JP2004158336A

JP2004158336A - Surface light source device and liquid crystal display device using the device

Info

Publication number: JP2004158336A
Application number: JP2002323866A
Authority: JP
Inventors: Seiji Sakai; 誠司境; Akihiro Mori; 明博森
Original assignee: Advanced Display Inc
Current assignee: Advanced Display Inc
Priority date: 2002-11-07
Filing date: 2002-11-07
Publication date: 2004-06-03
Anticipated expiration: 2022-11-07
Also published as: JP4153776B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source device in which brightness unevenness and chromaticity unevenness do not occur and which can cope with narrowing frame of a liquid crystal display device, and which is inexpensive. <P>SOLUTION: This surface light source device has a plurality of side faces in a facing pair of upper face and lower face and in the end edges of both the upper face and the lower face. This device is provided with a color mixing means in which a facing pair of planes are incident face and outgoing face among the side faces, and with a plurality of point-formed light sources which are adjacent to the plane of incidence of the color mixture means, and which are arranged along the longitudinal direction of the incident face, and with a rectangular light guide plate arranged nearly in parallel or nearly perpendicularly against the color mixing means. A transparent body having a higher refractive index than that of air is interposed in the optical path from the color mixing means to the light guide plate. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は面状光源装置および該装置を用いた液晶表示装置に関する。さらに詳しくは、Ｒ（赤色）、Ｇ（緑色）およびＢ（青色）の単色光を発する発光ダイオードなどの複数の点状光源を用いる面状光源装置および該装置を用いた液晶表示装置に関する。
【０００２】
【従来の技術】
液晶表示装置は、液晶が挟持された２枚のガラス基板からなる液晶表示素子と該液晶表示素子の裏面側に配置される面状光源装置とから構成されている。この面状光源装置としては、光源に線状の冷陰極管が用いられていたが、冷陰極管には水銀が使用されており、近年の環境問題に対して使用が難しくなってきている。また、水銀の消耗により輝度が劣化するという問題がある。
【０００３】
一方、携帯電話などの小型の液晶表示装置用として、冷陰極管に比べて、光源の寿命の長さおよび発光効率の良さから、発光ダイオード（ＬｉｇｈｔＥｍｉｔｔｉｎｇＤｉｏｄｅ：以下、単にＬＥＤという）を用いた面状光源装置が開発されている。
【０００４】
従来の発光ダイオードを用いた面状光源装置においては、光を投光するＬＥＤと、この投光を線光源化して出射面より出射する線状の導光体と、この線状化された光を光入射端面において入射し面光源化する導光板とを備えている（たとえば、特許文献１参照）。
【０００５】
【特許文献１】
特開平１０−２８３８１７号公報（［０００１］〜［０００２］、［００２７］、図１、図２および図８）
【０００６】
【発明が解決しようとする課題】
しかしながら、ＬＥＤを用いた従来の小型の液晶表示装置用面状光源装置の構成を、中小型、大型の液晶表示装置用の面状光源装置に適用した場合には、従来の小型の液晶表示装置のように、光源である白色ＬＥＤを１つ（赤色、緑色および青色の単色光を発するＬＥＤをそれぞれ１つ組み合わせた場合には１組）用いただけでは充分な輝度を得ることができない。このため、輝度を上げるために複数のＬＥＤを光源に用いると、複数のＬＥＤを導光体の光入射端面に沿って（特許文献１の図１におけるＹ方向に）配設することとなり、狭額縁化が困難であるという問題がある。
【０００７】
本発明は、叙上の事情に鑑み、輝度ムラおよび色度ムラが発生せず、液晶表示装置の狭額縁化に対応でき、かつ安価な面状光源装置を得ることができるとともに、この面状光源装置を用いることにより優れた表示特性を安価に得ることができる液晶表示装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明の面状光源装置は、対向する一対の上面および下面と該上面および下面の端縁に複数の側面を有しており、該側面のうち、対向する一対の面が入射面および出射面である混色手段と、該混色手段の入射面に近接し、当該入射面の長手方向に沿って配設される複数の点状光源と、前記混色手段に対して略平行または略垂直に配置される矩形状の導光板とを備える面状光源装置であって、前記混色手段から前記導光板への光路に空気より屈折率の高い透明体を介在してなることを特徴とする。
【０００９】
また、本発明の液晶表示装置は、前記面状光源装置と、該面状光源装置の上部に配置され、液晶が挟持された２枚のガラス基板からなる液晶表示素子と、該液晶表示素子に接続される駆動回路基板とを備えてなることを特徴とする。
【００１０】
【発明の実施の形態】
以下、添付図面に基づいて、本発明の面状光源装置および該装置を用いた液晶表示装置を説明する。
【００１１】
実施の形態１
図１は本発明の実施の形態１にかかわる液晶表示装置の概略構成を示す平面図、図２は図１に示す液晶表示装置のＩ−Ｉ線断面図、図３は図２における直角プリズムを通る光の光路を説明するための要部拡大図である。図１〜３において、１は混色手段であり、該混色手段１は、対向する一対の上面１ａ、下面１ｂと、該上面１ａ、下面１ｂの端縁を結んだ複数の側面のうち、対向する一対の面である入射面１ｃおよび出射面１ｄから構成されている。なお、混色手段１はすべての面が鏡面であることが好ましい。
【００１２】
ＬＥＤなどの点状光源２は、前記混色手段１の入射面１ｃに近接し、入射面１ｃの長手方向に沿って配設されており、赤色の光を発する第１の点状光源２ａと、緑色の光を発する第２の点状光源２ｂと、青色の光を発する第３の点状光源２ｃとから構成されている。なお、赤色（Ｒ）、緑色（Ｇ）および青色（Ｂ）の単色光を発するＬＥＤは、白色光を発するＬＥＤに比べて、発光効率が高く、カラーフィルタの赤色（Ｒ）、緑色（Ｇ）および青色（Ｂ）の透過特性と、ＬＥＤの発光スペクトルを合わせ込むことで、色再現性の高い表示装置を得ることができるので好ましい。複数の点状光源２が取り付けられた点状光源基板３は、赤色（Ｒ）、緑色（Ｇ）および青色（Ｂ）の単色の点状光源を組み合わせて、全体として白色光となるように配置されている。なお、本実施の形態１では、赤色光を発光する第１の点状光源１ａを２個連続して並べているが、本発明においては、これに限られるものではない。
【００１３】
リフレクタ４が、点状光源２からの光を混色手段１ｃの入射面１ｃへ集光するために、前記点状光源２の周囲に配置されている。矩形状の導光板５の導光板入射面５ａが、前記混色手段１の出射面１ｄと略平行に配置され、導光板上面５ｂを発光面としている。また、該導光板５の導光板下面５ｃには、光反射手段である反射シート６が配置されている。この導光板上面５ｂの上には、光を効率的に利用するための複数枚の光学シートからなる光学シート類７が配置されている。液晶表示素子８は、前記導光板上面５ｂ側に光学シート類７を介して配置されている。
【００１４】
なお、光学シート類７は、レンズシートを拡散シートで挟み込む構成であるが、このレンズシートは輝度の向上が必要な場合には、複数枚をその表面に形成されるプリズムの方向を考慮して組み合わせてもよい。また、拡散シートは、拡散性を向上させる場合には、２枚以上用いることは可能であるが、導光板５およびレンズシートの配向性によっては１枚または使用しなくてもよい。また、保護シート、プリズムシートまたは偏光反射プリズムを組み合わせてもよい。
【００１５】
また、前記液晶表示素子８は、図示しない上側または下側基板上に着色層、遮光層、スイッチング素子となる薄膜トランジスタ（以下、ＴＦＴという）、画素電極などの電極および配線が形成されたＴＦＴアレイ基板および対向基板、２枚の基板を等間隔に保持するスペーサ、２枚の基板を貼り合わせるシール材、２枚の基板とのあいだに液晶を注入したのちに封止する封止材、液晶に初期配向をもたせる配向膜および光を偏光させる偏光板などから構成されるが、本発明においては、既存の液晶表示素子を用いるので、以下、説明を省略する。
【００１６】
空気より屈折率の高い透明体は、本実施の形態１においては直角プリズム９の形状であり、直角をなす２つの面を反射面９ａ、９ｂとし、該反射面９ａ、９ｂに対して４５度の角度をなす面を斜面９ｃとする。なお、本実施の形態１においては、直角プリズム９の斜面９ｃを混色手段１の出射面１ｄと導光板５の導光板入射面５ａに対向するように配置している。また、反射面９ａ、９ｂは鏡面であることが好ましい。なお、１０は反射板であり、直角プリズム９の斜面９ｃ以外の面に配置されているが、直角プリズム９の斜面９ａ、９ｂで効率よく光を全反射できれば、配置する必要はない。。
【００１７】
前記混色手段１、導光板５および直角プリズム９の材料としては、主に光の透過率が高いＰＭＭＡ（ポリメチルメタクリレート）、ＰＣ（ポリカーボネート）またはガラスなどが用いられる。
【００１８】
前記第１の点状光源２ａ、第２の点状光源２ｂおよび第３の点状光源２ｃからなる複数の点状光源２、混色手段１、導光板５および直角プリズム９などを含めて面状光源装置と称す。また、前記液晶表示素子８は、駆動回路基板（図示せず）を備えており、該液晶表示素子８を面状光源装置の上部である導光板上面５ｂ側に配置することで液晶表示装置を構成する。
【００１９】
つぎに点状光源２から発せられた光が混色手段１、直角プリズム９および導光板５を通過したのち、液晶表示素子８に入射するまでの光路について説明する。
【００２０】
前記点状光源２である第１の点状光源２ａ、第２の点状光源２ｂおよび第３の点状光源２ｃから発せられた赤色、緑色および青色の単色光は、直接またはリフレクタ４によって反射され、入射面１ｃから混色手段１に入射する。混色手段１に入射する単色光は、混色手段１と空気との屈折率の違いにより全反射を繰り返しながら混色手段１内部を伝搬していく。単色光は混色手段１内部を伝搬していくうちに配光を広げるので、複数の点状光源２から発せられた赤色、緑色および青色の単色光は混色され白色光に均一化される。光の全反射条件が破られた光は混色手段１の出射面１ｄから出射することとなる。
【００２１】
前記混色手段１の出射面１ｄから出射した光は、混色手段１と直角プリズム９との間隙にある空気中を通過したのち、直角プリズム９の斜面９ｃに入射する。ここで、図３に基づいて直角プリズム９を通る光の光路を説明するが、説明を簡単にするために、直角プリズム９の屈折率を１．５とする。なお、本実施の形態１では直角プリズム９の周囲は空気で満たされているが、直角プリズム９より屈折率が低い材料で直角プリズム９の周囲を満たしてもよい。
【００２２】
図３に示されるように、空気中を通過した光は、直角プリズム９の斜面９ｃに対して入射角θ０（０°≦θ０≦９０°）で入射した場合には、屈折角をθ１とすると、スネルの法則から０°≦θ１≦ｓｉｎ^−１（１／ｎ・ｓｉｎθ０）＝４１．８１°を満たす屈折角θ１で屈折される。屈折された光は直角プリズム９内を進み、反射面９ａに対して入射角θ２＝４５°−θ１で入射する。ここで、反射面９ａで全反射する条件は、スネルの法則からθ２＝４５°−θ１≧ｓｉｎ^−１（１／ｎ）＝４１．８１°、θ１≦３．１９°、すなわちθ０≦４．７９°となる。
【００２３】
以上のように、直角プリズム９に屈折率１．５の材料を用いた場合に、直角プリズム９の斜面９ｃに対する入射角θ０を−４．７９°≦θ０≦４．７９°で光を入射することで、反射面９ａ、９ｂで光を全反射させることができる。逆に、直角プリズム９の斜面９ｃに対して４．７９°より大きな角度で入射した光は反射面９ａで全反射することなく透過され、直角プリズム９の斜面９ｃに対して−４．７９°より小さな角度で入射した光は反射面９ｂで全反射することなく透過される。透過された光は反射板１０によって反射され、再び直角プリズム９に入射される。この際、反射板１０において反射ロスが生じる。
【００２４】
なお、本実施の形態では、前記直角プリズム９の屈折率を１．５で説明したが、直角プリズム９を屈折率がより高い材料から作製することにより、反射面９ａ、９ｂで全反射する光の直角プリズム９の斜面９ｃに対する入射角θ０の範囲を広げることができる。逆に、直角プリズム９を屈折率が１．４１より低い材料から作製すると、直角プリズム９の斜面９ｃにあらゆる方向から入射した光は直角プリズム９の反射面９ａ、９ｂで全反射せず透過することとなる。このため、直角プリズム９としては、屈折率が１．４１以上の材料を用いることが好ましい。
【００２５】
前記反射面９ａまたは反射面９ｂで全反射した光、または直角プリズム９を透過して反射板１０によって反射されたのち、再び直角プリズム９に入射された光は、全反射または反射板１０での反射を繰り返し、反射板が設けられていない直角プリズム９の斜面９ｃから光の全反射条件が破られ出射する。
【００２６】
前記直角プリズム９の斜面９ｃから出射した光は、空気中を通過し、導光板５の導光板入射面５ａから入射する。導光板５に入射した光は、導光板５と空気との屈折率の違いにより全反射を繰り返しながら導光板５内部を伝搬していく。導光板上面５ｂと対向する導光板下面５ｃには、インクドットなどによる凹凸（図示せず）が形成されており、該凹凸に光があたり拡散することで、光の全反射条件が破られ導光板上面５ｂから光が出射する。また、導光板下面５ｂから出射された光は反射シート６によって反射され、再び導光板５に入射する。
【００２７】
前記導光板上面５ｂから出射した光は、拡散シート、保護シート、レンズシート、偏光反射シートまたはプリズムシートなどからなる光学シート類７を通過して液晶表示素子８に入射する。この液晶表示素子８は、前記ＴＦＴによる電圧のオンまたはオフによって液晶層が配光されることで、液晶表示素子８に入射した光は映像信号にあわせて変調され、赤色、緑色または青色の各色を表示する。
【００２８】
なお、本実施の形態１の面状光源装置では、透明体として直角プリズム９が用いられているが、本発明においては、これに限られるものではなく、たとえば図４に示されるように半円柱１１の透明体を用いても同様の作用効果を奏することができる。なお、図４は半円柱を透明体に用いた液晶表示装置の部分断面図であり、簡潔に説明するため図１〜２と同一または相当部品の説明は省略する。この半円柱１１の長方形の面１１ａは、混色手段１の出射面１ｄと導光板５の導光板入射面５ａに対向するよう配設されている。また、反射板１０は、半円柱１１に合わせて半円形に形成されている。
【００２９】
また、本実施の形態１の面状光源装置において、導光板５の導光板入射面５ａにサンドブラスト加工または梨地加工などにより表面を粗面化するか、または図５に示されるように、複数のプリズム形状の突部を形成することにより、導光板５の導光板入射面５ａに入射した光が導光板入射面５ａの近傍で導光板５の内部に拡散することで、輝度および色度の均一性が高い面状光源を得ることが可能である。なお、図５は突部を形成した導光板の部分拡大斜視図である。
【００３０】
以上のように、本発明の実施の形態１の液晶表示装置によれば、点状光源２から発せられた赤色、緑色および青色の単色光は、混色手段１および透明体９を介すことで、白色光として導光板に入射できるうえに、点状光源であった光源が面状光源化され、導光板４の導光板入射面５ａにおける入射光の強度が均一となり、導光板５の内部の導光板入射面５ａの近傍での色度ムラおよび輝度ムラの発生を抑制することができる。
【００３１】
また、液晶表示素子８に光を面状に出射する導光板５と、点状光源２からの単色光を白色光にする混色手段１との光路に、直角プリズム９を介すことにより、導光板５の下面５ｃと混色手段１の上面１ａとを対向させて重ねることができ、面状光源装置の厚さが薄くできるうえに、狭額縁化を図ることもできる。
【００３２】
さらに混色手段１から出射した光を直角プリズム９で全反射させたのち、導光板５に入射させることで、反射板１０による反射ロスを直角プリズム９の全反射により低減することができる。
【００３３】
実施の形態２
つぎに本発明の実施の形態２を説明する。図６は本発明の実施の形態２にかかわる液晶表示装置の部分断面図である。図６において、簡潔に説明するため図１〜２と同一または相当部品の説明は省略する。本実施の形態２における直角プリズム１２は、直角をなす２つの面を第１の面１２ａと第２の面１２ｂとし、この第１の面１２ａおよび第２の面１２ｂに対して４５度の角度をなす面を斜面１２ｃとする。なお、直角プリズム１２の第１の面１２ａを混色手段１の出射面１ｄに配置するとともに、直角プリズム１２の第２の面１２ｂを導光板５の導光板入射面５ａに対向するように配置している。また、斜面１２ｃは鏡面であることが好ましい。
【００３４】
なお、実施の形態２は、直角プリズム１２の第１の面１２ａを混色手段１の出射面１ｄに配置し、直角プリズム１２の第２の面１２ｂを導光板５の導光板入射面５ａに対向するように配置している点で前記実施の形態１と異なっており、後述する直角プリズム１２の配置による作用効果以外は、実施の形態１と同様の作用効果を奏する。
【００３５】
前記実施の形態１においては、図２に示されるように、導光板５の下面５ｃと混色手段１の上面１ａとを対向させて重ねているので、導光板５の下面５ｃ側の直角プリズム９の近傍に、たとえば駆動回路基板などの部品を配置することができないために、面状光源装置の設計に多少の制約がある。しかし、本実施の形態２においては、図６に示されるように、直角プリズム１２の第１の面１２ａを混色手段１の出射面１ｄに配置し、直角プリズム１２の第２の面１２ｂを導光板５の導光板入射面５ａに対向するように配置することで、混色手段１の出射面１ｄと導光板５の導光板入射面５ａとが直角をなし、導光板５の下面５ｃ側の直角プリズム１２の近傍にスペースを確保でき、駆動回路基板などを配置することができる。
【００３６】
実施の形態３
つぎに本発明の実施の形態３を説明する。図７は本発明の実施の形態３にかかわる液晶表示装置の部分断面図、図８は本発明の実施の形態３にかかわる液晶表示装置の変形例を示した部分断面図、図９は本発明の実施の形態３にかかわる液晶表示装置の他の変形例を示した部分断面図である。図７〜９において、簡潔に説明するため図１〜２と同一または相当部品の説明は省略する。まず図７に示されるように、本実施の形態３における第２の混色手段１３は、入射面１３ｃから出射面１３ｄに向かって直線的に厚さが増加する（傾斜角度をδ１とする）傾斜平面部１３ｅを有する形状にされている。また、図８に示されるように、本実施の形態３の変形例における第３の混色手段１４は、入射面１４ｃの近傍で入射面１４ｃに垂直な第１の平面部１４ｅと、該第１の平面部１４ｅに続いて出射面１４ｄに向かって直線的に厚さが増加する（傾斜角度をδ２とする）傾斜平面部１４ｆと、出射面１４ｄの近傍で傾斜平面部１４ｆに続いて厚さが前記第１の平面部１４ｅより厚い状態で出射面１４ｄに垂直な第２の平面部１４ｇとから構成されている。また、図９に示されるように、本実施の形態３の他の変形例における第４の混色手段１５は、入射面１５ｃに垂直な平面部１５ｅと、該平面部１５ｅに続いて出射面１５ｄに向かって直線的に厚さが増加する（傾斜角度をδ２とする）傾斜平面部１５ｆとから構成されている。
【００３７】
なお、本実施の形態３は、第２の混色手段１３、第３の混色手段１４および第４の混色手段１５の形状が矩形状でない点で前記実施の形態１と異なっており、後述する第２の混色手段１３、第３の混色手段１４および第４の混色手段１５の形状による作用効果以外は、実施の形態１と同様の作用効果を奏する。
【００３８】
本実施の形態３においては、図７に示されるように、第２の混色手段１３の上面１３ａおよび下面１３ｂが入射面１３ｃに対して同じ傾斜角度δ１で傾斜している傾斜平面部１３ｅを設けることで、実施の形態１における矩形状の混色手段１に比べて、第２の混色手段１３の内部を光が伝搬していき、傾斜平面部１３ｅに対する入射角が小さくなる。入射角が小さくなることで傾斜部平面１３ｅにおける反射角が小さくなり、これを繰り返すことで、第２の混色手段１３の内部から出射面１３ｄに入射する光の入射角の範囲が狭くなる。
【００３９】
したがって、実施の形態１における矩形状の混色手段１の出射面１ｄから出射した光の直角プリズム９への入射角の範囲に比べて、第２の混色手段１３の出射面１３ｄから出射した光の直角プリズム９への入射角の範囲が狭くなることで、直角プリズム９の反射面９ａ、９ｂで全反射される光の量が多くなり効率よく光の向きを変えることが可能である。
【００４０】
また、図８に示されるように、第３の混色手段１４において、傾斜平面部１４ｆにおける厚さより厚い部分を第２の平面部１４ｇとすることにより、導光板５の下面５ｃと第３の混色手段１４の上面側の第２の平面部１４ｇとを平行に配置することができるので、図７に示される第２の混色手段１３と導光板５との位置決めに比べて、位置決めを容易に行なうことができる。
【００４１】
また、第２の混色手段１３の上面１３ａおよび下面１３ｂが入射面１３ｃに対して傾斜している角度δ１を大きくすればするほど、第２の混色手段１３の内部の傾斜平面部１３ｅに対する光の入射角が小さくなり、傾斜部平面１３ｅにおける反射角が小さくなるので好ましい。
【００４２】
しかしながら、図６に示されるように、第２の混色手段１３は一つの側面で単一の傾斜平面部１３ｅを構成しているので、充分な傾斜角度δ１を得るために、第２の混色手段１３の厚さが厚くなり、装置として小型化および軽量化が難しくなる。しかし、実施の形態１における混色手段１に比べて、混色手段の出射面から出射する光の直角プリズム９への入射角の範囲を狭くするのであれば、図８〜９に示されるように、混色手段の側面に少なくとも１箇所だけ傾斜平面部１４ｆ、１５ｆを設けることにより、傾斜角度δ２が同じであっても、混色手段を薄くすることができ、図７に示される液晶表示装置に比べて、装置として小型化および軽量化が可能である。
【００４３】
なお、本実施の形態３においては、混色手段の上面および下面で同じ角度δで傾斜している傾斜平面部を設けているが、混色手段の上面および下面で異なる角度で傾斜している傾斜平面部を設けてもよい。また、本実施の形態３においては、混色手段の上面および下面に傾斜平面部を設けているが、混色手段の入射面および出射面を除く面の少なくなくとも１面に設ければ、実施の形態１における混色手段１に比べて、混色手段の出射面から出射する光の直角プリズム９への入射角の範囲を狭くすることが可能である。
【００４４】
実施の形態４
つぎに本発明の実施の形態４を説明する。図１０は本発明の実施の形態４にかかわる混色手段と透明体である直角プリズムとを一体に形成した液晶表示装置を示す部分断面図、図１１は本発明の実施の形態４にかかわる導光板と透明体である直角プリズムとを一体に形成した液晶表示装置を示す部分断面図、図１２は本発明の実施の形態４にかかわる混色手段、導光板および透明体である直角プリズムを一体に形成した液晶表示装置を示す部分断面図、図１３は本発明の実施の形態４にかかわる混色手段、導光板および透明体を一体に形成した他の液晶表示装置を示す部分断面図である。図１０〜１３において、簡潔に説明するため図４および図７と同一または相当部品の説明は省略する。
【００４５】
図１０に示される第２の混色手段１３と直角プリズム９、図１１に示される導光板５と直角プリズム９および図１２に示される第２の混色手段１３、導光板５および直角プリズム９は、第２の混色手段１３、直角プリズム９および導光板５をそれぞれ成形したのちに、透過率が高い両面テープで貼り付けるか、または紫外線硬化樹脂などで一体化されている。また、図１３に示される第２の混色手段１３、導光板５および半円柱１１は、矩形状の透明体を成形したのち、透明体を加熱しながら曲げることで所望の形状に一体加工されている。
【００４６】
なお、本実施の形態４は、第２の混色手段１３と直角プリズム９、導光板５と直角プリズム９、第２の混色手段１３、導光板５および直角プリズム９、または第２の混色手段１３、導光板５および半円柱１１が一体に形成されている点で前記実施の形態１および３と異なっており、後述する第２の混色手段１３と直角プリズム９、導光板５と直角プリズム９、第２の混色手段１３、導光板５および直角プリズム９または導光板を一体に形成することによる作用効果以外は、実施の形態１および３と同様の作用効果を奏する。
【００４７】
前記実施の形態３においては、図７に示されるように、第２の混色手段１３を出射した光は直角プリズム９の入射面である斜面９ｃ、および直角プリズム９を出射した光は導光板５の導光板入射面５ａに入射されるが、一部の光が斜面９ｃまたは導光板入射面５ａで反射され、光のロスを生じる。しかし、本実施の形態４においては、図１０に示されるように、第２の混色手段１３と直角プリズム９とを一体に形成することにより、実施の形態３のような斜面９ｃでの反射がなくなるため、高輝度の面状光源装置を得ることができる。また、図１１に示されるように、導光板５と直角プリズム９とを一体に形成することにより、実施の形態１のような導光板入射面５ａでの反射をなくすことができるため、高輝度の面状光源装置を得ることができる。また、図１２〜１３に示されるように、第２の混色手段１３、導光板５および直角プリズム９または半円柱１１を一体に形成することにより、実施の形態１および３のような斜面９ｃ、長方形の面１１ａおよび導光板入射面５ａでの反射をなくすことができるため、効果的に導光板上面５ｂまで光を導くことができ、高輝度の面状光源装置を得ることができる。
【００４８】
なお、図１２〜１３における面状光源装置においては、第２の混色手段１３の入射面１３ｃに、図５に示すような複数のプリズム形状の突部を形成することで、第２の混色手段１３の入射面１３ｃに入射した光を該入射面１３ｃの近傍で混色手段１３の内部に拡散させることができる。
【００４９】
【発明の効果】
本発明は、以下に示すような効果を奏する。
【００５０】
本発明は、混色手段から導光板への光路に空気より屈折率の高い透明体を介在しているので、点状光源であった光源が面状光源化され、導光板の入射面における入射光の強度が均一となり、導光板の内部の導光板の入射面の近傍での輝度ムラの発生を抑制することができる。
【００５１】
また、点状光源は、赤色の光を発する第１の点状光源と、緑色の光を発する第２の点状光源と、青色の光を発する第３の点状光源とからなるので、点状光源から発せられた赤色、緑色および青色の単色光を白色光として導光板に入射できる。
【００５２】
また、透明体は直角プリズムであり、直角プリズムの斜面を混色手段の出射面と導光板の入射面に対向するよう配設するか、または透明体は半円柱であり、半円柱の長方形の面を混色手段の出射面と導光板の入射面に対向するよう配設しているので、導光板と混色手段とを対向させて重ねることができ、面状光源装置の厚さが薄くできるうえに、狭額縁化を図ることができる。また、混色手段から出射した光を透明体で全反射させ導光板に入射させることで、反射板による反射ロスを透明体の全反射により低減することができる。
【００５３】
また、透明体は直角プリズムであり、混色手段の出射面に対向する第１の面と、導光板の入射面に対向する第２の面とを有し、第１の面と第２の面とが直角をなしているので、混色手段の出射面と導光板の導光板入射面とが直角をなし、導光板の下面側の直角プリズムの近傍にスペースが得ることができる。
【００５４】
また、混色手段が、混色手段の入射面から混色手段の出射面に向かって直線的に混色手段の厚さが増加する傾斜平面部を有するので、直角プリズムの反射面で全反射される光の量が多くなり効率よく光の向きを変えることができる。
【００５５】
また、混色手段が、混色手段の入射面近傍では、混色手段の入射面に垂直な第１の平面部と、第１の平面部に続いて混色手段の出射面に向かって直線的に混色手段の厚さが増加する傾斜平面部と、混色手段の出射面近傍では傾斜平面部に続いて混色手段の厚さが第１の平面部より厚い状態で混色手段の出射面に垂直な第２の平面部とにより構成されているので、直角プリズムの反射面で全反射される光の量が多くなり効率よく光の向きを変えることができる。また、導光板の下面と混色手段の上面側の第２の平面部とを平行に配置することができるので、位置決めを容易に行なうことができる。
【００５６】
また、混色手段が、混色手段の入射面近傍では、混色手段の入射面に垂直な平面部と、平面部に続いて混色手段の出射面に向かって直線的に混色手段の厚さが増加する傾斜平面部とにより構成されているので、直角プリズムの反射面で全反射される光の量が多くなり効率よく光の向きを変えることができる。
【００５７】
また、混色手段と透明体とを一体に形成したり、導光板と透明体とを一体に形成しているので、高輝度の面状光源装置を得ることができる。
【００５８】
また、混色手段、導光板および透明体を一体に形成しているので、効果的に導光板上面まで光を導くことができ、高輝度の面状光源装置を得ることができる。
【００５９】
また、混色手段の入射面にプリズム形状の突部を形成したり、導光板の入射面にプリズム形状の突部を形成しているので、混色手段の入射面に入射した光が入射面近傍で混色手段内部に拡散することで、輝度および色度の均一性が高い面状光源を得ることができる。
【００６０】
さらに本発明は、面状光源装置の上部に、液晶表示素子を備えているので、表示特性に優れた安価な液晶表示装置を得ることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態１にかかわる液晶表示装置の概略構成を示す平面図である。
【図２】図１に示す液晶表示装置のＩ−Ｉ線断面図である。
【図３】図２における直角プリズムを通る光の光路を説明するための要部拡大図である。
【図４】半円柱を透明体に用いた液晶表示装置の部分断面図である。
【図５】突部を形成した入射面の部分拡大拡大斜視図である。
【図６】本発明の実施の形態２にかかわる液晶表示装置の部分断面図である。
【図７】本発明の実施の形態３にかかわる液晶表示装置の部分断面図である。
【図８】本発明の実施の形態３にかかわる液晶表示装置の変形例を示した部分断面図である。
【図９】本発明の実施の形態３にかかわる液晶表示装置の他の変形例を示した部分断面図である。
【図１０】本発明の実施の形態４にかかわる混色手段と透明体である直角プリズムとを一体に形成した液晶表示装置を示す部分断面図である。
【図１１】本発明の実施の形態４にかかわる導光板と透明体である直角プリズムとを一体に形成した液晶表示装置を示す部分断面図である。
【図１２】本発明の実施の形態４にかかわる混色手段、導光板および透明体である直角プリズムを一体に形成した液晶表示装置を示す部分断面図である。
【図１３】本発明の実施の形態４にかかわる混色手段、導光板および透明体を一体に形成した他の液晶表示装置を示す部分断面図である。
【符号の説明】
１混色手段
１ａ上面
１ｂ下面
１ｃ入射面
１ｄ出射面
２点状光源
２ａ第１の点状光源
２ｂ第２の点状光源
２ｃ第３の点状光源
５導光板
５ａ導光板入射面
９、１２直角プリズム
９ｃ斜面
１１半円柱
１１ａ長方形の面
１２ａ第１の面
１２ｂ第２の面
１３第２の混色手段
１３ｃ、１４ｃ、１５ｃ入射面
１３ｄ、１４ｄ、１５ｄ出射面
１３ｅ傾斜平面部
１４第３の混色手段
１４ｅ第１の平面部
１４ｆ傾斜平面部
１４ｇ第２の平面部
１５第４の混色手段
１５ｅ平面部
１５ｆ傾斜平面部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a planar light source device and a liquid crystal display device using the same. More specifically, the present invention relates to a planar light source device using a plurality of point light sources such as light emitting diodes that emit monochromatic light of R (red), G (green), and B (blue), and a liquid crystal display device using the device.
[0002]
[Prior art]
2. Description of the Related Art A liquid crystal display device includes a liquid crystal display element including two glass substrates sandwiching liquid crystal, and a planar light source device disposed on the back side of the liquid crystal display element. In this planar light source device, a linear cold cathode tube is used as a light source. However, mercury is used in the cold cathode tube, and it has become difficult to use it in recent years due to environmental problems. In addition, there is a problem that luminance is deteriorated due to consumption of mercury.
[0003]
On the other hand, for a small liquid crystal display device such as a mobile phone, a light emitting diode (hereinafter simply referred to as an LED) is used because of a longer light source life and better light emission efficiency than a cold cathode tube. A planar light source device has been developed.
[0004]
In a conventional planar light source device using a light emitting diode, an LED that emits light, a linear light guide that converts the emitted light into a linear light source and emits the light from an emission surface, and the linearized light And a light guide plate which is incident on the light incident end face to be a surface light source (for example, see Patent Document 1).
[0005]
[Patent Document 1]
JP-A-10-283817 ([0001] to [0002], [0027], FIGS. 1, 2 and 8)
[0006]
[Problems to be solved by the invention]
However, when the configuration of a conventional small-sized planar light source device for a liquid crystal display device using LEDs is applied to a small-sized and large-sized planar light source device for a liquid crystal display device, the conventional small-sized liquid crystal display device is difficult to use. As described above, it is not possible to obtain a sufficient luminance by using only one white LED as a light source (one set in the case of combining one LED emitting red, green and blue monochromatic light). For this reason, if a plurality of LEDs are used as a light source in order to increase the brightness, the plurality of LEDs will be disposed along the light incident end face of the light guide (in the Y direction in FIG. 1 of Patent Document 1), and the width will be narrow. There is a problem that it is difficult to make a picture frame.
[0007]
In view of the circumstances described above, the present invention can provide an inexpensive planar light source device that does not generate luminance unevenness and chromaticity unevenness, can cope with a narrower frame of a liquid crystal display device, and can obtain this planar light source device. It is an object to provide a liquid crystal display device which can obtain excellent display characteristics at low cost by using a light source device.
[0008]
[Means for Solving the Problems]
The planar light source device of the present invention has a pair of opposed upper and lower surfaces and a plurality of side surfaces on edges of the upper surface and the lower surface, and among the side surfaces, the pair of opposed surfaces is an entrance surface and an exit surface. And a plurality of point-like light sources arranged in the vicinity of the entrance surface of the color mixing unit and along the longitudinal direction of the entrance surface, and arranged substantially parallel or substantially perpendicular to the color mixing unit. And a rectangular light guide plate comprising: a transparent body having a higher refractive index than air in an optical path from the color mixing means to the light guide plate.
[0009]
Further, the liquid crystal display device of the present invention is characterized in that the planar light source device, a liquid crystal display element disposed on the planar light source device and comprising two glass substrates sandwiching a liquid crystal, And a driving circuit board to be connected.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a planar light source device of the present invention and a liquid crystal display device using the same will be described with reference to the accompanying drawings.
[0011]
Embodiment 1
1 is a plan view showing a schematic configuration of a liquid crystal display device according to Embodiment 1 of the present invention, FIG. 2 is a cross-sectional view taken along line II of the liquid crystal display device shown in FIG. 1, and FIG. It is a principal part enlarged view for demonstrating the optical path of the light which passes. 1 to 3, reference numeral 1 denotes a color mixing means. The color mixing means 1 is opposed to a pair of opposed upper surfaces 1a and 1b and a plurality of side surfaces connecting edges of the upper surface 1a and the lower surface 1b. It is composed of a pair of surfaces, an entrance surface 1c and an exit surface 1d. It is preferable that all surfaces of the color mixing means 1 are mirror surfaces.
[0012]
A point light source 2 such as an LED is disposed near the incident surface 1c of the color mixing means 1 and is disposed along the longitudinal direction of the incident surface 1c, and a first point light source 2a emitting red light; It is composed of a second point light source 2b that emits green light and a third point light source 2c that emits blue light. Note that LEDs emitting monochromatic light of red (R), green (G) and blue (B) have higher luminous efficiency than LEDs emitting white light, and the red (R) and green (G) By matching the transmission characteristics of blue and blue (B) with the emission spectrum of the LED, a display device with high color reproducibility can be obtained, which is preferable. The point light source substrate 3 to which the plurality of point light sources 2 are attached is arranged such that white light as a whole is obtained by combining single point light sources of red (R), green (G), and blue (B). Have been. In the first embodiment, two first point light sources 1a that emit red light are arranged in a row, but the present invention is not limited to this.
[0013]
A reflector 4 is arranged around the point light source 2 in order to condense the light from the point light source 2 to the incident surface 1c of the color mixing means 1c. The light guide plate entrance surface 5a of the rectangular light guide plate 5 is disposed substantially parallel to the emission surface 1d of the color mixing means 1, and the light guide plate upper surface 5b is used as a light emitting surface. On the lower surface 5c of the light guide plate 5 of the light guide plate 5, a reflection sheet 6 as a light reflection means is disposed. On the light guide plate upper surface 5b, optical sheets 7 including a plurality of optical sheets for efficiently utilizing light are arranged. The liquid crystal display element 8 is disposed on the light guide plate upper surface 5b side with the optical sheets 7 interposed therebetween.
[0014]
Note that the optical sheets 7 have a configuration in which a lens sheet is sandwiched between diffusion sheets. When it is necessary to improve the brightness of this lens sheet, a plurality of the lens sheets are taken into consideration in consideration of the direction of a prism formed on the surface thereof. They may be combined. In order to improve the diffusivity, two or more diffusion sheets can be used. However, depending on the orientation of the light guide plate 5 and the lens sheet, one or no diffusion sheet may be used. Moreover, you may combine a protection sheet, a prism sheet, or a polarization reflection prism.
[0015]
In addition, the liquid crystal display element 8 is a TFT array substrate in which a coloring layer, a light shielding layer, a thin film transistor (hereinafter, referred to as a TFT) serving as a switching element, electrodes such as pixel electrodes, and wiring are formed on an upper or lower substrate (not shown). And an opposing substrate, a spacer for holding the two substrates at equal intervals, a sealing material for bonding the two substrates, a sealing material for injecting the liquid crystal between the two substrates, and then sealing the liquid crystal. It is composed of an alignment film for providing alignment, a polarizing plate for polarizing light, and the like. However, in the present invention, since an existing liquid crystal display element is used, description thereof will be omitted below.
[0016]
The transparent body having a higher refractive index than air has the shape of the right-angle prism 9 in the first embodiment, and two surfaces forming a right angle are reflection surfaces 9a and 9b, and are 45 degrees with respect to the reflection surfaces 9a and 9b. The surface forming the angle of is referred to as a slope 9c. In the first embodiment, the inclined surface 9c of the right-angle prism 9 is disposed so as to face the emission surface 1d of the color mixing means 1 and the light guide plate entrance surface 5a of the light guide plate 5. Further, it is preferable that the reflection surfaces 9a and 9b are mirror surfaces. Reference numeral 10 denotes a reflection plate, which is arranged on a surface other than the inclined surface 9c of the right-angle prism 9, but is not necessary if the inclined surfaces 9a and 9b of the right-angle prism 9 can efficiently totally reflect light. .
[0017]
As a material of the color mixing means 1, the light guide plate 5, and the right-angle prism 9, PMMA (polymethyl methacrylate), PC (polycarbonate), glass, or the like having high light transmittance is mainly used.
[0018]
A plurality of point light sources 2 including the first point light source 2a, the second point light source 2b, and the third point light source 2c, the color mixing means 1, the light guide plate 5, the right-angle prism 9, etc. It is called a light source device. Further, the liquid crystal display element 8 includes a drive circuit board (not shown), and the liquid crystal display element 8 is arranged on the upper surface 5b of the light guide plate, which is the upper part of the planar light source device. Constitute.
[0019]
Next, an optical path from the time when the light emitted from the point light source 2 passes through the color mixing means 1, the right-angle prism 9 and the light guide plate 5 to the time when the light enters the liquid crystal display element 8 will be described.
[0020]
The red, green, and blue monochromatic lights emitted from the first point light source 2a, the second point light source 2b, and the third point light source 2c, which are the point light sources 2, are reflected directly or by the reflector 4. Then, the light enters the color mixing means 1 from the incident surface 1c. The monochromatic light incident on the color mixing means 1 propagates inside the color mixing means 1 while repeating total reflection due to a difference in the refractive index between the color mixing means 1 and air. Since the monochromatic light spreads the light distribution while propagating inside the color mixing means 1, the red, green and blue monochromatic lights emitted from the plurality of point light sources 2 are mixed and uniformized to white light. The light whose total reflection condition has been broken is emitted from the emission surface 1d of the color mixing means 1.
[0021]
The light emitted from the exit surface 1d of the color mixing means 1 passes through the air in the gap between the color mixing means 1 and the right-angle prism 9, and then enters the inclined surface 9c of the right-angle prism 9. Here, an optical path of light passing through the right-angle prism 9 will be described with reference to FIG. 3. For simplicity, the refractive index of the right-angle prism 9 is set to 1.5. In the first embodiment, the periphery of the right-angle prism 9 is filled with air, but the periphery of the right-angle prism 9 may be filled with a material having a lower refractive index than that of the right-angle prism 9.
[0022]
As shown in FIG. 3, when the light that has passed through the air enters the inclined surface 9c of the right-angle prism 9 at an incident angle θ0 (0 ° ≦ θ0 ≦ 90 °), the refraction angle is set to θ1. 0 ° ≦ θ1 ≦ sin from Snell's law ^-1 The light is refracted at a refraction angle θ1 satisfying (1 / n · sin θ0) = 41.81 °. The refracted light travels through the right-angle prism 9 and enters the reflecting surface 9a at an incident angle θ2 = 45 ° −θ1. Here, the condition for total reflection on the reflecting surface 9a is as follows from the Snell's law: θ2 = 45 ° −θ1 ≧ sin ^-1 (1 / n) = 41.81 °, θ1 ≦ 3.19 °, that is, θ0 ≦ 4.79 °.
[0023]
As described above, when a material having a refractive index of 1.5 is used for the right-angle prism 9, light is incident at an incident angle θ0 of −4.79 ° ≦ θ0 ≦ 4.79 ° with respect to the inclined surface 9 c of the right-angle prism 9. Thus, light can be totally reflected by the reflection surfaces 9a and 9b. Conversely, light incident on the inclined surface 9c of the right-angle prism 9 at an angle larger than 4.79 ° is transmitted without being totally reflected on the reflecting surface 9a, and is -4.79 ° on the inclined surface 9c of the right-angle prism 9. Light incident at a smaller angle is transmitted without being totally reflected by the reflection surface 9b. The transmitted light is reflected by the reflection plate 10 and reenters the right-angle prism 9. At this time, reflection loss occurs in the reflection plate 10.
[0024]
In the present embodiment, the refractive index of the right-angle prism 9 has been described as 1.5. However, by making the right-angle prism 9 from a material having a higher refractive index, the light totally reflected by the reflection surfaces 9a and 9b can be obtained. Of the right angle prism 9 with respect to the inclined surface 9c can be widened. Conversely, when the right-angle prism 9 is made of a material having a refractive index lower than 1.41, light incident on the inclined surface 9c of the right-angle prism 9 from all directions is transmitted without being totally reflected by the reflection surfaces 9a and 9b of the right-angle prism 9. It will be. For this reason, it is preferable to use a material having a refractive index of 1.41 or more for the right-angle prism 9.
[0025]
The light totally reflected by the reflection surface 9a or the reflection surface 9b, or the light transmitted through the right-angle prism 9 and reflected by the reflection plate 10 and then incident on the right-angle prism 9 again, is totally reflected or reflected by the reflection plate 10. The light is repeatedly reflected, and the light is emitted from the inclined surface 9c of the right-angle prism 9 provided with no reflector, with the condition of total reflection of light being broken.
[0026]
The light emitted from the inclined surface 9c of the right-angle prism 9 passes through the air and enters from the light guide plate entrance surface 5a of the light guide plate 5. Light incident on the light guide plate 5 propagates inside the light guide plate 5 while repeating total reflection due to a difference in refractive index between the light guide plate 5 and air. Irregularities (not shown) such as ink dots are formed on the lower surface 5c of the light guide plate facing the upper surface 5b of the light guide plate. Light is emitted from the light plate upper surface 5b. Further, light emitted from the light guide plate lower surface 5b is reflected by the reflection sheet 6 and enters the light guide plate 5 again.
[0027]
Light emitted from the upper surface 5b of the light guide plate passes through optical sheets 7 such as a diffusion sheet, a protection sheet, a lens sheet, a polarization reflection sheet, a prism sheet, etc., and enters the liquid crystal display element 8. In the liquid crystal display element 8, the light incident on the liquid crystal display element 8 is modulated in accordance with the video signal by distributing the liquid crystal layer by turning on or off the voltage by the TFT, and each color of red, green or blue is Is displayed.
[0028]
In the planar light source device of the first embodiment, the right-angle prism 9 is used as the transparent body. However, the present invention is not limited to this, and for example, as shown in FIG. The same operation and effect can be obtained by using the eleventh transparent body. FIG. 4 is a partial cross-sectional view of a liquid crystal display device using a semi-cylindrical column as a transparent body. For simplicity, description of the same or equivalent parts as in FIGS. The rectangular surface 11 a of the semicircular column 11 is disposed so as to face the light exit surface 1 d of the color mixing means 1 and the light guide plate incident surface 5 a of the light guide plate 5. The reflecting plate 10 is formed in a semicircular shape in accordance with the semicircular column 11.
[0029]
Further, in the surface light source device of the first embodiment, the surface of the light guide plate entrance surface 5a of the light guide plate 5 is roughened by sandblasting or satin finish, or as shown in FIG. By forming the prism-shaped protrusions, light incident on the light guide plate incident surface 5a of the light guide plate 5 is diffused into the light guide plate 5 near the light guide plate incident surface 5a, so that brightness and chromaticity are uniform. It is possible to obtain a highly planar light source. FIG. 5 is a partially enlarged perspective view of the light guide plate on which the protrusion is formed.
[0030]
As described above, according to the liquid crystal display device of Embodiment 1 of the present invention, the red, green, and blue monochromatic lights emitted from the point light source 2 pass through the color mixing means 1 and the transparent body 9. In addition to being able to enter the light guide plate as white light, the light source, which was a point light source, is turned into a planar light source, and the intensity of the incident light on the light guide plate incident surface 5a of the light guide plate 4 becomes uniform. The occurrence of chromaticity unevenness and luminance unevenness in the vicinity of the light guide plate incident surface 5a can be suppressed.
[0031]
In addition, the light guide plate 5 that emits light to the liquid crystal display element 8 in a planar shape and the color mixing unit 1 that converts the monochromatic light from the point light source 2 to white light are guided through a right-angle prism 9 to pass through. The lower surface 5c of the light plate 5 and the upper surface 1a of the color mixing means 1 can be overlapped so as to face each other, so that the thickness of the planar light source device can be reduced and the frame can be narrowed.
[0032]
Further, after the light emitted from the color mixing means 1 is totally reflected by the right-angle prism 9 and then incident on the light guide plate 5, the reflection loss by the reflector 10 can be reduced by the total reflection of the right-angle prism 9.
[0033]
Embodiment 2
Next, a second embodiment of the present invention will be described. FIG. 6 is a partial sectional view of a liquid crystal display device according to Embodiment 2 of the present invention. 6, description of the same or equivalent parts as those in FIGS. 1 and 2 is omitted for the sake of simplicity. The right-angle prism 12 in the second embodiment has two surfaces forming a right angle as a first surface 12a and a second surface 12b, and an angle of 45 degrees with respect to the first surface 12a and the second surface 12b. Is a slope 12c. Note that the first surface 12a of the right-angle prism 12 is arranged on the emission surface 1d of the color mixing means 1, and the second surface 12b of the right-angle prism 12 is arranged to face the light guide plate entrance surface 5a of the light guide plate 5. ing. Further, the slope 12c is preferably a mirror surface.
[0034]
In the second embodiment, the first surface 12a of the right-angle prism 12 is disposed on the emission surface 1d of the color mixing means 1, and the second surface 12b of the right-angle prism 12 faces the light guide plate entrance surface 5a of the light guide plate 5. The first embodiment is different from the first embodiment in that the second embodiment is arranged so as to perform the same operation and effect as the first embodiment, except for the operation and effect by the arrangement of the right-angle prism 12 described later.
[0035]
In the first embodiment, as shown in FIG. 2, since the lower surface 5c of the light guide plate 5 and the upper surface 1a of the color mixing means 1 are overlapped so as to face each other, the right-angle prism 9 on the lower surface 5c side of the light guide plate 5 is provided. For example, since a component such as a drive circuit board cannot be arranged in the vicinity of, there are some restrictions on the design of the planar light source device. However, in the second embodiment, as shown in FIG. 6, the first surface 12a of the right-angle prism 12 is disposed on the exit surface 1d of the color mixing means 1, and the second surface 12b of the right-angle prism 12 is guided. By arranging it so as to face the light guide plate incident surface 5a of the light plate 5, the exit surface 1d of the color mixing means 1 and the light guide plate incident surface 5a of the light guide plate 5 form a right angle, and the right angle on the lower surface 5c side of the light guide plate 5 A space can be secured near the prism 12, and a drive circuit board and the like can be arranged.
[0036]
Embodiment 3
Next, a third embodiment of the present invention will be described. FIG. 7 is a partial cross-sectional view of a liquid crystal display device according to Embodiment 3 of the present invention, FIG. 8 is a partial cross-sectional view showing a modification of the liquid crystal display device according to Embodiment 3 of the present invention, and FIG. FIG. 21 is a partial cross-sectional view showing another modified example of the liquid crystal display device according to the third embodiment. 7 to 9, the same or corresponding parts as those in FIGS. First, as shown in FIG. 7, the second color mixing means 13 according to the third embodiment has a slope in which the thickness increases linearly from the incident surface 13c to the emission surface 13d (the inclination angle is δ1). It has a shape having a flat portion 13e. As shown in FIG. 8, the third color mixing means 14 in the modification of the third embodiment includes a first flat portion 14e near the incident surface 14c and perpendicular to the incident surface 14c, The thickness increases linearly toward the emission surface 14d following the plane portion 14e (the inclination angle is set to δ2), and the thickness near the emission surface 14d follows the inclined plane portion 14f. And a second flat portion 14g which is thicker than the first flat portion 14e and is perpendicular to the emission surface 14d. As shown in FIG. 9, the fourth color mixing means 15 in another modification of the third embodiment includes a plane portion 15e perpendicular to the entrance surface 15c, and an exit surface 15d following the plane portion 15e. And the inclined plane portion 15f whose thickness increases linearly (the inclination angle is δ2).
[0037]
Note that the third embodiment is different from the first embodiment in that the shapes of the second color mixing means 13, the third color mixing means 14, and the fourth color mixing means 15 are not rectangular. Except for the functions and effects of the shapes of the second color mixing means 13, the third color mixing means 14, and the fourth color mixing means 15, the same functions and effects as those of the first embodiment are exerted.
[0038]
In the third embodiment, as shown in FIG. 7, an inclined plane portion 13e in which the upper surface 13a and the lower surface 13b of the second color mixing means 13 are inclined at the same inclination angle δ1 with respect to the incident surface 13c is provided. As a result, compared with the rectangular color mixing means 1 in the first embodiment, light propagates inside the second color mixing means 13 and the incident angle with respect to the inclined plane portion 13e becomes smaller. By reducing the incident angle, the reflection angle on the inclined plane 13e is reduced, and by repeating this, the range of the incident angle of the light entering the emission surface 13d from inside the second color mixing means 13 is reduced.
[0039]
Therefore, compared to the range of the incident angle of the light emitted from the exit surface 1d of the rectangular color mixing means 1 to the right-angle prism 9 in the first embodiment, the light emitted from the emission surface 13d of the second color When the range of the incident angle to the right-angle prism 9 is narrowed, the amount of light totally reflected by the reflection surfaces 9a and 9b of the right-angle prism 9 increases, and the direction of the light can be changed efficiently.
[0040]
Further, as shown in FIG. 8, in the third color mixing means 14, a portion thicker than the thickness of the inclined flat portion 14f is set as the second flat portion 14g, so that the lower surface 5c of the light guide plate 5 and the third color mixing portion are formed. Since the second plane portion 14g on the upper surface side of the means 14 can be arranged in parallel, the positioning can be easily performed as compared with the positioning between the second color mixing means 13 and the light guide plate 5 shown in FIG. be able to.
[0041]
Further, the larger the angle δ1 at which the upper surface 13a and the lower surface 13b of the second color mixing means 13 are inclined with respect to the incident surface 13c, the more the light is transmitted to the inclined flat portion 13e inside the second color mixing means 13. This is preferable because the incident angle becomes smaller and the reflection angle on the inclined plane 13e becomes smaller.
[0042]
However, as shown in FIG. 6, since the second color mixing means 13 forms a single inclined plane portion 13e on one side, the second color mixing means 13 is required to obtain a sufficient inclination angle δ1. 13 becomes thicker, making it difficult to reduce the size and weight of the device. However, if the range of the incident angle of the light emitted from the exit surface of the color mixing means to the right-angle prism 9 is reduced as compared with the color mixing means 1 in the first embodiment, as shown in FIGS. By providing at least one inclined plane portion 14f, 15f on the side surface of the color mixing means, the color mixing means can be made thinner even if the inclination angle δ2 is the same, and compared with the liquid crystal display device shown in FIG. In addition, the device can be reduced in size and weight.
[0043]
In the third embodiment, the inclined plane portions inclined at the same angle δ are provided on the upper surface and the lower surface of the color mixing means, but the inclined plane portions inclined at different angles on the upper surface and the lower surface of the color mixing device are provided. A part may be provided. Further, in the third embodiment, the inclined plane portions are provided on the upper surface and the lower surface of the color mixing means. However, if at least one surface excluding the entrance surface and the emission surface of the color mixing device is provided on at least one surface, the embodiment can be implemented. Compared with the color mixing means 1 in the first embodiment, it is possible to narrow the range of the incident angle of the light emitted from the emission surface of the color mixing means to the right-angle prism 9.
[0044]
Embodiment 4
Next, a fourth embodiment of the present invention will be described. FIG. 10 is a partial cross-sectional view showing a liquid crystal display device in which a color mixing means according to a fourth embodiment of the present invention and a rectangular prism as a transparent body are integrally formed. FIG. 11 is a light guide plate according to a fourth embodiment of the present invention. FIG. 12 is a partial cross-sectional view showing a liquid crystal display device in which a transparent body and a right-angle prism as a transparent body are integrally formed. FIG. FIG. 13 is a partial sectional view showing another liquid crystal display device in which a color mixing means, a light guide plate and a transparent body according to Embodiment 4 of the present invention are integrally formed. 10 to 13, the same or corresponding parts as those in FIGS. 4 and 7 will be omitted for the sake of brevity.
[0045]
The second color mixing means 13 and the right angle prism 9 shown in FIG. 10, the light guide plate 5 and the right angle prism 9 shown in FIG. 11, and the second color mixing means 13, the light guide plate 5 and the right angle prism 9 shown in FIG. After the second color mixing means 13, the right-angle prism 9 and the light guide plate 5 are respectively formed, they are adhered with a double-sided tape having a high transmittance, or integrated with an ultraviolet curing resin or the like. The second color mixing means 13, the light guide plate 5, and the semi-cylindrical column 11 shown in FIG. 13 are formed into a desired shape by forming a rectangular transparent body and then bending the transparent body while heating. I have.
[0046]
In the fourth embodiment, the second color mixing means 13 and the right angle prism 9, the light guide plate 5 and the right angle prism 9, the second color mixing means 13, the light guide plate 5 and the right angle prism 9, or the second color mixing means 13 The third embodiment differs from the first and third embodiments in that the light guide plate 5 and the semi-cylindrical column 11 are integrally formed. The second color mixing means 13 and the right-angle prism 9 described later, the light guide plate 5 and the right-angle prism 9, Except for the function and effect obtained by integrally forming the second color mixing means 13, the light guide plate 5, and the right-angle prism 9 or the light guide plate, the same function and effect as those of the first and third embodiments are obtained.
[0047]
In the third embodiment, as shown in FIG. 7, the light emitted from the second color mixing means 13 is a slope 9c, which is an incident surface of the right-angle prism 9, and the light emitted from the right-angle prism 9 is a light guide plate 5. Is incident on the light guide plate incident surface 5a, but a part of the light is reflected by the inclined surface 9c or the light guide plate incident surface 5a, resulting in light loss. However, in the fourth embodiment, as shown in FIG. 10, by forming the second color mixing means 13 and the right-angle prism 9 integrally, reflection on the slope 9c as in the third embodiment is prevented. Therefore, a high-luminance planar light source device can be obtained. In addition, as shown in FIG. 11, by integrally forming the light guide plate 5 and the right-angle prism 9, reflection at the light guide plate incident surface 5a as in the first embodiment can be eliminated, so that high brightness is achieved. Can be obtained. Further, as shown in FIGS. 12 and 13, by forming the second color mixing means 13, the light guide plate 5 and the right-angle prism 9 or the semi-cylindrical column 11 integrally, the slope 9 c as in the first and third embodiments can be obtained. Since reflection at the rectangular surface 11a and the light guide plate incident surface 5a can be eliminated, light can be effectively guided to the light guide plate upper surface 5b, and a high-luminance planar light source device can be obtained.
[0048]
In the planar light source device shown in FIGS. 12 and 13, a plurality of prism-shaped protrusions as shown in FIG. 5 are formed on the incident surface 13 c of the second color mixing means 13 so that the second color mixing means can be formed. 13 can be diffused into the color mixing means 13 near the incident surface 13c.
[0049]
【The invention's effect】
The present invention has the following effects.
[0050]
According to the present invention, since a transparent body having a higher refractive index than air is interposed in the optical path from the color mixing means to the light guide plate, the light source which was a point light source is turned into a planar light source, and the incident light on the entrance surface of the light guide plate is Is uniform, and it is possible to suppress the occurrence of luminance unevenness near the incident surface of the light guide plate inside the light guide plate.
[0051]
In addition, the point light source includes a first point light source that emits red light, a second point light source that emits green light, and a third point light source that emits blue light. The red, green and blue monochromatic light emitted from the shape light source can be incident on the light guide plate as white light.
[0052]
Further, the transparent body is a right-angle prism, and the inclined surface of the right-angle prism is disposed so as to face the exit surface of the color mixing means and the entrance surface of the light guide plate, or the transparent body is a semi-column, and Is disposed so as to face the exit surface of the color mixing means and the incidence surface of the light guide plate, so that the light guide plate and the color mixing means can be overlapped facing each other, and the thickness of the planar light source device can be reduced. The frame can be narrowed. Further, the light emitted from the color mixing means is totally reflected by the transparent body and is incident on the light guide plate, so that the reflection loss by the reflecting plate can be reduced by the total reflection of the transparent body.
[0053]
The transparent body is a right-angle prism, and has a first surface facing the emission surface of the color mixing means, and a second surface facing the incidence surface of the light guide plate, and the first surface and the second surface. Form a right angle, the exit surface of the color mixing means and the light guide plate entrance surface of the light guide plate form a right angle, and a space can be obtained near the right-angle prism on the lower surface side of the light guide plate.
[0054]
Further, since the color mixing means has an inclined plane portion in which the thickness of the color mixing means increases linearly from the incident surface of the color mixing means to the emission surface of the color mixing means, the light totally reflected by the reflection surface of the right-angle prism is The amount increases and the direction of light can be changed efficiently.
[0055]
Further, in the vicinity of the entrance surface of the color mixing unit, the color mixing unit linearly extends from the first plane portion perpendicular to the incident surface of the color mixing unit to the emission surface of the color mixing unit following the first plane portion. And a second plane perpendicular to the emission surface of the color mixing means in a state where the thickness of the color mixing means is larger than the first plane part following the inclined plane part near the emission surface of the color mixing means. Since it is constituted by the flat portion, the amount of light totally reflected by the reflecting surface of the right-angle prism increases, and the direction of the light can be changed efficiently. Further, since the lower surface of the light guide plate and the second flat portion on the upper surface side of the color mixing means can be arranged in parallel, positioning can be easily performed.
[0056]
In addition, in the vicinity of the entrance surface of the color mixing unit, the thickness of the color mixing unit linearly increases in the vicinity of the plane of incidence of the color mixing unit, and linearly toward the exit surface of the color mixture unit following the plane portion. Since it is constituted by the inclined plane portion, the amount of light totally reflected by the reflecting surface of the right-angle prism increases, and the direction of light can be changed efficiently.
[0057]
Further, since the color mixing means and the transparent body are integrally formed, or the light guide plate and the transparent body are integrally formed, a high-luminance planar light source device can be obtained.
[0058]
Further, since the color mixing means, the light guide plate, and the transparent body are integrally formed, light can be effectively guided to the upper surface of the light guide plate, and a high-luminance planar light source device can be obtained.
[0059]
In addition, since a prism-shaped protrusion is formed on the incident surface of the color mixing means or a prism-shaped protrusion is formed on the light incident surface of the light guide plate, light incident on the incident surface of the color mixing means is near the incident surface. By diffusing into the inside of the color mixing means, a planar light source with high uniformity of luminance and chromaticity can be obtained.
[0060]
Further, according to the present invention, since the liquid crystal display element is provided above the planar light source device, an inexpensive liquid crystal display device having excellent display characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view illustrating a schematic configuration of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of the liquid crystal display device shown in FIG. 1 taken along the line II.
FIG. 3 is an enlarged view of a main part for describing an optical path of light passing through a right-angle prism in FIG. 2;
FIG. 4 is a partial cross-sectional view of a liquid crystal display device using a semicircular column as a transparent body.
FIG. 5 is a partially enlarged enlarged perspective view of an incident surface on which a projection is formed.
FIG. 6 is a partial cross-sectional view of a liquid crystal display device according to Embodiment 2 of the present invention.
FIG. 7 is a partial cross-sectional view of a liquid crystal display device according to Embodiment 3 of the present invention.
FIG. 8 is a partial sectional view showing a modification of the liquid crystal display device according to Embodiment 3 of the present invention.
FIG. 9 is a partial cross-sectional view showing another modified example of the liquid crystal display device according to Embodiment 3 of the present invention.
FIG. 10 is a partial cross-sectional view showing a liquid crystal display device in which a color mixing unit and a rectangular prism as a transparent body according to Embodiment 4 of the present invention are integrally formed.
FIG. 11 is a partial cross-sectional view showing a liquid crystal display device in which a light guide plate and a transparent rectangular prism are integrally formed according to a fourth embodiment of the present invention.
FIG. 12 is a partial cross-sectional view showing a liquid crystal display device in which a color mixing unit, a light guide plate, and a rectangular prism as a transparent body are integrally formed according to a fourth embodiment of the present invention.
FIG. 13 is a partial cross-sectional view showing another liquid crystal display device in which a color mixing means, a light guide plate, and a transparent body according to Embodiment 4 of the present invention are integrally formed.
[Explanation of symbols]
1 Color mixing means
1a Top surface
1b bottom surface
1c Incident surface
1d emission surface
2 point light source
2a First point light source
2b Second point light source
2c Third point light source
5 Light guide plate
5a Light guide plate incident surface
9,12 right angle prism
9c slope
11 half cylinder
11a Rectangular surface
12a First surface
12b Second surface
13 Second color mixing means
13c, 14c, 15c Incident surface
13d, 14d, 15d Outgoing surface
13e inclined plane
14 Third color mixing means
14e first plane portion
14f inclined plane
14g 2nd flat part
15 Fourth color mixing means
15e flat part
15f inclined plane

Claims

A color mixing means having a pair of opposed upper and lower surfaces and a plurality of side surfaces on edges of the upper and lower surfaces, of which the pair of opposed surfaces are an incident surface and an emission surface; A plurality of point-like light sources disposed in the vicinity of the entrance surface and arranged along the longitudinal direction of the entrance surface; and a rectangular light guide plate disposed substantially parallel or substantially perpendicular to the color mixing means. A planar light source device, wherein a transparent body having a higher refractive index than air is interposed in an optical path from the color mixing means to the light guide plate.

2. The point light source includes a first point light source that emits red light, a second point light source that emits green light, and a third point light source that emits blue light. 3. Surface light source device.

3. The planar light source device according to claim 1, wherein the transparent body is a right-angle prism, and an inclined surface of the right-angle prism is disposed so as to face an emission surface of the color mixing unit and an incidence surface of the light guide plate.

The transparent body is a right-angle prism, and has a first surface facing an emission surface of the color mixing means, and a second surface facing an incidence surface of the light guide plate. 3. The planar light source device according to claim 1, wherein the second surface is disposed at a right angle.

3. The planar light source according to claim 1, wherein the transparent body is a semi-cylinder, and a rectangular surface of the semi-cylinder is disposed so as to face an emission surface of the color mixing unit and an incidence surface of the light guide plate. apparatus.

3. The surface light source device according to claim 1, wherein the color mixing means has an inclined plane portion in which the thickness of the color mixing means increases linearly from an incident surface of the color mixing means to an emission surface of the color mixing means.

In the vicinity of the entrance surface of the color mixing unit, the color mixing unit has a first plane portion perpendicular to the entrance surface of the color mixture unit, and a straight line extending from the first plane portion toward the emission surface of the color mixture unit. The inclined plane portion where the thickness of the color mixing means is increased, and in the vicinity of the emission surface of the color mixing means, the thickness of the color mixing means is thicker than the first plane portion following the inclined plane portion. 3. The planar light source device according to claim 1, comprising a second plane portion perpendicular to an emission surface of the color mixing unit.

In the vicinity of the entrance surface of the color mixing unit, the color mixing unit includes: 3. The planar light source device according to claim 1, comprising an inclined plane portion having an increased thickness.

The planar light source device according to claim 1, wherein the color mixing unit and the transparent body are integrally formed.

The planar light source device according to claim 1, wherein the light guide plate and the transparent body are integrally formed.

The planar light source device according to claim 1, wherein the color mixing unit, the light guide plate, and the transparent body are integrally formed.

The planar light source device according to claim 11, wherein a prism-shaped protrusion is formed on an incident surface of the color mixing unit.

The planar light source device according to claim 1, wherein a prism-shaped protrusion is formed on an incident surface of the light guide plate.

The planar light source device according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, and a liquid crystal sandwiched between the planar light source device and the upper surface of the planar light source device. A liquid crystal display device, comprising: a liquid crystal display element formed of two glass substrates; and a drive circuit board connected to the liquid crystal display element.