JP3697778B2

JP3697778B2 - Organic thin film light emitting device

Info

Publication number: JP3697778B2
Application number: JP15198996A
Authority: JP
Inventors: 洋太郎白石; 正志山崎; 昌美黒田; 春雄川上
Original assignee: Fuji Electric Holdings Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 1995-07-04
Filing date: 1996-06-13
Publication date: 2005-09-21
Anticipated expiration: 2016-06-13
Also published as: JPH0971772A

Description

【０００１】
【産業上の利用分野】
この発明は、各種表示装置の発光源として用いられる有機薄膜発光素子に係り、特に電子注入層あるいは発光層に用いられる物質に関する。
【０００２】
【従来の技術】
従来のブラウン管に代わるフラットディスプレイの需要の急増に伴い、各種表示素子の開発及び実用化が精力的に進められている。エレクトロルミネッセンス素子（以下ＥＬ素子とする）もこうしたニ−ズに即するものであり、特に全固体の自発発光素子として、他のディスプレイにはない高解像度及び高視認性により注目を集めている。
【０００３】
現在実用化されているものは、発光層に主にＺｎＳ／Ｍｎ系を用いた無機材料からなるＥＬ素子である。しかしながらこの種の無機ＥＬ素子は交流駆動であり、駆動電圧が２００Ｖ程度以上と高いため、駆動方法が複雑となり製造コストが高い、また実用上十分な発光能を有する青色発光材料の開発が未だ見出されていないため、フルカラ−化が困難であるなどの問題点を抱えている。
【０００４】
これに対して、有機材料を用いた有機発光素子は、発光に必要な駆動電圧が大幅に低減でき、かつ各種発光材料の適応によりフルカラ−化の可能性を充分に持つことから、近年研究が活発化している（例えば米国特許３，５３０，３２５号、 Mol. Cryst. Liq. Cryst., 135, 355(1986)）。その中でも発光効率を向上させる目的で陽極／正孔注入層／発光層／負極からなる積層型の有機薄膜発光素子に、特定有機化合物からなる発光層と特定有機化合物からなる正孔注入層の積層薄膜を用いて、１０Ｖ以下の印加電圧で１，０００cd/m²以上の輝度が得られたという報告（Appl.Phys.Lett., 51, 913,(1987)，特開昭５７−５１７８１号公報，特開昭５９−１９４３９３号公報) がなされて以来、研究に拍車がかけられた。
【０００５】
また一層の性能向上を目指して、負極に用いる金属材料を最適化した素子（特開昭６３−２６４６９２号公報，特開平２−１５５９５号公報），発光層として特定有機化合物からなるホスト材料中にレーザー色素をドープした素子（J. Appl. Phys., 65, 3610(1989)，米国特許４，７６９，２９２号），特定有機化合物からなる電子注入層をさらに設けて陽極／正孔注入層／発光層／電子注入層／負極の積層型とした３原色の発光素子(Jpn. J. Appl. Phys., 27, 4, 713(1988)) などの試みがなされている。
【０００６】
【発明が解決しようとする課題】
以上のように有機薄膜発光素子は高輝度発光，低電圧駆動，三原色発光などフルカラー表示デバイスの可能性を強く示唆しているものの、実用化には多くの課題が残されている。特に連続駆動時の特性劣化（詳しくは所謂ダークスポットの発生と成長に伴う表示品質の低下，輝度の経時変化）は解決せねばならない課題である。また他の表示方式と競合しうる消費電力、耐候性など諸性能の向上も課題として挙げられる。
【０００７】
これら諸問題の原因の一つとして、有機化合物を用いた薄膜の機械的熱的不安定性および光―電子的機能の不足が指摘されている（例えばIEICE Technical Report, OME-92-9(1992)，日本学振光電相互変換第 125委第11回EL分科会資料, 7(1994))。
この発明は上述の点に鑑みてなされその目的は、薄膜状態での機械的熱的安定性に優れる上に、光電変換能や電荷注入性／輸送能の良好な有機物質を提供することにより、連続駆動時の特性劣化の少ない有機薄膜発光素子を提供することにある。
【０００８】
【課題を解決するための手段】
上述の目的は、本発明によれば、下記一般式ＩまたはＩＩで表されるチアジアゾール系化合物を電子注入層に、下記化学式ＩＩＩで示されるジアミン化合物を発光層に含有することにより達成される。また、一般式ＩまたはＩＩで表されるチアジアゾール系化合物と、化学式ＩＩＩで示されるジアミン化合物とを発光層に含有し、発光は該ジアミン化合物に起因することにより達成される。
【０００９】
【化３−１】

【００１０】
【化３−２】

【００１１】
【化４】

（式中Ａｒ^１は置換基を有しても良いアリール基もしくは複素環基または水素原子を表す。）
一般式ＩまたはＩＩで表されるチアジアゾール系化合物の具体例がそれぞれ化学式Ｉ−１ないし化学式Ｉ−３０、化学式ＩＩ−１ないし化学式ＩＩ−１７に示される。
【００１２】
【化５】

【００１３】
【化６】

【００１４】
【化７】

【００１５】
【化８】

【００１６】
【化９】

【００１７】
一般式ＩまたはIIに示したチアジアゾール系化合物は、例えばヒドラジド化合物とジクロライド化合物をピリジン還流下に反応させて前駆体を合成し、次いで得られた前駆体とＬａｗｅｓｓｏｎ試薬をトルエン還流下に反応させる二段階反応で合成され、一般的な分離精製手法によって容易に精製することができる。
【００１８】
【化１０】

【００１９】
〔作用〕
一般式ＩまたはIIに示されるチアジアゾール系化合物は電子注入層に用いたときに陰極から発光層への電子注入性／輸送能を向上させる。
一般式ＩまたはIIに示されるチアジアゾール系化合物は発光層に用いたときに電子注入性／輸送能を向上させる。この際に発光物質としても機能するものがある。
【００２０】
またチアジアゾール系化合物は融点および結晶化点が高く（結晶化点は１２５℃以上，融点は２５５℃以上）、熱に起因する凝集や結晶化が生じにくい。
【００２１】
【発明の実施の形態】
次にこの発明の実施例を図面に基づいて説明する。
図１はこの発明の実施例に係る有機薄膜発光素子を示す断面図である。
図２はこの発明の異なる実施例に係る有機薄膜発光素子を示す断面図である。図３はこの発明のさらに異なる実施例に係る有機薄膜発光素子を示す断面図である。
【００２２】
図４はこの発明のさらに異なる実施例に係る有機薄膜発光素子を示す断面図である。
上図で１は基板、２は陽極、３は正孔注入層、４は発光層、５は電子注入層、６は陰極、７は封止層、８は電源である。
基板１は有機薄膜発光素子の支持体であり、かつ発光を取り出す光学部材ともなるもので可視光に対して透明性が高いガラス，透明性樹脂等を用い、単一または複数の材料からなる積層体あるいは混合体，複合体であってもよい。
【００２３】
陽極２は効率良く正孔を注入し、低抵抗かつ可視光に対して透明性を有し、安定性が高いことが望ましい。陽極としては金属の半透膜，インジウムスズ酸化物（ＩＴＯ），酸化スズ，酸化亜鉛などの透明導電膜やポリピロール，ポリチオフェンなどの導電性高分子を用い、単一または複数種の材料からなる積層体あるいは混合体、複合体であってもよい。陽極の形成方法は抵抗加熱蒸着，電子ビーム蒸着，スパッタ, ゾルゲル, イオンプレーティングまたはキャスティング，電解重合，化学重合法が用いられる。陽極の膜厚は、発光を取り出す方向については透光性の見地から、発光波長領域での透過率が８０％以上となる範囲であることが望ましい。
【００２４】
正孔注入層３は正孔を効率良く輸送、注入することが必要で、可視光に対して透明であることが望ましい。正孔注入層には、イオン化ポテンシャルが大であり、且つ光学的エネルギーギャップが大である有機化合物，有機高分子化合物，無機高分子化合物等が用いられ、これらの少なくとも一つを積層体あるいは混合体、複合体として用いることができる。また正孔注入層には薄膜安定性等の他の機能性を付与し強化する目的で、他の化合物を含有せしめることもできる。正孔注入層の成膜方法としては抵抗加熱蒸着，分子線エピタキシー，スピンコート，キャスティング，ＬＢ法が用いられるが、生産性の見地から抵抗加熱蒸着法あるいはスピンコート法が好ましい。素子の動作電圧を下げる必要から正孔注入層の電界が印加される方向の膜厚は 5nmないし 100nmの範囲であることが好ましい。
【００２５】
電子注入層５は電子を効率良く輸送、注入することが必要で、可視光に対して透明であることが望ましい。電子注入層にはイオン化ポテンシャルが大であり、且つ電子親和力が大である有機化合物，有機高分子化合物，無機高分子化合物等が用いられ、これらの少なくとも一つを積層体あるいは混合体、複合体として用いることができる。また電子注入層には薄膜安定性等の他の機能性を付与し強化する目的で、他の化合物を含有せしめることもできる。電子注入層の成膜方法としては抵抗加熱蒸着，分子線エピタキシー，スピンコート，キャスティング，ＬＢ法が用いられるが、生産性の見地から抵抗加熱蒸着法あるいはスピンコート法が好ましい。素子の動作電圧を下げる必要から、電子注入層の電界が印加される方向の膜厚は 5nmないし 100nmの範囲であることが好ましい。
【００２６】
発光層４は正孔注入層３または陽極２から注入される正孔と、陰極６または電子注入層５から注入される電子との再結合により効率良く発光することが望ましい。発光層は、可視領域に発光帯をする必要があり、一般的には近紫外から可視領域に蛍光帯を有しかつ高い蛍光量子効率を有する有機化合物，有機高分子化合物，無機高分子化合物等が用いられ、これらの少なくとも一つを積層体あるいは混合体、複合体として用いることができる。また電子注入層には薄膜安定性等の他の機能性を付与し強化する目的で、他の化合物を含有せしめることもできる。
【００２７】
特に上述の正孔注入層もしくは電子注入層に用いられる化合物の少なくとも一つを発光層に含有せしめるか、または上述の正孔注入性能または電子注入性能の電荷注入性能と発光性能を具備する物質を発光層に含有せしめることで、電荷注入性の良好な発光層とすることも可能である。発光層の成膜方法としては抵抗加熱蒸着，分子線エピタキシー，スピンコート，キャスティング，ＬＢ法などが用いられるが、生産性の見地から抵抗加熱蒸着法またはスピンコート法が好ましい。素子の動作電圧を下げる必要から、正孔注入層の電界が印加される方向の膜厚は 5nmないし 100nmの範囲であることが好ましい。
【００２８】
陰極６は電子を効率良く有機層に注入することが必要である。陰極６としては仕事関数の小さいＭｇ，Ａｇ，Ｉｎ，Ｃａ，Ｓｃ，Ａｌ等およびこれらの合金、複合体、積層体が用いられる。陰極の成膜方法としては抵抗加熱蒸着，電子ビーム蒸着，スパッタ，イオンプレーティング法などが用いられる。
封止層７は有機薄膜発光素子の最外層に位置し、素子への外部からの酸素、水分等の侵入を防止し、かつ陰極６の破損、剥離を抑制するための補強構造として機能する。封止層は、疎水性かつ酸素，水の透過性が低い薄膜を形成する有機化合物，有機高分子化合物，無機高分子化合物，金属酸化物，金属，無機非晶質の少なくとも一つを積層体あるいは混合体、複合体の形で用いる事ができる。封止層の形成方法としては抵抗加熱蒸着，分子線エピタキシー，スピンコート，キャスティング，ＬＢ，キャン封止法などが用いられるが、陰極６の酸化あるいは積層素子のガス吸収を最小限に抑える必要があるため、少なくとも１層以上の封止層を、陰極６の成膜直後に真空を破ることなく連続して成膜することが好ましい。
実施例１
図１はこの発明の実施例に係る有機薄膜発光素子を示す断面図である。
【００２９】
膜厚１，０００ÅのＩＴＯパターンを陽極２として設けた５０ｍｍ角のガラス（ＮＡ４５：ＮＨテクノグラス製）基板１を洗浄した後、抵抗加熱蒸着装置内の基板ホルダーに装着し約１０^-4Ｐａまで真空排気した後、１５０℃で２時間の基板ベーキングを行った。その後基板を５０℃まで冷却し、温度と真空度を安定させて成膜を開始した。
【００３０】
発光層４として化学式III に示すジアミン化合物を、抵抗加熱式蒸発源にて加熱し、成膜速度を約３Å／秒として５００Å厚さに形成した。続いて電子注入層５として化学式Ｉ―１２に示しすチアジアゾール系化合物を抵抗加熱式蒸発源にて加熱し、成膜速度を約１Å／秒として４００Å厚さに形成した。さらに続いて陰極６としてＭｇＩｎ合金（Ｉｎ含有率約５体積％）を共蒸着法により２，０００Å厚さに形成した。さらに続いて封止層７としてフッ素樹脂をガラスウールに含浸させた試料を、抵抗加熱式蒸発源にて加熱し、成膜速度を約２０Å／秒として５，０００Å厚さに形成した。以上の全成膜工程は、５×１０^-4Ｐａ以下の真空を維持して連続して行った。以上の方法で作製された積層試料を給電線を配したガラス容器内に装着し、窒素ガスで置換したのちに該容器を封じ切って最終封止をおこなった。
【００３１】
【化１１】

【００３２】
実施例２
電子注入層として化学式Ｉ―１６に示したチアジアゾール系化合物を用いる他は実施例１と同様にして有機薄膜発光素子を作製した。
実施例３
電子注入層として化学式II―４に示したチアジアゾール系化合物を用いる他は実施例１と同様にして有機薄膜発光素子を作製した。
実施例４
電子注入層として化学式II―１１に示したチアジアゾール系化合物を用いる他は実施例１と同様にして有機薄膜発光素子を作製した。
比較例１
化学式III で示されるジアミン化合物を抵抗加熱式蒸発源にて加熱し、成膜速度を約４Å／秒として８００Å厚さに形成して発光層４を形成し且つ電子注入層５を設けない他は実施例１と同様にして有機薄膜発光素子を作製した。
【００３３】
実施例１〜４および比較例１に従って作製した有機薄膜発光素子を直流電源に接続し、初期輝度を１００ｃｄ／ｍ²として５００時間の連続駆動試験を実施した。各素子の発光色と、該試験開始時の輝度に対する終了時の輝度の保持率、および素子面積４ｍｍ²に対する非発光欠陥部（所謂ダークスポット）の面積率を表１と表３に示す。
【００３４】
【表１】

【００３５】
発光スペクトルから得られた有機薄膜発光素子の発光は化学式III に示すジアミン化合物に由来することが確認された。以上の結果から化学式III に示すジアミン化合物は正孔注入性発光物質として機能していること、電子注入層５に用いたチアジアゾール系化合物は比較例１との対比（表３参照）から有機薄膜発光素子の薄膜安定性と電子注入性を良好にしていることがわかる。
実施例５
図２はこの発明の異なる実施例に係る有機薄膜発光素子を示す断面図である。
【００３６】
膜厚１，０００ÅのＩＴＯパターンを陽極２として設けた５０ｍｍ角のガラス（ＮＡ４５：ＮＨテクノグラス製）基板１を洗浄した後、抵抗加熱蒸着装置内の基板ホルダーに装着し約１０^-4Ｐａまで真空排気した後、１５０℃で２時間の基板ベーキングを行った。その後基板を５０℃まで冷却し、温度と真空度を安定させて成膜を開始した。
【００３７】
正孔注入層３として化学式IVに示すジアミン化合物を抵抗加熱式蒸発源にて加熱し、成膜速度を約３Å／秒として５００Å厚さに形成した。続いて発光層４として化学式Ｉ―１０に示したチアジアゾール系化合物を抵抗加熱式蒸発源にて加熱し、成膜速度を約１Å／秒として４００Å厚さに形成した。さらに続けて陰極６としてＭｇＩｎ合金（Ｉｎ含有率約５体積％）を共蒸着法により２，０００Å厚さに形成した。さらに続けて封止層７としてフッ素樹脂をガラスウールに含浸させた試料を抵抗加熱式蒸発源にて加熱し、成膜速度を約２０Å／秒として５，０００Å厚さに形成した。以上の全成膜工程は、５×１０^-4Ｐａ以下の真空を維持して連続して行った。以上のようにして作製された積層試料を給電線を配したガラス容器内に装着し、窒素ガスで置換したのちに該容器を封じ切って最終封止をおこなった。
【００３８】
【化１２】

【００３９】
実施例６
発光層４として化学式Ｉ―１９に示したチアジアゾール系化合物を用いる他は実施例５と同様にして有機薄膜発光素子を作製した。
実施例７
発光層４として化学式II―１１に示したチアジアゾール系化合物を用いる他は実施例５と同様にして有機薄膜発光素子を作製した。
実施例８
発光層４として化学式II―１５に示したチアジアゾール系化合物を用いる他は実施例５と同様にして有機薄膜発光素子を作製した。
【００４０】
実施例５〜８および比較例１に従って作製した有機薄膜発光素子を直流電源に接続し、初期輝度を１００ｃｄ／ｍ²として５００時間の連続駆動試験を実施した。各素子の発光色と該試験開始時の輝度に対する終了時の輝度の保持率および素子面積４ｍｍ²に対する非発光欠陥部（所謂ダークスポット）の面積率を表２と表３に示す。
【００４１】
【表２】

【００４２】
発光スペクトルから得られた有機薄膜発光素子の発光はチアジアゾール系化合物に由来することが確認された。以上の結果からチアジアゾール系化合物は発光物質として機能していること、比較例１との対比（表３参照）から有機薄膜発光素子の薄膜安定性と電子注入性を良好にしていることがわかる。
実施例９
図３はこの発明のさらに異なる実施例に係る有機薄膜発光素子を示す断面図である。
【００４３】
膜厚１，０００ÅのＩＴＯパターンを陽極２として設けた５０ｍｍ角のガラス（ＮＡ４５：ＮＨテクノグラス製）基板１を洗浄した後、抵抗加熱蒸着装置内の基板ホルダーに装着し約１０^-4Ｐａまで真空排気した後１５０℃で２時間の基板ベーキングを行った。その後基板を５０℃まで冷却し、温度と真空度を安定させて成膜を開始した。
【００４４】
発光層４として化学式III に示すジアミン化合物と、化学式Ｉ―１２に示すチアジアゾール系化合物をそれぞれ別の抵抗加熱式蒸発源にて加熱し、成膜速度をそれぞれ約３Å／秒として同時共蒸着を行い、混合膜を８００Å厚さに形成した。続いて陰極６としてＭｇＩｎ合金（Ｉｎ含有率約５体積％）を共蒸着法により２，０００Å厚さに形成した。さらに続いて封止層７としてフッ素樹脂をガラスウールに含浸させた試料を抵抗加熱式蒸発源にて加熱し、成膜速度を約２０Å／秒として５，０００Å厚さに形成した。以上の全成膜工程は、５×１０^-4Ｐａ以下の真空を維持して連続して行った。以上のようにして作製された積層試料を給電線を配したガラス容器内に装着し、窒素ガスで置換したのちに該容器を封じ切って最終封止を行った。
実施例１０
化学式Ｉ―１２に示すチアジアゾール系化合物に替えて化学式Ｉ―１６に示すチアジアゾール系化合物を用いる他は実施例９と同様にして有機薄膜発光素子を作製した。
実施例１１
化学式Ｉ―１２に示すチアジアゾール系化合物に替えて化学式II―４に示すチアジアゾール系化合物を用いる他は実施例９と同様にして有機薄膜発光素子を作製した。
実施例１２
化学式Ｉ―１２に示すチアジアゾール系化合物に替えて化学式II―１１に示すチアジアゾール系化合物を用いる他は実施例９と同様にして有機薄膜発光素子を作製した。
【００４５】
実施例９〜１２および比較例１に従って作製した有機薄膜発光素子を直流電源に接続し、初期輝度を１００ｃｄ／ｍ²として５００時間の連続駆動試験を実施した。各素子の発光色と該試験開始時の輝度に対する終了時の輝度の保持率、ならびに素子面積４ｍｍ²に対する非発光欠陥部（所謂ダークスポット）の面積率を表３に示す。
【００４６】
【表３】

【００４７】
比較例１では最高輝度３５ｃｄ／ｍ²であったため、初期輝度２５ｃｄ／ｍ²として試験を実施した。
発光スペクトルから得られた有機薄膜発光素子の発光は化学式III に示すジアミン化合物に由来することが確認された。以上の結果から化学式III に示すジアミン化合物は正孔注入性発光物質として機能していること、チアジアゾール系化合物は比較例１との対比から有機薄膜発光素子の薄膜安定性と電子注入性を良好にしていることがわかる。
【００４８】
【発明の効果】
本発明によれば、上記の構成を採用した結果、薄膜の機械的熱的安定性とともに電子注入性／輸送能が向上し、連続駆動時に特性劣化の少ない有機薄膜発光素子が得られる。
【図面の簡単な説明】
【図１】この発明の実施例に係る有機薄膜発光素子を示す断面図
【図２】この発明の異なる実施例に係る有機薄膜発光素子を示す断面図
【図３】この発明のさらに異なる実施例に係る有機薄膜発光素子を示す断面図
【図４】この発明のさらに異なる実施例に係る有機薄膜発光素子を示す断面図
【符号の説明】
１基板
２陽極
３正孔注入層
４発光層
５電子注入層
６陰極
７封止層
８電源[0001]
[Industrial application fields]
The present invention relates to an organic thin film light emitting element used as a light source of various display devices, and more particularly to a material used for an electron injection layer or a light emitting layer.
[0002]
[Prior art]
With the rapid increase in demand for flat displays replacing conventional cathode ray tubes, various display elements have been developed and put into practical use. Electroluminescence elements (hereinafter referred to as EL elements) are also in line with these needs, and are attracting attention as high-resolution and high-visibility that are not found in other displays, particularly as all-solid-state spontaneous light-emitting elements.
[0003]
What is currently put into practical use is an EL element made of an inorganic material mainly using a ZnS / Mn system for a light emitting layer. However, since this type of inorganic EL element is driven by alternating current and the driving voltage is as high as about 200 V or more, the driving method is complicated, the manufacturing cost is high, and the development of a blue light emitting material having sufficient light emitting ability for practical use has not yet been seen. Since it has not been issued, it has problems such as difficulty in full colorization.
[0004]
On the other hand, organic light emitting devices using organic materials have recently been researched because the driving voltage required for light emission can be greatly reduced, and the possibility of full coloration is fully achieved by adapting various light emitting materials. (For example, US Pat. No. 3,530,325, Mol. Cryst. Liq. Cryst., 135, 355 (1986)). Among them, for the purpose of improving luminous efficiency, a laminated organic thin film light emitting device composed of anode / hole injection layer / light emitting layer / negative electrode is laminated with a light emitting layer made of a specific organic compound and a hole injection layer made of a specific organic compound. A report that a luminance of 1,000 cd / m ² or more was obtained with an applied voltage of 10 V or less using a thin film (Appl. Phys. Lett., 51, 913, (1987), Japanese Patent Laid-Open No. 57-51781 , JP 59-194393) has been spurred on by research.
[0005]
Further, in order to further improve the performance, an element in which a metal material used for the negative electrode is optimized (Japanese Patent Laid-Open Nos. 63-264692 and 2-15595), and a host material composed of a specific organic compound as a light emitting layer An element doped with a laser dye (J. Appl. Phys., 65, 3610 (1989), US Pat. No. 4,769,292), an electron injection layer made of a specific organic compound, and an anode / hole injection layer / Attempts have been made to produce a light emitting element of three primary colors (Jpn. J. Appl. Phys., 27, 4, 713 (1988)) having a light emitting layer / electron injection layer / negative electrode laminated type.
[0006]
[Problems to be solved by the invention]
As described above, although the organic thin film light emitting device strongly suggests the possibility of a full color display device such as high luminance light emission, low voltage drive, and three primary color light emission, many problems remain in practical use. In particular, characteristic deterioration during continuous driving (specifically, so-called dark spot generation and deterioration of display quality due to growth, luminance change with time) is a problem to be solved. Further, improvement of various performances such as power consumption and weather resistance that can compete with other display methods can be cited as problems.
[0007]
As one of the causes of these problems, mechanical thermal instability of thin films using organic compounds and lack of opto-electronic functions have been pointed out (for example, IEICE Technical Report, OME-92-9 (1992)). , Nippon Gakken Photoelectric Interconversion 125th Committee 11th EL Subcommittee Data, 7 (1994)).
The present invention has been made in view of the above points, and its object is to provide an organic material having excellent mechanical and thermal stability in a thin film state and having good photoelectric conversion ability and charge injection / transport ability. An object of the present invention is to provide an organic thin-film light-emitting element with little characteristic deterioration during continuous driving.
[0008]
[Means for Solving the Problems]
According to the present invention, the above-described object is achieved by containing a thiadiazole compound represented by the following general formula I or II in the electron injection layer and a diamine compound represented by the following chemical formula III in the light emitting layer. Further, the light-emitting layer contains a thiadiazole-based compound represented by the general formula I or II and a diamine compound represented by the chemical formula III, and light emission is achieved due to the diamine compound.
[0009]
Embedded image

[0010]
Embedded image

[0011]
[Formula 4]

(In the formula, Ar ¹ represents an aryl group or heterocyclic group which may have a substituent, or a hydrogen atom.)
Specific examples of the thiadiazole-based compound represented by the general formula I or II are represented by chemical formula I-1 to chemical formula I-30 and chemical formula II-1 to chemical formula II-17, respectively.
[0012]
[Chemical formula 5]

[0013]
[Chemical 6]

[0014]
[Chemical 7]

[0015]
[Chemical 8]

[0016]
[Chemical 9]

[0017]
The thiadiazole compound represented by the general formula I or II is prepared by, for example, reacting a hydrazide compound and a dichloride compound under a pyridine reflux to synthesize a precursor, and then reacting the obtained precursor with a Lawesson reagent under a toluene reflux. It is synthesized by a step reaction and can be easily purified by a general separation and purification technique.
[0018]
[Chemical Formula 10]

[0019]
[Action]
The thiadiazole compound represented by the general formula I or II improves the electron injection property / transport ability from the cathode to the light emitting layer when used in the electron injection layer.
The thiadiazole compound represented by the general formula I or II improves the electron injecting / transporting ability when used in the light emitting layer. At this time, there is a substance that also functions as a light-emitting substance.
[0020]
In addition, thiadiazole compounds have a high melting point and crystallization point (crystallization point is 125 ° C. or higher, melting point is 255 ° C. or higher), and aggregation and crystallization due to heat hardly occur.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an organic thin film light emitting device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an organic thin film light emitting device according to another embodiment of the present invention. FIG. 3 is a cross-sectional view showing an organic thin film light emitting device according to still another embodiment of the present invention.
[0022]
FIG. 4 is a cross-sectional view showing an organic thin film light emitting device according to still another embodiment of the present invention.
In the figure, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a light emitting layer, 5 is an electron injection layer, 6 is a cathode, 7 is a sealing layer, and 8 is a power source.
The substrate 1 is a support for an organic thin-film light-emitting element, and also serves as an optical member for extracting emitted light. The substrate 1 is made of a single material or a plurality of materials using glass, a transparent resin, etc. that are highly transparent to visible light. It may be a body, a mixture, or a complex.
[0023]
It is desirable that the anode 2 efficiently injects holes, has low resistance, is transparent to visible light, and has high stability. The anode is a semi-permeable metal film, a transparent conductive film such as indium tin oxide (ITO), tin oxide, or zinc oxide, or a conductive polymer such as polypyrrole or polythiophene. It may be a body, a mixture or a complex. The anode can be formed by resistance heating evaporation, electron beam evaporation, sputtering, sol-gel, ion plating or casting, electrolytic polymerization, or chemical polymerization. The film thickness of the anode is preferably in the range in which the transmittance in the emission wavelength region is 80% or more from the viewpoint of translucency in the direction of extracting light emission.
[0024]
The hole injection layer 3 needs to efficiently transport and inject holes, and is preferably transparent to visible light. For the hole injection layer, an organic compound, an organic polymer compound, an inorganic polymer compound or the like having a large ionization potential and a large optical energy gap is used, and at least one of these is laminated or mixed. It can be used as a body or a complex. Further, the hole injection layer may contain other compounds for the purpose of imparting and strengthening other functions such as thin film stability. As a method for forming the hole injection layer, resistance heating vapor deposition, molecular beam epitaxy, spin coating, casting, and LB method are used. From the viewpoint of productivity, the resistance heating vapor deposition method or the spin coating method is preferable. In order to reduce the operating voltage of the device, the thickness of the hole injection layer in the direction in which the electric field is applied is preferably in the range of 5 nm to 100 nm.
[0025]
The electron injection layer 5 needs to efficiently transport and inject electrons, and is preferably transparent to visible light. For the electron injection layer, an organic compound, an organic polymer compound, an inorganic polymer compound or the like having a large ionization potential and a large electron affinity is used, and at least one of them is a laminate, mixture, or composite. Can be used as Further, the electron injection layer may contain other compounds for the purpose of imparting and strengthening other functionalities such as thin film stability. As a method for forming the electron injection layer, resistance heating vapor deposition, molecular beam epitaxy, spin coating, casting, and LB method are used. From the viewpoint of productivity, the resistance heating vapor deposition method or the spin coating method is preferable. In order to reduce the operating voltage of the device, the thickness of the electron injection layer in the direction in which the electric field is applied is preferably in the range of 5 nm to 100 nm.
[0026]
The light emitting layer 4 desirably emits light efficiently by recombination of holes injected from the hole injection layer 3 or the anode 2 and electrons injected from the cathode 6 or the electron injection layer 5. The light emitting layer needs to have a light emission band in the visible region, and generally has an organic compound, an organic polymer compound, an inorganic polymer compound, etc. having a fluorescent band from the near ultraviolet to the visible region and having a high fluorescence quantum efficiency. And at least one of these can be used as a laminate, mixture, or composite. Further, the electron injection layer may contain other compounds for the purpose of imparting and strengthening other functionalities such as thin film stability.
[0027]
In particular, the light emitting layer contains at least one of the compounds used for the hole injection layer or the electron injection layer described above, or a substance having charge injection performance and light emission performance of the hole injection performance or electron injection performance described above. By containing it in the light emitting layer, a light emitting layer with good charge injection property can be obtained. As a method for forming the light emitting layer, resistance heating vapor deposition, molecular beam epitaxy, spin coating, casting, LB method, and the like are used. From the viewpoint of productivity, the resistance heating vapor deposition method or the spin coating method is preferable. In order to reduce the operating voltage of the device, the thickness of the hole injection layer in the direction in which the electric field is applied is preferably in the range of 5 nm to 100 nm.
[0028]
The cathode 6 needs to efficiently inject electrons into the organic layer. As the cathode 6, Mg, Ag, In, Ca, Sc, Al or the like having a small work function and alloys, composites, and laminates thereof are used. As a method for forming the cathode, resistance heating evaporation, electron beam evaporation, sputtering, ion plating, or the like is used.
The sealing layer 7 is located in the outermost layer of the organic thin film light emitting element, and functions as a reinforcing structure for preventing entry of oxygen, moisture, and the like from the outside into the element, and suppressing damage and peeling of the cathode 6. The sealing layer is a laminate of at least one of an organic compound, an organic polymer compound, an inorganic polymer compound, a metal oxide, a metal, and an inorganic amorphous material that forms a thin film that is hydrophobic and has low permeability to oxygen and water Alternatively, it can be used in the form of a mixture or a complex. As the forming method of the sealing layer, resistance heating vapor deposition, molecular beam epitaxy, spin coating, casting, LB, can sealing method, etc. are used, but it is necessary to minimize oxidation of the cathode 6 or gas absorption of the laminated element. Therefore, it is preferable to form at least one sealing layer continuously without breaking the vacuum immediately after the cathode 6 is formed.
Example 1
FIG. 1 is a cross-sectional view showing an organic thin film light emitting device according to an embodiment of the present invention.
[0029]
After cleaning a 50 mm square glass (NA45: NH Techno Glass) substrate 1 provided with an ITO pattern having a thickness of 1,000 mm as the anode 2, it is mounted on a substrate holder in a resistance heating vapor deposition apparatus up to about 10 ^-4 Pa. After evacuation, the substrate was baked at 150 ° C. for 2 hours. Thereafter, the substrate was cooled to 50 ° C., the temperature and the degree of vacuum were stabilized, and film formation was started.
[0030]
A diamine compound represented by the chemical formula III was heated as a light emitting layer 4 by a resistance heating evaporation source to form a film thickness of 500 mm with a film forming rate of about 3 mm / second. Subsequently, a thiadiazole-based compound represented by Chemical Formula I-12 was heated as the electron injection layer 5 with a resistance heating evaporation source to form a thickness of 400 mm at a film formation rate of about 1 mm / second. Subsequently, an MgIn alloy (In content of about 5% by volume) was formed as a cathode 6 to a thickness of 2,000 mm by co-evaporation. Subsequently, a sample obtained by impregnating glass wool with a fluororesin as the sealing layer 7 was heated with a resistance heating evaporation source to form a thickness of 5,000 mm at a film forming rate of about 20 mm / sec. All the above film forming steps were continuously performed while maintaining a vacuum of 5 × 10 ⁻⁴ Pa or less. The laminated sample produced by the above method was mounted in a glass container provided with a power supply line, and after replacing with nitrogen gas, the container was sealed and final sealing was performed.
[0031]
Embedded image

[0032]
Example 2
An organic thin film light emitting device was produced in the same manner as in Example 1 except that the thiadiazole compound represented by Chemical Formula I-16 was used as the electron injection layer.
Example 3
An organic thin film light emitting device was produced in the same manner as in Example 1 except that the thiadiazole compound represented by Chemical Formula II-4 was used as the electron injection layer.
Example 4
An organic thin film light emitting device was produced in the same manner as in Example 1 except that the thiadiazole compound represented by Chemical Formula II-11 was used as the electron injection layer.
Comparative Example 1
The diamine compound represented by the chemical formula III is heated by a resistance heating evaporation source, the film formation rate is set to about 4 mm / second to form a light emitting layer 4 and the electron injection layer 5 is not provided. An organic thin film light emitting device was produced in the same manner as in Example 1.
[0033]
Organic thin-film light-emitting devices manufactured according to Examples 1 to 4 and Comparative Example 1 were connected to a DC power source, and a continuous driving test for 500 hours was performed with an initial luminance of 100 cd / m ² . Tables 1 and 3 show the emission color of each element, the retention ratio of luminance at the end of the test relative to the luminance at the start of the test, and the area ratio of non-luminous defect portions (so-called dark spots) with respect to the element area of 4 mm ² .
[0034]
[Table 1]

[0035]
It was confirmed that the light emission of the organic thin film light emitting device obtained from the emission spectrum was derived from the diamine compound represented by the chemical formula III. From the above results, the diamine compound represented by the chemical formula III functions as a hole-injecting light-emitting substance, and the thiadiazole-based compound used in the electron-injecting layer 5 is light-emitting organic thin film in comparison with Comparative Example 1 (see Table 3). It can be seen that the thin film stability and electron injection property of the device are improved.
Example 5
FIG. 2 is a cross-sectional view showing an organic thin film light emitting device according to another embodiment of the present invention.
[0036]
After cleaning a 50 mm square glass (NA45: NH Techno Glass) substrate 1 provided with an ITO pattern having a thickness of 1,000 mm as the anode 2, it is mounted on a substrate holder in a resistance heating vapor deposition apparatus up to about 10 ^-4 Pa. After evacuation, the substrate was baked at 150 ° C. for 2 hours. Thereafter, the substrate was cooled to 50 ° C., the temperature and the degree of vacuum were stabilized, and film formation was started.
[0037]
A diamine compound represented by the chemical formula IV was heated as a hole injection layer 3 with a resistance heating evaporation source to form a film thickness of 500 mm with a film formation rate of about 3 mm / second. Subsequently, the thiadiazole compound represented by the chemical formula I-10 was heated as a light emitting layer 4 with a resistance heating evaporation source to form a film thickness of 400 mm with a film forming rate of about 1 mm / second. Subsequently, an MgIn alloy (In content of about 5% by volume) was formed as a cathode 6 to a thickness of 2,000 mm by co-evaporation. Further, a sample in which glass wool was impregnated with fluororesin as the sealing layer 7 was heated with a resistance heating evaporation source to form a thickness of 5,000 mm at a film forming rate of about 20 mm / second. All the above film forming steps were continuously performed while maintaining a vacuum of 5 × 10 ⁻⁴ Pa or less. The laminated sample produced as described above was mounted in a glass container provided with a power supply line, and after replacing with nitrogen gas, the container was sealed and final sealing was performed.
[0038]
Embedded image

[0039]
Example 6
An organic thin film light emitting device was produced in the same manner as in Example 5 except that the thiadiazole compound represented by Chemical Formula I-19 was used as the light emitting layer 4.
Example 7
An organic thin film light emitting device was produced in the same manner as in Example 5 except that the thiadiazole compound represented by Chemical Formula II-11 was used as the light emitting layer 4.
Example 8
An organic thin film light emitting device was produced in the same manner as in Example 5 except that the thiadiazole compound represented by Chemical Formula II-15 was used as the light emitting layer 4.
[0040]
Organic thin-film light-emitting devices fabricated according to Examples 5 to 8 and Comparative Example 1 were connected to a DC power source, and a continuous driving test for 500 hours was performed with an initial luminance of 100 cd / m ² . Tables 2 and 3 show the emission color of each element, the retention ratio of the luminance at the end of the test relative to the luminance at the start of the test, and the area ratio of the non-emitting defect portion (so-called dark spot) with respect to the element area of 4 mm ² .
[0041]
[Table 2]

[0042]
It was confirmed that the light emission of the organic thin film light emitting device obtained from the emission spectrum was derived from the thiadiazole compound. From the above results, it can be seen that the thiadiazole-based compound functions as a light-emitting substance, and that the thin film stability and the electron injection property of the organic thin film light-emitting element are improved from the comparison with Comparative Example 1 (see Table 3).
Example 9
FIG. 3 is a cross-sectional view showing an organic thin film light emitting device according to still another embodiment of the present invention.
[0043]
After cleaning a 50 mm square glass (NA45: NH Techno Glass) substrate 1 provided with an ITO pattern having a thickness of 1,000 mm as the anode 2, it is mounted on a substrate holder in a resistance heating vapor deposition apparatus up to about 10 ^-4 Pa. After evacuation, the substrate was baked at 150 ° C. for 2 hours. Thereafter, the substrate was cooled to 50 ° C., the temperature and the degree of vacuum were stabilized, and film formation was started.
[0044]
A diamine compound represented by Chemical Formula III and a thiadiazole-based compound represented by Chemical Formula I-12 are heated in separate resistance heating evaporation sources as the light emitting layer 4 to perform simultaneous co-evaporation at a deposition rate of about 3 mm / sec. The mixed film was formed to a thickness of 800 mm. Subsequently, an MgIn alloy (In content of about 5% by volume) was formed as a cathode 6 to a thickness of 2,000 mm by co-evaporation. Subsequently, a sample obtained by impregnating glass wool with a fluororesin as the sealing layer 7 was heated with a resistance heating evaporation source to form a thickness of 5,000 mm at a film forming rate of about 20 mm / sec. All the above film forming steps were continuously performed while maintaining a vacuum of 5 × 10 ⁻⁴ Pa or less. The laminated sample produced as described above was mounted in a glass container provided with a power supply line, and after replacing with nitrogen gas, the container was sealed and final sealing was performed.
Example 10
An organic thin film light emitting device was produced in the same manner as in Example 9 except that the thiadiazole compound represented by the chemical formula I-16 was used instead of the thiadiazole compound represented by the chemical formula I-12.
Example 11
An organic thin film light emitting device was produced in the same manner as in Example 9 except that the thiadiazole compound represented by Chemical Formula II-4 was used instead of the thiadiazole compound represented by Chemical Formula I-12.
Example 12
An organic thin film light emitting device was produced in the same manner as in Example 9 except that the thiadiazole compound represented by Chemical Formula II-11 was used instead of the thiadiazole compound represented by Chemical Formula I-12.
[0045]
Organic thin-film light-emitting devices fabricated according to Examples 9 to 12 and Comparative Example 1 were connected to a DC power source, and a continuous driving test was performed for 500 hours with an initial luminance of 100 cd / m ² . Table 3 shows the emission color of each element, the retention ratio of luminance at the end of the test relative to the luminance at the start of the test, and the area ratio of non-luminous defect portions (so-called dark spots) with respect to the element area of 4 mm ² .
[0046]
[Table 3]

[0047]
Because it was a comparative example maximum luminance 35 cd / m ² at 1, tests were carried out as the initial luminance 25 cd / m ^2.
It was confirmed that the light emission of the organic thin film light emitting device obtained from the emission spectrum was derived from the diamine compound represented by the chemical formula III. From the above results, the diamine compound represented by the chemical formula III functions as a hole-injecting light-emitting substance, and the thiadiazole-based compound improves the thin-film stability and the electron-injecting property of the organic thin-film light-emitting element in comparison with Comparative Example 1. You can see that
[0048]
【The invention's effect】
According to the present invention, as a result of employing the above-described configuration, an organic thin film light emitting device with improved electron injection / transport capability as well as mechanical and thermal stability of the thin film and less characteristic deterioration during continuous driving can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an organic thin film light emitting device according to an embodiment of the present invention. FIG. 2 is a cross sectional view showing an organic thin film light emitting device according to a different embodiment of the present invention. FIG. 4 is a cross-sectional view showing an organic thin-film light-emitting element according to another embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Light emitting layer 5 Electron injection layer 6 Cathode 7 Sealing layer 8 Power supply

Claims

An organic thin film light-emitting device comprising a thiadiazole compound represented by the following general formula I or II in an electron injection layer and a diamine compound represented by the following chemical formula III in a light emitting layer:

(In the formula, Ar ¹ represents an aryl group or heterocyclic group which may have a substituent, or a hydrogen atom.)

An organic thin-film light-emitting element comprising: a thiadiazole-based compound represented by the above general formula I or II; and a diamine compound represented by the above chemical formula III in a light-emitting layer, wherein light emission is caused by the diamine compound.