JP2004327324A

JP2004327324A - Backlight device and liquid crystal display

Info

Publication number: JP2004327324A
Application number: JP2003122412A
Authority: JP
Inventors: Hisanori Okazaki; 尚徳岡崎
Original assignee: TAMA FINE OPTO CO Ltd
Current assignee: TAMA FINE OPTO CO Ltd
Priority date: 2003-04-25
Filing date: 2003-04-25
Publication date: 2004-11-18
Anticipated expiration: 2023-04-25
Also published as: JP3944468B2

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the large-sizing of various electric components as a result of increase of drive voltage which is brought about by the enlargement of the axial length of the cylindrical light source (lamp) due to the large-sizing of an LCD and a backlight device. <P>SOLUTION: Two inverter circuit substrates 9U, 9D, 9L, 9R, 9UL, 9UC, 9UR, 9DL, 9DC, 9DR are arranged at both end positions on a short side and a long side directions of an opening part 1a of a case 1 of the LCD and the backlight device, and the electrode parts 5 of the cylindrical light sources 3, 3L 3R, 3U, 3D are connected to transformer terminals 5A, 5B of high voltage side of the two inverter circuit substrates 9U, 9D, 9L, 9R, 9UL, 9UC, 9UR, 9DL, 9DC, 9DR, and thereby the large-sizing of various electric components accompanied with increase of the drive voltage is prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は電子機器に用いて有用なバックライト装置及び液晶表示装置（以下ＬＣＤと記す）に係わり、特にバックライト装置及びＬＣＤの駆動電圧を低下させると共にバックライト装置或いはＬＣＤの照光面の輝度分布バランス及び温度分布バランスを改善したバックライト装置及びＬＣＤに関する。
【０００２】
【従来の技術】
従来から、ＬＣＤに使用されているバックライト装置はマイクロコンピュータ、テレビジョン受像機等の電子機器の表示装置として広く利用されている。ＬＣＤは大きく分けてカラーフィルタ、ＴＦＴアレイを生成した二枚のガラス基板間に液晶を封じたセル及びバックライト装置からなり、液晶セルだけでは非発光性のため、バックライト装置の様な外部照射用の光源を必要としている。
【０００３】
この様なＬＣＤのバックライト装置の円筒状光源としては冷陰極管又は熱陰極管等の細径の蛍光管（ランプ）を用いるのが一般的である。バックライト装置の構造としては、導光板の側面に円筒状光源を配設したエッジライト方式と、筐体内部に反射体（以下反射板と記す）及び円筒状光源を収納し、筐体の開口部に配設した光透過拡散板へ円筒状光源からの直接光及び円筒状光源からの光を反射板で反射させた光を光透過拡散板で入射拡散させて均一な面状光を出光させる様にした直下方式が知られている。
【０００４】
上述の直下方式或いはエッジライト方式はＬＣＤの要求性能に応じて選択されるが、直下方式は円筒状光源の直接光を利用するためエッジライト方式に比較して光の利用効率が高く、ノートブックパソコン、モニタ、テレビジョン受像機等の情報機器や電子機器の様に高輝度を必要とする用途に広く用いられている。
【０００５】
図９（Ａ）は従来の直下方式のバックライト装置を示す平面図であり、図９（Ｂ）は図９（Ａ）のＡ−Ａ断面矢視図、図９（Ｃ）は図９（Ａ）のＢ−Ｂ断面矢視図、図９（Ｄ）（Ｅ）は高電圧供給用のインバータ回路基板の取付け状態を示す略線的な平面図である。
【０００６】
図９（Ａ）乃至（Ｅ）に於いて、バックライト装置６のランプハウスとなる筐体１は上面に開口部１ａを有する例えば、矩形状の箱状と成され、合成樹脂で一体成型するか、金属板或いは金属板と成型用の合成樹脂を組み合わせて作製する。
【０００７】
筐体１内には高反射塗料を塗布するか、高反射フィルム材等を貼着させて反射面としての反射板２を形成する。図９（Ｂ）（Ｃ）に於いては、この反射板２は四辺を傾斜させた断面台形状の板材で形成されている。
【０００８】
円筒状光源３は筐体１の底面から１〜２ｍｍ程度離間した位置に保持する。高反射グレード樹脂の射出成型で得た円筒光源支持台に設けたジャックに円筒状光源３の両端に設けたプラグを挿通して電極部５を構成する。又、筺体１内に配置する円筒状光源３の本数はＬＣＤやバックライト装置６に要求される輝度によって決定する。
【０００９】
上記した各部品を組み立て、開口部１ａの上面に乳白色アクリル樹脂等を用いた光透過拡散板４を覆う様に配置させると共に、この光透過拡散板４上には図示しないが、少なくとも１枚以上の拡散シートや集光シートが配置されている。円筒状光源３から放射状に発した光は直接或いは筐体１内の反射板２で反射されて光透過拡散板４に到達し、光透過拡散板４で面発光に変換され、更に集光シートによって照光面の法線方向に光を集光させることでバックライト装置６が構成され、上述の拡散シートや集光シート上に液晶パネル８が載置されてＬＣＤを構成している。
【００１０】
上述の光透過拡散板４、集光シート、液晶パネル８等は筐体１の四辺に形成したフランジ部に取りつけた抑え部材を介して固定されている。この様なバックライト装置及びＬＣＤは特許文献１に開示されている。
【００１１】
また、筐体１の底部１ｂには図９（Ｂ）の断面図及び図９（Ｄ）の平面図に示すように、筺体１の右端側に切起片７が設けられる、この切起片７は円筒状光源３の電極部５の近傍に形成され、高圧電源供給用のインバータ回路基板９が切起片７を介して筺体１の底部１ｂに固定されている。図９（Ｅ）はインバータ回路基板９を筺体１の左端側に配し、複数のＵ字状に曲げた円筒状光源３の高低圧側の電極部５をインバータ回路基板９に接続し、筺体１の開口部１ａの短辺方向に並設させたものである。この様なバックライト装置及びＬＣＤは特許文献２に記載されている。
【００１２】
【特許文献１】
特許公開２００２−１１６７０５号公報（図１０〜図１２）
【特許文献２】
特許公開２０００−３５２７１８号公報（第４頁、段落番号００３０）
【００１３】
【発明が解決しようとする課題】
上述した、従来構成のＬＣＤ及びバックライト装置ではＬＣＤの大型化に伴って、バックライト装置の駆動電圧も輝度を向上させる為に高くなり、インバータ回路基板９の駆動電圧も高電圧化されている。
【００１４】
一方、ＬＣＤの表示品位の優劣を表す重要な要素にバックライト装置６の照射面の輝度均一性がある。この輝度均一性を表す要素の１つに輝度ムラがある。輝度ムラは照光面内の輝度分布を数値でとらえたものであり、照光面内の規定された測定ポイントにおける法線方向の最大輝度と最小輝度の比率で示される。すなわち、輝度ムラは（最低輝度／最大輝度）×１００％で定義される。
【００１５】
例えば、２９インチ（Ａ＝６８４ｍｍ×４２０ｍｍ）ＬＣＤで３φ、長さ６４２ｍｍの円筒状光源３を開口部１ａの短辺方向に等間隔で１６本並設し、円筒状光源３の入力電圧を１４Ｖ、入力電流を６．７Ａとし、消費電力は９４Ｗで測定した場合での平均輝度ムラは８６．２％である。
【００１６】
更に、上述のバックライト装置及びＬＣＤでは図１０の輝度特性曲線に示す様な特性に依って、輝度分布バランスが乱される問題があつた。図１０の輝度特性曲線の縦軸は輝度を、横軸は筐体１の開口部１ａの長辺に沿って並行に配設した円筒状光源３の長手方向を示すものであり、筐体１の開口部１ａ上に載置した光透過拡散板４上での輝度分布特性図を示すものである。
【００１７】
図１０に於いて、ＬＣＤ等の調光時には円筒状光源３の管電流が例えば、３ｍＡの如く低電流では、曲線１１の様にインバータ回路基板９のある側の輝度が高く（明るく）、低圧側が低く（暗く）なる。又、逆に円筒状光源３の管電流が例えば、７ｍＡの如く高電流では、インバータ回路基板９のある側の輝度が低く（暗く）、低圧側が高く（明るく）なり曲線１２の如き特性を示す。
【００１８】
此の様なことから、円筒状光源３の長手方向の略中央位置に輝度バランスを合わせるために、図１０の輝度バランス曲線１３に示すよう管電流を調整して最適化する必要が生ずる。図１０では管電流を５ｍＡに選択して、輝度バランスが円筒状光源３の長手方向の略中央位置で最高輝度と成るような最適化を行わなければならない課題を有していた。
【００１９】
又、図１１に示す様に、インバータ回路基板９を筺体１の右端側に配し、複数の直管状の円筒状光源３の高圧側及び低圧側の電極部５をインバータ回路基板９の高低圧側トランス端子５Ｈ及び５Ｌに接続し、筺体１の開口部１ａの短辺方向に並設させたものでは、円筒状光源３に高電流を流すとインバータ回路基板９側が発熱し、インバータ回路基板９側が非常に熱くなる。その結果、図１１に示す様に、筺体１の開口部１ａ上の照光面の右端側に高温度領域１５を生じ、インバータ回路基板９から左端側に行くに従って、中温度領域１６、小温度領域１７となり、１方向のインバータ回路基板９側の底板１ｂの温度が上昇し、照光面上の温度分布に傾斜を生ずることになる。
【００２０】
更に、図１２に示す様にインバータ回路基板９を筺体１の右端側に配し、複数の直管状の円筒状光源３の高圧側の電極部５をインバータ回路基板９の高低圧トランス端子５Ｈ、５Ｌに接続し、筺体１の開口部１ａの短辺方向に並設させたものでは、円筒状光源３の管軸長が長くなり、例えば、円筒状光源３の長さが１０００ｍｍにもなると、円筒状光源３を駆動する駆動電圧は１０００Ｖ以上の高電圧を必要とする。この円筒状光源３の駆動始動時には、定常時の略２倍程度の電圧が必要となり、例えば、円筒状光源３に１０００Ｖの電圧がかかる場合の駆動始動時には２０００Ｖの高電圧が円筒状光源３にかかるようになる。このため、インバータ回路基板９のトランスが大きくなり、バックライト装置及びＬＣＤの厚みが増すという課題を有していた。
【００２１】
本発明は叙上の課題を解消するために成されたもので、発明が解決しようとする課題はバックライト装置が大型化され、円筒状光源３の管軸方向の長さが長くなり、駆動電圧の高電圧化に伴ない、インバータ回路基板９が筺体１の底部１ｂ側に配設され、円筒状光源３の管軸長が例えば、３０インチ用以上となっても、円筒状光源３の管電流を供給するための駆動電圧及びインバータ回路基板９のトランス電圧を低減させ、照光面上の輝度分布バランスを改善する為に、円筒状光源３の管電流の最適化を行ったので輝度分布バランス及び温度分布の均一化が図られ、輝度ムラを減少可能なバックライト装置及びＬＣＤを提供することが出来る。
【００２２】
【課題を解決するための手段】
本発明のバックライト装置は、筐体内に円筒状光源を配設し、筺体にインバータ回路基板を配したバックライト装置に於いて、インバータ回路基板を筐体の開口部の長手方向或いは短辺方向の底面両端位置に配する様にしたものである。
【００２３】
本発明のバックライト装置は、バックライト装置の輝度分布特性を、筺体の開口部の底面両端位置に配したインバータ回路基板を中心に所定輝度値と成るように円筒状光源の管電流を調整する様にしたものである。
【００２４】
本発明のバックライト装置は、筺体の開口部の底面両端位置に配したインバータ回路基板から高電圧を円筒状光源の１対の電極部に印加し、円筒状光源を筺体の開口部内の上下或いは左右方向に並設させ、インバータ回路基板のトランスの分担電圧を低下させる様にしたものである。
【００２５】
本発明のバックライト装置は、筺体の開口部の底面両端位置に配したインバータ回路基板から高電圧を円筒状光源の１対の電極部に印加し、円筒状光源を筺体の開口部内の上下或いは左右方向に並設させ、筺体の開口部の底面両端位置に配したインバータ回路基板を中心に照光面の温度分布を均一化させる様にしたものである。
【００２６】
本発明のバックライト装置は、円筒状光源の１対の電極部の両端を筐体の開口部の底面両端位置に配したインバータ回路基板の高電圧供給側に接続し、複数の筐体を左右或いは上下方向に並設する様にしたものである。
【００２７】
本発明のバックライト装置は、円筒状光源の形状を曲管状とする様にしたものである。
【００２８】
本発明のバックライト装置は、円筒状光源の形状を筺体の開口部の底面両端位置に配したインバータ回路基板の一対の電極部間に至る区間にわたって延設された直管とする様にしたものである。
【００２９】
本発明の液晶表示装置は、筐体内に円筒状光源を配設し、筺体にインバータ回路基板を配したバックライトを有する液晶表示装置に於いて、インバータ回路基板を筐体の開口部の長手方向或いは短辺方向の底面両端位置に配する様にしたものである。
【００３０】
本発明の液晶表示装置は、バックライトの輝度分布特性を、筺体の開口部の底面両端位置に配したインバータ回路基板を中心に所定輝度値と成るように円筒状光源の管電流を調整する様にしたものである。
【００３１】
本発明の液晶表示装置は、筺体の開口部の底面両端位置に配したインバータ回路基板から高電圧を円筒状光源の１対の電極部に印加し、円筒状光源を筺体の開口部内の上下或いは左右方向に並設させ、インバータ回路基板のトランスの分担電圧を低下させる様にしたものである。
【００３２】
本発明の液晶表示装置は、筺体の開口部の底面両端位置に配したインバータ回路基板から高電圧を円筒状光源の１対の電極部に印加し、円筒状光源を筺体の開口部内の上下或いは左右方向に並設させ、筺体の開口部の底面両端位置に配したインバータ回路基板を中心に照光面の温度分布を均一化させる様にしたものである。
【００３３】
本発明のバックライト装置及びＬＣＤに依れば、バックライト装置及びＬＣＤが大型化され、円筒状光源の管軸方向の長さが長くなり、駆動電圧の高電圧化に伴って、インバータ回路基板が筺体の底部側に配設され、円筒状光源の管軸長が例えば、３０インチ用以上となっても、円筒状光源に管電流を供給する為の駆動電圧及びインバータ回路基板のトランス電圧の低減化が図られ、照光面上の輝度分布バランスを改善する為に、円筒状光源の管電流の最適化を行ったので輝度分布バランス及び温度分布の均一化が図られ、輝度ムラを減少可能なものを得ることが出来る。
【００３４】
【発明の実施の形態】
以下、本発明の１形態例を示すバックライト装置及びＬＣＤの構成を図１乃至図８によって説明する。尚、図９乃至図１２の従来構成との対応部分には同一符号を付して説明する。
【００３５】
図１（Ａ）乃至（Ｃ）は本発明のＬＣＤに用いるバックライト装置の筐体を上から見た略線図であり、光透過拡散板を開口部から除去した筐体の平面図を示すものであり、図２（Ａ）乃至（Ｊ）は図１と同様の本発明の他の形態を示すＬＣＤに用いるバックライト装置の略線的平面図と、曲管状の円筒状光源の正面図及び波形説明図である。
【００３６】
図１（Ａ）乃至（Ｃ）及び図２（Ａ）乃至（Ｊ）に示す本発明のバックライト装置６の筐体１は平面形状が長方形の箱型（厚みｔ＝２ｍｍのステンレス）であり、筐体１の内部には、複数本の円筒状光源（例えば、冷陰極管）３が、互に平行に配されている。筐体１の内面は図９（Ｂ）に示す様に白色の反射面と成る反射板が形成され、その四辺は反射効率を高めるため傾斜させ、断面略台形となる様に成されている。
【００３７】
更に、筐体１の開口部１ａの長辺方向の左右両端位置に図１（Ａ）の様に左右側インバータ回路基板９Ｌ、９Ｒが筐体１の底部１ｂの裏面に固定される。筺体１の開口部１ａの内面に並設される複数の円筒状光源群３の両面の電極部５は左右側インバータ回路基板９Ｌ、９Ｒの高圧側のトランス端子５Ａ、５Ｂに接続されている。
【００３８】
図１（Ａ）の筐体１では左右側インバータ回路基板９Ｌ、９Ｒが筺体１の底部１ｂの左右両端裏面に固定されるが、この固定方法は底部１ｂの裏面に左右側インバータ回路基板９Ｌ、９Ｒを直接固定しても、所定のスペーサを介して底部１ｂの裏面に固定する様にしてもよい。
【００３９】
図１（Ｂ）は本発明の他の形態例のバックライト装置を示すものであり、例えば横長のアスペクト比が９対１６等のハイビジョン用のＬＣＤに用いる筐体１の開口部１ａの長辺方向の左右両端位置に２個の左右側インバータ回路基板９Ｌ、９Ｒを夫々筐体１の底部１ｂの裏面に固定している。筺体１の開口部１ａの内面に並設される複数の円筒状光源群３の左右の電極部５は左右側インバータ回路基板９Ｌ、９Ｒの高圧側のトランス端子５Ａ、５Ｂに接続されている。
【００４０】
図１（Ｃ）は本発明の更に他の形態例のバックライト装置を示すものであり、実線で示すバックライト装置６の場合は、例えばアスペクト比が３対４等のＬＣＤに用いるものであり、筐体１の開口部１ａの短辺方向の上下位置に２個の上下側インバータ回路基板９Ｕ、９Ｄを筐体１の底部１ｂの裏面に固定している。筺体１の開口部１ａの内面に並設される複数の上下側に延設された円筒状光源群３の上下の電極部５は上下インバータ回路基板９Ｕ、９Ｄの高圧側のトランス端子５Ａ、５Ｂに接続されている。
【００４１】
図１（Ｃ）に於いて、破線で示すものは、例えば横長のアスペクト比が９対１６等のハイビジョン用のＬＣＤに用いるものであり、筐体１の開口部１ａの短辺方向の上下両端位置に夫々３個の上下インバータ回路基板９Ｕ、９Ｄ、９ＵＬ、９ＤＬ、９ＵＲ、９ＵＤを筐体１の底部１ｂの裏面に固定しているが上下側インバータ回路基板９Ｕ、９Ｄは必要な個数に分割可能であり、勿論、上下側の２個だけでもよい、筺体１の開口部１ａの内面に並設される複数の円筒状光源群３の上下の電極部５は上下インバータ回路基板９Ｕ、９Ｄの高圧側のトランス端子５Ａ、５Ｂに接続されている。
【００４２】
図２（Ａ）乃至（Ｃ）に示すものは本発明のバックライト装置の更に他の構成を示すものであり、図２（Ａ）は図１（Ａ）で示したと同様に左右側インバータ回路基板９Ｌ、９Ｒを筺体１の底部１ｂの左右両端裏面に固定し、左右側円筒状光源群３Ｌ、３Ｒを曲管状の略Ｕ字状とし、左右側円筒状光源３Ｌ、３Ｒの高電圧供給側の電極部５を左右側インバータ回路基板９Ｌ、９Ｒのトランス端子５Ａ、５Ｂに接続する様にプラグインさせたものである。
【００４３】
図２（Ｂ）は、例えば横長のアスペクト比が９対１６等のハイビジョン用のＬＣＤに用いるものであり、筐体１の開口部１ａの上下両端位置に夫々３個の上下側インバータ回路基板９Ｕ（９ＵＬ、９ＵＣ、９ＵＲ）及び９Ｄ（９ＤＬ、９ＤＣ、９ＤＲ）を筺体１の底部１ｂの裏面に固定している。筺体１の開口部１ａの内面に並設される複数の上下側の曲管状の略Ｕ字状となした上下側円筒状光源群３Ｕ、及び３Ｄの両方の電極部５は上下側インバータ回路基板９Ｕ（９ＵＬ、９ＵＣ、９ＵＲ）及び９Ｄ（９ＤＬ、９ＤＣ、９ＤＲ）の高圧側のトランス端子５Ａ、５Ｂに接続されている。
【００４４】
図２（Ｃ）に示すものは、本発明のバックライト装置の更に他の構成を示すものであり、図２（Ｃ）は図１（Ａ）及び図２（Ｂ）で示したと同様の左右側円筒状光源群３Ｌ、３Ｒの電極部（プラグ）５を筺体１の底部１ｂの左右両端裏面に固定した左右側インバータ回路基板９Ｌ、９Ｒに装着して、左右側円筒状光源群３Ｌ、３Ｒを曲管状の略Ｕ字状となしたものと、円筒状光源群３を直管状となしたものとを組み合わせたものであり、左右側円筒状光源群３Ｌ、３Ｒの高電圧供給側の電極部５を左右側インバータ回路基板９Ｌ、９Ｒの高電圧側のトランス端子５Ａ、５Ｂに接続する様にプラグインさせたものである。
【００４５】
上述の円筒状光源群３Ｌ、３Ｒ、３Ｕ、３Ｄでは、その形状を曲管状の略Ｕ字状となして円筒状光源群３Ｌ、３Ｒ、３Ｕ、３Ｄの高電圧供給側の電極部５を上下、左右側インバータ回路基板９Ｕ、９Ｄ、９Ｌ、９Ｒの高電圧側のトランス端子５Ａ、５Ｂに接続する様にプラグインさせたが、図２（Ｄ）乃至図２（Ｈ）に示すように種々の形状にすることが出来る。即ち、図２（Ｄ）は曲管部を略Ｍ字状となしたものであり、図２（Ｅ）は曲管部を略コ字状となしたものであり、図２（Ｆ）は曲管部を略Ω字状となしたものであり、図２（Ｇ）は曲管部を略Ｏ字状となし脚部を狭めたものであり、図２（Ｈ）は曲管部を略凸字状となし脚部を広げたものである。上述の形状の他に適宜の形状とすることができる。要するに、頂部を曲管状となせばよい。
【００４６】
図２（Ｉ）及び図２（Ｊ）に示すものは、例えば、図２（Ａ）に示すように、左右側円筒状光源３Ｌ、３Ｒを曲管状の略Ｕ字状となして左右側円筒状光源３Ｌ、３Ｒの両方の電極部５を左右側インバータ回路基板９Ｌ、９Ｒの高電圧側のトランス端子５Ａ、５Ｂ側に接続するようにプラグインさせたものであるが、左右インバータ回路基板９Ｌ、９Ｒのトランス端子５Ａには図２（Ｉ）の波形１８で示す入力電圧を印加し、トランス端子５Ｂ側には図２（Ｉ）の波形１８で示す入力電圧とは逆位相の図２（Ｊ）で示す入力電圧を印加するようにすれば曲管部で電圧が零となり入力電圧を低減することが出来て、トランスの小型化を図ることが出来る。
【００４７】
以下、本発明の１実施例を図３（Ａ）（Ｂ）及び図４（Ａ）（Ｂ）により説明する。図３（Ａ）は本発明のバックライト装置の筐体の光透過拡散板を開口部から除去した筐体の平面図を示すものであり、図３（Ｂ）は図３（Ａ）のＣ−Ｃ断面矢視図である。図３（Ａ）（Ｂ）に於いて、本発明のバックライト装置６の筐体１は平面形状が長方形の箱型（厚みｔ＝２ｍｍのステンレス）であり、筐体１の内部には、複数本の円筒状光源群例えば、冷陰極管）３が、互に平行に配されている。筐体１の内面は図３（Ｂ）に示す様に白色の反射面と成る反射板２が形成され、その四辺は反射効率を高めるため傾斜させ、断面略台形となる様に成されている。
【００４８】
図３（Ａ）及び図３（Ｂ）の筐体１では左右側インバータ回路基板９Ｌ，９Ｒが筺体１の開口部１ａの短辺方向と平行になる位置の底部１ｂの左右両端裏面に直接或いはスペーサ等を介して固定される。筺体１内に配される直管状の円筒状光源群３の電源部５は、この左右側インバータ回路基板９Ｌ、９Ｒの左右両端位置に配された筺体１の側板方向に延設されて高圧供給側トランス端子５Ａ、５Ｂに接続されている。この左右側インバータ回路基板９Ｌ、９Ｒは底部１ｂと一体的に形成された切起片７で保持される。
【００４９】
更に、本例のバックライト装置は図３（Ｂ）に示す様に筐体１の開口部１ａを覆う様に、例えば、乳白色アクリル樹脂からなる長方形状の光透過拡散板４及び集光シート２０をフランジ部２３に配設すると共に、集光シート２０上に液晶パネル８を枠部材２１や抑え部材２２を介して固定する様に成されている。
【００５０】
図４（Ａ）（Ｂ）に示す本発明のバックライト装置６は、更に他の構成を示すものであり、図４（Ａ）は平面図、図４（Ｂ）は図４（Ａ）のＤ−Ｄ断面矢視図である。図４（Ｂ）の構成ではＬＣＤが大型化され、例えば４０インチの場合、筐体１の長辺方向は図４（Ａ）に示すＬ１＝９００ｍｍ、短辺方向の長さＬ２＝５７０ｍｍ、高さ２ｃｍと成るため、例えば直径３φで長さが９００ｍｍ以上の円筒状光源３を得ることが困難と成るため、円筒状光源群３の軸長を５７０ｍｍと成るように筺体１の開口部１ａの短辺方向に上下円筒状光源群を配設したもので、本例では筐体１の短辺方向の上下両端位置に上下インバータ回路基板９Ｕ、９Ｄを配置し、この上下側インバータ回路基板９Ｕ、９Ｄ間に上下側円筒状光源群３が配置される。
【００５１】
従って、図４（Ａ）（Ｂ）に示すバックライト装置６では図４（Ａ）に示す筺体１の開口部１ａの短辺方向の上下両端位置に高電圧側のトランス端子５Ａ、５Ｂが設けられ、破線で示す様に筺体１の底部１ｂの裏面に固定した上下インバータ回路基板９Ｕ、９Ｄのトランス端子５Ａ、５Ｂに円筒状光源群３の両端の電極部５を接続させる。
【００５２】
又、底部１ｂ又は（及び）反射板２に必要に応じて透孔を穿ち、上下側インバータ回路基板９Ｕ、９Ｄの円筒状光源群３の管軸方向に沿って筐体１の短辺方向に並設したスリット状の打抜き部を形成し、円筒状光源群３と底板１ｂの浮遊容量を減少させる様にしても良い。勿論、筐体１の底部１ｂ又は（及び）反射板２に穿つ透孔の大きさ及びその数は筐体１が最低限強度を保つ様に選択される。
【００５３】
上述で詳記したバックライト装置６のうち図３（Ａ）（Ｂ）に示す筐体１の様に構成し、画面サイズとして２９インチを使用し、円筒状光源群３を１６本、並設した反射板２から円筒状光源群３までの高さを２ｍｍとし、ＥＩＡＪで定める条件の測定点での輝度測定時の１本の円筒状光源群３の入力電圧は１４Ｖ、入力電流は６．７Ａ、消費電力９４Ｗでの平均輝度ムラは９２．７％の値を示している。
【００５４】
又、Ｘ軸方向での輝度ムラＢｒｄ＝最小（ＭＩＮ）輝度／最大（ＭＡＸ）輝度×１００％の値は９２．７％で従来に比べて６．５％の改善が成されている。
【００５５】
図５（Ａ）は筺体１の開口部１ａの左右側の両端にインバータ回路基板９がある場合の画面左右及び中央の輝度比を計測したものであり、図５（Ｂ）は画面中央の輝度比を１．０００とした画面左右及び中央の輝度比を示すもので、ともに円筒状光源３の電極部５をインバータ回路基板９の左右側の両端の高電圧側に接続した場合の輝度を示す。同図で曲線１４ａは円筒状光源３の管電流が３ｍＡ、曲線１４ｃは円筒状光源３の管電流が４ｍＡ、曲線１４ｅは円筒状光源３の管電流が５ｍＡ、曲線１４ｇは円筒状光源３の管電流が６ｍＡ、曲線１４ｉは円筒状光源３の管電流が７ｍＡの場合を示し、インバータ回路基板９の高電圧側の管電流が大きい時から小さい時まで輝度特性曲線は図１０の曲線１３と同一の形状を示す。表１及び表２に実測値と円筒状光源３の中央輝度比を１．０００とし、左右側の両端にインバータ回路基板９（筺体１の開口部１ａの左右側）を配した時の輝度と管電流との関係データを示す。
【００５６】
【表１】

【００５７】
【表２】

【００５８】
又、本発明の上述の各構成に依れば、例えば上下側或いは左右側インバータ回路基板９Ｕ、９Ｄ、９Ｌ、９Ｒを筐体１の開口部１ａの短辺或は長辺方向の少なくとも上下或いは左右の両端位置に固定し、開口部１ａの長辺又は短辺に対し、左右或は上下方向に円筒状光源群３、３Ｌ、３Ｒ、３Ｕ、３Ｄを平行に配設する様にしたので、ＬＣＤの調光時に管電流が３ｍＡの様に低電流時、或は７ｍＡの様な高電流時に於いても、図５の曲線１４ａ乃至１４ｉの様に円筒状光源群３、３Ｌ、３Ｒ、３Ｕ、３Ｄの最高輝度（ＢＬｍａｘ）を上下側或いは左右側インバータ回路基板９Ｕ、９Ｄ、９Ｌ、９Ｒの高電圧供給側のトランス端子５Ａ、５Ｂの両端側（開口部１ａの長辺或は短辺方向の両端位置）に持ち来たすことで輝度特性の輝度曲線を管電流の大小にかかわらず輝度バランスを良好にすることが出来る。
【００５９】
即ち、図１０の如き輝度特性曲線を図５の如く、円筒状光源３の管電流を調整してＬＣＤ或はバックライト装置６の照光面上の画面左右及び中央の輝度比のバランスを良好にして、円筒状光源３Ｌ、３Ｒ、３Ｕ、３Ｄの管電流の最適化を図ることが出来る。
【００６０】
上述の様な輝度特性曲線を図６（Ａ）及び図６（Ｂ）により更に説明する。図６（Ａ）及び図６（Ｂ）は直径３ｍｍの円筒状光源３の電流依存性を示すものであり、縦軸は輝度比を示し、横軸は光透過拡散板４上の照光面位置であり、円筒状光源３の長軸方向を示しこの円筒状光源３の中央輝度比を１．０００とし、グランド側とインバータ回路基板９（筺体１の開口部１ａの右側）がある側の輝度を示している。又、図６（Ａ）は、インバータ回路基板９が底板１ｂの裏側にある場合であり、図６（Ｂ）は、インバータ回路基板９が底板１ｂの裏側に無い場合である。
【００６１】
図６（Ａ）は筺体１の開口部１ａの右側にインバータ回路基板９がある場合の画面中央の輝度比を１．０００とした高電圧側の輝度を示し、同図で曲線１４ａは円筒状光源３の管電流が３ｍＡ、曲線１４ｂは円筒状光源３の管電流が３．５ｍＡ、曲線１４ｃは円筒状光源３の管電流が４ｍＡ、曲線１４ｄは円筒状光源３の管電流が４．５ｍＡ、曲線１４ｅは円筒状光源３の管電流が５ｍＡ、曲線１４ｆは円筒状光源３の管電流が５．５ｍＡ、曲線１４ｇは円筒状光源３の管電流が６ｍＡ、曲線１４ｈは円筒状光源３の管電流が６．５ｍＡ、曲線１４ｉは円筒状光源３の管電流が７ｍＡの場合を示し、インバータ回路基板９の高電圧側の管電流が大きい時には輝度比は小さい値を示し、管電流が小さい時には輝度比は大きい値を示している。これは管電流が高圧側からグランド側に流れている間に、筺体１の底板１ｂとの間で生ずる浮遊容量を通して生ずる漏洩電流によって円筒状光源３のグランド側に流れる電流が小さくなっていく為に、グランド側の輝度が低くなると考えられる。又、高電圧側の管電流大きい時に輝度が小さい理由としては、後述する温度依存性により高電圧の円筒状光源３の発光効率が減少し高圧側の輝度が低くなると考えられる。表３に円筒状光源３の中央輝度比を１．０００とし、グランド側とインバータ回路基板９（筺体１の開口部１ａの右側）がある側の輝度と管電流との関係データを示す。
【００６２】
【表３】

【００６３】
図６（Ｂ）は筺体１の開口部１ａの右側にインバータ回路基板９が無い場合の画面中央の輝度比を１．０００とした高電圧側の輝度を示し、同図で曲線１４ａは円筒状光源３の管電流が３ｍＡ、曲線１４ｂは円筒状光源３の管電流が３．５ｍＡ、曲線１４ｃは円筒状光源３の管電流が４ｍＡ、曲線１４ｄは円筒状光源３の管電流が４．５ｍＡ、曲線１４ｅは円筒状光源３の管電流が５ｍＡ、曲線１４ｆは円筒状光源３の管電流が５．５ｍＡ、曲線１４ｇは円筒状光源３の管電流が６ｍＡ、曲線１４ｈは円筒状光源３の管電流が６．５ｍＡ、曲線１４ｉは円筒状光源３の管電流が７ｍＡの場合を示し、インバータ回路基板９の高電圧側の管電流が小さい時には輝度比は大きい値を示し、管電流が大きい時には輝度比は略１．０００を示している。これは管電流が高電圧側からグランド側に流れている間に、筺体１の底板１ｂとの間で生ずる浮遊容量を通して生ずる漏洩電流によって円筒状光源３のグランド側に流れる電流が少なくなっていくが、図６（Ｂ）と図６（Ａ）の輝度特性曲線とを比較すると、円筒状光源３の管電流が５ｍＡ乃至７ｍＡでは温度が輝度に影響を与えない事がわかる。従って管電流が大きい時には輝度特性は高能率化され高輝度になると解される。表４に円筒状光源３の中央輝度比を１．０００とし、インバータ回路基板９（筺体１の開口部１ａの右側）が無い場合の高電圧側の輝度と管電流との関係データを示す。
【００６４】
【表４】

【００６５】
これらの事から、円筒状光源３に高電流を流すとインバータ回路基板９の発熱により、温度が高い状態になり筺体１の底部１ｂに温度勾配が出来てインバータ回路基板９側の円筒状光源３の発光効率が悪くなり、低電圧側の円筒状光源３の発光効率が良くなり、高電圧側の輝度が低くなると解される。依って、本発明に依れば図５に示す様に管電流を調整して輝度特性曲線を上下側或いは左右側で円筒状光源群３、３Ｌ、３Ｒ、３Ｕ、３Ｄの最高輝度（ＢＬｍａｘ）にあわせた略平坦な輝度特性曲線を得ることが出来る。
【００６６】
更に、ＬＣＤ及びバックライト装置６の温度分布についても、従来では図１１に示した様に筐体１の照光面上の右側に高温度領域１５が偏り、特に管電流が高電流に成ると温度傾斜が激しく、インバータ回路基板９が配設された側の温度上昇によって、温度分布バランスは図１１の様に崩れることになる。
【００６７】
これに対し、本発明のＬＣＤ及びバックライト装置６に依れば、上下側或いは左右側インバータ回路基板９Ｕ、９Ｄ、９Ｌ、９Ｒは図７に示す様に筐体１の開口部１ａの長辺方向の上下側或いは左右側位置に持ち来たされているため、温度分布バランスも上下側或いは左右側インバータ回路基板９Ｕ、９Ｄ、９Ｌ、９Ｒを中心に照光面上の上下側或いは左右側が高温度領域１５となり、照光面上の中心が中温度領域１６と均一に温度分布が拡がって輝度分布バランスの崩れも生じにくくなる。
【００６８】
更に、ＬＣＤやバックライト装置６が３５乃至５０インチ、或はハイビジョン用のテレビ受像機等と同様のアスペクト比を持つ様な表示装置になると、円筒状光源３のランプ長が長くなり、起動時には定常時の２倍の耐電圧を必要とするためインバータ回路基板９に用いるトランス、その他の能動素子及び受動素子は耐電圧性を増すため大型化され、バックライト装置６の筐体（ランプハウス）１の厚み等が増加することに成り、図１２に示す様な筐体１の１端部にのみインバータ回路基板９を有するものではどうしても市場要求を充分に満足可能な薄型化が困難と成って来ている。
【００６９】
然るに、本発明のＬＣＤ及びバックライト装置６に依れば、例えば、図８に示す様に筐体１の開口部１ａの長辺方向の左右両端位置に左右側インバータ回路基板９Ｌ、９Ｒを設けて、円筒状光源群３の両端の電極部５を左右インバータ回路基板９Ｌ、９Ｒの高電圧側のトランス端子５Ａ及び５Ｂに接続し，開口部１ａの長辺方向と平行に並設する様にすることで、円筒状光源群３の１本毎の駆動電圧は１０００Ｖであったものが半分の５００Ｖで済むことになる。
【００７０】
その為、左右ンバータ回路基板９Ｌ、９Ｒのトランス及び各種能動素子及び受動素子の耐電圧を低くすることが可能で、バックライト装置、筐体１の厚みを薄くすることが出来るだけでなく、低電圧駆動可能で安全性の高いＬＣＤ及びバックライト装置が提供可能と成る。
【００７１】
更に、図２（Ａ）乃至（Ｈ）で説明した様な曲管状の円筒状光源３や左右、上下側円筒状光源群３Ｌ、３Ｒ、３Ｕ、３Ｄを用いることによって、高電圧供給側のトランス端子５Ａに図２（Ｉ）の駆動電圧（１／２Ｖ）を供給し、同じく高電圧供給側のトランス端子５Ｂに図２（Ｊ）の様に図２（Ｉ）と逆位相の駆動電圧（−１／２Ｖ）を供給することで直管状の円筒状光源３の管の中心位置及び左右、上下側円筒状光源群３Ｌ、３Ｒ、３Ｕ、３Ｄの曲管部分での電位は相殺されて零（接地電位）とすることが可能であり、入力用の駆動電圧を半分に低減可能なものが得られる。
【００７２】
【発明の効果】
本発明のＬＣＤ及びバックライト装置に依れば、これら装置が大型化され、円筒状光源の軸長が長くなり、駆動電圧の高電圧化が成されても、インバータ回路基板を筐体の開口部の長辺方向或いは短辺方向の上下側或いは左右側位置に持ち来たし、２個のインバータ回路基板間に複数の円筒状光源群を並設させたので、これらインバータ回路基板の駆動電圧の低圧駆動が可能と成り、トランスや各種電気部品の小型化を図ることが可能と成る。又、照光面上での輝度分布バランス及び温度分布バランスを管電流の調整及びインバータ回路基板の開口部の両端位置への移動で均一化させることが可能と成り、円筒状光源の管壁と筐体の底部間の浮遊容量を減少させることもでき、筐体内の温度上昇を抑制可能なＬＣＤ及びバックライト装置を提供することが出来る。
【図面の簡単な説明】
【図１】本発明のＬＣＤに用いるバックライト装置の１形態例を示す略線的平面図である。
【図２】本発明のＬＣＤに用いるバックライト装置の他の形態例を示す略線的平面図及び曲管円筒状光源の略線的平面図並びに駆動電圧波形図である。
【図３】本発明のＬＣＤに用いるバックライト装置の１実施例を示す平面図及び側断面図である。
【図４】本発明のＬＣＤに用いるバックライト装置の他のバックライト装置の他の実施例を示す平面図及び側断面図底面図である。
【図５】本発明のバックライト装置に用いる円筒状光源の管電流をパラメータとした輝度と円筒状光源軸長との関係を示す輝度特性曲線図である。
【図６】本発明のバックライト装置の管電流依存性及び温度依存性を説明するための略線的平面図である。
【図７】本発明のバックライト装置の温度分布を説明するための略線的平面図である。
【図８】本発明のバックライト装置の円筒状光源駆動用の入力電圧説明用の略線的平面図である。
【図９】従来のバックライト装置の平面図、側断面図並びに略線的な筐体の平面図である。
【図１０】従来のバックライト装置に用いる円筒状光源の管電流をパラメータとする輝度と円筒状光源軸長との関係を示す輝度特性曲線図である。
【図１１】従来のバックライト装置の温度分布を説明するための略線的平面図である。
【図１２】従来のバックライト装置の円筒状光源駆動用の入力電圧説明用の略線的平面図である。
【符号の説明】
１‥‥筐体、１ａ‥‥開口部、１ｂ‥‥底部、３（３Ｌ、３Ｒ、３Ｕ、３Ｄ）‥‥円筒状光源（円筒状光源群）、４‥‥光透過拡散板、５‥‥電極部、５Ａ，５Ｂ‥‥トランス端子、９、９Ｕ、９Ｄ、９Ｌ、９Ｒ、９ＵＬ、９ＵＣ、９ＵＲ、９ＤＬ、９ＤＣ、９ＤＲ‥‥インバータ回路基板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a backlight device and a liquid crystal display device (hereinafter, referred to as an LCD) useful for electronic devices, and more particularly to a backlight device and a drive voltage of the LCD, and a luminance distribution of an illumination surface of the backlight device or the LCD. The present invention relates to a backlight device and an LCD having improved balance and temperature distribution balance.
[0002]
[Prior art]
BACKGROUND ART Conventionally, backlight devices used for LCDs have been widely used as display devices for electronic devices such as microcomputers and television receivers. LCDs are roughly divided into a color filter, a cell in which liquid crystal is sealed between two glass substrates on which a TFT array is formed, and a backlight device. Since the liquid crystal cell alone does not emit light, external illumination such as a backlight device is used. Need a light source for
[0003]
In general, a thin fluorescent tube (lamp) such as a cold-cathode tube or a hot-cathode tube is used as a cylindrical light source of such an LCD backlight device. The structure of the backlight device includes an edge light type in which a cylindrical light source is disposed on a side surface of a light guide plate, a reflector (hereinafter, referred to as a reflective plate) and a cylindrical light source which are accommodated in a housing, and an opening in the housing. The direct light from the cylindrical light source and the light reflected from the cylindrical light source reflected by the reflecting plate are incident and diffused by the light transmitting / diffusing plate to the light transmitting / diffusing plate disposed in the section, thereby emitting uniform planar light. There is a known direct type.
[0004]
The above direct type or edge light type is selected according to the required performance of the LCD, but the direct type uses the direct light of the cylindrical light source, so that the light use efficiency is higher than the edge light type, and the notebook type It is widely used for applications requiring high luminance, such as information devices and electronic devices such as personal computers, monitors, and television receivers.
[0005]
FIG. 9A is a plan view showing a conventional direct-type backlight device, FIG. 9B is a cross-sectional view taken along the line AA of FIG. 9A, and FIG. FIG. 9A is a cross-sectional view taken along the line BB, and FIGS. 9D and 9E are schematic plan views showing a mounting state of an inverter circuit board for supplying a high voltage.
[0006]
9 (A) to 9 (E), a housing 1 serving as a lamp house of the backlight device 6 is formed in, for example, a rectangular box shape having an opening 1a on an upper surface, and is integrally molded with a synthetic resin. Alternatively, a metal plate or a combination of a metal plate and a synthetic resin for molding is used.
[0007]
A high-reflection paint is applied to the inside of the housing 1, or a high-reflection film material or the like is adhered to form the reflection plate 2 as a reflection surface. In FIGS. 9B and 9C, the reflection plate 2 is formed of a plate material having a trapezoidal cross section with four sides inclined.
[0008]
The cylindrical light source 3 is held at a position separated from the bottom surface of the housing 1 by about 1 to 2 mm. The electrode portions 5 are formed by inserting plugs provided at both ends of the cylindrical light source 3 into jacks provided on a cylindrical light source support obtained by injection molding of a high reflection grade resin. Further, the number of cylindrical light sources 3 arranged in the housing 1 is determined by the luminance required for the LCD and the backlight device 6.
[0009]
The above-described components are assembled and arranged on the upper surface of the opening 1a so as to cover the light transmission / diffusion plate 4 made of milky white acrylic resin or the like. Are provided. Light emitted radially from the cylindrical light source 3 is directly or reflected by the reflection plate 2 in the housing 1 and reaches the light transmission / diffusion plate 4, is converted into surface light by the light transmission / diffusion plate 4, and is further condensed. The backlight device 6 is configured by condensing light in the normal direction of the illuminating surface, and the liquid crystal panel 8 is mounted on the above-described diffusion sheet or condensing sheet to configure an LCD.
[0010]
The above-described light transmission / diffusion plate 4, light-collecting sheet, liquid crystal panel 8 and the like are fixed via holding members attached to flange portions formed on four sides of the housing 1. Such a backlight device and an LCD are disclosed in Patent Document 1.
[0011]
As shown in the cross-sectional view of FIG. 9B and the plan view of FIG. 9D, a cut-and-raised piece 7 is provided on the bottom 1b of the housing 1 on the right end side of the case 1. Numeral 7 is formed near the electrode section 5 of the cylindrical light source 3, and an inverter circuit board 9 for supplying high-voltage power is fixed to the bottom 1 b of the housing 1 via the cut-and-raised piece 7. FIG. 9E shows an arrangement in which the inverter circuit board 9 is arranged on the left end side of the housing 1, and the high and low voltage side electrode portions 5 of the plurality of U-shaped bent cylindrical light sources 3 are connected to the inverter circuit board 9. The openings 1a are arranged side by side in the short side direction. Such a backlight device and LCD are described in Patent Document 2.
[0012]
[Patent Document 1]
Patent Publication No. 2002-116705 (FIGS. 10 to 12)
[Patent Document 2]
Patent Publication No. 2000-352718 (page 4, paragraph number 0030)
[0013]
[Problems to be solved by the invention]
In the above-described conventional LCD and backlight device, as the size of the LCD increases, the driving voltage of the backlight device also increases to improve the luminance, and the driving voltage of the inverter circuit board 9 also increases. .
[0014]
On the other hand, an important factor indicating the display quality of the LCD is brightness uniformity of the irradiation surface of the backlight device 6. One of the elements representing the luminance uniformity is luminance unevenness. The luminance unevenness is a numerical value of the luminance distribution in the illuminated surface, and is indicated by a ratio between the maximum luminance and the minimum luminance in a normal direction at a specified measurement point in the illuminated surface. That is, the luminance unevenness is defined as (minimum luminance / maximum luminance) × 100%.
[0015]
For example, in a 29-inch (A = 684 mm × 420 mm) LCD, 16 cylindrical light sources 3 each having a diameter of 3φ and a length of 642 mm are arranged side by side at equal intervals in the short side direction of the opening 1 a, and the input voltage of the cylindrical light source 3 is 14 V The average luminance unevenness when the input current was measured at 6.7 A and the power consumption was 94 W was 86.2%.
[0016]
Further, in the above-described backlight device and LCD, there is a problem that the luminance distribution balance is disturbed by the characteristics as shown in the luminance characteristic curve of FIG. The vertical axis of the luminance characteristic curve in FIG. 10 indicates the luminance, and the horizontal axis indicates the longitudinal direction of the cylindrical light source 3 arranged in parallel along the long side of the opening 1 a of the housing 1. FIG. 3 is a diagram showing a luminance distribution characteristic diagram on the light transmission / diffusion plate 4 placed on the opening 1a of FIG.
[0017]
In FIG. 10, when the tube current of the cylindrical light source 3 is as low as 3 mA, for example, during dimming of an LCD or the like, the luminance on one side of the inverter circuit board 9 is high (bright) as indicated by a curve 11 and the low voltage is low. The side is low (dark). Conversely, when the tube current of the cylindrical light source 3 is as high as 7 mA, for example, the brightness on one side of the inverter circuit board 9 is low (dark) and the low voltage side is high (bright), indicating a characteristic as shown by a curve 12. .
[0018]
For this reason, it is necessary to adjust and optimize the tube current as shown by the luminance balance curve 13 in FIG. 10 in order to adjust the luminance balance to a substantially central position in the longitudinal direction of the cylindrical light source 3. In FIG. 10, there was a problem that the tube current was selected to be 5 mA and optimization had to be performed so that the luminance balance reached the maximum luminance at a substantially central position in the longitudinal direction of the cylindrical light source 3.
[0019]
As shown in FIG. 11, the inverter circuit board 9 is disposed on the right end side of the housing 1, and the high-voltage and low-voltage electrodes 5 of the plurality of straight tubular cylindrical light sources 3 are connected to the high-low voltage side of the inverter circuit board 9. In the one connected to the

transformer terminals

5H and 5L and arranged in the short side direction of the opening 1a of the housing 1, when a high current is applied to the cylindrical light source 3, the inverter circuit board 9 side generates heat and the inverter circuit board 9 side generates heat. It gets very hot. As a result, as shown in FIG. 11, a high-temperature region 15 is formed on the right end side of the illuminating surface on the opening 1a of the housing 1, and the medium-temperature region 16 and the small-temperature region As a result, the temperature of the bottom plate 1b on the side of the inverter circuit board 9 in one direction rises, and the temperature distribution on the illuminated surface is inclined.
[0020]
Further, as shown in FIG. 12, the inverter circuit board 9 is disposed on the right end side of the housing 1 and the high voltage side electrode portions 5 of the plurality of straight tubular cylindrical light sources 3 are connected to the high / low voltage transformer terminals 5H of the inverter circuit board 9; 5L, and arranged side by side in the short side direction of the opening 1a of the housing 1, if the tube axis length of the cylindrical light source 3 becomes long, for example, if the length of the cylindrical light source 3 becomes 1000 mm, A driving voltage for driving the cylindrical light source 3 requires a high voltage of 1000 V or more. At the start of driving of the cylindrical light source 3, a voltage approximately twice as high as that at the time of steady state is necessary. For example, at the time of driving start when a voltage of 1000 V is applied to the cylindrical light source 3, a high voltage of 2000 V is applied to the cylindrical light source 3. It becomes like this. For this reason, there is a problem that the transformer of the inverter circuit board 9 becomes large and the thickness of the backlight device and the LCD increases.
[0021]
The present invention has been made in order to solve the above-mentioned problems, and the problem to be solved by the present invention is that the backlight device is enlarged, the length of the cylindrical light source 3 in the tube axis direction is increased, and With the increase in the voltage, the inverter circuit board 9 is disposed on the bottom 1b side of the housing 1, and even if the tube axis length of the cylindrical light source 3 becomes, for example, 30 inches or more, the cylindrical light source 3 is In order to reduce the drive voltage for supplying the tube current and the transformer voltage of the inverter circuit board 9 and to improve the balance of the brightness distribution on the illuminated surface, the tube current of the cylindrical light source 3 was optimized, so that the brightness distribution was It is possible to provide a backlight device and an LCD in which balance and temperature distribution are made uniform and luminance unevenness can be reduced.
[0022]
[Means for Solving the Problems]
The backlight device of the present invention provides a backlight device in which a cylindrical light source is provided in a housing and an inverter circuit board is provided in the housing. Are arranged at both end positions of the bottom surface.
[0023]
In the backlight device of the present invention, the tube current of the cylindrical light source is adjusted so that the brightness distribution characteristic of the backlight device has a predetermined brightness value centered on the inverter circuit boards disposed at both ends of the bottom of the opening of the housing. It is what we did.
[0024]
The backlight device of the present invention applies a high voltage to a pair of electrodes of a cylindrical light source from an inverter circuit board disposed at both ends of a bottom surface of an opening of a housing, and applies the cylindrical light source to the upper and lower sides of the opening of the housing. They are arranged side by side in the left-right direction to reduce the voltage shared by the transformer on the inverter circuit board.
[0025]
The backlight device of the present invention applies a high voltage to a pair of electrodes of a cylindrical light source from an inverter circuit board disposed at both ends of a bottom surface of an opening of a housing, and applies the cylindrical light source to the upper and lower sides of the opening of the housing. The temperature distribution of the illuminating surface is made uniform, centered on the inverter circuit boards arranged at both ends of the bottom surface of the opening of the housing, juxtaposed in the left-right direction.
[0026]
In the backlight device of the present invention, both ends of a pair of electrode portions of a cylindrical light source are connected to a high voltage supply side of an inverter circuit board disposed at both ends of a bottom surface of an opening of a housing, and a plurality of housings are connected to each other. Alternatively, they are arranged side by side in the vertical direction.
[0027]
In the backlight device of the present invention, the cylindrical light source has a curved tubular shape.
[0028]
The backlight device according to the present invention is configured such that the shape of the cylindrical light source is a straight tube extending over a section extending between a pair of electrode portions of the inverter circuit board disposed at both ends of the bottom surface of the opening of the housing. It is.
[0029]
In a liquid crystal display device having a backlight in which a cylindrical light source is provided in a housing and an inverter circuit board is provided in the housing, the inverter circuit board may be disposed in a longitudinal direction of an opening of the housing. Alternatively, they are arranged at both ends of the bottom surface in the short side direction.
[0030]
In the liquid crystal display device of the present invention, the tube current of the cylindrical light source is adjusted so that the luminance distribution characteristic of the backlight has a predetermined luminance value centered on the inverter circuit boards disposed at both ends of the bottom of the opening of the housing. It was made.
[0031]
The liquid crystal display device of the present invention applies a high voltage to a pair of electrodes of a cylindrical light source from an inverter circuit board disposed at both ends of the bottom surface of the opening of the housing, and applies the cylindrical light source to the top and bottom of the opening of the housing or They are arranged side by side in the left-right direction to reduce the voltage shared by the transformer on the inverter circuit board.
[0032]
The liquid crystal display device of the present invention applies a high voltage to a pair of electrodes of a cylindrical light source from an inverter circuit board disposed at both ends of the bottom surface of the opening of the housing, and applies the cylindrical light source to the top and bottom of the opening of the housing or The temperature distribution of the illuminating surface is made uniform, centered on the inverter circuit boards arranged at both ends of the bottom surface of the opening of the housing, juxtaposed in the left-right direction.
[0033]
According to the backlight device and the LCD of the present invention, the size of the backlight device and the LCD is increased, and the length of the cylindrical light source in the tube axis direction is increased. Is disposed on the bottom side of the housing, and the drive voltage for supplying the tube current to the cylindrical light source and the transformer voltage of the inverter circuit board even if the tube axis length of the cylindrical light source becomes, for example, 30 inches or more. The tube current of the cylindrical light source has been optimized in order to reduce the luminance and improve the luminance distribution balance on the illuminated surface, so that the luminance distribution balance and the temperature distribution are made uniform and the luminance unevenness can be reduced. Can be obtained.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configurations of a backlight device and an LCD according to one embodiment of the present invention will be described with reference to FIGS. 9 to 12 are denoted by the same reference numerals and will be described.
[0035]
1 (A) to 1 (C) are schematic diagrams of a case of a backlight device used for an LCD according to the present invention as viewed from above, and show plan views of the case where a light transmission / diffusion plate is removed from an opening. FIGS. 2A to 2J are a schematic plan view of a backlight device used in an LCD showing another embodiment of the present invention similar to FIG. 1, and a front view of a curved tubular light source. FIG.
[0036]
The housing 1 of the backlight device 6 of the present invention shown in FIGS. 1A to 1C and FIGS. 2A to 2J is a rectangular box shape (stainless steel having a thickness t = 2 mm) in a planar shape. Inside the housing 1, a plurality of cylindrical light sources (for example, cold cathode tubes) 3 are arranged in parallel with each other. As shown in FIG. 9 (B), the inner surface of the housing 1 is formed with a reflecting plate serving as a white reflecting surface, and its four sides are inclined so as to increase the reflection efficiency, and have a substantially trapezoidal cross section.
[0037]
Further, the left and right inverter circuit boards 9L and 9R are fixed to the back surface of the bottom 1b of the housing 1 at both left and right end positions in the long side direction of the opening 1a of the housing 1 as shown in FIG. The electrode portions 5 on both surfaces of the plurality of cylindrical light source groups 3 arranged side by side on the inner surface of the opening 1a of the housing 1 are connected to the high voltage

side transformer terminals

5A and 5B of the left and right inverter circuit boards 9L and 9R.
[0038]
In the case 1 of FIG. 1A, the left and right inverter circuit boards 9L and 9R are fixed to the right and left rear surfaces of the bottom 1b of the case 1, respectively. 9R may be directly fixed, or may be fixed to the back surface of the bottom 1b via a predetermined spacer.
[0039]
FIG. 1B shows a backlight device according to another embodiment of the present invention. For example, a long side of an opening 1a of a housing 1 used for a high-definition LCD having a horizontally long aspect ratio of 9:16 or the like. Two left and right inverter circuit boards 9L and 9R are fixed to the back surface of the bottom 1b of the housing 1, respectively, at both left and right positions in the direction. The left and right electrode portions 5 of the plurality of cylindrical light source groups 3 arranged side by side on the inner surface of the opening 1a of the housing 1 are connected to the high voltage

side transformer terminals

5A and 5B of the left and right inverter circuit boards 9L and 9R.
[0040]
FIG. 1C shows a backlight device according to still another embodiment of the present invention. The backlight device 6 shown by a solid line is used for an LCD having an aspect ratio of 3 to 4, for example. The two upper and lower inverter circuit boards 9U and 9D are fixed to the back surface of the bottom 1b of the housing 1 at upper and lower positions in the short side direction of the opening 1a of the housing 1. The upper and lower electrode portions 5 of a plurality of vertically extending cylindrical light source groups 3 arranged side by side on the inner surface of the opening 1a of the housing 1 are

transformer terminals

5A and 5B on the high voltage side of the upper and lower inverter circuit boards 9U and 9D. It is connected to the.
[0041]
In FIG. 1C, those indicated by broken lines are used for a high-definition LCD having, for example, a horizontally long aspect ratio of 9:16, and include upper and lower ends of the opening 1a of the housing 1 in the short side direction. Three upper and lower inverter circuit boards 9U, 9D, 9UL, 9DL, 9UR, and 9UD are fixed to the rear surface of the bottom 1b of the housing 1, respectively, but the upper and lower inverter circuit boards 9U and 9D are divided into necessary numbers. The upper and lower electrode portions 5 of the plurality of cylindrical light source groups 3 arranged in parallel on the inner surface of the opening 1a of the housing 1 may be of course only two upper and lower sides. It is connected to the

transformer terminals

5A and 5B on the high voltage side.
[0042]
FIGS. 2A to 2C show still another configuration of the backlight device of the present invention. FIG. 2A shows the left and right inverter circuits as shown in FIG. 1A. The substrates 9L and 9R are fixed to the right and left back surfaces of the left and right ends of the bottom 1b of the housing 1, and the left and right cylindrical light source groups 3L and 3R are formed into a substantially U-shaped curved tube, and the high voltage supply sides of the left and right cylindrical light sources 3L and 3R are formed. Is connected to the

transformer terminals

5A, 5B of the left and right inverter circuit boards 9L, 9R.
[0043]
FIG. 2B is for use in a high-vision LCD having, for example, a horizontally long aspect ratio of 9:16. Three upper and lower inverter circuit boards 9U are provided at upper and lower ends of an opening 1a of the housing 1, respectively. (9UL, 9UC, 9UR) and 9D (9DL, 9DC, 9DR) are fixed to the back surface of the bottom 1b of the housing 1. Both the upper and lower electrode circuits 5 of the upper and lower curved substantially cylindrical U-shaped upper and lower cylindrical light sources 3U and 3D which are arranged in parallel on the inner surface of the opening 1a of the housing 1 are connected to the upper and lower inverter circuit boards. 9U (9UL, 9UC, 9UR) and 9D (9DL, 9DC, 9DR) are connected to high-voltage

side transformer terminals

5A, 5B.
[0044]
FIG. 2 (C) shows still another configuration of the backlight device of the present invention, and FIG. 2 (C) shows the same left and right as shown in FIGS. 1 (A) and 2 (B). The electrode portions (plugs) 5 of the side cylindrical light source groups 3L, 3R are mounted on the left and right inverter circuit boards 9L, 9R fixed to the left and right end back surfaces of the bottom 1b of the housing 1, and the left and right cylindrical light source groups 3L, 3R are mounted. And a combination of a tube-shaped light source group 3L and a right-side cylindrical light source group 3L, 3R on the high voltage supply side. The part 5 is plugged in so as to be connected to the

transformer terminals

5A and 5B on the high voltage side of the left and right inverter circuit boards 9L and 9R.
[0045]
In the above-mentioned cylindrical light source groups 3L, 3R, 3U, 3D, the shape is formed into a substantially tubular U-shape, and the electrodes 5 on the high voltage supply side of the cylindrical light source groups 3L, 3R, 3U, 3D are vertically moved. , Plugged into the high-

voltage transformer terminals

5A, 5B of the left and right inverter circuit boards 9U, 9D, 9L, 9R, as shown in FIGS. 2 (D) to 2 (H). Shape. That is, FIG. 2 (D) shows a curved tube portion having a substantially M-shape, FIG. 2 (E) shows a curved tube portion having a substantially U-shape, and FIG. FIG. 2 (G) shows a curved tube portion having a substantially O-shape and a narrow leg portion, and FIG. 2 (H) shows a curved tube portion having a substantially Ω shape. It has a substantially convex shape and an unfolded leg. An appropriate shape other than the above-mentioned shape can be adopted. In short, the top may be formed in a curved tubular shape.
[0046]
2 (I) and FIG. 2 (J), for example, as shown in FIG. 2 (A), the left and right cylindrical light sources 3L and 3R are formed into a substantially U-shaped curved tubular shape. Although both electrode portions 5 of the rectangular light sources 3L and 3R are plugged in so as to be connected to the

transformer terminals

5A and 5B on the high voltage side of the left and right inverter circuit boards 9L and 9R, the left and right inverter circuit boards 9L and 9R are connected. , 9R, to the transformer terminal 5A, the input voltage shown by the waveform 18 in FIG. 2 (I) is applied, and to the transformer terminal 5B side, the input voltage shown in the waveform 18 in FIG. If the input voltage indicated by J) is applied, the voltage becomes zero in the curved tube portion, the input voltage can be reduced, and the size of the transformer can be reduced.
[0047]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 3 (A) and 3 (B) and FIGS. 4 (A) and 4 (B). FIG. 3A is a plan view of the housing of the backlight device of the present invention in which the light transmission / diffusion plate is removed from the opening, and FIG. 3B is a plan view of C of FIG. 3A. FIG. 3A and 3B, the housing 1 of the backlight device 6 of the present invention has a rectangular box shape (stainless steel with a thickness t = 2 mm) in a planar shape. A plurality of cylindrical light source groups (for example, cold cathode tubes) 3 are arranged in parallel with each other. As shown in FIG. 3 (B), the inner surface of the housing 1 is formed with a reflecting plate 2 serving as a white reflecting surface, and its four sides are inclined so as to enhance the reflection efficiency, and have a substantially trapezoidal cross section. .
[0048]
In the case 1 of FIGS. 3A and 3B, the left and right inverter circuit boards 9L and 9R are directly or on the right and left back surfaces of the bottom 1b at a position parallel to the short side direction of the opening 1a of the case 1. It is fixed via a spacer or the like. The power supply unit 5 of the straight tubular cylindrical light source group 3 disposed in the housing 1 is extended in the direction of the side plate of the housing 1 disposed at the left and right end positions of the left and right inverter circuit boards 9L and 9R to supply a high voltage. It is connected to the

side transformer terminals

5A and 5B. The left and right inverter circuit boards 9L and 9R are held by a cut-and-raised piece 7 formed integrally with the bottom 1b.
[0049]
Further, as shown in FIG. 3 (B), the backlight device of the present embodiment covers, for example, a rectangular light transmission / diffusion plate 4 made of milky white acrylic resin and a light condensing sheet 20 so as to cover the opening 1 a of the housing 1. Is disposed on the flange portion 23, and the liquid crystal panel 8 is fixed on the light-collecting sheet 20 via the frame member 21 and the holding member 22.
[0050]
The backlight device 6 of the present invention shown in FIGS. 4 (A) and 4 (B) shows still another configuration. FIG. 4 (A) is a plan view and FIG. 4 (B) is a view of FIG. 4 (A). It is DD sectional arrow view. In the configuration shown in FIG. 4B, the size of the LCD is increased. For example, in the case of 40 inches, the long side direction of the housing 1 is L1 = 900 mm, the short side direction length L2 = 570 mm shown in FIG. Since it is difficult to obtain a cylindrical light source 3 having a diameter of 3φ and a length of 900 mm or more, for example, it is difficult to obtain a cylindrical light source group 3 having an axial length of 570 mm. In this example, upper and lower inverter circuit boards 9U and 9D are arranged at both upper and lower positions in the short side direction of the housing 1, and the upper and lower inverter circuit boards 9U and 9U are arranged in the short side direction. The upper and lower cylindrical light source groups 3 are arranged between 9D.
[0051]
Accordingly, in the backlight device 6 shown in FIGS. 4A and 4B, high-voltage-

side transformer terminals

5A and 5B are provided at both upper and lower positions in the short side direction of the opening 1a of the housing 1 shown in FIG. Then, as shown by the broken line, the electrode portions 5 at both ends of the cylindrical light source group 3 are connected to the

transformer terminals

5A and 5B of the upper and lower inverter circuit boards 9U and 9D fixed to the back surface of the bottom 1b of the housing 1.
[0052]
In addition, through holes are formed in the bottom portion 1b or / and the reflection plate 2 as necessary, and along the tube axis direction of the cylindrical light source group 3 of the upper and lower inverter circuit boards 9U and 9D in the short side direction of the housing 1. A slit-shaped punched portion may be formed in parallel to reduce the stray capacitance between the cylindrical light source group 3 and the bottom plate 1b. Of course, the size and number of through holes formed in the bottom 1b and / or the reflection plate 2 of the housing 1 are selected so that the housing 1 keeps the minimum strength.
[0053]
Of the backlight device 6 described above, the backlight device 6 is configured like the housing 1 shown in FIGS. 3A and 3B, uses a screen size of 29 inches, and has 16 cylindrical light source groups 3 arranged side by side. The height from the reflecting plate 2 to the cylindrical light source group 3 is 2 mm, and the input voltage and the input current of one cylindrical light source group 3 at the time of measuring the luminance at the measurement point under the conditions defined by EIAJ are 6. The average luminance unevenness at 7 A and power consumption of 94 W indicates a value of 92.7%.
[0054]
The value of luminance unevenness Brd = minimum (MIN) luminance / maximum (MAX) luminance × 100% in the X-axis direction is 92.7%, which is an improvement of 6.5% as compared with the conventional art.
[0055]
FIG. 5 (A) shows the measurement of the luminance ratio between the left, right and center of the screen when the inverter circuit boards 9 are provided at the left and right ends of the opening 1a of the housing 1, and FIG. 5 (B) shows the luminance at the center of the screen. It shows the luminance ratio between the left, right, and center of the screen with the ratio being 1.000, and shows the luminance when the electrode portion 5 of the cylindrical light source 3 is connected to the high voltage side at both ends on the left and right sides of the inverter circuit board 9. . In the figure, a curve 14a represents a tube current of the cylindrical light source 3 of 3 mA, a curve 14c represents a tube current of the cylindrical light source 3 of 4mA, a curve 14e represents a tube current of the cylindrical light source 3 of 5mA, and a curve 14g represents a curve of the cylindrical light source 3. The tube current is 6 mA, the curve 14i shows the case where the tube current of the cylindrical light source 3 is 7 mA, and the brightness characteristic curve from the time when the tube current on the high voltage side of the inverter circuit board 9 is large to small is the curve 13 in FIG. Show the same shape. Tables 1 and 2 show the measured values and the central luminance ratio of the cylindrical light source 3 as 1.000, and the luminance when the inverter circuit boards 9 (left and right sides of the opening 1a of the housing 1) are arranged on both left and right sides. 4 shows data relating to a tube current.
[0056]
[Table 1]

[0057]
[Table 2]

[0058]
Further, according to the above-described respective configurations of the present invention, for example, the upper and lower or left and right inverter circuit boards 9U, 9D, 9L, 9R are at least vertically or shorterly in the short side or long side direction of the opening 1a of the housing 1. The cylindrical light source groups 3, 3L, 3R, 3U, and 3D are arranged in parallel to the left and right sides of the opening 1a in the left and right or up and down directions. Even when the tube current is as low as 3 mA during the dimming of the LCD or when the tube current is as high as 7 mA, the cylindrical light source groups 3, 3L, 3R, and 3U as shown by the curves 14a to 14i in FIG. The maximum luminance (BLmax) of 3D is set at both ends of the

transformer terminals

5A and 5B on the high voltage supply side of the upper and lower or left and right inverter circuit boards 9U, 9D, 9L and 9R (in the long side or short side direction of the opening 1a). At both end positions), the brightness curve of the brightness It is possible to improve the brightness balance regardless of size.
[0059]
That is, the luminance characteristic curve as shown in FIG. 10 is adjusted as shown in FIG. 5 by adjusting the tube current of the cylindrical light source 3 to improve the balance of the luminance ratio between the left, right, and center of the screen on the illuminated surface of the LCD or the backlight device 6. Thus, it is possible to optimize the tube currents of the cylindrical light sources 3L, 3R, 3U, and 3D.
[0060]
The above-described luminance characteristic curve will be further described with reference to FIGS. 6 (A) and 6 (B). FIGS. 6A and 6B show the current dependence of the cylindrical light source 3 having a diameter of 3 mm, the vertical axis shows the luminance ratio, and the horizontal axis shows the position of the illuminating surface on the light transmitting / diffusing plate 4. The central luminance ratio of the cylindrical light source 3 is 1.000, and the luminance on the ground side and on the side where the inverter circuit board 9 (the right side of the opening 1a of the housing 1) is located. Is shown. FIG. 6A shows a case where the inverter circuit board 9 is on the back side of the bottom plate 1b, and FIG. 6B shows a case where the inverter circuit board 9 is not on the back side of the bottom plate 1b.
[0061]
FIG. 6A shows the luminance on the high voltage side when the luminance ratio at the center of the screen is 1.000 when the inverter circuit board 9 is located on the right side of the opening 1a of the housing 1. In FIG. The tube current of the light source 3 is 3 mA, the curve 14b is a tube current of the cylindrical light source 3 of 3.5 mA, the curve 14c is a tube current of the cylindrical light source 3 of 4 mA, and the curve 14d is a tube current of the cylindrical light source 3 of 4.5 mA. The curve 14e shows the tube current of the cylindrical light source 3 of 5 mA, the curve 14f shows the tube current of the cylindrical light source 3 of 5.5 mA, the curve 14g shows the tube current of the cylindrical light source 3 of 6 mA, and the curve 14h shows the curve of the cylindrical light source 3. The tube current is 6.5 mA, and the curve 14i shows the case where the tube current of the cylindrical light source 3 is 7 mA. When the tube current on the high voltage side of the inverter circuit board 9 is large, the luminance ratio shows a small value and the tube current is small. Sometimes the luminance ratio shows a large value. This is because while the tube current is flowing from the high voltage side to the ground side, the current flowing to the ground side of the cylindrical light source 3 becomes smaller due to the leakage current generated through the stray capacitance generated between the tube current and the bottom plate 1b of the housing 1. In addition, it is considered that the luminance on the ground side decreases. Also, the reason why the luminance is small when the tube current on the high voltage side is large is considered that the luminous efficiency of the high voltage cylindrical light source 3 decreases and the luminance on the high voltage side decreases due to the temperature dependency described later. Table 3 shows the relationship data between the luminance and the tube current on the ground side and on the side where the inverter circuit board 9 (the right side of the opening 1a of the casing 1) is located, with the central luminance ratio of the cylindrical light source 3 being 1.000.
[0062]
[Table 3]

[0063]
FIG. 6B shows the luminance on the high voltage side where the luminance ratio at the center of the screen is 1.000 when the inverter circuit board 9 is not provided on the right side of the opening 1a of the housing 1. In FIG. The tube current of the light source 3 is 3 mA, the curve 14b is a tube current of the cylindrical light source 3 of 3.5 mA, the curve 14c is a tube current of the cylindrical light source 3 of 4 mA, and the curve 14d is a tube current of the cylindrical light source 3 of 4.5 mA. The curve 14e shows the tube current of the cylindrical light source 3 of 5 mA, the curve 14f shows the tube current of the cylindrical light source 3 of 5.5 mA, the curve 14g shows the tube current of the cylindrical light source 3 of 6 mA, and the curve 14h shows the curve of the cylindrical light source 3. The tube current is 6.5 mA, and the curve 14i shows the case where the tube current of the cylindrical light source 3 is 7 mA. When the tube current on the high voltage side of the inverter circuit board 9 is small, the luminance ratio shows a large value and the tube current is large. Sometimes the luminance ratio shows around 1.000 This is because while the tube current is flowing from the high voltage side to the ground side, the current flowing to the ground side of the cylindrical light source 3 decreases due to the leakage current generated through the stray capacitance generated between the tube current and the bottom plate 1b. However, comparing the luminance characteristic curves of FIG. 6B and FIG. 6A, it can be seen that the temperature does not affect the luminance when the tube current of the cylindrical light source 3 is 5 mA to 7 mA. Therefore, it is understood that when the tube current is large, the luminance characteristics are improved and the luminance is increased. Table 4 shows the relationship data between the luminance on the high voltage side and the tube current when the central luminance ratio of the cylindrical light source 3 is 1.000 and there is no inverter circuit board 9 (to the right of the opening 1a of the housing 1).
[0064]
[Table 4]

[0065]
From these facts, when a high current is applied to the cylindrical light source 3, the temperature of the inverter circuit board 9 becomes high due to the heat generated by the inverter circuit board 9, and a temperature gradient is formed on the bottom 1 b of the housing 1, and the cylindrical light source 3 on the inverter circuit board 9 side It is understood that the luminous efficiency of the cylindrical light source 3 on the low voltage side is improved, and the luminance on the high voltage side is reduced. Therefore, according to the present invention, as shown in FIG. 5, the tube current is adjusted so that the brightness characteristic curve is changed to the highest brightness (BLmax) of the cylindrical light source groups 3, 3L, 3R, 3U, 3D on the upper and lower sides or the left and right sides. , A substantially flat luminance characteristic curve can be obtained.
[0066]
Further, regarding the temperature distribution of the LCD and the backlight device 6, as shown in FIG. 11, the high temperature region 15 is biased to the right on the illuminating surface of the housing 1 in the related art. The inclination is so steep that the temperature distribution balance is broken as shown in FIG. 11 due to the temperature rise on the side where the inverter circuit board 9 is provided.
[0067]
On the other hand, according to the LCD and the backlight device 6 of the present invention, the upper and lower or left and right inverter circuit boards 9U, 9D, 9L, 9R have the long sides of the opening 1a of the housing 1 as shown in FIG. The temperature distribution balance is high because the upper and lower sides or the left and right sides on the illuminated surface are centered on the upper and lower or left and right inverter circuit boards 9U, 9D, 9L and 9R. The temperature distribution becomes the area 15 and the center on the illuminated surface is evenly spread with the medium temperature area 16, so that the luminance distribution balance is less likely to be lost.
[0068]
Further, when the LCD or the backlight device 6 is a display device having an aspect ratio similar to that of a 35 to 50 inch or high-definition television receiver or the like, the lamp length of the cylindrical light source 3 increases, and at the time of startup, The transformer and other active elements and passive elements used for the inverter circuit board 9 are required to have a withstand voltage twice as large as the normal state, and are increased in size to increase the withstand voltage. As a result, it is difficult to reduce the thickness of the case 1 having the inverter circuit board 9 only at one end as shown in FIG. It is coming.
[0069]
However, according to the LCD and the backlight device 6 of the present invention, for example, as shown in FIG. 8, the left and right inverter circuit boards 9L and 9R are provided at both left and right positions in the long side direction of the opening 1a of the housing 1. Then, the electrode portions 5 at both ends of the cylindrical light source group 3 are connected to the

transformer terminals

5A and 5B on the high voltage side of the left and right inverter circuit boards 9L and 9R, and are arranged in parallel with the long side direction of the opening 1a. By doing so, the driving voltage for each of the cylindrical light source groups 3 is 1000 V, but only 500 V, which is a half.
[0070]
Therefore, the withstand voltage of the transformers of the left and right inverter circuit boards 9L and 9R and the various active elements and passive elements can be reduced, and not only the thickness of the backlight device and the housing 1 can be reduced, but also the thickness can be reduced. It is possible to provide a highly safe LCD and backlight device that can be driven by a voltage.
[0071]
Further, by using the curved tubular cylindrical light source 3 and the left and right, upper and lower cylindrical light source groups 3L, 3R, 3U, and 3D as described with reference to FIGS. The drive voltage (1/2 V) of FIG. 2 (I) is supplied to the terminal 5A, and the drive voltage (in the opposite phase to that of FIG. 2 (I)) as shown in FIG. By supplying −） V), the potentials at the center position of the tube of the straight tubular cylindrical light source 3 and at the curved portions of the left and right, upper and lower cylindrical light source groups 3L, 3R, 3U, and 3D are offset to zero. (Ground potential), so that the input drive voltage can be reduced by half.
[0072]
【The invention's effect】
According to the LCD and the backlight device of the present invention, even if these devices are enlarged, the axial length of the cylindrical light source is increased, and the driving voltage is increased, the inverter circuit board can be opened in the housing. Since a plurality of cylindrical light source groups are arranged side by side between two inverter circuit boards, the driving voltage of these inverter circuit boards is low. Driving becomes possible, and downsizing of a transformer and various electric components can be achieved. In addition, the luminance distribution balance and the temperature distribution balance on the illuminated surface can be made uniform by adjusting the tube current and moving to the both ends of the opening of the inverter circuit board. It is also possible to reduce the stray capacitance between the bottoms of the body and to provide an LCD and a backlight device capable of suppressing a rise in the temperature inside the housing.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing one embodiment of a backlight device used for an LCD of the present invention.
FIG. 2 is a schematic plan view, a schematic plan view of a curved tube cylindrical light source, and a drive voltage waveform diagram showing another embodiment of the backlight device used in the LCD of the present invention.
FIG. 3 is a plan view and a side sectional view showing one embodiment of a backlight device used for the LCD of the present invention.
FIG. 4 is a plan view and a side sectional view showing a bottom view of another embodiment of another backlight device used in the LCD of the present invention.
FIG. 5 is a luminance characteristic curve diagram showing the relationship between the luminance using the tube current of the cylindrical light source used in the backlight device of the present invention as a parameter and the axial length of the cylindrical light source.
FIG. 6 is a schematic plan view for explaining tube current dependency and temperature dependency of the backlight device of the present invention.
FIG. 7 is a schematic plan view for explaining a temperature distribution of the backlight device of the present invention.
FIG. 8 is a schematic plan view for explaining an input voltage for driving a cylindrical light source of the backlight device of the present invention.
FIG. 9 is a plan view, a side sectional view, and a schematic plan view of a housing of a conventional backlight device.
FIG. 10 is a luminance characteristic curve diagram showing a relationship between luminance using a tube current of a cylindrical light source used in a conventional backlight device as a parameter and an axial length of the cylindrical light source.
FIG. 11 is a schematic plan view illustrating a temperature distribution of a conventional backlight device.
FIG. 12 is a schematic plan view for explaining an input voltage for driving a cylindrical light source of a conventional backlight device.
[Explanation of symbols]
1 casing, 1a opening, 1b bottom, 3 (3L, 3R, 3U, 3D) cylindrical light source (cylindrical light source group), 4 light transmitting diffuser, 5 Electrode section, 5A, 5B {transformer terminal, 9, 9U, 9D, 9L, 9R, 9UL, 9UC, 9UR, 9DL, 9DC, 9DR} inverter circuit board

Claims

In a backlight device in which a cylindrical light source is provided in a housing and an inverter circuit board is provided in the housing,
A backlight device wherein the inverter circuit board is disposed at both ends of a bottom surface in a longitudinal direction or a short side direction of an opening of the casing.

The tube current of the cylindrical light source is adjusted such that the luminance distribution characteristic of the backlight device has a predetermined luminance value centered on the inverter circuit boards disposed at both ends of the bottom surface of the opening of the housing. The backlight device according to claim 1, wherein:

A high voltage is applied to the pair of electrodes of the cylindrical light source from the inverter circuit boards disposed at both ends of the bottom surface of the opening of the housing, and the cylindrical light source is moved vertically or vertically within the opening of the housing. 3. The backlight device according to claim 1, wherein the backlight device is arranged side by side in a left-right direction to reduce a voltage shared by a transformer of the inverter circuit board.

A high voltage is applied to the pair of electrodes of the cylindrical light source from the inverter circuit boards disposed at both ends of the bottom surface of the opening of the housing, and the cylindrical light source is moved vertically or vertically within the opening of the housing. 4. The temperature distribution of an illuminating surface is arranged in parallel in the left-right direction, and the temperature distribution of the illuminating surface is made uniform around the inverter circuit boards disposed at both ends of the bottom of the opening of the housing. The backlight device according to any one of the preceding claims.

Both ends of a pair of electrode portions of the cylindrical light source are connected to the high voltage supply side of an inverter circuit board disposed at both ends of the bottom surface of the opening of the housing, and a plurality of housings are arranged in a horizontal or vertical direction. The backlight device according to any one of claims 1 to 4, wherein the backlight device is arranged side by side.

The backlight device according to any one of claims 1 to 5, wherein the cylindrical light source has a curved tubular shape.

A straight tube extending over a section extending between a pair of electrode portions of the inverter circuit board, wherein the shape of the cylindrical light source is disposed at both ends of the bottom surface of the opening of the housing. The backlight device according to any one of claims 1 to 6.

In a liquid crystal display device having a backlight in which a cylindrical light source is provided in a housing and an inverter circuit board is provided in the housing,
A liquid crystal display device, wherein the inverter circuit board is arranged at both ends of a bottom surface in a longitudinal direction or a short side direction of an opening of the housing.

The tube current of the cylindrical light source is adjusted so that the luminance distribution characteristic of the backlight has a predetermined luminance value centered on the inverter circuit boards disposed at both ends of the bottom surface of the opening of the housing. 9. The liquid crystal display device according to claim 8, wherein:

A high voltage is applied to the pair of electrodes of the cylindrical light source from the inverter circuit boards disposed at both ends of the bottom surface of the opening of the housing, and the cylindrical light source is moved vertically or vertically within the opening of the housing. 9. The liquid crystal display device according to claim 8, wherein the liquid crystal display device is arranged side by side in the left-right direction to reduce a voltage shared by a transformer of the inverter circuit board.

A high voltage is applied to the pair of electrodes of the cylindrical light source from the inverter circuit boards disposed at both ends of the bottom surface of the opening of the housing, and the cylindrical light source is moved vertically or vertically within the opening of the housing. 9. The liquid crystal display according to claim 8, wherein the temperature distribution of the illuminating surface is made uniform around the inverter circuit board disposed at both ends of the bottom of the opening of the housing in a horizontal direction. apparatus.