。
【００４７】
本発明における光偏向素子４の狭視野化は、導光体３の光出射面３３からの出射光光度分布（ＸＺ面内）の広がりの程度（半値全幅）に影響されるため、光偏向素子４の出光面４２からの出射光輝度分布（ＸＺ面内）の半値全幅Ａの導光体３の光出射面３３からの出射光光度分布（ＸＺ面内）の半値全幅Ｂに対する割合も、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅Ｂによって変わる。例えば、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅Ｂが２６度未満の場合には、半値全幅Ａが半値全幅Ｂの３０〜９５％の範囲であることが好ましく、より好ましくは３０〜８０％の範囲であり、さらに好ましくは３０〜７０％の範囲である。また、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅Ｂが２６度以上の場合には、半値全幅Ａが半値全幅Ｂの３０〜８０％の範囲であることが好ましく、より好ましくは３０〜７０％の範囲であり、さらに好ましくは３０〜６０％の範囲である。特に、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅Ｂが２６〜３６度の場合には、半値全幅Ａが半値全幅Ｂの３０〜８０％の範囲であることが好ましく、より好ましくは３０〜７０％の範囲であり、さらに好ましくは３０〜６０％の範囲である。さらに、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅Ｂが３６度を超える場合には、半値全幅Ａが半値全幅Ｂの３０〜７０％の範囲であることが好ましく、より好ましくは３０〜６０％の範囲であり、さらに好ましくは３０〜５０％の範囲である。
【００４８】
一般に導光板の出射効率を高めようとすると、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅Ｂは大きくなり集光効率は低下するように思えるが、実際は上記のように狭視野化の効果は大きくなるため、狭視野化の効率および面光源装置としての光利用効率という点では出射光光度分布（ＸＺ面内）の半値全幅Ｂが２６度以上である導光体との組み合わせで光偏向素子を使用することが好ましく、より好ましくは半値全幅Ｂが３６度を超える導光体である。また、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅が小さい場合には狭視野化の効果は小さくなるが、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅が小さいものほど高輝度化を図ることができるため、高輝度化という点では出射光光度分布（ＸＺ面内）の半値全幅Ｂが２６度未満である導光体との組み合わせで光偏向素子を使用することが好ましい。
【００４９】
一次光源１はＹ方向に延在する線状の光源であり、該一次光源１としては例えば蛍光ランプや冷陰極管を用いることができる。なお、本発明においては、一次光源１としては線状光源に限定されるものではなく、ＬＥＤ光源、ハロゲンランプ、メタハロランプ等のような点光源を使用することもできる。特に、携帯電話機や携帯情報端末機等の比較的小さな画面寸法の表示装置に使用する場合には、ＬＥＤ等の小さな点光源を使用することが好ましい。また、一次光源１は、図１に示したように、導光体３の一方の側端面に設置する場合だけでなく、必要に応じて対向する他方の側端面にもさらに設置することもできる。
【００５０】
例えば、一次光源１としてＬＥＤ光源等の略点状光源を導光体３のコーナー等に配置して使用する場合には、導光体３に入射した光は光出射面３３と同一の平面内において一次光源１を略中心とした放射状に導光体３中を伝搬し、光出射面３３から出射する出射光も同様に一次光源１を中心とした放射状に出射する。このような放射状に出射する出射光を、その出射方向に関わらず効率よく所望の方向に偏向させるためには、光偏向素子４に形成するプリズム列を一次光源１を取り囲むように略弧状に略並列して配置することが好ましい。このように、プリズム列を一次光源１を取り囲むように略弧状に略並列して配置することにより、光出射面３３から放射状に出射する光の殆どが光偏向素子４のプリズム列に対して略垂直に入射するため、導光体３の光出射面３３の全領域で出射光を効率良く特定の方向に向けることができ、輝度の均一性を向上させることができる。光偏向素子４に形成する略弧状のプリズム列は、導光体３中を伝搬する光の分布に応じてその弧状の程度を選定し、光出射面３３から放射状に出射する光の殆どが光偏向素子４のプリズム列に対して略垂直に入射するようにすることが好ましい。具体的には、ＬＥＤ等の点状光源を略中心とした同心円状に円弧の半径が少しずつ大きくなるように略並列して配置されたものが挙げられ、プリズム列の半径の範囲は、面光源システムにおける点状光源の位置と、液晶表示エリアに相当する面光源の有効エリアとの位置関係や大きさによって決定される。
【００５１】
光源リフレクタ２は一次光源１の光をロスを少なく導光体３へ導くものである。材質としては、例えば表面に金属蒸着反射層有するプラスチックフィルムを用いることができる。図１に示されているように、光源リフレクタ２は、光反射素子５の端縁部外面から一次光源１の外面を経て光偏向素子４の出光面端縁部へと巻きつけられている。他方、光源リフレクタ２は、光偏向素子４を避けて、光反射素子５の端縁部外面から一次光源１の外面を経て導光体３の光出射面端縁部へと巻きつけることも可能である。
【００５２】
このような光源リフレクタ２と同様な反射部材を、導光体３の側端面３１以外の側端面に付することも可能である。光反射素子５としては、例えば表面に金属蒸着反射層を有するプラスチックシートを用いることができる。本発明においては、光反射素子５として反射シートに代えて、導光体３の裏面３４に金属蒸着等により形成された光反射層等とすることも可能である。
【００５３】
本発明の導光体３及び光偏向素子４は、光透過率の高い合成樹脂から構成することができる。このような合成樹脂としては、メタクリル樹脂、アクリル樹脂、ポリカーボネート系樹脂、ポリエステル系樹脂、塩化ビニル系樹脂が例示できる。特に、メタクリル樹脂が、光透過率の高さ、耐熱性、力学的特性、成形加工性に優れており、最適である。このようなメタクリル樹脂としては、メタクリル酸メチルを主成分とする樹脂であり、メタクリル酸メチルが８０重量％以上であるものが好ましい。導光体３及び光偏向素子４の粗面の表面構造やプリズム列等の表面構造を形成するに際しては、透明合成樹脂板を所望の表面構造を有する型部材を用いて熱プレスすることで形成してもよいし、スクリーン印刷、押出成形や射出成形等によって成形と同時に形状付与してもよい。また、熱あるいは光硬化性樹脂等を用いて構造面を形成することもできる。更に、ポリエステル系樹脂、アクリル系樹脂、ポリカーボネート系樹脂、塩化ビニル系樹脂、ポリメタクリルイミド系樹脂等からなる透明フィルムあるいはシート等の透明基材上に、活性エネルギー線硬化型樹脂からなる粗面構造またレンズ列配列構造を表面に形成してもよいし、このようなシートを接着、融着等の方法によって別個の透明基材上に接合一体化させてもよい。活性エネルギー線硬化型樹脂としては、多官能（メタ）アクリル化合物、ビニル化合物、（メタ）アクリル酸エステル類、アリル化合物、（メタ）アクリル酸の金属塩等を使用することができる。
【００５４】
以上のような一次光源１、光源リフレクタ２、導光体３、光偏向素子４および光反射素子５からなる面光源装置の発光面（光偏向素子４の出光面４２）上に、液晶表示素子を配置することにより液晶表示装置が構成される。液晶表示装置は、図１における上方から液晶表示素子を通して観察者により観察される。また、本発明においては、十分にコリメートされた狭い分布の光を面光源装置から液晶表示素子に入射させることができるため、液晶表示素子での階調反転等がなく明るさ、色相の均一性の良好な画像表示が得られるとともに、所望の方向に集中した光照射が得られ、この方向の照明に対する一次光源の発光光量の利用効率を高めることができる。
【００５５】
さらに、本発明においては、このように光偏向素子４によって狭視野化され高輝度化された光源装置において、輝度の低下をできる限り招くことなく、視野範囲を目的に応じて適度に制御するために、光偏向素子４の出光面上に光拡散素子６を隣接配置する。また、本発明においては、このように光拡散素子６を配置することによって、品位低下の原因となるぎらつきや輝度斑等を抑止し品位向上を図ることもできる。
【００５６】
光拡散素子６は、光偏向素子４の出光面側に光偏向素子４と一体化させてもよいし、光拡散素子６を個別に光偏向素子４の出光面側に載置してもよいが、個別に光拡散素子６を配置することが好ましい。個別に光拡散素子６を載置する場合には、光拡散素子６の光偏向素子４に隣接する側の面には、光偏向素子４とのスティッキングを防止するため、凹凸構造を付与することが好ましい。同様に、光拡散素子６の出射面においても、その上に配置される液晶表示素子との間でのスティッキングを考慮する必要があり、光拡散素子６の出射面にも凹凸構造を付与することが好ましい。この凹凸構造は、スティッキング防止の目的のみに付与する場合には、平均傾斜角が０．７度以上となるような構造とすることが好ましく、さらに好ましくは１度以上であり、より好ましくは１．５度以上である。
【００５７】
本発明においては、輝度特性、視認性および品位等のバランスを考慮して光偏向素子４からの出射光を適度に拡散させる光拡散特性を有する光拡散素子６を使用することが必要である。すなわち、光拡散素子６の光拡散性が低い場合には、視野角を十分に広げることが困難となり視認性を低下させるとともに、品位改善効果が十分でなくなる傾向にあり、逆に光拡散性が高すぎる場合には光偏向素子４による狭視野化の効果が損なわれるとともに、全光線透過率も低くなり輝度が低下する傾向にある。そこで、本発明の光拡散素子６においては、平行光を入射したときの出射光光度分布（ＸＺ面内）の半値全幅が１〜１３度の範囲であるものが使用される。光拡散素子６の半値全幅は、好ましくは３〜１１度の範囲、さらに好ましくは４〜８．５度の範囲である。なお、本発明において光拡散素子６の出射光光度分布（ＸＺ面内）の半値全幅とは、図２１に示すように、光拡散素子６に入射した平行光線が出射時にどの程度拡散して広がるかを示したもので、光拡散素子６を透過し拡散した光の出射光光度分布（ＸＺ面内）におけるピ−ク値に対する半値での広がり角の全幅の角度（Δθ_Ｈ）をいう。
【００５８】
このような光拡散特性は、光拡散素子６中に光拡散剤を混入したり、光拡散素子６の少なくとも一方の表面に凹凸構造を付与することによって付与することができる。表面に形成する凹凸構造は、光拡散素子６の一方の表面に形成する場合と両方の表面に形成する場合とでは、その程度が異なる。光拡散素子６の一方の表面に凹凸構造を形成する場合には、その平均傾斜角を０．８〜１２度の範囲とすることが好ましく、さらに好ましくは３．５〜７度であり、より好ましくは４〜６．５度である。光拡散素子６の両方の表面に凹凸構造を形成する場合には、一方の表面に形成する凹凸構造の平均傾斜角を０．８〜６度の範囲とすることが好ましく、さらに好ましくは２〜４度であり、より好ましくは２．５〜４度である。この場合、光拡散素子６の全光線透過率の低下を抑止するためには、光拡散素子６の入射面側の平均傾斜角を出射面側の平均傾斜角よりも大きくすることが好ましい。また、光拡散素子６のヘイズ値としては８〜８２％の範囲とすることが、輝度特性向上と視認性改良の観点から好ましく、さらに好ましくは３０〜７０％の範囲であり、より好ましくは４０〜６５％の範囲である。
【００５９】
本発明の光源装置においては、その発光面（光拡散素子６の出射面）の法線方向から観察した場合の表示エリア内における輝度が均一であることも要求される。この輝度の均一性は光源の表示エリアの大きさにも依存し、例えば、ノートパソコンやモニター等の表示エリアが大きい大型の光源装置では、比較的広い視野角特性が要求される場合があり、発光面からの出射する出射光光度分布（ＸＺ面内）をより広くすることが要求される。一方、携帯電話や携帯情報端末等の表示エリアが小さい小型の光源装置では、高輝度や表示品位向上が優先される場合があり、発光面からの出射する出射光光度分布（ＸＺ面内）は比較的狭くてもよい。このため、光拡散素子６としては、光源装置の表示エリアの大きさに応じて適切な光拡散特性を有するものを使用することが好ましい。
【００６０】
このような光源装置の表示エリアの大きさに応じた光拡散素子６の光拡散特性について、説明する。なお、光源装置の表示エリアの大きさは、その展開長を基準として説明する。ここで、光源装置の展開長（導光体３の展開長）とは、図２２に示したように、線状の冷陰極光源が一次光源１として導光体３の光入射面に配置された場合、導光体３に入射した光が導光する方向、すなわち光入射面と垂直な方向における表示エリアの最長距離Ｌをいう。また、図２３に示したように、導光体３のコ−ナにＬＥＤ等の点光源が一次光源１として配置された場合、光点源から最も遠い有効表示エリアと点光源を結ぶ直線上の表示エリアの距離Ｌをいう。
【００６１】
（１）導光体３の展開長が８ｃｍ以下の場合
このような光源装置は、一次光源１として線状の冷陰極管（一灯型）やＬＥＤ等が使用され、携帯電話、携帯情報端末、デジタルカメラ等の表示エリアが小さい表示装置に使用されるため、視野角をさほど大きくする必要はなく、品位低下の原因となるぎらつきや輝度斑等を抑える程度の光拡散性を光拡散素子６により付与し、光利用効率を高め高輝度を維持するとともに、消費電力を低く抑えることが必要となる。このため、光拡散素子６としては、出射光光度分布（ＸＺ面内）の半値全幅が１〜６度の範囲であることが好ましく、さらに好ましくは１〜５度、より好ましくは２〜５度の範囲である。また、ヘイズ値としては、８〜６０％の範囲であることが好ましく、さらに好ましくは８〜５０％、より好ましくは２０〜５０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その平均傾斜角が０．８〜５度の範囲であることが好ましく、さらに好ましくは０．８〜４度、より好ましくは２〜４度の範囲である。
【００６２】
（２）導光体３の展開長が８ｃｍを超え２３ｃｍ以下の場合（一次光源１として一灯型の冷陰極管を使用）
このような光源装置は、ノートパソコン、デスクトップ型パソコンのモニター、比較的小型の液晶テレビ等の表示装置に使用されるため、比較的広い視野角が必要であり、液晶表示装置の高解像度化に伴い品位の高い高輝度が必要となる。このため、光拡散素子６としては、出射光光度分布（ＸＺ面内）の半値全幅が３〜１１度の範囲であることが好ましく、さらに好ましくは４〜１０度、より好ましくは４〜９度の範囲である。また、ヘイズ値としては、３０〜８０％の範囲であることが好ましく、さらに好ましくは４０〜７３％、より好ましくは４５〜７０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その平均傾斜角が３〜９．５度の範囲であることが好ましく、さらに好ましくは３．５〜８．５度、より好ましくは４．５〜７度の範囲である。
【００６３】
導光体３の展開長が８ｃｍを超え１８ｃｍ以下の場合には、比較的小型のノートパソコンの表示装置に使用されるため、必要な視野角はやや狭いものである。このため、光拡散素子６としては、出射光光度分布（ＸＺ面内）の半値全幅が３〜８度の範囲であることが好ましく、さらに好ましくは４〜８度、より好ましくは４〜７度の範囲である。また、ヘイズ値としては、３０〜７０％の範囲であることが好ましく、さらに好ましくは４０〜６５％、より好ましくは４５〜６０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その平均傾斜角が３〜７度の範囲であることが好ましく、さらに好ましくは３．５〜６．５度、より好ましくは４．５〜６度の範囲である。
【００６４】
導光体３の展開長が１８ｃｍを超え２２ｃｍ以下の場合には、比較的大形のノートパソコンの表示装置に使用されるため、比較的広い視野角が必要であるとともに、表示エリア内での輝度の均一性を達成することが必要である。このため、光拡散素子６としては、出射光光度分布（ＸＺ面内）の半値全幅が４〜１０度の範囲であることが好ましく、さらに好ましくは５〜９度、より好ましくは５〜８．５度の範囲である。また、ヘイズ値としては、４０〜７５％の範囲であることが好ましく、さらに好ましくは５０〜７０％、より好ましくは５０〜６５％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その平均傾斜角が３．５〜８度の範囲であることが好ましく、さらに好ましくは４〜７度、より好ましくは４．５〜６．５度の範囲である。
【００６５】
導光体３の展開長が２２ｃｍを超え２３ｃｍ以下の場合は、比較的大型のノートパソコン等の表示装置に使用される。一灯型の冷陰極管を一次光源１として使用するノートパソコンとしては表示エリアが大きいものであり、導光体３の展開長が２２ｃｍ以下のものと比較すると、光利用効率をより高くし輝度を向上させることが必要となる。このように輝度をより高くしようとすると、例えば、光源装置の導光体３の裏面に配置される反射シートとして、指向性反射性の低い発泡ＰＥＴ反射フィルムに代えて指向性反射特性に優れる銀反射シ−トやアルミ反射シ−ト等の金属反射シートを使用する必要がある。しかし、金属反射シ−トを使用した場合には、金属反射特有のぎらつき、入射面近傍に現れる暗線輝線、入射面両端部近傍に現れる暗部等の欠陥が強く発現され、光源装置としての品位が損なわれる傾向にある。このような品位低下を抑止するためには、出射光光度分布（ＸＺ面内）の半値全幅が９度を超えるような光拡散性の高い光拡散素子６を使用することが必要となってくるが、このうような光拡散素子６を使用した場合には光拡散性が大きくなりすぎるとともに、全光線透過率の大幅な低下を招くため、十分に高い輝度が得られないという問題点を有する。このため、このような品位低下を導光体３や光偏向素子４にて抑止し、光拡散素子６としては、出射光光度分布（ＸＺ面内）の半値全幅が５〜１１度の範囲のものを使用することが好ましく、さらに好ましくは６〜１０度、より好ましくは７〜９度の範囲である。また、ヘイズ値としては、５０〜８０％の範囲であることが好ましく、さらに好ましくは５５〜７３％、より好ましくは５５〜７０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その平均傾斜角が４．５〜９．５度の範囲であることが好ましく、さらに好ましくは５〜８．５度、より好ましくは５〜７度の範囲である。
【００６６】
（３）導光体３の展開長が２２ｃｍを超え２８ｃｍ以下の場合（一次光源１として多灯型の冷陰極管を使用）
このような光源装置は、デスクトップ型パソコンのモニター、液晶テレビ等の表示装置に使用されるため、比較的広い視野角が必要であるとともに高い輝度が必要となる。このため、一次光源１としては導光体３の対向する２つの端面にそれぞれ１個以上の冷陰極管を配置した多灯型のものが使用される。このような光源装置では、一灯型の一次光源１を用いたものとは品位に関する視認性が異なり、後述するような出射光光度分布（ＸＺ面内）の非対称性はその特性を失い、光源装置の中央部付近の出射光光度分布（ＸＺ面内）は、図２４に示したように、光拡散素子６を使用しない場合でも対称性が向上する。さらに、光源に近い両端部近傍での出射光光度分布（ＸＺ面内）は、それぞれ最も近いところから導光される光の影響をうけ、若干非対称性を帯びた出射光光度分布（ＸＺ面内）となる。すなわち、図２４の左側の端部近傍では、光源側の出射光光度分布（ＸＺ面内）が急激に低下し、中央側の出射光光度分布（ＸＺ面内）は滑らかなテイリング傾向を有しているため、左端部近傍での光の出射方向はやや中央部へ向いている成分が多くなっている。一方、図２４の右側の端部近傍では、これと反対の出射光光度分布（ＸＺ面内）を有しており、光の出射方向はやや中央部へ向いている成分が多くなっている。このため、中央部から両端部近傍を観察したときの視認性に優れた出射光特性が得られ、端部まで高品位な、高い輝度を有する光源装置となる。このため、光拡散素子６としては、広い視野角を得る光拡散性が必要とされ、出射光光度分布（ＸＺ面内）の半値全幅が６〜１３度の範囲のものを使用することが好ましく、さらに好ましくは６．５〜１１度、より好ましくは７〜９度の範囲である。また、ヘイズ値としては、５０〜８２％の範囲であることが好ましく、さらに好ましくは６０〜７５％、より好ましくは６５〜７０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その平均傾斜角が４．５〜１２度の範囲であることが好ましく、さらに好ましくは５．５〜８．５度、より好ましくは６〜７度の範囲である。
【００６７】
本発明の光源装置においては、上記のような光拡散素子６を用いる場合、光偏向素子４からの出射光輝度分布（ＸＺ面内）の半値全幅が１９〜２６度程度の集光性が比較的弱い光偏向素子４を使用するとともに、光拡散性の比較的弱い光拡散素子６を使用した方がＹＺ面での拡散による輝度の低下を抑えられるため、輝度向上の観点からは好ましい場合がある。この場合、光拡散素子６としては、広い視野角を得る光拡散性が必要とされ、出射光光度分布（ＸＺ面内）の半値全幅が１〜８度の範囲のものを使用することが好ましく、さらに好ましくは２〜８度、より好ましくは３〜７度の範囲である。また、ヘイズ値としては、８〜７０％の範囲であることが好ましく、さらに好ましくは３０〜６５％、より好ましくは４０〜６０％の範囲である。さらに、光拡散素子６の一方の表面に凹凸構造を形成する場合には、その平均傾斜角が０．８〜７度の範囲であることが好ましく、さらに好ましくは３〜６．５度、より好ましくは３．５〜６度の範囲である。凹凸構造を両面に形成する場合には、その一方の表面の平均傾斜角が０．８〜４度の範囲であることが好ましく、さらに好ましくは１〜４度、より好ましくは２〜４度の範囲である。
【００６８】
本発明の光源装置においては、光偏向素子４の出光面から出射する出射光は図２５に示したような非対称的な出射光輝度分布（ＸＺ面内）を有する場合がある。この出射光輝度分布（ＸＺ面内）は、導光体３から出射した出射光光度分布（ＸＺ面内）に由来するものである。このような非対称的な出射光輝度分布（ＸＺ面内）は、例えば、光偏向素子４からの出射光輝度分布（ＸＺ面内）の半値全幅が、２０度以下の指向性の高い出射光が出射される場合に発現する傾向にある。特に、表示エリアの比較的大きな光源装置においては、このような出射光輝度分布（ＸＺ面内）の非対称性を緩和させるためには、光拡散性の比較的強い光拡散素子６を使用することが必要となる。一方、光拡散素子６として、出射光光度分布（ＸＺ面内）の半値全幅が４度以上、ヘイズ値が３５％以上のものを使用した場合には、光拡散素子６から出射する出射光光度分布（ＸＺ面内）のピーク角度が光偏向素子４からの出射光輝度分布（ＸＺ面内）のピーク角度に対して、光源と反対側の方向へ１〜３度程度偏角される。このため、光偏角素子からの出射光輝度分布（ＸＺ面内）のピーク角度が所望の方向（例えば法線方向）にある場合には、光拡散素子６を使用することによって所望の方向での輝度の低下を招くことになる。従って、光偏向素子４からの出射光輝度分布（ＸＺ面内）の半値全幅が２０度以下である場合に上記のような光拡散素子６を使用する際には、予め、光偏向素子４からの出射光輝度分布（ＸＺ面内）のピーク角度が所望の方向から光源側に０．５〜３度、さらに好ましくは０．５〜２度、より好ましくは１〜２度傾くように光偏向素子４等を設計しておくことが好ましい。
【００６９】
本発明においては、光拡散素子６として光拡散性に異方性を有するものを使用することが、光拡散素子６の全光線透過率を高め、光偏向素子４からの出射光を効率的に拡散でき、輝度を向上させることができるため好ましい。例えば、導光体３の一つの端面に線上の冷陰極管を一次光源１として配置した光源装置においては、狭視野化を図る光偏向素子４では、導光体３の光出射面から出射する出射光をＸＺ面において主として狭視野化を図るものであり、さらに光拡散素子６により狭視野化されたＸＺ面の光を主として拡散させ視野角を広げることを目的としている。しかし、光拡散素子６として等方性拡散性のものを使用した場合には、光偏角素子により狭視野化されていないＹＺ面の光も同等に拡散されるため、輝度の低下を招くことになる。そこで、図２６に示したように、ＸＺ面よりもＹＺ面での光拡散性が高いような異方拡散性を有する光拡散素子６を使用することにより、光偏向素子４により狭視野化されたＸＺ面の光を強く拡散し、狭視野化されていないＹＺ面の光の拡散を弱くすることができ、光偏向素子４からの出射光を効率的に拡散することができ、輝度の低下をできる限り最小に抑えることができる。
【００７０】
本発明においては、このような光拡散素子６の異方拡散性については、どのような異方性を有する光拡散素子６を使用するかは、上記のようにＸＺ面とＹＺ面での異方性に限定されるものではなく、導光体３の光出射機構、光偏向素子４のレンズ形状や配列、光源装置の用途等に応じて適宜選定することができる。すなわち、図２７に示したように、光拡散素子６の出射面に対する法線軸を含む任意の面（ＺＰ−ｎ面（ｎ＝１，２，・・・））を想定し、これらの任意の面における出射光光度分布（ＸＺ面内）の半値全幅を相違させることによって異方性を付与することができる。なお、ＺＰ−ｎ面の中で最も大きい半値全幅を最大半値全幅、最も小さい半値全幅を最小半値全幅とする。同様に、光拡散素子６に異方拡散性を付与する凹凸構造の平均傾斜角についても、ＺＰ−ｎ面と光拡散素子６（ＸＹ面）が交差する任意のＰ−ｎ方向における平均傾斜角を相違させることによって平均傾斜角の異方性を付与することができる。このとき、Ｐ−ｎ方向の中で最も大きい平均傾斜角を最大平均傾斜角、最も小さい平均傾斜角を最小平均傾斜角とする。
【００７１】
例えば、導光体３の一つの端面に線上の冷陰極管を配置し一次光源１とした場合、光偏向素子４は主としてＸＺ面で狭視野化を主として図り、ＹＺ面では殆ど作用しないため、ＸＺ面で効果的に出射光を拡散し、ＹＺ面では出射光を拡散させないような異方拡散性を有する光拡散素子６を使用することが最適である。従って、光拡散素子６としては、ＸＺ面で最大半値全幅を示し、ＹＺ面で最小半値全幅を示すような異方拡散性を有するものが好ましい。同様に、光拡散素子６に形成する凹凸構造も、Ｘ方向に最大平均傾斜角を有し、Ｙ方向に最小平均傾斜角を有するような構造あるいは配置とすることが好ましい。
【００７２】
このような異方拡散性を有する光拡散素子６においても、輝度特性、視認性および品位等のバランスを考慮して光偏向素子４からの出射光を適度に拡散させる光拡散特性を有する光拡散素子６を使用することが必要である。すなわち、光拡散素子６の光拡散性が低い場合には、視野角を十分に広げることが困難となり視認性を低下させるとともに、品位改善効果が十分でなくなる傾向にあり、逆に光拡散性が高すぎる場合には光偏向素子４による狭視野化の効果が損なわれるとともに、全光線透過率も低くなり輝度が低下する傾向にある。そこで、出射光光度分布（ＸＺ面内）の最大半値全幅が１〜１３度の範囲であるものが使用され、好ましくは３〜１１度の範囲、さらに好ましくは４〜９度の範囲である。また、最小半値全幅に対する最大半値全幅の比（最大半値全幅／最小半値全幅）が１．１〜２０の範囲であることが好ましく、さらに好ましくは２〜１５の範囲、より好ましくは４〜１０の範囲である。これは、最大半値全幅／最小半値全幅を１．１以上とすることによって光の利用効率を向上させ輝度を高めることができるためであり、２０以下とすることによって強い光拡散性による輝度の低下を抑止することができるためである。
【００７３】
光拡散素子６の一方の表面に凹凸構造を形成する場合には、その最大平均傾斜角を０．８〜１５度の範囲とすることが好ましく、さらに好ましくは３．５〜１１度であり、より好ましくは４〜９度である。また、最大半値全幅／最小半値全幅と同様の観点から、最小平均傾斜角に対する最大平均傾斜角の比（最大平均傾斜角／最小平均傾斜角）は、１．１〜２０の範囲であることが好ましく、さらに好ましくは２〜１５の範囲、より好ましくは４〜１０の範囲である。凹凸構造は、光拡散素子６の両方の表面に形成してもよく、この場合、光拡散素子６の全光線透過率の低下を抑止するためには、光拡散素子６の入射面側の平均傾斜角を出射面側の平均傾斜角よりも大きくすることが好ましい。また、光拡散素子６のヘイズ値としては８〜８２％の範囲とすることが、輝度特性向上と視認性改良の観点から好ましく、さらに好ましくは３０〜７０％の範囲であり、より好ましくは４０〜６５％の範囲である。
【００７４】
また、光拡散素子６としては、光源装置の表示エリアの大きさに応じて適切な光拡散特性を有するものを使用することが好ましい。導光体３の展開長が８ｃｍ以下の場合には、光拡散素子６としては、出射光光度分布（ＸＺ面内）の最大半値全幅が１〜６度の範囲であることが好ましく、さらに好ましくは１〜５度、より好ましくは２〜５度の範囲である。また、ヘイズ値としては、８〜６０％の範囲であることが好ましく、さらに好ましくは８〜５０％、より好ましくは２０〜５０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その最大平均傾斜角が０．８〜５度の範囲であることが好ましく、さらに好ましくは０．８〜４度、より好ましくは２〜４度の範囲である。
【００７５】
導光体３の展開長が８ｃｍを超え２３ｃｍ以下の場合（一次光源１として一灯型の冷陰極管を使用）には、光拡散素子６としては、出射光光度分布（ＸＺ面内）の最大半値全幅が３〜１１度の範囲であることが好ましく、さらに好ましくは４〜１０度、より好ましくは４〜９度の範囲である。また、ヘイズ値としては、３０〜８０％の範囲であることが好ましく、さらに好ましくは４０〜７３％、より好ましくは４５〜７０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その最大平均傾斜角が３〜１５度の範囲であることが好ましく、さらに好ましくは３．５〜１０度、より好ましくは４．５〜８度の範囲である。中でも、導光体３の展開長が８ｃｍを超え１８ｃｍ以下の場合には、光拡散素子６としては、出射光光度分布（ＸＺ面内）の最大半値全幅が３〜１０度の範囲であることが好ましく、さらに好ましくは４〜１０度、より好ましくは４〜９度の範囲である。また、ヘイズ値としては、３０〜７０％の範囲であることが好ましく、さらに好ましくは４０〜６５％、より好ましくは４５〜６０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その最大平均傾斜角が３〜９度の範囲であることが好ましく、さらに好ましくは３．５〜８度、より好ましくは４．５〜８度の範囲である。また、導光体３の展開長が１８ｃｍを超え２２ｃｍ以下の場合には、光拡散素子６としては、出射光光度分布（ＸＺ面内）の最大半値全幅が４〜１３度の範囲であることが好ましく、さらに好ましくは５〜１１度、より好ましくは５〜８．５度の範囲である。また、ヘイズ値としては、４０〜７５％の範囲であることが好ましく、さらに好ましくは５０〜７０％、より好ましくは５０〜６５％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その最大平均傾斜角が３．５〜１５度の範囲であることが好ましく、さらに好ましくは４〜９度、より好ましくは４．５〜６．５度の範囲である。さらに、導光体３の展開長が２２ｃｍを超え２３ｃｍ以下の場合は、光拡散素子６としては、出射光光度分布（ＸＺ面内）の最大半値全幅が５〜１３度の範囲のものを使用することが好ましく、さらに好ましくは６〜１２度、より好ましくは７〜９度の範囲である。また、ヘイズ値としては、５０〜８０％の範囲であることが好ましく、さらに好ましくは５５〜７３％、より好ましくは５５〜７０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その最大平均傾斜角が４．５〜１５度の範囲であることが好ましく、さらに好ましくは５〜１０度、より好ましくは５〜７度の範囲である。
【００７６】
導光体３の展開長が２２ｃｍを超え２８ｃｍ以下の場合（一次光源１として多灯型の連陰極管を使用）には、光拡散素子６としては、広い視野角を得る光拡散性が必要とされ、出射光光度分布（ＸＺ面内）の最大半値全幅が６〜１３度の範囲のものを使用することが好ましく、さらに好ましくは６．５〜１１度、より好ましくは７〜９度の範囲である。また、ヘイズ値としては、５０〜８２％の範囲であることが好ましく、さらに好ましくは６０〜７５％、より好ましくは６５〜７０％の範囲である。さらに、光拡散素子６の表面に凹凸構造を形成する場合には、その最大平均傾斜角が４．５〜１５度の範囲であることが好ましく、さらに好ましくは５．５〜１３度、より好ましくは６〜７度の範囲である。
【００７７】
このような異方拡散性を有する光拡散素子６の拡散性付与構造としては、例えば、図２８〜３０に示したような凹凸構造が挙げられる。図２８に示した凹凸構造は、一軸上に長く伸びたレンチキュラーレンズ列等の多数のレンズ列を略並列して連設した配列構造である。このようなレンズ列の配列ピッチは表示装置として使用される液晶素子のピッチおよび光偏向素子４のプリズム列等のレンズ列の配列ピッチに対してモアレの発生しにくいピッチを選定するか、ランダムな配列ピッチとすることが好まし。通常、レンズ列の配列ピッチは１〜７０μｍの範囲とすることが好ましく、製造の容易さやモアレの発生を防止する観点から５〜４０μｍがさらに好ましく、より好ましくは１０〜３０μｍの範囲である。また、レンズ列の長手方向と直交する方向の平均傾斜角は０．８〜１５度の範囲とすることが輝度向上と視認性の観点から好ましく、さらに好ましくは３．５〜１１度、より好ましくは４〜９度の範囲である。
【００７８】
図２９に示した凹凸構造は、多数のシリンドリカルレンズ形状体を離散的に配列した構造である。シリンドリカルレンズ形状体の配列間隔は、一定の規則的なピッチでもよく、ランダムな配列ピッチであってもよい。通常、シリンドリカルレンズ形状体の配列ピッチは、１〜７０μｍの範囲とすることが好ましく、製造の容易さやモアレの発生を防止する観点から５〜４０μｍがさらに好ましく、より好ましくは１０〜３０μｍの範囲である。また、シリンドリカルレンズ形状体の長手方向と直交する方向の平均傾斜角は０．８〜１５度とすることが輝度向上と視認性の観点から好ましく、さらに好ましくは３．５〜１１度、より好ましくは４〜９度の範囲である。このような離散的な配列構造は、光拡散素子６として最大半値全幅であることが必要な面と光拡散素子６の出射面との交差する線と、シリンドリカルレンズ形状体の長手方向が略直交する量的確率が高くなるように配列することが好ましい。また、光拡散素子６として最小半値全幅であることが必要な面と光拡散素子６の出射面と交差する線と、シリンドリカルレンズ形状体の長手方向が略平行になる量的確率が高くなるよう配列することが好ましい。
【００７９】
図３０に示した凹凸構造はヘアライン構造である。ヘアラインの延びる方向に直交方向の平均傾斜角は０．８〜１５度とすることが輝度向上と視認性の観点から好ましく、さらに好ましくは３．５〜１１度、より好ましくは４〜９度の範囲である。ヘアラインの延びる方向は、光拡散素子６として最大半値全幅であることが必要な面と光拡散素子６の出射面との交差する線と略直交する方向が好ましい。
【００８０】
このような異方拡散性を付与する凹凸構造が形成された面およびその裏面の少なくとも一方にマット構造を付与することにより、ぎらつきや輝度斑等を抑止することができ品位を向上させることができる。しかし、マット構造の光拡散性が強くなると異方拡散性が損なわれ輝度の低下を招く場合があるため、比較的光拡散性の弱いマット構造を付与することが好ましい。このようなマット構造としては、平均傾斜角度が０．５〜５度の範囲のものが好ましく、さらに好ましくは０．８〜４度、より好ましくは１〜３．５度の範囲である。なお、異方性付与凹凸構造の表面にマット構造を付与した場合のマット構造の平均傾斜角は、凹凸構造に起因する平均傾斜角度を除いたマット構造自体の平均傾斜角をいう。すなわち、凹凸構造の無い部分や凹凸構造の長手方向に平行な平均傾斜角を測定することができ、触針粗さ計による計測、光拡散素子６の断面形状を画像解析する方法、原子間力顕微鏡等によって測定することができる。
【００８１】
本発明においては、光偏向素子４を用いて導光体３からの出射光を法線方向等の特定な方向に出射させ、この出射光を異方拡散性を有する光拡散素子６を用いて所望の方向に出射させることもできる。この場合、光拡散素子６に異方拡散作用と光偏向角作用の両方の機能を付与することもできる。例えば、凹凸構造としてレンチキュラーレンズ列やシリンドリカルレンズ形状体を用いたものでは、その断面形状を非対称形状にすることで、異方拡散作用と光偏向作用の両機能を付与することができる。
【００８２】
また、本発明においては、光源装置としての視野角を調整し、品位を向上させる目的で、光偏向素子４や光拡散素子６に光拡散材を含有させることもできる。このような光拡散材としては、光偏向素子４や光拡散素子６を構成する材料と屈折率が異なる透明な微粒子を使用することができ、例えば、シリコンビーズ、ポリスチレン、ポリメチルメタクリレ−ト、フッ素化メタクリレ−ト等の単独重合体あるいは共重合体等が挙げられる。光拡散材としては、光偏向素子４による狭視野効果や光拡散素子６による適度な拡散効果を損なわないように、含有量、粒径、屈折率等を適宜選定する必要がある。例えば、光拡散材の屈折率は、光偏向素子４や光拡散素子６を構成する材料との屈折率差が小さすぎると拡散効果が小さく、大きすぎると過剰な散乱屈折作用が生じるため、屈折率差が０．０１〜０．１の範囲とすることが好ましく、さらに好ましくは０．０３〜０．０８、より好ましくは０．０３〜０．０５の範囲である。また、拡散材の粒径は、粒径が大きすぎると散乱が強くなりぎらつきや輝度の低下を引き起こし、小さすぎると着色が発生するため、平均粒径が０．５〜２０μｍの範囲とすることが好ましく、さらに好ましくは２〜１５μｍ、より好ましくは２〜１０μｍの範囲である。
【００８３】
なお、本発明のような光偏向素子を用いた光源装置の出射光輝度分布（ＸＺ面内）は、ピ−ク位置を境に、光源側での出射光輝度分布（ＸＺ面内）がピ−ク光から遠くなるにつれ急激に輝度が低下し、光源から遠い側での出射光輝度分布（ＸＺ面内）は比較的緩やかに輝度が低下する非対称な出射光輝度分布（ＸＺ面内）を示す場合がある。例えば、このような出射光輝度分布（ＸＺ面内）の光源装置を１０インチ以上のノ−ト型パソコン等の比較的広い視野角を必要とする液晶表示装置に用いる場合、比較的光拡散性の高い光拡散素子を光偏向素子の出光面上に配置し、出射光光度分布（ＸＺ面内）を広げて視野角を広げることが行われている。ヘイズ値が５０％以上という光拡散性の強い光拡散素子を用いる場合には、出射光光度分布（ＸＺ面内）のピーク角度が１〜３度程度光源から遠い側に偏向される。このため、光偏向素子からの出射光輝度分布（ＸＺ面内）のピーク角度がその出光面の法線方向に位置する場合、光拡散素子により出射光光度分布（ＸＺ面内）のピーク角度が、法線方向から１〜３度程度光源から遠い側に偏光され、結果として法線方向から観察した場合の輝度を極端に低下させることになる。これは、光拡散素子を使用することにより、光偏向素子から出射した出射光輝度分布（ＸＺ面内）の非対称性は幾分緩和されるものの、比較的急激に輝度が低下する出射光輝度分布（ＸＺ面内）の部位が法線方向位置するためである。このような輝度の極端な低下を避けるために、あらかじめ光偏向素子からの出射光輝度分布（ＸＺ面内）のピーク角度を法線方向から光源側に１〜３度傾けておくことが好ましい。
【００８４】
【実施例】
以下、実施例によって本発明を具体的に説明する。
なお、以下の実施例における各物性の測定は下記のようにして行った。
【００８５】
面光源装置の法線輝度、光度半値全幅の測定
光源として冷陰極管を用い、インバータ（ハリソン社製ＨＩＵ−７４２Ａ）にＤＣ１２Ｖを印加して高周波点灯させた。輝度は、面光源装置あるいは導光体の表面を２０ｍｍ四方の正方形に３×５分割し、各正方形の法線方向の輝度値の１５点平均を求めた。導光体の光度半値全幅は、導光体の表面に４ｍｍφのピンホールを有する黒色の紙をピンホールが表面の中央に位置するように固定し、輝度計の測定円が８〜９ｍｍとなるように距離を調整し、冷陰極管の長手方向軸と垂直方向および平行方向でピンホールを中心にゴニオ回転軸が回転するように調節した。それぞれの方向で回転軸を＋８０°〜−８０°まで１°間隔で回転させながら、輝度計で出射光の光度分布（ＸＺ面内）を測定し、ピーク角度、光度分布（ＸＺ面内）の半値全幅（ピーク値の１／２の分布（ＸＺ面内）の広がり角）を求めた。また、面光源装置の輝度半値全幅は、輝度計の視野角度を０．１度にし、面光源装置の中央の面に位置するよう調整し、ゴニオ回転軸が回転するように調節した。それぞれの方向で回転軸を＋８０°〜−８０°まで１°間隔で回転させながら、輝度計で出射光の輝度分布（ＸＺ面内）を測定し、ピーク輝度、ピーク角度を求めた。
【００８６】
平均傾斜角（θａ）の測定
ＩＳＯ４２８７／１−１９８７に従って、触針として０１０−２５２８（１μｍＲ、５５°円錐、ダイヤモンド）を用いた触針式表面粗さ計（東京精器（株）製サーフコム５７０Ａ）にて、粗面の表面粗さを駆動速度０．０３ｍｍ／秒で測定した。この測定により得られたチャートより、その平均線を差し引いて傾斜を補正し、前記式（１）式および（２）式によって計算して求めた。
【００８７】
ヘイズ値の測定
ヘイズ値は、ＪＩＳ　Ｋ−７１０５のＢ法に従って、５０ｍｍ×５０ｍｍの大きさの試料を積分球式反射透過率計（村上色彩技術研究社製ＲＴ−１００型）を用いて得られた全光線透過率（Ｔｔ）、拡散光線透過率（Ｔｄ）から、次の式（４）によって計算して求めた。
【００８８】
【数３】

光拡散分布角度の測定
光拡散分布角度は、５０ｍｍ×５０ｍｍの大きさの試料を自動変角光度計（村上色彩研究所社製ＧＰ−２００型）を用いて測定し、求めたピーク光度の１／２光度である半値半幅角度の２倍をサンプルの半値全幅角度（ａ）とした。なお、試料に入射させる光は、光源からの光をコンデンサーレンズによりピンホールに集光し、コリメーターレンズを通して平行光（平行度±０．５度以下）とし、光束絞り（開口径１０．５ｍｍ）を通過し試料の入射面に入射させる。試料を透過した光は、受光レンズ（開口径１１．４ｍｍを通り（試料面が平滑である場合は、受光絞りの位置に集光する）、受光絞りを通過して受光素子に達し、電圧値として出力する。また、試料を回転させ同様の測定を行い、最大半値全幅（Ｍａｘａ）と最小半値全幅（Ｍｉｎａ）を求めた。
【００８９】
実施例１
アクリル樹脂（三菱レイヨン（株）製アクリペットＶＨ５＃０００）を用い射出成形することによって一方の面がマットである導光体を作製した。該導光体は、２１６ｍｍ×２９０ｍｍ、厚さ２．０ｍｍ−０．７ｍｍのクサビ板状をなしていた。この導光体の鏡面側に、導光体の長さ２３０ｍｍの辺（短辺）と平行になるように、アクリル系紫外線硬化樹脂によってプリズム列のプリズム頂角１００°、ピッチ５０μｍのプリズム列が並列に連設配列されたプリズム層を形成した。導光体の長さ２９０ｍｍの辺（長辺）に対応する一方の側端面（厚さ２．０ｍｍの側の端面）に沿って冷陰極管を光源リフレクター（麗光社製銀反射フィルム）で覆い配置した。さらに、その他の側端面に光拡散反射フィルム（東レ社製Ｅ６０）を貼付し、プリズム列配列（裏面）に反射シートを配置した。以上の構成を枠体に組み込んだ。この導光体は、光入射面および光出射面の双方に垂直な面内での出射光光度分布（ＸＺ面内）の最大ピーク角度は光出射面法線方向に対して７０度、半値全幅は２２．５度であった。
【００９０】
一方、屈折率１．５０６４のアクリル系紫外線硬化性樹脂を用いて、表１に示したように、プリズム列を構成する一方のプリズム面（第１のプリズム面）を法線とのなす角度（α）が３２．５度の平面とし、他方のプリズム面（第２のプリズム面）をプリズム頂部からプリズム列の高さ２１．４μｍまでを短軸の曲率半径４００μｍ、長軸の曲率半径８００μｍの非球面形状（曲率半径８００μｍの曲面）の凸曲面（傾斜角＝５６．６度、β＝３３．８度）、プリズム頂部からプリズム列の高さ２１．４μｍ以上を曲率半径４００μｍの球面形状の凸曲面（傾斜角＝５９．０度）とする２つの凸曲面（プリズム頂部側からエリア１、２）で構成したピッチ５６．５μｍのプリズム列が略並列に連設されたプリズム列形成面を、厚さ１２５μｍのポリエステルフィルムの一方の表面に形成したプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は１．０３％であった。
【００９１】
得られたプリズムシートを、上記導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【００９２】
実施例２
プリズム列を構成する第２のプリズム面を、表１に示したように、プリズム頂部からプリズム列の高さ１６μｍまでを傾斜角を５５．２度の平面（β＝３４．８度）、プリズム列の高さ１６μｍからプリズム底部までをプリズム頂部に近い側から傾斜角が５５．５度、５６．２度、５７．０度、５７．８度、５８．４度、５９．４度の同一幅の６つの平面とする７つの平面（プリズム頂部側からエリア１、２・・・７）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は１．１０％であった。
【００９３】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【００９４】
実施例３
プリズム列を構成する第２のプリズム面を、表１に示したように、プリズム頂部からプリズム列の高さ１０．６μｍまでを傾斜角が５６．４度の平面（β＝３３．６度）、プリズム列の高さ１０．６〜２１．３μｍまでを傾斜角が５６．８度の平面、プリズム列の高さ２１．３μｍ以上を曲率半径４００μｍの球面形状の凸曲面（傾斜角＝５９．２度）とする２つの平面と１つの凸曲面（プリズム頂部側からエリア１、２、３）から構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は１．０３％であった。
【００９５】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【００９６】
実施例４
プリズム列を構成する第２のプリズム面を、表１に示したように、プリズム頂部からプリズム列の高さ２１．５μｍまでを傾斜角が５６．８度の平面（β＝３３．２度）、プリズム列の高さ２１．５μｍ以上を傾斜角が５８．７度の平面とする２つの平面（プリズム頂部側からエリア１、２）とから構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は０．７６％であった。
【００９７】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【００９８】
実施例５
表１に示したように、プリズム列を構成する第１のプリズム面と法線となす角度（α）を２９．０度、プリズム列を構成する第２のプリズム面を、プリズム頂部からプリズム列の高さ１６．０μｍまでを傾斜角を５５．３度の平面（β＝３４．７度）、プリズム列の高さ１６．０μｍからプリズム底部までをプリズム頂部に近い側から傾斜角が５５．７度、５６．５度、５７．４度、５８．２度、５９．０度、５９．６、６０．３度の同一幅の７つの平面とする８つの平面（プリズム頂部側からエリア１，２，・・　・８）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は０．７３％であった。
【００９９】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【０１００】
実施例６
表１に示したように、実施例５のプリズム列高さ１６．０μｍからプリズム底部までの７つのエリアの境界を通る曲面で構成した（プリズム頂部に近い側からの各エリアの傾斜角が５５．４度、５６．２度、５７．１度、５７．９度、５８．７度、５９．３、６０．０度）以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は０．０．６８％であった。
【０１０１】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【０１０２】
実施例７
表１に示したように、プリズム列を構成する第１のプリズム面を法線となす角度（α）が１５．０度の平面とし、第２のプリズム面をプリズム頂部からプリズム列の高さ１０．４μｍまでを傾斜角を５２．０度の平面（β＝３８度）、プリズム列の高さ１０．４μｍからプリズム底部までをプリズム頂部に近い側から傾斜角が５２．６度、５２．８度、５３．７度、５４．５度、５５．３度、５６．１度、５６．８度、５７．５度、５８．４度、６０．０度の同一幅の１０の平面とする１１の平面（プリズム頂部側からエリア１，２，・・　・１１）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は１．４８％であった。
【０１０３】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【０１０４】
実施例８
表１に示したように、プリズム列を構成する第１のプリズム面と法線となす角度（α）を１０．０度、第２のプリズム面をプリズム頂部からプリズム列の高さ１１．５μｍまでを傾斜角を５２．０度の平面（β＝３８．０度）、プリズム列の高さ１１．５μｍからプリズム底部までをプリズム頂部に近い側から傾斜角が５２．６度、５２．８度、５３．７度、５４．５度、５５．３度、５６．１度、５６．８度、５７．５度、５８．４度、の同一幅の９つの平面と６０度の平面とする１１の平面（プリズム頂部側からエリア１，２，・・　・１１）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は１．６４％であった。
【０１０５】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【０１０６】
実施例９
表１に示したように、プリズム列を構成する第１のプリズム面と法線のなす角度（α）を５度、第２のプリズム面をプリズム頂部からプリズム列の高さ１２．９μｍまでを傾斜角を５２．０度の平面（β＝３８度）、プリズム列の高さ１２．９μｍからプリズム底部までをプリズム頂部に近い側から傾斜角が５２．６度、５２．８度、５３．７度、５４．５度、５５．３度、５６．１度、５６．８度、５７．５度、５８．４度、の同一幅の９つの平面と６０度の平面とする１１の平面（プリズム頂部側からエリア１，２，・・　・１１）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は１．８３％であった。
【０１０７】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【０１０８】
実施例１０
表１に示したように、プリズム列を構成する第１のプリズム面と法線のなす角度（α）を０．１度、第２のプリズム面をプリズム頂部からプリズム列の高さ１４．５μｍまでを傾斜角を５２．０度の平面（β＝３８度）、プリズム列の高さ１４．５μｍからプリズム底部までをプリズム頂部に近い側から傾斜角が５２．６度、５２．８度、５３．７度、５４．５度、５５．３度、５６．１度、５６．８度、５７．５度、５８．４度、の同一幅の９つの平面と６０度の平面とする１１の平面（プリズム頂部側からエリア１，２，・・　・１１）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。プリズムシートの第２のプリズム面の仮想平面との最大距離（ｄ）のプリズム列のピッチ（Ｐ）に対する割合（ｄ／Ｐ）は２．０６％であった。
【０１０９】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【０１１０】
比較例１
プリズムシートのプリズム列を、２つのプリズム面がともに平面であり、プリズム頂角が６５．４度である断面二等辺三角形（α＝β＝３２．７度）とした以外は、実施例１と同様にして面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、ピーク輝度を１．００とし、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表２に示した。
【０１１１】
【表１】

【表２】

実施例１１〜２２
プリズム列を構成する第２のプリズム面を、表２に示した傾斜角および分割高さの３つの平面（プリズム頂部側からエリア１、２、３）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表３に示した。
【０１１２】
比較例２
プリズム列を構成する第２のプリズム面全体を曲率半径４５２μｍの球面形状の凸曲面（傾斜角＝５７．３度、β＝３６．３度）とした以外は、実施例１と同様にしてプリズムシートを作製した。得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表３に示した。
【０１１３】
【表３】

実施例２３〜３４
アクリル樹脂（三菱レイヨン（株）製アクリペットＶＨ５＃０００）を用い射出成形することによって一方の面がマットである導光体を作製した。該導光体は、２３０ｍｍ×３１０ｍｍ、厚さ３．５ｍｍ−１．２ｍｍのクサビ板状をなしていた。この導光体の鏡面側に、導光体の長さ２３０ｍｍの辺（短辺）と平行になるように、アクリル系紫外線硬化樹脂によってプリズム列のプリズム頂角１００°、ピッチ５０μｍのプリズム列が略並列に連設配列されたプリズム層を形成した。導光体の長さ３１０ｍｍの辺（長辺）に対応する一方の側端面（厚さ３．５ｍｍの側の端面）に沿って冷陰極管を光源リフレクター（麗光社製銀反射フィルム）で覆い配置した。さらに、その他の側端面に光拡散反射フィルム（東レ社製Ｅ６０）を貼付し、プリズム列配列（裏面）に反射シートを配置した。以上の構成を枠体に組み込んだ。この導光体は、光入射面および光出射面の双方に垂直な面内での出射光光度分布（ＸＺ面内）の最大ピーク角度は光出射面法線方向に対して７０度、半値全幅は３３度であった。
【０１１４】
一方、プリズム列を構成する第２のプリズム面を、表３に示した傾斜角および分割高さの３つの平面（プリズム頂部側からエリア１、２、３）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。
【０１１５】
得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例４を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表４に示した。
【０１１６】
比較例３
比較例２のプリズムシートを使用した以外は、実施例２３〜３４と同様にして、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例４を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表４に示した。
【０１１７】
比較例４
比較例１のプリズムシートを使用した以外は、実施例２３〜３４と同様にして、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、このピーク輝度を１．００とし、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表４に示した。
【０１１８】
【表４】

実施例３５〜３９
プリズム列を構成する一方のプリズム面（第１のプリズム面）と法線とのなす角度（α）、他方のプリズム面（第２のプリズム面）と法線とのなす角度（β）を表４に示した角度とし、第２のプリズム面を表４に示した傾斜角および分割高さの２つの平面（プリズム頂部側からエリア１、２）で構成した以外は、実施例１と同様にしてプリズムシートを作製した。得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表５に示した。
【０１１９】
比較例５
プリズム列を構成する第２のプリズム面全体を傾斜角５５．０度（β＝３５．０度）の平面とした以外は、実施例１と同様にしてプリズムシートを作製した。得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例５を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表５に示した。
【０１２０】
【表５】

実施例４０〜４４
プリズム列を構成する一方のプリズム面（第１のプリズム面）と法線とのなす角度（α）、他方のプリズム面（第２のプリズム面）と法線とのなす角度（β）を表５に示した角度とし、第２のプリズム面を表５に示した傾斜角および分割高さの２つの平面（プリズム頂部側からエリア１、２）で構成した以外は、実施例２３〜３４と同様にしてプリズムシートを作製した。得られたプリズムシートを、実施例１の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例６を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表６に示した。
【０１２１】
比較例６
プリズム列を構成する第２のプリズム面全体を傾斜角５５．０度（β＝３５．０度）の平面とした以外は、実施例１と同様にしてプリズムシートを作製した。得られたプリズムシートを、実施例２３〜３４の導光体の光出射面側にプリズム列形成面が向き、導光体の光入射面にプリズム稜線が平行であり第１のプリズム面が光源側となるように載置し、面光源装置を得た。この面光源装置の光入射面および光出射面の双方に垂直な面内での出射光輝度分布（ＸＺ面内）を求め、比較例１を基準とした場合のピーク輝度比率、ピーク角度、ピーク輝度の１／２の輝度を有する角度（半値全幅）、ピーク輝度の１／２の輝度を有する角度の差の絶対値（｜Δθ_ａ−Δθ_ｂ｜）を測定し、その結果を表６に示した。
【０１２２】
【表６】

実施例４５
実施例１の面光源装置に一方の表面が平均傾斜角度７．２７度のマット面で、他方の表面が平均傾斜角度が０．７度のマット面であり、出射光光度分布（ＸＺ面内）の半値全幅が９．４度の光拡散素子を光偏向素子の出光面上に、平均傾斜角度が７．２７度のマット面が光偏光素子側に向くように載置し、面光源装置を得た。作製された面光源装置の出射光輝度分布（ＸＺ面内）における比較例５を基準とした場合のピーク輝度比率、輝度半値全幅、目視で確認した品位の評価結果を表７に示した。
【０１２３】
実施例４６
一方の表面が平均傾斜角度５．０度のマット面で、他方の表面が平均傾斜角度が０．７度のマット面であり、出射光光度分布（ＸＺ面内）の半値全幅が６度の光拡散素子を光偏向素子の出光面上に、平均傾斜角度が５．０度のマット面が光偏光素子側に向くように載置した以外は、実施例１と同様にして面光源装置を得た。作製された面光源装置の出射光輝度分布（ＸＺ面内）における比較例５を基準とした場合のピーク輝度比率、輝度半値全幅、目視で確認した品位の評価結果を表７に示した。
【０１２４】
実施例４７
厚さ１２５μｍのポリエステルフィルムの一方の表面にピッチ３０μｍの多数のレンチキュラーレンズ列が略並列して連設され、レンチキュラーレンズ列の表面を平均傾斜角１度に粗面化した最大平均傾斜角度が１０．４度であり、最大傾斜角度／最小傾斜角度が１０．４であるレンズ配列構造を形成し、他方の表面には平均傾斜角度０．７度のマット面を形成した出射光光度分布（ＸＺ面内）の半値全幅が１１．２度の光拡散素子を、レンチキュラーレンズ列が光偏向素子のプリズム列と平行となり、レンズ配列構造面が光偏光素子側に向くように載置した以外は、実施例１と同様にして面光源装置を得た。作製された面光源装置の出射光輝度分布（ＸＺ面内）における比較例５を基準とした場合のピーク輝度比率、輝度半値全幅、目視で確認した品位の評価結果を表７に示した。
【０１２５】
実施例４８
厚さ１２５μｍのポリエステルフィルムの一方の表面に最大平均傾斜角度が８．２度のヘアラインを形成し、他方の表面には平均傾斜角度０．７度のマット面を形成した出射光光度分布（ＸＺ面内）の半値全幅が１０．５度の光拡散素子を、ヘアラインの方向を光偏向素子のプリズム列と略平行となり、ヘアライン形成面が光偏向素子側に向くように載置したとした以外は実施例１と同様にして、面光源装置を得た。作製された面光源装置の出射光輝度分布（ＸＺ面内）における比較例５を基準とした場合のピーク輝度比率、輝度半値全幅、目視で確認した品位の評価結果を表７に示した。
【０１２６】
実施例４９
厚さ１２５μｍのポリエステルフィルムの一方の表面にエッチングにより形成した幅３０μｍ、長さ６０μｍの多数のシリンドリカルレンズが同一方向に離散的に配列した最大平均傾斜角度が６．０度であり、最大傾斜角度／最小傾斜角度が６．０、であるレンズ配列構造を形成し、他方の表面には平均傾斜角度０．７度のマット面を形成した出射光光度分布（ＸＺ面内）の半値全幅が７．０度の光拡散素子を、シリンドリカルレンズの配列方向と光偏向素子のプリズム列が略平行となり、レンズ配列構造面が光偏向素子側に向くように載置したとした以外は実施例１と同様にして、面光源装置を得た。作製された面光源装置の出射光輝度分布（ＸＺ面内）における比較例５を基準とした場合のピーク輝度比率、輝度半値全幅、目視で確認した品位の評価結果を表７に示した。
【０１２７】
【表７】

【０１２８】
【発明の効果】
以上説明したように、本発明によれば、光偏向素子の入光面に形成されるプリズム列の少なくとも一方のプリズム面を傾斜角の異なる複数の平面あるいは凸曲面から構成することにより、一次光源から発せられる光を所要の観察方向へ集中して出射させる効率（一次光源の光量の利用効率）のい光源装置を提供することができる。
【図面の簡単な説明】
【図１】本発明による光源装置を示す模式的斜視図である。
【図２】本発明の光偏向素子の入光面のプリズム列の形状の説明図である。
【図３】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図４】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図５】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図６】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図７】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図８】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図９】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図１０】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図１１】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図１２】光偏向素子の第２プリズム面（平面）の各エリアからの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図１３】光偏向素子の第２プリズム面（平面）全体からの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図１４】本発明の光偏向素子の第２プリズム面全体からの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図１５】本発明の光偏向素子の入光面のプリズム列の形状の説明図である。
【図１６】本発明の光偏向素子の入光面のプリズム列の形状の説明図である。
【図１７】本発明の光偏向素子の入光面のプリズム列の形状の説明図である。
【図１８】本発明の光偏向素子の入光面のプリズム列の形状の説明図である。
【図１９】光偏向素子からの各種出射光輝度分布（ＸＺ面内）を示す説明図である。
【図２０】本発明の光偏向素子の入光面のプリズム列の形状の説明図である。
【図２１】出射光光度分布（ＸＺ面内）の半値全幅の説明図である。
【図２２】光源装置の展開長の説明図である。
【図２３】光源装置の展開長の説明図である。
【図２４】本発明の光源装置の光偏向素子からの出射光輝度分布（ＸＺ面内）を示す説明図である。
【図２５】本発明の光源装置の光偏向素子からの出射光輝度分布（ＸＺ面内）を示すグラフである。
【図２６】本発明の光拡散素子の異方拡散性の出射光光度分布（ＸＺ面内）を示す説明図である。
【図２７】本発明の光偏向素子の異方拡散性の説明図である。
【図２８】本発明の異方拡散性を有する光偏向素子の凹凸構造を示す概略図である。
【図２９】本発明の異方拡散性を有する光偏向素子の凹凸構造を示す概略図である。
【図３０】本発明の異方拡散性を有する光偏向素子の凹凸構造を示す概略図である。
【符号の説明】
１　　一次光源
２　　光源リフレクタ
３　　導光体
４　　光偏向素子
５　　光反射素子
６　　光拡散素子
３１　　光入射面
３２　　端面
３３　　光出射面
３４　　裏面
４１　　入光面
４２　　出光面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an edge light type light source device constituting a liquid crystal display device or the like used as a display unit in a notebook computer, a liquid crystal television, a mobile phone, a portable information terminal, and the like, and a light deflection element used therein. In particular, the present invention relates to an improvement in a light deflecting element arranged on a light exit surface side of a light guide.
[0002]
[Prior art]
2. Description of the Related Art In recent years, color liquid crystal display devices have been widely used in various fields as monitors of portable notebook personal computers and personal computers, or as display units of liquid crystal televisions and video-integrated liquid crystal televisions, mobile phones, personal digital assistants, and the like. I have. In addition, with an increase in information processing volume, diversification of needs, multimedia support, and the like, a large screen and high definition of a liquid crystal display device have been actively promoted.
[0003]
The liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, there are a direct type backlight unit in which a light source is disposed immediately below a liquid crystal display element unit and an edge light type backlight unit in which a light source is disposed so as to face a side end surface of a light guide. The edge light method is often used from the viewpoint of the realization.
[0004]
By the way, in recent years, in a liquid crystal display device used as a display unit of a mobile phone, for example, which is a display device having a relatively small screen size and a viewing direction range is relatively narrow, from the viewpoint of reducing power consumption, an edge light type is used. In order to effectively use the amount of light emitted from the primary light source, a backlight unit that reduces the spread angle of a light beam emitted from a screen as much as possible and emits light concentrated on a required angle range has been used. I have.
[0005]
The present invention is directed to a display device in which the range of observation directions is limited as described above, which is a light source device that concentrates light emission in a relatively narrow range in order to increase the use efficiency of the light amount of the primary light source and reduce power consumption. In Japanese Unexamined Patent Application Publication No. 2001-143515 (Patent Document 1), it has been proposed to use a prism sheet having a prism forming surface on both sides adjacent to a light exit surface of a light guide. In this double-sided prism sheet, a plurality of prism rows parallel to each other are formed on each of a light incident surface, which is one surface, and a light emitting surface, which is the other surface. And the prism rows are arranged at corresponding positions. Thereby, the light emitted from the light exit surface of the prism sheet has a peak of the emitted light in a direction inclined with respect to the light exit surface, and is emitted in an appropriate angle range. The light enters from the prism surface, is reflected internally by the other prism surface, and is refracted by the prism on the light exit surface, so that light is concentrated and emitted in a relatively narrow required direction.
[0006]
[Patent Document 1]
JP 2001-143515 A
[0007]
[Problems to be solved by the invention]
However, according to such a light source device, concentrated emission in a narrow angle range is possible. However, a plurality of prism rows parallel to each other on both sides as a prism sheet used as a light deflecting element are provided on a light entrance surface and a light exit surface. It is necessary to make the prism row directions coincide with each other and to arrange the prism rows at corresponding positions, and this molding becomes complicated.
[0008]
Therefore, an object of the present invention is to control the distribution of the emitted light to be very narrow and to improve the efficiency of using the light amount of the primary light source (that is, to concentrate the light emitted from the primary light source in a required observation direction). It is an object of the present invention to provide a light deflecting element and a light source device in which the image quality can be easily improved with a simplified configuration.
[0009]
[Means for Solving the Problems]
That is, the light deflecting element of the present invention has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has two prism surfaces. A plurality of prism rows are arranged substantially in parallel with each other, and at least one prism surface of the prism rows is composed of at least two planes having different inclination angles, and the inclination angle is closer to a plane closer to the light exit surface. The difference between the inclination angle of the plane closest to the light exit surface and the inclination angle of the plane farthest from the light exit surface is 15 degrees or less.
[0010]
Further, the light deflecting element of the present invention has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has two prism surfaces. A plurality of prism rows are arranged substantially in parallel with each other, and at least one prism surface of the prism rows is made up of at least three planes having different inclination angles, and the inclination angle becomes closer to the plane closer to the light exit surface. It is characterized by being large.
[0011]
Further, the light deflecting element of the present invention has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has two prism surfaces. A plurality of prism rows are arranged substantially in parallel with each other, and at least one prism surface of the prism rows is composed of at least two convex curved surfaces having different inclination angles, and the convex curved surface located closer to the light exit surface has a higher inclination. The feature is that the corner is large.
[0012]
Further, the light deflecting element of the present invention has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has two prism surfaces. A plurality of prism rows are arranged substantially in parallel with each other, and at least one prism surface of the prism rows is composed of at least two planes having different inclination angles and at least one convex curved surface, and is located on a side close to the light exit surface. The present invention is characterized in that the inclination angle is larger as the plane or the convex surface is located.
[0013]
Further, the light source device of the present invention includes a primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident, and a light exit surface for guiding and exiting the incident light; It is characterized by comprising the above-described light deflecting element arranged adjacent to the light emitting surface side of the body.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic perspective view showing one embodiment of the surface light source device according to the present invention. As shown in FIG. 1, the surface light source device of the present invention includes a light guide 3 having at least one side end surface as a light incident surface 31 and one surface almost orthogonal to the light exit surface 33 as a light exit surface 33. A primary light source 1 disposed opposite the light incident surface 31 of the light guide 3 and covered with the light source reflector 2, a light deflecting element 4 disposed on the light exit surface of the light guide 3, and a light guide. And a light reflection element 5 disposed opposite to the back surface 34 of the light exit surface 33 of the body 3.
[0015]
The light guide 3 is arranged parallel to the XY plane, and has a rectangular plate shape as a whole. The light guide 3 has four side end surfaces, of which at least one side end surface of a pair of side end surfaces parallel to the YZ plane is a light incident surface 31. The light incident surface 31 is arranged so as to face the light source 1, and light emitted from the light source 1 enters the light guide 3 from the light incident surface 31. In the present invention, for example, a light source may be arranged on another side end surface such as the side end surface 32 facing the light incident surface 31.
[0016]
The two main surfaces of the light guide 3 that are substantially perpendicular to the light incident surface 31 are located substantially parallel to the XY plane, respectively, and one of the surfaces (the upper surface in the figure) is a light emitting surface 33. At least one of the light emitting surface 33 and the rear surface 34 has a rough directional light emitting function unit and a number of lens arrays such as a prism array, a lenticular lens array, and a V-shaped groove. By providing a directional light-emitting function portion including a lens surface formed substantially parallel to the light guide surface 31, light incident from the light incident surface 31 is guided through the light guide 3 while light is incident from the light emission surface 33. The directional light is emitted in the luminous intensity distribution of the emitted light in a plane (XZ plane) orthogonal to the plane 31 and the light exit plane 33. Assuming that the angle between the direction of the peak of the luminous intensity distribution in the XZ plane and the light exit surface 33 is a, this angle a is preferably 10 to 40 degrees, and the full width at half maximum of the luminous intensity distribution is 10 to 40 degrees. Preferably, it is 40 degrees.
[0017]
The rough surface and the lens array formed on the surface of the light guide 3 should have an average inclination angle θa according to ISO 4287 / 1-1984 in the range of 0.5 to 15 degrees, so that the luminance in the light exit surface 33 can be improved. Is preferable from the viewpoint of achieving uniformity. The average inclination angle θa is more preferably in the range of 1 to 12 degrees, and more preferably in the range of 1.5 to 11 degrees. It is preferable that the optimum range of the average inclination angle θa is set by the ratio (L / t) of the thickness (t) of the light guide 3 and the length (L) in the direction in which the incident light propagates. That is, when the light guide 3 having an L / t of about 20 to 200 is used, the average inclination angle θa is preferably set to 0.5 to 7.5 degrees, and more preferably 1 to 5 degrees. Range, more preferably 1.5 to 4 degrees. When the light guide 3 having an L / t of about 20 or less is used, the average inclination angle θa is preferably set to 7 to 12 degrees, more preferably 8 to 11 degrees.
[0018]
The average inclination angle θa of the rough surface formed on the light guide 3 is obtained by measuring the rough surface shape using a stylus type surface roughness meter according to ISO 4287 / 1-1984, and setting the coordinates in the measurement direction as x. It can be obtained from the obtained inclination function f (x) using the following equations (1) and (2). Here, L is the measured length, and Δa is the tangent of the average inclination angle θa.
[0019]
(Equation 1)

Further, the light guide 3 preferably has a light emission rate in the range of 0.5 to 5%, more preferably 1 to 3%. This is because when the light emission rate is smaller than 0.5%, the amount of light emitted from the light guide 3 tends to be small and sufficient luminance cannot be obtained. When the light emission rate is larger than 5%, a large amount near the light source 1 is large. Is emitted, and the light in the X direction in the light exit surface 33 is significantly attenuated, and the uniformity of luminance on the light exit surface 33 tends to decrease. By setting the light emission rate of the light guide 3 to 0.5% to 5%, the angle (peak angle) of the peak light in the luminous intensity distribution (in the XZ plane) of the light emitted from the light emission surface is reduced. A light guide that emits light with high directivity such that the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) is 10 to 40 degrees with respect to the normal line of the light emitting surface. 3 can be efficiently deflected by the light deflecting element 4, and a surface light source element having high luminance can be provided.
[0020]
In the present invention, the light emission rate from the light guide 3 is defined as follows. At the edge of the light exit surface 33 on the light incident surface 31 side, the light intensity (I₀) And the emitted light intensity (I) at a position at a distance L from the edge on the light incident surface 31 side, assuming that the thickness (dimension in the Z direction) of the light guide 3 is t, the following (3) Satisfies the relationship as in the equation.
[0021]
(Equation 2)

Here, the constant A is the light emission rate, and the light guide 3 per unit length (length corresponding to the light guide thickness t) in the X direction orthogonal to the light incidence surface 31 on the light emission surface 33. Out of the light. The light emission rate A can be obtained from the gradient by plotting the logarithm of the light intensity of the light emitted from the light emission surface 23 on the vertical axis and (L / t) on the horizontal axis.
[0022]
In addition, the other main surface to which the directional light emitting function unit is not provided is provided with a light for controlling the directivity of light emitted from the light guide 3 on a plane (YZ plane) parallel to the light source 1. It is preferable to form a lens surface in which a number of lens arrays extending in a direction (X direction) substantially perpendicular to the incident surface 31 are arranged. In the embodiment shown in FIG. 1, a rough surface is formed on the light exit surface 33, and a lens surface formed of an array of a large number of lens rows extending substantially perpendicularly to the light incident surface 31 (X direction) on the back surface 34. Is formed. In the present invention, contrary to the embodiment shown in FIG. 1, a lens surface may be formed on the light emitting surface 33 and the back surface 34 may be roughened.
[0023]
As shown in FIG. 1, when a lens array is formed on the back surface 34 or the light emitting surface 33 of the light guide 3, the lens array includes a prism array extending substantially in the X direction, a lenticular lens array, and a V-shaped groove. However, it is preferable to form a prism array having a substantially triangular cross section in the YZ directions.
[0024]
In the present invention, when a prism row is formed as a lens row formed on the light guide 3, it is preferable that the apex angle be in the range of 70 to 150 degrees. This is because by setting the apex angle in this range, the light emitted from the light guide 3 can be sufficiently collected, and the luminance of the surface light source element can be sufficiently improved. In other words, by setting the prism apex angle within this range, the full width at half maximum of the emission light luminous intensity distribution is 35 to 65 degrees on a plane perpendicular to the XZ plane including the peak light in the emission light intensity distribution (in the XZ plane). The emitted light can be emitted, and the luminance as the surface light source element can be improved. When the prism array is formed on the light exit surface 33, the apex angle is preferably in the range of 80 to 100 degrees. When the prism array is formed on the back surface 34, the apex angle is 70 to 80 degrees. Alternatively, the angle is preferably in the range of 100 to 150 degrees.
[0025]
In the present invention, instead of forming the light emitting function portion on the light emitting surface 33 or the back surface 34 as described above or in combination with the light emitting function portion, the light diffusing fine particles are mixed and dispersed inside the light guide. It may have a directional light emission function. Further, the light guide 3 is not limited to the cross-sectional shape shown in FIG. 1, but may have various cross-sectional shapes such as a wedge shape and a hull shape.
[0026]
FIG. 2 is an explanatory diagram of the shape of the prism array of the light deflecting element 4. One of the main surfaces of the light deflecting element 4 is a light incident surface 41 and the other surface is a light emitting surface 42. A large number of prism rows are arranged on the light incident surface 41 in a substantially parallel manner. Each prism row has two prisms, a first prism face 44 located on the light source side and a second prism face 45 located on the far side from the light source. It is composed of faces. In the embodiment shown in FIG. 2, the first prism surface 44 is a plane, and the second prism surface 45 is composed of three planes 46 to 48 having different inclination angles. Is getting bigger. Further, among the planes 46 to 48, the difference in the inclination angle between the plane 48 closest to the light emitting surface and the plane 46 farthest from the light emitting surface is 15 degrees or less. In the present invention, the inclination angle of the plane refers to the inclination angle of each plane with respect to the prism array forming plane 43.
[0027]
In the light deflecting element 4 of the present invention, the second prism surface 45 is constituted by at least two planes having different inclination angles, and the inclination angle of these planes increases as the distance from the light exit surface increases. By setting the difference of the inclination angle with the plane far from the light emitting surface to 15 degrees or less, an extremely high light-collecting effect can be exhibited, and an extremely high luminance can be obtained as a light source device. The difference in the inclination angle between the plane closest to the light emitting surface and the plane farthest from the light emitting surface is preferably in the range of 0.5 to 10 degrees, and more preferably in the range of 1 to 7 degrees. When three or more planes having different inclination angles are formed, the difference between the inclination angles is preferably within the above range, but is not particularly limited to this range. Further, by configuring the second prism surface 45 to have such a structure, it is possible to easily design a deflecting element having a desired light condensing property, and to stably provide an optical deflecting element having certain optical characteristics. It can also be manufactured.
[0028]
Next, the shape of the prism surface of the light deflection element of the present invention will be described. 3 to 14 show that the peak angle of the luminous intensity distribution (in the XZ plane) emitted from the light guide by the conventional light deflecting element in which the two prism surfaces are both flat and the prism apex angle is 65.4 degrees. What emission light luminance distribution (in the XZ plane) is emitted from the light deflecting element on a plane perpendicular to both the light incident surface and the light emission surface of the light guide body at 20 degrees It is shown. 3 to 12 show a state where incident light incident from the first prism surface is totally reflected by the second prism surface and emitted from the light exit surface 42, and the second prism surface is equally divided into ten areas in the x direction. It is divided and shows the luminance distribution (in the XZ plane) of the emitted light from each area. The ten areas are named Part1, Part2,... Part10 in order from the one closer to the top of the prism. In the luminance distribution (in the XZ plane) of the entire light totally reflected and emitted by the second prism surface, as shown in FIG. 13, the peak light is emitted in the normal direction and has a half value of 22 degrees. Has full width.
[0029]
However, looking at the emission light luminance distribution (in the XZ plane) in each area of Part 1 to Part 10, the peak angle is about −9 degrees in Part 1 and Part 2 (a negative angle value is 0 degree in the normal direction). It is emitted near the light source.) The peak light shifts in the direction of 0 degree (the normal direction) in Part3 to Part7, and the peak light in Part8 to Part10 has a positive angle in order. You can see that it has shifted in the direction. The peak angle at which the light is totally reflected and emitted in the area (Part 10) closest to the light exit surface 42 is 7 degrees, and the peak angle spreads 16 degrees on the second prism surface (between Part 1 to Part 10). The intensity of the peak light from each area gradually decreases from Part1 to Part10.
[0030]
Thus, it can be seen that the light totally reflected and emitted by the prism surface composed of one plane is dispersed in a considerably wide range depending on the area of the prism surface that is totally reflected. The peak light in the luminance distribution (in the XZ plane) of the emitted light from each area is adjusted by adjusting the inclination angle of the prism surface in each area, and the peak angle is emitted in almost the same direction in all areas. Most of the emitted light can be concentrated and emitted in a specific direction. At this time, the inclination angle of the prism surface in each area is set in the order of Part1 to Part10, that is, the inclination angle of the prism surface in the area closer to the light exit surface 42 is increased. In this way, by adjusting the inclination angle of the prism surface in each area as shown in FIG. 14, the emitted light totally reflected by the entire prism surface can be collected in a certain direction, and the directivity can be further improved. And a light having a high peak intensity can be emitted.
[0031]
At least two areas may be set for each area obtained by dividing the prism surface. If the number of the areas (the number of planes having different inclination angles) is too small, the light condensing property of the light deflecting element is reduced, Since the effect of improving brightness tends to be impaired, the number is preferably three or more, more preferably five or more, and still more preferably six or more. When the number of areas is set to two, the difference between the inclination angles of the two planes must be set to 15 degrees or less in order to suppress the deterioration of the light-collecting characteristics to some extent. The range is 5 to 10 degrees, more preferably 1 to 7 degrees. Even when the number of areas is three or more, it is preferable from the viewpoint of light-collecting characteristics that the difference between the inclination angle of the plane closest to the light emission surface and the inclination angle of the plane farthest from the light emission surface be 15 degrees or less, It is more preferably in the range of 0.5 to 10 degrees, and still more preferably in the range of 1 to 7 degrees.
[0032]
On the other hand, when the number of areas is increased, the peak angle can be finely adjusted over the entire surface of the prism surface, so that the degree of concentration as a whole can be increased, but flat surfaces having different inclination angles must be formed finely. In addition, the design and manufacture of a cutting tool for forming a die for forming the prism surface of the light deflecting element are complicated, and it is also difficult to stably obtain a light deflecting element having certain optical characteristics. Therefore, the number of areas formed on the prism surface is preferably 20 or less, more preferably 12 or less. Although it is preferable that the prism surface is divided equally, it is not always necessary to divide the prism surface equally, and it can be adjusted according to a desired emission light distribution (in the XZ plane) of the entire prism surface. Further, the width of each plane having a different inclination angle (the length of each plane portion in the cross section of the prism array) is preferably in the range of 4 to 47%, more preferably 6 to 30%, of the pitch of the prism array. %, More preferably in the range of 7 to 20%.
[0033]
In the present invention, for example, as shown in FIGS. 15 and 16, at least one of the planes having different inclination angles as described above may be a convex curved surface, or all the planes may be convex curved surfaces. . In FIG. 15, the second prism surface 45 is divided into four areas and includes three planes 49 to 51 and one convex curved surface 52. In FIG. 16, the second prism surface 45 is divided into two areas, and is constituted by two convex curved surfaces 53 and 54 having different shapes. In the figure, 55 and 56 are aspherical shapes that determine the shapes of the two curved surfaces 53 and 54. Further, the second prism surface 45 may be formed as a curved surface passing through the boundary of each divided area. In this case, the curved surface is slightly deviated from the boundary of each area as long as the luminance does not significantly decrease. It may be shifted. For example, the deviation of the ratio of the passing position of the curved surface (distance from the top of the prism) to the pitch of the prism rows with respect to the ratio of the boundary of the area may be 4% or less, more preferably 2% or less, further preferably 1% or less. Range. In the present invention, the inclination angle of the convex curved surface means an average of the inclination angles at all positions of one convex curved surface. As described above, when the prism surface is constituted by a plurality of convex curved surfaces having different inclination angles, the number of areas can be reduced as compared with the case where the prism surface is constituted by planes having different inclination angles. It can be a number, and preferably ranges from 2 to 8. However, if the number of areas is too small, it becomes difficult to design each convex curved surface to adjust a desired emission light luminance distribution (within the XZ plane). Therefore, the number of areas is more preferably in the range of 3 to 8.
[0034]
The shape of the convex curved surface may be a spherical or aspherical cross section in the XZ direction. Further, when the prism surface is constituted by a plurality of convex curved surfaces, it is preferable that the shapes of the convex curved surfaces are different, and it is possible to combine a spherical convex curved surface and an aspherical convex curved surface. It is preferable that the convex curved surface has an aspherical shape. When a plurality of convex curved surfaces have a spherical shape, the curvature may be changed for each convex curved surface. Examples of the aspherical shape include a part of an elliptical shape and a part of a parabolic shape.
[0035]
Further, the convex curved surface preferably has a radius of curvature (r) in a ratio (r / P) to the pitch (P) of the prism rows in the range of 2 to 50, more preferably 5 to 30, and still more preferably. It is in the range of 7-10. If the r / P is less than 2 or more than 50, sufficient light-collecting characteristics cannot be exhibited, and the brightness tends to decrease.
[0036]
Such a plane and a convex curved surface having different inclination angles have a substantially constant peak angle in the emitted light luminance distribution (in the XZ plane) when the light totally reflected by each plane and the convex curved surface exits from the light exit surface. However, each peak angle does not necessarily have to be substantially constant, and can be designed in a range in which all peak angles are within 15 degrees, which is preferable. Is in the range of 10 degrees or less, more preferably 7 degrees or less, and still more preferably 5 degrees or less.
[0037]
Further, in the prism array having such a configuration, as shown in FIGS. 3 to 12, the intensity of light totally reflected in the areas of Part 1 to Part 5 and emitted from the light emitting surface in the emitted light luminance distribution (in the XZ plane) is Since the intensity of the light that is totally reflected by the entire prism surface and emitted from the light emitting surface occupies 75% or more of the intensity in the emitted light luminance distribution (in the XZ plane), the emitted light that is totally reflected and emitted in these areas is desired. Is particularly important. Therefore, when the height of the prism array from the top of the prism is h and the height of the entire prism array is H, a plane having a different inclination angle or at least a region of height h where h / H is 60% or less is provided. Preferably, at least two convex curved surfaces are formed, and more preferably, three or more convex curved surfaces are formed. The region with a height h is more preferably a region where h / H is 50% or less, and further preferably a region where h / H is 40% or less. If the region of the height h is too small, sufficient light-collecting characteristics tend not to be obtained, and the manufacture of the mold becomes complicated. Therefore, h / H is preferably 20% or more. In this case, the number of areas in the region with the height h is preferably in the range of 3 to 8, more preferably 3 to 6, and still more preferably 3 to 4.
[0038]
Further, when the prism surface is composed of a plurality of planes or convex curved surfaces having different inclination angles, a virtual plane Q connecting the top and the lower part of the prism row (FIG. 2, FIG. 15, 16) and a plurality of flat surfaces or convex curved surfaces (actual prism surfaces), the maximum distance d is preferably 0.4 to 5% as a ratio (d / P) to the pitch (P) of the prism rows. This is because, when d / P is less than 0.4% or more than 5%, the light-collecting characteristics tend to decrease, and it tends to be impossible to achieve a sufficient improvement in luminance. The range is 3%, and more preferably the range is 0.7 to 2.2%.
[0039]
In the present invention, the apex angle of the prism array is preferably 35 to 80 degrees, more preferably 35 to 70 degrees, and still more preferably 40 to 70 degrees in consideration of the light-collecting characteristics and light use efficiency. Range of degrees. The left and right distribution angles α and β of the prism apex angle with respect to the normal line (the inclination angles of the two prism surfaces with respect to the normal line) may be the same or different, but are substantially in the normal direction (the normal direction is 0 degree). In this case, it is preferable to set the angle to a different angle in order to efficiently increase the luminance of ± 10 degrees in the XZ plane. In this case, the distribution angle α located on the light source side is preferably 40 degrees or less, and β is preferably in the range of 25 to 50 degrees. When the difference between the apex angles α and β is small, the light use efficiency increases and the brightness can be further improved, so that the distribution angle α is 25 to 40 degrees and the distribution angle β is 25 to It is preferable that the absolute value (Iα−βI) of the difference between the distribution angles α and β is 0.5 to 10 degrees, more preferably 1 to 10 degrees, and still more preferably 1 to 8 degrees. Range. When the peak light in the emission light luminance distribution (in the XZ plane) is set to a direction other than the substantially normal direction, the peak light has a desired direction by adjusting the distribution angles α and β of the prism apex angles. An emission light luminance distribution (in the XZ plane) can be obtained.
[0040]
Also, by setting the distribution angle α to 20 degrees or less, the light use efficiency can be increased and the luminance can be further improved. The smaller the distribution angle α, the higher the light use efficiency can be. However, if the distribution angle α is too small, the apex angle of the prism row tends to be small, and it becomes difficult to manufacture a prism sheet. α is preferably in the range of 3 to 15 degrees, and more preferably in the range of 5 to 10 degrees. In this case, in order to increase the peak light in the emission light luminance distribution (within the XZ plane) within a range of ± 2 degrees from the normal direction, the distribution angle β should be set in the range of 35 to 40 degrees in order to improve the normal luminance. Just fine.
[0041]
When the distribution angle α is equal to or less than 20 degrees, the ratio of the length of two straight lines connecting the top and the bottom of the prism in the cross-sectional shape of the prism row (to the length L1 of the straight line closer to the light source). It is preferable that the ratio L2 / L1) of the length L2 of the straight line farther from the light source be 1.1 times or more. This is because by setting L2 / L1 to be 1.1 times or more, light incident from the prism surface closer to the light source can be efficiently received by the prism surface farther from the light source, and the light use efficiency can be increased. This is because the luminance can be further improved, more preferably 1.15 times or more, and further preferably 1.17 times or more. On the other hand, if L2 / L1 is too large, the apex angle of the prism row tends to be small, and it becomes difficult to manufacture the prism sheet. Therefore, the ratio is preferably 1.3 times or less, more preferably 1.25 times or less. , More preferably 1.2 times or less. Further, the ratio (L2 / P) of the length L2 of the straight line far from the light source to the pitch P of the prism rows is preferably 1.25 or more, more preferably 1.3 or more. And more preferably 1.4 times or more. On the other hand, if L2 / P is too large, the vertex angle of the prism row tends to be small, and it becomes difficult to manufacture the prism sheet. Therefore, the ratio is preferably 1.8 times or less, more preferably 1.6 times. Or less, more preferably 1.5 times or less.
[0042]
Further, the light deflecting element of the present invention forms a convex shape or a flat surface (light transmitting region) having a smaller inclination angle than the inclination angle of the prism array between the adjacent prism arrays as illustrated in FIGS. Is also good. By forming such a light transmitting region, external light incident from the liquid crystal panel side can be introduced into the light source device from this portion, and reflected by the reflection sheet 5 arranged on the back surface of the light guide. Then, by emitting the light to the liquid crystal panel again, external light can also be used effectively. At this time, in order to maintain the uniformity of the external light reflected by the reflection sheet 5, the reflection sheet is provided with a weak diffusibility, a light diffusion layer is formed on the light exit surface of the light deflection element, It is preferable to mount a light diffusion sheet on the light exit surface. Further, when the utilization efficiency of the external light is increased, the utilization efficiency of the light as the backlight is reduced. Therefore, it is necessary to determine the ratio of the light transmitting region in consideration of the usage pattern and the like. For example, the width of the light transmission region is preferably in the range of 20 to 50% of the pitch of the prism rows, and more preferably in the range of 20 to 40%. Examples of the light transmitting region include a planar shape 59 as shown in FIG. 17, a curved surface shape 60 as shown in FIG. 18, and a polygonal shape. Above all, it is preferable to form the light transmitting region into a polygonal shape or a curved surface, since the reflection of external light can be controlled.
[0043]
In the light deflecting element of the present invention, when the light is condensed and emitted, the luminous intensity distribution of the light emitted from the light guide is strongly reflected. (Inner) tends to have an asymmetric distribution at angles before and after the normal direction. In particular, when the second prism surface 45 is formed of one curved surface, the emission light luminance distribution (in the XZ plane) on the light incident surface side of the light guide rapidly decreases, and when observed from the normal direction. The asymmetry is strongly recognized within the effective viewing angle range. In the present invention, the asymmetry of the emission light luminance distribution (in the XZ plane) as described above can be reduced by forming the prism surface from a plurality of planes or convex curved surfaces having different inclination angles. That is, as shown in FIG. 19, the asymmetry of the emitted light luminance distribution (in the XZ plane) is such that the peak angle and luminance of the emitted light luminance distribution (in the XZ plane) emitted from the light deflecting element are the luminance (peak) of the peak light. Absolute value (spread width) Δθ of the angle difference that is の of the luminance_aAnd Δθ_bDifference (| Δθ_a−Δθ_b|). Therefore, this | Δθ_a−Δθ_bBy adjusting the inclination angle of the plane or the convex curved surface constituting the prism surface so that | becomes 9 degrees or less, the asymmetry of the emission light luminance distribution (in the XZ plane) can be reduced. This | Δθ_a−Δθ_b| Is more preferably 6 degrees or less, further preferably 4 degrees or less. | Δθ_a−Δθ_bWhen | is 9 degrees or less, visibility is almost good, and when | is 4 degrees or less, discomfort due to asymmetry is hardly felt.
[0044]
Further, in the light deflecting element 4 of the present invention, as shown in FIG. 20, the plane of the first prism surface 44 changes in shape due to warpage or the like generated when forming the prism row pattern (the top of the prism row). Displacement from the plane connecting the bottom and the bottom). However, when the displacement of such a plane is large, the optical characteristics of the light deflecting element 4 are affected, and it is preferable to suppress the displacement to a small value. That is, the displacement of the prism surface from the plane connecting the top and bottom of the prism row is preferably 0.008 or less as the ratio (S / P) of the maximum distance S from the plane to the pitch P of the prism row. Preferably it is 0.0065 or less, more preferably 0.005 or less. Since such a substantially planar deformation is mainly caused by polymerization shrinkage when forming a prism array pattern, the degree of deformation due to polymerization shrinkage is quantified in advance, and a mold is formed so as to cancel the degree. It is preferable to design the shape of the prism array.
[0045]
In the present invention, it is preferable that the prism surface having the above-mentioned convex curved surface portion 46 is formed at least on the surface (the second prism surface 45) far from the primary light source 1. According to this, it is possible to sufficiently reduce the distribution of the light emitted from the light deflecting element 4 in the emission light luminance distribution (in the XZ plane) when the primary light source is also arranged on the end face 32 of the light guide 3. The prism surface having the convex curved surface portion 46 is, for example, a light guide 3 when the ratio of light propagating through the light guide 3 to the end surface 32 opposite to the light incident surface 31 and returning is relatively high. When the primary light source 1 is disposed on each of two opposite end surfaces, it is more preferable that the prism surface (first prism surface 44) closer to the primary light source 1 has the same shape. On the other hand, when the rate at which the light propagating through the light guide 3 is reflected by the end face 32 opposite to the light incident surface 31 and returned is relatively low, the prism surface closer to the primary light source 1 is set to be substantially flat. Is also good. Further, in the light deflecting element 4 of the present invention, it is preferable that one of the tops of the prism row is formed of a substantially flat surface. It is possible to more accurately form the shape transfer surface shape of the molding die member for forming the prism array, and it is possible to suppress the occurrence of the sticking phenomenon when the light deflecting element 4 is mounted on the light guide 3. .
[0046]
As described above, the light deflecting element 4 as described above is mounted on the light exit surface 33 of the light guide 3 such that the prism row forming surface is on the light incident surface side, whereby the light guide 3 The luminous intensity distribution (in the XZ plane) of the directional outgoing light emitted from the light emitting surface 33 can be made narrower, and higher brightness and a narrower field of view as the light source device can be achieved. The full width at half maximum of the emission light luminance distribution (in the XZ plane) of the light emitted from the light deflector 4 is preferably in the range of 5 to 25 degrees, more preferably in the range of 10 to 20 degrees. More preferably, it is in the range of 12 to 18 degrees. This is because, by setting the full width at half maximum of the emission light luminance distribution (in the XZ plane) to 5 degrees or more, it is possible to prevent the visibility of an image or the like due to an extremely narrow visual field, and to set the luminance to 25 degrees or less to obtain high luminance. This is because it is possible to reduce the size and the field of view.
[0047]
Since the narrowing of the visual field of the light deflecting element 4 according to the present invention is affected by the extent (full width at half maximum) of the luminous intensity distribution (in the XZ plane) emitted from the light exit surface 33 of the light guide 3, The ratio of the luminous intensity distribution (in the XZ plane) of the light emission distribution 33 (in the XZ plane) of the luminous intensity distribution (in the XZ plane) of the light guide body 3 having the full width at half maximum A of the emission light luminance distribution (in the XZ plane) from the light exit surface 42 is also It depends on the full width at half maximum B of the luminous intensity distribution (in the XZ plane) of the light emitted from the light body 3. For example, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) emitted from the light guide 3 is less than 26 degrees, the full width at half maximum A is preferably in the range of 30 to 95% of the full width at half maximum B, It is more preferably in the range of 30 to 80%, and still more preferably in the range of 30 to 70%. Further, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) emitted from the light guide 3 is 26 degrees or more, the full width at half maximum A is preferably in the range of 30 to 80% of the full width at half maximum B, It is more preferably in the range of 30 to 70%, and still more preferably in the range of 30 to 60%. In particular, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) emitted from the light guide 3 is 26 to 36 degrees, the full width at half maximum A is preferably in the range of 30 to 80% of the full width at half maximum B. , More preferably in the range of 30 to 70%, and still more preferably in the range of 30 to 60%. Further, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 exceeds 36 degrees, the full width at half maximum A is preferably in the range of 30 to 70% of the full width at half maximum B, It is more preferably in the range of 30 to 60%, and still more preferably in the range of 30 to 50%.
[0048]
Generally, when it is attempted to increase the emission efficiency of the light guide plate, the full width at half maximum B of the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 seems to be large, and the light collection efficiency seems to be reduced. Since the effect of narrowing the visual field is increased, a light guide having a full width at half maximum B of 26 degrees or more in the emission light luminous intensity distribution (in the XZ plane) in terms of the efficiency of narrowing the visual field and the light use efficiency as a surface light source device. It is preferable to use a light deflecting element in a combination of the light guides, more preferably a light guide having a full width at half maximum B of more than 36 degrees. When the full width at half maximum of the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 is small, the effect of narrowing the visual field is reduced, but the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 is reduced. The smaller the full width at half maximum is, the higher the luminance can be. Therefore, in terms of the higher luminance, the light in combination with a light guide having a full width at half maximum B of the luminous intensity distribution (in the XZ plane) of less than 26 degrees. Preferably, a deflection element is used.
[0049]
The primary light source 1 is a linear light source extending in the Y direction. As the primary light source 1, for example, a fluorescent lamp or a cold cathode tube can be used. In the present invention, the primary light source 1 is not limited to a linear light source, but a point light source such as an LED light source, a halogen lamp, a metahalo lamp, or the like can also be used. In particular, when used in a display device having a relatively small screen size such as a mobile phone or a portable information terminal, it is preferable to use a small point light source such as an LED. In addition, as shown in FIG. 1, the primary light source 1 can be further installed not only on one side end face of the light guide 3 but also on the other side end face as necessary. .
[0050]
For example, when a substantially point-like light source such as an LED light source is used as the primary light source 1 at a corner of the light guide 3, the light incident on the light guide 3 is in the same plane as the light exit surface 33. The light propagates through the light guide 3 radially with the primary light source 1 substantially at the center, and the emitted light emitted from the light emitting surface 33 is also radially emitted with the primary light source 1 at the center. In order to efficiently deflect such emitted light in a desired direction irrespective of the emission direction, a prism array formed on the light deflecting element 4 is formed in a substantially arc shape so as to surround the primary light source 1. It is preferable to arrange them in parallel. In this way, by arranging the prism rows substantially in parallel in a substantially arc shape so as to surround the primary light source 1, most of the light radially emitted from the light exit surface 33 is substantially aligned with the prism row of the light deflection element 4. Since the light is incident perpendicularly, the emitted light can be efficiently directed to a specific direction in the entire region of the light emitting surface 33 of the light guide 3, and the uniformity of luminance can be improved. The substantially arc-shaped prism array formed on the light deflecting element 4 selects the degree of the arc according to the distribution of light propagating in the light guide 3, and most of the light radially emitted from the light exit surface 33 is light. It is preferable that the light is incident on the prism array of the deflecting element 4 substantially perpendicularly. Specifically, there is one in which the radius of the arc is arranged substantially in parallel so that the radius of the arc gradually increases in a concentric manner with the point light source such as an LED substantially at the center. It is determined by the positional relationship and size between the position of the point light source in the light source system and the effective area of the surface light source corresponding to the liquid crystal display area.
[0051]
The light source reflector 2 guides the light of the primary light source 1 to the light guide 3 with little loss. As the material, for example, a plastic film having a metal deposition reflective layer on the surface can be used. As shown in FIG. 1, the light source reflector 2 is wound from the outer surface of the edge of the light reflecting element 5 to the outer surface of the primary light source 1 to the edge of the light exit surface of the light deflecting element 4. On the other hand, the light source reflector 2 can be wound around the light emitting element 4 from the outer surface of the light reflecting element 5 to the light emitting surface of the light guide 3 via the outer surface of the primary light source 1, avoiding the light deflecting element 4. It is.
[0052]
A reflecting member similar to the light source reflector 2 can be attached to a side end surface other than the side end surface 31 of the light guide 3. As the light reflection element 5, for example, a plastic sheet having a metal deposition reflection layer on the surface can be used. In the present invention, instead of the reflection sheet, the light reflection element 5 may be a light reflection layer or the like formed on the back surface 34 of the light guide 3 by metal deposition or the like.
[0053]
The light guide 3 and the light deflecting element 4 of the present invention can be made of a synthetic resin having a high light transmittance. Examples of such a synthetic resin include a methacrylic resin, an acrylic resin, a polycarbonate resin, a polyester resin, and a vinyl chloride resin. In particular, methacrylic resin is optimal because of its high light transmittance, heat resistance, mechanical properties, and moldability. Such a methacrylic resin is a resin containing methyl methacrylate as a main component, and is preferably a resin having 80% by weight or more of methyl methacrylate. When forming the surface structure of the rough surface of the light guide 3 and the light deflecting element 4 and the surface structure such as the prism rows, the transparent synthetic resin plate is formed by hot pressing using a mold member having a desired surface structure. The shape may be provided simultaneously with the molding by screen printing, extrusion molding, injection molding, or the like. Further, the structural surface can also be formed by using a heat or light curable resin. Further, on a transparent substrate such as a transparent film or sheet made of a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin, etc., a rough surface structure made of an active energy ray-curable resin. Further, a lens array structure may be formed on the surface, or such a sheet may be joined and integrated on a separate transparent substrate by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylates, allyl compounds, metal salts of (meth) acrylic acid, and the like can be used.
[0054]
A liquid crystal display element is provided on the light emitting surface (light emitting surface 42 of the light deflecting element 4) of the surface light source device including the primary light source 1, the light source reflector 2, the light guide 3, the light deflecting element 4, and the light reflecting element 5 as described above. The liquid crystal display device is constituted by arranging. The liquid crystal display device is observed by an observer through the liquid crystal display element from above in FIG. In addition, in the present invention, since a sufficiently collimated light with a narrow distribution can be made to enter the liquid crystal display element from the surface light source device, there is no grayscale inversion or the like in the liquid crystal display element, and the uniformity of brightness and hue is obtained. In addition to obtaining good image display, light irradiation concentrated in a desired direction can be obtained, and the efficiency of using the amount of light emitted from the primary light source for illumination in this direction can be increased.
[0055]
Further, in the present invention, in the light source device having a narrow field of view and a high luminance by the light deflecting element 4 as described above, the range of the visual field can be appropriately controlled according to the purpose without causing a reduction in the luminance as much as possible. Next, the light diffusing element 6 is arranged adjacent to the light exit surface of the light deflecting element 4. Further, in the present invention, by arranging the light diffusing element 6 in this way, it is possible to suppress glare, uneven brightness, and the like that cause deterioration in quality, thereby improving the quality.
[0056]
The light diffusing element 6 may be integrated with the light deflecting element 4 on the light emitting surface side of the light deflecting element 4, or the light diffusing elements 6 may be individually mounted on the light emitting surface side of the light deflecting element 4. However, it is preferable to dispose the light diffusing elements 6 individually. When the light diffusing elements 6 are individually mounted, an uneven structure is provided on the surface of the light diffusing element 6 adjacent to the light deflecting element 4 in order to prevent sticking with the light deflecting element 4. Is preferred. Similarly, it is necessary to consider the sticking between the light emitting element 6 and the liquid crystal display element disposed on the light emitting element 6. Is preferred. When the uneven structure is provided only for the purpose of preventing sticking, it is preferable that the average inclination angle be 0.7 degrees or more, more preferably 1 degree or more, and more preferably 1 degree or more. 0.5 degrees or more.
[0057]
In the present invention, it is necessary to use the light diffusing element 6 having a light diffusing property for appropriately diffusing the light emitted from the light deflecting element 4 in consideration of the balance between the luminance characteristic, the visibility and the quality. That is, when the light diffusing property of the light diffusing element 6 is low, it is difficult to sufficiently widen the viewing angle, and the visibility is reduced, and the effect of improving the quality tends to be insufficient. If it is too high, the effect of narrowing the field of view by the light deflecting element 4 will be impaired, and the total light transmittance will also decrease, tending to lower the luminance. Therefore, as the light diffusing element 6 of the present invention, one having a full width at half maximum of the luminous intensity distribution (in the XZ plane) of emitted light when parallel light is incident within a range of 1 to 13 degrees is used. The full width at half maximum of the light diffusion element 6 is preferably in the range of 3 to 11 degrees, and more preferably in the range of 4 to 8.5 degrees. In the present invention, the full width at half maximum of the luminous intensity distribution (in the XZ plane) of the outgoing light from the light diffusion element 6 is, as shown in FIG. The angle (Δθ) of the full width of the divergence angle at half value with respect to the peak value in the emission light intensity distribution (in the XZ plane) of the light transmitted and diffused through the light diffusion element 6_H).
[0058]
Such light diffusion characteristics can be imparted by mixing a light diffusing agent into the light diffusing element 6 or imparting an uneven structure to at least one surface of the light diffusing element 6. The degree of the concavo-convex structure formed on the surface is different between the case where it is formed on one surface of the light diffusion element 6 and the case where it is formed on both surfaces. When an uneven structure is formed on one surface of the light diffusing element 6, the average inclination angle is preferably in the range of 0.8 to 12 degrees, more preferably 3.5 to 7 degrees, and more preferably 3.5 to 7 degrees. Preferably it is 4 to 6.5 degrees. When the uneven structure is formed on both surfaces of the light diffusing element 6, the average inclination angle of the uneven structure formed on one surface is preferably in the range of 0.8 to 6 degrees, more preferably 2 to 6. 4 degrees, more preferably 2.5 to 4 degrees. In this case, in order to suppress a decrease in the total light transmittance of the light diffusion element 6, it is preferable that the average inclination angle on the incident surface side of the light diffusion element 6 be larger than the average inclination angle on the emission surface side. Further, the haze value of the light diffusing element 6 is preferably in the range of 8 to 82% from the viewpoint of improving the luminance characteristics and the visibility, more preferably in the range of 30 to 70%, and more preferably 40 to 70%. ６５65%.
[0059]
In the light source device of the present invention, it is also required that the luminance in the display area when observed from the normal direction of the light emitting surface (the emission surface of the light diffusing element 6) is uniform. The uniformity of the luminance also depends on the size of the display area of the light source. For example, a large light source device having a large display area such as a notebook computer or a monitor may require a relatively wide viewing angle characteristic. It is required to further broaden the luminous intensity distribution (in the XZ plane) of the outgoing light emitted from the light emitting surface. On the other hand, in a small light source device having a small display area, such as a mobile phone or a portable information terminal, high luminance and improvement in display quality may be given priority, and the luminous intensity distribution (in the XZ plane) emitted from the light emitting surface is reduced. It may be relatively narrow. For this reason, it is preferable to use the light diffusion element 6 having an appropriate light diffusion characteristic according to the size of the display area of the light source device.
[0060]
The light diffusion characteristics of the light diffusion element 6 according to the size of the display area of such a light source device will be described. The size of the display area of the light source device will be described with reference to the developed length. Here, the development length of the light source device (the development length of the light guide 3) refers to a linear cold cathode light source arranged on the light incident surface of the light guide 3 as the primary light source 1, as shown in FIG. In this case, it refers to the longest distance L of the display area in the direction in which the light incident on the light guide 3 is guided, that is, in the direction perpendicular to the light incident surface. Also, as shown in FIG. 23, when a point light source such as an LED is disposed as a primary light source 1 at the corner of the light guide 3, a line connecting the effective display area farthest from the light point source and the point light source is formed. Means the distance L of the display area.
[0061]
(1) When the developed length of the light guide 3 is 8 cm or less
Such a light source device uses a linear cold-cathode tube (single-light type), LED, or the like as the primary light source 1, and is used for a display device having a small display area such as a mobile phone, a portable information terminal, or a digital camera. Therefore, it is not necessary to increase the viewing angle so much, and the light diffusing element 6 is provided with light diffusivity enough to suppress glare and luminance unevenness which cause deterioration in quality, thereby increasing light use efficiency and maintaining high luminance. At the same time, it is necessary to reduce power consumption. For this reason, as the light diffusing element 6, the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) is preferably in the range of 1 to 6 degrees, more preferably 1 to 5 degrees, more preferably 2 to 5 degrees. Range. Further, the haze value is preferably in the range of 8 to 60%, more preferably 8 to 50%, more preferably 20 to 50%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the average inclination angle is preferably in the range of 0.8 to 5 degrees, more preferably 0.8 to 4 degrees, more preferably 0.8 to 4 degrees. The range is 2 to 4 degrees.
[0062]
(2) When the developed length of the light guide 3 is more than 8 cm and 23 cm or less (a single-light cold cathode tube is used as the primary light source 1)
Since such a light source device is used for a display device such as a notebook computer, a desktop computer monitor, and a relatively small liquid crystal television, a relatively wide viewing angle is required. Accordingly, high quality and high brightness are required. For this reason, as the light diffusing element 6, the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) is preferably in the range of 3 to 11 degrees, more preferably 4 to 10 degrees, and even more preferably 4 to 9 degrees. Range. Further, the haze value is preferably in the range of 30 to 80%, more preferably 40 to 73%, and still more preferably 45 to 70%. Furthermore, when the uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 3 to 9.5 degrees, more preferably 3.5 to 8.5 degrees, and more preferably 3.5 to 8.5 degrees. Preferably it is in the range of 4.5 to 7 degrees.
[0063]
When the developed length of the light guide 3 is more than 8 cm and 18 cm or less, the light guide 3 is used for a display device of a relatively small notebook personal computer, so that a required viewing angle is slightly narrow. For this reason, as the light diffusing element 6, the full width at half maximum of the emitted light luminous intensity distribution (within the XZ plane) is preferably in the range of 3 to 8 degrees, more preferably 4 to 8 degrees, more preferably 4 to 7 degrees. Range. Further, the haze value is preferably in the range of 30 to 70%, more preferably 40 to 65%, and still more preferably 45 to 60%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the average inclination angle is preferably in the range of 3 to 7 degrees, more preferably 3.5 to 6.5 degrees, more preferably. The range is 4.5 to 6 degrees.
[0064]
When the developed length of the light guide 3 is more than 18 cm and not more than 22 cm, the light guide 3 is used for a display device of a relatively large notebook personal computer. It is necessary to achieve brightness uniformity. For this reason, as the light diffusing element 6, the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) is preferably in the range of 4 to 10 degrees, more preferably 5 to 9 degrees, more preferably 5 to 8 degrees. The range is 5 degrees. Further, the haze value is preferably in the range of 40 to 75%, more preferably 50 to 70%, and still more preferably 50 to 65%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 3.5 to 8 degrees, more preferably 4 to 7 degrees, and more preferably 4. The range is 5 to 6.5 degrees.
[0065]
When the developed length of the light guide 3 is more than 22 cm and not more than 23 cm, the light guide 3 is used for a display device such as a relatively large notebook computer. A notebook computer using a single-lamp cold-cathode tube as the primary light source 1 has a large display area, and has a higher light use efficiency and brightness compared to a light guide 3 having a development length of 22 cm or less. Needs to be improved. In order to increase the luminance in this way, for example, as a reflection sheet disposed on the back surface of the light guide 3 of the light source device, instead of a foamed PET reflection film having low directional reflection, silver having excellent directional reflection characteristics is used. It is necessary to use a metal reflection sheet such as a reflection sheet or an aluminum reflection sheet. However, when a metal reflection sheet is used, defects such as glare peculiar to metal reflection, a dark line bright line appearing near the incident surface, and a dark portion appearing near both ends of the incident surface are strongly exhibited, and the quality as a light source device is increased. Tend to be impaired. In order to suppress such deterioration in quality, it is necessary to use a light diffusion element 6 having a high light diffusion property such that the full width at half maximum of the luminous intensity distribution (in the XZ plane) exceeds 9 degrees. However, when such a light diffusing element 6 is used, the light diffusing property becomes too large and the total light transmittance is greatly reduced, so that there is a problem that a sufficiently high luminance cannot be obtained. . For this reason, such deterioration in quality is suppressed by the light guide 3 and the light deflecting element 4, and the light diffusion element 6 has a full width at half maximum of 5 to 11 degrees in the emission light luminous intensity distribution (in the XZ plane). It is preferable to use those, more preferably 6 to 10 degrees, and more preferably 7 to 9 degrees. Further, the haze value is preferably in the range of 50 to 80%, more preferably 55 to 73%, and still more preferably 55 to 70%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 4.5 to 9.5 degrees, more preferably 5 to 8.5 degrees, and more preferably 5 to 8.5 degrees. Preferably it is in the range of 5 to 7 degrees.
[0066]
(3) When the developed length of the light guide 3 is more than 22 cm and not more than 28 cm (a multi-light cold cathode tube is used as the primary light source 1)
Since such a light source device is used for a display device such as a monitor of a desktop personal computer and a liquid crystal television, a relatively wide viewing angle is required and a high luminance is required. Therefore, as the primary light source 1, a multi-lamp type light source in which one or more cold-cathode tubes are arranged on two opposite end faces of the light guide 3 is used. In such a light source device, the visibility related to the quality is different from that using the single-lamp type primary light source 1, and the asymmetry of the luminous intensity distribution (in the XZ plane) described later loses its characteristic, The luminous intensity distribution (in the XZ plane) near the center of the device has improved symmetry even when the light diffusing element 6 is not used, as shown in FIG. Furthermore, the luminous intensity distribution (in the XZ plane) of the emitted light near both ends near the light source is affected by the light guided from the nearest point, and the luminous intensity distribution (in the XZ plane) slightly asymmetry is obtained. ). That is, in the vicinity of the left end portion in FIG. 24, the emitted light luminous intensity distribution (in the XZ plane) on the light source side sharply decreases, and the emitted light luminous intensity distribution (in the XZ plane) on the central side has a smooth tailing tendency. Therefore, the light emission direction in the vicinity of the left end has many components directed slightly toward the center. On the other hand, in the vicinity of the right end portion in FIG. 24, an opposite luminous intensity distribution (in the XZ plane) is obtained, and the light emission direction has a large number of components slightly toward the center. For this reason, the emitted light characteristic with excellent visibility when observing the vicinity of both ends from the center is obtained, and a light source device having high quality and high brightness up to the ends is obtained. For this reason, the light diffusing element 6 is required to have a light diffusing property for obtaining a wide viewing angle, and it is preferable to use a light diffusing element having a full width at half maximum of 6 to 13 degrees in the luminous intensity distribution (in the XZ plane). More preferably, it is in the range of 6.5 to 11 degrees, more preferably in the range of 7 to 9 degrees. The haze value is preferably in the range of 50 to 82%, more preferably 60 to 75%, and even more preferably 65 to 70%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 4.5 to 12 degrees, more preferably 5.5 to 8.5 degrees, and more preferably 5.5 to 8.5 degrees. Preferably it is in the range of 6 to 7 degrees.
[0067]
In the light source device of the present invention, when the above-described light diffusing element 6 is used, the light-collecting properties where the full width at half maximum of the luminance distribution (in the XZ plane) emitted from the light deflecting element 4 is about 19 to 26 degrees are compared. It is preferable to use the light deflecting element 4 that is relatively weak and to use the light diffusing element 6 that has relatively low light diffusibility since the reduction in luminance due to diffusion on the YZ plane can be suppressed. is there. In this case, the light diffusing element 6 is required to have a light diffusing property for obtaining a wide viewing angle, and it is preferable to use a light diffusing element having a full width at half maximum of 1 to 8 degrees of the emitted light luminous intensity distribution (in the XZ plane). And more preferably in the range of 2 to 8 degrees, more preferably in the range of 3 to 7 degrees. Further, the haze value is preferably in the range of 8 to 70%, more preferably 30 to 65%, and still more preferably 40 to 60%. Further, when the uneven structure is formed on one surface of the light diffusion element 6, the average inclination angle is preferably in the range of 0.8 to 7 degrees, more preferably 3 to 6.5 degrees, and more preferably 3 to 6.5 degrees. Preferably it is in the range of 3.5 to 6 degrees. When the uneven structure is formed on both surfaces, the average inclination angle of one surface thereof is preferably in the range of 0.8 to 4 degrees, more preferably 1 to 4 degrees, more preferably 2 to 4 degrees. Range.
[0068]
In the light source device of the present invention, the outgoing light emitted from the outgoing light surface of the light deflector 4 may have an asymmetric outgoing light luminance distribution (in the XZ plane) as shown in FIG. The emitted light luminance distribution (in the XZ plane) is derived from the emitted light luminous intensity distribution (in the XZ plane) emitted from the light guide 3. Such an asymmetric outgoing light luminance distribution (in the XZ plane) is, for example, a high directivity outgoing light in which the full width at half maximum of the outgoing light luminance distribution (in the XZ plane) from the light deflecting element 4 is 20 degrees or less. It tends to appear when emitted. In particular, in a light source device having a relatively large display area, in order to reduce the asymmetry of the emitted light luminance distribution (in the XZ plane), the light diffusing element 6 having a relatively strong light diffusing property is used. Is required. On the other hand, when the half-width of the luminous intensity distribution (in the XZ plane) of 4 degrees or more and the haze value is 35% or more is used as the light diffusing element 6, the luminous intensity of the outgoing light emitted from the light diffusing element 6 The peak angle of the distribution (in the XZ plane) is deviated by about 1 to 3 degrees in the direction opposite to the light source with respect to the peak angle of the luminance distribution (in the XZ plane) of the emitted light from the light deflecting element 4. For this reason, when the peak angle of the luminance distribution (in the XZ plane) of the emitted light from the light deflection element is in a desired direction (for example, the normal direction), the light diffusion element 6 is used to change the light in the desired direction. This causes a decrease in the brightness of the image. Therefore, when the light diffusion element 6 as described above is used when the full width at half maximum of the luminance distribution (in the XZ plane) of the emitted light from the light deflection element 4 is 20 degrees or less, the light deflection element 4 must be Light deflection such that the peak angle of the emitted light luminance distribution (in the XZ plane) is inclined from the desired direction to the light source side by 0.5 to 3 degrees, more preferably 0.5 to 2 degrees, and more preferably 1 to 2 degrees. It is preferable to design the element 4 and the like.
[0069]
In the present invention, the use of a light diffusing element 6 having anisotropy in light diffusing property increases the total light transmittance of the light diffusing element 6 and efficiently emits light from the light deflecting element 4. This is preferable because it can diffuse and improve the luminance. For example, in a light source device in which a cold-cathode tube on a line is arranged as a primary light source 1 on one end face of the light guide 3, the light deflecting element 4 for narrowing the field of view emits light from the light exit surface of the light guide 3. The objective is to narrow the field of view of the emitted light mainly in the XZ plane, and to diffuse the light of the XZ plane narrowed by the light diffusion element 6 to broaden the viewing angle. However, when an isotropic diffusive element is used as the light diffusing element 6, light on the YZ plane, which is not narrowed by the light deflector, is equally diffused, resulting in a decrease in luminance. become. Therefore, as shown in FIG. 26, by using the light diffusing element 6 having anisotropic diffusing property such that the light diffusing property is higher on the YZ plane than on the XZ plane, the visual field is narrowed by the light deflecting element 4. The light on the XZ plane is strongly diffused, the light on the YZ plane that is not narrowed in the field of view can be weakly diffused, the light emitted from the light deflecting element 4 can be efficiently diffused, and the brightness decreases. Can be minimized as much as possible.
[0070]
In the present invention, regarding the anisotropic diffusivity of the light diffusing element 6, what kind of anisotropic light diffusing element 6 is used depends on the difference between the XZ plane and the YZ plane as described above. It is not limited to the anisotropy, and can be appropriately selected according to the light emitting mechanism of the light guide 3, the lens shape and arrangement of the light deflecting element 4, the use of the light source device, and the like. That is, as shown in FIG. 27, an arbitrary plane (ZP-n plane (n = 1, 2,...)) Including the normal axis to the exit plane of the light diffusion element 6 is assumed, and these arbitrary planes are assumed. The anisotropy can be imparted by making the full width at half maximum of the luminous intensity distribution (in the XZ plane) of the emitted light in the plane different. Note that the largest full width at half maximum is the maximum full width at half maximum and the smallest full width at half maximum is the minimum full width at half maximum in the ZP-n plane. Similarly, regarding the average inclination angle of the concavo-convex structure that imparts anisotropic diffusion to the light diffusion element 6, the average inclination angle in an arbitrary P-n direction where the ZP-n plane and the light diffusion element 6 (XY plane) intersect with each other. The anisotropy of the average inclination angle can be provided by making the difference. At this time, the largest average inclination angle in the P-n direction is defined as the maximum average inclination angle, and the smallest average inclination angle is defined as the minimum average inclination angle.
[0071]
For example, when a linear cold cathode tube is arranged on one end face of the light guide 3 to form the primary light source 1, the light deflecting element 4 mainly narrows the field of view mainly on the XZ plane and hardly acts on the YZ plane. It is optimal to use a light diffusing element 6 having anisotropic diffusion properties that effectively diffuses outgoing light on the XZ plane and does not diffuse outgoing light on the YZ plane. Therefore, it is preferable that the light diffusing element 6 has anisotropic diffusion such that the XZ plane shows the full width at half maximum and the YZ plane shows the minimum full width at half maximum. Similarly, it is preferable that the concavo-convex structure formed on the light diffusing element 6 also has a structure or arrangement having a maximum average inclination angle in the X direction and a minimum average inclination angle in the Y direction.
[0072]
The light diffusion element 6 having such anisotropic diffusion also has a light diffusion characteristic of appropriately diffusing light emitted from the light deflecting element 4 in consideration of the balance of luminance characteristics, visibility and quality. It is necessary to use element 6. That is, when the light diffusing property of the light diffusing element 6 is low, it is difficult to sufficiently widen the viewing angle, and the visibility is reduced, and the effect of improving the quality tends to be insufficient. If it is too high, the effect of narrowing the field of view by the light deflecting element 4 will be impaired, and the total light transmittance will also decrease, tending to lower the luminance. For this reason, an emission light luminous intensity distribution (within the XZ plane) having a full width at half maximum of 1 to 13 degrees is used, preferably 3 to 11 degrees, more preferably 4 to 9 degrees. Further, the ratio of the maximum full width at half maximum to the full width at half maximum (maximum full width at half maximum / minimum full width at half maximum) is preferably in the range of 1.1 to 20, more preferably in the range of 2 to 15, and more preferably in the range of 4 to 10. Range. This is because by setting the maximum full width at half maximum / minimum full width at half maximum to 1.1 or more, the light use efficiency can be improved and the luminance can be increased. This is because it can suppress.
[0073]
When the uneven structure is formed on one surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 0.8 to 15 degrees, more preferably 3.5 to 11 degrees, More preferably, it is 4 to 9 degrees. Also, from the same viewpoint as the maximum full width at half maximum / minimum full width at half maximum, the ratio of the maximum average inclination angle to the minimum average inclination angle (maximum average inclination angle / minimum average inclination angle) may be in the range of 1.1 to 20. Preferably, it is more preferably in the range of 2 to 15, more preferably 4 to 10. The concavo-convex structure may be formed on both surfaces of the light diffusing element 6. In this case, in order to suppress a decrease in the total light transmittance of the light diffusing element 6, the average of the incident surface side of the light diffusing element 6 is required. It is preferable that the inclination angle is larger than the average inclination angle on the emission surface side. Further, the haze value of the light diffusing element 6 is preferably in the range of 8 to 82% from the viewpoint of improving the luminance characteristics and the visibility, more preferably in the range of 30 to 70%, and more preferably 40 to 70%. ６５65%.
[0074]
Further, as the light diffusion element 6, it is preferable to use an element having appropriate light diffusion characteristics according to the size of the display area of the light source device. When the developed length of the light guide 3 is 8 cm or less, the light diffusion element 6 preferably has a maximum full width at half maximum of the luminous intensity distribution (in the XZ plane) of 1 to 6 degrees, more preferably. Is in the range of 1 to 5 degrees, more preferably 2 to 5 degrees. Further, the haze value is preferably in the range of 8 to 60%, more preferably 8 to 50%, more preferably 20 to 50%. Furthermore, when forming a concavo-convex structure on the surface of the light diffusion element 6, the maximum average inclination angle is preferably in the range of 0.8 to 5 degrees, more preferably 0.8 to 4 degrees, and more preferably 0.8 to 4 degrees. Is in the range of 2 to 4 degrees.
[0075]
In the case where the developed length of the light guide 3 is more than 8 cm and 23 cm or less (a single-lamp-type cold cathode tube is used as the primary light source 1), the light diffusing element 6 has the luminous intensity distribution (in the XZ plane) of the emitted light. The full width at half maximum is preferably in the range of 3 to 11 degrees, more preferably 4 to 10 degrees, and even more preferably 4 to 9 degrees. Further, the haze value is preferably in the range of 30 to 80%, more preferably 40 to 73%, and still more preferably 45 to 70%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 3 to 15 degrees, more preferably 3.5 to 10 degrees, more preferably 4 to 10 degrees. 0.5 to 8 degrees. In particular, when the developed length of the light guide 3 is more than 8 cm and not more than 18 cm, the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) is in the range of 3 to 10 degrees. Is more preferable, more preferably 4 to 10 degrees, more preferably 4 to 9 degrees. Further, the haze value is preferably in the range of 30 to 70%, more preferably 40 to 65%, and still more preferably 45 to 60%. Further, when the uneven structure is formed on the surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 3 to 9 degrees, more preferably 3.5 to 8 degrees, more preferably 4 to 8 degrees. 0.5 to 8 degrees. When the developed length of the light guide 3 is more than 18 cm and not more than 22 cm, the light diffusion element 6 should have a full width at half maximum of the luminous intensity distribution (in the XZ plane) of 4 to 13 degrees. Is more preferable, more preferably in the range of 5 to 11 degrees, and more preferably in the range of 5 to 8.5 degrees. Further, the haze value is preferably in the range of 40 to 75%, more preferably 50 to 70%, and still more preferably 50 to 65%. Further, when the uneven structure is formed on the surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 3.5 to 15 degrees, more preferably 4 to 9 degrees, more preferably 4 to 9 degrees. 0.5 to 6.5 degrees. Further, when the developed length of the light guide 3 is more than 22 cm and not more than 23 cm, the light diffusing element 6 whose full width at half maximum of the luminous intensity distribution of the emitted light (in the XZ plane) is in the range of 5 to 13 degrees is used. It is preferably in the range of 6 to 12 degrees, more preferably 7 to 9 degrees. Further, the haze value is preferably in the range of 50 to 80%, more preferably 55 to 73%, and still more preferably 55 to 70%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the maximum average inclination angle is preferably in the range of 4.5 to 15 degrees, more preferably 5 to 10 degrees, and more preferably 5 to 10 degrees. It is in the range of up to 7 degrees.
[0076]
When the developed length of the light guide 3 is more than 22 cm and not more than 28 cm (a multi-lamp type continuous cathode tube is used as the primary light source 1), the light diffusing element 6 needs to have a light diffusing property to obtain a wide viewing angle. It is preferable to use an emission light luminous intensity distribution (in the XZ plane) having a full width at half maximum of 6 to 13 degrees, more preferably 6.5 to 11 degrees, and more preferably 7 to 9 degrees. Range. The haze value is preferably in the range of 50 to 82%, more preferably 60 to 75%, and even more preferably 65 to 70%. Furthermore, when the uneven structure is formed on the surface of the light diffusion element 6, the maximum average inclination angle is preferably in the range of 4.5 to 15 degrees, more preferably 5.5 to 13 degrees, and more preferably. Is in the range of 6 to 7 degrees.
[0077]
As the diffusibility imparting structure of the light diffusing element 6 having such anisotropic diffusivity, for example, a concavo-convex structure as shown in FIGS. The concavo-convex structure shown in FIG. 28 is an array structure in which a large number of lens arrays such as a lenticular lens array extending long on one axis are arranged substantially in parallel. As the arrangement pitch of such lens arrays, a pitch in which moire is less likely to occur with respect to the pitch of the liquid crystal elements used as the display device and the arrangement pitch of the lens arrays such as the prism array of the light deflecting element 4 is selected, or a random pitch is selected. An array pitch is preferred. Usually, the arrangement pitch of the lens rows is preferably in the range of 1 to 70 μm, more preferably 5 to 40 μm, and still more preferably 10 to 30 μm, from the viewpoint of ease of production and prevention of moiré. The average inclination angle in the direction orthogonal to the longitudinal direction of the lens array is preferably in the range of 0.8 to 15 degrees from the viewpoints of luminance improvement and visibility, more preferably 3.5 to 11 degrees. Is in the range of 4 to 9 degrees.
[0078]
The uneven structure shown in FIG. 29 is a structure in which a large number of cylindrical lens-shaped bodies are discretely arranged. The arrangement interval of the cylindrical lens shapes may be a constant regular pitch or a random arrangement pitch. Usually, the arrangement pitch of the cylindrical lens shaped body is preferably in the range of 1 to 70 μm, more preferably 5 to 40 μm, more preferably 10 to 30 μm from the viewpoint of ease of production and prevention of moiré. is there. In addition, the average inclination angle in the direction orthogonal to the longitudinal direction of the cylindrical lens-shaped body is preferably 0.8 to 15 degrees from the viewpoints of luminance improvement and visibility, more preferably 3.5 to 11 degrees, and more preferably 3.5 to 11 degrees. Is in the range of 4 to 9 degrees. In such a discrete array structure, a line that intersects a surface that needs to have the full width at half maximum of the light diffusing element 6 with an emission surface of the light diffusing element 6 and a longitudinal direction of the cylindrical lens shape body are substantially orthogonal. It is preferable to arrange them in such a manner that the quantitative probability to perform them is high. Also, the quantitative probability that the longitudinal direction of the cylindrical lens-shaped body is substantially parallel to the line intersecting the surface that needs to have the minimum full width at half maximum as the light diffusing element 6 and the exit surface of the light diffusing element 6 is increased. Preferably, they are arranged.
[0079]
The uneven structure shown in FIG. 30 is a hairline structure. The average inclination angle in the direction orthogonal to the direction in which the hairline extends is preferably 0.8 to 15 degrees from the viewpoints of luminance improvement and visibility, more preferably 3.5 to 11 degrees, and more preferably 4 to 9 degrees. Range. The direction in which the hairline extends is preferably substantially perpendicular to the line that intersects the surface of the light diffusion element 6 that needs to have the full width at half maximum and the emission surface of the light diffusion element 6.
[0080]
By providing a mat structure on at least one of the surface on which the uneven structure imparting such anisotropic diffusivity is formed and the back surface thereof, it is possible to suppress glare and uneven brightness and improve the quality. it can. However, if the light diffusing property of the mat structure is increased, the anisotropic diffusing property may be impaired and the luminance may be reduced. Therefore, it is preferable to provide a mat structure having relatively weak light diffusing property. Such a mat structure preferably has an average inclination angle of 0.5 to 5 degrees, more preferably 0.8 to 4 degrees, and still more preferably 1 to 3.5 degrees. The average tilt angle of the mat structure when the mat structure is provided on the surface of the anisotropic uneven structure refers to the average tilt angle of the mat structure itself excluding the average tilt angle caused by the uneven structure. That is, it is possible to measure an average inclination angle parallel to the longitudinal direction of a portion having no uneven structure or the uneven structure, a measurement using a stylus roughness meter, a method of image-analyzing a cross-sectional shape of the light diffusing element 6, an atomic force, It can be measured by a microscope or the like.
[0081]
In the present invention, light emitted from the light guide 3 is emitted in a specific direction such as the normal direction using the light deflecting element 4, and the emitted light is emitted using the light diffusing element 6 having anisotropic diffusion property. It can also be emitted in a desired direction. In this case, both functions of the anisotropic diffusion function and the light deflection angle function can be given to the light diffusion element 6. For example, in the case of using a lenticular lens array or a cylindrical lens shaped body as the concavo-convex structure, by making the cross-sectional shape asymmetrical, it is possible to provide both functions of anisotropic diffusion action and light deflection action.
[0082]
In the present invention, the light deflecting element 4 and the light diffusing element 6 may contain a light diffusing material for the purpose of adjusting the viewing angle as the light source device and improving the quality. As such a light diffusing material, transparent fine particles having a different refractive index from the material constituting the light deflecting element 4 and the light diffusing element 6 can be used, for example, silicon beads, polystyrene, polymethyl methacrylate. And homopolymers and copolymers such as fluorinated methacrylate. As the light diffusing material, it is necessary to appropriately select the content, the particle diameter, the refractive index, and the like so as not to impair the narrow visual field effect by the light deflecting element 4 and the appropriate diffusion effect by the light diffusing element 6. For example, the refractive index of the light diffusing material is small if the difference between the refractive index of the light deflecting element 4 and the material forming the light diffusing element 6 is too small. The rate difference is preferably in the range of 0.01 to 0.1, more preferably 0.03 to 0.08, and still more preferably 0.03 to 0.05. Further, the particle size of the diffusing material is such that if the particle size is too large, scattering becomes strong, causing glare and a decrease in luminance, and if the particle size is too small, coloring occurs, so that the average particle size is in the range of 0.5 to 20 μm. Preferably, it is more preferably in the range of 2 to 15 μm, more preferably 2 to 10 μm.
[0083]
The emission light luminance distribution (in the XZ plane) of the light source device using the light deflecting element as in the present invention is such that the emission light luminance distribution (in the XZ plane) on the light source side starts at the peak position. The luminance sharply decreases as the distance from the light source increases, and the emitted light luminance distribution (in the XZ plane) on the side far from the light source has an asymmetrical emitted light luminance distribution (in the XZ plane) in which the luminance decreases relatively slowly. May be shown. For example, when a light source device having such an emitted light luminance distribution (within the XZ plane) is used for a liquid crystal display device requiring a relatively wide viewing angle, such as a note-type personal computer having a size of 10 inches or more, the light diffusing property is relatively high. The light diffusing element having a high refractive index is arranged on the light exit surface of the light deflecting element, and the luminous intensity distribution (in the XZ plane) of the emitted light is widened to widen the viewing angle. In the case of using a light diffusing element having a light diffusing property having a haze value of 50% or more, the peak angle of the emitted light luminous intensity distribution (in the XZ plane) is deflected about 1 to 3 degrees farther from the light source. Therefore, when the peak angle of the luminance distribution (in the XZ plane) of the emitted light from the light deflecting element is located in the normal direction of the light exit surface, the peak angle of the luminous intensity distribution (in the XZ plane) of the emitted light is determined by the light diffusing element. The light is polarized about 1 to 3 degrees farther from the light source from the normal direction, and as a result, the brightness when observed from the normal direction is extremely reduced. This is because although the asymmetry of the luminance distribution (in the XZ plane) of the emitted light emitted from the light deflecting element is somewhat reduced by using the light diffusing element, the emitted light luminance distribution in which the luminance decreases relatively sharply is reduced. This is because the portion (in the XZ plane) is located in the normal direction. In order to avoid such an extreme decrease in luminance, it is preferable that the peak angle of the luminance distribution (in the XZ plane) of the emitted light from the light deflecting element is previously inclined by 1 to 3 degrees from the normal direction toward the light source.
[0084]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples.
In addition, the measurement of each physical property in the following Examples was performed as follows.
[0085]
Measurement of normal luminance and full width at half maximum of luminous intensity of surface light source device
A cold cathode tube was used as a light source, and DC 12 V was applied to an inverter (HIU-742A manufactured by Harrison) to perform high-frequency lighting. The luminance was obtained by dividing the surface of the surface light source device or the light guide into 3 × 5 squares of 20 mm square and averaging 15 points of the luminance values in the normal direction of each square. The full width at half maximum luminous intensity of the light guide is fixed to black paper having a pinhole of 4 mmφ on the surface of the light guide so that the pinhole is located at the center of the surface, and the measurement circle of the luminance meter is 8 to 9 mm. The distance was adjusted so that the gonio rotation axis was rotated around the pinhole in the direction perpendicular and parallel to the longitudinal axis of the cold cathode tube. The luminous intensity distribution (in the XZ plane) of the emitted light was measured with a luminance meter while rotating the rotation axis in each direction from + 80 ° to −80 ° at 1 ° intervals, and the peak angle and the luminous intensity distribution (in the XZ plane) were measured. The full width at half maximum (the spread angle of the distribution (in the XZ plane) of half the peak value) was determined. The full width at half maximum of the luminance of the surface light source device was adjusted so that the viewing angle of the luminance meter was 0.1 °, the surface light source device was positioned at the center plane, and the gonio rotation axis was rotated. The luminance distribution (in the XZ plane) of the emitted light was measured with a luminance meter while rotating the rotation axis from + 80 ° to -80 ° at 1 ° intervals in each direction, and the peak luminance and peak angle were determined.
[0086]
Measurement of average inclination angle (θa)
According to ISO4287 / 1-1987, the surface of the rough surface was measured by a stylus type surface roughness meter (Surfcom 570A manufactured by Tokyo Seiki Co., Ltd.) using 010-2528 (1 μmR, 55 ° cone, diamond) as a stylus. The roughness was measured at a drive speed of 0.03 mm / sec. The inclination was corrected by subtracting the average line from the chart obtained by the measurement, and the inclination was corrected and calculated by the equations (1) and (2).
[0087]
Measurement of haze value
The haze value was measured according to the method B of JIS K-7105, and the total light transmittance of a sample having a size of 50 mm × 50 mm was measured using an integrating sphere reflection / transmittance meter (model RT-100 manufactured by Murakami Color Research Laboratory). From the rate (Tt) and the diffused light transmittance (Td), it was calculated by the following equation (4).
[0088]
(Equation 3)

Measurement of light diffusion distribution angle
The light diffusion distribution angle is a half value which is a half luminous intensity of a peak luminous intensity obtained by measuring a sample having a size of 50 mm × 50 mm using an automatic goniophotometer (Model GP-200 manufactured by Murakami Color Research Laboratory Co., Ltd.). Two times the half width angle was defined as the full width at half maximum (a) of the sample. As for light to be incident on the sample, light from a light source is condensed on a pinhole by a condenser lens, and is converted into parallel light (parallelism of ± 0.5 degrees or less) through a collimator lens. ), And is incident on the incident surface of the sample. The light transmitted through the sample passes through a light-receiving lens (passes through the aperture of 11.4 mm (when the sample surface is smooth, is condensed at the position of the light-receiving aperture)). The same measurement was performed by rotating the sample, and the maximum full width at half maximum (Maxa) and the minimum full width at half maximum (Mina) were obtained.
[0089]
Example 1
A light guide having a mat on one side was prepared by injection molding using an acrylic resin (Acrypet VH5 # 000 manufactured by Mitsubishi Rayon Co., Ltd.). The light guide had a wedge plate shape of 216 mm × 290 mm and a thickness of 2.0 mm-0.7 mm. On the mirror side of the light guide, a prism row having a prism apex angle of 100 ° and a pitch of 50 μm is formed by an acrylic ultraviolet curing resin so as to be parallel to a side (short side) of 230 mm in length of the light guide. The prism layers arranged in parallel were formed. A cold-cathode tube is illuminated with a light source reflector (silver reflection film manufactured by Reiko Co., Ltd.) along one side end surface (end surface on the side having a thickness of 2.0 mm) corresponding to the side (long side) having a length of 290 mm of the light guide. Covered and arranged. Further, a light diffusion reflection film (E60 manufactured by Toray Industries, Inc.) was attached to the other side end surface, and a reflection sheet was arranged on the prism array (back surface). The above configuration was incorporated in a frame. In this light guide, the maximum peak angle of the emitted light luminous intensity distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface is 70 degrees with respect to the normal direction of the light emitting surface, and the full width at half maximum Was 22.5 degrees.
[0090]
On the other hand, as shown in Table 1, an acrylic ultraviolet curable resin having a refractive index of 1.5064 is used to form an angle between one of the prism surfaces (first prism surface) constituting the prism row and the normal line (see FIG. 1). α) is a plane of 32.5 degrees, and the other prism surface (second prism surface) extends from the top of the prism to the height of the prism array of 21.4 μm with a short-axis radius of curvature of 400 μm and a long-axis radius of curvature of 800 μm. A convex curved surface (inclination angle = 56.6 degrees, β = 33.8 degrees) having an aspherical shape (curved surface with a radius of curvature of 800 μm), a spherical shape having a radius of curvature of 400 μm with a prism row height of 21.4 μm or more from the top of the prism. A prism row forming surface, in which prism rows having a pitch of 56.5 μm and formed of two convex curved faces (areas 1 and 2 from the prism top side) having a convex curved face (inclination angle = 59.0 degrees) are provided substantially in parallel, is used. , 125μm thick poly To prepare a prism sheet formed on one surface of ester film. The ratio (d / P) of the maximum distance (d) between the second prism surface of the prism sheet and the virtual plane to the pitch (P) of the prism rows was 1.03%.
[0091]
The obtained prism sheet is placed so that the prism row forming surface faces the light exit surface side of the light guide, the prism ridge line is parallel to the light entrance surface of the light guide, and the first prism surface faces the light source. The surface light source device was obtained by mounting. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0092]
Example 2
As shown in Table 1, the second prism surface constituting the prism array is a plane having an inclination angle of 55.2 degrees (β = 34.8 degrees) from the top of the prism to the height of 16 μm of the prism array. The same inclination angles of 55.5 degrees, 56.2 degrees, 57.0 degrees, 57.8 degrees, 58.4 degrees and 59.4 degrees from the row height of 16 μm to the bottom of the prism from the side close to the top of the prism. A prism sheet was produced in the same manner as in Example 1 except that the plane was constituted by seven planes (areas 1, 2,... 7 from the top of the prism) having six planes having a width. The ratio (d / P) of the maximum distance (d) of the second prism surface of the prism sheet to the virtual plane to the pitch (P) of the prism rows was 1.10%.
[0093]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0094]
Example 3
As shown in Table 1, the second prism surface constituting the prism array is a plane having an inclination angle of 56.4 degrees (β = 33.6 degrees) from the top of the prism to the height of 10.6 μm of the prism array. A convex curved surface having a slope angle of 56.8 degrees between a height of 10.6 to 21.3 μm of the prism row and a spherical curved surface having a radius of curvature of 400 μm over a height of 21.3 μm of the prism row (tilt angle = 59.degree.). A prism sheet was produced in the same manner as in Example 1 except that the prism sheet was composed of two flat surfaces (2 degrees) and one convex curved surface (areas 1, 2, and 3 from the prism top side). The ratio (d / P) of the maximum distance (d) between the second prism surface of the prism sheet and the virtual plane to the pitch (P) of the prism rows was 1.03%.
[0095]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0096]
Example 4
As shown in Table 1, the second prism surface forming the prism array is a plane having an inclination angle of 56.8 degrees (β = 33.2 degrees) from the top of the prism to a height of 21.5 μm of the prism array. And a prism array in the same manner as in Example 1 except that the height of the prism array is 21.5 μm or more and two planes (areas 1 and 2 from the top of the prism) having a tilt angle of 58.7 degrees. A sheet was prepared. The ratio (d / P) of the maximum distance (d) between the second prism surface of the prism sheet and the virtual plane to the pitch (P) of the prism rows was 0.76%.
[0097]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0098]
Example 5
As shown in Table 1, the angle (α) between the first prism surface forming the prism array and the normal line is 29.0 degrees, and the second prism surface forming the prism array is shifted from the prism top to the prism array. From the height of the prism array of 16.0 μm to the bottom of the prism from the side close to the top of the prism from the side close to the top of the prism to the height of 16.0 μm. Eight planes (7 areas, 56.5 degrees, 57.4 degrees, 58.2 degrees, 59.0 degrees, 59.6, and 60.3 degrees) having the same width and eight planes (area 1 from the prism top side) , 2,..., 8), except that the prism sheet was manufactured in the same manner as in Example 1. The ratio (d / P) of the maximum distance (d) between the second prism surface of the prism sheet and the virtual plane to the pitch (P) of the prism rows was 0.73%.
[0099]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution in a plane perpendicular to both the light incident surface and the light emission surface of this surface light source device is obtained, and the peak luminance ratio, peak angle, and 1/2 of the peak luminance based on Comparative Example 1 are determined. Angle (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0100]
Example 6
As shown in Table 1, the prism row of Example 5 was formed of a curved surface passing through the boundary of seven areas from the height of 16.0 μm to the bottom of the prism (the inclination angle of each area from the side near the top of the prism was 55). Except for the case of 0.4 degrees, 56.2 degrees, 57.1 degrees, 57.9 degrees, 58.7 degrees, 59.3 degrees, and 60.0 degrees), a prism sheet was produced in the same manner as in Example 1. The ratio (d / P) of the maximum distance (d) of the second prism surface of the prism sheet to the virtual plane to the pitch (P) of the prism rows was 0.0.68%.
[0101]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution in a plane perpendicular to both the light incident surface and the light emission surface of this surface light source device is obtained, and the peak luminance ratio, peak angle, and 1/2 of the peak luminance based on Comparative Example 1 are determined. Angle (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0102]
Example 7
As shown in Table 1, the first prism surface forming the prism array is a plane having an angle (α) of 15.0 degrees with respect to the normal, and the second prism surface is the height of the prism array from the top of the prism. A plane having an inclination angle of 52.0 degrees (β = 38 degrees) up to 10.4 μm, and an inclination angle of 52.6 degrees from the side close to the prism top from the height of the prism row 10.4 μm to the bottom of the prism. 10 planes of the same width of 8, 53.7, 54.5, 55.3, 56.1, 56.8, 57.5, 58.4, and 60.0 degrees A prism sheet was produced in the same manner as in Example 1 except that the plane was composed of 11 planes (areas 1, 2,...,... 11 from the top of the prism). The ratio (d / P) of the maximum distance (d) of the second prism surface of the prism sheet to the virtual plane to the pitch (P) of the prism rows was 1.48%.
[0103]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution in a plane perpendicular to both the light incident surface and the light emission surface of this surface light source device is obtained, and the peak luminance ratio, peak angle, and 1/2 of the peak luminance based on Comparative Example 1 are determined. Angle (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0104]
Example 8
As shown in Table 1, the angle (α) between the first prism surface forming the prism array and the normal is 10.0 degrees, and the height of the second prism surface is 11.5 μm from the top of the prism. Up to a plane having a tilt angle of 52.0 degrees (β = 38.0 degrees), and from the height of the prism array of 11.5 μm to the bottom of the prism, the tilt angles are 52.6 degrees and 52.8 from the side close to the top of the prism. 9 planes of the same width of 53.7 degrees, 53.7 degrees, 54.5 degrees, 55.3 degrees, 56.1 degrees, 56.8 degrees, 57.5 degrees, 58.4 degrees, and a plane of 60 degrees A prism sheet was produced in the same manner as in Example 1 except that the plane was composed of 11 planes (areas 1, 2,...,... 11 from the top of the prism). The ratio (d / P) of the maximum distance (d) of the second prism surface of the prism sheet to the virtual plane to the pitch (P) of the prism rows was 1.64%.
[0105]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution in a plane perpendicular to both the light incident surface and the light emission surface of this surface light source device is obtained, and the peak luminance ratio, peak angle, and 1/2 of the peak luminance based on Comparative Example 1 are determined. Angle (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0106]
Example 9
As shown in Table 1, the angle (α) between the first prism surface forming the prism array and the normal line is 5 degrees, and the second prism surface extends from the prism top to the prism array height of 12.9 μm. A plane having an inclination angle of 52.0 degrees (β = 38 degrees), the inclination angles from the prism row height of 12.9 μm to the bottom of the prism from the side near the top of the prism are 52.6 degrees, 52.8 degrees, and 53. 9 planes of the same width of 7 degrees, 54.5 degrees, 55.3 degrees, 56.1 degrees, 56.8 degrees, 57.5 degrees, 58.4 degrees, and 11 planes that are planes of 60 degrees A prism sheet was produced in the same manner as in Example 1 except that the prism sheet was composed of (areas 1, 2,...,... 11 from the top of the prism). The ratio (d / P) of the maximum distance (d) of the second prism surface of the prism sheet to the virtual plane to the pitch (P) of the prism rows was 1.83%.
[0107]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution in a plane perpendicular to both the light incident surface and the light emission surface of this surface light source device is obtained, and the peak luminance ratio, peak angle, and 1/2 of the peak luminance based on Comparative Example 1 are determined. Angle (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0108]
Example 10
As shown in Table 1, the angle (α) between the first prism surface forming the prism array and the normal line is 0.1 degree, and the height of the prism array is 14.5 μm from the top of the second prism surface. Up to a plane having a tilt angle of 52.0 degrees (β = 38 degrees), from the height of the prism row of 14.5 μm to the bottom of the prism, the tilt angles are 52.6 degrees, 52.8 degrees from the side near the top of the prism, 9 planes of the same width of 53.7 degrees, 54.5 degrees, 55.3 degrees, 56.1 degrees, 56.8 degrees, 57.5 degrees, 58.4 degrees, and a plane of 60 degrees 11 A prism sheet was produced in the same manner as in Example 1 except that the prism sheet was constituted by the flat surface (areas 1, 2,...,... 11 from the top of the prism). The ratio (d / P) of the maximum distance (d) of the second prism surface of the prism sheet to the virtual plane to the pitch (P) of the prism rows was 2.06%.
[0109]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution in a plane perpendicular to both the light incident surface and the light emission surface of this surface light source device is obtained, and the peak luminance ratio, peak angle, and 1/2 of the peak luminance based on Comparative Example 1 are determined. Angle (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0110]
Comparative Example 1
Example 1 was the same as Example 1 except that the prism row of the prism sheet was an isosceles triangle in cross section (α = β = 32.7 degrees) in which the two prism surfaces were both flat and the prism apex angle was 65.4 degrees. Similarly, a surface light source device was obtained. The emission light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emission surface of this surface light source device is obtained, the peak luminance is set to 1.00, the peak angle, and 1/2 of the peak luminance. Angle (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Was measured, and the results are shown in Table 2.
[0111]
[Table 1]

[Table 2]

Examples 11 to 22
Same as Example 1 except that the second prism surface constituting the prism array was constituted by three planes (areas 1, 2, and 3 from the prism top side) of the inclination angle and the division height shown in Table 2. To produce a prism sheet. The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 3.
[0112]
Comparative Example 2
A prism was formed in the same manner as in Example 1 except that the entire second prism surface forming the prism array was formed as a spherically convex surface (inclination angle = 57.3 degrees, β = 36.3 degrees) with a radius of curvature of 452 μm. A sheet was prepared. The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 3.
[0113]
[Table 3]

Examples 23 to 34
A light guide having a mat on one side was prepared by injection molding using an acrylic resin (Acrypet VH5 # 000 manufactured by Mitsubishi Rayon Co., Ltd.). The light guide had a wedge plate shape of 230 mm × 310 mm and a thickness of 3.5 mm-1.2 mm. On the mirror side of the light guide, a prism row having a prism apex angle of 100 ° and a pitch of 50 μm is formed by an acrylic ultraviolet curing resin so as to be parallel to a side (short side) of 230 mm in length of the light guide. Prism layers were formed in a substantially parallel arrangement. A cold-cathode tube is illuminated with a light source reflector (silver reflective film manufactured by Reiko Co., Ltd.) along one side end surface (end surface on the 3.5 mm side) corresponding to a side (long side) of 310 mm in length of the light guide. Covered and arranged. Further, a light diffusion reflection film (E60 manufactured by Toray Industries, Inc.) was attached to the other side end surface, and a reflection sheet was arranged on the prism array (back surface). The above configuration was incorporated in a frame. In this light guide, the maximum peak angle of the emitted light luminous intensity distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface is 70 degrees with respect to the normal direction of the light emitting surface, and the full width at half maximum Was 33 degrees.
[0114]
On the other hand, Example 1 was repeated except that the second prism surface constituting the prism array was constituted by three planes (areas 1, 2, and 3 from the prism top side) having the inclination angle and the division height shown in Table 3. In the same manner as in the above, a prism sheet was produced.
[0115]
The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emission surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak with reference to Comparative Example 4 are obtained. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Were measured, and the results are shown in Table 4.
[0116]
Comparative Example 3
A surface light source device was obtained in the same manner as in Examples 23 to 34 except that the prism sheet of Comparative Example 2 was used. The emission light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emission surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak with reference to Comparative Example 4 are obtained. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Were measured, and the results are shown in Table 4.
[0117]
Comparative Example 4
A surface light source device was obtained in the same manner as in Examples 23 to 34, except that the prism sheet of Comparative Example 1 was used. The emission light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emission surface of the surface light source device is obtained, and this peak luminance is set to 1.00, and the peak angle and 1 / (peak luminance) are obtained. 2 (full width at half maximum) and the absolute value of the difference between the angles having half the peak luminance (| Δθ_a−Δθ_b|) Were measured, and the results are shown in Table 4.
[0118]
[Table 4]

Examples 35 to 39
The angle (α) formed between one prism surface (first prism surface) and the normal line of the prism array, and the angle (β) formed between the other prism surface (second prism surface) and the normal line are shown. 4 in the same manner as in Example 1 except that the second prism surface was constituted by two planes (areas 1 and 2 from the prism top side) of the inclination angle and the division height shown in Table 4 To produce a prism sheet. The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 5.
[0119]
Comparative Example 5
A prism sheet was manufactured in the same manner as in Example 1, except that the entire second prism surface forming the prism array was a plane having an inclination angle of 55.0 degrees (β = 35.0 degrees). The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The emission light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emission surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak with reference to Comparative Example 5 are obtained. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 5.
[0120]
[Table 5]

Examples 40 to 44
The angle (α) formed between one prism surface (first prism surface) and the normal line of the prism array, and the angle (β) formed between the other prism surface (second prism surface) and the normal line are shown. Examples 23 to 34 were the same as those of Examples 23 to 34 except that the angle was set to the angle shown in FIG. 5, and the second prism surface was constituted by two planes (areas 1 and 2 from the prism top side) of the inclination angle and the division height shown in Table 5. Similarly, a prism sheet was produced. The prism sheet thus obtained is arranged such that the prism row forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incidence surface of the light guide, and the first prism surface faces the light source side. And a surface light source device was obtained. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 6 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 6.
[0121]
Comparative Example 6
A prism sheet was manufactured in the same manner as in Example 1, except that the entire second prism surface forming the prism array was a plane having an inclination angle of 55.0 degrees (β = 35.0 degrees). In the obtained prism sheet, the prism row forming surface faces the light emitting surface side of the light guide of Examples 23 to 34, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source. The surface light source device was obtained so as to be placed on the side. The outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light emitting surface of the surface light source device is obtained, and the peak luminance ratio, the peak angle, and the peak based on Comparative Example 1 are determined. The absolute value (| Δθ) of the difference between the angle having half of the luminance (full width at half maximum) and the angle having half of the peak luminance_a−Δθ_b|) Was measured, and the results are shown in Table 6.
[0122]
[Table 6]

Example 45
In the surface light source device of the first embodiment, one surface is a mat surface having an average inclination angle of 7.27 degrees, and the other surface is a mat surface having an average inclination angle of 0.7 degrees. )), A light diffusing element having a full width at half maximum of 9.4 degrees is mounted on the light exit surface of the light deflecting element such that a mat surface having an average inclination angle of 7.27 degrees faces the light polarizing element side. Got. Table 7 shows the peak luminance ratio, the full width at half maximum of the luminance, and the evaluation results of the quality visually confirmed based on Comparative Example 5 in the emission light luminance distribution (in the XZ plane) of the manufactured surface light source device.
[0123]
Example 46
One surface is a mat surface having an average inclination angle of 5.0 degrees, the other surface is a mat surface having an average inclination angle of 0.7 degrees, and the full width at half maximum of the luminous intensity distribution (in the XZ plane) is 6 degrees. A surface light source device was prepared in the same manner as in Example 1 except that the light diffusing element was mounted on the light emitting surface of the light deflecting element such that the mat surface having an average inclination angle of 5.0 degrees was directed to the light polarizing element side. Obtained. Table 7 shows the peak luminance ratio, the full width at half maximum of the luminance, and the evaluation results of the quality visually confirmed based on Comparative Example 5 in the emission light luminance distribution (in the XZ plane) of the manufactured surface light source device.
[0124]
Example 47
A large number of lenticular lens rows having a pitch of 30 μm are arranged substantially in parallel on one surface of a polyester film having a thickness of 125 μm, and the surface of the lenticular lens row is roughened to an average tilt angle of 1 degree. The output light intensity distribution (XZ) having a lens array structure having a maximum inclination angle / minimum inclination angle of 10.4 and a mat surface having an average inclination angle of 0.7 degree is formed on the other surface. A light diffusing element having an in-plane full width at half maximum of 11.2 degrees was placed so that the lenticular lens array was parallel to the prism array of the light deflecting element and the lens array structure surface was directed to the light polarizing element side. A surface light source device was obtained in the same manner as in Example 1. Table 7 shows the peak luminance ratio, the full width at half maximum of the luminance, and the evaluation results of the quality visually confirmed based on Comparative Example 5 in the emission light luminance distribution (in the XZ plane) of the manufactured surface light source device.
[0125]
Example 48
A luminous intensity distribution (XZ) in which a hairline having a maximum average inclination angle of 8.2 degrees is formed on one surface of a polyester film having a thickness of 125 μm and a mat surface having an average inclination angle of 0.7 degrees is formed on the other surface. Except that the light diffusing element whose full width at half maximum (in-plane) is 10.5 degrees is mounted such that the hairline direction is substantially parallel to the prism array of the light deflecting element and the hairline forming surface faces the light deflecting element side. In the same manner as in Example 1, a surface light source device was obtained. Table 7 shows the peak luminance ratio, the full width at half maximum of the luminance, and the evaluation results of the quality visually confirmed based on Comparative Example 5 in the emission light luminance distribution (in the XZ plane) of the manufactured surface light source device.
[0126]
Example 49
The maximum average tilt angle in which a number of cylindrical lenses having a width of 30 μm and a length of 60 μm formed by etching on one surface of a polyester film having a thickness of 125 μm and discretely arranged in the same direction is 6.0 degrees, and the maximum tilt angle is 6.0 degrees. / A lens array structure having a minimum inclination angle of 6.0 is formed, and a matte surface having an average inclination angle of 0.7 ° is formed on the other surface. Example 1 except that the 0.0 ° light diffusing element was mounted so that the arrangement direction of the cylindrical lenses and the prism array of the light deflecting element were substantially parallel, and the lens arrangement structure surface was directed to the light deflecting element side. Similarly, a surface light source device was obtained. Table 7 shows the peak luminance ratio, the full width at half maximum of the luminance, and the evaluation results of the quality visually confirmed based on Comparative Example 5 in the emission light luminance distribution (in the XZ plane) of the manufactured surface light source device.
[0127]
[Table 7]

[0128]
【The invention's effect】
As described above, according to the present invention, the primary light source is provided by forming at least one prism surface of the prism array formed on the light incident surface of the light deflection element from a plurality of planes or convex surfaces having different inclination angles. A light source device with high efficiency (light use efficiency of the primary light source) for concentrating and emitting light emitted from the light source in a required observation direction can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a light source device according to the present invention.
FIG. 2 is an explanatory diagram of a shape of a prism array on a light incident surface of the light deflecting element of the present invention.
FIG. 3 is an explanatory view showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 4 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 5 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 6 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 7 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 8 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 9 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 10 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 11 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of a second prism surface (plane) of the light deflecting element.
FIG. 12 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from each area of the second prism surface (plane) of the light deflecting element.
FIG. 13 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from the entire second prism surface (plane) of the light deflecting element.
FIG. 14 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from the entire second prism surface of the light deflecting element of the present invention.
FIG. 15 is an explanatory diagram of the shape of a prism array on the light incident surface of the light deflecting element of the present invention.
FIG. 16 is an explanatory diagram of the shape of a prism array on the light incident surface of the light deflecting element of the present invention.
FIG. 17 is an explanatory diagram of the shape of a prism array on the light incident surface of the light deflecting element of the present invention.
FIG. 18 is an explanatory diagram of a shape of a prism array on a light incident surface of the light deflecting element of the present invention.
FIG. 19 is an explanatory diagram showing a luminance distribution (in the XZ plane) of various emitted lights from the light deflection element.
FIG. 20 is an explanatory diagram of the shape of a prism array on the light incident surface of the light deflecting element of the present invention.
FIG. 21 is an explanatory diagram of the full width at half maximum of the luminous intensity distribution (in the XZ plane) of the emitted light.
FIG. 22 is an explanatory diagram of a developed length of the light source device.
FIG. 23 is an explanatory diagram of a developed length of the light source device.
FIG. 24 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from the light deflection element of the light source device of the present invention.
FIG. 25 is a graph showing a luminance distribution (in the XZ plane) of light emitted from the light deflection element of the light source device of the present invention.
FIG. 26 is an explanatory diagram showing an outgoing light luminous intensity distribution (in the XZ plane) of the anisotropic diffusive property of the light diffusing element of the present invention.
FIG. 27 is an explanatory diagram of anisotropic diffusivity of the light deflecting element of the present invention.
FIG. 28 is a schematic view showing a concavo-convex structure of a light deflecting element having anisotropic diffusion according to the present invention.
FIG. 29 is a schematic view showing a concavo-convex structure of the optical deflecting element having anisotropic diffusion properties of the present invention.
FIG. 30 is a schematic view showing a concavo-convex structure of a light deflecting element having anisotropic diffusion properties of the present invention.
[Explanation of symbols]
1 Primary light source
2 Light source reflector
3 Light guide
4 Light deflection element
5 Light reflection element
6 Light diffusion element
31 ° light incident surface
32 end face
33 ° light exit surface
34 back
41 Light incident surface
42 ° light emitting surface

Claims (17)

It has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has a prism array composed of two prism surfaces substantially parallel to each other. A plurality of prisms are arranged, and at least one prism surface of the prism array is formed of at least two planes having different inclination angles, and a plane located closer to the light exit surface has a larger inclination angle, and a plane closest to the light exit surface The difference between the inclination angle and the inclination angle of the plane farthest from the light exit surface is 15 degrees or less. It has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has a prism array composed of two prism surfaces substantially parallel to each other. An optical deflecting element comprising a plurality of arrays, wherein at least one prism surface of the prism array is formed of at least three planes having different inclination angles, and the plane located closer to the light exit surface has a larger inclination angle. It has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has a prism array composed of two prism surfaces substantially parallel to each other. A plurality of arrays, wherein at least one prism surface of the prism row is formed of at least two convex curved surfaces having different inclination angles, and the convex surface located closer to the light exit surface has a larger inclination angle. element. It has a light incident surface on which light is incident and a light exit surface which is located on the opposite side and emits incident light, and the light incident surface has a prism array composed of two prism surfaces substantially parallel to each other. A plurality of prisms are arranged, and at least one of the prism surfaces of the prism row includes at least two planes having different inclination angles and at least one convex curved surface, and the plane or convex curved surface located closer to the light exit surface has a larger inclination angle. A light deflecting element characterized by the above-mentioned. The difference between the inclination angle of a plane or a convex curved surface closest to the light exit surface and the inclination angle of a plane or a convex curved surface farthest from the light exit surface is 15 degrees or less. Light deflection element. The light deflecting element according to claim 3, wherein the shapes of the convex curved surfaces are different from each other. The optical deflection element according to claim 3, wherein a ratio (r / P) of a radius of curvature (r) of the convex curved surface to a pitch (P) of the prism rows is 2 to 50. 8. The light deflecting element according to claim 3, wherein at least one of the convex curved surfaces has an aspherical shape. At least two flat surfaces and / or convex curved surfaces are formed in a region having a height h from the top of the prism, and h / H is 60% or less when the height of the prism row is H. Item 9. The light deflection element according to any one of Items 1 to 8. The ratio (d / P) of the maximum distance (d) between the plane and / or the convex curved surface, the virtual plane connecting the top of the prism and the lower part of the prism to the pitch (P) of the prism rows is 0.4 to 5%. The light deflecting element according to claim 1, wherein: The light deflecting element according to any one of claims 1 to 10, wherein the distribution angle α of one of the apex angles of the prism array is 40 degrees or less, and the other distribution angle β is 25 to 50 degrees. . The optical deflection device according to claim 1, wherein an absolute value (| α−β |) of a difference between the distribution angles α and β of the two prism surfaces is 0.5 to 10 degrees. element. The light deflection element according to claim 1, wherein one of the distribution angles α constituting the prism array is equal to or less than 20 degrees. 14. The light deflecting element according to claim 1, wherein one of the prism surfaces forming the prism array is formed of the flat surface and / or the convex curved surface, and the other prism surface is substantially flat. . A primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident, and a light exit surface for guiding and exiting the incident light, and disposed adjacent to the light exit surface side of the light guide A light source device comprising the light deflection element according to claim 1. 16. The light source according to claim 15, wherein a light diffusing element having a full width at half maximum of 1 to 13 degrees of a luminous intensity distribution of emitted light when parallel light is incident is arranged adjacently on a light emitting surface of the light deflecting element. apparatus. 17. The light source device according to claim 15, wherein a light diffusing element having a haze value of 8 to 82% is arranged adjacent to the light exit surface of the light deflecting element.

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