JP2004006245A - Light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device having a primary light source excellent in light use efficiency, and excellent in a visual field angle characteristic and image quality without degrading a high-luminance characteristic. <P>SOLUTION: This light source device is at least provided with: the primary light source; a light guide body having a light-entering surface for entering light emitted from the primary light source and a light-emitting surface for guiding the entered light to emit it; a light-deflecting element disposed adjacently to the light-emitting surface of the light guide body; and a light-diffusing element disposed adjacently on the light-emitting surface of the light-deflecting element. In the light source device, the full width at the half maximum of the optical outgoing light luminous intensity distribution of the light-diffusing element in entering parallel light-rays is 1-13 degrees. <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が光出射面の法線に対し５０〜８０度の範囲にあり、光入射面と光出射面との双方に垂直なＸＺ面における出射光光度分布（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、高い輝度を有する光源装置を提供することができる。
【００２２】
本発明において、導光体３からの光出射率は次のように定義される。光出射面３３の光入射面３１側の端縁での出射光の光強度（Ｉ_０）と光入射面３１側の端縁から距離Ｌの位置での出射光強度（Ｉ）との関係は、導光体３の厚さ（Ｚ方向寸法）をｔとすると、次の（３）式のような関係を満足する。
【００２３】
【数２】

ここで、定数α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α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。
【００２４】
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。
【００２５】
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。
【００２６】
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、光源装置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、光源装置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゜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゜または１００〜１５０゜の範囲とすることが好ましい。
【００２７】
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、船型状等の種々の形状のものが使用できる。
【００２８】
光偏向素子４は、導光体３の光出射面３３上に配置されている。光偏向素子４の２つの主面４１，４２は互いに対向しており、それぞれ全体としてＸＹ面と平行に位置する。主面４１，４２のうちの一方（導光体３の光出射面３３側に位置する主面）は入光面４１とされており、他方が出光面４２とされている。出光面４２は、導光体３の光出射面３３と平行な平坦面とされている。入光面４１は、多数のＹ方向に延びるプリズム列が互いに平行に配列されたプリズム形成面とされている。プリズム形成面は、隣接するプリズム列の間に比較的幅の狭い平坦部（例えば、プリズム列ピッチと同程度あるいはそれより小さい幅の平坦部）を設けてもよいが、光の利用効率を高める点からは平坦部を設けることなくプリズム列を連続して形成することが好ましい。
【００２９】
図２は、光偏向素子４の入光面４１のプリズム列の形状の説明図である。入光面４１のプリズム列の形状は、次のようにして設定されている。
【００３０】
即ち、プリズム列配列のピッチをＰとして、先ず、断面三角形状の仮想プリズム列Ｉを設定する。この仮想プリズム列Ｉの２つのプリズム面Ｉ−１，Ｉ−２のなす角度（即ち仮想プリズム頂角）をθとする。この仮想プリズム頂角θは、導光体３の光出射面３３から到来する光のＸＺ面内の出射光光度分布のピーク光（傾斜角α）が仮想プリズム列Ｉに入射して仮想プリズム面Ｉ−２により内面全反射された上で、例えば出光面４２の法線方向へと進行するように設定されている。仮想プリズム頂角θは、例えば、光偏向素子４の出光面４２から出射される光のピーク光を出光面４２の法線方向近傍（例えば、法線方向から±１０度の範囲内）へ向ける場合には、５０〜８０度とすることが好ましく、さらに好ましくは５５〜７５度の範囲であり、より好ましくは６０〜７０度の範囲である。また、仮想プリズム列の一方のプリズム面の傾斜角（出光面４２に対してなす角度）は、導光体３からの出射光を光偏向素子４で効率よくの所望の方向に偏向させることから４５度以上とすることが好ましく、さらに好ましくは４７度以上、より好ましくは５０度以上である。
【００３１】
次に、以上のようにして形状が設定された仮想プリズム列Ｉの形状を基準として、その少なくとも一方のプリズム面が凸曲面形状となるように実際のプリズム列の形状を定める。具体的には、次のようにして実際のプリズム列の形状を定めることが好ましい。導光体３の光出射面３３から出射する光の出射光光度分布（ＸＺ面内）のピーク光（傾斜角α）が一次光源１側の隣接仮想プリズム列の頂部をかすめて仮想プリズムＩに入射する仮想光を設定し、この仮想光が仮想プリズム面Ｉ−１を通過する位置をＫ１とし、仮想プリズム面Ｉ−２に到達する位置をＫ２とする。
【００３２】
通常は、位置Ｋ２よりも出光面４２に近い全面を凸曲面形状とすることが好ましい。一方、仮想プリズム列Ｉにおけるプリズム面Ｉ−２の内面全反射位置Ｋ２よりも入光面４１に近い位置（即ち、出光面４２から遠い位置）では、平面形状としてもよく凸曲面形状としてもよい。いずれの場合も、位置Ｋ２の出光面４２側近傍のプリズム面形状を延長するような形状とすることが好ましく、プリズム列の頂部は仮想プリズム列の頂部と一致しなくてもよい。
【００３３】
プリズム列の形状は、仮想プリズム列Ｉにおけるプリズム面Ｉ−２の内面全反射位置Ｋ２よりも出光面４２に近い位置では、その少なくとも一部または全部にプリズム面の傾斜角が仮想プリズム列Ｉのプリズム面Ｉ−２の傾斜角よりも大きな傾斜角をもつような凸曲面形状とすることが好ましい。
【００３４】
これは、図２に示されている寸法ｚ（プリズム列の頂点と仮想プリズム面Ｉ−２の内面反射位置Ｋ２との間のＺ方向距離）が以下の式（４）：
【数３】

で示される値以上のＺ方向位置では、実際のプリズム面が以下の式（５）：
【数４】

で表される仮想プリズム列Ｉのプリズム面Ｉ−２より大きな傾斜角を持つようにすることである（なお、式中ｎはプリズム列の屈折率である。）。
【００３５】
入光面４１のプリズム列の形状をこのように設定することで、光偏向素子４から出射する光の輝度分布角度（半値全幅）を小さくすることができる。その理由は次のとおりである。即ち、仮想プリズム列Ｉにおけるプリズム面Ｉ−２の内面全反射位置Ｋ２よりも出光面４２に近い位置に到達する光は、一次光源側の隣接仮想プリズム列の頂部よりも下側からαより大きな傾斜角で入射する光線の集合である。従って、そのピーク光の方向は、αより大きな傾斜の方向であり、その内面全反射光のピーク光の方向は出光面４２の法線方向から内面全反射の仮想プリズム面に沿った方向の方へと傾斜した方向となる。このような光は出光面４２からの出射光の輝度分布を広げる作用をなす。そこで、特定方向へ光量を集中して出射させるために、仮想プリズム列Ｉにおけるプリズム面Ｉ−２の内面全反射位置Ｋ２よりも出光面４２に近い位置で、その少なくとも一部を実際のプリズム列のプリズム面の傾斜角を、対応する仮想プリズム面の傾斜角より大きくすることで、この領域で実際に内面全反射された光の進行方向を仮想プリズム面での反射光よりも出光面４２の法線方向の方へと移動させるように修正することができ、高輝度化、狭視野化を図ることができる。
【００３６】
以上のような凸曲面形状は、仮想プリズム列Ｉにおけるプリズム面Ｉ−２の内面全反射位置Ｋ２よりも出光面４２に近い位置全体に形成して、内面全反射位置Ｋ２よりも出光面４２から遠い位置では仮想プリズム列のプリズム面Ｉ−２のままの形状とすることもでき、内面全反射位置Ｋ２よりも出光面４２から遠い位置も含めてプリズム面全体を凸曲面形状とすることもできる。このような凸曲面形状としては、仮想プリズム列と少なくとも底部を共通にした曲率半径ｒの凸円柱面形状を例示することができる。
【００３７】
ここで、ピッチＰで規格化した曲率半径ｒの値（ｒ／Ｐ）としては、２〜８０の範囲とすることが好ましく、より好ましくは７〜３０の範囲であり、さらに好ましくは８〜２０の範囲である。これは、ｒ／Ｐをこの範囲とすることによって光偏向素子４の出光面４２から出射する出射光輝度分布（ＸＺ面内）の半値全幅を十分に狭くでき、光源装置としての輝度を十分に高くすることができるためである。例えば、プリズム列のピッチが４０〜６０μｍである場合には、曲率半径ｒは、２５０〜３０００μｍの範囲とすることが好ましく、より好ましくは３５０〜１０００μｍの範囲であり、さらに好ましくは４００〜７００μｍの範囲である。
【００３８】
また、光偏向素子４の各プリズム列の凸曲面形状としては、仮想プリズム列のプリズム面と凸曲面形状のプリズム面の最大距離ｄと前記プリズム列の配列ピッチＰとの比（ｄ／Ｐ）が０．０５〜５％の範囲となるような比較的緩やかな曲面形状とすることが好ましく、より好ましくは０．１〜３％の範囲であり、さらに好ましくは０．２〜２％の範囲である。これは、ｄ／Ｐが５％を超えると光偏向素子４による集光効果が損なわれ光の発散が起こる傾向にあり、光偏向素子４の出光面４２から出射する出射光輝度分布（ＸＺ面内）の半値全幅を十分に狭くできなくなる傾向にあるためである。逆に、ｄ／Ｐが０．０５％未満であると光偏向素子４による集光効果が不十分となる傾向にあり、光偏向素子４の出光面４２から出射する出射光輝度分布（ＸＺ面内）の半値全幅を十分に狭くできなくなる傾向にあるためである。
【００３９】
なお、本発明においては、光偏向素子４の各プリズム列の凸曲面形状は、上記のような曲率半径ｒの断面円弧状のものに限らず、上記のようなｄ／Ｐの範囲内であれば非球面状の凸曲面形状であってもよい。
【００４０】
本発明において、上記のような凸曲面形状のプリズム面は、少なくとも一次光源１から遠い側の面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１を配置する場合の光偏向素子４から出射する光の輝度分布を十分に小さくすることができる。凸曲面形状のプリズム面は、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には、一次光源１に近い側のプリズム面も凸曲面形状とすることがより好ましい。特に、一次光源１に近い側のプリズム面を出光面４２の法線方向に関して仮想プリズム面Ｉ−２に対応する実際のプリズム面と対称的な形状にするのが好ましい。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平面としてもよい。また、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目的でプリズム列の頂部を尖鋭にすること（頂部先端のエッジを明確に形成すること）が必要な場合には、一次光源１に近い側のプリズム面を平面とすることが、双方のプリズム面を凸曲面とした場合に比べて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ることに基づきプリズム列頂部を尖鋭に形成することが容易になることから好ましい。
【００４１】
本発明の光偏向素子においては、所望のプリズム形状を精確に作製し、安定した光学性能を得るとともに、組立作業時や光源装置としての使用時におけるプリズム頂部の摩耗や変形を抑止する目的で、プリズム列の頂部に平坦部あるいは曲面部を形成してもよい。この場合、プリズム頂部に形成する平坦部あるいは曲面部の幅は、３μｍ以下とすることが、光源装置としての輝度の低下やスティキング現象による輝度の不均一パターンの発生を抑止する観点から好ましく、より好ましくは２μｍ以下であり、さらに好ましくは１μｍ以下である。
【００４２】
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ＸＺ面内での出射光光度分布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ＸＺ面内での出射光輝度分布の半値全幅は、５〜２６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、２６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。
【００４３】
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。
【００４４】
このように、本発明においては、導光体３からの出射光光度分布（ＸＺ面内）の半値全幅が大きいものほど狭視野化の効果は大きくなるため、狭視野化の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３との組み合わせで光偏向素子４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３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３との組み合わせで光偏向素子４を使用することが好ましい。
【００４５】
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。
【００４６】
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。
【００４７】
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の出射光光度分布の半値全幅とは、図３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を透過拡散した出射光の光度光度分布におけるピ−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。
【００４８】
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。
【００４９】
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（即ち光源装置と組み合わせて使用される液晶表示素子等の表示素子の有効表示エリアに対応する有効発光領域）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輝度分布（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輝度分布（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。
【００５０】
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４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５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。
【００５１】
（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。
【００５２】
（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。
【００５３】
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。
【００５４】
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。
【００５５】
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。
【００５６】
（３）導光体３の展開長が８ｃｍ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輝度分布（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輝度分布（ＸＺ面内）は、図６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輝度分布（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輝度分布（ＸＺ面内）となる。すなわち、図６の左側の端部近傍では、光源側の出射光輝度分布（ＸＺ面内）が急峻で、中央側の出射光輝度分布（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６の右側の端部近傍では、これと反対の出射光輝度分布（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。
【００５７】
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、出射光光度分布の半値全幅が０．７〜１３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１〜１１度、より好ましくは２〜９度の範囲である。また、ヘイズ値としては、３０〜８２％の範囲であることが好ましく、さらに好ましくは３５〜７５％、より好ましくは４０〜７０％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０．８〜１２度の範囲であることが好ましく、さらに好ましくは１〜８．５度、より好ましくは１．５〜７度の範囲である。また、導光体３の展開長が２２ｃｍを超え２８ｃｍ以下である場合には、光拡散素子６としては、出射光光度分布の半値全幅が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７〜１１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。さらに、導光体３の展開長が８ｃｍを超え２２ｃｍ以下である場合には、光拡散素子６としては、出射光光度分布の半値全幅が０．７〜６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１〜５度、より好ましくは２〜４度の範囲である。また、ヘイズ値としては、３０〜６０％の範囲であることが好ましく、さらに好ましくは３５〜５５％、より好ましくは４０〜５０％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０．８〜６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１．５〜４．５度の範囲である。
【００５８】
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。
【００５９】
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７に示したような非対称的な出射光輝度分布（ＸＺ面内：光拡散素子なし）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（図７にこのような光拡散素子を使用した場合の出射光輝度分布を示した（光拡散素子あり）。）。一方、光拡散素子６として、出射光光度分布の半値全幅が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輝度分布（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、図７に示したように、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。
【００６０】
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８に示したように、ＹＺ面よりもＸＺ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。
【００６１】
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９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輝度分布（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。
【００６２】
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。
【００６３】
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。
【００６４】
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。
【００６５】
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。
【００６６】
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、出射光光度分布の最大半値全幅が３〜１３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。
【００６７】
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。
【００６８】
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。
【００６９】
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。
【００７０】
導光体３の展開長が８ｃｍ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、出射光光度分布の最大半値全幅が０．７〜１３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１〜１１度、より好ましくは２〜９度の範囲である。また、ヘイズ値としては、３０〜８２％の範囲であることが好ましく、さらに好ましくは３５〜７５％、より好ましくは４０〜７０％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０．８〜１５度の範囲であることが好ましく、さらに好ましくは１〜１３度、より好ましくは１．５〜７度の範囲である。また、導光体３の展開長が２２ｃｍを超え２８ｃｍ以下である場合には、光拡散素子６としては、出射光光度分布の半値全幅が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７〜１１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４．５〜１５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。さらに、導光体３の展開長が８ｃｍを超え２２ｃｍ以下である場合には、光拡散素子６としては、出射光光度分布の半値全幅が０．７〜６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１〜５度、より好ましくは２〜４度の範囲である。また、ヘイズ値としては、３０〜６０％の範囲であることが好ましく、さらに好ましくは３５〜５５％、より好ましくは４０〜５０％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０．８〜１０度の範囲であることが好ましく、さらに好ましくは１〜７度、より好ましくは１．５〜５度の範囲である。
【００７１】
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１０〜１２に示したような凹凸構造が挙げられる。図１０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レンズ列を多数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。
【００７２】
図１１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確率ができるだけ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確率ができるだけ高くなるよう配列することが好ましい。
【００７３】
図１２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。
【００７４】
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。
【００７５】
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。
【００７６】
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。
【００７７】
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。
【００７８】
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。
【００７９】
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。
【００８０】
本発明の導光体３、光偏向素子４および光拡散素子６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。
【００８１】
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、光拡散素子６および光反射素子５からなる光源装置の発光面（光拡散素子６の出光面）上に、液晶表示素子を配置することにより、本発明の光源装置をバックライトとした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輝度分布（ＸＺ面内）の光を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１の発光光量の利用効率を高めることができる。
【００８２】
尚、以上の実施形態は光源装置に関して説明したが、本発明はＹ方向寸法が例えば導光体３の厚さの５倍以下であるＸ方向に細長い棒状の光源装置にも適用できる。その場合、一次光源１としてはＬＥＤ等の略点状のものを使用することができる。
【００８３】
【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。
【００８４】
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度〜−８０度まで１度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、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度〜−８０度まで１度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、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。
【００８５】
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度円錐、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。
【００８６】
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（６）によって計算して求めた。
【００８７】
【数５】

光拡散素子の出射光光度分布の半値全幅の測定
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（α）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（Ｍａｘα）と最小半値全幅（Ｍｉｎα）を求めた。
【００８８】
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２１６ｍｍ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１３０度、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）に対向するようにして、長辺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、出射光光度分布（ＸＺ面内）の最大ピーク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。
【００８９】
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、片方のプリズム面の曲率半径が１０００μｍである凸曲面形状で、他方のプリズム面が平面形状で、ピッチ５０μｍの多数のプリズム列が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。この際、仮想プリズム列としては、プリズムシートからの出射光がその出光面の法線方向となるように、ピッチ５０μｍで、頂角６５．４度の断面二等辺三角形のプリズム列を設定した。
【００９０】
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列の稜線が平行でありプリズム斜面は直線面が向くように載置した。また、一方の表面が平均傾斜角度３．３７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、光出射光光度分布の半値全幅が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３．３７度のマット面が光偏向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ピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９１】
実施例２
プリズム列を構成する光源に近い側のプリズム面を平面とし、光源から遠い側のプリズム面を、プリズム列の高さ１６μｍ以上の面（プリズム列頂部近傍の面）を平面とし、高さ１６μｍ以下の面（プリズム列底部近傍の面）を曲率半径４００μｍである凸曲面形状（平面と凸曲面の境界とプリズム面の底部を結ぶ面のプリズムシート法線に対する傾斜角を３０度とした）とした以外は実施例１と同様にして、ピッチ５０μｍで、頂角６５．４度のプリズム列が一方の表面に形成されたプリズムシートを作製した。このプリズムシートを実施例１で得られた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になるように載置した。なお、この場合の仮想プリズム面の位置Ｋ２は、プリズム列の高さ２７μｍの位置となる。また、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、光出射光光度分布の半値全幅が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向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ピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９２】
実施例３
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、光出射光光度分布の半値全幅が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向素子側に向くように載置した以外は、実施例２と同様にして面光源装置を得た。作製した面光源装置のピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９３】
実施例４
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光出射光光度分布の半値全幅が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向素子側に向くように載置した以外は、実施例２と同様にして面光源装置を得た。作製した面光源装置のピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９４】
実施例５
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光出射光光度分布の半値全幅が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２と同様にして、面光源装置を得た。作製した面光源装置のピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９５】
実施例６
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光出射光光度分布の半値全幅が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２と同様にして、面光源装置を得た。作製した面光源装置のピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９６】
比較例１
プリズムシートとして両方のプリズム面が平面であるものを使用し、光拡散素子を使用しなかった以外は実施例１と同様にして面光源装置を得た。作製した面光源装置のピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９７】
比較例２
光拡散素子を使用しなかった以外は実施例１と同様にして面光源装置を得た。作製した面光源装置のピーク輝度の強度比と冷陰極管に垂直方向の面内での出射光輝度分布（ＸＺ面内）における半値全幅を求め、その結果を表１に示した。
【００９８】
【表１】

【００９９】
【発明の効果】
以上説明したように、本発明においては、光偏向素子の出光面上に特定の光拡散性を有する光拡散素子を配置することにより、一次光源の光利用効率に優れた高輝度特性を損なうことなく、視野角特性および画像品位に優れた光源装置を提供できる。
【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】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】光拡散素子の出射光光度分布の半値全幅の説明図である。
【図４】光源装置の展開長の説明図である。
【図５】光源装置の展開長の説明図である。
【図６】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７】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８】本発明の光拡散素子の異方拡散性の出射光光度分布を示す説明図である。
【図９】本発明の光偏向素子の異方拡散性の説明図である。
【図１０】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１１】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１２】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
Ｉ　　仮想プリズム列
Ｉ−１，Ｉ−２　　仮想プリズム列のプリズム面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an edge light type light source device constituting a liquid crystal display device or the like used as a display unit in a notebook computer, a liquid crystal television, a mobile phone, a portable information terminal, or the like.
[0002]
[Prior art]
2. Description of the Related Art In recent years, color liquid crystal display devices have been widely used in various fields as monitors of portable notebook personal computers and personal computers, or as display units of liquid crystal televisions and video-integrated liquid crystal televisions, mobile phones, personal digital assistants, and the like. I have. In addition, with an increase in information processing volume, diversification of needs, multimedia support, and the like, a large screen and high definition of a liquid crystal display device have been actively promoted.
[0003]
The liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, there are a direct type backlight unit in which a light source is disposed immediately below a liquid crystal display element unit and an edge light type backlight unit in which a light source is disposed so as to face a side end surface of a light guide. The edge light method is often used from the viewpoint of the realization.
[0004]
By the way, in recent years, in a liquid crystal display device used as a display unit of a mobile phone, for example, which is a display device having a relatively small screen size and a viewing direction range is relatively narrow, from the viewpoint of reducing power consumption, an edge light type is used. In order to effectively use the amount of light emitted from the primary light source, a backlight unit that reduces the spread angle of a light beam emitted from a screen as much as possible and emits light concentrated on a required angle range has been used. I have.
[0005]
The present invention is directed to a display device in which the range of observation directions is limited as described above, which is a light source device that concentrates light emission in a relatively narrow range in order to increase the use efficiency of the light amount of the primary light source and reduce power consumption. In Japanese Patent Application Laid-Open Publication No. 2002-143515 (Patent Document 1), it has been proposed to use a prism sheet having prism forming surfaces on both sides adjacent to a light exit surface of a light guide.
[0006]
[Patent Document 1]
JP-A-2002-143515
[0007]
[Problems to be solved by the invention]
In this double-sided prism sheet, a plurality of prism rows parallel to each other are formed on each of a light incident surface, which is one surface, and a light emitting surface, which is the other surface. And the prism rows are arranged at corresponding positions. Thereby, the light emitted from the light exit surface of the prism sheet has a peak of the emitted light in a direction inclined with respect to the light exit surface, and is emitted in an appropriate angle range. The light enters from the prism surface, is reflected internally by the other prism surface, and is refracted by the prism on the light exit surface, so that light is concentrated and emitted in a relatively narrow required direction.
[0008]
According to this light source device, concentrated emission in a narrow angle range is possible, but a plurality of prism arrays parallel to each other on both sides as a prism sheet used as a light deflecting element, and a prism array on a light entrance surface and a light exit surface. It is necessary to match the directions and arrange the prism rows at corresponding positions, which complicates the molding.
[0009]
In addition, since light emitted concentrated in such a narrow angle range causes strong glare, there is also a problem that the quality of the backlight is inferior. Further, such a light source device having a narrow viewing angle has no problem with a small backlight, but is used as a backlight for a liquid crystal display device of 4 inches or more, particularly a liquid crystal display device for a notebook personal computer of about 12 to 15 inches. The backlight used has a problem that the viewing angle is narrow and visibility is poor.
[0010]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a light source device having excellent viewing angle characteristics and high quality as a certificate for image formation without impairing high luminance characteristics excellent in light use efficiency of a primary light source.
[0011]
[Means for Solving the Problems]
That is, the light source device of the present invention includes a primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident, and a light exit surface for guiding and emitting the incident light; A light source device comprising at least a light deflecting element disposed adjacent to a light exit surface of a body, and a light diffusing element disposed adjacent to a light exit surface of the light deflecting element, wherein the light deflecting element is a light guide. It has a light entrance surface located opposite to the light exit surface of the body and a light exit surface on the opposite side, and the light entrance surface is formed with a plurality of prism rows arranged in parallel with each other, The prism array has two prism surfaces, and at least one of the prism surfaces is such that a peak light in an emission light distribution of light emitted from a light emission surface of the light guide enters from one virtual prism surface. Then, the inner surface is totally reflected by the other virtual prism surface, and a desired In the case of assuming a plurality of virtual prism rows having a triangular cross-section arranged at the same pitch as the array pitch of the prism rows of the light deflecting element, a convex curved surface shape is formed based on the shape of the virtual prism row. The light diffusing element is characterized in that the full width at half maximum of the luminous intensity distribution of the emitted light when parallel light is incident is 1 to 13 degrees.
[0012]
Further, the light source device of the present invention comprises: a primary light source; a light guide having a light incident surface on which light emitted from the primary light source is incident; and a light exit surface for guiding and exiting the incident light; A light source device comprising at least a light deflecting element disposed adjacent to a light exit surface of a body, and a light diffusing element disposed adjacent to a light exit surface of the light deflecting element, wherein the light deflecting element is a light guide. It has a light entrance surface located opposite to the light exit surface of the body and a light exit surface on the opposite side, and the light entrance surface is formed with a plurality of prism rows arranged in parallel with each other, The prism array has two prism surfaces, and at least one of the prism surfaces is such that a peak light in an emission light distribution of light emitted from a light emission surface of the light guide enters from one virtual prism surface. And the inner surface is totally reflected by the other virtual prism surface, and a desired direction from the light exit surface. When assuming a plurality of virtual prism rows that emit light and are arranged at the same pitch as the prism row of the light deflecting element and whose cross section is triangular, a convex curved surface is formed based on the shape of the virtual prism row. The full width at half maximum of the luminance distribution of light emitted from the light deflecting element is 19 to 26 degrees, and the full width at half maximum of the luminance distribution of light emitted from the light diffusion element when parallel light is incident is 1 to 8 degrees. It is characterized by the following.
[0013]
Further, the light source device of the present invention has a primary light source, two light incident surfaces which are arranged to face each other to receive the light emitted from the primary light source, and a light emitting surface which guides and emits the incident light. A light guide having a development length of more than 8 cm and not more than 28 cm; a light deflecting element disposed adjacent to a light exit surface of the light guide; and a light diffusion disposed adjacent to a light exit surface of the light deflecting element. A light deflecting element having at least a light incident surface facing the light exit surface of the light guide and a light exit surface opposite to the light exit surface. A plurality of prism rows arranged in parallel to each other are formed on the light surface, and the prism rows have two prism faces, and at least one of the prism faces is located at a distance from the light exit surface of the light guide. The peak light in the emission light distribution of the emitted light enters from one virtual prism surface. A plurality of virtual prism rows, which are totally internally reflected by the other virtual prism face, are emitted in a desired direction from the light exit surface, and are arranged at the same pitch as the array pitch of the prism rows of the light deflecting element and have a triangular cross section. Is assumed, the light diffusing element has a convex curved surface shape based on the shape of the virtual prism row, and the full width at half maximum of the luminous intensity distribution of light emitted from the light diffusing element is 0.7 to 6 degrees when parallel light is incident. It is characterized by the following.
[0014]
Further, the light source device of the present invention comprises: a primary light source; a light guide having a light incident surface on which light emitted from the primary light source is incident; and a light exit surface for guiding and exiting the incident light; A light source device comprising at least a light deflecting element arranged adjacent to a light emitting surface of a body and a light diffusing element arranged adjacent to a light emitting surface of the light deflecting element, wherein the light diffusing element emits parallel light. It is characterized in that the full width at half maximum of the luminous intensity distribution of the emitted light upon incidence has anisotropy.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is a schematic perspective view showing one embodiment of a planar light source device (surface light source device) according to the present invention. As shown in FIG. 1, the light source device of the present invention includes a light guide 3 in which at least one side end surface is a light incident surface 31 and one surface substantially orthogonal to the light incident surface 31 is a light exit surface 33. A primary light source 1 disposed opposite the light incident surface 31 of the light guide 3 and covered by the light source reflector 2; a light deflecting element 4 disposed on the light exit surface of the light guide 3; 4 includes a light diffusing element 6 disposed on the light exit surface 42 and a light reflecting element 5 disposed opposite the back surface 34 of the light exit surface 33 of the light guide 3.
[0017]
The light guide 3 is arranged parallel to the XY plane, and has a rectangular plate shape as a whole. The light guide 3 has four side end surfaces, of which at least one side end surface of a pair of side end surfaces parallel to the YZ plane is a light incident surface 31. The light incident surface 31 is arranged so as to face the light source 1, and light emitted from the light source 1 enters the light guide 3 from the light incident surface 31. In the present invention, for example, a light source may be arranged on another side end surface such as the side end surface 32 facing the light incident surface 31.
[0018]
The two main surfaces of the light guide 3 that are substantially perpendicular to the light incident surface 31 are located substantially parallel to the XY plane, respectively, and one of the surfaces (the upper surface in the figure) is a light emitting surface 33. At least one of the light emitting surface 33 and the rear surface 34 has a rough directional light emitting function unit and a number of lens arrays such as a prism array, a lenticular lens array, and a V-shaped groove. By providing a directional light emitting function or the like having a lens surface formed in parallel substantially parallel to the light guide 31, the light incident from the light incident surface 31 is guided from the light emitting surface 33 while being guided through the light guide 3. Directional light is emitted within a plane (XZ plane) orthogonal to the entrance plane 31 and the light exit plane 33. The angle between the direction of the peak of the luminous intensity distribution of the emitted light in the XZ plane distribution and the light emitting surface 33 is defined as α. The angle α is, for example, 10 to 40 degrees, and the full width at half maximum of the emitted light luminous intensity distribution is, for example, 10 to 40 degrees.
[0019]
The rough surface and the lens array formed on the surface of the light guide 3 should have an average inclination angle θa according to ISO 4287 / 1-1984 in the range of 0.5 to 15 degrees, so that the luminance in the light exit surface 33 can be improved. Is preferable from the viewpoint of achieving uniformity. The average inclination angle θa is more preferably in the range of 1 to 12 degrees, and more preferably in the range of 1.5 to 11 degrees. It is preferable that the optimum range of the average inclination angle θa is set by the ratio (L / t) of the thickness (t) of the light guide 3 and the length (L) in the direction in which the incident light propagates. That is, when the light guide 3 having an L / t of about 20 to 200 is used, the average inclination angle θa is preferably set to 0.5 to 7.5 degrees, and more preferably 1 to 5 degrees. Range, more preferably 1.5 to 4 degrees. When the light guide 3 having an L / t of about 20 or less is used, the average inclination angle θa is preferably set to 7 to 12 degrees, more preferably 8 to 11 degrees.
[0020]
The average inclination angle θa of the rough surface formed on the light guide 3 is obtained by measuring the rough surface shape using a stylus type surface roughness meter according to ISO 4287 / 1-1984, and setting the coordinates in the measurement direction as x. It can be obtained from the obtained inclination function f (x) using the following equations (1) and (2). Here, L is the measured length, and Δa is the tangent of the average inclination angle θa.
[0021]
(Equation 1)

Further, the light guide 3 preferably has a light emission rate in the range of 0.5 to 5%, more preferably 1 to 3%. This is because when the light emission rate is smaller than 0.5%, the amount of light emitted from the light guide 3 tends to be small and sufficient luminance cannot be obtained. When the light emission rate is larger than 5%, a large amount near the light source 1 is large. Is emitted, and the light in the X direction in the light exit surface 33 is significantly attenuated, and the uniformity of luminance on the light exit surface 33 tends to decrease. By setting the light emission rate of the light guide 3 to 0.5 to 5% as described above, the 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 adjusted to the light emission surface. The full width at half maximum of the emitted light luminous intensity distribution (in the XZ plane) in the XZ plane perpendicular to both the light incident surface and the light emitting surface is in the range of 50 to 80 degrees with respect to the normal line, and is 10 to 40 degrees. Light with high directivity and emission characteristics can be emitted from the light guide 3, the emission direction can be efficiently deflected by the light deflection element 4, and a light source device with high luminance can be provided. .
[0022]
In the present invention, the light emission rate from the light guide 3 is defined as follows. At the edge of the light exit surface 33 on the light incident surface 31 side, the light intensity (I₀) And the emitted light intensity (I) at a position at a distance L from the edge on the light incident surface 31 side, assuming that the thickness (dimension in the Z direction) of the light guide 3 is t, the following (3) Satisfies the relationship as in the equation.
[0023]
(Equation 2)

Here, the constant α is the light emission rate, and the light guide 3 per unit length (length corresponding to the light guide thickness t) in the X direction orthogonal to the light incidence surface 31 on the light emission surface 33. Out of the light. The light emission rate α can be obtained from the gradient by plotting the logarithm of the light intensity of the light emitted from the light emission surface 23 on the vertical axis and (L / t) on the horizontal axis.
[0024]
In addition, the other main surface to which the directional light emitting function unit is not provided is provided with a light for controlling the directivity of light emitted from the light guide 3 on a plane (YZ plane) parallel to the light source 1. It is preferable to form a lens surface in which a number of lens arrays extending in a direction (X direction) substantially perpendicular to the incident surface 31 are arranged. In the embodiment shown in FIG. 1, a rough surface is formed on the light exit surface 33, and a lens surface formed of an array of a large number of lens rows extending substantially perpendicularly to the light incident surface 31 (X direction) on the back surface 34. Is formed. In the present invention, contrary to the embodiment shown in FIG. 1, a lens surface may be formed on the light emitting surface 33 and the back surface 34 may be roughened.
[0025]
As shown in FIG. 1, when a lens array is formed on the back surface 34 or the light emitting surface 33 of the light guide 3, the lens array includes a prism array extending substantially in the X direction, a lenticular lens array, and a V-shaped groove. However, it is preferable to form a prism array having a substantially triangular cross section in the YZ directions.
[0026]
In the present invention, when a prism row is formed as a lens row formed on the light guide 3, it is preferable that the apex angle be in the range of 70 to 150 degrees. This is because, by setting the apex angle in this range, the light emitted from the light guide 3 can be sufficiently collected, and the luminance of the light source device can be sufficiently improved. In other words, by setting the prism apex angle within this range, the converged outgoing light having a full width at half maximum of 35 to 65 degrees on the plane perpendicular to the XZ plane including the peak light in the outgoing light luminous intensity distribution is 35 to 65 degrees. Can be emitted, and the luminance of the light source device can be improved. When the prism array is formed on the light exit surface 33, the apex angle is preferably in the range of 80 to 100 °, and when the prism array is formed on the back surface 34, the apex angle is 70 to 80 °. Alternatively, the angle is preferably in the range of 100 to 150 °.
[0027]
In the present invention, instead of forming the light emitting function portion on the light emitting surface 33 or the back surface 34 as described above or in combination with the light emitting function portion, the light diffusing fine particles are mixed and dispersed inside the light guide. It may have a directional light emission function. Further, the light guide 3 is not limited to the shape as shown in FIG. 1, and various shapes such as a wedge shape and a boat shape can be used.
[0028]
The light deflecting element 4 is arranged on the light exit surface 33 of the light guide 3. The two main surfaces 41 and 42 of the light deflecting element 4 are opposed to each other, and are respectively positioned as a whole in parallel with the XY plane. One of the principal surfaces 41 and 42 (the principal surface located on the light exit surface 33 side of the light guide 3) is a light entrance surface 41, and the other is a light exit surface 42. The light exit surface 42 is a flat surface parallel to the light exit surface 33 of the light guide 3. The light incident surface 41 is a prism forming surface in which a number of prism rows extending in the Y direction are arranged in parallel with each other. The prism forming surface may have a flat portion having a relatively narrow width (for example, a flat portion having a width approximately equal to or smaller than the pitch of the prism rows) between adjacent prism rows, but increases the light use efficiency. From the point of view, it is preferable to form the prism rows continuously without providing a flat portion.
[0029]
FIG. 2 is an explanatory diagram of the shape of the prism array on the light entrance surface 41 of the light deflecting element 4. The shape of the prism array on the light incident surface 41 is set as follows.
[0030]
That is, assuming that the pitch of the prism array is P, a virtual prism array I having a triangular cross section is first set. The angle between the two prism surfaces I-1 and I-2 of the virtual prism row I (that is, the virtual prism apex angle) is defined as θ. The virtual prism apex angle θ is such that the peak light (inclination angle α) of the luminous intensity distribution in the XZ plane of the light arriving from the light exit surface 33 of the light guide 3 is incident on the virtual prism array I and the virtual prism surface It is set so that, after being totally reflected on the inner surface by I-2, the light travels in the normal direction of the light exit surface 42, for example. The virtual prism vertex angle θ directs, for example, the peak light of the light emitted from the light exit surface 42 of the light deflecting element 4 to the vicinity of the normal direction of the light exit surface 42 (for example, within a range of ± 10 degrees from the normal direction). In such a case, the angle is preferably 50 to 80 degrees, more preferably 55 to 75 degrees, and still more preferably 60 to 70 degrees. The inclination angle of one of the prism surfaces of the virtual prism array (the angle formed with respect to the light emitting surface 42) is determined because the light deflecting element 4 efficiently deflects the light emitted from the light guide 3 to a desired direction. The angle is preferably 45 degrees or more, more preferably 47 degrees or more, and even more preferably 50 degrees or more.
[0031]
Next, based on the shape of the virtual prism array I whose shape has been set as described above, the actual prism array shape is determined so that at least one of the prism surfaces has a convex curved surface shape. Specifically, it is preferable to determine the actual shape of the prism array as follows. The peak light (inclination angle α) of the luminous intensity distribution (in the XZ plane) of the light emitted from the light exit surface 33 of the light guide 3 grazes the top of the adjacent virtual prism row on the primary light source 1 side to the virtual prism I. The virtual light to be incident is set, the position at which this virtual light passes through the virtual prism surface I-1 is K1, and the position at which the virtual light reaches the virtual prism surface I-2 is K2.
[0032]
Normally, it is preferable that the entire surface closer to the light emitting surface 42 than the position K2 has a convex curved surface shape. On the other hand, at a position closer to the light entrance surface 41 than the total internal reflection position K2 of the prism surface I-2 in the virtual prism array I (that is, a position farther from the light exit surface 42), a planar shape or a convex curved surface shape may be used. . In any case, it is preferable that the shape of the prism surface in the vicinity of the light exit surface 42 at the position K2 be extended so that the top of the prism array does not need to coincide with the top of the virtual prism array.
[0033]
At a position closer to the light emitting surface 42 than the total internal reflection position K2 of the prism surface I-2 in the virtual prism array I, the inclination angle of the prism surface of the virtual prism array I is at least partially or entirely. It is preferable to have a convex curved shape having an inclination angle larger than the inclination angle of the prism surface I-2.
[0034]
This is because the dimension z (distance in the Z direction between the vertex of the prism array and the inner surface reflection position K2 of the virtual prism surface I-2) shown in FIG.
(Equation 3)

At a position in the Z direction equal to or greater than the value indicated by the following expression, the actual prism surface has the following formula (5):
(Equation 4)

(Where n is the refractive index of the prism array).
[0035]
By setting the shape of the prism array on the light incident surface 41 in this way, the luminance distribution angle (full width at half maximum) of the light emitted from the light deflecting element 4 can be reduced. The reason is as follows. That is, light reaching the position closer to the light exit surface 42 than the total internal reflection position K2 of the prism surface I-2 in the virtual prism array I is larger than α from below the top of the adjacent virtual prism array on the primary light source side. It is a set of light rays incident at an oblique angle. Therefore, the direction of the peak light is a direction of inclination larger than α, and the direction of the peak light of the total internal reflection light is from the normal direction of the light exit surface 42 to the direction along the virtual prism surface of the total internal reflection. It becomes a direction inclined toward. Such light acts to broaden the luminance distribution of the light emitted from the light exit surface 42. Therefore, in order to concentrate and emit the light amount in a specific direction, at least a part of the virtual prism array I is closer to the light exit surface 42 than the total internal reflection position K2 of the prism surface I-2 in the actual prism array I. The inclination angle of the prism surface is made larger than the inclination angle of the corresponding virtual prism surface, so that the traveling direction of the light that has been totally internally reflected in this region is closer to the light exit surface 42 than the reflected light on the virtual prism surface. Correction can be made so as to move in the normal direction, and higher luminance and narrower visual field can be achieved.
[0036]
The above-mentioned convex curved surface shape is formed at an entire position closer to the light exit surface 42 than the total internal reflection position K2 of the prism surface I-2 in the virtual prism array I, and is closer to the light output surface 42 than the internal total reflection position K2. At a distant position, the prism surface I-2 of the virtual prism array can be kept as it is, and the entire prism surface, including a position farther from the light exit surface 42 than the internal total reflection position K2, can be formed into a convex curved surface shape. . An example of such a convex curved surface shape is a convex cylindrical surface shape having a radius of curvature r having at least a bottom portion common to the virtual prism array.
[0037]
Here, the value (r / P) of the radius of curvature r standardized by the pitch P is preferably in the range of 2 to 80, more preferably in the range of 7 to 30, and still more preferably in the range of 8 to 20. Range. This is because by setting r / P within this range, the full width at half maximum of the luminance distribution (in the XZ plane) of the emitted light emitted from the light exit surface 42 of the light deflecting element 4 can be sufficiently reduced, and the luminance of the light source device can be sufficiently increased. This is because it can be made higher. For example, when the pitch of the prism rows is 40 to 60 μm, the radius of curvature r is preferably in the range of 250 to 3000 μm, more preferably in the range of 350 to 1000 μm, and still more preferably in the range of 400 to 700 μm. Range.
[0038]
The convex curved shape of each prism array of the light deflecting element 4 is a ratio (d / P) of the maximum distance d between the prism surface of the virtual prism array and the convex curved prism surface and the array pitch P of the prism array. Is preferably in the range of 0.05 to 5%, more preferably in the range of 0.1 to 3%, and still more preferably in the range of 0.2 to 2%. It is. This is because if d / P exceeds 5%, the light condensing effect of the light deflecting element 4 is impaired, and light tends to diverge. This is because there is a tendency that the full width at half maximum of (in) cannot be sufficiently reduced. Conversely, if d / P is less than 0.05%, the light-condensing effect of the light deflecting element 4 tends to be insufficient, and the luminance distribution of the light emitted from the light-emitting surface 42 of the light deflecting element 4 (XZ plane) This is because there is a tendency that the full width at half maximum of (in) cannot be sufficiently reduced.
[0039]
In the present invention, the shape of the convex curved surface of each prism row of the light deflecting element 4 is not limited to the above-mentioned arcuate cross-section having a radius of curvature r, but may be in the range of d / P as described above. For example, an aspherical convex curved surface shape may be used.
[0040]
In the present invention, it is preferable that the prism surface having the above-mentioned convex curved surface is formed at least on the surface far from the primary light source 1. According to this, the luminance distribution of the light emitted from the light deflecting element 4 when the primary light source 1 is also arranged on the end face 32 of the light guide 3 can be sufficiently reduced. For example, the convex curved prism surface is close to the primary light source 1 when the ratio of the light propagating through the light guide 3 to the end surface 32 opposite to the light incident surface 31 and returning is relatively high. More preferably, the prism surface on the side also has a convex curved surface shape. In particular, it is preferable that the prism surface on the side close to the primary light source 1 has a shape symmetrical to the actual prism surface corresponding to the virtual prism surface I-2 with respect to the normal direction of the light emitting surface 42. On the other hand, when the rate at which light propagating through the light guide 3 is reflected by the end face 32 opposite to the light incident surface 31 and returned is relatively low, the prism surface closer to the primary light source 1 may be flat. Good. Further, it is necessary to sharpen the top of the prism array (clearly form the edge of the top end) in order to suppress the occurrence of the sticking phenomenon when the light deflecting element 4 is mounted on the light guide 3. In this case, making the prism surface on the side closer to the primary light source 1 a flat surface makes it possible to reduce the shape transfer surface shape of the molding die member for forming the prism rows as compared with the case where both prism surfaces are made into a convex curved surface. It is preferable because it is easy to form the top of the prism row sharply based on the fact that accurate formation becomes possible.
[0041]
In the light deflecting element of the present invention, for the purpose of accurately producing a desired prism shape, obtaining stable optical performance, and suppressing wear and deformation of the prism top during assembly work or when used as a light source device, A flat portion or a curved surface portion may be formed at the top of the prism row. In this case, the width of the flat portion or the curved surface portion formed on the prism apex is preferably 3 μm or less, from the viewpoint of suppressing a decrease in luminance as the light source device and the generation of a non-uniform luminance pattern due to a sticking phenomenon. It is more preferably 2 μm or less, and further preferably 1 μm or less.
[0042]
As described above, the light deflecting element 4 as described above is mounted on the light exit surface 33 of the light guide 3 such that the prism row forming surface is on the light incident surface side, whereby the light guide 3 The luminous intensity distribution of the directional outgoing light emitted from the light emitting surface 33 in the XZ plane can be narrowed, and high brightness and a narrow field of view of the light source device can be achieved. The full width at half maximum of the emission light luminance distribution in the XZ plane of the light emitted from the light deflection element 4 is preferably in the range of 5 to 26 degrees, more preferably in the range of 10 to 20 degrees, More preferably, it is in the range of 12 to 18 degrees. This is because, by setting the full width at half maximum of the emitted light luminance distribution (in the XZ plane) to 5 degrees or more, it is possible to prevent the visibility of an image or the like due to an extremely narrow visual field, and to set the luminance to 26 degrees or less to obtain high luminance. This is because it is possible to reduce the size and the field of view.
[0043]
Since the narrowing of the visual field of the light deflecting element 4 according to the present invention is affected by the extent (full width at half maximum) of the luminous intensity distribution (in the XZ plane) emitted from the light exit surface 33 of the light guide 3, The ratio of the luminous intensity distribution (in the XZ plane) of the light emission distribution 33 (in the XZ plane) of the luminous intensity distribution (in the XZ plane) of the light guide body 3 having the full width at half maximum A of the emission light luminance distribution (in the XZ plane) from the light exit surface 42 is also It depends on the full width at half maximum B of the luminous intensity distribution (in the XZ plane) of the light emitted from the light body 3. For example, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) emitted from the light guide 3 is less than 26 degrees, the full width at half maximum A is preferably in the range of 30 to 95% of the full width at half maximum B, It is more preferably in the range of 30 to 80%, and still more preferably in the range of 30 to 70%. Further, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) emitted from the light guide 3 is 26 degrees or more, the full width at half maximum A is preferably in the range of 30 to 80% of the full width at half maximum B, It is more preferably in the range of 30 to 70%, and still more preferably in the range of 30 to 60%. In particular, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) emitted from the light guide 3 is 26 to 36 degrees, the full width at half maximum A is preferably in the range of 30 to 80% of the full width at half maximum B. , More preferably in the range of 30 to 70%, and still more preferably in the range of 30 to 60%. Further, when the full width at half maximum B of the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 exceeds 36 degrees, the full width at half maximum A is preferably in the range of 30 to 70% of the full width at half maximum B, It is more preferably in the range of 30 to 60%, and still more preferably in the range of 30 to 50%.
[0044]
As described above, in the present invention, as the full width at half maximum of the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 is larger, the effect of narrowing the visual field is greater. It is preferable to use the light deflecting element 4 in combination with the light guide 3 having a full width at half maximum B of the luminous intensity distribution (in the XZ plane) of 26 degrees or more, and more preferably a light guide whose full width at half maximum B exceeds 36 degrees. Body 3. When the full width at half maximum of the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 is small, the effect of narrowing the visual field is reduced, but the luminous intensity distribution (in the XZ plane) of the light emitted from the light guide 3 is reduced. The smaller the full width at half maximum is, the higher the luminance can be. Therefore, in terms of higher luminance, a combination with the light guide 3 in which the full width at half maximum B of the luminous intensity distribution (in the XZ plane) of the emitted light is less than 26 degrees. It is preferable to use the light deflecting element 4.
[0045]
Further, in the present invention, in the light source device having a narrow field of view and a high luminance by the light deflecting element 4 as described above, the range of the visual field can be appropriately controlled according to the purpose without causing a reduction in the luminance as much as possible. Next, the light diffusing element 6 is arranged adjacent to the light exit surface of the light deflecting element 4. Further, in the present invention, by arranging the light diffusing element 6 in this way, it is possible to suppress glare, uneven brightness, and the like that cause deterioration in quality, thereby improving the quality.
[0046]
The light diffusing element 6 may be integrated with the light deflecting element 4 on the light emitting surface side of the light deflecting element 4, or the light diffusing elements 6 may be individually mounted on the light emitting surface side of the light deflecting element 4. However, it is preferable to dispose the light diffusing elements 6 individually. When the light diffusing elements 6 are individually mounted, an uneven structure is provided on the surface of the light diffusing element 6 adjacent to the light deflecting element 4 in order to prevent sticking with the light deflecting element 4. Is preferred. Similarly, it is necessary to consider the sticking between the light emitting element 6 and the liquid crystal display element disposed on the light emitting element 6. Is preferred. When the uneven structure is provided only for the purpose of preventing sticking, it is preferable that the average inclination angle be 0.7 degrees or more, more preferably 1 degree or more, and more preferably 1 degree or more. 0.5 degrees or more.
[0047]
In the present invention, it is necessary to use the light diffusing element 6 having a light diffusing property for appropriately diffusing the light emitted from the light deflecting element 4 in consideration of the balance between the luminance characteristic, the visibility and the quality. That is, when the light diffusing property of the light diffusing element 6 is low, it is difficult to sufficiently widen the viewing angle, and the visibility is reduced, and the effect of improving the quality tends to be insufficient. If it is too high, the effect of narrowing the field of view by the light deflecting element 4 will be impaired, and the total light transmittance will also decrease, tending to lower the luminance. Therefore, as the light diffusing element 6 of the present invention, an element having a full width at half maximum of the luminous intensity distribution of emitted light when parallel light is incident within a range of 1 to 13 degrees is used. The full width at half maximum of the light diffusion element 6 is preferably in the range of 3 to 11 degrees, and more preferably in the range of 4 to 8.5 degrees. In the present invention, the full width at half maximum of the luminous intensity distribution of the light emitted from the light diffusing element 6 indicates, as shown in FIG. Then, the full width angle (Δθ) of the divergence angle at half value with respect to the peak value in the luminous intensity distribution of the outgoing light transmitted and diffused through the light diffusing element 6_H).
[0048]
Such light diffusion characteristics can be imparted by mixing a light diffusing agent into the light diffusing element 6 or imparting an uneven structure to at least one surface of the light diffusing element 6. The degree of the concavo-convex structure formed on the surface is different between the case where it is formed on one surface of the light diffusion element 6 and the case where it is formed on both surfaces. When an uneven structure is formed on one surface of the light diffusing element 6, the average inclination angle is preferably in the range of 0.8 to 12 degrees, more preferably 3.5 to 7 degrees, and more preferably 3.5 to 7 degrees. Preferably it is 4 to 6.5 degrees. When the uneven structure is formed on both surfaces of the light diffusing element 6, the average inclination angle of the uneven structure formed on one surface is preferably in the range of 0.8 to 6 degrees, more preferably 2 to 6. 4 degrees, more preferably 2.5 to 4 degrees. In this case, in order to suppress a decrease in the total light transmittance of the light diffusion element 6, it is preferable that the average inclination angle on the incident surface side of the light diffusion element 6 be larger than the average inclination angle on the emission surface side. Further, the haze value of the light diffusing element 6 is preferably in the range of 8 to 82% from the viewpoint of improving the luminance characteristics and the visibility, more preferably in the range of 30 to 70%, and more preferably 40 to 70%. ６５65%.
[0049]
In the light source device of the present invention, the display area when viewed from the normal direction of the light emitting surface (the emission surface of the light diffusing element 6) (that is, the effectiveness of the display element such as a liquid crystal display element used in combination with the light source device). It is also required that the luminance within an effective light emitting area corresponding to the display area) is uniform. The uniformity of the luminance also depends on the size of the display area of the light source. For example, a large light source device having a large display area such as a notebook computer or a monitor may require a relatively wide viewing angle characteristic. It is required to further broaden the luminance distribution (in the XZ plane) of the emitted light emitted from the light emitting surface. 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 luminance and improvement of display quality may be given priority, and the emission light luminance 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 diffusion element 6 having an appropriate light diffusion characteristic according to the size of the display area of the light source device.
[0050]
The light diffusion characteristics of the light diffusion element 6 according to the size of the display area of such a light source device will be described. The size of the display area of the light source device will be described with reference to the developed length. Here, the development length of the light source device (the development length of the light guide 3) refers to a linear cold-cathode light source arranged as a primary light source 1 on the light incident surface of the light guide 3 as shown in FIG. In this case, it refers to the longest distance L of the display area in the direction in which the light incident on the light guide 3 is guided, that is, in the direction perpendicular to the light incident surface. Also, as shown in FIG. 5, when a point light source such as an LED is arranged as a primary light source 1 at the corner of the light guide 3, a straight line connecting the effective display area farthest from the light point source and the point light source is formed. Means the distance L of the display area.
[0051]
(1) When the developed length of the light guide 3 is 8 cm or less
Such a light source device uses a linear cold-cathode tube (single-light type), LED, or the like as the primary light source 1, and is used for a display device having a small display area such as a mobile phone, a portable information terminal, or a digital camera. Therefore, it is not necessary to increase the viewing angle so much, and the light diffusing element 6 is provided with light diffusivity enough to suppress glare and luminance unevenness which cause deterioration in quality, thereby increasing light use efficiency and maintaining high luminance. At the same time, it is necessary to reduce power consumption. For this reason, as the light diffusion element 6, the full width at half maximum of the luminous intensity distribution of the emitted light is preferably in the range of 1 to 6 degrees, more preferably 1 to 5 degrees, and still more preferably 2 to 5 degrees. Further, the haze value is preferably in the range of 8 to 60%, more preferably 8 to 50%, more preferably 20 to 50%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the average inclination angle is preferably in the range of 0.8 to 5 degrees, more preferably 0.8 to 4 degrees, more preferably 0.8 to 4 degrees. The range is 2 to 4 degrees.
[0052]
(2) When the developed length of the light guide 3 is more than 8 cm and 23 cm or less (a single-light cold cathode tube is used as the primary light source 1)
Since such a light source device is used for a display device such as a notebook computer, a desktop computer monitor, and a relatively small liquid crystal television, a relatively wide viewing angle is required. Accordingly, high quality and high brightness are required. For this reason, as the light diffusion element 6, the full width at half maximum of the emitted light luminous intensity distribution is preferably in the range of 3 to 11 degrees, more preferably 4 to 10 degrees, and even more preferably 4 to 9 degrees. Further, the haze value is preferably in the range of 30 to 80%, more preferably 40 to 73%, and still more preferably 45 to 70%. Furthermore, when the uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 3 to 9.5 degrees, more preferably 3.5 to 8.5 degrees, and more preferably 3.5 to 8.5 degrees. Preferably it is in the range of 4.5 to 7 degrees.
[0053]
When the developed length of the light guide 3 is more than 8 cm and 18 cm or less, the light guide 3 is used for a display device of a relatively small notebook personal computer, so that a required viewing angle is slightly narrow. For this reason, as the light diffusion element 6, the full width at half maximum of the luminous intensity distribution of the emitted light is preferably in the range of 3 to 8 degrees, more preferably 4 to 8 degrees, and still more preferably 4 to 7 degrees. Further, the haze value is preferably in the range of 30 to 70%, more preferably 40 to 65%, and still more preferably 45 to 60%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the average inclination angle is preferably in the range of 3 to 7 degrees, more preferably 3.5 to 6.5 degrees, more preferably. The range is 4.5 to 6 degrees.
[0054]
When the developed length of the light guide 3 is more than 18 cm and not more than 22 cm, the light guide 3 is used for a display device of a relatively large notebook personal computer. It is necessary to achieve brightness uniformity. For this reason, as the light diffusing element 6, the full width at half maximum of the emitted light luminous intensity distribution is preferably in the range of 4 to 10 degrees, more preferably 5 to 9 degrees, and even more preferably 5 to 8.5 degrees. is there. Further, the haze value is preferably in the range of 40 to 75%, more preferably 50 to 70%, and still more preferably 50 to 65%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 3.5 to 8 degrees, more preferably 4 to 7 degrees, and more preferably 4. The range is 5 to 6.5 degrees.
[0055]
When the developed length of the light guide 3 is more than 22 cm and not more than 23 cm, the light guide 3 is used for a display device such as a relatively large notebook computer. A notebook computer using a single-lamp cold-cathode tube as the primary light source 1 has a large display area, and has a higher light use efficiency and brightness compared to a light guide 3 having a development length of 22 cm or less. Needs to be improved. In order to increase the luminance in this way, for example, as a reflection sheet disposed on the back surface of the light guide 3 of the light source device, instead of a foamed PET reflection film having low directional reflection, silver having excellent directional reflection characteristics is used. It is necessary to use a metal reflection sheet such as a reflection sheet or an aluminum reflection sheet. However, when a metal reflection sheet is used, defects such as glare peculiar to metal reflection, a dark line bright line appearing near the incident surface, and a dark portion appearing near both ends of the incident surface are strongly exhibited, and the quality as a light source device is increased. Tend to be impaired. In order to suppress such a deterioration in quality, it is necessary to use a light diffusing element 6 having a high light diffusing property such that the full width at half maximum of the emitted light luminous intensity distribution exceeds 9 degrees. When a light diffusing element 6 is used, the light diffusing property becomes too large and the total light transmittance is greatly reduced, so that there is a problem that a sufficiently high luminance cannot be obtained. For this reason, such deterioration in quality is suppressed by the light guide 3 and the light deflecting element 4, and the light diffusing element 6 having a full width at half maximum of the luminous intensity distribution in the range of 5 to 11 degrees is used. Is preferably, more preferably, 6 to 10 degrees, and more preferably, 7 to 9 degrees. Further, the haze value is preferably in the range of 50 to 80%, more preferably 55 to 73%, and still more preferably 55 to 70%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 4.5 to 9.5 degrees, more preferably 5 to 8.5 degrees, and more preferably 5 to 8.5 degrees. Preferably it is in the range of 5 to 7 degrees.
[0056]
(3) When the development length of the light guide 3 is more than 8 cm and 28 cm or less (a multi-light cold cathode tube is used as the primary light source 1)
Since such a light source device is used for a display device such as a monitor of a desktop personal computer and a liquid crystal television, a relatively wide viewing angle is required and a high luminance is required. Therefore, as the primary light source 1, a multi-lamp type light source in which one or more cold-cathode tubes are arranged on two opposite end faces of the light guide 3 is used. In such a light source device, the visibility regarding the quality is different from that using the single-lamp type primary light source 1, and the asymmetry of the emitted light luminance distribution (in the XZ plane) loses its characteristic as described later. As shown in FIG. 6, the symmetry of the emitted light luminance distribution (in the XZ plane) near the center of the device is improved even when the light diffusing element 6 is not used. Further, the emitted light luminance distribution (in the XZ plane) near both ends near the light source is affected by the light guided from the nearest part, and the emitted light luminance distribution (in the XZ plane) is slightly asymmetric. ). That is, in the vicinity of the left end portion in FIG. 6, the emission light luminance distribution on the light source side (in the XZ plane) is steep, and the emission light luminance distribution on the center side (in the XZ plane) has a smooth tailing tendency. Therefore, in the light emission direction near the left end portion, the component which is slightly directed toward the center is increased. On the other hand, in the vicinity of the right end portion in FIG. 6, the emitted light has the opposite luminance distribution (in the XZ plane), and the light emission direction has many components slightly directed to the center. For this reason, the emitted light characteristic with excellent visibility when observing the vicinity of both ends from the center is obtained, and a light source device having high quality and high brightness up to the ends is obtained.
[0057]
For this reason, the light diffusing element 6 is required to have a light diffusing property to obtain a wide viewing angle, and it is preferable to use a light emitting element having a full width at half maximum of 0.7 to 13 degrees of the luminous intensity distribution of the emitted light, more preferably. Is in the range of 1 to 11 degrees, more preferably 2 to 9 degrees. Further, the haze value is preferably in the range of 30 to 82%, more preferably 35 to 75%, and still more preferably 40 to 70%. Further, 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 0.8 to 12 degrees, more preferably 1 to 8.5 degrees, more preferably. It is in the range of 1.5 to 7 degrees. When the developed length of the light guide 3 is more than 22 cm and 28 cm or less, it is preferable to use the light diffusing element 6 having a full width at half maximum of the emitted light luminous intensity distribution in the range of 6 to 13 degrees. The angle is more preferably 7 to 11 degrees, more preferably 7 to 9 degrees. The haze value is preferably in the range of 50 to 82%, more preferably 60 to 75%, and even more preferably 65 to 70%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the average inclination angle is preferably in the range of 4.5 to 12 degrees, more preferably 5.5 to 8.5 degrees, and more preferably 5.5 to 8.5 degrees. Preferably it is in the range of 6 to 7 degrees. Further, when the developed length of the light guide 3 is more than 8 cm and not more than 22 cm, the light diffusing element 6 having a full width at half maximum of the luminous intensity distribution in the range of 0.7 to 6 degrees should be used. Is more preferable, and 1 to 5 degrees is more preferable, and 2 to 4 degrees is more preferable. Further, the haze value is preferably in the range of 30 to 60%, more preferably 35 to 55%, and still more preferably 40 to 50%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the average inclination angle is preferably in the range of 0.8 to 6 degrees, more preferably 1 to 5 degrees, more preferably 1.degree. The range is 5 to 4.5 degrees.
[0058]
In the light source device of the present invention, when the above-described light diffusing element 6 is used, the light-collecting properties where the full width at half maximum of the luminance distribution (in the XZ plane) emitted from the light deflecting element 4 is about 19 to 26 degrees are compared. It is preferable to use the light deflecting element 4 that is relatively weak and to use the light diffusing element 6 that has relatively low light diffusibility since the reduction in luminance due to diffusion on the YZ plane can be suppressed. is there. In this case, the light diffusing element 6 is required to have a light diffusing property for obtaining a wide viewing angle, and it is preferable to use a light diffusing element having a full width at half maximum of 1 to 8 degrees, more preferably 2 to 8 degrees. -8 degrees, more preferably 3-7 degrees. Further, the haze value is preferably in the range of 8 to 70%, more preferably 30 to 65%, and still more preferably 40 to 60%. Further, when the uneven structure is formed on one surface of the light diffusion element 6, the average inclination angle is preferably in the range of 0.8 to 7 degrees, more preferably 3 to 6.5 degrees, and more preferably 3 to 6.5 degrees. Preferably it is in the range of 3.5 to 6 degrees. When the uneven structure is formed on both surfaces, the average inclination angle of one surface thereof is preferably in the range of 0.8 to 4 degrees, more preferably 1 to 4 degrees, more preferably 2 to 4 degrees. Range.
[0059]
In the light source device of the present invention, the outgoing light emitted from the outgoing light surface of the light deflecting element 4 may have an asymmetric outgoing light luminance distribution (in the XZ plane: no light diffusing element) as shown in FIG. . The emitted light luminance distribution (in the XZ plane) is derived from the emitted light luminous intensity distribution (in the XZ plane) emitted from the light guide 3. Such an asymmetric outgoing light luminance distribution (in the XZ plane) is, for example, a high directivity outgoing light in which the full width at half maximum of the outgoing light luminance distribution (in the XZ plane) from the light deflecting element 4 is 20 degrees or less. It tends to appear when emitted. In particular, in a light source device having a relatively large display area, in order to reduce the asymmetry of the emitted light luminance distribution (in the XZ plane), the light diffusing element 6 having a relatively strong light diffusing property is used. (Emission light luminance distribution when such a light diffusing element is used is shown in FIG. 7 (with light diffusing element)). On the other hand, when the light diffusing element 6 is such that the full width at half maximum of the emitted light luminous intensity distribution is 4 degrees or more and the haze value is 35% or more, the luminance distribution of the emitted light emitted from the light diffusing element 6 (in the XZ plane) ) Is deviated by about 1 to 3 degrees in the direction opposite to the light source with respect to the peak angle of the luminance distribution (in the XZ plane) of the emitted light from the light deflecting element 4. For this reason, when the peak angle of the luminance distribution (in the XZ plane) of the emitted light from the light deflection element is in a desired direction (for example, the normal direction), the light diffusion element 6 is used to change the light in the desired direction. This causes a decrease in the brightness of the image. Therefore, when the light diffusion element 6 as described above is used when the full width at half maximum of the luminance distribution (in the XZ plane) emitted from the light deflection element 4 is 20 degrees or less, as shown in FIG. In advance, the peak angle of the luminance distribution (in the XZ plane) of the light emitted from the light deflecting element 4 is 0.5 to 3 degrees, more preferably 0.5 to 2 degrees, more preferably 1 to 3 from the desired direction toward the light source. It is preferable to design the light deflecting element 4 and the like so as to be inclined by 2 degrees.
[0060]
In the present invention, the use of a light diffusing element 6 having anisotropy in light diffusing property increases the total light transmittance of the light diffusing element 6 and efficiently emits light from the light deflecting element 4. This is preferable because it can diffuse and improve the luminance. For example, in a light source device in which a cold-cathode tube on a line is arranged as a primary light source 1 on one end face of the light guide 3, the light deflecting element 4 for narrowing the field of view emits light from the light exit surface of the light guide 3. The objective is to narrow the field of view of the emitted light mainly in the XZ plane, and to diffuse the light of the XZ plane narrowed by the light diffusion element 6 to broaden the viewing angle. However, when an isotropic diffusive element is used as the light diffusing element 6, light on the YZ plane, which is not narrowed by the light deflector, is equally diffused, resulting in a decrease in luminance. become. Therefore, as shown in FIG. 8, by using the light diffusing element 6 having anisotropic diffusing property such that the light diffusing property in the XZ plane is higher than that in the YZ plane, the field of view is narrowed by the light deflecting element 4. The light on the XZ plane is strongly diffused, the light on the YZ plane that is not narrowed in the field of view can be weakly diffused, the light emitted from the light deflecting element 4 can be efficiently diffused, and the brightness decreases. Can be minimized as much as possible.
[0061]
In the present invention, regarding the anisotropic diffusivity of the light diffusing element 6, what kind of anisotropic light diffusing element 6 is used depends on the difference between the XZ plane and the YZ plane as described above. It is not limited to the anisotropy, and can be appropriately selected according to the light emitting mechanism of the light guide 3, the lens shape and arrangement of the light deflecting element 4, the use of the light source device, and the like. That is, as shown in FIG. 9, an arbitrary plane (ZP-n plane (n = 1, 2,...)) Including a normal axis to the emission plane of the light diffusion element 6 is assumed, and these arbitrary planes are assumed. Anisotropy can be imparted by making the full width at half maximum of the emission light luminance distribution (within the XZ plane) different on the surface. Note that the largest full width at half maximum is the maximum full width at half maximum and the smallest full width at half maximum is the minimum full width at half maximum in the ZP-n plane. Similarly, regarding the average inclination angle of the concavo-convex structure that imparts anisotropic diffusion to the light diffusion element 6, the average inclination angle in an arbitrary P-n direction where the ZP-n plane and the light diffusion element 6 (XY plane) intersect with each other. The anisotropy of the average inclination angle can be provided by making the difference. At this time, the largest average inclination angle in the P-n direction is defined as the maximum average inclination angle, and the smallest average inclination angle is defined as the minimum average inclination angle.
[0062]
For example, when a linear cold cathode tube is arranged on one end face of the light guide 3 to form the primary light source 1, the light deflecting element 4 mainly narrows the field of view mainly on the XZ plane and hardly acts on the YZ plane. It is optimal to use a light diffusing element 6 having anisotropic diffusion properties that effectively diffuses outgoing light on the XZ plane and does not diffuse outgoing light on the YZ plane. Therefore, it is preferable that the light diffusing element 6 has anisotropic diffusion such that the XZ plane shows the full width at half maximum and the YZ plane shows the minimum full width at half maximum. Similarly, it is preferable that the concavo-convex structure formed on the light diffusing element 6 also has a structure or arrangement having a maximum average inclination angle in the X direction and a minimum average inclination angle in the Y direction.
[0063]
The light diffusion element 6 having such anisotropic diffusion also has a light diffusion characteristic of appropriately diffusing light emitted from the light deflecting element 4 in consideration of the balance of luminance characteristics, visibility and quality. It is necessary to use element 6. That is, when the light diffusing property of the light diffusing element 6 is low, it is difficult to sufficiently widen the viewing angle, and the visibility is reduced, and the effect of improving the quality tends to be insufficient. If it is too high, the effect of narrowing the field of view by the light deflecting element 4 will be impaired, and the total light transmittance will also decrease, tending to lower the luminance. Therefore, the one having a maximum full width at half maximum of the luminous intensity distribution of the emitted light 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. Further, the ratio of the maximum full width at half maximum to the full width at half maximum (maximum full width at half maximum / minimum full width at half maximum) is preferably in the range of 1.1 to 20, more preferably in the range of 2 to 15, and more preferably in the range of 4 to 10. Range. This is because by setting the maximum full width at half maximum / minimum full width at half maximum to 1.1 or more, the light use efficiency can be improved and the luminance can be increased. This is because it can suppress.
[0064]
When the uneven structure is formed on one surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 0.8 to 15 degrees, more preferably 3.5 to 11 degrees, More preferably, it is 4 to 9 degrees. Also, from the same viewpoint as the maximum full width at half maximum / minimum full width at half maximum, the ratio of the maximum average inclination angle to the minimum average inclination angle (maximum average inclination angle / minimum average inclination angle) may be in the range of 1.1 to 20. Preferably, it is more preferably in the range of 2 to 15, more preferably 4 to 10. The concavo-convex structure may be formed on both surfaces of the light diffusing element 6. In this case, in order to suppress a decrease in the total light transmittance of the light diffusing element 6, the average of the incident surface side of the light diffusing element 6 is required. It is preferable that the inclination angle is larger than the average inclination angle on the emission surface side. Further, the haze value of the light diffusing element 6 is preferably in the range of 8 to 82% from the viewpoint of improving the luminance characteristics and the visibility, more preferably in the range of 30 to 70%, and more preferably 40 to 70%. ６５65%.
[0065]
Further, as the light diffusion element 6, it is preferable to use an element having appropriate light diffusion characteristics according to the size of the display area of the light source device. When the development length of the light guide 3 is 8 cm or less, the light diffusion element 6 preferably has a maximum full width at half maximum of the luminous intensity distribution in the range of 1 to 6 degrees, more preferably 1 to 5 degrees. , More preferably in the range of 2 to 5 degrees. Further, the haze value is preferably in the range of 8 to 60%, more preferably 8 to 50%, more preferably 20 to 50%. Furthermore, when forming a concavo-convex structure on the surface of the light diffusion element 6, the maximum average inclination angle is preferably in the range of 0.8 to 5 degrees, more preferably 0.8 to 4 degrees, and more preferably 0.8 to 4 degrees. Is in the range of 2 to 4 degrees.
[0066]
In the case where the developed length of the light guide 3 is more than 8 cm and 23 cm or less (a single-lamp-type cold cathode tube is used as the primary light source 1), as the light diffusion element 6, the full width at half maximum of the emitted light luminous intensity distribution is 3 The angle is preferably in the range of 13 to 13 degrees, more preferably 4 to 10 degrees, and even more preferably 4 to 9 degrees. Further, the haze value is preferably in the range of 30 to 80%, more preferably 40 to 73%, and still more preferably 45 to 70%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 3 to 15 degrees, more preferably 3.5 to 10 degrees, more preferably 4 to 10 degrees. 0.5 to 8 degrees.
[0067]
When the developed length of the light guide 3 is more than 8 cm and not more than 18 cm, the light diffusion element 6 preferably has a maximum full width at half maximum of the luminous intensity distribution of the emitted light in the range of 3 to 10 degrees, more preferably 4 to 10 degrees. It is in the range of 10 to 10 degrees, more preferably 4 to 9 degrees. Further, the haze value is preferably in the range of 30 to 70%, more preferably 40 to 65%, and still more preferably 45 to 60%. Further, when the uneven structure is formed on the surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 3 to 9 degrees, more preferably 3.5 to 8 degrees, more preferably 4 to 8 degrees. 0.5 to 8 degrees.
[0068]
When the developed length of the light guide 3 is more than 18 cm and not more than 22 cm, the light diffusion element 6 preferably has a full width at half maximum of the luminous intensity distribution in the range of 4 to 13 degrees, more preferably 5 to 13 degrees. The angle is in the range of 11 to 11 degrees, more preferably 5 to 8.5 degrees. Further, the haze value is preferably in the range of 40 to 75%, more preferably 50 to 70%, and still more preferably 50 to 65%. Further, when the uneven structure is formed on the surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 3.5 to 15 degrees, more preferably 4 to 9 degrees, more preferably 4 to 9 degrees. It is in the range of 0.5 to 6.5 degrees.
[0069]
When the developed length of the light guide 3 is more than 22 cm and 23 cm or less, it is preferable to use the light diffusing element 6 having a full width at half maximum of the emitted light luminous intensity distribution of 5 to 13 degrees, more preferably. Is in the range of 6 to 12 degrees, more preferably 7 to 9 degrees. Further, the haze value is preferably in the range of 50 to 80%, more preferably 55 to 73%, and still more preferably 55 to 70%. Further, when an uneven structure is formed on the surface of the light diffusion element 6, the maximum average inclination angle is preferably in the range of 4.5 to 15 degrees, more preferably 5 to 10 degrees, and more preferably 5 to 10 degrees. It is in the range of up to 7 degrees.
[0070]
When the developed length of the light guide 3 is more than 8 cm and not more than 28 cm (a multi-lamp type continuous cathode tube is used as the primary light source 1), the light diffusing element 6 needs to have a light diffusing property to obtain a wide viewing angle. It is preferable to use one having a full width at half maximum of 0.7 to 13 degrees, more preferably 1 to 11 degrees, and more preferably 2 to 9 degrees. Further, the haze value is preferably in the range of 30 to 82%, more preferably 35 to 75%, and still more preferably 40 to 70%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the maximum average inclination angle is preferably in the range of 0.8 to 15 degrees, more preferably 1 to 13 degrees, more preferably 1 to 13 degrees. 0.5 to 7 degrees. When the developed length of the light guide 3 is more than 22 cm and 28 cm or less, it is preferable to use the light diffusing element 6 having a full width at half maximum of the emitted light luminous intensity distribution in the range of 6 to 13 degrees. The angle is more preferably 7 to 11 degrees, more preferably 7 to 9 degrees. The haze value is preferably in the range of 50 to 82%, more preferably 60 to 75%, and even more preferably 65 to 70%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the average inclination angle is preferably in the range of 4.5 to 15 degrees, more preferably 5.5 to 13 degrees, more preferably It is in the range of 6 to 7 degrees. Further, when the developed length of the light guide 3 is more than 8 cm and not more than 22 cm, the light diffusing element 6 having a full width at half maximum of the luminous intensity distribution in the range of 0.7 to 6 degrees should be used. Is more preferable, and 1 to 5 degrees is more preferable, and 2 to 4 degrees is more preferable. Further, the haze value is preferably in the range of 30 to 60%, more preferably 35 to 55%, and still more preferably 40 to 50%. Further, when an uneven structure is formed on the surface of the light diffusing element 6, the average inclination angle is preferably in the range of 0.8 to 10 degrees, more preferably 1 to 7 degrees, more preferably 1. The range is 5 to 5 degrees.
[0071]
As the diffusibility imparting structure of the light diffusing element 6 having such anisotropic diffusivity, for example, a concavo-convex structure as shown in FIGS. The concavo-convex structure shown in FIG. 10 is an array structure in which a large number of lens rows such as a lenticular lens row extending long on one axis are arranged in parallel. As the arrangement pitch of such lens arrays, a pitch in which moire is less likely to occur with respect to the pitch of the liquid crystal elements used as the display device and the arrangement pitch of the lens arrays such as the prism array of the light deflecting element 4 is selected, or a random pitch is selected. An array pitch is preferred. Usually, the arrangement pitch of the lens rows is preferably in the range of 1 to 70 μm, more preferably 5 to 40 μm, and still more preferably 10 to 30 μm, from the viewpoint of ease of production and prevention of moiré. The average inclination angle in the direction orthogonal to the longitudinal direction of the lens array is preferably in the range of 0.8 to 15 degrees from the viewpoints of luminance improvement and visibility, more preferably 3.5 to 11 degrees. Is in the range of 4 to 9 degrees.
[0072]
The concavo-convex structure shown in FIG. 11 is a structure in which a large number of cylindrical lens bodies are discretely arranged. The arrangement interval of the cylindrical lens shapes may be a constant regular pitch or a random arrangement pitch. Usually, the arrangement pitch of the cylindrical lens shaped body is preferably in the range of 1 to 70 μm, more preferably 5 to 40 μm, more preferably 10 to 30 μm from the viewpoint of ease of production and prevention of moiré. is there. In addition, the average inclination angle in the direction orthogonal to the longitudinal direction of the cylindrical lens-shaped body is preferably 0.8 to 15 degrees from the viewpoints of luminance improvement and visibility, more preferably 3.5 to 11 degrees, and more preferably 3.5 to 11 degrees. Is in the range of 4 to 9 degrees. In such a discrete array structure, a line that intersects a surface that needs to have the full width at half maximum of the light diffusing element 6 with an emission surface of the light diffusing element 6 and a longitudinal direction of the cylindrical lens shape body are substantially orthogonal. It is preferable to arrange them in such a manner that the probability of performing them is as high as possible. In addition, an arrangement is made so that the probability that the longitudinal direction of the cylindrical lens-shaped body becomes substantially parallel to the line intersecting the surface required to have the minimum full width at half maximum and the exit surface of the light diffusion device 6 as light diffusion device 6 is as high as possible. Is preferred.
[0073]
The uneven structure shown in FIG. 12 is a hairline structure. The average inclination angle in the direction orthogonal to the direction in which the hairline extends is preferably 0.8 to 15 degrees from the viewpoints of luminance improvement and visibility, more preferably 3.5 to 11 degrees, and more preferably 4 to 9 degrees. Range. The direction in which the hairline extends is preferably substantially perpendicular to the line that intersects the surface of the light diffusion element 6 that needs to have the full width at half maximum and the emission surface of the light diffusion element 6.
[0074]
By providing a mat structure on at least one of the surface on which the uneven structure imparting such anisotropic diffusivity is formed and the back surface thereof, it is possible to suppress glare and uneven brightness and improve the quality. it can. However, if the light diffusing property of the mat structure is increased, the anisotropic diffusing property may be impaired and the luminance may be reduced. Therefore, it is preferable to provide a mat structure having relatively weak light diffusing property. Such a mat structure preferably has an average inclination angle of 0.5 to 5 degrees, more preferably 0.8 to 4 degrees, and still more preferably 1 to 3.5 degrees. The average tilt angle of the mat structure when the mat structure is provided on the surface of the anisotropic uneven structure refers to the average tilt angle of the mat structure itself excluding the average tilt angle caused by the uneven structure. That is, it is possible to measure an average inclination angle parallel to the longitudinal direction of a portion having no uneven structure or the uneven structure, a measurement using a stylus roughness meter, a method of image-analyzing a cross-sectional shape of the light diffusing element 6, an atomic force, It can be measured by a microscope or the like.
[0075]
In the present invention, light emitted from the light guide 3 is emitted in a specific direction such as the normal direction using the light deflecting element 4, and the emitted light is emitted using the light diffusing element 6 having anisotropic diffusion property. It can also be emitted in a desired direction. In this case, both functions of the anisotropic diffusion function and the light deflection angle function can be given to the light diffusion element 6. For example, in the case of using a lenticular lens array or a cylindrical lens shaped body as the concavo-convex structure, by making the cross-sectional shape asymmetrical, it is possible to provide both functions of anisotropic diffusion action and light deflection action.
[0076]
In the present invention, the light deflecting element 4 and the light diffusing element 6 may contain a light diffusing material for the purpose of adjusting the viewing angle as the light source device and improving the quality. As such a light diffusing material, transparent fine particles having a different refractive index from the material constituting the light deflecting element 4 and the light diffusing element 6 can be used, for example, silicon beads, polystyrene, polymethyl methacrylate. And homopolymers and copolymers such as fluorinated methacrylate. As the light diffusing material, it is necessary to appropriately select the content, the particle diameter, the refractive index, and the like so as not to impair the narrow visual field effect by the light deflecting element 4 and the appropriate diffusion effect by the light diffusing element 6. For example, the refractive index of the light diffusing material is small if the difference between the refractive index of the light deflecting element 4 and the material forming the light diffusing element 6 is too small. The rate difference is preferably in the range of 0.01 to 0.1, more preferably 0.03 to 0.08, and still more preferably 0.03 to 0.05. Further, the particle size of the diffusing material is such that if the particle size is too large, scattering becomes strong, causing glare and a decrease in luminance, and if the particle size is too small, coloring occurs, so that the average particle size is in the range of 0.5 to 20 μm. Preferably, it is more preferably in the range of 2 to 15 μm, more preferably 2 to 10 μm.
[0077]
The primary light source 1 is a linear light source extending in the Y direction. As the primary light source 1, for example, a fluorescent lamp or a cold cathode tube can be used. In the present invention, the primary light source 1 is not limited to a linear light source, but a point light source such as an LED light source, a halogen lamp, a metahalo lamp, or the like can also be used. In particular, when used in a display device having a relatively small screen size such as a mobile phone or a portable information terminal, it is preferable to use a small point light source such as an LED. In addition, as shown in FIG. 1, the primary light source 1 can be further installed not only on one side end face of the light guide 3 but also on the other side end face as necessary. .
[0078]
The light source reflector 2 guides the light of the primary light source 1 to the light guide 3 with little loss. As the material, for example, a plastic film having a metal deposition reflective layer on the surface can be used. As shown, the light source reflector 2 is wound from the outer surface of the edge of the light reflecting element 5 to the outer surface of the primary light source 1 to the edge of the light emitting surface of the light deflecting element 4. On the other hand, the light source reflector 2 can be wound around the light emitting element 4 from the outer surface of the light reflecting element 5 to the light emitting surface of the light guide 3 via the outer surface of the primary light source 1, avoiding the light deflecting element 4. It is.
[0079]
A reflecting member similar to the light source reflector 2 can be attached to a side end surface other than the side end surface 31 of the light guide 3. As the light reflection element 5, for example, a plastic sheet having a metal deposition reflection layer on the surface can be used. In the present invention, instead of the reflection sheet, the light reflection element 5 may be a light reflection layer or the like formed on the back surface 34 of the light guide 3 by metal deposition or the like.
[0080]
The light guide 3, the light deflecting element 4, and the light diffusing element 6 of the present invention can be made of a synthetic resin having a high light transmittance. Examples of such a synthetic resin include a methacrylic resin, an acrylic resin, a polycarbonate resin, a polyester resin, and a vinyl chloride resin. In particular, methacrylic resin is optimal because of its high light transmittance, heat resistance, mechanical properties, and moldability. Such a methacrylic resin is a resin containing methyl methacrylate as a main component, and is preferably a resin having 80% by weight or more of methyl methacrylate. When forming the surface structure of the rough surface of the light guide 3 and the light deflecting element 4 and the surface structure such as the prism rows, the transparent synthetic resin plate is formed by hot pressing using a mold member having a desired surface structure. The shape may be provided simultaneously with the molding by screen printing, extrusion molding, injection molding, or the like. Further, the structural surface can also be formed by using a heat or light curable resin. Further, on a transparent substrate such as a transparent film or sheet made of a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin, etc., a rough surface structure made of an active energy ray-curable resin. Further, a lens array structure may be formed on the surface, or such a sheet may be joined and integrated on a separate transparent substrate by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylates, allyl compounds, metal salts of (meth) acrylic acid, and the like can be used.
[0081]
On the light emitting surface (light emitting surface of the light diffusing element 6) of the light source device including the primary light source 1, the light source reflector 2, the light guide 3, the light deflecting element 4, the light diffusing element 6, and the light reflecting element 5 as described above, By arranging the liquid crystal display element, a liquid crystal display device having the light source device of the present invention as a backlight is configured. 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, since light of a sufficiently collimated narrow luminance distribution (within the XZ plane) can be made to enter the liquid crystal display element from the light source device, the brightness can be reduced without grayscale inversion in the liquid crystal display element. In addition, an image display with good hue uniformity can be obtained, and light irradiation concentrated in a desired direction can be obtained, and the efficiency of using the amount of light emitted from the primary light source 1 for illumination in this direction can be increased.
[0082]
Although the above embodiment has been described with respect to the light source device, the present invention is also applicable to a bar-shaped light source device that is elongated in the X direction and whose dimension in the Y direction is, for example, five times or less the thickness of the light guide 3. In that case, as the primary light source 1, a substantially point-like light source such as an LED can be used.
[0083]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples.
In addition, the measurement of each physical property in the following Examples was performed as follows.
[0084]
Measurement of normal luminance and full width at half maximum of luminous intensity of surface light source device
A cold cathode tube was used as a light source, and DC 12 V was applied to an inverter (HIU-742A manufactured by Harrison) to perform high-frequency lighting. The luminance was obtained by dividing the surface of the surface light source device or the light guide into 3 × 5 squares of 20 mm square and averaging 15 points of the luminance values in the normal direction of each square. The full width at half maximum luminous intensity of the light guide is fixed to black paper having a pinhole of 4 mmφ on the surface of the light guide so that the pinhole is located at the center of the surface, and the measurement circle of the luminance meter is 8 to 9 mm. The distance was adjusted so that the gonio rotation axis was rotated around the pinhole in the direction perpendicular and parallel to the longitudinal axis of the cold cathode tube. The luminous intensity distribution (in the XZ plane) of the emitted light was measured with a luminance meter while rotating the rotation axis in each direction from +80 degrees to -80 degrees at intervals of 1 degree, and the peak angle and full width at half maximum (1/1 of the peak value) were measured. 2 (in the XZ plane). The full width at half maximum of the luminance of the surface light source device was adjusted so that the viewing angle of the luminance meter was 0.1 °, the surface light source device was positioned at the center plane, and the gonio rotation axis was rotated. The luminance distribution (in the XZ plane) of the emitted light was measured with a luminance meter while rotating the rotation axis at an interval of 1 degree from +80 degrees to -80 degrees in each direction, and the peak luminance, full width at half maximum (1/1 of the peak value) were measured. 2 (in the XZ plane).
[0085]
Measurement of average inclination angle (θa)
According to ISO 4287 / 1-1987, the surface of the rough surface was measured by a stylus type surface roughness meter (Surfcom 570A manufactured by Tokyo Seiki Co., Ltd.) using 010-2528 (1 μmR, 55 ° cone, diamond) as a stylus. The roughness was measured at a drive speed of 0.03 mm / sec. The inclination was corrected by subtracting the average line from the chart obtained by the measurement, and the inclination was corrected and calculated by the equations (1) and (2).
[0086]
Measurement of haze value
The haze value was measured according to the method B of JIS K-7105, and the total light transmittance of a sample having a size of 50 mm × 50 mm was measured using an integrating sphere reflection / transmittance meter (model RT-100 manufactured by Murakami Color Research Laboratory). From the rate (Tt) and the diffused light transmittance (Td), it was calculated by the following equation (6).
[0087]
(Equation 5)

Measurement of full width at half maximum of luminous intensity distribution of light emitted from light diffusion element
The light diffusion distribution angle is a half value which is a half luminous intensity of a peak luminous intensity obtained by measuring a sample having a size of 50 mm × 50 mm using an automatic goniophotometer (Model GP-200 manufactured by Murakami Color Research Laboratory Co., Ltd.). Twice the half width angle was defined as the full width at half maximum (α) of the sample. As for light to be incident on the sample, light from a light source is condensed on a pinhole by a condenser lens, and is converted into parallel light (parallelism of ± 0.5 degrees or less) through a collimator lens. ), And is incident on the incident surface of the sample. The light transmitted through the sample passes through a light-receiving lens (passes through the aperture of 11.4 mm (when the sample surface is smooth, is focused on the position of the light-receiving aperture)), passes through the light-receiving aperture, reaches the light-receiving element, and has a voltage value. The same measurement was performed by rotating the sample, and the maximum full width at half maximum (Maxα) and the minimum full width at half maximum (Minα) were determined.
[0088]
Example 1
A light guide having a mat on one side was prepared by injection molding using an acrylic resin (Acrypet VH5 # 000 manufactured by Mitsubishi Rayon Co., Ltd.). The light guide had a wedge plate shape of 216 mm × 290 mm and a thickness of 2.0 mm-0.7 mm. On the mirror side of this light guide, a prism row having a prism apex angle of 130 degrees and a pitch of 50 μm is formed by an acrylic ultraviolet curable resin so as to be parallel to a side (short side) having a length of 216 mm of the light guide. The prism layers arranged in parallel were formed. A cold-cathode tube is placed along the long side of the light guide reflector (the end face on the side with a thickness of 2.0 mm) corresponding to one side end surface (end surface on the side with a thickness of 2.0 mm) corresponding to the side (long side) having a length of 290 mm of the light guide. (A silver reflection film manufactured by Reiko Co., Ltd.). Further, a light diffusion reflection film (E60 manufactured by Toray Industries, Inc.) was attached to the other side end surface, and a reflection sheet was arranged on the prism array (back surface). The above configuration was incorporated in a frame. In this light guide, the maximum peak of the emitted light luminous intensity distribution (in the XZ plane) was 70 degrees with respect to the normal direction of the light emitting surface, and the full width at half maximum was 22.5 degrees.
[0089]
On the other hand, using a UV curable acrylic resin having a refractive index of 1.5064, a large number of prism rows having a convex curved surface shape with one prism surface having a radius of curvature of 1000 μm, the other prism surface having a planar shape, and a pitch of 50 μm. Were formed on one surface of a polyester film having a thickness of 125 μm, in which a prism row forming surface provided in parallel was formed on one surface. At this time, as the virtual prism array, an isosceles triangular prism array having a pitch of 50 μm and an apex angle of 65.4 degrees was set so that the light emitted from the prism sheet would be in the normal direction of the light emission surface.
[0090]
The obtained prism sheet is mounted such that the prism row forming surface faces the light exit surface side of the light guide, the ridge line of the prism row is parallel to the light incidence surface of the light guide, and the prism slope faces the straight surface. Placed. In addition, one surface is a mat surface having an average inclination angle of 3.37 degrees, the other surface is a mat surface having an average inclination angle of 0.7 degrees, and light diffusion is such that the full width at half maximum of the light emission light intensity distribution is 4 degrees. The element was mounted on the light emitting surface of the light deflecting element such that the mat surface having an average inclination angle of 3.37 degrees was directed to the light deflecting element side, to obtain a surface light source device. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0091]
Example 2
The prism surface closer to the light source constituting the prism array is a flat surface, the prism surface farther from the light source is a surface having a height of 16 μm or more of the prism array (a surface near the top of the prism array) and a height of 16 μm or less. (The surface near the bottom of the prism array) was formed into a convex curved shape having a radius of curvature of 400 μm (the inclination angle of the surface connecting the boundary between the flat surface and the convex surface to the bottom of the prism surface with respect to the prism sheet normal to 30 °). A prism sheet having a pitch of 50 μm and an apex angle of 65.4 ° formed on one surface was prepared in the same manner as in Example 1 except for the above. The prism sheet was placed so that the prism row forming surface faced the light emitting surface side of the light guide obtained in Example 1 and the prism ridge line was parallel to the light incident surface of the light guide. In this case, the position K2 of the virtual prism surface is a position where the height of the prism row is 27 μm. In addition, one surface is a mat surface having an average inclination angle of 7.27 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 light emission light intensity distribution is 9.4 degrees. The light diffusing element was mounted on the light emitting surface of the light deflecting element such that the mat surface having an average inclination angle of 7.27 degrees was directed to the light deflecting element side, to obtain a surface light source device. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0092]
Example 3
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 a full width at half maximum of the light emission light luminous intensity distribution is 6 degrees. A surface light source device was obtained in the same manner as in Example 2 except that a mat surface having an average inclination angle of 5.0 degrees was placed on the light exit surface of the light deflecting element so as to face the light deflecting element. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0093]
Example 4
A large number of lenticular lens rows having a pitch of 30 μm are continuously 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 half-value of the luminous intensity distribution of light emission in which a lens array structure having a maximum inclination angle / minimum inclination angle of 10.4 is formed and a mat surface having an average inclination angle of 0.7 degree is formed on the other surface. The same as Example 2 except that the light diffusing element having an overall width of 11.2 degrees was mounted so that the lenticular lens array was parallel to the prism array of the light deflecting element, and the lens array structure surface was directed toward the light deflecting element. Thus, a surface light source device was obtained. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0094]
Example 5
A light emission distribution of a light emission light intensity distribution 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. Example 2 except that the light diffusing element having a full width at half maximum of 10.5 degrees was mounted so that the direction of the hairline was substantially parallel to the prism array of the light deflecting element, and the hairline forming surface faced the light deflecting element side. In the same manner as in the above, a surface light source device was obtained. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0095]
Example 6
The maximum average tilt angle in which a number of cylindrical lenses having a width of 30 μm and a length of 60 μm formed by etching on one surface of a polyester film having a thickness of 125 μm and discretely arranged in the same direction is 6.0 degrees, and the maximum tilt angle is 6.0 degrees. / A lens array structure having a minimum inclination angle of 6.0 is formed, and a matte surface having an average inclination angle of 0.7 degrees is formed on the other surface. The full width at half maximum of the light emission light intensity distribution is 7.0 degrees. A light diffusing element was mounted in the same manner as in Example 2, except that the arrangement direction of the cylindrical lens and the prism array of the light deflecting element were substantially parallel, and the lens array structure surface was directed to the light deflecting element side. A surface light source device was obtained. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0096]
Comparative Example 1
A surface light source device was obtained in the same manner as in Example 1 except that a prism sheet having both flat prism surfaces was used, and no light diffusing element was used. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0097]
Comparative Example 2
A surface light source device was obtained in the same manner as in Example 1 except that the light diffusing element was not used. The intensity ratio of the peak luminance of the manufactured surface light source device and the full width at half maximum in the emission light luminance distribution (in the XZ plane) in a plane perpendicular to the cold cathode tubes were obtained. The results are shown in Table 1.
[0098]
[Table 1]

[0099]
【The invention's effect】
As described above, in the present invention, by disposing a light diffusing element having a specific light diffusing property on the light emitting surface of the light deflecting element, the high luminance characteristic excellent in light use efficiency of the primary light source is impaired. In addition, a light source device excellent in viewing angle characteristics and image quality can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing a light source device according to the present invention.
FIG. 2 is an explanatory diagram of a shape of a prism array on a light incident surface of a light deflecting element.
FIG. 3 is an explanatory diagram of a full width at half maximum of a luminous intensity distribution of light emitted from a light diffusion element.
FIG. 4 is an explanatory diagram of a developed length of the light source device.
FIG. 5 is an explanatory diagram of a developed length of the light source device.
FIG. 6 is an explanatory diagram showing a luminance distribution (in the XZ plane) of light emitted from the light deflection element of the light source device of the present invention.
FIG. 7 is a graph showing a luminance distribution (in the XZ plane) of light emitted from the light deflection element of the light source device of the present invention.
FIG. 8 is an explanatory diagram showing the luminous intensity distribution of outgoing light of the anisotropic diffusion property of the light diffusion element of the present invention.
FIG. 9 is an explanatory diagram of anisotropic diffusivity of the light deflecting element of the present invention.
FIG. 10 is a schematic view showing a concavo-convex structure of a light deflecting element having anisotropic diffusion according to the present invention.
FIG. 11 is a schematic view showing a concavo-convex structure of an optical deflecting element having anisotropic diffusion according to the present invention.
FIG. 12 is a schematic view showing a concavo-convex structure of the optical deflection element having anisotropic diffusion according to the present invention.
[Explanation of symbols]
1 Primary light source
2 Light source reflector
3 Light guide
4 Light deflection element
5 Light reflection element
6 Light diffusion element
31 ° light incident surface
32 end face
33 ° light exit surface
34 back
41 Light incident surface
42 ° light emitting surface
I virtual prism array
I-1, I-2 Prism surface of virtual prism array

Claims (36)

A primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident and a light exit surface for guiding and exiting the incident light, and disposed adjacent to a light exit surface of the light guide. A light deflecting element, and a light source device comprising at least a light diffusing element disposed adjacent to the light exit surface of the light deflecting element,
The light deflecting element has a light incident surface and a light exit surface opposite to the light exit surface of the light guide, and a plurality of light entrance surfaces arranged in parallel with each other. A prism row is formed, and the prism row has two prism faces, and at least one of the prism faces has one peak light of light emitted from the light emission surface of the light guide. Light enters from the virtual prism surface, is totally internally reflected by the other virtual prism surface, exits from the light exit surface in a desired direction, and is arranged at the same pitch as the arrangement pitch of the prism rows of the light deflecting elements, and has a triangular cross section. When assuming a plurality of virtual prism rows, it has a convex curved surface shape based on the shape of the virtual prism row,
A light source device, wherein the light diffusion element has a full width at half maximum of 1 to 13 degrees in a luminous intensity distribution of light emitted when parallel light is incident. The light source device according to claim 1, wherein a haze value of the light diffusion element is 8 to 82%. The light source device according to claim 1, wherein an average inclination angle of at least one surface of the light diffusion element is 0.8 to 12 degrees. A primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident and a light exit surface for guiding and exiting the incident light, and disposed adjacent to a light exit surface of the light guide. A light deflecting element, and a light source device comprising at least a light diffusing element disposed adjacent to the light exit surface of the light deflecting element,
The light deflecting element has a light incident surface and a light exit surface opposite to the light exit surface of the light guide, and a plurality of light entrance surfaces arranged in parallel with each other. A prism array is formed, and the prism array has two prism surfaces, and at least one of the prism surfaces has a peak light in an emission light distribution of light emitted from the light emission surface of the light guide. The light enters from one virtual prism surface, is totally internally reflected by the other virtual prism surface, exits from the light exit surface in a desired direction, and is arranged at the same pitch as the prism array of the light deflecting element. When assuming a plurality of triangular virtual prism rows, it has a convex curved surface shape based on the shape of the virtual prism rows,
A light source device, wherein the light diffusion element has a haze value of 8 to 82%. The light source device according to claim 4, wherein the light diffusion element has a full width at half maximum of 1 to 13 degrees in a luminous intensity distribution of light emitted when parallel light is incident. The light source device according to claim 4, wherein an average inclination angle of at least one surface of the light diffusion element is 0.8 to 12 degrees. A primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident and a light exit surface for guiding and exiting the incident light, and disposed adjacent to a light exit surface of the light guide. A light deflecting element, and a light source device comprising at least a light diffusing element disposed adjacent to the light exit surface of the light deflecting element,
The light deflecting element has a light incident surface and a light exit surface opposite to the light exit surface of the light guide, and a plurality of light entrance surfaces arranged in parallel with each other. A prism array is formed, and the prism array has two prism surfaces, and at least one of the prism surfaces has a peak light in an emission light distribution of light emitted from the light emission surface of the light guide. The light enters from one virtual prism surface, is totally internally reflected by the other virtual prism surface, exits from the light exit surface in a desired direction, and is arranged at the same pitch as the prism array of the light deflecting element. When assuming a plurality of triangular virtual prism rows, it has a convex curved surface shape based on the shape of the virtual prism rows,
A light source device, wherein an average inclination angle of at least one surface of the light diffusion element is 0.8 to 12 degrees. The light source device according to claim 7, wherein the light diffusion element has a full width at half maximum of 1 to 13 degrees in a luminous intensity distribution of light emitted when parallel light is incident. The light source device according to claim 7, wherein a haze value of the light diffusion element is 8% to 82%. 2. The light guide according to claim 1, wherein the light guide has a development length of 8 cm or less, and the light diffusion element has a full width at half maximum of 1 to 6 degrees of a luminous intensity distribution of light emitted when parallel light is incident. The light source device according to claim 5. The light source according to any one of claims 2, 4 and 9, wherein a development length of the light guide is 8 cm or less, and a haze value of the light diffusion element is 8 to 60%. apparatus. 7. The light guide according to claim 3, wherein a development length of the light guide is 8 cm or less, and an average inclination angle of at least one surface of the light diffusion element is 0.8 to 5 degrees. 8. The light source device according to any one of 7. The development length of the light guide is more than 8 cm and 23 cm or less, and the light diffusion element has a full width at half maximum of 3 to 11 degrees in a luminous intensity distribution of light emitted when parallel light is incident. The light source device according to any one of claims 1, 5 and 8. 10. The light guide according to claim 2, wherein a development length of the light guide is more than 8 cm and 23 cm or less, and a haze value of the light diffusion element is 30 to 80%. The light source device according to any one of the preceding claims. 7. The light guide according to claim 3, wherein a development length of the light guide is more than 8 cm and 23 cm or less, and an average inclination angle of at least one surface of the light diffusion element is 3 to 9.5 degrees. The light source device according to claim 7. A primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident and a light exit surface for guiding and exiting the incident light, and disposed adjacent to a light exit surface of the light guide. A light deflecting element, and a light source device comprising at least a light diffusing element disposed adjacent to the light exit surface of the light deflecting element,
The light deflecting element has a light incident surface and a light exit surface opposite to the light exit surface of the light guide, and a plurality of light entrance surfaces arranged in parallel with each other. A prism array is formed, and the prism array has two prism surfaces, and at least one of the prism surfaces has a peak light in an emission light distribution of light emitted from the light emission surface of the light guide. The light enters from one virtual prism surface, is totally internally reflected by the other virtual prism surface, exits from the light exit surface in a desired direction, and is arranged at the same pitch as the prism array of the light deflecting element. When assuming a plurality of triangular virtual prism rows, it has a convex curved surface shape based on the shape of the virtual prism rows,
The full width at half maximum of the luminance distribution of light emitted from the light deflecting element is 19 to 26 degrees, and the full width at half maximum of the luminous intensity distribution of light emitted when the parallel light of the light diffusion element is incident is 1 to 8 degrees. Characteristic light source device. The light source device according to claim 16, wherein the haze value of the light diffusion element is 8 to 70%. 18. The light source device according to claim 16, wherein an average inclination angle of at least one surface of the light diffusion element is 0.8 to 7 degrees. It has a primary light source, two light entrance surfaces arranged to face each other for receiving light emitted from the primary light source, and a light exit surface for guiding and exiting the incident light, and a developed length exceeding 8 cm and 28 cm A light source device comprising at least a light guide, a light deflecting element disposed adjacent to a light exit surface of the light guide, and a light diffusing element disposed adjacent to a light exit surface of the light deflecting element. So,
The light deflecting element has a light incident surface and a light exit surface opposite to the light exit surface of the light guide, and a plurality of light entrance surfaces arranged in parallel with each other. A prism array is formed, and the prism array has two prism surfaces, and at least one of the prism surfaces has a peak light in an emission light distribution of light emitted from the light emission surface of the light guide. The light enters from one virtual prism surface, is totally internally reflected by the other virtual prism surface, exits from the light exit surface in a desired direction, and is arranged at the same pitch as the prism array of the light deflecting element. When assuming a plurality of triangular virtual prism rows, it has a convex curved surface shape based on the shape of the virtual prism rows,
A light source device, wherein the light diffusion element has a full width at half maximum of 0.7 to 13 degrees in a luminous intensity distribution of emitted light when parallel light is incident. 20. The light source device according to claim 1, wherein an average inclination angle of an incident surface of the light diffusion element is larger than an average inclination angle of an emission surface. The light source device according to any one of claims 1 to 20, wherein an entrance surface and an exit surface of the light diffusion element have an uneven structure. A primary light source, a light guide having a light incident surface on which light emitted from the primary light source is incident and a light exit surface for guiding and exiting the incident light, and disposed adjacent to a light exit surface of the light guide. A light deflecting element, and a light diffusing element disposed at least on the light exit surface of the light deflecting element, the light diffusing element having a light intensity distribution of an emitted light when parallel light is incident. A light source device characterized in that the full width at half maximum has anisotropy. 23. The light source device according to claim 22, wherein the light diffusing element has a maximum full width at half maximum of a luminous intensity distribution of emitted light upon incidence of parallel light of 1 to 13 degrees. 25. The light source device according to claim 22, wherein the light diffusing element has a maximum full width at half maximum of the luminous intensity distribution of emitted light when parallel light is incident, is at least 1.1 times the minimum full width at half maximum. 24. The light source device according to claim 22, wherein a haze value of the light diffusing element is 8 to 82%. 25. The light source device according to claim 22, wherein an average inclination angle of at least one surface of the light diffusion element has anisotropy. The light source device according to claim 26, wherein a maximum average inclination angle of at least one surface of the light diffusion element is 0.8 to 15 degrees. 28. The light guide according to claim 22, wherein the light guide has a development length of 8 cm or less, and the light diffusion element has a full width at half maximum of 1 to 6 degrees of a luminous intensity distribution of emitted light when parallel light is incident. The light source device according to any one of the above. The light source device according to any one of claims 28 to 28, wherein a development length of the light guide is 8 cm or less, and a haze value of the light diffusion element is 8 to 60%. 30. The light guide according to claim 22, wherein a development length of the light guide is 8 cm or less, and a maximum average inclination angle of at least one surface of the light diffusion element is 0.8 to 5 degrees. The light source device according to any one of the preceding claims. 23. The light guide according to claim 22, wherein a development length of the light guide is more than 8 cm and 23 cm or less, and the light diffusion element has a maximum full width at half maximum of 3 to 13 degrees of outgoing light when parallel light is incident. 28. The light source device according to any one of 27. 32. The light guide according to claim 22, wherein a development length of the light guide is more than 8 cm and 23 cm or less, and a haze value of the light diffusion element is 30 to 80%. Light source device. 28. The light guide according to claim 22, wherein a development length of the light guide is more than 8 cm and 23 cm or less, and a maximum average inclination angle of at least one surface of the light diffusion element is 3 to 15 degrees. 31. The light source device according to claim 32. The light source device according to any one of claims 22 to 33, wherein a maximum average inclination angle of an incident surface of the light diffusion element is larger than a maximum average inclination angle of an emission surface. The light source device according to any one of claims 22 to 34, wherein the maximum average inclination angle of the incident surface of the light diffusion element is 1.1 times or more the minimum average inclination angle. The light deflecting element has a light incident surface and a light exit surface opposite to the light exit surface of the light guide, and a plurality of light entrance surfaces arranged in parallel with each other on the light incident surface. A prism array is formed, and the prism array has two prism surfaces, and at least one of the prism surfaces has a peak light in an emission light distribution of light emitted from the light emission surface of the light guide. The light enters from one virtual prism surface, is totally internally reflected by the other virtual prism surface, exits from the light exit surface in a desired direction, and is arranged at the same pitch as the prism array of the light deflecting element. 36. The light source device according to claim 22, wherein when a plurality of triangular virtual prism arrays are assumed, the light source device has a convex curved surface shape based on the shape of the virtual prism arrays.

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