JP4228573B2 - Organic electroluminescence element and display device - Google Patents

Description

【００４３】
【化１４】

【００４５】
また、別の形態では、ホスト化合物と燐光性化合物の他に、燐光性化合物からの発光の極大波長よりも長波な領域に、蛍光極大波長を有する蛍光性化合物を少なくとも１種含有する場合もある。この場合、ホスト化合物と燐光性化合物からのエネルギー移動で、有機ＥＬ素子としての電界発光は蛍光性化合物からの発光が得られる。蛍光性化合物として好ましいのは、溶液状態で蛍光量子収率が高いものである。ここで、蛍光量子収率は１０％以上、特に３０％以上が好ましい。具体的には、クマリン系色素、ピラン系色素、シアニン系色素、クロコニウム系色素、スクアリウム系色素、オキソベンツアントラセン系色素、フルオレセイン系色素、ローダミン系色素、ピリリウム系色素、ペリレン系色素、スチルベン系色素、ポリチオフェン系色素、または、希土類錯体系蛍光体などが挙げられる。
【００４６】
以下、本発明に用いられるホスト化合物について説明する。
本発明のホスト化合物は分子内にオレフィンを含有している化合物であり、好ましくは一般式（１−１）〜一般式（８−２）に示される化合物である。
【００４７】
一般式（１−１）中、Ｒ₁、Ｒ₂、Ｒ₃、Ｒ₄は、水素原子、アルキル基、アルコキシ基、アリール基、複素環基又はシアノ基を表す。
【００４８】
アルキル基としては、例えばメチル基、エチル基、イソプロピル基、ヒドロキシエチル基、メトキシメチル基、トリフルオロメチル基、パーフルオロプロピル基、パーフルオロ−ｎ−ブチル基、パーフルオロ−ｔ−ブチル基、ｔ―ブチル基、ベンジル基等がある。
【００４９】
アルコキシ基としては、例えばメトキシ基、エトキシ基、イソプロポキシ基、ブトキシ基等がある。
【００５０】
アリール基としては、例えばフェニル基、ナフチル基、ｐ―トリル基、ｐ―クロロフェニル基等がある。
【００５１】
複素環基としては、ピロリル基、ピロリジル基、ピラゾリル基、イミダゾリル基、ピリジル基、トリアゾリル基、ベンズイミダゾリル基、ベンゾチアゾリル基、ベンゾオキサゾリル基、フリル基、チエニル基、チアゾリル基等がある。
【００５２】
これらの基はさらに置換されていてもよく、置換基としては、ハロゲン原子、ヒドロキシル基、ニトロ基、シアノ基、カルボキシル基、スルホ基、アルキル基、アリール基、アルコキシ基、アリールオキシ基、アルキルチオ基、アリールチオ基、アルキルスルホニル基、アリールスルホニル基、アルコキシカルボニル基、アリールオキシカルボニル基、アシル基、アシルオキシ基、アミノ基、カルボンアミド基、スルホンアミド基、カルバモイル基、スルファモイル基、ウレイド基、アルコキシカルボニルアミノ基、スルファモイルアミノ基等が挙げられる。
【００５３】
一般式（１−１）中、Ｒ₁、Ｒ₂、Ｒ₃、Ｒ₄のうち、少なくとも二つは、アリール基、または、複素環基である。
【００５４】
好ましくは、Ｒ₁、Ｒ₂、Ｒ₃、Ｒ₄のうち、２つがアリール基又はすべてアリール基の時である。
【００５５】
一般式（１−２）中、Ｘ₁、Ｘ₂はアリール基または、複素環基を表し、Ｒ₅、Ｒ₆はアリール基、複素環基、または、脂環式炭化水素の残基を表し、かつ、Ｒ₅、Ｒ₆のいずれか一方は脂環式炭化水素の残基を表す。Ｒ₅、Ｒ₆は脂環式の環を形成してもよい。脂環式炭化水素の残基としては、シクロアルキル基、シクロアルケニル基等の残基がある。脂環式炭化水素の残基として、特に好ましくは、シクロアルキル基（例えば、シクロペンチル基、シクロヘキシル基等）である。これらの基は、さらに置換されていても良い。
【００５６】
一般式（１−３）中、Ｘ₃、Ｘ₄はアリール基、または、複素環基を表し、Ｒ₇、Ｒ₈はアリール基、または、複素環基を表す。
【００５７】
一般式（２−２）、（２−３）中、Ａ₂₀、Ａ₂₁、Ａ₂₂、Ａ₂₃、Ａ₂₄、Ａ₂₅及び一般式（５）中、Ａ₅₁、Ａ₅₂、Ａ₅₃、Ａ₅₄は、それぞれ独立に単環の芳香族環または複素環を表す。単環の芳香族環または複素環の具体例としてはベンゼン、フラン、チオフェン、ピロール、オキサゾール、イミダゾール、チアゾール、トリアゾール、ピリジン、ピリダジン、ピリミジン、ピラジン、トリアジン等が挙げられる。
【００５８】
Ｒ₂₁からＲ₂₄は、水素原子、アルキル基、アルコキシ基、アリール基、複素環基又はシアノ基を表す。Ｒ₂₁からＲ₂₄で表される置換基としては、アルキル基（例えばメチル基、エチル基、イソプロピル基、ヒドロキシエチル基、メトキシメチル基、トリフルオロメチル基、パーフルオロプロピル基、パーフルオロ−ｎ−ブチル基、パーフルオロ−ｔ−ブチル基、ｔ−ブチル基、ベンジル基等）、シクロアルキル基（例えばシクロペンチル基、シクロヘキシル基等）、アラルキル基（例えばベンジル基、２−フェネチル基等）、アリール基（例えばフェニル基、ナフチル基、ｐ−トリル基、ｐ−クロロフェニル基、フルオレニル基等）、アルコキシ基（例えばエトキシ基、イソプロポキシ基、ブトキシ基等）等が挙げられる。これらの基はさらに置換されていてもよく、前記置換基としては、一般式（１−１）で挙げたものが挙げられる。
【００５９】
一般式（２−３）において、Ａ₂₂、Ａ₂₃が複素環の場合、ヘテロ原子が２個以上の場合が好ましい。
【００６０】
一般式（３）、（４）において、Ａ₃₁、Ａ₄₁、Ａ₄₂は、芳香族環、または、複素環を表す。これらの芳香族環、または、複素環は、単環基、縮合多環基、または、単環もしくは縮合多環を含む芳香族単位が連結した基である。具体的には、ベンゼン、トルエン、ナフタレン、アントラセン、フェナントレン、フルオレン、ピレン、ペリレン、トリフェニレン、アズレン、フルオレノン、フラン、チオフェン、ピロール、ピリジン、オキサゾール、ピラジン、ピリミジン、オキサジアゾール、トリアゾール、インドール、キノリン、イソキノリン、カルバゾール、アクリジン、ベンゾチアゾール、フェナントロリン、キナクリドン等の置換もしくは未置換の芳香族環もしくは縮合芳香環の残基、さらには、ビフェニル、ターフェニル、ビナフチル、トリフェニルベンゼン、ジフェニルアントラセン、ルブレン、ビピリジン、ビキノリン、ビチオフェン、等の芳香環構造単位同士が直接連結した残基である。
【００６１】
Ａ₄₁、Ａ₄₂は、スチリル基、または、置換スチリル基が置換基として導入された場合が最も好ましい。
【００６２】
一般式（６）において、Ａ₆₁ 及びＲ ₆₁ は芳香族環基、または、複素環基を表す。芳香族環基としては、フェニル基、ナフチル基、アントラニル基、フェナンスリル基、ピレニル基、コロニル基、ビフェニル基、ターフェニル基、フルオレニル基、フラニル基、チエニル基、ベンゾチエニル基、インドリル基、カルバゾリル基、ベンズイミダゾリル基、ベンゾオキサゾリル基、イミダゾリル基、等が挙げられる。
【００６３】
一般式（３）、（４）、（５）、（６）、（８−１）、（８−２）において、Ｒ ₃₁ 、Ｒ ₃₂ 、Ｒ ₈₁ 、Ｒ ₈₂ 、Ｒ ₈₉ 、Ｒ ₉₀ は、アリール基、または、複素環基を表し、Ｒ₃₃ 〜Ｒ₃₆、Ｒ₄₁〜Ｒ₄₈、Ｒ₅₁〜Ｒ₅₆、Ｒ₆₁〜Ｒ₆₃ 、Ｒ ₈₁〜Ｒ₉₂は、水素原子、または、置換基を表す。Ｒ₃₁〜Ｒ₃₆、Ｒ₄₁〜Ｒ₄₈、Ｒ₅₁〜Ｒ₅₆、Ｒ₆₁〜Ｒ₆₃、Ｒ₇₁〜Ｒ₇₆、Ｒ₈₃ 〜Ｒ ₈₅ 、Ｒ ₈₆ 、Ｒ ₈₇ 、Ｒ ₈₈ 、Ｒ ₉₁ 、Ｒ ₉₂ は水素原子、アルキル基、アルコキシ基、アリール基、複素環基又はシアノ基を表す。Ｒ₃₅、Ｒ₃₆が置換基を表す場合、好ましくは、脂環系炭化水素の残基である。Ｒ₄₁、Ｒ₄₂は、水素原子が好ましい。
【００６４】
一般式（８−１）、（８−２）において、Ｘ₅、Ｘ₆、Ｘ₇は、−Ｏ−，−Ｓ−，−ＮＲａ−を表す。ここで、Ｒａは置換基である。Ｚ₁、Ｚ₂、Ｚ₃は、５員環と共に縮合環を形成するのに必要な原子群である。具体的には、ベンゼン、ナフタレン、アントラセン、複素環等が挙げられる。
【００６５】
請求項１から１４で表されるホスト化合物は、分子内の部分構造としてトリアリールアミンを含有しても良い。また、素子の寿命に関しては，５配位のアルミニウム錯体を電子輸送層に導入いた場合、大きく改善され好ましい。
【００６６】
以下に、具体的化合物例を示すが、本発明のホスト化合物が、これらに限定されるものではない。
【００６７】
【化１６】

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【化１７】

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【０１００】
【化４９】

【０１０１】
【化５０】

【０１０２】
本発明の化合物は、固体状態において強い蛍光を持つ化合物であり、電場発光性にも優れており、発光材料として有効に使用できる。
【０１０３】
本発明の化合物は、従来既知の方法で合成できる。例えば、登録特許第３０８６２７２号や登録特許第３２１４６７４号等に詳しい。
【０１０４】
本発明の有機ＥＬ素子は、必要に応じ発光層の他に、正孔輸送層、電子輸送層、陽極バッファー層および陰極バッファー層等を有し、陰極と陽極で狭持された構造をとる。
【０１０５】
具体的には、
（i）陽極／発光層／陰極
（ii）陽極／正孔輸送層／発光層／陰極
（iii）陽極／発光層／電子輸送層／陰極
（iv）陽極／正孔輸送層／発光層／電子輸送層／陰極
（v）陽極／陽極バッファー層／正孔輸送層／発光層／電子輸送層／陰極バッファー層／陰極などの構造がある。
【０１０６】
本発明の化合物は、いずれの層中に含有されていてもかまわないが、発光層に含有されていることが好ましい。
【０１０７】
上記発光層は、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。
【０１０８】
発光材料は、発光性能の他に、正孔輸送機能や電子輸送機能を併せ持っていても良く、正孔輸送材料や電子輸送材料の殆どが、発光材料としても使用できる。
【０１０９】
この発光層は、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。
【０１１０】
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。
【０１１１】
次に正孔輸送層および電子輸送層について説明する。
正孔輸送層は、陽極より注入された正孔を発光層に伝達する機能を有し、この正孔輸送層を陽極と発光層の間に介在させることにより、より低い電界で多くの正孔が発光層に注入され、そのうえ、発光層に陰極、陰極バッファー層又は電子輸送層より注入された電子は、発光層と正孔輸送層の界面に存在する電子の障壁により、発光層内の界面に累積され発光効率が向上するなど発光性能の優れた素子となる。この正孔輸送層の材料（以下、正孔注入材料、正孔輸送材料という）については、前記の好ましい性質を有するものであれば特に制限はなく、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。
【０１１２】
上記正孔輸送材料は、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。この正孔輸送材料としては、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などが挙げられる。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。
【０１１３】
上記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）などが挙げられる。
【０１１４】
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。
【０１１５】
また、ｐ型−Ｓｉ，ｐ型−ＳｉＣなどの無機化合物も正孔輸送材料として使用することができる。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，ＬＢ法など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５ｎｍ〜５μｍ程度である。この正孔輸送層は、上記材料の一種又は二種以上からなる一層構造であってもよく、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。さらに、必要に応じて用いられる電子輸送層は、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。
【０１１６】
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、トリアゾール誘導体、フェナントロリン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。
【０１１７】
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。
【０１１８】
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用いられる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。
【０１１９】
この電子輸送層は、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。電子輸送層としての膜厚は、特に制限はないが、通常は５ｎｍ〜５μｍの範囲で選ばれる。この電子輸送層は、これらの電子輸送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。
【０１２０】
さらに、陽極と発光層または正孔注入層の間、および、陰極と発光層または電子注入層との間にはバッファー層（電極界面層）を存在させてもよい。
【０１２１】
バッファー層とは、駆動電圧低下や発光効率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」（第１２３頁〜第１６６頁）に詳細に記載されており、陽極バッファー層と陰極バッファー層とがある。
【０１２２】
陽極バッファー層は、特開平９−４５４７９号、同９−２６００６２号、同８−２８８０６９号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。
【０１２３】
陰極バッファー層は、特開平６−３２５８７１号、同９−１７５７４号、同１０−７４５８６号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、酸化リチウムに代表される酸化物バッファー層等が挙げられる。
【０１２４】
特に、本発明の有機ＥＬ素子において、陰極バッファー層が存在した場合、駆動電圧低下や発光効率向上が大きく得られた。
【０１２５】
上記バッファー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０．１〜１００ｎｍの範囲が好ましい。
【０１２６】
さらに上記基本構成層の他に必要に応じてその他の機能を有する層を積層してもよく、例えば特開平１１−２０４２５８号、同１１−２０４３５９号、および「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２３７頁等に記載されている正孔阻止（ホールブロック）層などのような機能層を有していても良い。
【０１２７】
次に有機ＥＬ素子の電極について説明する。有機ＥＬ素子の電極は、陰極と陽極からなる。
【０１２８】
この有機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などの金属、ＣｕＩ、インジウムチンオキシド（ＩＴＯ）、ＳｎＯ₂、ＺｎＯなどの導電性透明材料が挙げられる。
【０１２９】
上記陽極は、これらの電極物質を蒸着やスパッタリングなどの方法により、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１０ｎｍ〜１μｍ、好ましくは１０ｎｍ〜２００ｎｍの範囲で選ばれる。
【０１３０】
一方、陰極としては、仕事関数の小さい（４ｅＶ以下）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、ナトリウムーカリウム合金、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、希土類金属などが挙げられる。これらの中で、電子注入性及び酸化など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などが好適である。
【０１３１】
更に本発明の有機ＥＬ素子に用いる陰極としては、アルミニウム合金が好ましく、特にアルミニウム含有量が９０質量％以上１００質量％未満であることが好ましく、最も好ましくは９５質量％以上１００質量％未満である。これにより、有機ＥＬ素子の発光寿命や、最高到達輝度を非常に向上させることができる。
【０１３２】
上記陰極は、これらの電極物質を蒸着やスパッタリングなどの方法により、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〜１μｍ、好ましくは５０〜２００ｎｍの範囲で選ばれる。なお、発光を透過させるため、有機ＥＬ素子の陽極又は陰極のいずれか一方が、透明又は半透明であれば発光効率が向上し好都合である。
【０１３３】
本発明の有機ＥＬ素子に好ましく用いられる基板は、ガラス、プラスチックなど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。本発明のエレクトロルミネッセンス素子に好ましく用いられる基板としては例えばガラス、石英、光透過性プラスチックフィルムを挙げることができる。
【０１３４】
光透過性プラスチックフィルムとしては、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。
【０１３５】
次に、該有機ＥＬ素子を作製する好適な例を説明する。例として、前記の陽極／陽極バッファー層／正孔輸送層／発光層／電子輸送層／陰極バッファー層／陰極からなるＥＬ素子の作製法について説明すると、まず適当な基板上に、所望の電極物質、例えば陽極用物質からなる薄膜を、１μｍ以下、好ましくは１０〜２００ｎｍの範囲の膜厚になるように、蒸着やスパッタリングなどの方法により形成させ、陽極を作製する。次に、この上に陽極バッファー層、正孔輸送層、発光層、電子輸送層、陰極バッファー層の材料からなる薄膜を形成させる。
【０１３６】
この有機薄膜層の薄膜化の方法としては、前記の如くスピンコート法、キャスト法、蒸着法などがあるが、均質な膜が得られやすく、かつピンホールが生成しにくいなどの点から、真空蒸着法またはスピンコート法が特に好ましい。さらに層ごとに異なる製膜法を適用しても良い。製膜に蒸着法を採用する場合、その蒸着条件は、使用する化合物の種類、分子堆積膜の目的とする結晶構造、会合構造などにより異なるが、一般にボート加熱温度５０〜４５０℃、真空度１０^-6〜１０^-2Ｐａ、蒸着速度０．０１〜５０ｎｍ／秒、基板温度−５０〜３００℃、膜厚５ｎｍ〜５μｍの範囲で適宜選ぶことが望ましい。
【０１３７】
これらの層の形成後、その上に陰極用物質からなる薄膜を、１μｍ以下好ましくは５０〜２００ｎｍの範囲の膜厚になるように、例えば蒸着やスパッタリングなどの方法により形成させ、陰極を設けることにより、所望のＥＬ素子が得られる。この有機ＥＬ素子の作製は、一回の真空引きで一貫して正孔注入層から陰極まで作製するのが好ましいが、途中で取り出して異なる製膜法を施してもかまわないが、その際には作業を乾燥不活性ガス雰囲気下で行う等の配慮が必要となる。
【０１３８】
また作製順序を逆にして、陰極、陰極バッファー層、電子輸送層、発光層、正孔輸送層、陽極バッファー層、陽極の順に作製することも可能である。このようにして得られたＥＬ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５〜４０Ｖ程度を印加すると、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。
【０１３９】
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、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。
【０１４０】
【実施例】
以下、実施例を挙げて本発明を詳細に説明するが、本発明の態様はこれに限定されない。
【０１４１】
実施例１（燐光ホスト化合物としての使用）
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ｉ−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。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−１０、ＢＣ、Ａｌｑ₃をそれぞれ入れ真空蒸着装置に取付けた。
【０１４２】
次いで、真空槽を４×１０^-4Ｐａまで減圧した後、α−ＮＰＤの入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．２ｎｍ／ｓｅｃで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−１０の入ったボートをそれぞれ独立に通電してＣＢＰとＩｒ−１０の蒸着速度が１００：７になるように調節し膜厚３０ｎｍの厚さになるように蒸着し、発光層を設けた。
【０１４３】
ついで、ＢＣの入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．２ｎｍ／ｓｅｃで厚さ１０ｎｍの正孔阻止の役割もかねた電子輸送層を設けた。更に、Ａｌｑ₃の入った前記加熱ボートを通電して加熱し、蒸着速度０．１〜０．２ｎｍ／ｓｅｃで膜厚５０ｎｍの電子輸送層を設けた。
【０１４４】
次に、真空槽をあけ、電子輸送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／ｓｅｃ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／ｓｅｃ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）とすることにより、比較用有機ＥＬ素子ＯＬＥＤ１−１を作製した。
【０１４５】
【化５１】

【０１４６】
上記有機ＥＬ素子ＯＬＥＤ１−１のホスト化合物であるＣＢＰを表１に記載の化合物に替えた以外は有機エレクトロルミネッセンス素子ＯＬＥＤ１−１と同様にして、有機エレクトロルミネッセンス素子ＯＬＥＤ１−２〜２４を作製した。
【０１４７】
得られた本発明の有機発光素子を温度２３度、乾燥窒素ガス雰囲気下で、光り始めの電圧の測定を行い発光開始電圧とした。次に、９Ｖ直流電圧を印加した時の発光輝度（Ｌ）［ｃｄ／ｍ²］を測定した。発光輝度は有機エレクトロルミネッセンス素子ＯＬＥＤ１−１を１００とした時の相対値で表した。なお、発光開始電圧は、輝度が５０［ｃｄ／ｍ²］となった場合とした。発光輝度はミノルタ製ＣＳ−１０００を用いて測定した。結果を表１に示す。
【０１４８】
【表１】

【０１４９】
表１より、本発明の化合物を用いた有機ＥＬ素子は、発光輝度、発光開始時の電圧が改善されているのが分かる。上記で使用した化合物の構造を以下に示す。なお、発光色は青色だった。
【０１５０】
【化５２】

【０１５１】
燐光発光化合物をＩｒ−９またはＩｒ−１に代えた以外は、ＯＬＥＤ１−１からＯＬＥＤ１−２４と同様にして作製した有機ＥＬ素子においても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。
【０１５２】
実施例２
実施例１で作製した有機エレクトロルミネッセンス素子ＯＬＥＤ１−６の陰極をＡｌに置き換え、電子輸送層と陰極の間に酸化リチウムを膜厚１．５ｎｍ蒸着して陰極バッファー層を設け、正孔阻止の役割も兼ねた電子輸送層であるＢＣをＢＡｌｑに代えた以外は同様にして有機エレクトロルミネッセンス素子（ＯＬＥＤ２−１）を作製した。
【０１５３】
【化５３】

【０１５４】
実施例１と同様に、有機発光素子を温度２３度、乾燥窒素ガス雰囲気下で、９Ｖ直流電圧を印可した時の発光輝度（Ｌ）［ｃｄ／ｍ²］を測定した。また、輝度の半減する時間（τ）を測定した。有機エレクトロルミネッセンス素子ＯＬＥＤ１−６との相対比較で、発光輝度１０９、輝度の半減する時間１８８となり、特に、輝度の半減する時間に大きな改善効果が見られた。また、有機エレクトロルミネッセンス素子ＯＬＥＤ１−９〜１３、１５、１７、２０〜２３についても、同様に、陰極バッファー層とＢＡｌｑを導入すると輝度の半減寿命に大きな効果が見られた。
【０１５５】
実施例３
実施例１で作製したそれぞれ赤色、緑色、青色発光有機エレクトロルミネッセンス素子を同一基板上に並置し、特願２００１−１８１５４３に示す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た。
【０１５６】
該フルカラー表示装置を駆動することにより、輝度の高い鮮明なフルカラー動画表示が得られた。
【０１５７】
【発明の効果】
本発明により、発光輝度の向上および低駆動電圧化を実現できる燐光ホスト化合物を含有する高輝度で長寿命な有機エレクトロルミネッセンス素子、および該有機エレクトロルミネッセンス素子を用いた低消費電力、高輝度な表示装置を得た。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescence (hereinafter also abbreviated as organic EL) element and a display device. More specifically, the present invention relates to a long-life organic electroluminescence element having excellent emission luminance and a low driving voltage, and a display device having the organic electroluminescence element.
[0002]
[Prior art]
As a light-emitting electronic display device, there is an electroluminescence display (ELD). As a component of ELD, an inorganic electroluminescent element and an organic electroluminescent element are mentioned. Inorganic electroluminescent elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements. An organic electroluminescence element has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and injects electrons and holes into the light emitting layer to recombine excitons. It is an element that emits light by utilizing light emission (fluorescence / phosphorescence) generated when this exciton is deactivated, and can emit light at a voltage of several volts to several tens of volts. Therefore, it has a wide viewing angle, high visibility, and since it is a thin-film type complete solid-state device, it is attracting attention from the viewpoints of space saving and portability.
[0003]
However, in organic EL elements for practical use in the future, development of organic EL elements that emit light efficiently and with high luminance with lower power consumption is desired.
[0004]
In Japanese Patent No. 3093796, a small amount of phosphor is doped into a stilbene derivative, a distyrylarylene derivative or a tristyrylarylene derivative to achieve an improvement in light emission luminance and a longer device lifetime.
[0005]
An 8-hydroxyquinoline aluminum complex as a host compound, a device having an organic light-emitting layer doped with a small amount of phosphor (Japanese Patent Laid-Open No. 63-264692), an 8-hydroxyquinoline aluminum complex as a host compound, An element having an organic light emitting layer doped with a quinacridone dye (Japanese Patent Laid-Open No. 3-255190) is known.
[0006]
As described above, when light emission from excited singlet is used, the generation ratio of singlet excitons and triplet excitons is 1: 3, so that the generation probability of luminescent excited species is 25%, Therefore, the limit of the external extraction quantum efficiency (ηext) is set to 5%. However, since Princeton University reported on an organic EL device using phosphorescence emission from an excited triplet (MA Baldo et al., Nature, 395, 151-154 (1998)), Research on materials that exhibit phosphorescence has become active. For example, M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000), US Pat. No. 6,097,147, and the like. 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 attracts attention.
[0007]
The emission color of the phosphorescent compound used as the dopant is about 100% as the internal quantum efficiency in red and green, and 20,000 hours have been achieved (for example, Proceedings of the 62nd JSAP Scientific Lecture Meeting) 12-a-M7, Pioneer Technical Information Magazine, Vol. 11, No. 1), when a blue to blue-green phosphorescent compound is used as a dopant, there is an example in which CBP which is a carbazole derivative is used as a host compound. However, the external extraction quantum efficiency is 6%, which is inadequate for the use of the phosphorescent compound (for example, Proceedings of the 62nd Japan Society of Applied Physics, 12-a-M8) . This is considered that sufficient efficiency is not obtained because CBP as a host compound is incompatible with phosphorescent compounds of blue to blue green.
[0008]
Examples of the host when using a phosphorescent compound as a dopant include C.I. Adachi et al. , Appl. Phys. Lett. , 77, page 904 (2000), The 10th International Works on Inorganic and Organic Electroluminescence (EL2000, Hamamatsu) and the like, and the emission maximum wavelength is shorter than the emission maximum wavelength of the phosphorescent compound. It is necessary to have. On the other hand, the host compounds of iridium complexes emitting blue to blue green light that have recently been attracting attention require molecular design from a new point of view different from conventional CBP and electron transporting hosts. It is believed that a bright host compound is achieved.
[0009]
In recent years, there has been a growing demand for lower drive voltages for organic EL elements due to their use as portable information devices. For this reason, attempts have been made to lower the drive voltage by improving the hole injection layer and the hole transport layer, but satisfactory results have not been obtained.
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide a high-brightness and long-life organic electroluminescence device containing a phosphorescent host compound capable of realizing improvement in light emission luminance and reduction in driving voltage, and low power consumption and high luminance using the organic electroluminescence device Is to provide a simple display device.
[0011]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitutions.
[0013]
  1. In the organic electroluminescence device having a light emitting layer containing a host compound and a phosphorescent compound, the host compound is a compound represented by the general formula (1-1), and the phosphorescent compound is an iridium compound. An organic electroluminescence device characterized.
  However, the compound represented by the general formula (1-1) does not contain 4,4′-bis (2,2-diphenylethenyl) biphenyl.
[0015]
  2. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (1-3).
[0016]
  3. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (2-1).
[0017]
  4. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (2-3).
[0018]
  5. A in the above general formula (2-3)₂₂, A₂₃Is a heterocycle having two or more heteroatoms,4The organic electroluminescent element of description.
[0019]
  6. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (3).
[0022]
  7. 2. The organic electroluminescence device according to 1, wherein the host compound represented by the general formula (1-1) is the general formula (4).
[0023]
  8. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (5).
[0025]
  9. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (6).
[0028]
  10. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (8-1).
[0029]
  11. 2. The organic electroluminescence device according to 1 above, wherein the host compound represented by the general formula (1-1) is a compound represented by the general formula (8-2).
[0030]
  12. Z in the general formulas (8-1) and (8-2)₁, Z₂, Z₃1 comprises at least one heteroatom.0Or 11The organic electroluminescent element of description.
[0031]
  13. A compound having a triarylamine as a partial structure in the molecule is contained in the above 1-1.2Organic electroluminescent element of any one of these.
[0033]
  14. 1 to 13A display device comprising the organic electroluminescence element according to any one of the above.
[0034]
The present invention will be described in more detail. In the present invention, a phosphorescent compound is a compound in which light emission from an excited triplet in which two electron spins are in parallel is observed by photoexcitation. Here, in the phosphorescent compound according to the present invention, an excited triplet state is formed at room temperature (15 to 30 degrees) by the energy transfer from the excited singlet state or the excited triplet state of the fluorescent compound. It is considered. In general, phosphorescence was thought to be observable only at a low temperature of 77 K. However, in recent years, since compounds that can observe phosphorescence at room temperature have been discovered, many compounds have been synthesized mainly from heavy metal complexes such as iridium complexes. (For example, S. Lamansky et al., J. Am. Chem. Soc., 123, 4304, 2001).
[0035]
As the host compounds of iridium complexes emitting blue to blue green light that have recently been attracting attention, even if a conventional CBP or electron transporting host is used, sufficient external extraction quantum efficiency cannot be obtained. This is presumably because the efficiency of energy transfer to the iridium complex is poor for some reason.
[0036]
Therefore, as a result of intensive studies, the present inventors have found that by introducing an olefin or styryl group as a partial structure in the molecule, brightness can be improved and lifetime can be improved. A host compound having sufficient energy transfer efficiency to the compound has been found and the present invention has been completed.
[0037]
The host compound of the present invention is a compound having the largest mixing ratio (mass) in the light emitting layer composed of two or more compounds, and the other compounds are referred to as dopant compounds. 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. The phosphorescent compound in the present invention is a kind of dopant compound.
[0038]
The phosphorescent compound of the present invention is a compound in which light emission from an excited triplet is observed, and is a compound having a phosphorescence quantum yield of 0.001 or more at 25 ° C. Preferably it is 0.01 or more. More preferably, it is 0.1 or more.
[0039]
The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 version, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence quantum yield used in the present invention is only required to achieve the phosphorescence quantum yield in any solvent.
[0040]
  Phosphorescent compound of the present inventionIs a complex compound containing a group VIII metal in the periodic table of elements,IRigiuSystemA compound.
[0041]
Specific examples of the phosphorescent compound used in the present invention are shown below, but are not limited thereto. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like.
[0042]
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[0043]
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[0045]
In another embodiment, in addition to the host compound and the phosphorescent compound, at least one fluorescent compound having a fluorescence maximum wavelength may be contained in a region longer than the maximum wavelength of light emission from the phosphorescent compound. . In this case, electroluminescence as an organic EL element can be emitted from the fluorescent compound by energy transfer from the host compound and the phosphorescent compound. Preferred as the fluorescent compound is one having a high fluorescence quantum yield in a solution state. Here, the fluorescence quantum yield is preferably 10% or more, particularly preferably 30% or more. Specifically, coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes , Polythiophene dyes, or rare earth complex phosphors.
[0046]
Hereinafter, the host compound used in the present invention will be described.
The host compound of the present invention is a compound containing an olefin in the molecule, and is preferably a compound represented by general formula (1-1) to general formula (8-2).
[0047]
In general formula (1-1), R₁, R₂, R_Three, R_FourRepresents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano group.
[0048]
Examples of the alkyl group include methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, perfluoropropyl group, perfluoro-n-butyl group, perfluoro-t-butyl group, t -There are butyl and benzyl groups.
[0049]
Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, and a butoxy group.
[0050]
Examples of the aryl group include a phenyl group, a naphthyl group, a p-tolyl group, and a p-chlorophenyl group.
[0051]
Examples of the heterocyclic group include a pyrrolyl group, a pyrrolidyl group, a pyrazolyl group, an imidazolyl group, a pyridyl group, a triazolyl group, a benzimidazolyl group, a benzothiazolyl group, a benzoxazolyl group, a furyl group, a thienyl group, and a thiazolyl group.
[0052]
These groups may be further substituted, and examples of the substituent include a halogen atom, hydroxyl group, nitro group, cyano group, carboxyl group, sulfo group, alkyl group, aryl group, alkoxy group, aryloxy group, alkylthio group. , Arylthio group, alkylsulfonyl group, arylsulfonyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyl group, acyloxy group, amino group, carbonamido group, sulfonamido group, carbamoyl group, sulfamoyl group, ureido group, alkoxycarbonylamino Group, sulfamoylamino group and the like.
[0053]
  In general formula (1-1), R₁, R₂, R_Three, R_FourAt leasttwoOne is an aryl group or a heterocyclic group.
[0054]
Preferably R₁, R₂, R_Three, R_FourOf these, two are aryl groups or all aryl groups.
[0055]
In general formula (1-2), X₁, X₂Represents an aryl group or a heterocyclic group, R_Five, R₆Represents an aryl group, a heterocyclic group, or an alicyclic hydrocarbon residue, and R_Five, R₆Any one of these represents an alicyclic hydrocarbon residue. R_Five, R₆May form an alicyclic ring. Examples of the alicyclic hydrocarbon residue include residues such as a cycloalkyl group and a cycloalkenyl group. The residue of the alicyclic hydrocarbon is particularly preferably a cycloalkyl group (for example, a cyclopentyl group, a cyclohexyl group, etc.). These groups may be further substituted.
[0056]
  In general formula (1-3), X_Three, X_FourRepresents an aryl group or a heterocyclic group, R₇, R₈Is an aryl groupOrHeterocycleGroupTo express.
[0057]
In general formulas (2-2) and (2-3), A₂₀, A_{twenty one}, A_{twenty two}, A_{twenty three}, A_{twenty four}, A_{twenty five}And in general formula (5), A₅₁, A₅₂, A₅₃, A₅₄Each independently represents a monocyclic aromatic ring or heterocyclic ring. Specific examples of the monocyclic aromatic ring or heterocyclic ring include benzene, furan, thiophene, pyrrole, oxazole, imidazole, thiazole, triazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine and the like.
[0058]
  R_{twenty one}To R_{twenty four}Is a hydrogen atomRepresents an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano group.R_{twenty one}To R_{twenty four}As the substituent represented by the formula, an alkyl group (for example, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, perfluoropropyl group, perfluoro-n-butyl group, perfluoro group) -T-butyl group, t-butyl group, benzyl group etc.), cycloalkyl group (eg cyclopentyl group, cyclohexyl group etc.), aralkyl group (eg benzyl group, 2-phenethyl group etc.), aryl group (eg phenyl group, Naphthyl group, p-tolyl group, p-chlorophenyl group, fluorenyl group, etc.), alkoxy group (for example, ethoxy group, isopropoxy group, butoxy group, etc.))etcIs mentioned. These groups may be further substituted, and examples of the substituent include those exemplified in Formula (1-1).
[0059]
In general formula (2-3), A_{twenty two}, A_{twenty three}When is a heterocyclic ring, it is preferable that there are two or more heteroatoms.
[0060]
In general formulas (3) and (4), A₃₁, A₄₁, A₄₂Represents an aromatic ring or a heterocyclic ring. These aromatic rings or heterocyclic rings are monocyclic groups, condensed polycyclic groups, or groups in which aromatic units containing monocyclic or condensed polycycles are linked. Specifically, benzene, toluene, naphthalene, anthracene, phenanthrene, fluorene, pyrene, perylene, triphenylene, azulene, fluorenone, furan, thiophene, pyrrole, pyridine, oxazole, pyrazine, pyrimidine, oxadiazole, triazole, indole, quinoline , Residues of substituted or unsubstituted aromatic rings or condensed aromatic rings such as isoquinoline, carbazole, acridine, benzothiazole, phenanthroline, quinacridone, biphenyl, terphenyl, binaphthyl, triphenylbenzene, diphenylanthracene, rubrene, A residue in which aromatic ring structural units such as bipyridine, biquinoline, bithiophene and the like are directly linked to each other.
[0061]
A₄₁, A₄₂Is most preferably a styryl group or a substituted styryl group introduced as a substituent.
[0062]
  In general formula (6), A₆₁ And R ₆₁ Represents an aromatic ring group or a heterocyclic group. Aromatic ring groups include phenyl, naphthyl, anthranyl, phenanthryl, pyrenyl, coronyl, biphenyl, terphenyl, fluorenyl, furanyl, thienyl, benzothienyl, indolyl, carbazolyl Benzimidazolyl group, benzoxazolyl group, imidazolyl group, and the like.
[0063]
  General formula (3), (4), (5), (6), (8-1) and (8-2),R ₃₁ , R ₃₂ , R ₈₁ , R ₈₂ , R ₈₉ , R ₉₀ Represents an aryl group or a heterocyclic group,R_{3 3} ~ R₃₆, R₄₁~ R₄₈, R₅₁~ R₅₆, R₆₁~ R₆₃ , R ₈₁~ R₉₂Represents a hydrogen atom or a substituent. R₃₁~ R₃₆, R₄₁~ R₄₈, R₅₁~ R₅₆, R₆₁~ R₆₃, R₇₁~ R₇₆, R_{8 3} ~ R ₈₅ , R ₈₆ , R ₈₇ , R ₈₈ , R ₉₁ , R ₉₂ Represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano group.R₃₅, R₃₆When represents a substituent, preferably the residue of the alicyclic hydrocarbonOn the basisis there. R₄₁, R₄₂Is preferably a hydrogen atom.
[0064]
In general formulas (8-1) and (8-2), X_Five, X₆, X₇Represents -O-, -S-, -NRa-. Here, Ra is a substituent. Z₁, Z₂, Z_ThreeIs a group of atoms necessary for forming a condensed ring together with a 5-membered ring. Specific examples include benzene, naphthalene, anthracene, heterocycle and the like.
[0065]
  Claims 1 to 14The host compound represented by may contain triarylamine as a partial structure in the molecule. Regarding the lifetime of the element, it is preferable that a pentacoordinate aluminum complex is introduced into the electron transporting layer because it is greatly improved.
[0066]
Specific examples of the compound are shown below, but the host compound of the present invention is not limited to these examples.
[0067]
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[0068]
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[0069]
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[0070]
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[0071]
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[0072]
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[0073]
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[0074]
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[0075]
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[0076]
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[0077]
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[0078]
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[0079]
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[0090]
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[0100]
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[0101]
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[0102]
The compound of the present invention is a compound having strong fluorescence in a solid state, is excellent in electroluminescence, and can be effectively used as a light emitting material.
[0103]
The compound of the present invention can be synthesized by a conventionally known method. For example, it is detailed in registered patent No. 3086272 and registered patent No. 3214667.
[0104]
The organic EL device of the present invention has a hole transport layer, an electron transport layer, an anode buffer layer, a cathode buffer layer, and the like in addition to the light emitting layer as required, and has a structure sandwiched between a cathode and an anode.
[0105]
In particular,
(I) Anode / light emitting layer / cathode
(Ii) Anode / hole transport layer / light emitting layer / cathode
(Iii) Anode / light emitting layer / electron transport layer / cathode
(Iv) Anode / hole transport layer / light emitting layer / electron transport layer / cathode
(V) There are structures such as anode / anode buffer layer / hole transport layer / light emitting layer / electron transport layer / cathode buffer layer / cathode.
[0106]
The compound of the present invention may be contained in any layer, but is preferably contained in the light emitting layer.
[0107]
The light-emitting layer 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 an interface between adjacent layers.
[0108]
The light emitting material may have a hole transport function and an electron transport function in addition to the light emitting performance, and most of the hole transport material and the electron transport material can be used as the light emitting material.
[0109]
The light emitting layer can be formed by forming a film 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 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.
[0110]
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.
[0111]
Next, the hole transport layer and the electron transport layer will be described.
The hole transport layer has a function of transmitting holes injected from the anode to the light emitting layer. By interposing this hole transport layer between the anode and the light emitting layer, a large number of holes can be formed at a lower electric field. Are injected into the light emitting layer, and the electrons injected into the light emitting layer from the cathode, the cathode buffer layer, or the electron transport layer are interfacial in the light emitting layer due to an electron barrier existing at the interface between the light emitting layer and the hole transport layer. In other words, the light emitting efficiency is improved. The material of the hole transport layer (hereinafter referred to as a hole injection material and a hole transport material) is not particularly limited as long as it has the above-mentioned preferable properties. Any material commonly used as an injection transport material and known materials used for a hole transport layer of an EL element can be selected and used.
[0112]
The hole transport material has one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. Examples of the hole transport material include 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, stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers. 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.
[0113]
Representative examples of the aromatic tertiary amine compound and styrylamine compound 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; Bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p- Tolylaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N′-diphenyl-N, N -Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadri N; N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenyl Amino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbenzene; N-phenylcarbazole and further described in US Pat. No. 5,061,569 Having two condensed aromatic rings in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-3 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 8688 are linked in a starburst type ( MTDATA).
[0114]
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.
[0115]
Inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole transport material. 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, 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 nm-5 micrometers. The hole transport layer may have a single layer structure composed of one or more of the above materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions. Furthermore, the electron transport layer used as necessary only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and the material thereof is selected from any conventionally known compounds. Can be used.
[0116]
Examples of materials used for this electron transport layer (hereinafter referred to as electron transport materials) include heterocyclic tetracarboxylic anhydrides such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, carbodiimide, Examples include fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, triazole derivatives, and phenanthroline 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.
[0117]
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.
[0118]
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 , Ca, Sn, Ga or Pb can also be used as an electron transport material. 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. Further, a distyrylpyrazine derivative used as a material for the light-emitting layer can also be used as an electron transport material. Similarly to the hole transport layer, inorganic semiconductors such as n-type-Si and n-type-SiC can be used as an electron transport material Can be used as
[0119]
The electron transport 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 an electron carrying layer does not have a restriction | limiting in particular, Usually, it selects in 5 nm-5 micrometers. The electron transport layer may have a single layer structure composed of one or two or more of these electron transport materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.
[0120]
Furthermore, a buffer layer (electrode interface layer) may be present between the anode and the light emitting layer or hole injection layer and between the cathode and the light emitting layer or electron injection layer.
[0121]
The buffer layer is a layer that is provided between the electrode and the organic layer in order to lower the driving voltage and improve the light emission efficiency. “The organic EL element and the forefront of its industrialization (issued on November 30, 1998 by NTS Corporation) 2) Chapter 2 “Electrode Materials” (pages 123 to 166) in detail, and includes an anode buffer layer and a cathode buffer layer.
[0122]
The details of the anode buffer layer are described in JP-A-9-45479, 9-260062, and 8-288069. Specific examples thereof include a phthalocyanine buffer layer represented by copper phthalocyanine, and vanadium oxide. And an oxide buffer layer, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.
[0123]
The details of the cathode buffer layer are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, a metal buffer layer represented by strontium, aluminum and the like, Examples thereof include an alkali metal compound buffer layer typified by lithium fluoride, an alkaline earth metal compound buffer layer typified by magnesium fluoride, an oxide buffer layer typified by aluminum oxide and lithium oxide, and the like.
[0124]
In particular, in the organic EL device of the present invention, when the cathode buffer layer was present, a significant reduction in driving voltage and an improvement in luminous efficiency were obtained.
[0125]
The buffer layer is preferably a very thin film, and depending on the material, the film thickness is preferably in the range of 0.1 to 100 nm.
[0126]
Further, in addition to the basic constituent layer, a layer having other functions may be laminated as required. For example, JP-A-11-204258, JP-A-11-204359, and “Organic EL device and its industrialization front line ( It may have a functional layer such as a hole blocking layer described on page 237 of "November 30, 1998, NTS Corporation").
[0127]
Next, the electrode of the organic EL element will be described. The electrode of the organic EL element consists of a cathode and an anode.
[0128]
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.
[0129]
The anode may be formed by forming a thin film 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, or (100 μm when pattern accuracy is not required so much). As described above, 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, it is desirable that the transmittance is 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 nm to 1 μm, preferably 10 nm to 200 nm.
[0130]
On the other hand, as the cathode, a material having a low work function (4 eV or less) 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 from the viewpoint of durability against electron injecting and oxidation, for example, a magnesium / silver mixture, magnesium / Aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al₂O_Three) Mixtures, lithium / aluminum mixtures and the like are preferred.
[0131]
Furthermore, as the cathode used in the organic EL device of the present invention, an aluminum alloy is preferable, and the aluminum content is particularly preferably 90% by mass or more and less than 100% by mass, and most preferably 95% by mass or more and less than 100% by mass. . Thereby, the light emission lifetime and the highest reached luminance of the organic EL element can be greatly improved.
[0132]
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 1 μm, preferably 50 to 200 nm. In order to transmit light, if either the anode or the cathode of the organic EL element is transparent or translucent, the light emission efficiency is improved, which is convenient.
[0133]
The substrate preferably used for the organic EL device of the present invention is not particularly limited in the kind of glass, plastic and the like, and is not particularly limited as long as it is transparent. Examples of the substrate preferably used in the electroluminescent device of the present invention include glass, quartz, and a light transmissive plastic film.
[0134]
Examples of the light transmissive plastic film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, and polycarbonate (PC). And a film made of cellulose triacetate (TAC), cellulose acetate propionate (CAP), or the like.
[0135]
Next, a suitable example for producing the organic EL element will be described. As an example, a method for producing an EL device comprising the anode / anode buffer layer / hole transport layer / light emitting layer / electron transport layer / cathode buffer layer / cathode will be described. First, a desired electrode material is formed on a suitable substrate. For example, a thin film made of a material for an anode is formed by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 10 to 200 nm, to produce an anode. Next, a thin film made of materials of an anode buffer layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode buffer layer is formed thereon.
[0136]
As a method for thinning the organic thin film layer, there are a spin coating method, a casting method, a vapor deposition method and the like as described above. From the viewpoint that a homogeneous film is easily obtained and pinholes are not easily generated. Vapor deposition or spin coating is particularly preferred. Further, a different film forming method may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, the target crystal structure of the molecular deposition film, the association structure, etc., but generally a boat heating temperature of 50 to 450 ° C. and a degree of vacuum of 10^-6-10^-2It is desirable to select appropriately within the ranges of Pa, vapor deposition rate of 0.01 to 50 nm / second, substrate temperature of −50 to 300 ° C., and film thickness of 5 nm to 5 μm.
[0137]
After forming these layers, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired EL element can be obtained. The organic EL element is preferably produced from the hole injection layer to the cathode consistently by a single evacuation, but it may be taken out in the middle and subjected to a different film forming method. Therefore, it is necessary to consider that the work is performed in a dry inert gas atmosphere.
[0138]
Moreover, it is also possible to reverse the production order and produce the cathode, the cathode buffer layer, the electron transport layer, the light emitting layer, the hole transport layer, the anode buffer layer, and the anode in this order. When a DC voltage is applied to the EL element thus obtained, light emission can be observed by applying a voltage of about 5 to 40 V with the anode being + and the cathode being-. 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.
[0139]
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. Moreover, it is possible to produce a full-color display device by using two or more organic EL elements of the present invention having different emission colors.
[0140]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this.
[0141]
Example 1 (Use as phosphorescent host compound)
After patterning on a substrate (made by NH Techno Glass Co., Ltd .: NA-45) with a 150 nm ITO film on glass as the anode, the transparent support substrate provided with this ITO transparent electrode was ultrasonically cleaned with i-propyl alcohol. Then, it was dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. This transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while α-NPD, CBP, Ir-10, BC, Alq are attached to five molybdenum resistance heating boats._ThreeWere attached to a vacuum deposition apparatus.
[0142]
The vacuum chamber is then 4 × 10^-FourAfter reducing the pressure to Pa, the heating boat containing α-NPD is energized and heated, and deposited on the transparent support substrate to a thickness of 50 nm at a deposition rate of 0.1 to 0.2 nm / sec. A hole injection / transport layer was provided. Further, the heating boat containing CBP and the boat containing Ir-10 are energized independently to adjust the deposition rate of CBP and Ir-10 to 100: 7, so that the film thickness is 30 nm. The light emitting layer was provided.
[0143]
Subsequently, the heating boat containing BC was energized and heated, and an electron transport layer having a thickness of 10 nm was also provided at a deposition rate of 0.1 to 0.2 nm / sec. Furthermore, Alq_ThreeThe heating boat containing was energized and heated to provide an electron transport layer having a film thickness of 50 nm at a deposition rate of 0.1 to 0.2 nm / sec.
[0144]
Next, a vacuum chamber is opened, and a stainless steel rectangular perforated mask is placed on the electron transport layer. On the other hand, 3 g of magnesium is placed in a molybdenum resistance heating boat, and 0.02 of silver is placed 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 / sec. At this time, the silver basket was heated at the same time, and the deposition rate was 0.1 nm / sec. A comparative organic EL element OLED1-1 was produced by vapor-depositing silver to form a cathode (200 nm) made of a mixture of magnesium and silver.
[0145]
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[0146]
Organic electroluminescent elements OLED1-2 to 24 were produced in the same manner as organic electroluminescent element OLED1-1 except that CBP as the host compound of organic EL element OLED1-1 was changed to the compounds shown in Table 1.
[0147]
The obtained organic light-emitting device of the present invention was measured for a voltage at the start of light emission at a temperature of 23 ° C. in a dry nitrogen gas atmosphere to obtain a light emission start voltage. Next, light emission luminance (L) [cd / m when 9V DC voltage is applied]²] Was measured. The light emission luminance is expressed as a relative value when the organic electroluminescence element OLED1-1 is 100. The light emission start voltage has a luminance of 50 [cd / m.²]. The emission luminance was measured using Minolta CS-1000. The results are shown in Table 1.
[0148]
[Table 1]

[0149]
From Table 1, it can be seen that the organic EL device using the compound of the present invention has improved light emission luminance and voltage at the start of light emission. The structure of the compound used above is shown below. The emission color was blue.
[0150]
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[0151]
Similar effects were also obtained in organic EL devices produced in the same manner as OLED1-1 to OLED1-24, except that the phosphorescent compound was replaced with Ir-9 or Ir-1. 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.
[0152]
Example 2
The cathode of the organic electroluminescent element OLED1-6 produced in Example 1 is replaced with Al, and a cathode buffer layer is provided by depositing a lithium oxide film with a thickness of 1.5 nm between the electron transport layer and the cathode. An organic electroluminescence device (OLED2-1) was produced in the same manner except that BC, which was also an electron transport layer, was replaced with BAlq.
[0153]
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[0154]
  In the same manner as in Example 1, the organic light-emitting device was emitted at a luminance of 23 [deg.²] Was measured. Further, the time (τ) during which the luminance is reduced by half was measured. In comparison with the organic electroluminescence element OLED1-6, the light emission luminance was 109 and the luminance was reduced to 188. Particularly, the luminance was reduced by half. In addition, the organic electroluminescence element OLED1-9-13, 15, 17, 20~ 23Similarly, when a cathode buffer layer and BAlq were introduced, a great effect on the half life of luminance was observed.
[0155]
Example 3
The red, green, and blue light-emitting organic electroluminescence elements produced in Example 1 were juxtaposed on the same substrate, and an active matrix type full-color display device shown in Japanese Patent Application No. 2001-181543 was produced.
[0156]
By driving the full-color display device, a clear full-color moving image display with high luminance was obtained.
[0157]
【The invention's effect】
According to the present invention, a high-brightness and long-life organic electroluminescence element containing a phosphorescent host compound capable of improving emission luminance and lowering driving voltage, and low power consumption and high-brightness display using the organic electroluminescence element I got the device.

Claims (14)

In the organic electroluminescence device having a light emitting layer containing a host compound and a phosphorescent compound, the host compound is a compound represented by the following general formula (1-1), and the phosphorescent compound is an iridium compound. An organic electroluminescence device characterized.
However, the compound represented by the general formula (1-1) does not contain 4,4′-bis (2,2-diphenylethenyl) biphenyl.

[Wherein R ₁ , R ₂ , R ₃ , R ₄ represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group, or a cyano group, and R ₁ , R ₂ , R ₃ , R ₄ At least two substituents represent an aryl group or a heterocyclic group. ] The organic electroluminescent device according to claim 1, wherein the host compound represented by the general formula (1-1), characterized in that a compound represented by the following general formula (1-3).

Wherein, _X 3, _{X 4} is an aryl group, or a heterocyclic group, _R 7, _{R 8} is aryl group, or a heterocyclic group. ] The organic electroluminescent device according to claim 1, wherein the host compound represented by the general formula (1-1) is a compound represented by the following general formula ( 2-1 ).

Wherein, _{R 9, R 10, R 11} , R 12 is a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano _group, a _{R 9, R 10, R 11} , R 12 At least two substituents are represented by the following general formula (2-2) . ]
General formula (2-2)
* -A ₂₀ -A ₂₁ -R ₂₀
[ Wherein , A ₂₀ and A ₂₁ represent a monocyclic aromatic ring or a heterocyclic ring, R ₂₀ represents a hydrogen atom or a substituent, and * represents a bonding site. ] The organic electroluminescent device according to claim 1, wherein the host compound represented by the general formula (1-1) is a compound represented by the following general formula ( 2-3 ).

[ Wherein , A ₂₂ , A ₂₃ , A ₂₄ and A ₂₅ represent a monocyclic aromatic ring or a heterocyclic ring, and R ₂₁ , R ₂₂ , R ₂₃ and R ₂₄ represent a hydrogen atom, an alkyl group and an alkoxy group. Represents an aryl group, a heterocyclic group or a cyano group. ] _{A 22, A 23} above following general formula (2-3) An organic electroluminescence device according to claim 4, characterized in that the heterocycle containing a hetero atom 2 or more. The host compounds represented by the before following general formula (1-1) An organic electroluminescence device according to claim 1, characterized in that a compound represented by the following general formula (3).

_{Wherein, A 31} is an aromatic ring, or a _{heterocyclic,} R _{31, R 32,} an aryl group, or a heterocyclic _{group, R 33, R 34, R} 35, R 36 is a hydrogen atom Represents an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano group. ] The host compounds represented by the general formula (1-1) An organic electroluminescence device according to claim 1, wherein the Oh Rukoto the following general formula (4).

Wherein, _{A 41, A 42} is an aromatic ring, or a _{heterocyclic,} R _{41, R 42} represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or cyano _{group, R 43} , R ₄₄ , R ₄₅ , R ₄₆ , R ₄₇ , R ₄₈ each represents a hydrogen atom or a substituent . ] The organic electroluminescent device according to claim 1 , wherein the host compound represented by the general formula (1-1) is a compound represented by the following general formula (5) .

[ Wherein , A ₅₁ , A ₅₂ , A ₅₃ , A ₅₄ represent a monocyclic aromatic ring or a heterocyclic ring, and R ₅₁ , R ₅₂ , R ₅₃ , R ₅₄ , R ₅₅ , R ₅₆ represent a hydrogen atom Represents an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano group. ] The organic electroluminescence device according to claim 1, wherein the host compound represented by the general formula (1-1) is a compound represented by the following general formula ( 6 ).

Wherein, _{A 61} and _{R 61} is an aromatic group, or a heterocyclic group, _{R 62, R 63} are to table a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano group. n represents an integer of 3 . ] The organic electroluminescence device according to claim 1, wherein the host compound represented by the general formula (1-1) is a compound represented by the following general formula ( 8-1 ).

[In formula, Z < ₁ > , Z < ₂ > is an atomic group which forms a condensed ring with a 5-membered ring, and X < ₅ > , X < ₆ > represents -S-, -O-, -NR < ₈₅ > -. R ₈₁ , R ₈₂ , R ₈₃ , R ₈₄ and R ₈₅ represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or a cyano group. ] The organic electroluminescence device according to claim 1, wherein the host compound represented by the general formula (1-1) is a compound represented by the following general formula ( 8-2 ).

[Wherein, Z ₃ represents an atomic group that forms a condensed ring with a 5-membered ring, and X ₇ represents —S—, —O—, or —NR ₉₂ —. R ₈₉ and R ₉₀ represent an aryl group or a heterocyclic group, and R ₈₆ , R ₈₇ , R ₈₈ , R ₉₁ and R ₉₂ represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic group or cyano. Represents a group . ] The organic electroluminescent device according to claim 10 or 11 , wherein Z ₁ , Z ₂ , and Z ₃ in the general formulas ( 8-1) and (8-2) include at least one hetero atom. . The organic electroluminescent device according to any one of claims 1 to 12, wherein the organic electroluminescent device contains a compound having triarylamine as a partial structure in the molecule . A display device comprising the organic electroluminescence element according to claim 1 .