JP2004063125A - Discharge lamp lighting device, discharge lamp lighting method, and lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device having enhanced light emitting efficiency of a discharge lamp filled with a discharge medium mainly composed of xenon, and to provide a discharge lamp lighting method and a lighting system. <P>SOLUTION: This discharge lamp lighting device is equipped with the discharge lamp DL and a lighting circuit. The discharge lamp DL is equipped with a slender and translucent airtight vessel 1, a phosphor layer 2, a short internal electrode 4, the discharge medium mainly composed of xenon, and an external electrode 5. The lighting circuit is structured so that a pulsating voltage is output to be applied between the internal electrode 4 and the external electrode 5 of the discharge lamp DL, and the amount of total discharged charges Q (nC) produced in one cycle of a lamp current in response to the filled partial pressure (kPa) of xenon in the discharge lamp DL and a total pause period T<SB>S</SB>(μs) satisfy a formula: T<SB>S</SB>×P/Q ≥0.5 to light the discharge lamp. <P>COPYRIGHT: (C)2004,JPO

Description

また、全休止期間Ｔ_Ｓ（μｓ）は、ランプ電圧の１周期の間に生じる休止期間の和である。また、休止期間は、正および負の放電期間に続いて形成される。したがって、休止期間は、ランプ電圧の１周期の間に少なくとも２つ形成される。全休止期間は、それら休止期間の和である。
【００４１】
点灯回路から出力されて放電ランプの内外両電極間に印加される脈流電圧は、両極性および単極性のいずれであってもよい。また、交流電圧および適当な休止期間のある間欠的なパルス電圧のいずれであってもよい。交流電圧の場合、隣接する半波の間に休止期間のない態様およびＰＷＭ制御のためにパルス電圧列ごとに適当な休止期間のある態様のいずれであってもよい。パルス電圧の場合、単極性のパルスおよび両極性のパルスのいずれであってもよい。さらに、電圧の波形は、交流およびパルスのいずれであっても、矩形波（方形）、三角波、のこぎり波、階段波、積分波、微分波、インパルス波、正弦波など多様な波形を許容する。しかし、好適には図４に示すように矩形波の交流電圧および正または負のパルス電圧である。
【００４２】
図４は、本発明の実施に好適な矩形波の交流電圧波形およびパルス電圧波形を示す波形図である。そして、図４の（ａ）は矩形波交流電圧波形、（ｂ）は正極性の矩形波パルス電圧波形、（ｃ）は負極性の矩形波パルス電圧波形である。
【００４３】
交流電圧を点灯回路から出力して放電ランプに誘電体バリア放電を生起させる場合、ランプ電流は、ランプ電圧の半波の立ち上がり時にランプ電圧と同一極性の主電流がパルス状に流れる。また、回路条件によってはこれに続く逆極性の小さなオーバーシュート電流が主電流に続いて流れる。そして、ランプ電流が流れた後には、たとえ交流電圧の印加が継続していたとしても、休止期間が生じる。次に、印加電圧の極性が反転すると、再び半波の立ち上がり時にランプ電圧と同一極性の主電流がパルス状に流れる。また、回路条件によってはこれに続く逆極性の小さなオーバーシュート電流が主電流に続いて流れる。そして、同様にランプ電流の流れた後には、休止期間が生じる。このようにしてパルス状のランプ電流が交互に正負の極性で流れ、休止期間も各ランプ電流の間に間欠的に生じる。すなわち、休止期間のある交流のランプ電流が流れる。したがって、隣接する１組の正負の極性のランプ電流の絶対値を１周期にわたって時間積分した値が１周期内に生じる全放電電荷量Ｑである。また、全休止期間Ｔ_Ｓ（μｓ）は、正負両極性のランプ電圧の１周期の間に生じる全ての休止期間の和である。
【００４４】
一方、単極性のパルス電圧を点灯回路から出力して放電ランプに誘電体バリア放電を生起させる場合、ランプ電流は、パルス状のランプ電圧の立ち上がり時にランプ電圧と同一極性の主電流がパルス状に流れる。また、回路条件によってはこれに続く逆極性の小さなオーバーシュート電流が主電流に続いて流れる。そして、ランプ電流が流れた後には、たとえパルス電圧が継続して印加されていたとしても、休止期間が生じる。次に、ランプ電圧が立ち下がり時になると、ランプ電圧に対して逆極性の主電流がパルス状に流れる。また、回路条件によってはこれに続く逆極性の小さなオーバーシュート電流が主電流に続いて流れる。パルス電圧の印加が終了すると、次のパルス電圧が印加されるまでの間に休止期間がある。このようにしてパルス状のランプ電流が正負の極性に交互に流れ、休止期間も間欠的に生じる。すなわち、パルス電圧を印加して点灯する場合も、ランプ電流は休止期間のある交流になる。したがって、全放電電荷量Ｑ（ｎＣ）は、一つのパルス電圧が印加されて次のパルス電圧が印加されるまでの期間すなわち１周期に流れる正負両極性のランプ電流について上記のように積分した値となる。また、全休止期間Ｔ_Ｓ（μｓ）は、単極性のパルス電圧およびこれに続く休止期間からなる１周期の間に生じる全ての休止期間の和である。
【００４５】
ところで、本発明においては、上述のように数式１により放電ランプの点灯条件を規定している。この数式１は、以下の実験により求めることができる。すなわち、図１ないし図３に示す構成の放電ランプＤＬにおいて、放電媒体のキセノンガス封入分圧を５．５、９．３および１３．０ｋＰａにした３種類で、かつ、蛍光体層を備えている放電ランプと、放電ランプの陽光柱の状態を観察するために、蛍光体層を備えていない放電ランプをそれぞれ製作して、ランプ電流の１周期に生じる全放電電荷量Ｑ（ｎＣ）およびランプ電圧の１周期中の全休止期間Ｔｓ（μｓ）を種々変えたときの陽光柱の太さおよび拡散陽光柱の長さと発光効率とについて調査した。
【００４６】
放電ランプの陽光柱の観察は、高速ＣＣＤカメラ（たとえば、任意のタイミングでシャッターを開閉できるイメージインテンシファイヤーユニット高速電子シャッターを装着したＣＣＤカメラで、シャッタースピードが最短で３ｎｓのものが市販されている。）を用いて、シャッター開閉のタイミングを放電ランプへの印加電圧波形と同期させ、内部電極４から外部電極５へ向かってランプ電流が流れる放電期間すなわち正の放電期間に生じる陽光柱と、外部電極５から内部電極４へ向かってランプ電流が流れる放電期間すなわち負の放電期間に生じる陽光柱を撮影した結果、図５に示す写真のとおりであった。
【００４７】
図５は、本発明によらない場合に放電ランプの放電空間内に正の放電期間および負の放電期間に生じるに生じる陽光柱の状態を示す写真である。
【００４８】
正の放電期間における陽光柱は、外部電極がコイル状の場合、図５の（ａ）に示すように、透光性気密容器の内部に形成される全放電長の全域にわたって収縮した状態である。そして、図の左側に位置する内部電極の近傍の領域では外部電極の構造の如何にかかわらずほぼ管軸に沿って線状で、かつ、透光性気密容器の中心部に形成される。そして、図の右側に位置する内部電極から離隔したその他の領域では外部電極に対向する透光性気密容器の内壁面に沿って螺旋状に形成される。
【００４９】
これに対して、負の放電期間における陽光柱は、図５の（ｂ）に示すように、図の左側に位置する内部電極の近傍の領域で収縮状の陽光柱となる。しかし、図の右側に位置する内部電極から離隔したその他の領域では透光性気密容器の内部全体に広がる拡散状に広がった陽光柱が形成される。ここで、収縮状の陽光柱が形成される領域は、正の放電期間において、収縮状の陽光柱が管軸に沿って透光性気密容器の中心部に形成される領域と同じである。しかも、収縮状の陽光柱は、管径方向へ不規則に移動するため、発光にちらつきを生じる。
【００５０】
本発明は、負の放電期間において陽光柱が拡散状に広がった領域を全放電長の大部分に形成するように点灯する条件を明確にしたことによって特徴付けられているが、陽光柱の広がりを特定するために陽光柱の広がり率を以下により定義することとする。すなわち、陽光柱の広がり率ｋは、図６に示すように、透光性気密容器１の内部に形成される放電空間１ｄが円形の場合、拡散状の陽光柱もほぼ円形になるので、陽光柱の直径ｒ_Ｐの放電空間１ｄの直径ｒ_Ｇに対する比率ｒ_Ｐ／ｒ_Ｇにより求めることができる。
【００５１】
図６は、陽光柱の広がり率の定義を説明するための放電ランプの概念的横断面図である。図６および後述する図７において、図３と同一部分については同一符号を付して説明は省略する。また、Ｐは陽光柱を示す。
【００５２】
また、透光性気密容器１の内部に形成される放電空間１ｄが図７に示すように、非円形の場合は、陽光柱の広がりを以下のとおり定義する。
【００５３】
図７は、横断面形状が非円形の放電ランプにおける陽光柱の広がり率を説明するための概念的横断面図である。
【００５４】
すなわち、透光性気密容器１をその管軸に直交する面内においてある任意の径方向から観測したときの透光性気密容器１の内径がｒ_Ｇ（θ）、陽光柱の直径がｒ_Ｐ（θ）であるとすると、当該方向から見た陽光柱の広がり率は、ｋ（θ）＝ｒ_Ｐ（θ）／ｒ_Ｇ（θ）となる。次に、θを０°から３６０°まで変化させたときの陽光柱のそれぞれの広がり率ｋ（θ）を求める。それらの中の最大値ｋ（θ）_ＭＡＸをもって放電空間１ｄが非円形の場合の陽光柱の広がり率と定義する。図７に示す例では、最少の広がり率がｋ（０°）＝０．５で、最大の広がり率がｋ（２７０°）＝０．９であるから、陽光柱の広がり率は（θ）_ＭＡＸ＝０．９である。
【００５５】
次に、拡散状の陽光柱の長さは、陽光柱の広がり率が０．５以上の領域の長さの全放電長に占める割合をいう。
【００５６】
ところで、陽光柱の広がり率と蛍光体輝度の関係について調査した結果、図８に示す結果が得られた。
【００５７】
図８は、放電ランプの陽光柱の広がり率と蛍光体輝度の関係を示すグラフである。図において、横軸は陽光柱の広がり率ｋを、縦軸は蛍光体輝度（相対値）を、それぞれ示す。
【００５８】
図８から理解できるように、陽光柱の広がりｋが０．５以上になると、蛍光体輝度が顕著に高くなる。なお、陽光柱の広がり率ｋ＝０．５以上の領域すなわち図の中央から右方を拡散陽光柱、０．５未満の領域すなわち図の中央から左方を収縮陽光柱として便宜上区分することができる。
【００５９】
したがって、陽光柱の広がり率が０．５以上になる拡散状の陽光柱の領域が長くなれば、それだけ放電ランプの発光効率が高くなることが分る。
【００６０】
そこで、陽光柱の広がり率ｋが０．５以上になる拡散状の陽光柱の領域が全放電長の８０％以上になる点灯条件の限界データを、前記３種類の放電ランプについて求めた結果、図９が得られた。
【００６１】
図９は、本発明の放電ランプ点灯装置および放電ランプ点灯方法における数式１を示す実験式である。図において、横軸はＱ／Ｐ（ｎＣ／ｋＰａ）を、縦軸はＴ_Ｓ（μｓ）を、それぞれ示す。なお、Ｑはランプ電流の１周期に生じる全放電電荷量（ｎＣ）、Ｐはキセノンの封入分圧（ｋＰａ）であり、Ｔｓはランプ電流の１周期に生じる全休止期間（μｓ）である。また、図中、○はキセノンの封入分圧が５．５ｋＰａの放電ランプにおける限界データ、●は同じく９．３ｋＰａ、△は同じく１３．０ｋＰａである。こられのデータを結んで得られた直線から上に位置する領域が上記点灯条件を満足する。すなわち、この領域は数式１を満足する領域である。
【００６２】
次に、数式１を満足するように放電ランプを点灯するには、キセノンの封入分圧Ｐ（ｋＰａ）に応じてたとえば点灯回路から供給される主としてランプ電流、点灯回路の出力電圧の周波数などを適切に調整すればよい。なお、キセノンの封入分圧は、特段限定されないが、好ましくは１００Ｐａ〜３ＭＰａである。また、点灯回路の出力電圧の周波数は、特段限定されないが、好ましくは２０〜２００ｋＨｚの範囲である。
【００６３】
＜本発明の作用について＞　　外部電極を接地状態とし、放電ランプの内部電極と外部電極との間に点灯回路から脈動電圧を印加して、内部電極の電位が増加する期間（交流電圧の場合は、内部電極の電位が外部電極のそれより高くなる。）すなわち正の放電期間において、透光性気密容器を介して放電空間に電界が発生し、この電界が放電空間の放電破壊電界以上まで増加すると、放電空間に放電が発生する。それにより、内部電極から外部電極へ向かって放電電流すなわちランプ電流が流れる。しかし、放電路に直列に透光性気密容器の壁面からなる誘電体が介在しているから、誘電体表面に電荷が充電されると、放電空間の電界が打ち消されて零となり、放電が終了し、ランプ電流が零になる。
【００６４】
正の放電期間に生じる放電は、陽光柱が全領域にわたって収縮する。また、陽光柱は、透光性気密容器の外部電極に対向する内壁面に張り付いて形成される。したがって、外部電極がたとえば線状の場合、陽光柱は細くなる。また、外部電極が面状の場合、陽光柱は薄い面状になる。
【００６５】
次に、内部電極の電位が減少する期間（交流電圧の場合は、外部電極の電位が内外部電極のそれより高くなる。）すなわち負の放電期間において、放電空間には上記とは逆向きの電界が発生し、この電界が放電空間の放電破壊電界まで増加すると、放電空間で放電が発生する。それにより、外部部電極から内外部電極へ向かって放電電流すなわちランプ電流が流れる。しかし、放電路に直列に誘電体が介在しているから、誘電体表面に電荷が充電されると、放電空間の電界が打ち消されて零となり、放電が終了し、ランプ電流が零になる。
【００６６】
負の放電期間に生じる放電は、陽光柱が広がり率０．５以上の拡散状であり、しかも、全放電長の８０％以上の領域にわたって形成される。その結果、放電ランプの発光効率が向上する。
【００６７】
以上の動作が繰り返されて放電が継続されるため、印加電圧が交流および単極性のパルス電圧のいずれであっても、電流波形は、休止期間を挟んで正負に振動して交流となる。
【００６８】
本発明においては、前述の構成を具備していることにより、以上説明したように、負の放電期間において、十分に太くて、しかも、管軸方向の大部分にわたって拡散状の陽光柱の領域が発生し、その結果発光効率が向上する。
【００６９】
請求項２の発明の放電ランプ点灯装置は、請求項１記載の放電ランプ点灯装置において、ランプ電流が主として外部電極から内部電極へ流れる放電期間において、透光性気密容器の内部に生じる陽光柱は、透光性気密容器の管軸と直交する面内における広がり率０．５以上の領域が全放電長の８０％以上にわたって形成されることを特徴としている。
【００７０】
本発明は、高い発光効率の得られる拡散陽光柱の太さおよび管軸方向の領域の長さを規定している。
【００７１】
そうして、本発明によれば、放電ランプの発光効率が高いとともに、蛍光体層の輝度の高い領域が全放電長の大部分にわたって得られる。
【００７２】
請求項３の発明の放電ランプ点灯装置は、請求項１または２記載の放電ランプ点灯装置において、ランプ電流が主として外部電極から内部電極へ流れる放電期間に放射される波長８２８ｎｍの赤外線放射強度のピーク値が、ランプ電流が主として内外部電極から外内部電極へ流れる放電期間において透光性気密容器の内部に生じる放電期間における同様のピーク値の１．２倍以上となる領域が全放電長の８０％以上にわたって形成されることを特徴としている。
【００７３】
本発明は、波長８２８ｎｍの赤外線放射強度のピーク値を所定値にすることにより発光効率を向上させた構成を規定している。
【００７４】
すなわち、波長８２８ｎｍの赤外線は、キセノンの励起光である。したがって、放電ランプから放射される波長８２８ｎｍの赤外線放射強度のピーク値が大きいことは、放電ランプの発光効率が高いことを意味する。このため、波長８２８ｎｍの赤外線の放射量が多くなるように点灯条件を設定することにより、放電ランプの発光効率を高くすることができる。
【００７５】
また、放電により放射される波長８２８ｎｍの赤外線を検出することにより、放電ランプの蛍光体層が存在するために放電ランプの内部を透視できなくても、発光効率を間接的に推測することができる。本発明において、負の放電期間における波長８２８ｎｍの赤外線放射強度のピーク値を正の放電期間における同様のピーク値の１．２倍以上に規定している理由は、次のとおりである。すなわち、１．２倍未満であると、陽光柱の拡散が十分でなく、したがって発光効率が所望の程度まで向上しないからである。
【００７６】
請求項４の発明の放電ランプ点灯方法は、細長い透光性気密容器、透光性気密容器の内面側に配設された蛍光体層、透光性気密容器内に封装された短寸の内部電極、透光性気密容器内に封入されたキセノンを主体とする放電媒体および透光性気密容器の長手方向に沿い、かつ、外周面にほぼ接触して配設された導電性物質からなる外部電極を備えた放電ランプの内部電極および外部電極間に脈動電圧を印加して、放電ランプのキセノンの封入分圧Ｐ（ｋＰａ）に応じてランプ電流の１周期内に生じる全放電電荷量Ｑ（ｎＣ）および全休止期間Ｔ_Ｓ（μｓ）が数式１を満足するように点灯することを特徴としている。
【００７７】
【数１】
Ｔ_Ｓ・Ｐ／Ｑ≧０．５
請求項１が放電ランプ点灯装置の発明として規定しているのに対して、本発明は点灯方法として同様の内容を規定している点で異なる。
【００７８】
請求項５の発明の照明装置は、照明装置本体と；照明装置本体に配設された請求項１ないし３のいずれか一記載の放電ランプ点灯装置と；を具備していることを特徴としている。
【００７９】
本発明において、「照明装置」とは、放電ランプの発光を利用する全ての装置を含む広い概念であり、たとえばバックライト装置およびこれを備えた液晶表示装置、ならびに液晶表示装置を組み込んだ機器、自動車などの移動体用計器パネル照明装置、装飾用照明器具、ならびに読取装置およびこれを備えたイメージスキャナ、複写機およびファクシミリなどである。液晶表示装置を組み込んだ機器としては、たとえばパーソナルコンピュータ、ナビゲーション機器、携帯情報端末機および液晶テレビジョン受像装置などの電子機器などである。
【００８０】
また、「照明装置本体」とは、照明装置から放電ランプ点灯装置を除いた残余の部分をいう。
【００８１】
【発明の実施の形態】以下、図面を参照して本発明の実施の形態を説明する。
【００８２】
図１０および図１１は、本発明の放電ランプ点灯装置および放電ランプ点灯方法の第１の実施形態を示し、図１０はランプ電圧およびランプ電流を示す波形図、図１１は放電ランプの放電空間内に正の放電期間および負の放電期間に生じる陽光柱の状態を示す写真である。本実施形態は、放電ランプおよび点灯回路を備えている。
【００８３】
放電ランプは、図１ないし図３に示し、かつ、説明したのと同一構成である。したがって、その構成についてのここでの説明は省略する。
【００８４】
点灯回路は、交流矩形波電圧を出力し、この電圧を放電ランプＤＬの内部電極４と外部電極５との間に印加し、かつ、ランプ電流を供給する。矩形波交流電圧を出力するための回路としては、たとえばチョッパ回路と、その直流出力電圧を矩形波交流電圧に変換するフルブリッジ形インバータ回路とを主体として構成することができる。
【００８５】
放電ランプＤＬのランプ電圧は、期間Ｉ〜ＩＶで１周期である。期間ＩとＩＩが内部電極４の電位が外部電極５より高くなる正の半波であり、期間ＩＩＩとＩＶが外部電極５の電位が内部電極４より高くなる負の半波である。そして、期間Ｉが＋電圧の立ち上がりで、そのときにピーク値があり、期間ＩＩがほぼ平坦で、その終期に電圧の立ち下りがある。また、期間ＩＩＩが−電圧の立ち上がりで、そのときにピーク値があり、期間ＩＶがほぼ平坦で、その終期に電圧の立ち下りがある。上記において、ピーク値は１５００Ｖ、立ち下り時の瞬時値が８００Ｖ、１周期５０μｓ、すなわち周波数２０ｋＨｚである。
【００８６】
ランプ電流は、期間Ｉが正の放電期間、期間ＩＩＩが負の放電期間である。期間Ｉにおいては主として内部電極４から外部電極５へ向かう正極性のランプ電流が流れる。このときのピーク値は＋３８ｍＡである。期間ＩＩＩにおいては、主として外部電極５から内部電極４へ向かう負極性のランプ電流が流れる。このときのピーク値は−２０ｍＡである。
【００８７】
そうして、図１１に示すように、放電ランプＤＬの放電空間１ａ内には放電により陽光柱が生じる。正の放電期間に生じる陽光柱は、図１１の（ａ）に示すように全領域にわたって収縮している。これに対して、負の放電期間に生じる陽光柱は、図１１の（ｂ）に示すように、ほぼ全領域にわたって拡散している。すなわち、陽光柱の広がり率ｋは０．５以上で、拡散状陽光柱の長さＬ_Ｐは全放電長Ｌ_Ｔの８０％以上の大部分にわたっている。
【００８８】
図１２は、本発明の放電ランプ点灯装置および放電ランプ点灯方法の第２の実施形態におけるランプ電圧、ランプ電流および放射強度を示す波形図である。本実施形態は、点灯回路の出力電圧の周波数とランプ電流が異なる。
【００８９】
すなわち、ランプ電圧の１周期は２５μｓすなわち周波数が４０ｋＨｚ、ランプ電流は正の放電期間のピーク値が＋２１ｍＡ、負の放電期間のピーク値が−２３ｍＡである。
【００９０】
放射強度は、キセノンの励起光の８２８ｎｍを測定して得た値である。負の放電期間に生じる放射強度のピーク値Ｒ_Ｎは、拡散状をなし、正の放電期間に生じる放射強度のピーク値Ｒ_Ｐの１．２倍以上になっていることが容易に理解できる。
【００９１】
次に、図１３および図１４を参照して、本発明の放電ランプ点灯装置および放電ランプ点灯方法を実施する際に用いる放電ランプの他の例を示す。なお、図において、図１ないし図３と同一部分については同一符号を付して説明は省略する。
【００９２】
図１３は、外部電極の構造が異なる放電ランプの他の例を概念的に示す一部断面要部正面図および横断面図である。
【００９３】
図１３の（ａ）に示す例は、外部電極５が帯状のアルミニウム箔からなり、透光性気密容器１の上半部に密接して配設している。
【００９４】
図１３の（ｂ）に示す例は、外部電極５が帯状の透明導電膜（ＩＴＯ膜）からなり、透光性気密容器１の上半部に密接して配設している。
【００９５】
図１３の（ｃ）に示す例は、外部電極５が金属メッシュ構造体からなり、透光性気密容器１の全周にわたって密接して配設している。
【００９６】
図１４は、内部電極の構成が異なる放電ランプの他の例を示す縦断面図である。この放電ランプＤＬは、透光性気密容器１の内部両端部に封装された一対の内部電極４Ａ、４Ｂを備えている点で異なる。
【００９７】
図１５は、本発明の照明装置の一実施形態としての液晶用バックライト装置を示す断面図である。図において、図２と同一部分については同一符号を付してある。液晶用バックライト装置１０は、バックライト装置本体１１および放電ランプ点灯装置１２を備えて構成されている。なお、図中の符号１３は、液晶表示部である。
【００９８】
バックライト装置本体１１は、導光体１１ａ、樋状反射板１１ｂ、背面反射シート１１ｃ、拡散シート１１ｄ１および集光シート１１ｄ２備え、図示しないケースに収納される。
【００９９】
導光体１１ａは、透明アクリル樹脂やポリカーボネート樹脂などの高屈折率を有する透明体から構成されている。樋状反射板１１ｂは、放電ランプ１２から導光体１１ａに直接入射しない方向へ放射された光を反射して導光体１１ａに入射させるとともに、放電ランプ１２の発光が導光体１１ａ以外の箇所へ漏光しないように遮蔽する。背面反射シート１１ｃは、導光体１１ａの背面から出る光を反射して導光体１１ａの前面から出射させる。また、その際に光がなるべく面全体から均一に出射するように、背面反射シート１１ｃの反射率を部分的に制御することができる。拡散シート１１ｄ１は、導光体１１ａの前面に配設されて、導光体１１ａから前方へ出射する光を拡散して輝度分布をなるべく均一化する。集光シート１１ｄ２は、拡散シート１１ｄ１から出射した光を集光して、液晶表示部１３に対する入射効率を高める。
【０１００】
放電ランプ点灯装置１２は、放電ランプＤＬおよび図示しない点灯回路からなる。放電ランプＤＬは、図１ないし図３に示す
液晶表示部１３は、バックライト装置の前面に重ねて配設され、その背面からバックライト装置本体により照明され、透過式の液晶表示が行われる。
【０１０１】
【発明の効果】請求項１の発明によれば、内面側に蛍光体層を配設し、キセノンを主体とする放電媒体を封入した細長い透光性気密容器に封装された短寸の内部電極および透光性気密容器の長手方向に沿い、かつ、外周面にほぼ接触して配設された導電性物質からなる外部電極を備えた放電ランプと、脈動電圧を出力して放電ランプの内部電極および外部電極間に印加するとともに、放電ランプのキセノンの封入分圧Ｐ（ｋＰａ）に応じてランプ電流の１周期内に生じる全放電電荷量Ｑ（ｎＣ）および全休止期間Ｔ_Ｓ（μｓ）が数式１を満足するように放電ランプを点灯する点灯回路とを具備していることにより、放電ランプの発光効率を向上した放電ランプ点灯装置を提供することができる。
【０１０２】
【数１】
Ｔ_Ｓ・Ｐ／Ｑ≧０．５
請求項２の発明によれば、加えてランプ電流が主として外部電極から内部電極へ流れる放電期間において透光性気密容器の内部に生じる陽光柱は、透光性気密容器の管軸と直交する面内における広がり率０．５以上の領域が全放電長の８０％以上にわたって形成されることにより、放電ランプの発光効率が高いとともに、蛍光体層の輝度の高い領域が全放電長の大部分にわたって得られる放電ランプ点灯装置を提供することができる。
【０１０３】
請求項３の発明によれば、加えてランプ電流が主として外部電極から内部電極へ流れる放電期間に放射される波長８２８ｎｍの赤外線放射強度のピーク値が、ランプ電流が主として内部電極から外部電極へ流れる放電期間において透光性気密容器の内部に生じる放電期間における同様のピーク値の１．２倍以上となる管軸方向の領域の長さが全放電長の８０％以上であることにより、放電ランプの内部を透視できなくても、発光効率を間接的に推測できる放電ランプ点灯装置を提供することができる。
【０１０４】
請求項４の発明によれば、内面側に蛍光体層を配設し、キセノンを主体とする放電媒体を封入した細長い透光性気密容器に封装された短寸の内部電極および透光性気密容器の長手方向に沿い、かつ、外周面にほぼ接触して配設された導電性物質からなる外部電極を備えた放電ランプの内部電極および外部電極間に脈動電圧を印加するとともに、放電ランプのキセノンの封入分圧Ｐ（ｋＰａ）に応じてランプ電流の１周期内に生じる全放電電荷量Ｑ（ｎＣ）および全休止期間Ｔ_Ｓ（μｓ）が数式１を満足するように放電ランプを点灯することにより、発光効率を向上した放電ランプ点灯方法を提供することができる。
【０１０５】
【数１】
Ｔ_Ｓ・Ｐ／Ｑ≧０．５
請求項５の発明によれば、照明装置本体および請求項１ないし３記載の放電ランプ点灯装置を具備していることにより、請求項１ないし３の効果を有する照明装置を提供することができる。
【図面の簡単な説明】
【図１】希ガス放電用の放電ランプの一例を示す正面図
【図２】同じく縦断面図および点灯回路を示す回路図
【図３】同じく放電容器の横断面図
【図４】本発明の実施に好適な矩形波の交流電圧波形およびパルス電圧波形を示す波形図
【図５】本発明によらない場合の放電ランプの放電空間内に正の放電期間および負の放電期間に生じる陽光柱の状態を示す写真
【図６】陽光柱の広がり率の定義を説明するための放電ランプの概念的横断面図
【図７】横断面形状が非円形の放電ランプにおける陽光柱の広がり率を説明するための概念的横断面図
【図８】放電ランプの陽光柱の広がり率と蛍光体輝度の関係を示すグラフ
【図９】本発明の放電ランプ点灯装置および放電ランプ点灯方法における数式１を示す実験式
【図１０】本発明の放電ランプ点灯装置および放電ランプ点灯方法の第１の実施形態におけるランプ電圧およびランプ電流を示す波形図
【図１１】同じく放電ランプの放電空間内に正の放電期間および負の放電期間に生じる陽光柱の状態を示す写真
【図１２】本発明の放電ランプ点灯装置および放電ランプ点灯方法の第２の実施形態におけるランプ電圧、ランプ電流および放射強度を示す波形図
【図１３】外部電極の構造が異なる放電ランプの他の例を概念的に示す一部断面要部正面図および横断面図
【図１４】内部電極の構成が異なる放電ランプの他の例を示す縦断面図
【図１５】本発明の照明装置の一実施形態としての液晶用バックライト装置を示す断面図
【符号の説明】
１…透光性気密容器、２…蛍光体層、４…内部電極、５…外部電極、８…点灯回路、ＤＬ…放電ランプ[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device, a discharge lamp lighting method, and a lighting device for lighting a discharge lamp containing a discharge medium mainly composed of xenon.
2. Description of the Related Art A discharge lamp in which xenon is sealed does not use mercury, which has a large environmental load, and thus has little effect on the environment at the time of disposal, and has the advantage that brightness and discharge voltage are hardly affected by ambient temperature. .
[0002]
As a discharge lamp using discharge of a rare gas such as xenon, a discharge lamp having a structure as shown in FIGS. 1 to 3 has been developed by the present inventors.
[0003]
1 to 3 show an example of a discharge lamp for rare gas discharge and a lighting circuit. FIG. 1 is a front view of the discharge lamp, FIG. 2 is a vertical sectional view and a lighting circuit of the same, and FIG. FIG. In each of the drawings, the discharge lamp DL includes a light-transmitting airtight container 1, a phosphor layer 2, a lead wire 3, an internal electrode 4, an external electrode 5, a light-transmitting insulating tube 6, and a lead wire 7. In FIG. 2, reference numeral 8 denotes a lighting circuit, and 9a and 9b denote conductive lines.
[0004]
The translucent airtight container 1 is formed by sealing both ends of a glass tube, and a discharge medium mainly composed of xenon is sealed in a discharge space 1a formed therein. Further, the translucent airtight container 1 is made of hard glass, and the first and second end portions 1b and 1c are mainly composed of a glass bead stem. The first and second end portions 1b and 1c are formed by sealing a pair of bead stems at both ends of the glass tube of the cylindrical portion 1d.
[0005]
The phosphor layer 2 is made of a phosphor of a three-wavelength emission type, and is disposed on the inner surface side of the translucent airtight container 1.
[0006]
The introduction wire 3 is hermetically sealed from one end of the translucent airtight container 1 to the inside. The introduction wire 3 penetrates one end portion 1b of the light-transmitting airtight container 1 in an airtight manner, and the airtight penetration portion is made of Kovar of a sealing metal. And it is comprised by welding a nickel wire to the outer end part of Kovar.
[0007]
The internal electrode 4 is made of a cold cathode, is made of metal, is supported by the inner end of the introduction wire 3, and is sealed on the tube shaft at one end in the translucent airtight container 1.
[0008]
The external electrode 5 is made of a conductive metal wire such as nickel, for example, and is formed by winding the conductive metal wire in a coil shape. And is substantially in close contact with the outer peripheral surface of the translucent airtight container 1.
[0009]
The light-transmitting insulating tube 6 is formed by heating a transparent heat-shrinkable fluororesin sheet into a tube shape, and is coated over the external electrode 5 around the light-transmitting airtight container 1. 5 is fixed.
[0010]
The lead wire 7 is sealed at one end of the translucent airtight container 1 so as not to contact the discharge medium, the embedded portion is formed of Kovar, and the protruding portion is formed of a nickel wire. Then, the winding end portion of the external electrode 5 is connected to the nickel wire portion, and functions as an external connection means of the external electrode 5.
[0011]
The lighting circuit 8 applies a pulsating voltage, for example, a rectangular wave AC voltage or a pulse voltage, between the internal electrode 4 and the external electrode 5 via the conductive wires 9a and 9b, the lead wire 3 of the discharge lamp DL, and the lead wire 7. To light the discharge lamp DL.
[0012]
Then, when the output voltage from the lighting circuit 8 is applied between the internal electrode 4 and the external electrode 5 of the discharge lamp DL, a dielectric barrier discharge of xenon occurs in the translucent airtight container 1. Xenon emits ultraviolet radiation. The ultraviolet light excites the phosphor layer 2 to generate visible light, so that the ultraviolet light is eventually converted into visible light. Then, since the visible light is transmitted to the outside through the translucent airtight container 1, this visible light can be used as a light source.
A discharge lamp in which a discharge medium mainly composed of xenon is sealed has a problem that the brightness is generally insufficient compared with a discharge lamp using mercury.
[0013]
An object of the present invention is to provide a discharge lamp lighting device, a discharge lamp lighting method, and a lighting device in which the luminous efficiency of a discharge lamp in which a discharge medium mainly composed of xenon is sealed is improved.
[0014]
[Means for achieving the object]
The discharge lamp lighting device according to the first aspect of the present invention is an elongated light-transmitting airtight container, a phosphor layer disposed on the inner surface side of the light-transmitting airtight container, and a short inside sealed in the light-transmitting airtight container. An electrode, a discharge medium mainly composed of xenon enclosed in a light-transmitting airtight container, and a conductive material disposed along the longitudinal direction of the light-transmitting airtight container and almost in contact with the outer peripheral surface. A discharge lamp having an external electrode; a pulsating voltage is output and applied between the internal electrode and the external electrode of the discharge lamp, and within one cycle of the lamp current according to the xenon enclosed partial pressure P (kPa) of the discharge lamp. Discharge electric charge Q (nC) generated in the entire period and the entire idle period T _S And a lighting circuit for lighting the discharge lamp so that (μs) satisfies Equation 1.
[0015]
(Equation 1)
T _S ・ P / Q ≧ 0.5
In the present invention and each of the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.
[0016]
<Regarding Discharge Lamp> The discharge lamp includes a translucent airtight container, a phosphor layer, an internal electrode, a discharge medium, and an external electrode. The following is a description of each component of the discharge lamp.
[0017]
(Translucent airtight container) The translucent airtight container is preferably formed by sealing both ends of a glass bulb because it is the easiest to manufacture and the cost is low. May be formed. Note that as the glass, soft glass, semi-hard glass, hard glass, quartz glass, or the like can be appropriately selected and used. In particular, since the translucent airtight container acts as a dielectric in the dielectric barrier discharge, it is possible to take care to select a material having a desired relative dielectric constant in order to satisfy Equation 1 described below. The fact that the light-transmitting airtight container is light-transmitting does not necessarily mean that the entire light-transmitting airtight container is light-transmitting, and it is intended to derive at least visible light generated with discharge. This means that the portion to be transparent only needs to be translucent. Further, that the light-transmitting airtight container is elongated means that the light-transmitting airtight container has a length at least twice the outer diameter of the light-transmitting airtight container.
[0018]
Further, the translucent airtight container may be either a straight tube or an irregular shape. The “irregular shape” means that the shape of the translucent airtight container in the longitudinal direction is not a straight tube shape. For example, various shapes such as an L-shape, a U-shape, a U-shape, a W-shape, a ring shape, and a semi-annular shape are used. Can be adopted. Further, it is possible to form not only the above-described two-dimensional shape but also a three-dimensional arbitrary curved shape. Furthermore, in order to form into an irregular shape, after heating a straight tube-shaped glass tube, it bends by applying an external force, bends using a molding die, or joins a plurality of glass tubes. be able to.
[0019]
When the translucent airtight container has an irregular shape, it is possible to configure so that one discharge lamp can simultaneously enter a light guide plate of a backlight device for liquid crystal from two or more sides thereof, for example. That is, since the discharge lamp that performs rare gas discharge has a smaller amount of light than the discharge lamp that performs mercury vapor discharge, it is necessary to increase the light amount by lengthening the light-transmitting airtight container. Therefore, it is conceivable to arrange a plurality of discharge lamps in a straight tube shape on a plurality of end faces of the light guide plate to compensate for the insufficient light amount. However, such a configuration increases the cost and increases the backlight of the discharge lamp. Incorporation into the device becomes difficult, for example in terms of wiring and support of the discharge lamp. On the other hand, by making the translucent airtight container longer and having a different shape, one discharge lamp can be configured to simultaneously receive light from a plurality of end faces. For this reason, it is possible to reduce the cost and to easily incorporate the backlight device. On the other hand, since the amount of light emission can be increased by lengthening the discharge vessel, higher luminance can be obtained as compared with the case where one straight tube-shaped discharge lamp is used.
[0020]
Further, in the present invention, the translucent airtight container may have a non-circular shape such as a flat or elliptical cross section.
[0021]
(Phosphor layer) The phosphor layer is provided on the inner surface side of the translucent airtight container. The “inner surface side” may be any one of an embodiment in which the phosphor layer is directly formed on the inner surface of the translucent airtight container and an embodiment in which the phosphor layer is indirectly formed via a protective film, a reflective film, or the like. Means
[0022]
When the discharge lamp is for a backlight, it is preferable to form the phosphor layer using a white light emitting phosphor such as a three-wavelength light emitting phosphor or a halophosphate phosphor. In the case of reading, a phosphor of a green light emission type for monocolor and a phosphor of a white light emission type of three wavelength emission for full color are preferable. In short, a phosphor having a desired luminescent color, luminous efficiency, color rendering, and the like may be appropriately selected from known phosphors according to the use of the discharge lamp.
[0023]
Further, the phosphor layer may be formed on the entire peripheral surface of the light emitting region in the longitudinal direction of the light-transmitting airtight container, or a light guide slit in which the phosphor layer is not formed in the tube axis direction to form an aperture structure. You can also
[0024]
(Internal Electrode) The internal electrode is sealed in a light-transmitting airtight container, and has a short dimension. As such an internal electrode, a cold cathode type electrode or a hot cathode type electrode similar to that used for a normal internal electrode type discharge lamp can be used. In order to reduce the power loss (power loss based on the cathode drop voltage) due to the cold cathode electrode, an emitter material (electron emitting material) can be applied to the surface of the internal electrode. A ceramic electrode can be used as the hot cathode instead of the filament electrode.
[0025]
Regardless of the internal electrode having any of the above configurations, in order to seal it inside the light-transmitting airtight container, it is possible to appropriately select and use various known sealing means such as a flare seal, a bead seal, and a pinch seal. it can.
[0026]
The internal electrode is generally provided at an end of the light-transmitting hermetic container, but may be provided at an intermediate portion if desired. For example, it is possible to seal an internal electrode in the middle of the translucent airtight container, and to dispose a pair of external electrodes extending toward both ends of the translucent airtight container around the internal electrode in an insulating relationship with each other. it can. In this case, if the pair of external electrodes is connected to one pole of a different lighting circuit and the internal electrode is connected to the other pole of each lighting circuit with a common potential, the light-transmitting airtight container operates as two discharge lamps. Can be done. If the pair of external electrodes is connected to one pole of a single lighting circuit and the internal electrode is connected to the other pole, it operates like two discharge lamps connected in parallel.
[0027]
Furthermore, a pair of internal electrodes can be sealed at both ends inside the translucent airtight container. In this case, if the pair of internal electrodes is connected to one pole of the lighting circuit and the external electrode is connected to the other pole, the circuit operates like two discharge lamps connected in parallel. Also, if one pole of a pair of lighting circuits is connected to one pole of a pair of lighting circuits so as to share an external electrode, and the other pole of each lighting circuit is connected to a pair of internal electrodes, the apparatus operates as two discharge lamps.
[0028]
(Discharge Medium) The discharge medium is mainly composed of xenon, and is allowed to be used alone or mixed with a rare gas such as neon, argon, or krypton. Further, in addition to xenon, a halide of xenon or a simple halogen may be added. As the halogen, iodine, bromine, and chlorine can be used. If the element exists as vapor in the range of several mHg to several atmospheres, discharge is possible.
[0029]
(External Electrode) The external electrode substantially contacts the outer surface of the translucent airtight container, and is disposed along the longitudinal direction. Further, the external electrode is made of a conductive material. The external electrode may or may not extend to a region facing the internal electrode of the light-transmitting hermetic container. Also, that the external electrode is disposed `` almost in contact '' with the outer surface of the light-transmitting airtight container, it is preferable that the entire external electrode is in contact with the outer peripheral surface of the light-transmitting airtight container, This is not an essential requirement, but generally means that the external electrode only needs to be in contact with the outer surface of the translucent airtight container.
[0030]
Next, as the conductive material for forming the external electrode, a wire or foil of a conductive metal is generally used because it is easy to manufacture and relatively inexpensive. However, if necessary, a conductive film in which a conductive substance such as a metal, a metal oxide or a nitride is applied to the outer surface of the light-transmitting hermetic container by using a thin film forming means such as vacuum deposition or chemical vapor deposition (CVD) It may be. Alternatively, a conductive film formed using a so-called thick-film conductive film forming means in which a conductive paste containing fine powder of a conductive metal such as silver or copper is applied and fired may be used. Further, the conductive metal wire is generally used because a material having a circular cross section is a readily available material, but if necessary, a conductive metal wire having an irregular cross section such as a flat, square, or triangular cross section may be used. it can. As the conductive metal, for example, nickel, copper, aluminum, stainless steel, brass, and the like can be used.
[0031]
Further, it is preferable that the external electrode is provided over substantially the entire periphery of the light-transmitting airtight container. Note that "almost all around" means that the external electrodes are provided over a range of half or more around. Accordingly, the present invention can be applied to a so-called aperture type discharge lamp in which an aperture having an angle of less than half a circle, preferably 50 to 100 °, is formed between the external electrodes. In the case of an aperture type discharge lamp, the external electrode is preferably a conductive metal foil, a thick film conductive film, or the like.
[0032]
In the aspect in which the external electrode is provided over the entire periphery of the light-transmitting hermetic container, the external electrode is preferably a light-transmitting conductive film, a mesh electrode, a coil electrode, or the like. A common feature of all of these electrodes is that radiation can pass through the contours of the electrodes. As the translucent conductive film, for example, an ITO film, a Nesa film, or the like can be used. As the mesh electrode, for example, a knitted structure of a conductive metal wire, a punched conductive metal plate, or the like can be used. As the coil-shaped electrode, a configuration in which a conductive metal wire is wound at a predetermined pitch can be used. However, in any of the mesh-shaped electrode and the coil-shaped electrode, they can be formed using a thin conductive film formed through a mask pattern or a thick conductive film formed by printing or the like.
[0033]
Next, when the external electrode is formed of a coiled electrode, the coil of the external electrode is so formed that the ratio of the surface of the light-transmitting airtight container exposed from between the coils of the external electrode, that is, the opening ratio is 90% or more. Can be set as desired. Since the pitch of the coil of the external electrode affects the obtained luminance and illuminance, the pitch of the coil can be appropriately changed in order to achieve a desired luminance or illuminance distribution in the tube axis direction. For example, when the pitch of the coil of the external electrode is constant in the tube axis direction, the luminance is relatively large in a region relatively close to the internal electrode, and the luminance is relatively large in a region relatively far from the internal electrode. Since it tends to be smaller, the pitch of the coil can be changed continuously or stepwise according to the distance from the internal electrode in order to obtain a distribution of luminance or illuminance as uniform as possible in the tube axis direction. Also, one end of the coil can be directly led out. Instead, the base end of the lead wire is sealed to one end of the translucent airtight container so as not to be exposed to the discharge space, and one end of the coil is connected to this lead wire by soldering, caulking or welding. can do.
[0034]
(Other Configurations) Although not an essential configuration requirement in the present invention, the performance of the discharge lamp can be enhanced or functions can be added by adding the following configuration.
[0035]
1. Light-Transmissive Insulating Coating A light-transmissive insulating coating can be provided outside the external electrode to mechanically secure the external electrode and, if necessary, further improve the insulation of the discharge lamp. The translucent insulating coating is preferably transparent. The light-transmitting insulating coating can be formed by one or a combination of various means such as heat shrinkage of a light-transmitting insulating tube, winding of a light-transmitting insulating sheet, and dipping of a light-transmitting insulating resin solution. it can.
[0036]
2. Protective Film, etc. If necessary, a protective film made of alumina fine particles or the like and an electron-emitting material film can be formed on the inner surface of the light-transmitting airtight container. When forming the protective film, a protective film may be formed between the phosphor layer and the inner surface of the translucent airtight container, or the protective film may be formed on the inner surface of the phosphor layer on the discharge space side. Is also good. In addition, an electron emitting material film can be formed, and in this case, it is effective to avoid or reduce the occurrence of dark characteristics of the discharge lamp.
[0037]
<Regarding Lighting Circuit> The lighting circuit is means for lighting a discharge lamp by outputting a pulsating voltage applied between an internal electrode and an external electrode of the discharge lamp. Since the discharge lamp in the present invention performs dielectric barrier discharge by interposing the wall surface of the translucent airtight container as a dielectric, the discharge circuit has a configuration in which an equivalent circuit of the discharge circuit has a capacitor connected in series to the discharge path. There is no need for a current limiting reactance means such as an inductor for stabilizing the current. However, if desired, an impedance such as a capacitor can be connected in series with the discharge lamp for purposes such as limiting the lamp current to a desired value.
[0038]
Further, assuming that the sealed partial pressure of xenon in the discharge lamp is P (kPa), the lighting circuit determines the total discharge charge amount Q (nC) generated within one cycle of the lamp current according to the value of the sealed partial pressure P. And the total rest period T _S The discharge lamp is turned on so that (μs) satisfies Equation 1.
[0039]
(Equation 1)
T _S ・ P / Q ≧ 0.5
In Equation 1, the total discharge charge amount Q (nC) is obtained by integrating the absolute value | i (t) | of the instantaneous value i (t) of the lamp current in one cycle (0 ≦ t ≦ T) of the lamp current. Solution 2 One cycle of the lamp current is composed of positive and negative discharge periods. The positive discharge period is a period in which the lamp current mainly flows from the internal electrode to the external electrode. The negative discharge period is a period in which the lamp current mainly flows from the external electrode to the internal electrode. Therefore, the total discharge charge amount Q (nC) is a value obtained by integrating these lamp currents.
[0040]
(Equation 2)

In addition, the total suspension period T _S (Μs) is the sum of the idle periods that occur during one cycle of the lamp voltage. The pause period is formed following the positive and negative discharge periods. Therefore, at least two idle periods are formed during one cycle of the lamp voltage. The total pause period is the sum of those pause periods.
[0041]
The pulsating voltage output from the lighting circuit and applied between the inner and outer electrodes of the discharge lamp may be either bipolar or unipolar. Further, any of an AC voltage and an intermittent pulse voltage having an appropriate pause period may be used. In the case of the AC voltage, either a mode in which there is no pause between adjacent half-waves or a mode in which there is a pause suitable for each pulse voltage train for PWM control may be used. In the case of a pulse voltage, either a unipolar pulse or a bipolar pulse may be used. Further, the voltage waveform allows various waveforms such as a rectangular wave (square), a triangular wave, a sawtooth wave, a staircase wave, an integrated wave, a differential wave, an impulse wave, and a sine wave, regardless of whether the voltage is an alternating current or a pulse. However, as shown in FIG. 4, a rectangular wave AC voltage and a positive or negative pulse voltage are preferred.
[0042]
FIG. 4 is a waveform diagram showing a rectangular AC voltage waveform and a pulse voltage waveform suitable for implementing the present invention. 4A shows a rectangular AC voltage waveform, FIG. 4B shows a positive rectangular pulse voltage waveform, and FIG. 4C shows a negative rectangular pulse voltage waveform.
[0043]
When an AC voltage is output from the lighting circuit to cause a dielectric barrier discharge in the discharge lamp, a main current having the same polarity as the lamp voltage flows in a pulsed manner at the time of the rising half of the lamp voltage. Further, depending on circuit conditions, a small overshoot current having a reverse polarity following this flows following the main current. Then, after the lamp current flows, a pause period occurs even if the application of the AC voltage is continued. Next, when the polarity of the applied voltage is reversed, a main current having the same polarity as the lamp voltage flows in a pulse shape again when the half-wave rises again. Further, depending on circuit conditions, a small overshoot current having a reverse polarity following this flows following the main current. Then, similarly, after the lamp current flows, an idle period occurs. In this way, the pulsed lamp current alternately flows with positive and negative polarities, and a pause period also occurs intermittently between the lamp currents. That is, an alternating lamp current having a pause period flows. Therefore, a value obtained by time-integrating the absolute value of a pair of adjacent lamp currents having positive and negative polarities over one cycle is the total discharge charge amount Q generated within one cycle. In addition, the total suspension period T _S (Μs) is the sum of all idle periods that occur during one cycle of the positive and negative lamp voltages.
[0044]
On the other hand, when a unipolar pulse voltage is output from the lighting circuit to cause a dielectric barrier discharge in the discharge lamp, the main current having the same polarity as the lamp voltage is pulsed when the pulse lamp voltage rises. Flows. Further, depending on circuit conditions, a small overshoot current having a reverse polarity following this flows following the main current. After the lamp current flows, a pause period occurs even if the pulse voltage is continuously applied. Next, when the lamp voltage falls, a main current having a polarity opposite to that of the lamp voltage flows in a pulse shape. Further, depending on circuit conditions, a small overshoot current having a reverse polarity following this flows following the main current. When the application of the pulse voltage ends, there is a pause period until the next pulse voltage is applied. In this way, a pulsed lamp current alternately flows in positive and negative polarities, and a pause period occurs intermittently. That is, also when lighting is performed by applying a pulse voltage, the lamp current becomes an alternating current with a rest period. Therefore, the total discharge charge amount Q (nC) is a value obtained by integrating the positive and negative bipolar lamp currents flowing in one period from the application of one pulse voltage to the application of the next pulse voltage as described above. It becomes. In addition, the total suspension period T _S (Μs) is the sum of all the idle periods that occur during one cycle consisting of a unipolar pulse voltage and a subsequent idle period.
[0045]
By the way, in the present invention, the lighting condition of the discharge lamp is defined by Expression 1 as described above. Equation 1 can be obtained by the following experiment. That is, in the discharge lamp DL having the configuration shown in FIG. 1 to FIG. 3, the discharge lamp has three types in which the xenon gas filling partial pressure of the discharge medium is set to 5.5, 9.3, and 13.0 kPa, and includes the phosphor layer. In order to observe the state of the discharge lamp and the positive column of the discharge lamp, a discharge lamp without a phosphor layer was manufactured, and the total discharge charge amount Q (nC) generated in one cycle of the lamp current and the lamp were manufactured. The thickness of the positive column, the length of the diffused positive column, and the luminous efficiency when the total rest period Ts (μs) in one cycle of the voltage was changed were investigated.
[0046]
Observation of the positive column of the discharge lamp can be performed by using a high-speed CCD camera (for example, an image intensifier unit capable of opening and closing a shutter at an arbitrary timing. A CCD camera equipped with a high-speed electronic shutter and having a minimum shutter speed of 3 ns is commercially available. ), The timing of opening and closing the shutter is synchronized with the waveform of the voltage applied to the discharge lamp, and a positive column generated during a discharge period in which a lamp current flows from the internal electrode 4 toward the external electrode 5, that is, a positive discharge period, The positive column generated during the discharge period in which the lamp current flows from the external electrode 5 toward the internal electrode 4, that is, during the negative discharge period, was photographed, as shown in the photograph in FIG.
[0047]
FIG. 5 is a photograph showing the state of the positive column that occurs in the discharge space of the discharge lamp during the positive discharge period and the negative discharge period when not according to the present invention.
[0048]
When the external electrode has a coil shape during the positive discharge period, as shown in FIG. 5A, the positive column is in a state of contracting over the entire discharge length formed inside the translucent airtight container. . In the region near the internal electrode located on the left side of the figure, the electrode is formed substantially linearly along the tube axis and at the center of the translucent airtight container regardless of the structure of the external electrode. And, in the other area separated from the internal electrode located on the right side of the figure, a spiral is formed along the inner wall surface of the translucent airtight container facing the external electrode.
[0049]
On the other hand, as shown in FIG. 5B, the positive column in the negative discharge period becomes a contracted positive column in a region near the internal electrode located on the left side of the drawing. However, in the other area separated from the internal electrode located on the right side of the drawing, a positive column that spreads in a diffuse manner is formed that spreads over the entire inside of the light-transmitting airtight container. Here, the region where the contracted positive column is formed is the same as the region where the contracted positive column is formed at the center of the translucent airtight container along the tube axis during the positive discharge period. In addition, since the contracted positive column moves irregularly in the radial direction of the tube, the light emission flickers.
[0050]
The present invention is characterized by clarifying the lighting conditions such that a region where the positive column diffuses and spreads during the negative discharge period is formed over most of the total discharge length. In order to specify, the spread ratio of the positive column is defined as follows. That is, as shown in FIG. 6, when the discharge space 1d formed inside the translucent airtight container 1 has a circular shape, the diffused positive column has a substantially circular shape. Pillar diameter r _P Diameter r of the discharge space 1d _G Ratio r _P / R _G Can be obtained by
[0051]
FIG. 6 is a conceptual cross-sectional view of a discharge lamp for explaining the definition of the spreading ratio of the positive column. In FIG. 6 and FIG. 7, which will be described later, the same parts as those in FIG. P indicates a positive column.
[0052]
When the discharge space 1d formed inside the translucent airtight container 1 is non-circular as shown in FIG. 7, the expansion of the positive column is defined as follows.
[0053]
FIG. 7 is a conceptual cross-sectional view for explaining a spreading ratio of a positive column in a discharge lamp having a non-circular cross-sectional shape.
[0054]
That is, when the translucent airtight container 1 is observed from an arbitrary radial direction in a plane orthogonal to the tube axis, the inner diameter of the translucent airtight container 1 is r. _G (Θ), the diameter of the positive column is r _P (Θ), the spreading ratio of the positive column viewed from the direction is k (θ) = r _P (Θ) / r _G (Θ). Next, the spreading factor k (θ) of each positive column when θ is changed from 0 ° to 360 ° is obtained. The maximum value k (θ) among them _MAX Is defined as the spread ratio of the positive column when the discharge space 1d is non-circular. In the example shown in FIG. 7, since the minimum spread rate is k (0 °) = 0.5 and the maximum spread rate is k (270 °) = 0.9, the spread rate of the positive column is (θ). _MAX = 0.9.
[0055]
Next, the length of the diffused positive column refers to the ratio of the length of the region where the positive column spread rate is 0.5 or more to the total discharge length.
[0056]
By the way, as a result of examining the relationship between the spread ratio of the positive column and the luminance of the phosphor, the result shown in FIG. 8 was obtained.
[0057]
FIG. 8 is a graph showing the relationship between the spread ratio of the positive column of the discharge lamp and the luminance of the phosphor. In the figure, the horizontal axis indicates the positive column expansion rate k, and the vertical axis indicates the phosphor luminance (relative value).
[0058]
As can be understood from FIG. 8, when the spread k of the positive column is 0.5 or more, the phosphor luminance is significantly increased. It should be noted that, for the sake of convenience, the area where the spread ratio of the positive column is k = 0.5 or more, that is, the right side from the center of the figure is a diffusion positive column, and the area less than 0.5, that is, the left side from the center of the figure is a contracted positive column. it can.
[0059]
Therefore, it can be seen that the longer the diffused positive column area in which the positive column spread rate is 0.5 or more, the higher the luminous efficiency of the discharge lamp.
[0060]
Then, as a result of obtaining limit data of lighting conditions in which the area of the diffused positive column where the spread ratio k of the positive column is 0.5 or more becomes 80% or more of the total discharge length for the three types of discharge lamps, FIG. 9 is obtained.
[0061]
FIG. 9 is an empirical formula showing Equation 1 in the discharge lamp lighting device and the discharge lamp lighting method of the present invention. In the figure, the horizontal axis represents Q / P (nC / kPa), and the vertical axis represents T / P. _S (Μs) are shown. Note that Q is the total discharge charge (nC) generated in one cycle of the lamp current, P is the partial pressure of the sealed xenon (kPa), and Ts is the total rest period (μs) generated in one cycle of the lamp current. In the figure, ○ indicates limit data in a discharge lamp in which the partial pressure of xenon is 5.5 kPa, ● indicates 9.3 kPa, and Δ indicates 13.0 kPa. A region located above a straight line obtained by connecting these data satisfies the above-mentioned lighting condition. That is, this region is a region that satisfies Equation 1.
[0062]
Next, in order to light the discharge lamp so as to satisfy Equation 1, for example, mainly the lamp current supplied from the lighting circuit, the frequency of the output voltage of the lighting circuit, and the like according to the sealed partial pressure P (kPa) of xenon. Adjust it appropriately. The partial pressure of xenon is not particularly limited, but is preferably 100 Pa to 3 MPa. The frequency of the output voltage of the lighting circuit is not particularly limited, but is preferably in the range of 20 to 200 kHz.
[0063]
<Operation of the present invention> A period in which the external electrode is grounded, a pulsating voltage is applied from the lighting circuit between the internal electrode and the external electrode of the discharge lamp, and the potential of the internal electrode increases (in the case of AC voltage, The potential of the internal electrode is higher than that of the external electrode.) In other words, during the positive discharge period, an electric field is generated in the discharge space via the light-transmitting hermetic container, and this electric field increases to more than the discharge breakdown electric field of the discharge space. Then, discharge occurs in the discharge space. As a result, a discharge current, that is, a lamp current flows from the internal electrode to the external electrode. However, since a dielectric consisting of the wall of the translucent airtight container is interposed in series with the discharge path, when electric charges are charged on the dielectric surface, the electric field in the discharge space is canceled out to zero and the discharge ends. Then, the lamp current becomes zero.
[0064]
The discharge that occurs during the positive discharge period causes the positive column to contract over the entire area. The positive column is formed by sticking to the inner wall surface of the translucent airtight container facing the external electrode. Therefore, when the external electrode is, for example, linear, the positive column becomes thin. When the external electrode is planar, the positive column has a thin planar shape.
[0065]
Next, in a period during which the potential of the internal electrode decreases (in the case of an AC voltage, the potential of the external electrode becomes higher than that of the internal and external electrodes), that is, during a negative discharge period, the discharge space has a direction opposite to the above. When an electric field is generated and the electric field increases to a discharge breakdown electric field in the discharge space, a discharge occurs in the discharge space. As a result, a discharge current, that is, a lamp current flows from the outer electrode to the inner and outer electrodes. However, since the dielectric is interposed in the discharge path in series, when electric charge is charged on the dielectric surface, the electric field in the discharge space is canceled to zero, the discharge ends, and the lamp current becomes zero.
[0066]
The discharge generated during the negative discharge period has a positive column in a diffused shape with a spread rate of 0.5 or more, and is formed over a region of 80% or more of the entire discharge length. As a result, the luminous efficiency of the discharge lamp is improved.
[0067]
Since the above operation is repeated and the discharge is continued, the current waveform oscillates positively and negatively across the idle period and becomes AC, regardless of whether the applied voltage is AC or unipolar pulse voltage.
[0068]
In the present invention, by having the above-described configuration, as described above, during the negative discharge period, the region of the positive column that is sufficiently thick and diffused over most of the tube axis direction is formed. Occurs, resulting in improved luminous efficiency.
[0069]
A discharge lamp lighting device according to a second aspect of the present invention is the discharge lamp lighting device according to the first aspect, wherein a positive column generated inside the translucent airtight container during a discharge period in which a lamp current mainly flows from the external electrode to the internal electrode is provided. A region having a spread rate of 0.5 or more in a plane orthogonal to the tube axis of the translucent airtight container is formed over 80% or more of the entire discharge length.
[0070]
The present invention specifies the thickness of the diffused positive column and the length of the region in the tube axis direction, which can provide high luminous efficiency.
[0071]
Thus, according to the present invention, the luminous efficiency of the discharge lamp is high, and a region where the luminance of the phosphor layer is high can be obtained over most of the entire discharge length.
[0072]
According to a third aspect of the present invention, there is provided the discharge lamp lighting device according to the first or second aspect, wherein a peak of the infrared radiation intensity having a wavelength of 828 nm is emitted during a discharge period in which a lamp current mainly flows from the external electrode to the internal electrode. In the discharge period in which the lamp current mainly flows from the inner and outer electrodes to the outer and inner electrodes, a region where the peak value is 1.2 times or more the same peak value in the discharge period generated inside the light-tight hermetic container is 80% of the total discharge length. % Or more.
[0073]
The present invention specifies a configuration in which the emission efficiency is improved by setting the peak value of the infrared radiation intensity at a wavelength of 828 nm to a predetermined value.
[0074]
That is, infrared light having a wavelength of 828 nm is xenon excitation light. Therefore, a large peak value of the infrared radiation intensity at a wavelength of 828 nm emitted from the discharge lamp means that the luminous efficiency of the discharge lamp is high. For this reason, by setting the lighting conditions so that the amount of infrared light having a wavelength of 828 nm increases, the luminous efficiency of the discharge lamp can be increased.
[0075]
Further, by detecting infrared rays having a wavelength of 828 nm emitted by the discharge, the luminous efficiency can be indirectly estimated even if the inside of the discharge lamp cannot be seen through due to the presence of the phosphor layer of the discharge lamp. . In the present invention, the reason why the peak value of the infrared radiation intensity at the wavelength of 828 nm in the negative discharge period is specified to be 1.2 times or more the same peak value in the positive discharge period is as follows. That is, when the ratio is less than 1.2 times, the diffusion of the positive column is not sufficient, so that the luminous efficiency is not improved to a desired degree.
[0076]
According to a fourth aspect of the present invention, there is provided a method for lighting a discharge lamp, comprising: an elongated light-transmitting airtight container; a phosphor layer provided on an inner surface side of the light-transmitting airtight container; An electrode, a discharge medium mainly composed of xenon sealed in the light-transmitting airtight container, and an external material made of a conductive substance disposed along the longitudinal direction of the light-transmitting airtight container and almost in contact with the outer peripheral surface thereof A pulsating voltage is applied between an internal electrode and an external electrode of a discharge lamp provided with electrodes, and the total discharge charge amount Q (generated in one cycle of the lamp current in accordance with the xenon partial pressure P (kPa) of the discharge lamp. nC) and the total rest period T _S (Μs) is lit so as to satisfy Expression 1.
[0077]
(Equation 1)
T _S ・ P / Q ≧ 0.5
The present invention is different from the first embodiment in that the present invention defines the same contents as the lighting method, while claim 1 defines the invention of the discharge lamp lighting device.
[0078]
According to a fifth aspect of the present invention, there is provided a lighting device, comprising: a lighting device main body; and the discharge lamp lighting device according to any one of the first to third aspects disposed on the lighting device main body. .
[0079]
In the present invention, the "illumination device" is a broad concept including all devices utilizing the light emission of a discharge lamp, for example, a backlight device and a liquid crystal display device having the same, and a device incorporating the liquid crystal display device, An instrument panel illuminating device for a mobile body such as an automobile, a decorative illuminating device, a reading device and an image scanner, a copier and a facsimile provided with the reading device. Examples of devices incorporating a liquid crystal display device include electronic devices such as personal computers, navigation devices, portable information terminals, and liquid crystal television receivers.
[0080]
The “illumination device main body” refers to the remaining portion of the illumination device excluding the discharge lamp lighting device.
[0081]
Embodiments of the present invention will be described below with reference to the drawings.
[0082]
10 and 11 show a first embodiment of a discharge lamp lighting device and a discharge lamp lighting method according to the present invention. FIG. 10 is a waveform diagram showing a lamp voltage and a lamp current. FIG. 3 is a photograph showing a state of a positive column generated during a positive discharge period and a negative discharge period. This embodiment includes a discharge lamp and a lighting circuit.
[0083]
The discharge lamp has the same configuration as shown and described in FIGS. Therefore, the description of the configuration is omitted here.
[0084]
The lighting circuit outputs an AC square wave voltage, applies this voltage between the internal electrode 4 and the external electrode 5 of the discharge lamp DL, and supplies a lamp current. As a circuit for outputting a rectangular wave AC voltage, for example, a chopper circuit and a full-bridge inverter circuit for converting the DC output voltage into a rectangular wave AC voltage can be mainly configured.
[0085]
The lamp voltage of the discharge lamp DL is one cycle in the periods I to IV. Periods I and II are positive half-waves in which the potential of the internal electrode 4 is higher than the external electrode 5, and periods III and IV are negative half-waves in which the potential of the external electrode 5 is higher than the internal electrode 4. Then, the period I is the rising of the + voltage, at which time there is a peak value, the period II is almost flat, and the voltage falls at the end thereof. Further, the period III is the rising of the negative voltage, at which time there is a peak value, the period IV is almost flat, and the voltage falls at the end thereof. In the above description, the peak value is 1500 V, the instantaneous value at the time of falling is 800 V, and the period is 50 μs, that is, the frequency is 20 kHz.
[0086]
In the lamp current, the period I is a positive discharge period, and the period III is a negative discharge period. In the period I, a positive lamp current mainly flows from the internal electrode 4 to the external electrode 5. The peak value at this time is +38 mA. In the period III, a negative lamp current mainly flows from the external electrode 5 to the internal electrode 4. The peak value at this time is -20 mA.
[0087]
Then, as shown in FIG. 11, a positive column is generated in the discharge space 1a of the discharge lamp DL by the discharge. The positive column generated during the positive discharge period is contracted over the entire region as shown in FIG. On the other hand, the positive column generated during the negative discharge period is diffused over almost the entire region as shown in FIG. That is, the spreading ratio k of the positive column is 0.5 or more, and the length L of the diffused positive column is _P Is the total discharge length L _T Over 80% of the total.
[0088]
FIG. 12 is a waveform diagram showing a lamp voltage, a lamp current, and a radiation intensity in the second embodiment of the discharge lamp lighting device and the discharge lamp lighting method of the present invention. In this embodiment, the frequency of the output voltage of the lighting circuit and the lamp current are different.
[0089]
That is, one cycle of the lamp voltage is 25 μs, that is, the frequency is 40 kHz, and the lamp current has a peak value of +21 mA during the positive discharge period and −23 mA during the negative discharge period.
[0090]
The radiation intensity is a value obtained by measuring 828 nm of xenon excitation light. The peak value R of the radiation intensity generated during the negative discharge period _N Is a diffused, peak value R of the radiation intensity generated during the positive discharge period. _P It can be easily understood that the value is 1.2 times or more.
[0091]
Next, another example of a discharge lamp used when implementing the discharge lamp lighting device and the discharge lamp lighting method of the present invention will be described with reference to FIGS. In the drawings, the same portions as those in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted.
[0092]
FIG. 13 is a partial cross-sectional front view and a cross-sectional view conceptually showing another example of a discharge lamp having a different external electrode structure.
[0093]
In the example shown in FIG. 13A, the external electrodes 5 are made of strip-shaped aluminum foil, and are disposed in close contact with the upper half of the translucent airtight container 1.
[0094]
In the example shown in FIG. 13B, the external electrode 5 is made of a strip-shaped transparent conductive film (ITO film) and is disposed in close contact with the upper half of the translucent airtight container 1.
[0095]
In the example shown in FIG. 13C, the external electrodes 5 are made of a metal mesh structure, and are arranged closely over the entire periphery of the translucent airtight container 1.
[0096]
FIG. 14 is a longitudinal sectional view showing another example of a discharge lamp having a different configuration of the internal electrodes. This discharge lamp DL is different in that it has a pair of internal electrodes 4A, 4B sealed at both ends inside the translucent airtight container 1.
[0097]
FIG. 15 is a cross-sectional view showing a backlight device for a liquid crystal as one embodiment of the illumination device of the present invention. In the figure, the same parts as those in FIG. 2 are denoted by the same reference numerals. The liquid crystal backlight device 10 includes a backlight device main body 11 and a discharge lamp lighting device 12. Reference numeral 13 in the drawing is a liquid crystal display unit.
[0098]
The backlight device main body 11 includes a light guide 11a, a gutter-shaped reflection plate 11b, a back reflection sheet 11c, a diffusion sheet 11d1, and a light collection sheet 11d2, and is housed in a case (not shown).
[0099]
The light guide 11a is made of a transparent material having a high refractive index, such as a transparent acrylic resin or a polycarbonate resin. The gutter-shaped reflection plate 11b reflects light emitted from the discharge lamp 12 in a direction not directly incident on the light guide 11a and causes the light to enter the light guide 11a, and emits light from the discharge lamp 12 other than the light guide 11a. Shield so that light does not leak to the location. The back reflection sheet 11c reflects light emitted from the back of the light guide 11a and emits the light from the front of the light guide 11a. At this time, the reflectance of the back reflection sheet 11c can be partially controlled so that light is emitted from the entire surface as uniformly as possible. The diffusion sheet 11d1 is provided on the front surface of the light guide 11a, and diffuses light emitted forward from the light guide 11a to make the luminance distribution as uniform as possible. The condensing sheet 11d2 condenses the light emitted from the diffusion sheet 11d1, and increases the incident efficiency on the liquid crystal display unit 13.
[0100]
The discharge lamp lighting device 12 includes a discharge lamp DL and a lighting circuit (not shown). The discharge lamp DL is shown in FIGS.
The liquid crystal display unit 13 is disposed so as to overlap the front surface of the backlight device, and is illuminated from the back surface by the backlight device main body to perform a transmissive liquid crystal display.
[0101]
According to the first aspect of the present invention, a short internal electrode which is provided with a phosphor layer on the inner surface side and is sealed in an elongated light-transmitting airtight container in which a discharge medium mainly composed of xenon is sealed. And a discharge lamp having an external electrode made of a conductive substance disposed along the longitudinal direction of the light-transmitting airtight container and substantially in contact with the outer peripheral surface, and an internal electrode of the discharge lamp which outputs a pulsating voltage and outputs a pulsating voltage. And between the external electrodes and the total discharge charge Q (nC) and the total rest period T generated within one cycle of the lamp current in accordance with the xenon partial pressure P (kPa) of the discharge lamp. _S By providing a lighting circuit for lighting the discharge lamp so that (μs) satisfies Equation 1, it is possible to provide a discharge lamp lighting device with improved luminous efficiency of the discharge lamp.
[0102]
(Equation 1)
T _S ・ P / Q ≧ 0.5
According to the second aspect of the present invention, the positive column generated inside the light-transmitting hermetic container during the discharge period in which the lamp current mainly flows from the external electrode to the internal electrode has a surface orthogonal to the tube axis of the light-transmitting hermetic container. By forming a region having a spreading ratio of 0.5 or more within 80% or more of the entire discharge length, the luminous efficiency of the discharge lamp is high, and a region with a high luminance of the phosphor layer covers most of the total discharge length. The obtained discharge lamp lighting device can be provided.
[0103]
According to the third aspect of the present invention, in addition, the peak value of the infrared radiation intensity at a wavelength of 828 nm emitted during the discharge period in which the lamp current mainly flows from the external electrode to the internal electrode indicates that the lamp current mainly flows from the internal electrode to the external electrode. Since the length of the region in the tube axis direction where the same peak value is 1.2 times or more of the same peak value in the discharge period generated in the light-transmitting hermetic container in the discharge period is 80% or more of the entire discharge length, the discharge lamp Can provide a discharge lamp lighting device capable of indirectly estimating the luminous efficiency even if the inside of the discharge lamp cannot be seen through.
[0104]
According to the fourth aspect of the present invention, the phosphor layer is provided on the inner surface side, and the short internal electrode and the light-transmitting airtight sealed in an elongated light-transmitting airtight container enclosing a discharge medium mainly composed of xenon. A pulsating voltage is applied between an inner electrode and an outer electrode of a discharge lamp provided with an outer electrode made of a conductive substance disposed along the longitudinal direction of the container and substantially in contact with the outer peripheral surface thereof, and The total discharge charge amount Q (nC) generated in one cycle of the lamp current according to the xenon partial pressure P (kPa) and the total rest period T _S By lighting the discharge lamp so that (μs) satisfies Expression 1, it is possible to provide a discharge lamp lighting method with improved luminous efficiency.
[0105]
(Equation 1)
T _S ・ P / Q ≧ 0.5
According to the fifth aspect of the present invention, by providing the lighting device body and the discharge lamp lighting device according to the first to third aspects, it is possible to provide a lighting apparatus having the effects of the first to third aspects.
[Brief description of the drawings]
FIG. 1 is a front view showing an example of a discharge lamp for rare gas discharge.
FIG. 2 is a vertical sectional view and a circuit diagram showing a lighting circuit.
FIG. 3 is a cross-sectional view of the same discharge vessel.
FIG. 4 is a waveform chart showing a square wave AC voltage waveform and a pulse voltage waveform suitable for implementing the present invention.
FIG. 5 is a photograph showing the state of a positive column generated during a positive discharge period and a negative discharge period in a discharge space of a discharge lamp when not according to the present invention.
FIG. 6 is a conceptual cross-sectional view of a discharge lamp for explaining the definition of the spreading ratio of a positive column.
FIG. 7 is a conceptual cross-sectional view for explaining a spread ratio of a positive column in a discharge lamp having a non-circular cross-sectional shape.
FIG. 8 is a graph showing the relationship between the spread ratio of the positive column of the discharge lamp and the luminance of the phosphor.
FIG. 9 is an empirical formula showing Equation 1 in the discharge lamp lighting device and the discharge lamp lighting method of the present invention.
FIG. 10 is a waveform chart showing lamp voltage and lamp current in the first embodiment of the discharge lamp lighting device and the discharge lamp lighting method of the present invention.
FIG. 11 is a photograph showing a state of a positive column generated during a positive discharge period and a negative discharge period in a discharge space of a discharge lamp.
FIG. 12 is a waveform chart showing a lamp voltage, a lamp current, and a radiation intensity in the second embodiment of the discharge lamp lighting device and the discharge lamp lighting method of the present invention.
FIG. 13 is a partial cross-sectional front view and a cross-sectional view conceptually showing another example of a discharge lamp having a different external electrode structure.
FIG. 14 is a longitudinal sectional view showing another example of a discharge lamp having a different internal electrode configuration.
FIG. 15 is a cross-sectional view showing a backlight device for a liquid crystal as one embodiment of the lighting device of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Translucent airtight container, 2 ... Phosphor layer, 4 ... Internal electrode, 5 ... External electrode, 8 ... Lighting circuit, DL ... Discharge lamp

Claims (5)

An elongated translucent airtight container, a phosphor layer disposed on the inner surface side of the translucent airtight container, short internal electrodes sealed in the translucent airtight container, enclosed in the translucent airtight container A discharge lamp including a discharge medium mainly composed of xenon, and an external electrode made of a conductive substance disposed along the longitudinal direction of the light-transmitting airtight container and substantially in contact with the outer peripheral surface;
A pulsating voltage is output and applied between the internal and external electrodes of the discharge lamp, and the total discharge charge amount Q (nC) generated within one cycle of the lamp current in accordance with the xenon enclosed partial pressure P (kPa) of the discharge lamp. ) And a lighting circuit for lighting the discharge lamp such that the total rest period T _S (μs) satisfies Equation 1;
A discharge lamp lighting device, comprising:

The positive column generated inside the translucent airtight container during the discharge period in which the lamp current mainly flows from the outer electrode to the inner electrode has an area with a spreading ratio of 0.5 or more in a plane orthogonal to the tube axis of the translucent airtight container. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is formed over 80% or more of a total discharge length. The peak value of the infrared radiation intensity at a wavelength of 828 nm radiated during the discharge period in which the lamp current mainly flows from the external electrode to the internal electrode indicates that the peak value of the infrared radiation intensity is within the translucent airtight container during the discharge period in which the lamp current mainly flows from the internal electrode to the external electrode. 3. The discharge lamp lighting device according to claim 1, wherein a length of a region in the tube axis direction in which a similar peak value is 1.2 times or more in a generated discharge period is 80% or more of a total discharge length. . An elongated translucent airtight container, a phosphor layer disposed on the inner surface side of the translucent airtight container, short internal electrodes sealed in the translucent airtight container, enclosed in the translucent airtight container An internal electrode and an external electrode of a discharge lamp having an external electrode made of a conductive substance disposed along the longitudinal direction of a discharge medium mainly composed of xenon and a translucent airtight container and substantially in contact with the outer peripheral surface. by applying a pulsating voltage between the total discharge charge quantity Q (nC) and all sleep periods T _S occurring within one period of the lamp current in accordance with the enclosed partial pressure P (kPa) of xenon discharge lamp _(.mu.s) is A method for lighting a discharge lamp, wherein the lighting is performed so as to satisfy Expression 1.

A lighting device body;
A discharge lamp lighting device according to any one of claims 1 to 3, which is provided in a lighting device body;
A lighting device, comprising:

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