JP2004186027A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve brightness lifetime and secure heat-resisting characteristics of 100°C or higher, in an organic EL element in which a light emitting layer obtained by mixing a hole transporting material, an electronic transporting material, and a light emitting additive is pinched between a pair of electrodes. <P>SOLUTION: In the organic El element in which the light emitting layer 50 obtained by mixing the hole transporting material composed of a tertiary amine compound, the electron transporting material, and the light emitting additive is pinched between a pair of electrodes 20, 80, the hole transporting material is the tertiary amine compound in which the total number of the sites is 1 or 0, where two or more phenylene groups exist between nitrogen atoms in the molecular structure, and in which glass transition temperature is 100°C or higher. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

ここで、上記構造式（１）において、Ｌ１、Ｌ２は１環以上のフェニレン基であり、Ｍ１、Ｍ２は芳香族基または脂肪族基を表す。なお、Ｍ１、Ｍ２は結合する炭素原子を含めて例えばフルオレン基やシクロヘキサン基のように互いに環構造を形成しているものでもよい。
【００２２】
本発明のような３級アミン化合物を、発光層を構成するホール輸送性材料に用いることにより、従来に比べて大幅な輝度寿命の向上と１００℃以上の耐熱性の確保との両立を図ることができる。
【００２３】
ここで、請求項１に記載のホール輸送性材料として、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または上記構造式（１）で示される基が存在する箇所の総数が０である３級アミン化合物としては、請求項２の発明に記載のものにできる。
【００２４】
すなわち、請求項２に記載の発明では、請求項１に記載のホール輸送性材料を構成する３級アミン化合物が、下記構造式（２）で表される骨格を有する化合物であることを特徴とする。
【００２５】
【化１１】

ここで、構造式（２）において、Ｒ１〜Ｒ２０は、水素や下記構造式（３）、（４）、（５）で表される構造であるか、または、Ｒ１〜Ｒ２０のうちの隣接する基同士によって芳香族環を形成した構造であり、且つ、Ｒ１〜Ｒ２０のうち少なくとも１つは、下記構造式（３）、（４）、（５）のいずれかの構造を有するものである。
【００２６】
【化１２】

【００２７】
【化１３】

【００２８】
【化１４】

ここで、上記構造式（３）〜（５）において、Ｂ１〜Ｂ２、Ｃ１〜Ｃ３、Ｄ１〜Ｄ４は、置換または非置換のアリール基を表す。
【００２９】
また、請求項１に記載のホール輸送性材料として、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または上記構造式（１）で示される基が存在する箇所の総数が１個である３級アミン化合物としては、請求項３の発明に記載のものにできる。
【００３０】
すなわち、請求項３に記載の発明では、請求項１に記載のホール輸送性材料を構成する３級アミン化合物が、下記構造式（６）で表される骨格を有する化合物であることを特徴とする。
【００３１】
【化１５】

ここで、構造式（６）において、Ａは２個以上のフェニレン基、脂肪族基または前記構造式（１）で示される基である。なお、構造式（６）において、Ａは置換基を有していてもよい。
【００３２】
また、Ｒ１〜Ｒ２０は、水素や下記構造式（３）、（４）、（５）で表される構造であるか、または、Ｒ１〜Ｒ２０のうちの隣接する基同士によって芳香族環を形成した構造であり、且つ、Ｒ１〜Ｒ２０のうち少なくとも１つは構造式（３）、（４）、（５）のいずれかの構造を有するものである。
【００３３】
【化１６】

【００３４】
【化１７】

【００３５】
【化１８】

ここで、上記構造式（３）〜（５）において、Ｂ１〜Ｂ２、Ｃ１〜Ｃ３、Ｄ１〜Ｄ４は、置換または非置換のアリール基を表す。
【００３６】
さらに、有機ＥＬ素子における高温環境下での耐熱性を向上させるために、陽極と接する有機層すなわち正孔注入層として、銅フタロシアニン（ＣｕＰｃ）等の結晶性の材料を設け、陽極と有機層との密着性を高めることについて、検討を進めた。
【００３７】
単純に、陽極の上に結晶性の有機材料を使用すると、上述したように、結晶性の有機材料が高温環境下で結晶化が進行するという形態変化を示し、正孔の注入特性が劣化するという問題がある。この問題の発生原因について、本発明者等が行った実験のデータを基に、具体的に説明する。
【００３８】
ガラス基板上に陽極ＩＴＯ（透明電極）を形成し、アルゴンと酸素混合のプラズマによる表面処理を施した後、正孔注入層としてＣｕＰｃを材料加熱温度４２０℃で膜厚１０ｎｍにて成膜した後、正孔輸送層にトリフェニルアミン４量体、発光層としてジメチルキナクリドンが添加されたＡｌｑ、電子輸送層にＡｌｑ、電子注入層にＬｉＦ、陰極にＡｌを順次成膜し、封止缶で密封した有機ＥＬ素子を試作した。
【００３９】
この試作した素子は一般的な有機ＥＬ素子であり、以下、これを試作品という。ここで、上記有機薄膜のうちＣｕＰｃは結晶性であり、それ以外の層はアモルファスである。
【００４０】
この試作品を１００℃にて１２時間、高温放置した時の電圧−輝度特性（Ｖ−Ｉ特性）を図１６に示す。図１６に示すように、Ｖ−Ｉ特性は、上記高温放置前である初期に比べて、上記高温放置後では約３Ｖ程度プラス側にシフトしていることがわかった。
【００４１】
これは、駆動回路への負担を増加させることになり、回路設計上コストアップにつながる。また、同一素子内で部分的に発生するため、電流の流れやすい領域とそうでない領域を形成する結果、輝度ムラとして認識されることになる。
【００４２】
上記試作品における層すなわち有機薄膜のうちで最もＴｇ点が低い材料は、トリフェニルアミン４量体であり、約１４４℃である。１００℃の放置はこのトリフェニルアミン４量体のＴｇ点よりも４０℃以上低い環境下での放置なので、上記シフト現象に対して、ＣｕＰｃ以外のアモルファス膜の微結晶凝集構造の進行による影響は少ないと考えられる。
【００４３】
そこで、結晶性を有する有機材料であるＣｕＰｃ膜（正孔注入層）において、その結晶状態の変化に着目した。その結果、高温環境下の放置前後で、このＣｕＰｃ膜の結晶状態が大きく異なることを見出した。このＣｕＰｃ膜の結晶状態の変化について、具体的に調べた結果を示す。
【００４４】
この結晶状態変化の確認は効率良く行うため、放置環境温度を１２０℃と高くして加速し、放置時間は２Ｈｒで評価することとした。以下、この条件における放置を加速高温放置という。
【００４５】
上記したようにＶ−Ｉ特性に３Ｖ程度のシフトが発生した上記試作品と同じ条件で、ＩＴＯ付きガラス基板上にＣｕＰｃを成膜した。この場合におけるＣｕＰｃ膜の結晶性の状態を、上記加速高温放置の前と後でＸ線回折によって分析した結果を図１７に示す。
【００４６】
図１７に示すように、回折ピークにおいて、２θ＝６．６８°に発生しているピークがＣｕＰｃの結晶構造に由来している。図１７では、このピークにおいて実線で図示するものが加速高温放置の前のピークすなわち初期のピークであり、破線で図示するものが加速高温放置の後のピークすなわち１２０℃、２Ｈｒ後のピークである。
【００４７】
そして、このピーク値の積分値が大きい、すなわちピーク値が高いほど、結晶性が高いことを示している。つまり、１２０℃、２Ｈｒの加速高温放置によって、当該ピーク値（積分値）が加速高温放置前の１．５倍に変化している。
【００４８】
このことから、本発明者等は、上記試作品において、正孔注入層であるＣｕＰｃ膜上に正孔輸送層、発光層、電子輸送層、陰極等が成膜された後、つまり、発光素子形態になってから、ＣｕＰｃ膜がこのような結晶状態の変化を起こすことが、正孔の注入特性を劣化させ、高温環境下でのＶ−Ｉ特性変化を誘発し、輝度低下や輝度ムラを引き起こす大きな原因であると考えた。
【００４９】
そこで、本発明者等は、上記請求項１〜３に記載の有機ＥＬ素子において、陽極と接する有機層すなわち正孔注入層として結晶性の材料を使用する場合、高温環境下での有機材料の結晶状態の変化に対する対策としては、結晶性を有する有機材料を、成膜時にできるだけ結晶性が高くなるように成膜することが重要であると考えた。
【００５０】
請求項４に記載の発明は、このような考えに基づいて創出されたものであり、請求項１〜３に記載の有機ＥＬ素子において、一対の電極のどちらか一方と発光層との間に正孔注入層が介在されており、正孔注入層は、結晶性を示す有機材料からなり、結晶性を示す有機材料のＸ線回折法により現れる回折ピークの値において、有機ＥＬ素子の使用温度内の加熱による回折ピーク値の変化量が、加熱前の回折ピーク値の±２５％以内となっていることを特徴とする。
【００５１】
本発明のように、結晶性を示す有機材料のＸ線回折法により現れる回折ピークの値において、有機ＥＬ素子の使用温度内の加熱による回折ピーク値の変化量を、加熱前の回折ピーク値の±２５％以内と小さくすれば、高温環境下で使用しても、輝度の低下や輝度ムラが発生しない程度にまで、有機材料の結晶状態の変化を小さくすることができる。
【００５２】
よって、本発明によれば、一対の電極間に、ホール輸送性材料と電子輸送性材料と発光添加材料とを混合してなる発光層を挟んでなる有機ＥＬ素子において、輝度寿命の向上と１００℃以上の耐熱性の確保との両立を図るという効果を、より高いレベルにて実現することができる。
【００５３】
ここで、請求項５に記載の発明のように、基板上にインジウム−錫の酸化物からなるＩＴＯ膜が形成されており、結晶性を示す有機材料は、ＩＴＯ膜の上に形成された有機膜として構成されているものにできる。
【００５４】
さらに、請求項６に記載の発明のように、結晶性特性を示す有機材料は、銅フタロシアニン膜にすることができ、この場合、回折ピーク値は銅フタロシアニン膜における基板に平行な（２００）面の回折ピーク値である。
【００５５】
また、請求項７に記載の発明では、ＩＴＯ膜の平均表面粗さＲａが２ｎｍ以下であり、１０点平均表面粗さＲｚが２０ｎｍ以下であることを特徴とする。
【００５６】
また、陽極の上に位置する結晶性の有機材料を、結晶性が高く安定した膜に成膜するためには、陽極の表面粗度が重要となる。具体的には、本発明のように、正孔注入層と接する陽極としてのＩＴＯ膜のＲａを２ｎｍ以下、Ｒｚを２０ｎｍ以下とすることが望ましい。
【００５７】
【発明の実施の形態】
以下、本発明を図に示す実施形態について説明する。図１は本発明の実施形態に係る有機ＥＬ素子Ｓ１の概略断面構成を示す図である。
【００５８】
透明なガラス等からなる基板１０の上に、インジウム−錫の酸化物（以下、ＩＴＯという）からなる陽極２０が形成されている。陽極２０の上には、結晶性を有する有機材料としてＣｕＰｃ（銅フタロシアニン）からなる正孔注入層３０が形成され、正孔注入層３０の上には、ホール輸送性材料からなる正孔輸送層４０が形成されている。
【００５９】
正孔輸送層４０の上には、３級アミン化合物からなるホール輸送性材料と電子輸送性材料とをホスト材料とし、これにドーパントとして発光添加材料を混合してなる発光層５０が形成され、発光層５０の上には、電子輸送性材料からなる電子輸送層６０が形成されている。さらに、電子輸送層６０の上には、ＬｉＦからなる電子注入層７０が形成され、その上には、Ａｌからなる陰極８０が形成されている。
【００６０】
こうして、一対の電極２０、８０の間には、結晶性を有する有機材料からなる正孔注入層３０、正孔輸送層４０、発光層５０、電子輸送層６０および電子注入層７０が積層されて挟まれており、有機ＥＬ素子Ｓ１が形成されている。
【００６１】
この有機ＥＬ素子Ｓ１においては、陽極２０と陰極８０との間に電界を印加し、陽極２０から正孔が、一方、陰極８０から電子がそれぞれ発光層５０へ注入、輸送され、発光層５０にて電子と正孔とが再結合し、そのときのエネルギーによって発光層５０が発光するものである。そして、その発光は例えば、基板１０側から取り出され視認されるようになっている。
【００６２】
ここで、本実施形態の発光層５０は、３級アミン化合物からなるホール輸送性材料と電子輸送性材料と発光添加材料とを混合してなるが、用いられるホール輸送性材料は、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または下記構造式（１）で示される基が存在する箇所の総数が１個もしくは０であり、且つガラス転移温度が１００℃以上であるような３級アミン化合物である。
【００６３】
【化１９】

ここで、上記構造式（１）において、Ｌ１、Ｌ２は１環以上のフェニレン基であり、Ｍ１、Ｍ２は芳香族基または脂肪族基を表す。なお、Ｍ１、Ｍ２は結合する炭素原子を含めて例えばフルオレン基やシクロヘキサン基のように互いに環構造を形成しているものでもよい。
【００６４】
また、脂肪族基としては、例えば、メチレン基やエチレン基のような直鎖炭化水素基やシクロヘキサンのような環状炭化水素基等が挙げられる。
【００６５】
より具体的なホール輸送性材料として、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または上記構造式（１）で示される基が存在する箇所の総数が０である３級アミン化合物としては、下記構造式（２）で表される骨格を有する化合物であるものにできる。
【００６６】
【化２０】

ここで、構造式（２）において、Ｒ１〜Ｒ２０は、水素や下記構造式（３）、（４）、（５）で表される構造であるか、または、Ｒ１〜Ｒ２０のうちの隣接する基同士によって芳香族環を形成した構造であり、且つ、Ｒ１〜Ｒ２０のうち少なくとも１つは、下記構造式（３）、（４）、（５）のいずれかの構造を有するものである。
【００６７】
【化２１】

【００６８】
【化２２】

【００６９】
【化２３】

ここで、上記構造式（３）〜（５）において、Ｂ１〜Ｂ２、Ｃ１〜Ｃ３、Ｄ１〜Ｄ４は、置換または非置換のアリール基を表す。
【００７０】
また、より具体的なホール輸送性材料として、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または上記構造式（１）で示される基が存在する箇所の総数が１個である３級アミン化合物としては、下記構造式（６）で表される骨格を有する化合物であるものにできる。
【００７１】
【化２４】

ここで、構造式（６）において、Ａは２個以上のフェニレン基、脂肪族基または上記構造式（１）で示される基である。なお、構造式（６）において、Ａは置換基を有していてもよい。また、構造式（６）におけるＲ１〜Ｒ２０は、上記構造式（２）におけるＲ１〜Ｒ２０と同様のものにできる。
【００７２】
このような３級アミン化合物を、発光層５０を構成するホール輸送性材料に用いることにより、従来に比べて大幅な輝度寿命の向上と１００℃以上の耐熱性の確保との両立を図ることができる。
【００７３】
ところで、本実施形態の有機ＥＬ素子は、例えば、車載用のディスプレイ等に採用されるものであり、その使用温度は−４０℃〜１２０℃程度のものである。
【００７４】
また、結晶性を示す有機材料であるＣｕＰｃからなる正孔注入層３０すなわちＣｕＰｃ膜３０をＸ線回折法により測定したとき、基板１０と平行なＣｕＰｃ膜３０の（２００）面の回折ピークは、ＣｕＰｃ膜２０の結晶性を示す回折ピークである。この回折ピークは、上記図１７に示した２θ＝６．６８°に発生しているピークに相当するものであり、以下、ＣｕＰｃ結晶性ピークという。
【００７５】
そして、本実施形態では、好ましい形態として、このＣｕＰｃ結晶性ピーク（２θ＝６．６８°）の値つまりピークの積分値において、有機ＥＬ素子Ｓ１の使用温度（例えば−４０℃〜１２０℃）内の加熱による当該ＣｕＰｃ結晶性ピーク値の変化量が、加熱前の当該ＣｕＰｃ結晶性ピークの±２５％以内となっている。
【００７６】
このＣｕＰｃ結晶性ピーク値の加熱前後における変化量を±２５％以内に小さく抑えることにより、高温環境下で使用しても、輝度の低下や輝度ムラが発生しない程度にまで、有機材料の結晶状態の変化を小さくすることができる。そして、使用温度内において良好な輝度特性を実現することができ、輝度寿命の向上と１００℃以上の耐熱性の確保との両立を図るという効果をより高いレベルにて実現することができる。
【００７７】
ちなみに、上述したように、従来の結晶性を有する有機材料を有する有機ＥＬ素子では、上記図１７に示したように、加熱前のＣｕＰｃ結晶性ピーク値に比べ、加熱後のＣｕＰｃ結晶性ピーク値は１．５倍と大きく変化しており、ＩＴＯとＣｕＰｃ、ＣｕＰｃと発光層の界面の密着性の低下が発生し、上記図１６に示したように、Ｖ−Ｉ特性が大きくシフトして輝度の低下や輝度ムラを発生させている。
【００７８】
また、本実施形態では、陽極２０としてのＩＴＯ膜の平均表面粗さＲａが２ｎｍ以下であり、１０点平均表面粗さＲｚが２０ｎｍ以下であることが好ましい。これらＲａ、ＲｚはＪＩＳ（日本工業規格）に定義されたものである。
【００７９】
陽極２０の上に位置する結晶性の有機材料としての正孔注入層３０を、結晶性が高く安定した膜に成膜するためには、陽極２０の表面粗度が重要となる。当該ＩＴＯ膜のＲａを２ｎｍ以下、Ｒｚを２０ｎｍ以下とすることは本発明者らの検討の結果によるものである。
【００８０】
次に、本実施形態について、以下のような具体例および本発明の比較例を参照して、より具体的に説明する。
【００８１】
発光層５０のホール輸送材料となる３級アミン化合物について、これら具体例および比較例に用いた化合物の化学構造式を図２、図３、図４に示す。これらのうち化合物１、２、７、８が本実施形態の化合物である。まず、これら図２〜図４に示す３級アミン化合物の製法等について述べる。
【００８２】
［化合物１］（図２参照）
化合物１：Ｎ，Ｎ’−ビス｛４−［（１−ナフチル）フェニルアミノ］フェニル）｝−Ｎ，Ｎ’−ジフェニルベンジジンの合成について。
【００８３】
アセトアニリド２０．３ｇ（０．１５モル）と１、４−ジヨードベンゼン５９．４ｇ（０．１８モル）、無水炭酸カリウム２２．１ｇ（０．１６モル）、銅粉２．１６ｇ（０．０３４モル）、ニトロベンゼン３５ｍｌを混合し、１９０〜２０５℃で１０時間反応させた。
【００８４】
反応生成物をトルエン２００ｍｌで抽出し、不溶分をろ別除去後、濃縮乾固した。これをカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／酢酸エチル＝６／１）、Ｎ−（４−ヨードフェニル）アセトアニリド３０．３ｇ（収率６０％）を得た。
【００８５】
続いて、Ｎ−（４−ヨードフェニル）アセトアニリド１０．８ｇ（０．０３２モル）、（１−ナフチル）フェニルアミン８．０ｇ（０．０３９モル）、無水炭酸カリウム５．５３ｇ（０．０４０モル）及び銅粉０．４５ｇ（０．００７モル）、ニトロベンゼン１０ｍｌを混合し、２００〜２１２℃で１５時間反応させた。
【００８６】
反応生成物をトルエン１００ｍｌで抽出し、不溶分をろ別除去後、濃縮してオイル状物とした。オイル状物はイソアミルアルコール６０ｍｌに溶解し、水１ｍｌ、８５％水酸化カリウム２．６４ｇ（０．０４０モル）を加え、１３０℃で加水分解した。
【００８７】
水蒸気蒸留でイソアミルアルコールを留去後、トルエン２５０ｍｌで抽出し、水洗、乾燥して濃縮した。濃縮物はカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ’−ジフェニル−Ｎ−（１−ナフチル）−１，４−フェニレンジアミン８．６ｇ（収率７０．０％）を得た。
【００８８】
さらに、Ｎ，Ｎ’−ジフェニル−Ｎ−（１−ナフチル）−１，４−フェニレンジアミン８．１１ｇ（０．０２１モル）、４，４’−ジヨードビフェニル４．０６ｇ（０．０１モル）、無水炭酸カリウム２．９０ｇ（０．０２１モル）、銅粉０．３２ｇ（０．００５モル）、ニトロベンゼン１０ｍｌを混合し、１９５〜２１０℃で２０時間反応させた。
【００８９】
反応生成物をトルエン１４０ｍｌで抽出し、不溶分をろ別、濃縮後、ｎ−ヘキサン１２０ｍｌを加えて粗結晶を取りだした。粗結晶は、カラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ’−ビス｛４−［（１−ナフチル）フェニルアミノ］フェニル）｝−Ｎ，Ｎ’−ジフェニルベンジジン４．２ｇ（収率；４５．０％）を得た。ガラス転移温度は１３６℃であった。
【００９０】
［化合物２］（図２参照）
化合物２：４，４’，４”−トリス［（１−ナフチル）フェニルアミノ］トリフェニルアミンの合成について。
【００９１】
２００ｍｌの反応容器に４，４’，４”−トリヨードトリフェニルアミン２８．７ｇ（０．０４６モル）とＮ−（１−ナフチル）−アニリン５０．４ｇ（０．２３モル）と無水炭酸カリウム４４．２ｇ（０．３２モル）、銅粉４．３２ｇ（０．０６８モル）とデカリン５０ｍｌを加え、Ａｒ雰囲気中、オイルバスの温度２２０℃で２４時間加熱した。
【００９２】
反応終了後、トルエンを２００ｍｌ加え、濾過して不溶物を取り除き、濾液を水で洗浄し硫酸ナトリウムで乾燥した。乾燥後、この濾液より溶媒を留去し、残査を４回シリカゲルカラム精製（展開溶媒：ｎ−ヘキサン／トルエン混合溶媒）し、ヘキサン／トルエン混合溶媒、酢酸エチルより再結晶を繰り返し、真空乾燥後、４，４’，４”−トリス［（１−ナフチル）フェニルアミノ］トリフェニルアミン２４．７ｇ（収率６０．０％）を得た。
【００９３】
昇華精製により、高純度な４，４’，４”−トリス［（１−ナフチル）フェニルアミノ］トリフェニルアミンを得た（昇華精製収率：７０．０％）。ガラス転移温度は１１０℃であった。
【００９４】
［化合物３］（図２参照）
化合物３：Ｎ，Ｎ’−ジ（１−ナフチル）−Ｎ，Ｎ’−ジフェニルベンジジンの合成について。
【００９５】
（１−ナフチル）フェニルアミン４．６ｇ（０．０２１モル）、４，４’−ジヨードビフェニル４．０６ｇ（０．０１モル）、無水炭酸カリウム２．９０ｇ（０．０２１モル）、銅粉０．３２ｇ（０．００５モル）、ニトロベンゼン１０ｍｌを混合し、１９５〜２１０℃で２０時間反応させた。
【００９６】
反応生成物をトルエン１４０ｍｌで抽出し、不溶分をろ別、濃縮後、ｎ−ヘキサン１２０ｍｌを加えて粗結晶を取りだした。粗結晶は、カラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ’−ジ（１−ナフチル）−Ｎ，Ｎ’−ジフェニルベンジジン２．６ｇ（収率；４５．０％）を得た。ガラス転移温度は９６℃であった。
【００９７】
［化合物４］（図３参照）
化合物４：４，４’−ビス｛４−［（１−ナフチル）フェニルアミノ］フェニル｝トリフェニルアミンの合成について。
【００９８】
２００ｍｌの反応容器に４，４’−ビス［４−ヨード）フェニル］トリフェニルアミン２９．９ｇ（０．０４６モル）と（１−ナフチル）フェニルアミン３０．７ｇ（０．１４モル）と無水炭酸カリウム２７．６ｇ（０．２０モル）、銅粉２．７３ｇ（０．０４３モル）とデカリン５０ｍｌを加え、Ａｒ雰囲気中、オイルバスの温度２２０℃で２４時間加熱した。
【００９９】
反応終了後、トルエンを２００ｍｌ加え、濾過して不溶物を取り除き、濾液を水で洗浄し硫酸ナトリウムで乾燥した。乾燥後この濾液より溶媒を留去し、残査を４回シリカゲルカラム精製（展開溶媒：ｎ−ヘキサン／トルエン混合溶媒）し、ヘキサン／トルエン混合溶媒、酢酸エチルより再結晶を繰り返し、真空乾燥後、４，４’−ビス｛４−［（１−ナフチル）フェニルアミノ］フェニル｝トリフェニルアミン２４．８ｇ（収率６５．０％）を得た。
【０１００】
昇華精製により、高純度な４，４’−ビス｛４−［（１−ナフチル）フェニルアミノ］フェニル｝トリフェニルアミンを得た（昇華精製収率：７５．０％）。ガラス転移温度は１３３℃であった。
【０１０１】
［化合物５］（図３参照）
化合物５：Ｎ，Ｎ’−ビス［４−（４’−ジフェニルアミノビフェニル）］−Ｎ，Ｎ’−ジフェニルベンジジンの合成について。
【０１０２】
アセトアニリド２０．３ｇ（０．１５モル）と４，４′−ジヨードビフェニル７３．１ｇ（０．１８モル）、無水炭酸カリウム２２．１ｇ（０．１６モル）、銅粉２．１６ｇ（０．０３４モル）、ニトロベンゼン３５ｍｌを混合し、１９０〜２０５℃で１０時間反応させた。
【０１０３】
反応生成物をトルエン２００ｍｌで抽出し、不溶分をろ別除去後、濃縮乾固した。これをカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／酢酸エチル＝６／１）、Ｎ−［４−（４’−ヨードビフェニル）］アセトアニリド４０．２ｇ（収率６４．８％）を得た。
【０１０４】
続いてＮ−［４−（４’−ヨードビフェニル）］アセトアニリド１３．２ｇ（０．０３２モル）、ジフェニルアミン６．６０ｇ（０．０３９モル）、無水炭酸カリウム５．５３ｇ（０．０４０モル）及び銅粉０．４５ｇ（０．００７モル）、ニトロベンゼン１０ｍｌを混合し、２００〜２１２℃で１５時間反応させた。
【０１０５】
反応生成物をトルエン１００ｍｌで抽出し、不溶分をろ別除去後、濃縮してオイル状物とした。オイル状物はイソアミルアルコール６０ｍｌに溶解し、水１ｍｌ、８５％水酸化カリウム２．６４ｇ（０．０４０モル）を加え、１３０℃で加水分解した。水蒸気蒸留でイソアミルアルコールを留去後、トルエン２５０ｍｌで抽出し、水洗、乾燥して濃縮した。
【０１０６】
濃縮物はカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ，Ｎ’−トリフェニルベンジジン１０．５ｇ（収率７２．２％）を得た。
【０１０７】
更に、Ｎ，Ｎ，Ｎ’−トリフェニルベンジジン８．６６ｇ（０．０２１モル）、４，４’−ジヨードビフェニル４．０６ｇ（０．０１モル）、無水炭酸カリウム２．９０ｇ（０．０２１モル）、銅粉０．３２ｇ（０．００５モル）、ニトロベンゼン１０ｍｌを混合し、１９５〜２１０℃で２０時間反応させた。
【０１０８】
反応生成物をトルエン１４０ｍｌで抽出し、不溶分をろ別、濃縮後、ｎ−ヘキサン１２０ｍｌを加えて粗結晶を取りだした。粗結晶は、カラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ’−ビス［４−（４’−ジフェニルアミノビフェニル）］−Ｎ，Ｎ’−ジフェニルベンジジン４．７３ｇ（収率；４８．５％）を得た。ガラス転移温度は１４３℃であった。
【０１０９】
［化合物６］（図３参照）
化合物６：９，９−ビス｛４−［４’−（４−ジフェニルアミノフェニル）トリフェニルアミノ］｝フルオレンの合成について。
【０１１０】
アセトアニリド２０．３ｇ（０．１５モル）と４，４’−ジヨードビフェニル７３．１ｇ（０．１８モル）、無水炭酸カリウム２２．１ｇ（０．１６モル）、銅粉２．１６ｇ（０．０３４モル）、ニトロベンゼン３５ｍｌを混合し、１９０〜２０５℃で１０時間反応させた。
【０１１１】
反応生成物をトルエン２００ｍｌで抽出し、不溶分をろ別除去後、濃縮乾固した。これをカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／酢酸エチル＝６／１）、Ｎ−（４’−ヨード−４−ビフェニル）アセトアニリド４０．２ｇ（収率６４．８％）を得た。
【０１１２】
続いて、Ｎ−（４’−ヨード−４−ビフェニル）アセトアニリド１３．２ｇ（０．０３２モル）、ジフェニルアミン６．６０ｇ（０．０３９モル）、無水炭酸カリウム５．５３ｇ（０．０４０モル）及び銅粉０．４５ｇ（０．００７モル）、ニトロベンゼン１０ｍｌを混合し、２００〜２１２℃で１５時間反応させた。
【０１１３】
反応生成物をトルエン１００ｍｌで抽出し、不溶分をろ別除去後、濃縮してオイル状物とした。オイル状物はイソアミルアルコール６０ｍｌに溶解し、水１ｍｌ、８５％水酸化カリウム２．６４ｇ（０．０４０モル）を加え、１３０℃で加水分解した。水蒸気蒸留でイソアミルアルコールを留去後、トルエン２５０ｍｌで抽出し、水洗、乾燥して濃縮した。
【０１１４】
濃縮物はカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ，Ｎ’−トリフェニルベンジジン１０．５ｇ（収率７２．２％）を得た。
【０１１５】
更に、Ｎ，Ｎ，Ｎ’−トリフェニルベンジジン８．６６ｇ（０．０２１モル）、９，９−ビス−（４−ヨードフェニル）フルオレン５．７ｇ（０．０１モル）、無水炭酸カリウム２．９０ｇ（０．０２１モル）、銅粉０．３２ｇ（０．００５モル）、ニトロベンゼン１０ｍｌを混合し、１９５〜２１０℃で２０時間反応させた。
【０１１６】
反応生成物をトルエン１４０ｍｌで抽出し、不溶分をろ別、濃縮後、ｎ−ヘキサン１２０ｍｌを加えて粗結晶を取りだした。粗結晶は、カラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、９，９−ビス｛４−［４’−（４−ジフェニルアミノフェニル）トリフェニルアミノ］｝フルオレン５．７ｇ（収率；５０．０％）を得た。ガラス転移温度は１６１℃であった。
【０１１７】
［化合物７］（図４参照）
化合物７：Ｎ，Ｎ’−ビス｛４−［（１−ナフチル）フェニルアミノ］フェニル）｝−Ｎ，Ｎ’−ジフェニルエチレンジアミンの合成について。
【０１１８】
アセトアニリド２０．３ｇ（０．１５モル）と１、４−ジヨードベンゼン５９．４ｇ（０．１８モル）、無水炭酸カリウム２２．１ｇ（０．１６モル）、銅粉２．１６ｇ（０．０３４モル）、ニトロベンゼン３５ｍｌを混合し、１９０〜２０５℃で１０時間反応させた。
【０１１９】
反応生成物をトルエン２００ｍｌで抽出し、不溶分をろ別除去後、濃縮乾固した。これをカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／酢酸エチル＝６／１）、Ｎ−（４−ヨードフェニル）アセトアニリド３０．３ｇ（収率６０％）を得た。
【０１２０】
続いて、Ｎ−（４−ヨードフェニル）アセトアニリド１０．８ｇ（０．０３２モル）、（１−ナフチル）フェニルアミン８．０ｇ（０．０３９モル）、無水炭酸カリウム５．５３ｇ（０．０４０モル）及び銅粉０．４５ｇ（０．００７モル）、ニトロベンゼン１０ｍｌを混合し、２００〜２１２℃で１５時間反応させた。
【０１２１】
反応生成物をトルエン１００ｍｌで抽出し、不溶分をろ別除去後、濃縮してオイル状物とした。オイル状物はイソアミルアルコール６０ｍｌに溶解し、水１ｍｌ、８５％水酸化カリウム２．６４ｇ（０．０４０モル）を加え、１３０℃で加水分解した。
【０１２２】
水蒸気蒸留でイソアミルアルコールを留去後、トルエン２５０ｍｌで抽出し、水洗、乾燥して濃縮した。濃縮物はカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ’−ジフェニル−Ｎ−（１−ナフチル）−１，４−フェニレンジアミン８．６ｇ（収率７０．０％）を得た。
【０１２３】
さらに、Ｎ，Ｎ’−ジフェニル−Ｎ−（１−ナフチル）−１，４−フェニレンジアミン８．１１ｇ（０．０２１モル）、４，４’−ジヨードエチレン２．８２ｇ（０．０１モル）、無水炭酸カリウム２．９０ｇ（０．０２１モル）、銅粉０．３２ｇ（０．００５モル）、ニトロベンゼン１０ｍｌを混合し、１９５〜２１０℃で２０時間反応させた。
【０１２４】
反応生成物をトルエン１４０ｍｌで抽出し、不溶分をろ別、濃縮後、ｎ−ヘキサン１２０ｍｌを加えて粗結晶を取りだした。粗結晶は、カラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ’−ビス｛４−［（１−ナフチル）フェニルアミノ］フェニル）｝−Ｎ，Ｎ’−ジフェニルエチレンジアミン４．１ｇ（収率；４５．０％）を得た。ガラス転移温度は１００℃以上であった。
【０１２５】
［化合物８］（図４参照）
化合物８：９，９−ビス｛４−｛４’−［（１−ナフチル）フェニルアミノ］トリフェニルアミノ｝｝フルオレンの合成について。
【０１２６】
アセトアニリド２０．３ｇ（０．１５モル）と１，４’−ジヨードベンゼン５９．４ｇ（０．１８モル）、無水炭酸カリウム２２．１ｇ（０．１６モル）、銅粉２．１６ｇ（０．０３４モル）、ニトロベンゼン３５ｍｌを混合し、１９０〜２０５℃で１０時間反応させた。
【０１２７】
反応生成物をトルエン２００ｍｌで抽出し、不溶分をろ別除去後、濃縮乾固した。これをカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／酢酸エチル＝６／１）、Ｎ−（４−ヨードフェニル）アセトアニリド３０．３ｇ（収率６０％）を得た。
【０１２８】
続いて、Ｎ−（４−ヨードフェニル）アセトアニリド１０．８ｇ（０．０３２モル）、（１−ナフチル）フェニルアミン８．０ｇ（０．０３９モル）、無水炭酸カリウム５．５３ｇ（０．０４０モル）及び銅粉０．４５ｇ（０．００７モル）、ニトロベンゼン１０ｍｌを混合し、２００〜２１２℃で１５時間反応させた。
【０１２９】
反応生成物をトルエン１００ｍｌで抽出し、不溶分をろ別除去後、濃縮してオイル状物とした。オイル状物はイソアミルアルコール６０ｍｌに溶解し、水１ｍｌ、８５％水酸化カリウム２．６４ｇ（０．０４０モル）を加え、１３０℃で加水分解した。水蒸気蒸留でイソアミルアルコールを留去後、トルエン２５０ｍｌで抽出し、水洗、乾燥して濃縮した。
【０１３０】
濃縮物はカラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、Ｎ，Ｎ’−ジフェニル−Ｎ−（１−ナフチル）−１，４−フェニレンジアミン８．６ｇ（収率７０．０％）を得た。
【０１３１】
更に、Ｎ，Ｎ’−ジフェニル−Ｎ−（１−ナフチル）−１，４−フェニレンジアミン８．１１ｇ（０．０２１モル）、９，９−ビス−（４−ヨードフェニル）フルオレン５．７ｇ（０．０１モル）、無水炭酸カリウム２．９０ｇ（０．０２１モル）、銅粉０．３２ｇ（０．００５モル）、ニトロベンゼン１０ｍｌを混合し、１９５〜２１０℃で２０時間反応させた。
【０１３２】
反応生成物をトルエン１４０ｍｌで抽出し、不溶分をろ別、濃縮後、ｎ−ヘキサン１２０ｍｌを加えて粗結晶を取りだした。粗結晶は、カラムクロマトにより精製して（担体；シリカゲル、溶離液；トルエン／ｎ−ヘキサン＝１／２）、９，９−ビス｛４−｛４’−［（１−ナフチル）フェニルアミノ］トリフェニルアミノ｝｝フルオレン５．４３ｇ（収率；５０．０％）を得た。ガラス転移温度は１００℃以上であった。
【０１３３】
このような図２〜図４に示す３級アミン化合物を用いて、以下の具体例および比較例を行った。また、これら各例における耐久試験の結果は、図６に示されている。
【０１３４】
（具体例１）
ガラス基板１０上に陽極２０としてＩＴＯ膜（透明電極）を形成し、その表面を研磨して、Ｒａを約１ｎｍ、Ｒｚを約１０ｎｍとした。陽極２０の上に、結晶性を有する有機材料としてのＣｕＰｃからなる正孔注入層３０を１０ｎｍ形成した。
【０１３５】
正孔注入層３０の上に、正孔輸送層４０として３級アミン化合物を２０ｎｍ、発光層５０として３級アミン化合物と図５に示される電子輸送性材料及びルブレンを６０：２０：３の重量比により２０ｎｍ形成した。
【０１３６】
電子輸送層６０としてトリス（８−キノリノラト）アルミニウムを２０ｎｍ、電子注入層７０にＬｉＦ、陰極８０にＡｌを順次成膜し、乾燥窒素雰囲気内で封止缶で密封し有機ＥＬ素子を得た。３級アミン化合物としては、上記化合物１（図２参照）で示されるものを使用した。
【０１３７】
この素子を、８５℃環境下において初期輝度４００ｃｄ／ｍ^２、１／６４デューティー駆動で耐久試験を行った。その結果は図６に示すとおりであった。さらに、１００℃環境下での保存試験においては、５００ｈｒを超えても顕著なダークスポットの発生はなかった。
【０１３８】
（具体例２）
上記具体例１の素子構造において、３級アミン化合物として上記化合物２（図２参照）で示されるようなスターバースト系トリフェニルアミン誘導体を使用し、素子を作製した。
【０１３９】
この素子を、８５℃環境下において初期輝度４００ｃｄ／ｍ^２、１／６４デューティー駆動で耐久試験を行った。その結果は図６に示すとおりであった。さらに、１００℃環境下での保存試験においては、５００ｈｒを超えても顕著なダークスポットの発生はなかった。
【０１４０】
（比較例１）
上記具体例１の素子構造において、３級アミン化合物として上記化合物３（図２参照）、化合物４（図３参照）、化合物５（図３参照）で示されるようなトリフェニルアミン誘導体を使用し、素子をそれぞれ作製した。
【０１４１】
これらの素子を、８５℃環境下において初期輝度４００ｃｄ／ｍ^２、１／６４デューティー駆動で耐久試験を行った。その結果は図６に示すとおりであった。また、１００℃環境下での保存試験においては、化合物３でのみダークスポットが発生し、化合物４及び５については５００ｈｒを超えても顕著なダークスポットの発生はなかった。
【０１４２】
（比較例２）
上記具体例１の素子構造において、３級アミン化合物として上記化合物６（図３参照）で示されるようなトリフェニルアミン誘導体を使用し、素子をそれぞれ作製した。
【０１４３】
これらの素子を、８５℃環境化において初期輝度４００ｃｄ／ｍ^２、１／６４デューティー駆動で耐久試験を行った。その結果は図６に示すとおりであった。また、１００℃環境下での保存試験においては５００ｈｒを超えても顕著なダークスポットの発生はなかった。
【０１４４】
以上の具体例１、２および比較例１、２の結果を、各３級アミン化合物材料の物性値を含めて、図７の表にまとめた。
【０１４５】
図７において、輝度寿命については図６と同様に、初期を１として規格化し、耐久試験後４００ｈｒでの規格化輝度で示している。高温保存については、１００℃での保存試験によりダークスポットが発生したものについては×、発生しなかったものについては○としている。
【０１４６】
Ｔｇはガラス転移温度を示す。また、分子構造欄の数値は、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または上記構造式（１）（化学式１９参照）で示される基が存在する箇所の総数を示している。
【０１４７】
この結果から、輝度低下については分子構造との相関が確認できる。特に、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または上記構造式（１）で示される基が存在する箇所の総数が、１箇所もしくは０の場合において輝度寿命がよい。
【０１４８】
高温保存については、３級アミン化合物材料のガラス転移温度で理解できる。すなわち、環境温度（保存試験温度）よりもガラス転移温度が低いものの場合、ダークスポットが発生する。
【０１４９】
ここまでの結果から、化合物１や２のような３級アミン化合物材料を発光層３のホスト材料として使用することで、輝度低下の抑制と耐熱性とを両立できることが判明した。
【０１５０】
なお、上記具体例１の素子構造において、３級アミン化合物として上記化合物７、８（図４参照）で示されるような３級アミン化合物を使用し、素子を作製し、同様に、耐久試験および保存試験を行ったところ、具体例１と同様の結果が得られ、輝度低下の抑制と耐熱性とが両立できた。
【０１５１】
［輝度低下抑制の推定メカニズム］
ここで、発光層５０を混合ホスト層すなわち３級アミン化合物からなるホール輸送性材料と電子輸送性材料と発光添加材料とを混合してなる層とした本実施形態の有機ＥＬ素子において、化合物１〜３のような３級アミン化合物を用いた場合に、輝度低下が抑制されるメカニズムは、次のように推定される。
【０１５２】
発光層が単一ホスト材料の場合には下記式によって発光すると考えられる。
【０１５３】
【化２５】
Ｈ^＋＋Ｈ⁻＋Ｄ →（Ｈ＊＋Ｄ）→ Ｈ＋Ｄ＊ → Ｈ＋Ｄ
ここで、Ｈは電荷（ホールまたは電子）輸送材料分子、Ｄは発光添加材料分子、＊は一重項励起状態を示す。
【０１５４】
ホスト材料が単一のため、ホスト材料分子の各極性イオンＨ^＋、Ｈ⁻からゲスト材料分子Ｄに電荷移動し発光するか、もしくはホスト材料分子の励起状態Ｈ＊からゲスト材料分子Ｄに電荷移動する結果、ゲスト分子が励起状態Ｄ＊になり発光する。
【０１５５】
一方、発光層が混合ホスト層の場合には下記式によって発光すると考えられる。
【０１５６】
【化２６】
Ｈａ^＋＋Ｈｂ⁻＋Ｄ → Ｈａ＋Ｈｂ＋Ｄ＊ → Ｈａ＋Ｈｂ＋Ｄ
ここで、Ｈａ、Ｈｂは電荷輸送材料分子であり一方がホール輸送性、他方が電子輸送性である。また、Ｄは発光添加材料分子、＊は一重項励起状態を示す。
【０１５７】
ホスト材料であるＨａとＨｂはエネルギーバンドのずれが非常に大きいため、相互の電荷移動は発生しない。このためホスト材料は励起状態になることなく、ゲスト材料分子Ｄに電荷移動する結果、ゲスト分子が励起状態Ｄ＊になり発光する。
【０１５８】
このように、混合ホスト層では、ホスト分子Ｈａ、Ｈｂは励起状態にならないので、ホスト材料の劣化が起こりにくい。このことが、混合ホスト層としたことによる輝度寿命向上の一つの原因と推定される。
【０１５９】
しかしながら、発光層を混合ホスト層とした場合は、単一ホストの場合よりも、低減されてはいるものの、ホストの励起は起こっていると推定している。この混合ホスト層内で起こるホール輸送性材料の励起については、詳細メカニズムは明確になっていないが、分子構造に依存すると考えられる。
【０１６０】
［ダークスポットの原因検討］
図８は、上記化合物３を使用した素子について、１２０℃で５００ｈｒ保存した後の断面形状を走査電子顕微鏡を用いて観察した写真に基づいて模式的に表した図である。
【０１６１】
観察結果から、ホール輸送材料が存在する層（正孔輸送層４０、発光層５０）が部分的に空洞化していることが判明した。空洞化部分Ｋ１では、電流が流れないため非発光領域となり、ダークスポットとして認識されると考えられる。これは、環境温度が材料のガラス転移温度よりも高いため、体積変化を伴う結晶化が進行したためであると推定される。
【０１６２】
上記具体例１、２および比較例１、２では、発光層５０のホスト材料としての電子輸送性材料が、上記図５に示される化合物であった。この電子輸送性材料以外でも、ホール輸送性材料の分子構造に依存した輝度低下の存在を確認するため、下記の比較実験を行った。
【０１６３】
（比較例３）
ガラス基板１０上に陽極２０としてＩＴＯ膜（透明電極）を形成し、アルゴンと酸素混合のプラズマによる表面処理を施した後、正孔注入層３０としてＣｕＰｃを膜厚１０ｎｍ成膜した。
【０１６４】
その上に、正孔輸送層４０として上記化合物３（図２参照）を５０ｎｍ、発光層５０としてこの化合物３とトリス（８−キノリノラト）アルミニウム及びジメチルキナクリドンを５０：５０：１の重量比により２０ｎｍ成膜した。
【０１６５】
その上に、電子輸送層６０としてトリス（８−キノリノラト）アルミニウムを２０ｎｍ、電子注入層７０にＬｉＦ、陰極８０にＡｌを順次成膜し、乾燥窒素雰囲気内で封止缶で密封し有機ＥＬ素子を得た。
【０１６６】
この素子を、８５℃環境下において初期輝度２４００ｃｄ／ｍ^２、直流駆動で耐久試験を行ったところ、輝度半減寿命は７８時間であった。
【０１６７】
（比較例４）
ガラス基板１０上に陽極２０としてＩＴＯ膜（透明電極）を形成し、アルゴンと酸素混合のプラズマによる表面処理を施した後、正孔注入層３０としてＣｕＰｃを膜厚１０ｎｍ成膜した。
【０１６８】
その上に、正孔輸送層４０として上記化合物５（図２参照）を５０ｎｍ、発光層５０としてこの化合物５とトリス（８−キノリノラト）アルミニウム及びジメチルキナクリドンを５０：５０：１の重量比により２０ｎｍ成膜した。
【０１６９】
その上に、電子輸送層６０としてトリス（８−キノリノラト）アルミニウムを２０ｎｍ、電子注入層７０にＬｉＦ、陰極８０にＡｌを順次成膜し、乾燥窒素雰囲気内で封止缶で密封し有機ＥＬ素子を得た。
【０１７０】
この素子を、８５℃環境下において初期輝度２４００ｃｄ／ｍ^２、直流駆動で耐久試験を行ったところ、輝度半減寿命は２５時間であった。
【０１７１】
これら比較例３、４の結果を、図９の表にまとめた。ここで、輝度寿命については輝度半減時間で示している。分子構造欄の数値は、分子構造内の窒素原子の間に２個以上のフェニレン基、脂肪族基または上記構造式（１）（化学式１９参照）で示される基が存在する箇所の総数を示している。
【０１７２】
この結果から、電子輸送材料及び発光添加材料が異なる場合においても、輝度低下がホール輸送材料の分子構造に依存していることが確認された。
【０１７３】
（比較例５）
上記混合ホスト層での輝度低下の推定メカニズムによれば、混合ホスト層を用いない構造では、ホール輸送材料の分子構造に依存した差異は発現しないはずである。このため、混合ホスト層を用いずに単一ホスト層の発光層構造において検証を行った。
【０１７４】
ガラス基板１０上に陽極２０としてＩＴＯ膜（透明電極）を形成し、アルゴンと酸素混合のプラズマによる表面処理を施した後、正孔注入層３０としてＣｕＰｃを膜厚１０ｎｍ成膜した。
【０１７５】
その上に、正孔輸送層４０として３級アミン化合物を２０ｎｍ、発光層５０として上記図５に示される電子輸送性材料及びルブレンを２０：１の重量比により４０ｎｍ、電子輸送層６０としてトリス（８−キノリノラト）アルミニウムを２０ｎｍ、電子注入層７０にＬｉＦ、陰極８０にＡｌを順次成膜し、乾燥窒素雰囲気内で封止缶で密封し有機ＥＬ素子を得た。
【０１７６】
ここで、３級アミン化合物としては、上記化合物１、２、３、４、５（図２、図３参照）を適用した。この素子を、８５℃環境化において初期輝度４００ｃｄ／ｍ２ １／６４デューティー駆動で耐久試験を行った。その結果は、図１０の表に示される。上記図７の表と同様に輝度寿命については耐久試験後４００ｈｒでの規格化輝度で示している。
【０１７７】
この結果から、混合ホスト層に見られたホール輸送材料の分子構造との相関は見られない。このことから、本発明における上記した課題が混合ホスト層固有の問題であり、この問題を睨んで発明に至ったことが確認された。
【０１７８】
以上のように、本実施形態の３級アミン化合物を、発光層５０を構成するホール輸送性材料に用いることにより、従来に比べて大幅な輝度寿命の向上と１００℃以上の耐熱性の確保との両立を図れることが確認された。
【０１７９】
［ＣｕＰｃ結晶性ピークについて］
次に、本実施形態の好ましい形態として、正孔注入層３０を構成するＣｕＰｃにおいて、有機ＥＬ素子Ｓ１の使用温度（例えば−４０℃〜１２０℃）内の加熱によるＣｕＰｃ結晶性ピーク（２θ＝６．６８°）値の変化量が、加熱前の当該ＣｕＰｃ結晶性ピークの±２５％以内となるようにした根拠について、そのようなＣｕＰｃ膜３０の製造方法等も含めて具体的に述べる。
【０１８０】
［第１の製造方法］
ガラス基板１０の上に、陽極としてのＩＴＯ膜２０をスパッタ等により成膜し、ＩＴＯ膜２０の表面を３００℃に加熱しながら紫外線照射した。以下、このＩＴＯ膜２０に対する処理をＵＶ−３００℃処理という。
【０１８１】
このＵＶ−３００℃処理を行った後に、正孔注入層としてのＣｕＰｃ膜３０を蒸着法により材料加熱温度４２０℃で膜厚１０ｎｍにて成膜した。その後は、上記具体例１と同様に、正孔輸送層４０として３級アミン化合物である化合物１（図２参照）を２０ｎｍ、発光層５０として化合物１と図５に示される電子輸送性材料及びルブレンを６０：２０：３の重量比により２０ｎｍ形成した。
【０１８２】
さらに、電子輸送層６０としてトリス（８−キノリノラト）アルミニウムを２０ｎｍ、電子注入層７０にＬｉＦ、陰極８０にＡｌを順次成膜し、上記図１に示したような有機ＥＬ素子を得た。
【０１８３】
ここで、このＵＶ−３００℃処理を行ったＩＴＯ膜２０にＣｕＰｃ膜３０を成膜したものについて、「手段」の欄にて述べたのと同様に、加速高温放置（１２０℃、２ｈｒ）を行う前と後とで、Ｘ線回折分析を行った。
【０１８４】
その結果、２θ＝６．６８°に発生しているＣｕＰｃ結晶性ピークは、放置処理前の値に比べて放置処理後の値の比は１．０２と非常に小さいことが確認された。言い換えれば、本製造方法の成膜時のＣｕＰｃ膜３０の結晶性は、非常に高く安定であったことを示す。
【０１８５】
さらに、できあがった有機ＥＬ素子を封止缶で密封した密封素子を、１２０℃、２ｈｒの上記加速高温放置の条件で確認した結果、Ｖ−Ｉ特性のシフトはほとんど無く、輝度低下や輝度ムラは見られなかった。
【０１８６】
つまり、本第１の製造方法により製造された有機ＥＬ素子は、使用温度内においてＣｕＰｃと発光層の密着性が向上し、Ｖ−Ｉ特性のシフトはほとんど無く、輝度低下や輝度ムラのない特性を実現することができた。
【０１８７】
このような効果は、本製造方法におけるＵＶ−３００℃処理によるものであり、当該処理による効果の実現メカニズムについて、より詳細に説明する。
【０１８８】
陽極としてのＩＴＯ膜２０から、正孔注入層としてのＣｕＰｃ膜３０に効率良く正孔が注入されるためには、ＩＴＯ膜表面の洗浄処理は重要であることは以前から公知である。しかし、一般的には洗浄後のＩＴＯ膜表面のイオン化ポテンシャル（Ｉｐ）で評価されており、本発明者等は、正孔注入特性等を鑑みてＩＴＯ膜２０の洗浄処理直後にＩＴＯ膜２０のＩｐが５．５ｅＶ以下であれば問題無しという判断をしていた。
【０１８９】
しかし、本発明者等の検討では、アルゴンと酸素（比率１：１）のプラズマ洗浄処理を５分間行った時のＩＴＯ膜２０のＩｐは５．４５ｅＶ、ＵＶ処理のみを２０分間行った時のＩｐは５．５ｅＶ、上記ＵＶ−３００℃処理を２０分間行った時のＩｐは５．４６ｅＶと大きな差は見られなかった。
【０１９０】
それにもかかわらず、ＵＶ−３００℃処理を行った素子のみが、高温放置後のＶ−Ｉ特性シフトすなわち輝度低下や輝度ムラが発生しないという結果を得た。つまり、ＩＴＯ上に成膜される結晶性有機材料の結晶性はＩＴＯ膜２０のＩｐのみによって決定されるのではなく、他の要因も存在することを示している。
【０１９１】
そこで、ＵＶ−３００℃処理では、加熱処理が関係していることから、ＩＴＯ表面の水分に着目し、昇温脱離法（ｔｈｅｒｍａｌ ｄｅｓｏｒｐｔｉｏｎ ｍｅｔｈｏｄ、以下、ＴＤＳ法という）により、各温度での水分発生量すなわちＩＴＯ膜２０の表面からの水分離脱量を測定した。
【０１９２】
図１１は、ガラス基板１０の上にＩＴＯ膜２０を成膜した直後のＴＤＳ法による測定結果である。このＴＤＳスペクトルは、分子量つまりＴＤＳ法で言うＭ／ｚが１８であるＨ_２Ｏまたは１７であるＯＨのスペクトルを測定したものである。
【０１９３】
図１１に示す結果より、７０℃と３３０℃に水分離脱のピークがあることがわかる。前者はＩＴＯ膜２０に表面に物理的に吸着している吸着水として存在する分であり、後者はＩＴＯ膜２０の表面にてＩＴＯと化学的に結合している結合水として存在する水分であると考えられる。従って、ＩＴＯ膜２０の表面の結合水がＣｕＰｃ膜３０の成膜時における結晶性を決める一要因ではないかと考えられる。
【０１９４】
実際に、ガラス基板１０の上にＩＴＯ膜２０を成膜したものを、窒素雰囲気中で３００℃の温度にて加熱処理した場合のＴＤＳスペクトルを図１２に示す。この加熱処理を行わない場合すなわち上記図１１に示すＴＤＳスペクトルと比較して、３３０℃のピーク値が５０％程度まで低減している。さらに、この３００℃の加熱処理を真空中で行った場合のＴＤＳスペクトルを図１３に示す。この場合には、３３０℃のピークはほとんど認められない。
【０１９５】
これら窒素雰囲気中または真空中での３００℃での加熱処理により作成した有機ＥＬ素子を、封止缶で密封した密封素子を、１２０℃、２ｈｒの上記加速高温放置の条件で確認した結果、Ｖ−Ｉ特性のシフトはほとんど無く、輝度低下や輝度ムラは見られなかった。
【０１９６】
以上のことから、基板１０上にＩＴＯ膜２０を形成し、ＣｕＰｃ膜３０等の結晶性を示す有機材料をＩＴＯ膜２０の上に成膜する有機ＥＬ素子の製造方法においては、当該有機材料を成膜する前に、ＩＴＯ膜２０の表面の結合水を脱離処理することが有効であることがわかった。
【０１９７】
それによって、結晶性を有する有機材料の下地となるＩＴＯ膜２０の表面において、吸着水とともに結合水を低減することができるため、成膜された有機材料の結晶性を高いものにすることができ、使用温度内において良好な輝度特性を実現することができる。
【０１９８】
ここで、上記図１２に示したように、脱離処理後のＩＴＯ膜２０の表面における水分起因のＴＤＳスペクトルにおいて、３３０℃付近の結合水ピーク値が、脱離処理前のＩＴＯ膜２０の表面における結合水ピーク値と比較して５０％以内となるようにすることが好ましい。
【０１９９】
さらには、上記図１３に示したように、脱離処理後のＩＴＯ膜２０の表面における水分起因のＴＤＳスペクトルにおいて、３３０℃付近の結合水ピークが無くなるようにすれば、いっそう好ましい。
【０２００】
なお、ＩＴＯ膜２０の表面に存在する結合水を５０％以内程度にまで低減するには、ＣｕＰｃ膜３０等の結晶性の有機材料をＩＴＯ膜２０の上に成膜する前に、ＩＴＯ膜２０の加熱処理温度を２５０℃以上とすることが好ましい。
【０２０１】
また、本第１の製造方法によれば、基板１０上にインジウム−錫の酸化物からなるＩＴＯ膜２０を形成し、ＣｕＰｃ膜３０等の結晶性を示す有機材料を、ＩＴＯ膜の２０上に成膜してなる有機ＥＬ素子であって、ＩＴＯ膜２０は、その表面におけるＴＤＳ法により測定された水分起因のスペクトルにおける３３０℃付近の結合水ピークが無いものであることを特徴とした有機ＥＬ素子Ｓ１が提供される。
【０２０２】
そして、それによれば、使用温度内において、陽極ＩＴＯからの正孔注入特性が安定し、輝度低下や輝度ムラが抑制された、安定した輝度特性を実現することができる。
【０２０３】
［第２の製造方法］
上記した本実施形態の第１の製造方法では、結晶性を示す有機材料であるＣｕＰｃ膜３０等の下地となるＩＴＯ膜２０を加熱処理することにより、ＣｕＰｃ膜３０の結晶性を高めるようにしていた。
【０２０４】
本実施形態の第２の製造方法では、ＣｕＰｃ膜３０の成膜時の材料温度に着目した。ガラス基板１０の上に、陽極としてのＩＴＯ膜２０をスパッタ等により成膜する。このＩＴＯ膜付きガラス基板において、上述したアルゴンと酸素のプラズマ洗浄処理を行い、ＩＴＯ膜２０の上に、正孔注入層としてのＣｕＰｃ膜３０を蒸着法により材料加熱温度４２０℃で成膜した。これを、４２０℃成膜品ということにする。
【０２０５】
一方、ＩＴＯ膜付きガラス基板において、上述したアルゴンと酸素のプラズマ洗浄処理を行い、ＩＴＯ膜２０の上に、正孔注入層としてのＣｕＰｃ膜３０を蒸着法により材料加熱温度５２０℃で成膜した。これを、５２０℃成膜品ということにする。
【０２０６】
その後、４２０℃成膜品および５２０℃成膜品それぞれにおいて、ＣｕＰｃ膜３０の上に、上記第１の製造方法（つまり、上記具体例１）と同様、正孔輸送層４０、化合物１を用いた混合ホスト層である発光層５０、電子輸送層６０、電子注入層７０、陰極８０を順次成膜し、有機ＥＬ素子Ｓ１を製造した。
【０２０７】
ここで、４２０℃成膜品および５２０℃成膜品それぞれについて、上記した加速高温放置（１２０℃、２ｈｒ）を行う前と後とで、Ｘ線回折分析によるＣｕＰｃ結晶ピーク値の比を調べた。また、素子を封止缶で密封して上記した加速高温放置の前後におけるＶ−Ｉ特性のシフトを調べた。
【０２０８】
４２０℃成膜品の場合、「手段」の欄にて述べた試作品と同様に、ＣｕＰｃ結晶性ピークの比は約１．５（上記図１７参照）でシフト量は約３Ｖ（上記図１６参照）であったのに対し、５２０℃成膜品の場合、ＣｕＰｃ結晶性ピークの比が約１．１５でシフト量は約１Ｖと良好であった。
【０２０９】
さらに、第２の製造方法の他の例を示す。ガラス基板１０の上に、陽極としてのＩＴＯ膜２０をスパッタ等により成膜した。その表面を研磨して、Ｒａは約１ｎｍ、Ｒｚは約１０ｎｍとした。このＩＴＯ膜付きガラス基板におけるＩＴＯ膜２０の表面を１５０℃に加熱しながら紫外線照射した（ＵＶ−１５０℃処理）。
【０２１０】
続いて、ＩＴＯ膜２０の上に、正孔注入層としてのＣｕＰｃ膜３０を蒸着法により材料加熱温度５２０℃で成膜する。その後は、上記具体例１と同様に、正孔輸送層４０、化合物１を用いた混合ホスト層である発光層５０、電子輸送層６０、電子注入層７０、陰極８０を順次成膜し、乾燥窒素雰囲気内で封止缶で封止した有機ＥＬ素子を得た。
【０２１１】
このようにして得られた有機ＥＬ素子を封止缶で密封した密封素子を、１２０℃、２ｈｒの上記加速高温放置の条件で確認した結果、Ｖ−Ｉ特性のシフトは小さく、輝度低下や輝度ムラは見られなかった。ちなみに、加速高温放置の前後におけるＶ−Ｉ特性のシフト量は１．２Ｖであり、ＣｕＰｃ結晶性ピークの比は１．２１であった。
【０２１２】
本第２の製造方法のもう一つの他の例では、上記同様に形成したＩＴＯ膜付きガラス基板におけるＩＴＯ膜２０の表面を常温にて紫外線照射した（ＵＶ−常温処理）。続いて、ＩＴＯ膜２０の上に、正孔注入層としてのＣｕＰｃ膜３０を蒸着法により材料加熱温度５２０℃で成膜した。
【０２１３】
その後、上記同様、上層４０〜８０を順次成膜して得られた有機ＥＬ素子を封止缶で密封した密封素子を、１２０℃、２ｈｒの上記加速高温放置の条件で確認した。
【０２１４】
その結果、Ｖ−Ｉ特性のシフトは小さく、輝度低下や輝度ムラは見られなかった。本例では、加速高温放置の前後におけるＶ−Ｉ特性のシフト量は１．５Ｖであり、ＣｕＰｃ結晶性ピークの比は１．２１であった。
【０２１５】
このようにＣｕＰｃ膜３０の成膜温度を５２０℃とする第２の製造方法によれば、ＩＴＯ膜２０の表面処理方法に依らず、上記第１の製造方法で採用したＵＶ−３００℃処理を行わなくても、必要特性を満足する有機ＥＬ素子が得られる。このことは、ＣｕＰｃの結晶性に影響する因子がＩＴＯ表面のみならず、成膜方法にも存在することを示すものである。
【０２１６】
つまり、本実施形態の第２の製造方法によっても、ＣｕＰｃ膜３０の結晶性が非常に高く安定であり、それにより製造された有機ＥＬ素子Ｓ１は、使用温度内において良好な輝度特性を実現することができる。
【０２１７】
［第３の製造方法］
本実施形態の第３の製造方法は、結晶性を示す有機材料の膜であるＣｕＰｃ膜３０をＩＴＯ膜２０の上に形成した後、真空もしくは不活性ガス雰囲気中で加熱処理することにより、ＣｕＰｃ膜３０の成膜を完了させたものである。
【０２１８】
つまり、ガラス基板１０の上にＩＴＯ膜２０を形成し、その上に蒸着法等によりＣｕＰｃ膜３０を形成し、このＣｕＰｃ膜３０を加熱処理した後、その上の正孔輸送層４０、発光層５０、電子輸送層６０、電子注入層７０、陰極８０を順次成膜し、有機ＥＬ素子Ｓ１を製造する。この第３の製造方法について実施した応用例を述べる。
【０２１９】
（第３の製造方法の応用例１）
ガラス基板１０の上に、陽極としてのＩＴＯ膜２０をスパッタ等により成膜した。このＩＴＯ膜付きガラス基板におけるＩＴＯ膜２０の表面を研磨して、Ｒａは約１ｎｍ、Ｒｚは約１０ｎｍとした。さらに当該表面に対して、上述したアルゴンと酸素のプラズマ洗浄処理を施した。
【０２２０】
その後、ＩＴＯ膜２０の上に、正孔注入層としてのＣｕＰｃ膜３０を蒸着法により材料加熱温度４２０℃で膜厚１０ｎｍにて形成した。続いて、真空中にて基板温度１５０℃で２０分間加熱処理を行った。
【０２２１】
その後、ＣｕＰｃ膜３０の上に、上記第１の製造方法（つまり、上記具体例１）と同様、正孔輸送層４０、化合物１を用いた混合ホスト層である発光層５０、電子輸送層６０、電子注入層７０、陰極８０を順次成膜し、有機ＥＬ素子を得た。
【０２２２】
このようにして得られた有機ＥＬ素子を封止缶で密封した密封素子を、１２０℃、２ｈｒの上記加速高温放置の条件で確認した結果、Ｖ−Ｉ特性のシフトは小さく、輝度低下や輝度ムラは見られなかった。ちなみに、加速高温放置の前後におけるＶ−Ｉ特性のシフト量は１．０Ｖであり、ＣｕＰｃ結晶性ピークの比は１．１３であった。
【０２２３】
（第３の製造方法の応用例２）
上記第３の製造方法の応用例１と同様に、ガラス基板１０の上にＩＴＯ膜２０を成膜し、アルゴンと酸素のプラズマ洗浄処理を施した後、ＣｕＰｃ膜３０を蒸着法により材料加熱温度４２０℃で膜厚１０ｎｍにて形成した。続いて、本例では真空中にて基板温度１００℃で２０分間加熱処理を行った。
【０２２４】
その後、ＣｕＰｃ膜３０の上に、上記第１の製造方法（つまり、上記具体例１）と同様、正孔輸送層４０、化合物１を用いた混合ホスト層である発光層５０、電子輸送層６０、電子注入層７０、陰極８０を順次成膜し、有機ＥＬ素子を得た。
【０２２５】
その有機ＥＬ素子を封止缶で密封した密封素子を、１２０℃、２ｈｒの上記加速高温放置の条件で確認した。その結果、Ｖ−Ｉ特性のシフトは小さく、輝度低下や輝度ムラは見られなかった。本例では、加速高温放置の前後におけるＶ−Ｉ特性のシフト量は１．０Ｖであり、ＣｕＰｃ結晶性ピークの比は１．１５であった。
【０２２６】
（第３の製造方法の応用例３）
上記第３の製造方法の応用例１と同様に、ガラス基板１０の上にＩＴＯ膜２０を成膜し、アルゴンと酸素のプラズマ洗浄処理を施した後、ＣｕＰｃ膜３０を蒸着法により材料加熱温度４２０℃で膜厚１０ｎｍにて形成した。続いて、本例では真空中にて基板温度７０℃で２０分間加熱処理を行った。
【０２２７】
その後、ＣｕＰｃ膜３０の上に、上記第１の製造方法（つまり、上記具体例１）と同様、正孔輸送層４０、化合物１を用いた混合ホスト層である発光層５０、電子輸送層６０、電子注入層７０、陰極８０を順次成膜し、有機ＥＬ素子を得た。
【０２２８】
その有機ＥＬ素子を封止缶で密封した密封素子を、１２０℃、２ｈｒの上記加速高温放置の条件で確認した。その結果、Ｖ−Ｉ特性のシフトは小さく、輝度低下や輝度ムラは見られなかった。本例では、加速高温放置の前後におけるＶ−Ｉ特性のシフト量は１．６Ｖであり、ＣｕＰｃ結晶性ピークの比は１．２５であった。
【０２２９】
このように、第３の製造方法によれば、結晶性を示す有機材料の膜であるＣｕＰｃ膜３０をＩＴＯ膜２０の上に形成した後、真空もしくは不活性ガス雰囲気中で加熱処理することにより、成膜されたＣｕＰｃ膜３０の結晶性が当該加熱処理によって高められたものにすることができる。
【０２３０】
これは、ＣｕＰｃ膜３０中の分子が熱による活性化エネルギーによって振動し、固体状態がより安定な相へ移行するためと考えられる。このことは温度と強い相関がある。本発明者らの検討では、実際に、加熱処理する前よりも後の方が、Ｘ線回折によるＣｕＰｃ膜３０の結晶ピークが大きくなり、結晶性が向上していることが確認できている。
【０２３１】
そして、上記応用例１〜３より、第３の製造方法においてＣｕＰｃ膜３０を加熱処理する温度は７０℃以上であれば、十分にＣｕＰｃ膜３０の結晶性が高まり、高温環境下で使用しても、輝度の低下や輝度ムラさらにはショートやリークが発生しない程度にまで、ＣｕＰｃ膜３０の結晶状態の変化を小さくすることができる。
【０２３２】
このように第３の製造方法によっても、結晶性を有する有機材料を含む有機ＥＬ素子において、使用温度内において電流のショートおよびリークを防止し良好な輝度特性を実現することができる。なお、当該加熱処理によって、加熱される膜が再離脱しては元も子もないので、加熱処理温度の上限は加熱対象となる膜のの蒸発温度または昇華温度以下であることは勿論である。
【０２３３】
このように、ＣｕＰｃ結晶性ピークについて上記第１〜第３の製造方法に分けて述べてきたが、ここで、上記加速高温放置（１２０℃、２ｈｒ）の前と後でのＣｕＰｃ結晶性ピークの比とＶ−Ｉ特性シフト量との関係についてまとめておく。
【０２３４】
同関係を図１４にグラフとして示し、図１４の基となるデータを図１５に示す。なお、図１４、図１５ではＣｕＰｃ結晶性ピーク値の比は「Ｘ線回折ピーク比」、Ｖ−Ｉ特性シフト量は「Ｖ−Ｉシフト」として記載してある。
【０２３５】
上述したが、ＣｕＰｃ結晶性ピーク値の比は、加速高温放置の前のＣｕＰｃ結晶性ピークの積分値に対する加速高温放置の後のＣｕＰｃ結晶性ピークの積分値の比であり、当該比が１より大ならば加速高温放置によってＣｕＰｃ膜の結晶性が高くなり、１未満ならば低くなったことを示す。
【０２３６】
また、Ｖ−Ｉ特性シフト量は、加速高温放置の前のＶ−Ｉ特性を基準として加速高温放置の後のＶ−Ｉ特性が何ボルト、シフトしたかを見たものである。具体的には、上記図１７において、ＣｕＰｃ結晶性ピークの比が１．５と結晶性が大幅に高く変化したため、上記図１６に示したように、Ｖ−Ｉ特性シフト量が約３Ｖと大きくなっていた。
【０２３７】
また、図１５において、「洗浄前処理条件」は、ガラス基板１０の上に成膜したＩＴＯ膜２０をＣｕＰｃ膜３０の成膜前に洗浄する条件であり、「プラズマ」は上記アルゴンと酸素のプラズマ洗浄処理、「ＵＶ３００℃」、「ＵＶ２５０℃」、「ＵＶ１５０℃」、「ＵＶ常温」はそれぞれの温度で紫外線照射を行った処理を意味する。また、図１５において「材料加熱温度」はＣｕＰｃ膜３０の成膜時の材料温度である。
【０２３８】
さらに、図１５において、「成膜手法」には、上記第３の製造方法を採用した場合について、その条件が示されている。「成膜後加熱（１５０℃真空中）」、「成膜後加熱（１００℃真空中）」、「成膜後加熱（７０℃真空中）」はそれぞれ、上述した第３の製造方法の応用例１、応用例２、応用例３の場合である。
【０２３９】
図１４のグラフに示されている、Ｘ線回折ピーク比が１．２５、Ｖ−Ｉシフトが１．６Ｖの有機ＥＬ素子においては輝度ムラが明確に認識されなかった。しかし、Ｘ線回折ピーク比が約１．３、Ｖ−Ｉシフトが約２．０Ｖの有機ＥＬ素子では輝度ムラが明確に認識された。
【０２４０】
このことにより、商品性から考えるとＸ線回折ピーク比のしきい値は約１．２５で、Ｖ−Ｉシフトのしきい値は約１．６Ｖにあると言える。
【０２４１】
つまり、上述したように、ＣｕＰｃ結晶性ピークにおいて、有機ＥＬ素子Ｓ１の使用温度（例えば−４０℃〜１２０℃）内の加熱による当該ＣｕＰｃ結晶性ピーク値の変化量を、加熱前の当該ＣｕＰｃ結晶性ピークの±２５％以内に小さく抑えることにより、使用温度内において、実用レベルにて良好な輝度特性を実現することができる。
【０２４２】
また、図１５から、ＩＴＯ膜２０の加熱処理温度を２５０℃以上とすれば、下地となるＩＴＯ膜の表面において、吸着水とともに結合水を効果的に低減することができ、上記効果を達成すべく結晶性を高めた有機材料を成膜できることがわかる。
【０２４３】
また、加熱によるＣｕＰｃ結晶性ピーク値の変化は、増加する方向でなくても減少する方向であっても良い。つまり、当該変化量が、加熱前のＣｕＰｃ結晶性ピークの＋２５％以下かもしくは−２５％以上であればよく、図１４に示すように、Ｘ線回折ピーク比は０．７５以上でも良い。例えば、Ｘ線回折ピーク比が０．６８の場合、Ｖ−Ｉシフトは２．８Ｖであり、輝度ムラが認識された。
【０２４４】
以上が、本実施形態の好ましい形態として、正孔注入層３０を構成するＣｕＰｃにおいて、有機ＥＬ素子Ｓ１の使用温度（例えば−４０℃〜１２０℃）内の加熱によるＣｕＰｃ結晶性ピーク（２θ＝６．６８°）値の変化量が、加熱前の当該ＣｕＰｃ結晶性ピークの±２５％以内となるようにした根拠である。
【０２４５】
そして、この好ましい形態を採用して、ＣｕＰｃ結晶性ピーク値の加熱前後における変化量を±２５％以内に小さく抑えることにより、高温環境下で使用しても、輝度の低下や輝度ムラが発生しない程度にまで、有機材料の結晶状態の変化を小さくすることができる。
【０２４６】
それにより、使用温度内において良好な輝度特性を実現することができ、輝度寿命の向上と１００℃以上の耐熱性の確保との両立を図るという本実施形態の効果をより高いレベルにて実現することができる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る有機ＥＬ素子の概略断面図である。
【図２】具体例および比較例に用いた３級アミン化合物１〜３の化学構造を示す図である。
【図３】具体例および比較例に用いた３級アミン化合物４〜６の化学構造を示す図である。
【図４】具体例および比較例に用いた３級アミン化合物７、８の化学構造を示す図である。
【図５】具体例および比較例に用いた電子輸送性材料の化学構造を示す図である。
【図６】具体例１、２および比較例１、２における耐久試験の結果を示す図である。
【図７】具体例１、２および比較例１、２の結果を各３級アミン化合物材料の物性値を含めて示す図表である。
【図８】化合物３を使用した素子について、１２０℃で５００ｈｒ保存した後の断面形状を模式的に表した図である。
【図９】比較例３、４の結果を示す図表である。
【図１０】比較例５の結果を示す図表である。
【図１１】ガラス基板の上にＩＴＯ膜を成膜した直後のＴＤＳスペクトルを示す図である。
【図１２】窒素雰囲気中で３００℃の温度にて加熱処理した場合のＩＴＯ膜の表面のＴＤＳスペクトルを示す図である。
【図１３】真空中で３００℃の温度にて加熱処理した場合のＩＴＯ膜の表面のＴＤＳスペクトルを示す図である。
【図１４】１２０℃、２ｈｒで高温処理放置する前と後でのＣｕＰｃ結晶性ピークの比とＶ−Ｉ特性シフト量との関係を示す図である。
【図１５】図１４の基となるデータを示す図表である。
【図１６】本発明者等の試作品における１００℃、１２ｈｒで高温放置する前と後でのＶ−Ｉ特性シフトの様子を示す図である。
【図１７】本発明者等の試作品における１００℃、１２ｈｒで高温放置する前と後でのＣｕＰｃ膜のＸ線回折スペクトルを示す図である。
【符号の説明】
１０…基板、２０…陽極、３０…正孔注入層、５０…発光層、８０…陰極。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel organic EL (electroluminescence) element, and more particularly to an organic EL element having excellent thermal stability and luminous stability, and a thin film type having high luminance and high visibility such as a wide viewing angle. The present invention is applicable to a display, a lighting fixture, a vehicle-mounted display exposed to a high-temperature environment, and the like.
[0002]
[Prior art]
The organic EL element has excellent visibility due to self-emission, and can be driven at a low voltage of several V to several tens of V, so that the weight including the driving circuit can be reduced. Therefore, it can be expected to be used as a thin film display, lighting, and backlight. Further, the organic EL element is characterized by abundant color variations.
[0003]
In particular, performances such as high viewing angle, high contrast, and low-temperature operability are extremely promising for in-vehicle displays. However, for automotive applications, quality standards are extremely strict, and practical use has been difficult due to problems such as luminance reduction and heat resistance inherent in organic EL.
[0004]
As a method of improving the luminance lifetime, a method of applying a light emitting layer formed by mixing a hole transporting material and an electron transporting material as a host material and a light emitting additive material as a dopant has been conventionally proposed (Patent Reference 1)
However, in this method, according to the study of the present inventors, depending on the material, the heat resistance of the hole transporting material is insufficient, and therefore, when exposed to a high temperature environment such as 100 ° C., a dark spot or the like is generated. It became remarkable, and as a result, it was confirmed that the brightness was reduced.
[0005]
Conventionally, various hole injecting and transporting materials have been disclosed as host materials for the light emitting layer (see Patent Documents 2 and 3), but in these Patent Documents 2 and 3, the disclosed hole injecting and transporting materials are disclosed. There is no description at all that the compound is mixed with an electron transporting material and a light emitting additive material to form a light emitting layer.
[0006]
Factors necessary for improving the luminance life at high temperatures include improving the heat resistance of the material. At least the glass transition temperature of the constituent material must be higher than the highest temperature in the environment to which the organic EL element is exposed. When the glass transition temperature is low, a dark spot is generated due to crystallization of an amorphous material constituting the organic EL element, and a film is peeled off at an electrode interface, resulting in a decrease in luminance.
[0007]
Conventionally, as a method of improving the glass transition temperature of a material, there is a method of increasing the molecular weight by multimerizing a hole transporting material (see Patent Document 4). However, when the polymer obtained in such a manner is used as the host material of the light-emitting layer, the present inventors have confirmed that the luminance lifetime is low.
[0008]
As described above, conventionally, in an organic EL device having a light-emitting layer formed by mixing a hole-transporting material, an electron-transporting material, and a light-emitting additive material, both improvement in luminance life and ensuring heat resistance of 100 ° C. or more are compatible. Nothing could be achieved.
[0009]
In order to ensure the heat resistance of the organic EL element, the adhesion of each layer is important to improve the stability in a high temperature environment. In particular, in an organic EL element, an interface between an anode serving as a hole injection electrode made of indium-tin oxide (ITO) or the like and an organic layer is weak. This is probably because the difference between the two coefficients of linear expansion is large.
[0010]
Therefore, it is desirable to provide a crystalline material such as copper phthalocyanine (CuPc) as an organic layer in contact with the anode, that is, a hole injection layer, so as to reduce the difference in linear expansion coefficient between the anode and the organic layer. Incidentally, as an example of an organic EL device using an amorphous organic thin film, in which a hole transport layer and a light emitting layer are formed in a crystal structure, an example of using an organic thin film having a crystalline structure has been conventionally proposed. (See References 5 and 6)
However, according to the study of the present inventors, when a crystalline organic material is used on an anode in order to secure heat resistance in an organic EL element, the crystalline organic material may be used in a high-temperature environment. A morphological change in which crystallization progressed was shown, and it was found that there was a problem that the hole injection characteristics deteriorated.
[0011]
[Patent Document 1]
JP-A-8-48656
[0012]
[Patent Document 2]
JP 2000-156290 A
[0013]
[Patent Document 3]
WO 98/3007 pamphlet
[0014]
[Patent Document 4]
JP 07-126226 A
[0015]
[Patent Document 5]
JP-A-3-173095
[0016]
[Patent Document 6]
JP-A-5-182754
[0017]
[Problems to be solved by the invention]
The present invention has been made in view of the circumstances described above, and an organic EL having a light-emitting layer formed by mixing a hole-transporting material, an electron-transporting material, and a light-emitting additive material between a pair of electrodes. It is an object of the present invention to achieve both improvement of the luminance life and securing of heat resistance of 100 ° C. or more.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have conducted intensive studies, and in an organic EL device having a light emitting layer obtained by mixing a hole transporting material, an electron transporting material, and a light emitting additive material, a host material of the light emitting layer We focused on using a tertiary amine compound for the hole transporting material.
[0019]
In an organic EL device having a light-emitting layer formed by mixing a hole-transporting material composed of a tertiary amine compound, an electron-transporting material, and a light-emitting additive, a decrease in luminance is suppressed by the molecular structure of the hole-transporting material. This was experimentally found (see FIG. 6). In particular, it has been found that a specific tertiary amine compound having a high glass transition temperature is effective for suppressing a reduction in luminance and achieving compatibility with high heat resistance (see FIG. 7).
[0020]
According to the first aspect of the present invention, there is provided an organic EL device having a light emitting layer formed by mixing a hole transporting material made of a tertiary amine compound, an electron transporting material, and a light emitting additive material between a pair of electrodes. The tertiary amine compound constituting the hole transporting material has a total number of places where two or more phenylene groups, aliphatic groups, or groups represented by the following structural formula (1) exist between nitrogen atoms in the molecular structure. Is 1 or 0, and the glass transition temperature is 100 ° C. or more.
[0021]
Embedded image

Here, in the above structural formula (1), L1 and L2 are one or more phenylene groups, and M1 and M2 represent an aromatic group or an aliphatic group. In addition, M1 and M2 may include a bonding carbon atom and form a ring structure with each other, for example, a fluorene group or a cyclohexane group.
[0022]
By using a tertiary amine compound as in the present invention as a hole transporting material constituting a light emitting layer, it is possible to achieve both a significant improvement in luminance life and a heat resistance of 100 ° C. or higher as compared with the related art. Can be.
[0023]
Here, as the hole-transporting material according to claim 1, two or more phenylene groups, aliphatic groups or groups represented by the above structural formula (1) are present between nitrogen atoms in the molecular structure. The tertiary amine compound having a total number of 0 can be the one described in the second aspect of the present invention.
[0024]
That is, the invention according to claim 2 is characterized in that the tertiary amine compound constituting the hole transporting material according to claim 1 is a compound having a skeleton represented by the following structural formula (2). I do.
[0025]
Embedded image

Here, in the structural formula (2), R1 to R20 are hydrogen, a structure represented by the following structural formulas (3), (4), and (5), or an adjacent one of R1 to R20. It has a structure in which an aromatic ring is formed by groups, and at least one of R1 to R20 has a structure of any of the following structural formulas (3), (4), and (5).
[0026]
Embedded image

[0027]
Embedded image

[0028]
Embedded image

Here, in the structural formulas (3) to (5), B1 to B2, C1 to C3, and D1 to D4 represent a substituted or unsubstituted aryl group.
[0029]
Further, the total number of places where two or more phenylene groups, aliphatic groups, or groups represented by the above structural formula (1) exist between nitrogen atoms in the molecular structure as the hole transporting material according to claim 1. Is a single tertiary amine compound.
[0030]
That is, the invention according to claim 3 is characterized in that the tertiary amine compound constituting the hole transporting material according to claim 1 is a compound having a skeleton represented by the following structural formula (6). I do.
[0031]
Embedded image

Here, in the structural formula (6), A is two or more phenylene groups, an aliphatic group, or a group represented by the structural formula (1). In the structural formula (6), A may have a substituent.
[0032]
Further, R1 to R20 are hydrogen or a structure represented by the following structural formulas (3), (4), and (5), or form an aromatic ring by adjacent groups among R1 to R20. And at least one of R1 to R20 has any of the structural formulas (3), (4), and (5).
[0033]
Embedded image

[0034]
Embedded image

[0035]
Embedded image

Here, in the structural formulas (3) to (5), B1 to B2, C1 to C3, and D1 to D4 represent a substituted or unsubstituted aryl group.
[0036]
Further, in order to improve the heat resistance of the organic EL element under a high temperature environment, a crystalline material such as copper phthalocyanine (CuPc) is provided as an organic layer in contact with the anode, that is, a hole injection layer. Discussions were underway to improve the adhesiveness of the material.
[0037]
Simply, when a crystalline organic material is used on the anode, as described above, the crystalline organic material shows a morphological change in which crystallization proceeds in a high-temperature environment, and the hole injection characteristics deteriorate. There is a problem. The cause of this problem will be specifically described based on data of experiments performed by the present inventors.
[0038]
After forming an anode ITO (transparent electrode) on a glass substrate and subjecting it to a surface treatment using plasma of a mixture of argon and oxygen, CuPc is formed as a hole injection layer at a material heating temperature of 420 ° C. with a film thickness of 10 nm. The hole transport layer is formed of triphenylamine tetramer, the luminescent layer is formed of Alq with dimethylquinacridone added, the electron transport layer is formed of Alq, the electron injection layer is formed of LiF, and the cathode is formed of Al. The organic EL device thus manufactured was prototyped.
[0039]
The prototype device is a general organic EL device, and is hereinafter referred to as a prototype. Here, CuPc in the organic thin film is crystalline, and the other layers are amorphous.
[0040]
FIG. 16 shows voltage-luminance characteristics (VI characteristics) when the prototype was left at 100 ° C. for 12 hours at a high temperature. As shown in FIG. 16, it was found that the VI characteristics shifted to the plus side by about 3 V after the high-temperature storage compared to the initial state before the high-temperature storage.
[0041]
This increases the load on the drive circuit and leads to an increase in cost in circuit design. In addition, since the current is partially generated in the same element, a region where the current easily flows and a region where the current does not easily flow are formed.
[0042]
The material having the lowest Tg point among the layers in the prototype, that is, the organic thin film, is a triphenylamine tetramer at about 144 ° C. Since the storage at 100 ° C. is performed in an environment at least 40 ° C. lower than the Tg point of the triphenylamine tetramer, the shift phenomenon is not affected by the progress of the microcrystalline aggregation structure of the amorphous film other than CuPc. It is thought that there are few.
[0043]
Therefore, attention was paid to a change in the crystalline state of a CuPc film (hole injection layer), which is an organic material having crystallinity. As a result, they found that the crystal state of this CuPc film was significantly different before and after being left in a high-temperature environment. The results of specifically examining the change in the crystal state of the CuPc film are shown.
[0044]
In order to efficiently confirm the change in the crystal state, the temperature of the storage environment was increased to 120 ° C. and the temperature was accelerated, and the storage time was evaluated at 2 hours. Hereinafter, leaving under these conditions is referred to as accelerated high-temperature leaving.
[0045]
A CuPc film was formed on a glass substrate with ITO under the same conditions as in the above-mentioned prototype in which the VI characteristic shifted by about 3 V as described above. FIG. 17 shows the results of X-ray diffraction analysis of the crystallinity of the CuPc film in this case before and after the accelerated high-temperature storage.
[0046]
As shown in FIG. 17, in the diffraction peak, the peak occurring at 2θ = 6.68 ° originates from the crystal structure of CuPc. In FIG. 17, the peak shown by a solid line in FIG. 17 is the peak before the accelerated high-temperature standing, that is, the initial peak, and the peak shown by the broken line is the peak after the accelerated high-temperature standing, that is, a peak after 120 ° C. and 2 hours. .
[0047]
The larger the integrated value of the peak value, that is, the higher the peak value, the higher the crystallinity. In other words, the peak value (integral value) is changed to 1.5 times the value before the high-temperature storage at 120 ° C. and the high-temperature storage at 2 hours.
[0048]
From this, the present inventors have found that in the prototype, after the hole transport layer, the light emitting layer, the electron transport layer, the cathode, and the like are formed on the CuPc film as the hole injection layer, When the CuPc film forms such a state, such a change in the crystalline state deteriorates the hole injection characteristics, induces a change in the VI characteristics in a high-temperature environment, and causes a decrease in luminance and luminance unevenness. Thought it was a major cause.
[0049]
Therefore, the present inventors have found that, in the organic EL device according to any one of claims 1 to 3, when a crystalline material is used as the organic layer in contact with the anode, that is, the hole injection layer, the organic material under a high-temperature environment is used. As a countermeasure against a change in crystal state, it was considered important to form a film of an organic material having crystallinity so that the crystallinity becomes as high as possible during film formation.
[0050]
The invention according to claim 4 is created based on such an idea, and in the organic EL device according to claims 1 to 3, between one of the pair of electrodes and the light emitting layer. The hole injection layer is interposed. The hole injection layer is made of an organic material having crystallinity, and the temperature of the organic EL element is determined by the diffraction peak value of the organic material having crystallinity that appears by X-ray diffraction. The amount of change of the diffraction peak value due to heating within the region is within ± 25% of the diffraction peak value before heating.
[0051]
As in the present invention, the amount of change in the diffraction peak value due to heating within the operating temperature of the organic EL element is determined by the change in the diffraction peak value due to heating within the operating temperature of the organic EL element. If it is as small as within ± 25%, the change in the crystal state of the organic material can be reduced to such an extent that the luminance does not decrease or the luminance unevenness does not occur even when used in a high-temperature environment.
[0052]
Therefore, according to the present invention, in an organic EL device having a light-emitting layer formed by mixing a hole-transporting material, an electron-transporting material, and a light-emitting additive material between a pair of electrodes, an improvement in luminance life and an improvement in 100% The effect of achieving compatibility with the heat resistance of not less than ° C. can be realized at a higher level.
[0053]
Here, as in the invention according to claim 5, an ITO film made of an oxide of indium-tin is formed on the substrate, and the organic material having crystallinity is an organic material formed on the ITO film. It can be configured as a membrane.
[0054]
Further, as in the invention according to claim 6, the organic material exhibiting crystalline characteristics can be a copper phthalocyanine film, and in this case, the diffraction peak value is (200) plane parallel to the substrate in the copper phthalocyanine film. Is the diffraction peak value.
[0055]
According to a seventh aspect of the present invention, the ITO film has an average surface roughness Ra of 2 nm or less and a ten-point average surface roughness Rz of 20 nm or less.
[0056]
Further, in order to form a crystalline organic material located on the anode into a highly crystalline and stable film, the surface roughness of the anode is important. Specifically, as in the present invention, it is desirable that the Ra of the ITO film serving as the anode in contact with the hole injection layer be 2 nm or less and the Rz be 20 nm or less.
[0057]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention shown in the drawings will be described. FIG. 1 is a diagram showing a schematic sectional configuration of an organic EL element S1 according to an embodiment of the present invention.
[0058]
An anode 20 made of indium-tin oxide (hereinafter, referred to as ITO) is formed on a substrate 10 made of transparent glass or the like. A hole injection layer 30 made of CuPc (copper phthalocyanine) is formed on the anode 20 as a crystalline organic material, and a hole transport layer made of a hole transport material is formed on the hole injection layer 30. 40 are formed.
[0059]
A light emitting layer 50 is formed on the hole transport layer 40 by using a hole transporting material made of a tertiary amine compound and an electron transporting material as a host material, and mixing a light emitting additive material as a dopant with the host material. On the light emitting layer 50, an electron transport layer 60 made of an electron transport material is formed. Further, an electron injection layer 70 made of LiF is formed on the electron transport layer 60, and a cathode 80 made of Al is formed thereon.
[0060]
Thus, the hole injection layer 30, the hole transport layer 40, the light emitting layer 50, the electron transport layer 60, and the electron injection layer 70 made of an organic material having crystallinity are laminated between the pair of electrodes 20 and 80. The organic EL element S1 is sandwiched between them.
[0061]
In the organic EL device S1, an electric field is applied between the anode 20 and the cathode 80, holes are injected from the anode 20, and electrons are injected and transported from the cathode 80 to the light emitting layer 50, respectively. As a result, electrons and holes are recombined, and the energy at that time causes the light emitting layer 50 to emit light. Then, the emitted light is taken out from the substrate 10 side and is visually recognized.
[0062]
Here, the light emitting layer 50 of the present embodiment is formed by mixing a hole transporting material composed of a tertiary amine compound, an electron transporting material, and a light emitting additive material. The total number of places where two or more phenylene groups, aliphatic groups, or groups represented by the following structural formula (1) are present between the nitrogen atoms is 1 or 0, and the glass transition temperature is 100 ° C. or higher. Certain tertiary amine compounds.
[0063]
Embedded image

Here, in the above structural formula (1), L1 and L2 are one or more phenylene groups, and M1 and M2 represent an aromatic group or an aliphatic group. In addition, M1 and M2 may include a bonding carbon atom and form a ring structure with each other, for example, a fluorene group or a cyclohexane group.
[0064]
In addition, examples of the aliphatic group include a linear hydrocarbon group such as a methylene group and an ethylene group, and a cyclic hydrocarbon group such as cyclohexane.
[0065]
As a more specific hole transporting material, the total number of locations where two or more phenylene groups, aliphatic groups, or groups represented by the above structural formula (1) are present between nitrogen atoms in the molecular structure is 0. As the tertiary amine compound, a compound having a skeleton represented by the following structural formula (2) can be used.
[0066]
Embedded image

Here, in the structural formula (2), R1 to R20 are hydrogen, a structure represented by the following structural formulas (3), (4), and (5), or an adjacent one of R1 to R20. It has a structure in which an aromatic ring is formed by groups, and at least one of R1 to R20 has a structure of any of the following structural formulas (3), (4), and (5).
[0067]
Embedded image

[0068]
Embedded image

[0069]
Embedded image

Here, in the structural formulas (3) to (5), B1 to B2, C1 to C3, and D1 to D4 represent a substituted or unsubstituted aryl group.
[0070]
Further, as a more specific hole transporting material, the total number of locations where two or more phenylene groups, aliphatic groups, or groups represented by the above structural formula (1) are present between nitrogen atoms in the molecular structure is 1 The tertiary amine compound may be a compound having a skeleton represented by the following structural formula (6).
[0071]
Embedded image

Here, in the structural formula (6), A is two or more phenylene groups, an aliphatic group, or a group represented by the structural formula (1). In the structural formula (6), A may have a substituent. Further, R1 to R20 in the structural formula (6) can be the same as R1 to R20 in the structural formula (2).
[0072]
By using such a tertiary amine compound as a hole-transporting material constituting the light-emitting layer 50, it is possible to achieve both a significant improvement in luminance life and a heat resistance of 100 ° C. or higher as compared with the related art. it can.
[0073]
By the way, the organic EL element of the present embodiment is employed, for example, in a display for a vehicle and the like, and its operating temperature is about −40 ° C. to 120 ° C.
[0074]
When the hole injection layer 30 made of CuPc, which is an organic material exhibiting crystallinity, that is, the CuPc film 30 is measured by the X-ray diffraction method, the diffraction peak of the (200) plane of the CuPc film 30 parallel to the substrate 10 is as follows: 7 is a diffraction peak showing the crystallinity of the CuPc film 20. This diffraction peak corresponds to the peak generated at 2θ = 6.68 ° shown in FIG. 17, and is hereinafter referred to as a CuPc crystalline peak.
[0075]
In the present embodiment, as a preferred mode, the value of the CuPc crystalline peak (2θ = 6.68 °), that is, the integrated value of the peak, is within the operating temperature (for example, −40 ° C. to 120 ° C.) of the organic EL element S1. The change in the CuPc crystallinity peak value due to the heating is within ± 25% of the CuPc crystallinity peak before heating.
[0076]
By suppressing the variation of the CuPc crystallinity peak value before and after heating to within ± 25%, the crystal state of the organic material can be reduced to a level that does not cause a decrease in brightness or uneven brightness even when used in a high-temperature environment. Can be reduced. In addition, good luminance characteristics can be realized within a use temperature, and an effect of achieving both improvement in luminance life and securing heat resistance of 100 ° C. or more can be realized at a higher level.
[0077]
Incidentally, as described above, in the conventional organic EL element having an organic material having crystallinity, as shown in FIG. 17, the CuPc crystallinity peak value after heating is higher than the CuPc crystallinity peak value before heating. Is greatly changed to 1.5 times, and the adhesion of the interface between ITO and CuPc and between CuPc and the light emitting layer is reduced, and as shown in FIG. , And uneven brightness.
[0078]
In the present embodiment, the average surface roughness Ra of the ITO film serving as the anode 20 is preferably 2 nm or less, and the 10-point average surface roughness Rz is preferably 20 nm or less. These Ra and Rz are defined in JIS (Japanese Industrial Standard).
[0079]
The surface roughness of the anode 20 is important in order to form the hole injection layer 30 as a crystalline organic material located on the anode 20 into a film with high crystallinity and stability. The reason for setting the Ra of the ITO film to 2 nm or less and the Rz to 20 nm or less is based on the result of studies by the present inventors.
[0080]
Next, the present embodiment will be described more specifically with reference to the following specific examples and comparative examples of the present invention.
[0081]
With respect to the tertiary amine compound serving as the hole transporting material of the light emitting layer 50, the chemical structural formulas of the compounds used in these specific examples and comparative examples are shown in FIGS. Among these, compounds 1, 2, 7, and 8 are the compounds of the present embodiment. First, the method for producing the tertiary amine compound shown in FIGS. 2 to 4 will be described.
[0082]
[Compound 1] (see FIG. 2)
Compound 1: Synthesis of N, N'-bis {4-[(1-naphthyl) phenylamino] phenyl)}-N, N'-diphenylbenzidine.
[0083]
Acetanilide 20.3 g (0.15 mol), 1,4-diiodobenzene 59.4 g (0.18 mol), anhydrous potassium carbonate 22.1 g (0.16 mol), copper powder 2.16 g (0.034 mol) Mol) and 35 ml of nitrobenzene, and reacted at 190 to 205 ° C for 10 hours.
[0084]
The reaction product was extracted with 200 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to dryness. This was purified by column chromatography (carrier: silica gel, eluent: toluene / ethyl acetate = 6/1) to obtain 30.3 g of N- (4-iodophenyl) acetanilide (yield: 60%).
[0085]
Subsequently, 10.8 g (0.032 mol) of N- (4-iodophenyl) acetanilide, 8.0 g (0.039 mol) of (1-naphthyl) phenylamine, 5.53 g of anhydrous potassium carbonate (0.040 mol) ), 0.45 g (0.007 mol) of copper powder and 10 ml of nitrobenzene were mixed and reacted at 200 to 212 ° C. for 15 hours.
[0086]
The reaction product was extracted with 100 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to an oil. The oily substance was dissolved in isoamyl alcohol (60 ml), water (1 ml) and 85% potassium hydroxide (2.64 g, 0.040 mol) were added, and the mixture was hydrolyzed at 130 ° C.
[0087]
After isoamyl alcohol was distilled off by steam distillation, the mixture was extracted with 250 ml of toluene, washed with water, dried and concentrated. The concentrate is purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane = 1/2), and N, N'-diphenyl-N- (1-naphthyl) -1,4-phenylenediamine 8 0.6 g (70.0% yield) was obtained.
[0088]
Furthermore, 8.11 g (0.021 mol) of N, N'-diphenyl-N- (1-naphthyl) -1,4-phenylenediamine and 4.06 g (0.01 mol) of 4,4'-diiodobiphenyl. , Anhydrous potassium carbonate (2.90 g, 0.021 mol), copper powder (0.32 g, 0.005 mol) and nitrobenzene (10 ml) were mixed and reacted at 195 to 210 ° C for 20 hours.
[0089]
The reaction product was extracted with 140 ml of toluene, the insoluble matter was separated by filtration, and after concentration, 120 ml of n-hexane was added to take out crude crystals. The crude crystals are purified by column chromatography (carrier; silica gel, eluent; toluene / n-hexane = 1/2) to give N, N'-bis {4-[(1-naphthyl) phenylamino] phenyl)}. 4.2 g (yield; 45.0%) of -N, N'-diphenylbenzidine was obtained. The glass transition temperature was 136 ° C.
[0090]
[Compound 2] (see FIG. 2)
Compound 2: For the synthesis of 4,4 ′, 4 ″ -tris [(1-naphthyl) phenylamino] triphenylamine.
[0091]
In a 200 ml reaction vessel, 28.7 g (0.046 mol) of 4,4 ', 4 "-triiodotriphenylamine, 50.4 g (0.23 mol) of N- (1-naphthyl) -aniline and anhydrous potassium carbonate 44.2 g (0.32 mol), 4.32 g (0.068 mol) of copper powder and 50 ml of decalin were added, and the mixture was heated in an Ar atmosphere at a temperature of 220 ° C. in an oil bath for 24 hours.
[0092]
After completion of the reaction, 200 ml of toluene was added, and the mixture was filtered to remove insolubles. The filtrate was washed with water and dried over sodium sulfate. After drying, the solvent was distilled off from the filtrate, and the residue was purified by a silica gel column four times (developing solvent: n-hexane / toluene mixed solvent), recrystallized repeatedly from hexane / toluene mixed solvent and ethyl acetate, and dried in vacuo. Thereafter, 24.7 g (60.0% yield) of 4,4 ′, 4 ″ -tris [(1-naphthyl) phenylamino] triphenylamine was obtained.
[0093]
By sublimation purification, high-purity 4,4 ′, 4 ″ -tris [(1-naphthyl) phenylamino] triphenylamine was obtained (sublimation purification yield: 70.0%). The glass transition temperature was 110 ° C. there were.
[0094]
[Compound 3] (see FIG. 2)
Compound 3: Synthesis of N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine.
[0095]
4.6 g (0.021 mol) of (1-naphthyl) phenylamine, 4.06 g (0.01 mol) of 4,4'-diiodobiphenyl, 2.90 g (0.021 mol) of anhydrous potassium carbonate, copper powder 0.32 g (0.005 mol) and 10 ml of nitrobenzene were mixed and reacted at 195 to 210 ° C for 20 hours.
[0096]
The reaction product was extracted with 140 ml of toluene, the insoluble matter was separated by filtration, and after concentration, 120 ml of n-hexane was added to take out crude crystals. The crude crystals were purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane = 1/2) to give N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine. 6 g (yield; 45.0%) was obtained. The glass transition temperature was 96 ° C.
[0097]
[Compound 4] (see FIG. 3)
Compound 4: Synthesis of 4,4′-bis {4-[(1-naphthyl) phenylamino] phenyl} triphenylamine.
[0098]
In a 200 ml reaction vessel, 29.9 g (0.046 mol) of 4,4′-bis [4-iodo) phenyl] triphenylamine, 30.7 g (0.14 mol) of (1-naphthyl) phenylamine and carbonic anhydride 27.6 g (0.20 mol) of potassium, 2.73 g (0.043 mol) of copper powder and 50 ml of decalin were added, and the mixture was heated in an Ar atmosphere at a temperature of 220 ° C. in an oil bath for 24 hours.
[0099]
After completion of the reaction, 200 ml of toluene was added, and the mixture was filtered to remove insolubles. The filtrate was washed with water and dried over sodium sulfate. After drying, the solvent was distilled off from the filtrate, the residue was purified four times by a silica gel column (developing solvent: n-hexane / toluene mixed solvent), and recrystallization was repeated from a hexane / toluene mixed solvent and ethyl acetate. Thus, 24.8 g (yield: 65.0%) of 4,4′-bis {4-[(1-naphthyl) phenylamino] phenyl} triphenylamine was obtained.
[0100]
By sublimation purification, high-purity 4,4'-bis {4-[(1-naphthyl) phenylamino] phenyl} triphenylamine was obtained (sublimation purification yield: 75.0%). The glass transition temperature was 133 ° C.
[0101]
[Compound 5] (see FIG. 3)
Compound 5: Synthesis of N, N'-bis [4- (4'-diphenylaminobiphenyl)]-N, N'-diphenylbenzidine.
[0102]
Acetanilide 20.3 g (0.15 mol), 4,4'-diiodobiphenyl 73.1 g (0.18 mol), anhydrous potassium carbonate 22.1 g (0.16 mol), copper powder 2.16 g (0. 034 mol) and 35 ml of nitrobenzene were mixed and reacted at 190 to 205 ° C for 10 hours.
[0103]
The reaction product was extracted with 200 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to dryness. This was purified by column chromatography (carrier: silica gel, eluent: toluene / ethyl acetate = 6/1), and 40.2 g of N- [4- (4′-iodobiphenyl)] acetanilide (64.8% yield). ) Got.
[0104]
Subsequently, 13.2 g (0.032 mol) of N- [4- (4′-iodobiphenyl)] acetanilide, 6.60 g (0.039 mol) of diphenylamine, 5.53 g (0.040 mol) of anhydrous potassium carbonate and 0.45 g (0.007 mol) of copper powder and 10 ml of nitrobenzene were mixed and reacted at 200 to 212 ° C. for 15 hours.
[0105]
The reaction product was extracted with 100 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to an oil. The oily substance was dissolved in isoamyl alcohol (60 ml), water (1 ml) and 85% potassium hydroxide (2.64 g, 0.040 mol) were added, and the mixture was hydrolyzed at 130 ° C. After isoamyl alcohol was distilled off by steam distillation, the mixture was extracted with 250 ml of toluene, washed with water, dried and concentrated.
[0106]
The concentrate is purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane = 1/2) to give 10.5 g (yield: 72.2%) of N, N, N'-triphenylbenzidine. Obtained.
[0107]
Furthermore, 8.66 g (0.021 mol) of N, N, N'-triphenylbenzidine, 4.06 g (0.01 mol) of 4,4'-diiodobiphenyl, and 2.90 g (0.021 mol) of anhydrous potassium carbonate Mol), 0.32 g (0.005 mol) of copper powder, and 10 ml of nitrobenzene, and reacted at 195 to 210 ° C for 20 hours.
[0108]
The reaction product was extracted with 140 ml of toluene, the insoluble matter was separated by filtration, and after concentration, 120 ml of n-hexane was added to take out crude crystals. The crude crystals are purified by column chromatography (carrier; silica gel, eluent; toluene / n-hexane = 1/2) to give N, N'-bis [4- (4'-diphenylaminobiphenyl)]-N, 4.73 g (yield; 48.5%) of N'-diphenylbenzidine was obtained. The glass transition temperature was 143 ° C.
[0109]
[Compound 6] (see FIG. 3)
Compound 6: Synthesis of 9,9-bis {4- [4 '-(4-diphenylaminophenyl) triphenylamino]} fluorene.
[0110]
Acetanilide 20.3 g (0.15 mol), 4,4'-diiodobiphenyl 73.1 g (0.18 mol), anhydrous potassium carbonate 22.1 g (0.16 mol), copper powder 2.16 g (0. 034 mol) and 35 ml of nitrobenzene were mixed and reacted at 190 to 205 ° C for 10 hours.
[0111]
The reaction product was extracted with 200 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to dryness. This was purified by column chromatography (carrier: silica gel, eluent: toluene / ethyl acetate = 6/1), and 40.2 g of N- (4'-iodo-4-biphenyl) acetanilide (64.8% yield). Got.
[0112]
Subsequently, 13.2 g (0.032 mol) of N- (4′-iodo-4-biphenyl) acetanilide, 6.60 g (0.039 mol) of diphenylamine, 5.53 g (0.040 mol) of anhydrous potassium carbonate and 0.45 g (0.007 mol) of copper powder and 10 ml of nitrobenzene were mixed and reacted at 200 to 212 ° C. for 15 hours.
[0113]
The reaction product was extracted with 100 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to an oil. The oily substance was dissolved in isoamyl alcohol (60 ml), water (1 ml) and 85% potassium hydroxide (2.64 g, 0.040 mol) were added, and the mixture was hydrolyzed at 130 ° C. After isoamyl alcohol was distilled off by steam distillation, the mixture was extracted with 250 ml of toluene, washed with water, dried and concentrated.
[0114]
The concentrate is purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane = 1/2) to give 10.5 g (yield: 72.2%) of N, N, N'-triphenylbenzidine. Obtained.
[0115]
Further, 8.66 g (0.021 mol) of N, N, N'-triphenylbenzidine, 5.7 g (0.01 mol) of 9,9-bis- (4-iodophenyl) fluorene, and anhydrous potassium carbonate.2. 90 g (0.021 mol), 0.32 g (0.005 mol) of copper powder, and 10 ml of nitrobenzene were mixed and reacted at 195 to 210 ° C. for 20 hours.
[0116]
The reaction product was extracted with 140 ml of toluene, the insoluble matter was separated by filtration, and after concentration, 120 ml of n-hexane was added to take out crude crystals. The crude crystals were purified by column chromatography (carrier; silica gel, eluent; toluene / n-hexane = 1/2) to give 9,9-bis {4- [4 '-(4-diphenylaminophenyl) triphenyl [Amino]} fluorene (5.7 g, yield: 50.0%) was obtained. Glass transition temperature was 161 ° C.
[0117]
[Compound 7] (see FIG. 4)
Compound 7: Synthesis of N, N'-bis {4-[(1-naphthyl) phenylamino] phenyl)}-N, N'-diphenylethylenediamine.
[0118]
Acetanilide 20.3 g (0.15 mol), 1,4-diiodobenzene 59.4 g (0.18 mol), anhydrous potassium carbonate 22.1 g (0.16 mol), copper powder 2.16 g (0.034 mol) Mol) and 35 ml of nitrobenzene, and reacted at 190 to 205 ° C for 10 hours.
[0119]
The reaction product was extracted with 200 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to dryness. This was purified by column chromatography (carrier: silica gel, eluent: toluene / ethyl acetate = 6/1) to obtain 30.3 g of N- (4-iodophenyl) acetanilide (yield: 60%).
[0120]
Subsequently, 10.8 g (0.032 mol) of N- (4-iodophenyl) acetanilide, 8.0 g (0.039 mol) of (1-naphthyl) phenylamine, 5.53 g of anhydrous potassium carbonate (0.040 mol) ), 0.45 g (0.007 mol) of copper powder and 10 ml of nitrobenzene were mixed and reacted at 200 to 212 ° C. for 15 hours.
[0121]
The reaction product was extracted with 100 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to an oil. The oily substance was dissolved in isoamyl alcohol (60 ml), water (1 ml) and 85% potassium hydroxide (2.64 g, 0.040 mol) were added, and the mixture was hydrolyzed at 130 ° C.
[0122]
After isoamyl alcohol was distilled off by steam distillation, the mixture was extracted with 250 ml of toluene, washed with water, dried and concentrated. The concentrate is purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane = 1/2), and N, N'-diphenyl-N- (1-naphthyl) -1,4-phenylenediamine 8 0.6 g (70.0% yield) was obtained.
[0123]
Furthermore, 8.11 g (0.021 mol) of N, N'-diphenyl-N- (1-naphthyl) -1,4-phenylenediamine and 2.82 g (0.01 mol) of 4,4'-diiodoethylene , Anhydrous potassium carbonate (2.90 g, 0.021 mol), copper powder (0.32 g, 0.005 mol) and nitrobenzene (10 ml) were mixed and reacted at 195 to 210 ° C for 20 hours.
[0124]
The reaction product was extracted with 140 ml of toluene, the insoluble matter was separated by filtration, and after concentration, 120 ml of n-hexane was added to take out crude crystals. The crude crystals are purified by column chromatography (carrier; silica gel, eluent; toluene / n-hexane = 1/2) to give N, N'-bis {4-[(1-naphthyl) phenylamino] phenyl)}. 4.1 g (yield; 45.0%) of -N, N'-diphenylethylenediamine was obtained. The glass transition temperature was 100 ° C. or higher.
[0125]
[Compound 8] (see FIG. 4)
Compound 8: Synthesis of 9,9-bis {4- {4 '-[(1-naphthyl) phenylamino] triphenylamino} fluorene.
[0126]
Acetanilide 20.3 g (0.15 mol), 1,4'-diiodobenzene 59.4 g (0.18 mol), anhydrous potassium carbonate 22.1 g (0.16 mol), copper powder 2.16 g (0. 034 mol) and 35 ml of nitrobenzene were mixed and reacted at 190 to 205 ° C for 10 hours.
[0127]
The reaction product was extracted with 200 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to dryness. This was purified by column chromatography (carrier: silica gel, eluent: toluene / ethyl acetate = 6/1) to obtain 30.3 g of N- (4-iodophenyl) acetanilide (yield: 60%).
[0128]
Subsequently, 10.8 g (0.032 mol) of N- (4-iodophenyl) acetanilide, 8.0 g (0.039 mol) of (1-naphthyl) phenylamine, 5.53 g of anhydrous potassium carbonate (0.040 mol) ), 0.45 g (0.007 mol) of copper powder and 10 ml of nitrobenzene were mixed and reacted at 200 to 212 ° C. for 15 hours.
[0129]
The reaction product was extracted with 100 ml of toluene, the insolubles were removed by filtration, and the mixture was concentrated to an oil. The oily substance was dissolved in isoamyl alcohol (60 ml), water (1 ml) and 85% potassium hydroxide (2.64 g, 0.040 mol) were added, and the mixture was hydrolyzed at 130 ° C. After isoamyl alcohol was distilled off by steam distillation, the mixture was extracted with 250 ml of toluene, washed with water, dried and concentrated.
[0130]
The concentrate is purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane = 1/2), and N, N'-diphenyl-N- (1-naphthyl) -1,4-phenylenediamine 8 0.6 g (70.0% yield) was obtained.
[0131]
Further, 8.11 g (0.021 mol) of N, N′-diphenyl-N- (1-naphthyl) -1,4-phenylenediamine and 5.7 g of 9,9-bis- (4-iodophenyl) fluorene ( 0.01 mol), 2.90 g (0.021 mol) of anhydrous potassium carbonate, 0.32 g (0.005 mol) of copper powder, and 10 ml of nitrobenzene were mixed and reacted at 195 to 210 ° C. for 20 hours.
[0132]
The reaction product was extracted with 140 ml of toluene, the insoluble matter was separated by filtration, and after concentration, 120 ml of n-hexane was added to take out crude crystals. The crude crystals are purified by column chromatography (carrier: silica gel, eluent: toluene / n-hexane = 1/2) to give 9,9-bis {4-} 4 '-[(1-naphthyl) phenylamino]. 5.43 g (yield; 50.0%) of triphenylamino difluorene was obtained. The glass transition temperature was 100 ° C. or higher.
[0133]
The following specific examples and comparative examples were performed using such tertiary amine compounds shown in FIGS. The results of the durability test in each of these examples are shown in FIG.
[0134]
(Specific example 1)
An ITO film (transparent electrode) was formed as an anode 20 on a glass substrate 10 and its surface was polished to make Ra about 1 nm and Rz about 10 nm. On the anode 20, a 10-nm hole injection layer 30 made of CuPc as an organic material having crystallinity was formed.
[0135]
On the hole injection layer 30, a tertiary amine compound is 20 nm in weight as the hole transport layer 40, and a tertiary amine compound, the electron transporting material and rubrene shown in FIG. 20 nm was formed according to the ratio.
[0136]
Tris (8-quinolinolato) aluminum was deposited to a thickness of 20 nm as the electron transport layer 60, LiF was deposited to the electron injection layer 70, and Al was deposited to the cathode 80 in this order. As the tertiary amine compound, the compound represented by Compound 1 (see FIG. 2) was used.
[0137]
This element was subjected to an initial luminance of 400 cd / m 2 at 85 ° C. ² And a 1/64 duty drive. The result was as shown in FIG. Further, in a storage test in a 100 ° C. environment, no remarkable dark spot was generated even when the temperature exceeded 500 hours.
[0138]
(Specific example 2)
In the device structure of Specific Example 1, a device was manufactured using a starburst triphenylamine derivative as shown in Compound 2 (see FIG. 2) as the tertiary amine compound.
[0139]
This element was subjected to an initial luminance of 400 cd / m 2 at 85 ° C. ² And a 1/64 duty drive. The result was as shown in FIG. Further, in a storage test in a 100 ° C. environment, no remarkable dark spot was generated even when the temperature exceeded 500 hours.
[0140]
(Comparative Example 1)
In the device structure of the specific example 1, a triphenylamine derivative such as the compound 3 (see FIG. 2), the compound 4 (see FIG. 3), and the compound 5 (see FIG. 3) is used as the tertiary amine compound. And devices were produced.
[0141]
These devices were subjected to an initial luminance of 400 cd / m. ² And a 1/64 duty drive. The result was as shown in FIG. In a storage test in a 100 ° C. environment, a dark spot was generated only in the case of compound 3, and no remarkable dark spot was generated in the case of compounds 4 and 5 even when the temperature exceeded 500 hours.
[0142]
(Comparative Example 2)
In the device structure of the above specific example 1, a device was produced using a triphenylamine derivative as shown in the above compound 6 (see FIG. 3) as a tertiary amine compound.
[0143]
These devices were subjected to an initial luminance of 400 cd / m 2 at 85 ° C. ² And a 1/64 duty drive. The result was as shown in FIG. In a storage test under a 100 ° C. environment, no remarkable dark spot was generated even when the temperature exceeded 500 hours.
[0144]
The results of Specific Examples 1 and 2 and Comparative Examples 1 and 2 are summarized in the table of FIG. 7, including the physical property values of each tertiary amine compound material.
[0145]
In FIG. 7, as in FIG. 6, the luminance life is normalized by setting the initial value to 1, and is indicated by the normalized luminance at 400 hours after the durability test. Regarding the high-temperature preservation, X indicates that a dark spot was generated by a storage test at 100 ° C., and O indicates that no dark spot was generated.
[0146]
Tg indicates a glass transition temperature. The numerical value in the molecular structure column is the total number of places where two or more phenylene groups, aliphatic groups, or groups represented by the above structural formula (1) (see chemical formula 19) exist between nitrogen atoms in the molecular structure. Is shown.
[0147]
From this result, it is possible to confirm the correlation between the decrease in luminance and the molecular structure. In particular, when the total number of locations where two or more phenylene groups, aliphatic groups, or groups represented by the above structural formula (1) are present between nitrogen atoms in the molecular structure is one or zero, the luminance lifetime is low. Good.
[0148]
High temperature storage can be understood from the glass transition temperature of the tertiary amine compound material. That is, when the glass transition temperature is lower than the environmental temperature (storage test temperature), a dark spot is generated.
[0149]
From the results so far, it has been found that by using a tertiary amine compound material such as Compounds 1 and 2 as a host material of the light emitting layer 3, it is possible to achieve both suppression of luminance reduction and heat resistance.
[0150]
In the device structure of Example 1, a tertiary amine compound as shown in Compounds 7 and 8 (see FIG. 4) was used as a tertiary amine compound, and a device was prepared. When a storage test was performed, the same result as that of the specific example 1 was obtained, and both suppression of luminance reduction and heat resistance could be achieved.
[0151]
[Estimation mechanism of luminance reduction suppression]
Here, in the organic EL device of the present embodiment in which the light emitting layer 50 is a mixed host layer, that is, a layer formed by mixing a hole transporting material, an electron transporting material, and a light emitting additive material composed of a tertiary amine compound, When tertiary amine compounds such as に to ３ are used, the mechanism by which the decrease in luminance is suppressed is estimated as follows.
[0152]
When the light emitting layer is a single host material, it is considered that light is emitted according to the following formula.
[0153]
Embedded image
H ⁺ + H ⁻ + D → (H * + D) → H + D * → H + D
Here, H indicates a charge (hole or electron) transport material molecule, D indicates a light emission additive material molecule, and * indicates a singlet excited state.
[0154]
Since the host material is single, each polar ion H of the host material molecule ⁺ , H ⁻ From the excited state H * of the host material molecule to the guest material molecule D. As a result, the guest molecule becomes the excited state D * and emits light.
[0155]
On the other hand, when the light emitting layer is a mixed host layer, it is considered that light is emitted by the following formula.
[0156]
Embedded image
Ha ⁺ + Hb ⁻ + D → Ha + Hb + D * → Ha + Hb + D
Here, Ha and Hb are charge transporting material molecules, one having a hole transporting property and the other having an electron transporting property. D indicates a light emitting additive material molecule, and * indicates a singlet excited state.
[0157]
Since the difference between the energy bands of the host materials Ha and Hb is very large, mutual charge transfer does not occur. Therefore, the host material does not enter the excited state and moves to the guest material molecule D. As a result, the guest molecule enters the excited state D * and emits light.
[0158]
As described above, in the mixed host layer, the host molecules Ha and Hb do not enter an excited state, so that deterioration of the host material hardly occurs. This is presumed to be one cause of the improvement in luminance life due to the use of the mixed host layer.
[0159]
However, when the light-emitting layer is a mixed host layer, it is presumed that the excitation of the host is occurring although the amount is reduced as compared with the case of the single host. Although the detailed mechanism of the excitation of the hole transporting material occurring in the mixed host layer is not clear, it is considered to depend on the molecular structure.
[0160]
[Examination of the cause of dark spots]
FIG. 8 is a diagram schematically showing a cross-sectional shape of a device using the above-mentioned compound 3 after being stored at 120 ° C. for 500 hours, based on a photograph observed using a scanning electron microscope.
[0161]
From the observation results, it was found that the layers in which the hole transport material was present (the hole transport layer 40 and the light emitting layer 50) were partially hollow. Since no current flows in the hollowed portion K1, the region becomes a non-light emitting region and is considered to be recognized as a dark spot. This is presumed to be due to the fact that the environmental temperature is higher than the glass transition temperature of the material, and crystallization accompanied by a volume change has progressed.
[0162]
In the specific examples 1 and 2 and the comparative examples 1 and 2, the electron transporting material as the host material of the light emitting layer 50 was the compound shown in FIG. In addition to the electron transporting material, the following comparative experiment was performed in order to confirm the existence of a decrease in luminance depending on the molecular structure of the hole transporting material.
[0163]
(Comparative Example 3)
After forming an ITO film (transparent electrode) as the anode 20 on the glass substrate 10 and performing a surface treatment using plasma of a mixture of argon and oxygen, a 10-nm-thick CuPc film was formed as the hole injection layer 30.
[0164]
Further, the compound 3 (see FIG. 2) is 50 nm as the hole transport layer 40, and the compound 3 is mixed with tris (8-quinolinolato) aluminum and dimethylquinacridone at a weight ratio of 50: 50: 1 to 20 nm as the light emitting layer 50. A film was formed.
[0165]
On top of this, 20 nm of tris (8-quinolinolato) aluminum was formed as the electron transport layer 60, LiF was formed on the electron injection layer 70, and Al was formed on the cathode 80 in this order, and sealed in a dry nitrogen atmosphere with a sealing can. Got.
[0166]
This device was subjected to an initial luminance of 2400 cd / m 2 under an environment of 85 ° C. ² When a durability test was performed by DC drive, the half life of luminance was 78 hours.
[0167]
(Comparative Example 4)
After forming an ITO film (transparent electrode) as the anode 20 on the glass substrate 10 and performing a surface treatment using plasma of a mixture of argon and oxygen, a 10-nm-thick CuPc film was formed as the hole injection layer 30.
[0168]
The compound 5 (see FIG. 2) is 50 nm as the hole transport layer 40, and the compound 5 and tris (8-quinolinolato) aluminum and dimethylquinacridone are used as the light emitting layer 50 in a weight ratio of 50: 50: 1 to 20 nm. A film was formed.
[0169]
On top of this, 20 nm of tris (8-quinolinolato) aluminum was formed as the electron transport layer 60, LiF was formed on the electron injection layer 70, and Al was formed on the cathode 80 in this order, and sealed in a dry nitrogen atmosphere with a sealing can. Got.
[0170]
This device was subjected to an initial luminance of 2400 cd / m 2 under an environment of 85 ° C. ² When a durability test was performed by DC drive, the luminance half life was 25 hours.
[0171]
The results of Comparative Examples 3 and 4 are summarized in the table of FIG. Here, the luminance life is represented by the luminance half-life. The numerical value in the molecular structure column indicates the total number of places where two or more phenylene groups, aliphatic groups, or groups represented by the above structural formula (1) (see chemical formula 19) exist between nitrogen atoms in the molecular structure. ing.
[0172]
From this result, it was confirmed that even when the electron transporting material and the light emitting additive material were different, the decrease in luminance was dependent on the molecular structure of the hole transporting material.
[0173]
(Comparative Example 5)
According to the mechanism for estimating the decrease in luminance in the mixed host layer, the difference depending on the molecular structure of the hole transport material should not appear in the structure without the mixed host layer. For this reason, verification was performed on a single host layer light emitting layer structure without using a mixed host layer.
[0174]
After forming an ITO film (transparent electrode) as the anode 20 on the glass substrate 10 and performing a surface treatment using plasma of a mixture of argon and oxygen, a 10-nm-thick CuPc film was formed as the hole injection layer 30.
[0175]
The tertiary amine compound is 20 nm as the hole transporting layer 40, the electron transporting material and rubrene shown in FIG. 5 are 40 nm in a weight ratio of 20: 1 as the light emitting layer 50, and the tris ( 8-Quinolinolato) aluminum was deposited to a thickness of 20 nm, LiF was deposited on the electron injection layer 70, and Al was deposited on the cathode 80, and sealed in a dry nitrogen atmosphere with a sealing can to obtain an organic EL device.
[0176]
Here, as the tertiary amine compound, the above compounds 1, 2, 3, 4, and 5 (see FIGS. 2 and 3) were applied. This element was subjected to a durability test in an environment of 85 ° C. with an initial luminance of 400 cd / m 2 1/64 duty drive. The results are shown in the table of FIG. Similar to the table of FIG. 7, the luminance life is shown by normalized luminance at 400 hours after the durability test.
[0177]
From this result, there is no correlation with the molecular structure of the hole transporting material observed in the mixed host layer. From this, it was confirmed that the above-mentioned problem in the present invention was a problem peculiar to the mixed host layer, and the present invention was reached in view of this problem.
[0178]
As described above, by using the tertiary amine compound of the present embodiment as the hole transporting material constituting the light-emitting layer 50, it is possible to significantly improve the luminance life and secure the heat resistance of 100 ° C. or more as compared with the related art. It was confirmed that both can be achieved.
[0179]
[About CuPc crystalline peak]
Next, as a preferred embodiment of the present embodiment, in the CuPc constituting the hole injection layer 30, the CuPc crystallinity peak (2θ = 6) due to heating within the operating temperature (for example, −40 ° C. to 120 ° C.) of the organic EL element S1 is obtained. .68 °) The reason why the variation of the value is within ± 25% of the CuPc crystallinity peak before heating will be specifically described, including the method of manufacturing the CuPc film 30 and the like.
[0180]
[First manufacturing method]
An ITO film 20 as an anode was formed on the glass substrate 10 by sputtering or the like, and the surface of the ITO film 20 was irradiated with ultraviolet rays while being heated to 300 ° C. Hereinafter, the processing on the ITO film 20 is referred to as UV-300 ° C. processing.
[0181]
After performing this UV-300 ° C. treatment, a CuPc film 30 as a hole injection layer was formed to a thickness of 10 nm at a material heating temperature of 420 ° C. by a vapor deposition method. After that, as in the specific example 1, the hole transporting layer 40 is a tertiary amine compound 1 (see FIG. 2) at 20 nm, the light emitting layer 50 is the compound 1 and the electron transporting material shown in FIG. Rubrene was formed to a thickness of 20 nm at a weight ratio of 60: 20: 3.
[0182]
Further, 20 nm of tris (8-quinolinolato) aluminum was formed as the electron transport layer 60, LiF was formed on the electron injection layer 70, and Al was formed on the cathode 80 in this order, to obtain the organic EL device as shown in FIG.
[0183]
Here, in the case where the CuPc film 30 is formed on the ITO film 20 which has been subjected to the UV-300 ° C. treatment, the high-temperature storage (120 ° C., 2 hours) is performed in the same manner as described in the section of “Means”. X-ray diffraction analysis was performed before and after the operation.
[0184]
As a result, it was confirmed that the ratio of the value of the CuPc crystalline peak generated at 2θ = 6.68 ° after the standing treatment was 1.02, which was much smaller than the value before the standing treatment. In other words, it indicates that the crystallinity of the CuPc film 30 at the time of film formation in this manufacturing method was very high and stable.
[0185]
Furthermore, the completed organic EL element was sealed with a sealing can. The sealing element was confirmed under the conditions of the above-mentioned accelerated high-temperature storage at 120 ° C. for 2 hours. As a result, there was almost no shift in the VI characteristics, and there was no decrease in brightness or uneven brightness. I couldn't see it.
[0186]
That is, the organic EL device manufactured by the first manufacturing method has characteristics in which the adhesion between CuPc and the light emitting layer is improved within the operating temperature, there is almost no shift in VI characteristics, and there is no reduction in brightness or uneven brightness. Was realized.
[0187]
Such an effect is due to the UV-300 ° C. treatment in the present manufacturing method, and a mechanism for realizing the effect by the treatment will be described in more detail.
[0188]
It has been known for a long time that a cleaning treatment of the surface of the ITO film is important for efficiently injecting holes from the ITO film 20 as the anode into the CuPc film 30 as the hole injection layer. However, it is generally evaluated based on the ionization potential (Ip) of the surface of the ITO film after cleaning. In view of the hole injection characteristics and the like, the present inventors consider that the ITO film 20 is If Ip was 5.5 eV or less, it was determined that there was no problem.
[0189]
However, the present inventors have studied that the Ip of the ITO film 20 is 5.45 eV when the plasma cleaning process of argon and oxygen (ratio 1: 1) is performed for 5 minutes, and that the Ip of the ITO film 20 is only when the UV process is performed for 20 minutes. Ip was 5.5 eV, and when the above-mentioned UV-300 ° C. treatment was performed for 20 minutes, Ip was 5.46 eV, which was not a large difference.
[0190]
Nevertheless, only the element subjected to the UV-300 ° C. treatment did not cause a shift in the VI characteristic after being left at a high temperature, that is, a decrease in luminance or unevenness in luminance. In other words, it indicates that the crystallinity of the crystalline organic material formed on the ITO film is not determined only by the Ip of the ITO film 20, but also includes other factors.
[0191]
In the UV-300 ° C. treatment, since heat treatment is involved, attention is paid to the moisture on the ITO surface, and the moisture at each temperature is determined by a thermal desorption method (hereinafter, referred to as a TDS method). The generated amount, that is, the amount of water separated and removed from the surface of the ITO film 20 was measured.
[0192]
FIG. 11 shows a measurement result by the TDS method immediately after forming the ITO film 20 on the glass substrate 10. This TDS spectrum has a molecular weight, that is, H / M = 18 in the TDS method. ₂ The spectrum of OH which is O or 17 is measured.
[0193]
From the results shown in FIG. 11, it can be seen that there are peaks of water separation and removal at 70 ° C. and 330 ° C. The former is water present as adsorbed water physically adsorbed on the surface of the ITO film 20, and the latter is water present as bound water chemically bonded to ITO on the surface of the ITO film 20. it is conceivable that. Therefore, it is considered that the bound water on the surface of the ITO film 20 is one of the factors that determine the crystallinity when the CuPc film 30 is formed.
[0194]
FIG. 12 shows a TDS spectrum when an ITO film 20 actually formed on the glass substrate 10 is subjected to a heat treatment at a temperature of 300 ° C. in a nitrogen atmosphere. When the heat treatment is not performed, that is, the peak value at 330 ° C. is reduced to about 50% as compared with the TDS spectrum shown in FIG. FIG. 13 shows a TDS spectrum when the heat treatment at 300 ° C. is performed in a vacuum. In this case, a peak at 330 ° C. is hardly observed.
[0195]
As a result of confirming the sealed organic EL device prepared by heat treatment at 300 ° C. in a nitrogen atmosphere or in a vacuum with a sealing can at 120 ° C. for 2 hours under the above-mentioned accelerated high temperature condition, V There was almost no shift in the -I characteristic, and no decrease in luminance or luminance unevenness was observed.
[0196]
From the above, in the method for manufacturing an organic EL element in which the ITO film 20 is formed on the substrate 10 and an organic material having crystallinity such as the CuPc film 30 is formed on the ITO film 20, the organic material is It has been found that it is effective to remove bound water on the surface of the ITO film 20 before forming the film.
[0197]
Thereby, on the surface of the ITO film 20 serving as a base of the organic material having crystallinity, the amount of bound water can be reduced together with the amount of adsorbed water, so that the crystallinity of the formed organic material can be increased. In addition, good luminance characteristics can be realized within the operating temperature.
[0198]
Here, as shown in FIG. 12, in the TDS spectrum due to moisture on the surface of the ITO film 20 after the desorption treatment, the peak value of the bound water around 330 ° C. is the surface of the ITO film 20 before the desorption treatment. Is preferably within 50% of the peak value of the bound water.
[0199]
Further, as shown in FIG. 13, it is more preferable that the TDS spectrum attributable to moisture on the surface of the ITO film 20 after the desorption treatment eliminates the bound water peak near 330 ° C.
[0200]
Note that, in order to reduce the amount of bound water present on the surface of the ITO film 20 to about 50% or less, the ITO film 20 is formed before a crystalline organic material such as the CuPc film 30 is formed on the ITO film 20. Is preferably set to 250 ° C. or higher.
[0201]
Further, according to the first manufacturing method, the ITO film 20 made of indium-tin oxide is formed on the substrate 10, and an organic material exhibiting crystallinity such as the CuPc film 30 is formed on the ITO film 20. An organic EL device formed by forming a film, wherein the ITO film 20 has no bound water peak near 330 ° C. in a spectrum attributable to moisture measured by a TDS method on the surface thereof. An element S1 is provided.
[0202]
Then, according to this, the hole injection characteristics from the anode ITO are stable within the use temperature, and a stable luminance characteristic in which luminance reduction and luminance unevenness are suppressed can be realized.
[0203]
[Second manufacturing method]
In the above-described first manufacturing method of the present embodiment, the crystallinity of the CuPc film 30 is enhanced by heat-treating the ITO film 20 serving as a base such as the CuPc film 30 which is an organic material having crystallinity. Was.
[0204]
In the second manufacturing method of the present embodiment, attention was paid to the material temperature when the CuPc film 30 was formed. An ITO film 20 as an anode is formed on the glass substrate 10 by sputtering or the like. In this glass substrate with an ITO film, the above-described plasma cleaning treatment of argon and oxygen was performed, and a CuPc film 30 as a hole injection layer was formed on the ITO film 20 at a material heating temperature of 420 ° C. by an evaporation method. This is referred to as a 420 ° C. film-formed product.
[0205]
On the other hand, on the glass substrate with an ITO film, the above-described plasma cleaning treatment of argon and oxygen was performed, and a CuPc film 30 as a hole injection layer was formed on the ITO film 20 by a vapor deposition method at a material heating temperature of 520 ° C. . This is referred to as a 520 ° C. film-formed product.
[0206]
After that, in each of the 420 ° C. film-formed product and the 520 ° C. film-formed product, the hole transport layer 40 and the compound 1 are formed on the CuPc film 30 in the same manner as in the first manufacturing method (that is, the specific example 1). The light emitting layer 50, the electron transport layer 60, the electron injection layer 70, and the cathode 80, which were the mixed host layers, were sequentially formed to manufacture the organic EL device S1.
[0207]
Here, the ratio of CuPc crystal peak values by X-ray diffraction analysis was examined before and after performing the above-described accelerated high-temperature storage (120 ° C., 2 hr) for the 420 ° C. film-formed product and the 520 ° C. film-formed product. . Further, the device was sealed with a sealing can and the shift of VI characteristics before and after the above-mentioned accelerated high-temperature storage was examined.
[0208]
In the case of a 420 ° C. film-formed product, the ratio of the CuPc crystalline peak is about 1.5 (see FIG. 17) and the shift amount is about 3 V (see FIG. 16), similarly to the prototype described in the section of “Means”. On the other hand, in the case of the film formed at 520 ° C., the ratio of the crystalline peak of CuPc was about 1.15, and the shift amount was as good as about 1 V.
[0209]
Further, another example of the second manufacturing method will be described. An ITO film 20 as an anode was formed on the glass substrate 10 by sputtering or the like. The surface was polished so that Ra was about 1 nm and Rz was about 10 nm. The surface of the ITO film 20 in the glass substrate with the ITO film was irradiated with ultraviolet rays while being heated to 150 ° C. (UV-150 ° C. treatment).
[0210]
Subsequently, a CuPc film 30 as a hole injection layer is formed on the ITO film 20 at a material heating temperature of 520 ° C. by a vapor deposition method. After that, similarly to the specific example 1, the hole transport layer 40, the light emitting layer 50 as the mixed host layer using the compound 1, the electron transport layer 60, the electron injection layer 70, and the cathode 80 are sequentially formed and dried. An organic EL device sealed with a sealing can in a nitrogen atmosphere was obtained.
[0211]
As a result of confirming the sealing device obtained by sealing the organic EL device thus obtained in a sealing can under the conditions of the above-mentioned accelerated high-temperature standing at 120 ° C. for 2 hours, the shift of the VI characteristic was small, and the brightness was reduced and the brightness was reduced. No unevenness was seen. Incidentally, the shift amount of the VI characteristic before and after the storage at the accelerated high temperature was 1.2 V, and the ratio of the CuPc crystallinity peak was 1.21.
[0212]
In another example of the second manufacturing method, the surface of the ITO film 20 in the glass substrate with the ITO film formed in the same manner as above was irradiated with ultraviolet rays at normal temperature (UV-normal temperature treatment). Subsequently, a CuPc film 30 as a hole injection layer was formed on the ITO film 20 at a material heating temperature of 520 ° C. by a vapor deposition method.
[0213]
Thereafter, similarly to the above, the sealing element obtained by sequentially forming the upper layers 40 to 80 and sealing the organic EL element with a sealing can was confirmed under the conditions of the above-mentioned accelerated high-temperature standing at 120 ° C. for 2 hours.
[0214]
As a result, the shift of the VI characteristics was small, and no decrease in luminance or luminance unevenness was observed. In this example, the shift amount of the VI characteristic before and after the high-temperature storage was 1.5 V, and the ratio of the CuPc crystallinity peak was 1.21.
[0215]
As described above, according to the second manufacturing method in which the film forming temperature of the CuPc film 30 is set to 520 ° C., the UV-300 ° C. processing employed in the first manufacturing method is performed regardless of the surface treatment method of the ITO film 20. Even without performing this, an organic EL element satisfying the required characteristics can be obtained. This indicates that factors affecting the crystallinity of CuPc exist not only in the ITO surface but also in the film forming method.
[0216]
In other words, the crystallinity of the CuPc film 30 is also very high and stable according to the second manufacturing method of the present embodiment, and the organic EL element S1 manufactured thereby achieves good luminance characteristics within the operating temperature. be able to.
[0219]
[Third Manufacturing Method]
In the third manufacturing method of the present embodiment, a CuPc film 30 which is a film of an organic material having crystallinity is formed on the ITO film 20 and then heat-treated in a vacuum or an inert gas atmosphere. The film 30 has been completely formed.
[0218]
That is, an ITO film 20 is formed on a glass substrate 10, a CuPc film 30 is formed thereon by a vapor deposition method or the like, and the CuPc film 30 is subjected to a heat treatment. 50, an electron transport layer 60, an electron injection layer 70, and a cathode 80 are sequentially formed to manufacture the organic EL element S1. An application example of the third manufacturing method will be described.
[0219]
(Application Example 1 of Third Manufacturing Method)
An ITO film 20 as an anode was formed on the glass substrate 10 by sputtering or the like. The surface of the ITO film 20 in the glass substrate with the ITO film was polished to make Ra about 1 nm and Rz about 10 nm. Further, the surface was subjected to the above-described plasma cleaning treatment of argon and oxygen.
[0220]
Thereafter, a CuPc film 30 as a hole injection layer was formed on the ITO film 20 to a thickness of 10 nm at a material heating temperature of 420 ° C. by a vapor deposition method. Subsequently, heat treatment was performed in a vacuum at a substrate temperature of 150 ° C. for 20 minutes.
[0221]
After that, the hole transport layer 40, the light emitting layer 50 which is a mixed host layer using the compound 1, and the electron transport layer 60 are formed on the CuPc film 30 in the same manner as in the first manufacturing method (that is, the specific example 1). , An electron injection layer 70 and a cathode 80 were sequentially formed to obtain an organic EL device.
[0222]
As a result of confirming the sealing device obtained by sealing the organic EL device thus obtained in a sealing can under the conditions of the above-mentioned accelerated high-temperature standing at 120 ° C. for 2 hours, the shift of the VI characteristic was small, and the brightness was reduced and the brightness was reduced. No unevenness was seen. Incidentally, the shift amount of the VI characteristic before and after the storage at the accelerated high temperature was 1.0 V, and the ratio of the CuPc crystallinity peak was 1.13.
[0223]
(Application Example 2 of Third Manufacturing Method)
In the same manner as in the application example 1 of the third manufacturing method, an ITO film 20 is formed on a glass substrate 10 and subjected to a plasma cleaning treatment of argon and oxygen, and then a CuPc film 30 is heated at a material heating temperature by an evaporation method. It was formed at 420 ° C. with a film thickness of 10 nm. Subsequently, in this example, a heat treatment was performed in a vacuum at a substrate temperature of 100 ° C. for 20 minutes.
[0224]
After that, the hole transport layer 40, the light emitting layer 50 which is a mixed host layer using the compound 1, and the electron transport layer 60 are formed on the CuPc film 30 in the same manner as in the first manufacturing method (that is, the specific example 1). , An electron injection layer 70 and a cathode 80 were sequentially formed to obtain an organic EL device.
[0225]
The sealed element obtained by sealing the organic EL element with a sealing can was confirmed under the conditions of the accelerated high-temperature standing at 120 ° C. for 2 hours. As a result, the shift of the VI characteristics was small, and no decrease in luminance or luminance unevenness was observed. In this example, the shift amount of the VI characteristics before and after the accelerated high-temperature storage was 1.0 V, and the ratio of the CuPc crystallinity peak was 1.15.
[0226]
(Application Example 3 of Third Manufacturing Method)
In the same manner as in the application example 1 of the third manufacturing method, an ITO film 20 is formed on a glass substrate 10 and subjected to a plasma cleaning treatment of argon and oxygen, and then a CuPc film 30 is heated at a material heating temperature by an evaporation method. It was formed at 420 ° C. with a film thickness of 10 nm. Subsequently, in this example, heat treatment was performed in a vacuum at a substrate temperature of 70 ° C. for 20 minutes.
[0227]
After that, the hole transport layer 40, the light emitting layer 50 which is a mixed host layer using the compound 1, and the electron transport layer 60 are formed on the CuPc film 30 in the same manner as in the first manufacturing method (that is, the specific example 1). , An electron injection layer 70 and a cathode 80 were sequentially formed to obtain an organic EL device.
[0228]
The sealed element obtained by sealing the organic EL element with a sealing can was confirmed under the conditions of the accelerated high-temperature standing at 120 ° C. for 2 hours. As a result, the shift of the VI characteristics was small, and no decrease in luminance or luminance unevenness was observed. In this example, the shift amount of the VI characteristic before and after the high-temperature storage was 1.6 V, and the ratio of the CuPc crystallinity peak was 1.25.
[0229]
As described above, according to the third manufacturing method, the CuPc film 30, which is a film of an organic material exhibiting crystallinity, is formed on the ITO film 20 and then heat-treated in a vacuum or an inert gas atmosphere. In addition, the crystallinity of the formed CuPc film 30 can be improved by the heat treatment.
[0230]
It is considered that this is because molecules in the CuPc film 30 vibrate due to activation energy due to heat, and the solid state shifts to a more stable phase. This has a strong correlation with temperature. Investigations by the present inventors have confirmed that the crystal peak of the CuPc film 30 due to X-ray diffraction is actually larger after the heat treatment than before the heat treatment, and the crystallinity is improved.
[0231]
From the above-mentioned application examples 1 to 3, if the temperature at which the CuPc film 30 is heat-treated in the third manufacturing method is 70 ° C. or more, the crystallinity of the CuPc film 30 is sufficiently increased, and the CuPc film 30 is used in a high-temperature environment. Also, the change in the crystal state of the CuPc film 30 can be reduced to such an extent that the brightness does not decrease, the brightness becomes uneven, and the short circuit or the leak does not occur.
[0232]
As described above, according to the third manufacturing method as well, in the organic EL element including the organic material having crystallinity, short-circuit and leakage of current can be prevented within the operating temperature, and excellent luminance characteristics can be realized. In addition, since the film to be heated is re-desorbed by the heat treatment, there is no element or element, so the upper limit of the heat treatment temperature is, of course, lower than the evaporation temperature or the sublimation temperature of the film to be heated. .
[0233]
As described above, the CuPc crystallinity peak has been separately described in the first to third manufacturing methods. Here, the CuPc crystallinity peak before and after the accelerated high-temperature storage (120 ° C., 2 hr) is described. The relationship between the ratio and the VI characteristic shift amount will be summarized.
[0234]
The relationship is shown as a graph in FIG. 14, and the data on which FIG. 14 is based is shown in FIG. 14 and 15, the ratio of the CuPc crystallinity peak value is described as “X-ray diffraction peak ratio”, and the VI characteristic shift amount is described as “VI shift”.
[0235]
As described above, the ratio of the CuPc crystallinity peak value is the ratio of the integral value of the CuPc crystallinity peak after the accelerated high-temperature storage to the integral value of the CuPc crystallographic peak before the accelerated high-temperature storage. If it is large, it indicates that the crystallinity of the CuPc film is increased by the accelerated high-temperature storage, and if it is less than 1, it is decreased.
[0236]
The VI characteristic shift amount is obtained by observing how many volts the VI characteristic after the accelerated high-temperature storage was shifted with reference to the VI characteristic before the accelerated high-temperature storage. Specifically, in FIG. 17, the ratio of the CuPc crystallinity peak was 1.5, and the crystallinity was significantly higher. Therefore, as shown in FIG. 16, the VI characteristic shift amount was as large as about 3 V. Had become.
[0237]
In FIG. 15, “conditions before cleaning” are conditions for cleaning the ITO film 20 formed on the glass substrate 10 before forming the CuPc film 30, and “plasma” refers to the above-mentioned argon and oxygen. The plasma cleaning process, “UV300 ° C.”, “UV250 ° C.”, “UV150 ° C.”, and “UV normal temperature” mean processes in which ultraviolet irradiation is performed at each temperature. In FIG. 15, “material heating temperature” is a material temperature when the CuPc film 30 is formed.
[0238]
Further, in FIG. 15, the conditions for the case where the above-described third manufacturing method is adopted are shown in the “film formation method”. “Heating after film formation (in a vacuum at 150 ° C.)”, “heating after film formation (in a vacuum of 100 ° C.)”, and “heating after film formation (in a vacuum of 70 ° C.)” are each applications of the above-described third manufacturing method. This is the case of Example 1, Application Example 2, and Application Example 3.
[0239]
In the organic EL device shown in the graph of FIG. 14 where the X-ray diffraction peak ratio is 1.25 and the VI shift is 1.6 V, the luminance unevenness was not clearly recognized. However, in the organic EL device having an X-ray diffraction peak ratio of about 1.3 and a VI shift of about 2.0 V, uneven luminance was clearly recognized.
[0240]
From this, it can be said that the threshold value of the X-ray diffraction peak ratio is about 1.25 and the threshold value of the VI shift is about 1.6 V from the viewpoint of marketability.
[0241]
That is, as described above, in the CuPc crystalline peak, the amount of change in the CuPc crystalline peak value due to heating within the operating temperature of the organic EL element S1 (for example, −40 ° C. to 120 ° C.) By keeping the peak within a range of ± 25% of the characteristic peak, good luminance characteristics can be realized at a practical level within the operating temperature.
[0242]
Further, from FIG. 15, when the heat treatment temperature of the ITO film 20 is set to 250 ° C. or higher, the amount of bound water can be effectively reduced together with the adsorbed water on the surface of the underlying ITO film, and the above-mentioned effect is achieved. It can be seen that an organic material having as high a crystallinity as possible can be formed into a film.
[0243]
Further, the change in the CuPc crystallinity peak value due to the heating may not be in the increasing direction but may be in the decreasing direction. That is, the amount of change may be + 25% or less or −25% or more of the CuPc crystalline peak before heating, and the X-ray diffraction peak ratio may be 0.75 or more as shown in FIG. For example, when the X-ray diffraction peak ratio was 0.68, the VI shift was 2.8 V, and luminance unevenness was recognized.
[0244]
The above is a preferred embodiment of the present embodiment, in which CuPc constituting the hole injection layer 30 has a CuPc crystallinity peak (2θ = 6) due to heating within the operating temperature (for example, −40 ° C. to 120 ° C.) of the organic EL element S1. .68 °) is the reason that the amount of change in the value is within ± 25% of the CuPc crystalline peak before heating.
[0245]
Then, by adopting this preferred embodiment, by suppressing the change amount of the CuPc crystallinity peak value before and after heating to within ± 25%, even when used in a high-temperature environment, there is no decrease in brightness or uneven brightness. To the extent, the change in the crystalline state of the organic material can be reduced.
[0246]
As a result, good luminance characteristics can be realized within the operating temperature, and the effect of the present embodiment of achieving both improvement in luminance life and ensuring heat resistance of 100 ° C. or higher is realized at a higher level. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an organic EL device according to an embodiment of the present invention.
FIG. 2 is a view showing the chemical structures of tertiary amine compounds 1 to 3 used in specific examples and comparative examples.
FIG. 3 is a view showing the chemical structures of tertiary amine compounds 4 to 6 used in specific examples and comparative examples.
FIG. 4 is a view showing the chemical structures of tertiary amine compounds 7 and 8 used in specific examples and comparative examples.
FIG. 5 is a view showing a chemical structure of an electron transporting material used in a specific example and a comparative example.
FIG. 6 is a diagram showing the results of endurance tests in Specific Examples 1 and 2 and Comparative Examples 1 and 2.
FIG. 7 is a table showing the results of Specific Examples 1 and 2 and Comparative Examples 1 and 2, including the physical property values of each tertiary amine compound material.
FIG. 8 is a diagram schematically illustrating a cross-sectional shape of a device using Compound 3 after storage at 120 ° C. for 500 hours.
FIG. 9 is a table showing the results of Comparative Examples 3 and 4.
FIG. 10 is a chart showing the results of Comparative Example 5.
FIG. 11 is a diagram showing a TDS spectrum immediately after an ITO film is formed on a glass substrate.
FIG. 12 is a diagram showing a TDS spectrum of the surface of an ITO film when a heat treatment is performed at a temperature of 300 ° C. in a nitrogen atmosphere.
FIG. 13 is a diagram showing a TDS spectrum of the surface of an ITO film when a heat treatment is performed at a temperature of 300 ° C. in a vacuum.
FIG. 14 is a diagram showing the relationship between the ratio of the crystallinity peak of CuPc and the VI characteristic shift amount before and after the high-temperature treatment is left at 120 ° C. for 2 hours.
FIG. 15 is a table showing the data on which FIG. 14 is based;
FIG. 16 is a view showing a state of a VI characteristic shift before and after leaving at a high temperature of 100 ° C. and 12 hours in a prototype of the present inventors.
FIG. 17 is a diagram showing X-ray diffraction spectra of a CuPc film of a prototype manufactured by the present inventors before and after leaving at a high temperature of 100 ° C. for 12 hours.
[Explanation of symbols]
10: substrate, 20: anode, 30: hole injection layer, 50: light emitting layer, 80: cathode.

Claims (7)

An organic EL device having a light emitting layer formed by mixing a hole transporting material, an electron transporting material, and a light emitting additive material formed of a tertiary amine compound between a pair of electrodes,
The tertiary amine compound constituting the hole transporting material has a total number of places where two or more phenylene groups, aliphatic groups, or groups represented by the following structural formula (1) exist between nitrogen atoms in the molecular structure. Is one or zero, and has a glass transition temperature of 100 ° C. or higher.

(In the structural formula (1), L1 and L2 are one or more phenylene groups, and M1 and M2 represent an aromatic group or an aliphatic group.) The organic EL device according to claim 1, wherein the tertiary amine compound constituting the hole transporting material is a compound having a skeleton represented by the following structural formula (2).

(In the structural formula (2), R1 to R20 are hydrogen or a structure represented by the following structural formulas (3), (4) and (5);

Or a structure in which an aromatic ring is formed by adjacent groups among R1 to R20,
In addition, at least one of R1 to R20 has any one of the structural formulas (3), (4), and (5).
Here, B1 to B2, C1 to C3, and D1 to D4 represent a substituted or unsubstituted aryl group. ) The organic EL device according to claim 1, wherein the tertiary amine compound constituting the hole transporting material is a compound having a skeleton represented by the following structural formula (6).

(In the structural formula (6), A is two or more phenylene groups, an aliphatic group, or a group represented by the structural formula (1);
R1 to R20 are hydrogen or a structure represented by the following structural formulas (3), (4), and (5);

Or a structure in which an aromatic ring is formed by adjacent groups among R1 to R20,
In addition, at least one of R1 to R20 has any one of the structural formulas (3), (4), and (5).
Here, B1 to B2, C1 to C3, and D1 to D4 represent a substituted or unsubstituted aryl group. ) A hole injection layer is interposed between one of the pair of electrodes and the light emitting layer,
The hole injection layer is made of an organic material having crystallinity,
In the value of the diffraction peak appearing by the X-ray diffraction method of the organic material exhibiting the crystallinity, the amount of change in the diffraction peak value due to heating within the operating temperature of the organic EL element is ± 10% of the diffraction peak value before the heating. The organic EL device according to any one of claims 1 to 3, wherein the content is within 25%. An ITO film made of an oxide of indium-tin is formed on a substrate, and the organic material exhibiting crystallinity is constituted as an organic film formed on the ITO film. Item 5. The organic EL device according to item 4, The organic material exhibiting the crystallinity characteristic is a copper phthalocyanine film, and the diffraction peak value is a diffraction peak value of a (200) plane parallel to the substrate in the copper phthalocyanine film. The organic EL device according to the above. 7. The organic EL device according to claim 5, wherein the ITO film has an average surface roughness Ra of 2 nm or less, and a ten-point average surface roughness Rz of 20 nm or less.

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