JP4323189B2 - Optical deflection element and surface light source device - 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 &le;15&deg;. <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（Ｉ₀ ）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]
BACKGROUND OF THE INVENTION
The present invention relates to an edge-light-type light source device and a light deflecting element used therefor that constitute a liquid crystal display device used as a display unit in a notebook computer, a liquid crystal television, a mobile phone, a portable information terminal, etc. In particular, the present invention relates to an improvement of a light deflection element disposed on the light exit surface side of a light guide.
[0002]
[Prior art]
In recent years, color liquid crystal display devices have been widely used in various fields as monitors for portable notebook personal computers, personal computers, etc., or as display units for liquid crystal televisions, video integrated liquid crystal televisions, mobile phones, personal digital assistants, and the like. Yes. In addition, with the increase in the amount of information processing, diversification of needs, compatibility with multimedia, and the like, liquid crystal display devices have been increased in screen size and definition.
[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 with a light source arranged directly under the liquid crystal display element unit and an edge light type with a light source arranged so as to face the side end face of the light guide. The edge light method is frequently used from the viewpoint of realizing the same.
[0004]
By the way, in recent years, in a display device having a relatively small screen size and a relatively narrow viewing direction range, for example, a liquid crystal display device used as a display unit of a mobile phone, the edge light system is used from the viewpoint of reducing power consumption. In order to effectively use the amount of light emitted from the primary light source, a backlight unit has been used that emits light by concentrating it in a required angle range by making the spread angle of the light beam emitted from the screen as small as possible. Yes.
[0005]
In this way, the present application is a display device in which the viewing direction range is limited, and is a light source device that emits light concentrated 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 Laid-Open Patent Publication No. 2001-143515 (Patent Document 1), a person proposes to use a prism sheet having prism forming surfaces on both sides adjacent to the light emitting surface of the light guide. In this double-sided prism sheet, a plurality of prism rows parallel to each other are formed on the light incident surface that is one surface and the light exit surface that is the other surface, and the prism row direction is formed by the light incident surface and the light exit surface. And the prism rows are arranged at corresponding positions. Thus, the light emitted from the light exit surface of the light guide having a peak of the emitted light in a direction inclined with respect to the light exit surface and distributed in an appropriate angle range is transmitted to one of the light incident surfaces of the prism sheet. The light is incident from the prism surface, is internally reflected by the other prism surface, and is further refracted by the prism on the light exit surface, so that the 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, but a plurality of prism rows parallel to each other as a prism sheet used as a light deflecting element are arranged on a light incident surface and a light output surface. Therefore, it is necessary to match the prism row directions and to arrange the prism rows at corresponding positions, which complicates the molding.
[0008]
Therefore, an object of the present invention is to control the distribution of the emitted light so as to be very narrow and to improve the utilization efficiency of the light quantity of the primary light source (that is, to concentrate the light emitted from the primary light source in the required observation direction). It is an object of the present invention to provide a light deflection element and a light source device that can easily improve image quality with a simplified configuration.
[0009]
[Means for Solving the Problems]
That is, the light deflection element of the present invention has a light incident surface on which light is incident and a light exit surface that is located on the opposite side and that emits incident light, and the light incident surface includes 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 row is composed of at least two planes having different inclination angles, and the inclination angle is closer to a plane located 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]
The light deflecting element of the present invention has a light incident surface on which light is incident and a light exit surface that is located on the opposite side and emits incident light. The light incident surface includes two prism surfaces. A plurality of prism rows are arranged in substantially parallel to each other, and at least one prism surface of the prism row is composed of at least three planes having different inclination angles, and the inclination angle is closer to a plane closer to the light exit surface. It is characterized by being large.
[0011]
The light deflecting element of the present invention has a light incident surface on which light is incident and a light exit surface that is located on the opposite side and emits incident light. The light incident surface includes 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 on the side closer to the light exit surface has a slope thereof. It is characterized by a large angle.
[0012]
The light deflecting element of the present invention has a light incident surface on which light is incident and a light exit surface that is located on the opposite side and emits incident light. The light incident surface includes two prism surfaces. A plurality of prism rows are arranged in substantially parallel to each other, and at least one prism surface of the prism row is composed of at least two planes having different inclination angles and at least one convex curved surface, and is closer to the light exit surface. A flat or convex curved surface is characterized by a larger inclination angle.
[0013]
Furthermore, the light source device of the present invention includes a primary light source, a light incident surface on which light emitted from the primary light source is incident, a light emitting surface that guides and emits incident light, and the light guide. It comprises the above-mentioned light deflection element arranged adjacent to the light exit surface side of the body.
[0014]
DETAILED DESCRIPTION OF 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 a 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 a light exit surface 33 as one surface substantially orthogonal thereto. The primary light source 1 disposed opposite to the light incident surface 31 of the light guide 3 and covered with the light source reflector 2, the light deflection element 4 disposed on the light emitting surface of the light guide 3, and the light guide The light reflecting element 5 is disposed to face the back surface 34 of the light emitting surface 33 of the body 3.
[0015]
The light guide 3 is arranged in parallel with the XY plane and has a rectangular plate shape as a whole. The light guide 3 has four side end surfaces, and at least one of the pair of side end surfaces parallel to the YZ plane is a light incident surface 31. The light incident surface 31 is arranged 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 principal surfaces substantially orthogonal to the light incident surface 31 of the light guide 3 are respectively positioned substantially parallel to the XY plane, and one of the surfaces (upper surface in the drawing) serves as the light emitting surface 33. At least one of the light emitting surface 33 and the back surface 34 thereof is a directional light emitting function portion having a rough surface, and a large number of lens rows such as a prism row, a lenticular lens row, and a V-shaped groove. By providing a directional light emitting function unit composed of a lens surface substantially parallel to 31, the light incident from the light emitting surface 33 is guided while the light incident from the light incident surface 31 is guided through the light guide 3. Light having directivity is emitted in the emitted light intensity distribution in the surface (XZ plane) orthogonal to the surface 31 and the light emitting surface 33. If the angle between the peak direction of the emitted light luminous intensity distribution in the XZ plane and the light emitting surface 33 is a, this angle a is preferably 10 to 40 degrees, and the full width at half maximum of the emitted light luminous intensity distribution is 10 to 40 degrees. 40 degrees is preferable.
[0017]
The rough surface and the lens array formed on the surface of the light guide 3 have a luminance within the light emitting surface 33 that the average inclination angle θa according to ISO 4287 / 1-1984 is in the range of 0.5 to 15 degrees. It is preferable from the point of aiming at the degree of 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. The average inclination angle θa is preferably set in an optimum range by a ratio (L / t) between 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 a L / t of about 20 to 200 is used, the average inclination angle θa is preferably 0.5 to 7.5 degrees, more preferably 1 to 5 degrees. It is a range, More preferably, it is the range of 1.5-4 degree | times. When the light guide 3 having L / t of about 20 or less is used, the average inclination angle θa is preferably 7 to 12 degrees, and more preferably 8 to 11 degrees.
[0018]
The average inclination angle θa of the rough surface formed on the light guide 3 is obtained in accordance with ISO 4287 / 1-1984 by measuring the rough surface shape using a stylus type surface roughness meter and setting the coordinate in the measurement direction as x. From the obtained gradient function f (x), the following equation (1) and equation (2) can be used. Here, L is the measurement length, and Δa is the tangent of the average inclination angle θa.
[0019]
[Expression 1]

Further, the light guide 3 preferably has a light emission rate in the range of 0.5 to 5%, and more preferably in the range of 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 of light is emitted near the light source 1. This is because the light in the X direction in the light emitting surface 33 is remarkably attenuated, and the luminance uniformity on the light emitting surface 33 tends to decrease. Thus, 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 emission light intensity distribution (in the XZ plane) of the light emitted from the light emission surface is increased. Light having a high directivity and having a directivity that is in the range of 50 to 90 degrees with respect to the normal of the light emitting surface and the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) is 10 to 40 degrees 3, and the direction of emission can be efficiently deflected by the light deflection 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. The light intensity (I) of the emitted light at the edge of the light emitting surface 33 on the light incident surface 31 side.₀ ) And the outgoing light intensity (I) at the position of the distance L from the edge on the light incident surface 31 side, the thickness of the light guide 3 (dimension in the Z direction) is t (3) Satisfies the relationship of the formula.
[0021]
[Expression 2]

Here, the constant A is the light output rate, and the light guide 3 per unit length (a length corresponding to the light guide thickness t) in the X direction orthogonal to the light incident surface 31 on the light output surface 33. It is the ratio (%) at which light is emitted from. The light emission rate A can be obtained from the gradient by plotting the logarithm of the light intensity of light emitted from the light emission surface 23 on the vertical axis and (L / t) on the horizontal axis.
[0022]
Moreover, in order to control the directivity in the surface (YZ surface) parallel to the light source 1 of the emitted light from the light guide 3, the other main surface to which the directional light emitting function unit is not provided is light. It is preferable to form a lens surface in which a large number of lens rows extending in a direction substantially perpendicular to the incident surface 31 (X direction) are arranged. In the embodiment shown in FIG. 1, a lens surface formed by an array of a large number of lens rows, in which a rough surface is formed on the light emitting surface 33 and the back surface 34 extends in a direction substantially perpendicular to the light incident surface 31 (X direction). Is forming. In the present invention, conversely 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 a rough surface.
[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, a lenticular lens array, and a V-shaped groove extending substantially in the X direction. However, it is preferable that the YZ-direction cross-sectional shape be a substantially triangular prism array.
[0024]
In the present invention, when a prism row is formed as a lens row formed on the light guide 3, the apex angle is preferably in the range of 70 to 150 degrees. This is because by setting the apex angle within this range, the emitted light from the light guide 3 can be sufficiently collected, and the luminance as a surface light source element can be sufficiently improved. That is, by setting the prism apex angle within this range, the full width at half maximum of the emitted light luminous intensity distribution is 35 to 65 degrees on the plane perpendicular to the XZ plane including the peak light in the emitted light luminous intensity distribution (in the XZ plane). The emitted outgoing light can be emitted, and the luminance as a surface light source element can be improved. When the prism row is formed on the light emitting surface 33, the apex angle is preferably in the range of 80 to 100 degrees. When the prism row is formed on the back surface 34, the apex angle is 70 to 80 degrees. Or it is preferable to set it as the range of 100-150 degree | times.
[0025]
In the present invention, light diffusing fine particles are mixed and dispersed in the light guide instead of or in combination with the light emitting surface 33 or the back surface 34 as described above. What provided the directional light emission function may be used. In addition, the light guide 3 is not limited to the cross-sectional shape as shown in FIG. 1, and can 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 row of the light deflection element 4. The light deflection element 4 has one of the main surfaces as a light incident surface 41 and the other surface as a light emission surface 42. A large number of prism rows are arranged in parallel on the light incident surface 41, and each prism row has two prisms, a first prism surface 44 located on the light source side and a second prism surface 45 located on the side far from the light source. It is composed of surfaces. In the embodiment shown in FIG. 2, the first prism surface 44 is a flat surface, the second prism surface 45 is composed of three flat surfaces 46 to 48 having different inclination angles, and the inclination angle is closer to the plane closer to the light exit surface. Is getting bigger. Further, among the planes 46 to 48, the difference in inclination angle between the plane 48 closest to the light exit surface and the plane 46 farthest from the light exit surface is 15 degrees or less. In the present invention, the plane inclination angle refers to the inclination angle of each plane with respect to the prism array forming plane 43.
[0027]
In the light deflection element 4 of the present invention, the second prism surface 45 is composed of at least two planes having different inclination angles, and the inclination angles of these planes become larger as they are closer to the light emission surface, and the plane closest to the light emission surface is the most. By setting the difference in inclination angle with respect to a plane far from the light exit surface to 15 degrees or less, an extremely high light condensing effect can be exhibited, and extremely high luminance can be obtained as a light source device. The difference in inclination angle between the plane closest to the light exit surface and the plane farthest from the light exit 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 in the inclination angles is preferably within the above range, but is not particularly limited to this range. Further, by making the second prism surface 45 in such a structure, it is possible to easily design a deflecting element having a desired light condensing property, and to stabilize an optical deflecting element having a certain optical characteristic stably. 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, the peak angle of the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide by the conventional light deflection element in which the two prism surfaces are both flat and the prism apex angle is 65.4 degrees. What kind of outgoing 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 exit surface of the light guide, which is 20 degrees? 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 evenly divided into 10 areas in the x direction. FIG. 6 shows the luminance distribution (in the XZ plane) of the emitted light from each area. The ten areas are Part1, Part2,..., Part10 in order from the side closest to the top of the prism. In the emitted light luminance distribution (in the XZ plane) of the entire light that is totally reflected and emitted by the second prism surface, as shown in FIG. 13, the peak light is emitted in the normal direction, and the half value of 22 degrees. Full width.
[0029]
However, when these are seen in the emitted 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 (the negative angle value is 0 degrees in the normal direction) In the case of tilting in the direction of the light source, the peak light is emitted in the vicinity, the peak light is shifted in the direction of 0 degrees (normal direction) in Part 3 to Part 7, and the peak light is sequentially positive in Part 8 to Part 10. You can see that it is shifting in the direction. The peak angle at which light is totally reflected and emitted in the area closest to the light exit surface 42 (Part 10) is 7 degrees, and the peak angle of the second prism surface (between Part 1 to Part 10) is 16 degrees. In addition, the intensity of the peak light from each area gradually decreases from Part 1 to Part 10.
[0030]
Thus, it can be seen that the light that is totally reflected and emitted by the prism surface composed of one plane is dispersed in a considerably wide range depending on the total reflection area of the prism surface. By adjusting the inclination angle of the prism surface of each area, the peak light in each area is emitted in substantially the same direction, with the peak light in the emitted light luminance distribution (in the XZ plane) from each area, 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 made larger in the order of Part 1 to Part 10, that is, the prism surface in the area closer to the light exit surface 42. In this way, by adjusting the inclination angle of the prism surface in each area as shown in FIG. 14, the outgoing light totally reflected by the entire prism surface can be condensed in a certain direction, and more directivity can be achieved. Can emit light having a high peak intensity.
[0031]
Each area obtained by dividing the prism surface may be set by setting at least two areas. However, if the number of areas (the number of planes having different inclination angles) is too small, the light condensing performance by the light deflecting element is reduced. Since there exists a tendency for a brightness improvement effect to be impaired, it is preferable to set it as 3 or more, More preferably, it is 5 or more, More preferably, it is 6 or more. When the number of areas is two, the difference between the inclination angles of the two planes needs to be 15 degrees or less in order to suppress the deterioration of the light condensing characteristics to some extent. It is in the range of 5 to 10 degrees, more preferably in the range of 1 to 7 degrees. Even in the case where 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 exit surface and the inclination angle of the plane farthest from the light exit surface is 15 degrees or less, More preferably, it is in the range of 0.5 to 10 degrees, more preferably 1 to 7 degrees.
[0032]
On the other hand, if the number of areas is increased, the peak angle can be finely adjusted over the entire surface of the prism surface, so that the concentration level as a whole can be increased. However, planes with 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 deflection element is complicated, and it is difficult to stably obtain a light deflection element having a certain optical characteristic. For this reason, the number of areas formed on the prism surface is preferably 20 or less, and more preferably 12 or less. Although it is preferable to divide the prism surface equally, it is not always necessary to divide the prism surface equally, and the prism surface can be adjusted in accordance with the desired emission light intensity distribution (in the XZ plane) of the entire prism surface. Further, the width of each plane having different inclination angles (the length of each plane portion in the prism array section) is preferably in the range of 4 to 47%, more preferably 6 to 30 with respect to 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, and all the planes may be convex curved surfaces. . In FIG. 15, the second prism surface 45 is divided into four areas, and is composed of 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 composed of 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. In addition, the second prism surface 45 may be formed by a curved surface that passes through the boundary of each area, and in this case, the curved surface is slightly separated from the boundary of each area as long as it does not cause a significant decrease in luminance. It may shift. For example, the deviation of the ratio of the passage position of the curved surface (distance from the top of the prism) to the pitch of the prism row with respect to the ratio of the boundary of the area may be 4% or less, more preferably 2% or less, and even more preferably 1% or less. Range. In the present invention, the inclination angle on the convex curved surface means an average of the inclination angles at all positions of one convex curved surface. Thus, when the prism surface is composed of 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, preferably in the range of 2-8. However, if the number of areas is too small, it is difficult to design each convex curved surface for adjusting the desired emitted light luminance distribution (in the XZ plane), so the number of areas is more preferably in the range of 3-8.
[0034]
Further, the shape of the convex curved surface can be a spherical or aspherical cross-sectional shape in the XZ direction. Further, when the prism surface is constituted by a plurality of convex curved surfaces, the shape of each convex curved surface is preferably different, and a spherical convex surface and an aspherical convex curved surface can be combined, but at least one The convex curved surface is preferably aspherical. When the plurality of convex curved surfaces are spherical, 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]
Furthermore, the convex curved surface preferably has a radius of curvature (r) in the range of 2 to 50 (r / P) with respect to the pitch (P) of the prism row, more preferably 5 to 30, and still more preferably. It is in the range of 7-10. If this r / P is less than 2 or exceeds 50, sufficient light condensing characteristics cannot be exhibited and the luminance tends to decrease.
[0036]
In such planes and convex curved surfaces having different inclination angles, the peak angle in the emitted light luminance distribution (in the XZ plane) when the light totally reflected by each plane and convex curved surface is emitted from the light emitting surface is substantially constant. However, each peak angle does not necessarily have to be a substantially constant angle, and can be designed in a range in which all peak angles are within 15 degrees. Is 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 in the emitted light luminance distribution (in the XZ plane) of the light totally reflected in the areas of Part 1 to Part 5 and emitted from the light emitting surface is , It accounts for 75% or more of the intensity in the outgoing light luminance distribution (in the XZ plane) of the light that is totally reflected by the entire prism surface and emitted from the light exit surface. It is particularly important to collect light in the direction of. For this reason, when the height from the prism top of the prism row is h and the height of the entire prism row is H, at least a plane having a different inclination angle in a region of height h where h / H is 60% or less or Preferably, at least two convex curved surfaces are formed, more preferably three or more. The region of height h is more preferably a region where h / H is 50% or less, and even more preferably a region where 40% or less. Note that if the region of the height h becomes too small, sufficient light condensing characteristics tend not to be obtained, and the manufacture of the mold becomes complicated, so h / H is preferably 20% or more. In this case, the number of areas in the region of height h is preferably in the range of 3-8, more preferably in the range of 3-6, and even more preferably in the range of 3-4.
[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 (FIG. 2, FIG. 2) that connects the top and the bottom of the prism row in order to ensure sufficient light collection characteristics. 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 condensing property tends to be lowered, and sufficient luminance cannot be improved. It is in the range of 3%, more preferably in the range of 0.7 to 2.2%.
[0039]
In the present invention, the apex angle of the prism row is preferably 35 to 80 degrees, more preferably 35 to 70 degrees, and still more preferably 40 to 70 in consideration of light collecting characteristics and light utilization efficiency. It is a range of degrees. Further, the left and right distribution angles (inclination angles with respect to the normal lines of the two prism surfaces) α and β with respect to the normal line of the prism apex angle may be the same or different, but the substantially normal direction (the normal direction is 0 degree). In this case, it is preferable that the angle is set to a different angle in order to efficiently increase the brightness of ± 10 degrees in the XZ plane. In this case, it is preferable that the distribution angle α located on the light source side is 40 degrees or less and β is in the range of 25 to 50 degrees. When the apex distribution angles α and β are slightly different, the light utilization efficiency is increased and the luminance can be further improved. Therefore, the distribution angle α is 25 to 40 degrees and the distribution angle β is 25 to 25 degrees. The absolute value of the difference between the distribution angles α and β (Iα−βI) is preferably 0.5 to 10 degrees, more preferably 1 to 10 degrees, and still more preferably 1 to 8 degrees. It is a range. When the peak light in the emitted light luminance distribution (in the XZ plane) is not substantially in the normal direction, the peak light is provided in a desired direction by adjusting the distribution angles α and β of the prism apex angle. An outgoing light luminance distribution (in the XZ plane) can be obtained.
[0040]
Moreover, the light utilization efficiency can be increased and the luminance can be further improved by setting the distribution angle α to 20 degrees or less. The light utilization efficiency can be increased as the distribution angle α is decreased. However, if the distribution angle α is excessively decreased, the apex angle of the prism row tends to decrease, and it becomes difficult to manufacture the prism sheet. α is preferably in the range of 3 to 15 degrees, more preferably in the range of 5 to 10 degrees. In this case, in order to improve the normal luminance by setting the peak light in the emitted light luminance distribution (in the XZ plane) to a range of ± 2 degrees from the normal direction, the distribution angle β is set to a range of 35 to 40 degrees. That's fine.
[0041]
Thus, when the distribution angle α is set to 20 degrees or less, the ratio of the lengths of the two straight lines connecting the top and the valley 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) The ratio L2 / L1) of the length L2 of the straight line far from the light source is preferably 1.1 times or more. By setting L2 / L1 to 1.1 times or more, light incident from the prism surface near the light source can be efficiently received by the prism surface far from the light source, and the light utilization efficiency can be increased. This is because the luminance can be further improved, more preferably 1.15 times or more, and still more 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, it is 1.2 times or less. For the same reason, the ratio (L2 / P) of the straight line length L2 on the side far from the light source to the pitch P of the prism row is preferably 1.25 times or more, more preferably 1.3 times or more. Yes, more preferably 1.4 times or more. On the other hand, if this L2 / P is too large, the apex angle of the prism row tends to be small and it becomes difficult to manufacture the prism sheet. Therefore, it is preferably 1.8 times or less, more preferably 1.6 times. Hereinafter, it is more preferably 1.5 times or less.
[0042]
Further, as shown in FIGS. 17 and 18, the light deflection element of the present invention forms a convex shape or a plane (light transmission region) having a smaller inclination angle than the prism array between adjacent prism arrays. Also good. By forming such a light transmission 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 disposed on the back surface of the light guide. In addition, by emitting the light again to the liquid crystal panel side, 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, a weak diffusivity is imparted to the reflection sheet, a light diffusion layer is formed on the light exit surface of the light deflection element, It is preferable to place 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 lowered. Therefore, it is necessary to determine the ratio of the light transmission 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 row, and more preferably in the range of 20 to 40%. Examples of the light transmission region include a planar shape 59 as shown in FIG. 17, a curved surface shape 60 and a polygonal shape as shown in FIG. Among these, it is preferable to make the light transmission region polygonal or curved because the reflection of external light can be controlled.
[0043]
In the light deflection element of the present invention, when the light is condensed and emitted, the light intensity distribution emitted from the light guide is strongly reflected. Therefore, the light intensity distribution (XZ plane) from the light emission surface of the light deflection element is reflected. Inner) tends to have an asymmetric distribution in the angle before and after the normal direction. In particular, when the second prism surface 45 is composed of a single curved surface, the emitted light luminance distribution (in the XZ plane) on the light incident surface side of the light guide body is drastically reduced and observed from the normal direction. Asymmetry is strongly visible within the effective viewing angle range. In the present invention, the asymmetry of the emitted light luminance distribution (in the XZ plane) as described above can be reduced by configuring the prism surface from a plurality of flat surfaces or convex curved surfaces having different inclination angles. That is, asymmetry of the emitted light luminance distribution (in the XZ plane) is, as shown in FIG. 19, the peak angle and the luminance of the emitted light luminance distribution (in the XZ plane) emitted from the light deflection element are the luminance of the peak light (peak The absolute value (spreading width) Δθ of the angle difference that is 1/2 of (luminance)_aAnd Δθ_bDifference (| Δθ_a−Δθ_b|). Therefore, this | Δθ_a−Δθ_bThe asymmetry of the emitted light luminance distribution (in the XZ plane) can be relaxed by adjusting the inclination angle of the plane or convex curved surface constituting the prism surface so that | is 9 degrees or less. This | Δθ_a−Δθ_b| Is more preferably 6 degrees or less, and further preferably 4 degrees or less. | Δθ_a−Δθ_bVisibility is almost good when | is 9 degrees or less, and discomfort due to asymmetry is hardly felt when it is 4 degrees or less.
[0044]
Furthermore, in the light deflecting element 4 of the present invention, as shown in FIG. 20, the change in shape of the first prism surface 44 due to warpage or the like that occurs during prism array pattern formation (the top of the prism array). Displacement from the plane connecting the bottom to the bottom) may occur. However, when such a plane displacement is large, the optical characteristics of the light deflection element 4 are affected, and it is preferable to suppress the displacement to a minute amount. 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 in terms of 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, it is the range of 0.005 or less. Such a substantially flat deformation is mainly caused by the influence of polymerization shrinkage or the like when forming the prism row pattern. Therefore, the degree of deformation due to polymerization shrinkage is quantified in advance and the mold is offset so as to cancel it. It is preferable to design the shape of the prism row.
[0045]
In the present invention, it is preferable that the prism surface having the convex-curved surface portion 46 as described above is formed at least on the surface far from the primary light source 1 (second prism surface 45). According to this, the distribution in the emitted light luminance distribution (in the XZ plane) of the light emitted from the light deflection element 4 when the primary light source is also arranged on the end face 32 of the light guide 3 can be sufficiently reduced. For example, when the ratio of the light propagating through the light guide 3 that is reflected by the end face 32 on the side opposite to the light incident surface 31 is relatively high, the prism surface having the convex curved surface portion 46 is light guide 3. When the primary light source 1 is disposed on each of the two opposing end surfaces, it is more preferable that the prism surface (first prism surface 44) on the side close to the primary light source 1 has the same shape. On the other hand, when the ratio of the light propagating through the light guide 3 reflected by the end face 32 on the side opposite to the light incident surface 31 and returning is relatively low, the prism surface near the primary light source 1 is set as a substantially flat surface. Also good. In addition, in the light deflection element 4 of the present invention, it is preferable that either one of the tops of the prism rows is formed of a substantially flat surface. The shape transfer surface shape of the mold member for forming the prism array can be more accurately formed, and the occurrence of sticking phenomenon when the light deflection element 4 is placed on the light guide 3 can be suppressed. .
[0046]
As described above, the light deflection element 4 as described above is placed on the light emitting surface 33 of the light guide 3 so that the prism array forming surface is on the light incident surface side. The emitted light intensity distribution (within the XZ plane) of the directional emitted light emitted from the light emitting surface 33 can be made narrower, and high brightness and a narrow field of view as a light source device can be achieved. The full width at half maximum of the outgoing light luminance distribution (in the XZ plane) of the outgoing light from such a light deflection element 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 the range of 12-18 degree | times. This is because by making the full width at half maximum of this emitted light luminance distribution (in the XZ plane) 5 degrees or more, it is possible to eliminate the difficulty of viewing images and the like due to extremely narrow field of view, and by making it 25 degrees or less, high brightness This is because it is possible to reduce the size and field of view.
[0047]
Since the narrowing of the field of view of the light deflecting element 4 in the present invention is affected by the extent (full width at half maximum) of the emitted light luminous intensity distribution (in the XZ plane) from the light emitting surface 33 of the light guide 3, the light deflecting element The ratio of the emission light intensity distribution (in the XZ plane) of the light emission body 33 of the light guide 3 having the full width at half maximum of the emission light luminance distribution (in the XZ plane) from the light exit surface 42 to the full width at half maximum B is It varies depending on the full width at half maximum B of the luminous intensity distribution (in the XZ plane) from the light body 3. For example, when the full width at half maximum B of the emitted light intensity distribution (in the XZ plane) 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. More preferably, it is 30 to 80% of range, More preferably, it is 30 to 70% of range. Further, when the full width at half maximum B of the emitted light intensity distribution (in the XZ plane) 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, More preferably, it is 30 to 70% of range, More preferably, it is 30 to 60% of range. In particular, when the full width at half maximum B of the emitted light intensity distribution (in the XZ plane) 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, it is 30 to 70% of range, and still more preferably it is 30 to 60% of range. Furthermore, when the full width at half maximum B of the emitted light intensity distribution (in the XZ plane) 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. More preferably, it is 30 to 60% of range, More preferably, it is 30 to 50% of range.
[0048]
In general, when it is attempted to increase the emission efficiency of the light guide plate, it seems that 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 increases and the light collection efficiency decreases. Since the effect of narrowing the field of view becomes large, the light guide having a full width at half maximum B of the outgoing light luminous intensity distribution (in the XZ plane) of 26 degrees or more in terms of the efficiency of narrowing the field of view and the light utilization efficiency as the surface light source device It is preferable to use an optical deflecting element in combination, and more preferably a light guide body having a full width at half maximum B exceeding 36 degrees. Further, when the full width at half maximum of the emitted light luminous intensity distribution from the light guide 3 (in the XZ plane) is small, the effect of narrowing the field of view is reduced, but the emitted light luminous intensity distribution from the light guide 3 (in the XZ plane). As the full width at half maximum is smaller, the brightness can be increased. Therefore, in terms of increasing the brightness, light is combined with a light guide having a full width at half maximum B of the emitted light luminous intensity distribution (in the XZ plane) of less than 26 degrees. It is preferable to use a deflection element.
[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, and 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 is not only installed on one side end surface of the light guide 3, but can be further installed on the other side end surface facing each other as necessary. .
[0050]
For example, when a substantially point light source such as an LED light source is disposed as the primary light source 1 at a corner or the like of the light guide 3, the light incident on the light guide 3 is in the same plane as the light emitting surface 33. , The light emitted from the light emitting surface 33 is emitted radially around the primary light source 1 in the same manner. In order to efficiently deflect the emitted light emitted radially like this in a desired direction regardless of the emission direction, the prism array formed in the light deflection element 4 is substantially arc-shaped 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 in a substantially arc shape so as to surround the primary light source 1, most of the light emitted radially from the light emitting surface 33 is substantially the same as the prism rows of the light deflection element 4. Since the light is incident vertically, the emitted light can be efficiently directed in 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 row formed on the light deflecting element 4 is selected according to the distribution of the light propagating in the light guide 3, and most of the light emitted radially from the light emitting surface 33 is light. It is preferable that the light is incident substantially perpendicular to the prism row of the deflecting element 4. Specific examples include concentric circles that are substantially centered on a point light source such as an LED and are arranged substantially in parallel so that the radius of the arc gradually increases. 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 from the primary light source 1 to the light guide 3 with little loss. As a material, for example, a plastic film having a metal-deposited 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 edge of the light emitting surface of the light deflecting element 4 through the outer surface of the primary light source 1. On the other hand, the light source reflector 2 can be wound around the light emitting surface edge of the light guide 3 through the outer surface of the primary light source 1 from the outer surface of the light reflecting element 5, avoiding the light deflection element 4. It is.
[0052]
A reflection 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 reflecting element 5, for example, a plastic sheet having a metal vapor deposition reflecting layer on the surface can be used. In the present invention, the light reflecting element 5 may be a light reflecting layer or the like formed on the back surface 34 of the light guide 3 by metal vapor deposition or the like instead of the reflecting sheet.
[0053]
The light guide 3 and the light deflection element 4 of the present invention can be made of a synthetic resin having a high light transmittance. Examples of such synthetic resins include methacrylic resins, acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, methacrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and molding processability. Such a methacrylic resin is a resin mainly composed of methyl methacrylate, and preferably has a methyl methacrylate content of 80% by weight or more. When forming the rough surface structure of the light guide 3 and the light deflection element 4 and the surface structure such as the prism array, the transparent synthetic resin plate is formed by hot pressing using a mold member having a desired surface structure. Alternatively, the shape may be imparted simultaneously with molding by screen printing, extrusion molding, injection molding, or the like. The structural surface can also be formed using heat or a photocurable resin. Furthermore, on a transparent substrate such as a polyester film, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylamide resin, or other transparent substrate or rough surface structure made of an active energy ray curable resin. Moreover, a lens array arrangement structure may be formed on the surface, or such a sheet may be bonded and integrated on a separate transparent base material by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylic acid esters, allyl compounds, (meth) acrylic acid metal salts, and the like can be used.
[0054]
On the light emitting surface (the light exit surface 42 of the light deflection element 4) of the surface light source device composed of the primary light source 1, the light source reflector 2, the light guide 3, the light deflection element 4 and the light reflection element 5 as described above, a liquid crystal display element A liquid crystal display device is configured by disposing. The liquid crystal display device is observed by an observer through the liquid crystal display element from above in FIG. Further, in the present invention, a sufficiently collimated narrow distribution of light can be incident on the liquid crystal display element from the surface light source device, so that there is no gradation inversion in the liquid crystal display element and the brightness and hue uniformity. Can be obtained, and light irradiation concentrated in a desired direction can be obtained, and the utilization efficiency of the light emission amount of the primary light source for the illumination in this direction can be enhanced.
[0055]
Furthermore, in the present invention, in the light source device having a narrow field of view and a high brightness as described above by the light deflecting element 4, in order to appropriately control the field of view according to the purpose without causing a decrease in brightness as much as possible. Further, the light diffusing element 6 is disposed adjacent to the light exit surface of the light deflecting element 4. Further, in the present invention, by disposing the light diffusing element 6 in this manner, it is possible to suppress glare, brightness spots and the like that cause deterioration in quality and to improve quality.
[0056]
The light diffusing element 6 may be integrated with the light deflection element 4 on the light exit surface side of the light deflection element 4, or the light diffusion element 6 may be individually placed on the light exit surface side of the light deflection element 4. However, it is preferable to arrange the light diffusing elements 6 individually. When the light diffusing elements 6 are individually mounted, a concavo-convex 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 sticking between the light diffusing element 6 and the liquid crystal display element disposed thereon, and an uneven structure is also provided on the light diffusing element 6. Is preferred. In the case of providing this concavo-convex structure only for the purpose of preventing sticking, the concavo-convex structure is preferably a structure having an average inclination angle of 0.7 degrees or more, more preferably 1 degree or more, and more preferably 1 .5 degrees or more.
[0057]
In the present invention, it is necessary to use a light diffusing element 6 having a light diffusing characteristic for appropriately diffusing light emitted from the light deflecting element 4 in consideration of a balance of luminance characteristics, visibility, quality, and the like. That is, when the light diffusibility of the light diffusing element 6 is low, it is difficult to sufficiently widen the viewing angle and the visibility is lowered, 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 is impaired, and the total light transmittance is also lowered and the luminance tends to be lowered. Therefore, in the light diffusing element 6 of the present invention, an element having a full width at half maximum of 1 to 13 degrees in the emitted light luminous intensity distribution (in the XZ plane) when parallel light is incident is used. The full width at half maximum of the light diffusing element 6 is preferably in the range of 3 to 11 degrees, more preferably in the range of 4 to 8.5 degrees. In the present invention, the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) of the light diffusing element 6 is, as shown in FIG. 21, how much the parallel rays incident on the light diffusing element 6 are diffused and spread when emitted. The full width angle (Δθ) of the divergence angle at half the peak value in the luminous intensity distribution (in the XZ plane) of the light transmitted through and diffused through the light diffusing element 6 (in the XZ plane)_H).
[0058]
Such light diffusion characteristics can be imparted by mixing a light diffusing agent in the light diffusing element 6 or imparting a concavo-convex structure to at least one surface of the light diffusing element 6. The degree of the concavo-convex structure formed on the surface differs depending on whether it is formed on one surface of the light diffusing element 6 or on both surfaces. In the case of forming a concavo-convex structure 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 it is 4 to 6.5 degrees. When the concavo-convex structure is formed on both surfaces of the light diffusing element 6, the average inclination angle of the concavo-convex structure formed on one surface is preferably in the range of 0.8 to 6 degrees, more preferably 2 to 2. It is 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 diffusing element 6, it is preferable to make the average inclination angle on the incident surface side of the light diffusing element 6 larger than the average inclination angle on the exit 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 luminance characteristics and improving visibility, more preferably in the range of 30 to 70%, more preferably 40. It is in the range of ~ 65%.
[0059]
The light source device of the present invention is also required to have uniform luminance in the display area when observed from the normal direction of the light emitting surface (the exit surface of the light diffusing element 6). This uniformity of brightness also depends on the size of the display area of the light source. For example, a large light source device with a large display area such as a notebook computer or a monitor may require a relatively wide viewing angle characteristic. It is required that the luminous intensity distribution (in the XZ plane) emitted from the light emitting surface be wider. On the other hand, in a small light source device with a small display area such as a mobile phone or a portable information terminal, high brightness and display quality improvement may be prioritized, and the emitted light intensity distribution (in the XZ plane) emitted from the light emitting surface is It may be relatively narrow. For this reason, it is preferable to use the light diffusing element 6 having an appropriate light diffusing 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 unfolded length of the light source device (the unfolded length of the light guide 3) means that a linear cold cathode light source is arranged on the light incident surface of the light guide 3 as the primary light source 1, as shown in FIG. 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. Further, as shown in FIG. 23, when a point light source such as an LED is arranged at the corner of the light guide 3 as the primary light source 1, it is on a straight line connecting the effective display area farthest from the light point source and the point light source. The display area distance L.
[0061]
(1) When the unfolded length of the light guide 3 is 8 cm or less
In such a light source device, a linear cold cathode tube (single lamp type), an LED, or the like is used 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, and a digital camera. Therefore, it is not necessary to increase the viewing angle so much, and the light diffusing element 6 imparts light diffusibility to the extent that glare, luminance spots and the like that cause deterioration in quality are suppressed, thereby improving the light utilization efficiency and maintaining high luminance. At the same time, it is necessary to keep power consumption low. For this reason, the light diffusing element 6 preferably has a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 1 to 6 degrees, more preferably 1 to 5 degrees, and more preferably 2 to 5 degrees. Range. Moreover, as a haze value, it is preferable that it is the range of 8 to 60%, More preferably, it is 8 to 50%, More preferably, it is the range of 20 to 50%. Furthermore, when forming an uneven structure 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 It is in the range of 2-4 degrees.
[0062]
(2) When the developed length of the light guide 3 is more than 8 cm and not more than 23 cm (using a one-lamp type cold cathode tube as the primary light source 1)
Since such a light source device is used for a display device such as a monitor of a notebook personal computer, a desktop personal computer, a relatively small liquid crystal television, etc., a relatively wide viewing angle is necessary, and the resolution of the liquid crystal display device is increased. Accordingly, high brightness with high quality is required. Therefore, the light diffusing element 6 preferably has a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 3 to 11 degrees, more preferably 4 to 10 degrees, more preferably 4 to 9 degrees. Range. Moreover, as a haze value, it is preferable that it is the range of 30-80%, More preferably, it is 40-73%, More preferably, it is the range of 45-70%. Furthermore, when the 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 9.5 degrees, more preferably 3.5 to 8.5 degrees. Preferably it is the range of 4.5-7 degrees.
[0063]
When the development length of the light guide 3 is more than 8 cm and 18 cm or less, the required viewing angle is somewhat narrow because it is used for a display device of a relatively small notebook personal computer. For this reason, the light diffusing element 6 preferably has a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 3 to 8 degrees, more preferably 4 to 8 degrees, and more preferably 4 to 7 degrees. Range. Moreover, as a haze value, it is preferable that it is the range of 30 to 70%, More preferably, it is 40 to 65%, More preferably, it is the range of 45 to 60%. Furthermore, when forming a concavo-convex structure 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 It is in the range of 4.5 to 6 degrees.
[0064]
When the 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, so that a relatively wide viewing angle is required. It is necessary to achieve brightness uniformity. For this reason, the light diffusing element 6 preferably has a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 4 to 10 degrees, more preferably 5 to 9 degrees, and more preferably 5 to 8 degrees. The range is 5 degrees. Moreover, as a haze value, it is preferable that it is the range of 40 to 75%, More preferably, it is 50 to 70%, More preferably, it is the range of 50 to 65%. Furthermore, 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 3.5 to 8 degrees, more preferably 4 to 7 degrees, and still more preferably 4. It is in the range of 5 to 6.5 degrees.
[0065]
When the developed length of the light guide 3 is more than 22 cm and 23 cm or less, it is used for a display device such as a relatively large notebook personal computer. A notebook computer using a single-lamp type cold cathode tube as the primary light source 1 has a large display area. Compared with a light guide 3 with a developed length of 22 cm or less, the light utilization efficiency is increased and the luminance is increased. It is necessary to improve. When trying to increase the brightness in this way, for example, as a reflection sheet disposed on the back surface of the light guide 3 of the light source device, silver having excellent directional reflection characteristics instead of the foamed PET reflection film having low directional reflection 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, glare peculiar to metal reflection, dark line bright lines appearing near the incident surface, dark defects appearing near both ends of the incident surface are strongly expressed, and the quality as a light source device Tend to be damaged. In order to suppress such deterioration in quality, it is necessary to use a light diffusing element 6 having a high light diffusibility such that the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) exceeds 9 degrees. However, when such a light diffusing element 6 is used, the light diffusibility becomes too large, and the total light transmittance is greatly reduced, so 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 deflection element 4, and the light diffusing element 6 has a full width at half maximum of the outgoing light luminous intensity distribution (in the XZ plane) in the range of 5 to 11 degrees. It is preferable to use a thing, More preferably, it is 6 to 10 degree | times, More preferably, it is the range of 7 to 9 degree | times. Moreover, as a haze value, it is preferable that it is the range of 50 to 80%, More preferably, it is 55 to 73%, More preferably, it is the range of 55 to 70%. Furthermore, when forming an uneven | corrugated structure in the surface of the light-diffusion element 6, it is preferable that the average inclination angle is the range of 4.5-9.5 degree | times, More preferably, it is 5-8.5 degree | times, More Preferably it is 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 (using a multi-lamp type cold cathode tube 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 or a liquid crystal television, it requires a relatively wide viewing angle and high luminance. For this reason, the primary light source 1 is a multi-lamp type in which one or more cold-cathode tubes are arranged on two opposing end faces of the light guide 3. In such a light source device, the visibility regarding the quality is different from that using the one-lamp type primary light source 1, and the asymmetry of the emitted light luminous intensity distribution (in the XZ plane) as described later loses its characteristics, and the light source The emitted light luminous intensity distribution (in the XZ plane) near the center of the apparatus has improved symmetry even when the light diffusing element 6 is not used, as shown in FIG. Furthermore, the emitted light intensity distribution (in the XZ plane) in the vicinity of both ends close to the light source is influenced by the light guided from the nearest place, and the emitted light intensity distribution (in the XZ plane) having a slight asymmetry. ) That is, in the vicinity of the left end in FIG. 24, the emitted light luminous intensity distribution (in the XZ plane) on the light source side rapidly decreases, and the emitted light luminous intensity distribution (in the XZ plane) on the central side has a smooth tailing tendency. For this reason, the light emission direction in the vicinity of the left end portion has a component that is slightly toward the center portion. On the other hand, in the vicinity of the right end of FIG. 24, there is a light intensity distribution (in the XZ plane) opposite to this, and the light emission direction has a component that is slightly directed toward the center. For this reason, the emitted light characteristic excellent in visibility when observing the vicinity of both ends from the central part is obtained, and the light source device having high brightness and high brightness is obtained up to the end part. For this reason, the light diffusing element 6 is required to have a light diffusibility for obtaining a wide viewing angle, and it is preferable to use a light diffuser having a full width at half maximum of 6 to 13 degrees in the emitted light luminous intensity distribution (in the XZ plane). More preferably, it is in the range of 6.5 to 11 degrees, more preferably 7 to 9 degrees. Moreover, as a haze value, it is preferable that it is the range of 50 to 82%, More preferably, it is 60 to 75%, More preferably, it is the range of 65 to 70%. Furthermore, when forming an uneven | corrugated structure in the surface of the light-diffusion element 6, it is preferable that the average inclination | tilt angle is the range of 4.5-12 degree | times, More preferably, it is 5.5-8.5 degree | times, More Preferably it is the range of 6-7 degrees.
[0067]
In the light source device of the present invention, when the light diffusing element 6 as described above is used, the light condensing properties with a full width at half maximum of the emitted light luminance distribution (in the XZ plane) from the light deflecting element 4 of about 19 to 26 degrees are compared It is sometimes preferable from the viewpoint of improving the luminance to use the light deflecting element 4 which is weak enough and to use the light diffusing element 6 having a relatively weak light diffusibility because the decrease in luminance due to diffusion on the YZ plane can be suppressed. is there. In this case, the light diffusing element 6 needs to have a light diffusibility to obtain a wide viewing angle, and it is preferable to use a light diffuser having a full width at half maximum of 1 to 8 degrees in the emitted light luminous intensity distribution (in the XZ plane). More preferably, it is in the range of 2 to 8 degrees, more preferably 3 to 7 degrees. The haze value is preferably in the range of 8 to 70%, more preferably 30 to 65%, and still more preferably 40 to 60%. Furthermore, when forming an uneven | corrugated structure in one surface of the light-diffusion element 6, it is preferable that the average inclination | tilt angle is the range of 0.8-7 degree, More preferably, it is 3-6.5 degree, and more Preferably it is the range of 3.5-6 degrees. When the uneven structure is formed on both sides, 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. It is a range.
[0068]
In the light source device of the present invention, the outgoing light emitted from the outgoing surface of the light deflection element 4 may have an asymmetric outgoing light luminance distribution (in the XZ plane) as shown in FIG. This outgoing light luminance distribution (in the XZ plane) is derived from the outgoing light luminous intensity distribution (in the XZ plane) emitted from the light guide 3. Such an asymmetrical emitted light luminance distribution (in the XZ plane) is obtained by, for example, emitting highly directional emitted light whose full width at half maximum of the emitted 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 such asymmetry of the emitted light luminance distribution (in the XZ plane), the light diffusing element 6 having a relatively strong light diffusibility should be used. Is required. On the other hand, when the light diffusing element 6 having a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) of 4 degrees or more and a haze value of 35% or more is used, the emitted light intensity emitted from the light diffusing element 6 is used. 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 emitted light luminance distribution (in the XZ plane) from the light deflection element 4. For this reason, when the peak angle of the emitted light luminance distribution (in the XZ plane) from the light deflection element is in a desired direction (for example, the normal direction), the light diffusing element 6 is used to achieve the desired direction. This results in a decrease in brightness. Therefore, when the light diffusing element 6 is used when the full width at half maximum of the emitted light luminance distribution (in the XZ plane) from the light deflecting element 4 is 20 degrees or less, the light diffusing element 4 is used in advance. The light deflection is 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, more preferably 1 to 2 degrees. It is preferable to design the element 4 and the like.
[0069]
In the present invention, use of the light diffusing element 6 having anisotropy in the light diffusing property increases the total light transmittance of the light diffusing element 6, and efficiently emits the light emitted from the light deflecting element 4. It is preferable because it can diffuse and improve luminance. For example, in a light source device in which a cold cathode tube on a line is arranged on one end face of the light guide 3 as the primary light source 1, the light deflection element 4 for narrowing the field of view emits light from the light exit surface of the light guide 3. The emitted light is mainly intended to narrow the field of view on the XZ plane, and further, the light of the XZ plane narrowed by the light diffusing element 6 is mainly diffused to widen the viewing angle. However, when an isotropic diffusing element is used as the light diffusing element 6, the light on the YZ plane that is not narrowed by the light deflection angle element is also diffused equally, leading to a decrease in luminance. become. Therefore, as shown in FIG. 26, the light deflecting element 4 narrows the field of view by using the light diffusing element 6 having anisotropic diffusibility that has higher light diffusibility in the YZ plane than in the XZ plane. The light on the XZ plane can be diffused strongly, the diffusion of the light on the YZ plane that is not narrowed can be weakened, the light emitted from the light deflecting element 4 can be diffused efficiently, and the luminance can be reduced. Can be minimized as much as possible.
[0070]
In the present invention, regarding the anisotropic diffusivity of such a light diffusing element 6, what kind of anisotropy the light diffusing element 6 is used is different between the XZ plane and the YZ plane as described above. It is not limited to the directivity, and can be appropriately selected according to the light emitting mechanism of the light guide 3, the lens shape and arrangement of the light deflection element 4, the use of the light source device, and the like. That is, as shown in FIG. 27, an arbitrary surface (ZP-n surface (n = 1, 2,...)) Including a normal axis with respect to the exit surface of the light diffusing element 6 is assumed, and these arbitrary Anisotropy can be imparted by making the full width at half maximum of the outgoing light luminous intensity distribution (in the XZ plane) different on the surface. In the ZP-n plane, 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. Similarly, with respect to the average inclination angle of the concavo-convex structure imparting anisotropic diffusibility to the light diffusing element 6, the average inclination angle in an arbitrary Pn direction where the ZP-n plane intersects with the light diffusing element 6 (XY plane). It is possible to impart anisotropy of the average inclination angle by making the difference. At this time, the largest average inclination angle in the P-n direction is the maximum average inclination angle, and the smallest average inclination angle is the minimum average inclination angle.
[0071]
For example, when a cold cathode tube on a line is arranged on one end face of the light guide 3 to form the primary light source 1, the light deflection element 4 mainly aims at narrowing 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 diffusivity that effectively diffuses outgoing light on the XZ plane and does not diffuse outgoing light on the YZ plane. Therefore, the light diffusing element 6 preferably has an anisotropic diffusibility that exhibits the maximum full width at half maximum on the XZ plane and the full width at half maximum on the YZ plane. Similarly, the concavo-convex structure formed in the light diffusing element 6 is preferably configured or arranged so as to have a maximum average inclination angle in the X direction and a minimum average inclination angle in the Y direction.
[0072]
Also in the light diffusing element 6 having such anisotropic diffusibility, the light diffusion having the light diffusing characteristic for appropriately diffusing the emitted light from the light deflecting element 4 in consideration of the balance of the luminance characteristic, the visibility, the quality and the like. It is necessary to use element 6. That is, when the light diffusibility of the light diffusing element 6 is low, it is difficult to sufficiently widen the viewing angle and the visibility is lowered, 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 is impaired, and the total light transmittance is also lowered and the luminance tends to be lowered. Therefore, a light having a maximum full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 1 to 13 degrees is used, preferably in the range of 3 to 11 degrees, and more preferably in the range of 4 to 9 degrees. The ratio of the maximum full width at half maximum to the full width at half maximum (maximum full width at half maximum / full width at half maximum) is preferably in the range of 1.1 to 20, more preferably in the range of 2 to 15, more preferably 4 to 10. It is a range. This is because when the maximum full width at half maximum / minimum full width at half maximum is 1.1 or more, the light use efficiency can be improved and the luminance can be increased, and when it is 20 or less, the luminance is reduced due to strong light diffusibility. This is because it can be suppressed.
[0073]
In the case of forming a concavo-convex structure 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. Further, 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) is in the range of 1.1 to 20. More preferably, it is the range of 2-15, More preferably, it is the range of 4-10. The uneven 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 It is preferable to make the inclination angle larger than the average inclination angle on the exit 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 luminance characteristics and improving visibility, more preferably in the range of 30 to 70%, more preferably 40. It is in the range of ~ 65%.
[0074]
Further, as the light diffusing element 6, it is preferable to use an element having appropriate light diffusing characteristics according to the size of the display area of the light source device. When the development length of the light guide 3 is 8 cm or less, the light diffusing element 6 preferably has a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 1 to 6 degrees, more preferably. Is in the range of 1 to 5 degrees, more preferably 2 to 5 degrees. Moreover, as a haze value, it is preferable that it is the range of 8 to 60%, More preferably, it is 8 to 50%, More preferably, it is the range of 20 to 50%. Furthermore, when forming a concavo-convex structure on the surface of the light diffusing 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, more preferably Is in the range of 2-4 degrees.
[0075]
When the developed length of the light guide 3 is more than 8 cm and not more than 23 cm (using a single lamp type cold cathode tube as the primary light source 1), the light diffusing element 6 has a luminous intensity distribution (in the XZ plane). The full width at half maximum is preferably in the range of 3 to 11 degrees, more preferably in the range of 4 to 10 degrees, more preferably in the range of 4 to 9 degrees. Moreover, as a haze value, it is preferable that it is the range of 30-80%, More preferably, it is 40-73%, More preferably, it is the range of 45-70%. Furthermore, when forming a concavo-convex structure 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 .5 to 8 degrees. In particular, when the developed length of the light guide 3 exceeds 8 cm and is 18 cm or less, the light diffusing element 6 has a maximum full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 3 to 10 degrees. Is more preferable, more preferably 4 to 10 degrees, more preferably 4 to 9 degrees. Moreover, as a haze value, it is preferable that it is the range of 30 to 70%, More preferably, it is 40 to 65%, More preferably, it is the range of 45 to 60%. Furthermore, when forming a concavo-convex structure 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 .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 diffusing element 6 has a maximum full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the range of 4 to 13 degrees. Is more preferable, 5 to 11 degrees is more preferable, and 5 to 8.5 degrees is more preferable. Moreover, as a haze value, it is preferable that it is the range of 40 to 75%, More preferably, it is 50 to 70%, More preferably, it is the range of 50 to 65%. Furthermore, when forming a concavo-convex structure 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 The range is from 5 to 6.5 degrees. Furthermore, when the development length of the light guide 3 is more than 22 cm and 23 cm or less, the light diffusing element 6 having a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) of 5 to 13 degrees is used. Preferably, it is in the range of 6 to 12 degrees, more preferably 7 to 9 degrees. Moreover, as a haze value, it is preferable that it is the range of 50 to 80%, More preferably, it is 55 to 73%, More preferably, it is the range of 55 to 70%. Furthermore, when forming a concavo-convex structure on the surface of the light diffusing 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 It is in the range of -7 degrees.
[0076]
When the 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 light diffusibility to obtain a wide viewing angle. It is preferable to use one having a full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) of 6 to 13 degrees, more preferably 6.5 to 11 degrees, and more preferably 7 to 9 degrees. It is a range. Moreover, as a haze value, it is preferable that it is the range of 50 to 82%, More preferably, it is 60 to 75%, More preferably, it is the range of 65 to 70%. Furthermore, when forming a concavo-convex structure on the surface of the light diffusing element 6, the maximum average tilt 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 6-7 degrees.
[0077]
Examples of the diffusivity imparting structure of the light diffusing element 6 having such anisotropic diffusibility include an uneven 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. For such an arrangement pitch of the lens rows, a pitch that hardly causes moire is selected with respect to the pitch of the liquid crystal elements used as the display device and the arrangement pitch of the lens rows such as the prism rows of the light deflection element 4, or a random pitch is selected. It is preferable to use an array pitch. 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 more preferably in the range of 10 to 30 μm from the viewpoint of ease of manufacture and prevention of moire. In addition, 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 viewpoint of luminance improvement and visibility, more preferably 3.5 to 11 degrees, and more preferably. Is in the range of 4-9 degrees.
[0078]
The concavo-convex 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-shaped bodies may be a regular pitch or a random arrangement pitch. In general, the arrangement pitch of the cylindrical lens-shaped bodies is preferably in the range of 1 to 70 μm, more preferably 5 to 40 μm, more preferably in the range of 10 to 30 μm from the viewpoint of ease of manufacture and prevention of moire. 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 viewpoint of luminance improvement and visibility, more preferably 3.5 to 11 degrees, and more preferably. Is in the range of 4-9 degrees. In such a discrete array structure, a line intersecting the plane where the light diffusing element 6 needs to have a full width at half maximum and the exit surface of the light diffusing element 6 and the longitudinal direction of the cylindrical lens shape body are substantially orthogonal. It is preferable to arrange them so that the quantitative probability of doing so becomes high. In addition, the quantitative probability that the surface of the light diffusing element 6 that is required to have the minimum full width at half maximum and the line intersecting the emission surface of the light diffusing element 6 is substantially parallel to the longitudinal direction of the cylindrical lens shape body is increased. It is preferable to arrange.
[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 viewpoint of luminance improvement and visibility, more preferably 3.5 to 11 degrees, and more preferably 4 to 9 degrees. It is a range. The direction in which the hairline extends is preferably a direction that is substantially orthogonal to a line that intersects the light diffusing element 6 that requires the maximum full width at half maximum and the light diffusing element 6 exit surface.
[0080]
By imparting a mat structure to at least one of the surface on which the uneven structure imparting such anisotropic diffusibility and the back surface thereof are provided, glare, brightness spots, etc. can be suppressed and the quality can be improved. it can. However, if the light diffusibility of the mat structure is increased, the anisotropic diffusibility may be impaired and the luminance may be lowered. Therefore, it is preferable to provide a mat structure having a relatively weak light diffusibility. Such a mat structure preferably has an average inclination angle in the range of 0.5 to 5 degrees, more preferably 0.8 to 4 degrees, and more preferably 1 to 3.5 degrees. The average inclination angle of the mat structure when the mat structure is provided on the surface of the anisotropy imparting concavo-convex structure refers to the average inclination angle of the mat structure itself excluding the average inclination angle caused by the concavo-convex structure. That is, it is possible to measure the average inclination angle parallel to the longitudinal direction of the portion having no concavo-convex structure or the concavo-convex structure, measuring with a stylus roughness meter, image analysis of the cross-sectional shape of the light diffusing element 6, atomic force It can be measured with a microscope or the like.
[0081]
In the present invention, the light deflecting element 4 is used to emit light emitted from the light guide 3 in a specific direction such as a normal direction, and the light emitted from the light deflecting element 6 is anisotropically diffused. The light can be emitted in a desired direction. In this case, the light diffusing element 6 can be provided with both the functions of anisotropic diffusion and light deflection angle. For example, in the case where a lenticular lens array or a cylindrical lens shaped body is used as the concavo-convex structure, both functions of anisotropic diffusion and light deflection can be provided by making the cross-sectional shape asymmetric.
[0082]
In the present invention, the light deflection element 4 and the light diffusion 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 refractive index different from that of the material constituting the light deflecting element 4 or the light diffusing element 6 can be used, for example, silicon beads, polystyrene, polymethyl methacrylate. , Homopolymers or copolymers such as fluorinated methacrylates. As the light diffusing material, it is necessary to appropriately select the content, the particle size, the refractive index and the like so as not to impair the narrow field effect by the light deflecting element 4 and the appropriate diffusing effect by the light diffusing element 6. For example, the refractive index of the light diffusing material is such that if the difference in refractive index from the material constituting the light deflecting element 4 or the light diffusing element 6 is too small, the diffusing effect is small. The rate difference is preferably in the range of 0.01 to 0.1, more preferably 0.03 to 0.08, and more preferably 0.03 to 0.05. In addition, if the particle size of the diffusing material is too large, scattering becomes strong, causing glare and a decrease in luminance, and if it is too small, coloring occurs, so the average particle size is in the range of 0.5 to 20 μm. Preferably, it is 2-15 micrometers, More preferably, it is the range of 2-10 micrometers.
[0083]
Note that the emitted light luminance distribution (in the XZ plane) of the light source device using the light deflection element as in the present invention is the peak of the peak position, and the emitted light luminance distribution (in the XZ plane) on the light source side is the peak. -As the distance from the light increases, the luminance decreases rapidly, and the emitted light luminance distribution (in the XZ plane) on the side far from the light source has an asymmetric emitted light luminance distribution (in the XZ plane) in which the luminance decreases relatively slowly. May show. For example, when such a light source device having an emitted light luminance distribution (in the XZ plane) is used for a liquid crystal display device that requires a relatively wide viewing angle, such as a notebook personal computer of 10 inches or more, it is relatively light diffusive. A high light diffusing element is disposed on the light exit surface of the light deflecting element to widen the outgoing light luminous intensity distribution (in the XZ plane) and widen the viewing angle. When a light diffusing element having a haze value of 50% or more is used, the peak angle of the emitted light luminous intensity distribution (in the XZ plane) is deflected by about 1 to 3 degrees away from the light source. For this reason, when the peak angle of the emitted light luminance distribution (in the XZ plane) from the light deflecting element is positioned in the normal direction of the light emitting surface, the peak angle of the emitted light intensity distribution (in the XZ plane) is increased by the light diffusing element. The light is polarized to the side far from the light source by about 1 to 3 degrees from the normal direction, and as a result, the luminance when observed from the normal direction is extremely reduced. This is because, by using a light diffusing element, the asymmetry of the emitted light luminance distribution (in the XZ plane) emitted from the light deflecting element is somewhat relaxed, but the emitted light luminance distribution in which the luminance decreases relatively abruptly. This is because the region (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 emitted light luminance distribution (in the XZ plane) from the light deflection element is previously tilted by 1 to 3 degrees from the normal direction to the light source side.
[0084]
【Example】
Hereinafter, the present invention will be described specifically by way of examples.
In addition, the measurement of each physical property in the following examples was performed as follows.
[0085]
Measurement of normal brightness 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 Co., Ltd.) for high frequency lighting. For the luminance, the surface of the surface light source device or the light guide was divided into 3 × 5 squares of 20 mm squares, and the average of 15 luminance values in the normal direction of each square was obtained. The full width at half maximum of light intensity of the light guide is fixed with 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 in such a way that the gonio rotation axis was rotated about the pinhole in the direction perpendicular to and parallel to the longitudinal axis of the cold cathode tube. While rotating the rotation axis in each direction from + 80 ° to -80 ° at 1 ° intervals, the luminous intensity distribution (in the XZ plane) of the emitted light is measured with a luminance meter, and the peak angle and luminous intensity distribution (in the XZ plane) are measured. The full width at half maximum (the spread angle of the distribution of half the peak value (in the XZ plane)) was determined. Further, 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 degree and positioned on the center surface of the surface light source device, and the gonio rotation axis was rotated. While rotating the rotation axis in each direction from + 80 ° to −80 ° at 1 ° intervals, the luminance distribution of the emitted light (in the XZ plane) was measured with a luminance meter, and the peak luminance and the peak angle were obtained.
[0086]
Measurement of average inclination angle (θa)
In accordance with ISO4287 / 1-1987, the surface of the rough surface was measured with 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. Roughness was measured at a driving speed of 0.03 mm / sec. From the chart obtained by this measurement, the average line was subtracted to correct the inclination, and the calculation was made according to the equations (1) and (2).
[0087]
Measurement of haze value
The haze value is a total light transmission obtained by using a 50 mm × 50 mm sample with an integrating sphere type reflection transmittance meter (RT-100, manufactured by Murakami Color Research Co., Ltd.) according to the method B of JIS K-7105. It calculated | required by calculating by following Formula (4) from a rate (Tt) and a diffused light transmittance (Td).
[0088]
[Equation 3]

Measurement of light diffusion angle
The light diffusion distribution angle is a half value which is 1/2 light intensity of a peak light intensity obtained by measuring a sample having a size of 50 mm × 50 mm using an automatic variable angle photometer (GP-200 model manufactured by Murakami Color Research Laboratory). The half width angle (a) of the sample was twice the half width angle. The light incident on the sample is collected from the light source into a pinhole by a condenser lens, converted into parallel light (parallelism ± 0.5 degrees or less) through a collimator lens, and a light beam stop (aperture diameter 10.5 mm). ) And enter the incident surface of the sample. The light transmitted through the sample passes through a light receiving lens (passes through the aperture diameter of 11.4 mm (when the sample surface is smooth, it is condensed at the position of the light receiving aperture), reaches the light receiving element through the light receiving aperture, and has a voltage value. Further, the same measurement was performed by rotating the sample, and the maximum full width at half maximum (Maxa) and the full width at half maximum (Mina) were obtained.
[0089]
Example 1
A light guide with one surface being a mat was produced 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 surface side of the light guide, a prism row having a prism apex angle of 100 ° and a pitch of 50 μm is made of acrylic ultraviolet curable resin so as to be parallel to a side (short side) of 230 mm in length of the light guide. A prism layer arranged in parallel was formed. A cold-cathode tube along a side end surface (end surface on the thickness side of 2.0 mm) corresponding to the side (long side) of the light guide with a length of 290 mm is a light source reflector (silver reflection film manufactured by Reiko Co., Ltd.). Covered. Furthermore, a light diffusion reflection film (E60 manufactured by Toray Industries, Inc.) was attached to the other side end face, and a reflection sheet was arranged on the prism array (back face). The above configuration was incorporated into the 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, using an acrylic ultraviolet curable resin having a refractive index of 1.5064, as shown in Table 1, an angle formed between one prism surface (first prism surface) constituting the prism array and a normal line ( α) is a flat surface of 32.5 degrees, and the other prism surface (second prism surface) is from the top of the prism to the height of the prism row of 21.4 μm with a minor axis curvature radius of 400 μm and a major axis curvature radius of 800 μm. A convex 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 prism row height of 21.4 μm or more from the top of the prism with a spherical shape with a radius of curvature of 400 μm A prism array forming surface in which prism arrays with a pitch of 56.5 μm composed of two convex curved surfaces (areas 1 and 2 from the prism top side) having a convex curved surface (inclination angle = 59.0 degrees) are arranged substantially in parallel. , 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 row was 1.03%.
[0091]
The obtained prism sheet is arranged such that the prism array 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 is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance 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 flat surface with a tilt angle of 55.2 degrees (β = 34.8 degrees) from the top of the prism to the height of the prism array of 16 μm. Same angle of inclination of 55.5 degrees, 56.2 degrees, 57.0 degrees, 57.8 degrees, 58.4 degrees, 59.4 degrees from the side close to the prism top from the row height of 16 μm to the prism bottom A prism sheet was produced in the same manner as in Example 1 except that it was composed of seven planes (areas 1, 2,..., 7 from the prism top side) as six planes having a width. 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 row was 1.10%.
[0093]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance 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 from the top of the prism to the height of the prism array of 10.6 μm (β = 33.6 degrees). A prismatic height of 10.6 to 21.3 μm is a flat surface with an inclination angle of 56.8 degrees, and a prismatic height of 21.3 μm or more is a spherical convex surface with a curvature radius of 400 μm (inclination angle = 59. A prism sheet was fabricated in the same manner as in Example 1 except that the sheet was composed of two flat surfaces and two convex curved surfaces (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 row was 1.03%.
[0095]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance 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 constituting the prism array is a plane having an inclination angle of 56.8 degrees from the top of the prism to a height of 21.5 μm (β = 33.2 degrees). The prism array was constructed in the same manner as in Example 1 except that the prism array had a height of 21.5 μm or more and was composed of two planes (areas 1 and 2 from the prism top side) having an inclination angle of 58.7 degrees. A sheet was produced. 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 row was 0.76%.
[0097]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance 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 constituting the prism row and the normal line is 29.0 degrees, and the second prism surface constituting the prism row is arranged from the prism top to the prism row. A flat surface with an inclination angle of 55.3 degrees (β = 34.7 degrees) up to a height of 16.0 μm, and an inclination angle of 55.degree. From the side close to the prism top from the height of the prism row from 16.0 μm to the prism bottom. 7 planes of the same width of 7 degrees, 56.5 degrees, 57.4 degrees, 58.2 degrees, 59.0 degrees, 59.6 degrees, and 60.3 degrees (area 1 from the prism top side) , 2,... 8) A prism sheet was produced in the same manner as in Example 1 except that it was configured. 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 row was 0.73%.
[0099]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The 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 the surface light source device is obtained, and the peak luminance ratio, peak angle, and ½ of the peak luminance when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having the brightness of (the full width at half maximum) and the angle having the brightness of half the peak brightness_a−Δθ_b|) Was measured and the results are shown in Table 2.
[0100]
Example 6
As shown in Table 1, it was composed of curved surfaces passing through the boundaries of seven areas from the prism row height of 16.0 μm to the prism bottom in Example 5 (the inclination angle of each area from the side close to the prism top was 55 A prism sheet was produced in the same manner as in Example 1 except for 4 degrees, 56.2 degrees, 57.1 degrees, 57.9 degrees, 58.7 degrees, 59.3, and 60.0 degrees). 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 row was 0.0.68%.
[0101]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The 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 the surface light source device is obtained, and the peak luminance ratio, peak angle, and ½ of the peak luminance when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having the brightness of (the full width at half maximum) and the angle having the brightness of half the peak brightness_a−Δθ_b|) Was measured and the results are shown in Table 2.
[0102]
Example 7
As shown in Table 1, the angle (α) that makes the first prism surface constituting the prism array normal to the plane is a plane having a 15.0 degree angle, and the second prism surface is the height of the prism array from the top of the prism. A plane with 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 closer to the prism top from the height of the prism row of 10.4 μm to the prism bottom. 10 planes of the same width of 8 degrees, 53.7 degrees, 54.5 degrees, 55.3 degrees, 56.1 degrees, 56.8 degrees, 57.5 degrees, 58.4 degrees, and 60.0 degrees A prism sheet was produced in the same manner as in Example 1 except that the structure was composed of 11 planes (areas 1, 2,... 11 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 row was 1.48%.
[0103]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The 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 the surface light source device is obtained, and the peak luminance ratio, peak angle, and ½ of the peak luminance when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having the brightness of (the full width at half maximum) and the angle having the brightness of half the peak brightness_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 constituting the prism row and the normal line is 10.0 degrees, and the second prism surface is 11.5 μm in height from the prism top to 11.5 μm. A plane with an inclination angle of 52.0 degrees (β = 38.0 degrees), and a prism row height of 11.5 μm to the prism bottom is 52.6 degrees, 52.8 degrees from the side close to the prism top. 9 planes of the same width of 5 °, 53.7 °, 55.3 °, 55.3 °, 56.1 °, 56.8 °, 57.5 °, and 58.4 ° and a plane of 60 ° A prism sheet was produced in the same manner as in Example 1 except that the structure was composed of 11 planes (areas 1, 2,... 11 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 row was 1.64%.
[0105]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The 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 the surface light source device is obtained, and the peak luminance ratio, peak angle, and ½ of the peak luminance when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having the brightness of (the full width at half maximum) and the angle having the brightness of half the peak brightness_a−Δθ_b|) Was measured and the results are shown in Table 2.
[0106]
Example 9
As shown in Table 1, the angle (α) formed between the first prism surface constituting the prism array and the normal line is 5 degrees, and the second prism surface is arranged from the top of the prism to the height of the prism array of 12.9 μm. A plane having an inclination angle of 52.0 degrees (β = 38 degrees), and from the side close to the prism top from the height of the prism row from 12.9 μm to the prism bottom, the inclination angles are 52.6 degrees, 52.8 degrees, 53. Nine planes with the same width of 7 degrees, 54.5 degrees, 55.3 degrees, 56.1 degrees, 56.8 degrees, 57.5 degrees, and 58.4 degrees and 11 planes with a 60-degree plane A prism sheet was manufactured in the same manner as in Example 1 except that the area was composed of (areas 1, 2,..., 11 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 row was 1.83%.
[0107]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The 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 the surface light source device is obtained, and the peak luminance ratio, peak angle, and ½ of the peak luminance when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having the brightness of (the full width at half maximum) and the angle having the brightness of half the peak brightness_a−Δθ_b|) Was measured and the results are shown in Table 2.
[0108]
Example 10
As shown in Table 1, the angle (α) formed by the normal line with the first prism surface constituting the prism row is 0.1 degree, and the second prism surface is 14.5 μm in height from the prism top to 14.5 μm. A plane with an inclination angle of 52.0 degrees (β = 38 degrees), and an inclination angle of 52.6 degrees, 52.8 degrees from the side close to the prism top from the prism row height of 14.5 μm to the prism bottom, Nine planes of the same width of 53.7 degrees, 54.5 degrees, 55.3 degrees, 56.1 degrees, 56.8 degrees, 57.5 degrees, and 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 flat sheet was composed of the flat surfaces (areas 1, 2,..., 11 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 row was 2.06%.
[0109]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The 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 the surface light source device is obtained, and the peak luminance ratio, peak angle, and ½ of the peak luminance when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having the brightness of (the full width at half maximum) and the angle having the brightness of half the peak brightness_a−Δθ_b|) Was measured and the results are shown in Table 2.
[0110]
Comparative Example 1
The prism row of the prism sheet is the same as in Example 1 except that the two prism surfaces are both flat and the isosceles triangle section (α = β = 32.7 degrees) having a prism apex angle of 65.4 degrees. Similarly, a surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, the peak luminance is set to 1.00, the peak angle, and 1/2 of the peak luminance. The absolute value (| Δθ) of the difference between the angle having the brightness of (the full width at half maximum) and the angle having the brightness of 1/2 of the peak brightness_a−Δθ_b|) Was measured and the results are shown in Table 2.
[0111]
[Table 1]

[Table 2]

Examples 11-22
The second prism surface constituting the prism row is the same as in Example 1 except that the second prism surface is composed of three planes (areas 1, 2, and 3 from the prism top side) having the inclination angle and the divided height shown in Table 2. Thus, a prism sheet was produced. In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance of the peak luminance_a−Δθ_b|) Was measured and the results are shown in Table 3.
[0112]
Comparative Example 2
A prism is formed in the same manner as in Example 1 except that the entire second prism surface constituting the prism row is a spherical convex surface having a radius of curvature of 452 μm (inclination angle = 57.3 degrees, β = 36.3 degrees). A sheet was produced. In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance of the peak luminance_a−Δθ_b|) Was measured and the results are shown in Table 3.
[0113]
[Table 3]

Examples 23-34
A light guide with one surface being a mat was produced 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 to 1.2 mm. On the mirror surface side of the light guide, a prism row having a prism apex angle of 100 ° and a pitch of 50 μm is made of acrylic ultraviolet curable resin so as to be parallel to a side (short side) having a length of 230 mm of the light guide. Prism layers arranged in a row substantially in parallel were formed. A cold-cathode tube along a side end surface (end surface on the side of 3.5 mm thickness) corresponding to a 310 mm long side (long side) of the light guide with a light source reflector (silver reflective film manufactured by Reiko Co., Ltd.) Covered. Furthermore, a light diffusion reflection film (E60 manufactured by Toray Industries, Inc.) was attached to the other side end face, and a reflection sheet was arranged on the prism array (back face). The above configuration was incorporated into the 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 except that the second prism surface constituting the prism row is composed of three planes (areas 1, 2, and 3 from the prism top side) having the inclination angles and the divided heights shown in Table 3. A prism sheet was produced in the same manner as described above.
[0115]
In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 4 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance of the peak luminance_a−Δθ_b|) Was 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. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 4 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance of the peak luminance_a−Δθ_b|) Was 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. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, this peak luminance is set to 1.00, the peak angle, and 1 / of the peak luminance. The absolute value of the difference between the angle having the luminance of 2 (full width at half maximum) and the angle having the luminance of 1/2 of the peak luminance (| Δθ_a−Δθ_b|) Was measured and the results are shown in Table 4.
[0118]
[Table 4]

Examples 35-39
An angle (α) formed between one prism surface (first prism surface) and a normal line constituting the prism row, and an angle (β) formed between the other prism surface (second prism surface) and a normal line are represented. 4 except that the second prism surface is composed of two planes having the inclination angle and the divided height shown in Table 4 (areas 1 and 2 from the prism top side), as shown in Table 4. A prism sheet was prepared. In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance 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 produced in the same manner as in Example 1 except that the entire second prism surface constituting the prism row was a flat surface having an inclination angle of 55.0 degrees (β = 35.0 degrees). In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 5 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance of the peak luminance_a−Δθ_b|) Was measured and the results are shown in Table 5.
[0120]
[Table 5]

Examples 40-44
An angle (α) formed between one prism surface (first prism surface) and a normal line constituting the prism row, and an angle (β) formed between the other prism surface (second prism surface) and a normal line are represented. Example 23-34 except that the angle shown in FIG. 5 was used, and the second prism surface was composed of two planes (areas 1 and 2 from the prism top side) of the inclination angle and division height shown in Table 5. A prism sheet was produced in the same manner. In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guide of Example 1, the prism ridge line is parallel to the light incident surface of the light guide, and the first prism surface is the light source side. The surface light source device was obtained. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 6 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance 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 produced in the same manner as in Example 1 except that the entire second prism surface constituting the prism row was a flat surface having an inclination angle of 55.0 degrees (β = 35.0 degrees). In the obtained prism sheet, the prism array forming surface faces the light exit surface side of the light guides of Examples 23 to 34, the prism ridges are 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. An outgoing light luminance distribution (in the XZ plane) in a plane perpendicular to both the light incident surface and the light outgoing surface of the surface light source device is obtained, and the peak luminance ratio, peak angle, and peak when Comparative Example 1 is used as a reference. The absolute value (| Δθ) of the difference between the angle having half the luminance (full width at half maximum) and the angle having the half luminance 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 Example 1, 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, and the emitted light intensity distribution (in the XZ plane) ) Is placed on the light exit surface of the light deflection element such that the matte surface having an average inclination angle of 7.27 degrees faces the light polarization element side. Got. Table 7 shows the peak luminance ratio, the full width at half maximum of the luminance, and the visually evaluated quality evaluation results in the emitted light luminance distribution (in the XZ plane) of the manufactured surface light source device with reference to Comparative Example 5.
[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 emitted light luminous intensity distribution (in the XZ plane) is 6 degrees. The surface light source device was the same as in Example 1 except that the light diffusing element was placed on the light exit surface of the light deflecting element so that the matte surface with 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 visually evaluated quality evaluation results in the emitted light luminance distribution (in the XZ plane) of the manufactured surface light source device with reference to Comparative Example 5.
[0124]
Example 47
A large number of lenticular lens rows having a pitch of 30 μm are arranged 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. A luminous intensity distribution (XZ) in which a lens arrangement structure having a maximum inclination angle / minimum inclination angle of 10.4 is formed and a matte surface having an average inclination angle of 0.7 degrees is formed on the other surface. Except that the light diffusing element having an in-plane full width at half maximum of 11.2 degrees is placed such that the lenticular lens array is parallel to the prism array of the light deflecting element and the lens arrangement structure surface faces the light polarizing element side. A surface light source device was obtained in the same manner as in Example 1. Table 7 shows the evaluation results of the peak luminance ratio, the full width at half maximum, and the visually confirmed quality when the emission light luminance distribution (in the XZ plane) of the manufactured surface light source device is based on Comparative Example 5.
[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 having a full width at half maximum of 10.5 degrees is placed so 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. Obtained a surface light source device 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 visually evaluated quality evaluation results in the emitted light luminance distribution (in the XZ plane) of the manufactured surface light source device with reference to Comparative Example 5.
[0126]
Example 49
A maximum average tilt angle of 6.0 degrees, in which a large number of cylindrical lenses having a width of 30 μm and a length of 60 μm formed by etching on one surface of a 125 μm thick polyester film are arranged in the same direction, is the maximum tilt angle. The full width at half maximum of the emitted light intensity distribution (in the XZ plane) is 7 in which a lens arrangement structure having a minimum inclination angle of 6.0 and a mat surface having an average inclination angle of 0.7 degrees is formed on the other surface. Example 1 except that the .0 degree light diffusing element is placed so that the arrangement direction of the cylindrical lenses and the prism array of the light deflection element are substantially parallel and the lens arrangement structure surface faces the light deflection 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 visually evaluated quality evaluation results in the emitted light luminance distribution (in the XZ plane) of the manufactured surface light source device with reference to Comparative Example 5.
[0127]
[Table 7]

[0128]
【The invention's effect】
As described above, according to the present invention, at least one prism surface of the prism array formed on the light incident surface of the light deflection element is composed of a plurality of flat surfaces or convex curved surfaces having different inclination angles, thereby providing a primary light source. Thus, it is possible to provide a light source device that has a high efficiency (a use efficiency of the light amount of the primary light source) for concentrating and emitting light emitted from the light source in a required observation direction.
[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 the shape of prism rows on the light incident surface of the light deflection element of the present invention.
FIG. 3 is an explanatory diagram showing emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 4 is an explanatory diagram showing an emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 5 is an explanatory diagram showing emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 6 is an explanatory diagram showing emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 7 is an explanatory diagram showing emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 8 is an explanatory diagram showing emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 9 is an explanatory diagram showing emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 10 is an explanatory diagram showing an emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 11 is an explanatory diagram showing emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 12 is an explanatory diagram showing an emitted light luminance distribution (in the XZ plane) from each area of the second prism surface (plane) of the light deflection element;
FIG. 13 is an explanatory diagram showing an emitted light luminance distribution (in the XZ plane) from the entire second prism surface (plane) of the light deflection element;
FIG. 14 is an explanatory diagram showing an emitted light luminance distribution (in the XZ plane) from the entire second prism surface of the light deflection element of the present invention.
FIG. 15 is an explanatory diagram of the shape of a prism row on the light incident surface of the light deflection element of the present invention.
FIG. 16 is an explanatory diagram of the shape of the prism row on the light incident surface of the light deflection element of the present invention.
FIG. 17 is an explanatory diagram of the shape of the prism row on the light incident surface of the light deflection element of the present invention.
FIG. 18 is an explanatory diagram of the shape of the prism row on the light incident surface of the light deflection element of the present invention.
FIG. 19 is an explanatory diagram showing various emitted light luminance distributions (in the XZ plane) from the light deflection element;
FIG. 20 is an explanatory diagram of the shape of the prism row on the light incident surface of the light deflection element of the invention.
FIG. 21 is an explanatory diagram of the full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane).
FIG. 22 is an explanatory diagram of a development 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 emitted light from the light deflection element of the light source device of the present invention.
FIG. 25 is a graph showing the luminance distribution (in the XZ plane) of the emitted light from the light deflection element of the light source device of the present invention.
FIG. 26 is an explanatory diagram showing an emitted light intensity distribution (in the XZ plane) of anisotropic diffusivity of the light diffusing element of the present invention.
FIG. 27 is an explanatory diagram of the anisotropic diffusivity of the optical deflection element of the present invention.
FIG. 28 is a schematic view showing a concavo-convex structure of an optical deflecting element having anisotropic diffusivity according to the present invention.
FIG. 29 is a schematic view showing a concavo-convex structure of an optical deflection element having anisotropic diffusivity according to the present invention.
FIG. 30 is a schematic view showing a concavo-convex structure of an optical deflecting element having anisotropic diffusivity according to the present invention.
[Explanation of symbols]
1 Primary light source
2 Light source reflector
3 Light guide
4 Light deflection elements
5 Light reflecting elements
6 Light diffusing element
31 Light incident surface
32 End face
33 Light exit surface
34 Back
41 Light entrance
42 Light emitting surface

Claims (6)

A light incident surface on which light is incident and a light exit surface on the opposite side that emits incident light, and the light incident surface includes prism rows formed of two prism surfaces substantially parallel to each other. A plurality of arranged, at least one prism surface of the prism row is composed of two or three planes having different tilt angles, and a plane located closer to the light exit surface has a greater tilt angle and is the plane closest to the light exit surface. And the difference between the inclination angle of the plane farthest from the light exit surface and 7 degrees or less ,
The ratio (d / P) of the maximum distance (d) to the pitch (P) of the prism row between the plane and the virtual plane connecting the prism top and the prism bottom is 0.4 to 5%. An optical deflection element. A light incident surface on which light is incident, and a light exit surface on the opposite side that emits incident light. The light incident surface includes prism rows formed of two prism surfaces substantially parallel to each other. A plurality of arranged, at least one prism surface of the prism row is composed of 4 or more and 12 or less planes having different inclination angles, and a plane located closer to the light emitting surface has a larger inclination angle and is closest to the light emitting surface. The difference between the inclination angle of the plane and the inclination angle of the plane farthest from the light exit surface is 15 degrees or less,
The ratio (d / P) of the maximum distance (d) to the pitch (P) of the prism row between the plane and the virtual plane connecting the prism top and the prism bottom is 0.4 to 5%. An optical deflection element. Said plane, at least two formed in a region of a height h from the prism apexes, according the height of the elongated prism to claim 2 h / H when the H is equal to or less than 60% Optical deflection element. A light source having a primary light source, a light incident surface on which light emitted from the primary light source is incident, a light emitting surface that guides and emits the incident light, and a light emitting surface side adjacent to the light guide light source device characterized by comprising the light deflector according to any one of claims 1 to 3 described. 5. The light source according to claim 4 , wherein a light diffusing element having a full width at half maximum of 1 to 13 degrees of the emitted light luminous intensity distribution when collimated light is incident is disposed adjacent to the light emitting surface of the light deflecting element. apparatus. On Idemitsu surface of the light deflection element, the light source apparatus according to claim 4 or 5 haze value, characterized in that disposed adjacent the light diffusing element is 8-82%.

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