JP4106615B2 - LIGHT EMITTING ELEMENT AND LIGHTING DEVICE USING THE SAME - Google Patents

Description

【００３０】
【表２】

【００３１】
第一の素子１０及び第二の素子２０のいずれにおいても、上記複数の発光単位層、すなわち井戸層Ｗ１‥Ｗｎは、バンドギャップエネルギーの大小配列において、隣接するバンドギャップエネルギー間の差分値ΔＥが、０．４２ｅＶ以下、望ましくは０．２ｅＶ以下とされる。バンドギャップエネルギー間の差分値ΔＥが過度に大きくなると、単位スペクトルのピーク位置間の距離が大きくなりすぎ、合成された波形に大きな波打ちが生じて、滑らかなスペクトルが得られなくなる。なお、差分値ΔＥは、バンドギャップエネルギーが隣接する全ての発光単位層の組に対して等しく設定することもできるし、必要とする発光スペクトル形状に応じて、強度を意識的に高めたい波長域においては間隔を密とし、逆に強度を抑制したい波長域においては間隔を粗とするなど、少なくとも一部の発光単位層の組について不等間隔に設定することもできる。
【００３２】
各発光単位層からの発光強度は、井戸層Ｗ１‥Ｗｎの層厚により調整することができ、例えば後述の量子井戸構造をとらない場合は、ある層厚までは、層厚の増加に伴い発光強度を高めることができる。発光単位層中の井戸層の数が１である場合は、該層厚調整により発光強度の調整が可能である。他方、層厚を増加させる代わりに、図１３に示すように、１つの発光単位層中の井戸層の数を増やすこと、つまり同じバンドギャップエネルギー（Ｅｇ１，Ｅｇ２，‥，Ｅｇｎ）の井戸層を複数層形成することによって発光強度を増加させることができる。つまり、発光単位層からの発光強度は、井戸層の層数によっても調整可能である。この構造においては、個々の井戸層の厚さは増加しないので、キャリア閉じ込め効果の観点においてより有利であり、発光効率を高めることができる。すなわち、井戸層の層厚及び／又は層数にて発光単位層の発光強度が調整される。得るべき擬似連続スペクトルにおいて、発光強度の高い波長域ほど、該波長域に寄与する井戸層の層厚及び／又は層数を大きく設定すればよく、想定した擬似連続スペクトルを得るための発光単位層の設計を容易に行なうことができる。なお、図４に示すように、個々の井戸層は、その井戸層での発光に寄与しないキャリアが他の井戸層に向けて移動することが妨げられないように、障壁層の高さを略一定にそろえておくことが望ましい。その結果、発光波長の短い発光単位層（つまり、バンドギャップエネルギーが広い井戸層を有する発光単位層）ほど井戸深さを小さく設定しておくことが望ましい。
【００３３】
各発光単位層中の井戸層の数は、図１４に示すように、一律に同じ数ずつ設けることもできるし、図１５に示すように、発光単位層の波長域に応じて、井戸層の数を変化させることもできる。すなわち、発光強度の高い波長域ほど、該波長域に寄与する井戸層の層数を大きく設定すれば、擬似連続スペクトルの設計も一層容易となる。
【００３４】
図２及び図３に示すように、第一の素子１０及び第二の素子２０のダブルへテロ発光層部８，１８は、積層方向片側の主表面、すなわち第一の素子１０及び第二の素子２０の各第一主表面ＰＦが光取出面とされており、図４及び図７に示すように、発光単位層（井戸層Ｗ１‥Ｗｎ）は、発光波長の長いものほど、活性層の層厚方向において光取出面より遠い位置に配置されている。発光波長の短い光は、その発光波長のエネルギーよりも小さいバンドギャップを有する半導体に吸収されやすい傾向がある。しかし、上記のように、発光波長の長い発光単位層を光取出面から離して配置すれば、それよりも光取出面側に積層される発光単位層は、いずれも、下層側からの光のエネルギーよりもバンドギャップが広く、吸収が起こりにくくなる。従って、素子の光取出し効率を高めることができる。
【００３５】
他方、後述の演色性調整等の目的で、特定波長域の強度を強調あるいは抑制するために、図１６に示すように、上記のバンドギャップエネルギー順の発光単位層の配列を、一部で作為的に入れ替えることも可能である。バンドギャップエネルギーの順位入れ替えにより、光取出面に近づいた発光単位層（図１６では、バンドギャップエネルギーがＥｇｋ＋１の層）の光取出強度を相対的に強めたり、あるいはそれよりも下層側となる層（図１６では、バンドギャップエネルギーがＥｇｋの層）の発光を、該発光単位層により吸収して発光を抑制したりすることができる。
【００３６】
また、キャリア閉じ込め効果により発光効率を高めるには、量子井戸構造を有するものとして発光単位層を構成することが望ましい。この場合、量子効果発現のため、井戸層の厚さを電子の平均自由行程以下（通常、１０ｎｍ以下、例えば２〜５ｎｍ）に設定する必要がある。量子井戸構造の採用により、波長の安定化や発光効率の向上を図ることができる。また、障壁層厚さも１０ｎｍ以下（ただし、トンネル効果によるキャリア通過を阻むため、５ｎｍ以上が望ましい）に小さくすれば、２〜３％程度までであれば格子定数のずれが許容され、発光波長領域の拡大も容易である。また、バルクでは間接遷移領域となる短波長域でも、量子井戸によるキャリア局在化により直接遷移的な振る舞いに近づけることができ、短波長側への発光波長拡大を図る上で有利となる。
【００３７】
量子井戸構造においては、井戸層の厚さに上記のごとき制約があるため、層厚による発光強度の調整は期待できない。従って、量子井戸構造をなす発光単位層は、井戸層の層数にて発光強度が調整されることとなる。つまり、該発光単位層は、多重量子井戸構造を有したものとなる。多重量子井戸構造においては、サブバンド形成によりキャリア閉じ込め効果がさらに高められ、発光強度を向上させる目的においてより有利となる。なお、量子井戸構造において井戸層は、発光波長の短い発光単位層ほど、キャリアの平均自由行程が小さくなるため、層厚を小さく設定することが望ましい。
【００３８】
なお、発光単位層の変形例としては、図２０に示すように、発光波長の互いに異なる複数の発光単位層Ｗ_Ａを繰り返し単位として、該繰り返し単位Ｗ_Ａを活性層５の層厚方向において複数形成する構成を採用することもできる。この構成は、各波長成分の強度分布をなるべく均一化する必要が場合に有効である。例えば、ダブルへテロ発光層部８，１８の、積層方向片側の主表面が光取出面とされている場合は、繰り返し単位Ｗ_Ａ内にて発光単位層を、発光波長の長いものほど、活性層５，１５の層厚方向において光取出面より遠い位置に配置すれば、光吸収の影響を軽減できるので有利である。
【００３９】
さらに、図２１に示すように、１つの井戸層Ｗｋを、複数の混晶比の化合物半導体の積層体として形成することにより、井戸底形状を階段状としたバンド構造を採用することもできる。この構成は、障壁層の数が少なくて済むので、製造工程が簡略化できる利点がある。
【００４０】
本実施形態では、得るべき擬似連続スペクトルが、白熱電球の連続スペクトルを模した擬似電球光スペクトルを有するように、両素子１０及び２０の活性層５，１５を設計している。図１８は、タングステンフィラメントを用いた白熱電球を、色温度約３０００Ｋにて発光させたときのスペクトル波形である。強度ピークは破線にて示すように、近赤外域の８００ｎｍ付近に存在し、可視光帯域での強度分布は、発光波長とともに増加する傾向となる。相当強度の赤外線を含むため、光源の温度上昇が生じやすいことが直ちに理解できる。
【００４１】
本発明においては、図１８の連続スペクトルを、複数の発光単位層からの種々の波長の単色光（発光単位）を組み合わせて、いわばデジタル的に合成し、擬似連続スペクトルとする。第一の素子１０において、波長７００ｎｍ以上にて発光する井戸層を設けなければ、図１８に実線で示すように、赤外発光成分を大幅に削減できる。また、白熱電球の連続スペクトルにおいて短波長領域には、僅かではあるが有害な紫外線も含まれている。しかし、後述のように第二の素子２０において、波長３６０ｎｍ以下にて発光する井戸層を設けなければ、該紫外発光成分も削減できる。
【００４２】
本実施形態では、各素子１０，２０の活性層５，１５を、以下のように構成している。すなわち、図５及び図８に示すように、複数の発光単位層は、発光波長の長い発光単位層（井戸層）ほど発光強度が高くなるように調整される。具体的には、発光波長の長い発光単位層ほど、井戸層の厚さもしくは数を大きくする。図１８に示すスペクトル波形に近づけるには、例えば、６５０ｎｍでの強度Ｉ650と５６０ｎｍでの強度Ｉ560との比Ｉ650／Ｉ560が１．４前後となるように設定する。例えば、第一の素子１０において、バンドギャップエネルギーが略等間隔の１１の井戸層を形成する場合の、各層のバンドギャップエネルギー、層厚及び層数の設定例を表３に示す（混晶比は、表１を参照して定めるとよい）。また、第二の素子２０において、バンドギャップエネルギーが略等間隔の７つの量子井戸層を形成する場合の、各層のバンドギャップエネルギー、層厚及び層数の設定例を表４に示す。
【００４３】
【表３】

【００４４】
【表４】

【００４５】
図５及び図８に示すように、個々の発光単位層の発光スペクトル（以下、単位スペクトルという）は、それぞれ固有のピーク波長を有した分布の鋭いものになるが、これらが合成されて、破線で示すように、各単位スペクトルのピーク位置をつないだ形状の擬似連続スペクトルが、各素子１０，２０から出力される。なお、個々の発光単位層中の井戸層の数が多ければ多いほど、モデルとする熱放射型光源のスペクトル波形（可視光部分）を忠実に再現できるが、層数を削減したい場合の微調整手段として、層厚調整を補助的に導入することも可能である。また、発光単位層中の全ての井戸層を量子井戸とするのではなく、一部の井戸層を層厚の大きい非量子井戸とすることもできる。
【００４６】
いずれの素子１０，２０も、その発光スペクトルは波長が長くなるにつれ、発光強度は増加する。しかし、発光波長に対する可視光の相対視感度は、図６に示すように、明所では５５５ｎｍ付近で最大となる。図５および図８には、視感度補正係数Ｖの波長依存性を示す曲線を一点鎖線にて示している。視感度補正強度は、絶対強度Ｉと視感度補正係数Ｖとの積Ｖ・Ｉにて表すことができる。図５に示すように、第一の素子１０は絶対強度Ｉと視感度補正係数Ｖとの波長依存性が逆傾向なので、視感度補正強度Ｖ・Ｉは、中間波長域、具体的には黄色域からオレンジ色域にピークを生ずる。他方、図８に示すように、第二の素子２０は絶対強度Ｉと視感度補正係数Ｖとの波長依存性が同傾向なので、視感度補正強度Ｖ・Ｉは波長が長くなるとともに単調増加する。
【００４７】
そして、図１の照明用光源５０からは、長波長域側の第一の素子１０のスペクトルと短波長域側の第二の素子２０のスペクトルとが合成されて出力される。その結果、第一の素子１０のスペクトル波形ＳＡの短波長側に、第二の素子２０のスペクトル波形ＳＢが接続されて、図９のような擬似電球光スペクトルが最終的に得られる。すなわち、擬似電球光スペクトルの絶対強度Ｉは、図１８の白熱電球のスペクトル、すなわち視感度補正後の発光強度分布は、黄色域からオレンジ色域、すなわち５７０ｎｍ以上６４０ｎｍ以下に強度ピークを有し、白熱電球によく似た黄色味あるいはオレンジ色味を帯びた、暖かで柔らかい照明色が得られる。
【００４８】
なお、最終的な発光スペクトルの形状は、各波長の発光単位層の発光強度を、層数や層厚により調整することにより、所望のものを任意に形成できる。特に、自然光の演色性に近づけた照明光を得たい場合は、太陽光の連続スペクトルを模した擬似太陽光スペクトルを、擬似連続スペクトルとして合成すればよい。図１７は、可視領域の太陽光スペクトルを示すものであるが、色温度が６０００Ｋ前後と高いため、白熱電球と比べて、強度ピークは４００ｎｍ付近の短波長域に生ずる。また、可視光波長帯の略全域に渡って、波長が長くなるほど絶対強度Ｉは減少する傾向を示す。従って、図５及び図８とは全く逆に、複数の発光単位層は、発光波長の短い層ほど発光強度が高くなるように調整されればよい。表５に第一の素子１０の、また、表６に第二の素子２０の、各井戸層の層数の設定例を示す。
【００４９】
【表５】

【００５０】
【表６】

【００５１】
照明の分野においては、自然光の演色性を如何にすれば忠実にかつ安価に再現できるか、ということが長年にわたり１つ究極の課題であり続けてきた。例えば普及が著しい蛍光ランプは、白色光ではあるが、そのスペクトルは、自然光（太陽光）スペクトルとの相違が大きく、演色性に難点がある。図１９は、高演色性蛍光ランプのスペクトルの一例であるが、バックグラウンド部分のスペクトル波形は図１７の太陽光スペクトルと大きく隔たっていることがわかる。そこで、赤・緑・青（ＲＧＢ）の３波長領域での幅の狭い発光材料を組み合わせざるを得ないのであるが、各色の蛍光体のスペクトルが輝線状の鋭いピークとなって突出する。図１７との波形の相違から推察される通り、自然光との間には埋めがたい隔たりが生ずることは自明である。しかし、本発明を採用すれば、例えば表５あるいは表６に例示したような組合せにて、発光単位層のからの種々の波長の光を組み合わせることにより、図１７に示す太陽光スペクトルの可視光部分を、擬似太陽光スペクトルとして極めて忠実に再現できる。例えば、ＪＩＳ：Ｚ８７２６（１９９０）に規定された平均演色評価指数において８５以上は容易に実現でき、例えば、蛍光ランプの分野では、９０〜９５前後が限界といわれている平均演色評価指数を、これと同程度あるいはさらに高い値（例えば９５〜１００）に高めることも、比較的容易である。なお、図１９に示すような蛍光ランプの波形を、本発明の発光素子により合成することも可能である。
【００５２】
以上、熱放射型光源のスペクトル波形をなるべく忠実に再現したい場合の実施の形態について説明したが、特定の色調に対する演色性を高めるために、一部の波長域の強度分布を意図的に変更することも、本発明によれば、その波長域に対応する発光単位層の発光強度調整により、比較的容易に実現できる。具体的には、擬似連続スペクトルの有効波長域に属する予め定められた波長域を、当該波長域に対応する色調の演色性が、他の波長域に対応する色調への演色性よりも選択的に高められた演色波長域となるように、擬似連続スペクトルの強度分布を定めるようにする。このような光源により照明を行なうと、上記演色波長域として定めた色調を有する被照明体部分を鮮やかに目立たせることができる。図３２にそのような演色波長域を有する擬似連続スペクトルの例を示す。実線は赤領域である６５０ｎｍ付近に強度ピークが設けらており、赤系の色調（例えば、食肉の色などである）への演色性を高めることができる。他方、一点鎖線は、緑領域である５５０ｎｍ付近に強度ピークが設けらており、緑系の色調への演色性を高めることができる。特に、公園や庭などをライトアップしたとき、植物の緑を鮮やかに演出することができる。
【００５３】
このような演色波長域を形成するには、演色波長域に寄与する発光単位層の発光強度を、他の波長域に寄与する発光単位層の発光強度よりも高く設定すればよい。例えば、図１５には、演色波長域に寄与する発光単位層（Ｅｇｘ）の層数を、他の発光単位層の層数よりも選択的に増加させた例を示している。
【００５４】
以下、上記の光源モジュール５０を用いた照明装置の実施形態について説明する。図２３は、本発明の一実施形態である照明装置９０の回路図である。この照明装置９０は、発光素子１０，２０（光源モジュール５０）と、当該発光素子１０，２０に発光駆動電力を供給する電力供給部７０とを有し、発光素子１０，２０からの可視光を照明光として取り出す。電力供給部７０は、電源部１００からの出力電圧を発光素子駆動電圧に変換する電圧変換部９９，１１１，１２１を有する。本実施形態において、第一の素子１０は、ＡｌＧａＩｎＰ系の発光素子であり、駆動電圧は２Ｖ前後、動作電流値は１００ｍＡ〜１Ａ程度であり、消費電力は０．２〜２Ｗ程度である。また、第二の素子２０は、ＩｎＧａＡｌＮ系の発光素子であり、駆動電圧は３Ｖ前後、動作電流値は１００ｍＡ〜１Ａ程度であり、消費電力は０．３〜３Ｗ程度である。外部電源としては、商用交流（例えばＡＣ１００Ｖ）、乾電池（例えばＤＣ１．５Ｖ）あるいは自動車用バッテリー（ＤＣ９〜１５Ｖ）であり、電源回路（電圧変換部）により発光素子駆動電圧に変換して使用するのが妥当である。
【００５５】
光源モジュール５０は、半導体発光素子を用いているので白熱電球等と比較すればはるかに長寿命であるが、長期間使用していると発光強度が低下し、やがては寿命にいたる。従って、寿命到来した場合に、光源の交換ができるようになっていると便利である。図２３に示すように、電圧変換部１１１，１２１には、発光素子駆動電圧を出力する駆動電圧出力端子１３０，１３１，１３２が設けられている。また、光源モジュール５０は、図２２に示すように、発光素子１０，２０と受電端子６１，６２，６３とが一体化されたものとしておき、受電端子６１，６２，６３にて駆動電圧出力端子１３０，１３１，１３２に着脱可能に取り付けられるようにすればよい。このようにしておくと、寿命到来した光源モジュール５０を取り外し、新しい光源モジュール５０を受電端子６１，６２，６３にて駆動電圧出力端子１３０，１３１，１３２に装着するだけで、交換作業を簡単に行なうことができる。
【００５６】
図１に示す光源モジュール５０においては、金属導体よりなるカソード用ステージ５３上に、Ａｇペースト等の金属導体ペーストを介して両素子１０，２０の第二電極３，１３が接続されている。また、素子１０，２０の第一電極９，１９は、導体金具５１及び５２に金属リード９ａ、１９ａにより接続されている。カソード側となる第二電極３，１３は、カソード用ステージ５３にて共通結線され、該カソード用ステージ５３より、受電端子の１つをなすカソード端子６３が取り出される。一方、導体金具５１及び５２からは、受電端子をなす個別のアノード端子６１，６２が取り出されている。そして、これら受電端子６１，６２，６３を突出させた形で、カソード用ステージ５３、素子１０，２０及び導体金具５１及び５２の全体が、透光性の樹脂モールド６０により覆われて、光源モジュール５０が構成されている。樹脂モールド６０はアクリル樹脂等の熱可塑性樹脂を使用できるが、２素子からの光が十分に混合されるように、樹脂モールド６０中に、気泡やガラスあるいはセラミックよりなる光散乱粒子２６１を分散配合しておくとよい。
【００５７】
なお、光源モジュール５０に組み込む第一の素子１０及び第二の素子２０の数は、図１０に示すように、各々１つずつとすることもできるし、図１１及び図１２に示すように、複数個組み込むこともできる。図１１では、発光強度向上のため、各素子１０，２０をいずれも同数ずつ設けた例であり、発光波長帯域の異なる両素子１０，２０からの光を十分混合して出力できるよう、一定の経路（個々では、周方向）に沿って素子１０，２０を交互に配置してある。一方、図１２は、合成すべきスペクトルの波形調整や、あるいは両素子１０，２０の発光レベルをマッチングさせる等の目的で、素子１０，２０の数を異ならせて設けた例を示す。
【００５８】
図２３においては、電源部として商用交流電源１００が使用されている。そして、電圧変換部は、該商用交流電源を直流電圧に変換するＡＣ／ＤＣコンバータ９９を有するものとされている。これにより、商用交流による既存の電燈線等に、照明装置９０を簡単に取り付けて使用できる。ＡＣ／ＤＣコンバータ９９は、例えばコンセントプラグ等で構成された電源電端子１３５にて、商用交流電源１００に接続される。図２３の実施形態では、ＡＣ／ＤＣコンバータ９９は、商用交流電源１００の電源電圧（例えば１００Ｖ）を所定の電圧（例えば５〜１５Ｖ）に降圧するトランス１４０と、降圧後の交流を整流する整流部１４１を有する。ここでは、整流部１４１としてダイオードブリッジを用い、全波整流を行なうようにしている。
【００５９】
整流部１４１による整流波形は、コンデンサ１４２にて平滑化された後、各素子１０，２０の駆動安定化電源回路１１１，１２１に分配入力される。駆動安定化電源回路１１１，１２１は、それぞれレギュレータＩＣ１１２，１２２（コンデンサ１１３，１１４、１２３，１２４は発振防止用のものである）を有し、ＡＣ／ＤＣコンバータ９９からの入力電圧を、各素子１０，２０に適した直流駆動電圧に変換して、アノード側駆動電圧出力端子１３０，１３１に出力する。なお、素子１０，２０の共通化されたカソード端子６３は、接地側駆動電圧出力端子１３２を介して接地線Ｇに接続される。
【００６０】
図２２は、図２３の回路による照明装置９０を、電燈２６３として構成した例である。この例では、光源モジュール５０に端子ケース６６及び電球バルブ６５が組みつけられて、電球状の光源ユニット６４が形成されている。端子ケース６６の末端面からは、受電端子６１，６２，６３がピン状に引き出されている。また、端子ケース６６には、光源モジュール５０を覆う透光性の電球バルブ６５が一体化されている。電球バルブ６５は、ガラスあるいはアクリル樹脂等の透光性を有する熱可塑性樹脂にて構成でき、気泡やガラスあるいはセラミックよりなる光散乱粒子を分散配合しておくか、あるいは内面をすりガラス状の面粗し部としておくことにより、光分散効果、ひいては各素子１０，２０からの光の混合効果を高めることができる。
【００６１】
電燈２６３は本体ケース７３を有し、該本体ケース７３に取付凹部１３３ａを有する光源ソケット１３３が設けられている。光源ユニット６４は端子ケース６６にて光源ソケット１３３の取付凹部１３３ａに挿入され、その底面に設けられた雌コネクタ状の駆動電圧出力端子１３０，１３１，１３２に受電端子６１，６２，６３がそれぞれ差し込まれて装着される。駆動電圧出力端子１３０，１３１，１３２は、電力供給部７０の基板に接続され、さらに電力供給部７０への電力供給線１３４ａが、周知のスイッチボックス７２を経て、電源プラグ１３５を有した電源コード１３４に接続されている。電源プラグ１３５を商用交流コンセントに差し込めば、電力供給部７０を介して光源ユニット６４の光源モジュール５０に給電され、所期のスペクトルの照明光にて電燈２６３を点灯することができる。なお、操作部７４によりスイッチボックス７２を操作すれば、光源モジュール５０への給電がＯＮ／ＯＦＦされ、電燈２６３の点灯／消灯を簡単に行なうことができる。
【００６２】
なお、図２２の電燈２６３は、発光素子を用いた光源モジュール専用の装置として構成されていた。この場合、既存の白熱電球等を使用する照明装置には、光源モジュールを流用できない欠点がある。そこで、電圧変換部を、商用交流電源に直結された電球用ソケットに対し、電球用ソケットと互換性を有する装着導体部にて着脱可能に装着できるように構成しておけば、既存の電球用ソケットとの互換性を生じ、普及を促進することができる。以下、その例について説明する。まず、電球用ソケットに電圧変換部を直結できるようにするには、電圧変換部をなるべくコンパクトで小型に構成する必要がある。図２４に例示する回路９１の構成では、ＡＣ／ＤＣコンバータ１０１を、トランスに代えて、専用ＬＳＩ１０２（例えば、ローム（株）製、ＢＰ５０５７−１５など）により構成し、軽量化を図っている。該ＬＳＩ１０２は、周辺のダイオード１０９、コンデンサ１０３，１０６，１０８、抵抗１０４及びコイル１０７により、ステップダウン型降圧回路を構成する。これ以外の部分の回路構成は、図２３と全く同じなので詳細な説明は省略する。
【００６３】
図２５は、具体的な電燈８０の実施形態を示すものである。この構成では、電力供給部７０を有した変換アダプタ１５０を構成し、商用交流電源に直結された電球用ソケット８４に対し、これと互換性を有する装着導体部８７にて変換アダプタ１５０を着脱可能に装着できるようにしてある。電球用ソケット８４は、ベース８２とともにねじ等の締結部材８２ａにより天井や壁面などの被装着部に取り付けられる。そして、電球用ソケット８４の内面には、雌ねじ状のソケット金具８５と、これと絶縁状態で配置されたソケット側底部端子金具８６とが配置され、電燈線１３６により商用交流電源から受電する。変換アダプタ１５０は、電力供給部７０を収容したケース１５２を備え、電力供給部７０の２つの交流入力部（一方が接地である）にそれぞれ接続される、電球用口金と同形状の雄ねじ状の装着導体部８７と、アダプタ側底部端子金具８８とが、ケース１５２から突出して設けられている。ケース１５２には、図２２と略同一構造の電球ソケット１３３が設けられ（共通部分には同一の符号を付与して詳細な説明は省略する）ている。変換アダプタ１５０を装着導体部８７にて電球用ソケット８４に装着すると、装着導体部８７とソケット金具８５及びアダプタ側底部端子金具８８とソケット側底部端子金具８６とがそれぞれ導通し、電力供給部７０が電燈線１３６より商用交流を受電する。そして、該変換アダプタ１５０の電球ソケット１３３に光源ユニット６４を装着すれば、電燈８０を点灯させることができる。なお、光源ユニット６４を覆う透光性フード８１が、ねじ式等の着脱部８３にてベース８２に着脱可能とされている。
【００６４】
また、電力供給部７０と発光素子１０，２０（光源モジュール５０）とを一体不可分に結合し、電圧変換機能付光源ユニットを構成することも可能である。この構成によると、変換アダプタ１５０がなくても、電球用ソケット８４等に発光素子１０，２０を簡単に取り付けて使用することができる。図２６にその実例を示している。該電燈８０’は、図２５の構成と略同じであるが、電力供給部７０と装着導体部８７とが光源モジュール５０に一体化され、電圧変換機能付光源ユニット７９が構成されている。光源モジュール５０の寿命が尽きると、電圧変換機能付光源ユニット７９を単位として、電力供給部７０ごと交換を行なう。
【００６５】
以下、本発明の照明装置の他の実施形態について説明する。
図２７は、燃焼光源を模した照明装置の一例として、蝋燭状の外観を有する照明装置１６０を構成した例である。該照明装置１６０は、図１に示す光源モジュール５０を電力供給部７０により商用交流電源により点灯駆動する。回路構成は、図２３あるいは図２４と全く同じである。そして、光源モジュール５０の発光素子１０，２０の擬似連続スペクトルは、燃焼光の連続スペクトルを模した擬似燃焼光スペクトルを有するものである。具体的には、蝋燭光の連続スペクトルを模するため、図１８よりもさらに色温度の低い擬似連続スペクトル（例えば１５００Ｋ程度）が得られるように、活性層５，１５が設計されている。発光色はさらにオレンジないし赤みの強いものとなる。電力供給部７０は蝋燭の軸を模した本体１６２内に収容され、その先端に光源モジュール５０が配置されるとともに、その外側を、炎の外観形状を真似た透光性フード１６１で覆っている。電力供給部７０は、本体１６２から引き出された電源コード１３４及び電源プラグ１３５を介して、コンセントより受電する。
【００６６】
図２８の照明装置１７０は、複数の光源モジュール５０を直線的に配置して、直管状の蛍光ランプに代用できるようにしたものである。該照明装置１７０においては、本体ケース１７２内に電力供給部７０が収容されている。また、本体ケース１７２の長手方向の一側面上には、光源モジュール５０が予め定められた間隔にて配置されており、本体ケース１７２に着脱可能な透光性フード１７１により外側が覆われている。光源モジュール５０は、図３２に実線にて示すような、赤色領域に演色波長域を有するものである。例えば、食肉店や食肉売り場には、図２９に示すような商品２０１の陳列用冷蔵庫２００が配置されるが、その冷蔵庫２００の内側を照明装置１７０にて照明することができる。図３０に示すように、この照明装置１７０により照らされた食肉２０１ｍは赤色が鮮やかに映えて見え、消費者の購買意欲をくすぐることができる。
【００６７】
また、図３１の照明装置１８０及び１８１は野外照明用に構成した例であり、いずれも、図１と同タイプの光源モジュールを備えている。ここで使用される光源モジュールは、図３２に一点鎖線にて示すような、緑色領域に演色波長域を有するものである。例えば、図３１に示すように、これら照明装置１８０及び１８１により照らされた樹木ＴＲや芝生ＧＬ等の植物は緑色がひときわ鮮やかに浮き立って見え、夜間の庭や公園を美しく幻想的にライトアップすることができる。
【図面の簡単な説明】
【図１】本発明の発光素子を用いた光源モジュールの一例を示す模式図。
【図２】第一の発光素子の全体構成例を示す模式図。
【図３】第二の発光素子の全体構成例を示す模式図。
【図４】第一の発光素子の活性層の構成例を示すバンド図。
【図５】第一の発光素子による擬似連続スペクトルの概念説明図。
【図６】可視光に対する相対視感度の波長依存性を示すグラフ。
【図７】第二の発光素子の活性層の構成例を示すバンド図。
【図８】第二の発光素子による擬似連続スペクトルの概念説明図。
【図９】第一の発光素子と第二の発光素子との合成スペクトルの概念図。
【図１０】光源モジュールにおける第一の発光素子と第二の発光素子との第一配置例を示す平面図。
【図１１】同じく第二配置例を示す平面図。
【図１２】同じく第三配置例を示す平面図。
【図１３】活性層の第一変形例を示す伝導体底側のバンド図。
【図１４】活性層の第二変形例を示す伝導体底側のバンド図。
【図１５】活性層の第三変形例を示す伝導体底側のバンド図。
【図１６】活性層の第四変形例を示す伝導体底側のバンド図。
【図１７】可視光帯域の太陽光スペクトルを示す説明図。
【図１８】可視光帯域の白熱電球のスペクトルを示す説明図。
【図１９】蛍光ランプのスペクトルの一例を示す説明図。
【図２０】活性層の第五変形例を示す伝導体底側のバンド図。
【図２１】活性層の第六変形例を示す伝導体底側のバンド図。
【図２２】本発明の照明装置の第一実施形態を示す断面図。
【図２３】本発明の照明装置の第一回路構成例を示す図。
【図２４】本発明の照明装置の第二回路構成例を示す図。
【図２５】本発明の照明装置の第二実施形態を示す断面図。
【図２６】本発明の照明装置の第三実施形態を示す断面図。
【図２７】本発明の照明装置の第四実施形態を示す断面図。
【図２８】本発明の照明装置の第五実施形態を示す断面図。
【図２９】図２８の照明装置の使用例を示す図。
【図３０】図２９の効果説明図。
【図３１】本発明の照明装置の第六実施形態を示す断面図。
【図３２】本発明の発光素子により実現される、演色波長域を有する擬似連続スペクトルの例を示す模式図。
【図３３】有効波長域にブロードな単一ピークを有する擬似連続スペクトルの一例を示す模式図。
【図３４】擬似連続スペクトルのリップル率の定義を説明する図。
【符号の説明】
１０，２０ 発光素子
８，１８ ダブルへテロ発光層部
５，１５ 活性層
Ｗ１〜Ｗｎ 井戸層（発光単位層）
Ｂ 障壁層
１０ 第一の素子
２０ 第二の素子
５０ 光源モジュール
７０ 電力供給部
１００ 電源部
９９，１１１，１２１ 電圧変換部
１３０，１３１，１３２ 駆動電圧出力端子
６１，６２，６３ 受電端子
７９ 電圧変換機能付光源ユニット
８４ 電球用ソケット
８７ 装着導体部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting element and an illumination device using the light emitting element.
[0002]
[Prior art]
Incandescent light bulbs have long been used as a light source for illumination, and before the incandescent light bulb was invented, natural combustion light such as candles and torches were used for illumination. Both use visible light radiation from a high-temperature body as a light source, and are collectively referred to as a heat radiation type light source. Sunlight can also be approximated by a black body radiation spectrum having a color temperature of about 6000 K, and can be regarded as a kind of heat radiation type light source.
[0003]
Since the incandescent bulb uses the resistance heat generation of the filament, it has a short life and a large Joule heat loss, and thus has a disadvantage of poor efficiency. Moreover, since not only visible light but also infrared rays are radiated in large quantities with light emission, there is a significant problem that the temperature of the light source rises. In addition, natural combustion light is much harder to maintain because it has a shorter lifespan than a light bulb and generates not only combustion heat but also combustion products such as soot and carbon dioxide.
[0004]
On the other hand, there is a fluorescent lamp as a general illumination light source other than the incandescent lamp. A fluorescent lamp applies a high pressure to an electrode in a glass tube enclosing a small amount of mercury to generate thermoelectrons, and the phosphor applied to the inner surface of the glass tube is irradiated with ultraviolet rays emitted from the mercury excited by the thermoelectrons. Photoluminescence is emitted. Various phosphors can emit light depending on the phosphor used, but phosphors generally widely used are calcium halophosphate (3Ca ₃ (PO ₄ ) ₂ CaFCl / Sb, Mn), for example, white light with various color temperatures can be obtained by adjusting the amounts of F and Cl, Sb and Mn. Fluorescent lamps consume less power than incandescent bulbs, and are white and bright, which has replaced most of the applications that incandescent bulbs occupied in the past.
[0005]
[Problems to be solved by the invention]
However, fluorescent lamps also have the following drawbacks.
-Since ultraviolet rays are generated using cathode discharge, the life is likely to end relatively early due to evaporation of the electrodes.
-Power consumption is still not negligible even though it is small compared to incandescent bulbs because it requires high voltage.
• Mercury encapsulated in glass tubes is released as a source of ultraviolet light when the lamp is discarded, and it is expected that it will be avoided in the future from the viewpoint of environmental protection.
・ Since there is leakage of ultraviolet rays, it is easy to cause light burn such as paper.
Calcium halophosphate phosphorescence is white light, but its spectrum is greatly different from the natural light (sunlight) spectrum, and there is a difficulty in color rendering. For example, it is also possible to realize illumination with better color rendering by combining narrow emission in the three wavelength regions of red, green, and blue (RGB). Since there is a sharp peak in shape, there is an unfillable gap between natural light and color rendering.
[0006]
In recent years, incandescent bulbs that are soft and warm for indirect lighting and indoor lighting are being reconsidered, and the amount of use has begun to increase again. In addition, restaurants and other restaurants and accommodation facilities such as hotels tend to prefer a slightly darker and darker lighting color of yellow or orange to create a sense of quality and improve the appearance of dishes. For such purposes, natural combustion light such as incandescent bulbs and candles is inherently suitable, and substitution with white fluorescent lamps does not make sense, so these light sources are known for the aforementioned drawbacks. There are circumstances that must be actively used above.
[0007]
An object of the present invention is to easily and inexpensively generate visible light having a spectrum similar to that of a heat-emitting light source such as an incandescent bulb, sunlight, or natural combustion light, and at the same time, various disadvantages of a conventional light source. The object is to provide a light-emitting element that can be solved and a lighting device using the light-emitting element.
[0008]
[Means for solving the problems and actions / effects]
In order to solve the above-described problems, the light-emitting element of the present invention has a pseudo continuous spectrum that is a spectrum obtained by synthesize | combining a continuous spectrum of a thermal radiation type light source by combining a plurality of light emissions having different peak wavelengths. The visible light is emitted and output. In addition, the illumination device of the present invention includes the light emitting element of the present invention and a power supply unit that supplies light emission driving power to the light emitting element, and extracts visible light from the light emitting element as illumination light. It is characterized by.
[0009]
The light-emitting element of the present invention combines a plurality of light emission having different peak wavelengths (hereinafter also referred to as light-emitting units) generated by using light-emitting recombination of quantum optical carriers, thereby A continuous spectrum is synthesized in a pseudo manner. As a result, an emission spectrum similar to a combustion light source such as an incandescent bulb, sunlight, or candle can be easily synthesized by various combinations of emission units. Further, since a semiconductor light emitting element is used as the light source, the deterioration with time is small and the life is long. Basically, if there is only an energization circuit for the light emitting element, continuous light emission is possible, so that the circuit configuration can be simplified. Furthermore, no high voltage is required and the resistance loss is small, so that the power consumption is small. In addition, since an undesirable substance for environmental protection such as mercury in a fluorescent lamp is not used, an ecologically clean light emitting device can be realized.
[0010]
In the light emitting device of the present invention, the active layer of the double hetero light emitting layer portion made of a compound semiconductor is configured to include a plurality of light emitting unit layers having different band gap energies. Based on this, it can be configured to emit and output visible light having a pseudo continuous spectrum. The light emitting layer part (double hetero light emitting layer part) composed of compound semiconductors emits light with high efficiency due to the confinement effect because the clad layer on both sides of the active layer acts as a barrier to carriers. Is possible. In the above configuration, a plurality of light emitting unit layers having different band gap energies are formed in the active layer portion of such a double hetero light emitting layer portion, and light emission from each light emitting unit layer (hereinafter also referred to as a light emitting unit). Based on the combination, a continuous spectrum of a heat radiation type light source is synthesized in a pseudo manner. As a result, an active layer in which a plurality of light emitting unit layers having different wavelengths are formed (hereinafter also referred to as “composite active layer”) is used, so that a quasi-continuous spectrum in which a large number of light emission wavelengths are synthesized is reduced in the number of elements. Can be realized. In addition, the light source and its peripheral circuits can be greatly simplified, so that an inexpensive, high-performance and low power consumption lighting device can be realized. Therefore, when it is desired to suppress the generation of infrared rays, it is only necessary to select and combine light emitting unit layers whose emission wavelengths do not belong to the infrared region. When an element that suppresses the generation of ultraviolet rays is required, the emission wavelength is reduced to the ultraviolet region. What is necessary is just to select and combine the light emitting unit layer which does not belong.
[0011]
Incandescent bulbs and fluorescent lamps generate considerable amounts of infrared rays (heat rays) in the former and ultraviolet rays in the latter because of the inevitable circumstances derived from the light emission principle. On the other hand, in the light emitting device of the present invention, if a light emitting unit whose emission wavelength does not belong to the infrared region is selected and combined, a quasi-continuous spectrum not containing an infrared light emitting component having a wavelength of 710 nm or more can be easily obtained. On the other hand, if a light emitting unit whose emission wavelength does not belong to ultraviolet light is selected and combined, a quasi-continuous spectrum not containing an ultraviolet light emitting component having a wavelength of 350 nm or less can be easily obtained. That is, it is possible to easily and extremely effectively suppress the generation of infrared rays and ultraviolet rays, which are inevitable in incandescent bulbs and fluorescent lamps. Note that the emission spectrum from each light emitting unit layer made of a compound semiconductor generally has a peak waveform with a narrow half width, but in the background region, a small amount of infrared light emitting component and ultraviolet light emitting component is unavoidable. May be included. Such inevitable infrared or ultraviolet light-emitting components are regarded as belonging to the concept of “not included” in this specification unless they are actively utilized.
[0012]
The light emitting device of the present invention is characterized in that the analog continuous spectrum of the heat radiation type light source is digitally synthesized by combining light emitting units of various wavelengths with various intensities. Even in the pseudo continuous spectrum synthesized by the light emitting device of the present invention, as in the case of jaggy on the contour of a digital image with a low quantization level (that is, with low resolution), if the wavelength interval of each light emitting unit is too large, it will jump out. Waveforms corresponding to the wavelength peak of are easily generated in the spectrum waveform. Therefore, in order to realize a smooth continuous spectrum peculiar to the thermal radiation type light source, it is desirable to narrow the wavelength interval of the light emitting unit as much as possible. Specifically, the plurality of light emitting unit layers should have a difference value between adjacent band gap energies of 0.42 eV or less, more preferably 0.2 eV or less, in the band gap energy arrangement. . In addition, the smaller the lower limit value of the difference value, the smoother the spectrum waveform can be obtained.However, if the difference value is excessively small, the number of necessary light emitting unit layers becomes too large and the manufacturing cost is reduced. It leads to soaring. If the interval between the peak wavelengths of the light emitting units forming the pseudo continuous spectrum is narrower than the half width of the spectrum, the overlap between adjacent spectra becomes too large, resulting in a lot of waste. In a light-emitting element having a double hetero structure, it is desirable to set the difference value between the adjacent band gap energies to 0.05 eV or more, considering that the spectral half-value width of the light emission unit is approximately 20 nm.
[0013]
The thermal radiation type light source exhibits an emission spectrum that varies depending on the light source temperature. For example, in the case of a light source often used for illumination, such as an incandescent bulb (around 3000K) and combustion light (around 1500K), the light source temperature is not as high as that of sunlight, so it appears colored yellow or orange. . However, even though the light source is colored, it is known that the color rendering is not as severe as expected. This is related to the adaptation of the eye and the fact that the spectrum of the low-temperature heat-radiating light source covers the visible light wavelength component in a relatively wide band. In order to obtain a quasi-continuous spectrum in which the visual difference from an actual thermal radiation type light source is as inconspicuous as possible, in particular, from the viewpoint of the latter, the visible light component in the widest wavelength range should be included in the spectrum. desirable. Specifically, it is desirable that an effective wavelength region showing an emission intensity of 5% or more of the reference intensity is secured over a range of at least 500 nm or more and 600 nm or less using the emission intensity at the peak wavelength as the reference intensity. If the effective wavelength region is narrower than this, the color rendering properties of illumination may be significantly impaired. The effective wavelength region is desirably ensured over a range of at least 470 nm to 650 nm, and more preferably 400 nm to 670 nm. The effective wavelength range of the quasi-continuous spectrum is synthesized by four or more light emitting unit layers having different emission wavelengths (when two or more elements are combined as described later, the total number of light emitting unit layers is used). It is desirable to achieve a smooth spectral waveform and thus enhance color rendering.
[0014]
Note that even with a combination of RGB monochromatic light, it is possible to synthesize a light emission color that looks similar to that of a thermal radiation type light source by adjusting the intensity ratio, but its spectrum is only a bright line by the combination of RGB monochromatic light. However, the subtle illumination effect of the continuous spectrum cannot be realized. In the present invention, an effective wavelength region showing a light emission intensity of 5% or more of the reference intensity over a range of at least 500 nm or more and 600 nm or less can be ensured by a combination of monochromatic light emission with closer peak wavelength intervals than RGB single color light. Although it is a pseudo-synthesis spectrum, it is possible to reduce the subtle illumination effect of the continuous spectrum that the thermal radiation type light source has. In particular, a continuous spectrum in which an effective wavelength region showing an emission intensity of 10% or more (preferably 15% or more) of the reference intensity is secured at least 500 nm or more and 600 nm or less can be realized very easily with the light emitting device of the present invention. Although it is possible, it cannot be realized by a combination of RGB monochromatic lights.
[0015]
In this case, in the pseudo continuous spectrum to be realized by the light emitting device of the present invention, it is effective for reproducing a realistic light source color to reduce the ripple generated in the spectrum waveform as much as possible. Specifically, as shown in FIG. 34, on the spectrum, a first tangent line A that is in contact with both of two adjacent small peaks that form a ripple valley is drawn, and the ripple valley is parallel to the tangent A. When the second tangent line B is drawn, the distance in the intensity axis direction of both tangent lines is defined as the ripple depth d. When a straight line V parallel to the intensity axis is drawn through the bottom position of the ripple valley, an intersection point Q between the straight line V and the first tangent A is defined as a reference intensity H in the focused ripple. To realize a smooth quasi-continuous spectrum, the ripple rate defined by d / H is sufficiently small over the entire effective wavelength range, for example, 0.1 or less. desirable. In the present specification, if the ripple rate R is 0.1 or less, the two adjacent small peaks forming the ripple valley are ignored in the effective wavelength region of the pseudo continuous spectrum.
[0016]
Next, when trying to synthesize a quasi-continuous spectrum simulating a thermal radiation type light source (including sunlight (or natural light)) by the light emitting device of the present invention, it is a broad having a single peak in the effective wavelength region. It is desirable that the spectrum is a continuous spectrum, or that the intensity monotonously increases or decreases with respect to the wavelength in the effective wavelength region.
[0017]
That is, FIG. 17 shows the spectrum of natural light (sunlight), but since the light source temperature is as high as 6000 K, a peak occurs in the vicinity of a wavelength of 400 nm, and the intensity monotonously decreases as the wavelength increases in the above-described effective wavelength region. However, in the spectrum of the incandescent lamp shown in FIG. 18, the light source temperature is as low as 3000 K, so that the peak occurs on the long wavelength side near the wavelength of 700 nm. As a result, the intensity increases monotonously as the wavelength increases in the above effective wavelength range. Naturally, when the light source temperature is between 3000K and 6000K, a peak is generated in the effective wavelength range, so that the spectrum has a broad intensity distribution having a single peak in the effective wavelength range as shown in FIG. It will have. In the light emitting device of the present invention, synthesizing such a spectrum waveform as a quasi-continuous spectrum with a ripple ratio of 0.1 or less means that a plurality of light emitting unit layers forming the light emitting layer portion are arranged in a large and small band gap energy arrangement. This can be easily realized by setting the difference value between adjacent band gap energies to 0.2 eV or less, for example. Then, it is possible to realistically reproduce the emission spectrum of natural light or a heat radiation type light source, which can never be realized by a combination of RGB like a conventional fluorescent lamp called high color rendering.
[0018]
The double hetero luminescent layer portion can be composed of, for example, a III-V group compound semiconductor or a II-VI group compound semiconductor, and the luminescence wavelength of the luminescence unit layer included in the active layer constitutes the luminescence unit layer. It can be adjusted by the mixed crystal ratio of the mixed crystal compound semiconductor. In this case, when it is intended to realize a light emitting device having a wide effective wavelength region as described above, a single compound semiconductor system may not be able to cover all the wavelength regions with sufficient light emission intensity. Therefore, different types of compound semiconductor systems can be properly used depending on the wavelength range. Specifically, it is possible to employ a configuration in which a plurality of elements each having a double hetero luminescent layer portion formed of compound semiconductors of different systems are combined, and an emission spectrum from each element is synthesized and output. Depending on the wavelength range, select a compound semiconductor system that is advantageous for securing emission intensity, and configure individual elements, which are necessary according to the waveform of the pseudo continuous spectrum to be obtained in any wavelength range. Sufficient emission intensity can be easily secured. In this case, it is possible to achieve the effect of reducing the number of elements by configuring at least one of the plurality of elements as a composite active layer in which a plurality of light emitting unit layers are formed.
[0019]
As a specific example configured by dividing into a plurality of elements, each has a double heteroemission layer part made of a compound semiconductor, and the emission wavelength of the emission unit layer included in the active layer of the double heteroemission layer part is A configuration in which a first element set in a range of 520 nm to 700 nm and a second element similarly set in a range of 360 nm to 560 nm can be exemplified. Then, at least one of the first element and the second element is configured to include a plurality of light emitting unit layers in the active layer. The visible light band covers a relatively wide range from 360 nm to 700 nm, but in order to cover the entire band, it must be possible to change the band gap width in a wide range from 1.75 eV to 3.2 eV. . On the other hand, compound semiconductors currently used for light-emitting elements are of a type in which high emission intensity can be obtained only on either the long wavelength side (520 nm or more and 700 nm or less) or the short wavelength side (360 nm or more and 560 nm or less). There are many things. Therefore, combining such two types of elements can effectively cover substantially the entire visible light band, and since only two types of elements are used, the effect of reducing the number of elements is great. Furthermore, the wavelength ranges of the two types of elements are determined in such a manner that the green band of 490 to 560 nm is shared, but the green band that is the most widely included in the spectrum of the heat radiation type light source is divided into two types. By sharing the elements, it is possible to realize a high-quality pseudo continuous spectrum waveform that is smoother and has less band loss.
[0020]
Specifically, the first element has a double heteroemission layer portion (Al _x Ga _1-x ) _y In _1-y It is possible to obtain an element composed of P (however, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1: hereinafter also referred to as AlGaInP). This element can easily adjust the emission wavelength while maintaining high intensity in the range of 520 nm to 670 nm by setting the mixed crystal ratios x and y. Further, the second element has a double hetero luminescent layer portion of In _a Ga _b Al _1-ab It is possible to form an element composed of N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a + b ≦ 1: hereinafter also referred to as InGaAlN). This device can easily adjust the emission wavelength while maintaining high intensity in the range of 360 nm or more and 560 nm or less by setting the mixed crystal ratios a and b. In either case, the light emission drive voltage is as low as around 2V for the former and around 3V for the latter, and a sufficient light emission intensity for illumination can be obtained by energization of about 50 to 800 mA, and the drive circuit can be simplified. There is also an advantage of low power consumption.
[0021]
Each of the above elements uses a III-V group compound semiconductor, but the first element that covers a long wavelength range is GaAlAs (possible wavelength range of 640 nm to 700 nm) and doubles to it. It is also possible to constitute a terror emission layer part. Further, the second element covering the short wavelength region is, for example, Mg _a Zn _1-a It is also possible to form a double hetero luminescent layer portion with an O (where 0 ≦ a ≦ 1) type oxide or a II-VI group compound semiconductor such as SiC or ZnSe. When it is necessary to ensure a high intensity in the blue wavelength range as in the pseudo-sunlight spectrum, it is desirable to use the above-described InGaAlN-based or MgZnO-based light emitting layer portion having high emission intensity as the second element. However, when the intensity of the blue wavelength region is not so required as in the pseudo-bulb light spectrum, it is also possible to use a SiC or ZnSe-based light emitting layer portion with a slightly lower emission intensity. Further, depending on the type of the heat radiation type light source, it is possible to generate a pseudo continuous spectrum by a single light emitting element. For example, when it is not necessary to secure the intensity of the red wavelength region so much, a wide gap type InGaAlN-based compound semiconductor is used, and the light emission unit of the red wavelength region is small in intensity but in the same active layer. It is possible to incorporate layers. On the other hand, in the case where it is not necessary to ensure the intensity of the blue wavelength region, the light emitting element can be configured using only an AlGaInP compound semiconductor.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of an illumination light source using a light emitting element according to an embodiment of the present invention. The illumination light source 50 includes light emitting elements 10 and 20 according to the concept of the present invention. The light emitting elements 10 and 20 are a first element 10 and a second element 20, both of which are active layers of double hetero light emitting layer portions (hereinafter simply referred to as light emitting layer portions) 8 and 18 made of a compound semiconductor. (See FIGS. 2 and 3) includes a plurality of light emitting unit layers having different band gap energies. In the first element 10, the emission wavelength of the light emitting unit layer is set in the range of 520 nm to 700 nm, and in the second element 20, the emission wavelength of the light emitting unit layer is set in the range of 360 nm to 560 nm. Then, the illumination light source 50 mixes the light emitted from these two elements 10 and 20 and synthesizes the continuous spectrum of the thermal radiation light source in a pseudo manner to emit light as visible light having a pseudo continuous spectrum. Output.
[0023]
FIG. 2 illustrates the laminated structure of the first element 10. In the first element 10, a light emitting layer portion 8 is formed on a first main surface MP 1 of an n-type GaAs single crystal substrate (hereinafter simply referred to as a substrate) 1. An n-type GaAs buffer layer 2 is formed in contact with the first main surface MP 1 of the substrate 1, and a light emitting layer portion 8 is formed on the buffer layer 2. A current diffusion layer 7 is formed on the light emitting layer portion 8, and a first electrode 9 for applying a light emission driving voltage to the light emitting layer portion 8 is formed on the current diffusion layer 7. Similarly, the second electrode 3 is formed on the entire surface of the substrate 1 on the second main surface MP2 side. The first electrode 9 is formed substantially at the center of the first main surface PF of the first element 10, and a region around the first electrode 9 is a light extraction region from the light emitting layer portion 8.
[0024]
The light emitting layer portion 8 is made of (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 0.55, 0.45 ≦ y ≦ 0.55) active layer 5 made of a mixed crystal (for example, non-doped one: a dopant can be added if necessary) , P-type (Al _z Ga _1-z ) _y In _1-y A p-type cladding layer 6 made of P (where x <z ≦ 1) and an n-type (Al _z Ga _1-z ) _y In _1-y It has a structure sandwiched between n-type clad layers 4 made of P (where x <z ≦ 1). In FIG. 2, the p-type AlGaInP cladding layer 6 is disposed on the first electrode 9 side, and the n-type AlGaInP cladding layer 4 is disposed on the second electrode 3 side. Therefore, the energization polarity is positive on the first electrode 9 side. The term “non-dope” as used herein means “does not actively add a dopant”, and contains an inevitable dopant component in a normal manufacturing process (for example, 10%). ¹³ -10 ¹⁶ / Cm ³ Is not excluded). The current spreading layer 7 is formed as a p-type GaP layer.
[0025]
FIG. 3 illustrates the laminated structure of the second element 20. In the second element 20, a light emitting layer portion 18 is formed on a first main surface MP <b> 1 of an n-type SiC single crystal substrate (hereinafter simply referred to as a substrate) 11. An n-type GaN buffer layer 12 is formed in contact with the first main surface MP 1 of the substrate 11, and a light emitting layer portion 18 is formed on the buffer layer 12. A current diffusion layer 17 is formed on the light emitting layer portion 18, and a first electrode 19 for applying a light emission driving voltage to the light emitting layer portion 18 is formed on the current diffusion layer 17. Similarly, the second electrode 13 is formed in a dispersed form on the second main surface MP2 side of the substrate 11. The first electrode 19 is formed substantially at the center of the first main surface PF of the second element 20, and a region around the first electrode 19 is a light extraction region from the light emitting layer portion 18.
[0026]
The light emitting layer portion 18 is made of non-doped In _a Ga _b Al _1-ab The active layer 15 made of N mixed crystal is made p-type In _a Ga _b Al _1-ab A p-type cladding layer 16 made of N and an n-type (In _a Ga _b Al _1-ab It has a structure sandwiched between n-type cladding layers 14 made of N. In FIG. 3, the p-type InGaAlN cladding layer 16 is disposed on the first electrode 19 side, and the n-type cladding layer 14 is disposed on the second electrode 13 side. Therefore, the conduction polarity is positive on the first electrode 19 side. The current spreading layer 17 is made of p-type GaN.
[0027]
In any element, the epitaxial growth of each layer can be performed by a known metalorganic vapor phase epitaxy (MOVPE) method. In order to increase the light extraction intensity, a reflective layer may be provided between the light emitting layer portions 8 and 18 and the substrates 1 and 11.
[0028]
FIG. 4 schematically shows an example of the structure of the active layer 5 of the first element 10 in the form of a band diagram. FIG. 7 schematically shows an example of the structure of the active layer 15 of the second element 20 in the form of a band diagram. In the active layers 5 and 15, the light emitting unit layer is composed of well layers W1 to Wn sandwiched between two barrier layers B and B, respectively. By using the well layers W1... Wn sandwiched between the barrier layers B and B as the light emitting unit layers, the light emission efficiency of the individual light emitting unit layers can be increased due to the carrier confinement effect in the well layers. The emission wavelength of each well layer W1... Wn is the bandgap energy Eg1... Egn (FIG. 4), Eg′1... Eg′n (FIG. 7) (≡Ec-Ev value in each well layer: Ec The conductor bottom energy level, Ev, is determined according to the valence band top energy level. In this embodiment, each of the well layers W1... Wn has different band gap energies and forms individual light emitting unit layers. That is, the number of well layers included in one light emitting unit layer is one. However, as will be described later, a set of a plurality of well layers having the same band gap energy can be used as the light emitting unit layer. Table 1 shows (Al _x Ga _1-x ) _y In _1-y The relationship between the mixed crystal ratios x and y of P and the obtained band gap energy and emission wavelength (and emission color as a guide) is illustrated. When x ≧ 0.6, indirect light emission occurs and the light emission intensity decreases, so it is desirable to set x <0.6. Table 2 shows In _a Ga _1-a The relationship between the mixed crystal ratio a of N and the obtained band gap energy and emission wavelength (and emission color as a guide) is illustrated. In FIG. 4, the conductor bottom energy Ec in the well layer is set higher as the band gap energy of the well layer is larger, while the valence band top energy Ev is set lower as the band gap energy of the well layer is larger. However, the band structure is not limited to this. For example, the magnitude of the valence band top energy Ev may not uniquely correspond to the magnitude of the band gap energy depending on the composition of the well layer.
[0029]
[Table 1]

[0030]
[Table 2]

[0031]
In both the first element 10 and the second element 20, the plurality of light emitting unit layers, that is, the well layers W1... Wn have a difference value ΔE between adjacent band gap energies in a large and small band gap energy arrangement. 0.42 eV or less, preferably 0.2 eV or less. If the difference value ΔE between the band gap energies becomes excessively large, the distance between the peak positions of the unit spectrum becomes too large, resulting in a large wave in the synthesized waveform, and a smooth spectrum cannot be obtained. Note that the difference value ΔE can be set equal to the set of all light emitting unit layers adjacent to each other with the band gap energy, or the wavelength range where the intensity is consciously increased according to the required emission spectrum shape. For example, at least a part of the light emitting unit layers may be set at unequal intervals, for example, by narrowing the intervals and conversely increasing the intervals in the wavelength region where the intensity is desired to be suppressed.
[0032]
The light emission intensity from each light emitting unit layer can be adjusted by the layer thickness of the well layers W1... Wn. For example, when the quantum well structure described later is not used, the light emission increases with increasing layer thickness up to a certain layer thickness. Strength can be increased. When the number of well layers in the light emitting unit layer is 1, the light emission intensity can be adjusted by adjusting the layer thickness. On the other hand, instead of increasing the layer thickness, as shown in FIG. 13, the number of well layers in one light emitting unit layer is increased, that is, well layers having the same band gap energy (Eg1, Eg2,... Egn) are formed. The emission intensity can be increased by forming a plurality of layers. That is, the light emission intensity from the light emitting unit layer can be adjusted by the number of well layers. In this structure, since the thickness of each well layer does not increase, it is more advantageous from the viewpoint of the carrier confinement effect, and the luminous efficiency can be increased. That is, the light emission intensity of the light emitting unit layer is adjusted by the thickness and / or the number of layers of the well layers. In the quasi-continuous spectrum to be obtained, the light emitting unit layer for obtaining the assumed quasi-continuous spectrum may be set by increasing the layer thickness and / or the number of layers of the well layer that contributes to the wavelength region with higher emission intensity. Can be easily designed. As shown in FIG. 4, the height of the barrier layer is set so that each well layer does not prevent carriers that do not contribute to light emission in the well layer from moving toward other well layers. It is desirable to keep it constant. As a result, it is desirable to set the well depth smaller for the light emitting unit layer having a shorter emission wavelength (that is, the light emitting unit layer having a well layer with a wide band gap energy).
[0033]
The number of well layers in each light emitting unit layer can be uniformly set as shown in FIG. 14, or as shown in FIG. 15, the number of well layers depends on the wavelength range of the light emitting unit layer. You can also change the number. That is, if the number of well layers contributing to the wavelength region is set to be larger in the wavelength region where the emission intensity is higher, the quasi-continuous spectrum can be designed more easily.
[0034]
As shown in FIGS. 2 and 3, the double hetero light-emitting layer portions 8 and 18 of the first element 10 and the second element 20 are principal surfaces on one side in the stacking direction, that is, the first element 10 and the second element 20. Each first main surface PF of the element 20 is a light extraction surface. As shown in FIGS. 4 and 7, the light emitting unit layers (well layers W1. It is arranged at a position farther from the light extraction surface in the layer thickness direction. Light having a short emission wavelength tends to be easily absorbed by a semiconductor having a band gap smaller than the energy of the emission wavelength. However, as described above, if the light emitting unit layer having a long emission wavelength is arranged away from the light extraction surface, the light emitting unit layers stacked on the light extraction surface side of the light emission unit layer are all light from the lower layer side. The band gap is wider than energy, making absorption less likely. Therefore, the light extraction efficiency of the element can be increased.
[0035]
On the other hand, in order to enhance or suppress the intensity in a specific wavelength region for the purpose of adjusting the color rendering properties, which will be described later, as shown in FIG. It is also possible to replace them. A layer that is relatively enhanced in light extraction intensity of a light emitting unit layer (a layer having bandgap energy of Egk + 1 in FIG. 16) that is close to the light extraction surface by changing the order of bandgap energy, or a layer on the lower layer side. Light emission from the layer (bandgap energy is Egk in FIG. 16) can be absorbed by the light emitting unit layer to suppress light emission.
[0036]
In order to increase the light emission efficiency by the carrier confinement effect, it is desirable to configure the light emitting unit layer as having a quantum well structure. In this case, it is necessary to set the thickness of the well layer to be equal to or less than the mean free path of electrons (usually 10 nm or less, for example, 2 to 5 nm) in order to develop the quantum effect. By adopting the quantum well structure, it is possible to stabilize the wavelength and improve the light emission efficiency. Also, if the barrier layer thickness is reduced to 10 nm or less (however, 5 nm or more is desirable to prevent carrier passage due to the tunnel effect), the lattice constant deviation is allowed to about 2 to 3%, and the emission wavelength region Is easy to expand. Moreover, even in a short wavelength region that is an indirect transition region in the bulk, it can be brought close to a direct transition behavior by carrier localization by the quantum well, which is advantageous in increasing the emission wavelength to the short wavelength side.
[0037]
In the quantum well structure, since the thickness of the well layer is limited as described above, it is not expected to adjust the emission intensity by the layer thickness. Therefore, the emission intensity of the light emitting unit layer having the quantum well structure is adjusted by the number of well layers. That is, the light emitting unit layer has a multiple quantum well structure. In the multiple quantum well structure, the carrier confinement effect is further enhanced by forming the subband, which is more advantageous for the purpose of improving the emission intensity. In the quantum well structure, the well layer is preferably set to have a small thickness because the light emitting unit layer having a shorter emission wavelength has a smaller mean free path of carriers.
[0038]
As a modification of the light emitting unit layer, as shown in FIG. 20, a plurality of light emitting unit layers W having different light emission wavelengths are used. _A As a repeating unit, the repeating unit W _A It is also possible to adopt a configuration in which a plurality of layers are formed in the thickness direction of the active layer 5. This configuration is effective when it is necessary to make the intensity distribution of each wavelength component as uniform as possible. For example, when the main surface on one side in the stacking direction of the double hetero luminescent layer portions 8 and 18 is a light extraction surface, the repeating unit W _A If the light emitting unit layer has a longer emission wavelength, it is advantageous to dispose the light emitting unit layer at a position farther from the light extraction surface in the layer thickness direction of the active layers 5 and 15, since the effect of light absorption can be reduced.
[0039]
Furthermore, as shown in FIG. 21, by forming one well layer Wk as a stacked body of compound semiconductors having a plurality of mixed crystal ratios, a band structure in which the well bottom shape is stepped can be employed. This configuration has an advantage that the manufacturing process can be simplified because the number of barrier layers is small.
[0040]
In the present embodiment, the active layers 5 and 15 of both the elements 10 and 20 are designed so that the pseudo continuous spectrum to be obtained has a pseudo light bulb light spectrum imitating the continuous spectrum of an incandescent bulb. FIG. 18 shows a spectrum waveform when an incandescent bulb using a tungsten filament is caused to emit light at a color temperature of about 3000K. As indicated by the broken line, the intensity peak exists in the vicinity of 800 nm in the near infrared region, and the intensity distribution in the visible light band tends to increase with the emission wavelength. It can be readily understood that the temperature of the light source is likely to increase due to the fact that it includes a considerable intensity of infrared rays.
[0041]
In the present invention, the continuous spectrum in FIG. 18 is combined with monochromatic light (light emitting units) of various wavelengths from a plurality of light emitting unit layers, so to speak, and is digitally synthesized to form a pseudo continuous spectrum. If the first element 10 is not provided with a well layer that emits light at a wavelength of 700 nm or more, as shown by the solid line in FIG. 18, the infrared light emission component can be greatly reduced. Further, in the continuous spectrum of the incandescent lamp, the short wavelength region includes a slight but harmful ultraviolet ray. However, as will be described later, if the second element 20 is not provided with a well layer that emits light at a wavelength of 360 nm or less, the ultraviolet light emission component can also be reduced.
[0042]
In the present embodiment, the active layers 5 and 15 of the elements 10 and 20 are configured as follows. That is, as shown in FIGS. 5 and 8, the plurality of light emitting unit layers are adjusted such that the light emission unit layer (well layer) having a longer light emission wavelength has higher light emission intensity. Specifically, the thickness or number of the well layers is increased as the emission unit layer has a longer emission wavelength. In order to approach the spectrum waveform shown in FIG. 18, for example, the ratio I650 / I560 between the intensity I650 at 650 nm and the intensity I560 at 560 nm is set to about 1.4. For example, in the first element 10, when 11 well layers having substantially equal band gap energy are formed, the setting examples of the band gap energy, the layer thickness, and the number of layers of each layer are shown in Table 3 (mixed crystal ratio). May be determined with reference to Table 1). Table 4 shows setting examples of the band gap energy, the layer thickness, and the number of layers in each of the second elements 20 when seven quantum well layers having substantially equal intervals are formed.
[0043]
[Table 3]

[0044]
[Table 4]

[0045]
As shown in FIG. 5 and FIG. 8, the emission spectra of the individual emission unit layers (hereinafter referred to as unit spectra) each have a sharp distribution with a unique peak wavelength. As shown by, a pseudo continuous spectrum having a shape in which the peak positions of each unit spectrum are connected is output from each of the elements 10 and 20. As the number of well layers in each light emitting unit layer increases, the spectral waveform (visible light portion) of the model heat radiation light source can be faithfully reproduced, but fine adjustment is required when the number of layers is to be reduced. As a means, it is also possible to introduce layer thickness adjustment in an auxiliary manner. Further, not all well layers in the light emitting unit layer may be quantum wells, but some well layers may be non-quantum wells having a large layer thickness.
[0046]
In any of the elements 10 and 20, the emission intensity increases as the wavelength of the emission spectrum increases. However, the relative visibility of visible light with respect to the emission wavelength is maximized in the vicinity of 555 nm in a bright place as shown in FIG. 5 and 8, a curve indicating the wavelength dependence of the visibility correction coefficient V is indicated by a one-dot chain line. The visibility correction intensity can be represented by the product V · I of the absolute intensity I and the visibility correction coefficient V. As shown in FIG. 5, since the wavelength dependence of the absolute intensity I and the visibility correction coefficient V of the first element 10 is opposite, the visibility correction intensity V · I is in the intermediate wavelength range, specifically yellow. A peak occurs in the orange region from the region. On the other hand, as shown in FIG. 8, since the wavelength dependency of the absolute intensity I and the visibility correction coefficient V is the same in the second element 20, the visibility correction intensity V · I monotonously increases as the wavelength increases. .
[0047]
1, the spectrum of the first element 10 on the long wavelength region side and the spectrum of the second element 20 on the short wavelength region side are combined and output. As a result, the spectrum waveform SB of the second element 20 is connected to the short wavelength side of the spectrum waveform SA of the first element 10, and a pseudo light bulb light spectrum as shown in FIG. 9 is finally obtained. That is, the absolute intensity I of the pseudo-bulb light spectrum is the spectrum of the incandescent lamp in FIG. 18, that is, the luminous intensity distribution after the visibility correction has an intensity peak from the yellow range to the orange range, that is, from 570 nm to 640 nm, A warm and soft lighting color with a yellowish or orange tint similar to an incandescent bulb is obtained.
[0048]
In addition, the final shape of the emission spectrum can be arbitrarily formed by adjusting the emission intensity of the emission unit layer of each wavelength according to the number of layers and the layer thickness. In particular, when it is desired to obtain illumination light that is close to the color rendering properties of natural light, a pseudo sunlight spectrum that simulates the continuous spectrum of sunlight may be synthesized as a pseudo continuous spectrum. FIG. 17 shows the sunlight spectrum in the visible region, but since the color temperature is as high as about 6000 K, the intensity peak occurs in a short wavelength region around 400 nm as compared with an incandescent lamp. Further, the absolute intensity I tends to decrease as the wavelength increases over substantially the entire visible light wavelength band. Therefore, contrary to FIGS. 5 and 8, the plurality of light emitting unit layers may be adjusted so that the light emission intensity is higher as the light emission wavelength is shorter. Table 5 shows an example of setting the number of well layers in the first element 10 and Table 6 in the second element 20.
[0049]
[Table 5]

[0050]
[Table 6]

[0051]
In the field of lighting, how to reproduce the color rendering of natural light faithfully and inexpensively has been one of the ultimate challenges for many years. For example, fluorescent lamps that are remarkably widespread are white light, but their spectrum is greatly different from the natural light (sunlight) spectrum, and there is a difficulty in color rendering. FIG. 19 shows an example of the spectrum of the high color rendering fluorescent lamp. It can be seen that the spectrum waveform in the background portion is largely separated from the sunlight spectrum of FIG. Therefore, it is unavoidable to combine light emitting materials having a narrow width in the three wavelength regions of red, green, and blue (RGB), but the spectrum of each color phosphor protrudes as a sharp peak in a bright line shape. As inferred from the difference in waveform from FIG. 17, it is obvious that there is an unfillable gap with natural light. However, if the present invention is employed, visible light of the sunlight spectrum shown in FIG. 17 can be obtained by combining light of various wavelengths from the light emitting unit layer in combinations such as those illustrated in Table 5 or Table 6, for example. The part can be reproduced very faithfully as a simulated sunlight spectrum. For example, an average color rendering index of 85 or more in the average color rendering index defined in JIS: Z8726 (1990) can be easily realized. For example, in the field of fluorescent lamps, an average color rendering index of about 90 to 95 is said to be the limit. It is relatively easy to increase the value to the same level or higher (for example, 95 to 100). Note that the waveform of the fluorescent lamp as shown in FIG. 19 can be synthesized by the light emitting element of the present invention.
[0052]
As described above, the embodiment in the case where it is desired to reproduce the spectral waveform of the heat radiation type light source as faithfully as possible has been described. However, in order to improve the color rendering for a specific color tone, the intensity distribution in some wavelength regions is intentionally changed. In addition, according to the present invention, it can be realized relatively easily by adjusting the light emission intensity of the light emitting unit layer corresponding to the wavelength region. Specifically, for a predetermined wavelength range belonging to the effective wavelength range of the quasi-continuous spectrum, the color rendering property of the color tone corresponding to the wavelength range is more selective than the color rendering property of the color tone corresponding to the other wavelength range. The intensity distribution of the quasi-continuous spectrum is determined so that the color rendering wavelength region is increased. When illumination is performed using such a light source, it is possible to make the illuminated portion having the color tone defined as the color rendering wavelength range vividly visible. FIG. 32 shows an example of a pseudo continuous spectrum having such a color rendering wavelength region. The solid line has an intensity peak in the vicinity of 650 nm, which is a red region, and can improve the color rendering property to a red color tone (for example, meat color). On the other hand, the alternate long and short dash line has an intensity peak in the vicinity of 550 nm, which is a green region, and can improve the color rendering property to a green color tone. In particular, when the park or garden is lit up, the green of the plant can be vividly produced.
[0053]
In order to form such a color rendering wavelength region, the light emission intensity of the light emitting unit layer contributing to the color rendering wavelength region may be set higher than the light emission intensity of the light emitting unit layer contributing to other wavelength regions. For example, FIG. 15 shows an example in which the number of light emitting unit layers (Egx) contributing to the color rendering wavelength region is selectively increased as compared with the number of other light emitting unit layers.
[0054]
Hereinafter, an embodiment of an illumination device using the light source module 50 will be described. FIG. 23 is a circuit diagram of a lighting device 90 according to an embodiment of the present invention. The lighting device 90 includes the light emitting elements 10 and 20 (light source module 50) and a power supply unit 70 that supplies light emission driving power to the light emitting elements 10 and 20, and emits visible light from the light emitting elements 10 and 20. Take out as illumination light. The power supply unit 70 includes voltage conversion units 99, 111, and 121 that convert an output voltage from the power supply unit 100 into a light emitting element driving voltage. In the present embodiment, the first element 10 is an AlGaInP-based light emitting element, the driving voltage is about 2 V, the operating current value is about 100 mA to 1 A, and the power consumption is about 0.2 to 2 W. The second element 20 is an InGaAlN-based light emitting element having a driving voltage of about 3 V, an operating current value of about 100 mA to 1 A, and a power consumption of about 0.3 to 3 W. The external power source is a commercial alternating current (for example, AC 100V), a dry cell (for example, DC 1.5V), or an automobile battery (DC 9 to 15V), which is converted into a light emitting element driving voltage by a power circuit (voltage conversion unit). Is reasonable.
[0055]
Since the light source module 50 uses a semiconductor light emitting element, the life of the light source module 50 is much longer than that of an incandescent light bulb or the like. However, if the light source module 50 is used for a long period of time, the light emission intensity decreases and eventually the life is reached. Therefore, it is convenient if the light source can be replaced when the lifetime has come. As shown in FIG. 23, the voltage converters 111 and 121 are provided with drive voltage output terminals 130, 131, and 132 that output light-emitting element drive voltages. Further, as shown in FIG. 22, the light source module 50 is assumed that the light emitting elements 10 and 20 and the power receiving terminals 61, 62, and 63 are integrated, and the power receiving terminals 61, 62, and 63 are driving voltage output terminals. What is necessary is just to make it attach to 130,131,132 so that attachment or detachment is possible. In this way, the light source module 50 that has reached the end of its life is removed, and a new light source module 50 is simply attached to the drive voltage output terminals 130, 131, and 132 at the power receiving terminals 61, 62, and 63. Can be done.
[0056]
In the light source module 50 shown in FIG. 1, the second electrodes 3 and 13 of both elements 10 and 20 are connected to a cathode stage 53 made of a metal conductor via a metal conductor paste such as an Ag paste. The first electrodes 9 and 19 of the elements 10 and 20 are connected to the conductor fittings 51 and 52 by metal leads 9a and 19a. The second electrodes 3 and 13 on the cathode side are connected in common at the cathode stage 53, and the cathode terminal 63 that is one of the power receiving terminals is taken out from the cathode stage 53. On the other hand, individual anode terminals 61 and 62 serving as power receiving terminals are taken out from the conductor fittings 51 and 52. The cathode stage 53, the elements 10, 20, and the conductor fittings 51 and 52 are entirely covered with a translucent resin mold 60 with the power receiving terminals 61, 62, 63 protruding, and a light source module. 50 is configured. The resin mold 60 can use a thermoplastic resin such as an acrylic resin, but the light scattering particles 261 made of bubbles, glass, or ceramic are dispersed and blended in the resin mold 60 so that the light from the two elements is sufficiently mixed. It is good to keep.
[0057]
The number of the first elements 10 and the second elements 20 incorporated in the light source module 50 can be one each as shown in FIG. 10, or as shown in FIGS. A plurality can be incorporated. FIG. 11 shows an example in which the same number of elements 10 and 20 are provided in order to improve the light emission intensity, and it is constant so that light from both elements 10 and 20 having different emission wavelength bands can be mixed and output. Elements 10 and 20 are alternately arranged along a path (in each case, a circumferential direction). On the other hand, FIG. 12 shows an example in which the number of elements 10 and 20 is different for the purpose of adjusting the waveform of the spectrum to be synthesized or matching the light emission levels of both elements 10 and 20.
[0058]
In FIG. 23, a commercial AC power supply 100 is used as a power supply unit. The voltage converter has an AC / DC converter 99 that converts the commercial AC power source into a DC voltage. Thereby, the illuminating device 90 can be easily attached and used for the existing electric wire etc. by commercial alternating current. The AC / DC converter 99 is connected to the commercial AC power supply 100 at a power supply terminal 135 configured by, for example, an outlet plug or the like. In the embodiment of FIG. 23, the AC / DC converter 99 includes a transformer 140 that steps down the power supply voltage (for example, 100 V) of the commercial AC power supply 100 to a predetermined voltage (for example, 5 to 15 V), and rectification that rectifies the alternating current after stepping down. Part 141. Here, a diode bridge is used as the rectifier 141, and full-wave rectification is performed.
[0059]
The rectified waveform by the rectifier 141 is smoothed by the capacitor 142 and then distributed and input to the drive stabilization power supply circuits 111 and 121 of the elements 10 and 20. The drive stabilization power supply circuits 111 and 121 have regulator ICs 112 and 122 (capacitors 113, 114, 123, and 124 are for preventing oscillation), respectively, and input voltage from the AC / DC converter 99 is supplied to each element. It is converted into a DC drive voltage suitable for 10 and 20, and output to the anode side drive voltage output terminals 130 and 131. The common cathode terminal 63 of the elements 10 and 20 is connected to the ground line G via the ground side drive voltage output terminal 132.
[0060]
FIG. 22 shows an example in which the lighting device 90 having the circuit shown in FIG. In this example, a terminal case 66 and a bulb bulb 65 are assembled to the light source module 50 to form a bulb-like light source unit 64. From the terminal surface of the terminal case 66, the power receiving terminals 61, 62, and 63 are drawn out in a pin shape. The terminal case 66 is integrated with a translucent bulb bulb 65 that covers the light source module 50. The bulb bulb 65 can be made of a light-transmitting thermoplastic resin such as glass or acrylic resin, and light scattering particles made of bubbles, glass or ceramic are dispersed and blended, or the inner surface is ground glass-like rough surface. By providing the ridge portion, it is possible to enhance the light dispersion effect and, in turn, the mixing effect of the light from the elements 10 and 20.
[0061]
The electric lamp 263 has a main body case 73, and the main body case 73 is provided with a light source socket 133 having a mounting recess 133a. The light source unit 64 is inserted into the mounting recess 133a of the light source socket 133 by the terminal case 66, and the power receiving terminals 61, 62, 63 are inserted into the female connector-like drive voltage output terminals 130, 131, 132 provided on the bottom surface thereof. It is installed. The drive voltage output terminals 130, 131, 132 are connected to the substrate of the power supply unit 70, and the power supply line 134 a to the power supply unit 70 is connected to the power supply unit 70 via the known switch box 72 and the power cord having the power plug 135. 134. If the power plug 135 is inserted into a commercial AC outlet, power is supplied to the light source module 50 of the light source unit 64 via the power supply unit 70, and the electric lamp 263 can be turned on with illumination light having an intended spectrum. If the switch box 72 is operated by the operation unit 74, the power supply to the light source module 50 is turned on / off, and the lamp 263 can be easily turned on / off.
[0062]
Note that the electric lamp 263 in FIG. 22 is configured as a device dedicated to a light source module using a light emitting element. In this case, the illumination device using the existing incandescent bulb has a drawback that the light source module cannot be diverted. Therefore, if the voltage converter is configured so that it can be detachably attached to a light bulb socket that is directly connected to a commercial AC power source with a mounting conductor that is compatible with the light bulb socket, Compatibility with sockets can be created and popularization can be promoted. Examples thereof will be described below. First, in order to be able to connect the voltage conversion unit directly to the light bulb socket, it is necessary to configure the voltage conversion unit as compact and small as possible. In the configuration of the circuit 91 illustrated in FIG. 24, the AC / DC converter 101 is configured by a dedicated LSI 102 (for example, BP5057-15 manufactured by Rohm Co., Ltd.) instead of a transformer to reduce the weight. The LSI 102 constitutes a step-down step-down voltage circuit by a peripheral diode 109, capacitors 103, 106, 108, a resistor 104 and a coil 107. The rest of the circuit configuration is exactly the same as in FIG.
[0063]
FIG. 25 shows a specific embodiment of the electric lamp 80. In this configuration, the conversion adapter 150 having the power supply unit 70 is configured, and the conversion adapter 150 can be attached to and detached from the light bulb socket 84 directly connected to the commercial AC power source by the mounting conductor portion 87 having compatibility therewith. It can be attached to. The light bulb socket 84 is attached to a mounting portion such as a ceiling or a wall surface by a fastening member 82a such as a screw together with the base 82. Then, on the inner surface of the light bulb socket 84, a female screw-shaped socket fitting 85 and a socket-side bottom terminal fitting 86 arranged in an insulated state are arranged, and the electric power is received from the commercial AC power source by the electric wire 136. The conversion adapter 150 includes a case 152 in which the power supply unit 70 is accommodated, and has a male screw shape that is the same shape as the cap for a light bulb and is connected to two AC input units (one of which is grounded) of the power supply unit 70. A mounting conductor portion 87 and an adapter-side bottom terminal fitting 88 are provided so as to protrude from the case 152. The case 152 is provided with a light bulb socket 133 having substantially the same structure as that shown in FIG. 22 (the same reference numerals are assigned to the common portions and detailed description thereof is omitted). When the conversion adapter 150 is attached to the light bulb socket 84 by the attachment conductor portion 87, the attachment conductor portion 87 and the socket fitting 85, the adapter side bottom terminal fitting 88 and the socket side bottom terminal fitting 86 are electrically connected to each other, and the power supply portion 70 is connected. Receives commercial AC from the electric wire 136. If the light source unit 64 is attached to the light bulb socket 133 of the conversion adapter 150, the electric lamp 80 can be turned on. A translucent hood 81 that covers the light source unit 64 is attachable to and detachable from the base 82 by an attaching / detaching portion 83 such as a screw type.
[0064]
In addition, the power supply unit 70 and the light emitting elements 10 and 20 (light source module 50) can be inseparably combined to form a light source unit with a voltage conversion function. According to this configuration, even if the conversion adapter 150 is not provided, the light emitting elements 10 and 20 can be easily attached to the light bulb socket 84 or the like. FIG. 26 shows an actual example. The electric lamp 80 'has substantially the same configuration as that shown in FIG. 25, but the power supply unit 70 and the mounting conductor unit 87 are integrated with the light source module 50 to form a light source unit 79 with a voltage conversion function. When the life of the light source module 50 expires, the power supply unit 70 is replaced with the light source unit with voltage conversion function 79 as a unit.
[0065]
Hereinafter, other embodiment of the illuminating device of this invention is described.
FIG. 27 shows an example in which a lighting device 160 having a candle-like appearance is configured as an example of a lighting device that simulates a combustion light source. The lighting device 160 is driven to light the light source module 50 shown in FIG. The circuit configuration is exactly the same as in FIG. And the pseudo | simulation continuous spectrum of the light emitting elements 10 and 20 of the light source module 50 has a pseudo combustion light spectrum imitating the continuous spectrum of combustion light. Specifically, in order to simulate the continuous spectrum of candlelight, the active layers 5 and 15 are designed so that a pseudo continuous spectrum (for example, about 1500 K) having a color temperature lower than that in FIG. 18 is obtained. The emission color is more orange or reddish. The power supply unit 70 is housed in a main body 162 simulating a candle shaft, the light source module 50 is disposed at the tip thereof, and the outer side thereof is covered with a translucent hood 161 simulating the appearance of a flame. . The power supply unit 70 receives power from an outlet through the power cord 134 and the power plug 135 drawn from the main body 162.
[0066]
The illuminating device 170 of FIG. 28 has a plurality of light source modules 50 arranged in a straight line so that a straight tube fluorescent lamp can be substituted. In the illumination device 170, the power supply unit 70 is accommodated in the main body case 172. Further, the light source modules 50 are arranged at predetermined intervals on one side surface in the longitudinal direction of the main body case 172, and the outer side is covered with a translucent hood 171 that can be attached to and detached from the main body case 172. . The light source module 50 has a color rendering wavelength region in a red region as indicated by a solid line in FIG. For example, a refrigerator 200 for displaying products 201 as shown in FIG. 29 is arranged in a meat shop or a meat counter, and the inside of the refrigerator 200 can be illuminated by the lighting device 170. As shown in FIG. 30, the meat 201m illuminated by the lighting device 170 appears brightly in red, which can tick consumers' willingness to purchase.
[0067]
Moreover, the illuminating devices 180 and 181 of FIG. 31 are examples configured for outdoor illumination, and each includes a light source module of the same type as that of FIG. The light source module used here has a color rendering wavelength region in a green region as shown by a one-dot chain line in FIG. For example, as shown in FIG. 31, plants such as trees TR and lawns GL illuminated by these lighting devices 180 and 181 appear to stand out vividly in green, and light up the garden and park at night beautifully and fantastically. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a light source module using a light emitting element of the present invention.
FIG. 2 is a schematic diagram illustrating an example of the overall configuration of a first light emitting element.
FIG. 3 is a schematic diagram illustrating an example of the overall configuration of a second light-emitting element.
FIG. 4 is a band diagram illustrating a configuration example of an active layer of the first light-emitting element.
FIG. 5 is a conceptual explanatory diagram of a pseudo continuous spectrum by a first light emitting element.
FIG. 6 is a graph showing the wavelength dependence of relative visibility with respect to visible light.
FIG. 7 is a band diagram illustrating a configuration example of an active layer of a second light-emitting element.
FIG. 8 is a conceptual explanatory diagram of a pseudo continuous spectrum by a second light emitting element.
FIG. 9 is a conceptual diagram of a combined spectrum of a first light emitting element and a second light emitting element.
FIG. 10 is a plan view showing a first arrangement example of a first light emitting element and a second light emitting element in a light source module.
FIG. 11 is a plan view showing a second arrangement example.
FIG. 12 is a plan view showing a third arrangement example.
FIG. 13 is a band diagram on the bottom side of a conductor showing a first modification of the active layer.
FIG. 14 is a band diagram on the bottom side of a conductor showing a second modification of the active layer.
FIG. 15 is a band diagram of the conductor bottom side showing a third modification of the active layer.
FIG. 16 is a band diagram on the conductor bottom side showing a fourth modification of the active layer.
FIG. 17 is an explanatory diagram showing a sunlight spectrum in a visible light band.
FIG. 18 is an explanatory diagram showing a spectrum of an incandescent bulb in the visible light band.
FIG. 19 is an explanatory diagram showing an example of a spectrum of a fluorescent lamp.
FIG. 20 is a band diagram of a conductor bottom side showing a fifth modification of the active layer.
FIG. 21 is a band diagram on the bottom side of a conductor showing a sixth modification of the active layer.
FIG. 22 is a cross-sectional view showing a first embodiment of a lighting device of the present invention.
FIG. 23 is a diagram showing a first circuit configuration example of a lighting device according to the present invention.
FIG. 24 is a diagram showing a second circuit configuration example of the illumination device of the present invention.
FIG. 25 is a cross-sectional view showing a second embodiment of the illumination device of the present invention.
FIG. 26 is a cross-sectional view showing a third embodiment of the illumination device of the present invention.
FIG. 27 is a sectional view showing a fourth embodiment of the lighting device of the present invention.
FIG. 28 is a cross-sectional view showing a fifth embodiment of the illumination device of the present invention.
29 is a diagram showing a usage example of the lighting device of FIG. 28;
30 is an explanatory diagram of the effect of FIG. 29. FIG.
FIG. 31 is a cross-sectional view showing a sixth embodiment of the illumination device of the present invention.
FIG. 32 is a schematic diagram showing an example of a pseudo continuous spectrum having a color rendering wavelength region realized by the light emitting element of the present invention.
FIG. 33 is a schematic diagram showing an example of a pseudo continuous spectrum having a broad single peak in an effective wavelength region.
FIG. 34 is a diagram for explaining a definition of a ripple rate of a pseudo continuous spectrum.
[Explanation of symbols]
10, 20 Light emitting device
8,18 Double hetero luminescent layer
5,15 Active layer
W1-Wn Well layer (light emitting unit layer)
B barrier layer
10 First element
20 Second element
50 Light source module
70 Power supply unit
100 Power supply
99, 111, 121 Voltage converter
130, 131, 132 Drive voltage output terminal
61, 62, 63 Power receiving terminal
79 Light source unit with voltage conversion function
84 Light bulb socket
87 Installed conductor

Claims (21)

A light emitting element that emits and outputs visible light having a pseudo continuous spectrum, which is a spectrum obtained by combining a plurality of light emission having different peak wavelengths in a pseudo manner.
In the light emitting element, an active layer of a double hetero light emitting layer portion made of a compound semiconductor includes a plurality of light emitting unit layers having different band gap energies, and the pseudo-light emitting element is based on a combination of light emitted from the light emitting unit layers. It emits and emits visible light with a continuous spectrum,
The light emitting unit layer is composed of a well layer sandwiched between two barrier layers. When the well layer is a quantum well, the number of the well layers is used. When the well layer is a non-quantum well, the well layer is a well layer. The well layer that contributes to the wavelength region in the quasi-continuous spectrum where the emission intensity of the emission unit layer is adjusted by the layer thickness and / or the number of layers and the emission intensity is higher in the pseudo continuous spectrum is the quantum well. In the case where the number of the well layers is a non-quantum well that contributes to the wavelength region, the thickness and / or the number of layers of the well layers are set large.
In the well layer, the light emitting unit layer having a shorter emission wavelength in the quasi-continuous spectrum, the well depth is set smaller,
The plurality of well layers are formed of a light emitting unit layer that emits light at a wavelength of 360 nm to 700 nm, and in a light emission intensity distribution after correcting the visibility by the light emitting unit layer, a color ranging from a yellow region to an orange region is developed from 570 nm to 640 nm. Has an intensity peak below,
The plurality of light emitting unit layers are adjusted so that the emission intensity peak monotonously increases with respect to the increase in the layer having a long emission wavelength,
The quasi-continuous spectrum has a pseudo-bulb light spectrum imitating a continuous spectrum of an incandescent bulb in an effective wavelength region.   The light emitting device according to claim 1, wherein the light emitting unit layer has a quantum well structure.   3. The light emitting device according to claim 2, wherein the well layer has a smaller thickness as the light emitting unit layer has a shorter emission wavelength.   The double hetero light emitting layer portion has a main surface on one side in the stacking direction as a light extraction surface, and the light emitting unit layer has a longer emission wavelength than the light extraction surface in the layer thickness direction of the active layer. The light emitting device according to claim 1, wherein the light emitting device is disposed at a distant position.   5. The light emission according to claim 1, wherein a plurality of the light emitting unit layers having different emission wavelengths are used as a repeating unit, and a plurality of the repeating units are formed in the layer thickness direction of the active layer. element.   In the double hetero light-emitting layer part, the main surface on one side in the stacking direction is a light extraction surface, and the light-emitting unit layer in the repeating unit has a longer light emission wavelength, and the active layer has a thickness direction. The light emitting device according to claim 5, wherein the light emitting device is disposed at a position far from the light extraction surface.   2. The light emitting device according to claim 1, wherein the plurality of light emitting unit layers have a difference value between adjacent band gap energies of 0.42 eV or less in a band gap energy arrangement.   The quasi-continuous spectrum is characterized in that an effective wavelength region showing an emission intensity of 5% or more of the reference intensity is secured over a range of at least 500 nm or more and 600 nm or less, with the emission intensity at a peak wavelength as a reference intensity. The light emitting device according to claim 1.   The quasi-continuous spectrum is characterized in that an effective wavelength region showing an emission intensity of 5% or more of the reference intensity is secured over a range of at least 470 nm or more and 650 nm or less, with the emission intensity at a peak wavelength as a reference intensity. The light emitting device according to claim 1.   The light emitting device according to claim 8 or 9, wherein the effective wavelength region of the pseudo continuous spectrum is synthesized by four or more light emitting unit layers having different light emission wavelengths.   The light-emitting element according to claim 10, wherein the pseudo continuous spectrum has a ripple rate of 0.1 or less over the entire effective wavelength region.   The predetermined wavelength range belonging to the effective wavelength range of the pseudo-continuous spectrum selectively enhances the color rendering of the color tone corresponding to the wavelength range than the color rendering property to the color tone corresponding to the other wavelength range. The light-emitting element according to claim 1, wherein the intensity distribution of the pseudo continuous spectrum is determined so as to be in a color rendering wavelength region.   The light emitting device according to claim 12, wherein the light emission intensity of the light emission unit layer contributing to the color rendering wavelength region is set higher than the light emission intensity of the light emission unit layer contributing to another wavelength region.   A first light emission layer portion comprising a compound semiconductor and a light emission wavelength of a light emission unit layer included in an active layer of the double hetero light emission layer portion is set in a range of 520 nm to 700 nm. And a second element set in the range of 360 nm or more and 560 nm or less, and at least one of the first element and the second element is the light emitting unit in the active layer. The light emitting device according to claim 1, comprising a plurality of layers. In the first element, the double hetero light-emitting layer portion is composed of (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1), In the second element, the double hetero light-emitting layer portion is composed of In _a Ga _b Al _1-ab N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a + b ≦ 1). The light-emitting element according to claim 14.   16. A light emitting device according to claim 1, and a power supply unit that supplies light emission driving power to the light emitting device, wherein the visible light from the light emitting device is extracted as illumination light. A lighting device characterized by that.   The lighting device according to claim 16, wherein the power supply unit includes a voltage conversion unit that converts an output voltage from the power supply unit into a light emitting element driving voltage.   The voltage converter is provided with a driving voltage output terminal for outputting the light emitting element driving voltage, and a light source module in which the light emitting element and the power receiving terminal are integrated is attached to and detached from the driving voltage output terminal at the power receiving terminal. The lighting device according to claim 17, wherein the lighting device can be attached.   The lighting device according to claim 17 or 18, wherein a commercial AC power source is used as the power source unit, and the voltage conversion unit includes an AC / DC converter that converts the commercial AC power source into a DC voltage. The voltage conversion unit, the commercial AC power source against the directly coupled bulb socket, lighting device detachably mounted by claim 19, wherein at mounting conductor portion having a socket compatible for the bulb.   The lighting device according to claim 17, wherein the voltage conversion unit and the light emitting element are inseparably coupled to each other to constitute a light source unit with a voltage conversion function.

Images