JP3925265B2 - Organic electroluminescence element and display device using the same - Google Patents

Description

【００４１】
【化２２】

【００４２】
【化２３】

【００４３】
【化２４】

【００４４】
【化２５】

【００４５】
【化２６】

【００４６】
本発明に係る上記化合物は、既知の合成方法に従って容易にごうせいすることができるが、以下に示す合成ルートにより、より簡便に合成することができる。
【００４７】
【化２７】

【００４８】
上記反応は、オーガニックレター誌、Ｖｏｌ．３，Ｎｏ．１６，ｐ２５７９〜２５８１（２００１年）に詳細に説明されている。
【００４９】
また、本発明者等は、リン光性化合物のホスト化合物について鋭意検討を重ねた結果、本発明に係るフェニルピリジン化合物をホスト化合物として用いて、有機エレクトロルミネッセンス素子を作製した場合に、素子の発光輝度および寿命が改善されることを見出した。
【００５０】
本発明でいうホスト化合物とは、２種以上の化合物で構成される発光層中において、混合比（質量比）の最も高い化合物であり、それ以外の化合物はドーパント化合物という。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。
【００５１】
以上のような定義より、本発明に係るリン光性化合物は、ドーパント化合物の一種である。
【００５２】
本発明に係るリン光性化合物とは励起三重項からの発光が観測される化合物であり、リン光量子収率が、２５℃において０．００１以上の化合物である。好ましくは０．０１以上である。更に好ましくは０．１以上である。
【００５３】
上記リン光量子収率は、第４版実験化学講座７の分光IIの３９８ページ（１９９２年版、丸善）に記載の方法により測定できる。溶液中でのリン光量子収率は種々の溶媒を用いて測定できるが、本発明で用いられるリン光性化合物とは、任意の溶媒のいずれかにおいて上記リン光量子収率が達成されれば良い。
【００５４】
好ましくは、元素の周期律表でVIII属の金属を含有する錯体系化合物であり、さらに好ましくは、イリジウム、オウミウム、または白金錯体系化合物であり、より好ましくはイリジウム錯体系化合物である。
【００５５】
以下に、本発明で用いられるリン光性化合物の具体例を示すが、これらに限定されるものではない。これらの化合物は、例えば、Ｉｎｏｒｇ．Ｃｈｅｍ．４０巻、１７０４−１７１１に記載の方法等により合成できる。
【００５６】
【化２８】

【００５７】
【化２９】

【００５８】
【化３０】

【００５９】
また、別の態様では、ホスト化合物とリン光性化合物の他に、リン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、ホスト化合物とリン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０．１以上、特に０．３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。ここでいう蛍光量子収率も、前記第４版実験化学講座７の分光IIの３６２ページ（１９９２年版、丸善）に記載の方法により測定することができる。
【００６０】
以下、本発明の有機エレクトロルミネッセンス素子の構成要素について説明する。
【００６１】
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、本発明これに限定されるものではない。
【００６２】
（ｉ）陽極／発光層／電子輸送層／陰極
（ii）陽極／正孔輸送層／発光層／電子輸送層／陰極
（iii）陽極／正孔輸送層／発光層／正孔阻止層／電子輸送層／陰極
（iv）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
（ｖ）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
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。
【００６３】
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−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１０〜１０００ｎｍ、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。
【００６４】
次に、注入層、正孔輸送層、電子輸送層、発光層等について説明する。
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。
【００６５】
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。
【００６６】
陽極バッファー層（正孔注入層）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。
【００６７】
陰極バッファー層（電子注入層）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、酸化アルミニウムに代表される酸化物バッファー層等が挙げられる。
【００６８】
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０．１〜１００ｎｍの範囲が好ましい。
【００６９】
阻止層は、上記のごとく、有機化合物薄膜の基本構成層の他に必要に応じて設けられるものである。例えば、特開平１１−２０４２５８号、同１１−２０４３５９号及び「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２３７頁等に記載されている正孔阻止（ホールブロック）層がある。
【００７０】
正孔阻止層とは広義では電子輸送層であり、電子を輸送する機能を有しつつ正孔を輸送する能力が著しく小さい材料からなり、電子を輸送しつつ正孔を阻止することで電子と正孔の再結合確率を向上させることができる。
【００７１】
一方、電子阻止層とは広義では正孔輸送層であり、正孔を輸送する機能を有しつつ電子を輸送する能力が著しく小さい材料からなり、正孔を輸送しつつ電子を阻止することで電子と正孔の再結合確率を向上させることができる。
【００７２】
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。
【００７３】
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。
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、発光層内であっても発光層と隣接層との界面であっても良い。
【００７４】
発光層に使用される材料（以下、発光材料という）は、蛍光または燐光を発する有機化合物または錯体であることが好ましく、有機ＥＬ素子の発光層に使用される公知のものの中から適宜選択して用いることができる。このような発光材料は、主に有機化合物であり、所望の色調により、例えば、Ｍａｃｒｏｍｏｌ．Ｓｙｎｔｈ．，１２５巻，１７〜２５頁に記載の化合物等を用いることができる。
【００７５】
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。
【００７６】
発光材料は、ｐ−ポリフェニレンビニレンやポリフルオレンのような高分子材料でも良く、さらに前記発光材料を高分子鎖に導入した、または前記発光材料を高分子の主鎖とした高分子材料を使用しても良い。
【００７７】
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１種又は２種以上からなる単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２種以上の材料からなり、その内の少なくとも１種が本発明に係る化合物の場合である。
【００７８】
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。
【００７９】
前述のように、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う。ドーパントの混合比は、好ましくは質量比で０．１％以上、１５％未満である。
【００８０】
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、好ましくは蛍光極大波長がドーパントよりも短波長であることである。
【００８１】
ホスト化合物としては、有機ＥＬ素子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、また後述の正孔輸送材料や電子輸送材料の殆どが発光層ホスト化合物としても使用できる。
【００８２】
ポリビニルカルバゾールやポリフルオレンのような高分子材料でもよく、さらに前記ホスト化合物を高分子鎖に導入した、または前記ホスト化合物を高分子の主鎖とした高分子材料を使用してもよい。
【００８３】
ホスト化合物としては、正孔輸送能、電子輸送能を有しつつ、かつ高Ｔｇ（ガラス転移温度）である化合物が好ましい。
【００８４】
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。
【００８５】
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。
【００８６】
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。
【００８７】
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。
【００８８】
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。
【００８９】
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。
【００９０】
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。
【００９１】
また、本発明においては、正孔輸送層の正孔輸送材料は発光層に用いられる化合物に比べ、蛍光極大波長がより短波長であり、かつ高Ｔｇである化合物が好ましい。
【００９２】
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。
【００９３】
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。
【００９４】
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。
【００９５】
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。
【００９６】
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。
【００９７】
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。
【００９８】
電子輸送層に用いられる化合物も、正孔輸送層に用いられる化合物と同様に、発光層で用いられる化合物に比べ、蛍光極大波長がより短波長であり、かつ高Ｔｇである化合物が好ましい。
【００９９】
本発明の有機ＥＬ素子に好ましく用いられる基体は、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。
【０１００】
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。
【０１０１】
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。
【０１０２】
本発明の有機エレクトロルミネッセンス素子において、室温における発光の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。
【０１０３】
また、カラーフィルター等の色相改良フィルター等を併用してもよい。
本発明の表示装置は、少なくとも２種類の異なる発光極大波長を有する有機ＥＬ素子からなるが、有機ＥＬ素子を作製する好適な例を説明する。例として、陽極／正孔注入層／正孔輸送層／発光層／電子輸送層／電子注入層／陰極からなる有機ＥＬ素子の作製法について説明すると、まず適当な基体上に、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の膜厚になるように、蒸着やスパッタリング等の方法により形成させ、陽極を作製する。次に、この上に素子材料である正孔注入層、正孔輸送層、発光層、電子輸送層、電子注入層、正孔阻止層の有機化合物薄膜を形成させる。
【０１０４】
この有機化合物薄膜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、インクジェット法、蒸着法、印刷法等があるが、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等の点から、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よい。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等により異なるが、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０．１ｎｍ〜５μｍの範囲で適宜選ぶことが望ましい。
【０１０５】
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等の方法により形成させ、陰極を設けることにより、所望の有機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。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。
【０１０６】
本発明の表示装置は、発光層形成時のみシャドーマスクを設け、他層は共通であるのでシャドー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、印刷法等で膜を形成できる。
【０１０７】
発光層のみパターニングを行う場合、その方法に限定はないが、好ましくは蒸着法、インクジェット法、印刷法である。蒸着法を用いる場合においてはシャドーマスクを用いたパターニングが好ましい。
【０１０８】
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。
【０１０９】
このようにして得られた多色の表示装置に、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、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。
【０１１０】
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。
【０１１１】
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。
【０１１２】
発光光源としては、家庭用照明、車内照明、時計や液晶用のバックライト、看板広告、信号機、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に限定するものではない。
【０１１３】
また、本発明の有機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。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に限定するものではない。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。
【０１１４】
【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。
【０１１５】
実施例１
《有機ＥＬ素子の作製》
陽極としてガラス上にＩＴＯ（インジウムチンオキシド）を厚さ１５０ｎｍで成膜した基板（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た後、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、モリブデン製抵抗加熱ボートにα―ＮＰＤを２００ｍｇ入れ、別のモリブデン製抵抗加熱ボートに比較化合物１を２００ｍｇ入れ、別のモリブデン製抵抗加熱ボートにバソキュプロイン（ＢＣＰ）を２００ｍｇ入れ、さらに別のモリブデン製抵抗加熱ボートにＡｌｑ₃を２００ｍｇ入れ、真空蒸着装置に取付けた。
【０１１６】
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０．１〜０．３ｎｍ／ｓｅｃで透明支持基板に膜厚５０ｎｍで蒸着し、正孔輸送層を設けた。蒸着時の基板温度は室温であった。
【０１１７】
次いで、比較化合物１の入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．３ｎｍ／ｓｅｃで膜厚３０ｎｍの発光層を設けた。更に、ＢＣＰの入った前記加熱ボートを通電して加熱し、膜厚１０ｎｍの正孔阻止層を設けた。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０．１〜０．３ｎｍ／ｓｅｃで膜厚２０ｎｍの電子輸送層を設けた。
【０１１８】
次に、真空槽をあけ、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／ｓｅｃでマグネシウムを蒸着した。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とすることにより、表１に示す比較用の有機ＥＬ素子ＯＬＥＤ１−１を作製した。
【０１１９】
次いで、上記有機ＥＬ素子ＯＬＥＤ１−１の作製において、比較化合物１を表１に記載の各化合物に変更した以外は同様にして、有機ＥＬ素子ＯＬＥＤ１−２〜１−１０を作製した。なお、各有機ＥＬ素子の発光色は青色から緑色を示した。
【０１２０】
【化３１】

【０１２１】
【化３２】

【０１２２】
《有機ＥＬ素子の評価》
上記作製した各有機ＥＬ素子を、温度２３度、乾燥窒素ガス雰囲気下で１０Ｖ直流電圧印加による連続点灯を行い、点灯開始時の発光輝度（ｃｄ／ｍ²）および輝度の半減する時間を測定した。発光輝度は、有機ＥＬ素子ＯＬＥＤ１−１の発光輝度を１００とした時の相対値で表し、輝度の半減する時間は有機エレクトロルミネッセンス素子ＯＬＥＤ１−１の発光輝度が半減する時間を１００とした相対値で表した。なお、発光輝度（ｃｄ／ｍ²）は、ミノルタ製ＣＳ−１０００を用いて測定した。
【０１２３】
以上により得られた結果を表１に示す。
【０１２４】
【表１】

【０１２５】
表１より明らかなように、本発明に係る化合物を用いた有機ＥＬ素子は、比較例に対して、点灯開始時の発光輝度及び発光輝度が半減するまでの時間が改善されているのが分かる。
【０１２６】
実施例２
実施例１に記載の有機ＥＬ素子の作製において、本発明に係る例示化合物２４とＤＣＭ２を１００：１の質量比で蒸着した膜厚３０ｎｍの発光層を用い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。上記作製した有機ＥＬ素子ＯＬＥＤ２−１を、温度２３度、乾燥窒素ガス雰囲気下で１０Ｖ直流電圧印加すると、赤色の発光が得られた。
【０１２７】
また、上記有機エレクトロルミネッセンス素子ＯＬＥＤ２−１の作製において、ＤＣＭ２をＱｄ２またはＢＣｚＶＢｉに代えることにより、それぞれ、緑色または青色の発光が得られた。
【０１２８】
【化３３】

【０１２９】
実施例３
《有機ＥＬ素子の作製》
陽極としてガラス上にＩＴＯ（インジウムチンオキシド）を膜厚１５０ｎｍで成膜した基板（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た後、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、モリブデン製抵抗加熱ボートに、ｍ―ＭＴＤＡＴＡを２００ｍｇ入れ、別のモリブデン製抵抗加熱ボートにＤＰＶＢｉを２００ｍｇ入れ、また、別のモリブデン製抵抗加熱ボートにＢＣＰを２００ｍｇを入れ真空蒸着装置に取付けた。
【０１３０】
次いで、真空槽を４×１０^-4Ｐａまで減圧した後、ｍ―ＭＴＤＡＴＡの入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．３ｎｍ／ｓｅｃで透明支持基板に膜厚２５ｎｍで蒸着し、更に、ＤＰＶＢｉの入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．３ｎｍ／ｓｅｃで膜厚２０ｎｍで蒸着し、発光層を設けた。蒸着時の基板温度は室温であった。
【０１３１】
次いで、ＢＣＰの入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．３ｎｍ／ｓｅｃで膜厚３０ｎｍの電子輸送層を設けた。
【０１３２】
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とすることにより、比較用有機ＥＬ素子ＯＬＥＤ３−１を作製した。
【０１３３】
上記有機ＥＬ素子ＯＬＥＤ３−１の作製において、ＢＣＰを表２に記載の各化合物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ＯＬＥＤ３−２〜１２を作製した。
【０１３４】
【化３４】

【０１３５】
《有機ＥＬ素子の評価》
上記作製した各有機ＥＬ素子を、温度２３度、乾燥窒素ガス雰囲気下で１０Ｖ直流電圧印加による連続点灯を行い、点灯開始時の発光輝度（ｃｄ／ｍ²）および輝度の半減する時間を測定した。発光輝度は、有機ＥＬ素子ＯＬＥＤ３−１の発光輝度を１００とした時の相対値で表し、輝度の半減する時間は有機エレクトロルミネッセンス素子ＯＬＥＤ３−１の発光輝度が半減する時間を１００とした相対値で表した。発光輝度（ｃｄ／ｍ²）は、ミノルタ製ＣＳ−１０００を用いて測定した。なお、全ての有機ＥＬ素子の発光色は、青色であった。
【０１３６】
【表２】

【０１３７】
表２より明らかなように、本発明に係る化合物を用いた有機ＥＬ素子は、比較例に対して、点灯開始時の発光輝度、発光効率及び輝度の半減する時間が改善されて、特には、輝度の半減する時間が改善されているのが分かる。
【０１３８】
実施例４
実施例３で作製した有機ＥＬ素子ＯＬＥＤ３−１１の陰極をＡｌに置き換え、電子輸送層と陰極の間にフッ化リチウムを膜厚０．５ｎｍとなるように蒸着して陰極バッファー層を設けた以外は同様にして有機ＥＬ素子ＯＬＥＤ４−１を作製した。
【０１３９】
上記作製した有機ＥＬ素子ＯＬＥＤ４−１を、実施例３に記載の方法と同様にして、点灯開始時の発光輝度（ｃｄ／ｍ²）、および輝度の半減する時間を測定したところ、有機エレクトロルミネッセンス素子ＯＬＥＤ３−１との相対比較で、発光輝度２１４、輝度の半減する時間４０５となった。また、有機ＥＬ素子ＯＬＥＤ３−３〜１０、３−１２についても、有機ＥＬ素子ＯＬＥＤ４−１と同様にして、陰極バッファー層を導入した結果、その効果がより一層発揮されることを確認することができた。
【０１４０】
実施例５
実施例３で作製した各有機ＥＬ素子の発光層において、ＤＰＶＢｉからそれぞれＡｌｑ₃またはＡｌｑ₃とＤＣＭ２を１００：１の質量比で蒸着した発光層に変更した以外は同様にして、各有機エレクトロルミネッセンス素子を作製し、同様の方法で点灯開始時の発光輝度（ｃｄ／ｍ²）および輝度の半減する時間を測定した。その結果、実施例３と同様に、本発明に係る化合物を電子輸送層に用いた有機ＥＬ素子は、比較例（有機ＥＬ素子３−１、３−２）に対して、点灯開始時の発光輝度（ｃｄ／ｍ²）および輝度の半減する時間の改善が確認された。
【０１４１】
なお、Ａｌｑ₃を発光層に用いた場合は緑色の発光が得られ、Ａｌｑ₃とＤＣＭ２を１００：１で共蒸着した発光層では、赤色の発光が得られた。
【０１４２】
実施例６
《有機ＥＬ素子の作製》
有機ＥＬ素子ＯＬＥＤ６−１〜６−８を、以下の記載の方法に準じて作製した。
【０１４３】
陽極として１００ｍｍ×１００ｍｍ×１．１ｍｍのガラス基板上にＩＴＯ（インジウムチンオキシド）を膜厚１５０ｎｍで成膜した基板（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イソ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た後、ＵＶオゾン洗浄を５分間行なった。
【０１４４】
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、モリブデン製抵抗加熱ボートに、α−ＮＰＤを２００ｍｇ入れ、別のモリブデン製抵抗加熱ボートにＣＢＰを２００ｍｇ入れ、別のモリブデン製抵抗加熱ボートにバソキュプロイン（ＢＣＰ）を２００ｍｇ入れ、別のモリブデン製抵抗加熱ボートに例示化合物Ｉｒ−１（燐光性化合物）を１００ｍｇ入れ、さらに別のモリブデン製抵抗加熱ボートにＡｌｑ₃を２００ｍｇ入れ、真空蒸着装置に取付けた。
【０１４５】
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０．１ｎｍ／ｓｅｃで透明支持基板に蒸着し、膜厚４５ｎｍの正孔輸送層を設けた。さらに、ＣＢＰとＩｒ−１の入った前記加熱ボートに通電して加熱し、それぞれ蒸着速度０．１ｎｍ／ｓｅｃ、０．０１ｎｍ／ｓｅｃで前記正孔輸送層上に共蒸着して膜厚２０ｎｍの発光層を設けた。なお、蒸着時の基板温度は室温であった。さらに、ＢＣＰの入った前記加熱ボートに通電して加熱し、蒸着速度０．１ｎｍ／ｓｅｃで前記発光層の上に蒸着して膜厚１０ｎｍの正孔阻止の役割も兼ねた電子輸送層を設けた。その上に、さらに、Ａｌｑ₃の入った前記加熱ボートに通電して加熱し、蒸着速度０．１ｎｍ／ｓｅｃで前記電子輸送層の上に蒸着して更に膜厚４０ｎｍの電子注入層を設けた。なお、蒸着時の基板温度は室温であった。
【０１４６】
次に、ＬｉＦを膜厚０．５ｎｍで、またＡｌを膜厚１１０ｎｍで蒸着して陰極を形成し、有機ＥＬ素子ＯＬＥＤ６−１を作製した。
【０１４７】
上記有機ＥＬ素子ＯＬＥＤ６−１の作製において、発光層のホスト化合物としてＣＢＰに代えて、表３に記載の各化合物を用いた以外は全く同様にして、有機ＥＬ素子ＯＬＥＤ６−２〜６−１２を作製した。
【０１４８】
【化３５】

【０１４９】
《有機ＥＬ素子の評価》
上記作製した有機ＥＬ素子ＯＬＥＤ６−１〜６−１２について、発光輝度および発光寿命の評価を行った。各有機ＥＬ素子を、温度２３℃、乾燥窒素ガス雰囲気下で９Ｖ直流電圧を印加した時の発光輝度および輝度の半減時間（発光寿命）を測定した。発光輝度は有機ＥＬ素子ＯＬＥＤ６−１の発光輝度を１００とした時の相対値で表し、輝度の半減する時間も有機ＥＬ素子ＯＬＥＤ６−１を１００とした時の相対値で表し、得られた結果を表３に示す。なお、発光輝度（ｃｄ／ｍ²）については、ミノルタ製ＣＳ−１０００を用いて測定した。なお、各有機ＥＬ素子は、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緑色の発光を示した。
【０１５０】
【表３】

【０１５１】
表３から明らかなように、本発明に係る化合物をホスト化合物とした有機ＥＬ素子は、比較例に対して、発光輝度が高く、発光寿命が長いことから、有機ＥＬ素子として非常に有用であることを確認することができた。
【０１５２】
更に、上記作製した各有機ＥＬ素子について、燐光性化合物Ｉｒ−１に代えて、例示化合物Ｉｒ−１１またはＩｒ−９を用いて、各有機ＥＬ素子を作製し、同様の評価を行った結果、上記と同様の効果が得られた。なお、例示化合物Ｉｒ−１１を用いた素子は青色の発光を、また例示化合物Ｉｒ−９を用いた素子では赤色の発光が得られた。
【０１５３】
実施例７
《有機ＥＬ素子の作製》
上記実施例６で作製した有機ＥＬ素子ＯＬＥＤ６−１において、電子輸送層で用いたＢＣＰを、表４に記載の各化合物に変更した以外は同様にして、有機ＥＬ素子ＯＬＥＤ７−１〜７−１１を作製した。
【０１５４】
《有機ＥＬ素子の評価》
上記作製した有機ＥＬ素子ＯＬＥＤ７−１〜７−１１及び実施例６で作製した有機ＥＬ素子ＯＬＥＤ６−１について、発光輝度および発光寿命の評価を行った。各有機ＥＬ素子を、温度２３℃、乾燥窒素ガス雰囲気下で９Ｖ直流電圧を印加した時の発光輝度および輝度の半減時間を測定した。発光輝度は有機ＥＬ素子ＯＬＥＤ６−１の発光輝度を１００とした時の相対値で表し、輝度の半減する時間も有機ＥＬ素子ＯＬＥＤ６−１を１００とした時の相対値で表し、得られた結果を表４に示した。なお、発光輝度（ｃｄ／ｍ²）については、ミノルタ製ＣＳ−１０００を用いて測定し、得られた結果を表４に示す。なお、各有機ＥＬ素子は、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緑色の発光を示した。
【０１５５】
【表４】

【０１５６】
表４から明らかなように、本発明に係る化合物を電子輸送層（正孔阻止層）に用いた各有機ＥＬ素子は、比較例に対して、発光輝度が高く、発光寿命が長いことから、有機ＥＬ素子として非常に有用であることがわかった。
【０１５７】
更に、上記作製した各有機ＥＬ素子７−１〜７−１１について、燐光性化合物Ｉｒ−１に代えて、例示化合物Ｉｒ−１１またはＩｒ−９を用いて、各有機ＥＬ素子を作製し、同様の評価を行った結果、上記と同様の効果が得られた。なお、例示化合物Ｉｒ−１１を用いた素子は青色の発光を、また例示化合物Ｉｒ−９を用いた素子では赤色の発光が得られた。
【０１５８】
実施例８
実施例６で作製したそれぞれ赤色、緑色、青色発光の各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、図１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。
【０１５９】
図１には作製したフルカラー表示装置の表示部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、フルカラー表示が可能となる。図２は、１画素当たりの回路図である。
【０１６０】
上記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。
【０１６１】
【発明の効果】
本発明により、特定構造のフェニルピリジン化合物を用いて素子の発光輝度の向上および耐久性の両立ができ、また、フェニルピリジン化合物を燐光性発光用のホスト化合物として用いること、または、フェニルピリジン化合物を電子輸送材料（ホールブロッカー）として用いることにより、発光輝度の向上および耐久性を両立した有機エレクトロルミネッセンス素子及びそれを用いた発光輝度の高い、長寿命な表示装置を提供することができた。
【図面の簡単な説明】
【図１】本発明の有機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】本発明の有機ＥＬ素子の１画像当たりの回路の一例を示した回路図である。
【符号の説明】
１ ガラス基板
２ 配線部
３ 画素
５ 走査線
６ データ線
７ 電源ライン
１０ 有機エレクトロルミネッセンス素子
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
１０１ 表示部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescence (hereinafter also abbreviated as organic EL) element and a display device using the same, and more specifically, an organic electroluminescence element excellent in emission luminance and a display device using the same.
[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 device has a structure in which a light-emitting layer containing a light-emitting compound is sandwiched between a cathode and an anode, and excitons (excitons) are generated by injecting electrons and holes into the light-emitting layer and recombining them. The device emits light using the emission of light (fluorescence / phosphorescence) when the 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 completely solid element, it has attracted attention from the viewpoints of space saving and portability.
[0003]
However, for 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]
Various organic EL elements have been reported so far. For example, Appl. Phys. Lett. , Vol. 51, 913, or a combination of a hole injection layer and an organic light emitting layer described in JP-A-59-194393, a hole injection layer and an electron injection-transport layer described in JP-A-63-295695 , Jpn. Journal of Applied Physics, vol. 127, no. 2 A combination of the hole transfer layer, the light emitting layer, and the electron transfer layer described on pages 269 to 271 is disclosed. However, a device with higher luminance is demanded, and further improvement in energy conversion efficiency and light emission quantum efficiency is expected.
[0005]
In addition, a problem that the light emission life is short has been pointed out. The cause of such deterioration in luminance over time has not been fully elucidated, but electroluminescent devices that emit light are decomposed by the decomposition of the organic compounds themselves that make up the thin film due to the light emitted by itself and the heat generated at that time. Factors derived from organic compounds that are organic EL element materials, such as crystallization of organic compounds in the field, have also been pointed out.
[0006]
At present, electron transport materials have little knowledge, and in combination with the use of antibonding orbitals, no useful high-performance electron transport materials that can withstand practical use have been found. For example, a research group at Kyushu University has obtained 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole (t-BuPBD), which is an oxadiazole derivative. First, 1,3-bis (4-tert-butylphenyl-1,3,4-oxadizolyl) biphenylene (OXD-1), 1,3-bis, which is an oxadiazole dimer derivative with improved thin film stability (4-t-butylphenyl-1,3,4-oxadizolyl) phenylene (OXD-7) (Jpn. J. Appl. Phys. Vol. 31 (1992), p. 1812) has been proposed. In addition, a research group at Yamagata University has produced a white light-emitting element by using a triazole electron transport material having excellent electron blocking properties (Science, 3 March 1995, Vol. 267, p. 1332). Further, JP-A-5-331459 describes that phenanthroline derivatives are useful as electron transport materials.
[0007]
However, the conventional electron transporting material has a low thin film forming ability and easily crystallizes, so that there is a problem that the light emitting element is destroyed, and the element performance that can withstand practical use cannot be expressed.
[0008]
As organic electroluminescent materials for solving these problems, JP-A-9-87616, JP-A-9-194487, and JP-A-2000-186094 are examples in which a compound containing a silicon atom in a molecule is used as a light emitting material or an electron transporting material. Although described, it has not been sufficient for achieving both luminous efficiency and luminous lifetime.
[0009]
On the other hand, a technique has been reported in which the luminous efficiency is improved by constituting the light emitting layer with a host compound and a small amount of phosphor. For example, in Japanese Patent No. 3093796, a small amount of a phosphor is doped into a stilbene derivative, a distyrylarylene derivative or a tristyrylarylene derivative to achieve improvement in light emission luminance and a longer device lifetime. 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. As described above, the emission luminance is improved by doping a phosphor having a high fluorescence quantum yield as compared with the conventional device.
[0010]
However, the light emission from the small amount of the phosphor to be doped is light emission from the excited singlet, and when the light emission from the excited singlet is used, the generation ratio of the singlet exciton and the triplet exciton is 1: Since the generation probability of the luminescent excited species is 25% and the light extraction efficiency is about 20%, the external extraction quantum efficiency (η _ext ) Is 5%. However, since the University of Princeton reported an organic EL device using phosphorescence emission from an excited triplet (MA Baldo et al., Nature, 395, 151-154 (1998)), it has been reported at room temperature. Research on materials exhibiting phosphorescence has been active (for example, MA Baldo et al., Nature, 403, 17, 750-753 (2000), US Pat. No. 6,097,147, etc.). When the excited triplet is used, the upper limit of the internal quantum efficiency is 100%. In principle, the luminous efficiency is up to four times that of the excited singlet, and almost the same performance as a cold cathode tube is obtained. It can be applied to and is attracting attention.
[0011]
Of course, the host when using the 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, but there are other conditions to be satisfied. I understand that.
[0012]
The 10th International Workshop on Inorganic and Organic Electroluminescence (EL '00, Hamamatsu) reports on several phosphorescent compounds. For example, Ikai et al. Use a hole transporting compound as a host of a phosphorescent compound. In addition, M.M. E. Thompson et al. Use various electron transport materials as a host of phosphorescent compounds doped with a novel iridium complex. Furthermore, Tsutsui et al. Have obtained high luminous efficiency by introducing a hole blocking layer. The hole blocking layer is structurally the same as the electron transport layer used in a normal organic EL element, but the function of holes leaking from the light emitting layer to the cathode side rather than the electron transport function. It is named as a hole block layer because it has a powerful function of preventing movement, and can be interpreted as a kind of electron transport layer.
[0013]
Therefore, in the present application, the hole block layer is also referred to as an electron transport layer, and a material (hole blocker) used in the layer is also referred to as an electron transport material.
[0014]
As for the host compound of the phosphorescent compound, for example, C.I. Adachi et al. , Appl. Phys. Lett. 77, page 904 (2000), etc., but a new approach is required for the properties required for the host compound to obtain a high-brightness organic electroluminescence device. .
[0015]
However, the present situation is that none of the reports has obtained a configuration capable of achieving both improvement in light emission luminance and durability of the element.
[0016]
[Problems to be solved by the invention]
Therefore, the present invention has been made for the purpose of achieving both improvement in light emission luminance and durability of the device by using a phenylpyridine compound having a specific structure, and the present invention uses a phenylpyridine compound for phosphorescence emission. By using as a host compound, or by using a phenylpyridine compound as an electron transport material (hole blocker), an organic electroluminescence device that achieves both improvement in emission luminance and durability and high emission luminance using the same, A long-life display device is provided.
[0017]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitution.
[0018]
1. An organic electroluminescence device comprising at least one compound represented by the general formula (1).
[0019]
2. 2. The organic electroluminescence device according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the general formula (2).
[0020]
3. 2. The organic electroluminescence device according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the general formula (3).
[0021]
4). 2. The organic electroluminescence device according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the general formula (4).
[0022]
5. 2. The organic electroluminescence device according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the general formula (5).
[0023]
6). 2. The organic electroluminescence device according to 1 above, wherein the compound represented by the general formula (1) is a compound represented by the general formula (6).
[0024]
7). 2. The organic electroluminescence device according to item 1, wherein the compound represented by the general formula (1) is a compound represented by the general formula (7).
[0025]
8). 2. The organic electroluminescence device according to item 1, wherein the compound represented by the general formula (1) is a compound represented by the general formula (8).
[0026]
9. An electron transport layer contains at least one compound selected from the compounds represented by the general formulas (1) to (8).
[0027]
10. The light emitting layer contains at least one compound selected from the compounds represented by the general formulas (1) to (8), and the organic electroluminescence device.
[0028]
11. In the organic electroluminescence device having a light emitting layer containing a host compound and a phosphorescent compound, the host compound is at least one compound selected from the compounds represented by the general formulas (1) to (8). An organic electroluminescence device characterized by the above.
[0029]
12 12. The organic electroluminescence device as described in 11 above, wherein the phosphorescent compound is an iridium compound, an osmium compound or a platinum compound.
[0030]
13. 12. The organic electroluminescence device as described in 11 above, wherein the phosphorescent compound is an iridium compound.
[0031]
14 14. A display device comprising the organic electroluminescence element according to any one of 1 to 13 above.
[0032]
The present invention is described in detail below.
First, the compound represented by the general formula (1) will be described.
[0033]
In the general formula (1), the n-valent linking group represented by Z is not particularly limited, but is preferably Z in the general formula (2) to the general formula (7). ₁ ~ Z ₆ It is a coupling group represented by these.
[0034]
In the general formula (1), R ₁ ~ R ₈ Each represents a hydrogen atom or a substituent. Examples of the substituent include an alkyl group (for example, a methyl group, an ethyl group, an i-propyl group, a hydroxyethyl group, a methoxymethyl group, a trifluoromethyl group, a t-butyl group). Group, cyclopentyl group, cyclohexyl group, benzyl group, etc.), alkenyl group (eg, vinyl group, propenyl group, styryl group, etc.), alkynyl group (eg, ethynyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.) p-tolyl group, p-chlorophenyl group, etc.), alkyloxy group (eg, methoxy group, ethoxy group, i-propoxy group, butoxy group, etc.), aryloxy group (eg, phenoxy group, etc.), alkylthio group (eg, Methylthio group, ethylthio group, i-propylthio group, etc.), arylthio group (for example, phenylthio group) Etc.), halogen atoms (eg fluorine atom, chlorine atom, bromine atom, iodine atom etc.), amino groups (eg dimethylamino group, methylamino group, diphenylamino group etc.), cyano group, nitro group, heterocyclic group (For example, pyrrole group, pyrrolidyl group, pyrazolyl group, imidazolyl group, pyridyl group, benzimidazolyl group, benzothiazolyl group, benzoxazolyl group, etc.). Examples of the aromatic group include the above aryl group and heteroaryl group (for example, pyrrole group, pyrazolyl group, imidazolyl group, pyridyl group, benzimidazolyl group, benzothiazolyl group, benzoxazolyl group). Adjacent substituents may be condensed with each other to form a ring.
[0035]
In the general formulas (2) to (7), R _a ~ R _f Each represents a hydrogen atom or a substituent, and specific examples thereof are the R ₁ ~ R ₈ It is synonymous with.
[0036]
In the general formulas (1) to (7), the divalent arylene group represented by Ar is a residue obtained by removing two hydrogen atoms or substituents from any position of any aromatic compound. The arylene group may be composed of a hydrocarbon, a heterocycle containing a heteroatom, or may be condensed.
[0037]
In the general formula (8), Ar ₁ The m-valent arylene group represented by is a residue obtained by removing m hydrogen atoms or substituents from an arbitrary position of an arbitrary aromatic compound, and the arylene group is composed of a hydrocarbon. May be a heterocyclic ring containing a hetero atom or may be condensed.
[0038]
Each compound according to the present invention represented by the general formulas (1) to (8) is a compound having strong fluorescence in a solid state, is excellent in electroluminescence, and can be effectively used as a light emitting material. In addition, since the excellent electron injecting property and electron transporting property from the metal electrode are very excellent, in the device using the other light emitting material or the above compound according to the present invention as the light emitting material, the compound according to the present invention is an electron. When used as a transport material or hole blocker, it exhibits excellent luminous efficiency.
[0039]
Specific examples of the compounds represented by the general formulas (1) to (8) are listed below, but the present invention is not limited to these.
[0040]
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[0041]
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[0042]
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[0043]
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[0044]
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[0045]
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[0046]
The above-mentioned compound according to the present invention can be easily synthesized according to a known synthesis method, but can be synthesized more easily by the synthesis route shown below.
[0047]
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[0048]
The above reaction is described in Organic Letter, Vol. 3, No. 16, p 2579-2581 (2001).
[0049]
In addition, as a result of intensive studies on the host compound of the phosphorescent compound, the present inventors, as a result of producing an organic electroluminescence device using the phenylpyridine compound according to the present invention as the host compound, emitted light from the device. It has been found that brightness and lifetime are improved.
[0050]
The host compound as used in the field of this invention is a compound with the highest mixing ratio (mass ratio) in the light emitting layer comprised by 2 or more types of compounds, and a compound other than that is called a dopant compound. 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.
[0051]
From the above definitions, the phosphorescent compound according to the present invention is a kind of dopant compound.
[0052]
The phosphorescent compound according to 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.
[0053]
The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescence quantum yield used in the present invention is only required to achieve the phosphorescence quantum yield in any solvent.
[0054]
Preferred are complex compounds containing a Group VIII metal in the periodic table of elements, more preferred are iridium, onium, or platinum complex compounds, and more preferred are iridium complex compounds.
[0055]
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.
[0056]
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[0057]
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[0058]
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[0059]
In another embodiment, in addition to the host compound and the phosphorescent compound, at least one fluorescent compound having a fluorescence maximum wavelength is contained in a region longer than the maximum wavelength of light emission from the phosphorescent compound. There is also. 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 0.1 or more, particularly preferably 0.3 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. The fluorescence quantum yield here can also be measured by the method described on page 362 (1992 version, Maruzen) of Spectroscopic II of the Fourth Edition Experimental Chemistry Course 7.
[0060]
Hereinafter, components of the organic electroluminescence element of the present invention will be described.
[0061]
In the present invention, preferred specific examples of the layer structure of the organic EL element are shown below, but the present invention is not limited thereto.
[0062]
(I) Anode / light emitting layer / electron transport layer / cathode
(Ii) Anode / hole transport layer / light emitting layer / electron transport layer / cathode
(Iii) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode
(Iv) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode
(V) Anode / anode buffer layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode
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. ₂ And conductive transparent materials such as ZnO. IDIXO (In ₂ O _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, or when the pattern accuracy is not required (100 μm or more) 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, 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 to 1000 nm, preferably 10 to 200 nm.
[0063]
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 (Al ₂ O _Three ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O _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 to 1000 nm, preferably 50 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.
[0064]
Next, an injection layer, a hole transport layer, an electron transport layer, a light emitting layer and the like will be described.
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.
[0065]
An injection layer is a layer provided between an electrode and an organic layer in order to lower drive voltage or improve light emission luminance. “Organic EL element and its forefront of industrialization (issued on November 30, 1998 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).
[0066]
The details of the anode buffer layer (hole injection layer) are described in JP-A Nos. 9-45479, 9-260062, and 8-288069, and a specific example is represented by copper phthalocyanine. Examples thereof include a phthalocyanine buffer layer, an oxide buffer layer typified by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.
[0067]
The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, 9-17574, 10-74586, and the like, and specifically, strontium, aluminum, and the like are representative. A metal buffer layer, an alkali metal compound buffer layer typified by lithium fluoride, an alkaline earth metal compound buffer layer typified by magnesium fluoride, and an oxide buffer layer typified by aluminum oxide.
[0068]
The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 to 100 nm, although it depends on the material.
[0069]
As described above, the blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film. For example, JP-A Nos. 11-204258 and 11-204359 and “Organic EL devices and their forefront of industrialization” (issued on November 30, 1998 by NTS, Inc.), page 237, etc. There is a hole blocking layer.
[0070]
The hole blocking layer is an electron transporting layer in a broad sense, and is made of a material that has a function of transporting electrons and has a very small ability to transport holes. By blocking holes while transporting electrons, The recombination probability of holes can be improved.
[0071]
On the other hand, the electron blocking layer is a hole transport layer in a broad sense, and is made of a material that has a function of transporting holes and has a very small ability to transport electrons, and blocks electrons while transporting holes. The recombination probability of electrons and holes can be improved.
[0072]
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.
[0073]
The hole transport layer and the electron transport layer can be provided as a single layer or a plurality of layers.
The light emitting layer is a layer that emits light by recombination of electrons and holes injected from the electrode, electron transport layer, or hole transport layer, and the light emitting portion is adjacent to the light emitting layer even in the light emitting layer. It may be an interface with the layer.
[0074]
The material used for the light emitting layer (hereinafter referred to as the light emitting material) is preferably an organic compound or complex that emits fluorescence or phosphorescence, and is appropriately selected from known materials used for the light emitting layer of the organic EL device. Can be used. Such a light-emitting material is mainly an organic compound, and has a desired color tone, for example, Macromol. Synth. 125, pages 17 to 25, and the like.
[0075]
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.
[0076]
The light-emitting material may be a polymer material such as p-polyphenylene vinylene or polyfluorene, and a polymer material in which the light-emitting material is introduced into a polymer chain or the light-emitting material is a polymer main chain is used. May be.
[0077]
The 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. 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. In a preferred embodiment of the organic EL device of the present invention, the light emitting layer is composed of two or more materials, and at least one of them is the compound according to the present invention.
[0078]
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.
[0079]
As described above, when the material of the light emitting layer is two or more kinds, the main component is called a host and the other components are called dopants. The mixing ratio of the dopant is preferably 0.1% or more and less than 15% by mass ratio.
[0080]
The host compound of the light emitting layer is preferably an organic compound or a complex, and in the present invention, preferably the fluorescence maximum wavelength is shorter than the dopant.
[0081]
As the host compound, any of known materials used in organic EL devices can be selected and used, and most of the hole transport materials and electron transport materials described below are also used as the light emitting layer host compound. it can.
[0082]
A polymer material such as polyvinyl carbazole or polyfluorene may be used, and a polymer material in which the host compound is introduced into a polymer chain or the host compound as a polymer main chain may be used.
[0083]
As the host compound, a compound having a hole transport ability and an electron transport ability and a high Tg (glass transition temperature) is preferable.
[0084]
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.
[0085]
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.
[0086]
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.
[0087]
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.
[0088]
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 ′ -Di (4-methoxy) N), 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-diphenyl) Vinyl) benzene; 3-methoxy-4′-N, N-diphenylaminostilbenzene; N-phenylcarbazole, as well as two fused aromatics described in US Pat. No. 5,061,569. Those having a ring in the molecule, for example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), described in JP-A-4-308688 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (MTDATA) in which three triphenylamine units are linked in a starburst type. .
[0089]
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.
[0090]
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.
[0091]
In the present invention, the hole transport material of the hole transport layer is preferably a compound having a shorter fluorescence maximum wavelength and a higher Tg than the compound used for the light emitting layer.
[0092]
This 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.
[0093]
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.
[0094]
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.
[0095]
Examples of materials used for this 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.
[0096]
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.
[0097]
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), and the like, and the central metal of these metal complexes is In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga, or Pb can also be used as the 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. 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.
[0098]
Similarly to the compound used for the hole transport layer, the compound used for the electron transport layer is preferably a compound having a shorter fluorescence maximum wavelength and a higher Tg than the compound used for the light emitting layer.
[0099]
The substrate preferably used for the organic EL device of the present invention is not particularly limited in the type of glass, plastic, etc., and is not particularly limited as long as it is transparent. Examples of the substrate preferably used include glass and quartz. And a light transmissive resin film. A particularly preferable substrate is a resin film that can give flexibility to the organic EL element.
[0100]
Examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose. Examples include films made of triacetate (TAC), cellulose acetate propionate (CAP), and the like.
[0101]
An inorganic or organic coating or a hybrid coating of both may be formed on the surface of the resin film.
[0102]
In the organic electroluminescence device of the present invention, the external extraction efficiency of light emission at room temperature 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.
[0103]
Further, a hue improving filter such as a color filter may be used in combination.
The display device of the present invention includes at least two types of organic EL elements having different light emission maximum wavelengths. A suitable example for producing the organic EL elements will be described. As an example, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection 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 10 to 200 nm, to produce an anode. Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer, which are element materials, is formed thereon.
[0104]
As described above, there are spin coating methods, casting methods, ink jet methods, vapor deposition methods, printing methods, and the like as methods for thinning the organic compound thin films, but it is easy to obtain a uniform film and pinholes are not easily generated. In view of the above, the vacuum deposition method or the spin coating method is particularly preferable. Further, different film forming methods 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, but generally a boat heating temperature of 50 to 450 ° C. and a degree of vacuum of 10 ^-6 -10 ^-2 It 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 0.1 nm to 5 μm.
[0105]
After these layers are formed, 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 thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired organic 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 may be taken out halfway and subjected to different film forming methods. In that case, it is necessary to consider that the work is performed in a dry inert gas atmosphere.
[0106]
The display device of the present invention is provided with a shadow mask only at the time of forming a light emitting layer, and the other layers are common, so patterning such as a shadow mask is unnecessary, and vapor deposition, casting, spin coating, ink jet, and printing are performed on one side. A film can be formed by a method or the like.
[0107]
When patterning is performed only on the light-emitting layer, the method is not limited, but a vapor deposition method, an inkjet method, and a printing method are preferable. In the case of using a vapor deposition method, patterning using a shadow mask is preferable.
[0108]
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.
[0109]
When a DC voltage is applied to the multicolor display device thus obtained, 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.
[0110]
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.
[0111]
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.
[0112]
Light emitting sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard 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. However, it is not limited to this.
[0113]
Moreover, you may use as an organic EL element which gave the organic EL element of this invention the resonator structure. 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 what you want. Moreover, you may use for the said use by making a laser oscillation.
[0114]
【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.
[0115]
Example 1
<< Production of organic EL element >>
After patterning a substrate (NH Techno Glass Co., Ltd .: NA-45) on which ITO (Indium Tin Oxide) was formed on a glass with a thickness of 150 nm as an anode, a transparent supporting substrate provided with this ITO transparent electrode was i. -Ultrasonic cleaning with propyl alcohol and drying with dry nitrogen gas, followed by UV ozone cleaning for 5 minutes. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus, while 200 mg of α-NPD was put in a molybdenum resistance heating boat, and 200 mg of Comparative Compound 1 was put in another molybdenum resistance heating boat. Add 200 mg of bathocuproine (BCP) to a resistance heating boat made of molybdenum, and add Alq to another resistance heating boat made of molybdenum. _Three 200 mg was added and attached to a vacuum deposition apparatus.
[0116]
The vacuum chamber is then 4 × 10 ^-Four After reducing the pressure to Pa, the heating boat containing α-NPD was energized and heated, and deposited on the transparent support substrate at a film thickness of 50 nm at a deposition rate of 0.1 to 0.3 nm / sec. Provided. The substrate temperature during vapor deposition was room temperature.
[0117]
Next, the heating boat containing the comparative compound 1 was energized and heated to provide a light emitting layer having a film thickness of 30 nm at a deposition rate of 0.1 to 0.3 nm / sec. Further, the heating boat containing BCP was heated by energization to provide a hole blocking layer having a thickness of 10 nm. Furthermore, Alq _Three The heating boat containing was energized and heated to provide an electron transport layer having a thickness of 20 nm at a deposition rate of 0.1 to 0.3 nm / sec.
[0118]
Next, a vacuum chamber is opened, and a stainless steel rectangular perforated mask is placed on the electron injection 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 ^-Four After reducing the pressure to Pa, a magnesium-containing boat was energized to deposit magnesium at a deposition rate of 1.5 to 2.0 nm / sec. At this time, the silver basket is heated at the same time, and silver is deposited at a deposition rate of 0.1 nm / sec to form a cathode made of the mixture of magnesium and silver, thereby making the comparative organic EL element OLED1 shown in Table 1. -1 was produced.
[0119]
Next, organic EL elements OLED1-2 to 1-10 were prepared in the same manner as in the preparation of the organic EL element OLED1-1 except that the comparative compound 1 was changed to each compound shown in Table 1. In addition, the luminescent color of each organic EL element showed blue to green.
[0120]
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[0121]
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[0122]
<< Evaluation of organic EL elements >>
Each of the produced organic EL elements was continuously lit by applying a DC voltage of 10 V in a dry nitrogen gas atmosphere at a temperature of 23 ° C., and the emission luminance (cd / m at the start of lighting) ² ) And the time to reduce the luminance by half. The light emission luminance is expressed as a relative value when the light emission luminance of the organic EL element OLED1-1 is 100, and the time when the luminance is halved is a relative value when the time when the light emission luminance of the organic electroluminescence element OLED1-1 is halved is 100. Expressed in Note that the emission luminance (cd / m ² ) Was measured using Minolta CS-1000.
[0123]
The results obtained as described above are shown in Table 1.
[0124]
[Table 1]

[0125]
As is apparent from Table 1, it can be seen that the organic EL device using the compound according to the present invention has improved light emission luminance at the start of lighting and time until the light emission luminance is reduced by half compared to the comparative example. .
[0126]
Example 2
In the production of the organic EL device described in Example 1, organic electroluminescence was similarly conducted except that a light emitting layer having a film thickness of 30 nm obtained by evaporating the exemplified compound 24 according to the present invention and DCM2 at a mass ratio of 100: 1 was used. Element OLED2-1 was produced. When the produced organic EL element OLED2-1 was applied with a DC voltage of 10 V in a dry nitrogen gas atmosphere at a temperature of 23 degrees, red light emission was obtained.
[0127]
Further, in the production of the organic electroluminescence element OLED2-1, green or blue light emission was obtained by replacing DCM2 with Qd2 or BCzVBi, respectively.
[0128]
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[0129]
Example 3
<< Production of organic EL element >>
After patterning a substrate (NH Techno Glass Co., Ltd .: NA-45) having a film thickness of 150 nm of ITO (indium tin oxide) formed on glass as an anode, the transparent support substrate provided with this ITO transparent electrode is i. -Ultrasonic cleaning with propyl alcohol and drying with dry nitrogen gas, followed by UV ozone cleaning for 5 minutes. This transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while 200 mg of m-MTDATA is put into a molybdenum resistance heating boat, and 200 mg of DPVBi is put into another resistance heating boat made of molybdenum. 200 mg of BCP was placed in a molybdenum resistance heating boat and attached to a vacuum evaporation system.
[0130]
The vacuum chamber is then 4 × 10 ^-Four After depressurizing to Pa, energize and heat the heating boat containing m-MTDATA, deposit it on a transparent support substrate at a film thickness of 25 nm at a deposition rate of 0.1 to 0.3 nm / sec, and further contain DPVBi. Further, the heating boat was energized and heated, and vapor deposition was performed at a deposition rate of 0.1 to 0.3 nm / sec with a film thickness of 20 nm to provide a light emitting layer. The substrate temperature during vapor deposition was room temperature.
[0131]
Subsequently, the heating boat containing BCP was energized and heated to provide an electron transport layer having a film thickness of 30 nm at a deposition rate of 0.1 to 0.3 nm / sec.
[0132]
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 ^-Four After 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. Comparative organic EL element OLED3-1 was produced by vapor-depositing silver into a cathode made of the mixture of magnesium and silver.
[0133]
In the production of the organic EL element OLED3-1, organic electroluminescence elements OLED3-2 to 12 were produced in the same manner except that BCP was replaced with each compound described in Table 2.
[0134]
Embedded image

[0135]
<< Evaluation of organic EL elements >>
Each of the produced organic EL elements was continuously lit by applying a DC voltage of 10 V in a dry nitrogen gas atmosphere at a temperature of 23 ° C., and the emission luminance (cd / m at the start of lighting) ² ) And the time to reduce the luminance by half. The light emission luminance is expressed as a relative value when the light emission luminance of the organic EL element OLED3-1 is 100, and the time when the luminance is halved is a relative value when the time when the light emission luminance of the organic electroluminescence element OLED3-1 is halved is 100. Expressed in Luminance (cd / m ² ) Was measured using Minolta CS-1000. In addition, the luminescent color of all the organic EL elements was blue.
[0136]
[Table 2]

[0137]
As is apparent from Table 2, the organic EL device using the compound according to the present invention has improved light emission luminance at the start of lighting, light emission efficiency, and a time for halving the luminance with respect to the comparative example. It can be seen that the time to reduce the luminance by half is improved.
[0138]
Example 4
The cathode of the organic EL element OLED3-11 produced in Example 3 was replaced with Al, and lithium fluoride was deposited between the electron transport layer and the cathode so as to have a film thickness of 0.5 nm, and a cathode buffer layer was provided. Produced an organic EL element OLED4-1 in the same manner.
[0139]
In the same manner as described in Example 3, the produced organic EL element OLED4-1 was subjected to emission luminance (cd / m at the start of lighting). ² ), And the time when the luminance is reduced by half, the light emission luminance 214 and the time when the luminance is reduced by half 405 are obtained in a relative comparison with the organic electroluminescence element OLED3-1. Moreover, also about organic EL element OLED3-3-10, 3-12, it is confirming that the effect is exhibited more as a result of introducing a cathode buffer layer like organic EL element OLED4-1. did it.
[0140]
Example 5
In the light emitting layer of each organic EL device produced in Example 3, each of Alq from DPVBi _Three Or Alq _Three Each of the organic electroluminescence elements is manufactured in the same manner except that the light emitting layer is deposited in a mass ratio of 100: 1 and DCM2, and the light emission luminance (cd / m at the start of lighting) is obtained in the same manner. ² ) And the time to reduce the luminance by half. As a result, as in Example 3, the organic EL device using the compound according to the present invention for the electron transport layer emitted light at the start of lighting with respect to the comparative example (organic EL device 3-1, 3-2). Luminance (cd / m ² ) And an improvement in the time to reduce the luminance by half.
[0141]
Alq _Three Is used for the light emitting layer, green light emission is obtained, and Alq _Three And DCM2 were co-evaporated at 100: 1, red light emission was obtained.
[0142]
Example 6
<< Production of organic EL element >>
Organic EL elements OLED6-1 to 6-8 were produced according to the method described below.
[0143]
After patterning on a substrate (NA-45 manufactured by NH Techno Glass) having a film thickness of 150 nm of ITO (indium tin oxide) formed on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode, this ITO transparent electrode The transparent support substrate provided with was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and then subjected to UV ozone cleaning for 5 minutes.
[0144]
This transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while 200 mg of α-NPD is put into a molybdenum resistance heating boat, and 200 mg of CBP is put into another resistance heating boat made of molybdenum. 200 mg of bathocuproine (BCP) is put into a resistance heating boat made of aluminum, 100 mg of Illustrated compound Ir-1 (phosphorescent compound) is put into another resistance heating boat made of molybdenum, and Alq is put into another resistance heating boat made of molybdenum. _Three 200 mg was added and attached to a vacuum deposition apparatus.
[0145]
The vacuum chamber is then 4 × 10 ^-Four After depressurizing to Pa, the heating boat containing α-NPD was energized and heated, and deposited on a transparent support substrate at a deposition rate of 0.1 nm / sec to provide a 45 nm thick hole transport layer. Further, the heating boat containing CBP and Ir-1 was energized and heated, and co-deposited on the hole transport layer at a deposition rate of 0.1 nm / sec and 0.01 nm / sec, respectively, to have a film thickness of 20 nm. A light emitting layer was provided. In addition, the substrate temperature at the time of vapor deposition was room temperature. Further, an electron transport layer that also serves as a hole blocking function with a film thickness of 10 nm is provided by energizing and heating the heating boat containing BCP and depositing on the light emitting layer at a deposition rate of 0.1 nm / sec. It was. In addition, Alq _Three The heating boat containing was heated by energizing, and was deposited on the electron transport layer at a deposition rate of 0.1 nm / sec to further provide an electron injection layer having a thickness of 40 nm. In addition, the substrate temperature at the time of vapor deposition was room temperature.
[0146]
Next, LiF was vapor-deposited with a film thickness of 0.5 nm and Al was vapor-deposited with a film thickness of 110 nm to form a cathode, and an organic EL element OLED6-1 was produced.
[0147]
In the production of the organic EL element OLED6-1, the organic EL elements OLED6-2 to 6-12 were made in exactly the same manner except that each compound shown in Table 3 was used instead of CBP as the host compound of the light emitting layer. Produced.
[0148]
Embedded image

[0149]
<< Evaluation of organic EL elements >>
About the produced said organic EL element OLED6-1 to 6-12, the light-emitting luminance and the light emission lifetime were evaluated. Each organic EL element was measured for emission luminance and luminance half-life (emission lifetime) when a DC voltage of 9 V was applied at a temperature of 23 ° C. in a dry nitrogen gas atmosphere. The light emission luminance is expressed as a relative value when the light emission luminance of the organic EL element OLED6-1 is set to 100, and the time during which the luminance is reduced by half is also expressed as a relative value when the organic EL element OLED6-1 is set to 100. Is shown in Table 3. Note that the emission luminance (cd / m ² ) Was measured using Minolta CS-1000. Each organic EL element started to flow at an initial driving voltage of 3 V, and showed green light emission from the phosphorescent compound as the dopant of the light emitting layer.
[0150]
[Table 3]

[0151]
As is apparent from Table 3, the organic EL device using the compound according to the present invention as the host compound is very useful as an organic EL device because it has higher emission luminance and longer emission lifetime than the comparative example. I was able to confirm that.
[0152]
Furthermore, about each produced said organic EL element, it replaced with phosphorescent compound Ir-1 and produced each organic EL element using exemplary compound Ir-11 or Ir-9, As a result of performing the same evaluation, The same effect as above was obtained. In addition, the element using Illustrated Compound Ir-11 emitted blue light, and the element using Illustrated Compound Ir-9 emitted red light.
[0153]
Example 7
<< Production of organic EL element >>
In the organic EL element OLED6-1 prepared in Example 6 above, the organic EL elements OLED7-1 to 7-11 were similarly performed except that the BCP used in the electron transport layer was changed to each compound described in Table 4. Was made.
[0154]
<< Evaluation of organic EL elements >>
With respect to the organic EL elements OLED7-1 to 7-11 prepared above and the organic EL element OLED6-1 prepared in Example 6, the light emission luminance and the light emission lifetime were evaluated. Each organic EL element was measured for emission luminance and luminance half time when a 9 V DC voltage was applied in a dry nitrogen gas atmosphere at a temperature of 23 ° C. The light emission luminance is expressed as a relative value when the light emission luminance of the organic EL element OLED6-1 is set to 100, and the time during which the luminance is reduced by half is also expressed as a relative value when the organic EL element OLED6-1 is set to 100. Are shown in Table 4. Note that the emission luminance (cd / m ² ) Was measured using Minolta CS-1000, and the obtained results are shown in Table 4. Each organic EL element started to flow at an initial driving voltage of 3 V, and showed green light emission from the phosphorescent compound as the dopant of the light emitting layer.
[0155]
[Table 4]

[0156]
As is apparent from Table 4, each organic EL device using the compound according to the present invention for the electron transport layer (hole blocking layer) has higher emission luminance and longer emission lifetime than the comparative example. It was found to be very useful as an organic EL device.
[0157]
Further, for each of the produced organic EL elements 7-1 to 7-11, each organic EL element was produced using the exemplified compound Ir-11 or Ir-9 instead of the phosphorescent compound Ir-1, and the same. As a result of the evaluation, the same effects as described above were obtained. In addition, the element using Illustrated Compound Ir-11 emitted blue light, and the element using Illustrated Compound Ir-9 emitted red light.
[0158]
Example 8
The red, green, and blue light-emitting organic electroluminescence elements produced in Example 6 were juxtaposed on the same substrate, and the active matrix type full-color display device shown in FIG. 1 was produced.
[0159]
FIG. 1 shows only a schematic diagram of a display portion of the produced full-color display device. That is, a wiring portion including a plurality of scanning lines 5 and data lines 6 and a plurality of juxtaposed pixels 3 (light emission color is a red region pixel, a green region pixel, a blue region pixel, etc.) on the same substrate. The scanning line 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 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, full-color display is possible by appropriately juxtaposing the red, green, and blue pixels. FIG. 2 is a circuit diagram per pixel.
[0160]
By driving the full-color display device, a clear full-color moving image display with high luminance was obtained.
[0161]
【The invention's effect】
According to the present invention, the use of a phenylpyridine compound having a specific structure makes it possible to improve both the luminance and durability of the device, and to use the phenylpyridine compound as a host compound for phosphorescent light emission. By using it as an electron transport material (hole blocker), it was possible to provide an organic electroluminescence element that has both improved emission luminance and durability, and a display device with high emission luminance and long life using the organic electroluminescence element.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a display device composed of an organic EL element of the present invention.
FIG. 2 is a circuit diagram showing an example of a circuit per image of the organic EL element of the present invention.
[Explanation of symbols]
1 Glass substrate
2 Wiring part
3 pixels
5 scanning lines
6 Data lines
7 Power line
10 Organic electroluminescence device
11 Switching transistor
12 Driving transistor
13 Capacitor
101 Display

Claims (14)

An organic electroluminescence device comprising at least one compound represented by the following general formula (1).

[Wherein, Z represents an n-valent linking group or a mere bond, Ar represents a divalent arylene group, and R _{1 to} R ₈ each represent a hydrogen atom or a substituent. n represents an integer of 2 to 6. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2).

[Where Z ₁ is

N represents a substituent of 2 or more and 6 or less. At least two of R _{a to} R _e are

The plurality of substituents may be the same or different. R _{a to} R _e which are not the substituents each represent a hydrogen atom or an arbitrary substituent, and adjacent substituents may be condensed with each other to form a ring. Ar represents a divalent arylene group, and R _{1 to} R ₈ each represents a hydrogen atom or a substituent. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (3).

[In the formula, Z ₂ is

N represents a substituent of 2 or more and 6 or less. At least two of R _{a to} R _f are

The plurality of substituents may be the same or different. R _{a to} R _f which are not the substituents each represent a hydrogen atom or an arbitrary substituent, and adjacent substituents may be condensed with each other to form a ring. Ar represents a divalent arylene group, and R _{1 to} R ₈ each represents a hydrogen atom or a substituent. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (4).

[In the formula, Z ₃ is

N represents a substituent of 2 or more and 6 or less. At least two of R _{a to} R _f are

The plurality of substituents may be the same or different. R _{a to} R _f which are not the substituents each represent a hydrogen atom or an arbitrary substituent, and adjacent substituents may be condensed with each other to form a ring. Ar represents a divalent arylene group, and R _{1 to} R ₈ each represents a hydrogen atom or a substituent. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (5).

[In the formula, Z ₄ is

N represents 2 or 3. At least two of R _{a to} R _c are

The plurality of substituents may be the same or different. R _{a to} R _c which are not the substituent each represent a hydrogen atom or an arbitrary substituent. Ar represents a divalent arylene group, and R _{1 to} R ₈ each represents a hydrogen atom or a substituent. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (6).

[Where Z ₅ is

N represents 2 or 3. At least two of R _{a to} R _c are

The plurality of substituents may be the same or different. R _{a to} R _c which are not the substituent each represent a hydrogen atom or an arbitrary substituent. Ar represents a divalent arylene group, and R _{1 to} R ₈ each represents a hydrogen atom or a substituent. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (7).

[Where Z ₆ is

N represents 2 or 3. At least two of R _{a to} R _d are

The plurality of substituents may be the same or different. R _{a to} R _d that are not the substituents each represent a hydrogen atom or an arbitrary substituent, and adjacent substituents may be condensed with each other to form a ring. Ar represents a divalent arylene group, and R _{1 to} R ₈ each represents a hydrogen atom or a substituent. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (8).

[Wherein, Ar ₁ represents an m-valent arylene group, and R _{1 to} R ₈ each represents a hydrogen atom or a substituent. n represents an integer of 2 to 6. Among R ₁ to R _8, adjacent substituents may form a ring condensed with each other. ] An electron transport layer contains at least one compound selected from the compounds represented by the general formulas (1) to (8). A light emitting layer contains the at least 1 sort (s) of compound chosen from the compound represented by said general formula (1)-(8), The organic electroluminescent element characterized by the above-mentioned. In the organic electroluminescence device having a light emitting layer containing a host compound and a phosphorescent compound, the host compound is at least one compound selected from the compounds represented by the general formulas (1) to (8). An organic electroluminescence device characterized by the above. 12. The organic electroluminescence device according to claim 11, wherein the phosphorescent compound is an iridium compound, an osmium compound, or a platinum compound. The organic electroluminescence device according to claim 11, wherein the phosphorescent compound is an iridium compound. A display device comprising the organic electroluminescence element according to claim 1.

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