JP4552382B2 - ORGANIC ELECTROLUMINESCENT ELEMENT, ORGANIC ELECTROLUMINESCENT ELEMENT MATERIAL, DISPLAY DEVICE AND LIGHTING DEVICE - Google Patents

Description

【００５３】
【化７】

【００５４】
【化８】

【００５５】
本発明においては、発光層にりん光性ドーパントを併用するが、ＥＬ素子のりん光性ドーパントとして使用される公知のものの中から任意のものを選択して用いることができる。
【００５６】
例えば、特開２００１−２４７８５９号明細書に挙げられるイリジウム錯体あるいはＷＯ００／７０，６５５号明細書１６〜１８ページに挙げられるような式で表される、例えば、トリス（２−フェニルピリジン）イリジウム等やオスミウム錯体、あるいは２，３，７，８，１２，１３，１７，１８−オクタエチル−２１Ｈ，２３Ｈ−ポルフィリン白金錯体のような白金錯体もドーパントとして挙げられる。ドーパントとしてこのようなりん光性化合物を用いることにより、内部量子効率の高い発光有機ＥＬ素子を実現できる。
【００５７】
これらのりん光性化合物として具体的に好ましいのは、特に元素の周期律表でVIII属の金属を中心金属とする錯体系化合物である。更に好ましくは、中心金属がオスミウム、イリジウムまたは白金錯体系化合物である。最も、好ましくは、イリジウム錯体である。
【００５８】
これらのりん光性化合物ドーパントとしては、以下の化合物が挙げられる。
【００５９】
【化９】

【００６０】
【化１０】

【００６１】
【化１１】

【００６２】
このほかにも、例えば、Ｊ．Ａｍ．Ｃｈｅｍ．Ｓｏｃ．１２３巻４３０４〜４３１２頁（２００１年）、ＷＯ００／７０６５５号、ＷＯ０２／１５６４５号、特開２００１−２４７８５９号、特開２００１−３４５１８３号、特開２００２−１１７９７８号、特開２００２−１７０６８４号、特開２００２−２０３６７８号、特開２００２−２３５０７６号、特開２００２−３０２６７１号、特開２００２−３２４６７９号、特開２００２−３３２２９１号、特開２００２−３３２２９２号、特開２００２−３３８５８８号等に記載の一般式であげられるイリジウム錯体あるいは具体的例として挙げられるイリジウム錯体、特開２００２−８８６０号記載の式（IV）で表されるイリジウム錯体等が挙げられる。
【００６３】
これらの発光層は、上記化合物を、例えば真空蒸着法、スピンコート法、キャスト法、ＬＢ法などの公知の薄膜化法により製膜して形成することができる。
【００６４】
発光層は、これらの発光材料一種又は二種以上からなる一層構造であってもよいし、あるいは、同一組成又は異種組成の複数層からなる積層構造であってもよい。
【００６５】
本発明のりん光性化合物は溶液中のりん光量子収率が、２５℃において０．００１以上である。好ましくは、０．０１以上である。さらに、好ましくは、０．１以上である。りん光量子収率は、第４版実験化学講座７の分光IIの３９８ページ（１９９２年版、丸善）に記載の方法で測定することが出来る。
【００６６】
本発明において、発光層と陰極の間に正孔阻止層が設けられていることが好ましい。具体的には、特開平１１−４０３６７号に記載のアルミニウム錯体、トリアゾール誘導体、オキサジアゾール誘導体、トリアジン誘導体、ピリミジン誘導体、カルバゾール誘導体、または、ボロン誘導体等が挙げられる。好ましくは、トリアゾール誘導体、オキサジアゾール誘導体、または、ボロン誘導体である。
正孔阻止層は、正孔輸送層から移動してくる正孔を陰極に到達するのを阻止する役割と、陰極から注入された電子を効率よく発光層の方向に輸送することができる化合物より形成される。正孔阻止層を構成する材料に求められる物性としては、電子移動度が高く正孔移動度が低いこと、および、正孔を効率的に発光層内に閉じこめるために、発光層のイオン化ポテンシャルより大きいイオン化ポテンシャルの値を有するか、発光層のバンドギャップより大きいバンドギャップを有することが好ましい。正孔阻止層は正孔と電子を発光層内に閉じこめて、発光効率を向上させる機能を有する。
【００６７】
好ましくは、前記一般式（４）〜（６）で表される化合物が挙げられる。一般式（４）から（６）においてアルキル基、アリール基としては一般式（１）のＺ₁、Ｚ₂の置換基で述べたものと同様の基を挙げることができる。複素環としては、例えば、ピロリル基、ピリジル基、フリル基、チエニル基等が挙げられる。
【００６８】
一般式（４）〜（６）で表される化合物の具体例としては以下の化合物が挙げられるが、これらに限定されるものではない。
【００６９】
【化１２】

【００７０】
【化１３】

【００７１】
【化１４】

【００７２】
本発明の一般式（１）の化合物は、複数の発光性ドーパントと組み合わせて、白色の発光を生じる有機エレクトロルミネッセンス素子に関するものも含まれるが、現在のところ単一の発光材料で白色発光を示すものがないため、複数の発光材料により複数の発光色を同時に発光させて混色により白色発光を得ている。複数の発光色の組み合わせとしては、青色、緑色、赤色の３原色の３つの発光極大波長を含有させたものでも良いし、青色と黄色、青緑と橙色等の補色の関係を利用した２つの発光極大波長を含有したものでも良い。
【００７３】
また、複数の発光色を得るための発光材料の組み合わせは、複数の燐光または蛍光で発光する材料を、複数組み合わせたもの、蛍光または燐光で発光する発光材料と、発光材料からの光を励起光として発光する色素材料との組み合わせたもののいずれでも良い。
【００７４】
発光層の材料としては特に制限はなく、ＣＦ特性に対応した波長範囲に適合するように、公知の発光材料の中から任意のものを選択して組み合わせて白色化すれば良いが、特に、燐光を利用して発光する素子を形成する場合に用いられる発光ホストとしては、カルバゾール誘導体、ビフェニル誘導体、スチリル誘導体、ベンゾフラン誘導体、チオフェン誘導体、アリールシラン誘導体等の部分構造を単位として含む材料が挙げられる。なかでもカルバゾール誘導体とビフェニル誘導体は高い発光効率を示す好ましい発光材料である。最も好ましくは、本発明の一般式（１）で表される化合物である。
【００７５】
正孔輸送層を設ける場合は、材料に特に制限はないが、アノード電極からの正孔を発光する層に伝達する機能を有していれば良く、従来、光導電材料において、正孔の電荷注入材料として慣用されているものや、ＥＬ素子の正孔輸送層に用いられている公知のものの中から任意のものを選択して用いることができる。
【００７６】
電子輸送層を設ける場合においても、特に制限がなく、カソード電極からの電子を発光する層に伝達する機能を有していれば、従来公知の材料の中から任意のものを選択して用いることができる。
【００７７】
《有機ＥＬ素子の構成層》
本発明の有機ＥＬ素子の構成層について説明する。
【００７８】
本発明において、有機ＥＬ素子の層構成の好ましい具体例を以下に示すが、本発明はこれらに限定されない。
（ｉ）陽極／正孔輸送層／発光層／正孔阻止層／電子輸送層／陰極
（ii）陽極／正孔輸送層／発光層／正孔阻止層／電子輸送層／陰極バッファー層／陰極
（iii）陽極／陽極バッファー層／正孔輸送層／発光層／正孔阻止層／電子輸送層／陰極バッファー層／陰極
《陽極》
有機ＥＬ素子における陽極としては、仕事関数の大きい（４ｅＶ以上）金属、合金、電気伝導性化合物及びこれらの混合物を電極物質とするものが好ましく用いられる。このような電極物質の具体例としてはＡｕ等の金属、ＣｕＩ、インジウムチンオキシド（ＩＴＯ）、ＳｎＯ₂、ＺｎＯ等の導電性透明材料が挙げられる。また、ＩＤＩＸＯ（Ｉｎ₂Ｏ₃−ＺｎＯ）等非晶質で透明導電膜を作製可能な材料を用いてもよい。陽極は、これらの電極物質を蒸着やスパッタリング等の方法により、薄膜を形成させ、フォトリソグラフィー法で所望の形状のパターンを形成してもよく、あるいはパターン精度をあまり必要としない場合は（１００μｍ以上程度）、上記電極物質の蒸着やスパッタリング時に所望の形状のマスクを介してパターンを形成してもよい。この陽極より発光を取り出す場合には、透過率を１０％より大きくすることが望ましく、また、陽極としてのシート抵抗は数百Ω／□以下が好ましい。さらに膜厚は材料にもよるが、通常１０〜１０００ｎｍ、好ましくは１０〜２００ｎｍの範囲で選ばれる。
【００７９】
《陰極》
一方、陰極としては、仕事関数の小さい（４ｅＶ未満）金属（電子注入性金属と称する）、合金、電気伝導性化合物及びこれらの混合物を電極物質とするものが用いられる。このような電極物質の具体例としては、ナトリウム、ナトリウム−カリウム合金、マグネシウム、リチウム、マグネシウム／銅混合物、マグネシウム／銀混合物、マグネシウム／アルミニウム混合物、マグネシウム／インジウム混合物、アルミニウム／酸化アルミニウム（Ａｌ₂Ｏ₃）混合物、インジウム、リチウム／アルミニウム混合物、希土類金属等が挙げられる。これらの中で、電子注入性及び酸化等に対する耐久性の点から、電子注入性金属とこれより仕事関数の値が大きく安定な金属である第二金属との混合物、例えばマグネシウム／銀混合物、マグネシウム／アルミニウム混合物、マグネシウム／インジウム混合物、アルミニウム／酸化アルミニウム（Ａｌ₂Ｏ₃）混合物、リチウム／アルミニウム混合物、アルミニウム等が好適である。陰極は、これらの電極物質を蒸着やスパッタリング等の方法により、薄膜を形成させることにより、作製することができる。また、陰極としてのシート抵抗は数百Ω／□以下が好ましく、膜厚は通常１０ｎｍ〜１０００ｎｍ、好ましくは５０ｎｍ〜２００ｎｍの範囲で選ばれる。
なお、発光を透過させるため、有機ＥＬ素子の陽極または陰極のいずれか一方が、透明または半透明であれば発光輝度が向上し好都合である。
【００８０】
次に、本発明の有機ＥＬ素子の構成層として用いられる、注入層、正孔輸送層、電子輸送層等について説明する。
【００８１】
《注入層》：電子注入層、正孔注入層
注入層は必要に応じて設け、電子注入層と正孔注入層があり、上記のごとく陽極と発光層または正孔輸送層の間、及び、陰極と発光層または電子輸送層との間に存在させてもよい。
【００８２】
注入層とは、駆動電圧低下や発光輝度向上のために電極と有機層間に設けられる層のことで、「有機ＥＬ素子とその工業化最前線（１９９８年１１月３０日 エヌ・ティー・エス社発行）」の第２編第２章「電極材料」（１２３〜１６６頁）に詳細に記載されており、正孔注入層（陽極バッファー層）と電子注入層（陰極バッファー層）とがある。
【００８３】
陽極バッファー層（正孔注入層）は、特開平９−４５４７９号公報、同９−２６００６２号公報、同８−２８８０６９号公報等にもその詳細が記載されており、具体例として、銅フタロシアニンに代表されるフタロシアニンバッファー層、酸化バナジウムに代表される酸化物バッファー層、アモルファスカーボンバッファー層、ポリアニリン（エメラルディン）やポリチオフェン等の導電性高分子を用いた高分子バッファー層等が挙げられる。
【００８４】
陰極バッファー層（電子注入層）は、特開平６−３２５８７１号公報、同９−１７５７４号公報、同１０−７４５８６号公報等にもその詳細が記載されており、具体的にはストロンチウムやアルミニウム等に代表される金属バッファー層、フッ化リチウムに代表されるアルカリ金属化合物バッファー層、フッ化マグネシウムに代表されるアルカリ土類金属化合物バッファー層、酸化アルミニウムに代表される酸化物バッファー層等が挙げられる。
【００８５】
上記バッファー層（注入層）はごく薄い膜であることが望ましく、素材にもよるが、その膜厚は０．１ｎｍ〜１００ｎｍの範囲が好ましい。
【００８６】
正孔輸送層とは正孔を輸送する機能を有する材料からなり、広い意味で正孔注入層、電子阻止層も正孔輸送層に含まれる。
【００８７】
正孔輸送層、電子輸送層は単層もしくは複数層設けることができる。
本発明の有機ＥＬ素子においては、発光層のホスト、発光層に隣接する正孔輸送層、発光層に隣接する正孔阻止層すべての材料のりん光極大波長が３００ｎｍ以上４６０ｎｍ以下であることが好ましい。本発明でいうりん光波長とは、化合物をエタノールとメタノールの比率が４：１の溶媒に溶解し、温度７７Ｋで測定したりん光スペクトルにおいて、０−０バンドに相当する波長である。
【００８８】
《発光層》
本発明に係る発光層は、電極または電子輸送層、正孔輸送層から注入されてくる電子および正孔が再結合して発光する層であり、発光する部分は発光層の層内であっても発光層と隣接層との界面であっても良い。
【００８９】
この発光層は、上記化合物を、例えば真空蒸着法、スピンコート法、キャスト法、ＬＢ法などの公知の薄膜化法により製膜して形成することができる。発光層としての膜厚は、特に制限はないが、通常は５ｎｍ〜５μｍの範囲で選ばれる。
この発光層は、これらの発光材料一種又は二種以上からなる一層構造であってもよいし、あるいは、同一組成又は異種組成の複数層からなる積層構造であってもよい。本発明の有機ＥＬ素子の好ましい態様は、発光層が二種以上の材料からなり、その内の一種が本発明の化合物であるときである。
【００９０】
また、この発光層は、特開昭５７−５１７８１号公報に記載されているように、樹脂などの結着材と共に上記発光材料を溶剤に溶かして溶液としたのち、これをスピンコート法などにより薄膜化して形成することができる。このようにして形成された発光層の膜厚については、特に制限はなく、状況に応じて適宜選択することができるが、通常は５ｎｍ〜５μｍの範囲である。
【００９１】
発光層の材料が２種以上であるとき、主成分をホスト、その他の成分をドーパントといい、本発明に係る、前記一般式（１）〜（３）又は構造式（Ａ）で表される各部分構造を有する各々の化合物は、ホストとして用いられることが好ましい。その場合、主成分であるホスト化合物に対するドーパントの混合比は好ましくは質量で０．１質量％〜１５質量％未満である。
【００９２】
（ホスト化合物）
「ホスト化合物（単にホストともいう）」とは、２種以上の化合物で構成される発光層中にて混合比（質量）の最も多い化合物のことを意味し、それ以外の化合物については「ドーパント化合物（単に、ドーパントともいう）」という。例えば、発光層を化合物Ａ、化合物Ｂという２種で構成し、その混合比がＡ：Ｂ＝１０：９０であれば化合物Ａがドーパント化合物であり、化合物Ｂがホスト化合物である。更に、発光層を化合物Ａ、化合物Ｂ、化合物Ｃの３種から構成し、その混合比がＡ：Ｂ：Ｃ＝５：１０：８５であれば、化合物Ａ、化合物Ｂがドーパント化合物であり、化合物Ｃがホスト化合物である。
【００９３】
発光層のホスト化合物は、有機化合物または錯体であることが好ましく、本発明においては、好ましくはりん光極大波長が４６０ｎｍ以下である。ホスト化合物の極大波長を４６０ｎｍ以下にすることにより可視光、特にＢＧＲ発光が可能となる。また４６０ｎｍ以下のりん光を有することからワイドバンドギャップ（イオン化ポテンシャル−電子親和力）であるので、キャリアトラップ型にも有利に働く。
【００９４】
ホスト化合物としては、高Ｔｇ（ガラス転移温度）である化合物が好ましい。
（ドーパント）
次にドーパントについて述べる。
【００９５】
原理としては２種挙げられ、一つはキャリアが輸送されるホスト上でキャリアの再結合が起こってホスト化合物の励起状態が生成し、このエネルギーをドーパントに移動させることでドーパントからの発光を得るというエネルギー移動型、もう一つはドーパントがキャリアトラップとなり、ドーパント化合物上でキャリアの再結合が起こりドーパントからの発光が得られるというキャリアトラップ型であるが、いずれの場合においても、ドーパント化合物の励起状態のエネルギーはホスト化合物の励起状態のエネルギーよりも低いことが条件である。
【００９６】
《正孔輸送層》
正孔輸送層とは正孔を輸送する機能を有する材料からなり、広い意味で正孔注入層、電子阻止層も正孔輸送層に含まれる。正孔輸送層は単層もしくは複数層設けることができる。
【００９７】
正孔輸送材料としては、特に制限はなく、従来、光導伝材料において、正孔の電荷注入輸送材料として慣用されているものやＥＬ素子の正孔注入層、正孔輸送層に使用される公知のものの中から任意のものを選択して用いることができる。
【００９８】
正孔輸送材料は、正孔の注入もしくは輸送、電子の障壁性のいずれかを有するものであり、有機物、無機物のいずれであってもよい。例えばトリアゾール誘導体、オキサジアゾール誘導体、イミダゾール誘導体、ポリアリールアルカン誘導体、ピラゾリン誘導体及びピラゾロン誘導体、フェニレンジアミン誘導体、アリールアミン誘導体、アミノ置換カルコン誘導体、オキサゾール誘導体、スチリルアントラセン誘導体、フルオレノン誘導体、ヒドラゾン誘導体、スチルベン誘導体、シラザン誘導体、アニリン系共重合体、また、導電性高分子オリゴマー、特にチオフェンオリゴマー等が挙げられる。
【００９９】
正孔輸送材料としては、上記のものを使用することができるが、ポルフィリン化合物、芳香族第三級アミン化合物及びスチリルアミン化合物、特に芳香族第三級アミン化合物を用いることが好ましい。
【０１００】
芳香族第三級アミン化合物及びスチリルアミン化合物の代表例としては、Ｎ，Ｎ，Ｎ′，Ｎ′−テトラフェニル−４，４′−ジアミノフェニル；Ｎ，Ｎ′−ジフェニル−Ｎ，Ｎ′−ビス（３−メチルフェニル）−〔１，１′−ビフェニル〕−４，４′−ジアミン（ＴＰＤ）；２，２−ビス（４−ジ−ｐ−トリルアミノフェニル）プロパン；１，１−ビス（４−ジ−ｐ−トリルアミノフェニル）シクロヘキサン；Ｎ，Ｎ，Ｎ′，Ｎ′−テトラ−ｐ−トリル−４，４′−ジアミノビフェニル；１，１−ビス（４−ジ−ｐ−トリルアミノフェニル）−４−フェニルシクロヘキサン；ビス（４−ジメチルアミノ−２−メチルフェニル）フェニルメタン；ビス（４−ジ−ｐ−トリルアミノフェニル）フェニルメタン；Ｎ，Ｎ′−ジフェニル−Ｎ，Ｎ′−ジ（４−メトキシフェニル）−４，４′−ジアミノビフェニル；Ｎ，Ｎ，Ｎ′，Ｎ′−テトラフェニル−４，４′−ジアミノジフェニルエーテル；４，４′−ビス（ジフェニルアミノ）クオードリフェニル；Ｎ，Ｎ，Ｎ−トリ（ｐ−トリル）アミン；４−（ジ−ｐ−トリルアミノ）−４′−〔４−（ジ−ｐ−トリルアミノ）スチリル〕スチルベン；４−Ｎ，Ｎ−ジフェニルアミノ−（２−ジフェニルビニル）ベンゼン；３−メトキシ−４′−Ｎ，Ｎ−ジフェニルアミノスチルベンゼン；Ｎ−フェニルカルバゾール、さらには、米国特許第５，０６１，５６９号明細書に記載されている２個の縮合芳香族環を分子内に有するもの、例えば４，４′−ビス〔Ｎ−（１−ナフチル）−Ｎ−フェニルアミノ〕ビフェニル（ＮＰＤ）、特開平４−３０８６８８号公報に記載されているトリフェニルアミンユニットが３つスターバースト型に連結された４，４′，４″−トリス〔Ｎ−（３−メチルフェニル）−Ｎ−フェニルアミノ〕トリフェニルアミン（ＭＴＤＡＴＡ）等が挙げられる。
【０１０１】
さらにこれらの材料を高分子鎖に導入した、またはこれらの材料を高分子の主鎖とした高分子材料を用いることもできる。
【０１０２】
また、ｐ型−Ｓｉ，ｐ型−ＳｉＣ等の無機化合物も正孔注入材料、正孔輸送材料として使用することができる。
【０１０３】
この正孔輸送層は、上記正孔輸送材料を、例えば真空蒸着法、スピンコート法、キャスト法、インクジェット法、ＬＢ法等の公知の方法により、薄膜化することにより形成することができる。正孔輸送層の膜厚については特に制限はないが、通常は５〜５０００ｎｍ程度である。この正孔輸送層は、上記材料の一種または二種以上からなる一層構造であってもよい。
【０１０４】
《電子輸送層》
電子輸送層とは電子を輸送する機能を有する材料からなり、広い意味で電子注入層、正孔阻止層も電子輸送層に含まれる。電子輸送層は単層もしくは複数層設けることができる。
【０１０５】
電子輸送層は、陰極より注入された電子を発光層に伝達する機能を有していればよく、その材料としては従来公知の化合物の中から任意のものを選択して用いることができる。
【０１０６】
この電子輸送層に用いられる材料（以下、電子輸送材料という）の例としては、ニトロ置換フルオレン誘導体、ジフェニルキノン誘導体、チオピランジオキシド誘導体、ナフタレンペリレンなどの複素環テトラカルボン酸無水物、カルボジイミド、フレオレニリデンメタン誘導体、アントラキノジメタン及びアントロン誘導体、オキサジアゾール誘導体などが挙げられる。さらに、上記オキサジアゾール誘導体において、オキサジアゾール環の酸素原子を硫黄原子に置換したチアジアゾール誘導体、電子吸引基として知られているキノキサリン環を有するキノキサリン誘導体も、電子輸送材料として用いることができる。
【０１０７】
さらにこれらの材料を高分子鎖に導入した、またはこれらの材料を高分子の主鎖とした高分子材料を用いることもできる。
【０１０８】
また、８−キノリノール誘導体の金属錯体、例えばトリス（８−キノリノール）アルミニウム（Ａｌｑ）、トリス（５，７−ジクロロ−８−キノリノール）アルミニウム、トリス（５，７−ジブロモ−８−キノリノール）アルミニウム、トリス（２−メチル−８−キノリノール）アルミニウム、トリス（５−メチル−８−キノリノール）アルミニウム、ビス（８−キノリノール）亜鉛（Ｚｎｑ）など、及びこれらの金属錯体の中心金属がＩｎ、Ｍｇ、Ｃｕ、Ｃａ、Ｓｎ、Ｇａ又はＰｂに置き替わった金属錯体も、電子輸送材料として用いることができる。その他、メタルフリー若しくはメタルフタロシアニン、又はそれらの末端がアルキル基やスルホン酸基などで置換されているものも、電子輸送材料として好ましく用いることができる。また、発光層の材料として例示したジスチリルピラジン誘導体も、電子輸送材料として用いることができるし、正孔注入層、正孔輸送層と同様に、ｎ型−Ｓｉ、ｎ型−ＳｉＣなどの無機半導体も電子輸送材料として用いることができる。
【０１０９】
《基体（基板、基材、支持体等ともいう）》
本発明の有機ＥＬ素子に係る基体としては、ガラス、プラスチック等の種類には特に限定はなく、また、透明のものであれば特に制限はないが、好ましく用いられる基板としては例えばガラス、石英、光透過性樹脂フィルムを挙げることができる。特に好ましい基体は、有機ＥＬ素子にフレキシブル性を与えることが可能な樹脂フィルムである。
【０１１０】
樹脂フィルムとしては、例えばポリエチレンテレフタレート（ＰＥＴ）、ポリエチレンナフタレート（ＰＥＮ）、ポリエーテルスルホン（ＰＥＳ）、ポリエーテルイミド、ポリエーテルエーテルケトン、ポリフェニレンスルフィド、ポリアリレート、ポリイミド、ポリカーボネート（ＰＣ）、セルローストリアセテート（ＴＡＣ）、セルロースアセテートプロピオネート（ＣＡＰ）等からなるフィルム等が挙げられる。
【０１１１】
樹脂フィルムの表面には、無機物もしくは有機物の被膜またはその両者のハイブリッド被膜が形成されていてもよい。
【０１１２】
本発明の有機エレクトロルミネッセンス素子の発光の室温における外部取り出し効率は１％以上であることが好ましく、より好ましくは２％以上である。ここに、外部取り出し量子効率（％）＝有機ＥＬ素子外部に発光した光子数／有機ＥＬ素子に流した電子数×１００である。
【０１１３】
本発明の表示装置は、表示デバイス、ディスプレー、各種発光光源として用いることができる。表示デバイス、ディスプレーにおいて、青、赤、緑発光の３種の有機ＥＬ素子を用いることにより、フルカラーの表示が可能となる。
【０１１４】
表示デバイス、ディスプレーとしてはテレビ、パソコン、モバイル機器、ＡＶ機器、文字放送表示、自動車内の情報表示等が挙げられる。特に静止画像や動画像を再生する表示装置として使用してもよく、動画再生用の表示装置として使用する場合の駆動方式は単純マトリックス（パッシブマトリックス）方式でもアクティブマトリックス方式でもどちらでもよい。
【０１１５】
また、本発明に係る有機ＥＬ素子に共振器構造を持たせた有機ＥＬ素子として用いてもよい。
【０１１６】
このような共振器構造を有した有機ＥＬ素子の使用目的としては光記憶媒体の光源、電子写真複写機の光源、光通信処理機の光源、光センサーの光源等が挙げられるが、これらに限定されない。また、レーザー発振をさせることにより、上記用途に使用してもよい。
【０１１７】
本発明の有機ＥＬ素子は、照明用や露光光源のような一種のランプとして使用しても良いし、画像を投影するタイプのプロジェクション装置や、静止画像や動画像を直接視認するタイプの表示装置（ディスプレイ）として使用しても良い。
動画再生用の表示装置として使用する場合の駆動方式は単純マトリクス（パッシブマトリクス）方式でもアクティブマトリクス方式でもどちらでも良い。または、異なる発光色を有する本発明の有機ＥＬ素子を２種以上使用することにより、フルカラー表示装置を作製することが可能である。
【０１１８】
最も簡便に照明用の白色発光素子を構成するには、発光層における、ホスト化合物と共に用いる発光材料に、発光特性が互いに補色の関係にある、例えば青と黄または青緑と橙等補色の関係にある発光色を有する２種のドーパントを組み合わせる、また、青、緑、赤にそれぞれ３色に発光するドーパント（リン光性化合物）を、その発光効率を考慮しながら、適宜、混合してドープすることによって得ることが出来る。勿論、充分な白色光を得るために４種以上の発光材料を組み合わせてもよい。
【０１１９】
本発明の白色発光の有機エレクトロルミネッセンス素子は、基本的にはドーパントを混合するだけで、発光層もしくは正孔輸送層或いは電子輸送層等の形成時のみマスクを設け、マスクにより塗り分けるなど単純に配置するだけでよく、他層は共通であるのでマスク等のパターニングは不要であり、一面に蒸着法、キャスト法、スピンコート法、インクジェット法、印刷法等で例えば電極膜を形成でき、生産性も向上するものである。この方法によれば、複数色の発光素子をアレー状に並列配置した白色有機ＥＬ装置と異なり、素子自体が発光白色である。
【０１２０】
また作製順序を逆にして、陰極、電子注入層、電子輸送層、発光層、正孔輸送層、正孔注入層、陽極の順に作製することも可能である。
【０１２１】
このようにして得られた白色表示素子に、直流電圧を印加する場合には、陽極を＋、陰極を−の極性として電圧２〜４０Ｖ程度を印加すると、白色の発光が観測できる。また、逆の極性で電圧を印加しても電流は流れずに発光は全く生じない。さらに、交流電圧を印加する場合には、陽極が＋、陰極が−の状態になったときのみ発光する。なお、印加する交流の波形は任意でよい。
【０１２２】
本発明の白色発光の有機ＥＬ素子は、表示デバイス、ディスプレー、各種発光光源に用いることができるが、家庭用照明用、車内照明、また露光光源のような一種のランプとして、また液晶表示装置のバックライトとして表示装置にも有用に用いられる。
【０１２３】
その他、時計等のバックライト、看板広告、信号機、光記憶媒体等の光源、電子写真複写機の光源、光通信処理機の光源、光センサーの光源等、更には表示装置を必要とする一般の家庭用電気器具等広い範囲の用途が挙げられる。
【０１２４】
【発明の実施の形態】
本発明の有機ＥＬ素子から構成される表示装置の一例を図面に基づいて以下に説明する。
【０１２５】
図１は、有機ＥＬ素子から構成される表示装置の一例を示した模式図である。
有機ＥＬ素子の発光により画像情報の表示を行う、例えば、携帯電話等のディスプレイの模式図である。
【０１２６】
ディスプレイ１は、複数の画素を有する表示部Ａ、画像情報に基づいて表示部Ａの画像走査を行う制御部Ｂ等からなる。
【０１２７】
制御部Ｂは、表示部Ａと電気的に接続され、複数の画素それぞれに外部からの画像情報に基づいて走査信号と画像データ信号を送り、走査信号により走査線毎の画素が画像データ信号に応じて順次発光して画像走査を行って画像情報を表示部Ａに表示する。
【０１２８】
図２は、表示部Ａの模式図である。
表示部Ａは基板上に、複数の走査線５及びデータ線６を含む配線部と、複数の画素３等とを有する。表示部Ａの主要な部材の説明を以下に行う。
【０１２９】
図においては、画素３の発光した光が、白矢印方向（下方向）へ取り出される場合を示している。
【０１３０】
配線部の走査線５及び複数のデータ線６は、それぞれ導電材料からなり、走査線５とデータ線６は格子状に直交して、直交する位置で画素３に接続している（詳細は図示せず）。
【０１３１】
画素３は、走査線５から走査信号が印加されると、データ線６から画像データ信号を受け取り、受け取った画像データに応じて発光する。発光の色が赤領域の画素、緑領域の画素、青領域の画素を、適宜、同一基板上に並置することによって、フルカラー表示が可能となる。
【０１３２】
次に、画素の発光プロセスを説明する。
図３は、画素の模式図である。
【０１３３】
画素は、有機ＥＬ素子１０、スイッチングトランジスタ１１、駆動トランジスタ１２、コンデンサ１３等を備えている。複数の画素に有機ＥＬ素子１０として、赤色、緑色、青色発光の有機ＥＬ素子を用い、これらを同一基板上に並置することでフルカラー表示を行うことができる。
【０１３４】
図３において、制御部Ｂからデータ線６を介してスイッチングトランジスタ１１のドレインに画像データ信号が印加される。そして、制御部Ｂから走査線５を介してスイッチングトランジスタ１１のゲートに走査信号が印加されると、スイッチングトランジスタ１１の駆動がオンし、ドレインに印加された画像データ信号がコンデンサ１３と駆動トランジスタ１２のゲートに伝達される。
【０１３５】
画像データ信号の伝達により、コンデンサ１３が画像データ信号の電位に応じて充電されるとともに、駆動トランジスタ１２の駆動がオンする。駆動トランジスタ１２は、ドレインが電源ライン７に接続され、ソースが有機ＥＬ素子１０の電極に接続されており、ゲートに印加された画像データ信号の電位に応じて電源ライン７から有機ＥＬ素子１０に電流が供給される。
【０１３６】
制御部Ｂの順次走査により走査信号が次の走査線５に移ると、スイッチングトランジスタ１１の駆動がオフする。しかし、スイッチングトランジスタ１１の駆動がオフしてもコンデンサ１３は充電された画像データ信号の電位を保持するので、駆動トランジスタ１２の駆動はオン状態が保たれて、次の走査信号の印加が行われるまで有機ＥＬ素子１０の発光が継続する。順次走査により次に走査信号が印加されたとき、走査信号に同期した次の画像データ信号の電位に応じて駆動トランジスタ１２が駆動して有機ＥＬ素子１０が発光する。
【０１３７】
すなわち、有機ＥＬ素子１０の発光は、複数の画素それぞれの有機ＥＬ素子１０に対して、アクティブ素子であるスイッチングトランジスタ１１と駆動トランジスタ１２を設けて、複数の画素３それぞれの有機ＥＬ素子１０の発光を行っている。このような発光方法をアクティブマトリクス方式と呼んでいる。
【０１３８】
ここで、有機ＥＬ素子１０の発光は、複数の階調電位を持つ多値の画像データ信号による複数の階調の発光でもよいし、２値の画像データ信号による所定の発光量のオン、オフでもよい。
【０１３９】
また、コンデンサ１３の電位の保持は、次の走査信号の印加まで継続して保持してもよいし、次の走査信号が印加される直前に放電させてもよい。
【０１４０】
本発明においては、上述したアクティブマトリクス方式に限らず、走査信号が走査されたときのみデータ信号に応じて有機ＥＬ素子を発光させるパッシブマトリクス方式の発光駆動でもよい。
【０１４１】
図４は、パッシブマトリクス方式による表示装置の模式図である。図４において、複数の走査線５と複数の画像データ線６が画素３を挟んで対向して格子状に設けられている。
【０１４２】
順次走査により走査線５の走査信号が印加されたとき、印加された走査線５に接続している画素３が画像データ信号に応じて発光する。
【０１４３】
パッシブマトリクス方式では画素３にアクティブ素子が無く、製造コストの低減が計れる。
【０１４４】
【実施例】
以下、実施例により本発明を説明するが、本発明はこれらに限定されない。
【０１４５】
実施例１
化合物（１）の合成
２−ブロモ−ニトロベンゼン２５ｇと銅粉１７ｇをジメチルホルムアミドに溶解し、５時間１５０度で加熱した。溶液をろ過した後、水と酢酸エチルを加えて分液後、有機層を抽出し硫酸マグネシウムで乾燥させた。溶媒を留去して、２，２′ジニトロビフェニルを１４ｇ得た。得られた２，２′ジニトロビフェニルをエタノール２００ｍｌ、濃塩酸８０ｍｌに溶解し、スズ２８ｇを加えて３時間加熱還流した。反応液を中和、ろ過後、ろ液に酢酸エチル、水を加えて有機層を抽出した。硫酸マグネシウムで乾燥後、溶媒を減圧留去してからカラムクロマトグラフィーで精製し２，２′ジアミノビフェニルを１０ｇ得た。
【０１４６】
さらに、２，２′ジアミノビフェニル１ｇと２，２′ジブロモビフェニル３．５ｇをビスジベンジリデンアセトンパラジウム錯体とトリ−ｔｅｒｔ−ブチルホスフィンを触媒として、トルエン溶媒中で、塩基としてナトリウム−ｔ−ブトキシドを使用して４時間加熱攪拌した。反応終了後、酢酸エチルとテトラヒドロフランと水を加えて有機層を抽出した。硫酸マグネシウムで乾燥後、溶媒を減圧留去してからカラムクロマトグラフィーで精製した後、酢酸エチルで再結晶し、化合物（１）を１．８ｇ得た（収率６９％）。
【０１４７】
ＮＭＲスペクトル、マススペクトルにより化合物（１）であることを確認した。融点２４８〜２５０度であった。エタノールとメタノールの比率が４：１の溶媒に溶解し、温度７７Ｋで測定したりん光スペクトルにおいて、０−０バンドに相当する波長は、ＣＢＰが４６５ｎｍに対して、化合物（１）は４１３ｎｍであり、高い最低励起三重項エネルギーを有することが分かった。
【０１４８】
¹Ｈ ＮＭＲ（４００ＭＨｚ，ＤＭＳＯ−ｄ₆）は、δｐｐｍ：６．９５〜６．９８（８Ｈ）、７．３４〜７．３８（ｔ，４Ｈ）、７．５４〜７．５８（ｔ，４Ｈ）、７．８３（ｓ，ｂｒ，４Ｈ）、７．９５〜７．９７（ｄ，４Ｈ）であった。
【０１４９】
この化合物は、有機ＥＬ素子材料への用途はもちろんであるが、電子写真用の感光体等への用途も考えられる。
【０１５０】
又、原料の２−ブロモ−ニトロベンゼンに代えて、２−ブロモ−４−メチル−ニトロベンゼンを使用することで、本発明の化合物（５）を得ることができる。
【０１５１】
実施例２
《有機ＥＬ素子ＯＬＥＤ１−１の作製》：比較用
陽極としてガラス上にＩＴＯを１５０ｎｍ成膜した基板（ＮＨテクノグラス社製：ＮＡ−４５）にパターニングを行った後、このＩＴＯ透明電極を設けた透明支持基板をｉｓｏ−プロピルアルコールで超音波洗浄し、乾燥窒素ガスで乾燥し、ＵＶオゾン洗浄を５分間行った。
【０１５２】
この透明支持基板を、市販の真空蒸着装置の基板ホルダーに固定し、一方、５つのモリブデン製抵抗加熱ボートに、α−ＮＰＤ、ＣＢＰ、Ｉｒ−１２、ＢＣ、Ａｌｑ₃をそれぞれ入れ真空蒸着装置に取付けた。
【０１５３】
次いで、真空槽を４×１０^-4Ｐａまで減圧した後、α−ＮＰＤを透明支持基板に膜厚５０ｎｍの厚さになるように蒸着し、正孔注入／輸送層を設けた。さらに、ＣＢＰの入った前記加熱ボートとＩｒ−１２の入ったボートをそれぞれ独立に通電してＣＢＰとＩｒ−１２の蒸着速度が１００：７になるように調節し膜厚３０ｎｍになるように蒸着し、発光層を設けた。
【０１５４】
ついで、ＢＣを蒸着し厚さ１０ｎｍの正孔阻止層を設けた。さらに、Ａｌｑ₃を蒸着し膜厚４０ｎｍの電子輸送層を設けた。
【０１５５】
次に、真空槽を空け、電子注入層の上にステンレス鋼製の長方形穴あきマスクを設置し、一方、モリブデン製抵抗加熱ボートにマグネシウム３ｇを入れ、タングステン製の蒸着用バスケットに銀を０．５ｇ入れ、再び真空槽を２×１０^-4Ｐａまで減圧した後、マグネシウム入りのボートに通電して蒸着速度１．５〜２．０ｎｍ／秒でマグネシウムを蒸着し、この際、同時に銀のバスケットを加熱し、蒸着速度０．１ｎｍ／秒で銀を蒸着し、前記マグネシウムと銀との混合物から成る陰極（２００ｎｍ）として、比較用有機ＥＬ素子ＯＬＥＤ１−１を作製した。
【０１５６】
【化１５】

【０１５７】
《有機ＥＬ素子ＯＬＥＤ１−２〜１−１３の作製》
上記の有機ＥＬ素子ＯＬＥＤ１−１の作製において、発光層の作製に用いたＣＢＰと正孔阻止層に用いたＢＣを表１に記載の化合物に替えた以外は同様にして、有機ＥＬ素子ＯＬＥＤ１−２〜１−１３を各々作製した。
【０１５８】
得られた有機ＥＬ素子ＯＬＥＤ１−１〜１−１３の各々について下記のような評価を行った。
【０１５９】
《発光輝度、発光寿命》
有機ＥＬ素子ＯＬＥＤ１−２〜１−１３の各々の素子を温度２３度、乾燥窒素ガス雰囲気下で２．５ｍＡ／ｃｍ²の電流を供給した時の発光輝度（Ｌ）［ｃｄ／ｍ²］、及び輝度の半減する時間（τ）を測定した。ここで、発光輝度の測定等はＣＳ−１０００（ミノルタ製）を用いた。
【０１６０】
評価結果を表１に記載するにあたり、発光輝度、輝度の半減する時間（発光寿命ともいう）は、各々有機ＥＬ素子ＯＬＥＤ１−１を１００とした時の相対値で表した。得られた結果を表１に示す。
【０１６１】
【表１】

【０１６２】
【化１６】

【０１６３】
表１から、ＯＬＥＤ１−１〜１−１３で示される素子において比較化合物を用いたＯＬＥＤ１−１〜１−４と比べて、本発明に係る化合物を用いたＯＬＥＤ１−５〜ＯＬＥＤ１−１３の各試料は、発光輝度、および発光寿命のいずれにおいても優れていることが判る。
【０１６４】
更に、燐光性化合物であるＩｒ−１２をＩｒ−１に替えた以外は同様にしてＯＬＥＤ１−５ＧからＯＬＥＤ１−１３Ｇを、また、Ｉｒ−１２をＩｒ−９に代えた以外は同様にしてＯＬＥＤ１−５ＲからＯＬＥＤ１−１３Ｒを作製した。この有機ＥＬ素子においても上記Ｉｒ−１２を使用した時と同様の効果が得られた。
なお、Ｉｒ−１を用いた素子からは緑色の発光が、Ｉｒ−９を用いた素子からは赤色の発光が得られた。
【０１６５】
実施例３
《フルカラー表示装置の作製》
（青色発光素子の作製）
実施例２の有機ＥＬ素子ＯＬＥＤ１−１の作製において、正孔注入／輸送層にｍ−ＭＴＤＡＴＸＡを用い、発光層に化合物（１）＋Ｉｒ−１２（蒸着速度が１００：７になるように調節）を用い、正孔阻止層にＢ２を用い、電子輸送層Ａｌｑ₃の上に引き続きフッ化リチウム０．５ｎｍ及びアルミニウム１１０ｎｍを蒸着して、陰極バッファー層、陰極を各々形成した以外は同様にして、青色発光素子を作製した。
【０１６６】
【化１７】

【０１６７】
（緑色発光素子の作製）
上記の青色発光素子の作製において、発光層にＩｒ−１２の代わりにＩｒ−１（蒸着速度が１００：７になるように調節）を用いた以外は同様にして、緑色発光素子を作製した。
【０１６８】
（赤色発光素子の作製）
上記の青色発光素子の作製において、発光層にＩｒ−１２の代わりにＩｒ−９（蒸着速度が１００：７になるように調節）を用いた以外は同様にして、赤色発光素子を作製した。
【０１６９】
上記で作製した、各々赤色、緑色、青色発光素子を同一基板上に並置し、図１に記載のような形態を有するアクティブマトリクス方式フルカラー表示装置を作製し、図２には、作製した前記表示装置の表示部Ａの模式図のみを示した。即ち、同一基板上に、複数の走査線５及びデータ線６を含む配線部と、並置した複数の画素３（発光の色が赤領域の画素、緑領域の画素、青領域の画素等）とを有し、配線部の走査線５及び複数のデータ線６はそれぞれ導電材料からなり、走査線５とデータ線６は格子状に直交して、直交する位置で画素３に接続している（詳細は図示せず）。前記複数画素３は、それぞれの発光色に対応した有機ＥＬ素子、アクティブ素子であるスイッチングトランジスタと駆動トランジスタそれぞれが設けられたアクティブマトリクス方式で駆動されており、走査線５から走査信号が印加されると、データ線６から画像データ信号を受け取り、受け取った画像データに応じて発光する。この様に各赤、緑、青の画素を適宜、並置することによって、フルカラー表示装置を作製した。
【０１７０】
該フルカラー表示装置を駆動することにより、輝度が高く、高耐久性を有し、且つ、鮮明なフルカラー動画表示が得られることが判った。
【０１７１】
実施例４
（白色有機エレクトロルミネッセンス素子の作製）
本実施例により構成された有機エレクトロルミネッセンス素子は、低分子材料の発光ホストと、燐光ドーパントのＩｒ−６、Ｉｒ−１２の燐光を利用した２つの発光極大波長をもつ発光が同時に行われることによって白色発光を実現するものであるが、本発明の有機エレクトロルミネッセンス素子の実施態様がこれに限定されるものではない。
【０１７２】
まず、酸素プラズマにより有機エレクトロルミネッセンス素子を形成するベースフィルム表面のエッチングを行った。次に、エッチングを行ったベースフィルム上にスパッタ法によりＩＴＯを１００ｎｍの膜厚で成膜し、透明電極層となる透明なアノード電極を形成した。次に、１００ｍｍ×１００ｍｍの開口部をもつステンレンス薄膜板をマスキングに利用して、真空度１０^-4Ｐａの環境下で、真空蒸着法の抵抗加熱によりα−ＮＰＤを蒸着レート５Å／ｓで蒸着して２０ｎｍ膜厚で成膜して正孔輸送層とした。次に、正孔輸送層の上にマスクを利用して抵抗加熱により発光ホストのＣＢＰを蒸着レート５Å／ｓ、燐光ドーパントＩｒ−６を蒸着レート０．０５Å／ｓ、燐光ドーパントＩｒ−１２を蒸着レート０．２Å／ｓで共蒸着して３０ｎｍの膜厚で成膜して発光層とした。次に、発光層の上にマスクを利用して抵抗加熱によりＢＣを蒸着レート５Å／ｓで蒸着して１０ｎｍ膜厚で成膜し、正孔阻止層を兼ねた電子輸送層とした後、さらにＡｌｑ₃を蒸着レート５Å／ｓで蒸着して４０ｎｍ膜厚で成膜し、ＢＣ層とＡｌｑ₃層による積層構成の電子輸送層を形成した。
【０１７３】
次に、所定の電極パターン形状の開口部を持つステンレスマスクを利用して、抵抗加熱によりフッ化リチウムを蒸着レート０．１Å／ｓで蒸着して０．５ｎｍの膜厚で成膜した後、アルミニウムを蒸着レート１０Å／ｓで蒸着して１００ｎｍの膜厚で成膜して反電極層となるメタルカソード電極を形成して、比較例としての有機エレクトロルミネッセンス素子ＯＬＥＤ２−１を作製した。
【０１７４】
さらに、発光ホストとして用いる化合物を表２に示す化合物に置き換えた以外は有機エレクトロルミネッセンス素子ＯＬＥＤ２−１と同様にして、本発明の実施例である有機エレクトロルミネッセンス素子ＯＬＥＤ２−２〜２−６を作製した。
【０１７５】
〈有機エレクトロルミネッセンス素子の評価〉
作製した有機エレクトロルミネッセンス素子の評価を以下のようにして行い、結果を表２に示す。
【０１７６】
（発光輝度、発光効率）
有機エレクトロルミネッセンス素子ＯＬＥＤ２−１では、初期駆動電圧３Ｖで電流が流れ始め、発光層のドーパントである燐光性化合物からの白色の発光を示した。有機エレクトロルミネッセンス素子ＯＬＥＤ２−１〜２−６を温度２３℃、乾燥窒素ガス雰囲気下で１０Ｖ直流電圧を印加した時の発光輝度（ｃｄ／ｍ²）、発光効率（ｌｍ／Ｗ）を測定した。
【０１７７】
発光輝度、発光効率は有機エレクトロルミネッセンス素子ＯＬＥＤ２−１を１００とした時の相対値で表した。発光輝度については、ＣＳ−１０００（ミノルタ製）を用いて測定した。
【０１７８】
（発光寿命）
１０ｍＡ／ｃｍ²の一定電流で駆動したときに初期輝度が元の半分に低下するのに要した時間である半減寿命時間を指標として表した。半減寿命時間は有機ＥＬ素子ＯＬＥＤ２−１を１００とした時の相対値で表した。
【０１７９】
【表２】

【０１８０】
表２から明らかであるとおり、本発明の白色発光有機エレクトロルミネッセンス素子は高い発光輝度と発光効率、さらに大幅に改善された耐久性を有している。正孔阻止層をＢＡｌｑ、ＴＡＺ、ＯＸＤ７、Ｂ２に置き換えた場合、発光輝度、発光効率、発光寿命は、比較に比べて十分高い特性が見られた。また表２に記載した以外にも、本発明に記載した例示化合物を発光ホストに用いて構成した素子においても、同様の効果が得られた。
【０１８１】
【発明の効果】
本発明により、高い発光輝度を示し、且つ、発光寿命の長い有機エレクトロルミネッセンス素子及び表示装置を提供することが出来た。
【図面の簡単な説明】
【図１】有機ＥＬ素子から構成される表示装置の一例を示した模式図である。
【図２】表示部Ａの模式図である。
【図３】画素の模式図である。
【図４】パッシブマトリクス方式による表示装置の模式図である。
【符号の説明】
１ ディスプレイ
３ 画素
５ 走査線
６ データ線
７ 電源ライン
１０ 有機ＥＬ素子
１１ スイッチングトランジスタ
１２ 駆動トランジスタ
１３ コンデンサ
Ａ 表示部
Ｂ 制御部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescence element, a display device, and a lighting device.
[0002]
[Prior art]
Conventionally, there is an electroluminescence display (ELD) as a light-emitting electronic display device. Examples of constituent elements of ELD include inorganic electroluminescent elements and organic electroluminescent elements (hereinafter also referred to as organic EL elements). Inorganic electroluminescent elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements.
[0003]
On the other hand, an organic electroluminescence device has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and excitons (excitons) by injecting electrons and holes into the light emitting layer and recombining them. Is a device that emits light using the emission of light (fluorescence / phosphorescence) when this exciton is deactivated, and can emit light at a voltage of several volts to several tens of volts. Since it is a mold, it has a wide viewing angle, has high visibility, and is a thin-film complete solid-state device, and therefore has attracted attention from the viewpoints of space saving, portability, and the like.
[0004]
For the development of organic EL elements for practical use in the future, organic EL elements that emit light efficiently and with high brightness with lower power consumption are desired. For example, stilbene derivatives, distyrylarylene derivatives, or tris A technique for doping a styrylarylene derivative with a small amount of a phosphor to improve emission luminance and extend the lifetime of the device (see, for example, Patent Document 1), and using 8-hydroxyquinoline aluminum complex as a host compound, An organic light emitting layer having an organic light emitting layer doped with a small amount of a phosphor (see, for example, Patent Document 2), further comprising an 8-hydroxyquinoline aluminum complex as a host compound and doped with a quinacridone dye. There is a report on an element having the above (for example, see Patent Document 3). Regarding blue, an organic EL element having excellent blue color purity and a long lifetime (see, for example, Patent Document 4) is produced by introducing a linking group into the biaryl moiety in the middle of the carbazole derivative molecule.
[0005]
In the technique disclosed in the above document, when the emission from the excited singlet is used, the generation ratio of the singlet exciton and the triplet exciton is 1: 3, so the generation probability of the luminescent excited species is 25%. Since the light extraction efficiency is about 20%, the limit of the external extraction quantum efficiency (ηext) is set to 5%.
[0006]
However, since the University of Princeton reported on organic EL devices using phosphorescence emission from excited triplets (see, for example, Non-Patent Document 1), research on materials that exhibit phosphorescence at room temperature (for example, Non-Patent Documents). 2, see Patent Document 5).
[0007]
When excited triplets are used, the upper limit of internal quantum efficiency is 100%, so in principle the luminous efficiency is four times that of excited singlets, and the performance is almost the same as that of cold cathode tubes. It can be applied to and is attracting attention.
[0008]
Of course, the host when using a phosphorescent compound as a dopant needs to have an emission maximum wavelength in a region shorter than the emission maximum wavelength of the phosphorescent compound. I know that there is.
[0009]
When a blue to blue-green phosphorescent compound is used as a dopant, there is an example in which a carbazole derivative such as 4,4′-bis (9-carbazoyl) biphenyl (hereinafter referred to as CBP) is used as a host compound. The external extraction quantum efficiency is 6%, which is an inadequate result (see, for example, Non-Patent Document 3), and there is room for improvement. Furthermore, in addition to the carbazole derivative used in Patent Document 4, when a specific five-coordinate metal complex is used for the hole blocking layer and a phosphorescent compound is used as a dopant, the luminous efficiency is improved. Driving stability is achieved (for example, see Patent Document 6). In addition, there are disclosures about a plurality of carbazole derivatives as a host combined with a phosphorescent compound typified by an iridium complex (see, for example, Patent Document 7), but the carbazole derivative described in the patent and a hole blocking layer, or However, the combination of phosphorescent compounds has not yet reached a luminous efficiency and luminous lifetime that can withstand practical use. This is because a phosphorescent organic EL device that emits blue light requires a compound having a minimum excited triplet energy equal to or higher than the lowest excited triplet of the phosphorescent compound as a light emitting host. However, no highly efficient blue light emitting element has been found yet.
[0010]
At present, there is no single light-emitting material that emits white light, so that a plurality of light-emitting colors are simultaneously emitted by a plurality of light-emitting materials to obtain white light emission by color mixing. Combinations of multiple emission colors include those containing three emission maximum wavelengths of the three primary colors of blue, green and red, and two emission maximums utilizing the complementary colors such as blue and yellow, blue green and orange Although the thing containing a wavelength etc. can be considered, the present condition is that the element of a white light emission with high efficiency is not discovered also about the white as long as it utilizes blue anyway.
[0011]
[Patent Document 1]
Japanese Patent No. 3093796
[0012]
[Patent Document 2]
Japanese Unexamined Patent Publication No. 63-264692
[0013]
[Patent Document 3]
JP-A-3-255190
[0014]
[Patent Document 4]
JP 2000-21572 A
[0015]
[Non-Patent Document 1]
M.M. A. Baldo et al. , Nature, 395,
151-154 pages (1998)
[0016]
[Non-Patent Document 2]
M.M. A. Baldo et al. , Nature, volume 403,
17, 750-753 pages (2000)
[0017]
[Patent Document 5]
US Pat. No. 6,097,147
[0018]
[Non-Patent Document 3]
62nd Japan Society of Applied Physics Academic Lecture Proceedings 12-a-M8
[0019]
[Patent Document 6]
Japanese Patent Laid-Open No. 2002-8860
[0020]
[Patent Document 7]
US 2002/0034656 (Claim 75)
[0021]
[Problems to be solved by the invention]
An object of the present invention is to provide an organic electroluminescence element and a display device that exhibit high emission luminance and have a long lifetime. In particular, in blue light emission, the object is to achieve both the light emission luminance and the light emission life of the device. The present invention provides an organic electroluminescence device that achieves both light emission luminance and light emission life in blue light emission, and the present invention. The present invention provides a display device and an illuminating device having high emission luminance and long life using the organic electroluminescence element.
[0022]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitutions.
[0023]
1. An organic electroluminescence device comprising a compound represented by the general formula (1).
[0024]
  2. Has a light-emitting layer containing a host compound and a phosphorescent compoundRukoAnd featuresAs described in 1 aboveOrganic electroluminescence device.
[0025]
  3.The compound represented by the general formula (1) isCompound represented by the general formula (2)IsIt is characterized byThe 1 or 2Organic electroluminescence device.
[0026]
  4).The compound represented by the general formula (2) isCompound represented by the general formula (3)IsIt is characterized byAs described in 3 aboveOrganic electroluminescence device
[0027]
  5.The compound represented by the general formula (3) isCompound represented by the structural formula (A)IsIt is characterized byAs described in 4 aboveOrganic electroluminescence device.
[0028]
6).SaidGeneral formulas (1), (2), (3) andSaid6. The organic electroluminescence device according to any one of 1 to 5, wherein at least one compound selected from compounds represented by the structural formula (A) is used in the light emitting layer.
[0029]
7). 7. The organic electroluminescence device according to any one of 1 to 6, wherein a hole blocking layer is provided between the light emitting layer and the cathode.
[0030]
8). 8. The organic electroluminescence device as described in 7 above, wherein the hole blocking layer is composed of at least one compound of a triazole derivative, an oxadiazole derivative, or a boron derivative.
[0031]
  9.The triazole derivative, the oxadiazole derivative, or the boron derivative isAt least one of the compounds represented by the general formula (4), (5), or (6)is there9. The organic electroluminescence device as described in 8 above.
[0032]
  10.SaidThe phosphorescent compound is osmium, iridium, or a platinum complex compound,2The organic electroluminescent element of any one of 1-9.
[0033]
  11.SaidThe phosphorescent compound is an iridium complex compound,2The organic electroluminescent element of any one of 1-9.
[0034]
  12 2. The organic electroluminescent device according to 1 above, comprising a compound of the general formula (1) and a plurality of light-emitting dopants, and exhibiting white light emission.
  13. 13. An illuminating device comprising the white light-emitting organic electroluminescent element as described in 12 above.
  14 A display device comprising the organic electroluminescence element according to any one of 1 to 12 above.
[0035]
  15. An organic electroluminescence element material represented by the general formula (1).
[0036]
  16. 16. The organic electroluminescence element material according to 15, wherein the organic electroluminescence element material represented by the general formula (1) is an organic electroluminescence element material represented by the general formula (2).
[0037]
  17. 17. The organic electroluminescence element material according to 16, wherein the organic electroluminescence element material represented by the general formula (2) is an organic electroluminescence element material represented by the general formula (3).
[0038]
  18. 18. The organic electroluminescence device material according to 17, wherein the organic electroluminescence device material represented by the general formula (3) is an organic electroluminescence device material represented by the structural formula (A).
[0039]
The present invention will be described in more detail. As a result of intensive studies, the present inventors have used at least one of the compounds represented by the general formulas (1), (2), (3) or the structural formula (A) and a phosphorescent compound in an organic EL device. The present inventors have found that it is possible to provide an organic EL element that exhibits high emission luminance and has a long emission lifetime, and a display device and a lighting device including the element. These materials are desirably contained in the light emitting layer. Furthermore, it was found that a high-efficiency full-color image display device can be obtained by using a hole blocking layer between the light emitting layer and the cathode.
[0040]
The molecular structure of the compound used for the hole blocking layer is preferably composed of at least one compound of a triazole derivative, an oxadiazole derivative, or a boron derivative. More preferably, the triazole derivative is represented by the general formula (4), the oxadiazole derivative is represented by the general formula (5), and the boron derivative is represented by the general formula (6).
[0041]
In the carbazole derivatives described in JP-A Nos. 2000-21572 and 2002-8860, a linking group is introduced at the biaryl site in the middle of the molecule. However, in order to function as a sufficient performance as a blue phosphorescent host compound, a carbazole derivative having a linking group attached to CBP has its lowest excited triplet energy (T₁) Is limited in improving the light emission efficiency, and the lifetime is insufficient even when a 5-coordinated aluminum complex is used. As a result of intensive studies, we have improved the lifetime of organic EL devices while maintaining the basic skeleton of CBP.₁It was found to be important. As a specific means, a compound in which a carbazolyl group is introduced at the 2,2′-position of an aromatic ring typified by biphenyl is used while maintaining the basic skeleton of CBP.₁It was found that both high luminous efficiency and long life can be achieved. In this case, when this type of organic EL device material is used in the light emitting layer as a host of a phosphorescent compound, it has been found that the characteristics are remarkably improved as compared with the conventional CBP. As a result of the study by the present inventors, it has been found that the properties of the compound used for the hole blocking layer are also important in order to maximize the characteristics of this type of compound. In particular, in the case of a phosphorescent organic EL element, the role of a hole blocking material that efficiently confines holes and electrons in the light emitting layer is considered to be large, and this effect greatly changes the characteristics of the organic EL element.
[0042]
The compound of the present invention will be described in more detail. The present invention is characterized by being an organic EL device having a compound represented by the general formula (1), (2), (3) or the structural formula (A) and a phosphorescent compound. In general formula (1), (2), (3) or structural formula (A), general formula (2), (3) or structural formula (A) is preferable, but general formula (3) or structural formula (A) is most preferred.
[0043]
The compounds represented by the general formulas (1), (2), (3) and the structural formula (A) of the present invention will be described.
[0044]
  In the general formula (1) of the present invention, Z₁, Z₂IsA benzene ring or a pyridine ring, and the benzene ring or the pyridine ring isAlthough it may or may not have a substituent, the substituent is any one of a halogen atom, an alkyl group, an aryl group, and an alkoxy group. R₁~ R₁₆Is a hydrogen atom or a monovalent substituent.
[0045]
In the general formula (2) of the present invention, R₂₀~ R₃₅Is a hydrogen atom or a monovalent substituent. R₃₆~ R₄₃Is a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group.
[0046]
In the general formula (3) of the present invention, R₅₀~ R₆₅Is a hydrogen atom or a monovalent substituent. R₆₆~ R₆₉Is a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group.
[0047]
  In the general formula (1), Z₁, Z₂ Is a benzene ring or a pyridine ring,When these rings have a substituent, examples of the substituent include a halogen atom (fluorine atom and the like), an alkyl group (for example, a methyl group, an ethyl group, an isopropyl group, a hydroxyethyl group, a methoxymethyl group, a t-butyl group). Etc.), an alkoxy group (for example, methoxy group, ethoxy group, etc.), and an aryl group (for example, phenyl group, biphenyl group, mesityl group, etc.). Particularly preferred examples of the substituent include a methyl group, a phenyl group, a methoxy group, and a fluorine atom.
[0048]
R₁~ R₁₆, R₂₀~ R₃₅, R₅₀~ R₆₅Each independently represents a hydrogen atom or a substituent,₁~ R₁₆, R₂₀~ R₃₅, R₅₀~ R₆₅When represents a substituent, examples of the substituent include an alkyl group (for example, a methyl group, an ethyl group, an isopropyl group, a hydroxyethyl group, a methoxymethyl group, a t-butyl group), a cycloalkyl group (for example, a cyclopentyl group, cyclohexyl group). Group), aralkyl group (eg benzyl group, 2-phenethyl group etc.), aryl group (eg phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, mesityl group etc.), alkoxy group (eg ethoxy group, Isopropoxy group, butoxy group etc.), aryloxy group (eg phenoxy group etc.), cyano group, hydroxyl group, alkenyl group (eg vinyl group etc.), halogen atom (fluorine atom etc.) and the like. These groups may be further substituted.
[0049]
R₁~ R₁₆, R₂₀~ R₃₅, R₅₀~ R₆₅When represents a substituent, it is preferably a halogen atom, an alkyl group, an alkoxy group, or an aryl group.
[0050]
R₃₆~ R₄₃, R₆₆~ R₆₉Is a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group. Specific examples of the halogen atom, alkyl group, aryl group or alkoxy group include Z₁, Z₂And the same groups as those described above for the substituent.
[0051]
Specific examples of the compound of the present invention are shown below, but the present invention is not limited thereto.
[0052]
[Chemical 6]

[0053]
[Chemical 7]

[0054]
[Chemical 8]

[0055]
In the present invention, a phosphorescent dopant is used in combination in the light-emitting layer, and any known one used as the phosphorescent dopant of the EL element can be selected and used.
[0056]
For example, an iridium complex listed in JP-A No. 2001-247859 or a formula shown in WO 00 / 70,655, pages 16 to 18, for example, tris (2-phenylpyridine) iridium, etc. Examples of the dopant include platinum complexes such as platinum complex, osmium complex, and 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin platinum complex. By using such a phosphorescent compound as a dopant, a light-emitting organic EL device having high internal quantum efficiency can be realized.
[0057]
Particularly preferred as these phosphorescent compounds are complex compounds having a group VIII metal as a central metal in the periodic table of elements. More preferably, the central metal is an osmium, iridium or platinum complex compound. Most preferably, it is an iridium complex.
[0058]
Examples of these phosphorescent compound dopants include the following compounds.
[0059]
[Chemical 9]

[0060]
Embedded image

[0061]
Embedded image

[0062]
In addition, for example, J. et al. Am. Chem. Soc. 123, 4304-4312 (2001), WO00 / 70655, WO02 / 15645, JP2001-247859, JP2001-345183, JP2002-117978, JP2002-170684, special JP 2002-203678, JP 2002-235076, JP 2002-302671, JP 2002-324679, JP 2002-332291, JP 2002-332292, JP 2002-338588, etc. The iridium complex mentioned by general formula of this, the iridium complex mentioned as a specific example, the iridium complex represented by Formula (IV) of Unexamined-Japanese-Patent No. 2002-8860, etc. are mentioned.
[0063]
These light emitting layers can be formed by forming the above compound by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method.
[0064]
The light emitting layer may have a single layer structure composed of one or more of these light emitting materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.
[0065]
The phosphorescent compound of the present invention has a phosphorescence quantum yield in solution of 0.001 or more at 25 ° C. Preferably, it is 0.01 or more. Furthermore, it is preferably 0.1 or more. The phosphorescence quantum yield can be measured by the method described in the fourth edition, Experimental Chemistry Course 7, Spectral II, page 398 (1992 edition, Maruzen).
[0066]
In the present invention, a hole blocking layer is preferably provided between the light emitting layer and the cathode. Specific examples include aluminum complexes, triazole derivatives, oxadiazole derivatives, triazine derivatives, pyrimidine derivatives, carbazole derivatives, and boron derivatives described in JP-A-11-40367. A triazole derivative, an oxadiazole derivative, or a boron derivative is preferable.
The hole blocking layer has a role of blocking the holes moving from the hole transport layer from reaching the cathode, and a compound that can efficiently transport the electrons injected from the cathode toward the light emitting layer. It is formed. The physical properties required for the material constituting the hole blocking layer include high electron mobility and low hole mobility, and the ionization potential of the light emitting layer in order to efficiently confine holes in the light emitting layer. It is preferable to have a large ionization potential value or a band gap larger than that of the light emitting layer. The hole blocking layer has a function of confining holes and electrons in the light emitting layer to improve luminous efficiency.
[0067]
Preferably, the compounds represented by the general formulas (4) to (6) are mentioned. In general formulas (4) to (6), the alkyl group and aryl group may be Z in general formula (1).₁, Z₂And the same groups as those described above for the substituent. Examples of the heterocyclic ring include a pyrrolyl group, a pyridyl group, a furyl group, and a thienyl group.
[0068]
Specific examples of the compounds represented by the general formulas (4) to (6) include the following compounds, but are not limited thereto.
[0069]
Embedded image

[0070]
Embedded image

[0071]
Embedded image

[0072]
The compound of the general formula (1) of the present invention includes those related to an organic electroluminescence device that produces white light emission in combination with a plurality of light emitting dopants, but currently exhibits white light emission with a single light emitting material. Since there is nothing, a plurality of light emitting colors are simultaneously emitted by a plurality of light emitting materials to obtain white light emission by color mixing. The combination of a plurality of emission colors may include three emission maximum wavelengths of the three primary colors of blue, green, and red, or two of the complementary colors such as blue and yellow, blue green and orange, etc. The thing containing the light emission maximum wavelength may be used.
[0073]
In addition, a combination of light emitting materials for obtaining a plurality of emission colors is a combination of a plurality of phosphorescent or fluorescent light emitting materials, a light emitting material that emits fluorescence or phosphorescent light, and light from the light emitting material as excitation light. As a combination with a dye material that emits light as:
[0074]
There is no particular limitation on the material of the light emitting layer, and any white light emitting material selected from known light emitting materials may be combined and whitened so as to match the wavelength range corresponding to the CF characteristics. Examples of the light-emitting host used in forming an element that emits light by using a material include materials containing a partial structure such as a carbazole derivative, a biphenyl derivative, a styryl derivative, a benzofuran derivative, a thiophene derivative, and an arylsilane derivative as a unit. Of these, a carbazole derivative and a biphenyl derivative are preferable light emitting materials exhibiting high light emission efficiency. Most preferably, it is a compound represented by General formula (1) of this invention.
[0075]
In the case of providing a hole transport layer, there is no particular limitation on the material, but it is sufficient if it has a function of transmitting holes from the anode electrode to the light emitting layer. Any material commonly used as an injection material and known materials used for a hole transport layer of an EL element can be selected and used.
[0076]
Even in the case of providing an electron transport layer, there is no particular limitation, and any known material can be selected and used as long as it has a function of transmitting electrons from the cathode electrode to the light emitting layer. Can do.
[0077]
<< Constituent layers of organic EL elements >>
The constituent layers of the organic EL element of the present invention will be described.
[0078]
In this invention, although the preferable specific example of the layer structure of an organic EL element is shown below, this invention is not limited to these.
(I) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode
(Ii) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode
(Iii) Anode / anode buffer layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode
"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, CuI, indium tin oxide (ITO), SnO.₂And conductive transparent materials such as ZnO. IDIXO (In₂O_Three-ZnO) or other amorphous material capable of producing a transparent conductive film may be used. For the anode, a thin film may be formed by depositing these electrode materials by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method. Degree), a pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. When light emission is extracted from the anode, the transmittance is desirably greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.
[0079]
"cathode"
On the other hand, as the cathode, a material having a work function (less than 4 eV) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al₂O_Three) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, such as a magnesium / silver mixture, magnesium, from the viewpoint of electron injectability and durability against oxidation, etc. / Aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al₂O_Three) Mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 1000 nm, preferably 50 nm to 200 nm.
In order to transmit light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.
[0080]
Next, an injection layer, a hole transport layer, an electron transport layer, etc. used as a constituent layer of the organic EL element of the present invention will be described.
[0081]
<< Injection layer >>: Electron injection layer, hole injection layer
The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, and as described above, exists between the anode and the light emitting layer or the hole transport layer, and between the cathode and the light emitting layer or the electron transport layer. You may let them.
[0082]
An injection layer is a layer provided between an electrode and an organic layer in order to reduce driving voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (November 30, 1998, issued by NTS Corporation) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).
[0083]
The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.
[0084]
The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer represented by lithium, alkali metal compound buffer layer represented by lithium fluoride, alkaline earth metal compound buffer layer represented by magnesium fluoride, oxide buffer layer represented by aluminum oxide, etc. .
[0085]
The buffer layer (injection layer) is preferably a very thin film, and although it depends on the material, the film thickness is preferably in the range of 0.1 nm to 100 nm.
[0086]
The hole transport layer is made of a material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer.
[0087]
The hole transport layer and the electron transport layer can be provided as a single layer or a plurality of layers.
In the organic EL device of the present invention, the phosphorescence maximum wavelength of all the materials of the host of the light emitting layer, the hole transport layer adjacent to the light emitting layer, and the hole blocking layer adjacent to the light emitting layer is from 300 nm to 460 nm. preferable. The phosphorescence wavelength referred to in the present invention is a wavelength corresponding to the 0-0 band in a phosphorescence spectrum measured by dissolving a compound in a solvent having a ratio of ethanol and methanol of 4: 1 and measuring at a temperature of 77K.
[0088]
<Light emitting layer>
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May also be the interface between the light emitting layer and the adjacent layer.
[0089]
This light emitting layer can be formed by forming the above compound by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method. Although the film thickness as a light emitting layer does not have a restriction | limiting in particular, Usually, it selects in the range of 5 nm-5 micrometers.
This light emitting layer may have a single layer structure composed of one or two or more of these light emitting materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions. A preferred embodiment of the organic EL device of the present invention is when the light emitting layer is composed of two or more materials, and one of them is the compound of the present invention.
[0090]
Further, as described in JP-A-57-51781, this light emitting layer is prepared by dissolving the above light emitting material in a solvent together with a binder such as a resin, and then using a spin coating method or the like. It can be formed as a thin film. There is no restriction | limiting in particular about the film thickness of the light emitting layer formed in this way, Although it can select suitably according to a condition, Usually, it is the range of 5 nm-5 micrometers.
[0091]
When there are two or more materials for the light emitting layer, the main component is called a host and the other components are called dopants, which are represented by the general formulas (1) to (3) or the structural formula (A) according to the present invention. Each compound having each partial structure is preferably used as a host. In that case, the mixing ratio of the dopant to the host compound as the main component is preferably 0.1% by mass to less than 15% by mass.
[0092]
(Host compound)
“Host compound (also simply referred to as host)” means a compound having the largest mixing ratio (mass) in a light-emitting layer composed of two or more kinds of compounds. Compound (simply referred to as dopant) ". For example, if the light emitting layer is composed of two types of compound A and compound B and the mixing ratio is A: B = 10: 90, compound A is a dopant compound and compound B is a host compound. Furthermore, if a light emitting layer is comprised from 3 types of compound A, compound B, and compound C, and the mixing ratio is A: B: C = 5: 10: 85, compound A and compound B are dopant compounds, Compound C is a host compound.
[0093]
The host compound of the light emitting layer is preferably an organic compound or a complex. In the present invention, the phosphorescent maximum wavelength is preferably 460 nm or less. Visible light, particularly BGR emission can be achieved by setting the maximum wavelength of the host compound to 460 nm or less. In addition, since it has a phosphorescence of 460 nm or less, it has a wide band gap (ionization potential-electron affinity), so that it is advantageous for the carrier trap type.
[0094]
As the host compound, a compound having a high Tg (glass transition temperature) is preferable.
(Dopant)
Next, the dopant will be described.
[0095]
There are two types of principles. One is the recombination of carriers on the host to which the carriers are transported to generate an excited state of the host compound, and this energy is transferred to the dopant to obtain light emission from the dopant. The other is the carrier trap type in which the dopant becomes a carrier trap and carrier recombination occurs on the dopant compound, and light emission from the dopant is obtained. In either case, the dopant compound is excited. The condition is that the energy of the state is lower than the energy of the excited state of the host compound.
[0096]
《Hole transport layer》
The hole transport layer is made of a material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.
[0097]
The hole transport material is not particularly limited, and is conventionally used as a hole charge injection / transport material in an optical transmission material or a well-known material used for a hole injection layer or a hole transport layer of an EL element. Any one can be selected and used.
[0098]
The hole transport material has one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbenes Derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers, particularly thiophene oligomers, and the like can be given.
[0099]
As the hole transport material, those described above can be used, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.
[0100]
Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl; N, N′-diphenyl-N, N′— Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4′-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and two more described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 are linked in a starburst type ( MTDATA) and the like.
[0101]
Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.
[0102]
In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material.
[0103]
The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, it is about 5-5000 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.
[0104]
《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.
[0105]
The electron transport layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and any material can be selected from conventionally known compounds.
[0106]
Examples of materials used for the electron transport layer (hereinafter referred to as electron transport materials) include heterocyclic tetracarboxylic acid anhydrides such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, carbodiimides, Examples include fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, and oxadiazole derivatives. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material.
[0107]
Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.
[0108]
In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum, Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and the central metals of these metal complexes are In, Mg, Cu Metal complexes replaced with Ca, Sn, Ga, or Pb can also be used as electron transport materials. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transport material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and similarly to the hole injection layer and the hole transport layer, inorganic such as n-type-Si and n-type-SiC. A semiconductor can also be used as an electron transport material.
[0109]
<< Substrate (also referred to as substrate, substrate, support, etc.) >>
The substrate of the organic EL device of the present invention is not particularly limited to the type of glass, plastic, etc., and is not particularly limited as long as it is transparent. Examples of substrates that are preferably used include glass, quartz, A light transmissive resin film can be mentioned. A particularly preferable substrate is a resin film that can give flexibility to the organic EL element.
[0110]
Examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose triacetate. Examples thereof include films made of (TAC), cellulose acetate propionate (CAP) and the like.
[0111]
An inorganic or organic coating or a hybrid coating of both may be formed on the surface of the resin film.
[0112]
The external extraction efficiency at room temperature for light emission of the organic electroluminescence device of the present invention is preferably 1% or more, more preferably 2% or more. Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.
[0113]
The display device of the present invention can be used as a display device, a display, and various light emission sources. In a display device or a display, full-color display is possible by using three types of organic EL elements of blue, red, and green light emission.
[0114]
Examples of the display device and display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in an automobile. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.
[0115]
Further, the organic EL element according to the present invention may be used as an organic EL element having a resonator structure.
[0116]
Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, and a light source of an optical sensor. Not. Moreover, you may use for the said use by making a laser oscillation.
[0117]
The organic EL element of the present invention may be used as a kind of lamp such as an illumination or exposure light source, or a projection device that projects an image, or a display device that directly recognizes a still image or a moving image. (Display) may be used.
When used as a display device for reproducing moving images, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. Alternatively, a full-color display device can be manufactured by using two or more organic EL elements of the present invention having different emission colors.
[0118]
For the simplest construction of a white light emitting element for illumination, the light emitting material used together with the host compound in the light emitting layer has a complementary color relationship with each other, for example, blue and yellow, or a complementary color relationship such as blue green and orange. In addition, two dopants having the emission colors described above are combined, and dopants (phosphorescent compounds) that emit light in three colors, blue, green, and red, are mixed and doped as appropriate in consideration of the light emission efficiency. Can be obtained. Of course, in order to obtain sufficient white light, four or more kinds of light emitting materials may be combined.
[0119]
The white light emitting organic electroluminescence device of the present invention is basically simply mixed with a dopant, and a mask is provided only when forming a light emitting layer, a hole transport layer, an electron transport layer, etc. Since the other layers are common, patterning such as a mask is unnecessary, and for example, an electrode film can be formed on one side by vapor deposition, casting, spin coating, ink jet, printing, etc. It will also improve. According to this method, unlike a white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the elements themselves are luminescent white.
[0120]
In addition, it is also possible to reverse the production order and produce the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order.
[0121]
When a DC voltage is applied to the white display element thus obtained, white light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.
[0122]
The white light-emitting organic EL device of the present invention can be used for display devices, displays, and various light-emitting sources, but as a kind of lamp for home lighting, interior lighting, exposure light source, and liquid crystal display devices. It is also useful for a display device as a backlight.
[0123]
Others such as backlights for watches, signboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. There are a wide range of uses such as household appliances.
[0124]
DETAILED DESCRIPTION OF THE INVENTION
An example of a display device composed of the organic EL element of the present invention will be described below with reference to the drawings.
[0125]
FIG. 1 is a schematic diagram illustrating an example of a display device including organic EL elements.
It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element.
[0126]
The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like.
[0127]
The control unit B is electrically connected to the display unit A, and sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. The pixels for each scanning line are converted into image data signals by the scanning signal. In response to this, light is sequentially emitted and image scanning is performed to display image information on the display unit A.
[0128]
FIG. 2 is a schematic diagram of the display unit A.
The display unit A includes a wiring unit including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.
[0129]
In the figure, the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).
[0130]
The scanning lines 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a lattice shape and are connected to the pixels 3 at the orthogonal positions (details are shown in FIG. Not shown).
[0131]
When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data. Full color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region that emit light on the same substrate.
[0132]
Next, the light emission process of the pixel will be described.
FIG. 3 is a schematic diagram of a pixel.
[0133]
The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 10 in a plurality of pixels, and juxtaposing them on the same substrate.
[0134]
In FIG. 3, an image data signal is applied from the control unit B to the drain of the switching transistor 11 through the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is supplied to the capacitor 13 and the driving transistor 12. Is transmitted to the gate.
[0135]
By transmitting the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the drive of the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10, and the power supply line 7 connects to the organic EL element 10 according to the potential of the image data signal applied to the gate. Current is supplied.
[0136]
When the scanning signal is moved to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, even if the driving of the switching transistor 11 is turned off, the capacitor 13 maintains the potential of the charged image data signal, so that the driving of the driving transistor 12 is kept on and the next scanning signal is applied. Until then, the light emission of the organic EL element 10 continues. When the scanning signal is next applied by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.
[0137]
That is, the organic EL element 10 emits light by the switching transistor 11 and the drive transistor 12 that are active elements for the organic EL element 10 of each of the plurality of pixels, and the light emission of the organic EL element 10 of each of the plurality of pixels 3. It is carried out. Such a light emitting method is called an active matrix method.
[0138]
Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or on / off of a predetermined light emission amount by a binary image data signal. But you can.
[0139]
The potential of the capacitor 13 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.
[0140]
In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which an organic EL element emits light according to a data signal only when a scanning signal is scanned.
[0141]
FIG. 4 is a schematic view of a passive matrix display device. In FIG. 4, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape so as to face each other with the pixel 3 interposed therebetween.
[0142]
When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal.
[0143]
In the passive matrix system, the pixel 3 has no active element, and the manufacturing cost can be reduced.
[0144]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.
[0145]
Example 1
Synthesis of compound (1)
25 g of 2-bromo-nitrobenzene and 17 g of copper powder were dissolved in dimethylformamide and heated at 150 degrees for 5 hours. After the solution was filtered, water and ethyl acetate were added for liquid separation, and the organic layer was extracted and dried over magnesium sulfate. The solvent was distilled off to obtain 14 g of 2,2′dinitrobiphenyl. The obtained 2,2′dinitrobiphenyl was dissolved in 200 ml of ethanol and 80 ml of concentrated hydrochloric acid, 28 g of tin was added, and the mixture was heated to reflux for 3 hours. After neutralizing and filtering the reaction solution, ethyl acetate and water were added to the filtrate to extract the organic layer. After drying with magnesium sulfate, the solvent was distilled off under reduced pressure and purified by column chromatography to obtain 10 g of 2,2′diaminobiphenyl.
[0146]
Further, 1 g of 2,2′diaminobiphenyl and 3.5 g of 2,2′dibromobiphenyl were added with bisdibenzylideneacetone palladium complex and tri-tert-butylphosphine as a catalyst and sodium t-butoxide as a base in a toluene solvent. Used and stirred for 4 hours. After completion of the reaction, ethyl acetate, tetrahydrofuran and water were added to extract the organic layer. After drying over magnesium sulfate, the solvent was distilled off under reduced pressure, and the residue was purified by column chromatography and recrystallized from ethyl acetate to obtain 1.8 g of compound (1) (yield 69%).
[0147]
The compound (1) was confirmed by NMR spectrum and mass spectrum. The melting point was 248 to 250 degrees. In the phosphorescence spectrum measured at a temperature of 77 K and dissolved in a solvent having a ratio of ethanol to methanol of 4: 1, the wavelength corresponding to the 0-0 band is 413 nm for compound (1) versus 465 nm for CBP. It was found to have a high lowest excited triplet energy.
[0148]
¹1 H NMR (400 MHz, DMSO-d₆): Δ ppm: 6.95 to 6.98 (8H), 7.34 to 7.38 (t, 4H), 7.54 to 7.58 (t, 4H), 7.83 (s, br, 4H), 7.95-7.97 (d, 4H).
[0149]
This compound can be used not only for organic EL element materials but also for electrophotographic photoreceptors.
[0150]
Further, by using 2-bromo-4-methyl-nitrobenzene instead of the starting material 2-bromo-nitrobenzene, the compound (5) of the present invention can be obtained.
[0151]
Example 2
<< Preparation of organic EL element OLED1-1 >>: For comparison
After patterning on a substrate (NH Techno Glass Co., Ltd .: NA-45) having a 150 nm ITO film formed on glass as an anode, the transparent support substrate provided with this ITO transparent electrode was ultrasonically cleaned with iso-propyl alcohol. Then, it was dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.
[0152]
This transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while α-NPD, CBP, Ir-12, BC, Alq is attached to five molybdenum resistance heating boats._ThreeWere attached to a vacuum deposition apparatus.
[0153]
The vacuum chamber is then 4 × 10^-FourAfter reducing the pressure to Pa, α-NPD was deposited on the transparent support substrate to a thickness of 50 nm to provide a hole injection / transport layer. Further, the heating boat containing CBP and the boat containing Ir-12 are energized independently to adjust the deposition rate of CBP and Ir-12 to 100: 7, so that the film thickness is 30 nm. The light emitting layer was provided.
[0154]
Subsequently, BC was vapor-deposited to provide a 10 nm thick hole blocking layer. Furthermore, Alq_ThreeWas deposited to provide an electron transport layer having a thickness of 40 nm.
[0155]
Next, a vacuum chamber is opened, and a rectangular hole mask made of stainless steel is placed on the electron injection layer. On the other hand, 3 g of magnesium is put in a resistance heating boat made of molybdenum, and 0.03 of silver is put in a tungsten vapor deposition basket. Put 5g and again vacuum tank 2 × 10^-FourAfter depressurizing to Pa, power was applied to the magnesium-containing boat to deposit magnesium at a deposition rate of 1.5 to 2.0 nm / second. At this time, the silver basket was simultaneously heated, and the deposition rate was 0.1 nm / second. Silver was vapor-deposited, and a comparative organic EL element OLED1-1 was produced as a cathode (200 nm) made of a mixture of magnesium and silver.
[0156]
Embedded image

[0157]
<< Production of Organic EL Elements OLED1-2 to 1-13 >>
In the production of the organic EL element OLED1-1, the organic EL element OLED1- was prepared in the same manner except that the CBP used for the production of the light emitting layer and the BC used for the hole blocking layer were changed to the compounds shown in Table 1. 2 to 1-13 were prepared.
[0158]
The following evaluation was performed about each of obtained organic EL element OLED1-1 to 1-13.
[0159]
《Luminescence brightness, Luminescence life》
Each element of the organic EL elements OLED1-2 to 1-13 is 2.5 mA / cm at a temperature of 23 degrees and in a dry nitrogen gas atmosphere.²Luminance (L) [cd / m²], And the time (τ) during which the luminance is reduced by half. Here, CS-1000 (manufactured by Minolta) was used for measurement of light emission luminance and the like.
[0160]
In describing the evaluation results in Table 1, the light emission luminance and the time during which the luminance is reduced by half (also referred to as the light emission lifetime) are expressed as relative values when the organic EL element OLED1-1 is set to 100, respectively. The obtained results are shown in Table 1.
[0161]
[Table 1]

[0162]
Embedded image

[0163]
From Table 1, each sample of OLED1-5 to OLED1-13 using the compound according to the present invention compared to OLED1-1 to 1-4 using the comparative compound in the elements shown by OLED1-1 to 1-13 It can be seen that both are excellent in emission luminance and emission lifetime.
[0164]
Further, except that Ir-12, which is a phosphorescent compound, is changed to Ir-1, OLED1-5G to OLED1-13G are similarly changed, and except that Ir-12 is changed to Ir-9, OLED1- OLED1-13R was produced from 5R. In this organic EL device, the same effect as that obtained when Ir-12 was used was obtained.
In addition, green light emission was obtained from the element using Ir-1, and red light emission was obtained from the element using Ir-9.
[0165]
Example 3
<Production of full-color display device>
(Production of blue light emitting element)
In the production of the organic EL element OLED1-1 of Example 2, m-MTDATXA was used for the hole injection / transport layer, and the compound (1) + Ir-12 was adjusted for the light emitting layer (adjusted so that the deposition rate was 100: 7). , B2 is used for the hole blocking layer, the electron transport layer Alq_ThreeSubsequently, 0.5 nm of lithium fluoride and 110 nm of aluminum were vapor-deposited on the substrate, and a blue light emitting device was produced in the same manner except that a cathode buffer layer and a cathode were respectively formed.
[0166]
Embedded image

[0167]
(Production of green light emitting element)
A green light emitting device was produced in the same manner as in the production of the blue light emitting device, except that Ir-1 (adjusted so that the deposition rate was 100: 7) was used instead of Ir-12 in the light emitting layer.
[0168]
(Production of red light emitting element)
In the production of the blue light-emitting element, a red light-emitting element was produced in the same manner except that Ir-9 (adjusted so that the deposition rate was 100: 7) was used instead of Ir-12 in the light-emitting layer.
[0169]
Each of the red, green, and blue light-emitting elements produced above is juxtaposed on the same substrate to produce an active matrix type full-color display device having the form shown in FIG. 1, and FIG. 2 shows the produced display. Only a schematic view of the display part A of the apparatus is shown. That is, a wiring portion including a plurality of scanning lines 5 and data lines 6 on the same substrate, and a plurality of juxtaposed pixels 3 (light emission color is a red region pixel, a green region pixel, a blue region pixel, etc.) The scanning lines 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a lattice shape and are connected to the pixels 3 at the orthogonal positions ( Details are not shown). The plurality of pixels 3 are driven by an active matrix system provided with an organic EL element corresponding to each emission color, a switching transistor as an active element, and a driving transistor, and a scanning signal is applied from a scanning line 5. Then, an image data signal is received from the data line 6 and light is emitted according to the received image data. In this way, a full color display device was produced by appropriately juxtaposing the red, green, and blue pixels.
[0170]
It has been found that by driving the full-color display device, a clear full-color moving image display having high luminance, high durability, and clearness can be obtained.
[0171]
Example 4
(Production of white organic electroluminescence device)
The organic electroluminescence device configured according to this example is configured to emit light having two light emission maximum wavelengths using phosphorescence of a phosphorescent dopant Ir-6 and Ir-12 at the same time. Although it implement | achieves white light emission, the embodiment of the organic electroluminescent element of this invention is not limited to this.
[0172]
First, the surface of the base film for forming the organic electroluminescence element was etched with oxygen plasma. Next, an ITO film having a thickness of 100 nm was formed on the etched base film by a sputtering method to form a transparent anode electrode serving as a transparent electrode layer. Next, using a stainless thin film plate having an opening of 100 mm × 100 mm for masking, the degree of vacuum is 10^-FourUnder the environment of Pa, α-NPD was vapor-deposited at a vapor deposition rate of 5 加熱 / s by resistance heating in a vacuum vapor deposition method to form a hole transport layer with a film thickness of 20 nm. Next, the CBP of the light emitting host is deposited at a deposition rate of 5 Å / s, the phosphorescent dopant Ir-6 is deposited at a deposition rate of 0.05 Å / s, and the phosphorescent dopant Ir-12 is deposited on the hole transport layer by resistance heating using a mask. Co-evaporated at a rate of 0.2 Å / s to form a light emitting layer by forming a film with a thickness of 30 nm. Next, BC is vapor-deposited at a deposition rate of 5 Å / s by resistance heating using a mask on the light-emitting layer to form a film with a thickness of 10 nm, and an electron transport layer that also serves as a hole blocking layer is formed. Alq_ThreeWas deposited at a deposition rate of 5 Å / s to a film thickness of 40 nm, and the BC layer and Alq_ThreeAn electron transport layer having a laminated structure of layers was formed.
[0173]
Next, using a stainless steel mask having an opening having a predetermined electrode pattern shape, lithium fluoride was vapor-deposited at a deposition rate of 0.1 Å / s by resistance heating to form a film with a thickness of 0.5 nm, Aluminum was vapor-deposited at a deposition rate of 10 成膜 / s to form a metal cathode electrode serving as a counter electrode layer by forming a film with a film thickness of 100 nm, thereby producing an organic electroluminescent element OLED2-1 as a comparative example.
[0174]
Further, organic electroluminescent elements OLED2-2 to 2-6 as examples of the present invention were produced in the same manner as the organic electroluminescent element OLED2-1 except that the compounds used as the light emitting host were replaced with the compounds shown in Table 2. did.
[0175]
<Evaluation of organic electroluminescence device>
The produced organic electroluminescence device was evaluated as follows, and the results are shown in Table 2.
[0176]
(Luminance, luminous efficiency)
In the organic electroluminescence element OLED2-1, a current started to flow at an initial driving voltage of 3 V, and white light was emitted from the phosphorescent compound as a dopant of the light emitting layer. Luminous luminance (cd / m) when a 10 V DC voltage is applied to the organic electroluminescent elements OLED2-1 to 2-6 at a temperature of 23 ° C. in a dry nitrogen gas atmosphere²) And luminous efficiency (lm / W) were measured.
[0177]
Luminance and luminous efficiency were expressed as relative values when the organic electroluminescence element OLED2-1 was taken as 100. The light emission luminance was measured using CS-1000 (Minolta).
[0178]
(Luminescent life)
10 mA / cm²The half-life time, which is the time required for the initial luminance to drop to half of the original luminance when driven at a constant current, was expressed as an index. The half-life time was expressed as a relative value when the organic EL element OLED2-1 was set to 100.
[0179]
[Table 2]

[0180]
As is apparent from Table 2, the white light-emitting organic electroluminescence device of the present invention has high light emission luminance and light emission efficiency, and further improved durability. When the hole blocking layer was replaced with BAlq, TAZ, OXD7, and B2, the light emission luminance, light emission efficiency, and light emission lifetime were sufficiently high compared to the comparison. Further, in addition to those described in Table 2, the same effect was also obtained in an element constituted by using the exemplified compound described in the present invention as a light emitting host.
[0181]
【The invention's effect】
According to the present invention, an organic electroluminescence element and a display device that exhibit high emission luminance and have a long emission lifetime can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a display device composed of organic EL elements.
FIG. 2 is a schematic diagram of a display unit A.
FIG. 3 is a schematic diagram of a pixel.
FIG. 4 is a schematic diagram of a display device using a passive matrix method.
[Explanation of symbols]
1 Display
3 pixels
5 scanning lines
6 data lines
7 Power line
10 Organic EL elements
11 Switching transistor
12 Driving transistor
13 Capacitor
A display
B Control unit

Claims (18)

The organic electroluminescent element characterized by containing the compound represented by following General formula (1).

[In the formula, Z ₁ and Z ₂ are a benzene ring or a pyridine ring, and the benzene ring or the pyridine ring may or may not have a substituent, but has a substituent. The substituent is any one of a halogen atom, an alkyl group, an aryl group, and an alkoxy group. R _{1 to} R ₁₆ are a hydrogen atom or a monovalent substituent. ]   The organic electroluminescent device according to claim 1, further comprising a light emitting layer containing a host compound and a phosphorescent compound. The organic electroluminescent element according to claim 1 or 2, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2).

[Wherein, R _{20 to} R ₃₅ are a hydrogen atom or a monovalent substituent. R _{36 to} R ₄₃ are any of a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group. ] The organic electroluminescence device according to claim 3, wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3).

[Wherein, R _{50 to} R ₆₅ are a hydrogen atom or a monovalent substituent. R _{66 to} R ₆₉ are any one of a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group. ] The organic electroluminescence device according to claim 4, wherein the compound represented by the general formula (3) is a compound represented by the following structural formula (A).

  The at least one compound selected from the compounds represented by the general formulas (1), (2), (3) and the structural formula (A) is used for the light emitting layer. 6. The organic electroluminescence device according to any one of 5 above.   The organic electroluminescence device according to claim 1, wherein a hole blocking layer is provided between the light emitting layer and the cathode.   The organic electroluminescence device according to claim 7, wherein the hole blocking layer is composed of at least one compound of a triazole derivative, an oxadiazole derivative, or a boron derivative. 9. The triazole derivative, the oxadiazole derivative, or the boron derivative is at least one compound represented by the following general formula (4), (5), or (6). The organic electroluminescent element of description.

[Wherein, Ra ₁ , Ra ₂ , Ra ₃ , Rb ₁ , Rb _{2 each} represents an alkyl group, an aryl group, or a heterocyclic group. Ar ₁ , Ar ₂ , and Ar _{3 each} represents an aryl group or a heterocyclic group. ]   10. The organic electroluminescence device according to claim 2, wherein the phosphorescent compound is osmium, iridium, or a platinum complex compound. 11.   10. The organic electroluminescence device according to claim 2, wherein the phosphorescent compound is an iridium complex-based compound. 11.   2. The organic electroluminescence device according to claim 1, comprising a compound of the general formula (1) and a plurality of light-emitting dopants, and exhibiting white light emission.   An illuminating device comprising the organic electroluminescence element according to claim 12.   A display device comprising the organic electroluminescence element according to claim 1. An organic electroluminescence element material represented by the following general formula (1).

[In the formula, Z ₁ and Z ₂ are a benzene ring or a pyridine ring, and the benzene ring or the pyridine ring may or may not have a substituent, but has a substituent. The substituent is any one of a halogen atom, an alkyl group, an aryl group, and an alkoxy group. R _{1 to} R ₁₆ are a hydrogen atom or a monovalent substituent. ] 16. The organic electroluminescence element material according to claim 15, wherein the organic electroluminescence element material represented by the general formula (1) is an organic electroluminescence element material represented by the following general formula (2).

[Wherein, R _{20 to} R ₃₅ are a hydrogen atom or a monovalent substituent. R _{36 to} R ₄₃ are any of a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group. ] The organic electroluminescence device material according to claim 16, wherein the organic electroluminescence device material represented by the general formula (2) is an organic electroluminescence device material represented by the following general formula (3).

[Wherein, R _{50 to} R ₆₅ are a hydrogen atom or a monovalent substituent. R _{66 to} R ₆₉ are any one of a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group. ] The organic electroluminescence device material according to claim 17, wherein the organic electroluminescence device material represented by the general formula (3) is an organic electroluminescence device material represented by the following structural formula (A).

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