JP4656816B2 - Light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device in which the occurrence of chromaticity deviation caused by a change in ambient temperature is suppressed. <P>SOLUTION: In the light-emitting device including a light-emitting element, and a phosphor which absorbs at least a part of light emitted from the light-emitting element and emits light having a different wavelength, the phosphor includes a first phosphor which emits light in a green region from an yellow region, and a second phosphor which emits light in a red region, and light-emitting output reduction rates of the first phosphor and the second phosphor with respect to temperature elevation are approximately equal. <P>COPYRIGHT: (C)2004,JPO&amp;NCIPI

Description

ただし、各原料の配合比率を変更することにより、目的とする蛍光体の組成を変更することができる。
【００６０】
焼成温度は、１２００から１７００℃の範囲で焼成を行うことができるが、１４００から１７００℃の焼成温度が好ましい。焼成は、徐々に昇温を行い１２００から１５００℃で数時間焼成を行う一段階焼成を使用することが好ましいが、８００から１０００℃で一段階目の焼成を行い、徐々に加熱して１２００から１５００℃で二段階目の焼成を行う二段階焼成（多段階焼成）を使用することもできる。蛍光体の原料は、窒化ホウ素（ＢＮ）材質の坩堝、ボートを用いて焼成を行うことが好ましい。窒化ホウ素材質の坩堝の他に、アルミナ（Ａｌ_２Ｏ_３）材質の坩堝を使用することもできる。
【００６１】
以上の製造方法を使用することにより、目的とする蛍光体を得ることが可能である。
【００６２】
本発明の実施例において、赤味を帯びた光を発光する蛍光体として、特に窒化物系蛍光体を使用するが、本発明においては、上述したＹＡＧ系蛍光体と赤色系の光を発光可能な蛍光体とを備える発光装置とすることも可能である。このような赤色系の光を発光可能な蛍光体は、波長が４００〜６００ｎｍの光によって励起されて発光する蛍光体であり、例えば、Ｙ_２Ｏ_２Ｓ：Ｅｕ、Ｌａ_２Ｏ_２Ｓ：Ｅｕ、ＣａＳ：Ｅｕ、ＳｒＳ：Ｅｕ、ＺｎＳ：Ｍｎ、ＺｎＣｄＳ：Ａｇ，Ａｌ、ＺｎＣｄＳ：Ｃｕ，Ａｌ等が挙げられる。このようにＹＡＧ系蛍光体とともに赤色系の光を発光可能な蛍光体を使用することにより発光装置の演色性を向上させることが可能である。
【００６３】
（第１の蛍光体及び第２の蛍光体）
本実施の形態において、窒化物系蛍光体は、ＬＥＤチップ１０２によって発光された青色光の一部を吸収して黄から赤色領域の光を発光する。窒化物系蛍光体をＹＡＧ系蛍光体と共に上記の構成を有する発光装置に使用して、ＬＥＤチップ１０２により発光された青色光と、窒化物系蛍光体による黄色から赤色光とが混色により暖色系の白色に発光する発光装置を提供する。窒化物系蛍光体の他に加える蛍光体には、セリウムで付活されたイットリウム・アルミニウム酸化物蛍光物質が含有されていることが好ましい。前記イットリウム・アルミニウム酸化物蛍光物質を含有することにより、所望の色度に調節することができるからである。セリウムで付活されたイットリウム・アルミニウム酸化物蛍光物質は、ＬＥＤチップ１０２により発光された青色光の一部を吸収して黄色領域の光を発光する。ここで、ＬＥＤチップ１０２により発光された青色光と、イットリウム・アルミニウム酸化物蛍光物質の黄色光とが混色により青白い白色に発光する。従って、このイットリウム・アルミニウム酸化物蛍光物質と赤色発光する蛍光体とを、透光性を有するコーティング部材１０１中に一緒に混合し、ＬＥＤチップ１０２により発光された青色光とを組み合わせることにより白色系の混色光を発光する発光装置を提供することができる。特に好ましいのは、色度が色度図における黒体放射の軌跡上に位置する白色の発光装置である。但し、所望の色温度の発光装置を提供するため、イットリウム・アルミニウム酸化物蛍光物質の蛍光体量と、赤色発光の蛍光体量を適宜変更することもできる。この白色系の混色光を発光する発光装置は、特殊演色評価数Ｒ９の改善を図っている。
【００６４】
従来、半導体素子を用いた白色系の発光装置は、発光素子からの青色光と蛍光体からの緑から赤色光のバランスを人間の視感度に合わせて調整し、これら光の混色により得ている。通常、半導体発光素子を用いた発光装置の白色系の色調は発光装置の出力特性が安定する定格駆動領域で発光のバランスを調整し得られる。しかし、これら発光装置は液晶バックライト、調光可能な照明光源の場合、投入電力、電流密度を変化させて用いる。従来技術では発光装置の出力調整のため電流密度を変化させると、発光のバランスが崩れ色調ズレが生じ、光源の品質を低下させていた。以下に本発明の実施の形態を詳細に説明する。
【００６５】
まず、図２を参照する。
【００６６】
発光素子は、投入電流を増加することにより、発光素子が持つ発光スペクトルのピーク波長は、短波長側に移行する。これは、投入電流を増加すると、電流密度が大きくなり、エネルギー準位が上がる。これによって、バンドギャップが大きくなることなどの要因による。発光素子への電流密度が小さい場合の発光スペクトルのピーク波長と、投入電流を増加させた時の発光スペクトルのピーク波長との変動の振り幅は、例えば、本実施の形態では２０ｍＡから１００ｍＡの投入電流を増加させたとき、約１０ｎｍ程度である。
【００６７】
図３及び図４を用いて説明する。
【００６８】
例えば、第１の蛍光体として、ＹＡＧ系蛍光体を使用する。蛍光体３のＹＡＧ系蛍光体は、励起スペクトルのピーク波長が約４４８ｎｍである。この励起スペクトルのピーク波長４４８ｎｍの発光強度を１００とした場合、４６０ｎｍでの発光強度は９５である。そのため、４６０ｎｍでＹＡＧ系蛍光体を励起させたときよりも、４４８ｎｍでＹＡＧ系蛍光体を励起させたときの方が高い発光強度を有する。このことから、発光素子と第１の蛍光体との関係を概説する。発光素子に電流を投入した直後、発光素子の発光ピーク波長が４６０ｎｍである発光素子を選定する。この発光素子は、青色に発光する。この発光素子の青色光により励起されたＹＡＧ系蛍光体は、約５３０ｎｍの緑色に発光する。次に、発光素子の投入電流を増加させ１００ｍＡの電流を投入する。これにより半導体素子の発光出力が増加しこれに伴い発光素子及び周辺温度が増加する。また、発光素子の発光ピーク波長は、４６０ｎｍから４５０ｎｍの短波長側に移行いる。このときＹＡＧ系蛍光体は、励起スペクトルのピーク波長が４６０ｎｍよりも４５０ｎｍの方が、発光強度が高い。そのため、ＹＡＧ系蛍光体は、励起光が４６０ｎｍよりも４５０ｎｍの方が、相対的に高い発光輝度を示す。また、青色光は、４５０ｎｍの方が、４６０ｎｍよりも視感効率が低い。よって、発光素子の青色光とＹＡＧ系蛍光体の緑色光は輝度が高くなるため、青色光に対する緑色光の相対的な強度が強くなる。従って発光装置の色調は、青色光と緑色光とを結ぶ直線において、緑色光側にわずかに移行する。一方、周囲温度増加により蛍光体は輝度を低下するため、青色光に対する緑色光の相対的な強度が弱くなる。従って発光装置の色調は、青色光と緑色光とを結ぶ直線において、青色光側にわずかに移行する。
これらのバランスにより色調ズレが抑制される。
【００６９】
図５及び図６を用いて説明する。
【００７０】
例えば、第２の蛍光体として、窒化物系蛍光体を使用する。蛍光体５の窒化物系蛍光体は、３５０ｎｍから５００ｎｍの間において、励起スペクトルのピーク波長が約４５０ｎｍである。この励起スペクトルのピーク波長４５０ｎｍの発光強度を１００とした場合、４６０ｎｍでの発光強度は９５である。そのため、４６０ｎｍで窒化物系蛍光体を励起させたときよりも、４５０ｎｍでＹＡＧ系蛍光体を励起させたときの方が高い発光強度を有する。このことから、発光素子と第２の蛍光体との関係を概説する。発光素子への投入電流密度が低い時、発光素子の発光ピーク波長が４６０ｎｍである発光素子を選定する。この発光素子は、第１の蛍光体を励起させるときに使用するものと同じものを使用する。この発光素子は、青色に発光する。この発光素子の青色光により励起された窒化物系蛍光体は、約６３７ｎｍの赤色に発光する。次に、発光素子の投入電流を増加させ１００ｍＡの電流を投入する。これにより、半導体素子の発光出力が増加しこれに伴い発光素子及び周辺温度が増加する。また、発光素子の発光ピーク波長は、４６０ｎｍから４５０ｎｍの短波長側に移行する。このとき窒化物系蛍光体は、励起スペクトルのピーク波長が４６０ｎｍよりも４５０ｎｍの方が、相対的に発光強度が高い。そのため、窒化物系蛍光体は、励起光が４６０ｎｍよりも４５０ｎｍの方が、高い発光輝度を示す。また、青色光は、４５０ｎｍの方が、４６０ｎｍよりも視感効率が低い。よって、発光素子の青色光と窒化物系蛍光体の赤色光は、赤色光の輝度が高くなるため、青色光に対する赤色光の相対的な強度が強くなる。従って発光装置の色調は、青色光と赤色光とを結ぶ直線において、赤色光側にわずかに移行する。一方、周囲温度増加により蛍光体は輝度を低下するため、青色光に対する緑色光の相対的な強度が弱くなる。従って発光装置の色調は、青色光と赤色光とを結ぶ直線において、青色光側にわずかに移行する。これらのバランスにより色調ズレが抑制される。
【００７１】
第１の蛍光体と第２の蛍光体との関係を概説する。窒化物系蛍光体は、発光素子からの光だけでなく、ＹＡＧ系蛍光体の発光スペクトルのピーク波長（約５３０ｎｍ）付近の光も吸収し、励起される。
【００７２】
さらに、前述の発光素子と第１の蛍光体及び第２の蛍光体との相互関係を詳述する。発光素子に電流を投入することにより発熱が生じる。発光素子への投入電流を増加することにより、発熱量も増加する。この発光素子で生じた熱の大部分は、コーティング部材や蛍光体に蓄積される。これにより、周囲温度が上昇し蛍光体自身の発光出力の低下が生じる。これに対して、発光素子への投入電流を増加することにより、前述のように発光素子の発光スペクトルのピーク波長が短波長側に移行して、第１の蛍光体の発光強度が増加する。これらの相互作用により、第１の蛍光体は、色調及び発光出力をほとんど変化することなく維持することができる。また、第２の蛍光体も第１の蛍光体と同様に、色調及び発光出力をほとんど変化することなく維持することができる。
【００７３】
以上の発光素子と第１の蛍光体と第２の蛍光体とのそれぞれの発光の相互作用により、発光装置の色調が決まる。つまり、発光素子は、投入電流の増加に伴い、発光スペクトルのピーク波長が短波長側に移行する。これに伴い、該発光素子により励起される第１の蛍光体及び第２の蛍光体の発光強度は、増加する。一方、発光素子への投入電流の増加に伴い、発光素子が発熱する。この発熱により、第１の蛍光体及び第２の蛍光体やコーティング部材などに熱が蓄積される。この蓄熱により、これらの蛍光体の発光出力が低下する。従って、発光素子への投入電流を増加した場合でも、発光装置の色調ズレを抑制することができる。第１の蛍光体及び第２の蛍光体の選定により、発光装置に色調ズレが生じる場合であっても、視覚的にほとんど色調ズレを感じなくすることができる。発光素子と第１の蛍光体と第２の蛍光体との相互作用を勘案すると、発光装置の色調は、色調ｘが増加する方向、色調ｙも増加する方向に移行する。この色調がずれる方向は、黒体放射の軌跡に沿って変動する。黒体放射の軌跡に沿った色ズレは、黒体放射の軌跡に垂直な方向の色ズレと比べて、人間の視覚において、色ズレを感じる感度が低い。また、第１の蛍光体と第２の蛍光体との相互作用（自己吸収等）によって、色ズレの振り幅が狭い。よって、本発明は、色調ズレを防止した発光装置を提供することができる。本発明は、熱の影響を受けやすい発光装置、例えば、ＤＣ駆動や投入電力が大きいパワー系の半導体発光装置、放熱が困難で、蓄熱しやすい発光装置や、駆動環境下で、特に効果が大きい。
【００７４】
なお、発光素子が投入電力の増加により、の短波長側に移行する範囲で、励起スペクトルがほとんど変化しない蛍光体を用いることもできる。例えば、実施例の蛍光体５の窒化物系蛍光体を使用する場合、４２０ｎｍから４５０ｎｍでほとんど励起スペクトルが変化していないが、本発明の特徴を有するＹＡＧとの組み合わせにより、効果を示す。また、上述のような蛍光体の温度特性の特徴を有し、励起スペクトルと発光素子との特徴を有する、上記以外の他の蛍光体を用いる場合でも、本発明の発光装置を提供することができる。
【００７５】
また、発光装置の熱抵抗値や放熱特性、発光素子のジャンクション温度等を考慮して、励起スペクトルと発光素子のピーク波長の位置を調整することもできる。
【００７６】
尚、明細書における色名と色度座標との関係は、全てＪＩＳ規格に基づく（ＪＩＳ Ｚ８１１０）。
【００７７】
また、粒径は、Ｆ．Ｓ．Ｓ．Ｓ．Ｎｏ．（Fisher Sub Sieve Sizer's No.）という空気透過法による値である。
【００７８】
［ＬＥＤチップ１０２］
本発明において使用される発光素子は、ＬＥＤチップ１０２である。蛍光体と発光素子とを組み合わせ、蛍光体を励起させることによって波長変換した光を出光させる発光装置とする場合、蛍光体を励起可能な波長の光を出光するＬＥＤチップが使用される。ＬＥＤチップ１０２は、ＭＯＣＶＤ法等により基板上にＧａＡｓ、ＩｎＰ、ＧａＡｌＡｓ、ＩｎＧａＡｌＰ、ＩｎＮ、ＡｌＮ、ＧａＮ、ＩｎＧａＮ、ＡｌＧａＮ、ＩｎＧａＡｌＮ等の半導体を発光層として形成させる。半導体の構造としては、ＭＩＳ接合、ＰＩＮ接合やＰＮ接合などを有するホモ構造、ヘテロ構造あるいはダブルへテロ構成のものが挙げられる。半導体層の材料やその混晶度によって発光波長を種々選択することができる。また、半導体活性層を量子効果が生ずる薄膜に形成させた単一量子井戸構造や多重量子井戸構造とすることもできる。好ましくは、蛍光体を効率良く励起できる比較的短波長を効率よく発光可能な窒化物系化合物半導体（一般式Ｉｎ_iＧａ_jＡｌ_kＮ、ただし、０≦ｉ、０≦ｊ、０≦ｋ、ｉ＋ｊ＋ｋ＝１）である。
【００７９】
窒化ガリウム系化合物半導体を使用した場合、半導体基板にはサファイア、スピネル、ＳｉＣ、Ｓｉ、ＺｎＯ、ＧａＮ等の材料が好適に用いられる。結晶性の良い窒化ガリウムを形成させるためにはサファイア基板を用いることがより好ましい。サファイア基板上に半導体膜を成長させる場合、ＧａＮ、ＡｌＮ等のバッファー層を形成しその上にＰＮ接合を有する窒化ガリウム半導体を形成させることが好ましい。また、サファイア基板上にＳｉＯ₂をマスクとして選択成長させたＧａＮ単結晶自体を基板として利用することもできる。この場合、各半導体層の形成後ＳｉＯ₂をエッチング除去させることによって発光素子とサファイア基板とを分離させることもできる。窒化ガリウム系化合物半導体は、不純物をドープしない状態でＮ型導電性を示す。発光効率を向上させるなど所望のＮ型窒化ガリウム半導体を形成させる場合は、Ｎ型ドーパントとしてＳｉ、Ｇｅ、Ｓｅ、Ｔｅ、Ｃ等を適宜導入することが好ましい。一方、Ｐ型窒化ガリウム半導体を形成させる場合は、Ｐ型ドーパンドであるＺｎ、Ｍｇ、Ｂｅ、Ｃａ、Ｓｒ、Ｂａ等をドープさせる。
【００８０】
窒化ガリウム系化合物半導体は、Ｐ型ドーパントをドープしただけではＰ型化しにくいためＰ型ドーパント導入後に、炉による加熱、低速電子線照射やプラズマ照射等によりアニールすることでＰ型化させることが好ましい。具体的な発光素子の層構成としては、窒化ガリウム、窒化アルミニウムなどを低温で形成させたバッファー層を有するサファイア基板や炭化珪素上に、窒化ガリウム半導体であるＮ型コンタクト層、窒化アルミニウム・ガリウム半導体であるＮ型クラッド層、Ｚｎ及びＳｉをドープさせた窒化インジュウムガリウム半導体である活性層、窒化アルミニウム・ガリウム半導体であるＰ型クラッド層、窒化ガリウム半導体であるＰ型コンタクト層が積層されたものが好適に挙げられる。ＬＥＤチップ１０２を形成させるためにはサファイア基板を有するＬＥＤチップ１０２の場合、エッチングなどによりＰ型半導体及びＮ型半導体の露出面を形成させた後、半導体層上にスパッタリング法や真空蒸着法などを用いて所望の形状の各電極を形成させる。ＳｉＣ基板の場合、基板自体の導電性を利用して一対の電極を形成させることもできる。
【００８１】
次に、形成された半導体ウエハー等をダイヤモンド製の刃先を有するブレードが回転するダイシングソーにより直接フルカットするか、又は刃先幅よりも広い幅の溝を切り込んだ後（ハーフカット）、外力によって半導体ウエハーを割る。あるいは、先端のダイヤモンド針が往復直線運動するスクライバーにより半導体ウエハーに極めて細いスクライブライン（経線）を例えば碁盤目状に引いた後、外力によってウエハーを割り半導体ウエハーからチップ状にカットする。このようにして窒化物系化合物半導体であるＬＥＤチップ１０２を形成させることができる。
【００８２】
蛍光体を励起させて発光させる本発明の発光装置においては、蛍光体との補色等を考慮してＬＥＤチップ１０２の主発光波長は３５０ｎｍ以上５３０ｎｍ以下が好ましい。
【００８３】
［導電性ワイヤー１０３］
導電性ワイヤー１０３としては、ＬＥＤチップ１０２の電極とのオーミック性、機械的接続性、電気伝導性及び熱伝導性がよいものが求められる。熱伝導度としては０．０１ｃａｌ／（ｓ）（ｃｍ^２）（℃／ｃｍ）以上が好ましく、より好ましくは０．５ｃａｌ／（ｓ）（ｃｍ^２）（℃／ｃｍ）以上である。また、作業性などを考慮して導電性ワイヤーの直径は、好ましくは、Φ１０μｍ以上、Φ４５μｍ以下である。特に、蛍光体が含有されたコーティング部と蛍光体が含有されていないモールド部材との界面で導電性ワイヤーが断線しやすい。それぞれ同一材料を用いたとしても蛍光体が入ることにより実質的な熱膨張量が異なるため断線しやすいと考えられる。そのため、導電性ワイヤーの直径は、２５μｍ以上がより好ましく、発光面積や扱い易さの観点から３５μｍ以下がより好ましい。
【００８４】
このような導電性ワイヤーとして具体的には、金、銅、白金、アルミニウム等の金属及びそれらの合金を用いた導電性ワイヤーが挙げられる。このような導電性ワイヤーは、各ＬＥＤチップの電極と、インナー・リード及びマウント・リードなどと、をワイヤーボンディング機器によって容易に接続させることができる。
【００８５】
［マウント・リード１０５］
マウント・リード１０５としては、ＬＥＤチップ１０２を配置させるものであり、ダイボンド機器などで積載するのに十分な大きさがあれば良い。また、ＬＥＤチップを複数設置しマウント・リードをＬＥＤチップの共通電極として利用する場合においては、十分な電気伝導性とボンディングワイヤー等との接続性が求められる。また、マウント・リード上のカップ内にＬＥＤチップを配置すると共に蛍光体を内部に充填させる場合は、近接して配置させた別の発光ダイオードからの光により疑似点灯することを防止することができる。
【００８６】
ＬＥＤチップ１０２とマウント・リード１０５のカップとの接着は熱硬化性樹脂などによって行うことができる。具体的には、エポキシ樹脂、アクリル樹脂やイミド樹脂などが挙げられる。また、フェースダウンＬＥＤチップなどによりマウント・リードと接着させると共に電気的に接続させるためにはＡｇペースト、カーボンペースト、金属バンプ等を用いることができる。さらに、発光ダイオードの光利用効率を向上させるためにＬＥＤチップが配置されるマウント・リードの表面を鏡面状とし、表面に反射機能を持たせても良い。この場合の表面粗さは、０．１Ｓ以上０．８Ｓ以下が好ましい。また、マウント・リードの具体的な電気抵抗としては３００μΩ−ｃｍ以下が好ましく、より好ましくは、３μΩ−ｃｍ以下である。また、マウント・リード上に複数のＬＥＤチップを積置する場合は、ＬＥＤチップからの発熱量が多くなるため熱伝導度がよいことが求められる。具体的には、０．０１ｃａｌ／（ｓ）（ｃｍ^２）（℃／ｃｍ）以上が好ましくより好ましくは ０．５ｃａｌ／（ｓ）（ｃｍ^２）（℃／ｃｍ）以上である。これらの条件を満たす材料としては、鉄、銅、鉄入り銅、錫入り銅、メタライズパターン付きセラミック等が挙げられる。
【００８７】
［インナー・リード１０６］
インナー・リード１０６としては、マウント・リード１０５上に配置されたＬＥＤチップ１０２と接続された導電性ワイヤー１０３との接続を図るものである。マウント・リード上に複数のＬＥＤチップを設けた場合は、各導電性ワイヤー同士が接触しないよう配置できる構成とする必要がある。具体的には、マウント・リードから離れるに従って、インナー・リードのワイヤーボンディングさせる端面の面積を大きくすることなどによってマウント・リードからより離れたインナー・リードと接続させる導電性ワイヤーの接触を防ぐことができる。導電性ワイヤーとの接続端面の粗さは、密着性を考慮して１．６Ｓ以上１０Ｓ以下が好ましい。インナー・リードの先端部を種々の形状に形成させるためには、あらかじめリードフレームの形状を型枠で決めて打ち抜き形成させてもよく、あるいは全てのインナー・リードを形成させた後にインナー・リード上部の一部を削ることによって形成させても良い。さらには、インナー・リードを打ち抜き形成後、端面方向から加圧することにより所望の端面の面積と端面高さを同時に形成させることもできる。
【００８８】
インナー・リードは、導電性ワイヤーであるボンディングワイヤー等との接続性及び電気伝導性が良いことが求められる。具体的な電気抵抗としては、３００μΩ−ｃｍ以下が好ましく、より好ましくは３μΩ−ｃｍ以下である。これらの条件を満たす材料としては、鉄、銅、鉄入り銅、錫入り銅及び銅、金、銀をメッキしたアルミニウム、鉄、銅等が挙げられる。
【００８９】
［コーティング部１０１］
本願発明に用いられるコーティング部１０１とは、モールド部材１０４とは別にマウント・リードのカップに設けられるものでありＬＥＤチップの発光を変換する蛍光体が含有されるものである。コーティング部の具体的材料としては、エポキシ樹脂、ユリア樹脂、シリコーンなどの耐候性に優れた透明樹脂や、耐光性に優れたシリカゾル、硝子などの透光性無機材料が好適に用いられる。ここで特に、酸化珪素や酸化アルミニウムを具体的材料とするコーティング部は、エチルシリケートやアルミニウムアルコレートのような金属アルコキシドに蛍光体を含有させた溶液をカップ内に充填後、焼結・乾燥させることにより形成される。また、蛍光体と共に拡散剤を含有させても良い。具体的な拡散剤としては、チタン酸バリウム、酸化チタン、酸化アルミニウム、酸化珪素、二酸化珪素等が好適に用いられる。
【００９０】
［モールド部材１０４］
モールド部材１０４は、発光ダイオードの使用用途に応じてＬＥＤチップ１０２、導電性ワイヤー１０３、蛍光体が含有されたコーティング部１０１などを外部から保護するために設けることができる。モールド部材は、一般には樹脂を用いて形成させることができる。また、蛍光体を含有させることによって視野角を増やすことができるが、樹脂モールドに拡散剤を含有させることによってＬＥＤチップ１０２からの指向性を緩和させ視野角をさらに増やすことができる。更にまた、モールド部材１０４を所望の形状にすることによってＬＥＤチップからの発光を集束させたり拡散させたりするレンズ効果を持たせることができる。従って、モールド部材１０４は複数積層した構造でもよい。具体的には、凸レンズ形状、凹レンズ形状さらには、発光観測面から見て楕円形状やそれらを複数組み合わせた物である。モールド部材１０４の具体的材料としては、主としてエポキシ樹脂、ユリア樹脂、シリコーン樹脂などの耐候性に優れた透明樹脂や硝子などが好適に用いられる。また、拡散剤としては、チタン酸バリウム、酸化チタン、酸化アルミニウム、酸化珪素、二酸化珪素等が好適に用いられる。さらに、拡散剤に加えてモールド部材中にも蛍光体を含有させることもできる。したがって、蛍光体はモールド部材中に含有させてもそれ以外のコーティング部などに含有させて用いてもよい。また、コーティング部を蛍光体が含有された樹脂、モールド部材を硝子などに変えた異なる部材を用いて形成させても良い。この場合、生産性良くより水分などの影響が少ない発光装置とすることができる。また、屈折率を考慮してモールド部材とコーティング部とを同じ部材を用いて形成させても良い。本願発明においてモールド部材に拡散剤や着色剤を含有させることは、発光観測面側から見た蛍光体の着色を隠すことができる。なお、蛍光体の着色とは、本願発明の蛍光体が強い外光からの光のうち、青色成分を吸収し発光する。そのため黄色に着色しているように見えることである。特に、凸レンズ形状などモールド部材の形状によっては、着色部が拡大されて見えることがある。このような着色は、意匠上など好ましくない場合がある。モールド部材に含有された拡散剤は、モールド部材を乳白色に着色剤は所望の色に着色することで着色を見えなくさせることができる。したがって、このような発光観測面側から蛍光体の色が観測されることはない。
【００９１】
また、ＬＥＤチップから放出される光の主発光波長が４３０ｎｍ以上では、光安定化剤である紫外線吸収剤をモールド部材中に含有させた方が耐候性上より好ましい。
【００９２】
【実施例】
以下、本発明に係る実施例について、比較例を交えながら詳述する。なお、本発明は以下に示す実施例のみに限定されないことは言うまでもない。
【００９３】
（実施例１）
図１に示されるように、本比較例１から５において形成された発光ダイオード１００は、マウント・リード１０５とインナー・リード１０６とを備えたリードタイプの発光ダイオードであって、マウント・リード１０５のカップ部上にＬＥＤチップ１０２が載置され、カップ部内に、ＬＥＤチップ１０２を覆うように、下記表２のように組み合わせた蛍光体を含むコーティング部１０１が充填された後に、モールド部材１０４により樹脂モールドされて構成される。ここで、ＬＥＤチップ１０２のｎ側電極及びｐ側電極はそれぞれ、マウント・リード１０５とインナー・リード１０６とにワイヤー１０３を用いて接続される。
【００９４】
図３は、本実施例で使用されるＹＡＧ系蛍光体の励起吸収スペクトルを示す。また、図４は、本実施例で使用されるＹＡＧ系蛍光体の発光スペクトルを示す。本実施例では、それぞれ組成の異なるＹＡＧ系蛍光体として、（Ｙ_０．８Ｇｄ_０．２）_３Ａｌ_５Ｏ_１２：Ｃｅ（以下「蛍光体１」と呼ぶ）、Ｙ_３Ａｌ_５Ｏ_１２：Ｃｅ（以下「蛍光体２」と呼ぶ）、およびＹ_３（Ａｌ_０．８Ｇａ_０．２）_５Ｏ_{１ ２}：Ｃｅ（以下「蛍光体３」と呼ぶ）を使用した。これらの蛍光体は、ＬＥＤチップからの青色光を吸収して励起し、黄色系から緑色系の光を発光する蛍光体である。
【００９５】
図５は本実施例で使用される窒化物蛍光体の励起吸収スペクトルを示す。また、図６は本実施例で使用される窒化物蛍光体の発光スペクトルを示す。本実施例では、それぞれ組成の異なる窒化物蛍光体として、（Ｃａ_{０．９８５}Ｅｕ_{０．０１５}）_２Ｓｉ_５Ｎ_８（以下「蛍光体４」と呼ぶ）、および（Ｓｒ_{０．６７９}Ｃａ_{０．２９１}Ｅｕ_０．０３）_２Ｓｉ_５Ｎ_８（以下「蛍光体５」と呼ぶ）を使用した。これらの蛍光体は、ＬＥＤチップからの青色光を吸収して励起し、赤色系の光を発光する蛍光体である。以下に、上記蛍光体の組成と発光スペクトルのピーク波長を示す。
【００９６】
【表１】

まず、蛍光体１から蛍光体５を１種類ずつ使用して発光ダイオードを形成した後、２０ｍＡのパルス電流を加えることによりＬＥＤチップ自体の発熱が無視できる条件下にて周囲温度を上昇させ、周囲温度に対する発光ダイオードの発光出力を測定した。次に、蛍光体１から蛍光体５のそれぞれについて、２５℃を基準とするＬＥＤ発光の相対出力を求め、周囲温度−相対光出力特性として図１０から図１４に示した。図１０は、本発明の一実施例における蛍光体１の周囲温度−相対光出力特性を示す図である。図１１は、本発明の一実施例における蛍光体２の周囲温度−相対光出力特性を示す図である。図１２は、本発明の一実施例における蛍光体３の周囲温度−相対光出力特性を示す図である。図１３は、本発明の一実施例における蛍光体４の周囲温度−相対光出力特性を示す図である。図１４は、本発明の一実施例における蛍光体５の周囲温度−相対光出力特性を示す図である。図１０から図１４は、いずれもＩｆ＝２０ｍＡ、ｆ＝２００Ｈｚ、Ｄｕｔｙ＝１％の条件である。また、発光ダイオードの周囲温度を１℃変化させたときＬＥＤ発光相対出力の低下率を各蛍光体について求め、第１の蛍光体と第２の蛍光体の温度上昇に対する発光出力低下率として以下の表２に示す。
【００９７】
【表２】

本実施例にて蛍光体を励起するために使用するＬＥＤチップ１０２は、ＩｎＧａＡｌＮ系化合物半導体を発光層として形成させた発光素子であり、発光スペクトルのピーク波長は４６０ｎｍである。また、電流密度を３〜３００Ａ／ｃｍ^２の間で高くすることにより色度座標が黒体放射軌跡に沿って低色温度側へシフトする。図２は、ＬＥＤチップ１０２に流す電流を変化させたときの発光スペクトルの電流特性を示す図である。図２は、蛍光体励起用４６０ｎｍＬＥＤの電流−相対発光スペクトル特性を示し、Ｔａ＝２５℃、ｆ＝２００Ｈｚ、Ｄｕｔｙ＝１％の条件である。図２に示されるように、発光スペクトルの電流特性は、投入電流を増加させていくに従って、ピーク波長が短波長側にシフトする。
【００９８】
そこで、図３に示されるように、ＬＥＤチップに投入される電流の増加によりＬＥＤチップの発光スペクトルのピーク波長がシフトした位置に、上記３つの蛍光体１から３の励起吸収スペクトルのピーク波長の位置をほぼ一致させる。ここで、蛍光体１から３の励起吸収スペクトルのピーク波長と、ＬＥＤチップの発光スペクトルのピーク波長との差が、４０ｎｍ以下であることが好ましい。このような蛍光体を使用することにより、該蛍光体の励起効率が向上し、波長変換されることなくＬＥＤから出光してくる光の量が減少するため、発光装置の色度ズレを防ぐことができる。
【００９９】
ここで、蛍光体３を使用した場合、蛍光体３の発光スペクトルは、図４に示されるように蛍光体１の発光スペクトルよりも短波長側に移動する。従って、ＹＡＧ系蛍光体の励起吸収スペクトルのピーク位置をずらすことによって発光装置の色度ズレが防止できたものの発光装置の発光は黒体放射軌跡から外れているため、蛍光体４あるいは蛍光体５を加えることにより混色光に赤味成分を付加し、黒体放射軌跡付近に色度座標を調整する。
【０１００】
ＹＡＧ系蛍光体に対する窒化物蛍光体の調合比を以下の表３に示す。
【０１０１】
【表３】

実施例１および比較例１から３において発光ダイオードを形成した場合の光学特性の測定結果を以下の表４に示す。
【０１０２】
【表４】

表４に示されるように実施例１および比較例３の場合の演色性は、共にＲａが８５以上となり他の比較例と比べて演色性を向上させることができる。また、図７は、実施例１および比較例１から３について、周囲温度に対する色度の変化を示す図である。図７は、Ｉｆ＝２０ｍＡ、ｆ＝２００Ｈｚ、Ｄｕｔｙ＝１％の条件である。図７に示されるように、実施例１および比較例１から３の何れも温度上昇によって図中の太矢印の方向に色度が変化する。
【０１０３】
図８は、実施例１および比較例１から３について、ＬＥＤチップに投入されるパルス電流に対する色度の変化を示す図である。図８は、Ｔａ＝ＲＴ（室温）、ｆ＝２００Ｈｚ、Ｄｕｔｙ＝１％の条件である。本実施例においては１〜１００ｍＡ（１、５、１０、２０、４０、６０、８０、１００ｍＡ）のパルス電流をＬＥＤチップに加えることにより、ＬＥＤチップの発熱が無視できる条件下で、白色ＬＥＤに赤み成分を付加したＬＥＤの電流特性を確認した。図８に示されるように、比較例１から比較例３の場合は、投入電流を増加させていくに従って、色度は黒体放射軌跡から矢印の方向に遠離っていくように高色温度領域に移動する。一方、実施例１の場合は、色度が黒体放射軌跡にほぼ沿うように矢印の方向に低色度側に移動することが分かる。
【０１０４】
図９は、実施例１および比較例１について、ＤＣ駆動させたときの色度の変化を示す図である。図９は、Ｉｆ＝１ｍＡ、５ｍＡ、１０ｍＡ、２０ｍＡ、４０ｍＡ、６０ｍＡ、Ｔａ＝ＲＴ（室温）、ＤＣ駆動の条件である。比較例１の場合は、電流を１ｍＡから５ｍＡ、１０ｍＡ、２０ｍＡ、４０ｍＡ、６０ｍＡと増加させていくと、それぞれの電流値における色度が黒体放射軌跡から矢印の方向に遠ざかるように高色度側に移動する。一方、実施例１の場合は、混色による光の色度の変動が、色度図上において、Ｘ座標が０．３２６から０．３３３、Ｙ座標が０．３４３から０．３４８の範囲内にある。即ち、実施例１の場合、混色による光の色度は、電流を増加させても黒体放射軌跡にほぼ沿う位置で移動し、色度の変化がほとんど生じない。このように実施例１の場合に色度の変化が殆ど生じないのは、周囲温度−色度特性として図７に示されるような黒体放射軌跡に沿う高色度側への色度の変化と、投入電流−色度特性として図８に示されるような黒体放射軌跡に沿う低色度側への色度の変化とが互いに相殺し合った結果である。
【０１０５】
実施例１の構成は、組み合わせる蛍光体の周囲温度に対する発光出力低下率が共に２．０×１０^−３［ａ．ｕ．／℃］以下と他の実施例の蛍光体と比較して小さく、かつ発光出力低下率の差が２．０×１０^−４［ａ．ｕ．／℃］と他の実施例と比較して小さい組み合わせとしたものである。即ち、蛍光体３と蛍光体５の温度上昇に対する発光出力低下率がほぼ等しい。このように構成することにより、発光素子の発熱等による周囲温度の上昇によって蛍光体３および蛍光体５それぞれの発光出力が低下した場合であっても、蛍光体３と蛍光体５の発光出力差は、周囲温度の影響を受けることなく殆ど同じ値に保たれる。即ち、本発明の構成とすることにより、発光装置の周囲温度、特に電流の変化による発光装置の周囲温度の変化によらず演色性を向上させ、かつ色度ズレが殆ど生じない発光装置とすることが可能である。また、本発明に係る発光装置と、該発光装置から出光した光を発光観測面側に導く導光板とを組み合わせ、液晶ディスプレイの構成部材として使用可能なバックライト光源を形成した場合、周囲温度の変化によらず演色性を向上させ、かつ色度ズレが殆ど生じないバックライト光源とすることが可能である。
【０１０６】
（実施例２、３）
本実施例においては、ＹＡＧ系蛍光体と、窒化物系蛍光体を組み合わせて、暖かみのある光、いわゆる電球色領域（色温度２５００Ｋ〜３８００Ｋ）の光が発光可能な発光装置を形成する。本実施例で使用するＹＡＧ系蛍光体（蛍光体６、７）および窒化物系蛍光体（蛍光体８、９）の組成式、発光ピーク波長λｐ［ｎｍ］、および色調は、以下の表５に示す通りである。
【０１０７】
【表５】

また、実施例１と同様にして測定した各蛍光体の発光出力低下率［ａ．ｕ．／℃］は、以下の表６に示す通りである。
【０１０８】
【表６】

本実施例では以下の表７に示される重量比にて、樹脂、蛍光体７と蛍光体８および蛍光体９とをそれぞれ組み合わせ、実施例１と同様にして発光装置を形成し、電球色を発光可能とする。
【０１０９】
【表７】

実施例２および実施例３において形成した発光装置の光学特性の測定結果を以下の表８に示す。
【０１１０】
【表８】

図１９は、実施例２および実施例３について、ＤＣ駆動させたときの色度の変化を示す図である。図１９は、Ｔａ＝ＲＴ（室温）の条件である。以下に述べられる比較例４の場合は、電流を１ｍＡから５ｍＡ、１０ｍＡ、２０ｍＡ、４０ｍＡ、６０ｍＡと増加させていくと、それぞれの電流値における色度が黒体放射軌跡と交差して高色温度側に移動する。一方、実施例２および実施例３の場合は、投入電流を変化させても色度はほとんど変化しない。実施例２および実施例３の構成は、組み合わせる蛍光体の周囲温度に対する発光出力低下率が共に３．０×１０^−３［ａ．ｕ．／℃］以下として、比較例４の蛍光体６と比較して小さくしたものである。本発明の構成とすることにより、発光素子の周囲温度、特に電流の変化による蛍光体の周囲温度の変化によらず色度ズレが殆ど生じない、かつ演色性を向上させた発光装置とすることが可能である。
【０１１１】
表５に示されるＹＡＧ系蛍光体６を単独で用いて、上述した実施例２、３と同様に電球色を発光可能な発光装置を比較例４として形成する。ここで、本比較例における樹脂と蛍光体との重量比を表７中に示す。また、比較例４として形成した発光装置の光学特性の測定結果を実施例２、３と共に以下の表８中に示す。さらに、図１９中に、比較例４について、ＤＣ駆動させたときの色度の変化を示す。図１９に示されるように本比較例における発光装置は、電流を１ｍＡから５ｍＡ、１０ｍＡ、２０ｍＡ、４０ｍＡ、６０ｍＡと増加させていくと、それぞれの電流値における色度が黒体放射軌跡と交差して高色温度側に移動する。これは、ＬＥＤチップの発光ピーク波長は、図２に示されるように電流の増加につれて短波長側に移動し、図１５に示される蛍光体６の励起吸収スペクトルのピーク波長からずれていくため、蛍光体の波長変換効率が低下し、蛍光体によって波長変換されないＬＥＤチップからの光の波長成分が多くなっていくためと思われる。一方、実施例２および実施例３で使用される蛍光体７の励起吸収スペクトルのピーク波長は、蛍光体６のピーク波長と比較して短波長側にあり、かつＬＥＤチップの発光ピーク波長が投入電流の変化により移動する範囲内にあるため、蛍光体の波長変換効率が低下することがない。さらに、実施例２および実施例３の場合は、励起吸収スペクトルのピーク波長が、ＬＥＤチップの発光ピーク波長が投入電流の変化により移動する範囲内にある窒化物系蛍光体をＹＡＧ系蛍光体と組み合わせて使用することにより、電流の変化による発光素子の周囲温度、すなわち蛍光体の周囲温度の変化にかかわらず色度ズレが殆ど生じない、かつ演色性が向上した電球色を発光可能な発光装置とすることができる。
【０１１２】
（実施例４）
本発明において、表１および表５中に示したＹＡＧ系蛍光体の他、組成式がＹ_{２．９６５}Ｃｅ_{０．０３５}Ａｌ_５Ｏ_１２で表される蛍光体を基準にして、ＡｌをＧａで置換あるいはＹをＧｄで置換して蛍光体を得る。即ち、Ｇａによる置換については、一般式Ｙ_{２．９６５}Ｃｅ_{０．０３５}（Ａｌ_１−ＸＧａ_Ｘ）_５Ｏ_１２において、０＜Ｘ≦０．８の範囲で置換した蛍光体を任意に形成し、Ｇｄによる置換については、一般式（Ｙ_１−ＹＧｄ_Ｙ）_{２．９６５}Ｃｅ_{０．０３５}Ａｌ_５Ｏ_１２において、０＜Ｘ≦０．９の範囲で置換した蛍光体を任意に形成する。また、一般式Ｙ_３−ＺＣｅ_ＺＡｌ_５Ｏ_１２において、０．０１５≦Ｚ≦０．６００の範囲で任意に蛍光体を形成する。
【０１１３】
上述した実施例と同様に、本実施例における蛍光体と窒化物系蛍光体とを適宜組み合わせることにより色度ズレが殆ど生じず、演色性を向上させかつ所望の色調が発光可能な発光装置とすることができる。
【０１１４】
【発明の効果】
本発明により、発光素子の周囲温度の変化、特に発光装置の投入電流の変化による蛍光体の周囲温度の変化によっても従来技術と比較して色度ズレが縮小でき、かつ演色性を向上させた発光装置を形成することが可能である。
【０１１５】
【図面の簡単な説明】
【図１】 本発明の一実施例に係る発光ダイオードの模式的な断面図である。
【図２】 本発明の一実施例におけるＬＥＤチップの発光スペクトル特性を示す図である。
【図３】 本発明の一実施例におけるＹＡＧ系蛍光体の励起吸収スペクトルを示す図である。
【図４】 本発明の一実施例におけるＹＡＧ系蛍光体の発光スペクトルを示す図である。
【図５】 本発明の一実施例における窒化物系蛍光体の励起吸収スペクトルを示す図である。
【図６】 本発明の一実施例における窒化物系蛍光体の発光スペクトルを示す図である。
【図７】 本発明の一実施例における周囲温度−色度特性（パルス駆動による測定）を示す図である。
【図８】 本発明の一実施例における電流−色度特性（パルス駆動による測定）を示す図である。
【図９】 本発明の一実施例における電流−色度特性（ＤＣ駆動による測定）を示す図である。
【図１０】 本発明の一実施例における蛍光体１の周囲温度−相対光出力特性を示す図である。
【図１１】 本発明の一実施例における蛍光体２の周囲温度−相対光出力特性を示す図である。
【図１２】 本発明の一実施例における蛍光体３の周囲温度−相対光出力特性を示す図である。
【図１３】 本発明の一実施例における蛍光体４の周囲温度−相対光出力特性を示す図である。
【図１４】 本発明の一実施例における蛍光体５の周囲温度−相対光出力特性を示す図である。
【図１５】 本発明の一実施例におけるＹＡＧ系蛍光体の励起吸収スペクトルを示す図である。
【図１６】 本発明の一実施例におけるＹＡＧ系蛍光体の発光スペクトルを示す図である。
【図１７】 本発明の一実施例における窒化物系蛍光体の励起吸収スペクトルを示す図である。
【図１８】 本発明の一実施例における窒化物系蛍光体の発光スペクトルを示す図である。
【図１９】 本発明の一実施例における電流−色度特性（ＤＣ駆動による測定）を示す図である。
【図２０】 蛍光体１０〜１３のＹＡＧ系蛍光体をＥＸ＝４６０ｎｍで励起させたときの発光スペクトルを示す図である。
【図２１】 蛍光体１０〜１３のＹＡＧ系蛍光体の反射スペクトルを示す図である。
【図２２】 蛍光体１０〜１３のＹＡＧ系蛍光体の励起スペクトルを示す図である。
【図２３】 蛍光体１４及び蛍光体１５のＹＡＧ系蛍光体をＥＸ＝４６０ｎｍで励起させたときの発光スペクトルを示す図である。
【図２４】 蛍光体１４のＹＡＧ系蛍光体の励起スペクトルを示す図である。
【図２５】 蛍光体１５のＹＡＧ系蛍光体の励起スペクトルを示す図である。
【符号の説明】
１００・・・発光ダイオード
１０１・・・コーティング部
１０２・・・ＬＥＤチップ
１０３・・・ワイヤー
１０４・・・モールド部材
１０５・・・マウント・リード
１０６・・・インナー・リード[0001]
BACKGROUND OF THE INVENTION
The present invention is used for fluorescent display tubes, displays, PDPs, CRTs, FLs, FEDs, projection tubes, and the like, in particular, white light emitting devices that have extremely excellent light emission characteristics using blue light emitting diodes or ultraviolet light emitting diodes as light sources. The present invention relates to a phosphor. In addition, the white light-emitting device having the phosphor according to the present invention can be used for fluorescent lamps for storefront display lighting, medical site lighting, etc., as well as backlight light sources for liquid crystal displays, light-emitting diodes ( It can also be applied to the field of LEDs.
[0002]
[Prior art]
As a light emitting device using an LED, there is a light emitting device that obtains a desired light emission color by mixing light from an LED and light obtained by wavelength-converting light from the LED with a phosphor. For example, an LED that emits white light (hereinafter referred to as “white LED”) is an LED that emits blue light having an emission spectrum peak wavelength of about 460 nm, and an yttrium / aluminum / garnet system having an excitation absorption spectrum peak wavelength around 460 nm. It is a light emitting diode that obtains white light by mixing yellow light generated by wavelength conversion of blue light by a phosphor (hereinafter referred to as “YAG phosphor”). In such a white LED, a phosphor that emits light having a peak wavelength of an emission spectrum in a red region is used for the purpose of improving the color rendering property of the mixed color light obtained by additive color mixture of blue and yellow. Used together with the body (for example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application No. 2000-31534
[0004]
[Problems to be solved by the invention]
However, when the light-emitting device is used as an illumination light source that continuously emits strong light, for example, the excitation efficiency of various phosphors decreases due to heat generation of the light-emitting elements, and thus the luminous flux [lm] of the entire light-emitting device decreases. Problems arise. Further, when a light emitting device is formed by combining a plurality of phosphors whose excitation efficiencies are reduced at different rates due to heat generation, the difference in the light emission output of each phosphor fluctuates with a change in ambient temperature, so that light is emitted from the light emitting device. There was a color shift observed at a position where the chromaticity of light deviated from the desired chromaticity.
[0005]
In the light emitting element, as the input current increases, the peak wavelength of the emission spectrum of the light emitting element shifts to the short wavelength side (see, for example, FIG. 2). When the peak wavelength shifts to the short wavelength side, the emission intensity of the phosphor excited by the light emitting element varies. In particular, when two or more kinds of phosphors are combined, the variation in the emission intensity greatly affects the color shift.
[0006]
Even if such color misregistration is slight, when the light emitting device is used as a light source of a liquid crystal projector, for example, it has a problem of greatly affecting the color tone of a color image projected and projected on a screen. Occurs.
[0007]
Therefore, an object of the present invention is to provide a light-emitting device that can suppress the decrease in luminous flux [lm] and the occurrence of chromaticity deviation even when the ambient temperature changes.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a light emitting element, a first phosphor that emits light of a different wavelength by absorbing at least part of the light from the light emitting element, and at least the light from the light emitting element. A second phosphor that absorbs a part and emits light of a different wavelength, and a peak wavelength of an emission spectrum of the light emitting element is equal to an excitation spectrum of the first phosphor. The present invention relates to a light emitting device having a peak wavelength and a wavelength longer than a peak wavelength of an excitation spectrum of the second phosphor. Thereby, the light-emitting device which suppressed generation | occurrence | production of chromaticity deviation can be provided. In particular, since the color deviation occurs along the locus of black body radiation in this light emitting device, color deviation may be perceived in human vision compared to the case where color deviation occurs in a direction perpendicular to the locus of black body radiation. Few. In addition, due to the interaction between the first phosphor and the second phosphor, the amplitude of the color misregistration is extremely narrow.
[0009]
In the light emitting element, as the current density increases, the peak wavelength of the emission spectrum of the light emitting element is shifted to the short wavelength side. When the input current of the light emitting element is increased, the current density is increased, and the peak wavelength of the emission spectrum of the light emitting element is shifted to the short wavelength side. By utilizing this action, a light-emitting device that prevents color misregistration is provided.
[0010]
It is preferable that the first phosphor and the second phosphor have substantially the same change in emission intensity due to a change in ambient temperature of the first phosphor and the second phosphor. By adopting such a configuration, the temperature characteristics of the first phosphor and the second phosphor whose excitation efficiency fluctuates due to a change in ambient temperature accompanying an increase in input power of the phosphor become substantially the same, and the ambient temperature changes. Even in this case, it is possible to provide a light emitting device capable of suppressing the occurrence of color misregistration. In particular, it is possible to provide a light emitting device in which the occurrence of color misregistration is further suppressed by the interaction between the color misregistration accompanying an increase in the current density of the light emitting element and the color misregistration accompanying a change in ambient temperature of the phosphor.
[0011]
The change in the ambient temperature of the first phosphor and the second phosphor is mainly due to the change in the input current to the light emitting element. By adopting such a configuration, the temperature change of the first phosphor and the second phosphor whose excitation efficiency changes due to the influence of heat from the light emitting element becomes almost the same, and the ambient temperature of the phosphor changes. In addition, a light emitting device capable of suppressing the occurrence of color misregistration can be formed.
[0012]
The light emitting element preferably has a peak wavelength of an emission spectrum of 350 nm to 530 nm. In particular, 400 nm to 530 nm having a color tone to light from the light emitting element is preferable. With this configuration, it is possible to control the color shift of the entire light emitting device by controlling the color tone change of the semiconductor light emitting element and the color tone change of the phosphor.
[0013]
In the first phosphor, in the range of wavelength change of the light emitting element that occurs when the current density of the light emitting element is changed, the short wavelength side of the wavelength change range has higher excitation efficiency than the long wavelength side, in other words, For example, the present invention relates to a light emitting device in which light emission of a phosphor by excitation light on the short wavelength side of the light emitting element has higher emission intensity than light emission of the phosphor by excitation light on the long wavelength side of the light emitting element. Thereby, when the current density of the light emitting element is increased, the light emission intensity of the first phosphor increases. Further, as will be described later, the emission intensity of the second phosphor also increases. Therefore, it is possible to provide a light-emitting device in which color shift is extremely suppressed.
[0014]
The first phosphor has an excitation spectrum of the first phosphor on the short wavelength side of the wavelength change range in the range of wavelength change of the light emitting element that occurs when the current density of the light emitting element is changed. It is preferable to have a peak wavelength of Since the peak wavelength of the emission spectrum of the light emitting element is at the position of the peak wavelength with the largest excitation absorption of the first phosphor, the first phosphor can emit light most efficiently, and the light flux of the entire light emitting device can be reduced. This is because maximum control is possible.
[0015]
The first phosphor includes Y and Al, and includes at least one element selected from Lu, Sc, La, Gd, Tb, Eu, and Sm, and one element selected from Ga and In. It is preferable to include an yttrium / aluminum / garnet phosphor activated by at least one element selected from rare earth elements. By adopting such a configuration, it is possible to suppress the occurrence of color misregistration even when the ambient temperature changes, and it is also possible to suppress a relative decrease in the luminous flux [lm] of the entire light emitting device that generates heat. A light emitting device can be obtained. The peak wavelength of the excitation absorption spectrum of the yttrium / aluminum / garnet phosphor is preferably 420 nm to 470 nm. By adopting such a structure, it is possible to form a light emitting device in which the chromaticity shift due to the input current is reduced as compared with the conventional technique and the color rendering property is improved.
[0016]
The difference between the peak wavelength of the excitation spectrum of the first phosphor and the peak wavelength of the emission spectrum of the light emitting element is preferably 40 nm or less. By adopting such a structure, it is possible to form a light emitting device in which the chromaticity shift due to the input current is reduced as compared with the conventional technique and the color rendering property is improved.
[0017]
In the second phosphor, in the range of wavelength change of the light emitting element that occurs when the current density of the light emitting element is changed, the short wavelength side of the wavelength change range has higher excitation efficiency than the long wavelength side, in other words, For example, the present invention relates to a light emitting device in which light emission of a phosphor by excitation light on the short wavelength side of the light emitting element has higher emission intensity than light emission of the phosphor by excitation light on the long wavelength side of the light emitting element. Thereby, when the current density of the light emitting element is increased, the light emission intensity of the second phosphor increases. Further, as described above, the emission intensity of the first phosphor also increases. Therefore, it is possible to provide a light-emitting device in which color shift is extremely suppressed.
[0018]
The second phosphor contains N and includes at least one element selected from Be, Mg, Ca, Sr, Ba, and Zn, and C, Si, Ge, Sn, Ti, Zr, and Hf. It is preferable to include a nitride-based phosphor including at least one element selected and activated by at least one element selected from rare earth elements. By adopting such a configuration, a light emitting device that can suppress the occurrence of color misregistration even when the ambient temperature changes, and further can suppress a decrease in the luminous flux [lm] of the entire light emitting device that generates heat, Is possible. The second phosphor is preferably a phosphor that emits light when excited with light having a wavelength of 350 to 600 nm. By adopting such a structure, it is possible to form a light emitting device in which the chromaticity shift due to the input current is reduced as compared with the conventional technique and the color rendering property is improved.
[0019]
The light emitting device is preferably a backlight light source of a liquid crystal display or a light source for illumination. By adopting such a configuration, it is possible to form a liquid crystal display or an illumination light source in which color misregistration is less likely to occur in comparison with the prior art due to changes in ambient temperature.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies a light emitting device for embodying the technical idea of the present invention, and the present invention does not limit the light emitting device to the following. Moreover, although the size and positional relationship of the members shown in each drawing are exaggerated for clarity of explanation, they correspond to the facts.
[0021]
The phosphor used in the present invention is a phosphor including a first phosphor and a second phosphor whose light emission intensity change with a change in ambient temperature of the phosphor is substantially equal to that of the first phosphor. Furthermore, the phosphor includes a second phosphor whose light emission intensity change is substantially equal to that of the first phosphor under a condition in which the ambient temperature of the phosphor changes due to a change in input current to the light emitting element. In particular, the phosphor used in the present embodiment emits a first phosphor that emits light having a peak wavelength of the emission spectrum in the yellow to green region, and light having a peak wavelength of the emission spectrum in the red region. This is the second phosphor. The first phosphor includes Y and Al, and includes at least one element selected from Lu, Sc, La, Gd, Tb, Eu, and Sm, and one element selected from Ga and In. A YAG phosphor activated with cerium can be obtained. The second phosphor contains N and contains at least one element selected from Be, Mg, Ca, Sr, Ba, and Zn, and C, Si, Ge, Sn, Ti, Zr, and Hf. A nitride phosphor containing at least one selected element and activated by Eu and / or rare earth elements can be obtained.
[0022]
The light emitting diode 100 of FIG. 1 is a lead type light emitting diode having a mount lead 105 and an inner lead 106, and an LED chip 102 is provided on the cup portion of the mount lead 105, and in the cup portion, After the coating portion 101 containing the phosphor is filled so as to cover the LED chip 102, it is configured by resin molding with a molding member 104. Here, the n-side electrode and the p-side electrode of the LED chip 102 are connected to the mount lead 105 and the inner lead 106 using the wire 103, respectively.
[0023]
In the light emitting diode configured as described above, part of the light emitted by the light emitting element (LED chip) 102 (hereinafter referred to as “LED light”) excites the phosphor contained in the coating unit 101. Fluorescence having a wavelength different from that of the LED light is generated, and the fluorescence generated by the phosphor and the LED light output without contributing to excitation of the phosphor are mixed and output.
[0024]
In general, since the excitation efficiency of a phosphor decreases with increasing ambient temperature, the output of light emitted from the phosphor also decreases. In the present embodiment, the decrease rate of the relative light output when the ambient temperature is changed by 1 ° C. is defined as the light output decrease rate, and both the light output decrease rates of the first phosphor and the second phosphor are the same. 4.0 × 10^-3[A. u. / ° C] or less, preferably 3.0 × 10^-3[A. u. / ° C.] or less, more preferably 2.0 × 10^-3[A. u. / [Deg.] C.] or less, and the configuration can further suppress the decrease in the luminous flux [lm] of the entire light emitting device that generates heat as compared with the prior art. Further, the light emission output reduction rate with respect to the temperature rise of the first phosphor and the second phosphor is substantially equal. That is, the difference in the light output reduction rate between the first phosphor and the second phosphor is 2.0 × 10^-3[A. u. / ° C.] or less, more preferably 2.0 × 10^-4[A. u. / ° C.] or less, the light emission output reduction rate is made substantially the same. By doing so, the temperature characteristics of the phosphors whose excitation efficiency decreases due to heat generation are substantially the same, and a light emitting device capable of suppressing the occurrence of color misregistration even when the ambient temperature changes can be formed.
[0025]
Hereafter, each structure of embodiment of this invention is explained in full detail.
[0026]
[Phosphor]
The phosphor used in the present embodiment may be a combination of an yttrium / aluminum / garnet phosphor and a phosphor capable of emitting red light, particularly a nitride phosphor. These YAG phosphors and nitride phosphors may be mixed and contained in the coating unit 101, or may be separately contained in the coating unit 101 composed of a plurality of layers. Hereinafter, each phosphor will be described in detail.
[0027]
(Yttrium / Aluminum / Garnet phosphor)
The yttrium-aluminum-garnet-based phosphor (YAG-based phosphor) used in the present embodiment includes at least one selected from Lu, Sc, La, Gd, Tb, Eu, and Sm, including Y and Al. And a phosphor activated by at least one element selected from rare earth elements, and visible light or ultraviolet light emitted from the LED chip 102. It is a phosphor that emits light when excited. In particular, in the present embodiment, two or more kinds of yttrium / aluminum oxide phosphors activated by Ce or Pr and having different compositions can be used. For example, YAlO₃: Ce, Y₃Al₅O₁₂Y: Ce (YAG: Ce) or Y₄Al₂O₉: Ce, and also a mixture thereof. In addition, at least one of Ba, Sr, Mg, Ca, and Zn may be contained, and by further containing Si, the crystal growth reaction can be suppressed and the phosphor particles can be aligned. Here, the YAG-based phosphor activated with Ce is to be interpreted in a broad sense, and part or all of yttrium is converted into at least one element selected from the group consisting of Lu, Sc, La, Gd and Sm. It is substituted or a part or all of aluminum is used in a broad sense including a phosphor having a fluorescent action in which any one or both of Ba, Tl, Ga, and In are substituted. More specifically, the general formula (Y_zGd_1-z)_ThreeAl_FiveO₁₂: Photoluminescence phosphor represented by Ce (where 0 <z ≦ 1) or a general formula (Re_1-aSm_a)_ThreeRe ’_FiveO₁₂: Ce (where 0 ≦ a <1, 0 ≦ b ≦ 1, Re is at least one selected from Y, Gd, La, Sc, and Re ′ is at least one selected from Al, Ga, In) The photoluminescence phosphor shown in FIG.
[0028]
Blue light emitted from a light emitting element using a nitride compound semiconductor in the light emitting layer and green light and red light emitted from a phosphor whose body color is yellow to absorb blue light, or When yellow light and green light and red light are mixedly displayed, a desired white light emission color display can be performed. In order to cause this color mixture, the light emitting device preferably contains phosphor powder or bulk in various resins such as epoxy resin, acrylic resin or silicone resin, and inorganic materials such as silicon oxide and aluminum oxide. Thus, the thing containing the fluorescent substance can be variously used according to uses, such as a dot-like thing and a layer-like thing formed so thinly that the light from the LED chip is transmitted. Arbitrary color tones such as a light bulb color including white can be provided by variously adjusting the ratio, coating, and filling amount of the phosphor and the resin, and selecting the emission wavelength of the light emitting element.
[0029]
In addition, by arranging two or more kinds of phosphors in order with respect to the incident light from the light emitting element, a light emitting device capable of efficiently emitting light can be obtained. That is, on a light emitting element having a reflective member, a color conversion member containing a phosphor that has an absorption wavelength on the long wavelength side and can emit light at a long wavelength, and an absorption wavelength on the longer wavelength side that has a longer wavelength. The reflected light can be used effectively by laminating a color conversion member capable of emitting light at a wavelength.
[0030]
When a YAG phosphor is used, the irradiance is (Ee) = 0.1 W · cm^-21000W ・ cm^-2Even in the case where the following LED chips are in contact with or in close proximity to each other, a light-emitting device having sufficient light resistance can be obtained with high efficiency.
[0031]
The cerium-activated yttrium / aluminum oxide phosphor used in the present embodiment, which is a green-based YAG phosphor capable of emitting light, has a garnet structure and is resistant to heat, light and moisture, and is excited and absorbed. The peak wavelength of the spectrum can be in the vicinity of 420 nm to 470 nm. Also, the emission peak wavelength λp is near 510 nm, and has a broad emission spectrum that extends to the vicinity of 700 nm. On the other hand, the YAG phosphor that emits red light, which is an yttrium-aluminum oxide phosphor activated by cerium, has a garnet structure, is resistant to heat, light and moisture, and has a peak wavelength of 420 nm in the excitation absorption spectrum. To about 470 nm. Further, the emission peak wavelength λp is in the vicinity of 600 nm, and has a broad emission spectrum that extends to the vicinity of 750 nm.
[0032]
Of the composition of YAG phosphors with a garnet structure, the emission spectrum is shifted to the short wavelength side by substituting part of Al with Ga, and part of Y of the composition is replaced with Gd and / or La. By doing so, the emission spectrum shifts to the long wavelength side. Such a YAG-based phosphor can also be obtained, for example, by firing a raw material adjusted so as to add an excess of substitutional elements relative to the stoichiometric ratio. If the substitution of Y is less than 20%, the green component is large and the red component is small. On the other hand, at 80% or more, although the reddish component increases, the luminance rapidly decreases. Similarly, the excitation absorption spectrum is shifted to the short wavelength side by substituting part of Al with Ga in the composition of the YAG phosphor having a garnet structure. By substituting a part of Gd and / or La, the excitation absorption spectrum is shifted to the longer wavelength side. The peak wavelength of the excitation absorption spectrum of the YAG phosphor is preferably on the shorter wavelength side than the peak wavelength of the emission spectrum of the light emitting element. With this configuration, when the current input to the light emitting element is increased, the peak wavelength of the excitation absorption spectrum substantially matches the peak wavelength of the emission spectrum of the light emitting element, so that the excitation efficiency of the phosphor is not reduced. Thus, a light emitting device in which the occurrence of chromaticity deviation is suppressed can be formed.
[0033]
Such phosphors use oxides or compounds that easily become oxides at high temperatures as raw materials for Y, Gd, Ce, La, Al, Sm and Ga, and mix them well in a stoichiometric ratio. And get the raw materials. Alternatively, a coprecipitated oxide obtained by co-precipitation of a solution obtained by coprecipitation of a solution obtained by dissolving a rare earth element of Y, Gd, Ce, La, and Sm in an acid at a stoichiometric ratio with oxalic acid, and aluminum oxide or gallium oxide. To obtain a mixed raw material. Fluoride such as ammonium fluoride or NH as flux₄A suitable amount of Cl is mixed and packed in a crucible, and fired in air at a temperature of 1350 to 1450 ° C. for 2 to 5 hours to obtain a fired product, and then the fired product is ball milled in water for washing, separation, drying, Finally, it can be obtained by passing through a sieve. Further, in the method for manufacturing a phosphor according to another embodiment, a first firing step in which a mixture composed of a mixture of phosphor materials and a flux is mixed in the atmosphere or in a weak reducing atmosphere, and in a reducing atmosphere. It is preferable to perform the baking in two stages, which includes the second baking step performed in step (b). Here, the weak reducing atmosphere refers to a weak reducing atmosphere set to include at least the amount of oxygen necessary in the reaction process of forming a desired phosphor from the mixed raw material. By performing the first firing step until the formation of the phosphor structure is completed, blackening of the phosphor can be prevented and a decrease in light absorption efficiency can be prevented. In addition, the reducing atmosphere in the second firing step refers to a reducing atmosphere stronger than the weak reducing atmosphere. By firing in two stages in this way, a phosphor with high absorption efficiency at the excitation wavelength can be obtained. Therefore, when a light emitting device is formed with the phosphor thus formed, the amount of the phosphor necessary for obtaining a desired color tone can be reduced, and a light emitting device with high light extraction efficiency can be formed. Can do.
[0034]
Yttrium / aluminum oxide phosphors activated with two or more types of cerium having different compositions may be used in combination, or may be arranged independently. When the phosphors are arranged independently, it is preferable to arrange the phosphors in the order of the phosphor that easily absorbs and emits light from the light emitting element on the shorter wavelength side and the phosphor that easily absorbs and emits light on the longer wavelength side. This makes it possible to efficiently absorb and emit light.
[0035]
In the present embodiment, when a YAG phosphor is used as the first phosphor, for example, one having the following composition can be used.
[0036]
Phosphor 10: (Y_0.90Gd_0.10)_2.85Ce_0.15Al_FiveO₁₂,
Phosphor 11: (Y_0.395Gd_0.605)_2.85Ce_0.15Al_FiveO₁₂,
Phosphor 12: Y_2.965Ce_0.035(Al_0.8Ga_0.2)_FiveO₁₂,
Phosphor 13: (Y_0.8, Gd_0.2)_2.965Ce_0.035Al_FiveO₁₂,
Phosphor 14: Y_2.965Ce_0.035(Al_0.5, Ga_0.5)_FiveO₁₂,
Phosphor 15: Y_2.85Ce_0.15Al_FiveO₁₂.
[0037]
The YAG phosphor in the present invention is not limited to these.
[0038]
The phosphors 10 to 15 will be described in more detail with reference to FIGS.
FIG. 20 is a diagram showing an emission spectrum when the YAG phosphors of phosphors 10 to 13 are excited at EX = 460 nm. FIG. 21 is a diagram showing a reflection spectrum of the YAG phosphors of phosphors 10 to 13. FIG. 22 is a diagram showing an excitation spectrum of YAG phosphors of phosphors 10 to 13. FIG. 23 is a diagram showing an emission spectrum when the YAG phosphors of the phosphor 14 and the phosphor 15 are excited at EX = 460 nm. FIG. 24 is a diagram showing an excitation spectrum of the YAG phosphor of the phosphor 14. FIG. 25 is a diagram showing an excitation spectrum of the YAG phosphor of the phosphor 15.
[0039]
Since these YAG phosphors of the phosphors 10 to 15 have different emission peak wavelengths, YAG phosphors having a desired color tone are selected. Next, a light emitting element is selected from the excitation spectrum and the reflection spectrum. For example, the YAG phosphor of the phosphor 10 has a peak wavelength on the long wavelength side of the excitation spectrum of about 456 nm. Considering the case where the light emitting element shifts to the short wavelength side with an increase in input current, a light emitting element having an emission peak wavelength on the long wavelength side about 5 to 10 nm from the 456 nm is selected. Further, the light emitting element is selected in consideration of the excitation spectrum of the second phosphor.
[0040]
On the other hand, when a YAG phosphor is selected after selecting a phosphor that emits light at a certain wavelength as the second phosphor, the following points are considered. For example, from the relationship between the second phosphor and the light emitting element, when the input current is low, a light emitting element having an emission peak wavelength of 457 nm is used at a rated drive of 20 mA. When the YAG phosphor of the phosphor 15 is selected, the peak wavelength of the excitation spectrum of the YAG phosphor of the phosphor 15 is 457 nm. Therefore, when the input current density to the light emitting element is relatively low, the YAG phosphor of the phosphor 15 emits light most efficiently. However, as the input current to the light emitting element increases, the peak wavelength of the emission spectrum of the light emitting element shifts by about 10 nm to the short wavelength side. When the emission peak wavelength shifts to the short wavelength side of about 10 nm, the excitation efficiency of the YAG phosphor of the phosphor 15 decreases, and the relative emission intensity of the YAG phosphor decreases. That is, the ratio of the emission intensity of the converted light to the excitation light is relatively lowered. Therefore, the light emitting device using the YAG phosphor of the phosphor 15 causes a color shift due to an increase in current applied to the light emitting element. On the other hand, when the YAG phosphor of the phosphor 14 is selected, the peak wavelength of the excitation spectrum is 440 nm. As the input current to the light emitting element is increased, the emission intensity of the YAG phosphor of the phosphor 14 is improved. On the other hand, normally, the light emission output of the YAG phosphor decreases as the light emitting element generates heat. Therefore, in the light emitting device using the YAG phosphor of the phosphor 14, even when the input current to the light emitting element is increased, the color shift due to heat and the color shift due to the spectrum shift accompanying the increase in the current density of the light emitting element. Therefore, it is possible to provide a light emitting device that emits light stably and has little color misregistration. Therefore, when a YAG-based phosphor having the same peak wavelength as that when the input current of the light emitting element is increased for the first phosphor or having a peak wavelength of the excitation spectrum on the short wavelength side is used, the color tone and the emission intensity are reduced. Very little change. In addition to the phosphors described above, various YAG phosphors can be used.
[0041]
(Nitride phosphor)
The first phosphor used in the present invention contains N and at least one element selected from Be, Mg, Ca, Sr, Ba, and Zn, and C, Si, Ge, Sn, Ti, A nitride-based phosphor containing at least one element selected from Zr and Hf and activated by at least one element selected from rare earth elements. Further, the nitride-based phosphor used in the present embodiment refers to a phosphor that emits light by being absorbed by absorbing visible light, ultraviolet light, and light emitted from the YAG-based phosphor emitted from the LED chip 102. . In particular, the phosphor according to the present invention includes Mn-added Sr—Ca—Si—N: Eu, Ca—Si—N: Eu, Sr—Si—N: Eu, Sr—Ca—Si—O—N: Eu, Ca-Si-ON: Eu, Sr-Si-ON: Eu-based silicon nitride. The basic constituent element of this phosphor is represented by the general formula L_XSi_YN_{(2 / 3X + 4 / 3Y)}: Eu or L_XSi_YO_ZN_{(2 / 3X + 4 / 3Y-2 / 3Z)}: Eu (L is any of Sr, Ca, Sr and Ca. 0.5 ≦ X ≦ 3 and 1.5 ≦ Y ≦ 8). In the general formula, X and Y are preferably X = 2, Y = 5, or X = 1, Y = 7, but any can be used. Specifically, Mn is added as a basic constituent element (Sr_XCa_1-X)₂Si₅N₈: Eu, Sr₂Si₅N₈: Eu, Ca₂Si₅N₈: Eu, Sr_XCa_1-XSi₇N₁₀: Eu, SrSi₇N₁₀: Eu, CaSi₇N₁₀: It is preferable to use a phosphor represented by Eu, but in the composition of this phosphor, from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr and Ni At least one or more selected may be contained. However, the present invention is not limited to this embodiment and examples.
[0042]
L is any one of Sr, Ca, Sr and Ca. The mixing ratio of Sr and Ca can be changed as desired.
[0043]
By using Si for the composition of the phosphor, it is possible to provide a phosphor having good crystallinity at low cost.
[0044]
Europium Eu, which is a rare earth element, is used for the emission center. Europium mainly has bivalent and trivalent energy levels. The phosphor of the present invention has Eu as a base material for alkaline earth metal silicon nitride.²⁺Is used as an activator. Eu²⁺Is easily oxidized and trivalent Eu₂O₃It is marketed with the composition. However, commercially available Eu₂O₃Then, the involvement of O is large, and it is difficult to obtain a good phosphor. Therefore, Eu₂O₃It is preferable to use a product obtained by removing O from the system. For example, it is preferable to use europium alone or europium nitride. However, this is not the case when Mn is added.
[0045]
The additive Mn is Eu.²⁺Is promoted to improve luminous efficiency such as luminous brightness, energy efficiency, and quantum efficiency. Mn is contained in the raw material, or Mn alone or a Mn compound is contained in the manufacturing process and fired together with the raw material. However, Mn is not contained in the basic constituent elements after firing, or even if contained, only a small amount remains compared to the initial content. This is probably because Mn was scattered in the firing step.
[0046]
The phosphor has at least one selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, O and Ni in the basic constituent element or together with the basic constituent element. Contains the above. These elements have actions such as increasing the particle diameter and increasing the luminance of light emission. Further, B, Al, Mg, Cr and Ni have an effect that afterglow can be suppressed.
[0047]
Such a nitride-based phosphor absorbs part of the blue light emitted by the LED chip 102 and emits light in the yellow to red region. Using a nitride-based phosphor together with a YAG-based phosphor in the light-emitting device having the above-described configuration, the blue light emitted from the LED chip 102 and the yellow to red light by the nitride-based phosphor are mixed and warmed Provided is a light emitting device that emits white light. It is preferable that the phosphor added in addition to the nitride-based phosphor contains an yttrium / aluminum oxide phosphor activated with cerium. This is because it can be adjusted to a desired chromaticity by containing the yttrium aluminum oxide phosphor. The yttrium / aluminum oxide phosphor activated with cerium absorbs part of the blue light emitted by the LED chip 102 and emits light in the yellow region. Here, the blue light emitted by the LED chip 102 and the yellow light of the yttrium / aluminum oxide fluorescent material emit light blue-white by mixing colors. Therefore, the yttrium / aluminum oxide phosphor and the phosphor emitting red light are mixed together in the coating member 101 having translucency and combined with the blue light emitted by the LED chip 102 to produce a white system. Can be provided. Particularly preferred is a white light emitting device whose chromaticity is located on the locus of black body radiation in the chromaticity diagram. However, in order to provide a light emitting device having a desired color temperature, the amount of phosphor of the yttrium / aluminum oxide phosphor and the amount of phosphor of red light emission can be appropriately changed. This light-emitting device that emits white-based mixed color light improves the special color rendering index R9. A conventional light emitting device that emits white light only in combination with a blue light emitting element and a yttrium aluminum oxide phosphor activated by cerium has a special color rendering index R9 of nearly 0 at a color temperature of Tcp = 4600K, The red component was insufficient. Therefore, increasing the special color rendering index R9 has been a problem to be solved. In the present invention, the special color rendering index near the color temperature Tcp = 4600K is obtained by using the phosphor emitting red light together with the yttrium aluminum oxide phosphor. R9 can be increased to around 40.
[0048]
Next, the phosphor according to the present invention ((Sr_XCa_1-X)₂Si₅N₈: Eu) manufacturing method will be described, but is not limited to this manufacturing method. The phosphor contains Mn and O.
[0049]
Raw materials Sr and Ca are pulverized. The raw materials Sr and Ca are preferably used alone, but compounds such as imide compounds and amide compounds can also be used. The raw materials Sr and Ca include B, Al, Cu, Mg, Mn, and Al.₂O₃Etc. may be contained. The raw materials Sr and Ca are pulverized. Sr and Ca obtained by pulverization preferably have an average particle diameter of about 0.1 μm to 15 μm, but are not limited to this range. The purity of Sr and Ca is preferably 2N or higher, but is not limited thereto. In order to improve the mixed state, at least one of the metal Ca, the metal Sr, and the metal Eu can be alloyed, nitrided, pulverized, and used as a raw material.
[0050]
The raw material Si is pulverized. The raw material Si is preferably a simple substance, but a nitride compound, an imide compound, an amide compound, or the like can also be used. For example, Si₃N₄, Si (NH₂)₂, Mg₂Si and the like. The purity of the raw material Si is preferably 3N or more, but Al₂O₃, Mg, metal boride (Co₃B, Ni₃B, CrB), manganese oxide, H₃BO₃, B₂O₃, Cu₂Compounds such as O and CuO may be contained. Si is also pulverized in the same manner as the raw materials Sr and Ca. The average particle size of the Si compound is preferably about 0.1 μm to 15 μm.
[0051]
Next, the raw materials Sr and Ca are nitrided in a nitrogen atmosphere. This reaction formula is shown in the following formula 1 and formula 2, respectively.
[0052]
3Sr + N₂  → Sr₃N₂  ... (Formula 1)
3Ca + N₂  → Ca₃N₂  ... (Formula 2)
Sr and Ca are nitrided in a nitrogen atmosphere at 600 to 900 ° C. for about 5 hours. Sr and Ca may be mixed and nitrided, or may be individually nitrided. Thereby, a nitride of Sr and Ca can be obtained. Sr and Ca nitrides are preferably of high purity, but commercially available ones can also be used.
[0053]
The raw material Si is nitrided in a nitrogen atmosphere. This reaction formula is shown in the following formula 3.
[0054]
3Si + 2N₂  → Si₃N₄  ... (Formula 3)
Silicon Si is also nitrided in a nitrogen atmosphere at 800 to 1200 ° C. for about 5 hours. Thereby, silicon nitride is obtained. The silicon nitride used in the present invention is preferably highly pure, but commercially available ones can also be used.
[0055]
Sr, Ca or Sr—Ca nitride is pulverized.
Similarly, Si nitride is pulverized. Similarly, Eu compound Eu₂O₃Crush. Europium oxide is used as the Eu compound, but metal europium, europium nitride, and the like can also be used. In addition, as the raw material Z, an imide compound or an amide compound can also be used. Europium oxide preferably has a high purity, but commercially available products can also be used. The average particle size of the alkaline earth metal nitride, silicon nitride and europium oxide after pulverization is preferably about 0.1 μm to 15 μm.
[0056]
The raw material may contain at least one selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, O, and Ni. In addition, the above elements such as Mg, Zn, and B can be mixed by adjusting the blending amount in the following mixing step. These compounds can be added alone to the raw material, but are usually added in the form of compounds. This type of compound includes H₃BO₃, Cu₂O₃MgCl₂, MgO / CaO, Al₂O₃, Metal borides (CrB, Mg₃B₂, AlB₂, MnB), B₂O₃, Cu₂O, CuO, and the like.
[0057]
After the pulverization, Sr, Ca, Sr—Ca nitride, Si nitride, Eu compound Eu₂O₃And add Mn.
[0058]
Finally, Sr, Ca, Sr—Ca nitride, Si nitride, Eu compound Eu₂O₃The mixture is calcined in an ammonia atmosphere. Mn was added by firing (Sr_XCa_1-X)₂Si₅N₈: A phosphor represented by Eu can be obtained. The reaction formula of the base nitride phosphor by this firing is shown below.
[0059]
[Chemical 1]

However, the composition of the target phosphor can be changed by changing the blending ratio of each raw material.
[0060]
The firing temperature can be in the range of 1200 to 1700 ° C, but the firing temperature is preferably 1400 to 1700 ° C. It is preferable to use a one-step baking in which the temperature is gradually raised and the baking is performed at 1200 to 1500 ° C. for several hours, but the first baking is performed at 800 to 1000 ° C. and the heating is gradually started from 1200. Two-stage firing (multi-stage firing) in which the second stage firing is performed at 1500 ° C. can also be used. The phosphor material is preferably fired using a boron nitride (BN) crucible and boat. In addition to crucible made of boron nitride, alumina (Al₂O₃) Material crucibles can also be used.
[0061]
By using the above manufacturing method, it is possible to obtain a target phosphor.
[0062]
In the embodiment of the present invention, a nitride-based phosphor is used as the phosphor that emits reddish light. In the present invention, the above-described YAG-based phosphor can emit red light. It is also possible to provide a light emitting device including a simple phosphor. Such a phosphor capable of emitting red light is a phosphor that emits light when excited by light having a wavelength of 400 to 600 nm.₂O₂S: Eu, La₂O₂S: Eu, CaS: Eu, SrS: Eu, ZnS: Mn, ZnCdS: Ag, Al, ZnCdS: Cu, Al, and the like. Thus, by using a phosphor capable of emitting red light together with a YAG phosphor, it is possible to improve the color rendering properties of the light emitting device.
[0063]
(First phosphor and second phosphor)
In the present embodiment, the nitride-based phosphor absorbs part of the blue light emitted by the LED chip 102 and emits light in the yellow to red region. Using a nitride-based phosphor together with a YAG-based phosphor in the light-emitting device having the above-described configuration, the blue light emitted from the LED chip 102 and the yellow to red light by the nitride-based phosphor are mixed and warmed Provided is a light emitting device that emits white light. It is preferable that the phosphor added in addition to the nitride-based phosphor contains an yttrium / aluminum oxide phosphor activated with cerium. This is because it can be adjusted to a desired chromaticity by containing the yttrium aluminum oxide phosphor. The yttrium / aluminum oxide phosphor activated with cerium absorbs part of the blue light emitted by the LED chip 102 and emits light in the yellow region. Here, the blue light emitted by the LED chip 102 and the yellow light of the yttrium / aluminum oxide fluorescent material emit light blue-white by mixing colors. Therefore, the yttrium / aluminum oxide phosphor and the phosphor emitting red light are mixed together in the coating member 101 having translucency and combined with the blue light emitted by the LED chip 102 to produce a white system. Can be provided. Particularly preferred is a white light emitting device whose chromaticity is located on the locus of black body radiation in the chromaticity diagram. However, in order to provide a light emitting device having a desired color temperature, the amount of phosphor of the yttrium / aluminum oxide phosphor and the amount of phosphor of red light emission can be appropriately changed. This light-emitting device that emits white-based mixed color light improves the special color rendering index R9.
[0064]
Conventionally, a white light emitting device using a semiconductor element is obtained by adjusting the balance between blue light from a light emitting element and green to red light from a phosphor in accordance with human visual sensitivity and mixing these lights. . Usually, the white color tone of a light emitting device using a semiconductor light emitting element can be adjusted by adjusting the balance of light emission in a rated drive region where the output characteristics of the light emitting device are stable. However, in the case of a liquid crystal backlight and a dimmable illumination light source, these light emitting devices are used by changing input power and current density. In the prior art, if the current density is changed to adjust the output of the light emitting device, the balance of light emission is lost and color tone deviation occurs, reducing the quality of the light source. Hereinafter, embodiments of the present invention will be described in detail.
[0065]
First, referring to FIG.
[0066]
By increasing the input current, the light emitting element shifts the peak wavelength of the emission spectrum of the light emitting element to the short wavelength side. This is because when the input current is increased, the current density increases and the energy level increases. This is due to factors such as an increased band gap. The amplitude of fluctuation between the peak wavelength of the emission spectrum when the current density to the light emitting element is small and the peak wavelength of the emission spectrum when the input current is increased is, for example, from 20 mA to 100 mA in this embodiment. When the current is increased, it is about 10 nm.
[0067]
This will be described with reference to FIGS.
[0068]
For example, a YAG phosphor is used as the first phosphor. The YAG phosphor of the phosphor 3 has an excitation spectrum peak wavelength of about 448 nm. When the emission intensity at the peak wavelength of 448 nm of this excitation spectrum is 100, the emission intensity at 460 nm is 95. Therefore, the emission intensity is higher when the YAG phosphor is excited at 448 nm than when the YAG phosphor is excited at 460 nm. From this, the relationship between the light emitting element and the first phosphor will be outlined. Immediately after supplying current to the light emitting element, a light emitting element having a light emission peak wavelength of 460 nm is selected. This light emitting element emits blue light. The YAG phosphor excited by the blue light of the light emitting element emits green light of about 530 nm. Next, the input current of the light emitting element is increased and a current of 100 mA is input. As a result, the light emission output of the semiconductor element increases, and the light emitting element and the ambient temperature increase accordingly. In addition, the emission peak wavelength of the light emitting element shifts from 460 nm to 450 nm. At this time, the YAG-based phosphor has higher emission intensity when the peak wavelength of the excitation spectrum is 450 nm than 460 nm. For this reason, the YAG phosphor exhibits relatively high emission luminance when the excitation light is 450 nm rather than 460 nm. Moreover, the luminous efficiency of blue light is lower at 450 nm than at 460 nm. Therefore, since the luminance of the blue light of the light emitting element and the green light of the YAG phosphor increases, the relative intensity of the green light with respect to the blue light increases. Therefore, the color tone of the light emitting device slightly shifts to the green light side in the straight line connecting the blue light and the green light. On the other hand, since the phosphor decreases in luminance due to an increase in ambient temperature, the relative intensity of green light to blue light becomes weak. Therefore, the color tone of the light emitting device slightly shifts to the blue light side in the straight line connecting the blue light and the green light.
Color balance is suppressed by these balances.
[0069]
This will be described with reference to FIGS.
[0070]
For example, a nitride-based phosphor is used as the second phosphor. The nitride phosphor of phosphor 5 has an excitation spectrum peak wavelength of about 450 nm between 350 nm and 500 nm. When the emission intensity at a peak wavelength of 450 nm of this excitation spectrum is 100, the emission intensity at 460 nm is 95. Therefore, the emission intensity is higher when the YAG phosphor is excited at 450 nm than when the nitride phosphor is excited at 460 nm. From this, the relationship between the light emitting element and the second phosphor will be outlined. When the input current density to the light emitting element is low, a light emitting element having a light emission peak wavelength of 460 nm is selected. This light emitting element is the same as that used when exciting the first phosphor. This light emitting element emits blue light. The nitride phosphor excited by the blue light of the light emitting element emits red light of about 637 nm. Next, the input current of the light emitting element is increased and a current of 100 mA is input. As a result, the light emission output of the semiconductor element increases, and the light emitting element and the ambient temperature increase accordingly. In addition, the emission peak wavelength of the light emitting element shifts from 460 nm to 450 nm. At this time, the nitride-based phosphor has a relatively high emission intensity when the peak wavelength of the excitation spectrum is 450 nm rather than 460 nm. Therefore, the nitride-based phosphor exhibits higher light emission luminance when the excitation light is 450 nm than at 460 nm. Moreover, the luminous efficiency of blue light is lower at 450 nm than at 460 nm. Therefore, the blue light of the light emitting element and the red light of the nitride-based phosphor have high brightness of the red light, so that the relative intensity of the red light with respect to the blue light is increased. Therefore, the color tone of the light emitting device slightly shifts to the red light side in the straight line connecting the blue light and the red light. On the other hand, since the phosphor decreases in luminance due to an increase in ambient temperature, the relative intensity of green light to blue light becomes weak. Therefore, the color tone of the light emitting device slightly shifts to the blue light side in the straight line connecting the blue light and the red light. Color balance is suppressed by these balances.
[0071]
The relationship between the first phosphor and the second phosphor will be outlined. The nitride-based phosphor absorbs not only light from the light-emitting element but also light near the peak wavelength (about 530 nm) of the emission spectrum of the YAG-based phosphor, and is excited.
[0072]
Further, the interrelationship between the aforementioned light emitting element and the first phosphor and the second phosphor will be described in detail. Heat is generated by supplying current to the light emitting element. Increasing the input current to the light emitting element increases the amount of heat generation. Most of the heat generated in the light emitting element is accumulated in the coating member and the phosphor. Thereby, ambient temperature rises and the light emission output of fluorescent substance itself falls. On the other hand, by increasing the input current to the light emitting element, the peak wavelength of the emission spectrum of the light emitting element shifts to the short wavelength side as described above, and the emission intensity of the first phosphor increases. By these interactions, the first phosphor can maintain the color tone and the light emission output with almost no change. Also, the second phosphor can maintain the color tone and the light emission output with almost no change, like the first phosphor.
[0073]
The color tone of the light emitting device is determined by the interaction of light emission of the light emitting element, the first phosphor, and the second phosphor. That is, in the light emitting element, the peak wavelength of the emission spectrum shifts to the short wavelength side as the input current increases. Along with this, the emission intensity of the first phosphor and the second phosphor excited by the light emitting element increases. On the other hand, as the input current to the light emitting element increases, the light emitting element generates heat. Due to this heat generation, heat is accumulated in the first phosphor, the second phosphor, the coating member, and the like. Due to this heat storage, the light emission output of these phosphors decreases. Therefore, even when the input current to the light emitting element is increased, the color tone shift of the light emitting device can be suppressed. By selecting the first phosphor and the second phosphor, even when the color tone shift occurs in the light emitting device, it is possible to hardly feel the color shift visually. Considering the interaction between the light emitting element, the first phosphor, and the second phosphor, the color tone of the light emitting device shifts in the direction in which the color tone x increases and the color tone y also increases. The direction in which the color tone shifts varies along the locus of black body radiation. The color misregistration along the locus of black body radiation is less sensitive to human color perception than the color misalignment in the direction perpendicular to the locus of black body radiation. In addition, due to the interaction (self-absorption, etc.) between the first phosphor and the second phosphor, the width of the color shift is narrow. Therefore, the present invention can provide a light-emitting device that prevents color shift. INDUSTRIAL APPLICABILITY The present invention is particularly effective in light-emitting devices that are easily affected by heat, for example, power-driven semiconductor light-emitting devices with large DC drive and input power, light-emitting devices that are difficult to dissipate and store heat easily, and driving environments .
[0074]
It is also possible to use a phosphor whose excitation spectrum hardly changes within a range in which the light emitting element shifts to the short wavelength side due to an increase in input power. For example, when the nitride-based phosphor of the phosphor 5 of the example is used, the excitation spectrum hardly changes from 420 nm to 450 nm, but the effect is exhibited by the combination with YAG having the characteristics of the present invention. In addition, the present invention provides the light emitting device of the present invention even when a phosphor other than the above having the characteristics of the temperature characteristics of the phosphor and having the characteristics of the excitation spectrum and the light emitting element is used. it can.
[0075]
In addition, the position of the excitation spectrum and the peak wavelength of the light emitting element can be adjusted in consideration of the thermal resistance value and heat dissipation characteristics of the light emitting device, the junction temperature of the light emitting element, and the like.
[0076]
The relationship between the color name and the chromaticity coordinates in the specification is based on the JIS standard (JIS Z8110).
[0077]
The particle size is F. S. S. S. No. (Fisher Sub Sieve Sizer's No.) Value by air permeation method.
[0078]
[LED chip 102]
The light emitting element used in the present invention is the LED chip 102. When a light emitting device that emits light having a wavelength converted by exciting the phosphor by combining the phosphor and the light emitting element, an LED chip that emits light having a wavelength that can excite the phosphor is used. In the LED chip 102, a semiconductor such as GaAs, InP, GaAlAs, InGaAlP, InN, AlN, GaN, InGaN, AlGaN, or InGaAlN is formed as a light emitting layer on a substrate by MOCVD or the like. Examples of the semiconductor structure include a homostructure having a MIS junction, a PIN junction, a PN junction, etc., a heterostructure, or a double heterostructure. Various emission wavelengths can be selected depending on the material of the semiconductor layer and the degree of mixed crystal. In addition, a single quantum well structure or a multiple quantum well structure in which the semiconductor active layer is formed in a thin film in which a quantum effect is generated can be used. Preferably, a nitride compound semiconductor (general formula In) capable of efficiently emitting a relatively short wavelength capable of efficiently exciting the phosphor._iGa_jAl_kN, where 0 ≦ i, 0 ≦ j, 0 ≦ k, i + j + k = 1).
[0079]
When a gallium nitride compound semiconductor is used, a material such as sapphire, spinel, SiC, Si, ZnO, or GaN is preferably used for the semiconductor substrate. In order to form gallium nitride with good crystallinity, it is more preferable to use a sapphire substrate. When a semiconductor film is grown on a sapphire substrate, it is preferable to form a gallium nitride semiconductor having a PN junction on a buffer layer made of GaN, AlN or the like. In addition, SiO on the sapphire substrate₂A GaN single crystal itself selectively grown using as a mask can also be used as a substrate. In this case, after forming each semiconductor layer, SiO₂It is also possible to separate the light emitting element and the sapphire substrate by etching away. Gallium nitride-based compound semiconductors exhibit N-type conductivity without being doped with impurities. When forming a desired N-type gallium nitride semiconductor such as improving luminous efficiency, Si, Ge, Se, Te, C, etc. are preferably introduced as appropriate as N-type dopants. On the other hand, when a P-type gallium nitride semiconductor is formed, a P-type dopant such as Zn, Mg, Be, Ca, Sr, or Ba is doped.
[0080]
Since a gallium nitride compound semiconductor is difficult to become P-type only by doping with a P-type dopant, it is preferable to make it P-type by annealing by heating in a furnace, low-speed electron beam irradiation, plasma irradiation, etc. after introducing the P-type dopant. . Specific examples of the layer structure of the light-emitting element include an N-type contact layer, which is a gallium nitride semiconductor, and an aluminum nitride / gallium semiconductor on a sapphire substrate or silicon carbide having a buffer layer in which gallium nitride, aluminum nitride, or the like is formed at a low temperature. An N-type cladding layer, an active layer that is an indium gallium nitride semiconductor doped with Zn and Si, a P-type cladding layer that is an aluminum nitride-gallium semiconductor, and a P-type contact layer that is a gallium nitride semiconductor Are preferable. In order to form the LED chip 102, in the case of the LED chip 102 having a sapphire substrate, an exposed surface of a P-type semiconductor and an N-type semiconductor is formed by etching or the like, and then a sputtering method or a vacuum evaporation method is performed on the semiconductor layer. Each electrode is formed in a desired shape. In the case of a SiC substrate, a pair of electrodes can be formed using the conductivity of the substrate itself.
[0081]
Next, the formed semiconductor wafer or the like is directly fully cut by a dicing saw with a blade having a diamond cutting edge, or a groove having a width wider than the cutting edge width is cut (half cut), and then the semiconductor is applied by an external force. Break the wafer. Alternatively, after a very thin scribe line (meridian) is drawn on the semiconductor wafer by, for example, a grid shape by a scriber in which the diamond needle at the tip moves reciprocally linearly, the wafer is divided by an external force and cut into chips. In this way, the LED chip 102 which is a nitride compound semiconductor can be formed.
[0082]
In the light emitting device of the present invention that excites the phosphor to emit light, the main emission wavelength of the LED chip 102 is preferably 350 nm or more and 530 nm or less in consideration of the complementary color with the phosphor and the like.
[0083]
[Conductive wire 103]
The conductive wire 103 is required to have good ohmic properties with the electrodes of the LED chip 102, mechanical connectivity, electrical conductivity and thermal conductivity. The thermal conductivity is 0.01 cal / (s) (cm²) (° C./cm) or more, more preferably 0.5 cal / (s) (cm²) (° C./cm) or more. In consideration of workability and the like, the diameter of the conductive wire is preferably Φ10 μm or more and Φ45 μm or less. In particular, the conductive wire is likely to break at the interface between the coating portion containing the phosphor and the mold member not containing the phosphor. Even if the same material is used, it is considered that wire breakage easily occurs because the substantial amount of thermal expansion differs depending on the phosphor. Therefore, the diameter of the conductive wire is more preferably 25 μm or more, and more preferably 35 μm or less from the viewpoint of light emission area and ease of handling.
[0084]
Specific examples of such conductive wires include conductive wires using metals such as gold, copper, platinum, and aluminum, and alloys thereof. Such a conductive wire can easily connect the electrode of each LED chip to the inner lead, the mount lead, and the like by a wire bonding device.
[0085]
[Mount lead 105]
As the mount lead 105, the LED chip 102 is disposed, and it is sufficient that the mount lead 105 has a size sufficient to be stacked by a die bond apparatus or the like. In addition, when a plurality of LED chips are installed and the mount lead is used as a common electrode of the LED chip, sufficient electrical conductivity and connectivity with a bonding wire or the like are required. Further, when the LED chip is arranged in the cup on the mount lead and the phosphor is filled inside, it is possible to prevent the pseudo lighting by the light from another light emitting diode arranged in the vicinity. .
[0086]
The LED chip 102 and the mount lead 105 can be bonded to each other with a thermosetting resin or the like. Specifically, an epoxy resin, an acrylic resin, an imide resin, etc. are mentioned. In addition, Ag paste, carbon paste, metal bumps, or the like can be used for bonding and electrical connection with the mount lead using a face-down LED chip or the like. Further, in order to improve the light utilization efficiency of the light emitting diode, the surface of the mount lead on which the LED chip is arranged may be a mirror surface, and the surface may have a reflection function. In this case, the surface roughness is preferably 0.1 S or more and 0.8 S or less. The specific electric resistance of the mount lead is preferably 300 μΩ-cm or less, more preferably 3 μΩ-cm or less. In addition, when a plurality of LED chips are stacked on the mount lead, the heat generation from the LED chip increases, so that the thermal conductivity is required to be good. Specifically, 0.01 cal / (s) (cm²) (° C./cm) or more, preferably 0.5 cal / (s) (cm²) (° C./cm) or more. Examples of materials that satisfy these conditions include iron, copper, iron-containing copper, tin-containing copper, and ceramic with a metallized pattern.
[0087]
[Inner lead 106]
The inner lead 106 is intended to connect the conductive wire 103 connected to the LED chip 102 disposed on the mount lead 105. When a plurality of LED chips are provided on the mount lead, it is necessary to be able to arrange the conductive wires so that they are not in contact with each other. Specifically, as the distance from the mount lead increases, the area of the end surface of the inner lead that is wire-bonded increases to prevent contact of the conductive wire that is connected to the inner lead that is further away from the mount lead. it can. The roughness of the connecting end surface with the conductive wire is preferably 1.6 S or more and 10 S or less in consideration of adhesion. In order to form the tip of the inner lead in various shapes, the shape of the lead frame may be determined in advance by the mold, and it may be punched or formed, or after all the inner leads are formed, the upper part of the inner lead You may form by shaving a part of. Furthermore, after punching and forming the inner lead, it is possible to simultaneously form the desired end face area and end face height by applying pressure from the end face direction.
[0088]
The inner lead is required to have good connectivity and electrical conductivity with a bonding wire or the like that is a conductive wire. The specific electric resistance is preferably 300 μΩ-cm or less, more preferably 3 μΩ-cm or less. Examples of materials that satisfy these conditions include iron, copper, iron-containing copper, tin-containing copper and copper, gold, silver plated aluminum, iron, copper, and the like.
[0089]
[Coating part 101]
The coating portion 101 used in the present invention is provided on the cup of the mount lead separately from the mold member 104, and contains a phosphor that converts the light emission of the LED chip. As a specific material for the coating portion, a transparent resin having excellent weather resistance such as epoxy resin, urea resin, and silicone, and a light-transmitting inorganic material such as silica sol and glass having excellent light resistance are preferably used. Here, in particular, the coating portion using silicon oxide or aluminum oxide as a specific material is filled with a solution containing a phosphor in a metal alkoxide such as ethyl silicate or aluminum alcoholate, and then sintered and dried. Is formed. Moreover, you may contain a diffusing agent with fluorescent substance. As a specific diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, silicon dioxide or the like is preferably used.
[0090]
[Mold member 104]
The mold member 104 can be provided in order to protect the LED chip 102, the conductive wire 103, the coating portion 101 containing the phosphor, and the like from the outside according to the use application of the light emitting diode. In general, the mold member can be formed using a resin. Moreover, although a viewing angle can be increased by containing a fluorescent substance, the directivity from the LED chip 102 can be relaxed and the viewing angle can be further increased by adding a diffusing agent to the resin mold. Furthermore, by forming the mold member 104 in a desired shape, it is possible to have a lens effect that focuses or diffuses light emitted from the LED chip. Accordingly, a plurality of mold members 104 may be stacked. Specifically, a convex lens shape, a concave lens shape, an elliptical shape as viewed from the light emission observation surface, or a combination of them. As a specific material of the mold member 104, a transparent resin or glass having excellent weather resistance such as an epoxy resin, a urea resin, or a silicone resin is preferably used. As the diffusing agent, barium titanate, titanium oxide, aluminum oxide, silicon oxide, silicon dioxide, or the like is preferably used. Furthermore, in addition to the diffusing agent, a phosphor can also be contained in the mold member. Therefore, the phosphor may be contained in the mold member or may be contained in other coating portions. Alternatively, the coating portion may be formed using a resin containing a phosphor, and a different member obtained by replacing the mold member with glass or the like. In this case, a light-emitting device with high productivity and less influence of moisture or the like can be obtained. Further, in consideration of the refractive index, the mold member and the coating portion may be formed using the same member. In the present invention, adding a diffusing agent or a coloring agent to the mold member can hide the coloring of the phosphor viewed from the light emission observation surface side. In addition, the coloring of the phosphor means that the phosphor of the present invention emits light by absorbing the blue component of the strong external light. Therefore, it seems to be colored yellow. In particular, depending on the shape of the mold member such as a convex lens shape, the colored portion may appear enlarged. Such coloring may be undesirable in terms of design. The diffusing agent contained in the mold member can make the mold member invisible white by coloring the mold member milky white and the colorant in a desired color. Therefore, the color of the phosphor is not observed from such a light emission observation surface side.
[0091]
Moreover, when the main light emission wavelength of the light emitted from the LED chip is 430 nm or more, it is more preferable in terms of weather resistance to contain an ultraviolet absorber as a light stabilizer in the mold member.
[0092]
【Example】
Hereinafter, examples according to the present invention will be described in detail with reference to comparative examples. Needless to say, the present invention is not limited to the following examples.
[0093]
Example 1
As shown in FIG. 1, the light emitting diode 100 formed in Comparative Examples 1 to 5 is a lead type light emitting diode including a mount lead 105 and an inner lead 106. After the LED chip 102 is placed on the cup part and the coating part 101 containing phosphors combined as shown in Table 2 below is filled in the cup part so as to cover the LED chip 102, the resin is formed by the mold member 104. Molded and configured. Here, the n-side electrode and the p-side electrode of the LED chip 102 are connected to the mount lead 105 and the inner lead 106 using the wire 103, respectively.
[0094]
FIG. 3 shows the excitation absorption spectrum of the YAG phosphor used in this example. FIG. 4 shows the emission spectrum of the YAG phosphor used in this example. In this example, as YAG phosphors having different compositions, (Y_0.8Gd_0.2)₃Al₅O₁₂: Ce (hereinafter referred to as “phosphor 1”), Y₃Al₅O₁₂: Ce (hereinafter referred to as “phosphor 2”), and Y₃(Al_0.8Ga_0.2)₅O_{1 2}: Ce (hereinafter referred to as “phosphor 3”) was used. These phosphors are phosphors that absorb and excite blue light from the LED chip and emit yellow to green light.
[0095]
FIG. 5 shows the excitation absorption spectrum of the nitride phosphor used in this example. FIG. 6 shows an emission spectrum of the nitride phosphor used in this example. In this example, as nitride phosphors having different compositions, (Ca_0.985Eu_0.015)₂Si₅N₈(Hereinafter referred to as “phosphor 4”), and (Sr_0.679Ca_0.291Eu_0.03)₂Si₅N₈(Hereinafter referred to as “phosphor 5”) was used. These phosphors are phosphors that absorb and excite blue light from the LED chip and emit red light. The composition of the phosphor and the peak wavelength of the emission spectrum are shown below.
[0096]
[Table 1]

First, after forming a light emitting diode by using phosphors 1 to 5 one by one, a 20 mA pulse current is applied to raise the ambient temperature under conditions where the heat generation of the LED chip itself can be ignored, The light emission output of the light emitting diode with respect to temperature was measured. Next, with respect to each of the phosphors 1 to 5, the relative output of LED light emission based on 25 ° C. was obtained, and the ambient temperature-relative light output characteristics are shown in FIGS. 10 to 14. FIG. 10 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 1 in one embodiment of the present invention. FIG. 11 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 2 in one embodiment of the present invention. FIG. 12 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 3 in one embodiment of the present invention. FIG. 13 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 4 in one embodiment of the present invention. FIG. 14 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 5 in one embodiment of the present invention. 10 to 14 are all conditions of If = 20 mA, f = 200 Hz, and Duty = 1%. Further, when the ambient temperature of the light emitting diode is changed by 1 ° C., the LED light emission relative output reduction rate is obtained for each phosphor, and the light emission output reduction rate with respect to the temperature rise of the first phosphor and the second phosphor is as follows. It shows in Table 2.
[0097]
[Table 2]

The LED chip 102 used for exciting the phosphor in this embodiment is a light emitting element in which an InGaAlN compound semiconductor is formed as a light emitting layer, and the peak wavelength of the emission spectrum is 460 nm. The current density is 3 to 300 A / cm.²The chromaticity coordinates are shifted to the low color temperature side along the black body radiation locus. FIG. 2 is a diagram showing current characteristics of the emission spectrum when the current flowing through the LED chip 102 is changed. FIG. 2 shows the current-relative emission spectral characteristics of the phosphor excitation 460 nm LED under the conditions of Ta = 25 ° C., f = 200 Hz, and Duty = 1%. As shown in FIG. 2, in the current characteristics of the emission spectrum, the peak wavelength shifts to the short wavelength side as the input current is increased.
[0098]
Therefore, as shown in FIG. 3, the peak wavelength of the excitation absorption spectrum of the three phosphors 1 to 3 is located at the position where the peak wavelength of the emission spectrum of the LED chip is shifted by the increase of the current input to the LED chip. Make the position almost the same. Here, the difference between the peak wavelength of the excitation absorption spectrum of the phosphors 1 to 3 and the peak wavelength of the emission spectrum of the LED chip is preferably 40 nm or less. By using such a phosphor, the excitation efficiency of the phosphor is improved, and the amount of light emitted from the LED without being wavelength-converted is reduced, thereby preventing the chromaticity deviation of the light emitting device. Can do.
[0099]
Here, when the phosphor 3 is used, the emission spectrum of the phosphor 3 moves to a shorter wavelength side than the emission spectrum of the phosphor 1 as shown in FIG. Therefore, although the chromaticity shift of the light emitting device can be prevented by shifting the peak position of the excitation absorption spectrum of the YAG phosphor, the light emission of the light emitting device deviates from the black body radiation locus. Is added to the mixed color light to adjust the chromaticity coordinates near the black body radiation locus.
[0100]
The compounding ratio of the nitride phosphor to the YAG phosphor is shown in Table 3 below.
[0101]
[Table 3]

Table 4 below shows the measurement results of the optical characteristics when the light emitting diodes were formed in Example 1 and Comparative Examples 1 to 3.
[0102]
[Table 4]

As shown in Table 4, the color rendering properties in the case of Example 1 and Comparative Example 3 are both Ra of 85 or more, and the color rendering properties can be improved as compared with other comparative examples. Moreover, FIG. 7 is a figure which shows the change of chromaticity with respect to ambient temperature about Example 1 and Comparative Examples 1-3. FIG. 7 shows the conditions of If = 20 mA, f = 200 Hz, and Duty = 1%. As shown in FIG. 7, the chromaticity changes in the direction of the thick arrow in the figure as the temperature rises in both Example 1 and Comparative Examples 1 to 3.
[0103]
FIG. 8 is a diagram showing a change in chromaticity with respect to a pulse current applied to the LED chip in Example 1 and Comparative Examples 1 to 3. FIG. 8 shows the conditions of Ta = RT (room temperature), f = 200 Hz, and Duty = 1%. In this embodiment, by applying a pulse current of 1 to 100 mA (1, 5, 10, 20, 40, 60, 80, 100 mA) to the LED chip, the white LED is formed under the condition that the heat generation of the LED chip can be ignored. The current characteristics of the LED to which the red component was added were confirmed. As shown in FIG. 8, in the case of Comparative Example 1 to Comparative Example 3, as the input current is increased, the chromaticity is in the high color temperature region so as to move away from the black body radiation locus in the direction of the arrow. Move to. On the other hand, in the case of Example 1, it can be seen that the chromaticity moves to the low chromaticity side in the direction of the arrow so as to substantially follow the black body radiation locus.
[0104]
FIG. 9 is a diagram illustrating a change in chromaticity when DC driving is performed for Example 1 and Comparative Example 1. FIG. FIG. 9 shows the conditions of If = 1 mA, 5 mA, 10 mA, 20 mA, 40 mA, 60 mA, Ta = RT (room temperature), and DC drive. In the case of Comparative Example 1, when the current is increased from 1 mA to 5 mA, 10 mA, 20 mA, 40 mA, and 60 mA, the chromaticity at each current value increases from the black body radiation locus to the direction of the arrow. Move to the side. On the other hand, in the case of the first embodiment, the change in the chromaticity of light due to the color mixture is within the range of the X coordinate from 0.326 to 0.333 and the Y coordinate from 0.343 to 0.348 on the chromaticity diagram. is there. That is, in the case of Example 1, the chromaticity of the light due to the color mixture moves at a position substantially along the black body radiation locus even when the current is increased, and the chromaticity hardly changes. As described above, the change in chromaticity hardly occurs in the case of Example 1 because the change in chromaticity toward the high chromaticity along the black body radiation locus as shown in FIG. 7 as the ambient temperature-chromaticity characteristic. And the change in chromaticity toward the low chromaticity side along the black body radiation locus as shown in FIG. 8 as the input current-chromaticity characteristics cancel each other.
[0105]
In the configuration of Example 1, the emission output decrease rate with respect to the ambient temperature of the phosphors to be combined is 2.0 × 10.^-3[A. u. / ° C.] and smaller than the phosphors of the other examples, and the difference in the light output reduction rate is 2.0 × 10^-4[A. u. / ° C.] and a smaller combination than the other examples. That is, the light emission output reduction rate with respect to the temperature rise of the phosphor 3 and the phosphor 5 is substantially equal. With this configuration, even if the light emission outputs of the phosphor 3 and the phosphor 5 are reduced due to an increase in ambient temperature due to heat generation of the light emitting element, the light emission output difference between the phosphor 3 and the phosphor 5 is different. Are kept almost the same without being affected by the ambient temperature. That is, by employing the structure of the present invention, the color rendering property is improved regardless of a change in the ambient temperature of the light-emitting device, in particular, the ambient temperature of the light-emitting device due to a change in current, and a light-emitting device in which chromaticity deviation hardly occurs. It is possible. In addition, when the light emitting device according to the present invention and a light guide plate that guides the light emitted from the light emitting device to the light emission observation surface side are combined to form a backlight light source that can be used as a constituent member of a liquid crystal display, It is possible to improve a color rendering property regardless of a change and to provide a backlight light source that hardly causes chromaticity deviation.
[0106]
(Examples 2 and 3)
In this embodiment, a YAG phosphor and a nitride phosphor are combined to form a light emitting device capable of emitting warm light, that is, light in a so-called light bulb color region (color temperature 2500K to 3800K). The composition formula, emission peak wavelength λp [nm], and color tone of the YAG phosphors (phosphors 6, 7) and nitride phosphors (phosphors 8, 9) used in this example are shown in Table 5 below. As shown in
[0107]
[Table 5]

Further, the emission output decrease rate of each phosphor measured in the same manner as in Example 1 [a. u. / ° C.] is as shown in Table 6 below.
[0108]
[Table 6]

In this example, resin, phosphor 7, phosphor 8, and phosphor 9 were combined in the weight ratios shown in Table 7 below to form a light emitting device in the same manner as in Example 1, and the light bulb color was changed. Enable to emit light.
[0109]
[Table 7]

The measurement results of the optical characteristics of the light emitting devices formed in Example 2 and Example 3 are shown in Table 8 below.
[0110]
[Table 8]

FIG. 19 is a diagram illustrating a change in chromaticity when DC driving is performed in the second and third embodiments. FIG. 19 shows the condition of Ta = RT (room temperature). In the case of Comparative Example 4 described below, when the current is increased from 1 mA to 5 mA, 10 mA, 20 mA, 40 mA, and 60 mA, the chromaticity at each current value intersects with the black body radiation locus, resulting in a high color temperature. Move to the side. On the other hand, in the case of Example 2 and Example 3, the chromaticity hardly changes even when the input current is changed. In the configurations of Example 2 and Example 3, the emission output decrease rate with respect to the ambient temperature of the phosphors to be combined is 3.0 × 10.^-3[A. u. / ° C.] The following is made smaller than the phosphor 6 of Comparative Example 4. By adopting the structure of the present invention, a light emitting device in which the chromaticity shift hardly occurs and the color rendering property is improved regardless of the ambient temperature of the light emitting element, in particular, the ambient temperature of the phosphor due to the change of current. Is possible.
[0111]
A light emitting device capable of emitting a light bulb color is formed as Comparative Example 4 in the same manner as in Examples 2 and 3 described above using the YAG phosphor 6 shown in Table 5 alone. Here, the weight ratio of the resin and the phosphor in this comparative example is shown in Table 7. The measurement results of the optical characteristics of the light emitting device formed as Comparative Example 4 are shown in Table 8 below together with Examples 2 and 3. Further, FIG. 19 shows a change in chromaticity when DC driving is performed for Comparative Example 4. As shown in FIG. 19, in the light emitting device in this comparative example, when the current is increased from 1 mA to 5 mA, 10 mA, 20 mA, 40 mA, and 60 mA, the chromaticity at each current value crosses the black body radiation locus. Move to the higher color temperature. This is because the emission peak wavelength of the LED chip moves to the short wavelength side as the current increases as shown in FIG. 2, and shifts from the peak wavelength of the excitation absorption spectrum of the phosphor 6 shown in FIG. This is probably because the wavelength conversion efficiency of the phosphor decreases, and the wavelength component of light from the LED chip that is not wavelength-converted by the phosphor increases. On the other hand, the peak wavelength of the excitation absorption spectrum of the phosphor 7 used in Example 2 and Example 3 is shorter than the peak wavelength of the phosphor 6, and the emission peak wavelength of the LED chip is input. Since it exists in the range which moves by the change of an electric current, the wavelength conversion efficiency of fluorescent substance does not fall. Further, in the case of Example 2 and Example 3, a nitride-based phosphor in which the peak wavelength of the excitation absorption spectrum is within a range in which the emission peak wavelength of the LED chip moves due to a change in input current is referred to as a YAG-based phosphor. Light emitting device capable of emitting light bulb color with almost no chromaticity deviation and improved color rendering regardless of the ambient temperature of the light emitting element due to the change of current, that is, the change of the ambient temperature of the phosphor. It can be.
[0112]
(Example 4)
In the present invention, in addition to the YAG phosphors shown in Tables 1 and 5, the composition formula is Y_2.965Ce_0.035Al₅O₁₂With reference to the phosphor represented by the formula, the phosphor is obtained by substituting Al for Ga or Y for Gd. That is, for substitution with Ga, the general formula Y_2.965Ce_0.035(Al_1-XGa_X)₅O₁₂In the above, a phosphor substituted in the range of 0 <X ≦ 0.8 is arbitrarily formed._1-YGd_Y)_2.965Ce_0.035Al₅O₁₂Then, a phosphor substituted in the range of 0 <X ≦ 0.9 is arbitrarily formed. In addition, the general formula Y_3-ZCe_ZAl₅O₁₂, A phosphor is arbitrarily formed in the range of 0.015 ≦ Z ≦ 0.600.
[0113]
Similar to the above-described embodiment, a light emitting device capable of improving a color rendering property and emitting a desired color tone with almost no chromaticity deviation by appropriately combining the phosphor and the nitride phosphor in the present embodiment. can do.
[0114]
【The invention's effect】
According to the present invention, the chromaticity shift can be reduced and the color rendering can be improved by changing the ambient temperature of the light emitting element, in particular, the ambient temperature of the phosphor due to the change of the input current of the light emitting device. A light emitting device can be formed.
[0115]
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a light emitting diode according to an embodiment of the present invention.
FIG. 2 is a graph showing an emission spectrum characteristic of an LED chip in an example of the present invention.
FIG. 3 is a diagram showing an excitation absorption spectrum of a YAG phosphor in one example of the present invention.
FIG. 4 is a diagram showing an emission spectrum of a YAG phosphor in one example of the present invention.
FIG. 5 is a diagram showing an excitation absorption spectrum of a nitride-based phosphor in one example of the present invention.
FIG. 6 is a diagram showing an emission spectrum of a nitride-based phosphor in one example of the present invention.
FIG. 7 is a diagram showing ambient temperature-chromaticity characteristics (measurement by pulse driving) in one embodiment of the present invention.
FIG. 8 is a diagram showing current-chromaticity characteristics (measurement by pulse driving) in one embodiment of the present invention.
FIG. 9 is a diagram showing current-chromaticity characteristics (measurement by DC driving) in one embodiment of the present invention.
FIG. 10 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 1 in one embodiment of the present invention.
FIG. 11 is a diagram showing ambient temperature-relative light output characteristics of the phosphor 2 in one embodiment of the present invention.
FIG. 12 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 3 in one embodiment of the present invention.
FIG. 13 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 4 in one embodiment of the present invention.
FIG. 14 is a diagram showing the ambient temperature-relative light output characteristics of the phosphor 5 in one embodiment of the present invention.
FIG. 15 is a diagram showing an excitation absorption spectrum of a YAG phosphor in an example of the present invention.
FIG. 16 is a view showing an emission spectrum of a YAG phosphor in one example of the present invention.
FIG. 17 is a diagram showing an excitation absorption spectrum of a nitride-based phosphor in an example of the present invention.
FIG. 18 is a diagram showing an emission spectrum of a nitride-based phosphor in one example of the present invention.
FIG. 19 is a diagram showing current-chromaticity characteristics (measurement by DC driving) in an example of the present invention.
FIG. 20 is a diagram showing an emission spectrum when the YAG phosphors of phosphors 10 to 13 are excited at EX = 460 nm.
FIG. 21 is a view showing a reflection spectrum of YAG phosphors of phosphors 10 to 13;
FIG. 22 is a diagram showing excitation spectra of YAG phosphors of phosphors 10 to 13;
FIG. 23 is a diagram showing an emission spectrum when the YAG phosphors of the phosphor 14 and the phosphor 15 are excited at EX = 460 nm.
FIG. 24 is a diagram showing an excitation spectrum of a YAG phosphor of phosphor 14.
FIG. 25 is a diagram showing an excitation spectrum of a YAG phosphor of phosphor 15.
[Explanation of symbols]
100: Light emitting diode
101 ... Coating part
102 ... LED chip
103 ... Wire
104 ... Mold member
105 ... Mount lead
106 ... Inner lead

Claims (9)

A light emitting element, a first phosphor that emits light of a different wavelength by absorbing at least part of light from the light emitting element, and light of different wavelength by absorbing at least part of the light from the light emitting element. A second phosphor that emits light,
The emission peak wavelength of the second phosphor is on the longer wavelength side than the emission peak wavelength of the first phosphor,
The peak wavelength of the emission spectrum of the light emitting element is on the longer wavelength side than the peak wavelength of the excitation spectrum of the first phosphor and the excitation spectrum of the second phosphor,
The light emitting element, as the current density increases, the peak wavelength of the emission spectrum of the light emitting element is shifted to the short wavelength side,
The first phosphor has higher excitation efficiency on the short wavelength side than on the long wavelength side in the wavelength change range that occurs when the current density of the light emitting element is changed,
In the second phosphor, in the range of wavelength change that occurs when the current density of the light emitting element is changed, the short wavelength side of the wavelength change range has higher excitation efficiency than the long wavelength side,
When the current density of the light emitting element is increased, light emitted from the light emitting device changes in chromaticity so as to follow a black body radiation locus . The first phosphor and the second phosphor, to claim 1 where the light output reduction rate due to the change in the ambient temperature of the first phosphor and the second phosphor is characterized in that approximately equal The light emitting device described. The light emitting device according to claim 2 , wherein a change in ambient temperature of the first phosphor and the second phosphor is due to a change in input current to the light emitting element. The light emitting device according to any one of claims 1 to 3 , wherein the light emitting element has a peak wavelength of an emission spectrum of 350 nm to 530 nm. The first phosphor has a peak wavelength of an excitation spectrum of the first phosphor on the short wavelength side of the wavelength change range in a wavelength change range that occurs when the current density of the light emitting element is changed. The light emitting device according to claim 1, wherein The first phosphor includes Y and Al, and includes at least one element selected from Lu, Sc, La, Gd, Tb, Eu, and Sm, and one element selected from Ga and In. The light emitting device according to claim 1 , further comprising an yttrium / aluminum / garnet phosphor activated by at least one element selected from rare earth elements. The peak wavelength of excitation spectrum which the first phosphor has the difference between the peak wavelength of the emission spectrum of the light emitting device has found any one of claims 1 to 6, characterized in that at 40nm or less The light-emitting device as described in one. The second phosphor contains N and contains at least one element selected from Be, Mg, Ca, Sr, Ba, and Zn, and C, Si, Ge, Sn, Ti, Zr, and Hf. and at least one element selected, any one of claims 1 to 5, characterized in that it comprises at least one nitride is activated by element phosphor selected from rare earth elements The light emitting device according to 1. The light emitting device according to any one of claims 1 to 8 , wherein the light emitting device is a backlight light source of a liquid crystal display or a light source for illumination.

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