JP4389494B2 - Method for purifying organic electroluminescent materials - Google Patents

Description

【００７０】
【化２】

【００７１】
【化３】

【００７２】
発光ドーパントは１種のみを用いてもよいし、複数種類を用いてもよく、これらドーパントからの発光を同時に取り出すことにより、複数の発光極大波長を持つ発光素子を構成することもできる。また、例えば燐光性ドーパントと、蛍光性ドーパントの両方が加えられていてもよい。複数の発光層を積層して有機ＥＬ素子を構成する場合、それぞれの層に含有される発光ドーパントは同じであっても異なっていても、単一種類であっても複数種類であってもよい。
【００７３】
さらには、前記発光ドーパントを高分子鎖に導入した、または前記発光ドーパントを高分子の主鎖とした高分子材料を使用してもよい。
【００７４】
上記ホスト化合物としては、例えばカルバゾール誘導体、トリアリールアミン誘導体、芳香族ボラン誘導体、含窒素複素環化合物、チオフェン誘導体、フラン誘導体、オリゴアリーレン化合物等の基本骨格を有するものが挙げられ、後述の電子輸送材料及び正孔輸送材料もその相応しい一例として挙げられる。青色または白色の発光素子、表示装置及び照明装置に適用する場合には、ホスト化合物の蛍光極大波長が４１５ｎｍ以下であることが好ましく、燐光性ドーパントを用いる場合、ホスト化合物の燐光の０−０バンドが４５０ｎｍ以下であることがさらに好ましい。発光ホストとしては、正孔輸送能、電子輸送能を有しつつ、かつ、発光の長波長化を防ぎ、なおかつ高Ｔｇ（ガラス転移温度）である化合物が好ましい。
【００７５】
発光ホストの具体例としては、例えば以下の文献に記載されている化合物が好適である。
【００７６】
特開２００１−２５７０７６、同２００２−３０８８５５、同２００１−３１３１７９、同２００２−３１９４９１、同２００１−３５７９７７、同２００２−３３４７８６、同２００２−８８６０、同２００２−３３４７８７、同２００２−１５８７１、同２００２−３３４７８８、同２００２−４３０５６、同２００２−３３４７８９、同２００２−７５６４５、同２００２−３３８５７９、同２００２−１０５４４５、同２００２−３４３５６８、同２００２−１４１１７３、同２００２−３５２９５７、同２００２−２０３６８３、同２００２−３６３２２７、同２００２−２３１４５３、同２００３−３１６５、同２００２−２３４８８８、同２００３−２７０４８、同２００２−２５５９３４、同２００２−２６０８６１、同２００２−２８０１８３、同２００２−２９９０６０、同２００２−３０２５１６、同２００２−３０５０８３、同２００２−３０５０８４、同２００２−３０８８３７等。
【００７７】
これらのホスト化合物は、超臨界または亜臨界状態の溶媒に溶解または接触する工程を含む精製方法により精製されるのが好ましい。超臨界または亜臨界状態の溶媒に溶解または接触する工程を含む精製方法としては、好ましくは超臨界または亜臨界状態の溶媒中に注入し、クロマトグラフ法を用いて不純物を除去する精製方法、超臨界または亜臨界状態の溶媒を用いて抽出する精製方法あるいは超臨界または亜臨界状態の溶媒を用いて晶析する精製方法が挙げられる。
【００７８】
発光ドーパントはホスト化合物を含有する層全体に分散されていてもよいし、部分的に分散されていてもよい。発光層にはさらに別の機能を有する化合物が加えられていてもよい。
【００７９】
上記の材料を用いて、例えば蒸着法、スピンコート法、キャスト法、ＬＢ法、インクジェット転写法、印刷法等の公知の方法により薄膜化することにより、発光層を形成することができるが、形成された発光層は、特に分子堆積膜であることが好ましい。ここで、分子堆積膜とは、上記化合物の気相状態から沈着され形成された薄膜や、該化合物の溶融状態または液相状態から固体化され形成された膜のことである。通常、この分子堆積膜とＬＢ法により形成された薄膜（分子累積膜）とは、凝集構造、高次構造の相違や、それに起因する機能的な相違により区別することができる。
【００８０】
この分子堆積膜からなる発光層は、具体的には、例えば、特開昭５７−５１７８１号公報に記載されているように、樹脂等の結着材とともに上記発光材料を溶剤に溶かして溶液とした後、これをスピンコート法等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。
【００８１】
（正孔注入層及び正孔輸送層）
正孔注入層に用いられる正孔注入材料は、正孔の注入、電子の障壁性のいずれかを有するものである。また、正孔輸送層に用いられる正孔輸送材料は、電子の障壁性を有するとともに正孔を発光層まで輸送する働きを有するものである。従って、本発明においては、正孔輸送層は正孔注入層に含まれる。これら正孔注入材料及び正孔輸送材料は、有機物、無機物のいずれであってもよい。具体的には、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、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、ポルフィリン化合物、チオフェンオリゴマー等の導電性高分子オリゴマーが挙げられる。これらのうちでは、アリールアミン誘導体及びポルフィリン化合物が好ましい。アリールアミン誘導体の中では、芳香族第三級アミン化合物及びスチリルアミン化合物が好ましく、芳香族第三級アミン化合物がより好ましい。
【００８２】
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）ビフェニル；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；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（以下、α−ＮＰＤと略す。）、特開平４−３０８６８８号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。また、ｐ型−Ｓｉ、ｐ型−ＳｉＣ等の無機化合物も正孔注入材料として使用することができる。
【００８３】
また、本発明においては正孔輸送層の正孔輸送材料は４１５ｎｍ以下に蛍光極大波長を有することが好ましい。すなわち、正孔輸送材料は、正孔輸送能を有しつつかつ、発光の長波長化を防ぎ、なおかつ高Ｔｇである化合物が好ましい。
【００８４】
正孔注入層及び正孔輸送層は、上記正孔注入材料及び正孔輸送材料を、例えば、真空蒸着法、スピンコート法、キャスト法、ＬＢ法、インクジェット法、転写法、印刷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。
【００８５】
正孔注入層及び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。なお、上記正孔注入層及び正孔輸送層は、それぞれ上記材料の１種または２種以上からなる１層構造であってもよく、同一組成または異種組成の複数層からなる積層構造であってもよい。また、正孔注入層と正孔輸送層を両方設ける場合には、上記の材料のうち、通常、異なる材料を用いるが、同一の材料を用いてもよい。
【００８６】
（電子注入層及び電子輸送層）
電子注入層は、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。この電子注入層に用いられる材料（以下、電子注入材料ともいう）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等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等が挙げられる。
【００８７】
また、特開昭５９−１９４３９３号公報に記載されている一連の電子伝達性化合物は、該公報では発光層を形成する材料として開示されているが、本発明者らが検討の結果、電子注入材料として用いうることが分かった。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、電子注入材料として用いることができる。
【００８８】
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（Ａｌｑ₃と略す。）、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）等、及びこれらの金属錯体の中心金属がＩｎ、Ｍｇ、Ｃｕ、Ｃａ、Ｓｎ、ＧａまたはＰｂに置き替わった金属錯体も電子注入材料として用いることができる。
【００８９】
その他、メタルフリーやメタルフタロシアニン、またはそれらの末端がアルキル基やスルホン酸基等で置換されているものも電子注入材料として好ましく用いることができる。また、正孔注入層と同様にｎ型−Ｓｉ、ｎ型−ＳｉＣ等の無機半導体も電子注入材料として用いることができる。
【００９０】
電子輸送層に用いられる好ましい化合物は、４１５ｎｍ以下に蛍光極大波長を有することが好ましい。すなわち、電子輸送層に用いられる化合物は、電子輸送能を有しつつかつ、発光の長波長化を防ぎ、なおかつ高Ｔｇである化合物が好ましい。
【００９１】
この電子注入層は、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、インクジェット法、転写法、印刷法等の公知の薄膜化法により成膜して形成することができる。電子注入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。この電子注入層は、これらの電子注入材料の１種または２種以上からなる１層構造であってもよいし、あるいは同一組成または異種組成の複数層からなる積層構造であってもよい。
【００９２】
なお、本明細書においては、前記電子注入層のうち、発光層と比較してイオン化エネルギーが大きい場合には、特に電子輸送層と呼ぶこととする。従って、本明細書においては、電子輸送層は電子注入層に含まれる。
【００９３】
上記電子輸送層は、正孔阻止層（ホールブロック層）とも呼ばれ、その例としては、例えば、ＷＯ ００／７０６５５号公報、特開２００１−３１３１７８号公報、特開平１１−２０４２５８号公報、同１１−２０４３５９号公報、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）」の第２３７頁等に記載されているものが挙げられる。特に発光層にオルトメタル錯体系ドーパントを用いるいわゆる「リン光発光素子」においては、前記（ｖ）及び（vi）のように電子輸送層（正孔阻止層）を有する構成を採ることが好ましい。
【００９４】
（バッファー層）
さらに、陽極と発光層または正孔注入層の間、及び、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。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１２３〜１６６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。
【００９５】
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。
【００９６】
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、酸化アルミニウムに代表される酸化物バッファー層等が挙げられる。
【００９７】
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。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適宜積層してもよい。
【００９８】
（陰極）
上述のように有機ＥＬ素子の陰極としては、一般に仕事関数の小さい（４ｅＶ未満）金属（以下、電子注入性金属と称する）、合金、金属の電気伝導性化合物あるいはこれらの混合物を電極物質とするものが用いられる。
【００９９】
このような電極物質の具体例としては、ナトリウム、マグネシウム、リチウム、アルミニウム、インジウム、希土類金属、ナトリウム−カリウム合金、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、リチウム／アルミニウム混合物等が挙げられる。
【０１００】
本発明においては、上記に列挙したものを陰極の電極物質として用いてもよいが、本発明の効果をより有効に発揮させる点からは、陰極は第１３族金属元素を含有してなることが好ましい。すなわち本発明では、後述するように陰極の表面をプラズマ状態の酸素ガスで酸化して、陰極表面に酸化皮膜を形成することにより、それ以上の陰極の酸化を防止し、陰極の耐久性を向上させることができる。
【０１０１】
従って、陰極の電極物質としては、陰極に要求される好ましい電子注入性を有する金属であって、緻密な酸化皮膜を形成しうる金属であることが好ましい。
【０１０２】
前記第１３族金属元素を含有してなる陰極の電極物質としては、具体的には、例えば、アルミニウム、インジウム、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等が挙げられる。なお、上記混合物の各成分の混合比率は、有機ＥＬ素子の陰極として従来公知の比率を採用することができるが、特にこれに限定されない。上記陰極は、上記の電極物質を蒸着やスパッタリング等の方法により、前記有機化合物層（有機ＥＬ層）上に薄膜形成することにより、作製することができる。
【０１０３】
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、発光光を透過させるために、有機ＥＬ素子の陽極または陰極のいずれか一方を透明または半透明にすると、発光効率が向上して好ましい。
【０１０４】
本発明の有機ＥＬ材料を用いて作製した有機ＥＬ素子からなる表示装置を作製する好適な例を説明する。
【０１０５】
〔有機ＥＬ素子の作製方法〕
本発明の有機ＥＬ素子の作製方法の一例として、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。
【０１０６】
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。
【０１０７】
これら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同、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。
【０１０８】
これらの層を形成後、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、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。
【０１０９】
〔表示装置〕
本発明の有機ＥＬ素子を用いる多色表示装置は、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。
【０１１０】
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。
【０１１１】
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。
【０１１２】
このようにして得られた多色表示装置に、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。
【０１１３】
多色表示装置は、表示デバイス、ディスプレー、各種発光光源として用いることができる。表示デバイス、ディスプレーにおいて、青、赤、緑発光の３種の有機ＥＬ素子を用いることにより、フルカラーの表示が可能となる。
【０１１４】
表示デバイス、ディスプレーとしてはテレビ、パソコン、モバイル機器、ＡＶ機器、文字放送表示、自動車内の情報表示等が挙げられる。特に静止画像や動画像を再生する表示装置として使用してもよく、動画再生用の表示装置として使用する場合の駆動方式は単純マトリックス（パッシブマトリックス）方式でもアクティブマトリックス方式でもどちらでもよい。
【０１１５】
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。
【０１１６】
また、本発明に係る有機ＥＬ素子に共振器構造を持たせた有機ＥＬ素子として用いてもよい。
【０１１７】
このような共振器構造を有した有機ＥＬ素子の使用目的としては、光記憶媒体の光源、電子写真複写機の光源、光通信処理機の光源、光センサーの光源等が挙げられるが、これらに限定されない。また、レーザー発振をさせることにより、上記用途に使用してもよい。
【０１１８】
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よいし、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）として使用してもよい。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よい。または、異なる発光色を有する本発明の有機ＥＬ素子を２種以上使用することにより、フルカラー表示装置を作製することが可能である。
【０１１９】
本発明の有機ＥＬ素子から構成される表示装置の一例を図面に基づいて以下に説明する。
【０１２０】
図４は、有機ＥＬ素子から構成される表示装置の一例を示した模式図である。有機ＥＬ素子の発光により画像情報の表示を行う、例えば、携帯電話等のディスプレイの模式図である。ディスプレイ４１は、複数の画素を有する表示部Ａ、画像情報に基づいて表示部Ａの画像走査を行う制御部Ｂ等からなる。制御部Ｂは、表示部Ａと電気的に接続され、複数の画素それぞれに外部からの画像情報に基づいて走査信号と画像データ信号を送り、走査信号により走査線毎の画素が画像データ信号に応じて順次発光して画像走査を行って画像情報を表示部Ａに表示する。
【０１２１】
図５は、表示部Ａの模式図である。表示部Ａは基板上に、複数の走査線５５及びデータ線５６を含む配線部と、複数の画素５３等とを有する。表示部Ａの主要な部材の説明を以下に行う。
【０１２２】
図５においては、画素５３の発光した光が、白矢印方向（下方向）へ取り出される場合を示している。配線部の走査線５５及び複数のデータ線５６は、それぞれ導電材料からなり、走査線５５とデータ線５６は格子状に直交して、直交する位置で画素５３に接続している（詳細は図示せず）。画素５３は、走査線５５から走査信号が印加されると、データ線５６から画像データ信号を受け取り、受け取った画像データに応じて発光する。発光の色が赤領域の画素、緑領域の画素、青領域の画素を、適宜、同一基板上に並置することによって、フルカラー表示が可能となる。
【０１２３】
次に、画素の発光プロセスを説明する。図６は、画素の模式図である。画素は、有機ＥＬ素子６０、スイッチングトランジスタ６１、駆動トランジスタ６２、コンデンサ６３等を備えている。複数の画素に有機ＥＬ素子６０として、赤色、緑色、青色発光の有機ＥＬ素子を用い、これらを同一基板上に並置することでフルカラー表示を行うことができる。
【０１２４】
図６において、制御部Ｂ（図６には図示せず、図４に示す）からデータ線５６を介してスイッチングトランジスタ６１のドレインに画像データ信号が印加される。そして、制御部Ｂから走査線５５を介してスイッチングトランジスタ６１のゲートに走査信号が印加されると、スイッチングトランジスタ６１の駆動がオンし、ドレインに印加された画像データ信号がコンデンサ６３と駆動トランジスタ６２のゲートに伝達される。
【０１２５】
画像データ信号の伝達により、コンデンサ６３が画像データ信号の電位に応じて充電されるとともに、駆動トランジスタ６２の駆動がオンする。駆動トランジスタ６２は、ドレインが電源ライン６７に接続され、ソースが有機ＥＬ素子６０の電極に接続されており、ゲートに印加された画像データ信号の電位に応じて電源ライン６７から有機ＥＬ素子６０に電流が供給される。
【０１２６】
制御部Ｂの順次走査により走査信号が次の走査線５５に移ると、スイッチングトランジスタ６１の駆動がオフする。しかし、スイッチングトランジスタ６１の駆動がオフしてもコンデンサ６３は充電された画像データ信号の電位を保持するので、駆動トランジスタ６２の駆動はオン状態が保たれて、次の走査信号の印加が行われるまで有機ＥＬ素子６０の発光が継続する。順次走査により、次に走査信号が印加されたとき、走査信号に同期した次の画像データ信号の電位に応じて駆動トランジスタ６２が駆動して有機ＥＬ素子６０が発光する。すなわち、有機ＥＬ素子６０の発光は、複数の画素それぞれの有機ＥＬ素子６０に対して、アクティブ素子であるスイッチングトランジスタ６１と駆動トランジスタ６２を設けて、複数の画素５３（図６には図示せず、図５に示す）それぞれの有機ＥＬ素子６０の発光を行っている。このような発光方法をアクティブマトリクス方式と呼んでいる。
【０１２７】
ここで、有機ＥＬ素子６０の発光は、複数の階調電位を持つ多値の画像データ信号による複数の階調の発光でもよいし、２値の画像データ信号による所定の発光量のオン、オフでもよい。
【０１２８】
また、コンデンサ６３の電位の保持は、次の走査信号の印加まで継続して保持してもよいし、次の走査信号が印加される直前に放電させてもよい。
【０１２９】
本発明においては、上述したアクティブマトリクス方式に限らず、走査信号が走査されたときのみデータ信号に応じて有機ＥＬ素子を発光させるパッシブマトリクス方式の発光駆動でもよい。
【０１３０】
図７は、パッシブマトリクス方式による表示装置の模式図である。図７において、複数の走査線５５と複数の画像データ線５６が画素５３を挟んで対向して格子状に設けられている。順次走査により走査線５５の走査信号が印加されたとき、印加された走査線５５に接続している画素５３が画像データ信号に応じて発光する。パッシブマトリクス方式では画素５３にアクティブ素子が無く、製造コストの低減を図ることができる。
【０１３１】
【実施例】
以下、実施例によって本発明を詳しく説明するが、本発明の実施様態はこれに限定されるものではない。
【０１３２】
実施例１
３００ｍｌの三つ口フラスコに１−ヨードナフタレン（東京化成社製）２．０ｇ、Ｎ，Ｎ′−ジフェニルベンジジン（広島和光純薬社製）１．０ｇ、無水炭酸カリウム３ｇ及び銅粉１．０ｇを加え、２００ｍｌのジメチルスルホキシドに溶解し２００℃で８時間攪拌して反応させた。反応終了後、反応液を濾過し、母液を塩化メチレンで抽出した。そして、ロータリーエバポレーターで溶媒を留去し、残渣をシリカゲル（広島和光純薬社製）を充填したカラムクロマトでトルエンを展開溶媒として精製し、淡黄色粉末（α−ＮＰＤの粗製品）０．３ｇを得た。
【０１３３】
（試料１０１の作製）
日本分光社製超臨界流体クロマトグラフィーシステムを用いて以下の条件にてα−ＮＰＤを分取した。
【０１３４】
超臨界ＣＯ₂送液ポンプ：ＳＣＦ−Ｇｅｔ
全自動圧力調整弁：ＳＦＣ−Ｂｐｇ
カラムオーブン：ＧＣ−３５３Ｂ
インジェクタ：７１２５ｉ
カラム：Ｃ１８−Ｓｉｌｉｃａ、３μｍ、４．６×２５０ｍｍ
移動層：二酸化炭素
移動層流量：３ｍｌ／ｍｉｎ
圧力：１８ＭＰａ
温度：４０℃
検出：紫外検出器（２１０ｎｍ）
上記条件によって１００ｍｇのα−ＮＰＤを得た。このα−ＮＰＤを試料１０１とする。
【０１３５】
（試料１０２の作製）
日本分光社製超臨界抽出装置を用い、以下の条件でα−ＮＰＤを超臨界抽出した。
【０１３６】
超臨界ＣＯ₂送液ポンプ：ＳＣＦ−Ｇｅｔ
全自動圧力調整弁：ＳＦＣ−Ｂｐｇ
抽出槽：ＣＯ−１５６０
抽出溶媒：二酸化炭素（３ｍｌ／ｍｉｎ）
温度：８０℃
圧力：２５ＭＰａ
抽出管容量：１ｍｌ
抽出時間：３０分
上記条件にて１００ｍｇのα−ＮＰＤを得た。これを試料１０２とする。
【０１３７】
（試料１０３の作製）
以下の日本分光社製超臨界晶析装置、操業条件を用いてα−ＮＰＤを超臨界晶析した。
【０１３８】
超臨界ＣＯ₂送液ポンプ：ＳＣＦ−Ｇｅｔ
全自動圧力調整弁：ＳＦＣ−Ｂｐｇ
試薬溶液送液ポンプ：ＰＵ−１５８０
高温槽：ＣＯ１５６０
α−ＮＰＤを流量：３ｍｌ／ｍｉｎ、圧力１８ＭＰａ、４０℃の超臨界状態中にある二酸化炭素中に溶解し、晶析容器に導入した。別途ポンプから晶析容器にトルエン０．２ｍｌ／ｍｉｎを混入させたところα−ＮＰＤが析出した。このα−ＮＰＤを試料１０３とする。
【０１３９】
（試料１０４の作製）
α−ＮＰＤをアルバック理工社製有機色素精製装置ＴＲＳ−１を用い、ボート温度３２０℃、１０^-3Ｐａの条件で２回昇華精製し、１００ｍｇのα−ＮＰＤを得た。これを試料１０４とする。
【０１４０】
（試料１０５の作製）
α−ＮＰＤを再度トルエンに溶解し、シリカゲルを充填したオープンカラムに通し、精製した。これを試料１０５とする。
【０１４１】
（試料１０６の作製）
分取液体クロマトグラフを用いて以下の条件でα−ＮＰＤを精製した。
【０１４２】
送液ポンプ：日立社製、Ｌ−６２００インテリジェントＨＰＬＣポンプ
検出器：日立社製、Ｌ−４２５０ＵＶ／ＶＩＳディテクター
カラム温度：４０℃
流速：１．５ｍｌ／ｍｉｎ
溶離液：シクロヘキサン（関東化学、ＨＰＬＣグレード）／トルエン（関東化学、特級）＝８５体積％／１５体積％
カラム：ＧＬサイエンス社製、イナートシルＰＲＥＰ−ＳＩＬ（２００ｍｍ×２５０ｍｍ）
検出波長：３１０ｎｍ
保持時間１０分に溶離する成分を分取した。これを試料１０６とする。
【０１４３】
〔有機ＥＬ素子の作製〕
陽極としてガラス上にＩＴＯを１５０ｎｍ成膜した基板（ＮＨテクノグラス社製：ＮＡ−４５）にパターニングを行った後、このＩＴＯ透明電極を設けた透明支持基板をｉｓｏ−プロピルアルコールで超音波洗浄し、乾燥窒素ガスで乾燥し、ＵＶオゾン洗浄を５分間行った。
【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、５つのタンタル製抵抗加熱ボートに、上記作製した試料１０１、ＣＢＰ、Ｉｒ−１、ＢＣＰ、Ａｌｑ₃をそれぞれ入れ、真空蒸着装置（第１真空槽）に取付けた。
【０１４５】
さらにタンタル製抵抗加熱ボートにフッ化リチウムを、タングステン製抵抗加熱ボートにアルミニウムをそれぞれ入れ、真空蒸着装置の第２真空槽に取り付けた。
【０１４６】
まず、第１真空槽を４×１０^-4Ｐａまで減圧した後、試料１０１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／秒で透明支持基板に膜厚２５ｎｍ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−１の入ったボートをそれぞれ独立に通電して、発光ホストであるＣＢＰと発光ドーパントであるＩｒ−１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。
【０１４７】
ついで、ＢＣＰの入った前記加熱ボートに通電して加熱し、蒸着速度０．１〜０．２ｎｍ／秒で厚さ１０ｎｍの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／秒で膜厚４０ｎｍの電子注入層を設けた。
【０１４８】
次に、前記の如く電子注入層まで製膜した素子を真空のまま第２真空槽に移した後、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が配置されるように装置外部からリモートコントロールして設置した。
【０１４９】
第２真空槽を２×１０^-4Ｐａまで減圧した後、フッ化リチウム入りのボートに通電して蒸着速度０．０１〜０．０２ｎｍ／秒で膜厚０．５ｎｍの陰極バッファー層を設け、次いでアルミニウムの入ったボートに通電して蒸着速度１〜２ｎｍ／秒で膜厚１５０ｎｍの陰極をつけた。さらにこの有機ＥＬ素子を大気に接触させることなく窒素雰囲気下のグローブボックス（純度９９．９９９％以上の高純度窒素ガスで置換したグローブボックス）へ移し、図８に示したような封止構造にして、有機ＥＬ素子ＯＬＥＤ１−１を作製した。以下、試料１０１に代えて試料１０２〜１０６を用いて、同様にしてＯＬＥＤ１−２〜１−６を作製した。
【０１５０】
【化４】

【０１５１】
（有機ＥＬ素子の評価）
作製した有機ＥＬ素子について、下記のようにして発光輝度、発光効率及び半減時間を測定した。評価の結果を表１に示す。
【０１５２】
（発光輝度、発光効率）
有機ＥＬ素子ＯＬＥＤ１−１〜１−６に発光色は緑色であった。有機ＥＬ素子ＯＬＥＤ１−１は初期駆動電圧２．８Ｖで電流が流れ始めた。
【０１５３】
有機ＥＬ素子ＯＬＥＤ１−１〜１−６に２３℃、乾燥窒素ガス雰囲気下で１０Ｖ直流電圧を印加した時の発光輝度（ｃｄ／ｍ²）、発光効率（ｌｍ／Ｗ）を測定した。
【０１５４】
発光輝度、発光効率は有機ＥＬ素子ＯＬＥＤ１−１を１００とした相対値で表した。発光輝度についてはＣＳ−１０００（ミノルタ製）を用いて測定した。
【０１５５】
（半減時間）
有機ＥＬ素子ＯＬＥＤ１−１〜１−６の各々を２．５ｍＡ／ｃｍ²の一定電流で駆動したときに初期輝度が元の半分に低下するのに要した時間である半減時間を指標として耐久性を評価した。また、半減時間は有機ＥＬ素子ＯＬＥＤ１−１を１００とした時の相対値で表した。
【０１５６】
【表１】

【０１５７】
表１より本発明の精製方法で精製した有機ＥＬ材料を含む層を有する有機ＥＬ素子は、発光輝度、発光効率及び半減時間が比較例よりも上回っており好ましいことが分かった。
【０１５８】
なお、有機ＥＬ素子ＯＬＥＤ１−４において、ＣＢＰ及びＩｒ−１を超臨界クロマトグラフィーにて精製した試料を用いて作製したＯＬＥＤ１−７、ＣＢＰ及びＩｒ−１を超臨界抽出した試料を用いて作製したＯＬＥＤ１−８、ＣＢＰ及びＩｒ−１を超臨界晶析にて精製した試料を用いて作製したＯＬＥＤ１−９は、いずれも発光輝度、発光効率及び半減時間がＯＬＥＤ１−４に対し上回っていた。
【０１５９】
実施例２
実施例１の試料１０２と同様の装置により、２−（４′−ビフェニル）−５−（４″−ｔｅｒｔ−ブチルフェニル）１，３，４−オキサジアゾールを超臨界抽出し精製した。
【０１６０】
〔有機ＥＬ素子の作製〕
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、ＵＶオゾン洗浄を５分間行なった。
【０１６１】
この透明支持基板上にＰＥＤＯＴ／ＰＥＳＳ溶液（ポリエチレンジオキシチオフェン−ポリスルフォン酸ドープ体：ｂａｙｔｒｏｎ（バイエル社製））を膜厚約１００ｎｍでスピンコートした後、真空加熱乾燥した。この上にポリ（Ｎ−ビニルカルバゾール：東京化成社製）１０ｇ、Ｉｒ−１を２５０ｍｇ、フッ化カルシウム１ｍｇ、先に超臨界抽出し精製した２−（４′−ビフェニル）−５−（４″−ｔｅｒｔ−ブチルフェニル）１，３，４−オキサジアゾール５ｍｇをクロロホルム１５００ｍｌに溶解し、その溶液をスピンコートすることで膜厚１５０ｎｍの発光層を得た。
【０１６２】
この基板を市販の真空蒸着装置の基板ホルダーに固定し、フッ化リチウム０．５ｎｍ及びアルミニウム１１０ｎｍを蒸着して陰極を形成した。この有機ＥＬ素子をＯＬＥＤ２−１とする。
【０１６３】
超臨界処理を行わなかった２−（４′−ビフェニル）−５−（４″−ｔｅｒｔ−ブチルフェニル）１，３，４−オキサジアゾールを用いて同様にして、有機ＥＬ素子ＯＬＥＤ２−２を作製した。
【０１６４】
作製した有機ＥＬ素子について、実施例１と同様にして発光輝度、発光効率及び半減時間を測定した。評価の結果を表２に示す。
【０１６５】
【表２】

【０１６６】
表２より本発明の精製方法で精製した有機ＥＬ材料を含む層を有する有機ＥＬ素子は、発光輝度、発光効率及び半減時間が改善されていることが分かる。
【０１６７】
実施例３
〔フルカラー表示装置の作製〕
実施例１の有機ＥＬ素子ＯＬＥＤ１−１の作製において、Ｉｒ−１（発光ドーパント）の代わりに、Ｉｒ−１２、Ｉｒ−６を各々用いた以外は同様にして、有機ＥＬ素子ＯＬＥＤ３−１（青色発光）、有機ＥＬ素子ＯＬＥＤ３−２（赤色発光）を作製した。
【０１６８】
実施例１で作製した有機ＥＬ素子ＯＬＥＤ１−１（緑色発光）、上記作製した有機ＥＬ素子ＯＬＥＤ３−１、３−２を同一基板上に並置し、図４に示すような形態を有するアクティブマトリクス方式フルカラー表示装置を作製し、図５には、作製したフルカラー表示装置の表示部Ａの模式図のみを示した。
【０１６９】
即ち、同一基板上に、複数の走査線５５及びデータ線５６を含む配線部と、並置した複数の画素５３（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５５及び複数のデータ線５６はそれぞれ導電材料からなり、走査線５５とデータ線５６は格子状に直交して、直交する位置で画素５３に接続している（詳細は図示せず）。前記複数の画素５３は、図４に示すような、それぞれの発光色に対応した有機ＥＬ素子６０、アクティブ素子であるスイッチングトランジスタ６１と駆動トランジスタ６２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５５から走査信号が印加されると、データ線５６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。このように各赤、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。
【０１７０】
フルカラー表示装置を駆動することにより、輝度が高く、高耐久性（半減時間が長い）を示し、且つ、鮮明なフルカラー動画表示が得られることが分かった。
【０１７１】
実施例４
〔照明装置の作製〕
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）の電極を２０ｍｍ×２０ｍｍにパターニングし、その上に実施例１と同様に正孔注入／輸送層として試料１０１の入った加熱ボートに通電して２５ｎｍの厚さで成膜し、さらに、ＣＢＰの入った加熱ボートとＩｒ−６の入ったボート及びＩｒ−１２の入ったボートをそれぞれ独立に通電して発光ホストであるＣＢＰと発光ドーパントであるＩｒ−６及びＩｒ−１２の蒸着速度が１００：１：４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。
【０１７２】
ついで、ＢＣＰを１０ｎｍ製膜して電子輸送層を設けた。更に、Ａｌｑ₃を４０ｎｍで製膜し電子注入層を設けた。
【０１７３】
次に、実施例１と同様に、電子注入層の上にステンレス鋼製の透明電極とほぼ同じ形状の正方形穴あきマスクを設置し、陰極バッファー層としてフッ化リチウム０．５ｎｍ及び陰極としてアルミニウム１５０ｎｍを蒸着成膜した。この有機ＥＬ素子ＯＬＥＤ４−１を実施例１と同様な方法及び同様な構造の封止缶を具備させ平面ランプを作製した。
【０１７４】
このＯＬＥＤ４−１を有する平面ランプに通電したところ、ほぼ白色の光が得られ、照明装置として使用できることが分かった。試料１０１に代えて試料１０２、１０３を用いてＯＬＥＤ４−２、４−３を作製し、通電したところいずれもほぼ白色の光が得られ、照明装置として使用できることが分かった。
【０１７５】
図９に平面ランプの平面図（Ａ）及び側面図（Ｂ）を示す。
【０１７６】
【発明の効果】
本発明により、発光輝度、発光効率、寿命特性に優れた有機エレクトロルミネッセンス材料の精製方法を工業規模で提供することができる。
【図面の簡単な説明】
【図１】充填カラムを用いた精製装置の概略図である。
【図２】抽出を用いた精製装置の模式図である。
【図３】晶析を用いた精製装置の模式図である。
【図４】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５】表示部Ａの模式図である。
【図６】画素の模式図である。
【図７】パッシブマトリクス方式による表示装置の模式図である。
【図８】封止構造の有機ＥＬ素子の側面図である。
【図９】平面ランプの平面図（Ａ）及び側面図（Ｂ）である。
【符号の説明】
１１、２１ 超臨界流体
１２ ポンプ
１３ モディファイヤ
１４ インジェクタ
１５ カラム
１６ カラムオーブン
１７ 検出器
１８ 圧力調整弁
２２ 弁
２３ 抽出管
２４ 採取ビン
３１ タンク
３２ ポンプ
３３ 容器
３４ フィルター
３５ 混合
３６ 背圧弁
３７ 採取
３８ 圧力計
３９ 予熱部
４０ 保温部
４１ ディスプレイ
５３ 画素
５５ 走査線
５６ データ線
６０ 有機ＥＬ素子
６１ スイッチングトランジスタ
６２ 駆動トランジスタ
６３ コンデンサ
６７ 電源ライン
７１ 透明電極付きガラス基板
７２ 有機ＥＬ層
７３ 陰極
７４ ガラス製封止缶
７５ 酸化バリウム（捕水剤）
７６ 窒素ガス
７７ 紫外線硬化型接着剤
Ａ 表示部
Ｂ 制御部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for purifying an organic electroluminescent material. To the law Related.
[0002]
[Prior art]
As a light-emitting electronic display device, there is an electroluminescence display (ELD). As a constituent element of ELD, an inorganic electroluminescence element (hereinafter also referred to as an inorganic EL element) and an organic electroluminescence element (hereinafter also referred to as an organic EL element) can be given.
[0003]
Inorganic EL elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements. On the other hand, an organic EL 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 by utilizing 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.
[0004]
However, for organic EL elements for practical use in the future, it is desired to develop organic EL elements that emit light efficiently and with high brightness with further low power consumption, and that emit light for a long time.
[0005]
As a known technique of the organic EL element as described above, for example, a small amount of a phosphor is doped into a stilbene derivative, a distyrylarylene derivative or a tristyrylarylene derivative, thereby achieving improvement in emission luminance and extending the lifetime of the element. (For example, refer to Patent Document 1), 8-hydroxyquinoline aluminum complex as a host compound, and a device having an organic light emitting layer doped with a trace amount of phosphor (for example, refer to Patent Document 2), 8-hydroxy There is an element (for example, see Patent Document 3) having an organic light emitting layer doped with a quinoline aluminum complex as a host compound and doped with a quinacridone-based dye, and both techniques dope phosphors having a high fluorescence quantum yield. As a result, the light emission luminance is improved as compared with the conventional organic EL element.
[0006]
Furthermore, in recent years, since organic EL devices using phosphorescence from excited triplets with higher luminous efficiency have been reported (for example, see Non-Patent Document 1), research on materials that exhibit phosphorescence at room temperature has become active. (For example, see Patent Document 4 and Non-Patent Document 2). C. As reported by Adachi et al. (J. Appl. Phys., 90, 5048 (2001)), such an organic EL device is not limited to a display until the luminous efficiency reaches 60 lm / W. Application to lighting is expected.
[0007]
As described above, an organic EL element that emits light efficiently and with high luminance with low power consumption and has a long-lasting light emission is desired. In order to realize such an organic EL element, Patent Nos. 3290432, 3357857, JP-A Nos. 2002-373785 and 2002-373786 have examined the amount of impurities in the organic layer. As for the achievement means, Japanese Patent No. 3290432 and Japanese Patent Application Laid-Open No. 2002-373785 describe a sublimation purification method or a reprecipitation method, but there is no mention of details thereof. In addition to this, JP-A-2001-214159 also describes impurities, but at present, no detailed study has been made on means for achieving them. In addition, the purification method in the above-mentioned reference is generally performed in a laboratory, and is performed in a vacuum system or a system that consumes a large amount of an organic solvent, which is difficult to perform on an industrial production scale. From an industrial production point of view, it has been eagerly desired to provide a method for obtaining a large amount of material quickly and with high purity with a low environmental load.
[0008]
[Patent Document 1]
Japanese Patent No. 3,093,796
[0009]
[Patent Document 2]
Japanese Unexamined Patent Publication No. 63-264692
[0010]
[Patent Document 3]
JP-A-3-255190
[0011]
[Patent Document 4]
US Pat. No. 6,097,147
[0012]
[Non-Patent Document 1]
M.M. A. Baldo et al. , Nature, 395, 151-154 (1998)
[0013]
[Non-Patent Document 2]
M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000)
[0014]
[Problems to be solved by the invention]
The object of the present invention is to purify organic electroluminescent materials having excellent light emission luminance, light emission efficiency, and lifetime characteristics. The law To provide on an industrial scale.
[0015]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following constitution.
[0017]
1 . In the method for purifying an organic electroluminescent material, comprising the step of dissolving or contacting the organic electroluminescent material in a supercritical or subcritical solvent. Organic electroluminescent materials Above It is characterized by being injected into a supercritical or subcritical solvent and removing impurities using a chromatographic method. Have For purification of electroluminescent materials.
[0018]
2 . In the method for purifying an organic electroluminescent material, comprising the step of dissolving or contacting the organic electroluminescent material in a supercritical or subcritical solvent. Organic electroluminescent materials Above It is characterized by extraction using a supercritical or subcritical solvent. Have For purification of electroluminescent materials.
[0019]
3 . In the method for purifying an organic electroluminescent material, comprising the step of dissolving or contacting the organic electroluminescent material in a supercritical or subcritical solvent. Organic electroluminescent materials Above It is characterized by crystallization using a supercritical or subcritical solvent. Have For purification of electroluminescent materials.
[0026]
As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above-mentioned problems can be achieved by purifying the organic electroluminescent material using a supercritical or subcritical solvent.
[0027]
In the present invention, in the purification step of these organic electroluminescent materials (hereinafter also referred to as organic EL materials), the organic EL materials are dissolved in a solvent in a supercritical state or a subcritical state (hereinafter also referred to as a supercritical state). A step or a step of contacting with a solvent such as a supercritical state. By refining in a solvent in a supercritical state or the like, it is possible to provide an organic EL material that is surprisingly high in brightness, has a long lifetime, and exhibits excellent characteristics that cannot be seen by other purification methods.
[0028]
In the present invention, the organic EL material refers to a compound that can be used for an organic electroluminescence layer (hereinafter also referred to as an organic EL layer) formed between an anode and a cathode described later. In addition, a light emitting element composed of an anode, a cathode, and an organic EL layer using an organic EL material is referred to as an organic EL element.
[0029]
[Supercritical state]
The supercritical state or subcritical state will be described. Substances change between three states of gas, liquid, and solid due to changes in environmental conditions such as temperature, pressure (or volume), etc., and this is determined by the balance between intermolecular force and kinetic energy. A phase diagram (phase diagram) shows the transition of the gas-liquid solid state with temperature on the horizontal axis and pressure on the vertical axis. The three phases of gas, liquid, and solid coexist in this state. The point at is called the triple point. When the temperature is higher than the triple point, the liquid and its vapor are in equilibrium. The pressure at this time is a saturated vapor pressure and is represented by an evaporation curve (vapor pressure line). At a pressure lower than the pressure represented by this curve, all the liquid is vaporized, and when a pressure higher than this is applied, all the vapor is liquefied. Even if the pressure is kept constant and the temperature is changed, if this curve is exceeded, the liquid becomes vapor and the vapor becomes liquid. This evaporation curve has an end point on the high temperature and high pressure side, which is called a critical point. The critical point is an important point that characterizes a substance, and the interface between gas and liquid disappears in a state where it is impossible to distinguish between liquid and vapor.
[0030]
When the temperature is higher than the critical point, the transition between the liquid and the gas can be performed without causing a gas-liquid coexistence state. A fluid that is above the critical temperature and above the critical pressure is called a supercritical fluid, and a temperature / pressure region that gives the supercritical fluid is called a supercritical region. Supercritical fluids can be understood as high-density fluids with high kinetic energy, and exhibit liquid behavior in terms of dissolving solutes and gaseous characteristics in terms of density variability. Although there are various solvent properties of supercritical fluids, it is important to have low viscosity, high diffusivity, and excellent permeability to solid materials.
[0031]
For example, if the supercritical state is carbon dioxide, the critical temperature (hereinafter also referred to as Tc) is 31 ° C., and the critical pressure (hereinafter also referred to as Pc) is 7.38 × 10. ⁶ Pa, propane (Tc = 96.7 ° C., Pc = 43.4 × 10 ^Five Pa), ethylene (Tc = 9.9 ° C., Pc = 52.2 × 10 ^Five Above this region, such as Pa), the fluid has a large diffusion coefficient and a low viscosity, so that mass transfer and concentration equilibrium are reached quickly, and the density is high like a liquid, so that efficient separation is possible. In addition, the recovery is quickened by using a substance that becomes a gas at normal pressure and normal temperature, such as carbon dioxide. In addition, there are no various obstacles resulting from residual trace amounts of solvent that are unavoidable in the purification method using a liquid solvent. The subcritical state refers to a fluid in which either temperature or pressure exceeds Tc and Pc.
[0032]
As the solvent in the supercritical state, carbon dioxide, dinitrogen monoxide, ammonia, water, methanol, ethanol, 2-propanol, ethane, propane, butane, hexane, pentane and the like are preferably used. It can be preferably used. One kind of supercritical solvent can be used alone, or a so-called modifier or entrainer for adjusting the polarity can be added. Examples of entrainers include hydrocarbon solvents such as hexane, cyclohexane, benzene, and toluene, halogenated hydrocarbon solvents such as methyl chloride, dichloromethane, dichloroethane, and chlorobenzene, alcohol solvents such as methanol, ethanol, propanol, and butanol, Ether solvents such as diethyl ether and tetrahydrofuran, acetal solvents such as acetaldehyde diethyl acetal, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and butyl acetate, carboxylic acids such as formic acid, acetic acid and trifluoroacetic acid Examples thereof include system solvents, nitrogen compound solvents such as acetonitrile, pyridine and N, N-dimethylformamide, sulfur compound solvents such as carbon disulfide and dimethyl sulfoxide, water, nitric acid, sulfuric acid and the like.
[0033]
The operating temperature of the supercritical fluid and subcritical fluid is basically not limited as long as it is equal to or higher than the temperature at which the organic EL material is dissolved, but if the temperature is too low, the organic EL material enters the supercritical fluid or subcritical fluid. Since the solubility of the organic EL material may be degraded when the temperature is too high, the use temperature range is preferably 20 to 600 ° C.
[0034]
The working pressure of the supercritical fluid and subcritical fluid is not particularly limited as long as it is basically higher than the critical pressure of the substance to be used, but if the pressure is too low, the dissolution of the organic EL material into the supercritical fluid or subcritical fluid is possible. If the pressure is too high, problems may occur in terms of durability of the production apparatus, safety during operation, and the like. Therefore, the working pressure is preferably 1 to 100 MPa.
[0035]
A device using a supercritical fluid or subcritical fluid is limited as long as the device has a function of dissolving an organic EL material in the supercritical fluid or subcritical fluid in contact with the supercritical fluid or subcritical fluid. For example, a batch system that uses a supercritical fluid or subcritical fluid in a closed system, a distribution system that circulates and uses a supercritical fluid or a subcritical fluid, a combined system that combines a batch system and a distribution system, etc. Can be used.
[0036]
[Purification method]
As a purification method using a solvent in a supercritical state, a chromatograph, extraction, and crystallization using a packed column, an open column, and a capillary column can be preferably used.
[0037]
(Chromatograph method)
In the purification method using a packed column, as shown in FIG. 1, a supercritical fluid 11, a pump 12, a modifier 13 if necessary, an injector 14 for injecting an organic EL material to be separated, and a separation column 15 are further required. If so, a device comprising the detector 17 and the pressure regulating valve 18 may be used. The temperature of the column 15 is adjusted in a column oven 16. As the filler, silica used in conventional chromatographic methods, surface-modified silica, or the like can be selected as appropriate.
[0038]
(Extraction method)
As a purification method using extraction, a method of allowing a supercritical solvent to pass through an extraction tube 23 filled with a product to be purified as shown in FIG.
[0039]
(Crystallization method)
Preferred examples of the purification method using crystallization include a method of changing the pressure and temperature of the supercritical solvent, a method of changing the solubility by mixing the solvent, and the like.
[0040]
FIG. 3 shows a configuration example of a refining apparatus that purifies an organic EL material using a supercritical fluid and a subcritical fluid. In the case where the organic EL material is crystallized by mixing with a solvent, in FIG. 3, the solvent is sent from a tank 31 containing a solvent used as a supercritical fluid or a subcritical fluid by a pump 32, and a target temperature, Use supercritical fluid or subcritical fluid under pressure. The organic EL material previously put in the container 33 is dissolved in the supercritical fluid or subcritical fluid, and when it passes through the filter 34, it is mixed with the solvent 35 to precipitate crystals. The obtained crystal of the organic EL material is collected 37 through the back pressure valve 36. 38 is a pressure gauge, 39 is a preheating part, 40 is a heat retention part. In addition, in the case where the organic EL material is crystallized by changing the temperature, in FIG. 3, a temperature control unit is installed between the steps of connecting the filter 34 and the back pressure valve 36, so The temperature of the critical fluid is changed by the temperature control unit to precipitate crystals.
[0041]
[Organic EL device]
Organic EL device using organic EL material purified by the above method (Hereinafter also referred to as the organic EL device of the present invention) Details are described below.
[0042]
As described above, the organic EL device of the present invention has a structure in which an anode and a cathode and one or more organic compound layers (organic EL layers) are held between these electrodes on a substrate.
[0043]
(substrate)
Although it does not specifically limit as a board | substrate which can be used, A glass substrate and a plastic substrate are mentioned, Any may be used in this invention. In addition, as a board | substrate, in order to prevent the penetration | invasion of oxygen and water from the board | substrate side, in the test based on JISZ-0208, the thickness is 1 micrometer or more, and water-vapor-permeation rate is 1 g / m. ² -The thing below 1 atm * 24hr (25 degreeC) is desirable.
[0044]
Specific examples of the glass substrate include alkali-free glass, low alkali glass, and soda lime glass. Of these, alkali-free glass is preferable from the viewpoint of low moisture adsorption, but any of these may be used as long as it is sufficiently dried.
[0045]
Plastic substrates have been attracting attention in recent years because of their high flexibility, light weight and resistance to cracking, and the ability to further reduce the thickness of organic EL elements. Is relatively high and contains moisture inside. Therefore, when using such a plastic substrate, it is preferable to provide a resin base material with a film for sealing water vapor (hereinafter referred to as a water vapor sealing film).
[0046]
Examples of the material constituting the water vapor sealing film include metal oxide, metal oxynitride, and metal nitride. Metal oxide, metal oxynitride or metal nitride includes silicon oxide, titanium oxide, indium oxide, tin oxide, metal oxide such as ITO (indium tin oxide), aluminum oxide, metal nitride such as silicon nitride, acid Examples thereof include metal oxynitrides such as silicon nitride and titanium oxynitride.
[0047]
The resin substrate is not particularly limited. Specifically, polyester, polyethylene, polypropylene, cellophane, cellulose esters or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate. , Norbornene resin, polymethylpentene, polyetherketone, polyimide, polyethersulfone, polysulfones, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylates, organic-inorganic hybrid resin, etc. be able to. Examples of the organic-inorganic hybrid resin include those obtained by combining an organic resin and an inorganic polymer (for example, silica, alumina, titania, zirconia, etc.) obtained by a sol-gel reaction. Of these, norbornene (or cycloolefin-based) resins such as Arton (manufactured by JSR) or Apel (manufactured by Mitsui Chemicals) are particularly preferable.
[0048]
The method for providing the water vapor sealing film on the resin base material is not particularly limited, and any method may be used. Specifically, for example, sol-gel method, vacuum deposition, sputtering, CVD method (chemical vapor deposition), etc. Is mentioned. Of these, the method by plasma CVD treatment at atmospheric pressure or near atmospheric pressure is preferable because a dense film can be formed.
[0049]
[Anode, organic compound layer (organic EL layer), cathode]
(anode)
As the anode of the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound of metal or a mixture thereof having a high work function (4 eV or more) is preferably used. Here, the “metal conductive compound” refers to a compound of a metal and another substance having electrical conductivity, and specifically, for example, a metal oxide, a halide or the like. That has electrical conductivity.
[0050]
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. The anode can be produced by forming a thin film made of these electrode materials on the substrate by a known method such as vapor deposition or sputtering.
[0051]
In addition, a pattern having a desired shape may be formed on the thin film by a photolithography method, and when the pattern accuracy is not so high (about 100 μm or more), a desired shape can be formed at the time of vapor deposition or sputtering of the electrode material. A pattern may be formed through a mask.
[0052]
When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%. The sheet resistance as the anode is preferably several hundred Ω / □ or less. Furthermore, although the film thickness of an anode is based also on the material to comprise, it is normally selected in the range of 10 nm-1 micrometer, Preferably it is 10 nm-200 nm.
[0053]
(Organic EL layer)
The organic compound layer (organic EL layer) includes at least a light-emitting layer. In a broad sense, the light-emitting layer refers to a layer that emits light when an electric current is passed through an electrode composed of a cathode and an anode. Refers to a layer containing an organic compound that emits light when an electric current is passed through an electrode composed of a cathode and an anode.
[0054]
The organic EL device used in the present invention may have a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer in addition to the light emitting layer as necessary, and these layers are cathodes. And a structure sandwiched between the anode and the anode.
[0055]
In particular,
(I) Anode / light emitting layer / cathode
(Ii) Anode / hole injection layer / light emitting layer / cathode
(Iii) Anode / light emitting layer / electron injection layer / cathode
(Iv) Anode / hole injection layer / light emitting layer / electron injection layer / cathode
(V) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode
(Vi) Anode / hole transport layer / light emitting layer / electron transport layer / cathode
And the like.
[0056]
Further, a cathode buffer layer (for example, lithium fluoride) may be inserted between the electron injection layer and the cathode, and an anode buffer layer (for example, copper phthalocyanine) may be inserted between the anode and the hole injection layer. ) May be inserted.
[0057]
(Light emitting layer)
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer. The light emitting layer may be a layer having a single composition, or may be a laminated structure including a plurality of layers having the same or different compositions.
[0058]
The light emitting layer itself may be provided with functions such as a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer. That is, (1) an injection function capable of injecting holes from an anode or a hole injection layer and applying electrons from a cathode or an electron injection layer when an electric field is applied to the light emitting layer, and (2) injection At least one of a transport function that moves electric charges (electrons and holes) by the force of an electric field, and (3) a light-emitting function that provides a recombination field of electrons and holes inside the light-emitting layer and connects it to light emission. A function may be added. Note that the light emitting layer may have a difference in the ease of hole injection and the ease of electron injection, and the transport function represented by the mobility of holes and electrons may be large or small. The one having a function of moving at least one of the charges is preferable.
[0059]
There is no restriction | limiting in particular about the kind of light emitting material used for this light emitting layer, The conventionally well-known thing can be used as a light emitting material in an organic EL element. Such a light-emitting material is mainly an organic compound, and has a desired color tone, for example, Macromol. Symp. 125, pages 17-26. Further, 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 side chain or a polymer material having the light emitting material as a polymer main chain. May be used. Note that, as described above, since the light emitting material may have a hole injection function and an electron injection function in addition to the light emission performance, most of the hole injection material and the electron injection material described later may be used as the light emitting material. Can be used.
[0060]
In a layer constituting an organic EL element, when the layer is composed of two or more organic compounds, the main component is called a host, the other components are called dopants, and the host and dopant are used in combination in the light emitting layer of this patent. The mixing ratio of the light-emitting layer dopant (hereinafter also referred to as light-emitting dopant) to the host compound as the main component is preferably less than 0.1 to 30% by mass.
[0061]
The dopant used in the light emitting layer is roughly classified into two types, that is, a fluorescent dopant that emits fluorescence and a phosphorescent dopant that emits phosphorescence.
[0062]
Representative examples of fluorescent dopants include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes. Stilbene dyes, polythiophene dyes, rare earth complex phosphors, and other known fluorescent compounds.
[0063]
In the present invention, it is preferable that at least one light emitting layer contains a phosphorescent compound.
[0064]
In the present invention, a phosphorescent compound 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. The phosphorescence quantum yield is preferably 0.01 or more, more preferably 0.1 or more. The phosphorescent 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. 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 above phosphorescence quantum yield in any solvent.
[0065]
The phosphorescent dopant is a phosphorescent compound, and a typical example thereof is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, or rhodium. A compound, a palladium compound, or a platinum compound (platinum complex compound), among which an iridium compound, a rhodium compound, and a platinum compound are preferable, and an iridium compound is most preferable.
[0066]
Examples of the dopant are compounds described in the following documents or patent publications. J. et al. Am. Chem. Soc. 123, 4304-4312, WO 00/70655, 01/93642, 02/02714, 02/15645, 02/44189, 02/081488, JP-A-2002-280178, 2001-181616, 2002. -280179, 2001-181617, 2002-280180, 2001-247859, 2002-299860, 2002-313178, 2002-302671, 2001-345183, 2002-324679, 2002-332291, 2002 -50484, 2002-332292, 2002-83684, 2002-540572, 2002-117578, 2002-338588, 2002-170684, 2002-35. 2960, 2002-50483, 2002-100476, 2002-173664, 2002-359082, 2002-17584, 2002-363552, 2002-184582, 2003-7469, JP 2002-525808, JP 2003-7471, Special Table 2002-525833, JP-A-2003-31366, 2002-226495, 2002-234894, 2002-2335076, 2002-241751, 2001-319780, 2001-319780, 2002-62824. 2002-1000047, 2002-203679, 2002-343572, 2002-203678, and the like.
[0067]
These phosphorescent dopants are preferably purified by a purification method including a step of dissolving or contacting in a supercritical or subcritical solvent. As a purification method including a step of dissolving or contacting in a supercritical or subcritical solvent, a purification method in which impurities are preferably removed by using a chromatographic method after injection into a supercritical or subcritical solvent, Examples thereof include a purification method in which extraction is performed using a solvent in a critical or subcritical state and a purification method in which crystallization is performed using a solvent in a supercritical or subcritical state.
[0068]
Although the specific example of a phosphorescent dopant is given to the following, this invention is not limited to these.
[0069]
[Chemical 1]

[0070]
[Chemical formula 2]

[0071]
[Chemical 3]

[0072]
Only one kind of light emitting dopant may be used, or a plurality of kinds may be used, and by simultaneously taking out light emitted from these dopants, a light emitting element having a plurality of light emission maximum wavelengths can be formed. For example, both a phosphorescent dopant and a fluorescent dopant may be added. When an organic EL element is formed by laminating a plurality of light emitting layers, the light emitting dopants contained in each layer may be the same or different, may be a single type, or may be a plurality of types. .
[0073]
Furthermore, a polymer material in which the light-emitting dopant is introduced into a polymer chain or the light-emitting dopant is used as a polymer main chain may be used.
[0074]
Examples of the host compound include those having a basic skeleton such as a carbazole derivative, a triarylamine derivative, an aromatic borane derivative, a nitrogen-containing heterocyclic compound, a thiophene derivative, a furan derivative, and an oligoarylene compound. Materials and hole transport materials are also suitable examples. When applied to a blue or white light emitting element, a display device, and a lighting device, the host compound preferably has a maximum fluorescence wavelength of 415 nm or less. When a phosphorescent dopant is used, the 0-0 band of the phosphorescence of the host compound is used. Is more preferably 450 nm or less. As the light-emitting host, a compound having a hole transporting ability and an electron transporting ability, preventing emission light from being increased in wavelength, and having a high Tg (glass transition temperature) is preferable.
[0075]
As specific examples of the light-emitting host, for example, compounds described in the following documents are suitable.
[0076]
JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2 02-280183, same 2002-299060, 2002-302516 same, same 2002-305083, 2002-305084 same, same 2002-308837, and the like.
[0077]
These host compounds are preferably purified by a purification method including a step of dissolving or contacting in a supercritical or subcritical solvent. As a purification method including a step of dissolving or contacting in a supercritical or subcritical solvent, a purification method in which impurities are preferably removed by using a chromatographic method after injection into a supercritical or subcritical solvent, Examples thereof include a purification method in which extraction is performed using a solvent in a critical or subcritical state, and a purification method in which crystallization is performed using a solvent in a supercritical or subcritical state.
[0078]
The light emitting dopant may be dispersed throughout the layer containing the host compound or may be partially dispersed. A compound having another function may be added to the light emitting layer.
[0079]
A light emitting layer can be formed by using the above-mentioned materials to form a thin film by a known method such as vapor deposition, spin coating, casting, LB, ink jet transfer, or printing. The light emitting layer formed is particularly preferably a molecular deposited film. Here, the molecular deposition film refers to a thin film formed by deposition from the vapor phase state of the compound or a film formed by solidification from the molten state or liquid phase state of the compound. Usually, this molecular deposited film and a thin film (molecular accumulation film) formed by the LB method can be distinguished from each other by a difference in aggregated structure and higher order structure and a functional difference resulting therefrom.
[0080]
Specifically, for example, as described in JP-A-57-51781, the light-emitting layer comprising the molecular deposited film is prepared by dissolving the light-emitting material in a solvent together with a binder such as resin. Then, it can be formed into a thin film by spin coating or the like. 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.
[0081]
(Hole injection layer and hole transport layer)
The hole injection material used for the hole injection layer has either a hole injection property or an electron barrier property. The hole transport material used for the hole transport layer has an electron barrier property and a function of transporting holes to the light emitting layer. Therefore, in the present invention, the hole transport layer is included in the hole injection layer. These hole injection material and hole transport material may be either organic or inorganic. Specifically, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives , Hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, porphyrin compounds, thiophene oligomers and other conductive polymer oligomers. Of these, arylamine derivatives and porphyrin compounds are preferred. Among the arylamine derivatives, aromatic tertiary amine compounds and styrylamine compounds are preferable, and aromatic tertiary amine compounds are more preferable.
[0082]
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) biphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbene; N-phenylcarbazole, as well as two of those described in US Pat. No. 5,061,569 Those having a condensed aromatic ring in the molecule, for example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter abbreviated as α-NPD), JP-A-4 4,308'-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in No. -308688 are linked in a starburst type ( In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material.
[0083]
In the present invention, the hole transport material of the hole transport layer preferably has a fluorescence maximum wavelength at 415 nm or less. That is, the hole transport material is preferably a compound that has a hole transport ability, prevents the emission of light from becoming longer, and has a high Tg.
[0084]
For the hole injection layer and the hole transport layer, the above-described hole injection material and hole transport material are known, for example, vacuum deposition method, spin coating method, cast method, LB method, ink jet method, transfer method, printing method, etc. This method can be formed by thinning the film.
[0085]
Although there is no restriction | limiting in particular about the film thickness of a positive hole injection layer and a positive hole transport layer, Usually, it is about 5 nm-5 micrometers. The hole injection layer and the hole transport layer may each have a single-layer structure composed of one or more of the above materials, or a laminated structure composed of a plurality of layers having the same composition or different compositions. Also good. Moreover, when providing both a positive hole injection layer and a positive hole transport layer, although a different material is normally used among said materials, you may use the same material.
[0086]
(Electron injection layer and electron transport layer)
The electron injecting layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and any material can be selected from conventionally known compounds. Examples of materials used for this electron injection layer (hereinafter also referred to as electron injection materials) include heterocyclic tetracarboxylic acid anhydrides such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, and carbodiimides. , Fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like.
[0087]
Further, a series of electron transfer compounds described in JP-A-59-194393 is disclosed as a material for forming a light emitting layer in the publication, but as a result of investigations by the present inventors, electron injection It was found that it can be used as a material. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, or a quinoxaline derivative having a quinoxaline ring known as an electron-withdrawing group can also be used as an electron injection material.
[0088]
Further, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq _Three Abbreviated. ), 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 metal complexes in which the central metal of these metal complexes is replaced with In, Mg, Cu, Ca, Sn, Ga, or Pb are also used as electron injection materials. be able to.
[0089]
In addition, metal-free, metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron injection material. Similarly to the hole injection layer, an inorganic semiconductor such as n-type-Si or n-type-SiC can also be used as the electron injection material.
[0090]
It is preferable that the preferable compound used for an electron carrying layer has a fluorescence maximum wavelength in 415 nm or less. That is, the compound used for the electron transport layer is preferably a compound that has an electron transport ability, prevents emission of longer wavelengths, and has a high Tg.
[0091]
The electron injection 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, an LB method, an ink jet method, a transfer method, or a printing method. . Although the film thickness as an electron injection layer does not have a restriction | limiting in particular, Usually, it selects in 5 nm-5 micrometers. This electron injection layer may have a single layer structure composed of one or more of these electron injection materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.
[0092]
In the present specification, when the ionization energy of the electron injection layer is larger than that of the light emitting layer, it is particularly referred to as an electron transport layer. Therefore, in this specification, an electron carrying layer is contained in an electron injection layer.
[0093]
The electron transport layer is also referred to as a hole blocking layer (hole block layer), and examples thereof include WO 00/70655, JP 2001-313178, JP 11-204258, and the like. No. 11-204359, and “Organic EL elements and the forefront of industrialization” (issued on November 30, 1998 by NTS, Inc.), page 237, and the like. In particular, in the so-called “phosphorescent light emitting device” using an ortho metal complex dopant in the light emitting layer, it is preferable to adopt a configuration having an electron transport layer (hole blocking layer) as in the above (v) and (vi).
[0094]
(Buffer layer)
Further, a buffer layer (electrode interface layer) may be present between the anode and the light emitting layer or the hole injection layer and between the cathode and the light emitting layer or the electron injection layer. 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) ) ", Chapter 2, Chapter 2," Electrode Materials "(pages 123-166), which includes an anode buffer layer and a cathode buffer layer.
[0095]
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.
[0096]
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, and an oxide buffer layer typified by aluminum oxide.
[0097]
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. Furthermore, in addition to the basic constituent layers, layers having other functions may be appropriately laminated as necessary.
[0098]
(cathode)
As described above, the cathode of the organic EL device generally uses a metal having a low work function (less than 4 eV) (hereinafter referred to as an electron injecting metal), an alloy, a metal electroconductive compound, or a mixture thereof as an electrode material. Things are used.
[0099]
Specific examples of such electrode materials include sodium, magnesium, lithium, aluminum, indium, rare earth metals, sodium-potassium alloys, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / Aluminum oxide (Al ₂ O _Three ) Mixtures, lithium / aluminum mixtures and the like.
[0100]
In the present invention, those listed above may be used as the electrode material of the cathode. However, from the viewpoint of more effectively exerting the effects of the present invention, the cathode may contain a Group 13 metal element. preferable. That is, in the present invention, as described later, the surface of the cathode is oxidized with oxygen gas in a plasma state to form an oxide film on the cathode surface, thereby preventing further oxidation of the cathode and improving the durability of the cathode. Can be made.
[0101]
Therefore, the cathode electrode material is preferably a metal having a preferable electron injecting property required for the cathode and capable of forming a dense oxide film.
[0102]
Specific examples of the cathode electrode material containing the Group 13 metal element include aluminum, indium, magnesium / aluminum mixture, magnesium / indium mixture, and aluminum / aluminum oxide (Al ₂ O _Three ) Mixtures, lithium / aluminum mixtures and the like. In addition, the mixing ratio of each component of the said mixture can employ | adopt a conventionally well-known ratio as a cathode of an organic EL element, However It is not limited to this in particular. The cathode can be produced by forming a thin film on the organic compound layer (organic EL layer) using the electrode material described above by a method such as vapor deposition or sputtering.
[0103]
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 the emitted light, it is preferable that either one of the anode or the cathode of the organic EL element is transparent or semi-transparent because the light emission efficiency is improved.
[0104]
A suitable example for producing a display device comprising an organic EL element produced using the organic EL material of the present invention will be described.
[0105]
[Method for producing organic EL element]
As an example of the method for producing the organic EL device of the present invention, 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.
[0106]
First, a thin film made of a desired electrode material, for example, an anode material is formed on a suitable substrate 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, thereby producing an anode. To do. 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.
[0107]
As described above, there are spin coating methods, casting methods, ink jet methods, vapor deposition methods, printing methods, etc. as methods for thinning these organic compound thin films, but it is easy to obtain a uniform film and pinholes are generated. From the viewpoint of difficulty, vacuum deposition or spin coating 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 the boat heating temperature is 50 to 450, and the degree of vacuum is 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.
[0108]
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 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. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere.
[0109]
[Display device]
The multicolor display device using the organic EL element 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, vapor deposition method, casting method, A film can be formed by a spin coating method, an inkjet method, a printing method, or the like.
[0110]
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.
[0111]
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.
[0112]
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.
[0113]
The multicolor display device can be used as a display device, a display, or various light emission sources. In a display device or a display, full-color display is possible by using three types of organic EL elements of blue, red, and green light emission.
[0114]
Examples of the display device and display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in an automobile. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.
[0115]
Light 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. For example, but not limited to.
[0116]
Further, the organic EL element according to the present invention may be used as an organic EL element having a resonator structure.
[0117]
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 processing machine, and a light source of an optical sensor. It is not limited. Moreover, you may use for the said use by making a laser oscillation.
[0118]
The organic EL device of the present invention may be used as a kind of lamp such as an illumination or exposure light source, 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. The driving method when used as a display device for moving image reproduction may be either a simple matrix (passive matrix) method or an active matrix method. Alternatively, a full-color display device can be manufactured by using two or more organic EL elements of the present invention having different emission colors.
[0119]
An example of a display device composed of the organic EL element of the present invention will be described below with reference to the drawings.
[0120]
FIG. 4 is a schematic diagram illustrating an example of a display device including organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element. The display 41 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like. The control unit B is electrically connected to the display unit A, and sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. The pixels for each scanning line are converted into image data signals by the scanning signal. In response to this, light is sequentially emitted and image scanning is performed to display image information on the display unit A.
[0121]
FIG. 5 is a schematic diagram of the display unit A. The display unit A includes a wiring unit including a plurality of scanning lines 55 and data lines 56, a plurality of pixels 53, and the like on a substrate. The main members of the display unit A will be described below.
[0122]
FIG. 5 shows a case where the light emitted from the pixel 53 is extracted in the white arrow direction (downward). The scanning lines 55 and the plurality of data lines 56 in the wiring portion are each made of a conductive material, and the scanning lines 55 and the data lines 56 are orthogonal to each other in a lattice shape and are connected to the pixels 53 at the orthogonal positions (details are shown in the figure). Not shown). When a scanning signal is applied from the scanning line 55, the pixel 53 receives an image data signal from the data line 56, and emits light according to the received image data. Full color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region that emit light on the same substrate.
[0123]
Next, the light emission process of the pixel will be described. FIG. 6 is a schematic diagram of a pixel. The pixel includes an organic EL element 60, a switching transistor 61, a driving transistor 62, a capacitor 63, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 60 for a plurality of pixels, and juxtaposing them on the same substrate.
[0124]
In FIG. 6, an image data signal is applied to the drain of the switching transistor 61 from the control unit B (not shown in FIG. 6 but shown in FIG. 4) via the data line 56. When a scanning signal is applied from the control unit B to the gate of the switching transistor 61 through the scanning line 55, the driving of the switching transistor 61 is turned on, and the image data signal applied to the drain is supplied to the capacitor 63 and the driving transistor 62. Is transmitted to the gate.
[0125]
By transmitting the image data signal, the capacitor 63 is charged according to the potential of the image data signal, and the drive of the drive transistor 62 is turned on. The drive transistor 62 has a drain connected to the power supply line 67 and a source connected to the electrode of the organic EL element 60, and the power supply line 67 changes to the organic EL element 60 according to the potential of the image data signal applied to the gate. Current is supplied.
[0126]
When the scanning signal is moved to the next scanning line 55 by the sequential scanning of the control unit B, the driving of the switching transistor 61 is turned off. However, even if the driving of the switching transistor 61 is turned off, the capacitor 63 holds the potential of the charged image data signal, so that the driving of the driving transistor 62 is kept on and the next scanning signal is applied. Until then, the organic EL element 60 continues to emit light. When the scanning signal is next applied by sequential scanning, the driving transistor 62 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 60 emits light. That is, the organic EL element 60 emits light by providing a switching transistor 61 and a driving transistor 62 as active elements for the organic EL elements 60 of the plurality of pixels, and a plurality of pixels 53 (not shown in FIG. 6). The organic EL element 60 emits light (shown in FIG. 5). Such a light emitting method is called an active matrix method.
[0127]
Here, the light emission of the organic EL element 60 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or on / off of a predetermined light emission amount by a binary image data signal. But you can.
[0128]
The potential of the capacitor 63 may be maintained until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.
[0129]
In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.
[0130]
FIG. 7 is a schematic view of a passive matrix display device. In FIG. 7, a plurality of scanning lines 55 and a plurality of image data lines 56 are provided in a lattice shape so as to face each other with the pixel 53 interposed therebetween. When the scanning signal of the scanning line 55 is applied by sequential scanning, the pixel 53 connected to the applied scanning line 55 emits light according to the image data signal. In the passive matrix method, there is no active element in the pixel 53, and the manufacturing cost can be reduced.
[0131]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the embodiment of this invention is not limited to this.
[0132]
Example 1
In a 300 ml three-necked flask, 2.0 g of 1-iodonaphthalene (Tokyo Kasei Co., Ltd.), 1.0 g of N, N'-diphenylbenzidine (Hiroshima Wako Pure Chemical Industries), 3 g of anhydrous potassium carbonate and 1.0 g of copper powder Was dissolved in 200 ml of dimethyl sulfoxide and stirred at 200 ° C. for 8 hours for reaction. After completion of the reaction, the reaction solution was filtered, and the mother liquor was extracted with methylene chloride. Then, the solvent was distilled off with a rotary evaporator, and the residue was purified by column chromatography packed with silica gel (manufactured by Hiroshima Wako Pure Chemical Industries, Ltd.) using toluene as a developing solvent to obtain 0.3 g of a pale yellow powder (crude α-NPD product). Got.
[0133]
(Preparation of sample 101)
Α-NPD was fractionated under the following conditions using a supercritical fluid chromatography system manufactured by JASCO Corporation.
[0134]
Supercritical CO ₂ Liquid feed pump: SCF-Get
Fully automatic pressure regulating valve: SFC-Bpg
Column oven: GC-353B
Injector: 7125i
Column: C18-Silica, 3 μm, 4.6 × 250 mm
Moving bed: carbon dioxide
Moving bed flow rate: 3ml / min
Pressure: 18MPa
Temperature: 40 ° C
Detection: UV detector (210 nm)
Under the above conditions, 100 mg of α-NPD was obtained. This α-NPD is designated as sample 101.
[0135]
(Preparation of sample 102)
Α-NPD was supercritically extracted under the following conditions using a supercritical extraction device manufactured by JASCO Corporation.
[0136]
Supercritical CO ₂ Liquid feed pump: SCF-Get
Fully automatic pressure regulating valve: SFC-Bpg
Extraction tank: CO-1560
Extraction solvent: carbon dioxide (3 ml / min)
Temperature: 80 ° C
Pressure: 25MPa
Extraction tube capacity: 1 ml
Extraction time: 30 minutes
100 mg of α-NPD was obtained under the above conditions. This is designated as sample 102.
[0137]
(Preparation of sample 103)
Α-NPD was supercritically crystallized using the following supercritical crystallizer and operating conditions manufactured by JASCO Corporation.
[0138]
Supercritical CO ₂ Liquid feed pump: SCF-Get
Fully automatic pressure regulating valve: SFC-Bpg
Reagent solution pump: PU-1580
High temperature bath: CO1560
α-NPD was dissolved in carbon dioxide in a supercritical state at a flow rate of 3 ml / min, a pressure of 18 MPa, and 40 ° C., and introduced into a crystallization vessel. Separately, when 0.2 ml / min of toluene was mixed into the crystallization vessel from the pump, α-NPD was deposited. This α-NPD is taken as a sample 103.
[0139]
(Preparation of sample 104)
α-NPD using an organic pigment purifier TRS-1 manufactured by ULVAC-RIKO, with a boat temperature of 320 ° C., 10 ^-3 Sublimation purification was performed twice under the conditions of Pa to obtain 100 mg of α-NPD. This is designated as sample 104.
[0140]
(Preparation of sample 105)
α-NPD was dissolved again in toluene and purified by passing through an open column packed with silica gel. This is designated as sample 105.
[0141]
(Preparation of sample 106)
Α-NPD was purified using a preparative liquid chromatograph under the following conditions.
[0142]
Liquid feeding pump: Hitachi, L-6200 intelligent HPLC pump
Detector: Hitachi, L-4250UV / VIS detector
Column temperature: 40 ° C
Flow rate: 1.5 ml / min
Eluent: cyclohexane (Kanto Chemical, HPLC grade) / toluene (Kanto Chemical, special grade) = 85% by volume / 15% by volume
Column: manufactured by GL Sciences, Inertsil PREP-SIL (200 mm × 250 mm)
Detection wavelength: 310 nm
The components that elute at a retention time of 10 minutes were collected. This is designated as sample 106.
[0143]
[Production of organic EL elements]
After patterning on a substrate (made by NH Techno Glass Co., Ltd .: NA-45) having a 150 nm ITO film formed on glass as an anode, the transparent support substrate provided with this ITO transparent electrode was ultrasonically cleaned with iso-propyl alcohol. Then, it was dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.
[0144]
The transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while the sample 101, CBP, Ir-1, BCP, Alq prepared above are attached to five tantalum resistance heating boats. _Three Were attached to a vacuum deposition apparatus (first vacuum chamber).
[0145]
Further, lithium fluoride was placed in a resistance heating boat made of tantalum, and aluminum was placed in a resistance heating boat made of tungsten.
[0146]
First, the first vacuum chamber is 4 × 10 ^-Four After reducing the pressure to Pa, the heating boat containing the sample 101 was energized and heated, and deposited on the transparent support substrate to a thickness of 25 nm at a deposition rate of 0.1 to 0.2 nm / second, A hole injection / transport layer was provided. Further, the heating boat containing CBP and the boat containing Ir-1 are energized independently to adjust the deposition rate of CBP as the light emitting host and Ir-1 as the light emitting dopant to 100: 7. And it vapor-deposited so that it might become a film thickness of 30 nm, and provided the light emitting layer.
[0147]
Then, the heating boat containing BCP was heated by applying electricity, and an electron transport layer having a thickness of 10 nm was provided at a deposition rate of 0.1 to 0.2 nm / second. Furthermore, Alq _Three The heating boat containing was energized and heated to provide an electron injection layer having a film thickness of 40 nm at a deposition rate of 0.1 to 0.2 nm / second.
[0148]
Next, after the element formed up to the electron injection layer as described above is transferred to the second vacuum chamber in a vacuum state, a stainless steel rectangular perforated mask is disposed on the electron injection layer from the outside of the apparatus. Installed with remote control.
[0149]
2 × 10 2nd vacuum chamber ^-Four After depressurizing to Pa, energize a boat containing lithium fluoride to provide a cathode buffer layer having a film thickness of 0.5 nm at a deposition rate of 0.01 to 0.02 nm / second, and then energize the boat containing aluminum. A cathode having a film thickness of 150 nm was attached at a deposition rate of 1 to 2 nm / second. Further, this organic EL element is transferred to a glove box under a nitrogen atmosphere (a glove box substituted with a high purity nitrogen gas having a purity of 99.999% or more) without being brought into contact with the air, and a sealing structure as shown in FIG. 8 is obtained. Thus, an organic EL element OLED1-1 was produced. Hereinafter, OLEDs 1-2 to 1-6 were produced in the same manner using samples 102 to 106 instead of sample 101.
[0150]
[Formula 4]

[0151]
(Evaluation of organic EL elements)
About the produced organic EL element, luminous luminance, luminous efficiency, and half time were measured as follows. The evaluation results are shown in Table 1.
[0152]
(Luminance, luminous efficiency)
The emission color of the organic EL elements OLED1-1 to 1-6 was green. The organic EL element OLED1-1 began to flow at an initial drive voltage of 2.8V.
[0153]
Luminance (cd / m) when a 10 V DC voltage is applied to the organic EL elements OLED1-1 to 1-6 at 23 ° C. in a dry nitrogen gas atmosphere ² ) And luminous efficiency (lm / W) were measured.
[0154]
Luminance and luminous efficiency were expressed as relative values with the organic EL element OLED1-1 as 100. The emission luminance was measured using CS-1000 (Minolta).
[0155]
(Half time)
Each of the organic EL elements OLED1-1 to 1-6 is 2.5 mA / cm. ² The durability was evaluated using as an index the half time required for the initial luminance to drop to half of the original luminance when driven at a constant current. Moreover, the half time was expressed as a relative value when the organic EL element OLED1-1 was set to 100.
[0156]
[Table 1]

[0157]
From Table 1, it was found that an organic EL device having a layer containing an organic EL material purified by the purification method of the present invention is preferable because it has higher luminance, luminous efficiency and half time than the comparative examples.
[0158]
In addition, in organic EL element OLED1-4, it produced using the sample which supercritically extracted OLED1-7 produced using the sample which refine | purified CBP and Ir-1 by the supercritical chromatography, and CBP and Ir-1. OLED1-9 produced using the sample which refine | purified OLED1-8, CBP, and Ir-1 by the supercritical crystallization had all exceeded luminous brightness, luminous efficiency, and half time with respect to OLED1-4.
[0159]
Example 2
2- (4′-biphenyl) -5- (4 ″ -tert-butylphenyl) 1,3,4-oxadiazole was supercritically extracted and purified by the same apparatus as that of Sample 102 of Example 1.
[0160]
[Production of organic EL elements]
After patterning on a substrate (NH Techno Glass Co., Ltd .: NA-45) in which ITO (Indium Tin Oxide) was deposited to a thickness of 150 nm on a 100 mm × 100 mm × 1.1 mm glass substrate as an anode, this ITO transparent electrode was provided. The transparent support substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.
[0161]
A PEDOT / PESS solution (polyethylenedioxythiophene-polysulfonic acid dope: baytron (manufactured by Bayer)) was spin-coated on the transparent support substrate with a film thickness of about 100 nm, and then dried by heating under vacuum. On top of this, 10 g of poly (N-vinylcarbazole: manufactured by Tokyo Chemical Industry Co., Ltd.), 250 mg of Ir-1, 1 mg of calcium fluoride, and 2- (4′-biphenyl) -5- (4 ″, which was previously supercritically extracted and purified. -Tert-Butylphenyl) 1,3,4-oxadiazole 5 mg was dissolved in 1500 ml of chloroform, and the solution was spin-coated to obtain a light-emitting layer having a thickness of 150 nm.
[0162]
This substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus, and 0.5 nm of lithium fluoride and 110 nm of aluminum were deposited to form a cathode. This organic EL element is referred to as OLED2-1.
[0163]
Using 2- (4′-biphenyl) -5- (4 ″ -tert-butylphenyl) 1,3,4-oxadiazole not subjected to supercritical treatment, the organic EL element OLED2-2 was similarly prepared. Produced.
[0164]
About the produced organic EL element, it carried out similarly to Example 1, and measured the luminance, the luminous efficiency, and the half time. The evaluation results are shown in Table 2.
[0165]
[Table 2]

[0166]
From Table 2, it can be seen that the organic EL device having the layer containing the organic EL material purified by the purification method of the present invention has improved light emission luminance, light emission efficiency and half time.
[0167]
Example 3
[Production of full-color display device]
In the production of the organic EL element OLED1-1 of Example 1, the organic EL element OLED3-1 (blue) was similarly used except that Ir-12 and Ir-6 were used instead of Ir-1 (light emitting dopant). Light emission), an organic EL element OLED3-2 (red light emission) was produced.
[0168]
An active matrix system in which the organic EL element OLED1-1 (green light emission) produced in Example 1 and the produced organic EL elements OLED3-1, 3-2 are juxtaposed on the same substrate and have a form as shown in FIG. A full-color display device was manufactured, and FIG. 5 shows only a schematic diagram of the display portion A of the manufactured full-color display device.
[0169]
That is, on the same substrate, a wiring portion including a plurality of scanning lines 55 and data lines 56 and a plurality of juxtaposed pixels 53 (emission color is a red region pixel, a green region pixel, a blue region pixel, etc.) The scanning lines 55 and the plurality of data lines 56 in the wiring portion are each made of a conductive material, and the scanning lines 55 and the data lines 56 are orthogonal to each other in a grid pattern and are connected to the pixels 53 at orthogonal positions ( Details are not shown). The plurality of pixels 53 are driven by an active matrix system provided with an organic EL element 60 corresponding to each emission color, a switching transistor 61 as an active element, and a driving transistor 62 as shown in FIG. When a scanning signal is applied from the scanning line 55, an image data signal is received from the data line 56, 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.
[0170]
It was found that by driving a full-color display device, high brightness, high durability (long half time), and a clear full-color moving image display can be obtained.
[0171]
Example 4
[Production of lighting device]
An electrode of a substrate (made by NH Techno Glass Co., Ltd .: NA-45) having a 150 nm ITO film formed on glass as an anode was patterned to 20 mm × 20 mm, and a sample was formed thereon as a hole injection / transport layer in the same manner as in Example 1. A heating boat containing 101 is energized to form a film with a thickness of 25 nm, and a heating boat containing CBP, a boat containing Ir-6, and a boat containing Ir-12 are energized independently. The light emitting host CBP and the light emitting dopants Ir-6 and Ir-12 were adjusted to have a deposition rate of 100: 1: 4, and were deposited to a thickness of 30 nm to provide a light emitting layer. .
[0172]
Next, BCP was deposited to a thickness of 10 nm to provide an electron transport layer. Furthermore, Alq _Three Was formed at 40 nm to provide an electron injection layer.
[0173]
Next, as in Example 1, a square perforated mask having the same shape as the transparent electrode made of stainless steel was placed on the electron injection layer, lithium fluoride 0.5 nm as the cathode buffer layer and aluminum 150 nm as the cathode. Was deposited. This organic EL element OLED4-1 was equipped with a sealing can having the same method and the same structure as in Example 1 to produce a flat lamp.
[0174]
When a flat lamp having this OLED 4-1 was energized, it was found that substantially white light was obtained and it could be used as a lighting device. When the OLEDs 4-2 and 4-3 were produced using the samples 102 and 103 instead of the sample 101 and were energized, almost white light was obtained, and it was found that they could be used as a lighting device.
[0175]
FIG. 9 shows a plan view (A) and a side view (B) of the flat lamp.
[0176]
【The invention's effect】
According to the present invention, a method for purifying an organic electroluminescent material excellent in luminous luminance, luminous efficiency, and lifetime characteristics The law It can be provided on an industrial scale.
[Brief description of the drawings]
FIG. 1 is a schematic view of a purification apparatus using a packed column.
FIG. 2 is a schematic diagram of a purification apparatus using extraction.
FIG. 3 is a schematic view of a purification apparatus using crystallization.
FIG. 4 is a schematic diagram illustrating an example of a display device including organic EL elements.
5 is a schematic diagram of a display unit A. FIG.
FIG. 6 is a schematic diagram of a pixel.
FIG. 7 is a schematic view of a display device using a passive matrix method.
FIG. 8 is a side view of an organic EL element having a sealing structure.
FIG. 9 is a plan view (A) and a side view (B) of a flat lamp.
[Explanation of symbols]
11, 21 Supercritical fluid
12 Pump
13 Modifier
14 Injector
15 columns
16 column oven
17 Detector
18 Pressure regulating valve
22 Valve
23 Extraction tube
24 collection bins
31 tanks
32 pumps
33 containers
34 Filter
35 mixing
36 Back pressure valve
37 collection
38 Pressure gauge
39 Preheating section
40 Thermal insulation part
41 display
53 pixels
55 scan lines
56 data lines
60 Organic EL elements
61 Switching transistor
62 Drive transistor
63 capacitors
67 Power line
71 Glass substrate with transparent electrode
72 Organic EL layer
73 Cathode
74 Glass sealing can
75 Barium oxide (water trapping agent)
76 Nitrogen gas
77 UV curable adhesive
A display
B Control unit

Claims (3)

In a method for purifying an organic electroluminescent material comprising the step of dissolving or contacting the organic electroluminescent material in a supercritical or subcritical solvent, the organic electroluminescent material is injected into the supercritical or subcritical solvent. And a method for purifying an organic electroluminescent material, wherein impurities are removed using a chromatographic method. In a method for purifying an organic electroluminescent material comprising the step of dissolving or contacting the organic electroluminescent material in a solvent in a supercritical or subcritical state, the organic electroluminescent material is used by using the solvent in the supercritical or subcritical state. method for purifying organic electroluminescent material you and extracts. In a method for purifying an organic electroluminescent material comprising the step of dissolving or contacting the organic electroluminescent material in a solvent in a supercritical or subcritical state, the organic electroluminescent material is used by using the solvent in the supercritical or subcritical state. method for purifying organic electroluminescent material you characterized by the crystallization.

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